publicationDate,title,abstract,id
2019-11-27,How spin-orbital entanglement depends on the spin-orbit coupling in a Mott insulator,"The concept of the entanglement between spin and orbital degrees of freedom
plays a crucial role in understanding various phases and exotic ground states
in a broad class of materials, including orbitally ordered materials and spin
liquids. We investigate how the spin-orbital entanglement in a Mott insulator
depends on the value of the spin-orbit coupling of the relativistic origin. To
this end, we numerically diagonalize a 1D spin-orbital model with the
'Kugel-Khomskii' exchange interactions between spins and orbitals on different
sites supplemented by the on-site spin-orbit coupling. In the regime of small
spin-orbit coupling w.r.t. the spin-orbital exchange, the ground state to a
large extent resembles the one obtained in the limit of vanishing spin-orbit
coupling. On the other hand, for large spin-orbit coupling the ground state
can, depending on the model parameters, either still show negligible
spin-orbital entanglement, or can evolve to a highly spin-orbitally entangled
phase with completely distinct properties that are described by an effective
XXZ model. The presented results suggest that: (i) the spin-orbital
entanglement may be induced by large on-site spin-orbit coupling, as found in
the 5d transition metal oxides, such as the iridates; (ii) for Mott insulators
with weak spin-orbit coupling of Ising-type, such as e.g. the alkali
hyperoxides, the effects of the spin-orbit coupling on the ground state can, in
the first order of perturbation theory, be neglected.",1911.12180v2
2016-09-11,Spin-Orbit Coupling Induced Spin Squeezing in Three-Component Bose Gases,"We observe spin squeezing in three-component Bose gases where all three
hyperfine states are coupled by synthetic spin-orbit coupling. This phenomenon
is a direct consequence of spin-orbit coupling, as can be seen clearly from an
effective spin Hamiltonian. By solving this effective model analytically with
the aid of a Holstein-Primakoff transformation for spin-1 system in the low
excitation limit, we conclude that the spin-nematic squeezing, a novel category
of spin squeezing existing exclusively in large spin systems, is enhanced with
increasing spin-orbit intensity and effective Zeeman field, which correspond to
Rabi frequency and two-photon detuning within the Raman scheme for synthetic
spin-orbit coupling, respectively. These trends of dependence are in clear
contrast to spin-orbit coupling induced spin squeezing in spin-1/2 systems. We
also analyze the effects of harmonic trap and interaction with realistic
experimental parameters numerically, and find that a strong harmonic trap
favors spin-nematic squeezing. We further show spin-nematic squeezing can be
interpreted as two-mode entanglement or two-spin squeezing at low excitation.
Our findings can be observed in ^{87}Rb gases with existing techniques of
synthetic spin-orbit coupling and spin-selectively imaging.",1609.03141v1
2020-09-24,Evolution of Spin-Orbital Entanglement with Increasing Ising Spin-Orbit Coupling,"Several realistic spin-orbital models for transition metal oxides go beyond
the classical expectations and could be understood only by employing the
quantum entanglement. Experiments on these materials confirm that spin-orbital
entanglement has measurable consequences. Here, we capture the essential
features of spin-orbital entanglement in complex quantum matter utilizing 1D
spin-orbital model which accommodates SU(2)xSU(2) symmetric Kugel-Khomskii
superexchange as well as the Ising on-site spin-orbit coupling. Building on the
results obtained for full and effective models in the regime of strong
spin-orbit coupling, we address the question whether the entanglement found on
superexchange bonds always increases when the Ising spin-orbit coupling is
added. We show that (i) quantum entanglement is amplified by strong spin-orbit
coupling and, surprisingly, (ii) almost classical disentangled states are
possible. We complete the latter case by analyzing how the entanglement
existing for intermediate values of spin-orbit coupling can disappear for
higher values of this coupling.",2009.11773v1
2011-08-31,Curvature-induced spin-orbit coupling and spin relaxation in a chemically clean single-layer graphene,"The study of spin-related phenomena in materials requires knowledge on the
precise form of effective spin-orbit coupling of conducting carriers in the
solid-states systems. We demonstrate theoretically that curvature induced by
corrugations or periodic ripples in single-layer graphenes generates two types
of effective spin-orbit coupling. In addition to the spin-orbit coupling
reported previously that couples with sublattice pseudospin and corresponds to
the Rashba-type spin-orbit coupling in a corrugated single-layer graphene,
there is an additional spin-orbit coupling that does not couple with the
pseudospin, which can not be obtained from the extension of the
curvature-induced spin-orbit coupling of carbon nanotubes. Via numerical
calculation we show that both types of the curvature-induced spin-orbit
coupling make the same order of contribution to spin relaxation in chemically
clean single-layer graphene with nanoscale corrugation. The spin relaxation
dependence on the corrugation roughness is also studied.",1108.6128v3
2007-01-31,Coupled spin-charge drift-diffusion approach for a two-dimensional electron gas with Rashba spin-orbit coupling,"Based on kinetic equations for the density matrix, drift-diffusion equations
are derived for a two-dimensional electron gas with Rashba spin-orbit coupling.
Universal results are obtained for the weak coupling case. Most interesting is
the observation that with increasing spin-orbit coupling strengths there is a
sharp transition between spin diffusion and ballistic spin transport. For
strong spin-orbit coupling, when the elastic scattering time is much larger
than the spin relaxation time, undamped spin-coherent waves are identified. The
existence of these long-lived spin-coherent states is confirmed by exact
analytical results obtained from microscopic kinetic equations valid in the
ballistic regime.",0701782v1
2015-05-28,Intrinsic spin Hall effect in systems with striped spin-orbit coupling,"The Rashba spin-orbit coupling arising from structure inversion asymmetry
couples spin and momentum degrees of freedom providing a suitable (and very
intensively investigated) environment for spintronic effects and devices. Here
we show that in the presence of strong disorder, non-homogeneity in the
spin-orbit coupling gives rise to a finite spin Hall conductivity in contrast
with the corresponding case of a homogeneous linear spin-orbit coupling. In
particular, we examine the inhomogeneity arising from a striped structure for a
two-dimensional electron gas, affecting both density and Rashba spin-orbit
coupling. We suggest that this situation can be realized at oxide interfaces
with periodic top gating.",1505.07667v1
2018-05-25,Generation of Spin Current from Lattice Distortion Dynamics: Spin-Orbit Routes,"Generation of spin current from lattice distortion dynamics in metals is
studied with special attention on the effect of spin-orbit coupling. Treating
the lattice distortion by local coordinate transformation, we calculate spin
current and spin accumulation with the linear response theory. It is found that
there are two routes to the spin-current generation, one via the spin Hall
effect and the other via the spin accumulation. The present effect due to
spin-orbit coupling can be comparable to, or even larger than, the one based on
the spin-vorticity coupling in systems with strong spin-orbit coupling.",1805.10328v2
2009-10-16,Current-induced spin polarization for a general two-dimensional electron system,"In this paper, current-induced spin polarization for two-dimensional electron
gas with a general spin-orbit interaction is investigated. For isotropic energy
spectrum, the in-plane current-induced spin polarization is found to be
dependent on the electron density for non-linear spin-orbit interaction and
increases with the increment of sheet density, in contrast to the case for $\bm
k$-linear spin-orbit coupling model. The numerical evaluation is performed for
InAs/InSb heterojunction with spin-orbit coupling of both linear and cubic
spin-orbit coupling types. For $\delta$-type short-range electron-impurity
scattering, it is found that the current-induced spin polarization increases
with increasing the density when cubic spin-orbit couplings are considered.
However, for remote disorders, a rapid enhancement of current-induced spin
polarization is always observed at high electron density, even in the case
without cubic spin-orbit coupling. This result demonstrates the
collision-related feature of current-induced spin polarization. The effects of
different high order spin-orbit couplings on spin polarization can be
comparable.",0910.3050v1
2018-10-08,Zeeman spin-orbit coupling in antiferromagnetic conductors,"This article is a brief review of Zeeman spin-orbit coupling, arising in a
low-carrier commensurate N\'eel antiferromagnet subject to magnetic field. The
field tends to lift the degeneracy of the electron spectrum. However, a hidden
symmetry protects double degeneracy of Bloch eigenstates at special momenta in
the Brillouin zone. The effective transverse $g$-factor vanishes at such
points, thus acquiring a substantial momentum dependence, which turns a
textbook Zeeman term into a spin-orbit coupling. After describing the symmetry
underpinnings of the Zeeman spin-orbit coupling, I compare it with its
intrinsic counterparts such as Rashba coupling, and then show how Zeeman
spin-orbit coupling may survive in the presence of intrinsic spin-orbit
coupling. Finally, I outline some of the likely experimental manifestations of
Zeeman spin-orbit coupling, and compare it with similar phenomena in other
settings such as semiconducting quantum wells.",1810.03720v1
2021-01-27,Spin-memory loss induced by bulk spin-orbit coupling at ferromagnet/heavy-metal interfaces,"A spin current through a ferromagnet/heavy-metal interface may shrink due to
the spin-flip at the interface, resulting in the spin-memory loss. Here we
propose a mechanism of the spin-memory loss. In contrast to other mechanisms
based on interfacial spin-orbit coupling, our mechanism is based on the bulk
spin-orbit coupling in a heavy-metal. We demonstrate that the bulk spin-orbit
coupling induces the entanglement between the spin and orbital degrees of
freedom and this spin-orbital entanglement can give rise to sizable spin-flip
at the interface even when the interfacial spin-orbit coupling is weak. Our
mechanism emphasizes crucial roles of the atomic orbital degree of freedom and
induces the strong spin-memory loss near band crossing points between bands of
different orbital characters.",2101.11438v1
2023-10-07,"Orbital diffusion, polarization and swapping in centrosymmetric metals","We propose a general theory of charge, spin and orbital diffusion based on
Keldysh formalism. Our findings indicate that the diffusivity of orbital
angular momentum in metals is much lower than that of spin or charge due to the
strong orbital intermixing in crystals. Furthermore, our theory introduces the
concept of spin-orbit polarization by which a pure orbital (spin) current
induces a longitudinal spin (orbital) current, a process as efficient as spin
polarization in ferromagnets. Finally, we find that orbital currents undergo
momentum swapping, even in the absence of spin-orbit coupling. This theory
establishes several key parameters for orbital transport of direct importance
to experiments.",2310.04763v1
2018-04-28,Spin-1 Bosons in the Presence of Spin-orbit Coupling,"In this paper, I'm going to talk about the theoretical and experimental
progress in studying spin-orbit coupled spin-1 bosons. Realization of
spin-orbit coupled quantum gases opens a new avenue in cold atom physics. In
particular, the interplay between spin-orbit coupling and inter-atomic
interaction leads to many intriguing phenomena. Moreover, the non-zero momentum
of ground states can be controlled by external fields, which allows for good
quantum control.",1805.00001v1
2021-03-10,Magnetic phases for two $t_{2g}$ holes with spin-orbit coupling and crystal field,"We investigate two holes in the the $t_{2g}$ levels of a square-lattice Mott
insulator with strong spin-orbit coupling. Exact diagonalization of a
spin-orbital model valid at strong onsite interactions, but arbitrary
spin-orbit coupling and crystal field is complemented by an effective triplon
model (valid for strong spin-orbit coupling) and by a semiclassical variant of
the model. We provide the magnetic phase diagram depending on crystal field and
spin-orbit coupling, which largely agrees for the semiclassical and quantum
models, as well as excitation spectra characterizing the various phases.",2103.06033v1
2007-10-28,Some symmetry properties of spin currents and spin polarizations in multi-terminal mesoscopic spin-orbit coupled systems,"We study theoretically some symmetry properties of spin currents and spin
polarizations in multi-terminal mesoscopic spin-orbit coupled systems. Based on
a scattering wave function approach, we show rigorously that in the equilibrium
state no finite spin polarizations can exist in a multi-terminal mesoscopic
spin-orbit coupled system (both in the leads and in the spin-orbit coupled
region) and also no finite equilibrium terminal spin currents can exist. By use
of a typical two-terminal mesoscopic spin-orbit coupled system as the example,
we show explicitly that the nonequilibrium terminal spin currents in a
multi-terminal mesoscopic spin-orbit coupled system are non-conservative in
general. This non-conservation of terminal spin currents is not caused by the
use of an improper definition of spin current but is intrinsic to
spin-dependent transports in mesoscopic spin-orbit coupled systems. We also
show that the nonequilibrium lateral edge spin accumulation induced by a
longitudinal charge current in a thin strip of \textit{finite} length of a
two-dimensional electronic system with intrinsic spin-orbit coupling may be
non-antisymmetric in general, which implies that some cautions may need to be
taken when attributing the occurrence of nonequilibrium lateral edge spin
accumulation induced by a longitudinal charge current in such a system to an
intrinsic spin Hall effect.",0710.5316v1
2023-11-18,Thermal Spin Orbit Torque with Dresselhaus Spin Orbit Coupling,"Based on the spinor Boltzmann equation, we obtain a temperature dependent
thermal spin-orbit torque in terms of the local equilibrium distribution
function in a two dimensional ferromagnet with Dresselhaus spin-orbit coupling.
We also derive the continuity equation of spin accumulation and spin current,
the spin diffusion equation in Dresselhaus ferromagnet, which contains the
thermal spin orbit torque under local equilibrium assumption. This temperature
dependent thermal spin-orbit torque originates from the temperature gradient
applied to the system. it is also sensitive to temperature due to the local
equilibrium distribution function therein. In the spin diffusion equation, we
can single out the usual spin-orbit torque as well as the spin transfer torque,
which is conceded to our previous results. Finally, we illustrate them by an
example of spin-polarized transport through a ferromagnet with Dresselhaus
spin-orbit coupling driven by temperature gradient, those torques including
thermal spin-orbit torque are demonstrated numerically.",2311.14719v1
2017-12-15,Large spin relaxation anisotropy and valley-Zeeman spin-orbit coupling in WSe2/Gr/hBN heterostructures,"Large spin-orbital proximity effects have been predicted in graphene
interfaced with a transition metal dichalcogenide layer. Whereas clear evidence
for an enhanced spin-orbit coupling has been found at large carrier densities,
the type of spin-orbit coupling and its relaxation mechanism remained unknown.
We show for the first time an increased spin-orbit coupling close to the charge
neutrality point in graphene, where topological states are expected to appear.
Single layer graphene encapsulated between the transition metal dichalcogenide
WSe$_2$ and hBN is found to exhibit exceptional quality with mobilities as high
as 100000 cm^2/V/s. At the same time clear weak anti-localization indicates
strong spin-orbit coupling and a large spin relaxation anisotropy due to the
presence of a dominating symmetric spin-orbit coupling is found. Doping
dependent measurements show that the spin relaxation of the in-plane spins is
largely dominated by a valley-Zeeman spin-orbit coupling and that the intrinsic
spin-orbit coupling plays a minor role in spin relaxation. The strong
spin-valley coupling opens new possibilities in exploring spin and valley
degree of freedom in graphene with the realization of new concepts in spin
manipulation.",1712.05678v2
2007-01-05,Deformation of SU(4) singlet spin-orbital state due to Hund's rule coupling,"We investigate the ground-state property and the excitation gap of a
one-dimensional spin-orbital model with isotropic spin and anisotropic orbital
exchange interactions, which represents the strong-coupling limit of a
two-orbital Hubbard model including the Hund's rule coupling ($J$) at quarter
filling, by using a density-matrix renormalization group method. At J=0, spin
and orbital correlations coincide with each other with a peak at $q=\pi/2$,
corresponding to the SU(4) singlet state. On the other hand, spin and orbital
states change in a different way due to the Hund's rule coupling. With
increasing $J$, the peak position of orbital correlation changes to $q=\pi$,
while that of spin correlation remains at $q=\pi/2$. In addition, orbital dimer
correlation becomes robust in comparison with spin dimer correlation,
suggesting that quantum orbital fluctuation is enhanced by the Hund's rule
coupling. Accordingly, a relatively large orbital gap opens in comparison with
a spin gap, and the system is described by an effective spin system on the
background of the orbital dimer state.",0701092v1
2010-04-08,Coupling of bonding and antibonding electron orbitals in double quantum dots by spin-orbit interaction,"We perform a systematic exact diagonalization study of spin-orbit coupling
effects for stationary few-electron states confined in quasi two-dimensional
double quantum dots. We describe the spin-orbit-interaction induced coupling
between bonding and antibonding orbitals and its consequences for
magneto-optical absorption spectrum. The spin-orbit coupling for odd electron
numbers (one, three) %only weakly perturbs the ground-state wave functions.
%Nevertheless, %the spin-orbit interaction opens avoided crossings between low
energy excited levels of opposite spin orientation and opposite spatial parity.
For two-electrons the spin-orbit coupling allows for low-energy optical
transitions that are otherwise forbidden by spin and parity selection rules. We
demonstrate that the energies of optical transitions can be significantly
increased by an in-plane electric field but only for odd electron numbers.
Occupation of single-electron orbitals and effects of spin-orbit coupling on
electron distribution between the dots are also discussed.",1004.1250v1
2021-11-22,Particle and spin transports of spin-orbit coupled Fermi gas through a Quantum Point Contact,"The particle and spin transport through a quantum point contact between two
Fermi gases with Raman-induced spin-orbit coupling are investigated. We show
that the particle and spin conductances both demonstrate the structure of
plateau due to the mesoscopic scale of the quantum point contact. Compared with
the normal Fermi gases the particle conductance can be significantly enhanced
by the spin-orbit coupling effect. Furthermore, the conversion of the particle
and spin currents can take place in the spin-orbit coupled system, and we find
that it is controlled by the parameter of two-photon detuning. When the
parameter of two-photon detuning vanishes the particle and spin currents
decouple.",2111.11054v1
2017-01-25,Direct Mapping of Spin and Orbital Entangled Wavefunction under Interband Spin-Orbit coupling of Rashba Spin-Split Surface States,"We use spin- and angle-resolved photoemission spectroscopy (SARPES) combined
with polarization-variable laser and investigate the spin-orbit coupling effect
under interband hybridization of Rashba spin-split states for the surface
alloys Bi/Ag(111) and Bi/Cu(111). In addition to the conventional band mapping
of photoemission for Rashba spin-splitting, the different orbital and spin
parts of the surface wavefucntion are directly imaged into energy-momentum
space. It is unambiguously revealed that the interband spin-orbit coupling
modifies the spin and orbital character of the Rashba surface states leading to
the enriched spin-orbital entanglement and the pronounced momentum dependence
of the spin-polarization. The hybridization thus strongly deviates the spin and
orbital characters from the standard Rashba model. The complex spin texture
under interband spin-orbit hybridyzation proposed by first-principles
calculation is experimentally unraveled by SARPES with a combination of p- and
s-polarized light.",1701.07269v1
2002-11-05,"SU(4) Spin-Orbital Two-Leg Ladder, Square and Triangle Lattices","Based on the generalized valence bond picture, a Schwinger boson mean field
theory is applied to the symmetric SU(4) spin-orbital systems. For a two-leg
SU(4) ladder, the ground state is a spin-orbital liquid with a finite energy
gap, in good agreement with recent numerical calculations. In two-dimensional
square and triangle lattices, the SU(4) Schwinger bosons condense at
(\pi/2,\pi/2) and (\pi/3,\pi/3), respectively. Spin, orbital, and coupled
spin-orbital static susceptibilities become singular at the wave vectors, twice
of which the bose condensation arises at. It is also demonstrated that there
are spin, orbital, and coupled spin-orbital long-range orderings in the ground
state.",0211074v1
2013-08-29,Spin-orbit coupling and spin Hall effect for neutral atoms without spin-flips,"We propose a scheme which realizes spin-orbit coupling and the spin Hall
effect for neutral atoms in optical lattices without relying on near resonant
laser light to couple different spin states. The spin-orbit coupling is created
by modifying the motion of atoms in a spin-dependent way by laser recoil. The
spin selectivity is provided by Zeeman shifts created with a magnetic field
gradient. Alternatively, a quantum spin Hamiltonian can be created by
all-optical means using a period- tripling, spin-dependent superlattice.",1308.6349v1
2003-01-28,Spin-orbital gapped phase with least symmetry breaking in the one-dimensional symmetrically coupled spin-orbital model,"To describe the spin-orbital energy gap formation in the one-dimensional
symmetrically coupled spin-orbital model, we propose a simple mean field theory
based on an SU(4) constraint fermion representation of spins and orbitals. A
spin-orbital gapped phase is formed due to a marginally relevant spin-orbital
valence bond pairing interaction. The energy gap of the spin and orbital
excitations grows extremely slowly from the SU(4) symmetric point up to a
maximum value and then decreases rapidly. By calculating the spin, orbital, and
spin-orbital tensor static susceptibilities at zero temperature, we find a
crossover from coherent to incoherent magnetic excitations as the spin-orbital
coupling decreasing from large to small values.",0301533v2
2013-12-11,Spin-orbit coupling in quantum gases,"Spin-orbit coupling links a particle's velocity to its quantum mechanical
spin, and is essential in numerous condensed matter phenomena, including
topological insulators and Majorana fermions. In solid-state materials,
spin-orbit coupling originates from the movement of electrons in a crystal's
intrinsic electric field, which is uniquely prescribed. In contrast, for
ultracold atomic systems, the engineered ""material parameters"" are tuneable: a
variety of synthetic spin-orbit couplings can be engineered on demand using
laser fields. Here we outline the current experimental and theoretical status
of spin-orbit coupling in ultracold atomic systems, discussing unique features
that enable physics impossible in any other known setting.",1312.3292v1
2012-08-28,Spin-orbit coupled particle in a spin bath,"We consider a spin-orbit coupled particle confined in a quantum dot in a bath
of impurity spins. We investigate the consequences of spin-orbit coupling on
the interactions that the particle mediates in the spin bath. We show that in
the presence of spin-orbit coupling, the impurity-impurity interactions are no
longer spin-conserving. We quantify the degree of this symmetry breaking and
show how it relates to the spin-orbit coupling strength. We identify several
ways how the impurity ensemble can in this way relax its spin by coupling to
phonons. A typical resulting relaxation rate for a self-assembled Mn-doped ZnTe
quantum dot populated by a hole is 1 $\mu$s. We also show that decoherence
arising from nuclear spins in lateral quantum dots is still removable by a spin
echo protocol, even if the confined electron is spin-orbit coupled.",1208.5606v1
2023-10-08,Vortex Lattice Formation in Spin-Orbit-Coupled Spin-2 Bose-Einstein Condensate Under Rotation,"We investigate the vortex lattice configuration in a rotating spin
orbit-coupled spin-2 Bose-Einstein condensate confined in a
quasi-two-dimensional harmonic trap. By considering the interplay between
rotation frequency, spin-orbit couplings, and inter atomic interactions, we
explore a variety of vortex lattice structures emerging as a ground state
solution. Our study focuses on the combined effects of spin-orbit coupling and
rotation, analyzed by using the variational method for the single-particle
Hamiltonian. We observe that the interplay between rotation and Rashba
spin-orbit coupling gives rise to different effective potentials for the
bosons. Specifically, at higher rotation frequencies, isotropic spin-orbit
coupling leads to an effective toroidal potential, while fully anisotropic
spin-orbit coupling results in a symmetric double-well potential. To obtain
these findings, we solve the five coupled Gross-Pitaevskii equations for the
spin-2 BEC with spin-orbit coupling under rotation. Notably, we find that the
antiferromagnetic, cyclic, and ferromagnetic phases exhibit similar behavior at
higher rotation.",2310.05160v1
2007-09-21,Weak and strong coupling limits of the two-dimensional Fröhlich polaron with spin-orbit Rashba interaction,"The continuous progress in fabricating low-dimensional systems with large
spin-orbit couplings has reached a point in which nowadays materials may
display spin-orbit splitting energies ranging from a few to hundreds of meV.
This situation calls for a better understanding of the interplay between the
spin-orbit coupling and other interactions ubiquitously present in solids, in
particular when the spin-orbit splitting is comparable in magnitude with
characteristic energy scales such as the Fermi energy and the phonon frequency.
  In this article, the two-dimensional Fr\""ohlich electron-phonon problem is
reformulated by introducing the coupling to a spin-orbit Rashba potential,
allowing for a description of the spin-orbit effects on the electron-phonon
interaction. The ground state of the resulting Fr\""ohlich-Rashba polaron is
studied in the weak and strong coupling limits of the electron-phonon
interaction for arbitrary values of the spin-orbit splitting. The weak coupling
case is studied within the Rayleigh-Schr\""odinger perturbation theory, while
the strong-coupling electron-phonon regime is investigated by means of
variational polaron wave functions in the adiabatic limit. It is found that,
for both weak and strong coupling polarons, the ground state energy is
systematically lowered by the spin-orbit interaction, indicating that the
polaronic character is strengthened by the Rashba coupling. It is also shown
that, consistently with the lowering of the ground state, the polaron effective
mass is enhanced compared to the zero spin-orbit limit. Finally, it is argued
that the crossover between weakly and strongly coupled polarons can be shifted
by the spin-orbit interaction.",0709.3429v2
2021-02-02,"Coupled spin-orbital fluctuations in a three orbital model for $4d$ and $5d$ oxides with electron fillings $n=3,4,5$ -- Application to $\rm NaOsO_3$, $\rm Ca_2RuO_4$, and $\rm Sr_2IrO_4$","A unified approach is presented for investigating coupled spin-orbital
fluctuations within a realistic three-orbital model for strongly spin-orbit
coupled systems with electron fillings $n=3,4,5$ in the $t_{2g}$ sector of
$d_{yz},d_{xz},d_{xy}$ orbitals. A generalized fluctuation propagator is
constructed which is consistent with the generalized self-consistent
Hartree-Fock approximation where all Coulomb interaction contributions
involving orbital diagonal and off-diagonal spin and charge condensates are
included. Besides the low-energy magnon, intermediate-energy orbiton and
spin-orbiton, and high-energy spin-orbit exciton modes, the generalized
spectral function also shows other high-energy excitations such as the Hund's
coupling induced gapped magnon modes. We relate the characteristic features of
the coupled spin-orbital excitations to the complex magnetic behavior resulting
from the interplay between electronic bands, spin-orbit coupling, Coulomb
interactions, and structural distortion effects, as realized in the compounds
$\rm NaOsO_3$, $\rm Ca_2RuO_4$, and $\rm Sr_2IrO_4$.",2102.01400v2
2023-07-27,Spin-orbit torque emerging from orbital textures in centrosymmetric materials,"We unveil a hitherto concealed spin-orbit torque mechanism driven by orbital
degrees of freedom in centrosymmetric two-dimensional transition metal
dichalcogenides (focusing on PtSe${}_2$ ). Using first-principles simulations,
tight-binding models and large-scale quantum transport calculations, we show
that such a mechanism fundamentally stems from a spatial localization of
orbital textures at opposite sides of the material, which imprints their
symmetries onto spin-orbit coupling effects, further producing efficient and
tunable spin-orbit torque. Our study suggests that orbital-spin entanglement at
play in centrosymmetric materials can be harnessed as a resource for
outperforming conventional spin-orbit torques generated by the Rashba-type
effects.",2307.14673v1
2001-08-01,The Rashba Effect within the Coherent Scattering Formalism,"The influence of spin-orbit coupling in two-dimensional systems is
investigated within the framework of the Landauer-Buettiker coherent scattering
formalism. This formalism usually deals with spin-independent stationary states
and, therefore, it does not include a spin-orbit contribution to the current.
In this article, we will rederive the coherent scattering formalism, accounting
for the changes brought about by the spin-orbit coupling. After a short review
of the features of spin-orbit coupling in two-dimensional electron gases, we
define the creation/annihilaton operators in the stationary states of the
spin-orbit coupling Hamiltonian and use them to calculate the current operator
within the Landauer-Buettiker formalism. The current is expressed as it is in
the standard spin-independent case, but with the spin label replaced by a new
label which we call the spin-orbit coupling label. The spin-orbit coupling
effects can then be represented in a scattering matrix which relates the
spin-orbit coupling stationary states in different leads. This scattering
matrix is calculated in the case of a four-port beamsplitter, and it is shown
to mix states with different spin-orbit coupling labels in a manner that
depends on the angle between the leads. The formalism is then used to calculate
the effect of spin-orbit coupling on the current and noise in two examples of
electron collision.",0108021v1
2006-06-22,"Spin-orbit coupling in curved graphene, fullerenes, nanotubes, and nanotube caps","A continuum model for the effective spin orbit interaction in graphene is
derived from a tight-binding model which includes the $\pi$ and $\sigma$ bands.
We analyze the combined effects of the intra-atomic spin-orbit coupling,
curvature, and applied electric field, using perturbation theory. We recover
the effective spin-orbit Hamiltonian derived recently from group theoretical
arguments by Kane and Mele. We find, for flat graphene, that the intrinsic
spin-orbit coupling $\Hi \propto \Delta^ 2$ and the Rashba coupling due to a
perpendicular electric field ${\cal E}$, $\Delta_{\cal E} \propto \Delta$,
where $\Delta$ is the intra-atomic spin-orbit coupling constant for carbon.
Moreover we show that local curvature of the graphene sheet induces an extra
spin-orbit coupling term $\Delta_{\rm curv} \propto \Delta$. For the values of
$\cal E$ and curvature profile reported in actual samples of graphene, we find
that $\Hi < \Delta_{\cal E} \lesssim \Delta_{\rm curv}$. The effect of
spin-orbit coupling on derived materials of graphene, like fullerenes,
nanotubes, and nanotube caps, is also studied. For fullerenes, only $\Hi$ is
important. Both for nanotubes and nanotube caps $\Delta_{\rm curv}$ is in the
order of a few Kelvins. We reproduce the known appearance of a gap and
spin-splitting in the energy spectrum of nanotubes due to the spin-orbit
coupling. For nanotube caps, spin-orbit coupling causes spin-splitting of the
localized states at the cap, which could allow spin-dependent field-effect
emission.",0606580v3
2014-01-18,Position and Spin Control by Dynamical Ultrastrong Spin-Orbit Coupling,"Focusing on the efficient probe and manipulation of single-particle spin
states, we investigate the coupled spin and orbital dynamics of a spin 1/2
particle in a harmonic potential subject to ultrastrong spin-orbit interaction
and external magnetic field. The advantage of these systems is the clear
visualization of the strong spin-orbit coupling in the orbital dynamics. We
also investigate the effect of a time-dependent coupling: Its nonadiabatic
change causes an interesting interplay of spin and orbital motion which is
related to the direction and magnitude of the applied magnetic field. This
result suggests that orbital state manipulation can be realized through
ultrastrong spin-orbit interactions, becoming a useful tool for handling
entangled spin and orbital degrees of freedom to produce, for example, spin
desirable polarizations in time interesting for spintronics implementations.",1401.4554v1
2005-10-03,Spin relaxation in quantum dots with random spin-orbit coupling,"We investigate the longitudinal spin relaxation arising due to spin-flip
transitions accompanied by phonon emission in quantum dots where the strength
of the Rashba spin-orbit coupling is a random function of the lateral
(in-plane) coordinate on the spatial nanoscale. In this case the Rashba
contribution to the spin-orbit coupling cannot be completely removed by
applying a uniform external bias across the quantum dot plane. Due to the
remnant random contribution, the spin relaxation rate cannot be decreased by
more than two orders of magnitude even when the external bias fully compensates
the regular part of the spin-orbit coupling.",0510050v1
2009-05-05,Transport through a band insulator with Rashba spin-orbit coupling: metal-insulator transition and spin-filtering effects,"We calculate the current-voltage characteristic of a one-dimensional band
insulator with magnetic field and Rashba spin-orbit coupling which is connected
to nonmagnetic leads. Without spin-orbit coupling we find a complete
spin-filtering effect, meaning that the electric transport occurs in one spin
channel only. For a large magnetic field which closes the band gap, we show
that spin-orbit coupling leads to a transition from metallic to insulating
behavior. The oscillations of the different spin-components of the current with
the length of the transport channel are studied as well.",0905.0611v1
2013-04-11,Large spin-orbit coupling in carbon nanotubes,"It has recently been recognized that the strong spin-orbit interaction
present in solids can lead to new phenomena, such as materials with non-trivial
topological order. Although the atomic spin-orbit coupling in carbon is weak,
the spin-orbit coupling in carbon nanotubes can be significant due to their
curved surface. Previous works have reported spin-orbit couplings in reasonable
agreement with theory, and this coupling strength has formed the basis of a
large number of theoretical proposals. Here we report a spin-orbit coupling in
three carbon nanotube devices that is an order of magnitude larger than
measured before. We find a zero-field spin splitting of up to 3.4 meV,
corresponding to a built-in effective magnetic field of 29 T aligned along the
nanotube axis. While the origin of the large spin-orbit coupling is not
explained by existing theories, its strength is promising for applications of
the spin-orbit interaction in carbon nanotubes devices.",1304.3234v1
2020-02-18,Majorana-like localized spin density without bound states in topologically trivial spin-orbit coupled nanowires,"In the topological phase of spin-orbit coupled nanowires Majorana bound
states are known to localize at the nanowire edges and to exhibit a spin
density orthogonal to both the magnetic field and the spin-orbit field. By
investigating a nanowire exposed to a uniform magnetic field with an interface
between regions with different spin-orbit couplings, we find that the
orthogonal spin density is pinned at the interface even when both interface
sides are in the topologically trivial phase, and even when no bound state is
present at all. A trivial bound state may additionally appear at the interface,
especially if the spin-orbit coupling takes opposite signs across the
interface. However, it can be destroyed by a smoothening of the spin-orbit
profile or by a magnetic field component parallel to the spin-orbit field. In
contrast, the orthogonal spin density persists in various and realistic
parameter ranges. We also show that, while the measurement of bulk equilibrium
spin currents has been elusive so far, such robust orthogonal spin density peak
may provide a way to detect spin current variations across interfaces.",2002.07779v2
2014-11-12,Fermi Gases with Synthetic Spin-Orbit Coupling,"We briefly review recent progress on ultracold atomic Fermi gases with
different types of synthetic spin-orbit coupling, including the one-dimensional
(1D) equal weight Rashba-Dresselhaus and two-dimensional (2D) Rasbha spin-orbit
couplings. Theoretically, we show how the single-body, two-body and many-body
properties of Fermi gases are dramatically changed by spin-orbit coupling. In
particular, the interplay between spin-orbit coupling and interatomic
interaction may lead to several long-sought exotic superfluid phases at low
temperatures, such as anisotropic superfluid, topological superfluid and
inhomogeneous superfluid. Experimentally, only the first type - equal weight
combination of Rasbha and Dresselhaus spin-orbit couplings - has been realized
very recently using a two-photon Raman process. We show how to characterize a
normal spin-orbit coupled atomic Fermi gas in both non-interacting and
strongly-interacting limits, using particularly momentum-resolved
radio-frequency spectroscopy. The experimental demonstration of a
strongly-interacting spin-orbit coupled Fermi gas opens a promising way to
observe various exotic superfluid phases in the near future.",1411.3043v1
2024-01-19,Extremely strong spin-orbit coupling effect in light element altermagnetic materials,"Spin-orbit coupling is a key to realize many novel physical effects in
condensed matter physics, but the mechanism to achieve strong spin-orbit
coupling effect in light element antiferromagnetic compounds has not been
explored. In this work, based on symmetry analysis and the first-principles
electronic structure calculations, we demonstrate that strong spin-orbit
coupling effect can be realized in light element altermagnetic materials, and
propose a mechanism for realizing the corresponding effective spin-orbit
coupling. This mechanism reveals the cooperative effect of crystal symmetry,
electron occupation, electronegativity, electron correlation, and intrinsic
spin-orbit coupling. Our work not only promotes the understanding of light
element compounds with strong spin-orbit coupling effect, but also provides an
alternative for realizing light element compounds with an effective strong
spin-orbit coupling.",2401.11065v1
2012-11-09,Spin-orbit Coupled Bose-Einstein Condensates in Spin-dependent Optical Lattices,"We investigate the ground-state properties of spin-orbit coupled
Bose-Einstein condensates in spin-dependent optical lattices. The competition
between the spin-orbit coupling strength and the depth of the optical lattice
leads to a rich phase diagram. Without spin-orbit coupling, the spin-dependent
optical lattices separate the condensates into alternating spin domains with
opposite magnetization directions. With relatively weak spin-orbit coupling,
the spin domain wall is dramatically changed from N\'{e}el wall to Bloch wall.
For sufficiently strong spin-orbit coupling, vortex chains and antivortex
chains are excited in the spin-up and spin-down domains respectively,
corresponding to the formation of a lattice composed of meron-pairs and
antimeron-pairs in the pseudospin representation. We also discuss how to
observe these phenomena in real experiments.",1211.2097v3
2015-04-11,Collapse of spin-orbit coupled Bose-Einstein condensates,"A finite-size quasi two-dimensional Bose-Einstein condensate collapses if the
attraction between atoms is sufficiently strong. Here we present a theory of
collapse for condensates with the interatomic attraction and spin-orbit
coupling. We consider two realizations of spin-orbit coupling: the axial Rashba
coupling and balanced, effectively one-dimensional, Rashba-Dresselhaus one. In
both cases spin-dependent ""anomalous"" velocity, proportional to the spin-orbit
coupling strength, plays a crucial role. For the Rashba coupling, this velocity
forms a centrifugal component in the density flux opposite to that arising due
to the attraction between particles and prevents the collapse at a sufficiently
strong coupling. For the balanced Rashba-Dresselhaus coupling, the
spin-dependent velocity can spatially split the initial state in one dimension
and form spin-projected wavepackets, reducing the total condensate density.
Depending on the spin-orbit coupling strength, interatomic attraction, and the
initial state, this splitting either prevents the collapse or modifies the
collapse process. These results show that the collapse can be controlled by a
spin-orbit coupling, thus, extending the domain of existence of condensates of
attracting atoms.",1504.02860v1
2015-05-16,Dynamics of a macroscopic spin qubit in spin-orbit coupled Bose-Einstein condensates,"We consider a macroscopic spin qubit based on spin-orbit coupled
Bose-Einstein condensates, where, in addition to the spin-orbit coupling, spin
dynamics strongly depends on the interaction between particles. The evolution
of the spin for freely expanding, trapped, and externally driven condensates is
investigated. For condensates oscillating at the frequency corresponding to the
Zeeman splitting in the synthetic magnetic field, the spin Rabi frequency does
not depend on the interaction between the atoms since it produces only internal
forces and does not change the total momentum. However, interactions and
spin-orbit coupling bring the system into a mixed spin state, where the total
spin is inside rather than on the Bloch sphere. This greatly extends the
available spin space making it three-dimensional, but imposes limitations on
the reliable spin manipulation of such a macroscopic qubit. The spin dynamics
can be modified by introducing suitable spin-dependent initial phases,
determined by the spin-orbit coupling, in the spinor wave function.",1505.04301v1
2005-07-01,Spin-orbit coupling and spin transport,"Recent achievements in semiconductor spintronics are discussed. Special
attention is paid to spin-orbit interaction, coupling of electron spins to
external electric fields, and spin transport in media with spin-orbit coupling,
including the mechanisms of spin-Hall effect. Importance of spin-transport
parameters at spin-precession wave vector $k_{\rm so}$ is emphasized, and
existence of an universal relation between spin currents and spin accumulation
at the spatial scale of $\ell_{\rm so}\approx k_{\rm so}^{-1}$ is conjectured.",0507007v2
2015-05-14,Spatiotemporal spin fluctuations caused by spin-orbit-coupled Brownian motion,"We develop a theory of thermal fluctuations of spin density emerging in a
two-dimensional electron gas. The spin fluctuations probed at spatially
separated spots of the sample are correlated due to Brownian motion of
electrons and spin-obit coupling. We calculate the spatiotemporal correlation
functions of the spin density for both ballistic and diffusive transport of
electrons and analyze them for different types of spin-orbit interaction
including the isotropic Rashba model and persistent spin helix regime. The
measurement of spatial spin fluctuations provides direct access to the
parameters of spin-orbit coupling and spin transport in conditions close to the
thermal equilibrium.",1505.03826v1
2022-07-13,Jahn-Teller states mixed by spin-orbit coupling in an electromagnetic field,"Spin-orbit coupling plays a pivotal role in condensed matter physics. For
instance, spin-orbit interactions affect the magnetization and transport
dynamics in solids, while spins and momenta are locked in topological matter.
Alternatively, spin-orbit entanglement may play an important role in exotic
phenomena, like quantum spin liquids in 4d and 5d systems. An interesting
question is how electronic states mixed by spin orbit coupling interact with
electromagnetic fields, which may hold potential to tune their properties and
reveal interesting physics. Motivated by our recent discovery of large
gyrotropic signals in some Jahn-Teller manganites, here we explore the
interaction of light with spin-mixed states in a d4 transition metal. We show
that spin-orbit mixing enables electronic transitions that are sensitive to
circularly polarized light, giving rise to a gyrotropic response that increases
with spin-orbit coupling. Interestingly, photoexcited transitions that involve
spin reversal are behind such gyrotropic resonances. Additionally, we find that
the interaction with the electromagnetic field depends strongly on the relative
orientation of the propagation of light with respect to Jahn-Teller distortions
and spin quantization. We suggest that such interactions offer the opportunity
to use electromagnetic waves at optical wavelengths to entangle orbital and
spin degrees of freedom. Our approach, which includes a group-theoretical
treatment of spin-orbit coupling, has wide applicability and provides a
versatile tool to explore the interaction of electromagnetic fields with
electronic states in transition metals with arbitrary spin-orbit coupling
strength and pointgroup symmetries.",2207.06501v1
2016-06-27,Nonreciprocal Transverse Photonic Spin and Magnetization-Induced Electromagnetic Spin-Orbit Coupling,"A study of nonreciprocal transverse-spin angular-momentum-density shifts for
evanescent waves in magneto-optic waveguide media is presented. Their
functional relation to electromagnetic spin- and orbital-momenta is presented
and analyzed. It is shown that the magneto-optic gyrotropy can be
re-interpreted as the nonreciprocal electromagnetic spin-density shift per unit
energy flux, thus providing an interesting alternative physical picture for the
magneto-optic gyrotropy. The transverse spin-density shift is found to be
thickness-dependent in slab optical waveguides. This dependence is traceable to
the admixture of minority helicity components in the transverse spin angular
momentum. It is also shown that the transverse spin is magnetically tunable. A
formulation of electromagnetic spin-orbit coupling in magneto-optic media is
presented, and an alternative source of spin-orbit coupling to non-paraxial
optics vortices is proposed. It is shown that magnetization-induced
electromagnetic spin-orbit coupling is possible, and that it leads to spin to
orbital angular momentum conversion in magneto-optic media evanescent waves.",1606.08334v2
2022-06-10,Quantum heat engine based on a spin-orbit and Zeeman-coupled Bose-Einstein condensate,"We explore the potential of a spin-orbit coupled Bose-Einstein condensate for
thermodynamic cycles. For this purpose we propose a quantum heat engine based
on a condensate with spin-orbit and Zeeman coupling as a working medium. The
cooling and heating are simulated by contacts of the condensate with an
external magnetized media and demagnetized media. We examine the condensate
ground state energy and its dependence on the strength of the synthetic
spin-orbit and Zeeman couplings and interatomic interaction. Then we study the
efficiency of the proposed engine. The cycle has a critical value of spin-orbit
coupling related to the engine maximum efficiency.",2206.05041v1
2005-06-23,Spin properties of single electron states in coupled quantum dots,"Spin properties of single electron states in laterally coupled quantum dots
in the presence of a perpendicular magnetic field are studied by exact
numerical diagonalization. Dresselhaus (linear and cubic) and Bychkov-Rashba
spin-orbit couplings are included in a realistic model of confined dots based
on GaAs. Group theoretical classification of quantum states with and without
spin orbit coupling is provided. Spin-orbit effects on the g-factor are rather
weak. It is shown that the frequency of coherent oscillations (tunneling
amplitude) in coupled dots is largely unaffected by spin-orbit effects due to
symmetry requirements. The leading contributions to the frequency involves the
cubic term of the Dresselhaus coupling. Spin-orbit coupling in the presence of
magnetic field leads to a spin-dependent tunneling amplitude, and thus to the
possibility of spin to charge conversion, namely spatial separation of spin by
coherent oscillations in a uniform magnetic field. It is also shown that spin
hot spots exist in coupled GaAs dots already at moderate magnetic fields, and
that spin hot spots at zero magnetic field are due to the cubic Dresselhaus
term only.",0506610v1
2012-11-05,Spin-orbital Texture in Topological Insulators,"Relativistic spin-orbit coupling plays an essential role in the field of
topological insulators and quantum spintronics. It gives rise to the
topological non-trivial band structure and enables electric manipulation of the
spin degree of freedom. Because of the spin-orbit coupling, rich spin-orbital
coupled textures can exist both in momentum and in real space. For three
dimensional topological insulators in the Bi$_2$Se$_3$ family, topological
surface states with p$_z$ orbitals have a left-handed spin texture for the
upper Dirac cone and a right-handed spin texture for the lower Dirac cone. In
this work, we predict a new form of the spin-orbital texture associated with
the p$_x$ and p$_y$ orbitals. For the upper Dirac cone, a left-handed
(right-handed) spin texture is coupled to the ""radial"" (""tangential"") orbital
texture, whereas for the lower Dirac cone, the coupling of spin and orbital
textures is the exact opposite. The ""tangential"" (""radial"") orbital texture is
dominant for the upper (lower) Dirac cone, leading to the right-handed spin
texture for the in-plane orbitals of both the upper and lower Dirac cones. A
spin-resovled and photon polarized angle-resolved photoemission spectroscopy
experiment is proposed to observe this novel spin-orbital texture.",1211.0762v1
2012-06-14,Magnetic ordering phenomena of interacting quantum spin Hall models,"The two-dimensional Hubbard model defined for topological band structures
exhibiting a quantum spin Hall effect poses fundamental challenges in terms of
phenomenological characterization and microscopic classification. In the limit
of infinite coupling U at half filling, the spin model Hamiltonians resulting
from a strong coupling expansion show various forms of magnetic ordering
phenomena depending on the underlying spin-orbit coupling terms. We investigate
the infinite U limit of the Kane-Mele Hubbard model with z-axis intrinsic
spin-orbit coupling as well as its generalization to a generically
multi-directional spin orbit term which has been claimed to account for the
physical scenario in monolayer Na2IrO3. We find that the axial spin symmetry
which is kept in the former but broken in the latter has a fundamental impact
on the magnetic phase diagram as we vary the spin orbit coupling strength.
While the Kane-Mele spin model shows a continuous evolution from conventional
honeycomb Neel to XY antiferromagnetism which avoids the frustration imposed by
the increased spin-orbit coupling, the multi-directional spin-orbit term
induces a commensurate to incommensurate transition at intermediate coupling
strength, and yields a complex spiral state with a 72 site unit cell in the
limit of infinite spin-orbit coupling. From our findings, we conjecture that in
the case of broken axial spin symmetry there is a large propensity for an
additional phase at sufficiently large spin-orbit coupling and intermediate U.",1206.3103v2
2010-12-27,The multi-state CASPT2 spin-orbit method,"We propose the multi-state complete-active-space second-order perturbation
theory spin-orbit method (MS-CASPT2-SO) for electronic structure calculations.
It is a two-step spin-orbit coupling method that does not make use of energy
shifts and that intrinsically guarantees the correct characters of the small
space wave functions that are used to calculate the spin-orbit couplings, in
contrast with previous two-step methods.",1012.5572v1
2011-06-21,Effective one body Hamiltonian of two spinning black-holes with next-to-next-to-leading order spin-orbit coupling,"Building on the recently computed next-to-next-to-leading order (NNLO)
post-Newtonian (PN) spin-orbit Hamiltonian for spinning binaries
\cite{Hartung:2011te} we extend the effective-one-body (EOB) description of the
dynamics of two spinning black-holes to NNLO in the spin-orbit interaction. The
calculation that is presented extends to NNLO the next-to-leading order (NLO)
spin-orbit Hamiltonian computed in Ref. \cite{Damour:2008qf}. The present EOB
Hamiltonian reproduces the spin-orbit coupling through NNLO in the
test-particle limit case. In addition, in the case of spins parallel or
antiparallel to the orbital angular momentum, when circular orbits exist, we
find that the inclusion of NNLO spin-orbit terms moderates the effect of the
NLO spin-orbit coupling.",1106.4349v3
2014-07-13,Orbital angular momentum driven intrinsic spin Hall effect,"We propose a mechanism of intrinsic spin Hall effect (SHE). In this
mechanism, local orbital angular momentum (OAM) induces electron position shift
and couples with the bias electric field to generate orbital Hall effect (OHE).
SHE then emerges as a concomitant effect of OHE through the atomic spin-orbit
coupling. Spin Hall conductivity due to this mechanism is estimated to be
comparable to experimental values for heavy metals. This mechanism predicts the
sign change of the spin Hall conductivity as the spin-orbit polarization
changes its sign, and also correlation between the spin Hall conductivity and
the splitting of the Rashba-type spin splitting at surfaces.",1407.3446v1
2010-04-08,Spin-charge and spin-orbital coupling effects on spin dynamics in ferromagnetic manganites,"Correlation-induced spin-charge and spin-orbital coupling effects on spin
dynamics in ferromagnetic manganites are calculated with realistic parameters
in order to provide a quantitative comparison with experimental results for
spin stiffness, magnon dispersion, magnon damping, anomalous zone-boundary
magnon softening, and Curie temperature. The role of orbital degeneracy,
orbital ordering, and orbital correlations on spin dynamics in different doping
regimes is highlighted.",1004.1352v2
2016-07-29,Twisted spin vortices in a spinor-dipolar Bose-Einstein condensate with Rashba spin-orbit coupling,"We consider a spin-1 Bose-Einstein condensate with Rashba spin-orbit coupling
and dipole-dipole interaction confined in a cigar-shaped trap. Due to the
combined effects of spin-orbit coupling, dipole-dipole interaction, and trap
geometry, the system exhibits a rich variety of ground-state spin structures,
including twisted spin vortices. The ground-state phase diagram is determined
with respect to the strengths of the spin-orbit coupling and dipole-dipole
interaction.",1607.08724v1
2021-06-09,Chiral control of quantum states in non-Hermitian spin-orbit-coupled fermions,"Spin-orbit coupling is an essential mechanism underlying quantum phenomena
such as the spin Hall effect and topological insulators. It has been widely
studied in well-isolated Hermitian systems, but much less is known about the
role dissipation plays in spin-orbit-coupled systems. Here, we implement
dissipative spin-orbit-coupled bands filled with ultracold fermions, and
observe parity-time symmetry breaking as a result of the competition between
the spin-orbit coupling and dissipation. Tunable dissipation, introduced by
state-selective atom loss, enables us to tune the energy gap and close it at
the critical dissipation value, the so-called exceptional point. In the
vicinity of the critical point, the state evolution exhibits a chiral response,
which enables us to tune the spin-orbit coupling and dissipation dynamically,
revealing topologically robust chiral spin transfer when the quantum state
encircles the exceptional point. This demonstrates that we can explore
non-Hermitian topological states with spin-orbit coupling.",2106.04874v2
2013-10-15,Vanishing of interband light absorption in a persistent spin helix state,"Spin-orbit coupling plays an important role in various properties of very
different materials. Moreover efforts are underway to control the degree and
quality of spin-orbit coupling in materials with a concomitant control of
transport properties. We calculate the frequency dependent optical conductivity
in systems with both Rashba and Dresselhaus spin-orbit coupling. We find that
when the linear Dresselhaus spin-orbit coupling is tuned to be equal to the
Rashba spin-orbit coupling, the interband optical conductivity disappears. This
is taken to be the signature of the recovery of SU(2) symmetry. The presence of
the cubic Dresselhaus spin-orbit coupling modifies the dispersion relation of
the charge carriers and the velocity operator. Thus the conductivity is
modified, but the interband contribution remains suppressed at most but not all
photon energies for a cubic coupling of reasonable magnitude. Hence, such a
measurement can serve as a diagnostic probe of engineered spin-orbit coupling.",1310.3916v1
2010-07-28,Current-induced torques in the presence of spin-orbit coupling,"In systems with strong spin-orbit coupling, the relationship between
spin-transfer torque and the divergence of the spin current is generalized to a
relation between spin transfer torques, total angular momentum current, and
mechanical torques. In ferromagnetic semiconductors, where the spin-orbit
coupling is large, these considerations modify the behavior of the spin
transfer torques. One example is a persistent spin transfer torque in a spin
valve: the spin transfer torque does not decay away from the interface, but
approaches a constant value. A second example is a mechanical torque at single
ferromagnetic-nonmagnetic interface.",1007.5037v1
2021-02-10,Suppression of effective spin-orbit coupling by thermal fluctuations in spin-orbit coupled antiferromagnets,"We apply the finite-temperature variational cluster approach to a strongly
correlated and spin-orbit coupled model for four electrons (i.e. two holes) in
the $t_{2g}$ subshell. We focus on parameters suitable for antiferromagnetic
Mott insulators, in particular Ca$_2$RuO$_4$, and identify a crossover from the
low-temperature regime, where spin-orbit coupling is essential, to the
high-temperature regime where it leaves few signatures. The crossover is seen
in one-particle spectra, where $xz$ and $yz$ spectra are almost one dimensional
(as expected for weak spin-orbit coupling) at high temperature. At lower
temperature, where spin-orbit coupling mixes all three orbitals, they become
more two dimensional. However, stronger effects are seen in two-particle
observables like the weight in states with definite onsite angular momentum. We
thus identify the enigmatic intermediate-temperature 'orbital-order phase
transition', which has been reported in various X-ray diffraction and
absorption experiments at $T\approx 260\;K$, as the signature of the onset of
spin-orbital correlations.",2102.05489v1
2016-04-20,Second post-Newtonian Lagrangian dynamics of spinning compact binaries,"The leading-order spin-orbit coupling is included in a post-Newtonian
Lagrangian formulation of spinning compact binaries, which consists of the
Newtonian term, first post-Newtonian (1PN) and 2PN non-spin terms and 2PN
spin-spin coupling. This makes a 3PN spin-spin coupling occur in the derived
Hamiltonian. The spin-spin couplings are mainly responsible for chaos in the
Hamiltonians. However, the 3PN spin-spin Hamiltonian is small and has different
signs, compared with the 2PN spin-spin Hamiltonian equivalent to the 2PN
spin-spin Lagrangian. As a result, the probability of the occurrence of chaos
in the Lagrangian formulation without the spin-orbit coupling is larger than
that in the Lagrangian formulation with the spin-orbit coupling. Numerical
evidences support the claim.",1604.05810v2
2001-09-13,Formation of energy gap in higher dimensional spin-orbital liquids,"A Schwinger boson mean field theory is developed for spin liquids in a
symmetric spin-orbital model in higher dimensions. Spin, orbital and coupled
spin-orbital operators are treated equally. We evaluate the dynamic correlation
functions and collective excitations spectra. As the collective excitations
have a finite energy gap, we conclude that the ground state is a spin-orbital
liquid with a two-fold degeneracy, which breaks the discrete spin-orbital
symmetry. Possible relevence of this spin liquid state to several realistic
systems, such as CaV$_4$V$_9$ and Na$_2$Sb$_2$Ti$_2$O, are discussed.",0109234v1
2018-09-20,Multiple-$Q$ magnetic orders in Rashba-Dresselhaus metals,"We study magnetic textures realized in noncentrosymmetric Kondo lattice
models, in which localized magnetic moments weakly interact with itinerant
electrons subject to Rashba and Dresselhaus spin-orbit couplings. By virtue of
state-of-the-art numerical simulations as well as variational calculations, we
uncover versatile multiple-$Q$ orderings under zero magnetic field, which are
found to originate in the instabilities of the Fermi surface whose spin
degeneracy is lifted by the spin-orbit couplings. In the case with
equally-strong Rashba and Dresselhaus spin-orbit couplings, which is known to
realize a persistent spin helix in semiconductor quantum wells, we discover a
sextuple-$Q$ magnetic ordering with a checkerboard-like spatial pattern of the
spin scalar chirality. In the presence of either Rashba or Dresselhaus
spin-orbit coupling, we find out another multiple-$Q$ ordering, which is
distinct from Skyrmion crystals discussed under the same symmetry. Our results
indicate that the cooperation of the spin-charge and spin-orbit couplings
brings about richer magnetic textures than those studied within effective spin
models. The situations would be experimentally realized, e.g., in
noncentrosymmetric heavy-fermion compounds and heterostructures of spin-orbit
coupled metals and magnetic insulators.",1809.07582v1
2007-01-11,Some exact identities connecting one- and two-particle Green's functions in spin-orbit coupling systems,"Some exact identities connecting the one- and two-particle Green's functions
in the presence of spin-orbit coupling have been derived. These identities is
similar to the usual Ward identity in the particle or charge transport theory
and a satisfying spin transport theory in spin-orbit coupling system should
also preserve these identities.",0701227v1
2015-07-25,Quantum entanglement in the one-dimensional spin-orbital SU(2)$\otimes XXZ$ model,"We investigate the phase diagram and the spin-orbital entanglement of a
one-dimensional SU(2)$\otimes XXZ$ model with SU(2) spin exchange and
anisotropic $XXZ$ orbital exchange interactions and negative exchange coupling.
As a unique feature, the spin-orbital entanglement entropy in the entangled
ground states increases here linearly with system size. In the case of Ising
orbital interactions we identify an emergent phase with long-range spin-singlet
dimer correlations triggered by a quadrupling of correlations in the orbital
sector. The peculiar translational invariant spin-singlet dimer phase has
finite von Neumann entanglement entropy and survives when orbital quantum
fluctuations are included. It even persists in the isotropic
SU(2)$\otimes$SU(2) limit. Surprisingly, for finite transverse orbital coupling
the long-range spin singlet correlations also coexist in the antiferromagnetic
spin and alternating orbital phase making this phase also unconventional.
Moreover we also find a complementary orbital singlet phase that exists in the
isotropic case but does not extend to the Ising limit. The nature of
entanglement appears essentially different from that found in the frequently
discussed model with positive coupling. Furthermore we investigate the
collective spin and orbital wave excitations of the disentangled
ferromagnetic-spin/ferro-orbital ground state and explore the continuum of
spin-orbital excitations. Interestingly one finds among the latter excitations
two modes of exciton bound states. Their spin-orbital correlations differ from
the remaining continuum states and exhibit logarithmic scaling of the von
Neumann entropy with increasing system size.",1507.07103v1
2015-11-16,Drude weight and optical conductivity of a two-dimensional heavy-hole gas with $k$-cubic spin-orbit interactions,"We present detailed theoretical study on zero-frequency Drude weight and
optical conductivity of a two-dimensional heavy-hole gas(2DHG) with $k$-cubic
Rashba and Dresselhaus spin-orbit interactions. The presence of $k$-cubic
spin-orbit couplings strongly modifies the Drude weight in comparison to the
electron gas with $k$-linear spin-orbit couplings. For large hole density and
strong $k$-cubic spin-orbit couplings, the density dependence of Drude weight
deviates from the linear behavior. We establish a relation between optical
conductivity and the Berry connection. Unlike two-dimensional electron gas with
$k$-linear spin-orbit couplings, we explicitly show that the optical
conductivity does not vanish even for equal strength of the two spin-orbit
couplings. We attribute this fact to the non-zero Berry phase for equal
strength of $k$-cubic spin-orbit couplings. The least photon energy needed to
set in the optical transition in hole gas is one order of magnitude smaller
than that of electron gas. Types of two van Hove singularities appear in the
optical spectrum are also discussed.",1511.04917v3
2017-04-03,Inverse spin galvanic effect in the presence of impurity spin-orbit scattering: a diagrammatic approach,"Spin-charge interconversion is currently the focus of intensive experimental
and theoretical research both for its intrinsic interest and for its potential
exploitation in the realization of new spintronic functionalities. Spin-orbit
coupling is one of the key microscopic mechanisms to couple charge currents and
spin polarizations. The Rashba spin-orbit coupling in a two-dimensional
electron gas has been shown to give rise to the inverse spin galvanic effect,
i.e. the generation of a non-equilibrium spin polarization by a charge current.
Whereas the Rashba model may be applied to the interpretation of experimental
results in many cases, in general in a given real physical system spin-orbit
coupling also occurs due other mechanisms such as Dresselhaus bulk inversion
asymmetry and scattering from impurities. In this work we consider the inverse
spin galvanic effect in the presence of Rashba, Dresselhaus and impurity
spin-orbit scattering. We find that the size and form of the inverse spin
galvanic effect is greatly modified by the presence of the various sources of
spin-orbit coupling. Indeed, spin-orbit coupling affects the spin relaxation
time by adding the Elliott-Yafet mechanism to the Dyakonov-Perel and,
furthermore, it changes the non-equilibrium value of the current-induced spin
polarization by introducing a new spin generation torque. We use a diagrammatic
Kubo formula approach to evaluate the spin polarization-charge current response
function. We finally comment about the relevance of our results for the
interpretation of experimental results.",1704.00532v1
2010-03-08,Spin-orbit coupling in a graphene bilayer and in graphite,"The intrinsic spin-orbit interactions in bilayer graphene and in graphite are
studied, using a tight binding model, and an intraatomic LS coupling. The
spin-orbit interactions in bilayer graphene and graphite are larger, by about
one order of magnitude, than the interactions in single layer graphene, due to
the mixing of pi and sigma bands by interlayer hopping. Their value is in the
range 0.1 - 1K. The spin-orbit coupling opens a gap in bilayer graphene, and it
also gives rise to two edge modes. The spin-orbit couplings are largest, 1-4K,
in orthorhombic graphite, which does not have a center of inversion.",1003.1618v1
2022-02-28,Observation of long-range orbital transport and giant orbital torque,"Modern spintronics relies on the generation of spin currents through
spin-orbit coupling. The spin-current generation has been believed to be
triggered by current-induced orbital dynamics, which governs the angular
momentum transfer from the lattice to the electrons in solids. The fundamental
role of the orbital response in the angular momentum dynamics suggests the
importance of the orbital counterpart of spin currents: orbital currents.
However, evidence for its existence has been elusive. Here, we demonstrate the
generation of giant orbital currents and uncover fundamental features of the
orbital response. We experimentally and theoretically show that orbital
currents propagate over longer distances than spin currents by more than an
order of magnitude in a ferromagnet and nonmagnets. Furthermore, we find that
the orbital current enables electric manipulation of magnetization with
efficiencies significantly higher than the spin counterpart. These findings
open the door to orbitronics that exploits orbital transport and spin-orbital
coupled dynamics in solid-state devices.",2202.13896v2
2005-01-09,Electron Spin Dynamics in Impure Quantum Wells for Arbitrary Spin-Orbit Coupling,"Strong interest has arisen recently on low-dimensional systems with strong
spin-orbit interaction due to their peculiar properties of interest for some
spintronic applications. Here, the time evolution of the electron spin
polarization of a disordered two-dimensional electron gas is calculated exactly
within the Boltzmann formalism for arbitrary couplings to a Rashba spin-orbit
field. The classical Dyakonov-Perel mechanism of spin relaxation is shown to
fail for sufficiently strong Rashba fields, in which case new regimes of spin
decay are identified. These results suggest that spin manipulation can be
greatly improved in strong spin-orbit interaction materials.",0501174v3
2007-09-21,Spin-orbit mediated anisotropic spin interaction in interacting electron systems,"We investigate interactions between spins of strongly correlated electrons
subject to the spin-orbit interaction. Our main finding is that of a novel,
spin-orbit mediated anisotropic spin-spin coupling of the van der Waals type.
Unlike the standard exchange, this interaction does not require the wave
functions to overlap. We argue that this ferromagnetic interaction is important
in the Wigner crystal state where the exchange processes are severely
suppressed. We also comment on the anisotropy of the exchange between spins
mediated by the spin-orbital coupling.",0709.3521v2
2012-03-06,Short-range correlations in dilute atomic Fermi gases with spin-orbit coupling,"We study the short-range correlation strength of three dimensional spin half
dilute atomic Fermi gases with spin-orbit coupling. The interatomic interaction
is modeled by the contact pseudopotential. In the high temperature limit, we
derive the expression for the second order virial expansion of the
thermodynamic potential via the ladder diagrams. We further evaluate the second
order virial expansion in the limit that the spin-orbit coupling constants are
small, and find that the correlation strength between the fermions increases as
the forth power of the spin-orbit coupling constants. At zero temperature, we
consider the cases in which there are symmetric spin-orbit couplings in two or
three directions. In such cases, there is always a two-body bound state of zero
net momentum. In the limit that the average interparticle distance is much
larger than the dimension of the two-body bound state, the system primarily
consists of condensed bosonic molecules that fermions pair to form; we find
that the correlation strength also becomes bigger compared to that in the
absence of spin-orbit coupling. Our results indicate that generic spin-orbit
coupling enhances the short-range correlations of the Fermi gases. Measurement
of such enhancement by photoassociation experiment is also discussed.",1203.1159v1
2018-02-01,Spin Seebeck effect and thermal spin galvanic effect in Ni80Fe20/p-Si bilayers,"The development of spintronics and spin-caloritronics devices need efficient
generation, detection and manipulation of spin current. The thermal spin
current from spin-Seebeck effect has been reported to be more energy efficient
than the electrical spin injection methods. But, spin detection has been the
one of the bottlenecks since metals with large spin-orbit coupling is an
essential requirement. In this work, we report an efficient thermal generation
and interfacial detection of spin current. We measured a spin-Seebeck effect in
Ni80Fe20 (25 nm)/p-Si (50 nm) (polycrystalline) bilayers without heavy metal
spin detector. The p-Si, having the centosymmetric crystal structure, has
insignificant intrinsic spin-orbit coupling leading to negligible spin-charge
conversion. We report a giant inverse spin-Hall effect, essential for detection
of spin-Seebeck effect, in the Ni80Fe20/p-Si bilayer structure, which
originates from Rashba spin orbit coupling due to structure inversion asymmetry
at the interface. In addition, the thermal spin pumping in p-Si leads to spin
current from p-Si to Ni80Fe20 layer due to thermal spin galvanic effect and
spin-Hall effect causing spin-orbit torques. The thermal spin-orbit torques
leads to collapse of magnetic hysteresis of 25 nm thick Ni80Fe20 layer. The
thermal spin-orbit torques can be used for efficient magnetic switching for
memory applications. These scientific breakthroughs may give impetus to the
silicon spintronics and spin-caloritronics devices.",1802.00132v1
2017-03-18,Spin-orbit scattering visualized in quasiparticle interference,"In the presence of spin-orbit coupling, electron scattering off impurities
depends on both spin and orbital angular momentum of electrons -- spin-orbit
scattering. Although some transport properties are subject to spin-orbit
scattering, experimental techniques directly accessible to this effect are
limited. Here we show that a signature of spin-orbit scattering manifests
itself in quasiparticle interference (QPI) imaged by spectroscopic-imaging
scanning tunneling microscopy. The experimental data of a polar semiconductor
BiTeI are well reproduced by numerical simulations with the $T$-matrix
formalism that include not only scalar scattering normally adopted but also
spin-orbit scattering stronger than scalar scattering. To accelerate the
simulations, we extend the standard efficient method of QPI calculation for
momentum-independent scattering to be applicable even for spin-orbit
scattering. We further identify a selection rule that makes spin-orbit
scattering visible in the QPI pattern. These results demonstrate that
spin-orbit scattering can exert predominant influence on QPI patterns and thus
suggest that QPI measurement is available to detect spin-orbit scattering.",1703.06234v1
2011-11-17,Intrinsic Spin Swapping,"Here, we study diffusive spin transport in two dimensions and demonstrate
that an intrinsic analog to a previously predicted extrinsic spin swapping
effect, where the spin polarization and the direction of flow are interchanged
due to spin-orbit coupling at extrinsic impurities, can be induced by intrinsic
(Rashba) spin-orbit coupling. The resulting accumulation of intrinsically
spin-swapped polarizations is shown to be much larger than for the extrinsic
effect. Intrinsic spin swapping is particularly strong when the system
dimensions exceed the spin-orbit precession length and the generated transverse
spin currents are of the order of the injected primary spin currents. In
contrast, spin accumulations and spin currents caused by extrinsic spin
swapping are proportional to the spin-orbit coupling. We present numerical and
analytical results for the secondary spin currents and accumulations generated
by intrinsic spin swapping, and we derive analytic expressions for the induced
spin accumulation at the edges of a narrow strip, where a long-range
propagation of spin polarizations takes place.",1111.4072v2
2017-10-09,Tunable superconducting critical temperature in ballistic hybrid structures with strong spin-orbit coupling,"We present a theoretical description and numerical simulations of the
superconducting transition in hybrid structures including strong spin-orbit
interactions. The spin-orbit coupling is taken to be of Rashba type for
concreteness, and we allow for an arbitrary magnitude of the spin-orbit
strength as well as an arbitrary thickness of the spin-orbit coupled layer.
This allows us to make contact with the experimentally relevant case of
enhanced interfacial spin-orbit coupling via atomically thin heavy metal
layers. We consider both interfacial spin-orbit coupling induced by inversion
asymmetry in an S/F-junction, as well as in-plane spin-orbit coupling in the
ferromagnetic region of an S/F/S- and an S/F-structure. Both the pair
amplitudes, local density of states and critical temperature show dependency on
the Rashba strength and, importantly, the orientation of the exchange field. In
general, spin-orbit coupling increases the critical temperature of a proximity
system where a magnetic field is present, and enhances the superconducting gap
in the density of states. We perform a theoretical derivation which explains
these results by the appearance of long-ranged singlet correlations. Our
results suggest that $T_c$ in ballistic spin-orbit coupled superconducting
structures may be tuned by using only a single ferromagnetic layer.",1710.03228v2
2021-04-14,Spin-orbit gaps in the s and p orbital bands of an artificial honeycomb lattice,"Muffin-tin methods have been instrumental in the design of honeycomb lattices
that show, in contrast to graphene, separated s and in-plane p bands, a p
orbital Dirac cone, and a p orbital flat band. Recently, such lattices have
been experimentally realized using the 2D electron gas on Cu(111). A possible
next avenue is the introduction of spin-orbit coupling to these systems.
Intrinsic spin-orbit coupling is believed to open topological gaps, and create
a topological flat band. Although Rashba coupling is straightforwardly
incorporated in the muffin-tin approximation, intrinsic spin-orbit coupling has
only been included either for a very specific periodic system, or only close to
the Dirac point. Here, we introduce general intrinsic and Rashba spin-orbit
terms in the Hamiltonian for both periodic and finite-size systems. We observe
a strong band opening over the entire Brillouin zone between the p orbital flat
band and Dirac cone hosting a pronounced edge state, robust against the effects
of Rashba spin-orbit coupling.",2104.06912v1
2007-10-15,Intersubband spin-orbit coupling and spin splitting in symmetric quantum wells,"In semiconductors with inversion asymmetry, spin-orbit coupling gives rise to
the well-known Dresselhaus and Rashba effects. If one considers quantum wells
with two or more conduction subbands, an additional, intersubband-induced
spin-orbit term appears whose strength is comparable to the Rashba coupling,
and which remains finite for symmetric structures. We show that the conduction
band spin splitting due to this intersubband spin-orbit coupling term is
negligible for typical III-V quantum wells.",0710.2866v1
2009-02-19,Impurity induced spin-orbit coupling in graphene,"We study the effect of impurities in inducing spin-orbit coupling in
graphene. We show that the sp3 distortion induced by an impurity can lead to a
large increase in the spin-orbit coupling with a value comparable to the one
found in diamond and other zinc-blende semiconductors. The spin-flip scattering
produced by the impurity leads to spin scattering lengths of the order found in
recent experiments. Our results indicate that the spin-orbit coupling can be
controlled via the impurity coverage.",0902.3244v1
2011-10-04,Spin-orbit-coupled dipolar Bose-Einstein condensates,"We propose an experimental scheme to create spin-orbit coupling in spin-3 Cr
atoms using Raman processes. Employing linear Zeeman effect and optical Stark
shift, two spin states within the ground electronic manifold are selected,
which results in a pseudo-spin-1/2 model. We further study the ground state
structures of a spin-orbit-coupled Cr condensate. We show that, in addition to
the stripe structures induced by the spin-orbit coupling, the magnetic
dipole-dipole interaction gives rise to the vortex phase, in which spontaneous
spin vortex is formed.",1110.0558v3
2016-01-26,Double-Quantum Spin Vortices in SU(3) Spin-Orbit Coupled Bose Gases,"We show that double-quantum spin vortices, which are characterized by doubly
quantized circulating spin currents and unmagnetized filled cores, can exist in
the ground states of SU(3) spin-orbit coupled Bose gases. It is found that the
SU(3) spin-orbit coupling and spin-exchange interaction play important roles in
determining the ground-state phase diagram. In the case of effective
ferromagnetic spin interaction, the SU(3) spin-orbit coupling induces a
three-fold degeneracy to the magnetized ground state, while in the
antiferromagnetic spin interaction case, the SU(3) spin-orbit coupling breaks
the ordinary phase rule of spinor Bose gases, and allows the spontaneous
emergence of double-quantum spin vortices. This exotic topological defect is in
stark contrast to the singly quantized spin vortices observed in existing
experiments, and can be readily observed by the current magnetization-sensitive
phase-contrast imaging technique.",1601.06935v2
2021-10-14,Thermalization in a Spin-Orbit coupled Bose gas by enhanced spin Coulomb drag,"An important component of the structure of the atom, the effects of
spin-orbit coupling are present in many sub-fields of physics. Most of these
effects are present continuously. We present a detailed study of the dynamics
of changing the spin-orbit coupling in an ultra-cold Bose gas, coupling the
motion of the atoms to their spin. We find that the spin-orbit coupling greatly
increases the damping towards equilibrium. We interpret this damping as spin
drag, which is enhanced by spin-orbit coupling rate, scaled by a remarkable
factor of $8.9(6)$~s. We also find that spin-orbit coupling lowers the final
temperature of the Bose gas after thermalization.",2110.07094v3
2012-04-10,Spin-current absorption by inhomogeneous spin-orbit coupling,"We investigate the spin-current absorption induced by an inhomogeneous
spin-orbit coupling due to impurities in metals. We consider the system with
spin currents driven by the electric field or the spin accumulation. The
resulting diffusive spin currents, including the gradient of the spin-orbit
coupling strength, indicate the spin-current absorption at the interface, which
is exemplified with experimentally relevant setups.",1204.2189v2
2014-03-19,Spin-orbit coupling effects on spin-dependent inelastic electronic lifetimes in ferromagnets,"For the 3d ferromagnets iron, cobalt and nickel we compute the spin-dependent
inelastic electronic lifetimes due to carrier-carrier Coulomb interaction
including spin-orbit coupling. We find that the spin-dependent
density-of-states at the Fermi energy does not, in general, determine the spin
dependence of the lifetimes because of the effective spin-flip transitions
allowed by the spin mixing. The majority and minority electron lifetimes
computed including spin-orbit coupling for these three 3-d ferromagnets do not
differ by more than a factor of 2, and agree with experimental results.",1403.4728v1
2013-06-27,Meron Ground State of Rashba Spin-Orbit-Coupled Dipolar Bosons,"We study the effects of dipolar interactions on a Bose-Einstein condensate
with synthetically generated Rashba spin-orbit coupling. The dipolar
interaction we consider includes terms that couple spin and orbital angular
momentum in a way perfectly congruent with the single-particle Rashba coupling.
We show that this internal spin-orbit coupling plays a crucial role in the rich
ground-state phase diagram of the trapped condensate. In particular, we predict
the emergence of a thermodynamically stable ground state with a meron spin
configuration.",1306.6610v2
2007-01-25,Spin-Hall effect and spin-coherent excitations in a strongly confined two-dimensional hole gas,"Based on a rigorous quantum-kinetic approach, spin-charge coupled
drift-diffusion equations are derived for a strongly confined two-dimensional
hole gas. An electric field leads to a coupling between the spin and charge
degrees of freedom. For weak spin-orbit interaction, this coupling gives rise
to the intrinsic spin-Hall effect. There exists a threshold value of the
spin-orbit coupling constant that separates spin diffusion from ballistic spin
transport. In the latter regime, undamped spin-coherent oscillations are
observed. This result is confirmed by an exact microscopic approach valid in
the ballistic regime.",0701612v1
2020-06-05,Intrinsic and extrinsic spin-orbit coupling and spin relaxation in monolayer PtSe$_2$,"Monolayer PtSe$_2$ is a semiconducting transition metal dichalcogenide
characterized by an indirect band gap, space inversion symmetry, and high
carrier mobility. Strong intrinsic spin-orbit coupling and the possibility to
induce extrinsic spin-orbit fields by gating make PtSe$_2$ attractive for
fundamental spin transport studies as well as for potential spintronics
applications. We perform a systematic theoretical study of the spin-orbit
coupling and spin relaxation in this material. Specifically, we employ first
principles methods to obtain the basic orbital and spin-orbital properties of
PtSe$_2$, also in the presence of an external transverse electric field. We
calculate the spin mixing parameters $b^2$ and the spin-orbit fields $\Omega$
for the Bloch states of electrons and holes. This information allows us to
predict the spin lifetimes due to the Elliott-Yafet and D'yakonov-Perel
mechanisms. We find that $b^2$ is rather large, on the order of $10^{-2}$ and
$10^{-1}$, while $\Omega$ varies strongly with doping, being about $10^{3} -
10^{4}$\,ns$^{-1}$ for %typical Fermi levels in the interval $(10-100)$ meV,
carrier density in the interval $10^{13}-10^{14}$\,cm$^{-2}$ at the electric
field of 1 V/nm. We estimate the spin lifetimes to be on the picosecond level.",2006.03384v1
2016-11-06,Effective magnetic interactions in spin-orbit coupled $d^4$ Mott insulators,"Transition metal compounds with the $(t_{2g})^4$ electronic configuration are
expected to be nonmagnetic atomic singlets both in the weakly interacting
regime due to spin-orbit coupling, as well as in the Coulomb dominated regime
with oppositely aligned $L=1$ and $S=1$ angular momenta. However, starting with
the full multi-orbital electronic Hamiltonian, we show the low energy effective
magnetic Hamiltonian contains isotropic superexchange spin interactions but
anisotropic orbital interactions. By tuning the ratio of superexchange to
spin-orbit coupling $J_\mathrm{SE}/\lambda$, we obtain a phase transition from
nonmagnetic atomic singlets to novel magnetic phases depending on the strength
of Hund's coupling, the crystal structure and the number of active orbitals.
Spin-orbit coupling plays a non-trivial role in generating a triplon condensate
of weakly interacting excitations at antiferromagnetic ordering vector $\vec
k=\vec \pi$, regardless of whether the local spin interactions are
ferromagnetic or antiferromagnetic. In the large $J_\mathrm{SE} / \lambda$
regime, the localized spin and orbital moments produce anisotropic orbital
interactions that are frustrated or constrained even in the absence of
geometric frustration. Orbital frustration leads to frustration in the spin
channel opening up the possibility of spin-orbital liquids with both spin and
orbital entanglement.",1611.01840v1
2021-06-04,Efficient conversion of orbital Hall current to spin current for spin-orbit torque switching,"Spin Hall effect, an electric generation of spin current, allows for
efficient control of magnetization. Recent theory revealed that orbital Hall
effect creates orbital current, which can be much larger than spin Hall-induced
spin current. However, orbital current cannot directly exert a torque on a
ferromagnet, requiring a conversion process from orbital current to spin
current. Here, we report two effective methods of the conversion through
spin-orbit coupling engineering, which allows us to unambiguously demonstrate
orbital-current-induced spin torque, or orbital Hall torque. We find that
orbital Hall torque is greatly enhanced by introducing either a rare-earth
ferromagnet Gd or a Pt interfacial layer with strong spin-orbit coupling in
Cr/ferromagnet structures, indicating that the orbital current generated in Cr
is efficiently converted into spin current in the Gd or Pt layer. Furthermore,
we show that the orbital Hall torque can facilitate the reduction of switching
current of perpendicular magnetization in spin-orbit-torque-based spintronic
devices.",2106.02286v2
2014-12-17,Energy spectra of two interacting fermions with spin-orbit coupling in a harmonic trap,"We explore the two-body spectra of spin-$1/2$ fermions in isotropic harmonic
traps with external spin-orbit potentials and short range two-body
interactions. Using a truncated basis of total angular momentum eigenstates,
non-perturbative results are presented for experimentally realistic forms of
the spin-orbit coupling: a pure Rashba coupling, Rashba and Dresselhaus
couplings in equal parts, and a Weyl-type coupling. The technique is easily
adapted to bosonic systems and other forms of spin-orbit coupling.",1412.5634v2
2017-09-20,Superfluid transition temperature of spin-orbit and Rabi coupled fermions with tunable interactions,"We obtain the superfluid transition temperature of equal Rashba-Dresselhaus
spin-orbit and Rabi coupled Fermi superfluids, from the
Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) regimes in
three dimensions. Spin-orbit coupling enhances the critical temperature in the
BEC limit, and can convert a first order phase transition in the presence of
Rabi coupling into second order, as a function of the Rabi coupling for fixed
interactions. We derive the Ginzburg-Landau equation to sixth power in the
superfluid order parameter to describe both first and second order transitions
as a function of spin-orbit and Rabi couplings.",1709.07042v1
2012-12-03,Normal state properties of spin-orbit coupled Fermi gases in the upper branch of energy spectrum,"We investigate normal state properties of spin-orbit coupled Fermi gases with
repulsive s-wave interaction, in the absence of molecule formation, i.e., in
the so-called ""upper branch"". Within the framework of random phase
approximation, we derive analytical expressions for the quasi-particle lifetime
$\tau_s$, the effective mass $m_s^*$, and the Green's function renormalization
factor $Z_s$ in the presence of Rashba spin-orbit coupling. In contrast to
spin-orbit coupled electron gas with Coulomb interaction, we show that the
modifications are dependent on the Rashba band index s, and occur in the first
order of the spin-orbit coupling strength. We also calculate experimental
observable such as spectral weight, density of state and specific heat, which
exhibit significant differences from their counterparts without spin-orbit
coupling. We expect our microscopic calculations of these Fermi liquid
parameters would have the immediate applications to the spin-orbit coupled
Fermi gases in the upper branch of the energy spectrum.",1212.0420v5
2016-10-07,The Role of Interaction in the Pairing of Two Spin-orbit Coupled Fermions,"We investigate the role of a repulsive s-wave interaction in the two-body
problem in the presence of spin orbit couplings, motivated by current interests
in exploring exotic superfluid phases in spin-orbit coupled Fermi gases. For
weak spin orbit coupling where the density of states is not significantly
altered, we analytically show that the high-energy states become more important
in determining the binding energy when the interaction strength decreases.
Consequently, tuning the interaction gives rise to a rich ground state
behavior, including a zigzag of the ground state momentum or inducing
transitions among the meta-stable states. By exactly solving the two-body
problem for a spin-orbit coupled Fermi mixture, we demonstrate that our
analysis can also apply to the case when the density of states is significantly
modified by the spin-orbit coupling. Our findings pave the way for
understanding and controlling the paring of fermions in the presence of spin
orbit couplings.",1610.02927v2
2018-07-17,Effects of spin-orbit coupling on the optical response of a material,"We investigate the effects of spin-orbit coupling on the optical response of
materials. In particular, we study the effects of the commutator between the
spin-orbit coupling part of the potential and the position operator on the
optical matrix elements. Using a formalism that separates a fullyrelativistic
Kleinman-Bylander pseudopotential into the scalar-relativistic and
spin-orbit-coupling parts, we calculate the contribution of the commutator
arising from spin-orbit coupling to the squared optical matrix elements of
isolated atoms, monolayer transition metal dichalcogenides, and topological
insulators. In the case of isolated atoms from H ($Z = 1$) to Bi ($Z = 83$),
the contribution of spin-orbit coupling to the squared matrix elements can be
as large as 14 %. On the other hand, in the cases of monolayer transition metal
dichalcogenides and topological insulators, we find that this contribution is
less than 1 % and that it is sufficient to calculate the optical matrix
elements and subsequent physical quantities without considering the commutator
arising from spin-orbit coupling.",1807.06669v1
2011-10-31,Spin-Orbit Coupled Quantum Gases,"In this review we will discuss the experimental and theoretical progresses in
studying spin-orbit coupled degenerate atomic gases during the last two years.
We shall first review a series of pioneering experiments in generating
synthetic gauge potentials and spin-orbit coupling in atomic gases by
engineering atom-light interaction. Realization of spin-orbit coupled quantum
gases opens a new avenue in cold atom physics, and also brings out a lot of new
physical problems. In particular, the interplay between spin-orbit coupling and
inter-atomic interaction leads to many intriguing phenomena. Here, by reviewing
recent theoretical studies of both interacting bosons and fermions with
isotropic Rashba spin-orbit coupling, the key message delivered here is that
spin-orbit coupling can enhance the interaction effects, and make the
interaction effects much more dramatic even in the weakly interacting regime.",1110.6798v1
2010-02-02,Spin-resolved scattering through spin-orbit nanostructures in graphene,"We address the problem of spin-resolved scattering through spin-orbit
nanostructures in graphene, i.e., regions of inhomogeneous spin-orbit coupling
on the nanometer scale. We discuss the phenomenon of spin-double refraction and
its consequences on the spin polarization. Specifically, we study the
transmission properties of a single and a double interface between a normal
region and a region with finite spin-orbit coupling, and analyze the
polarization properties of these systems. Moreover, for the case of a single
interface, we determine the spectrum of edge states localized at the boundary
between the two regions and study their properties.",1002.0441v2
2014-09-19,Angular dependence of spin-orbit spin transfer torques,"In ferromagnet/heavy metal bilayers, an in-plane current gives rise to
spin-orbit spin transfer torque which is usually decomposed into field-like and
damping-like torques. For two-dimensional free-electron and tight-binding
models with Rashba spin-orbit coupling, the field-like torque acquires
nontrivial dependence on the magnetization direction when the Rashba spin-orbit
coupling becomes comparable to the exchange interaction. This nontrivial
angular dependence of the field-like torque is related to the Fermi surface
distortion, determined by the ratio of the Rashba spin-orbit coupling to the
exchange interaction. On the other hand, the damping-like torque acquires
nontrivial angular dependence when the Rashba spin-orbit coupling is comparable
to or stronger than the exchange interaction. It is related to the combined
effects of the Fermi surface distortion and the Fermi sea contribution. The
angular dependence is consistent with experimental observations and can be
important to understand magnetization dynamics induced by spin-orbit spin
transfer torques",1409.5600v1
2006-08-18,Electric Dipole Spin Resonance for Heavy Holes in Quantum Dots,"We propose and analyze a new method for manipulation of a heavy hole spin in
a quantum dot. Due to spin-orbit coupling between states with different orbital
momenta and opposite spin orientations, an applied rf electric field induces
transitions between spin-up and spin-down states. This scheme can be used for
detection of heavy-hole spin resonance signals, for the control of the spin
dynamics in two-dimensional systems, and for determining important parameters
of heavy-holes such as the effective $g$-factor, mass, spin-orbit coupling
constants, spin relaxation and decoherence times.",0608410v1
2007-05-25,Interplay of the Rashba and Dresselhaus spin-orbit coupling in the optical spin susceptibility of 2D electron systems,"We present calculations of the frequency-dependent spin susceptibility tensor
of a two-dimensional electron gas with competing Rashba and Dresselhaus
spin-orbit interaction. It is shown that the interplay between both types of
spin-orbit coupling gives rise to an anisotropic spectral behavior of the spin
density response function which is significantly different from that of
vanishing Rashba or Dresselhaus case. Strong resonances are developed in the
spin susceptibility as a consequence of the angular anisotropy of the energy
spin-splitting. This characteristic optical modulable response may be useful to
experimentally probe spin accumulation and spin density currents in such
systems.",0705.3849v1
2008-07-23,Dynamics of coupled spins in quantum dots with strong spin-orbit interaction,"We investigated the time dependence of two-electron spin states in a double
quantum dot fabricated in an InAs nanowire. In this system, spin-orbit
interaction has substantial influence on the spin states of confined electrons.
Pumping single electrons through a Pauli spin-blockade configuration allowed to
probe the dynamics of the two coupled spins via their influence on the pumped
current. We observed spin-relaxation with a magnetic field dependence different
from GaAs dots, which can be explained by spin-orbit interaction. Oscillations
were detected for times shorter than the relaxation time, which we attribute to
coherent evolution of the spin states.",0807.3654v1
2010-12-21,Spin dephasing and pumping in graphene due to random spin-orbit interaction,"We consider spin effects related to the random spin-orbit interaction in
graphene. Such a random interaction can result from the presence of ripples
and/or other inhomogeneities at the graphene surface. We show that the random
spin-orbit interaction generally reduces the spin dephasing (relaxation) time,
even if the interaction vanishes on average. Moreover, the random spin-orbit
coupling also allows for spin manipulation with an external electric field. Due
to the spin-flip interband as well as intraband optical transitions, the spin
density can be effectively generated by periodic electric field in a relatively
broad range of frequencies.",1012.4757v1
2015-05-11,Current-induced spin polarization and spin-orbit torque in graphene,"Using the Green function formalism we calculate a current-induced spin
polarization of weakly magnetized graphene with Rashba spin-orbit interaction.
In a general case, all components of the current-induced spin polarization are
nonzero, contrary to the nonmagnetic limit, where the only nonvanishing
component of spin polarization is that in the graphene plane and normal to
electric field. When the induced spin polarization is exchange-coupled to the
magnetization, it exerts a spin-orbit torque on the latter. Using the Green
function method we have derived some analytical formulas for the spin
polarization and also determined the corresponding spin-orbit torque
components.",1505.02530v2
2012-04-25,Spin freezing by Anderson localization in one-dimensional semiconductors,"One-dimensional quantum wires are considered as prospective elements for spin
transport and manipulation in spintronics. We study spin dynamics in
semiconductor GaAs-like nanowires with disorder and spin-orbit interaction by
using a rotation in the spin subspace gauging away the spin-orbit field. If the
disorder is sufficiently strong, the spin density after a relatively short
relaxation time reaches a plateau. This effect is a manifestation of the
Anderson localization and depends in a universal way on the disorder and the
spin-orbit coupling strength. As a result, at a given disorder, semiconductor
nanowires can permit a long-term spin polarization tunable with the spin-orbit
interactions.",1204.5597v1
2024-01-17,Spin Orbit Torque on a Curved Surface,"We provide a general formulation of the spin-orbit coupling on a 2D curved
surface. Considering the wide applicability of spin-orbit effect in
spinor-based condensed matter physics, a general spin-orbit formulation could
aid the study of spintronics, Dirac graphene, topological systems, and quantum
information on curved surfaces. Particular attention is then devoted to the
development of an important spin-orbit quantity known as the spin-orbit torque.
As devices trend smaller in dimension, the physics of local geometries on
spin-orbit torque, hence spin and magnetic dynamics shall not be neglected. We
derived the general expression of a spin-orbit anisotropy field for the curved
surfaces and provided explicit solutions in the special contexts of the
spherical, cylindrical and flat coordinates. Our expressions allow spin-orbit
anisotropy fields and hence spin-orbit torque to be computed over the entire
surfaces of devices of any geometry.",2401.08966v1
2014-06-10,"Weak Localization, Spin Relaxation, and Spin-Diffusion: The Crossover Between Weak and Strong Rashba Coupling Limits","Disorder scattering and spin-orbit coupling are together responsible for the
diffusion and relaxation of spin-density in time-reversal invariant systems. We
study spin-relaxation and diffusion in a two-dimensional electron gas with
Rashba spin-orbit coupling and spin-independent disorder, focusing on the role
of Rashba spin-orbit coupling in transport. Spin-orbit coupling contributes to
spin relaxation, transforming the quantum interference contribution to
conductivity from a negative weak localization (WL) correction to a positive
weak anti-localization (WAL) correction. The importance of spin channel mixing
in transport is largest in the regime where the Bloch state energy uncertainty
$\hbar/\tau$ and the Rashba spin-orbit splitting $\Delta_\mathrm{SO}$ are
comparable. We find that as a consequence of this spin channel mixing, the
WL-WAL crossover is non-monotonic in this intermediate regime, and use our
results to address recent experimental studies of transport at two-dimensional
oxide interfaces.",1406.2715v2
2011-04-04,Topological phase transitions between chiral and helical spin textures in a lattice with spin-orbit coupling and a magnetic field,"We consider the combined effects of large spin-orbit couplings and a
perpendicular magnetic field in a 2D honeycomb fermionic lattice. This system
provides an elegant setup to generate versatile spin textures propagating along
the edge of a sample. The spin-orbit coupling is shown to induce topological
phase transitions between a helical quantum spin Hall phase and a chiral
spin-imbalanced quantum Hall state. Besides, we find that the spin orientation
of a single topological edge state can be tuned by a Rashba spin-orbit
coupling, opening an interesting route towards quantum spin manipulation. We
discuss the possible realization of our results using cold atoms trapped in
optical lattices, where large synthetic magnetic fields and spin-orbit
couplings can be engineered and finely tuned. In particular, this system would
lead to the observation of a time-reversal-symmetry-broken quantum spin Hall
phase.",1104.0643v2
2005-02-14,Orbitronics: the Intrinsic Orbital Hall Effect in p-Doped Silicon,"The spin Hall effect depends crucially on the intrinsic spin-orbit coupling
of the energy band. Because of the smaller spin-orbit coupling in silicon, the
spin Hall effect is expected to be much reduced. We show that the electric
field in p-doped silicon can induce a dissipationless orbital current in a
fashion reminiscent of the spin Hall effect. The vertex correction due to
impurity scattering vanishes and the effect is therefore robust against
disorder. The orbital Hall effect can lead to the accumulation of local orbital
momentum at the edge of the sample, and can be detected by the Kerr effect.",0502345v1
2018-03-09,Spin-vorticity coupling in viscous electron fluids,"We consider spin-vorticity coupling - the generation of spin polarization by
vorticity - in viscous two-dimensional electron systems with spin-orbit
coupling. We first derive hydrodynamic equations for spin and momentum
densities in which their mutual coupling is determined by the rotational
viscosity. We then calculate the rotational viscosity microscopically in the
limits of weak and strong spin-orbit coupling. We provide estimates that show
that the spin-orbit coupling achieved in recent experiments is strong enough
for the spin-vorticity coupling to be observed. On the one hand, this coupling
provides a way to image viscous electron flows by imaging spin densities. On
the other hand, we show that the spin polarization generated by spin-vorticity
coupling in the hydrodynamic regime can, in principle, be much larger than that
generated, e.g. by the spin Hall effect, in the diffusive regime.",1803.03549v1
2013-10-29,Self-Quenching of Nuclear Spin Dynamics in Central Spin Problem,"We consider, in the framework of the central spin $s=1/2$ model, driven
dynamics of two electrons in a double quantum dot subject to hyperfine
interaction with nuclear spins and spin-orbit coupling. The nuclear subsystem
dynamically evolves in response to Landau-Zener singlet-triplet transitions of
the electronic subsystem controlled by external gate voltages. Without noise
and spin-orbit coupling, subsequent Landau-Zener transitions die out after
about $10^4$ sweeps, the system self-quenches, and nuclear spins reach one of
the numerous glassy dark states. We present an analytical model that captures
this phenomenon. We also account for the multi-nuclear-specie content of the
dots and numerically determine the evolution of around $10^7$ nuclear spins in
up to $2\times10^5$ Landau-Zener transitions. Without spin-orbit coupling,
self-quenching is robust and sets in for arbitrary ratios of the nuclear spin
precession times and the waiting time between Landau-Zener sweeps as well as
under moderate noise. In presence of spin-orbit coupling of a moderate
magnitude, and when the waiting time is in resonance with the precession time
of one of the nuclear species, the dynamical evolution of nuclear polarization
results in stroboscopic screening of spin-orbit coupling. However, small
deviations from the resonance or strong spin-orbit coupling destroy this
screening. We suggest that the success of the feedback loop technique for
building nuclear gradients is based on the effect of spin-orbit coupling.",1310.7847v1
2015-11-11,Spin Swapping Transport and Torques in Ultrathin Magnetic Bilayers,"Planar spin transport in disordered ultrathin magnetic bilayers comprising a
ferromagnet and a normal metal (typically used for spin pumping, spin Seebeck
and spin-orbit torque experiments) is investigated theoretically. Using a
tight-binding model that treats extrinsic spin Hall effect, spin swapping and
spin relaxation on equal footing, we show that the nature of spin-orbit coupled
transport dramatically depends on ratio between the layers thickness $d$ and
the mean free path $\lambda$. While spin Hall effect dominates in the diffusive
limit ($d\gg\lambda$), spin swapping dominates in Knudsen regime
($d\lesssim\lambda$). A remarkable consequence is that the symmetry of the
spin-orbit torque exerted on the ferromagnet is entirely different in these two
regimes.",1511.03454v1
2007-08-20,Manipulating the spin texture in spin-orbit superlattice by terahertz radiation,"The spin texture in a gate-controlled superlattice with Rashba spin-orbit
coupling is studied in the presence of external terahertz radiation causing the
superlattice miniband transitions. It is shown that the local distribution of
spin density can be flipped by tuning the radiation intensity, allowing the
controlled coupling of spins and photons with different polarizations.",0708.2595v2
2012-01-20,Josephson dynamics of a spin-orbit coupled Bose-Einstein condensate in a double well potential,"We investigate the quantum dynamics of an experimentally realized spin-orbit
coupled Bose-Einstein condensate in a double well potential. The spin-orbit
coupling can significantly enhance the atomic inter-well tunneling. We find the
coexistence of internal and external Josephson effects in the system, which are
moreover inherently coupled in a complicated form even in the absence of
interatomic interactions. Moreover, we show that the spin-dependent tunneling
between two wells can induce a net atomic spin current referred as spin
Josephson effects. Such novel spin Josephson effects can be observable for
realistically experimental conditions.",1201.4306v1
2014-08-27,Spin-orbit Coupling and Multiple Phases in Spin-triplet Superconductor Sr$_2$RuO$_4$,"We study the spin-orbit coupling in spin-triplet Cooper pairs and clarify
multiple superconducting (SC) phases in Sr$_2$RuO$_4$. Based on the analysis of
the three-orbital Hubbard model with atomic LS coupling, we show some selection
rules of the spin-orbit coupling in Cooper pairs. The spin-orbit coupling is
small when the two-dimensional $\gamma$-band is the main cause of the
superconductivity, although the LS coupling is much larger than the SC gap.
Considering this case, we investigate multiple SC transitions in the magnetic
fields for both H // [001] and H // [100] using the Ginzburg-Landau theory and
the quasi-classical theory. Rich phase diagrams are obtained because the spin
degree of freedom in Cooper pairs is not quenched by the spin-orbit coupling.
Experimental indications for the multiple phases in Sr$_2$RuO$_4$ are
discussed.",1408.6353v1
2009-08-20,Theory of anisotropic exchange in laterally coupled quantum dots,"The effects of spin-orbit coupling on the two-electron spectra in lateral
coupled quantum dots are investigated analytically and numerically. It is
demonstrated that in the absence of magnetic field the exchange interaction is
practically unaffected by spin-orbit coupling, for any interdot coupling,
boosting prospects for spin-based quantum computing. The anisotropic exchange
appears at finite magnetic fields. A numerically accurate effective spin
Hamiltonian for modeling spin-orbit-induced two-electron spin dynamics in the
presence of magnetic field is proposed.",0908.2961v2
2013-10-30,Spin-orbital state induced by strong spin-orbit coupling,"To clarify a crucial role of a spin-orbit coupling in the emergence of novel
spin-orbital states in $5d$-electron compounds such as Sr$_{2}$IrO$_{4}$, we
investigate ground state properties of a $t_{\rm 2g}$-orbital Hubbard model on
a square lattice by Lanczos diagonalization. In the absence of the spin-orbit
coupling, the ground state is spin singlet. When the spin-orbit coupling is
strong enough, the ground state turns into a weak ferromagnetic state. The weak
ferromagnetic state is a singlet state in terms of an effective total angular
momentum. Regarding the orbital state, we find the so-called complex orbital
state, in which real $xy$, $yz$, and $zx$ orbital states are mixed with complex
coefficients.",1310.8016v1
2015-12-05,Kinetic theory of spin-polarized systems in electric and magnetic fields with spin-orbit coupling: II. RPA response functions and collective modes,"The spin and density response functions in the random phase approximation
(RPA) are derived by linearizing the kinetic equation including a magnetic
field, the spin-orbit coupling, and mean fields with respect to an external
electric field. Different polarization functions appear describing various
precession motions showing Rabi satellites due to an effective Zeeman field.
The latter turns out to consist of the mean-field magnetization, the magnetic
field, and the spin-orbit vector. The collective modes for charged and neutral
systems are derived and a threefold splitting of the spin waves dependent on
the polarization and spin-orbit coupling is shown. The dielectric function
including spin-orbit coupling, polarization and magnetic fields is presented
analytically for long wave lengths and in the static limit. The dynamical
screening length as well as the long-wavelength dielectric function shows an
instability in charge modes, which are interpreted as spin segregation and
domain formation. The spin response describes a crossover from damped
oscillatory behavior to exponentially damped behavior dependent on the
polarization and collision frequency. The magnetic field causes ellipsoidal
trajectories of the spin response to an external electric field and the
spin-orbit coupling causes a rotation of the spin axes. The spin-dephasing
times are extracted and discussed in dependence on the polarization, magnetic
field, spin-orbit coupling and single-particle relaxation times.",1512.01661v1
2013-07-09,Multi-Orbital Superconductivity in SrTiO3 /LaAlO3 Interface and SrTiO3 Surface,"We investigate the superconductivity in two-dimensional electron systems
formed in SrTiO3 nanostructures. Our the- oretical analysis is based on the
three-orbital model, which takes into account t2g orbitals of Ti ions. Because
of the interfacial breaking of mirror symmetry, a Rashba-type antisymmetric
spin-orbit coupling arises from the cooperation of intersite and interorbital
hybridyzation and atomic LS coupling. This model shows a characteristic spin
texture and carrier density dependence of Rashba spin-orbit coupling through
the orbital degree of freedom. Superconductivity is mainly caused by heavy
quasiparticles consisting of dyz and dzx orbitals at high carrier densities. We
find that the Rashba spin-orbit coupling stabilizes a quasi-one-dimensional
superconducting phase caused by one of the dyz or dzx orbitals at high magnetic
fields along interfaces. This quasi-one-dimensional superconducting phase is
protected against para- magnetic depairing effects by the Rashba spin-orbit
coupling and realizes a large upper critical field Hc2 beyond the
Pauli-Clogston-Chandrasekhar limit. This finding is consistent with an
extraordinarily large upper critical field observed in SrTiO3 /LaAlO3
interfaces and its carrier density dependence. The possible coexistence of
superconductivity and fer- romagnetism in SrTiO3 /LaAlO3 interfaces may also be
attributed to this quasi-one-dimensional superconducting phase.",1307.2363v1
2020-09-15,Spin-orbital polarization of Majorana edge states in oxides nanowires,"We investigate a paradigmatic case of topological superconductivity in a
one-dimensional nanowire with $d-$orbitals and a strong interplay of
spin-orbital degrees of freedom due to the competition of orbital Rashba
interaction, atomic spin-orbit coupling, and structural distortions. We
demonstrate that the resulting electronic structure exhibits an orbital
dependent magnetic anisotropy which affects the topological phase diagram and
the character of the Majorana bound states (MBSs). The inspection of the
electronic component of the MBSs reveals that the spin-orbital polarization
generally occurs along the direction of the applied Zeeeman magnetic field, and
transverse to the magnetic and orbital Rashba fields. The competition of
symmetric and antisymmetric spin-orbit coupling remarkably leads to a
misalignment of the spin and orbital moments transverse to the orbital Rashba
fields, whose manifestation is essentially orbital dependent. The behavior of
the spin-orbital polarization along the applied Zeeman field reflects the
presence of multiple Fermi points with inequivalent orbital character in the
normal state. Additionally, the response to variation of the electronic
parameters related with the degree of spin-orbital entanglement leads to
distinctive evolution of the spin-orbital polarization of the MBSs. These
findings unveil novel paths to single-out hallmarks relevant for the
experimental detection of MBSs.",2009.06956v1
2021-03-30,Numerical analysis of the spin-orbit coupling parameters in III-V quantum wells using 8-band Kane model and finite-difference method,"By means the envelope function approximation, 8-band Kane model and a
finite-difference scheme with the coordinate space discretization, we
numerically performed calculations of the spin-orbit coupling parameters for 2D
electron gas confined in both symmetric and asymmetric [0 0 1] quantum wells
based on zinc-blende III-V semiconductors. Influence of the quantum well band
parameters and width as well as the magnitude of the external electric field
applied along the growth direction on the Dresselhaus and Rashba spin-orbit
coupling parameters is investigated. It has been found that in the symmetric
InGaAs/GaAs quantum wells linear-in-momentum spin-orbit coupling disappears for
the third electron subband at certain values of well width and the indium
content. It is also shown that in asymmetric InGaAs/GaAs structures the
spin-orbit coupling parameters can be equal at a certain electric field that is
the condition for the realization of the SU(2) spin symmetry and formation of
persistent spin helices. Besides, we calculated the spin-orbit coupling in the
persistent spin helix regime as a function of the well width, indium content
and external field. The proposed approach for the calculation of the spin-orbit
coupling parameters can be applied to other 2D structures with the spin-orbit
coupling.",2103.16721v1
2011-02-11,Chiral spin states in polarized kagome spin systems with spin-orbit coupling,"We study quantum spin systems with a proper combination of geometric
frustration, spin-orbit coupling and ferromagnetism. We argue that such a
system is likely to be in a chiral spin state, a fractional quantum Hall (FQH)
state for bosonic spin degrees of freedom. The energy scale of the bosonic FQH
state is of the same order as the spin-orbit coupling and ferromagnetism ---
overall much higher than the energy scale of FQH states in semiconductors.",1102.2406v1
2013-04-30,Can electrostatic field lift spin degeneracy?,"There are two well known mechanisms which lead to lifting of energy spin
degeneracy of single electron systems - magnetic field and spin-orbit coupling.
We investigate the possibility for existence of a third mechanism in which
electrostatic field can lead to lifting of spin-degeneracy directly without the
mediation of spin-orbit coupling. A novel argument is provided for the need of
spin-orbit coupling different from the usual relativistic considerations. It is
shown that due to preserved translational invariance spin splitting purely by
electrostatic field is not possible for Bloch states. A possible lifting of
spin degeneracy by electrostatic field characterized by broken inversion and
translational invariance is considered.",1304.7968v2
2011-09-22,Intrinsic coupling of orbital excitations to spin fluctuations in Mott insulators,"We show how the general and basic asymmetry between two fundamental degrees
of freedom present in strongly correlated oxides, spin and orbital, has very
profound repercussions on the elementary spin and orbital excitations. Whereas
the magnons remain largely unaffected, orbitons become inherently coupled with
spin fluctuations in spin-orbital models with antiferromagnetic and
ferroorbital ordered ground states. The composite orbiton-magnon modes that
emerge fractionalize again in one dimension, giving rise to spin-orbital
separation in the peculiar regime where spinons are faster than orbitons.",1109.4745v1
2012-11-05,Tailoring spin-orbit torque in diluted magnetic semiconductors,"We study the spin orbit torque arising from an intrinsic linear Dresselhaus
spin-orbit coupling in a single layer III-V diluted magnetic semiconductor. We
investigate the transport properties and spin torque using the linear response
theory and we report here : (1) a strong correlation exists between the angular
dependence of the torque and the anisotropy of the Fermi surface; (2) the spin
orbit torque depends nonlinearly on the exchange coupling. Our findings suggest
the possibility to tailor the spin orbit torque magnitude and angular
dependence by structural design.",1211.0867v2
2015-06-02,Spin-orbit coupling rule in bound fermions systems,"Spin-orbit coupling characterizes quantum systems such as atoms, nuclei,
hypernuclei, quarkonia, etc., and is essential for understanding their
spectroscopic properties. Depending on the system, the effect of spin-orbit
coupling on shell structure is large in nuclei, small in quarkonia,
perturbative in atoms. In the standard non-relativistic reduction of the
single-particle Dirac equation, we derive a universal rule for the relative
magnitude of the spin-orbit effect that applies to very different quantum
systems, regardless of whether the spin-orbit coupling originates from the
strong or electromagnetic interaction. It is shown that in nuclei the near
equality of the mass of the nucleon and the difference between the large
repulsive and attractive potentials explains the fact that spin-orbit
splittings are comparable to the energy spacing between major shells. For a
specific ratio between the particle mass and the effective potential whose
gradient determines the spin-orbit force, we predict the occurrence of giant
spin-orbit energy splittings that dominate the single-particle excitation
spectrum.",1506.00911v2
2006-06-07,An Exact SU(2) Symmetry and Persistent Spin Helix in a Spin-Orbit Coupled System,"Spin-orbit coupled systems generally break the spin rotation symmetry.
However, for a model with equal Rashba and Dresselhauss coupling constant (the
ReD model), and for the $[110]$ Dresselhauss model, a new type of SU(2) spin
rotation symmetry is discovered. This symmetry is robust against
spin-independent disorder and interactions, and is generated by operators whose
wavevector depends on the coupling strength. It renders the spin lifetime
infinite at this wavevector, giving rise to a Persistent Spin Helix (PSH). We
obtain the spin fluctuation dynamics at, and away, from the symmetry point, and
suggest experiments to observe the PSH.",0606196v1
2010-08-09,Gate-dependent spin-orbit coupling in multi-electron carbon nanotubes,"Understanding how the orbital motion of electrons is coupled to the spin
degree of freedom in nanoscale systems is central for applications in
spin-based electronics and quantum computation. We demonstrate this coupling of
spin and orbit in a carbon nanotube quantum dot in the general multi-electron
regime in presence of finite disorder. Further, we find a strong systematic
dependence of the spin-orbit coupling on the electron occupation of the quantum
dot. This dependence, which even includes a sign change is not demonstrated in
any other system and follows from the curvature-induced spin-orbit split
Dirac-spectrum of the underlying graphene lattice. Our findings unambiguously
show that the spin-orbit coupling is a general property of nanotube quantum
dots which provide a unique platform for the study of spin-orbit effects and
their applications.",1008.1600v2
2006-03-23,Intense terahertz laser fields on a quantum dot with Rashba spin-orbit coupling,"We investigate the effects of the intense terahertz laser field and the
spin-orbit coupling on single electron spin in a quantum dot. The laser field
and the spin-orbit coupling can strongly affect the electron density of states
and can excite a magnetic moment.
  The direction of the magnetic moment depends on the symmetries of the system,
and its amplitude can be tuned by the strength and frequency of the laser field
as well as the spin-orbit coupling.",0603614v2
2008-10-30,Berry Phase in a Single Quantum Dot with Spin-Orbit Interaction,"Berry phase in a single quantum dot with Rashba spin-orbit coupling is
investigated theoretically. Berry phases as functions of magnetic field
strength, dot size, spin-orbit coupling and photon-spin coupling constants are
evaluated. It is shown that the Berry phase will alter dramatically from 0 to
$2\pi$ as the magnetic field strength increases. The threshold of magnetic
field depends on the dot size and the spin-orbit coupling constant.",0810.5405v1
2011-06-28,Phase separation in a polarized Fermi gas with spin-orbit coupling,"We study the phase separation of a spin polarized Fermi gas with spin-orbit
coupling near a wide Feshbach resonance. As a result of the competition between
spin-orbit coupling and population imbalance, the phase diagram for a uniform
gas develops a rich structure of phase separation involving gapless superfluid
states which are topologically non-trivial. We find that these novel gapless
phases can be stabilized by intermediate spin-orbit coupling strengths. We then
demonstrate the phase separation induced by an external trapping potential and
discuss the optimal parameter region for the experimental observation of the
gapless superfluid phases.",1106.5667v2
2013-12-09,The Pairing of Spin-orbit Coupled Fermi Gas in Optical Lattice,"We investigate Rashba spin-orbit coupled Fermi gases in square optical
lattice by using the determinant quantum Monte Carlo (DQMC) simulations which
is free of the sign-problem. We show that the Berezinskii-Kosterlitz-Thoules
phase transition temperature is firstly enhanced and then suppressed by
spin-orbit coupling in the strong attraction region. In the intermediate
attraction region, spin-orbit coupling always suppresses the transition
temperature. We also show that the spin susceptibility becomes anisotropic and
retains finite values at zero temperature.",1312.2292v1
2020-12-27,Microwave spectroscopy of spin-orbit coupled states: energy detuning versus interdot coupling modulation,"We study the AC field induced current peaks of a spin blockaded double
quantum dot with spin-orbit interaction. The AC field modulates either the
interdot tunnel coupling or the energy detuning, and we choose the AC field
frequency range to induce two singlet-triplet transitions giving rise to two
current peaks. We show that for a large detuning the two current peaks can be
significantly stronger when the AC field modulates the tunnel coupling, thus
making the detection of the spin-orbit gap more efficient. We also demonstrate
the importance of the time dependence of the spin-orbit interaction.",2012.13914v1
2020-10-05,Detection of the Orbital Hall Effect by the Orbital-Spin Conversion,"The intrinsic orbital Hall effect (OHE), the orbital counterpart of the spin
Hall effect, was predicted and studied theoretically for more than one decade,
yet to be observed in experiments. Here we propose a strategy to convert the
orbital current in OHE to the spin current via the spin-orbit coupling from the
contact. Furthermore, we find that OHE can induce large nonreciprocal
magnetoresistance when employing magnetic contact. Both the generated spin
current and the orbital Hall magnetoresistance can be applied to probe the OHE
in experiments and design orbitronic devices.",2010.01970v1
2018-12-19,Manifestations of spin-orbit coupling in a cuprate superconductor,"Exciting new work on Bi2212 shows the presence of non-trivial spin-orbit
coupling effects as seen in spin resolved ARPES data [Gotlieb et al., Science,
362, 1271-1275 (2018)]. Motivated by these observations we consider how the
picture of spin-orbit coupling through local inversion symmetry breaking might
be observed in cuprate superconductors. Furthermore, we examine two spin-orbit
driven effects, the spin-Hall effect and the Edelstein effect, focusing on the
details of their realizations within both the normal and superconducting
states.",1812.07949v2
2014-08-08,Spin-Orbital Order Modified by Orbital Dilution in Transition Metal Oxides: From Spin Defects to Frustrated Spins Polarizing Host Orbitals,"We study the $3d$ substitution in $4d$ transition metal oxides in the cases
of $3d^3$ doping at either $3d^2$ or $4d^4$ sites which realize orbital
dilution. We derive the effective $3d-4d$ (or $3d-3d$) superexchange in a Mott
insulator with different ionic valencies, underlining the emerging structure of
the spin-orbital coupling between the impurity and the host sites and
demonstrate that it is qualitatively different from that encountered in the
host itself. This derivation shows that the interaction between the host and
the impurity depends in a crucial way on the type of doubly occupied $t_{2g}$
orbital. One finds that in some cases, due to the quench of the orbital degree
of freedom at the $3d$ impurity, the spin and orbital order within the host is
drastically modified by doping. The impurity acts either as a spin defect
accompanied by an orbital vacancy in the spin-orbital structure when the
host-impurity coupling is weak, or it favors doubly occupied active orbitals
(orbital polarons) along the $3d-4d$ bond leading to antiferromagnetic or
ferromagnetic spin coupling. This competition between different magnetic
couplings leads to quite different ground states. We find that magnetic
frustration and spin degeneracy can be lifted by the quantum orbital flips of
the host but they are robust in special regions of the incommensurate phase
diagram. The spin-orbit coupling can lead to anisotropic spin and orbital
patterns along the symmetry directions and cause a radical modification of the
order imposed by the spin-orbital superexchange. Our findings are expected to
be of importance for future theoretical understanding of experimental results
for doped $4d$ transition metal oxides doped with $3d^3$ ions. We suggest how
the local or global changes of the spin-orbital order induced by such
impurities could be detected experimentally.",1408.1838v3
2014-04-21,Graphene with wedge disclination in the presence of intrinsic and Rashba spin orbit couplings,"In this article, the modified Kane-Mele Hamiltonian is derived for graphene
with wedge disclination and spin orbit couplings (intrinsic and Rashba). The
wedge disclination changes the flat lattice into the conical lattice and hence
modifies the spin orbit couplings. The Hamiltonian is exactly solved for the
intrinsic spin orbit interaction and perturbatively for the Rashba spin orbit
interaction. It is shown that there exists the Kramer's degenerate midgap
localized spin separated fluxon states around the defect. These zero energy
spin separated states occur at the external magnetic flux value
$\Phi\pm\Delta\Phi$. The external magnetic flux $\Phi$ is introduced to make
the wave-function periodic when the electron circulates around the defect. It
is found that this separation occurs due to the effect of the conical curvature
on the spin orbit coupling. Further, we find these results are robust to the
addition of the Rashba spin orbit interaction which is important for the
application to spintronics and nanoelectronics.",1404.5150v2
2004-08-18,Hole dynamics in spin and orbital ordered vanadium perovskites,"Hole dynamics in spin and orbital ordered vanadates with perovskite structure
is investigated. A mobile hole coupled to the spin excitation (magnon) in the
spin G-type and orbital C-type (SG/OC) ordered phase, and that to the orbital
excitation (orbiton) in the spin C-type and orbital G-type (SC/OG) one are
formulated on an equal footing. The observed fragile character of the (SG/OC)
order is attributed to the orbiton softening caused by a reduction of the
taggered magnetic order parameter. It is proposed that the qualitatively
different hole dynamics in the two spin-orbital ordered phases in vanadates can
be probed by the optical spectra.",0408395v1
2020-02-05,Correlated motion of particle-hole excitations across the renormalized spin-orbit gap in $\rm Sr_2 Ir O_4$,"The high-energy collective modes of particle-hole excitations across the
spin-orbit gap in $\rm Sr_2IrO_4$ are investigated using the transformed
Coulomb interaction terms in the pseudo-spin-orbital basis constituted by the
$J=1/2$ and $3/2$ states arising from spin-orbit coupling. With appropriate
interaction strengths and renormalized spin-orbit gap, these collective modes
yield two well-defined propagating spin-orbit exciton modes, with energy scale
and dispersion in excellent agreement with resonant inelastic X-ray scattering
(RIXS) measurements.",2002.02415v1
2006-11-06,Spin relaxation in a generic two-dimensional spin-orbit coupled system,"We study the relaxation of a spin density injected into a two-dimensional
electron system with generic spin-orbit interactions. Our model includes the
Rashba as well as linear and cubic Dresselhaus terms. We explicitly derive a
general spin-charge coupled diffusion equation. Spin diffusion is characterized
by just two independent dimensionless parameters which control the interplay
between different spin-orbit couplings. The real-time representation of the
diffuson matrix (Green's function of the diffusion equation) is evaluated
analytically. The diffuson describes space-time dynamics of the injected spin
distribution. We explicitly study two regimes: The first regime corresponds to
negligible spin-charge coupling and is characterized by standard charge
diffusion decoupled from the spin dynamics. It is shown that there exist
several qualitatively different dynamic behaviors of the spin density, which
correspond to various domains in the spin-orbit coupling parameter space. We
discuss in detail a few interesting phenomena such as an enhancement of the
spin relaxation times, real space oscillatory dynamics, and anisotropic
transport. In the second regime, we include the effects of spin-charge
coupling. It is shown that the spin-charge coupling leads to an enhancement of
the effective charge diffusion coefficient. We also find that in the case of
strong spin-charge coupling, the relaxation rates formally become complex and
the spin/charge dynamics is characterized by real time oscillations. These
effects are qualitatively similar to those observed in spin-grating experiments
[Weber et al., Nature 437, 1330 (2005)].",0611165v1
2011-10-06,Spin and pseudospin symmetry along with orbital dependency of the Dirac-Hulthen problem,"The role of the Hulthen potential on the spin and pseudospin symmetry
solutions is investigated systematically by solving the Dirac equation with
attractive scalar S(r) and repulsive vector V(r) potentials. The spin and
pseudospin symmetry along with orbital dependency (pseudospin-orbit and
spin-orbit dependent couplings) of the Dirac equation are included to the
solution by introducing the Hulthen-square approximation. This effective
approach is based on forming the spin and pseudo-centrifugal kinetic energy
term from the square of the Hulthen potential. The analytical solutions of the
Dirac equation for the Hulthen potential with the spin-orbit and
pseudospin-orbit-dependent couplings are obtained by using the Nikiforov-Uvarov
(NU) method. The energy eigenvalue equations and wave functions for various
degenerate states are presented for several spin-orbital, pseudospin-orbital
and radial quantum numbers under the condition of the spin and pseudospin
symmetry. Keywords: Spin and pseudospin symmetry; orbital dependency; Dirac
equation; Hulthen potential; Nikiforov-Uvarov Method.",1110.1225v1
2013-11-07,Spin-Orbit Torques and Anisotropic Magnetization Damping in Skyrmion Crystals,"The length scale of the magnetization gradients in chiral magnets is
determined by the relativistic Dzyaloshinskii-Moriya interaction. Thus, even
conventional spin-transfer torques are controlled by the relativistic
spin-orbit coupling in these systems, and additional relativistic corrections
to the current-induced torques and magnetization damping become important for a
complete understanding of the current-driven magnetization dynamics. We
theoretically study the effects of reactive and dissipative homogeneous
spin-orbit torques and anisotropic damping on the current-driven skyrmion
dynamics in cubic chiral magnets. Our results demonstrate that spin-orbit
torques play a significant role in the current-induced skyrmion velocity. The
dissipative spin-orbit torque generates a relativistic Magnus force on the
skyrmions, whereas the reactive spin-orbit torque yields a correction to both
the drift velocity along the current direction and the transverse velocity
associated with the Magnus force. The spin-orbit torque corrections to the
velocity scale linearly with the skyrmion size, which is inversely proportional
to the spin-orbit coupling. Consequently, the reactive spin-orbit torque
correction can be the same order of magnitude as the non-relativistic
contribution. More importantly, the dissipative spin-orbit torque can be the
dominant force that causes a deflected motion of the skyrmions if the torque
exhibits a linear or quadratic relationship with the spin-orbit coupling. In
addition, we demonstrate that the skyrmion velocity is determined by
anisotropic magnetization damping parameters governed by the skyrmion size.",1311.1778v1
2016-02-15,Effects of Dephasing on Spin Lifetime in Ballistic Spin-Orbit Materials,"We theoretically investigate spin dynamics in spin-orbit-coupled materials.
In the ballistic limit, the spin lifetime is dictated by dephasing that arises
from energy broadening plus a non-uniform spin precession. For the case of
clean graphene, we find a strong anisotropy with spin lifetimes that can be
short even for modest energy scales, on the order of a few ns. These results
offer deeper insight into the nature of spin dynamics in graphene, and are also
applicable to the investigation of other systems where spin-orbit coupling
plays an important role.",1602.04611v1
2018-12-20,Non-local Spin-charge Conversion via Rashba Spin-Orbit Interaction,"We show theoretically that conversion between spin and charge by spin-orbit
interaction in metals occurs even in a non-local setup where magnetization and
spin-orbit interaction are spatially separated if electron diffusion is taken
into account. Calculation is carried out for the Rashba spin-orbit interaction
treating the coupling with a ferromagnet perturbatively. The results indicate
the validity of the concept of effective spin gauge field (spin motive force)
in the non-local configuration. The inverse Rashba-Edelstein effect observed
for a trilayer of a ferromagnet, a normal metal and a heavy metal can be
explained in terms of the non-local effective spin gauge field.",1812.08884v1
2003-09-24,Orbital Wave and its Observation in Orbital Ordered Titanates and Vanadates,"We present a theory of the collective orbital excitation termed orbital wave
in perovskite titanates and vanadates with the triply degenerate $t_{2g}$
orbitals. The dispersion relations of the orbital waves for the orbital ordered
LaVO$_3$, YVO$_3$ and YTiO$_3$ are examined in the effective spin-orbital
coupled Hamiltonians associated with the Jahn-Teller type couplings. We propose
possible scattering processes for the Raman and inelastic neutron scatterings
from the orbital wave and calculate the scattering spectra for titanates and
vanadates. It is found that both the excitation spectra and the observation
methods of the orbital wave are distinct qualitatively from those for the $e_g$
orbital ordered systems.",0309538v2
2013-12-31,Anisotropic exchange coupling in a nanowire double quantum dot with strong spin-orbit coupling,"A spin-orbit qubit is a hybrid qubit that contains both orbital and spin
degrees of freedom of an electron in a quantum dot. Here we study the exchange
coupling between two spin-orbit qubits in a nanowire double quantum dot (DQD)
with strong spin-orbit coupling (SOC). We find that while the total tunneling
in the DQD is irrelevant to the SOC, both the spin-conserved and spin-flipped
tunnelings are SOC dependent and can compete with each other in the strong SOC
regime. Moreover, the Coulomb repulsion between electrons can combine with the
SOC-dependent tunnelings to yield an anisotropic exchange coupling between the
two spin-orbit qubits. Also, we give an explicit physical mechanism for this
anisotropic exchange coupling.",1401.0101v2
2023-11-15,Chirality-induced emergent spin-orbit coupling in topological atomic lattices,"Spin-orbit coupled dynamics are of fundamental interest in both quantum
optical and condensed matter systems alike. In this work, we show that photonic
excitations in pseudospin-1/2 atomic lattices exhibit an emergent spin-orbit
coupling when the geometry is chiral. This spin-orbit coupling arises naturally
from the electric dipole interaction between the lattice sites and leads to
spin polarized excitation transport. Using a general quantum optical model, we
determine analytically the conditions that give rise to spin-orbit coupling and
characterize the behavior under various symmetry transformations. We show that
chirality-induced spin textures are associated with a topologically nontrivial
Zak phase that characterizes the chiral setup. Our results demonstrate that
chiral atom arrays are a robust platform for realizing spin-orbit coupled
topological states of matter.",2311.09303v1
2012-05-15,Spin-Injection Spectroscopy of a Spin-Orbit Coupled Fermi Gas,"The coupling of the spin of electrons to their motional state lies at the
heart of recently discovered topological phases of matter. Here we create and
detect spin-orbit coupling in an atomic Fermi gas, a highly controllable form
of quantum degenerate matter. We reveal the spin-orbit gap via spin-injection
spectroscopy, which characterizes the energy-momentum dispersion and spin
composition of the quantum states. For energies within the spin-orbit gap, the
system acts as a spin diode. To fully inhibit transport, we open an additional
spin gap, thereby creating a spin-orbit coupled lattice whose spinful band
structure we probe. In the presence of s-wave interactions, such systems should
display induced p-wave pairing, topological superfluidity, and Majorana edge
states.",1205.3483v1
1998-12-02,Theory of Orbital Excitation and Resonant Inelastic X-ray Scattering in Manganites,"We study theoretically the collective orbital excitation named orbital wave
in the orbital ordered manganites.The dispersion relation of the orbital wave
is affected by the static spin structure through the coupling between spin and
orbital degrees of freedom. As a probe to detect the dispersion relation, we
propose two possible methods by utilizing resonant inelastic x-ray scattering.
The transition probability of the orbital wave scattering is formulated, and
the momentum and polarization dependences of the structure factor are
calculated in several types of the orbital and spin structures. The elastic
x-ray scattering in the L-edge case to observe the orbital ordering is also
discussed.",9812028v1
2016-04-29,Tunable spin-charge conversion through topological phase transitions in zigzag nanoribbons,"We study spin-orbit torques and charge pumping in magnetic quasi-one
dimensional zigzag nanoribbons with hexagonal lattice, in the presence of large
intrinsic spin-orbit coupling. Such a system experiences topological phase
transition from a trivial band insulator to a quantum spin Hall insulator
either by tuning the magnetization direction or the intrinsic spin-orbit
coupling. We find that spin-charge conversion efficiency (i.e. spin-orbit
torque and charge pumping) is dramatically enhanced at the topological
transition, displaying a substantial angular anisotropy.",1604.08782v1
2014-02-24,Low-Energy Effective Hamiltonian for Giant-Gap Quantum Spin Hall Insulators in Honeycomb X-Hydride/Halide (X=N-Bi) Monolayers,"Using the tight-binding method in combination with first-principles
calculations, we systematically derive a low-energy effective Hilbert subspace
and Hamiltonian with spin-orbit coupling for two-dimensional hydrogenated and
halogenated group-V monolayers. These materials are proposed to be giant-gap
quantum spin Hall insulators with record huge bulk band gaps opened by the
spin-orbit coupling at the Dirac points, e.g., from 0.74 to 1.08 eV in
Bi\textit{X} (\textit{X} = H, F, Cl, and Br) monolayers. We find that the
low-energy Hilbert subspace mainly consists of $p_{x}$ and $p_{y}$ orbitals
from the group-V elements, and the giant first-order effective intrinsic
spin-orbit coupling is from the on-site spin-orbit interaction. These features
are quite distinct from those of group-IV monolayers such as graphene and
silicene. There, the relevant orbital is $p_z$ and the effective intrinsic
spin-orbit coupling is from the next-nearest-neighbor spin-orbit interaction
processes. These systems represent the first real 2D honeycomb lattice
materials in which the low-energy physics is associated with $p_{x}$ and
$p_{y}$ orbitals. A spinful lattice Hamiltonian with an on-site spin-orbit
coupling term is also derived, which could facilitate further investigations of
these intriguing topological materials.",1402.5817v2
2002-08-27,Conductance of a quantum point contact in the presence of spin-orbit interaction,"A recursive Green's function technique is developed to calculate the
spin-dependent conductance in mesoscopic structures. Using this technique, we
study the spin-dependent electronic transport of quantum point contacts in the
presence of the Rashba spin-orbit interaction. We observed that some
oscillations in the `quantized' conductance are induced by the spin-orbit
interaction, and indicated that the oscillations may stem from the spin-orbit
coupling associated multiple reflections. It is also indicated that the 0.7
structure of the conductance observed in mesoscopic experiments would not stem
from the spin-orbit interaction.",0208506v1
2022-01-27,Superfluid transition temperature and fluctuation theory of spin-orbit and Rabi-coupled fermions with tunable interactions,"We obtain the superfluid transition temperature of equal Rashba-Dresselhaus
spin-orbit and Rabi-coupled Fermi superfluids, from the
Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) regimes in
three dimensions for tunable $s$-wave interactions. In the presence of Rabi
coupling, we find that spin-orbit coupling enhances (reduces) the critical
temperature in the BEC (BCS) limit. For fixed interactions, we show that
spin-orbit coupling can convert a first-order (discontinuous) phase transition
into a second-order (continuous) phase transition, as a function of Rabi
coupling. We derive the Ginzburg-Landau free energy to sixth power in the
superfluid order parameter to describe both continuous and discontinuous phase
transitions as a function of spin-orbit and Rabi couplings. Lastly, we develop
a time-dependent Ginzburg-Landau fluctuation theory for an arbitrary mixture of
Rashba and Dresselhaus spin-orbit couplings at any interaction strength.",2201.11823v2
2009-05-12,Pauli Spin Blockade in the Presence of Strong Spin-Orbit Coupling,"We study electron transport in a double quantum dot in the Pauli spin
blockade regime, in the presence of strong spin-orbit coupling. The effect of
spin-orbit coupling is incorporated into a modified interdot tunnel coupling.
We elucidate the role of the external magnetic field, the nuclear fields in the
dots, and spin relaxation. We find qualitative agreement with experimental
observations, and we propose a way to extend the range of magnetic fields in
which blockade can be observed.",0905.1818v1
2012-09-21,Adiabatic pumping through an interacting quantum dot with spin-orbit coupling,"We study adiabatic pumping through a two-level quantum dot with spin-orbit
coupling. Using a diagrammatic real-time approach, we calculate both the pumped
charge and spin for a periodic variation of the dot's energy levels in the
limit of weak tunnel coupling. Thereby, we compare the two limits of vanishing
and infinitely large charging energy on the quantum dot. We discuss the
dependence of the pumped charge and pumped spin on gate voltages, the symmetry
in the tunnel-matrix elements and spin-orbit coupling strength. We identify the
possibility to generate pure spin currents in the absence of charge currents.",1209.4770v2
2017-07-14,Insights into the orbital magnetism of noncollinear magnetic systems,"The orbital magnetic moment is usually associated with the relativistic
spin-orbit interaction, but recently it has been shown that noncollinear
magnetic structures can also be its driving force. This is important not only
for magnetic skyrmions, but also for other noncollinear structures, either
bulk-like or at the nanoscale, with consequences regarding their experimental
detection. In this work we present a minimal model that contains the effects of
both the relativistic spin-orbit interaction and of magnetic noncollinearity on
the orbital magnetism. A hierarchy of models is discussed in a step-by-step
fashion, highlighting the role of time-reversal symmetry breaking for
translational and spin and orbital angular motions. Couplings of spin-orbit and
orbit-orbit type are identified as arising from the magnetic noncollinearity.
We recover the atomic contribution to the orbital magnetic moment, and a
nonlocal one due to the presence of circulating bound currents, exploring
different balances between the kinetic energy, the spin exchange interaction,
and the relativistic spin-orbit interaction. The connection to the scalar spin
chirality is examined. The orbital magnetism driven by magnetic noncollinearity
is mostly unexplored, and the presented model contributes to laying its
groundwork.",1707.04518v1
2023-11-22,Effects of magnetic fields and orbital angular momentum on excitonic condensation in two-orbital Hubbard model,"We investigate the magnetic-field effects on a two-orbital Hubbard model that
describes multiple spin states. Cobalt oxides have been investigated as
materials possessing spin-state degrees of freedom due to the interplay between
the Hund coupling interaction and crystalline field effect. In the competing
region, quantum hybridizations between distinct spin states are expected to
emerge, corresponding to excitonic condensation. Applied magnetic fields could
also induce such a competition. To understand magnetic-field effects on
excitonic condensation in multi-orbital systems, it is crucial to account for
contributions from both spin and orbital degrees of freedom to magnetic
properties. Here, we study field-induced phenomena in the two-orbital Hubbard
model by focusing on the role of the orbital angular momentum. We
comprehensively analyze this model on a square lattice employing the
Hartree-Fock approximation. Omitting contributions from the orbital moment, we
find that an applied magnetic field gives rise to two excitonic phases, besides
the spin-state ordered phase, between the nonmagnetic low-spin and
spin-polarized high-spin phases. One of these excitonic phases manifests a
staggered-type spin-state order, interpreted as an excitonic supersolid state.
Conversely, the other phase is not accompanied by it and exhibits only a spin
polarization due to the applied magnetic field. When spin-orbit coupling is
present, this phase displays a ferrimagnetic spin alignment attributed to spin
anisotropy. Our analysis also reveals that incorporating the contribution of
the orbital magnetic moment to the Zeeman term significantly alters the overall
structure of the phase diagram. Notably, the orbital magnetization destabilizes
the excitonic phase in contrast to scenarios without this contribution. We also
discuss the relevance of our findings to real materials, such as cobalt oxides.",2311.13191v1
2016-06-27,Supercurrent-Induced Spin-Orbit Torques,"We theoretically investigate the supercurrent-induced magnetization dynamics
of a two-dimensional lattice of ferromagnetically ordered spins placed on a
conventional superconductor with broken spatial inversion symmetry and strong
spin-orbit coupling. We develop a phenomenological description of the coupled
dynamics of the superconducting condensate and the spin system, and demonstrate
that supercurrents produce a reactive spin-orbit torque on the magnetization.
By performing a microscopic self-consistent calculation, we show that the
spin-orbit torque originates from a spin-polarization of the Cooper pairs due
to current-induced spin-triplet correlations. Interestingly, we find that there
exists an intrinsic limitation for the maximum achievable spin-orbit torque,
which is determined by the coupling strength between the condensate and the
spin system. In proximitized hole-doped semiconductors, the maximum achievable
spin-orbit torque field is estimated to be on the order of $0.16$ mT, which is
comparable to the critical field for current-induced magnetization switching in
ferromagnetic semiconductors.",1606.08470v1
2005-08-02,Spin Accumulation in the Extrinsic Spin Hall Effect,"The drift-diffusion formalism for spin-polarized carrier transport in
semiconductors is generalized to include spin-orbit coupling. The theory is
applied to treat the extrinsic spin Hall effect using realistic boundary
conditions. It is shown that carrier and spin diffusion lengths are modified by
the presence of spin-orbit coupling and that spin accumulation due to the
extrinsic spin Hall effect is strongly and qualitatively influenced by boundary
conditions. Analytical formulas for the spin-dependent carrier recombination
rates and inhomogeneous spin densities and currents are presented.",0508076v1
2021-08-13,Coupling the Higgs mode and ferromagnetic resonance in spin-split superconductors with Rashba spin-orbit coupling,"We consider the Higgs mode at nonzero momentum in superconductors and
demonstrate that in the presence of Rashba spin-orbit coupling, it couples
linearly with an external exchange field. The Higgs-spin coupling dramatically
modifies the spin susceptibility near the superconducting critical temperature
and consequently enhances the spin pumping effect in a ferromagnetic
insulator/superconductor bilayer system. We show that this effect can be
detected by measuring the magnon-induced voltage generated by the inverse spin
Hall effect.",2108.06202v2
2020-06-03,"Magnetic reorientation transition in a three orbital model for $\rm Ca_2 Ru O_4$ -- Interplay of spin-orbit coupling, tetragonal distortion, and Coulomb interactions","Including the orbital off-diagonal spin and charge condensates in the self
consistent determination of magnetic order within a realistic three-orbital
model for the $4d^4$ compound $\rm Ca_2 Ru O_4$, reveals a host of novel
features including strong and anisotropic spin-orbit coupling (SOC)
renormalization, coupling of strong orbital magnetic moments to orbital fields,
and a magnetic reorientation transition. Highlighting the rich interplay
between orbital geometry and overlap, spin-orbit coupling, Coulomb
interactions, tetragonal distortion, and staggered octahedral tilting and
rotation, our investigation yields a planar antiferromagnetic (AFM) order for
moderate tetragonal distortion, with easy $a-b$ plane and easy $b$ axis
anisotropies, along with small canting of the dominantly $yz,xz$ orbital
moments. With decreasing tetragonal distortion, we find a magnetic
reorientation transition from the dominantly planar AFM order to a dominantly
$c$ axis ferromagnetic (FM) order with significant $xy$ orbital moment.",2006.02114v2
2019-12-11,Selective tuning of spin-orbital Kondo contributions in parallel-coupled quantum dots,"We use co-tunneling spectroscopy to investigate spin-, orbital-, and
spin-orbital Kondo transport in a strongly confined system of InAs double
quantum dots (QDs) parallel-coupled to source and drain. In the one-electron
transport regime, the higher symmetry spin-orbital Kondo effect manifests at
orbital degeneracy and no external magnetic field. We then proceed to show that
the individual Kondo contributions can be isolated and studied separately;
either by orbital detuning in the case of spin-Kondo transport, or by spin
splitting in the case of orbital Kondo transport. By varying the inter-dot
tunnel coupling, we show that lifting of the spin degeneracy is key to
confirming the presence of an orbital degeneracy, and to detecting a small
orbital hybridization gap. Finally, in the two-electron regime, we show that
the presence of a spin-triplet ground state results in spin-Kondo transport at
zero magnetic field.",1912.05181v2
2018-01-25,Spin-relaxation anisotropy in a nanowire quantum dot with strong spin-orbit coupling,"We study the impacts of the magnetic field direction on the spin-manipulation
and the spin-relaxation in a one-dimensional quantum dot with strong spin-orbit
coupling. The energy spectrum and the corresponding eigenfunctions in the
quantum dot are obtained exactly. We find that no matter how large the
spin-orbit coupling is, the electric-dipole spin transition rate as a function
of the magnetic field direction always has a $\pi$ periodicity. However, the
phonon-induced spin relaxation rate as a function of the magnetic field
direction has a $\pi$ periodicity only in the weak spin-orbit coupling regime,
and the periodicity is prolonged to $2\pi$ in the strong spin-orbit coupling
regime.",1801.08349v2
2012-05-10,"3D quaternionic condensations, Hopf invariants, and skyrmion lattices with synthetic spin-orbit coupling","We study the topological configurations of the two-component condensates of
bosons with the $3$D $\vec{\sigma}\cdot \vec{p}$ Weyl-type spin-orbit coupling
subject to a harmonic trapping potential. The topology of the condensate
wavefunctions manifests in the quaternionic representation. In comparison to
the $U(1)$ complex phase, the quaternionic phase manifold is $S^3$ and the spin
orientations form the $S^2$ Bloch sphere through the 1st Hopf mapping. The
spatial distributions of the quaternionic phases exhibit the 3D skyrmion
configurations, and the spin distributions possess non-trivial Hopf invariants.
Spin textures evolve from the concentric distributions at the weak spin-orbit
coupling regime to the rotation symmetry breaking patterns at the intermediate
spin-orbit coupling regime. In the strong spin-orbit coupling regime, the
single-particle spectra exhibit the Landau-level type quantization. In this
regime, the three-dimensional skyrmion lattice structures are formed when
interactions are below the energy scale of Landau level mixings. Sufficiently
strong interactions can change condensates into spin-polarized plane-wave
states, or, superpositions of two plane-waves exhibiting helical spin spirals.",1205.2162v3
2013-01-21,Spin-orbit-induced bound state and molecular signature of the degenerate Fermi gas in a narrow Feshbach resonance,"In this paper we explore the spin-orbit-induced bound state and molecular
signature of the degenerate Fermi gas in a narrow Feshbach resonance based on a
generalized two-channel model. Without the atom-atom interactions, only one
bound state can be found even if spin-orbit coupling exists. Moreover, the
corresponding bound-state energy depends strongly on the strength of spin-orbit
coupling, but is influenced slightly by its type. In addition, we find that
when increasing the strength of spin-orbit coupling, the critical point at
which the molecular fraction vanishes shifts from zero to the negative
detuning. In the weak spin-orbit coupling, this shifting is proportional to the
square of its strength. Finally, we also show that the molecular fraction can
be well controlled by spin-orbit coupling.",1301.4718v2
2015-12-08,Multi-orbital quantum antiferromagnetism in iron pnictides --- effective spin couplings and quantum corrections to sublattice magnetization,"Towards understanding the multi-orbital quantum antiferromagnetism in iron
pnictides, effective spin couplings and spin fluctuation induced quantum
corrections to sublattice magnetization are obtained in the $(\pi,0)$ AF state
of a realistic three band interacting electron model involving $xz$, $yz$, and
$xy$ Fe 3d orbitals. The $xy$ orbital is found to be mainly responsible for the
generation of strong ferromagnetic spin coupling in the $b$ direction, which is
critically important to fully account for the spin wave dispersion as measured
in inelastic neutron scattering experiments. The ferromagnetic spin coupling is
strongly suppressed as the $xy$ band approaches half filling, and is ascribed
to particle-hole exchange in the partially filled $xy$ band. The strongest AF
spin coupling in the $a$ direction is found to be in the orbital off diagonal
sector involving the $xz$ and $xy$ orbitals. First order quantum corrections to
sublattice magnetization are evaluated for the three orbitals, and yield a
significant $37\%$ average reduction from the Hartree-Fock value.",1512.02398v1
2003-10-01,Rashba coupling in quantum dots: exact solution,"We present an analytic solution to the problem of the Rashba spin-orbit
coupling in semiconductor quantum dots. We calculate the exact energy spectrum,
wave-functions, and spin--flip relaxation times. We discuss various effects
inaccessible via perturbation theory. In particular, we find that the effective
gyromagnetic ratio is strongly suppressed by the spin-orbit coupling. The
spin-flip relaxation rate has a maximum as a function of the spin-orbit
coupling and is therefore suppressed in both the weak- and strong coupling
limits.",0310024v2
2003-05-30,Mesoscopic effects in adiabatic spin pumping,"We show that temporal shape modulations (pumping) of a quantum dot in the
presence of spin-orbital coupling lead to a finite dc spin current. Depending
on the strength of the spin-orbit coupling, the spin current is polarized
perpendicular to the plane of the two-dimensional electron gas, or has an
arbitrary direction subject to mesoscopic fluctuations. We analyze the
statistics of the spin and charge currents in the adiabatic limit for the full
cross-over from weak to strong spin-orbit coupling.",0306001v2
2003-10-06,Spin Current in Spin-Orbit Coupling Systems,"We present a simple and pedagogical derivation of the spin current as the
linear response to an external electric field for both Rashba and Luttinger
spin-orbital coupling Hamiltonians. Except for the adiabatic approximation, our
derivation is exact to the linear order of the electric field for both models.
The spin current is a direct result of the difference in occupation levels
between different bands. Moreover, we show a general topological spin current
can be defined for a broad class of spin-orbit coupling systems.",0310093v2
2006-04-21,Dissipationless spin-current between Heisenberg ferromagnets with spin-orbit coupling,"A system exhibiting multiple simultaneously broken symmetries offers the
opportunity to influence physical phenomena such as tunneling currents by means
of external control parameters. Time-reversal symmetry and inversion symmetry
are both absent in ferromagnetic metals with substantial spin-orbit coupling.
We here study transport of spin in a system consisting of two ferromagnets with
spin-orbit coupling separated by an insulating tunneling junction. A persistent
spin-current across the junction is found, which can be controlled in a
well-defined manner by external magnetic and electric fields. The behavior of
the spin-current for important geometries and limits is studied.",0604510v1
2007-08-27,Diffusive-Ballistic Crossover and the Persistent Spin Helix,"Conventional transport theory focuses on either the diffusive or ballistic
regimes and neglects the crossover region between the two. In the presence of
spin-orbit coupling, the transport equations are known only in the diffusive
regime, where the spin precession angle is small. In this paper, we develop a
semiclassical theory of transport valid throughout the diffusive - ballistic
crossover of a special SU(2) symmetric spin-orbit coupled system. The theory is
also valid in the physically interesting regime where the spin precession angle
is large. We obtain exact expressions for the density and spin structure
factors in both 2 and 3 dimensional samples with spin-orbit coupling.",0708.3618v1
2014-03-17,Single-parameter spin-pumping in driven metallic rings with spin-orbit coupling,"We consider the generation of a pure spin-current at zero bias voltage with a
single time-dependent potential. To such end we study a device made of a
mesoscopic ring connected to electrodes and clarify the interplay between a
magnetic flux, spin-orbit coupling and non-adiabatic driving in the production
of a spin and electrical current. By using Floquet theory, we show that the
generated spin to charge current ratio can be controlled by tuning the
spin-orbit coupling.",1403.4265v1
2005-03-07,Topological Orbital Angular Momentum Hall Current,"We show that there is a fundamental difference between spin Hall current and
orbital angular momentum Hall current in Rashba- Dresselhaus spin orbit
coupling systems. The orbital angular momentum Hall current has a pure
topological contribution which is originated from the existence of magnetic
flux in momentum space while there is no such topological nature for the spin
Hall current. Moreover, we show that the orbital Hall conductance is always
larger than the spin Hall conductance in the presence of both couplings. The
topological part is expected to be free from the effect of disorder due to the
topological nature. Therefore, the orbital angular momentum Hall current should
be the major effect in real experiments.",0503149v2
2016-07-19,Emergent spin-valley-orbital physics by spontaneous parity breaking,"The spin-orbit coupling in the absence of spatial inversion symmetry plays an
important role in realizing intriguing electronic states in solids, such as
topological insulators and unconventional superconductivity. Usually, the
inversion symmetry breaking is inherent in the lattice structures, and hence,
it is not easy to control these interesting properties by external parameters.
We here theoretically investigate the possibility of generating the
spin-orbital entanglement by spontaneous electronic ordering caused by electron
correlations. In particular, we focus on the centrosymmetric lattices with
local asymmetry at the lattice sites, e.g., zig-zag, honeycomb, and diamond
structures. In such systems, conventional staggered orders, such as charge
order and antiferromagnetic order, break the inversion symmetry and activate
the antisymmetric spin-orbit coupling, which is hidden in a
sublattice-dependent form in the paramagnetic state. Considering a minimal
two-orbital model on a honeycomb lattice, we scrutinize the explicit form of
the antisymmetric spin-orbit coupling for all the possible staggered charge,
spin, orbital, and spin-orbital orders. We show that the complete table is
useful for understanding of spin-valley-orbital physics, such as spin and
valley splitting in the electronic band structure and generalized
magnetoelectric responses in not only spin but also orbital and spin-orbital
channels, reflecting in peculiar magnetic, elastic, and optical properties in
solids.",1607.05782v1
2022-07-21,"Spin-orbit transitions in the N$^+$($^3P_{J_A}$) + H$_2$ $\rightarrow$ NH$^+$($X^2Π$, $^4Σ^-$)+ H($^2S$) reaction, using adiabatic and mixed quantum-adiabatic statistical approaches","The cross section and rate constants for the title reaction are calculated
for all the spin-orbit states of N$^+$($^3P_{J_A}$) using two statistical
approaches, one purely adiabatic and the other one mixing quantum capture for
the entrance channel and adiabatic treatment for the products channel. This is
made by using a symmetry adapted basis set combining electronic (spin and
orbital) and nuclear angular momenta in the reactants channel. To this aim,
accurate {\it ab initio} calculations are performed separately for reactants
and products. In the reactants channel, the three lowest electronic states
(without spin-orbit couplings) have been diabatized, and the spin-orbit
couplings have been introduced through a model localizing the spin-orbit
interactions in the N$^+$ atom, which yields accurate results as compared to
{\it ab initio} calculations including spin-orbit couplings. For the products,
eleven purely adiabatic spin-orbit states have been determined with {\it ab
initio} calculations. The reactive rate constants thus obtained are in very
good agreement with the available experimental data for several ortho-H$_2$
fractions, assuming a thermal initial distribution of spin-orbit states. The
rate constants for selected spin-orbit $J_A$ states are obtained, to provide a
proper validation of the spin-orbit effects to obtain the experimental rate
constants.",2207.10360v1
2016-01-28,Interfacial spin-orbit torque without bulk spin-orbit coupling,"An electric current in the presence of spin-orbit coupling can generate a
spin accumulation that exerts torques on a nearby magnetization. We demonstrate
that, even in the absence of materials with strong bulk spin-orbit coupling, a
torque can arise solely due to interfacial spin-orbit coupling, namely
Rashba-Eldestein effects at metal/insulator interfaces. In magnetically soft
NiFe sandwiched between a weak spin-orbit metal (Ti) and insulator
(Al$_2$O$_3$), this torque appears as an effective field, which is
significantly larger than the Oersted field and sensitive to insertion of an
additional layer between NiFe and Al$_2$O$_3$. Our findings point to new routes
for tuning spin-orbit torques by engineering interfacial electric dipoles.",1601.07687v2
2023-06-05,Accurate and efficient treatment of spin-orbit coupling via second variation employing local orbitals,"A new method is presented that allows for efficient evaluation of spin-orbit
coupling (SOC) in density-functional theory calculations. In the so-called
second-variational scheme, where Kohn-Sham functions obtained in a
scalar-relativistic calculation are employed as a new basis for the
spin-orbit-coupled problem, we introduce a rich set of local orbitals as
additional basis functions. Also relativistic local orbitals can be used. The
method is implemented in the all-electron full-potential code \exciting. We
show that, for materials with strong SOC effects, this approach can reduce the
overall basis-set size and thus computational costs tremendously.",2306.02965v1
2011-06-26,Intrinsic spin-orbit coupling in superconducting δ-doped SrTiO3 heterostructures,"We report the violation of the Pauli limit due to intrinsic spin-orbit
coupling in SrTiO3 heterostructures. Via selective doping down to a few
nanometers, a two-dimensional superconductor is formed, geometrically
suppressing orbital pair-breaking. The spin-orbit scattering is exposed by the
robust in-plane superconducting upper critical field, exceeding the Pauli limit
by a factor of 4. Transport scattering times several orders of magnitude higher
than for conventional thin film superconductors enables a new regime to be
entered, where spin-orbit coupling effects arise non-perturbatively.",1106.5193v1
2020-01-23,Bright solitons in a spin-tensor-momentum-coupled Bose-Einstein condensate,"Synthetic spin-tensor-momentum coupling has recently been proposed to realize
in atomic Bose-Einstein condensates. Here we study bright solitons in
Bose-Einstein condensates with spin-tensor-momentum coupling and spin-orbit
coupling. The properties and dynamics of spin-tensor-momentum-coupled and
spin-orbit-coupled bright solitons are identified to be different. We
contribute the difference to the different symmetries.",2001.08794v1
2022-01-17,Spin-orbit-coupled superconductivity with spin-singlet non-unitary pairing,"An unconventional superconductor is distinguished with two types of gap
functions: unitary and non-unitary. This core subject has been concentrated on
purely spin-triplet or singlet-triplet mixed superconductors. However, the
generalization to a purely spin-singlet superconductor has remained primarily
of theoretical interest, which requires at least a multi-orbital correlated
electronic systems. In this work, we present a possible establishment of both
unitary and non-unitary pairings for spin-singlet superconductors with two
atomic orbitals. Then we investigate the effects of atomic spin-orbit coupling
and find a new spin-orbit-coupled non-unitary superconductor that supports
exotic phenomena. Remarkably, there are mainly three features. Firstly, the
atomic spin-orbit coupling locks the electron spins to be out-of-plane, which
could give birth to the Type II Ising superconductivity with a large in-plane
upper critical field compared to the Pauli limit. Secondly, topological chiral
or helical Majorana edge state could be realized even in the absence of
external magnetic fields or Zeeman fields. In addition, a spin-polarized
superconducting state could even be generated by spin-singlet non-unitary
pairings with spontaneous time-reversal breaking, which severs as a smoking gun
to detect this exotic state by measuring the spin-resolved density of states.
Therefore, our work might pave a new avenue to spin-orbit-coupled
superconductors with spin-singlet non-unitary pairing symmetries.",2201.06265v2
2017-12-08,Spin-orbit coupling induced valley Hall effects in transition-metal dichalcogenides,"In transition-metal dichalcogenides, electrons in the K-valleys can
experience both Ising and Rashba spin-orbit couplings. In this work, we show
that the coexistence of Ising and Rashba spin-orbit couplings leads to a
special type of valley Hall effect, which we call spin-orbit coupling induced
valley Hall effect. Importantly, near the conduction band edge, the
valley-dependent Berry curvatures generated by spin-orbit couplings are highly
tunable by external gates and dominate over the intrinsic Berry curvatures
originating from orbital degrees of freedom under accessible experimental
conditions. We show that the spin-orbit coupling induced valley Hall effect is
manifested in the gate dependence of the valley Hall conductivity, which can be
detected by Kerr effect experiments.",1712.02942v2
2003-06-27,Orbital moment in CoO and in NiO,"The total, orbital and spin moment of the Co2+ ion in CoO has been calculated
within the quasi-atomic approach with taking into account strong correlations,
crystal-field interactions and the intra-atomic spin-orbit coupling. The
orbital moment of 1.39 \mu B amounts at 0 K, in the magnetically-ordered state,
to more than 34% of the total moment (4.01 \mu B). The same calculations yield
for NiO the orbital and total moment of 0.46 \mu B and 2.45 \mu B,
respectively.
  PACS No: 71.70.E; 75.10.D
  Keywords: 3d magnetism, crystal field, spin-orbit coupling, orbital moment,
CoO, NiO",0306695v2
2008-02-10,Coupling of Spin and Orbital Motion of Electrons in Carbon Nanotubes,"Electrons in atoms possess both spin and orbital degrees of freedom. In
non-relativistic quantum mechanics, these are independent, resulting in large
degeneracies in atomic spectra. However, relativistic effects couple the spin
and orbital motion leading to the well-known fine structure in their spectra.
The electronic states in defect-free carbon nanotubes (NTs) are widely believed
to be four-fold degenerate, due to independent spin and orbital symmetries, and
to also possess electron-hole symmetry. Here we report measurements
demonstrating that in clean NTs the spin and orbital motion of electrons are
coupled, thereby breaking all of these symmetries. This spin-orbit coupling is
directly observed as a splitting of the four-fold degeneracy of a single
electron in ultra-clean quantum dots. The coupling favours parallel alignment
of the orbital and spin magnetic moments for electrons and anti-parallel
alignment for holes. Our measurements are consistent with recent theories that
predict the existence of spin-orbit coupling in curved graphene and describe it
as a spin-dependent topological phase in NTs. Our findings have important
implications for spin-based applications in carbon-based systems, entailing new
design principles for the realization of qubits in NTs and providing a
mechanism for all-electrical control of spins in NTs.",0802.1351v1
2013-09-16,Spin Hot Spots in Single-Electron GaAs-based Quantum Dots,"Spin relaxation of a single electron in a weakly coupled double quantum dot
is calculated numerically. The phonon assisted spin flip is allowed by the
presence of the linear and cubic spin-orbit couplings and nuclear spins. The
rate is calculated as a function of the interdot coupling, the magnetic field
strength and orientation, and the dot bias. In an in-plane magnetic field, the
rate is strongly anisotropic with respect to the magnetic field orientation,
due to the anisotropy of the spin-orbit interactions. The nuclear spin
influence is negligible. In an out-of-plane field, the nuclear spins play a
more important role due selection rules imposed on the spin-orbit couplings.
Our theory shows a very good agreement with data measured in [Srinivasa, et
al., PRL 110, 196803 (2013)], allowing us to extract information on the linear
spin-orbit interactions strengths in that experiment. We estimate that they
correspond to spin-orbit lengths of about 5-15 $\mu$m.",1309.3852v1
2015-02-18,Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots,"The central-spin problem, in which an electron spin interacts with a nuclear
spin bath, is a widely studied model of quantum decoherence. Dynamic nuclear
polarization (DNP) occurs in central spin systems when electronic angular
momentum is transferred to nuclear spins and is exploited in spin-based quantum
information processing for coherent electron and nuclear spin control. However,
the mechanisms limiting DNP remain only partially understood. Here, we show
that spin-orbit coupling quenches DNP in a GaAs double quantum dot, even though
spin-orbit coupling in GaAs is weak. Using Landau-Zener sweeps, we measure the
dependence of the electron spin-flip probability on the strength and direction
of in-plane magnetic field, allowing us to distinguish effects of the
spin-orbit and hyperfine interactions. To confirm our interpretation, we
measure high-bandwidth correlations in the electron spin-flip probability and
attain results consistent with a significant spin-orbit contribution. We
observe that DNP is quenched when the spin-orbit component exceeds the
hyperfine, in agreement with a theoretical model. Our results shed new light on
the surprising competition between the spin-orbit and hyperfine interactions in
central-spin systems.",1502.05400v1
2003-10-08,Efficient electron spin manipulation in a quantum well by an in-plane electric field,"Electron spins in a semiconductor quantum well couple to an electric field
{\it via} spin-orbit interaction. We show that the standard spin-orbit coupling
mechanisms can provide extraordinary efficient electron spin manipulation by an
in-plane ac electric field.",0310192v1
2007-07-26,Quasiclassical approach and spin-orbit coupling,"We discuss the quasiclassical Green function method for a two-dimensional
electron gas in the presence of spin-orbit coupling, with emphasis on the
meaning of the $\xi$-integration procedure. As an application of our approach,
we demonstrate how the spin-Hall conductivity, in the presence of spin-flip
scattering, can be easily obtained from the spin-density continuity equation.",0707.3908v1
2007-06-04,Kinetic investigation on extrinsic spin Hall effect induced by skew scattering,"The kinetics of the extrinsic spin Hall conductivity induced by the skew
scattering is performed from the fully microscopic kinetic spin Bloch equation
approach in $(001)$ GaAs symmetric quantum well. In the steady state, the
extrinsic spin Hall current/conductivity vanishes for the linear-$\mathbf k$
dependent spin-orbit coupling and is very small for the cubic-$\mathbf k$
dependent spin-orbit coupling. The spin precession induced by the
Dresselhaus/Rashba spin-orbit coupling plays a very important role in the
vanishment of the extrinsic spin Hall conductivity in the steady state. An
in-plane spin polarization is induced by the skew scattering, with the help of
the spin-orbit coupling. This spin polarization is very different from the
current-induced spin polarization.",0706.0370v2
2013-02-05,Inertial effect on spin orbit coupling and spin transport,"We theoretically study the renormalization of inertial effects on the spin
dependent transport of conduction electrons in a semiconductor by taking into
account the interband mixing on the basis of k.p perturbation theory. In our
analysis, for the generation of spin current we have used the extended Drude
model where the spin orbit coupling plays an important role. We predict
enhancement of the spin current resulting from the rerormalized spin orbit
coupling effective in our model in cubic and non cubic crystal. Attention has
been paid to clarify the importance of gauge fields in the spin transport of
this inertial system. A theoretical proposition of a perfect spin filter has
been done through the Aharanov Casher like phase corresponding to this inertial
system. For a time dependent acceleration, effect of $\vec{k} . \vec{p}$
perturbation on the spin current and spin polarization has also been addressed.
Furthermore, achievement of a tunable source of polarized spin current through
the non uniformity of the inertial spin orbit coupling strength has also been
discussed.",1302.1063v3
2020-02-04,Isotropic All-electric Spin analyzer based on a quantum ring with spin-orbit coupling,"Here we propose an isotropic all electrical spin analyzer in a quantum ring
with spin-orbit coupling by analytically and numerically modeling how the
charge transmission rates depend on the polarization of the incident spin. The
formalism of spin transmission and polarization rates in an arbitrary direction
is also developed by analyzing the Aharonov-Bohm and the Aharonov-Casher
effects. The topological spin texture induced by the spin-orbit couplings
essentially contributes to the dynamic phase and plays an important role in
spin transport. The spin transport features derived analytically has been
confirmed numerically. This interesting two-dimensional electron system can be
designed as a spin filter, spin polarizer and general analyzer by simply tuning
the spin-orbit couplings, which paves the way for realizing the tunable and
integrable spintronics device.",2002.01151v1
2006-02-23,Spin-orbit interaction in quantum dots in the presence of exchange correlations,"We discuss the problem of spin-orbit interaction in a 2D chaotic or diffusive
quantum dot in the presence of exchange correlations. Spin-orbit scattering
breaks spin rotation invariance, and in the crossover regime between different
symmetries of the spin-orbit coupling, the problem has no closed solution. A
conventional choice of a many-particle basis in a numerical diagonalization is
the set of Slater determinants built from the single-particle eigenstates of
the one-body Hamiltonian (including the spin-orbit terms). We develop a
different approach based on the use of a good-spin many-particle basis that is
composed of the eigenstates of the universal Hamiltonian in the absence of
spin-orbit scattering. We introduce a complete labelling of this good-spin
basis and use angular momentum algebra to calculate in closed form the matrix
elements of the spin-orbit interaction in this basis. Spin properties, such as
the ground-state spin distribution and the spin excitation function, are easily
calculated in this basis.",0602552v1
2011-10-30,Quasiparticle velocities in 2D electron/hole liquids with spin-orbit coupling,"We study the influence of spin-orbit interactions on quasiparticle
dispersions in two-dimensional electron and heavy-hole liquids in III-V
semiconductors. To obtain closed-form analytical results, we restrict ourselves
to spin-orbit interactions with isotropic spectrum and work within the screened
Hartree-Fock approximation, valid in the high-density limit. For electrons
having a linear-in-momentum Rashba (or, equivalently, Dresselhaus) spin-orbit
interaction, we show that the screened Hartree-Fock approximation recovers
known results based on the random-phase approximation and we extend those
results to higher order in the spin-orbit coupling. While the well-studied case
of electrons leads only to a weak modification of quasiparticle properties in
the presence of the linear-in-momentum spin-orbit interaction, we find two
important distinctions for hole systems (with a leading nonlinear-in-momentum
spin-orbit interaction). First, the group velocities associated with the two
hole-spin branches acquire a significant difference in the presence of
spin-orbit interactions, allowing for the creation of spin-polarized
wavepackets in zero magnetic field. Second, we find that the interplay of
Coulomb and spin-orbit interactions is significantly more important for holes
than for electrons and can be probed through the quasiparticle group
velocities. These effects should be directly observable in magnetotransport,
Raman scattering, and femtosecond-resolved Faraday rotation measurements. Our
results are in agreement with a general argument on the velocities, which we
formulate for an arbitrary choice of the spin-orbit coupling.",1110.6661v2
2003-11-04,Twisted exchange interaction between localized spins embedded in a one- or two-dimensional electron gas with Rashba spin-orbit coupling,"We study theoretically the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction
in one- and two-dimensions in presence of a Rashba spin-orbit (SO) coupling. We
show that rotation of the spin of conduction electrons due to SO coupling
causes a twisted RKKY interaction between localized spins which consists of
three different terms: Heisenberg, Dzyaloshinsky-Moriya, and Ising
interactions. We also show that the effective spin Hamiltonian reduces to the
usual RKKY interaction Hamiltonian in the twisted spin space where the spin
quantization axis of one localized spin is rotated.",0311054v1
2005-07-13,Role of spin-orbit coupling on the spin triplet pairing in Na_{x}CoO_{2}yH_{2}O I: d-vector under zero magnetic field,"The d-vector in possibile spin triplet superconductor Na_{x}CoO_{2}yH_{2}O is
microscopically investigated on the basis of the multi-orbital Hubbard model
including the atomic spin-orbit coupling. As a result of the perturbation
theory, we obtain the stable spin triplet superconductivity where the p-wave
and f-wave states can be stabilized. If we neglect the spin-orbit coupling,
superconducting state has 6-fold (3-fold) degeneracy in the p-wave (f-wave)
state. This degeneracy is lifted by the spin-orbit coupling. We determine the
d-vector within the linearlized Dyson-Gorkov equation. It is shown that the
d-vector is always along the plane when the pairing symmetry is p-wave, while
it depends on the parameters in case of the f-wave state. The lifting of
degeneracy is significant in the p-wave state while it is very small in the
f-wave state. This is because the first order term with respect to the
spin-orbit coupling is effective in the former case, while it is ineffective in
the latter case. The consistency of these results with NMR and \muSR
measurements are discussed.",0507305v1
2015-03-02,The Kondo Temperature of a Two-dimensional Electron Gas with Rashba Spin-orbit Coupling,"We use the Hirsch-Fye quantum Monte Carlo method to study the single magnetic
impurity problem in a two-dimensional electron gas with Rashba spin-orbit
coupling. We calculate the spin susceptibility for various values of spin-orbit
coupling, Hubbard interaction, and chemical potential. The Kondo temperatures
for different parameters are estimated by fitting the universal curves of spin
susceptibility. We find that the Kondo temperature is almost a linear function
of Rashba spin-orbit energy when the chemical potential is close to the edge of
the conduction band. When the chemical potential is far away from the band
edge, the Kondo temperature is independent of the spin-orbit coupling. These
results demonstrate that, for single impurity problem in this system, the most
important reason to change the Kondo temperature is the divergence of density
of states near the band edge, and the divergence is induced by the Rashba
spin-orbit coupling.",1503.00449v2
2013-09-05,Current-induced torques and interfacial spin-orbit coupling,"In bilayer systems consisting of an ultrathin ferromagnetic layer adjacent to
a metal with strong spin-orbit coupling, an applied in-plane current induces
torques on the magnetization. The torques that arise from spin-orbit coupling
are of particular interest. Here, we calculate the current-induced torque in a
Pt-Co bilayer to help determine the underlying mechanism using first principles
methods. We focus exclusively on the analogue to the Rashba torque, and do not
consider the spin Hall effect. The details of the torque depend strongly on the
layer thicknesses and the interface structure, providing an explanation for the
wide variation in results found by different groups. The torque depends on the
magnetization direction in a way similar to that found for a simple Rashba
model. Artificially turning off the exchange spin splitting and separately the
spin-orbit coupling potential in the Pt shows that the primary source of the
""field-like"" torque is a proximate spin-orbit effect on the Co layer induced by
the strong spin-orbit coupling in the Pt.",1309.1356v1
2022-04-25,Harmonic generation in bent graphene with artificially-enhanced spin-orbit coupling,"We theoretically investigate the nonlinear response of bent graphene, in the
presence of artificially-enhanced spin-orbit coupling, which can occur either
via adatom deposition, or by placing the sheet of bent graphene in contact with
a spin-orbit active substrate. We discuss the interplay between the spin-orbit
coupling and the artificial magnetic field generated by the bending, for both
the cases of Rashba and intrinsic spin-orbit coupling. For the latter, we
introduce a spin-field interaction Hamiltonian addressing directly the electron
spin as a degree of freedom. Our findings reveal that in this case, by
controlling the amount of spin-orbit coupling, it is possible to significantly
tune the spectrum of the nonlinear signal, achieving, in principle, efficient
conversion of light from THz to UV region.",2204.11664v3
2009-04-07,Curvature-enhanced spin-orbit coupling in a carbon nanotube,"Structure of the spin-orbit coupling varies from material to material and
thus finding the correct spin-orbit coupling structure is an important step
towards advanced spintronic applications. We show theoretically that the
curvature in a carbon nanotube generates two types of the spin-orbit coupling,
one of which was not recognized before. In addition to the topological
phase-related contribution of the spin-orbit coupling, which appears in the
off-diagonal part of the effective Dirac Hamiltonian of carbon nanotubes, there
is another contribution that appears in the diagonal part. The existence of the
diagonal term can modify spin-orbit coupling effects qualitatively, an example
of which is the electron-hole asymmetric spin splitting observed recently, and
generate four qualitatively different behavior of energy level dependence on
parallel magnetic field. It is demonstrated that the diagonal term applies to a
curved graphene as well. This result should be valuable for spintronic
applications of graphitic materials.",0904.1185v2
2020-03-23,Spin-orbit-coupling-assisted roton softening and superstripes in a Rydberg-dressed Bose-Einstein Condensate,"Rotons can exist in ultracold atomic gases either with long-range
interactions or with spin-orbitcoupled dispersions. We find that two different
kinds of rotons coexist in a joint system combining long-range interactions and
spin-orbit coupling. One roton originates from spin-orbit coupling and two
others come from long-range interactions. Their softening can be controlled
separately. The interesting new phenomenon which we find is that
spin-orbit-coupled roton can push down the energy of one long-range-interaction
roton. The spin-orbit coupling accelerates the softening of this roton. The
post phase of spin-orbit-coupling-assisted roton softening and instability is
identified as a superstripe.",2003.10090v2
2022-04-14,Double version of the Rashba and Dresselhaus spin-orbit coupling,"The Rashba and Dresselhaus types of spin-orbit coupling are two typical
linear coupling forms. We establish the fundamental physics of a model which
can be viewed as the double version of the Rashba and Dresselhaus spin-orbit
coupling. This model describes the low energy physics of a class of massless
Dirac fermions in spin-orbit systems. The physical properties of the massless
Dirac fermions are determined by the mathematical relations of spin-orbit
coefficients. For equal Rashba and Dresselhauss coupling constants,
k-independent eigenspinors and a persistent spin helix combined with massless
birefringent Dirac fermions emerge in this model. The spin-orbit coupled
systems described by this model have potential technological applications from
spintronics to quantum computation.",2204.06680v1
2019-04-01,Spin-charge coupled transport in van der Waals systems with random tunneling,"We study the electron and spin transport in a van der Waals system formed by
one layer with strong spin-orbit coupling and a second layer without spin-orbit
coupling, in the regime when the interlayer tunneling is random. We find that
in the layer without intrinsic spin-orbit coupling spin-charge coupled
transport can be induced by two distinct mechanisms. First, the gapless
diffusion modes of the two isolated layers hybridize in the presence of
tunneling, which constitutes a source of spin-charge coupled transport in the
second layer. Second, the random tunneling introduces spin-orbit coupling in
the effective disorder-averaged single-particle Hamiltonian of the second
layer. This results in non-trivial spin transport and, for sufficiently strong
tunneling, in spin-charge coupling. As an example, we consider a van der Waals
system formed by a two-dimensional electron gas (2DEG)--such as graphene--and
the surface of a topological insulator (TI) and show that the proximity of the
TI induces a coupling of the spin and charge transport in the 2DEG. In
addition, we show that such coupling can be tuned by varying the doping of the
TI's surface. We then obtain, for a simple geometry, the current-induced
non-equilibrium spin accumulation (Edelstein effect) caused in the 2DEG by the
coupling of charge and spin transport.",1904.01015v1
2014-11-14,Spin-orbit coupling and chaotic rotation for eccentric coorbital bodies,"The presence of a co-orbital companion induces the splitting of the well
known Keplerian spin-orbit resonances. It leads to chaotic rotation when those
resonances overlap.",1411.3950v1
2017-01-03,Universal Absence of Walker Breakdown and Linear Current-Velocity Relation via Spin-Orbit Torques in Coupled and Single Domain Wall Motion,"We consider theoretically domain wall motion driven by spin-orbit and spin
Hall torques. We find that it is possible to achieve universal absence of
Walker breakdown for all spin-orbit torques using experimentally relevant
spin-orbit coupling strengths. For spin-orbit torques other than the pure
Rashba spin-orbit torque, this gives a linear current-velocity relation instead
of a saturation of the velocity at high current densities. The effect is very
robust and is found in both soft and hard magnetic materials, as well as in the
presence of the Dzyaloshinskii-Moriya interaction and in coupled domain walls
in synthetic antiferromagnets, where it leads to very high domain wall
velocities. Moreover, recent experiments have demonstrated that the switching
of a synthetic antiferromagnet does not obey the usual spin Hall
angle-dependence, but that domain expansion and contraction can be selectively
controlled toggling only the applied in-plane magnetic field magnitude and not
its sign. We show for the first time that the combination of spin Hall torques
and interlayer exchange coupling produces the necessary relative velocities for
this switching to occur.",1701.00786v2
2024-04-09,Hydrostatic pressure control of the spin-orbit proximity effect and spin relaxation in a phosphorene-WSe$_2$ heterostructure,"Effective control of interlayer interactions is a key element in modifying
the properties of van der Waals heterostructures and the next step toward their
practical applications. Focusing on the phosphorene-WSe$_2$ heterostructure, we
demonstrate, using first-principles calculations, how the spin-orbit coupling
can be transferred from WSe$_2$, a strong spin-orbit coupling material, to
phosphorene and further amplified by applying vertical pressure. We simulate
external pressure by changing the interlayer distance between bilayer
constituents and show that it is possible to tune the spin-orbit field of
phosphorene holes in a controllable way. By fitting effective electronic states
of the proposed Hamiltonian to the first principles data, we reveal that the
spin-orbit coupling in phosphorene hole bands is enhanced more than two times
for experimentally accessible pressures up to 17 kbar. Finally, we find that
the pressure-enhanced spin-orbit coupling boosts the Dyakonov-Perel spin
relaxation mechanism, reducing the spin lifetime of phosphorene holes by factor
4.",2404.06097v1
2019-03-08,Intra- and inter-orbital correlated electron spin dynamics in $\rm Sr_2 Ir O_4$: spin-wave gap and spin-orbit exciton,"Transformation of Coulomb interaction terms to the pseudo-orbital basis
constituted by $J=1/2$ and $3/2$ states arising from spin-orbit coupling
provides a versatile tool. This formalism is applied to investigate magnetic
anisotropy effects on low-energy spin-wave excitations as well as high-energy
spin-orbit exciton modes in $\rm Sr_2 Ir O_4$. The Hund's coupling term
explictly yields easy-plane anisotropy, resulting in gapless (in-plane) and
gapped (out-of-plane) modes, in agreement with recent resonant inelastic x-ray
scattering (RIXS) measurements. The collective mode of inter-orbital,
spin-flip, particle-hole excitations with appropriate interaction strengths and
renormalized spin-orbit gap yields two well-defined propagating spin-orbit
exciton modes, with energy scale and dispersion in good agreement with RIXS
studies.",1903.03360v1
2005-11-22,Entanglement production in chaotic quantum dots subject to spin-orbit coupling,"We study numerically the production of orbital and spin entangled states in
chaotic quantum dots for non-interacting electrons. The introduction of
spin-orbit coupling permit us to identify signatures of time-reversal symmetry
correlations in the entanglement production previously unnoticed, resembling
weak-(anti)localization quantum corrections to the conductance. We find the
entanglement to be strongly dependent on spin-orbit coupling, showing universal
features for broken time-reversal and spin-rotation symmetries.",0511555v3
2007-07-30,Temperature Dependence of Rashba Spin-orbit Coupling in Quantum Wells,"We perform an all-optical spin-dynamic measurement of the Rashba spin-orbit
interaction in (110)-oriented GaAs/AlGaAs quantum wells. The crystallographic
direction of quantum confinement allows us to disentangle the contributions to
spin-orbit coupling from the structural inversion asymmetry (Rashba term) and
the bulk inversion asymmetry. We observe an unexpected temperature dependence
of the Rashba spin-orbit interaction strength that signifies the importance of
the usually neglected higher-order terms of the Rashba coupling.",0707.4493v1
2007-08-19,Coupling of electron rotation with spin in semiconductors,"Account of an intrinsic spin-orbit coupling in the valence bands of common
semiconductors yields the scalar spin-orbit-rotation term in the effective-mass
Hamiltonian of the conduction-band electron. This result is obtained within the
multiband envelope function approximation. Fundamentally, the
spin-orbit-rotation coupling can be described in purely geometric terms as a
consequence of the difference in the Berry phase acquired by the components of
the spin-orbitally mixed Kramers-doublet during its cyclic evolution in the
reciprocal momentum space.",0708.2565v2
2019-09-01,Switchable Josephson current in junctions with spin-orbit coupling,"We study the Josephson current in two types of lateral junctions with
spin-orbit coupling and an exchange field. The first system (type 1 junction)
consists of superconductors with heavy metal interlayers linked by a
ferromagnetic bridge, such that the spin-orbit coupling is finite only at the
superconductor/heavy metal interface. In the second type (type 2) of system we
assume that the spin orbit coupling is finite in the bridge region. The length
of both junctions is larger than the magnetic decay length such that the
Josephson current is carried uniquely by the long-range triplet component of
the condensate. The latter is generated by the spin-orbit coupling via two
mechanisms, spin precession and inhomogeneous spin-relaxation. We show that the
current can be controlled by rotating the magnetization of the bridge or by
tuning the strength of the spin-orbit coupling in type 2 junctions., and also
discuss how the ground-state of the junction can be tuned from a $0$ to a $\pi$
phase difference between the superconducting electrodes. In leading order in
the spin-orbit coupling, the spin precession dominates the behavior of the
triplet component and both
  junctions behave similarly. However, when spin relaxation effects are
included junction of type 2 offers a wider parameter range in which $0$-$\pi$
transitions take place.",1909.00401v1
2004-06-29,Spin current and polarization in impure 2D electron systems with spin-orbit coupling,"We derive the transport equations for two-dimensional electron systems with
spin-orbit interaction and short-range spin-independent disorder. In the limit
of slow spatial variations of the electron distribution we obtain coupled
diffusion equations for the electron density and spin. Using these equations we
calculate electric-field induced spin accumulation in a finite-size sample for
arbitrary ratio between spin-orbit energy splitting and elastic scattering
rate. We demonstrate that the spin-Hall conductivity vanishes in an infinite
system independent of this ratio.",0406730v2
2011-11-23,Rashba spin torque in an ultrathin ferromagnetic metal layer,"In a two-dimensional ferromagnetic metal layer lacking inversion symmetry,
the itinerant electrons mediate the interaction between the Rashba spin-orbit
interaction and the ferromagnetic order parameter, leading to a Rashba spin
torque exerted on the magnetization. Using Keldysh technique, in the presence
of both magnetism and a spin-orbit coupling, we derive a spin diffusion
equation that provides a coherent description to the diffusive spin dynamics.
The characteristics of the spin torque and its implication on magnetization
dynamics are discussed in the limits of large and weak spin-orbit coupling.",1111.5466v1
2016-08-07,Spin-orbit coupling in Fe-based superconductors,"We study the spin resonance peak in recently discovered iron-based
superconductors. The resonance peak observed in inelastic neutron scattering
experiments agrees well with predicted results for the extended $s$-wave
($s_\pm$) gap symmetry. Recent neutron scattering measurements show that there
is a disparity between longitudinal and transverse components of the dynamical
spin susceptibility. Such breaking of the spin-rotational invariance in the
spin-liquid phase can occur due to spin-orbit coupling. We study the role of
the spin-orbit interaction in the multiorbital model for Fe-pnictides and show
how it affects the spin resonance feature.",1608.02230v1
1995-11-26,Spin-flip scattering in the quantum Hall regime,"We present a microscopic theory of spin-orbit coupling in the integer quantum
Hall regime. The spin-orbit scattering length is evaluated in the limit of
long-range random potential. The spin-flip rate is shown to be determined by
rare fluctuations of anomalously high electric field. A mechanism of strong
spin-orbit scattering associated with exchange-induced spontaneous
spin-polarization is suggested. Scaling of the spin-splitting of the
delocalization transition with the strength of spin-orbit and exchange
interactions is also discussed.",9511123v2
2013-04-09,Spin-orbital liquids in non-Kramers magnet on Kagome lattice,"Localized magnetic moments with crystal-field doublet or pseudo-spin 1/2 may
arise in correlated insulators with even number of electrons and strong
spin-orbit coupling. Such a non-Kramers pseudo-spin 1/2 is the consequence of
crystalline symmetries as opposed to the Kramers doublet arising from
time-reversal invariance, and is necessarily a composite of spin and orbital
degrees of freedom. We investigate possible spin-orbital liquids with fermionic
spinons for such non-Kramers pseudo-spin 1/2 systems on the Kagome lattice.
Using the projective symmetry group analysis, we find {\it ten} new phases that
are not allowed in the corresponding Kramers systems. These new phases are
allowed due to unusual action of the time reversal operation on non-Kramers
pseudo-spins. We compute the spin-spin dynamic structure factor that shows
characteristic features of these non-Kramers spin-orbital liquids arising from
their unusual coupling to neutrons, which is therefore relevant for neutron
scattering experiments. We also point out possible anomalous broadening of
Raman scattering intensity that may serve as a signature experimental feature
for gapless non-Kramers spin-orbital liquids.",1304.2766v1
2019-06-11,Spin imbalance of charge carriers induced by an electric current,"We analyze the contribution of the inhomogeneous magnetic field induced by an
electrical current to the spin Hall effect in metals. The Zeeman coupling
between the field and the electron spin leads to a spin dependent force, and to
spin accumulation at the edges. We compare the effect of this relativistic
correction to the electron dynamics to the features induced by the spin-orbit
interaction. The effect of current induced magnetic fields on the spin Hall
effect can be comparable to the extrinsic contribution from the spin-orbit
interaction, although it does not require the presence of heavy elements with a
strong spin-orbit interaction. The induced spins are oriented normal to the
metal slab.",1906.04851v1
2011-10-24,Manipulation of single electron spin in a GaAs quantum dot through the application of geometric phases: The Feynman disentangling technique,"The spin of a single electron in an electrically defined quantum dot in a
2DEG can be manipulated by moving the quantum dot adiabatically in a closed
loop in the 2D plane under the influence of applied gate potentials. In this
paper we present analytical expressions and numerical simulations for the
spin-flip probabilities during the adiabatic evolution in the presence of the
Rashba and Dresselhaus linear spin-orbit interactions. We use the Feynman
disentanglement technique to determine the non-Abelian Berry phase and we find
exact analytical expressions for three special cases: (i) the pure Rashba
spin-orbit coupling, (ii) the pure Dresselhause linear spin-orbit coupling, and
(iii) the mixture of the Rashba and Dresselhaus spin-orbit couplings with equal
strength. For a mixture of the Rashba and Dresselhaus spin-orbit couplings with
unequal strengths, we obtain simulation results by solving numerically the
Riccati equation originating from the disentangling procedure. We find that the
spin-flip probability in the presence of the mixed spin-orbit couplings is
generally larger than those for the pure Rashba case and for the pure
Dresselhaus case, and that the complete spin-flip takes place only when the
Rashba and Dresselhaus spin-orbit couplings are mixed symmetrically.",1110.5366v1
2022-02-10,Local breaking of the spin degeneracy in the vortex states of Ising superconductors: Induced antiphase ferromagnetic order,"Ising spin-orbital coupling is usually easy to identify in the Ising
superconductors via an in-plane critical field enhancement, but we show that
the Ising spin-orbital coupling also manifests in the vortex physics for
perpendicular magnetic fields. By self-consistently solving the Bogoliubov-de
Gennes equations of a model Hamiltonian built on the honeycomb lattice with the
Ising spin-orbital coupling pertinent to the transition metal dichalcogenides,
we numerically investigate the local breaking of the spin and sublattice
degeneracies in the presence of a perpendicular magnetic field. It is revealed
that the ferromagnetic orders are induced inside the vortex core region by the
Ising spin-orbital coupling. The induced magnetic orders are antiphase in terms
of their opposite polarizations inside the two nearest-neighbor vortices with
one of the two polarizations coming dominantly from one sublattice sites,
implying the local breaking of the spin and sublattice degeneracies. The
finite-energy peaks of the local-density-of-states for spin-up and spin-down
in-gap states are split and shifted oppositely by the Ising spin-orbital
coupling, and the relative shifts of them on sublattices $A$ and $B$ are also
of opposite algebraic sign. The calculated results and the proposed scenario
may not only serve as experimental signatures for identifying the Ising
spin-orbital coupling in the Ising superconductors, but also be prospective in
manipulation of electron spins in motion through the orbital effect in the
superconducting vortex states.",2202.04797v1
2011-01-27,Magnetic excitations in one-dimensional spin-orbital models,"We study the dynamics and thermodynamics of one-dimensional spin-orbital
models relevant for transition metal oxides. We show that collective spin,
orbital, and combined spin-orbital excitations with infinite lifetime can
exist, if the ground state of both sectors is ferromagnetic. Our main focus is
the case of effectively ferromagnetic (antiferromagnetic) exchange for the spin
(orbital) sector, respectively, and we investigate the renormalization of spin
excitations via spin-orbital fluctuations using a boson-fermion representation.
We contrast a mean-field decoupling approach with results obtained by treating
the spin-orbital coupling perturbatively. Within the latter self-consistent
approach we find a significant increase of the linewidth and additional
structures in the dynamical spin structure factor as well as Kohn anomalies in
the spin-wave dispersion caused by the scattering of spin excitations from
orbital fluctuations. Finally, we analyze the specific heat c(T) by comparing a
numerical solution of the model obtained by the density-matrix renormalization
group with perturbative results. At low temperatures T we find numerically c(T)
T pointing to a low-energy effective theory with dynamical critical exponent
z=1.",1101.5301v1
2016-10-05,Exotic orbits due to spin-spin coupling around Kerr black holes,"We report exotic orbital phenomena of spinning test particles orbiting around
a Kerr black hole, i.e., some orbits of spinning particles are asymmetrical
about the equatorial plane. When a nonspinning test particle orbits around a
Kerr black hole in a strong field region, due to relativistic orbital
precessions, the pattern of trajectories is symmetrical about the equatorial
plane of the Kerr black hole. However, the patterns of the spinning particles'
orbit are no longer symmetrical about the equatorial plane for some orbital
configurations and large spins. We argue that these asymmetrical patterns come
from the spin-spin interactions between spinning particles and Kerr black
holes, because the directions of spin-spin forces can be arbitrary, and
distribute asymmetrically about the equatorial plane.",1610.01534v3
2023-11-01,Theory of Orbital Pumping,"We develop a theory of orbital pumping, which corresponds to the emission of
orbital currents from orbital dynamics. This phenomenon exhibits two distinct
characteristics compared to spin pumping. Firstly, while spin pumping generates
solely spin (angular momentum) currents, orbital pumping yields both orbital
angular momentum currents and orbital angular position currents. Secondly,
lattice vibrations induce orbital dynamics and associated orbital pumping as
the orbital angular position is directly coupled to the lattice. These pumped
orbital currents can be detected as transverse electric voltages via the
inverse orbital(-torsion) Hall effect, stemming from orbital textures. Our work
proposes a new avenue for generating orbital currents and provides a broader
understanding of angular momentum dynamics encompassing spin, orbital, and
phonon.",2311.00362v1
2016-06-18,Spin Transport at Interfaces with Spin-Orbit Coupling: Formalism,"We generalize magnetoelectronic circuit theory to account for spin transfer
to and from the atomic lattice via interfacial spin-orbit coupling. This
enables a proper treatment of spin transport at interfaces between a
ferromagnet and a heavy-metal non-magnet. This generalized approach describes
spin transport in terms of drops in spin and charge accumulations across the
interface (as in the standard approach), but additionally includes the
responses from in-plane electric fields and offsets in spin accumulations. A
key finding is that in-plane electric fields give rise to spin accumulations
and spin currents that can be polarized in any direction, generalizing the
Rashba-Edelstein and spin Hall effects. The spin accumulations exert torques on
the magnetization at the interface when they are misaligned from the
magnetization. The additional out-of-plane spin currents exert torques via the
spin-transfer mechanism on the ferromagnetic layer. To account for these
phenomena we also describe spin torques within the generalized circuit theory.
The additional effects included in this generalized circuit theory suggest
modifications in the interpretations of experiments involving spin orbit
torques, spin pumping, spin memory loss, the Rashba-Edelstein effect, and the
spin Hall magnetoresistance.",1606.05758v1
2020-03-27,Generalized magnetoelectronic circuit theory and spin relaxation at interfaces in magnetic multilayers,"Spin transport at metallic interfaces is an essential ingredient of various
spintronic device concepts, such as giant magnetoresistance, spin-transfer
torque, and spin pumping. Spin-orbit coupling plays an important role in many
such devices. In particular, spin current is partially absorbed at the
interface due to spin-orbit coupling. We develop a general magnetoelectronic
circuit theory and generalize the concept of the spin mixing conductance,
accounting for various mechanisms responsible for spin-flip scattering. For the
special case when exchange interactions dominate, we give a simple expression
for the spin mixing conductance in terms of the contributions responsible for
spin relaxation (i.e., spin memory loss), spin torque, and spin precession. The
spin-memory loss parameter $\delta$ is related to spin-flip transmission and
reflection probabilities. There is no straightforward relation between spin
torque and spin memory loss. We calculate the spin-flip scattering rates for
N|N, F|N, F|F interfaces using the Landauer-B\""uttiker method within the linear
muffin-tin orbital method and determine the values of $\delta$ using circuit
theory.",2003.12221v1
2015-11-03,Spin-Orbit Coupling Induced Back-action Cooling in Cavity-Optomechanics with a Bose-Einstein Condensate,"We report a spin-orbit coupling induced back-action cooling in an
optomechanical system, composed of a spin-orbit coupled Bose-Einstein
condensate trapped in an optical cavity with one movable end mirror, by
suppressing heating effects of quantum noises. The collective density
excitations of the spin-orbit coupling mediated hyperfine states - serving as
atomic oscillators equally coupled to the cavity field - trigger strongly
driven atomic back-action. We find that the back-action not only revamps
low-temperature dynamics of its own but also provides an opportunity to cool
the mechanical mirror to its quantum mechanical ground state. Further, we
demonstrate that the strength of spin-orbit coupling also superintends dynamic
structure factor and squeezes nonlinear quantum noises, like thermo-mechanical
and photon shot noise, which enhances optomechanical features of hybrid cavity
beyond the previous investigations. Our findings are testable in a realistic
setup and enhance the functionality of cavity-optomechanics with spin-orbit
coupled hyperfine states in the field of quantum optics and quantum
computation.",1511.01109v2
2008-06-03,Spin-Orbit Coupling in an f-electron Tight-Binding Model,"We extend a tight-binding method to include the effects of spin-orbit
coupling, and apply it to the study of the electronic properties of the
actinide elements Th, U, and Pu. These tight-binding parameters are determined
for the fcc crystal structure using the equivalent equilibrium volumes. In
terms of the single particle energies and the electronic density of states, the
overall quality of the tight-binding representation is excellent and of the
same quality as without spin-orbit coupling. The values of the optimized
tight-binding spin-orbit coupling parameters are comparable to those determined
from purely atomic calculations.",0806.0420v1
2011-07-04,Anomalous Hall conductivity from the dipole mode of spin-orbit-coupled cold-atom systems,"Motivated by recent experiments [Lin {\it et al.}, Nature {\bf 417}, 83
(2011)] that engineered spin-orbit coupling in ultra-cold mixtures of bosonic
atoms, we study the dipole oscillation of trapped spin-orbit-coupled
non-condensed Bose and Fermi gases. We find that different directions of
oscillation are coupled by the spin-orbit interactions. The phase difference
between oscillatory motion in orthogonal directions and the trapping
frequencies of the modes are shown to be related to the anomalous Hall
conductivity. Our results can be used to experimentally determine the anomalous
Hall conductivity for cold-atom systems.",1107.0578v1
2011-08-10,"Erratum: Engineering a p+ip Superconductor: Comparison of Topological Insulator and Rashba Spin-Orbit Coupled Materials [Phys. Rev. B 83, 184520 (2011)]","In this erratum, we revisit the issue of bulk-disorder on proposals to
realize an effective p+ip superconductor from spin-orbit coupled materials.
Contrary to the claim in [Phys. Rev. B 83, 184520 (2011)], we show that the
pair breaking effects of bulk-disorder are negligible, and that bulk disorder
does not suppress the induced superconductivity. This argument does not apply
to our conclusions regarding impurities residing in the spin-orbit coupled
material or disorder at the interface to the bulk superconductor, both of which
tend to suppress superconductivity unless spin-orbit coupling is large.",1108.2260v1
2013-01-16,Vortex lattice solutions to the Gross-Pitaevskii equation with spin-orbit coupling in optical lattices,"Effective spin-orbit coupling can be created in cold atom systems using
atom-light interaction. We study the BECs in an optical lattice using the
Gross-Pitaevskii equation with spin-orbit coupling. Bloch states for the linear
equation are numerically obtained, and compared with stationary solutions to
the Gross-Pitaevskii equation with nonlinear terms. Various vortex lattice
states are found when the spin-orbit coupling is strong.",1301.3565v1
2018-11-22,Enhanced Rashba spin-orbit coupling in core-shell nanowires by the interfacial effect,"We report on $\vec{k}\cdot\vec{p}$ calculations of Rashba spin-orbit coupling
controlled by external gates in InAs/InAsP core-shell nanowires. We show that
charge spilling in the barrier material allows for a stronger symmetry breaking
than in homoegenous nano-materials, inducing a specific interface-related
contribution to spin-orbit coupling. Our results qualitatively agree with
recent experiments [S. Futhemeier \textit{et al.}, Nat. Commun. \textbf{7},
12413 (2016)] and suggest additional wavefunction engineering strategies to
enhance and control spin-orbit coupling.",1811.09088v1
2017-01-17,Vortex pairs in a spin-orbit coupled Bose-Einstein condensate,"Static and dynamic properties of vortices in a two-component Bose-Einstein
condensate with Rashba spin-orbit coupling are investigated. The mass current
around a vortex core in the plane-wave phase is found to be deformed by the
spin-orbit coupling, and this makes the dynamics of the vortex pairs quite
different from those in a scalar Bose-Einstein condensate. The velocity of a
vortex-antivortex pair is much smaller than that without spin-orbit coupling,
and there exist stationary states. Two vortices with the same circulation move
away from each other or unite to form a stationary state.",1701.04591v1
2023-07-22,Spin-orbit-coupling-induced phase separation in trapped Bose gases,"In a trapped spin-1/2 Bose-Einstein condensate with miscible interactions, a
two-dimensional spin-orbit coupling can introduce an unconventional spatial
separation between the two components. We reveal the physical mechanism of such
a spin-orbit-coupling-induced phase separation. Detailed features of the phase
separation are identified in a trapped Bose-Einstein condensate. We further
analyze differences of phase separation in Rashba and anisotropic
spin-orbit-coupled Bose gases. An adiabatic splitting dynamics is proposed as
an application of the phase separation.",2307.12177v2
2000-06-30,On a q-analogue of the spin-orbit coupling,"Based on the tensor method, a q-analoque of the spin-orbit coupling is
introduced in a q-deformed Schroedinger equation, previously derived for a
central potential. Analytic expressions for the matrix elemnets of the
representation j=l\pm 1/2 are derived. The spectra of the harmonic oscillator
and the Coulomb potential are calculated numerically as a function of the
deformation parameter, without and with the spin-orbit coupling. The harmonic
oscillator spectrum presents strong analogies with the bound spectrum of an
Woods-Saxon potential customarily used in nuclear physics. The Coulomb spectrum
simulates relativistic effects. The addition of the spin-orbit coupling
reinforces this picture.",0006081v1
2011-10-28,Artificial spin-orbit coupling in ultra-cold Fermi superfluids,"We develop a theory for interacting fermions in the presence of spin-orbit
coupling and Zeeman fields, and show that many new superfluids phases, which
are topological in nature, emerge. Depending on values of spin-orbit coupling,
Zeeman fields, and interactions, initially gapped s-wave superfluids acquire
p-wave, d-wave, f-wave and higher angular momentum components, which produce
zeros in the excitation spectrum, rendering the superfluid gapless. Several
multi-critical points, which separate topological superfluid phases from normal
or non-uniform, are accessible depending on spin-orbit coupling, Zeeman fields
or interactions, setting the stage for the study of tunable topological
superfluids.",1110.6364v1
2014-01-03,Spin-Orbit Coupled Bose Gases at Finite Temperatures,"Spin-orbit coupling is predicted to have dramatic effects on thermal
properties of a two-component atomic Bose gas. We show that in three spatial
dimensions it lowers the critical temperature of condensation and enhances
thermal depletion of the condensate fraction. In two dimensions we show that
spin-orbit coupling destroys superfluidity at any finite temperature, modifying
dramatically the cerebrated Berezinskii-Kosterlitz-Thouless scenario. We
explain this by the increase of the number of low energy states induced by
spin-orbit coupling, enhancing the role of quantum fluctuations.",1401.0575v1
2021-09-07,Creating moving gap solitons in spin-orbit-coupled Bose-Einstein condensates,"A simple and efficient method to create gap solitons is proposed in a
spin-orbit-coupled spin-1 Bose-Einstein condensate. We find that a free
expansion along the spin-orbit coupling dimension can generate two moving gap
solitons, which are identified from a generalized massive Thirring model. The
dynamics of gap solitons can be controlled by adjusting spin-orbit coupling
parameters.",2109.02871v1
2023-02-10,Patterning by dynamically unstable spin-orbit-coupled Bose-Einstein condensates,"In a two-dimensional atomic Bose-Einstein condensate, we demonstrate Rashba
spin-orbit coupling can always introduce dynamical instability into specific
zero-quasimomentum states in all parameter regimes. During the evolution of the
zero-quasimomentum states, such spin-orbit-coupling-induced instability can
fragment the states and lead to a dynamically patterning process.
  The features of formed patterns are identified from the symmetries of the
Bogoliubov-de Gennes Hamiltonian. We show that spin-orbit-coupled Bose-Einstein
condensates provide an interesting platform for the investigation of pattern
formations.",2302.05101v2
2017-05-12,Analytical slave-spin mean-field approach to orbital selective Mott insulators,"We use the slave-spin mean-field approach to study particle-hole symmetric
one- and two-band Hubbard models in presence of Hund's coupling interaction. By
analytical analysis of Hamiltonian, we show that the locking of the two
orbitals vs.\,orbital-selective Mott transition can be formulated within a
Landau-Ginzburg framework. By applying the slave-spin mean-field to impurity
problem, we are able to make a correspondence between impurity and lattice. We
also consider the stability of the orbital selective Mott phase to the
hybridization between the orbitals and study the limitations of the slave-spin
method for treating inter-orbital tunnellings in the case of multi-orbital
Bethe lattices with particle-hole symmetry.",1705.04427v1
2014-11-11,Striped Ferronematic ground states in a spin-orbit coupled $S=1$ Bose gas,"We theoretically establish the mean-field phase diagram of a homogeneous
spin-$1$, spin-orbit coupled Bose gas as a function of the spin-dependent
interaction parameter, the Raman coupling strength and the quadratic Zeeman
shift. We find that the interplay between spin-orbit coupling and
spin-dependent interactions leads to the occurrence of ferromagnetic or
ferronematic phases which also break translational symmetry. For weak Raman
coupling, increasing attractive spin-dependent interactions (as in $^{87}$Rb or
$^7$Li) induces a transition from a uniform to a stripe XY ferromagnet (with no
nematic order). For repulsive spin-dependent interactions however (as in
$^{23}$Na), we find a transition from an $XY$ spin spiral phase ($<S_{z} >= 0$
and uniform total density) with uniaxial nematic order, to a biaxial
ferronematic, where the total density, spin vector and nematic director
oscillate in real space. We investigate the stability of these phases against
the quadratic Zeeman effect, which generally tends to favor uniform phases with
either ferromagnetic or nematic order but not both. We discuss the relevance of
our results to ongoing experiments on spin-orbit coupled, spinor Bose gases.",1411.2990v1
2018-12-21,Influence of spin-orbit and spin-Hall effects on the spin Seebeck current beyond linear response,"We study the spin transport theoretically in heterostructures consisting of a
ferromagnetic metallic thin film sandwiched between heavy-metal and oxide
layers. The spin current in the heavy metal layer is generated via the spin
Hall effect, while the oxide layer induces at the interface with the
ferromagnetic layer a spin-orbital coupling of the Rashba type. Impact of the
spin Hall effect and Rashba spin-orbit coupling on the spin Seebeck current is
explored with a particular emphasis on nonlinear effects. Technically, we
employ the Fokker-Planck approach and contrast the analytical expressions with
full numerical micromagnetic simulations. We show that when an external
magnetic field is aligned parallel (antiparallel) to the Rashba field, the
spin-orbit coupling enhances (reduces) the spin pumping current. In turn, the
spin Hall effect and the Dzyaloshinskii-Moriya interaction are shown to
increase the spin pumping current.",1812.09270v1
1998-12-16,Elementary excitations of magnetically ordered systems with orbital degeneracy,"The Holstein-Primakoff transformation is generalized to develop a quantum
flavor wave theory for spin systems with orbital degeneracy. Elementary
excitations consist of spin, orbital, and spin-orbital waves. Spin and
spin-orbital waves couple each other due to orbital anisotropy and Hund's rule,
resulting in new modes observable by inelastic neutron scattering. In the SU(4)
limit, flavor waves are dispersionless along one or more directions, and give
rise to quantum fluctuations of reduced dimensionality.",9812289v1
2011-10-01,Spin-orbital phase synchronization in the magnetic field-driven electron dynamics in a double quantum dot,"We study the dynamics of an electron confined in a one-dimensional double
quantum dot in the presence of driving external magnetic fields. The orbital
motion of the electron is coupled to the spin dynamics by spin orbit
interaction of the Dresselhaus type. We derive an effective time-dependent
Hamiltonian model for the orbital motion of the electron and obtain a
synchronization condition between the orbital and the spin dynamics. From this
model we deduce an analytical expression for the Arnold tongue and propose an
experimental scheme for realizing the synchronization of the orbital and spin
dynamics.",1110.0114v1
2013-01-16,Mechanical generation of spin current by spin-rotation coupling,"Spin-rotation coupling, which is responsible for angular momentum conversion
between the electron spin and rotational deformations of elastic media, is
exploited for generating spin current. This method requires neither magnetic
moments nor spin-orbit interaction. The spin current generated in nonmagnets is
calculated in presence of surface acoustic waves. We solve the spin diffusion
equation, extended to include spin-rotation coupling, and find that larger spin
currents can be obtained in materials with longer spin lifetimes. Spin
accumulation induced on the surface is predicted to be detectable by
time-resolved Kerr spectroscopy.",1301.3596v1
2009-10-30,Gravitational waveforms from unequal-mass binaries with arbitrary spins under leading order spin-orbit coupling,"The paper generalizes the structure of gravitational waves from orbiting
spinning binaries under leading order spin-orbit coupling, as given in the work
by K\""onigsd\""orffer and Gopakumar [PRD 71, 024039 (2005)] for single-spin and
equal-mass binaries, to unequal-mass binaries and arbitrary spin
configurations. The orbital motion is taken to be quasi-circular and the
fractional mass difference is assumed to be small against one. The emitted
gravitational waveforms are given in analytic form.",0910.5931v2
2022-04-15,Quantum phases of spin-orbital-angular-momentum coupled bosonic gases in optical lattices,"Spin-orbit coupling plays an important role in understanding exotic quantum
phases. In this work, we present a scheme to combine
spin-orbital-angular-momentum (SOAM) coupling and strong correlations in
ultracold atomic gases. Essential ingredients of this setting is the interplay
of SOAM coupling and Raman-induced spin-flip hopping, engineered by lasers that
couples different hyperfine spin states. In the presence of SOAM coupling only,
we find rich quantum phases in the Mott-insulating regime, which support
different types of spin defects such as spin vortex and composite vortex with
antiferromagnetic core surrounded by the outer spin vortex. Based on an
effective exchange model, we find that these competing spin textures are a
result of the interplay of Dzyaloshinskii-Moriya and Heisenberg exchange
interactions. In the presence of both SOAM coupling and Raman-induced spin-flip
hopping, more many-body phases appear, including canted-antiferromagnetic and
stripe phases. Our prediction suggests that SOAM coupling could induce rich
exotic many-body phases in the strongly interacting regime.",2204.07323v2
2017-08-24,Strong influence of spin-orbit coupling on magnetotransport in two-dimensional hole systems,"With a view to electrical spin manipulation and quantum computing
applications, recent significant attention has been devoted to semiconductor
hole systems, which have very strong spin-orbit interactions. However,
experimentally measuring, identifying, and quantifying spin-orbit coupling
effects in transport, such as electrically-induced spin polarizations and
spin-Hall currents, are challenging. Here we show that the magnetotransport
properties of two dimensional (2D) hole systems display strong signatures of
the spin-orbit interaction. Specifically, the low-magnetic field Hall
coefficient and longitudinal conductivity contain a contribution that is second
order in the spin-orbit interaction coefficient and is non-linear in the
carrier number density. We propose an appropriate experimental setup to probe
these spin-orbit dependent magnetotransport properties, which will permit one
to extract the spin-orbit coefficient directly from the magnetotransport.",1708.07247v2
2018-07-13,Spin-orbit coupling and correlations in three-orbital systems,"We investigate the influence of spin-orbit coupling $\lambda$ in
strongly-correlated multiorbital systems that we describe by a three-orbital
Hubbard-Kanamori model on a Bethe lattice. We solve the problem at all integer
fillings $N$ with the dynamical mean-field theory using the continuous-time
hybridization expansion Monte Carlo solver. We investigate how the
quasiparticle renormalization $Z$ varies with the strength of spin-orbit
coupling. The behavior can be understood for all fillings except $N=2$ in terms
of the atomic Hamiltonian (the atomic charge gap) and the polarization in the
$j$-basis due to spin-orbit induced changes of orbital degeneracies and the
associated kinetic energy. At $N=2$, $\lambda$ increases $Z$ at small $U$ but
suppresses it at large $U$, thus eliminating the characteristic Hund's metal
tail in $Z(U)$. We also compare the effects of the spin-orbit coupling to the
effects of a tetragonal crystal field. Although this crystal field also lifts
the orbital degeneracy, its effects are different, which can be understood in
terms of the different form of the interaction Hamiltonian expressed in the
respective diagonal single-particle basis.",1807.05106v2
2013-06-28,"The role of orbital order in the stabilization of the $(π,0)$ ordered magnetic state in a minimal two-band model for iron pnictides","Spin wave excitations and stability of the ($\pi,0$) ordered magnetic state
are investigated in a minimal two-band itinerant-electron model for iron
pnictides. Presence of hopping anisotropy generates a strong ferro-orbital
order in the $d_{xz}$ and $d_{yz}$ Fe orbitals. The orbital order sign is as
observed in experiments. The induced ferro-orbital order strongly enhances the
spin wave energy scale and stabilizes the magnetic state by optimizing the
strength of the emergent AF and F spin couplings through optimal band fillings
in the two orbitals. The calculated spin-wave dispersion is in quantitative
agreement with neutron scattering measurements. Finite inter-orbital Hund's
coupling is shown to further enhance the spin wave energies state by coupling
the two magnetic sub-systems. A more realistic two-band model with less hopping
anisotropy is also considered which yields not only the circular hole pockets,
also correct ferro-orbital order and emergent F spin coupling.",1306.6727v2
2024-02-02,Photonic Spin-Orbit Coupling Induced by Deep-Subwavelength Structured Light,"We demonstrate both theoretically and experimentally beam-dependent photonic
spin-orbit coupling in a two-wave mixing process described by an equivalent of
the Pauli equation in quantum mechanics. The considered structured light in the
system is comprising a superposition of two orthogonal spin-orbit-coupled
states defined as spin up and spin down equivalents. The spin-orbit coupling is
manifested by prominent pseudo spin precession as well as
spin-transport-induced orbital angular momentum generation in a photonic
crystal film of wavelength thickness. The coupling effect is significantly
enhanced by using a deep-subwavelength carrier envelope, different from
previous studies which depend on materials. The beam-dependent coupling effect
can find intriguing applications; for instance, it is used in precisely
measuring variation of light with spatial resolution up to 15 nm.",2402.01080v1
2018-01-09,Inverse engineering for fast transport and spin control of spin-orbit-coupled Bose-Einstein condensates in moving harmonic traps,"We investigate fast transport and spin manipulation of tunable
spin-orbit-coupled Bose-Einstein condensates in a moving harmonic trap.
Motivated by the concept of ""shortcuts to adiabaticity"", we design inversely
the time-dependent trap position and spin-orbit coupling strength. By choosing
appropriate boundary conditions we obtain fast transport and spin flip
simultaneously. The non-adiabatic transport and relevant spin dynamics are
illustrated with numerical examples, and compared with the adiabatic transport
with constant spin-orbit-coupling strength and velocity. Moreover, the
influence of nonlinearity induced by interatomic interaction is discussed in
terms of the Gross-Pitaevskii approach, showing the robustness of the proposed
protocols. With the state-of-the-art experiments, such inverse engineering
technique paves the way for coherent control of spin-orbit-coupled
Bose-Einstein condensates in harmonic traps.",1801.02887v1
2019-08-03,Experimental evidence for Zeeman spin-orbit coupling in layered antiferromagnetic conductors,"Most of solid-state spin physics arising from spin-orbit coupling, from
fundamental phenomena to industrial applications, relies on symmetry-protected
degeneracies. So does the Zeeman spin-orbit coupling, expected to manifest
itself in a wide range of antiferromagnetic conductors. Yet, experimental proof
of this phenomenon has been lacking. Here, we demonstrate that the N\'eel state
of the layered organic superconductor $\kappa$-(BETS)$_2$FeBr$_4$ shows no spin
modulation of the Shubnikov-de Haas oscillations, contrary to its paramagnetic
state. This is unambiguous evidence for the spin degeneracy of Landau levels, a
direct manifestation of the Zeeman spin-orbit coupling. Likewise, we show that
spin modulation is absent in electron-doped Nd$_{1.85}$Ce$_{0.15}$CuO$_4$,
which evidences the presence of N\'eel order in this cuprate superconductor
even at optimal doping. Obtained on two very different materials, our results
demonstrate the generic character of the Zeeman spin-orbit coupling.",1908.01236v2
2018-03-14,Inter-orbital topological superconductivity in spin-orbit coupled superconductors with inversion symmetry breaking,"We study the superconducting state of multi-orbital spin-orbit coupled
systems in the presence of an orbitally driven inversion asymmetry assuming
that the inter-orbital attraction is the dominant pairing channel. Although the
inversion symmetry is absent, we show that superconducting states that avoid
mixing of spin-triplet and spin-singlet configurations are allowed, and
remarkably, spin-triplet states that are topologically nontrivial can be
stabilized in a large portion of the phase diagram. The orbital-dependent
spin-triplet pairing generally leads to topological superconductivity with
point nodes that are protected by a nonvanishing winding number. We demonstrate
that the disclosed topological phase can exhibit Lifshitz-type transitions upon
different driving mechanisms and interactions, e.g., by tuning the strength of
the atomic spin-orbit and inversion asymmetry couplings or by varying the
doping and the amplitude of order parameter. Such distinctive signatures of the
nodal phase manifest through an extraordinary reconstruction of the low-energy
excitation spectra both in the bulk and at the edge of the superconductor.",1803.05158v2
2011-12-02,The contribution of spin torque to spin Hall coefficient and spin motive force in spin-orbit coupling system,"We derive rigorously the relativistic angular momentum conservation equation
by means of quantum electrodynamics. The novel nonrelativistic spin current and
torque in the spin-orbit coupling system, up to the order of $1/c^{4}$, are
exactly investigated by using Foldy-Wouthuysen transformation. We find a
perfect spin Hall coefficient including the contribution of spin torque dipole.
A novel spin motive force, analogue to the Lorentz force, is also obtained for
understanding of the spin Hall effect.",1112.0394v1
2005-09-23,Physical Limits of the ballistic and non-ballistic Spin-Field-Effect Transistor: Spin Dynamics in Remote Doped Structures,"We investigate the spin dynamics and relaxation in remotely-doped two
dimensional electron systems where the dopants lead to random fluctuations of
the Rashba spin-orbit coupling. Due to the resulting random spin precession,
the spin relaxation time is limited by the strength and spatial scale of the
random contribution to the spin-orbit coupling. We concentrate on the role of
the randomness for two systems where the direction of the spin-orbit field does
not depend on the electron momentum: the spin field-effect transistor with
balanced Rashba and Dresselhaus couplings and the (011) quantum well. Both of
these systems are considered as promising for the spintronics applications
because of the suppression of the Dyakonov-Perel' mechanism there makes the
realization of a spin field effect transistor in the diffusive regime possible.
We demonstrate that the spin relaxation through the randomness of spin-orbit
coupling imposes important physical limitations on the operational properties
of these devices.",0509611v1
2016-08-23,The effect of spin-orbit coupling on the effective-spin correlation in YbMgGaO4,"Motivated by the recent experiments on the triangular lattice spin liquid
YbMgGaO$_4$, we explore the effect of spin-orbit coupling on the effective-spin
correlation of the Yb local moments. We point out the anisotropic interaction
between the effective-spins on the nearest neighbor bonds is sufficient to
reproduce the spin-wave dispersion of the fully polarized state in the presence
of strong magnetic field normal to the triangular plane. We further evaluate
the effective-spin correlation within the mean-field spherical approximation.
We explicitly demonstrate that, the nearest-neighbor anisotropic effective-spin
interaction, originating from the strong spin-orbit coupling, enhances the
effective-spin correlation at the M points in the Brillouin zone. We identify
these results as the strong evidence for the anisotropic interaction and the
strong spin-orbit coupling in YbMgGaO$_4$.",1608.06445v2
2024-01-27,Interplay of altermagnetism and weak ferromagnetism in two-dimensional RuF$_4$,"Gaining growing attention in spintronics is a class of magnets displaying
zero net magnetization and spin-split electronic bands called altermagnets.
Here, by combining density functional theory and symmetry analysis, we show
that RuF$_4$ monolayer is a two-dimensional $d$-wave altermagnet. Spin-orbit
coupling leads to pronounced spin splitting of the electronic bands at the
$\Gamma$ point by $\sim 100$ meV and turns the RuF$_4$ into a weak ferromagnet
due to non trivial spin-momentum locking that cants the Ru magnetic moments.
The net magnetic moment scales linearly with the spin-orbit coupling strength.
Using group theory we derive an effective spin Hamiltonian capturing the
spin-splitting and spin-momentum locking of the electronic bands.
Disentanglement of the altermagnetic and spin-orbit coupling induced spin
splitting uncovers to which extent the altermagnetic properties are affected by
the spin-orbit coupling. Our results move the spotlight to the non trivial
spin-momentum locking and weak ferromagnetism in the two-dimensional
altermagnets relevant for novel venues in this emerging field of material
science research.",2401.15424v1
2012-11-09,Interaction induced staggered spin-orbit order in two-dimensional electron gas,"We propose and formulate an interaction induced staggered spin-orbit order as
a new emergent phase of two-dimensional Fermi gases. We show that when some
form of inherent spin-splitting via Rashba-type spin-orbit coupling renders two
helical Fermi surfaces to become significantly `nested', a Fermi surface
instability arises. To lift this degeneracy, a spontaneous symmetry breaking
spin-orbit density wave develops, causing a surprisingly large quasiparticle
gapping with chiral electronic states. Since the staggered spin-orbit order is
associated with a condensation energy, quantified by the gap value, destroying
such spin-orbit interaction costs sufficiently large perturbation field or
temperature or de-phasing time. BiAg$_2$ surface state is shown to be a
representative system for realizing such novel spin-orbit interaction with
tunable and large strength, and the spin-splitting is decoupled from charge
excitations. These functional properties are relevant for spin-electronics,
spin-caloritronics, and spin-Hall effect applications.",1211.2018v1
2011-07-13,BCS-BEC crossover in spin-orbit coupled two-dimensional Fermi gases,"The recent experimental realization of spin-orbit coupling for ultra-cold
atoms has generated much interest in the physics of spin-orbit coupled
degenerate Fermi gases. Although recently the BCS-BEC crossover in
three-dimensional (3D) spin-orbit coupled Fermi gases has been intensively
studied, the corresponding two-dimensional (2D) crossover physics has remained
unexplored. In this paper, we investigate, both numerically and analytically,
the BCS-BEC crossover physics in 2D degenerate Fermi gases in the presence of a
Rashba type of spin-orbit coupling. We derive the mean field gap and atom
number equations suitable for the 2D spin-orbit coupled Fermi gases and solve
them numerically and self-consistently, from which the dependence of the ground
state properties (chemical potential, superfluid pairing gap, ground state
energy per atom) on the system parameters (e.g., binding energy, spin-orbit
coupling strength) is obtained. Furthermore, we derive analytic expressions for
these ground state quantities, which agree well with our numerical results
within a broad parameter region. Such analytic expressions also agree
qualitatively with previous numerical results for the 3D spin-orbit coupled
Fermi gases, where analytic results are lacked. We show that with an increasing
SOC strength, the chemical potential is shifted by a constant determined by the
SOC strength. The superfluid pairing gap is enhanced significantly in the BCS
limit for strong SOC, but only increases slightly in the BEC limit.",1107.2627v3
2018-07-19,Three-boson spectrum in the presence of 1D spin-orbit coupling: Efimov's generalized radial scaling law,"Spin-orbit coupled cold atom systems, governed by Hamiltonians that contain
quadratic kinetic energy terms typical for a particle's motion in the usual
Schr\""odinger equation and linear kinetic energy terms typical for a particle's
motion in the usual Dirac equation, have attracted a great deal of attention
recently since they provide an alternative route for realizing fractional
quantum Hall physics, topological insulators, and spintronics physics. The
present work focuses on the three-boson system in the presence of 1D spin-orbit
coupling, which is most relevant to ongoing cold atom experiments. In the
absence of spin-orbit coupling terms, the three-boson system exibits the Efimov
effect: the entire energy spectrum is uniquely determined by the $s$-wave
scattering length and a single three-body parameter, i.e., using one of the
energy levels as input, the other energy levels can be obtained via Efimov's
radial scaling law, which is intimately tied to a discrete scaling symmetry. It
is demonstrated that the discrete scaling symmetry persists in the presence of
1D spin-orbit coupling, implying the validity of a generalized radial scaling
law in five-dimensional space. The dependence of the energy levels on the
scattering length, spin-orbit coupling parameters, and center-of-mass momentum
is discussed. It is conjectured that three-body systems with other types of
spin-orbit coupling terms are also governed by generalized radial scaling laws,
provided the system exhibits the Efimov effect in the absence of spin-orbit
coupling.",1807.07653v1
2020-10-05,Terrestrial Orbit-Spin Coupling Torque Episodes in Late 2020,"Orbit-spin coupling torques on the Earth in November 2020 are larger than at
any other time between 2000 and 2050. This affords an opportunity to observe
the terrestrial atmospheric response to the putative torque in near real time.",2010.02289v1
2006-01-30,Electric Dipole Induced Spin Resonance in Quantum Dots,"An alternating electric field, applied to a quantum dot, couples to the
electron spin via the spin-orbit interaction. We analyze different types of
spin-orbit coupling known in the literature and find two efficient mechanisms
of spin control in quantum dots. The linear in momentum Dresselhaus and Rashba
spin-orbit couplings give rise to a fully transverse effective magnetic field
in the presence of a Zeeman splitting at lowest order in the spin-orbit
interaction. The cubic in momentum Dresselhaus terms are efficient in a quantum
dot with non-harmonic confining potential and give rise to a spin-electric
coupling proportional to the orbital magnetic field. We derive an effective
spin Hamiltonian, which can be used to implement spin manipulation on a
timescale of $10 {\rm ns}$ with the current experimental setups.",0601674v2
2001-11-22,Theory for high spin systems with orbital degeneracy,"High-spin systems with orbital degeneracy are studied in the large spin
limit. In the absence of Hund's coupling, the classical spin model is mapped
onto disconnected orbital systems with spins up and down, respectively. The
ground state of the isotropic model is an orbital valence bond state where each
bond is an orbital singlet with parallel spins, and neighbouring bonds interact
antiferromagnetically. The possible relevance to the transition metal oxides
are discussed.",0111426v1
2015-03-23,Spin-Orbit Torques in Two-Dimensional Rashba Ferromagnets,"Magnetization dynamics in single-domain ferromagnets can be triggered by
charge current if spin-orbit coupling is sufficiently strong. We apply
functional Keldysh theory to investigate Rashba spin-orbit torques in metallic
two-dimensional ferromagnets. A reactive, anti-damping-like spin-orbit torque
as well as a dissipative, field-like torque are calculated microscopically, to
the leading order in the spin-orbit interaction strength. By calculating the
first vertex correction we show that the intrinsic anti-damping-like torque
vanishes unless the scattering rates are spin-dependent.",1503.06872v2
2024-03-11,Spin-orbit coupling in symmetric and mixed spin-symmetry,"Synthetically spin-orbit coupling in cold atoms couples the pseudo-spin and
spatial degrees of freedom, and therefore the inherent spin symmetry of the
system plays an important role. In systems of two pseudo-spin degrees, two
particles configure symmetric states and anti-symmetric states, but the spin
symmetry can be mixed for more particles. We study the role of mixed spin
symmetry in the presence of spin-orbit coupling and consider the system of
three bosons with two hyper-fine states trapped in a harmonic potential. We
investigate the ground state and the energy spectrum by implementing exact
diagonalization. It is found that the interplay between spin-orbit coupling and
repulsive interactions between anti-aligned pseudo-spins increases the
population of the unaligned spin components in the ground state. The emergence
of the mixed spin symmetric states compensates for the rise of the interaction
energy. With the aligned interaction on, the avoided crossing between the
ground state and the first excited state is observed only for small
interaction, and this causes shape changes in the spin populations.
Furthermore, we find that the pair correlation of the ground state shows
similarly to that of Tonks-Girardeau gas even for relatively small contact
interactions and such strong interaction feature is enhanced by the spin-orbit
coupling.",2403.07188v1
2012-06-04,Von Neumann Entropy Spectra and Entangled Excitations in Spin-Orbital Models,"We consider the low-energy excitations of one-dimensional spin-orbital models
which consist of spin waves, orbital waves, and joint spin-orbital excitations.
Among the latter we identify strongly entangled spin-orbital bound states which
appear as peaks in the von Neumann entropy (vNE) spectral function introduced
in this work. The strong entanglement of bound states is manifested by a
universal logarithmic scaling of the vNE with system size, while the vNE of
other spin-orbital excitations saturates. We suggest that spin-orbital
entanglement can be experimentally explored by the measurement of the dynamical
spin-orbital correlations using resonant inelastic x-ray scattering, where
strong spin-orbit coupling associated with the core hole plays a role.",1206.1062v1
2004-07-16,Influences of spin accumulation on the intrinsic spin Hall effect in two dimensional electron gases with Rashba spin-orbit coupling,"In a two dimensional electron gas with Rashba spin-orbit coupling, the
external electric field may cause a spin Hall current in the direction
perpendicular to the electric field. This effect was called the intrinsic spin
Hall effect. In this paper, we investigate the influences of spin accumulation
on this intrinsic spin Hall effect. We show that due to the existence of
boundaries in a real sample, the spin Hall current generated by the intrinsic
spin Hall effect will cause spin accumulation near the edges of the sample, and
in the presence of spin accumulation, the spin Hall conductivity will not have
a universal value. The influences of spin accumulation on the intrinsic spin
Hall effect in narrow strips of two dimensional electron gases with Rashba
spin-orbit coupling are investigated in detail.",0407419v1
2020-08-03,Interfacial spin-orbit torques,"Spin-orbit torques offer a promising mechanism for electrically controlling
magnetization dynamics in nanoscale heterostructures. While spin-orbit torques
occur predominately at interfaces, the physical mechanisms underlying these
torques can originate in both the bulk layers and at interfaces. Classifying
spin-orbit torques based on the region that they originate in provides clues as
to how to optimize the effect. While most bulk spin-orbit torque contributions
are well studied, many of the interfacial contributions allowed by symmetry
have yet to be fully explored theoretically and experimentally. To facilitate
progress, we review interfacial spin-orbit torques from a semiclassical
viewpoint and relate these contributions to recent experimental results. Within
the same model, we show the relationship between different interface transport
parameters. For charges and spins flowing perpendicular to the interface,
interfacial spin-orbit coupling both modifies the mixing conductance of
magnetoelectronic circuit theory and gives rise to spin memory loss. For
in-plane electric fields, interfacial spin-orbit coupling gives rise to torques
described by spin-orbit filtering, spin swapping and precession. In addition,
these same interfacial processes generate spin currents that flow into the
non-magnetic layer. For in-plane electric fields in trilayer structures, the
spin currents generated at the interface between one ferromagnetic layer and
the non-magnetic spacer layer can propagate through the non-magnetic layer to
produce novel torques on the other ferromagnetic layer.",2008.01182v1
2019-08-02,Two-dimensional orbital Hall insulators,"The orbital-Hall effect (OHE), similarly to the spin-Hall effect (SHE),
refers to the creation of a transverse flow of orbital angular momentum that is
induced by a longitudinally applied electric field. For systems in which the
spin-orbit coupling (SOC) is sizeable, the orbital and spin angular momentum
degrees of freedom are coupled, and an interrelationship between charge, spin
and orbital angular momentum excitations is naturally established. The OHE has
been explored mostly in metallic systems, where it can be quite strong.
However, several of its features remain unexplored in two-dimensional (2D)
materials. Here, we investigate the role of orbital textures for the OHE
displayed by multi-orbital 2D materials. We predict the appearance of a rather
large orbital Hall effect in these systems both in their metallic and
insulating phases. In some cases, the orbital Hall currents are larger than the
spin Hall ones, and their use as information carriers widens the development
possibilities of novel spin-orbitronic devices.",1908.00927v2
2023-05-10,Inverse orbital Hall effect and orbitronic terahertz emission observed in the materials with weak spin-orbit coupling,"The Orbital Hall effect, which originates from materials with weak spin-orbit
coupling, has attracted considerable interest for spin-orbitronic applications.
Here, we demonstrate the inverse effect of the orbital Hall effect and observe
orbitronic terahertz emission in the Ti and Mn materials. Through spin-orbit
transition in the ferromagnetic layer, the generated orbital current can be
converted to charge current in the Ti and Mn layers via the inverse orbital
Hall effect. Furthermore, the inserted W layer provides an additional
conversion of the orbital-charge current in the Ti and Mn layers, significantly
enhancing the orbitronic terahertz emission. Moreover, the orbitronic terahertz
emission can be manipulated by cooperating with the inverse orbital Hall effect
and the inverse spin Hall effect in the different sample configurations. Our
results not only discover the physical mechanism of condensed matter physics
but also pave the way for designing promising spin-orbitronic devices and
terahertz emitters.",2305.05830v1
2024-01-11,Orbital Hanle Magnetoresistance in a 3d Transition Metal,"The Hanle magnetoresistance is a telltale signature of spin precession in
nonmagnetic conductors, in which strong spin-orbit coupling generates edge spin
accumulation via the spin Hall effect. Here, we report the existence of a large
Hanle magnetoresistance in single layers of Mn with weak spin-orbit coupling,
which we attribute to the orbital Hall effect. The simultaneous observation of
a sizable Hanle magnetoresistance and vanishing small spin Hall
magnetoresistance in BiYIG/Mn bilayers corroborates the orbital origin of both
effects. We estimate an orbital Hall angle of 0.016, an orbital relaxation time
of 2 ps and diffusion length of the order of 2 nm in disordered Mn. Our
findings indicate that current-induced orbital moments are responsible for
magnetoresistance effects comparable to or even larger than those determined by
spin moments, and provide a tool to investigate nonequilibrium orbital
transport phenomena.",2401.05703v1
2020-03-01,Spin-orbit interaction and spin selectivity for tunneling electron transfer in DNA,"Electron transfer (ET) in biological molecules such as peptides and proteins
consists of electrons moving between well defined localized states (donors to
acceptors) through a tunneling process. Here we present an analytical model for
ET by tunneling in DNA, in the presence of Spin-Orbit (SO) interaction, to
produce a strong spin asymmetry with the intrinsic atomic SO strength in meV
range. We obtain a Hamiltonian consistent with charge transport through $\pi$
orbitals on the DNA bases and derive the behavior of ET as a function of the
injection state momentum, the spin-orbit coupling and barrier length and
strength. A highly consistent scenario arises where two concomitant mechanisms
for spin selection arises; spin interference and differential spin amplitude
decay. High spin filtering can take place at the cost of reduced amplitude
transmission assuming realistic values for the spin-orbit coupling. The spin
filtering scenario is completed by addressing the spin dependent torque under
the barrier, with a consistent conserved definition for the spin current.",2003.00582v2
2013-05-16,Interplay between spin-orbit interactions and a time-dependent electromagnetic field in monolayer graphene,"We apply a circularly and linearly polarized terahertz field on a monolayer
of graphene taking into account spin-orbit interactions of the intrinsic and
Rashba type. It turns out that the field can not only be used to induce a gap
in the energy spectrum, but also to close an existing gap due to the different
reaction of the spin components on circularly polarized light. Signatures of
spin-orbit coupling on the density of states of the driven system can be
observed even for energies where the static density of states is independent of
spin-orbit interactions. Furthermore it is shown that the time evolution of the
spin polarization and the orbital dynamics of an initial wave packet can be
modulated by varying the ratio of the spin-orbit coupling parameters. Assuming
that the system acquires a quasi stationary state, the optical conductivity of
the irradiated sample is calculated. Our results confirm the multi step nature
of the conductivity obtained recently, where the number of intermediate steps
can be changed by adjusting the spin-orbit coupling parameters and the
orientation of the field.",1305.3810v2
2024-03-14,Spin-Orbit Coupled Insulators and Metals on the Verge of Kitaev Spin Liquids in Ilmenite Heterostructures,"Competition and cooperation between electron correlation and relativistic
spin-orbit coupling give rise to diverse exotic quantum phenomena in solids. An
illustrative example is spin-orbit entangled quantum liquids, which exhibit
remarkable features such as topological orders and fractional excitations. The
Kitaev honeycomb model realizes such interesting states, called the Kitaev spin
liquids, but its experimental feasibility is still challenging. Here we
theoretically investigate hexagonal heterostructures including a candidate for
the Kitaev magnets, MgIrO$_3$, to actively manipulate the electronic and
magnetic properties toward realizing the Kitaev spin liquids. For three
different structure types of ilmenite bilayers MgIrO$_3$/$A$TiO$_3$ with $A$ =
Mn, Fe, Co, and Ni, we obtain the optimized lattice structures, the electronic
band structures, the stable magnetic orders, and the effective magnetic
couplings. We find that the spin-orbital coupled bands characterized by the
pseudospin $j_{\rm eff}=$ 1/2 are retained in the MgIrO$_3$ layer for all the
heterostructures, but the magnetic state and the band gap depend on the types
of heterostructures as well as the $A$ atoms. In particular, one type becomes
metallic irrespective of $A$, while the other two are mostly insulating. We
show that the insulating cases provide spin-orbit coupled Mott insulating
states with dominant Kitaev-type interactions, accompanied by different
combinations of subdominant interactions depending on the heterostructural type
and $A$, while the metallic cases realize spin-orbit coupled metals with
various doping rates. Our results indicate that these hexagonal
heterostructures are a good platform for engineering electronic and magnetic
properties of the spin-orbital coupled correlated materials, including the
possibility of Majorana Fermi surfaces and topological superconductivity.",2403.09112v1
2013-08-15,Spintronics and Pseudospintronics in Graphene and Topological Insulators,"The two-dimensional electron systems in graphene and in topological
insulators are described by massless Dirac equations. Although the two systems
have similar Hamiltonians, they are polar opposites in terms of spin-orbit
coupling strength. We briefly review the status of efforts to achieve long spin
relaxation times in graphene with its weak spin-orbit coupling, and to achieve
large current-induced spin polarizations in topological-insulator surface
states that have strong spin-orbit coupling. We also comment on differences
between the magnetic responses and dilute-moment coupling properties of the two
systems, and on the pseudospin analog of giant magnetoresistance in bilayer
graphene.",1308.3428v1
2012-06-05,Spin-Orbit Coupling in LaAlO$_3$/SrTiO$_3$ interfaces: Magnetism and Orbital Ordering,"The combination of Rashba spin-orbit coupling and electron correlations can
induce unusual phenomena in the metallic interface between SrTiO$_3$ and
LaAlO$_3$. We consider effects of Rashba spin-orbit coupling at this interface
in the context of the recent observation of anisotropic magnetism. Firstly, we
show how Rashba spin-orbit coupling in a system near a band-edge can account
for the observed magnetic anisotropy. Secondly, we investigate the coupling
between in-plane magnetic-moment anisotropy and nematicity in the form of an
orbital imbalance between d$_{xz}$ / d$_{yz}$ orbitals. We estimate this
coupling to be substantial in the low electron density regime. Such an orbital
ordering can affect magneto transport.",1206.1060v2
2016-06-24,Low-energy physics of three-orbital impurity model with Kanamori interaction,"We discuss the low-energy physics of the three-orbital Anderson impurity
model with the Coulomb interaction term of the Kanamori form which has orbital
SO(3) and spin SU(2) symmetry and describes systems with partially occupied
$t_{2g}$ shells. We focus on the case with two electrons in the impurity that
is relevant to Hund's metals. Using the Schrieffer-Wolff transformation we
derive an effective Kondo model with couplings between the bulk and impurity
electrons expressed in terms of spin, orbital, and orbital quadrupole
operators. The bare spin-spin Kondo interaction is much smaller than the
orbit-orbit and spin-orbital couplings or is even ferromagnetic. Furthermore,
the perturbative scaling equations indicate faster renormalization of the
couplings related to orbital degrees of freedom compared to spin degrees of
freedom. Both mechanisms lead to a slow screening of the local spin moment. The
model thus behaves similarly to the related quantum impurity problem with a
larger SU(3) orbital symmetry (Dworin-Narath interaction) where this was first
observed. We find that the two problems actually describe the same low-energy
physics since the SU(3) symmetry is dynamically established through the
renormalization of the splittings of coupling constants to zero. The
perturbative renormalization group results are corroborated with the
numerical-renormalization group (NRG) calculations. The dependence of spin
Kondo temperatures and orbital Kondo temperatures as a function of interaction
parameters, the hybridization, and the impurity occupancy is calculated and
discussed.",1606.07654v1
2016-05-16,Characteristics of persistent spin current components in a quasi-periodic Fibonacci ring with spin-orbit interactions: Prediction of spin-orbit coupling and on-site energy,"In the present work we investigate the behavior of all three components of
persistent spin current in a quasi-periodic Fibonacci ring subjected to Rashba
and Dresselhaus spin-orbit interactions. Analogous to persistent charge current
in a conducting ring where electrons gain a Berry phase in presence of magnetic
flux, spin Berry phase is associated during the motion of electrons in presence
of a spin-orbit field which is responsible for the generation of spin current.
The interplay between two spin-orbit fields along with quasi-periodic Fibonacci
sequence on persistent spin current is described elaborately, and from our
analysis, we can estimate the strength of any one of two spin-orbit couplings
together with on-site energy, provided the other is known.",1605.04716v2
2013-01-27,Kondo Effect in the Presence of Spin-Orbit Coupling,"Recently, a series of noncentrosymmetric superconductors has been a subject
of considerable interest since the discovery of superconductivity in CePt_3Si.
In noncentrosymmetric materials, the degeneracy of bands is lifted in the
presence of spin-orbit coupling. This will bring about new effects in the Kondo
effect since the band degeneracy plays an important role in the scattering of
electrons by localized spins. We investigate the single-impurity Kondo problem
in the presence of spin-orbit coupling. We examine the effect of spin-orbit
coupling on the scattering of conduction electrons, by using the Green's
function method, for the s-d Hamiltonian, with employing a decoupling
procedure. As a result, we obtain a closed system of equations of Green's
functions, from which we can calculate physical quantities. The Kondo
temperature T_K is estimated from a singularity of Green's functions. We show
that T_K is reduced as the spin-orbit coupling constant \alpha is increased.
When 2\alpha k_F is comparable to or greater than k_BT_K(\alpha=0), T_K shows
an abrupt decrease as a result of the band splitting. This suggests a Kondo
collapse accompanied with a sharp decrease of T_K. The log T-dependence of the
resistivity will be concealed by the spin-orbit interaction.",1301.6355v1
2002-06-20,Spin switching in semiconductor quantum dots through spin-orbit coupling,"The spin-orbit coupling influences the total spin of semiconductor quantum
dots. We analyze the theoretical prediction for the combined effects of
spin-orbit coupling, weak vertical magnetic fields and deformation of the dot.
Our results allow the characterization of the quantum dots as spin switches,
controllable with electric gates.",0206387v2
2002-08-22,Electronic spin precession in semiconductor quantum dots with spin-orbit coupling,"The electronic spin precession in semiconductor dots is strongly affected by
the spin-orbit coupling. We present a theory of the electronic spin resonance
at low magnetic fields that predicts a strong dependence on the dot occupation,
the magnetic field and the spin-orbit coupling strength. Coulomb interaction
effects are also taken into account in a numerical approach.",0208425v1
2005-02-16,Vanishing of the Dissipationless Spin Hall Effect in a Diffusive Two-Dimensional Electron Gas with Spin-Orbit Coupling,"We propose a nonequilibrium Green's function approach to study the spin-Hall
effect in a two-dimensional electron system with both the Rashba and
Dresselhaus spin-orbit couplings. By taking into account the long-range
electron-impurity scattering, the derived kinetic equations are solved
numerically. It is found the vanishing of the total zero-temperature
dissipationless spin-Hall effect, contributing from the intrinsic and
disorder-mediated processes. This result has been examined in the wide ranges
of spin-orbit coupling constants and electron density.",0502392v1
2012-03-29,Soliton Magnetization Dynamics in Spin-Orbit Coupled Bose-Einstein Condensates,"Ring-trapped Bose-Einstein condensates subject to spin-orbit coupling support
localized dark soliton excitations that show periodic density dynamics in real
space. In addition to the density feature, solitons also carry a localized
pseudo-spin magnetization that exhibits a rich and tunable dynamics. Analytic
results for Rashba-type spin-orbit coupling and spin-invariant interactions
predict a conserved magnitude and precessional motion for the soliton
magnetization that allows for the simulation of spin-related geometric phases
recently seen in electronic transport measurements.",1203.6684v1
2012-03-19,Spin-orbit couplings between distant electrons trapped individually on liquid helium,"We propose an approach to entangle spins of electrons floating on liquid
helium by coherently manipulating their spin-orbit interactions. The
configuration consists of single electrons, confined individually on liquid
helium by the microelectrodes, moving along the surface as the harmonic
oscillators. It has been known that the spin of an electron could be coupled to
its orbit (i.e., the vibrational motion) by properly applying a magnetic field.
Based on this single electron spin-orbit coupling, here we show that a
Jaynes-Cummings (JC) type interaction between the spin of an electron and the
orbit of another electron at a distance could be realized via the strong
Coulomb interaction between the electrons. Consequently, the proposed JC
interaction could be utilized to realize a strong orbit-mediated spin-spin
coupling and implement the desirable quantum information processing between the
distant electrons trapped individually on liquid helium.",1203.4079v2
2012-01-08,Spin-orbit coupled Fermi liquid theory of ultra-cold magnetic dipolar fermions,"We investigate Fermi liquid states of the ultra-cold magnetic dipolar Fermi
gases in the simplest two-component case including both thermodynamic
instabilities and collective excitations. The magnetic dipolar interaction is
invariant under the simultaneous spin-orbit rotation, but not under either the
spin or the orbit one. Therefore, the corresponding Fermi liquid theory is
intrinsically spin-orbit coupled. This is a fundamental feature of magnetic
dipolar Fermi gases different from electric dipolar ones. The Landau
interaction matrix is calculated and is diagonalized in terms of the spin-orbit
coupled partial-wave channels of the total angular momentum J. The leading
thermodynamic instabilities lie in the channels of ferromagnetism hybridized
with the ferronematic order with J = 1+ and the spin-current mode with J = 1-,
where + and - represent even and odd parities, respectively. An exotic
propagating collective mode is identified as spin-orbit coupled Fermi surface
oscillations in which spin distribution on the Fermi surface exhibits a
topologically nontrivial hedgehog configuration.",1201.1607v3
2023-11-27,Gilbert damping in two-dimensional metallic anti-ferromagnets,"A finite spin life-time of conduction electrons may dominate Gilbert damping
of two-dimensional metallic anti-ferromagnets or anti-ferromagnet/metal
heterostructures. We investigate the Gilbert damping tensor for a typical
low-energy model of a metallic anti-ferromagnet system with honeycomb magnetic
lattice and Rashba spin-orbit coupling for conduction electrons. We distinguish
three regimes of spin relaxation: exchange-dominated relaxation for weak
spin-orbit coupling strength, Elliot-Yafet relaxation for moderate spin-orbit
coupling, and Dyakonov-Perel relaxation for strong spin-orbit coupling. We
show, however, that the latter regime takes place only for the in-plane Gilbert
damping component. We also show that anisotropy of Gilbert damping persists for
any finite spin-orbit interaction strength provided we consider no spatial
variation of the N\'eel vector. Isotropic Gilbert damping is restored only if
the electron spin-orbit length is larger than the magnon wavelength. Our theory
applies to MnPS3 monolayer on Pt or to similar systems.",2311.16268v2
2018-09-28,Spin-orbit crossed susceptibility in topological Dirac semimetals,"We theoretically study the spin-orbit crossed susceptibility of topological
Dirac semimetals. Because of strong spin-orbit coupling, the orbital motion of
electrons is modulated by Zeeman coupling, which contributes to orbital
magnetization. We find that the spin-orbit crossed susceptibility is
proportional to the separation of the Dirac points and it is highly
anisotropic. The orbital magnetization is induced only along the rotational
symmetry axis. We also study the conventional spin susceptibility. The spin
susceptibility exhibits anisotropy and the spin magnetization is induced only
along the perpendicular to the rotational symmetry axis in contrast to the
spin-orbit crossed susceptibility. We quantitatively compare the two
susceptibilities and find that they can be comparable.",1809.10852v2
2019-03-29,Spin-Orbital Hallmarks of Unconventional Superconductors Without Inversion Symmetry,"The spin-orbital polarization of superconducting excitations in momentum
space is shown to provide distinctive marks of unconventional pairing in the
presence of inversion symmetry breaking.Taking the prototypical example of an
electronic system with atomic spin-orbit and orbital-Rashba couplings, we
provide a general description of the spin-orbital textures and their most
striking changeover moving from the normal to the superconducting state. We
find that the variation of the spin-texture is strongly imprinted by the
combination of the misalignment of spin-triplet d-vector with the inversion
asymmetry g-vector coupling and the occurrence of superconducting nodal
excitations. Remarkably, the multi-orbital character of the superconducting
state allows to unveil a unique type of topological transition for the
spin-winding around the nodal points. This finding indicates the fundamental
topological relation between chiral and spin-winding in nodal superconductors.
By analogy between spin- and orbital-triplet pairing we point out how orbital
polarization patterns can be also employed to assess the character of the
superconducting state.",1903.12379v2
2024-03-21,Spin-orbit interaction with large spin in the semi-classical regime,"We consider the time dependent Schr\""odinger equation with a coupling
spin-orbit in the semi-classical regime $\hbar\searrow 0$ and large spin number
$\spin\rightarrow +\infty$ such that $\hbar^\delta\spin=c$ where $c>0$ and
$\delta>0$ are constant. The initial state $\Psi(0)$ is a product of an orbital
coherent state in $L^2(\R^d)$ and a spin coherent state in a spin irreducible
representation space ${\mathcal H}_{2\spin +1}$. For $\delta <1$, at the
leading order in $\hbar$, the time evolution $\Psi(t)$ of $ \Psi(0)$ is well
approximated by the product of an orbital and a spin coherent state.
Nevertheless for $1/2<\delta<1$ the quantum orbital leaves the classical
orbital. For $\delta=1$ we prove that this last claim is no more true when the
interaction depends on the orbital variables.
  For the Dicke model, we prove that the orbital partial trace of the projector
on $\Psi(t)$ is a mixed state in $L^2(\R)$ for small $t>0$.",2403.14408v1
2011-12-19,Counterflow of spontaneous mass currents in trapped spin-orbit coupled Fermi gases,"We use the Bogoliubov-de Gennes formalism and study the ground-state phases
of trapped spin-orbit coupled Fermi gases in two dimensions. Our main finding
is that the presence of a symmetric (Rashba type) spin-orbit coupling
spontaneously induces counterflowing mass currents in the vicinity of the trap
edge, i.e. $\uparrow$ and $\downarrow$ particles circulate in opposite
directions with equal speed. These currents flow even in noninteracting
systems, but their strength decreases toward the molecular BEC limit, which can
be achieved either by increasing the spin-orbit coupling or the interaction
strength. These currents are also quite robust against the effects of
asymmetric spin-orbit couplings in $x$ and $y$ directions, gradually reducing
to zero as the spin-orbit coupling becomes one dimensional. We compare our
results with those of chiral p-wave superfluids/superconductors.",1112.4468v2
2012-03-13,Impact of Dresselhaus vs. Rashba spin-orbit coupling on the Holstein polaron,"We utilize an exact variational numerical procedure to calculate the ground
state properties of a polaron in the presence of Rashba and linear Dresselhaus
spin-orbit coupling. We find that when the linear Dresselhaus spin-orbit
coupling approaches the Rashba spin-orbit coupling, the Van-Hove singularity in
the density of states will be shifted away from the bottom of the band and
finally disappear when the two spin-orbit couplings are tuned to be equal. The
effective mass will be suppressed; the trend will become more significant for
low phonon frequency. The presence of two dominant spin-orbit couplings will
make it possible to tune the effective mass with more varied observables.",1203.2795v1
2012-11-09,Metal-insulator transition in three-band Hubbard model with strong spin-orbit interaction,"Recent investigations suggest that both spin-orbit coupling and electron
correlation play very crucial roles in the $5d$ transition metal oxides. By
using the generalized Gutzwiller variational method and dynamical mean-field
theory with the hybridization expansion continuous time quantum Monte Carlo as
impurity solver, the three-band Hubbard model with full Hund's rule coupling
and spin-orbit interaction terms, which contains the essential physics of
partially filled $t_{2g}$ sub-shell of $5d$ materials, is studied
systematically. The calculated phase diagram of this model exhibits three
distinct phase regions, including metal, band insulator and Mott insulator
respectively. We find that the spin-orbit coupling term intends to greatly
enhance the tendency of the Mott insulator phase. Furthermore, the influence of
the electron-electron interaction on the effective strength of spin-orbit
coupling in the metallic phase is studied in detail. We conclude that the
electron correlation effect on the effective spin-orbit coupling is far beyond
the mean-field treatment even in the intermediate coupling region.",1211.2055v1
2013-07-05,Spin-orbit coupled fermions in ladder-like optical lattices at half-filling,"We study the ground-state phase diagram of two-component fermions loaded in a
ladder-like lattice at half filling in the presence of spin-orbit coupling. For
repulsive fermions with unidirectional spin-orbit coupling along the legs we
identify a N\'{e}el state which is separated from rung-singlet and
ferromagnetic states by Ising phase transition lines. These lines cross for
maximal spin-orbit coupling and a direct Gaussian phase transition between
rung-singlet and ferro phases is realized. For the case of Rashba-like
spin-orbit coupling, besides the rung singlet phases two distinct striped
ferromagnetic phases are formed. In case of attractive fermions with spin-orbit
coupling at half-filling for decoupled chains we identify a dimerized state
that separates a singlet superconductor and a ferromagnetic states.",1307.1607v1
2015-04-19,Hydrodynamics of Normal Atomic Gases with Spin-orbit Coupling,"Successful realization of spin-orbit coupling in atomic gases by the NIST
scheme opens the prospect of studying the effects of spin-orbit coupling on
many-body physics in an unprecedentedly controllable way. Here we derive the
linearized hydrodynamic equations for the normal atomic gases of the spin-orbit
coupling by the NIST scheme with zero detuning. We show that the hydrodynamics
of the system crucially depends on the momentum susceptibilities which can be
modified by the spin-orbit coupling. We reveal the effects of the spin-orbit
coupling on the sound velocities and the dipole mode frequency of the gases by
applying our formalism to the ideal Fermi gas. We also discuss the
generalization of our results to other situations.",1504.04786v2
2017-10-29,Contact theory for spin-orbit-coupled Fermi gases,"We develop the contact theory for spin-orbit-coupled Fermi gases. By using a
perturbation method, we derive analytically the universal two-body behavior at
short distance, which does not depend on the short-range details of interatomic
potentials. We find that two new scattering parameters need to be introduced
because of spin-orbit coupling, besides the traditional $s$- and $p$-wave
scattering length (volume) and effective ranges. This is a general and unique
feature for spin-orbit-coupled systems. Consequently, two new adiabatic energy
relations with respect to the new scattering parameters are obtained, in which
a new contact is involved because of spin-orbit coupling. In addition, we
derive the asymptotic behavior of the large-momentum distribution, and find
that the subleading tail is corrected by the new contact. This work paves the
way for exploring the profound properties of spin-orbit-coupled many-body
systems, according to two-body solutions.",1710.10579v2
2018-10-16,Induced spin-orbit coupling in silicon thin films by bismuth doping,"We demonstrate an enhancement of the spin-orbit coupling in silicon (Si) thin
films by doping with bismuth (Bi), a heavy metal, using ion implantation.
Quantum corrections to conductance at low temperature in phosphorous-doped Si
before and after Bi implantation is measured to probe the increase of the
spin-orbit coupling, and a clear modification of magnetoconductance signals is
observed: Bi doping changes magnetoconductance from weak localization to the
crossover between weak localization and weak antilocalization. The elastic
diffusion length, phase coherence length and spin-orbit coupling length in Si
with and without Bi implantation are estimated, and the spin-orbit coupling
length after the Bi doping becomes the same order of magnitude (Lso = 54 nm)
with the phase coherence length (L{\phi} = 35 nm) at 2 K. This is an
experimental proof that the spin-orbit coupling strength in Si thin film is
tunable by doping with heavy metals.",1810.06878v1
2011-01-06,Quantum phase transitions in a strongly entangled spin-orbital chain: A field-theoretical approach,"Motivated by recent experiments on quasi-1D vanadium oxides, we study quantum
phase transitions in a one-dimensional spin-orbital model describing a Haldane
chain and a classical Ising chain locally coupled by the relativistic
spin-orbit interaction. By employing a field-theoretical approach, we analyze
the topology of the ground-state phase diagram and identify the nature of the
phase transitions. In the strong coupling limit, a long-range N\'eel order of
entangled spin and orbital angular momentum appears in the ground state. We
find that, depending on the relative scales of the spin and orbital gaps, the
linear chain follows two distinct routes to reach the N\'eel state. First, when
the orbital exchange is the dominating energy scale, a two-stage ordering takes
place in which the magnetic transition is followed by melting of the orbital
Ising order; both transitions belong to the two-dimensional Ising universality
class. In the opposite limit, the low-energy orbital modes undergo a continuous
reordering transition which represents a line of Gaussian critical points. On
this line the orbital degrees of freedom form a Tomonaga-Luttinger liquid. We
argue that the emergence of the Gaussian criticality results from merging of
the two Ising transitions in the strong hybridization region where the
characteristic spin and orbital energy scales become comparable. Finally, we
show that, due to the spin-orbit coupling, an external magnetic field acting on
the spins can induce an orbital Ising transition.",1101.1268v3
2015-03-23,Critical Temperature and Tunneling Spectroscopy of Superconductor-Ferromagnet Hybrids with Intrinsic Rashba-Dresselhaus Spin-Orbit Coupling,"We investigate theoretically how the proximity effect in
superconductor/ferromagnet hybrid structures with intrinsic spin-orbit coupling
manifests in the density of states and critical temperature. To describe a
general scenario, we allow for both Rashba and Dresselhaus type spin-orbit
coupling. Our results are obtained via the quasiclassical theory of
superconductivity, extended to include spin-orbit coupling in the Usadel
equation and Kupriyanov--Lukichev boundary conditions. Unlike previous works,
we have derived a Riccati parametrization of the Usadel equation with
spin-orbit coupling which allows us to address the full proximity regime.
First, we consider the density of states in both SF bilayers and SFS trilayers,
where the spectroscopic features in the latter case are sensitive to the phase
difference between the two superconductors. We find that the presence of
spin-orbit coupling leaves clear spectroscopic fingerprints in the density of
states due to its role in creating spin-triplet Cooper pairs. Unlike SF and SFS
structures without spin-orbit coupling, the density of states in the present
case depends strongly on the direction of magnetization. We show that the
spin-orbit coupling can stabilize singlet superconductivity even in the
presence of a strong exchange field $h \gg \Delta$. This leads to the
possibility of a magnetically tunable minigap: changing the direction of the
exchange field opens and closes the minigap. We also determine how the critical
temperature $T_c$ of an SF bilayer is affected by spin-orbit coupling and
demonstrate that one can achieve a spin-valve effect with a single ferromagnet.
We find that $T_c$ displays highly non-monotonic behavior both as a function of
the magnetization direction and the type and direction of the spin-orbit
coupling, offering a new way to exert control over the superconductivity of
proximity structures.",1503.06835v2
2019-03-17,Sensing Kondo correlations in a suspended carbon nanotube mechanical resonator with spin-orbit coupling,"We study electron mechanical coupling in a suspended carbon nanotube (CNT)
quantum dot device. Electron spin couples to the flexural vibration mode due to
spin-orbit coupling in the electron tunneling processes. In the weak coupling
limit, i.e. electron-vibration coupling is much smaller than the electron
energy scale, the damping and resonant frequency shift of the CNT resonator can
be obtained by calculating the dynamical spin susceptibility. We find that
strong spin-flip scattering processes in Kondo regime significantly affect the
mechanical motion of the carbon nanotube: Kondo effect induces strong damping
and frequency shift of the CNT resonator.",1903.07049v1
2017-11-19,SU($N$) spin-wave theory: Application to spin-orbital Mott insulators,"We present the application of the SU($N$) ($N>2$) spin-wave theory to
spin-orbital Mott insulators whose ground states exhibit magnetic orders. When
taking both the spin and orbital degrees of freedom into account rather than
projecting onto the Kramers doublet, the lowest spin-orbital locking energy
levels, due to the inevitable spin-orbital multipole exchange interactions, the
SU($N$) spin-wave theory should take the place of the SU($2$) one. To implement
the application, we introduce an efficient general local mean field approach
which involves all the local fluctuations into the SU($N$) linear spin-wave
theory. Our approach is tested firstly by calculating the multipolar spin-wave
spectra of the SU($4$) antiferromagnetic model. Then we apply it to
spin-orbital Mott insulators. It is revealed that the Hund's coupling would
influence the effectiveness of the isospin-$1/2$ representation when the spin
orbital coupling is not large enough. Besides, we also calculate the spin-wave
spectra based on the first principle calculations for two concrete materials,
$\alpha$-RuCl$_3$ and Sr$_2$IrO$_4$. The SU($N$) spin-wave theory appropriately
depicts the low-energy magnons and the spin-orbital excitations qualitatively.",1711.07041v1
2020-06-24,Landau levels in spin-orbit coupling proximitized graphene: bulk states,"We study the magnetic-field dependence of Landau levels in graphene
proximitized by large spin-orbit coupling materials, such as transition-metal
dichalcogenides or topological insulators. In addition to the Rashba coupling,
two types of intrinsic spin-orbit interactions, uniform (Kane-Mele type) and
staggered (valley Zeeman type), are included, to resolve their interplay with
magnetic orbital effects. Employing a continuum model approach, we derive
analytic expressions for low-energy Landau levels, which can be used to extract
local orbital and spin-orbit coupling parameters from scanning probe
spectroscopy experiments. We compare different parameter regimes to identify
fingerprints of relative and absolute magnitudes of intrinsic spin-orbit
coupling in the spectra. The inverted band structure of graphene proximitized
by WSe$_2$ leads to an interesting crossing of Landau states across the bulk
gap at a crossover field, providing insights into the size of Rashba spin-orbit
coupling. Landau level spectroscopy can help to resolve the type and signs of
the intrinsic spin-orbit coupling by analyzing the symmetry in energy and
number of crossings in the Landau fan chart. Finally, our results suggest that
the strong response to the magnetic field of Dirac electrons in proximitized
graphene can be associated with extremely large self-rotating magnetic moments.",2006.13651v1
2023-03-21,Intrinsic Magnon Orbital Hall Effect in Honeycomb Antiferromagnets,"We theoretically investigate the transport of magnon orbitals in a honeycomb
antiferromagnet. We find that the magnon orbital Berry curvature is finite even
without spin-orbit coupling and thus the resultant magnon orbital Hall effect
is an intrinsic property of the honeycomb antiferromagnet rooted only in the
exchange interaction and the lattice structure. Due to the intrinsic nature of
the magnon orbital Hall effect, the magnon orbital Nernst conductivity is
estimated to be orders of magnitude larger than the predicted values of the
magnon spin Nernst conductivity that requires finite spin-orbit coupling. For
the experimental detection of the predicted magnon orbital Hall effect, we
invoke the magnetoelectric effect that couples the magnon orbital and the
electric polarization, which allows us to detect the magnon orbital
accumulation through the local voltage measurement. Our results pave a way for
a deeper understanding of the topological transport of the magnon orbitals and
also its utilization for low-power magnon-based orbitronics, namely magnon
orbitronics.",2303.11687v1
2010-03-13,Motion and gravitational wave forms of eccentric compact binaries with orbital-angular-momentum-aligned spins under next-to-leading order in spin-orbit and leading order in spin(1)-spin(2) and spin-squared couplings,"A quasi-Keplerian parameterisation for the solutions of second post-Newtonian
(PN) accurate equations of motion for spinning compact binaries is obtained
including leading order spin-spin and next-to-leading order spin-orbit
interactions. Rotational deformation of the compact objects is incorporated.
For arbitrary mass ratios the spin orientations are taken to be parallel or
anti-parallel to the orbital angular momentum vector. The emitted gravitational
wave forms are given in analytic form up to 2PN point particle, 1.5PN spin
orbit and 1PN spin-spin contributions, where the spins are counted of 0PN
order.",1003.2735v4
2010-04-18,Spin Orbit Coupling and Spin Waves in Ultrathin Ferromagnets: The Spin Wave Rashba Effect,"We present theoretical studies of the influence of spin orbit coupling on the
spin wave excitations of the Fe monolayer and bilayer on the W(110) surface.
The Dzyaloshinskii-Moriya interaction is active in such films, by virtue of the
absence of reflection symmetry in the plane of the film. When the magnetization
is in plane, this leads to a linear term in the spin wave dispersion relation
for propagation across the magnetization. The dispersion relation thus assumes
a form similar to that of an energy band of an electron trapped on a
semiconductor surfaces with Rashba coupling active. We also show SPEELS
response functions that illustrate the role of spin orbit coupling in such
measurements. In addition to the modifications of the dispersion relations for
spin waves, the presence of spin orbit coupling in the W substrate leads to a
substantial increase in the linewidth of the spin wave modes. The formalism we
have developed applies to a wide range of systems, and the particular system
explored in the numerical calculations provides us with an illustration of
phenomena which will be present in other ultrathin ferromagnet/substrate
combinations.",1004.3066v1
2019-06-27,Extrinsic Spin-Orbit Coupling and Spin Relaxation in Phosphorene,"An effective Hamiltonian is derived to describe the conduction band of
monolayer black phosphorus (phosphorene) in the presence of spin-orbit coupling
and external electric field. Envelope function approximation along with
symmetry arguments and Lowdin partitioning are utilized to derive extrinsic
spin-orbit coupling. The resulting spin splitting appears in fourth order
perturbation terms and is shown to be linear in both the magnitude of the
external electric field and the strength of the atomic spin-orbit coupling,
similar to the Bychkov-Rashba expression but with an in-plane anisotropy. The
anisotropy depends on the coupling between conduction band and other bands both
close and distant in energy. The spin relaxation of conduction electrons is
then calculated within the Dyakonov-Perel mechanism where momentum scattering
randomizes the polarization of a spin ensemble. We show how the anisotropic
Fermi contour and the anisotropic extrinsic spin splitting contribute to the
anisotropy of spin-relaxation time. Scattering centers in the substrate are
considered to be charged impurities with screened Coulomb potential.",1906.11939v2
2017-07-31,Spin-orbit torques from interfacial spin-orbit coupling for various interfaces,"We use a perturbative approach to study the effects of interfacial spin-orbit
coupling in magnetic multilayers by treating the two-dimensional Rashba model
in a fully three-dimensional description of electron transport near an
interface. This formalism provides a compact analytic expression for
current-induced spin-orbit torques in terms of unperturbed scattering
coefficients, allowing computation of spin-orbit torques for various contexts,
by simply substituting scattering coefficients into the formulas. It applies to
calculations of spin-orbit torques for magnetic bilayers with bulk magnetism,
those with interface magnetism, a normal metal/ferromagnetic insulator
junction, and a topological insulator/ferromagnet junction. It predicts a
dampinglike component of spin-orbit torque that is distinct from any intrinsic
contribution or those that arise from particular spin relaxation mechanisms. We
discuss the effects of proximity-induced magnetism and insertion of an
additional layer and provide formulas for in-plane current, which is induced by
a perpendicular bias, anisotropic magnetoresistance, and spin memory loss in
the same formalism.",1707.09847v1
2015-12-20,Magnetic and nematic phases in a Weyl type spin-orbit-coupled spin-1 Bose gas,"We present a variational study of the spin-1 Bose gases in a harmonic trap
with three-dimensional spin-orbit coupling of Weyl type. For weak spin-orbit
coupling, we treat the single-particle ground states as the form of
perturbational harmonic oscillator states in the lowest total angular momentum
manifold with $j=1, m_j=1,0,-1$. When the two-body interaction is considered,
we set the trail order parameter as the superposition of three degenerate
single-particle ground-states and the weight coefficients are determined by
minimizing the energy functional. Two ground state phases, namely the magnetic
and the nematic phases, are identified depending on the spin-independent and
the spin-dependent interactions. Unlike the non-spin-orbit-coupled spin-1
Bose-Einstein condensate for which the phase boundary between the magnetic and
the nematic phase lies exactly at zero spin-dependent interaction, the boundary
is modified by the spin-orbit-coupling. We find the magnetic phase is featured
with phase-separated density distributions, 3D skyrmion-like spin textures and
competing magnetic and biaxial nematic orders, while the nematic phase is
featured with miscible density distributions, zero magnetization and spatially
modulated uniaxial nematic order. The emergence of higher spin order creates
new opportunities for exploring spin-tensor-related physics in spin-orbit
coupled superfluid.",1512.06394v1
2002-11-29,Spin-Orbit induced semiconductor spin guides,"The tunability of the Rashba spin-orbit coupling allows to build
semiconductor heterostructures with space modulated coupling intensities. We
show that a wire-shaped spin-orbit modulation in a quantum well can support
propagating electronic states inside the wire only for a certain spin
orientation and, therefore, it acts as an effective spin transmission guide for
this particular spin orientation.",0211694v1
2003-07-27,Universal Intrinsic Spin-Hall Effect,"We describe a new effect in semiconductor spintronics that leads to
dissipationless spin-currents in paramagnetic spin-orbit coupled systems. We
argue that in a high mobility two-dimensional electron system with substantial
Rashba spin-orbit coupling, a spin-current that flows perpendicular to the
charge current is intrinsic. In the usual case where both spin-orbit split
bands are occupied, the spin-Hall conductivity has a universal value.",0307663v2
2004-12-22,Spin-orbit induced interference in polygon-structures,"We investigate the spin-orbit induced spin-interference pattern of ballistic
electrons travelling along any regular polygon. It is found that the
spin-interference depends strongly on the Rashba and Dresselhaus spin-orbit
constants as well as on the sidelength and alignment of the polygon. We derive
the analytical formulae for the limiting cases of either zero Dresselhaus or
zero Rashba spin-orbit coupling, including the result obtained for a circle. We
calculate the nonzero Dresselhaus and Rashba case numerically for the square,
triangle, hexagon, and circle and discuss the observability of the
spin-interference which can potentially be used to measure the Rashba and
Dresselhaus coefficients.",0412609v1
2018-08-24,"Residual spin susceptibility in the spin-triplet, orbital-singlet model","Nuclear magnetic resonance (NMR) and Knight shift measurements are critical
tools in the identification of spin-triplet superconductors. We discuss the
effects of spin orbit coupling on the Knight shift and susceptibilities for a
variety of spin triplet multi-orbital gap functions with orbital-singlet
character and compare their responses to ""traditional"" single band spin-triplet
($p_x+ip_y$) superconductors. We observe a non-negligible residual
spin-susceptibility at low temperature.",1808.08029v1
2006-03-14,Spin entanglement induced by spin-orbit interactions in coupled quantum dots,"We theoretically explore the possibility of creating spin quantum
entanglement in a system of two electrons confined respectively in two
vertically coupled quantum dots in the presence of Rashba type spin-orbit
coupling. We find that the system can be described by a generalized Jaynes -
Cummings model of two modes bosons interacting with two spins. The lower
excitation states of this model are calculated to reveal the underlying physics
of the far infrared absorption spectra. The analytic perturbation approach
shows that an effective transverse coupling of spins can be obtained by
eliminating the orbital degrees of freedom in the large detuning limit. Here,
the orbital degrees of freedom of the two electrons, which are described by two
modes of bosons, serve as a quantized data bus to exchange the quantum
information between two electrons. Then a nontrivial two-qubit logic gate is
realized and spin entanglement between the two electrons is created by virtue
of spin-orbit coupling.",0603363v2
2006-04-27,Orbital and spin relaxation in single and coupled quantum dots,"Phonon-induced orbital and spin relaxation rates of single electron states in
lateral single and double quantum dots are obtained numerically for realistic
materials parameters. The rates are calculated as a function of magnetic field
and interdot coupling, at various field and quantum dot orientations. It is
found that orbital relaxation is due to deformation potential phonons at low
magnetic fields, while piezoelectric phonons dominate the relaxation at high
fields. Spin relaxation, which is dominated by piezoelectric phonons, in single
quantum dots is highly anisotropic due to the interplay of the Bychkov-Rashba
and Dresselhaus spin-orbit couplings. Orbital relaxation in double dots varies
strongly with the interdot coupling due to the cyclotron effects on the
tunneling energy. Spin relaxation in double dots has an additional anisotropy
due to anisotropic spin hot spots which otherwise cause giant enhancement of
the rate at useful magnetic fields and interdot couplings. Conditions for the
absence of the spin hot spots in in-plane magnetic fields (easy passages) and
perpendicular magnetic fields (weak passages) are formulated analytically for
different growth directions of the underlying heterostructure. It is shown that
easy passages disappear (spin hot spots reappear) if the double dot system
loses symmetry by an xy-like perturbation.",0604633v1
2017-12-21,Cooper Pairing in A Doped 2D Antiferromagnet with Spin-Orbit Coupling,"We study the two-dimensional Hubbard model with the Rashba type spin-orbit
coupling within and beyond the mean-field theory. The antiferromagnetic ground
state for the model at half-filling and the Cooper pairing induced by
antiferromagnetic spin fluctuations near half-filling are examined based on the
random-phase approximation. We show that the antiferromagnetic order is
suppressed and the magnetic susceptibility turns out to be anisotropic in the
presence of the spin-orbit coupling. Energy spectrums of transverse spin
fluctuations are obtained and the effective interactions between holes mediated
by antiferromagnetic spin fluctuations are deduced in the case of low hole
doping. It seems that the spin-orbit coupling tends to form s+p-wave Cooper
pairs, while the s+d-wave pairing is dominant when the spin-orbit coupling is
absent.",1712.07908v1
2011-05-21,Quantum states and linear response in dc and electromagnetic fields for charge current and spin polarization of electrons at Bi/Si interface with giant spin-orbit coupling,"An expansion of the nearly free-electron model constructed by Frantzeskakis,
Pons and Grioni [Phys. Rev. B {\bf 82}, 085440 (2010)] describing quantum
states at Bi/Si(111) interface with giant spin-orbit coupling is developed and
applied for the band structure and spin polarization calculation, as well as
for the linear response analysis for charge current and induced spin caused by
dc field and by electromagnetic radiation. It is found that the large
spin-orbit coupling in this system may allow resolving the spin-dependent
properties even at room temperature and at realistic collision rate. The
geometry of the atomic lattice combined with spin-orbit coupling leads to an
anisotropic response both for current and spin components related to the
orientation of the external field. The in-plane dc electric field produces only
the in-plane components of spin in the sample while both the in-plane and
out-of-plane spin components can be excited by normally propagating
electromagnetic wave with different polarizations.",1105.4215v1
2021-06-21,Spin structure factors of doped monolayer Germanene in the presence of spin-orbit coupling,"In this paper, we present a Kane-Mele model in the presence of magnetic field
and next nearest neighbors hopping amplitudes for investigations of the spin
susceptibilities of Germanene layer. Green's function approach has been
implemented to find the behavior of dynamical spin susceptibilities of
Germanene layer within linear response theoryand in the presence of magnetic
field and spin-orbit coupling at finite temperature. Our results show the
magnetic excitation mode for both longitudinal and transverse components of
spin tends to higher frequencies with spin-orbit coupling strength. Moreover
the frequency positions of sharp peaks in longitudinal dynamical spin
susceptibility are not affected by variation of magnetic field while the peaks
in transverse dynamical susceptibility moves to lower frequencies with magnetic
field. The effects of electron doping on frequency behaviors of spin
susceptibilities have been addressed in details. Finally the temperature
dependence of static spin structure factors due to the effects of spin-orbit
coupling, magnetic field and chemical potential has been studied.",2106.11377v1
2015-11-28,Spin-orbit torque engineering via oxygen manipulation,"Spin transfer torques allow the electrical manipulation of the magnetization
at room temperature, which is desirable in spintronic devices such as spin
transfer torque memories. When combined with spin-orbit coupling, they give
rise to spin-orbit torques which are a more powerful tool for magnetization
control and can enrich device functionalities. The engineering of spin-orbit
torques, based mostly on the spin Hall effect, is being intensely pursued. Here
we report that the oxidation of spin-orbit torque devices triggers a new
mechanism of spin-orbit torque, which is about two times stronger than that
based on the spin Hall effect. We thus introduce a way to engineer spin-orbit
torques via oxygen manipulation. Combined with electrical gating of the oxygen
level, our findings may also pave the way towards reconfigurable logic devices.",1511.08868v1
2002-11-29,The orbital moment in CoO,"The orbital and spin moment of the Co2+ ion in CoO has been calculated within
the quasi-atomic approach with taking into account the intra-atomic spin-orbit
coupling. The orbital moment of 1.38 \mu_{B} amounts at 0 K, in the
magnetically-ordered state, to more than 34% of the total moment (4.02 \mu_{B})
and yields the L/S ratio of 1.04, close to the experimental value.
  PACS No: 71.70.E; 75.10.D Keywords: 3d magnetism, crystal field, spin-orbit
coupling, orbital moment, CoO",0211705v1
2011-06-24,Spin-orbit coupling induced Mott transition in Ca$_{2-x}$Sr$_{x}$RuO$_{4}$ (0<x<0.2),"We propose a new mechanism for the paramagnetic metal-insulator transition in
the layered perovskite Ca$_{2-x}$Sr$_{x}$RuO$_{4}$ (0<x<0.2). The LDA+U
approach including spin-orbit coupling is used to calculate the electronic
structures. In Ca$_{2}$RuO$_{4}$, we show that the spin-orbit effect is
strongly enhanced by the Coulomb repulsion, which leads to an insulating phase.
When Ca is substituted by Sr, the effective spin-orbit splitting is reduced due
to the increasing bandwidth of the degenerate $d_{xz}$ and $d_{yz}$ orbitals.
For x=0.2, the compound is found to be metallic. We show that these results are
in good agreement with the experimental phase diagram.",1106.5046v1
2024-01-30,A novel non-adiabatic spin relaxation mechanism in molecular qubits,"The interaction of electronic spin and molecular vibrations mediated by
spin-orbit coupling governs spin relaxation in molecular qubits. I derive an
extended molecular spin Hamiltonian that includes both adiabatic and
non-adiabatic spin-dependent interactions, and I implement the computation of
its matrix elements using state-of-the-art density functional theory. The new
molecular spin Hamiltonian contains a novel spin-vibrational orbit interaction
with non-adiabatic origin together with the traditional molecular Zeeman and
zero-field splitting interactions with adiabatic origin. The spin-vibrational
orbit interaction represents a non-Abelian Berry curvature on the ground-state
electronic manifold and corresponds to an effective magnetic field in the
electronic spin dynamics. I further develop a spin relaxation rate model that
estimates the spin relaxation time via the two-phonon Raman process. An
application of the extended molecular spin Hamiltonian together with the spin
relaxation rate model to Cu(II) porphyrin, a prototypical $S=1/2$ molecular
qubit, demonstrates that the spin relaxation time at elevated temperatures is
dominated by the non-adiabatic spin-vibrational orbit interaction. The computed
spin relaxation rate and its magnetic field orientation dependence are in
excellent agreement with experimental measurements.",2401.16738v1
2001-10-25,Re-examination of orbital ordering in LaMnO$_3$: Electron-electron and electron-lattice interactions,"The interactions between $e_g$ orbitals in neighboring sites are investigated
in LaMnO$_3$ by taking into account virtual exchange of electrons and phonons.
The spin and orbital ordering temperatures and the spin wave dispersion
relation are calculated. We find that the orbital ordering is mainly caused by
the electronic interactions and that the Jahn-Teller coupling is much smaller
than that reported previously. We propose that the elastic constant shows a
characteristic change at the N{\'e}el temperature by the spin and orbital
coupling and the higher-order Jahn-Teller coupling.",0110534v1
2022-10-02,Spin-orbit coupling and Kondo resonance in Co adatom on Cu(100) surface: DFT+ED study,"We report density functional theory plus exact diagonalization of the
multi-orbital Anderson impurity model calculations for the Co adatom on the top
of Cu(001) surface. For the Co atom $d$-shell occupation $n_d \approx$ 8, a
singlet many-body ground state and Kondo resonance are found, when the
spin-orbit coupling is included in the calculations. The differential
conductance is evaluated in a good agreement with the scanning tuneling
microscopy measurements. The results illustrate the essential role which the
spin-orbit coupling is playing in a formation of Kondo singlet for the
multi-orbital impurity in low dimensions.",2210.00600v1
2014-03-17,Spin Hall and Edelstein effects in metallic films: from 2D to 3D,"A normal metallic film sandwiched between two insulators may have strong
spin-orbit coupling near the metal-insulator interfaces, even if spin-orbit
coupling is negligible in the bulk of the film. In this paper we study two
technologically important and deeply interconnected effects that arise from
interfacial spin-orbit coupling in metallic films. The first is the spin Hall
effect, whereby a charge current in the plane of the film is partially
converted into an orthogonal spin current in the same plane. The second is the
Edelstein effect, in which a charge current produces an in-plane, transverse
spin polarization. At variance with strictly two-dimensional Rashba systems, we
find that the spin Hall conductivity has a finite value even if spin-orbit
interaction with impurities is neglected and ""vertex corrections"" are properly
taken into account. Even more remarkably, such finite value becomes ""universal""
in a certain configuration. This is a direct consequence of the spatial
dependence of spin-orbit coupling on the third dimension, perpendicular to the
film plane. The non-vanishing spin Hall conductivity has a profound influence
on the Edelstein effect, which we show to consist of two terms, the first with
the standard form valid in a strictly two-dimensional Rashba system, and a
second arising from the presence of the third dimension. Whereas the standard
term is proportional to the momentum relaxation time, the new one scales with
the spin relaxation time. Our results, although derived in a specific model,
should be valid rather generally, whenever a spatially dependent Rashba
spin-orbit coupling is present and the electron motion is not strictly
two-dimensional.",1403.4195v1
2008-11-24,Dynamics of Black Hole Pairs II: Spherical Orbits and the Homoclinic Limit of Zoom-Whirliness,"Spinning black hole pairs exhibit a range of complicated dynamical behaviors.
An interest in eccentric and zoom-whirl orbits has ironically inspired the
focus of this paper: the constant radius orbits. When black hole spins are
misaligned, the constant radius orbits are not circles but rather lie on the
surface of a sphere and have acquired the name ""spherical orbits"". The
spherical orbits are significant as they energetically frame the distribution
of all orbits. In addition, each unstable spherical orbit is asymptotically
approached by an orbit that whirls an infinite number of times, known as a
homoclinic orbit. A homoclinic trajectory is an infinite whirl limit of the
zoom-whirl spectrum and has a further significance as the separatrix between
inspiral and plunge for eccentric orbits. We work in the context of two
spinning black holes of comparable mass as described in the 3PN Hamiltonian
with spin-orbit coupling included. As such, the results could provide a testing
ground of the accuracy of the PN expansion. Further, the spherical orbits could
provide useful initial data for numerical relativity. Finally, we comment that
the spinning black hole pairs should give way to chaos around the homoclinic
orbit when spin-spin coupling is incorporated.",0811.3798v1
2010-06-07,Duality of the spin and density dynamics for two-dimensional electrons with a spin-orbit coupling,"We study spin dynamics in a two-dimensional electron gas with a pure gauge
non-Abelian spin-orbit field, for which systems with balanced Rashba and
Dresselhaus spin-orbit couplings, and the (110)-axis grown GaAs quantum wells
are typical examples. We demonstrate the duality of the spin evolution and the
electron-density dynamics in a system without spin-orbit coupling, which
considerably simplifies and deepens the analysis of spin-dependent processes.
This duality opens a venue for the understanding of this class of systems,
highly interesting for their applications in spintronics, through known
properties of the systems without spin-orbit coupling.",1006.1202v3
2016-11-04,Limits on dynamically generated spin-orbit coupling: Absence of $l=1$ Pomeranchuk instabilities in metals,"An ordered state in the spin sector that breaks parity without breaking
time-reversal symmetry, i.e., that can be considered as dynamically generated
spin-orbit coupling, was proposed to explain puzzling observations in a range
of different systems. Here we derive severe restrictions for such a state that
follow from a Ward identity related to spin conservation. It is shown that
$l=1$ spin-Pomeranchuk instabilities are not possible in non-relativistic
systems since the response of spin-current fluctuations is entirely incoherent
and non-singular. This rules out relativistic spin-orbit coupling as an
emergent low-energy phenomenon. We illustrate the exotic physical properties of
the remaining higher angular momentum analogues of spin-orbit coupling and
derive a geometric constraint for spin-orbit vectors in lattice systems.",1611.01442v2
2018-03-19,Spin-Dependent Conductance in a Junction with Dresselhaus Spin-Orbit Coupling,"We studied spin-dependent conductance in a normal metal (NM)/NM junction with
Dresselhaus spin-orbit coupling (DSOC) and magnetization. As a reference, we
also studied the spin-dependent conductance in such a junction with Rashba
spin-orbit coupling (RSOC). Using a standard scattering method, we calculated
the gate-voltage dependence of the spin-dependent conductances in DSOC and
RSOC. In addition, we calculated the gate-voltage dependence of the
conductances in a ferromagnetic metal (FM)/NM junction with spin-orbit coupling
and magnetization, which we call ferromagnetic spin-orbit metal (FSOM). From
these results, we discuss the relation between these conductance in the
presence of DSOC and that in the presence of RSOC. We found that conductance in
DSOC is the same as that in RSOC for the NM/FSOM junction. In addition, we
found that in the FM/FSOM junction, the conductance in DSOC is the same as that
in RSOC only when the FM magnetization is along the out-of-plane direction.",1803.07091v3
2020-12-04,Effects of hybridization and spin-orbit coupling to induce odd frequency pairing in two-band superconductors,"The effects of spin independent hybridization potential and spin orbit
coupling on two band superconductor with equal time s-wave inter band pairing
order parameter is investigated theoretically. To study symmetry classes in two
band superconductors the Gorkov equations are solved analytically. By defining
spin singlet and spin triplet s wave order parameter due to two band degree of
freedom the symmetry classes of Cooper pair are studied. For spin singlet case
it is shown that spin independent hybridization generates Cooper pair belongs
to even frequency spin singlet even momentum even band parity (ESEE) symmetry
class for both intraband and interband pairing correlations. For spin triplet
order parameter, intraband pairing correlation generates odd frequency spin
triplet even momentum even band parity (OTEE) symmetry class whereas, interband
pairing correlation generates even frequency spin triplet even momentum odd
band parity ETEO) class. For the spin singlet, spin orbit coupling generates
pairing correlation that belongs to odd frequency spin singlet odd momentum
even band parity (OSOE) symmetry class and even frequency spin singlet even
momentum even band parity (ESEE) for intraband and interband pairing
correlation respectively. In the spin triplet case for itraband and interband
correlation, spin orbit coupling generates even-frequency spin triplet odd
momentum even band parity (ETOE) and even frequency spin triplet even momentum
odd band parity (ETEO) respectively.",2012.02810v1
2008-11-25,Spin-orbital frustrations and anomalous metallic state in iron-pnictide superconductors,"We develop an understanding of the anomalous metal state of the parent
compounds of recently discovered iron based superconductors starting from a
strong coupling viewpoint, including orbital degrees of freedom. On the basis
of an intermediate-spin (S=1) state for the Fe^{2+} ions, we derive a
Kugel-Khomskii spin-orbital Hamiltonian for the active t_{2g} orbitals. It
turns out to be a highly complex model with frustrated spin and orbital
interactions. We compute its classical phase diagrams and provide an
understanding for the stability of the various phases by investigating its
spin-only and orbital-only limits. The experimentally observed spin-stripe
state is found to be stable over a wide regime of physical parameters and can
be accompanied by three different types of orbital orders. Of these the
orbital-ferro and orbital-stripe orders are particularly interesting since they
break the in-plane lattice symmetry -- a robust feature of the undoped
compounds. We compute the magnetic excitation spectra for the effective spin
Hamiltonian, observing a strong reduction of the ordered moment, and point out
that the proposed orbital ordering pattern can be measured in resonant X-ray
diffraction.",0811.4104v1
2005-10-07,Theory of orbital state and spin interactions in ferromagnetic titanates,"A spin-orbital superexchange Hamiltonian in a Mott insulator with $t_{2g}$
orbital degeneracy is investigated. More specifically, we focus on a spin
ferromagnetic state of the model and study a collective behavior of orbital
angular momentum. Orbital order in the model occurs in a nontrivial way -- it
is stabilized exclusively by quantum effects through the order-from-disorder
mechanism. Several energetically equivalent orbital orderings are identified.
Some of them are specified by a quadrupole ordering and have no unquenched
angular momentum at low energy. Other states correspond to a noncollinear
ordering of the orbital angular momentum and show the magnetic Bragg peaks at
specific positions. Order parameters are unusually small because of strong
quantum fluctuations. Orbital contribution to the resonant x-ray scattering is
discussed. The dynamical magnetic structure factor in different ordered states
is calculated. Predictions made should help to observe elementary excitations
of orbitals and also to identify the type of the orbital order in ferromagnetic
titanates. Including further a relativistic spin-orbital coupling, we derive an
effective low-energy spin Hamiltonian and calculate a spin-wave spectrum, which
is in good agreement with recent experimental observations in YTiO$_3$.",0510175v1
2006-12-01,Gilbert damping and spin Coulomb drag in a magnetized electron liquid with spin-orbit interaction,"We present a microscopic calculation of the Gilbert damping constant for the
magnetization of a two-dimensional spin-polarized electron liquid in the
presence of intrinsic spin-orbit interaction. First we show that the Gilbert
constant can be expressed in terms of the auto-correlation function of the
spin-orbit induced torque. Then we specialize to the case of the Rashba
spin-orbit interaction and we show that the Gilbert constant in this model is
related to the spin-channel conductivity. This allows us to study the Gilbert
damping constant in different physical regimes, characterized by different
orderings of the relevant energy scales -- spin-orbit coupling, Zeeman
coupling, momentum relaxation rate, spin-momentum relaxation rate, spin
precession frequency -- and to discuss its behavior in various limits.
Particular attention is paid to electron-electron interaction effects,which
enter the spin conductivity and hence the Gilbert damping constant via the spin
Coulomb drag coefficient.",0612015v1
2011-01-11,Multipole correlations of $t_{\rm 2g}$-orbital Hubbard model with spin-orbit coupling,"We investigate the ground-state properties of a one-dimensional $t_{\rm
2g}$-orbital Hubbard model including an atomic spin-orbit coupling by using
numerical methods, such as Lanczos diagonalization and density-matrix
renormalization group. As the spin-orbit coupling increases, we find a
ground-state transition from a paramegnetic state to a ferromagnetic state. In
the ferromagnetic state, since the spin-orbit coupling mixes spin and orbital
states with complex number coefficients, an antiferro-orbital state with
complex orbitals appears. According to the appearance of the complex orbital
state, we observe an enhancement of $\Gamma_{4u}$ octupole correlations.",1101.2055v1
2012-05-31,Effect of spin-orbit coupling on magnetic and orbital order in MgV$_2$O$_4$,"Recent measurements on MgV$_2$O$_4$ single crystal have reignited the debate
on the role of spin-orbit (SO) coupling in dictating the orbital order in
Vanadium spinel systems. Density functional theory calculations were performed
using the full-potential linearized augmented-plane-wave method within the
local spin density approximation (LSDA), Coulomb correlated LSDA+U, and with SO
interaction (LSDA+U+SO) to study the magnetic and orbital ordering in low
temperature phase of MgV$_2$O$_4$. It is observed that the spin-orbit coupling
in the experimentally observed antiferromagnetic phase, affects the orbital
order differently in alternate V-atom chains along c-axis. This observation is
found to be consistent with the experimental prediction that the effect of
spin-orbit coupling is intermediate between that in case of ZnV$_2$O$_4$ and
MnV$_2$O$_4$.",1205.6950v1
2005-07-29,Interplay between electron spin and orbital pseudospin in double quantum dots,"We investigate theoretically spin and orbital pseudospin magnetic properties
of a molecular orbital in parabolic and elliptic double quantum dots (DQDs). In
our many body calculation we include intra- and inter-dot electron-electron
interactions, in addition to the intradot exchange interaction of `p' orbitals.
We find for parabolic DQDs that, except for the half or completely filled
molecular orbital, spins in different dots are ferromagnetically coupled while
orbital pseudospins are antiferromagnetically coupled. For elliptic DQDs spins
and pseudospins are either ferromagnetically or antiferromagnetically coupled,
depending on the number of electrons in the molecular orbital. We have
determined orbital pseudospin quantum numbers for the groundstates of elliptic
DQDs. An experiment is suggested to test the interplay between orbital
pseudospin and spin magnetism.",0507702v1
2019-11-21,"Evidence for orbital ordering in Ba$_2$NaOsO$_6$, a Mott insulator with strong spin orbit coupling, from First Principles","We present first principles calculations of the magnetic and orbital
properties of Ba$_2$NaOsO$_6$ (BNOO), a 5$d^1$ Mott insulator with strong spin
orbit coupling (SOC) in its low temperature emergent quantum phases. Our
computational method takes into direct consideration recent NMR results that
established that BNOO develops a local octahedral distortion preceding the
formation of long range magnetic order. We found that the two-sublattice canted
ferromagnetic ground state identified in Lu \etal, Nature Comm. {\bf 8}, 14407
(2017) is accompanied by a two-sublattice staggered orbital ordering pattern in
which the $t_{2g}$ orbitals are selectively occupied as a result of strong spin
orbit coupling. The staggered orbital order found here using first principles
calculations asserts the previous proposal of Chen \etal, Phys. Rev. B {\bf
82}, 174440 (2010) and Lu \etal, Nature Comm. {\bf 8}, 14407 (2017), that
two-sublattice magnetic structure is the very manifestation of staggered
quadrupolar order. Therefore, our results affirm the essential role of
multipolar spin interactions in the microscopic description of magnetism in
systems with locally entangled spin and orbital degrees of freedom.",1911.09244v1
2021-10-21,The spin-spin problem in Celestial Mechanics,"We study the dynamics of two homogeneous rigid ellipsoids subject to their
mutual gravitational influence. We assume that the spin axis of each ellipsoid
coincides with its shortest physical axis and is perpendicular to the orbital
plane. Due to such assumptions, the problem is planar and depends on particular
parameters of the ellipsoids, most notably, the equatorial oblateness and the
flattening with respect to the shortest physical axes. We consider two models
for such configuration: while in the full model, there is a coupling between
the orbital and rotational motions, in the Keplerian model, the centers of mass
of the bodies are constrained to move on coplanar Keplerian ellipses. The
Keplerian case, in the approximation that includes the coupling between the
spins of the two ellipsoids, is what we call spin-spin problem, that is a
generalization of the classical spin-orbit problem. In this paper we continue
the investigations of [Mis21] on the spin-spin problem by comparing it with the
spin-orbit problem and also with the full model.
  Beside detailing the models associated to the spin-orbit and spin-spin
problems, we introduce the notions of standard and balanced resonances, which
lead us to investigate the existence of periodic and quasi-periodic solutions.
We also give a qualitative description of the phase space and provide results
on the linear stability of solutions for the spin-orbit and spin-spin problems.
We conclude by providing a comparison between the full and the Keplerian models
with particular reference to the interaction between the rotational and orbital
motions.",2110.11152v1
2015-09-21,Nature of Valance Band Splitting on Multilayer MoS2,"Understanding the origin of splitting of valance band is important since it
governs the unique spin and valley physics in few-layer MoS2. With first
principle methods, we explore the effects of spin-orbit coupling and layer's
coupling on few-layer MoS2. It is found that intra-layer spin-orbit coupling
has a major contribution to the splitting of valance band at K. In double-layer
MoS2, the layer's coupling results in the widening of energy gap of splitted
states induced by intra-layer spin-orbit coupling. The valance band splitting
of bulk MoS_2 in K can follow this model. We also find the effect of
inter-layer spin-orbit coupling in triple-layer MoS2. In addition, the
inter-layer spin-orbit coupling is found to become to be stronger under the
pressure and results in the decrease of main energy gap in the splitting
valance bands at K.",1509.06118v1
2016-07-06,Orbital mapping of energy bands and the truncated spin polarization in three-dimensional Rashba semiconductors,"Associated with spin-orbit coupling (SOC) and inversion symmetry breaking,
Rashba spin polarization opens a new avenue for spintronic applications that
was previously limited to ordinary magnets. However, spin polarization effects
in actual Rashba systems are far more complicated than what conventional
single-orbital models would suggest. By studying via first-principles DFT and a
multi-orbital k.p model a 3D bulk Rashba system (free of complications by
surface effects) we find that the physical origin of the leading spin
polarization effects is SOC-induced hybridization between spin and multiple
orbitals, especially those with nonzero orbital angular momenta. In this
framework we establish a general understanding of the orbital mapping, common
to the surface of topological insulators and Rashba system. Consequently, the
intrinsic mechanism of various spin polarization effects, which pertain to all
Rashba systems even those with global inversion symmetry, is understood as a
manifestation of the orbital textures. This finding suggests a route for
designing high spin-polarization materials by considering the atomic-orbital
content.",1607.01692v2
2015-01-16,Entanglement Driven Phase Transitions in Spin-Orbital Models,"To demonstrate the role played by the von Neumann entropy spectra in quantum
phase transitions we investigate the one-dimensional anisotropic SU(2)$\otimes
XXZ$ spin-orbital model with negative exchange parameter. In the case of
classical Ising orbital interactions we discover an unexpected novel phase with
Majumdar-Ghosh-like spin-singlet dimer correlations triggered by spin-orbital
entanglement and having $k=\pi/2$ orbital correlations, while all the other
phases are disentangled. For anisotropic $XXZ$ orbital interactions both
spin-orbital entanglement and spin-dimer correlations extend to the
antiferro-spin/alternating-orbital phase. This quantum phase provides a unique
example of two coupled order parameters which change the character of the phase
transition from first-order to continuous. Hereby we have established the von
Neumann entropy spectral function as a valuable tool to identify the change of
ground state degeneracies and of the spin-orbital entanglement of elementary
excitations in quantum phase transitions.",1501.04022v3
2009-07-13,A virtual intersubband spin-flip spin-orbit coupling induced spin relaxation in GaAs (110) quantum wells,"A spin relaxation mechanism is proposed based on a second-order spin-flip
intersubband spin-orbit coupling together with the spin-conserving scattering.
The corresponding spin relaxation time is calculated via the Fermi golden rule.
It is shown that this mechanism is important in symmetric GaAs (110) quantum
wells with high impurity density. The dependences of the spin relaxation time
on electron density, temperature and well width are studied with the underlying
physics analyzed.",0907.2092v2
2006-09-19,Far Infrared absorption of non center of mass modes and optical sum rule in a few electron quantum dot with Rashba spin-orbit coupling,"Spin-orbit interaction in a quantum dot couples far infrared radiation to non
center of mass excitation modes, even for parabolic confinement and dipole
approximation. The intensities of the absorption peaks satisfy the optical sum
rule, giving direct information on the total number of electrons inside the
dot. In the case of a circularly polarized radiation the sum rule is
insensitive to the strength of a Rashba spin-orbit coupling due to an electric
field orthogonal to the dot plane, but not to other sources of spin-orbit
interaction, thus allowing to discriminate between the two.",0609456v1
2012-02-08,Role of spin-orbit coupling on the electronic structure and properties of SrPtAs,"The effect of spin-orbit coupling on the electronic structure of the layered
iron-free pnictide superconductor, SrPtAs, has been studied using the full
potential linearized augmented plane wave method. The anisotropy in Fermi
velocity, conductivity and plasma frequency stemming from the layered structure
are found to be enhanced by spin-orbit coupling. The relationship between
spin-orbit interaction and the lack of two-dimensional inversion in the PtAs
layers is analyzed within a tight-binding Hamiltonian based on the
first-principles calculations. Finally, the band structure suggests that
electron doping could increase $T_c$.",1202.1604v1
2013-02-22,Anderson Localization of cold atomic gases with effective spin-orbit interaction in a quasiperiodic optical lattice,"We theoretically investigate the localization properties of a spin-orbit
coupled spin-1/2 particle moving in a one-dimensional quasiperiodic potential,
which can be experimentally implemented using cold atoms trapped in a
quasiperiodic optical lattice potential and external laser fields. We present
the phase diagram in the parameter space of the disorder strength and those
related to the spin-orbit coupling. The phase diagram is verified via
multifractal analysis of the atomic wavefunctions and the numerical simulation
of diffusion dynamics. We found that spin-orbit coupling can lead to the
spectra mixing (coexistence of extended and localized states) and the
appearance of mobility edges.",1302.5465v1
2015-11-10,Boundary conditions and Green function approach of the spin-orbit interaction in the graphitic nanocone,"The boundary effects affecting the Hamiltonian for the nanocone with
curvatureinduced spin orbit coupling were considered and the corresponding
electronic structure was calculated. These boundary effects include the spin
orbit coupling, the electron mass acquisition and the Coulomb interaction.
Different numbers of the pentagonal defects in the tip were considered. The
Green function approach into the second order was used for getting more precise
results in the case of the spin orbit coupling.",1511.03004v2
2012-01-23,Strong Enhancement of Rashba spin-orbit coupling with increasing anisotropy in the Fock-Darwin states of a quantum dot,"We have investigated the electronic properties of elliptical quantum dots in
a perpendicular external magnetic field, and in the presence of the Rashba
spin-orbit interaction. Our work indicates that the Fock-Darwin spectra display
strong signature of Rashba spin-orbit coupling even for a low magnetic field,
as the anisotropy of the quantum dot is increased. An explanation of this
pronounced effect with respect to the anisotropy is presented. The strong
spin-orbit coupling effect manifests itself prominently in the corresponding
dipole-allowed optical transitions, and hence is susceptible to direct
experimental observation.",1201.4842v2
2005-06-09,Screening in the two-dimensional electron gas with spin-orbit coupling,"We study the interplay between electron-electron interaction and Rashba
spin-orbit coupling in the two-dimensional electron gas. Using the random phase
approximation we predict new screening properties of the electron gas which
result in extension of the region of particle-hole excitations and in
spin-orbit induced suppression of collective modes. In particular, we observe
that the spin-orbit coupling gives a finite lifetime to plasmons and
longitudinal optical phonons, which can be resolved in inelastic Raman
scattering. We evaluate the experimentally measurable dynamic structure factor
and estimate the range of parameters where the described phenomena are mostly
pronounced.",0506227v2
2009-11-17,Large polaron formation induced by Rashba spin-orbit coupling,"Here the electron-phonon Holstein model with Rashba spin-orbit interaction is
studied for a two dimensional square lattice in the adiabatic limit. It is
demonstrated that a delocalized electron at zero spin-orbit coupling localizes
into a large polaron state as soon as the Rashba term is nonzero. This
spin-orbit induced polaron state has localization length inversely proportional
to the Rashba coupling $\gamma$, and it dominates a wide region of the
$\gamma$-$\lambda$ phase diagram, where $\lambda$ is the electron-phonon
interaction.",0911.3206v2
2008-03-06,Effective one body approach to the dynamics of two spinning black holes with next-to-leading order spin-orbit coupling,"Using a recent, novel Hamiltonian formulation of the gravitational
interaction of spinning binaries, we extend the Effective One Body (EOB)
description of the dynamics of two spinning black holes to next-to-leading
order (NLO) in the spin-orbit interaction. The spin-dependent EOB Hamiltonian
is constructed from four main ingredients: (i) a transformation between the
``effective'' Hamiltonian and the ``real'' one, (ii) a generalized effective
Hamilton-Jacobi equation involving higher powers of the momenta, (iii) a
Kerr-type effective metric (with Pad\'e-resummed coefficients) which depends on
the choice of some basic ``effective spin vector'' $\bf{S}_{\rm eff}$, and
which is deformed by comparable-mass effects, and (iv) an additional effective
spin-orbit interaction term involving another spin vector $\bsigma$. As a first
application of the new, NLO spin-dependent EOB Hamiltonian, we compute the
binding energy of circular orbits (for parallel spins) as a function of the
orbital frequency, and of the spin parameters. We also study the
characteristics of the last stable circular orbit: binding energy, orbital
frequency, and the corresponding dimensionless spin parameter $\hat{a}_{\rm
LSO}\equiv c J_{\rm LSO}/\boldsymbol(G(H_{\rm LSO}/c^2)^2\boldsymbol)$. We find
that the inclusion of NLO spin-orbit terms has a significant ``moderating''
effect on the dynamical characteristics of the circular orbits for large and
parallel spins.",0803.0915v1
2012-05-30,Conservation law in noncommutative geometry -- Application to spin-orbit coupled systems,"The quantization scheme by noncommutative geometry developed in string theory
is applied to establish the conservation law of twisted spin and spin current
densities in the spin-orbit coupled systems. Starting from the pedagogical
introduction to Hopf algebra and deformation quantization, the detailed
derivation of the conservation law is given.",1205.6629v1
2002-08-29,Semiclassical spin coherent state method in the weak spin-orbit coupling limit,"We apply the semiclassical spin coherent state method for the density of
states by Pletyukhov et al. (2002) in the weak spin-orbit coupling limit and
recover the modulation factor in the semiclassical trace formula found by Bolte
and Keppeler (1998, 1999).",0208047v1
2022-03-23,Effects of a single impurity in a Luttinger liquid with spin-orbit coupling,"In quasi-1D conducting nanowires spin-orbit coupling destructs spin-charge
separation, intrinsic to Tomonaga-Luttinger liquid (TLL). We study
renormalization of a single scattering impurity in a such liquid. Performing
bosonization of low-energy excitations and exploiting perturbative
renormalization analysis we extend the phase portrait in $K_s$ - $K_c$ space,
obtained previously for TLL with decoupled spin-charge channels.",2203.12263v1
2015-05-29,Topological Surface States Originated Spin-Orbit Torques in Bi2Se3,"Three dimensional topological insulator bismuth selenide (Bi2Se3) is expected
to possess strong spin-orbit coupling and spin-textured topological surface
states, and thus exhibit a high charge to spin current conversion efficiency.
We evaluate spin-orbit torques in Bi2Se3/Co40Fe40B20 devices at different
temperatures by spin torque ferromagnetic resonance measurements. As
temperature decreases, the spin-orbit torque ratio increases from ~ 0.047 at
300 K to ~ 0.42 below 50 K. Moreover, we observe a significant out-of-plane
torque at low temperatures. Detailed analysis indicates that the origin of the
observed spin-orbit torques is topological surface states in Bi2Se3. Our
results suggest that topological insulators with strong spin-orbit coupling
could be promising candidates as highly efficient spin current sources for
exploring next generation of spintronic applications.",1505.07937v1
1995-06-08,Coalescing binary systems of compact objects to (post)$^{5/2}-Newtonian order. V. Spin Effects,"We examine the effects of spin-orbit and spin-spin coupling on the inspiral
of a coalescing binary system of spinning compact objects and on the
gravitational radiation emitted therefrom. Using a formalism developed by
Blanchet, Damour, and Iyer, we calculate the contributions due to the spins of
the bodies to the symmetric trace-free radiative multipole moments which are
used to calculate the waveform, energy loss, and angular momentum loss from the
inspiralling binary. Using equations of motion which include terms due to
spin-orbit and spin-spin coupling, we evolve the orbit of a coalescing binary
and use the orbit to calculate the emitted gravitational waveform. We find the
spins of the bodies affect the waveform in several ways: 1) The spin terms
contribute to the orbital decay of the binary, and thus to the accumulated
phase of the gravitational waveform. 2) The spins cause the orbital plane to
precess, which changes the orientation of the orbital plane with respect to an
observer, thus causing the shape of the waveform to be modulated. 3) The spins
contribute directly to the amplitude of the waveform. We discuss the size and
importance of spin effects for the case of two coalescing neutron stars, and
for the case of a neutron star orbiting a rapidly rotating $10M_\odot$ black
hole.",9506022v1
2021-06-02,Enhanced spin-orbit coupling and orbital moment in ferromagnets by electron correlations,"In atomic physics, the Hund rule says that the largest spin and orbital state
is realized due to the interplay of the spin-orbit coupling (SOC) and the
Coulomb interactions. Here, we show that in ferromagnetic solids the effective
SOC and the orbital magnetic moment can be dramatically enhanced by a factor of
$1/[1-(2U^\prime-U-J_H)\rho_0]$, where $U$ and $U^\prime$ are the on-site
Coulomb interaction within the same oribtals and between different orbitals,
respectively, $J_H$ is the Hund coupling, and $\rho_0$ is the average density
of states. This factor is obtained by using the two-orbital as well as
five-orbital Hubbard models with SOC. We also find that the spin polarization
is more favorable than the orbital polarization, being consistent with
experimental observations. This present work provides a fundamental basis for
understanding the enhancements of SOC and orbital moment by Coulomb
interactions in ferromagnets, which would have wide applications in
spintronics.",2106.01046v1
2017-11-07,Spin-Orbit Coupling and Magnetic Anisotropy in Iron-Based Superconductors,"We determine theoretically the effect of spin-orbit coupling on the magnetic
excitation spectrum of itinerant multi-orbital systems, with specific
application to iron-based superconductors. Our microscopic model includes a
realistic ten-band kinetic Hamiltonian, atomic spin-orbit coupling, and
multi-orbital Hubbard interactions. Our results highlight the remarkable
variability of the resulting magnetic anisotropy despite constant spin-orbit
coupling. At the same time, the magnetic anisotropy exhibits robust universal
behavior upon changes in the bandstructure corresponding to different materials
of iron-based superconductors. A natural explanation of the observed
universality emerges when considering optimal nesting as a resonance
phenomenon. Our theory is also of relevance to other itinerant system with
spin-orbit coupling and nesting tendencies in the bandstructure.",1711.02460v1
2008-09-30,Multi-terminal Spin Transport: Non applicability of linear response and Equilibrium spin currents,"We present generalized scattering theory for multi-terminal spin transport in
systems with broken SU(2) symmetry either due to spin-orbit
interaction,magnetic impurities or magnetic leads. We derive equation for spin
current consistent with charge conservation. It is shown that resulting spin
current equations can not be expressed as difference of potential pointing to
{\it non applicability of linear response for spin currents} and as a
consequence equilibrium spin currents(ESC) in the leads are non zero. We
illustrate the theory by calculating ESC in two terminal normal system in
presence of Rashba spin orbit coupling and show that it leads to spin
rectification consistent with the non linear nature of spin transport.",0809.5119v1
2003-12-16,Three-body spin-orbit forces from chiral two-pion exchange,"Using chiral perturbation theory, we calculate the density-dependent
spin-orbit coupling generated by the two-pion exchange three-nucleon
interaction involving virtual $\Delta$-isobar excitation. From the
corresponding three-loop Hartree and Fock diagrams we obtain an isoscalar
spin-orbit strength $F_{\rm so}(k_f)$ which amounts at nuclear matter
saturation density to about half of the empirical value of $90 $MeVfm$^5$. The
associated isovector spin-orbit strength $G_{\rm so}(k_f)$ comes out about a
factor of 20 smaller. Interestingly, this three-body spin-orbit coupling is not
a relativistic effect but independent of the nucleon mass $M$. Furthermore, we
calculate the three-body spin-orbit coupling generated by two-pion exchange on
the basis of the most general chiral $\pi\pi NN$-contact interaction. We find
similar (numerical) results for the isoscalar and isovector spin-orbit
strengths $F_{\rm so}(k_f)$ and $G_{\rm so}(k_f)$ with a strong dominance of
the p-wave part of the $\pi\pi NN$-contact interaction and the Hartree
contribution.",0312058v1
2011-08-21,Vortices in spin-orbit-coupled Bose-Einstein condensates,"Realistic methods to create vortices in spin-orbit-coupled Bose-Einstein
condensates are discussed. It is shown that, contrary to common intuition,
rotation of the trap containing a spin-orbit condensate does not lead to an
equilibrium state with static vortex structures, but gives rise instead to
non-equilibrium behavior described by an intrinsically time-dependent
Hamiltonian. We propose here the following alternative methods to induce
thermodynamically stable static vortex configurations: (1) to rotate both the
lasers and the anisotropic trap; and (2) to impose a synthetic Abelian field on
top of synthetic spin-orbit interactions. Effective Hamiltonians for spin-orbit
condensates under such perturbations are derived for most currently known
realistic laser schemes that induce synthetic spin-orbit couplings. The
Gross-Pitaevskii equation is solved for several experimentally relevant
regimes. The new interesting effects include spatial separation of left- and
right-moving spin-orbit condensates, the appearance of unusual vortex
arrangements, and parity effects in vortex nucleation where the topological
excitations are predicted to appear in pairs. All these phenomena are shown to
be highly non-universal and depend strongly on a specific laser scheme and
system parameters.",1108.4212v1
2016-10-07,Spin-orbit coupling controlled $J=3/2$ electronic ground state in 5$d^{3}$ oxides,"Entanglement of spin and orbital degrees of freedom drives the formation of
novel quantum and topological physical states. Discovering new spin-orbit
entangled ground states and emergent phases of matter requires both
experimentally probing the relevant energy scales and applying suitable
theoretical models. Here we report resonant inelastic x-ray scattering
measurements of the transition metal oxides Ca$_3$LiOsO$_6$ and Ba$_2$YOsO$_6$.
We invoke an intermediate coupling approach that incorporates both spin-orbit
coupling and electron-electron interactions on an even footing and reveal the
ground state of $5d^3$ based compounds, which has remained elusive in
previously applied models, is a novel spin-orbit entangled J=3/2 electronic
ground state. This work reveals the hidden diversity of spin-orbit controlled
ground states in 5d systems and introduces a new arena in the search for
spin-orbit controlled phases of matter.",1610.02375v1
2017-01-13,Bose-Einstein condensates in the presence of Weyl spin-orbit coupling,"We consider two-component Bose-Einstein condensates subject to Weyl
spin-orbit coupling. We obtain mean-field ground state phase diagram by
variational method. In the regime where interspecies coupling is larger than
intraspecies coupling, the system is found to be fully polarized and condensed
at a finite momentum lying along the quantization axis. We characterize this
phase by studying the excitation spectrum, the sound velocity, the quantum
depletion of condensates, the shift of ground state energy, and the static
structure factor. We find that spin-orbit coupling and interspecies coupling
generally leads to competing effects.",1701.03673v1
2021-05-10,Self-Bound Quantum Droplet with Internal Stripe Structure in 1D Spin-Orbit-Coupled Bose Gas,"We study the quantum-droplet state in a 3-dimensional (3D) Bose gas in the
presence of 1D spin-orbit-coupling and Raman coupling, especially the stripe
phase with density modulation, by numerically computing the ground state energy
including the mean-field energy and Lee-HuangYang correction. In this droplet
state, the stripe can exist in a wider range of Raman coupling, compared with
the BEC-gas state. More intriguingly, both spin-orbit-coupling and Raman
coupling strengths can be used to tune the droplet density.",2105.04172v1
2004-05-12,The role of orbital dynamics in spin relaxation and weak antilocalization in quantum dots,"We develop a semiclassical theory for spin-dependent quantum transport to
describe weak (anti)localization in quantum dots with spin-orbit coupling. This
allows us to distinguish different types of spin relaxation in systems with
chaotic, regular, and diffusive orbital classical dynamics. We find, in
particular, that for typical Rashba spin-orbit coupling strengths, integrable
ballistic systems can exhibit weak localization, while corresponding chaotic
systems show weak antilocalization. We further calculate the magnetoconductance
and analyze how the weak antilocalization is suppressed with decreasing quantum
dot size and increasing additional in-plane magnetic field.",0405266v2
2023-04-25,Designing Valley-Dependent Spin-Orbit Interaction by Curvature,"We construct a general theoretical framework for describing curvature-induced
spin-orbit interactions on the basis of group theory. Our theory can
systematically determine the emergence of spin splitting in the band structure
according to symmetry in the wavenumber space and the bending direction of the
material. As illustrative examples, we derive the curvature-induced spin-orbit
coupling for carbon and silicon nanotubes. Our theory offers a strategy for
designing valley-contrasting spin-orbit coupled materials by tuning their
curvatures.",2304.12928v1
2005-08-03,Spin and orbital valence bond solids in a one-dimensional spin-orbital system: Schwinger boson mean field theory,"A generalized one-dimensional $SU(2)\times SU(2)$ spin-orbital model is
studied by Schwinger boson mean-field theory (SBMFT). We explore mainly the
dimer phases and clarify how to capture properly the low temperature properties
of such a system by SBMFT. The phase diagrams are exemplified. The three dimer
phases, orbital valence bond solid (OVB) state, spin valence bond solid (SVB)
state and spin-orbital valence bond solid (SOVB) state, are found to be favored
in respectively proper parameter regions, and they can be characterized by the
static spin and pseudospin susceptibilities calculated in SBMFT scheme. The
result reveals that the spin-orbit coupling of $SU(2)\times SU(2)$ type serves
as both the spin-Peierls and orbital-Peierles mechanisms that responsible for
the spin-singlet and orbital-singlet formations respectively.",0508086v1
2017-11-09,Relativistic Spin-Orbit Interactions of Photons and Electrons,"Laboratory optics, typically dealing with monochromatic light beams in a
single reference frame, exhibits numerous spin-orbit interaction phenomena due
to the coupling between the spin and orbital degrees of freedom of light.
Similar phenomena appear for electrons and other spinning particles. Here we
examine transformations of paraxial photon and relativistic-electron states
carrying the spin and orbital angular momenta (AM) under the Lorentz boosts
between different reference frames. We show that transverse boosts inevitably
produce a rather nontrivial conversion from spin to orbital AM. The converted
part is then separated between the intrinsic (vortex) and extrinsic (transverse
shift or Hall effect) contributions. Although the spin, intrinsic-orbital, and
extrinsic-orbital parts all point in different directions, such complex
behavior is necessary for the proper Lorentz transformation of the total AM of
the particle. Relativistic spin-orbit interactions can be important in
scattering processes involving photons, electrons, and other relativistic
spinning particles, as well as when studying light emitted by fast-moving
bodies.",1711.03255v2
2003-06-25,Dimerization versus Orbital Moment Ordering in the Mott insulator YVO$_3$,"We use exact diagonalization combined with mean-field theory to investigate
the phase diagram of the spin-orbital model for cubic vanadates. The spin-orbit
coupling competes with Hund's exchange and triggers a novel phase, with the
ordering of $t_{2g}$ orbital magnetic moments stabilized by the tilting of
VO$_6$ octahedra. It explains qualitatively spin canting and reduction of
magnetization observed in YVO$_3$. At finite temperature an orbital Peierls
instability in the $C$-type antiferromagnetic phase induces modulation of
magnetic exchange constants even in absence of lattice distortions. The
calculated spin structure factor shows a magnon splitting due to the orbital
Peierls dimerization.",0306637v1
2017-06-19,Chiral and Topological Orbital Magnetism of Spin Textures,"Using a semiclassical Green's function formalism, we discover the emergence
of chiral and topological orbital magnetism in two-dimensional chiral spin
textures by explicitly finding the corrections to the orbital magnetization,
proportional to the powers of the gradients of the texture. We show that in the
absence of spin-orbit coupling, the resulting orbital moment can be understood
as the electronic response to the emergent magnetic field associated with the
real-space Berry curvature. By referring to the Rashba model, we demonstrate
that by tuning the parameters of surface systems the engineering of emergent
orbital magnetism in spin textures can pave the way to novel concepts in
orbitronics.",1706.06068v1
2011-06-18,Orbital order and magnetism of FeNCN,"Based on density functional calculations, we report on the orbital order and
microscopic magnetic model of FeNCN, a prototype compound for orbital-only
models. Despite having a similar energy scale, the spin and orbital degrees of
freedom in FeNCN are only weakly coupled. The ground-state configuration
features the doubly occupied d_{3z^2-r^2} (a1g) orbital and four
singly-occupied d orbitals resulting in the spin S=2 on the Fe+2 atoms, whereas
alternative (Eg') configurations are about 75 meV/f.u. higher in energy.
Calculated exchange couplings and band gap are in good agreement with the
available experimental data. Experimental effects arising from possible orbital
excitations are discussed.",1106.3665v1
2012-04-17,Compensation effect in carbon nanotube quantum dots coupled to polarized electrodes in the presence of spin-orbit coupling,"We study theoretically the Kondo effect in carbon nanotube quantum dot
attached to polarized electrodes. Since both spin and orbit degrees of freedom
are involved in such a system, the electrode polarization contains the spin-
and orbit-polarizations as well as the Kramers polarization in the presence of
the spin-orbit coupling. In this paper we focus on the compensation effect of
the effective fields induced by different polarizations by applying magnetic
field. The main results are i) while the effective fields induced by the spin-
and orbit-polarizations remove the degeneracy in the Kondo effect, the
effective field induced by the Kramers polarization enhances the degeneracy
through suppressing the spin-orbit coupling; ii) while the effective field
induced by the spin-polarization can not be compensated by applying magnetic
field, the effective field induced by the orbit-polarization can be
compensated; and iii) the presence of the spin-orbit coupling does not change
the compensation behavior observed in the case without the spin-orbit coupling.
These results are observable in an ultraclean carbon-nanotube quantum dot
attached to ferromagnetic contacts under a parallel applied magnetic field
along the tube axis and it would deepen our understanding on the Kondo physics
of the carbon nanotube quantum dot.",1204.3728v1
2014-08-28,Interplay of spin-orbit and hyperfine interactions in dynamical nuclear polarization in semiconductor quantum dots,"We theoretically study the interplay of spin-orbit and hyperfine interactions
in dynamical nuclear polarization in two-electron semiconductor double quantum
dots near the singlet $(S)$ - triplet $(T_+)$ anticrossing. The goal of the
scheme under study is to extend the singlet $(S)$ - triplet $(T_0)$ qubit
decoherence time $T_2^{*}$ by dynamically transferring the polarization from
the electron spins to the nuclear spins. This polarization transfer is achieved
by cycling the electron spins over the $S-T_+$ anticrossing. Here, we
investigate, both quantitatively and qualitatively, how this hyperfine mediated
dynamical polarization transfer is influenced by the Rashba and Dresselhaus
spin-orbit interaction. In addition to $T_2^*$, we determine the singlet return
probability $P_s$, a quantity that can be measured in experiments. Our results
suggest that the spin-orbit interaction establishes a mechanism that can
polarize the nuclear spins in the opposite direction compared to hyperfine
mediated nuclear spin polarization. In materials with relatively strong
spin-orbit coupling, this interplay of spin-orbit and hyperfine mediated
nuclear spin polarizations prevents any notable increase of the $S-T_0$ qubit
decoherence time $T_2^{*}$.",1408.6700v1
2020-08-17,Terahertz spin dynamics driven by an optical spin-orbit torque,"Spin torques are at the heart of spin manipulations in spintronic devices.
Here, we examine the existence of an optical spin-orbit torque, a relativistic
spin torque originating from the spin-orbit coupling of an oscillating applied
field with the spins. We compare the effect of the nonrelativistic Zeeman
torque with the relativistic optical spin-orbit torque for ferromagnetic
systems excited by a circularly polarised laser pulse. The latter torque
depends on the helicity of the light and scales with the intensity, while being
inversely proportional to the frequency. Our results show that the optical
spin-orbit torque can provide a torque on the spins, which is quantitatively
equivalent to the Zeeman torque. Moreover, temperature dependent calculations
show that the effect of optical spin-orbit torque decreases with increasing
temperature. However, the effect does not vanish in a ferromagnetic system,
even above its Curie temperature.",2008.07308v2
2013-12-20,Effects of the spin-orbital coupling on the vacancy-induced magnetism on the honeycomb lattice,"The local magnetism induced by vacancies in the presence of the spin-orbital
interaction is investigated based on the half-filled Kane-Mele-Hubbard model on
the honeycomb lattice. Using the self-consistent mean-field theory, we find
that the spin-orbital coupling will enhance the localization of the spin
moments near a single vacancy. We further study the magnetic structures along
the zigzag edges formed by a chain of vacancies. We find that the spin-orbital
coupling tends to suppress the counter-polarized ferrimagnetic order on the
upper and lower edges, because of the open of the spin-orbital gap. As a
result, in the case of the balance number of sublattices, it will suppress
completely this kind of ferrimagnetic order. But, for the imbalance case, a
ferrimagnetic order along both edges exists because additional zero modes will
not be affected by the spin-orbital coupling.",1312.5809v1
2022-01-26,Magnetoconductance Anisotropies and Aharonov-Casher Phases,"The spin-orbit interaction is a key tool for manipulating and functionalizing
spin-dependent electron transport. However, the precise value of the spin-orbit
coupling constant is hard to determine and control. Here we propose a
measurement of the geometric (Aharonov-Casher) phase of the electron
wavefunction generated by the spin-orbit coupling as a means to deduce the
spin-orbit coupling strength in weak links. Unlike other proposed measurements
of geometric phases, which rely on interference, we show that the anisotropy of
the magnetoconductance, measured at different directions of an external
magnetic field,is determined by the geometric phase. Specifically we consider
weak links in which the Rashba interaction is caused by an external electric
field, but our method is expected to apply also for other forms of the
spin-orbit coupling. Measuring this magnetoconductance anisotropy thus allows
calibrating Rashba spintronic devices by an external electric field that tunes
the spin-orbit interaction.",2201.10845v2
2020-12-13,Pure Bulk Orbital and Spin Photocurrent in Two-Dimensional Ferroelectric Materials,"We elucidate light-induced orbital and spin current through nonlinear
response theory, which generalizes the well-known bulk photovoltaic effect in
centrosymmetric broken materials from charge to the spin and orbital degrees of
freedom. We use two-dimensional nonmagnetic ferroelectric materials (such as
GeS and its analogues) to illustrate this bulk orbital/spin photovoltaic
effect, through first-principles calculations. These materials possess a
vertical mirror symmetry and time-reversal symmetry but lack of inversion
symmetry. We reveal that in addition to the conventional photocurrent that
propagates parallel to the mirror plane (under linearly polarized light), the
symmetric forbidden current perpendicular to the mirror actually contains
electron flows, which carry angular momentum information and move oppositely.
One could observe a pure orbital moment current with zero electric charge
current. This hidden photo-induced orbital current leads to a pure spin current
via spin-orbit coupling interactions. Therefore, a four-terminal device can be
designed to detect and measure photo-induced charge, orbital, and spin currents
simultaneously. All these currents couple with electric polarization $P$, hence
their amplitude and direction can be manipulated through ferroelectric phase
transition. Our work provides a route to generalizing nanoscale devices from
their photo-induced electronics to orbitronics and spintronics.",2012.06933v1
2013-08-06,Chirality from interfacial spin-orbit coupling effects in magnetic bilayers,"As nanomagnetic devices scale to smaller sizes, spin-orbit coupling due to
the broken structural inversion symmetry at interfaces becomes increasingly
important. Here we study interfacial spin-orbit coupling effects in magnetic
bilayers using a simple Rashba model. The spin-orbit coupling introduces
chirality into the behavior of the electrons and through them into the
energetics of the magnetization. In the derived form of the magnetization
dynamics, all of the contributions that are linear in the spin-orbit coupling
follow from this chirality, considerably simplifying the analysis. For these
systems, an important consequence is a correlation between the
Dzyaloshinskii-Moriya interaction and the spin-orbit torque. We use this
correlation to analyze recent experiments.",1308.1198v2
2014-03-11,Renormalization of anticrossings in interacting quantum wires with Rashba and Dresselhaus spin-orbit couplings,"We discuss how electron-electron interactions renormalize the spin-orbit
induced anticrossings between different subbands in ballistic quantum wires.
Depending on the ratio of spin-orbit coupling and subband spacing,
electron-electron interactions can either increase or decrease anticrossing
gaps. When the anticrossings are closing due to a special combination of Rashba
and Dresselhaus spin-orbit couplings, their gap approaches zero as an
interaction dependent power law of the spin-orbit couplings, which is a
consequence of Luttinger liquid physics. Monitoring the closing of the
anticrossings allows to directly measure the related renormalization group
scaling dimension in an experiment. If a magnetic field is applied parallel to
the spin-orbit coupling direction, the anticrossings experience different
renormalizations. Since this difference is entirely rooted in electron-electron
interactions, unequally large anticrossings also serve as a direct signature of
Luttinger liquid physics. Electron-electron interactions furthermore increase
the sensitivity of conductance measurements to the presence of anticrossing.",1403.2759v2
2016-11-15,Surface orbitronics: new twists from orbital Rashba physics,"When the inversion symmetry is broken at a surface, spin-orbit interaction
gives rise to spin-dependent energy shifts - a phenomenon which is known as the
spin Rashba effect. Recently, it has been recognized that an orbital
counterpart of the spin Rashba effect - the orbital Rashba effect - can be
realized at surfaces even without spin- orbit coupling. Here, we propose a
mechanism for the orbital Rashba effect based on sp orbital hybridization,
which ultimately leads to the electric polarization of surface states. As a
proof of principle, we show from first principles that this effect leads to
chiral orbital textures in $\mathbf{k}$-space of the BiAg$_2$ monolayer. In
predicting the magnitude of the orbital moment arising from the orbital Rashba
effect, we demonstrate the crucial role that the Berry phase theory plays for
the magnitude and variation of the orbital textures. As a result, we predict a
pronounced manifestation of various orbital effects at surfaces, and proclaim
the orbital Rashba effect to be a key platform for surface orbitronics.",1611.04674v1
2002-08-22,"Spin-Orbit Coupling, Antilocalization, and Parallel Magnetic Fields in Quantum Dots","We investigate antilocalization due to spin-orbit coupling in ballistic GaAs
quantum dots. Antilocalization that is prominent in large dots is suppressed in
small dots, as anticipated theoretically. Parallel magnetic fields suppress
both antilocalization and also, at larger fields, weak localization, consistent
with random matrix theory results once orbital coupling of the parallel field
is included. In situ control of spin-orbit coupling in dots is demonstrated as
a gate-controlled crossover from weak localization to antilocalization.",0208436v2
2022-11-09,Giant efficiency of long-range orbital torque in Co/Nb bilayers,"We report unambiguously experimental evidence of a strong orbital current in
Nb films with weak spin-orbit coupling via the spin-torque ferromagnetic
resonance (ST-FMR) spectrum for Fe/Nb and Co/Nb bilayers. The sign change of
the damping-like torque in Co/Nb demonstrates a large spin-orbit correlation
and thus great efficiency of orbital torque in Co/Nb. By studying the
efficiency as a function of the thickness of Nb sublayer, we reveal a long
orbital diffusion length (~3.1 nm) of Nb. Further planar Hall resistance (PHE)
measurements at positive and negative applying current confirm the nonlocal
orbital transport in ferromagnetic-metal/Nb heterostructures.",2211.04809v1
2006-08-13,Spin-orbit interactions in black-hole binaries,"We perform numerical simulations of black-hole binaries to study the exchange
of spin and orbital angular momentum during the last, highly nonlinear, stages
of the coalescence process. To calculate the transfer of angular momentum from
orbital to spin, we start with two quasi-circular configurations, one with
initially non-spinning black holes, the other with corotating black holes. In
both cases the binaries complete almost two orbits before merging. We find
that, during these last orbits, the specific spin (a/m) of each horizon
increases by only 0.012 for the initially non-spinning configuration, and by
only 0.006 for the initially corotating configuration. By contrast, the
corotation value for the specific spin should increase from 0.1 at the initial
proper separation of 10M to 0.33 when the proper separation is 5M. Thus the
spin-orbit coupling is far too weak to tidally lock the binary to a corotating
state during the late-inspiral phase. We also study the converse transfer from
spin into orbital motion. In this case, we start the simulations with parallel,
highly-spinning non-boosted black holes. As the collision proceeds, the system
acquires a non-head-on orbital motion, due to spin-orbit coupling, that leads
to the radiation of angular momentum. We are able to accurately measure the
energy and angular momentum losses and model their dependence on the initial
spins.",0608275v4
2003-10-14,Spin-Hall and spin-diagonal conductivity in the presence of Rashba and Dresselhaus spin-orbit coupling,"We investigate the spin-current linear response conductivity tensor to an
electric field in a paramagnetic two dimensonal electron gas with both Rashba
and Dresselhaus spin-orbit coupling in the weak scattering regime. In the
ususal case where both spin-orbit-split bands are occupied, we find that the
spin-Hall conductivity depends only on the sign of the difference in magnitude
of the Rashba and Dresselhaus coupling strengths except within a narrow window
where both coupling strengths are equal. We also find a new effect in which a
spin current is generated in the direction of the driving field whenever the
Dresselhaus spin-orbit coupling is nonzero. We discuss experimental
implications of this finding taking into account the finite mobility and
typical parameters of current samples and possible experimental set ups for its
detection.",0310315v1
2007-01-17,Spin polarization effects in a two dimensional mesoscopic electronic structure with Rashba spin-orbit and lateral confinement,"Because of the peculiar coupling of spatial and spin degrees of freedom
effected by the Rashba spin-orbit interaction, lateral confinement of a two
dimensional electronic system leads to a finite transverse spin polarization
near the longitudinal edges of a current carrying quantum wire. The sign of
this component of the polarization is opposite at the two edges and can be
reversed upon inversion of the current. Interestingly for small spin orbit
coupling this is the largest contribution to the total polarization, its
magnitude being of second order in the coupling constant. As a consequence this
phenomenon cannot be revealed in lowest order perturbative approaches. An in
plane spin polarization component is also present that is perpendicular to the
current. Within the same model this component would be also present in the
bulk. On the other hand while in the latter case its magnitude is linear in the
coupling constant, we find that it only represents a third order effect in the
wire geometry. Our results are consistent with a general rigorous argument on
the parity of the components of the spin polarization with respect to the sign
of the spin orbit coupling constant.",0701415v1
2017-08-24,Magnetization in pristine graphene with Zeeman splitting and variable spin-orbit coupling,"The aim of this work is to describe the spin magnetization of graphene with
Rashba spinorbit coupling and Zeeman effect. It is shown that the magnetization
depends critically on the spin-orbit coupling l that is controlled with an
external electric field. In turn, by manipulating the density of charge
carriers, it is shown that spin up and down Landau levels mix introducing jumps
in the spin magnetization. Two magnetic oscillations phases are described that
can be tunable through the applied external fields. The maximum and minimum of
the oscillations can be alternated by taking into account how the energy levels
are filled when the Rashba-spin-orbit coupling is turned on. The results
obtained are of importance to design superlattices with variable spin-orbit
coupling with different configurations in which spin oscillations and spin
filters can be developed.",1708.07574v1
2015-08-04,Spin structure of harmonically trapped one-dimensional atoms with spin-orbit coupling,"We introduce a theoretical approach to determine the spin structure of
harmonically trapped atoms with two-body zero-range interactions subject to an
equal mixture of Rashba and Dresselhaus spin-orbit coupling created through
Raman coupling of atomic hyperfine states. The spin structure of bosonic and
fermionic two-particle systems with finite and infinite two-body interaction
strength $g$ is calculated. Taking advantage of the fact that the $N$-boson and
$N$-fermion systems with infinitely large coupling strength $g$ are
analytically solvable for vanishing spin-orbit coupling strength $k_{so}$ and
vanishing Raman coupling strength $\Omega$, we develop an effective spin model
that is accurate to second-order in $\Omega$ for any $k_{so}$ and infinite $g$.
The three- and four-particle systems are considered explicitly. It is shown
that the effective spin Hamiltonian, which contains a Heisenberg exchange term
and an anisotropic Dzyaloshinskii-Moriya exchange term, describes the
transitions that these systems undergo with the change of $k_{so}$ as a
competition between independent spin dynamics and nearest-neighbor spin
interactions.",1508.00932v1
2022-06-01,Substrate Effects on Spin Relaxation in Two-Dimensional Dirac Materials with Strong Spin-Orbit Coupling,"Understanding substrate effects on spin dynamics and relaxation in
two-dimensional (2D) materials is of key importance for spintronics and quantum
information applications. However, the key factors that determine the substrate
effect on spin relaxation, in particular for materials with strong spin-orbit
coupling, have not been well understood. Here we performed first-principles
real-time density-matrix dynamics simulations with spin-orbit coupling (SOC)
and quantum descriptions of electron-phonon and electron-impurity scattering
for the spin lifetimes of supported/free-standing germanene, a prototypical
strong SOC 2D Dirac material. We show that the effects of different substrates
on spin lifetime can surprisingly differ by two orders of magnitude. We find
that substrate effects on $\tau_s$ are closely related to substrate-induced
modifications of the SOC-field anisotropy, which changes the spin-flip
scattering matrix elements. We propose a new electronic quantity, named
spin-flip angle $\theta^{\uparrow\downarrow}$, to characterize spin relaxation
caused by intervalley spin-flip scattering. We find that the spin relaxation
rate is approximately proportional to the averaged value of
$\mathrm{sin}^{2}\left(\theta^{\uparrow\downarrow}/2\right)$, which can be used
as a guiding parameter of controlling spin relaxation.",2206.00784v2
2023-08-23,Spin pumping from a ferromagnetic insulator into an altermagnet,"A class of antiferromagnets with spin-polarized electron bands, yet zero net
magnetization, called altermagnets is attracting increasing attention due to
their potential use in spintronics. Here, we study spin injection into an
altermagnet via spin pumping from a ferromagnetic insulator. We find that the
spin pumping behaves qualitatively different depending on how the altermagnet
is crystallographically oriented relative the interface to the ferromagnetic
insulator. The altermagnetic state can enhance or suppress spin pumping, which
we explain in terms of spin-split altermagnetic band structure and the
spin-flip probability for the incident modes. Including the effect of
interfacial Rashba spin-orbit coupling, we find that the spin-pumping effect is
in general magnified, but that it can display a non-monotonic behavior as a
function of the spin-orbit coupling strength. We show that there exists an
optimal value of the spin-orbit coupling strength which causes an order of
magnitude increase in the pumped spin current, even for the crystallographic
orientation of the altermagnet which suppresses the spin pumping.",2308.12335v1
2006-06-07,Spin-Orbital Entanglement and Phase Diagram of Spin-orbital Chain with $SU(2) \times SU(2)$ Symmetry,"Spin-orbital entanglement in quantum spin-orbital systems is quantified by a
reduced von Neumann entropy, and is calculated for the ground state of a
coupled spin-orbital chain with $SU(2)\times SU(2)$ symmetry. By analyzing the
discontinuity and local extreme of the reduced entropy as functions of the
model parameters, we deduce a rich phase diagram to describe the quantum phase
transitions in the model. Our approach provides an efficient and powerful
method to identify phase boundaries in a system with complex correlation
between multiply degrees of freedom.",0606194v1
2001-03-14,Threshold suppression of Lambda spin-orbit splitting,"New experimental data on medium to heavy single Lambda hypernuclei revealed a
much larger spin-orbit splitting than observed in older measurements of light
hypernuclei. Taking into account particle threshold effects and the
density-dependence of in-medium coupling constants the apparent suppression of
spin-orbit strength in light hypernuclei as well as the spin-orbit structure
observed in medium to heavy nuclei are explained in a unified manner within the
density dependent relativistic hadron field theory. It is concluded that the
most valuable information on the Lambda spin-orbit dynamics in finite nuclei
has to be extracted from medium to heavy mass nuclei.",0103035v1
2020-05-11,Effect of the spin-orbit interaction on thermodynamic properties of liquid uranium,"We present the first quantum molecular dynamics calculation of zero-pressure
isobar of solid and liquid uranium that account for spin-orbit coupling. We
demonstrate that inclusion of spin-orbit interaction leads to higher degree of
the thermal expansion of uranium, especially in the liquid phase. Full
accounting of relativistic effects for valence electrons, particularly
spin-orbital splitting of the 5f band, is substantial for the reproduction of
the experimental density of molten uranium at the melting temperature.
Influence of the spin-orbit interaction on the thermodynamic properties at high
temperatures and pressures is also analyzed.",2005.05468v1
2010-05-17,Anomalous spin Hall effects in Dresselhaus (110) quantum wells,"Anomalous spin Hall effects that belong to the intrinsic type in Dresselhaus
(110) quantum wells are discussed. For the out-of-plane spin component,
antisymmetric current-induced spin polarization induces opposite spin Hall
accumulation, even though there is no spin-orbit force due to Dresselhaus (110)
coupling. A surprising feature of this spin Hall induction is that the spin
accumulation sign does not change upon bias reversal. Contribution to the spin
Hall accumulation from the spin Hall induction and the spin deviation due to
intrinsic spin-orbit force as well as extrinsic spin scattering, can be
straightforwardly distinguished simply by reversing the bias. For the inplane
component, inclusion of a weak Rashba coupling leads to a new type of $S_y$
intrinsic spin Hall effect solely due to spin-orbit-force-driven spin
separation.",1005.2948v4
2004-03-22,Spin polarization of electrons with Rashba double-refraction,"We demonstrate how the Rashba spin-orbit coupling in semiconductor
heterostructures can produce and control a spin-polarized current without
ferromagnetic leads. Key idea is to use spin-double refraction of an electronic
beam with a nonzero incidence angle. A region where the spin-orbit coupling is
present separates the source and the drain without spin-orbit coupling. We show
how the transmission and the beam spin-polarization critically depend on the
incidence angle. The transmission halves when the incidence angle is greater
than a limit angle and a significant spin-polarization appears. Increasing the
spin-orbit coupling one can obtain the modulation of the intensity and of the
spin-polarization of the output electronic current when the input current is
unpolarized. Our analysis shows the possibility to realize a spin-field-effect
transistor based on the propagation of only one mode with the region with
spin-orbit coupling. Where the original Datta and Das device [Appl.Phys.Lett.
{\bf 56}, 665 (1990)] use the spin-precession that originates from the
interference between two modes with orthogonal spin.",0403534v3
2020-12-19,Non-orthogonal Spin-Momentum Locking,"Spin-momentum locking is a unique intrinsic feature of strongly spin-orbit
coupled materials and a key to their promise of applications in spintronics and
quantum computation. Much of the existing work, in topological and
non-topological pure materials, has been focused on the orthogonal locking in
the vicinity of the $\Gamma$ point where the directions of spin and momentum
vectors are locked perpendicularly. With the orthogonal case, enforced by the
symmetry in pure systems, mechanisms responsible for non-orthogonal
spin-momentum locking (NOSML) have drawn little attention, although it has been
reported on the topological surface of $\alpha$-$Sn$. Here, we demonstrate
that, the presence of the spin-orbit scattering from dilute spinless impurities
can produce the NOSML state in the presence of a strong intrinsic spin-orbit
coupling in the pristine material. We also observe an interesting coupling
threshold for the NOSML state to occur.
  The relevant parameter in our analysis is the deflection angle from
orthogonality which can be extracted experimentally from the
spin-and-angle-resolved photoemission (S-ARPES) spectra. Our formalism is
applicable to all strongly spin-orbit coupled systems with impurities and not
limited to topological ones. The understanding of NOSML bears on spin-orbit
dependent phenomena, including issues of spin-to-charge conversion and the
interpretation of quasiparticle interference (QPI) patterns as well as
scanning-tunneling spectra (STS) in general spin-orbit coupled materials.",2012.10647v5
2013-07-17,Non-monotonic spin relaxation and decoherence in graphene quantum dots with spin-orbit interactions,"We investigate the spin relaxation and decoherence in a single-electron
graphene quantum dot with Rashba and intrinsic spin-orbit interactions. We
derive an effective spin-phonon Hamiltonian via the Schrieffer-Wolff
transformation in order to calculate the spin relaxation time T_1 and
decoherence time T_2 within the framework of the Bloch-Redfield theory. In this
model, the emergence of a non-monotonic dependence of T_1 on the external
magnetic field is attributed to the Rashba spin-orbit coupling-induced
anticrossing of opposite spin states. A rapid decrease of T_1 occurs when the
spin and orbital relaxation rates become comparable in the vicinity of the
spin-mixing energy-level anticrossing. By contrast, the intrinsic spin-orbit
interaction leads to a monotonic magnetic field dependence of the spin
relaxation rate which is caused solely by the direct spin-phonon coupling
mechanism. Within our model, we demonstrate that the decoherence time T_2 ~ 2
T_1 is dominated by relaxation processes for the electron-phonon coupling
mechanisms in graphene up to leading order in the spin-orbit interaction.
Moreover, we show that the energy anticrossing also leads to a vanishing pure
spin dephasing rate for these states for a super-Ohmic bath.",1307.4668v1
2018-07-12,Spin-Phonon coupling parameters from maximally localized Wannier functions and first principles electronic structure: the case of durene single crystal,"Spin-orbit interaction is an important vehicle for spin relaxation. At finite
temperature lattice vibrations modulate the spin-orbit interaction and thus
generate a mechanism for spin-phonon coupling, which needs to be incorporated
in any quantitative analysis of spin transport. Starting from a density
functional theory \textit{ab initio} electronic structure, we calculate
spin-phonon matrix elements over the basis of maximally localized Wannier
functions. Such coupling terms form an effective Hamiltonian to be used to
extract thermodynamic quantities, within a multiscale approach particularly
suitable for organic crystals. The symmetry of the various matrix elements are
analyzed by using the $\Gamma$-point phonon modes of a one-dimensional chain of
Pb atoms. Then the method is employed to extract the spin-phonon coupling of
solid durene, a high-mobility crystal organic semiconducting. Owing to the
small masses of carbon and hydrogen spin-orbit is weak in durene and so is the
spin-phonon coupling. Most importantly we demonstrate that the largest
contribution to the spin-phonon interaction originates from Holstein-like
phonons, namely from internal molecular vibrations.",1807.04579v1
2020-11-20,Anisotropy of the spin-orbit coupling driven by a magnetic field in InAs nanowires,"We use the $\mathbf{k} \cdot \mathbf{p}$ theory and the envelope function
approach to evaluate the Rashba spin-orbit coupling induced in a semiconductor
nanowire by a magnetic field at different orientations, taking explicitely into
account the prismatic symmetry of typical nano-crystals. We make the case for
the strongly spin-orbit-coupled InAs semiconductor nanowires and investigate
the anisotropy of the spin-orbit constant with respect to the field direction.
At sufficiently high magnetic fields perpendicular to the nanowire, a 6-fold
anisotropy results from the interplay between the orbital effect of field and
the prismatic symmetry of the nanowire. A back-gate potential, breaking the
native symmetry of the nano-crystal, couples to the magnetic field inducing a
2-fold anisotropy, with the spin-orbit coupling being maximized or minimized
depending on the relative orientation of the two fields. We also investigate
in-wire field configurations, which shows a trivial 2-fold symmetry when the
field is rotated off the axis. However, isotropic spin-orbit coupling is
restored if a sufficiently high gate potential is applied. Our calculations are
shown to agree with recent experimental analysis of the vectorial character of
the spin-orbit coupling for the same nanomaterial, providing a microscopic
interpretation of the latter.",2011.10483v1
2000-05-30,Dynamical Properties of Spin-Orbital Chains in a Magnetic Field,"The excitation spectrum of the one-dimensional spin-orbital model in a
magnetic field is studied, using a recently developed dynamical density matrix
renormalization group technique. The method is employed on chains with up to 80
sites, and examined for test cases such as the spin-1/2 antiferromagnetic
Heisenberg chain, where the excitation spectrum is known exactly from the Bethe
Ansatz. In the spin-orbital chain, the characteristic dynamical response
depends strongly on the model parameters and the applied magnetic field. The
coupling between the spin and orbital degrees of freedom is found to influence
the incommensuration at finite magnetizations. In the regions of the phase
diagram with only massive spin and orbital excitations, a finite field is
required to overcome the spin gap. An incommensurate orbital mode is found to
become massless in this partially spin-polarized regime, indicating a strong
coupling between the two degrees of freedom. In the critical region with three
elementary gapless excitations, a prominent particle-hole excitation is
observed at higher energies, promoted by the biquadratic term in the model
Hamiltonian of the spin-orbital chain.",0005526v2
2022-07-13,"Giant orbital Hall effect and orbital-to-spin conversion in 3d, 5d, and 4f metallic heterostructures","The orbital Hall effect provides an alternative means to the spin Hall effect
to convert a charge current into a flow of angular momentum. Recently,
compelling signatures of orbital Hall effects have been identified in 3d
transition metals. Here, we report a systematic study of the generation,
transmission, and conversion of orbital currents in heterostructures comprising
3d, 5d, and 4f metals. We show that the orbital Hall conductivity of Cr reaches
giant values of the order of 5*10^5 Ohm^{-1} m^{-1} and that Pt presents a
strong orbital Hall effect in addition to the spin Hall effect. Measurements
performed as a function of thickness of nonmagnetic Cr, Mn, and Pt layers and
ferromagnetic Co and Ni layers reveal how the orbital and spin currents compete
or assist each other in determining the spin-orbit torques acting on the
magnetic layer. We further show how this interplay can be drastically modulated
by introducing 4 f spacers between the nonmagnetic and magnetic layers. Gd and
Tb act as very efficient orbital-to-spin current converters, boosting the
spin-orbit torques generated by Cr by a factor of 4 and reversing the sign of
the torques generated by Pt. To interpret our results, we present a generalized
drift-diffusion model that includes both spin and orbital Hall effects and
describes their interconversion mediated by spin-orbit coupling.",2207.06347v1
2012-06-28,Spin-orbit coupled transport and spin torque in a ferromagnetic heterostructure,"Ferromagnetic heterostructures provide an ideal platform to explore the
nature of spin-orbit torques arising from the interplay mediated by itinerant
electrons between a Rashba-type spin-orbit coupling and a ferromagnetic
exchange interaction. For such a prototypic system, we develop a set of coupled
diffusion equations to describe the diffusive spin dynamics and spin-orbit
torques. We characterize the spin torque and its two prominent--out-of-plane
and in-plane--components for a wide range of relative strength between the
Rashba coupling and ferromagnetic exchange. The symmetry and angular dependence
of the spin torque emerging from our simple Rashba model is in an agreement
with experiments. The spin diffusion equation can be generalized to incorporate
dynamic effect such as spin pumping and magnetic damping.",1206.6726v2
2017-03-17,Spin-Degenerate Regimes for Single Quantum Dots in Transition Metal Dichalcogenide Monolayers,"Strong spin-orbit coupling in transition metal dichalcogenide (TMDC)
monolayers results in spin resolvable band structures about the $K$ and $K'$
valleys such that the eigenbasis of a 2D quantum dot (QD) in a TMDC monolayer
in zero field is described by the Kramers pairs
$|0\rangle_-=|K'\uparrow\rangle$, $|1\rangle_-=|K\downarrow\rangle$ and
$|0\rangle_+=|K\uparrow\rangle$, $|1\rangle_+=|K'\downarrow\rangle$. The strong
spin-orbit coupling limits the usefulness of single TMDC QDs as spin qubits.
Possible regimes of spin-degenerate states, overcoming the spin-orbit coupling
in monolayer TMDC QDs are investigated in both zero field, where the spin and
valley degrees of freedom become fourfold degenerate, and twofold degeneracy in
some magnetic field, localised to a given valley. Such regimes are shown to be
achievable in MoS$_{2}$, where the spin orbit coupling is sufficiently low and
of the right sign such that the spin resolved conduction bands intersect at
points about the $K$ and $K'$ valleys and as such may be exploited by selecting
suitable critical dot radii.",1703.05986v2
2019-06-20,Effects of spin-orbit coupling on the neutron spin resonance in iron-based superconductors,"The so-called neutron spin resonance consists of a prominent enhancement of
the magnetic response at a particular energy and momentum transfer upon
entering the superconducting state of unconventional superconductors. In the
case of iron-based superconductors, the neutron resonance has been extensively
studied experimentally, and a peculiar spin-space anisotropy has been
identified by polarized inelastic neutron scattering experiments. Here we
perform a theoretical study of the energy- and spin-resolved magnetic
susceptibility in the superconducting state with $ s_{+-} $-wave order
parameter, relevant to iron-pnictide and iron-chalcogenide superconductors. Our
model is based on a realistic bandstructure including spin-orbit coupling with
electronic Hubbard-Hund interactions included at the RPA level. Spin-orbit
coupling is taken into account both in the generation of spin-fluctuation
mediated pairing, as well as the numerical computation of the spin
susceptibility in the superconducting state. We find that spin-orbit coupling
and superconductivity in conjunction can reproduce the salient experimentally
observed features of the magnetic anisotropy of the neutron resonance. This
includes the possibility of a double resonance, the tendency for a $c$-axis
polarized resonance, and the existence of enhanced magnetic anisotropy upon
entering the superconducting phase.",1906.08566v1
2018-07-31,Spin absorption at ferromagnetic-metal/platinum-oxide interface,"We investigate the absorption of a spin current at a
ferromagnetic-metal/Pt-oxide interface by measuring current-induced
ferromagnetic resonance. The spin absorption was characterized by the magnetic
damping of the heterostructure. We show that the magnetic damping of a
Ni$_{81}$Fe$_{19}$ film is clearly enhanced by attaching Pt-oxide on the
Ni$_{81}$Fe$_{19}$ film. The damping enhancement is disappeared by inserting an
ultrathin Cu layer between the Ni$_{81}$Fe$_{19}$ and Pt-oxide layers. These
results demonstrate an essential role of the direct contact between the
Ni$_{81}$Fe$_{19}$ and Pt-oxide to induce sizable interface spin-orbit
coupling. Furthermore, the spin-absorption parameter of the
Ni$_{81}$Fe$_{19}$/Pt-oxide interface is comparable to that of intensively
studied heterostructures with strong spin-orbit coupling, such as an oxide
interface, topological insulators, metallic junctions with Rashba spin-orbit
coupling. This result illustrates strong spin-orbit coupling at the
ferromagnetic-metal/Pt-oxide interface, providing an important piece of
information for quantitative understanding the spin absorption and spin-charge
conversion at the ferromagnetic-metal/metallic-oxide interface.",1807.11806v1
2011-12-07,Singlet-triplet splitting in double quantum dots due to spin orbit and hyperfine interactions,"We analyze the low-energy spectrum of a two-electron double quantum dot under
a potential bias in the presence of an external magnetic field. We focus on the
regime of spin blockade, taking into account the spin orbit interaction and
hyperfine coupling of electron and nuclear spins. Starting from a model for two
interacting electrons in a double dot, we derive a perturbative, effective
two-level Hamiltonian in the vicinity of an avoided crossing between singlet
and triplet levels, which are coupled by the spin-orbit and hyperfine
interactions. We evaluate the level splitting at the anticrossing, and show
that it depends on a variety of parameters including the spin orbit coupling
strength, the orientation of the external magnetic field relative to an
internal spin-orbit axis, the potential detuning of the dots, and the
difference between hyperfine fields in the two dots. We provide a formula for
the splitting in terms of the spin orbit length, the hyperfine fields in the
two dots, and the double dot parameters such as tunnel coupling and Coulomb
energy. This formula should prove useful for extracting spin orbit parameters
from transport or charge sensing experiments in such systems. We identify a
parameter regime where the spin orbit and hyperfine terms can become of
comparable strength, and discuss how this regime might be reached.",1112.1644v1
2017-09-28,Spin-orbit interaction of light induced by transverse spin angular momentum engineering,"We report the first demonstration of a direct interaction between the
extraordinary transverse spin angular momentum in evanescent waves and the
intrinsic orbital angular momentum in optical vortex beams. By tapping the
evanescent wave of whispering gallery modes in a micro-ring-based optical
vortex emitter and engineering the transverse spin state carried therein, a
transverse-spin-to-orbital conversion of angular momentum is predicted in the
emitted vortex beams. Numerical and experimental investigations are presented
for the proof-of-principle demonstration of this unconventional interplay
between the spin and orbital angular momenta, which could provide new
possibilities and restrictions on the optical angular momentum manipulation
techniques on the sub-wavelength scale. This phenomenon further gives rise to
an enhanced spin-direction coupling effect in which waveguide or surface modes
are unidirectional excited by incident optical vortex, with the directionality
jointly controlled by spin-orbit states. Our results enrich the spin-orbit
interaction phenomena by identifying a previously unknown pathway between the
polarization and spatial degrees of freedom of light, and can enable a variety
of functionalities employing spin and orbital angular momenta of light in
applications such as communications and quantum information processing.",1709.09811v1
2021-11-26,Thermal Spin-Orbit Torque in Spintronics,"Within the spinor Boltzmann equation (SBE) formalism, we derived a
temperature dependent thermal spin-orbit torque based on local equilibrium
assumption in a system with Rashba spin-orbit interaction. If we expand the
distribution function of spinor Boltzmann equation around local equilibrium
distribution, we can obtain the spin diffusion equation from SBE, then the spin
transfer torque, spin orbit torque as well as thermal spin-orbit torque we seek
to can be read out from this equation. It exhibits that this thermal spin-orbit
torque originates from the temperature gradient of local equilibrium
distribution function, which is explicit and straightforward than previous
works. Finally, we illustrate them by an example of spin-polarized transport
through a ferromagnet with Rashba spin-orbit coupling, in which those torques
driven whatever by temperature gradient or bias are manifested quantitatively.",2112.01370v1
2014-12-19,Magnetic interactions in strongly correlated systems: spin and orbital contributions,"We present a technique to map an electronic model with local interactions (a
generalized multi-orbital Hubbard model) onto an effective model of interacting
classical spins, by requiring that the thermodynamic potentials associated to
spin rotations in the two systems are equivalent up to second order in the
rotation angles. This allows to determine the parameters of relativistic and
non-relativistic magnetic interactions in the effective spin model in terms of
equilibrium Green's functions of the electronic model. The Hamiltonian of the
electronic system includes, in addition to the non-relativistic part,
relativistic single-particle terms such as the Zeeman coupling to an external
magnetic fields, spin-orbit coupling, and arbitrary magnetic anisotropies; the
orbital degrees of freedom of the electrons are explicitly taken into account.
We determine the complete relativistic exchange tensors, accounting for
anisotropic exchange, Dzyaloshinskii-Moriya interactions, as well as additional
non-diagonal symmetric terms (which may include dipole-dipole interaction). Our
procedure provides the complete exchange tensors in a unified framework,
including previously disregarded features such as the vertices of two-particle
Green's functions and non-local self-energies. We do not assume any smallness
in spin-orbit coupling, so our treatment is in this sense exact. Finally, we
show how to distinguish and address separately the spin, orbital and
spin-orbital contributions to magnetism.",1412.6441v2
2023-08-05,Optical vortex harmonic generation facilitated by photonic spin-orbit entanglement,"Photons can undergo spin-orbit coupling, by which the polarization (spin) and
spatial profile (orbit) of the electromagnetic field interact and mix. Strong
photonic spin-orbit coupling may reportedly arise from light propagation
confined in a small cross-section, where the optical modes feature spin-orbit
entanglement. However, while photonic Hamiltonians generally exhibit
nonlinearity, the role and implication of spin-orbit entanglement in nonlinear
optics have received little attention and are still elusive. Here, we report
the first experimental demonstration of nonlinear optical frequency conversion,
where spin-orbit entanglement facilitates spin-to-orbit transfer among
different optical frequencies. By pumping a multimode optical nanofiber with a
spin-polarized Gaussian pump beam, we produce an optical vortex at the third
harmonic, which has long been regarded as a forbidden process in isotropic
media. Our findings offer a unique and powerful means for efficient optical
vortex generation that only incorporates a single Gaussian pump beam, in sharp
contrast to any other approaches employing structured pump fields or
sophisticatedly designed media. Our work opens up new possibilities of
spin-orbit-coupling subwavelength waveguides, inspiring fundamental studies of
nonlinear optics involving various types of structured light, as well as paving
the way for the realization of hybrid quantum systems comprised of telecom
photonic networks and long-lived quantum memories.",2308.02911v1
2016-06-16,"Magnetic Properties from the Viewpoints of Electronic Hamiltonian: Spin Exchange Parameters, Spin Orientation and Spin-Half Misconception","In this chapter we review the quantitative and qualitative aspects of
describing the properties of magnetic solids on the basis of electronic
Hamiltonian. We show that a spin Hamiltonian approach becomes consistent with
an electronic Hamiltonian approach if the spin lattice and its associated spin
exchange parameters, to be used for the spin Hamiltonian, are determined by the
energy-mapping analysis based on DFT calculations. The preferred spin
orientation (i.e., the magnetic anisotropy) of a magnetic ion is not predicted
by a spin Hamiltonian because it does not include the orbital degree of freedom
explicitly. In contrast, the magnetic anisotropy is readily predicted by
electronic structure theories employing both orbital and spin degrees of
freedom, if one takes into consideration the spin-orbit coupling (SOC). It was
shown that the preferred spin orientation of a magnetic ion can be predicted
and understood in terms of the HOMO-LUMO interactions of the magnetic ion by
taking SOC as perturbation. A spin Hamiltonian gives rise to the spin-half
misconception, namely, the blind belief that spin-half magnetic ions do not
possess magnetic anisotropy that arise from SOC. This misconception is a direct
consequence from the limitedness of a spin Hamiltonian that it lacks the
orbital degree of freedom. We show that the magnetic properties of 5d ion
oxides are better explained by the LS-coupling than by the jj-coupling scheme
of SOC, that the spin-orbital entanglement of 5d ions is not as strong as has
been assumed.",1606.05220v1
2009-12-17,An improved effective-one-body Hamiltonian for spinning black-hole binaries,"Building on a recent paper in which we computed the canonical Hamiltonian of
a spinning test particle in curved spacetime, at linear order in the particle's
spin, we work out an improved effective-one-body (EOB) Hamiltonian for spinning
black-hole binaries. As in previous descriptions, we endow the effective
particle not only with a mass m, but also with a spin S*. Thus, the effective
particle interacts with the effective Kerr background (having spin S_Kerr)
through a geodesic-type interaction and an additional spin-dependent
interaction proportional to S*. When expanded in post-Newtonian (PN) orders,
the EOB Hamiltonian reproduces the leading order spin-spin coupling and the
spin-orbit coupling through 2.5PN order, for any mass-ratio. Also, it
reproduces all spin-orbit couplings in the test-particle limit. Similarly to
the test-particle limit case, when we restrict the EOB dynamics to spins
aligned or antialigned with the orbital angular momentum, for which circular
orbits exist, the EOB dynamics has several interesting features, such as the
existence of an innermost stable circular orbit, a photon circular orbit, and a
maximum in the orbital frequency during the plunge subsequent to the inspiral.
These properties are crucial for reproducing the dynamics and
gravitational-wave emission of spinning black-hole binaries, as calculated in
numerical relativity simulations.",0912.3517v2
2005-06-16,Design and control of spin gates in two quantum dots arrays,"We study the spin-spin interaction between quantum dots coupled through a two
dimensional electron gas with spin-orbit interaction. We show that the
interplay between transverse electron focusing and spin-orbit coupling allows
to dynamically change the symmetry of the effective spin-spin Hamiltonian. That
is, the interaction can be changed from Ising-like to Heisenberg-like and vice
versa. The sign and magnitude of the coupling constant can also be tuned.",0506414v1
2019-07-26,Universal relations for spin-orbit-coupled Fermi gases in two and three dimensions,"We present a comprehensive derivation of a set of universal relations for
spin-orbit-coupled Fermi gases in three or two dimension, which follow from the
short-range behavior of the two-body physics. Besides the adiabatic energy
relations, the large-momentum distribution, the grand canonical potential and
pressure relation derived in our previous work for three-dimensional systems
{[}Phys. Rev. Lett. 120, 060408 (2018){]}, we further derive high-frequency
tail of the radio-frequency spectroscopy and the short-range behavior of the
pair correlation function. In addition, we also extend the derivation to
two-dimensional systems with Rashba type of spin-orbit coupling. To simply
demonstrate how the spin-orbit-coupling effect modifies the two-body
short-range behavior, we solve the two-body problem in the sub-Hilbert space of
zero center-of-mass momentum and zero total angular momentum, and
perturbatively take the spin-orbit-coupling effect into account at short
distance, since the strength of the spin-orbit coupling should be much smaller
than the corresponding scale of the finite range of interatomic interactions.
The universal asymptotic forms of the two-body wave function at short distance
are then derived, which do not depend on the short-range details of interatomic
potentials. We find that new scattering parameters need to be introduced
because of spin-orbit coupling, besides the traditional $s$- and $p$-wave
scattering length (volume) and effective ranges. This is a general and unique
feature for spin-orbit-coupled systems. We show how these two-body parameters
characterize the universal relations in the presence of spin-orbit coupling.
This work probably shed light for understanding the profound properties of the
many-body quantum systems in the presence of the spin-orbit coupling.",1907.11433v1
2003-06-10,Correlation functions for 1d interacting fermions with spin-orbit coupling,"We compute correlation functions for one-dimensional electron systems which
spin and charge degrees of freedom are coupled through spin-orbit coupling.
Charge density waves, spin density waves, singlet- triplet- superconducting
fluctuations are studied. We show that the spin-orbit interaction modify the
exponents and the phase diagram of the system, changing the dominant
fluctuations and making new susceptibilities diverge for low temperature.",0306251v1
2006-07-08,Harper-Hofstadter problem for 2D electron gas with ${\bf k}$-linear Rashba spin-orbit coupling,"The Harper-Hofstadter problem for two-dimensional electron gas with Rashba
spin-orbit coupling subject to periodic potential and perpendicular magnetic
field is studied analytically and numerically. The butterfly-like energy
spectrum, spinor wave functions as well as the spin density and average spin
polarization are calculated for actual parameters of semiconductor structure.
Our calculations show that in two-dimensional electron gas subject to periodic
potential and uniform magnetic field the effects of energy spectrum splitting
caused by large spin-orbit Rashba coupling can be observed experimentally.",0607216v1
2012-11-05,Bright solitons in spin-orbit-coupled Bose-Einstein condensates,"We study bright solitons in a Bose-Einstein condensate with a spin-orbit
coupling that has been realized experimentally. Both stationary bright solitons
and moving bright solitons are found. The stationary bright solitons are the
ground states and possess well-defined spin-parity, a symmetry involving both
spatial and spin degrees of freedom; these solitons are real valued but not
positive definite, and the number of their nodes depends on the strength of
spin-orbit coupling. For the moving bright solitons, their shapes are found to
change with velocity due to the lack of Galilean invariance in the system.",1211.0771v2
2012-11-27,Short range asymptotic behavior of the wave-functions of interacting spin-half fermionic atoms with spin-orbit coupling: a model study,"We consider spin-half fermionic atoms with isotropic Rashba spin-orbit
coupling in three directions. The interatomic potential is modeled by a square
well potential. We derive the analytic form of the asymptotic wave-functions at
short range of two fermions in the subspace of zero net momentum and zero total
angular momentum. We show that the spin-orbit coupling has perturbative effects
on the short range asymptotic behavior of the wave-functions away from
resonances. We argue that our conclusion should hold generally.",1211.6221v2
2014-01-15,Dark Solitons with Majorana Fermions in Spin-Orbit-Coupled Fermi Gases,"We show that a single dark soliton can exist in a spin-orbit-coupled Fermi
gas with a high spin imbalance, where spin-orbit coupling favors uniform
superfluids over non-uniform Fulde-Ferrell-Larkin-Ovchinnikov states, leading
to dark soliton excitations in highly imbalanced gases. Above a critical spin
imbalance, two topological Majorana fermions (MFs) without interactions can
coexist inside a dark soliton, paving a way for manipulating MFs through
controlling solitons. At the topological transition point, the atom density
contrast across the soliton suddenly vanishes, suggesting a signature for
identifying topological solitons.",1401.3777v2
2015-02-19,Enhanced photogalvanic effect in graphene due to Rashba spin-orbit coupling,"We analyze theoretically optical generation of a spin-polarized charge
current (photogalvanic effect) and spin polarization in graphene with Rashba
spin-orbit coupling. An external magnetic field is applied in the graphene
plane, which plays a crucial role in the mechanism of current generation. We
predict a highly efficient resonant-like photogalvanic effect in a narrow
frequency range which is determined by the magnetic field. A relatively less
efficient photogalvanic effect appears in a broader frequency range, determined
by the electron concentration and spin-orbit coupling strength.",1502.05683v1
2014-09-24,Understanding spin Hall effect in two-dimensional fermionic systems with generic spin-orbit interaction,"We delve into spin Hall effect in generic spin-orbit coupled two-dimensional
fermionic systems. We derive analytically the spin-orbit force responsible for
the spin Hall effect, and find that it has `Lorentz force'-like form. We also
derive the pseudo magnetic field responsible for this force. We establish the
relation between the spin Hall conductivity, flux quanta and this pseudo
magnetic field, similar to the one between charge Hall conductivity, flux
quanta and the external field. We also present an exact closed-form expression
of the spin Hall conductivity in a generic spin-orbit coupled system. Depending
on the dimensionality of the spin-orbit interactions, the spin Hall
conductivity depends on different combinations of Rashba parameter and fermion
density.",1409.6897v2
2024-03-19,Unraveling the dynamics of magnetization in topological insulator-ferromagnet heterostructures via spin-orbit torque,"Spin-orbit coupling stands as a pivotal determinant in the realm of condensed
matter physics. In recent, its profound influence on spin dynamics opens up a
captivating arena with promising applications. Notably, the topological
insulator-ferromagnet heterostructure has been recognized for inducing spin
dynamics through applied current, driven by spin-orbit torque. Building upon
recent observations revealing spin flip signals within this heterostructure,
our study elucidates the conditions governing spin flips by studying the
magnetization dynamics. We establish that the interplay between spin-anisotropy
and spin-orbit torque plays a crucial role in shaping the physics of
magnetization dynamics within the heterostructure. Furthermore, we categorize
various modes of magnetization dynamics, constructing a comprehensive phase
diagram across distinct energy scales, damping constants, and applied
frequencies. This research not only offers insights into controlling spin
direction but also charts a new pathway to the practical application of
spin-orbit coupled systems.",2403.12701v1
2009-02-23,Polaron formation in the presence of Rashba spin-orbit coupling: implications for spintronics,"We study the effects of the Rashba spin-orbit coupling on the polaron
formation, using a suitable generalization of the Momentum Average
approximation. Contrary to previous investigations of this problem, we find
that the spin-orbit interaction decreases the effective electron-phonon
coupling. It is thus possible to lower the effective mass of the polaron by
increasing the spin-orbit coupling. We also show that when the spin-orbit
coupling is large as compared to the phonon energy, the polaron retains only
one of the spin polarized bands in its coherent spectrum. This has major
implications for the propagation of spin-polarized currents in such materials,
and thus for spintronic applications.",0902.3853v1
2011-06-18,Evolution from BCS to BEC superfluidity in the presence of spin-orbit coupling,"We discuss the evolution from BCS to BEC superfluids in the presence of
spin-orbit coupling, and show that this evolution is just a crossover in the
balanced case. The dependence of several thermodynamic properties, such as the
chemical potential, order parameter, pressure, entropy, isothermal
compressibility and spin susceptibility tensor on the spin-orbit coupling and
interaction parameter at low temperatures are analyzed. We studied both the
case of equal Rashba and Dresselhaus (ERD) and the Rashba-only (RO) spin-orbit
coupling. Comparisons between the two cases reveal several striking differences
in the corresponding thermodynamic quantities. Finally we propose measuring the
spin susceptibility as a means to detect the spin-orbit coupling effect.",1106.3613v1
2013-12-23,Long-Range Spin-Triplet Helix in Proximity Induced Superconductivity in Spin-Orbit-Coupled Systems,"We study proximity induced triplet superconductivity in a spin-orbit-coupled
system, and show that the \textbf{d} vector of the induced triplet
superconductivity undergoes precession that can be controlled by varying the
relative strengths of Rashba and Dresselhaus spin-orbit couplings. In
particular, a long-range spin-triplet helix is predicted when these two
spin-orbit couplings have equal strengths. We also study the Josephson junction
geometry and show that a transition between 0 and $\pi$ junctions can be
induced by controlling the spin-orbit coupling with a gate voltage. An
experimental setup is proposed to verify these effects. Conversely, the
observation of these effects can serve as a direct confirmation of triplet
superconductivity.",1312.6458v3
2014-09-29,Absence of a transport signature of spin-orbit coupling in graphene with indium adatoms,"Enhancement of the spin-orbit coupling in graphene may lead to various
topological phenomena and also find applications in spintronics. Adatom
absorption has been proposed as an effective way to achieve the goal. In
particular, great hope has been held for indium in strengthening the spin-orbit
coupling and realizing the quantum spin Hall effect. To search for evidence of
the spin-orbit coupling in graphene absorbed with indium adatoms, we carry out
extensive transport measurements, i.e., weak localization magnetoresistance,
quantum Hall effect and non-local spin Hall effect. No signature of the
spin-orbit coupling is found. Possible explanations are discussed.",1409.8090v1
2016-06-14,Modulation instability in quasi two-dimensional spin-orbit coupled Bose-Einstein condensates,"We theoretically investigate the dynamics of modulation instability (MI) in
two-dimensional spin-orbit coupled Bose-Einstein condensates (BECs). The
analysis is performed for equal densities of pseudo-spin components. Different
combination of the signs of intra- and inter-component interaction strengths
are considered, with a particular emphasize on repulsive interactions. We
observe that the unstable modulation builds from originally miscible
condensates, depending on the combination of the signs of the intra- and
inter-component interaction strengths. The repulsive intra- and inter-component
interactions admit instability and the MI immiscibility condition is no longer
significant. Influence of interaction parameters such as spin-orbit and Rabi
coupling on MI are also investigated. The spin-orbit coupling (SOC) inevitably
contributes to instability regardless of the nature of the interaction. In the
case of attractive interaction, SOC manifest in enhancing the MI. Thus, a
comprehensive study of MI in two-dimensional spin-orbit coupled binary BECs of
pseudo-spin components is presented.",1606.04426v2
2012-04-09,Spin-Orbit Coupled Degenerate Fermi Gases,"Spin-orbit coupling plays an increasingly important role in the modern
condensed matter physics. For instance, it gives birth to topological
insulators and topological superconductors. Quantum simulation of spin-orbit
coupling using ultracold Fermi gases will offer opportunities to study these
new phenomena in a more controllable setting. Here we report the first
experimental study of a spin-orbit coupled Fermi gas. We observe spin dephasing
in spin dynamics and momentum distribution asymmetry in the equilibrium state
as hallmarks of spin-orbit coupling. We also observe evidences of Lifshitz
transition where the topology of Fermi surfaces change. This serves as an
important first step toward finding Majorana fermions in this system.",1204.1887v1
2017-05-16,Theory of electron spin resonance in one-dimensional topological insulators with spin-orbit couplings,"Edge/surface states often appear in a topologically nontrivial phase, when
the system has a boundary. The edge state of a one-dimensional topological
insulator is one of the simplest examples. Electron Spin Resonance (ESR) is an
ideal probe to detect and analyze the edge state for its high sensitivity and
precision. We consider ESR of the edge state of a generalized
Su-Schrieffer-Heeger model with a next-nearest neighbor (NNN) hopping and a
staggered spin-orbit coupling. The spin-orbit coupling is generally expected to
bring about nontrivial changes on the ESR spectrum. Nevertheless, in the
absence of the NNN hoppings, we find that the ESR spectrum is unaffected by the
spin-orbit coupling thanks to the chiral symmetry. In the presence of both the
NNN hopping and the spin-orbit coupling, on the other hand, the edge ESR
spectrum exhibits a nontrivial frequency shift. We derive an explicit
analytical formula for the ESR shift in the second order perturbation theory,
which agrees very well with a non-perturbative numerical calculation.",1705.05826v3
2018-12-19,Global phase diagram of a spin-orbit-coupled Kondo lattice model on the honeycomb lattice,"Motivated by the growing interest in the novel quantum phases in materials
with strong electron correlations and spin-orbit coupling, we study the
interplay between the spin-orbit coupling, Kondo interaction, and magnetic
frustration of a Kondo lattice model on a two-dimensional honeycomb lattice. We
calculate the renormalized electronic structure and correlation functions at
the saddle point based on a fermionic representation of the spin operators. We
find a global phase diagram of the model at half-filling, which contains a
variety of phases due to the competing interactions. In addition to a Kondo
insulator, there is a topological insulator with valence bond solid
correlations in the spin sector, and two antiferromagnetic phases. Due to a
competition between the spin-orbit coupling and Kondo interaction, the
direction of the magnetic moments in the antiferromagnetic phases can be either
within or perpendicular to the lattice plane. The latter antiferromagnetic
state is topologically nontrivial for moderate and strong spin-orbit couplings.",1812.07979v1
2022-10-04,Spin-orbit enhancement in Si/SiGe heterostructures with oscillating Ge concentration,"We show that Ge concentration oscillations within the quantum well region of
a Si/SiGe heterostructure can significantly enhance the spin-orbit coupling of
the low-energy conduction-band valleys. Specifically, we find that for Ge
oscillation wavelengths near $\lambda = 1.57~\text{nm}$ with an average Ge
concentration of $\bar{n}_{\text{Ge}} = 5\%$ in the quantum well region, a
Dresselhaus spin-orbit coupling is induced, at all physically relevant electric
field strengths, which is over an order of magnitude larger than what is found
in conventional Si/SiGe heterostructures without Ge concentration oscillations.
This enhancement is caused by the Ge concentration oscillations producing
wave-function satellite peaks a distance $2 \pi/\lambda$ away in momentum space
from each valley, which then couple to the opposite valley through Dresselhaus
spin-orbit coupling. Our results indicate that the enhanced spin-orbit coupling
can enable fast spin manipulation within Si quantum dots using electric dipole
spin resonance in the absence of micromagnets. Indeed, our calculations yield a
Rabi frequency $\Omega_{\text{Rabi}}/B > 500~\text{MHz/T}$ near the optimal Ge
oscillation wavelength $\lambda = 1.57~\text{nm}$.",2210.01700v2
2006-05-18,Spin Order accompanying Loop-Current Order in Cuprates,"The theory of the long range order of orbital current loops in the pseudogap
phase is generalized to include the effects of spin-orbit scattering. It is
shown by symmetry arguments as well as by microscopic calculation that a
specific in-plane spin-order must necessarily accompany the loop-current order.
The microscopic theory also allows an estimate of the magnitude of the ordered
spin-moment. Exchange coupling between the generated spins further modifies the
in-plane direction of the spin moments. The structure and form factor for the
spin and orbital moments combined with the induced spin order is consistent
with the direction of moments deduced from polarization analysis in the neutron
scattering experiment.",0605468v2
2006-06-24,Magnetoconductivity in the presence of Bychkov-Rashba spin-orbit interaction,"A closed-form analytic formula for the magnetoconductivity in the diffusive
regime is derived in the presence of Bychkov-Rashba spin-orbit interaction in
two dimensions. It is shown that at low fields B << B_{so}, where B_{so} is the
characteristic field associated with spin precession, D'yakonov-Perel'
mechanism leads to spin relaxation, while for B >> B_{so} spin relaxation is
suppressed and the resulting spin precession contributes a Berry phase-like
spin phase to the magnetoconductivity. The relative simplicity of the formula
greatly facilitates data fitting, allowing for the strength of the spin-orbit
coupling to be easily extracted.",0606630v1
2007-05-02,Charge current driven by spin dynamics in disordered Rashba spin-orbit system,"Pumping of charge current by spin dynamics in the presence of the Rashba
spin-orbit interaction is theoretically studied. Considering disordered
electron, the exchange coupling and spin-orbit interactions are treated
perturbatively. It is found that dominant current induced by the spin dynamics
is interpreted as a consequence of the conversion from spin current via the
inverse spin Hall effect. We also found that the current has an additional
component from a fictitious conservative field. Results are applied to the case
of moving domain wall.",0705.0277v3
2014-03-03,Chaos in two black holes with next-to-leading order spin-spin interactions,"We take into account the dynamics of a complete third post-Newtonian
conservative Hamiltonian of two spinning black holes, where the orbital part
arrives at the third post-Newtonian precision level and the spin-spin part with
the spin-orbit part includes the leading-order and next-to-leading-order
contributions. It is shown through numerical simulations that the
next-to-leading order spin-spin couplings play an important role in chaos. A
dynamical sensitivity to the variation of single parameter is also
investigated. In particular, there are a number of \textit{observable} orbits
whose initial radii are large enough and which become chaotic before
coalescence.",1403.0378v1
2014-06-18,Engineering spin-orbit coupling for photons and polaritons in microstructures,"One of the most fundamental properties of electromagnetism and special
relativity is the coupling between the spin of an electron and its orbital
motion. This is at the origin of the fine structure in atoms, the spin Hall
effect in semiconductors, and underlies many intriguing properties of
topological insulators, in particular their chiral edge states. Configurations
where neutral particles experience an effective spin-orbit coupling have been
recently proposed and realized using ultracold atoms and photons. Here we use
coupled micropillars etched out of a semiconductor microcavity to engineer a
spin-orbit Hamiltonian for photons and polaritons in a microstructure. The
coupling between the spin and orbital momentum arises from the polarisation
dependent confinement and tunnelling of photons between micropillars arranged
in the form of a hexagonal photonic molecule. Dramatic consequences of the
spin-orbit coupling are experimentally observed in these structures in the
wavefunction of polariton condensates, whose helical shape is directly visible
in the spatially resolved polarisation patterns of the emitted light. The
strong optical nonlinearity of polariton systems suggests exciting perspectives
for using quantum fluids of polaritons11 for quantum simulation of the
interplay between interactions and spin-orbit coupling.",1406.4816v1
2021-10-03,Giant Spin Lifetime Anisotropy and Spin-Valley Locking in Silicene and Germanene from First-Principles Density-Matrix Dynamics,"Through First-Principles real-time Density-Matrix (FPDM) dynamics
simulations, we investigate spin relaxation due to electron-phonon and
electron-impurity scatterings with spin-orbit coupling in two-dimensional Dirac
materials - silicene and germanene, at finite temperatures and under external
fields. We discussed the applicability of conventional descriptions of spin
relaxation mechanisms by Elliott-Yafet (EY) and D'yakonov-Perel' (DP) compared
to our FPDM method, which is determined by a complex interplay of intrinsic
spin-orbit coupling, external fields, and electron-phonon coupling strength,
beyond crystal symmetry. For example, the electric field dependence of spin
relaxation time is close to DP mechanism for silicene at room temperature, but
rather similar to EY mechanism for germanene. Due to its stronger spin-orbit
coupling strength and buckled structure in sharp contrast to graphene,
germanene has a giant spin lifetime anisotropy and spin valley locking effect
under nonzero Ez and relatively low temperature. More importantly, germanene
has extremely long spin lifetime (~100 ns at 50 K) and ultrahigh carrier
mobility, which makes it advantageous for spin-valleytronic applications.",2110.01128v1
2020-04-13,Theory of Current-Induced Angular Momentum Transfer Dynamics in Spin-Orbit Coupled Systems,"Motivated by the importance of understanding competing mechanisms to
current-induced spin-orbit torque in complex magnets, we develop a unified
theory of current-induced spin-orbital coupled dynamics. The theory describes
angular momentum transfer between different degrees of freedom in solids, e.g.,
the electron orbital and spin, the crystal lattice, and the magnetic order
parameter. Based on the continuity equations for the spin and orbital angular
momenta, we derive equations of motion that relate spin and orbital current
fluxes and torques describing the transfer of angular momentum between
different degrees of freedom. We then propose a classification scheme for the
mechanisms of the current-induced torque in magnetic bilayers. Based on our
first-principles implementation, we apply our formalism to two different
magnetic bilayers, Fe/W(110) and Ni/W(110), which are chosen such that the
orbital and spin Hall effects in W have opposite sign and the resulting spin-
and orbital-mediated torques can compete with each other. We find that while
the spin torque arising from the spin Hall effect of W is the dominant
mechanism of the current-induced torque in Fe/W(110), the dominant mechanism in
Ni/W(110) is the orbital torque originating in the orbital Hall effect of W. It
leads to negative and positive effective spin Hall angles, respectively, which
can be directly identified in experiments. This clearly demonstrates that our
formalism is ideal for studying the angular momentum transfer dynamics in
spin-orbit coupled systems as it goes beyond the ""spin current picture"" by
naturally incorporating the spin and orbital degrees of freedom on an equal
footing. Our calculations reveal that, in addition to the spin and orbital
torque, other contributions such as the interfacial torque and self-induced
anomalous torque within the ferromagnet are not negligible in both material
systems.",2004.05945v2
2003-11-14,Spin-orbit coupling and Berry phase with ultracold atoms in 2D optical lattices,"We show how spin-orbit coupling and Berry phase can appear in two-dimensional
optical lattices by coupling atoms' internal degrees of freedom to radiation.
The Rashba Hamiltonian, a standard description of spin-orbit coupling for
two-dimensional electrons, is obtained for the atoms under certain
circumstances. We discuss the possibility of observing associated phenomena,
such as the anomalous Hall and spin Hall effects, with cold atoms in optical
lattices.",0311356v2
2006-12-19,Effect of spin-orbit coupling on the excitation spectrum of Andreev billiards,"We consider the effect of spin-orbit coupling on the low energy excitation
spectrum of an Andreev billiard (a quantum dot weakly coupled to a
superconductor), using a dynamical numerical model (the spin Andreev map).
Three effects of spin-orbit coupling are obtained in our simulations: In zero
magnetic field: (1) the narrowing of the distribution of the excitation gap;
(2) the appearance of oscillations in the average density of states. In strong
magnetic field: (3) the appearance of a peak in the average density of states
at zero energy. All three effects have been predicted by random-matrix theory.",0612501v1
2014-11-25,Angular spin-orbit coupling in cold atoms,"We propose coupling two internal atomic states using a pair of Raman beams
operated in Laguerre-Gaussian laser modes with unequal phase windings. This
generates a coupling between the atom's pseudo-spin and its orbital angular
momentum. We analyze the single-particle properties of the system using
realistic parameters and provide detailed studies of the spin texture of the
ground state. Finally, we consider a weakly interacting atomic condensate
subject to this angular spin-orbit coupling and show how the inter-atomic
interactions modifies the single-particle physics.",1411.6895v1
2012-08-14,Chaos-driven dynamics in spin-orbit coupled atomic gases,"The dynamics, appearing after a quantum quench, of a trapped, spin-orbit
coupled, dilute atomic gas is studied. The characteristics of the evolution is
greatly influenced by the symmetries of the system, and we especially compare
evolution for an isotropic Rashba coupling and for an anisotropic spin-orbit
coupling. As we make the spin-orbit coupling anisotropic, we break the
rotational symmetry and the underlying classical model becomes chaotic; the
quantum dynamics is affected accordingly. Within experimentally relevant
time-scales and parameters, the system thermalizes in a quantum sense. The
corresponding equilibration time is found to agree with the Ehrenfest time,
i.e. we numerically verify a ~log(1/h) scaling. Upon thermalization, we find
the equilibrated distributions show examples of quantum scars distinguished by
accumulation of atomic density for certain energies. At shorter time-scales we
discuss non-adiabatic effects deriving from the spin-orbit coupled induced
Dirac point. In the vicinity of the Dirac point, spin fluctuations are large
and, even at short times, a semi-classical analysis fails.",1208.2923v2
2017-07-08,Interaction-induced exotic vortex states in an optical lattice clock with spin-orbit coupling,"Motivated by a recent experiment [L. F. Livi, et al., Phys. Rev. Lett. 117,
220401(2016)], we study the ground-state properties of interacting fermions in
a one-dimensional optical lattice clock with spin-orbit coupling. As the
electronic and the hyperfine-spin states in the clock-state manifolds can be
treated as effective sites along distinct synthetic dimensions, the system can
be considered as multiple two-leg ladders with uniform magnetic flux
penetrating the plaquettes of each ladder. As the inter-orbital spin-exchange
interactions in the clock-state manifolds couple individual ladders together,
we show that exotic interaction-induced vortex states emerge in the
coupled-ladder system, which compete with existing phases of decoupled ladders
and lead to a rich phase diagram. Adopting the density matrix renormalization
group approach, we map out the phase diagram, and investigate in detail the
currents and the density-density correlations of the various phases. Our
results reveal the impact of interactions on spin-orbit coupled systems, and
are particularly relevant to the on-going exploration of spin-orbit coupled
optical lattice clocks.",1707.02379v2
2022-06-21,Faraday patterns in spin-orbit coupled Bose-Einstein condensates,"We study the Faraday patterns generated by spin-orbit-coupling induced
parametric resonance in a spinor Bose-Einstein condensate with repulsive
interaction. The collective elementary excitations of the Bose-Einstein
condensate, including density waves and spin waves, are coupled as the result
of the Raman-induced spin-orbit coupling and a quench of the relative phase of
two Raman lasers without the modulation of any of the system's parameters. We
observed several higher parametric resonance tongues at integer multiples of
the driving frequency and investigated the interplay between Faraday
instabilities and modulation instabilities when we quench the
spin-orbit-coupled Bose-Einstein condensate from zero-momentum phase to
plane-wave phase. If the detuning is equal to zero, the wave number of
combination resonance barely changes as the strength of spin-orbit coupling
increases. If the detuning is not equal to zero after a quench, a single
combination resonance tongue will split into two parts.",2206.10222v1
2019-06-30,Intrinsic Spin Hall Effect with Spin-Tensor-Momentum Coupling,"We derive the spin continuity equation by using the Noether's theorem. A new
type of spin-tensor Hall current is found in the continuity equation. The
spin-tensor Hall current is originating from the coupling of the spin-tensor
and the momentum. The intrinsic spin Hall effect in the two-dimensional fermion
model with the spin-orbit coupling and spin-tensor-momentum coupling is
studied. The total spin Hall conductivity with the presence of the spin-tensor
Hall current is calculated. The numerical results indicate that the total spin
Hall conductivity is enhanced by the contribution of the spin-tensor-momentum
coupling. The spin-tensor-momentum coupling may increase the spin transport in
the intrinsic spin Hall effect.",1907.00319v2
2010-12-16,Spin Relaxation in Quantum Wires,"The spin dynamics and spin relaxation of itinerant electrons in quantum wires
with spin-orbit coupling is reviewed. We give an introduction to spin dynamics,
and review spin-orbit coupling mechanisms in semiconductors. The spin diffusion
equation with spin-orbit coupling is derived, using only intuitive, classical
random walk arguments. We give an overview of all spin relaxation mechanisms,
with particular emphasis on the motional narrowing mechanism in disordered
conductors, the D'yakonov-Perel'-Spin relaxation. Here, we discuss in
particular, the existence of persistent spin helix solutions of the spin
diffusion equation, with vanishing spin relaxation rates. We then, derive
solutions of the spin diffusion equation in quantum wires, and show that there
is an effective alignment of the spin-orbit field in wires whose width is
smaller than the spin precession length $L_{\rm SO}$. We show that the
resulting reduction in the spin relaxation rate results in a change in the sign
of the quantum corrections to the conductivity. Finally, we present recent
experimental results which confirm the decrease of the spin relaxation rate in
wires whose width is smaller than $L_{\rm SO}$: the direct optical measurement
of the spin relaxation rate, as well as transport measurements, which show a
dimensional crossover from weak antilocalization to weak localization as the
wire width is reduced. Open problems remain, in particular in narrower,
ballistic wires, were optical and transport measurements seem to find opposite
behavior of the spin relaxation rate: enhancement, suppression, respectively.
We conclude with a review of these and other open problems which still
challenge the theoretical understanding and modeling of the experimental
results.",1012.3575v1
2000-12-06,Comment on ''Alternating spin and orbital dimerization and spin-gap formation in coupled spin-orbital systems'',"By this Comment we would like to point out [2] that, though such
consideration can be quite sophisticated, the consideration of a
spin-pseudo-spin Hamiltonian has nothing in common with the reality. It means
that such the consideration are useless as far as the properties of real
systems are concerned.",0012074v1
2017-04-22,Observation of Spin Nernst effect in Platinum,"Central focus of spintronics is concentrated on generation of pure spin
current and associated spin torque. Pure spin current can be generated by spin
Hall effect in heavy metals by passing charge current. By spin Seebeck effect
pure spin current can also be generated in ferromagnet. In this work we
experimentally demonstrate that if heavy metals like Platinum with high spin
orbit coupling carry heat current it can convert it into spin current due to
relativistic spin orbit interaction. This conversion of heat current into spin
current in non magnet is equivalent of thermally driven spin Hall effect or it
is known as spin Nernst effect. We observed spin Nernst effect in Ni/Pt
bi-layer experimentally and we confirm that when Pt is replaced by low spin
orbit material like Al spin Nernst effect significantly reduces. So we have
detected spin Nernst effect unambiguously and compare its strength with
electrical spin Hall effect.",1704.06788v1
2020-06-15,Control of Spin Relaxation Anisotropy by Spin-Orbit-Coupled Diffusive Spin Motion,"Spatiotemporal spin dynamics under spin-orbit interaction is investigated in
a (001) GaAs two-dimensional electron gas using magneto-optical Kerr rotation
microscopy. Spin polarized electrons are diffused away from the excited
position, resulting in spin precession because of the diffusion-induced
spin-orbit field. Near the cancellation between spin-orbit field and external
magnetic field, the induced spin precession frequency depends nonlinearly on
the diffusion velocity, which is unexpected from the conventional linear
relation between the spin-orbit field and the electron velocity.This behavior
originates from an enhancement of the spin relaxation anisotropy by the
electron velocity perpendicular to the diffused direction. We demonstrate that
the spin relaxation anisotropy, which has been regarded as a material constant,
can be controlled via diffusive electron motion.",2006.08253v1
2023-12-11,Dzyaloshinskii-Moriya interaction from unquenched orbital angular momentum,"Orbitronics is an emerging and fascinating field that explores the
utilization of the orbital degree of freedom of electrons for information
processing. An increasing number of orbital phenomena are being currently
discovered, with spin-orbit coupling mediating the interplay between orbital
and spin effects, thus providing a wealth of control mechanisms and device
applications. In this context, the orbital analog of spin Dzyaloshinskii-Moriya
interaction (DMI), i.e. orbital DMI, deserves to be explored in depth, since it
is believed to be capable of inducing chiral orbital structures. Here, we
unveil the main features and microscopic mechanisms of the orbital DMI in a
two-dimensional square lattice using a tight-binding model of t2g orbitals in
combination with the Berry phase theory. This approach allows us to investigate
and transparently disentangle the role of inversion symmetry breaking, strength
of orbital exchange interaction and spin-orbit coupling in shaping the
properties of the orbital DMI. By scrutinizing the band-resolved contributions
we are able to understand the microscopic mechanisms and guiding principles
behind the orbital DMI and its anisotropy in two dimensional magnetic
materials, and uncover a fundamental relation between the orbital DMI and its
spin counterpart, which is currently explored very intensively. The insights
gained from our work contribute to advancing our knowledge of orbitalrelated
effects and their potential applications in spintronics, providing a path for
future research in the field of chiral orbitronics.",2312.06054v2
2003-06-06,Orbital mechanisms of electron spin manipulation by an electric field,"A theory of spin manipulation of quasi-two-dimensional (2D) electrons by a
time-dependent gate voltage applied to a quantum well is developed. The
Dresselhaus and Rashba spin-orbit coupling mechanisms are shown to be rather
efficient for this purpose. The spin response to a perpendicular-to-plane
electric field is due to a deviation from the strict 2D limit and is controlled
by the ratios of the spin, cyclotron and confinement frequencies. The
dependence of this response on the magnetic field direction is indicative of
the strenghts of the competing spin-orbit coupling mechanisms.",0306165v1
2019-05-29,Spin-Orbit Coupling and the Evolution of Transverse Spin,"We investigate the evolution of transverse spin in tightly focused circularly
polarized beams of light, where spin-orbit coupling causes a local rotation of
the polarization ellipses upon propagation through the focal volume. The effect
can be explained as a relative Gouy-phase shift between the circularly
polarized transverse field and the longitudinal field carrying orbital angular
momentum. The corresponding rotation of the electric transverse spin density is
observed experimentally by utilizing a recently developed reconstruction
scheme, which relies on transverse-spin-dependent directional scattering of a
nano-probe.",1905.12539v1
2004-07-11,Non-vanishing spin Hall currents in disordered spin-orbit coupling systems,"Spin currents that flow perpendicular to the electric field direction are
generic in metals and doped semiconductors with spin-orbit coupling. It has
recently been argued that the spin Hall conductivity can be dominated by an
intrinsic contribution which follows from Bloch state distortion in the
presence of an electric field. Here we report on an numerical demonstration of
the robustness of this effect in the presence of disorder scattering for the
case of a two-dimensional electron-gas with Rashba spin-orbit interactions
(R2DES).",0407279v2
2016-03-24,Semiclassical Landau quantization of spin-orbit coupled systems,"A semiclassical quantization condition is derived for Landau levels in
general spin-orbit coupled systems. This generalizes the Onsager quantization
condition via a matrix-valued phase which describes spin dynamics along the
classical cyclotron trajectory. We discuss measurement of the matrix phase via
magnetic oscillations and electron spin resonance, which may be used to probe
the spin structure of the precessing wavefunction. We compare the resulting
semiclassical spectrum with exact results which are obtained for a variety of
spin-orbit interactions in 2D systems.",1603.07450v1
2014-03-24,Optical spin injection in graphene with Rashba spin-orbit interaction,"We calculate the efficiency of infrared optical spin injection in
single-layer graphene with Rashba spin-orbit coupling and for in-plane magnetic
field. The injection rate in the photon frequency range corresponding to the
Rashba splitting is shown to be proportional to the ratio of the Zeeman and
Rashba splittings. As a result, large spin polarization can be controllably
achieved for experimentally available values of the spin-orbit coupling and in
magnetic fields below 10 Tesla.",1403.6159v1
2023-04-25,Magnetization Switching in van der Waals Systems by Spin-Orbit Torque,"Electrical switching of magnetization via spin-orbit torque (SOT) is of great
potential in fast, dense, energy-efficient nonvolatile magnetic memory and
logic technologies. Recently, enormous efforts have been stimulated to
investigate switching of perpendicular magnetization in van der Waals systems
that have unique, strong tunability and spin-orbit coupling effect compared to
conventional metals. In this review, we first give a brief, generalized
introduction to the spin-orbit torque and van der Waals materials. We will then
discuss the recent advances in magnetization switching by the spin current
generated from van der Waals materials and summary the progress in the
switching of Van der Waals magnetization by the spin current.",2304.12632v1
2000-05-22,Charge and Orbital Ordering and Spin State Transition Driven by Structural Distortion in YBaCo_2O_5,"We have investigated electronic structures of antiferromagnetic YBaCo_2O_5
using the local spin-density approximation (LSDA) + U method. The charge and
orbital ordered insulating ground state is correctly obtained with the strong
on-site Coulomb interaction. Co^{2+} and Co^{3+} ions are found to be in the
high spin (HS) and intermediate spin (IS) state, respectively. It is considered
that the tetragonal to orthorhombic structural transition is responsible for
the ordering phenomena and the spin states of Co ions. The large contribution
of the orbital moment to the total magnetic moment indicates that the
spin-orbit coupling is also important in YBaCo_2O_5.",0005344v1
2009-05-09,Spin-state transition and phase separation in multi-orbital Hubbard model,"We study spin-state transition and phase separation involving this transition
based on the milti-orbital Hubbard model. Multiple spin states are realized by
changing the energy separation between the two orbitals and the on-site Hund
coupling. By utilizing the variational Monte-Carlo simulation, we analyze the
electronic and magnetic structures in hole doped and undoped states. Electronic
phase separation occurs between the low-spin band insulating state and the
high-spin ferromagnetic metallic one. Difference of the band widths in the two
orbitals is of prime importance for the spin-state transition and the phase
separation.",0905.1389v1
2013-06-20,Induced spin filtering in electron transmission through chiral molecular layers adsorbed on metals with strong spin-orbit coupling,"Recent observations of considerable spin polarization in photoemission from
metal surfaces through monolayers of chiral molecules were followed by several
efforts to rationalize the results as the effect of spin-orbit interaction that
accompanies electronic motion on helical, or more generally strongly curved,
potential surfaces. In this paper we (a) argue, using simple models, that
motion in curved force-fields with the typical energies used and the
characteristic geometry of DNA cannot account for such observations; (b)
introduce the concept of induced spin filtering, whereupon selectivity in the
transmission of the electron orbital angular momentum can induce spin
selectivity in the transmission process provided there is strong spin-orbit
coupling in the substrate; and (c) show that the spin polarizability in the
tunneling current as well as the photoemission current from gold covered by
helical adsorbates can be of the observed order of magnitude. Our results can
account for most of the published observations that involved gold and silver
substrates, however recent results obtained with an aluminum substrate can be
rationalized within the present model only if strong spin-orbit coupling is
caused by the built-in electric field at the molecule-metal interface.",1306.4904v1
2015-12-05,Kinetic theory of spin-polarized systems in electric and magnetic fields with spin-orbit coupling: I. Kinetic equation and anomalous Hall and spin-Hall effects,"The coupled kinetic equation for density and spin Wigner functions are
derived including spin-orbit coupling, electric and magnetic field as well as
selfconsistent Hartree meanfields suited for SU(2) transport. The interactions
are assumed to be with scalar and magnetic impurities as well as scalar and
spin-flip potentials among the particles. The spin-orbit interaction is used in
a form suitable to solid state physics with Rashba or Dresselhaus coupling,
graphene, extrinsic spin-orbit coupling as well as effective nuclear matter
coupling. The deficiencies of the two-fluid model are worked out consisting in
the appearance of an effective in-medium spin-precession. The stationary
solution of all these systems shows a band splitting controlled by an effective
medium-dependent Zeeman field. The selfconsistent precession direction is
discussed and a cancellation of linear spin-orbit coupling at zero temperature
is reported. The precession of spin around this effective direction caused by
spin-orbit coupling leads to anomalous charge and spin currents in an electric
field. Anomalous Hall conductivity is shown to consists of the known results
obtained from Kubo formula or Berry phases and a new symmetric part interpreted
as inverse Hall effect. Analogously the spin-Hall and inverse spin-Hall effect
of spin currents are discussed which are present even without magnetic fields
showing a spin accumulation triggered by currents. The analytical dynamical
expressions for zero temperature are derived and discussed in dependence on the
magnetic field and effective magnetizations. The anomalous Hall and spin-Hall
effect changes sign at higher than a critical frequency dependent on the
relaxation time.",1512.01660v1
2014-08-16,Two-Dimensional TaSe2 Metallic Crystals: Spin-Orbit Scattering Length and Breakdown Current Density,"We have determined the spin-orbit scattering length of two-dimensional
layered 2H-TaSe2 metallic crystals by detailed characterization of the weak
anti-localization phenomena in this strong spin-orbit interaction material. By
fitting the observed magneto-conductivity, the spin-orbit scattering length for
2H-TaSe2 is determined to be 17 nm in the few-layer films. This small
spin-orbit scattering length is comparable to that of Pt, which is widely used
to study the spin Hall effect, and indicates the potential of TaSe2 for use in
spin Hall effect devices. In addition to strong spin-orbit coupling, a material
must also support large charge currents to achieve spin-transfer-torque via the
spin Hall effect. Therefore, we have characterized the room temperature
breakdown current density of TaSe2 in air, where the best breakdown current
density reaches 3.7$\times$10$^7$ A/cm$^2$. This large breakdown current
further indicates the potential of TaSe2 for use in spin-torque devices and
two-dimensional device interconnect applications.",1408.3753v1
2010-12-05,Electron spin diffusion and transport in graphene,"We investigate the spin diffusion and transport in a graphene monolayer on
SiO$_2$ substrate by means of the microscopic kinetic spin Bloch equation
approach. The substrate causes a strong Rashba spin-orbit coupling field $\sim
0.15$ meV, which might be accounted for by the impurities initially present in
the substrate or even the substrate-induced structure distortion. By surface
chemical doping with Au atoms, this Rashba spin-orbit coupling is further
strengthened as the adatoms can distort the graphene lattice from $sp^2$ to
$sp^3$ bonding structure. By fitting the Au doping dependence of spin
relaxation from Pi {\sl et al.} [Phys. Rev. Lett. {\bf 104}, 187201 (2010)],
the Rashba spin-orbit coupling coefficient is found to increase approximately
linearly from 0.15 to 0.23 meV with the increase of Au density. With this
strong spin-orbit coupling, the spin diffusion or transport length is
comparable with the experimental values. In the strong scattering limit
(dominated by the electron-impurity scattering in our study), the spin
diffusion is uniquely determined by the Rashba spin-orbit coupling strength and
insensitive to the temperature, electron density as well as scattering. With
the presence of an electric field along the spin injection direction, the spin
transport length can be modulated by either the electric field or the electron
density. (The remaining is omitted due to the limit of space)",1012.0973v2
2015-04-15,Spin diffusion in ultracold spin-orbit coupled $^{40}$K gas,"We investigate the steady-state spin diffusion for ultracold spin-orbit
coupled $^{40}$K gas by the kinetic spin Bloch equation approach both
analytically and numerically. Four configurations, i.e., the spin diffusions
along two specific directions with the spin polarization perpendicular
(transverse configuration) and parallel (longitudinal configuration) to the
effective Zeeman field are studied. It is found that the behaviors of the
steady-state spin diffusion for the four configurations are very different,
which are determined by three characteristic lengths: the mean free path
$l_{\tau}$, the Zeeman oscillation length $l_{\Omega}$ and the spin-orbit
coupling oscillation length $l_{\alpha}$. It is analytically revealed and
numerically confirmed that by tuning the scattering strength, the system can be
divided into {\it five} regimes: I, weak scattering regime ($l_{\tau}\gtrsim
l_{\Omega}, l_{\alpha}$); II, Zeeman field-dominated moderate scattering regime
($l_{\Omega}\ll l_{\tau}\ll l_{\alpha}$); III, spin-orbit coupling-dominated
moderate scattering regime ($l_{\alpha}\ll l_{\tau}\ll l_{\Omega}$); IV,
relatively strong scattering regime ($l_{\tau}^c\ll l_{\tau}\ll l_{\Omega},
l_{\alpha}$); V, strong scattering regime ($l_{\tau}\ll l_{\Omega},
l_{\alpha},l_{\tau}^c$), with $l_{\tau}^c$ representing the crossover length
between the relatively strong and strong scattering regimes. In different
regimes, the behaviors of the spacial evolution of the steady-state spin
polarization are very rich, showing different dependencies on the scattering
strength, Zeeman field and spin-orbit coupling strength. The rich behaviors of
the spin diffusions in different regimes are hard to be understood in the
framework of the simple drift-diffusion model or the direct inhomogeneous
broadening picture in the literature. ...",1504.03786v1
2017-02-10,Orbital and spin order in spin-orbit coupled $d^1$ and $d^2$ double perovskites,"We consider strongly spin-orbit coupled double perovskites A$_2$BB'O$_6$ with
B' magnetic ions in either $d^1$ or $d^2$ electronic configuration and
non-magnetic B ions. We provide insights into several experimental puzzles,
such as the predominance of ferromagnetism in $d^1$ versus antiferromagnetism
in $d^2$ systems, the appearance of negative Curie-Weiss temperatures for
ferromagnetic materials, and the size of effective magnetic moments. We develop
and solve a microscopic model with both spin and orbital degrees of freedom
within the Mott insulating regime at finite temperature using mean field
theory. The interplay between anisotropic orbital degrees of freedom and
spin-orbit coupling results in complex ground states in both $d^1$ and $d^2$
systems. We show that the ordering of orbital degrees of freedom in $d^1$
systems results in coplanar canted ferromagnetic and 4-sublattice
antiferromagnetic structures. In $d^2$ systems we find additional colinear
antiferromagnetic and ferromagnetic phases not appearing in $d^1$ systems. At
finite temperatures, we find that orbital ordering driven by both superexchange
and Coulomb interactions may occur at much higher temperatures compared to
magnetic order and leads to distinct deviations from Curie-Weiss law.",1702.03199v1
2021-06-14,Semi-Implicit finite-difference methods to study the spin-orbit and coherently coupled spinor Bose-Einstein condensates,"We develop time-splitting finite difference methods, using implicit
Backward-Euler and semi-implicit Crank-Nicolson discretization schemes, to
study the spin-orbit coupled spinor Bose Einstein condensates with coherent
coupling in quasi-one and quasi-two-dimensional traps. The split equations
involving kinetic energy and spin-orbit coupling operators are solved using
either time-implicit Backward-Euler or semi-implicit Crank-Nicolson methods. We
explicitly develop the method for pseudospin-1/2, spin-1, and spin-2
condensates. The results for ground states obtained with time-splitting
Backward-Euler and Crank-Nicolson methods are in excellent agreement with
time-splitting Fourier spectral method which is one of the popular methods to
solve the mean-field models for spin-orbit coupled spinor condensates. We
confirm the emergence of different phases in spin-orbit coupled pseudospin-1/2,
spin-1, and spin-2 condensates with coherent coupling.",2106.07762v1
2013-11-05,Spin accumulation detection of FMR driven spin pumping in silicon-based metal-oxide-semiconductor heterostructures,"The use of the spin Hall effect and its inverse to electrically detect and
manipulate dynamic spin currents generated via ferromagnetic resonance (FMR)
driven spin pumping has enabled the investigation of these dynamically injected
currents across a wide variety of ferromagnetic materials. However, while this
approach has proven to be an invaluable diagnostic for exploring the spin
pumping process it requires strong spin-orbit coupling, thus substantially
limiting the materials basis available for the detector/channel material
(primarily Pt, W and Ta). Here, we report FMR driven spin pumping into a weak
spin-orbit channel through the measurement of a spin accumulation voltage in a
Si-based metal-oxide-semiconductor (MOS) heterostructure. This alternate
experimental approach enables the investigation of dynamic spin pumping in a
broad class of materials with weak spin-orbit coupling and long spin lifetime
while providing additional information regarding the phase evolution of the
injected spin ensemble via Hanle-based measurements of the effective spin
lifetime.",1311.0965v1
2019-10-19,Current-induced spin-orbit field in permalloy interfaced with ultrathin Ti and Cu,"How spin-orbit torques emerge from materials with weak spin-orbit coupling
(e.g., light metals) is an open question in spintronics. Here, we report on a
field-like spin-orbit torque (i.e., in-plane spin-orbit field transverse to the
current axis) in SiO$_2$-sandwiched permalloy (Py), with the top Py-SiO$_2$
interface incorporating ultrathin Ti or Cu. In both SiO$_2$/Py/Ti/SiO$_2$ and
SiO$_2$/Py/Cu/SiO$_2$, this spin-orbit field opposes the classical Oersted
field. While the magnitude of the spin-orbit field is at least a factor of 3
greater than the Oersted field, we do not observe evidence for a significant
damping-like torque in SiO$_2$/Py/Ti/SiO$_2$ or SiO$_2$/Py/Cu/SiO$_2$. Our
findings point to contributions from a Rashba-Edelstein effect or spin-orbit
precession at the (Ti, Cu)-inserted interface.",1910.08669v2
2005-01-03,Rashba-control for the spin excitation of a fully spin polarized vertical quantum dot,"Far infrared radiation absorption of a quantum dot with few electrons in an
orthogonal magnetic field could monitor the crossover to the fully spin
polarized state. A Rashba spin-orbit coupling can tune the energy and the spin
density of the first excited state which has a spin texture carrying one extra
unit of angular momentum. The spin orbit coupling can squeeze a flipped spin
density at the center of the dot and can increase the gap in the spectrum.",0501021v1
2008-08-01,Electric-field driven long-lived spin excitations on a cylindrical surface with spin-orbit interaction,"Based on quantum-kinetic equations, coupled spin-charge drift-diffusion
equations are derived for a two-dimensional electron gas on a cylindrical
surface. Besides the Rashba and Dresselhaus spin-orbit interaction, the elastic
scattering on impurities, and a constant electric field are taken into account.
  From the solution of the drift-diffusion equations, a long-lived spin
excitation is identified for spins coupled to the Rashba term on a cylinder
with a given radius. The electric-field driven weakly damped spin waves are
manifest in the components of the magnetization and have the potential for
non-ballistic spin-device applications.",0808.0069v1
2011-04-09,Spin Distribution in Diffraction Pattern of Two-dimensional Electron Gas with Spin-orbit Coupling,"Spin distribution in the diffraction pattern of two-dimensional electron gas
by a split gate and a quantum point contact is computed in the presence of the
spin-orbit coupling. After diffracted, the component of spin perpendicular to
the two-dimensional plane can be generated up to 0.42 $\hbar$. The non-trivial
spin distribution is the consequence of a pure spin current in the transverse
direction generated by the diffraction. The direction of the spin current can
be controlled by tuning the chemical potential.",1104.1684v1
2011-08-09,Nonlinear spin Hall effect in GaAs (110) quantum wells,"We consider stationary spin current in a (110)-oriented GaAs-based symmetric
quantum well due to a nonlinear response to an external periodic electric
field. The model assumed includes the Dresselhaus spin-orbit interaction and
the random Rashba spin-orbit coupling. The Dresselhaus term is uniform in the
quantum well plane and gives rise to spin splitting of the electron band. The
external electric field of frequency $\omega$ - in the presence of random
Rashba coupling -- leads to virtual spin-flip transitions between spin
subbands, generating stationary pure spin current proportional to the square of
the field amplitude.",1108.1899v1
2015-01-07,Superfluidity of pure spin current in ultracold Bose gases,"We study the superfluidity of a pure spin current that is a spin current
without mass current. We examine two types of pure spin currents, planar and
circular, in spin-1 Bose gas. For the planar current, it is usually unstable,
but can be stabilized by the quadratic Zeeman effect. The circular current can
be generated with spin-orbit coupling. When the spin-orbit coupling strength is
weak, we find that the circular pure spin current is the ground state of the
system and thus a super-flow. We discuss the experimental schemes to realize
and detect a pure spin current.",1501.01362v1
2012-01-23,Spin-Selective Transport of Electron in DNA Double Helix,"The experiment that the high spin selectivity and the length-dependent spin
polarization are observed in double-stranded DNA [Science ${\bf 331}$, 894
(2011)], is elucidated by considering the combination of the spin-orbit
coupling, the environment-induced dephasing, and the helical symmetry. We show
that the spin polarization in double-stranded DNA is significant even in the
case of weak spin-orbit coupling, while no spin polarization appears in
single-stranded DNA. Furthermore, the underlying physical mechanism and the
parameters-dependence of the spin polarization are studied.",1201.4888v1
2022-08-19,Spin-triplet Superconductivity in Nonsymmorphic crystals,"Spin-triplet superconductivity is known to be a rare quantum phenomenon. Here
we show that nonsymmorphic crystalline symmetries can dramatically assist
spin-triplet superconductivity in the presence of spin-orbit coupling. Even
with a weak spin-orbit coupling, the spin-triplet pairing can be the leading
pairing instability in a lattice with a nonsymmorphic symmetry. The underlining
mechanism is the spin-sublattice-momentum lock on electronic bands that are
protected by the nonsymmorphic symmetry. We use the nonsymmorphic space group
P4/nmm to demonstrate these results and discuss related experimental
observables. Our work paves a new way in searching for spin-triplet
superconductivity.",2208.09409v1
2022-12-22,The spin Hall effect,"In metallic systems with spin-orbit coupling a longitudinal charge current
may generate a transverse pure spin current; vice-versa an injected pure spin
current may result in a transverse charge current. Such direct and inverse spin
Hall effects share the same microscopic origin: intrinsic band/device structure
properties, external factors such as impurities, or a combination of both. They
allow all-electrical manipulation of the electronic spin degrees of
freedom,i.e. without magnetic elements, and their transverse nature makes them
potentially dissipationless. It is customary to talk of spin Hall effects in
plural form, referring to a group of related phenomena typical of spin-orbit
coupled systems of lowered symmetry.",2212.11686v1
2016-03-24,Interplay of Coulomb interaction and spin-orbit coupling,"We employ the Gutzwiller variational approach to investigate the interplay of
Coulomb interaction and spin-orbit coupling in a three-orbital Hubbard model.
Already in the paramagnetic phase we find a substantial renormalization of the
spin-orbit coupling that enters the effective single-particle Hamiltonian for
the quasi-particles. Only close to half band-filling and for sizable Coulomb
interaction we observe clear signatures of Hund's atomic rules for spin,
orbital, and total angular momentum. For a finite local Hund's-rule exchange
interaction we find a ferromagnetically ordered state. The spin-orbit coupling
considerably reduces the size of the ordered moment, it generates a small
ordered orbital moment, and it induces a magnetic anisotropy. To investigate
the magnetic anisotropy energy, we use an external magnetic field that tilts
the magnetic moment away from the easy axis $(1,1,1)$.",1603.07544v3
2012-01-15,Electron spin relaxation in rippled graphene with low mobilities,"We investigate spin relaxation in rippled graphene where curvature induces a
Zeeman-like spin-orbit coupling with opposite effective magnetic fields along
the graphene plane in ${\bf K}$ and ${\bf K}^\prime$ valleys. The joint effect
of this Zeeman-like spin-orbit coupling and the intervalley electron-optical
phonon scattering opens a spin relaxation channel, which manifests itself in
low-mobility samples with the electron mean free path being smaller than the
ripple size. Due to this spin relaxation channel, with the increase of
temperature, the relaxation time for spins perpendicular to the effective
magnetic field first decreases and then increases, with a minimum of several
hundred picoseconds around room temperature. However, the spin relaxation along
the effective magnetic field is determined by the curvature-induced Rashba-type
spin-orbit coupling, leading to a temperature-insensitive spin relaxation time
of the order of microseconds. Therefore, the in-plane spin relaxation in
low-mobility rippled graphene is anisotropic. Nevertheless, in the presence of
a small perpendicular magnetic field, as usually applied in the Hanle spin
precession measurement, the anisotropy of spin relaxation is strongly
suppressed.",1201.3064v1
2003-09-18,Electron spin operation by electric fields: spin dynamics and spin injection,"Spin-orbit interaction couples electron spins to electric fields and allows
electrical monitoring of electron spins and electrical detection of spin
dynamics. Competing mechanisms of spin-orbit interaction are compared, and
optimal conditions for the electric operation of electrons spins in a quantum
well by a gate voltage are established. Electric spin injection into
semiconductors is discussed with a special emphasis on the injection into
ballistic microstructures. Dramatic effect of a long range Coulomb interaction
on transport phenomena in space-quantized low-dimensional conductors is
discussed in conclusion.",0309441v1
2009-04-13,Semiclassical spin transport in spin-orbit-coupled systems,"This article discusses spin transport in systems with spin-orbit interactions
and how it can be understood in a semiclassical picture. I will first present a
semiclassical wave-packet description of spin transport, which explains how the
microscopic motion of carriers gives rise to a spin current. Due to spin
non-conservation the definition of the spin current has some arbitrariness. In
the second part I will briefly review the physics from a density matrix point
of view, which makes clear the relationship between spin transport and spin
precession and the important role of scattering.",0904.1999v1
2017-08-04,Quantification of spin accumulation causing spin-orbit torque in Pt/Co/Ta stack,"Spin accumulation induced by spin-orbit coupling is experimentally quantified
in stack with in-plane magnetic anisotropy via the contribution of spin
accumulation to Hall resistances. Using a biasing direct current the spin
accumulation within the structure can be tuned, enabling quantification.
Quantification shows the spin accumulation can be more than ten percentage of
local magnetization, when the electric current is 1E11 A/m*m. The spin
accumulation is dependent of the thickness of Ta layer, the trend agrees with
that of spin Hall angle indicating the capability of Ta and Pt in generating
spins.",1709.07948v1
2011-07-14,Extending the effective-one-body Hamiltonian of black-hole binaries to include next-to-next-to-leading spin-orbit couplings,"In the effective-one-body (EOB) approach the dynamics of two compact objects
of masses m1 and m2 and spins S1 and S2 is mapped into the dynamics of one test
particle of mass mu = m1 m2/(m1+m2) and spin S* moving in a deformed Kerr
metric with mass M = m1+m2 and spin Skerr. In a previous paper we computed an
EOB Hamiltonian for spinning black-hole binaries that (i) when expanded in
post-Newtonian orders, reproduces the leading order spin-spin coupling and the
leading and next-to-leading order spin-orbit couplings for any mass ratio, and
(iii) reproduces all spin-orbit couplings in the test-particle limit. Here we
extend this EOB Hamiltonian to include next-to-next-to-leading spin-orbit
couplings for any mass ratio. We discuss two classes of EOB Hamiltonians that
differ by the way the spin variables are mapped between the effective and real
descriptions. We also investigate the main features of the dynamics when the
motion is equatorial, such as the existence of the innermost stable circular
orbit and of a peak in the orbital frequency during the plunge subsequent to
the inspiral.",1107.2904v2
2014-08-10,"Strong interactions, narrow bands, and dominant spin-orbit coupling in Mott insulating quadruple perovskite CaCo3V4O12","We investigate the electronic and magnetic structures and the character and
direction of spin and orbital moments of the recently synthesized quadruple
perovskite cobaltovanadate CaCo3V4O12 using a selection of methods from density
functional theory. Implementing the generalized gradient approximation and the
Hubbard U correction (GGA+U), ferromagnetic spin alignment leads to
half-metallicity rather than the observed narrow gap insulating behavior.
Including spin-orbit coupling (SOC) leaves a half-semimetallic spectrum which
is essentially Mott insulating. SOC is crucial for the Mott insulating
character of the V d^1 ion, breaking the d_{m=\pm 1} degeneracy and also giving
a substantial orbital moment. Evidence is obtained of the large orbital moments
on Co that have been inferred from the measured susceptibility. Switching to
the orbital polarization (OP) functional, GGA+OP+SOC also displays clear
tendencies toward very large orbital moments but in its own distinctive manner.
In both approaches, application of SOC, which requires specification of the
direction of the spin, introduces large differences in the orbital moments of
the three Co ions in the primitive cell. We study a fictitious but simpler
cousin compound Ca3CoV4O12 (Ca replacing two of the Co atoms) to probe in more
transparent fashion the interplay of spin and orbital degrees of freedom with
the local environment of the planar CoO4 units. The observation that the
underlying mechanisms seems to be local to a CoO4 plaquette, and that there is
very strong coupling of the size of the orbital moment to the spin direction,
strongly suggest non-collinear spins, not only on Co but on the V sublattice as
well.",1408.2261v1
2011-01-24,Identifying spin-triplet pairing in spin-orbit coupled multi-band superconductors,"We investigate the combined effect of Hund's and spin-orbit (SO) coupling on
superconductivity in multi-orbital systems. Hund's interaction leads to
orbital-singlet spin-triplet superconductivity, where the Cooper pair wave
function is antisymmetric under the exchange of two orbitals. We identify three
d-vectors describing even-parity orbital-singlet spin-triplet pairings among
t2g-orbitals, and find that the three d-vectors are mutually orthogonal to each
other. SO coupling further assists pair formation, pins the orientation of the
d-vector triad, and induces spin-singlet pairings with a relative phase
difference of \pi/2. In the band basis the pseudospin d-vectors are aligned
along the z-axis and correspond to momentum-dependent inter- and intra-band
pairings. We discuss quasiparticle dispersion, magnetic response, collective
modes, and experimental consequences in light of the superconductor Sr2RuO4.",1101.4656v3
2024-01-22,Finite-momentum and field-induced pairings in orbital-singlet spin-triplet superconductors,"Finite-momentum pairing in a Pauli-limited spin-singlet superconductor arises
from the pair-breaking effects of an external Zeeman field, a mechanism which
is not applicable in odd-parity spin-triplet superconductors. However, in
multiorbital systems, the relevant bands originating from different orbitals
are usually separated in momentum space, implying that orbital-singlet pairing
is a natural candidate for a finite-momentum pairing state. We show that
finite-momentum pairing arises in even-parity orbital-singlet spin-triplet
superconductors via the combination of orbitally-nontrivial kinetic terms and
Hund's coupling. The finite-momentum pairing is then suppressed with an
increasing spin-orbit coupling, stabilizing a uniform pseudospin-singlet
pairing. We also examine the effects of the magnetic field and find
field-induced superconductivity at large fields. We apply these findings to the
multiorbital superconductor with spin-orbit coupling, Sr$_{2}$RuO$_{4}$ and
show that a finite-momentum pseudospin-singlet state appears between the
uniform pairing and normal states. Future directions of inquiry relating to our
findings are also discussed.",2401.12320v1
2008-05-07,Frustration and entanglement in the $t_{2g}$ spin--orbital model on a triangular lattice: valence--bond and generalized liquid states,"We consider the spin--orbital model for a magnetic system with singly
occupied but triply degenerate $t_{2g}$ orbitals coupled into a planar,
triangular lattice, as would be exemplified by NaTiO$_2$. We investigate the
ground states of the model for interactions which interpolate between the
limits of pure superexchange and purely direct exchange interactions. By
considering ordered and dimerized states at the mean--field level, and by
interpreting the results from exact diagonalization calculations on selected
finite systems, we demonstrate that orbital interactions are always frustrated,
and that orbital correlations are dictated by the spin state, manifesting an
intrinsic entanglement of these degrees of freedom. In the absence of Hund
coupling, the ground state changes from a highly resonating, dimer--based,
symmetry--restored spin and orbital liquid phase, to one based on completely
static, spin--singlet valence bonds. The generic properties of frustration and
entanglement survive even when spins and orbitals are nominally decoupled in
the ferromagnetic phases stabilized by a strong Hund coupling. By considering
the same model on other lattices, we discuss the extent to which frustration is
attributable separately to geometry and to interaction effects.",0805.1028v1
2021-03-08,Spin-orbital model for fullerides,"The multiorbital Hubbard model in the strong coupling limit is analyzed for
the effectively antiferromagnetic Hund's coupling relevant to fulleride
superconductors with three orbitals per molecule. The localized spin-orbital
model describes the thermodynamics of the half-filled (three-electron) state
with total spin-1/2, composed of singlon and doublon placed on the two of three
orbitals. The model is solved using the mean-field approximation and magnetic
and electric ordered states are clarified through the temperature dependences
of the order parameters. Combining the model with the band structure from {\it
ab initio} calculation, we also semi-quantitavely analyze the realistic model
and the corresponding physical quantities. In the A15-structure fulleride
model, there is an antiferromagnetic ordered state, and subsequently the two
orbital ordered state appears at lower temperatures. It is argued that the
origin of these orbital orders is related to the $T_h$ point group symmetry. As
for the fcc-fulleride model, the time-reversal broken orbital ordered state is
identified. Whereas the spin degeneracy remains in our treatment for the
geometrically frustrated lattice, it is expected to be lifted by some magnetic
ordering or quantum fluctuations, but not by the spin-orbital coupling which is
effectively zero for fullerides in the strong-coupling regime.",2103.04960v1
2022-11-11,Orbital Origin of Intrinsic Planar Hall Effect,"Recent experiments reported an antisymmetric planar Hall effect, where the
Hall current is odd in the in-plane magnetic field and scales linearly with
both electric and magnetic fields applied. Existing theories rely exclusively
on a spin origin, which requires spin-orbit coupling to take effect. Here, we
develop a general theory for the intrinsic planar Hall effect (IPHE),
highlighting a previously unknown orbital mechanism and connecting it to a band
geometric quantity -- the anomalous orbital polarizability (AOP). Importantly,
the orbital mechanism does not request spin-orbit coupling, so sizable IPHE can
occur and is dominated by orbital contribution in systems with weak spin-orbit
coupling. Combined with first-principles calculations, we demonstrate our
theory with quantitative evaluation for bulk materials $\mathrm{TaSb_{2}}$,
$\mathrm{NbAs_{2}}$, and $\mathrm{SrAs_{3}}$. We further show that AOP and its
associated orbital IPHE can be greatly enhanced at topological band crossings,
offering a new way to probe topological materials.",2211.05978v2
2024-01-16,Active Control of Ballistic Orbital Transport,"Orbital current, defined as the orbital character of Bloch states in solids,
can ballistically travel with larger coherence length through a broader range
of materials than its spin counterpart, facilitating a robust, higher density
and energy efficient information transmission. Hence, active control of orbital
transport plays a pivotal role in propelling the progress of the evolving field
of quantum information technology. Unlike spin angular momentum, orbital
angular momentum (OAM), couples to phonon angular momentum (PAM) efficiently
via orbital-crystal momentum (L-k) coupling, giving us the opportunity to
control orbital transport through crystal field potential mediated angular
momentum transfer. Here, leveraging the orbital dependant efficient L-k
coupling, we have experimentally demonstrated the active control of orbital
current velocity using THz emission spectroscopy. Our findings include the
identification of a critical energy density required to overcome collisions in
orbital transport, enabling a swifter flow of orbital current. The capability
to actively control the ballistic orbital transport lays the groundwork for the
development of ultrafast devices capable of efficiently transmitting
information over extended distance.",2401.08373v1
2024-04-06,Consistent Second-Order Treatment of Spin-Orbit Coupling and Dynamic Correlation in Quasidegenerate N-Electron Valence Perturbation Theory,"We present a formulation and implementation of second-order quasidegenerate
N-electron valence perturbation theory (QDNEVPT2) that provides a balanced and
accurate description of spin-orbit coupling and dynamic correlation effects in
multiconfigurational electronic states. In our approach, the energies and
wavefunctions of electronic states are computed by treating electron repulsion
and spin-orbit coupling operators as equal perturbations to the
non-relativistic complete active-space wavefunctions and their contributions
are incorporated fully up to the second order. The spin-orbit effects are
described using the Breit-Pauli (BP) or exact two-component Douglas-Kroll-Hess
(DKH) Hamiltonians within spin-orbit mean-field approximation. The resulting
second-order methods (BP2- and DKH2-QDNEVPT2) are capable of treating
spin-orbit coupling effects in nearly degenerate electronic states by
diagonalizing an effective Hamiltonian expanded in a compact non-relativistic
basis. For a variety of atoms and small molecules across the entire periodic
table, we demonstrate that DKH2-QDNEVPT2 is competitive in accuracy with
variational two-component relativistic theories. BP2-QDNEVPT2 shows high
accuracy for the second- and third-period elements, but its performance
deteriorates for heavier atoms and molecules. We also consider the first-order
spin-orbit QDNEVPT2 approximations (BP1- and DKH1-QDNEVPT2), among which
DKH1-QDNEVPT2 is reliable but less accurate than DKH2-QDNEVPT2. Both DKH1- and
DKH2-QDNEVPT2 hold promise as efficient and accurate electronic structure
methods for treating electron correlation and spin-orbit coupling in a variety
of applications.",2404.04716v1
2012-08-29,Radio-frequency spectroscopy of weakly bound molecules in spin-orbit coupled atomic Fermi gases,"We investigate theoretically radio-frequency spectroscopy of weakly bound
molecules in an ultracold spin-orbit-coupled atomic Fermi gas. We consider two
cases with either equal Rashba and Dresselhaus coupling or pure Rashba
coupling. The former system has been realized very recently at Shanxi
University [Wang et al., arXiv:1204.1887] and MIT [Cheuk et al.,
arXiv:1205.3483]. We predict realistic radio-frequency signals for revealing
the unique properties of anisotropic molecules formed by spin-orbit coupling.",1208.5841v1
2018-04-30,Superconducting tunneling spectroscopy of spin-orbit coupling and orbital depairing in Nb:SrTiO$_3$,"We have examined the intrinsic spin-orbit coupling (SOC) and orbital
depairing in thin films of Nb-doped SrTiO$_3$ by superconducting tunneling
spectroscopy. The orbital depairing is geometrically suppressed in the
two-dimensional limit, enabling a quantitative evaluation of the Fermi level
spin-orbit scattering using Maki's theory. The response of the superconducting
gap under in-plane magnetic fields demonstrates short spin-orbit scattering
times $\tau_{so} \leq 1.1$ ps. Analysis of the orbital depairing indicates that
the heavy electron band contributes significantly to pairing. These results
suggest that the intrinsic spin-orbit scattering time in SrTiO$_3$ is
comparable to those associated with Rashba effects in SrTiO$_3$ interfacial
conducting layers and can be considered significant in all forms of
superconductivity in SrTiO$_3$.",1805.00047v1
2020-03-30,Intrinsic orbital moment and prediction of a large orbital Hall effect in the 2D transition metal dichalcogenides,"Carrying information using generation and detection of the orbital current,
instead of the spin current, is an emerging field of research, where the
orbital Hall effect (OHE) is an important ingredient. Here, we propose a new
mechanism of the OHE that occurs in {\it non-}centrosymmetric materials. We
show that the broken inversion symmetry in the 2D transition metal
dichalcogenides (TMDCs) causes a robust orbital moment, which flow in different
directions due to the opposite Berry curvatures under an applied electric
field, leading to a large OHE. This is in complete contrast to the
inversion-symmetric systems, where the orbital moment is induced only by the
external electric field. We show that the valley-orbital locking as well as the
OHE both appear even in the absence of the spin-orbit coupling. The non-zero
spin-orbit coupling leads to the well-known valley-spin locking and the spin
Hall effect, which we find to be weak, making the TMDCs particularly suitable
for direct observation of the OHE, with potential application in {\it
orbitronics}.",2003.13181v1
2017-05-26,Role of the spin-orbit coupling in the Kugel-Khomskii model on the honeycomb lattice,"We study the effective spin-orbital model for honeycomb-layered transition
metal compounds, applying the second-order perturbation theory to the
three-orbital Hubbard model with the anisotropic hoppings. This model is
reduced to the Kitaev model in the strong spin-orbit coupling limit. Combining
the cluster mean-field approximations with the exact diagonalization, we treat
the Kugel-Khomskii type superexchange interaction and spin-orbit coupling on an
equal footing to discuss ground-state properties. We find that a zigzag ordered
state is realized in the model within nearest-neighbor interactions. We clarify
how the ordered state competes with the nonmagnetic state, which is
adiabatically connected to the quantum spin liquid state realized in a strong
spin-orbit coupling limit. Thermodynamic properties are also addressed. The
present work should provide another route to account for the Kitaev-based
magnetic properties in candidate materials.",1705.09659v1
2019-08-21,Spin-orbit-coupled quantum memory of a double quantum dot,"The concept of quantum memory plays an incisive role in the quantum
information theory. As confirmed by several recent rigorous mathematical
studies, the quantum memory inmate in the bipartite system $\rho_{AB}$ can
reduce uncertainty about the part $B$, after measurements done on the part $A$.
In the present work, we extend this concept to the systems with a spin-orbit
coupling and introduce a notion of spin-orbit quantum memory. We
self-consistently explore Uhlmann fidelity, pre and post measurement
entanglement entropy and post measurement conditional quantum entropy of the
system with spin-orbit coupling and show that measurement performed on the spin
subsystem decreases the uncertainty of the orbital part. The uncovered effect
enhances with the strength of the spin-orbit coupling. We explored the concept
of macroscopic realism introduced by Leggett and Garg and observed that POVM
measurements done on the system under the particular protocol are
non-noninvasive. For the extended system, we performed the quantum Monte Carlo
calculations and explored reshuffling of the electron densities due to the
external electric field.",1908.07766v2
2019-07-01,Spin dynamics of moving bodies in rotating black hole spacetimes,"The dynamics of spinning test bodies, moving in rotating black hole (Kerr,
Bardeen-like and Hayward-like) spacetimes, are investigated. In Kerr spacetime,
all the spherical, zoom-whirl and unbound orbits are considered numerically.
Along spherical orbits and for high spin, an amplitude modulation is found in
the harmonic evolution of the spin precessional angular velocity, caused by the
spin-curvature coupling. Along the discussed zoom-whirl and unbound orbits, the
test body approaches the center so much that it passes through the ergosphere.
Near and inside the ergosphere, the variation of the spin direction can be very
rapid. The effects of the spin-curvature coupling is also investigated. The
initial values are chosen such a way, that the body and its spin move in the
equatorial plane of the coordinate space and of the comoving frame,
respectively. Hence, a clear effect of the spin-curvature coupling is observed
as the orbit and the spin vector leave the equatorial plane. Additional effects
in the spin precessional angular velocity and in the evolution of the
Boyer-Lindquist coordinate components of the spin vector is also considered.
Finally, in case of different regular black holes, the spin-curvature coupling
influences differently the orbit and the spin evolutions.",1907.00974v2
2016-12-11,The Spinon Fermi Surface U(1) Spin Liquid in a Spin-Orbit-Coupled Triangular Lattice Mott Insulator YbMgGaO4,"Motivated by the recent progress on the spin-orbit-coupled triangular lattice
spin liquid candidate YbMgGaO4, we carry out a systematic projective symmetry
group analysis and mean-field study of candidate U(1) spin liquid ground
states. Due to the spin-orbital entanglement of the Yb moments, the space group
symmetry operation transforms both the position and the orientation of the
local moments, and hence brings different features for the projective
realization of the lattice symmetries from the cases with spin-only moments.
Among the eight U(1) spin liquids that we find with the fermionic parton
construction, only one spin liquid state, that was proposed and analyzed in Yao
Shen, et al, Nature 540, 559-562 (2016) and labeled as U1A00 in the present
work, stands out and gives a large spinon Fermi surface and provides a
consistent explanation for the spectroscopic results in YbMgGaO4. Further
connection of this spinon Fermi surface U(1) spin liquid with YbMgGaO4 and the
future directions are discussed. Finally, our results may apply to other
spin-orbit-coupled triangular lattice spin liquid candidates, and more broadly,
our general approach can be well extended to spin-orbit-coupled spin liquid
candidate materials.",1612.03447v4
2011-08-08,"Spin-Orbital Locking, Emergent Pseudo-Spin, and Magnetic order in Honeycomb Lattice Iridates","The nature of the effective spin Hamiltonian and magnetic order in the
honeycomb iridates is explored by considering a trigonal crystal field effect
and spin-orbit coupling. Starting from a Hubbard model, an effective spin
Hamiltonian is derived in terms of an emergent pseudo-spin-1/2 moment in the
limit of large trigonal distortions and spin-orbit coupling. The present
pseudo-spins arise from a spin-orbital locking and are different from the jeff
= 1/2 moments that are obtained when the spin-orbit coupling dominates and
trigonal distortions are neglected. The resulting spin Hamiltonian is
anisotropic and frustrated by further neighbour interactions. Mean field theory
suggests a ground state with 4-sublattice zig-zag magnetic order in a parameter
regime that can be relevant to the honeycomb iridate compound Na2IrO3, where
similar magnetic ground state has recently been observed. Various properties of
the phase, the spin-wave spectrum and experimental consequences are discussed.
The present approach contrasts with the recent proposals to understand iridate
compounds starting from the strong spin-orbit coupling limit and neglecting
non-cubic lattice distortions.",1108.1806v3
2005-02-03,Spin resolved Hall effect driven by spin-orbit coupling,"Spin and electric Hall currents are calculated numerically in a
two-dimensional mesoscopic system with Rashba and Dresselhaus spin-orbit
coupling by means of the Landauer-Buttiker formalism. It is found that both
electric and spin Hall currents circulate when two spin-orbit couplings
coexist, while the electric Hall conductance vanishes if either one is absent.
The electric and spin Hall conductances are suppressed in strong disorder, but
survive in weak disorder. Physically it can be understood that the spinomotive
transverse ""force"" generated by spin-orbit coupling is responsible for the
formation of the spin Hall current and the lack of transverse reflection
symmetry is the origin of the electric Hall current.",0502102v2
2012-05-28,Dzyaloshinskii-Moriya Interaction and Spiral Order in Spin-orbit Coupled Optical Lattices,"We show that the recent experimental realization of spin-orbit coupling in
ultracold atomic gases can be used to study different types of spin spiral
order and resulting multiferroic effects. Spin-orbit coupling in optical
lattices can give rise to the Dzyaloshinskii-Moriya (DM) spin interaction which
is essential for spin spiral order. By taking into account spin-orbit coupling
and an external Zeeman field, we derive an effective spin model in the Mott
insulator regime at half filling and demonstrate that the DM interaction in
optical lattices can be made extremely strong with realistic experimental
parameters. The rich finite temperature phase diagrams of the effective spin
models for fermions and bosons are obtained via classical Monte Carlo
simulations.",1205.6211v2
2021-12-09,Impact of Kondo correlations and spin-orbit coupling on spin-polarized transport in carbon nanotube quantum dot,"Spin polarized transport through a quantum dot coupled to ferromagnetic
electrodes with noncollinear magnetizations is discussed in terms of
nonequilibrium Green functions formalism in the finite-U slave boson mean field
approximation. The difference of orientations of the magnetizations of
electrodes opens off-diagonal spin-orbital transmission and apart from spin
currents of longitudinal polarization also spin-flip currents appear. We also
study equilibrium pure spin current at zero bias and discuss its dependence on
magnetization orientation, spin-orbit coupling strength and gate voltage.
Impact of these factors on tunneling magnetoresistance (TMR) is also
undertaken. In general spin-orbit coupling weakens TMR, but it can change its
sign.",2112.04765v1
2016-04-15,Determining the spin-orbit coupling via spin-polarized spectroscopy of magnetic impurities,"We study the spin-resolved spectral properties of the impurity states
associated to the presence of magnetic impurities in two-dimensional, as well
as one-dimensional systems with Rashba spin-orbit coupling. We focus on Shiba
bound states in superconducting materials, as well as on impurity states in
metallic systems. Using a combination of a numerical T-matrix approximation and
a direct analytical calculation of the bound state wave function, we compute
the local density of states (LDOS) together with its Fourier transform (FT). We
find that the FT of the spin-polarized LDOS, a quantity accessible via
spin-polarized STM, allows to accurately extract the strength of the spin-orbit
coupling. Also we confirm that the presence of magnetic impurities is strictly
necessary for such measurement, and that non-spin-polarized experiments cannot
have access to the value of the spin-orbit coupling.",1604.04623v3
2018-09-28,Engineering long spin coherence times of spin-orbit systems,"Spin-orbit coupling fundamentally alters spin qubits, opening pathways to
improve the scalability of quantum computers via long distance coupling
mediated by electric fields, photons, or phonons. It also allows for new
engineered hybrid and topological quantum systems. However, spin qubits with
intrinsic spin-orbit coupling are not yet viable for quantum technologies due
to their short ($\sim1~\mu$s) coherence times $T_2$, while qubits with long
$T_2$ have weak spin-orbit coupling making qubit coupling short-ranged and
challenging for scale-up. Here we show that an intrinsic spin-orbit coupled
""generalised spin"" with total angular momentum $J=\tfrac{3}{2}$, which is
defined by holes bound to boron dopant atoms in strained $^{28}\mathrm{Si}$,
has $T_2$ rivalling the electron spins of donors and quantum dots in
$^{28}\mathrm{Si}$. Using pulsed electron paramagnetic resonance, we obtain
$0.9~\mathrm{ms}$ Hahn-echo and $9~\mathrm{ms}$ dynamical decoupling $T_2$
times, where strain plays a key role to reduce spin-lattice relaxation and the
longitudinal electric coupling responsible for decoherence induced by electric
field noise. Our analysis shows that transverse electric dipole can be
exploited for electric manipulation and qubit coupling while maintaining a weak
longitudinal coupling, a feature of $J=\tfrac{3}{2}$ atomic systems with a
strain engineered quadrupole degree of freedom. These results establish
single-atom hole spins in silicon with quantised total angular momentum, not
spin, as a highly coherent platform with tuneable intrinsic spin-orbit coupling
advantageous to build artificial quantum systems and couple qubits over long
distances.",1809.10859v2
2013-06-03,The role of the Rashba coupling in spin current of monolayer gapped graphene,"In the current work we have investigated the influence of the Rashba
spin-orbit coupling on spin-current of a single layer gapped graphene. It was
shown that the Rashba coupling has a considerable role in generation of the
spin-current of vertical spins in mono-layer graphene. The behavior of the
spin-current is determined by density of impurities. It was also shown that the
spin-current of the system could increase by increasing the Rashba coupling
strength and band-gap of the graphene and the sign of the spin-current could be
controlled by the direction of the current-driving electric field.",1306.0611v1
2016-11-25,Spin-orbit Hamiltonian for organic crystals from first principles electronic structure and Wannier functions,"Spin-orbit coupling in organic crystals is responsible for many
spin-relaxation phenomena, going from spin diffusion to intersystem crossing.
With the goal of constructing effective spin-orbit Hamiltonians to be used in
multiscale approaches to the thermodynamical properties of organic crystals, we
present a method that combines density functional theory with the construction
of Wannier functions. In particular we show that the spin-orbit Hamiltonian
constructed over maximally localised Wannier functions can be computed by
direct evaluation of the spin-orbit matrix elements over the Wannier functions
constructed in absence of spin-orbit interaction. This eliminates the prob- lem
of computing the Wannier functions for almost degenerate bands, a problem
always present with the spin-orbit-split bands of organic crystals. Examples of
the method are presented for isolated molecules, for mono-dimensional chains of
Pb and C atoms and for triarylamine-based one-dimansional single crystals.",1611.08424v2
2008-01-07,Spin-orbit and tensor mean-field effects on spin-orbit splitting including self-consistent core polarizations,"A new strategy of fitting the coupling constants of the nuclear energy
density functional is proposed, which shifts attention from ground-state bulk
to single-particle properties. The latter are analyzed in terms of the bare
single-particle energies and mass, shape, and spin core-polarization effects.
Fit of the isoscalar spin-orbit and both isoscalar and isovector tensor
coupling constants directly to the f5/2-f7/2 spin-orbit splittings in 40Ca,
56Ni, and 48Ca is proposed as a practical realization of this new programme. It
is shown that this fit requires drastic changes in the isoscalar spin-orbit
strength and the tensor coupling constants as compared to the commonly accepted
values but it considerably and systematically improves basic single-particle
properties including spin-orbit splittings and magic-gap energies. Impact of
these changes on nuclear binding energies is also discussed.",0801.0924v1
2014-08-18,"Charge noise, spin-orbit coupling, and coherence of single-spin qubits","Spin-orbit coupling is ubiquitous in quantum dot quantum computing
architectures, and makes spin qubits susceptible to charge noise. We derive a
Hamiltonian describing the effect of spin-orbit and noise on a single-spin
qubit in a quantum dot. Relaxation is due to noise coupling different orbital
levels and is dominated by screened whole charge defects near the dot.
Dephasing stems from noise causing relative fluctuations between orbital
levels, and is driven by screened whole charge defects and unscreened dipole
defects in the substrate. Dephasing times are vastly different between common
materials such as Si and GaAs. They can be enhanced by increasing gate fields,
choosing materials with weak spin-orbit such as Si, making dots narrower, or
using accumulation dots.",1408.4123v2
2021-02-04,Spin-orbit-entangled electronic phases in 4$d$ and 5$d$ transition-metal compounds,"Complex oxides with $4d$ and $5d$ transition-metal ions recently emerged as a
new paradigm in correlated electron physics, due to the interplay between
spin-orbit coupling and electron interactions. For $4d$ and $5d$ ions, the
spin-orbit coupling, $\zeta$, can be as large as 0.2-0.4 eV, which is
comparable with and often exceeds other relevant parameters such as Hund's
coupling $J_{\rm H}$, noncubic crystal field splitting $\Delta$, and the
electron hopping amplitude $t$. This gives rise to a variety of
spin-orbit-entangled degrees of freedom and, crucially, non-trivial
interactions between them that depend on the $d$-electron configuration, the
chemical bonding, and the lattice geometry. Exotic electronic phases often
emerge, including spin-orbit assisted Mott insulators, quantum spin liquids,
excitonic magnetism, multipolar orderings and correlated topological
semimetals. This paper provides a selective overview of some of the most
interesting spin-orbit-entangled phases that arise in $4d$ and $5d$
transition-metal compounds.",2102.02740v1
2008-08-18,Dilution effect in correlated electron system with orbital degeneracy,"Theory of dilution effect in orbital ordered system is presented. The $e_g$
orbital model without spin degree of freedom and the spin-orbital coupled model
in a three-dimensional simple-cubic lattice are analyzed by the Monte-Carlo
simulation and the cluster expansion method. In the $e_g$ orbital model without
spin degree of freedom, reduction of the orbital ordering temperature due to
dilution is steeper than that in the dilute magnet. This is attributed to a
modification of the orbital wave-function around vacant sites. In the
spin-orbital coupled model, it is found that magnetic structure is changed from
the A-type antiferromagnetic order into the ferromagnetic one. Orbital
dependent exchange interaction and a sign change of this interaction around
vacant sites bring about this novel phenomena. Present results explain the
recent experiments in transition-metal compounds with orbital dilution.",0808.2372v1
2019-08-06,Spectral properties of spin-orbital polarons as a fingerprint of orbital order,"Transition metal oxides are a rich group of materials with very interesting
physical properties that arise from the interplay of the charge, spin, orbital,
and lattice degrees of freedom. One interesting consequence of this,
encountered in systems with orbital degeneracy, is the coexistence of long
range magnetic and orbital order, and the coupling between them. In this paper
we develop and study an effective spin-orbital superexchange model for $e_g^3$
systems and use it to investigate the spectral properties of a charge (hole)
injected into the system, which is relevant for photoemission spectroscopy.
Using an accurate, semi-analytical, magnon expansion method, we gain insight
into various physical aspects of these systems and demonstrate a number of
subtle effects, such as orbital to magnetic polaron crossover, the coupling
between orbital and magnetic order, as well as the orbital order driving the
system towards one-dimensional quantum spin liquid behavior. Our calculations
also suggest a potentially simple experimental verification of the character of
the orbital order in the system, something that is not easily accessible
through most experimental techniques.",1908.02232v1
2017-03-24,Gate control of the spin mobility through the modification of the spin-orbit interaction in two-dimensional systems,"Spin drag measurements were performed in a two-dimensional electron system
set close to the crossed spin helix regime and coupled by strong intersubband
scattering. In a sample with uncommon combination of long spin lifetime and
high charge mobility, the drift transport allows us to determine the spin-orbit
field and the spin mobility anisotropies. We used a random walk model to
describe the system dynamics and found excellent agreement for the Rashba and
Dresselhaus couplings. The proposed two-subband system displays a large tuning
lever arm for the Rashba constant with gate voltage, which provides a new path
towards a spin transistor. Furthermore, the data shows large spin mobility
controlled by the spin-orbit constants setting the field along the direction
perpendicular to the drift velocity. This work directly reveals the resistance
experienced in the transport of a spin-polarized packet as a function of the
strength of anisotropic spin-orbit fields.",1703.08405v2
2006-01-27,Spin-orbit effects on the Larmor dispersion relation in GaAs quantum wells,"We have studied the relevance of spin-orbit coupling to the dispersion 00009
relation of the Larmor resonance observed in inelastic light scattering and
electron-spin resonance experiments on GaAs quantum wells. We show that the
spin-orbit interaction, here described by a sum of Dresselhaus and
Bychkov-Rashba terms, couples Zeeman and spin-density excitations. We have
evaluated its contribution to the spin splitting as a function of the magnetic
field $B$, and have found that in the small $B$ limit, the spin-orbit
interaction does not contribute to the spin splitting, whereas at high magnetic
fields it yields a $B$ independent contribution to the spin splitting given by
$2(\lambda_R^2-\lambda_D^2)$, with $\lambda_{R,D}$ being the intensity of the
Bychkov-Rashba and Dresselhaus spin-orbit terms.",0601635v1
2013-04-01,Origin and Transport Signatures of Spin-Orbit Interactions in One- and Two-Dimensional SrTiO$_3$-Based Heterostructures,"We study origin of Rashba spin-orbit interaction at SrTiO$_3$ surfaces and
LaAlO$_3$/SrTiO$_3$ interfaces by considering the interplay between atomic
spin-orbit coupling and inversion asymmetry at the surface or interface. We
show that, in a simple tight-binding model involving 3d $t_{2g}$ bands of Ti
ions, the induced spin-orbit coupling in the $d_{xz}$ and $d_{yz}$ bands is
cubic in momentum whereas the spin-orbit interaction in the $d_{xy}$ band has
linear momentum dependence. We also find that the spin-orbit interaction in
one-dimensional channels at LaAlO$_3$/SrTiO$_3$ interfaces is linear in
momentum for all bands. We discuss implications of our results for transport
experiments on SrTiO$_3$ surfaces and LaAlO$_3$/SrTiO$_3$ interfaces. In
particular, we analyze the effect of a given spin-orbit interaction term on
magnetotransport of LaAlO$_3$/SrTiO$_3$ by calculating weak anti-localization
corrections to the conductance and to universal conductance fluctuations.",1304.0464v2
2020-11-02,Spin-orbital magnetic response of relativistic fermions with band hybridization,"Spins of relativistic fermions are related to their orbital degrees of
freedom. In order to quantify the effect of hybridization between relativistic
and nonrelativistic degrees of freedom on spin-orbit coupling, we focus on the
spin-orbital (SO) crossed susceptibility arising from spin-orbit coupling. The
SO crossed susceptibility is defined as the response function of their spin
polarization to the ""orbital"" magnetic field, namely the effect of magnetic
field on the orbital motion of particles as the vector potential. Once
relativistic and nonrelativistic fermions are hybridized, their SO crossed
susceptibility gets modified at the Fermi energy around the band hybridization
point, leading to spin polarization of nonrelativistic fermions as well. These
effects are enhanced under a dynamical magnetic field that violates thermal
equilibrium, arising from the interband process permitted by the band
hybridization. Its experimental realization is discussed for Dirac electrons in
solids with slight breaking of crystalline symmetry or doping, and also for
quark matter including dilute heavy quarks strongly hybridized with light
quarks, arising in a relativistic heavy-ion collision process.",2011.00882v2
2022-07-11,Spin-Orbit Proximity Effect in Bi/Co Multilayer: The Role of Interface Scattering,"The Spin-Orbit Proximity Effect is the raise of Spin-Orbit Coupling at a
layer near to the interface with a strong spin-orbit material. It has been seen
in several system such as graphene and ferromagnetic layers. The control of the
Spin-Orbit Coupling can be a pathway to discover novel and exotic phases in
superconductor and semimetallic systems. Here, we study the magnetoelectrical
transport, i.e., magnetoresistance and anomalous Hall effect, in Cobalt/Bismuth
multilayers looking for traces of spin-orbit proximity effect and evaluate the
origin of such effect. Our results point for an increase of Spontaneous
Magnetic Anisotropy of Resistivity and Anomalous Hall Resistivity at very low
thicknesses of Cobalt. The analysis of the Anomalous Hall Resisitivity indicate
that the Bismuth layers change the scattering mechanism of Hall effect to the
extrinsic skew-scattering type, indicating that the spin-orbit proximity effect
could be related to the elastic scattering of cobalt free carriers by bismuth
sites at the interface.",2207.04937v1
2023-10-08,Nonlinear Orbital and Spin Edelstein Effect in Centrosymmetric Metals,"Nonlinear spintronics combines nonlinear dynamics with spintronics, opening
up new possibilities beyond linear responses. A recent theoretical work [Xiao
et al., Phys. Rev. Lett. 130, 166302 (2023)] predicts the nonlinear generation
of spin density [nonlinear spin Edelstein effect (NSEE)] in centrosymmetric
metals based on symmetry analysis combined with first principle calculation.
However, its microscopic mechanism is limited to a specific set of materials
with local inversion symmetry breaking and is not applicable to general
materials. This paper focuses on the fundamental role of orbital degrees of
freedom for the nonlinear generation in centrosymmetric systems. Using a
combination of tight-binding model and density functional theory calculations,
we demonstrate that nonlinear orbital density can arise independently of
spin-orbit coupling. In contrast, spin density follows through spin-orbit
coupling. We further elucidate the microscopic mechanism responsible for this
phenomenon, which involves the NSEE induced by electric-field-induced orbital
Rashba texture. In addition, we also explore the potential applications of the
nonlinear orbital and spin Edelstein effect for field-free switching of
magnetization.",2310.05113v4
2003-06-03,Spin transport in nanowires,"We study high-field spin transport of electrons in a quasi one-dimensional
channel of a $GaAs$ gate controlled spin interferometer (SPINFET) using a
semiclassical formalism (spin density matrix evolution coupled with Boltzmann
transport equation). Spin dephasing (or depolarization) is predominantly caused
by D'yakonov-Perel' relaxation associated with momentum dependent spin orbit
coupling effects that arise due to bulk inversion asymmetry (Dresselhaus spin
orbit coupling) and structural inversion asymmetry (Rashba spin orbit
coupling). Spin dephasing length in a one dimensional channel has been found to
be an order of magnitude higher than that in a two dimensional channel. This
study confirms that the ideal configuration for a SPINFET is one where the
ferromagnetic source and drain contacts are magnetized along the axis of the
channel. The spin dephasing length in this case is about 22.5 microns at
lattice temperature of 30K and 10 microns at lattice temperature of 77 K for an
electric field of 2 kV/cm. Spin dephasing length has been found to be weakly
dependent on the driving electric field and strongly dependent on the lattice
temperature.",0306082v1
2009-10-28,"Orbital fluctuations, spin-orbital coupling, and anomalous magnon softening in an orbitally degenerate ferromagnet","The correlated motion of electrons in the presence of strong orbital
fluctuations and correlations is investigated with respect to magnetic
couplings and excitations in an orbitally degenerate ferromagnet. Introduction
of the orbital degree of freedom results in a class of diagrams representing
spin-orbital coupling which become particularly important near the orbital
ordering instability. Low-energy staggered orbital fluctuation modes,
particularly with momentum near (\pi/2,\pi/2,0) (corresponding to CE-type
orbital correlations), are shown to generically yield strong intrinsically
non-Heisenberg (1-\cos q)^2 magnon self energy correction, resulting in no spin
stiffness reduction, but strongly suppressed zone-boundary magnon energies in
the Gamma-X direction. The zone-boundary magnon softening is found to be
strongly enhanced with increasing hole doping and for narrow-band materials,
which provides insight into the origin of zone-boundary anomalies observed in
ferromagnetic manganites.",0910.5321v2
2000-05-26,Theory of the solid-state physics on the turn: II. Importance of the spin-orbit coupling for 3d-ion compounds: the case of NiO,"The orbital and spin moment of the Ni2+ ion in NiO has been calculated at 0 K
to be 0.54mB and 1.99 mB respectively. Such large orbital moment, more than 20%
of the total moment of 2.53 mB, proves the need for the ''unquenching'' of the
orbital moment in compounds containing 3d ions. It turns out that the
spin-orbit coupling is indispensable for description of magnetic and electronic
properties of 3d-ion compounds. These two findings, largely ignored at the
nowadays in-fashion solid-state thories, call for an advanced solid-state
physics theory.",0005471v1
2005-06-16,Orbital order and spin-orbit coupling in BaVS3,"The correlated 3d sulphide BaVS3 undergoes a sequence of three symmetry
breaking transitions which are reflected in the temperature dependence of the
magnetic susceptibility, and its anisotropy. We introduce a microscopic model
based on the coexistence of wide band a(1g) and localized e(g) d-electrons, and
give the classification of the order parameters under the double space group
and time reversal symmetries. Allowing for the relativistic spin-orbit
coupling, the d-shell multipoles acquire a mixed spin-orbital character. It
follows that orbital ordering is accompanied by a change in the susceptibility
anisotropy",0506409v1
2018-11-24,Collective dipole oscillations of a spin-orbit coupled Fermi gas,"The collective dipole mode is induced and measured in a spin-orbit (SO)
coupled degenerate Fermi gas of $^{173}$Yb atoms. Using a differential optical
Stark shift, we split the degeneracy of three hyperfine states in the ground
manifold, and independently couple consecutive spin states with the equal Raman
transitions. A relatively long-lived spin-orbit-coupled Fermi gas, readily
being realized with a narrow optical transition, allows to explore a
single-minimum dispersion where three minima of spin-1 system merge into and to
monitor collective dipole modes of fermions in the strong coupling regime. The
measured oscillation frequency of the dipole mode is compared with the
semi-classical calculation in the single-particle regime. Our work should pave
the way towards the characterization of spin-orbit-coupled fermions with large
spin $s>\frac{1}{2}$ in the strong coupling regime.",1811.09846v1
2016-11-16,Ferromagnetic order induced on graphene by Ni/Co proximity effects,"We build a tight-binding Hamiltonian describing Co/Ni over graphene,
contemplating ATOP (a Co/Ni atom on top of each Carbon atom of one graphene
sublattice) and HCP (one Co/Ni atom per Graphene plaquette) configurations. For
the ATOP configuration the orbitals involved, for the Co/Ni, are the
$d_{z^2-r^2}$ which most strongly couple to one graphene sublattice and the
$d_{xz}$, $d_{yz}$ orbitals that couple directly to the second sublattice site.
Such configuration is diagonal in pseudo-spin and spin space, yielding electron
doping of the graphene and antiferro-magnetic ordering in the primitive cell in
agreement with DFT calculations. The second, HCP configuration is symmetric in
the graphene sublattices and only involves coupling to the $d_{xz}$, $d_{yz}$
orbitals. The register of the lattices in this case allows for a new coupling
between nearest neighbour sites, generating non-diagonal terms in the
pseudo-spin space and novel spin-kinetic couplings mimicking a spin-orbit
coupling generated by a magnetic coupling. The resulting proximity effect in
this case yields ferromagnetic order in the graphene substrate. We derive the
band structure in the vicinity of the K points for both configurations, the
Bloch wavefunctions and their spin polarization.",1611.05464v1
2016-11-21,Relativistic orbits around spinning supermassive black holes. Secular evolution to 4.5 post-Newtonian order,"We derive the secular evolution of the orbital elements of a stellar-mass
object orbiting a spinning massive black hole. We use the post-Newtonian
approximation in harmonic coordinates, with test-body equations of motion for
the conservative dynamics that are valid through 3PN order, including
spin-orbit, quadrupole and (spin)$^2$ effects, and with radiation-reaction
contributions linear in the mass of the body that are valid through 4.5PN
order, including the 4PN damping effects of spin-orbit coupling. The evolution
equations for the osculating orbit elements are iterated to high PN orders
using a two-timescale approach and averaging over orbital timescales. We derive
a criterion for terminating the orbit when its Carter constant drops below a
critical value, whereupon the body plunges across the event horizon at the next
closest approach. The results are valid for arbitrary eccentricities and
arbitrary inclinations. We then analyze numerically the orbits of objects
injected into high-eccentricity orbits via interactions within a surrounding
star cluster, obtaining the number of orbits and the elapsed time between
injection and plunge, and the residual orbital eccentricity at plunge as a
function of inclination. We derive an analytic approximation for the time to
plunge in terms of initial orbital variables. We show that, if the black hole
is spinning rapidly, the flux of gravitational radiation during the final orbit
before plunge may be suppressed by as much as three orders of magnitude if the
orbit is retrograde on the equatorial plane compared to its prograde
counterpart.",1611.06931v1
2000-05-22,The orbital moment in NiO,"The orbital and spin moment of the Ni2+ ion in NiO has been calculated within
the quasi-atomic approach. The orbital moment of 0.54 mB amounts at 0 K, in the
magnetically-ordered state, to more than 20% of the total moment (2.53 mB). For
this outcome, being in nice agreement with the recent experimental finding
taking into account the spin-orbit coupling is indispensable.",0005358v1
2000-08-18,Large Orbital Magnetic Moment in Febr2,"Magnetic moment of the Fe2+ ion in FeBr2 has been calculated to be 4.32 mB in
the magnetically-ordered state at 0 K. It is composed from the spin moment of
3.52 mB and the orbital moment of +0.80 mB. These calculations show that for
the meaningful analysis of e-m properties of FeBr2 the spin-orbit coupling is
essentially important and that the orbital moment is largely unquenched.",0008274v1
2001-12-12,Exchange Interaction in Binuclear Complexes with Rare Earth and Copper Ions: A Many-Body Model Study,"We have used a many-body model Hamiltonian to study the nature of the
magnetic ground state of hetero-binuclear complexes involving rare-earth and
copper ions. We have taken into account all diagonal repulsions involving the
rare-earth 4f and 5d orbitals and the copper 3d orbital. Besides, we have
included direct exchange interaction, crystal field splitting of the rare-earth
atomic levels and spin-orbit interaction in the 4f orbitals. We have identified
the inter-orbital $4f$ repulsion, U$_{ff}$ and crystal field parameter,
$\Delta_f$ as the key parameters involved in controlling the type of exchange
interaction between the rare earth $4f$ and copper 3d spins. We have explored
the nature of the ground state in the parameter space of U$_{ff}$, $\Delta_f$,
spin-orbit interaction strength $\lambda$ and the $4f$ filling n$_f$. We find
that these systems show low-spin or high-spin ground state depending on the
filling of the $4f$ levels of the rare-earth ion and ground state spin is
critically dependent on U$_{ff}$ and $\Delta_f$. In case of half-filling
(Gd(III)) we find a reentrant low-spin state as U$_{ff}$ is increased, for
small values of $\Delta_f$, which explains the recently reported apparent
anomalous anti-ferromagnetic behaviour of Gd(III)-radical complexes. By varying
U$_{ff}$ we also observe a switch over in the ground state spin for other
fillings . We have introduced a spin-orbit coupling scheme which goes beyond
L-S or j-j coupling scheme and we find that spin-orbit coupling does not
significantly alter the basic picture.",0112208v1
2012-03-06,Energy spectrum and Landau levels in bilayer graphene with spin-orbit interaction,"We present a theoretical study of the bandstructure and Landau levels in
bilayer graphene at low energies in the presence of a transverse magnetic field
and Rashba spin-orbit interaction in the regime of negligible trigonal
distortion. Within an effective low energy approach (L\""owdin partitioning
theory) we derive an effective Hamiltonian for bilayer graphene that
incorporates the influence of the Zeeman effect, the Rashba spin-orbit
interaction, and inclusively, the role of the intrinsic spin-orbit interaction
on the same footing. Particular attention is spent to the energy spectrum and
Landau levels. Our modeling unveil the strong influence of the Rashba coupling
$\lambda_R $ in the spin-splitting of the electron and hole bands. Graphene
bilayers with weak Rashba spin-orbit interaction show a spin-splitting linear
in momentum and proportional to $\lambda_R $, but scales inversely proportional
to the interlayer hopping energy $\gamma_1$. However, at robust spin-orbit
coupling $\lambda_R $ the energy spectrum shows a strong warping behavior near
the Dirac points. We find the bias-induced gap in bilayer graphene to be
decreasing with increasing Rashba coupling, a behavior resembling a topological
insulator transition. We further predict an unexpected assymetric
spin-splitting and crossings of the Landau levels due to the interplay between
the Rashba interaction and the external bias voltage. Our results are of
relevance for interpreting magnetotransport and infrared cyclotron resonance
measurements, including also situations of comparatively weak spin-orbit
coupling.",1203.1094v2
2013-01-22,Validity of single-channel model for a spin-orbit coupled atomic Fermi gas near Feshbach resonances,"We theoretically investigate a Rashba spin-orbit coupled Fermi gas near
Feshbach resonances, by using mean-field theory and a two-channel model that
takes into account explicitly Feshbach molecules in the close channel. In the
absence of spin-orbit coupling, when the channel coupling $g$ between the
closed and open channels is strong, it is widely accepted that the two-channel
model is equivalent to a single-channel model that excludes Feshbach molecules.
This is the so-called broad resonance limit, which is well-satisfied by
ultracold atomic Fermi gases of $^{6}$Li atoms and $^{40}$K atoms in current
experiments. Here, with Rashba spin-orbit coupling we find that the condition
for equivalence becomes much more stringent. As a result, the single-channel
model may already be insufficient to describe properly an atomic Fermi gas of
$^{40}$K atoms at a moderate spin-orbit coupling. We determine a characteristic
channel coupling strength $g_{c}$ as a function of the spin-orbit coupling
strength, above which the single-channel and two-channel models are
approximately equivalent. We also find that for narrow resonance with small
channel coupling, the pairing gap and molecular fraction is strongly suppressed
by SO coupling. Our results can be readily tested in $^{40}$K atoms by using
optical molecular spectroscopy.",1301.5071v1
2007-09-03,Enhancement of polarization in a spin-orbit coupling quantum wire with a constriction,"We investigate the enhancement of spin polarization in a quantum wire in the
presence of a constriction and a spin-orbit coupling segment. It is shown that
the spin-filtering effect is significantly heightened in comparison with the
configuration without the constriction. It is understood in the studies that
the constriction structure plays a critical role in enhancing the spin
filtering by means of confining the incident electrons to occupy one channel
only while the outgoing electrons occupy two channels. The enhancement of
spin-filtering has also been analyzed within the perturbation theory. Because
the spin polarization arises mainly from the scattering between the
constriction and the segment with spin-orbit coupling, the sub-band mixing
induced by spin-orbit interaction in the scattering process and the
interferences result in higher spin-filtering effect.",0709.0203v1
2009-09-13,Fluctuations of spin transport through chaotic quantum dots with spin-orbit coupling,"As devices to control spin currents using the spin-orbit interaction are
proposed and implemented, it is important to understand the fluctuations that
spin-orbit coupling can impose on transmission through a quantum dot. Using
random matrix theory, we estimate the typical scale of transmitted charge and
spin currents when a spin current is injected into a chaotic quantum dot with
strong spin-orbit coupling. These results have implications for the functioning
of the spin transistor proposed by Schliemann, Egues, and Loss. We use a
density matrix formalism appropriate for treating arbitrary input currents and
indicate its connections to the widely used spin-conductance picture. We
further consider the case of currents entangled between two leads, finding
larger fluctuations.",0909.2443v1
2012-07-27,Spin transition rates in nanowire superlattices: Rashba spin-orbit coupling effects,"We investigate the influence of Rashba spin-orbit coupling in a parabolic
nanowire modulated by longitudinal periodic potential. The modulation potential
can be obtained from realistically grown supperlattices (SLs). Our study shows
that the Rashba spin-orbit interaction induces the level crossing point in the
parabolic nanowire SLs. We estimate large anticrossing width (approximately 117
$\mu eV$) between singlet-triplet states. We study the phonon and
electromagnetic field mediated spin transition rates in the parabolic nanowire
SLs. We report that the phonon mediated spin transition rate is several order
of magnitude larger than the electromagnetic field mediated spin transition
rate. Based on the Feynman disentangling technique, we find the exact spin
transition probability. For the case wave vector $k=0$, we report that the
transition probability can be tuned in the form of resonance at fixed time
interval. For the general case ($k\neq 0$), we solve the Riccati equation and
find that the arbitrary values of $k$ induces the damping in the transition
probability. At large value of Rashba spin-orbit coupling coefficients for
($k\neq 0$), spin transition probability freezes.",1207.6580v2
2015-07-16,Strong Linear Dichroism in Spin-Polarized Photoemission from Spin-Orbit-Coupled Surface States,"A comprehensive understanding of spin-polarized photoemission is crucial for
accessing the electronic structure of spin-orbit coupled materials. Yet, the
impact of the final state in the photoemission process on the photoelectron
spin has been difficult to assess in these systems. We present experiments for
the spin-orbit split states in a Bi-Ag surface alloy showing that the
alteration of the final state with energy may cause a complete reversal of the
photoelectron spin polarization. We explain the effect on the basis of ab
initio one-step photoemission theory and describe how it originates from linear
dichroism in the angular distribution of photoelectrons. Our analysis shows
that the modulated photoelectron spin polarization reflects the intrinsic spin
density of the surface state being sampled differently depending on the final
state, and it indicates linear dichroism as a natural probe of spin-orbit
coupling at surfaces.",1507.04664v2
2015-03-23,Quantum spin Hall phase in multilayer graphene,"The so called quantum spin Hall phase is a topologically non trivial
insulating phase that is predicted to appear in graphene and graphene-like
systems. In this work we address the question of whether this topological
property persists in multilayered systems. We consider two situations: purely
multilayer graphene and heterostructures where graphene is encapsulated by
trivial insulators with a strong spin-orbit coupling. We use a four orbital
tight-binding model that includes the full atomic spin-orbit coupling and we
calculate the $Z_{2}$ topological invariant of the bulk states as well as the
edge states of semi-infinite crystals with armchair termination. For
homogeneous multilayers we find that even when the spin-orbit interaction opens
a gap for all the possible stackings, only those with odd number of layers host
gapless edge states while those with even number of layers are trivial
insulators. For the heterostructures where graphene is encapsulated by trivial
insulators, it turns out that the interlayer coupling is able to induce a
topological gap whose size is controlled by the spin-orbit coupling of the
encapsulating materials, indicating that the quantum spin Hall phase can be
induced by proximity to trivial insulators.",1503.06736v1
2016-02-04,Spin-orbit coupling measurement by the scanning gate microscopy,"We propose a procedure for extraction of the Fermi surface for a
two-dimensional electron gas with a strong Rashba spin-orbit coupling from
conductance microscopy. Due to the interplay between the effective spin-orbit
magnetic field and the external one within the plane of confinement, the
backscattering induced by a charged tip of an atomic force microscope located
above the sample, leads to the spin precession, and thus to the spin mixing of
the incident and reflected modes. This mixing leads to a characteristic
angle-dependent beating pattern visible in the conductance maps. We show that
the structure of the Fermi level, bearing signatures of the spin-orbit
coupling, can be extracted from the Fourier transform of the interference
fringes in the conductance maps as a function of the magnetic field direction.
We propose a simple analytical model which can be used to fit the experimental
data in order to obtain the spin-orbit coupling constant.",1602.01653v1
2014-05-22,Fragmentation of Spin-orbit Coupled Spinor Bose-Einstein Condensates,"The fragmentation of spin-orbit coupled spin-1 Bose gas with a weak
interaction in external harmonic trap is explored by both exact diagonalization
and mean-field theory. This fragmentation tendency, which originates from the
total angular momentum conservation, is affected obviously by the spin-orbit
coupling strength and the spin-dependent interaction. Strong spin-orbit
interaction raises the inverse participation ratio, which describes the number
of significantly occupied single-particle states. As the spin-dependent
interaction changes from anti-ferromagnetic to ferromagnetic, the peak values
in the inverse participation ratio become lower. Without the confinement of the
appointed total angular momentum, the condensate chooses a zero or finite total
angular momentum ground state, which is determined by both the interaction and
the spin-orbit coupling strength.",1405.5708v1
2006-06-19,Spin-Orbit Coupling and Tunneling Current in a Parabolic Quantum Dot,"We propose a novel approach to explore the properties of a quantum dot in the
presence of the spin-orbit interaction and in a tilted magnetic field. The
spin-orbit coupling within the quantum dot manifest itself as anti-crossing of
the energy levels when the tilt angle is varied. The anti-crossing gap has a
non-monotonic dependence on the magnitude of the magnetic field and exhibits a
peak at some finite values of the magnetic field. From the dependence of the
tunneling current through the quantum dot on the bias voltage and the tilt
angle, the anti-crossing gap and most importantly the spin-orbit strength can
be uniquely determined.",0606500v1
2007-02-16,Spin-orbit induced anisotropy in the tunneling magnetoresistance of magnetic tunnel junctions,"The effects of the spin-orbit interaction on the tunneling magnetoresistance
of magnetic tunnel junctions are investigated. A model in which the
experimentally observed two-fold symmetry of the anisotropic tunneling
magnetoresistance (TAMR) originates from the interference between Dresselhaus
and Bychkov-Rashba spin-orbit couplings is formulated. Bias induced changes of
the Bychkov-Rashba spin-orbit coupling strength can result in an inversion of
the TAMR. The theoretical calculations are in good agreement with the TAMR
experimentally observed in epitaxial Fe/GaAs/Au tunnel junctions.",0702387v2
2007-11-05,Magnetic excitations in vanadium spinels,"We study magnetic excitations in vanadium spinel oxides AV$_2$O$_4$ (A=Zn,
Mg, Cd) using two models: first one is a superexchange model for vanadium S=1
spins, second one includes in addition spin-orbit coupling, and crystal
anisotropy. We show that the experimentally observed magnetic ordering can be
obtained in both models, however the orbital ordering is different with and
without spin-orbit coupling and crystal anisotropy. We demonstrate that this
difference strongly affects the spin-wave excitation spectrum above the
magnetically ordered state, and argue that the neutron measurement of such
dispersion is a way to distinguish between the two possible orbital orderings
in AV$_2$O$_4$.",0711.0732v1
2008-03-26,Does Spin-Orbit Coupling Effect Favor Planar Structures for Small Platinum Clusters?,"We have performed full-relativistic density functional theory calculations to
study the geometry and binding energy of different isomers of free platinum
clusters Pt$_{n}$ ($n=4-6$) within the spin multiplicities from singlet to
nonet. The spin-orbit coupling effect has been discussed for the minimum-energy
structures, relative stabilities, vibrational frequencies, magnetic moments,
and the highest occupied and lowest unoccupied molecular-orbital gaps. It is
found in contrast to some of the previous calculations that 3-dimentional
configurations are still lowest energy structures of these clusters, although
spin-orbit effect makes some planar or quasi-planar geometries more stable than
some other 3-dimentional isomers.",0803.3694v1
2015-11-09,Spin-orbit interaction in the graphitic nanocone,"The Hamiltonian for nanocones with curvature induced spin orbit coupling have
been derived. The effect of curvature induced spin orbit coupling on the
electronic properties of graphitic nanocones is considered. Energy spectra for
different numbers of the pentagonal defects in the tip of the nanocones are
calculated. It was shown that the spin orbit interaction considerably affects
the local density of states of the graphitic nanocone. This influence depends
on the number of defects present at the tip of the nanocone. This property
could be applied in atomic force microscopy for the construction of the probing
tip.",1511.02765v1
2020-05-06,Angular momentum conservation in counter-propagating vectorially structured light,"It is well-known that electric spin angular momentum and electric orbital
angular momentum are conserved under paraxial propagation of travelling waves
in free-space. Here we study the electric and magnetic angular momentum in
counter-propagating waves and show both theoretically and experimentally that
neither component alone is conserved except in special cases. We attribute this
non-conservation to spin-spin and orbit-orbit coupling between the electric and
magnetic fields. This work generalises previous findings based on travelling
waves, explains the apparent spin-orbit coupling in counter-propagating
paraxial light, and broadens our understanding of angular momentum conservation
in arbitrary structured light waves.",2005.02739v1
2020-05-12,Magnetically-textured superconductivity in elemental Rhenium,"Recent $\mu$SR measurements revealed remarkable signatures of spontaneous
magnetism coexisting with superconductivity in elemental rhenium. Here we
provide a quantitative theory that uncovers the nature of the superconducting
instability by incorporating every details of the electronic structure together
with spin-orbit coupling and multi-orbital physics. We show that conventional
$s$-wave superconductivity combined with strong spin-orbit coupling is inducing
even-parity odd-orbital spin triplet Cooper pairs, and in presence of a screw
axis Cooper pairs' migration between the induced equal-spin triplet component
leads to an exotic magnetic state.",2005.05702v2
2012-02-09,Spin-orbit coupling induced fractionalized Skyrmion excitations in rotating and rapidly quenched spin-1 Bose-Einstein condensates,"We investigate the fractionalized Skyrmion excitations induced by spin-orbit
coupling in rotating and rapidly quenched spin-1 Bose-Einstein condensates. Our
results show that the fractionalized Skyrmion excitation depends on the
combination of spin-orbit coupling and rotation, and it originates from a
dipole structure of spin which is always embedded in three vortices constructed
by each condensate component respectively. When spin-orbit coupling is larger
than a critical value, the fractionalized Skyrmions encircle the center with
one or several circles to form a radial lattice, which occurs even in the
strong ferromagnetic/antiferromagnetic condensates. We can use both the
spin-orbit coupling and the rotation to adjust the radial lattice. The
realization and the detection of the fractionalized Skyrmions are compatible
with current experimental technology.",1202.1911v3
2010-07-20,RKKY interaction in a disordered two-dimensional electron gas with Rashba and Dresselhaus spin-orbit couplings,"We study theoretically the statistical properties of the
Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between localized magnetic
moments in a disordered two-dimensional electron gas with both Rashba and
Dresselhaus spin-orbit couplings. Averaging over disorder, the static spin
susceptibility tensor is evaluated diagrammatically in the mesoscopic
(phase-coherent) regime. The disorder-averaged susceptibility leads to a
twisted exchange interaction suppressed exponentially with distance, whereas
the second-order correlations, which determine the fluctuations (variance) of
the RKKY energy, decay with the same power-law as in the clean case. We obtain
analytic expressions in the limits of large/small spin orbit interactions and
for equal Rashba and Dresselhaus couplings. Beside these limiting cases, we
study numerically the variance of the RKKY interaction in the presence of pure
Rashba spin-orbit coupling. Our results are relevant for magnetic impurities or
nuclear moments embedded in III-V two-dimensional heterostructures or in
contact with surface states of metals and metal alloys, which can display a
sizable Rashba spin-orbit coupling.",1007.3506v2
2012-11-29,Topological transport in a spin-orbit coupled bosonic Mott insulator,"We investigate topological transport in a spin-orbit coupled bosonic Mott
insulator. We show that interactions can lead to anomalous quasi-particle
dynamics even when the spin-orbit coupling is abelian. To illustrate the
latter, we consider the spin-orbit coupling realized in the experiment of Lin
\textit{et al}. [Nature (London) \textbf{471}, 83 (2011)]. For this spin-orbit
coupling, we compute the quasiparticle dispersions and spectral weights, the
interaction-induced momentum space Berry curvature, and the momentum space
distribution of spin density, and propose experimental signatures. Furthermore,
we find that in our approximation for the single-particle propagator, the
ground state can in principle support an integer Hall conductivity if the sum
of the Chern numbers of the hole bands is nonzero.",1211.6924v2
2012-12-03,Collective modes of spin-orbit coupled Fermi gases in the repulsive regime,"We investigate the collective modes in the spin-orbit coupled Fermi gas with
repulsive s-wave interaction. The interplay between spin-orbit coupling and
atom-atom interactions plays the crucial role in the collective behaviors of
Fermi gas. In contrast with ordinary Fermi liquid, spin-orbit coupled Fermi gas
has strongly correlated spin and density excitations. Within the scheme of
random phase approximation, we classify collective modes based on the symmetry
group and determine their properties via the poles of corresponding correlation
functions. Besides, the particle-hole continuum is obtained, where the
imaginary part of these correlation functions become non-vanishing. We make
comparisons with collective excitations in the ordinary Fermi liquid without
spin-orbit coupling and in a helical liquid, i.e., surface states of a three
dimensional topological insulator. We also propose an experimental protocol for
detecting these collective modes and discuss corresponding experimental
signatures in the ultracold Fermi gases experiment.",1212.0424v3
2013-04-14,FFLO or Majorana superfluids: The fate of fermionic cold atoms in spin-orbit coupled optical lattices,"The recent experimental realization of spin-orbit coupling (SOC) for
ultra-cold atoms opens a completely new avenue for exploring new quantum
matter. In experiments, the SOC is implemented simultaneously with a Zeeman
field. Such spin-orbit coupled Fermi gases are predicted to support Majorana
fermions with non-Abelian exchange statistics in one dimension (1D). However,
as shown in recent theory and experiments for 1D spin-imbalanced Fermi gases,
the Zeeman field can lead to the long-sought Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) superfluids with non-zero momentum Cooper pairings, in contrast to the
zero momentum pairing in Majorana superfluids. Therefore a natural question to
ask is which phase, FFLO or Majorana superfluids, will survive in spin-orbit
coupled Fermi gases in the presence of a large Zeeman field. In this paper, we
address this question by studying the mean field quantum phases of 1D
(quasi-1D) spin-orbit coupled fermionic cold atom optical lattices.",1304.3926v2
2014-02-26,Superconductivity in a two-dimensional superconductor with Rashba and Dresselhaus spin-orbit couplings,"We present a general model with both Rashba and Dresselhaus spin-orbit
couplings to describe a two-dimensional noncentrosymmetric superconductor. The
combined effects of the two spin-orbit couplings on superconductivity are
investigated in the framework of mean-field theory. We find that the Rashba and
Dresselhaus spin-orbit couplings result in similar effects on superconductivity
if they are present solely in the system. Mixing of spin-singlet and triplet
pairings in electron band is induced under the assumption that each
quasiparticle band is p-wave paired. If the two types of spin-orbit couplings
appear jointly, both the singlet and triplet pairings are weakened and
decreased down to their minimum values in the equal-Rashba-Dresselhaus case.",1402.6483v1
2014-09-20,Interference of spin-orbit coupled Bose-Einstein condensates,"Interference of atomic Bose-Einstein condensates, observed in free expansion
experiments, is a basic characteristic of their quantum nature. The ability to
produce synthetic spin-orbit coupling in Bose-Einstein condensates has recently
opened a new research field. Here we theoretically describe interference of two
noninteracting spin-orbit coupled Bose-Einstein condensates in an external
synthetic magnetic field. We demonstrate that the spin-orbit and the Zeeman
couplings strongly influence the interference pattern determined by the angle
between the spins of the condensates, as can be seen in time-of-flight
experiments. We show that a quantum backflow, being a subtle feature of the
interference, is, nevertheless, robust against the spin-orbit coupling and
applied synthetic magnetic field.",1409.5889v1
2014-10-07,Pairing Superfluidity in Spin-Orbit Coupled Ultracold Fermi Gases,"We review some recent progresses on the study of ultracold Fermi gases with
synthetic spin-orbit coupling. In particular, we focus on the pairing
superfluidity in these systems at zero temperature. Recent studies have shown
that different forms of spin-orbit coupling in various spatial dimensions can
lead to a wealth of novel pairing superfluidity. A common theme of these
variations is the emergence of new pairing mechanisms which are direct results
of spin-orbit-coupling-modified single-particle dispersion spectra. As
different configurations can give rise to single-particle dispersion spectra
with drastic differences in symmetry, spin dependence and low-energy density of
states, spin-orbit coupling is potentially a powerful tool of quantum control,
which, when combined with other available control schemes in ultracold atomic
gases, will enable us to engineer novel states of matter.",1410.1595v1
2012-05-03,Current-induced torques in textured Rashba ferromagnets,"In systems with small spin-orbit coupling, current-induced torques on the
magnetization require inhomogeneous magnetization textures. For large
spin-orbit coupling, such torques exist even without gradients in the
magnetization direction. Here, we consider current-induced torques in
ferromagnetic metals with both Rashba spin-orbit coupling and inhomogeneous
magnetization. We first phenomenologically construct all torques that are
allowed by the symmetries of the system, to first order in
magnetization-direction gradients and electric field. Second, we use a
Boltzmann approach to calculate the spin torques that arise to second order in
the spin-orbit coupling. We apply our results to current-driven domain walls
and find that the domain-wall mobility is strongly affected by torques that
result from the interplay between spin-orbit coupling and inhomogeneity of the
magnetization texture.",1205.0653v1
2020-05-16,Spin-orbit-parity coupled superconductivity in topological monolayer WTe$_2$,"Recent experiments reported gate-induced superconductivity in the monolayer
1T$'$-WTe$_2$ which is a two-dimensional topological insulator in its normal
state [1, 2]. The in-plane upper critical field $B_{c2}$ is found to exceed the
conventional Pauli paramagnetic limit $B_p$ by 1-3 times. The enhancement
cannot be explained by conventional spin-orbit coupling which vanishes due to
inversion symmetry. In this work, we unveil some distinctive superconducting
properties of centrosymmetric 1T$'$-WTe$_2$ which arise from the coupling of
spin, momentum and band parity degrees of freedom. As a result of this
spin-orbit-parity coupling: (i) there is a first-order superconductor-metal
transition at $B_{c2}$ much higher than the Pauli paramagnetic limit $B_p$,
(ii) spin-susceptibility is anisotropic with respect to in-plane directions and
results in anisotropic $B_{c2}$ and (iii) the $B_{c2}$ exhibits a strong gate
dependence as the spin-orbit-parity coupling is significant only near the
topological band crossing points. The importance of SOPC on the topologically
nontrivial inter-orbital pairing phase is also discussed. Our theory generally
applies to centrosymmetric materials with topological band inversions.",2005.08007v2
2020-10-19,Ultrafast dynamics in relativistic Mott insulators,"We study the photoinduced ultrafast dynamics in relativistic Mott insulators,
i.e., Mott insulators with strong spin-orbit coupling. For this purpose, we
consider a minimal one-band Hubbard model on lattices with square and
triangular symmetries, as relevant for layered transition metal compounds such
as Sr$_2$IrO$_4$. Depending on the lattice and the spin-orbit coupling, the
systems have canted antiferromagnetic or $120^\circ$ order. They are excited by
simulating a short laser pulse, and the dynamics is solved using nonequilibrium
dynamical mean-field theory. The pulse generates hot carriers, which
subsequently perturb the magnetic order due to the coupling between the
collective order and photocarriers. We find that this dynamics, which is known
form regular antiferromagnets, depends sensitively on the spatial structure of
the spin-orbit coupling. On the triangular lattice, in particular, relaxation
times are influenced by the spin-orbit coupling for the chiral $120^\circ$
order, while on the square lattice with canted antiferromagnetic order the
spin-orbit induced canting angle remains unchanged after the excitation. Our
study opens up new possibilities of controlling magnetism and exotic spin
states on the ultrafast timescales.",2010.09253v1
2019-04-26,Effects of Interface Steps on the Valley Orbit coupling in a Si/SiGe quantum dot,"Valley-orbit coupling is a key parameter for a silicon quantum dot in
determining its suitability for applications in quantum information processing.
In this paper we study the effect of interface steps on the magnitude and phase
of valley-orbit coupling for an electron in a silicon quantum dot. Within the
effective mass approximation, we find that the location of a step on the
interface is important in determining both the magnitude and the phase of the
valley-orbit coupling in a Si/SiGe quantum dot. Specifically, our numerical
results show that the magnitude of valley orbit coupling can be suppressed up
to 75\% by a step of one atomic monolayer, and its phase can change by almost
$\pi$. When two steps are present, the minimum value of the valley-orbit
coupling can even approach zero. We also clarify the effects of an applied
external magnetic field and the higher orbital states on the valley-orbit
coupling. Overall, our results illustrate how interface roughness affect the
valley-orbit coupling in silicon, and how spin qubits in silicon may be
affected.",1904.11944v1
2020-10-08,Spin-orbit coupling induced splitting of Yu-Shiba-Rusinov states in antiferromagnetic dimers,"Magnetic atoms coupled to the Cooper pairs of a superconductor induce
Yu-Shiba-Rusinov states (in short Shiba states). In the presence of
sufficiently strong spin-orbit coupling, the bands formed by hybridization of
the Shiba states in ensembles of such atoms can support low-dimensional
topological superconductivity with Majorana bound states localized on the
ensembles' edges. Yet, the role of spin-orbit coupling for the hybridization of
Shiba states in dimers of magnetic atoms, the building blocks for such systems,
is largely unexplored. Here, we reveal the evolution of hybridized
multi-orbital Shiba states from a single Mn adatom to artificially constructed
ferromagnetically and antiferromagnetically coupled Mn dimers placed on a
Nb(110) surface. Upon dimer formation, the atomic Shiba orbitals split for both
types of magnetic alignment. Our theoretical calculations attribute the
unexpected splitting in antiferromagnetic dimers to spin-orbit coupling and
broken inversion symmetry at the surface. Our observations point out the
relevance of previously unconsidered factors on the formation of Shiba bands
and their topological classification.",2010.04031v1
2004-03-29,"Ground state, electronic structure and magnetism of LaMnO3","We have calculated the discrete low-energy electronic structure in LaMnO3
originating from the atomic-like states of the strongly correlated 3d4
electronic system occurring in the Mn3+ ion. We take into account very strong
intra-atomic correlations, crystal field interactions and the intra-atomic
spin-orbit coupling. We calculated magnetic and paramagnetic state of LaMnO3
within the consistent description given by Quantum Atomistic Solid State Theory
(QUASST). Our studies indicate that the intra-atomic spin-orbit coupling and
the orbital magnetism are indispensable for the physically adequate description
of electronic and magnetic properties of LaMnO3.
  Keywords: 3d oxides, crystal field, spin-orbit coupling, LaMnO3
  PACS: 71.70Ej, 75.10Dg",0403714v1
2007-01-18,Cooperative Effect of Electron Correlation and Spin-Orbit Coupling on the Electronic and Magnetic Properties of Ba2NaOsO6,"The electronic and magnetic properties of the cubic double perovskite
Ba2NaOsO6 were examined by performing first-principles density functional
theory calculations and analyzing spin-orbit coupled states of an Os7+ (d1) ion
at an octahedral crystal field. The insulating behavior of Ba2NaOsO6 was shown
to originate from a cooperative effect of electron correlation and spin-orbit
coupling. This cooperative effect is responsible not only for the absence of
orbital ordering in Ba2 NaOsO6 but also for a small magnetic moment and a weak
magnetic anisotropy in Ba2NaOsO6.",0701460v1
2015-07-21,Cooperative effects of lattice and spin-orbit coupling on the electronic structure of orthorhombic SrIrO3,"Orthorhombic SrIrO3 subjected to strain show tunable transport properties.
With underlying symmetry remaining invariant, these properties are associated
with IrO6 octahedral tilting. Adopting to first-principles methods, the effects
of crystal field, spin-orbit coupling, and Coulomb correlations, on comparable
interaction length scales, are discussed. While tilting induces a t2g-eg
crystal-field splitting and band narrowing, spin-orbit coupling induces a
partial splitting of the Jeff bands rendering SrIrO3 a semi-metallic ground
state. The SOC enhanced hybridization of Ir-O orbitals, serve as a explanation
to why the critical Hubbard correlation strength increases with increasing SOC
strength in SrIrO3 to induce an insulating phase.",1507.05704v1
2023-05-21,Spin-orbit torque on nuclear spins exerted by a spin accumulation via hyperfine interactions,"Spin-transfer and spin-orbit torques allow controlling magnetic degrees of
freedom in various materials and devices. However, while the transfer of
angular momenta between electrons has been widely studied, the contribution of
nuclear spins has yet to be explored further. This article demonstrates that
the hyperfine coupling, which consists of Fermi contact and dipolar
interactions, can mediate the application of spin-orbit torques acting on
nuclear spins. Our starting point is a sizable nuclear spin in a metal with
electronic spin accumulation. Then, via the hyperfine interactions, the nuclear
spin modifies the an electronic spin density. The reactions to the equilibrium
and nonequilibrium components of the spin density is a torque on the nucleus
with field-like and damping-like components, respectively. This nuclear
spin-orbit torque is a step toward stabilizing and controlling nuclear magnetic
momenta, in magnitude and direction, and realizing nuclear spintronics.",2305.12390v2
2022-12-16,Transverse currents in spin transistors,"In many systems, planar Hall effect wherein transverse signal appears in
response to longitudinal stimulus is rooted in spin-orbit coupling. A spin
transistor put forward by Datta and Das on the other hand consists of
ferromagnetic leads connected to spin-orbit coupled central region and its
conductance can be controlled by tuning the strength of spin-orbit coupling. We
find that transverse currents also appear in Datta-Das transistors made by
connecting two two-dimensional ferromagnetic reservoirs to a central spin-orbit
coupled two-dimensional electron gas. We find that the spin transistor exhibits
a nonzero transverse conductivity which depends on the direction of
polarization in ferromagnets and the location where it is measured. We study
the conductivities for the system with finite and infinite widths. The
conductivities exhibit Fabry-P\'erot type oscillations as the length of the
spin-orbit coupled regions is varied. Interestingly, even in the limit when
longitudinal conductivity is made zero by cutting off the junction between the
central spin-orbit coupled region and the ferromagnetic lead on one side
(right), the transverse conductivities remain nonzero in the regions that are
on the left side of the cut-off junction.",2212.08301v4
2020-04-02,Tunable and Enhanced Rashba Spin-Orbit Coupling in Iridate-Manganite Heterostructures,"Tailoring spin-orbit interactions and Coulomb repulsion are the key features
to observe exotic physical phenomena such as magnetic anisotropy and
topological spin texture at oxide interfaces. Our study proposes a novel
platform for engineering the magnetism and spin-orbit coupling at LaMnO3/SrIrO3
(3d-5d oxide) interfaces by tuning the LaMnO3 growth conditions which controls
the lattice displacement and spin-correlated interfacial coupling through
charge transfer. We report on a tunable and enhanced interface-induced Rashba
spin-orbit coupling and Elliot-Yafet spin relaxation mechanism in LaMnO3/SrIrO3
bilayer with change in the underlying magnetic order of LaMnO3. We also
observed enhanced spin-orbit coupling strength in LaMnO3/SrIrO3 compared to
previously reported SrIrO3 layers. The X-Ray spectroscopy measurement reveals
the quantitative valence of Mn and their impact on charge transfer. Further, we
performed angle-dependent magnetoresistance measurements, which show signatures
of magnetic proximity effect in SrIrO3 while reflecting the magnetic order of
LaMnO3. Our work thus demonstrates a new route to engineer the interface
induced Rashba spin-orbit coupling and magnetic proximity effect in 3d-5d oxide
interfaces which makes SrIrO3 an ideal candidate for spintronics applications.",2004.00800v1
2021-06-30,Higher angular momentum pairings in interorbital shadowed-triplet superconductors: Application to Sr$_{2}$RuO$_{4}$,"Even-parity interorbital spin-triplet pairing emerges as an intriguing
candidate in multiorbital superconductors with significant Hund's and
spin-orbit coupling. Within such a state, the pairing is dominated by the
intraband pseudospin-singlet component via the spin-orbit coupling,
distinguishing it from a pure spin triplet and motivating the name, shadowed
triplet. With atomic spin-orbit coupling, it was shown that this pairing
exhibits an anisotropic $s$-wave character, while higher angular momentum
pairing symmetries such as $d$- or $g$-wave have been proposed based on
phenomenological analyses in candidate systems. A natural question is then
whether higher angular momentum pairings may arise with this form of
spin-triplet pairing. Here, we examine the interplay between spin-orbit
coupling and the electronic dispersions in correlated metals and demonstrate
how they can be realized. We apply this idea to Sr$_{2}$RuO$_{4}$ and determine
the competition among different pairing states as multiple spin-orbit coupling
parameters are tuned. The presence of both $d$- and $g$-wave pairings,
including a $d+ig$ state, are found when momentum-dependent spin-orbit coupling
with $d$-wave character is increased. Implications of the theory and future
directions are also discussed.",2107.00047v2
2011-12-14,Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides,"We show that inversion symmetry breaking together with spin-orbit coupling
leads to coupled spin and valley physics in monolayers of MoS2 and other
group-VI dichalcogenides, making possible controls of spin and valley in these
2D materials. The spin-valley coupling at the valence band edges suppresses
spin and valley relaxation, as flip of each index alone is forbidden by the
valley contrasting spin splitting. Valley Hall and spin Hall effects coexist in
both electron-doped and hole-doped systems. Optical interband transitions have
frequency-dependent polarization selection rules which allow selective
photoexcitation of carriers with various combination of valley and spin
indices. Photo-induced spin Hall and valley Hall effects can generate long
lived spin and valley accumulations on sample boundaries. The physics discussed
here provides a route towards the integration of valleytronics and spintronics
in multi-valley materials with strong spin-orbit coupling and inversion
symmetry breaking.",1112.3144v3
2012-11-26,Coupled Spin-Orbital Texture in a Prototypical Topological Insulator,"One of the most important properties of topological insulators (TIs) is the
helical spin texture of the Dirac surface states, which has been theoretically
and experimentally argued to be left-handed helical above the Dirac point and
right handed helical below. However, since the spin is not a good quantum
number in these strongly spin-orbit coupled systems, this can not be a complete
statement, and we must consider the total angular momentum J = L + S that is a
contribution of the spin and orbital terms. Using a combination of orbital and
spin-resolved angle-resolved photoemission spectroscopy (ARPES), we show a
direct link between the different orbital and spin components, with a
""backwards"" spin texture directly observed for the in-plane orbital states of
Bi2Se3.",1211.5998v1
2005-03-11,Ferromagnetic fluctuation and superconductivity in Na_0.35CoO_2*1.3H_2O: FLEX study of multi-orbital Hubbard model,"Spin and charge fluctuations and superconductivity in Na_0.35CoO_2*1.3H_2O
are studied based on a multi-orbital Hubbard model. By applying the fluctuation
exchange (FLEX) approximation, we show that the Hund's-rule coupling between
the Co t2g orbitals causes ferromagnetic spin fluctuation. Triplet pairing is
favored by this ferromagnetic fluctuation on the hole-pocket band. We propose
that, in Na_0.35CoO_2*1.3H_2O, Co t2g orbitals and inter-orbital Hund's-rule
coupling play important roles on the triplet pairing, and this compound can be
a first example of the triplet superconductor mediated by
inter-orbital-interaction-induced ferromagnetic fluctuation.",0503262v1
2016-06-02,"First-principles studies of orbital and spin-orbit properties of GaAs, GaSb, InAs, and InSb zinc-blende and wurtzite semiconductors","We employ first-principles techniques tailored to properly describe
semiconductors (modified Becke-Johnson potential added to the
exchange-correlation functional), to obtain the electronic band structures of
both the zinc-blende and wurtzite phases of GaAs, GaSb, InAs, and InSb. We
extract the spin-orbit fields for the relevant valence and conduction bands at
zone center, by fitting the spin-splittings resulting from the lack of space
inversion symmetry of these bulk crystal structures, to known functional
forms---third-order polynomials. We also determine the orientations of the
spin-orbit vector fields (for conduction bands) and the average spins (valence
bands) in the momentum space. We describe the dependence of the spin-orbit
parameters on the cation and anion atomic weights. These results should be
useful for spin transport, spin relaxation, and spin optical orientation
modeling of semiconductor heterostructures, as well as for realistic studies of
semiconductor-based Majorana nanowires, for which accurate values of spin-orbit
couplings are needed.",1606.00588v1
2016-05-10,A long-lived spin-orbit-coupled degenerate dipolar Fermi gas,"We describe the creation of a long-lived spin-orbit-coupled gas of quantum
degenerate atoms using the most magnetic fermionic element, dysprosium.
Spin-orbit-coupling arises from a synthetic gauge field created by the
adiabatic following of degenerate dressed states comprised of optically coupled
components of an atomic spin. Because of dysprosium's large electronic orbital
angular momentum and large magnetic moment, the lifetime of the gas is limited
not by spontaneous emission from the light-matter coupling, as for gases of
alkali-metal atoms, but by dipolar relaxation of the spin. This relaxation is
suppressed at large magnetic fields due to Fermi statistics. We observe
lifetimes up to 400 ms, which exceeds that of spin-orbit-coupled fermionic
alkali atoms by a factor of 10-100, and is close to the value obtained from a
theoretical model. Elastic dipolar interactions are also observed to influence
the Rabi evolution of the spin, revealing an interacting fermionic system. The
long lifetime of this weakly interacting spin-orbit-coupled degenerate Fermi
gas will facilitate the study of quantum many-body phenomena manifest at longer
timescales, with exciting implications for the exploration of exotic
topological quantum liquids.",1605.03211v2
2013-02-22,Controlling hole spins in quantum dots and wells,"We review recent theoretical results for hole spins influenced by spin-orbit
coupling and Coulomb interaction in two-dimensional quantum wells as well as
the decoherence of single hole spins in quantum dots due to hyperfine
interaction with surrounding nuclear spins. After reviewing the different forms
of spin-orbit coupling that are relevant for electrons and heavy holes in III-V
semiconductor quantum wells, we illustrate the combined effect of spin-orbit
coupling and Coulomb interactions for hole systems on spin-dependent
quasiparticle group velocities. We further analyze spin-echo decay for a single
hole spin in a nuclear-spin bath, demonstrating that this decoherence source
can be controlled in these systems by entering a motional-averaging regime.
Throughout this review, we emphasize physical effects that are unique to hole
spins (rather than electrons) in nanoscale systems.",1302.5470v2
2009-10-06,Diffusive and precessional spin dynamics in a two-dimensional electron gas with disorder: a gauge theory view,"We develop a gauge theory for diffusive and precessional spin dynamics in
two-dimensional electron gas with disorder. Our approach reveals a direct
connections between the absence of the equilibrium spin current and strong
anisotropy in the spin relaxation: both effects arise if the spin-orbit
coupling is reduced to a pure gauge SU(2) field. In this case, by a gauge
transformation in the form of a local SU(2) rotation in the spin subspace the
spin-orbit coupling can be removed. The resulting spin dynamics is exactly
described in terms of two kinetic coefficients: the spin diffusion and electron
mobility. After the inverse transformation, full diffusive and precessional
spin density dynamics, including the anisotropic spin relaxation, formation of
stable spin structures, and spin precession induced by a macroscopic current,
is restored. Explicit solutions of the spin evolution equations are found for
the initially uniform spin density and for stable nonuniform structures. Our
analysis demonstrates a universal relation between the spin relaxation rate and
spin diffusion coefficient.",0910.0951v2
2009-04-17,Spin Relaxation in Isotopically Purified Silicon Quantum Dots,"We investigate spin-flip processes of Si quantum dots due to spin-orbit
coupling. We utilize the spin-orbit coupling constants related to bulk and
structure inversion asymmetry obtained numerically for two dimensional
heterostructures. We find that the spin-flip rate is very sensitive to these
coupling constants. We investigate the nuclei-mediated spin-flip process and
find the level of the isotope $^{29}$Si concentration for which this mechanism
become dominant.",0904.2592v1
2015-12-16,Spin orbit coupling at the level of a single electron,"We utilize electron counting techniques to distinguish a spin conserving fast
tunneling process and a slower process involving spin flips in
AlGaAs/GaAs-based double quantum dots. By studying the dependence of the rates
on the interdot tunnel coupling of the two dots, we find that as many as 4% of
the tunneling events occur with a spin flip related to spin-orbit coupling in
GaAs. Our measurement has a fidelity of 99 % in terms of resolving whether a
tunneling event occurred with a spin flip or not.",1512.05149v1
2014-07-08,Spin Orbit Coupling in Periodically Driven Optical Lattices,"We propose a method for the emulation of artificial spin orbit coupling in a
system of ultracold, neutral atoms trapped in a tight-binding lattice. This
scheme does not involve near-resonant laser fields, avoiding the heating
processes connected to the spontaneous emission of photons. In our case, the
necessary spin dependent tunnel matrix elements are generated by a rapid, spin
dependent, periodic force, which can be described in the framework of an
effective, time averaged Hamiltonian. An additional radio frequency coupling
between the spin states leads to a mixing of the spin bands.",1407.1953v2
2008-06-10,"Spin-orbit effects in Na$_4$Ir$_3$O$_8$, a hyper-kagomé lattice antiferromagnet","We consider spin-orbit coupling effects in Na$_4$Ir$_3$O$_8$, a material in
which Ir$^{4+}$ spins form an hyper-kagom\'{e} lattice, a three-dimensional
network of corner-sharing triangles. We argue that both low temperature
thermodynamic measurements and the impurity susceptibility induced by dilute
substitution of Ti for Ir are suggestive of significant spin-orbit effects.
Because of uncertainties in the crystal-field parameters, we consider two
limits in which the spin-orbit coupling is either weak or strong compared to
the non-cubic atomic splittings. A semi-microscopic calculation of the exchange
Hamiltonian confirms that indeed large antisymmetric Dzyaloshinskii-Moriya (DM)
and/or symmetric exchange anisotropy may be present. In the strong spin-orbit
limit, the Ir-O-Ir superexchange contribution consists of unfrustrated strong
symmetric exchange anisotropy, and we suggest that spin-liquid behavior is
unlikely. In the weak spin-orbit limit, and for strong spin-orbit and direct
Ir-Ir exchange, the Hamiltonian consists of Heisenberg and DM interactions. The
DM coupling is parametrized by a three component DM vector (which must be
determined empirically). For a range of orientation of this vector, frustration
is relieved and an ordered state occurs. For other orientations, even the
classical ground states are very complex. We perform spin-wave and exact
diagonalization calculations which suggest the persistence of a quantum spin
liquid in the latter regime. Applications to Na$_4$Ir$_3$O$_8$ and broader
implications are discussed.",0806.1573v3
2010-10-23,Robust to impurity-scattering spin Hall effect in two-dimensional electron gas,"We propose a mechanism of spin Hall effect in two-dimensional electron gas
with spatially random Rashba spin-orbit interaction. The calculations based on
the Kubo formalism and kinetic equation show that in contrast to the constant
spin-orbit coupling, spin Hall conductivity in the random spin-orbit field is
not totally suppressed by the potential impurity scattering. Even if the
regular contribution is removed by the vertex corrections, the terms we
consider, remain. Therefore, the intrinsic spin-Hall effect exists being,
however, non-universal.",1010.4900v1
2010-12-22,Non-adiabatic generation of a pure spin current in a 1D quantum ring with spin-orbit interaction,"We demonstrate the theoretical possibility of obtaining a pure spin current
in a 1D ring with spin-orbit interaction by irradiation with a non-adiabatic,
two-component terahertz laser pulse, whose spatial asymmetry is reflected by an
internal dephasing angle $\phi$. The stationary solutions of the equation of
motion for the density operator are obtained for a spin-orbit coupling linear
in the electron momentum (Rashba) and used to calculate the time-dependent
charge and spin currents. We find that there are critical values of $\phi$ at
which the charge current disappears, while the spin current reaches a maximum
or a minimum value.",1012.4952v1
2016-11-29,Spin-sensitive atom mirror via spin-orbit interaction,"Based on the spin-orbit coupling recently implemented in a neutral cold-atom
gas, we propose a scheme to realize spin-dependent scattering of cold atoms. In
particular we consider a matter wave packet of cold-atom gas impinging upon a
step potential created by the optical light field, inside of which the atoms
are subject to spin-orbit interaction. We show that the proposed system can act
as a spin polarizer or spin-selective atom mirror for the incident atomic beam.
The principle and the operating parameter regime of the system are carefully
discussed.",1611.09617v1
2014-01-29,Josephson physics of spin-orbit coupled elongated Bose-Einstein condensates,"We consider an ultracold bosonic binary mixture confined in a one-dimensional
double-well trap. The two bosonic components are assumed to be two hyperfine
internal states of the same atom. We suppose that these two components are
spin-orbit coupled between each other. We employ the two-mode approximation
starting from two coupled Gross-Pitaevskii equations and derive a system of
ordinary differential equations governing the temporal evolution of the
inter-well population imbalance of each component and that between the two
bosonic species. We study the Josephson oscillations of these spin-orbit
coupled Bose-Einstein condensates by analyzing the interplay between the
interatomic interactions and the spin-orbit coupling and the self-trapped
dynamics of the inter-species imbalance. We show that the dynamics of this
latter variable is crucially determined by the relationship between the
spin-orbit coupling, the tunneling energy, and the interactions.",1401.7693v1
2012-02-07,BCS-BEC crossover in three-dimensional Fermi gases with spherical spin-orbit coupling,"We present a systematic theoretical study of the BCS-BEC crossover problem in
three-dimensional atomic Fermi gases at zero temperature with a spherical
spin-orbit coupling which can be generated by a synthetic non-Abelian gauge
field coupled to neutral fermions. Our investigations are based on the path
integral formalism which is a powerful theoretical scheme for the study of the
properties of the bound state, the superfluid ground state, and the collective
excitations in the BCS-BEC crossover. At large spin-orbit coupling, the system
enters the BEC state of a novel type of bound state (referred to as rashbon)
which possesses a non-trivial effective mass. Analytical results and
interesting universal behaviors for various physical quantities at large
spin-orbit coupling are obtained. Our theoretical predictions can be tested in
future experiments of cold Fermi gases with three-dimensional spherical
spin-orbit coupling.",1202.1492v3
2012-10-22,Fate of a Bose-Einstein Condensate in the Presence of Spin-Orbit Coupling,"Intensive theoretical studies have recently predicted that a Bose-Einstein
condensate will exhibit a variety of novel properties if spin-orbit coupling is
present. However, an unambiguous fact has also been pointed out: Rashba
coupling destroys a condensate of noninteracting bosons even in high
dimensions. Therefore, a conceptually important question arises as to whether
or not a condensate exists in the presence of interaction and a general type of
spin-orbit coupling. Here we show that interaction qualitatively changes the
ground state of bosons under Rashba spin-orbit coupling. Any infinitesimal
repulsion forces bosons either to condense at one or two momentum states or to
form a superfragmented state that is a superposition of infinite numbers of
fragmented condensates. The superfragmented state is unstable against the
anisotropy of spin-orbit coupling in systems with large numbers of particles,
leading to the revival of a condensate in current experiments.",1210.5853v2
2021-06-04,Spin-orbit coupling effects over thermoelectric transport properties in quantum dots,"We study the effects caused by Rashba and Dresselhaus spin-orbit coupling
over the thermoelectric transport properties of a single-electron transistor,
viz., a quantum dot connected to one-dimensional leads. Using linear response
theory and employing the numerical renormalization group method, we calculate
the thermopower, electrical and thermal conductances, dimensionless
thermoelectric figure of merit, and study the Wiedemann-Franz law, showing
their temperature maps. Our results for all those properties indicate that
spin-orbit coupling drives the system into the Kondo regime. We show that the
thermoelectric transport properties, in the presence of spin-orbit coupling,
obey the expected universality of the Kondo strong coupling fixed point. In
addition, our results show a notable increase in the thermoelectric figure of
merit, caused by the spin-orbit coupling in the one-dimensional quantum dot
leads.",2106.02184v1
2022-01-21,Superconductivity in Correlated Multi-Orbital Systems with Spin-Orbit Coupling: Coexistence of Even- and Odd-Frequency Pairing and the Case of Strontium Ruthenate,"The superconducting order parameter of strontium ruthenate is the center of a
lasting puzzle calling for theoretical studies that include the
seldom-considered effects of spin-orbit coupling and the frequency-dependence
of the order parameters. Here we generalize the frequency-dependent theory of
superconductivity mediated by spin and charge fluctuations to include
spin-orbit coupling in multi-orbital systems and we characterize the
superconducting states using the spin-parity-orbital-time $SPOT$ quantum
numbers, group theory, and phase distributions in the complex plane. We derive
a pseudospin formulation that maps the inter-pseudospin sector of the normal
state Eliashberg equation to a pseudospin-diagonal one. Possible
superconducting order parameters for strontium ruthenate are obtained starting
from a realistic density-functional-theory normal state. We find that
spin-orbit coupling leads to ubiquitous entanglement of spin and orbital
quantum numbers, along with notable mixing between even- and odd-frequency
correlations. We propose a phase diagram obtained from the temperature
dependence of the leading and subleading symmetries in the pseudospin-orbital
basis. An accidental degeneracy between leading inter-pseudospin symmetries in
strontium ruthenate, B$_{1g}^+$ and A$_{2g}^-$, could resolve apparent
experimental contradictions.",2201.08918v3
2021-08-23,Large spin-charge interconversion induced by interfacial spin-orbit coupling at a highly conducting all-metallic system,"Spin-charge interconversion in systems with spin-orbit coupling has provided
a new route for the generation and detection of spin currents in functional
devices for memory and logic such as spin-orbit torque switching in magnetic
memories or magnetic state reading in spin-based logic. Disentangling the bulk
(spin Hall effect) from the interfacial (inverse spin galvanic effect)
contribution has been a common issue to properly quantify the spin-charge
interconversion in these systems, being the case of Au paradigmatic. Here, we
obtain a large spin-charge interconversion at a highly conducting Au/Cu
interface which is experimentally shown to arise from the inverse spin galvanic
effect of the interface and not from the spin Hall effect of bulk Au. We use
two parameters independent of the microscopic details to properly quantify the
spin-charge interconversion and the spin losses due to the interfacial
spin-orbit coupling, providing an adequate benchmarking to compare with any
spin-charge interconversion system. The good performance of this metallic
interface, not based in Bi, opens the path to the use of much simpler
light/heavy metal systems.",2108.10409v1
2006-01-20,Conserved Spin and Orbital Angular Momentum Hall Current in a Two-Dimensional Electron System with Rashba and Dresselhaus Spin-orbit Coupling,"We study theoretically the spin and orbital angular momentum (OAM) Hall
effect in a high mobility two-dimensional electron system with Rashba and
Dresselhuas spin-orbit coupling by introducing both the spin and OAM torque
corrections, respectively, to the spin and OAM currents. We find that when both
bands are occupied, the spin Hall conductivity is still a constant (i.e.,
independent of the carrier density) which, however, has an opposite sign to the
previous value. The spin Hall conductivity in general would not be cancelled by
the OAM Hall conductivity. The OAM Hall conductivity is also independent of the
carrier density but depends on the strength ratio of the Rashba to Dresselhaus
spin-orbit coupling, suggesting that one can manipulate the total Hall current
through tuning the Rashba coupling by a gate voltage. We note that in a pure
Rashba system, though the spin Hall conductivity is exactly cancelled by the
OAM Hall conductivity due to the angular momentum conservation, the spin Hall
effect could still manifest itself as nonzero magnetization Hall current and
finite magnetization at the sample edges because the magnetic dipole moment
associated with the spin of an electron is twice as large as that of the OAM.
We also evaluate the electric field-induced OAM and discuss the origin of the
OAM Hall current. Finally, we find that the spin and OAM Hall conductivities
are closely related to the Berry vector (or gauge) potential.",0601466v2
2019-07-11,Spin-orbit coupling in elemental two-dimensional materials,"The fundamental spin-orbit coupling and spin mixing in graphene and rippled
honeycomb lattice materials silicene, germanene, stanene, blue phosphorene,
arsenene, antimonene, and bismuthene is investigated from first principles. The
intrinsic spin-orbit coupling in graphene is revisited using multi-band $k\cdot
p$ theory, showing the presence of non-zero spin mixing in graphene despite the
mirror symmetry. However, the spin mixing itself does not lead to the the
Elliott-Yafet spin relaxation mechanism, unless the mirror symmetry is broken
by external factors. For other aforementioned elemental materials we present
the spin-orbit splittings at relevant symmetry points, as well as the spin
admixture $b^2$ as a function of energy close to the band extrema or Fermi
levels. We find that spin-orbit coupling scales as the square of the atomic
number Z, as expected for valence electrons in atoms. For isolated bands, it is
found that $b^2\sim Z^4$. The spin-mixing parameter also exhibits giant
anisotropy which, to a large extent, can be controlled by tuning the Fermi
level. Our results for $b^2$ can be directly transferred to spin relaxation
time due to the Elliott-Yafet mechanism, and therefore provide an estimate of
the upper limit for spin lifetimes in materials with space inversion center.",1907.05152v1
2016-10-24,Prototypical topological orbital ferromagnet $γ$-FeMn,"We predict from first principles an entirely topological orbital
magnetization in the noncoplanar bulk antiferromagnet $\gamma$-FeMn originating
in the nontrivial topology of the underlying spin structure, without any
reference to spin-orbit interaction. Studying the influence of strain,
composition ratio, and spin texture on the topological orbital magnetization
and the accompanying topological Hall effect, we promote the scalar spin
chirality as key mechanism lifting the orbital degeneracy. The system is thus a
prototypical topological orbital ferromagnet, the macroscopic orbital
magnetization of which is prominent even without spin-orbit coupling. One of
the remarkable features of $\gamma$-FeMn is the possibility for pronounced
orbital magnetostriction mediated by the complex spin topology in real space.",1610.07573v1
1997-12-15,Pressure Effects in Manganites with Layered Perovskite Structure,"Pressure effects on the charge and spin dynamics in the bilayer manganite
compounds $La_{2-2x}Sr_{1+2x}Mn_2O_7$ are studied theoretically by taking into
account the orbital degrees of freedom. The orbital degrees are active in the
layered crystal structure, and applied hydrostatic pressure stabilizes the
$3d_{x^2-y^2}$ orbital in comparison with $3d_{3z^2-r^2}$. The change of the
orbital states weakens the interlayer charge and spin couplings, and suppresses
the three dimensional ferromagnetic transition. Numerical results, based on an
effective Hamiltonian which includes the energy level difference of the
orbitals, show that the applied pressure controls the dimensionality of the
spin and charge dynamics through changes of the orbital states.",9712162v1
2000-10-14,"Mean-Field Approach to Charge, Orbital, and Spin Ordering in Manganites","We present a mean-field theory of charge, orbital, and spin ordering in
manganites at 50% and 0% dopings by considering Jahn-Teller interaction,
nearest-neighbor repulsion, and no single-site double occupancy. For spinless
fermions, we show that Jahn-Teller distortion and charge-orbital ordering occur
simultaneously. In our two-dimensional model at 50% doping, for small
nearest-neighbor repulsion the system is orbitally polarized while for larger
repulsion the system undergoes CE type ordering. As for the 0% doping case, the
ground state is orbitally antiferromagnetic. Upon including spin degree of
freedom, at both 50% and 0% dopings the ordering remains the same at small
antiferromagnetic coupling between adjacent core spins.",0010197v1
2018-12-04,Anomalous orbital moment in the ferromagnetic phase of the Sr4Ru3O10,"The coupling of spin and orbital degrees of freedom in the trilayer Sr4Ru3O10
sets a long-standing puzzle, due to the peculiar anisotropic coexistence of
out-of-plane ferromagnetism and in-plane metamagnetism. Recently, the induced
magnetic structure by in-plane applied fields has been investigated by means of
spin-polarized neutron diffraction, which allowed to extract a substantial
orbital component of the magnetic densities at Ru sites. It has been argued
that the latter is at the origin of the evident layer dependent magnetic
anisotropy, where the inner layers carry larger magnetic moments than the outer
ones. We present a spin-polarized neutron diffraction study in order to
characterize the nature of the ferromagnetic state of Sr4Ru3O10, in the
presence of a magnetic field applied along the c-axis. The components of the
magnetic densities at the Ru sites reveal a vanishing contribution of the
orbital magnetic moment which is unexpected for a material system where orbital
and spin degeneracy are lifted by spin-orbit coupling and ferromagnetism. We
employ a model that includes the Coulomb interaction and spin-orbit coupling at
the Ru site to address the origin of the suppression of the orbital magnetic
moment. The emerging scenario is that of non-local orbital degrees of freedom
playing a significant role in the ferromagnetic phase, with the Coulomb
interaction that is crucial to make anti-aligned orbital moments at short
distance resulting in a ground state with vanishing local orbital moments.",1812.01359v2
2001-08-08,Ordered valence bond states in symmetric two-dimensional spin-orbital systems,"We consider a superexchange Hamiltonian, $H=-\sum_{<i,j>}(2{\bf S}_i\cdot
{\bf S}_j-\frac 12)(2{\bf T}_i\cdot {\bf T}_j-\frac 12)$, which describes
systems with orbital degeneracy and strong electron-phonon coupling in the
limit of large on-site repulsion. In an SU(4) Schwinger boson representation, a
reduced spin-orbital interaction is derived {\it exactly}, and a mean field
theory has been developed by introducing a symmetric valence bond pairing order
parameter. In one dimension, a spin-orbital liquid state with a finite gap is
obtained. On a two-dimensional square lattice a novel type of spin-orbital
ferromagnetically ordered state appears, while spin and orbital are
antiferromagnetic. Moreover, an important relation has been found, relating the
spin and orbital correlation functions to the combined spin-orbital ones.",0108134v1
2009-07-09,Excitation spectrum and magnetic field effects in a quantum critical spin-orbital system:FeSc$_2$S$_4$,"The orbitally degenerate A-site spinel compound FeSc2S4 has been
experimentally identified as a ``spin-orbital liquid'', with strong
fluctuations of both spins and orbitals. Assuming that the second neighbor spin
exchange J2 is the dominant one, we argued in a recent theoretical study [Chen
et al., Phys. Rev. Lett. 102, 096406 (2009)] that FeSc2S4 is in a local
``spin-orbital singlet'' state driven by spin orbit coupling, close to a
quantum critical point, which separates the ``spin-orbital singlet'' phase from
a magnetically and orbitally ordered phase. In this paper, we refine further
and develop this theory of FeSc2S4 . First, we show that inclusion of a small
first neighbor exchange J1 induces a narrow region of incommensurate phase near
the quantum critical point. Next, we derive the phase diagram in the presence
of an external magnetic field B, and show that the latter suppresses the
ordered phase. Lastly, we compute the field dependent dynamical magnetic
susceptibility $\chi(k, \omega; B)$, from which we extract a variety of
physical quantities. Comparison with and suggestions for experiment are
discussed.",0907.1692v1
2009-07-17,Model for frustrated spin-orbital chains: application to CaV2O4,"Motivated by recent interest in quasi-one-dimensional compound CaV2O4, we
study the ground states of a spin-orbital chain characterized by an Ising-like
orbital Hamiltonian and frustrated interactions between S=1 spins. The on-site
spin-orbit interaction and Jahn-Teller effect compete with inter-site
superexchange leading to a rich phase diagram in which an antiferro-orbital
phase is separated from the orbital paramagnet by a continuous Ising
transition. Two distinct spin liquids depending on the underlying orbital order
are found in the limit of small spin-orbit coupling. In the opposite limit, the
zigzag chain behaves as a spin-2 chain with Ising anisotropy. The implications
for CaV2O4 are discussed.",0907.3006v2
2012-05-29,Exact spin-orbital separation in a solvable model in one dimension,"A one-dimensional model of coupled spin-1/2 spins and pseudospin-1/2 orbitals
with nearest-neighbor interaction is rigorously shown to exhibit spin-orbital
separation by means of a non-local unitary transformation. On an open chain,
this transformation completely decouples the spins from the orbitals in such a
way that the spins become paramagnetic while the orbitals form the soluble XXZ
Heisenberg model. The nature of various correlations is discussed. The more
general cases, which allow spin-orbital separation by the same method, are
pointed out. A generalization for the orbital pseudospin greater than 1/2 is
also discussed. Some qualitative connections are drawn with the recently
observed spin-orbital separation in Sr2CuO3.",1205.6436v3
2020-04-01,Large spin-Hall effect in Si at room temperature,"Silicon's weak intrinsic spin-orbit coupling and centrosymmetric crystal
structure are a critical bottleneck to the development of Si spintronics,
because they lead to an insignificant spin-Hall effect (spin current
generation) and inverse spin-Hall effect (spin current detection). Here, we
undertake current, magnetic field, crystallography dependent magnetoresistance
and magneto thermal transport measurements to study the spin transport behavior
in freestanding Si thin films. We observe a large spin-Hall magnetoresistance
in both p-Si and n-Si at room temperature and it is an order of magnitude
larger than that of Pt. One explanation of the unexpectedly large and efficient
spin-Hall effect is spin-phonon coupling instead of spin-orbit coupling. The
macroscopic origin of the spin-phonon coupling can be large strain gradients
that can exist in the freestanding Si films. This discovery in a light, earth
abundant and centrosymmetric material opens a new path of strain engineering to
achieve spin dependent properties in technologically highly-developed
materials.",2004.00665v1
2022-12-14,Spin singlet topological superconductivity in the attractive Rashba Hubbard model,"Fully gapped, spin singlet superconductors with antisymmetric spin-orbit
coupling in a Zeeman magnetic field provide a promising route to realize
superconducting states with non-Abelian topological order and therefore
fault-tolerant quantum computation. Here we use a quantum Monte Carlo dynamical
cluster approximation to study the superconducting properties of a doped
two-dimensional attractive Hubbard model with Rashba spin-orbit coupling in a
Zeeman magnetic field. We generally find that the Rashba coupling has a
beneficial effect towards s-wave superconductivity. In the presence of a finite
Zeeman field, when superconductivity is suppressed by Pauli pair-breaking, the
Rashba coupling counteracts the spin imbalance created by the Zeeman field by
mixing the spins, and thus restores superconductivity at finite temperatures.
We show that this favorable effect of the spin-orbit coupling is traced to a
spin-flip driven enhancement of the amplitude for the propagation of a pair of
electrons in time-reversed states. Moreover, by inspecting the Fermi surface of
the interacting model, we show that for sufficiently large Rashba coupling and
Zeeman field, the superconducting state is expected to be topologically
non-trivial.",2212.07251v1
2022-04-22,Controlling magnetism with light in a zero orbital angular momentum antiferromagnet,"Antiferromagnetic materials feature intrinsic ultrafast spin dynamics, making
them ideal candidates for future magnonic devices operating at THz frequencies.
A major focus of current research is the investigation of optical methods for
the efficient generation of coherent magnons in antiferromagnetic insulators.
In magnetic lattices endowed with orbital angular momentum, spin-orbit coupling
enables spin dynamics through the resonant excitation of low-energy electric
dipoles such as phonons and orbital resonances which interact with spins.
However, in magnetic systems with zero orbital angular momentum, microscopic
pathways for the resonant and low-energy optical excitation of coherent spin
dynamics are lacking. Here, we consider experimentally the relative merits of
electronic and vibrational excitations for the optical control of zero orbital
angular momentum magnets, focusing on a limit case: the antiferromagnet
manganese thiophoshate (MnPS3), constituted by orbital singlet Mn2+ ions. We
study the correlation of spins with two types of excitations within its band
gap: a bound electron orbital excitation from the singlet orbital ground state
of Mn2+ into an orbital triplet state, which causes coherent spin precession,
and a vibrational excitation of the crystal field that causes thermal spin
disorder. Our findings cast orbital transitions as key targets for magnetic
control in insulators constituted by magnetic centers of zero orbital angular
momentum.",2204.10574v1
2011-03-31,Emergent patterns in a spin-orbit coupled spin-2 Bose-Einstein condensate,"The ground-state phases of a spin-orbit (SO) coupled atomic spin-2
Bose-Einstein condensate (BEC) are studied. Interesting density patterns
spontaneously formed are widespread due to the competition between SO coupling
and spin-dependent interactions like in a SO coupled spin-1 condensate. Unlike
the case of spin-1 condensates, which are characterized by either ferromagnetic
or polar phase in the absence of SO, spin-2 condensates can take a cyclic
phase, where we find the patterns formed due to SO are square or triangular in
their spin component densities for axial symmetric SO interaction. Both
patterns are found to continuously evolve into striped forms with increased
asymmetry of the SO coupling.",1103.6074v1
2003-10-03,Spin-Spin and Spin-Orbit Interactions in Strongly Coupled Gauge Theories,"We evaluate the spin-orbit and spin-spin interaction between two fermions in
strongly coupled gauge theories in their Coulomb phase. We use the
quasi-instantaneous character of Coulomb's law at strong coupling to resum a
class of ladder diagrams. For ${\cal N}=4$ SYM we derive both weak and strong
coupling limits of the the spin-orbit and spin-spin interactions, and find that
in the latter case these interactions are subleading corrections and do not
seriously affect the deeply bound Coulomb states with large angular momentum,
pointed out in our previous paper. The results are important for understanding
of the regime of intermediate coupling, which is the case for QCD somewhat
above the chiral transition temperature.",0310031v1
2007-09-04,"On the Bohr radius relationship to spin-orbit interaction, spin magnitude, and Thomas precession","The dynamics of the spin-orbit interaction in atomic hydrogen are studied in
a classical electrodynamics-like setting. A Rutherfordian atomic model is used
assuming a circular electron orbit, without the quantum principle as imposed
arbitrarily in the Bohr model, but with an ad hoc incorporation in the electron
of intrinsic spin and associated magnetic dipole moment. Analyzing the motions
of the electron spin and orbital angular momenta, it is found that in the
presence of Thomas precession, the total angular momentum averaged over the
orbit is not generally a constant of the motion. It is noted this differs from
the finding of Thomas in a similar assessment of 1927, and the reason for this
difference is provided. It is found that although the total orbit-averaged
angular momentum is not a constant of the motion, it precesses around a fixed
axis similarly to the precession of the total angular momentum vector seen in
spin-orbit coupling in quantum theory. The magnitude of the angular velocity of
the total orbit-averaged angular momentum is seen to vanish only when the spin
and orbital angular momenta are antiparallel and their mutual precession
frequencies equate. It is then found, there is a unique radius where the mutual
precession frequencies equate. Assuming the electron magnetic moment is the
Bohr magneton, and an electron g-factor of two, this radius corresponds to
where the orbital angular momentum is the reduced Planck's constant. The orbit
radius for stationary total angular momentum for the circular orbit model with
nonzero orbital angular momentum is thus the ground-state radius of the Bohr
model.",0709.0319v4
2018-04-26,Topological zero-line mode of bilayer graphene with Rashba spin-orbital coupling and staggered sublattice potentials,"Domain wall in bilayer graphene with Rashba spin-orbital coupling and
staggered sublattice potentials, at the interface between two domains with
different gated voltages, is studied. Varying type of zero-line modes are
identified, including zero-line mode with pure spin filtering effect. The
Y-shape current partition at the junction among three different domains are
proposed.",1804.09881v2
2011-06-22,Integrable relativistic systems given by Hamiltonians with momentum-spin-orbit coupling,"In the paper we investigate the evolution of the relativistic particle
(massive and massless) with spin defined by Hamiltonian containing the terms
with momentum-spin-orbit coupling. We integrate the corresponding Hamiltonian
equations in quadratures and express their solutions in terms of elliptic
functions.",1106.4480v1
2011-12-12,Spontaneous generation of spin-orbit coupling in magnetic dipolar Fermi gases,"The stability of an unpolarized two-component dipolar Fermi gas is studied
within mean-field theory. Besides the known instability towards spontaneous
magnetization with Fermi sphere deformation, another instability towards
spontaneous formation of a spin-orbit coupled phase with a Rashba-like spin
texture is found. A phase diagram is presented and consequences are briefly
discussed.",1112.2596v1
2017-02-15,Optimal dense coding and swap operation between two coupled electronic spins: effects of nuclear field and spin-orbit interaction,"The effects of nuclear field and spin-orbit interaction on dense coding and
swap operation are studied in detail for both the antiferromagnetic (AFM) and
ferromagnetic (FM) coupling cases. The conditions for a valid dense coding and
under which swap operation is feasible are given.",1702.04454v1
2005-12-22,Bulk electron spin polarization generated by the spin Hall current,"It is shown that the spin Hall current generates a non-equilibrium spin
polarization in the interior of crystals with reduced symmetry in a way that is
drastically different from the previously well-known equilibrium polarization
during the spin relaxation process. The steady state spin polarization value
does not depend on the strength of spin-orbit interaction offering possibility
to generate relatively high spin polarization even in the case of weak
spin-orbit coupling.",0512566v2
2008-01-11,Phonon modulation of the spin-orbit interaction as a spin relaxation mechanism in quantum dots,"We calculate the spin relaxation rates in a parabolic InSb quantum dots due
to the spin interaction with acoustical phonons. We considered the deformation
potential mechanism as the dominant electron-phonon coupling in the
Pavlov-Firsov spin-phonon Hamiltonian. By studying suitable choices of magnetic
field and lateral dot size, we determine regions where the spin relaxation
rates can be practically suppressed. We analyze the behavior of the spin
relaxation rates as a function of an external magnetic field and mean quantum
dot radius. Effects of the spin admixture due to Dresselhaus contribution to
spin-orbit interaction are also discussed.",0801.1699v1
2013-03-23,Spin-Orbit mediated spin relaxation in monolayer MoS2,"We study the intra-valley spin-orbit mediated spin relaxation in monolayers
of MoS2 within a two bands effective Hamiltonian. The intrinsic spin splitting
of the valence band as well as a Rashba-like coupling due to the breaking of
the out-of-plane inversion symmetry are considered. We show that, in the hole
doped regime, the out-of-plane spin relaxation is not very efficient since the
spin splitting of the valence band tends to stabilize the spin polarization in
this direction. We obtain spin lifetimes larger than nanoseconds, in agreement
with recent valley polarization experiments.",1303.5860v2
2021-09-30,Observation of the orbital Hall effect in a light metal Ti,"The orbital angular momentum is a core ingredient of orbital magnetism, spin
Hall effect, giant Rashba spin splitting, orbital Edelstein effect, and
spin-orbit torque. However, its experimental detection is tricky. In
particular, direct detection of the orbital Hall effect remains elusive despite
its importance for electrical control of magnetic nanodevices. Here we report
the direct observation of the orbital Hall effect in a light metal Ti. The Kerr
rotation by the accumulated orbital magnetic moment is measured at Ti surfaces,
whose result agrees with theoretical calculations semiquantitatively and is
supported by the orbital torque measurement in Ti-based magnetic
heterostructures. The results confirm the electron orbital angular momentum as
an essential dynamic degree of freedom, which may provide a novel mechanism for
the electric control of magnetism. The results may also deepen the
understanding of spin, valley, phonon, and magnon dynamics coupled with orbital
dynamics.",2109.14847v1
2022-09-19,Unidirectional orbital magnetoresistance in light metal/ferromagnet bilayers,"We report the observation of a unidirectional magnetoresistance (UMR) that
originates from the nonequilibrium orbital momentum induced by an electric
current in a naturally oxidized Cu/Co bilayer. The orbital-UMR scales with the
torque efficiency due to the orbital Rashba-Edelstein effect upon changing the
Co thickness and temperature, reflecting their common origin. We attribute the
UMR to orbital-dependent electron scattering and orbital-to-spin conversion in
the ferromagnetic layer. In contrast to the spin-current induced UMR, the
magnon contribution to the orbital-UMR is absent in thin Co layers, which we
ascribe to the lack of coupling between low energy magnons and orbital current.
The magnon contribution to the UMR emerges in Co layers thicker than about 5
nm, which is comparable to the orbital-to-spin conversion length. Our results
provide insight into orbital-to-spin momentum transfer processes relevant for
the optimization of spintronic devices based on light metals and orbital
transport.",2209.09355v1
2004-05-04,Transverse Electron Focusing in Systems with Spin-Orbit Coupling,"We study the transverse electron focusing in a two dimensional electron gas
with Rashba spin-orbit coupling. We show that the interplay between the
external magnetic field and the spin-orbit coupling gives two branches of
states with different cyclotron radius within the same energy window. This
effect generates a splitting of the first focusing peak in two contributions.
Each one of these contributions is spin polarized. The surface reflection mixes
the two branches and the second focusing peak does not present the same effect.
While for GaAs/AlGaAs heterostructures the effect is small, in systems like
InSb/InAlSb the effect should be clearly observed.",0405061v1
2004-07-06,Theory of Edge States in Systems with Rashba Spin-Orbit Coupling,"We study the edge states in a two dimensional electron gas with a transverse
magnetic field and Rashba spin-orbit coupling. In the bulk, the interplay
between the external field perpendicular to the gas plane and the spin-orbit
coupling leads to two branches of states that, within the same energy window,
have different cyclotron radii. For the edge states, surface reflection
generates hybrid states with the two cyclotron radii. We analyze the spectrum
and spin structure of these states and present a semiclassical picture of them.",0407138v1
2004-10-03,Spin-Orbit Effects in Diluted Magnetic Semiconductors,"We present a theoretical study of diluted magnetic semiconductors that treats
the local sp-d exchange interaction J between the itinerant carriers and the Mn
d electrons within a realistic band structure and goes beyond previous
mean-field approaches. In case of (Ga,Mn)As, we find that strong exchange
potentials tightly bind carriers near impurity sites. Spin-orbit coupling is
found to have a more pronounced effect on spin polarization at weak coupling
and this feature can be exploited for magnetotransport. For low doping regime,
we predict that spin-orbit coupling splits impurity bands and can induce a
novel insulating phase.",0410051v1
2004-04-04,Spin-orbit coupling and magnetic spin states in cylindrical quantum dots,"We make detailed analysis of each possible spin-orbit coupling of zincblende
narrow-gap cylindrical quantum dots built in two-dimensional electron gas.
These couplings are related to both bulk (Dresselhaus) and structure (Rashba)
inversion asymmetries. We study the competition between electron-electron and
spin-orbit interactions on electronic properties of 2-electron quantum dots.",0404017v1
2008-01-20,Orbital magnetization and its effects in spin-chiral ferromagnetic kagome lattice in the general spin-coupling region,"The orbital magnetization and its effects on the two-dimensional kagom\'{e}
lattice with spin anisotropies included in the general Hund's coupling region
have been theoretically studied. The results show that the strength of the
Hund's coupling, as well as the spin chirality, contributes to the orbital
magnetization $\mathcal{M}$. Upon varying both these parameters, it is found
that the two parts of $\mathcal{M}$, i.e., the conventional part
$\mathbf{M}_{c}$ and the Berry-phase correction part $\mathbf{M}_{\Omega}$,
oppose each other. The anomalous Nernst conductivity is also calculated and a
peak-valley structure as a function of the electron Fermi energy is obtained.",0801.3061v1
2008-08-21,Unconventional pairing in excitonic condensates under spin-orbit coupling,"It is shown that the Rashba and Dresselhaus spin orbit couplings enhance the
conclusive power in the experiments on the excitonic condensed state by at
least three low temperature effects. First, spin orbit coupling facilitates the
photoluminescense measurements via enhancing the bright contribution in the
otherwise dominantly dark exciton condensed state. The second is the presence
of a power law temperature dependence of the thermodynamic observables in low
temperatures and the weakening of the second order transition at the critical
temperature. The third is the appearance of the nondiagonal elements in the
static spin susceptibility.",0808.2900v2
2011-07-21,Transverse Josephson effect due to spin-orbit coupling: Generation of transverse current without time-reversal symmetry breaking,"We investigate transverse Josephson current in superconductor/normal
metal/superconductor junctions where the normal metal has Rashba type
spin-orbit coupling. It is shown that trans- verse current arises from the
spin-orbit coupling in the normal metal. This effect is specific to
superconducting current and the transverse current vanishes in the normal
state. In addition, this transverse Josephson effect is purely stationary and
applied magnetic field is unnecessary to realize this effect, in contrast to
the Hall effect in the normal state. We also discuss physical interpretation of
this effect, comparing with the spin Hall effect.",1107.4202v3
2011-08-09,Spin-orbit coupling and $g$-factor of $X$-valley in cubic GaN,"We report our theoretically investigation on the spin-orbit coupling and
$g$-factor of the $X$-valley in cubic GaN. We find that the spin-orbit coupling
coefficient from $sp^3d^5s^\ast$ tight-binding model is 0.029\,eV$\cdot${\AA},
which is comparable with that in cubic GaAs. By employing the ${\bf k}\cdot{\bf
p}$ theory, we find that the $g$-factor in this case is only slightly different
from the free electron $g$-factor. These results are expected to be important
for the on-going study on spin dynamics far away from equilibrium in cubic GaN.",1108.2059v1
2012-03-28,Direct Observation of Interband Spin-Orbit Coupling in a Two-Dimensional Electron System,"We report the direct observation of interband spin-orbit (SO) coupling in a
two-dimensional (2D) surface electron system, in addition to the anticipated
Rashba spin splitting. Using angle-resolved photoemission experiments and
first-principles calculations on Bi/Ag/Au heterostructures we show that the
effect strongly modifies the dispersion as well as the orbital and spin
character of the 2D electronic states, thus giving rise to considerable
deviations from the Rashba model. The strength of the interband SO coupling is
tuned by the thickness of the thin film structures.",1203.6190v1
2012-12-17,Spin-Orbit Coupling in Multilayer Superconductors with Charge Imbalance,"In this study, we investigate the spin susceptibility in the superconducting
state of a multilayer system with a layer-dependent Rashba spin-orbit coupling,
representing a locally non-centrosymmetric superconductor. We show that the
charge imbalance between different layers yields a strong layer dependence on
the susceptibility, most significantly for a weak spin-orbit coupling, which is
in contrast to a situation with an equally distributed charge. These results
can be relevant for experimental test in multilayer high-Tc cuprates as well as
in superconducting CeCoIn5/YbCoIn5 superlattices with more than two layers.",1212.3862v2
2016-08-12,Magnetotransport signatures of the proximity exchange and spin-orbit couplings in graphene,"Graphene on an insulating ferromagnetic substrate---ferromagnetic insulator
or ferromagnetic metal with a tunnel barrier---is expected to exhibit giant
proximity exchange and spin-orbit couplings. We use a realistic transport model
of charge-disorder scattering and solve the linearized Boltzmann equation
numerically exactly for the anisotropic Fermi contours of modified Dirac
electrons to find magnetotransport signatures of these proximity effects:
proximity anisotropic magnetoresistance, inverse spin-galvanic effect, and the
planar Hall resistivity. We establish the corresponding anisotropies due to the
exchange and spin-orbit couplings, with respect to the magnetization
orientation. We also present parameter maps guiding towards optimal regimes for
observing transport magnetoanisotropies in proximity graphene.",1608.03879v1
2019-03-19,Quantum corrections to a spin-orbit coupled Bose-Einstein Condensate,"We study systematically the quantum corrections to a weakly interacting
Bose-Einstein condensate with spin-orbit coupling. We show that quantum
fluctuations, enhanced by the spin-orbit coupling, modify quantitatively the
mean-field properties such as the superfluid density, spin polarizability, and
sound velocity. We find that the phase boundary between the plane wave and zero
momentum phases is shifted to a smaller transverse field. We also calculate the
Beliaev and Landau damping rates and find that the Landau process dominates the
quasiparticle decay even at low temperature.",1903.08182v3
2016-02-10,Spin-dependent Seebeck Effect in Aharonov-Bohm Rings with Rashba and Dresselhaus Spin-orbit Interactions,"We theoretically investigate the spin-dependent Seebeck effect in an
Aharonov-Bohm mesoscopic ring in the presence of both Rashba and Dresselhaus
spin-orbit interactions under magnetic flux perpendicular to the ring. We apply
the Green's function method to calculate the spin Seebeck coefficient employing
the tight-binding Hamiltonian. It is found that the spin Seebeck coefficient is
proportional to the slope of the energy-dependent transmission coefficients. We
study the strong dependence of spin Seebeck coefficient on the Fermi energy,
magnetic flux, strength of spin-orbit coupling, and temperature. Maximum spin
Seebeck coefficients can be obtained when the strengths of Rashba and
Dresselhaus spin-orbit couplings are slightly different. The spin Seebeck
coefficient can be reduced by increasing temperature and disorder.",1602.03272v1
2019-02-21,Spin-orbit coupling and spin relaxation in phosphorene: Intrinsic versus extrinsic effects,"First-principles calculations of the essential spin-orbit and spin relaxation
properties of phosphorene are performed. Intrinsic spin-orbit coupling induces
spin mixing with the probability of $b^2 \approx 10^{-4}$, exhibiting a large
anisotropy, following the anisotropic crystalline structure of phosphorene. For
realistic values of the momentum relaxation times, the intrinsic
(Elliott--Yafet) spin relaxation times are hundreds of picoseconds to
nanoseconds. Applying a transverse electric field (simulating gating and
substrates) generates extrinsic $C_{2v}$ symmetric spin-orbit fields in
phosphorene, which activate the D'yakonov--Perel' mechanism for spin
relaxation. It is shown that this extrinsic spin relaxation also has a strong
anisotropy, and can dominate over the Elliott-Yafet one for strong enough
electric fields. Phosphorene on substrates can thus exhibit an interesting
interplay of both spin relaxation mechanisms, whose individual roles could be
deciphered using our results.",1902.07957v1
2014-11-28,Position-dependent spin-orbit coupling for ultracold atoms,"We theoretically explore atomic Bose-Einstein condensates (BECs) subject to
position-dependent spin-orbit coupling (SOC). This SOC can be produced by
cyclically laser coupling four internal atomic ground (or metastable) states in
an environment where the detuning from resonance depends on position. The
resulting spin-orbit coupled BEC phase-separates into domains, each of which
contain density modulations - stripes - aligned either along the x or y
direction. In each domain, the stripe orientation is determined by the sign of
the local detuning. When these stripes have mismatched spatial periods along
domain boundaries, non-trivial topological spin textures form at the interface,
including skyrmions-like spin vortices and anti-vortices. In contrast to
vortices present in conventional rotating BECs, these spin-vortices are stable
topological defects that are not present in the corresponding homogenous
stripe-phase spin-orbit coupled BECs.",1411.7813v2
2015-10-27,Extrinsic Spin Hall Effect from Anisotropic Rashba Spin-Orbit Coupling in Graphene,"We study the effect of anisotropy of the Rashba coupling on the extrinsic
spin Hall effect due to spin-orbit active adatoms on graphene. In addition to
the intrinsic spin-orbit coupling, a generalized anisotropic Rashba coupling
arising from the breakdown of both mirror and hexagonal symmetries of pristine
graphene is considered. We find that Rashba anisotropy can strongly modify the
dependence of the spin Hall angle on carrier concentration. Our model provides
a simple and general description of the skew scattering mechanism due to the
spin-orbit coupling that is induced by proximity to large adatom clusters.",1510.07771v1
2017-10-23,Time-reversal-invariant spin-orbit-coupled bilayer Bose-Einstein Condensates,"Time-reversal invariance plays a crucial role for many exotic quantum phases,
particularly for topologically nontrivial states, in spin-orbit coupled
electronic systems. Recently realized spin-orbit coupled cold-atom systems,
however, lack the time-reversal symmetry due to the inevitable presence of an
effective transverse Zeeman field. We address this issue by analyzing a
realistic scheme to preserve time-reversal symmetry in spin-orbit coupled
ultracold atoms, with the use of Hermite-Gaussian-laser induced Raman
transitions that preserve spin-layer time-reversal symmetry. We find that the
system's quantum states form Kramers pairs, resulting in symmetry-protected gap
closing of the lowest two bands at arbitrarily large Raman coupling. We also
show that Bose gases in this setup exhibit interaction-induced layer-stripe and
uniform phases as well as intriguing spin-layer symmetry and spin-layer
correlation.",1710.08323v2
2018-01-11,Thermoelectric properties of a quantum dot coupled to magnetic leads by Rashba spin-orbit interaction,"We consider a single-level quantum dot coupled to two leads which are
ferromagnetic in general. Apart from tunneling processes conserving electron
spin, we also include processes associated with spin-flip of tunneling
electrons, which appear due to Rashba spin-orbit coupling. Charge and heat
currents are calculated within the non-equilibrium Green's function technique.
When the electrodes are half-metallic (fully spin polarized), the Rashba
spin-orbit coupling leads to Fano-like interference effects, which result in an
enhanced thermoelectric response. It is also shown that such a system can
operate as efficient heat engine. Furthermore, the interplay of Rashba
spin-orbit coupling and Zeeman splitting due to an external magnetic field is
shown to allow control over such parameters of the heat engine as the power and
efficiency.",1801.03700v1
2020-01-16,Spontaneous Antisymmetric Spin Splitting in Noncollinear Antiferromagnets without Spin-Orbit Coupling,"We propose a realization of an antisymmetric spin-split band structure
through magnetic phase transitions without spin-orbit coupling. It enables us
to utilize for a variety of magnetic-order-driven cross-correlated and
nonreciprocal transport phenomena as similar to those in the
spin-orbit-coupling oriented systems. We unveil its general condition as an
emergence of a bond-type magnetic toroidal multipole (polar tensor) in the
triangular unit with the noncollinear 120$^{\circ}$-AFM structures. By using
the concept of augmented multipoles, we systematically analyze the phenomena in
terms of an effective multipole coupling. Our multipole description is
ubiquitously applied to any trigonal and hexagonal structures including the
triangular, kagome, and breathing kagome structures, which provides how to
design and engineer materials with a giant antisymmetric spin splitting and its
physical responses even without the spin-orbit coupling.",2001.05630v2
2020-04-27,Spin-orbit coupled superconductivity: Rashba-Hubbard model on the square lattice,"The weak-coupling renormalization group method is an asymptotically exact
method to find superconducting instabilities of a lattice model of correlated
electrons. Here we extend it to spin-orbit coupled lattice systems and study
the emerging superconducting phases of the Rashba-Hubbard model. Since Rashba
type spin-orbit coupling breaks inversion symmetry, the arising superconducting
phases may be a mixture of spin-singlet and spin-triplet states. We study the
two-dimensional square lattice as a paradigm and discuss the symmetry
properties of the arising spin-orbit coupled superconducting states including
helical spin-triplet superconductivity. We also discuss how to best deal with
split energy bands within a method which restricts paired electrons to momenta
on the Fermi surface.",2004.12624v2
2019-01-02,Dresselhaus spin-orbit coupling in [111]-oriented semiconductor nanowires,"The contribution of bulk inversion asymmetry to the total spin-orbit coupling
is commonly neglected for group III-V nanowires grown in the generic [111]
direction. We have solved the complete Hamiltonian of the circular nanowire
accounting for bulk inversion asymmetry via exact numerical diagonalization.
Three different symmetry classes of angular momentum states exist, which
reflects the threefold rotation symmetry of the crystal lattice about the [111]
axis. A particular group of angular momentum states contains degenerate modes
which are strongly coupled via the Dresselhaus Hamiltonian, which results in a
significant energy splitting with increasing momentum. Hence, under certain
conditions Dresselhaus spin-orbit coupling is relevant for [111] InAs and [111]
InSb nanowires. We demonstrate momentum-dependent energy splittings and the
impact of Dresselhaus spin-orbit coupling on the dispersion relation. In view
of possible spintronics applications relying on bulk inversion asymmetry we
calculate the spin expectation values and the spin texture as a function of the
Fermi energy. Finally, we investigate the effect of an axial magnetic field on
the energy spectrum and on the corresponding spin polarization.",1901.00362v2
2018-06-27,Tunable spin-orbit coupling and magnetic superstripe phase in a BEC,"Superstripe phases in Bose-Einstein condensates (BECs), possessing both
crystalline structure and superfluidity, opens a new avenue for exploring
exotic quantum matters---supersolids. However, conclusive detection and further
exploration of a superstripe is still challenging in experiments because of its
short period, low visibility, fragility against magnetic field fluctuation or
short lifetime. Here we propose a scheme in a spin-orbit coupled BEC which
overcomes these obstacles and generates a robust magnetic superstripe phase,
with only spin (no total) density modulation due to the magnetic translational
symmetry, ready for direct real-space observation. In the scheme, two hyperfine
spin states are individually Raman coupled with a largely-detuned third state,
which induce a momentum-space separation between two lower band dispersions,
yielding an effective spin-1/2 system with tunable spin-orbit coupling and
Zeeman fields. Without effective Zeeman fields, spin-dependent interaction
dominates, yielding a magnetic superstripe phase with a long tunable period and
high visibility. Our scheme provides a platform for observing and exploring
exotic properties of superstripe phases as well as novel physics with tunable
spin-orbit coupling.",1806.10568v2
2017-10-05,Dirac and topological phonons with spin-orbital entangled orders,"We propose to study novel quantum phases and excitations for a 2D spin-orbit
(SO) coupled bosonic $p$-orbital optical lattice based on the recent
experiments. The orbital and spin degrees of freedom with SO coupling compete
and bring about nontrivial interacting quantum effects. We develop a
self-consistent method for bosons and predict a spin-orbital entangled order
for the ground phase, in sharp contrast to spinless high-orbital systems.
Furthermore, we investigate the Bogoliubov excitations, showing that the Dirac
and topological phonons are obtained corresponding to the predicted different
spin-orbital orders. In particular, the topological phonons exhibit a bulk gap
which can be several times larger than the single-particle gap of $p$-bands,
reflecting the enhancement of topological effect by interaction. Our results
highlight the rich physics predicted in SO coupled high-orbital systems and
shall attract experimental efforts in the future.",1710.02070v2
2014-02-26,Harmonically trapped two-atom systems: Interplay of short-range s-wave interaction and spin-orbit coupling,"The coupling between the spin degrees of freedom and the orbital angular
momentum has a profound effect on the properties of nuclei, atoms and condensed
matter systems. Recently, synthetic gauge fields have been realized
experimentally in neutral cold atom systems, giving rise to a spin-orbit
coupling term with ""strength"" $k_{\text{so}}$. This paper investigates the
interplay between the single-particle spin-orbit coupling term of Rashba type
and the short-range two-body $s$-wave interaction for cold atoms under external
confinement. Specifically, we consider two different harmonically trapped
two-atom systems. The first system consists of an atom with spin-orbit coupling
that interacts with a structureless particle through a short-range two-body
potential. The second system consists of two atoms that both feel the
spin-orbit coupling term and that interact through a short-range two-body
potential. Treating the spin-orbit term perturbatively, we determine the
correction to the ground state energy for various generic parameter
combinations. Selected excited states are also treated. An important aspect of
our study is that the perturbative treatment is not limited to small $s$-wave
scattering lengths but provides insights into the system behavior over a wide
range of scattering lengths, including the strongly-interacting unitary regime.
Our perturbative results are confirmed by numerical calculations that expand
the eigenfunctions of the two-particle Hamiltonian in terms of basis functions
that contain explicitly correlated Gaussians.",1402.6734v1
2004-09-02,Spin-orbit coupling and anisotropy of spin splitting in quantum dots,"In lateral quantum dots, the combined effect of both Dresselhaus and
Bychkov-Rashba spin orbit coupling is equivalent to an effective magnetic field
B_so which has the opposite sign for s_z=1/2 spin electrons. When the external
magnetic field is perpendicular to the planar structure, the field B_so
generates an additional splitting for electron states as compared to the spin
splitting in the in-plane field orientation. The anisotropy of spin splitting
has been measured and then analyzed in terms of spin-orbit coupling in several
AlGaAs/GaAs quantum dots by means of resonanat tunneling spectroscopy. From the
measured values and sign of the anisotropy we are able to determine the
dominating spin-orbit coupling mechanism.",0409054v1
2020-08-06,Near Total Electronic Spin Separation as Caused by Nuclear Dynamics: Perturbing a Real-Valued Conical Intersection with Complex-Valued Spin-Orbit Coupling,"We investigate the nuclear dynamics near a real-valued conical intersection
that is perturbed by a complex-valued spin-orbit coupling. For a model
Hamiltonian with two outgoing channels, we find that even a small spin-orbit
coupling can dramatically affect the pathway selection on account of Berry
force, leading to extremely large spin selectivity (sometime as large as 100%).
Thus, this Letter opens the door for organic chemists to start designing
spintronic devices that use nuclear motion and conical intersections (combined
with standard spin-orbit coupling) in order to achieve spin selection. Vice
versa, for physical chemists, this Letter also emphasizes that future
semiclassical simulations of intersystem crossing (which have heretofore
ignored Berry force) should be corrected to account for the spin polarization
that inevitably arises when dynamics pass near conical intersections.",2008.02443v1
2003-05-14,Persistent current in ballistic mesoscopic rings with Rashba spin-orbit coupling,"The presence of spin-orbit coupling affects the spontaneously flowing
persistent currents in mesoscopic conducting rings. Here we analyze their
dependence on magnetic flux with emphasis on identifying possibilities to prove
the presence and extract the strength of Rashba spin splitting in
low-dimensional systems. Effects of disorder and mixing between
quasi-onedimensional ring subbands are considered. The spin-orbit coupling
strength can be inferred from the values of flux where sign changes occur in
the persistent charge current. As an important consequence of the presence of
spin splitting, we identify a nontrivial persistent spin current that is not
simply proportional to the charge current. The different flux dependences of
persistent charge and spin currents are a unique signature of spin-orbit
coupling affecting the electronic structure of the ring.",0305310v1
2017-03-10,Spin-orbit dynamics of single acceptor atoms in silicon,"Two-level quantum systems with strong spin-orbit coupling allow for
all-electrical qubit control and long-distance qubit coupling via microwave and
phonon cavities, making them of particular interest for scalable quantum
information technologies. In silicon, a strong spin-orbit coupling exists
within the spin-3/2 system of acceptor atoms and their energy levels and
properties are expected to be highly tunable. Here we show the influence of
local symmetry tuning on the acceptor spin-dynamics, measured in the
single-atom regime. Spin-selective tunneling between two coupled boron atoms in
a commercial CMOS transistor is utilised for spin-readout, which allows for the
probing of the two-hole spin relaxation mechanisms. A relaxation-hotspot is
measured and explained by the mixing of acceptor heavy and light hole states.
Furthermore, excited state spectroscopy indicates a magnetic field controlled
rotation of the quantization axes of the atoms. These observations demonstrate
the tunability of the spin-orbit states and dynamics of this spin-3/2 system.",1703.03538v1
2017-08-25,Spin Liquid versus Spin Orbit Coupling on the Triangular Lattice,"In this paper, we explore the relationship between strong spin-orbit coupling
and spin liquid physics. We study a very general model on the triangular
lattice where spin-orbit coupling leads to the presence of highly anisotropic
interactions. We use variational Monte Carlo to study both $U(1)$ quantum spin
liquid states and ordered ones, via the Gutzwiller projected fermion
construction. We thereby obtain the ground state phase diagram in this phase
space. We furthermore consider effects beyond the Gutzwiller wavefunctions for
the spinon Fermi surface quantum spin liquid, which are of particular
importance when spin-orbit coupling is present.",1708.07856v3
2020-07-07,Unidirectional spin transport of a spin-orbit-coupled atomic matter wave using a moving Dirac $δ$-potential well,"We study the transport of a spin-orbit-coupled atomic matter wave using a
moving Dirac $\delta$-potential well. In a spin-orbit-coupled system, bound
states can be formed in both ground and excited energy levels with a Dirac
$\delta$ potential. Because Galilean invariance is broken in a
spin-orbit-coupled system, moving of the potential will induce a
velocity-dependent effective detuning. This induced detuning breaks the spin
symmetry and makes the ground-state transporting channel be spin-$\uparrow$
($\downarrow$) favored while makes the excited-state transporting channel be
spin-$\downarrow$ ($\uparrow$) favored for a positive-direction
(negative-direction) transporting. When the $\delta$-potential well moves at a
small velocity, both the ground-state and the excited-state channels contribute
to the transportation, and thus both the spin components can be efficiently
transported. However, when the moving velocity of the $\delta$-potential well
exceeds a critical value, the induced detuning is large enough to eliminate the
excited bound state, and makes the ground bound state the only transporting
channel, in which only the spin-$\uparrow$ ($\downarrow$) component can be
efficiently transported in a positive (negative) direction. This work
demonstrates a prototype of unidirectional spin transport.",2007.03147v1
2016-05-18,Pairing mechanism of unconventional superconductivity in doped Kane-Mele model,"We study the pairing symmetry of a doped Kane-Mele model on a honeycomb
lattice with on-site Coulomb interaction. The pairing instability of Cooper
pair is calculated based on the linearized Eliashberg equation within the
random phase approximation (RPA). When the magnitude of the spin-orbit coupling
is weak, even-frequency spin-singlet even-parity (ESE) pairing is dominant. On
the other hand, with the increase of the spin-orbit coupling, we show that the
even-frequency spin-triplet odd-parity (ETO) f-wave pairing exceeds ESE one.
ETO f-wave pairing is supported by the longitudinal spin fluctuation. Since the
transverse spin fluctuation is strongly suppressed by spin-orbit coupling, ETO
f-wave pairing becomes dominant for large magnitude of spin-orbit coupling.",1605.05563v3
2023-07-06,Classification and magic magnetic-field directions for spin-orbit-coupled double quantum dots,"The spin of a single electron confined in a semiconductor quantum dot is a
natural qubit candidate. Fundamental building blocks of spin-based quantum
computing have been demonstrated in double quantum dots with significant
spin-orbit coupling. Here, we show that spin-orbit-coupled double quantum dots
can be categorised in six classes, according to a partitioning of the
multi-dimensional space of their $g$-tensors. The class determines physical
characteristics of the double dot, i.e., features in transport, spectroscopy
and coherence measurements, as well as qubit control, shuttling, and readout
experiments. In particular, we predict that the spin physics is highly
simplified due to pseudospin conservation, whenever the external magnetic field
is pointing to special directions (`magic directions'), where the number of
special directions is determined by the class. We also analyze the existence
and relevance of magic loops in the space of magnetic-field directions,
corresponding to equal local Zeeman splittings. These results present an
important step toward precise interpretation and efficient design of spin-based
quantum computing experiments in materials with strong spin-orbit coupling.",2307.02958v1
2023-08-21,Displacement-field-tunable superconductivity in an inversion-symmetric twisted van der Waals heterostructure,"We investigate the superconducting properties of inversion-symmetric twisted
trilayer graphene by considering different parent states, including
spin-singlet, triplet, and SO(4) degenerate states, with or without nodal
points. By placing transition metal dichalcogenide layers above and below
twisted trilayer graphene, spin-orbit coupling is induced in TTLG and, due to
inversion symmetry, the spin-orbit coupling does not spin-split the bands. The
application of a displacement field ($D_0$) breaks the inversion symmetry and
creates spin-splitting. We analyze the evolution of the superconducting order
parameters in response to the combined spin-orbit coupling and $D_0$-induced
spin-splitting. Utilizing symmetry analysis combined with both a direct
numerical evaluation and a complementary analytical study of the gap equation,
we provide a comprehensive understanding of the influence of spin-orbit
coupling and $D_0$ on superconductivity. These results contribute to a better
understanding of the superconducting order in twisted trilayer graphene.",2308.10530v1
2018-07-17,Field-free spin-orbit torque switching from geometrical domain wall pinning,"Spin-orbit torques, which utilize spin currents arising from the spin-orbit
coupling, offer a novel method to electrically switch the magnetization with
perpendicular anisotropy. However, the necessity of an external magnetic field
to achieve a deterministic switching is an obstacle for realizing practical
spin-orbit torque devices with all-electric operation. Here, we report a
field-free spin-orbit torque switching by exploiting the domain wall motion in
an anti-notched microwire with perpendicular anisotropy, which exhibits
multi-domain states stabilized by the domain wall surface tension. The
combination of spin-orbit torque, Dzyaloshinskii-Moriya interaction, and domain
wall surface tension induced geometrical pinning allows a deterministic control
of the domain wall and offers a novel method to achieve a field-free spin-orbit
torque switching. Our work demonstrates the proof of concept of a perpendicular
memory cell which can be readily adopted in a three-terminal magnetic memory.",1807.06287v1
2003-04-16,Electron spin precession in semiconductor quantum wires with Rashba spin-orbit coupling,"The influence of the Rashba spin-orbit coupling on the electron spin dynamics
is investigated for a ballistic semiconductor quantum wire with a finite width.
We monitor the spin evolution using the time-dependent Schr\""odinger equation.
The pure spin precession characteristic of the 1D limit is lost in a 2D wire
with a finite lateral width. In general, the time evolution in the latter case
is characterized by several frequencies and a nonrigid spin motion.",0304372v1
2004-03-08,Conductance modulation in spin field-efect transistors under finite bias voltages,"The conductance modulations in spin field-effect transistors under finite
bias voltages were studied. It was shown that when a finite bias voltage is
applied between two terminals of a spin field-effect transistor, the spin
precession states of injected spin-polarized electrons in the semiconductor
channel of the device will depend not only the gate-voltage controlled Rashba
spin-orbit coupling but also depend on the bias voltage and, hence, the
conductance modulation in the device due to Rashba spin-orbit coupling may also
depend sensitively on the bias voltage.",0403199v1
2005-06-21,Intrinsic Spin Hall Edges,"The prediction of intrinsic spin Hall currents by Murakami \textit{et al.}
and Sinova \textit{et al.} raised many questions about methods of detection and
the effect of disorder. We focus on a contact between a Rashba type spin orbit
coupled region with a normal two-dimensional electron gas and show that the
spin Hall currents, though vanishing in the bulk of the sample, can be
recovered from the edges. We also show that the current induced spin
accumulation in the spin orbit coupled system diffuses into the normal region
and contributes to the spin current in the leads.",0506531v2
2010-01-26,Effect of spin-conserving scattering on Gilbert damping in ferromagnetic semiconductors,"The Gilbert damping in ferromagnetic semiconductors is theoretically
investigated based on the $s$-$d$ model. In contrast to the situation in
metals, all the spin-conserving scattering in ferromagnetic semiconductors
supplies an additional spin relaxation channel due to the momentum dependent
effective magnetic field of the spin-orbit coupling, thereby modifies the
Gilbert damping. In the presence of a pure spin current, we predict a new
contribution due to the interplay of the anisotropic spin-orbit coupling and a
pure spin current.",1001.4576v1
2011-02-15,Kondo Spin Screening Cloud in Two-dimensional Electron Gas with Spin-orbit Couplings,"A spin-1/2 Anderson impurity in a semiconductor quantum well with Rashba and
Dresselhaus spin-orbit couplings is studied by using a variational wave
function method. The local magnetic moment is found to be quenched at low
temperatures. The spin-spin correlations of the impurity and the conduction
electron density show anisotropy in both spatial and spin spaces, which
interpolates the Kondo spin screenings of a conventional metal and of a surface
of three-dimensional topological insulators.",1102.2947v1
2012-12-13,Spin dynamics in tunneling decay of a metastable state,"We analyze spin dynamics in the tunneling decay of a metastable localized
state in the presence of spin-orbit coupling. We find that the spin
polarization at short time scales is affected by the initial state while at
long time scales both the probability- and the spin density exhibit
diffraction-in-time phenomenon. We find that in addition to the tunneling time
the tunneling in general can be characterized by a new parameter, the tunneling
length. Although the tunneling length is independent on the spin-orbit
coupling, it can be accessed by the spin rotation measurement.",1212.3325v1
2013-02-08,Spin dynamics of cold fermions with synthetic spin-orbit coupling,"We consider spin relaxation dynamics in cold Fermi gases with a pure-gauge
spin-orbit coupling corresponding to recent experiments. We show that such
experiments can give a direct access to the collisional spin drag rate, and
establish conditions for the observation of spin drag effects. In the recent
experiments the dynamics is found to be mainly ballistic leading to new regimes
of reversible spin relaxation-like processes.",1302.2121v1
2017-08-22,Spin-dependent Andreev reflection in spin-orbit coupled systems by breaking time-reversal symmetry,"We study theoretically the differential conductance at a junction between a
time reversal symmetry broken spin orbit coupled system with a tunable band gap
and a superconductor. We look for spin-dependent Andreev reflection (i.e,
sub-gap transport) and show that when various mass terms compete in energy,
there is substantial difference of Andreev reflection probability depending on
the spin of the incident electron. We further analyze the origin of such
spin-dependence and show how the incident angle of the electrons controls the
spin-dependence of the transport.",1708.06773v2
2017-07-13,Spin filtering effect generated by the inter-subband spin-orbit coupling in the bilayer nanowire with the quantum point contact,"The spin filtering effect in the bilayer nanowire with quantum point contact
is investigated theoretically. We demonstrate the new mechanism of the spin
filtering based on the lateral inter-subband spin-orbit coupling, which for the
bilayer nanowires has been reported to be strong. The proposed spin filtering
effect is explained as the joint effect of the Landau-Zener inter-subband
transitions caused by the hybridization of states with opposite spin (due to
the lateral Rashba SO interaction) and the confinement of carriers in the
quantum point contact region.",1707.04086v1
2012-05-30,"Multiple Superconducting Gaps, Anisotropic Spin Fluctuations and Spin-Orbit Coupling in Iron-Pnictides","This article reviews the NMR and NQR studies on iron-based high-temperature
superconductors by the IOP/Okayama group. It was found that the electron pairs
in the superconducting state are in the spin-singlet state with multiple
fully-opened energy gaps. The antiferromagnetic spin fluctuations in the normal
state are found to be closely correlated with the superconductivity. Also the
antiferromagnetic spin fluctuations are anisotropic in the spin space, which is
different from the case in copper oxide superconductors. This anisotropy
originates from the spin-orbit coupling and is an important reflection of the
multiple-bands nature of this new class of superconductors.",1205.6589v1
2017-05-15,Spin and tunneling dynamics in an asymmetrical double quantum dot with spin - orbit coupling,"In this article we study the spin and tunneling dynamics as a function of
magnetic field in a one-dimensional GaAs double quantum dot with both the
Dresselhaus and Rashba spin-orbit coupling. In particular we consider different
spatial widths for the spin-up and spin-down electronic states. We find that
the spin dynamics is a superposition of slow as well as fast Rabi oscillations.
It is found that the Rashba interaction strength as well as the external
magnetic field strongly modifies the slow Rabi oscillations which is
particularly useful for single qubit manipulation for possible quantum computer
applications.",1705.05395v1
2023-03-10,Chiral spin channels in curved graphene $pn$ junctions,"We show that the chiral modes in circular graphene $pn$ junctions provide an
advantage for spin manipulation via spin-orbit coupling compared to
semiconductor platforms. We derive the effective Hamiltonian for the spin
dynamics of the junction's zero modes and calculate their quantum phases. We
find a sweet spot in parameter space where the spin is fully in-plane and
radially polarized for a given junction polarity. This represents a shortcut to
singular spin configurations that would otherwise require spin-orbit coupling
strengths beyond experimental reach.",2303.05833v2
2003-10-28,Phonon-induced decay of the electron spin in quantum dots,"We study spin relaxation and decoherence in a
  GaAs quantum dot due to spin-orbit interaction. We derive an effective
Hamiltonian which couples the electron spin to phonons or any other fluctuation
of the dot potential. We show that the spin decoherence time $T_2$ is as large
as the spin relaxation time $T_1$, under realistic conditions. For the
Dresselhaus and Rashba spin-orbit couplings, we find that, in leading order,
the effective magnetic field can have only fluctuations transverse to the
applied magnetic field. As a result, $T_2=2T_1$ for arbitrarily large Zeeman
splittings, in contrast to the naively expected case
  $T_2\ll T_1$. We show that the spin decay is drastically suppressed for
certain magnetic field directions and values of the
  Rashba coupling constant. Finally, for the spin coupling to acoustic phonons,
we show that
  $T_2=2T_1$ for all spin-orbit mechanisms in leading order in the
electron-phonon interaction.",0310655v1
2012-02-07,Prediction of Giant Spin Motive Force due to Rashba Spin-Orbit Coupling,"Magnetization dynamics in a ferromagnet can induce a spin-dependent electric
field through spin motive force. Spin current generated by the spin-dependent
electric field can in turn modify the magnetization dynamics through
spin-transfer torque. While this feedback effect is usually weak and thus
ignored, we predict that in Rashba spin-orbit coupling systems with large
Rashba parameter $\alpha_{\rm R}$, the coupling generates the spin-dependent
electric field [$\pm(\alpha_{\rm R}m_e/e\hbar) (\vhat{z}\times \partial
\vec{m}/\partial t)]$, which can be large enough to modify the magnetization
dynamics significantly. This effect should be relevant for device applications
based on ultrathin magnetic layers with strong Rashba spin-orbit coupling.",1202.1406v2
2015-03-11,Spin-wave-induced spin torque in Rashba spin-orbit coupling system,"We study the effects of Rashba spin-orbit coupling on the spin torque induced
by spin waves, which are the plane wave dynamics of magnetization. The spin
torque is derived from linear response theory, and we calculate the dynamic
spin torque by considering the impurity-ladder-sum vertex corrections. This
dynamic spin torque is divided into three terms: a damping term, a $distortion$
term, and a correction term for the equation of motion. The $distorting$ torque
describes a phenomenon unique to the Rashba spin-orbit coupling system, where
the distorted motion of magnetization precession is subjected to the
anisotropic force from the Rashba coupling. The oscillation mode of the
precession exhibits an elliptical trajectory, and the ellipticity depends on
the strength of the nesting effects, which could be reduced by decreasing the
electron lifetime.",1503.03171v2
2016-12-13,Spin precession and spin waves in a chiral electron gas: beyond Larmor's theorem,"Larmor's theorem holds for magnetic systems that are invariant under spin
rotation. In the presence of spin-orbit coupling this invariance is lost and
Larmor's theorem is broken: for systems of interacting electrons, this gives
rise to a subtle interplay between the spin-orbit coupling acting on individual
single-particle states and Coulomb many-body effects. We consider a
quasi-two-dimensional, partially spin-polarized electron gas in a semiconductor
quantum well in the presence of Rashba and Dresselhaus spin-orbit coupling.
Using a linear-response approach based on time-dependent density-functional
theory, we calculate the dispersions of spin-flip waves. We obtain analytic
results for small wave vectors and up to second order in the Rashba and
Dresselhaus coupling strengths $\alpha$ and $\beta$. Comparison with
experimental data from inelastic light scattering allows us to extract $\alpha$
and $\beta$ as well as the spin-wave stiffness very accurately. We find
significant deviations from the local density approximation for spin-dependent
electron systems.",1612.04314v1
2021-03-11,Spin-charge conversion and current vortex in spin-orbit coupled systems,"Using response theory, we calculate the charge-current vortex generated by
spin pumping at a point-like contact in a system with Rashba spin-orbit
coupling. We discuss the spatial profile of the current density for finite
temperature and for the zero-temperature limit. The main observation is that
the Rashba spin precession leads to a charge current that oscillates as a
function of the distance from the spin-pumping source, which is confirmed by
numerical simulations. In our calculations, we consider a Rashba model on a
square lattice, for which we first review the basic properties related to
charge and spin transport. In particular, we define the charge- and
spin-current operators for the tight-binding Hamiltonian as the currents
coupled linearly with the U(1) and SU(2) gauge potentials, respectively. By
analogy to the continuum model, the spin-orbit-coupling Hamiltonian on the
lattice is then introduced as the generator of the spin current.",2103.06540v2
2020-12-12,Dilemma in strongly correlated materials: Hund's metal vs relativistic Mott insulator,"We point out the generic competition between the Hund's coupling and the
spin-orbit coupling in correlated materials, and this competition leads to an
electronic dilemma between the Hund's metal and the relativistic insulators.
Hund's metals refer to the fate of the would-be insulators where the Hund's
coupling suppresses the correlation and drives the systems into correlated
metals. Relativistic Mott insulators refer to the fate of the would-be metals
where the relativistic spin-orbit coupling enhances the correlation and drives
the systems into Mott insulators. These contradictory trends are naturally
present in many correlated materials. We study the competition between Hund's
coupling and spin-orbit coupling in correlated materials and explore the
interplay and the balance from these two contradictory trends. The system can
become a spin-orbit-coupled Hund's metal or a Hund's assisted relativistic Mott
insulator. Our observation could find a broad application and relevance to many
correlated materials with multiple orbitals.",2012.06752v1
2021-03-23,The Onset of Chaos in Permanently Deformed Binaries from Spin-Orbit and Spin-Spin Coupling,"Permanently deformed objects in binary systems can experience complex
rotation evolution, arising from the extensively studied effect of spin-orbit
coupling as well as more nuanced dynamics arising from spin-spin interactions.
The ability of an object to sustain an aspheroidal shape largely determines
whether or not it will exhibit non-trivial rotational behavior. In this work,
we adopt a simplified model of a gravitationally interacting primary and
satellite pair, where each body's quadrupole moment is approximated by two
diametrically opposed point masses. After calculating the net gravitational
torque on the satellite from the primary, and the associated equations of
motion, we employ a Hamiltonian formalism which allows for a perturbative
treatment of the spin-orbit and retrograde and prograde spin-spin coupling
states. By analyzing the resonances individually and collectively, we determine
the criteria for resonance overlap and the onset of chaos, as a function of
orbital and geometric properties of the binary. We extend the 2D planar
geometry to calculate the obliquity evolution, and find that satellites in
spin-spin resonances undergo precession when inclined out of the plane, but do
not tumble. We apply our resonance overlap criteria to the contact binary
system (216) Kleopatra, and find that its satellites, Cleoselene and
Alexhelios, may plausibly be exhibiting chaotic rotational dynamics from the
overlap of the spin-orbit and retrograde spin-spin resonances. While this model
is by construction generalizable to any binary system, it will be particularly
useful to study small bodies in the solar system, whose irregular shapes make
them ideal candidates for exotic rotational states.",2103.12484v1
2011-11-30,Theory of spin-orbit coupling in bilayer graphene,"Theory of spin-orbit coupling in bilayer graphene is presented. The
electronic band structure of the AB bilayer in the presence of spin-orbit
coupling and a transverse electric field is calculated from first-principles
using the linearized augmented plane wave method implemented in the WIEN2k
code. The first-principles results around the K points are fitted to a
tight-binding model. The main conclusion is that the spin-orbit effects in
bilayer graphene derive essentially from the single-layer spin-orbit coupling
which comes almost solely from the d orbitals. The intrinsic spin-orbit
splitting (anticrossing) around the K points is about 24\mu eV for the
low-energy valence and conduction bands, which are closest to the Fermi level,
similarly as in the single layer graphene. An applied transverse electric field
breaks space inversion symmetry and leads to an extrinsic (also called
Bychkov-Rashba) spin-orbit splitting. This splitting is usually linearly
proportional to the electric field. The peculiarity of graphene bilayer is that
the low-energy bands remain split by 24\mu eV independently of the applied
external field. The electric field, instead, opens a semiconducting band gap
separating these low-energy bands. The remaining two high-energy bands are
spin-split in proportion to the electric field; the proportionality coefficient
is given by the second intrinsic spin-orbit coupling, whose value is 20\mu eV.
All the band-structure effects and their spin splittings can be explained by
our tight-binding model, in which the spin-orbit Hamiltonian is derived from
symmetry considerations. The magnitudes of intra- and interlayer
couplings---their values are similar to the single-layer graphene ones---are
determined by fitting to first-principles results.",1111.7223v2
2015-05-12,Spin-orbit interactions of light,"Light carries spin and orbital angular momentum. These dynamical properties
are determined by the polarization and spatial degrees of freedom of light.
Modern nano-optics, photonics, and plasmonics, tend to explore subwavelength
scales and additional degrees of freedom of structured, i.e.,
spatially-inhomogeneous, optical fields. In such fields, spin and orbital
properties become strongly coupled with each other. We overview the fundamental
origins and important applications of the main spin-orbit interaction phenomena
in optics. These include: spin-Hall effects in inhomogeneous media and at
optical interfaces, spin-dependent effects in nonparaxial (focused or
scattered) fields, spin-controlled shaping of light using anisotropic
structured interfaces (metasurfaces), as well as robust spin-directional
coupling via evanescent near fields. We show that spin-orbit interactions are
inherent in all basic optical processes, and they play a crucial role at
subwavelength scales and structures in modern optics.",1505.02864v2
2020-09-14,Many-Body Phases of a Planar Bose-Einstein Condensate with Cavity-Induced Spin-Orbit Coupling,"We explore the many-body phases of a two-dimensional Bose-Einstein condensate
with cavity-mediated dynamic spin-orbit coupling. By the help of two transverse
non-interfering, counterpropagating pump lasers and a single standing-wave
cavity mode, two degenerate Zeeman sub-levels of the quantum gas are Raman
coupled in a double-$\Lambda$-configuration. Beyond a critical pump strength
the cavity mode is populated via coherent superradiant Raman scattering from
the two pump lasers, leading to the appearance of a dynamical spin-orbit
coupling for the atoms. We identify three quantum phases with distinct atomic
and photonic properties: the normal ``homogeneous'' phase, the superradiant
``spin-helix'' phase, and the superradiant ``supersolid spin-density-wave''
phase. The latter exhibits an emergent periodic atomic density distribution
with an orthorhombic centered rectangular-lattice structure due to the
interplay between the coherent photon scattering into the resonator and the
collision-induced momentum coupling. The transverse lattice spacing of the
emergent crystal is set by the dynamic spin-orbit coupling.",2009.06475v1
2006-04-01,Doping dependence of spin and orbital correlations in layered manganites,"We investigate the interplay between spin and orbital correlations in
monolayer and bilayer manganites using an effective spin-orbital t-J model
which treats explicitly the e_g orbital degrees of freedom coupled to classical
t_{2g} spins. Using finite clusters with periodic boundary conditions, the
orbital many-body problem is solved by exact diagonalization, either by
optimizing spin configuration at zero temperature, or by using classical
Monte-Carlo for the spin subsystem at finite temperature. In undoped
two-dimensional clusters, a complementary behavior of orbital and spin
correlations is found - the ferromagnetic spin order coexists with alternating
orbital order, while the antiferromagnetic spin order, triggered by t_{2g} spin
superexchange, coexists with ferro-orbital order. With finite crystal field
term, we introduce a realistic model for La_{1-x}Sr_{1+x}MnO_4, describing a
gradual change from predominantly out-of-plane 3z^2-r^2 to in-plane x^2-y^2
orbital occupation under increasing doping. The present electronic model is
sufficient to explain the stability of the CE phase in monolayer manganites at
doping x=0.5, and also yields the C-type antiferromagnetic phase found in
Nd_{1-x}Sr_{1+x}MnO_4 at high doping. Also in bilayer manganites magnetic
phases and the accompanying orbital order change with increasing doping. Here
the model predicts C-AF and G-AF phases at high doping x>0.75, as found
experimentally in La_{2-2x}Sr_{1+2x}Mn_2O_7.",0604014v1
2009-05-14,Orbitally induced string formation in the spin-orbital polarons,"We study the spectral function of a single hole doped into the (a,b) plane of
the Mott insulator LaVO$_3$, with antiferromagnetic (AF) spin order of S=1
spins accompanied by alternating orbital (AO) order of active
$\{d_{yz},d_{zx}\}$ orbitals. Starting from the respective t-J model, with
spin-orbital superexchange and effective three-site hopping terms, we derive
the polaron Hamiltonian and show that a hole couples simultaneously to the
collective excitations of the AF/AO phase, magnons and orbitons. Next, we solve
this polaron problem using the self-consistent Born approximation and find a
stable quasiparticle solution -- a spin-orbital polaron. We show that the
spin-orbital polaron resembles the orbital polaron found in $e_g$ systems, as
e.g. in K$_2$CuF$_4$ or (to some extent) in LaMnO$_3$, and that the hole may be
seen as confined in a string-like potential. However, the spins also play a
crucial role in the formation of this polaron -- we explain how the orbital
degrees of freedom: (i) confine the spin dynamics acting on the hole as the
classical Ising spins, and (ii) generate the string potential which is of the
joint spin-orbital character. Finally, we discuss the impact of the results
presented here on the understanding of the phase diagrams of the lightly doped
cubic vanadates.",0905.2380v1
2007-05-14,Cooling Torsional Nanomechanical Vibration by Spin-Orbit Interactions,"We propose and study a spin-orbit interaction based mechanism to actively
cool down the torsional vibration of a nanomechanical resonator made by
semiconductor materials. We show that the spin-orbit interactions of electrons
can induce a coherent coupling between the electron spins and the torsional
modes of nanomechanical vibration. This coherent coupling leads to an active
cooling for the torsional modes via the dynamical thermalization of the
resonator and the spin ensemble.",0705.1964v1
2009-02-19,Spin-orbit induced non-collinear spin structure in deposited transition metal clusters,"The influence of the spin-orbit coupling on the magnetic structure of
deposited transition metal nanostructure systems has been studied by fully
relativistic electronic structure calculations. The interplay of exchange
coupling and magnetic anisotropy was monitored by studying the corresponding
magnetic torque calculated within ab-initio and model approaches. It is found
that a spin-orbit induced Dzyaloshinski-Moriya interaction can stabilise a
non-collinear spin structure even if there is a pronounced isotropic
ferromagnetic exchange interaction between the magnetic atoms.",0902.3336v1
2013-08-25,Entanglement of spin-orbit qubits induced by Coulomb interaction,"Spin-orbit qubit (SOQ) is the dressed spin by the orbital degree of freedom
through a strong spin-orbit coupling. We show that Coulomb interaction between
two electrons in quantum dots located separately in two nanowires can
efficiently induce quantum entanglement between two SOQs. The physical
mechanism to achieve such quantum entanglement is based on the feasibility of
the SOQ responding to the external electric field via an intrinsic electric
dipole spin resonance.",1308.5387v1
2009-01-19,Spin-orbit effect on electron-electron interaction and fine structure of electron complexes in quantum dots,"Spin-orbit effects on electron-electron interaction are studied
theoretically. The corrections to the Coulomb interaction of quantum well
electrons induced by the spin-orbit coupling are derived. The developed theory
is applied to calculate the energy spectrum fine structure of an electron pair
triplet states localized in small lateral disk-shaped quantum dots. We show
that the spin degeneracy of a triplet state is completely lifted in anisotropic
quantum dots. Isotropic quantum dots also demonstrate peculiar fine structure
of triplet states caused by the spin-orbit interaction.",0901.2893v2
2020-02-24,Phase diagram of the interacting persistent spin-helix state,"We study the phase diagram of the interacting two-dimensional electron gas
(2DEG) with equal Rashba and Dresselhaus spin-orbit coupling, which for weak
coupling gives rise to the well-known persistent spin-helix phase. We construct
the full Hartree-Fock phase diagram using a classical Monte-Carlo method
analogous to that used in Phys.Rev.B 96, 235425 (2017). For the 2DEG with only
Rashba spin-orbit coupling, it was found that at intermediate values of the
Wigner-Seitz radius rs the system is characterized by a single Fermi surface
with an out-of-plane spin polarization, while at slightly larger values of rs
it undergoes a transition to a state with a shifted Fermi surface and an
in-plane spin polarization. The various phase transitions are first-order, and
this shows up in discontinuities in the conductivity and the appearance of
anisotropic resistance in the in-plane polarized phase. In this work, we show
that the out-of-plane spin-polarized region shrinks as the strength of the
Dresselhaus spin-orbit interaction increases, and entirely vanishes when the
Rashba and Dresselhaus spin-orbit coupling strengths are equal. At this point,
the system can be mapped onto a 2DEG without spin-orbit coupling, and this
transformation reveals the existence of an in-plane spin-polarized phase with a
single, displaced Fermi surface beyond rs > 2.01. This is confirmed by
classical Monte-Carlo simulations. We discuss experimental observation and
useful applications of the novel phase, as well as caveats of using the
classical Monte-Carlo method.",2002.10036v1
2007-04-02,Reexamination of spin decoherence in semiconductor quantum dots from equation-of-motion approach,"The longitudinal and transversal spin decoherence times, $T_1$ and $T_2$, in
semiconductor quantum dots are investigated from equation-of-motion approach
for different magnetic fields, quantum dot sizes, and temperatures. Various
mechanisms, such as the hyperfine interaction with the surrounding nuclei, the
Dresselhaus spin-orbit coupling together with the electron--bulk-phonon
interaction, the $g$-factor fluctuations, the direct spin-phonon coupling due
to the phonon-induced strain, and the coaction of the
electron--bulk/surface-phonon interaction together with the hyperfine
interaction are included. The relative contributions from these spin
decoherence mechanisms are compared in detail. In our calculation, the
spin-orbit coupling is included in each mechanism and is shown to have marked
effect in most cases. The equation-of-motion approach is applied in studying
both the spin relaxation time $T_1$ and the spin dephasing time $T_2$, either
in Markovian or in non-Markovian limit. When many levels are involved at finite
temperature, we demonstrate how to obtain the spin relaxation time from the
Fermi Golden rule in the limit of weak spin-orbit coupling. However, at high
temperature and/or for large spin-orbit coupling, one has to use the
equation-of-motion approach when many levels are involved. Moreover, spin
dephasing can be much more efficient than spin relaxation at high temperature,
though the two only differs by a factor of two at low temperature.",0704.0148v5
2016-11-20,"The influence of Coulomb Correlations and Spin-Orbit Coupling in the electronic structure of double perovskites Sr$_2$XOsO$_6$ (X$=$Sc, Mg)","We investigate the antiferromagnetic insulating state of the recently
discovered double perovskites Sr$_2$XOsO$_6$ (X$=$Sc, Mg) by using ab-initio
calculations (based on Density Functional Theory and Dynamical Mean-Field
Theory) to elucidate the interplay between electronic correlations and
spin-orbit coupling. The structural details of Sr$_2$XOsO$_6$ (X$=$Sc, Mg)
induce band narrowing effects which enhance local electronic correlations. The
half-filled $5d^3$ orbitals of Os in Sr$_2$ScOsO$_6$ fall into a magnetically
ordered correlated regime, which is slightly affected and reduced by the
spin-orbit coupling. The electronic configuration $5d^2$ of Os in
Sr$_2$MgOsO$_6$ responses differently to electronic correlations promoting a
less localized state than Sr$_2$ScOsO$_6$ at the same strength of electronic
interactions. We find that the inclusion of spin-orbit coupling drives
Sr$_2$MgOsO$_6$ toward insulating behaviour and promotes a large tendency in
formation of orbital magnetization antiparallel to the spin moment. The
formation of the AFM state is linked to the evidence of correlated Hubbard
bands in the paramagnetic solution of Sr$_2$XOsO$_6$ (X$=$Sc, Mg).",1611.06482v1
2016-05-10,Electric-field-induced interferometric resonance of a one-dimensional spin-orbit-coupled electron,"We consider a one-dimensional spin-orbit-coupled nanowire quantum dot, driven
by external electric and magnetic fields, and theoretically formulate an
electric mechanism to interfere its electron orbits. Owing to the existence of
spin-orbit coupling and a pulsed electric field, different spin-orbit states
are shown to interfere with each other, generating intriguing
interference-resonant patterns. We also reveal that an in-plane magnetic field
does not affect the strength interval of any neighboring resonant peaks, but
contributes a weak shift of each peak, which is sensitive to the direction of
the magnetic field. We find that this proposed external-field-controlled scheme
should be regarded as a new type of quantum-dot-based interferometry. Finally,
this interferometry has an important application in precisely measuring
relative experimental parameters, such as the Rashba and Dresselhaus
spin-orbit-coupling strengths, as well as the Lande-g factor.",1605.02871v3
2016-05-20,The effect of gravitational spin-orbit coupling on the circular photon orbit in the Schwarzschild geometry,"The (1, 0)+(0, 1) representation of the group SL(2, C) provides a
six-component spinor equivalent to the electromagnetic field tensor. By means
of the (1, 0)+(0, 1) description, one can treat the photon field in curved
spacetime via spin connection and the tetrad formalism, which is of great
advantage to study the gravitational spin-orbit coupling of photons. Once the
gravitational spin-orbit coupling is taken into account, the traditional radius
of the circular photon orbit in the Schwarzschild geometry should be replaced
with two different radiuses corresponding to the photons with the helicities of
+1 and -1, respectively. Owing to the splitting of energy levels induced by the
spin-orbit coupling, photons (from Hawking radiations, say) escaping from a
Schwarzschild black hole are partially polarized, provided that their initial
velocities possess nonzero tangential components.",1605.06427v1
2016-01-11,Theory of electronic and spin-orbit proximity effects in graphene on Cu(111),"We study orbital and spin-orbit proximity effects in graphene adsorbed to the
Cu(111) surface by means of density functional theory (DFT). The proximity
effects are caused mainly by the hybridization of graphene $\pi$ and copper d
orbitals. Our electronic structure calculations agree well with the
experimentally observed features. We carry out a graphene-Cu(111) distance
dependent study to obtain proximity orbital and spin-orbit coupling parameters,
by fitting the DFT results to a robust low energy model Hamiltonian. We find a
strong distance dependence of the Rashba and intrinsic proximity induced
spin-orbit coupling parameters, which are in the meV and hundreds of $\mu$eV
range, respectively, for experimentally relevant distances. The Dirac spectrum
of graphene also exhibits a proximity orbital gap, of about 20 meV.
Furthermore, we find a band inversion within the graphene states accompanied by
a reordering of spin and pseudospin states, when graphene is pressed towards
copper.",1601.02445v1
2018-05-15,Spin-orbit effects on the spin and pseudospin polarization in ac-driven silicene,"We study the pseudospin and spin dynamical effects in single-layer silicene
due to a perpendicular electric field periodically driven and its interplay
with the intrinsic and extrinsic (Rashba) spin-orbit interaction. We find that
the spin nonconserving processes of the real spin of the quasiparticles in
silicene, -- induced by the rather weak spin-orbit mechanisms --, manifest
themselves as shifts of the resonances of its quasienergy spectrum in the low
coupling regime to the driving field. We show that there is an interesting
cooperative effect among the, in principle, competing Rashba and intrinsic
spin-orbit contributions. This is explicitly illustrated by exact and
approximated analytical solutions of the dynamical equations. In addition, we
show that a finite Rashba spin-orbit interaction is indeed necessary in order
to achieve a nonvanishing spin polarization. As additional feature, trivial and
nontrivial topological phases might be distinguished from each other as fast or
slow dynamical fluctuations of the spin polarization. We mention the possible
experimental detection schemes of our theoretical results and their relevance
in new practical implementation of periodically driven interactions in silicene
physics and related two-dimensional systems.",1805.05833v1
2020-06-14,Spin-orbit torque generated by amorphous Fe$_{x}$Si$_{1-x}$,"While tremendous work has gone into spin-orbit torque and spin current
generation, charge-to-spin conversion efficiency remains weak in silicon to
date, generally stemming from the low spin-orbit coupling (low atomic number,
Z) and lack of bulk lattice inversion symmetry breaking. Here we report the
observation of spin-orbit torque in an amorphous, non-ferromagnetic
Fe$_{x}$Si$_{1-x}$ / cobalt bilayer at room temperature, using spin torque
ferromagnetic resonance and harmonic Hall measurements. Both techniques provide
a minimum spin torque efficiency of about 3 %, comparable to prototypical heavy
metals such as Pt or Ta. According to the conventional theory of the spin Hall
effect, a spin current in an amorphous material is not expected to have any
substantial contribution from the electronic bandstructure. This, combined with
the fact that Fe$_{x}$Si$_{1-x}$ does not contain any high-Z element, paves a
new avenue for understanding the underlying physics of spin-orbit interaction
and opens up a new class of material systems - silicides - that is directly
compatible with complementary metal-oxide-semiconductor (CMOS) processes for
integrated spintronics applications.",2006.07786v1
2024-03-22,Orbital-doublet-driven even spin Chern insulators,"Quantum spin Hall insulators hosting edge spin currents hold great potential
for low-power spintronic devices. In this work, we present a universal approach
to achieve a high and near-quantized spin Hall conductance plateau within a
sizable bulk gap. Using a nonmagnetic four-band model Hamiltonian, we
demonstrate that an even spin Chern (ESC) insulator can be accessed by tuning
the sign of spin-orbit coupling (SOC) within a crystal symmetry-enforced
orbital doublet. With the assistance of a high spin Chern number of $C_{S}=2$
and spin $U$(1) quasi-symmetry, this orbital-doublet-driven ESC phase is
endowed with the near-double-quantized spin Hall conductance. We identify 12
crystallographic point groups supporting such a sign-tunable SOC. Furthermore,
we apply our theory to realistic examples, and show the phase transition from a
trivial insulator governed by positive SOC in RuI$_{3}$ monolayer to an ESC
insulator dominated by negative SOC in RuBr$_{3}$ monolayer. This
orbital-doublet-driven ESC insulator, RuBr$_{3}$, showcases nontrivial
characteristics including helical edge states, near-double-quantized spin Hall
conductance, and robust corner states. Our work provides new pathways in the
pursuit of the long-sought quantum spin Hall insulators.",2403.14893v1
2008-03-17,Energy levels of a two-dimensional hydrogen atom with spin-orbit Rashba interaction,"Electronic bound states around charged impurities in two-dimensional systems
with structural inversion asymmetry can be described in terms of a
two-dimensional hydrogen atom in the presence of a Rashba spin-orbit
interaction. Here, the energy levels of the bound electron are evaluated
numerically as a function of the spin-orbit interaction, and analytic
expressions for the weak and strong spin-orbit coupling limits are compared
with the numerical results. It is found that, besides the level splitting due
to the lack of inversion symmetry, the energy levels are lowered for
sufficiently strong spin-orbit coupling, indicating that the electron gets more
tightly bound to the ion as the spin-orbit interaction increases. Similarities
and differences with respect to the two-dimensional Fr\""ohlich polaron with
Rashba coupling are discussed.",0803.2416v1
2014-01-08,Signatures of spin-orbit coupling in scanning gate conductance images of electron flow from quantum point contacts,"Electron flow through a quantum point contact in presence of spin-orbit
coupling is investigated theoretically in the context of the scanning gate
microscopy (SGM) conductance mapping. Although in the absence of the floating
gate the spin-orbit coupling does not significantly alter the conductance, we
find that the angular dependence of the SGM images of the electron flow at the
conductance plateaux is substantially altered as the spin-orbit interaction
mixes the orbital modes that enter the quantum point contact. The radial
interference fringes that are obtained in the SGM maps at conductance steps are
essentially preserved by the spin-orbit interaction as backscattering by the
tip preserves the electron spin although the effects of the mode mixing are
visible.",1401.1707v2
2015-01-23,General framework for transport in spin-orbit-coupled superconducting heterostructures: Nonuniform spin-orbit coupling and spin-orbit-active interfaces,"Electronic spin-orbit coupling (SOC) is essential for various newly
discovered phenomena in condensed-matter systems. In particular,
one-dimensional topological heterostructures with SOC have been widely
investigated in both theory and experiment for their distinct transport
signatures indicating the presence of emergent Majorana fermions. However, a
general framework for the SOC-affected transport in superconducting
heterostructures, especially with the consideration of interfacial effects, has
not been developed even regardless of the topological aspects. We hereby
provide one for an effectively one-dimensional superconductor-normal
heterostructure with nonuniform magnitude and direction of both Rashba and
Dresselhaus SOC as well as a spin-orbit-active interface. We extend the
Blonder-Tinkham-Klapwijk treatment to analyze the current-voltage relation and
obtain a rich range of transport behaviors. Our work provides a basis for
characterizing fundamental physics arising from spin-orbit interactions in
heterostructures and its implications for topological systems, spintronic
applications, and a whole variety of experimental setups.",1501.05699v2
2023-07-09,Enhancement and anisotropy of electron Lande factor due to spin-orbit interaction in semiconductor nanowires,"We investigate the effective Lande factor in semiconductor nanowires with
strong Rashba spin-orbit coupling. Using the $\mathbf{k}\cdot\mathbf{p}$ theory
and the envelope function approach we derive a conduction band Hamiltonian
where the tensor $g^*$ is explicitly related to the spin-orbit coupling
constant $\alpha_R$. Our model includes orbital effects from the Rashba
spin-orbit term, leading to a significant enhancement of the effective Lande
factor which is naturally anisotropic. For nanowires based on the low-gap, high
spin-orbit coupled material InSb, we investigate the anisotropy of the
effective Lande factor with respect to the magnetic field direction, exposing a
twofold symmetry for the bottom gate architecture. The anisotropy results from
the competition between the localization of the envelope function and the spin
polarization of the electronic state, both determined by the magnetic field
direction.",2307.04265v2
2024-03-22,Robust realization of electrically tunable spin-orbit locked vortex pairs in polariton condensates at room temperature,"Coupling of orbital and spin degrees of freedom gives rise to intriguing
physical phenomena in bosonic condensates, such as formation of stripe phases
and domains with vortex arrays. However, the robust locking of spin and orbital
degrees of freedom of nonlinear topological objects such as vortices in bosonic
condensates at room temperature remains challenging. In the present work, we
realize a non-equilibrium room-temperature condensate in a liquid crystal (LC)
planar photonic microcavity with the perovskite CsPbBr3 as optically active
material. We use the interplay of TE-TM mode splitting and Rashba-Dresselhaus
spin-orbit coupling (RDSOC) to realize electrically tunable polariton vortex
pairs with locked spin and orbital angular momentum. Our results are robust
against sample imperfections and pave the way to investigate coupling and
locking of vortex orbital and spin degrees of freedom in a quantum fluid of
light at room temperature, offering potential for generation of complex states
of light for optical information processing with optoelectronic chips.",2403.15133v1
2013-06-19,"Asymmetric Ferromagnetic Resonance, Universal Walker Breakdown, and Counterflow Domain Wall Motion in the Presence of Multiple Spin-Orbit Torques","We study the motion of several types of domain wall profiles in spin-orbit
coupled magnetic nanowires and also the influence of spin-orbit interaction on
the ferromagnetic resonance of uniform magnetic films. We extend previous
studies by fully considering not only the field-like contribution from the
spin-orbit torque, but also the recently derived Slonczewski-like spin-orbit
torque. We show that the latter interaction affects both the domain wall
velocity and the Walker breakdown threshold non-trivially, which suggests that
it should be accounted in experimental data analysis. We find that the presence
of multiple spin-orbit torques may render the Walker breakdown to be universal
in the sense that the threshold is completely independent on the
material-dependent Gilbert damping, non-adiabaticity, and the chirality of the
domain wall. We also find that domain wall motion against the current injection
is sustained in the presence of multiple spin-orbit torques and that the wall
profile will determine the qualitative influence of these different types of
torques (e.g. field-like and Slonczewski-like). In addition, we consider a
uniform ferromagnetic layer under a current bias, and find that the resonance
frequency becomes asymmetric against the current direction in the presence of
Slonczewski-like spin-orbit coupling. This is in contrast with those cases
where such an interaction is absent, where the frequency is found to be
symmetric with respect to the current direction. This finding shows that
spin-orbit interactions may offer additional control over pumped and absorbed
energy in a ferromagnetic resonance setup by manipulating the injected current
direction.",1306.4680v1
2017-12-08,Spin Hall and spin swapping torques in diffusive ferromagnets,"A complete set of the generalized drift-diffusion equations for a coupled
charge and spin dynamics in ferromagnets in the presence of extrinsic
spin-orbit coupling is derived from the quantum kinetic approach, covering
major transport phenomena, such as the spin and anomalous Hall effects, spin
swapping, spin precession and relaxation processes. We argue that the spin
swapping effect in ferromagnets is enhanced due to spin polarization, while the
overall spin texture induced by the interplay of spin-orbital and spin
precessional effects displays a complex spatial dependence that can be
exploited to generate torques and nucleate/propagate domain walls in
centrosymmetric geometries without use of external polarizers, as opposed to
the conventional understanding of spin-orbit mediated torques.",1712.03009v1
2021-09-05,Electric field effect on electron gas spins in two-dimensional magnets with strong spin-orbit coupling,"The recent rise of material platforms combining magnetism and
two-dimensionality of mobile carriers reveals a diverse spectrum of spin-orbit
phenomena and stimulates its ongoing theoretical discussions. In this work we
use the density matrix approach to provide a unified description of subtle
microscopic effects governing the electron gas spin behavior in the clean limit
upon electric perturbations in two-dimensional magnets with strong spin-orbit
coupling. We discuss that an inhomogeneity of electrostatic potential generally
leads to the electron gas spin tilting with the subsequent formation of
equilibrium skyrmion-like spin textures and demonstrate that several
microscopic mechanisms of 2DEG spin response are equally important for this
effect. We analyze the dynamics of 2DEG spin upon an oscillating electric field
with a specific focus on the emergent electric dipole spin resonance. We
address the resonant enhancement of magneto-optical phenomena from the spin
precession equation perspective and discuss it in terms of the resonant spin
generation. We also clarify the connection of both static and dynamic spin
phenomena arising in response to a scalar perturbation with the electronic band
Berry curvature.",2109.02151v1
2021-10-05,Effective potentials in a rotating spin-orbit-coupled spin-1 spinor condensate,"We theoretically study the stationary-state vortex lattice configurations of
rotating spin-orbit- and coherently-coupled spin-1 Bose-Einstein condensates
trapped in quasi-two-dimensional harmonic potentials. The combined effects of
rotation, spin-orbit and coherent couplings are analyzed systematically from
the single-particle perspective. Through the single-particle Hamiltonian, which
is exactly solvable for one-dimensional coupling, under specific coupling and
rotation strengths, we illustrate that a boson in these rotating spin-orbit-
and coherently-coupled condensates are subjected to effective toroidal,
symmetric double-well, or asymmetric double-well potentials. In the presence of
mean-field interactions, using the coupled Gross-Pitaevskii formalism at
moderate to high rotation frequencies, the analytically obtained effective
potential minima and the numerically obtained coarse-grained density maxima
position are in excellent agreement. On rapid rotation, we further find that
the spin expectation per particle of an antiferromagnetic spin-1 Bose-Einstein
condensate approaches unity indicating a similarity in the response with
ferromagnetic spin-orbit-coupled condensates.",2110.02185v3
2013-12-11,Spin-orbit coupling and the static polarizability of single-wall carbon nanotubes,"We calculate the static longitudinal polarizability of single-wall carbon
nanotubes in the long wavelength limit taking into account spin-orbit effects.
We use a four-orbital orthogonal tight-binding formalism to describe the
electronic states and the random phase approximation to calculate the
dielectric function. We study the role of both the Rashba as well as the
intrinsic spin-orbit interactions on the longitudinal dielectric response, i.e.
when the probing electric field is parallel to the nanotube axis. The
spin-orbit interaction modifies the nanotube electronic band dispersions, which
may especially result in a small gap opening in otherwise metallic tubes. The
bandgap size and state features, the result of competition between Rashba and
intrinsic spin-orbit interactions, result in drastic changes in the
longitudinal static polarizability of the system. We discuss results for
different nanotube types, and the dependence on nanotube radius and spin-orbit
couplings.",1312.3155v1
2015-10-19,Role of local geometry in spin and orbital structure of transition metal compounds,"We analyze the role of local geometry in the spin and orbital interaction in
transition metal compounds with orbital degeneracy. We stress that the tendency
observed for the most studied case (transition metals in O$_6$ octahedra with
one common oxygen -- common corner of neighboring octahedra and with $\sim
180^{\circ}$ metal--oxygen--metal bonds), that ferro-orbital ordering renders
antiferro-spin coupling, and, {\it vice versa}, antiferro-orbitals give
ferro-spin ordering, is not valid in general case, in particular for octahedra
with common edge and with $\sim 90^{\circ}$ M--O--M bonds. Special attention is
paid to the ``third case'', neighboring octahedra with common face (three
common oxygens) -- the case practically not considered until now, although
there are many real systems with this geometry. Interestingly enough, the
spin--orbital exchange in this case turns out to be to be simpler and more
symmetric than in the first two cases. We also consider, which form the
effective exchange takes for different geometries in case of strong spin--orbit
coupling.",1510.05371v1
2003-05-28,Spin splitting and precession in quantum dots with spin-orbit coupling: the role of spatial deformation,"Extending a previous work on spin precession in GaAs/AlGaAs quantum dots with
spin-orbit coupling, we study the role of deformation in the external
confinement. Small elliptical deformations are enough to alter the precessional
characteristics at low magnetic fields. We obtain approximate expressions for
the modified $g$ factor including weak Rashba and Dresselhaus spin-orbit terms.
For more intense couplings numerical calculations are performed. We also study
the influence of the magnetic field orientation on the spin splitting and the
related anisotropy of the $g$ factor. Using realistic spin-orbit strengths our
model calculations can reproduce the experimental spin-splittings reported by
Hanson et al. (cond-mat/0303139) for a one-electron dot. For dots containing
more electrons, Coulomb interaction effects are estimated within the
local-spin-density approximation, showing that many features of the
non-iteracting system are qualitatively preserved.",0305648v1
2011-11-04,Spin Currents Induced by Nonuniform Rashba-Type Spin-Orbit Field,"We study the spin relaxation torque in nonmagnetic or ferromagnetic metals
with nonuniform spin-orbit coupling within the Keldysh Green's function
formalism. In non-magnet, the relaxation torque is shown to arise when the
spin-orbit coupling is not uniform. In the absence of an external field, the
spin current induced by the relaxation torque is proportional to the vector
chirality of Rashba-type spin-orbit field (RSOF). In the presence of an
external field, on the other hand, spin relaxation torque arises from the
coupling of the external field and vector chirality of RSOF. Our result
indicates that spin-sink or source effects are controlled by designing RSOF in
junctions.",1111.1197v1
2019-10-06,Spin-orbit coupling in the presence of strong atomic correlations,"We explore the influence of contact interactions on a synthetically
spin-orbit coupled system of two ultracold trapped atoms. Even though the
system we consider is bosonic, we show that a regime exists in which the
competition between the contact and spin-orbit interactions results in the
emergence of a ground state that contains a significant contribution from the
anti-symmetric spin state. This ground state is unique to few-particle systems
and does not exist in the mean-field regime. The transition to this state is
signalled by an inversion in the average momentum from being dominated by
centre-of-mass momentum to relative momentum and also affects the global
entanglement shared between the real- and pseudo-spin spaces. Indeed,
competition between the interactions can also result in avoided crossings in
the groundstate which further enhances these correlations. However, we find
that correlations shared between the pseudo-spin states are strongly depressed
due to the spin-orbit coupling and therefore the system does not contain
spin-spin entanglement.",1910.02399v2
2009-06-09,Quantum criticality near the Stoner transition in a two-dot with spin-orbit coupling,"We study a system of two tunnel-coupled quantum dots, with the first dot
containing interacting electrons (described by the Universal Hamiltonian) not
subject to spin-orbit coupling, whereas the second contains non-interacting
electrons subject to spin-orbit coupling. We focus on describing the behavior
of the system near the Stoner transition. Close to the critical point quantum
fluctuations become important and the system enters a quantum critical regime.
The large-$N$ approximation allows us to calculate physical quantitites
reliably even in this strongly fluctuating regime. In particular, we find a
scaling function to describe the crossover of the quasiparticle decay rate
between the renormalized Fermi liquid regime and the quantum critical regime.",0906.1838v1
2010-04-23,Spin-orbit coupling and perpendicular Zeeman field for fermionic cold atoms: observation of the intrinsic anomalous Hall effect,"We propose a scheme for generating Rashba spin-orbit coupling and
perpendicular Zeeman field simultaneously for cold fermionic atoms in a
harmonic trap through the coupling between atoms and laser fields. The
realization of Rashba spin-orbit coupling and perpendicular Zeeman field
provides opportunities for exploring many topological phenomena using cold
fermionic atoms. We focus on the intrinsic anomalous Hall effect and show that
it may be observed through the response of atomic density to a rotation of the
harmonic trap.",1004.4231v3
2011-12-27,Synthetic 3D Spin-Orbit Coupling,"We describe a method for creating a three-dimensional analogue to Rashba
spin-orbit coupling in systems of ultracold atoms. This laser induced coupling
uses Raman transitions to link four internal atomic states with a tetrahedral
geometry, and gives rise to a Dirac point that is robust against environmental
perturbations. We present an exact result showing that such a spin-orbit
coupling in a fermionic system always rise to a molecular bound state.",1112.6022v2
2012-07-23,Synthetic spin-orbit coupling in ultracold $Λ$-type atoms,"We consider the simulation of non-abelian gauge potentials in ultracold atom
systems with atom-field interaction in the $\Lambda$ configuration where two
internal states of an atom are coupled to a third common one with a detuning.
We find the simulated non-abelian gauge potentials can have the same structures
as those simulated in the tripod configuration if we parameterize Rabi
frequencies properly, which means we can design spin-orbit coupling simulation
schemes based on those proposed in the tripod configuration. We show the
simulated spin-orbit coupling in the $\Lambda$ configuration can only be of a
form similar to $p_{x}\sigma_{y}$ even when the Rabi frequencies are not much
smaller than the detuning.",1207.5369v1
2013-06-28,Quantum quasicrystals of spin-orbit coupled dipolar bosons,"We study quasi-two-dimensional dipolar Bose gases in which the bosons
experience a Rashba spin-orbit coupling. We show that the degenerate dispersion
minimum due to the spin-orbit coupling, combined with the long-range dipolar
interaction, can stabilize a number of quantum crystalline and quasicrystalline
ground states. Coupling the bosons to a fermionic species can further stabilize
these phases. We estimate that the crystalline and quasicrystalline phases
should be detectable in realistic dipolar condensates, e.g., dysprosium, and
discuss their symmetries and excitations.",1307.0002v2
2014-12-12,Tunable Spin-Orbit Coupling via Strong Driving in Ultracold Atom Systems,"Spin-orbit coupling (SOC) is an essential ingredient in topological
materials, conventional and quantum-gas based alike.~Engineered spin-orbit
coupling in ultracold atom systems --unique in their experimental control and
measurement opportunities-- provides a major opportunity to investigate and
understand topological phenomena.~Here we experimentally demonstrate and
theoretically analyze a technique for controlling SOC in a two component
Bose-Einstein condensate using amplitude-modulated Raman coupling.",1412.4064v1
2016-06-24,Topological quantum phase transition driven by anisotropic spin-orbit coupling in trinuclear organometallic coordination crystals,"We show how quasi-one-dimensional correlated insulating states arise at
two-thirds filling in organometallic multinuclear coordination complexes
described by layered decorated honeycomb lattices. The interplay of spin-orbit
coupling and electronic correlations leads to pseudospin-1 moments arranged in
weakly coupled chains with highly anisotropic exchange and a large trigonal
splitting. This leads to a quantum phase transition from a Haldane phase to a
topologically trivial phase as the relative strength of the spin-orbit coupling
increases.",1606.07691v1
2014-12-08,Theory of Weyl orbital semimetals and predictions of several materials classes,"Graphene, topological insulators, and Weyl semimetals are three widely
studied materials classes which possess Dirac or Weyl cones arising from either
sublattice symmetry or spin-orbit coupling. In this work, we present a theory
of a new class of bulk Dirac and Weyl cones, dubbed Weyl orbital semimetals,
where the orbital polarization and texture inversion between two electronic
states at discrete momenta lend itself into protected Dirac or Weyl cones
without spin-orbit coupling. We also predict several families of Weyl orbital
semimetals including V$_3$S$_4$, NiTi3S6, BLi, and PbO$_2$ via first-principle
band structure calculations. We find that the highest Fermi velocity predicted
in some of these materials is even larger than that of the existing Dirac
materials. The synthesis of Weyl orbital semimetals will not only expand the
territory of Dirac materials beyond the quintessential spin-orbit coupled
systems and hexagonal lattice to the entire periodic table, but it may also
open up new possibilities for orbital controlled electronics or `orbitronics'.",1412.2607v2
2011-03-16,Spin relaxation in Rashba rings,"Spin relaxation dynamics in rings with Rashba spin-orbit coupling is
investigated using spin kinetic equation. We find that the spin relaxation in
rings occurs toward a persistent spin configuration whose final shape depends
on the initial spin polarization profile. As an example, it is shown that a
homogeneous parallel to the ring axis spin polarization transforms into a
persistent crown-like spin structure. It is demonstrated that the ring geometry
introduces a geometrical contribution to the spin relaxation rate speeding up
the transient dynamics. Moreover, we identify several persistent spin
configurations as well as calculate the Green function of spin kinetic
equation.",1103.3231v1
2015-06-03,"Synchronization of spin-transfer torque oscillators by spin pumping, inverse spin Hall, and spin Hall effects","We have proposed a method to synchronize multiple spin-transfer torque
oscillators based on spin pumping, inverse spin Hall, and spin Hall effects.
The proposed oscillator system consists of a series of nano-magnets in junction
with a normal metal with high spin-orbit coupling, and an accumulative feedback
loop. We conduct simulations to demonstrate the effect of modulated charge
currents in the normal metal due to spin pumping from each nano-magnet. We show
that the interplay between the spin Hall effect and inverse spin Hall effect
results in synchronization of the nano-magnets.",1506.01357v1
2015-08-07,Rashbon bound states associated with a spherical spin-orbit coupling in an ultracold Fermi gas with an $s$-wave interaction,"We investigate the formation of rashbon bound states and strong-coupling
effects in an ultracold Fermi gas with a spherical spin-orbit interaction,
$H_{\rm so}=\lambda{\bf p}\cdot{\bf \sigma}$ (where ${\bf
\sigma}=(\sigma_x,\sigma_y,\sigma_z)$ are Pauli matrices). Extending the
strong-coupling theory developed by Nozi\`eres and Schmitt-Rink (NSR) to
include this spin-orbit coupling, we determine the superfluid phase transition
temperature $T_{\rm c}$, as functions of the strength of a pairing interaction
$U_s$, as well as the spin-orbit coupling strength $\lambda$. Evaluating poles
of the NSR particle-particle scattering matrix describing fluctuations in the
Cooper channel, we clarify the region where rashbon bound states dominate the
superfluid phase transition in the $U_{s}$-$\lambda$ phase diagram. Since the
antisymmetric spin-orbit interaction $H_{\rm so}$ breaks the inversion symmetry
of the system, rashbon bound states naturally have, not only a spin-singlet and
even-parity symmetry, but also a spin-triplet and odd-parity symmetry. Thus,
our results would be also useful for the study of this parity mixing effect in
the BCS-BEC crossover regime of a spin-orbit coupled Fermi gas.",1508.01673v1
2014-09-03,Theory of coupled spin-charge transport due to spin-orbit interaction in inhomogeneous two-dimensional electron liquids,"Spin-orbit interactions in two-dimensional electron liquids are responsible
for many interesting transport phenomena in which particle currents are
converted to spin polarizations and spin currents and viceversa. Prime examples
are the spin Hall effect, the Edelstein effect, and their inverses. By similar
mechanisms it is also possible to partially convert an optically induced
electron-hole density wave to a spin density wave and viceversa. In this paper
we present a unified theoretical treatment of these effects based on quantum
kinetic equations that include not only the intrinsic spin-orbit coupling from
the band structure of the host material, but also the spin-orbit coupling due
to an external electric field and a random impurity potential. The
drift-diffusion equations we derive in the diffusive regime are applicable to a
broad variety of experimental situations, both homogeneous and non-homogeneous,
and include on equal footing ""skew scattering"" and ""side-jump"" from
electron-impurity collisions. As a demonstration of the strength and usefulness
of the theory we apply it to the study of several effects of current
experimental interest: the inverse Edelstein effect, the spin-current swapping
effect, and the partial conversion of an electron-hole density wave to a spin
density wave in a two-dimensional electron gas with Rashba and Dresselhaus
spin-orbit couplings, subject to an electric field.",1409.1202v1
2023-01-24,Longitudinal coupling between electrically driven spin-qubits and a resonator,"At the core of the semiconducting spin qubits success is the ability to
manipulate them electrically, enabled by the spin-orbit interactions. However,
most implementations require external magnetic fields to define the spin qubit,
which in turn activate various charge noise mechanisms. Here we study spin
qubits confined in quantum dots at zero magnetic fields, that are driven
periodically by electrical fields and are coupled to a microwave resonator.
Using Floquet theory, we identify a well-defined Floquet spin-qubit originating
from the lowest degenerate spin states in the absence of driving. We find both
transverse and longitudinal couplings between the Floquet spin qubit and the
resonator, which can be selectively activated by modifying the driving
frequency. We show how these couplings can facilitate fast qubit readout and
the implementation of a two-qubit CPHASE gate. Finally, we use adiabatic
perturbation theory to demonstrate that the spin-photon couplings originate
from the non-Abelian geometry of states endowed by the spin-orbit interactions,
rendering these findings general and applicable to a wide range of solid-state
spin qubits.",2301.10163v1
2019-05-08,Study of edge states and conductivity in spin-orbit coupled bilayer graphene,"We present an elaborate and systematic study of the conductance properties of
a zigzag bilayer graphene nanoribbon modeled by a Kane-Mele (KM) Hamiltonian.
The interplay of the Rashba and the intrinsic spin-orbit couplings with the
edge states, electronic band structures, charge and spin transport are explored
in details. We have analytically derived the conditions for the edge states for
a bilayer KM nanoribbon and show how these modes decay for lattice sites inside
the bulk. It is particularly interesting to note that for a finite-size ribbon
an even number of zigzag ribbon hosts a finite energy gap at the Dirac points,
while the odd ones do not. This asymmetry is present both in presence and
absence of a bias voltage that may exist between the layers. The interlayer
Rashba spin-orbit coupling, along with the intralayer intrinsic spin-orbit and
intralayer Rashba spin-orbit couplings seem to destroy the quantum spin Hall
(QSH) phase where the QSH phase is identified by the presence of a conductance
plateau (of magnitude 4e/h) in the vicinity of zero Fermi energy. The plateau
is sensitive to the values of the spin-orbit coupling parameters. Further, the
spin polarized conductance data reveal that a bilayer KM ribbon is found to be
more efficient for spintronic applications compared to a monolayer graphene.
Finally, a quick check with experiments is done via computing the effective
mass of electrons.",1905.03167v1
2005-12-29,Theory of phonon-induced spin relaxation in laterally coupled quantum dots,"Phonon-induced spin relaxation in coupled lateral quantum dots in the
presence of spin-orbit coupling is calculated. The calculation for single dots
is consistent with experiment. Spin relaxation in double dots at useful
interdot couplings is dominated by spin hot spots that are strongly
anisotropic. Spin hot spots are ineffective for a diagonal crystallographic
orientation of the dots with a transverse in-plane field. This geometry is
proposed for spin-based quantum information processing.",0512713v2
2023-02-06,Probing type-II Ising pairing using the spin-mixing parameter,"The immunity of Ising superconductors to external magnetic fields originates
from a spin locking of the paired electrons to an intrinsic Zeeman-like field.
The spin-momentum locking in non-centrosymmetric crystalline materials leads to
type-I Ising pairing in which the direction of the intrinsic field can be
deduced from the spin expectation values. Conversely, in centrosymmetric
crystals the electron spins locked to the orbitals can form Ising type-II pairs
consisting of spin-orbit split doublets. Due to time-reversal symmetry, the
doublets are spin degenerate, making it difficult to read the spin polarization
of bands and the direction of spin-orbit fields. Here we present an efficient
approach to determine the direction of the intrinsic field using the
spin-mixing parameter $b^2$. Using first principles calculations based on the
density functional theory, we study monolayer transition metal dichalcogenide
superconductors PdTe$_2$, NbTe$_2$, and TiSe$_2$ with the 1T structure. We
calculate $b^2$ for individual Fermi pockets and provide a general picture of
possible Ising type-II pairing within the full Brillouin zone. In order to
complement our first principles results, we use group theory to provide a
detailed picture of spin-orbit coupling and spin mixing in the relevant bands
forming Fermi pockets. We demonstrate that contrary to the anticipated effects
of spin-orbit locking, not every spin-orbit split spin doublet actively
participates in Ising pairing. Finally, by connecting the spin-mixing parameter
$b^2$ with the intrinsic out-of-plane Zeeman field we estimate the upper
in-plane critical magnetic field.",2302.02699v2
2005-08-19,Influence of spin-orbit interaction on quantum cascade transitions,"We have investigated the effect of spin-orbit (SO) coupling on the emission
spectra of a quantum cascade laser. In an externally applied magnetic field
parallel to the electron plane, the SO coupling would result in a double-peak
structure of the optical spectra. This structure can be observed within some
interval of magnetic fields and only for diagonal optical transitions when the
SO coupling is different in different quantum wells.",0508473v1
2014-03-10,Orbit Maneuver of Spinning Tether via Tidal Force,"Recently, the spinning tethered system is regarded as a typical and
fundamental space structure attracting great interest of the aerospace
engineers, and has been discussed primarily for specific space missions in past
decades, including on-orbit capture and propellantless orbit transfer etc. The
present work studies the dynamical behaviours of a fast spinning tethered
binary system under central gravitational field, and derives principles of the
basic laws of orbital maneuver. Considering the characteristics of coupled
librational and orbital motions, an averaging method is introduced to deal with
the slow-fast system equation, thus a definite equivalent model is derived. The
general orbit motion is completely determined analytically, including the orbit
geometry, periodicity, conversations and moving region etc. Since the
possibility of orbit control using tether reaction has been proved by previous
studies, special attention is paid to the transportation mode of angular
momentum and mechanical energy between the orbit and libration. The effect of
tether length change on the orbit shape is verified both in the averaged model
and original model. The results show the orbit angular momentum and mechanical
energy can be controlled independently, and the operating principles of tether
reactions are derived for special modification of orbit shape.",1403.2221v1
2023-09-26,Orbital Pumping by Magnetization Dynamics in Ferromagnets,"We show that dynamics of the magnetization in ferromagnets can pump the
orbital angular momentum, which we denote by orbital pumping. This is the
reciprocal phenomenon to the orbital torque that induces magnetization dynamics
by the orbital angular momentum in non-equilibrium. The orbital pumping is
analogous to the spin pumping established in spintronics but requires the
spin-orbit coupling for the orbital angular momentum to interact with the
magnetization. We develop a formalism that describes the generation of the
orbital angular momentum by magnetization dynamics within the adiabatic
perturbation theory. Based on this, we perform first-principles calculation of
the orbital pumping in prototypical $3d$ ferromagnets, Fe, Co, and Ni. The
results show that the ratio between the orbital pumping and the spin pumping
ranges from 5 to 15 percents, being smallest in Fe and largest in Ni. This
implies that ferromagnetic Ni is a good candidate for measuring the orbital
pumping. Implications of our results on experiments are also discussed.",2309.14817v2
2014-04-04,Observation of inverse spin Hall effect in bismuth selenide,"Bismuth Selenide (Bi2Se3) is a topological insulator exhibiting helical spin
polarization and strong spin-orbit coupling. The spin-orbit coupling links the
charge current to spin current via the spin Hall effect (SHE). We demonstrate a
Bi2Se3 spin detector by injecting the pure spin current from a magnetic
permalloy layer to a Bi2Se3 thin film and detect the inverse SHE in Bi2Se3. The
spin Hall angle of Bi2Se3 is found to be 0.0093 and the spin diffusion length
in Bi2Se3 to be 6.2 nm at room temperature. Our results suggest that
topological insulators with strong spin-orbit coupling can be used in
functional spintronic devices.",1404.1146v2
2014-09-05,Room temperature spin thermoelectrics in metallic films,"Considering metallic films at room temperature, we present the first
theoretical study of the spin Nernst and thermal Edelstein effects which takes
into account dynamical spin-orbit coupling, i.e., direct spin-orbit coupling
with the vibrating lattice (phonons) and impurities. This gives rise to two
novel processes, namely a dynamical Elliott-Yafet spin relaxation and a
dynamical side-jump mechanism. Both are the high-temperature counterparts of
the well-known $T = 0$ Elliott-Yafet and side-jump, central to the current
understanding of the spin Hall, spin Nernst and Edelstein effects at low $T$.
We consider the experimentally relevant regime $T > T_D$, with $T_D$ the Debye
temperature, as the latter is lower than room temperature in transition metals
such as Pt, Au and Ta typically employed in spin injection/extraction
experiments. We show that the interplay between intrinsic (Bychkov-Rashba type)
and extrinsic (dynamical) spin-orbit coupling yields a nonlinear $T$-
dependence of the spin Nernst and spin Hall conductivities.",1409.1809v1
2018-05-28,A spin dephasing mechanism mediated by the interplay between the spin-orbit coupling and the asymmetrical confining potential in semiconductor quantum dot,"Understanding the spin dephasing mechanism is of fundamental importance in
all potential applications of the spin qubit. Here we demonstrate a spin
dephasing mechanism in semiconductor quantum dot due to the $1/f$ charge noise.
The spin-charge interaction is mediated by the interplay between the spin-orbit
coupling and the asymmetrical quantum dot confining potential. The dephasing
rate is proportional to both the strength of the spin-orbit coupling and the
degree of the asymmetry of the confining potential. For parameters typical of
the InSb, InAs, and GaAs quantum dots with a moderate well-height $V_{0}=10$
meV, we find the spin dephasing times are ${\rm T}^{*}_{2}=7$ $\mu$s, $275$
$\mu$s, and $55$ ms, respectively. In particular, the spin dephasing can be
enhanced by lowering the well-height. When the well-height is as small as
$V_{0}=5$ meV, the spin depahsing times in the InSb, InAs, and GaAs quantum
dots are decreased to ${\rm T}^{*}_{2}=0.38$ $\mu$s, $18$ $\mu$s, and $9$ ms,
respectively.",1805.10792v2
2019-12-10,Spin-relaxation times exceeding seconds for color centers with strong spin-orbit coupling in SiC,"Spin-active color centers in solids show good performance for quantum
technologies. Several transition-metal defects in SiC offer compatibility with
telecom and semiconductor industries. However, whether their strong spin-orbit
coupling degrades their spin lifetimes is not clear. We show that a combination
of a crystal-field with axial symmetry and spin-orbit coupling leads to a
suppression of spin-lattice and spin-spin interactions, resulting in remarkably
slow spin relaxation. Our optical measurements on an ensemble of Mo impurities
in SiC show a spin lifetime $T_1$ of $2,4$ s at $2$ K.",1912.04612v1
2023-09-26,Spin-photon interaction in a nanowire quantum dot with asymmetrical confining potential,"The electron (hole) spin-photon interaction is studied in an asymmetrical
InSb (Ge) nanowire quantum dot. The spin-orbit coupling in the quantum dot
mediates not only a transverse spin-photon interaction, but also a longitudinal
spin-photon interaction due to the asymmetry of the confining potential. Both
the transverse and the longitudinal spin-photon interactions have non-monotonic
dependence on the spin-orbit coupling. For realistic spin-orbit coupling in the
quantum dot, the longitudinal spin-photon interaction is much (at least one
order) smaller than the transverse spin-photon interaction. The order of the
transverse spin-photon interaction is about 1 nm in terms of length $|z_{eg}|$,
or 0.1 MHz in terms of frequency $eE_{0}|z_{eg}|/h$ for a moderate cavity
electric field strength $E_{0}=0.4$ V/m.",2309.14693v2
2024-04-08,Quantum Spin Liquids in Weak Mott Insulators with a Spin-Orbit Coupling,"The weak Mott insulating regime of the triangular lattice Hubbard model
exhibits a rich magnetic phase diagram as a result of the ring exchange
interaction in the spin Hamiltonian. These phases include the Kalmeyer-Laughlin
type chiral spin liquid (CSL) and a valence bond solid (VBS). A natural
question arises regarding the robustness of these phases in the presence of a
weak spin-orbit coupling (SOC). In this study, we derive the effective spin
model for the spin-orbit coupled triangular lattice Hubbard model in the weak
Mott insulting regime, including all SOC-mediated spin-bilinears and
ring-exchange interactions. We then construct a simplified spin model keeping
only the most relevant SOC-mediated spin interactions. Using infinite density
matrix renormalization group (iDMRG) we show that the CSL and VBS phases of the
triangular lattice Hubbard model can be stabilized in the presence of a weak
SOC. The stabilization results from a compensation between the
Dzyaloshinskii-Moriya interaction and a SOC-mediated ring exchange interaction.
We also provide additional qualitative arguments to intuitively understand the
compensation mechanism in the iDMRG quantum phase diagrams. This mechanism for
stabilization can potentially be useful for the experimental realization of
quantum spin liquids.",2404.05806v1
2018-02-01,Phase separation and hidden vortices induced by spin-orbit coupling in spin-1 Bose-Einstein condensates,"We investigate phase separation and hidden vortices in spin-orbit coupled
ferromagnetic BoseEinstein condensates with rotation and Rabi coupling. The
hidden vortices are invisible in density distribution but are visible in phase
distribution, which can carry angular momentum like the ordinary quantized
vortices. In the absence of the rotation, we observe the phase separation
induced by the spin-orbit coupling and determine the entire phase diagram of
the existence of phase separation. For the rotation case, in addition to the
phase separation, we demonstrate particularly that the spin-orbit coupling can
result in the hidden vortices and hidden vortex-antivortex pairs. The
corresponding entire phase diagrams are determined, depending on the interplay
of the spin-orbit coupling strength, the rotation frequency, and Rabi
frequency, which reveals the critical condition of the occurrence of the hidden
vortices and vortex-antivortex pairs. The hidden vortices here are proved to be
long-lived in the time scale of experiment by the dynamic analysis. These
findings not only provide a clear illustration of the phase separation in
spin-orbit coupled spinor Bose-Einstein condensates, but also open a new
direction for investigating the hidden vortices in high-spin quantum system.",1802.00138v1
2006-09-19,Large spin-orbit effects in small quantum dots,"We consider small ballistic quantum dots weakly coupled to the leads in the
chaotic regime and look for significant spin-orbit effects. We find that these
effects can become quite prominent in the vicinity of degeneracies of many-body
energies. We illustrate the idea by considering a case where the intrinsic
exchange term -JS^2 brings singlet and triplet many-body states near each
other, while an externally tunable Zeeman term then closes the gap between the
singlet and the one of the triplet states (with spin projection parallel the
external field). Near this degeneracy, the spin-orbit coupling leads to a
striking temperature dependence of the conductance, with observable effects of
order unity at temperatures lower than the strength of the spin-orbit coupling.
Under favorable circumstances, spelled out in the paper, these order unity
effects in the conductance persist to temperatures much higher than the
spin-orbit coupling strength. Our conclusions are unaffected by the presence of
non-universal perturbations. We suggest a class of experiments to explore this
regime.",0609460v1
2016-10-05,Effect of disorder on superconductivity and Rashba spin-orbit coupling in LaAlO3/SrTiO3 interfaces,"A rather unique feature of the two-dimensional electron gas (2-DEG) formed at
the interface between the two insulators LaAlO3 and SrTiO3 is to host both
gate-tunable superconductivity and strong spin-orbit coupling. In the present
work, we use the disorder generated by Cr substitution of Al atoms in LaAlO3 as
a tool to explore the nature of superconductivity and spin-orbit coupling in
these interfaces. A reduction of the superconducting Tc is observed with Cr
doping consistent with an increase of electron-electron interaction in presence
of disorder. In addition, the evolution of spin-orbit coupling with gate
voltage and Cr doping suggests a D'Yakonov-Perel mechanism of spin relaxation
in the presence of a Rashba-type spin-orbit interaction.",1610.01380v1
2016-12-09,Spin-orbit coupling in {Mo$_3$S$_7$(dmit)$_3$},"Spin-orbit coupling in crystals is known to lead to unusual direction
dependent exchange interactions, however understanding of the consequeces of
such effects in molecular crystals is incomplete. Here we perform four
component relativistic density functional theory computations on the
multi-nuclear molecular crystal {Mo$_3$S$_7$(dmit)$_3$} and show that both
intra- and inter-molecular spin-orbit coupling are significant. We determine a
long-range relativistic single electron Hamiltonian from first principles by
constructing Wannier spin-orbitals. We analyse the various contributions
through the lens of group theory. Intermolecular spin-orbit couplings like
those found here are known to lead to quantum spin-Hall and topological
insulator phases on the 2D lattice formed by the tight-binding model predicted
for a single layer of {Mo$_3$S$_7$(dmit)$_3$}.",1612.02929v1
2017-11-15,Kondo temperature of Anderson impurity model in a quantum wire with spin-orbit coupling,"We use two different methods, the Hirsch-Fye quantum Monte Carlo simulation
and the slave-boson mean field analysis to estimate the effect of spin-orbit
coupling on the Kondo temperature in a quantum wire. In quantum Monte Carlo
simulation, we calculate the product of spin susceptibility and temperature for
different spin-orbit couplings and impurity energies. The variation of the
Kondo temperature is estimated via the low temperature universal curves. In the
mean field analysis, the Kondo temperature is estimated as the condensation
temperature of slave-boson. Both the two methods demonstrate that the Kondo
temperature is almost a linear function of the spin-orbit energy, and that the
Kondo temperature is suppressed by the spin-orbit coupling. Our results are
dramatically different from those given by the perturbative renormalization
group analysis.",1711.05505v1
2015-12-09,Spectrum of a family of spin-orbit coupled Hamiltonians with singular perturbation,"The present study is the first such attempt to examine rigorously and
comprehensively the spectral properties of a three-dimensional ultracold atom
when both the spin-orbit interaction and the Zeeman field are taken into
account. The model operator is the Rashba spin-orbit coupled operator in
dimension three. The self-adjoint extensions are constructed using the theory
of singular perturbations, where regularized rank two perturbations describe
spin-dependent contact interactions. The spectrum of self-adjoint extensions is
investigated in detail laying emphasis on the effects due to spin-orbit
coupling. When the spin-orbit-coupling strength is small enough, the
asymptotics of eigenvalues is obtained. The conditions for the existence of
eigenvalues above the threshold are discussed in particular.",1512.02833v1
2023-05-18,Proximity spin-orbit coupling in an armchair carbon nanotube on monolayer bismuthene,"We study spin-orbit proximity effects in a hybrid heterostructure build of a
one-dimensional (1D) armchair carbon nanotube and two-dimensional (2D) buckled
monolayer bismuthene. We show, by performing first-principles calculations,
that Dirac electrons in the nanotube exhibit large spin-orbit coupling due to a
close vicinity of bismuthene. The calculated low-energy band structures of the
proximized nanotube display a strong dependence on the position of the nanotube
on the substrate, similar to twist-angle dependence found in 2D
heterostructures. Based on the first-principles results, we formulate an
effective low-energy Hamiltonian of the nanotube and identify key interactions
governing the proximity spin-orbit coupling. The proximity-induced spin
splitting of Dirac cone bands is in meV range, confirming an efficient transfer
of spin-orbit coupling from bismuthene to the nanotube.",2305.10902v1
2005-05-16,Magnetic flux induced spin polarization in semiconductor multichannel rings with Rashba spin orbit coupling,"We show that a finite magnetic flux threading a multichannel semiconductor
ring induces spin accumulation at the borders of the sample when the Rashba
spin-orbit interaction is taken into account even in the absence of external
electric fields.",0505394v1
2013-03-21,Anisotropic quantum transport in monolayer graphene in the presence of Rashba spin-orbit coupling,"We have studied spin-depend electron tunnelling through the Rashba barrier in
a monolayer graphene lattice. The transfer matrix method, have been employed to
obtain the spin dependent transport properties of the chiral particles. It is
shown that graphene sheets in presence of Rashba spin-orbit barrier will act as
an electron spin- inverter.",1303.5209v1
2012-09-03,Dynamical Jahn-Teller Effect in Spin-Orbital Coupled System,"Dynamical Jahn-Teller (DJT) effect in a spin-orbital coupled system on a
honeycomb lattice is examined, motivated from recently observed spin-liquid
behavior in Ba$_3$CuSb$_2$O$_9$. An effective vibronic Hamiltonian, where the
superexchange interaction and the DJT effect are taken into account, is
derived. We find that the DJT effect induces a spin-orbital resonant state
where local spin-singlet states and parallel orbital configurations are
entangled with each other. This spin-orbital resonant state is realized in
between an orbital ordered state, where spin-singlet pairs are localized, and
an antiferromagnetic ordered state. Based on the theoretical results, a
possible scenario for Ba$_3$CuSb$_2$O$_9$ is proposed.",1209.0239v2
2003-12-24,Dynamic generation of spin orbit coupling,"Spin-orbit coupling plays an important role in determining the properties of
solids, and is crucial for spintronics device applications. Conventional
spin-orbit coupling arises microscopically from relativistic effects described
by the Dirac equation, and is described as a single particle band effect. In
this work, we propose a new mechanism in which spin-orbit coupling can be
generated dynamically in strongly correlated, non-relativistic systems as the
result of fermi surface instabilities in higher angular momentum channels.
Various known forms of spin-orbit couplings can emerge in these new phases, and
their magnitudes can be continuously tuned by temperature or other quantum
parameters.",0312632v4
2014-03-06,The evolution of magnetic structure driven by a synthetic spin-orbit coupling in two-component Bose-Hubbard model,"We study the evolution of magnetic structure driven by a synthetic spin-orbit
coupling in a one-dimensional two-component Bose-Hubbard model. In addition to
the Mott insulator-superfluid transition, we found in Mott insulator phases a
transition from a gapped ferromagnetic phase to a gapless chiral phase by
increasing the strength of spin-orbit coupling. Further increasing the
spin-orbit coupling drives a transition from the gapless chiral phase to a
gapped antiferromagnetic phase. These magnetic structures persist in superfluid
phases. In particular, in the chiral Mott insulator and chiral superfluid
phases, incommensurability is observed in characteristic correlation functions.
These unconventional Mott insulator phase and superfluid phase demonstrate the
novel effects arising from the competition between the kinetic energy and the
spin-orbit coupling.",1403.1316v2
2017-01-07,Chiral Supersolid in Spin-Orbit-Coupled Bose Gases with Soft-Core Long-Range Interactions,"Chirality represents a kind of symmetry breaking characterized by the
noncoincidence of an object with its mirror image and has been attracting
intense attention in a broad range of scientific areas. The recent realization
of spin-orbit coupling in ultracold atomic gases provides a new perspective to
study quantum states with chirality. In this Letter, we demonstrate that the
combined effects of spin-orbit coupling and interatomic soft-core long-range
interaction can induce an exotic supersolid phase in which the chiral symmetry
is broken with spontaneous emergence of circulating particle current. This
implies that a finite angular momentum can be generated with neither rotation
nor effective magnetic field. The direction of the angular momentum can be
altered by adjusting the strength of spin-orbit coupling or interatomic
interaction. The predicted chiral supersolid phase can be experimentally
observed in Rydberg-dressed Bose-Einstein condensates with spin-orbit coupling.",1701.01869v4
2007-03-22,Electron-phonon effects on spin-orbit split bands of two dimensional systems,"The electronic self-energy is studied for a two dimensional electron gas
coupled to a spin-orbit Rashba field and interacting with dispersionless
phonons. For the case of a momentum independent electron-phonon coupling
(Holstein model) we solve numerically the self-consistent non-crossing
approximation for the self-energy and calculate the electron mass enhancement
$m^*/m$ and the spectral properties. We find that, even for nominal weak
electron-phonon interaction, for strong spin-orbit couplings the electrons
behave as effectively strongly coupled to the phonons. We interpret this result
by a topological change of the Fermi surface occurring at sufficiently strong
spin-orbit coupling, which induces a square-root divergence in the electronic
density of states at low energies. We provide results for $m^*/m$ and for the
density of states of the interacting electrons for several values of the
electron filling and of the spin-orbit interaction.",0703584v2
2014-04-18,"Topological phases, topological flat bands, and topological excitations in a one-dimensional dimerized lattice with spin-orbit coupling","The Su-Schrieffer-Heeger (SSH) model describes a one-dimensional $Z_{2}$
topological insulator, which has two topological distinct phases corresponding
to two different dimerizations. When spin-orbit coupling is introduced into the
SSH model, we find the structure of the Bloch bands can be greatly changed, and
most interestingly, a new topological phase with single zero-energy bound state
which exhibits non-Abelian statistics at each end emerges, which suggests that
a new topological invariant is needed to fully classify all phases. In a
comparatively large range of parameters, we find that spin-orbit coupling
induces completely flat band with nontrivial topology. For the case with
non-uniform dimerizaton, we find that spin-orbit coupling changes the
symmetrical structure of topological excitations known as solitons and
antisolitons and when spin-orbit coupling is strong enough to induce a
topological phase transition, the whole system is topologically nontrivial but
with the disappearance of solitons and antisolitons, consequently, the system
is a real topological insulator with well-protected end states.",1404.4681v1
2016-01-31,Dirac monopoles with polar-core vortex induced by spin-orbit coupling in spinor Bose-Einstein condensates,"We report Dirac monopoles with polar-core vortex induced by spin-orbit
coupling in ferromagnetic Bose-Einstein condensates, which are attached to two
nodal vortex lines along the vertical axis. These monopoles are more stable in
the time scale of experiment and can be detected through directly imaging
vortex lines. When the strength of spin-orbit coupling increases, Dirac
monopoles with vortex can be transformed into those with square lattice. In the
presence of spin-orbit coupling, increasing the strength of interaction can
induce a cyclic phase transition from Dirac monopoles with polar-core vortex to
those with Mermin-Ho vortex. The spin-orbit coupled Bose-Einstein condensates
not only provide a new unique platform for investigating exotic monopoles and
relevant phase transitions, but also can preserve stable monopoles after a
quadrupole field is turned off.",1602.00189v2
2019-05-21,Induced spin-orbit coupling in twisted graphene-TMDC heterobilayers: twistronics meets spintronics,"We propose an interband tunneling picture to explain and predict the
interlayer twist angle dependence of the induced spin-orbit coupling in
heterostructures of graphene and monolayer transition metal dichalcogenides
(TMDCs). We obtain a compact analytic formula for the induced valley Zeeman and
Rashba spin-orbit coupling in terms of the TMDC band structure parameters and
interlayer tunneling matrix elements. We parametrize the tunneling matrix
elements with few parameters, which in our formalism are independent of the
twist angle between the layers. We estimate the value of the tunneling
parameters from existing DFT calculations at zero twist angle and we use them
to predict the induced spin-orbit coupling at non-zero angles. Provided that
the energy of the Dirac point of graphene is close to the TMDC conduction band,
we expect a sharp increase of the induced spin-orbit coupling around a twist
angle of 18 degrees.",1905.08688v1
2015-12-14,Anderson Localization in Degenerate Spin-Orbit Coupled Fermi Gases with Disorder,"Competition between superconductivity and disorder plays an essential role in
understanding the metal-insulator transition. Based on the Bogoliubov-de Gennes
equation, we studied an s-wave superconductor with both spin-orbit coupling and
disorder are presented. With increasing the strength of disorder, the mean
superconducting order parameter will vanish while the energy gap will persist,
which indicates that the system undergoes a transition from a superconducting
state to an insulating state. This can be confirmed by calculating the inverse
participation ratio. We also find that, if the strength of disorder is small,
the superconducting order parameter and the energy gap will decrease if we
increase the strength of spin-orbit coupling and Zeeman field. In the large
disorder limits, increasing the strength of spin-orbit coupling will increase
the mean superconducting order parameter. This phenomenon shows that the system
is more insensitive to disorder if the spin-orbit coupling is presented.
Numerical computing also shows that the whole system breaks up into several
superconducting islands instead of being superconductivity.",1512.04211v2
2018-08-27,Transverse instability of dark solitons in spin-orbit coupled polariton condensates,"We consider dark solitons and their stability in spin-orbit coupled polariton
condensates. The system supports spinor solitons of two types: conventional
(symmetric) dark solitons and asymmetric half-dark solitons. They demonstrate
essentially different behavior upon variation of the strength of spin-orbit
coupling. One-dimensional spin-orbit coupled dark solitons are usually
unstable, while half-dark solitons can be stable. Two-dimensional dark solitons
at early stages of the development of transverse instabilities turn into
asymmetric snaking patterns and later into sets of vortex-antivortex solitons
with notably different shapes. Depending on the sign of spin-orbit coupling two
distinct instability scenarios are possible for such solitons, in which
vortices in one component correspond to vortices or antivortices in other
component. The decay of two-dimensional half-dark solitons results in the
formation of half-vortex chains.",1808.08861v2
2020-05-28,High-harmonic generation in spin-orbit coupled systems,"We study high-harmonic generation in two-dimensional electron systems with
Rashba and Dresselhaus spin-orbit coupling and derive harmonic generation
selection rules with the help of group theory. Based on the bandstructures of
these minimal models and explicit simulations we reveal how the spin-orbit
parameters control the cutoff energy in the high-harmonic spectrum. We also
show that the magnetic field and polarization dependence of this spectrum
provides information on the magnitude of the Rashba and Dresselhaus spin-orbit
coupling parameters. The shape of the Fermi surface can be deduced at least
qualitatively and if only one type of spin-orbit coupling is present, the
coupling strength can be determined.",2005.14293v1
2021-03-17,Spin-orbit coupling within tightly focused circularly polarized spatiotemporal vortex wavepacket,"Spin-orbital coupling and interaction as intrinsic light fields
characteristics have been extensively studied. Previous studies involve the
spin angular momentum (SAM) carried by circular polarization and orbital
angular momentum (OAM) associated with a spiral phase wavefront within the beam
cross section, where both the SAM and OAM are in parallel with the propagation
direction. In this work, we study a new type of spin-orbital coupling between
the longitudinal SAM and the transverse OAM carried by a spatiotemporal optical
vortex (STOV) wavepacket under tight focusing condition. Intricate
spatiotemporal phase singularity structures are formed when a circularly
polarized STOV wavepacket is tightly focused by a high numerical aperture
objective lens. For the transversely polarized components, phase singularity
orientation can be significantly tilted away from the transverse direction
towards the optical axis due to the coupling between longitudinal SAM and
transverse OAM. The connection between the amount of rotation and the temporal
width of the wavepacket is revealed. More interestingly, spatiotemporal phase
singularity structure with a continuous evolution from longitudinal to
transverse orientation through the wavepacket is observed for the
longitudinally polarized component. These exotic spin-orbit coupling phenomena
are expected to render new effects and functions when they are exploited in
light matter interactions.",2103.09467v1
2023-02-22,Compressing the atomic cloud in a matter-wave stripe soliton,"We consider an attractive quasi-one dimensional spin-orbit coupled
Bose-Einstein condensate (SOC BEC) confined in a periodic potential produced by
the combination of linear and nonlinear optical lattices, and study the effects
of squeezing a stripe soliton by varying the inter-atomic interaction in the
nonlinear lattice. It is observed that the nodes on the soliton arising
entirely due to the effect of spin-orbit coupling tend to disappear as we
increase the squeezing effect to finally get a stable fundamental soliton. This
leads us to conclude that external pressure can reduce the effect of spin-orbit
coupling in the SOC BEC and even convert the system to a traditional BEC
without spin-orbit coupling. We make use of an information theoretic measure to
visualize how does the atomic density distribution in the condensate respond to
continual reduction in the spin-orbit coupling effect.",2302.11626v2
2010-08-22,High density limit of the two-dimensional electron liquid with Rashba spin-orbit coupling,"We discuss by analytic means the theory of the high-density limit of the
unpolarized two-dimensional electron liquid in the presence of Rashba or
Dresselhaus spin-orbit coupling. A generalization of the ring-diagram expansion
is performed. We find that in this regime the spin-orbit coupling leads to
small changes of the exchange and correlation energy contributions, while
modifying also, via repopulation of the momentum states, the noninteracting
energy. As a result, the leading corrections to the chirality and total energy
of the system stem from the Hartree-Fock contributions. The final results are
found to be vanishing to lowest order in the spin-orbit coupling, in agreement
with a general property valid to every order in the electron-electron
interaction. We also show that recent quantum Monte Carlo data in the presence
of Rashba spin-orbit coupling are well understood by neglecting corrections to
the exchange-correlation energy, even at low density values.",1008.3729v2
2012-11-16,Topological phases in gated bilayer graphene: Effects of Rashba spin-orbit coupling and exchange field,"We present a systematic study on the influence of Rashba spin-orbit coupling,
interlayer potential difference and exchange field on the topological
properties of bilayer graphene. In the presence of only Rashba spin-orbit
coupling and interlayer potential difference, the band gap opening due to
broken out-of-plane inversion symmetry offers new possibilities of realizing
tunable topological phase transitions by varying an external gate voltage. We
find a two-dimensional $Z_2$ topological insulator phase and a quantum valley
Hall phase in $AB$-stacked bilayer graphene and obtain their effective
low-energy Hamiltonians near the Dirac points. For $AA$ stacking, we do not
find any topological insulator phase in the presence of large Rashba spin-orbit
coupling. When the exchange field is also turned on, the bilayer system
exhibits a rich variety of topological phases including a quantum anomalous
Hall phase, and we obtain the phase diagram as a function of the Rashba
spin-orbit coupling, interlayer potential difference, and exchange field.",1211.3802v1
2014-11-18,A Band of Critical States in Anderson Localization at Strong Magnetic Field with Random Spin-Orbit Scattering,"Anderson localization problem for non-interacting two-dimensional electron
gas subject to strong magnetic field, disordered potential and spin-orbit
coupling is studied numerically on a square lattice. The nature of the
corresponding localization-delocalization transition and the properties of the
pertinent extended states depend on the nature of the spin-orbit coupling
(uniform or fully random). For uniform spin-orbit coupling (such as Rashba
coupling), there is a band of extended states in the center of a Landau band as
in a ""standard"" Anderson metal-insulator transition. However, for fully random
spin-orbit coupling, the familiar pattern of Landau bands disappears. Instead,
there is a central band of critical states with definite fractal structure
separated at two critical energies from two side bands of localized states.
Moreover, finite size scaling analysis suggests that for this novel transition,
on the localized side of a critical energy $E_c$, the localization length
diverges as $\xi(E) \propto\exp(\alpha/\sqrt{|E-E_c|})$, a behavior which,
along with the band of critical states, is reminiscent of a
Berezinskii-Kosterlitz-Thouless transition.",1411.4838v1
2015-09-11,An exactly solvable model for a strongly spin-orbit-coupled nanowire quantum dot,"In the presence of spin-orbit coupling, quantum models for semiconductor
materials are generally not exactly solvable. As a result, understanding of the
strong spin-orbit coupling effects in these systems remains poor. Here we
develop an analytical method to solve the one-dimensional hard-wall quantum dot
problem in the presence of strong spin-orbit coupling and magnetic field, which
allows us to obtain exact eigenenergies and eigenstates of a single electron.
With the help of the exact solution, we demonstrate some unique effects from
the strong spin-orbit coupling in a semiconductor quantum dot, in particular
the anisotropy of the electron g-factor and its tunability.",1509.03402v1
2021-05-06,Spin-orbit coupling driven superfluid states in optical lattices at zero and finite temperatures,"We investigate the quantum phase transitions of a two-dimensional
Bose-Hubbard model in the presence of a Rashba spin-orbit coupling with and
without thermal fluctuations. The interplay of single-particle hopping,
strength of spin-orbit coupling, and interspin interaction leads to superfluid
phases with distinct properties. With interspin interactions weaker than
intraspin interactions, the spin-orbit coupling induces two finite-momentum
superfluid phases. One of them is a phase-twisted superfluid that exists at low
hopping strengths and reduces the domain of insulating phases. At comparatively
higher hopping strengths, there is a transition from the phase-twisted to a
finite momenta stripe superfluid. With interspin interactions stronger than the
intraspin interactions, the system exhibits phase-twisted to ferromagnetic
phase transition. At finite temperatures, the thermal fluctuations destroy the
phase-twisted superfluidity and lead to a wide region of normal-fluid states.
These findings can be observed in recent quantum gas experiments with
spin-orbit coupling in optical lattices.",2105.02747v2
2022-05-24,Universal scattering phase shift in the presence of spin-orbit coupling,"Scattering phase shift, as a key parameter in scattering theory, plays an
important role in characterizing low-energy collisions between ultracold atoms.
In this work, we theoretically investigate the universal low-energy behavior of
the scattering phase shifts for cold atoms in the presence of spin-orbit
coupling. We first construct the asymptotic form of the two-body wave function
when two fermions get as close as the interaction range, and consider
perturbatively the correction of the spin-orbit coupling up to the second
order, in which new scattering parameters are introduced. Then for elastic
collisions, the scattering phase shifts are defined according to the unitary
scattering $S$ matrix. We show how the low-energy behavior of the scattering
phase shifts is modified by these new scattering parameters introduced by
spin-orbit coupling. The universality of the scattering phase shifts is
manifested as the independence of the specific form of the interatomic
potential. The explicit forms of the new scattering parameters are analytically
derived within a model of the spherical-square-well potential. Our method
provides a unified description of the low-energy properties of scattering phase
shifts in the presence of spin-orbit coupling.",2205.11732v1
2007-09-13,Spin polarization in biased Rashba-Dresselhaus two-dimensional electron systems,"Based on spin-charge coupled drift-diffusion equations, which are derived
from kinetic equations for the spin-density matrix in a rigorous manner, the
electric-field-induced nonequilibrium spin polarization is treated for a
two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit
coupling. Most emphasis is put on the consideration of the field-mediated spin
dynamics for a model with equal Rashba and Dresselhaus coupling constants, in
which the spin relaxation is strongly suppressed. Weakly damped
electric-field-induced spin excitations are identified, which remind of
space-charge waves in crystals.",0709.2054v1
2020-11-19,Coupling spins to nanomechanical resonators: Toward quantum spin-mechanics,"Spin-mechanics studies interactions between spin systems and mechanical
vibrations in a nanomechanical resonator and explores their potential
applications in quantum information processing. In this tutorial, we summarize
various types of spin-mechanical resonators and discuss both the
cavity-QED-like and the trapped-ion-like spin-mechanical coupling processes.
The implementation of these processes using negatively charged nitrogen vacancy
and silicon vacancy centers in diamond is reviewed. Prospects for reaching the
full quantum regime of spin-mechanics, in which quantum control can occur at
the level of both single spin and single phonon, are discussed with an emphasis
on the crucial role of strain coupling to the orbital degrees of freedom of the
defect centers.",2011.09990v1
2018-08-29,Spin-orbit effects surfacing on manganites,"Spin-orbit coupling in magnetic systems lacking inversion symmetry can give
rise to non trivial spin textures. Magnetic thin films and heterostructures are
potential candidates for the formation of skyrmions and other non-collinear
spin configurations as inversion symmetry is inherently lost at their surfaces
and interfaces. However, manganites, in spite of their extraordinarily rich
magnetic phase diagram, have not yet been considered of interest within this
context as their spin-orbit coupling is assumed to be negligible. We
demonstrate here, by means of angular dependent X-ray linear dichroism
experiments and theoretical calculations, the existence of a noncollinear
antiferromagnetic ordering at the surface of ferromagnetic
La$_{2/3}$Sr$_{1/3}$MnO$_3$ thin films whose properties can only be explained
by an unexpectedly large enhancement of the spin-orbit interaction. Our results
reveal that spin-orbit coupling, usually assumed to be very small on
manganites, can be significantly enhanced at surfaces and interfaces adding a
new twist to the possible magnetic orders that can arise in electronically
reconstructed systems.",1808.09990v1
2014-05-18,Magnetotransport properties of two-dimensional fermions with $k$-cubic Rashba spin-orbit interaction,"The spin-orbit interaction in heavy hole gas formed at $p$-doped
semiconductor heterojunctions and electron gas at {\mbox SrTiO}${}_3$ surfaces
is cubic in momentum. Here we report magnetotransport properties of k-cubic
Rashba spin-orbit coupled two-dimensional fermionic systems. We study
longitudinal (Shubnikov-de Haas (SdH) oscillations) and Hall component of the
resistivity tensor analytically as well as numerically. The longitudinal
resistivity shows beating pattern due to different SdH oscillation frequencies
$ f_{\pm} $ for spin-up and spin-down fermions. We propose empirical forms of $
f_{\pm} $ as exact expressions are not available, which are being used to find
location of the beating nodes. The beating nodes and the number of oscillations
between any two successive nodes obtained from exact numerical results are in
excellent agreement with those calculated from the proposed empirical form. In
the Hall resistivity, an additional Hall plateau appears in between two
conventional ones as spin-orbit coupling constant increases. The width of this
additional plateau increases with spin-orbit coupling constant.",1405.4533v2
2020-04-21,Surface Rashba-Edelstein Spin-Orbit Torque Revealed by Molecular Self-Assembly,"We report the observation of a spin-orbit torque (SOT) originating from the
surface Rashba-Edelstein effect. We found that the SOT in a prototypical
spin-orbitronic system, a Pt/Co bilayer, can be manipulated by molecular
self-assembly on the Pt surface. This evidences that the Rashba spin-orbit
coupling at the Pt surface generates a sizable SOT, which has been hidden by
the strong bulk and interface spin-orbit coupling. We show that the molecular
tuning of the surface Rashba-Edelstein SOT is consistent with density
functional theory calculations. These results illustrate the crucial role of
the surface spin-orbit coupling in the SOT generation, which alters the
landscape of metallic spin-orbitronic devices.",2004.09852v1
2022-02-24,Proximity spin-orbit and exchange coupling in ABA and ABC trilayer graphene van der Waals heterostructures,"We investigate the proximity spin-orbit and exchange couplings in ABA and ABC
trilayer graphene encapsulated within monolayers of semiconducting
transition-metal dichalcogenides and the ferromagnetic semiconductor
Cr$_2$Ge$_2$Te$_6$. Employing first-principles calculations we obtain the
electronic structures of the multilayer stacks and extract the relevant
proximity-induced orbital and spin interaction parameters by fitting the
low-energy bands to model Hamiltonians. We also demonstrate the tunability of
the proximity effects by a transverse electric field. Using the model
Hamiltonians we also study mixed spin-orbit/exchange coupling encapsulation,
which allows to tailor the spin interactions very efficiently by the applied
field. We also summarize the spin-orbit physics of bare ABA, ABC, and ABB
trilayers, and provide, along with the first-principles results of the
electronic band structures, density of states, spin splittings, and
electric-field tunabilities of the bands, qualitative understanding of the
observed behavior and realistic model parameters as a resource for model
simulations of transport and correlation physics in trilayer graphene.",2202.11922v1
2022-11-08,Spin effects in Spherical Harmonic Modes of Gravitational Waves from Eccentric Compact Binary Inspirals,"We compute the leading and sub-leading spin effects through the second
post-Newtonian order (2PN) in spherical harmonic modes of gravitational
waveforms from inspiralling compact binaries in non-circular orbits with
non-precessing components. The two spin couplings, linear-in-spin (spin-orbit;
SO) and quadratic-in-spin (spin-spin; SS), that appear in 2PN waveforms are
computed with desired accuracy and explicit expressions for relevant modes are
derived. The modes that have spin corrections through 2PN include $(\ell,
|m|)$=$((2,2),\,(2,1),\,(3,3),\,(3,2),\,(3,1),\,(4,3),\,(4,1))$ modes. Closed
form expressions for these modes for compact binaries in general orbits as well
as in elliptical orbits are being provided. While the general orbit results can
be used to study signals from binaries in orbits of arbitrary shape and nature,
elliptical orbit results are applicable to systems with arbitrary
eccentricities. We also express the elliptical orbit results as leading
eccentric corrections to the circular results. Our prescription represents, the
first, fully analytical treatment that combines spins, eccentricity and higher
modes together and completes computation of spin effects through 2PN order.
These should find immediate applications in inspiral-merger-ringdown modelling
for eccentric mergers including the effect of non-precessing spins and higher
modes as well as in parameter estimation analyses employing inspiral waveform.",2211.04155v2
2013-11-24,The Raman dressed spin-1 spin-orbit coupled quantum gas,"The recently realized spin-orbit coupled quantum gases (Y.-J Lin {\it et
al}., Nature 471, 83-86 (2011); P. Wang {\it et al}., PRL 109, 095301 (2012);
L. W. Cheuk {\it et al}., PRL 109, 095302 (2012)) mark a breakthrough in the
cold atom community. In these experiments, two hyperfine states are selected
from a hyperfine manifold to mimic a pseudospin-1/2 spin-orbit coupled system
by the method of Raman dressing, which is applicable to both bosonic and
fermionic gases. In this work, we show that the method used in these
experiments can be generalized to create any large pseudospin spin-orbit
coupled gas if more hyperfine states are coupled equally by the Raman lasers.
As an example, we study in detail a quantum gas with three hyperfine states
coupled by the Raman lasers, and show when the state-dependent energy shifts of
the three states are comparable, triple-degenerate minima will appear at the
bottom of the band dispersions, thus realizing a spin-1 spin-orbit coupled
quantum gas. A novel feature of this three minima regime is that there can be
two different kinds of stripe phases with different wavelengths, which has an
interesting connection to the ferromagnetic and polar phases of spin-1 spinor
BECs without spin-orbit coupling.",1311.6177v2
2019-12-18,Spin-Orbital Textures and Interferometers by Nanoscale Geometric Design of Quantum Rings with Orbital Rashba Coupling,"We derive an effective continuum model for describing the propagation of
electrons in ballistic one-dimensional curved nanostructure which are marked by
a strong interplay of spin-orbital degrees of freedom due to local electronic
states with $d-$orbital symmetry, atomic spin-orbit and orbital Rashba
couplings. We demonstrate how a planar inhomogeneous spatial curvature of the
nanochannel can generate both spin and orbital textures represented through
loops on the corresponding Bloch spheres. In particular, we employ the
paradigmatic case of an elliptically shaped quantum ring to investigate the
role of geometry in steering the electron transport at low energy. We find that
in this regime spin and orbital textures exhibit equal windings around the
radial or out-of-plane directions. Remarkably, the spin and orbital windings
can be not only tuned through a modification of the nanoscale shape, as for the
spin Rashba effect, but also via a change in the electron density by electrical
gating. We show that the presence of textures is related to patterns in the
geometric Aharonov-Anandan phase acquired in a cycle within the quantum ring.
Furthermore, differently from the single band Rashba-coupled nanoring, a
manipulation of the conductance can be achieved by electron density variation
and, indirectly, through changes of the strength of the inversion asymmetric
interactions.",1912.08621v1
2022-12-07,Surfing in the phase space of spin-orbit coupling in binary asteroid systems,"For a satellite with an irregular shape, which is the common shape among
asteroids, the well-known spin-orbit resonance problem could be changed to a
spin-orbit coupling problem since a decoupled model does not accurately capture
the dynamics of the system. In this paper, having provided a definition for
close binary asteroid systems, we explore the structure of the phase space in a
classical Hamiltonian model for spin-orbit coupling in a binary system. To map
out the geography of resonances analytically and the cartography of resonances
numerically, we reformulate a fourth-order gravitational potential function, in
Poincare variables, via Stokes coefficients. For a binary system with a
near-circular orbit, isolating the Hamiltonian near each resonance yields the
pendulum model. Analysis of the results shows the geographical information,
including the location and width of resonances, is modified due to the
prominent role of the semi-major axis in the spin-orbit coupling model but not
structurally altered. However, this resulted in modified Chirikov criterion to
predict onset of large-scale chaos. For a binary system with arbitrary closed
orbit, we thoroughly surf in the phase space via cartography of resonances
created by fast Lyapunov indicator (FLI) maps. The numerical study confirms the
analytical results, provides insight into the spin-orbit coupling, and shows
some bifurcations in the secondary resonances which can occur due to material
transfer. Also, we take the (65803) Didymos binary asteroid as a case to show
analytical and numerical results.",2212.03837v1
2016-08-03,Minimal Ingredients for Orbital Texture Switches at Dirac Points in Strong Spin-Orbit Coupled Materials,"Recent angle resolved photoemission spectroscopy measurements on strong
spin-orbit coupled materials have shown an in-plane orbital texture switch at
their respective Dirac points, regardless of whether they are topological
insulators or ""trivial"" Rashba materials. This feature has also been
demonstrated in a few materials ($\text{Bi}_2\text{Se}_3$,
$\text{Bi}_2\text{Te}_3$, and $\text{BiTeI}$) though DFT calculations. Here we
present a minimal orbital-derived tight binding model to calculate the electron
wave-function in a two-dimensional crystal lattice. We show that the orbital
components of the wave-function demonstrate an orbital-texture switch in
addition to the usual spin switch seen in spin polarized bands. This orbital
texture switch is determined by the existence of three main properties: local
or global inversion symmetry breaking, strong spin-orbit coupling, and
non-local physics (the electrons are on a lattice). Using our model we
demonstrate that the orbital texture switch is ubiquitous and to be expected in
many real systems. The orbital hybridization of the bands is the key aspect for
understanding the unique wave function properties of these materials, and this
minimal model helps to establish the quantum perturbations that drive these
hybridizations.",1608.01387v1
2022-04-21,Tailoring neuromorphic switching by CuNx-mediated orbital currents,"Current-induced spin-orbit torque (SOT) is regarded as a promising mechanism
for driving neuromorphic behavior in spin-orbitronic devices. In principle, the
strong SOT in heavy metal-based magnetic heterostructure is attributed to the
spin-orbit coupling (SOC)-induced spin Hall effect (SHE) and/or the spin
Rashba-Edelstein effect (SREE). Recently, SOC-free mechanisms such as the
orbital angular momentum (OAM)-induced orbital Hall effect (OHE) and/or the
orbital Rashba-Edelstein effect (OREE) have been proposed to generate sizable
torques comparable to those from the conventional spin Hall mechanism. In this
work, we show that the orbital current can be effectively generated by the
nitrided light metal Cu. The overall damping-like SOT efficiency, which
consists of both the spin and the orbital current contributions, can be
tailored from ~ 0.06 to 0.4 in a Pt/Co/CuNx magnetic heterostructure by tuning
the nitrogen doping concentration. Current-induced magnetization switching
further verifies the efficacy of such orbital current with a critical switching
current density as low as Jc ~ 5 x 10^10 A/m2. Most importantly, the
orbital-current-mediated memristive switching behavior can be observed in such
heterostructures, which reveals that the gigantic SOT and efficient
magnetization switching are the tradeoffs for the applicable window of
memristive switching. Our work provides insights into the role of orbital
current might play in SOT neuromorphic devices and paves a new route for making
energy-efficient spin-orbitronic devices.",2204.09846v3
2007-07-24,Spin Hall Effect and Spin Orbit coupling in Ballistic Nanojunctions,"We propose a new scheme of spin filtering based on nanometric crossjunctions
in the presence of Spin Orbit interaction, employing ballistic nanojunctions
patterned in a two-dimensional electron gas. We demonstrate that the flow of a
longitudinal unpolarized current through a ballistic X junction patterned in a
two-dimensional electron gas with Spin Orbit coupling (SOC) induces a spin
accumulation which has opposite signs for the two lateral probes. This spin
accumulation, corresponding to a transverse pure spin current flowing in the
junction, is the main observable signature of the spin Hall effect in such
nanostructures.
  We benchmark the effects of two different kinds of Spin Orbit interactions.
The first one ($\alpha$-SOC) is due to the interface electric field that
confines electrons to a two-dimensional layer, whereas the second one
($\beta$-SOC) corresponds to the interaction generated by a lateral confining
potential.",0707.3580v1
2007-11-07,Hamiltonian of two spinning compact bodies with next-to-leading order gravitational spin-orbit coupling,"A Hamiltonian formulation is given for the gravitational dynamics of two
spinning compact bodies to next-to-leading order ($G/c^4$ and $G^2/c^4$) in the
spin-orbit interaction. We use a novel approach (valid to linear order in the
spins), which starts from the second-post-Newtonian metric (in ADM coordinates)
generated by two spinless bodies, and computes the next-to-leading order
precession, in this metric, of suitably redefined ``constant-magnitude''
3-dimensional spin vectors ${\bf S}_1$, ${\bf S}_2$. We prove the Poincar\'e
invariance of our Hamiltonian by explicitly constructing ten phase-space
generators realizing the Poincar\'e algebra. A remarkable feature of our
approach is that it allows one to derive the {\it orbital} equations of motion
of spinning binaries to next-to-leading order in spin-orbit coupling without
having to solve Einstein's field equations with a spin-dependent stress tensor.
We show that our Hamiltonian (orbital and spin) dynamics is equivalent to the
dynamics recently obtained by Faye, Blanchet, and Buonanno, by solving
Einstein's equations in harmonic coordinates.",0711.1048v2
2015-07-22,Observation of correlated spin-orbit order in a strongly anisotropic quantum wire system,"Quantum wires with spin-orbit coupling provide a unique opportunity to
simultaneously control the coupling strength and the screened Coulomb
interactions where new exotic phases of matter can be explored. Here we report
on the observation of an exotic spin-orbit density wave in Pb-atomic wires on
Si(557) surfaces by mapping out the evolution of the modulated spin-texture at
various conditions with spin- and angle-resolved photoelectron spectroscopy.
The results are independently quantified by surface transport measurements. The
spin polarization, coherence length, spin dephasing rate, and the associated
quasiparticle gap decrease simultaneously as the screened Coulomb interaction
decreases with increasing excess coverage, providing a new mechanism for
generating and manipulating a spin-orbit entanglement effect via electronic
interaction. Despite clear evidence of spontaneous spin-rotation symmetry
breaking and modulation of spin-momentum structure as a function of excess
coverage, the average spin-polarization over the Brillouin zone vanishes,
indicating that time-reversal symmetry is intact as theoretically predicted.",1507.06152v1
2007-01-30,Anisotropic spin transport in GaAs quantum wells in the presence of competing Dresselhaus and Rashba spin-orbit-coupling strengths,"Aiming at the optimization of the spin diffusion length in (001) GaAs quantum
wells, we explore the effect of the anisotropy of the spin-orbit coupling on
the competition between the Rashba and the Dresselhaus spin-orbit couplings by
solving the kinetic spin Bloch equations with the electron-phonon and the
electron-electron scattering explicitly included. For identical strengths of
the Rashba and the Dresselhaus spin-orbit couplings, the spin diffusion length
shows strong anisotropy not only for the spin polarization direction but also
for the spin diffusion direction. Two special directions are used seeking for
the large diffusion length: ($\bar{1}$10) and (110). Without the cubic term of
the Dresselhaus spin-orbit coupling and with the identical Dresselhaus and
Rashba strengths, infinite diffusion lengths can be obtained {\em either} for
the spin diffusion/injection direction along $(\bar110)$, regardless of the
direction of spin polarization, {\em or} for the spin polarization along
$(110)$, regardless of the direction of the spin diffusion/injection.
  However, the cubic Dresselhaus term cannot be neglected, resulting into a
finite spin diffusion length which decreases with the temperature and the
electron density, and of which the anisotropy for the spin diffusion direction
and spin polarization direction is maintained. For the spin diffusion/injection
direction along ($\bar{1}$10), the spin diffusion length increases first with
the increase of the Rashba strength (from 0) which can be tuned by the external
gate voltage; when the Rashba strength is slightly smaller than (in stead of
equal to) the Dresselhaus strength, the diffusion length reaches its maximum;
and then it decreases with the Rashba strength.",0701762v2
2005-07-21,Spin relaxation under identical Dresselhaus and Rashba coupling strengths in GaAs quantum wells,"Spin relaxation under identical Dresselhaus and Rashba coupling strengths in
GaAs quantum wells is studied in both the traditional collinear statistics,
where the energy spectra do not contain the spin-orbit coupling terms, and the
helix statistics, where the spin-orbit couplings are included in the energy
spectra. We show that there is only marginal difference between the spin
relaxation times obtained from these two different statistics. We further show
that with the cubic term of the Dresselhaus spin-orbit coupling included, the
spin relaxation time along the (1,1,0) direction becomes finite, although it is
still much longer than that along the other two perpendicular directions. The
properties of the spin relaxation along this special direction under varies
conditions are studied in detail.",0507497v3
2011-10-17,Acoustic phonons mediated non-equilibrium spin current in the presence of Rashba and Dresselhaus spin-orbit couplings,"The influence of the electrons interaction with longitudinal acoustic phonons
on magnetoeletric and spin-related transport effects are investigated. The
physical system under consideration has been assumed to be a two dimensional
electron gas system with both Rashba and Dreesselhaus spin-orbit couplings. In
the works which have been previously performed in this field it has been shown
that in the non-equilibrium regime, the Rashba and Dreesselhaus couplings can
not be responsible for spin-current where in the absence of other interactions
such as lattice vibrations identically vanishes. In the current work we have
employed a semi-classical method by using the Boltzmann approach. It was shown
that the spin-current of the system, in general, does not go all the way to
zero at any value of the spin-orbit couplings. It was also shown that the spin
accumulation of the system can be influenced by the electron-phonon coupling.",1110.3667v3
2022-06-29,"Continuously tracked, stable, large excursion trajectories of dipolar coupled nuclear spins","We report an experimental approach to excite, stabilize, and continuously
track Bloch sphere orbits of dipolar-coupled nuclear spins in a solid. We
demonstrate these results on a model system of hyperpolarized 13C nuclear spins
in diamond. Without quantum control, inter-spin coupling leads to rapid spin
decay in T2*=1.5ms. We elucidate a method to preserve trajectories for over
T2'>27s at excursion solid angles up to 16 degrees, even in the presence of
strong inter-spin coupling. This exploits a novel spin driving strategy that
thermalizes the spins to a long-lived dipolar many-body state, while driving
them in highly stable orbits. We show that motion of the spins can be
quasi-continuously tracked for over 35s in three dimensions on the Bloch
sphere. In this time the spins complete >68,000 closed precession orbits,
demonstrating high stability and robustness against error. We experimentally
probe the transient approach to such rigid motion, and thereby show the ability
to engineer highly stable ""designer"" spin trajectories. Our results suggest new
ways to stabilize and interrogate strongly-coupled quantum systems through
periodic driving and portend powerful applications of rigid spin orbits in
quantum sensing.",2206.14945v2
2016-12-23,Spin-orbital order in undoped manganite LaMnO3 at finite temperature,"We investigate the evolution of spin and orbital order in undoped LaMnO$_3$
under increasing temperature with a model including both superexchange and
Jahn-Teller interactions. We used several cluster mean field calculation
schemes and find coexisting $A$-type antiferromagnetic ($A$-AF) and $C$-type
alternating orbital order at low temperature. The value of the Jahn-Teller
coupling between strongly correlated $e_g$ orbitals is estimated from the
orbital transition temperature at $T_{\rm OO}\simeq 780$ K. By a careful
analysis of on-site and on-bond correlations we demonstrate that spin-orbital
entanglement is rather weak. We have verified that the magnetic transition
temperature is influenced by entangled spin-orbital operators as well as by
entangled orbital operators on the bonds but the errors introduced by
decoupling such operators partly compensate each other. Altogether, these
results justify why the commonly used disentangled spin-orbital model is so
successful in describing the magnetic properties and the temperature dependence
of the optical spectral weights for LaMnO$_3$.",1612.08016v1
2020-01-10,Orbital Hall Insulating Phase in Transition Metal Dichalcogenide Monolayers,"We show that H-phase transition metal dichalcogenides (TMDs) monolayers such
as MoS$_2$ and WSe$_2$, are orbital Hall insulators. They present very large
orbital Hall conductivity plateaus in their semiconducting gap, where the spin
Hall conductivity vanishes. Our results open the possibility of using TMDs for
orbital current injection and orbital torque transfers that surpass their
spin-counterparts in spin-orbitronics devices. The orbital Hall effect (OHE) in
TMD monolayers occurs even in the absence of spin-orbit coupling. It can be
linked to exotic momentum-space Dresselhaus-like orbital textures, analogous to
the spin-momentum locking in 2D Dirac fermions that arise from a combination of
orbital attributes and lattice symmetry.",2001.03592v2
2019-03-04,Orbital Torque: Torque Generation by Orbital Current Injection,"We propose a mechanism of torque generation by injection of an orbital
current, which we call $\textit{orbital torque}$. In a magnetic bilayer
consisting of a nonmagnet (NM) and a ferromagnet (FM), we consider a situation
where the spin-orbit coupling (SOC) is present only in the FM. Although the SOC
is absent in the NM, the orbital Hall effect can arise in the NM. When the
resulting orbital Hall current is injected to the FM, the SOC of the FM
converts the orbital angular momentum into spin, which exerts torque to the
magnetization of the FM. Remarkably, even for small SOC strength comparable to
that of $3d$ FMs, the orbital torque can be comparable to the spin torque
induced by the spin Hall effect of the NM with strong SOC. This provides a way
to experimentally probe the OHE and opens a new venue to achieving spin-torque
devices based on light elements that exhibit gigantic orbital response.
Experimental implications are discussed.",1903.01085v3
2010-01-20,Spin electric effects in molecular antiferromagnets,"Molecular nanomagnets show clear signatures of coherent behavior and have a
wide variety of effective low-energy spin Hamiltonians suitable for encoding
qubits and implementing spin-based quantum information processing. At the
nanoscale, the preferred mechanism for control of quantum systems is through
application of electric fields, which are strong, can be locally applied, and
rapidly switched. In this work, we provide the theoretical tools for the search
for single molecule magnets suitable for electric control. By group-theoretical
symmetry analysis we find that the spin-electric coupling in triangular
molecules is governed by the modification of the exchange interaction, and is
possible even in the absence of spin-orbit coupling. In pentagonal molecules
the spin-electric coupling can exist only in the presence of spin-orbit
interaction. This kind of coupling is allowed for both $s=1/2$ and $s=3/2$
spins at the magnetic centers. Within the Hubbard model, we find a relation
between the spin-electric coupling and the properties of the chemical bonds in
a molecule, suggesting that the best candidates for strong spin-electric
coupling are molecules with nearly degenerate bond orbitals. We also
investigate the possible experimental signatures of spin-electric coupling in
nuclear magnetic resonance and electron spin resonance spectroscopy, as well as
in the thermodynamic measurements of magnetization, electric polarization, and
specific heat of the molecules.",1001.3584v1
2009-04-08,Spin--orbital physics in transition metal oxides,"We present the main features of the spin-orbital superexchange which
describes the magnetic and optical properties of Mott insulators with orbital
degrees of freedom. In contrast to the SU(2) symmetry of spin superexchange,
the orbital part of the superexchange obeys the lower cubic symmetry of the
lattice and is intrinsically frustrated. This intrinsic frustration and
spin-orbital entanglement induce enhanced quantum fluctuations, and we point
out a few situations where this leads to disordered states. Strong coupling
between the spin and orbital degrees of freedom is discussed on the example of
the $R$VO$_3$ perovskites, with $R$ standing for rare-earth ion, La,...,Lu. We
explain the observed evolution of the orbital $T_{\rm OO}$ and N\'eel $T_{N1}$
transition temperature in the $R$VO$_3$ series with decreasing ionic radius
$r_R$. A few open problems and the current directions of research in the field
of spin-orbital physics are pointed out.",0904.1297v1
2023-08-13,Tunable persistent currents in a spin-orbit coupled pseudospin-1 fermionic quantum ring,"We conduct a thorough study of the persistent currents in a spin-orbit
coupled ${\alpha}-T_3$ pseudospin-1 fermionic quantum ring (QR) that smoothly
interpolates between graphene (${\alpha} = 0$, pseudospin-1/2) and a dice
lattice (${\alpha} = 1$, pseudospin-1). In particular, we have considered both
intrinsic spin-orbit coupling (ISOC) and Rashba spin-orbit coupling (RSOC) in
addition to an external magnetic field, and have systematically enumerated
their individual and combined effects on the charge, valley and the
spin-polarized persistent currents. The energy levels of the system comprise of
the conduction bands, valence bands, and flat bands which show non-monotonic
dependencies on the ring radius, R of the QR, in the sense that, for small R,
the energy levels vary as 1/R, while the variation is linear in R for large R.
The cases corresponding to zero magnetic fields are benchmarked with those for
finite external fields. Further, it is noted that the flat bands demonstrate
dispersive behavior, and hence can contribute to the transport properties only
when ISOC is non-zero. Moreover, the RSOC yields spin-split bands, thereby
contributing to the spin-resolved currents, together with distinct degeneracies
for different spin branches. The persistent currents in the charge, valley, and
spin sectors for each of these cases oscillate as a function of the magnetic
field with a period equal to the flux quantum, as they should be, and depend
upon the spin-orbit coupling terms. Further, we have explored the role played
by the parameter ${\alpha}$ in our entire analysis to ascertain the effect of
the flat bands.",2308.06804v1
2024-02-14,Giant asymmetric proximity-induced spin-orbit coupling in twisted graphene/SnTe heterostructure,"We analyze the spin-orbit coupling effects in a three-degree twisted bilayer
heterostructure made of graphene and an in-plane ferroelectric SnTe, with the
goal of transferring the spin-orbit coupling from SnTe to graphene, via the
proximity effect. Our results indicate that the point-symmetry breaking due to
the incompatible mutual symmetry of the twisted monolayers and a strong
hybridization has a massive impact on the spin splitting in graphene close to
the Dirac point, with the spin splitting values greater than 20 meV. The band
structure and spin expectation values of graphene close to the Dirac point can
be described using a symmetry-free model, triggering different types of
interaction with respect to the threefold symmetric graphene/transition-metal
dichalcogenide heterostructure. We show that the strong hybridization of the
Dirac cone's right movers with the SnTe band gives rise to a large asymmetric
spin splitting in the momentum space. Furthermore, we discover that the
ferroelectricity-induced Rashba spin-orbit coupling in graphene is the dominant
contribution to the overall Rashba field, with the effective in-plane electric
field that is almost aligned with the (in-plane) ferroelectricity direction of
the SnTe monolayer. We also predict an anisotropy of the in-plane spin
relaxation rates. Our results demonstrate that the group-IV monochalcogenides
MX (M=Sn, Ge; X=S, Se, Te) are a viable alternative to transition-metal
dichalcogenides for inducing strong spin-orbit coupling in graphene.",2402.09045v1
2013-08-16,Theory of metallic double perovskites with spin orbit coupling and strong correlations; application to ferrimagnetic Ba2FeReO6,"We consider a model of the double perovskite Ba2FeReO6, a room temperature
ferrimagnet with correlated and spin-orbit coupled Re t2g electrons moving in
the background of Fe moments stabilized by Hund's coupling. We show that for
such 3d/5d double perovskites, strong correlations on the 5d-element (Re) are
essential in driving a half-metallic ground state. Incorporating both strong
spin-orbit coupling and the Hubbard repulsion on Re leads to a band structure
consistent with ab initio calculations. Using our model, we find a large spin
polarization at the Fermi level, and obtain a semi-quantitative understanding
of the saturation magnetization of Ba2FeReO6, as well as X-ray magnetic
circular dichroism data indicating a significant orbital magnetization. Based
on the orbital populations obtained in our theory, we predict a specific doping
dependence to the tetragonal distortion accompanying ferrimagnetic order.
Finally, the combination of a net magnetization and spin-orbit interactions is
shown to induce Weyl nodes in the band structure, and we predict a significant
intrinsic anomalous Hall effect in hole-doped Ba2FeReO6. The uncovered
interplay of strong correlations and spin-orbit coupling lends partial support
to our previous work, which used a local moment description to capture the spin
wave dispersion found in neutron scattering measurements. Our work is of broad
interest for understanding metallic 4d-based and 5d-based double perovskites
which are of fundamental interest and of possible relevance to spintronic
applications.",1308.3701v2
2024-02-08,Quantum Anomalous Hall Effect in $d$-Electron Kagome Systems: Chern Insulating States from Transverse Spin-Orbit Coupling,"Inspired by the discovery of metal-organic frameworks, the possibility of
quantum anomalous Hall effect (QAHE) in two-dimensional kagome systems with
$d$-orbital electrons is studied within a multi-orbital tight-binding model. In
the absence of exchange-type spin-orbit coupling, isotropic Slater-Koster
integrals give a band structure with relativistic (Dirac) and quadratic band
crossing points at high symmetry spots in the Brillouin zone. A quantized
topological invariant requires a flux-creating spin-orbit coupling, giving
Chern number (per spin sector) $C=1$ not only from the familiar Dirac points at
the six corners of the Brillouin zone, but also from the quadratic band
crossing point at the center $\Gamma$. Surprisingly, this QAHE comes from the
nontrivial effective flux induced by the transverse part of the spin-orbit
coupling, exhibited by electrons in the $d$-orbital state with $m_l=0$
($d_{z^2}$ orbital), in stark contrast to the more familiar form of QAHE due to
the $d$-orbitals with $m_l \neq 0$, driven by the Ising part of spin-orbit
coupling. The $C=1$ Chern plateau (per spin sector) due to Dirac point extends
over a smaller region of Fermi energy than that due to quadratic band crossing.
Our result hints at the promising potential of kagome metal-organic frameworks
as a platform for dissipationless electronics by virtue of its unique QAHE.",2402.05845v1
2011-04-24,Competition of crystal field splitting and Hund's rule coupling in two-orbital magnetic metal-insulator transitions,"Competition of crystal field splitting and Hund's rule coupling in magnetic
metal-insulator transitions of half-filled two-orbital Hubbard model is
investigated by multi-orbital slave-boson mean field theory. We show that with
the increase of Coulomb correlation, the system firstly transits from a
paramagnetic (PM) metal to a {\it N\'{e}el} antiferromagnetic (AFM) Mott
insulator, or a nonmagnetic orbital insulator, depending on the competition of
crystal field splitting and the Hund's rule coupling. The different AFM Mott
insulator, PM metal and orbital insulating phase are none, partially and fully
orbital polarized, respectively. For a small $J_{H}$ and a finite crystal
field, the orbital insulator is robust. Although the system is nonmagnetic, the
phase boundary of the orbital insulator transition obviously shifts to the
small $U$ regime after the magnetic correlations is taken into account. These
results demonstrate that large crystal field splitting favors the formation of
the orbital insulating phase, while large Hund's rule coupling tends to destroy
it, driving the low-spin to high-spin transition.",1104.4599v1
2022-01-31,Precisely computing bound orbits of spinning bodies around black holes II: Generic orbits,"In this paper, we continue our study of the motion of spinning test bodies
orbiting Kerr black holes. Non-spinning test bodies follow geodesics of the
spacetime in which they move. A test body's spin couples to the curvature of
that spacetime, introducing a ""spin-curvature force"" which pushes the body's
worldline away from a geodesic trajectory. The spin-curvature force is an
important example of a post-geodesic effect which must be modeled carefully in
order to accurately characterize the motion of bodies orbiting black holes. One
motivation for this work is to understand how to include such effects in models
of gravitational waves produced from the inspiral of stellar mass bodies into
massive black holes. In this paper's predecessor, we describe a technique for
computing bound orbits of spinning bodies around black holes with a
frequency-domain description which can be solved very precisely. In that paper,
we present an overview of our methods, as well as present results for orbits
which are eccentric and nearly equatorial (i.e., the orbit's motion is no more
than $\mathcal{O}(S)$ out of the equatorial plane). In this paper, we apply
this formulation to the fully generic case -- orbits which are inclined and
eccentric, with the small body's spin arbitrarily oriented. We compute the
trajectories which such orbits follow, and compute how the small body's spin
affects important quantities such as the observable orbital frequencies
$\Omega_r$, $\Omega_\theta$ and $\Omega_\phi$.",2201.13335v2
1999-12-11,Low-energy behavior of the spin-tube and spin-orbital models,"The low-energy effective Hamiltonian of three coupled spin chains with
periodic boundary conditions (spin tube) is expressed, in the limit of strong
interchain coupling, in terms of XXZ chains coupled by biquadratic exchange
interaction. A similar class of models was proposed to describe the coupling of
spins to orbital degrees of freedom in materials such as NaV2O5. We investigate
these models by means of bosonization and renormalization group techniques, and
find that the generic phase diagram comprises a gapless region and gapped
regions consisting of a spin liquid phase and various antiferromagnetic phases.
We discuss the properties of the spin liquid phase, in particular the nature of
the ground state and of the elementary excitations above it. We then study the
effect of a magnetic field, and conclude that a strong enough magnetic field
can suppress the dimerized phase leading to a two component Luttinger liquid.
The critical exponents at the transition gapful-gapless are calculated and
shown to be non-universal in the spin tube case as well as in the generic spin
orbital problem.",9912200v1
2016-01-29,Crossover to the Anomalous Quantum Regime in the Extrinsic Spin Hall Effect of Graphene,"Recent reports of spin-orbit coupling enhancement in chemically modified
graphene have opened doors to studies of the spin Hall effect with massless
chiral fermions. Here, we theoretically investigate the interaction and
impurity density dependence of the extrinsic spin Hall effect in spin-orbit
coupled graphene. We present a nonperturbative quantum diagrammatic calculation
of the spin Hall response function in the strong-coupling regime that
incorporates skew scattering and anomalous impurity density-independent
contributions on equal footing. The spin Hall conductivity dependence on Fermi
energy and electron-impurity interaction strength reveals the existence of
experimentally accessible regions where anomalous quantum processes dominate.
Our findings suggest that spin-orbit-coupled graphene is an ideal model system
for probing the competition between semiclassical and bona fide quantum
scattering mechanisms underlying the spin Hall effect.",1601.08076v2
2012-08-06,Microscopic theory for the Doppler velocimetry of spin propagation in semiconductor quantum wells,"We provide a microscopic theory for the Doppler velocimetry of spin
propagation in the presence of spatial inhomogeneity, driving electric field
and the spin orbit coupling in semiconductor quantum wells in a wide range of
temperature regime based on the kinetic spin Bloch equation. It is analytically
shown that under an applied electric field, the spin density wave gains a
time-dependent phase shift $\phi(t)$. Without the spin-orbit coupling, the
phase shift increases linearly with time and is equivalent to a normal Doppler
shift in optical measurements. Due to the joint effect of spin-orbit coupling
and the applied electric field, the phase shift behaviors differently at the
early and the later stages. At the early stage, the phase shifts are the same
with or without the spin-orbit coupling. While at the later stage, the phase
shift deviates from the normal Doppler one when the spin-orbit coupling is
present. The crossover time from the early normal Doppler behavior to the
anomalous one at the later stage is inversely proportional to the spin
diffusion coefficient, wave vector of the spin density wave and the spin-orbit
coupling strength. In the high temperature regime, the crossover time becomes
large as a result of the decreased spin diffusion coefficient. The analytic
results capture all the quantitative features of the experimental results,
while the full numerical calculations agree quantitatively well with the
experimental data obtained from the Doppler velocimetry of spin propagation
[Yang {\it et al.}, Nat. Phys. {\bf 8}, 153 (2012)]. We further predict that
the coherent spin precession, originally thought to be broken down at high
temperature, is robust up to the room temperature for narrow quantum wells. We
point out that one has to carry out the experiments longer to see the effect of
the coherent spin precession at higher temperature due to the larger crossover
time.",1208.1081v2
2015-01-03,Exact results for itinerant ferromagnetism in a $t_{2g}$ orbital system on cubic and square lattices,"We study itinerant ferromagnetism in a $t_{2g}$ multi-orbital Hubbard system
in the cubic lattice, which consists of three planar oriented orbital bands of
$d_{xy}$, $d_{yz}$, and $d_{zx}$. Electrons in each orbital band can only move
within a two-dimensional plane in the three-dimensional lattice parallel to the
corresponding orbital orientation. Electrons of different orbitals interact
through the on-site multi-orbital interactions including Hund's coupling. The
strong coupling limit is considered in which there are no doubly occupied
orbitals but multiple on-site occupations are allowed. We show that, in the
case in which there is one and only one hole for each orbital band in each
layer parallel to the orbital orientation, the ground state is a fully
spin-polarized itinerant ferromagnetic state, which is unique apart from the
trivial spin degeneracy. When the lattice is reduced into a single
two-dimensional layer, the $d_{zx}$ and $d_{yz}$ bands become
quasi-one-dimensional while the $d_{xy}$ band remains two-dimensional. The
ground state ferromagnetism also appears in the strong-coupling limit as a
generalization of the double exchange mechanism. Possible applications to the
systems of SrRuO$_3$ and LaAlO$_3$/SrTiO$_3$ interface are discussed.",1501.00536v2
2005-12-19,Intrinsic vs. Extrinsic Spin Currents. Old Ideas in a New Light,"We have described the electron spin dynamics in the presence of Rashba spin-
orbit interaction and disorder using the spin-density matrix method. We showed
that in the Born approximation in the scattering amplitude the spin current is
zero for an arbitrary ratio of the spin-orbit splitting and the scattering rate
and for an arbitrary disorder potential. We also describe some magnetotransport
phenomena such as negative magnetoresistance and a negative charge Hall effect
which occur in the presence of spin-orbit coupling.",0512458v1
2018-11-13,Spin and Charge Transport of Multi-Orbital Quantum Spin Hall Insulators,"The fabrication of bismuthene on top of SiC paved the way for substrate
engineering of room temperature quantum spin Hall insulators made of group V
atoms. We perform large-scale quantum transport calculations in these 2d
materials to analyse the rich phenomenology that arises from the interplay
between topology, disorder, valley and spin degrees of freedom. For this
purpose, we consider a minimal multi-orbital real-space tight-binding
hamiltonian and use a Chebyshev polynomial expansion technique. We discuss how
the quantum spin Hall states are affected by disorder, sublattice resolved
potential and Rashba spin-orbit coupling.",1811.05054v1
2019-01-17,Novel Block Excitonic Condensate at $n=3.5$ in a Spin-Orbit Coupled $t_{2g}$ Multiorbital Hubbard Model,"Theoretical studies recently predicted the condensation of spin-orbit
excitons at momentum $q$=$\pi$ in $t_{2g}^4$ spin-orbit coupled three-orbital
Hubbard models at electronic density $n=4$. In parallel, experiments involving
iridates with non-integer valence states for the Ir ions are starting to
attract considerable attention. In this publication, using the density matrix
renormalization group technique we present evidence for the existence of a
novel excitonic condensate at $n=3.5$ in a one-dimensional Hubbard model with a
degenerate $t_{2g}$ sector, when in the presence of spin-orbit coupling. At
intermediate Hubbard $U$ and spin-orbit $\lambda$ couplings, we found an
excitonic condensate at the unexpected momentum $q$=$\pi/2$ involving
$j_{\textrm{eff}}=3/2,m=\pm1/2$ and $j_{\textrm{eff}}=1/2,m=\pm1/2$ bands in
the triplet channel, coexisting with an also unexpected block magnetic order.
We also present the entire $\lambda$ vs $U$ phase diagram, at a fixed and
robust Hund coupling. Interestingly, this new `block excitonic phase' is
present even at large values of $\lambda$, unlike the $n=4$ excitonic phase
discussed before. Our computational study helps to understand and predict the
possible magnetic phases of materials with $d^{3.5}$ valence and robust
spin-orbit coupling.",1901.05578v1
2016-01-12,The effects of electron correlation and spin-orbit coupling in the isovalent Pd-doped superconductor SrPt$_3$P,"We present a systematical study on the roles of electron correlation and
spin-orbit coupling in the isovalent Pd-doped superconductor SrPt$_3$P. By
using solid state reaction method, we fabricated the strong spin-orbit coupling
superconductors Sr(Pt$_{1-x}$Pd$_x$)$_3$P with strong electron correlated Pd
dopant of the $4d$ orbital. As increasing the isovalent Pd concentrations
without introducing any extra electron/hole carriers, the superconducting
transition temperature $T_c$ decreases monotonously, which suggests the
existence of competition between spin-orbit coupling and electron correlation
in the superconducting state. In addition, the electronic band structure
calculations demonstrate that the strength of electron susceptibility is
suppressed gradually by the Pd dopant suggesting the incompatible relation
between spin-orbit coupling and electron correlation, which is also consistent
with experimental measurements. Our results provide significant insights in the
natures of the interplay between the spin-orbit coupling and the electron
correlation in superconductivity, and may pave a way for understanding the
mechanism of superconductivity in this 5d-metal-based compound.",1601.02782v1
2011-07-13,Observation of the inverse spin Hall effect in silicon,"The spin-orbit interaction in a solid couples the spin of an electron to its
momentum. This coupling gives rise to mutual conversion between spin and charge
currents: the direct and inverse spin Hall effects. The spin Hall effects have
been observed in metals and semiconductors. However, the spin/charge conversion
has not been realized in one of the most fundamental semiconductors, silicon,
where accessing the spin Hall effects has been believed to be difficult because
of its very weak spin-orbit interaction. Here we report observation of the
inverse spin Hall effect in silicon at room temperature. The spin/charge
current conversion efficiency, the spin Hall angle, is obtained as 0.0001 for a
p-type silicon film. In spite of the small spin Hall angle, we found a clear
electric voltage due to the inverse spin Hall effect in the p-Si film,
demonstrating that silicon can be used as a spin-current detector.",1107.2585v2
2018-05-21,Tunable spinful matter wave valve,"We investigate the transport problem that a spinful matter wave is incident
on a strong localized spin-orbit-coupled Bose-Einstein condensate in optical
lattices, where the localization is admitted by atom interaction only existing
at one particular site, and the spin-orbit coupling arouse spatial rotation of
the spin texture. We find that tuning the spin orientation of the localized
Bose-Einstein condensate can lead to spin-nonreciprocal / spin-reciprocal
transport, meaning the transport properties are dependent on / independent of
the spin orientation of incident waves. In the former case, we obtain the
conditions to achieve transparency, beam-splitting, and blockade of the
incident wave with a given spin orientation, and furthermore the ones to
perfectly isolate incident waves of different spin orientation, while in the
latter, we obtain the condition to maximize the conversion of different spin
states. The result may be useful to develop a novel spinful matter wave valve
that integrates spin switcher, beam-splitter, isolator, and converter. The
method can also be applied to other real systems, e.g., realizing perfect
isolation of spin states in magnetism, which is otherwise rather difficult.",1805.08129v1
2015-06-30,Experimental Demonstration of Efficient Spin-Orbit Torque Switching of an MTJ with sub-100 ns Pulses,"Efficient generation of spin currents from charge currents is of high
importance for memory and logic applications of spintronics. In particular,
generation of spin currents from charge currents in high spin-orbit coupling
metals has the potential to provide a scalable solution for embedded memory. We
demonstrate a net reduction in critical charge current for spin torque driven
magnetization reversal via using spin-orbit mediated spin current generation.
We scaled the dimensions of the spin-orbit electrode to 400 nm and the
nanomagnet to 270 nm x 68 nm in a three terminal spin-orbit torque, magnetic
tunnel junction (SOT-MTJ) geometry. Our estimated effective spin Hall angle is
0.15-0.20 using the ratio of zero temperature critical current from spin Hall
switching and estimated spin current density for switching the magnet. We show
bidirectional transient switching using spin-orbit generated spin torque at 100
ns switching pulses reliably followed by transient read operations. We finally
compare the static and dynamic response of the SOT-MTJ with transient spin
circuit modeling showing the performance of scaled SOT-MTJs to enable
nanosecond class non-volatile MTJs.",1506.09177v4
2007-07-31,Theory of spin qubits in nanostructures,"We review recent advances on the theory of spin qubits in nanostructures. We
focus on four selected topics. First, we show how to form spin qubits in the
new and promising material graphene. Afterwards, we discuss spin relaxation and
decoherence in quantum dots. In particular, we demonstrate how charge
fluctations in the surrounding environment cause spin decay via spin--orbit
coupling. We then turn to a brief overview of how one can use electron-dipole
spin resonance (EDSR) to perform single spin rotations in quantum dots using an
oscillating electric field. The final topic we cover is the spin-spin coupling
via spin-orbit interaction which is an alternative to the usual spin-spin
coupling via the Heisenberg exchange interaction.",0707.4622v1
2018-06-07,Strong and Tunable Spin Lifetime Anisotropy in Dual-Gated Bilayer Graphene,"We report the discovery of a strong and tunable spin lifetime anisotropy with
excellent spin lifetimes up to 7.8 ns in dual-gated bilayer graphene.
Remarkably, this realizes the manipulation of spins in graphene by
electrically-controlled spin-orbit fields, which is unexpected due to
graphene's weak intrinsic spin-orbit coupling. We utilize both the in-plane
magnetic field Hanle precession and oblique Hanle precession measurements to
directly compare the lifetimes of out-of-plane vs. in-plane spins. We find that
near the charge neutrality point, the application of a perpendicular electric
field opens a band gap and generates an out-of-plane spin-orbit field that
stabilizes out-of-plane spins against spin relaxation, leading to a large spin
lifetime anisotropy. This intriguing behavior occurs because of the unique
spin-valley coupled band structure of bilayer graphene. Our results demonstrate
the potential for highly tunable spintronic devices based on dual-gated 2D
materials.",1806.02477v1
2023-07-22,Dense plasma irradiated platinum with improved spin Hall effect,"The impurity incorporation in host high-spin orbit coupling materials like
platinum has shown improved charge-to-spin conversion by modifying the up-spin
and down-spin electron trajectories by bending or skewing them in opposite
directions. This enables efficient generation, manipulation, and transport of
spin currents. In this study, we irradiate the platinum with non-focus dense
plasma to incorporate the oxygen ion species. We systematically analyze the
spin Hall angle of the oxygen plasma irradiated Pt films using spin torque
ferromagnetic resonance. Our results demonstrate a 2.4 times enhancement in the
spin Hall effect after plasma treatment of Pt as compared to pristine Pt. This
improvement is attributed to the introduction of disorder and defects in the Pt
lattice, which enhances the spin-orbit coupling and leads to more efficient
charge-to-spin conversion without breaking the spin-orbit torque symmetries.
Our findings offer a new method of dense plasma-based modification of material
for the development of advanced spintronic devices based on Pt and other heavy
metals.",2307.12139v1
2023-06-28,Universal theory of spin-momentum-orbital-site locking,"Spin textures, i.e., the distribution of spin polarization vectors in
reciprocal space, exhibit diverse patterns determined by symmetry constraints,
resulting in a variety of spintronic phenomena. Here, we propose a universal
theory to comprehensively describe the nature of spin textures by incorporating
three symmetry flavors of reciprocal wavevector, atomic orbital and atomic
site. Such approach enables us to establish a complete classification of spin
textures constrained by the little co-group and predict unprecedentedly
reported spin texture types, such as Zeeman-type spin splitting in
antiferromagnets and quadratic spin texture. To examine the impact of atomic
orbitals and sites, we predict orbital-dependent spin texture and anisotropic
spin-momentum-site locking effects and corresponding material candidates
validated through first-principles calculations. Our theory not only covers all
possible spin textures in crystal solids described by magnetic space groups,
but also introduces new possibilities for designing innovative spin textures by
the coupling of multiple degrees of freedom.",2306.16312v1
2014-06-09,Spontaneous Parity Breaking in Spin-Orbital Coupled Systems,"Effects of spontaneous parity breaking by charge, spin, and orbital orders
are investigated in a two-band Hubbard model on a honeycomb lattice. This is a
minimal model in which the inter-orbital hopping, atomic spin-orbit coupling,
and strong electron correlation give rise to fascinating properties, such as
the magnetoelectric effects, quantum spin Hall effect, and spin or valley
splitting in the band structure. We perform the symmetry analysis of possible
broken-parity states and the mean-field analysis of their competition. We find
that the model at 1/4 filling exhibits a spin-orbital composite ordered state
and a charge ordered state, in addition to a paramagnetic quantum spin-Hall
insulator. We show that the composite ordered phase exhibits two types of
magnetoelectric responses. The charge ordered state shows spin splitting in the
band structure, while the topological nature varies depending on electron
correlations.",1406.2093v1
2019-05-20,Spin dynamics of hot excitons in diluted magnetic semiconductors with spin-orbit interaction,"We explore the impact of a Rashba-type spin-orbit interaction in the
conduction band on the spin dynamics of hot excitons in diluted magnetic
semiconductor quantum wells. In materials with strong spin-orbit coupling, we
identify parameter regimes where spin-orbit effects greatly accelerate the spin
decay and even change the dynamics qualitatively in the form of damped
oscillations. Furthermore, we show that the application of a small external
magnetic field can be used to either mitigate the influence of spin-orbit
coupling or entirely remove its effects for fields above a material-dependent
threshold.",1905.07947v3
2010-05-12,Spin effects in the phasing of gravitational waves from binaries on eccentric orbits,"We compute here the spin-orbit and spin-spin couplings needed for an accurate
computation of the phasing of gravitational waves emitted by comparable-mass
binaries on eccentric orbits at the second post-Newtonian (PN) order. We use a
quasi-Keplerian parametrization of the orbit free of divergencies in the zero
eccentricity limit. We find that spin-spin couplings induce a residual
eccentricity for coalescing binaries at 2PN, of the order of
$10^{-4}$-$10^{-3}$ for supermassive black hole binaries in the LISA band.
Spin-orbit precession also induces a non-trivial pattern in the evolution of
the eccentricity, which could help to reduce the errors on the determination of
the eccentricity and spins in a gravitational wave measurement.",1005.2046v1
2024-02-19,Emergence of radial Rashba spin-orbit fields in twisted van der Waals heterostructures,"Rashba spin-orbit coupling is a quintessential spin interaction appearing in
virtually any electronic heterostructure. Its paradigmatic spin texture in the
momentum space forms a tangential vector field. Using first-principles
investigations, we demonstrate that in twisted homobilayers and
hetero-multilayers, the Rashba coupling can be predominantly radial, parallel
to the momentum. Specifically, we study four experimentally relevant
structures: twisted bilayer graphene (Gr), twisted bilayer WSe$_2$, and twisted
multilayers WSe$_2$/Gr/WSe$_2$ and WSe$_2$/Gr/Gr/WSe$_2$. We show, that the
Rashba spin-orbit field texture in such structures can be controlled by an
electric field, allowing to tune it from radial to tangential. Such spin-orbit
engineering should be useful for designing novel spin-charge conversion and
spin-orbit torque schemes, as well as for controlling correlated phases and
superconductivity in van der Waals materials.",2402.12353v1
2008-09-20,Unconventional Bose-Einstein condensations from spin-orbit coupling,"According to the ""no-node"" theorem, many-body ground state wavefunctions of
conventional Bose-Einstein condensations (BEC) are positive-definite, thus
time-reversal symmetry cannot be spontaneously broken. We find that
multi-component bosons with spin-orbit coupling provide an unconventional type
of BECs beyond this paradigm. We focus on the subtle case of isotropic Rashba
spin-orbit coupling and the spin-independent interaction. In the limit of the
weak confining potential, the condensate wavefunctions are frustrated at the
Hartree-Fock level due to the degeneracy of the Rashba ring. Quantum zero-point
energy selects the spin-spiral type condensate through the
""order-from-disorder"" mechanism. In a strong harmonic confining trap, the
condensate spontaneously generates a half-quantum vortex combined with the
skyrmion type of spin texture. In both cases, time-reversal symmetry is
spontaneously broken. These phenomena can be realized in both cold atom systems
with artificial spin-orbit couplings generated from atom-laser interactions and
exciton condensates in semi-conductor systems.",0809.3532v5
2012-10-22,Spin polarization anisotropy in a narrow spin-orbit-coupled nanowire quantum dot,"One and two-electron systems confined in a single and coupled quantum dots
defined within a nanowire with a finite radius are studied in the context of
spin-orbit coupling effects. Anisotropy of the spin-orbit interaction is
discussed in terms of the system geometry and orientation of the external
magnetic field vector. We find that there are easy and hard spin polarization
axes and in the quantum dot with strong lateral confinement electron spin
becomes well defined in spite of the presence of spin-orbit coupling. We
present an analytical solution for the one-dimensional limit and study its
validity for nanowires of finite radii by comparing the results with a full
three-dimensional calculation. The results are also confronted with the recent
measurements of the effective Lande factor and avoided crossing width
anisotropy in InSb nanowire quantum dots [S. Nadj-Perge et al., Phys. Rev.
Lett. 108, 166801 (2012)].",1210.5901v3
2017-02-17,Spin-orbit torque in MgO/CoFeB/Ta/CoFeB/MgO symmetric structure with interlayer antiferromagnetic coupling,"Spin current generated by spin Hall effect in the heavy metal would diffuse
up and down to adjacent ferromagnetic layers and exert torque on their
magnetization, called spin-orbit torque. Antiferromagnetically coupled
trilayers, namely the so-called synthetic antiferromagnets (SAF), are usually
employed to serve as the pinned layer of spintronic devices based on spin
valves and magnetic tunnel junctions to reduce the stray field and/or increase
the pinning field. Here we investigate the spin-orbit torque in
MgO/CoFeB/Ta/CoFeB/MgO perpendicularly magnetized multilayer with interlayer
antiferromagnetic coupling. It is found that the magnetization of two CoFeB
layers can be switched between two antiparallel states simultaneously. This
observation is replicated by the theoretical calculations by solving
Stoner-Wohlfarth model and Landau-Lifshitz-Gilbert equation. Our findings
combine spin-orbit torque and interlayer coupling, which might advance the
magnetic memories with low stray field and low power consumption.",1702.05331v1
2014-03-27,Itinerant magnetism in Weyl spin-orbit coupled Fermi gas,"Magnetic ordering of itinerant fermionic systems is at the forefront of
condensed matter physics dating back to Stoner's instability. Spin-orbit
coupling (SOC) which couples two essential ingredients of an itinerant
fermionic system, namely spin and orbital motion, opens up new horizons to this
long-standing problem. Here we report that the itinerant ferromagnetism is
absent in 3D Fermi gas with a Weyl SOC and various itinerant spin density waves
emerge instead, which is deeply rooted in the unique symmetry and spin-momentum
locking effect in spin-orbit coupled systems. What is more appealing is that,
the strong SOC provides a new and efficient mechanism to realize itinerant spin
density waves at extremely weak repulsion---a significant benefit for present
ultra-cold atom experiment. These novel phenomena can be probed by Bragg
spectroscopy, time of flight imaging and {\sl In-Situ } measurements in
ultra-cold atom experiment.",1403.7031v6
2017-01-18,Finite Temperature Phases of Two Dimensional Spin-Orbit Coupled Bosons,"We determine the finite temperature phase diagram of two dimensional bosons
with two hyperfine (pseudo-spin) states coupled via Rashba-Dresselhaus
spin-orbit interaction using classical field Monte Carlo calculations. For
anisotropic spin-orbit coupling, we find a transition to a
Berenzinskii-Kosterlitz-Thouless superfluid phase with quasi-long range order.
We show that the spin-order of the quasi-condensate is driven by the anisotropy
of interparticle interaction, favoring either a homogeneous plane wave state or
stripe phase with broken translational symmetry. Both phases show
characteristic behavior in the algebraically decaying spin density correlation
function. For fully isotropic interparticle interaction, our calculations
indicate a fractionalized quasi-condensate where the mean-field degeneracy of
plane wave and stripe phase remains robust against critical fluctuations. In
the case of fully isotropic spin-orbit coupling, the circular degeneracy of the
single particle ground state destroys the algebraic ordered phase in the
thermodynamic limit, but a cross-over remains for finite size systems.",1701.05002v1
2017-07-17,Interfacial Rashba magnetoresistance of two-dimensional electron gas at LaAlO$_3$/SrTiO$_3$ interface,"We report the angular dependence of magnetoresistance in two-dimensional
electron gas at LaAlO$_3$/SrTiO$_3$ interface. We find that this interfacial
magnetoresistance exhibits a similar angular dependence to the spin Hall
magnetoresistance observed in ferromagnet/heavy metal bilayers, which has been
so far discussed in the framework of bulk spin Hall effect of heavy metal
layer. The observed magnetoresistance is in qualitative agreement with
theoretical model calculation including both Rashba spin-orbit coupling and
exchange interaction. Our result suggests that magnetic interfaces subject to
spin-orbit coupling can generate a nonnegligible contribution to the spin Hall
magnetoresistance and the interfacial spin-orbit coupling effect is therefore
key to the understanding of various spin-orbit-coupling-related phenomena in
magnetic/non-magnetic bilayers.",1707.04977v1
2021-04-27,Magnon modes as a joint effect of surface ferromagnetism and spin-orbite coupling in CoSi chiral topological semimetal,"CoSi single crystal is a known realization of a chiral topological semimetal
with simultaneously broken mirror and inversion symmetries. In addition to the
symmetry-induced spin-orbit coupling, surface ferromagnetism is known in
nominally diamagnetic CoSi structures, which appears due to the distorted bonds
and ordered vacancies near the surface. We experimentally investigate electron
transport through a thin CoSi flake at high current density. Surprisingly, we
demonstrate $dV/dI(I)$ curves which are qualitatively similar to ones for
ferromagnetic multilayers with characteristic $dV/dI$ magnon peaks and
unconventional magnetic field evolution of the peaks' positions. We understand
these observations as a result of current-induced spin polarization due to the
significant spin-orbit coupling in CoSi. Scattering of non-equilibrium
spin-polarized carriers within the surface ferromagnetic layer is responsible
for the precessing spin-wave excitations, so the observed magnon modes are the
joint effect of surface ferromagnetism and spin-orbit coupling in a CoSi chiral
topological semimetal. Thus, thin CoSi flakes behave as magnetic conductors
with broken inversion symmetry, which is important for different spintronic
phenomena.",2104.13252v1
2021-09-14,Magnon Condensation in Dimerized Antiferromagnets with Spin-Orbit Coupling,"Bose-Einstein condensation (BEC) of triplet excitations triggered by a
magnetic field, sometimes called magnon BEC, in dimerized antiferromagnets
gives rise to a long-range antiferromagnetic order in the plane perpendicular
to the applied magnetic field. To explore the effects of spin-orbit coupling on
magnon condensation, we study a spin model on a distorted honeycomb lattice
with dimerized Heisenberg exchange ($J$ terms) and uniform off-diagonal
exchange ($\Gamma'$ terms) interactions. Via variational Monte Carlo
calculations and spin-wave theory, we find that an out-of-plane magnetic field
can induce different types of long-range magnetic orders, no matter if the
ground state is a non-magnetic dimerized state or an ordered N\'{e}el state.
Furthermore, the critical properties of field-driven phase transitions in the
presence of spin-orbit couplings, as illustrated from spin-wave spectrum and
interpreted by effective field theory, can be different from the conventional
magnon BEC. Our study is helpful to understand the rich phases of spin-orbit
coupled antiferromagnets induced by magnetic fields.",2109.06518v2
2022-05-16,Chiral anomaly in noncentrosymmetric systems induced by spin-orbit coupling,"The chiral anomaly may be realized in condensed matter systems with pairs of
Weyl points. Here we show that the chiral anomaly can be realized in diverse
noncentrosymmetric systems even without Weyl point pairs when spin-orbit
coupling induces nonzero Berry curvature flux through Fermi surfaces. This
motivates the condensed matter chiral anomaly to be interpreted as a Fermi
surface property rather than a Weyl point property. The
spin-orbit-coupling-induced anomaly reproduces the well-known charge transport
properties of the chiral anomaly such as the negative longitudinal
magnetoresistance and the planar Hall effect in Weyl semimetals. Since it is of
spin-orbit coupling origin, it also affects the spin transport and gives rise
to anomaly-induced longitudinal spin currents and the magnetic spin Hall
effect, which are absent in conventional Weyl semimetals.",2205.07451v2
2022-09-21,Spin-orbit-coupled spinor gap solitons in Bose-Einstein condensates,"Spin-1 spin-orbit-coupled spinor Bose-Einstein condensates have been realized
in experiment. We study spin-orbit-coupled spinor gap solitons in this
experimentally realizable system with an optical lattice. The spin-dependent
parity symmetry of the spin-orbit coupling plays an important role in
properties of gap solitons. Two families of solitons with opposite
spin-dependent parity are found. Using an approximating model by replacing the
optical lattice with a Harmonic trap, we demonstrate the physical origination
of these two families. For a large negative quadratic Zeeman shift, we also
find a type of gap solitons that spontaneously breaks the spin-dependent parity
symmetry due to the ferromagnetic spinor interactions.",2209.10190v2
2023-02-28,Quantum phases in spin-orbit-coupled Floquet spinor Bose gases,"We propose a spin-orbit-coupled Floquet spinor Bose-Einstein condensate (BEC)
which can be implemented by Floquet engineering of a quadratic Zeeman field.
The Floquet spinor BEC has a Bessel-function-modulated Rabi frequency and a
Floquet-induced spin-exchange interaction. The quantum phase diagram of the
spin-orbit-coupled Floquet spinor BEC is investigated by considering
antiferromagnetic or ferromagnetic spin-spin interactions. In comparison with
the usual spin-orbit-coupled spin-1 BEC, we find that a stripe phase for
antiferromagnetic interactions can exist in a large quadratic Zeeman field
regime, and a different stripe phase with an experimentally favorable contrast
for ferromagnetic interactions is uncovered.",2302.14232v2
2023-06-21,Topological state transitions in electromagnetic topological defects,"The recent emergence of electromagnetic topological defects has attracted
wide interest in fields from topological photonics to deep-subwavelength
light-mater interactions. Previously, much of the research has focused on
constructing specific topological defects but the fundamental theory describing
the physical mechanisms underlying their formation and transitions is lacking.
Here, we present a spin-orbit coupling based theory describing such mechanisms
for various configurations of spin topological defects in confined
electromagnetic fields. The results reveal that their formation originates from
the conservation of total angular momentum and that their transitions are
determined by anisotropic spin-orbit couplings. By engineering the spin-orbit
couplings, we observe the formation and transitions of Neel-type, twisted-type,
and Bloch-type spin topological defects in confined electromagnetic fields. A
stable Block-type spin topological defect is reported for the first time. Our
theory can also describe the transitions of field topological defects. The
findings enrich the portfolio of electromagnetic topological defects, deepen
our understanding of conserved laws, spin-orbit couplings and transitions of
topological defects in confined electromagnetic systems, and predict
applications in high-density optical data transmissions and chiral quantum
optics.",2306.12024v1
2007-09-16,Measurement of Rashba and Dresselhaus spin-orbit magnetic fields,"Spin-orbit coupling is a manifestation of special relativity. In the
reference frame of a moving electron, electric fields transform into magnetic
fields, which interact with the electron spin and lift the degeneracy of
spin-up and spin-down states. In solid-state systems, the resulting spin-orbit
fields are referred to as Dresselhaus or Rashba fields, depending on whether
the electric fields originate from bulk or structure inversion asymmetry,
respectively. Yet, it remains a challenge to determine the absolute value of
both contributions in a single sample. Here we show that both fields can be
measured by optically monitoring the angular dependence of the electrons' spin
precession on their direction of movement with respect to the crystal lattice.
Furthermore, we demonstrate spin resonance induced by the spin-orbit fields. We
apply our method to GaAs/InGaAs quantum-well electrons, but it can be used
universally to characterise spin-orbit interactions in semiconductors,
facilitating the design of spintronic devices.",0709.2509v1
2016-07-22,Spin-orbit interaction in relativistic nuclear structure models,"Relativistic self-consistent mean-field (SCMF) models naturally account for
the coupling of the nucleon spin to its orbital motion, whereas
non-relativistic SCMF methods necessitate a phenomenological ansatz for the
effective spin-orbit potential. Recent experimental studies aim to explore the
isospin properties of the effective spin-orbit interaction in nuclei. SCMF
models are very useful in the interpretation of the corresponding data, however
standard relativistic mean-field and non-relativistic Hartree-Fock models use
effective spin-orbit potentials with different isovector properties, mainly
because exchange contributions are not treated explicitly in the former. The
impact of exchange terms on the effective spin-orbit potential in relativistic
mean-field models is analysed, and it is shown that it leads to an isovector
structure similar to the one used in standard non-relativistic Hartree-Fock.
Data on the isospin dependence of spin-orbit splittings in spherical nuclei
could be used to constrain the isovector-scalar channel of relativistic
mean-field models. The reproduction of the empirical kink in the isotope shifts
of even Pb nuclei by relativistic effective interactions points to the
occurrence of pseudospin symmetry in the single-neutron spectra in these
nuclei.",1607.06567v1
2001-10-22,Magnetoconductance of a two-dimensional metal in the presence of spin-orbit coupling,"We show that in the metallic phase of a two dimensional electron gas the
spin-orbit coupling due to structure inversion asymmetry leads to a
characteristic anisotropy in the magnetoconductance. Within the assumption that
the metallic phase can be described by a Fermi liquid, we compute the
conductivity in the presence of an in-plane magnetic field. Both the spin-orbit
coupling and the Zeeman coupling with the magnetic field give rise to two spin
subbands, in terms of which most of the transport properties can be discussed.
  The strongest conductivity anisotropy occurs for Zeeman energies of the order
of the Fermi energy corresponding to the depopulation of the upper spin
subband. The energy scale associated with the spin-orbit coupling controls the
strength of the effect. More in particular, we find that the detailed behavior
and the sign of the anisotropy depends on the underlying scattering mechanism.
Assuming small angle scattering to be the dominant scattering mechanism our
results agree with recent measurement on Si-MOSFET's in the vicinity of the
metal-insulator transition.",0110454v1
2018-02-28,Beliaev Damping in Spin-$\frac{1}{2}$ Interacting Bosons with Spin-Orbit Coupling,"Beliaev damping provides one of the most important mechanisms for dissipation
of quasiparticles through beyond-mean-field effects at zero temperature. Here
we present the first analytical result of Beliaev damping in low-energy
excitations of spin-$\frac{1}{2}$ interacting bosons with equal Rashba and
Dresslhaus spin-orbit couplings. We identify novel features of Beliaev decay
rate due to spin-orbit coupling, in particular, it shows explicit dependence on
the spin-density interaction and diverges at the interaction-modified phase
boundary between the zero-momentum and plane-wave phases. This represents a
manifestation of the effect of spin-orbit coupling in the beyond-mean-field
regime, which by breaking Galilean invariance couples excitations in the
density- and spin-channels. By describing the Beliaev damping in terms of the
observable dynamic structure factors, our results allow direct experimental
access within current facilities.",1802.10295v1
2019-04-11,Spin-exchange-induced exotic superfluids in a Bose-Fermi spinor mixture,"We consider a mixture of spin-1/2 bosons and fermions, where only the bosons
are subjected to the spin-orbit coupling induced by Raman beams. The fermions,
although not directly coupled to the Raman lasers, acquire an effective
spin-orbit coupling through the spin-exchange interaction between the two
species. Our calculation shows that this is a promising way of obtaining
spin-orbit coupled Fermi gas without Raman-induced heating, where the
long-sought topological Fermi superfluids and topological bands can be
realized. Conversely, we find that the presence of fermions not only provides a
new way to create the supersolid stripe phase of the bosons, but more
strikingly it can also greatly increase the spatial period of the bosonic
density stripes, and hence makes this phase directly observable in the
experiment. This system provides a new and practical platform to explore the
physics of spin-orbit coupling, which possesses a dynamic nature through the
interaction between the two species.",1904.05486v2
2021-08-04,Manipulating polariton condensates by Rashba-Dresselhaus coupling at room temperature,"The spin-orbit coupling plays an important role in the spin Hall effect and
the topological insulators. In addition, the spin-orbit coupled Bose-Einstein
condensates show remarkable quantum many-body phase transition. In this work we
tune the exciton polariton condensate by virtue of the Rashba-Dresselhaus (RD)
spin-orbit coupling in a liquid-crystal filled microcavity where perovskite
CsPbBr3 microplates act as the gain material at room temperature. We realize an
artificial gauge field on the CsPbBr3 exciton polariton condensate, which
splits the condensates with opposite spins in both momentum and real spaces.
Our work paves the way to manipulate the exciton polariton condensate with a
synthetic gauge field based on the RD spin-orbit coupling at room temperature.",2108.02057v2
2014-11-06,Spin - orbital-angular-momentum coupling in Bose-Einstein condensates,"Spin-orbit coupling (SOC) plays a crucial role in many branches of physics.
In this context, the recent experimental realization of the coupling between
spin and linear momentum of ultracold atoms opens a completely new avenue for
exploring new spin-related superfluid physics. Here we propose that another
important and fundamental SOC, the coupling between spin and orbital angular
momentum (SOAM), can be implemented for ultracold atoms using higher-order
Laguerre-Gaussian laser beams to induce Raman coupling between two hyperfine
spin states of atoms. We study the ground-state phase diagrams of SOAM-coupled
Bose-Einstein condensates on a ring trap and explore their applications in
gravitational force detection. Our results may provide the basis for further
investigation of intriguing superfluid physics induced by SOAM coupling, such
as collective excitations.",1411.1737v3
2007-05-03,Coupled spin-charge drift-diffusion equations for the Rashba model,"Coupled spin-charge drift-diffusion equations are derived for a biased
two-dimensional electron gas with weak Rashba spin-orbit interaction. The basic
equations formally agree with recent results obtained for spin-orbit coupled
small polarons. It is shown that effects of an in-plane electric field on a
homogeneous spin system can completely be described by an associated in-plane
magnetic field. Exploiting this analogy, we predict among other things the
electric-field equivalent of the Hanle effect.",0705.0415v1
2010-11-17,Magnetotransport and spin dynamics in an electron gas formed at oxide interfaces,"We investigate the spin-dependent transport properties of a two-dimensional
electron gas formed at oxides' interface in the presence of a magnetic field.
We consider several scenarios for the oxides' properties, including oxides with
co-linear or spiral magnetic and ferroelectric order. For spiral multiferroic
oxides, the magnetoelectric coupling and the topology of the localized magnetic
moments introduce additional, electric field controlled spin-orbit coupling
that affects the magneto-oscillation of the current. An interplay of this
spin-orbit coupling, the exchange field, and of the applied magnetic field
results in a quantum, gate-controlled spin and charge Hall conductance.",1011.3924v1
2004-04-30,"Orbital and spin interplay in spin-gap formation in pyroxene titanium oxides ATiSi2O6 (A=Na, Li)","Interplay between orbital and spin degrees of freedom is theoretically
studied for the phase transition to the spin-singlet state with lattice
dimerization in pyroxene titanium oxides ATiSi2O6 (A=Na, Li). For the quasi
one-dimensional spin-1/2 systems, we derive an effective spin-orbital-lattice
coupled model in the strong correlation limit with explicitly taking account of
the t_2g orbital degeneracy, and investigate the model by numerical simulation
as well as the mean-field analysis. We find a nontrivial feedback effect
between orbital and spin degrees of freedom; as temperature decreases,
development of antiferromagnetic spin correlations changes the sign of orbital
correlations from antiferro to ferro type, and finally the ferro-type orbital
correlations induce the dimerization and the spin-singlet formation. As a
result of this interplay, the system undergoes a finite-temperature transition
to the spin-dimer and orbital-ferro ordered phase concomitant with the
Jahn-Teller lattice distortion. The numerical results for the magnetic
susceptibility show a deviation from the Curie-Weiss behavior, and well
reproduce the experimental data. The results reveal that the Jahn-Teller energy
scale is considerably small and the orbital and spin exchange interactions play
a decisive role in the pyroxene titanium oxides.",0404730v2
2013-01-11,A new type of nuclear collective motion - the spin scissors mode,"The coupled dynamics of low lying modes and various giant resonances are
studied with the help of the Wigner Function Moments method on the basis of
Time Dependent Hartree-Fock equations in the harmonic oscillator model
including spin-orbit potential plus quadrupole-quadrupole and spin-spin
residual interactions. New low lying spin dependent modes are analyzed. Special
attention is paid to the spin scissors mode.",1301.2513v1
2013-06-13,Electrical control of phonon mediated spin relaxation rate in semiconductor quantum dots: the Rashba vs the Dresselhaus spin-orbit couplings,"In symmetric quantum dots (QDs), it is well known that the spin-hot spot
(i.e., the cusp-like structure due to the presence of degeneracy near the level
or anticrossing point) is present for the pure Rashba case but is absent for
the pure Dresselhaus case [Phys. Rev. Lett. 95, 076805 (2005)]. Since the
Dresselhaus spin-orbit coupling dominates over the Rashba spin-orbit coupling
in GaAs and GaSb QDs, it is important to find the exact location of the
spin-hot spot or the cusp-like structure even for the pure Dresselhaus case. In
this paper, for the first time, we present analytical and numerical results
that show that the spin-hot spot can also be seen for the pure Dresselhaus
spin-orbit coupling case by inducing large anisotropy through external gates.
At or nearby the spin-hot spot, the spin transition rate enhances and the
decoherence time reduces by several orders of magnitude compared to the case
with no spin-hot spot. Thus one should avoid such locations when designing QD
spin based transistors for the possible implementation in quantum logic gates,
solid state quantum computing and quantum information processing. It is also
possible to extract the exact experimental data (Phys. Rev. Lett. 100, 046803
(2008)) for the phonon mediated spin-flip rates from our developed theoretical
model.",1306.3135v1
2007-05-18,Magnetoresistance due to edge spin accumulation,"Because of spin-orbit interaction, an electrical current is accompanied by a
spin current resulting in spin accumulation near the sample edges. Due again to
spin-orbit interaction this causes a small decrease of the sample resistance.
An applied magnetic field will destroy the edge spin polarization leading to a
positive magnetoresistance. This effect provides means to study spin
accumulation by electrical measurements. The origin and the general properties
of the phenomenological equations describing coupling between charge and spin
currents are also discussed.",0705.2738v2
2007-05-22,Spin dynamics in rolled-up two dimensional electron gases,"A curved two dimensional electron gas with spin-orbit interactions due to the
radial confinement asymmetry is considered. At certain relation between the
spin-orbit coupling strength and curvature radius the tangential component of
the electron spin becomes a conserved quantity for any spin-independent
scattering potential that leads to a number of interesting effects such as
persistent spin helix and strong anisotropy of spin relaxation times. The
effect proposed can be utilized in the non-ballistic spin-field-effect
transistors.",0705.3174v1
2016-05-10,Controlling Spin-Polarization in Graphene by Cloaking Magnetic and Spin-Orbit Scatterers,"We consider spin-dependent scatterers with large scattering cross-sections in
graphene -a Zeeman-like and an intrinsic spin-orbit coupling impurity- and show
that a gated ring around them can be engineered to produce an effcient control
of the spin dependent transport, like current spin polarization and spin Hall
angle. Our analysis is based on a spin-dependent partial-waves expansion of the
electronic wave-functions in the continuum approximation, described by the
Dirac equation.",1605.02814v2
2023-08-25,Enhanced Spin Hall Ratio in Two-Dimensional III-V Semiconductors,"Spin Hall effect plays a critical role in spintronics since it can convert
charge current to spin current. Using state-of-the-art ab initio calculations
including quadrupole and spin-orbit coupling, the charge and spin transports
have been investigated in pristine and doped two-dimensional III-V
semiconductors. Valence bands induce a strong scattering which limits charge
conductivity in the hole-doped system, where spin Hall conductivity is enhanced
by the spin-orbit splitting, yielding an ultrahigh spin Hall ratio
$\xi\approx0.9$ in GaAs monolayer at room temperature.",2308.13692v1
2021-05-06,Spin-photon coupling for atomic qubit devices in silicon,"Electrically addressing spin systems is predicted to be a key component in
developing scalable semiconductor-based quantum processing architectures, to
enable fast spin qubit manipulation and long-distance entanglement via
microwave photons. However, single spins have no electric dipole, and therefore
a spin-orbit mechanism must be integrated in the qubit design. Here, we propose
to couple microwave photons to atomically precise donor spin qubit devices in
silicon using the hyperfine interaction intrinsic to donor systems and an
electrically-induced spin-orbit coupling. We characterise a one-electron system
bound to a tunnel-coupled donor pair (1P-1P) using the tight-binding method,
and then estimate the spin-photon coupling achievable under realistic
assumptions. We address the recent experiments on double quantum dots (DQDs) in
silicon and indicate the differences between DQD and 1P-1P systems. Our
analysis shows that it is possible to achieve strong spin-photon coupling in
1P-1P systems in realistic device conditions without the need for an external
magnetic field gradient.",2105.02904v1
2016-08-01,Spin-orbit coupled two-electron Fermi gases of ytterbium atoms,"We demonstrate all-optical implementation of spin-orbit coupling (SOC) in a
two-electron Fermi gas of $^{173}$Yb atoms by coupling two hyperfine ground
states with a narrow optical transition. Due to the SU($N$) symmetry of the
$^1$S$_0$ ground-state manifold which is insensitive to external magnetic
fields, an optical AC Stark effect is applied to split the ground spin states,
which exhibits a high stability compared with experiments on alkali and
lanthanide atoms, and separate out an effective spin-1/2 subspace from other
hyperfine levels for the realization of SOC. The dephasing spin dynamics when a
momentum-dependent spin-orbit gap being suddenly opened and the asymmetric
momentum distribution of the spin-orbit coupled Fermi gas are observed as a
hallmark of SOC. The realization of all-optical SOC for ytterbium fermions
should offer a new route to a long-lived spin-orbit coupled Fermi gas and
greatly expand our capability in studying novel spin-orbit physics with
alkaline-earth-like atoms.",1608.00478v3
2019-12-10,Ligand-field contributions to spin-phonon coupling in a family of Vanadium molecular qubits from multi-reference electronic structure theory,"Molecular electronic spins represent one of the most promising building
blocks for the design of quantum computing architectures. However, the
advancement of this technology requires the increase of spin lifetime at
ambient temperature. Spin-phonon coupling has been recognized as the key
interaction dictating spin relaxation at high temperature in molecular crystals
and the search for chemical-design principles to control such interaction are a
fundamental challenge in the field. Here we present a multi-reference
first-principles analysis of the g-tensor and the spin-phonon coupling in a
series of four exa-coordinate Vanadium(IV) molecular complexes, where the
catecholate ligand donor atom is progressively changed from Oxygen to Sulphur,
Selenium and Tellurium. A ligand field interpretation of the multi-reference
electronic structure theory results made it possible to rationalize the
correlation between the molecular g-shifts and the average spin-phonon coupling
coefficients, revealing the role of spin-orbit coupling, chemical bond
covalency and energy splitting of d-like orbitals in spin relaxation. Our study
reveals the simultaneous increase of metal-ligand covalency and electronic
excited state energy separation as key elements of an optimal strategy towards
long spin-lattice lifetimes in molecular qubits.",1912.04545v1
2006-04-13,"Spin photocurrent, its spectra dependence, and current-induced spin polarization in an InGaAs/InAlAs two-dimensional electron gas","Converse effect of spin photocurrent and current induced spin polarization
are experimentally demonstrated in the same two-dimensional electron gas system
with Rashba spin splitting. Their consistency with the strength of the Rashba
coupling as measured from beating of the Shubnikov-de Haas oscillations reveals
a unified picture for the spin photocurrent, current-induced spin polarization
and spin orbit coupling. In addition, the observed spectral inversion of the
spin photocurrent indicates the system with dominating structure inversion
asymmetry.",0604331v1
2007-11-21,Josephson Effect between Conventional and Rashba Superconductors,"We study the Josephson effect between a conventional s-wave superconductor
and a non-centrosymmetric superconductor with Rashba spin-orbit coupling.
Rashba spin-orbit coupling affects the Josephson pair tunneling in a
characteristic way. The Josephson coupling can be decomposed into two parts, a
`spin-singlet-like' and a `spin-triplet-like' component. The latter component
can lead to shift of the Josephson phase by \pi relative to the former
coupling. This has important implications on interference effects and may
explain some recent experimental results for the Al/CePt3Si junction.",0711.3241v2
2007-04-06,Effect of electron-electron interaction on the phonon-mediated spin relaxation in quantum dots,"We estimate the spin relaxation rate due to spin-orbit coupling and acoustic
phonon scattering in weakly-confined quantum dots with up to five interacting
electrons. The Full Configuration Interaction approach is used to account for
the inter-electron repulsion, and Rashba and Dresselhaus spin-orbit couplings
are exactly diagonalized. We show that electron-electron interaction strongly
affects spin-orbit admixture in the sample. Consequently, relaxation rates
strongly depend on the number of carriers confined in the dot. We identify the
mechanisms which may lead to improved spin stability in few electron (>2)
quantum dots as compared to the usual one and two electron devices. Finally, we
discuss recent experiments on triplet-singlet transitions in GaAs dots subject
to external magnetic fields. Our simulations are in good agreement with the
experimental findings, and support the interpretation of the observed spin
relaxation as being due to spin-orbit coupling assisted by acoustic phonon
emission.",0704.0868v2
2011-11-22,Spatial Analogue of Quantum Spin Dynamics via Spin-Orbit Interaction,"We map electron spin dynamics from time to space in quantum wires with
spatially uniform and oscillating Rashba spin-orbit coupling. The presence of
the spin-orbit interaction introduces pseudo-Zeeman couplings of the electron
spins to effective magnetic fields. We show that by periodically modulating the
spin-orbit coupling along the quantum wire axis, it is possible to create the
spatial analogue of spin resonance, without the need for any real magnetic
fields. The mapping of time-dependent operations onto a spatial axis suggests a
new mode for quantum information processing in which gate operations are
encoded into the band structure of the material. We describe a realization of
such materials within nanowires at the interface of LaAlO3/SrTiO3
heterostructures.",1111.5311v1
2013-08-10,Spin Chaos Manifestation in a Driven Quantum Billiard with Spin-Orbit Coupling,"The coupling of orbital and spin degrees of freedom is the source of many
interesting phenomena. Here, we study the electron dynamics in a quantum
billiard --a mesoscopic rectangular quantum dot-- with spin-orbit coupling
driven by a periodic electric field. We find that both the spatial and temporal
profiles of the observables demonstrate the transition to chaotic dynamics with
qualitative modifications of the power spectra and patterns of probability and
spin density. The time dependence of the wavefunctions and spin density
distributions indicates spin-charge separation {seen in the decay of the
spin-charge density correlators}. This new spin chaos effect can be
experimentally verified leading to a better understanding of the interplay
between spin and spatial degrees of freedom, relevant to fundamental and
applied quantum physics.",1308.2333v2
2014-03-16,Anisotropic intrinsic spin Hall effect in quantum wires,"We use numerical simulations to investigate the spin Hall effect in quantum
wires in the presence of both Rashba and Dresselhaus spin-orbit coupling. We
find that the intrinsic spin Hall effect is highly anisotropic with respect to
the orientation of the wire, and that the nature of this anisotropy depends
strongly on the electron density and the relative strengths of the Rashba and
Dresselhaus spin-orbit coupling. In particular, at low densities when only one
subband of the quantum wire is occupied, the spin Hall effect is strongest for
electron momentum along the $[\bar{1}10]$ axis, which is opposite than what is
expected for the purely 2D case. In addition, when more than one subband is
occupied, the strength and anisotropy of the spin Hall effect can vary greatly
over relatively small changes in electron density, which makes it difficult to
predict which wire orientation will maximize the strength of the spin Hall
effect. These results help to illuminate the role of quantum confinement in
spin-orbit-coupled systems, and can serve as a guide for future experimental
work on the use of quantum wires for spin-Hall-based spintronic applications.",1403.3936v1
2006-05-23,All-electrical control of single ion spins in a semiconductor,"We propose a method for all-electrical initialization, control and readout of
the spin of single ions substituted into a semiconductor. Mn ions in GaAs form
a natural example. In the ion's ground state the Mn core spin magnetic moment
locks antiparallel to the spin and orbital magnetic moment of a bound valence
hole from the GaAs host. Direct electrical manipulation of the ion spin is
possible because electric fields manipulate the orbital wave function of the
hole, and through the spin-orbit coupling the spin is reoriented as well.
Coupling two or more ion spins can be achieved using electrical gates to
control the size of the valence hole wave function near the semiconductor
surface. This proposal for coherent manipulation of individual ionic spins and
controlled coupling of ionic spins via electrical gates alone may find
applications in extremely high density information storage and in scalable
coherent or quantum information processing.",0605203v2
2014-08-04,Spiral spin textures of bosonic Mott insulator with SU(3) spin-orbit coupling,"We study the Mott phase of three-component bosons, with one particle per
site, in an optical lattice by mapping it onto an SU(3) spin model. In the
simplest case of full SU(3) symmetry, one obtains a ferromagnetic Heisenberg
model. Introducing an SU(3) analog of spin-orbit coupling, additional spin-spin
interactions are generated. We first consider the scenario of spin-dependent
hopping phases, leading to Dzyaloshinskii-Moriya-type interactions. They result
in the formation of spiral spin textures, which in one dimension can be
understood by a local unitary transformation. Applying classical Monte Carlo
simulations, we extend our study to two-dimensional systems, and systems with
""true"" spin-orbit coupling, involving spin-changing hoppings.",1408.0769v2
2017-04-12,Spin Hall effect emerging from a chiral magnetic lattice without spin-orbit coupling,"The spin Hall effect (SHE), which converts a charge current into a transverse
spin current, has long been believed to be a phenomenon induced by the
spin--orbit coupling. Here, we propose an alternative mechanism to realize the
intrinsic SHE through a chiral magnetic structure that breaks the spin rotation
symmetry. No spin--orbit coupling is needed even when the scalar spin chirality
vanishes, different from the case of the topological Hall effect. In known
chiral antiferromagnetic compounds Mn$_3X$ ($X=$ Ga, Ge, and Sn), for example,
we indeed obtain large spin Hall conductivities based on \textit{ab initio}
calculations. Apart further developing the conceptual understanding of the SHE,
our work suggests an alternative strategy to design spin Hall materials without
involving heavy elements, which may be advantageous for technological
applications.",1704.03917v2
2024-03-15,Giant Spin Splitting and its Origin in Methylhydrazinium Lead Halide Perovskites,"Spin splitting, or removal of spin degeneracy in the electronic energy
band/level is often a measure of spin-orbit coupling strength and a way to
manipulate spin degrees of freedom. We use first-principles simulations to
predict giant spin splitting in methylhydrazinium lead halide (MHyPbX$_3$, MHy
= CH$_3$NH$_2$NH$_2$, X = Br and Cl) hybrid organic-inorganic perovskites. The
values can reach up to 408.0~meV at zero Kelvin and 281.6~meV at room
temperature. The origin of the effect is traced to the large distortion of
PbX$_3$ framework, driven primarily by Pb ions in the ferroelectric
$\Gamma^{3-}$ mode. The Pb displacements consist of combination of polar and
antipolar arrangements and result in up to 39.2~meV/atom enhancement of the
spin-orbit coupling energy in the polar phase of the materials. The spin-orbit
coupling gives origin to highly persistent spin textures in MHyPbX$_3$, which
are desirable for applications in spintronics and quantum computing. Our
findings reveal an additional functionality for hybrid organic-inorganic
perovskite and open a way for the design of more materials with giant spin
splitting.",2403.10035v1
2007-10-29,Cyclotron motion and magnetic focusing in semiconductor quantum wells with spin-orbit coupling,"We investigate the ballistic motion of electrons in III-V semiconductor
quantum wells with Rashba spin-orbit coupling in a perpendicular magnetic
field. Taking into account the full quantum dynamics of the problem, we explore
the modifications of classical cyclotron orbits due to spin-orbit interaction.
As a result, for electron energies comparable with the cyclotron energy the
dynamics are particularly rich and not adequately described by semiclassical
approximations. Our study is complementary to previous semiclassical approaches
concentrating on the regime of weaker fields.",0710.5395v2
2012-06-21,Momentum-resolved radio-frequency spectroscopy of ultracold atomic Fermi gases in a spin-orbit coupled lattice,"We investigate theoretically momentum-resolved radio-frequency (rf)
spectroscopy of a noninteracting atomic Fermi gas in a spin-orbit coupled
lattice. This lattice configuration has been recently created at MIT [Cheuk et
al., arXiv:1205.3483] for 6Li atoms, by coupling the two hyperfine spin-states
with a pair of Raman laser beams and additional rf coupling. Here, we show that
momentum-resolved rf spectroscopy can measure single-particle energies and
eigenstates and therefore resolve the band structure of the spin-orbit coupled
lattice. In our calculations, we take into account the effects of temperatures
and harmonic traps. Our predictions are to be confronted with future
experiments on spin-orbit coupled Fermi gases of 40K atoms in a lattice
potential.",1206.4778v1
2018-09-04,Proximity-Induced Spin-Orbit Coupling in Graphene-Bi$_{1.5}$Sb$_{0.5}$Te$_{1.7}$Se$_{1.3}$ Heterostructures,"The weak intrinsic spin-orbit coupling in graphene can be greatly enhanced by
proximity coupling. Here we report on the proximity-induced spin-orbit coupling
in graphene transferred by hexagonal boron nitride (hBN) onto the topological
insulator Bi$_{1.5}$Sb$_{0.5}$Te$_{1.7}$Se$_{1.3}$ (BSTS) which was grown on a
hBN substrate by vapor solid synthesis. Phase coherent transport measurements,
revealing weak localization, allow us to extract the carrier density-dependent
phase coherence length $l_\phi$. While $l_\phi$ increases with increasing
carrier density in the hBN/graphene/hBN reference sample, it decreases in
BSTS/graphene due to the proximity-coupling of BSTS to graphene. The latter
behavior results from D'yakonov-Perel-type spin scattering in graphene with a
large proximity-induced spin-orbit coupling strength of at least 2.5 meV.",1809.01113v2
2021-12-11,Itinerant ferromagnetism of a dipolar Fermi gas with Raman-induced spin-orbit coupling,"We elucidate the itinerant ferromagnetism of a dipolar Fermi gas with a
Raman-induced spin-orbit coupling by investigating the exotic phase diagrams at
zero and finite temperature. It is revealed that the dipolar interaction along
with spin-orbit coupling can corroborate the formation of ferromagnetism and
the Raman coupling adversely eliminates the tendency to this ferromagnetism
transition, which greatly transcends the general understanding of this subject
with contact interaction only. We explore the ground states through the density
and spin-flip distribution in momentum space, which exhibits novel degeneracy
at strong Raman coupling indicated by a non-zero entropy at zero temperature.
We calculate the transition temperatures well within the reach of an
experimental system when altering the dipolar and spin-orbit coupling strength,
which paves a way to the further experimental realization.",2112.05898v2
2015-12-17,Multi-$Q$ hexagonal spin density waves and dynamically generated spin-orbit coupling: time-reversal invariant analog of the chiral spin density wave,"We study hexagonal spin-channel (""triplet"") density waves with commensurate
$M$-point propagation vectors. We first show that the three $Q=M$ components of
the singlet charge density and charge-current density waves can be mapped to
multi-component $Q=0$ nonzero angular momentum order in three dimensions ($3D$)
with cubic crystal symmetry. This one-to-one correspondence is exploited to
define a symmetry classification for triplet $M$-point density waves using the
standard classification of spin-orbit coupled electronic liquid crystal phases
of a cubic crystal. Through this classification we naturally identify a set of
non-coplanar spin density and spin-current density waves: the chiral spin
density wave and its time-reversal invariant analog. These can be thought of as
$3D$ $L=2$ and $L=4$ spin-orbit coupled isotropic $\beta$-phase orders. In
contrast, uniaxial spin density waves are shown to correspond to
$\alpha$-phases. The non-coplanar triple-$M$ spin-current density wave realizes
a novel $2D$ semimetal state with three flavors of four-component spin-momentum
locked Dirac cones, protected by a crystal symmetry akin to non-symmorphic
symmetry, and sits at the boundary between a trivial and topological insulator.
In addition, we point out that a special class of classical spin states,
defined as classical spin states respecting all lattice symmetries up to global
spin rotation, are naturally obtained from the symmetry classification of
electronic triplet density waves. These symmetric classical spin states are the
classical long-range ordered limits of chiral spin liquids.",1512.05673v3
2021-07-01,Orbitally-selective Breakdown of the Fermi Liquid and Simultaneous Enhancement of Metallic and Insulating States in Correlated Multi-band Systems with Spin-orbit Coupling,"We show that spin-orbit coupling (SOC) plays Janus-faced roles on the
orbitally-selective Mott transitions in a three-orbital Hubbard model with
crystal field splitting at a specific filling of $2/3$, which is a minimal
Hamiltonian for ruthenates. While the SOC favors metallic state due to
enhancement of orbital hybridization at smaller on-site Coulomb repulsions, it
stabilizes the Mott insulating state ascribed to lifting of orbital
degeneracies and enhancement of band polarizations at larger electronic
interaction. Moreover, an orbitally-selective non-Fermi liquid (OSnFL), where
breakdown and retention of the Fermi liquid coexist in different orbitals,
emerges between the orbitally-selective Mott phase and the Fermi-liquid state.
This novel state can be used to account for the exotic metallic behavior
observed in 4$d$ materials, such as Ca$_{1.8}$Sr$_{0.2}$RuO$_4$, Ba$_2$RuO$_4$
under strain and Sr$_2$RuO$_4$ under uniaxial pressure. We propose that
orbitally-selective Kondo breakdown may account for the OSnFL.",2107.00419v1
2023-12-07,Resolving the Orbital Character of Low-energy Excitations in Mott Insulator with Intermediate Spin-orbit Coupling,"Multi-band Mott insulators with moderate spin-orbit and Hund's coupling are
key reference points for theoretical concept developments of correlated
electron systems. The ruthenate Mott insulator Ca$_{2}$RuO$_{4}$ has therefore
been intensively studied by spectroscopic probes. However, it has been
challenging to resolve the fundamental excitations emerging from the hierarchy
of electronic energy scales. Here we apply state-of-the-art resonant inelastic
x-ray scattering to probe deeper into the electronic excitations found in
Ca$_{2}$RuO$_{4}$. In this fashion, we probe a series of spin-orbital
excitations at low energies and resolve the level splitting of the
intra-$t_{2g}$ structure due to spin-orbit coupling and crystal field
splitting. Most importantly, the low-energy excitations exhibit strong orbital
character. Such direct determination of relevant electronic energy scales is
important, as it sharpens the target for theory developments of Mott
insulators' orbital degree of freedom.",2312.04406v1
2020-11-06,Acoustic spin Hall effect in strong spin-orbit metals,"We report on the observation of the acoustic spin Hall effect that
facilitates lattice motion induced spin current via spin orbit interaction
(SOI). Under excitation of surface acoustic wave (SAW), we find a spin current
flows orthogonal to the propagation direction of a surface acoustic wave (SAW)
in non-magnetic metals. The acoustic spin Hall effect manifests itself in a
field-dependent acoustic voltage in non-magnetic metal (NM)/ferromagnetic metal
(FM) bilayers. The acoustic voltage takes a maximum when the NM layer thickness
is close to its spin diffusion length, vanishes for NM layers with weak SOI and
increases linearly with the SAW frequency. To account for these results, we
find the spin current must scale with the SOI and the time derivative of the
lattice displacement. Such form of spin current can be derived from a Berry
electric field associated with time varying Berry curvature and/or an
unconventional spin-lattice interaction mediated by SOI. These results, which
imply the strong coupling of electron spins with rotating lattices via the SOI,
show the potential of lattice dynamics to supply spin current in strong spin
orbit metals.",2011.03246v2
2007-10-28,On the nature of steady states of spin distributions in the presence of spin-orbit interactions,"In the presence of spin-orbit interactions, the steady state established for
spin distributions in an electric field is qualitatively different from the
steady state for charge distributions. This is primarily because the steady
state established for spin distributions involves spin precession due to
spin-orbit coupling. We demonstrate in this work that the spin density matrix
in an external electric field acquires two corrections with different
dependencies on the characteristic momentum scattering time. One part is
associated with conserved spins, diverges in the clean limit and is responsible
for the establishment of a steady-state spin density in electric fields.
Another part is associated with precessing spins, is finite in the clean limit
and is responsible for the establishment of spin currents in electric fields.
Scattering between these distributions has important consequences for spin
dynamics and spin-related effects in general, and explains some recent puzzling
observations, which are captured by our unified theory.",0710.5260v1
2018-04-23,Microscopic linear response theory of spin relaxation and relativistic transport phenomena in graphene,"We present a unified theoretical framework for the study of spin dynamics and
relativistic transport phenomena in disordered two-dimensional Dirac systems
with pseudospin-spin coupling. The formalism is applied to the paradigmatic
case of graphene with uniform Bychkov-Rashba interaction and shown to capture
spin relaxation processes and associated charge-to-spin interconversion
phenomena in response to generic external perturbations, including spin density
fluctuations and electric fields. A controlled diagrammatic evaluation of the
generalized spin susceptibility in the diffusive regime of weak spin-orbit
interaction allows us to show that the spin and momentum lifetimes satisfy the
standard Dyakonov-Perel relation for both weak (Gaussian) and resonant
(unitary) nonmagnetic disorder. Finally, we demonstrate that the spin
relaxation rate can be derived in the zero-frequency limit by exploiting the
SU(2) covariant conservation laws for the spin observables. Our results set the
stage for a fully quantum-mechanical description of spin relaxation in both
pristine graphene samples with weak spin-orbit fields and in graphene
heterostructures with enhanced spin-orbital effects currently attracting much
attention.",1804.08634v2
2019-04-08,Orbital Edelstein effect from density-wave order,"Coupling between charge and spin, and magnetoelectric effects more generally,
have been an area of great interest for several years, with the sought-after
ability to control magnetic degrees of freedom via charge currents serving as
an impetus. The orbital Edelstein effect (OEE) is a kinetic magnetoelectric
effect consisting of a bulk orbital magnetization induced by a charge current.
It is the orbital analogue of the spin Edelstein effect in spin-orbit coupled
materials, in which a charge current drives nonzero electron spin
magnetization. The OEE has recently been investigated in the context of Weyl
semimetals and Weyl metals. Motivated by these developments, we study a model
of electrons without spin-orbit coupling which exhibits line nodes that get
gapped out by via symmetry breaking due to an interaction-induced charge
density wave order. This model is shown to exhibit a temperature dependent OEE,
which appears due to symmetry reduction into a gyrotropic crystal class.",1904.04280v1
2011-10-30,Chaotic spin-dependent electron dynamics in a field-driven double dot potential,"We study the nonlinear classical dynamics of an electron confined in a double
dot potential and subjected to a spin-orbit coupling and a constant external
magnetic field. It is shown that due to the spin orbit coupling, the energy can
be transferred from the spin to the orbital motion. This naturally heats up the
orbital motion which, due to the presence of the separatrix line in the phase
space of the system, results in a motion of the electron between the dots. It
is shown that depending on the strength of the spin orbit coupling and the
energy of the system, the electronic orbital motion undergoes a transition from
the regular to the chaotic regime.",1110.6597v1
2018-02-23,Generation and detection of dissipationless spin current in MgO/Si bilayer,"Spintronics is an analogue to electronics where spin of the electron rather
than its charge is functionally controlled for devices. The generation and
detection of spin current without ferromagnetic or exotic/scarce materials are
two the biggest challenges for spintronics devices. In this study, we report a
solution to the two problems of spin current generation and detection in Si.
Using non-local measurement, we experimentally demonstrate the generation of
helical dissipationless spin current using spin-Hall effect. Contrary to the
theoretical prediction, we observe the spin-Hall effect in both n-doped and
p-doped Si. The helical spin current is attributed to the site-inversion
asymmetry of the diamond cubic lattice of Si and structure inversion asymmetry
in MgO/Si bilayer. The spin to charge conversion in Si is insignificant due to
weak spin-orbit coupling. For the efficient detection of spin current, we
report spin to charge conversion at the MgO (1nm)/Si (2 um) (p-doped and
n-doped) thin film interface due to Rashba spin-orbit coupling. We detected the
spin current at a distance of >100 um, which is an order of magnitude larger
than the longest spin diffusion length measured using spin injection
techniques. The existence of spin current in Si is verified from coercivity
reduction in Co/Pd multilayer due to spin-orbit torque generated by spin
current from Si.",1802.08627v1
2016-07-20,Electron dynamics in graphene with spin-orbit couplings and periodic potentials,"We use both continuum and lattice models to study the energy-momentum
dispersion and the dynamics of a wave packet for an electron moving in graphene
in the presence of spin-orbit couplings and either a single potential barrier
or a periodic array of potential barriers. Both Kane-Mele and Rashba spin-orbit
couplings are considered. A number of special things occur when the Kane-Mele
and Rashba couplings are equal in magnitude. In the absence of a potential, the
dispersion then consists of both massless Dirac and massive Dirac states. A
periodic potential is known to generate additional Dirac points; we show that
spin-orbit couplings generally open gaps at all those points, but if the two
spin-orbit couplings are equal, some of the Dirac points remain gapless. We
show that the massless and massive states respond differently to a potential
barrier; the massless states transmit perfectly through the barrier at normal
incidence while the massive states reflect from it. In the presence of a single
potential barrier, we show that there are states localized along the barrier.
Finally, we study the time evolution of a wave packet in the presence of a
periodic potential. We discover special points in momentum space where there is
almost no spreading of a wave packet; there are six such points in graphene
when the spin-orbit couplings are absent.",1607.05904v2
2000-12-07,Stripes Induced by Orbital Ordering in Layered Manganites,"Spin-charge-orbital ordered structures in doped layered manganites are
investigated using an orbital-degenerate double-exchange model tightly coupled
to Jahn-Teller distortions. In the ferromagnetic phase, unexpected diagonal
stripes at $x$=$1/m$ ($m$=integer) are observed, as in recent experiments.
These stripes are induced by the orbital degree of freedom, which forms a
staggered pattern in the background. A $\pi$-shift in the orbital order across
stripes is identified, analogous to the $\pi$-shift in spin order across
stripes in cuprates. At $x$=1/4 and 1/3, another non-magnetic phase with
diagonal static charge stripes is stabilized at intermediate values of the
$t_{\rm 2g}$-spins exchange coupling.",0012098v2
2004-07-15,Lattice Dynamics in a strongly dimerized low-dimensional model with orbital ordering,"We study the interplay of spin, orbital and lattice degrees of freedom in a
one-dimensional Kugel-Khomskii model coupled to phonons. In the vicinity of the
dimer point we analyze the excitation spectrum, mapping the spin and orbital
degrees of freedom to bond operators. In particular we study the
renormalization of the phonon propagator due to coupling to the orbital and
magnetic excitations. Considering both, ferro- and antiferro-orbital ordering
we will show that the appearance of orbiton shake-up processes in the phonon
spectrum is sensitive to the type of Jahn-Teller distortion. The relevance of
our results for optical spectroscopy on low dimensional transition metal
compounds will be discussed.",0407394v2
2006-06-30,Quantum Spin Hall Effect and Enhanced Magnetic Response by Spin-Orbit Coupling,"We show that the spin Hall conductivity in insulators is related with a
magnetic susceptibility representing the strength of the spin-orbit coupling.
We use this relationship as a guiding principle to search real materials
showing quantum spin Hall effect. As a result, we theoretically predict that
bismuth will show the quantum spin Hall effect, both by calculating the helical
edge states, and by showing the non-triviality of the Z_2 topological number,
and propose possible experiments.",0607001v2
2006-08-28,Inverse Spin Hall Effect by Spin Injection,"Motivated by a recent experiment[Nature {\bf 442}, 176 (2006)], we present a
quantitative microscopic theory to investigate the inverse spin-Hall effect
with spin injection into aluminum considering both intrinsic and extrinsic
spin-orbit couplings using the orthogonalized-plane-wave method. Our
theoretical results are in good agreement with the experimental data. It is
also clear that the magnitude of the anomalous Hall resistivity is mainly due
to contributions from extrinsic skew scattering, while its spatial variation is
determined by the intrinsic spin-orbit coupling.",0608594v2
2006-11-13,Anisotropic current-induced spin accumulation in the two-dimensional electron gas with spin-orbit coupling,"We investigate the magnetoelectric (or inverse spin-galvanic) effect in the
two dimensional electron gases with both Rashba and Dresselhaus spin-orbit
coupling using an exact solution of the Boltzmann equation for electron spin
and momentum. The spin response to an in-plane electric field turns out to be
highly anisotropic while the usual charge conductivity remains isotropic,
contrary to earlier statements.",0611328v2
2010-11-03,Direction Dependence of Spin Relaxation in Confined 2D Systems,"The dependence of spin relaxation on the direction of the quantum wire under
Rashba and Dresselhaus (linear and cubic) spin orbit coupling is studied.
Comprising the dimensional reduction of the wire in the diffusive regime, the
lowest spin relaxation and dephasing rates for (001) and (110) systems are
found. The analysis of spin relaxation reduction is then extended to
non-diffusive wires where it is shown that, in contrast to the theory of
dimensional crossover from weak localization to weak antilocalization in
diffusive wires, the relaxation due to cubic Dresselhaus spin orbit coupling is
reduced and the linear part shifted with the number of transverse channels.",1011.0850v1
2017-09-01,Spin Hall mode in a trapped thermal Rashba gas,"We theoretically investigate a two-dimensional harmonically-trapped gas of
identical atoms with Rashba spin-orbit coupling and no interatomic
interactions. In analogy with the spin Hall effect in uniform space, the gas
exhibits a spin Hall mode. In particular, in response to a displacement of the
center-of-mass of the system, spin-dipole moment oscillations occur. We
determine the properties of these oscillations exactly, and find that their
amplitude strongly depends on the spin-orbit coupling strength and the quantum
statistics of the particles.",1709.00426v1
2007-05-29,Parametric spin excitations in lateral quantum dots,"In this work, the spin dynamics of a single electron under parametric
modulation of a lateral quantum dot's electrostatic potential in the presence
of spin-orbit coupling is investigated. Numerical and theoretical calculations
demonstrate that, by squeezing and/or moving the electron's wave function, spin
rotations with Rabi frequencies on the order of tens of megahertz can be
achieved with experimentally accessible parameters in both parabolic and square
lateral quantum dots. Applications of parametric excitations for determining
spin-orbit coupling parameters and for increasing the spin polarization in the
electronic ground are demonstrated.",0705.4231v2
2010-03-29,Spontaneous persistent currents in magnetically ordered graphene ribbons,"We present a new mechanism for dissipationless persistent charge current. Two
dimensional topological insulators hold dissipationless spin currents in their
edges so that, for a given spin orientation, a net charge current flows which
is exactly compensated by the counter-flow of the opposite spin. Here we show
that ferromagnetic order in the edge upgrades the spin currents into persistent
charge currents, without applied fields. For that matter, we study an
interacting graphene zigzag ribbon with spin-orbit coupling. We find three
electronic phases with magnetic edges that carry currents reaching 0.4nA,
comparable to persistent currents in metallic rings, for the small spin orbit
coupling in graphene. One of the phases is a valley half-metal.",1003.5692v1
2010-04-07,Suppression of Spin Dephasing in a Two-Dimensional Electron Gas with a Quantum Point Contact,"Spin-orbit coupling is a source of strong spin dephasing in two- and
three-dimensional semiconducting systems. We report that spin dephasing in a
two-dimensional electron gas can be suppressed by introducing a quantum point
contact. Surprisingly, this suppression was not limited to the vicinity of the
contact but extended to the entire two-dimensional electron gas. This
facilitates the electrical control of the spin degree of freedom in a
two-dimensional electron gas through spin-orbit coupling.",1004.1006v2
2010-06-24,Local spin polarization of Landau levels under Rashba spin-orbit coupling,"We investigate the local spin polarization texture of Landau levels under
Rashba spin-orbit coupling in bulk two-dimensional electron gas (2DEG) systems.
In order to analyze the spin polarization as a function of two-dimensional
coordinates within the 2DEG, we first solve the system eigenstates in the
symmetric gauge. Our exact analytical wavefunction solutions are shown to be
gauge invariant with solutions obtained in the commonly used Landau gauge. We
illustrate the two-dimensional spatial spin profile for a single Landau level
and suggest means to measure and utilize the local polarization in practice.",1006.4679v1
2016-09-02,"Room-temperature transport properties of spin-orbit coupled Fermi systems: Spin thermoelectric effects, phonon skew scattering","In this note we summarize our recent results for the temperature dependence
of transport coefficients of metallic films in the presence of spin-orbit
coupling. Our focus is on (i) the spin Nernst and the thermal Edelstein
effects, and (ii) the phonon skew scattering contribution to the spin Hall
conductivity, which is relevant for the temperature dependence of the spin Hall
angle. Depending on the parameters, the latter is expected to show a
non-monotonous behavior.",1609.00561v1
2020-04-26,Spin soliton of Holstein model with spin-orbit coupling in one-dimensional conjugated polymers,"For Holstein model with Rashba spin-orbit coupling (SOC) we establish the
nonlinear Schr\""odinger equations and obtain exact soliton solution
analytically. It is found that the soliton is spin polarized determined both by
the SOC and the electron-phonon (e-ph) interaction. The soliton can be used to
describe the spin transport or spin current in organic semiconductors.",2004.12278v1
2001-12-01,"Coulomb ""blockade"" of Nuclear Spin Relaxation in Quantum Dots","We study the mechanism of nuclear spin relaxation in quantum dots due to the
electron exchange with 2D gas. We show that the nuclear spin relaxation rate is
dramatically affected by the Coulomb blockade and can be controlled by gate
voltage. In the case of strong spin-orbit coupling the relaxation rate is
maximal in the Coulomb blockade valleys whereas for the weak spin-orbit
coupling the maximum of the nuclear spin relaxation rate is near the Coulomb
blockade peaks.",0112013v3
2004-06-04,Competition between Spin-Orbit Interaction and Zeeman Coupling in Rashba 2DEGs,"We investigate systematically how the interplay between Rashba spin-orbit
interaction and Zeeman coupling affects the electron transport and the spin
dynamics in InGaAs-based 2D electron gases. From the quantitative analysis of
the magnetoconductance, measured in the presence of an in-plane magnetic field,
we conclude that this interplay results in a spin-induced breaking of time
reversal symmetry and in an enhancement of the spin relaxation time. Both
effects, due to a partial alignment of the electron spin along the applied
magnetic field, are found to be in excellent agreement with recent theoretical
predictions.",0406106v1
2005-12-15,On the conservation of spin currents in spin-orbit coupled systems,"Applying the Gordon-decomposition-like technique, the convective spin current
(CSC) is extracted from the total angular-momentum current. The CSC describes
the transport properties of the electron spin and is conserved in the
relativistic quantum mechanics approach where the spin-orbit coupling has been
intrinsically taken into account. Arrestingly, in the presence of external
electromagnetic field, the component of the convective spin along the field
remain still conserved. This conserved CSC is also derived for the first time
in the nonrelativistic limit using the Foldy-Wouthuysen transformation.",0512345v1
2007-12-21,Tailoring hole spin splitting and polarization in nanowires,"Spin splitting in p-type semiconductor nanowires is strongly affected by the
interplay between quantum confinement and spin-orbit coupling in the valence
band. The latter's particular importance is revealed in our systematic
theoretical study presented here, which has mapped the range of spin-orbit
coupling strengths realized in typical semiconductors. Large controllable
variations of the g-factor with associated characteristic spin polarization are
shown to exist for nanowire subband edges, which therefore turn out to be a
versatile laboratory for investigating the complex spin properties exhibited by
quantum-confined holes.",0712.3624v1
2008-01-27,Spin dynamics of two-dimensional electrons with Rashba spin-orbit coupling and electron-electron interactions,"We study the spin dynamics of two dimensional electron gases (2DEGs) with
Rashba spin-orbit coupling by taking account of electron-electron interactions.
The diffusion equations for charge and spin densities are derived by making use
of the path-integral approach and the quasiclassical Green's function.
Analyzing the effect of the interactions, we show that the spin-relaxation time
can be enhanced by the electron-electron interaction in the ballistic regime.",0801.4132v2
2009-02-22,"Graphene with Structure-Induced Spin-Orbit Coupling: Spin-Polarized States, Spin Zero Modes, and Quantum Hall Effect","Spin splitting of the energy spectrum of single-layer graphene on Au/Ni(111)
substrate has been recently reported. I show that eigenstates of spin-orbit
coupled graphene are polarized in-plane and perpendicular to electron momentum
$\bf k$; the magnitude of spin polarization $\bf S$ vanishes when $k \to 0$. In
a perpendicular magnetic field $\bf B$, $\bf S$ is parallel to $\bf B$, and two
zero modes emerge in the Landau level spectrum. Singular $\bf B$-dependence of
their magnetization suggests existence of a novel magnetic instability. They
also manifest themselves in a new unconventional quantum Hall effect.",0902.3806v1
2014-01-18,Spin injection via (110)-grown semiconductor barriers,"We study the tunneling of conduction electrons through a (110)-oriented
single-barrier heterostructure grown from III-V semiconductor compounds. It is
shown that, due to low spatial symmetry of such a barrier, the tunneling
current through the barrier leads to an electron spin polarization. The inverse
effect, generation of a direct tunneling current by spin polarized electrons,
is also predicted. We develop the microscopic theory of the effects and show
that the spin polarization emerges due to the combined action of the
Dresselhaus spin-orbit coupling within the barrier and the Rashba spin-orbit
coupling at the barrier interfaces.",1401.4526v1
2014-12-15,Characterization of S-T$_+$ Transition Dynamics via Correlation Measurements,"Nuclear spins are an important source of dephasing for electron spin qubits
in GaAs quantum dots. Most studies of their dynamics have focused on the
relatively slow longitudinal polarization. We show, based on a semiclassical
model and experimentally, that the dynamics of the transverse hyperfine field
can be probed by correlating individual Landau-Zener sweeps across the S-T$_+$
transition of a two-electron spin qubit. The relative Larmor precession of
different nuclear spin species leads to oscillations in these correlations,
whose decay arises from dephasing of the nuclei. In the presence of spin orbit
coupling, oscillations with the absolute Larmor frequencies whose amplitude
reflects the spin orbit coupling strength are expected.",1412.4551v1
2022-05-24,Electron spin orientation dependence on momentum in pseudo gap phase of Bi2212,"The aim of the paper is to study the electron spin direction dependence on
momentum due to the presence of Rashba spin-orbit coupling in the pseudo-gap
phase of Bi2212 bilayer. The non-trivial spin texture in k-space is found
tuneable by electric field. The dependence is reported earlier by a group of
workers in a spin- and angle-resolved photoemission spectroscopic measurement.
The synthetic spin-orbit coupling, characterized by the broken time-reversal
symmetry, is expected to be useful for the manipulation of the spin
orientation.",2205.11975v1
2020-02-05,Microscopic Origin of Spin-Orbit Torque in Ferromagnetic Heterostructures: A First Principles Approach,"We present an {\it ab initio}-based theoretical framework which elucidates
the origin of the spin-orbit torque (SOT) in Normal-Metal(NM)/Ferromagnet(FM)
heterostructures. The SOT is decomposed into two contributions, namely, {\it
spin-Hall} and the {\it spin-orbital} components. We find that {\it (i)} the
Field-Like (FL) SOT is dominated by the spin-orbital component and {\it (ii)}
both components contribute to the damping-like torque with comparable magnitude
in the limit of thick Pt film. The contribution of the spin-orbital component
to the DL-SOT is present only for NMs with strong SOC coupling strength. We
demonstrate that the FL-SOT can be expressed in terms of the non-equilibrium
spin-resolved orbital moment accumulation. The calculations reveal that the
experimentally reported oxygen-induced sign-reversal of the FL-SOT in Pt/Co
bilayers is due to the significant reduction of the majority-spin orbital
moment accumulation on the interfacial NM atoms.",2002.01983v1
2019-02-08,Spin dynamics of a millisecond pulsar orbiting closely around a massive black hole,"We investigate the spin dynamics of a millisecond pulsar (MSP) in a tightly
bounded orbit around a massive black hole. These binaries are progenitors of
the extreme-mass-ratio-inspirals (EMRIs) and intermediate-mass-ratio-inspirals
(IMRIs) gravitational wave events. The Mathisson-Papapetrou-Dixon (MPD)
formulation is used to determine the orbital motion and spin modulation and
evolution. We show that the MSP will not be confined in a planar Keplerian
orbit and its spin will exhibit precession and nutation induced by spin-orbit
coupling and spin-curvature interaction. These spin and orbital behaviours will
manifest observationally in the temporal variations in the MSP's pulsed
emission and, with certain geometries, in the self-occultation of the pulsar's
emitting poles. Radio pulsar timing observations will be able to detect such
signatures. These extreme-mass-ratio binaries (EMRBs) and
intermediate-mass-ratio binaries (IMRBs) are also strong gravitational wave
sources. Combining radio pulsar timing and gravitational wave observations will
allow us to determine the dynamics of these systems in high precision and hence
the subtle behaviours of spinning masses in strong gravity.",1902.03146v1
2022-11-07,Determining Perpendicular Magnetic Anisotropy in Fe/MgO/Fe Magnetic Tunnel Junction: A DFT-Based Spin-Orbit Torque Method,"In our JunPy package, we have combined the first-principles calculated
self-consistent Hamiltonian with divide-and-conquer technique to successfully
determine the magnetic anisotropy (MA) in an Fe/MgO/Fe magnetic tunnel junction
(MTJ). We propose a comprehensive analytical derivation to clarify the crucial
roles of spin-orbit coupling that mediates the exchange and spin-orbit
components of spin torque, and the kinetic and spin-orbit components of spin
current accumulation. The angular dependence of cumulative spin-orbit torque
(SOT) indicates a uniaxial MA corresponding to the out-of-plane rotations of
magnetic moments of the free Fe layers. Different from the conventional MA
energy calculation and the phenomenological theory for a whole MTJ, our results
provide insight into the orbital-resolved SOT for atomistic spin dynamics
simulation in emergency complex magnetic heterojunctions.",2211.03603v3
2017-04-20,Dynamics of a j=3/2 quantum spin liquid,"We study a spin-orbital model for 4$d^{1}$ or 5$d^{1}$ Mott insulators in
ordered double perovskites with strong spin-orbit coupling. This model is
conveniently written in terms of pseudospin and pseudo-orbital operators
representing multipoles of the effective $j=3/2$ angular momentum. Similarities
between this model and the effective theories of Kitaev materials motivate the
proposal of a chiral spin-orbital liquid with Majorana fermion excitations. The
thermodynamic and spectroscopic properties of this quantum spin liquid are
characterized using parton mean-field theory. The heat capacity, spin-lattice
relaxation rate, and dynamic structure factor for inelastic neutron scattering
are calculated and compared with the experimental data for the spin liquid
candidate Ba$_{2}$YMoO$_{6}$. Moreover, based on a symmetry analysis, we
discuss the operators involved in resonant inelastic X-ray scattering (RIXS)
amplitudes for double perovskite compounds. In general, the RIXS cross sections
allow one to selectively probe pseudospin and pseudo-orbital degrees of
freedom. For the chiral spin-orbital liquid in particular, these cross sections
provide information about the spectrum for different flavors of Majorana
fermions.",1704.06134v3
2010-09-23,Time dependent configuration interaction simulations of spin swap in spin orbit coupled double quantum dots,"We perform time-dependent simulations of spin exchange for an electron pair
in laterally coupled quantum dots. The calculation is based on configuration
interaction scheme accounting for spin-orbit (SO) coupling and
electron-electron interaction in a numerically exact way. Noninteracting
electrons exchange orientations of their spins in a manner that can be
understood by interdot tunneling associated with spin precession in an
effective SO magnetic field that results in anisotropy of the spin swap. The
Coulomb interaction blocks the electron transfer between the dots but the spin
transfer and spin precession due to SO coupling is still observed. The
electron-electron interaction additionally induces an appearance of spin
components in the direction of the effective SO magnetic field which are
opposite in both dots. Simulations indicate that the isotropy of the spin swap
is restored for equal Dresselhaus and Rashba constants and properly oriented
dots.",1009.4562v1
2003-12-11,Orbital and spin contributions to the $g$-tensors in metal nanoparticles,"We present a theoretical study of the mesoscopic fluctuations of $g$-tensors
in a metal nanoparticle. The calculations were performed using a semi-realistic
tight-binding model, which contains both spin and orbital contributions to the
$g$-tensors. The results depend on the product of the spin-orbit scattering
time $\tau_{\textrm{\small so}}$ and the mean-level spacing $\delta$, but are
otherwise weakly affected by the specific shape of a {\it generic}
nanoparticle. We find that the spin contribution to the $g$-tensors agrees with
Random Matrix Theory (RMT) predictions. On the other hand, in the strong
spin-orbit coupling limit $\delta \tau_{\textrm{\small so}}/\hbar \to 0$, the
orbital contribution depends crucially on the space character of the
quasi-particle wavefunctions: it levels off at a small value for states of $d$
character but is strongly enhanced for states of $sp$ character. Our numerical
results demonstrate that when orbital coupling to the field is included, RMT
predictions overestimate the typical $g$-factor of orbitals that have dominant
$d$-character. This finding points to a possible source of the puzzling
discrepancy between theory and experiment.",0312278v1
2016-01-26,Jahn-Teller effect in systems with strong on-site spin-orbit coupling,"When strong spin-orbit coupling removes orbital degeneracy, it would at the
same time appear to render the Jahn-Teller mechanism ineffective. We discuss
such a situation, the t_2g manifold of iridates, and show that, while the
Jahn-Teller effect does indeed not affect the j_eff=1/2 antiferromagnetically
ordered ground state, it leads to distinctive signatures in the j_eff=3/2
spin-orbit exciton. It allows for a hopping of the spin-orbit exciton between
the nearest neighbor sites without producing defects in the j_eff=1/2
antiferromagnet. This arises because the lattice-driven Jahn-Teller mechanism
only couples to the orbital degree of freedom, but is not sensitive to the
phase of the wave function that defines isospin j_z. This contrasts sharply
with purely electronic propagation, which conserves isospin, and presence of
Jahn-Teller coupling can explain some of the peculiar features of measured
resonant inelastic x-ray scattering spectra of Sr_2IrO_4.",1601.07069v1
2017-02-14,Spin-relaxation time in materials with broken inversion symmetry and large spin-orbit coupling,"We study the spin-relaxation time in materials where a large spin-orbit
coupling (SOC) is present which breaks the spatial inversion symmetry. Such a
spin-orbit coupling is realized in zincblende structures and heterostructures
with a transversal electric field and the spin relaxation is usually described
by the so-called D'yakonov-Perel' (DP) mechanism. We combine a Monte Carlo
method and diagrammatic calculation based approaches in our study; the former
tracks the time evolution of electron spins in a quasiparticle dynamics
simulation in the presence of the built-in spin-orbit magnetic fields and the
latter builds on the spin-diffusion propagator by Burkov and Balents [Burkov
and Balents Phys. Rev. B. 69, 245312 (2004).]. Remarkably, we find a parameter
free quantitative agreement between the two approaches and it also returns the
conventional result of the DP mechanism in the appropriate limit. We discuss
the full phase space of spin relaxation as a function of SOC strength, its
distribution, and the magnitude of the momentum relaxation rate. This allows us
to identify two novel spin-relaxation regimes; where spin relaxation is
strongly non-exponential and the spin relaxation equals the momentum
relaxation. A compelling analogy between the spin-relaxation theory and the NMR
motional narrowing is highlighted.",1702.04162v1
2017-12-30,Spin driven emergent antiferromagnetism and metal insulator transition in nanoscale p-Si,"The entanglement of the charge, spin and orbital degrees of freedom can give
rise to emergent behavior especially in thin films, surfaces and interfaces.
Often, materials that exhibit those properties require large spin orbit
coupling. We hypothesize that the emergent behavior can also occur due to spin,
electron and phonon interactions in widely studied simple materials such as Si.
That is, large intrinsic spin-orbit coupling is not an essential requirement
for emergent behavior. The central hypothesis is that when one of the specimen
dimensions is of the same order (or smaller) as the spin diffusion length, then
non-equilibrium spin accumulation due to spin injection or spin-Hall effect
(SHE) will lead to emergent phase transformations in the non-ferromagnetic
semiconductors. In this experimental work, we report spin mediated emergent
antiferromagnetism and metal insulator transition in a Pd (1 nm)/Ni81Fe19 (25
nm)/MgO (1 nm)/p-Si (~400 nm) thin film specimen. The spin-Hall effect in p-Si,
observed through Rashba spin-orbit coupling mediated spin-Hall
magnetoresistance behavior, is proposed to cause the spin accumulation and
resulting emergent behavior. The phase transition is discovered from the
diverging behavior in longitudinal third harmonic voltage, which is related to
the thermal conductivity and heat capacity.",1801.00071v1
2017-10-20,Spin relaxation of a donor electron coupled to interface states,"An electron spin qubit in a silicon donor atom is a promising candidate for
quantum information processing because of its long coherence time. To be sensed
with a single-electron transistor, the donor atom is usually located near an
interface, where the donor states can be coupled with interface states. Here we
study the phonon-assisted spin-relaxation mechanisms when a donor is coupled to
confined (quantum-dot-like) interface states. We find that both Zeeman
interaction and spin-orbit interaction can hybridize spin and orbital states,
each contributing to phonon-assisted spin relaxation in addition to the spin
relaxation for a bulk donor or a quantum dot. When the applied magnetic field
$B$ is weak (compared to orbital spacing), the phonon assisted spin relaxation
shows the $B^5$ dependence. We find that there are peaks (hot-spots) in the
$B$-dependent and detuning dependent spin relaxation due to strong
hybridization of orbital states with opposite spin. We also find spin
relaxation dips (cool-spots) due to the interference of different relaxation
channels. Qubit operations near spin relaxation hot-spots can be useful for the
fast spin initialization and near cool-spots for the preservation of quantum
information during the transfer of spin qubits.",1710.07674v2
2007-06-17,Frequency dependence of induced spin polarization and spin current in quantum wells,"Dynamic response of two-dimensional electron systems with spin-orbit
interaction is studied theoretically on the basis of quantum kinetic equation,
taking into account elastic scattering of electrons. The spin polarization and
spin current induced by the applied electric field are calculated for the whole
class of electron systems described by p-linear spin-orbit Hamiltonians. The
absence of nonequilibrium intrinsic static spin currents is confirmed for these
systems with arbitrary (nonparabolic) electron energy spectrum. Relations
between the spin polarization, spin current, and electric current are
established. The general results are applied to the quantum wells grown in
[001] and [110] crystallographic directions, with both Rashba and Dresselhaus
types of spin-orbit coupling. It is shown that the existence of the fixed
(momentum-independent) precession axes in [001]-grown wells with equal Rashba
and Dresselhaus spin velocities or in symmetric [110]-grown wells leads to
vanishing spin polarizability at arbitrary frequency of the applied electric
field. This property is explained by the absence of Dyakonov-Perel-Kachorovskii
spin relaxation for the spins polarized along these precession axes. As a
result, a considerable frequency dispersion of spin polarization at very low
frequency in the vicinity of the fixed precession axes is predicted. Possible
effects of extrinsic spin-orbit coupling on the obtained results are discussed.",0706.2463v1
2023-07-21,Symmetry analysis with spin crystallographic groups: Disentangling effects free of spin-orbit coupling in emergent electromagnetism,"Recent studies identified spin-order-driven phenomena such as spin-charge
interconversion without relying on the relativistic spin-orbit interaction.
Those physical properties can be prominent in systems containing light magnetic
atoms due to sizable exchange splitting and may pave the way for realization of
giant responses correlated with the spin degree of freedom. In this paper, we
present a systematic symmetry analysis based on the spin crystallographic
groups and identify the physical property of a vast number of magnetic
materials up to 1500 in total. By decoupling the spin and orbital degrees of
freedom, our analysis enables us to take a closer look into the relation
between the dimensionality of spin structures and the resultant physical
properties and to identify the spin and orbital contributions separately. In
stark contrast to the established analysis with magnetic space groups, the spin
crystallographic group manifests richer symmetry including spin-translation
symmetry and leads to emergent responses. For representative examples, we
discuss the geometrical nature of the anomalous Hall effect and magnetoelectric
effect and classify the spin Hall effect arising from the nonrelativistic
spin-charge coupling. Using the power of computational analysis, we apply our
symmetry analysis to a wide range of magnets, encompassing complex magnets such
as those with noncoplanar spin structures as well as collinear and coplanar
magnets. We identify emergent multipoles relevant to physical responses and
argue that our method provides a systematic tool for exploring sizable
electromagnetic responses driven by spin order.",2307.11560v2
2000-11-04,Orbital polarons and ferromagnetic insulators in manganites,"We argue that in lightly hole doped perovskite-type Mn oxides the holes
(Mn$^{4+}$ sites) are surrounded by nearest neighbor Mn$^{3+}$ sites in which
the occupied $3d$ orbitals have their lobes directed towards the central hole
(Mn$^{4+}$) site and with spins coupled ferromagnetically to the central spin.
This composite object, which can be viewed as a combined orbital-spin-lattice
polaron, is accompanied by the breathing type (Mn$^{4+}$) and Jahn-Teller type
(Mn$^{3+}$) local lattice distortions. We present calculations which indicate
that for certain doping levels these orbital polarons may crystallize into a
charge and orbitally ordered ferromagnetic insulating state.",0011070v1
2013-06-08,Effect of Spin-Orbit Interaction on (4d)^3- and (5d)^3 -Based Transition-Metal Oxides,"The effects of a spin-orbit interaction on transition-metal ions of (4d)^3-
and (5d)^3 -based oxides in which three electrons occupy t_{2g} orbitals are
studied. The amplitude of the magnetic moment of d electrons on the 5d and 4d
orbitals is estimated by numerical diagonalization. It is found that the
magnetic moment is reduced by the spin-orbit interaction. It is suggested that
(4d)^3- and (5d)^3 -based oxides are located in the middle of the L-S and J-J
coupling schemes.",1306.1880v1
2024-02-03,Gravitational losses for the binary systems induced by the next-to-leading spin-orbit coupling effects,"The orbital energy and momentum of the compact binary systems will loss due
to gravitational radiation. Based on the mass and mass-current multipole
moments of the binary system with the spin vector defined by Boh\'{e} et al.
[Class. Quantum Grav. 30, 075017 (2013)], we calculate the loss rates of
energy, angular and linear momentum induced by the next-to-leading spin-orbit
effects. For the case of circular orbit, the formulations for these losses are
given in terms of the orbital frequency.",2402.02170v1
2021-08-23,Hydrodynamic theory of vorticity-induced spin transport,"Electron spin transport in a disordered metal is theoretically studied from
the hydrodynamic viewpoint focusing on the role of electron vorticity. The
spin-resolved momentum flux density of electrons is calculated taking account
of the spin-orbit interaction and uniform magnetization, and the expression for
the spin motive force is obtained as the linear response to a driving electric
field. It is shown that the spin-resolved momentum flux density and motive
force are characterized by troidal moments expressed as vector products of the
applied external electric field and the spin polarization and/or magnetization.
The spin-vorticity and magnetization-vorticity couplings studied recently are
shown to arise from the toridal moments contribution to the momentum flux
density. Spin motive force turns out to have a nonconservative contribution
besides the conventional conservative one due to the spin-vorticity coupling.
Spin accumulation induced by an electric field is calculated to demonstrate the
direct relation between vorticity and induced spin, and the spin Hall effect is
interpreted as due to the spin-vorticity coupling. The spin-vorticity coupling
is shown to give rise to a vorticity-induced torque and a spin relaxation. The
vorticity-induced torque is a linear effect of the spin-orbit interaction and
is expected to be larger than the second-order torques such as nonadiabatic
($\beta$) current-induced torque due to magnetization structure. The intrinsic
inverse spin Hall effect is argued to correspond to the antisymmetric
components of the momentum flux density in the hydrodynamic context.",2108.09919v1
2020-04-20,Current-induced torque originating from orbital current,"The electrical manipulation of magnetization by current-induced spin torques
has given access to realize a plethora of ultralow power and fast spintronic
devices such as non-volatile magnetic memories, spin-torque nano-oscillators,
and neuromorphic computing devices. Recent advances have led to the notion that
relativistic spin-orbit coupling is an efficient source for current-induced
torques, opening the field of spin-orbitronics. Despite the significant
progress, however, the fundamental mechanism of magnetization manipulation, the
requirement of spin currents in generating current-induced torques, has
remained unchanged. Here, we demonstrate the generation of current-induced
torques without the use of spin currents. By measuring the current-induced
torque for naturally-oxidized-Cu/ferromagnetic-metal bilayers, we observed an
exceptionally high effective spin Hall conductivity at low temperatures despite
the absence of strong spin-orbit coupling. Furthermore, we found that the
direction of the torque depends on the choice of the ferromagnetic layer, which
counters the conventional understanding of the current-induced torque. These
unconventional features are best interpreted in terms of an orbital counterpart
of the spin torque, an orbital torque, which arises from the orbital Rashba
effect and orbital current. These findings will shed light on the underlying
physics of current-induced magnetization manipulation, potentially altering the
landscape of spin-orbitronics.",2004.09165v1
2003-12-30,A universal Hamiltonian for a quantum dot in the presence of spin-orbit interaction,"We derive a universal Hamiltonian for a quantum dot in the presence of
spin-orbit interaction in the symmetry limits of a strong spin-dependent
Aharonov-Bohm-like term. We also derive a closed expression for the conductance
through such a dot, and use it to study the effects of spin-orbit on the
conductance peak statistics in the presence of an exchange interaction. For a
realistic strength of the exchange interaction, we find that the width of the
peak-spacing distribution is sensitive to spin-orbit coupling only in the
absence of an orbital magnetic field. We also find that spin-orbit coupling
modifies the shape of the peak-spacing distribution and suppresses the
peak-height fluctuations.",0312691v1
2012-09-23,Strength of reduced two-body spin-orbit interaction from chiral three-nucleon force,"The contribution of a chiral three-nucleon force to the strength of an
effective spin-orbit coupling is estimated. We first construct a reduced
two-body interaction by folding one-nucleon degrees of freedom of the
three-nucleon force in nuclear matter. The spin-orbit strength is evaluated by
a Scheerbaum factor obtained by the $G$-matrix calculation in nuclear matter
with the two-nucleon interaction plus the reduced two-nucleon interaction. The
problem of the insufficiency of modern realistic two-nucleon interactions to
account for the empirical spin-orbit strength is resolved. It is also indicated
that the spin-orbit coupling is weaker in the neutron-rich environment. Because
the spin-orbit component from the three-nucleon force is determined by the
low-energy constants fixed in the two-nucleon sector, there is little
uncertainty in the present estimation.",1209.5048v1
2016-01-04,Optical conductivity of a 2DEG with anisotropic Rashba interaction at the interface of LaAlO$_3$/SrTiO$_3$,"We study optical conductivity of a two-dimensional electron gas with
anisotropic $k$-cubic Rashba spin-orbit interaction formed at the
LaAlO$_3$/SrTiO$_3$ interface. The anisotropic spin splitting energy gives rise
to different features of the optical conductivity in comparison to the
isotropic $k$-cubic Rashba spin-orbit interaction. For large carrier density
and strong spin-orbit couplings, the density dependence of Drude weight
deviates from the linear behavior. The charge and optical conductivities remain
isotropic despite anisotropic nature of the Fermi contours. An infinitesimally
small photon energy would suffice to initiate inter-band optical transitions
due to degeneracy along certain directions in momentum space. The optical
conductivity shows a single peak at a given photon energy depending on the
system parameters and then falls off to zero at higher photon energy. These
features are lacking for systems with isotropic $k$-cubic Rashba spin-orbit
coupling. These striking features can be used to extract the information about
nature of the spin-orbit interaction experimentally and illuminate some light
on the orbital origin of the two-dimensional electron gas.",1601.00591v2
2020-11-02,Intrinsic Mechanism for Magneto-Thermal Conductivity Oscillations in Spin-Orbit-Coupled Nodal Superconductors,"We describe a mechanism by which the longitudinal thermal conductivity
$\kappa_{xx}$, measured in an in-plane magnetic field, oscillates as a function
of field angle in layered nodal superconductors. These oscillations occur when
the spin-orbit splitting at the nodes is larger than the nodal scattering rate,
and are complementary to vortex-induced oscillations identified previously. In
sufficiently anisotropic materials, the spin-orbit mechanism may be dominant.
As a particular application, we focus on the cuprate high-temperature
superconductor YBa$_2$Cu$_3$O$_{6+x}$. This material belongs to the class of
Rashba bilayers, in which individual CuO$_2$ layers lack inversion symmetry
although the crystal itself is globally centrosymmetric. We show that
spin-orbit coupling endows $\kappa_{xx}/T$ with a characteristic dependence on
magnetic field angle that should be easily detected experimentally, and argue
that for underdoped samples the spin-orbit contribution is larger than the
vortex contribution. A key advantage of the magneto-thermal conductivity is
that it is a bulk probe of spin-orbit physics, and therefore not sensitive to
inversion breaking at surfaces.",2011.01074v1
2022-02-15,Spin orbital reorientation transitions induced by magnetic field,"Here we report on a new effect similar to the spin reorientation transition
(SRT) that takes place at two magnetic fields of $B_{SORT1}$ and $B_{SORT2}$.
The effect is observed in the magnetization curves of small Mn$^{3+}$ magnetic
clusters in the wurtzite GaN (being in a paramagnetic state) calculated using
crystal field model approach. The obtained results suggest that the computed
magnetic anisotropy (MA) reverses its sign on increasing $B$ across $B_{SORT}$.
Detailed analysis show however that MA is unchanged for high magnetic fields.
We show that the observed effect arises from the interplay of the crystalline
environment and the spin-orbit coupling $\lambda \hat{\textbf{S}}
\hat{\textbf{L}}$, therefore we name it spin orbital reorientation transition
(SORT). The value of $B_{SORT1}$ depends on the crystal field model parameters
and the number of ions $N$ in a given cluster, whereas $B_{SORT2}$ is
controlled mostly by the magnitude of the spin-orbit coupling $\lambda$. The
explanation of SORT is given in terms of the spin $M_S$ and orbital momentum
$M_L$ contributions to the total magnetization $M = M_S + M_L$. The similar
effect should also be present in other materials with not completely quenched
(non zero) orbital angular momentum $L$, a uniaxial magnetic anisotropy and the
positive value of $\lambda$.",2202.07443v1
2006-03-29,Unipolar Inductor Model coupled to GW emission: energy budget and model application to RX J0806+15 and RX J1914+24,"We further discuss the Unipolar Inductor Model (UIM) coupled to GW emission
(Dall'Osso et al. 2005) and compare it to observed properties of the two
candidate ultrashort period binaries RX J0806+15 and RX J1914+24 . We consider
the measured orbital periods, period derivatives and inferred X-ray
luminosities of these two sources and find constraints on system parameters in
order for the model to account for them. We find that these properties point to
the two sources being in different regimes of the UIM, with the requirement of
low magnetic moment primaries ($\sim 10^{30} G cm^3$) for both. Given this weak
magnetization, RX J0806+15 has a sufficiently low luminosity that it can be
interpreted as having a primary spin almost synchronous to and just slightly
slower than the orbital motion. Its measured orbital spin-up is only slightly
affected by spin-orbit coupling and is mostly due to GW emission. RX J1914+24,
on the other hand, is too bright in X-rays and has too slow an orbital spin-up
for the same regime to apply. We suggest that this binary system may be
emitting GWs at a significantly higher rate than implied by its measured
$\dot{\omega}_o = 6 \times 10^{-17} rad s^{-2}$. The latter is explained, in
this framework, by the primary spin being slightly faster than the orbital
motion ($\alpha <or= 1.1$). In this case, the associated spin-orbit coupling
transfers to the orbit a significant amount of angular momentum, thus partially
balancing that lost to GW emission. All expectations can be tested in the near
future to confirm the viability of the model.",0603795v1
2012-01-23,Out-of-plane equilibrium spin current in a quasi-two-dimensional electron gas under in-plane magnetic field,"Equilibrium spin-current is calculated in a quasi-two-dimensional electron
gas with finite thickness under in-plane magnetic field and in the presence of
Rashba- and Dresselhaus spin-orbit interactions. The transverse confinement is
modeled by means of a parabolic potential. An orbital effect of the in-plane
magnetic field is shown to mix a transverse quantized spin-up state with
nearest-neighboring spin-down states. The out-off-plane component of the
equilibrium spin current appears to be not zero in the presence of an in-plane
magnetic field, provided at least two transverse-quantized levels are filled.
In the absence of the magnetic field the obtained results coincide with the
well-known results, yielding cubic dependence of the equilibrium spin current
on the spin-orbit coupling constants. The persistent spin-current vanishes in
the absence of the magnetic field if Rashba- and Dresselhaus spin-orbit
coefficients,{\alpha} and {\beta}, are equal each other. In-plane magnetic
field destroys this symmetry, and accumulates a finite spin-current as {\alpha}
\rightarrow {\beta}. Magnetic field is shown to change strongly the equilibrium
current of the in-plane spin components, and gives new contributions to the
cubic-dependent on spin-orbit constants terms. These new terms depend linearly
on the spin-orbit constants.",1201.4683v1
2013-04-12,"Space group symmetry, spin-orbit coupling and the low energy effective Hamiltonian for iron based superconductors","We construct the symmetry adapted low energy effective Hamiltonian for the
electronic states in the vicinity of the Fermi level in iron based
superconductors. We use Luttinger's method of invariants, expanding about Gamma
and M points in the Brillouin zone corresponding to two iron unit cell, and
then matching the coefficients of the expansion to the 5- and 8-band models. We
then use the method of invariants to study the effects of the spin-density wave
order parameters on the electronic spectrum, with and without spin-orbit
coupling included. Among the results of this analysis is the finding that the
nodal spin-density wave is unstable once spin-orbit coupling is included.
Similar analysis is performed for the A_{1g} spin singlet superconducting
state. Without spin-orbit coupling there is one pairing invariant near the
Gamma point, but two near the M point. This leads to an isotropic spectral gap
at the hole Fermi surface near Gamma, but anisotropic near M. The relative
values of these three parameters determine whether the superconducting state is
s_{++}, s_{+-}, or nodal. Inclusion of spin-orbit coupling leads to additional
mixing of spin triplet pairing, with one additional pairing parameter near
Gamma and one near M. This leads to an anisotropic spectral gap near both hole
and electron Fermi surfaces, the latter no longer cross, but rather split.",1304.3723v1
2017-09-08,Magnetoconductance correction in zinc-blende semiconductor nanowires with spin-orbit coupling,"We study the effects of spin-orbit coupling on the magnetoconductivity in
diffusive cylindrical semiconductor nanowires. Following up on our former study
on tubular semiconductor nanowires, we focus in this paper on nanowire systems
where no surface accumulation layer is formed but instead the electron wave
function extends over the entire cross section. We take into account the
Dresselhaus spin-orbit coupling resulting from a zinc-blende lattice and the
Rashba spin-orbit coupling, which is controlled by a lateral gate electrode.
The spin relaxation rate due to Dresselhaus spin-orbit coupling is found to
depend neither on the spin density component nor on the wire growth direction
and is unaffected by the radial boundary. In contrast, the Rashba spin
relaxation rate is strongly reduced for a wire radius that is smaller than the
spin precession length. The derived model is fitted to the data of
magnetoconductance measurements of a heavily doped back-gated InAs nanowire and
transport parameters are extracted. At last, we compare our results to previous
theoretical and experimental studies and discuss the occurring discrepancies.",1709.02621v2
2006-12-05,Topological Change of the Fermi Surface in Low Density Rashba Gases: Application to Superconductivity,"Strong spin-orbit coupling can have a profound effect on the electronic
structure in a metal or semiconductor, particularly for low electron
concentrations. We show how, for small values of the Fermi energy compared to
the spin-orbit splitting of Rashba type, a topological change of the Fermi
surface leads to an effective reduction of the dimensionality in the electronic
density of states. We investigate its consequences on the onset of the
superconducting instability. We show, by solving the Eliashberg equations for
the critical temperature as a function of spin-orbit coupling and electron
density, that the superconducting critical temperature is significantly tuned
in this regime by the spin-orbit coupling. We suggest that materials with
strong spin-orbit coupling are good candidates for enhanced superconductivity.",0612107v1
2008-03-03,Strong spin-orbit coupling effects on the Fermi surface of Sr2RuO4 and Sr2RhO4,"We present a first-principle study of spin-orbit coupling effects on the
Fermi surface of Sr2RuO4 and Sr2RhO4. For nearly degenerate bands, spin-orbit
coupling leads to a dramatic change of the Fermi surface with respect to
non-relativistic calculations; as evidenced by the comparison with experiments
on Sr2RhO4, it cannot be disregarded. For Sr2RuO4, the Fermi surface
modifications are more subtle but equally dramatic in the detail: spin-orbit
coupling induces a strong momentum dependence, normal to the RuO2 planes, for
both orbital and spin character of the low-energy electronic states. These
findings have profound implications for the understanding of unconventional
superconductivity in Sr2RuO4.",0803.0352v1
2013-05-09,Competing superfluid orders in spin-orbit coupled fermionic cold atom optical lattices,"The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, a superconducting state
with non-zero total momentum Cooper pairs in a large magnetic field, was first
predicted about 50 years ago, and since then became an important concept in
many branches of physics. Despite intensive search in various materials,
unambiguous experimental evidence for the FFLO phase is still lacking in
experiments. In this paper, we show that both FF (uniform order parameter with
plane-wave phase) and LO phase (spatially varying order parameter amplitude)
can be observed using fermionic cold atoms in spin-orbit coupled optical
lattices. The increasing spin-orbit coupling enhances the FF phase over the LO
phase. The coexistence of superfluid and magnetic orders is also found in the
normal BCS phase. The pairing mechanism for different phases is understood by
visualizing superfluid pairing densities in different spin-orbit bands. The
possibility of observing similar physics using spin-orbit coupled
superconducting ultra-thin films is also discussed.",1305.2152v2
2016-04-20,Topological Insulators from Electronic Superstructures,"The possibility of realizing topological insulators by spontaneous formation
of electronic superstructure is theoretically investigated in a minimal
two-orbital model including both the spin-orbit coupling and electron
correlations on a triangular lattice. Using the mean-field approximation, we
show that the model exhibits several different types of charge ordered
insulators, where the charge disproportionation forms a honeycomb or kagome
superstructure. We find that the charge ordered insulators in the presence of
strong spin-orbit coupling can be topological insulators showing quantized spin
Hall conductivity. Their band gap is dependent on electron correlations as well
as the spin-orbit coupling, and even vanishes with showing the massless Dirac
dispersion at the transition to a trivial charge ordered insulator. Our results
suggest a new route to realize and control topological states of quantum matter
by the interplay between the spin-orbit coupling and electron correlations.",1604.05851v2
2013-09-29,Sensitively Temperature-Dependent Spin Orbit Coupling in SrIrO3 Thin Films,"Spin orbit coupling plays a non-perturbation effect in many recently
developed novel fields including topological insulators and spin-orbit
assistant Mott insulators. In this paper, strongly temperature-dependent spin
orbit coupling, revealed by weak anti-localization, is observed at low
temperature in 5d strongly correlated compound, SrIrO3. As the temperature
rising, increase rate of Rashba coefficient is nearly 30%-45%/K. The increase
is nearly 100 times over that observed in semiconductor heterostructures.
Microscopically, the large increase of Rashba coefficient is attributed to the
significant evolution of effective Land\'e g factor on temperature, whose
mechanism is discussed. Sensitively temperature-dependent spin orbit coupling
in SrIrO3 might be applied in spintronic devices",1309.7566v1
2019-08-07,Thermodynamics of spin-orbit coupled bosons in two dimensions from complex Langevin,"We investigate the thermal properties of interacting spin-orbit coupled
bosons with contact interactions in two spatial dimensions. To that end, we
implement the complex Langevin method, motivated by the appearance of a sign
problem, on a square lattice with periodic boundary conditions. We calculate
the density equation of state non-perturbatively in a range of spin-orbit
couplings and chemical potentials. Our results show that mean-field solutions
tend to underestimate the average density, especially for stronger values of
the spin-orbit coupling. Additionally, the finite nature of the simulation
volume induces the formation of pseudo-condensates. These have been observed to
be destroyed by the spin-orbit interactions.",1908.02715v2
2023-06-21,Correlated Phases in Spin-Orbit-Coupled Rhombohedral Trilayer Graphene,"Recent experiments indicate that crystalline graphene multilayers exhibit
much of the richness of their twisted counterparts, including cascades of
symmetry-broken states and unconventional superconductivity. Interfacing Bernal
bilayer graphene with a WSe$_2$ monolayer was shown to dramatically enhance
superconductivity -- suggesting that proximity-induced spin-orbit coupling
plays a key role in promoting Cooper pairing. Motivated by this observation, we
study the phase diagram of spin-orbit-coupled rhombohedral trilayer graphene
via self-consistent Hartree-Fock simulations, elucidating the interplay between
displacement field effects, long-range Coulomb repulsion, short-range (Hund's)
interactions, and substrate-induced Ising spin-orbit coupling. In addition to
generalized Stoner ferromagnets, we find various flavors of intervalley
coherent ground states distinguished by their transformation properties under
electronic time reversal, ${\rm C}_3$ rotations, and an effective anti-unitary
symmetry. We pay particular attention to broken-symmetry phases that yield
Fermi surfaces compatible with zero-momentum Cooper pairing, identifying
promising candidate orders that may support spin-orbit-enhanced
superconductivity.",2306.12486v2
2023-05-11,Non-thermal superconductivity in photo-doped multi-orbital Hubbard systems,"Superconductivity in laser-excited correlated electron systems has attracted
considerable interest due to reports of light-induced superconducting-like
states. Here we explore the possibility of non-thermal superconducting order in
strongly interacting multi-orbital Hubbard systems, using non-equilibrium
dynamical mean field theory. We find that a staggered $\eta$-type
superconducting phase can be realized on a bipartite lattice in the high
photo-doping regime, if the effective temperature of the photo-carriers is
sufficiently low. The $\eta$ superconducting state is stabilized by Hund
coupling - a positive Hund coupling favors orbital-singlet spin-triplet $\eta$
pairing, whereas a negative Hund coupling stabilizes spin-singlet
orbital-triplet $\eta$ pairing.",2305.06760v1
2007-10-24,Spin-orbit induced interference in quantum corrals,"Lack of inversion symmetry at a metallic surface can lead to an observable
spin-orbit interaction. For certain metal surfaces, such as the Au(111)
surface, the experimentally observed spin-orbit coupling results in spin
rotation lengths on the order of tens of nanometers, which is the typical
length scale associated with quantum corral structures formed on metal
surfaces. In this work, multiple scattering theory is used to calculate the
local density of states (LDOS) of quantum corral structures comprised of
nonmagnetic adatoms in the presence of spin-orbit coupling. Contrary to
previous theoretical predictions, spin-orbit coupling induced modulations are
observed in the theoretical LDOS, which should be observable using scanning
tunneling microscopy.",0710.4587v1
2008-04-21,"Magnetic phenomena, spin-orbit effects, and Landauer conductance in Pt nanowire contacts","Platinum monatomic nanowires were predicted to spontaneously develop
magnetism, involving a sizable orbital moment via spin orbit coupling, and a
colossal magnetic anisotropy. We present here a fully-relativistic (spin-orbit
coupling included) pseudo-potential density functional calculation of
electronic and magnetic properties, and of Landauer ballistic conductance of Pt
model nanocontacts consisting of short nanowire segments suspended between Pt
leads or tips, reprented by bulk planes. Even if short, and despite the
nonmagnetic Pt leads, the nanocontact is found to be locally magnetic with
magnetization strictly parallel to its axis. Especially under strain, the
energy barrier to flip the overall spin direction is predicted to be tens of
meV high, and thus the corresponding blocking temperatures large, suggesting
the use of static Landauer ballistic electrical conductance calculations. We
carry out such calculations, to find that inclusion of spin-orbit coupling and
of magnetism lowers the ballistic conductance by about $15\div20$% relative to
the nonmagnetic case, yielding $ G\sim 2 G_0$ ($G_0=2e^2/h$), in good agreement
with break junction results. The spin filtering properties of this highly
unusual spontaneously magnetic nanocontact are also analysed.",0804.3340v1
2008-05-29,Wave packet dynamics in 2DEG with spin orbit coupling: splitting and zitterbewegung,"We study the effect of splitting and zitterbewegung of 1D and 2D electron
wave packets in the semiconductor quantum well under the influence of the
Rashba spin orbit coupling. Results of our investigations show that the spin
orbit interaction induces dramatic qualitative changes in the evolution of spin
polarized wave packet. The initial wave packet splits into two parts with
different spin polarization propagating with unequal group velocity. This
splitting appears due to the presence of two branches of electron spectrum
corresponding to the stationary states with different chirality. It is
demonstrated also that in the presence of external magnetic field B$
perpendicular to the electron gas plane the wave packet splits into two parts
which rotates with different cyclotron frequencies. It was shown that after
some periods the electron density distributes around cyclotron orbit and the
motion acquire an irregular character. Our calculations were made for both
cases of weak and strong spin orbit coupling.",0805.4489v2
2009-07-04,"Quantum rings with time dependent spin-orbit coupling: Rabi oscillations, spintronic Schrodinger-cat states, and conductance properties","The strength of the (Rashba-type) spin-orbit coupling in mesoscopic
semiconductor rings can be tuned with external gate voltages. Here we consider
the case of a periodically changing spin-orbit interaction strength as induced
by sinusoidal voltages. In a closed one dimensional quantum ring with weak
spin-orbit coupling, Rabi oscillations are shown to appear. We find that the
time evolution of initially localized wave packets exhibits a series of
collapse and revival phenomena. Partial revivals -- that are typical in
nonlinear systems -- are shown to correspond to superpositions of states
localized at different spatial positions along the ring. These ""spintronic
Schrodinger-cat sates"" appear periodically, and similarly to their counterparts
in other physical systems, they are found to be sensitive to environment
induced disturbances. The time dependent spin transport problem, when leads are
attached to the ring, is also solved. We show that the ""sideband currents""
induced by the oscillating spin-orbit interaction strength can become the
dominant output channel, even in the presence of moderate thermal fluctuations
and random scattering events.",0907.0766v1
2013-03-12,Spin-orbit coupling in hydrogenated graphene,"First-principles calculations of the spin-orbit coupling in graphene with
hydrogen adatoms in dense and dilute limits are presented. The chemisorbed
hydrogen induces a giant local enhancement of spin-orbit coupling due to $sp^3$
hybridization which depends strongly on the local lattice distortion. Guided by
the reduced symmetry and the local structure of the induced dipole moments we
use group theory to propose realistic minimal Hamiltonians that reproduce the
relevant spin-orbit effects for both single-side semihydrogenated graphene
(graphone) and for a single hydrogen adatom in a large supercell. The principal
linear spin-orbit band splittings are driven by the breaking of the local
pseudospin inversion symmetry and the emergence of spin flips on the same
sublattice.",1303.2806v1
2015-11-23,Spin-orbit coupling controlled ground state in Sr$_2$ScOsO$_6$,"We report neutron scattering experiments which reveal a large spin gap in the
magnetic excitation spectrum of weakly-monoclinic double perovskite Sr2ScOsO6.
The spin gap is demonstrative of appreciable spin-orbit-induced anisotropy,
despite nominally orbitally-quenched 5d3 Os5+ ions. The system is successfully
modeled including nearest neighbor interactions in a Heisenberg Hamiltonian
with exchange anisotropy. We find that the presence of the spin-orbit-induced
anisotropy is essential for the realization of the type I antiferromagnetic
ground state. This demonstrates that physics beyond the LS or JJ coupling
limits plays an active role in determining the collective properties of 4d3 and
5d3 systems, and that theoretical treatments must include spin-orbit coupling.",1511.07486v3
2020-05-05,"Heterostructures of graphene and topological insulators Bi$_2$Se$_3$, Bi$_2$Te$_3$, and Sb$_2$Te$_3$","Prototypical three-dimensional topological insulators of the Bi$_2$Se$_3$
family provide a beautiful example of the appearance of the surface states
inside the bulk band gap caused by spin-orbit coupling-induced topology. The
surface states are protected against back scattering by time reversal symmetry,
and exhibit spin-momentum locking whereby the electron spin is polarized
perpendicular to the momentum, typically in the plane of the surface. On the
other hand, graphene is a prototypical two-dimensional material, with
negligible spin-orbit coupling. When graphene is placed on the surface of a
topological insulator, giant spin-orbit coupling is induced by the proximity
effect, enabling interesting novel electronic properties of its Dirac
electrons. We present a detailed theoretical study of the proximity effects of
monolayer graphene and topological insulators Bi$_2$Se$_3$, Bi$_2$Te$_3$, and
Sb$_2$Te$_3$, and elucidate the appearance of the qualitatively new spin-orbit
splittings well described by a phenomenological Hamiltonian, by analyzing the
orbital decomposition of the involved band structures. This should be useful
for building microscopic models of the proximity effects between the surfaces
of the topological insulators and graphene.",2005.02026v1
2020-05-18,Cooperative orbital moments and edge magnetoresistance in monolayer WTe$_2$,"We argue that edge electrons in monolayer WTe$_2$ can possess a ""cooperative""
orbital moment (COM) that critically impacts its edge magnetoresistance
behavior. Arising from the cooperative action of both Rashba and Ising spin
orbit coupling, COM quickly achieves large magnitudes (of order few Bohr
magnetons) even for relatively small spin-orbit coupling strengths. As we
explain, such large COM magnitudes arise from an unconventional cooperative
spin canting of edge spins when Rashba and Ising spin orbit coupling act
together. Strikingly, COM can compete with spin moments to produce an unusual
anisotropic edge magnetoresistance oriented at an oblique angle. In particular,
this competition produces a direction along which $\mathbf{B}$ is ineffective
at gapping out the edge spectrum leaving it nearly gapless. As a result, large
contrasts in gap sizes manifest as $\mathbf{B}$ is rotated granting giant
anisotropic magnetoresistance of 0.1-10 million % at 10 T and low temperature.",2005.08986v1
2020-09-10,Global polarization effect and spin-orbit coupling in strong interaction,"In non-central high energy heavy ion collisions the colliding system posses a
huge orbital angular momentum in the direction opposite to the normal of the
reaction plane. Due to the spin-orbit coupling in strong interaction, such huge
orbital angular momentum leads to the polarization of quarks and anti-quarks in
the same direction. This effect, known as the global polarization effect, has
been recently observed by STAR Collaboration at RHIC that confirms the
theoretical prediction made more than ten years ago. The discovery has
attracted much attention on the study of spin effects in heavy ion collision.
It opens a new window to study properties of QGP and a new direction in high
energy heavy ion physics -- Spin Physics in Heavy Ion Collisions. In this
chapter, we review the original ideas and calculations that lead to the
predictions. We emphasize the role played by spin-orbit coupling in high energy
spin physics and discuss the new opportunities and challenges in this
connection.",2009.04803v2
2016-10-06,Copper adatoms on graphene: theory of orbital and spin-orbital effects,"We present a combined DFT and model Hamiltonian analysis of spin-orbit
coupling in graphene induced by copper adatoms in the bridge and top positions,
representing isolated atoms in the dilute limit. The orbital physics in both
systems is found to be surprisingly similar, given the fundamental difference
in the local symmetry. In both systems the Cu p and d contributions at the
Fermi level are very similar. Based on the knowledge of orbital effects we
identify that the main cause of the locally induced spin-orbit couplings are Cu
p and d orbitals. By employing the DFT+U formalism as an analysis tool we find
that both the p and d orbital contributions are equally important to spin-orbit
coupling, although p contributions to the density of states are much higher. We
fit the DFT data with phenomenological tight-binding models developed
separately for the top and bridge positions. Our model Hamiltonians describe
the low-energy electronic band structure in the whole Brillouin zone and allow
us to extract the size of the spin-orbit interaction induced by the local Cu
adatom to be in the tens of meV. By application of the phenomenological models
to Green's function techniques, we find that copper atoms act as resonant
impurities in graphene with large lifetimes of 50 and 100~fs for top and
bridge, respectively.",1610.01798v1
2013-10-14,Ballistic spin resonance in multisubband quantum wires,"Ballistic spin resonance was experimentally observed in a
quasi-one-dimensional wire by Frolov et al. [Nature (London) 458, 868 (2009)].
The spin resonance was generated by a combination of an external static
magnetic field and the oscillating effective spin-orbit magnetic field due to
periodic bouncings of the electrons off the boundaries of a narrow channel. An
increase of the D'yakonov-Perel spin relaxation rate was observed when the
frequency of the spin-orbit field matched that of the Larmor precession
frequency around the external magnetic field. Here we develop a model to
account for the D'yakonov-Perel mechanism in multisubband quantum wires with
both the Rashba and Dresselhaus spin-orbit interactions. Considering elastic
spin-conserving impurity scatterings in the time-evolution operator (Heisenberg
representation), we extract the spin relaxation time by evaluating the
time-dependent average of the spin operators. The magnetic field dependence of
the nonlocal voltage, which is related to the spin relaxation time behavior,
shows a wide plateau, in agreement with the experimental observation. This
plateau arises due to injection in higher subbands and small-angle scattering.
In this quantum mechanical approach, the spin resonance occurs near the
spin-orbit induced energy anticrossings of the quantum wire subbands with
opposite spins. We also predict anomalous dips in the spin relaxation time as a
function of the magnetic field in systems with strong spin-orbit couplings.",1310.3707v2
2011-02-07,Impact of spin-orbit coupling on the Holstein polaron,"We utilize an exact variational numerical procedure to calculate the ground
state properties of a polaron in the presence of a Rashba-like spin orbit
interaction. Our results corroborate with previous work performed with the
Momentum Average approximation and with weak coupling perturbation theory. We
find that spin orbit coupling increases the effective mass in the regime with
weak electron phonon coupling, and decreases the effective mass in the
intermediate and strong electron phonon coupling regime. Analytical strong
coupling perturbation theory results confirm our numerical results in the small
polaron regime. A large amount of spin orbit coupling can lead to a significant
lowering of the polaron effective mass.",1102.1421v1
2013-07-10,"Scaling of spin Hall angle in 3d, 4d and 5d metals from Y3Fe5O12/metal spin pumping","Pure spin currents generated by spin pumping in ferromagnet/nonmagnet (FM/NM)
bilayers produce inverse spin Hall effect (ISHE) voltages in the NM, from which
spin pumping and transport characteristics of the NM can be extracted. Due to
its exceptionally low damping, Y3Fe5O12 (YIG) is an important and widely used
FM for microwave devices and ferromagnetic resonance (FMR) spin pumping. Here
we report systematic investigation of spin pumping from 20-nm thick YIG thin
films to a series of 3d, 4d and 5d normal metals (Cu, Ag, Ta, W, Pt and Au)
with various spin-orbit coupling strengths. From enhanced Gilbert damping
obtained from the frequency dependence of FMR linewidths and ISHE signals, the
spin Hall angles and YIG/NM interfacial spin mixing conductances are
quantitatively determined for these metals. The spin Hall angles largely vary
as the fourth power of the atomic number, corroborating the dominant role of
spin-orbit coupling across a broad range in the inverse spin Hall effect.",1307.2648v2
2015-05-14,Crossover between spin swapping and Hall effect in metallic systems,"We theoretically study the crossover between spin Hall effect and spin
swapping, a recently predicted phenomenon that consists in the interchange
between the current flow and its spin polarization directions [Lifshits and
Dyakonov, Phys. Rev. Lett. 103, 186601 (2009)]. Using a tight-binding model
with spin-orbit coupled disorder, spin Hall effect, spin relaxation and spin
swapping are treated on equal footing. We demonstrate that spin Hall effect and
spin swapping present very different dependences as a function of the
spin-orbit coupling and disorder strengths. As a consequence, we show that spin
swapping may even exceed spin Hall effect. Three set-ups are proposed for the
experimental observation of the spin swapping effect in metals.",1505.03661v1
2002-09-21,Dynamical spin-electric coupling in a quantum dot,"Due to the spin-orbital coupling in a semiconductor quantum dot, a freely
precessing electron spin produces a time-dependent charge density. This creates
a sizeable electric field outside the dot, leading to promising applications in
spintronics. The spin-electric coupling can be employed for non-invasive single
spin detection by electrical methods. We also consider a spin relaxation
mechanism due to long-range coupling to electrons in gates and elsewhere in the
system, and find a contribution comparable to, and in some cases dominant over
previously discussed mechanisms.",0209507v1
2015-03-17,Coupled wire construction of chiral spin liquids,"We develop a coupled wire construction of chiral spin liquids. The starting
point are individual wires of electrons in the Mott regime that are subject to
a Zeeman field and Rashba spin-orbit coupling. Suitable spin-flip couplings
between the wires yield an Abelian chiral spin liquid state which supports
spinon excitations above a bulk gap, and chiral edge states. The approach
generalizes to non-Abelian chiral spin liquids at level k with parafermionic
edge states.",1503.05051v2
2005-08-12,Electron spin-orbit splitting in InGaAs/InP quantum well studied by means of the weak antilocalization and spin-zero effects in tilted magnetic fields,"The coupling between Zeeman spin splitting and Rashba spin-orbit terms has
been studied experimentally in a gated InGaAs/InP quantum well structure by
means of simultaneous measurements of the weak antilocalization (WAL) effect
and beating in the SdH oscillations. The strength of the Zeeman splitting was
regulated by tilting the magnetic field with the spin-zeros in the SdH
oscillations, which are not always present, being enhanced by the tilt. In
tilted fields the spin-orbit and Zeeman splittings are not additive, and a
simple expression is given for the energy levels. The Rashba parameter and the
electron g-factor were extracted from the position of the spin zeros in tilted
fields. A good agreement is obtained for the spin-orbit coupling strength from
the spin-zeros and weak antilocalization measurements.",0508328v2
2007-08-04,Spin Injection in Quantum Wells with Spatially Dependent Rashba Interaction,"We consider Rashba spin-orbit effects on spin transport driven by an electric
field in semiconductor quantum wells. We derive spin diffusion equations that
are valid when the mean free path and the Rashba spin-orbit interaction vary on
length scales larger than the mean free path in the weak spin-orbit coupling
limit. From these general diffusion equations, we derive boundary conditions
between regions of different spin-orbit couplings. We show that spin injection
is feasible when the electric field is perpendicular to the boundary between
two regions. When the electric field is parallel to the boundary, spin
injection only occurs when the mean free path changes within the boundary, in
agreement with the recent work by Tserkovnyak et al. [cond-mat/0610190].",0708.0597v1
2008-12-10,Spin-Orbit-Mediated Spin Relaxation in Graphene,"We investigate how spins relax in intrinsic graphene. The spin-orbit coupling
arises from the band structure and is enhanced by ripples. The orbital motion
is influenced by scattering centers and ripple-induced gauge fields. Spin
relaxation due to Elliot-Yafet and Dyakonov-Perel mechanisms and gauge fields
in combination with spin-orbit coupling are discussed. In intrinsic graphene,
the Dyakonov-Perel mechanism and spin flip due to gauge fields dominate and the
spin-flip relaxation time is inversely proportional to the elastic scattering
time. The spin relaxation anisotropy depends on an intricate competition
between these mechanisms. Experimental consequences are discussed.",0812.1921v3
2018-04-27,Electrical control of a confined electron spin in a silicene quantum dot,"We study spin control for an electron confined in a flake of silicene. We
find that the lowest-energy conduction-band levels are split by the diagonal
intrinsic spin-orbit coupling into Kramers doublets with a definite projection
of the spin on the orbital magnetic moment. We study the spin control by AC
electric fields using the non-diagonal Rashba component of the spin-orbit
interactions with the time-dependent atomistic tight-binding approach. The
Rashba interactions in AC electric fields produce Rabi spin-flips times of the
order of a nanosecond. These times can be reduced to tens of picoseconds
provided that the vertical electric field is tuned to an avoided crossing open
by the Rashba spin-orbit interaction. We demonstrate that the speedup of the
spin transitions is possible due to the intervalley coupling induced by the
armchair edge of the flake. The study is confronted with the results for
circular quantum dots decoupled from the edge with well defined angular
momentum and valley index.",1804.10496v1
2017-04-13,The influence of anisotropic Rashba spin-orbit coupling on current-induced spin polarization in graphene,"We consider a disordered graphene layer with anisotropic Rashba spin-orbit
coupling subjected to a longitudinal electric field. Using the linear response
theory we calculate current-induced spin polarization including in-plane normal
and parallel components with respect to the electric field direction. Unlike
the case of isotropic Rashba spin-orbit where the normal component of spin
polarization is linear in terms of Fermi energy around the Dirac point,
anisotropic Rashba spin-orbit can result in non-linear dependence of this
component at such energies within the Lifshitz points. Furthermore, we show
that anisotropic Rashba interaction allows for tuning the direction of spin
polarization from perpendicular direction to the parallel one such that for
certain values of Rashba parameters the magnitudes of both components can also
be quenched. The effect of carriers scattering on randomly distributed
non-magnetic disorders is also taken into account by calculating vertex
correction. This results in modification of spin polarization components
depending on the relative strength of Rashba parameters.",1704.04188v2
2020-01-01,Pseudo-spin rotation symmetry breaking by Coulomb interaction terms in spin-orbit coupled systems,"By transforming from the pure-spin-orbital ($t_{\rm 2g}$) basis to the
spin-orbital entangled pseudo-spin-orbital basis, the pseudo-spin rotation
symmetry of the different Coulomb interaction terms is investigated under SU(2)
transformation in pseudo-spin space. While the Hubbard and density interaction
terms are invariant, the Hund's coupling and pair-hopping interaction terms
explicitly break pseudo-spin rotation symmetry systematically. The form of the
symmetry-breaking terms obtained from the transformation of the Coulomb
interaction terms accounts for the easy $x$-$y$ plane anisotropy and magnon gap
for the out-of-plane mode, highlighting the importance of mixing with the
nominally non-magnetic $J$=3/2 sector, and providing a physically transparent
approach for investigating magnetic ordering and anisotropy effects in
perovskite ($\rm Sr_2 Ir O_4$) and other $d^5$ pseudo-spin compounds.",2001.00190v2
2019-01-11,Spin-orbit torques in heavy metal/ferromagnet bilayers with varying strength of interfacial spin-orbit coupling,"Despite intense efforts it has remained unresolved whether and how
interfacial spin-orbit coupling (ISOC) affects spin transport across heavy
metal (HM)/ferromagnet (FM) interfaces. Here we report conclusive experiment
evidence that the ISOC at HM/FM interfaces is the dominant mechanism for ""spin
memory loss"". An increase in ISOC significantly reduces, in a linear manner,
the dampinglike spin-orbit torque (SOT) exerted on the FM layer via degradation
of the spin transparency of the interface for spin currents generated in the
HM. In addition, the fieldlike SOT is also dominated by the spin Hall
contribution of the HM and decreases with increasing ISOC. This work reveals
that ISOC at HM/FM interfaces should be minimized to advance efficient SOT
devices through atomic layer passivation of the HM/FM interface or other means.",1901.03632v1
2007-01-08,Post-Newtonian gravitational radiation and equations of motion via direct integration of the relaxed Einstein equations. IV. Radiation reaction for binary systems with spin-spin coupling,"Using post-Newtonian equations of motion for fluid bodies that include
radiation-reaction terms at 2.5 and 3.5 post-Newtonian (PN) order O[(v/c)^5]
and O[(v/c)^7] beyond Newtonian order), we derive the equations of motion for
binary systems with spinning bodies, including spin-spin effects. In particular
we determine the effects of radiation-reaction coupled to spin-spin effects on
the two-body equations of motion, and on the evolution of the spins. We find
that radiation damping causes a 3.5PN order, spin-spin induced precession of
the individual spins. This contrasts with the case of spin-orbit coupling,
where there is no effect on the spins at 3.5PN order. Employing the equations
of motion and of spin precession, we verify that the loss of total energy and
total angular momentum induced by spin-spin effects precisely balances the
radiative flux of those quantities calculated by Kidder et al.",0701047v2
2013-02-27,Ferromagnetic to antiferromagnetic transition of one-dimensional spinor Bose gases with spin-orbit coupling,"We have analytically solved one-dimensional interacting two-component bosonic
gases with spin-orbit (SO) coupling by the Bethe-ansatz method. Through a gauge
transformation, the effect of SO coupling is incorporated into a spin-dependent
twisted boundary condition. Our result shows that the SO coupling can influence
the eigenenergy in a periodical pattern. The interplay between interaction and
SO coupling may induce the energy level crossing for the ground state, which
leads to a transition from the ferromagnetic to antiferromagnetic state.",1302.6901v2
2002-12-16,Entropy Driven Dimerization in a One-Dimensional Spin-Orbital Model,"We study a new version of the one-dimensional spin-orbital model with spins
S=1 relevant to cubic vanadates. At small Hund's coupling J_H we discover
dimerization in a pure electronic system solely due to a dynamical spin-orbital
coupling. Above a critical value J_H, a uniform ferromagnetic state is
stabilized at zero temperature. More surprisingly, we observe a temperature
driven dimerization of the ferrochain, which occurs due to a large entropy
released by dimer states. This dynamical dimerization seems to be the mechanism
driving the peculiar intermediate phase of YVO_3.",0212368v1
2008-09-26,Mott Insulators in the Strong Spin-Orbit Coupling Limit: From Heisenberg to a Quantum Compass and Kitaev Models,"We study the magnetic interactions in Mott-Hubbard systems with partially
filled $t_{2g}$-levels and with strong spin-orbit coupling. The latter
entangles the spin and orbital spaces, and leads to a rich variety of the low
energy Hamiltonians that extrapolate from the Heisenberg to a quantum compass
model depending on the lattice geometry. This gives way to ""engineer"" in such
Mott insulators an exactly solvable spin model by Kitaev relevant for quantum
computation. We, finally, explain ""weak"" ferromagnetism, with an anomalously
large ferromagnetic moment, in Sr$_2$IrO$_4$.",0809.4658v2
2009-11-04,Nonvanishing anisotropic magnetoresistance in Rashba two-dimensional electron systems with nonmagnetic disorders,"We study anisotropic magnetoresistance (AMR) in a spin-polarized
two-dimensional electron gas with Rashba spin-orbit coupling and nonmagnetic
disorder collision. We show that AMR exists, arising from the combined effect
of in-plane magnetization, spin-orbit coupling, and nonmagnetic remote disorder
scattering. Further, numerical evaluation demonstrates that the smoothness of
the remote disorder can strongly affect AMR, and this AMR is sensitive to the
electron density. Large magnitude of AMR ($\approx24%$) is obtained for low
density system with strong spin-orbit splitting.",0911.0732v1
2014-02-28,$^{3}$He-R: A Topological $s^{\pm}$ Superfluid with Triplet Pairing,"We show that when spin and orbital angular momenta are entangled by
spin-orbit coupling, this transforms a topological spin-triplet
superfluid/superconductor state, such as $^{3}$He-B, into a topological
$s^{\pm}$ state, with non-trivial gapless edge states. Similar to $^{3}$He-B,
the $s^{\pm}$ state also minimizes on-site Coulomb repulsion for weak to
moderate interactions. A topological phase transition into a $d$-wave state
occurs for sufficiently strong spin-orbit coupling.",1402.7372v2
2016-04-28,Spin evolution of cold atomic gases in SU(2)$\otimes $U(1) fields,"We consider response function and spin evolution in spin-orbit coupled cold
atomic gases in a synthetic gauge magnetic field influencing solely the orbital
motion of atoms. We demonstrate that various regimes of spin-orbit coupling
strength, magnetic field, and disorder can be treated within a single approach
based on the representation of atomic motion in terms of auxiliary collective
classical trajectories. Our approach allows for a unified description of
fermionic and bosonic gases.",1604.08522v1
2021-09-17,Anomalous Hall effect in the coplanar antiferromagnetic coloring-triangular lattice,"We study the anomalous Hall effect on the antiferromagnetic
coloring-triangular lattice with a coplanar magnetic configuration in presence
of a spin-orbit interaction. The effect of the spin-orbit coupling is included
at effective level as a rotation of the electronic spin as the electrons hop
from site to site. Our result reveals that a finite Hall conductivity in the
planar 120$^{\circ}$ structure takes place if a finite spin-orbit coupling is
present. A quantized Hall conductivity occurs at global band gaps resulting
from the topologically non-trivial band structure.",2109.08570v1
2022-02-21,Chiral superconductivity in cuprates mediated by spin-orbit coupling to spinon superfluidity,"We utilize the Hubbard model to demonstrate that doping of the
antiferromagnetic parent compounds of cuprate superconductors stabilizes a spin
liquid state. Superconductivity in such a state emerges due to the spin-orbit
coupling between charge current and superfluidity of spinon condensate,
resulting in a chiral relation between the order parameter phase gradient and
supercurrent. We propose simple experimental tests for the presented mechanism.",2202.09965v5
1999-05-18,Spin-orbit scattering in d-wave superconductors,"When non-magnetic impurities are introduced in a d-wave superconductor, both
thermodynamic and spectral properties are strongly affected if the impurity
potential is close to the strong resonance limit. In addition to the scalar
impurity potential, the charge carriers are also spin-orbit coupled to the
impurities. Here it is shown that (i) close to the unitarity limit for the
impurity scattering, the spin-orbit contribution is of the same order of
magnitude than the scalar scattering and cannot be neglected, (ii) the
spin-orbit scattering is pair-breaking and (iii) induces a small id_xy
component to the off-diagonal part of the self-energy.",9905262v1
2003-01-06,"Orbital-Spin Structure and Coupling to Lattice in RTiO$_3$ with R=La,Pr,Nd and Sm","The origin of the G-type antiferromagnetism (AFM(G)) and puzzling properties
of RTiO$_3$ with R=La are studied. We clarify that the crystal field from La
caused by the GdFeO$_3$-type distortion lifts the $t_{2g}$ degeneracy at Ti 3d
orbitals. The lift stabilizes the AFM(G) with spin-exchange constant in
agreement with neutron scattering results. The orbital-spin structures for
R=Pr, Nd and Sm are also consistent with experiments. We propose that the
GdFeO$_3$-type distortion has a universal mechanism of controlling orbital-spin
structure competing with the Jahn-Teller (JT) mechanism.",0301049v1
1996-02-07,The Breathing Modes of the $B=2$ Skyrmion and the Spin-Orbit Interaction,"The coupling of the breathing and rotational modes of the skyrmion-skyrmion
system leads to a nucleon-nucleon spin-orbit interaction of short range, as
well as to spin-orbit potentials for the transitions $NN \to N(1440)N$, $NN \to
NN(1440)$ and $NN \to N(1440)N(1440)$. The longest range behaviour of these
spin-orbit potentials is calculated in closed form.",9602008v1
2009-02-25,Curvature-induced anisotropic spin-orbit splitting in carbon nanotubes,"We have theoretically explored the spin-orbit interaction in carbon
nanotubes. We have found that, besides the dependence on chirality and
diameter, the effects of spin-orbit coupling are anisotropic: spin splitting is
larger for the higher valence or the lower electron band depending on the
specific tube. Different tube behaviors can be grouped in three families,
according to the so called chiral index. Curvature-induced changes in the
orbital hybridization have a crucial role, and they are shown to be
family-dependent. Our results explain recent experiments without invoking
external fields.",0902.4401v1
2011-04-28,Spin and Orbital Characters of Excitations in Iron Arsenide Superconductors Revealed by Simulated Fe L-Edge RIXS,"We theoretically examine the orbital excitations coupled to the spin degree
of freedom in the parent state of the iron-arsenide superconductor, based on
the calculation in a five-band itinerant model. The calculated Fe $L_3$-edge
resonant inelastic x-ray scattering (RIXS) spectra disclose the presence of
spin-flip excitations involving several specific orbitals. Magnon excitations
predominantly composed of a single orbital component can be seen in
experiments, although its spectral weight is smaller than spin-flipped
interorbital high-energy excitations. The detailed polarization and momentum
dependence is also discussed with predictions for the experiments.",1104.5424v2
2019-05-14,Thermodynamics of symmetric spin--orbital model: One- and two-dimensional cases,"The specific heat and susceptibilities for the two- and one-dimensional
spin--orbital models are calculated in the framework of a spherically symmetric
self-consistent approach at different temperatures and relations between the
parameters of the system. It is shown that even in the absence of the
long-range spin and orbital order, the system exhibits the features in the
behavior of thermodynamic characteristics, which are typical of those
manifesting themselves at phase transitions. Such features are attributed to
the quantum entanglement of the coupled spin and orbital degrees of freedom.",1905.05791v1
2009-12-22,Inelastic decay rate of quasiparticles in a two-dimensional spin-orbit coupled electron system,"We present a study of the inelastic decay rate of quasiparticles in a
two-dimensional electron gas with spin-orbit interaction. The study is done
within the G0W0 approximation. The spin-orbit interaction is taken in the most
general form that includes both Rashba and Dresselhaus contributions linear in
magnitude of the electron 2D momentum. Spin-orbit interaction effect on the
inelastic decay rate is examined at different parameters characterizing the
interaction strength in the electron gas.",0912.4358v2
2018-03-17,Emergence of spin-orbit order in the spinel CuCr$_2$O$_4$,"We determined the magnetic structure of CuCr$_2$O$_4$ using neutron
diffraction and irreducible representation analysis. The measurements
identified a new phase between 155 K and 125 K as nearly collinear magnetic
ordering in the Cr pyrochlore lattice. Below 125 K, a Cu-Cr ferrimagnetic
component develops the noncollinear order. Along with the simultaneously
obtained O positions and the quantum effect of spin-orbit coupling, the
magnetic structure is understood to involve spin-orbit ordering, accompanied by
an appreciably deformed orbital of presumably spin-only Cu and Cr.",1803.06447v1
2017-07-06,Antisymmetric Spin-Orbit Coupling Effect on Kondo-Induced Electric Polarization in a Triangular Triple Quantum Dot,"We study the local antisymmetric spin-orbit (ASO) coupling effect on spin,
orbital, and charge degrees of freedom for the Kondo effect in a triangular
triple quantum dot (TTQD). Here, one of the three QDs is coupled to a metallic
lead through electron tunneling, and a local electric polarization is induced
by the Kondo effect. The ASO interaction is introduced in the other two coupled
QDs on the opposite side of the lead. Generally, the ASO coupling effect is
very weak and not easily detectable, but it essentially causes spin and charge
reconfigurations in the TTQD through the Kondo effect. Using an extended
Anderson model for the TTQD Kondo system, we elucidate that the ASO coupling
gives rise to a considerable reduction of the emergent electric polarization,
as a consequence of the parity mixing of molecular orbitals in the triangular
loop as well as the spin-up and spin-down coupling of local electrons. The
latter leads to a local diamagnetic susceptibility owing to the ASO coupled
spins. We also show that the Kondo-induced electric polarization can be
controlled by the ASO coupling as well as by the magnetic flux penetrating
through the TTQD.",1707.01676v1
2023-06-20,Spin-orbit interaction enabled electronic Raman scattering from charge collective modes,"Electronic Raman scattering in the fully symmetric channel couples to the
charge excitations in the system, including the plasmons. However, the plasmon
response has a spectral weight of $\sim q^2$, where $q$, the momentum
transferred by light, is small. In this work, we show that in inversion
symmetry broken systems where Rashba type spin-orbit coupling affects the
states at the Fermi energy (which is a known low energy effect) as well as the
transition elements to other states (a high energy effect), there is an
additional coupling of the plasmons to the Raman vertex, even at zero momentum
transfer, that results in a spectral weight that is proportional to the
spin-orbit coupling. The high energy effect is due to the breaking of SU(2)
spin invariance in the spin-flip transitions to the intermediate state. We
present a theory for this coupling near the resonant regime of Raman scattering
and show that in giant Rashba systems it can dominate over the conventional
$q^2$ weighted coupling. We also provide experimental support along with a
symmetry based justification for this spin-mediated coupling by identifying a
prominent c-axis plasmon peak in the fully symmetric channel of the resonant
Raman spectrum of the giant Rashba material BiTeI. This new coupling could lead
to novel ways of manipulating coherent charge excitations in inversion-broken
systems. This process is also relevant for spectroscopic studies in ultrafast
spectroscopies, certain driven Floquet systems and topologically non-trivial
phases of matter where strong inversion-breaking spin-orbit coupling plays a
role.",2306.11240v2
2016-08-10,Competing interactions in population-imbalanced two-component Bose-Einstein condensates,"We consider a two-component Bose-Einstein condensate with and without
synthetic ""spin-orbit"" interactions in two dimensions. Density- and
phase-fluctuations of the condensate are included, allowing us to study the
impact of thermal fluctuations and density-density interactions on the physics
originating with spin-orbit interactions. In the absence of spin-orbit
interactions, we find that inter-component density interactions deplete the
minority condensate. The thermally driven phase transition is driven by coupled
density and phase-fluctuations, but is nevertheless shown to be a
phase-transition in the Kosterlitz-Thouless universality class with close to
universal amplitude ratios irrespective of whether both the minority- and
majority condensates exist in the ground state, or only one condensate exists.
In the presence of spin-orbit interactions we observe three separate phases,
depending on the strength of the spin-orbit coupling and inter-component
density-density interactions: a phase-modulated phase with uniform amplitudes
for small intercomponent interactions, a completely imbalanced, effectively
single-component, condensate for intermediate spin-orbit coupling strength and
suficciently large inter-component interactions, and a phase-modulated
\textit{and} amplitude-modulated phase for sufficiently large values of both
the spin-orbit coupling and the inter-component density-density interactions.
The phase which is modulated by a single $\bv q$-vector only is observed to
transition into an isoptropic liquid through a strong de-pinning transition
with periodic boundary conditions, which weakens with open boundaries.",1608.03300v1
2019-10-01,Low-symmetry nanowire cross-sections for enhanced Dresselhaus spin-orbit interaction,"We study theoretically the spin-orbit interaction of low-energy electrons in
semiconducting nanowires with a zinc-blende lattice. The effective Dresselhaus
term is derived for various growth directions, including <11(-2)>-oriented
nanowires. While a specific configuration exists where the Dresselhaus
spin-orbit coupling is suppressed even at confinement potentials of low
symmetry, many configurations allow for a strong Dresselhaus coupling. In
particular, we discuss qualitative and quantitative results for nanowire
cross-sections modeled after sectors of rings or circles. The parameter
dependence is analyzed in detail, enabling predictions for a large variety of
setups. For example, we gain insight into the spin-orbit coupling in recently
fabricated GaAs-InAs nanomembrane-nanowire structures. By combining the
effective Dresselhaus and Rashba terms, we find that such structures are
promising platforms for applications where an electrically controllable
spin-orbit interaction is needed. If the nanowire cross-section is scaled down
and InAs replaced by InSb, remarkably high Dresselhaus-based spin-orbit
energies of the order of millielectronvolt are expected. A Rashba term that is
similar to the effective Dresselhaus term can be induced via electric gates,
providing means to switch the spin-orbit interaction on and off. By varying the
central angle of the circular sector, we find, among other things, that
particularly strong Dresselhaus couplings are possible when nanowire
cross-sections resemble half-disks.",1910.00562v1
2002-02-14,Spin and Orbital States and Their Phase Transitions of the Perovskite-Type Ti Oxides: Weak coupling Approach,"The magnetic phase diagram of the perovskite-type Ti oxides as a function of
the GdFeO3-type distortion is examined by using the Hartree-Fock analysis of a
multiband d-p Hamiltonian from a viewpoint of competitions of the spin-orbit
interaction, the Jahn-Teller (JT) level-splitting and spin-orbital
superexchange interactions. Near the antiferromagnetic (AFM)-to-ferromagnetic
(FM) phase boundary, A-type AFM [AFM(A)] and FM states accompanied by a certain
type of orbital ordering are lowered in energy at large JT distortion, which is
in agreement with the previous strong coupling study. With increasing the
GdFeO3-type distortion, their phase transition occurs. Through this magnetic
phase transition, the orbital state hardly changes, which induces nearly
continuous change in the spin coupling along the c-axis from negative to
positive. The resultant strong two-dimensionality in the spin coupling near the
phase boundary is attributed to the strong suppression of T_N and T_C, which is
experimentally observed. On the other hand, at small GdFeO3-type without JT
distortions, which correspond to LaTiO3, the most stable solution is not G-type
AFM [AFM(G)] but FM. Although the spin-orbit interaction has been considered to
be relevant at the small or no JT distortion of LaTiO3 in the literature, our
analysis indicates that the spin-orbit interaction is irrelevant to the AFM(G)
state in LaTiO3 and superexchange-type interaction dominates. On the basis of
further investigations on the nature of this FM state and other solutions, this
discrepancy is discussed in detail.",0202242v1
1999-04-30,Does spin-orbit coupling play a role in metal-nonmetal transition in two-dimensional systems?,"We propose an experiment, which would allow to pinpoint the role of
spin-orbit coupling in the metal-nonmetal transition observed in a number of
two-dimensional systems at low densities. Namely, we demonstrate that in a
parallel magnetic field the interplay between the spin-orbit coupling and the
Zeeman splitting leads to a characteristic anisotropy of resistivity with
respect to the direction of the in-plane magnetic field. Though our analytic
calculation is done in the deeply insulating regime, the anisotropy is expected
to persist far beyond that regime.",9904451v2
2001-07-18,Spin-orbit coupling effects on quantum transport in lateral semiconductor dots,"The effects of interplay between spin-orbit coupling and Zeeman splitting on
weak localisation and universal conductance fluctuations in lateral
semiconductor quantum dots are analysed: All possible symmetry classes of
corresponding random matrix theories are listed and crossovers between them
achievable by sweeping magnetic field and changing the dot parameters are
described. We also suggest experiments to measure the spin-orbit coupling
constants.",0107385v1
2004-03-06,Luttinger liquid with strong spin-orbital coupling and Zeeman splitting in quantum wires,"We study a one-dimensional interacting electron gas with the strong Rashba
spin-orbit coupling and Zeeman splitting in a quantum well. A bosonization
theory is developed for this system. The tunneling current may deviate from a
simple power law which is that in an ordinary Luttinger liquid. The microscopic
interacting coupling and the spin-orbital parameter may be measured by varying
the external magnetic field in the tunneling experiment.",0403183v1
2005-09-28,Quantum transport phenomena in disordered electron systems with spin-orbit coupling in two dimensions and below,"Electron transport phenomena in disordered electron systems with spin-orbit
coupling in two dimensions and below are studied numerically. The scaling
hypothesis is checked by analyzing the scaling of the quasi-1D localization
length. A logarithmic increase of the mean conductance is also confirmed. These
support the theoretical prediction that the two dimensional metal in systems
with spin-orbit coupling has a perfect conductivity. Transport through a
Sierpinski carpet is also reported.",0509718v1
2006-01-02,"Crystal field, spin-orbit coupling and magnetism in a ferromagnet YTiO3","Magnetic properties of stechiometric YTiO3 has been calculated within the
single-ion-based paradigm taking into account the low-symmetry crystal field
and the intra-atomic spin-orbit coupling of the Ti3+ ion. Despite of the very
simplified approach the calculations reproduce perfectly the value of the
magnetic moment and its direction as well as temperature dependence of the
magnetic susceptibility chi(T). It turns out that the spin-orbit coupling is
fundamentally important for 3d magnetism and magnetic properties are determined
by lattice distortions.",0601005v1
2007-03-02,Topological Force and Torque in Spin-Orbit Coupling System,"The topological force and torque are investigated in the systems with
spin-orbit coupling. Our results show that the topological force and torque
appears as a pure relativistic quantum effect in an electromagnetic field. The
origin of both topological force and torque is the Zitterbewegung effect.
Considering nonlinear behaviors of spin-orbit coupling, we address possible
phenomena driven by the topological forces.",0703048v1
2008-02-18,Spin-orbit coupling and crystal-field splitting in the electronic and optical properties of nitride quantum dots with a wurtzite crystal structure,"We present an $sp^3$ tight-binding model for the calculation of the
electronic and optical properties of wurtzite semiconductor quantum dots (QDs).
The tight-binding model takes into account strain, piezoelectricity, spin-orbit
coupling and crystal-field splitting. Excitonic absorption spectra are
calculated using the configuration interaction scheme. We study the electronic
and optical properties of InN/GaN QDs and their dependence on structural
properties, crystal-field splitting, and spin-orbit coupling.",0802.2436v1
2010-01-05,Tuning spin-orbit coupling and superconductivity at the SrTiO3/LaAlO3 interface: a magneto-transport study,"The superconducting transition temperature, Tc, of the SrTiO3/LaAlO3
interface was varied by the electric field effect. The anisotropy of the upper
critical field and the normal state magneto-transport were studied as a
function of gate voltage. The spin-orbit coupling energy is extracted. This
tunable energy scale is used to explain the strong gate dependence of the
mobility and of the anomalous Hall signal observed. The spin-orbit coupling
energy follows Tc for the electric field range under study.",1001.0781v1
2011-12-26,Kondo effect in the presence of spin-orbit coupling,"We study the T=0 Kondo physics of a spin-1/2 impurity in a
non-centrosymmetric metal with spin-orbit interaction. Within a simple
variational approach we compute ground state properties of the system for an
{\it arbitrary} form of spin-orbit coupling consistent with the crystal
symmetry. This coupling produces an unscreened impurity magnetic moment and can
lead to a significant change of the Kondo energy. We discuss implications of
this finding both for dilute impurities and for heavy-fermion materials without
inversion symmetry.",1112.5875v2
2012-07-22,Condensation transition of ultracold Bose gases with Rashba spin-orbit coupling,"We study the Bose-Einstein condensate phase transition of three-dimensional
ultracold bosons with isotropic Rashba spin-orbit coupling. Investigating the
structure of Ginzburg-Landau free energy as a function of the condensate
density, we show, within the Bogoliubov approximation, that the condensate
phase transition is first order with a jump in the condensate density. We
calculate the transition temperature and the jump in the condensate density at
the transition for large spin-orbit coupling, where the transition temperature
depends linearly on the density of particles. Finally, we discuss the
feasibility of producing the phase transition experimentally.",1207.5263v2
2013-02-24,Mapping trapped atomic gas with spin-orbit coupling to quantum Rabi-like model,"We construct a connection of the ultracold atomic system in a harmonic trap
with Raman-induced spin-orbit coupling to the quantum Rabi-like model. By
mapping the trapped atomic system to a Rabi-like model, we can get the exact
solution of the Rabi-like model following the methods to solve the quantum Rabi
model. The existence of such a mapping implies that we can study the basic
model in quantum optics by using trapped atomic gases with spin-orbit coupling.",1302.5933v1
2013-06-08,A Raman-induced Feshbach resonance in an effectively single-component Fermi gas,"Ultracold gases of interacting spin-orbit coupled fermions are predicted to
display exotic phenomena such as topological superfluidity and its associated
Majorana fermions. Here, we experimentally demonstrate a route to
strongly-interacting single-component atomic Fermi gases by combining an s-wave
Feshbach resonance (giving strong interactions) and spin-orbit coupling
(creating an effective p-wave channel). We identify the Feshbach resonance by
its associated atomic loss feature and show that, in agreement with our
single-channel scattering model, this feature is preserved and shifted as a
function of the spin-orbit coupling parameters.",1306.1965v1
2013-10-16,Superconductivity in non-centrosymmetric LaNiC2,"We present a discussion of superconductivity in non-centrosymmetric
superconductors with spin-orbit coupling. A general expression for the
quasiparticle excitation energy is derived. The superconducting states for the
point group C2v are classified by symmetry in the limit of weak spin-orbit
coupling. A non-unitary triplet pairing gap function can account for
observations of broken time-reversal symmetry and nodes in the superconducting
state of LaNiC2; however such a gap function also has a gapless branch and
requires vanishing spin-orbit coupling.",1310.4523v1
2013-10-31,Topological quantum phase transitions and edge states in spin-orbital coupled Fermi gases,"We study the superconducting state in the presence of spin-orbital coupling
and the Zeeman field. It is found that a phase transition from the
Fulde-Ferrell-Larkin-Ovchinnikov state to the topological superconducting state
occurs upon increasing the spin-orbital coupling. The nature of this
topological phase transition and its critical property are investigated
numerically. Physical properties of topological superconducting phase are also
explored. Moreover, the local density of states is calculated, through which
the topological feature may be tested experimentally.",1310.8562v3
2013-11-16,Two-dimensional quasi-ideal Fermi gas with Rashba spin-orbit coupling,"We investigate the zero-temperature properties of a quasi-ideal Fermi gas
with Rashba spin-orbit coupling. We find that the spin-orbit term strongly
affects the speeds of zero sound and first sound in the Fermi gas, due to the
presence of a third-order quantum phase transition. In addition, including a 2D
harmonic confinement we show that also the shape of the density profile of the
cloud crucially depends on the strength of the Rashba coupling.",1311.4080v3
2014-01-02,Superfluid-Mott insulator transition in spin-orbit coupled Bose-Hubbard Model,"We consider a square optical lattice in two dimensions and study the effects
of both the strength and symmetry of spin-orbit-coupling (SOC) and Zeeman field
on the ground-state, i.e., Mott insulator (MI) and superfluid (SF), phases and
phase diagram, i.e., MI-SF phase transition boundary, of the two-component
Bose-Hubbard model. In particular, based on a variational Gutzwiller ansatz,
our numerical calculations show that the spin-orbit coupled SF phase is a
nonuniform (twisted) one with its phase (but not the magnitude) of the order
parameter modulating from site to site. Fully analytical insights into the
numerical results are also given.",1401.0527v1
2014-11-09,Spin-orbit Coupling in Optical lattices,"In this review, we discuss the physics of spin-orbit coupled quantum gases in
optical lattices. After reviewing some relevant experimental techniques, we
introduce the basic theoretical model and discuss some of its generic features.
In particular, we concentrate on the interplay between spin-orbit coupling and
strong interactions and show how it leads to various exotic quantum phases in
both the Mott insulating and superfluid regimes. Phase transitions between the
Mott and superfluid states are also discussed.",1411.2297v1
2014-12-11,Spin-orbit couplings of quantum fields in Schwarzschild spacetime,"In Schwarzschild spacetime, the gravitational spin-orbit couplings of the
massless Dirac field and the photon field can be studied in a unified way. In
contrary to the previous investigations presented mainly at the
quantum-mechanical level, our work is presented at the level of quantum field
theory without resorting to the Foldy-Wouthuysen transformation. If massless
Dirac particles and photons have the same momentums, their energy-level
splittings due to the gravitational spin-orbit couplings are the same. Massless
Dirac particles and photons coming from the Hawking radiations are partially
polarized as long as their original momentums are not parallel to the radial
direction of a Schwarzschild black hole.",1412.3522v1
2015-08-03,Odd-parity superconductivity in the vicinity of inversion symmetry breaking in spin-orbit-coupled systems,"We study superconductivity in spin-orbit-coupled systems in the vicinity of
inversion symmetry breaking. We find that due to the presence of spin-orbit
coupling, fluctuations of the incipient parity-breaking order generate an
attractive pairing interaction in an odd-parity pairing channel, which competes
with the s-wave pairing. We show that applying a Zeeman field suppresses the
s-wave pairing and promotes the odd-parity superconducting state. Our work
provides a new mechanism for odd-parity pairing and opens a route to novel
topological superconductivity.",1508.00574v1
2015-10-01,Dynamics of quantized vortices in Bose-Einstein condensates with laser-induced spin-orbit coupling,"We study vortex dynamics in trapped two-component Bose-Einstein condensates
with a laser- induced spin-orbit coupling using the numerical analysis of the
Gross-Pitaevskii equation. The spin-orbit coupling leads to three distinct
ground state phases, which depend on some experimentally controllable
parameters. When a vortex is put in one or both of the two-component
condensates, the vortex dynamics exhibits very different behaviors in each
phase, which can be observed in experiments. These dynamical behaviors can be
understood by clarifying the stable vortex structure realized in each phase.",1510.00142v1
2016-01-26,Electric control of superconducting transition through a spin-orbit coupled interface,"We demonstrate theoretically all-electric control of the superconducting
transition temperature using a device comprised of a conventional
superconductor, a ferromagnetic insulator, and semiconducting layers with
intrinsic spin-orbit coupling. By using analytical calculations and numerical
simulations, we show that the transition temperature of such a device can be
controlled by electric gating which alters the ratio of Rashba to Dresselhaus
spin-orbit coupling. The results offer a new pathway to control
superconductivity in spintronic devices.",1601.07176v2
2013-08-26,Emergent Kinetics and Fractionalized Charge in 1D Spin-Orbit Coupled Flatband Optical Lattices,"Recent ultracold atomic gas experiments implementing synthetic spin-orbit
coupling allow access to flatbands that emphasize interactions. We model
spin-orbit coupled fermions in a one-dimensional flatband optical lattice. We
introduce an effective Luttinger-liquid theory to show that interactions
generate collective excitations with emergent kinetics and fractionalized
charge, analogous to properties found in the two-dimensional fractional quantum
Hall regime. Observation of these excitations would provide an important
platform for exploring exotic quantum states derived solely from interactions.",1308.5601v3
2011-11-18,Phase Diagram of Two-dimensional Polarized Fermi Gas With Spin-Orbit Coupling,"We investigate the ground state of the two-dimensional polarized Fermi gas
with spin-orbit coupling and construct the phase diagram at zero temperature.
We find there exist phase separation when the binding energy is low. As the
binding energy increasing, the topological nontrivial superfluid phase coexist
with topologically trivial superfluid phase which is topological phase
separation. The spin-orbit coupling interaction enhance the triplet pairing and
destabilize the phase separation against superfluid phase.",1111.4277v1
2011-11-23,Majorana fermions in carbon nanotubes,"We show that carbon nanotubes (CNT) are good candidates for realizing
one-dimensional topological superconductivity with Majorana fermions localized
near the end points. The physics behind topological superconductivity in CNT is
novel and is mediated by a recently reported curvature-induced spin-orbit
coupling which itself has a topological origin. In addition to the spin-orbit
coupling, an important new requirement for a robust topological state is broken
chirality symmetry about the nanotube axis. We use topological arguments to
show that, for recently realized strengths of spin-orbit coupling and broken
chirality symmetry, a robust topological gap of around 500 mK is achievable in
carbon nanotubes.",1111.5622v1
2012-01-09,Josephson Current through a Semiconductor Nanowire: effect of strong spin-orbit coupling and Zeeman splitting,"We study coherent transport through a semiconductor nanowire in the presence
of spin-orbit coupling and Zeeman splitting due to an applied magnetic field.
By employing analytical and numerical techniques we develop a theory for the
Josephson effect in the superconductor-semiconductor nanowire-superconductor
structure. We show that Josephson current through the clean semiconductor
nanowire exhibits a number of interesting features due to the interplay between
the Zeeman splitting and spin-orbit coupling. We also study effect how disorder
in the nanowire affects Andreev bound-state energy spectrum and calculate local
density of states at the junction.",1201.1918v2
2012-04-03,Magnetic Impurities in Two-Dimensional Superfluid Fermi Gas with Spin-Orbit Coupling,"We consider magnetic impurities in a two dimensional superfluid Fermi gas in
the presence of spin-orbit coupling. By using the methods of t-matrix and
Green's function, we find spin-orbit coupling has some dramatic impacts on the
effects of magnetic impurities. For the single impurity problem, the number of
bound states localized around the magnetic impurity is doubled. For the finite
concentration $n$ of impurities, the energy gap is reduced and the density of
states in the gapless region is greatly modified.",1204.0571v1
2014-05-16,Spin-orbit coupled Bose-Einstein condensates in a one-dimensional optical lattice,"The realization of artificial gauge fields and spin-orbit coupling for
ultra-cold quantum gases promises new insight into paradigm solid state
systems. Here we experimentally probe the dispersion relation of a spin-orbit
coupled Bose-Einstein condensate loaded into a translating optical lattice by
observing its dynamical stability, and develop an effective band structure that
provides a theoretical understanding of the locations of the band edges. This
system presents exciting new opportunities for engineering condensed-matter
analogs using the flexible toolbox of ultra-cold quantum gases.",1405.4048v1
2015-12-12,Influence of Induced Interactions on Superfluid Properties of Quasi-Two Dimensional Dilute Fermi Gases With Spin-Orbit Coupling,"We study the effects of induced interactions on the pairing gap, transition
temperature and chemical potential of a quasi-two dimensional Fermi gas of
atoms with spin-orbit coupling. We find that these mean-field parameters are
significantly modified when induced interactions are taken into account. We
also investigate the implications of induced interactions corrections for the
BCS-BEC crossover driven by spin-orbit coupling, that happens even for small
(compared to the Fermi energy) values of the binding energy.",1512.03964v1
2017-07-28,Moving obstacle potential in a spin-orbit-coupled Bose-Einstein condensate,"We investigate the dynamics around an obstacle potential moving in the
plane-wave state of a pseudospin-$1/2$ Bose-Einstein condensate with Rashba
spin-orbit coupling. We numerically investigate the dynamics of the system and
find that it depends not only on the velocity of the obstacle but also
significantly on the direction of obstacle motion, which are verified by a
Bogoliubov analysis. The excitation diagram with respect to the velocity and
direction is obtained. The dependence of the critical velocity on the strength
of the spin-orbit coupling and the size of the obstacle is also investigated.",1707.09136v1
2018-10-01,Monoclinic SrIrO$_3$ - A Dirac semimetal produced by non-symmorphic symmetry and spin-orbit coupling,"SrIrO$_3$ crystallizes in a monoclinic structure of distorted hexagonal
perovskite at ambient pressure. The transport measurements show that the
monoclinic SrIrO$_3$ is a low-carrier density semimetal, as in the orthorhombic
perovskite polymorph. The electronic structure calculation indicates a
semimetallic band structure with Dirac bands at two high-symmetry points of
Brillouin zone only when spin-orbit coupling is incorporated, suggesting that
the semimetallic state is produced by the strong spin-orbit coupling. We argue
that the Dirac bands are protected by the non-symmorphic symmetry of lattice.",1810.00815v1
2019-09-30,Mixed-parity superconductivity near Lifshitz transitions in strongly spin-orbit-coupled metals,"We consider a strongly spin-orbit-coupled metal, one of whose Fermi surfaces
is close to a Lifshitz (topological) transition. Via a renormalization group
analysis of the square-lattice Hubbard model with strong Rashba spin-orbit
coupling, we show that such a metal is generically unstable to the formation of
mixed-parity superconductivity with a helical triplet component.",1909.13570v2
2021-01-25,Effects of spin orbit coupling in superconducting proximity devices -- application to $\mathrm{CoSi_2 / TiSi_2}$ heterostructures,"Motivated by the recent findings of unconventional superconductivity in
$\mathrm{CoSi_2 / TiSi_2}$ heterostructures, we study the effect of interface
induced Rashba spin orbit coupling on the conductance of a three terminal ""T""
shape superconducting device. We calculate the differential conductance for
this device within the quasi-classical formalism that includes the mixing of
triplet-singlet pairing due to the Rashba spin orbit coupling. We discuss our
result in the light of the conductance spectra reported by Chiu {\it et al.}
for $\mathrm{CoSi_2 / TiSi_2}$ heterostructures.",2101.10197v2
2017-11-18,Spin-orbit coupling and magnetic field dependence of carriers states in a self-assembled quantum dot,"In this work I investigate the influence of spin-orbit coupling on the
magnetic field dependence of carrier states in a self-assembled quantum dot. I
calculate the hole energy levels using the 6, 8 and 14 band k.p model. Through
a detailed study within these models, I extract the information about the
impact of various spin-orbital coupling channels in the hole p-shell. I also
show that complicated magnetic field dependence of the hole p-shell resulting
from numerical simulations, can be very well fitted using a phenomenological
model. I compare the electron and hole g-factors calculated within 8 and 14
band k.p models and show that these methods give reasonably good agreement.",1711.06934v1
2018-08-16,{\em Zitterbewegung} in Spin-Orbit Coupled Systems and Ehrenfest's Theorem,"We use Ehrenfest's theorem to provide a particularly simple derivation of the
{\em zitterbewegung} in the dynamics of initial Gaussian wave packets in a
two-dimensional electron gas. For initial packets which are very wide in the
$y$-direction, the {\em zitterbewegung} is only in the $y$-component of the
velocity. We extend our Ehrenfest theorem based calculation to the spin-orbit
coupled spinor Bose-Einstein condensate (BEC) to predict that there can be {\em
zitterbewegung} in the $x$-component of the velocity in this situation driven
by a combination of the nonlinear interaction in the condensate and the
splitting due to the spin-orbit coupling.",1808.05397v1
2020-05-25,Visible stripe phases in spin-orbital-angular-momentum coupled Bose-Einstein condensates,"Recently, stripe phases in spin-orbit coupled Bose-Einstein condensates
(BECs) have attracted much attention since they are identified as supersolid
phases. In this paper, we exploit experimentally reachable parameters and show
theoretically that annular stripe phases with large stripe spacing and high
stripe contrast can be achieved in spin-orbital-angular-momentum coupled
(SOAMC) BECs. In addition to using Gross-Pitaevskii numerical simulations, we
develop a variational ansatz that captures the essential interaction effects to
first order, which are not present in the ansatz employed in previous
literature. Our work should open the possibility toward directly observing
stripe phases in SOAMC BECs in experiments.",2005.12007v1
2021-02-26,Distinctive magnetic properties of CrI3 and CrBr3 monolayers caused by spin-orbit coupling,"After the discovery of magnetism in monolayer CrI3, the magnetic properties
of different 2D materials from the chromium-trihalide family are intuitively
assumed to be similar, yielding magnetic anisotropy from the spin-orbit
coupling on halide ligands. Here we reveal significant differences between the
CrI3 and CrBr3 magnetic monolayers in their magnetic anisotropy, resulting
Curie temperature, hysteresis in external magnetic field, and evolution of
magnetism with strain, all predominantly attributed to distinctly different
interplay of atomic contributions to spin-orbit coupling in two materials.",2102.13325v1
2023-11-23,Supercurrent-carrying supersolid in spin-orbit-coupled Bose-Einstein condensates,"One of brilliant achievements in spin-orbit-coupled Bose-Einstein condensates
is the discovery and observation of the supersolid stripe states. So far, all
studied supersolid stripe states do not carry supercurrent. In this work, we
reveal the existence of novel supercurrent-carrying supersolids in
spin-orbit-coupled Bose-Einstein condensates. The supersolid family has a
parabolic-like dispersion relation and carries supercurrent which is
proportional to the quasimomentum. Energetic and dynamical instabilities can
break supercurrent-carrying ability of this supersolid family. An insightful
interpretation of the dynamical instability of supercurrent-carrying
supersolids from the pure plane-wave phase is provided.",2311.13786v1
2019-07-03,Large spin-relaxation anisotropy in bilayer-graphene/WS$_2$ heterostructures,"We study spin-transport in bilayer-graphene (BLG), spin-orbit coupled to a
tungsten di sulfide (WS$_2$) substrate, and measure a record spin lifetime
anisotropy ~40-70, i.e. ratio between the out-of-plane $\tau_{\perp}$ and
in-plane spin relaxation time $\tau_{||}$. We control the injection and
detection of in-plane and out-of-plane spins via the shape-anisotropy of the
ferromagnetic electrodes. We estimate $\tau_{\perp}$ ~ 1-2 ns via Hanle
measurements at high perpendicular magnetic fields and via a new tool we
develop: Oblique Spin Valve measurements. Using Hanle spin-precession
experiments we find a low $\tau_{||}$ ~ 30 ps in the electron-doped regime
which only weakly depends on the carrier density in the BLG and conductivity of
the underlying WS$_2$, indicating proximity-induced spin-orbit coupling (SOC)
in the BLG. Such high $\tau_{\perp}$ and spin lifetime anisotropy are clear
signatures of strong spin-valley coupling for out-of-plane spins in BLG/WS$_2$
systems in the presence of SOC, and unlock the potential of BLG/transition
metal dichalcogenide heterostructures for developing future spintronic
applications.",1907.01975v1
2019-07-08,Theory of Spin Injection in Two-dimensional Metals with Proximity-Induced Spin-Orbit Coupling,"Spin injection is a powerful experimental probe into a wealth of
nonequilibrium spin-dependent phenomena displayed by materials with spin-orbit
coupling (SOC). Here, we develop a theory of coupled spin-charge diffusive
transport in two-dimensional spin-valve devices. The theory describes a
realistic proximity-induced SOC with both spatially uniform and random
components of the SOC due to adatoms and imperfections, and applies to the two
dimensional electron gases found in two-dimensional materials and van der Walls
heterostructures. The various charge-to-spin conversion mechanisms known to be
present in diffusive metals, including the spin Hall effect and several
mechanisms contributing current-induced spin polarization are accounted for.
Our analysis shows that the dominant conversion mechanisms can be discerned by
analyzing the nonlocal resistance of the spin-valve for different polarizations
of the injected spins and as a function of the applied in-plane magnetic field.",1907.03727v1
2023-05-29,Inverse spin-Hall effect and spin-swapping in spin-split superconductors,"When a spin-splitting field is introduced to a thin film superconductor, the
spin currents polarized along the field couples to energy currents that can
only decay via inelastic scattering. We study spin and energy injection into
such a superconductor where spin-orbit impurity scattering yields inverse
spin-Hall and spin-swapping currents. We show that the combined presence of a
spin-splitting field, superconductivity, and inelastic scattering gives rise to
a renormalization of the spin-Hall and spin-swap angles. In addition to an
enhancement of the ordinary inverse spin-Hall effect, spin-splitting gives rise
to unique inverse spin-Hall and spin-swapping signals five orders of magnitude
stronger than the ordinary inverse spin-Hall signal. These can be completely
controlled by the orientation of the spin-splitting field, resulting in a
long-range charge and spin accumulations detectable much further from the
injector than in the normal-state. Our results demonstrate that superconductors
provide tunable inverse spin-Hall and spin-swapping signals with high detection
sensitivity.",2305.18525v1
2023-08-19,Fermi Surface Spin Texture and Topological Superconductivity in Spin-Orbit Free Non-Collinear Antiferromagnets,"We explore the relationship among the magnetic ordering in real space, the
resulting spin texture on the Fermi surface, and the related superconducting
gap structure in non-collinear antiferromagnetic metals without spin-orbit
coupling. Via a perturbative approach, we show that a non-collinear magnetic
ordering in a metal can generate a momentum-dependent spin texture on its Fermi
surface, even in the absence of spin-orbit coupling, if the metal has more than
three sublattices in its magnetic unit cell. Thus, our theory naturally extends
the idea of altermagnetism to non-collinear spin structures. When
superconductivity is developed in a magnetic metal, as the gap-opening
condition is strongly constrained by the spin texture, the nodal structure of
the superconducting state is also enforced by the magnetism-induced spin
texture. Taking the non-collinear antiferromagnet on the kagome lattice as a
representative example, we demonstrate how the Fermi surface spin texture
induced by noncollinear antiferromagnetism naturally leads to odd-parity
spin-triplet superconductivity with nontrivial topological properties.",2308.09925v2
2022-05-05,Spin Manipulation by Giant Valley-Zeeman Spin-Orbit Field in Atom-Thick WSe2,"The phenomenon originating from spin-orbit coupling (SOC) provides
energy-efficient strategies for spin manipulation and device applications. The
broken inversion symmetry interface and resulting electric field induce a
Rashba-type spin-orbit field (SOF), which has been demonstrated to generate
spin-orbit torque for data storage applications. In this study, we found that
spin flipping can be achieved by the valley-Zeeman SOF in monolayer WSe2 at
room temperature, which manifests as a negative magnetoresistance in the
vertical spin valve. Quantum transmission calculations based on an effective
model near the K valley of WSe2 confirm the precessional spin transport of
carriers under the giant SOF, which is estimated to be 650 T. In particular,
the valley-Zeeman SOF-induced spin dynamics was demonstrated to be tunable with
the layer number and stacking phase of WSe2 as well as the gate voltage, which
provides a novel strategy for spin manipulation and can benefit the development
of ultralow-power spintronic devices.",2205.02876v1
2004-07-28,Effects of Quantum-Well Inversion Asymmetry on Electron-Nuclear Spin Coupling in the Fractional Quantum Hall Regime,"We examine effects of inversion asymmetry of a GaAs/Al0.3Ga0.7As quantum well
(QW) on electron-nuclear spin coupling in the fractional quantum Hall (QH)
regime. Increasing the QW potential asymmetry at a fixed Landau-level filling
factor (nu) with gate voltages suppresses the current-induced nuclear spin
polarization in the nu = 2/3 Ising QH ferromagnet, while it significantly
enhances the nuclear spin relaxation at general nu. These findings suggest that
mixing of different spin states due to the Rashba spin-orbit interaction
strongly affects the electron-nuclear spin coupling.",0407729v1
2008-05-08,Spin-Electric Coupling in Molecular Magnets,"We study the triangular antiferromagnet Cu$_3$ in external electric fields,
using symmetry group arguments and a Hubbard model approach. We identify a
spin-electric coupling caused by an interplay between spin exchange, spin-orbit
interaction, and the chirality of the underlying spin texture of the molecular
magnet. This coupling allows for the electric control of the spin (qubit)
states, e.g. by using an STM tip or a microwave cavity. We propose an
experimental test for identifying molecular magnets exhibiting spin-electric
effects.",0805.1158v1
2010-02-26,Bends In Nanotubes Allow Electric Spin Control and Coupling,"We investigate combined effects of spin-orbit coupling and magnetic field in
carbon nanotubes containing one or more bends along their length. We show how
bends can be used to provide electrical control of confined spins, while spins
confined in straight segments remain insensitive to electric fields. Device
geometries that allow general rotation of single spins are presented and
analyzed. In addition, capacitive coupling along bends provides coherent
spin-spin interaction, including between otherwise disconnected nanotubes,
completing a universal set of one- and two-qubit gates.",1003.0037v2
2005-05-02,Orbital order in vanadium spinels,"Motivated by recent theoretical and experimental controversy, we present a
theoretical study to clarify the orbital symmetry of the ground state of
vanadium spinel oxides AV$_2$O$_4$ (A=Zn, Mg, Cd). The study is based on an
effective Hamiltonian with spin-orbital superexchange interaction and a local
spin-orbit coupling term. We construct a classical phase-diagram and prove the
complex orbital nature of the ground state. Remarkably, with our new analysis
we predict correctly also the coherent tetragonal flattening of oxygen
octahedra. Finally, through analytical considerations as well as numerical
ab-initio simulations, we propose how to detect the predicted complex orbital
ordering through vanadium K edge resonant x-ray scattering.",0505031v1
2017-07-13,Density matrix renormalization group study of a three-orbital Hubbard model with spin-orbit coupling in one dimension,"Using the Density Matrix Renormalization Group technique we study the effect
of spin-orbit coupling on a three-orbital Hubbard model in the $(t_{2g})^{4}$
sector and in one dimension. Fixing the Hund coupling to a robust value
compatible with some multiorbital materials, we present the phase diagram
varying the Hubbard $U$ and spin-orbit coupling $\lambda$, at zero temperature.
Our results are shown to be qualitatively similar to those recently reported
using the Dynamical Mean Field Theory in higher dimensions, providing a robust
basis to approximate many-body techniques. Among many results, we observe an
interesting transition from an orbital-selective Mott phase to an excitonic
insulator with increasing $\lambda$ at intermediate $U$. In the strong $U$
coupling limit, we find a non-magnetic insulator with an effective angular
momentum $\langle(\textbf{J}^{eff})^{2}\rangle \ne 0$ near the excitonic phase,
smoothly connected to the $\langle(\textbf{J}^{eff})^{2}\rangle = 0$ regime. We
also provide a list of quasi-one dimensional materials where the physics
discussed in this publication could be realized.",1707.04313v1
2010-09-25,Pulse-pumped double quantum dot with spin-orbit coupling,"We consider the full driven quantum dynamics of a qubit realized as spin of
electron in a one-dimensional double quantum dot with spin-orbit coupling. The
driving perturbation is taken in the form of a single half-period pulse of
electric field. Spin-orbit coupling leads to a nontrivial evolution in the spin
and charge densities making the dynamics in both quantities irregular. As a
result, the charge density distribution becomes strongly spin-dependent. The
transition from the field-induced tunneling to the strong coupling regime is
clearly seen in the charge and spin channels. These results can be important
for the understanding of the techniques for the spin manipulation in
nanostructures.",1009.5013v1
2014-02-17,Incommensurate spin density wave as a signature of spin-orbit coupling,"Close to half filling and in the limit of strong interactions the Hubbard
model leads a spin Hamiltonian. In its original isotropic form this is the
Heisenberg model with antiferromagnetic coupling $J$. On a square lattice there
is no frustration and the ground state is a classical antiferromagnet denoted
by the commensurate order vector ${\bf Q}=(\pi,\pi)$. In this work we show that
the inclusion of spin orbit coupling (SOC) in the fermionic Hubbard model on a
square lattice leads to an incommensurate spin density wave (ISDW) in the
strong interactions limit at half filling. In this limit the Hubbard model
leads to a non-diagonal and anisotropic spin Hamiltonian which exhibits the
incommensurate spin order as its classical ground state. We note that an ISDW
can be found in systems regardless of spin orbit-coupling due to nesting and
lattice distortion. These effects, however, can usually be recognized by
experimental probes.",1402.4093v1
2016-11-22,Spin-charge coupling effects in a two-dimensional electron gas,"In these lecture notes we study the disordered two-dimensional electron gas
in the presence of Rashba spin-orbit coupling, by using the Keldysh
non-equilibrium Green function technique. We describe the effects of the
spin-orbit coupling in terms of a SU(2) gauge field and derive a generalized
Boltzmann equation for the charge and spin distribution functions. We then
apply the formalism to discuss the spin Hall and the inverse spin galvanic
(Edelstein) effects. Successively we show how to include, within the
generalized Boltzmann equation, the side jump, the skew scattering and the spin
current swapping processes originating from the extrinsic spin-orbit coupling
due to impurity scattering.",1611.07210v1
2015-12-10,Quantized one-dimensional edge channels with strong spin-orbit coupling in 3D topological insulators,"A strong coupling between the electron spin and its motion is one of the
prerequisites of spin-based data storage and electronics. A major obstacle is
to find spin-orbit coupled materials where the electron spin can be probed and
manipulated on macroscopic length scales, for instance across the gate channel
of a spin-transistor. Here, we report on millimeter-scale edge channels with a
conductance quantized at a single quantum 1 $\times$ $e^2/h$ at zero magnetic
field. The quantum transport is found at the lateral edges of three-dimensional
topological insulators made of bismuth chalcogenides. The data are explained by
a lateral, one-dimensional quantum confinement of non-topological surface
states with a strong Rashba spin-orbit coupling. This edge transport can be
switched on and off by an electrostatic field-effect. Our results are
fundamentally different from an edge transport in quantum spin Hall insulators
and quantum anomalous Hall insula-tors.",1512.03237v1
2016-06-14,Spin orbit torque in disordered antiferromagnets,"We investigate the current-induced spin-orbit torque in antiferromangnetic
materials in the presence of Rashba spin orbit coupling using both the linear
response theory and the non-equilibrium Green's function technique implemented
on a tight-binding model. We show that a staggered spin density arises from
interband contributions. The effect of the disorder is restricted to the
diminution of the torque magnitude and does not bring any anomalous behavior to
the dependences of the torque on the spin orbit strength and the exchange
interaction between the antiferromagnetic local moments and the itinerant
electrons spins. We prove that the spin orbit torque is robust against the
application of the disorder compared to the case of the antiferromagnetic
spin-valve spin transfer torque.",1606.04261v1
2018-01-29,Current-induced spin-orbit torques in ferromagnetic and antiferromagnetic systems,"Spin-orbit coupling in inversion-asymmetric magnetic crystals and structures
has emerged as a powerful tool to generate complex magnetic textures,
interconvert charge and spin under applied current, and control magnetization
dynamics. Current-induced spin-orbit torques mediate the transfer of angular
momentum from the lattice to the spin system, leading to sustained magnetic
oscillations or switching of ferromagnetic as well as antiferromagnetic
structures. The manipulation of magnetic order, domain walls and skyrmions by
spin-orbit torques provides evidence of the microscopic interactions between
charge and spin in a variety of materials and opens novel strategies to design
spintronic devices with potentially high impact in data storage, nonvolatile
logic, and magnonic applications. This paper reviews recent progress in the
field of spin-orbitronics, focusing on theoretical models, material properties,
and experimental results obtained on bulk noncentrosymmetric conductors and
multilayer heterostructures, including metals, semiconductors, and topological
insulator systems. Relevant aspects for improving the understanding and
optimizing the efficiency of nonequilibrium spin-orbit phenomena in future
nanoscale devices are also discussed.",1801.09636v2
2017-06-15,Ballistic spin transport in the presence of interfaces with strong spin-orbit coupling,"The inversion symmetry breaking at the interface between different materials
generates a strong interfacial spin-orbit coupling (ISOC) that may influence
the spin and charge transport in hybrid structures. Here we use a simple
analytically solvable model to study in the ballistic approximation various
spin transport phenomena induced by ISOC in a bilayer metallic system. In this
model a non-equilibrium steady state carrying a spin current is created by
applying a spin dependent bias across the metallic junction. Physical
observables are then calculated using the scattering matrix approach. In
particular we calculate the absorption of the spin current at the interface
(the interface spin-loss) and study the interface spin-to-charge conversion.
The latter consists of an in-plane interface charge current generated by the
spin dependent bias applied to the junction, which can be viewed as a spin
galvanic effect mediated by ISOC. Finally we demonstrate that ISOC leads to an
interfacial spin current swapping, that is, the ""primary"" spin current flowing
through the spin-orbit active interface is necessarily accompanied with a
""secondary' swapped spin current flowing along the interface and polarized in
the direction perpendicular to that of the ""primary"" current. Using the exact
spin continuity equation we relate the swapping effect to the intefacial
spin-loss, and argue that this effect is generic and independent on the
ballistic approximation used for specific calculations.",1706.04797v1
2001-08-23,Filtering spin with tunnel-coupled electron wave guides,"We show how momentum-resolved tunneling between parallel electron wave guides
can be used to observe and exploit lifting of spin degeneracy due to Rashba
spin-orbit coupling. A device is proposed that achieves spin filtering without
using ferromagnets or the Zeeman effect.",0108373v2
1997-04-14,Dynamics of PSR J0045-7319/B-star Binary and Neutron Star Formation,"Recent timing observations have revealed the presence of orbital precession
due to spin-orbit coupling and rapid orbital decay due to dynamical tidal
interaction in the PSR J0045-7319/B-star binary system. They can be used to put
concrete constraints on the age, initial spin and velocity of the neutron star.",9704134v1
2001-08-06,Cancellation of Spin-Orbit Effects in Quantum Gates Based on the Exchange Coupling in Quantum Dots,"We study the effect of the spin-orbit interaction on quantum gate operations
based on the spin exchange coupling where the qubit is represented by the
electron spin in a quantum dot or a similar nanostructure. Our main result is
the exact cancellation of the spin-orbit effects in the sequence producing the
quantum XOR gate for the ideal case where the pulse shapes of the exchange and
spin-orbit interactions are identical. For the non-ideal case, the two pulse
shapes can be made almost identical and the gate error is strongly suppressed
by two small parameters, the spin-orbit constant and the deviation of the two
pulse shapes. We show that the dipole-dipole interaction leads only to very
small errors in the XOR gate.",0108101v2
2019-09-16,"Spin-orbit coupling in the hydrogen atom, the Thomas precession, and the exact solution of Dirac's equation","Bohr's model of the hydrogen atom can be extended to account for the observed
spin-orbit interaction, either with the introduction of the Thomas precession,
or with the stipulation that, during a spin-flip transition, the orbital radius
remains intact. In other words, if there is a desire to extend Bohr's model to
accommodate the spin of the electron, then experimental observations mandate
the existence of the Thomas precession, which is a questionable hypothesis, or
the existence of artificially robust orbits during spin-flip transitions. This
is tantamount to admitting that Bohr's model, which is a poor man's way of
understanding the hydrogen atom, is of limited value, and that one should
really rely on Dirac's equation for the physical meaning of spin, for the
mechanism that gives rise to the gyromagnetic coefficient g=2, for Zeeman
splitting, for relativistic corrections to Schr\""odinger's equation, for
Darwin's term, and for the correct 1/2 factor in the spin-orbit coupling
energy.",1909.07333v1
2004-09-21,Spin Frustration and Orbital Order in Vanadium Spinels,"We present the results of our theoretical study on the effects of geometrical
frustration and the interplay between spin and orbital degrees of freedom in
vanadium spinel oxides $A$V$_2$O$_4$ ($A$ = Zn, Mg or Cd). Introducing an
effective spin-orbital-lattice coupled model in the strong correlation limit
and performing Monte Carlo simulation for the model, we propose a reduced spin
Hamiltonian in the orbital ordered phase to capture the stabilization mechanism
of the antiferromagnetic order. Orbital order drastically reduces spin
frustration by introducing spatial anisotropy in the spin exchange
interactions, and the reduced spin model can be regarded as weakly-coupled
one-dimensional antiferromagnetic chains. The critical exponent estimated by
finite-size scaling analysis shows that the magnetic transition belongs to the
three-dimensional Heisenberg universality class. Frustration remaining in the
mean-field level is reduced by thermal fluctuations to stabilize a collinear
ordering.",0409526v1
2013-12-18,Spin-Orbit Qubit on a Multiferroic Insulator in a Superconducting Resonator,"We propose a spin-orbit qubit in a nanowire quantum dot on the surface of a
multiferroic insulator with a cycloidal spiral magnetic order. The spiral
exchange field from the multiferroic insulator causes an inhomogeneous
Zeeman-like interaction on the electron spin in the quantum dot, producing a
spin-orbit qubit. The absence of an external magnetic field benefits the
integration of such spin-orbit qubit into high-quality superconducting
resonators. By exploiting the Rashba spin-orbit coupling in the quantum dot via
a gate voltage, one can obtain an effective spin-photon coupling with an
efficient on/off switching. This makes the proposed device controllable and
promising for hybrid quantum communications.",1312.5159v2
2014-01-06,The empirical Monod-Beuneu relation of spin-relaxation revisited for elemental metals,"Monod and Beuneu [Monod and Beuneu, Phys. Rev. B 19, 911 (1979)] established
the validity of the Elliott-Yafet theory for elemental metals through
correlating the experimental electron spin resonance line-width with the
so-called spin-orbit admixture coefficients and the momentum-relaxation theory.
The spin-orbit admixture coefficients data were based on atomic spin-orbit
splitting. We highlight two shortcomings of the previous description: i) the
momentum-relaxation involves the Debye temperature and the electron-phonon
coupling whose variation among the elemental metals was neglected, ii) the
Elliott-Yafet theory involves matrix elements of the spin-orbit coupling (SOC),
which are however not identical to the SOC induced energy splitting of the
atomic levels, even though the two have similar magnitudes. We obtain the
empirical spin-orbit admixture parameters for the alkali metals by considering
the proper description of the momentum relaxation theory. In addition, we
present a model calculation which highlights the difference between the SOC
matrix element and energy splitting.",1401.1048v1
2017-10-19,DNA mechanical deformations and chiral spin selectivity,"The strength of the spin-orbit interaction relevant to transport in a low
dimensional structure depends critically on the relative geometrical
arrangement of current carrying orbitals. Recent tight-binding orbital models
for spin transport in DNA-like molecules, have surmised that the band
spin-orbit coupling arises from the particular angular relations between
orbitals of neighboring bases on the helical chain. Such arrangement could be
probed by inducing deformations in the molecule in a conductive probe AFM type
setup, as it was recently reported by Kiran, Cohen and Naaman\cite{Kiran}. Here
we report deformation dependent spin selectivity when a double strand DNA model
is compressed or stretched. We find that the equilibrium geometry is not
optimal with respect to the SO coupling strength and thus spin selectivity can
be tuned by deformations. The latter can be increased by stretching the helical
structure taking into account its elastic properties through the Poisson ratio.
The spin filtering gap is also found to be tunable with uniaxial deformations.",1710.07204v1
2010-11-08,Rapidly fluctuating orbital occupancy above the orbital ordering transition in spin-gap compounds,"Several spin systems with low dimensionality develop a spin-dimer phase
within a molecular orbital below TS, competing with long-range
antiferromagnetic order. Very often, preferential orbital occupancy and
ordering are the actual driving force for dimerization, as in the so-called
orbitally-driven spin-Peierls compounds (MgTi2O4, CuIr2S4, La4Ru2O10,
NaTiSi2O6, etc.). Through a microscopic analysis of the thermal conductivity k
(T) in La4Ru2O10, we show that the orbital occupancy fluctuates rapidly above
TS, resulting in an orbital-liquid state. The strong orbital-lattice coupling
introduces dynamic bond-length fluctuations that scatter the phonons to produce
a k (T) proportional to T (i.e. glass-like) above TS. This phonon-glass to
phonon-crystal transition is shown to occur in other spin-dimer systems, like
NaTiSi2O6, pointing to a general phenomenon.",1011.1860v1
2015-07-30,Orbital ordering of Ir-t2g states in the double perovskite Sr2CeIrO6,"The electronic and magnetic properties of monoclinic double perovskite
Sr$_2$CeIrO$_6$ were examined based on both experiments and first-principles
density functional theory calculations. From the calculations we conclude that
low-spin-state Ir$^{4+}$ (5$\textit{d}^5$, S=$\frac{1}{2}$) shows t$_{2g}$ band
derived anti-ferro type orbital ordering implying alternating occupations of
$\textit{d}_{yz}$ and $\textit{d}_{xz}$ orbitals at the two symmetrically
independent Ir sites. The experimentally determined Jahn-Teller type distorted
monoclinic structure is consistent with the proposed orbital ordering picture.
Surprisingly, the Ir-5$\textit{d}$ orbital magnetic moment was found to be
$\approx$ 1.3 times larger than the spin magnetic moment. The experimentally
observed AFM-insulating states are consistent with the calculations. Both
electron-electron correlation and spin-orbit coupling (SOC) are required to
drive the experimentally observed AFM-insulating ground state. This single
active site double perovskite provides a rare platform with a prototype
geometrically frustrated fcc lattice where among the different degrees of
freedom (i.e spin, orbital, and lattice), spin-orbit interaction and Coulomb
correlation energy scales compete and interact with each other.",1507.08682v1
2008-06-04,Symmetry of superconducting states with two orbitals on a tetragonal lattice: application to $LaO_{1-x}F_{x}FeAs$,"We use group theory to classify the superconducting states of systems with
two orbitals on a tetragonal lattice. The orbital part of the superconducting
gap function can be either symmetric or anti-symmetric. For the orbital
symmetric state, the parity is even for spin singlet and odd for spin triplet;
for the orbital anti-symmetric state, the parity is odd for spin singlet and
even for spin triplet. The gap basis functions are obtained with the use of the
group chain scheme by taking into account the spin-orbit coupling. In the weak
pairing limit, the orbital anti-symmetric state is only stable for the
degenerate orbitals. Possible application to iron-based superconductivity is
discussed.",0806.0712v3
2017-12-31,Spinful Aubry-Andre model in a magnetic field: Delocalization facilitated by a weak spin-orbit coupling,"We have incorporated spin-orbit coupling into the Aubry-Andre model of
tight-binding electron motion in the presence of periodic potential with a
period incommensurate with lattice constant. This model is known to exhibit an
insulator-metal transition upon increasing the hopping amplitude. Without
external magnetic field, spin-orbit coupling leads to a simple renormalization
of the hopping amplitude. However, when the degeneracy of the on-site energies
is lifted by an external magnetic field, the interplay of Zeeman splitting and
spin-orbit coupling has a strong effect on the localization length. We studied
this interplay numerically by calculating the energy dependence of the Lyapunov
exponent in the insulating regime. Numerical results can be unambiguously
interpreted in the language of the phase-space trajectories. As a first step,
we have explained the plateau in the energy dependence of the localization
length in the original Aubry-Andre model. Our main finding is that a very weak
spin-orbit coupling leads to delocalization of states with energies smaller
than the Zeeman shift. The origin of the effect is the spin-orbit-induced
opening of new transport channels. We have also found that restructuring of the
phase-space trajectories, which takes place at certain energies in the
insulating regime, causes a singularity in the energy dependence of the
localization length.",1801.00305v1
2020-09-21,Reversible engineering the spin-orbit coupling of monolayer MoS2 via laser irradiation under controlled gas atmospheres,"Monolayer transition metal dichalcogenides (TMDs) with strong spin-orbit
coupling combined with broken inversion symmetry, leading to a coupling of spin
and valley degrees of freedom, make these materials highly interesting for
potential spintronics and valleytronic applications. However, engineering the
spin-orbit coupling (SOC) at room temperature as demand after device
fabrication is still a great challenge for their practical applications. Here
we reversibly engineer the spin-orbit coupling of monolayer MoS2 by laser
irradiation under controlled gas environments, where the spin-orbit splitting
has been effectively regulated within 120 meV to 200 meV. Furthermore, the
photoluminescence (PL) intensity of B exciton can be invertible manipulation
over 2 orders of magnitude. We attribute the engineering of spin-orbit
splitting to the reduction of binding energy combined with band
renormalization, originating from the enhanced absorption coefficient of
monolayer MoS2 under inert gases and subsequent the significantly boosted
carrier concentrations. Reflectance contrast spectra during the engineering
stage provide unambiguous proof to support our interpretation. Our approach
offers a new avenue to actively control the SOC strength in TMDs materials at
room temperature and paves the way for designing innovative spintronics
devices.",2009.09565v2
2004-08-05,Spin Dynamics and Spin Transport,"Spin-orbit (SO) interaction critically influences electron spin dynamics and
spin transport in bulk semiconductors and semiconductor microstructures. This
interaction couples electron spin to dc and ac electric fields. Spin coupling
to ac electric fields allows efficient spin manipulating by the electric
component of electromagnetic field through the electric dipole spin resonance
(EDSR) mechanism. Usually, it is much more efficient than the magnetic
manipulation due to a larger coupling constant and the easier access to spins
at a nanometer scale. The dependence of the EDSR intensity on the magnetic
field direction allows measuring the relative strengths of the competing SO
coupling mechanisms in quantum wells. Spin coupling to an in-plane electric
field is much stronger than to a perpendicular field. Because electron bands in
microstructures are spin split by SO interaction, electron spin is not
conserved and spin transport in them is controlled by a number of competing
parameters, hence, it is rather nontrivial. The relation between spin
transport, spin currents, and spin populations is critically discussed.
Importance of transients and sharp gradients for generating spin magnetization
by electric fields and for ballistic spin transport is clarified.",0408119v1
2005-06-23,Imaging mesoscopic spin Hall flow: Spatial distribution of local spin currents and spin densities in and out of multiterminal spin-orbit coupled semiconductor nanostructures,"We introduce the concept of bond spin current, which describes the spin
transport between two sites of the lattice model of a multiterminal spin-orbit
(SO) coupled semiconductor nanostructure, and express it in terms of the
spin-dependent nonequilibrium (Landauer-Keldysh) Green functions of the device.
This formalism is applied to obtain the spatial distribution of microscopic
spin currents in {\em clean} phase-coherent two-dimensional electron gas with
the Rashba-type of SO coupling attached to four external leads. Together with
the corresponding profiles of the stationary spin density, such visualization
of the phase-coherent spin flow allow us to resolve several key issues for the
understanding of mechanisms which generate pure spin Hall currents in the
transverse leads of ballistic devices due to the flow of unpolarized charge
current through their longitudinal leads. The local spin current profiles
crucially depend on whether the sample is smaller or greater than the spin
precession length, thereby demonstrating its essential role as the
characteristic mesoscale for the spin Hall effect in ballistic multiterminal
semiconductor nanostructures. Although static spin-independent disorder reduces
the magnitude of the total spin current in the leads, the bond spin currents
continue to flow through the whole diffusive 2DEG sample, without being
localized as edge spin currents around any of its boundaries.",0506588v1
2010-01-25,Spin relaxation due to deflection coupling in nanotube quantum dots,"We consider relaxation of an electron spin in a nanotube quantum dot due to
its coupling to flexural phonon modes, and identify a new spin-orbit mediated
coupling between the nanotube deflection and the electron spin. This mechanism
dominates other spin relaxation mechanisms in the limit of small energy
transfers. Due to the quadratic dispersion law of long wavelength flexons,
$\omega \propto q^2$, the density of states $dq/d\omega \propto \omega^{-1/2}$
diverges as $\omega \to 0$. Furthermore, because here the spin couples directly
to the nanotube deflection, there is an additional enhancement by a factor of
$1/q$ compared to the deformation potential coupling mechanism. We show that
the deflection coupling robustly gives rise to a minimum in the magnetic field
dependence of the spin lifetime $T_1$ near an avoided crossing between
spin-orbit split levels in both the high and low-temperature limits. This
provides a mechanism that supports the identification of the observed $T_1$
minimum with an avoided crossing in the single particle spectrum by Churchill
et al.[Phys. Rev. Lett. {\bf 102}, 166802 (2009)].",1001.4306v2
2021-08-12,Theory of spin-charge-coupled transport in proximitized graphene: An SO(5) algebraic approach,"Establishing the conditions under which orbital, spin and lattice-pseudospin
degrees of freedom are mutually coupled in realistic nonequilibrium conditions
is a major goal in the emergent field of graphene spintronics. Here, we use
linear-response theory to obtain a unified microscopic description of spin
dynamics and coupled spin-charge transport in graphene with an
interface-induced Bychkov-Rashba effect. Our method makes use of an SO(5)
extension of the familiar inverse-diffuson approach to obtain a quantum kinetic
equation for the single-particle density matrix that treats spin and pseudospin
on equal footing and is valid for arbitrary external perturbations. As an
application of the formalism, we derive a complete set of drift-diffusion
equations for proximitized graphene with scalar impurities in the presence of
electric and spin-injection fields which vary slowly in space and time. Our
approach is amenable to a wide variety of generalizations, including the study
of coupled spin-charge dynamics in layered materials with strong spin-valley
coupling and spin-orbit torques in van der Waals heterostructures.",2108.05559v2
2010-05-14,Conductance oscillations of a spin-orbit stripe with polarized contacts,"We investigate the linear conductance of a stripe of spin-orbit interaction
in a 2D electron gas; that is, a 2D region of length $\ell$ along the transport
direction and infinite in the transverse one in which a spin-orbit interaction
of Rashba type is present. Polarization in the contacts is described by means
of Zeeman fields. Our model predicts two types of conductance oscillations:
Ramsauer oscillations in the minority spin transmission, when both spins can
propagate, and Fano oscillations when only one spin propagates. The latter are
due to the spin-orbit coupling with quasibound states of the non propagating
spin. In the case of polarized contacts in antiparallel configuration Fano-like
oscillations of the conductance are still made possible by the spin orbit
coupling, even though no spin component is bound by the contacts. To describe
these behaviors we propose a simplified model based on an ansatz wave function.
In general, we find that the contribution for vanishing transverse momentum
dominates and defines the conductance oscillations. Regarding the oscillations
with Rashba coupling intensity, our model confirms the spin transistor
behavior, but only for high degrees of polarization. Including a position
dependent effective mass yields additional oscillations due to the mass jumps
at the interfaces.",1005.2480v1
2024-01-27,Challenges and Opportunities in Searching for Rashba-Dresselhaus Materials for Efficient Spin-Charge Interconversion at Room Temperature,"Spintronic logic devices require efficient spin-charge interconversion:
converting charge current to spin current and spin current to charge current.
In spin-orbit materials that are regarded as the most promising candidate for
spintronic logic devices, one mechanism that is responsible for spin-charge
interconversion is Edelstein and inverse Edelstein effects based on
spin-momentum locking in materials with Rashba-type spin-orbit coupling. Over
last decade, there has been rapid progresses for increasing interconversion
efficiencies due to the Edelstein effect in a few Rashba-Dresselhaus materials
and topological insulators, making Rashba spin-momentum locking a promising
technological solution for spin-orbit logic devices. However, despite the rapid
progress that leads to high spin-charge interconversion efficiency at cryogenic
temperatures, the room-temperature efficiency needed for technological
applications is still low. This paper presents our understanding on the
challenges and opportunities in searching for Rashba-Dresselhaus materials for
efficient spin-charge interconversion at room temperature by focusing on
materials properties such as Rashba coefficients, momentum relaxation times,
spin-momentum locking relations and electrical conductivities.",2401.15524v1
2009-03-26,Emergence of the persistent spin helix in semiconductor quantum wells,"According to Noethers theorem, for every symmetry in nature there is a
corresponding conservation law. For example, invariance with respect to spatial
translation corresponds to conservation of momentum. In another well-known
example, invariance with respect to rotation of the electrons spin, or SU(2)
symmetry, leads to conservation of spin polarization. For electrons in a solid,
this symmetry is ordinarily broken by spin-orbit coupling, allowing spin
angular momentum to flow to orbital angular momentum. However, it has recently
been predicted that SU(2) can be achieved in a two-dimensional electron gas,
despite the presence of spin-orbit coupling. The corresponding conserved
quantities include the amplitude and phase of a helical spin density wave
termed the persistent spin helix. SU(2) is realized, in principle, when the
strength of two dominant spin-orbit interactions, the Rashba (strength
parameterized by \alpha) and linear Dresselhaus (\beta_1), are equal. This
symmetry is predicted to be robust against all forms of spin-independent
scattering, including electron-electron interactions, but is broken by the
cubic Dresselhaus term (\beta_3) and spin-dependent scattering. When these
terms are negligible, the distance over which spin information can propagate is
predicted to diverge as \alpha approaches \beta_1. Here we observe
experimentally the emergence of the persistent spin helix in GaAs quantum wells
by independently tuning \alpha and \beta_1. Using transient spin-grating
spectroscopy, we find a spin-lifetime enhancement of two orders of magnitude
near the symmetry point.........",0903.4709v2
2023-10-05,Intervalley coherence and intrinsic spin-orbit coupling in rhombohedral trilayer graphene,"Rhombohedral graphene multilayers provide a clean and highly reproducible
platform to explore the emergence of superconductivity and magnetism in a
strongly interacting electron system. Here, we use electronic compressibility
and local magnetometry to explore the phase diagram of this material class in
unprecedented detail. We focus on rhombohedral trilayer in the quarter metal
regime, where the electronic ground state is characterized by the occupation of
a single spin and valley isospin flavor. Our measurements reveal a subtle
competition between valley imbalanced (VI) orbital ferromagnets and intervalley
coherent (IVC) states in which electron wave functions in the two momentum
space valleys develop a macroscopically coherent relative phase. Contrasting
the in-plane spin susceptibility of the IVC and VI phases reveals the influence
of graphene's intrinsic spin-orbit coupling, which drives the emergence of a
distinct correlated phase with hybrid VI and IVC character. Spin-orbit also
suppresses the in-plane magnetic susceptibility of the VI phase, which allows
us to extract the spin-orbit coupling strength of $\lambda \approx 50\mu$eV for
our hexagonal boron nitride-encapsulated graphene system. We discuss the
implications of finite spin-orbit coupling on the spin-triplet superconductors
observed in both rhombohedral and twisted graphene multilayers.",2310.03781v2
2022-04-25,Active orbital degree of freedom and potential spin-orbit-entangled moments in Kitaev magnet candidate BaCo$_2$(AsO$_4$)$_2$,"Candidate materials for Kitaev spin liquid phase have been intensively
studied recently because of their potential applications in fault-tolerant
quantum computing. Although most of the studies on Kitaev spin liquid have been
done in 4$d$ and 5$d$ based transition metal compounds, recently there has been
a growing research interest in Co-based quasi-two-dimensional honeycomb
magnets, such as BaCo$_2$(AsO$_4$)$_2$ because of formation of
spin-orbit-entangled $J_{\rm eff}$ = 1/2 pseudospin moments at Co$^{2+}$ sites
and potential realizations of Kitaev-like magnetism therein. Here, we obtain
high-accuracy crystal and electronic structure of BaCo$_2$(AsO$_4$)$_2$ by
employing a combined density functional and dynamical mean-field theory
calculations, which correctly capture the Mott-insulating nature of the target
system. We show that Co$^{2+}$ ions form a high spin configuration, $S=3/2$,
with an active $L_{\rm eff}=1$ orbital degree of freedom, in the absence of
spin-orbit coupling. The size of trigonal distortion within CoO$_6$ octahedra
is found to be not strong enough to completely quench the orbital degree of
freedom, so that the presence of spin-orbit coupling can give rise to the
formation of spin-orbit-entangled moments and the Kitaev exchange interaction.
Our finding supports recent studies on potential Kitaev magnetism in this
compound and other Co-based layered honeycomb systems.",2204.11465v2
2000-03-13,Spin-orbit coupling in interacting quasi-one-dimensional electron systems,"We present a new model for the study of spin-orbit coupling in interacting
quasi-one-dimensional systems and solve it exactly to find the spectral
properties of such systems. We show that the combination of spin-orbit coupling
and electron-electron interactions results in: the replacement of separate spin
and charge excitations with two new kinds of bosonic mixed-spin-charge
excitation, and a characteristic modification of the spectral function and
single-particle density of states. Our results show how manipulation of the
spin-orbit coupling, with external electric fields, can be used for the
experimental determination of microscopic interaction parameters in quantum
wires.",0003219v1
2002-08-08,Random matrix theory for closed quantum dots with weak spin-orbit coupling,"To lowest order in the coupling strength, the spin-orbit coupling in quantum
dots results in a spin-dependent Aharonov-Bohm flux. This flux decouples the
spin-up and -down random matrix theory ensembles of the quantum dot. We employ
this ensemble and find significant changes in the distribution of the Coulomb
blockade peak height, in particular a decrease of the width of the
distribution. The puzzling disagreement between standard random matrix theory
and the experimental distributions by Patel et al. might possibly be attributed
to these spin-orbit effects.",0208177v2
2005-08-16,Path-integral Monte Carlo simulations for interacting few-electron quantum dots with spin-orbit coupling,"We develop path-integral Monte Carlo simulations for a parabolic
two-dimensional (2D) quantum dot containing $N$ interacting electrons in the
presence of Dresselhaus and/or Rashba spin-orbit couplings. Our method solves
in a natural way the spin contamination problem and allows for numerically
exact finite-temperature results at weak spin-orbit coupling. For $N<10$
electrons, we present data for the addition energy, the particle density, and
the total spin $S$ in the Wigner molecule regime of strong Coulomb
interactions. We identify magic numbers at N=3 and N=7 via a peak in the
addition energy. These magic numbers differ both from weak-interaction and
classical predictions, and are stable with respect to (weak) spin-orbit
couplings.",0508375v2
2006-03-21,Spin-Orbit Mediated Control of Spin Qubits,"We propose to use the spin-orbit interaction as a means to control electron
spins in quantum dots, enabling both single qubit and two qubit operations.
Very fast single qubit operations may be achieved by temporarily displacing the
electrons. For two qubit operations the coupling mechanism is based on a
combination of the spin-orbit coupling and the mutual long-ranged Coulomb
interaction. Compared to existing schemes using the exchange coupling, the
spin-orbit induced coupling is less sensitive to random electrical fluctuations
in the electrodes defining the quantum dots.",0603559v2
2004-03-03,Universal Quantum Computation through Control of Spin-Orbit Coupling,"We propose a method for quantum computation which uses control of spin-orbit
coupling in a linear array of single electron quantum dots. Quantum gates are
carried out by pulsing the exchange interaction between neighboring electron
spins, including the anisotropic corrections due to spin-orbit coupling.
Control over these corrections, even if limited, is sufficient for universal
quantum computation over qubits encoded into pairs of electron spins. The
number of voltage pulses required to carry out either single qubit rotations or
controlled-Not gates scales as the inverse of a dimensionless measure of the
degree of control of spin-orbit coupling.",0403023v3
2008-08-19,Spin-density induced by electromagnetic wave in two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit couplings,"We consider the magnetic response of a two-dimensional electron gas (2DEG)
with both Rashba and Dresselhaus spin-orbit coupling to a microwave excitation.
We generalize the results of [A. Shnirman and I. Martin, Europhys. Lett. 78,
27001 (2007).], where pure Rashba coupling was studied. We observe that the
microwave with the in-plane electric field and the out-of-plane magnetic field
creates an out-of-plane spin polarization. The effect is more prominent in
clean systems with resolved spin-orbit-split subbands. Considered as response
to the microwave magnetic field, the spin-orbit contribution to the
magnetization far exceeds the usual Zeeman contribution in the clean limit. The
effect vanishes when the Rashba and the Dresselhaus couplings have equal
strength.",0808.2607v2
2009-08-07,Spin-orbit coupling and semiclassical electron dynamics in noncentrosymmetric metals,"Spin-orbit coupling of electrons with the crystal lattice plays a crucial
role in materials without inversion symmetry, lifting spin degeneracy of the
Bloch states and endowing the resulting nondegenerate bands with complex spin
textures and topologically nontrivial wavefunctions. We present a detailed
symmetry-based analysis of the spin-orbit coupling and the band degeneracies in
noncentrosymmetric metals. We systematically derive the semiclassical equations
of motion for fermionic quasiparticles near the Fermi surface, taking into
account both the spin-orbit coupling and the Zeeman interaction with an applied
magnetic field. Some of the lowest-order quantum corrections to the equations
of motions can be expressed in terms of a fictitious ""magnetic field"" in the
momentum space, which is related to the Berry curvature of the band
wavefunctions. The band degeneracy points or lines serve as sources of a
topologically nontrivial Berry curvature. We discuss the observable effects of
the wavefunction topology, focusing, in particular, on the modifications to the
Lifshitz-Onsager semiclassical quantization condition and the de Haas-van
Alphen effect in noncentrosymmetric metals.",0908.1105v1
2015-03-30,Nonequilibrium dynamics of spin-orbit coupled lattice bosons,"We study the non-equilibrium dynamics of two component bosonic atoms in a
one-dimensional optical lattice in the presence of spin-orbit coupling. In the
Mott insulating regime, the two-component bosonic system at unity filling can
be described by the quantum spin XXZ model. The atoms are initially prepared in
their lower spin states. The system becomes out of equilibrium by suddenly
introducing spin-orbit coupling to the atoms. The system shows the relaxation
and non-stationary dynamics, respectively, in the different interaction
regimes. We find that the time average of magnetization is useful to
characterize the many-body dynamics. The effects of even and odd numbers of
sites are discussed. Our result sheds light on non-equilibrium dynamics due to
the interplay between spin-orbit coupling and atomic interactions.",1503.08605v2
2011-11-28,Vortex line in spin-orbit coupled atomic Fermi gases,"It has recently been shown that the spin-orbit coupling gives rise to
topologically-nontrivial and thermodynamically-stable gapless superfluid phases
when the pseudo-spin populations of an atomic Fermi gas is imbalanced, with the
possibility of featuring Majorana zero-energy quasiparticles. In this paper, we
consider a Rashba-type spin-orbit coupling, and use the Bogoliubov-de Gennes
formalism to analyze a single vortex line along a finite cylinder with a
periodic boundary condition. We show that the signatures for the appearance of
core- and edge-bound states can be directly found in the density of
single-particle states and particle-current density. In particular, we find
that the pseudo-spin components counterflow near the edge of the cylinder, the
strength of which increases with increasing spin-orbit coupling.",1111.6450v2
2014-05-16,Topological phases in spin-orbit coupled dipolar lattice bosons,"We study the topological phases in spin-orbit coupled dipolar bosons in a
one-dimensional optical lattice. The magnetic dipolar interactions between
atoms give rise to the inter-site interactions. In the Mott-insulating regime,
this system can be described by the quantum XYZ spin model with the
Dzyaloshinskii-Moriya interactions in a transverse field. We focus on
investigating the effect of dipolar interactions on the topological phase. The
topological phase can be shown when spin-orbit coupling incorporates with the
repulsive dipolar interaction. We find that the dipolar interaction can broaden
the range of parameters of spin-orbit coupling and transverse field for
exhibiting the topological phase. The sum of spin correlations between the two
nearest neighbouring atoms can be used to indicate the topological phase. This
may be useful for detecting topological phases in experiments.",1405.4068v3
2016-12-02,Fourier transform spectroscopy of a spin-orbit coupled Bose gas,"We describe a Fourier transform spectroscopy technique for directly measuring
band structures, and apply it to a spin-1 spin-orbit coupled Bose-Einstein
condensate. In our technique, we suddenly change the Hamiltonian of the system
by adding a spin-orbit coupling interaction and measure populations in
different spin states during the subsequent unitary evolution. We then
reconstruct the spin and momentum resolved spectrum from the peak frequencies
of the Fourier transformed populations. In addition, by periodically modulating
the Hamiltonian, we tune the spin-orbit coupling strength and use our
spectroscopy technique to probe the resulting dispersion relation. The
frequency resolution of our method is limited only by the coherent evolution
timescale of the Hamiltonian and can otherwise be applied to any system, for
example, to measure the band structure of atoms in optical lattice potentials.",1612.00819v1
2021-12-21,Quasiclassical boundary conditions for spin-orbit coupled interfaces with spin-charge conversion,"The quasiclassical theory of superconductivity provides a methodology to
study emergent phenomena in hybrid structures comprised of superconductors
interfaced with other materials. A key component in this theory is the boundary
condition that the Green functions describing the materials must satisfy.
Recently, progress has been made toward formulating such a boundary condition
for interfaces with spin-orbit coupling, the latter playing an important role
for several phenomena in spintronics. Here, we derive a boundary condition for
spin-orbit coupled interfaces that includes gradient terms which enables the
description of spin-Hall like effects with superconductors due to such
interfaces. As an example, we show that the boundary conditions predict that a
supercurrent flowing through a superconductor that is coupled to a normal metal
via a spin-orbit interface can induce a non-local magnetization in the normal
metal.",2112.11469v2
2022-08-10,Collective spin modes in Fermi liquids with spin-orbit coupling,"A combination of spin-orbit coupling and electron-electron interaction gives
rise to a new type of collective spin modes, which correspond to oscillations
of magnetization even in the absence of the external magnetic field. We review
recent progress in theoretical understanding and experimental observation of
such modes, focusing on three examples of real-life systems: a two-dimensional
electron gas with Rashba and/or Dresselhaus spin-orbit coupling, graphene with
proximity-induced spin-orbit coupling, and the Dirac state on the surface of a
three-dimensional topological insulator. This paper is dedicated to the 95th
birthday of Professor Emmanuel I. Rashba.",2208.05123v2
2022-12-11,Effects of spin orbit coupling on proximity induced superconductivity,"We investigate the effect of spin orbit coupling on proximity induced
superconductivity in a normal metal attached to a superconductor. Specifically,
we consider a heterostructure where the presence of interfaces gives rise to a
Rashba spin orbit coupling. The properties of the induced superconductivity in
these systems are addressed within the tunneling Hamiltonian formalism. We find
that the spin orbit coupling induces a mixture of singlet and triplet pairing
and, under specific circumstances, an odd frequency, even parity, spin triplet
pairs can arise. We also address the effect of impurity scattering on the
induced pairs, and discuss our results in context of heterostructures
consisting of materials with spin-momentum locking.",2212.05550v2
2023-02-23,Flavor symmetry breaking in spin-orbit coupled bilayer graphene,"Recent experimental discovery of flavor symmetry breaking metallic phases in
Bernal-stacked bilayer graphene points to the strongly interacting nature of
electrons near the top (bottom) of its valence (conduction) band.
Superconductivity was also observed in between these symmetry breaking phases
when the graphene bilayer is placed under a small in-plane magnetic field or in
close proximity to a monolayer WSe$_2$ substrate. Here we address the
correlated nature of the band edge electrons and obtain the quantum phase
diagram of their many-body ground states incorporating the effect of proximity
induced spin-orbit coupling. We find that in addition to the spin/valley flavor
polarized half and quarter metallic states, two types of intervalley coherent
phases emerge near the phase boundaries between the flavor polarized metals.
Both spin-orbit coupling and in-plane magnetic field disfavor the
spin-unpolarized valley coherent phase. Our findings suggest possible
competition between intervalley coherence and superconducting orders, arising
from the intriguing correlation effects in bilayer graphene in the presence of
spin-orbit coupling.",2302.12284v3
2020-04-16,On-Chip Spin-Orbit Controlled Excitation of Quantum Emitters Coupled to Hybrid Plasmonic Nanocircuits,"On-chip realization of complex photonic functionalities is essential for
further progress in planar integrated nanophotonics, especially when involving
nonclassical light sources such as quantum emitters (QEs). Hybrid plasmonic
nanocircuits integrated with QEs have been attracting considerable attention
due to the prospects of significantly enhancing QE emission rates and
miniaturizing quantum nanophotonic components. Spin-orbit interactions on
subwavelength scales have been increasingly explored in both conventional and
quantum nanophotonics for realization and utilization of the spin-dependent
flow of light. Here, we propose and realize a dielectric-loaded plasmonic
nanocircuit consisting of an achiral spin-orbit coupler for unidirectional
routing of pump radiation into branched QE-integrated waveguides. We
demonstrate experimentally the circular-polarization controlled coupling of
532-nm pump laser light into polymer-loaded branched waveguides followed by the
excitation of spatially separated (by a distance of ~ 10 {\mu}m) QEs,
nanodiamonds, with multiple nitrogen vacancy centres, that are embedded in and
efficiently coupled to the corresponding waveguides. The realization of on-chip
spin-orbit controlled excitation of different QEs coupled to branched
waveguides opens new avenues for designing complex quantum plasmonic
nanocircuits exploiting the spin degree of freedom within chiral quantum
nanophotonics.",2004.07483v1
2021-11-12,Whirling interlayer fields as a source of stable topological order in moiré CrI3,"The moir\'e engineering of two-dimensional magnets opens unprecedented
opportunities to design novel magnetic states with promises for spintronic
device applications. The possibility of stabilizing skyrmions in these
materials without chiral spin-orbit couplings or dipolar interactions is yet to
be explored. Here, we investigate the formation and control of ground state
topological spin textures (TSTs) in moir\'e CrI3 using stochastic
Landau-Lifshitz-Gilbert simulations. We unveil the emergence of interlayer
vortex and antivortex Heisenberg exchange fields, stabilizing spontaneous and
field-assisted ground state TSTs with various topologies. The developed study
accounts for the full bilayer spin dynamics, thermal fluctuations, and
intrinsic spin-orbit couplings. By examining the effect of the Kitaev
interaction and the next nearest-neighbor Dzyaloshinskii-Moriya interaction, we
propose the latter as the unique spin-orbit coupling mechanism compatible with
experiments on monolayer and twisted CrI3. Our findings contribute to the
current knowledge about moir\'e skyrmionics and uncover the nature of
spin-orbit coupling in CrI3.",2111.06936v2
2023-09-15,Charge pumping with strong spin-orbit coupling: Fermi surface breathing and higher harmonic generation,"Spin and charge pumping induced by a precessing magnetization has been
instrumental to the development of spintronics. Nonetheless, most theoretical
studies so far treat the spin-orbit coupling as a perturbation, which
disregards the dynamical competition between exchange and spin-orbit fields. In
this work, based on Keldysh formalism and Wigner expansion, we develop an
adiabatic theory of spin and charge pumping adapted to multiorbital systems
with arbitrary spin-orbit coupling. We apply this theory to the magnetic Rashba
gas and magnetic graphene cases and discuss the pumped ac and dc current. We
show that the pumped current possesses both intrinsic and extrinsic
contributions, akin to the magnetic damping. In addition, we find that higher
harmonics can be generated under large angle precession and we propose a couple
of experimental setups where such an effect could be experimentally observed.",2309.08597v1
2020-10-23,Maximizing spin-orbit torque efficiency of Ta(O)/Py via modulating oxygen-induced interface orbital hybridization,"Spin-orbit torques due to interfacial Rashba and spin Hall effects have been
widely considered as a potentially more efficient approach than the
conventional spin-transfer torque to control the magnetization of ferromagnets.
We report a comprehensive study of spin-orbit torque efficiency in
Ta(O)/Ni81Fe19 bilayers by tuning low-oxidation of \b{eta}-phase tantalum, and
find that the spin Hall angle {\theta}DL increases from ~ -0.18 of the pure
Ta/Py to the maximum value ~ -0.30 of Ta(O)/Py with 7.8% oxidation.
Furthermore, we distinguish the efficiency of the spin-orbit torque generated
by the bulk spin Hall effect and by interfacial Rashba effect, respectively,
via a series of Py/Cu(0-2 nm)/Ta(O) control experiments. The latter has more
than twofold enhancement, and even more significant than that of the former at
the optimum oxidation level. Our results indicate that 65% enhancement of the
efficiency should be related to the modulation of the interfacial Rashba-like
spin-orbit torque due to oxygen-induced orbital hybridization cross the
interface. Our results suggest that the modulation of interfacial coupling via
oxygen-induced orbital hybridization can be an alternative method to boost the
change-spin conversion rate.",2010.12253v1
2021-08-15,Spin susceptibility for orbital-singlet Cooper pair in the three-dimensional Sr$_2$RuO$_4$ superconductor,"We study the spin susceptibility of the orbital-singlet pairings, including
the spin-triplet/orbital-singlet/$s$-wave $E_g$ representation proposed by Suh
\textit{et al}., [H.\ G.\ Suh \textit{et al}., Phys.\ Rev.\ Research
\textbf{2}, 032023 (2020)], for a three-orbital model of superconducting
Sr$_2$RuO$_4$ in three dimensions. For the pseudospin-singlet states
represented in the band basis, the spin susceptibility decreases when reducing
the temperature, irrespective of the direction of the applied magnetic fields,
even if they are spin-triplet/orbital-singlet pairings in the spin-orbital
space. However, because the pseudospin-triplet \textbf{d}-vector in the band
basis is not completely aligned in the $xy$-plane (along $z$-axis) owing to the
strong atomic spin-orbit coupling, the spin susceptibility for
spin-singlet/orbital-singlet/odd-parity pairings is reduced around $5$-$10$
percent with the decrease of the temperature along the $z$ ($x$) axis. We can
determine the symmetry of the pseudospin structure of the Cooper pair by the
temperature dependence of the spin susceptibility measured by nuclear magnetic
resonance experiments. Our obtained results serve as a guide to determine the
pairing symmetry of Sr$_2$RuO$_4$.",2108.06718v4
2005-05-09,Spin and orbital degrees of freedom in transition metal oxides and oxide thin films studied by soft x-ray absorption spectroscopy,"The class of transition metal compounds shows an enormous richness of
physical properties, such as metal-insulator transitions, colossal
magneto-resistance, super-conductivity, magneto-optics and spin-depend
transport. It now becomes more and more clear that in order to describe
transition metal compounds the charge, orbital, spin and lattice degrees of
freedom should all be taken into account. With the recognition that the local
orbital occupation plays an important role in many of the transition metal
compounds there is a need for experimental techniques that can measure the
orbital occupation. This technique is soft x-ray absorption spectroscopy.
Within this PhD. Thesis we will illustrate the usefulness of this technique by
some examples: 1) Magnetic versus crystal-field linear dichroism in NiO thin
films. 2) The importance of spin-orbit coupling in CoO bulk and CoO thin films.
3) Aligning spins in anti ferromagneticfilms using antiferromagnets. 4) The
spin-state puzzle in the cobaltates. 5) Determination of the orbital momentum
and crystal-field splitting in LaTiO3. 6) Orbital-assisted metal-insulator
transition in VO2.",0505214v1
2011-10-03,Phase transitions in spin-orbital models with spin-space anisotropies for iron-pnictides: A study through Monte Carlo simulations,"The common phase diagrams of superconducting iron pnictides show interesting
material specificities in the structural and magnetic phase transitions. In
some cases the two transitions are separate and second order, while in others
they appear to happen concomitantly as a single first order transition. We
explore these differences using Monte Carlo simulations of a two-dimensional
Hamiltonian with coupled Heisenberg-spin and Ising-orbital degrees of freedom.
In this spin-orbital model, the finite-temperature orbital-ordering transition
results in a tetragonal-to-orthorhombic symmetry reduction and is associated
with the structural transition in the iron-pnictide materials. With a zero or
very small spin space anisotropy, the magnetic transition separates from the
orbital one in temperature, and the orbital transition is found to be in the
Ising universality class. With increasing anisotropy, the two transitions
rapidly merge together and tend to become weakly first order. We also study the
case of a single-ion anisotropy and propose that the preferred spin-orientation
along the antiferromagnetic direction in these materials is driven by orbital
order.",1110.0434v2
2010-06-11,Mott Transition in Multi-Orbital Models for Iron Pnictides,"The bad-metal behavior of the iron pnictides has motivated a theoretical
description in terms of a proximity to Mott localization. Since the parent
compounds of the iron pnictides contain an even number of 3d-electrons per Fe,
it is important to determine whether a Mott transition robustly exists and the
nature of the possible Mott insulating phases. We address these issues in a
minimal two-orbital model and a more realistic four-orbital model for the
parent iron pnictides using a slave-spin approach. In the two-orbital model
with two electrons per Fe, we identify a transition from metal to Mott
insulator. The critical coupling, $U_c$, is greatly reduced by the Hund's
coupling. Depending on the ratio between the inter- and intra-orbital Coulomb
repulsions, the insulating state can be either a spin-Mott insulator or an
orbital-Mott insulator. In the four-orbital model with four electrons per Fe,
we find an orbitally selective metal-to-insulator transition in the case of
zero Hund's coupling; the transition to a Mott insulator in the $xz$ and $yz$
orbitals takes place at the same critical coupling as the transition to a band
insulator in the $xy$ and $x^2-y^2$ orbitals. In the presence of a finite
Hund's coupling, however, the localization transition is into a spin-Mott
state.",1006.2337v3
1995-05-09,SPIN-ORBIT INTERACTION IN NEUTRON STAR/MAIN SEQUENCE BINARIES AND IMPLICATIONS FOR PULSAR TIMING,"The spin-induced quadrupole moment of a rapidly rotating star changes the
orbital dynamics in a binary system, giving rise to advance (or regression) of
periastron and precession of the orbital plane. We show that these effects are
important in the recently discovered radio pulsar/main sequence star binary
system PSR J0045$-$7319, and can reliably account for the observed peculiar
timing residuals. Precise measurements of the apsidal motion and orbital plane
precession can yield valuable information on the internal structure and
rotation of the star. The detection of orbital precession implies that the spin
of the companion star is not aligned with the orbital angular momentum, and
suggests that the supernova gave the pulsar a kick out of the original orbital
plane. Tidal excitation of g-mode oscillations in the PSR J0045$-$7319 system
induces an orbital period change of order $|\Delta P_{\rm orb}/P_{\rm orb}|\sim
10^{-6}$ at each periastron passage, but the secular trend depends on the
radiative damping time of the g-modes. We also discuss the spin-orbit coupling
effects for the accreting X-ray pulsars and the other known radio pulsar/main
sequence binary, PSR B1259$-$63.",9505042v1
2014-01-18,Von Neumann spin measurements with Rashba fields,"We show that dynamics in spin-orbit coupling field simulates the von Neumann
measurement of a particle spin. We demonstrate how the measurement influences
the spin and coordinate evolution of a particle by comparing two examples of
such a procedure. First example is a simultaneous measurement of spin
components, $\sigma _{x}$ and $\sigma _{y}$, corresponding to non-commuting
operators, which cannot be accurately obtained together at a given time instant
due to the Heisenberg uncertainty ratio. By mapping spin dynamics onto a
spatial walk such a procedure determines measurement-time averages of $\sigma
_{x}$ and $\sigma _{y}$, which already can be precisely evaluated in a single
short-time measurement. The other, qualitatively different, example is the spin
of a one-dimensional particle in a magnetic field. Here the outcome depends on
the angle between the spin-orbit coupling and magnetic fields. These results
can be applied to studies of spin-orbit coupled cold atoms and electrons in
solids.",1401.4551v1
2015-04-20,Emergent topological properties in interacting one-dimensional systems with spin-orbit coupling,"We present analysis of a single channel interacting quantum wire problem in
the presence of spin-orbit interaction. The spin-orbit coupling breaks the
spin-rotational symmetry from SU(2) to U(1) and breaks inversion symmetry. The
low-energy theory is then a two band model with a difference of Fermi
velocities $\delta v$. Using bosonization and a two-loop renormalization group
procedure we show that electron-electron interactions can open a gap in the
spin sector of the theory when the interaction strength $U$ is smaller than
$\delta v$ in appropriate units. For repulsive interactions, the resulting
strong coupling phase is of the spin-density-wave type. We show that this phase
has peculiar emergent topological properties. The gapped spin sector behaves as
a topological insulator, with zero-energy edge modes with fractional spin. On
the other hand, the charge sector remains critical, meaning the entire system
is metallic. However, this bulk electron liquid as a whole exhibits properties
commonly associated with the one-dimensional edge states of two-dimensional
spin-Hall insulators, in particular, the conduction of $2e^2/h$ is robust
against nonmagnetic impurities.",1504.05016v2
2016-04-21,Spin Transport at Interfaces with Spin-Orbit Coupling: Phenomenology,"This paper presents the boundary conditions needed for drift-diffusion models
to treat interfaces with spin-orbit coupling. Using these boundary conditions
for heavy metal/ferromagnet bilayers, solutions of the drift-diffusion
equations agree with solutions of the spin-dependent Boltzmann equation and
allow for a much simpler interpretation of the results. A key feature of these
boundary conditions is their ability to capture the role that in-plane electric
fields have on the generation of spin currents that flow perpendicularly to the
interface. The generation of these spin currents is a direct consequence of the
effect of interfacial spin-orbit coupling on interfacial scattering. In heavy
metal/ferromagnet bilayers, these spin currents provide an important mechanism
for the creation of damping-like and field-like torques; they also lead to
possible reinterpretations of experiments in which interfacial contributions to
spin torques are thought to be suppressed.",1604.06502v2
2016-10-17,Single-particle theory of persistent spin helices in two-dimensional electron gas: the general approach for quantum wells with different growth direction,"We present a detailed theoretical investigation of persistent spin helices in
two-dimensional electron systems with spin-orbit coupling. For this purpose we
consider a single-particle effective mass Hamiltonian with generalized
linear-in-k spin-orbit coupling term corresponding to a quantum well grown in
an arbitrary crystallographic direction, and derive the general condition for
the formation of the persistent spin helix. This condition applied for the
Hamiltonians describing quantum wells with different growth directions
indicates the possibility of existence of the persistent spin helix in a wide
class of 2D systems apart from [001] model with equal Rashba and Dresselhaus
spin-orbit coupling strengths and the [110] Dresselhaus model. In addition, we
employ the translation operator formalism for analytical calculation of
space-resolved spin density and visualization of the persistent spin helix
patterns.",1610.05251v1
2016-10-28,Density matrix based time-dependent configuration interaction approach to ultrafast spin-flip dynamics,"Recent developments in attosecond spectroscopy yield access to the correlated
motion of electrons on their intrinsic time scales. Spin-flip dynamics is
usually considered in the context of valence electronic states, where
spin-orbit coupling is weak and processes related to the electron spin are
usually driven by nuclear motion. However, for core-excited states, where the
core hole has a nonzero angular momentum, spin-orbit coupling is strong enough
to drive spin-flips on a much shorter time scale. Using density matrix based
time-dependent restricted active space configuration interaction including
spin-orbit coupling, we address an unprecedentedly short spin-crossover for the
example of L-edge (2p$\rightarrow$3d) excited states of a prototypical Fe(II)
complex. This process occurs on a time scale, which is faster than that of
Auger decay ($\sim$4\,fs) treated here explicitly. Modest variations of carrier
frequency and pulse duration can lead to substantial changes in the spin-state
yield, suggesting its control by soft X-ray light.",1610.09264v2
2012-01-26,Anisotropic effects and phonon induced spin relaxation in gate-controlled semiconductor quantum dots,"In this paper, a detailed analysis of anisotropic effects on the phonon
induced spin relaxation rate in III-V semiconductor quantum dots (QDs) is
carried out. We show that the accidental degeneracy due to level crossing
between the first and second excited states of opposite electron spin states in
both isotropic and anisotropic QDs can be manipulated with the application of
externally applied gate potentials. In particular, anisotropic gate potentials
enhance the phonon mediated spin-flip rate and reduce the cusp-like structure
to lower magnetic fields, in addition to the lower QDs radii in III-V
semiconductor QDs. In InAs QDs, only the Rashba spin-orbit coupling contributes
to the phonon induced spin relaxation rate. However, for GaAs QDs, the Rashba
spin-orbit coupling has a contribution near the accidental degeneracy point and
the Dresselhaus spin-orbit coupling has a contribution below and above the
accidental degeneracy point in the manipulation of phonon induced spin
relaxation rates in QDs.",1201.5549v1
2013-02-06,Exotic pairing states in a Fermi gas with three-dimensional spin-orbit coupling,"We investigate properties of exotic pairing states in a three-dimensional
Fermi gas with three-dimensional spin-orbit coupling and an effective Zeeman
field. The interplay of spin-orbit coupling, effective Zeeman field and pairing
can lead to first-order phase transitions between different phases, and to
interesting nodal superfluid states with gapless surfaces in the momentum
space. We then demonstrate that pairing states with zero center-of-mass
momentum are unstable against finite center-of-mass momentum
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, with the center-of-mass
momentum of the pairs opposite to the direction of the effective Zeeman field.
Unlike conventional FFLO states, these FFLO states are induced by the
coexistence of spin-orbit coupling and Fermi surface deformation, and have
intriguing features like first-order transitions between different FFLO states,
nodal FFLO states with gapless surfaces in momentum space, and exotic fully
gapped FFLO states. With the recent theoretical proposals for realizing
three-dimensional spin-orbit coupling in ultracold atom gases, our work is
helpful for the future experimental studies, and provides valuable information
for the general understanding of pairing physics in spin-orbit coupled
fermionic systems.",1302.1303v2
2019-04-18,Tuning Topological Superconductivity in Phase-Controlled Josephson Junctions with Rashba and Dresselhaus Spin-Orbit Coupling,"Recently, topological superconductors based on Josephson junctions in
two-dimensional electron gases with strong Rashba spin-orbit coupling have been
proposed as attractive alternatives to wire-based setups. Here, we elucidate
how phase-controlled Josephson junctions based on quantum wells with [001]
growth direction and an arbitrary combination of Rashba and Dresselhaus
spin-orbit coupling can also host Majorana bound states for a wide range of
parameters as long as the magnetic field is oriented appropriately. Hence,
Majorana bound states based on Josephson junctions can appear in a wide class
of two-dimensional electron gases. We study the effect of spin-orbit coupling,
the Zeeman energies, and the superconducting phase difference to create a full
topological phase diagram and find the optimal stability region to observe
Majorana bound states in narrow junctions. Surprisingly, for equal Rashba and
Dresselhaus spin-orbit coupling, well localized Majorana bound states can
appear only for phase differences $\phi\neq\pi$ as the topological gap
protecting the Majorana bound states vanishes at $\phi=\pi$. Our results show
that the ratio between Rashba and Dresselhaus spin-orbit coupling or the choice
of the in-plane crystallographic axis along which the superconducting phase
bias is applied offer additional tunable knobs to test Majorana bound states in
these systems. Finally, we discuss signatures of Majorana bound states that
could be probed experimentally by tunneling conductance measurements at the
edge of the junction.",1904.08981v2
2018-07-27,"An Ab Initio Investigation on the Electronic Structure, Defect Energetics, and Magnesium Kinetics in Mg$_3$Bi$_2$","We present a comprehensive ab initio investigation on Mg$_3$Bi$_2$, a
promising Mg-ion battery anode material with high rate capacity. Through
combined DFT (PBE, HSE06) and $G_0W_0$ electronic structure calculations, we
find that Mg$_3$Bi$_2$ is likely to be a small band gap semiconductor.
  DFT-based defect formation energies indicate that Mg vacancies are likely to
form in this material, with relativistic spin-orbit coupling significantly
lowering the defect formation energies. We show that a transition state
searching methodology based on the hybrid eigenvector-following approach can be
used effectively to search for the transition states in cases where full
spin-orbit coupling is included. Mg migration barriers found through this
hybrid eigenvector-following approach indicate that spin-orbit coupling also
lowers the migration barrier, decreasing it to a value of 0.34 eV with
spin-orbit coupling. Finally, recent experimental results on Mg diffusion are
compared to the DFT results and show good agreement. This work demonstrates
that vacancy defects and the inclusion of relativistic spin-orbit coupling in
the calculations have a profound effect in Mg diffusion in this material. It
also sheds light on the importance of relativistic spin-orbit coupling in
studying similar battery systems where heavy elements play a crucial role.",1807.10856v1
2008-08-29,Effect of Induced Spin-Orbit Coupling for Atoms via Laser Fields,"We propose an experimental scheme to study spin-orbit coupling effects in a
of two-dimensional (2D) Fermi atomic gas cloud by coupling its internal
electronic states (pseudospins) to radiation in a delta configuration. The
induced spin-orbit coupling can be of the Dresselhaus and Rashba type with and
without a Zeeman term. We show that the optically induced spin-orbit coupling
can lead to a spin-dependent effective mass under appropriate condition, with
one of them able to be tuned between positive and negative effective mass. As a
direct observable we show that in the expansion dynamics of the atomic cloud
the initial atomic cloud splits into two clouds for the positive effective mass
case regime, and into four clouds for the negative effective mass regime.",0808.4137v2
2016-10-15,Bloch Oscillations in Optical and Zeeman Lattices in the Presence of Spin-Orbit Coupling,"We address Bloch oscillations of a spin-orbit coupled atom in periodic
potentials of two types: Optical and Zeeman lattices. We show that in optical
lattices the spin-orbit coupling allows controlling the direction of atomic
motion and may lead to complete suppression of the oscillations at specific
values of the coupling strength. In Zeeman lattices the energy bands are found
to cross each other at the boundaries of the Brillouin zone, resulting in
period-doubling of the oscillations. In all cases, the oscillations are
accompanied by rotation of the pseudo-spin, with a dynamics that is determined
by the strength of the spin-orbit coupling. The predicted effects are discussed
also in terms of a Wannier-Stark ladder, which in optical lattices consist of
two mutually-shifted equidistant sub-ladders.",1610.04716v2
2018-04-09,Crystal-field effects in graphene with interface-induced spin-orbit coupling,"We consider theoretically the influence of crystalline fields on the
electronic structure of graphene placed on a layered material with reduced
symmetry and large spin-orbit coupling (SOC). We use a perturbative procedure
combined with the Slater-Koster method to derive the low-energy effective
Hamiltonian around the $K$ points and estimate the magnitude of the effective
couplings. Two simple models for the envisaged graphene-substrate hybrid
bilayer are considered, in which the relevant atomic orbitals hybridize with
either top or hollow sites of the graphene honeycomb lattice. In both cases,
the interlayer coupling to a crystal-field-split substrate is found to generate
highly anisotropic proximity spin-orbit interactions, including in-plane
'spin-valley' coupling. Interestingly, when an anisotropic intrinsic-type SOC
becomes sizeable, the bilayer system is effectively a quantum spin Hall
insulator characterized by in-plane helical edge states robust against
Bychkov-Rashba effect. Finally, we discuss the type of substrate required to
achieve anisotropic proximity-induced SOC and suggest possible candidates to
further explore crystal field effects in graphene-based heterostructures.",1804.03187v1
2018-01-22,Universal relations for spin-orbit coupled Fermi gas near an s-wave resonance,"The synthetic spin-orbit coupled quantum gases is widely studied both
experimentally and theoretically in recent years. As previous studies show,
this modification of single-body dispersion will in general couple different
partial waves and thus distort the wave-function of bound states which
determines the short-distance behavior of many-body wave function. In this
work, we focus on the two-component Fermi gas with one-dimensional or
three-dimensional spin-orbit coupling near an s-wave resonance. Using the
method of effective field theory and the operator product expansion, we derive
universal relations for both systems, and obtain the momentum distribution
matrix $\left<\psi^\dagger_a(\mathbf{q})\psi_b(\mathbf{q})\right>$ at large
$\mathbf{q}$ ($a,b$ are spin index), which shows anisotropic features. We also
discuss the experimental implication of these results depending on the
realization of the spin-orbit coupling.",1801.07001v2
2020-05-28,Multiple odd-parity superconducting phases in bilayer transition metal dichalcogenides,"We study unconventional superconductivity in a two-dimensional locally
noncentrosymmetric triangular lattice. The model is relevant to bilayer
transition metal dichalcogenides with 2H$_b$ stacking structure, for example.
The superconducting instability is analyzed by solving the linearized
Eliashberg equation within the random phase approximation. We show that
ferromagnetic fluctuations are dominant owing to the existence of disconnected
Fermi pockets near van Hove singularity, and hence odd-parity spin-triplet
superconductivity is favored. In the absence of the spin-orbit coupling, we
find that odd-parity $f$-wave superconducting state is stabilized in a wide
range of carrier density and interlayer coupling. Furthermore, we investigate
impacts of the layer-dependent staggered Rashba and Zeeman spin-orbit coupling
on the superconductivity. Multiple odd-parity superconducting phase diagrams
are obtained as a function of the spin-orbit coupling and Coulomb interaction.
Especially, a topological chiral $p$-wave pairing state is stabilized in the
presence of a moderate Zeeman spin-orbit coupling. Our results shed light on a
possibility of odd-parity superconductivity in various ferromagnetic van der
Waals materials.",2005.13963v1
2021-04-20,Analytical results for the superflow of spin-orbit-coupled Bose-Einstein condensates in optical lattices,"In this paper, we show that for sufficiently strong atomic interactions,
there exist analytical solutions of current-carrying nonlinear Bloch states at
the Brillouin zone edge to the model of spin-orbit-coupled Bose-Einstein
condensates (BECs) with symmetric spin interaction loaded into optical
lattices. These simple but generic exact solutions provide an analytical
demonstration of some intriguing properties which have neither an analog in the
regular BEC lattice systems nor in the uniform spin-orbit-coupled BEC systems.
It is an analytical example for understanding the superfluid and other related
properties of the spin-orbit-coupled BEC lattice systems.",2104.09796v2
2011-10-19,Fano resonances and electron spin transport through a two-dimensional spin-orbit-coupled quantum ring,"Electron transport through a spin-orbit-coupled quantum ring is investigated
within linear response theory. We show that the finite width of the ring
results in the appearance of Fano resonances in the conductance. This turns out
to be a consequence of the spin-orbit interaction that leads to a breaking of
the parity of the states localized in the ring. The resonances appear when the
system is close to maxima of Aharonov-Casher conductance oscillations where
spin transfer is heavily modified. When the spin-orbit coupling strength is
detuned from the Aharonov-Casher maxima the resonances are broadened resulting
in a dependence of the spin transport on the electron Fermi energy in contrast
to predictions from one-dimensional models",1110.4233v1
2013-01-04,Observation of Zitterbewegung in a spin-orbit coupled Bose-Einstein condensate,"Spin-orbit coupled ultra-cold atoms provide an intriguing new avenue for the
study of rich spin dynamics in superfluids. In this Letter, we observe
Zitterbewegung, the simultaneous velocity (thus position) and spin
oscillations, of neutral atoms between two spin-orbit coupled bands in a
Bose-Einstein condensate (BEC) through sudden quantum quenches of the
Hamiltonian. The observed Zitterbewegung oscillations are perfect on a short
time scale but gradually damp out on a long time scale, followed by sudden and
strong heating of the BEC. As an application, we also demonstrate how
Zitterbewegung oscillations can be exploited to populate the upper spin-orbit
band, and observe a subsequent dipole motion. Our experimental results are
corroborated by a theoretical and numerical analysis and showcase the great
flexibility that ultra-cold atoms provide for investigating rich spin dynamics
in superfluids.",1301.0658v2
2015-08-27,Localization and spin transport in honeycomb structures with spin-orbit coupling,"Transfer-matrix methods are used for a tight-binding description of electron
transport in graphene-like geometries, in the presence of spin-orbit couplings.
Application of finite-size scaling and phenomenological renormalization
techniques shows that, for strong enough spin-orbit interactions and increasing
on-site disorder, this system undergoes a metal-insulator transition
characterized by the exponents $\nu=2.71(8)$, $\eta=0.174(2)$. We show how one
can extract information regarding spin polarization decay with distance from an
injection edge, from the evolution of wave-function amplitudes in the
transfer-matrix approach. For (relatively weak) spin-orbit coupling intensity
$\mu$, we obtain that the characteristic length $\Lambda_s$ for
spin-polarization decay behaves as $\Lambda_s \propto \mu^{-2}$.",1508.06873v2
2016-10-03,Orbital driven impurity spin effect on the magnetic order of quasi-three dimensional cupric oxide,"Density functional calculations are performed to study the magnetic order of
the severely distorted square planar cupric oxide (CuO) and local spin disorder
in it in the presence of the transition metal impurities M (= Cr, Mn, Fe, Co
and Ni). The distortion in the crystal structure, arisen to reduce the band
energy by minimizing the covalent interaction, creates two crisscrossing zigzag
spin-1/2 chains. From the spin dimer analysis we find that while the spin chain
along [10$\bar 1$] has strong Heisenberg type antiferromagnetic coupling (J ~
127 meV), along [101] it exhibits weak, but robust, ferromagnetic coupling (J ~
9 meV) mediated by reminiscent p-d covalent interactions. The impurity effect
on the magnetic ordering is independent of M and purely orbital driven. If the
given spin-state of M is such that the d$_{x^2-y^2}$ orbital is spin-polarized,
then the original long-range ordering is maintained. However, if d$_{x^2-y^2}$
orbital is unoccupied, the absence of corresponding covalent interaction breaks
the weak ferromagnetic coupling and a spin-flip takes place at the impurity
site leading to breakdown of the long range magnetic ordering.",1610.00458v1
2017-01-12,Optical spin transfer and spin-orbit torques in thin film ferromagnets,"We study the optically induced torques in thin film ferromagnetic layers
under excitation by circularly polarized light. We study cases both with and
without Rashba spin-orbit coupling using a 4-band model. In the absence of
Rashba spin-orbit coupling, we derive an analytic expression for the optical
torques, revealing the conditions under which the torque is mostly derived from
optical spin transfer torque (i.e. when the torque is along the direction of
optical angular momentum), versus when the torque is derived from the inverse
Faraday effect (i.e. when the torque is perpendicular to the optical angular
momentum). We find the optical spin transfer torque dominates provided that the
excitation energy is far away from band edge transitions, and the magnetic
exchange splitting is much greater than the lifetime broadening. For the case
with large Rashba spin-orbit coupling and out-of-plane magnetization, we find
the torque is generally perpendicular to the photon angular momentum and is
ascribed to an optical Edelstein effect.",1701.03495v2
2010-02-02,Generalized Rashba spin-orbit coupling for cold atoms,"We study the possibility to generate a new type of spin-orbit coupling for
the center of mass motion of cold atoms, using laser beams that resonantly
couple N atomic internal ground states to an extra state. After a general
analysis of the scheme, we concentrate on the tetrapod setup (N=4) where the
atomic state can be described by a three-component spinor, evolving under the
action of a Rashba-type spin-orbit coupling for a spin 1 particle. We
illustrate a consequence of this coupling by studying the negative refraction
of atoms at a potential step, and show that the amplitude of the refracted beam
is significantly increased in comparison to the known case of spin 1/2 Rashba
coupling. Finally we explore a possible implementation of this tetrapod setup,
using stimulated Raman couplings between Zeeman sublevels of the ground state
of alkali atoms.",1002.0578v2
2017-04-04,Phonon-derived ultrafast relaxation of spin-valley polarized states in MoS_{2},"The valley degree of freedom and the possibility of spin-valley coupling of
solid materials have attracted growing interest, and the relaxation dynamics of
spin- and valley-polarized states has become an important focus of recent
studies. In spin-orbit-coupled inversion-asymmetric two-dimensional materials,
such as MoS_{2} it has been found that the spin randomization is
characteristically faster than the time scales for inter- and intra-valley
scatterings. In this study, we examined the ultrafast non-collinear spin
dynamics of an electron valley in monolayer MoS_{2} by using real-time
propagation time-dependent density functional theory. We found that the spin
precession of an electron in the valley is sharply coupled with the
lowest-lying optical phonon that release the in-plane mirror symmetry. This
indicates that the spin randomization of MoS_{2} is mainly caused by
spin-phonon interaction. We further suggest that flipping of spins in a
spin-orbit-coupled system can be achieved by the control over phonons.",1704.00921v1
2018-06-03,Quantum Spin Dynamics in a Normal Bose Gas with Spin-orbit Coupling,"In this Letter, we investigate spin dynamics of a two-component Bose gas with
spin-orbit coupling realised in cold atom experiments. We derive coupled
hydrodynamic equations for number and spin densities as well as their
associated currents. Specialising to quasi-one-dimensional situation, we obtain
analytic solutions of the spin helix structure and its dynamics in both
adiabatic and diabatic regimes. In the adiabatic regime, the transverse spin
decays parabolically in the short-time limit and exponentially in the long time
limit, depending on initial polarisation. In contrast, in the diabatic regime,
transverse spin density and current oscillate in a way similar to the
charge-current oscillation in an undamped LC circuit. The effects of Rabi
coupling on the short-time spin dynamics is also discussed. Finally, using
realistic experimental parameters for $^{87}$Rb, we show that the time scales
for spin dynamics is of order of milliseconds to a few seconds and can be
observed experimentally.",1806.00766v2
2015-03-24,Innermost stable circular orbits of spinning test particles in Schwarzschild and Kerr space-times,"We consider the motion of classical spinning test particles in Schwarzschild
and Kerr metrics and investigate innermost stable circular orbits (ISCO). The
main goal of this work is to find analytically the small-spin corrections for
the parameters of ISCO (radius, total angular momentum, energy, orbital angular
frequency) of spinning test particles in the case of vectors of black hole
spin, particle spin and orbital angular momentum being collinear to each other.
We analytically derive the small-spin linear corrections for arbitrary Kerr
parameter $a$. The cases of Schwarzschild, slowly rotating and extreme Kerr
black hole are considered in details. For a slowly rotating black hole the ISCO
parameters are obtained up to quadratic in $a$ and particle's spin $s$ terms.
From the formulae obtained it is seen that the spin-orbital coupling has
attractive character when spin and angular momentum are parallel and repulsive
when they are antiparallel. For the case of the extreme Kerr black hole with
co-rotating particle we succeed to find the exact analytical solution for the
limiting ISCO parameters for arbitrary spin. It has been shown that the
limiting values of ISCO radius and frequency do not depend on the particle's
spin while values of energy and total angular momentum depend on it. We have
also considered circular orbits of arbitrary radius and have found small-spin
linear corrections for the total angular momentum and energy at given radius.
System of equations for numerical calculation of ISCO parameters for arbitrary
$a$ and $s$ is also explicitly written.",1503.07060v2
2017-03-24,Effects of anisotropy in spin molecular-orbital coupling on effective spin models of trinuclear organometallic complexes,"We consider layered decorated honeycomb lattices at two-thirds filling, as
realized in some trinuclear organometallic complexes. Localized $S=1$ moments
with a single-spin anisotropy emerge from the interplay of Coulomb repulsion
and spin molecular-orbit coupling (SMOC). Magnetic anisotropies with bond
dependent exchange couplings occur in the honeycomb layers when the direct
intracluster exchange and the spin molecular-orbital coupling are both present.
We find that the effective spin exchange model within the layers is an XXZ +
120$^\circ$ honeycomb quantum compass model. The intrinsic non-spherical
symmetry of the multinuclear complexes leads to very different transverse and
longitudinal spin molecular-orbital couplings, which greatly enhances the
single-spin and exchange coupling anisotropies. The interlayer coupling is
described by a XXZ model with anisotropic biquadratic terms. As the correlation
strength increases the systems becomes increasingly one-dimensional. Thus, if
the ratio of SMOC to the interlayer hopping is small this stabilizes the
Haldane phase. However, as the ratio increases there is a quantum phase
transition to the topologically trivial `$D$-phase'. We also predict a quantum
phase transition from a Haldane phase to a magnetically ordered phase at
sufficiently strong external magnetic fields.",1703.08343v3
2023-09-20,Generalized Kohn-Sham Approach for the Electronic Band Structure of Spin-Orbit Coupled Materials,"Spin-current density functional theory (SCDFT) is a formally exact framework
designed to handle the treatment of interacting many-electron systems including
spin-orbit coupling at the level of the Pauli equation. In practice, robust and
accurate calculations of the electronic structure of these systems call for
functional approximations that depend not only on the densities, but also on
spin-orbitals. Here we show that the call can be answered by resorting to an
extension of the Kohn-Sham formalism, which admits the use of non-local
effective potentials, yet it is firmly rooted in SCDFT. The power of the
extended formalism is demonstrated by calculating the spin-orbit-induced
band-splittings of inversion-asymmetric MoSe$_2$ monolayer and
inversion-symmetric bulk $\alpha$-MoTe$_2$. We show that quantitative agreement
with experimental data is obtainable via global hybrid approximations by
setting the fraction of Fock exchange at the same level which yields accurate
values of the band gap. Key to these results is the ability of the method to
self-consistently account for the spin currents induced by the spin-orbit
interaction. The widely used method of refining spin-density functional theory
by a second-variational treatment of spin-orbit coupling is unable to match our
SCDFT results.",2309.11158v2
2005-07-07,Classical memory effects on spin dynamics in two-dimensional systems,"We discuss classical dynamics of electron spin in two-dimensional
semiconductors with a spin-split spectrum. We focus on a special case, when
spin-orbit induced random magnetic field is directed along a fixed axis. This
case is realized in III-V-based quantum wells grown in [110] direction and also
in [100]-grown quantum wells with equal strength of Dresselhaus and
Bychkov-Rashba spin-orbit couplings. We show that in such wells the long-time
spin dynamics is determined by non-Markovian memory effects. Due to these
effects the non-exponential tail $1/t^2$ appears in the spin polarization.",0507171v2
2008-11-25,Anisotropic profiles in the spin polarization of multichannel semiconductor rings with Rashba spin orbit coupling,"We investigate the spin accumulation effect in eccentric semiconductor
multichannel rings with Rashba spin-orbit interaction and threaded by a
magnetic flux. Due to the finite eccentricity, the spin polarization induced at
the borders of the sample is anisotropic and exhibits different patterns and
intensities at specific angular directions. This effect, reminiscent of the
spin polarization drift induced by the application of an in plane electric
field, could be used to manipulate and functionalize the spin polarization in
electronic nanorings.",0811.4125v1
2009-05-07,Electron spin relaxation in n-type InAs quantum wires,"We investigate the electron spin relaxation of $n$-type InAs quantum wires by
numerically solving the fully microscopic kinetic spin Bloch equations with the
relevant scattering explicitly included. We find that the quantum-wire size and
the growth direction influence the spin relaxation time by modulating the
spin-orbit coupling. Due to inter-subband scattering in connection with the
spin-orbit interaction, spin-relaxation in quantum wires can show different
characteristics from those in bulk or quantum wells and can be effectively
manipulated by various means.",0905.0937v2
2009-05-08,Tuning the Spin Hall Effect in a Two-Dimensional Electron Gas,"We provide a theoretical framework for the electric field control of the
electron spin in systems with diffusive electron motion. The approach is valid
in the experimentally important case where both intrinsic and extrinsic
spin-orbit interaction in a two-dimensional electron gas are present
simultaneously. Surprisingly, even when the extrinsic mechanism is the dominant
driving force for spin Hall currents, the amplitude of the spin Hall
conductivity may be considerably tuned by varying the intrinsic spin-orbit
coupling via a gate voltage. Furthermore we provide an explanation of the
experimentally observed out-of-plane spin polarization in a (110) GaAs quantum
well.",0905.1269v1
2011-06-02,Spin-dependent inertial force and spin current in accelerating systems,"The spin-dependent inertial force in an accelerating system under the
presence of electromagnetic fields is derived from the generally covariant
Dirac equation. Spin currents are evaluated by the force up to the lowest order
of the spin-orbit coupling in both ballistic and diffusive regimes. We give an
interpretation of the inertial effect of linear acceleration on an electron as
an effective electric field and show that mechanical vibration in a high
frequency resonator can create a spin current via the spin-orbit interaction
augmented by the linear acceleration.",1106.0366v1
2013-09-17,Theory of Electrical Spin Manipulation in Spin-Orbit Coupling Systems,"By associating a spin-orbit interaction with a non-Abelian gauge potential,
we theoretically present a spin polarization in a quite general form using an
effective Yang-Mills field and a usual electromagnetic field. In this gauge
invariant result, we focus on a purely electrically-induced spin contribution.
We find that both the inverse spin galvanic effect and the spin Hall effect
arise from the same origin, i.e., the SU(2)$\times$U(1) Hall effect. We also
discover that a large effective magnetic field of the order of 1T is induced in
the Rashba system.",1309.4205v1
2017-11-21,Current-induced spin polarization in isotropic k-cubed Rashba model: Theoretical study for p-doped semiconductor heterostructures and perovskite oxides interfaces,"Using the Matsubara Green's function formalism we calculate the temperature
dependence of the nonequilibrium spin polarization induced by an external
electric field in the presence of spin-orbit coupling. The model Hamiltonian
includes an isotropic k-cubed form of the Rashba spin-orbit interaction. Such a
Hamiltonian captures the electronic and spin properties of two-dimensional
electron (hole) gas at the surfaces or interfaces of transition metal oxides or
in p-doped semiconductor heterostructures. The induced spin polarization is
calculated for the nonmagnetic as well as magnetic electron/hole gas. Relation
of the spin polarization to the Berry curvature is also discussed.",1711.07707v1
2009-03-06,The two-impurity Kondo model with spin-orbit interactions,"We study the two-impurity Kondo model (TIKM) in two dimensions with
spin-orbit coupled conduction electrons. In the first part of the paper we
analyze how spin-orbit interactions of Rashba as well as Dresselhaus type
influence the Kondo and RKKY interactions in the TIKM, generalizing results
obtained by H. Imamura {\em et al.} (2004) and J. Malecki (2007). Using our
findings we then explore the effect from spin-orbit interactions on the
non-Fermi liquid quantum critical transition between the RKKY-singlet and
Kondo-screened RKKY-triplet states. We argue that spin-orbit interactions under
certain conditions produce a line of critical points exhibiting the same
leading scaling behavior as that of the ordinary TIKM. In the second part of
the paper we shift focus and turn to the question of how spin-orbit
interactions affect the entanglement between two localized RKKY-coupled spins
in the parameter regime where the competition from the direct Kondo interaction
can be neglected. Using data for a device with two spinful quantum dots
patterned in a gated InAs heterostructure we show that a gate-controlled
spin-orbit interaction may drive a maximally entangled state to one with
vanishing entanglement, or vice versa (as measured by the concurrence). This
has important implications for proposals using RKKY interactions for nonlocal
control of qubit entanglement in semiconductor heterostructures.",0903.1207v2
2022-12-15,Electric field tuning of magnetic states in single magnetic molecules,"Single magnetic molecules may be the smallest functional magnets. An
electric-field controllable spin state of magnetic molecules is of fundamental
importance for applications while its realization remains challenging. To date
the observed spin-electric interaction based on spin-orbit coupling or spin
dipole coupling is useful to tune fine spin structures but too weak to flip the
spin state. In this work, we propose a new mechanism to realize enhanced
spin-electric coupling and flip the spin states by tuning the spin
superexchange between local spins. Using first-principles calculations and
Heisenberg Hamiltonian, we demonstrate this effect in a family of magnetic
molecules, transition metallic Porphyrins. We show that their d-{\pi} and
{\pi}-{\pi} spin superexchange couplings are determined by the relative
energies of d and {\pi} electronic states, which are sensitive to the applied
electric field. Therefore, applying electric field can tune a wide range of
magnetic ground states, including ferromagnetic, ferrimagnetic, and
antiferromagnetic configurations. This spin-electric coupling may provide a new
approach for designing and controlling molecular spintronics.",2212.08010v1
2003-03-19,Anomalous spin-orbit effects in a strained InGaAs/InP quantum well structure,"There currently is a large effort to explore spin-orbit effects in
semiconductor structures with the ultimate goal of manipulating electron spins
with gates. A search for materials with large spin-orbit coupling is therefore
important. We report results of a study of spin-orbit effects in a strained
InGaAs/InP quantum well. The spin-orbit relaxation time, determined from the
weak antilocalization effect, was found to depend non-monotonically on gate
voltage. The spin orbit scattering rate had a maximum value of $5\times
10^{10}s^{-1}$ at an electron density of $n=3\times 10^{15} m^{-2}$. The
scattering rate decreased from this for both increasing and decreasing
densities. The smallest measured value was approximately $10^9 s^{-1}$ at an
electron concentration of $n=6\times 10^{15} m^{-2}$. This behavior could not
be explained by either the Rashba nor the bulk Dresselhaus mechanisms but is
attributed to asymmetry or strain effects at dissimilar quantum well
interfaces.",0303401v2
2006-02-20,Exact Landau Levels in Two-Dimensional Electron Systems with Rashba and Dresselhaus Spin-Orbit Interactions in a Perpendicular Magnetic Field,"We study a two-dimensional electron system in the presence of both Rashba and
Dresselhaus spin-orbit interactions in a perpendicular magnetic field. Defining
two suitable boson operators and using the unitary transformations we are able
to obtain the exact Landau levels in the range of all the parameters. When the
strengths of the Rashba and Dresselhaus spin-orbit interactions are equal, a
new analytical solution for the vanishing Zeeman energy is found, where the
orbital and spin wave functions of electron are separated. It is also shown
that in this case the Zeeman and spin-orbit splittings are independent of the
Landau level index $n$. Due to the Zeeman energy, new crossing between the
eigenstates $|n, k, s=1, \sigma>$ and $|n+1, k, s^\prime =-1, \sigma^\prime>$
is produced at certain magnetic field for larger Rashba spin-orbit coupling.
This degeneracy leads to a resonant spin Hall conductance if it happens at the
Fermi level.",0602473v1
2021-05-10,Spin-orbit correlations and exchange-bias control in twisted Janus dichalcogenide multilayers,"Janus dichalcogenide multilayers provide a paradigmatic platform to engineer
electronic phenomena dominated by spin-orbit coupling. Their unique spin-orbit
effects stem from local mirror symmetry breaking in each layer, which induces a
colossal Rashba spin-orbit effect in comparison with the conventional
dichalcogenide counterparts. Here we put forward twisted dichalcogenide
bilayers as a simple platform to realize spin-orbit correlated states. We
demonstrate the emergence of flat bands featuring strong spin-momentum locking
and the emergence of non-collinear symmetry broken states when interactions are
included. We further show that the symmetry broken states can be controlled by
means of a magnetic substrate, strongly impacting the non-collinear magnetic
texture of the moire unit cell. Our results put forward twisted Janus
multilayers as a powerful platform to explore spin-orbit correlated physics,
and highlighting the versatility of magnetic substrates to control
unconventional moire magnetism.",2105.04502v3
2010-09-28,Intrinsic spin-orbit interactions in flat and curved graphene nanoribbons,"Recent theoretical and experimental works on carbon nanotubes and graphene
samples have revealed that spin-orbit interactions, though customarily ignored
in carbon-based materials, are more important and complex than it was thought.
We study the intrinsic spin-orbit coupling effects on graphene nanoribbons,
both flat and bent. Calculations are performed within the tight-binding model
with the inclusion of a four-orbital basis set. Thereby the full symmetry of
the honeycomb lattice and the hybridization of $\sigma$ and $\pi$ bands are
considered. In addition to the zero-energy $\pi$-edge states, $\sigma$-derived
edge states are found for the three investigated ribbon geometries. The
$\sigma$ states are also spin-filtered and localized at the boundaries of the
ribbons. The calculated spin-orbit splittings are larger for the $\sigma$- than
for the $\pi$-derived edge states. Due to this enhancement, spin-orbit
splittings of the $\sigma$-states reach values of the order of a few Kelvin.
These spin-filtered edge states are robust under $\sigma-\pi$ hybridization and
curvature effects.",1009.5560v1
2017-03-06,Estimating spin diffusion length and spin Hall angle from spin pumping-induced inverse spin Hall voltages,"There exists considerable confusion in estimating the spin diffusion length
of materials with high spin-orbit coupling from spin pumping experiments. For
designing functional devices, it is important to determine the spin diffusion
length with sufficient accuracy from experimental results. An inaccurate
estimation of spin diffusion length also affects the estimation of other
parameters (e.g., spin mixing conductance, spin Hall angle) concomitantly. The
spin diffusion length for platinum (Pt) has been reported in literature in a
wide range of 0.5 - 14 nm, and particularly it is a constant value independent
of Pt's thickness. Here, the key reasonings behind such wide range of reported
values of spin diffusion length have been identified comprehensively.
Particularly, it is shown here that a thickness-dependent conductivity and spin
diffusion length is necessary to simultaneously match the experimental results
of effective spin mixing conductance and inverse spin Hall voltage due to spin
pumping. Such thickness-dependent spin diffusion length is tantamount to
Elliott-Yafet spin relaxation mechanism, which bodes well for transitional
metals. This conclusion is not altered even when there is significant
interfacial spin memory loss. Furthermore, the variations in the estimated
parameters are also studied, which is important for technological applications.",1704.02339v2
2014-04-10,Spin force and intrinsic spin Hall effect in spintronics systems,"We investigate the spin Hall effect (SHE) in a wide class of spin-orbit
coupling systems by using spin force picture. We derive the general relation
equation between spin force and spin current and show that the longitudinal
force component can induce a spin Hall current, from which we reproduce the
spin Hall conductivity obtained previously using Kubo's formula. This simple
spin force picture gives a clear and intuitive explanation for SHE.",1404.2732v1
2004-03-15,Dynamically generated dimension reduction and crossover in a spin orbital model,"We study a spin orbital model in which the spin-spin interaction couples
linearly to the orbital isospin. Fluctuations drive the transition from
paramagnetic state to C type ordered state into a strongly first order one, as
observed in $V_2O_3$. At T=0, there is a FOCS to FOGS transition. Close to the
transition point, the system shows dynamically generated dimension reduction
and crossover, resulting in one or more spin reentrant transitions.",0403370v1
2005-10-10,Role of the spin-orbit splitting and the dynamical fluctuations in the Si(557)-Au surface,"Our it ab initio calculations show that spin-orbit coupling is crucial to
understand the electronic structure of the Si(557)-Au surface. The spin-orbit
splitting produces the two one-dimensional bands observed in photoemission,
which were previously attributed to spin-charge separation in a Luttinger
liquid. This spin splitting might have relevance for future device
applications. We also show that the apparent Peierls-like transition observed
in this surface by scanning tunneling microscopy is a result of the dynamical
fluctuations of the step-edge structure, which are quenched as the temperature
is decreased.",0510239v1
2009-05-04,Spin-Orbit Interactions in Bilayer Exciton-Condensate Ferromagnets,"Bilayer electron-hole systems with unequal electron and hole densities are
expected to have exciton condensate ground states with spontaneous
spin-polarization in both conduction and valence bands. In the absence of
spin-orbit and electron-hole exchange interactions there is no coupling between
the spin-orientations in the two quantum wells. In this article we show that
Rashba spin-orbit interactions lead to unconventional magnetic anisotropies,
whose strength we estimate, and to ordered states with unusual quasiparticle
spectra.",0905.0392v1
2016-10-24,Spin orbit effects in CoFeB/MgO hetereostructures with heavy metal underlayers,"We study effects originating from the strong spin orbit coupling in CoFeB/MgO
heterostructures with heavy metal (HM) underlayers. The perpendicular magnetic
anisotropy at the CoFeB/MgO interface, the spin Hall angle of the heavy metal
layer, current induced torques and the Dzyaloshinskii-Moriya interaction at the
HM/CoFeB interfaces are studied for films in which the early 5d transition
metals are used as the HM underlayer. We show how the choice of the HM layer
influences these intricate spin orbit effects that emerge within the bulk and
at interfaces of the heterostructures.",1610.07473v1
2015-09-11,Effective spin Hall properties of a mixture of materials with and without spin-orbit coupling: Tailoring the effective spin-diffusion length,"We study theoretically the effective spin Hall properties of a composite
consisting of two materials with and without spin-orbit (SO) coupling. In
particular, we assume that SO material represents a system of grains in a
matrix with no SO. We calculate the effective spin Hall angle and the effective
spin diffusion length of the mixture. Our main qualitative finding is that,
when the bare spin diffusion length is much smaller than the radius of the
grain, the effective spin diffusion length is strongly enhanced, well beyond
the ""geometrical"" factor. The physical origin of this additional enhancement is
that, with small diffusion length, the spin current mostly flows around the
grain without suffering much loss. We also demonstrate that the voltage,
created by a spin current, is sensitive to a very weak magnetic field directed
along the spin current, and even reverses sign in a certain domain of fields.
The origin of this sensitivity is that the spin precession, caused by magnetic
field, takes place outside the grains where SO is absent.",1509.03373v1
2016-11-23,Room temperature manipulation of long lifetime spins in metallic-like carbon nanospheres,"The time-window for processing electron spin information (spintronics) in
solid-state quantum electronic devices is determined by the spin-lattice (T1)
and spin-spin (T2) relaxation times of electrons. Minimising the effects of
spin-orbit coupling and the local magnetic contributions of neighbouring atoms
on T1 and T2 at room temperature remain substantial challenges to practical
spintronics. Here, we report a record-high conduction electron T1=T2 of 175 ns
at 300 K in 37 nm +/- 7 nm carbon spheres, which exceeds by far the highest
values observed for any conducting solid state material of comparable size. The
long T1=T2 is due to quantum confinement effects, to the intrinsically weak
spin-orbit coupling of carbon, and to the protecting nature of the outer shells
of the inner spins from the influences of environmental disturbances. Following
the observation of spin polarization by electron spin resonance, we controlled
the quantum state of the electron spin by applying short bursts of an
oscillating magnetic field and observed coherent oscillations of the spin
state. These results demonstrate the feasibility of operating electron spins in
conducting carbon nanospheres as quantum bits at room temperature.",1611.07690v1
2010-04-16,Random Spin-orbit Coupling in Spin Triplet Superconductors: Stacking Faults in Sr_2RuO_4 and CePt_3Si,"The random spin-orbit coupling in multicomponent superconductors is
investigated focusing on the non-centrosymmetric superconductor CePt_3Si and
the spin triplet superconductor Sr_2RuO_4. We find novel manifestations of the
random spin-orbit coupling in the multicomponent superconductors with
directional disorders, such as stacking faults. The presence of stacking faults
is indicated for the disordered phase of CePt_3Si and Sr_2RuO_4. It is shown
that the d-vector of spin triplet superconductivity is locked to be d = k_y x -
k_x y with the anisotropy \Delta T_c/T_c0 \sim \bar{\alpha}^2/T_c0 W_z, where
\bar{\alpha}, T_c0, and W_z are the mean square root of random spin-orbit
coupling, the transition temperature in the clean limit, and the kinetic energy
along the c-axis, respectively. This anisotropy is much larger (smaller) than
that in the clean bulk Sr_2RuO_4 (CePt_3Si). These results indicate that the
helical pairing state d = k_y x - k_x y in the eutectic crystal
Sr_2RuO_4-Sr_3Ru_2O_7 is stabilized in contrast to the chiral state d = (k_x
\pm i k_y) z in the bulk Sr_2RuO_4. The unusual variation of T_c in CePt_3Si is
resolved by taking into account the weak pair-breaking effect arising from the
uniform and random spin-orbit couplings. These superconductors provide a basis
for discussing recent topics on Majorana fermions and non-Abelian statistics.",1004.2762v4
2023-07-28,Magnetic supersolid phases of two-dimensional extended Bose-Hubbard model with spin-orbit coupling,"The study of ultracold atomic spin systems with long-range interaction
provides the possibility of searching for magnetic supersolid phases in quantum
many-body scenarios. In this paper, we consider two-species Bose gases with
spin-orbit coupling and nearest-neighbor interaction confined in a
two-dimensional optical lattice. The competition between spin-orbit coupling
and interactions creates rich ground-state diagrams with supersolid phases
exhibiting phase modulations or magnetic orderings. We obtain the phase-twisted
and phase-striped pair checkboard supersolid phases that are generated by the
combination of spin-orbit coupling and intraspecies nearest-neighbor
interaction. The introduction of interspecies nearest-neighbor interaction
enriches the quantum phases of the system. It leads to the appearance of the
phase-twisted and phase-striped lattice supersolid phases. In addition to the
lattice supersolid phase, we find the emergence of nontrivial supersolid phases
that depend on the interspecies on-site interaction strength. The
lattice-insulated supersolid phase with supersolidility in one species but
insulation in the other exists in the miscible domain, while the pair striped
supersolid phase with stripe structures in each species is in the immiscible
domain. Finally, to further characterize each phase, we discuss their
spin-dependent momentum distributions and spin textures. The magnetic textures,
such as antiferromagnetic, spiral and stripe orders, are shown in SS phases.
The results here could help in the observe for these magnetic supersolid phases
in ultracold atomic experiments with nearest-neighbor interaction and
spin-orbit coupling in optical lattice.",2307.15310v2
2018-02-19,Spin-orbit coupling effects in zinc-blende InSb and wurtzite InAs nanowires: Realistic calculations with multiband $\vec{k} \cdot \vec{p}$ method,"A systematic numerical investigation of spin-orbit fields in the conduction
bands of III-V semiconductor nanowires is performed. Zinc-blende InSb nanowires
are considered along [001], [011], and [111] directions, while wurtzite InAs
nanowires are studied along [0001] and [10$\overline{1}$0] or
[11$\overline{2}$0] directions. Realistic multiband $\vec{k} \cdot \vec{p}\,$
Hamiltonians are solved by using plane-wave expansions of real-space
parameters. In all cases the linear and cubic spin-orbit coupling parameters
are extracted for nanowire widths from 30 to 100 nm. Typical spin-orbit
energies are on the $\mu$eV scale, except for InAs wurtzite nanowires grown
along [10$\overline{1}$0] or [11$\overline{2}$0], in which the spin-orbit
energy is about meV, largely independent of the wire diameter. Significant
spin-orbit coupling is obtained by applying a transverse electric field,
causing the Rashba effect. For an electric field of about 4 mV/nm the obtained
spin-orbit energies are about 1 meV for both materials in all investigated
growth directions. The most favorable system, in which the spin-orbit effects
are maximal, are InAs WZ nanowires grown along [1010] or [11$\overline{2}$0],
since here spin-orbit energies are giant (meV) already in the absence of
electric field. The least favorable are InAs WZ nanowires grown along [0001],
since here even the electric field does not increase the spin-orbit energies
beyond 0.1 meV. The presented results should be useful for investigations of
optical orientation, spin transport, weak localization, and superconducting
proximity effects in semiconductor nanowires.",1802.06734v2
2013-01-23,Unconventional states of bosons with synthetic spin-orbit coupling,"Spin-orbit coupling with bosons gives rise to novel properties that are
absent in usual bosonic systems. Under very general conditions, the
conventional ground state wavefunctions of bosons are constrained by the
""no-node"" theorem to be positive-definite. In contrast, the linear-dependence
of spin-orbit coupling leads to complex-valued condensate wavefunctions beyond
this theorem. In this article, we review the study of this class of
unconventional Bose-Einstein condensations focusing on their topological
properties. Both the 2D Rashba and 3D $\vec{\sigma} \cdot \vec{p}$-type Weyl
spin-orbit couplings give rise to Landau-level-like quantization of
single-particle levels in the harmonic trap. The interacting condensates
develop the half-quantum vortex structure spontaneously breaking time-reversal
symmetry and exhibit topological spin textures of the skyrmion type. In
particular, the 3D Weyl coupling generates topological defects in the
quaternionic phase space as an SU(2) generalization of the usual U(1) vortices.
Rotating spin-orbit coupled condensates exhibit rich vortex structures due to
the interplay between vorticity and spin texture. In the Mott-insulating states
in optical lattices, quantum magnetism is characterized by the
Dzyaloshinskii-Moriya type exchange interactions.",1301.5403v3
2000-10-17,Spin-Orbit Coupling in the ab initio Pseudopotential Framework,"We describe the implementation of total angular momentum dependent
pseudopotentials in a plane wave formulation of density functional theory. Our
approach thus goes beyond the scalar-relativistic approximation usually made in
ab initio pseudopotential calculations and explicitly includes spin-orbit
coupling. We outline the necessary extensions and compare the results to
available all-electron calculations and experimental data.",0010225v1
2005-02-21,Comments on spin-orbit interaction of anyons,"The coupling of non-relativistic anyons (called exotic particles) to an
electromagnetic field is considered. Anomalous coupling is introduced by adding
a spin-orbit term to the Lagrangian. Alternatively, one has two Hamiltonian
structures, obtained by either adding the anomalous term to the Hamiltonian, or
by redefining the mass and the NC parameter. The model can also be derived from
its relativistic counterpart.",0502181v1
2010-07-26,Tunneling into d-wave superconductors: Effects of interface spin-orbit coupling,"Tunneling conductance of a clean normal metal/d-wave superconductor junction
is studied by using the extended Blonder-Tinkham-Klapwijk formalism. We show
that the conductance is significantly affected by the interface spin-orbit
coupling of the Rashba type, which is inevitably present due to the asymmetry
of the junction.",1007.4483v1
2011-09-19,Condensate Fraction and Pair Coherence Lengths of Two-Dimension Fermi Gases with Spin-Orbit Coupling,"The effects of Rashba spin-orbit coupling on BCS-BEC crossover, the
condensate fraction and pair coherence lengths for a two-component attractive
Fermi gas in two dimension are studied. The results at $T=0K$ indicate that (1)
when the strength of SOC is beyond a critical value, BCS-BEC crossover does not
happen in a conventional sense; (2) SOC enhances the condensate fraction, but
suppresses pair coherence lengths.",1109.3970v1
2014-11-29,Influence of Hund's exchange and spin-orbit coupling on spectral properties of fcc-Ce: DFT+DMFT study,"Spectral properties of fcc-Ce have been calculated in frames of modern
DFT+DMFT method with Hybridization expansion CT-QMC solver. The influence of
Hund's exchange and spin-orbit coupling (SOC) on spectral properties of Ce were
investigated. SOC is responsible for the shape of spectra near the Fermi level
and Hund's exchange interaction doesn't change the obtained spectra and can be
neglected.",1412.0140v1
2011-09-22,Ground-state phases of ultracold bosons with Rashba-Dresselhaus spin-orbit coupling,"We study ultracold bosons in three dimensions with an anisotropic
Rashba-Dresselhaus spin-orbit coupling. We first carry out the exact summation
of ladder diagrams for the two-boson t-matrix at zero energy. Then, with the
t-matrix as the effective interaction, we find the ground-state phase diagrams
of bosons in mean field as a function of the spin-orbit coupling, the
anisotropy, and the scattering lengths between particles in the same and in
different pseudospin states. The resulting phase diagrams have much richer
structures than those obtained using mean-field couplings, exhibiting three
different phases: a plane-wave condensate, a striped condensate, and an
unstable phase. The differences between the present approach using the t-matrix
compared to using mean-field couplings is significant for large scattering
lengths, large spin-orbit-coupling strength, or small anisotropy.",1109.4954v2
2017-01-15,Analytical coupled-channels treatment of two-body scattering in the presence of three-dimensional isotropic spin-orbit coupling,"It is shown that the single-particle spin-orbit coupling terms, which---in
the cold atom context---are associated with synthetic gauge fields, can
significantly and non-trivially modify the phase accumulation at small
interparticle distances even if the length scale $(k_{\text{so}})^{-1}$
associated with the spin-orbit coupling term is significantly larger than the
van der Waals length $r_{\text{vdW}}$ that characterizes the two-body
interaction potential. A theoretical framework, which utilizes a generalized
local frame transformation and accounts for the phase accumulation
analytically, is developed. Comparison with numerical coupled-channels
calculations demonstrates that the phase accumulation can, to a very good
approximation, be described over a wide range of energies by the free-space
scattering phase shifts---evaluated at a scattering energy that depends on
$k_{\text{so}}$---and the spin-orbit coupling strength $k_{\text{so}}$.",1701.03979v1
2017-09-11,Controlling the superconducting transition by spin-orbit coupling,"Whereas there exists considerable evidence for the conversion of singlet
Cooper pairs into triplet Cooper pairs in the presence of inhomogeneous
magnetic fields, recent theoretical proposals have suggested an alternative way
to exert control over triplet generation: intrinsic spin-orbit coupling in a
homogeneous ferromagnet coupled to a superconductor. Here, we proximity-couple
Nb to an asymmetric Pt/Co/Pt trilayer, which acts as an effective spin-orbit
coupled ferromagnet owing to structural inversion asymmetry. Unconventional
modulation of the superconducting critical temperature as a function of
in-plane and out-of- plane applied magnetic fields suggests the presence of
triplets that can be controlled by the magnetic orientation of a single
homogeneous ferromagnet. Our studies demonstrate for the first time an active
role of spin-orbit coupling in controlling the triplets -- an important step
towards the realization of novel superconducting spintronic devices.",1709.03504v2
2023-09-27,Quantifying the large contribution from orbital Rashba effect to the effective damping-like torque on magnetization,"The generation of large spin currents, and the associated spin torques, which
are at the heart of modern spintronics, have long been achieved by
charge-to-spin conversion mechanisms, i.e. the spin Hall effect and/or the
Rashba effect, intrinsically linked to a strong spin-orbit coupling. Recently,
a novel path has been predicted and observed for achieving significant
current-induced torques originating from light elements, hence possessing a
weak spin-orbit interaction. These findings point out to the potential
involvement of the orbital counterpart of electrons, namely the orbital Hall
and orbital Rashba effects. In this study, we aim at quantifying these
orbital-related contributions to the effective torques acting on a thin Co
layer in different systems. First, in Pt|Co|Cu|AlOx stacking, we demonstrate a
comparable torque strength coming from the conversion due to the orbital Rashba
effect at the Cu|AlOx interface and the one from the effective spin Hall effect
in bottom Pt|Co system. Secondly, in order to amplify the orbital-to-spin
conversion, we investigate the impact of an intermediate Pt layer in
Co|Pt|Cu|CuOx. From the Pt thickness dependence of the effective torques
determined by harmonic Hall measurements complemented by spin Hall
magneto-resistance and THz spectroscopy experiments, we demonstrate that a
large orbital Rashba effect is present at the Cu|CuOx interface, leading to a
twofold enhancement of the net torques on Co for the optimal Pt thickness. Our
findings not only demonstrate the crucial role that orbital currents can play
in low-dimensional systems with weak spin-orbit coupling, but also reveal that
they enable more energy efficient manipulation of magnetization in spintronic
devices.",2309.15987v2
2000-10-16,Quantum Numbers of the V3+ Ion in V2o3,"It is argued that the V3+ ion in V2O3 should be considered as described by
quantum numbers S=1 and L=3. It results from Hund's rules and means that the
two d electrons form the highly- correlated electron system with the importance
of the intra-atomic spin-orbit coupling. Keywords: highly-correlated electron
system, crystal-field, spin- orbit coupling, orbital moment, V3+ ion. PACS:
71.70.E, 75.10.D, 75.30.Gw",0010218v1
2002-09-07,Variational study of the nu=1 quantum Hall ferromagnet in the presence of spin-orbit interaction,"We investigate the nu=1 quantum Hall ferromagnet in the presence of
spin-orbit coupling of the Rashba or Dresselhaus type by means of
Hartree-Fock-typed variational states. In the presence of Rashba (Dresselhaus)
spin-orbit coupling the fully spin-polarized quantum Hall state is always
unstable resulting in a reduction of the spin polarization if the product of
the particle charge $q$ and the effective $g$-factor is positive (negative). In
all other cases an alternative variational state with O(2) symmetry and finite
in-plane spin components is lower in energy than the fully spin-polarized state
for large enough spin-orbit interaction. The phase diagram resulting from these
considerations differs qualitatively from earlier studies.",0209185v2
2004-09-23,Spin relaxation and anticrossing in quantum dots: Rashba versus Dresselhaus spin-orbit coupling,"The spin-orbit splitting of the electron levels in a two-dimensional quantum
dot in a perpendicular magnetic field is studied. It is shown that at the point
of an accidental degeneracy of the two lowest levels above the ground state the
Rashba spin-orbit coupling leads to a level anticrossing and to mixing of
spin-up and spin-down states, whereas there is no mixing of these levels due to
the Dresselhaus term. We calculate the relaxation and decoherence times of the
three lowest levels due to phonons. We find that the spin relaxation rate as a
function of a magnetic field exhibits a cusp-like structure for Rashba but not
for Dresselhaus spin-orbit interaction.",0409614v2
2013-07-01,Phenomenology of Current-Induced Spin-Orbit Torques,"Currents induce magnetization torques via spin-transfer when the spin angular
momentum is conserved or via relativistic spin-orbit coupling. Beyond simple
models, the relationship between material properties and spin-orbit torques is
not known. Here, we present a novel phenomenology of current-induced torques
that is valid for any strength of intrinsic spin-orbit coupling. In $\rm
Pt|Co|AlO_x$, we demonstrate that the domain walls move in response to a novel
relativistic dissipative torque that is dependent on the domain wall structure
and that can be controlled via the Dzyaloshinskii-Moriya interaction. Unlike
the non-relativistic spin-transfer torque, the new torque can, together with
the spin-Hall effect in the Pt-layer, move domain walls by means of electric
currents parallel to the walls.",1307.0395v3
2015-07-30,Hierarchical spin-orbital polarisation of a giant Rashba system,"The Rashba effect is one of the most striking manifestations of spin-orbit
coupling in solids, and provides a cornerstone for the burgeoning field of
semiconductor spintronics. It is typically assumed to manifest as a
momentum-dependent splitting of a single initially spin-degenerate band into
two branches with opposite spin polarisation. Here, combining
polarisation-dependent and resonant angle-resolved photoemission measurements
with density-functional theory calculations, we show that the two ""spin-split""
branches of the model giant Rashba system BiTeI additionally develop disparate
orbital textures, each of which is coupled to a distinct spin configuration.
This necessitates a re-interpretation of spin splitting in Rashba-like systems,
and opens new possibilities for controlling spin polarisation through the
orbital sector.",1507.08588v1
2016-10-23,Unusual UUDD magnetic chain structure of the spin-1/2 tetragonally distorted spinel GeCu2O4,"GeCu2O4 exhibits a tetragonal spinel structure due to the strong Jahn-Teller
distortion associated with Cu2+ ions. We show that its magnetic structure can
be described as slabs composed of a pair of layers with orthogonally oriented
spin 1/2 Cu chains in the basal ab plane. The spins between the two layers
within a slab are collinearly aligned while the spin directions of neighboring
slabs are perpendicular to each other. Interestingly, we find that spins along
each chain form an unusual up-up-down-down (UUDD) pattern, suggesting a
non-negligible nearest-neighbor biquadratic exchange interaction in the
effective classical spin Hamiltonian. We hypothesize that spin-orbit coupling
and orbital mixing of Cu2+ ions in this system is non-negligible, which calls
for future calculations using perturbation theory with extended Hilbert (spin
and orbital) space and calculations based on density functional theory
including spin-orbit coupling and looking at the global stability of the UUDD
state.",1610.07113v1
2014-03-04,$α$-RuCl3: a Spin-Orbit Assisted Mott Insulator on a Honeycomb Lattice,"We examine the role of spin-orbit coupling in the electronic structure of
$\alpha$-RuCl3, in which Ru ions in 4d5 configuration form a honeycomb lattice.
The measured optical spectra exhibit a clear optical gap and excitations within
the t2g orbitals. The spectra can be described very well with first-principles
electronic structure calculations obtained by taking into account both spin
orbit coupling and electron correlations. Furthermore, our X-ray absorption
spectroscopy measurements at the Ru L-edges exhibit distinct spectral features
associated with the presence of substantial spin- orbit coupling, as well as an
anomalously large branching ratio. We propose that $\alpha$-RuCl3 is a
spin-orbit assisted Mott insulator, and the bond-dependent Kitaev interaction
may be relevant for this compound.",1403.0883v2
2019-10-30,Excitonic Magnetism at the intersection of Spin-orbit coupling and crystal-field splitting,"Excitonic magnetism involving superpositions of singlet and triplet states is
expected to arise for two holes in strongly correlated and spin-orbit coupled
$t_{2g}$ orbitals. However, uncontested material examples for its realization
are rare. Applying the Variational Cluster Approach to the square lattice, we
find conventional spin antiferromagnetism combined with orbital order at weak
and excitonic order at strong spin-orbit coupling. We address the specific
example of Ca$_2$RuO$_4$ using ab-initio modeling and conclude it to realize
excitonic magnetism despite its pronounced orbital polarization.",1910.13977v3
2023-07-17,SOiCISCF: Combining SOiCI and iCISCF for Variational Treatment of Spin-orbit Coupling,"It has recently been shown that the SOiCI approach [J. Phys.: Condens. Matter
34 (2022) 224007], in conjunction with the spin-separated exact two-component
relativistic Hamiltonian, can provide very accurate fine structures of systems
containing heavy elements by treating electron correlation and spin-orbit
coupling (SOC) on an equal footing. Nonetheless, orbital
relaxations/polarizations induced by SOC are not yet fully accounted for, due
to the use of scalar relativistic orbitals. This issue can be resolved by
further optimizing the still real-valued orbitals self-consistently in the
presence of SOC, as done in the spin-orbit coupled CASSCF approach [J. Chem.
Phys. 138 (2013) 104113] but with the iCISCF algorithm [J. Chem. Theory Comput.
17 (2021) 7545] for large active spaces. The resulting SOiCISCF employs both
double group and time reversal symmetries for computational efficiency and
assignment of target states. The fine structures of $p$-block elements are
taken as showcases to reveal the efficacy of SOiCISCF.",2307.08219v1
2015-04-22,Spontaneous Edge Accumulation of Spin Currents in Finite-Size Two-Dimensional Diffusive Spin-Orbit Coupled SFS Heterostructures,"We theoretically study spin and charge currents through finite-size
two-dimensional $s$-wave superconductor/uniform ferromagnet/s-wave
superconductor (SFS) junctions with intrinsic spin-orbit interactions (ISOIs)
using a quasiclassical approach. Considering experimentally realistic
parameters, we demonstrate that the combination of spontaneously broken
time-reversal symmetry and lack of inversion symmetry can result in
spontaneously accumulated spin currents at the edges of finite-size
two-dimensional magnetic SF hybrids. Due to the spontaneous edge spin
accumulation, the corners of the F wire host the maximum spin current density.
We further reveal that this type edge phenomena are robust and independent of
either the actual type of ISOIs or exchange field orientation. Moreover, we
study spin current-phase relations in these diffusive spin-orbit coupled SFS
junctions. Our results unveil net spin currents, not accompanied by charge
supercurrent, that spontaneously accumulate at the sample edges through a
modulating superconducting phase difference. Finally, we discuss possible
experimental implementations to observe these edge phenomena.",1504.05950v1
2015-09-22,Rare-earth triangular lattice spin liquid: a single-crystal study of YbMgGaO$_{4}$,"YbMgGaO$_{4}$, a structurally perfect two-dimensional triangular lattice with
odd number of electrons per unit cell and spin-orbit entangled effective
spin-1/2 local moments of Yb$^{3+}$ ions, is likely to experimentally realize
the quantum spin liquid ground state. We report the first experimental
characterization of single crystal YbMgGaO$_{4}$ samples. Due to the spin-orbit
entanglement, the interaction between the neighboring Yb$^{3+}$ moments depends
on the bond orientations and is highly anisotropic in the spin space. We carry
out the thermodynamic and the electron spin resonance measurements to confirm
the anisotropic nature of the spin interaction as well as to quantitatively
determine the couplings. Our result is a first step towards the theoretical
understanding of the possible quantum spin liquid ground state in this system
and sheds new lights on the search of quantum spin liquids in strong spin-orbit
coupled insulators.",1509.06766v1
2024-01-03,"Minimal Model for Chirally Induced Spin Selectivity: Spin-orbit coupling, tunneling and decoherence","Chirally Induced Spin Selectivity (CISS) is a transport phenomenon observed
in both linear and non-linear regimes, where the spin-orbit coupling (SOC) acts
as the key driver and electron tunneling serves as the dominant mechanism for
charge transfer. Despite SOC's inherent time-reversal symmetry (TRS)
preservation, conventional reciprocity relations limit spin polarization and
the differential treatment of spin species. In experimental systems, an
additional factor, spin-independent decoherence, disrupts TRS and reciprocity.
We introduce decoherence using the Buttiker voltage probe within the scattering
matrix framework. Our results reveal the importance of under-the-barrier
decoherence as an order-of-magnitude polarization enhancement mechanism.
Polarization arises by the disruption of spin precession around the spin-orbit
magnetic field with a new spin component along the field direction. The
alignment of polarization depends on interference effects produced by the
voltage probe. We discuss the connection of our model to a more realistic
decoherence mechanism in molecular systems.",2401.01994v1
2007-03-19,Non-equilibrium spin dynamics in a trapped Fermi gas with effective spin-orbit interaction,"We consider a trapped atomic system in the presence of spatially varying
laser fields. The laser-atom interaction generates a pseudospin degree of
freedom (referred to simply as spin) and leads to an effective spin-orbit
coupling for the fermions in the trap. Reflections of the fermions from the
trap boundaries provide a physical mechanism for effective momentum relaxation
and non-trivial spin dynamics due to the emergent spin-orbit coupling. We
explicitly consider evolution of an initially spin-polarized Fermi gas in a
two-dimensional harmonic trap and derive non-equilibrium behavior of the spin
polarization. It shows periodic echoes with a frequency equal to the harmonic
trapping frequency. Perturbations, such as an asymmetry of the trap, lead to
the suppression of the spin echo amplitudes. We discuss a possible experimental
setup to observe spin dynamics and provide numerical estimates of relevant
parameters.",0703500v2
2007-08-02,Extracting current-induced spins: spin boundary conditions at narrow Hall contacts,"We consider the possibility to extract spins that are generated by an
electric current in a two-dimensional electron gas with Rashba-Dresselhaus
spin-orbit interaction (R2DEG) in the Hall geometry. To this end, we discuss
boundary conditions for the spin accumulations between a spin-orbit coupled
region and contact without spin-orbit coupling, i.e. a normal two-dimensional
electron gas (2DEG). We demonstrate that in contrast to contacts that extend
along the whole sample, a spin accumulation can diffuse into the normal region
through finite contacts and detected by e.g. ferromagnets. For an
impedance-matched narrow contact the spin accumulation in the 2DEG is equal to
the current induced spin accumulation in the bulk of R2DEG up to a
geometry-dependent numerical factor.",0708.0244v1
2015-05-29,Theory of spin-orbit induced spin relaxation in functionalized graphene,"We perform a comparative study of the spin relaxation by spin-orbit coupling
induced from adatoms (hydrogen and fluorine) in graphene. Two methods are
applied, giving consistent results: a full quantum transport simulation of a
graphene nanoribbon, and a T-matrix calculation using Green's functions for a
single adatom in graphene. For hydrogenated graphene the dominant spin-orbit
term for spin relaxation is PIA, the hitherto neglected interaction due to
pseudospin inversion asymmetry. In contrast, in fluorinated graphene PIA and
Rashba couplings destructively interfere, reducing the total spin relaxation
rate. In this case we also predict a strong deviation from the expected 2:1
spin relaxation anisotropy for out- and in-plane spin orientations. Our
findings should be useful to benchmark spin relaxation and weak localization
experiments of functionalized graphene.",1506.00040v1
2015-12-18,Interplay between resonant tunneling and spin precession oscillations in all-electric all-semiconductor spin transistors,"We investigate the transmission properties of a spin transistor coupled to
two quantum point contacts acting as spin injector and detector. In the
Fabry-Perot regime, transport is mediated by quasibound states formed between
tunnel barriers. Interestingly, the spin-orbit interaction of the Rashba type
can be tuned in such a way that nonuniform Rashba fields can point along
distinct directions in different points of the sample. We discuss both
spin-conserving and spin-flipping transitions as the spin-orbit angle of
orientation increases from parallel to antiparallel configurations. Spin
precession oscillations are clearly seen as a function of the length of the
central channel. Remarkably, we find that these oscillations combine with the
Fabry-Perot motion giving rise to quasiperiodic transmissions in the purely
one-dimensional case. Furthermore, we consider the more realistic case of a
finite width in the transverse direction and find that the coherent
oscillations become deteriorated for moderate values of the spin-orbit
strength. Our results then determine the precise role of the Rashba
intersubband coupling potential in the Fabry-Perot-Datta-Das intermixed
oscillations.",1512.05958v2
2021-01-22,Chiral Bloch states in single layer graphene with Rashba spin-orbit coupling: Spectrum and spin current density,"We study the Bloch spectrum and spin physics of 2D massless Dirac electrons
in single layer graphene subject to a one dimensional periodic Kronig-Penney
potential and Rashba spin-orbit coupling. The Klein paradox exposes novel
features in the band dispersion and in graphene spintronics. In particular it
is shown that: (1) The Bloch energy dispersion $\veps(p)$ has unusual
structure: There are {\it two Dirac points} at Bloch momenta $\pm p \ne 0$ and
a narrow band emerges between the wide valence and conduction bands. (2) The
charge current and the spin density vector vanish. (3) Yet, all the
non-diagonal elements of the spin current density tensor are finite and their
magnitude increases linearly with the spin-orbit strength. In particular, there
is a spin density current whose polarization is perpendicular to the graphene
plane. (4) The spin density currents are space-dependent, hence their
continuity equation includes a finite spin torque density.",2101.09224v1
2012-11-05,First Law of Mechanics for Black Hole Binaries with Spins,"We use the canonical Hamiltonian formalism to generalize to spinning point
particles the first law of mechanics established for binary systems of
non-spinning point masses moving on circular orbits [Le Tiec, Blanchet, and
Whiting, Phys. Rev. D 85, 064039 (2012)]. We find that the redshift observable
of each particle is related in a very simple manner to the canonical
Hamiltonian and, more generally, to a class of Fokker-type Hamiltonians. Our
results are valid through linear order in the spin of each particle, but hold
also for quadratic couplings between the spins of different particles. The
knowledge of spin effects in the Hamiltonian allows us to compute spin-orbit
terms in the redshift variable through 2.5PN order, for circular orbits and
spins aligned or anti-aligned with the orbital angular momentum. To describe
extended bodies such as black holes, we supplement the first law for spinning
point-particle binaries with some ""constitutive relations"" that can be used for
diagnosis of spin measurements in quasi-equilibrium initial data.",1211.1060v2
2014-11-12,Spin transport in intermediate-energy heavy-ion collisions as a probe of in-medium spin-orbit interactions,"The spin up-down splitting of collective flows in intermediate-energy
heavy-ion collisions as a result of the nuclear spin-orbit interaction is
investigated within a spin- and isospin-dependent Boltzmann-Uehing-Uhlenbeck
transport model SIBUU12. Using a Skyrme-type spin-orbit coupling quadratic in
momentum, we found that the spin splittings of the directed flow and elliptic
flow are largest in peripheral Au+Au collisions at beam energies of about
100-200 MeV/nucleon, and the effect is considerable even in smaller systems
especially for nucleons with high transverse momenta. The collective flows of
light clusters of different spin states are also investigated using an improved
dynamical coalescence model with spin. Our study can be important in
understanding the properties of in-medium nuclear spin-orbit interactions once
the spin-dependent observables proposed in this work can be measured.",1411.3057v2
2017-06-19,Spin Hall effect from hybridized 3$d$-4$p$ orbitals,"Electrical manipulation of magnetization by spin-orbit torque (SOT) has shown
promise for realizing reliable magnetic memories and oscillators. To date, the
generation of transverse spin current and SOT, whether it is of spin Hall
effect (SHE), Rashba-Edelstein effect or spin-momentum locking origin, relies
primarily on materials or heterostructures containing 5$d$ or 6$p$ heavy
elements with strong spin-orbit coupling. Here we show that a paramagnetic CoGa
compound possesses large enough spin Hall angle to allow robust SOT switching
of perpendicularly-magnetized ferrimagnetic MnGa films in CoGa/MnGa/Oxide
heterostructures. The spin Hall efficiency estimated via spin Hall
magnetoresistance and harmonic Hall measurements is +0.05$\pm$0.01, which is
surprisingly large for a system that does not contain any heavy metal element.
First-principles calculations corroborate our experimental observations and
suggest that the hybridized Co 3$d$ - Ga 4$p$ orbitals along R-X in the
Brillouin zone is responsible for the intrinsic SHE. Our results suggest that
efficient spin current generation can be realized in intermetallic by alloying
a transition metal with a $p$-orbital element and by Fermi level tuning.",1706.05846v1
2005-08-03,Spin filter using a semiconductor quantum ring side-coupled to a quantum wire,"We introduce a new spin filter based on spin-resolved Fano resonances due to
spin-split levels in a quantum ring (QR) side-coupled to a quantum wire (QW).
Spin-orbit coupling inside the QR, together with external magnetic fields,
induces spin splitting, and the Fano resonances due to the spin-split levels
result in perfect or considerable suppression of the transport of either spin
direction. Using the numerical renormalization group method, we find that the
Coulomb interaction in the QR enhances the spin filter operation by widening
the separation between dips in conductances for different spins and by allowing
perfect blocking for one spin direction and perfect transmission for the other.
The spin-filter effect persists as long as the temperature is less than the
broadening of QR levels due to the QW-QR coupling. We discuss realistic
conditions for the QR-based spin filter and its advantages to other similar
devices.",0508099v1
2021-06-23,Correlation Between Spin and Orbital Dynamics During Laser-Induced Femtosecond Demagnetization,"Spin and orbital angular momenta are two intrinsic properties of an electron
and are responsible for the physics of a solid. How the spin and orbital evolve
with respect to each other on several hundred femtoseconds is largely unknown,
but it is at the center of laser-induced ultrafast demagnetization. In this
paper, we introduce a concept of the spin-orbital correlation diagram, where
spin angular momentum is plotted against orbital angular momentum, much like
the position-velocity phase diagram in classical mechanics. We use four sets of
highly accurate time-resolved x-ray magnetic circular dichroism (TR-XMCD) data
to construct four correlation diagrams for iron and cobalt. To our surprise, a
pattern emerges. The trace on the correlation diagram for iron is an arc, and
at the end of demagnetization, it has a pronounced cusp. The correlation
diagram for cobalt is different and appears more linear, but with kinks. We
carry out first-principles calculations with two different methods:
time-dependent density functional theory (TDDFT) and time-dependent Liouville
density functional theory (TDLDFT). These two methods agree that the
experimental findings for both Fe and Co are not due t experimental errors. It
is the spin-orbit coupling that correlates the spin dynamics to the orbital
dynamics.Microscopically, Fe and Co have different orbital occupations, which
leads to distinctive correlation diagrams. We believe that this correlation
diagram presents a useful tool to better understand spin and orbital dynamics
on an ultrafast time scale. A brief discussion on the magnetic anisotropy
energy is also provided.",2106.12679v1
2010-12-07,Reducing orbital eccentricity of precessing black-hole binaries,"Building initial conditions for generic binary black-hole evolutions without
initial spurious eccentricity remains a challenge for numerical-relativity
simulations. This problem can be overcome by applying an eccentricity-removal
procedure which consists in evolving the binary for a couple of orbits,
estimating the eccentricity, and then correcting the initial conditions. The
presence of spins can complicate this procedure. As predicted by post-Newtonian
theory, spin-spin interactions and precession prevent the binary from moving
along an adiabatic sequence of spherical orbits, inducing oscillations in the
radial separation and in the orbital frequency. However, spin-induced
oscillations occur at approximately twice the orbital frequency, therefore they
can be distinguished from the initial spurious eccentricity, which occurs at
approximately the orbital frequency. We develop a new removal procedure based
on the derivative of the orbital frequency and find that it is successful in
reducing the eccentricity measured in the orbital frequency to less than 0.0001
when moderate spins are present. We test this new procedure using
numerical-relativity simulations of binary black holes with mass ratios 1.5 and
3, spin magnitude 0.5 and various spin orientations. The numerical simulations
exhibit spin-induced oscillations in the dynamics at approximately twice the
orbital frequency. Oscillations of similar frequency are also visible in the
gravitational-wave phase and frequency of the dominant mode.",1012.1549v2
2009-07-23,Spin-orbit fields in ferromagnetic metal/semiconductor junctions,"The methodology used to obtain the values of the spin-orbit couplings from
the spin expectation values from perturbation theory was incorrect. As a result
Figs. 2 and 3 are incorrect.",0907.4149v3
2004-02-28,Resonant Spin Hall Conductance in Two-Dimensional Electron Systems with Rashba Interaction in a Perpendicular Magnetic Field,"We study transport properties of a two-dimensional electron system with
Rashba spin-orbit coupling in a perpendicular magnetic field. The spin orbit
coupling competes with Zeeman splitting to introduce additional degeneracies
between different Landau levels at certain magnetic fields. This degeneracy, if
occuring at the Fermi level, gives rise to a resonant spin Hall conductance,
whose height is divergent as 1/T and whose weight is divergent as $-\ln T$ at
low temperatures. The Hall conductance is unaffected by the Rashba coupling.",0403005v1
2006-12-12,Spin-orbit induced spin-qubit control in nanowires,"We elaborate on a number of issues concerning our recent proposal for
spin-qubit manipulation in nanowires using the spin-orbit coupling. We discuss
the experimental status and describe in further detail the scheme for
single-qubit rotations. We present a derivation of the effective two-qubit
coupling which can be extended to higher orders in the Coulomb interaction. The
analytic expression for the coupling strength is shown to agree with numerics.",0612293v1
2007-01-25,Spin-polarization coupling in multiferroic transition-metal oxides,"A systematic microscopic theory of magnetically induced ferroelectricity and
lattice modulation is presented for all electron configurations of
Mott-insulating transition-metal oxides. Various mechanisms of polarization are
identified in terms of a strong-coupling perturbation theory. Especially, the
spin-orbit interaction acting on the ligand p orbitals is shown to give the
ferroelectric polarization of the spin-current form, which plays a crucial role
particularly in eg systems. Semiquantitative agreements with the multiferroic
TbMnO3 are obtained. Predictions for X-ray and neutron scattering experiments
are proposed to clarify the microscopic mechanism of the spin-polarization
coupling in different materials.",0701614v1
2012-09-19,Spin-orbit coupling assisted by flexural phonons in graphene,"We analyze the couplings between spins and phonons in graphene. We present a
complete analysis of the possible couplings between spins and flexural, out of
plane, vibrations. From tight-binding models we obtain analytical and numerical
estimates of their strength. We show that dynamical effects, induced by quantum
and thermal fluctuations, significantly enhance the spin-orbit gap.",1209.4382v2
2016-09-21,Highly efficient and tuneable spin-to-charge conversion through Rashba coupling at oxide interfaces,"The spin-orbit interaction couples the electrons' motion to their spin.
Accordingly, passing a current in a material with strong spin-orbit coupling
generates a transverse spin current (spin Hall effect, SHE) and vice-versa
(inverse spin Hall effect, ISHE). The emergence of SHE and ISHE as
charge-to-spin interconversion mechanisms offers a variety of novel spintronics
functionalities and devices, some of which do not require any ferromagnetic
material. However, the interconversion efficiency of SHE and ISHE (spin Hall
angle) is a bulk property that rarely exceeds ten percent, and does not take
advantage of interfacial and low-dimensional effects otherwise ubiquitous in
spintronics hetero- and mesostructures. Here, we make use of an
interface-driven spin-orbit coupling mechanism - the Rashba effect - in the
oxide two-dimensional electron system (2DES) LaAlO3/SrTiO3 to achieve
spin-to-charge conversion with unprecedented efficiency. Through spin-pumping,
we inject a spin current from a NiFe film into the oxide 2DES and detect the
resulting charge current, which can be strongly modulated by a gate voltage. We
discuss the amplitude of the effect and its gate dependence on the basis of the
electronic structure of the 2DES.",1609.06464v1
2003-10-27,Orbital and spin moment in CoO,"The orbital and spin moment of the Co2+ ion in CoO has been calculated within
the quasi-atomic approach with taking into account the intra-atomic spin-orbit
coupling and crystal field interactions. The orbital moment of 1.38 m_B amounts
at 0 K, in the magnetically-ordered state, to more than 34% of the total moment
4.02 m_B and yields the L/S ratio of 1.04, close to the recent experimental
value. This paper has been motivated by a recent paper in Phys. Rev. B 65
(2002) 125111, in which a presented theoretical approach was unable to
calculate the orbital moment.
  PACS No: 71.70.E; 75.10.D
  Keywords: crystal field, spin-orbit coupling, orbital moment, CoO",0310622v2
2003-08-01,Orbital evolution of a particle around a black hole: II. Comparison of contributions of spin-orbit coupling and the self force,"We consider the evolution of the orbit of a spinning compact object in a
quasi-circular, planar orbit around a Schwarzschild black hole in the extreme
mass ratio limit. We compare the contributions to the orbital evolution of both
spin-orbit coupling and the local self force. Making assumptions on the
behavior of the forces, we suggest that the decay of the orbit is dominated by
radiation reaction, and that the conservative effect is typically dominated by
the spin force. We propose that a reasonable approximation for the
gravitational waveform can be obtained by ignoring the local self force, for
adjusted values of the parameters of the system. We argue that this
approximation will only introduce small errors in the astronomical
determination of these parameters.",0308003v1
2020-07-14,"Role of orbital off-diagonal spin and charge condensates in a three orbital model for $\rm Ca_2RuO_4$ -- Coulomb renormalized spin-orbit coupling, orbital moment, and tunable magnetic order","Strongly anisotropic spin-orbit coupling (SOC) renormalization and strongly
enhanced orbital magnetic moments are obtained in the fully self consistent
approach including the orbital off-diagonal spin and charge condensates. For
moderate tetragonal distortion as in $\rm Ca_2 RuO_4$, dominantly planar
antiferromagnetic (AFM) order with small canting of moments in and about the
crystal $c$ axis are obtained. For reduced tetragonal distortion, we find a
tunable regime wherein the magnetic order can be tuned (AFM or FM) by the bare
SOC strength and octahedral tilting magnitude. In this regime, with decreasing
tetragonal distortion, AFM order is maintained by progressively decreasing
octahedral tilting, as observed in $\rm Ca_{2-x}Sr_x RuO_4$. For purely planar
order, the only self consistent solution is FM order along crystal $b$ axis,
which is relevant for the bilayer ruthenate compound $\rm Ca_3 Ru_2 O_7$.",2007.06978v2
2012-06-26,Transport and semiclassical dynamics of coupled quantum dots interacting with a local magnetic moment,"We present a theory of magnetotransport through a system of two coupled
electronic orbitals, where the electron spin interacts with a (large) local
magnetic moment via an exchange interaction. For the physical realization of
such a set-up we have in mind, for example, semiconductor quantum dots coupled
to an ensemble of nuclear spins in the host material or molecular orbitals
coupled to a local magnetic moment. Using a semiclassical approximation, we
derive a set of Ehrenfest equations of motion for the electron density matrix
and the mean value of the external spin (Landau equations): Due to the spin
coupling they turn out to be nonlinear and, importantly, also coherences
between electron states with different spin directions need to be considered.
The electronic spin-polarized leads are implemented in form of a Lindblad-type
dissipator in the infinite bias limit. We have solved this involved dynamical
system numerically for various isotropic and anisotropic coupling schemes. For
isotropic spin coupling and spin-polarized leads we study the effect of
current-induced magnetization of the attached spin and compare this with a
single quantum dot set-up. We further demonstrate that an anisotropic coupling
can lead to a rich variety of parametric oscillations in the average current
reflecting the complicated interplay between the Larmor precession of the
external spin and the dissipative coherent dynamics of the electron spin.",1206.5994v2
2004-04-29,Strongly-correlated crystal-field approach to 3d oxides - the orbital magnetism in 3d-ion compounds,"We have developed the crystal-field approach with strong electron
correlations, extended to the Quantum Atomistic Solid-State theory (QUASST), as
a physically relevant theoretical model for the description of electronic and
magnetic properties of 3d-atom compounds. Its applicability has been
illustrated for LaCoO3, FeBr2 and Na2V3O7. According to the QUASST theory in
compounds containing open 3d-/4f-/5f-shell atoms the discrete atomic-like
low-energy electronic structure survives also when the 3d atom becomes the full
part of a solid matter. This low-energy atomic-like electronic structure, being
determined by local crystal-field interactions and the intra-atomic spin-orbit
coupling, predominantly determines electronic and magnetic properties of the
whole compound.
  We understand our theoretical research as a continuation of the Van Vleck's
studies on the localized magnetism. We point out, however, the importance of
the orbital magnetism and the intra-atomic spin-orbit coupling for the
physically adequate description of real 3d-ion compounds and 3d magnetism. Our
studies clearly indicate that it is the highest time to ''unquench'' the
orbital moment in solid-state physics in description of 3d-atom containing
compounds.
  PACS No: 75.10.D; 71.70.E
  Keywords: magnetism, transition-metal compounds, 3d magnetism, crystal field,
spin-orbit coupling, orbital magnetism",0404713v1
2010-07-21,Spin and orbital fluctuations in non-equilibrium transport through quantum dots: A renormalisation-group analysis,"We study non-equilibrium current and occupation probabilities of a
two-orbital quantum dot. The couplings to the leads are allowed to be
asymmetric and orbital dependent as it is generically the case in transport
experiments on molecules and nanowires. Starting from a two-orbital Anderson
model, we perform a generalised Schrieffer-Wolff transformation to derive an
effective Kondo model. This generates an orbital potential scattering
contribution which is of the same order as the spin exchange interaction. In a
first perturbative analysis we identify a regime of negative differential
conductance and a cascade resonance in the presence of an external magnetic
field, which both originate from the non-equilibrium occupation of the
orbitals. We then study the logarithmic enhancement of these signatures by
means of a renormalisation-group treatment. We find that the orbital potential
scattering qualitatively changes the renormalisation of the spin exchange
couplings and strongly affects the differential conductance for asymmetric
couplings.",1007.3605v2
2014-03-05,Scattering theory of spin-orbit active adatoms on graphene,"The scattering of two-dimensional massless Dirac fermions from local
spin-orbit interactions with an origin in dilute concentrations of physisorbed
atomic species on graphene is theoretically investigated. The hybridization
between graphene and the adatoms' orbitals lifts spin and valley degeneracies
of the pristine host material, giving rise to rich spin-orbit coupling
mechanisms with features determined by the exact adsorption position on the
honeycomb lattice - bridge, hollow or top position - and the adatoms'
outer-shell orbital type. Effective graphene-only Hamiltonians are derived from
symmetry considerations, while a microscopic tight-binding approach connects
effective low-energy couplings and graphene-adatom hybridization parameters.
Within the $T$-matrix formalism, a theory for (spin-dependent) scattering
events involving graphene's charge carriers, and the spin-orbit active adatoms
is developed. Spin currents associated with intravalley and intervalley
scattering are found to tend to oppose each other. We establish that under
certain conditions, hollow-position adatoms give rise to the spin Hall effect,
through skew scattering, while top-position adatoms induce transverse charge
currents via trigonal potential scattering. We also identify the critical Fermi
energy range where the spin Hall effect is dramatically enhanced, and the
associated transverse spin currents can be reversed.",1403.1251v2
1998-02-13,Spin and orbital excitations in magnetic insulators with Jahn-Teller ions,"The elementary excitations of a model Hamiltonian that captures the low
energy behavior of a simple two-fold degenerate Hubbard Hamiltonian with Hund's
rule coupling, is studied. The phase diagram in the mean-field limit and in a
two-site approach reveals a rich variety of phases where both the orbital and
the spin degrees of freedom are ordered. We show that besides usual spin waves
(magnons) there exist also orbital waves (orbitons) and, most interestingly, in
a completely ferromagnetically coupled system, a combined spin-orbital
excitation which can be visualized as a bound state of magnons and orbitons.
For a completely degenerate system the bound states are found to be the lowest
lying elementary excitations, both in one- and two-dimensions. Finally we
extend our treatment to almost-degenerate systems. This can serve as an example
that the elementary excitations in orbitally degenerate strongly correlated
electron systems in general carry both spin and orbital character.",9802146v1
2007-01-09,Direct Measurement of the Spin-Orbit Interaction in a Two-Electron InAs Nanowire Quantum Dot,"We demonstrate control of the electron number down to the last electron in
tunable few-electron quantum dots defined in catalytically grown InAs
nanowires. Using low temperature transport spectroscopy in the Coulomb blockade
regime we propose a simple method to directly determine the magnitude of the
spin-orbit interaction in a two-electron artificial atom with strong spin-orbit
coupling. Due to a large effective g-factor |g*|=8+/-1 the transition from
singlet S to triplet T+ groundstate with increasing magnetic field is dominated
by the Zeeman energy rather than by orbital effects. We find that the
spin-orbit coupling mixes the T+ and S states and thus induces an avoided
crossing with magnitude $\Delta_{SO}$=0.25+/-0.05 meV. This allows us to
calculate the spin-orbit length $\lambda_{SO}\approx$127 nm in such systems
using a simple model.",0701161v1
2009-11-11,Orbitally controlled Kondo effect of Co ad-atoms on graphene,"Based on ab-initio calculations we identify possible scenarios for the Kondo
effect due to Co ad-atoms on graphene. General symmetry arguments show that for
magnetic atoms in high-symmetry positions, the Kondo effect in graphene is
controlled not only by the spin but also by the orbital degree of freedom. For
a Co atom absorbed on top of a carbon atom, the Kondo effect is quenched by
spin-orbit coupling below an energy scale of $\sim 15$\,K. For Co with spin
$S=1/2$ located in the center of a hexagon, an SU(4) Kondo model describes the
entanglement of orbital moment and spin at higher energies, while below \sim
60$\,meV spin-orbit coupling leads to a more conventional SU(2) Kondo effect.
The interplay of the orbital Co physics and the peculiar band-structure of
graphene is directly accessible in Fourier transform tunneling spectroscopy or
in the gate-voltage dependence of the Kondo temperature displaying a very
strong, characteristic particle-hole asymmetry.",0911.2103v2
2011-03-21,Spin-orbit coupling and the conservation of angular momentum,"In nonrelativistic quantum mechanics, the total (i.e. orbital plus spin)
angular momentum of a charged particle with spin that moves in a Coulomb plus
spin-orbit-coupling potential is conserved. In a classical nonrelativistic
treatment of this problem, in which the Lagrange equations determine the
orbital motion and the Thomas equation yields the rate of change of the spin,
the particle's total angular momentum in which the orbital angular momentum is
defined in terms of the kinetic momentum is generally not conserved. However, a
generalized total angular momentum, in which the orbital part is defined in
terms of the canonical momentum, is conserved. This illustrates the fact that
the quantum-mechanical operator of momentum corresponds to the canonical
momentum of classical mechanics.",1103.4092v3
2014-07-13,A Renormalization-Group Study of the Symmetry-Breaking Order Parameters in Spin-Orbit Coupled Iridates and Related Systems,"We study the competition between various forms of density-wave-like order
parameters that may arise in multi-orbital correlated materials with strong
spin-orbit coupling (SOC) within a renormalization-group (RG) approach. The
calculations are restricted to models with two spin-orbit split bands having
strong inter-band Fermi surface nesting. We find that for such Fermi surface
topology, the interplay between the inter-band nesting and SOC strongly
enhances the inter-orbital Coulomb interaction (relative to other interactions)
as the system approaches a stable fixed point. This results in an exotic
spin-orbit density wave (SODW) to become the energetically favorable
symmetry-broken state. While the conclusions are generic to such a Fermi
surface topology, the band structure and the numerical results are presented
for the iridate systems. We also find that the electronic fingerprints of the
SODW are in better agreement with various experimental results than a
conventional spin density wave (SDW), explaining the long-standing problem of
the origin of the metal-insulator transition in these systems.",1407.3440v1
2020-07-19,Interfacial Dzyaloshinskii-Moriya interaction and spin-orbit torque in Au1-xPtx/Co bilayers with varying interfacial spin-orbit coupling,"The quantitative roles of the interfacial spin-orbit coupling (SOC) in
Dzyaloshinskii-Moriya interaction (DMI) and dampinglike spin-orbit torque
({\tau}DL) have remained unsettled after a decade of intensive study. Here, we
report a conclusive experiment evidence that, because of the critical role of
the interfacial orbital hybridization, the interfacial DMI is not necessarily a
linear function of the interfacial SOC, e.g. at Au1-xPtx/Co interfaces where
the interfacial SOC can be tuned significantly via strongly composition
(x)-dependent spin-orbit proximity effect without varying the bulk SOC and the
electronegativity of the Au1-xPtx layer. We also find that {\tau}DL in the
Au1-xPtx/Co bilayers varies distinctly from the interfacial SOC as a function
of x, indicating no important {\tau}DL contribution from the interfacial
Rashba-Edelstein effect.",2007.09817v2
2018-08-16,Gigantic intrinsic orbital Hall effects in weakly spin-orbit coupled metals,"A recent paper [Go $\textit{et al}$., Phys. Rev. Lett. $\textbf{121}$, 086602
(2018)] proposed that the intrinsic orbital Hall effect (OHE) can emerge from
momentum-space orbital texture in centrosymmetric materials. In searching for
real materials with strong OHE, we investigate the intrinsic OHE in metals with
small spin-orbit coupling (SOC) in face-centered cubic and body-centered cubic
structures (Li, Al, V, Cr, Mn, Ni, and Cu). We find that orbital Hall
conductivities (OHCs) in these materials are gigantic $\sim 10^3-10^4\
(\hbar/e)(\Omega\cdot\mathrm{cm})^{-1}$, which are comparable or larger than
spin Hall conductivity (SHC) of Pt. Although SHCs in these materials are
smaller than OHCs due to small SOC, we found that SHCs are still sizable and
the spin Hall angles may be of the order of 0.1. We discuss implications on
recent spin-charge interconversion experiments on materials having small SOC.",1808.05546v3
2020-10-19,Human psychophysical discrimination of spatially dependant Pancharatnam-Berry phases in optical spin-orbit states,"We tested the ability of human observers to discriminate distinct profiles of
spatially dependant geometric phases when directly viewing stationary
structured light beams. Participants viewed polarization coupled orbital
angular momentum (OAM) states, or ``spin-orbit'' states, in which the OAM was
induced through Pancharatnam-Berry phases. The coupling between polarization
and OAM in these beams manifests as spatially dependant polarization. Regions
of uniform polarization are perceived as specifically oriented Haidinger's
brushes, and study participants discriminated between two spin-orbit states
based on the rotational symmetry in the spatial orientations of these brushes.
Participants used self-generated eye movements to prevent adaptation to the
visual stimuli. After initial training, the participants were able to correctly
discriminate between two spin-orbit states, differentiated by OAM $=\pm1$, with
an average success probability of $69\%$ ($S.D. = 22\%$, $p = 0.013$). These
results support our previous observation that human observers can directly
perceive spin-orbit states, and extend this finding to non-rotating beams, OAM
modes induced via Pancharatnam-Berry phases, and the discrimination of states
that are differentiated by OAM.",2010.09619v1
2020-05-30,Experimental analysis of the spin-orbit coupling dependence on the drift velocity of a spin packet,"Spin transport was studied in a two-dimensional electron gas hosted in a wide
GaAs quantum well occupying two subbands. Using space and time Kerr rotation
microscopy to image drifting spin packets under an in-plane accelerating
electric field, optical injection and detection of spin polarization were
achieved in a pump-probe configuration. The experimental data exhibited high
spin mobility and long spin lifetimes allowing to obtain the spin-orbit fields
as a function of the spin velocities. Surprisingly, above moderate electric
fields of 0.4V/cm with velocities higher than 2$\mu$m/ns, we observed a
dependence of both bulk and structure-related spin-orbit interactions on the
velocity magnitude. A remarkable feature is the increase of the cubic
Dresselhaus term to approximately half of the linear coupling when the velocity
is raised to 10$\mu$m/ns. In contrast, the Rashba coupling for both subbands
decreases to about half of its value in the same range. These results yield new
information for the application of drift models in spin-orbit fields and about
limitations for the operation of spin transistors.",2006.00309v2
2022-04-26,Probing details of spin--orbit coupling through Pauli spin blockade,"Spin--orbit interaction (SOI) plays a fundamental role in many
low-dimensional semiconductor and hybrid quantum devices. In the rapidly
evolving field of semiconductor spin qubits, SOI is an essential ingredient
that can allow for ultrafast qubit control. The exact manifestation of SOI in a
given device is, however, often both hard to predict theoretically and probe
experimentally. Here, we develop a detailed theoretical connection between the
leakage current through a double quantum dot in Pauli spin blockade and the
underlying SOI in the system. We present a general analytic expression for the
leakage current, which allows to connect experimentally observable features to
both the magnitude and orientation of the effective spin--orbit field acting on
the moving carriers. Motivated by the large recent interest in hole-based
quantum devices, we further zoom in on the case of Pauli blockade of hole
spins, assuming a strong transverse confinement potential. In this limit we
also find an analytic expression for the current at low external magnetic
field, that includes the effect of hyperfine coupling of the hole spins to
randomly fluctuating nuclear spin baths. This result can be used to extract
detailed information about both hyperfine and spin--orbit coupling parameters
for hole spins in devices with a significant fraction of non-zero nuclear
spins.",2204.12546v1
2017-07-10,Theory of in-plane current induced spin torque in metal/ferromagnet bilayers,"Using a semiclassical approach that simultaneously incorporates the spin Hall
effect (SHE), spin diffusion, quantum well states, and interface spin-orbit
coupling (SOC), we address the interplay of these mechanisms as the origin of
the in-plane current induced spin torque observed in the normal
metal/ferromagnetic metal bilayer thin films. Focusing on the bilayers with a
ferromagnet much thinner than its spin diffusion length, such as Pt/Co with
$\sim 10$nm thickness, our approach addresses simultaneously the two
contributions to the spin torque, namely the spin-transfer torque (SHE-STT) due
to SHE induced spin injection, and the spin-orbit torque (SOT) due to SOC
induced spin accumulation. The SOC produces an effective magnetic field at the
interface, hence it modifies the angular momentum conservation expected for the
SHE-STT. The SHE induced spin voltage and the interface spin current are
mutually dependent, hence are solved in a self-consistent manner. In addition,
the spin transport mediated by the quantum well states may be responsible for
the experimentally observed rapid variation of the spin torque with respect to
the thickness of the ferromagnet.",1707.02771v1
2013-07-17,"Anisotropic Quantum Spin Hall Effect, Spin-Orbital Textures and Mott Transition","We investigate the interplay between topological effects and Mott physics in
two dimensions on a graphene-like lattice, via a tight-binding model containing
an anisotropic spin-orbit coupling on the next-nearest-neighbour links and the
Hubbard interaction. We thoroughly analyze the resulting phases, namely a
topological band insulator phase or anisotropic quantum Spin Hall phase until
moderate interactions, a N\'eel and Spiral phase at large interactions in the
Mott regime, as well as the formation of a spin-orbital texture in the bulk at
the Mott transition. The emergent magnetic orders at large interactions are
analyzed through a spin wave analysis and mathematical arguments. At weak
interactions, by analogy with the Kane-Mele model, the system is described
through a Z_2 topological invariant. In addition, we describe how the
anisotropic spin-orbit coupling already produces an exotic spin texture at the
edges. The physics at the Mott transition is described in terms of a U(1) slave
rotor theory. Taking into account gauge fluctuations around the mean-field
saddle point solution, we show how the spin texture now proliferates into the
bulk above the Mott critical point. The latter emerges from the response of the
spinons under the insertion of monopoles and this becomes more pronounced as
the spin-orbit coupling becomes prevalent. We discuss implications of our
predictions for thin films of the iridate compound Na2IrO3 and also
graphene-like systems.",1307.4597v2
2015-08-31,Interaction driven exotic quantum phases in spin-orbit coupled spin$-1$ bosons,"We study the interplay between large-spin, spin-orbit coupling, and
superfluidity for bosons in a two dimensional optical lattice, focusing on the
spin-1 spin-orbit coupled system recently realized at the Joint Quantum
Institute [Campbell et. al., arXiv:1501.05984]. We find a rich quantum phase
diagram, where, in addition to the conventional phases ---superfluid and
insulator--- contained in the spin-$1$ Bose-Hubbard model, there are new
lattice symmetry breaking phases. For weak interactions, the interplay between
two length scales, the lattice momentum and the spin-orbit wave-vector induce a
phase transition from a uniform superfluid to a phase where bosons
simultaneously condense at the center and edge of the Brillouin zone at a
non-zero spin-orbit strength. This state is characterized by spin density wave
order, which arises from the spin-$1$ nature of the system. Interactions
suppress spin density wave order, and favor a superfluid \textit{only} at the
Brillouin zone edge. This state has spatially oscillating mean field order
parameters, but a homogeneous density. We show that the spin density wave
superfluid phase survives in a two dimensional harmonic trap, and thus
establish that our results are directly applicable to experiments on $^{87}$Rb,
$^7$Li, and $^{41}$K.",1509.00005v2
2015-01-03,Unconventional symmetries of Fermi liquid and Cooper pairing properties with electric and magnetic dipolar fermions,"The rapid experimental progress of ultra-cold dipolar fermions opens up a
whole new opportunity to investigate novel many-body physics of fermions. In
this article, we review theoretical studies of the Fermi liquid theory and
Cooper pairing instabilities of both electric and magnetic dipolar fermionic
systems from the perspective of unconventional symmetries. When the electric
dipole moments are aligned by the external electric field, their interactions
exhibit the explicit $d_{r^2-3z^2}$ anisotropy. The Fermi liquid properties,
including the single-particle spectra, thermodynamic susceptibilities, and
collective excitations, are all affected by this anisotropy. The electric
dipolar interaction provides a mechanism for the unconventional spin triplet
Cooper pairing, which is different from the usual spin-fluctuation mechanism in
solids and the superfluid $^3$He. Furthermore, the competition between pairing
instabilities in the singlet and triplet channels gives rise to a novel
time-reversal symmetry breaking superfluid state. Unlike electric dipole
moments which are induced by electric fields and unquantized, magnetic dipole
moments are intrinsic proportional to the hyperfine-spin operators with a Lande
factor. Its effects even manifest in unpolarized systems exhibiting an
isotropic but spin-orbit coupled nature. The resultant spin-orbit coupled Fermi
liquid theory supports a collective sound mode exhibiting a topologically
non-trivial spin distribution over the Fermi surface. It also leads to a novel
$p$-wave spin triplet Cooper pairing state whose spin and orbital angular
momentum are entangled to the total angular momentum $J=1$ dubbed the
$J$-triplet pairing. This $J$-triplet pairing phase is different from both the
spin-orbit coupled $^3$He-$B$ phase with $J=0$ and the spin-orbit decoupled
$^3$He-$A$ phase.",1501.00540v1
2003-11-03,Dissipationless Spin Current in Anisotropic p-Doped Semiconductors,"Recently, dissipationless spin current has been predicted for the p-doped
semiconductors with spin-orbit coupling. Here we investigate the effect of
spherical symmetry breaking on the dissipationless spin current, and obtain
values of the intrinsic spin Hall conductivity for realistic semiconductor band
structures with cubic symmetry.",0311024v2
2008-12-09,Spin-Wave Relaxation in a Quantum Hall Ferromagnet,"We study spin wave relaxation in quantum Hall ferromagnet regimes. Spin-orbit
coupling is considered as a factor determining spin nonconservation, and
external random potential as a cause of energy dissipation making spin-flip
processes irreversible. We compare this relaxation mechanism with other
relaxation channels existing in a quantum Hall ferromagnet.",0812.1703v1
1999-08-17,Numerical Study of the One-Dimensional Spin-Orbit Coupled System with SU(2)$\otimes$SU(2) Symmetry,"We numerically study the SU(2)$\otimes$SU(2) symmetric spin-orbit coupled
model as a lower symmetric generalization of the SU(4) exchange model. On the
symmetric line with respect to the spin and orbit, our result shows the
essentially singular gap formation in consistent with the analytic approach,
which is different from the previous numerical calculation. Furthermore, we
find new critical phases around the SU(4) point, surrounding the previously
known gapless symmetric line. In these novel phases either spin or orbital
excitations around momentum $q=\pi$ form massless continua which split from the
excitations belonging to the $[2^2]$ irreducible representation at the SU(4)
point. On the critical symmetric line, the additional coupled spin-orbit
excitations around $q=\pi/2$ originating from [$2^11^2$] become critical, too.",9908237v1
2002-06-19,Gate-Controlled Spin-Orbit Quantum Interference Effects in Lateral Transport,"In situ control of spin-orbit coupling in coherent transport using a clean
GaAs/AlGaAs 2DEG is realized, leading to a gate-tunable crossover from weak
localization to antilocalization. The necessary theory of 2D magnetotransport
in the presence of spin-orbit coupling beyond the diffusive approximation is
developed and used to analyze experimental data. With this theory the Rashba
contribution and linear and cubic Dresselhaus contributions to spin-orbit
coupling are separately estimated, allowing the angular dependence of
spin-orbit precession to be extracted at various gate voltages.",0206375v4
2004-10-16,Phase transitions in spin-orbital coupled model for pyroxene titanium oxides,"We study the competing phases and the phase transition phenomena in an
effective spin-orbital coupled model derived for pyroxene titanium oxides
ATiSi2O6 (A=Na, Li). Using the mean-field-type analysis and the numerical
quantum transfer matrix method, we show that the model exhibits two different
ordered states, the spin-dimer and orbital-ferro state and the spin-ferro and
orbital-antiferro state. The transition between two phases is driven by the
relative strength of the Hund's-rule coupling to the onsite Coulomb repulsion
and/or by the external magnetic field. The ground-state phase diagram is
determined. There is a keen competition between orbital and spin degrees of
freedom in the multicritical regime, which causes large fluctuations and
significantly affects finite-temperature properties in the paramagnetic phase.",0410411v1
2008-04-21,Anisotropic plasmons in a two-dimensional electron gas with spin-orbit interaction,"Spin-orbit coupling induced anisotropies of plasmon dynamics are investigated
in two-dimensional semiconductor structures. The interplay of the linear
Bychkov-Rashba and Dresselhaus spin-orbit interactions drastically affects the
plasmon spectrum: the dynamical structure factor exhibits variations over
several decades, prohibiting plasmon propagation in specific directions. While
this plasmon filtering makes the presence of spin-orbit coupling in plasmon
dynamics observable, it also offers a control tool for plasmonic devices.
Remarkably, if the strengths of the two interactions are equal, not only the
anisotropy, but all the traces of the linear spin-orbit coupling in the
collective response disappear.",0804.3366v3
2015-09-14,Spin Orbit Coupling in Graphene Induced by Heavy Adatoms with Electrons in the Outer-Shell $p$ Orbitals,"Many of the exotic properties proposed to occur in graphene rely on the
possibility of increasing the spin orbit coupling (SOC). By combining
analytical and numerical tight binding calculations, in this work we study the
SOC induced by heavy adatoms with active electrons living in $p$ orbitals.
Depending on the position of the adatoms on graphene different kinds of SOC
appear. Adatoms located in hollow position induce spin conserving intrinsic
like SOC whereas a random distribution of adatoms induces a spin flipping
Rashba like SOC. The induced SOC is linearly proportional to the adatoms
concentration, indicating the inexistent interference effects between different
adatoms. By computing the Hall conductivity we have proved the stability of the
topological quantum Hall phases created by the adatoms against inhomogeneous
spin orbit coupling . For the case of Pb adatoms, we find that a concentration
of 0.1 adatom per carbon atom generates SOC's of the order of $\sim$40$meV$.",1509.04024v1
2017-03-22,Anisotropy of transport in bulk Rashba metals,"The recent experimental discovery of three-dimensional (3D) materials hosting
a strong Rashba spin-orbit coupling calls for the theoretical investigation of
their transport properties. Here we study the zero temperature dc conductivity
of a 3D Rashba metal in the presence of static diluted impurities. We show
that, at variance with the two-dimensional case, in 3D systems spin-orbit
coupling affects dc charge transport in all density regimes. We find in
particular that the effect of spin-orbit interaction strongly depends on the
direction of the current, and we show that this yields strongly anisotropic
transport characteristics. In the dominant spin-orbit coupling regime where
only the lowest band is occupied, the SO-induced conductivity anisotropy is
governed entirely by the anomalous component of the renormalized current. We
propose that measurements of the conductivity anisotropy in bulk Rashba metals
may give a direct experimental assessment of the spin-orbit strength.",1703.07701v2
2018-05-22,Spin-orbit torque in completely compensated synthetic antiferromagnet,"Synthetic antiferromagnets (SAF) have been proposed to replace ferromagnets
in magnetic memory devices to reduce the stray field, increase the storage
density and improve the thermal stability. Here we investigate the spin-orbit
torque in a perpendicularly magnetized Pt/[Co/Pd]/Ru/[Co/Pd] SAF structure,
which exhibits completely compensated magnetization and an exchange coupling
field up to 2100 Oe. The magnetizations of two Co/Pd layers can be switched
between two antiparallel states simultaneously by spin-orbit torque. The
magnetization switching can be read out due to much stronger spin-orbit
coupling at bottom Pt/[Co/Pd] interface compared to its upper counterpart
without Pt. Both experimental and theoretical analyses unravel that the torque
efficiency of antiferromagnetic coupled stacks is significantly higher than the
ferromagnetic counterpart, making the critical switching current of SAF
comparable to the conventional single ferromagnet. Besides adding an important
dimension to spin-orbit torque, the efficient switching of completely
compensated SAF might advance magnetic memory devices with high density, high
speed and low power consumption.",1805.08486v2
2023-01-27,Non-Lifshitz invariants corrections to Dzyaloshinskii-Moriya interaction energy,"We study the continuum limit of two-dimensional chiral magnets in which
Dzyaloshinskii-Moriya interaction (DMI) is due to the interplay between a
smooth magnetic texture and spin-orbit coupling. The resulting free-energy
density of the system contains linear terms in the spatial gradient of the
magnetic texture, which mark an instability of the system towards the formation
of nontrivial magnetic orders such as skyrmions or chiral domain walls. We
perform a microscopic analysis of DMI tensors responsible for this contribution
to free energy based on a Berry phase formulation in the mixed space of
momentum and position, and reveal that they exhibit non-Lifshitz invariants
features. In particular, a perturbation theory shows in the case of Rashba
spin-orbit interactions the presence of non-Lifshitz invariants to third order
in the small spin-orbit interaction and fourth order in the small exchange
coupling. The higher-order terms may even lead to an enhancement of DMI
interaction at strong spin-orbit coupling due to divergences in the density of
states at the bottom of the conduction band. Finally, we also study the DMI
free energy generated from Rashba spin-orbit interaction in different symmetry
groups.",2301.11855v2
2010-08-11,Strong and Tunable Spin-Orbit Coupling of One-Dimensional Holes in Ge/Si Core/Shell Nanowires,"We investigate the low-temperature magneto-transport properties of individual
Ge/Si core/shell nanowires. Negative magneto-conductance was observed, which is
a signature of one-dimensional weak antilocalization of holes in the presence
of strong spin-orbit coupling. The temperature and back gate dependences of
phase coherence length, spin-orbit relaxation time, and background conductance
were studied. Specifically, we show the spin-orbit coupling strength can be
modulated by more than five folds with an external electric field. These
results suggest the Ge/Si nanowire system possesses strong and tunable
spin-orbit interactions and may serve as a candidate for spintronics
applications.",1008.1882v1
2014-01-06,Engineering spin-orbital magnetic insulator by tailoring superlattices,"Novel interplay of spin-orbit coupling and electron correlations in complex
Ir oxides recently emerged as a new paradigm for correlated electron physics.
Because of a large spin-orbit coupling of ~0.5 eV, which is comparable to the
transfer energy t and the crystal field splitting $\Delta$ and Coulomb U, a
variety of ground states including magnetic insulator, band insulator,
semimetal and metal, shows up in a narrow materials phase space. Utilizing such
subtle competition of the ground states, we successfully tailor a spin-orbital
magnetic insulator out of a semimetal SrIrO$_3$ by controlling dimensionality
using superlattice of [(SrIrO$_3$)$_m$, SrTiO$_3$] and show that a magnetic
ordering triggers the transition to magnetic insulator. Those results can be
described well by a first-principles calculation. This study is an important
step towards the design and the realization of topological phases in complex Ir
oxides with very strong spin-orbit coupling.",1401.1066v1
2015-03-20,Topological states in multi-orbital HgTe honeycomb lattices,"Research on graphene has revealed remarkable phenomena arising in the
honeycomb lattice. However, the quantum spin Hall effect predicted at the K
point could not be observed in graphene and other honeycomb structures of light
elements due to an insufficiently strong spin-orbit coupling. Here we show
theoretically that 2D honeycomb lattices of HgTe can combine the effects of the
honeycomb geometry and strong spin-orbit coupling. The conduction bands,
experimentally accessible via doping, can be described by a tight-binding
lattice model as in graphene, but including multi-orbital degrees of freedom
and spin-orbit coupling. This results in very large topological gaps (up to 35
meV) and a flattened band detached from the others. Owing to this flat band and
the sizable Coulomb interaction, honeycomb structures of HgTe constitute a
promising platform for the observation of a fractional Chern insulator or a
fractional quantum spin Hall phase.",1503.06066v1
2020-02-27,Electric control of spin orbit coupling in graphene-based nanostructures with broken rotational symmetry,"Spin and angular momenta of light are important degrees of freedom in
nanophotonics which control light propagation, optical forces and information
encoding. Typically, optical angular momentum is generated using q-plates or
spatial light modulators. Here, we show that graphene-supported plasmonic
nanostructures with broken rotational symmetry provide a surprising spin to
orbital angular momentum conversion, which can be continuously controlled by
changing the electrochemical potential of graphene. Upon resonant illumination
by a circularly polarized plane wave, a polygonal array of indium-tin-oxide
nanoparticles on a graphene sheet generates scattered field carrying
electrically-tunable orbital angular momentum. This unique photonic spin-orbit
coupling occurs due to the strong coupling of graphene plasmon polaritons and
localised surface plasmons of the nanoparticles and leads to the controlled
directional excitation of graphene plasmons. The tuneable spin-orbit conversion
pave the way to high-rate information encoding in optical communications,
electric steering functionalities in optical tweezers, and nanorouting of
higher-dimensional entangled photon states.",2002.12058v1
2024-03-09,Hybrid Spin-Orbit Exciton-Magnon Excitations in FePS$_3$,"FePS$_3$ is a layered van der Waals (vdW) Ising antiferromagnet that has
recently been studied in the context of true 2D magnetism, and emerged as an
ideal material platform for investigating strong spin-phonon coupling, and
non-linear magneto-optical phenomena. In this work, we demonstrate an important
unresolved role of spin-orbit coupling (SOC) in the ground state and
excitations of this compound. Combining first principles calculations with
Linear Flavor Wave Theory (LFWT), we find strong mixing and spectral overlap of
different spin-orbital single-ion states. As such, the low-lying excitations
form complex mixtures of local degrees of freedom most accurately viewed as
hybrid spin-orbit exciton-magnon modes. Complete parameterization of the
resulting low-energy model including all such degrees of freedom requires
nearly half a million coupling constants. Despite this complexity, we show that
such a model can be inexpensively derived using local many-body-based
approaches, which yield quantitative agreement with recent experiments. The
results highlight the importance of SOC even in first row transition metals,
and provide essential insight into the properties of 2D magnets with unquenched
orbital moments.",2403.05958v1
2002-03-27,Electron Double Refraction in Hybrid Systems with Rashba Spin-Orbit Coupling,"We study the scattering of an electron in a definite state of spin at an
interface of an hybrid system with a Rashba spin-orbit coupling on one side.
Out of the normal incidence the double refraction phenomenon appears, with one
or two limit angles for the total reflection. We show that this double
refraction gives rise to a spin-dependent conductance of a Quantum Point
Contact separating a ferromagnet and a two dimensional electron gas. The
birefringence allows the spin filtering with a single interface.",0203569v2
2004-08-20,Spin Splitting and Spin Current in Strained Bulk Semiconductors,"We present a theory for two recent experiments in bulk strained
semiconductors \cite{kato1, kato2} and show that a new, previously overlooked,
strain spin-orbit coupling term may play a fundamental role. We propose simple
experiments that could clarify the origin of strain-induced spin-orbit coupling
terms in inversion asymmetric semiconductors. We predict that a uniform
magnetization parallel to the electric field will be induced in the samples
studied in \cite{kato1, kato2} for specific directions of the applied electric
field. We also propose special geometries to detect spin currents in strained
semiconductors.",0408442v1
2006-02-23,Two-dimensional electron scattering in regions of nonuniform spin-orbit coupling,"We present a theoretical study of elastic spin-dependent electron scattering
caused by a nonuniform Rashba spin-orbit coupling strength. Using the
spin-generalized method of partial waves the scattering amplitude is exactly
derived for the case of a circular shape of scattering region. We found that
the polarization of the scattered waves are strongly anisotropic functions of
the scattering angle. This feature can be utilized to design a good
all-electric spin-polarizer. General properties of the scattering process are
also investigated in the high and low energy limits.",0602560v1
2006-03-06,Edge states generated by spin-orbit coupling at domain walls in magnetic semiconductors,"Electronic states localized at domain walls between ferromagnetically ordered
phases in two-dimensional electron systems are generated by moderate spin-orbit
coupling. The spin carried by these states depends on the slope of the magnetic
background at the domain wall. The number of localized states is determined by
a real space topological number, and spin perpendicular to the ferromagnetic
order accumulates in these localized states at domain walls. These trapped
states may be observed in experiments that probe either spin density or
conduction paths in quantum wells.",0603145v3
2007-02-03,Two dimensional electron liquid in the presence of Rashba spin-orbit coupling: symmetric momentum space occupation states,"The orientation of the local electron spin quantization axis in momentum
space is identified as the most significant physical variable in determining
the states of a two-dimensional electron liquid in the presence of Rashba
spin-orbit coupling. Within mean field theory several phases can be identified
that are characterized by a simple symmetric momentum space occupation. The
problem admits uniform paramagnetic as well as spin polarized chiral solutions.
The latter have a nontrivial spin texture in momentum space and are constructed
out of states that are not solutions of the non interacting Hamiltonian. The
concept of generalized chirality as well as the stability of spatially
homogeneous states are also discussed.",0702060v1
2007-12-23,Spin-orbit coupling in bulk GaAs,"We study the spin-orbit coupling in the whole Brillouin zone for GaAs using
both the $sp^3s^{\ast}d^5$ and $sp^3s^{\ast}$ nearest-neighbor tight-binding
models. In the $\Gamma$-valley, the spin splitting obtained is in good
agreement with experimental data. We then further explicitly present the
coefficients of the spin splitting in GaAs $L$ and $X$ valleys. These results
are important to the realization of spintronic device and the investigation of
spin dynamics far away from equilibrium.",0712.3890v3
2008-10-19,A scheme for spin transistor with extremely large on/off current ratio,"Quantum wires with periodic local Rashba spin-orbit couplings are proposed
for a higher performance of spin field-effect transistor. Fano-Rashba quantum
interference due to the spin-dependent modulated structure gives rise to a
broad energy range of vanishingly small transmission. Tuning Rashba spin-orbit
couplings can provide the on- or off-currents with extremely large on/off
current ratios even in the presence of a strong disorder.",0810.3319v2
2009-09-08,Inverse Spin Hall Effect in SNS Josephson Junctions,"We consider DC supercurrents in SNS junctions. Spin-orbit coupling in
combination with Zeeman fields can induce an effective vector potential in the
normal conductor. As a consequence, an out-of-plane spin-density varying along
the transverse direction causes a longitudinal phase difference between the
superconducting terminals. The resulting equilibrium phase coherent
supercurrent is analogue to the non-equilibrium inverse spin Hall effect in
normal conductors. We explicitly compute the effect for the Rashba spin orbit
coupling in a disordered two-dimensional electron gas with an inhomogeneous
perpendicular Zeeman field.",0909.1416v1
2010-09-30,Spin Texture in Quantum Point Contacts in the Presence of Lateral Spin Orbit Coupling,"A non-equilibrium Green's function formalism is used to study in detail the
ballistic conductance of asymmetrically biased side-gated quantum point
contacts (QPCs) in the presence of lateral spin-orbit coupling and
electron-electron interaction for a wide range of QPC dimensions and gate bias
voltage. Various conductance anomalies are predicted below the first quantized
conductance plateau (G0=2e2/h) which occur due to spontaneous spin polarization
in the narrowest portion of the QPC. The number of observed conductance
anomalies increases with increasing aspect ratio (length/width) of the QPC
constriction. These anomalies are fingerprints of spin textures in the narrow
portion of the QPC.",1009.6211v1
2011-05-23,Persistent spin oscillations in a spin-orbit-coupled superconductor,"Quasi-two-dimensional superconductors with tunable spin-orbit coupling are
very interesting systems with properties that are also potentially useful for
applications. In this manuscript we demonstrate that these systems exhibit
undamped collective spin oscillations that can be excited by the application of
a supercurrent. We propose to use these collective excitations to realize
persistent spin oscillators operating in the frequency range of 10 GHz - 1 THz.",1105.4451v2
2011-06-22,Anisotropic super-spin at the end of a carbon nanotube,"Interaction-induced magnetism at the ends of carbon nanotubes is studied
theoretically, with a special focus on magnetic anisotropies. Spin-orbit
coupling, generally weak in ordinary graphene, is strongly enhanced in
nanotubes. In combination with Coulomb interactions, this enhanced spin-orbit
coupling gives rise to a super-spin at the ends of carbon nanotubes with an XY
anisotropy on the order of 10 mK. Furthermore, it is shown that this anisotropy
can be enhanced by more than one order of magnitude via a partial suppression
of the super-spin.",1106.4549v1
2011-07-21,Metal-Mott Insulator Transition and Spin Exchange of Two-Component Fermi Gas with Spin-Orbit Coupling in Two-Dimension Square Optical Lattices,"Effects of spin-orbit coupling (SOC) on metal-Mott insulator transition
(MMIT) and spin exchange physics (SEP) of two-component Fermi gases in
two-dimension half-filling square optical lattices are investigated. In the
frame of Kotliar and Ruckenstein slave boson and the second order perturbation
theory, the phase boundary of paramagnetic MMIT and spin exchange Hamiltonian
are calculated. In addition by adopting two mean-field ansatzs including
antiferromagnetic, ferromagnetic and spiral phases, we find that SOC can drive
a quantum phase transition from antiferromagnet to spiral phase.",1107.4213v2
2012-02-02,Spin-dependent electron transport in waveguide with continuous shape,"We study effects of the shape of a two-dimensional waveguide on the
spin-dependent electron transport in the presence of spin-orbit coupling. The
transition from classical motion to the tunneling regime can be controlled
there by modulating the strength of spin-orbit coupling if the waveguide has a
constriction. The spin precession strongly depends on the shape of the
waveguide.",1202.0541v1
2012-02-29,Inverse Spin Hall Effect in Ferromagnetic Metal with Rashba Spin Orbit Coupling,"We report an intrinsic form of the inverse spin Hall effect (ISHE) in
ferromagnetic (FM) metal with Rashba spin orbit coupling (RSOC), which is
driven by a normal charge current. Unlike the conventional form, the ISHE can
be induced without the need for spin current injection from an external source.
Our theoretical results show that Hall voltage is generated when the FM moment
is perpendicular to the ferromagnetic layer. The polarity of the Hall voltage
is reversed upon switching the FM moment to the opposite direction, thus
promising a useful readback mechanism for memory or logic applications.",1202.6428v1
2013-02-14,Spin-Hall Conductivity and Electric Polarization in Metallic Thin Films,"We predict theoretically that, when a normal metallic thin film (without bulk
spin-orbit coupling, such as Cu or Al) is sandwiched by two insulators, two
prominent effects arise due to the interfacial spin-orbit coupling: a giant
spin-Hall conductivity due to the surface scattering and a transverse electric
polarization due to the spin-dependent phase shift in the spinor wave
functions.",1302.3490v2
2013-12-06,Charge and spin current in a quasi-one-dimensional quantum wire with spin-orbit coupling,"We show that Rashba spin-orbit coupling may result in an energy gap in the
spectrum of electrons in a two-mode quantum wire if a suitable confining
potential is chosen. This leads to a dip in the conductance and a spike in the
spin current at the corresponding position of the Fermi level. Therefore one
may control the charge and spin currents by means of electrostatic gates
without using magnetic field or magnetic materials.",1312.1980v2
2014-01-10,Antiferromagnetic Order in a Semiconductor Quantum Well with Spin-Orbit Coupling,"An argument is made on the existence of a low-temperature itinerant
antiferromagnetic (AF) spin alignment, rather than persistent helical (PH), in
the ground state of a two dimensional electron gas in a semiconductor quantum
well with linear spin-orbit Rashba-Dresselhaus interaction at equal coupling
strengths, $\alpha$. This result is obtained on account of the opposite-spin
single-particle state degeneracy at $\mb k = 0$ that makes the spin instability
possible. A theory of the resulting magnetic phase is formulated within the
Hartree-Fock approximation of the Coulomb interaction. In the AF state the
direction of the fractional polarization is obtained to be aligned along the
displacement vector of the single-particle states.",1401.2427v1
2015-02-06,Microscopic theory of Gilbert damping in metallic ferromagnets,"We present a microscopic theory for magnetization relaxation in metallic
ferromagnets of nanoscopic dimensions that is based on the dynamic spin
response matrix in the presence of spin-orbit coupling. Our approach allows the
calculation of the spin excitation damping rate even for perfectly crystalline
systems, where existing microscopic approaches fail. We demonstrate that the
relaxation properties are not completely determined by the transverse
susceptibility alone, and that the damping rate has a non-negligible frequency
dependence in experimentally relevant situations. Our results indicate that the
standard Landau-Lifshitz-Gilbert phenomenology is not always appropriate to
describe spin dynamics of metallic nanostructure in the presence of strong
spin-orbit coupling.",1502.02068v1
2015-08-14,Proximity-induced triplet superconductivity in Rashba materials,"We study a proximity junction between a conventional s-wave superconductor
and a conductor with Rashba spin-orbit coupling, with a specific focus on the
spin structure of the induced pairing amplitude. We find that spin-triplet
pairing correlations are induced by spin-orbit coupling in both one- and
two-dimensional systems due to the lifted spin degeneracy. Additionally, this
induced triplet pairing has a component with an odd frequency dependence that
is robust to disorder. Our predictions are based on the solutions of the exact
Gor'kov equations and are beyond the quasiclassical approximation.",1508.03623v2
2018-02-02,Unique Spin Vortices in Quantum Dots with Spin-orbit Couplings,"Spin textures of one or two electrons in a quantum dot with Rashba or
Dresselhaus spin-orbit couplings reveal several intriguing properties. We show
that even at the single-electron level spin vortices with different topological
charges exist. These topological textures appear in the {\it ground state} of
the dots. The textures are stabilized by time-reversal symmetry breaking and
are robust against the eccentricity of the dot. The phenomenon persists for the
interacting two-electron dot in the presence of a magnetic field.",1802.00788v1
2016-08-13,Spin-orbit coupling mediated tunable electron heat capacity of quantum wells,"The heat capacity of conduction electrons obtained from the Sommerfeld
expansion is shown to be tunable via the Rashba and Dresselhaus spin-orbit
coupling parameters. Using an AlInSb/InSb/AlInSb as a representative
heterostructure with alterable well and asymmetric barrier regions, the heat
capacity is found to be higher for the spin-down electrons and suffers a
reduction for wider wells. A further lowering is obtained through the
application of an uniaxial strain. Finally, we suggest a method to determine
the spin lifetimes for spins relaxing via the D'yakonov-Perel' mechanism from
experimental estimates of thermodynamic potentials such as the Helmholtz free
energy and the heat capacity.",1608.03998v2
2016-12-27,Reinventing atomistic magnetic simulations with spin-orbit coupling,"We propose a powerful extension to combined molecular and spin dynamics that
fully captures the coupling between the atomic and spin subsystems via
spin-orbit interactions. Its foundation is the inclusion of the local magnetic
anisotropies that arise as a consequence of the lattice symmetry breaking due
to phonons or defects. We demonstrate that our extension enables the exchange
of angular momentum between the atomic and spin subsystems, which is critical
to the challenges arising in the study of fluctuations and non-equilibrium
processes in complex, natural, and engineered magnetic materials.",1612.08503v1
2012-05-09,Exotic quantum spin models in spin-orbit-coupled Mott insulators,"We study cold atoms in an optical lattice with synthetic spin-orbit coupling
in the Mott-insulator regime. We calculate the parameters of the corresponding
tight-binding model using Peierls substitution and ""localized Wannier states
method"" and derive the low-energy spin Hamiltonian for fermions and bosons. The
spin Hamiltonian is a combination of Heisenberg model, quantum compass model
and Dzyaloshinskii-Moriya interactions and it has a rich classical phase
diagram with collinear, spiral and vortex phases.",1205.2110v1
2017-05-31,Macroscopic random Paschen-Back effect in ultracold atomic gases,"We consider spin- and density-related properties of single-particle states in
a one-dimensional system with random spin-orbit coupling. We show that the
presence of an additional Zeeman field $\Delta$ induces both nonlinear spin
polarization and delocalization of states localized at $\Delta=0$,
corresponding to a random macroscopic analogue of the Paschen-Back effect.
While the conventional Paschen-Back effect corresponds to a saturated
$\Delta-$dependence of the spin polarization, here the gradual suppression of
the spin-orbit coupling effects by the Zeeman field is responsible both for the
spin saturation and delocalization of the particles.",1705.11157v1
2021-06-05,Weak anti-localization in spin-orbit coupled lattice systems: effect of non-adiabatic transitions and estimation of spin relaxation length,"This study investigates the quantum correction effect on electrical
conductivity using a two-dimensional Wolff Hamiltonian, which is an effective
model of the spin-orbit coupling (SOC) lattice system. The non-adiabatic
transition processes in impurity scattering suppress the weak anti-localization
(WAL) effect. The WAL effect in the SOC lattice system strongly depends on the
spin relaxation length when compared with the Hikami-Larkin-Nagaoka (HLN)
theory. The spin relaxation length in Bi thin film is discussed.",2106.02761v2
2003-01-31,Entanglement of Electron Spin and Orbital States in Spintronic Quantum Transport,"An electron within a mesoscopic (quantum-coherent) spintronic structure is
described by a single wave function which, in the presence of both charge
scattering and spin-orbit coupling, encodes an information about {\em
entanglement} of its spin and orbital degrees of freedom. The quantum state--an
{\em improper} mixture--of experimentally detectable spin subsystem is
elucidated by evaluating quantum information theory measures of entanglement in
the scattering states which determine {\em quantum transport} properties of
spin-polarized electrons injected into a two-dimensional disordered Rashba
spin-split conductor that is attached to the ferromagnetic source and drain
electrodes. Thus, the Landauer transmission matrix, traditionally evaluated to
obtain the spin-resolved conductances, also yields the reduced spin density
operator allowing us to extract quantum-mechanical measures of the detected
electron spin-polarization and spin-coherence, thereby pointing out how to
avoid detrimental {\em decoherence} effects on spin-encoded information
transport through semiconductor spintronic devices.",0301614v3
2013-08-20,Hole Spin Helix: Anomalous Spin Diffusion in Anisotropic Strained Hole Quantum Wells,"We obtain the spin-orbit interaction and spin-charge coupled transport
equations of a two-dimensional heavy hole gas under the influence of strain and
anisotropy. We show that a simple two-band Hamiltonian can be used to describe
the holes. In addition to the well-known cubic hole spin-orbit interaction,
anisotropy causes a Dresselhaus-like term, and strain causes a Rashba term. We
discover that strain can cause a shifting symmetry of the Fermi surfaces for
spin up and down holes. We predict an enhanced spin lifetime associated with a
spin helix standing wave similar to the Persistent Spin Helix which exists in
the two-dimensional electron gas with equal Rashba and Dresselhaus spin-orbit
interactions. These results may be useful both for spin-based experimental
determination of the Luttinger parameters of the valence band Hamiltonian and
for creating long-lived spin excitations.",1308.4248v3
2021-04-12,Quasiparticle interference and quantum confinement in a correlated Rashba spin-split 2D electron liquid,"Exploiting inversion symmetry breaking (ISB) in systems with strong
spin-orbit coupling promises control of spin through electric fields - crucial
to achieve miniaturization in spintronic devices. Delivering on this promise
requires a two-dimensional electron gas with a spin precession length shorter
than the spin coherence length and a large spin splitting so that spin
manipulation can be achieved over length scales of nanometers. Recently, the
transition metal oxide terminations of delafossite oxides were found to exhibit
a large Rashba spin splitting dominated by ISB. In this limit, the Fermi
surface exhibits the same spin texture as for weak ISB, but the orbital texture
is completely different, raising questions about the effect on quasiparticle
scattering. We demonstrate that the spin-orbital selection rules relevant for
conventional Rashba system are obeyed as true spin selection rules in this
correlated electron liquid and determine its spin coherence length from
quasiparticle interference imaging.",2104.05718v1
2006-11-08,Control of electron spin and orbital resonance in quantum dots through spin-orbit interactions,"Influence of resonant oscillating electromagnetic field on a single electron
in coupled lateral quantum dots in the presence of phonon-induced relaxation
and decoherence is investigated. Using symmetry arguments it is shown that spin
and orbital resonance can be efficiently controlled by spin-orbit interactions.
The control is possible due to the strong sensitivity of Rabi frequency to the
dot configuration (orientation of the dot and a static magnetic field) as a
result of the anisotropy of the spin-orbit interactions. The so called easy
passage configuration is shown to be particularly suitable for magnetic
manipulation of spin qubits, ensuring long spin relaxation time and protecting
the spin qubit from electric field disturbances accompanying on-chip
manipulations.",0611228v2
2013-04-11,Controlling a Nanowire Spin-Orbit Qubit via Electric-Dipole Spin Resonance,"A semiconductor nanowire quantum dot with strong spin-orbit coupling (SOC)
can be used to achieve a spin-orbit qubit. In contrast to a spin qubit, the
spin-orbit qubit can respond to an external ac electric field, an effect called
electric-dipole spin resonance. Here we develop a theory that can apply in the
strong SOC regime. We find that there is an optimal SOC strength
\eta_{opt}=\sqrt{2}/2, where the Rabi frequency induced by the ac electric
field becomes maximal. Also, we show that both the level spacing and the Rabi
frequency of the spin-orbit qubit have periodic responses to the direction of
the external static magnetic field. These responses can be used to determine
the SOC in the nanowire.",1304.3257v2
2013-05-31,Engineering Quantum Spin Hall Effect in Graphene Nanoribbons via Edge Functionalization,"Kane and Mele predicted that in presence of spin-orbit interaction graphene
realizes the quantum spin Hall state. However, exceptionally weak intrinsic
spin-orbit splitting in graphene ($\approx 10^{-5}$ eV) inhibits experimental
observation of this topological insulating phase. To circumvent this problem,
we propose a novel approach towards controlling spin-orbit interactions in
graphene by means of covalent functionalization of graphene edges with
functional groups containing heavy elements. Proof-of-concept first-principles
calculations show that very strong spin-orbit coupling can be induced in
realistic models of narrow graphene nanoribbons with tellurium-terminated
edges. We demonstrate that electronic bands with strong Rashba splitting as
well as the quantum spin Hall state spanning broad energy ranges can be
realized in such systems. Our work thus opens up new horizons towards
engineering topological electronic phases in nanostructures based on graphene
and other materials by means of locally introduced spin-orbit interactions.",1305.7392v1
2022-01-14,An Anderson impurity interacting with the helical edge states in a quantum spin Hall insulator,"Using the natural orbitals renormalization group (NORG) method, we have
investigated the screening of the local spin of an Anderson impurity
interacting with the helical edge states in a quantum spin Hall insulator. We
find that there is a local spin formed at the impurity site and the local spin
is completely screened by electrons in the quantum spin Hall insulator.
Meanwhile, the local spin is screened dominantly by a single active natural
orbital. We then show that the Kondo screening mechanism becomes transparent
and simple in the framework of natural orbitals formalism. We project the
active natural orbital respectively into real space and momentum space to
characterize its structure. And we confirm the spin-momentum locking property
of the edge states based on the occupancy of a Bloch state in the edge to which
the impurity couples. Furthermore, we study the dynamical property of the
active natural orbital represented by the local density of states, from which
we observe the Kondo resonance peak.",2201.05308v1
1992-11-19,Spin effects in the inspiral of coalescing compact binaries,"We derive the contributions of spin-orbit and spin-spin coupling to the
gravitational radiation from coalescing binary systems of spinning compact
objects. We calculate spin effects in the symmetric, trace-free radiative
multipoles that determine the gravitational waveform, and the rate of energy
loss. Assuming a balance between energy radiated and orbital energy lost, we
determine the spin effects in the evolution of the orbital frequency and
orbital radius. Assuming that a laser interferometric gravitational observatory
can track the gravitational-wave frequency (twice the orbital frequency) as it
sweeps through its sensitive bandwidth between about 10 Hz and one kHz, we
estimate the accuracy with which the spins of the component bodies can be
determined from the gravitational-wave signal.",9211025v1
2013-05-20,Spin-Triplet Pairing State of Sr2RuO4 in the c-Axis Magnetic Field,"We investigate the spin-triplet superconducting state of Sr2RuO4 in the
magnetic field along the c-axis on the basis of the four-component
Ginzburg-Landau (GL) model with a weak spin-orbit coupling. We consider
superconducting states described by the d-vector parallel to the ab-plane, and
find that three spin-triplet pairing states are stabilized in the magnetic
field-temperature phase diagram. Although a helical state is stable at low
magnetic fields, a chiral II state is stabilized at high magnetic fields. A
non-unitary spin-triplet pairing state appears near the transition temperature
owing to the coupling of magnetic field and chirality. We elucidate synergistic
and/or competing roles of the magnetic field, chirality, and spin-orbit
coupling. It is shown that a fractional vortex lattice is stabilized in the
chiral II phase owing to the spin-orbit coupling.",1305.4494v2
2013-07-20,Spin Precession in Inertial and Gravitational Fields,"We discuss the motion of spin in inertial and gravitational fields. The
coupling of spin with rotation and the gravitomagnetic field has already been
extensively studied; therefore, we focus here on the inertial and gravitational
spin-orbit couplings. In particular, we investigate the classical and quantum
aspects of spin precession and spin-orbit coupling in an arbitrary
translationally accelerated frame of reference as well as the exterior
Schwarzschild spacetime. Moreover, in connection with Einstein's principle of
equivalence, we clarify the relation between the inertial and gravitational
spin-orbit couplings.",1307.5470v2
2015-03-06,Controllable magnetic correlation between two impurities by spin-orbit coupling in graphene,"Two magnetic impurities on the edge of a zigzag graphene nanoribbon strongly
interact with each other via indirect coupling, which can be mediated by
conducting carriers. By means of Quantum Monte Carlo (QMC) simulations, we find
that the spin-orbit coupling $\lambda$ and the chemical potential $\mu$ in
system can be used to drive the transition of local-spin exchange from
ferromagnetism to anti-ferromagnetism. Since the tunable ranges for $\lambda$
and $\mu$ in graphene are experimentally reachable, we thus open the
possibilities for its device application. The symmetry in spatial distribution
is broken by the vertical and the transversal spin-spin correlations due to the
effect of spin-orbit coupling, leading to the spatial anisotropy of spin
exchange, which distinguish our findings from the case in normal Fermi liquid.",1503.01994v1
2021-08-10,Zero-field spin resonance in graphene with proximity-induced spin-orbit coupling,"We investigate collective spin excitations in graphene with proximity-induced
spin-orbit coupling (SOC) of the Rashba and valley-Zeeman types, as it is the
case, e.g., for graphene on transition- metal-dichalcogenide substrates. It is
shown that, even in the absence of an external magnetic field, such a system
supports collective modes, which correspond to coupled oscillations of the
uniform and valley-staggered magnetizations. These modes can be detected via
both zero-field electron spin resonance (ESR) and zero-field electric-dipole
spin resonance (EDSR), with EDSR response coming solely from Rashba SOC. We
analyze the effect of electron-electron interaction within the Fermi- liquid
kinetic equation and show that the interaction splits both the ESR and EDSR
peaks into two. The magnitude of splitting and the relative weights of the
resonances can be used to extract the spin-orbit coupling constants and
many-body interaction parameters that may not be accessible by other methods.",2108.04420v1
2013-10-16,Terahertz out-of-plane resonances due to spin-orbit coupling,"A microscopic kinetic theory is developed which allows to investigate
non-Abelian SU(2) systems interacting with meanfields and spin-orbit coupling
under magnetic fields in one, two, and three dimensions. The coupled kinetic
equations for the scalar and spin components are presented and linearized with
respect to an external electric field. The dynamical classical and quantum Hall
effect are described in this way as well as the anomalous Hall effect where a
new symmetric dynamical contribution to the conductivity is presented. The
coupled density and spin response functions to an electric field are derived
including arbitrary magnetic fields. The magnetic field induces a staircase
structure at frequencies of the Landau levels. It is found that for linear
Dresselhaus and Rashba spin-orbit coupling a dynamical out-of-plane spin
response appears at these Landau level frequencies establishing terahertz
resonances.",1310.4405v1
2018-09-24,Spin-orbit coupling and spin relaxation of hole states in [001]- and [111]-orientedquantum dots of various geometry,"We study the influence of spin-orbit coupling on the hole states in InAs/GaAs
quantum dots grown on [001]- and [111]-oriented substrates belonging to
symmetry point groups: C2v, C3v and D2d. We investigate the impact of various
spin-orbit mechanisms on the strength of coupling between s- and p-shell
states, which is a significant spin-flip channel in quantum dots. We calculate
spin relaxation rates between the states of lowest Zeeman doublet and show that
the [111]-oriented structure offers one order of magnitude slower relaxation
compared to the usual [001]-oriented self-assembled QD. The magnetic-field
dependence of the hole states is calculated using multiband (up to 14 bands)
k.p model. We identify the irreducible representations linked to the states and
discuss the selection rules, which govern the avoided-crossing pattern in
magnetic-field dependence of the energy levels. We show that dominant
contribution to the coupling between some of these states comes from the shear
strain. On the other hand, we demonstrate no coupling between s- and p-shell
states in the [111]-oriented structure.",1809.09062v3
2023-08-04,Spin-valley locking in Kekulé-distorted graphene with Dirac-Rashba interactions,"The joint effects of Kekul\'e lattice distortions and Rashba-type spin-orbit
coupling on the electronic properties of graphene are explored. We modeled the
position dependence of the Rashba energy term in a manner that allows its
seamless integration into the scheme introduced by Gamayun et al.[New J. Phys.
20, 023016 (2018)] to describe graphene with Kekul\'e lattice distortion.
Particularly for the Kekul\'e-Y texture, the effective low energy Dirac
Hamiltonian contains a new spin-valley locking term, in addition to the
well-known Rashba-induced momentum-pseudospin and spin-pseudospin couplings,
and the Kekul\'e-induced momentum-valley coupling term. We report on the
low-energy band structure and Landau level spectra of Rashba-spin-orbit-coupled
Kek-Y graphene, and propose an experimental scheme to discern between the
presence of Rashba spin-orbit coupling, Kek-Y lattice distortion, and both,
based on doping-dependent magnetotransport measurements.",2308.02130v1
2016-02-19,Electronic orders in multi-orbital Hubbard models with lifted orbital degeneracy,"We study the symmetry-broken phases in two- and three-orbital Hubbard models
with lifted orbital degeneracy using dynamical mean field theory. On the
technical level, we explain how symmetry relations can be exploited to measure
the four-point correlation functions needed for the calculation of the lattice
susceptibilities. In the half-filled two-orbital model with crystal field
splitting, we find an instability of the metallic phase to spin-orbital order
with neither spin nor orbital moment. This ordered phase is shown to be related
to the recently discovered fluctuating-moment induced spin-triplet
superconducting state in the orbitally degenerate model with shifted chemical
potential. In the three-orbital case, we consider the effect of a crystal field
splitting on the spin-triplet superconducting state in the model with positive
Hund coupling, and the spin-singlet superconducting state in the case of
negative Hund coupling. It is demonstrated that for certain crystal field
splittings the higher energy orbitals instead of the lower ones are relevant
for superconductivity, and that $T_c$ can be enhanced by the crystal field
effect. We comment on the implications of our results for the superconductivity
in strontium ruthenates, and for the recently reported light-enhanced
superconducting state in alkali-doped fullerides.",1602.06054v1
2008-09-15,Magnetic breakdown of cyclotron orbits in systems with Rashba and Dresselhaus spin-orbit coupling,"We study the effect of the interplay between the Rashba and the Dresselhaus
spin-orbit couplings on the transverse electron focusing in two-dimensional
electron gases. Depending on their relative magnitude, the presence of both
couplings can result in the splitting of the first focusing peak into two or
three. This splitting has information about the relative value of spin-orbit
couplings and therefore about the shape of the Fermi surface. More interesting,
the presence of the third peak is directly related to the tunneling probability
(""magnetic breakdown"") between orbits corresponding to the different sheets of
the Fermi surface. In addition, destructive interference effects between paths
that involve tunneling and those that do not can be observed in the second
focusing condition. Such electron paths (orbits) could be experimentally
detected using current techniques for imaging the electron flow opening the
possibility to directly observe and characterize the magnetic breakdown effect
in this system.",0809.2575v1
2012-11-26,Complex Orbital State Stabilized by Strong Spin-Orbit Coupling in a Metallic Iridium Oxide IrO$_{2}$,"Resonant x-ray diffraction experiments were performed for the metallic
iridium oxide IrO$_{2}$. We observed anisotropic tensor of susceptibility (ATS)
scattering, the spectrum of which shows a sharp contrast between the $L_{3}$
and $L_{2}$ edges. At the $L_{3}$ edge, resonance excitations were clearly
observed from the core 2$p$ orbitals to both the 5$d$ $t_{2g}$ and $e_{g}$
orbitals. In contrast, the resonance mode associated with 5$d$ $t_{2g}$
orbitals was indiscernible at the $L_{2}$ edge. This contrasting behavior
indicates that Ir 5$d$ $t_{2g}$ orbitals are fairly close to the $J_{\rm eff}$
= 1/2 state due to the strong spin--orbit coupling in 5$d$ transition metal
ions, as in the Mott insulator Sr$_{2}$IrO$_{4}$. Our results clearly
demonstrate that ATS scattering is a useful probe for investigating complex
orbital states in a metallic state. Such states induce novel phenomena such as
the spin Hall effect.",1211.5855v1
2014-04-14,Orbital magnetization of correlated electrons with arbitrary band topology,"Spin-orbit coupling introduces chirality into electronic structure. This can
have profound effects on the magnetization induced by orbital motion of
electrons. Here we derive a formula for the orbital magnetization of
interacting electrons in terms of the full Green's function and vertex
functions. The formula is applied within dynamical mean-field theory to the
Kane-Mele-Hubbard model that allows both topological and trivial insulating
phases. We study the insulating and metallic phases in the presence of an
exchange magnetic field. In the presence of interactions, the orbital
magnetization of the quantum spin Hall insulating phase with inversion symmetry
is renormalized by the bulk quasi-particle weight. The orbital magnetization
vanishes for the in-plane antiferromagnetic phase with trivial topology. In the
metallic phase, the enhanced effective spin-orbit coupling due to the
interaction sometimes leads to an enhancement of the orbital magnetization.
However, at low doping, magnetization is suppressed at large interaction
strengths.",1404.3673v3
2018-02-02,Spin-orbit coupling induced magnetic anisotropy and large spin wave gap in $\rm Na Os O_3$,"The role of spin-orbit coupling and Hund's rule coupling on magnetic
ordering, anisotropy, and excitations are investigated within a minimal
three-orbital model for the $5d^3$ compound $\rm Na Os O_3$. Asymmetry between
the magnetic moments for the $xy$ and $xz,yz$ orbitals, arising from the
hopping asymmetry generated by the $\rm Os O_6$ octahedral tilting and
rotation, together with the weak correlation effect, are shown to be crucial
for the large SOC induced magnetic anisotropy and spin wave gap observed in
this compound. Due to the intrinsic SOC-induced changes in the electronic
densities under rotation of the staggered field, their coupling with the
orbital energy offset is also found to contribute significantly to the magnetic
anisotropy energy.",1802.01449v2
2013-06-08,Formation of Feshbach molecules in the presence of artificial spin-orbit coupling and Zeeman fields,"We derive general conditions for the emergence of singlet Feshbach molecules
in the presence of artificial Zeeman fields for arbritary mixtures of Rashba
and Dresselhaus spin-orbit orbit coupling in two or three dimensions. We focus
on the formation of two-particle bound states resulting from interactions
between ultra-cold spin-1/2 fermions, under the assumption that interactions
are short-ranged and occur only in the s-wave channel. In this case, we
calculate explicitly binding energies of Feshbach molecules and analyze their
dependence on spin-orbit couplings, Zeeman fields, interactions and center of
mass momentum, paying particular attention to the experimentally relevant case
of spin-orbit couplings with equal Rashba and Dresselhaus (ERD) amplitudes.",1306.1964v1
2008-07-23,Kondo effect in carbon nanotube quantum dots with spin-orbit coupling,"Motivated by recent experimental observation of spin-orbit coupling in carbon
nanotube quantum dots [F. Kuemmeth \textsl{et al.}, Nature (London) {\bf 452},
448 (2008)], we investigate in detail its influence on the Kondo effect. The
spin-orbit coupling intrinsically lifts out the fourfold degeneracy of a single
electron in the dot, thereby breaking the SU(4) symmetry and splitting the
Kondo resonance even at zero magnetic field. When the field is applied, the
Kondo resonance further splits and exhibits fine multipeak structures resulting
from the interplay of spin-orbit coupling and Zeeman effect. A microscopic
cotunneling process for each peak can be uniquely identified. Finally, a purely
orbital Kondo effect in the two-electron regime is also obtained.",0807.3595v2
2021-10-11,Universal excitonic superexchange in spin-orbit-coupled Mott insulators,"We point out the universal presence of the excitonic superexchange in
spin-orbit-coupled Mott insulators. It is observed that, the restriction to the
lowest spin-orbit-entangled ""$J$"" states may sometimes be insufficient to
characterize the microscopic physics, and the virtual excitonic processes via
the upper ""$J$"" states provide an important correction to the superexchange. We
illustrate this excitonic superexchange from a two-dimensional $5d$ iridate
Sr$_2$IrO$_4$ and explain its physical consequences such as the orbital-like
coupling to the external magnetic flux and the nonlinear magnetic
susceptibility. The universal presence of the excitonic superexchange in other
spin-orbit-coupled Mott insulators such as $3d$ Co-based Kitaev magnets and
even $f$ electron rare-earth magnets is further discussed.",2110.05212v2
2015-03-26,Spin-orbit excitations and electronic structure of the putative Kitaev magnet $α$-RuCl$_3$,"Mott insulators with strong spin-orbit coupling have been proposed to host
unconventional magnetic states, including the Kitaev quantum spin liquid. The
4$d$ system $\alpha$-RuCl$_3$ has recently come into view as a candidate Kitaev
system, with evidence for unusual spin excitations in magnetic scattering
experiments. We apply a combination of optical spectroscopy and Raman
scattering to study the electronic structure of this material. Our measurements
reveal a series of orbital excitations involving localized total angular
momentum states of the Ru ion, implying that strong spin-orbit coupling and
electron-electron interactions coexist in this material. Analysis of these
features allows us to estimate the spin-orbit coupling strength, as well as
other parameters describing the local electronic structure, revealing a
well-defined hierarchy of energy scales within the Ru $d$ states. By comparing
our experimental results with density functional theory calculations, we also
clarify the overall features of the optical response. Our results demonstrate
that $\alpha$-RuCl$_3$ is an ideal material system to study spin-orbit coupled
magnetism on the honeycomb lattice.",1503.07593v2
2023-06-17,Proximity-induced spin-orbit coupling in phosphorene on a WSe$_2$ monolayer,"We investigate, using first-principles methods and effective-model
simulations, the spin-orbit coupling proximity effects in a bilayer
heterostructure comprising phosphorene and WSe$_2$ monolayers. We specifically
analyze holes in phosphorene around the $\Gamma$ point, at which we find a
significant increase of the spin-orbit coupling that can be attributed to the
strong hybridization of phosphorene with the WSe$_2$ bands. We also propose an
effective spin-orbit model based on the ${\bf C}_{1{\rm v}}$ symmetry of the
studied heterostructure. The corresponding spin-orbit field can be divided into
two parts: the in-plane field, present due to the broken nonsymmorphic
horizontal glide mirror plane symmetry, and the dominant out-of-plane field
triggered by breaking the out-of-plane rotational symmetry of the phosphorene
monolayer. Furthermore, we also demonstrate that a heterostructure with
60$^\circ$ twist angle exhibits an opposite out-of-plane spin-orbit field,
indicating that the coupling can effectively be tuned by twisting. The studied
phosphorene/WSe$_2$ bilayer is a prototypical low common-symmetry
heterostructure in which the proximity effect can be used to engineer the spin
texture of the desired material.",2306.10291v2
2018-06-05,Theory of superconductivity in hole-doped monolayer MoS$_{2}$,"We theoretically investigate the Cooper-pair symmetry to be realized in
hole-doped monolayer MoS$_2$ by solving linearized BCS gap equations on the
three-orbital attractive Hubbard-like model in the presence of the atomic
spin-orbit coupling. In hole-doped monolayer MoS$_2$, both spin-orbit coupling
and the multi-orbital effects are more prominent than those of electron-doped
system. Near the valence band edge, the Fermi surfaces are composed of three
different types of hole pockets, namely, one mainly consisting of the almost
spin-degenerate $|d_{z^{2}}\rangle$ orbital near $\Gamma$ point, and the others
of the spin-split upper and lower bands near ${\rm K}$ and ${\rm K}'$ points
arising from the $|d_{x^{2}-y^{2}}\rangle$ and $|d_{xy}\rangle$ orbitals. The
number of relevant Fermi pockets increases with increase of the doping. At very
low doping, the upper split bands of $|d_{x^{2}-y^{2}}\rangle$ and
$|d_{xy}\rangle$ are concerned, yielding extremely low $T_{\rm c}$ due to small
density of states of the split bands. For further doping, the conventional
spin-singlet state (SS) appears in the $\Gamma$ pocket, which has a mixture of
the spin-triplet (orbital-singlet) (ST-OS) and spin-singlet (orbital-triplet)
(SS-OT) states in the K and K$'$ pockets. The ratio of the mixture depends on
the relative strength of the interactions, and the sign of the exchange
interactions. Moderately strong ferromagnetic exchange interactions even lead
to the pairing state with the dominant ST-OS state over the conventional SS
one. With these observations, we expect that the fascinating pairing with
relatively high $T_{\rm c}$ emerges at high doping that involves all the three
Fermi pockets.",1806.01447v1
2018-01-17,First-principles quantum transport modeling of spin-transfer and spin-orbit torques in magnetic multilayers,"We review a unified approach for computing: (i) spin-transfer torque in
magnetic trilayers like spin-valves and magnetic tunnel junction, where
injected charge current flows perpendicularly to interfaces; and (ii)
spin-orbit torque in magnetic bilayers of the type
ferromagnet/spin-orbit-coupled-material, where injected charge current flows
parallel to the interface. Our approach requires to construct the torque
operator for a given Hamiltonian of the device and the steady-state
nonequilibrium density matrix, where the latter is expressed in terms of the
nonequilibrium Green's functions and split into three contributions. Tracing
these contributions with the torque operator automatically yields field-like
and damping-like components of spin-transfer torque or spin-orbit torque
vector, which is particularly advantageous for spin-orbit torque where the
direction of these components depends on the unknown-in-advance orientation of
the current-driven nonequilibrium spin density in the presence of spin-orbit
coupling. We provide illustrative examples by computing spin-transfer torque in
a one-dimensional toy model of a magnetic tunnel junction and realistic
Co/Cu/Co spin-valve, both of which are described by first-principles
Hamiltonians obtained from noncollinear density functional theory calculations;
as well as spin-orbit torque in a ferromagnetic layer described by a
tight-binding Hamiltonian which includes spin-orbit proximity effect within
ferromagnetic monolayers assumed to be generated by the adjacent monolayer
transition metal dichalcogenide.",1801.05793v2
2024-03-01,Unveiling the physics of the spin-orbit coupling at the surface of a model topological insulator: from theory to experiments,"Spin-orbit interaction affects the band structure of topological insulators
beyond the opening of an inverted gap in the bulk bands, and the understanding
of its effects on the surface states is of primary importance to access the
underlying physics of these exotic states. Here, we propose an $\textit{ab
initio}$ approach benchmarked by pump-probe angle-resolved photoelectron
spectroscopy data to model the effect of spin-orbit coupling on the surface
states of a topological insulator. The critical novelty of our approach lies in
the possibility of accounting for a partial transfer of the spin-orbit coupling
to the surface states, mediated by the hybridization with the surface resonance
states. In topological insulators, the fraction of transferred spin-orbit
coupling influences the strength of the hexagonal warping of the surface
states, which we use as a telltale of the capability of our model to reproduce
the experimental dispersion. The comparison between calculations and
measurements, of both the unoccupied and part of the occupied Dirac cone,
indicates that the fraction of spin-orbit coupling transferred to the surface
states by hybridization with the resonance states is between 70% and 85% of its
full atomic value. This offers a valuable insight to improve the modeling of
surface state properties in topological insulators for both scientific purposes
and technological applications.",2403.01029v1
2022-09-11,Orbital correlations in ultrathin films of late transition metals,"We develop a two-orbital Hubbard model of electron correlations in ultrathin
(111)-oriented fcc films of late transition metals such as Co and Ni. Our model
indicates that the Mott-Hund's interaction results in ferromagnetic
nearest-neighbor orbital correlations. Frustration associated with the mismatch
between orbital and crystal symmetries prevents orbital ordering, resulting in
the orbital liquid state. This state can be manifested in phenomena involving
spin-orbit coupling, such as magnetic anisotropy.",2209.04949v3
2005-06-23,Nondissipative Spin Hall Effect via Quantized Edge Transport,"The spin Hall effect in a two-dimensional electron system on honeycomb
lattice with both intrinsic and Rashba spin-orbit couplings is studied
numerically. Integer quantized spin Hall conductance is obtained at zero Rashba
coupling limit when electron Fermi energy lies in the energy gap created by the
intrinsic spin-orbit coupling, in agreement with recent theoretical prediction.
While nonzero Rashba coupling destroys electron spin conservation, the spin
Hall conductance is found to remain near the quantized value, being insensitive
to disorder scattering, until the energy gap collapses with increasing the
Rashba coupling. We further show that the charge transport through
counterpropagating spin-polarized edge channels is well quantized, which is
associated with a topological invariant of the system.",0506589v2
2012-09-04,Quantum nanostructures in strongly spin-orbit coupled two-dimensional systems,"Recent progress in experimental studies of low-dimensional systems with
strong spin-orbit coupling poses a question on the effect of this coupling on
the energy spectrum of electrons in semiconductor nanostructures. It is shown
in the paper that this effect is profound in the strong coupling limit. In
circular quantum dots a soft mode develops, in strongly elongated dots electron
spin becomes protected from the effects of the environment, and the lower
branch of the energy spectrum of quantum wires becomes nearly flat in a wide
region of the momentum space.",1209.0828v1
2019-05-10,Bound-State Band Reconstruction and Resonance in Spin-1/2 Bose Gas with 1D Spin-Orbit Coupling,"In this work, we study two-body bound states in two-component Bose gas with a
one-dimensional (1D) spin-orbit coupling (SOC) induced by Raman lasers. The
finite Raman coupling strength generates coupling among three spin channels,
resulting in the reconstruction of three bound-state bands. In addition,
multiple resonances can be induced at finite scattering lengths. By tuning the
interaction in one intra-species channel, one bound-state band can be lifted
and three resonances can be achieved at different center-of-mass momenta, which
can be observable under current experimental conditions in ${}^{87}$Rb atoms.",1905.03979v1
2017-11-14,Vortex dipole precession in a Fermi superfluid with Rashba spin-orbit coupling,"We present a closed-form expression for the time dynamics of a balanced Fermi
superfluid with s-wave pairing and Rashba spin-orbit (SO) coupling. Solving the
associated self-consistency conditions for an initial number density given by a
Gaussian and an initial gap containing a vortex dipole, we show that Rashba SO
coupling results in precession of the vortex dipole. The integrated
self-consistent gap decays as a function of time, characterising a ""transient
Fermi superfluid"". Our analytic solution forms a starting point for studies of
vortex dynamics -- in particular braiding of Majorana fermions -- in Fermi
superfluids in the presence of spin population imbalance and two-dimensional SO
coupling, which are both required to realize a topological atomic Fermi gas in
experiments.",1711.04970v1
2023-06-15,Predictable gate-field control of spin in altermagnets with spin-layer coupling,"Spintronics, a technology harnessing electron spin for information
transmission, offers a promising avenue to surpass the limitations of
conventional electronic devices. While the spin directly interacts with the
magnetic field, its control through the electric field is generally more
practical, and has become a focal point in the field of spintronics. Current
methodologies for generating spin polarization via an electric field generally
necessitate spin-orbit coupling. Here, we propose an innovative mechanism that
accomplishes this task without dependence on spin-orbit coupling. Our method
employs two-dimensional altermagnets with valley-mediated spin-layer coupling
(SLC), in which electronic states display symmetry-protected and
valley-contrasted spin and layer polarization. The SLC facilitates predictable,
continuous, and reversible control of spin polarization using a gate electric
field. Through symmetry analysis and ab initio calculations, we pinpoint
high-quality material candidates that exhibit SLC. We ascertain that applying a
gate field of $0.2$ eV/\AA~ to monolayer Ca(CoN)$_2$ can induce significant
spin splitting up to 123 meV. As a result, perfect and switchable
spin/valley-currents, and substantial tunneling magnetoresistance can be
achieved in these materials using only a gate field. These findings provide new
opportunities for generating predictable spin polarization and designing novel
spintronic devices based on coupled spin, valley and layer physics.",2306.08902v1
2023-05-26,Can Orbital-Selective Néel Transitions Survive Strong Nonlocal Electronic Correlations?,"Spin- or orbital-selective behaviours in correlated electron materials offer
rich promise for spintronics or orbitronics phenomena and applications deriving
from them. Strong local electronic Coulomb correlations might lead to an
orbital-selective Mott state, characterised by the coexistence of localized
electrons in some orbitals with itinerant electrons in others. Nonlocal
electronic fluctuations are much more entangled in orbital space than the local
ones. For this reason, finding orbital-selective phenomena related to nonlocal
correlations, such as orbital-selective magnetic transitions, is a challenge.
In this work we investigate possibilities to realize an orbital-selective
N\'eel transition (OSNT). We illustrate that stabilising this state requires a
decoupling of magnetic fluctuations in different orbitals, which can only be
realized in the absence of Hund's exchange coupling. On the basis of
two-orbital calculations for a Hubbard model with different bandwidths we show
that the proposed OSNT can be found all the way from the weak to the strong
coupling regime. In the weak coupling regime the transition is governed by a
Slater mechanism and thus occurs first for the narrow orbital. At strong
coupling a Heisenberg mechanism of the OSNT sets in, and the transition occurs
first for the wide orbital. Remarkably, at intermediate values of the
interaction we find a non-trivial regime of the OSNT, where the Slater
mechanism leads to a N\'eel transition occurring first for the wide orbital.
Our work suggests strategies for searching for orbital-selective N\'eel
ordering in real materials, in view of possible spin-orbitronics applications.",2305.16730v2
2015-12-01,Gyroscopes orbiting black holes: A frequency-domain approach to precession and spin-curvature coupling for spinning bodies on generic Kerr orbits,"A small body orbiting a black hole follows a trajectory that, at leading
order, is a geodesic of the black hole spacetime. Much effort has gone into
computing ""self force"" corrections to this motion, arising from the small
body's own contributions to the system's spacetime. Another correction to the
motion arises from coupling of the small body's spin to the black hole's
spacetime curvature. Spin-curvature coupling drives a precession of the small
body, and introduces a ""force"" (relative to the geodesic) which shifts the
small body's worldline. These effects scale with the small body's spin at
leading order. In this paper, we show that the equations which govern
spin-curvature coupling can be analyzed with a frequency-domain decomposition,
at least to leading order in the small body's spin. We show how to compute the
frequency of precession along generic orbits, and how to describe the small
body's precession and motion in the frequency domain. We illustrate this
approach with a number of examples. This approach is likely to be useful for
understanding spin coupling effects in the extreme mass ratio limit, and may
provide insight into modeling spin effects in the strong field for non-extreme
mass ratios.",1512.00376v2
2005-02-24,Non-exponential spin relaxation in magnetic field in quantum wells with random spin-orbit coupling,"We investigate the spin dynamics of electrons in quantum wells where the
Rashba type of spin-orbit coupling is present in the form of random nanosize
domains. We study the effect of magnetic field on the spin relaxation in these
systems and show that the spatial randomness of spin-orbit coupling limits the
minimum relaxation rate and leads to a Gaussian time-decay of spin polarization
due to memory effects. In this case the relaxation becomes faster with increase
of the magnetic field in contrast to the well known magnetic field suppression
of spin relaxation.",0502593v3
2006-07-15,Degradation of electron-hole entanglement by spin-orbit coupling,"Electron-hole pairs produced by tunneling in a degenerate electron gas lose
their spin entanglement by spin-orbit coupling, which transforms the fully
entangled Bell state into a partially entangled mixed density matrix of the
electron and hole spins. We calculate the dependence of the entanglement
(quantified by the concurrence) on the spin-orbit coupling time tau_so and on
the diffusion time (or dwell time) tau_dwell of electron and hole in the
conductors (with conductances >> e^2/h) at the two sides of the tunnel barrier
(with conductance << e^2/h). The entanglement disappears when the ratio
tau_dwell/tau_so exceeds a critical value of order unity. The results depend on
the type of conductor (disordered wire or chaotic quantum dot), but they are
independent of other microscopic parameters (number of channels, level
spacing). Our analytical treatment relies on an ""isotropy approximation"" (no
preferential basis in spin space), which allows us to express the concurrence
entirely in terms of spin correlators. We test this approximation for the case
of chaotic dynamics with a computer simulation (using the spin kicked rotator)
and find good agreement.",0607395v2
2007-05-16,Charge and spin density response functions of the clean two-dimensional electron gas with Rashba spin-orbit coupling at finite momenta and frequencies,"We analytically evaluate charge and spin density response functions of the
clean two-dimensional electron gas with Rashba spin-orbit coupling at finite
momenta and frequencies. On the basis of our exact expressions we discuss the
accuracy of the long-wavelength and the quasiclassical approximations. We also
derive the static limit of spin susceptibilities and demonstrate, in
particular, how the Kohn-like anomalies in their derivatives are related to the
spin-orbit modification of the Ruderman-Kittel-Kasuya-Yosida interaction.
Taking into account screening and exchange effects of the Coulomb interaction,
we describe the collective charge and spin density excitation modes which
appear to be coupled due to nonvanishing spin-charge response function.",0705.2419v1
2008-03-05,"Spin-orbit coupling, edge states and quantum spin Hall criticality due to Dirac fermion confinement: The case study of graphene","We propose a generalized Dirac fermion description for the electronic state
of graphene terminated by a zigzag edge. This description admits a spin-orbit
coupling needed to preserve time-reversal invariance of the zigzag confinement,
otherwise, for spinless particles, showing the parity anomaly typical of
quantum electrodynamics in (2+1) dimensions. At a certain critical strength the
spin-orbit coupling induces a phase transition of the quantum-spin-Hall type.
It is manifested by a novel type of the edge states consisting of a Kramers'
pair of counter-propagating modes with opposite spin orientations. Such edge
states are capable of accumulating an integer spin in response to a transverse
electric field in the absence of a magnetic one. They exist without any
excitation gap in the bulk, due to which our system stands out among other
quantum spin Hall systems studied earlier. We show that at the transition the
local density of states is discontinuous and its energy dependence reflects the
phase diagram of the system.",0803.0713v3
2008-09-24,Electron spin relaxation in cubic GaN quantum dots,"The spin relaxation time $T_{1}$ in zinc blende GaN quantum dot is
investigated for different magnetic field, well width and quantum dot diameter.
The spin relaxation caused by the two most important spin relaxation mechanisms
in zinc blende semiconductor quantum dots, {i.e.} the electron-phonon
scattering in conjunction with the Dresselhaus spin-orbit coupling and the
second-order process of the hyperfine interaction combined with the
electron-phonon scattering, are systematically studied. The relative importance
of the two mechanisms are compared in detail under different conditions. It is
found that due to the small spin orbit coupling in GaN, the spin relaxation
caused by the second-order process of the hyperfine interaction combined with
the electron-phonon scattering plays much more important role than it does in
the quantum dot with narrower band gap and larger spin-orbit coupling, such as
GaAs and InAs.",0809.4103v2
2014-07-23,Topological Yu-Shiba-Rusinov chain from spin-orbit coupling,"We investigate the possibility of realizing a topological state in the
impurity band formed by a chain of classical spins embedded in a
two-dimensional singlet superconductor with Rashba spin-orbit coupling. In
contrast to similar proposals which require a helical spin texture of the
impurity spins for a nontrivial topology, here we show that spin-flip
correlations due to the spin-orbit coupling in the superconductor produces a
topological state for ferromagnetic alignment of the impurity spins. From the
Bogoliubov-de Gennes equations we derive an effective tight-binding model for
the subgap states which resembles a spinless superconductor with long-range
hopping and pairing terms. We evaluate the topological invariant, and show that
a topologically non-trivial state is generically present in this model.",1407.6345v4
2014-10-06,Surprisingly large inverse spin Hall effect and systematic variation of spin-orbit coupling with d-orbital filling in 3d transition metals,"It is generally believed that spin-orbit coupling (SOC) follows Z4 (atomic
number) dependence and becomes significant only in heavy elements.
Consequently, SOC in 3d transition metals should be negligible given their
small Z. Using dynamic spin pumping of Y3Fe5O12-based structures, we uncover a
systematic evolution of spin Hall angle with d-orbital filling in a series of
3d metals, reminiscent of behavior observed in 5d metals. In particular, Cr and
Ni show very large spin Hall angle (half of that for Pt), indicating that
d-orbital filling rather than Z plays a dominant role in spin Hall effect (SHE)
in 3d metals. This result enriches our understanding of SHE and broadens the
scope of materials available for exploring the rich phenomena enabled by SOC as
well as presenting a guidepost for testing theoretical models of spin-orbit
coupling in transition metals.",1410.1590v1
2018-04-10,Theory of the inverse spin galvanic effect in quantum wells,"The understanding of the fundamentals of spin and charge densities and
currents interconversion by spin-orbit coupling can enable efficient
applications beyond the possibilities offered by conventional electronics. For
this purpose we consider various forms of the frequency-dependent inverse spin
galvanic effect (ISGE) in semiconductor quantum wells and epilayers taking into
account the cubic in the electron momentum spin-orbit coupling in the Rashba
and Dresselhaus forms, concentrating on the current-induced spin polarization
(CISP). We find that including the cubic terms qualitatively explains recent
findings of the CISP in InGaAs epilayers being the strongest if the internal
spin-orbit coupling field is the smallest and vice versa (Norman et . 2014,
Luengo et al. 2017), in contrast to the common understanding. Our results
provide a promising framework for the control of spin transport in future
spintronics devices.",1804.03607v1
2017-01-30,Omnidirectional spin Hall effect in a Weyl spin-orbit coupled atomic gas,"We show that in the presence of a three-dimensional (Weyl) spin-orbit
coupling, a transverse spin current is generated in response to either a
constant spin-independent force or a time-dependent Zeeman field in an
arbitrary direction. This effect is the non-Abelian counterpart of the
universal intrinsic spin Hall effect characteristic to the two-dimensional
Rashba spin-orbit coupling. We quantify the strength of such an omnidirectional
spin Hall effect by calculating the corresponding conductivity for fermions and
non-condensed bosons. The absence of any kind of disorder in ultracold-atom
systems makes the observation of this effect viable.",1701.08773v2
2009-12-17,Solid-State Spin-Photon Quantum Interface without Spin-Orbit Coupling,"We show that coherent optical manipulation of a single confined spin is
possible even in the absence of spin-orbit coupling. To this end, we consider
the non-Markovian dynamics of a single valence orbital hole spin that has
optically induced spin exchange coupling to a low temperature partially
polarized electron gas. We show that the fermionic nature of the reservoir
induces a coherent component to the hole spin dynamics that does not generate
entanglement with the reservoir modes. We analyze in detail the competition of
this reservoir-assisted coherent contribution with dissipative components
displaying markedly different behavior at different time scales and determine
the fidelity of optically controlled spin rotations.",0912.3378v1
2016-08-22,Spin Seebeck effect and thermoelectric phenomena in superconducting hybrids with magnetic textures or spin-orbit coupling,"We theoretically consider the spin Seebeck effect, the charge Seebeck
coefficient, and the thermoelectric figure of merit in superconducting hybrid
structures including either magnetic textures or intrinsic spin-orbit coupling.
We demonstrate that large magnitudes for all these quantities are obtainable in
Josephson-based systems with either zero or a small externally applied magnetic
field. This provides an alternative to the thermoelectric effects generated in
high-field ($\sim 1$ T) superconducting hybrid systems, which were recently
experimentally demonstrated. The systems studied contain either textured
ferromagnets, spin-active interfaces, or spin-orbit coupling. We present a
framework for calculating the linear thermoelectric response for both spin and
charge of a system upon applying temperature and voltage gradients based on
quasiclassical theory which allows for arbitrary spin-dependent textures and
fields to be conveniently incorporated.",1608.06285v2
2018-07-18,Extrinsic Spin-Charge Coupling in Diffusive Superconducting Systems,"We present a theoretical study of diffusive superconducting systems with
extrinsic spin-orbit coupling and arbitrarily strong impurity potential. We
derive from a microscopic Hamiltonian a diffusion equation for the
quasi-classical Green function, and demonstrate that all mechanisms related to
the spin-orbit coupling are expressed in terms of three kinetic coefficients:
the spin Hall angle, the spin current swapping coefficient, and the spin
relaxation rate due to Elliott-Yafet mechanism. The derived diffusion equation
contains a hitherto unknown term describing a spin-orbit torque that appears
exclusively in the superconducting state. As an example, we provide a
qualitative description of a magnetic vortex in a superconductor with triplet
correlations, and show that the novel term describes a spin torque proportional
to the vector product between the spectral angular momentum of the condensate
and the triplet vector. Our equation opens up the possibility to explore
spintronic effects in superconductors with no counterparts in the normal
metallic state.",1807.07029v2
2021-05-22,Photoinduced spin-Hall resonance in a k^3-Rashba spin-orbit coupled two dimensional hole system,"We study the band structure modulation and spin-Hall effect of a
two-dimensional heavy-hole system with $k^3$-Rashba spin-orbit coupling (RSOC),
irradiated by linearly polarized light. We find that the band structure becomes
anisotropic under the illumination by the light. Most remarkably, a pair of
additional spin-degeneracy points (apart from $\Gamma$ point) emerge in the
energy dispersion, the locations of which are solely determined by the strength
of the amplitude of the incident light. If this degeneracy occurs around the
Fermi level, the spin-Hall conductivity (SHC) exhibits a resonance. Away from
the degeneracy points, the light rotates the average spin polarization. The
possible effects of $k^3$-Dresselhaus spin-orbit coupling are also discussed.",2105.10732v2
2021-12-27,Incoherent chiral-induced spin selectivity,"The observation of spin-dependent transport through organic chiral structures
has sparked numerous fundamental and applicative questions ranging from biology
to spintronics. By now, there is a broad consensus that the effect results from
the combination of spin-orbit coupling and the systems' unique geometry.
However, two key challenges remain. Firstly, accounting for the magnitude of
the measured effect in light of the weak spin-orbit coupling in organic
systems. Secondly, understanding its observation not only in
tunneling-dominated short molecules, but also in longer ones where
phonon-assisted hopping via localized states is operative. We focus on the
latter and find that localization and the complete loss of coherence due to
phonons do not impede strong spin polarization of charge carriers passing
through the molecule. Moreover, hopping decouples the energy scale for
observing spin-selective transport from the magnitude of the spin-orbit
coupling. Thus, our result may explain the observation of large spin
selectivity at room temperature and under large applied voltages.",2112.13561v2
2022-04-14,Collective excitations in cigar-shaped spin-orbit coupled spin-1 Bose-Einstein condensates,"We theoretically study the collective excitations of a spin-orbit-coupled
spin-1 Bose-Einstein condensate with antiferromagnetic spin-exchange
interactions in a cigar-shaped trapping potential at zero and finite
temperatures using the Hartree-Fock-Bogoliubov theory with Popov approximation.
The collective modes at zero temperature are corroborated by the real-time
evolution of the ground state subjected to a perturbation suitable to excite a
density or a spin mode. We have also calculated a few low-lying modes
analytically and found a very good agreement with the numerical results. We
confirm the presence of excitations belonging to two broad categories, namely
density, and spin excitations, based on the calculation of dispersion. The
degeneracy between a pair of spin modes is broken by the spin-orbit coupling.
At finite temperature, spin and density excitations show qualitatively
different behavior as a function of temperature.",2204.06898v2
2022-09-21,Stabilizing fluctuating spin-triplet superconductivity in graphene via induced spin-orbit coupling,"A recent experiment showed that proximity induced Ising spin-orbit coupling
enhances the spin-triplet superconductivity in Bernal bilayer graphene. Here,
we show that, due to the nearly perfect spin rotation symmetry of graphene, the
fluctuations of the spin orientation of the triplet order parameter suppress
the superconducting transition to nearly zero temperature. Our analysis shows
that both Ising spin-orbit coupling and in-plane magnetic field can eliminate
these low-lying fluctuations and can greatly enhance the transition
temperature, consistent with the recent experiment. Our model also suggests the
possible existence of a phase at small anisotropy and magnetic field which
exhibits quasi-long-range ordered spin-singlet charge 4e superconductivity,
even while the triplet 2e superconducting order only exhibits short-ranged
correlations. Finally, we discuss relevant experimental signatures.",2209.10560v1
2024-03-08,Superconductivity in Two-Dimensional Systems with Unconventional Rashba Bands,"In two-dimensional system with Rashba spin-orbit coupling, it is well-known
that superconductivity can have mixed spin-singlet and -triplet parity, and the
$\boldsymbol{d}$-vector of spin-triplet pairing is parallel to
$\boldsymbol{g}$-vector of Rashba spin-orbit coupling. Here, we propose a model
to describe a two-dimensional system with unconventional Rashba bands and study
its superconductivity. We show that the $\boldsymbol{d}$-vector of spin-triplet
pairing can be either parallel or perpendicular to $\boldsymbol{g}$-vector of
Rashba spin-orbit coupling depending on the different pairing interaction. We
also propose a junction to generate tunneling spin current depending on the
direction of $\boldsymbol{d}$-vector. It provides a detecable evidence to
distinguish these two different but very similar pairing channels. Furthermore,
we find this model can give arise to a subleading spin-singlet chiral $p$-wave
topological superconducting state. More significantly, we find that such
unconventional Rashba bands and unconventional superconudcting pairings can be
realized on surface of some superconducting topological materials, such as
trigonal layered PtBi$_{2}$.",2403.05051v2
2011-10-13,Evolution of the Kondo resonance feature and its relationship to spin-orbit coupling across the quantum critical point in Ce2Rh{1-x}CoxSi3,"We investigate the evolution of the electronic structure of Ce2Rh{1-x}CoxSi3
as a function of x employing high resolution photoemission spectroscopy. Co
substitution at the Rh sites in antiferromagnetic Ce2RhSi3 leads to a
transition from an antiferromagnetic system to a Kondo system, Ce2CoSi3 via the
Quantum Critical Point (QCP). High resolution photoemission spectra reveal
distinct signature of the Kondo resonance feature (KRF) and its spin orbit
split component (SOC) in the whole composition range indicating finite Kondo
temperature scale at the quantum critical point. We observe that the intensity
ratio of the Kondo resonance feature and its spin orbit split component,
KRF/SOC gradually increases with the decrease in temperature in the strong
hybridization limit. The scenario gets reversed if the Kondo temperature
becomes lower than the magnetic ordering temperature. While finite Kondo
temperature within the magnetically ordered phase indicates applicability of
the spin density wave picture at the approach to QCP, the dominant temperature
dependence of the spin-orbit coupled feature suggests importance of spin-orbit
interactions in this regime.",1110.2836v1
2013-03-21,Breakdown of singlets and triplets in Sr2RuO4 revealed by spin-resolved ARPES,"Spin-orbit coupling has been conjectured to play a key role in the low-energy
electronic structure of Sr2RuO4. Using circularly polarized light combined with
spin- and angle-resolved photoemission spectroscopy, we directly measure the
value of the effective spin-orbit coupling to be 130 +/- 30 meV. This is even
larger than theoretically predicted and comparable to the energy splitting of
the dxy and dxz,yz orbitals around the Fermi surface, resulting in a strongly
momentum-dependent entanglement of spin and orbital character. As demonstrated
by the spin expectation value obtained for a pair of electrons with zero total
momentum, the classification of the Cooper pairs in terms of pure singlets or
triplets fundamentally breaks down, necessitating a description of the
unconventional superconducting state of Sr2RuO4 in terms of these newly found
spin-orbital entangled eigenstates.",1303.5444v2
2015-02-19,Long-Range Spin-Triplet Correlations and Edge Spin Currents in Diffusive Spin-Orbit Coupled SNS Hybrids with a Single Spin-Active Interface,"Utilizing a SU(2) gauge symmetry technique in the quasiclassical diffusive
regime, we theoretically study finite-sized two-dimensional intrinsic
spin-orbit coupled superconductor/normal-metal/superconductor (S/N/S) hybrid
structures with a single spin-active interface. We consider intrinsic
spin-orbit interactions (ISOIs) that are confined within the N wire and absent
in the s-wave superconducting electrodes (S). Using experimentally feasible
parameters, we demonstrate that the coupling of the ISOIs and spin moment of
the spin-active interface results in maximum singlet-triplet conversion and
accumulation of spin current density at the corners of the N wire nearest the
spin-active interface. By solely modulating the superconducting phase
difference, we show how the opposing parities of the charge and spin currents
provide an effective venue to experimentally examine pure edge spin currents
not accompanied by charge currents. These effects occur in the absence of
externally imposed fields, and moreover are insensitive to the arbitrary
orientations of the interface spin moment. The experimental implementation of
these robust edge phenomena are also discussed.",1502.05719v2
2023-07-28,Strong tunable coupling between two distant superconducting spin qubits,"Superconducting (or Andreev) spin qubits have recently emerged as an
alternative qubit platform with realizations in semiconductor-superconductor
hybrid nanowires. In these qubits, the spin degree of freedom is intrinsically
coupled to the supercurrent across a Josephson junction via the spin-orbit
interaction, which facilitates fast, high-fidelity spin readout using circuit
quantum electrodynamics techniques. Moreover, this spin-supercurrent coupling
has been predicted to facilitate inductive multi-qubit coupling. In this work,
we demonstrate a strong supercurrent-mediated coupling between two distant
Andreev spin qubits. This qubit-qubit interaction is of the longitudinal type
and we show that it is both gate- and flux-tunable up to a coupling strength of
178 MHz. Finally, we find that the coupling can be switched off in-situ using a
magnetic flux. Our results demonstrate that integrating microscopic spin states
into a superconducting qubit architecture can combine the advantages of both
semiconductors and superconducting circuits and pave the way to fast two-qubit
gates between remote spins.",2307.15654v1
2023-08-24,Methods for transverse and longitudinal spin-photon coupling in silicon quantum dots with intrinsic spin-orbit effect,"In a full-scale quantum computer with a fault-tolerant architecture, having
scalable, long-range interaction between qubits is expected to be a highly
valuable resource. One promising method of achieving this is through the
light-matter interaction between spins in semiconductors and photons in
superconducting cavities. This paper examines the theory of both transverse and
longitudinal spin-photon coupling and their applications in the silicon
metal-oxide-semiconductor (SiMOS) platform. We propose a method of coupling
which uses the intrinsic spin-orbit interaction arising from orbital
degeneracies in SiMOS qubits. Using theoretical analysis and experimental data,
we show that the strong coupling regime is achievable in the transverse scheme.
We also evaluate the feasibility of a longitudinal coupling driven by an AC
modulation on the qubit. These coupling methods eschew the requirement for an
external micromagnet, enhancing prospects for scalability and integration into
a large-scale quantum computer.",2308.12626v1
2020-07-24,Thermal and orbital evolution of low-mass exoplanets,"Thermal, orbital, and rotational dynamics of tidally loaded exoplanets are
interconnected by intricate feedback. The rheological structure of the planet
determines its susceptibility to tidal deformation and, as a consequence,
participates in shaping its orbit. The orbital parameters and the spin state,
conversely, control the rate of tidal dissipation and may lead to substantial
changes of the interior. We investigate the coupled thermal-orbital evolution
of differentiated rocky exoplanets governed by the Andrade viscoelastic
rheology. The coupled evolution is treated by a semi-analytical model, 1d
parametrized heat transfer and self-consistently calculated tidal dissipation.
First, we conduct several parametric studies, exploring the effect of the
rheological properties, the planet's size, and the orbital eccentricity on the
tidal locking and dissipation. These tests show that the role of tidal locking
into high spin-orbit resonances is most prominent on low eccentric orbits,
where it results in substantially higher tidal heating than the synchronous
rotation. Second, we calculate the long-term evolution of three currently known
low-mass exoplanets with nonzero orbital eccentricity and absent or yet unknown
eccentricity forcing (namely GJ 625 b, GJ 411 b, and Proxima Centauri b). The
tidal model incorporates the formation of a stable magma ocean and a
consistently evolving spin rate. We find that the thermal state is strongly
affected by the evolution of eccentricity and spin state and proceeds as a
sequence of thermal equilibria. Final despinning into synchronous rotation
slows down the orbital evolution and helps to maintain long-term stable orbital
eccentricity.",2007.12459v1
2010-08-07,Energy spectra for quantum wires and 2DEGs in magnetic fields with Rashba and Dresselhaus spin-orbit interactions,"We introduce an analytical approximation scheme to diagonalize parabolically
confined two dimensional electron systems with both the Rashba and Dresselhaus
spin-orbit interactions. The starting point of our perturbative expansion is a
zeroth-order Hamiltonian for an electron confined in a quantum wire with an
effective spin-orbit induced magnetic field along the wire, obtained by
properly rotating the usual spin-orbit Hamiltonian. We find that the
spin-orbit-related transverse coupling terms can be recast into two parts W and
V, which couple crossing and non-crossing adjacent transverse modes,
respectively. Interestingly, the zeroth-order Hamiltonian together with W can
be solved exactly, as it maps onto the Jaynes-Cummings model of quantum optics.
We treat the V coupling by performing a Schrieffer-Wolff transformation. This
allows us to obtain an effective Hamiltonian to third order in the coupling
strength k_Rl of V, which can be straightforwardly diagonalized via an
additional unitary transformation. We also apply our approach to other types of
effective parabolic confinement, e.g., 2D electrons in a perpendicular magnetic
field. To demonstrate the usefulness of our approximate eigensolutions, we
obtain analytical expressions for the n^th Landau-level g_n-factors in the
presence of both Rashba and Dresselhaus couplings. For small values of the bulk
g-factors, we find that spin-orbit effects cancel out entirely for particular
values of the spin-orbit couplings. By solving simple transcendental equations
we also obtain the band minima of a Rashba-coupled quantum wire as a function
of an external magnetic field. These can be used to describe Shubnikov-de Haas
oscillations. This procedure makes it easier to extract the strength of the
spin-orbit interaction in these systems via proper fitting of the data.",1008.1317v1
2015-04-16,Coupling ferroelectricity with spin-valley physics in oxide-based heterostructure,"The coupling of spin and valley physics is nowadays regarded as a promising
route toward next-generation spintronic and valleytronic devices. In the aim of
engineering functional properties for valleytronic applications, we focus on
the ferroelectric heterostructure BiAlO3/BiIrO3, where the complex interplay
among trigonal crystal field, layer degrees of freedom and spin-orbit coupling
mediates a strong spin-valley coupling. Furthermore, we show that
ferroelectricity provides a non-volatile handle to manipulate and switch the
emerging valley-contrasting spin polarization.",1504.04091v1
2022-08-29,The Effect of Duschinskii Rotations on Spin-Dependent Electron Transfer Dynamics,"We investigate spin-dependent electron transfer in the presence of a
Duschinskii rotation. In particular, we propagate dynamics for a two-level
model system for which spin-orbit coupling introduces an interstate coupling of
the form $e^{iWx}$, which is both position(x)-dependent and complex-valued. We
demonstrate that two-level systems coupled to Brownian oscillators with
Duschinskii rotations (and thus entangled normal modes) can produce marked
increases in transient spin polarization relative to two-level systems coupled
to simple shifted harmonic oscillators. These conclusions should have
significant relevance for modeling the effect of nuclear motion on chiral
induced spin selectivity.",2208.13378v1
2023-02-26,Spin-Orbit Coupling of Europa's Ice Shell and Interior,"Europa is an icy ocean world, differentiated into a floating ice shell and
solid interior, separated by a global ocean. The classical spin-orbit coupling
problem considers a satellite as a single rigid body, but in the case of
Europa, the existence of the subsurface ocean enables independent motion of the
ice shell and solid interior. This paper explores the spin-orbit coupling
problem for Europa from a dynamical perspective, yielding illuminating
analytical and numerical results. We determine that the spin behavior of Europa
is influenced by processes not captured by the classical single rigid body
spin-orbit coupling analysis. The tidal locking process for Europa is governed
by the strength of gravity-gradient coupling between the ice shell and solid
interior, with qualitatively different behavior depending on the scale of this
effect. In this coupled rigid model, the shell can potentially undergo large
angular displacements from the solid interior, and the coupling plays an
outsize role in the dynamical evolution of the moon, even without incorporating
the dissipative effects of shell non-rigidity. We additionally discuss the
effects of a realistic viscoelastic shell, and catalogue other torques that we
expect to be sub-dominant in Europa's spin dynamics, or whose importance is
unknown. Finally, we explore how the choice of tidal model affects the
resulting equilibrium spin state.",2302.13226v3
2019-07-29,"Spin-polarized current, spin-transfer torque and spin Hall effect in presence of an electromagnetic non-minimal coupling","In this contribution, we start off from a fully relativistic description of a
single electron non-minimally coupled to an external electromagnetic field.
Making direct use of the field equation, instead of canonically deriving from
the Lagrangian density, the relativistic total angular momentum is attained,
where the effect of the relativistic torque due to the external sources is also
taken into account. Both the spin density and the orbital angular momentum
tensors are identified in the relativistic-covariant approach. Furthermore, the
symmetric and gauge invariant energy-momentum tensor is derived as well. In
addition, to inspect the non-relativistic regime, a perturbative expansion of
the field equation up to the leading order in $\left(v/c\right)$ is carried
out, where spin-orbit interaction terms naturally emerge in the
non-relativistic Hamiltonian as a consequence of the non-minimal coupling.
Features related to the spin currents, the spin-transfer torque and their
dependence on both magnetic and electric external fields are then calculated
and discussed. Considering that spin-orbit coupled systems are of particular
interest in the study of spin Hall effect, a two-dimensional (planar) scenario
of the system is contemplated, where the contributions to the Landau levels are
re-assessed. As a consequence of the planar regime and the non-minimal
coupling, a peculiar sort of fractionalization of the spin-up and -down
components emerges with the different spin components localized in distinct
positions.",1907.12196v2
2023-01-09,Spin-lattice and magnetoelectric couplings enhanced by orbital degrees of freedom in polar magnets,"Orbital degrees of freedom mediating an interaction between spin and lattice
were predicted to raise strong magnetoelectric effect, i.e. realize an
efficient coupling between magnetic and ferroelectric orders. However, the
effect of orbital fluctuations have been considered only in a few
magnetoelectric materials, as orbital degeneracy driven Jahn-Teller effect
rarely couples to polarization. Here, we explore the spin-lattice coupling in
multiferroic Swedenborgites with mixed valence and Jahn-Teller active
transition metal ions on a stacked triangular/Kagome lattice using infrared and
dielectric spectroscopy. On one hand, in CaBa$M_4$O$_7$ ($M$ = Co, Fe), we
observe strong magnetic order induced shift in the phonon frequencies and a
corresponding large change in the dielectric response. Remarkably, as an
unusual manifestation of the spin-phonon coupling, the spin-fluctuations reduce
the phonon life-time by an order of magnitude at the magnetic phase
transitions. On the other hand, lattice vibrations, dielectric response, and
electric polarization show no variation at the N\'eel temperature of
CaBaFe$_2$Co$_2$O$_7$, which is built up by orbital singlet ions. Our results
provide a showcase for orbital degrees of freedom enhanced magnetoelectric
coupling via the example of Swedenborgites.",2301.03292v1
2006-05-16,Direct electronic measurement of the spin Hall effect,"The generation, manipulation and detection of spin-polarized electrons in
nanostructures define the main challenges of spin-based electronics[1]. Amongst
the different approaches for spin generation and manipulation, spin-orbit
coupling, which couples the spin of an electron to its momentum, is attracting
considerable interest. In a spin-orbit-coupled system, a nonzero spin-current
is predicted in a direction perpendicular to the applied electric field, giving
rise to a ""spin Hall effect""[2-4]. Consistent with this effect,
electrically-induced spin polarization was recently detected by optical
techniques at the edges of a semiconductor channel[5] and in two-dimensional
electron gases in semiconductor heterostructures[6,7]. Here we report
electrical measurements of the spin-Hall effect in a diffusive metallic
conductor, using a ferromagnetic electrode in combination with a tunnel barrier
to inject a spin-polarized current. In our devices, we observe an induced
voltage that results exclusively from the conversion of the injected spin
current into charge imbalance through the spin Hall effect. Such a voltage is
proportional to the component of the injected spins that is perpendicular to
the plane defined by the spin current direction and the voltage probes. These
experiments reveal opportunities for efficient spin detection without the need
for magnetic materials, which could lead to useful spintronics devices that
integrate information processing and data storage.",0605423v1
2021-01-12,Role of Berry curvature in the generation of spin currents in Rashba systems,"We study the background (equilibrium), linear and nonlinear spin currents in
2D Rashba spin-orbit coupled systems with Zeeman splitting and in 3D
noncentrosymmetric metals using modified spin current operator by inclusion of
the anomalous velocity. The linear spin Hall current arises due to the
anomalous velocity of charge carriers induced by the Berry curvature. The
nonlinear spin current occurs due to the band velocity and/or the anomalous
velocity. For 2D Rashba systems, the background spin current saturates at high
Fermi energy (independent of the Zeeman coupling), linear spin current exhibits
a plateau at the Zeeman gap and nonlinear spin currents are peaked at the gap
edges. The magnitude of the nonlinear spin current peaks enhances with the
strength of Zeeman interaction. The linear spin current is polarized out of
plane, while the nonlinear ones are polarized in-plane. We witness pure
anomalous nonlinear spin current with spin polarization along the direction of
propagation. In 3D noncentrosymmetric metals, background and linear spin
currents are monotonically increasing functions of Fermi energy, while
nonlinear spin currents vary non-monotonically as a function of Fermi energy
and are independent of the Berry curvature. These findings may provide useful
information to manipulate spin currents in Rashba spin-orbit coupled systems.",2101.04435v2
2018-06-20,Teetering Stars: Resonant Excitation of Stellar Obliquities by Hot and Warm Jupiters with External Companions,"Stellar spin-orbit misalignments (obliquities) in hot Jupiter systems have
been extensively probed. Such obliquities may reveal clues about hot Jupiter
dynamical histories. Common explanations for generating obliquities include
high-eccentricity migration and primordial disk misalignment. This paper
investigates another mechanism for producing stellar spin-orbit misalignments
in systems hosting a close-in planet with an external, modestly inclined
companion. Spin-orbit misalignment may be excited due to a secular resonance,
occurring when the precession rate of the stellar spin axis (driven by the
inner planet) becomes comparable to the nodal precession rate of the inner
planet (driven by the companion). Due to the spin-down of the host star via
magnetic braking, this resonance may be achieved during the star's
main-sequence lifetime for a wide range of planet masses and orbital
architectures. Obliquity excitation is accompanied by a decrease in mutual
inclination between the inner planet and perturber, and can thus erase high
inclinations. For hot Jupiters, the stellar spin axis is strongly coupled to
the orbital axis, and obliquity excitation by a giant planet companion requires
a strong perturber, usually located within 1-2 AU. For warm Jupiters, the spin
and orbital axes are more weakly coupled, and the resonance may be achieved for
distant giant planet perturbers (at several to tens of AU). Since warm Jupiters
have a high occurrence rate of distant planetary companions with appropriate
properties for resonant obliquity excitation, stellar obliquities in warm
Jupiter systems may be common, particularly for warm Jupiters orbiting cool
stars that have undergone significant spin-down.",1806.07892v2
2003-08-18,The orientation and magnitude of the orbital precession velocity of a binary pulsar system with double spins,"The measurability of the spin--orbit (S--L) coupling induced orbital effect
is dependent on the orientation and magnitude of the orbital precession
velocity, ${\bf \Omega}_0$. This paper derives ${\bf \Omega}_0$ in the case
that both spins in the binary system contribute to the spin--orbit (S--L)
coupling, which is suitable for the most popular binary pulsars, Neutron
star--White Dwarf star (NS--WD) binaries (as well as for NS--NS binaries). This
paper shows that from two constraints, the conservation of the total angular
momentum and the triangle formed by the orbital angular momentum, ${\bf L}$,
the sum the spin angular momenta of the two stars, ${\bf S}$, and the total
angular momentum, ${\bf J}$, the orbital precession velocity, ${\bf \Omega}_0$,
along ${\bf J}$ is inevitable. Moreover, by the relation, $S/L\ll 1$, which is
satisfied for a general binary pulsar, a significant ${\bf \Omega}_0$ (in
magnitude) is inevitable, 1.5 Post Newtonian order (PN). Which are similar to
the case of one spin as discussed by many authors. However unlike the one spin
case, the magnitude of the precession velocity of ${\bf \Omega}_0$ varies
significantly due to the variation of the sum the spin angular momenta of the
two stars, ${\bf S}$, which can lead to significant secular variabilities in
binary pulsars.",0308286v1
2018-04-26,Spin transport in graphene/transition metal dichalcogenide heterostructures,"Since its discovery, graphene has been a promising material for spintronics:
its low spin-orbit coupling, negligible hyperfine interaction, and high
electron mobility are obvious advantages for transporting spin information over
long distances. However, such outstanding transport properties also limit the
capability to engineer active spintronics, where strong spin-orbit coupling is
crucial for creating and manipulating spin currents. To this end, transition
metal dichalcogenides, which have larger spin-orbit coupling and good interface
matching, appear to be highly complementary materials for enhancing the
spin-dependent features of graphene while maintaining its superior charge
transport properties. In this review, we present the theoretical framework and
the experiments performed to detect and characterize the spin-orbit coupling
and spin currents in graphene/transition metal dichalcogenide heterostructures.
Specifically, we will concentrate on recent measurements of Hanle precession,
weak antilocalization and the spin Hall effect, and provide a comprehensive
theoretical description of the interconnection between these phenomena.",1804.10000v1
2015-07-31,"Edge states, spin transport and impurity induced local density of states in spin-orbit coupled graphene","We study graphene which has both spin-orbit coupling (SOC), taken to be of
the Kane-Mele form, and a Zeeman field induced due to proximity to a
ferromagnetic material. We show that a zigzag interface of graphene having SOC
with its pristine counterpart hosts robust chiral edge modes in spite of the
gapless nature of the pristine graphene; such modes do not occur for armchair
interfaces. Next we study the change in the local density of states (LDOS) due
to the presence of an impurity in graphene with SOC and Zeeman field, and
demonstrate that the Fourier transform of the LDOS close to the Dirac points
can act as a measure of the strength of the spin-orbit coupling; in addition,
for a specific distribution of impurity atoms, the LDOS is controlled by a
destructive interference effect of graphene electrons which is a direct
consequence of their Dirac nature. Finally, we study transport across junctions
which separates spin-orbit coupled graphene with Kane-Mele and Rashba terms
from pristine graphene both in the presence and absence of a Zeeman field. We
demonstrate that such junctions are generally spin active, namely, they can
rotate the spin so that an incident electron which is spin polarized along some
direction has a finite probability of being transmitted with the opposite spin.
This leads to a finite, electrically controllable, spin current in such
graphene junctions. We discuss possible experiments which can probe our
theoretical predictions.",1507.08762v3
2020-01-14,Anomalous Josephson Hall effect charge and transverse spin currents in superconductor/ferromagnetic insulator/superconductor junctions,"Interfacial spin-orbit coupling in Josephson junctions offers an intriguing
way to combine anomalous Hall and Josephson physics in a single device. We
study theoretically how the superposition of both effects impacts
superconductor/ferromagnetic insulator/superconductor junctions' transport
properties. Transverse momentum-dependent skew tunneling of Cooper pairs
through the spin-active ferromagnetic insulator interface creates sizable
transverse Hall supercurrents, to which we refer as anomalous Josephson Hall
effect currents. We generalize the Furusaki-Tsukada formula, which got
initially established to quantify usual (tunneling) Josephson current flows, to
evaluate the transverse current components and demonstrate that their
amplitudes are widely adjustable by means of the spin-orbit coupling strengths
or the superconducting phase difference across the junction. As a clear
spectroscopic fingerprint of Josephson junctions, well-localized subgap bound
states form around the interface. By analyzing the spectral properties of these
states, we unravel an unambiguous correlation between spin-orbit
coupling-induced asymmetries in their energies and the transverse current
response, founding the currents' microscopic origin. Moreover, skew tunneling
simultaneously acts like a transverse spin filter for spin-triplet Cooper pairs
and complements the discussed charge current phenomena by their spin current
counterparts. The junctions' universal spin-charge current cross ratios provide
valuable possibilities to experimentally detect and characterize interfacial
spin-orbit coupling.",2001.04691v2
2005-06-27,Spatial imaging of the spin Hall effect and current-induced polarization in two-dimensional electron gases,"Spin-orbit coupling in semiconductors relates the spin of an electron to its
momentum and provides a pathway for electrically initializing and manipulating
electron spins for applications in spintronics and spin-based quantum
information processing. This coupling can be regulated with quantum confinement
in semiconductor heterostructures through band structure engineering. Here we
investigate the spin Hall effect and current-induced spin polarization in a
two-dimensional electron gas confined in (110) AlGaAs quantum wells using Kerr
rotation microscopy. In contrast to previous measurements, the spin Hall
profile exhibits complex structure, and the current-induced spin polarization
is out-of-plane. The experiments map the strong dependence of the
current-induced spin polarization to the crystal axis along which the electric
field is applied, reflecting the anisotropy of the spin-orbit interaction.
These results reveal opportunities for tuning a spin source using quantum
confinement and device engineering in non-magnetic materials.",0506704v1
2015-02-04,Effective-one-body Hamiltonian with next-to-leading order spin-spin coupling,"We propose a way of including the next-to-leading (NLO) order spin-spin
coupling into an effective-one-body (EOB) Hamiltonian. This work extends [S.
Balmelli and P. Jetzer, Phys. Rev. D 87, 124036 (2013)], which is restricted to
the case of equatorial orbits and aligned spins, to general orbits with
arbitrary spin orientations. This is done applying appropriate canonical
phase-space transformations to the NLO spin-spin Hamiltonian in
Arnowitt-Deser-Misner (ADM) coordinates, and systematically adding ""effectiv""
quantities at NLO to all spin-squared terms appearing in the EOB Hamiltonian.
As required by consistency, the introduced quantities reduce to zero in the
test- mass limit. We expose the result both in a general gauge and in a
gauge-fixed form. The last is chosen such as to minimize the number of new
coefficients that have to be inserted into the effective spin squared. As a
result, the 25 parameters that describe the ADM NLO spin-spin dynamics get
condensed into only 12 EOB terms.",1502.01343v1
2015-10-20,Effective spin-chain model for strongly interacting one-dimensional atomic gases with an arbitrary spin,"We present a general form of the effective spin-chain model for strongly
interacting atomic gases with an arbitrary spin in the one-dimensional(1D)
traps. In particular, for high-spin systems the atoms can collide in multiple
scattering channels, and we find that the resulted form of spin-chain model
generically follows the same structure as that of the interaction potentials.
This is a unified form working for any spin, statistics (Bose or Fermi) and
confinement potentials. We adopt the spin-chain model to reveal both the
ferromagnetic(FM) and anti-ferromagnetic(AFM) magnetic orders for strongly
interacting spin-1 bosons in 1D traps. We further show that by adding the
spin-orbit coupling, the FM/AFM orders can be gradually destroyed and
eventually the ground state exhibits universal spin structure and contacts that
are independent of the strength of spin-orbit coupling.",1510.06087v2
2016-09-19,Switching ferromagnetic spins by an ultrafast laser pulse: Emergence of giant optical spin-orbit torque,"Faster magnetic recording technology is indispensable to massive data storage
and big data sciences. {All-optical spin switching offers a possible solution},
but at present it is limited to a handful of expensive and complex rare-earth
ferrimagnets. The spin switching in more abundant ferromagnets may
significantly expand the scope of all-optical spin switching. Here by studying
40,000 ferromagnetic spins, we show that it is the optical spin-orbit torque
that determines the course of spin switching in both ferromagnets and
ferrimagnets. Spin switching occurs only if the effective spin angular momentum
of each constituent in an alloy exceeds a critical value. Because of the strong
exchange coupling, the spin switches much faster in ferromagnets than
weakly-coupled ferrimagnets. This establishes a paradigm for all-optical spin
switching. The resultant magnetic field (65 T) is so big that it will
significantly reduce high current in spintronics, thus representing the
beginning of photospintronics.",1609.05855v1
2014-06-18,Spin-helical Dirac states in graphene induced by polar-substrate surfaces with giant spin-orbit interaction: a new platform for spintronics,"Spintronics, or spin electronics, is aimed at efficient control and
manipulation of spin degrees of freedom in electron systems. To comply with
demands of nowaday spintronics, the studies of electron systems hosting giant
spin-orbit-split electron states have become one of the most important
directions providing us with a basis for desirable spintronics devices. In
construction of such devices, it is also tempting to involve graphene, which
has attracted great attention because of its unique and remarkable electronic
properties and was recognized as a viable replacement for silicon in
electronics. In this case, a challenging goal is to make graphene Dirac states
spin-polarized. Here, we report on absolutely new promising pathway to create
spin-polarized Dirac states based on coupling of graphene and polar-substrate
surface states with giant Rashba-type spin-splitting. We demonstrate how the
spin-helical Dirac states are formed in graphene deposited on the surface of
BiTeCl. This coupling induces spin separation of the originally spin-degenerate
graphene states and results in fully helical in-plane spin polarization of the
Dirac electrons.",1406.4795v1
2019-02-07,Spin current generation in organic antiferromagnets,"Spin current--a flow of electron spins without a charge current--is an ideal
information carrier free from Joule heating for electronic devices. The
celebrated spin Hall effect, which arises from the relativistic spin-orbit
coupling, enables us to generate and detect spin currents in inorganic
materials and semiconductors, taking advantage of their constituent heavy
atoms. In contrast, organic materials consisting of molecules with light
elements have been believed to be unsuited for spin current generation. Here we
show that a class of organic antiferromagnets with checker-plate type molecular
arrangements can serve as a spin current generator by applying a thermal
gradient or an electric field, even with vanishing spin-orbit coupling. Our
findings provide another route to create a spin current distinct from the
conventional spin Hall effect and open a new field of spintronics based on
organic magnets having advantages of small spin scattering and long lifetime.",1902.02506v1
2019-04-24,Enhanced spin-triplet pairing in magnetic junctions with s-wave superconductors,"A common path to superconducting spintronics, Majorana fermions, and
topologically-protected quantum computing relies on spin-triplet
superconductivity. While naturally occurring spin-triplet pairing is elusive
and even common spin-triplet candidates, such as Sr$_2$RuO$_4$, support
alternative explanations, proximity effects in heterostructures can overcome
these limitations. It is expected that robust spin-triplet superconductivity in
magnetic junctions should rely on highly spin-polarized magnets or complex
magnetic multilayers. Instead, we predict that the interplay of interfacial
spin-orbit coupling and the barrier strength in simple magnetic junctions, with
only a small spin polarization and s-wave superconductors, can lead to nearly
complete spin-triplet superconducting proximity effects. This peculiar behavior
arises from an effective perfect transparency: interfacial spin-orbit coupling
counteracts the native potential barrier for states of a given spin and wave
vector. We show that the enhanced spin-triplet regime is characterized by a
huge increase in conductance magnetoanisotropy, orders of magnitude larger than
in the normal state.",1904.10773v1
2021-06-27,Electrical control of valley-Zeeman spin-orbit coupling-induced spin precession at room temperature,"The ultimate goal of spintronics is achieving electrically controlled
coherent manipulation of the electron spin at room temperature to enable
devices such as spin field-effect transistors. With conventional materials,
coherent spin precession has been observed in the ballistic regime and at low
temperatures only. However, the strong spin anisotropy and the valley character
of the electronic states in 2D materials provide unique control knobs to
manipulate spin precession. Here, by manipulating the anisotropic spin-orbit
coupling in bilayer graphene by the proximity effect to WSe$_2$, we achieve
coherent spin precession in the absence of an external magnetic field, even in
the diffusive regime. Remarkably, the sign of the precessing spin polarization
can be tuned by a back gate voltage and by a drift current. Our realization of
a spin field-effect transistor at room temperature is a cornerstone for the
implementation of energy-efficient spin-based logic.",2106.14237v1
2022-05-08,Coupled superconducting spin qubits with spin-orbit interaction,"Superconducting spin qubits, also known as Andreev spin qubits, promise to
combine the benefits of superconducting qubits and spin qubits defined in
quantum dots. While most approaches to control these qubits rely on controlling
the spin degree of freedom via the supercurrent, superconducting spin qubits
can also be coupled to each other via the superconductor to implement two-qubit
quantum gates. We theoretically investigate the interaction between
superconducting spin qubits in the weak tunneling regime and concentrate on the
effect of spin-orbit interaction (SOI), which can be large in
semiconductor-based quantum dots and thereby offers an additional tuning
parameter for quantum gates. We find analytically that the effective
interaction between two superconducting spin qubits consists of Ising,
Heisenberg, and Dzyaloshinskii-Moriya interactions and can be tuned by the
superconducting phase difference, the tunnel barrier strength, or the SOI
parameters. The Josephson current becomes dependent on SOI and spin
orientations. We demonstrate that this interaction can be used for fast
controlled phase-flip gates with a fidelity >99.99%. We propose a scalable
network of superconducting spin qubits which is suitable for implementing the
surface code.",2205.03843v2
2017-02-23,Correlation effects and hidden spin-orbit entangled electronic order in parent and electron-doped iridates Sr$_2$IrO$_4$,"Analogs of the high-T$_c$ cuprates have been long sought after in transition
metal oxides. Due to the strong spin-orbit coupling (SOC), the $5d$ perovskite
iridates Sr$_2$IrO$_4$ exhibit a low-energy electronic structure remarkably
similar to the cuprates. Whether a superconducting state exists as in the
cuprates requires understanding the correlated spin-orbit entangled electronic
states. Recent experiments discovered hidden order in the parent and electron
doped iridates, some with striking analogies to the cuprates, including Fermi
surface pockets, Fermi arcs, and pseudogap. Here, we study the correlation and
disorder effects in a five-orbital model derived from the band theory. We find
that the experimental observations are consistent with a $d$-wave spin-orbit
density wave order that breaks the symmetry of a joint two-fold spin-orbital
rotation followed by a lattice translation. There is a Berry phase and a
plaquette spin flux due to spin procession as electrons hop between Ir atoms,
akin to the intersite SOC in quantum spin Hall insulators. The associated
staggered circulating $J_\text{eff}=1/2$ spin current can be probed by advanced
techniques of spin-current detection in spintronics. This electronic order can
emerge spontaneously from the intersite Coulomb interactions between the
spatially extended iridium $5d$ orbitals, turning the metallic state into an
electron doped quasi-2D Dirac semimetal with important implications on the
possible superconducting state suggested by recent experiments.",1702.07070v4
2022-03-29,Electronic structure of $\boldsymbolα$-RuCl$_3$ by fixed-node and fixed-phase diffusion Monte Carlo methods,"Layered material $\alpha$-RuCl$_3$ has caught wide attention due to its
possible realization of Kitaev's spin liquid and its electronic structure that
involves the interplay of electron-electron correlations and spin-orbit
effects. Several DFT$+U$ studies have suggested that both electron-electron
correlations and spin-orbit effects are crucial for accurately describing the
band gap. This work studies the importance of these two effects using
fixed-node and fixed-phase diffusion Monte Carlo calculations both in
spin-averaged and explicit spin-orbit formalisms. In the latter, the
Slater-Jastrow trial function is constructed from two-component spin-orbitals
using our recent quantum Monte Carlo (QMC) developments and thoroughly tested
effective core potentials. Our results show that the gap in the ideal crystal
is already accurately described by the spin-averaged case, with the dominant
role being played by the magnetic ground state with significant exchange and
electron correlation effects. We find qualitative agreement between hybrid DFT,
DFT+$U$, and QMC. In addition, QMC results agree very well with available
experiments, and we identify the values of exact Fock exchange mixing that
provide comparable gaps. Explicit spin-orbit QMC calculations reveal that the
effect of spin-orbit coupling on the gap is minor, of the order of 0.2 eV,
which corresponds to the strength of the spin-orbit of the Ru atom.",2203.15949v2
2014-06-18,Charge and spin polarized currents in mesoscopic rings with Rashba spin-orbit interactions coupled to an electron reservoir,"The electronic states of a mesoscopic ring are assessed in the presence of
Rashba Spin Orbit coupling and a $U(1)$ gauge field. Spin symmetric coupling to
an ideal lead is implemented following B\""uttiker's voltage probe. The exact
density of states is derived using the reservoir uncoupled eigenstates as basis
functions mixed by the reservoir coupling. The decay time of uncoupled electron
eigenstates is derived by fitting the broadening profiles. The spin and charge
persistent currents are computed in the presence of the SO interaction and the
reservoir coupling for two distinct scenarios of the electron filling fraction.
The degradation of the persistent currents depends uniformly on the reservoir
coupling but nonuniformly in temperature, the latter due to the fact that
currents emerge from different depths of the Fermi sea, and thus for some
regimes of flux, they are provided with a protective gap. Such flux regimes can
be tailored by the SO coupling for both charge and spin currents.",1406.4659v1
2007-02-28,Cubic Dresselhaus Spin-Orbit Coupling in 2D Electron Quantum Dots,"We study effects of the oft-neglected cubic Dresselhaus spin-orbit coupling
(i.e., $\propto p^3$) in GaAs/AlGaAs quantum dots. Using a semiclassical
billiard model, we estimate the magnitude of the spin-orbit induced avoided
crossings in a closed quantum dot in a Zeeman field. Using these results,
together with previous analyses based on random matrix theory, we calculate
corresponding effects on the conductance through an open quantum dot. Combining
our results with an experiment on conductance through an 8 um^2 quantum dot [D
M Zumbuhl et al., Phys. Rev. B 72, 081305 (2005)] suggests that 1) the GaAs
Dresselhaus coupling constant, $\gamma$, is approximately 9 eVA^3,
significantly less than the commonly cited value of 27.5 eVA^3 and 2) the
majority of the spin-flip component of spin-orbit coupling can come from the
cubic Dresselhaus term.",0702667v1
2007-08-17,The Two Dimensional Kondo Model with Rashba Spin-Orbit Coupling,"We investigate the effect that Rashba spin-orbit coupling has on the low
energy behaviour of a two dimensional magnetic impurity system. It is shown
that the Kondo effect, the screening of the magnetic impurity at temperatures T
< T_K, is robust against such spin-orbit coupling, despite the fact that the
spin of the conduction electrons is no longer a conserved quantity. A proposal
is made for how the spin-orbit coupling may change the value of the Kondo
temperature T_K in such systems and the prospects of measuring this change are
discussed. We conclude that many of the assumptions made in our analysis
invalidate our results as applied to recent experiments in semi-conductor
quantum dots but may apply to measurements made with magnetic atoms placed on
metallic surfaces.",0708.2435v2
2012-08-08,Tuning Rashba and Dresselhaus spin-orbit couplings: Effects on singlet and triplet condensation with Fermi atoms,"We investigate the pair condensation of a two-spin-component Fermi gas in the
presence of both Rashba and Dresselhaus spin-orbit couplings. We calculate the
condensate fraction in the BCS-BEC crossover both in two and in three
dimensions by taking into account singlet and triplet pairings. These
quantities are studied by varying the spin-orbit interaction from the case with
the only Rashba to the equal-Rashba-Dresselhaus one. We find that, by mixing
the two couplings, the singlet pairing decreases while the triplet pairing is
suppressed in the BCS regime and increased in the BEC regime, both in two and
three dimensions. At fixed spin-orbital strength, the greatest total condensate
fraction is obtained when only one coupling (only Rashba or only Dresselhaus)
is present.",1208.1637v2
2012-11-07,Finite-Momentum Dimer Bound State in Spin-Orbit Coupled Fermi Gas,"We investigate the two-body properties of a spin-1/2 Fermi gas subject to a
spin-orbit coupling induced by laser fields. When an attractive s-wave
interaction between unlike spins is present, the system may form a dimer bound
state. Surprisingly, in the presence of a Zeeman field along the direction of
the spin-orbit coupling, the bound state obtains finite center-of-mass
mechanical momentum, whereas under the same condition but in the absence of the
two-body interaction, the system has zero total momentum. This unusual result
can be regarded as a consequence of the broken Galilean invariance by the
spin-orbit coupling. Such a finite-momentum bound state will have profound
effects on the many-body properties of the system.",1211.1700v2
2012-12-12,Feshbach Resonance in a Synthetic Non-Abelian Gauge Field,"We study the Feshbach resonance of spin-1/2 particles in the presence of a
uniform synthetic non-Abelian gauge field that produces spin orbit coupling
along with constant spin potentials. We develop a renormalizable quantum field
theory that includes the closed channel boson which engenders the Feshbach
resonance, in the presence of the gauge field. By a study of the scattering of
two particles in the presence of the gauge field, we show that the Feshbach
magnetic field, where the apparent low energy scattering length diverges,
depends on the conserved centre of mass momentum of the two particles. For high
symmetry gauge fields, such as the one which produces an isotropic Rashba spin
orbit coupling, we show that the system supports two bound states over a regime
of magnetic fields for a negative background scattering length and resonance
width comparable to the energy scale of the spin orbit coupling. We discuss the
consequences of these findings for the many body setting, and point out that a
broad resonance (width larger than spin orbit coupling energy scale) is most
favourable for the realization of the rashbon condensate.",1212.2858v1
2014-11-24,Numerical analysis of spin-orbit coupled one dimensional Fermi gas in the magnetic field,"We use the density matrix renormalization group method(DMRG) and the infinite
time evolved block decimation method(iTEBD) to investigate the ground states of
the spin-orbit coupled Fermi gas in a one dimensional optical lattice with a
transverse magnetic field. We discover that the system with attractive
interaction can have a polarized insulator(PI), a superconducting phase(SC), a
Luther-Emery(LE) phase and a band insulator(BI) phase as we vary the chemical
potential and the strength of magnetic field. We find that spin-orbit coupling
induces a triplet pairing order at zero momentum with the same critical
exponent as that of the singlet pairing one in both the SC and the LE phase. In
contrast to the FFLO phase found in the spin imbalanced system without
spin-orbit coupling, pairings at finite momentum in these two phases have a
larger exponent hence do not dictate the long range behavior. We also find good
agreements of the dominant correlations between numerical results and the
prediction from the bosonization method. The presence of Majorana fermions is
tested. However, unlike results from the mean field study, we do not find
positive evidence of Majorana fermions in our system.",1411.6439v1
2016-05-28,Manifestation of chirality in the vortex lattice in a two-dimensional topological superconductor,"We study the vortex lattice in a two-dimensional s-wave topological
superconductor with Rashba spin-orbit coupling and Zeeman field by solving the
Bogoliubov-de Gennes equations self-consistently for the superconducting order
parameter. We find that when spin-orbit coupling is relatively weak, one of the
two underlying chiralities in the topological superconducting state can be
strongly manifest in the vortex core structure and govern the response of the
system to vorticity and a nonmagnetic impurity where the vortex is pinned. The
Majorana zero mode in the vortex core is found to be robust against the
nonmagnetic impurity in that it remains effectively a zero-energy bound state
regardless of the impurity potential strength and the major chirality. The spin
polarization of the Majorana bound state depends on the major chirality for
weak spin-orbit coupling, while it is determined simply by the vorticity when
spin-orbit coupling is relatively strong.",1605.08934v2
2019-06-19,Superconductivity of mixed parity and frequency in an anisotropic spin-orbit coupling,"We illuminate the superconducting phases in [001]-grown-noncentrosymmetric
quantum wells with an anisotropic spin-orbit coupling in the presence of
on-site Hubbard interaction. Within the random phase approximation, we
investigate the spin-fluctuation-mediated pairing in the presence of
Rashba/Dresselhaus antisymmetric spin-orbit couplings. Although the existence
of spatial inversion symmetry desires a dominant d-wave pairing for all filling
levels, a broken inversion symmetry generates antisymmetric spin-orbit coupling
and mixes the even- and odd-parity in the superconducting gap. We study the
symmetry of the mixed-parity gap for various strengths of Hubbard interaction.
Besides, we consider a superconductor-ferromagnet junction to survey the
modifications of superconducting order parameters and observe an admixture of
even- and odd-frequencies due to the ferromagnet exchange field.",1906.08130v1
2019-04-26,The quasiclassical theory for interfaces with spin--orbit coupling,"In recent years, substantial progress has been made regarding the application
of quasiclassical theory on superconducting hybrid structures. This theoretical
framework is reliant on a proper set of boundary conditions in order to
describe multilayered systems. With the advent of the field of superconducting
spintronics, systems which combine heavy metal layers, in which there is large
spin--orbit coupling, with ferromagnets have received a great deal of
attention, due to their potential for generating long range triplet
superconductivity. In contrast to interfaces of strongly spin polarized
materials, which are well understood, a quasiclassical theory for interfaces in
systems where there is significant spin--orbit coupling does not yet exist.
After reviewing the quasiclassical theory for interfaces, we here solve this
problem by deriving a new set of boundary conditions which take spin--orbit
coupling explicitly into account. We then go on to apply these boundary
conditions to a superconductor-ferromagnet (SF) bilayer and an SFS Josephson
weak link, demonstrating the emergence of long range triplet superconductivity
in these systems.",1904.11986v2
2003-03-23,Spin-Orbit Coupling and Time-Reversal Symmetry in Quantum Gates,"We study the effect of spin-orbit coupling on quantum gates produced by
pulsing the exchange interaction between two single electron quantum dots.
Spin-orbit coupling enters as a small spin precession when electrons tunnel
between dots. For adiabatic pulses the resulting gate is described by a unitary
operator acting on the four-dimensional Hilbert space of two qubits. If the
precession axis is fixed, time-symmetric pulsing constrains the set of possible
gates to those which, when combined with single qubit rotations, can be used in
a simple CNOT construction. Deviations from time-symmetric pulsing spoil this
construction. The effect of time asymmetry is studied by numerically
integrating the Schr\""odinger equation using parameters appropriate for GaAs
quantum dots. Deviations of the implemented gate from the desired form are
shown to be proportional to dimensionless measures of both spin-orbit coupling
and time asymmetry of the pulse.",0303474v3
2007-09-18,Intense terahertz laser fields on a two-dimensional hole gas with Rashba spin-orbit coupling,"We investigate the influence on the density of states and the density of spin
polarization for a two-dimensional hole gas with Rashba spin-orbit coupling
under intense terahertz laser fields. Via Floquet theorem, we solve the
time-dependent Schr\""{o}dinger equation and calculate these densities. It is
shown that a terahertz magnetic moment can be induced for low hole
concentration. Different from the electron case, the induced magnetic moment is
quite anisotropic due to the anisotropic spin-orbit coupling. Both the
amplitude and the direction of the magnetic moment depend on the direction of
the terahertz field. We further point out that for high hole concentration, the
magnetic moment becomes very small due to the interference caused by the
momentum dependence of the spin-orbit coupling. This effect also appears in
two-dimensional electron systems.",0709.2774v1
2008-11-27,Interference of heavy holes in an Aharonov-Bohm ring,"We study the coherent transport of heavy holes through a one-dimensional ring
in the presence of spin-orbit coupling. Spin-orbit interaction of holes, cubic
in the in-plane components of momentum, gives rise to an angular momentum
dependent spin texture of the eigenstates and influences transport. We analyze
the dependence of the resulting differential conductance of the ring on hole
polarization of the leads and the signature of the textures in the
Aharonov-Bohm oscillations when the ring is in a perpendicular magnetic field.
We find that the polarization-resolved conductance reveals whether the dominant
spin-orbit coupling is of Dresselhaus or Rashba type, and that the cubic
spin-orbit coupling can be distinguished from the conventional linear coupling
by observing the four-peak structure in the Aharonov-Bohm oscillations.",0811.4566v1
2011-02-20,Mean-field Dynamics of Spin-Orbit Coupled Bose-Einstein Condensates,"Spin-orbit coupling (SOC), the interaction between the spin and momentum of a
quantum particle, is crucial for many important condensed matter phenomena. The
recent experimental realization of SOC in neutral bosonic cold atoms provides a
new and ideal platform for investigating spin-orbit coupled quantum many-body
physics. In this Letter, we derive a generic Gross-Pitaevskii equation as the
starting point for the study of many-body dynamics in spin-orbit coupled
Bose-Einstein condensates. We show that different laser setups for realizing
the same SOC may lead to different mean field dynamics. Various ground state
phases (stripe, phase separation, etc.) of the condensate are found in
different parameter regions. A new oscillation period induced by the SOC,
similar to the Zitterbewegung oscillation, is found in the center of mass
motion of the condensate.",1102.4045v3
2011-09-09,Trapped two-dimensional condensates with synthetic spin-orbit coupling,"We study trapped 2D atomic Bose-Einstein condensates with spin-independent
interactions in the presence of an isotropic spin-orbit coupling, showing that
a rich physics results from the non-trivial interplay between spin-orbit
coupling, confinement and inter-atomic interactions. For low interactions two
types of half-vortex solutions with different winding occur, whereas
strong-enough repulsive interactions result in a stripe-phase similar to that
predicted for homogeneous condensates. Intermediate interaction regimes are
characterized for large enough spin-orbit coupling by an hexagonally-symmetric
phase with a triangular lattice of density minima similar to that observed in
rapidly rotating condensates.",1109.2045v2
2012-05-31,Three-Dimensional Spin-Orbit Coupling in a Trap,"We investigate the properties of an atom under the influence of a synthetic
three-dimensional spin-orbit coupling (Weyl coupling) in the presence of a
harmonic trap. The conservation of total angular momentum provides a
numerically efficient scheme for finding the spectrum and eigenfunctions of the
system. We show that at large spin-orbit coupling the system undergoes
dimensional reduction from three to one dimension at low energies, and the
spectrum is approximately Landau level-like. At high energies, the spectrum is
approximately given by the three-dimensional isotropic harmonic oscillator. We
explore the properties of the ground state in both position and momentum space.
We find the ground state has spin textures with oscillations set by the
spin-orbit length scale.",1206.0018v2
2012-06-06,Trapped Fermi gases with Rashba spin-orbit coupling in two dimensions,"We use the Bogoliubov-de Gennes formalism to analyze harmonically trapped
Fermi gases with Rashba-type spin-orbit coupling in two dimensions. We consider
both population-balanced and -imbalanced Fermi gases throughout the BCS-BEC
evolution, and study the effects of spin-orbit coupling on the spontaneously
induced countercirculating mass currents and the associated intrinsic angular
momentum. In particular, we find that even a small spin-orbit coupling
destabilizes Fulde-Ferrel-Larkin-Ovchinnikov (FFLO)-type spatially modulated
superfluid phases as well as the phase-separated states against the polarized
superfluid phase. We also show that the continuum of quasiparticle and
quasihole excitation spectrum can be connected by zero, one or two discrete
branches of interface modes, depending on the number of interfaces between a
topologically trivial phase (e.g. locally unpolarized/low-polarized superfluid
or spin-polarized normal) and a topologically nontrivial one (e.g. locally
high-polarized superfluid) that may be present in a trapped system.",1206.1240v1
2014-02-26,Topological metallic states in spin-orbit coupled bilayer systems,"We investigate the influence of different spin-orbit couplings on topological
phase transitions in the bilayer Kane-Mele model. We find that the competition
between intrinsic spin-orbit coupling and Rashba spin-orbit coupling can lead
to two dimensional topological metallic states with nontrivial topology. Such
phases, although having a metallic bulk, still possess edge states with
well-defined topological invariants. Specifically, we show that with preserved
time reversal symmetry, the system can exhibit a $\mathbb{Z}_2$-metallic phase
with spin helical edge states and a nontrivial $\mathbb{Z}_2$ invariant. When
time reversal symmetry is broken, a Chern metallic phase could appear with
chiral edge states and a nontrivial Chern invariant.",1402.6502v1
2014-04-15,Localization of a spin-orbit coupled Bose-Einstein condensate in a bichromatic optical lattice,"We study the localization of a noninteracting and weakly interacting
Bose-Einstein condensate with spin-orbit coupling loaded in a quasiperiodic
bichromatic optical lattice potential using the numerical solution and
variational approximation of a binary mean-field Gross-Pitaevskii equation with
two pseudo-spin components. We confirm the existence of the stationary
localized states in the presence of the spin-orbit and Rabi couplings for an
equal distribution of atoms in the two components. We find that the interaction
between the spin-orbit and Rabi couplings favors the localization or
delocalization of the BEC depending on the the phase difference between the
components. We also studied the oscillation dynamics of the localized states
for an initial population imbalance between the two components.",1404.4017v2
2014-10-21,Bose-Einstein condensation with spin-orbit coupling,"The recent realization of synthetic spin-orbit coupling represents an
outstanding achievement in the physics of ultracold quantum gases. In this
review we explore the properties of a spin-orbit-coupled Bose-Einstein
condensate with equal Rashba and Dresselhaus strengths. This system presents a
rich phase diagram, which exhibits a tricritical point separating a
zero-momentum phase, a spin-polarized plane-wave phase, and a stripe phase. In
the stripe phase translational invariance is spontaneously broken, in analogy
with supersolids. Spin-orbit coupling also strongly affects the dynamics of the
system. In particular, the excitation spectrum exhibits intriguing features,
including the suppression of the sound velocity, the emergence of a roton
minimum in the plane-wave phase, and the appearance of a double gapless band
structure in the stripe phase. Finally, we discuss a combined procedure to make
the stripes visible and stable, thus allowing for a direct experimental
detection.",1410.5526v2
2017-03-02,Simple spin-orbit based devices for electron spin polarization,"We propose quantum devices having spin-orbit coupling (but no magnetic fields
or magnetic materials) that, when attached to leads, yield a high degree of
transmitted electron polarization. An example of such a simple device is
treated within a tight binding model composed of two 1D chains coupled by
several consecutive rungs (i.e., a ladder) and subject to a gate voltage. The
ensuing scattering problem (with Rashba spin-orbit coupling) is solved, and a
sizable polarization is predicted. When the ladder is twisted into a helix (as
in DNA), the curvature energy augments the polarization. For a system with
random spin-orbit coupling, the distribution of polarization is broad, hence a
high degree of polarization can be obtained in a measurement of a given
disorder-realization. When disorder occurs in a double helix structure then,
depending on scattering energy, the variance of the polarization distribution
can increase even further due to helix curvature.",1703.00717v2
2018-04-05,Derivation of a Ginzburg-Landau free energy density containing mixed gradient terms of a $p+ip$ superconductor with spin-orbit coupling,"A Ginzburg-Landau free energy for a superconducting chiral p-wave order
parameter is derived from a two-dimensional tight binding lattice model with
weak spin-orbit coupling included as a general symmetry-breaking field.
Superconductivity is accounted for by a BCS-type nearest neighbor opposite-spin
interaction where we project the potential onto the $p$-wave irreducible
representation of the square lattice symmetry group and assume this to be the
dominating order. The resulting free energy contains kinetic terms that mix
components of the order parameter as well as directional gradients --- so
called mixed gradient terms --- as a virtue of the symmetry of the order
parameter. Spin-orbit coupling and electron-hole anisotropy lead to additional
contributions to the coefficients of these terms, increasing the number of
necessary phenomenological parameters by one compared to previous work, and
leading to an increase in the coefficient measuring Fermi surface anisotropy
for Rashba spin-orbit coupling in the continuum limit.",1804.01808v1
2010-05-17,Trigonal warping and anisotropic band splitting in monolayer graphene due to Rashba spin-orbit coupling,"We study the electronic band structure of monolayer graphene when Rashba
spin-orbit coupling is present. We show that if the Rashba spin-orbit coupling
is stronger than the intrinsic spin-orbit coupling, the low energy bands
undergo trigonal-warping deformation and that for energies smaller than the
Lifshitz energy, the Fermi circle breaks up into separate parts. The effect is
very similar to what happens in bilayer graphene at low energies. We discuss
the possible experimental implications, such as threefold increase of the
minimal conductivity for low electron densities, the wavenumber dependence of
the band splitting and the spin polarization structure. Our theoretical
predictions are in agreement with recent experimental results.",1005.2933v2
2016-11-06,Quasiclassical theory of magnetoelectric effects in superconducting heterostructures in the presence of the spin-orbit coupling,"The quasiclassical theory in terms of equations for the Green's functions
(Eilenberger equations) is generalized in order to allow for quantitative
description of the magneto-electric effects and proximity-induced triplet
correlations in the presence of spin-orbit coupling in hybrid superconducting
systems. The formalism is valid under the condition that the spin-orbit
coupling is weak with respect to the Fermi energy, but exceeds the
superconducting energy scale considerably. On the basis of the derived
formalism it is shown that the triplet correlations in the spin-orbit coupled
normal metal can be induced by proximity to a singlet superconductor without
any exchange or external magnetic field. They contain an odd-frequency
even-momentum component, which is stable against disorder. The value of the
proximity-induced triplet correlations is of the order of
$\Delta_{so}/\varepsilon_F$, that is absent in the framework of the standard
quasiclassical approximation, but can be described by our theory. The spin
polarization, induced by the Josephson current flowing through the
superconductor/Rashba metal/superconductor junction, is also calculated.",1611.01737v2
2014-05-09,Dicke-type phase transition in a spin-orbit coupled Bose-Einstein condensate,"Spin-orbit coupled Bose-Einstein condensates (BECs) provide a powerful tool
to investigate interesting gauge-field related phenomena. We study the ground
state properties of such a system and show that it can be mapped to the
well-known Dicke model in quantum optics, which describes the interactions
between an ensemble of atoms and an optical field. A central prediction of the
Dicke model is a quantum phase transition between a superradiant phase and a
normal phase. Here we detect this transition in a spin-orbit coupled BEC by
measuring various physical quantities across the phase transition. These
quantities include the spin polarization, the relative occupation of the nearly
degenerate single particle states, the quantity analogous to the photon field
occupation, and the period of a collective oscillation (quadrupole mode). The
applicability of the Dicke model to spin-orbit coupled BECs may lead to
interesting applications in quantum optics and quantum information science.",1405.2132v1
2012-05-21,Stationary States of Trapped Spin-Orbit-Coupled Bose-Einstein Condensates,"We numerically investigate low-energy stationary states of pseudospin-1
Bose-Einstein condensates in the presence of Rashba-Dresselhaus-type spin-orbit
coupling. We show that for experimentally feasible parameters and strong
spin-orbit coupling, the ground state is a square vortex lattice irrespective
of the nature of the spin-dependent interactions. For weak spin-orbit coupling,
the lowest-energy state may host a single vortex. Furthermore, we analytically
derive constraints that explain why certain stationary states do not emerge as
ground states. Importantly, we show that the distinct stationary states can be
observed experimentally by standard time-of-flight spinindependent absorption
imaging.",1205.4601v4
2019-12-04,Enhanced Edelstein effect and interdimensional effects in an electron gas with Rashba spin-orbit coupling interface,"We examine the bound-state and free-state contributions to the density of
states in a three-dimensional electron gas with a two-dimensional interface
with Rashba spin-orbit coupling. Confinement of electrons to the interface is
achieved through the inclusion of an attractive potential in the interface.
Motivation for our research comes from interest in heterostructure materials
that exhibit the Edelstein and inverse Edelstein effects on surfaces or
interfaces due to large Rashba spin-orbit coupling. By modifying the
Hamiltonian of a three-dimensional free electron gas to include an interface
with Rashba spin-orbit coupling and an attractive potential, we are able to
calculate the bound-state and free-state wavefunctions and corresponding
density of states analytically. We find that one of the spin-split energy bands
in the interface has an upper bound, resulting in an enhancement of the
Edelstein and inverse Edelstein effect.",1912.01804v1
2023-11-09,Electronic g-factor and tunable spin-orbit coupling in a gate-defined InSbAs quantum dot,"We investigate transport properties of stable gate-defined quantum dots
formed in an InSb$_{0.87}$As$_{0.13}$ quantum well. High $\textit{g}$-factor
and strong spin-orbit-coupling make InSb$_x$As$_{1-x}$ a promising platform for
exploration of topological superconductivity and spin-based devices. We extract
a nearly isotropic in-plane effective $\textit{g}$-factor by studying the
evolution of Coulomb blockade peaks and differential conductance as a function
of the magnitude and direction of magnetic field. The in-plane
$\textit{g}$-factors, $|g^*_{[1\bar{1}0]}|$ and $|g^*_{[110]}|$, range from 49
- 58. Interestingly, this $\textit{g}$-factor is higher than that found in
quantum dots fabricated from pure InSb quantum wells. We demonstrate tunable
spin-orbit-coupling by tracking a spin-orbit-coupling mediated avoided level
crossing between the ground state and an excited state in magnetic field. By
increasing the electron density, we observed an increase in an avoided crossing
separation, $\Delta_{SO}$. The maximum energy separation extracted is
$\Delta_{SO}$$\sim$100 $\mu$eV.",2311.05693v1
2018-04-06,Intrinsic Spin and Orbital Hall Effects from Orbital Texture,"We show theoretically that both intrinsic spin Hall effect (SHE) and orbital
Hall effect (OHE) can arise in centrosymmetric systems through momentum-space
orbital texture, which is ubiquitous even in centrosymmetric systems unlike
spin texture. OHE occurs even without spin-orbit coupling (SOC) and is
converted into SHE through SOC. The resulting spin Hall conductivity is large
(comparable to that of Pt) but depends on the SOC strength in a nonmonotonic
way. This mechanism is stable against orbital quenching. This work suggests a
path for an ongoing search for materials with stronger SHE. It also calls for
experimental efforts to probe orbital degrees of freedom in OHE and SHE.
Possible ways for experimental detection are briefly discussed.",1804.02118v2
2022-07-15,Tunable spin and orbital Edelstein effect at (111) LaAlO$_3$/SrTiO$_3$ interface,"Converting charge current into spin current is one of the main mechanisms
exploited in spintronics. One prominent example is the Edelstein effect, namely
the generation of a magnetization in response to an external electric field,
which can be realized in systems with lack of inversion symmetry. If a system
has electrons with an orbital angular momentum character, an orbital
magnetization can be generated by the applied electric field giving rise to the
so-called orbital Edelstein effect. Oxide heterostructures are the ideal
platform for these effects due to the strong spin-orbit coupling and the lack
of inversion symmetries. Beyond a gate-tunable spin Edelstein effect, we
predict an orbital Edelstein effect an order of magnitude larger then the spin
one at the (111) LaAlO$_3$/SrTiO$_3$ interface. We model the material as a
bilayer of $t_{2g}$ orbitals using a tight-binding approach, while transport
properties are obtained in the Boltzmann approach. We give an effective model
at low filling which explains the non-trivial behaviour of the Edelstein
response, showing that the hybridization between the electronic bands crucially
impacts the Edelstein susceptibility.",2207.07663v1
2022-12-28,Intrinsic orbital and spin Hall effect in bismuth semimetal,"We investigate the intrinsic orbital Hall conductivity (OHC) and spin Hall
conductivity (SHC) in a bismuth semimetal, by employing an sp-orbital
tight-binding model. We report a notable difference between the anisotropy of
OHC and SHC whose orbital and spin polarizations lie within the basal plane. We
do not observe a substantial correlation between the orbital and spin Berry
curvatures with spin-orbit coupling (SOC) at the Fermi energy, disproving the
correlation between OHC and SHC in a strong SOC regime. We argue the huge SHC
in a Bi semimetal is attributed to its gigantic SOC which strongly affects the
hybridization of the p orbitals, despite its relatively small magnitude of OHC.
We hope the distinct anisotropy of OHC and SHC provides a feasible means to
differentiate between the two effects in experiments.",2212.13891v2
2024-03-12,Negative orbital Hall effect in Germanium,"Our investigation reveals a groundbreaking discovery of a negative inverse
orbital Hall effect (IOHE) in Ge thin films. We employed the innovative orbital
pumping technique where spin-orbital coupled current is injected into Ge films
using YIG/Pt(2)/Ge($t_{Ge}$) and YIG/W(2)/Ge($t_{Ge}$) heterostructures.
Through comprehensive analysis, we observe significant reductions in the
signals generated by coherent (RF-driven) and incoherent (thermal-driven)
spin-orbital pumping techniques. These reductions are attributed to the
presence of a remarkable strong negative IOHE in Ge, showing its magnitude
comparable to the spin-to-charge signal in Pt. Our findings reveal that
although the spin-to-charge conversion in Ge is negligible, the
orbital-to-charge conversion exhibits large magnitude. Our results are
innovative and pioneering in the investigation of negative IOHE by the
injection of spin-orbital currents.",2403.07254v1
1999-02-09,The effect of the spin-orbit geometric phase on the spectrum of Aharonov-Bohm oscillations in a semiconductor mesoscopic ring,"Taking into account the spin precession caused by the spin-orbit splitting of
the conduction band in semiconductor quantum wells, we have calculated the
Fourier spectra of conductance and state-density correlators in a 2D ring, in
order to investigate the structure of the main peak corresponding to
Aharonov-Bohm oscillations. In narrow rings the peak structure is determined by
the competition between the spin-orbit and the Zeeman couplings. The latter
leads to a peak broadening, and produces the peak splitting in the
state-density Fourier spectrum. We have found an oscillation of the peak
intensity as a function of the spin-orbit coupling constant, and this effect of
the quantum interference caused by the spin geometric phase is destroyed with
increasing Zeeman coupling.",9902122v1
2011-08-08,Two-Impurity Kondo Model: Spin-Orbit Interactions and Entanglement,"Motivated by proposals to employ RKKY-coupled spins as building blocks in a
solid-state quantum computer, we analyze how the RKKY interaction in a 2D
electron gas is influenced by spin-orbit interactions. Using a two-impurity
Kondo model with added Dresselhaus and Rashba spin-orbit interactions we find
that spin-rotational invariance of the RKKY interaction - essential for having
a well-controllable two-qubit gate - is restored when tuning the Rashba
coupling to have the same strength as the Dresselhaus coupling. We also discuss
the critical properties of the two-impurity Kondo model in the presence of
spin-orbit interactions, and extract the leading correction to the block
entanglement scaling due to these interactions.",1108.1817v1
2011-10-03,Spin selective transport through helical molecular systems,"Highly spin selective transport of electrons through a helically shaped
electrostatic potential is demonstrated in the frame of a minimal model
approach. The effect is significant even in the case of weak spin-orbit
coupling. Two main factors determine the selectivity, an unconventional Rashba-
like spin-orbit interaction, reflecting the helical symmetry of the system, and
a weakly dispersive electronic band of the helical system. The weak electronic
coupling, associated with the small dispersion, leads to a low mobility of the
charges in the system and allows even weak spin-orbit interactions to be
effective. The results are expected to be generic for chiral molecular systems
displaying low spin-orbit coupling and low conductivity.",1110.0354v2
2016-06-08,Current driven spin-orbit torque oscillator: ferromagnetic and antiferromagnetic coupling,"We consider theoretically the impact of Rashba spin-orbit coupling on spin
torque oscillators (STOs) in synthetic ferromagnets and antiferromagnets that
have either a bulk multilayer or a thin film structure. The synthetic magnets
consist of a fixed polarizing layer and two free magnetic layers that interact
through the Ruderman-Kittel-Kasuya-Yosida interaction. We determine
analytically which collinear states along the easy axis that are stable, and
establish numerically the phase diagram for when the system is in the STO mode
and when collinear configurations are stable, respectively. It is found that
the Rashba spin-orbit coupling can induce anti-damping in the vicinity of the
collinear states, which assists the spin transfer torque in generating
self-sustained oscillations, and that it can substantially increase the STO
part of the phase diagram. Moreover, we find that the STO phase can extend deep
into the antiferromagnetic regime in the presence of spin-orbit torques.",1606.02720v2
2013-08-08,Strong coupling theory of spin and orbital excitations in Sr2IrO4,"We study the low-lying excitations in 5d transition-metal oxide Sr_2IrO_4 on
the localized electron picture. We find that Hund's coupling together with the
spin-orbit interaction leads to exchange anisotropy which causes the spin wave
gap. Introducing the isospin operators acting on Kramers' doublet in Ir atoms,
we derive the effective spin Hamiltonian from a multi-orbital Hubbard model
with the t_{2g} orbitals in the square lattice. We introduce the Green's
functions including the anomalous type for the boson operators by expanding the
spin operators in terms of boson operators in the lowest order of 1/S, and
solve the coupled equations of motion for those functions. Two modes are found
to emerge with slightly different energies, in contrast to the spin waves in
the isotropic Heisenberg model. At the $\Gamma$-point, one mode has the zero
excitation energy while another has a finite energy. They have the same
excitation energy at the M point, but still have different energies at the X
point.",1308.1816v2
2019-04-21,Generation and detection of spin-orbit coupled neutron beams,"Spin-orbit coupling of light has come to the fore in nano-optics and
plasmonics, and is a key ingredient of topological photonics and chiral quantum
optics. We demonstrate a basic tool for incorporating analogous effects into
neutron optics: the generation and detection of neutron beams with coupled spin
and orbital angular momentum. $^3$He neutron spin-filters are used in
conjunction with specifically oriented triangular coils to prepare neutron
beams with lattices of spin-orbit correlations, as demonstrated by their
spin-dependant intensity profiles. These correlations can be tailored to
particular applications, such as neutron studies of topological materials.",1904.09520v1
2023-05-23,Emergent correlated phases in rhombohedral trilayer graphene induced by proximity spin-orbit and exchange coupling,"The impact of proximity-induced spin-orbit and exchange coupling on the
correlated phase diagram of rhombohedral trilayer graphene (RTG) is
investigated theoretically. By employing \emph{ab initio}-fitted effective
models of RTG encapsulated by transition metal dichalcogenides (spin-orbit
proximity effect) and ferromagnetic Cr$_2$Ge$_2$Te$_6$ (exchange proximity
effect), we incorporate the Coulomb interactions within the random-phase
approximation to explore potential correlated phases at different displacement
field and doping. We find a rich spectrum of spin-valley resolved Stoner and
intervalley coherence instabilities induced by the spin-orbit proximity
effects, such as the emergence of a \textit{spin-valley-coherent} phase due to
the presence of valley-Zeeman coupling. Similarly, proximity exchange removes
the phase degeneracies by biasing the spin direction, enabling a
magneto-correlation effect -- strong sensitivity of the correlated phases to
the relative magnetization orientations (parallel or antiparallel) of the
encapsulating ferromagnetic layers.",2305.14277v2
2009-03-02,Proposed Orbital Ordering in MnV2O4 from First-principles Calculations,"Based on density functional calculations, we propose a possible orbital
ordering in MnV2O4 which consists of orbital chains running along
crystallographic a and b directions with orbitals rotated alternatively by
about 45 degrees within each chain. We show that the consideration of
correlation effects as implemented in the local spin density approximation
(LSDA)+U approach is crucial for a correct description of the space group
symmetry. This implies that the correlation-driven orbital ordering has a
strong influence on the structural transitions in this system. Inclusion of
spin-orbit effects does not seem to influence the orbital ordering pattern. We
further find that the proposed orbital arrangement favours a noncollinear
magnetic ordering of V spins, as observed experimentally. Exchange couplings
among V spins are also calculated and discussed.",0903.0254v2
2022-02-24,Orbital entangled antiferromagnetoc order and spin-orbit-distortion exciton in $\rm Sr_2VO_4$,"With electron filling $n=1$ in the $\rm Sr_2VO_4$ compound, the octahedrally
coordinated $t_{\rm 2g}$ orbitals are strongly active due to tetragonal
distortion induced crystal field tuning by external agent such as pressure.
Considering the full range of crystal field induced tetragonal splitting in a
realistic three-orbital model, collective spin-orbital excitations are
investigated using the generalized self consistent and fluctuation approach.
The variety of self consistent states obtained including orbital entangled
ferromagnetic and antiferromagnetic orders reflects the rich spin-orbital
physics resulting from the interplay between the band, spin-orbit coupling,
crystal field, and Coulomb interaction terms. The behavior of the calculated
energy scales of collective excitations with crystal field is consistent with
that of the transition temperatures with pressure as obtained from
susceptibility and resistivity anomalies in high-pressure studies.",2202.11971v1
2023-07-05,Monopole-like orbital-momentum locking and the induced orbital transport in topological chiral semimetals,"The interplay between chirality and topology nurtures many exotic electronic
properties. For instance, topological chiral semimetals display multifold
chiral fermions that manifest nontrivial topological charge and spin texture.
They are an ideal playground for exploring chirality-driven exotic physical
phenomena. In this work, we reveal a monopole-like orbital-momentum locking
texture on the three-dimensional Fermi surfaces of topological chiral
semimetals with B20 structures (e.g., RhSi and PdGa). This orbital texture
enables a large orbital Hall effect (OHE) and a giant orbital magnetoelectric
(OME) effect in the presence of current flow. Different enantiomers exhibit the
same OHE which can be converted to the spin Hall effect by spin-orbit coupling
in materials. In contrast, the OME effect is chirality-dependent and much
larger than its spin counterpart. Our work reveals the crucial role of orbital
texture for understanding OHE and OME effects in topological chiral semimetals
and paves the path for applications in orbitronics, spintronics, and enantiomer
recognition.",2307.02668v2
2008-09-08,Interplay between quantum dissipation and an in-plane magnetic field in the spin ratchet effect,"We investigate the existence of the pure spin ratchet effect in a dissipative
quasi-one-dimensional system with Rashba spin-orbit interaction. The system is
additionally placed into a transverse uniform stationary in-plane magnetic
field. It is shown that the effect exists at low temperatures and pure spin
currents can be generated by applying an unbiased ac driving to the system. An
analytical expression for the ratchet spin current is derived. From this
expression it follows that the spin ratchet effect appears as a result of the
simultaneous presence of the spin-orbit interaction, coupling between the
orbital degrees of freedom and spatial asymmetry. In this paper we consider the
case of a broken spatial symmetry by virtue of asymmetric periodic potentials.
It turns out that an external magnetic field does not have any impact on the
existence of the spin ratchet effect, but it influences its efficiency
enhancing or reducing the magnitude of the spin current.",0809.1296v2
2006-05-23,Zero-bias spin separation,"Spin-orbit coupling provides a versatile tool to generate and to manipulate
the spin degree of freedom in low-dimensional semiconductor structures. The
spin Hall effect, where an electrical current drives a transverse spin current
and causes a nonequilibrium spin accumulation observed near the sample
boundary, the spin-galvanic effect, where a nonequilibrium spin polarization
drives an electric current, or the reverse process, in which an electrical
current generates a nonequilibrium spin polarization, are all consequences of
spin-orbit coupling. In order to observe a spin Hall effect a bias driven
current is an essential prerequisite. The spin separation is caused via
spin-orbit coupling either by Mott scattering (extrinsic spin Hall effect) or
by Rashba or Dresselhaus spin splitting of the band structure (intrinsic spin
Hall effect). Here we provide evidence for an elementary effect causing spin
separation which is fundamentally different from that of the spin Hall effect.
In contrast to the spin Hall effect it does not require an electric current to
flow: It is spin separation achieved by spin-dependent scattering of electrons
in media with suitable symmetry. We show that by free carrier (Drude)
absorption of terahertz radiation spin separation is achieved in a wide range
of temperatures from liquid helium up to room temperature. Moreover the
experimental results give evidence that simple electron gas heating by any
means is already sufficient to yield spin separation due to spin-dependent
energy relaxation processes of nonequilibrium carriers.",0605556v2
2013-06-18,The confinement induced resonance in spin-orbit coupled cold atoms with Raman coupling,"We investigate the confinement induced resonance in spin-orbit coupled cold
atoms with Raman coupling. We find that the quasi-bound levels induced by the
spin-orbit coupling and Raman coupling result in the Feshbach-type resonances.
For sufficiently large Raman coupling, the bound states in one dimension exist
only for sufficiently strong attractive interaction. Furthermore, the bound
states in quasi-one dimension exist only for sufficient large ratio of the
length scale of confinement to three dimensional s-wave scattering length. The
Raman coupling substantially changes the confinement-induced resonance
position. We give a proposal to realize confinement induced resonance by
increasing the Raman coupling strength in experiments.",1306.4099v5
2023-05-11,Photo-induced Non-collinear Interlayer RKKY Coupling in Bulk Rashba Semiconductors,"The interplay between light-matter, spin-orbit, and magnetic interactions
allows the investigation of light-induced magnetic phenomena that is otherwise
absent without irradiation. We present our analysis of light-driving effects on
the interlayer exchange coupling mediated by a bulk Rashba semiconductor in a
magnetic multilayer. The collinear magnetic exchange coupling mediated by the
photon-dressed spin-orbit coupled electrons of BiTeI develops light-induced
oscillation periods and displays new decay powers laws, both of which are
enhanced with an increasing light-matter coupling. For magnetic layers with
non-collinear magnetization, we find a non-collinear magnetic exchange coupling
uniquely generated by light-driving of the multilayer. As the non-collinear
magnetic exchange coupling mediated by the electrons of BiTeI is unique to the
irradiated system and it is enhanced with increasing light-matter coupling,
this effect offers a promising platform of investigation of light-driving
effects on magnetic phenomena in spin-orbit coupled systems.",2305.06861v1
2003-07-11,To the origin of large reduction of the effective moment in Na2V3O7,"We have shown that the observed large reduction of the effective moment in
Na2V3O7 may be caused by conventional crystal-field interactions and the
intra-atomic spin-orbit coupling of the V4+ ion. The fine discrete electronic
structure of the 3d1 configuration with the weakly-magnetic Kramers-doublet
ground state, caused by the large orbital moment, is the reason for anomalous
properties of Na2V3O7. Moreover, according to the Quantum Atomistic Solid-State
Theory (QUASST), Na2V3O7 is expected to exhibit pronounced heavy-fermion
phenomena at low temperatures.
  PACS No: 71.70.E; 75.10.D
  Keywords: crystal-field interactions, spin-orbit coupling, orbital moment.
Na2V3O7",0307272v2
2009-04-20,Tunneling anisotropic magnetoresistance in Fe/GaAs/Au junctions: orbital effects,"We report experiments on epitaxially grown Fe/GaAs/Au tunnel junctions
demonstrating that the tunneling anisotropic magnetoresistance (TAMR) effect
can be controlled by a magnetic field. Theoretical modelling shows that the
interplay of the orbital effects of a magnetic field and the Dresselhaus
spin-orbit coupling in the GaAs barrier leads to an independent contribution to
the TAMR effect with uniaxial symmetry, whereas the Bychkov-Rashba spin-orbit
coupling does not play a role. The effect is intrinsic to barriers with bulk
inversion asymmetry.",0904.3017v1
2017-11-01,Tuning Ising superconductivity with layer and spin-orbit coupling in two-dimensional transition-metal dichalcogenides,"Systems that simultaneously exhibit superconductivity and spin-orbit coupling
are predicted to provide a route toward topological superconductivity and
unconventional electron pairing, driving significant contemporary interest in
these materials. Monolayer transition-metal dichalcogenide (TMD)
superconductors in particular lack inversion symmetry, enforcing a spin-triplet
component of the superconducting wavefunction that increases with the strength
of spin-orbit coupling. In this work, we present an experimental and
theoretical study of two intrinsic TMD superconductors with large spin-orbit
coupling in the atomic layer limit, metallic 2H-TaS$_2$ and 2H-NbSe$_2$. For
the first time in TaS$_2$, we investigate the superconducting properties as the
material is reduced to a monolayer and show that high-field measurements point
to the largest upper critical field thus reported for an intrinsic TMD
superconductor. In few-layer samples, we find that the enhancement of the upper
critical field is sustained by the dominance of spin-orbit coupling over weak
interlayer coupling, providing additional platforms for unconventional
superconducting states in two dimensions.",1711.00468v1
2004-05-19,Spin-Hall transport of heavy holes in III-V semiconductor quantum wells,"We investigate spin transport of heavy holes in III-V semiconductor quantum
wells in the presence of spin-orbit coupling of the Rashba type due to
structure-inversion asymmetry. Similarly to the case of electrons, the
longitudinal spin conductivity vanishes, whereas the off-diagonal elements of
the spin-conductivity tensor are finite giving rise to an intrinsic spin-Hall
effect. For a clean system we find a closed expression for the spin-Hall
conductivity depending on the length scale of the Rashba coupling and the hole
density. In this limit the spin-Hall conductivity is enhanced compared to its
value for electron systems, and it vanishes with increasing strength of the
impurity scattering. As an aside, we also derive explicit expressions for the
Fermi momenta and the densities of holes in the different dispersion branches
as a function of the spin-orbit coupling parameter and the total hole density.
These results are of relevance for the interpretation of possible Shubnikov-de
Haas measurements detecting the Rashba spin splitting.",0405436v4
2006-04-06,Shot Noise of Spin-Decohering Transport in Spin-Orbit Coupled Nanostructures,"We generalize the scattering theory of quantum shot noise to include the full
spin-density matrix of electrons injected from a spin-filtering or
ferromagnetic electrode into a quantum-coherent nanostructure governed by
various spin-dependent interactions. This formalism yields the spin-resolved
shot noise power for different experimental measurement setups--with
ferromagnetic source and ferromagnetic or normal drain electrodes--whose
evaluation for the diffusive multichannel quantum wires with the Rashba (SO)
spin-orbit coupling shows how spin decoherence and dephasing lead to
substantial enhancement of charge current fluctuations (characterized by Fano
factors $> 1/3$). However, these processes and the corresponding shot noise
increase are suppressed in narrow wires, so that charge transport experiments
measuring the Fano factor $F_{\uparrow \to \uparrow \downarrow}$ in a
ferromagnet/SO-coupled-wire/paramagnet setup also quantify the degree of
phase-coherence of transported spin--we predict a one-to-one correspondence
between the magnitude of the spin polarization vector and $F_{\uparrow \to
\uparrow \downarrow}$.",0604187v2
2020-05-18,Spin squeezing in a spin-orbit coupled Bose-Einstein condensate,"We study the spin squeezing in a spin-1/2 Bose-Einstein condensates (BEC)
with Raman induced spin-orbit coupling (SOC). Under the condition of two-photon
resonance and weak Raman coupling strength, the system possesses two degenerate
ground states, using which we construct an effective two-mode model. The
Hamiltonian of the two-mode model takes the form of the one-axis-twisting
Hamiltonian which is known to generate spin squeezing. More importantly, we
show that the SOC provides a convenient control knob to adjust the spin
nonlinearity responsible for spin squeezing. Specifically, the spin
nonlinearity strength can be tuned to be comparable to the two-body
density-density interaction, hence is much larger than the intrinsic
spin-dependent interaction strength in conventional two-component BEC systems
such as $^{87}$Rb and $^{23}$Na in the absence of the SOC. We confirm the spin
squeezing by carrying out a fully beyond-mean-field numerical calculation using
the truncated Wigner method. Additionally, the experimental implementation is
also discussed.",2005.08532v2
2021-03-10,Electric-dipole-induced resonance and decoherence of a dressed spin in a quantum dot,"Electron spin qubit in a quantum dot has been studied extensively for
scalable quantum information processing over the past two decades. Recently,
high-fidelity and fast single-spin control and strong spin-photon coupling have
been demonstrated using a synthetic spin-orbit coupling created by a
micromagnet. Such strong electrical driving suggests a strongly coupled
spin-photon system. Here we study the relaxation, pure dephasing, and
electrical manipulation of a dressed-spin qubit based on a driven single
electron in a quantum dot. We find that the pure dephasing of a dressed qubit
due to charge noise can be suppressed substantially at a sweet spot of the
dressed qubit. The relaxation at low magnetic fields exhibits non-monotonic
behavior due to the energy compensation from the driving field. Moreover, the
longitudinal component of the synthetic spin-orbit field could provide fast
electric-dipole-induced dressed-spin resonance (EDDSR). Based on the slow
dephasing and fast EDDSR, we further propose a scheme for dressed-spin-based
semiconductor quantum computing.",2103.05817v1
2022-01-04,Mechanism of antisymmetric spin polarization in centrosymmetric multiple-$Q$ magnets based on bilinear and biquadratic spin cross products,"We investigate how to engineer an antisymmetric spin-split band structure
under spin density waves with finite ordering wave vectors in centrosymmetric
systems without the relativistic spin-orbit coupling. On the basis of a
perturbative analysis for the spin-charge coupled model in centrosymmetric
itinerant magnets, we show that nonzero chiral-type bilinear and biquadratic
spin cross products in momentum space under the magnetic orderings are related
to an antisymmetric spin polarization in the electronic band structure. We
apply the derived formula to the single-$Q$ cycloidal spiral and double-$Q$
noncoplanar states including the meron-antimeron and skyrmion crystals. Our
results present a clue to realize a giant antisymmetric spin splitting driven
by magnetic phase transitions in the centrosymmetric lattice structures without
the spin-orbit coupling.",2201.01354v1
2003-04-09,Weak localization and conductance fluctuations in a quantum dot with parallel magnetic field and spin-orbit scattering,"In the presence of both spin-orbit scattering and a magnetic field the
conductance of a chaotic GaAs quantum dot displays quite a rich behavior. Using
a Hamiltonian derived by Aleiner and Falko [Phys. Rev. Lett. 87, 256801 (2001)]
we calculate the weak localization correction and the covariance of the
conductance, as a function of parallel and perpendicular magnetic field and
spin-orbit coupling strength. We also show how the combination of an in-plane
magnetic field and spin-orbit scattering gives rise to a component to the
magnetoconductance that is anti-symmetric with respect to reversal of the
perpendicular component of the magnetic field and how spin-orbit scattering
leads to a ""magnetic-field echo"" in the conductance autocorrelation function.
Our results can be used for a measurement of the Dresselhaus and Bychkov-Rashba
spin-orbit scattering lengths in a GaAs/GaAlAs heterostructure.",0304222v1
2006-05-15,Entanglements in Systems with Multiple Degrees of Freedom,"We present the entanglement properties of the spin-orbital coupling systems
with multiple degrees of freedom. After constructing the maximally entangled
spin-orbital basis of bipartite, we find that the quantum entanglement length
in the noninteracting itinerant Fermion system with spin and orbit is
considerably larger than that in the system with only spin. In the
SU(2)$\otimes$SU(2) spin-orbital interacting system, the entanglement,
expressed in terms of the spin-orbital correlation functions, clearly manifests
the close relationship with the quantum phases in strongly correlated systems;
and the entanglement phase diagram of the finite-size systems is in agreement
with the magnetic and orbital phase diagram of the infinite systems. The
application of the present theory on nucleon systems is suggested.",0605378v1
2009-08-06,Finite temperature spin-dynamics and phase transitions in spin-orbital models,"We study finite temperature properties of a generic spin-orbital model
relevant to transition metal compounds, having coupled quantum Heisenberg-spin
and Ising-orbital degrees of freedom. The model system undergoes a phase
transition, consistent with that of a 2D Ising model, to an orbitally ordered
state at a temperature set by short-range magnetic order. At low temperatures
the orbital degrees of freedom freeze-out and the model maps on to a quantum
Heisenberg model. The onset of orbital excitations causes a rapid scrambling of
the spin spectral weight away from coherent spin-waves, which leads to a sharp
increase in uniform magnetic susceptibility just below the phase transition,
reminiscent of the observed behavior in the Fe-pnictide materials.",0908.0800v2
2016-02-22,Spin-Orbit States of Neutron Wavepackets,"We propose a method to prepare an entangled spin-orbit state between the spin
and the orbital angular momenta of a neutron wavepacket. This spin-orbit state
is created by passing neutrons through the center of a quadrupole magnetic
field, which provides a coupling between the spin and orbital degrees of
freedom. A Ramsey fringe type measurement is suggested as a means of verifying
the spin-orbit correlations.",1602.06644v2
2018-10-31,"Chern number spectrum of ultra-cold fermions in optical lattices tuned independently via artificial magnetic, Zeeman and spin-orbit fields","We discuss the Chern number spectrum of ultra-cold fermions in square optical
lattices as a function of artificial magnetic, Zeeman and spin-orbit fields
that can be tuned independently. We show the existence of topological quantum
phase transitions induced by Zeeman and spin-orbit fields, where the total
number and chirality of edge states change for fixed magnetic flux ratio, thus
leading to topological-insulator phases which are different from those found at
zero Zeeman and spin-orbit fields. We construct phase diagrams of chemical
potential versus Zeeman field or spin-orbit coupling and characterize all
insulating phases by their topological invariants. Lastly, we obtain a
staircase structure in the filling factor versus chemical potential for various
Zeeman and spin-orbit fields, showing the existence of incompressible states at
rational filling factors derived from a generalized Diophantine equation.",1811.00136v1
2011-11-07,Rashba spin orbit interaction in a quantum wire superlattice,"In this work we study the effects of a longitudinal periodic potential on a
parabolic quantum wire defined in a two-dimensional electron gas with Rashba
spin-orbit interaction. For an infinite wire superlattice we find, by direct
diagonalization, that the energy gaps are shifted away from the usual Bragg
planes due to the Rashba spin-orbit interaction. Interestingly, our results
show that the location of the band gaps in energy can be controlled via the
strength of the Rashba spin-orbit interaction. We have also calculated the
charge conductance through a periodic potential of a finite length via the
non-equilibrium Green's function method combined with the Landauer formalism.
We find dips in the conductance that correspond well to the energy gaps of the
infinite wire superlattice. From the infinite wire energy dispersion, we derive
an equation relating the location of the conductance dips as a function of the
(gate controllable) Fermi energy to the Rashba spin-orbit coupling strength. We
propose that the strength of the Rashba spin-orbit interaction can be extracted
via a charge conductance measurement.",1111.1534v1
2019-03-06,Effects of geometry on spin-orbit Kramers states in semiconducting nanorings,"The holonomic manipulation of spin-orbital degenerate states, encoded in the
Kramers doublet of narrow semiconducting channels with spin-orbit interaction,
is shown to be intimately intertwined with the geometrical shape of the
nanostructures. The presence of doubly degenerate states is not sufficient to
guarantee a non-trivial mixing by only changing the Rashba spin-orbit coupling.
We demonstrate that in nanoscale quantum rings the combination of arbitrary
inhomogeneous curvature and adiabatic variation of the spin-orbit amplitude,
e.g. through electric-field gating, can be generally employed to get
non-trivial combinations of the degenerate states. Shape symmetries of the
nanostructure act to constrain the adiabatic quantum evolution. While for
circular rings the geometric phase is not generated along a non-cyclic path in
the parameters space, remarkably, for generic mirror-symmetric shape deformed
rings the spin-orbit driving can lead to a series of dynamical quantum phase
transitions. We explicitly show this occurrence and propose a route to detect
such topological transitions by measuring a variation of the electron tunneling
amplitude into the semiconducting channel.",1903.02455v1
2019-04-06,Spin-orbit effects in the hydrogenic impurity levels of wurtzite semiconductors,"The corrections to the $E_2^*$ energy level of hydrogenic impurities in
semiconductors with wurtzite crystal structure are calculated using first-order
perturbation theory in the envelope-function approximation. We consider the
intrinsic (Dresselhaus) spin-orbit effective Hamiltonian in the conduction band
and compare its effects to the renormalized extrinsic (Rashba) spin-orbit
interaction which is analogous to the spin-orbit interaction in the bare
hydrogen atom. In order to evaluate the extrinsic spin-orbit interaction we
obtain the renormalized coupling constant $\lambda^*$ for wurtzite
semiconductors from 8-band Kane theory. We apply our theory to four
representative binary semiconductors with wurtzite crystal structure, namely,
GaN, ZnO, InN and AlN, and discuss the relative strength of the effects of the
intrinsic and extrinsic spin-orbit contributions.",1904.03374v1
2019-12-19,Magnetic phase transitions in quantum spin-orbital liquids,"We investigate the spin and orbital correlations of a superexchange model
with spin $S=1$ and orbital $L=1$ relevant for $5d^4$ transition metal Mott
insulators, using exact diagonalization and density matrix renormalization
group (DMRG). For spin-orbit coupling $\lambda=0$, the orbitals are in an
entangled state that is decoupled from the spins. We find two phases with
increasing $\lambda$: (I) the S2 phase with two peaks in the structure factor
for $\lambda\le\lambda_{c1}\approx 0.34 J$ where $J$ is the ferromagnetic
exchange; and, (II) the $S1$ phase for
$\lambda_{c1}<\lambda\le\lambda_{c2}\approx 1.2 J$ with emergent
antiferromagnetic correlations. Both S1 and S2 phases are shown to exhibit
power law correlations, indicative of a gapless spectrum. Upon increasing
$\lambda > \lambda_{c2}$ leads to a product state of local spin-orbital
singlets that exhibit exponential decay of correlations, indicative of a gapped
phase. We obtain insights into the phases from the well-known
Uimin-Lai-Sutherland (ULS) model in an external field that provides an
approximate description of our model within mean field theory.",1912.09516v1
2008-05-15,Orbital fluctuation mechanism for superconductivity in iron-based compounds,"We propose orbital fluctuations in a multi-band ground state as the
superconducting pairing mechanism in the new iron-based materials. We develop a
general SU(4) theoretical framework for studying a two-orbital model and
discuss a number of scenarios that may be operational within this orbital
fluctuation paradigm. The orbital and spin symmetry of the superconducting
order parameter is argued to be highly non-universal and dependent on the
details of the underlying band structure. We introduce a minimal two-orbital
model for the Fe-pnictides characterized by non-degenerate orbitals that
strongly mix with each other. They correspond to the iron ""d_xy"" orbital and to
an effective combination of ""d_zx"" and ""d_zy"", respectively. Using this
effective model we perform RPA calculations of susceptibilities and effective
pairing interactions. We find that spin and orbital fluctuations are,
generally, strongly coupled and we identify the parameters that control this
coupling as well as the relative strength of various channels.",0805.2150v2
2000-04-11,Spin Effects in the Local Density of States of GaAs,"We present spin-resolved measurements of the local density of states in Si
doped GaAs. Both spin components exhibit strong mesoscopic fluctuations. In the
magnetic quantum limit, the main features of the spin-up and spin-down
components of the local density of states are found to be identical apart from
Zeeman splitting. Based on this observation, we introduce a mesoscopic method
to measure the $g$-factor in a material where macroscopic methods are severely
restricted by disorder. Differences between the spin-up and spin-down
components are discussed in terms of spin relaxation due to spin-orbit
coupling.",0004165v1
2005-09-16,Streda-like formula in spin Hall effect,"A generalized Streda formula is derived for the spin transport in spin-orbit
coupled systems. As compared with the original Streda formula for charge
transport, there is an extra contribution of the spin Hall conductance whenever
the spin is not conserved. For recently studied systems with quantum spin Hall
effect in which the z-component spin is conserved, this extra contribution
vanishes and the quantized value of spin Hall conductivity can be reproduced in
the present approach. However, as spin is not conserved in general, this extra
contribution can not be neglected, and the quantization is not exact.",0509453v1
2011-06-23,Spin dephasing in Silicon Germanium nanowires,"We study spin polarized transport in silicon germanium nanowires using a
semiclassical monte carlo approach. Spin depolarization in the channel is
caused due to D'yakonov-Perel (DP) relaxation associated with Rashba spin orbit
coupling and due to Elliott- Yafet (EY) relaxation. We investigate the
dependence of spin dephasing on germanium mole fraction in silicon germanium
nanowires. The spin dephasing lengths decrease with an increase in the
germanium mole fraction. We also find that the temperature has a strong
influence on the dephasing rate and spin relaxation lengths increase with
decrease in temperature. The ensemble averaged spin components and the steady
state distribution of spin components vary with initial polarization.",1106.4619v1
2014-04-26,Slow spin relaxation in a quantum Hall ferromagnet state,"Electron spin relaxation in a spin-polarized quantum Hall state is studied.
Long spin relaxation times that are at least an order of magnitude longer than
those measured in previous experiments were observed and explained within the
spin-exciton relaxation formalism. Absence of any dependence of the spin
relaxation time on the electron temperature and on the spin-exciton density,
and specific dependence on the magnetic field indicate the definite relaxation
mechanism -- spin-exciton annihilation mediated by spin-orbit coupling and
smooth random potential.",1404.6521v1
2014-08-07,Spin Hanle effect in mesoscopic superconductors,"We present a theoretical study of spin transport in a superconducting
mesoscopic spin valve under the action of a magnetic field misaligned with
respect to the injected spin. We demonstrate that superconductivity can either
strongly enhance or suppress the coherent spin rotation depending on the type
of spin relaxation mechanism being dominated either by spin-orbit coupling or
spin-flip scattering at impurities. We also predict a hitherto unknown subgap
contribution to the nonlocal conductance in multiterminal superconducting
hybrid structures which completely eliminates the effect of spin rotation at
sufficiently low temperatures.",1408.1632v2
2016-03-05,Datta-and-Das spin transistor controlled by a high-frequency electromagnetic field,"We developed the theory of spin dependent transport through a spin-modulator
device (so-called Datta-and-Das spin transistor) in the presence of a
high-frequency electromagnetic field (dressing field). Solving the
Schr\""odinger problem for dressed electrons, we demonstrated that the field
drastically modifies the spin transport. In particular, the dressing field
leads to renormalization of spin-orbit coupling constants that varies
conductivity of the spin transistor. The present effect paves the way for
controlling the spin-polarized electron transport with light in prospective
spin-optronic devices.",1603.01678v2
2017-11-15,Orbital physics in transition metal compounds: new trends,"In the present review different effects related to the orbital degrees of
freedom are discussed. Leaving aside such aspects as the superexchange
mechanism of the cooperative Jahn-Teller distortions and different properties
of ""Kugel-Khomskii""-like models, we mostly concentrate on other phenomena,
which are in the focus of the modern condensed matter physics. After a general
introduction we start with the discussion of the concept of effective reduction
of dimensionality due to orbital degrees of freedom and consider such phenomena
as the orbitally-driven Peierls effect and the formation of small clusters of
ions in the vicinity of a Mott transition, which behave like ""molecules""
embedded in a solid. The second large section is devoted to the
orbital-selective effects such as the orbital-selective Mott transition and the
suppression of magnetism due to the fact that part of the orbitals start to
form singlet molecular orbitals. At the end the rapidly growing field of the
so-called ""spin-orbit-dominated"" transition metal compounds is briefly reviewed
including such topics as the interplay between the spin-orbit coupling and the
Jahn-Teller effect, the formation of the spin-orbit driven Mott and Peierls
states, the role of orbital degrees of freedom in generation of the Kitaev
exchange coupling, and the singlet (excitonic) magnetism in $4d$ and $5d$
transition metal compounds.",1711.05409v2
2016-09-15,Diffused vorticity and moment of inertia of a spin-orbit coupled Bose-Einstein condensate,"By developing the hydrodynamic theory of spinor superfluids we calculate the
moment of inertia of a harmonically trapped Bose-Einstein condensate with
spin-orbit coupling. We show that the velocity field associated with the
rotation of the fluid exhibits diffused vorticity, in contrast to the
irrotational behavior characterizing a superfluid. Both Raman-induced and
Rashba spin-orbit couplings are considered. In the first case the moment of
inertia takes the rigid value at the transition between the plane wave and the
single minimum phase, while in the latter case the rigid value is achieved in
the limit of isotropic Rashba coupling. A procedure to generate the rigid
rotation of the fluid and to measure the moment of inertia is proposed. The
quenching of the quantum of circulation $h/m$, caused by Raman induced
spin-orbit coupling in a toroidal geometry, is also discussed.",1609.04694v2
2015-12-23,Bose-Einstein condensate in an optical lattice with Raman-assisted two-dimensional spin-orbit coupling,"In a recent experiment by Wu {\textit et al.} (arXiv:1511.08170), a
Raman-assisted two-dimensional spin-orbit coupling has been realized for a
Bose-Einstein condensate in an optical lattice potential. In light of this
exciting progress, we study in detail key properties of the system. As the
Raman lasers inevitably couple atoms to high-lying bands, the behaviors of the
system in both the single- and many-particle sectors are significantly
affected. In particular, the high-band effects enhance the plane-wave phase and
lead to the emergence of ""roton"" gaps at low Zeeman fields. Furthermore, we
identify high-band-induced topological phase boundaries in both the
single-particle and the quasi-particle spectra. We then derive an effective
two-band model, which captures the high-band physics in the experimentally
relevant regime. Our results not only offer valuable insights into the novel
two-dimensional lattice spin-orbit coupling, but also provide a systematic
formalism to model high-band effects in lattice systems with Raman-assisted
spin-orbit couplings.",1512.07448v3
2019-06-18,Non uniform superconductivity in wires with strong spin-orbit coupling,"We study theoretically the onset of nonuniform superconductivity in a
one-dimensional single wire in presence of Zeeman (or exchange field) and
spin-orbit coupling. Using the Green's function formalism, we show that the
spin-orbit coupling stabilizes modulated superconductivity in a broad range of
temperatures and Zeeman fields. We investigate the anisotropy of the
temperature-Zeeman field phase diagram, which is related to the orientation of
the Zeeman field. In particular, the inhomogeneous superconducting state
disappears if this latter field is aligned or perpendicular to the wire
direction. We identify two regimes corresponding to weak and strong spin-orbit
coupling respectively. The wave-vector of the modulated phase is evaluated in
both regimes. The results also pertain for quasi-1D superconductors made of
weakly coupled 1D chains.",1906.07572v3
2021-04-01,Critical temperature in the BCS-BEC crossover with spin-orbit coupling,"We review the study of the superfluid phase transition in a system of
fermions whose interaction can be tuned continuously along the crossover from
Bardeen-Cooper-Schrieffer (BCS) superconducting phase to a Bose-Einstein
condensate (BEC), also in the presence of a spin-orbit coupling. Below a
critical temperature the system is characterized by an order parameter.
Generally a mean field approximation cannot reproduce the correct behavior of
the critical temperature $T_c$ over the whole crossover. We analyze the crucial
role of quantum fluctuations beyond the mean-field approach useful to find
$T_c$ along the crossover in the presence of a spin-orbit coupling, within a
path integral approach. A formal and detailed derivation for the set of
equations useful to derive $T_c$ is performed in the presence of Rashba,
Dresselhaus and Zeeman couplings. In particular in the case of only Rashba
coupling, for which the spin-orbit effects are more relevant, the two-body
bound state exists for any value of the interaction, namely in the full
crossover. As a result the effective masses of the emerging bosonic excitations
are finite also in the BCS regime.",2104.00570v1
2024-02-12,Topological excitations in a spin-orbit coupled spin-1 Bose-Einstein condensate under sinusoidally varying magnetic fields,"We present a theoretical study of a spin-orbit coupled spin-1 Bose-Einstein
condensate under the influence of sinusoidally varying magnetic fields. In the
ground state of the ferromagnetic spin-1 condensate, we investigate topological
excitations in the system arising due to the combined effect of Rashba
spin-orbit coupling and an in-plane sinusoidally varying magnetic field. In
this work, we offer a comparative study for various choices of magnetic fields
in the $x\rm{-}y$ plane. For a fixed field strength, the spin-orbit coupled
system sustains a rich variety of exotic vortex structures ranging from
vortex-antivortex lattices to vortex clusters as we increase the coupling
strength.",2402.08118v1
2007-01-15,Hall Conductance of a Two-Dimensional Electron Gas with Spin-Orbit Coupling at the Presence of Lateral Periodic Potential,"We evaluate the distribution of Hall conductances in magnetic subbands of
two-dimensional electron gas with Rashba spin-orbit (SO) coupling placed in a
periodic potential and perpendicular magnetic field. In this semiconductor
structure the spin-orbit coupling mixes the states of different magnetic
subbands and changes the distribution of their Hall conductances in comparison
with the case of spinless particles. The calculations were made for
semiconductor structures with a weak ($AlGaAs/GaAs$) and relatively strong
($GaAs/InGaAs$) SO and Zeeman interactions. The Hall conductances of fully
occupied magnetic subbands depend on the system parameters and can be changed
when neighboring subbands touch each other. It was shown that in the real
semiconductor structures with relatively strong SO coupling the distribution of
Hall conductance differs from the quantization law predicted by Thouless et
al\cite{Thoul} for systems without spin-orbit coupling. In the case of weak SO
interaction and relatively large lattice period the Hall conductance of
magnetic subbands are the same as for spinless particles, but as the lattice
period decreases and two neighboring subbands touch each other the distribution
of Hall conductances is changed drastically.",0701316v1
2011-12-13,Critical temperature of a Rashba spin-orbit coupled Bose gas in harmonic traps,"We investigate theoretically Bose-Einstein condensation of an ideal, trapped
Bose gas in the presence of Rashba spin-orbit coupling. Analytic results for
the critical temperature and condensate fraction are derived, based on a
semi-classical approximation to the single-particle energy spectrum and density
of states, and are compared with exact results obtained by explicitly summing
discrete energy levels for small number of particles. We find a significant
decrease of the critical temperature and of the condensate fraction due to a
finite spin-orbit coupling. For large coupling strength and finite number of
particles $N$, the critical temperature scales as $N^{2/5}$ and $N^{2/3}$ in
three and two dimensions, respectively, contrasted to the predictions of
$N^{1/3}$ and $N^{1/2}$ in the absence of spin-orbit coupling. Finite size
corrections in three dimensions are also discussed.",1112.2799v2
2013-02-04,Many-body \textit{T}-matrix theory of a strongly interacting spin-orbit coupled Fermi gas: Momentum-resolved radio-frequency spectroscopy and fermionic pairing,"Interacting Fermi gases with spin-orbit coupling are responsible for many
intriguing phenomena such as topological superfluids and Majorana fermions.
Here we characterize theoretically fermionic pairing in a strongly interacting
spin-orbit coupled Fermi gas, by using momentum-resolved radio-frequency
spectroscopy. We develop a strong-coupling $T$-matrix theory and present a
phase diagram near the unitary resonance limit. A smooth transition from atomic
to molecular responses in the momentum-resolved spectroscopy is predicted, with
a clear signature of anisotropic pairing at and below resonance. Our prediction
with many-body pairing can be directly tested in a spin-orbit coupled Fermi gas
of $^{40}$K or $^{6}$Li atoms near broad Feshbach resonances.",1302.0559v2
2013-10-14,Fulde-Ferrell pairing instability of a Rashba spin-orbit coupled Fermi gas,"We theoretically analyze the pairing instability of a three-dimensional
ultracold atomic Fermi gas towards a Fulde-Ferrell superfluid, in the presence
of Rashba spin-orbit coupling and in-plane Zeeman field. We use the standard
Thouless criterion for the onset of superfluidity, with which the effect of
pair fluctuations is partially taken into account by approximately using a
mean-field chemical potential at zero temperature. This gives rise to an
improved prediction of the superfluid transition temperature beyond mean-field,
particularly in the strong-coupling unitary limit. We also investigate the
pairing instability with increasing Rashba spin-orbit coupling, along the
crossover from a Bardeen-Cooper-Schrieffer superfluid to a Bose-Einstein
condensate of Rashbons (i.e., the tightly bound state of two fermions formed by
strong Rashba spin-orbit coupling",1310.3558v1
2014-05-18,Ultracold Spin-Orbit Coupled Bose-Einstein Condensate in a Cavity: Route to Magnetic Phases Through Cavity Transmission,"We study the spin orbit coupled ultra cold Bose-Einstein condensate placed in
a single mode Fabry-P\'erot cavity. The cavity introduces a quantum optical
lattice potential which dynamically couples with the atomic degrees of freedom
and realizes a generalized extended Bose Hubbard model whose zero temperature
phase diagram can be controlled by tuning the cavity parameters. In the
non-interacting limit, where the atom-atom interaction is set to zero, the
resulting atomic dispersion shows interesting features such as bosonic analogue
of Dirac points, cavity controlled Hofstadter spectrum which bears the hallmark
of pseudo-spin-1/2 bosons in presence of Abelian and non-Abelian gauge field
(the later due to spin-orbit coupling) in a cavity induced optical lattice
potential. In the presence of atom-atom interaction, using a mapping to a
generalized Bose Hubbard model of spin-orbit coupled bosons in classical
optical lattice, we show that the system realizes a host of quantum magnetic
phases whose magnetic order can be be detected from the cavity transmission.
This provides an alternative approach for detecting quantum magnetism in ultra
cold atoms. We discuss the effect of cavity induced optical bistability on this
phases and their experimental consequences.",1405.4500v1
2018-05-07,Quantum transport by spin-polarized edge states in graphene nanoribbons in the quantum spin Hall and quantum anomalous Hall regimes,"Using the non-equilibrium Green\noindent 's function method and the Keldysh
formalism, we study the effects of spin-orbit interactions and time-reversal
symmetry breaking exchange fields on non-equilibrium quantum transport in
graphene armchair nanoribbons. We identify signatures of the quantum spin Hall
(QSH) and the quantum anomalous Hall (QAH) phases in non-equilibrium edge
transport by calculating the spin-resolved real space charge density and local
currents at the nanoribbon edges. We find that the QSH phase, which is realized
in a system with intrinsic spin-orbit coupling, is characterized by chiral
counter-propagating local spin currents summing up to a net charge flow with
opposite spin polarization at the edges. In the QAH phase, emerging in the
presence of the Rashba spin-orbit coupling and a ferromagnetic exchange field,
two chiral edge channels with opposite spins propagate in the same direction at
each edge, generating an unpolarized charge current and a quantized Hall
conductance $G = 2 e^2/h$. Increasing the intrinsic spin-orbit coupling causes
a transition from the QAH to the QSH phase, evinced by characteristic changes
in the non-equilibrium edge transport. In contrast, an antiferromagnetic
exchange field can coexist with a QSH phase, but can never induce a QAH phase
due to a symmetry that combines time-reversal and sublattice translational
symmetry.",1805.02418v2
2023-07-18,Effect of Spin Orbit Coupling in non-centrosymmetric half-Heusler alloys,"Spin-orbit coupled electronic structure of two representative non-polar
half-Heusler alloys, namely 18 electron compound CoZrBi and 8 electron compound
SiLiIn have been studied in details. An excursion through the Brillouin zone of
these alloys from one high symmetry point to the other revealed rich local
symmetry of the associated wave vectors resulting in non-trivial spin splitting
of the bands and consequent diverse spin textures in the presence of spin-orbit
coupling. Our first principles calculations supplemented with low energy
$\boldsymbol{k.p}$ model Hamiltonian revealed the presence of linear
Dresselhaus effect at the X point having $D_{2d}$ symmetry and Rashba effect
with both linear and non-linear terms at the L point with $C_{3v}$ point group
symmetry. Interestingly we have also identified non-trivial Zeeman spin
splitting at the non-time reversal invariant W point and a pair of
non-degenerate bands along the path $\Gamma$ to L displaying vanishing spin
polarization due to the non-pseudo polar point group symmetry of the wave
vectors. Further a comparative study of CoZrBi and SiLiIn suggest, in addition,
to the local symmetry of the wave vectors, important role of the participating
orbitals in deciding the nature and strength of spin splitting. Our
calculations identify half-Heusler compounds with heavy elements displaying
diverse spin textures may be ideal candidate for spin valleytronics where spin
textures can be controlled by accessing different valleys around the high
symmetry k-points.",2308.03760v2
2019-03-14,Spin-Orbital-Intertwined Nematic State in FeSe,"The importance of the spin-orbit coupling (SOC) effect in Fe-based
superconductors (FeSCs) has recently been under hot debate. Considering the
Hund's coupling-induced electronic correlation, the understanding of the role
of SOC in FeSCs is not trivial and is still elusive. Here, through a
comprehensive study of 77Se and 57Fe nuclear magnetic resonance, a nontrivial
SOC effect is revealed in the nematic state of FeSe. First, the
orbital-dependent spin susceptibility, determined by the anisotropy of the 57Fe
Knight shift, indicates a predominant role from the 3dxy orbital, which
suggests the coexistence of local and itinerant spin degrees of freedom
(d.o.f.) in the FeSe. Then, we reconfirm that the orbital reconstruction below
the nematic transition temperature (Tnem ~ 90 K) happens not only on the 3dxz
and 3dyz orbitals but also on the 3dxy orbital, which is beyond a trivial
ferro-orbital order picture. Moreover, our results also indicate the
development of a coherent coupling between the local and itinerant spin d.o.f.
below Tnem, which is ascribed to a Hund's coupling-induced electronic crossover
on the 3dxy orbital. Finally, due to a nontrivial SOC effect, sizable in-plane
anisotropy of the spin susceptibility emerges in the nematic state, suggesting
a spin-orbital-intertwined nematicity rather than simply spin- or
orbital-driven nematicity}. The present work not only reveals a nontrivial SOC
effect in the nematic state but also sheds light on the mechanism of nematic
transition in FeSe.",1903.05798v2
2017-08-15,Weak Localization and Antilocalization in Topological Materials with Impurity Spin-Orbit Interactions,"Topological materials have attracted considerable experimental and
theoretical attention. They exhibit strong spin-orbit coupling both in the band
structure (intrinsic) and in the impurity potentials (extrinsic), although the
latter is often neglected. Here we discuss weak localization and
antilocalization of massless Dirac fermions in topological insulators and
massive Dirac fermions in Weyl semimetal thin films taking into account both
intrinsic and extrinsic spin-orbit interactions. The physics is governed by the
complex interplay of the chiral spin texture, quasiparticle mass, and scalar
and spin-orbit scattering. We demonstrate that terms linear in the extrinsic
spin-orbit scattering are generally present in the Bloch and momentum
relaxation times in all topological materials, and the correction to the
diffusion constant is linear in the strength of the extrinsic spin-orbit. In
TIs, which have zero quasiparticle mass, the terms linear in the impurity
spin-orbit coupling lead to an observable density dependence in the weak
antilocalization correction. They produce substantial qualitative modifications
to the magnetoconductivity, differing greatly from the conventional HLN formula
traditionally used in experimental fits, which predicts a crossover from weak
localization to antilocalization as a function of the extrinsic spin-orbit
strength. In contrast, our analysis reveals that topological insulators always
exhibit weak antilocalization. In WSM thin films having intermediate to large
values of the quasiparticle mass extrinsic spin-orbit scattering strongly
affects the boundary of the weak localization to antilocalization transition.
We produce a complete phase diagram for this transition as a function of the
mass and spin-orbit scattering strength. We discuss implications for
experiments and provide a brief comparison with transition metal
dichalcogenides.",1708.04930v1
2015-02-27,Quantum phases of Bose-Einstein condensates with synthetic spin - orbital-angular-momentum coupling,"The experimental realization of emergent spin-orbit coupling through
laser-induced Raman transitions in ultracold atoms paves the way for exploring
novel superfluid physics and simulating exotic many-body phenomena. A recent
proposal with the use of Laguerre-Gaussian lasers enables another fundamental
type of coupling between spin and orbital angular momentum (SOAM) in ultracold
atoms. We hereby study quantum phases of a realistic Bose-Einstein condensate
(BEC) with this synthetic SOAM coupling in a disk-shaped geometry, respecting
radial inhomogeneity of the Raman coupling. We find that the experimental
system naturally resides in a strongly interacting regime in which the phase
diagram significantly deviates from the single-particle picture. The interplay
between SOAM coupling and interaction leads to rich structures in spin-resolved
position and momentum distributions, including a stripe phase and various types
of immiscible states. Our results would provide a guide for an experimental
investigation of SOAM-coupled BECs.",1502.08052v2
2008-11-08,Ballistic Spin Resonance,"The phenomenon of spin resonance has had far reaching influence since its
discovery nearly 70 years ago. Electron spin resonance (ESR) driven by high
frequency magnetic fields has informed our understanding of quantum mechanics,
and finds application in fields as diverse as medicine and quantum information.
Spin resonance induced by high frequency electric fields, known as electric
dipole spin resonance (EDSR), has also been demonstrated recently. EDSR is
mediated by spin-orbit interaction (SOI), which couples the spin degree of
freedom and the momentum vector. Here, we report the observation of a novel
spin resonance due to SOI that does not require external driving fields.
Ballistic spin resonance (BSR) is driven by an internal spin-orbit field that
acts upon electrons bouncing at gigaHertz frequencies in narrow channels of
ultra-clean two-dimensional electron gas (2DEG). BSR is manifested in
electrical measurements of pure spin currents as a strong suppression of spin
relaxation length when the motion of electrons is in resonance with spin
precession. These findings point the way to gate-tunable coherent spin
rotations in ballistic nanostructures without external a.c. fields.",0811.1244v1
2009-06-27,Steady-state spin densities and currents,"This article reviews steady-state spin densities and spin currents in
materials with strong spin-orbit interactions. These phenomena are intimately
related to spin precession due to spin-orbit coupling which has no equivalent
in the steady state of charge distributions. The focus will be initially on
effects originating from the band structure. In this case spin densities arise
in an electric field because a component of each spin is conserved during
precession. Spin currents arise because a component of each spin is continually
precessing. These two phenomena are due to independent contributions to the
steady-state density matrix, and scattering between the conserved and
precessing spin distributions has important consequences for spin dynamics and
spin-related effects in general. In the latter part of the article extrinsic
effects such as skew scattering and side jump will be discussed, and it will be
shown that these effects are also modified considerably by spin precession.
Theoretical and experimental progress in all areas will be reviewed.",0906.5111v1
2015-11-01,Reciprocal spin Hall effects in conductors with strong spin-orbit coupling: a review,"Spin Hall effect and its inverse provide essential means to convert charge to
spin currents and vice versa, which serve as a primary function for spintronic
phenomena such as the spin-torque ferromagnetic resonance and the spin Seebeck
effect. These effects can oscillate magnetization or detect a thermally
generated spin splitting in the chemical potential. Importantly this conversion
process occurs via the spin-orbit interaction, and requires neither magnetic
materials nor external magnetic fields. However, the spin Hall angle, i.e., the
conversion yield between the charge and spin currents, depends severely on the
experimental methods. Here we discuss the spin Hall angle and the spin
diffusion length for a variety of materials including pure metals such as Pt
and Ta, alloys and oxides determined by the spin absorption method in a lateral
spin valve structure.",1511.00332v1
2016-08-01,Coherent control over three-dimensional spin polarization for the spin-orbit coupled surface state of Bi$_2$Se$_3$,"Interference of spin-up and spin-down eigenstates depicts spin rotation of
electrons, which is a fundamental concept of quantum mechanics and accepts
technological challenges for the electrical spin manipulation. Here, we
visualize this coherent spin physics through laser spin- and angle-resolved
photoemission spectroscopy on a spin-orbital entangled surface-state of a
topological insulator. It is unambiguously revealed that the linearly polarized
laser can simultaneously excite spin-up and spin-down states and these quantum
spin-basis are coherently superposed in photoelectron states. The superposition
and the resulting spin rotation is arbitrary manipulated by the direction of
the laser field. Moreover, the full observation of the spin rotation displays
the phase of the quantum states. This presents a new facet of
laser-photoemission technique for investigation of quantum spin physics opening
new possibilities in the field of quantum spintronic applications.",1608.00479v3
2018-09-17,Cross-shaped nanostructures for the study of spin to charge interconversions using spin-orbit coupling in non-magnetic materials,"Several spin-orbit effects allow performing spin to charge inter-conversion:
the spin Hall effects, the Rashba effect, or the spin-momentum locking in
topological insulators. Here we focus on how the detection of this
inter-conversion can be made electrically, using three different cross-shaped
nanostructures. We apply these measurement configurations to the case of the
spin Hall effect in Pt, using CoFe electrodes to detect and inject spins. Both
the direct and inverse spin Hall effect can be detected, with a spin Hall
signal up to two order of magnitude higher than that of nonlocal measurements
in metallic lateral spin valves, and with a much simpler fabrication protocol.
We compare the respective signal amplitude of the three proposed geometries.
Finally, comparison of the observed spin signals with finite element method
calculations allows extracting the spin Hall angle and the spin diffusion
length of Pt.",1809.06145v1
2000-12-01,Magnetic and orbital ordering in cuprates and manganites,"The mechanisms of magnetic and orbital interactions due to double exchange
(DE) and superexchange (SE) in transition metal oxides with degenerate e_g
orbitals are presented. Specifically, we study the effective spin-orbital
models derived for the d^9 ions as in KCuF_3, and for the d^4 ions as in
LaMnO_3, for spins S=1/2 and S=2, respectively. Such models are characterized
by three types of elementary excitations: spin waves, orbital waves, and
spin-and-orbital waves. The SE interactions between Cu^{2+} (d^9) ions are
inherently frustrated, which leads to a new mechanism of spin liquid which
operates in three dimensions. The SE between Mn^{3+} (d^4) ions explains the
A-type antiferromagnetic order in LaMnO_3 which coexists with the orbital
order. In contrast, the ferromagnetic metallic phase and isotropic spin waves
observed in doped manganites are explained by DE for degenerate e_g orbitals.
It is shown that although a hole does not couple to spin excitations in
ferromagnetic planes of LaMnO_3, the orbital excitations change the energy
scale for the coherent hole propagation and cause a large redistribution of
spectral weight. Finally, we point out some open problems in the present
understanding of doped manganites.",0012013v1
2019-04-26,"Spin, orbital and topological order in models of strongly correlated electrons","Different types of order are discussed in the context of strongly correlated
transition metal oxides, involving pure compounds and $3d^{3}-4d^{4}$ and
$3d^{2}-4d^{4}$ hybrids. Apart from standard, long-range spin and orbital
orders we observe also exotic non-colinear spin patterns. Such patters can
arise in presence of atomic spin-orbit coupling, which is a typical case, or
due to spin-orbital entanglement at the bonds in its absence, being much less
trivial. Within a special interacting one-dimensional spin-orbital model it is
also possible to find a rigorous topological magnetic order in a gapless phase
that goes beyond any classification tables of topological states of matter.
This is an exotic example of a strongly correlated topological state. Finally,
in the less correlated limit of $4d^{4}$ oxides, when orbital selective Mott
localization can occur it is possible to stabilize by a $3d^{3}$ doping
one-dimensional zigzag antiferromagnetic phases. Such phases have exhibit
nonsymmorphic spatial symmetries that can lead to various topological
phenomena, like single and mutliple Dirac points that can turn into nodal rings
or multiple topological charges protecting single Dirac points. Finally, by
creating a one-dimensional $3d^{2}-4d^{4}$ hybrid system that involves orbital
pairing terms, it is possible to obtain an insulating spin-orbital model where
the orbital part after fermionization maps to a non-uniform Kitaev model. Such
model is proved to have topological phases in a wide parameter range even in
the case of completely disordered $3d^{2}$ impurities. What more, it exhibits
hidden Lorentz-like symmetries of the topological phase, that live in the
parameters space of the model.",1904.11772v1
2024-03-13,Synergy between Spin and Orbital Angular Momenta on a Möbius Strip,"Spin and orbital angular momenta are fundamental physical characteristics
described by polarization and spatial degrees of freedom, respectively.
Polarization is a feature of vector fields while spatial phase gradient
determines the orbital angular momentum ubiquitous to any scalar field. Common
wisdom treats these two degrees of freedom as distinct and independent
principles to manipulate wave propagations. Here, we demonstrate their synergy.
This is achieved by introducing two orthogonal $p$-orbitals as eigenbases,
whose spatial modal features are exploited to generate orbital angular momenta
and the associated orbital orientations provide means to simultaneously
manipulate polarizations. Through periodic modulation and directional coupling,
we realize a full cyclic evolution of the synchronized and synergized
spin-orbital angular momenta. Remarkably, this evolution acquires a nontrivial
geometric phase, leading to its representation on a M\""obius strip.
Experimentally, an acoustic cavity array is designed, whose dipole resonances
precisely mimic the $p$-orbitals. The acoustic waves, uniquely, see the
pressure (scalar) field as a spatial feature and carry an intrinsic
polarization defined by the velocity (vector) field, serving as an ideal
platform to observe the synergy of spin and orbital angular momenta. Based on
such a property, we further showcase a spin-orbital-Hall effect, highlighting
the intricate locking of handedness, directionality, spin density and spatial
mode profile. Our study unveils a fundamental connection between spin and
orbital angular momenta, promising avenues for novel applications in
information coding and high-capacity communications.",2403.08276v1
2005-02-24,Spin polarization in a T-shape conductor induced by strong Rashba spin-orbit coupling,"We investigate numerically the spin polarization of the current in the
presence of Rashba spin-orbit interaction in a T-shaped conductor proposed by
A.A. Kiselev and K.W. Kim (Appl. Phys. Lett. {\bf 78} 775 (2001)). The
recursive Green function method is used to calculate the three terminal spin
dependent transmission probabilities. We focus on single-channel transport and
show that the spin polarization becomes nearly 100 % with a conductance close
to $e^{2}/h$ for sufficiently strong spin-orbit coupling. This is interpreted
by the fact that electrons with opposite spin states are deflected into an
opposite terminal by the spin dependent Lorentz force. The influence of the
disorder on the predicted effect is also discussed. Cases for multi-channel
transport are studied in connection with experiments.",0502572v2
2008-10-19,Spin accumulation with spin-orbit interaction,"Spin accumulation is a crucial but imprecise concept in spintronics. In
metal-based spintronics it is characterized in terms of semiclassical
distribution functions. In semiconductors with a strong spin-orbit coupling the
spin accumulation is interpreted as a superposition of coherent eigenstates.
Both views can be reconciled by taking into account the electron-electron
interaction: a sufficiently strong self-consistent exchange field reduces a
spin accumulation to a chemical potential difference between the two spin bands
even in the presence of spin-orbit coupling. We demonstrate the idea on a clean
two-dimensional electron gas (2DEG) by showing how the exchange field protects
a spin accumulation from dephasing and introduces an easy-plane anisotropy.",0810.3386v2
2013-04-23,In-plane electric field effect on a spin-orbit coupled two-dimensional electron system in presence of magnetic field,"The effect of in-plane electric field on Landau level spacing, spin splitting
energy, average spin polarization and average spin current in the bulk as well
as at the edges of a two-dimensional electron system with Rashba spin-orbit
coupling are presented here. The spin splitting energy for a particular
magnetic field is found to be reduced by the external in-plane electric field.
Unlike the case of a two-dimensional electron system without Rashba spin-orbit
interaction, here the Landau level spacing is electric field dependent. This
dependency becomes stronger at the edges in comparison to the bulk. The average
spin polarization vector rotates anti-clockwise with the increase of electric
field. The average spin current also gets influenced significantly by the
application of the in-plane electric field.",1304.6253v2
2013-10-07,Simulations of electric-dipole spin resonance for spin-orbit-coupled quantum dots in Overhauser field: fractional resonances and selection rules,"We consider spin rotations in single- and two-electron quantum dots that are
driven by external AC electric field with two mechanisms that couple the
electron spatial motion and the spin degree of freedom: the spin-orbit
interaction and a random fluctuation of the Overhauser field due to nuclear
spin bath. We perform a systematic numerical simulation of the driven system
using a finite difference approach with an exact account taken for the
electron-electron correlation. The simulation demonstrates that the electron
oscillation in fluctuating nuclear field is translated into an effective
magnetic field during the electron wave packet motion. The effective magnetic
field drives the spin transitions according to the electric-dipole spin
resonance mechanism. We find distinct signatures of selection rules for direct
and higher-order transitions in terms of the spin-orbital symmetries of the
wave functions. The selection rules are violated by the random fluctuation of
the Overhauser field.",1310.1689v1
2017-02-27,Current-induced spin polarization of a magnetized two-dimensional electron gas with Rashba spin-orbit interaction,"Current-induced spin polarization in a two-dimensional electron gas with
Rashba spin-orbit interaction is considered theoretically in terms of the
Matsubara Green functions. This formalism allows to describe temperature
dependence of the induced spin polarization. The electron gas is assumed to be
coupled to a magnetic substrate via exchange interaction. Analytical and
numerical results on the temperature dependence of spin polarization have been
obtained in the linear response regime. The spin polarization has been
presented as a sum of two terms - one proportional to the relaxation time and
the other related to the Berry phase corresponding to the electronic bands of
the magnetized Rashba gas. The spin-orbit torque due to Rashba interaction is
also discussed. Such a torque appears as a result of the exchange coupling
between the non-equilibrium spin polarization and magnetic moment of the
underlayer.",1702.08162v1
2018-05-25,Quasiclassical theory of the spin-orbit magnetoresistance of three-dimensional Rashba metals,"The magnetoresistance of a three-dimensional Rashba material placed on top of
a ferromagnetic insulator is theoretically investigated. In addition to the
intrinsic Rashba spin-orbit interaction, we also consider extrinsic spin-orbit
coupling via side-jump and skew scattering, and the Elliott-Yafet spin
relaxation mechanism. The latter is anisotropic due to the mass anisotropy
which reflects the noncentrosymmetric crystal structure of three-dimensional
Rashba metals. A quasiclassical approach is employed to derive a set of coupled
spin-diffusion equations, which are supplemented by boundary conditions that
account for the spin-transfer torque at the interface of the bilayer. The
magnetoresistance is fully determined by the current-induced spin polarization,
i.e., it cannot in general be ascribed to a single (bulk) spin Hall angle. Our
theoretical results reproduce several features of the experiments, at least
qualitatively, and contain established phenomenological results in the relevant
limiting cases. In particular, the anisotropy of the Elliott-Yafet spin
relaxation mechanism plays a major role for the interpretation of the observed
magnetoresistance.",1805.10245v1
2017-07-11,Hole spin resonance and spin-orbit coupling in a silicon metal-oxide-semiconductor field-effect transistor,"We study hole spin resonance in a p-channel silicon metal-oxide-semiconductor
field-effect transistor. In the sub-threshold region, the measured source-drain
current reveals a double dot in the channel. The observed spin resonance
spectra agree with a model of strongly coupled two-spin states in the presence
of a spin-orbit-induced anti-crossing. Detailed spectroscopy at the
anti-crossing shows a suppressed spin resonance signal due to
spin-orbit-induced quantum state mixing. This suppression is also observed for
multi-photon spin resonances. Our experimental observations agree with
theoretical calculations.",1707.03106v1
2019-03-29,Boundary conditions for spin and charge diffusion in the presence of interfacial spin-orbit coupling,"Breaking of the inversion symmetry at the interface between different
materials may dramatically enhance spin-orbit interaction in the vicinity of
the interface. We incorporate the effects of this interfacial spin-orbit
coupling (ISOC) into the standard drift-diffusion theory by deriving
generalized boundary conditions for diffusion equations. Our theoretical scheme
is based on symmetry arguments, providing a natural classification and
parametrization of all spin-charge and spin-spin conversion effects that occur
due to ISOC at macroscopically isotropic interfaces between nonmagnetic
materials. We illustrate our approach with specific examples of spin-charge
conversion in hybrid structures. In particular, for a lateral metal-insulator
structure we predict an ""ISOC-gating"" effect which can be used to detect spin
currents in metallic films with weak bulk SOC.",1903.12592v1
2010-04-03,Spin-selective Peierls transition in interacting one-dimensional conductors with spin-orbit interaction,"Interacting one-dimensional conductors with Rashba spin-orbit coupling are
shown to exhibit a spin-selective Peierls-type transition into a mixed
spin-charge-density-wave state. The transition leads to a gap for one-half of
the conducting modes, which is strongly enhanced by electron-electron
interactions. The other half of the modes remains in a strongly renormalized
gapless state and conducts opposite spins in opposite directions, thus
providing a perfect spin filter. The transition is driven by magnetic field and
by spin-orbit interactions. As an example we show for semiconducting quantum
wires and carbon nanotubes that the gap induced by weak magnetic fields or
intrinsic spin-orbit interactions can get renormalized by 1 order of magnitude
up to 10 - 30 K.",1004.0467v2
2015-11-14,Spin current generation and magnetic response in carbon nanotubes by the twisting phonon mode,"We theoretically investigate spin current and magnetic response induced by
the twisting phonon mode in carbon nanotubes via the spin-rotation coupling. An
effective magnetic field due to the twisting mode induces both spin and orbital
magnetizations. The induced spin and orbital magnetizations have both radial
and axial components. We show that ac pure spin current is generated by the
twisting phonon mode. The magnitude of the spin current and orbital
magnetization for a (10,10) armchair nanotube is estimated as an example. We
find that the ac pure spin current is detectable in magnitude when the
frequency of the twisting mode is of the order of GHz, and that the orbital
magnetization is found to be larger than the spin magnetization.",1511.04526v1
2021-05-28,Spin-orbit interactions of transverse sound,"Spin-orbit interactions (SOIs) endow light with intriguing properties and
applications such as photonic spin-Hall effects and spin-dependent vortex
generations. However, it is counterintuitive that SOIs can exist for sound,
which is a longitudinal wave that carries no intrinsic spin. Here, we
theoretically and experimentally demonstrate that airborne sound can possess
artificial transversality in an acoustic micropolar metamaterial and thus carry
both spin and orbital angular momentum. This enables the realization of
acoustic SOIs with rich phenomena beyond those in conventional acoustic
systems. We demonstrate that acoustic activity of the metamaterial can induce
coupling between the spin and linear crystal momentum k, which leads to
negative refraction of the transverse sound. In addition, we show that the
scattering of the transverse sound by a dipole particle can generate
spin-dependent acoustic vortices via the geometric phase effect. The acoustic
SOIs can provide new perspectives and functionalities for sound manipulations
beyond the conventional scalar degree of freedom and may open an avenue to the
development of spin-orbit acoustics.",2105.13558v1
2002-12-06,Spin-Orbital Fluctuations and a large mass enhancement in LiV_2O_4,"We present a scenario that the multi-component fluctuations, especially those
of the spin-orbital coupled modes, lead to the mass enhancement observed in
LiV_2O_4. This phenomena is possible because all these modes are fluctuating
due to the geometrical frustration. To illustrate this mechanism, the
t_{2g}-orbital Hubbard model on the pyrochlore lattice is studied based on the
random-phase approximation. We derive the generalized susceptibility in the
SU(6) spin-orbital space and calculate the free energy by using a
coupling-constant integration. The estimated specific heat coefficient is of
the correct order of magnitude to explain the experiment.",0212149v1
2005-12-13,Triplet pairing due to spin-orbit-assisted electron-phonon coupling,"We propose a microscopic mechanism for triplet pairing due to
spin-orbit-assisted electron interaction with optical phonons in a crystal with
a complex unit cell. Using two examples of electrons with symmetric Fermi
surfaces in crystals with either a cubic or a layered square lattice, we show
that spin-orbit-assisted electron-phonon coupling can, indeed, generate triplet
pairing and that, in each case, it predetermines the tensor structure of a
p-wave order parameter.",0512284v1
2008-04-04,Coulomb-Enhanced Spin-Orbit Splitting: The Missing Piece in the Sr2RhO4 Puzzle,"The outstanding discrepancy between the measured and calculated
(local-density approximation) Fermi surfaces in the well-characterized,
paramagnetic Fermi liquid Sr2RhO4 is resolved by including the spin-orbit
coupling and Coulomb repulsion. This results in an effective spin-orbit
coupling constant enhanced 2.15 times over the bare value. A simple formalism
allows discussion of other systems. For Sr2RhO4, the experimental specific-heat
and mass enhancements are found to be 2.2.",0804.0762v2
2008-11-07,Global nuclear structure aspects of tensor interaction,"A direct fit of the isoscalar spin-orbit and both isoscalar and isovector
tensor coupling constants to the f5/2-f7/2 SO splittings in 40Ca, 56Ni, and
48Ca requires: (i) a significant reduction of the standard isoscalar spin-orbit
strength and (ii) strong attractive tensor coupling constants. The aim of this
paper is to address the consequences of these strong attractive tensor and weak
spin-orbit fields on total binding energies, two-neutron separation energies
and nuclear deformability.",0811.1139v1
2010-06-20,Semiclassical study of edge states and transverse electron focusing for strong spin-orbit coupling,"We studied the edge states and transverse electron focusing in the presence
of spin-orbit interaction in a two dimensional electron gas. Assuming strong
spin-orbit coupling we derived semiclassical quantization conditions to
describe the dispersion of the edge states. Using the dispersion relation we
then make predictions about certain properties of the focusing spectrum.
Comparison of our analytical results with quantum mechanical transport
calculations reveals that certain features of the focusing spectrum can be
quite well understood in terms of the interference of the edge states while the
explanation of other features seems to require a different approach.",1006.3953v2
2010-08-12,Two exact properties of the perturbative expansion for the two-dimensional electron liquid with Rashba or Dresselhaus spin-orbit coupling,"We have identified two useful exact properties of the perturbative expansion
for the case of a two-dimensional electron liquid with Rashba or Dresselhaus
spin-orbit interaction and in the absence of magnetic field. The results allow
us to draw interesting conclusions regarding the dependence of the exchange and
correlation energy and of the quasiparticle properties on the strength of the
spin-orbit coupling which are valid to all orders in the electron-electron
interaction.",1008.2227v2
2010-08-28,Resonant Inelastic X-ray Scattering on Spin-Orbit Coupled Insulating Iridates,"We determine how the elementary excitations of iridium-oxide materials, which
are dominated by a strong relativistic spin-orbit coupling, appear in Resonant
Inelastic X-ray Scattering (RIXS). Whereas the RIXS spectral weight at the L2
x-ray edge vanishes, we find it to be strong at the L3-edge. Applying this to
Sr2IrO4, we observe that RIXS, besides being sensitive to local doublet to
quartet transitions, meticulously maps out the strongly dispersive delocalized
excitations of the low-lying spin-orbit doublets.",1008.4862v1
2013-05-10,Bound states of the spin-orbit coupled ultracold atom in a one-dimensional short-range potential,"We solve the bound state problem for the Hamiltonian with the spin-orbit and
the Raman coupling included. The Hamiltonian is perturbed by a one-dimensional
short-range potential V which describes the impurity scattering. In addition to
the bound states obtained by considering weak solutions through the Fourier
transform or by solving the eigenvalue equation on a suitable domain directly,
it is shown that ordinary point-interaction representations of V lead to
spin-orbit induced extra states.",1305.2316v1
2013-10-24,Interplay of Kondo effect and strong spin-orbit coupling in multi-hole ultraclean carbon nanotubes,"We report on cotunneling spectroscopy magnetoconductance measurements of
multi-hole ultraclean carbon nanotube quantum dots in the SU(4) Kondo regime
with strong spin-orbit coupling. Successive shells show a gradual weakening of
the Kondo effect with respect to the spin-orbital splittings, leading to an
evolution from SU(4) to SU(2) symmetry with a suppressed conductance at half
shell filling. The extracted energy level spectrum, overally consistent with
negligible disorder in the nanotube, shows in the half filled case large
renormalizations due to Coulombian effects.",1310.6530v1
2014-12-01,Wigner-localized states in spin-orbit-coupled bosonic ultracold atoms with dipolar interaction,"We investigate the occurence of Wigner-localization phenomena in bosonic
dipolar ultracold few-body systems with Rashba-like spin-orbit coupling. We
show that the latter strongly enhances the effects of the dipole-dipole
interactions, allowing to reach the Wigner-localized regime for strengths of
the dipole moment much smaller than those necessary in the spin-orbit-free
case.",1412.0505v1
2014-12-09,Magnetism and electronic structure calculation of SmN,"The results of the electronic structure calculations performed on SmN by
using the LDA+U method with and without including the spin-orbit coupling are
presented. Within the LDA+U approach, a N(2$p$) band polarization of $\simeq
0.3\ \mu_B$ is induced by Sm(4$f$)-N(2$p$) hybridization, and a half-metallic
ground state is obtained. By including spin-orbit coupling the magnetic
structure was shown to be antiferromagnetic of type II, with Sm spin and
orbital moments nearly cancelling. This results into a semiconducting ground
state, which is in agreement with experimental results.",1412.2966v1
2015-07-22,Theoretical Study of Coulomb Correlations and Spin-Orbit Coupling in SrIrO3,"Given that energy scales associated with crystal field splitting, spin orbit
coupling and coulomb correlations in iridates are comparable, hence leading to
exotic properties, we investigate the physical properties of orthorhombic
SrIrO3 using density functional theory. Our calculations, however, show that
SrIrO 3 is a bad metal with no long range magnetic ordering, unlike its sister
compounds Sr2IrO4 and Sr3Ir2O7. Moreover, despite having large band width, it
appears conclusive that the larger resistivity in SrIrO 3 is due to spin orbit
interactions. Besides, the effects of electron-electron correlations on its
electronic structure and magnetic properties are also discussed.",1507.06058v1
2016-03-11,Majorana fermions in charge carrier hole quantum wires,"Luttinger holes with strong Zeemann and spin-orbit interactions in a wire
proximity-coupled to a superconductor is a promising system for observation of
Majorana fermions. Earlier treatments of confined Luttinger holes in wires
ignored a mutual transformation of heavy and light holes upon reflection from
the heteroboundaries. This effect is crucial for Zeemann and spin-orbit
coupling in the ground subband of holes with several spin-orbit terms linear in
momentum. We discuss the criterion for realizing Majorana modes in charge
carrier hole systems. GaAs or InSb hole wires shall exhibit stronger
topological superconducting pairing compared to InSb electron systems in
similar or weaker magnetic fields.",1603.03750v1
2015-12-25,Effect of spin-orbit coupling on spectral and transport properties of tubular electron gas in InAs nanowires,"We constructed the Hamiltonian of spin-orbit splitting for carriers of a
tubular electron gas in InAs nanowires. The spectral problem is solved using an
exact numerical diagonalization. It is shown that the contribution of k-linear
Dresselhaus-like spin-orbit (SO) coupling leads to renormalization of so-called
SO-gaps and appearance of anticrossings in subband spectrum. These features can
be detected in ballistic transport.",1512.08021v1
2019-11-06,CPT-Violating Gravitational Orbital Perturbations,"A model for spontaneous symmetry breaking using a specific form of the
bumblebee model is analyzed in the context of a Schwarzschild background
metric. The resulting back reaction of the symmetry-breaking field on the
metric is computed to second order. Consistency with conventional
(pseudo)Riemannian geometry is demonstrated. This background field is coupled
to fermions via a spin-dependent CPT-violating coupling term of a type commonly
considered in the Standard-Model Extension. The perturbations of various
orbital trajectories are discussed. Specifically, a spin-dependent orbital
velocity is found as well as a spin-dependent precession rate.",1911.02542v1
2020-02-13,Semi-realistic tight-binding model for spin-orbit torques,"We compute the spin-orbit torque in a transition metal heterostructure using
Slater-Koster parameterization in the two-center tight-binding approximation
and accounting for d-orbitals only. In this method, the spin-orbit coupling is
modeled within Russel-Saunders scheme, which enables us to treat interfacial
and bulk spin-orbit transport on equal footing. The two components of the
spin-orbit torque, dissipative (damping-like) and reactive (field-like), are
computed within Kubo linear response theory. By systematically studying their
thickness and angular dependence, we were able to accurately characterize these
components beyond the traditional ""inverse spin galvanic"" and ""spin Hall""
effects. Whereas the conventional field-like torque is purely interfacial, we
unambiguously demonstrate that the conventional the damping-like torque
possesses both an interfacial and a bulk contribution. In addition, both
field-like and damping-like torques display substantial angular dependence with
strikingly different thickness behavior. While the planar contribution of the
field-like torque decreases smoothly with the nonmagnetic metal thickness, the
planar contribution of the damping-like torque increases dramatically with the
nonmagnetic metal thickness. Finally, we investigate the self-torque exerted on
the ferromagnet when the spin-orbit coupling of the nonmagnetic metal is turned
off. Our results suggest that the spin accumulation that builds up inside the
ferromagnet can be large enough to induce magnetic excitations.",2002.05533v1
2020-10-19,The spin-spin model and the capture into the double synchronous resonance,"The aim of this article is to propose a model, that is a planar version of
the Full Two-Body Problem, and discuss the existence and stability of a
relevant periodic solution. Consider two homogeneous ellipsoids orbiting around
each other in fixed coplanar Keplerian orbits. Moreover, their respective spin
axes are assumed to be perpendicular to the orbital plane, that is also a
common equatorial plane. The spin-spin model deals with the coupled rotational
dynamics of both ellipsoids. For a non-zero orbital eccentricity, it has the
structure of a non-autonomous system of coupled pendula. This model is a
natural extension of the classical spin-orbit problem for two extended bodies.
In addition, we consider dissipative tidal torques, that can trigger the
capture of the system into spin-orbit and spin-spin resonances. In this paper
we give some theoretical results for both the conservative model and the
dissipative one. The conservative model has a Hamiltonian structure. We use
properties of Hamiltonian systems to give some sufficient conditions in the
space of parameters of the model, that guarantee existence, uniqueness and
linear stability of an odd periodic solution. This solution represents a double
synchronous resonance in the conservative regime. Such solution can be
continued to the dissipative regime, where it becomes asymptotically stable. We
see asymptotic stability as a dynamical mechanism for the capture into the
double synchronous resonance. Finally we apply our results to several cases
including the Pluto-Charon binary system and the Trojan binary asteroid 617
Patroclus, target of the LUCY mission.",2010.09354v1
2004-08-25,Measurement of gravitational spin-orbit coupling in a binary pulsar system,"In relativistic gravity, a spinning pulsar will precess as it orbits a
compact companion star. We have measured the effect of such precession on the
average shape and polarization of the radiation from PSR B1534+12. We have also
detected, with limited precision, special-relativistic aberration of the
revolving pulsar beam due to orbital motion. Our observations fix the system
geometry, including the misalignment between the spin and orbital angular
momenta, and yield a measurement of the precession timescale consistent with
the predictions of General Relativity.",0408457v1
2002-09-03,Generalized hole-particle transformations and spin reflection positivity in multi-orbital systems,"We propose a scheme combining spin reflection positivity and generalized
hole-particle and orbital transformations to characterize the symmetry
properties of the ground state for some correlated electron models on bipartite
lattices. In particular, we rigorously determine at half-filling and for
different regions of the parameter space the spin, orbital and $\eta$ pairing
pseudospin of the ground state of generalized two-orbital Hubbard models which
include the Hund's rule coupling.",0209062v1
2011-11-02,Alternating spin-orbital order in tetragonal Sr2VO4,"Considering spin-orbit coupling, the tetragonal crystal-field, and all
relevant superexchange processes including quantum interference, we derive
expressions for the energy levels of the vanadium ions in tetragonal Sr2VO4.
The used parameters of the model Hamiltonian allow to describe well the
excitation spectra observed in neutron scattering and optical experiments at
low temperatures. The free energy exhibits a minimum which corresponds to a
novel alternating spin-orbital order with strong thermal fluctuation of the
orbital mixing parameter.",1111.0668v1
2020-04-03,PhD Thesis: Searching for an emergent SU(4) symmetry in real materials,"The enhancement of the spin-space symmetry from the usual $\mathrm{SU}(2)$ to
$\mathrm{SU}(N)$ with $N>2$ is promising for finding nontrivial quantum spin
liquids, but the realization of $\mathrm{SU}(N)$ spin systems in real materials
is still challenging. Although there is a proposal in cold atomic systems, in
magnetic materials with a spin-orbital degree of freedom it is difficult to
achieve the $\mathrm{SU}(N)$ symmetry by fine tuning. Here we propose a new
mechanism by which the $\mathrm{SU}(4)$ symmetry emerges in the strong
spin-orbit coupling limit. In $d^1$ transition metal compounds with
edge-sharing anion octahedra, the spin-orbit coupling gives rise to strongly
bond-dependent and apparently $\mathrm{SU}(4)$-breaking hopping between the
$J_\textrm{eff}=3/2$ quartets. However, in the honeycomb structure, a gauge
transformation maps the system to an $\mathrm{SU}(4)$-symmetric Hubbard model,
which means that the system has a hidden symmetry in spite of its large
spin-orbit coupling. In the strong repulsion limit at quarter filling, as
expected in $\alpha$-ZrCl$_3,$ the low-energy effective model is the
$\mathrm{SU}(4)$ Heisenberg model on the honeycomb lattice, which cannot have a
trivial gapped ground state and is expected to host a gapless spin-orbital
liquid. In such quantum spin-orbital liquids, both the spin and orbital degrees
of freedom become fractionalized and correlated together at low temperature due
to the strong frustrated interactions between them. Similarly to spinons in
pure quantum spin liquids, quantum spin-orbital liquids can host not only
spinon excitations, but also fermionic ""orbitalon"" excitations at low
temperature, which we have named here in distinction from orbitons in the
symmetry-broken Jahn-Teller phases.",2004.01716v1
2004-06-04,"Orbital Polarization, Surface Enhancement and Quantum Confinement in Nano-cluster Magnetism","Within a rather general tight-binding framework, we studied the magnetic
properties of Ni$_{n}$ clusters with $n=9$ through 60. In addition to usual
hopping, exchange, and spin-orbit coupling terms, our Hamiltonian also included
orbital correlation and valence orbital shift of surface atoms. We show that
orbital moment not only contributes appreciably to the total moment in this
range of cluster size, but also dominates the oscillation of total moment with
respect to the cluster size. Surface enhancement is found to occur not only for
spin but, even stronger, also for orbital moment. The magnitude of this
enhancement depends mainly on the coordination deficit of surface atoms, well
described by a simple interpolation. For very small clusters ($n \leq 20$),
quantum confinement of 4s electrons has drastic effects on 3$d$ electron
occupation, and thus greatly influences both spin and orbital magnetic moments.
With physically reasonable parameters to account for orbital correlation and
surface valence orbital shift, our results are in good quantitative agreement
with available experiments, evidencing the construction of a unified
theoretical framework for nano-cluster magnetism.",0406114v1
2019-05-09,Exotic Cooper pairing in multi-orbital models of Sr$_2$RuO$_4$,"The unconventional superconductivity in Sr$_2$RuO$_4$ continues to defy a
unified interpretation. In this paper, we focus on some novel aspects of its
superconducting pairing by exploiting the orbital degree of freedom in this
material. The multi-orbital nature, combined with the symmetry of the orbitals
involved, leads to a plethora of exotic Cooper pairings not accessible in
single-orbital systems. Essential physics is illustrated first using a
two-orbital model with $d_{xz}$- and $d_{yz}$-orbitals. We classify the gap
functions according to the underlying lattice symmetries, analyze the effective
theories of a few representative pairings, and make connections to
Sr$_2$RuO$_4$ in the course. In particular, we show how spin-orbit coupling may
entangle spin-triplet and spin-singlet pairings. For completeness, the
classification is generalized to the three-orbital model involving the
$d_{xy}$-orbital as well. The orbital-basis approach distinguishes from the
itinerant-band description for Sr$_2$RuO$_4$, and hence offers an alternative
perspective to investigate its enigmatic superconducting state.",1905.03523v4
2022-11-30,Emergent Orbital Skyrmion Lattice in a Triangular Atom Array,"Multi-orbital optical lattices have been attracting rapidly growing research
interests in the last several years, providing fascinating opportunities for
orbital-based quantum simulations. Here, we consider bosonic atoms loaded in
the degenerate $p$-orbital bands of a two-dimensional triangular optical
lattice. This system is described by a multi-orbital Bose-Hubbard model. We
find the confined atoms in this system develop spontaneous orbital
polarization, which forms a chiral Skyrmion lattice pattern in a large regime
of the phase diagram. This is in contrast to its spin analogue which largely
requires spin-orbit couplings. The emergence of the Skyrmion lattice is
confirmed in both bosonic dynamical mean-field theory (BDMFT) and exact
diagonalization (ED) calculations. By analyzing the quantum tunneling induced
orbital-exchange interaction in the strong interaction limit, we find the
Skyrmion lattice state arises due to the interplay of $p$-orbital symmetry and
the geometric frustration of the triangular lattice. We provide experimental
consequences of the orbital Skyrmion state, that can be readily tested in cold
atom experiments. Our study implies orbital-based quantum simulations could
bring exotic scenarios unexpected from their spin analogue.",2212.00167v2
2005-10-02,Orbital order and fluctuations in Mott insulators,"Basic mechanisms controlling orbital order and orbital fluctuations in
transition metal oxides are discussed. The lattice driven classical orbital
picture, e.g. like in manganites LaMnO$_3$, is contrasted to the quantum
behavior of orbitals in frustrated superexchange models as realised in
pseudocubic titanites ATiO$_3$ and vanadates AVO$_3$. In YVO$_3$, the lattice
and superexchange effects strongly compete -- this explains the extreme
sensitivity of magnetic states to temperature and doping. Lifting the $t_{2g}$
orbital degeneracy by a relativistic spin-orbital coupling is considered on
example of the layered cobaltates. We find that the spin-orbital mixing of
low-energy states leads to unusual magnetic correlations in a triangular
lattice of the CoO$_2$ parent compound. Finally, the magnetism of sodium-rich
compounds Na$_{1-x}$CoO$_2$ is discussed in terms of a spin/orbital polaronic
liquid.",0510025v2
2008-01-29,Orbital order driven quantum criticality,"Charge, spin, and orbital degrees of freedom underlie the physics of
transition metal compounds. Much work has revealed quantum critical points
associated with spin and charge degrees of freedom in many of these systems.
Here we illustrate that the simplest models that embody the orbital degrees of
freedom - the two- and three-dimensional quantum orbital compass models -
exhibit an exact quantum critical behavior on diluted square and cubic lattices
(with a doping fraction of 1/4 and 1/2 respectively). This raises the
possibility of quantum critical points triggered by the degradation of orbital
order upon doping (or applying pressure to) such transition metal systems. We
prove the existence of an orbital spin glass in several related systems in
which the orbital couplings are made non-uniform. Moreover, a new orbital
Larmor precession (i.e., a periodic change in the orbital state) is predicted
when uniaxial pressure is applied.",0801.4391v2
2005-07-07,Orbital and spin physics in LiNiO2 and NaNiO2,"We derive a spin-orbital Hamiltonian for a triangular lattice of e_g orbital
degenerate (Ni^{3+}) transition metal ions interacting via 90 degree
superexchange involving (O^{2-}) anions, taking into account the on-site
Coulomb interactions on both the anions and the transition metal ions. The
derived interactions in the spin-orbital model are strongly frustrated, with
the strongest orbital interactions selecting different orbitals for pairs of Ni
ions along the three different lattice directions. In the orbital ordered
phase, favoured in mean field theory, the spin-orbital interaction can play an
important role by breaking the U(1) symmetry generated by the much stronger
orbital interaction and restoring the threefold symmetry of the lattice. As a
result the effective magnetic exchange is non-uniform and includes both
ferromagnetic and antiferromagnetic spin interactions. Since ferromagnetic
interactions still dominate, this offers yet insufficient explanation for the
absence of magnetic order and the low-temperature behaviour of the magnetic
susceptibility of stoichiometric LiNiO_2. The scenario proposed to explain the
observed difference in the physical properties of LiNiO_2 and NaNiO_2 includes
small covalency of Ni-O-Li-O-Ni bonds inducing weaker interplane superexchange
in LiNiO_2, insufficient to stabilize orbital long-range order in the presence
of stronger intraplane competition between superexchange and Jahn-Teller
coupling.",0507169v1
2018-03-09,Spin exchange-induced spin-orbit coupling in a superuid mixture,"We investigate the ground-state properties of a dual-species spin-1/2
Bose-Einstein condensate. One of the species is subjected to a pair of Raman
laser beams that induces spin-orbit (SO) coupling, whereas the other species is
not coupled to the Raman laser. In certain limits, analytical results can be
obtained. It is clearly shown that, through the inter-species spin-exchange
interaction, the second species also exhibits SO coupling. This mixture system
displays a very rich phase diagram, with many of the phases not present in an
SO coupled single-species condensate. Our work provides a new way of creating
SO coupling in atomic quantum gases, and opens up a new avenue of research in
SO coupled superfluid mixtures. From a practical point of view, the spin
exchange-induced SO coupling may overcome the heating issue for certain atomic
species when subjected to the Raman beams.",1803.03387v1
2018-08-23,Spin field-effect transistor in a quantum spin-Hall device,"We discuss the transport properties of a quantum spin-Hall insulator with
sizable Rashba spin-orbit coupling in a disk geometry. The presence of
topologically protected helical edge states allows for the control and
manipulation of spin polarized currents: when ferromagnetic leads are coupled
to the quantum spin-Hall device, the ballistic conductance is modulated by the
Rashba strength. Therefore, by tuning the Rashba interaction via an
all-electric gating, it is possible to control the spin polarization of
injected electrons.",1808.07818v1
2003-04-11,Magnetotransport in Two-Dimensional Electron Systems with Spin-Orbit Interaction,"We present magnetotransport calculations for homogeneous two-dimensional
electron systems including the Rashba spin-orbit interaction, which mixes the
spin-eigenstates and leads to a modified fan-chart with crossing Landau levels.
The quantum mechanical Kubo formula is evaluated by taking into account
spin-conserving scatterers in an extension of the self-consistent Born
approximation that considers the spin degree of freedom. The calculated
conductivity exhibits besides the well-known beating in the Shubnikov-de Haas
(SdH) oscillations a modulation which is due to a suppression of scattering
away from the crossing points of Landau levels and does not show up in the
density of states. This modulation, surviving even at elevated temperatures
when the SdH oscillations are damped out, could serve to identify spin-orbit
coupling in magnetotransport experiments. Our magnetotransport calculations are
extended also to lateral superlattices and predictions are made with respect to
1/B periodic oscillations in dependence on carrier density and strength of the
spin-orbit coupling.",0304260v1
2010-04-06,Giant Intrinsic Spin-Orbit Coupling in Bilayer Graphene,"The intrinsic spin-orbit coupling (ISOC) in bilayer graphene is investigated.
We find that the largest ISOC between $\pi$ electrons origins from the
following hopping processes: a $\pi$ electron hops to $\sigma$ orbits of the
other layer and further to $\pi$ orbits with the opposite spin through the
intra-atomic ISOC. The magnitude of this ISOC is about $0.46meV$, 100 times
larger than that of the monolayer graphene. The Hamiltonians including this
ISOC in both momentum and real spaces are derived. Due to this ISOC, the
low-energy states around the Dirac point exhibit a special spin polarization,
in which the electron spins are oppositely polarized in the upper and lower
layers. This spin polarization state is robust, protected by the time-reversal
symmetry. In addition, we provide a hybrid system to select a certain spin
polarization state by an electric manipulation.",1004.0881v1
2013-03-06,Spin-orbit effects in nanowire-based wurtzite semiconductor quantum dots,"We study the effect of the Dresselhaus spin-orbit interaction on the
electronic states and spin relaxation rates of cylindrical quantum dots defined
on quantum wires having wurtzite lattice structure. The linear and cubic
contributions of the bulk Dresselhaus spin-orbit coupling are taken into
account, along with the influence of a weak external magnetic field. The
previously found analytic solution for the electronic states of cylindrical
quantum dots with zincblende lattice structures with Rashba interaction is
extended to the case of quantum dots with wurtzite lattices. For the electronic
states in InAs dots, we determine the spin texture and the effective g-factor,
which shows a scaling collapse when plotted as a function of an effective
renormalized dot-size dependent spin-orbit coupling strength. The
acoustic-phonon-induced spin relaxation rate is calculated and the transverse
piezoelectric potential is shown to be the dominant one.",1303.1363v1
2013-07-28,Origin of Rashba-splitting in the quantized subbands at Bi2Se3 surface,"We study the band structure of the $\text{Bi}_2\text{Se}_3$ topological
insulator (111) surface using angle-resolved photoemission spectroscopy. We
examine the situation where two sets of quantized subbands exhibiting different
Rashba spin-splitting are created via bending of the conduction (CB) and the
valence (VB) bands at the surface. While the CB subbands are strongly Rashba
spin-split, the VB subbands do not exhibit clear spin-splitting. We find that
CB and VB experience similar band bending magnitudes, which means, a
spin-splitting discrepancy due to different surface potential gradients can be
excluded. On the other hand, by comparing the experimental band structure to
first principles LMTO band structure calculations, we find that the strongly
spin-orbit coupled Bi 6$p$ orbitals dominate the orbital character of CB,
whereas their admixture to VB is rather small. The spin-splitting discrepancy
is, therefore, traced back to the difference in spin-orbit coupling between CB
and VB in the respective subbands' regions.",1307.7384v2
2015-09-15,Relaxation and coherent oscillations in the spin dynamics of II-VI diluted magnetic quantum wells,"We study theoretically the ultrafast spin dynamics of II-VI diluted magnetic
quantum wells in the presence of spin-orbit interaction. We extend a recent
study where it was shown that the spin-orbit interaction and the exchange sd
coupling in bulk and quantum wells can compete resulting in qualitatively new
dynamics when they act simultaneously. We concentrate on
Hg$_{1-x-y}$Mn$_x$Cd$_y$Te quantum wells, which have a highly tunable Rashba
spin-orbit coupling. Our calculations use a recently developed formalism which
incorporates electronic correlations originating from the exchange
$sd$-coupling. We find that the dependence of electronic spin oscillations on
the excess energy changes qualitatively depending on whether or not the
spin-orbit interaction dominates or is of comparable strength with the sd
interaction.",1509.04588v1
2016-02-12,Rashba splitting of Cooper pairs,"We investigate theoretically the properties of a weak link between two
superconducting leads, which has the form of a non-superconducting nanowire
with a strong Rashba spin-orbit coupling caused by an electric field. In the
Coulomb blockade regime of single-electron tunneling, we find that such a weak
link acts as a ""spin splitter"" of the spin states of Cooper pairs tunneling
through the link, to an extent that depends on the direction of the electric
field. We show that the Josephson current is sensitive to interference between
the resulting two transmission channels, one where the spins of both members of
a Cooper pair are preserved and one where they are both flipped. As a result,
the current is a periodic function of the strength of the spin-orbit
interaction and of the bending angle of the nanowire (when mechanically bent);
an identical effect appears due to strain-induced spin-orbit coupling. In
contrast, no spin-orbit induced interference effect can influence the current
through a single weak link connecting two normal metals.",1602.04161v3
2017-09-15,"Energy spectrum, the spin polarization, and the optical selection rules of the Kronig-Penney superlattice model with spin-orbit coupling","The Kronig-Penney model, an exactly solvable one-dimensional model of crystal
in solid physics, shows how the allowed and forbidden bands are formed in
solids. In this paper, we study this model in the presence of both strong
spin-orbit coupling and the Zeeman field. We analytically obtain four
transcendental equations that represent an implicit relation between the energy
and the Bloch wavevector. Solving these four transcendental equations, we
obtain the spin-orbital bands exactly. In addition to the usual band gap opened
at the boundary of the Brillouin zone, a much larger spin-orbital band gap is
also opened at some special sites inside the Brillouin zone. The $x$-component
of the spin-polarization vector is an even function of the Bloch wavevector,
while the $z$-component of the spin-polarization vector is an odd function of
the Bloch wavevector. At the band edges, the optical transition rates between
adjacent bands are nonzero.",1709.05039v2
2017-09-17,Intrinsic spin-orbit coupling gap and the evidence of a topological state in graphene,"In 2005 Kane & Mele[C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95, 226801
(2005)], predicted that at sufficiently low energy, graphene exhibits a
topological state of matter with an energy gap generated by the atomic
spin-orbit interaction. However, this intrinsic gap has not been measured to
this date. In this letter, we exploit the chirality of the low energy states to
resolve this gap. We probe the spin states experimentally, by employing low
temperature microwave excitation in a resistively detected electron spin
resonance on graphene. The structure of the topological bands is reflected in
our transport experiments, where our numerical models allow us to identify the
resonance signatures. We determine the intrinsic spin-orbit bulk gap to be
exactly 42.2 {\mu}eV. Electron-spin resonance experiments can reveal the
competition between the intrinsic spin-orbit coupling and classical Zeeman
energy that arises at low magnetic fields and demonstrate that graphene remains
to be a material with surprising properties.",1709.05705v2
2019-11-05,Spin-orbit Interaction driven Topological Features in a Quantum Ring,"One-dimensional quantum rings with Rashba and Dresselhaus spin-orbit
couplings are studied analytically and are in perfect agreement with the
numerical results. The topological charge of the spin field defined by the
winding number along the ring is also studied analytically and numerically in
the presence of the spin-orbit interactions. We also demonstrate the cases
where the one-dimensional model is invalid for a relatively large radius.
However, the numerical results of the two-dimensional model always remain
reliable. Just as many physical properties of the quantum rings are influenced
by the Aharonov-Bohm effect, the topological charge is also found to vary
periodically due to the step-like change of the angular momentum with an
increase of the magnetic field. This is significantly different from the cases
of quantum dots. We also study how the current is induced by the magnetic field
and spin-orbit couplings, which is strong enough that it could to be detected.
The magnetic induction lines induced by the spin field and the current are also
analyzed which can be observed and could perhaps help identifying the
topological features of the spin fields in a quantum ring.",1911.01613v1
2020-10-25,Absence of significant spin current generation in Ti/FeCoB bilayers with strong interfacial spin-orbit coupling,"After one decade of the intensive theoretical and experimental explorations,
whether interfacial spin-orbit coupling (ISOC) at metallic magnetic interfaces
can effectively generate a spin current has remained in dispute. Here,
utilizing the Ti/FeCoB bilayers that are unique for the negligible bulk spin
Hall effect and the strong tunable ISOC, we establish that there is no
significant charge-to-spin conversion at magnetic interfaces via spin-orbit
filtering effect or Rashba-Edelstein(-like) effect even when the ISOC is
stronger than that of a typical Pt/ferromagnet interface and can promote strong
perpendicular magnetic anisotropy. We also find a minimal orbital Hall effect
in 3d Ti.",2010.13137v2
2024-02-22,Spin-dependent interactions in orbital-density-dependent functionals: non-collinear Koopmans spectral functionals,"The presence of spin-orbit coupling or non-collinear magnetic spin states can
have dramatic effects on the ground-state and spectral properties of materials,
in particular on the band structure. Here, we develop non-collinear
Koopmans-compliant functionals based on Wannier functions and
density-functional perturbation theory, targeting accurate spectral properties
in the quasiparticle approximation. Our non-collinear Koopmans-compliant theory
involves functionals of four-component orbitals densities, that can be obtained
from the charge and spin-vector densities of Wannier functions. We validate our
approach on three emblematic and diverse semiconductors where the effect of
spin-orbit coupling goes from small to very large: the III-IV semiconductor
GaAs, the transition-metal dichalcogenide WSe$_2$, and the cubic perovskite
CsPbBr$_3$. The predicted band gaps are comparable in accuracy to
state-of-the-art many-body perturbation theory and include spin-dependent
interactions and screening effects that are missing in standard diagrammatic
approaches based on the random phase approximation. While the inclusion of
orbital- and spin-dependent interactions in many-body perturbation theory
requires self-screening or vertex corrections, that emerges naturally in the
Koopmans-functionals framework.",2402.14575v1
2012-08-18,Maximum intrinsic spin-Hall conductivity in two-dimensional systems with k-linear spin-orbit interaction,"We analytically calculate the intrinsic spin-Hall conductivity (ISHC)
($\sigma^z_{xy}$ and $\sigma^z_{yx}$) in a clean, two-dimensional system with
generic k-linear spin-orbit interaction. The coefficients of the product of the
momentum and spin components form a spin-orbit matrix $\widetilde{\beta}$. We
find that the determinant of the spin-orbit matrix $\detbeta$ describes the
effective coupling of the spin $s_z$ and orbital motion $L_z$. The decoupling
of spin and orbital motion results in a sign change of the ISHC and the
band-overlapping phenomenon. Furthermore, we show that the ISHC is in general
unsymmetrical ($\sigma^z_{xy}\neq-\sigma^z_{yx}$), and it is governed by the
asymmetric response function $\Deltabeta$, which is the difference in
band-splitting along two directions: those of the applied electric field and
the spin-Hall current. The obtained non-vanishing asymmetric response function
also implies that the ISHC can be larger than $e/8\pi$, but has an upper bound
value of $e/4\pi$. We will that the unsymmetrical properties of the ISHC can
also be deduced from the manifestation of the Berry curvature at the nearly
degenerate area. On the other hand, by investigating the equilibrium spin
current, we find that $\detbeta$ determines the field strength of the SU(2)
non-Abelian gauge field.",1208.3755v3
2023-02-23,Photo-assisted spin transport in double quantum dots with spin-orbit interaction,"We investigate the effect of spin-orbit interaction on the intra- and
interdot particle dynamics of a double quantum dot under ac electric fields.
The former is modeled as an effective ac magnetic field that produces
electric-dipole spin resonance transitions, while the latter is introduced via
spin-flip tunneling amplitudes. We observe the appearance of non-trivial
spin-polarized dark states, arising from an ac-induced interference between
photo-assisted spin-conserving and spin-flip tunneling processes. These dark
states can be employed to precisely measure the spin-orbit coupling in quantum
dot systems. Furthermore, we show that the interplay between photo-assisted
transitions and spin-flip tunneling allows the system to operate as a highly
tunable spin filter. Finally, we investigate the operation of the system as a
resonant flopping-mode qubit for arbitrary ac voltage amplitudes, allowing for
high tunability and enhanced qubit control possibilities.",2302.12272v2
2021-08-09,"Spin and Orbital Effects on Asymmetric Exchange Interaction in Polar Magnets: M(IO3)2 (M = Cu, Mn)","We study how spin and orbital effects influence the capability of promoting
Dzyaloshinskii-Moriya (DM) interaction by studying the two magnetic polar
materials, Cu(IO3)2 (S = 1/2 with orbital contribution) and Mn(IO3)2 (S = 5/2
with quenched orbital magnetism) and connecting their electronic and magnetic
properties with their structures. The chemically controlled low-temperature
synthesis of these complexes resulted in pure polycrystalline samples,
providing a viable pathway to prepare bulk forms of transition-metal io-dates.
Rietveld refinements of the powder synchrotron X-ray diffraction data reveal
that these materials exhibit different crystal structures but crystallize in
the same polar and chiral P21 space group, giving rise to an electric
polarization along the b-axis direction. The presence and absence of an evident
phase transition to a possible topologically distinct state observed in
Cu(IO3)2 and Mn(IO3)2, respectively, implies the important role of spin-orbit
coupling. Neutron diffraction experiments reveal helpful insights into the
magnetic ground state of these materials. While the long-wavelength
incommensurability of Cu(IO3)2 is in harmony with orbital effects and
anisotropic magnetic exchange, the commensurate stripe AFM ground state of
Mn(IO3)2 is attributed to quenched orbital angular momentum and isotropic
magnetic coupling. The work demonstrates connections between combined spin and
orbital effects, magnetic coupling dimensionality and DM exchange, providing a
worthwhile approach for tuning asymmetric interaction which promotes evolution
of topologically distinct spin phases.",2108.04290v2
2012-07-06,SU(3) Spin-Orbit Coupling in Systems of Ultracold Atoms,"Motivated by the recent experimental success in realizing synthetic
spin-orbit coupling in ultracold atomic systems, we consider N-component atoms
coupled to a non-Abelian SU(N) gauge field. More specifically, we focus on the
case, referred to here as ""SU(3) spin-orbit-coupling,"" where the internal
states of three-component atoms are coupled to their momenta via a matrix
structure that involves the Gell-Mann matrices (in contrast to the Pauli
matrices in conventional SU(2) spin-orbit-coupled systems). It is shown that
the SU(3) spin-orbit-coupling gives rise to qualitatively different phenomena
and in particular we find that even a homogeneous SU(3) field on a simple
square lattice enables a topologically non-trivial state to exist, while such
SU(2) systems always have trivial topology. In deriving this result, we first
establish an exact equivalence between the Hofstadter model with a 1/N Abelian
flux per plaquette and a homogeneous SU(N) non-Abelian model. The former is
known to have a topological spectrum for N>2, which is thus inherited by the
latter. It is explicitly verified by an exact calculation for N=3, where we
develop and use a new algebraic method to calculate topological indices in the
SU(3) case. Finally, we consider a strip geometry and establish the existence
of three gapless edge states -- the hallmark feature of such an SU(3)
topological insulator.",1207.1728v2
2004-12-17,The low-energy electronic structure and the orbital magnetism in NiO,"The orbital and spin moment of the Ni2+ ion in NiO has been calculated within
the quasi-atomic approach. The orbital moment of 0.46 mu_B amounts at 0 K, in
the magnetically-ordered state, to about 20% of the total moment (2.45 mu_B).
For this outcome, being in nice agreement with the recent experimental finding
of the orbital moment, taking into account the intra-atomic spin-orbit coupling
is indispensable.
  PACS: 75.25.+z, 75.10.Dg
  Keywords: Crystalline Electric Field, 3d oxides, magnetism, NiO",0412484v1
2017-04-01,Anomalous Hall Effect and Spontaneous Orbital Magnetization in Antiferromagnetic Weyl Metal,"We study the anomalous Hall effect and orbital magnetization in chiral
antiferromagnets, constructing a simple tight-binding model on a stacked Kagome
lattice structure with spin-orbit coupling and the exchange interaction between
the localized spins and itinerant electrons. It is shown that the ground state
is an orbital ferromagnet with the easy-plane anisotropy. The relation between
the orbital magnetization and the configuration of the Weyl points are
discussed.",1704.00094v3
2001-08-01,Order from disorder: Quantum spin gap in magnon spectra of LaTiO_3,"A theory of the anisotropic superexchange and low energy spin excitations in
a Mott insulator with t_{2g} orbital degeneracy is presented. We observe that
the spin-orbit coupling induces frustrating Ising-like anisotropy terms in the
spin Hamiltonian, which invalidate noninteracting spin wave theory. The
frustration of classical states is resolved by an order from disorder
mechanism, which selects a particular direction of the staggered moment and
generates a quantum spin gap. The theory explains well the observed magnon gaps
in LaTiO_3. As a test case, a specific prediction is made on the splitting of
magnon branches at certain momentum directions.",0108016v2
2005-04-12,Spin precession in a fractional quantum Hall state with spin-orbit coupling,"Experimental attempts to realize spin-devices based on concepts derived from
single-particle theoretical approaches have not been very successful yet. This
raises the fundamental question of whether inter-electron interactions can be
neglected in planar electron-based spintronics devices. We report on our
results of a many-body approach to the spin configuration in a quantum Hall
state in the presence of Bychkov-Rashba type spin-orbit interaction. While some
properties of this system are found to be ideally suited for exploitation in
spin devices, others might seem to limit its applicability. The latter can
however be optimized for device performance.",0504310v1
2006-11-28,Generation of dc spin current in a narrow channel with Rashba and Dresselhaus spin-orbit interaction,"We consider a finite range ac-biased front gate acting upon a quantum channel
with Rashba and Dresselhaus spin-orbit interaction effects. The ac-biased gate,
giving rise to a dynamical Rashba coupling, causes spin-resolved coherent
resonant inelastic scattering. A pure dc spin current is subsequently generated
without accompanying charge current. In the presence of Dresselhaus effect, the
dc spin current is suppressed in the low kinetic energy regime but is assisted
in the high kinetic energy regime.",0611703v1
2011-05-17,Spin-current in generic hybrid structures due to interfacial spin-orbit scattering,"We demonstrate a general principle that hybrid structures of any sort
inevitably will give rise to a pure spin-current flowing parallel to the
interface region when a charge-current is injected. This stems from the broken
mirror symmetry near the interface which gives rise to spin-orbit coupling that
deflects incoming electrons in a spin-discriminating fashion. We establish a
general analytical condition for the appearance of this effect, and calculate
the transverse spin-current explicitly using two different models. In addition,
we investigate how the process of Andreev-reflection influences this phenomenon
in the scenario where one of the materials is superconducting.",1105.3484v1
2011-06-19,Electronic charge and spin density distribution in a quantum ring with spin-orbit and Coulomb interactions,"Charge and spin density distributions are studied within a nano-ring
structure endowed with Rashba and Dresselhaus spin orbit coupling (SOI). For a
small number of interacting electrons, in the presence of an external magnetic
field, the energy spectrum of the system is calculated through an exact
numerical diagonalization procedure. The eigenstates thus determined are used
to estimate the charge and spin densities around the ring. We find that when
more than two electrons are considered, the charge-density deformations induced
by SOI are dramatically flattened by the Coulomb repulsion, while the spin
density ones are amplified.",1106.3697v1
2015-09-14,Spin-dependent Klein tunneling in polariton graphene with photonic spin-orbit interaction,"We study Klein tunneling in polariton graphene. We show that the photonic
spin-orbit coupling associated with the energy splitting between TE and TM
photonic modes can be described as an emergent gauge field. It suppresses the
Klein tunnelling in small energy range close to the Dirac points. Thanks to
polariton spin-anisotropic interactions, polarized optical pumping allows to
create potential barriers acting on a single polariton spin. We show that the
resulting spin-dependent Klein tunneling can be used to create a perfectly
transmitting polarization rotator operating at microscopic scale.",1509.04009v1
2000-03-31,Spin-flip transitions between Zeeman sublevels in semiconductor quantum dots,"We have studied spin-flip transitions between Zeeman sublevels in GaAs
electron quantum dots. Several different mechanisms which originate from
spin-orbit coupling are shown to be responsible for such processes.
  It is shown that spin-lattice relaxation for the electron localized in a
quantum dot is much less effective than for the free electron. The spin-flip
rates due to several other mechanisms not related to the spin-orbit interaction
are also estimated.",0003513v2
2001-10-22,Anisotropic spin and charge transport in Rashba Hamiltonian,"We explore spin and charge transport phenomena in two dimensional electron
gas in presence of Rashba spin-orbit coupling connected to two ideal
Ferromagnetic leads. In particular we show through a combination of analytical
and numerical calculation that the spin polarization which is transported
depends on the Magnetization direction of ferromagnet even if the magnetization
of both FM's are parallel.Conductance is also shown to be anisotropic. These
anisotrpies present in spin and charge transport are a consequence of breaking
of rotational invariance due to Rashba spin-orbit interaction and are present
irrespective of the Hamiltonian considered being an effective mass Hamiltonian
or tight binding model Hamiltonian.",0110440v1
2002-11-08,Diffuse transport and spin accumulation in a Rashba two-dimensional electron gas,"The Rashba Hamiltonian describes the splitting of the conduction band as a
result of spin-orbit coupling in the presence of an asymmetric confinement
potential and is commonly used to model the electronic structure of confined
narrow-gap semiconductors. Due to the mixing of spin states some care has to be
exercised in the calculation of transport properties. We derive the diffusive
conductance tensor for a disordered two-dimensional electron gas with
spin-orbit interaction and show that the applied bias induces a spin
accumulation, but that the electric current is not spin-polarized.",0211153v1
2004-10-01,Spin interferometry with electrons in nanostructures: A road to spintronic devices,"The wave nature of electrons in semiconductor nanostructures results in
spatial interference effects similar to those exhibited by coherent light. The
presence of spin-orbit coupling renders interference in spin space and in real
space interdependent, making it possible to manipulate the electron's spin
state by addressing its orbital degree of freedom. This suggests the utility of
electronic analogs of optical interferometers as blueprints for new spintronics
devices. We demonstrate the usefulness of this concept using the Mach-Zehnder
interferometer as an example. Its spin-dependent analog realizes a
spin-controlled field-effect transistor without magnetic contacts and may be
used as a quantum logical gate.",0410008v1
2006-11-03,Spin transport in mesoscopic rings with inhomogeneous spin-orbit coupling,"We revisit the problem of electron transport through mesoscopic rings with
spin-orbit (SO) interaction. In the well-known path-integral approach, the
scattering states for a quasi-1D ring with quasi-1D leads can be expressed in
terms of spinless electrons subject to a fictitious magnetic flux. We show that
spin-dependent quantum-interference effects in small rings are strongest for
spatially inhomogeneous SO interactions, in which case spin currents can be
controlled by a small external magnetic field. Mesoscopic spin Hall effects in
four-terminal rings can also be understood in terms of the fictitious magnetic
flux.",0611086v2
2007-01-23,Spin densities in parabolic quantum wires with Rashba spin-orbit interaction,"Using canonical transformations we diagonalize approximately the Hamiltonian
of a gaussian wire with Rashba spin-orbit interaction. This proceedure allows
us to obtain the energy dispersion relations and the wavefunctions with good
accuracy, even in systems with relatively strong Rashba coupling. With these
eigenstates one can calculate the non-equilibrium spin densities induced by
applying bias voltages across the sample. We focus on the $z$-component of the
spin density, which is related to the spin Hall effect.",0701564v1
2008-05-08,Spin Hall effect in a two-dimensional electron gas in the presence of a magnetic field,"We study the spin Hall effect of a two-dimensional electron gas in the
presence of a magnetic field and both the Rashba and Dresselhaus spin-orbit
interactions. We show that the value of the spin Hall conductivity, which is
finite only if the Zeeman spin splitting is taken into account, may be tuned by
varying the ratio of the in-plane and out-of-plane components of the applied
magnetic field. We identify the origin of this behavior with the different role
played by the interplay of spin-orbit and Zeeman couplings for in-plane and
out-of-plane magnetic field components.",0805.1155v1
2009-12-17,Scalable Quantum Computing based on Spin Qubits in CNT QD,"We study experimentally demonstrated single-electron ${}^{12}$C CNT QD with
significant spin-orbit interaction as a scalable quantum computer candidate.
Both electron spin and orbital angular momentum can serve as a logical qubit
for quantum processing. We introduce macroscopic quantum memory for the system
in a form of injected either magnetic or spin carrying atomic ensemble into the
nanotube. CNT provides with a stable atomic trap in finite temperature and with
one-dimensional nuclear spin lattice in an external magnetic field. The
electron is coupled to the atomic ensemble through either magnetic or hyperfine
interaction. Easy electron and nuclear spin read-out procedure for this system
is possible.",0912.3547v1
2014-05-24,Spin measurements and control of cold atoms using spin-orbit fields,"We show that by switching on a spin-orbit interaction in a cold-atom system,
experiencing a Zeeman-like coupling to an external field, e.g., in a
Bose-Einstein condensate, one can simulate a quantum measurement on a
precessing spin. Depending on the realization, the measurement can access both
the ergodic and the Zeno regimes, while {the time dependence} of the spin's
decoherence may vary from a Gaussian to an inverse fractional power law. Back
action of the measurement forms time- and coordinate-dependent profiles of the
atoms' density, resulting in its translation, spin-dependent fragmentation, and
appearance of interference patterns.",1405.6302v1
2016-05-28,Spin splitting of electron states in lattice-mismatched (110)-oriented quantum wells,"We show that for lattice-mismatched zinc-blende-type (110)-grown quantum
wells a significant contribution to the zero-magnetic-field spin splitting of
electron subbands comes from strain-induced spin-orbit coupling. Combining
envelope function theory and atomistic tight-binding approach we calculate
spin-orbit splitting constants for realistic quantum wells. It is found that
the strain due to lattice mismatch in conventional GaAs/AlGaAs structures may
noticeably modify the spin splitting while in InGaAs/GaAs structures it plays a
major role and may even change the sign of the spin splitting constant.",1605.08942v1
2010-08-24,Modeling of diffusion of injected electron spins in spin-orbit coupled microchannels,"We report on a theoretical study of spin dynamics of an ensemble of
spin-polarized electrons injected in a diffusive microchannel with linear
Rashba and Dresselhaus spin-orbit coupling. We explore the dependence of the
spin-precession and spin-diffusion lengths on the strengths of spin-orbit
interaction and external magnetic fields, microchannel width, and orientation.
Our results are based on numerical Monte Carlo simulations and on approximate
analytical formulas, both treating the spin dynamics quantum-mechanically. We
conclude that spin-diffusion lengths comparable or larger than the
precession-length occur i) in the vicinity of the persistent spin helix regime
for arbitrary channel width, and ii) in channels of similar or smaller width
than the precession length, independent of the ratio of Rashba and Dresselhaus
fields. For similar strengths of the Rashba and Dresselhaus fields, the
steady-state spin-density oscillates or remains constant along the channel for
channels parallel to the in-plane diagonal crystal directions. An oscillatory
spin-polarization pattern tilted by 45$^{\circ}$ with respect to the channel
axis is predicted for channels along the main cubic crystal directions. For
typical experimental system parameters, magnetic fields of the order of Tesla
are required to affect the spin-diffusion and spin-precession lengths.",1008.4030v2
2017-08-01,"Coupling between Charge, Lattice, Orbital, and Spin in a Charge Density Wave of 1$T$-TaS$_2$","Two-dimensional layered transition metal dichalcogenide (TMDC) materials
often exhibit exotic quantum matter phases due to the delicate coupling and
competitions between the charge, lattice, orbital, and spin degrees of freedom.
Surprisingly, we here present, based on first-principles density-functional
theory calculations, the incorporation of all such degrees of freedom in a
charge density wave (CDW) of monolayer (ML) TMDC 1$T$-TaS$_2$. We reveal that
the CDW formed via the electron-phonon coupling is significantly stabilized by
the orbital hybridization. The resulting lattice distortion to the ""David-star""
superstructure constituted of one cental, six nearest-neighbor, and six
next-nearest-neighbor Ta atoms is accompanied by the formation of
quasimolecular orbitals due to a strong hybridization of the Ta $t_{\rm 2g}$
orbitals. Furthermore, the flat band of the quasimolecular orbital at the Fermi
level has a spin splitting caused by an intramolecular exchange, yielding a
full spin polarization with a band-gap opening. Our finding of the intricate
charge-lattice-orbital-spin coupling in ML 1$T$-TaS$_2$ provides a framework
for the exploration of various CDW phases observed in few-layer or bulk
1$T$-TaS$_2$.",1708.00213v1
2018-02-08,Spin-Orbital Excitations in Ca$_{2}$RuO$_4$ Revealed by Resonant Inelastic X-ray Scattering,"The strongly correlated insulator Ca$_{2}$RuO$_4$ is considered as a
paradigmatic realization of both spin-orbital physics and a band-Mott
insulating phase, characterized by orbitally selective coexistence of a band
and a Mott gap. We present a high-resolution oxygen $K$-edge resonant inelastic
X-ray scattering study of the antiferromagnetic Mott insulating state of
Ca$_{2}$RuO$_4$. A set of low-energy ($\sim$80 and 400 meV) and high-energy
($\sim$1.3 and 2.2 eV) excitations are reported that show strong incident light
polarization dependence. Our results strongly support a spin-orbit coupled
band-Mott scenario and explore in detail the nature of its exotic excitations.
Guided by theoretical modelling, we interpret the low-energy excitations as a
result of composite spin-orbital excitations. Their nature unveil the intricate
interplay of crystal-field splitting and spin-orbit coupling in the band-Mott
scenario. The high-energy excitations correspond to intra-atomic
singlet-triplet transitions at an energy scale set by the Hund's coupling. Our
findings give a unifying picture of the spin and orbital excitations in the
band-Mott insulator Ca$_{2}$RuO$_4$.",1802.02909v1
2019-01-03,Strain Healing of Spin-Orbit Coupling: A Cause for Enhanced Magnetic Moment in Epitaxial SrRuO3 Thin Films,"Enhanced magnetic moment and coercivity in SrRuO3 thin films are significant
issues for advanced technological usages and hence are researched extensively
in recent times. Most of the previous reports on thin films with enhanced
magnetic moment attributed the high spin state for the enhancement. Our
magnetization results show high magnetic moment of 3.3 Bohr-magnetron/Ru ion in
the epitaxial thin films grown on LSAT substrate against 1.2 Bohr-magnetron/Ru
ion observed in bulk compound. Contrary to the expectation the Ru ions are
found to be in low spin state and the orbital moment is shown to be
contributing significantly in the enhancement of magnetic moment. We employed
x-ray absorption spectroscopy and resonant valance band spectroscopy to probe
the spin state and orbital contributions in these films. The existence of
strong spin-orbit coupling responsible for the de-quenching of the 4d orbitals
is confirmed by the observation of the non-statistical large branching ratio at
the Ru M2,3 absorption edges. The relaxation of orbital quenching by strain
engineering provides a new tool for enhancing magnetic moment. Strain disorder
is shown to be an efficient mean to control the spin-orbit coupling.",1901.00613v1
2021-08-09,Spin-orbit effects in pentavalent Iridates: Models and materials,"Spin-orbit effects in heavy 5$d$ transition metal oxides, in particular,
iridates, have received enormous current interest due to the prediction as well
as the realization of a plethora of exotic and unconventional magnetic
properties. While a bulk of these works are based on tetravalent iridates
($d^5$), where the counter-intuitive insulating state of the rather extended
5$d$ orbitals are explained by invoking strong spin-orbit coupling, the recent
quest in iridate research has shifted to the other valencies of Ir, of which
pentavalent iridates constitute a notable representative. In contrast to the
tetravalent iridates, spin-orbit entangled electrons in $d^4$ systems are
expected to be confined to the $J = 0$ singlet state without any resultant
moment or magnetic response. However, it has been recently predicted that,
magnetism in $d^4$ systems may occur via magnetic condensation of excitations
across spin-orbit-coupled states. In reality, the magnetism in Ir$^{5+}$
systems are often quite debatable both from theoretical as well as experimental
point of view. Here we provide a comprehensive overview of the spin-orbit
coupled $d^4$ model systems and its implications in the studied pentavalent
iridates. In particular, we review here the current experimental and
theoretical understanding of the double perovskite ($A_2B$YIrO$_6$, $A =$ Sr,
Ba, $B =$Y, Sc, Gd), 6H-perovskite (Ba$_3M$Ir$_2$O$_9$, $M =$ Zn, Mg, Sr, Ca),
post-perovskite (NaIrO$_3$), and Hexagonal (Sr$_3$MIrO$_6$) iridates, along
with a number of open questions that require future investigation.",2108.04158v1
2018-12-16,High-resolution photoemission on Sr2RuO4 reveals correlation-enhanced effective spin-orbit coupling and dominantly local self-energies,"We explore the interplay of electron-electron correlations and spin-orbit
coupling in the model Fermi liquid Sr2RuO4 using laser-based angle-resolved
photoemission spectroscopy. Our precise measurement of the Fermi surface
confirms the importance of spin-orbit coupling in this material and reveals
that its effective value is enhanced by a factor of about two, due to
electronic correlations. The self-energies for the $\beta$ and $\gamma$ sheets
are found to display significant angular dependence. By taking into account the
multi-orbital composition of quasiparticle states, we determine self-energies
associated with each orbital component directly from the experimental data.
This analysis demonstrates that the perceived angular dependence does not imply
momentum-dependent many-body effects, but arises from a substantial orbital
mixing induced by spin-orbit coupling. A comparison to single-site dynamical
mean-field theory further supports the notion of dominantly local orbital
self-energies, and provides strong evidence for an electronic origin of the
observed non-linear frequency dependence of the self-energies, leading to
`kinks' in the quasiparticle dispersion of Sr2RuO4.",1812.06531v2
2011-03-17,A spin-orbit coupled Bose-Einstein condensate,"Spin-orbit (SO) coupling -- the interaction between a quantum particle's spin
and its momentum -- is ubiquitous in nature, from atoms to solids. In condensed
matter systems, SO coupling is crucial for the spin-Hall effect and topological
insulators, which are of extensive interest; it contributes to the electronic
properties of materials such as GaAs, and is important for spintronic devices.
Ultracold atoms, quantum many-body systems under precise experimental control,
would seem to be an ideal platform to study these fascinating SO coupled
systems. While an atom's intrinsic SO coupling affects its electronic
structure, it does not lead to coupling between the spin and the center-of-mass
motion of the atom. Here, we engineer SO coupling (with equal Rashba and
Dresselhaus strengths) in a neutral atomic Bose-Einstein condensate by dressing
two atomic spin states with a pair of lasers. Not only is this the first SO
coupling realized in ultracold atomic gases, it is also the first ever for
bosons. Furthermore, in the presence of the laser coupling, the interactions
between the two dressed atomic spin states are modified, driving a quantum
phase transition from a spatially spin-mixed state (lasers off) to a phase
separated state (above a critical laser intensity). The location of this
transition is in quantitative agreement with our theory. This SO coupling --
equally applicable for bosons and fermions -- sets the stage to realize
topological insulators in fermionic neutral atom systems.",1103.3522v1
2019-06-15,Theory of giant skew scattering by spin cluster,"Skew scattering of electrons induced by a spin cluster is studied
theoretically focusing on metals with localized magnetic moments. The
scattering probability is calculated by a non-perturbative $T$ matrix method;
this method is valid for arbitrary strength of electron-spin coupling. We show
the scattering of electrons by a three-spin cluster produces a skew angle of
order $0.1\pi$ rad when the electron-spin coupling is comparable to the
bandwidth. This is one or two orders of magnitude larger than the usual skew
angle by an impurity with spin-orbit interaction. Systematic analysis of the
scattering probability of one-, two-, and three-spin clusters show that three
spins are necessary for skew scattering. We also discuss the relation between
anomalous/spin Hall effects and the spin chiralities; we find that the spin
Hall effect requires three spins while it is related to the vector spin
chirality defined by a pair of spins. The relevance of these results to the
large extrinsic anomalous and spin Hall effects in noncentrosymmetric and/or
frustrated magnets is also discussed.",1906.06501v1
2014-10-23,Spin-orbiton and quantum criticality in FeSc2S4,"In FeSc2S4 spin-orbital exchange competes with strong spin-orbit coupling,
suppressing long-range spin and orbital order and, hence, this material
represents one of the rare examples of a spin-orbital liquid ground state.
Moreover, it is close to a quantum-critical point separating the ordered and
disordered regimes. Using THz and FIR spectroscopy we study low-lying
excitations in FeSc2S4 and provide clear evidence for a spin-orbiton, an
excitation of strongly entangled spins and orbitals. It becomes particularly
well pronounced upon cooling, when advancing deep into the quantum-critical
regime. Moreover, indications of an underlying structureless excitation
continuum are found, a possible signature of quantum criticality.",1410.6459v2
2023-09-13,Orbital magnetization senses topological phase transition in spin-orbit coupled $α$-$T_3$ system,"The $\alpha$-$T_3$ system undergoes a topological phase transition(TPT)
between two distinct quantum spin-Hall phases across $\alpha=0.5$ when the
spin-orbit interaction of Kane-Mele type is taken into consideration. As a
hallmark of such a TPT, we find that the Berry curvature and the orbital
magnetic moment change their respective signs across the TPT. The trails of the
TPT found in another physical observable e.g. the orbital magnetization(OM) are
understood in terms of valley and spin physics. The valley-resolved OM(VROM)
and the spin-resolved OM(SROM) exhibit interesting characteristics related to
the valley and the spin Chern number when the chemical potential is tuned in
the forbidden gap(s) of the energy spectrum. In particular, we find that the
slope of the VROM vs the chemical potential in the forbidden gap changes its
sign abruptly across the TPT which is also consistent with the corresponding
change in the valley Chern number. Moreover, the slope of the SROM demonstrates
a sudden jump by one unit of $e/h$, (where $e$ is the electronic charge and $h$
is the Planck's constant), across the TPT which is also in agreement with the
corresponding change in the spin Chern number.",2309.07074v1
2015-07-06,Zitterbewegung of a heavy hole in presence of spin-orbit interactions,"We study the $zitterbewegung$ of a heavy hole in presence of both cubic
Rashba and cubic Dresselhaus spin-orbit interactions. On contrary to the
electronic case, $zitterbewegung$ does not vanish for equal strength of Rashba
and Dresselhaus spin-orbit interaction. This non-vanishing of $zitterbewegung$
is associated with the Berry phase. Due to the presence of the spin-orbit
coupling the spin associated with the heavy hole precesses about an effective
magnetic field. This spin precession produces a transverse spin-orbit force
which also generates an electric voltage associated with $zitterbewegung$. We
have estimated the magnitude of this voltage for a possible experimental
detection of $zitterbewegung$.",1507.01393v2
2019-03-04,Spin-Phonon Relaxation in Molecular Qubits from First Principles Spin Dynamics,"The coupling between electronic spins and lattice vibrations is fundamental
for driving relaxation in magnetic materials. The debate over the nature of
spin-phonon coupling dates back to the 40's, but the role of spin-spin,
spin-orbit and hyperfine interactions, has never been fully established. Here
we present a comprehensive study of the spin dynamics of a crystal of
Vanadyl-based molecular qubits by means of first-order perturbation theory and
first-principles calculations. We quantitatively determine the role of the
Zeeman, hyperfine and electronic spin dipolar interactions in the direct
mechanism of spin relaxation. We show that, in a high magnetic field regime,
the modulation of the Zeeman Hamiltonian by the intra-molecular components of
the acoustic phonons dominates the relaxation mechanism. In low fields,
hyperfine coupling takes over, with the role of spin-spin dipolar interaction
remaining the less important for the spin relaxation.",1903.01424v1
2008-12-30,Boltzmann approach to the spin Hall effect revisited and electric field modified collision integrals,"The intrinsic contribution to the spin Hall effect in a 2DEG with
non-magnetic impurities is studied in a quantum Boltzmann approach. It is shown
that if the steady state response is perturbative in the spin-orbit coupling
parameter $\lambda$, then the precession term--vital for Dyakonov-Perel
relaxation and the key to the spin Hall effect in previous similar Boltzmann
studies--must be left out to first order in spin-orbit coupling. In such a case
one would have that to lowest order in the parameters electric field,
spin-orbit coupling, impurity strength and impurity concentration there is no
intrinsic contribution to the spin Hall effect, not only for a Rashba coupling
but for a general spin-orbit coupling. To cover all possible lowest order terms
we consider also electric field induced corrections to the collision integral
in the Keldysh formalism. However, these corrections turn out to be of second
order in $\lambda$. For comparison we derive some familiar results in the case
when the response is not assumed to be perturbative in $\lambda$. We also
include a detailed discussion of why a relaxation time approximation of the
collision integral fails. Finally we make a comment on pseudospin currents in
bilayer graphene.",0812.4800v2
2018-04-05,Tight-binding model and ab initio calculation of silicene with strong spin-orbit coupling in low-energy limit,"We carry out both the tight-binding model and the $ab\ initio$ to study the
layered silicene, the spin, valley, sublattice degrees of freedom are taken
into consider and the effects of electric field, magnetic field, and even the
light in finite frequency together with its interesting optical propertice,
which are all closely related to the spin-orbit coupling and Rashba coupling
and lead to the tunable phase transitions (between the nontrivial topological
phase which has nonzero Chern number or nonzero spin Chern number and the
trivial phase). An exotic quantum anomalous Hall insulator phase are found
which has nonzero spin Chern number and nonzero valley Chern number and as a
giant-application-potential spintronic and valleytronics in the two-ternimate
devices based on the monolayer silicene for the information transmission. In
fact, the gap-out action can be understanded by analyse the Dirac mass as well
as the Zeeman splitting or the external-field-induced symmetry-broken, and the
changes of gap has a general nonmonotone-variation characteristic under both
the effects of electron filed-induced Rashba-coupling $R_{2}(E_{\perp})$ and
the electron field-induced band gap, and the band inversion related to the
spin-orbit coupling which absorbs both the spin and orbital angular of momentum
may happen during this process. The quantized Hall/longitudinal conductivity
together with the optical conductivity are also explored, we see that even in
the quantum spin Hall phase without any magnetic field, the two-terminate
conductivity can be reduced to the value $e^{2}/h$ by controlling the helical
edge model, and it can be further reduced to $e^{2}/2h$ by applying the
magnetic field which similar to the graphene.",1804.01695v1
2021-11-12,Spin-orbit coupling matrix elements from the explicitly connected expressions of the response functions within the coupled-cluster theory,"In this work we present a coupled cluster based approach to the computation
of the spin orbit coupling matrix elements. The working expressions are derived
from the quadratic response function with the coupled cluster parametrization,
using the auxiliary excitation operator S. Systematic approximations are
proposed with the CCSD and CC3 levels of theory. The new method is tested by
computing lifetimes of several electronic states of Ca, Sr and Ba atoms, with
Gaussian and Slater basis sets. The results are compared with available
theoretical and experimental data.",2111.06802v1
2022-11-11,Simulating Spin-Orbit Coupling With Quasidegenerate N-Electron Valence Perturbation Theory,"We present the first implementation of spin-orbit coupling effects in fully
internally contracted second-order quasidegenerate N-electron valence
perturbation theory (SO-QDNEVPT2). The SO-QDNEVPT2 approach enables the
computations of ground- and excited-state energies and oscillator strengths
combining the description of static electron correlation with an efficient
treatment of dynamic correlation and spin-orbit coupling. In addition to
SO-QDNEVPT2 with the full description of one- and two-body spin-orbit
interactions at the level of two-component Breit-Pauli Hamiltonian, our
implementation also features a simplified approach that takes advantage of
spin-orbit mean-field approximation (SOMF-QDNEVPT2). The accuracy of these
methods is tested for the group 14 and 16 hydrides, 3d and 4d transition metal
ions, and two actinide dioxides (neptunyl and plutonyl dications). The
zero-field splittings of group 14 and 16 molecules computed using SO-QDNEVPT2
and SOMF-QDNEVPT2 are in a good agreement with the available experimental data.
For the 3d transition metal ions, the SO-QDNEVPT2 method is significantly more
accurate than SOMF-QDNEVPT2, while no substantial difference in the performance
of two methods is observed for the 4d ions. Finally, we demonstrate that for
the actinide dioxides the results of SO-QDNEVPT2 and SOMF-QDNEVPT2 are in a
good agreement with the data from previous theoretical studies of these
systems. Overall, our results demonstrate that SO-QDNEVPT2 and SOMF-QDNEVPT2
are promising multireference methods for treating spin-orbit coupling with a
relatively low computational cost.",2211.06466v3
2009-11-03,Two-step stabilization of orbital order and the dynamical frustration of spin in the model charge-transfer insulator KCuF3,"We report a combined experimental and theoretical study of KCuF3, which
offers - because of this material's relatively simple lattice structure and
valence configuration (d9, i.e., one hole in the d-shell) - a particularly
clear view of the essential role of the orbital degree of freedom in governing
the dynamical coupling between the spin and lattice degrees of freedom. We
present Raman and x-ray scattering evidence that the phase behaviour of KCuF3
is dominated above the Neel temperature (T_N = 40 K) by coupled orbital/lattice
fluctuations that are likely associated with rotations of the CuF6 octahedra,
and we show that these orbital fluctuations are interrupted by a static
structural distortion that occurs just above T_N. A detailed model of the
orbital and magnetic phases of KCuF3 reveals that these orbital fluctuations -
and the related frustration of in-plane spin-order-are associated with the
presence of nearly degenerate low-energy spin-orbital states that are highly
susceptible to thermal fluctuations over a wide range of temperatures. A
striking implication of these results is that the ground state of KCuF3 at
ambient pressure lies near a quantum critical point associated with an
orbital/spin liquid phase that is obscured by emergent Neel ordering of the
spins; this exotic liquid phase might be accessible via pressure studies.",0911.0619v1
2019-09-30,Coherent spin mixing via spin-orbit coupling in Bose gases,"We study beyond-mean-field properties of interacting spin-1 Bose gases with
synthetic Rashba-Dresselhaus spin-orbit coupling at low energies. We derive a
many-body Hamiltonian following a tight-binding approximation in quasi-momentum
space, where the effective spin dependence of the collisions that emerges from
spin-orbit coupling leads to dominant correlated tunneling processes that
couple the different bound states. We discuss the properties of the spectrum of
the derived Hamiltonian and its experimental signatures. In a certain region of
the parameter space, the system becomes integrable, and its dynamics becomes
analogous to that of a spin-1 condensate with spin-dependent collisions.
Remarkably, we find that such dynamics can be observed in existing experimental
setups through quench experiments that are robust against magnetic
fluctuations.",1909.13840v1
2017-11-23,Chaos in two-dimensional Kepler problem with spin-orbit coupling,"We consider classical two-dimensional Kepler system with spin-orbit coupling
and show that at a sufficiently strong coupling it demonstrates a chaotic
behavior. The chaos emerges since the spin-orbit coupling reduces the number of
the integrals of motion as compared to the number of the degrees of freedom.
This reduction is manifested in the equations of motion as the emergence of the
anomalous velocity determined by the spin orientation. By using analytical and
numerical arguments, we demonstrate that the chaotic behavior, being driven by
this anomalous term, is related to the system energy dependence on the initial
spin orientation. We observe the critical dependence of the dynamics on the
initial conditions, where system can enter and exit a stability domain by very
small changes in the initial spin orientation. Thus, this system can
demonstrate a reentrant order-from-disorder transition driven by very small
variations in the initial conditions.",1711.08773v1
2019-02-02,Bloch oscillations of spin-orbit-coupled cold atoms in an optical lattice and spin current generation,"We study the Bloch oscillation dynamics of a spin-orbit-coupled cold atomic
gas trapped inside a one-dimensioanl optical lattice. The eigenspectra of the
system is identified as two interpenetrating Wannier-Stark ladder. Based on
that, we carefully analyzed the Bloch oscillation dynamics and found out that
intraladder coupling between neighboring rungs of Wannier-Stark ladder give
rise to ordinary Bloch oscillation while interladder coupling lead to small
amplitude high frequency oscillation superimposed on it. Specifically
spin-orbit interaction breaks Galilean invariance, which can be reflected by
out-of-phase oscillation of the two spin components in the accelerated frame.
The possibility of generating spin current in this system are also explored.",1902.00634v1
2017-07-07,Protected pseudohelical edge states in proximity graphene ribbons and flakes,"We investigate topological properties of models that describe graphene on
realistic substrates which induce proximity spin-orbit coupling in graphene. A
$\mathbb{Z}_2$ phase diagram is calculated for the parameter space of
(generally different) intrinsic spin-orbit coupling on the two graphene
sublattices, in the presence of Rashba coupling. The most fascinating case is
that of staggered intrinsic spin-orbit coupling which, despite being
topologically trivial, $\mathbb{Z}_2 = 0$, does exhibit edge states protected
against time-reversal scattering for zigzag ribbons as wide as micrometers. We
call these states pseudohelical as their helicity is locked to the sublattice.
The spin character and robustness of the pseudohelical modes is best exhibited
on a finite flake, which shows that the edge states have zero $g$-factor, carry
a finite spin current in the crossection of the flake, and exhibit spin-flip
reflectionless tunneling at the armchair edges.",1707.02124v1
2012-05-10,"Bose Hubbard Models with Synthetic Spin-Orbit Coupling: Mott Insulators, Spin Textures and Superfluidity","Motivated by the experimental realization of synthetic spin-orbit coupling
for ultracold atoms, we investigate the phase diagram of the Bose Hubbard model
in a non-abelian gauge field in two dimensions. Using a strong coupling
expansion in the combined presence of spin-orbit coupling and tunable
interactions, we find a variety of interesting magnetic Hamiltonians in the
Mott insulator (MI), which support magnetic textures such as spin spirals and
vortex and Skyrmion crystals. An inhomogeneous mean field treatment shows that
the superfluid (SF) phases inherit these exotic magnetic orders from the MI and
display, in addition, unusual modulated current patterns. We present a slave
boson theory which gives insight into such intertwined spin-charge orders in
the SF, and discuss signatures of these orders in Bragg scattering, in situ
microscopy, and dynamic quench experiments.",1205.2319v1
2021-03-16,Effect of spin-orbit coupling on the high harmonics from the topological Dirac semimetal Na3Bi,"In this work, we performed extensive first-principles simulations of
high-harmonic generation in the topological Diract semimetal Na3Bi using a
time-dependent density functional theory framework, focusing on the effect of
spin-orbit coupling (SOC) on the harmonic response. We also derived a general
analytical model describing the microscopic mechanism of strong-field dynamics
in presence of spin-orbit coupling, starting from a locally U(1)xSU(2)
gauge-invariant Hamiltonian. Our results reveal that SOC: (i) affects the
strong-field ionization by modifying the bandstructure of Na3Bi, (ii) modifies
the electron velocity, making each spin channel to react differently to the
pump laser field, (iii) changes the emission timing of the emitted harmonics.
Moreover, we show that the SOC affects the harmonic emission by directly
coupling the charge current to the spin currents, paving the way to the
high-harmonic spectroscopy of spin currents in solids.",2103.09322v1
2021-06-13,Fragile topology in nodal-line semimetal superconductors,"We study the band topology of the superconducting nodal-line semimetal
(SC-NLSM) protected by the inversion symmetry with and without the spin-orbital
coupling. Without the spin-orbital coupling, both the $s$-wave SC-NLSM and the
chiral $p$-wave SC-NLSM are topologically nontrivial and can be described by
the nonzero winding number. Based on the Wilson loop method, we verify that
they are both the fragile topological superconductors, namely, their nontrivial
band topologies can be moved off by coupling to additional topologically
trivial bands. The fragile topological phase persists in spinful system with
the time-reversal symmetry when a spin-orbital coupling term is added. For the
spinful system, both the $p$-wave SC-NLSM and the $s$-wave SC-NLSM are
second-order fragile topological superconductors. We propose that the fragile
topology in the SC-NLSM system depends strongly on the degeneracy of the
Majorana zero modes and the parity of the superconducting gap function.
Interestingly, in presence of a vortex line, the spinful $s$-wave SC-NLSM
system hosts two pairs of stable Majorana zero modes in the vortex core.",2106.06928v2
2013-07-12,Quasiparticle Berry curvature and Chern numbers in spin-orbit coupled bosonic Mott insulators,"We study the ground-state topology and quasiparticle properties in bosonic
Mott insulators with two- dimensional spin-orbit couplings in cold atomic
optical lattices. We show that the many-body Chern and spin-Chern number can be
expressed as an integral of the quasihole Berry curvatures over the Brillouin
zone. Using a strong-coupling perturbation theory, for an experimentally
feasible spin-orbit coupling, we compute the Berry curvature and the spin Chern
number and find that these quantities can be generated purely by interactions.
We also compute the quasiparticle dispersions, spectral weights, and the
quasimomentum space distribution of particle and spin density, which can be
accessed in cold-atom experiments and used to deduce the Berry curvature and
Chern numbers.",1307.3594v2
2016-05-04,Orbit-spin coupling and the interannual variability of global-scale dust storm occurrence on Mars,"A new physical hypothesis predicts that a weak coupling of the orbital and
rotational motions of extended bodies may give rise to a modulation of
circulatory flows within their atmospheres. Driven cycles of intensification
and relaxation of large-scale circulatory flows are predicted, with the phasing
of these changes linked directly to the rate of change of the orbital angular
momentum with respect to inertial frames. We test the hypothesis that
global-scale dust storms (GDS) on Mars may occur when periods of circulatory
intensification (associated with positive and negative extrema of the waveform)
coincide with the southern summer dust storm season on Mars. The orbit-spin
coupling hypothesis additionally predicts that the intervening transitional
periods, which are characterized by the disappearance and subsequent sign
change of this waveform, may be unfavorable for the occurrence of GDS, when
they occur during the southern summer dust storm season. These hypotheses are
confirmed through comparisons between calculated dynamical time series of the
time rate of change of orbital angular momentum and historic observations. All
of the nine known global-scale dust storms on Mars took place during Mars years
when circulatory intensification during the dust storm season is predicted
under the orbit-spin coupling hypothesis. No historic global-scale dust storms
were recorded during transitional intervals. Orbit-spin coupling accelerations
evidently contribute to the interannual variability of the Mars atmosphere.",1605.01452v1
2005-07-22,The 5f localization/delocalization in square and hexagonal americium monolayers: A FP-LAPW electronic structure study,"The electronic and geometrical properties of bulk americium and square and
hexagonal americium monolayers have been studied with the full-potential
linearized augmented plane wave (FP-LAPW) method. The effects of several common
approximations are examined: (1) non-spin polarization (NSP) vs. spin
polarization (SP); (2) scalar-relativity (no spin-orbit coupling (NSO)) vs.
full-relativity (i.e., with spin-orbit (SO) coupling included); (3)
local-density approximation (LDA) vs. generalized-gradient approximation (GGA).
Our results indicate that both spin polarization and spin orbit coupling play
important roles in determining the geometrical and electronic properties of
americium bulk and monolayers. A compression of both americium square and
hexagonal monolayers compared to the americium bulk is also observed. In
general, the LDA is found to underestimate the equilibrium lattice constant and
give a larger total energy compared to the GGA calculations. While spin orbit
coupling shows a similar effect on both square and hexagonal monolayer
calculations regardless of the model, GGA versus LDA, an unusual spin
polarization effect on both square and hexagonal monolayers is found in the LDA
results as compared with the GGA results. The 5f delocalization transition of
americium is employed to explain our observed unusual spin polarization effect.
In addition, our results at the LDA level of theory indicate a possible 5f
delocalization could happen in the americium surface within the same Am II (fcc
crystal structure) phase, unlike the usually reported americium 5f
delocalization which is associated with crystal structure change. The
similarities and dissimilarities between the properties of an Am monolayer and
a Pu monolayer are discussed in detail.",0507536v1
2006-04-12,Description of spin transport and precession in spin-orbit coupling systems and a general equation of continuity,"By generalizing the usual current density to a matrix with respect to spin
variables, a general equation of continuity satisfied by the density matrix and
current density matrix has been derived. This equation holds in arbitrary
spin-orbit coupling systems as long as its Hamiltonian can be expressed in
terms of a power series in momentum. Thereby, the expressions of the current
density matrix and a torque density matrix are obtained. The current density
matrix completely describes both the usual current and spin current as well;
while the torque density matrix describes the spin precession caused by a total
effective magnetic field, which may include a realistic and an effective one
due to the spin-orbit coupling. In contrast to the conventional definition of
spin current, this expression contains an additional term if the Hamiltonian
includes nonlinear spin-orbit couplings. Moreover, if the degree of the full
Hamiltonian $\geq3$, then the particle current must also be modified in order
to satisfy the local conservation law of number.",0604320v8
2018-05-21,Odd-frequency superconducting pairing in junctions with Rashba spin-orbit coupling,"We consider normal-superconductor (NS) and
superconductor-normal-superconductor (SNS) junctions based on one-dimensional
nanowires with Rashba spin-orbit coupling and proximity-induced $s$-wave
spin-singlet superconductivity and analytically demonstrate how both even- and
odd-frequency and spin-singlet and -triplet superconducting pair correlations
are always present. In particular, by using a fully quantum mechanical
scattering approach, we show that Andreev reflection induces mixing of spatial
parities at interfaces, thus being the unique process which generates
odd-frequency pairing; on the other hand, both Andreev and normal reflections
contribute to even-frequency pairing. We further find that locally neither
odd-frequency nor spin-triplet correlations are induced, but only
even-frequency spin-singlet pairing. In the superconducting regions of NS
junctions, the interface-induced amplitudes decay into the bulk, with the
odd-frequency components being generally much larger than the even-frequency
components at low frequencies. The odd-frequency pairing also develops short
and long-period oscillations due to the chemical potential and spin-orbit
coupling, respectively, leading to a visible beating feature in their
magnitudes. Moreover, we find that in short SNS junctions at $\pi$-phase
difference and strong spin-orbit coupling, the odd-frequency spin-singlet and
-triplet correlations strongly dominate with an alternating spatial pattern for
a large range of sub-gap frequencies.",1805.07948v2
2020-05-10,Controlling stable tunneling in a non-Hermitian spin-orbit coupled bosonic junction,"In this paper, we study how to apply a periodic driving field to control
stable spin tunneling in a non-Hermitian spin-orbit coupled bosonic double-well
system. By means of a high-frequency approximation, we obtain the analytical
Floquet solutions and their associated quasienergies and thus construct the
general non-Floquet solutions of the dissipative spin-orbit coupled bosonic
system. Based on detailed analysis of the Floquet quasienergy spectrum, the
profound effect of system parameters and the periodic driving field on the
stability of spin-dependent tunneling is investigated analytically and
numerically for both balanced and unbalanced gain-loss between two wells. Under
balanced gain and loss, we find that the stable spin-flipping tunneling is
preferentially suppressed with the increase of gain-loss strength. When the
ratio of Zeeman field strength to periodic driving frequency $\Omega/\omega$ is
even, there is a possibility that \emph{continuous} stable parameter regions
will exist. When $\Omega/\omega$ is odd, nevertheless, only \emph{discrete}
stable parameter regions are found. Under unbalanced gain and loss, whether
$\Omega/\omega$ is even or odd, we can get parametric equilibrium conditions
for the existence of stable spin tunneling. The results could be useful for the
experiments of controlling stable spin transportation in a non-Hermitian
spin-orbit coupled system.",2005.04627v2
2024-03-05,Unraveling spin texture and spin-orbit coupling contributions in spin triplet superconductivity,"Over the past decade, it has been proposed theoretically and confirmed
experimentally that long-range spin triplet (LRT) superconductivity can be
generated in ferromagnet-superconductor hybrids either by the presence of spin
textures (ST-LRT) or thanks to spin-orbit coupling (SOC-LRT). Nevertheless,
there has been no theoretical or experimental investigation to date suggesting
that both contributions could simultaneously exist within an experimental
system. To disentangle these contributions, we present a comprehensive study of
superconducting quasiparticle interference effects taking place inside a
ferromagnetic layer interfacing a superconductor, through the investigation of
above-gap conductance anomalies (CAs) related to MacMillan-Rowell resonances.
The bias dependence of the CAs has been studied under a wide range of in-plane
(IP) and out-of-plane (OOP) magnetic fields in two types of epitaxial,
V/MgO/Fe-based ferromagnet-superconductor junctions with interfacial spin-orbit
coupling. We observe an anisotropy of the CAs amplitude under small IP and OOP
magnetic fields while remaining weakly affected by high fields, and implement
micromagnetic simulations to help us distinguish between the ST-LRT and SOC-LRT
contributions. Our findings suggest that further exploration of Fabry-P\'erot
type interference effects in electron transport could yield valuable insights
into the hybridization between superconductors and ferromagnets induced by
spin-orbit coupling and spin textures.",2403.02819v2
1999-04-24,Quantum melting of magnetic long-range order near orbital degeneracy. Classical phases and Gaussian fluctuations,"We study the effective spin-orbital model derived for the d9 ions in a
three-dimensional perovskite lattice, as in KCuF_3, where at each site the
doubly degenerate eg orbitals contain a single hole. The model describes the
superexchange interactions that depend on the pattern of orbitals occupied. We
present the ground state properties of this model, depending on the splitting
between the eg orbitals E_z, and the Hund's rule coupling in the excited d8
states, J_H. The classical phase diagram consists of six magnetic phases which
all have different orbital ordering: two antiferromagnetic (AF) phases with
G-AF order and either x2-y2 or 3z2-r2 orbitals occupied, two phases with mixed
orbital (MO) patterns and A-AF order, and two other MO phases with either C-AF
or G-AF order. All of them become degenerate at the multicritical point
M=(E_z,J_H)=(0,0). Using a generalization of linear spin-wave theory we study
both the transverse excitations which are spin-waves and
spin-and-orbital-waves, as well as the longitudinal (orbital) excitations. The
transverse modes couple to each other, and the spin-and-orbital-wave turns into
a soft mode near the M point. Therefore, quantum corrections to the
long-range-order parameter are drastically increased near the orbital
degeneracy, and classical order is suppressed in a crossover regime between the
G-AF and A-AF phases in the (E_z,J_H) plane. This behavior is reminiscent of
that found in frustrated spin models, and we conclude that orbital degeneracy
provides a new and physically realizable mechanism which stabilizes a spin
liquid ground state due to inherent frustration of magnetic interactions. We
also point out that such a disordered magnetic phase is likely to be realized
in LiNiO_2.",9904355v1
2023-06-21,Spin-orbit torques due to warped topological insulator surface states with an in-plane magnetization,"We investigate the extrinsic spin-orbit torque (SOT) on the surface of
topological insulators (TIs), which are characterized by two-dimensional warped
Dirac surface states, in the presence of an in-plane magnetization. The
interplay between extrinsic spin-orbit scattering and the in-plane
magnetization results in a net spin density leading to a SOT. Previous theory
suggested that the SOT could only be generated by an out-of-plane magnetic
field component, and any in-plane magnetic contribution could be gauged away.
However, we demonstrate theoretically that with an in-plane magnetization, the
SOT can be finite in TIs due to extrinsic spin-orbit scattering. In the case of
a TI model with a linear dispersion relation, the skew scattering term is zero,
and the extrinsic spin-orbit scattering influences the side-jump scattering,
leading to a finite SOT in TIs. However, when considering the warping term,
finite intrinsic and skew scattering terms will arise, in addition to
modifications to other scattering terms. We further show that the SOT depends
on the azimuthal angles of the magnetization and an external electric field. By
adjusting the extrinsic spin-orbit strength, Fermi energy, magnetization
strength and warping strength, the resulting SOTs can be maximized. These
findings shed light on the interplay between spin-orbit coupling and
magnetization in TIs, offering insights into the control and manipulation of
spin currents in these systems.",2306.12557v1
2011-01-20,"Mean-field Study of Charge, Spin, and Orbital Orderings in Triangular-lattice Compounds ANiO2 (A=Na, Li, Ag)","We present our theoretical results on the ground states in layered
triangular-lattice compounds ANiO2 (A=Na, Li, Ag). To describe the interplay
between charge, spin, orbital, and lattice degrees of freedom in these
materials, we study a doubly-degenerate Hubbard model with electron-phonon
couplings by the Hartree-Fock approximation combined with the adiabatic
approximation. In a weakly-correlated region, we find a metallic state
accompanied by \sqroot3x\sqroot3 charge ordering. On the other hand, we obtain
an insulating phase with spin-ferro and orbital-ferro ordering in a wide range
from intermediate to strong correlation. These phases share many
characteristics with the low-temperature states of AgNiO2 and NaNiO2,
respectively. The charge-ordered metallic phase is stabilized by a compromise
between Coulomb repulsions and effective attractive interactions originating
from the breathing-type electronphonon coupling as well as the Hund's-rule
coupling. The spin-orbital-ordered insulating phase is stabilized by the
cooperative effect of electron correlations and the Jahn-Teller coupling, while
the Hund's-rule coupling also plays a role in the competition with other
orbital-ordered phases. The results suggest a unified way of understanding a
variety of low-temperature phases in ANiO2. We also discuss a keen competition
among different spin-orbital-ordered phases in relation to a puzzling behavior
observed in LiNiO2.",1101.3828v1
2006-01-23,Quasiclassical approach to the spin-Hall effect in the two-dimensional electron gas,"We study the spin-charge coupled transport in a two-dimensional electron
system using the method of quasiclassical ($\xi$-integrated) Green's functions.
In particular we derive the Eilenberger equation in the presence of a generic
spin-orbit field. The method allows us to study spin and charge transport from
ballistic to diffusive regimes and continuity equations for spin and charge are
automatically incorporated. In the clean limit we establish the connection
between the spin-Hall conductivity and the Berry phase in momentum space. For
finite systems we solve the Eilenberger equation numerically for the special
case of the Rashba spin-orbit coupling and a two-terminal geometry. In
particular, we calculate explicitly the spin-Hall induced spin polarization in
the corners, predicted by Mishchenko et al. [13]. Furthermore we find universal
spin currents in the short-time dynamics after switching on the voltage across
the sample, and calculate the corresponding spin-Hall polarization at the
edges. Where available, we find perfect agreement with analytical results.",0601525v1
2009-06-08,Pure spin-current generated by reflection at a normal metal/2DEG interface,"The concept of a spin-current is a useful tool in understanding
spin-transport in hybrid systems, but its very definition is problematic in
systems where spin-orbit coupling effects are strong. In the absence of
spin-dependent scattering, the spin-current remains well-defined. We here
propose a method for generating pure spin-currents in a normal metal where the
spin-current consequently does not suffer from the aforementioned problems
pertaining to its very definition or spin-relaxation processes. More
specifically, we show how an unpolarized incident charge-current can induce a
pure transverse spin-current by means of scattering at a normal metal/2DEG
interface. This occurs for both Rashba and Dresselhaus spin-orbit coupling. An
experimental setup for observation of this effect is proposed.",0906.1581v2
2011-10-01,Phase diagram of the strongly correlated Kane-Mele-Hubbard model,"We explore the phase diagram of the strongly correlated Hubbard model with
intrinsic spin orbit coupling on the honeycomb lattice. We obtain the low
energy effective model describing the spin degree of freedom. We study the
resulting model within the Schwinger boson and Schwinger fermion approaches.
The Schwinger boson approach gives the boundary between the spin liquid phase
and the magnetically ordered phases, Neel order and incommensurate Neel order.
We find that increasing the strength of the spin orbit coupling, narrows the
width of the spin liquid region. The Schwinger fermion approach sheds further
light on the nature of the spin liquid phase. We obtain three different
candidates for the spin liquid phase within the mean field approximation which
are gapless spin liquid, topological Mott insulator, and the chiral spin liquid
phases. We argue that the gauge fluctuations and the instanton effect may
suppress the first two spin liquids, while the chiral spin liquid is stable
against gauge fluctuations due to its nontrivial topology.",1110.0116v2
2015-08-03,Spin orbit coupling controlled spin pumping effect,"Effective spin mixing conductance (ESMC) across the nonmagnetic metal
(NM)/ferromagnet interface, spin Hall conductivity (SHC) and spin diffusion
length (SDL) in the NM layer govern the functionality and performance of pure
spin current devices with spin pumping technique. We show that all three
parameters can be tuned significantly by the spin orbit coupling (SOC) strength
of the NM layer in systems consisting of ferromagnetic insulating Y3Fe5O12
layer and metallic Pd1-xPtx layer. Surprisingly, the ESMC is observed to
increase significantly with x changing from 0 to 1.0. The SHC in PdPt alloys,
dominated by the intrinsic term, is enhanced notably with increasing x.
Meanwhile, the SDL is found to decrease when Pd atoms are replaced by heavier
Pt atoms, validating the SOC induced spin flip scattering model in polyvalent
PdPt alloys. The capabilities of both spin current generation and spin charge
conversion are largely heightened via the SOC. These findings highlight the
multifold tuning effects of the SOC in developing the new generation of
spintronic devices.",1508.00352v3
2016-10-12,Microscopic derivation of magnon spin current in a topological insulator/ferromagnet heterostructure,"We investigate a spin-electricity conversion effect in a topological
insulator/ferromagnet heterostructure. In the spin-momentum-locked surface
state, an electric current generates nonequilibrium spin accumulation, which
causes a spin-orbit torque that acts on the ferromagnet. When spins in the
ferromagnet are completely parallel to the accumulated spin, this spin-orbit
torque is zero. In the presence of spin excitations, however, a coupling
between magnons and electrons enables us to obtain a nonvanishing torque. In
this paper, we consider a model of the heterostructure in which a
three-dimensional magnon gas is coupled with a two-dimensional massless Dirac
electron system at the interface. We calculate the torque induced by an
electric field, which can be interpreted as a magnon spin current, up to the
lowest order of the electron-magnon interaction. We derive the expressions for
high and low temperatures and estimate the order of magnitude of the induced
spin current for realistic materials at room temperature.",1610.03636v3
2018-04-27,Spin Connections for Nonrelativistic Electrons on Curves and Surfaces,"We propose a basic theory of nonrelativistic spinful electrons on curves and
surfaces. In particular, we discuss the presence and effects of spin
connections, which describe how spinors and vectors couple to the geometry of
curves and surfaces. We derive explicit expressions of spin connections by
performing simple dimensional reduction from the three-dimensional flat space.
The spin connections act on electrons as spin-dependent magnetic fields, which
have been known as `pseudomagnetic fields' in the context of, e.g., graphenes
and Dirac/Weyl semimetals. We propose that these spin-dependent magnetic fields
are present universally on curves and surfaces, acting on electrons regardless
of the kinds of their spinorial degrees of freedom and their dispersion
relations. We discuss that the curvature effects via spin connections will
induce the spin Hall effect and induce the Dzyaloshinskii--Moriya interactions
between magnetic moments on curved surfaces, without relying on the
relativistic spin-orbit couplings. We also mention the importance of spin
connections on orbital physics of electrons on curved geometry.",1804.10613v2
2016-08-20,Enhancement of Rashba spin-orbit coupling by electron-electron interaction,"We studied how the electron-electron (e-e) interaction enhances the strength
of the Rashba spin-orbit coupling (RSOC) and opens the possibility of
generating a spin-polarized output current from an unpolarized electric current
without any magnetic elements. In this regard, we proposed a novel design of a
graphene-like junction based on the $e$-$e$ interaction and the $RSOC$. The
results showed that the $e$-$e$ interaction with $RSOC$ opens a spin energy gap
and extremely enhances the $RSOC$ in this spin energy gap. Interestingly, the
junction produces a large spin-polarized current and could act as a
high-efficiency spin filter device (nearly 100\% spin polarization) at room
temperature even at low Rashba and e-e interaction strengths. However, with an
appropriate design, we showed that RSOC could strongly weaken the
spin-polarized current and the spin energy gap, which is solely produced by the
$e$-$e$ interaction, but a high spin polarization persists in some energy
ranges.",1608.05841v1
2017-05-02,Reversible spin texture in ferroelectric HfO2,"Spin-orbit coupling effects occurring in non-centrosymmetric materials are
known to be responsible for non-trivial spin configurations and a number of
emergent physical phenomena. Ferroelectric materials may be especially
interesting in this regard due to reversible spontaneous polarization making
possible for a non-volatile electrical control of the spin degrees of freedom.
Here, we explore a technologically relevant oxide material, HfO2, which has
been shown to exhibit robust ferroelectricity in a non-centrosymmetric
orthorhombic phase. Using theoretical modelling based on density-functional
theory, we investigate the spin-dependent electronic structure of the
ferroelectric HfO2 and demonstrate the appearance of chiral spin textures
driven by spin-orbit coupling. We analyze these spin configurations in terms of
the Rashba and Dresselhaus effects within the k.p Hamiltonian model and find
that the Rashba-type spin texture dominates around the valence band maximum,
while the Dresselhaus-type spin texture prevails around the conduction band
minimum. The latter is characterized by a very large Dresselhaus constant
{\alpha}D = 0.578 eV {\AA}, which allows using this material as a tunnel
barrier to produce tunneling anomalous and spin Hall effects that are
reversible by ferroelectric polarization.",1705.00768v1
2021-05-06,Visualization of optical polarization transfer to photoelectron spin vector emitted from the spin-orbit coupled surface state,"Similar to light polarization that is selected by a superposition of optical
basis, electron spin direction can be controlled through a superposition of
spin basis. We investigate such a spin interference occurring in photoemission
of the spin-orbit coupled surface state in Bi2Se3 by using spin- and
angle-resolved photoemission spectroscopy combined with laser light source
(laser-SARPES). Our laser-SARPES with three-dimensional spin detection and
tunable laser polarization including elliptical and circular polarization
enables us to directly visualize how the direction of the fully-polarized
photoelectron spin changes according to the optical phase and orientation of
the incident laser polarization. By this advantage of our laser-SARPES, we
demonstrate that such optical information can be projected to the
three-dimensional spin vector of the photoelectrons. Our results, therefore,
present a novel spin-polarized electron source permitting us to optically
control the pure spin state pointing to the arbitrary direction.",2105.02749v2
2021-11-18,"Long-range, Non-local Switching of Spin Textures in a Frustrated Antiferromagnet","Antiferromagnetic spintronics is an emerging area of quantum technologies
that leverage the coupling between spin and orbital degrees of freedom in
exotic materials. Spin-orbit interactions allow spin or angular momentum to be
injected via electrical stimuli to manipulate the spin texture of a material,
enabling the storage of information and energy. In general, the physical
process is intrinsically local: spin is carried by an electrical current,
imparted into the magnetic system, and the spin texture then rotates. The
collective excitations of complex spin textures have rarely been utilized in
this context, even though they can in principle transport spin over much longer
distances, using much lower power. In this study, we show that spin information
can be transported and stored non-locally in the material Fe$_x$NbS$_2$. We
propose that collective modes leverage the strong magnetoelastic coupling in
the system to achieve this, revealing a novel way to store spin information in
complex magnetic systems",2111.09882v2
2022-10-08,Comprehensive Demonstration of Spin-Hall Hanle Effects in Epitaxial Pt Thin Films,"We demonstrate a nonlinear Hall effect due to the boundary spin accumulation
in Pt films grown on Al2O3 substrates. This Hall effect and the previously
demonstrated Hanle magnetoresistance provide a complete picture of the
spin-precession control of the spin and charge transport at the boundary of a
spin-orbit coupled material, which we refer to as spin-Hall Hanle effects
(SHHE). We also show that the SHHE can be employed to measure the spin
diffusion length, the spin-Hall angle, and the spin relaxation time of heavy
metal without the need of magnetic interface or the input from other
measurements. The comprehensive demonstration of SHHE in such a simple system
suggests they may be ubiquitous and needs to be considered for unravelling the
spin and charge transport in more complex thin film structures of spin-orbit
coupled materials.",2210.03863v1
2023-06-15,Universal spin superconducting diode effect from spin-orbit coupling,"We propose a universal spin superconducting diode effect (SDE) induced by
spin-orbit coupling (SOC), where the critical spin supercurrents in opposite
directions are unequal. By analysis from both the Ginzburg-Landau theory and
energy band analysis, we show that the spin-$\uparrow \uparrow$ and
spin-$\downarrow \downarrow$ Cooper pairs possess opposite phase gradients and
opposite momenta from the SOC, which leads to the spin SDE. Two superconductors
with SOC, a $p$-wave superconductor as a toy model and a practical
superconducting nanowire, are numerically studied and they both exhibit spin
SDE. In addition, our theory also provides a unified picture for both spin and
charge SDEs. Besides, we propose spin-polarized detection and nonlocal spin
transport, as mature experimental technologies, to confirm the spin SDE in
superconducting nanowires.",2306.09113v1
2023-10-27,Ultrafast switchable spin-orbit coupling for silicon spin qubits via spin valves,"Recent experimental breakthroughs, particularly for single-qubit and
two-qubit gates exceeding the error correction threshold, highlight silicon
spin qubits as leading candidates for fault-tolerant quantum computation. In
the existing architecture, intrinsic or synthetic spin-orbit coupling (SOC) is
critical in various aspects, including electrical control, addressability,
scalability, etc. However, the high-fidelity SWAP operation and quantum state
transfer (QST) between spin qubits, crucial for qubit-qubit connectivity,
require the switchable nature of SOC which is rarely considered. Here, we
propose a flexible architecture based on spin valves by electrically changing
its magnetization orientation within sub-nanoseconds to generate ultrafast
switchable SOC. Based on the switchable SOC architecture, both SWAP operation
of neighbor spin qubits and resonant QST between distant spins can be realized
with fidelity exceeding 99% while considering the realistic experimental
parameters. Benefiting from the compatible processes with the modern
semiconductor industry and experimental advances in spin valves and spin
qubits, our results pave the way for future construction of silicon-based
quantum chips.",2310.17993v1
2009-07-17,Mott physics and band topology in materials with strong spin-orbit interaction,"Recent theory and experiment have revealed that strong spin-orbit coupling
can have dramatic qualitative effects on the band structure of weakly
interacting solids. Indeed, it leads to a distinct phase of matter, the
topological band insulator. In this paper, we consider the combined effects of
spin-orbit coupling and strong electron correlation, and show that the former
has both quantitative and qualitative effects upon the correlation-driven Mott
transition. As a specific example we take Ir-based pyrochlores, where the
subsystem of Ir 5d electrons is known to undergo a Mott transition. At weak
electron-electron interaction, we predict that Ir electrons are in a metallic
phase at weak spin-orbit interaction, and in a topological band insulator phase
at strong spin-orbit interaction. Very generally, we show that with increasing
strength of the electron-electron interaction, the effective spin-orbit
coupling is enhanced, increasing the domain of the topological band insulator.
Furthermore, in our model, we argue that with increasing interactions, the
topological band insulator is transformed into a ""topological Mott insulator""
phase, which is characterized by gapless surface spin-only excitations. The
full phase diagram also includes a narrow region of gapless Mott insulator with
a spinon Fermi surface, and a magnetically ordered state at still larger
electron-electron interaction.",0907.2962v1
2016-04-18,Crossed responses of spin and orbital magnetism in topological insulators,"Crossed magnetic responses between spin and orbital angular momentum are
studied in time-reversal symmetric topological insulators. Due to spin-orbit
coupling in the quantum spin Hall systems and three-dimensional topological
insulators, the magnetic susceptibility has crossed (intersectional) components
between spin and orbital part of magnetism. In this study, the crossed
susceptibility for the orbital magnetization is studied in two- and
three-dimensional topological insulator models, in which an external magnetic
field interacts with the electron spin by Zeeman coupling via distinct
g-factors for conduction and valence energy bands. The crossed susceptibility
in two-dimensional quantum spin Hall insulators shows a quantized signature of
the $\mathbb{Z}_2$ topological phase in response to Zeeman coupling via an
averaged g-factor, and the quantization persists even when
$\sigma^z$-conservation of electrons is broken by a tilted magnetic field. The
bulk orbital magnetization is interpreted by the persistent edge current
attributed to the chiral anomaly at the (1+1)-dimensional boundary. In
three-dimensional topological insulators, we found that the crossed
susceptibility is proportional to the difference of g-factors of conduction and
valence electrons, which is qualitatively different from the two-dimensional
case. Steep changes of the crossed susceptibility in three dimensions at the
phase transition points are explained by the surface Dirac fermion theory.
Finally, dependence of the crossed susceptibility on g-factors in two- and
three-dimensional cases is discussed from the viewpoint of time-reversal and
particle-hole symmetries.",1604.04991v2
2014-03-06,Spin-orbital Entangled Molecular $j_{\rm eff}$ States in Lacunar Spinel Compounds,"The entanglement of the spin and orbital degrees of freedom through the
spin-orbit coupling has been actively studied in condensed matter physics. In
several iridium-oxide systems, the spin-orbital entangled state, identified by
the effective angular momentum $j_{\rm eff}$, can host novel quantum phases
with the help of electron correlations. Here, we show that a series of lacunar
spinel compounds, Ga$M_4X_8$ ($M$ = Nb, Mo, Ta, and W and $X$ = S, Se, and Te),
gives rise to a $\textit{molecular}$ $j_{\rm eff}$ state as a new spin-orbital
composite on which the low energy effective Hamiltonian is based. A wide range
of electron correlations is accessible by tuning the bandwidth under external
and/or chemical pressure, enabling us to investigate the interesting
cooperation between spin-orbit coupling and electron correlations. As
illustrative examples, a two-dimensional topological insulating phase and an
anisotropic spin Hamiltonian are investigated in the weak and strong coupling
regimes, respectively. Our finding can provide an ideal platform for exploring
$j_{\rm eff}$ physics and the resulting emergent phenomena.",1403.1358v2
2019-10-11,Coupled density-spin Bose-Einstein condensates dynamics and collapse in systems with quintic nonlinearity,"We investigate the effects of spin-orbit coupling and Zeeman splitting on the
coupled density-spin dynamics and collapse of the Bose-Einstein condensate
driven by the quintic self-attraction in the same- and cross-spin channels. The
characteristic feature of the collapse is the decrease in the width as given by
the participation ratio of the density rather than by the expectation values of
the coordinate. Qualitative arguments and numerical simulations reveal the
existence of a critical spin-orbit coupling strength which either prohibits or
leads to the collapse, and its dependence on other parameters, such as the
condensates norm, spin-dependent nonlinear coupling, and the Zeeman splitting.
The entire nonlinear dynamics critically depend on the initial spin sate.",1910.05023v1
2014-02-24,Photon assisted tunneling through three quantum dots with spin-orbit-coupling,"The effect of an ac electric field on quantum transport properties in a
system of three quantum dots, two of which are connected in parallel while the
third is coupled to one of the other two, is investigated theoretically. Based
on the Keldysh nonequilibrium Green's function method, the spin-dependent
current, occupation number and spin accumulation can be obtained in our model.
An external magnetic flux, Rashba spin orbit coupling (SOC) and intradot
Coulomb interactions are considered. The magnitude of the spin-dependent
average current and the positions of the photon assisted tunneling (PAT) peaks
can be accurately controlled and manipulated by simply varying the strength of
the coupling and the frequency of the ac field. A particularly interesting
result is the observation of a new kind of PAT peak and a multiple
electron-photon pump effect that can generated and controlled by the coupling
between the quantum dots. In addition, the spin occupation number and spin
accumulation can be well controlled by the Rashba SOC and the magnetic flux.",1402.5711v1
2015-10-13,Interacting spin-orbit-coupled spin-1 Bose-Einstein condensates,"The recent experimental realization of spin-orbit (SO) coupling for spin-1
ultracold atoms opens an interesting avenue for exploring SO-coupling-related
physics in large-spin systems, which is generally unattainable in electronic
materials. In this paper, we study the effects of interactions between atoms on
the ground states and collective excitations of SO-coupled spin-1 Bose-Einstein
condensates (BECs) in the presence of a spin-tensor potential. We find that
ferromagnetic interaction between atoms can induce a stripe phase exhibiting
in-phase or out-of-phase modulating patterns between spin-tensor and
zero-spin-component density waves. We characterize the phase transitions
between different phases using the spin-tensor density as well as the
collective dipole motion of the BEC. We show that there exists a double
maxon-roton structure in the Bogoliubov-excitation spectrum, attributed to the
three band minima of the SO-coupled spin-1 BEC.",1510.03787v3
2014-10-31,Spin-orbit coupling in fluorinated graphene,"We report on theoretical investigations of the spin-orbit coupling effects in
fluorinated graphene. First-principles density functional calculations are
performed for the dense and dilute adatom coverage limits. The dense limit is
represented by the single-side semifluorinated graphene, which is a metal with
spin-orbit splittings of about 10 meV. To simulate the effects of a single
adatom, we also calculate the electronic structure of a $10 \times 10$
supercell, with one fluorine atom in the top position. Since this dilute limit
is useful to study spin transport and spin relaxation, we also introduce a
realistic effective hopping Hamiltonian, based on symmetry considerations,
which describes the supercell bands around the Fermi level. We provide the
Hamiltonian parameters which are best fits to the first-principles data. We
demonstrate that, unlike for the case of hydrogen adatoms, fluorine's own
spin-orbit coupling is the principal cause of the giant induced local
spin-orbit coupling in graphene. The $sp^3$ hybridization induced transfer of
spin-orbit coupling from graphene's $\sigma$ bonds, important for hydrogenated
graphene, contributes much less. Furthermore, the magnitude of the induced
spin-orbit coupling due to fluorine adatoms is about $1000$ times more than
that of pristine graphene, and 10 times more than that of hydrogenated
graphene. Also unlike hydrogen, the fluorine adatom is not a narrow resonant
scatterer at the Dirac point. The resonant peak in the density of states of
fluorinated graphene in the dilute limit lies 260 meV below the Dirac point.
The peak is rather broad, about 300 meV, making the fluorine adatom only a
weakly resonant scatterer.",1411.0016v2
2003-02-06,Semiclassical theory of spin-orbit interaction in the extended phase space,"We consider the semiclassical theory in a joint phase space of spin and
orbital degrees of freedom. The method is developed from the path integrals
using the spin-coherent-state representation, and yields the trace formula for
the density of states. We discuss special cases, such as weak and strong
spin-orbit coupling, and relate the present theory to the earlier approaches.",0302011v2
2023-12-05,Current induced magnetisation in metal without space-inversion symmetry,"Magneto-electric effect, that is an appearance of magnetisation induced by
electric current is allowed by symmetry in metals with crystal structure
without space inversion. The microscopic origin of this effect is spin-orbit
coupling of electrons with a non-centrosymmetric crystal lattice lifting spin
degeneracy of electron energy and mixing spin and orbital degrees of freedom.
The presented calculation of magnetisation induced by current based on the
application of kinetic equation for the matrix distribution function of
electrons occupying the states in two bands split by the spin-orbit
interaction.",2312.04592v2
2004-03-08,Zeeman energy and anomalous spin splitting in lateral GaAs quantum dots,"The level splittings induced by a horizontal magnetic field in a parabolic
two-dimensional quantum dot with spin-orbit interaction are obtained.
Characteristic features induced by the spin-orbit coupling are the appearance
of zero-field gaps as well as energy splittings that depend on the electronic
state and the orientation of the magnetic field in the quantum-dot plane. It is
suggested that these quantum-dot properties could be used to determine the
Rashba and Dresselhaus spin-orbit intensities",0403202v1
2004-10-27,Spin-orbit-driven coherent oscillations in a few-electron quantum dot,"We propose an experiment to observe coherent oscillations in a single quantum
dot with the oscillations driven by spin-orbit interaction. This is achieved
without spin-polarised leads, and relies on changing the strength of the
spin-orbit coupling via an applied gate pulse. We derive an effective model of
this system which is formally equivalent to the Jaynes-Cummings model of
quantum optics. For parameters relevant to a InGaAs dot, we calculate a Rabi
frequency of 2 GHz.",0410714v2
2005-12-20,Ballistic transport in one-dimensional loops with Rashba and Dresselhaus spin-orbit coupling,"We discuss the combined effect of Rashba and Dresselhaus spin-orbit
interactions in polygonal loops formed by quantum wires, when the electron are
injected in a node and collected at the opposite one. The conditions that allow
perfect localization are found. Furthermore, we investigate the suppression of
the Al'tshuler--Aronov--Spivak oscillations that appear, in presence of a
magnetic flux, when the electrons are injected and collected at the same node.
Finally, we point out that a recent realization of a ballistic spin
interferometer can be used to obtain a reliable estimate of the magnitude ratio
of the two spin-orbit interactions.\bigskip",0512499v1
2009-03-16,Extrinsic and intrinsic ratchet response of a quantum dissipative spin-orbit medium,"Traditionally the charge ratchet effect is considered as a consequence of the
extrinsic spatial asymmetry engineered by external asymmetric periodic
potentials. Here we demonstrate that electrically and magnetically driven
dissipative systems with spin-orbit interactions represent an exception from
this standard idea. The charge and spin ratchet currents appear just due to the
coexistence of quantum dissipation with the intrinsic spatial asymmetry of the
spin-orbit coupling. The extrinsic spatial asymmetry is inessential.",0903.2765v1
2014-09-07,Quantum spin Hall effect in a two-orbital model on a honeycomb lattice,"The spin Hall effect is investigated in a two-orbital tight-binding model on
a honeycomb lattice. We show that the model exhibits three
topologically-different insulating phases at half filling, which are
distinguished by different quantized values of the spin Hall conductivity. We
analytically determine the phase boundaries, where the valence and conduction
bands touch with each other with forming the Dirac nodes at the Fermi level.
The results are discussed in terms of the effective antisymmetric spin-orbit
coupling. The relation to the Kane-Mele model and implications for a
magnetoelectric effect are also discussed.",1409.2142v1
2019-03-08,Spin-perturbed orbits near black holes,"Inspirals of rotating stellar-mass compact objects into massive black holes
are influenced by the spin-curvature coupling, which drives the compact body
away from geodesic motion due to its rotation. I formulate the Hamilton-Jacobi
equation for a spinning test body orbiting a Kerr black hole, solve it to
linear order in spin, and use the perturbative solution to compute the
fundamental frequencies of motion along the orbit. This result provides one of
the necessary ingredients for waveform models for the upcoming space-based
gravitational-wave detector LISA.",1903.03649v1
2016-02-01,Facet-dependent giant spin orbit torque in single crystalline antiferromagnetic Ir-Mn / ferromagnetic permalloy bilayers,"There has been considerable interest in spin-orbit torques for the purpose of
manipulating the magnetization of ferromagnetic (FM) films or nano-elements for
spintronic technologies. Spin-orbit torques are derived from spin currents
created from charge currents in materials with significant spin-orbit coupling
that diffuse into an adjacent FM material. There have been intensive efforts to
search for candidate materials that exhibit large spin Hall angles, i.e.
efficient charge to spin current conversion. Here we report, using spin torque
ferromagnetic resonance, the observation of a giant spin Hall angle of up to
~0.35 in (100) oriented single crystalline antiferromagnetic (AF) IrMn3 thin
films, coupled to ferromagnetic permalloy layers, and a spin Hall angle that is
about three times smaller in (111) oriented films. For the (100) oriented
samples we show that the magnitude of the spin Hall angle can be significantly
changed by manipulating the populations of the various AF domains through field
annealing. Using ab-initio calculations we show that the triangular AF
structure of IrMn3 gives rise to a substantial intrinsic spin Hall conductivity
that is three times larger for the (100) than for the (111) orientations,
consistent with our experimental findings.",1602.00670v1
2013-06-12,Atomic spin-orbit coupling synthesized with magnetic-field-gradient pulses,"We discuss a general scheme for creating atomic spin-orbit coupling (SOC)
such as the Rashba or Dresselhaus types using magnetic-field-gradient pulses.
In contrast to conventional schemes based on adiabatic center-of-mass motion
with atomic internal states restricted to a dressed-state subspace, our scheme
works for the complete subspace of a hyperfine-spin manifold by utilizing the
coupling between the atomic magnetic moment and external magnetic fields. A
spatially dependent pulsed magnetic field acts as an internal-state-dependent
impulse, thereby coupling the atomic internal spin with its orbital
center-of-mass motion, as in the Einstein-de Haas effect. This effective
coupling can be dynamically manipulated to synthesize SOC of any type (Rashba,
Dresselhaus, or any linear combination thereof). Our scheme can be realized
with most experimental setups of ultracold atoms and is especially suited for
atoms with zero nuclear spins.",1306.2829v1
2021-07-13,Supersolid phase of a spin-orbit-coupled Bose-Einstein condensate: a perturbation approach,"The phase diagram of a Bose-Einstein condensate with Raman-induced spin-orbit
coupling includes a stripe phase with supersolid features. In this work we
develop a perturbation approach to study the ground state and the Bogoliubov
modes of this phase, holding for small values of the Raman coupling. We obtain
analytical predictions for the most relevant observables (including the
periodicity of stripes, sound velocities, compressibility, and magnetic
susceptibility) which are in excellent agreement with the exact (non
perturbative) numerical results, obtained for significantly large values of the
coupling. We further unveil the nature of the two gapless Bogoliubov modes in
the long-wavelength limit. We find that the spin branch of the spectrum,
corresponding in this limit to the dynamics of the relative phase between the
two spin components, describes a translation of the fringes of the equilibrium
density profile, thereby providing the crystal Goldstone mode typical of a
supersolid configuration. Finally, using sum-rule arguments, we show that the
superfluid density can be experimentally accessed by measuring the ratio of the
sound velocities parallel and perpendicular to the direction of the spin-orbit
coupling.",2107.06425v2
2017-10-07,Coupled spin-charge dynamics in helical Fermi liquids beyond the random phase approximation,"We consider a helical system of fermions with a generic spin (or pseudospin)
orbit coupling. Using the equation of motion approach for the single-particle
distribution functions, and a mean-field decoupling of the higher order
distribution functions, we find a closed form for the charge and spin density
fluctuations in terms of the charge and spin density linear response functions.
Approximating the nonlocal exchange term with a Hubbard-like local-field
factor, we obtain coupled spin and charge density response matrix beyond the
random phase approximation, whose poles give the dispersion of four collective
spin-charge modes. We apply our generic technique to the well-explored
two-dimensional system with Rashba spin-orbit coupling and illustrate how it
gives results for the collective modes, Drude weight, and spin-Hall
conductivity which are in very good agreement with the results obtained from
other more sophisticated approaches.",1710.02712v1
2019-06-27,Spin-dependent conductance statistics in systems with spin-orbit coupling,"Spin-dependent partial conductances are evaluated in a tight-binding
description of electron transport in the presence of spin-orbit (SO) couplings,
using transfer-matrix methods. As the magnitude of SO interactions increases,
the separation of spin-switching channels from non-spin-switching ones is
gradually erased. Spin-polarised incident beams are produced by including a
Zeeman-like term in the Hamiltonian. The exiting polarisation is shown to
exhibit a maximum as a function of the intensity of SO couplings. For moderate
site disorder, and both weak and strong SO interactions, no evidence is found
for a decay of exiting polarisation against increasing system length. With very
low site disorder and weak SO couplings a spin-filter effect takes place, as
polarisation {\em increases} with increasing system length.",1906.11804v3
2021-03-08,Spin-valley coupling in single-electron bilayer graphene quantum dots,"Understanding how the electron spin is coupled to orbital degrees of freedom,
such as a valley degree of freedom in solid-state systems is central to
applications in spin-based electronics and quantum computation. Recent
developments in the preparation of electrostatically-confined quantum dots in
gapped bilayer graphene (BLG) enables to study the low-energy single-electron
spectra in BLG quantum dots, which is crucial for potential spin and
spin-valley qubit operations. Here, we present the observation of the
spin-valley coupling in a bilayer graphene quantum dot in the single-electron
regime. By making use of a highly-tunable double quantum dot device we achieve
an energy resolution allowing us to resolve the lifting of the fourfold spin
and valley degeneracy by a Kane-Mele type spin-orbit coupling of $\approx
65~\mu$eV. Also, we find an upper limit of a potentially disorder-induced
mixing of the $K$ and $K'$ states below $20~\mu$eV.",2103.04825v3
2007-01-18,Persistent spin and charge currents and magnification effects in open ring conductors subject to Rashba coupling,"We analyze the effect of Rashba spin-orbit coupling and of a local tunnel
barrier on the persistent spin and charge currents in a one-dimensional
conducting Aharonov-Bohm (AB) ring symmetrically coupled to two leads. First,
as an important consequence of the spin-splitting, it is found that a
persistent spin current can be induced which is not simply proportional to the
charge current. Second, a magnification effect of the persistent spin current
is shown when one tunes the Fermi energy near the Fano-type antiresonances of
the total transmission coefficient governed by the tunnel barrier strength. As
an unambiguous signature of spin-orbit coupling we also show the possibility to
produce a persistent pure spin current at the interference zeros of the
transmittance. This widens the possibilities of employing mesoscopic conducting
rings in phase-coherent spintronics applications.",0701453v1
2021-12-14,Coherent control of spin tunneling in a spin-orbit coupled bosonic triple well,"We study the coherent control of spin tunneling for a spin-orbit (SO) coupled
boson held in a driven triple well. Under high-frequency approximation, we
analytically obtain the quasienergies of the SO-coupled bosonic triple-well
system and fine energy band structure is displayed. By adjusting the driving
parameters, we reveal that the directed selective spin-flipping or
spin-conserving tunneling of a SO-coupled boson occurs along different pathways
and in different directions. The analytical results are numerically confirmed
and perfect agreements are found. Further, a scheme of quantum spin switch with
or without spin-flipping is presented. These results may be useful for quantum
information processing and the design of spintronic devices.",2112.07166v1
2004-11-18,Quantum transport theory for nanostructures with Rashba spin-orbital interaction,"We report on a general theory for analyzing quantum transport through devices
in the Metal-QD-Metal configuration where QD is a quantum dot or the device
scattering region which contains Rashba spin-orbital and electron-electron
interactions. The metal leads may or may not be ferromagnetic, they are assumed
to weakly couple to the QD region. Our theory is formulated by second
quantizing the Rashba spin-orbital interaction in spectral space (instead of
real space), and quantum transport is then analyzed within the Keldysh
nonequilibrium Green's function formalism. The Rashba interaction causes two
main effects to the Hamiltonian: (i) it gives rise to an extra spin-dependent
phase factor in the coupling matrix elements between the leads and the QD; (ii)
it gives rise to an inter-level spin-flip term but forbids any intra-level
spin-flips. Our formalism provides a starting point for analyzing many quantum
transport issues where spin-orbital effects are important. As an example, we
investigate transport properties of a Aharnov-Bohm ring in which a QD having
Rashba spin-orbital and e-e interactions is located in one arm of the ring. A
substantial spin-polarized conductance or current emerges in this device due to
a combined effect of a magnetic flux and the Rashba interaction. The direction
and strength of the spin-polarization are shown to be controllable by both the
magnetic flux and a gate voltage.",0411469v1
2007-03-16,Spin relaxation at the singlet-triplet crossing in a quantum dot,"We study spin relaxation in a two-electron quantum dot in the vicinity of the
singlet-triplet crossing. The spin relaxation occurs due to a combined effect
of the spin-orbit, Zeeman, and electron-phonon interactions. The
singlet-triplet relaxation rates exhibit strong variations as a function of the
singlet-triplet splitting. We show that the Coulomb interaction between the
electrons has two competing effects on the singlet-triplet spin relaxation. One
effect is to enhance the relative strength of spin-orbit coupling in the
quantum dot, resulting in larger spin-orbit splittings and thus in a stronger
coupling of spin to charge. The other effect is to make the charge density
profiles of the singlet and triplet look similar to each other, thus
diminishing the ability of charge environments to discriminate between singlet
and triplet states. We thus find essentially different channels of
singlet-triplet relaxation for the case of strong and weak Coulomb interaction.
Finally, for the linear in momentum Dresselhaus and Rashba spin-orbit
interactions, we calculate the singlet-triplet relaxation rates to leading
order in the spin-orbit interaction, and find that they are proportional to the
second power of the Zeeman energy, in agreement with recent experiments on
triplet-to-singlet relaxation in quantum dots.",0703427v2
2021-10-11,Interaction-induced quantum spin Hall insulator in the organic Dirac electron system $α$-(BEDT-TSeF)$_2$I$_3$,"Focusing on the recently-discovered candidate topological insulator
$\alpha$-(BEDT-TSeF)$_2$I$_3$ -- having two-dimensional charge-neutral Dirac
cones in a low symmetry lattice -- we combine ab-initio and extended-Hubbard
model calculations to deal with spin-orbit and non-local repulsive
interactions, and find a realization of an interaction-induced quantum spin
Hall (QSH) insulator, similar to the one proposed in the honeycomb lattice
under next-nearest neighbor repulsions. In the absence of repulsive
interactions, a topological insulator appears by the spin-orbit coupling and is
characterized by a nonzero spin Chern number. By considering up to next-nearest
neighbor repulsions at Hartree-Fock level, the intrinsic spin-orbit gap is
found to grow by orders of magnitude and a QSH insulating phase appears that
has both a finite spin Chern number and order parameter. Transport coefficients
and spin susceptibility are calculated and found to consistently account for
most of the experimental findings, including the metal-to-insulator crossover
occurring at $\sim50$ K as well as the Berry phase change from 0 to $\pi$ under
hydrostatic pressure. We argue that such a QSH insulating phase does not
necessitate a sizeable spin-orbit interaction to generate a large insulating
gap, which is highly advantageous for the search of novel topological phases in
generic materials having low symmetry lattice and/or small spin-orbit coupling.",2110.05010v5
2003-06-19,Theory of the Mercury's spin-orbit motion and analysis of its main librations,"The upcoming space missions, MESSENGER and BepiColombo with onboard
instrumentation capable of measuring the rotational parameters stimulate the
objective to reach an accurate theory of the rotational motion of Mercury. For
obtaining the real motion of Mercury, we have used our relativistic BJV model
of solar system integration including the coupled spin-orbit motion of the
Moon. We have extended this model by generalizing the spin-orbit couplings to
the terrestrial planets, notably Mercury. The updated model is called SONYR
(acronym of Spin-Orbit N-BodY Relativistic model). The SONYR model giving an
accurate solution of the spin-orbit motion of Mercury permits to analyze the
different families of the Hermean rotational librations. The spin-orbit motion
of Mercury is characterized by two proper frequencies (namely 15.847 and 1066
years) and its 3:2 resonance presents a second synchronism which can be
understood as a spin-orbit secular resonance (278 898 years). By using the
SONYR model, we find a new determination of the mean obliquity, namely 1.6
arcminutes. Besides, we identify in the Hermean librations the impact of the
uncertainty of the greatest principal moment of inertia (\cmr2) on the
obliquity and on the libration in longitude (2.3 mas and 0.45 as respectively
for an increase of 1% on the \cmr2 value). These determinations prove to be
suitable for providing constraints on the internal structure of Mercury.",0306387v2
2013-05-09,Correlated quantum phenomena in the strong spin-orbit regime,"We discuss phenomena arising from the combined influence of electron
correlation and spin-orbit coupling, with an emphasis on emergent quantum
phases and transitions in heavy transition metal compounds with 4d and 5d
elements. A common theme is the influence of spin-orbital entanglement produced
by spin-orbit coupling, which influences the electronic and magnetic structure.
In the weak-to-intermediate correlation regime, we show how non-trivial
band-like topology leads to a plethora of phases related to topological
insulators. We expound these ideas using the example of pyrochlore iridates,
showing how many novel phases such as the Weyl semi-metal, axion insulator,
topological Mott insulator, and topological insulators may arise in this
context. In the strong correlation regime, we argue that spin-orbital
entanglement fully or partially removes orbital degeneracy, reducing or
avoiding the normally ubiquitous Jahn-Teller effect. As we illustrate for the
honeycomb lattice iridates and double perovskites, this leads to enhanced
quantum fluctuations of the spin-orbital entangled states and the chance to
promote exotic quantum spin liquid and multipolar ordered ground states.
Connections to experiments, materials, and future directions are discussed.",1305.2193v2
2012-02-28,U(1) Slave-spin theory and its application to Mott transition in a multi-orbital model for iron pnictides,"A U(1) slave-spin representation is introduced for multi-orbital Hubbard
models. As with the $Z_2$ form of L. de'Medici et al. (Phys. Rev. B 72, 205124
(2005)), this approach represents a physical electron operator as the product
of a slave spin and an auxiliary fermion operator. For non-degenerate
multi-orbital models, our U(1) approach is advantageous in that it captures the
non-interacting limit at the mean-field level. For systems with either a single
orbital or degenerate multiple orbitals, the U(1) and $Z_2$ slave-spin
approachs yield the same results in the slave-spin-condensed phase. In general,
the U(1) slave-spin approach contains a U(1) gauge redundancy, and properly
describes a Mott insulating phase. We apply the U(1) slave-spin approach to
study the metal-to-insulator transition in a five-orbital model for parent iron
pnictides. We demonstrate a Mott transition as a function of the interactions
in this model. The nature of the Mott insulating state is influenced by the
interplay between the Hund's rule coupling and crystal field splittings. In the
metallic phase, when the Hund's rule coupling is beyond a threshold, there is a
crossover from a weakly correlated metal to a strongly correlated one, through
which the quasiparticle speactral weight rapidly drops. The existence of such a
strongly correlated metallic phase supports the incipient Mott picture of the
parent iron pnictides. In the parameter regime for this phase and in the
vicinity of the Mott transition, we find that an orbital selective Mott state
has nearly as competitive a ground state energy.",1202.6115v1
2015-07-17,Transverse spin and spin-orbit coupling in silicon waveguides,"Evanescent and tightly confined propagating waves exhibit a remarkable
transverse spin density since the longitudinal component of the electric field
is not negligible. In this work, we obtain via numerical simulations the
electric field components of the fundamental guided modes of two waveguides
typically used in silicon photonics: the strip and the slot waveguide. We
obtain the relation between transverse and longitudinal field components, the
transverse spin densities and other important parameters, such as the
longitudinal component of the so-called Belinfante spin momentum density. By
asymmetrically placing a circularly-polarized point-like dipole source in
regions showing local circular polarization, the guided mode is excited
unidirectionally via spin-orbit coupling. In contrast to metal plates
supporting surface plasmons, the multimode behavior of silicon waveguides
results in different spin-orbit coupling properties for each guided mode. Our
results may find application in silicon photonic devices, integrated quantum
optics and polarization manipulation at the nanoscale.",1507.04859v2
2010-05-28,"Terahertz radiation-induced conductivity, Kerr and Faraday angles, and spin textures in a two-dimensional electron gas with spin-orbit coupling subjected to a high magnetic field and periodic potential","The terahertz radiation-induced conductivity and dielectric polarization
tensors as well as the Faraday and Kerr rotation angles and the non-equilibrium
spin textures are studied for two-dimensional electron gas with strong
spin-orbit coupling subjected to high magnetic field and to tunable periodic
potential of a two-dimensional gated superlattice. It is found that both real
and imaginary parts of the frequency-dependent induced conductivity approach
maximum values with sharp and detectable peaks at frequencies corresponding to
the inter-subband transitions between spin-split magnetic subbands. The
observed properties of the conductivity tensor frequency dependence are applied
for the description of the Kerr and Faraday rotation angles which can be used
as another experimental tool for describing the electron gas in periodic
structures with significant spin-orbit coupling. The formation of
radiation-induced spin textures is predicted having both in-plane and
out-of-plane components with space distribution scale comparable to the
superlattice cell size which can be observed experimentally.",1005.5219v2
2019-10-10,Momentum space imaging of locally noncentrosymmetric superconductors,"The failure of spatial inversion symmetry in noncentrosymmetric materials
introduces two different types of spin-independent and spin-dependent electron
hopping. The spin-dependent term can be translated into a quasi-spin-orbit
coupling and may affect the electronic structure. In the locally
noncentrosymmetric crystals, the presence of a sublattice degree of freedom
generates a distinction between the inter- and intra-sublattice hopping
integrals. The spin-dependent part of the former (latter), which is even (odd)
under parity, is called symmetric (antisymmetric) quasi-spin-orbit coupling.
Here, we show the consequences of such quasi-spin-orbit couplings on the
electronic band structure and study their characteristic features via the
quasiparticle interference method. We extend our discussions to a realistic
class of materials, known as transition metal oxides.",1910.04513v2
2021-07-22,Variability of electron and hole spin qubits due to interface roughness and charge traps,"Semiconductor spin qubits may show significant device-to-device variability
in the presence of spin-orbit coupling mechanisms. Interface roughness, charge
traps, layout or process inhomogeneities indeed shape the real space wave
functions, hence the spin properties. It is, therefore, important to understand
how reproducible the qubits can be, in order to assess strategies to cope with
variability, and to set constraints on the quality of materials and
fabrication. Here we model the variability of single qubit properties (Larmor
and Rabi frequencies) due to disorder at the Si/SiO$_2$ interface (roughness,
charge traps) in metal-oxide-semiconductor devices. We consider both electron
qubits (with synthetic spin-orbit coupling fields created by micro-magnets) and
hole qubits (with intrinsic spin-orbit coupling). We show that charge traps are
much more limiting than interface roughness, and can scatter Rabi frequencies
over one order of magnitude. We discuss the implications for the design of spin
qubits and for the choice of materials.",2107.10902v2
2023-05-24,Theory of spin-polarized high-resolution electron energy loss spectroscopy from nonmagnetic surfaces with a large spin-orbit coupling,"The scattering theory of low-energy (slow) electrons has been developed by
Evans and Mills [Phys. Rev. B 5, 4126 (1972)]. The formalism is merely based on
the electrostatic Coulomb interaction of the scattering electrons with the
charge-density fluctuations above the surface and can describe most of the
interesting features observed in the high-resolution electron energy-loss
spectroscopy experiments. Here we extend this theory by including the
spin-orbit coupling in the scattering process. We discuss the impact of this
interaction on the scattering cross section. In particular, we discuss cases in
which a spin-polarized electron beam is scattered from nonmagnetic surfaces
with a strong spin-orbit coupling. We show that under some assumptions one can
derive an expression for the scattering cross section, which can be used for
numerical calculations of the spin-polarized spectra recorded by spin-polarized
high-resolution electron energy-loss spectroscopy experiments.",2305.14887v1
2006-08-11,Fulde-Ferrel-Larkin-Ovchinnikov State due to Antisymmetric Spin-Orbit-Coupling in Noncentrosymmetric Superconductivity CePt$_3$Si,"When the inversion symmetry is broken, the spin-orbit coupling reduces the
transition temperature of some types of spin triplet superconductivity, which
is similar to the case that magnetic field reduces the spin singlet
superconductivity due to Zeeman splitting. It is well known that
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state of spin singlet superconductivity
is realized near the Pauli limit (or Chandrasekhar-Clogston limit) of external
magnetic field. In FFLO state the amplitude of the order parameter is not
uniform in space. In this paper we study the FFLO state in the spin triplet
superconductivity in the absence of magnetic field due to the spin-orbit
coupling. Although the FFLO state is not realized in the simple model with
spherical Fermi surface, it will be stabilized if some condition is favorable
for it. We discuss the possibility of FFLO state in CePt$_3$Si in the absence
of external magnetic field.",0608256v1
2006-09-29,Nonuniform Spin Triplet Superconductivity due to Antisymmetric Spin-Orbit Coupling in Noncentrosymmetric Superconductor CePt$_3$Si,"We show that the nonuniform state (Fulde-Ferrel-Larkin-Ovchinnikov (FFLO)
state) of the spin triplet superconductivity in noncentrosymmetric systems is
stabilized by antisymmetric spin-orbit coupling even if the magnetic field is
absent. The transition temperature of the spin triplet superconductivity is
reduced by the antisymmetric spin-orbit coupling in general. This pair breaking
effect is shown to be similar to the Pauli pair breaking effect due to magnetic
field for the spin singlet superconductivity, in which FFLO state is stabilized
near the Pauli limit (or Chandrasekhar-Clogston limit) of external magnetic
field. Since there are gapless excitations in nonuniform superconducting state,
some physical quantities such as specific heat and penetration depth should
obey the power low temperature-dependences. We discuss the possibility of the
realization of nonuniform state in CePt$_3$Si.",0609751v1
2007-08-20,Density Functional Theory Characterization of the Multiferroicity in Spin Spiral Chain Cuprates,"The ferroelectricity of the spiral magnets LiCu2O2 and LiCuVO4 was examined
by calculating the electric polarizations of their spin spiral states on the
basis of density functional theory with spin-orbit coupling. Our work
unambiguously reveals that spin-orbit coupling is responsible for the
ferroelectricity with the primary contribution from the spin-orbit coupling on
the Cu sites, but the asymmetric density distribution responsible for the
electric polarization occurs mainly around the O atoms. The electric
polarization is calculated to be much greater for the ab- than for the bc-plane
spin spiral. The observed spin-spiral plane is found to be consistent with the
observed direction of the electric polarization for LiCuVO4, but inconsistent
for LiCu2O2.",0708.2582v2
2011-06-06,Quantum Spin Hall Insulators with Interactions and Lattice Anisotropy,"We investigate the interplay between spin-orbit coupling and
electron-electron interactions on the honeycomb lattice combining the cellular
dynamical mean-field theory and its real space extension with analytical
approaches. We provide a thorough analysis of the phase diagram and temperature
effects at weak spin-orbit coupling. We systematically discuss the stability of
the quantum spin Hall phase toward interactions and lattice anisotropy
resulting in the plaquette-honeycomb model. We also show the evolution of the
helical edge states characteristic of quantum spin Hall insulators as a
function of Hubbard interaction and anisotropy. At very weak spin-orbit
coupling and intermediate electron-electron interactions, we substantiate the
existence of a quantum spin liquid phase.",1106.0943v2
2012-10-25,Circular dichroism in angle-resolved photoemission spectroscopy of topological insulators,"Topological insulators are a new phase of matter that exhibits exotic surface
electronic properties. Determining the spin texture of this class of material
is of paramount importance for both fundamental understanding of its
topological order and future spin-based applications. In this article, we
review the recent experimental and theoretical studies on the differential
coupling of left- versus right-circularly polarized light to the topological
surface states in angle-resolved photoemission spectroscopy. These studies have
shown that the polarization of light and the experimental geometry plays a very
important role in both photocurrent intensity and spin polarization of
photoelectrons emitted from the topological surface states. A general
photoemission matrix element calculation with spin-orbit coupling can
quantitatively explain the observations and is also applicable to topologically
trivial systems. These experimental and theoretical investigations suggest that
optical excitation with circularly polarized light is a promising route towards
mapping the spin-orbit texture and manipulating the spin orientation in
topological and other spin-orbit coupled materials.",1210.6941v1
2013-05-10,Spin dynamics in a spin-orbit coupled Fermi gas,"We study the dynamics of a non-degenerate, harmonically trapped Fermi gas
following a sudden ramp of the spin-orbit coupling strength. In the
non-interacting limit, we solve the Boltzmann equation in the presence of spin
orbit coupling analytically, and derive expressions for the dynamics of an
arbitrary initial spin state. In particular we show that for a fully spin
polarized initial state, the total magnetization exhibits collapse and revival
dynamics in time with a period set by the trapping potential. In real space,
this corresponds to oscillations between a fully polarized state and a spin
helix. We numerically study the effect of interactions on the dynamics using a
collisionless Boltzmann equation.",1305.2443v3
2016-02-15,Kubo-Bastin approach for the spin Hall conductivity of decorated graphene,"Theoretical predictions and recent experimental results suggest one can
engineer spin Hall effect in graphene by enhancing the spin-orbit coupling in
the vicinity of an impurity. We use a Chebyshev expansion of the Kubo-Bastin
formula to compute the spin conductivity tensor for a tight-binding model of
graphene with randomly distributed impurities absorbed on top of carbon atoms.
We model the impurity-induced spin-orbit coupling with a graphene-only
Hamiltonian that takes into account three different
contributions~\cite{Gmitra2013} and show how the spin Hall and longitudinal
conductivities depend on the strength of each spin-orbit coupling and the
concentration of impurities. Additionally, we calculate the real-space
projection of the density of states in the vicinity of the Dirac point for
single and multiple impurities and correlate these results with the
conductivity calculations.",1602.04864v1
2017-12-30,Singlet-Quintet Mixing in Spin-Orbit Coupled Superconductors with j=3/2 Fermions,"In non-centrosymmetric superconductors, spin-orbit coupling can induce an
unconventional superconducting state with a mixture of s-wave spin-singlet and
p-wave spin-triplet channels, which leads to a variety of exotic phenomena,
including anisotropic upper critical field, magnetoelectric effect, topological
superconductivity, et al. It is commonly thought that inversion symmetry
breaking is substantial for pairing-mixed superconducting states. In this work,
we theoretically propose that a new type of pairing-mixed state, namely the
mixture of s-wave spin-singlet and d-wave spin-quintet channels, can be induced
by spin-orbit coupling even in the presence of inversion symmetry when
electrons effectively carry ""spin-3/2"" in superconductors. As a physical
consequence of the singlet-quintet pairing mixing, topological nodal-line
superconductivity is found in such system and gives rise to flat surface
Majorana bands. Our work provides a possible explanation of unconventional
superconducting behaviors observed in superconducting half-Heusler compounds.",1801.00083v2
2020-01-23,Magnetic oscillations induced by phonons in non-magnetic materials,"An unexpected finding two decades ago demonstrated that Shockley electron
states in noble metal surfaces are spin-polarized, forming a circulating spin
texture in reciprocal space. The fundamental role played by the spin degree of
freedom was then revealed, even for a non-magnetic system, whenever the
spin-orbit coupling was present with some strength. Here we demonstrate that
similarly to electrons in the presence of spin-orbit coupling, the propagating
vibrational modes are also accompanied by a well-defined magnetic oscillation
even in non-magnetic materials. Although this effect is illustrated by
considering a single layer of the WSe2 dichalogenide, the phenomenon is
completely general and valid for any non-magnetic material with spin-orbit
coupling. The emerging phonon-induced magnetic oscillation acts as an
additional effective flipping mechanism for the electron spin and its
implications in the transport and scattering properties of the material are
evident and profound.",2001.08629v1
2003-03-12,Unusual Symmetries in the Kugel-Khomskii Hamiltonian,"The Kugel-Khomskii Hamiltonian for cubic titanates describes spin and orbital
superexchange interactions between $d^1$ ions having three-fold degenerate
$t_{2g}$ orbitals. Since orbitals do not couple along ""inactive"" axes,
perpendicular to the orbital planes, the total number of electrons in $|\alpha
>$ orbitals in any such plane and the corresponding total spin are both
conserved. A Mermin-Wagner construction shows that there is no long-range spin
ordering at nonzero temperatures. Inclusion of spin-orbit coupling allows such
ordering, but even then the excitation spectrum is gapless due to a continuous
symmetry. Thus, the observed order and gap require more symmetry breaking
terms.",0303219v1
2018-09-27,Hund's coupling stabilized superconductivity in the presence of spin-orbit interactions,"The intraorbital repulsive Hubbard interaction cannot lead to attractive
superconducting pairing states, except through the Kohn-Luttinger mechanism.
This situation may change when we include additional local interactions such as
the interorbital repulsion $U^\prime$ and Hund's interactions $J$. Adding these
local interactions, we study the nature of the superconducting pairs in systems
with tetragonal crystal symmetry including the $d_{xz}$ and $d_{yz}$ orbitals,
and in octahedral systems including all three of $d_{xz}$, $d_{yz}$, and
$d_{xy}$ orbitals. In the tetragonal case, spin-orbit interactions can
stabilize attractive pairing channels containing spin triplet, orbital singlet
character. Depending on the form of spin-orbit coupling, pairing channels
belonging to degenerate, non-trivial irreducible representations may be
stabilized. In the octahedral case, the pairing interactions of superconducting
channels are found to depend critically on the number of bands crossing the
Fermi energy.",1809.10714v1
2020-05-13,Understanding Semiconductor Valence Mass,"The Bloch theorem mathematically proves that in a periodic crystal, electrons
can acquire a negative mass. The present work aims to provide a physical
understanding for why this is so. We successively analyze the consequences of
the 3-fold orbital valence state coupling to (i) a non-degenerate orbital level
in the conduction band, (ii) a 3-fold orbital level in the conduction band, and
(iii) spin states through spin-orbit interaction. We show that it is not at all
trivial for valence electrons to acquire a negative mass for whatever their
momentum with respect to the crystal axes: it is necessary to not only have a
coupling to a degenerate orbital conduction level, but also a symmetry breaking
of the 3-fold valence subspace by the spin quantization axis, as induced by
spin-orbit interaction. Due to the relativistic origin of this interaction, the
existence of negative valence masses thus constitutes an unexpected signature
of quantum relativity.",2005.06328v1
2021-03-11,"Perpendicular magnetic anisotropy at Fe/Au(111) interface studied by Mössbauer, x-ray absorption, and photoemission spectroscopies","The origin of the interfacial perpendicular magnetic anisotropy (PMA) induced
in the ultrathin Fe layer on the Au(111) surface was examined using
synchrotron-radiation-based M\""{o}ssbauer spectroscopy (MS), X-ray magnetic
circular dichroism (XMCD), and angle-resolved photoemission spectroscopy
(ARPES). To probe the detailed interfacial electronic structure of orbital
hybridization between the Fe 3$d$ and Au 6$p$ bands, we detected the
interfacial proximity effect, which modulates the valence-band electronic
structure of Fe, resulting in PMA. MS and XMCD measurements were used to detect
the interfacial magnetic structure and anisotropy in orbital magnetic moments,
respectively. $In$-$situ$ ARPES also confirms the initial growth of Fe on large
spin-orbit coupled surface Shockley states under Au(111) modulated electronic
states in the vicinity of the Fermi level. This suggests that PMA in the
Fe/Au(111) interface originates from the cooperation effects among the spin,
orbital magnetic moments in Fe, and large spin-orbit coupling in Au. These
findings pave the way to develop interfacial PMA using $p$-$d$ hybridization
with a large spin-orbit interaction.",2103.06572v1
2021-07-15,Spin-orbit coupling and magnetism in $\rm Sr_2CrO_4$,"With octahedrally coordinated $t_{\rm 2g}$ orbitals which are active at
filling $n=2$, the $\rm Sr_2CrO_4$ compound exhibits rich interplay of
spin-orbital physics with tetragonal distortion induced crystal field tuning by
external agent such as pressure. Considering both reversed and restored crystal
field regimes, collective spin-orbital excitations are investigated in the
antiferromagnetic state using the generalized self consistent + fluctuations
approach including spin-orbit coupling (SOC). A transition is found from
staggered to entangled orbital order at critical SOC value in the realistic
regime. Behavior of the calculated energy scales of collective excitations with
crystal field is in striking similarity to that of the transition temperatures
with pressure as obtained from susceptibility and resistivity anomalies in
high-pressure studies.",2107.07214v3
2022-01-31,Precisely computing bound orbits of spinning bodies around black holes I: General framework and results for nearly equatorial orbits,"Very large mass ratio binary black hole systems are of interest both as a
clean limit of the two-body problem in general relativity, as well as for their
importance as sources of low-frequency gravitational waves. At lowest order,
the smaller body moves along a geodesic of the larger black hole's spacetime.
Post-geodesic effects include the gravitational self force, which incorporates
the backreaction of gravitational-wave emission, and the spin-curvature force,
which arises from coupling of the small body's spin to the black hole's
spacetime curvature. In this paper, we describe a method for precisely
computing bound orbits of spinning bodies about black holes. Our analysis
builds off of pioneering work by Witzany which demonstrated how to describe the
motion of a spinning body to linear order in the small body's spin. Exploiting
the fact that in the large mass-ratio limit spinning-body orbits are close to
geodesics and using closed-form results due to van de Meent describing
precession of the small body's spin along black hole orbits, we develop a
frequency-domain formulation of the motion which can be solved very precisely.
We examine a range of orbits with this formulation, focusing in this paper on
orbits which are eccentric and nearly equatorial (i.e., the orbit's motion is
$\mathcal{O}(S)$ out of the equatorial plane), but for which the small body's
spin is arbitrarily oriented. We discuss generic orbits with general small-body
spin orientation in a companion paper. We characterize the behavior of these
orbits and show how the small body's spin shifts the frequencies $\Omega_r$ and
$\Omega_\phi$ which affect orbital motion. These frequency shifts change
accumulated phases which are direct gravitational-wave observables,
illustrating the importance of precisely characterizing these quantities for
gravitational-wave observations. (Abridged)",2201.13334v2
2004-11-17,Violation of the Curie law in Na2V3O7 as the crystal-field and spin-orbit coupling effect,"We have shown that the observed drastic violation of the Curie-Weiss law in
Na2V3O7, reported in Phys. Rev. Lett. 90 (2003) 167202, is caused by
conventional crystal-field interactions and the intra-atomic spin-orbit
coupling of the V4+ ion. The fine discrete electronic structure of the 3d1
configuration, with a substantial orbital moment, is the reason for anomalous
low-temperature properties of Na2V3O7. According to the Quantum Atomistic
Solid-State Theory (QUASST) Na2V3O7 is expected to exhibit pronounced
heavy-fermion phenomena at low temperatures. This study confirm our earlier
claim that the orbital moment has to be unquenched in description of 3d-atom
compounds.
  PACS: 71.70.E, 75.10.D
  Keywords: crystal-field interactions, spin-orbit coupling, orbital moment,
Na2V3O7",0411455v1
2012-09-22,Dynamical Mean-Field Study of Local Pairing Interaction Mediated by Spin and Orbital Fluctuations in Iron Pnictide Superconductors,"We investigate the two-orbital Hubbard model, which reproduces the electron
and hole Fermi surfaces in the iron pnictide superconductors, in the presence
of the Jahn-Teller electron-phonon coupling by using the dynamical mean-field
theory. When the intra- and inter-orbital Coulomb interactions, $U$ and $U'$,
increase with $U=U'$, both the local spin and orbital susceptibilities,
$\chi_{s}$ and $\chi_{o}$, increase with $\chi_{s}=\chi_{o}$ because of the
spin-orbital symmetry. Due to the Hund's rule coupling $J$, $\chi_{s}$ is
enhanced and dominates over $\chi_{o}$ resulting in the repulsive local pairing
interaction $V_{\rm loc}>0$, while due to the electron-phonon coupling $g$,
$\chi_{o}$ is enhanced and dominates over $\chi_{s}$ resulting in the
attractive one $V_{\rm loc}<0$ which induces the intra-orbital s-wave pairing.
Remarkably, $V_{\rm loc}$ is weakly dependent on doping and can be attractive
for heavily electron-doped regime where the superconductivity is observed
without Fermi surface nesting.",1209.4954v2
2017-08-21,Spin-orbit coupling in three-orbital Kanamori impurity model and its relevance for transition-metal oxides,"We investigate the effects of the spin-orbit coupling (SOC) in a
three-orbital impurity model with Kanamori interaction using the numerical
renormalization group method. We focus on the impurity occupancy $N_d=2$
relevant to the dynamical mean-field theory studies of Hund's metals. Depending
on the strength of SOC $\lambda$ we identify three regimes: usual Hund's
impurity for $|\lambda|<\lambda_c$, van-Vleck non-magnetic impurity for
$\lambda > \lambda_c$, and a $J=2$ impurity for $\lambda < -\lambda_c$. They
all correspond to a Fermi liquid but with very different quasiparticle phase
shifts and different physical properties. The crossover between these regimes
is controlled by an emergent scale, the orbital Kondo temperature, $\lambda_c
=T_K^\mathrm{orb}$ that drops with increasing interaction strength. This
implies that oxides with strong electronic correlations are more prone to the
effects of the spin-orbit coupling.",1708.06089v1
2017-05-06,Exciton Polaritons in a Two-Dimensional Lieb Lattice with Spin-Orbit Coupling,"We study exciton-polaritons in a two-dimensional Lieb lattice of
micropillars. The energy spectrum of the system features two flat bands formed
from $S$ and $P_{x,y}$ photonic orbitals, into which we trigger bosonic
condensation under high power excitation. The symmetry of the orbital wave
functions combined with photonic spin-orbit coupling gives rise to emission
patterns with pseudospin texture in the flat band condensates. Our work shows
the potential of polariton lattices for emulating flat band Hamiltonians with
spin-orbit coupling, orbital degrees of freedom and interactions.",1705.03006v2
2023-10-25,Polar Kerr Effect in Multiband Spin-Orbit Coupled Superconductors,"We undertake a theoretical analysis to probe the Kerr spectrum within the
superconducting phase of strontium ruthenate, where the Kerr rotation
experiments demonstrate the existence of a superconducting state with broken
time reversal symmetry. We find that spin-orbit coupling changes the
hybridization along the Fermi surface's diagonal zone mainly affects Hall
transport. We show that the dominant Hall response arises mainly from the
quasi-1D orbitals $d_{yz}$ and $d_{xz}$, linked to their hybridization, while
other contributions are negligible. This establishes that, the breaking of time
reversal symmetry of quasi-1D orbitals can account for the existence of the
Kerr angle, irrespective of the order symmetry specific to the $d_{xy}$
orbital. Moreover, the optical Hall conductivity and Kerr angle estimated for
the hypothesised superconducting orders also closely match the experimental
findings, providing important novel insight on the role of the spin-orbit
coupling, hybridization, and emergent order.",2310.16623v1
2012-06-21,Magnetism and spin-orbit coupling in Ir-based double perovskites La$_(2-x$Sr$_x$CoIrO$_6$,"We have studied Ir spin and orbital magnetic moments in the double
perovskites La$_{2-x}$Sr$_x$CoIrO$_6$ by x-ray magnetic circular dichroism. In
La$_2$CoIrO$_6$, Ir$^{4+}$ couples antiferromagnetically to the weak
ferromagnetic moment of the canted Co$^{2+}$ sublattice and shows an unusually
large negative total magnetic moment (-0.38\,$\mu_{\text B}$/f.u.) combined
with strong spin-orbit interaction. In contrast, in Sr$_2$CoIrO$_6$, Ir$^{5+}$
has a paramagnetic moment with almost no orbital contribution. A simple
kinetic-energy-driven mechanism including spin-orbit coupling explains why Ir
is susceptible to the induction of substantial magnetic moments in the double
perovskite structure.",1206.4830v1
2012-09-21,Theory of spin-orbit coupling at LaAlO3/SrTiO3 interfaces and SrTiO3 surfaces,"The theoretical understanding of the spin-orbit coupling (SOC) effects at
LaAlO$_{3}$/SrTiO$_{3}$ interfaces and SrTiO$_{3}$ surfaces is still in its
infancy. We perform first-principles density-functional-theory calculations and
derive from these a simple tight-binding Hamiltonian, through a Wannier
function projection and group theoretical analysis. We find striking
differences to the standard Rashba theory for spin-orbit coupling in
semiconductor heterostructures due to multi-orbital effects: by far the biggest
SOC effect is at the crossing point of the $xy$ and $yz$ (or $zx$) orbitals;
and around the $\Gamma$ point a Rashba spin splitting with a cubic dependence
on the wave vector $\vec{k}$ is possible.",1209.4705v2
2014-09-30,Direct observation of spin-orbit coupling in iron-based superconductors,"Spin-orbit coupling (SOC) is a fundamental interaction in solids which can
induce a broad spectrum of unusual physical properties from topologically
non-trivial insulating states to unconventional pairing in superconductors. In
iron-based superconductors (IBS) its role has so far been considered
insignificant with the models based on spin- or orbital fluctuations pairing
being the most advanced in the field. Using angle-resolved photoemission
spectroscopy we directly observe a sizeable spin-orbit splitting in all main
families of IBS. We demonstrate that its impact on the low-energy electronic
structure and details of the Fermi surface topology is much stronger than that
of possible nematic ordering. Intriguingly, the largest pairing gap is always
supported exactly by SOC-induced Fermi surfaces.",1409.8669v2
2022-03-04,Interplay of the Jahn--Teller Effect and Spin-Orbit Coupling: The Case of Trigonal Vibronic Modes,"We study an interplay between the orbital degeneracy and spin-orbit coupling
giving rise to spin-orbital entangled states. As a specific example, we analyze
the interaction of electrons occupying triply degenerate single-ion $t_{2g}$
levels with trigonal vibronic modes (the $t\otimes T$ problem). A more general
problem of the electron-lattice interaction involving both tetragonal and
trigonal vibrations is also considered. It is shown that the result of such
interaction crucially depends on the occupation of $t_{2g}$ levels leading to
either the suppression or enhancement of the Jahn-Teller effect by the
spin-orbit coupling.",2203.02243v2
2023-08-20,Exact solutions of a spin-orbit coupling model in two-dimensional central-potentials and quantum-classical correspondence,"In this paper we present both the classical and quantum periodic-orbits of a
neutral spinning particle constrained in two-dimensional central-potentials
with a cylindrically symmetric electric-field in addition which leads to an
effective non-Abelian gauge field generated by the spin-orbit coupling.
Coherent superposition of orbital angular-eigenfunctions obtained explicitly at
the condition of zero-energy exhibits the quantum-classical correspondence in
the meaning of exact coincidence between classical orbits and spatial patterns
of quantum wave-functions, which as a consequence results in the fractional
quantization of orbital angular-momentum by the requirement of the same
rotational symmetry of quantum and classical orbits. A non-Abelian anyon-model
emerges in a natural way.",2308.10256v1
2007-02-27,Pairing symmetry in a two-orbital Hubbard model on a square lattice,"We investigate superconductivity in a two-orbital Hubbard model on a square
lattice by applying fluctuation exchange approximation. In the present model,
the symmetry of the two orbitals are assumed to be that of an s orbital. Then,
we find that an s-wave spin-triplet orbital-antisymmetric state and a p-wave
spin-singlet orbital-antisymmetric state appear when Hund's rule coupling is
large. These states are prohibited in a single-orbital model within states with
even frequency dependence, but allowed for multi-orbital systems. We also
discuss pairing symmetry in other models which are equivalent to the
two-orbital Hubbard model except for symmetry of orbitals. Finally, we show
that pairing states with a finite total momentum, even without a magnetic
field, are possible in a system with two Fermi-surfaces.",0702624v2
2020-06-12,Occupation switching of $d$ orbitals probed via hyperfine interactions in vanadium dioxide,"Metal-insulator transition was microscopically investigated by
orbital-resolved nuclear magnetic resonance (OR-NMR) spectroscopy in a single
crystal of vanadium dioxide VO$_2$. Observations of the anisotropic $^{51}$V
Knight shift and the nuclear quadrupole frequency allow us to evaluate
orbital-dependent spin susceptibility and $d$ orbital occupations. The result
is consistent with the degenerated $t_{2g}$ orbitals in a correlated metallic
phase and the $d$ orbital ordering in a nonmagnetic insulating phase. The
predominant orbital pointing along the chain facilitates a spin-singlet
formation triggering metal-insulator transition. The asymmetry of magnetic and
electric hyperfine tensors suggests the $d$ orbital reformation favored by a
low-symmetry crystal field, forming a localized molecular orbital. The result
highlights the cooperative electron correlation and electron-phonon coupling in
Mott transition with orbital degrees of freedom.",2006.07030v1
2011-02-02,Elastic Instabilities within Antiferromagnetically Ordered Phase in the Orbitally-Frustrated Spinel GeCo$_2$O$_4$,"Ultrasound velocity measurements of the orbitally-frustrated GeCo$_2$O$_4$
reveal unusual elastic instabilities due to the phonon-spin coupling within the
antiferromagnetic phase. Shear moduli exhibit anomalies arising from the
coupling to short-range ferromagnetic excitations. Diplike anomalies in the
magnetic-field dependence of elastic moduli reveal magnetic-field-induced
orbital order-order transitions. These results strongly suggest the presence of
geometrical orbital frustration which causes novel orbital phenomena within the
antiferromagnetic phase.",1102.0469v3
2019-02-14,Anomalous Spin-Orbit Torques in Magnetic Single-Layer Films,"Spin-orbit interaction (SOI) couples charge and spin transport, enabling
electrical control of magnetization. A quintessential example of SOI-induced
transport is the anomalous Hall effect (AHE), first observed in 1880, in which
an electric current perpendicular to the magnetization in a magnetic film
generates charge accumulation on the surfaces. Here we report the observation
of a counterpart of the AHE that we term the anomalous spin-orbit torque
(ASOT), wherein an electric current parallel to the magnetization generates
opposite spin-orbit torques on the surfaces of the magnetic film. We interpret
the ASOT as due to a spin-Hall-like current generated with an efficiency of
0.053+/-0.003 in Ni80Fe20, comparable to the spin Hall angle of Pt. Similar
effects are also observed in other common ferromagnetic metals, including Co,
Ni, and Fe. First principles calculations corroborate the order of magnitude of
the measured values. This work suggests that a strong spin current with spin
polarization transverse to magnetization can exist in a ferromagnet, despite
spin dephasing. It challenges the current understanding of spin-orbit torque in
magnetic/nonmagnetic bilayers, in which the charge-spin conversion in the
magnetic layer has been largely neglected.",1902.05490v1
2015-03-26,Spin-orbit interaction in bent carbon nanotubes: resonant spin transitions,"We develop an effective tight-binding Hamiltonian for spin-orbit (SO)
interaction in bent carbon nanotubes (CNT) for the electrons forming the $\pi$
bonds between the nearest neighbor atoms. We account for the bend of the CNT
and the intrinsic spin-orbit interaction which introduce mixing of $\pi$ and
$\sigma$ bonds between the $p_z$ orbitals along the CNT. The effect contributes
to the main origin of the SO coupling--the folding of the graphene plane into
the nanotube. We discuss the bend-related contribution of the SO coupling for
resonant single-electron spin and charge transitions in a double quantum dot.
We report that although the effect of the bend-related SO coupling is weak for
the energy spectra, it produces a pronounced increase of the spin transition
rates driven by an external electric field. We find that spin-flipping
transitions driven by alternate electric fields have usually larger rates when
accompanied by charge shift from one dot to the other. Spin-flipping transition
rates are non-monotonic functions of the driving amplitude since they are
masked by stronger spin-conserving charge transitions. We demonstrate that the
fractional resonances--counterparts of multiphoton transitions for atoms in
strong laser fields--occurring in electrically controlled nanodevices already
at moderate ac amplitudes--can be used to maintain the spin-flip transitions.",1503.07764v2
2015-09-30,Generic helical edge states due to Rashba spin-orbit coupling in a topological insulator,"We study the helical edge states of a two-dimensional topological insulator
without axial spin symmetry due to the Rashba spin-orbit interaction. Lack of
axial spin symmetry can lead to so-called generic helical edge states, which
have energy-dependent spin orientation. This opens the possibility of inelastic
backscattering and thereby nonquantized transport. Here we find analytically
the new dispersion relations and the energy dependent spin orientation of the
generic helical edge states in the presence of Rashba spin-orbit coupling
within the Bernevig-Hughes-Zhang model, for both a single isolated edge and for
a finite width ribbon. In the single-edge case, we analytically quantify the
energy dependence of the spin orientation, which turns out to be weak for a
realistic HgTe quantum well. Nevertheless, finite size effects combined with
Rashba spin-orbit coupling result in two avoided crossings in the energy
dispersions, where the spin orientation variation of the edge states is very
significantly increased for realistic parameters. Finally, our analytical
results are found to compare well to a numerical tight-binding regularization
of the model.",1509.09183v2
2015-12-07,An anisotropic spin model of strong spin-orbit-coupled triangular antiferromagnets,"Motivated by the recent experimental progress on the strong
spin-orbit-coupled rare earth triangular antiferromagnet, we analyze the highly
anisotropic spin model that describes the interaction between the
spin-orbit-entangled Kramers' doublet local moments on the triangular lattice.
We apply the Luttinger-Tisza method, the classical Monte Carlo simulation, and
the self-consistent spin wave theory to analyze the anisotropic spin
Hamiltonian. The classical phase diagram includes the 120-degree state and two
distinct stripe ordered phases. The frustration is very strong and
significantly suppresses the ordering temperature in the regimes close to the
phase boundary between two ordered phases. Going beyond the semiclassical
analysis, we include the quantum fluctuations of the spin moments within a
self-consistent Dyson-Maleev spin-wave treatment. We find that the strong
quantum fluctuations melt the magnetic order in the frustrated regions. We
explore the magnetic excitations in the three different ordered phases as well
as in strong magnetic fields. Our results provide a guidance for the future
theoretical study of the generic model and are broadly relevant for strong
spin-orbit-coupled triangular antiferromagnets such as YbMgGaO4, RCd3P3,
RZn3P3, RCd3As3, RZn3As3, and R2O2CO3.",1512.02151v3
2009-04-24,Anisotropic magnetoresistance of spin-orbit coupled carriers scattered from polarized magnetic impurities,"Anisotropic magnetoresistance (AMR) is a relativistic magnetotransport
phenomenon arising from combined effects of spin-orbit coupling and broken
symmetry of a ferromagnetically ordered state of the system. In this work we
focus on one realization of the AMR in which spin-orbit coupling enters via
specific spin-textures on the carrier Fermi surfaces and ferromagnetism via
elastic scattering of carriers from polarized magnetic impurities. We report
detailed heuristic examination, using model spin-orbit coupled systems, of the
emergence of positive AMR (maximum resistivity for magnetization along
current), negative AMR (minimum resistivity for magnetization along current),
and of the crystalline AMR (resistivity depends on the absolute orientation of
the magnetization and current vectors with respect to the crystal axes)
components. We emphasize potential qualitative differences between pure
magnetic and combined electro-magnetic impurity potentials, between short-range
and long-range impurities, and between spin-1/2 and higher spin-state carriers.
Conclusions based on our heuristic analysis are supported by exact solutions to
the integral form of the Boltzmann transport equation in archetypical
two-dimensional electron systems with Rashba and Dresselhaus spin-orbit
interactions and in the three-dimensional spherical Kohn-Littinger model. We
include comments on the relation of our microscopic calculations to standard
phenomenology of the full angular dependence of the AMR, and on the relevance
of our study to realistic, two-dimensional conduction-band carrier systems and
to anisotropic transport in the valence band of diluted magnetic
semiconductors.",0904.3785v2
2020-10-15,Longitudinal and transverse electric field manipulation of hole spin-orbit qubits in one-dimensional channels,"Holes confined in semiconductor nanostructures realize qubits where the
quantum mechanical spin is strongly mixed with the quantum orbital angular
momentum. The remarkable spin-orbit coupling allows for fast all electrical
manipulation of such qubits. We study an idealization of a CMOS device where
the hole is strongly confined in one direction (thin film geometry), while it
is allowed to move more extensively along a one-dimensional channel. Static
electric bias and $ac$ electrical driving are applied by metallic gates
arranged along the channel. In quantum devices based on materials with a bulk
inversion symmetry, such as silicon or germanium, there exists different
possible spin-orbit coupling based mechanisms for qubit manipulation. One of
them, the $g$-tensor magnetic resonance ($g$-TMR), relies on the dependence of
the effective $g$-factors on the electrical confinement. In this configuration
the hole is driven by an $ac$ field parallel to the static electric field and
perpendicular to the channel (transverse driving). Another mechanism, which we
refer to here as iso-Zeeman electric dipole spin resonance (IZ-EDSR), is due to
the Rashba spin-orbit coupling that leads to an effective time-dependent
magnetic field experienced by the pseudo-spin oscillating along the quantum
channel (longitudinal driving). We compare these two modes of operation and we
describe the conditions where the magnitudes of the Rabi frequencies are the
largest. Different regimes can be attained by electrical tuning where the
coupling to the $ac$ electric field is made either weak or strong...",2010.07787v2
1998-07-02,"Diamagnetic Effects, Spin Dependent Fermi Surfaces, and the Giant Magnetoresistance in Metallic Multilayers","We study the role of diamagnetic effects on the transport properties of
metallic magnetic multilayers to elucidate whether they can explain the Giant
Magnetoresistance (GMR) effect observed in those systems. Realistic Fermi
surface topologies in layered ferromagnets are taken into account, with the
possibilities of different types of orbits depending on the electron spin. Both
configurations, with ferromagnetic and anti-ferromagnetic couplings between
magnetic layers, are considered and the transmission coefficient for scattering
at the interface boundary is modelled to include magnetic and roughness
contributions. We assume that scattering processes conserve the electron spin,
due to large spin diffusion lengths in multilayer samples. Scattering from the
spacer mixes different orbit topologies in a way similar to magnetic
`breakdown' phenomena. For antiferromagnetic coupling, majority and minority
spins are interchanged from one magnetic layer to the next. Cyclotron orbits
are also traveled in opposite directions, producing a compensation-like effect
that yields a huge GMR, particularly for closed orbits. For open orbits, one
may get the `inverse' magnetoresistance effect along particular directions.",9807026v1
2007-10-21,Two-dimensional magnetoexcitons in the presence of spin-orbit coupling,"We study theoretically the effect of spin-orbit coupling on quantum well
excitons in a strong magnetic field. We show that, in the presence of an
in-plane field component, the excitonic absorption spectrum develops a
double-peak structure due to hybridization of bright and dark magnetoexcitons.
If the Rashba and Dresselhaus spin-orbit constants are comparable, the
magnitude of splitting can be tuned in a wide interval by varying the azimuthal
angle of the in-plane field. We also show that the interplay between spin-orbit
and Coulomb interactions leads to an anisotropy of exciton energy dispersion in
the momentum plane. The results suggest a way for direct optical measurements
of spin-orbit parameters.",0710.3797v2
2009-07-04,Mott Insulating Ground State and its Proximity to Spin-Orbit Insulators in Na$_{2}$IrO$_{3}$,"We present an anti-ferromagnetically ordered ground state of
  Na$_{2}$IrO$_{3}$ based on density-functional-theory calculations including
both spin-orbit coupling and on-site Coulomb interaction $U$. We show that the
splitting of $e_{g}'$ doublet states by the strong spin-orbit coupling is
mainly responsible for the intriguing nature of its insulating gap and magnetic
ground state. Due to its proximity to the spin-orbit insulator phase, the
magnetic ordering as obtained with finite $U$ is found to exhibit a strong
in-plane anisotropy. The phase diagram of Na$_{2}$IrO$_{3}$ suggests a possible
interplay between spin-orbit insulator and Mott anti-ferromagnetic insulator
phases.",0907.0743v1
2020-07-15,Janus Monolayers of Magnetic Transition Metal Dichalcogenides as an All-in-One Platform for Spin-Orbit Torque,"We theoretically predict that vanadium-based Janus dichalcogenide monolayers
constitute an ideal platform for spin-orbit-torque memories. Using first
principles calculations, we demonstrate that magnetic exchange and magnetic
anisotropy energies are higher for heavier chalcogen atoms, while the broken
inversion symmetry in the Janus form leads to the emergence of Rashba-like
spin-orbit coupling. The spin-orbit torque efficiency is evaluated using
optimized quantum transport methodology and found to be comparable to heavy
nonmagnetic metals. The coexistence of magnetism and spin-orbit coupling in
such materials with tunable Fermi-level opens new possibilities for monitoring
magnetization dynamics in the perspective of non-volatile magnetic random
access memories.",2007.07579v1
2013-08-14,Spin-orbit interaction induced singularity of the charge density relaxation propagator,"The charge density relaxation propagator of a two dimensional electron
system, which is the slope of the imaginary part of the polarization function,
exhibits singularities for bosonic momenta having the order of the spin-orbit
momentum and depending on the momentum orientation. We have provided an
intuitive understanding for this non-analytic behavior in terms of the inter
chirality subband electronic transitions, induced by the combined action of
Bychkov-Rashba (BR) and Dresselhaus (D) spin-orbit coupling. It is shown that
the regular behavior of the relaxation propagator is recovered in the presence
of only one BR or D spin-orbit field or for spin-orbit interaction with equal
BR and D coupling strengths. This creates a new possibility to influence
carrier relaxation properties by means of an applied electric field.",1308.3264v2
2014-06-04,Vortices and vortex states in Rashba spin-orbit-coupled condensates,"The Rashba spin-orbit coupling is equivalent to the finite Yang-Mills flux of
a static SU(2) gauge field. It gives rise to the protected edge states in
two-dimensional topological band-insulators, much like magnetic field yields
the integer quantum Hall effect. An outstanding question is which collective
topological behaviors of interacting particles are made possible by the Rashba
spin-orbit coupling. Here we addresses one aspect of this question by exploring
the Rashba SU(2) analogues of vortices in superconductors. Using the
Landau-Ginzburg approach and conservation laws, we classify the prominent
two-dimensional condensates of two- and three-component spin-orbit-coupled
bosons, and characterize their vortex excitations. There are two prominent
types of condensates that take advantage of the Rashba spin-orbit coupling.
Their vortices exist in multiple flavors whose number is determined by the spin
representation, and interact among themselves through logarithmic or linear
potentials as a function of distance. The vortices that interact linearly
exhibit confinement and asymptotic freedom similar to quarks in quantum
chromodynamics. One of the two condensate types supports small metastable
neutral quadruplets of vortices, and their tiles as metastable vortex lattices.
Quantum melting of such vortex lattices could give rise to non-Abelian
fractional topological insulators, SU(2) analogues of fractional quantum Hall
states. The physical systems in which these states could exist are trapped two-
and three-component bosonic ultra-cold atoms subjected to artificial gauge
fields, as well as solid-state quantum wells made either from Kondo insulators
such as SmB$_6$ or conventional topological insulators interfaced with
conventional superconductors.",1406.1198v1
2018-09-06,Topological Hall Effect in Magnetic Topological Insulator Films,"Geometric Berry phase can be induced either by spin-orbit coupling, giving
rise to the anomalous Hall effect in ferromagnetic materials, or by chiral spin
texture, such as skyrmions, leading to the topological Hall effect. Recent
experiments have revealed that both phenomena can occur in topological
insulator films with magnetic doping, thus providing us with an intriguing
platform to study the interplay between these two phenomena. In this work, we
numerically study the anomalous Hall and topological Hall effects in a
four-band model that can properly describe the quantum well states in the
magnetic topological insulator films by combining Landauer-Buttiker formula and
the iterative Green's function method. Our numerical results suggest that
spin-orbit coupling in this model plays a different role in the quantum
transport in the clean and disordered limits. In the clean limit, spin-orbit
coupling mainly influences the longitudinal transport but does not have much
effect on topological Hall conductance. Such behavior is further studied
through the analytical calculation of scattering cross-section due to skyrmion
within the four-band model. In the disordered limit, the longitudinal transport
is determined by disorder scattering and spin-orbit coupling is found to affect
strongly the topological Hall conductance. This sharp contrast unveils a
dramatic interplay between spin-orbit coupling and disorder effect in
topological Hall effect in magnetic topological insulator systems.",1809.02210v1
2005-03-29,Triplet-Singlet Spin Relaxation via Nuclei in a Double Quantum Dot,"The spin of a confined electron, when oriented originally in some direction,
will lose memory of that orientation after some time. Physical mechanisms
leading to this relaxation of spin memory typically involve either coupling of
the electron spin to its orbital motion or to nuclear spins. Relaxation of
confined electron spin has been previously measured only for Zeeman or exchange
split spin states, where spin-orbit effects dominate relaxation, while spin
flips due to nuclei have been observed in optical spectroscopy studies. Using
an isolated GaAs double quantum dot defined by electrostatic gates and direct
time domain measurements, we investigate in detail spin relaxation for
arbitrary splitting of spin states. Results demonstrate that electron spin
flips are dominated by nuclear interactions and are slowed by several orders of
magnitude when a magnetic field of a few millitesla is applied. These results
have significant implications for spin-based information processing.",0503687v3
2002-01-11,Spin Accumulation in Quantum Wires with Strong Rashba Spin-Orbit Coupling,"We present analytical and numerical results for the effect of Rashba
spin-orbit coupling on band structure, transport, and interaction effects in
quantum wires when the spin precession length is comparable to the wire width.
In contrast to the weak-coupling case, no common spin-quantization axis can be
defined for eigenstates within a single-electron band. The situation with only
the lowest spin-split subbands occupied is particularly interesting because
electrons close to Fermi points of the same chirality can have approximately
parallel spins. We discuss consequences for spin-dependent transport and
effective Tomonaga-Luttinger descriptions of interactions in the quantum wire.",0201164v2
2004-09-11,Andreev reflection resonant tunneling through a precessing spin,"We investigate Andreev reflection (AR) resonant tunneling through a
precessing spin which is coupled to a normal metallic lead and a
superconducting lead. The formula of the AR conductance at zero temperature is
obtained as a function of chemical potential and azimuthal angle of the spin
precessing by using the nonequilibrium Green function method. It is found that
as the local spin precesses in a weak external magnetic field at Larmor
frequency $\omega_l$, the AR tunneling conductance exhibits an oscillation at
the frequency $2\omega_l$ alone. The amplitude of AR conductance oscillation
enhances with spin-flip tunneling coupling increasing. The study also shows
that spin-orbit interaction in tunneling barriers is crucial for the
oscillations of AR conductance. The effect of spin-flip tunneling coupling
caused by spin-orbit interaction and local spin precessing on resonant behavior
of the AR conductance are examined.",0409286v1
2006-01-30,Boundary conditions for spin diffusion,"We develop a general scheme of deriving boundary conditions for spin-charge
coupled transport in disordered systems with spin-orbit interactions. To
illustrate the application of the method, we explicitly derive boundary
conditions for spin diffusion in the Rashba model. Due to the surface spin
precession, the boundary conditions are non-trivial and contain terms, which
couple different components of the spin density. We argue that boundary
conditions and the corresponding electric-field-induced spin accumulation
generally depend on the nature of the boundary and therefore the spin Hall
effect in a spin-orbit coupled system can be viewed as a non-universal edge
phenomenon.",0601677v4
2006-02-18,Spin conversion rates due to dipolar interactions in mono-isotopic quantum dots at vanishing spin-orbit coupling,"Dipolar interaction between the magnetic moments of electrons is studied as a
source for electron spin decay in quantum dots or arrays of quantum dots. This
magnetic interaction will govern spin decay, after other sources, such as the
coupling to nuclear spins or spin orbit coupling, have been eliminated by a
suitable sample design. Electron-electron (Coulomb) interactions, important for
magnetic properties, are included. Decomposing the dipolar operator according
to the symmetric group of electron permutations allows one to deduce vanishing
decay channels as a function of electron number and spatial symmetries of the
quantum dot(s). Moreover, we incorporate the possibility of rapid phonon
induced spin conserving transitions which crucially affect the temperature
dependence of spin decay rates. An interesting result is that a sharp increase
of the spin decay rate occurs already at relatively low temperatures.",0602441v1
2010-03-31,Inverse Spin Hall Effect and Anomalous Hall Effect in a Two-Dimensional Electron Gas,"We study the coupled dynamics of spin and charge currents in a
two-dimensional electron gas in the transport diffusive regime. For systems
with inversion symmetry there are established relations between the spin Hall
effect, the anomalous Hall effect and the inverse spin Hall effect. However, in
two-dimensional electron gases of semiconductors like GaAs, inversion symmetry
is broken so that the standard arguments do not apply. We demonstrate that in
the presence of a Rashba type of spin-orbit coupling (broken structural
inversion symmetry) the anomalous Hall effect, the spin Hall and inverse spin
Hall effect are substantially different effects. Furthermore we discuss the
inverse spin Hall effect for a two-dimensional electron gas with Rashba and
Dresselhaus spin-orbit coupling; our results agree with a recent experiment.",1003.6018v1
2010-04-01,Electron spin dynamics and electron spin resonance in graphene,"A theory of spin relaxation in graphene including intrinsic, Bychkov-Rashba,
and ripple spin-orbit coupling is presented. We find from spin relaxation data
by Tombros et al. [Nature 448, 571 (2007).] that intrinsic spin-orbit coupling
dominates over other contributions with a coupling constant of 3.7 meV.
Although it is 1-3 orders of magnitude larger than those obtained from first
principles, we show that comparable values are found for other honeycomb
systems, MgB2 and LiC6; the latter is studied herein by electron spin resonance
(ESR). We predict that spin coherence is longer preserved for spins
perpendicular to the graphene plane, which is beneficial for spintronics. We
identify experimental conditions when bulk ESR is realizable on graphene.",1004.0210v1
2011-10-13,Competing Hyperfine and Spin-Orbit Couplings: Spin Relaxation in a Quantum Hall Ferromagnet,"Spin relaxation in a quantum Hall ferromagnet, where filling is $\nu=1, 1/3,
1/5,...$, can be considered in terms of spin wave annihilation/creation
processes. Hyperfine coupling with the nuclei of the GaAs matrix provides spin
non-conservation in the two-dimensional electron gas and determines spin
relaxation in the quantum Hall system. This mechanism competes with spin-orbit
coupling channels of spin-wave decay and can even dominate in a low-temperature
regime where $T$ is much smaller than the Zeeman gap. In this case the
spin-wave relaxation process occurs non-exponentially with time and does not
depend on the temperature. The competition of different relaxation channels
results in crossovers in the dominant mechanism, leading to non-monotonic
behavior of the characteristic relaxation time with the magnetic field. We
predict that the relaxation times should reach maxima at $B\simeq 18\,$T in the
$\nu=1$ Quantum Hall system and at $B\simeq 12\,$T for that of $\nu=1/3\,$. We
estimate these times as $\sim10\,-\,30\,\mu$s and $\sim2\,-\,5\,\mu$s,
respectively.",1110.3006v1
2022-08-23,Topological states in chiral electronic chains,"We consider the influence of topological phases, or their vicinity, on the
spin density and spin polarization through a chiral chain. We show the
quantization of the Berry phase in a one-dimensional polarization helix
structure, under the presence of an external magnetic field, and show its
influence on the spin density. The polar angle of the momentum space spin
density becomes quantized in the regime that the Berry phase is quantized, as a
result of the combined effect of the induced spin-orbit coupling and the
external transverse magnetic field, while the edge states do not show the polar
angle quantization, in contrast with the bulk states. Under appropriate
conditions, the model can be generalized to have similarities with a chain with
nonhomogeneous Rashba spin- orbit couplings, with zero- or low-energy edge
states. Due to the breaking of time-reversal symmetry, we recover the effect of
chiral-induced spin polarization and spin transport across the chiral chain,
when coupling to external leads. Some consequences of the quantized spin
polarization and low-energy states on the spin transport are discussed.",2208.10807v1
2018-11-23,All-Optical Generation and Tuning of Ultrafast Spin-Hall Current via Optical Vortices,"Spin Hall effect, one of the cornerstones in spintronics refers to the
emergence of an imbalance in the spin density transverse to a charge flow in a
sample under voltage bias. This study points to a novel way for an ultrafast
generation and tuning of a unidirectional nonlinear spin Hall current by means
of subpicosecond laser pulses of optical vortices. When interacting with
matter, the optical orbital angular momentum (OAM) carried by the vortex and
quantified by its topological charge is transferred to the charge carriers. The
residual spin-orbital coupling in the sample together with confinement effects
allow exploiting the absorbed optical OAM for spatio-temporally controlling the
spin channels. Both the non-linear spin Hall current and the dynamical spin
Hall angle increase for a higher optical topological charge. The reason is the
transfer of a higher amount of OAM and the enhancement of the effective
spin-orbit interaction strength. No bias voltage is needed. We demonstrate that
the spin Hall current can be all-optically generated in an open circuit
geometry for ring-structured samples. These results follow from a full-fledged
propagation of the spin-dependent quantum dynamics on a time-space grid coupled
to the phononic environment. The findings point to a versatile and controllable
tool for the ultrafast generation of spin accumulations with a variety of
applications such as a source for ultrafast spin transfer torque and charge and
spin current pulse emitter.",1811.09519v1
2018-04-13,A note on spin rescalings in post-Newtonian theory,"Usually, the reduced mass $\mu$ is viewed as a dropped factor in $\mu l$ and
$\mu h$, where $l$ and $h$ are dimensionless Lagrangian and Hamiltonian
functions. However, it must be retained in post-Newtonian systems of spinning
compact binaries under a set of scaling spin transformations
$\mathbf{S}_i=\mathbf{s}_iGM^{2}$ because $l$ and $h$ do not keep the
consistency of the orbital equations and the spin precession equations but
$(\mu/M) l$ and $(\mu/M) h$ do. When another set of scaling spin
transformations $\mathbf{S}_i=\mathbf{s}_iG\mu M$ are adopted, the consistency
of the orbital and spin equations is kept in $l$ or $h$, and the factor $\mu$
can be eliminated. In addition, there are some other interesting results as
follows. The next-to-leading-order spin-orbit interaction is induced in the
accelerations of the simple Lagrangian of spinning compact binaries with the
Newtonian and leading-order spin-orbit contributions, and the
next-to-leading-order spin-spin coupling is present in a post-Newtonian
Hamiltonian that is exactly equivalent to the Lagrangian formalism. If any
truncations occur in the Euler-Lagrangian equations or the Hamiltonian, then
the Lagrangian and Hamiltonian formulations lose their equivalence. In fact,
the Lagrangian including the accelerations with or without truncations can be
chaotic for the two bodies spinning, whereas the Hamiltonian without the
spin-spin term is integrable.",1804.04768v1
2017-08-07,A generalized Stoner criterion and versatile spin ordering in two-dimensional spin-orbit coupled electron systems,"Spin-orbit coupling is a single-particle phenomenon known to generate
topological order, and electron-electron interactions cause ordered many-body
phases to exist. The rich interplay of these two mechanisms is present in a
broad range of materials, and has been the subject of considerable ongoing
research and controversy. Here we demonstrate that interacting two-dimensional
electron systems with strong spin-orbit coupling exhibit a variety of time
reversal symmetry breaking phases with unconventional spin alignment. We first
prove that a Stoner-type criterion can be formulated for the spin polarization
response to an electric field, which predicts that the spin polarization
susceptibility diverges at a certain value of the electron-electron interaction
strength. The divergence indicates the possibility of unconventional
ferromagnetic phases even in the absence of any applied electric or magnetic
field. This leads us, in the second part of this work, to study interacting
Rashba spin-orbit coupled semiconductors in equilibrium in the Hartree-Fock
approximation as a generic minimal model. Using classical Monte-Carlo
simulations we construct the complete phase diagram of the system as a function
of density and spin-orbit coupling strength. It includes both an out-of-plane
spin polarized phase and in-plane spin-polarized phases with shifted Fermi
surfaces and rich spin textures, reminiscent of the Pomeranchuk instability, as
well as two different Fermi-liquid phases having one and two Fermi surfaces,
respectively, which are separated by a Lifshitz transition. We discuss
possibilities for experimental observation and useful application of these
novel phases, especially in the context of electric-field-controlled
macroscopic spin polarizations.",1708.01971v1
2021-06-18,Study of Spin-Orbit Interactions and Interlayer Ferromagnetic Coupling in Co/Pt/Co Trilayers in Wide Range of Heavy Metal Thickness,"The spin-orbit torque, a torque induced by a charge current flowing through
the heavy-metal conducting layer with strong spin-orbit interactions, provides
an efficient way to control the magnetization direction in
heavy-metal/ferromagnet nanostructures, required for applications in the
emergent magnetic technologies like random access memories, high-frequency nano
oscillators, or bio-inspired neuromorphic computations. We study the interface
properties, magnetization dynamics, magnetostatic features and spin-orbit
interactions within the multilayer system
Ti(2)/Co(1)/Pt(0-4)/Co(1)/MgO(2)/Ti(2) (thicknesses in nanometers) patterned by
optical lithography on micrometer-sized bars. In the investigated devices, Pt
is used as a source of the spin current and as a non-magnetic spacer with
variable thickness, which enables the magnitude of the interlayer ferromagnetic
exchange coupling to be effectively tuned. We also find the Pt
thickness-dependent changes in magnetic anisotropies, magnetoresistance,
effective Hall angle and, eventually, spin-orbit torque fields at interfaces.
The experimental findings are supported by the relevant interface
structure-related simulations, micromagnetic, macrospin, as well as the spin
drift-diffusion models. Finally, the contribution of the spin-orbital
Edelstein-Rashba interfacial fields is also briefly discussed in the analysis.",2106.10103v1
2007-01-13,Theory of conserved spin current and its application to two dimensional hole gas,"We present a detailed microscopic theory of the conserved spin current which
is introduced by us [Phys. Rev. Lett. \textbf{96}, 196602 (2006)] and satisfies
the spin continuity equation even for spin-orbit coupled systems. The spin
transport coefficients $\sigma_{\mu\nu}^{s}$ as a response to the electric
field are shown to consist of two parts, i.e., the conventional part
$\sigma_{\mu\nu}^{s0}$ and the spin torque dipole correction $\sigma_{\mu\nu
}^{s\tau}$. As one key result, an Onsager relation between $\sigma_{\mu\nu
}^{s}$ and other kinds of transport coefficients are shown. The expression for
$\sigma_{\mu\nu}^{s}$ in terms of single-particle Bloch states are derived, by
use of which we study the conserved spin Hall conductivity in the two
dimensional hole gas modeled by a combined Luttinger and SIA Rashba spin-orbit
coupling. It is shown that the two components in spin Hall conductivity usually
have the opposite contributions. While in the absence of Rashba spin splitting,
the spin Hall transport is dominated by the conventional contribution, the
presence of Rashba spin splitting stirs up a large enhancement of the spin
torque dipole correction, leading to an overall sign change for the total spin
Hall conductivity. Furthermore, an approximate two-band calculation and the
subsequent comparison with the exact four-band results are given, which reveals
that the coupling between the heavy hole and light hole bands should be taken
into account for strong Rashba spin splitting.",0701293v1
2014-09-05,Edge binding of sine-Gordon solitons in spin-orbit coupled Bose-Einstein condensates,"In recent experiments with ultracold gases a Raman coupling scheme is used to
produce both spin-orbit (SO) and Zeeman-type couplings [Y.-J. Lin et al.,
Nature 471, 83 (2011)]. Their competition drives a phase transition to a
magnetized state with broken $Z_2$ symmetry. Using a hydrodynamic approach we
study a confined binary condensate subject to both SO and Zeeman-type
couplings. We find that in the limit of small healing length and in the phase
with unbroken symmetry, the boundary magnetization profile has an analytical
solution in the form of a sine-Gordon soliton. The soliton is bound to the edge
of the system by the nontrivial boundary condition resulting from the combined
effect of the SO coupling and the drop in the particle density. The same
boundary condition is important in the magnetized phase as well, where we
characterize numerically the boundary spin structure. We further discuss how
the nontrivial magnetization structure affects the density profile near the
boundary, yet another prediction that can be tested in current experiments of
spin-orbit coupled condensates.",1409.1885v2
2014-10-22,Polarization of a quasi two-dimensional repulsive Fermi gas with Rashba spin-orbit coupling: a variational study,"Motivated by the remarkable experimental control of synthetic gauge fields in
ultracold atomic systems, we investigate the effect of an artificial Rashba
spin-orbit coupling on the spin polarization of a two-dimensional repulsive
Fermi gas. By using a variational many-body wavefunction, based on a suitable
spinorial structure, we find that the polarization properties of the system are
indeed controlled by the interplay between spin-orbit coupling and repulsive
interaction. In particular, two main effects are found: 1) The Rashba coupling
determines a gradual increase of the degree of polarization beyond the critical
repulsive interaction strength, at variance with conventional 2D Stoner
instability. 2) The critical interaction strength, above which finite
polarization is developed, shows a dependence on the Rashba coupling, i.e. it
is enhanced in case the Rashba coupling exceeds a critical value. A simple
analytic expression for the critical interaction strength is further derived in
the context of our variational formulation, which allows for a straightforward
and insightful analysis of the present problem.",1410.5938v1
2013-08-16,Strong Coupling Expansion of the Extended Hubbard Model with Spin-Orbit Coupling,"We study the strong coupling limit of the extended Hubbard model in two
dimensions. The model consists of hopping, on-site interaction,
nearest-neighbor interaction, spin-orbit coupling and Zeeman spin splitting.
While the study of this model is motivated by a search for topological phases
and in particular a topological superconductor, the methodology we develop may
be useful for a variety of systems. We begin our treatment with a canonical
transformation of the Hamiltonian to an effective model which is appropriate
when the (quartic) interaction terms are larger than the (quadratic) kinetic
and spin-orbit coupling terms. We proceed by analyzing the strong coupling
model variationally. Since we are mostly interested in a superconducting phase
we use a Gutzwiller projected BCS wavefunction as our variational state. To
continue analytically we employ the Gutzwiller approximation and compare the
calculated energy with Monte-Carlo calculations. Finally we determine the
topology of the ground state and map out the topology phase diagram.",1308.3731v2
2007-11-09,Semiconductor Spintronics,"Spintronics refers commonly to phenomena in which the spin of electrons in a
solid state environment plays the determining role. In a more narrow sense
spintronics is an emerging research field of electronics: spintronics devices
are based on a spin control of electronics, or on an electrical and optical
control of spin or magnetism. This review presents selected themes of
semiconductor spintronics, introducing important concepts in spin transport,
spin injection, Silsbee-Johnson spin-charge coupling, and spindependent
tunneling, as well as spin relaxation and spin dynamics. The most fundamental
spin-dependent nteraction in nonmagnetic semiconductors is spin-orbit coupling.
Depending on the crystal symmetries of the material, as well as on the
structural properties of semiconductor based heterostructures, the spin-orbit
coupling takes on different functional forms, giving a nice playground of
effective spin-orbit Hamiltonians. The effective Hamiltonians for the most
relevant classes of materials and heterostructures are derived here from
realistic electronic band structure descriptions. Most semiconductor device
systems are still theoretical concepts, waiting for experimental
demonstrations. A review of selected proposed, and a few demonstrated devices
is presented, with detailed description of two important classes: magnetic
resonant tunnel structures and bipolar magnetic diodes and transistors. In most
cases the presentation is of tutorial style, introducing the essential
theoretical formalism at an accessible level, with case-study-like
illustrations of actual experimental results, as well as with brief reviews of
relevant recent achievements in the field.",0711.1461v1
2022-09-06,Semiclassical spin transport in LaO/STO system in the presence of multiple Rashba spin orbit couplings,"The interaction between the linear and cubic spin-orbit coupling with
magnetic moments and mobile spin-polarized carriers in the LaO/STO system
provides new avenues for spin transport applications. We study the interplay
between linear and cubic Rashba spin orbit coupling (RSOC) on in-plane magnetic
moments in the LaO/STO system using the Boltzmann transport theory based on the
relaxation time approximation (RTA) and the more refined Schliemann-Loss (SL)
delta-potential scattering model. In general, both methods yield a linear
(quadratic) relationship between the spin accumulation (spin current) when one
of the three RSOC strengths is varied and the other two fixed. The simultaneous
presence of multiple types of RSOC with distinct angular dependences is a key
ingredient in breaking the k-space symmetry of the Fermi surface, thus ensuring
a finite spin accumulation upon integration over the entire Fermi surface.
While the oft-used RTA method is sufficiently accurate for spin accumulation
calculations, the more refined SL model is required for spin current
calculations because the RTA method neglects the anisotropy of the Fermi
contour arising from the cubic RSOC terms. Based on the refined SL model and
under optimal tuning of the RSOC parameters, the spin charge conversion values
in LaO/STO is predicted to reach a remarkable efficiency of 30.",2209.02859v1
2014-03-31,Degenerate Quantum Gases with Spin-Orbit Coupling,"This review focuses on recent developments on studying synthetic spin-orbit
(SO) coupling in ultracold atomic gases. Two types of SO coupling are
discussed. One is Raman process induced coupling between spin and motion along
one of the spatial directions, and the other is Rashba SO coupling. We
emphasize their common features in both single-particle and two-body physics
and their consequences in many-body physics. For instance, single particle
ground state degeneracy leads to novel features of superfluidity and richer
phase diagram; increased low-energy density-of-state enhances interaction
effects; the absence of Galilean invariance and spin-momentum locking give rise
to intriguing behaviors of superfluid critical velocity and novel quantum
dynamics; and mixing of two-body singlet and triplet states yields novel
fermion pairing structure and topological superfluids. With these examples, we
show that investigating SO coupling in cold atom systems can enrich our
understanding of basic phenomena such as superfluidity, provide a good platform
for simulating condensed matter states such as topological superfluids, and
more importantly, result in novel quantum systems such as SO coupled unitary
Fermi gas or high spin quantum gases. Finally we also point out major
challenges and possible future directions.",1403.8021v2
2017-06-27,Nonlinear spin current generation in noncentrosymmetric spin-orbit coupled systems,"Spin current plays a central role in spintronics. In particular, finding more
efficient ways to generate spin current has been an important issue and studied
actively. For example, representative methods of spin current generation
include spin polarized current injections from ferromagnetic metals, spin Hall
effect, and spin battery. Here we theoretically propose a new mechanism of spin
current generation based on nonlinear phenomena. By using Boltzmann transport
theory, we show that a simple application of the electric field $\bf{E}$
induces spin current proportional to $\bf{E^2}$ in noncentrosymmetric
spin-orbit coupled systems. We demonstrate that the nonlinear spin current of
the proposed mechanism is supported in the surface state of three-dimensional
topological insulators and two-dimensional semiconductors with the Rashba
and/or Dresselhaus interaction. In the latter case, the angular dependence of
the nonlinear spin current can be manipulated by the direction of the electric
field and by the ratio of the Rashba and Dresselhaus interactions. We find that
the magnitude of the spin current largely exceeds those in the previous methods
for a reasonable magnitude of the electric field. Furthermore, we show that
application of AC electric fields (e.g. terahertz light) leads to the
rectifying effect of the spin current where DC spin current is generated. These
findings will pave a new route to manipulate the spin current in
noncentrosymmetric crystals.",1706.08647v1
2013-11-01,Anomalous D'yakonov-Perel' spin relaxation in InAs (110) quantum wells under strong magnetic field: role of Hartree-Fock self-energy,"We investigate the influence of the Hartree-Fock self-energy, acting as an
effective magnetic field, on the anomalous D'yakonov-Perel' spin relaxation in
InAs (110) quantum wells when the magnetic field in the Voigt configuration is
much stronger than the spin-orbit-coupled field. The transverse and
longitudinal spin relaxations are discussed both analytically and numerically.
For the transverse configuration, it is found that the spin relaxation is very
sensitive to the Hartree-Fock effective magnetic field, which is very different
from the conventional D'yakonov-Perel' spin relaxation. Even an extremely small
spin polarization ($P=0.1\%$) can significantly influence the behavior of the
spin relaxation. It is further revealed that this comes from the {\em unique}
form of the effective inhomogeneous broadening, originated from the mutually
perpendicular spin-orbit-coupled field and strong magnetic field. It is shown
that this effective inhomogeneous broadening is very small and hence very
sensitive to the Hartree-Fock field. Moreover, we further find that in the spin
polarization dependence, the transverse spin relaxation time decreases with the
increase of the spin polarization in the intermediate spin polarization regime,
which is also very different from the conventional situation, where the spin
relaxation is always suppressed by the Hartree-Fock field. It is revealed that
this {\em opposite} trends come from the additional spin relaxation channel
induced by the HF field. For the longitudinal configuration, we find that the
spin relaxation can be either suppressed or enhanced by the Hartree-Fock field
if the spin polarization is parallel or antiparallel to the magnetic field.",1311.0097v1
2018-11-15,Decays of Majorana or Andreev oscillations induced by steplike spin-orbit coupling,"The Majorana zero mode in the semiconductor-superconductor nanowire is one of
the promising candidates for topological quantum computing. Recently, in
islands of nanowires, subgap-state energies have been experimentally observed
to oscillate as a function of the magnetic field, showing a signature of
overlapped Majorana bound states. However, the oscillation amplitude either
dies away after an overshoot or decays, sharply opposite to the theoretically
predicted enhanced oscillations for Majorana bound states. We reveal that a
steplike distribution of spin-orbit coupling in realistic devices can induce
the decaying Majorana oscillations, resulting from the coupling-induced energy
repulsion between the quasiparticle spectra on the two sides of the step. This
steplike spin-orbit coupling can also lead to decaying oscillations in the
spectrum of the Andreev bound states. For Coulomb-blockade peaks mediated by
the Majorana bound states, the peak spacings have been predicted to correlate
with peak heights by a $\pi/2$ phase shift, which was ambiguous in recent
experiments and may be explained by the steplike spin-orbit coupling. Our work
will inspire more works to reexamine effects of the nonuniform spin-orbit
coupling, which is generally present in experimental devices.",1811.06136v3
2002-04-18,Quantum dots with Rashba spin-orbit coupling,"We present results on the effects of spin-orbit coupling on the electronic
structure of few-electron interacting quantum dots. The ground-state properties
as a function of the number of electrons in the dot $N$ are calculated by means
of spin density functional theory. We find a suppression of Hund's rule due to
the competition of the Rashba effect and exchange interaction. Introducing an
in-plane Zeeman field leads to a paramagnetic behavior of the dot in a closed
shell configuration, and to spin texture in space.",0204410v2
2003-07-01,Spin-orbit coupling and intrinsic spin mixing in quantum dots,"Spin-orbit coupling effects are studied in quantum dots in InSb, a narrow-gap
material. Competition between different Rashba and Dresselhaus terms is shown
to produce wholesale changes in the spectrum. The large (and negative)
$g$-factor and the Rashba field produce states where spin is no longer a good
quantum number and intrinsic flips occur at moderate magnetic fields. For dots
with two electrons, a singlet-triplet mixing occurs in the ground state, with
observable signatures in intraband FIR absorption, and possible importance in
quantum computation.",0307027v1
2005-06-29,Rashba spin-orbit coupling and spin precession in carbon nanotubes,"The Rashba spin-orbit coupling in carbon nanotubes and its effect on
spin-dependent transport properties are analyzed theoretically. We focus on
clean non-interacting nanotubes with tunable number of subbands $N$. The
peculiar band structure is shown to allow in principle for Datta-Das
oscillatory behavior in the tunneling magnetoresistance as a function of gate
voltage, despite the presence of multiple bands. We discuss the conditions for
observing Datta-Das oscillations in carbon nanotubes.",0506761v2
2007-04-07,Spin state mixing in InAs double quantum dots,"We quantify the contributions of hyperfine and spin-orbit mediated
singlet-triplet mixing in weakly coupled InAs quantum dots by electron
transport spectroscopy in the Pauli spin blockade regime. In contrast to double
dots in GaAs, the spin-orbit coupling is found to be more than two orders of
magnitudes larger than the hyperfine mixing energy. It is already effective at
magnetic fields of a few mT, where deviations from hyperfine mixing are
observed.",0704.0980v1
2013-05-14,Graphene with time-dependent spin-orbit coupling: Truncated Magnus expansion approach,"We analyze the role of ac-driven Rashba spin-orbit coupling in monolayer
graphene including a spin-dependent mass term. Using the Magnus expansion as a
semi-analytical approximation scheme a full account of the quasienergie
spectrum of spin states is given. We discuss the subtleties arising in
correctly applying the Magnus expansion technique in order to determine the
quasienergy spectrum. Comparison to the exact numerical solution gives
appropriate boundaries to the validity of the Magnus expansion solution.",1305.3140v1
2014-04-25,Spin-orbit coupling and optical spin Hall effect in photonic graphene,"We study the spin-orbit coupling induced by the splitting between TE and TM
optical modes in a photonic honeycomb lattice. Using a tight-binding approach,
we calculate analytically the band structure. Close to the Dirac point,we
derive an effective Hamiltonian. We find that the local reduced symmetry
($\mathrm{D_{3h}}$) transforms the TE-TM effective magnetic field into an
emergent field with a Dresselhaus symmetry. As a result, particles become
massive, but no gap opens. The emergent field symmetry is revealed by the
optical spin Hall effect.",1404.6395v1
2016-07-18,Signature of topological transition in persistent current in a Dirac Ring,"We study the persistent current in a one dimensional Dirac ring and show that
the change of spin current with respect to an applied perpendicular electric
field can be used to identify the topological phases. We further study the
effect of Rashba spin orbit coupling and show that the Aharonov-Casher phase
appearing due to Rashba spin orbit coupling vanishes in topologically
nontrivial regime and thus can identify the topological phases. This
Aharonov-Casher phase causes a finite spin-valley current in presence of valley
mixing perturbation and is thus useful to detect the topological phases even in
presence of such impurity.",1607.05052v1
2008-07-03,Zero-size objects in Riemann-Cartan spacetime,"We use the conservation law of the stress-energy and spin tensors to study
the motion of massive zero-size objects in Riemann-Cartan geometry. The
resultant world line equations turn out to exhibit a novel spin-curvature
coupling. In particular, the spin of the Dirac particle does not couple to the
background curvature. This is a consequence of its truly zero size which
consistently rules out the orbital degrees of freedom. As a test of
consistency, the wave packet solution of the free Dirac equation is considered.
It is shown that the wave packet spin and orbital angular momentum disappear
simultaneously in the zero-size limit.",0807.0596v1
2019-06-24,Quantum Spin Hall Effect in Electric and Magnetic Fields without Spin-Orbit Coupling,"From the Dirac equation of an electron in an anisotropic conduction band, the
anisotropy of its motion dramatically affects its interaction with applied
electric and magnetic fields. The quantum spin Hall effect (QSHE) is observable
in two-dimensional metals without spin-orbit coupling. The dimensionality of
the Zeeman interaction plays an important role in the QSHE, and profoundly
modifies many interpretations of measurements of the Knight shift and of the
upper critical field in highly anisotropic superconductors.",1906.10164v1
2017-05-10,Optical Selection Rules in Spin-Orbit Coupled Systems on Honeycomb Lattice,"We investigate the optical properties in a minimal model of spin-orbit
coupled systems on honeycomb lattice at half-filling. The absorption of the
circularly polarized light in the charge and antiferromagnetic ordered states
is particularly studied, and the spin-valley selective excitation depending on
the handedness of the light is found. It is shown that the optical selection
rules plainly differ with the type of broken symmetries and topological
properties of the electronic states. Consequently, the abrupt change of
spin-valley selectivity in the optical absorption occurs at the topological
transition caused by changing the magnitude of the order parameters.",1705.03632v1
2017-11-12,Highly relativistic spin-gravity-$Λ$ coupling,"The effects of highly relativistic spin-gravity coupling in the
Schwarzschild-de Sitter background which follow from the Mathisson-Papapetrou
equations are investigated. The dependence of gravitoelectric and
gravitomagnetic components of gravitational field on the velocity of an
observer which is moving in Schwarzschild-de Sitter's background is estimated.
The action of gravitomagnetic components on a fast moving spinning particle is
considered. Different cases of the highly relativistic circular orbits of a
spinning particle which essentially differ from the corresponding geodesic
orbits are described.",1711.04270v2
2018-03-13,Berry curvature and symmetry broken induced Hall effect in MoS2,"Inversion symmetry breaking and spin-orbit coupling lead to valley and spin
Hall effect in MoS2. Because of the large valley separation in momentum space,
the valley index is expected to be robust. In this paper, quantum Hall effect
in MoS2 originated from Berry curvature is analyzed after review of symmetry
structure and spin-orbit coupling Hamiltonian of MoS2. Finally an expression
and rough calculation is given for valley and spin Hall effect.",1803.05325v1
2013-04-08,Study of unconventional superfluid phases and the phase dynamics in spin-orbit coupled bose system,"We study the phase distribution and its dynamics in spin-orbit coupled two
component ultracold Bosons for finite size system. Using an inhomogeneous
meanfield analysis we demonstrate how phase distribution evolves as we tune the
spin-orbit coupling $\gamma$ and $t$, the spin-independent hopping. For
$t>>\gamma$ we find the homogeneous superfluid phase. As we increase $\gamma$,
differences in the phases of the order parameter grows leading to twisted
superfluid phase. For $t \sim \gamma$ competing orderings in the phase
distribution is observed. At large $\gamma$ limit a Ferro-Magnetic stripe
ordering appears along the diagonal. We explain that this is due to the
frustration bought in by the spin-orbit interaction. Isolated vortex formation
is also shown to appear. We also investigate the possible collective modes. In
deep superfluid regime we derive the equation of motion for the phases
following a semi-classical approximation. Imaginary frequencies indicating the
damped modes are seen to appear and the dynamics of lowest normal modes are
discussed.",1304.2098v1
2013-12-14,Spin-Orbit Driven Transitions Between Mott Insulators and Finite Momentum Superfluids of Bosons in Optical Lattices,"Synthetic spin-orbit coupling in ultracold atomic gases can be taken to
extremes rarely found in solids. We study a two dimensional Hubbard model of
bosons in an optical lattice in the presence of spin-orbit coupling strong
enough to drive direct transitions from Mott insulators to superfluids. Here we
find phase-modulated superfluids with finite momentum that are generated
entirely by spin-orbit coupling. We investigate the rich phase patterns of the
superfluids, which may be directly probed using time-of-flight imaging of the
spin-dependent momentum distribution.",1312.4011v2
2015-03-17,Self-force gravitational waveforms for extreme and intermediate mass ratio inspirals. III: Spin-orbit coupling revisited,"The first- and second-order dissipative self force and the first order
conservative self force are applied together with spin-orbit coupling to the
quasi-circular motion of a test mass in the spacetime of a Schwarzschild black
hole, for extreme or intermediate mass ratios. The partial dephasing of the
gravitational waveform (at the order that is independent of the system's mass
ratio) due to the self force is compared with that of spin-orbit coupling. We
find that accurate waveforms for parameter estimation need to include both
effects. Specifically, we find a particular value for the spin parameter such
that the spin-orbit effect cancels out the self-force effect on the waveform.
Exclusion of dephasing effects that are independent of the mass ratio therefore
might lead to a non-perturbative error in the estimation of the system's
parameters.",1503.05097v2
2015-06-05,Unconventional dc transport in Rashba electron gases,"We discuss the transport properties of a disordered two-dimensional electron
gas with strong Rashba spin-orbit coupling. We show that in the high-density
regime where the Fermi energy overcomes the energy associated with spin-orbit
coupling, dc transport is accurately described by a standard Drude's law, due
to a non-trivial compensation between the suppression of back-scattering and
the relativistic correction to the quasi-particle velocity. On the contrary,
when the system enters the opposite dominant spin-orbit regime, Drude's
paradigm breaks down and the dc conductivity becomes strongly sensitive to the
spin-orbit coupling strength, providing a suitable tool to test the
entanglement between spin and charge degrees of freedom in these",1506.01944v2
2016-09-07,Motion of solitons in one-dimensional spin-orbit-coupled Bose-Einstein condensates,"Solitons play a fundamental role in dynamics of nonlinear excitations. Here
we explore the motion of solitons in one-dimensional uniform Bose-Einstein
condensates subjected to a spin-orbit coupling (SOC). We demonstrate that the
spin dynamics of solitons is governed by a nonlinear Bloch equation. The spin
dynamics influences the orbital motion of the solitons leading to the
spin-orbit effects in the dynamics of the macroscopic quantum objects
(mean-field solitons). The latter perform oscillations with a frequency
determined by the SOC, Raman coupling, and intrinsic nonlinearity. These
findings reveal unique features of solitons affected by the SOC, which is
confirmed by analytical considerations and numerical simulations of the
underlying Gross-Pitaevskii equations.",1609.02164v1
2017-08-17,Spin-orbit enhanced carrier lifetimes in noncentrosymmetric semiconductors,"We show that the carrier recombination rate of noncentrosymmetric materials
can be strongly modified by spin-orbit coupling. Our proposed mechanism
involves the separation of conduction and valence bands into their respective
spin components, which changes the transition dipole moments between them. The
change in the carrier recombination can be either positive or negative in sign,
or vary depending on the location of carriers in the Brillouin zone. We have
performed a large scale DFT screening study to identify candidate materials
that display this effect. We have selected three materials, Pb$_4$SeBr$_6$,
ReTe$_3$Br$_5$, and CsCu(BiS$_2$)$_2$, which span the range of behaviors, and
discuss their electronic band structure in greater detail. We find transition
dipole moment enhancement factors of up to three orders of magnitude,
reflecting the physical impact of spin-orbit coupling on the carrier lifetime.
Therefore, further explorations of the spin-orbit coupling and lattice symmetry
could prove to be useful for manipulating the photophysics of materials.",1708.05436v1
2018-03-19,Spin-orbital-lattice entangled states in cubic $d^1$ double perovskites,"Interplay of spin-orbit coupling and vibronic coupling on heavy $d^1$ site of
cubic double perovskites is investigated by ab initio calculations. The
stabilization energy of spin-orbital-lattice entangled states is found
comparable to or larger than the exchange interactions, suggesting the presence
of Jahn-Teller dynamics in the systems. In Ba$_2$YMoO$_6$, the pseudo JT
coupling enhances the mixing of the ground and excited spin-orbit multiplet
states, which results in strong temperature dependence of effective magnetic
moments. The entanglement of the spin and lattice degrees of freedom induces a
strong magneto-elastic response. This multiferroic effect is at the origin of
the recently reported breaking of local point symmetry accompanying the
development of magnetic ordering in Ba$_2$NaOsO$_6$.",1803.06945v3
2020-05-22,Swapping Exchange and Spin-Orbit Coupling in 2D van der Waals Heterostructures,"The concept of swapping the two most important spin interactions -- exchange
and spin-orbit coupling -- is proposed based on two-dimensional multilayer van
der Waals heterostructures. Specifically, we show by performing realistic ab
initio simulations, that a single device consisting of a bilayer graphene
sandwiched by a 2D ferromagnet Cr$_2$Ge$_2$Te$_6$ (CGT) and a monolayer WS$_2$,
is able not only to generate, but also to swap the two interactions. The highly
efficient swapping is enabled by the interplay of gate-dependent layer
polarization in bilayer graphene and short-range spin-orbit and exchange
proximity effects affecting only the layers in contact with the sandwiching
materials. We call these structures ex-so-tic, for supplying either exchange
(ex) or spin-orbit (so) coupling in a single device, by gating. Such
bifunctional devices demonstrate the potential of van der Waals spintronics
engineering using 2D crystal multilayers.",2005.11058v2
2021-12-17,Triplet character of 2D-fermion dimers arising from $s$-wave attraction via spin-orbit coupling and Zeeman splitting,"We theoretically study spin-$1/2$ fermions confined to two spatial dimensions
and experiencing isotropic short-range attraction in the presence of both
spin-orbit coupling and Zeeman spin splitting - a prototypical system for
developing topological superfluidity in the many-body sector. Exact solutions
for two-particle bound states are found to have a triplet contribution that
dominates over the singlet part in an extended region of parameter space where
the combined Zeeman- and center-of-mass-motion-induced spin-splitting energy is
large. The triplet character of dimers is purest in the regime of weak $s$-wave
interaction strength. Center-of-mass momentum is one of the parameters
determining the existence of bound states, which we map out for both two- and
one-dimensional types of spin-orbit coupling. Distinctive features emerging in
the orbital part of the bound-state wave function, including but not limited to
its $p$-wave character, provide observable signatures of unconventional
pairing.",2112.09336v2
2022-01-25,Moiré Engineering of Spin-Orbit Coupling in Twisted Platinum Diselenide,"We study the electronic structure and correlated phases of twisted bilayers
of platinum diselenide using large-scale ab initio simulations combined with
the functional renormalization group. PtSe$_2$ is a group-X transition metal
dichalcogenide, which hosts emergent flat bands at small twist angles in the
twisted bilayer. Remarkably, we find that moir\'e engineering can be used to
tune the strength of Rashba spin-orbit interactions, altering the electronic
behavior in a novel manner. We reveal that an effective triangular lattice with
a twist-controlled ratio between kinetic and spin-orbit coupling scales can be
realized. Even dominant spin-orbit coupling can be accessed in this way and we
discuss consequences for the interaction driven phase diagram, which features
pronounced exotic superconducting and entangled spin-charge density waves.",2201.10615v1
2015-04-20,Orbital-lattice coupling and orbital ordering instability in iron pnictides,"Orbital-ordering instability arising due to the intrapocket nesting is
investigated for the tight-binding models of pnictides in the presence of
orbital-lattice coupling. The incommensurate instabilities with small momentum,
which may play an important role in the nematic-ordering transition, vary from
model to model besides being more favorable in comparison to the spin-density
wave instability in the absence of good interpocket nesting. We also examine
the doping dependence of such instabilities. The electron-phonon coupling
parameter required to induce them are compared with the first-principle
calculations.",1504.04915v1
2013-08-19,Vibronic Excitation Dynamics in Orbitally Degenerate Correlated Electron System,"Orbital-lattice coupled excitation dynamics in orbitally degenerate
correlated systems are examined. We present a theoretical framework, where both
local vibronic excitations and superexchange-type inter-site interactions are
dealt with on an equal footing. We generalize the spin-wave approximation so as
to take local vibronic states into account. Present method is valid from weak
to strong Jahn-Teller coupling magnitudes. Two characteristic excitation modes
coexist; a low-energy dispersive mode and high-energy multi-peak mode. These
are identified as a collective vibronic mode, and Flanck-Condon excitations in
a single Jahn-Teller center modified by the inter-site interactions,
respectively. Present formalism covers vibronic dynamics in several
orbital-lattice coupled systems.",1308.3997v1
2017-04-20,Orbital and spin ordering physics of the Mn$_3$O$_4$ spinel,"Motivated by recent experiments, we present a comprehensive theoretical study
of the geometrically frustrated strongly correlated magnetic insulator
Mn$_3$O$_4$ spinel oxide based on a microscopic Hamiltonian involving lattice,
spin and orbital degrees of freedom. Possessing the physics of degenerate e$_g$
orbitals, this system shows a strong Jahn-Teller effect at high temperatures.
Further, careful attention is paid to the special nature of the superexchange
physics arising from the 90$^o$ Mn-O-Mn bonding angle. The Jahn-Teller and
superexchange-based orbital-spin Hamiltonians are then analysed in order to
track the dynamics of orbital and spin ordering. We find that a
high-temperature structural transition results in orbital ordering whose nature
is mixed with respect to the two originally degenerate $e_{g}$ orbitals. This
ordering of orbitals is shown to relieve the intrinsic geometric frustration of
the spins on the spinel lattice, leading to ferrimagnetic Yafet-Kittel ordering
at low-temperatures. Finally, we develop a model for a magnetoelastic coupling
in Mn$_3$O$_4$, enabling a systematic understanding of the experimentally
observed complexity in the low-temperature structural and magnetic
phenomenology of this spinel. Our analysis predicts that a quantum
fluctuation-driven orbital-spin liquid phase may be stabilised at low
temperatures upon the application of pressure.",1704.06026v1
2013-07-17,Spin-orbit interaction induced spin selective transmission through a multi-terminal mesoscopic ring,"Spin dependent transport in a multi-terminal mesoscopic ring is investigated
in presence of Rashba and Dresselhaus spin-orbit interactions. Within a
tight-binding framework we use a general spin density matrix formalism to
evaluate all three components ($P_x$, $P_y$ and $P_z$) of the polarization
vector associated with the charge current through the outgoing leads. It
explores the dynamics of the spin polarization vector of current propagating
through the system subjected to the Rashba and/or the Dresselhaus spin-orbit
couplings. The sensitivity of the polarization components on the electrode-ring
interface geometry is discussed in detail. Our present analysis provides an
understanding of the coupled spin and electron transport in mesoscopic bridge
systems.",1307.4506v2
2014-04-05,Effect of boundary scattering on spin-hall effect,"The spin dependent reflection in quasi-two-dimensional electron gas from an
impenetrable barrier in presence of Rashba and Dresselhaus spin-orbit coupling
is analyzed in detail. It is shown that due to spin-orbit effects the reflected
beam split in two beams gives rise to multiple reflection analogous to
phenomena birefringence. The interplay between Rashba and Dresselhaus
spin-orbit coupling gives rise to anisotropy in Fermi energy surface and a
non-zero net spin-polarized current oscillating with two frequencies for all
the values of incident angle except at $45^{o}$ when averaged over all
components of reflected beam. It is also shown that in over critical region,
all the three polarization components as well as net polarization has non-zero
values and are exponentially decaying as distance from the barrier increases
which in turns spin-accumulation near the barrier is an important consequence
of spin-hall effect.",1404.1453v2
2015-11-13,Magnified Damping under Rashba Spin Orbit Coupling,"The spin orbit coupling spin torque consists of the field-like [REF: S.G. Tan
et al., arXiv:0705.3502, (2007).] and the damping-like terms [REF: H.
Kurebayashi et al., Nature Nanotechnology 9, 211 (2014).] that have been widely
studied for applications in magnetic memory. We focus, in this article, not on
the spin orbit effect producing the above spin torques, but on its magnifying
the damping constant of all field like spin torques. As first order precession
leads to second order damping, the Rashba constant is naturally co-opted,
producing a magnified field-like damping effect. The Landau-Liftshitz-Gilbert
equations are written separately for the local magnetization and the itinerant
spin, allowing the progression of magnetization to be self-consistently locked
to the spin.",1511.04227v1
2016-10-05,Prominent role of spin-orbit coupling in FeSe,"In most existing theories for iron-based superconductors, spin-orbit coupling
(SOC) has been assumed insignificant. Even though recent experiments have
revealed an influence of SOC on the electronic band structure, whether SOC
fundamentally affects magnetism and superconductivity remains an open question.
Here we use spin-polarised inelastic neutron scattering to show that collective
low-energy spin fluctuations in the orthorhombic (or ""nematic"") phase of FeSe
possess nearly no in-plane component. Such spin-space anisotropy can only be
caused by SOC. It is present over an energy range greater than the
superconducting gap 2$\Delta _\mathrm{sc}$ and gets fully inherited in the
superconducting state, resulting in a distinct $c$-axis polarised ""spin
resonance"". Our result demonstrates the importance of SOC in defining the
low-energy spin excitations in FeSe, which helps to elucidate the nearby
magnetic instabilities and the debated interplay between spin and orbital
degrees of freedom. The prominent role of SOC also implies a possible unusual
nature of the superconducting state.",1610.01277v1
2020-07-28,Spin and charge distributions in Graphene/Nickel (111) substrate under Rashba spin-orbital coupling,"To understand the coupling factor between Rashba spin-orbital interaction and
ferromagnetic proximity effect, we design a Monte Carlo algorithm to simulate
the spin and charge distributions for the room-temperature Rashba material,
Graphene/Nickel(111) substrate, at finite temperature. We observe that the rate
of exchange fluctuation is a key player to produce giant Rashba spin-orbit
splitting in graphene. More importantly, we monitor the Rashba spin-splitting
phenomenon where the spin-polarized electrons may be escaped from two opposite
edges upon heating. However, the escaped electrons show Gaussian-like
distribution in interior area that is important for spintronic engineers to
optimize the efficiency of spin-state detection. In addition, we investigate if
our Monte Carlo model can explain why room-temperature Rashba effect is
observed in Graphene/Nickel(111) substrate experimentally. All results are
presented in physical units.",2007.14060v1
2011-11-02,The influence of anisotropic gate potentials on the phonon induced spin-flip rate in GaAs quantum dots,"We study the anisotropic orbital effect in the electric field tunability of
the phonon induced spin-flip rate in quantum dots (QDs). Our study shows that
anisotropic gate potential enhances the spin-flip rate and reduces the level
crossing point to a lower quantum dot radius due to the suppression of the
Land$\acute{e}$ g-factor towards bulk crystal. In the range of $10^4-10^6$
V/cm, the electric field tunability of the phonon induced spin-flip rate can be
manipulated through strong Dresselhaus spin-orbit coupling. These results might
assist the development of a spin based solid state quantum computer by
manipulating phonon induced spin-flip rate through spin-orbit coupling with the
application of anisotropic gate potential in a regime where the g-factor
changes its sign.",1111.0558v2
2014-06-14,Electric-field coupling to spin waves in a centrosymmetric ferrite,"We experimentally demonstrate that the spin-orbit interaction can be utilized
for direct electric-field tuning of the propagation of spin waves in a
single-crystal yttrium iron garnet magnonic waveguide. Magnetoelectric coupling
not due to the spin-orbit interaction, and hence an order of magnitude weaker,
leads to electric-field modification of the spin-wave velocity for waveguide
geometries where the spin-orbit interaction will not contribute. A theory of
the phase shift, validated by the experiment data, shows that, in the exchange
spin wave regime, this electric tuning can have high efficiency. Our findings
point to an important avenue for manipulating spin waves and developing
electrically tunable magnonic devices.",1406.3675v1
2018-01-17,Exploring Hidden Acoustic Spin Underwater,"Investigating wave propagation in fluid enables a variety of important
applications in underwater communications, object detections and unmanned robot
control. Conventionally, momentum and spin reveal fundamental physical
properties about propagating waves. Yet, vast previous research focused on the
orbital angular momentum of acoustics without thinking about the existence
possibility of spin due to the longitudinal wave nature. Here, we show that
underwater acoustic wave processes the non-trivial spin angular momentum
intrinsically, which is associated with its special spin-orbital coupling
relation for longitudinal waves. Furthermore, we demonstrate that this
intrinsic spin, although unobservable in plane wave form, can be detected by
four approaches: wave interference, Gaussian exponential decay form, boundary
evanescent wave, and waveguide mode. We further show that the strong
spin-orbital coupling can be exploited to achieve unidirectional excitation and
backscattering immune transport. We hope the present results can improve the
geometric and topological understanding about underwater acoustic wave and pave
the way on the spin-related underwater applications.",1801.05790v2
2019-06-15,Spin-orbit driven spin depolarization in the ferromagnetic Weyl semimetal Co3Sn2S2,"Co$_3$Sn$_2$S$_2$ has recently emerged as a ferromagnetic Weyl semi-metal.
Theoretical investigation of the spin-split bands predicted half metalicity in
the compound. Here, we report the detection of a spin polarized supercurrent
through a Nb/Co$_3$Sn$_2$S$_2$ point contact where Andreev reflection is seen
to be large indicating a large deviation from half metallicity. In fact,
analysis of the Andreev reflection spectra reveals only 50\% spin polarization
at the Fermi level of Co$_3$Sn$_2$S$_2$. Our theoretical calculations of
electronic Density of States (DOS) reveal a spin depolarizing effect near the
Fermi energy when the role of spin-orbit coupling is included. Inclusion of
spin-orbit coupling also reveals particle-hole asymmetry that explains a large
asymmetry observed in our experimental Andreev reflection spectra.",1906.06557v1
2006-08-10,Universal spin-Hall conductance fluctuations in two dimensions,"We report a theoretical investigation on spin-Hall conductance fluctuation of
disordered four terminal devices in the presence of Rashba or/and Dresselhaus
spin-orbital interactions in two dimensions. As a function of disorder, the
spin-Hall conductance $G_{sH}$ shows ballistic, diffusive and insulating
transport regimes. For given spin-orbit interactions, a universal spin-Hall
conductance fluctuation (USCF) is found in the diffusive regime. The value of
the USCF depends on the spin-orbit coupling $t_{so}$, but is independent of
other system parameters. It is also independent of whether Rashba or
Dresselhaus or both spin-orbital interactions are present. When $t_{so}$ is
comparable to the hopping energy $t$, the USCF is a universal number $\sim 0.18
e/4\pi$. The distribution of $G_{sH}$ crosses over from a Gaussian distribution
in the metallic regime to a non-Gaussian distribution in the insulating regime
as the disorder strength is increased.",0608240v1
2017-11-29,Spin-orbit torque in 3D topological insulator-ferromagnet heterostructure: crossover between bulk and surface transport,"Current-driven spin-orbit torques are investigated in a heterostructure
composed of a ferromagnet deposited on top of a three dimensional topological
insulator using the linear response formalism. We develop a tight-binding model
of the heterostructure adopting a minimal interfacial hybridization scheme that
promotes induced magnetic exchange on the topological surface states, as well
as induced Rashba-like spin-orbit coupling in the ferromagnet. Therefore, our
model accounts for spin Hall effect from bulk states together with inverse spin
galvanic and magnetoelectric effects at the interface on equal footing. By
varying the transport energy across the band structure, we uncover a crossover
from surface-dominated to bulk-dominated transport regimes. We show that the
spin density profile and the nature of the spin-orbit torques differ
substantially in both regimes. Our results, which compare favorably with
experimental observations, demonstrate that the large damping torque reported
recently is more likely attributed to interfacial magnetoelectric effect, while
spin Hall torque remains small even in the bulk-dominated regime.",1711.11016v2
2021-03-29,Spin Dynamics of Extrasolar Giant Planets in Planet-Planet Scattering,"Planet-planet scattering best explains the eccentricity distribution of
extrasolar giant planets. Past literature showed that the orbits of planets
evolve due to planet-planet scattering. This work studies the spin evolution of
planets in planet-planet scattering in 2-planet systems. Spin can evolve
dramatically due to spin-orbit coupling made possible by the evolving spin and
orbital precession during the planet-planet scattering phase. The main source
of torque to planet spin is the stellar torque, and the total planet-plane
torque contribution is negligible. As a consequence of the evolution of the
spin, planets can end up with significant obliquity (the angle between a
planet's own orbit normal and spin axis) like planets in our Solar System.",2103.15902v1
2021-07-16,Spinning test particle motion around a traversable wormhole,"The motion of spinning test particles around a traversable wormhole is
investigated using the Mathisson Papapetrous Dixon equations, which couple the
Riemann tensor with the antisymmetric tensor $S^{ab}$, related to the spin of
the particle. Hence, we study the effective potential, circular orbits, and
innermost stable circular orbit ISCO of spinning particles. We found that the
spin affects significantly the location of the ISCO, in contrast with the
motion of nonspinning particles, where the ISCO is the same in both the upper
and lower universes. On the other hand, since the dynamical fourmomentum and
kinematical fourvelocity of the spinning particle are not always parallel, we
also consider a superluminal bound on the particles motion. In the case of
circular orbits at the ISCO, we found that the motion of particles with an
adimensional spin parameter lower greater than $s=-1.5$ $(1.5)$ is forbidden.
The spin interaction becomes important for Kerr black hole orbiting super
massive wormholes SMWH.",2107.07998v1
2005-06-07,Dependence of the intrinsic spin Hall effect on spin-orbit interaction character,"We report on a comparative numerical study of the spin Hall conductivity in
two-dimensions for three different spin-orbit interaction models; the standard
k-linear Rashba model, the k-cubic Rashba model that describes two-dimensional
hole systems, and a modified k-linear Rashba model in which the spin-orbit
coupling strength is energy dependent. Numerical finite-size Kubo formula
results indicate that the spin Hall conductivity of the k-linear Rashba model
vanishes for frequency $\omega$ much smaller than the scattering rate
$\tau^{-1}$, with order one relative fluctuations surviving out to large system
sizes. For the k-cubic Rashba model case, the spin Hall conductivity does not
depend noticeably on $\omega \tau$ and is finite in the {\em dc} limit, in
agreement with experiment. For the modified k-linear Rashba model the spin Hall
conductivity is noticeably $\omega \tau$ dependent but approaches a finite
value in the {\em dc} limit. We discuss these results in the light of a
spectral decomposition of the spin Hall conductivity and associated sum rules,
and in relation to a proposed separation of the spin Hall conductivity into
skew-scattering, intrinsic, and interband vertex correction contributions.",0506189v1
2007-07-06,Mesoscopic spin confinement during acoustically induced transport,"Long coherence lifetimes of electron spins transported using moving potential
dots are shown to result from the mesoscopic confinement of the spin vector.
The confinement dimensions required for spin control are governed by the
characteristic spin-orbit length of the electron spins, which must be larger
than the dimensions of the dot potential. We show that the coherence lifetime
of the electron spins is independent of the local carrier densities within each
potential dot and that the precession frequency, which is determined by the
Dresselhaus contribution to the spin-orbit coupling, can be modified by varying
the sample dimensions resulting in predictable changes in the spin-orbit length
and, consequently, in the spin coherence lifetime.",0707.1047v1
2017-06-01,Current-induced spin polarization in InGaAs and GaAs epilayers with varying doping densities,"The current-induced spin polarization and momentum-dependent spin-orbit field
were measured in In$_{x}$Ga$_{1-x}$As epilayers with varying indium
concentrations and silicon doping densities. Samples with higher indium
concentrations and carrier concentrations and lower mobilities were found to
have larger electrical spin generation efficiencies. Furthermore,
current-induced spin polarization was detected in GaAs epilayers despite the
absence of measurable spin-orbit fields, indicating that the extrinsic
contributions to the spin polarization mechanism must be considered.
Theoretical calculations based on a model that includes extrinsic contributions
to the spin dephasing and the spin Hall effect, in addition to the intrinsic
Rashba and Dresselhaus spin-orbit coupling, are found to qualitatively agree
with the experimental results.",1706.00351v1
2020-02-28,Spin-orbit torques driven by the interface-generated spin currents,"The spin currents generated by spin-orbit coupling (SOC) in the nonmagnetic
metal layer or at the interface with broken inversion symmetry are of
particular interest and importance. Here, we have explored the spin current
generation mechanisms through the spin-orbit torques (SOTs) measurements in the
Ru/Fe heterostructures with weak perpendicular magnetic anisotropy (PMA).
Although the spin Hall angle (SHA) of Ru is smaller than that in Pt, Ta or W,
reversible SOT in Ru/Fe heterostructures can still be realized. Through
non-adiabatic harmonic Hall voltage measurements and macrospin simulation, the
effective SHA in Ru/Fe heterostructures is compared with Pt. Moreover, we also
explore that the spin current driven by interface strongly depends on the
electrical conductivities. Our results suggest a new method for efficiently
generating finite spin currents in ferromagnet/nonmagnetic metal bilayers,
which establishes new opportunities for fundamental study of spin dynamics and
transport in ferromagnetic systems.",2002.12545v1
2023-06-15,Transverse spin-orbit interaction of light,"Light carries both longitudinal and transverse spin angular momentum. The
spin can couple with its orbital counterpart via the Berry phase, known as the
spin-orbit interaction (SOI) of light. The SOI of light discovered previously
belongs to the longitudinal one, which relies on the Berry phase in momentum
space, such as the optical Magnus effect and the spin Hall effect. Here, we
show that transverse SOI, relying on the Berry phase in real space, is inherent
in the Helmholtz equation when transverse spinning light propagates in curved
paths. The transverse SOI lifts the degeneracy of dispersion relations of light
for opposite transverse spin states, analogous to the Dresselhaus effect.
Transverse SOI is ubiquitous in nanophotonic systems where transverse spin and
optical path bending are inevitable. It can also explain anomalous effects like
the dispersion relation of surface plasmon polariton on curved paths and the
energy level of whispering gallery modes. Our results reveal the analogies of
spin photonics and spintronics and offer a new degree of freedom for integrated
photonics, spin photonics, and astrophysics.",2306.08975v1
2004-09-25,Competing effects of interactions and spin-orbit coupling in a quantum wire,"We study the interplay of electron-electron interactions and Rashba
spin-orbit coupling in one-dimensional ballistic wires. Using the
renormalization group approach we construct the phase diagram in terms of
Rashba coupling, Tomonaga-Luttinger stiffness and backward scattering strength.
We identify the parameter regimes with a dynamically generated spin gap and
show where the Luttinger liquid prevails. We also discuss the consequences for
the operation of the Datta-Das transistor.",0409678v2
2013-07-05,Unconventional superfluidity in quasi-one-dimensional systems,"We show that an unconventional superfluid triggered by spin-orbit coupling is
realized for repulsively interacting quasi-one-dimensional fermions. A
competition between spin-singlet and -triplet pairings occurs due to the
breaking of inversion symmetry. We show that both superfluid correlations decay
algebraically with the same exponent except for special coupling constants for
which a dominant superfluid is controlled by the spin-orbit coupling. We also
discuss a possible experiment to observe such phases with cold atoms.",1307.1639v2
2016-07-25,Spin-orbit-coupling-induced magnetic heterostructure in the bilayer Bose-Hubbard system,"We investigate magnetic phase in the bilayer system of ultra-cold bosons in
an optical lattice, which is involved with Raman-induced spin-orbit (SO)
coupling and laser-assisted interlayer tunneling. It is shown that there exit a
rich of spin textures such as hetero ferromagnet, heterochiral magnet, chiral
magnet with interlayer antiferromagnet. In particular, heterochiral magnet
induced by SO coupling occurs extremely rarely in real solid-state materials.
We present detailed experimental setup of realizing such a model in cold atom
system.",1607.07336v1
2017-08-30,Two-dimensional Rashba metals: unconventional low-temperature transport properties,"Rashba spin-orbit coupling emerges in materials lacking of structural
inversion symmetry, such as heterostructures, quantum wells, surface alloys and
polar materials, just to mention few examples. It yields a coupling between the
spin and momentum of electrons formally identical to that arising from the
weakly-relativistic limit of the Dirac equation. The purpose of the present
work is to give an overview of the unconventional dc transport properties of
two-dimensional metals with strong Rashba spin-orbit coupling, discussing in
addition the effects of thermal broadening.",1708.09331v1
2013-08-07,Calculation of Multipolar Exchange Interactions in Spin-Orbital Coupled Systems,"A new method of computing multipolar exchange interaction in spin-orbit
coupled systems is developed using multipolar tensor expansion of the density
matrix in LDA+U electronic structure calculation. Within mean-field
approximation, exchange constants can be mapped into a series of total energy
calculations by pair-flip technique. Application to Uranium dioxide shows an
antiferromagnetic superexchange coupling in dipoles but ferromagnetic in
quadrupoles which is very different from past studies. Further calculation of
spin-lattice interaction indicates it is of the same order with superexchange
and characterizes the overall behavior of quadrupolar part as a competition
between them.",1308.1488v1
2017-12-15,Pauli metallic ground-state in Hubbard clusters with Rashba spin-orbit coupling,"We study the ""phase diagram"" of a Hubbard plaquette with Rashba spin-orbit
coupling. We show that the peculiar way in which Rashba coupling breaks the
spin-rotational symmetry of the Hubbard model allows a mixing of singlet and
triplet components in the ground-state that slows down and it changes the
nature of the Mott transition and of the Mott insulating phases.",1712.05618v2
2010-04-29,Computing waveforms for spinning compact binaries in quasi-eccentric orbits,"Several scenarios have been proposed in which the orbits of binary black
holes enter the band of a gravitational wave detector with significant
eccentricity. To avoid missing these signals or biasing parameter estimation it
is important that we consider waveform models that account for eccentricity.
The ingredients needed to compute post-Newtonian (PN) waveforms produced by
spinning black holes inspiralling on quasi-eccentric orbits have been available
for almost two decades at 2 PN order, and this work has recently been extended
to 2.5 PN order. However, the computational cost of directly implementing these
waveforms is high, requiring many steps per orbit to evolve the system of
coupled differential equations. Here we employ the standard techniques of a
separation of timescales and a generalized Keplerian parameterization of the
orbits to produce efficient waveforms describing spinning black hole binaries
with arbitrary masses and spins on quasi-eccentric orbits to 1.5 PN order. We
separate the fast orbital timescale from the slow spin-orbit precession
timescale by solving for the orbital motion in a non-interial frame of
reference that follows the orbital precession. We outline a scheme for
extending our approach to higher post-Newtonian order.",1004.5322v4
1998-09-14,Small-$q$ Anomaly in the Dielectric Function and High-Temperature Oscillations of Screening Potential in 2D Electron Gas with Spin-Orbit Coupling,"We study the static dielectric function $\epsilon(q)$ of 2D electron system
with spin-orbit coupling in the frame of the random phase approximation. We
demonstrate that, in addition to the well-known $2k_F$-Kohn anomaly, spin-orbit
coupling gives rise to the novel anomaly in the dielectric function at small
$q=q_0\ll k_F$, where $q_0$ is the distance between two Fermi surfaces. As a
result of this anomaly a large-distance behavior of the potential from a point
charge exhibits (in addition to the conventional Friedel oscillations) novel
oscillations with a period $2\pi/q_0$. The remarkable feature of these
oscillations is that they are not smeared out by the temperature. We show that
the small-$q$ anomaly also modifies the indirect exchange interaction of
localized magnetic moments (RKKY interaction). In the presense of spin-orbit
coupling this interaction acquires a high-temperature component.",9809207v1
2000-05-29,Electronic and Magnetic Properties of Febr2,"Electronic and magnetic (e-m) properties of FeBr2 have been surprisingly well
described as originating from the Fe2+ ions and their fine electronic
structure. The fine electronic structure have been evaluated taking into
account the spin-orbit (s-o) coupling, crystal-field and inter-site
spin-dependent interactions. The required magnetic doublet ground state with an
excited singlet at D=2.8 meV results from the trigonal distortion. This effect
of the trigonal distortion and a large magnetic moment of iron, of 4.4 mB, can
be theoretically derived provided the s-o coupling is correctly taking into
account. The obtained good agreement with experimental data indicates on
extremaly strong correlations of the six 3d electrons in the Fe2+ ion yielding
their full localization and the insulating state. These calculations show that
for the meaningful analysis of e-m properties of FeBr2 the spin-orbit coupling
is essentially important and that the orbital moment (0.74 mB) is largely
unquenched (by the off-cubic trigonal distortion in the presence of the
spin-orbit coupling).",0005502v1
2005-02-18,Rashba effect in quantum networks,"We present a formalism to study quantum networks made up by single-channel
quantum wires in the presence of Rashba spin-orbit coupling and magnetic field.
In particular, linear transport through one-dimensional and two-dimensional
finite-size networks is studied by means of the scattering formalism. In some
particular quantum networks, the action of the magnetic field or of the Rashba
spin-orbit coupling induces localization of the electron wave function. This
phenomenon, which relies on both the quantum-mechanical interference and the
geometry of the network, is manifested through the suppression of the
conductance for specific values of the spin-orbit-coupling strength or of the
magnetic field. Furthermore, the interplay of the Aharonov-Bohm phases and of
the non-Abelian phases introduced by spin-orbit coupling, is discussed in a
number of cases.",0502455v2
2005-09-07,Energy levels and magneto-optical transitions in parabolic quantum dots with spin-orbit coupling,"We report on the electronic properties of few interacting electrons confined
in a parabolic quantum dot based on a theoretical approach developed to
investigate the influence of Bychkov-Rashba spin-orbit (SO) interaction on such
a system. We note that the spin-orbit coupling profoundly influences the energy
spectrum of interacting electrons in a quantum dot. Here we present accurate
results for the energy levels and optical-absorption spectra for parabolic
quantum dots containing upto four interacting electrons, in the presence of
spin-orbit coupling and under the influence of an externally applied,
perpendicular magnetic field. We have described in detail about a very accurate
numerical scheme to evaluate these quantities. We have evaluated the effects of
SO coupling on the Fock-Darwin spectra for quantum dots made out of three
different semiconductor systems, InAs, InSb, and GaAs.",0509170v1
2005-10-25,Intrinsically s-wave like property of triplet superconductors with spin-orbit coupling,"We have studied a general property of unconventional superconductors with
spin-orbit coupling by solving the Bogoliubov-de Gennes equation and found that
the two of four eigenfunctions for triplet pairing coincide with those for
s-wave pairing when a relation holds between pairing symmetry and spin-orbit
coupling, indicative of an intrinsically s-wave like property of triplet
superconductors. Applying the result, we have studied the tunneling conductance
in normal metal / insulator / unconventional superconductor junctions with a
candidate of pairing symmetry of CePt$_3$Si. The effect of Rashba spin-orbit
coupling (RSOC) is taken into account. We have found that the RSOC induces a
peak at the energy gap like s-wave superconductors in the tunneling spectrum.",0510659v1
2006-05-08,Large Bychkov-Rashba spin-orbit coupling in high-mobility GaN/AlGaN heterostructures,"We present low temperature magnetoconductivity measurements of a
density-tunable and high mobility two-dimensional electron gas confined in the
wide bandgap GaN/AlGaN system. We observed pronounced anti-localization minima
in the low-field conductivity, indicating the presence of strong spin-orbit
coupling. Density dependent measurements of magnetoconductivity indicate that
the coupling is mainly due to the Bychkov-Rashba mechanism. In addition, we
have derived a closed-form expression for the magnetoconductivity, allowing us
to extract reliable transport parameters for our devices. The Rashba spin-orbit
coupling constant is $\alpha_{so}$ $\sim$ 6$\times$ 10$^{-13}$eVm, while the
conduction band spin-orbit splitting energy amounts to $\Delta_{so}$ $\sim$
0.3meV at n$_e$=1$\times10^{16}$m$^{-2}$.",0605155v1
2007-09-19,Splitting of Andreev levels in a Josephson junction by spin-orbit coupling,"We consider the effect of spin-orbit coupling on the energy levels of a
single-channel Josephson junction below the superconducting gap. We investigate
quantitatively the level splitting arising from the combined effect of
spin-orbit coupling and the time-reversal symmetry breaking by the phase
difference between the superconductors. Using the scattering matrix approach we
establish a simple connection between the quantum mechanical time delay matrix
and the effective Hamiltonian for the level splitting. As an application we
calculate the distribution of level splittings for an ensemble of chaotic
Josephson junctions. The distribution falls off as a power law for large
splittings, unlike the exponentially decaying splitting distribution given by
the Wigner surmise -- which applies for normal chaotic quantum dots with
spin-orbit coupling in the case that the time-reversal symmetry breaking is due
to a magnetic field.",0709.3054v1
2007-11-14,$Σ$-nuclear spin-orbit coupling from two-pion exchange,"Using SU(3) chiral perturbation theory we calculate the density-dependent
complex-valued spin-orbit coupling strength $U_{\Sigma ls}(k_f)+ i W_{\Sigma
ls}(k_f)$ of a $\Sigma$ hyperon in the nuclear medium. The leading long-range
$\Sigma N$ interaction arises from iterated one-pion exchange with a $\Lambda$
or a $\Sigma$ hyperon in the intermediate state. We find from this unique
long-range dynamics a sizeable ``wrong-sign'' spin-orbit coupling strength of
$U_{\Sigma ls}(k_{f0}) \simeq -20$ MeVfm$^2$ at normal nuclear matter density
$\rho_0 = 0.16 $fm$^{-3}$. The strong $\Sigma N\to \Lambda N$ conversion
process contributes at the same time an imaginary part of $W_{\Sigma
ls}(k_{f0}) \simeq -12$ MeVfm$^2$. When combined with estimates of the
short-range contribution the total $\Sigma$-nuclear spin-orbit coupling becomes
rather weak.",0711.2237v1
2009-04-02,Few-electron physics in a nanotube quantum dot with spin-orbit coupling,"We study the few-electron eigenspectrum of a nanotube quantum dot with
spin-orbit coupling. The two-electron phase diagram as a function of the length
of the dot and the applied parallel magnetic field shows clear signatures of
both spin-orbit coupling and electron-electron interaction. Below a certain
critical length, ground state transitions are correctly predicted by a
single-particle picture and are mainly independent of the length of the dot
despite the presence of strong correlations. However, for longer quantum dots
the critical magnetic field strongly decreases with increasing length, which is
a pure interaction effect. In fact, the new ground state is spin- and
valley-polarized, which implies a strong occupation of higher longitudinal
modes.",0904.0445v2
2010-06-04,The effect of spin-orbit interaction and attractive Coulomb potential on the magnetic properties of Ga$_{1-x}$Mn$_{x}$As,"We employ the dynamical mean-field approximation to study the magnetic
properties of a model relevant for the dilute magnetic semiconductors. Our
model includes the spin-orbit coupling on the hole bands, the exchange
interaction, and the attractive Coulomb potential between the negatively
charged magnetic ions and the itinerant holes. The inclusion of the Coulomb
potential significantly renormalizes the exchange coupling and enhances the
ferromagnetic transition temperature for a wide range of couplings. We also
explore the effect of the spin-orbit interaction by using two different values
of the ratio of the effective masses of the heavy and light holes. We show that
in the regime of small $J_{c}$-$V$ the spin-orbit interaction enhances $T_{c}$,
while for large enough values of $J_{c}$-$V$ magnetic frustration reduces $T_c$
to values comparable to the previously calculated strong coupling limit.",1006.0998v2
2010-07-18,Robustness of Majorana Modes and Minigaps in a Spin-Orbit-Coupled Semiconductor-Superconductor Heterostructure,"We study the robustness of Majorana zero energy modes and minigaps of
quasiparticle excitations in a vortex by numerically solving
Bogoliubov-deGennes equations in a heterostructure composed of an \textit{s}
-wave superconductor, a spin-orbit-coupled semiconductor thin film, and a
magnetic insulator. This heterostructure was proposed recently as a platform
for observing non-Abelian statistics and performing topological quantum
computation. The dependence of the Majorana zero energy states and the minigaps
on various physics parameters (Zeeman field, chemical potential, spin-orbit
coupling strength) is characterized. We find the minigaps depend strongly on
the spin-orbit coupling strength. In certain parameter region, the minigaps are
linearly proportional to the \textit{s}-wave superconducting pairing gap
$\Delta_{s}$, which is very different from the $\Delta_{s}^{2}$ dependence in a
regular \textit{s-} or \textit{\p}-wave superconductor. We characterize the
zero energy chiral edge state at the boundary and calculate the STM signal in
the vortex core that shows a pronounced zero energy peak. We show that the
Majorana zero energy states are robust in the presence of various types of
impurities. We find the existence of impurity potential may increase the
minigaps and thus benefit topological quantum computation.",1007.2972v2
2011-03-01,Two-orbital Kondo effect in quantum dot coupled to ferromagnetic leads,"We study the Kondo effect of a two-orbital vertical quantum dot (QD) coupled
to two ferromagnetic leads by employing an equation of motion method. When the
ferromagnetic leads are coupled with parallel spin polarization, we find three
peaks in the single-particle excitation spectra. The middle one is the Kondo
resonance caused by the orbital degrees of freedom. In magnetic fields, the
Kondo effect vanishes. However, at a certain magnetic field new two-fold
degenerate states arise and the Kondo effect emerges there. In contrast, when
the ferromagnetic leads are coupled with antiparallel spin polarization, the
Kondo effect caused by the spin (orbital) degrees of freedom survives (is
suppressed) in magnetic fields. We investigate the field dependence of the
conductance in the parallel and antiparallel spin polarizations of the leads
and find that the conductance changes noticeably in magnetic fields.",1103.0304v2
2011-05-11,Spin-Orbit Coupled Fermi Gases across a Feshbach Resonance,"In this letter we study both ground state properties and the superfluid
transition temperature of a spin-1/2 Fermi gas across a Feshbach resonance with
a synthetic spin-orbit coupling, using mean-field theory and exact solution of
two-body problem. We show that a strong spin-orbit coupling can significantly
enhance the pairing gap for 1/(k_F a_s)<=0 due to increased density-of-state.
Strong spin-orbit coupling also significantly enhances the superfluid
transition temperature when 1/(k_F a_s)<=0, while suppresses it slightly when
1/(k_F a_s)>0. The universal interaction energy and pair size at resonance are
also discussed.",1105.2250v3
2011-05-28,Paired Superfluidity and Fractionalized Vortices in Spin-orbit Coupled Bosons,"In this letter we study finite temperature properties of spin-1/2 interacting
bosons with spin-orbit coupling in two dimensions. When the ground state has
stripe order, we show that thermal fluctuations will first melt the stripe
order and lead to a superfluid of boson pairs if the spin-orbit coupling is
isotropic or nearly isotropic. Such a phase supports fractionalized quantum
vortices. The Kosterlize-Thouless transition from superfluid to normal state is
driven by proliferation of half vortices. When the ground state is a plane wave
state, the transition to normal state is driven by conventional
Kosterlize-Thouless transition. However, the critical temperature will drop to
zero for isotropic spin-orbit coupling.",1105.5700v1
2011-08-22,Spin-orbit coupled weakly interacting Bose-Einstein condensates in harmonic traps,"We investigate theoretically the phase diagram of a spin-orbit coupled Bose
gas in two-dimensional harmonic traps. We show that discrete Landau levels
develop at strong spin-orbit coupling. For a weakly interacting gas, quantum
states with skyrmion lattice patterns emerge spontaneously and preserve either
parity symmetry or combined parity-time-reversal symmetry. These phases can be
readily observed by experimentally engineering spin-orbit coupling and
interatomic interactions for a cloud of $^{87}$Rb atoms in a highly oblate
trap.",1108.4233v3
2012-10-08,Momentum-resolved radio-frequency spectroscopy of a spin-orbit coupled atomic Fermi gas near a Feshbach resonance in harmonic traps,"We theoretically investigate the momentum-resolved radio-frequency
spectroscopy of a harmonically trapped atomic Fermi gas near a Feshbach
resonance in the presence of equal Rashba and Dresselhaus spin-orbit coupling.
The system is qualitatively modeled as an ideal gas mixture of atoms and
molecules, in which the properties of molecules, such as the wavefunction,
binding energy and effective mass, are determined from the two-particle
solution of two-interacting atoms. We calculate separately the radio-frequency
response from atoms and molecules at finite temperatures by using the standard
Fermi golden rule, and take into account the effect of harmonic traps within
local density approximation. The total radio-frequency spectroscopy is
discussed, as functions of temperature and spin-orbit coupling strength. Our
results give a qualitative picture of radio-frequency spectroscopy of a
resonantly interacting spin-orbit coupled Fermi gas and can be directly tested
in atomic Fermi gases of K40 atoms at Shanxi University and of Li6 atoms at
MIT.",1210.2160v2
2012-12-17,Spectral Gaps of Spin-orbit Coupled Particles in Deformed Traps,"We consider a spin-orbit coupled system of particles in an external trap that
is represented by a deformed harmonic oscillator potential. The spin-orbit
interaction is a Rashba interaction that does not commute with the trapping
potential and requires a full numerical treatment in order to obtain the
spectrum. The effect of a Zeeman term is also considered. Our results
demonstrate that variable spectral gaps occur as a function of strength of the
Rashba interaction and deformation of the harmonic trapping potential. The
single-particle density of states and the critical strength for superfluidity
vary tremendously with the interaction parameter. The strong variations with
Rashba coupling and deformation implies that the few- and many-body physics of
spin-orbit coupled systems can be manipulated by variation of these parameters.",1212.4051v4
2013-05-21,Ultracold collision in the presence of synthetic spin-orbit coupling,"We present an analytic description of ultracold collision between two
spin-$\frac{1}{2}$ fermions with isotropic spin-orbit coupling of the Rashba
type. We show that regardless of how weak the spin-orbit coupling may be, the
ultracold collision at sufficiently low energies is significantly modified,
including the ubiquitous Wigner threshold behavior. We further show that the
particles are preferably scattered into the lower-energy helicity state due to
the break of parity conservation, thus establishing interaction with spin-orbit
coupling as one mechanism for the spontaneous emergence of handedness.",1305.4750v1
2013-07-11,Unconventional Fulde-Ferrell-Larkin-Ovchinnikov pairing states in a Fermi gas with spin-orbit coupling,"We study the phase diagram in a two-dimensional Fermi gas with the synthetic
spin-orbit coupling that has recently been realized experimentally. In
particular, we characterize in detail the properties and the stability region
of the unconventional Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states in such a
system, which are induced by spin-orbit coupling and Fermi surface asymmetry.
We identify several distinct nodal FFLO states by studying the topology of
their respective gapless contours in momentum space. We then examine the phase
structure and the number density distributions in a typical harmonic trapping
potential under the local density approximation. Our studies provide detailed
information on the FFLO pairing states with spin-orbit coupling and Fermi
surface asymmetry, and will facilitate experimental detection of these
interesting pairing states in the future.",1307.3117v1
2014-04-24,Beating pattern in quantum magnetotransport coefficients of spin-orbit coupled Dirac fermions in gated silicene,"We report theoretical study of magnetotransport coefficients of spin-orbit
coupled gated silicene in presence and absence of spatial periodic modulation.
The combined effect of spin-orbit coupling and perpendicular electric field
manifests through formation of regular beating pattern in Weiss and SdH
oscillations. Analytical results, in addition to the numerical results, of the
beating pattern formation are provided. The analytical results yield a beating
condition which will be useful to determine the spin-orbit coupling constant by
simply counting the number of oscillation between any two successive nodes.
Moreover, the numerical results of modulation effect on collisional and Hall
conductivities are presented.",1404.6188v1
2014-10-30,Nonadiabatic multichannel dynamics of a spin-orbit coupled condensate,"We investigate the nonadiabatic dynamics of a driven spin-orbit-coupled
Bose-Einstein condensate in both weak and strong driven force. It is shown that
the standard Landau-Zener (LZ) tunneling fails in the regime of weak driven
force and/or strong spin-orbital coupling, where the full nonadiabatic dynamics
requires a new mechanism through multichannel effects. Beyond the semiclassical
approach, our numerical and analytical results show an oscillating power-law
decay in the quantum limit, different from the exponential decay in the
semiclassical limit of the LZ effect. Furthermore, the condensate density
profile is found to be dynamically fragmented by the multichannel effects and
enhanced by interaction effects. Our work therefore provides a complete picture
to understand the nonadiabatic dynamics of a spin-orbit coupled condensate,
including various range of driven force and interaction effects through
multichannel interference. The experimental indication of these nonadiabatic
dynamics is also discussed.",1410.8444v2
2014-11-11,"Three-dimensional spin-orbit coupled Fermi gases: Fulde-Ferrell pairing, Majorana fermions, Weyl fermions and gapless topological superfluidity","We theoretically investigate a three-dimensional Fermi gas with Rashba
spin-orbit coupling in the presence of both out-of-plane and in-plane Zeeman
fields. We show that, driven by a sufficiently large Zeeman field, either
out-of-plane or in-plane, the superfluid phase of this system exhibits a number
of interesting features, including inhomogeneous Fulde-Ferrell pairing, gapped
or gapless topological order and exotic quasi-particle excitations known as
Weyl fermions that have linear energy dispersions in momentum space (i.e.,
massless Dirac fermions). The topological superfluid phase can have either four
or two topologically protected Weyl nodes. We present the phase diagrams at
both zero and finite temperatures and discuss the possibility of their
observation in an atomic Fermi gas with synthetic spin-orbit coupling. In this
context, topological superfluid phases with an imperfect Rashba spin-orbit
coupling are also studied.",1411.2993v1
2015-06-01,Spin-orbit coupling and proximity effects in metallic carbon nanotubes,"We study spin-orbit coupling in metallic carbon nanotubes (CNTs) within the
many-body Tomonaga-Luttinger liquid (TLL) framework. For a well defined
sub-class of metallic CNTs, that contains both achiral zig-zag as well as a
sub-set of chiral tubes, an effective low energy field theory description is
derived. We aim to describe system at finite dopings, but close to the charge
neutrality point (commensurability). A new regime is identified where
spin-orbit coupling leads to an inverted hierarchy of mini-gaps of bosonic
modes. We then add a proximity coupling to a superconducting (SC) substrate and
show that the only order parameter that is supported within the novel,
spin-orbit induced phase is a topologically trivial s-SC.",1506.00465v2
2015-07-28,Topological features of hydrogenated graphene,"Hydrogen adatoms are one of the most the promising proposals for the
functionalization of graphene. Hydrogen induces narrow resonances near the
Dirac energy, which lead to the formation of magnetic moments. Furthermore,
they also create local lattice distortions which enhance the spin-orbit
coupling. The combination of magnetism and spin-orbit coupling allows for a
rich variety of phases, some of which have non trivial topological features. We
analyze the interplay between magnetism and spin-orbit coupling in ordered
arrays of hydrogen on graphene monolayers, and classify the different phases
that may arise. We extend our model to consider arrays of adsorbates in
graphene-like crystals with stronger intrinsic spin-orbit couplings.",1507.07714v2
2015-11-05,Phase diagram and topological superfluid state of spin-orbit coupled Fermi gas with attractive interactions in a one-dimensional optical lattice,"Based on density matrix renormalization group method, we investigate the
spin-orbit coupled Fermi gas with attractive interactions in one-dimensional
optical lattice and present a complete phase diagram for a quarter-filling
system with intermediate strong interactions. We unveil the exotic pairings
induced by spin-orbit couplings and the phase transitions between different
pairing states, and further demonstrate the existence of the long-sought
topological superfluid state at moderate magnetic field and spin-orbit coupling
strength. For the particle conserved system, this topological superfluid state
can be fixed by its gapless single particle excitation, Luttinger parameter and
non-trivial boundary effect. Our study removes out the widespread doubt on the
existence of topological superfluid in one dimension and paves the way for
simulating topological superfluid states in cold atom settings.",1511.01762v1
2016-02-10,Excitation spectra of a Bose-Einstein condensate with an angular spin-orbit coupling,"A theoretical model of a Bose-Einstein condensate with angular spin-orbit
coupling has recently been proposed and it has been established that a
half-skyrmion represents the ground state in a certain regime of spin-orbit
coupling and interaction. Here we investigate low-lying excitations of this
phase by using the Bogoliubov method and numerical simulations of the
time-dependent Gross-Pitaevskii equation. We find that a sudden shift of the
trap bottom results in a complex two-dimensional motion of the system's center
of mass that is markedly different from the response of a competing phase, and
comprises two dominant frequencies. Moreover, the breathing mode frequency of
the half-skyrmion is set by both the spin-orbit coupling and the interaction
strength, while in the competing state it takes a universal value. Effects of
interactions are especially pronounced at the transition between the two
phases.",1602.03538v2
2016-09-18,Exotic Multi-fold Vortex Lattices of Spin-Orbit Coupled Bose-Einstein Condensates in Optical Lattices,"We investigate the ground state of two-dimensional Bose-Einstein condensates
with Rashba spin-orbit coupling in square optical lattices and demonstrate the
existence of rich phases with different lattice structures, which is closely
related to the degenerate structure of single particle energy spectrum induced
by the competition of spin-orbit coupling and optical lattices. We find that
the ground state is in the phase with either parity-time-reversal or parity
symmetry by direct numerical simulation. We show the phase diagram of ground
state in the whole regime of spin-orbit coupling strength, and particularly
find that the system supports multi-fold vortex lattices, in which ground state
holds half-quantum vortex lattices, vortex-antivortex pair lattices and
fundamental vortex lattices, simultaneously, when single particle energy
minimums touch the boundary of the first Brillouin zone.",1609.05489v1
2016-09-23,The mechanism of spin-orbit coupling in a 2D oxide interface,"The presence of spin-orbit coupling drives the anomalous magnetotransport at
oxide interfaces and forms the basis for numerous intriguing properties of
these 2D electron systems, such as topologically protected phases or
anti-localization. For many of those systems, the identification of the
underlying coupling mechanism is obfuscated by multi-band effects. We therefore
analyze the transport of LaAlO$_3$/SrTiO$_3$ interfaces under high pressures, a
technique to single out the multi-band contributions. We argue that the
observed magnetoresistance is due to quantum interference and not related to
Coulomb interaction. Therefore, this system is an excellent candidate to
generate a metal-insulator transition of the long-sought symplectic 2D
universality class. It is shown that the spin-orbit coupling can be linked
unambiguously to the band structure with a cubic (Dresselhaus-like) rather than
a linear (Rashba-like) spin-orbit band splitting.",1609.07425v1
2017-02-10,Phase space curvature in spin-orbit coupled ultracold atom systems,"We consider a system with spin-orbit coupling and derive equations of motion
which include the effects of Berry curvatures. We apply these equations to
investigate the dynamics of particles with equal Rashba-Dresselhaus spin-orbit
coupling in one dimension. In our derivation, the adiabatic transformation is
performed first and leads to quantum Heisenberg equations of motion for
momentum and position operators. These equations explicitly contain
position-space, momentum-space, and phase-space Berry curvature terms.
Subsequently, we perform the semiclassical approximation, and obtain the
semiclassical equations of motion. Taking the low-Berry-curvature limit results
in equations that can be directly compared to previous results for the motion
of wavepackets. Finally, we show that in the semiclassical regime, the
effective mass of the equal Rashba-Dresselhaus spin-orbit coupled system can be
viewed as a direct effect of the phase-space Berry curvature.",1702.03298v2
2018-04-21,Topological phase and chiral edge states of bilayer graphene with staggered sublattice potentials and Hubbard interaction,"Gated heterostructures containing bilayer graphene with staggered sublattice
potentials are investigated by tight binding model with Rashba spin-orbital
coupling and Hubbard interaction. The topological phase diagrams depend on the
combinations of substrates and the Hubbard interaction. The presence of the
staggered sublattice potential favor the topological phase transition with
small Rashba spin-orbital coupling strength. The presence of the Hubbard
interaction modified the topological phase boundaries, increasing the minimal
spin-orbital coupling strength for topological phase transition. A phase space
of topological semi-metal with indirect band gap is identified in the
non-interacting systems. For the bilayer graphene with different staggered
sublattice potentials in the two layers, the conditions for the zigzag
nanoribbons to host edge polarized chiral edge states are discussed. The
conditions require moderate or vanishing Rashba spin-orbital coupling strength,
as well as proper range of the gate voltage. The conditions for the systems
with and without the Hubbard interaction are compared. The edge polarization
can be controlled by the gate voltage.",1804.07868v4
2013-08-30,Ferromagnetism in a two-component Bose-Hubbard model with a synthetic spin-orbit coupling,"We study the effect of the synthetic spin-orbit coupling in a two-component
Bose-Hubbard model in one dimension by employing the density-matrix
renormalization group method. A ferromagnetic long-range order emerges in both
Mott insulator and superfluid phases resulting from the spontaneous breaking of
the $Z_2$ symmetry, when the spin-orbit coupling term becomes comparable to the
hopping kinetic energy and the inter-component interaction is smaller than the
intra-one as well. This novel effect is expected to be detectable with the
present realization of the synthetic spin-orbit coupling in experiments.",1308.6710v3
2013-09-26,Proximity effect of spin orbit coupling in Pt/Co2FeAl and Pt/Permalloy bilayers_810571,"Proximity effect of spin orbit coupling is investigated through anomalous
Hall effect in Pt/Co2FeAl and Pt/Permalloy bilayers. A series of nontrivial
magnetotransport behaviors, resulting from a strong impact of phonons on skew
scattering, is observed in these films with ultrathin ferromagnetic layers. The
parameters representing skew scattering, side jump and intrinsic contributions
are dramatically enhanced when the ferromagnetic layer is very thin, and they
have clear linear dependences on the reciprocal of ferromagnetic layer
thickness, indicating a powerful influence of Pt/Ferromagnet interface. Further
study on Cu/Co2FeAl and Ta/Co2FeAl bilayers reveals that a simple interface
scattering without intense spin orbit coupling is not sufficient to trigger
such a phenomenon. The proximity effect of spin orbit coupling is thus
suggested to occur at the Pt/Ferromagnet interface, and as a result quite large
anomalous Hall angle (0.036) and Nernst angle (0.23) are confirmed in the
Pt/CFA films at room temperature.",1309.7023v1
2016-08-23,Calculating branching ratio and spin-orbit coupling from first-principles: A formalism and its application to iridates,"We present a simple technique to calculate spin-orbit coupling, $\langle {\bf
L}\cdot{\bf S} \rangle$, and branching ratio measured in x-ray absorption
spectroscopy. Our method is for first-principles electronic structure
calculation and its implementation is straightforward for any of standard
formulations and codes. We applied this technique to several different large
spin-orbit coupling iridates. The calculated $\langle{ {\bf L}\cdot{\bf S}}
\rangle$ and branching ratio of a prototype $j_{\rm eff}$=1/2 Mott insulator,
Sr$_2$IrO$_4$, are in good agreement with recent experimental data over the
wide range of Rh-doping. Three different double perovskite iridates (namely,
Sr$_2$MgIrO$_6$, Sr$_2$ScIrO$_6$, and Sr$_2$TiIrO$_6$) are also well described.
This technique can serve as a promising tool for studying large spin-orbit
coupling materials from first-principles and for understanding experiments.",1608.06388v1
2016-12-06,Odd-petal states and persistent flows in spin-orbit-coupled Bose-Einstein condensates,"We study the phase diagram of a Rashba spin-orbit-coupled Bose-Einstein
condensate confined in a two-dimensional toroidal trap. In the immiscible
regime we find an azimuthally periodic density distribution, with the
periodicity highly tuneable as a function of the spin-orbit coupling strength
and which favours an odd number of petals in each component. This allows for a
wide range of states that can be created. We further show that in the miscible
regime, both components possess states with persistent flows with a unit
winding number difference between them and with the absolute values of these
winding numbers depending on the spin-orbit coupling strength. All features of
the odd-petal and the persistent flow states can be explained using a simple
but effective model.",1612.01713v3
2016-12-08,Topological Phonon Modes in A Two-Dimensional Wigner Crystal,"We investigate the spin-orbit coupling effect in a two-dimensional Wigner
crystal. We show that sufficiently strong spin-orbit coupling and an
appropriate sign of g-factor could transform the Wigner crystal to a
topological phonon system. We demonstrate the existence of chiral phonon edge
modes in finite size samples, as well as the robustness of the modes in the
topological phase. We explore the possibility of realizing the topological
phonon system in two-dimensional Wigner crystals confined in semiconductor
quantum wells/heterostructure. We find that the spin-orbit coupling is too weak
for driving a topological phase transition in these systems. We argue that one
may look for the topological phonon system in correlated Wigner crystals with
emergent effective spin-orbit coupling.",1612.02871v1
2017-07-08,Spin-Orbit Coupling and Electronic Correlations in Sr2RuO4,"We investigate the interplay of spin-orbit coupling (SOC) and electronic
correlations in Sr2RuO4 using dynamical mean-field theory. We find that SOC
does not affect the correlation-induced renormalizations, which validates the
Hund's metal picture of ruthenates even in the presence of the sizable SOC
relevant to these materials. Nonetheless, SOC found to change significantly the
electronic structure at k-points where a degeneracy applies in its absence. We
explain why these two observations are consistent with one another and
calculate effects of SOC on the correlated electronic structure. The magnitude
of these effects is found to depend on the energy of the quasiparticle state
under consideration, leading us to introduce the notion of an ""energy-dependent
quasiparticle spin-orbit coupling"". This notion is generally applicable to all
materials in which both the spin-orbit coupling and electronic correlations are
sizable.",1707.02462v2
2018-01-24,Superconducting monolayer deposited on substrate: effects of the spin-orbit coupling induced by proximity effects,"The spin-orbit coupling can lead to exotic states of matter and unexpected
behavior of the system properties. In this paper, we investigate the influence
of spin-orbit coupling induced by proximity effects on a monolayer of
superconductor (with s-wave or d-wave pairing) placed on an insulating bulk. We
show that the critical temperatures $T_{c}$ of the superconducting states can
be tuned by the spin-orbit coupling both in the case of on-site and inter-site
pairing. Moreover, we discuss a possibility of changing the location of the
maximal $T_{c}$ from the half-filling into the underdoped or overdoped regimes.",1801.08055v1
2019-06-18,Topological phase transition induced by magnetic proximity effect in two dimensions,"We study the magnetic proximity effect on a two-dimensional topological
insulator in a CrI$_3$/SnI$_3$/CrI$_3$ trilayer structure. From
first-principles calculations, the BiI$_3$-type SnI$_3$ monolayer without
spin-orbit coupling has Dirac cones at the corners of the hexagonal Brillouin
zone. With spin-orbit coupling turned on, it becomes a topological insulator,
as revealed by a non-vanishing $Z_2$ invariant and an effective model from
symmetry considerations. Without spin-orbit coupling, the Dirac points are
protected if the CrI$_3$ layers are stacked ferromagnetically, and are gapped
if the CrI$_3$ layers are stacked antiferromagnetically, which can be explained
by the irreducible representations of the magnetic space groups $C_{3i}^1$ and
$C_{3i}^1(C_3^1)$, corresponding to ferromagnetic and antiferromagnetic
stacking, respectively. By analyzing the effective model including the
perturbations, we find that the competition between the magnetic proximity
effect and spin-orbit coupling leads to a topological phase transition between
a trivial insulator and a topological insulator.",1906.07507v1
2019-09-26,Anharmonicity Induced Supersolidity In Spin-Orbit Coupled Bose-Einstein Condensates,"Supersolid, a fascinating quantum state of matter, features novel phenomena
such as the non-classical rotational inertia and transport anomalies. It is a
long standing issue of the coexistence of superfluidity and broken
translational symmetry in condensed matter physics. By recent experimental
advances to create tunable synthetic spin-orbit coupling in ultracold gases,
such highly controllable atomic systems would provide new possibilities to
access supersolidity with no counterpart in solids. Here we report that the
combination of anharmonicity of trapping potential and spin-orbit coupling will
provide a new paradigm to achieve supersolids. By means of imaginary time
evolution of the Gross-Pitaevskii equation, we demonstrate that a supersolid
state can be found when considering a trapped Rashba-type spin-orbit coupled
bosonic atoms loaded in a one-dimensional optical lattice. Furthermore, a
skyrmion-anti-skyrmion lattice is associated with the appearance of such
supersoildity, indicating the topological nontrivial properties of our proposed
supersolids.",1909.11871v1
2012-05-30,Spin-Orbit Coupling in Iridium-Based 5d Compounds Probed by X-ray Absorption Spectroscopy,"We have performed x-ray absorption spectroscopy (XAS) measurements on a
series of Ir-based 5d transition metal compounds, including Ir, IrCl3, IrO2,
Na2IrO3, Sr2IrO4, and Y2Ir2O7. By comparing the intensity of the ""white-line""
features observed at the Ir L2 and L3 absorption edges, it is possible to
extract valuable information about the strength of the spin-orbit coupling in
these systems. We observe remarkably large, non-statistical branching ratios in
all Ir compounds studied, with little or no dependence on chemical composition,
crystal structure, or electronic state. This result confirms the presence of
strong spin-orbit coupling effects in novel iridates such as Sr2IrO4, Na2IrO3,
and Y2Ir2O7, and suggests that even simple Ir-based compounds such as IrO2 and
IrCl3 may warrant further study. In contrast, XAS measurements on Re-based 5d
compounds, such as Re, ReO2, ReO3, and Ba2FeReO6, reveal statistical branching
ratios and negligible spin-orbit coupling effects.",1205.6540v1
2017-09-06,An oscillating Casimir potential between two impurities in a spin-orbit coupled Bose-Einstein condensate,"We study the Casimir potential between two impurities immersed in a
spin-orbit coupled BoseEinstein condensate (BEC) with plane-wave order. We find
that, by exchanging the virtual phonons/excitations, a remarkable anisotropic
oscillating potential with both positive and negative parts can be induced
between the impurities, with the period of the oscillation depending on the
spin-orbit coupling strength. As a consequence, this would inevitably lead to a
non-central Casimir force, which can be tuned by varying the strength of
spin-orbit coupling . These results are elucidated for BECs with
one-dimensional Raman-induced and two-dimensional Rashba-type SOC.",1709.01978v1
2017-09-20,Bound States in the Continuum in Spin-Orbit Coupled Atomic Systems,"We show that the interplay between spin-orbit coupling and Zeeman splitting
in atomic systems can lead to the existence of bound states in the continuum
(BICs) supported by trapping potentials. Such states have energies falling well
within the continuum spectrum, but nevertheless they are localized and fully
radiationless. We report the existence of BICs, in some cases in exact
analytical form, in systems with tunable spin-orbit coupling and show that the
phenomenon is physically robust. We also found that BIC states may be excited
in spin-orbit-coupled Bose-Einstein condensates, where under suitable
conditions they may be metastable with remarkably long lifetimes.",1709.06987v1
2018-03-10,Topological Nonlinear Optics with Spin-Orbit coupled Bose-Einstein Condensate in Cavity,"We report topological nonlinear optics with spin-orbit coupled Bose-Einstein
condensate in a cavity. The cavity is driven by a pump laser and weak probe
laser which excite Bose-Einstein condensate to an intermediate storage level,
where the standard Raman process engineers spin-orbit coupling. We show that
the nonlinear photonic interactions at the transitional pathways of dressed
states result in new type of optical transparencies, which get completely
inverted with atom induced gain. These nonlinear interactions also implant
topological sort of features in probe transmission modes by inducing gapless
Dirac-like cones, which become gaped in presence of Raman detuning. The
topological features get interestingly enhanced in gain regime where the
gapless topological edge-like states emerge among the probe modes, which can
cause non-trivial phase transition. We show that spin-orbit coupling and Zeeman
field effects also impressively revamp fast and slow probe light. The
manipulation of dressed states for quantum nonlinear optics with topological
characteristics in our findings could be a crucial step towards topological
quantum computation.",1803.03815v1
2018-08-06,Thermal Hall Conductivity in Superconducting Phase on Kagome Lattice,"Motivated by a previous ""$sd^2$-graphene"" study, the pairing symmetry in the
superconducting state and the thermal Hall conductivity are investigated by a
self-consistent Bogoliubov--de Gennes approach on the kagome lattice with
intrinsic spin-orbit coupling near van Hove fillings. While the topologically
trivial state with broken time-reversal symmetry appears in the absence of
spin-orbit coupling, the highest flat band becomes dispersive with a hexagonal
symmetry due to spin-orbit coupling, which leads to a topological
superconducting state. Since the thermal Hall conductivity in the
low-temperature limit is associated with the topological property of
time-reversal symmetry breaking superconductors, we study its temperature
dependence near van Hove fillings. In particular, the pairing symmetry in the
highest flat band is sensitive to the amplitudes of spin-orbit coupling and the
attractive interaction, which is reflected remarkably in the thermal Hall
conductivity. The obtained result may enable us to investigate the stable
superconducting state on the kagome lattice.",1808.01765v2
2019-02-22,Quantum solitons in spin-orbit-coupled Bose-Bose mixtures,"Recent experimental and theoretical results show that weakly interacting
atomic Bose-Bose mixtures with attractive interspecies interaction are
stabilized by beyond-mean-field effects. Here we consider the peculiar
properties of these systems in a strictly one-dimensional configuration, taking
also into account the nontrivial role of spin-orbit and Rabi couplings. We show
that when the value of inter- and intraspecies interaction strengths are such
that mean-field contributions to the energy cancel, a self-bound bright soliton
fully governed by quantum fluctuations exists. We derive the phase diagram of
the phase transition between a single-peak soliton and a multipeak (striped)
soliton, produced by the interplay between spin-orbit, Rabi couplings and
beyond-mean-field effects, which also affect the breathing mode frequency of
the atomic cloud. Finally, we prove that a phase imprinting of the single-peak
soliton leads to a self-confined propagating solitary wave even in the presence
of spin-orbit coupling.",1902.08603v2
2019-04-15,Charge transport of a spin-orbit-coupled Luttinger liquid,"The charge transport of a (Tomonaga-)Luttinger liquid with tunnel barriers
exhibits universal scaling: the current-voltage curves measured at various
temperatures collapse into a single curve upon rescaling. The exponent
characterizing this single curve can be used to extract the strength of
electron-electron interaction. Motivated by a recent experiment on InAs
nanowires [Sato et al., Phys. Rev. B 99, 155304 (2019)], we theoretically
investigate the analogous behavior of a spin-orbit-coupled Luttinger liquid. We
find that the scaling exponent differs for different impurity strengths, being
weak (disorder potential) or strong (tunnel barriers), and their positions,
either in the bulk or near the edge of the wire. For each case we quantify the
exponent of the universal scaling and its modification due to the spin-orbit
coupling. Our findings serve as a guide in the determination of the interaction
strength of quasi-one-dimensional spin-orbit-coupled quantum wires from
transport measurements.",1904.06869v2
2020-05-11,Universal relations for hybridized $s$- and $p$-wave interactions from spin-orbital coupling,"In this work, we study the universal relations for one-dimensional
spin-orbital-coupled fermions near both $s$- and $p$-wave resonances using
effective field theory. Since the spin-orbital coupling mixes different partial
waves, a contact matrix is introduced to capture the non-trivial correlation
between dimers. We find the signature of the spin-orbital coupling appears at
the leading order for the off-diagonal components of the momentum distribution
matrix, which is proportional to $1/q^{3}$ ($q$ is the relative momentum). We
further derive the large frequency behavior of the Raman spectroscopy, which
serves as an independent measurable quantity for contacts. Finally, we give an
explicit example of contacts by considering a two-body problem.",2005.04997v2
2020-10-08,Fraunhofer oscillations of the critical current at a varying Zeeman field in a spin-orbit coupled Josephson junction,"The Zeeman interaction results in spontaneous current through a Josephson
contact with a spin-orbit coupled normal metal, even in the absence of any
voltage, or phase bias. In the case of the Rashba spin orbit coupling of
electrons in a two-dimensional (2D) electron gas this effect takes place for
the Zeeman field which is parallel to the 2D system and to superconducting
contacts. At the same time, the spontaneous current is absent when this field
is perpendicular to the contacts. It is shown that in the latter case it may
manifest itself in oscillations of the critical Josephson current at the
varying Zeeman energy. These oscillations have a form of the Fraunhofer
diffraction pattern. The Josephson current under the phase bias was calculated
based on the semiclassical Green functions for a disordered 2D electron gas
with the strong spin orbit coupling, as well as for surface electrons of a
three dimensional topological insulator. In the latter case the diffraction
pattern was found to be most pronounced, while in the Rashba gas the
oscillations of the critical current are weaker.",2010.03932v1
2021-05-20,Coexistence of ferromagnetism and spin-orbit coupling by incorporation of platinum in two-dimensional VSe$_2$,"We report on a novel material, namely two-dimensional (2D)
V$_{1-x}$Pt$_x$Se$_2$ alloy, exhibiting simultaneously ferromagnetic order and
Rashba spin-orbit coupling. While ferromagnetism is absent in 1T-VSe$_2$ due to
the competition with the charge density wave phase, we demonstrate
theoretically and experimentally that the substitution of vanadium by platinum
in VSe$_2$ (10-50 %) to form an homogeneous 2D alloy restores ferromagnetic
order with Curie temperatures of 6 K for 5 monolayers and 25 K for one
monolayer of V$_{0.65}$Pt$_{0.35}$Se$_2$. Moreover, the presence of platinum
atoms gives rise to Rashba spin-orbit coupling in (V,Pt)Se$_2$ providing an
original platform to study the interplay between ferromagnetism and spin-orbit
coupling in the 2D limit.",2105.10022v1
2021-12-23,On the effective models of spin-orbit coupling in a two-dimensional electron gas,"We use the method of invariants to derive one- and two-band effective
Hamiltonians of a noncentrosymmetric two-dimensional electron gas, in the
presence of magnetic field. A complete classification of the antisymmetric
spin-orbit and magnetic coupling terms near the $\Gamma$ point is developed for
all two-dimensional crystal symmetries. The effective Hamiltonian depends on
the symmetry of the Bloch bands at the $\Gamma$ point, which is described by
one of the double-valued corepresentations of the two-dimensional magnetic
point group. In some bands, the spin-orbit coupling is cubic in the electron
momentum and the effective Zeeman interaction is strongly anisotropic. As an
example of a two-band effective Hamiltonian, we introduce a simple model of a
topological insulator with the intraband and interband spin-orbit coupling and
investigate its bulk and boundary properties.",2112.12657v1
2022-05-07,Interplay between the extended s-wave symmetry of the gap and the spin-orbit coupling in the low-electron concentration regime of quasi-two-dimensional superconductors,"We analyze the real-space paired state with the $\mathbf{k}$-dependent
superconducting gap in the presence of Rashba type spin-orbit coupling and
external magnetic field. We show that the $extended$ $s$-$wave$ pairing
symmetry is the most probable scenario to appear in the low-electron
concentration regime. According to our study, the van Hove singularity induced
by the spin-orbit coupling may lead to a significant enhancement of the
superconducting gap, critical temperature and critical magnetic field.
Moreover, the combined effect of the spin-orbit coupling and the external
magnetic field results in a non-zero total momentum of the Cooper pairs, which
is a characteristic feature of the so-called helical state. In such situation,
due to the C$_4$ symmetry breaking, a small $d$-$wave$ and $p$-$wave$
contributions to the pairing appear, which significantly change the character
of the helical state. The obtained results are discussed in the context of the
experimental data related with the unconventional superconducting features of
the transition metal oxide interfaces as well as the recently reported
supercurrent diode effect.",2205.03632v3
2022-06-24,Elementary excitations in a spin-orbit-coupled spin-1 Bose-Einstein condensate,"While a spin-orbit-coupled spin-1 Bose-Einstein condensate has been
experimentally observed, its elementary excitations remain unclear in the
stripe phase. Here, we systematically study the elementary excitations in three
distinct phases of a spin-orbit-coupled spin-1 Bose-Einstein condensate. We
find that the excitation spectrum as well as the corresponding static response
function and structure factor depend strongly on spin-orbit coupling parameters
such as the quadratic Zeeman field and the Rabi frequency. In the stripe phase,
besides two gapless Goldstone modes, we show the existence of roton
excitations. Finally, we demonstrate that quantum phase transitions between
these different phases including the zero-momentum, plane wave and stripe
phases are characterized by the sound velocities and the quantum depletion.",2206.12053v1
2022-08-16,Tunable planar Josephson junctions driven by time-dependent spin-orbit coupling,"Integrating conventional superconductors with common III-V semiconductors
provides a versatile platform to implement tunable Josephson junctions (JJs)
and their applications. We propose that with gate-controlled time-dependent
spin-orbit coupling, it is possible to strongly modify the current-phase
relations and Josephson energy and provide a mechanism to drive the JJ
dynamics, even in the absence of any bias current. We show that the transition
between stable phases is realized with a simple linear change in the strength
of the spin-orbit coupling, while the transition rate can exceed the
gate-induced electric field GHz changes by an order of magnitude. The resulting
interplay between the constant effective magnetic field and changing spin-orbit
coupling has direct implications for superconducting spintronics, controlling
Majorana bound states, and emerging qubits. We argue that topological
superconductivity, sought for fault-tolerant quantum computing, offers simpler
applications in superconducting electronics and spintronics.",2208.07512v2
2024-02-13,Spin-coupled molecular orbitals: chemical intuition meets quantum chemistry,"Molecular orbital theory is powerful both as a conceptual tool for
understanding chemical bonding, and as a theoretical framework for ab initio
quantum chemistry. Despite its undoubted success, MO theory has well documented
shortcomings, most notably that it fails to correctly describe diradical states
and homolytic bond fission. In this contribution, we introduce a generalised MO
theory that includes spin-coupled radical states. We show through archetypical
examples that when bonds break, the electronic state transitions between a
small number of valence configurations, characterised by occupation of both
delocalised molecular orbitals and spin-coupled localised orbitals. Our theory
provides a model for chemical bonding that is both chemically intuitive and
qualitatively accurate when combined with ab initio theory. Although
exploitation of our theory presents significant challenges for classical
computing, the predictable structure of spin-coupled states is ideally suited
to algorithms that exploit quantum computers. Our approach provides a
systematic route to overcoming the initial state overlap problem and unlocking
the potential of quantum computational chemistry.",2402.08858v1
2024-02-06,Emergence of Weyl Points due to Spin Orbit Coupling in LK-99,"Recent reports of room temperature ambient pressure superconductivity in
LK-99 sparked tremendous excitement. While the materials is no longer believed
to be superconducting, interest in its electronic and topological properties
still stands. Here, we utilize first-principle density functional theory and
augment a recently proposed model tight-binding Hamiltonian to study the band
topology including the impact of spin-orbit coupling. In the absence of
spin-orbit coupling, we observed the presence of two isolated bands situated
near the Fermi level. However, upon the introduction of spin-orbit coupling,
these two bands split into four bands and generate multiple Weyl points with
Chern number $\pm 2$. We also find accidental crossings along high symmetry
lines which, at the level of our minimal Hamiltonian, extend as nodal surfaces
away from these lines.",2402.18588v1
2018-11-04,Nonequatorial circular orbits of spinning particles in the Schwarzschild-de Sitter background,"In this paper analytical solutions of the Mathisson-Papapetrou equations that
describe nonequatorial circular orbits of a spinning particle in the
Schwarzschild-de Sitter background are studied, and the role of the
cosmological constant is emphasized. It is shown that generally speaking a
highly relativistic velocity of the particle is a necessary condition of motion
along this type of orbits, with an exception of orbits locating close to the
position of the static equilibrium, where low velocities are possible as well.
Depending on the correlation between the spin orientation of the particle and
its orbital velocity some of the possible nonequatorial circular orbits exist
due to the repulsive action on the particle caused by the spin-gravity coupling
and the others are caused by the attractive action.Here values of the energy of
the particle on the corresponding orbits are also analyzed.",1811.01391v2
2016-11-23,Dynamics of extended bodies with spin-induced quadrupole in Kerr spacetime: generic orbits,"We discuss motions of extended bodies in Kerr spacetime by using
Mathisson-Papapetrou-Dixon equations. We firstly solve the conditions for
circular orbits, and calculate the orbital frequency shift due to the mass
quadrupoles. The results show that we need not consider the spin-induced
quadrupoles in extreme-mass-ratio inspirals for spatial gravitational wave
detectors. We quantitatively investigate the temporal variation of rotational
velocity of the extended body due to the coupling of quadrupole and background
gravitational field. For generic orbits, we numerically integrate the
Mathisson-Papapetrou-Dixon equations for evolving the motion of an extended
body orbiting a Kerr black hole. By comparing with the monopole-dipole
approximation, we reveal the influences of quadrupole moments of extended
bodies on the orbital motion and chaotic dynamics of extreme-mass-ratio
systems. We do not find any chaotic orbits for the extended bodies with
physical spins and spin-induced quadrupoles. Possible implications for
gravitational wave detection and pulsar timing observation are outlined.",1611.07602v1
2015-11-04,Quantum Loop States in Spin-Orbital Models on the Honeycomb Lattice,"We construct a physically realistic and analytically tractable model for
spin-1 systems with orbital degeneracy on the honeycomb lattice, relevant to
honeycomb materials with large Hund's and weak spin-orbit couplings, and two
electrons in t2g orbitals. This model realizes many new phases whose building
blocks are orbital loops decorated by Haldane chains. These include a Haldane
loop crystal, a symmetry-protected topological phase, and, notably, a regime
where the decorated loops resonate. When taken to the three-dimensional
hyperhoneycomb lattice, the latter regime becomes a (symmetry-enriched) U(1)
quantum spin-orbital liquid, ""disordered"" both in the spin and orbital
channels. We hope this construction will pave the way for realizing many of the
Haldane-chain-based phases which have been theoretically proposed in the
literature.",1511.01505v1
2022-06-15,Bond Ordering and Molecular Spin-Orbital Fluctuations in the Cluster Mott Insulator GaTa$_4$Se$_8$,"For materials where spin-orbit coupling is competitive with electronic
correlations, the spatially anisotropic spin-orbital wavefunctions can
stabilize degenerate states that lead to many and diverse quantum phases of
matter. Here, we find evidence for a dynamical spin-orbital state preceding a
T$^*$=50 K order-disorder spin-orbital ordering transition in the $j\!=\!3/2$
lacunar spinel GaTa$_4$Se$_8$. Above T$^*$, GaTa$_4$Se$_8$ has an average cubic
crystal structure, but total scattering measurements indicate local non-cubic
distortions of Ta$_4$ tetrahedral clusters for all measured temperatures $2 < T
< 300$ K. Inelastic neutron scattering measurements reveal the dynamic nature
of these local distortions through symmetry forbidden optical phonon modes that
modulate $j\!=\!3/2$ molecular orbital occupation as well as intercluster Ta-Se
bonds. Spin-orbital ordering at T$^*$ cannot be attributed to a classic
Jahn-Teller mechanism and based on our findings, we propose that intercluster
interactions acting on the scale of T$^*$ act to break global symmetry. The
resulting staggered intercluster dimerization pattern doubles the unit cell,
reflecting a spin-orbital valence bond ground state.",2206.07738v1
2016-07-11,Orbital-differentiated coherence-incoherence crossover identified by photoemission spectroscopy in LiFeAs,"In the iron-based superconductors (FeSCs), orbital differentiation is an
important phenomenon, whereby correlations stronger on the dxy orbital than on
the dxz/yz orbital yield quasi-particles with dxy} orbital character having
larger mass renormalization and abnormal temperature evolution. However, the
physical origin of this orbital differentiation is debated between the Hund's
coupling induced unbinding of spin and orbital degrees of freedom and the
Hubbard interaction instigated orbital selective Mott transition. Here we use
angle-resolved photoemission spectroscopy to identify an orbital-dependent
correlation-induced quasi-particle (QP) anomaly in LiFeAs. The excellent
agreement between our photoemission measurements and first-principles many-body
theory calculations shows that the orbital-differentiated QP lifetime anomalies
in LiFeAs are controlled by the Hund's coupling.",1607.02947v1
2002-07-23,From the bulk to monatomic wires: An ab-initio study of magnetism in Co systems with various dimensionality,"A systematic ab-initio study within the framework of the local-spin-density
approximation including spin-orbit coupling and an orbital-polarization term is
performed for the spin and orbital moments and for the X-ray magnetic circular
dichroism (XMCD) spectra in hcp Co, in a Pt supported and a free standing Co
monolayer, and in a Pt supported and a free standing monatomic Co wire. When
including the orbital-polarization term, the orbital moments increase
drastically when going to lower dimensionality, and there is an increasing
asymmetry between the L_2 and L_3 XMCD signal. It is shown that spin and
orbital moments can be obtained with good accuracy from the XMCD spectra via
the sum rules. The <T_z> term of the spin sum rule is surprisingly small for
the wires, and the reason for this is discussed.",0207561v1
2002-05-08,"Interplay of charge, spin, orbital and lattice correlations in colossal magnetoresistance manganites","We derive a realistic microscopic model for doped colossal magnetoresistance
manganites, which includes the dynamics of charge, spin, orbital and lattice
degrees of freedom on a quantum mechanical level. The model respects the SU(2)
spin symmetry and the full multiplet structure of the manganese ions within the
cubic lattice. Concentrating on the hole doped domain ($0\le x\le 0.5$) we
study the influence of the electron-lattice interaction on spin and orbital
correlations by means of exact diagonalisation techniques. We find that the
lattice can cause a considerable suppression of the coupling between spin and
orbital degrees of freedom and show how changes in the magnetic correlations
are reflected in dynamic phonon correlations. In addition, our calculation
gives detailed insights into orbital correlations and demonstrates the
possibility of complex orbital states.",0205150v2
2016-12-09,The Fermi surface of Sr2RuO4: spin-orbit and anisotropic Coulomb interaction effects,"The topology of the Fermi surface of Sr2RuO4 is well described by
local-density approximation calculations with spin-orbit interaction, but the
relative size of its different sheets is not. By accounting for many-body
effects via dynamical mean-field theory, we show that the standard isotropic
Coulomb interaction alone worsens or does not correct this discrepancy. In
order to reproduce experiments, it is essential to account for the Coulomb
anisotropy. The latter is small but has strong effects; it competes with the
Coulomb-enhanced spin-orbit coupling and the isotropic Coulomb term in
determining the Fermi surface shape. Its effects are likely sizable in other
correlated multi-orbital systems. In addition, we find that the low-energy
self-energy matrix -- responsible for the reshaping of the Fermi surface --
sizably differ from the static Hartree-Fock limit. Finally, we find a strong
spin-orbital {entanglement}; this supports the view that the conventional
description of Cooper pairs via factorized spin and orbital part might not
apply to Sr2RuO4.",1612.03060v1
2007-07-18,Oscillation of spin polarization in a two-dimensional hole gas under a perpendicular magnetic field,"Spin-charge coupling is studied for a strongly confined two-dimensional hole
gas subject to a perpendicular magnetic field. The study is based on
spin-charge coupled drift-diffusion equations derived from quantum-kinetic
equations in an exact manner. The spin-orbit interaction induces an extra
out-of-plane spin polarization. This contribution exhibits a persistent
oscillatory pattern in the strong-coupling regime.",0707.2644v1
2009-07-17,Electrically controlled persistent spin currents at the interface of multiferroic oxides,"We predict the appearance of a persistent spin current in a two-dimensional
electron gas formed at the interface of multiferroic oxides with a transverse
helical magnetic order. No charge current is generated. This is the result of
an effective spin-orbit coupling generated by the topology of the oxide local
magnetic moments. The effective coupling and the generated spin current depend
linearly on the magnetic spiral helicity which, due to the magneto-electric
coupling, is tunable by a transverse electric field offering thus a new mean
for the generation of electrically controlled persistent spin currents.",0907.3023v1
2020-05-14,Vibrational Origin of Exchange Splitting and Chirality Induced Spin Selectivity,"Electron exchange and correlations emerging from the coupling between ionic
vibrations and electrons are addressed. Spin-dependent electron-phonon coupling
originates from the spin-orbit interaction, and it is shown that such
electron-phonon coupling introduces exchange splitting between the spin
channels in the structure. By application of these results to a model for a
chiral molecular structure mounted between metallic leads, the chirality
induced spin selectivity is found to become several tens of percents using
experimentally feasible parameters.",2005.06753v1
2021-12-09,Sign-Free Determinant Quantum Monte Carlo Study of Excitonic Density Orders in a Two-Orbital Hubbard-Kanamori Model,"While excitonic instabilities in multiorbital systems recently have come
under scrutiny in a variety of transition-metal compounds, understanding
emergence of these instabilities from strong electronic interactions has
remained a challenge. Here, we present a sign-problem-free determinant quantum
Monte Carlo study of excitonic density orders in a half-filled two-orbital
Hubbard-Kanamori model with broken orbital degeneracy, which accounts for the
role of Hund's coupling in transition-metal compounds. For strong inverted
(negative) Hund's exchange, we find numerical evidence for the emergence of
excitonic density order, with competition between anti-ferro-orbital order and
$\mathbf{Q} = (\pi,\pi)$ excitonic density order as a function of orbital
splitting and Hund's coupling. While inverted Hund's coupling stabilizes a
spin-singlet excitonic density phase for weak orbital splitting, positive
Hund's coupling favors a spin-triplet excitonic density phase.",2112.04718v1
2023-09-13,Spin-orbital correlations from complex orbital order in MgV$_{2}$O$_{4}$,"MgV$_{2}$O$_{4}$ is a spinel based on magnetic V$^{3+}$ ions which host both
spin ($S=1$) and orbital ($l_{eff}=1$) moments. Owing to the underlying
pyrochlore coordination of the magnetic sites, the spins in MgV$_{2}$O$_{4}$
only antiferromagnetically order once the frustrating interactions imposed by
the $Fd\overline{3}m$ lattice are broken through an orbitally-driven structural
distortion at T$_{S}$ $\simeq$ 60 K. Consequently, a N\'eel transition occurs
at T$_{N}$ $\simeq$ 40 K. Low temperature spatial ordering of the electronic
orbitals is fundamental to both the structural and magnetic properties, however
considerable discussion on whether it can be described by complex or real
orbital ordering is ambiguous. We apply neutron spectroscopy to resolve the
nature of the orbital ground state and characterize hysteretic spin-orbital
correlations using x-ray and neutron diffraction. Neutron spectroscopy finds
multiple excitation bands and we parameterize these in terms of a multi-level
(or excitonic) theory based on the orbitally degenerate ground state.
Meaningful for the orbital ground state, we report an ""optical-like"" mode at
high energies that we attribute to a crystal-field-like excitation from the
spin-orbital $j_{eff}$=2 ground state manifold to an excited $j_{eff}$=1 energy
level. We parameterize the magnetic excitations in terms of a Hamiltonian with
spin-orbit coupling and local crystalline electric field distortions resulting
from deviations from perfect octahedra surrounding the V$^{3+}$ ions. We
suggest that this provides compelling evidence for complex orbital order in
MgV$_{2}$O$_{4}$. We then apply the consequences of this model to understand
hysteretic effects in the magnetic diffuse scattering where we propose that
MgV$_{2}$O$_{4}$ displays a high temperature orbital memory of the low
temperature spin order.",2309.06853v1
2006-04-24,Theory of spin-Hall transport of heavy holes in semiconductor quantum wells,"Based on a proper definition of the spin current, we investigate the
spin-Hall effect of heavy holes in narrow quantum wells in the presence of
Rashba spin-orbit coupling by using a spin-density matrix approach. In contrast
to previous results obtained on the basis of the conventional definition of the
spin current, we arrive at the conclusion that an electric-field-induced
steady-state spin-Hall current does not exist in both, pure and disordered
infinite samples. Only an ac field can induce a spin-Hall effect in such
systems.",0604539v1
2006-07-19,Topological aspects of quantum spin Hall effect in graphene: Z$_2$ topological order and spin Chern number,"For generic time-reversal invariant systems with spin-orbit couplings, we
clarify a close relationship between the Z$_2$ topological order and the spin
Chern number proposed by Kane and Mele and by Sheng {\it et al.}, respectively,
in the quantum spin Hall effect. It turns out that a global gauge
transformation connects different spin Chern numbers (even integers) modulo 4,
which implies that the spin Chern number and the Z$_2$ topological order yield
the same classification. We present a method of computing spin Chern numbers
and demonstrate it in single and double plane of graphene.",0607484v1
2008-08-20,Electrical probing of the spin conductance of mesoscopic cavities,"We investigate spin-dependent transport in three--terminal mesoscopic
cavities with spin--orbit coupling. Focusing on the inverse spin Hall effect,
we show how injecting a pure spin current or a polarized current from one
terminal generates additional charge current and/or voltage across the two
output terminals. This allows to extract the spin conductance of the cavity
from two purely electrical measurements on the output. We use random matrix
theory to show that the spin conductance of chaotic ballistic cavities
fluctuates universally about zero mesoscopic average and describe experimental
implementations of mesoscopic spin to charge current converters.",0808.2756v2
2014-09-25,Interfacial Spin and Heat Transfer between Metals and Magnetic Insulators,"We study the role of thermal magnons in the spin and heat transport across a
normal-metal/insulating-ferromagnet interface, which is beyond an elastic
electronic spin transfer. Using an interfacial exchange Hamiltonian, which
couples spins of itinerant and localized orbitals, we calculate spin and energy
currents for an arbitrary interfacial temperature difference and misalignment
of spin accumulation in the normal metal relative to the ferromagnetic order.
The magnonic contribution to spin current leads to a temperature-dependent
torque on the magnetic order parameter; reciprocally, the coherent precession
of the magnetization pumps spin current into the normal metal, the magnitude of
which is affected by the presence of thermal magnons.",1409.7128v1
2004-02-26,Decoherence of transported spin in multichannel spin-orbit coupled spintronic devices: Scattering approach to spin density matrix from the ballistic to the localized regime,"By viewing current in the detecting lead of a spintronic device as being an
ensemble of flowing spins corresponding to a mixed quantum state, where each
spin itself is generally described by an improper mixture generated during the
transport where it couples to other degrees of freedom due to spin-orbit (SO)
interactions or inhomogeneous magnetic fields, we introduce the spin density
operator associated with such current expressed in terms of the spin-resolved
Landauer transmission matrix of the device. This formalism, which provides
complete description of coupled spin-charge quantum transport in open
finite-size systems attached to external probes, is employed to understand how
initially injected pure spin states, comprising fully spin-polarized current,
evolve into the mixed ones corresponding to partially polarized current. We
analyze particular routes that diminish spin coherence (signified by decay of
the off-diagonal elements of the current spin density matrix) in
two-dimensional electron gas-based devices due to the interplay of the Rashba
and/or Dresselhaus SO coupling and: (i) scattering at the boundaries or
lead-wire interface in ballistic semiconductor nanowires; or (ii)
spin-independent scattering off static impurities in both weakly and strongly
localized disordered nanowires. The physical interpretation of spin decoherence
in the course of multichannel quantum transport in terms of the entanglement of
spin to an effectively zero-temperature ``environment'' composed of more than
one open orbital conducting channels offers insight into some of the key
challenges for spintronics: controlling decoherence of transported spins and
emergence of partially coherent spin states in all-electrical spin manipulation
schemes based on the SO interactions in realistic semiconductor structures.",0402662v3
2019-02-04,Visualizing Complex-Valued Molecular Orbitals,"We report an implementation of a program for visualizing complex-valued
molecular orbitals. The orbital phase information is encoded on each of the
vertices of triangle meshes using the standard color wheel. Using this program,
we visualized the molecular orbitals for systems with spin-orbit couplings,
external magnetic fields, and complex absorbing potentials. Our work has not
only created visually attractive pictures, but also clearly demonstrated that
the phases of the complex-valued molecular orbitals carry rich chemical and
physical information of the system, which has often been unnoticed or
overlooked.",1902.01284v1
2024-02-29,Coupling a single spin to high-frequency motion,"Coupling a single spin to high-frequency mechanical motion is a fundamental
bottleneck of applications such as quantum sensing, intermediate and
long-distance spin-spin coupling, and classical and quantum information
processing. Previous experiments have only shown single spin coupling to
low-frequency mechanical resonators, such as diamond cantilevers.
High-frequency mechanical resonators, having the ability to access the quantum
regime, open a range of possibilities when coupled to single spins, including
readout and storage of quantum states. Here we report the first experimental
demonstration of spin-mechanical coupling to a high-frequency resonator. We
achieve this all-electrically on a fully suspended carbon nanotube device. A
new mechanism gives rise to this coupling, which stems from spin-orbit
coupling, and it is not mediated by strain. We observe both resonant and
off-resonant coupling as a shift and broadening of the electric dipole spin
resonance (EDSR), respectively. We develop a complete theoretical model taking
into account the tensor form of the coupling and non-linearity in the motion.
Our results propel spin-mechanical platforms to an uncharted regime. The
interaction we reveal provides the full toolbox for promising applications
ranging from the demonstration of macroscopic superpositions, to the operation
of fully quantum engines, to quantum simulators.",2402.19288v1
1998-07-20,Alternating Spin and Orbital Dimerization in Strong-coupling Two-band Models,"We study a one-dimensional Hamiltonian consisting of coupled SU(2) spin and
orbital degrees of freedom. Using the density matrix renormalization group, we
calculate the phase-diagram and the ground state correlation functions for this
model. We find that, in addition to the ferromagnetic and power-law
antiferromagnetic phases for spin and orbital degrees of freedom, this model
has a gapless line extending from the ferromagnetic phase to the Bethe ansatz
solvable SU(4) critical point, and a gapped phase with doubly degenerate ground
states which form alternating spin and orbital singlets. The spin-gap and the
order parameters are evaluated and the relevance to several recently discovered
spin-gap materials is discussed.",9807270v1
2006-08-10,Weak antilocalization and zero-field electron spin splitting in AlGaN/AlN/GaN heterostructures with a polarization induced two-dimensional electron gas,"Spin-orbit coupling is studied using the quantum interference corrections to
conductance in AlGaN/AlN/GaN two-dimensional electron systems where the carrier
density is controlled by the persistent photoconductivity effect. All the
samples studied exhibit a weak antilocalization feature with a spin-orbit field
of around 1.8 mT. The zero-field electron spin splitting energies extracted
from the weak antilocalization measurements are found to scale linearly with
the Fermi wavevector with an effective linear spin-orbit coupling parameter
5.5x10^{-13} eV m. The spin-orbit times extracted from our measurements varied
from 0.74 to 8.24 ps within the carrier density range of this experiment.",0608254v1
2013-02-19,Chirality Sensitive Domain Wall Motion in Spin-Orbit Coupled Ferromagnets,"Using the Lagrangian formalism, we solve analytically the equations of motion
for current-induced domain-wall dynamics in a ferromagnet with Rashba
spin-orbit coupling. An exact solution for the domain wall velocity is
provided, including the effect of non-equilibrium conduction electron
spin-density, Gilbert damping, and the Rashba interaction parameter. We
demonstrate explicitly that the influence of spin-orbit interaction can be
qualitatively different from the role of non-adiabatic spin-torque in the sense
that the former is sensitive to the chirality of the domain wall whereas the
latter is not: the domain wall velocity shows a reentrant behavior upon
changing the chirality of the domain wall. This could be used to experimentally
distinguish between the spin-orbit and non-adiabatic contribution to the wall
speed. A quantitative estimate for the attainable domain wall velocity is
given, based on an experimentally relevant set of parameters for the system.",1302.4744v1
2013-05-01,"Electronic Structure of a Two-Dimensional Graphene-Like Topological Insulator, Bi14Rh3I9","Very recently, a new two-dimensional graphene-like topological insulator,
Bi14Rh3I9, has been synthesized. The Bi-Rh sheets with a strong spin-orbit
interaction are graphene analogues with a honeycomb net composed of RhBi8
cubes. Here we derive the low-energy effective Hamiltonian involving spin-orbit
coupling for Bi14Rh3I9. In the absence of spin-orbit coupling, the Bi-Rh sheets
show two inequivalent Dirac cones at the corners of the hexagonal Brillouin
zone. The spin-orbit interaction opens a 2400 K bandgap at the Dirac points and
establishes the quantum spin Hall effect in the Bi-Rh sheets. Our result
indicates that the Bi14Rh3I9 may combine many unique electronic properties of
graphene and topological insulators, and it should host a combination of
quantum valley and spin Hall effects.",1305.0121v2
2019-05-28,Spin-Orbit Torque in a Single Ferromagnetic Layer with Large Spin-Orbit Coupling,"Spin-orbit torque in heavy metal/ferromagnet heterostructures with broken
spatial inversion symmetry provides an efficient mechanism for manipulating
magnetization using a charge current. Here, we report the presence of a spin
torque in a single ferromagnetic layer in both asymmetric MgO/Fe0.8Mn0.2 and
symmetric MgO/Fe0.8Mn0.2/MgO structures, which manifests itself in the form of
an effective field transverse to the charge current. The current to effective
field conversion efficiency, which is characterized using both the nonlinear
magnetoresistance and second-order planar Hall effect methods, is comparable to
the efficiency in typical heavy metal/ferromagnet bilayers. We argue that the
torque is caused by spin rotation in the vicinity of the surface via impurity
scattering in the presence of a strong spin-orbit coupling. Instead of
cancelling off with each other, the torques from the top and bottom surfaces
simply add up, leading to a fairly large net torque, which is readily observed
experimentally.",1905.11565v1
2018-09-06,Zero-Field Splitting Parameters from Four-Component Relativistic Methods,"We report an approach for determination of zero-field splitting parameters
from four-component relativistic calculations. Our approach involves neither
perturbative treatment of spin-orbit interaction nor truncation of the
spin-orbit coupled states. We make use of a multi-state implementation of
relativistic complete active space perturbation theory (CASPT2), partially
contracted N-electron valence perturbation theory (NEVPT2), and multi-reference
configuration interaction theory (MRCI), all with the fully internally
contracted ansatz. A mapping is performed from the Dirac Hamiltonian to the
pseudospin Hamiltonian, using correlated energies and the magnetic moment
matrix elements of the reference wavefunctions. Direct spin-spin coupling is
naturally included through the full 2-electron Breit interaction. Benchmark
calculations on chalcogen diatomics and pseudotetrahedral cobalt(II) complexes
show accuracy comparable to the commonly used state-interaction with spin-orbit
(SI-SO) approach, while tests on a uranium(III) single-ion magnet suggest that
for actinide complexes the strengths of our approach through the more robust
treatment of spin-orbit effects and the avoidence of state truncation are of
greater importance.",1809.02151v1
2019-03-08,Field-free spin-orbit torque switching in Co/Pt/Co multilayer with mixed magnetic anisotropies,"Spin-orbit-torque (SOT) induced magnetization switching in Co/Pt/Co trilayer,
with two Co layers exhibiting magnetization easy axes orthogonal to each other
is investigated. Pt layer is used as a source of spin-polarized current as it
is characterized by relatively high spin-orbit coupling. The spin Hall angle of
Pt, $\theta = 0.08$ is quantitatively determined using spin-orbit torque
ferromagnetic resonance technique. In addition, Pt serves as a spacer between
two Co layers and depending on it's thickness, different interlayer exchange
coupling (IEC) energy between ferromagnets is induced. Intermediate IEC
energies, resulting in a top Co magnetization tilted from the perpendicular
direction, allows for SOT-induced feld-free switching of the top Co layer. The
switching process is discussed in more detail, showing the potential of the
system for neuromorphic applications.",1903.03368v1
2019-12-23,Complete Magneto-Optic Modulation of Lateral and Angular Shifts in Spin-Orbit Coupled Members of the Graphene Family,"The intrinsic spin-orbit coupling in the 2D staggered monolayer
semiconductors is very large as compared to graphene. The large spin orbit
interaction in these materials leads to the opening of a gap in the energy
spectrum and spin-splitting of the bands in each valley. In this paper, we
theoretically investigate the mechanical steering of beams from these
spin-orbit rich, staggered 2D materials. Mechanical steering results in
noticeable deviations of the reflected and transmitted ray profiles as
predicted from classical laws of optics. These effects are generally called the
Goos-Hanchen (GH) and Imbert-Fedorov shifts. We find that electric and magnetic
field modulated giant spatial and angular GH shifts can be achieved in these
materials for incident angles in the vicinity of Brewster angle in terahertz
regime. We also determine the dependence of beam shifts on the chemical
potential and find that the Brewster angle and the sign of GH shift can be
controlled by varying the chemical potential. This allows the possibility of
realizing spin and valley dependent optical effects that can be useful readout
markers for experiments in quantum information processing, biosensing and
valleytronics, employed in the terahertz regime.",1912.10727v1
2020-11-24,Optical isolation induced by subwavelength spinning particle via spin-orbit interaction,"Optical isolation enables nonreciprocal manipulations of light with broad
applications in optical communications. Optical isolation by rotating
structures has drawn considerable attention due to its magnetic-free nature and
unprecedented performance. Conventional rotation-based optical isolation relies
on the use of bulky cavities hindering applications in subwavelength photonics.
Here, we propose a novel mechanism of optical isolation by integrating the
unique dispersion of a hyperbolic metamaterial with the transverse spin-orbit
interaction of evanescent waves. We show that rotation of a subwavelength
hyperbolic nanoparticle breaks the time-reversal symmetry and yields two
resonant chiral modes that selectively couple to the transverse spin of
waveguide modes. Remarkably, the transverse spin-orbit interaction can give
rise to unidirectional coupling and $>95\%$ isolation of infrared light at an
experimentally feasible rotation speed. Our work fuses the two important fields
of optical isolation and photonic spin-orbit interactions, leading to
magnetic-free yet compact nonreciprocal devices for novel applications in
optical communications, chiral quantum optics, and topological photonics.",2011.11973v2
2021-07-27,All-electrical control of hole singlet-triplet spin qubits at low leakage points,"We study the effect of the spin-orbit interaction on heavy holes confined in
a double quantum dot in the presence of a magnetic field of arbitrary
direction. Rich physics arise as the two hole states of different spin are not
only coupled by the spin-orbit interaction but additionally by the effect of
site-dependent anisotropic $g$ tensors. It is demonstrated that these effects
may counteract in such a way as to cancel the coupling at certain detunings and
tilting angles of the magnetic field. This feature may be used in
singlet-triplet qubits to avoid leakage errors and implement an electrical
spin-orbit switch, suggesting the possibility of task-tailored two-axes
control. Additionally, we investigate systems with a strong spin-orbit
interaction at weak magnetic fields. By exact diagonalization of the dominant
Hamiltonian we find that the magnetic field may be chosen such that the qubit
ground state is mixed only within the logical subspace for realistic system
parameters, hence reducing leakage errors and providing reliable control over
the qubit.",2107.12622v1
2022-07-21,Influence of nonuniform magnetization reorientation on spin-orbit torque measurements,"Measurements of spin-orbit torques in a ferromagnetic/nonmagnetic multilayer
are typically based on an assumption that the entire ferromagnetic layer
uniformly responds to the spin-orbit torque. This assumption breaks down when
the thickness of the ferromagnetic layer is comparable to the dynamic exchange
coupling length, which can be as short as a few nanometers in certain
measurement geometries. The nonuniform magnetization reorientation coupled with
nonuniform contribution of each magnetic sublayer to the magnetoresistance or
the Kerr effect may impact the accuracy in the extrapolation of spin-orbit
torque, particularly if a thick ferromagnetic layer is used. In this paper, we
use numerical models to investigate such an impact in three different
techniques: the magneto-optic-Kerr-effect method, the second-harmonic method
and the spin torque ferromagnetic resonance method. We show that the
second-harmonic and magneto-optic-Kerr-effect methods are prone to be
influenced by the nonuniform magnetization reorientation, while the spin torque
ferromagnetic resonance method is much less impacted.",2207.10349v1
2018-07-03,Weak anti-localization of two-dimensional holes in germanium beyond the diffusive regime,"Gate-controllable spin-orbit coupling is often one requisite for spintronic
devices. For practical spin field-effect transistors, another essential
requirement is ballistic spin transport, where the spin precession length is
shorter than the mean free path such that the gate-controlled spin precession
is not randomized by disorder. In this letter, we report the observation of a
gate-induced crossover from weak localization to weak anti-localization in the
magneto-resistance of a high-mobility two-dimensional hole gas in a strained
germanium quantum well. From the magneto-resistance, we extract the
phase-coherence time, spin-orbit precession time, spin-orbit energy splitting,
and cubic Rashba coefficient over a wide density range. The mobility and the
mean free path increase with increasing hole density, while the spin precession
length decreases due to increasingly stronger spin-orbit coupling. As the
density becomes larger than $\sim6\times 10^{11}$cm$^{-2}$, the spin precession
length becomes shorter than the mean free path, and the system enters the
ballistic spin transport regime. We also report here the numerical methods and
code developed for calculating the magneto-resistance in the ballistic regime,
where the commonly used HLN and ILP models for analyzing weak localization and
anti-localization are not valid. These results pave the way toward
silicon-compatible spintronic devices.",1807.01400v1
2021-11-17,Anisotropic $g$-tensors in hole quantum dots: The role of the transverse confinement direction,"Qubits encoded in the spin state of heavy holes confined in Si- and Ge-based
semiconductor quantum dots are currently leading the efforts toward spin-based
quantum information processing. The virtual absence of spinful nuclei in
purified samples yields long qubit coherence times and the intricate coupling
between spin and momentum in the valence band can provide very fast
spin-orbit-based qubit control, e.g., via electrically induced modulations of
the heavy-hole $g$-tensor. A thorough understanding of all aspects of the
interplay between spin-orbit coupling, the confining potentials, and applied
magnetic fields is thus quintessential for the development of the optimal
hole-spin-based qubit platform. Here we theoretically investigate the
manifestation of the effective $g$-tensor and effective mass of heavy holes in
two-dimensional hole gases as well as in lateral quantum dots. We include the
effects of the anisotropy of the effective Luttinger Hamiltonian (particularly
relevant for Si-based systems) and we focus on the detailed role of the
orientation of the transverse confining potential. We derive most general
analytic expressions for the anisotropic $g$-tensor and we present a general
and straightforward way to calculate corrections to this $g$-tensor for
localized holes due to various types of spin-orbit interaction, exemplifying
the approach by including a simple linear Rashba-like term. Our results thus
contribute to the understanding needed to find optimal points in parameter
space for hole-spin qubits, where confinement is effective and
spin-orbit-mediated electric control over the spin states is efficient.",2111.09164v1
1997-04-24,Structural Aspects of Magnetic Coupling in CaV4O9,"The strong corrugation of the V4O9 layer in the spin gap system CaV4O9 is
examined for its impact on the exchange coupling constants between the spin 1/2
V ions. Local spin density (LSD) calculations show that the V spin occupies a
d(x^2-y^2) orbital (x and y are the V-V directions). The Kanamori-Goodenough
superexchange rules, and the degeneracy of ferromagnetic and antiferromagnetic
alignments within LSD, suggest that 2nd neighbor couplings dominate over
nearest neighbor, resulting in two coupled S=1/2 metaplaquette systems.",9704203v1
2003-06-13,Rashba spin splitting in different quantum channels,"Rashba precession of spins moving along a one-subband quantum channel is
calculated. The quantitative influence of unoccupied higher subbands depends on
the shape of the transversal confinement and can be accounted for
perturbatively. Coulomb interactions are included within the
Tomonaga--Luttinger model with spin-orbit coupling incorporated. Increasing
interaction strength at decreasing carrier density is found to {\sl enhance}
spin precession.",0306358v1
2004-05-18,Multichannel field-effect spin barrier selector,"We have studied spin carrier dynamics under full spin-orbit coupling. The
anisotropy of dispersions for independent circular spinor polarizations is
explored as a possible vertical multichannel voltage controlled spin-filter.
Small voltage variations are found to select the current polarizations in a
resonant tunneling geometry.",0405418v1
2005-02-18,The spin-double refraction in two-dimensional electron gas,"We briefly review the phenomenon of the spin-double refraction that
originates at an interface separating a two-dimensional electron gas with
Rashba spin-orbit coupling from a one without. We demonstrate how this
phenomenon in semiconductor heterostructures can produce and control a
spin-polarized current without ferromagnetic leads.",0502456v1
2021-07-15,Colossal orbital-Edelstein effect in non-centrosymmetric superconductors,"In superconductors that lack inversion symmetry, the flow of supercurrent can
induce a non-vanishing magnetization, a phenomenon which is at the heart of
non-dissipative magneto-electric effects, also known as Edelstein effects. For
electrons carrying spin and orbital moments a question of fundamental relevance
deals with the orbital nature of magneto-electric effects in conventional
spin-singlet superconductors with Rashba coupling. Remarkably, we find that the
supercurrent-induced orbital magnetization is more than one order of magnitude
greater than that due to the spin, giving rise to a colossal magneto-electric
effect. The induced orbital magnetization is shown to be sign tunable, with the
sign change occurring for the Fermi level lying in proximity of avoiding
crossing points in the Brillouin zone and in the presence of superconducting
phase inhomogeneities, yielding domains with opposite orbital moment
orientation. The orbital-dominated magneto-electric phenomena, hence, have
clear-cut marks for detection both in the bulk and at the edge of the system
and are expected to be a general feature of multi-orbital superconductors
without inversion symmetry breaking.",2107.07476v1
2012-06-23,Spin Structures of Spin-Orbit Coupled Square-Lattice Antiferromagnets,"We have realized that our results have a strong overlap with those previously
published in J Chovan, N Papanicolaou, and S Komineas,
Phys.Rev.B65,064433(2002).",1206.5381v2
2005-04-13,NMR relaxation rate in non-centrosymmetric superconductors,"The spin-lattice relaxation rate of nuclear magnetic resonance in a clean
superconductor without inversion center is calculated for arbitrary pairing
symmetry and band structure, in the presence of strong spin-orbit coupling.",0504342v1
2016-08-21,"Hidden orbital polarization in diamond, silicon, germanium, gallium arsenide and layered materials","It was previously believed that the Bloch electronic states of non-magnetic
materials with inversion symmetry cannot have finite spin polarizations.
However, since the seminal work by Zhang et al. [Nat. Phys. 10, 387-393 (2014)]
on local spin polarizations of Bloch states in non-magnetic, centrosymmetric
materials, the scope of spintronics has been significantly broadened. Here, we
show, using a framework that is universally applicable independent of whether
hidden spin polarizations are small (e.g., diamond, Si, Ge, and GaAs) or large
(e.g., MoS2 and WSe2), that the corresponding quantity arising from orbital -
instead of spin - degrees of freedom, the hidden orbital polarization, is (i)
much more abundant in nature since it exists even without spin-orbit coupling
and (ii) more fundamental since the interband matrix elements of the
site-dependent orbital angular momentum operator determines the hidden spin
polarization. We predict that the hidden spin polarization of transition metal
dichalcogenides is reduced significantly upon compression. We suggest
experimental signatures of hidden orbital polarization from photoemission
spectroscopies and demonstrate that the current-induced hidden orbital
polarization may play a far more important role than its spin counterpart in
antiferromagnetic information technology by calculating the current-driven
antiferromagnetism in compressed silicon.",1608.05989v4
2020-12-08,Flipping spins in mass transferring binaries and origin of spin-orbit misalignment in binary black holes,"Close stellar binaries are prone to undergo a phase of stable mass transfer
in which a star loses mass to its companion. Assuming that the donor star loses
mass along the instantaneous interstellar axis, we derive the orbit-averaged
equations of motion describing the evolution of the donor rotational angular
momentum vector (spin) which accompanies the transfer of mass. We consider: (i)
a model in which the mass transfer rate is constant within each orbit and (ii)
a phase-dependent rate in which all mass per orbit is lost at periapsis. In
both cases, we find that the ejection of $\gtrsim 30$ per cent of the donor's
initial mass causes its spin to nearly flip onto the orbital plane of the
binary, independently of the initial spin-orbit alignment. Moreover, we show
that the spin flip due to mass transfer can easily dominate over tidal
synchronisation in any giant stars and main-sequence stars with masses
$\sim1.5$ to $5\,\rm M_\odot$. Finally, the general equations of motion,
including tides, are used to evolve a realistic population of massive binary
stars leading to the formation of binary black holes. Assuming that the stellar
core and envelope are fully coupled, the resulting tilt of the first-born black
hole reduces its spin projection onto the orbit normal by a factor
$\sim\mathcal{O}(0.1)$. This result supports previous studies in favour of an
insignificant contribution to the effective spin projection, $\chi_{\rm eff}$,
in binary black holes formed from the evolution of field binaries.",2012.06329v2
2005-11-30,Spin Hall effect in clean two dimensional electron gases with Rashba spin-orbit coupling,"We study the spin polarization induced by a current flow in clean two
dimensional electron gases with Rashba spin-orbit coupling. This geometric
effect originates from special properties of the electron's scattering at the
edges of the sample. In wide samples, the spin polarization has it largest
value at low energies (close to the bottom of the band) and goes to zero at
higher energies. In this case, the spin polarization is dominated by the
presence of evanescent modes which have an explicit spin component outside the
plane. In quantum wires, on the other hand, the spin polarization is dominated
by interference effects induced by multiple scattering at the edges. Here, the
spin polarization is quite sensitive to the value of the Fermi energy,
especially close to the point where a new channel opens up. We analyzed
different geometries and found that the spin polarization can be strongly
enhanced.",0511750v1
2005-12-16,Hole spin dephasing in $p$-type semiconductor quantum wells,"Hole spin dephasing time due to the D'yakonov-Perel' mechanism in $p$-type
GaAs (100) quantum wells with well separated light-hole and heavy-hole bands is
studied by constructing and numerically solving the kinetic spin Bloch
equations. We include all the spin-conserving scattering such as the
hole-phonon and the hole-nonmagnetic impurity as well as the hole-hole Coulomb
scattering in our calculation. Different effects such as the temperature, the
hole density, the impurity density and the Rashba coefficient on the spin
dephasing are investigated in detail. We also show that the Coulomb scattering
makes marked contribution to the spin dephasing. The spin dephasing time can
either increase or decrease with temperature, hole/impurity density or the
inclusion of the Coulomb scattering depending on the relative importance of the
spin-orbit coupling and the scattering. It is also shown that due to the
different spin-orbit coupling strengthes, many spin dephasing properties of
holes are quite different from those of electrons.",0512398v2
2010-06-15,Non-magnetic Stern-Gerlach Experiment from Electron Diffraction,"Using the wave nature of the electrons, we demonstrate that a transverse spin
current can be generated simply by the diffraction through a single slit in the
spin-orbital coupling system of the two-dimensional electron gas. The
diffracted electron picks up the transverse momentum. The up spin electron goes
one way and the down spin electron goes the other, producing the coherent spin
current. In the system of spin-orbital coupling $\sim10^{-13}$ eV$\cdot$m, the
\emph{out-of-plane} component of the spin of the electron can be generated up
to 0.42 $\hbar$. Based on this effect, a novel device of grating to distill
spin is designed. Two first diffraction peaks of electron carry different
spins, duplicating the non-magnetic version of Stern-Gerlach experiment. The
direction of the spin current can be controlled by the gate voltage with low
energy cost.",1006.2872v1
2013-04-24,Effect of Dresselhaus spin-orbit coupling on spin dephasing in asymmetric and macroscopically symmetric (110)-grown quantum wells,"We develop the microscopic theory of electron spin dephasing in (110)-grown
quantum wells where the electron scattering time is comparable to or exceeds
the period of spin precession in the effective magnetic field caused by
spin-orbit coupling. Structures with homogeneous and fluctuating Rashba field,
which triggers the dephasing of electron spins aligned along the growth
direction, are analyzed. We show that the Dresselhaus field, which is always
present in zinc-blende-type quantum wells, suppresses the spin dephasing
enabling very long spin lifetime of conduction electrons. The dependence of the
spin lifetime on the electron mobility is found to be nonmonotonic reaching the
minimum in structures where the scattering time is comparable to the period of
spin precession in the effective magnetic field.",1304.6600v1
2013-10-08,Spin-Orbit Coupled One-Dimensional Fermi Gases with Infinite Repulsion,"The current efforts of studying many-body effects with spin-orbit coupling
(SOC) using alkali-metal atoms are impeded by the heating effects due to
spontaneous emission. Here, we show that even for SOCs too weak to cause any
heating, dramatic many-body effects can emerge in a one-dimensional(1D) spin
1/2 Fermi gas provided the interaction is sufficiently repulsive. For weak
repulsion, the effect of a weak SOC (with strength $\Omega$) is perturbative.
inducing a weak spin spiral (with magnitude proportional to $\Omega$). However,
as the repulsion $g$ increases beyond a critical value ($g_c\sim 1/\Omega$),
the magnitude of the spin spiral rises rapidly to a value of order 1
(independent of $\Omega$). Moreover, near $g=+\infty$, the spins of neighboring
fermions can interfere destructively due to quantum fluctuations of particle
motion, strongly distorting the spin spiral and pulling the spins substantially
away from the direction of the local field at various locations. These effects
are consequences of the spin-charge separation in the strongly repulsive limit.
They will also occur in other 1D quantum gases with higher spins.",1310.1993v2
2014-07-16,Spin Excitation Spectra of Spin-Orbit Coupled Bosons in Optical Lattice,"Spin-wave excitation plays important roles in the investigation of the
magnetic phases. In this paper, we study the spin-wave excitation spectra of
two-component Bose gases with spin-orbit coupling on a deep square optical
lattice using spin-wave theory. We find that, while the excitation spectrum of
the vortex crystal phase is gapless with a linear dispersion in the vicinity of
the minimum point, the spectra of the commensurate spiral spin phase and the
skyrmion crystal phase are gapped. Significantly, the spin fluctuations
strongly destabilize the classical ground state of the skyrmion phase. It
suggests the emergence of a new state in the phase diagram. Such features of
the spin excitation spectra provide further insights into the exploration of
the exotic spin phases.",1407.4172v1
2016-07-26,Strain-controlled spin splitting in the conduction band of monolayer WS2,"Spin splitting bands that arises in conduction band minimum (CBM) of WS2
monolayer (ML) play an important role in the new spin-orbit phenomena such as
spin-valley coupled electronics. However, application of strain strongly
modifies electronic properties of the WS2 ML, which is expected to
significantly affect to the properties of the spin splitting bands. Here, by
using fully-relativistic first-principles calculations based on
density-functional theory, we show that a substantial spin spliting bands
observed in the CBM is effectively controlled and tuned by applying the biaxial
strain. We also find that these spin splitting bands induce spin textures
exhibiting fully out-of-plane spin polarization in the opposite direction
between the K and Q points and their time reversals in the first Brillouin
zone. Our study clarify that the strain plays an significant role in the
spin-orbit coupling of the WS2 ML, which has very important implications in
designing future spintronics devices.",1607.07566v1
2020-02-26,"Strain Engineering of Spin and Rashba properties in Group-III Monochalcogenide MX (M=Ga, In and X=S, Se, Te) Monolayer","In this paper, spin properties of monolayer MX (M=Ga, In and X=S, Se, Te) in
the presence of strain are studied. Density functional theory is used to
investigate spin properties. The strain changes modification of bandgap due to
spin-orbit coupling, the results indicate the spin-orbit coupling has a higher
effect in the compressive regime. Also, spin splitting in the conduction and
valence bands respect to strain are compared for six materials. The location of
conduction band minimum (CBM) imposed a type of spin properties. These
materials with mirror symmetry can display the Rashba effect while M valley is
located at CBM. Strain tunes the conduction band minimum in three valleys (K, M
and $\Gamma$ valleys) and determines which spin effect (spin splitting, Rashba
splitting or no spin splitting) has occurred in each strain for every material.
Lastly, the relation between the Rashba parameter and the atomic mass is
explored and it is observed that there is a linear correlation between atomic
mass and Rashba coefficient.",2002.11426v1
2022-11-14,Degeneracy removal of spin bands in antiferromagnets with non-interconvertible spin motif pair,"Energy bands in antiferromagnets are generally spin degenerate in the absence
of spin-orbit coupling (SOC). Recent studies [Physical Review B 102, 014422
(2020)] identified formal symmetry conditions for crystals for which this
degeneracy can be lifted even in the zero SOC limit. Such materials could
enable ""spin-split"" antiferromagnetic spintronics without the burden of use of
heavy atom compounds. Here, we show that these formal symmetry conditions can
be interpreted in terms of easy-to-visualize local motif pair, such as
octahedra or tetrahedra, each carrying opposite magnetic moments. Collinear
antiferromagnets with such spin motif pair whose components interconvert by
neither translation nor spatial inversion will show splitting of spin bands.
Such real-space motif-based approach enables an easy way to identify and design
of materials having spin splitting without the need for spin orbit coupling,
and offers insights on the magnitude of spin splitting.",2211.07803v1
2000-05-30,"Comment on ""Spin relaxation in quantum Hall systems""","W. Apel and Yu.A. Bychkov have recently considered the spin relaxation in a
2D quantum Hall system for the filling factor close to unity [PRL v.82, 3324
(1999)]. The authors considered only one spin flip mechanism (direct
spin-phonon coupling) among several possible spin-orbit related ones and came
to the conclusion that the spin relaxation time due to this mechanism is quite
short: around $10^{-10}$ s at B=10 T (for GaAs). This time is much shorter than
the typical time ($10^{-5}$ s) obtained earlier by D. Frenkel while considering
the spin relaxation of 2D electrons in a quantizing magnetic field without the
Coulomb interaction and for the same spin-phonon coupling. I show that the
authors' conclusion about the value of the spin-flip time is wrong and have
deduced the correct time which is by several orders of magnitude longer. I also
discuss the admixture mechanism of the spin-orbit interaction.",0005522v1
2003-09-19,Semiclassical theory of spin transport in spin-orbit coupled systems,"Motivated by recent interest in novel spintronics effects, we develop a
semiclassical theory of spin transport that is valid for spin-orbit coupled
bands. Aside from the obvious convective term in which the average spin is
transported at the wavepacket group velocity, the spin current has additional
contributions from the wavepacket's spin and torque dipole moments. Electric
field corrections to the group velocity and carrier spin contribute to the
convective term. Summing all terms we obtain an expression for the intrinsic
spin-Hall conductivity of a hole-doped semiconductor, which agrees with the
Kubo formula prediction for the same quantity. We discuss the calculation of
spin accumulation, which illustrates the importance of the torque dipole near
the boundary of the system.",0309475v4
2014-08-11,Spin Seebeck Effect in Asymmetric Four-Terminal Systems with Rashba Spin-Orbit Coupling,"We propose a new type of the spin Seebeck effect (SSE) emerging from the
Rashba spin-orbit coupling in asymmetric four-terminal electron systems. This
system generates spin currents or spin voltages along the longitudinal
direction parallel to the temperature gradient in the absence of magnetic
fields. The remarkable result arises from the breaking of reflection symmetry
along the transverse direction. In the meantime, the SSE along the transverse
direction, so-called the spin Nernst effect, with spin currents or spin
voltages perpendicular to the temperature gradient can be simultaneously
realized in our system. We further find that it is possible to use the
temperature differences between four leads to tune the spin Seebeck
coefficients.",1408.2300v1
2008-07-14,Electric-field induced spin excitations in two-dimensional spin-orbit coupled systems,"Rigorous coupled spin-charge drift-diffusion equations are derived from
quantum-kinetic equations for the spin-density matrix that incorporate effects
due to k-linear spin-orbit interaction, an in-plane electric field, and the
elastic scattering on nonmagnetic impurities. The explicit analytical solution
for the induced magnetization exhibits a pole structure, from which the
dispersion relations of spin excitations are identified. Applications of the
general approach refer to the excitation of long-lived field-induced spin waves
by optically generated spin and charge patterns. This approach transfers
methods known in the physics of space-charge waves to the treatment of spin
eigenmodes. In addition, the amplification of an oscillating electric field by
spin injection is demonstrated.",0807.2142v1
2022-03-07,Nonlinear spin Hall effect in $\mathcal{PT}$-symmetric collinear magnets,"We theoretically investigate a nonlinear spin Hall effect in
$\mathcal{PT}$-symmetric antiferromagnetic metals, which serve as an efficient
spin current generator. We elucidate that an emergent spin-dependent Berry
curvature dipole is a microscopic origin of the nonlinear spin Hall effect,
which becomes nonzero with neither relativistic spin-orbit coupling, uniform
magnetization, nor spin-split band structure. By analyzing a microscopic
antiferromagnetic model without spin-orbit coupling for an intuitive
understanding of the phenomena, we elucidate essential hopping processes and a
condition to enhance the nonlinear spin Hall conductivity. We also provide a
complete table to include useful correspondence among the N\'eel vector,
odd-parity multipoles, nonlinear spin conductivity tensor, and candidate
materials in all the $\mathcal{PT}$-symmetric black-and-white magnetic point
groups.",2203.03754v2
2022-10-19,Many-body correction to the intrinsic anomalous and spin Hall conductivities,"Broken Galilean invariance in a spin-orbit coupled system can amplify
many-body effects on its different responses. We study the anomalous Hall and
spin Hall conductivities of a magnetic two-dimensional electron gas with Rashba
spin-orbit coupling. We show that both of these conductivities in the intrinsic
limit are fully specified in terms of the longitudinal and transverse spin-spin
response functions. We include the effect of electron-electron interaction in
the spin-spin linear response functions, going beyond the random-phase
approximation. We do this by incorporating the local-field correction in the
response functions, which takes into account the many-body exchange-correlation
effects. We observe a significant enhancement of the static anomalous Hall
conductivity due to the electron-electron interaction. The many-body correction
on the spin Hall effects is more non-trivial, and strong electron-electron
interaction can even reverse the sign of the static spin Hall conductivity.",2210.10531v1
2023-03-16,Ultrafast dynamics of electrons excited by femtosecond laser pulses: spin polarization and spin-polarized currents,"Laser radiation incident on a ferromagnetic sample produces excited electrons
and currents whose spin polarization must not be aligned with the magnetization
-- an effect due to spin-orbit coupling that is ubiquitous in spin- and
angle-resolved photoemission. In this Paper, we report on a systematic
investigation of the dynamics of spin polarization and spin-polarized currents
produced by femtosecond laser pulses, modeled within our theoretical framework
EVOLVE. The spin polarization depends strongly on the properties of the laser
pulse and on the sample composition, as is shown by comparing results for
Cu(100), Co(100), and a Co/Cu heterostructure. We find a transition from
coherence before the laser pulse's maximum to incoherence thereafter. Moreover,
the time dependence of the spin-polarization components induced by spin-orbit
coupling differ significantly in Cu and Co: in Cu, we find long-period
oscillations with tiny rapid modulations, whereas in Co prominent rapid
oscillations with long period ones are superimposed. The pronounced spatial
dependencies of the signals underline the importance of inhomogeneities, in
particular magnetic/non-magnetic interfaces `act as source' for ultrafast
spin-polarization effects. Our investigation provides detailed insight into
electron dynamics during and shortly after a femtosecond laser excitation.",2303.09291v1
2005-06-14,"Orbital order, anisotropic spin couplings, and the spin-wave spectrum of the ferromagnetic Mott insulator YTiO3","Using a point-charge calculation of the electrostatic crystal field, we
determine the non-degenerate orbital ground state of the ferromagnetic Mott
insulator YTiO3, which is found to agree perfectly with experiment. Based on
the orbital order, we obtain by perturbation theory an effective spin
Hamiltonian that describes the magnetic superexchange between nearest-neighbor
Ti ions. The superexchange Hamiltonian includes, in addition to the isotropic
Heisenberg coupling, antisymmetric (Dzyaloshinskii-Moriya) and symmetric
anisotropy terms, caused by the spin-orbit interaction on the Ti ions. We find
ferromagnetic Heisenberg couplings for Ti-Ti bonds in the crystallographic ab
planes, but antiferromagnetic ones for Ti-Ti bonds between planes, in
contradiction with experiment (which gives ferromagnetic couplings for both).
Difficulties in calculating realistic values for the isotropic couplings of
YTiO3 have been already reported in the literature. We discuss possible origins
for these discrepancies. However, the much smaller values we obtain for the
symmetric and antisymmetric anisotropies may be expected to be reliable. We
therefore combine the experimentally-deduced isotropic coupling with the
calculated anisotropic ones to determine the magnetic order of the Ti ions,
which is found to be in satisfactory agreement with experiment. Based on this
magnetic order, we derive the spin-wave spectrum. We find an acoustic branch
with a very small zone-center gap and three optical spin-wave modes with
sizeable zone-center gaps. The acoustic branch reproduces the one reported in
experiment, and the optical ones are in a satisfactory agreement with
experiment, upon a proper folding of the magnetic Brillouin zone.",0506328v1
2022-03-16,Theoretical analysis of single-ion anisotropy in $d^3$ Mott insulators,"An effective spin model for Mott insulators is determined by the symmetries
involved among magnetic sites, electron fillings, and their interactions. Such
a spin Hamiltonian offers insight to mechanisms of magnetic orders and magnetic
anisotropy beyond the Heisenberg model. For a spin moment S bigger than 1/2,
single-ion anisotropy is in principle allowed. However, for $d^3$ Mott
insulators with large cubic crystal field splitting, the single-ion anisotropy
is absent within the LS coupling, despite S = 3/2 local moment. On the other
hand, preferred magnetic moment directions in $d^3$ materials have been
reported, which calls for a further theoretical investigation. Here we derive
the single-ion anisotropy interaction using the strong-coupling perturbation
theory. The cubic crystal field splitting including $e_g$ orbitals, trigonal
distortions, Hund's coupling, and spin-orbit coupling beyond the LS scheme are
taken into account. For compressed distortion, the spin-orbit coupling at
magnetic sites can favor either the easy-axis or the easy-plane while that of
anions leads to easy-axis anisotropy. We apply the theory on $\rm{CrX}_3$ with
X = Cl and I, and show the dependence of the single-ion anisotropy on the
strength of the spin-orbit couplings of both magnetic and anion sites.
Significance of the single-ion anisotropy in ideal two-dimensional magnets is
also discussed.",2203.08836v3
2014-03-19,Observation of two-orbital spin-exchange interactions with ultracold SU(N)-symmetric fermions,"We report on the direct observation of spin-exchanging interactions in a
two-orbital SU(N)-symmetric quantum gas of ytterbium in an optical lattice. The
two orbital states are represented by two different (meta-)stable electronic
configurations of fermionic Yb-173. A strong spin-exchange between particles in
the two separate orbitals is mediated by the contact interaction between atoms,
which we characterize by clock shift spectroscopy in a 3D optical lattice. We
find the system to be SU(N)-symmetric within our measurement precision and
characterize all relevant scattering channels for atom pairs in combinations of
the ground and the excited state. Elastic scattering between the orbitals is
dominated by the antisymmetric channel, which leads to the strong spin-exchange
coupling. The exchange process is directly observed, by characterizing the
dynamic equilibration of spin imbalances between two large ensembles in the two
orbital states, as well as indirectly in atom pairs via interaction shift
spectroscopy in a 3D lattice. The realization of a stable SU(N)-symmetric
two-orbital Hubbard Hamiltonian opens the route towards experimental quantum
simulation of condensed-matter models based on orbital interactions, such as
the Kondo lattice model.",1403.4761v3
2017-11-27,"Emergent odd-parity multipoles and magnetoelectric effects on a diamond structure: implication to 5$d$ transition metal oxides $A$OsO$_4$ ($A=$ K, Rb, and Cs)","We report our theoretical predictions on the linear magnetoelectric (ME)
effects originating from odd-parity multipoles associated with spontaneous spin
and orbital ordering on a diamond structure. We derive a two-orbital model for
$d$ electrons in $e_g$ orbitals by including the effective spin-orbit coupling
which arises from the mixing between $e_g$ and $t_{2g}$ orbitals. We show that
the model acquires a net antisymmetric spin-orbit coupling once staggered spin
and orbital orders occur spontaneously. The staggered orders are accompanied by
odd-parity multipoles: magnetic monopole, quadrupoles, and toroidal dipoles. We
classify the types of the odd-parity multipoles according to the symmetry of
the spin and orbital orders. Furthermore, by computing the ME tensor using the
linear response theory, we show that the staggered orders induce a variety of
the linear ME responses. We elaborate all possible ME responses for each
staggered order, which are useful to identify the order parameter and to detect
the odd-parity multipoles by measuring the ME effects. We also elucidate the
effect of lowering symmetry by a tetragonal distortion, which leads to richer
ME responses. The implications of our results are discussed for $5d$ transition
metal oxides, $A$OsO$_4$ ($A=$ K, Rb, and Cs), in which the order parameters
are not fully identified.",1711.09507v1
2007-07-11,Electrical control of spin relaxation in a quantum dot,"We demonstrate electrical control of the spin relaxation time T_1 between
Zeeman split spin states of a single electron in a lateral quantum dot. We find
that relaxation is mediated by the spin-orbit interaction, and by manipulating
the orbital states of the dot using gate voltages we vary the relaxation rate
W= (T_1)^-1 by over an order of magnitude. The dependence of W on orbital
confinement agrees with theoretical predictions and from these data we extract
the spin-orbit length. We also measure the dependence of W on magnetic field
and demonstrate that spin-orbit mediated coupling to phonons is the dominant
relaxation mechanism down to 1T, where T_1 exceeds 1s.",0707.1656v1
2011-03-05,Orbital elementary excitations as probes of entanglement and quantum phase transitions of collective spins in an entangled Bose-Einstein condensate,"A mixture of two species of pseudospin-1/2 Bose gases exhibits interesting
interplay between spin and orbital degrees of freedom. Expectation values of
various quantities of the collective spins of the two species play crucial
roles in the Gross-Pitaevskii-like equations governing the four orbital wave
functions in which Bose-Einstein condensation occurs. Consequently, the
elementary excitations of these orbital wave functions reflect properties of
the collective spins. When the coupling between the two collective spins is
isotropic, the energy gap of the gapped orbital excitation peaks, while there
is a quantum phase transition in the ground state of the effective Hamiltonian
of the two collective spins, which have previously been found to be maximally
entangled.",1103.1022v1
2019-05-16,Electrical control of spins and giant g-factors in ring-like coupled quantum dots,"Emerging theoretical concepts for quantum technologies have driven a
continuous search for structures where a quantum state, such as spin, can be
manipulated efficiently. Central to many concepts is the ability to control a
system by electric and magnetic fields, relying on strong spin-orbit
interaction and a large g-factor. Here, we present a new mechanism for spin and
orbital manipulation using small electric and magnetic fields. By hybridizing
specific quantum dot states at two points inside InAs nanowires, nearly perfect
quantum rings form. Large and highly anisotropic effective g-factors are
observed, explained by a strong orbital contribution. Importantly, we find that
the orbital and spin-orbital contributions can be efficiently quenched by
simply detuning the individual quantum dot levels with an electric field. In
this way, we demonstrate not only control of the effective g-factor from 80 to
almost 0 for the same charge state, but also electrostatic change of the ground
state spin.",1905.06616v1
2014-03-10,Thermoelectric effects in graphene with local spin-orbit interaction,"We investigate the transport properties of a graphene layer in the presence
of Rashba spin-orbit interaction. Quite generally, spin-orbit interactions
induce spin splittings and modifications of the graphene bandstructure. We
calculate within the scattering approach the linear electric and thermoelectric
responses of a clean sample when the Rashba coupling is localized around a
finite region. We find that the thermoelectric conductance, unlike its electric
counterpart, is quite sensitive to external modulations of the Fermi energy.
Therefore, our results suggest that thermocurrent measurements may serve as a
useful tool to detect nonhomogeneous spin-orbit interactions present in a
graphene-based device. Furthermore, we find that the junction thermopower is
largely dominated by an intrinsic term independently of the spin-orbit
potential scattering. We discuss the possibility of cancelling the intrinsic
thermopower by resolving the Seebeck coefficient in the subband space. This
causes unbalanced populations of electronic modes which can be tuned with
external gate voltages or applied temperature biases.",1403.2178v2
2012-01-30,"Exchange constants and spin waves of the orbital ordered, non-collinear spinel MnV$_2$O$_4$","We study the exchange constants of MnV$_2$O$_4$ using magnetic force theorem
and local spin density approximation of density functional theory supplemented
with a correction due to on-site Hubbard interaction U. We obtain the exchanges
for three different orbital orderings of the Vanadium atoms of the spinel. We
then map the exchange constants to a Heisenberg model with single-ion
anisotropy and solve for the spin-wave excitations in the non-collinear, low
temperature phase of the spinel. The single-ion anisotropy parameters are
obtained from an atomic multiplet exact-diagonalization program, taking into
effect the crystal-field splitting and the spin-orbit coupling. We find good
agreement between the spin waves of one of our orbital ordered setups with
previously reported experimental spin waves as determined by neutron
scattering. We can therefore determine the correct orbital order from various
proposals that exist in the literature.",1201.6375v2
2017-07-12,Tunability of Andreev levels via spin-orbit coupling in Zeeman-split Josephson junctions,"We study Andreev reflection and Andreev levels $\varepsilon$ in Zeeman-split
superconductor/Rashba wire/Zeeman-split superconductor junctions by solving the
Bogoliubov de-Gennes equation. We theoretically demonstrate that the Andreev
levels $\varepsilon$ can be controlled by tuning either the strength of Rashba
spin-orbit interaction or the relative direction of the Rashba spin-orbit
interaction and the Zeeman field. In particular, it is found that the magnitude
of the band splitting is tunable by the strength of the Rashba spin-orbit
interaction and the rength of the wire, which can be interpreted by a spin
precession in the Rashba wire. We also find that if the Zeeman field in the
superconductor has the component parallel to the direction of the junction, the
$\varepsilon$-$\phi$ curve becomes asymmetric with respect to the
superconducting phase difference $\phi$. Whereas the Andreev reflection
processes associated with each pseudospin band are sensitive to the relative
orientation of the spin-orbit field and the exchange field, the total electric
conductance interestingly remains invariant.",1707.03723v2
2021-07-05,Imaging chiral Andreev reflection in the presence of Rashba spin-orbit coupling,"In this work, we theoretically study transverse magnetic focusing in a
two-dimensional electron gas with strong Rashba spin-orbit interaction when
proximitized along its edge with a superconducting contact. The presence of
superconducting correlations leads to the emergence of chiral Andreev edge
states which -- within this weak magnetic field regime -- may be pictured as
states following semiclassical skipping orbits with alternating electron-hole
nature. The spin-orbit induced splitting of the Fermi surface causes these
carriers to move along cyclotron orbits with different radii, allowing for
their spatial spin separation. When Andreev reflection takes place at the
superconducting lead, scattered carriers flip both their charge and spin,
generating distinguishable features in the transport properties of the device.
In particular, we report a notable enhancement of the separation between the
spin-split focal points, which scales linearly with the number of Andreev
scattering events at the anomalous terminal. We support our results by
calculating conductance maps to arbitrary points in the sample that provide a
complete image of the ballistic electron-hole cyclotron paths.",2107.02188v1
2023-07-10,Angular dependence of spin-orbit torque in monolayer $Fe_3GeTe_2$,"In ferromagnetic systems lacking inversion symmetry, an applied electric
field can control the ferromagnetic order parameters through the spin-orbit
torque. The prototypical example is a bilayer heterostructure composed of a
ferromagnet and a heavy metal that acts as a spin current source. In addition
to such bilayers, spin-orbit coupling can mediate spin-orbit torques in
ferromagnets that lack bulk inversion symmetry. A recently discovered example
is the two-dimensional monolayer ferromagnet $Fe_3GeTe_2$. In this work, we use
first-principles calculations to study the spin-orbit torque and ensuing
magnetic dynamics in this material. By expanding the torque versus
magnetization direction as a series of vector spherical harmonics, we find that
higher order terms (up to $\ell=4$) are significant and play important roles in
the magnetic dynamics. They give rise to deterministic, magnetic field-free
electrical switching of perpendicular magnetization.",2307.04900v2
2020-04-24,Quantitative comparison of electrically induced spin and orbital polarizations in heavy-metal/3d-metal bilayers,"Electrical control of magnetization is of crucial importance for integrated
spintronics devices. Spin-orbit torques (SOT) in heavy-metal/ferromagnetic
heterostructures have emerged as promising tool to achieve efficiently
current-induced magnetization reversal. However, the microscopic origin of the
SOT is being debated,with the spin Hall effect (SHE) due to nonlocal spin
currents and the spin Rashba-Edelstein effect (SREE) due to local spin
polarization at the interface being the primary candidates. We investigate the
electrically induced out-of-equilibrium spin and orbital polarizations in pure
Pt films and in Pt/3d-metal (Co, Ni, Cu) bilayer films using ab initio
electronic structure methods and linear-response theory. We compute
atom-resolved response quantities that allow us to identify the induced
spin-polarization contributions that lead to fieldlike SOTs, mostly associated
with the SREE, and dampinglike (DL) SOTs, mostly associated with the SHE, and
compare their relative magnitude, dependence on the magnetization direction, as
well as their Pt-layer thickness dependence. We find that both the FL and DL
components contribute to the resulting SOT at the Pt/Co and Pt/Ni interfaces,
with the former contributions being larger at the Pt interface layer and the
latter larger in the Co or Ni layers. Our calculations show that the
electrically-induced transverse orbital polarization is exceedingly larger than
the induced spin polarization and present even without spin-orbit coupling, in
contrast to the spin polarization.",2004.11942v5
2019-04-01,X-ray spectroscopy of current-induced spin-orbit torques and spin accumulation in Pt/3d transition metal bilayers,"An electric current flowing in Pt, a material with strong spin-orbit
coupling, leads to spins accumulating at the interfaces by virtue of the spin
Hall effect and interfacial charge-spin conversion. We measure the influence of
these interfacial magnetic moments onto adjacent 3d transition metal layers by
x-ray absorption spectroscopy and x-ray magnetic circular dichroism in a
quantitative and element-selective way, with sensitivity below $10^{-5}~\mu_B$
per atom. In Pt(6 nm)/Co(2.5 nm), the accumulated spins cause a deviation of
the Co magnetization direction, which corresponds to an effective spin-Hall
angle of 0.08. The spin and orbital magnetic moments of Co are affected in
equal proportion by the absorption of the spin current, showing that the
transfer of orbital momentum from the recently predicted orbital Hall effect is
either below our detection limit, or not directed to the 3d states of Co. For
Pt/NM (NM = Ti, Cr, Cu), we find upper limits for the amount of injected spins
corresponding to about $3\times 10^{-6}~\mu_B$ per atom.",1904.00877v2
2022-09-06,Spin-filtering in a $p$-orbital helical atomic chain,"We theoretically analyze spin filtering in two-terminal systems, induced by
the spin-orbit interaction (SOI), as a possible origin of the
``chirality-induced spin selectivity'' (CISS) effect observed experimentally in
chiral molecules, such as DNA. Due to Bardarson's theorem, spin filtering
cannot be realized in a molecule containing one orbital-channel. However, when
two orbitals are involved, SOI can induce spin filtering in a molecule coupled
to two terminals without braking time-reversal symmetry. In particular, we
provide an example of a $4 \times 4$ reflection matrix for a spinful electron
passing through a molecule containing two orbital-channels, which complies with
Bardarson's theorem and produces a finite spin conductance. As a microscopic
toy model realizing a single strand of DNA, we consider a $p$-orbital helical
atomic chain with intra-atomic SOI's and a strong crystalline field along the
helix. This model exhibits two-orbital spin filtering: For various parameters
preserving the helical symmetry, the model hosts spin asymmetric states
carrying pairs of up and down spins propagating in opposite directions. The
typical energy scale of the helical states is the product of the intra-atomic
SOI and the curvature. The large value of this energy identifies our model as a
likely candidate to explain the CISS in organic molecules.",2209.02303v1
2023-11-21,Proximity-enabled control of spin-orbit coupling in phosphorene symmetrically and asymmetrically encapsulated by WSe$_2$ monolayers,"We analyze, using first-principles calculations and the method of invariants,
the spin-orbit proximity effects in trilayer heterostructures comprising
phosphorene and encapsulating WSe$_2$ monolayers. We focus on four different
configurations, in which the top/bottom WSe$_2$ monolayer is twisted by 0 or 60
degrees with respect to phosphorene, and analyze the spin splitting of
phosphorene hole bands around the $\Gamma$ point. Our results show that the
spin texture of phosphorene hole bands can be dramatically modified by
different encapsulations of phosphorene monolayer. For a symmetrically
encapsulated phosphorene, the momentum-dependent spin-orbit field has the
out-of-plane component only, simulating the spin texture of phosphorene-like
group-IV monochalcogenide ferroelectrics. Furthermore, we reveal that the
direction of the out-of-plane spin-orbit field can be controlled by switching
the twist angle from 0 to 60 degrees. Finally, we show that the spin texture in
asymmetrically encapsulated phosphorene has the dominant in-plane component of
the spin-orbit field, comparable to the Rashba effect in phosphorene with an
applied sizable external electric field. Our results confirm that the
significant modification and control of the spin texture is possible in low
common-symmetry heterostructures, paving the way for using different substrates
to modify spin properties in materials important for spintronics.",2311.12463v2
2009-05-07,"Regarding Llewellyn Thomas's paper of 1927 and the ""hidden momentum"" of a magnetic dipole in an electric field","L. H. Thomas, in his 1927 paper, ""The Kinematics of an Electron with an
Axis"", explained the then-anomalous factor of one-half in atomic spin-orbit
coupling as due to a relativistic precession of the electron spin axis.
Thomas's explanation required also that the total of the orbit-averaged, or
""secular"", orbital and spin angular momenta of the electron be a conserved
quantity, as he found to be the case for either of two possible equations of
translational motion of the magnetic electron. Thomas's finding is seen in the
present work to require the ""hidden momentum"" of the electron intrinsic
magnetic moment in the Coulomb field of the proton be omitted from its equation
of translational motion. Omission of the hidden momentum is contrary to the
position of standard modern electrodynamics texts, and leads to violation of
Newton's law of action and reaction, negating Thomas's result. Including the
hidden momentum results in linear momentum conservation, but in the presence of
Thomas precession, the total angular momentum is not generally conserved. The
total angular momentum precesses for non-aligned spin and orbit, even in the
absence of externally-applied magnetic field. As Thomas observes that secular
angular momentum conservation is a necessary condition for a consistent
simultaneous description of spin-orbit coupling and the anomalous Zeeman
effect, such is not possible within classical electrodynamics in its absence.",0905.0927v4
2002-09-30,Datta-Das transistor with enhanced spin control,"We consider a two-channel spin transistor with weak spin-orbit induced
interband coupling. We show that the coherent transfer of carriers between the
coupled channels gives rise to an \textit{additional} spin rotation. We
calculate the corresponding spin-resolved current in a Datta-Das geometry and
show that a weak interband mixing leads to enhanced spin control.",0209682v2
2005-12-30,Kondo effect and spin filtering in coupled quantum dots,"The coherent transport through a set of N quantum dots coupled in parallel is
considered in the limit of infinite intradot and finite or infinite interdot
interactions. The mean field slave boson approach and the equation of motion
method are used. For the full spin-orbit degenerate case the low energy
behavior is characterized by an SU(2N) symmetry with entangled spin and charge
correlations. The magnetic field breaks the spin degeneracy, but for the
special choices of gate voltages the degeneracy might be recovered in one spin
channel allowing the spin filtering.",0512720v1
2007-01-03,Suppression of spin relaxation in an InAs nanowire double quantum dot,"We investigate the triplet-singlet relaxation in a double quantum dot defined
by top-gates in an InAs nanowire. In the Pauli spin blockade regime, the
leakage current can be mainly attributed to spin relaxation. While at weak and
strong inter-dot coupling relaxation is dominated by two individual mechanisms,
the relaxation is strongly reduced at intermediate coupling and finite magnetic
field. In addition we observe a charateristic bistability of the spin-non
conserving current as a function of magnetic field. We propose a model where
these features are explained by the polarization of nuclear spins enabled by
the interplay between hyperfine and spin-orbit mediated relaxation.",0701054v1
2007-04-28,Spin filtering implemented through Rashba and weak magnetic modulations,"We present two theoretical schemes for spin filters in one-dimensional
semiconductor quantum wires with spatially modulated Rashba spin-orbit coupling
(SOC) as well as weak magnetic potential. For case I, the SOC is periodic and
the weak magnetic potential is applied uniformly along the wire. Full spin
polarizations with opposite signs are obtained within two separated energy
intervals. For case II, the weak magnetic potential is periodic while the SOC
is uniform. An ideal negative/positive switching effect for spin polarization
is realized by tuning the strength of SOC. The roles of SOC, magnetic
potential, and their coupling on the spin filtering are analyzed.",0704.3799v1
2007-12-17,Field-induced spin excitations in Rashba-Dresselhaus two-dimensional electron systems probed by surface acoustic waves,"A spin-rotation symmetry in spin-orbit coupled two-dimensional electron
systems gives rise to a long-lived spin excitation that is robust against
short-range impurity scattering. The influence of a constant in-plane electric
field on this persistent spin helix is studied. To probe the field-induced
eigen-modes of the spin-charge coupled system, a surface acoustic wave is
exploited that provides the wave-vector for resonant excitation. The approach
takes advantage of methods worked out in the field of space-charge waves. Sharp
resonances in the field dependence of the in-plane and out-of-plane
magnetization are identified.",0712.2647v1
2008-04-09,Electric field control of spin-orbit splittings in GaAs/AlGaAs coupled quantum wells,"Electron spin dynamics is investigated in n-i-n GaAs/AlGaAs coupled quantum
wells. The electron spin dephasing time is measured as a function of an
external electrical bias under resonant excitation of the 1sHH intrawell
exciton using a time-resolved Kerr rotation technique. It is found a strong
electron spin dephasing time anisotropy caused by an interference of the
structure inversion asymmetry and the bulk inversion asymmetry. This anisotropy
is shown to be controlled by an electrical bias. A theoretical analysis of
electron spin dephasing time anisotropy is developed. The ratio of Rashba and
Dresselhaus spin splittings is studied as a function of applied bias.",0804.1483v1
2010-01-21,Spin Dependent Joule Heating due to Rashba Coupling and Zitterbewegung,"Investigating microwave absorption in asymmetric Si quantum wells in an
external magnetic field, we discover a spin dependent component of Joule
heating at spin resonance. We explain this effect in terms of Rashba spin-orbit
coupling which results in a current induced spin precession and Zitterbewegung.
Evidence is based on the observation of a specific dependence of the electron
spin resonance line shape and its amplitude on the experimental geometry which
in some range suggests a ""negative"" differential power absorption.",1001.3746v2
2011-08-24,Current-Conserving Aharonov-Bohm Interferometry with Arbitrary Spin Interactions,"We propose a general scattering matrix formalism that guarantees the charge
conservation at junctions between conducting arms with arbitrary spin
interactions. By using our formalism, we find that the spin-flip scattering can
happen even at nonmagnetic junctions if the spin eigenstates in arms are not
orthogonal. We apply our formalism to the Aharonov-Bohm interferometer
consisting of $n$-type semiconductor ring with both the Rashba spin-orbit
coupling and the Zeeman splitting. We discuss the characteristics of the
interferometer as conditional/unconditional spin switch in the
weak/strong-coupling limit, respectively.",1108.4775v1
2023-10-17,Optical Regulation of Chiral-Induced Spin Selectivity,"We present a non-perturbative theory that describes how light regulates
chiral-induced spin selectivity (CISS) from the perspective of strong
light-matter interactions. The research results indicate that 1) light can have
opposite effects on the CISS, 2) the difference in CISS is caused by the steady
states of nuclei coupled to spin electrons and 3) this steady state differences
are caused by the different light-induced Lorentz forces felt by spin-up and
spin-down electrons. The fundamental reason for these results is the impact of
light on spin-orbital coupling (SOC), which is a complex process. This
theoretical framework is verified by the calculations of Floquet SOC
non-adiabatic nuclear dynamics.",2310.10929v1
2023-10-26,Gravitational Spin Hall Effect of Dirac Particle and the Weak Equivalence Principle,"We present a spin-induced none-geodesic effect of Dirac wave packets in a
static uniform gravitational field. Our approach is based on the
Foldy-Wouthuysen transformation of Dirac equation in a curved spacetime, which
predicts the gravitational spin-orbit coupling. Due to this coupling, we find
that the dynamics of the free-fall Dirac wave packets with opposite spin
polarization will yield the transverse splitting in the direction perpendicular
to spin orientation and gravity, which is known as the gravitational spin Hall
effect. Even in a static uniform gravitational field, such effect suggests that
the weak equivalence principle is violated for quantum particles.",2310.17581v1
2019-04-02,Nematic-orbit coupling and nematic density waves in spin-1 condensates,"We propose the creation of artificial nematic-orbit coupling in spin-1
Bose-Einstein condensates, in analogy to spin-orbit coupling. Using a suitably
designed microwave chip, the quadratic Zeeman shift, normally uniform in space,
can be made to be spatio-temporally varying, leading to a coupling between
spatial and nematic degrees of freedom. A phase diagram is explored where three
quantum phases with the nematic order emerge: easy-axis, easy-plane with
single-well and easy-plane with double well structure in momentum space. By
including spin-dependent and spin-independent interactions, we also obtain the
low energy excitation spectra in these three phases. Lastly, we show that the
nematic-orbit coupling leads to a periodic nematic density modulation in
relation to the period $\lambda_T$ of the cosinusoidal quadratic Zeeman term.
Our results point to the rich possibilities for manipulation of tensorial
degrees of freedom in ultracold gases without requiring Raman lasers, and
therefore, obviating light-scattering induced heating.",1904.01635v2
2020-06-16,Generating Giant Vortex in a Fermi Superfluid via Spin-Orbital-Angular-Momentum Coupling,"Spin-orbital-angular-momentum (SOAM) coupling has been realized in recent
experiments of Bose-Einstein condensates [Chen et al., Phys. Rev. Lett. 121,
113204 (2018) and Zhang et al., Phys. Rev. Lett. 122, 110402 (2019)], where the
orbital angular momentum imprinted upon bosons leads to quantized vortices. For
fermions, such an exotic synthetic gauge field can provide fertile ground for
fascinating pairing schemes and rich superfluid phases, which are yet to be
explored. Here we demonstrate how SOAM coupling stabilizes vortices in Fermi
superfluids through a unique mechanism that can be viewed as the angular analog
to that of the spin-orbit-coupling-induced Fulde-Ferrell state under a Fermi
surface deformation. Remarkably, the vortex size is comparable with the beam
waist of Raman lasers generating the SOAM coupling, which is typically much
larger than previously observed vortices in Fermi superfluids. With tunable
size and core structure, these giant vortex states provide unprecedented
experimental access to topological defects in Fermi superfluids.",2006.08898v2
2022-05-17,Charge to Spin Conversion in van der Waals Metal NbSe2,"Quantum materials with a large charge current-induced spin polarization are
promising for next-generation all-electrical spintronic science and technology.
Van der Waals metals with high spin-orbit coupling and novel spin textures have
attracted significant attention for an efficient charge to spin conversion
process. Here, we demonstrate the electrical generation of spin polarization in
NbSe2 up to room temperature. To probe the current-induced spin polarization in
NbSe2, we used a graphene-based non-local spin-valve device, where the
spin-polarization in NbSe2 is efficiently injected and detected using non-local
spin-switch and Hanle spin precession measurements. A significantly higher
charge-spin conversion in NbSe2 is observed at a lower temperature, below the
superconducting transition temperature Tc ~ 7 K of NbSe2. However, the
charge-spin conversion signal could only be observed with a higher bias current
above the superconducting critical current, limiting the observation of the
signal only to the non-superconducting state of NbSe2. Systematic measurements
provide the possible origins of the spin polarization to be predominantly due
to the spin Hall effect or Rashba-Edelstein effect in NbSe2, considering
different symmetry allowed charge-spin conversion processes.",2205.08327v1
2022-07-29,Unusual Spin Polarization in the Chirality Induced Spin Selectivity,"Chirality-induced spin selectivity (CISS) refers to the fact that electrons
get spin polarized after passing through organic chiral molecules in a
nanoscale device. In CISS, chiral molecules are commonly believed to be a spin
filter through which one favored spin transmits and the opposite spin gets
reflected, i.e., transmitted and reflected electrons exhibit opposite spin
polarization. In this work, we point out that such a spin filter scenario
contradicts the principle that equilibrium spin current must vanish. Instead,
we find that both transmitted and reflected electrons present the same type
spin polarization, which is actually ubiquitous for a two-terminal device. More
accurately, chiral molecules play the role of a spin polarizer rather than a
spin filter. The direction of spin polarization is determined by the molecule
chirality and the electron incident direction. And the magnitude of spin
polarization replies on local spin-orbit coupling in the device. Our work
brings a deeper understanding on CISS and interprets recent experiments, for
example, the CISS-driven anomalous Hall effect.",2208.00043v2
2005-03-17,Transverse Spin-Orbit Force in the Spin Hall Effect in Ballistic Semiconductor Wires,"We introduce the spin and momentum dependent {\em force operator} which is
defined by the Hamiltonian of a {\em clean} semiconductor quantum wire with
homogeneous Rashba spin-orbit (SO) coupling attached to two ideal (i.e., free
of spin and charge interactions) leads. Its expectation value in the
spin-polarized electronic wave packet injected through the leads explains why
the center of the packet gets deflected in the transverse direction. Moreover,
the corresponding {\em spin density} will be dragged along the transverse
direction to generate an out-of-plane spin accumulation of opposite signs on
the lateral edges of the wire, as expected in the phenomenology of the spin
Hall effect, when spin-$\uparrow$ and spin-$\downarrow$ polarized packets
(mimicking the injection of conventional unpolarized charge current) propagate
simultaneously through the wire. We also demonstrate that spin coherence of the
injected spin-polarized wave packet will gradually diminish (thereby
diminishing the ``force'') along the SO coupled wire due to the entanglement of
spin and orbital degrees of freedom of a single electron, even in the absence
of any impurity scattering.",0503415v2
2016-03-30,Rashba-type Spin-orbit Coupling in Bilayer Bose-Einstein Condensates,"We explore a new way of producing the Rashba spin-orbit coupling (SOC) for
ultracold atoms by using a two-component (spinor) atomic Bose-Einstein
condensate (BEC) confined in a bilayer geometry. The SOC of the Rashba type is
created if the atoms pick up a {\pi} phase after completing a cyclic transition
between four combined spin-layer states composed of two spin and two layer
states. The cyclic coupling of the spin-layer states is carried out by
combining an intralayer Raman coupling and an interlayer laser assisted
tunneling. We theoretically determine the ground-state phases of the
spin-orbit-coupled BEC for various strengths of the atom-atom interaction and
the laser-assisted coupling. It is shown that the bilayer scheme provides a
diverse ground-state phase diagram. In an intermediate range of the atom-light
coupling two interlacing lattices of half- skyrmions and half-antiskyrmions are
spontaneously created. In the strong-coupling regime, where the SOC of the
Rashba-type is formed, the ground state represents plane-wave or standing-wave
phases depending on the interaction between the atoms. A variational analysis
is shown to be in a good agreement with the numerical results.",1603.09043v2
2019-09-18,Dzyaloshinskii-Moriya coupling in 3d insulators,"We present an overview of the microscopic theory of the Dzyaloshinskii-Moriya
(DM) coupling in strongly correlated 3d compounds. Most attention in the paper
centers around the derivation of the Dzyaloshinskii vector, its value,
orientation, and sense (sign) under different types of the (super)exchange
interaction and crystal field. We consider both the Moriya mechanism of the
antisymmetric interaction and novel contributions, in particular, that of
spin-orbital coupling on the intermediate ligand ions. We have predicted a
novel magnetic phenomenon, {\it weak ferrimagnetism} in mixed weak ferromagnets
with competing signs of the Dzyaloshinskii vectors.
  We revisit a problem of the DM coupling for a single bond in cuprates
specifying the local spin-orbital contributions to Dzyaloshinskii vector
focusing on the oxygen term. We predict a novel puzzling effect of the on-site
staggered spin polarization to be a result of the on-site spin-orbital coupling
and the the cation-ligand spin density transfer. The intermediate ligand NMR
measurements are shown to be an effective tool to inspect the effects of the DM
coupling in an external magnetic field. We predict the effect of a $strong$
oxygen weak antiferromagnetism in edge-shared CuO$_2$ chains due to
uncompensated oxygen Dzyaloshinskii vectors. We revisit the effects of
symmetric spin anisotropy directly induced by the DM coupling. A critical
analysis will be given of different approaches to exchange-relativistic
coupling based on the cluster and the DFT based calculations. Theoretical
results are applied to different classes of 3d compounds from conventional weak
ferromagnets ($\alpha$-Fe$_2$O$_3$, FeBO$_3$, FeF$_3$, RFeO$_3$, RCrO$_3$,.. )
to unconventional systems such as weak ferrimagnets (e.g.,
RFe$_{1-x}$Cr$_x$O$_3$), helimagnets (e.g., CsCuCl$_3$), and parent cuprates
(La$_2$CuO$_4$,...).",1909.08342v1
2004-04-27,Orbital and spin correlations in Ca$_{2-x}$Sr$_x$RuO$_4$: A mean field study,"The alloy Ca$_{2-x}$Sr$_x$RuO$_4$ exhibits a complex phase diagram with
peculiar magnetic metallic phases. In this paper some aspects of this alloy are
discussed based on a mean field theory for an effective Kugel-Khomskii model of
localized orbital and spin degrees of freedom. This model results from an
orbital selective Mott transition which in the three-band system localized two
orbitals while leaving the third one itinerant. Special attention is given to
the region around a structure quantum phase transition at $ x \approx 0.5 $
where the crystal lattice changes from tetragonal to orthorhombic symmetry
while leaving the system metallic. This transition yields, a change from
ferromagnetic to antiferromagnetic spin correlations. The complete mean field
phase diagram for this transition is given including orbital and spin order.
The anisotropy of spin susceptibility, a consequence of spin-orbit coupling and
orbital correlation, is a tell-tale sign of one of these phases. In the
predominantly antiferromagnetic phase we describe a metamagnetic transition in
a magnetic field and show that coupling of the itinerant band to the localized
degrees of freedom yields an anomalous longitudinal magnetoresistance
transition. Both phenomena are connected with the evolution of the
ferromagnetic and antiferromagnetic domains in the external magnetic field and
agree qualitatively with the experimental findings.",0404661v1
2015-09-27,A new effective-one-body Hamiltonian with next-to-leading order spin-spin coupling,"We present a new effective-one-body (EOB) Hamiltonian with next-to-leading
order (NLO) spin-spin coupling for black hole binaries endowed with arbitrarily
oriented spins. The Hamiltonian is based on the model for parallel spins and
equatorial orbits developed in [Physical Review D 90, 044018 (2014)], but
differs from it in several ways. In particular, the NLO spin-spin coupling is
not incorporated by a redefinition of the centrifugal radius $r_c$, but by
separately modifying certain sectors of the Hamiltonian, which are identified
according to their dependence on the momentum vector. The gauge-fixing
procedure we follow allows us to reduce the 25 different terms of the NLO
spin-spin Hamiltonian in Arnowitt-Deser-Misner coordinates to only 9 EOB terms.
This is an improvement with respect to the EOB model recently proposed in
[Physical Review D 91, 064011 (2015)], where 12 EOB terms were involved.
Another important advantage is the remarkably simple momentum structure of the
spin-spin terms in the effective Hamiltonian, which is simply quadratic up to
an overall square root. Moreover, a Damour-Jaranowski-Sch\""afer-type gauge
could be established, thus allowing one to concentrate, in the case of circular
and equatorial orbits, the whole spin-spin interaction in a single radial
potential.",1509.08135v1
2020-07-24,"Determination of the spin Hall angle, spin mixing conductance and spin diffusion length in Ir/CoFeB for spin-orbitronic devices","Iridium is a very promising material for spintronic applications due to its
interesting magnetic properties such as large RKKY exchange coupling as well as
its large spin-orbit coupling value. Ir is for instance used as a spacer layer
for perpendicular synthetic antiferromagnetic or ferrimagnet systems. However,
only a few studies of the spintronic parameters of this material have been
reported. In this paper, we present inverse spin Hall effect - spin pumping
ferromagnetic resonance measurements on CoFeB/Ir based bilayers to estimate the
values of the effective spin Hall angle, the spin diffusion length within
iridium, and the spin mixing conductance in the CoFeB/Ir bilayer. In order to
have reliable results, we performed the same experiments on CoFeB/Pt bilayers,
which behavior is well known due to numerous reported studies. Our experimental
results show that the spin diffusion length within iridium is 1.3 nm for
resistivity of 250 n$\Omega$.m, the spin mixing conductance $g_{eff}^{\uparrow
\downarrow}$ of the CoFeB/Ir interface is 30 nm$^{-2}$, and the spin Hall angle
of iridium has the same sign than the one of platinum and is evaluated at 26%
of the one of platinum. The value of the spin Hall angle found is 7.7% for Pt
and 2% for Ir. These relevant parameters shall be useful to consider Ir in new
concepts and devices combining spin-orbit torque and spin-transfer torque.",2007.12413v1
2019-09-03,Effects of spin-orbit coupling on spin-fluctuation induced pairing in iron-based superconductors,"We perform a theoretical study of the leading pairing instabilities and the
associated superconducting gap functions within the spin-fluctuation mediated
pairing scenario in the presence of spin-orbit coupling (SOC). Focussing on
iron-based superconductors (FeSCs), our model Hamiltonian consists of a
realistic density functional theory (DFT)-derived ten-band hopping term,
spin-orbit coupling, and electron-electron interactions included via the
multi-orbital Hubbard-Hund Hamiltonian. We perform an extensive parameter sweep
and investigate different doping regimes including cases with only hole- or
only electron Fermi pockets. In addition, we explore two different
bandstructures: a rather generic band derived for LaFeAsO but known to
represent standard DFT-obtained bands for iron-based superconductors, and a
band specifically tailored for FeSe which exhibits a notably different Fermi
surface compared to the generic case. It is found that for the generic FeSCs
band, even rather large SOC has negligible effect on the resulting gap
structure; the $s_{+-}$ (pseudo-)spin singlet pairing remains strongly favored
and SOC does not lead to any SOC-characteristic gap oscillations along the
various Fermi surfaces. By contrast in the strongly hole-doped case featuring
only hole-pockets around the $\Gamma$-point, the leading solution is $d$-wave
pseudo-spin singlet, but with a notable SOC-driven tendency towards helical
pseudo-spin triplet pairing, which may even become the leading instability. In
the heavily electron doped situation, featuring only electron pockets centered
around the $M$-point, the leading superconducting instabilities are pseudo-spin
singlets with SOC favoring the $s$-wave case as compared to $d$-wave pairing,
which is the favored gap symmetry for vanishing SOC.",1909.01313v1
2020-05-18,Pseudospin-electric coupling for holes beyond the envelope-function approximation,"In the envelope-function approximation, interband transitions produced by
electric fields are neglected. However, electric fields may lead to a spatially
local ($k$-independent) coupling of band (internal, pseudospin) degrees of
freedom. Such a coupling exists between heavy-hole and light-hole (pseudo-)spin
states for holes in III-V semiconductors, such as GaAs, or in group IV
semiconductors (germanium, silicon, ...) with broken inversion symmetry. Here,
we calculate the electric-dipole (pseudospin-electric) coupling for holes in
GaAs from first principles. We find a transition dipole of $0.5$ debye, a
significant fraction of that for the hydrogen-atom $1s\to2p$ transition. In
addition, we derive the Dresselhaus spin-orbit coupling that is generated by
this transition dipole for heavy holes in a triangular quantum well. A
quantitative microscopic description of this pseudospin-electric coupling may
be important for understanding the origin of spin splitting in quantum wells,
spin coherence/relaxation ($T_2^*/T_1$) times, spin-electric coupling for
cavity-QED, electric-dipole spin resonance, and spin non-conserving tunneling
in double quantum dot systems.",2005.08821v2
2018-09-07,Spin angular momentum in planar and cylindrical waveguides induced by transverse confinement and intrinsic helicity of guided light,"In recent years, extraordinary spin angular momenta have been investigated in
a variety of structured electromagnetic waves, being of especial interest in
sub-wavelength evanescent fields. Here we demonstrate analytically that, in
planar and cylindrical waveguides supporting transverse electric/magnetic
modes, transverse spin density arises inside the waveguide (different from the
spin induced in the evanescent region outside the waveguide), carrying indeed
longitudinal extraordinary (so-called) Belinfante's spin momentum. Such
contribution depends linearly on the mode transverse wave vector, and is thus
induced by mode confinement. Cylindrical waveguides support in addition hybrid
modes that exhibit a richer phenomenology with not only azimuthal
(confinement-related) spin, but also an intrinsic helicity which leads to
longitudinal spin density and transverse helicity-dependent spin momentum.
Results are indeed presented for configurations relevant to spin-orbit coupling
in nanophotonic waveguides and to manipulating optical forces in
IR-to-microwave water-filled channels. Thus guided modes intrinsically carrying
confinement-induced transverse spin, combined with intrinsic-helicity-induced
longitudinal spin (when hybrid), hold promise of superb devices to control
spin-orbit interaction and optical forces within confined geometries throughout
the electromagnetic spectra.",1809.02406v1
2004-09-01,Spin-Hall Effect in Two-Dimensional Electron Systems with Rashba Spin-Orbit Coupling and Disorder,"Using the four-terminal Landauer-B\""{u}ttiker formula and Green's function
approach, we calculate numerically the spin-Hall conductance in a
two-dimensional junction system with the Rashba spin-orbit (SO) coupling and
disorder. We find that the spin-Hall conductance can be much greater or smaller
than the universal value $e/8\pi$, depending on the magnitude of the SO
coupling, the electron Fermi energy and the disorder strength. The spin-Hall
conductance does not vanish with increasing sample size for a wide range of
disorder strength. Our numerical calculation reveals that a nonzero SO coupling
can induce electron delocalization for disorder strength smaller than a
critical value, and the nonvanishing spin-Hall effect appears mainly in the
metallic regime.",0409038v3
2011-12-02,Spin-dependent Klein tunneling in graphene: Role of Rashba spin-orbit coupling,"Within an effective Dirac theory the low-energy dispersions of monolayer
graphene in the presence of Rashba spin-orbit coupling and spin-degenerate
bilayer graphene are described by formally identical expressions. We explore
implications of this correspondence for transport by choosing chiral tunneling
through pn and pnp junctions as a concrete example. A real-space Green's
function formalism based on a tight-binding model is adopted to perform the
ballistic transport calculations, which cover and confirm previous theoretical
results based on the Dirac theory. Chiral tunneling in monolayer graphene in
the presence of Rashba coupling is shown to indeed behave like in bilayer
graphene. Combined effects of a forbidden normal transmission and spin
separation are observed within the single-band n to p transmission regime. The
former comes from real-spin conservation, in analogy with pseudospin
conservation in bilayer graphene, while the latter arises from the intrinsic
spin-Hall mechanism of the Rashba coupling.",1112.0552v2
2014-09-30,Collective modes in two- and three-dimensional electron systems with Rashba spin-orbit coupling,"In addition to charge plasmons, a 2D electron system with Rashba-type
spin-orbit coupling (SOC) also supports three collective modes in the spin
sector: the chiral-spin modes. We study the dispersions of the charge and spin
modes and their coupling to each other within a generalized Random Phase
Approximation for arbitrarily strong SOC, and both in 2D and 3D systems. In
both 2D and 3D, we find that the charge plasmons are coupled to only one of the
three chiral-spin modes. This coupling is shown to affect the dispersions of
the modes at finite but not at zero wavenumbers. In 3D, the chiral-spin modes
are strongly damped by particle-hole excitations and disappear for weak
electron-electron interaction. Landau damping of the chiral-spin modes in 3D is
directly related to the fact that, in contrast to 2D, there is no gap for
particle-hole excitations between spin-split subbands. The gapless continuum is
also responsible for Landau damping of the charge plasmon in 3D - a
qualitatively new feature of the SOC system. We also discuss the optical
conductivity of clean 2D and 3D systems and show that SOC introduces spectral
weight at finite frequency in a such way that the sum rule is satisfied. The
in-plane tranverse chiral-spin mode shows up as dispersing peak in the optical
conductivity at finite number which can can be measured in the presence of
diffraction grating. We also discuss possible experimental manifestations of
chiral-spin modes in semiconductor quantum wells such InGaAs/AlGaAs and 3D
giant Rashba materials of the BiTeI family.",1409.8666v1
2021-10-01,Spin liquid in twisted homobilayers group-VI gichalcogenides,"Twisted transition metal dichalcogenide (TMD) homobilayers have recently
emerged as a powerful platform for studying correlated insulating states. In
the strongly correlated limit, we construct an effective spin Hamiltonian on a
honeycomb lattice that includes the Heisenberg interaction and nonsymmetric
interactions such as a Dzyaloshinskii-Moriya interaction and a Kane-Mele
coupling for the Mott-insulating phase at half-filling. For the twisted TMD
homobilayers, the spin-orbit coupling in the Hubbard model, which is expected
to induce the antisymmetric exchange couplings in the effective spin
Hamiltonian, is a highly tunable and experimentally accessible quantity that
can be tuned by an applied electric field. In this study, we investigate
classical and quantum phase diagrams of the effective spin Hamiltonian using
analytical and numerical methods. We show that the model exhibits a rich
classical phase diagram including an antiferromagnetic (AFM) phase, a planar
spiral ordered phase with high classical degeneracy, a $z$-AFM phase, a
noncoplanar phase, a noncollinear phase, and a 120$^{\circ}$-AFM phase. In the
quantum treatment, we calculate low-energy magnon excitation spectrum, ground
state energy, and static spin structure factor using linear spin-wave theory
and density matrix renormalization group methods to compose the quantum phase
diagram of the effective spin Hamiltonian. Beyond the Heisenberg interaction,
we find that the existence of these antisymmetric couplings is responsible for
the quantum spin liquid, $z$-AFM, noncoplanar, and 120$^{\circ}$ phases.
Twisted TMD homobilayers, therefore, offer rich platforms for realizing rich
phases of matter such as quantum spin liquid, noncoplanar, and 120$^{\circ}$,
resulting from the spin-orbit coupling.",2110.00536v1
2010-01-18,Effect of Spin-Orbit Interaction in Spin-Triplet Superconductor: Structure of ${\bf d}$-vector and Anomalous $^{17}$O-NQR Relaxation in Sr$_2$RuO$_4$,"Supposing the spin-triplet superconducting state of Sr$_2$RuO$_4$, the
spin-orbit (SO) coupling associated with relative motion in Cooper pairs is
calculated by extending the method for the dipole-dipole coupling given by
Leggett in the superfluid $^{3}$He. It is shown that the SO coupling works only
in the equal-spin pairing (ESP) state to make the pair angular momentum
$\hbar{\vec L}$ and the pair spin angular momentum ${\rm i}{\vec d}\times{\vec
d}^{*}$ parallel with each other. The SO coupling gives rise to the internal
Josephson effect in a chiral ESP state as in superfluid A-phase of $^3$He with
a help of an additional anisotropy arising from SO coupling of atomic origin
which works to direct the {\bf d}-vector into $ab$-plane. This resolves the
problem of the anomalous relaxation of $^{17}$O-NQR and the structure of {\bf
d}-vector in Sr$_2$RuO$_4$.",1001.2999v1
2011-08-13,First Principle Study of Magnetism and Magneto-structural Coupling in Gallium Ferrite,"We report a first-principles study of the magnetic properties, site disorder
and magneto-structural coupling in multiferroic gallium ferrite (GFO) using
local spin density approximation (LSDA+U) of density functional theory. The
calculations of the ground state A-type antiferromagnetic structure predict
magnetic moments consistent with the experiments whilst consideration of
spin-orbit coupling yields a net orbital moment of ~ 0.025 Bohr magneton/Fe
site also in good accordance with the experiments. We find that though site
disorder is not spontaneous in the ground state, interchange between Fe2 and
Ga2 sites is most favored in the disordered state. The results show that
ferrimagnetism in GFO is due to Ga-Fe site disordering such that Fe spins at
Ga1 and Ga2 sites are antiferromagnetically aligned while maintaining
ferromagnetic coupling between Fe spins at Ga1 and Fe1 sites as well as between
Fe spins at Ga2 and Fe2 sites. The effect of spin configuration on the
structural distortion clearly indicates presence of magneto-structural coupling
in GFO.",1108.2773v1
2011-10-21,Spin-orbit-induced strong coupling of a single spin to a nanomechanical resonator,"We theoretically investigate the deflection-induced coupling of an electron
spin to vibrational motion due to spin-orbit coupling in suspended carbon
nanotube quantum dots. Our estimates indicate that, with current capabilities,
a quantum dot with an odd number of electrons can serve as a realization of the
Jaynes-Cummings model of quantum electrodynamics in the strong-coupling regime.
A quantized flexural mode of the suspended tube plays the role of the optical
mode and we identify two distinct two-level subspaces, at small and large
magnetic field, which can be used as qubits in this setup. The strong intrinsic
spin-mechanical coupling allows for detection, as well as manipulation of the
spin qubit, and may yield enhanced performance of nanotubes in sensing
applications.",1110.4893v2
2014-05-09,Magnetization dynamics and damping due to electron-phonon scattering in a ferrimagnetic exchange model,"We present a microscopic calculation of magnetization damping for a magnetic
""toy model."" The magnetic system consists of itinerant carriers coupled
antiferromagnetically to a dispersionless band of localized spins, and the
magnetization damping is due to coupling of the itinerant carriers to a phonon
bath in the presence of spin-orbit coupling. Using a mean-field approximation
for the kinetic exchange model and assuming the spin-orbit coupling to be of
the Rashba form, we derive Boltzmann scattering integrals for the distributions
and spin coherences in the case of an antiferromagnetic exchange splitting,
including a careful analysis of the connection between lifetime broadening and
the magnetic gap. For the Elliott-Yafet type itinerant spin dynamics we extract
dephasing and magnetization times T_1 and T_2 from initial conditions
corresponding to a tilt of the magnetization vector, and draw a comparison to
phenomenological equations such as the Landau-Lifshitz or the Gilbert damping.
We also analyze magnetization precession and damping for this system including
an anisotropy field and find a carrier mediated dephasing of the localized spin
via the mean-field coupling.",1405.2347v1
2021-10-21,Radiation Modulated Spin coupling in DNA,"The spin activity in macromolecules such as DNA and oligopeptides, in the
context of the Chiral Induced Spin Selectivity (CISS) has been proposed to be
due to the atomic Spin-Orbit Coupling (SOC) and the associated chiral symmetry
of the structures. This coupling, associated with carbon, nitrogen and oxygen
atoms in biological molecules, albeit small (meV), can be enhanced by the
geometry, and strong local polarization effects such as hydrogen bonding (HB).
A novel way to manipulate the spin degree of freedom is by modifying the
spectrum using a coupling to the appropriate electromagnetic radiation field.
Here we use the Floquet formalism in order to show how the half filled band
Hamiltonian for DNA, can be modulated by the radiation to produce a up to a
tenfold increase of the effective SOC once the intrinsic coupling is present.
On the other hand, the chiral model, once incorporating the orbital angular
momentum of electron motion on the helix, opens a gap for different helicity
states (helicity splitting) that chooses spin polarization according to
transport direction and chirality, without breaking time reversal symmetry. The
observed effects are feasible in physically reasonable parameter ranges for the
radiation field amplitude and frequency.",2110.11250v1
2023-07-27,Spin Coupling Effect on Geometry-Dependent X-ray Absorption of Diradicals,"We theoretically investigate the influence of diradical electron spin
coupling on the time-resolved X-ray absorption spectra of the photochemical
ring opening of furanone. We predict geometry dependent carbon K-edge signals
involving transitions from core orbitals to both singly and unoccupied
molecular orbitals. The most obvious features of the ring opening come from the
carbon atom directly involved in the bond breaking, through its transition to
both the newly formed SOMO and the available LUMO state. In addition to this
primary feature, the singlet spin coupling of four unpaired electrons that
arises in the core-to-LUMO states creates additional geometry dependence in
some spectral features, with both oscillator strengths and relative excitation
energies varying observably as a function of the ring opening. We attribute
this behavior to a spin-occupancy-induced selection rule, which occurs when
singlet spin coupling is enforced in the diradical state. Notably, one of these
geometry-sensitive core-to-LUMO transitions excites core electrons from a
backbone carbon not involved in the bond breaking, providing a novel non-local
X-ray probe of chemical dynamics arising from electron spin coupling.",2307.15207v1
2020-03-14,Enhanced longevity of the spin helix in low-symmetry quantum wells,"In a semiconductor, collective excitations of spin textures usually decay
rather fast due to D'yakonov-Perel' spin relaxation. The latter arises from
spin-orbit coupling, which induces wave-vector-dependent spin rotations that,
in conjunction with random disorder scattering, generate spin decoherence.
However, symmetries occurring under certain conditions can prevent the
relaxation of particular homogeneous and inhomogeneous spin textures. The
inhomogeneous spin texture, termed as persistent spin helix, is especially
appealing as it enables us to manipulate the spin orientation while retaining a
long spin lifetime. Recently, it was predicted that such symmetries can be
realized in zinc-blende two-dimensional electron gases if at least two
growth-direction Miller indices agree in modulus and the coefficients of the
Rashba and linear Dresselhaus spin-orbit couplings are suitably matched [PRL
117, 236801 (2016)]. In the present paper, we systematically analyze the impact
of the symmetry-breaking cubic Dresselhaus spin-orbit coupling, which
generically coexists in these systems, on the stability of the emerging spin
helices with respect to the growth direction. We find that, as an interplay
between orientation and strength of the effective magnetic field induced by the
cubic Dresselhaus terms, the spin relaxation is weakest for a low-symmetry
growth direction that can be well approximated by a [225] lattice vector. These
quantum wells yield a 30\% spin-helix lifetime enhancement compared to
[001]-oriented electron gases and, remarkably, require a negligible Rashba
coefficient. The rotation axis of the corresponding spin helix is only slightly
tilted out of the quantum-well plane. This makes the experimental study of the
spin-helix dynamics readily accessible for conventional optical spin
orientation measurements where spins are excited and detected along the
quantum-well growth direction.",2003.06544v2
2012-10-30,Fractional quantum Hall states of a Bose gas with spin-orbit coupling,"We study the fractional quantum Hall phases of a pseudospin-1/2 Bose gas in
an artificial gauge field. In addition to an external magnetic field, the gauge
field also mimics an intrinsic spin-orbit coupling of the Rashba type. While
the spin degeneracy of the Landau levels is lifted by the spin-orbit coupling,
the crossing of two Landau levels at certain coupling strengths gives rise to a
new degeneracy. We therefore take into account two Landau levels, and perform
exact diagonalization of the many-body Hamiltonian. We study and characterize
the quantum Hall phases which occur in the vicinity of the degeneracy point.
Notably, we describe the different states appearing at the Laughlin filling,
\nu=1/2. While for this filling incompressible phases disappear at the
degeneracy point, denser systems at \nu=3/2 and \nu=2 are found to be clearly
gapped. For filling factors \nu=2/3 and \nu=4/3, we discuss the connection of
the exact ground state to the non-Abelian spin singlet states, obtained as the
ground state of k+1 body contact interactions.",1210.8035v2
2014-11-10,Spin-orbit coupling and electronic charge effects in Mott insulators,"We derive the effective charge- and current-density operators for the
strong-coupling limit of a single-band Mott insulator in the presence of
spin-orbit coupling and show that the spin-orbit contribution to the effective
charge density leads to novel mechanisms for multiferroic behavior. In some
sense, these mechanisms are the electronic counterpart of the ionic-based
mechanisms, which have been proposed for explaining the electric polarization
induced by spiral spin orderings. The new electronic mechanisms are illustrated
by considering cycloidal and proper screw magnetic orderings on sawtooth and
kagome lattices. As for the isotropic case, geometric frustration is crucial
for achieving this purely electronic coupling between spin and charge degrees
of freedom.",1411.2511v1
2014-12-08,Magnetization Dynamics driven by Non-equilibrium Spin-Orbit Coupled Electron Gas,"The dynamics of magnetization coupled to an electron gas via s-d exchange
interaction is investigated by using density matrix technique. Our theory shows
that non-equilibrium spin accumulation induces a spin torque and the electron
bath leads to a damping of the magnetization. For the two-dimensional
magnetization thin film coupled to the electron gas with Rashba spin-orbit
coupling, the result for the spin-orbit torques is consistent with the previous
semi-classical theory. Our theory predicts a damping of the magnetization,
which is absent in the semi-classical theory. The magnitude of the damping due
to the electron bath is comparable to the intrinsic Gilbert damping and may be
important in describing the magnetization dynamics of the system.",1412.2479v1
2016-04-05,Conductance measurement of spin-orbit coupling in the two-dimensional electron systems with in-plane magnetic field,"We consider determination of spin-orbit (SO) coupling constants for the
two-dimensional electron gas from measurements of electric properties in
rotated in-plane magnetic field. %Due to the interplay Due to the SO coupling
the electron backscattering is accompanied by spin precession and spin mixing
of the incident and reflected electron waves. The competition of the external
and SO-related magnetic fields produces a characteristic conductance dependence
on the in-plane magnetic field value and orientation which, in turn, allows for
determination of the absolute value of the effective spin-orbit coupling
constant as well as the ratio of the Rashba and Dresselhaus SO contributions.",1604.01270v2
2016-09-25,Effects of Spin-Orbit Coupling on Jaynes-Cummings and Tavis-Cummings Models,"We consider ultracold atoms inside a ring optical cavity that supports a
single plane-wave mode. The cavity field, together with an external coherent
laser field, drives a two-photon Raman transition between two internal
pseudo-spin states of the atom. This gives rise to an effective coupling
between atom's pseudo-spin and external center-of-mass (COM) motion. For the
case of a single atom inside the cavity, We show how the spin-orbit coupling
modifies the static and dynamic properties of the Jaynes-Cummings (JC) model.
In the case of many atoms in thermodynamic limit, we show that the spin-orbit
coupling modifies the Dicke superradiance phase transition boundary and the
non-superradiant normal phase may become reentrant in some regimes.",1609.07815v2
2017-04-03,Spin-orbit-coupling induced localization in the expansion of an interacting Bose-Einstein condensate,"By developing a hydrodynamic formalism, we investigate the expansion dynamics
of the single-minimum phase of a binary spin-orbit coupled Bose-Einstein
condensate, after releasing from an external harmonic trap. We find that the
expansion of the condensate along the direction of the spin-orbit coupling is
dramatically slowed down near the transition between the single-minimum phase
and the plane-wave phase. Such a slow expansion, resembling a form of an
effective localization, is due to the quenching of the superfluid motion which
results in a strong increase of the effective mass. In the single-minimum phase
the anisotropic expansion of the Bose gas, which is spin balanced at
equilibrium, is accompanied by the emergence of a local spin polarization. Our
analytic scaling solutions emerging from hydrodynamic picture are compared with
a full numerical simulation based on the coupled Gross-Pitaevskii equations.",1704.00677v1
2020-12-28,Effect of proximity-induced spin-orbit coupling in graphene mesoscopic billiards,"Van der Waals heterostructures based on two-dimensional materials have
recently become a very active topic of research in spintronics, both aiming at
a fundamental description of spin dephasing processes in nanostructures and as
a potential element in spin-based information processing schemes. Here, we
theoretically investigate the magnetoconductance of mesoscopic devices built
from graphene proximity-coupled to a high spin-orbit coupling material. Through
numerically exact tight-binding simulations, we show that the interfacial
breaking of inversion symmetry generates robust weak antilocalization even when
the $z\rightarrow -z$ symmetric spin-orbit coupling in the quantum dot
dominates over the Bychkov--Rashba interaction. Our findings are in interpreted
on the light of random matrix theory, which links the observed behavior of
quantum interference corrections to a transition from circular-orthogonal to
circular-sympletic ensemble.",2012.14216v2
2018-12-28,Impact of the Rashba Spin Orbit Coupling on $f$-electron Materials,"The combination of strong spin orbit coupling and strong correlations holds
tremendous potential for interesting physical phenomena as well as applications
in spintronics and quantum computation. In this context, we here study the
interplay between the Rashba spin-orbit coupling (RSOC) and the Kondo screening
in noncentrosymmetric $f$-electron materials. We show that the Kondo coupling
of the $f$-electrons becomes anisotropic at high temperatures due to the RSOC.
However, an isotropic Kondo effect is restored at low temperature which leads
to a complete Kondo screening. We furthermore demonstrate that the Kondo effect
has influence on the Rashba splitting in the band structure, which becomes
temperature dependent. Although the $f$-electrons are localized at high
temperature, a helical spin polarization of the conduction band emerges due to
the scattering with the $f$-electrons. With decreasing temperature, the Kondo
screening occurs, which leads to drastic changes in the band structure.
Remarkably, these changes in the band structure depend on the helical spin
polarization. For strong RSOC, we observe that the hybridization gap of one of
the helical bands is closed at low temperature and a helical half-metal is
formed.",1812.10888v1
2019-03-22,Modified exchange interaction between magnetic impurities in spin-orbit coupled quantum wires,"Indirect exchange interaction between magnetic impurities in one dimensional
systems is a matter of long discussions since Kittel has established that in
the asymptotic limit it decays as the inverse of distance x between the
impurities. In this work we investigate this problem in a quantum wire with
Rashba spin-orbit coupling (SOC). By employing a second order perturbation
theory we find that one additional oscillatory term appears in each of the
RKKY, the Dzaloshinkii-Moryia and the Ising couplings. Remarkably, these extra
terms resulting from the spin precession of the conduction electrons induced by
the SOC do not decay as in the usual RKKY interaction. We show that these extra
oscillations arise from the finite momenta band splitting induced by the
spin-orbit coupling that modifies the spin-flip scatterings occurring at the
Fermi energy. Our findings open up a new perspective in the long-distance
magnetic interactions in solid state systems.",1903.09700v1
2021-09-03,Excited-state quantum phase transitions in spin-orbit coupled Bose gases,"Excited-state quantum phase transitions depend on and reveal the structure of
the whole spectrum of many-body systems. While they are theoretically well
understood, finding suitable signatures and detect them in actual experiments
remains challenging. For instance, in spinor gases, excited-state phases have
been identified and characterized through a topological order parameter that is
challenging to measure in experiments. Here, we propose the Raman-dressed
spin-orbit coupled gas as a novel platform to explore excited-state quantum
phase transitions. In a weakly-coupled regime, the dressed system is equivalent
to a spinor gas with tunable spin-spin interactions. Through this equivalence
we are able to define a new excited-state phase of the dressed gas. The phase
is characterize by the the behavior of the spatial density modulations, or
stripes, induced by spin-orbit coupling, and can in principle be measured in
current state-of-the-art experiments with ultracold atoms. Conversely, we show
that the properties of the excited phase can be exploited to prepare stripe
states with large and stable density modulations.",2109.01495v1
2013-12-25,Electron spin relaxation due to D'yakonov-Perel' and Elliot-Yafet mechanisms in monolayer MoS$_2$: Role of intravalley and intervalley processes,"We investigate the in-plane spin relaxation of electrons due to the
D'yakonov-Perel' and Elliot-Yafet mechanisms including the intra- and
inter-valley processes in monolayer MoS$_2$. We construct the effective
Hamiltonian for the conduction band using the L\""{o}wdin partition method from
the anisotropic two-band Hamiltonian with the intrinsic spin-orbit coupling of
the conduction band included. The spin-orbit coupling of the conduction band
induces the intra- and inter-valley D'yakonov-Perel' spin relaxation. In
addition, the Elliot-Yafet spin relaxation also takes place due to the
interband spin mixing. We find that the D'yakonov-Perel' mechanism dominates
the in-plane spin relaxation. In the framework of this mechanism, the
intravalley process is shown to play a more important role at low temperature
whereas the intervalley one becomes more important at high temperature. At the
temperature in between, the leading process of the in-plane spin relaxation
changes from the intervalley to intravalley one as the electron density
increases. Moreover, we find that the intravalley process is dominated by the
electron-electron Coulomb scattering even with high impurity density since the
dominant term in the spin-orbit coupling is isotropic, which does not lead to
the spin relaxation together with the electron-impurity scattering. This is
very different from the previous studies in semiconductors and graphene.",1312.6985v1
2015-01-28,Spin-orbit coupled repulsive Fermi atoms in a one-dimensional optical lattice,"Motivated by recent experimental development, we investigate spin-orbit
coupled repulsive Fermi atoms in a one-dimensional optical lattice. Using the
density-matrix renormalization group method, we calculate momentum distribution
function, gap, and spin-correlation function to reveal rich ground-state
properties. We find that spin-orbit coupling (SOC) can generate unconventional
momentum distribution, which depends crucially on the filling. We call the
corresponding phase with zero gap the SOC-induced metallic phase. We also show
that SOC can drive the system from the antiferromagnetic to ferromagnetic Mott
insulators with spin rotating. As a result, a second-order quantum phase
transition between the spin-rotating ferromagnetic Mott insulator and the
SOC-induced metallic phase is predicted at the strong SOC. Here the spin
rotating means that the spin orientations of the nearest-neighbor sites are not
parallel or antiparallel, i.e., they have an intersection angle $\theta \in
(0,\pi )$. Finally, we show that the momentum $k_{\mathrm{peak}}$, at which
peak of the spin-structure factor appears, can also be affected dramatically by
SOC. The analytical expression of this momentum with respect to the SOC
strength is also derived. It suggests that the predicted spin-rotating
ferromagnetic ($k_{\mathrm{peak}% }<\pi /2$) and antiferromagnetic ($\pi
/2<k_{\mathrm{peak}}<\pi $) correlations can be detected experimentally by
measuring the SOC-dependent spin-structure factor via the time-of-flight
imaging.",1501.07004v2
2021-10-13,Electric-field control of magnetic anisotropies: applications to Kitaev spin liquids and topological spin textures,"Magnetic anisotropies often originate from the spin-orbit coupling and
determine magnetic ordering patterns. We develop a microscopic theory for DC
electric-field controls of magnetic anisotropies in magnetic Mott insulators
and discuss its applications to Kitaev materials and topological spin textures.
Throughout this paper, we take a microscopic approach based on Hubbard-like
lattice models, tight-binding models with on-site interactions. We derive a
low-energy spin Hamiltonian from a fourth-order perturbation expansion of the
Hubbard-like model. We show in the presence of a strong intra-atomic spin-orbit
coupling that DC electric fields add non-Kitaev interactions such as a
Dzyaloshinskii-Moriya interaction and an off-diagonal $\Gamma'$ interaction to
the Kitaev-Heisenberg model and can induce a topological quantum phase
transition between Majorana Chern insulating phases. We also investigate the
inter-atomic Rashba spin-orbit coupling and its effects on topological spin
textures. DC electric fields turn out to create and annihilate magnetic
skyrmions, hedgehogs, and chiral solitons. We propose several methods of
creating topological spin textures with external electromagnetic fields. Our
theory clarifies that the strong but feasible electric field can control Kitaev
spin liquids and topological spin textures.",2110.06503v4
2014-08-06,Orbital magnetic moments in insulating Dirac systems: Impact on magnetotransport in graphene van der Waals heterostructures,"In honeycomb Dirac systems with broken inversion symmetry, orbital magnetic
moments coupled to the valley degree of freedom arise due to the topology of
the band structure, leading to valley-selective optical dichroism. On the other
hand, in Dirac systems with prominent spin-orbit coupling, similar orbital
magnetic moments emerge as well. These moments are coupled to spin, but
otherwise have the same functional form as the moments stemming from spatial
inversion breaking. After reviewing the basic properties of these moments,
which are relevant for a whole set of newly discovered materials, such as
silicene and germanene, we study the particular impact that these moments have
on graphene nanoengineered barriers with artificially enhanced spin-orbit
coupling. We examine transmission properties of such barriers in the presence
of a magnetic field. The orbital moments are found to manifest in transport
characteristics through spin-dependent transmission and conductance, making
them directly accessible in experiments. Moreover, the Zeeman-type effects
appear without explicitly incorporating the Zeeman term in the models, i.e., by
using minimal coupling and Peierls substitution in continuum and the
tight-binding methods, respectively. We find that a quasiclassical view is able
to explain all the observed phenomena.",1408.1200v2
2006-03-27,Spin and charge optical conductivities in spin-orbit coupled systems,"We study the frequency dependent spin- and charge- conductivity tensors of a
two-dimensional electron gas (2DEG) with Rashba and Dresselhaus spin-orbit
interaction. We show that the angular anisotropy of the spin-splitting energy
induced by the interplay between the Rashba and Dresselhaus couplings gives
rise to a characteristic spectral behavior of the spin and charge response
which is significantly different from that of pure Rashba or Dresselhaus case.
Such new spectral structures open the possibility for control of the optical
response by applying an external bias and/or by adjusting the light frequency.
In addition, it is shown that the relative strength of the spin-orbit coupling
parameters can be obtained through optical probing.",0603722v3
2006-03-28,Kinetic magnetoelectric effect in a 2D semiconductor strip due to boundary-confinement induced spin-orbit coupling,"In a thin strip of a two-dimensional semiconductor electronic system,
spin-orbit coupling may be induced near both edges of the strip due to the
substantial spatial variation of the confining potential in the boundary
regions. In this paper we show that, in the presence of boundary-confinement
induced spin-orbit coupling, a longitudinal charge current circulating through
a 2D semiconductor strip may cause \textit{strong} non-equilibrium spin
accumulation near both edges of the strip. The spins will be polarized along
the normal of the 2DEG plane but in opposite directions at both edges of the
strip. This phenomenon is essentially a kinetic magnetoelectric effect from the
theoretical points of view, but it manifests in a very similar form as was
conceived in a spin Hall effect.",0603755v1
2010-01-14,Spin-orbit coupled Bose-Einstein condensate in a tilted optical lattice,"Bloch oscillations appear for a particle in a weakly tilted periodic
potential. The intrinsic spin Hall effect is an outcome of a spin-orbit
coupling. We demonstrate that both these phenomena can be realized
simultaneously in a gas of weakly interacting ultracold atoms exposed to a
tilted optical lattice and to a set of spatially dependent light fields
inducing an effective spin-orbit coupling. It is found that both the spin Hall
as well as the Bloch oscillation effects may coexist, showing, however, a
strong correlation between the two. These correlations are manifested as a
transverse spin current oscillating in-phase with the Bloch oscillations.",1001.2527v2
2011-07-01,Spin Hall effect in iron-based superconductors: A Dirac-point effect,"We have theoretically explored the intrinsic spin Hall effect (SHE) in the
iron-based superconductor family with a variety of materials. The study is
motivated by an observation that, in addition to an appreciable spin-orbit
coupling in the Fe 3d states, a character of the band structure in which Dirac
cones appear below the Fermi energy may play a crucial role in producing a
large SHE. Our investigation does indeed predict a substantially large spin
Hall conductivity in the heavily hole-doped regime such as KFe$_2$As$_2$. The
magnitude of the SHE has turned out to be comparable with that for Pt despite a
relatively small spin-orbit coupling, which we identify to come from a huge
contribution from the gap opening induced by the spin-orbit coupling at the
Dirac point, which can become close to the Fermi energy for the heavy hole
doping.",1107.0122v2
2013-03-08,Rashba spin-orbit coupling effects in quasiparticle interference of non-centrosymmetric superconductors,"The theory of quasiparticle interference (QPI) for non-centrosymmetric (NCS)
superconductors with Rashba spin-orbit coupling is developed using T-matrix
theory in Born approximation. We show that qualitatively new effects in the QPI
pattern originate from the Rashba spin-orbit coupling: The resulting spin
coherence factors lead to a distinct difference of charge- and spin- QPI and to
an induced spin anisotropy in the latter even for isotropic magnetic impurity
scattering. In particular a cross - QPI appears describing the spin oscillation
pattern due to nonmagnetic impurity scattering which is directly related to the
Rashba vector. We apply our theory to a 2D model for the NCS heavy fermion
unconventional superconductor CePt$_3$Si and discuss the new QPI features for a
gap model with accidental node lines due to its composite singlet-triplet
nature.",1303.1974v2
2014-02-15,Spin-orbit coupling and the up-down differential transverse flow in intermediate-energy heavy-ion collisions,"To explore the strength, isospin dependence, and density dependence of the
in-medium spin-orbit coupling that is poorly known but relevant for
understanding the structure of rare isotopes, the nucleon spin up-down
differential transverse flow is studied systematically by varying the beam
energy and impact parameter of Au+Au collisions within a spin-isospin dependent
transport model recently developed for investigating spin-related phenomena in
intermediate-energy heavy-ion collisions. The optimal reaction conditions for
delineating and disentangling effects of different terms in the spin-orbit
coupling are discussed.",1402.3670v2
2014-09-09,Most spin-1/2 transition-metal ions do have single ion anisotropy,"The cause for the preferred spin orientation in magnetic systems containing
spin-1/2 transition-metal ions was explored by studying the origin of the
easy-plane anisotropy of the spin-1/2 Cu2+ ions in CuCl2.2H2O, LiCuVO4, CuCl2
and CuBr2 on the basis of density functional theory and magnetic dipole-dipole
energy calculations as well as a perturbation theory treatment of the
spin-orbit coupling. We find that the spin orientation observed for these
spin-1/2 ions is not caused by their anisotropic spin exchange interactions,
nor by their magnetic dipole-dipole interactions, but by the spin-orbit
coupling associated with their crystal-field split d-states. Our study also
predicts in-plane anisotropy for the Cu2+ ions of Bi2CuO4 and Li2CuO2. The
results of our investigations dispel the mistaken belief that magnetic systems
with spin-1/2 ions have no magnetic anisotropy induced by spin-orbit coupling.",1409.2795v2
2014-09-23,Bound state and persistent currents in the presence of torsion and Rashba spin-orbit coupling,"We study a model of an electron on a cylindrical surface, which is coupled to
the torsion field due to a dislocation along the axis of the cylinder. We
discuss the effect of this torsion field on the energy spectrum of the
electrons and analytically calculate persistent currents in the presence of
Rashba spin-orbit coupling. We also analyze bound state energy spectra in
presence of Rashba spin-orbit interaction. Our results show that the presence
of the torsional field due to the dislocation significantly modifies the energy
spectrum of the system. The dislocation induced persistent spin current in this
system is calculated, and we find a correspondence between the dislocation
mediated spin current and the azimuthal spin current.",1409.6756v1
2015-02-11,One-Dimensional Edge States with Giant Spin Splitting in a Bismuth Thin Film,"To realize a one-dimensional (1D) system with strong spin-orbit coupling is a
big challenge in modern physics, since the electrons in such a system are
predicted to exhibit exotic properties unexpected from the 2D or 3D
counterparts, while it was difficult to realize genuine physical properties
inherent to the 1D system. We demonstrate the first experimental result that
directly determines the purely 1D band structure by performing spin-resolved
angle-resolved photoemission spectroscopy of Bi islands on a silicon surface
that contains a metallic 1D edge structure with unexpectedly large Rashba-type
spin-orbit coupling suggestive of the nontopological nature. We have also found
a sizable out-of-plane spin polarization of the 1D edge state, consistent with
our first-principles band calculations. Our result provides a new platform to
realize exotic quantum phenomena at the 1D edge of the strong
spin-orbit-coupling systems.",1502.03197v1
2015-02-16,Gap Solitons in Spin-Orbit-Coupled Bose-Einstein Condensates in Optical Lattices,"While different ways to realize spin-orbit coupling in Bose-Einstein
condensates exist, not all are currently experimentally implementable. Here we
present a detailed study of gap solitons in a Bose- Einstein condensate with
experimentally realizable spin-orbit coupling and discuss two cases relating to
a spin-dependent parity symmetry. In the parity symmetric case, two families of
fundamental gap solitons in second linear energy gap are demonstrated with
opposite sign of the parity, with one family having single humped densities and
the other double humped ones. In the case of broken parity symmetry, the
fundamental modes manifest spin-polarization. Both families possess an opposite
sign of the spin-polarization.",1502.04409v2
2015-03-19,Coulomb-exchange effects in nanowires with spin splitting due to a radial electric field,"We present a theoretical study of Coulomb exchange interaction for electrons
confined in a cylindrical quantum wire and subject to a Rashba-type spin-orbit
coupling with radial electric field. The effect of spin splitting on the
single-particle band dispersions, the quasiparticle effective mass, and the
system's total exchange energy per particle are discussed. Exchange interaction
generally suppresses the quasiparticle effective mass in the lowest nanowire
subband, and a finite spin splitting is found to significantly increase the
magnitude of the quasiparticle-mass suppression (by upto 15\% in the
experimentally relevant parameter regime). In contrast, spin-orbit coupling
causes a modest (1\%-level) reduction of the magnitude of the exchange energy
per particle. Our results shed new light on the interplay of spin-orbit
coupling and Coulomb interaction in quantum-confined systems, including those
that are expected to host exotic quasiparticle excitations.",1503.05627v2
2017-02-01,Strain Controlled Spin and Charge Pumping in Graphene Devices via Spin-orbit Coupled Barriers,"We theoretically propose a graphene-based adiabatic quantum pump with
intrinsic spin-orbit coupling (SOC) subject to strain where two time-dependent
extrinsic spin-orbit coupled barriers drive spin and charge currents. We study
three differing operation modes where i) location, ii) chemical potential, and
iii) SOC of the two barriers oscillate periodically and out of phase around
their equilibrium states. Our results demonstrate that the amplitude of
adiabatically pumped currents highly depends on the considered operation mode.
We find that such a device operates with highest efficiency and in a broader
range of parameters where the barriers chemical potential drives the quantum
pump. Our results also reveal that by introducing strain to the system, one can
suppress or enhance the charge and spin currents separately, depending on
strain direction.",1702.00246v1
2018-02-09,Spin-susceptibility of spin-orbit coupled Fermi superfluids,"Under the self-consistent mean-field approach for the BCS-BEC crossover
problem, we derive a closed-form analytical expression for the general spin
response of noncentrosymmetric Fermi superfluids with arbitrary spin-orbit
coupling and Zeeman fields. In addition to the paramagnetic, i.e., the Pauli
intra-helicity and Van Vleck type inter-helicity, contributions to the
spin-susceptibility tensor that have normal-state counterparts, we identify a
diamagnetic inter-helicity contribution that is unique to the superfluid state.
Our extensive numerical calculations for the Weyl, Rashba and equal
Rashba-Dresselhaus spin-orbit couplings illustrate that it is this diamagnetic
contribution that grows gradually with pairing and cancels precisely the Van
Vleck contribution away from the BCS regime in general.",1802.03157v2
2018-05-21,Dynamical suppression of tunneling and spin switching of a spin-orbit-coupled atom in a double-well trap,"We predict wide-band suppression of tunneling of spin-orbit-coupled atoms (or
noninteracting Bose-Einstein condensate) in a double-well potential with
periodically varying depths of the potential wells. The suppression of
tunneling is possible for a single state and for superposition of two states,
i.e. for a qbit. By varying spin-orbit coupling one can drastically increase
the range of modulation frequencies in which an atom remains localized in one
of the potential wells, the effect connected with crossing of energy levels.
This range of frequencies is limited because temporal modulation may also
excite resonant transitions between lower and upper states in different wells.
The resonant transitions enhance tunneling and are accompanied by pseudo-spin
switching. Since the frequencies of the resonant transitions are independent of
potential modulation depth, in contrast to frequencies at which suppression of
tunneling occurs, by varying this depth one can dynamically control both
spatial localization and pseudo-spin of the final state.",1805.07961v1
2011-11-21,Tunable Spin-orbit Coupling and Quantum Phase Transition in a Trapped Bose-Einstein Condensate,"Spin-orbit coupling (SOC), the intrinsic interaction between a particle spin
and its motion, is responsible for various important phenomena, ranging from
atomic fine structure to topological condensed matter physics. The recent
experimental breakthrough on the realization of SOC for ultra-cold atoms
provides a completely new platform for exploring spin-orbit coupled superfluid
physics. However, the SOC strength in the experiment, determined by the applied
laser wavelengths, is not tunable. In this Letter, we propose a scheme for
tuning the SOC strength through a fast and coherent modulation of the laser
intensities. We show that the many-body interaction between atoms, together
with the tunable SOC, can drive a \textit{quantum phase transition} (QPT) from
spin-balanced to spin-polarized ground states in a harmonic trapped
Bose-Einstein condensate (BEC). This transition realizes the long-sought QPT in
the quantum Dicke model, and may have important applications in quantum optics
and quantum information. We characterize the QPT using the periods of
collective oscillations (center of mass motion and scissors mode) of the BEC,
which show pronounced peaks and damping around the quantum critical point.",1111.4778v1
2019-07-04,Nonperturbative Matrix Mechanics Approach to Spin-Split Landau Levels and g-Factor in Spin-Orbit Coupled Solids,"We have proposed a fully quantum approach to non-perturbatively calculate the
spin-split Landau levels and g-factor of various spin-orbit coupled solids,
based on the k.p theory in the matrix mechanics representation. The new method
considers the detailed band structure and the multiband effect of spin-orbit
coupling irrespective of the magnetic field strength. An application of this
method to PbTe, a typical Dirac electron system, is shown. Contrary to popular
belief, it is shown that the spin-splitting parameter M, which is the ratio of
the Zeeman to cyclotron energy, exhibits a remarkable
magnetic-field-dependence. This field-dependence can rectify the existing
discrepancy between experimental and theoretical results. We have also shown
that M evaluated from the fan diagram plot is different from that determined as
the ratio of the Zeeman to cyclotron energy, which also overturns common
belief.",1907.02254v1
2019-08-19,Planar Hall Effect and Anisotropic Magnetoresistance in a polar-polar interface of LaVO$_3$-KTaO$_3$ with strong spin-orbit coupling,"Among the perovskite oxide family, KTaO$_3$ (KTO) has recently attracted
considerable interest as a possible system for the realization of the Rashba
effect. In this work, we improvise a novel conducting interface by juxtaposing
KTO with another insulator, namely LaVO$_3$ (LVO) and report planar Hall effect
(PHE) and anisotropic magnetoresistance (AMR) measurements. This interface
exhibits a signature of strong spin-orbit coupling. Our experimental
observation of two fold AMR at low magnetic fields can be intuitively
understood using a phenomenological theory for a Rashba spin-split system. At
high fields ($\sim$8 T), we see a two fold to four fold transition in the AMR
that could not be explained using only Rashba spin-split energy spectra. We
speculate that it might be generated through an intricate process arising from
the interplay between strong spin-orbit coupling, broken inversion symmetery,
relativistic conduction electron and possible uncompensated localized vanadium
spins.",1908.06636v1
2020-05-21,Magnetism and topological phases in an interacting decorated honeycomb lattice with spin-orbit coupling,"We study the interplay between spin-orbit coupling (SOC) and Coulomb
repulsion in a Hubbard model on a decorated honeycomb lattice which leads to a
plethora of phases. While a quantum spin hall insulator is stable at weak
Coulomb repulsion and moderate SOC, a semimetallic phase emerges at large SOC
in a broad range of Coulomb repulsion. This semimetallic phase has topological
properties not observed in conventional metals such as a finite, non-quantized
spin Hall conductivity. At large Coulomb repulsion and negligible spin-orbit
coupling, electronic correlations stabilize a resonance valence bond (RVB) spin
liquid state in contrast to the classical antiferromagnetic state predicted by
mean-field theory. Under sufficiently strong SOC, such RVB state is transformed
into a magnetic insulator consisting on S~3/2 localized moments on a honeycomb
lattice with antiferromagnetic order and topological features.",2005.10776v2
2020-11-13,Manipulation of Spin Transport in Graphene/Transition Metal Dichalcogenide Heterobilayers upon Twisting,"Proximity effects are one of the pillars of exotic phenomena and
technological applications of two dimensional materials. However, the
interactions nature depends strongly on the materials involved, their
crystalline symmetries, and interfacial properties. Here we used large-scale
first-principle calculations to demonstrate that strain and twist-angle are
efficient knobs to tailor the spin-orbit coupling in graphene transition metal
dichalcogenide heterobilayers. We found that by choosing a twist-angle of 30
degrees, the spin relaxation times increase by two orders of magnitude, opening
a path to improve these heterostructures spin transport capability. Moreover,
we demonstrate that strain and twist angle will modify the relative values of
valley-Zeeman and Rashba spin-orbit coupling, allowing to tune the system into
an ideal Dirac-Rashba regime. These results enable us to envision an answer for
the variability of spin-orbit coupling found in different experiments and have
significant consequences for applications that depend on polycrystallinity,
where grains form at different orientations.",2011.06714v2
2021-04-19,Spin transfer torque and anisotropic conductance in spin orbit coupled graphene,"We theoretically study spin-transfer torque (STT) in a graphene system with
spin-orbit coupling (SOC). We consider a graphene-based junction where the
spin-orbit coupled region is sandwiched between two ferromagnetic (F) segments.
The magnetization in each ferromagnetic segment can possess arbitrary
orientations. Our results show that the presence of SOC results in
anisotropically modified STT, magnetoresistance, and charge conductance as a
function of relative magnetization misalignment in the F regions. We have found
that within the Klein regime, where particles hit the interfaces
perpendicularly, the spin-polarized Dirac fermions transmit perfectly through
the boundaries of an F-F junction (i.e., with zero reflection), regardless of
the relative magnetization misalignment and exert zero STT. In the presence of
SOC, however, due to band structure modification, a nonzero STT reappears. Our
findings can be exploited for experimentally examining proximity-induced SOC
into a graphene system",2104.09039v1
2021-10-04,Spin-Phonon Resonances in Nearly Polar Metals with Spin-Orbit Coupling,"In metals in the vicinity of a polar transition, interactions between
electrons and soft phonon modes remain to be determined. Here we explore the
consequences of spin-orbit assisted electron-phonon coupling on the collective
modes of such nearly polar metals in the presense of magnetic field. We find
that the soft polar phonon hybridizes with spin-flip electronic excitations of
the Zeeman-split bands leading to an anticrossing. The associated energy
splitting allows for an unambiguous determination of the strength of the
spin-orbit mediated coupling to soft modes in polar metals by spectroscopic
experiments. The approach to the polar transition is reflected by the softening
of the effective g-factor of the hybridized spin-flip mode. Analyzing the
static limit, we find that the polar order parameter can be oriented by
magnetic field. This provides possibilities for new switching protocols in
polar metallic materials. We demonstrate that the effects we predict can be
observed with current experimental techniques and discuss promising material
candidates.",2110.01642v2
2021-11-04,Quantum interference tuning of spin-orbit coupling in twisted van der Waals trilayers,"We show that in van der Waals stacks of twisted hexagonal layers the
proximity induced Rashba spin-orbit coupling can be affected by quantum
interference. We calculate the quantum phase responsible for this effect in
graphene--transition metal dichalcogenide bilayers as a function of interlayer
twist angle. We show how this quantum phase affects the spin-polarization of
the graphene bands and discuss its potential effect on spin-to-charge
conversion measurements. In twisted trilayers symmetries can be broken as well
as restored for certain twist angles. This can be used to deduce the effects of
induced spin-orbit coupling on spin-lifetime anisotropy and magnetoconductance
measurements.",2111.02781v2
2023-01-08,"Chiral anomalies in 3D spin-orbit coupled metals: electrical, thermal, and gravitational anomaly","The discovery of a chiral anomaly in Weyl semimetals, the non-conservation of
chiral charge and energy across two opposite chirality Weyl nodes, has sparked
immense interest in understanding its impact on various physical phenomena.
Here, we demonstrate the existence of electrical, thermal, and gravitational
quantum chiral anomalies in 3D spin-orbit coupled systems. Notably, these
anomalies involve chiral charge transfer across two Fermi surfaces linked to a
single Weyl-like point, rather than across opposite chirality Weyl nodes as in
Weyl semimetals. Our findings reveal that the Berry curvature flux piercing the
Fermi surface plays a critical role in distinguishing the `chirality' of the
carriers and the corresponding chiral charge and energy transfer. Importantly,
we demonstrate that these quantum chiral anomalies lead to interesting thermal
spin transport such as the spin Nernst effect. Our results suggest that 3D
spin-orbit coupled metals offer a promising platform for investigating the
interplay between quantum chiral anomalies and charge and spin transport in
non-relativistic systems.",2301.02965v1
2006-03-10,Theory of Spin Hall Effects in Semiconductors,"Spin Hall effects are a collection of phenomena, resulting from spin-orbit
coupling, in which an electrical current flowing through a sample can lead to
spin transport in a perpendicular direction and spin accumulation at lateral
boundaries. These effects, which do not require an applied magnetic field, can
originate in a variety of intrinsic and extrinsic spin-orbit coupling
mechanisms and depend on geometry, dimension, impurity scattering, and carrier
density of the system--making the analysis of these effects a diverse field of
research. In this article, we give an overview of the theoretical background of
the spin Hall effects and summarize some of the most important results. First,
we explain effective spin-orbit Hamiltonians, how they arise from band
structure, and how they can be understood from symmetry considerations;
including intrinsic coupling due to bulk inversion or structure asymmetry or
due to strain, and extrinsic coupling due to impurities. This leads to
different mechanisms of spin transport: spin precession, skew scattering, and
side jump. Then we present the kinetic (Boltzmann) equations, which describe
the spin-dependent distribution function of charge carriers, and the diffusion
equation for spin polarization density. Next, we define the notion of spin
currents and discuss their relation to spin polarization. Finally, we explain
the electrically induced spin effects; namely, spin polarization and currents
in bulk and near boundaries (the focus of most current theoretical research
efforts), and spin injection, as well as effects in mesoscopic systems and in
edge states.",0603306v3
2004-02-11,Spin-precession in an adiabatically rotating electric field,"Due to spin-orbit coupling, the adiabatic perturbation of an electron's
orbital motion induced by a revolving external electric field lead to the
electron spin-precession. The obtained results describe both transverse and
longitudinal dynamics of an effective spin, for conical and figure-8
trajectories of a driving electric field, and elucidate the link between the
quantum-mechanical, geometrical, and classical pictures of spin rotation.
Within the limit of adiabatic approximation the derived formulas are valid
regardless of whether eigenvectors of the total Hamiltonian of the problem are
explicitly available or not, and are convenient for approximate calculations.
The main expression for the time evolution of the Bloch vector has pure
geometric character and is independent of the physical context.",0402319v1
2005-03-13,Anti-crossings of spin-split Landau levels in an InAs two-dimensional electron gas with spin-orbit coupling,"We report tilted-field transport measurements in the quantum-Hall regime in
an InAs/In_0.75Ga_0.25As/In_0.75Al_0.25As quantum well. We observe
anti-crossings of spin-split Landau levels, which suggest a mixing of spin
states at Landau level coincidence. We propose that the level repulsion is due
to the presence of spin-orbit and of band-non-parabolicity terms which are
relevant in narrow-gap systems. Furthermore, electron-electron interaction is
significant in our structure, as demonstrated by the large values of the
interaction-induced enhancement of the electronic g-factor.",0503314v1
2006-10-16,Mixing of two-electron spin states in a semiconductor quantum dot,"We show that the low lying spin states of two electrons in a semiconductor
quantum dot can be strongly mixed by electron-electron asymmetric exchange.
This mixing is generated by the coupling of electron spin to its orbital motion
and to the relative orbital motion of the two electrons. The asymmetric
exchange can be as large as 50% of the isotropic exchange, even for cylindrical
quantum dots. The resulting spin mixing contributes to understanding spin
dynamics in quantum dots, including light polarization reversal.",0610405v1
2002-07-02,Gravitational Waves from Spinning Compact Binaries,"Binary systems of rapidly spinning compact objects, such as black holes or
neutron stars, are prime targets for gravitational wave astronomers. The
dynamics of these systems can be very complicated due to spin-orbit and
spin-spin couplings. Contradictory results have been presented as to the nature
of the dynamics. Here we confirm that the dynamics - as described by the second
post-Newtonian approximation to general relativity - is chaotic, despite claims
to the contrary. When dissipation due to higher order radiation reaction terms
are included, the chaos is dampened. However, the inspiral-to-plunge transition
that occurs toward the end of the orbital evolution does retain an imprint of
the chaotic behaviour.",0207016v1
2005-09-07,A Note on Frame Dragging,"The measurement of spin effects in general relativity has recently taken
centre stage with the successfully launched Gravity Probe B experiment coming
toward an end, coupled with recently reported measurements using laser ranging.
Many accounts of these experiments have been in terms of frame-dragging. We
point out that this terminology has given rise to much confusion and that a
better description is in terms of spin-orbit and spin-spin effects. In
particular, we point out that the de Sitter precession (which has been mesured
to a high accuracy) is also a frame-dragging effect and provides an accurate
benchmark measurement of spin-orbit effects which GPB needs to emulate.",0509025v1
2008-10-30,Spin-Orbit gauge and quantum spin Hall effect,"We have shown that the non-Abelian spin-orbit gauge field strength of the
Rashba and Dresselhaus interactions, when split into two Abelian field
strengths, the Hamiltonian of the system can be re-expressed as a Landau level
problem with a particular relation between the two coupling parameters. The
quantum levels are created with up and down spins with opposite chirality and
leads to the quantum spin Hall effect.",0810.5436v1
2016-10-26,Classical spin liquid instability driven by off-diagonal exchange in strong spin-orbit magnets,"We show that the off-diagonal exchange anisotropy drives Mott insulators with
strong spin-orbit coupling to a classical spin liquid regime, characterized by
an infinite number of ground states and Ising variables living on closed or
open strings. Depending on the sign of the anisotropy, quantum fluctuations
either fail to lift the degeneracy down to very low temperatures, or select
non-collinear magnetic states with unconventional spin correlations. The
results apply to all 2D and 3D tri-coordinated materials with bond-directional
anisotropy, and provide a consistent interpretation of the suppression of the
x-ray magnetic circular dichroism signal reported recently for
$\beta$-Li$_2$IrO$_3$ under pressure.",1610.08463v1
2014-03-02,Spin disorder in an Ising honeycomb chain cobaltate,"We report on a member of the spin-disordered honeycomb lattice
antiferromagnet in a quasi-one-dimensional cobaltate Ba_3Co_2O_6(CO_3)_0.7.
Resistivity exhibits as semimetallic along the face-sharing CoO6 chains.
Magnetic susceptibility shows strongly anisotropic Ising-spin character with
the easy axis along the chain due to significant spin-orbit coupling and a
trigonal crystal field. Nevertheless, ^135Ba NMR detects no indication of the
long-range magnetic order down to 0.48 K. Marginally itinerant electrons
possess large entropy and low-lying excitations with a Wilson ratio R_W = 116,
which highlight interplays of charge, spin, and orbital in the disordered
ground state.",1403.0208v1
2005-03-20,On A Proper Definition of Spin Current,"The conventional definition of spin current is incomplete and unphysical in
describing spin transport in systems with spin-orbit coupling. A proper and
measurable spin current is established in this study, which fits well into the
standard framework of near-equilibrium transport theory and has the desirable
property to vanish in insulators with localized orbitals. Experimental
implications of our theory are discussed.",0503505v5
2005-12-30,Orbital Kondo effect and spin polarized transport through quantum dots,"The coherent spin dependent transport through a set of two capacitively
coupled quantum dots placed in a magnetic field is considered within the
equation of motion method. The magnetic field breaks the spin degeneracy. For
special choices of gate voltages the dot levels are tuned to resonance and the
orbital Kondo effect results. For different Zeemann splittings at the dots the
Kondo resonance can be formed for only one spin channel. In this case the
system operates as an efficient spin filter.",0512726v1
2006-07-05,Measurements of the spin relaxation rate at low magnetic fields in a quantum dot,"We measure the relaxation rate $W \equiv T_{1}^{-1}$ of a single electron
spin in a quantum dot at magnetic fields from 7 T down to 1.75 T, much lower
than previously measured. At 1.75 T we find that $T_{1}$ is 170 ms. We find
good agreement between our measurements and theoretical predictions of the
relaxation rate caused by the spin-orbit interaction, demonstrating that
spin-orbit coupling can account for spin relaxation in quantum dots.",0607110v1
2015-06-03,Curvature effect on spin polarization in a three-terminal geometry in presence of Rashba spin-orbit interaction,"The robust effect of curvature on spin polarization is reported in a
three-terminal bridge system where the bridging material is subjected to Rashba
spin-orbit interaction. The results are examined considering two different
geometric configurations, ring- and linear-like, of the material which is
coupled to one input and two output leads. Our results exhibit absolute zero
spin polarization for the linear sample, while finite polarization is obtained
in output leads for the ring-like sample.",1506.01252v1
2017-08-22,Defect-induced large spin-orbit splitting in the monolayer of PtSe$_2$,"The effect of spin-orbit coupling (SOC) on the electronic properties of
monolayer (ML) PtSe$_2$ is dictated by the presence of the crystal inversion
symmetry to exhibit spin polarized band without characteristic of spin
splitting. Through fully-relativistic density-functional theory calculations,
we show that large spin-orbit splitting can be induced by introducing point
defects. We calculate stability of native point defects such as a Se vacancy
(V$_{\texttt{Se}}$), a Se interstitial (Se$_{i}$), a Pt vacancy
(V$_{\texttt{Pt}}$), and a Pt interstitial (Pt$_{i}$), and find that both the
V$_{\texttt{Se}}$ and Se$_{i}$ have the lowest formation energy. We also find
that in contrast to the Se$_{i}$ case exhibiting spin degeneracy in the defect
states, the large spin-orbit splitting up to 152 meV is observed in the defect
states of the V$_{\texttt{Se}}$. Our analyses of orbital contributions to the
defect states show that the large spin splitting is originated from the strong
hybridization between Pt-$d_{x{^2}+y{^2}}+d_{xy}$ and Se-$p_{x}+p_{y}$
orbitals. Our study clarifies that the defects play an important role in the
spin splitting properties of the PtSe$_2$ ML, which is important for designing
future spintronic devices.",1708.06487v1
2015-09-03,Configuration-averaged 4f orbitals in ab initio calculations of low-lying crystal field levels in lanthanide(III) complexes,"A successful and commonly used ab initio method for the calculation of
crystal field levels and magnetic anisotropy of lanthanide complexes consists
of spin-adapted state-averaged CASSCF calculations followed by state
interaction with spin-orbit coupling (SI-SO). Based on two observations valid
for Ln(III) complexes, namely: (i) CASSCF 4f orbitals are expected to change
very little when optimized for different states belonging to the 4f electronic
configuration, (ii) due to strong spin-orbit coupling the total spin is not a
good quantum number, we show here via a straightforward analysis and direct
calculation that the CASSCF/SI-SO method can be simplified to a single
configuration-averaged HF calculation and one complete active space CI
diagonalization, including spin-orbit coupling, on determinant basis. Besides
its conceptual simplicity, this approach has the advantage that all spin states
of the 4f$^n$ configuration are automatically included in the SO coupling,
thereby overcoming one of the computational limitations of the existing
CASSCF/SI-SO approach. As an example, we consider three isostructural complexes
[Ln(acac)$_3$(H$_2$O)$_2$], Ln = Dy$^{3+}$, Ho$^{3+}$, Er$^{3+}$, and find that
the proposed simplified method yields crystal field levels and magnetic
g-tensors that are in very good agreement with those obtained with
CASSCF/SI-SO.",1509.00974v2
2004-10-11,Electron Correlations in a Quantum Dot with Bychkov-Rashba Coupling,"We report on a theoretical approach developed to investigate the influence of
Bychkov-Rashba interaction on a few interacting electrons confined in a quantum
dot. We note that the spin-orbit coupling profoundly influences the energy
spectrum of interacting electrons in a quantum dot. Inter-electron interaction
causes level crossings in the ground state and a jump in magnetization. As the
coupling strength is increased, that jump is shifted to lower magnetic fields.
Low-field magnetization will therefore provide a direct probe of the spin-orbit
coupling strength in a quantum dot.",0410248v1
2012-06-27,Graphene p-n junctions with nonuniform Rashba spin-orbit coupling,"Linear conductance of graphene-based p-n junctions with Rashba spin-orbit
coupling is considered theoretically. A square potential step is used to model
the junctions, while the coupling is introduced in terms of the Kane-Mele model
(C.L. Kane and E.J. Mele, Phys.Rev.Lett. 95, 226801(2005)). The main objective
is a description of electronic transport in junctions where Rashba parameter is
nonuniform. Such a nonuniformity can appear when graphene is asymmetrically
covered with atomic layers, or when Rashba coupling is strongly dependent on
electric field. It is shown that conductance is significantly modified by the
considered nonuniformity, which is most clearly manifested by an anomalous
minimum at a certain potential step height.",1206.6503v1
2017-03-23,Boson-vortex duality in compressible spin-orbit coupled BECs,"Using a (1+2)-dimensional boson-vortex duality between non-linear
electrodynamics and a two-component compressible Bose-Einstein condensate (BEC)
with spin-orbit (SO) coupling, we obtain generalised versions of the
hydrodynamic continuity and Euler equations where the phase defect and
non-defect degrees of freedom enter separately. We obtain the generalised
Magnus force on vortices under SO coupling, and associate the linear
confinement of vortices due to SO coupling with instanton fluctuations of the
dual theory.",1703.07918v1
2011-11-22,z/-z Symmetry of spin-orbit coupling and weak localization in graphene,"We show that the influence of spin-orbit (SO) coupling on the weak
localization effect for electrons in graphene depends on the lack or presence
of z/-z symmetry in the system. While for z/-z asymmetric SO coupling,
disordered graphene should display a weak anti-localization behavior at lowest
temperature, z/-z symmetric coupling leads to an effective saturation of
decoherence time which can be partially lifted by an in-plane magnetic field,
thus, tending to restore the weak localization effect.",1111.5267v1
2017-10-10,Flipping-shuttle oscillations of bright one- and two-dimensional solitons in spin-orbit-coupled Bose-Einstein condensates with Rabi mixing,"We analyze a possibility of macroscopic quantum effects in the form of
coupled structural oscillations and shuttle motion of bright two-component
spin-orbit-coupled striped (one-dimensional, 1D) and semi-vortex
(two-dimensional, 2D) matter-wave solitons, under the action of linear mixing
(Rabi coupling) between the components. In 1D, the intrinsic oscillations
manifest themselves as flippings between spatially even and odd components of
striped solitons, while in 2D the system features periodic transitions between
zero-vorticity and vortical components of semi-vortex solitons. The
consideration is performed by means of a combination of analytical and
numerical methods.",1710.03664v1
2021-11-16,Pairing of electro-magnetic bosons under spin-orbit coupling,"We discuss pairing of light-matter bosons under effective spin-orbit (SO)
coupling in two-dimensional semiconductors. The SO coupling is shown to induce
dynamical broadening of a two-body bound state. Application of a transverse
magnetic field yields the rich Feshbach resonance phenomenology. We predict
quantum bosonic halos with a synthetic angular momentum L=2. The d-wave-like
dressing of the nominally s-wave bound state is induced by SO coupling to the
continuum in the open channel. The fundamental properties of the emergent
quantum number remain to be explored.",2111.08782v1
2021-11-29,Competing Correlated Insulators in multi-orbital systems coupled to phonons,"We study the interplay between electron-electron interaction and a
Jahn-Teller phonon coupling in a two-orbital Hubbard model. We demonstrate that
the e-ph interaction coexists with the Mott localization driven by the Hubbard
repulsion U, but it competes with the Hund's coupling J. This interplay leads
to two spectacularly different Mott insulators, a standard high-spin Mott
insulator with frozen phonons which is stable when the Hund's coupling
prevails, and a low-spin Mott-bipolaronic insulator favoured by phonons, where
the characteristic features of Mott insulators and bipolarons coexist. The two
phases are separated by a sharp boundary along which an intriguing intermediate
solution emerges as a kind of compromise between the two solutions.",2111.14663v1
2007-05-16,Spin-Hall edge spin polarization in a ballistic 2D electron system,"Universal properties of spin-Hall effect in ballistic 2D electron systems are
addressed. The net spin polarization across the edge of the conductor is second
order, ~\lambda^2, in spin-orbit coupling constant independent of the form of
the boundary potential, with the contributions of normal and evanescent modes
each being ~ \sqrt{\lambda} but of opposite signs. This general result is
confirmed by the analytical solution for a hard-wall boundary, which also
yields the detailed distribution of the local spin polarization. The latter
shows fast (Friedel) oscillations with the spin-orbit coupling entering via the
period of slow beatings only. Long-wavelength contributions of evanescent and
normal modes exactly cancel each other in the spectral distribution of the
local spin density.",0705.2424v3
2008-04-17,Spin-selective localization due to intrinsic spin-orbit coupling,"We study spin-dependent diffusive transport in the presence of a tunable
spin-orbit (SO) interaction in a two-dimensional electron system. The spin
precession of an electron in the SO coupling field is expressed in terms of a
covariant curvature, affecting the quantum interference between different
electronic trajectories. Controlling this curvature field by modulating the SO
coupling strength and its gradients by, e.g., electric or elastic means, opens
intriguing possibilities for exploring spin-selective localization physics. In
particular, applying a weak magnetic field allows the control of the electron
localization independently for two spin directions, with the spin-quantization
axis that could be ""engineered"" by appropriate SO interaction gradients.",0804.2706v3
2013-05-15,Anomalous and Spin Hall Effects in a Magnetic Tunnel Junction with Rashba Spin-Orbit Coupling,"Anomalous and spin Hall effects are investigated theoretically for a magnetic
tunnel junction where the applied voltage produces a Rashba spin-or bit
coupling within the tunneling barrier layer. The ferromagnetic electrodes are
the source of the spin-polarized current. The tunneling electrons experience a
spin-orbit coupling inside the barrier due to the applied electrical field.
Charge and spin Hall currents are calculated as functions of the position
inside the barrier and the angle between the magnetizations of the electrodes.
We find that both charge and spin Hall currents are located inside the barrier
near the in terfaces. The dependence of the currents on magnetic configuration
of the magnetic tunnel junction makes possible the manipulation by the Hall
currents via rotation of the magnetization of the electrodes.",1305.3467v1
2017-02-05,Spin-polarized transport in helical membranes due to spin-orbit coupling,"The spin-dependent electron transmission through a helical membrane with
account of linear spin-orbit interaction has been investigated by numerically
solving the Schr\""odinger equation in cylindrical coordinates . It is shown
that the spin precession is affected by the magnitude of geometric parameters
and chirality of the membrane. This effect is also explained analytically by
using the perturbation theory in the weak coupling regime. In the strong
coupling regime, the current spin polarization is evident when the number of
the open modes in leads is larger than that of the open channels in the
membrane. Moreover, we find that the chirality of the helical membrane can
determine the orientation of current spin polarization. Therefore, one may get
totally opposite spin currents from the helical membranes rolled against
different directions.",1702.01375v1
2014-06-20,Spin-valley filtering in strained graphene structures with artificially induced carrier mass and spin-orbit coupling,"The interplay of massive electrons with spin-orbit coupling in bulk graphene
results in a spin-valley dependent gap. Thus, a barrier with such properties
can act as a filter, transmitting only opposite spins from opposite valleys. In
this Letter we show that strain induced pseudomagnetic field in such a barrier
will enforce opposite cyclotron trajectories for the filtered valleys, leading
to their spatial separation. Since spin is coupled to the valley in the
filtered states, this also leads to spin separation, demonstrating a
spin-valley filtering effect. The filtering behavior is found to be
controllable by electrical gating as well as by strain.",1406.5443v2
2022-04-15,Quantum control of hole spin qubits in double quantum dots,"Hole spin qubits in semiconductor quantum dots (QDs) are promising candidates
for quantum information processing due to their weak hyperfine coupling to
nuclear spins, and to the strong spin-orbit coupling which allows for rapid
operation time. We propose a coherent control on two heavy-hole spin qubits in
a double QD by a fast adiabatic driving protocol, which helps to achieve higher
fidelities than other experimentally commonly used protocols as linear ramping,
$\pi$-pulses or Landau-Zener passages. Using fast quasiadiabatic driving via
spin-orbit coupling, it is possible to reduce charge noise significantly for
qubit manipulation and achieve high robustness for the qubit initialization. We
also implement one and two-qubit gates, in particular, NOT, CNOT, and SWAP-like
gates, of hole spins in a double QD achieving fidelities above $99\%$,
exhibiting the capability of hole spins to implement universal gates for
quantum computing.",2204.07453v2
2023-07-19,Spin-valley dependent double Andreev reflections in the proximitized graphene/superconductor junction,"We study the Andreev reflections and the quantum transport in the
proximitized graphene/superconductor junction. The proximitized graphene
possesses the pseudospin staggered potential and the intrinsic spin-orbit
coupling induced by substrate, which are responsible for the spin-valley
dependent double Andreev reflections and the anomalous transport properties in
the junction. The pure specular Andreev reflection can happen in the
superconducting gap for the $K\uparrow$ and $K'\downarrow$ electrons while the
pure retro-Andreev reflection happens for the $K\downarrow$ and $K'\uparrow$
electrons. The coexisting two types of Andreev reflections related to the fixed
spin-valley indices strongly depend on the chemical potential of the
proximitized graphene. The condition of the emergence of the specific type of
Andreev reflection for the electrons with the fixed spin-valley index is
clarified. The spin-valley dependent Andreev reflections bring about the
peculiar conductance spectra of the junction, which can help determine the
values of the pseudospin staggered potential and the intrinsic spin-orbit
coupling induced in graphene. Hence, our research results not only provide an
experimental method to detect the induced potential and coupling in graphene
but also establish the foundation of the superconductor electronics based on
the spin-valley indices.",2307.09833v1
2023-10-15,A singlet-triplet hole-spin qubit in MOS silicon,"Holes in silicon quantum dots are promising for spin qubit applications due
to the strong intrinsic spin-orbit coupling. The spin-orbit coupling produces
complex hole-spin dynamics, providing opportunities to further optimize spin
qubits. Here, we demonstrate a singlet-triplet qubit using hole states in a
planar metal-oxide-semiconductor double quantum dot. We observe rapid qubit
control with singlet-triplet oscillations up to 400 MHz. The qubit exhibits
promising coherence, with a maximum dephasing time of 600 ns, which is enhanced
to 1.3 us using refocusing techniques. We investigate the magnetic field
anisotropy of the eigenstates, and determine a magnetic field orientation to
improve the qubit initialisation fidelity. These results present a step forward
for spin qubit technology, by implementing a high quality singlet-triplet
hole-spin qubit in planar architecture suitable for scaling up to 2D arrays of
coupled qubits.",2310.09722v1
2002-06-14,Intersubband spin-density excitations in quantum wells with Rashba spin splitting,"In inversion-asymmetric semiconductors, spin-orbit coupling induces a
k-dependent spin splitting of valence and conduction bands, which is a
well-known cause for spin decoherence in bulk and heterostructures.
Manipulating nonequilibrium spin coherence in device applications thus requires
understanding how valence and conduction band spin splitting affects carrier
spin dynamics. This paper studies the relevance of this decoherence mechanism
for collective intersubband spin-density excitations (SDEs) in quantum wells. A
density-functional formalism for the linear spin-density matrix response is
presented that describes SDEs in the conduction band of quantum wells with
subbands that may be non-parabolic and spin-split due to bulk or structural
inversion asymmetry (Rashba effect). As an example, we consider a 40 nm
GaAs/AlGaAs quantum well, including Rashba spin splitting of the conduction
subbands. We find a coupling and wavevector-dependent splitting of the
longitudinal and transverse SDEs. However, decoherence of the SDEs is not
determined by subband spin splitting, due to collective effects arising from
dynamical exchange and correlation.",0206251v1
2014-04-01,BCS-BEC crossover and quantum phase transition in an ultracold Fermi gas under spin-orbit coupling,"In this work, we study the BCS-BEC crossover and quantum phase transition in
a Fermi gas under Rashba spin-orbit coupling close to a Feshbach resonance. By
adopting a two-channel model, we take into account of the closed channel
molecules, and show that combined with spin-orbit coupling, a finite background
scattering in the open channel can lead to two branches of solution for both
the two-body and the many-body ground states. The branching of the two-body
bound state solution originates from the avoided crossing between bound states
in the open and the closed channels, respectively. For the many-body states, we
identify a quantum phase transition in the upper branch regardless of the sign
of the background scattering length, which is in clear contrast to the case
without spin-orbit coupling. For systems with negative background scattering
length in particular, we show that the bound state in the open channel, and
hence the quantum phase transition in the upper branch, are induced by
spin-orbit coupling. We then characterize the critical detuning of the quantum
phase transition for both positive and negative background scattering lengths,
and demonstrate the optimal parameters for the critical point to be probed
experimentally.",1404.0140v2
2015-03-09,Dual gate control of bulk transport and magnetism in the spin-orbit insulator Sr2IrO4,"The 5d iridates have been the subject of much recent attention due to the
predictions of a large array of novel electronic phases driven by twisting
strong spin-orbit coupling and Hubbard correlation. As a prototype, the single
layered perovskite Sr2IrO4 was first revealed to host a Jeff=1/2 Mott
insulating state. In this material, the approximate energy scale of a variety
of interactions, involving spin-orbit coupling, magnetic exchange interaction,
and the Mott gap, allows close coupling among the corresponding physical
excitations, opening the possibility of cross control of the physical
properties. Here, we experimentally demonstrate the effective gate control of
both the transport and magnetism in a Sr2IrO4-based field effect transistor
using an ionic liquid dielectric. This approach could go beyond the
surface-limited field effect seen in conventional transistors, reflecting the
unique aspect of the Jeff=1/2 state. The simultaneous modulation of conduction
and magnetism confirms the proposed intimate coupling of charge, orbital, and
spin degrees of freedom in this oxide. These phenomena are probably related to
an enhanced deviation from the ideal Jeff=1/2 state due to the gate-promoted
conduction. The present work would have important implications in modelling the
unusual physics enabled by strong spin-orbit coupling, and provides a new route
to explore those emergent quantum phases in iridates.",1503.02513v1
2016-04-20,Vector chirality for effective total momentum $J_{\textrm{eff}}$ in a nonfrustrated Mott insulator: Effects of strong spin-orbit coupling and broken inversion symmetry,"I propose the emergence of the spin-orbital-coupled vector chirality in a
non-frustrated Mott insulator with the strong spin-orbit coupling due to
$ab$-plane's inversion-symmetry (IS) breaking. I derive the superexchange
interactions for a $t_{2g}$-orbital Hubbard model on a square lattice with the
strong spin-orbit coupling and the IS-breaking-induced hopping integrals, and
explain the microscopic origins of the Dzyaloshinsky-Moriya (DM) -type and the
Kitaev-type interactions. Then, by adopting the mean-field approximation to a
minimal model including only the Heisenberg-type and the DM-type
nearest-neighbor interactions, I show that the IS breaking causes the
spin-orbital-coupled chirality as a result of stabilizing the screw state. I
also highlight the limit of the hard-pseudospin approximation in discussing the
stability of the screw states in the presence of both the DM-type and the
Kitaev-type interactions, and discuss its meaning. I finally discuss the
effects of tetragonal crystal field and $J_{\textrm{eff}}=\frac{3}{2}$ states,
and the application to the iridates near the $[001]$ surface of
Sr$_{2}$IrO$_{4}$ and the interface between Sr$_{2}$IrO$_{4}$ and
Sr$_{3}$Ir$_{2}$O$_{7}$.",1604.05867v3
2016-08-19,Scattering framework for two particles with isotropic spin-orbit coupling applicable to all energies,"Previous work developed a K-matrix formalism applicable to positive energies
for the scattering between two $s$-wave interacting particles with two internal
states, isotropic spin-orbit coupling and vanishing center-of-mass momentum [H.
Duan, L. You and B. Gao, Phys. Rev A {\bf{87}}, 052708 (2013)]. This work
extends the formalism to the entire energy regime. Explicit solutions are
obtained for the total angular momentum $J=0$ and $1$ channels. The behavior of
the partial cross sections in the negative energy regime is analyzed in detail.
We find that the leading contributions to the partial cross sections at the
negative energy thresholds are governed by the spin-orbit coupling strength
$k_{\text{so}}$ and the mass ratio. The fact that these contributions are
independent of the two-body scattering length $a_s$ is a direct consequence of
the effective reduction of the dimensionality, and hence of the density of
states, near the scattering thresholds due to the single-particle spin-orbit
coupling terms. The results are analytically continued to the energy regime
where bound states exist. It is shown that our results are consistent with
results obtained by alternative approaches. Our formulation, which can be
regarded as an extension of the standard textbook partial wave decomposition,
can be generalized to two-body systems with other types of spin-orbit coupling,
including cases where the center-of-mass momentum does not vanish.",1608.05753v1
2020-11-22,Master's Thesis: Excitation Spectrum of a Weakly Interacting Spin-Orbit Coupled Bose-Einstein Condensate,"A weakly interacting, spin-orbit coupled, two-component, ultracold Bose gas
bound to a Bravais lattice is studied. Motivated by recent experimental
advances in the field of synthetically spin-orbit coupled, ultracold, neutral
atomic gases showing Bose-Einstein condensation, an analytic framework with
which to describe such systems in the superfluid regime is presented. This is
applied to a Rashba spin-orbit-coupled Bose gas in a two-dimensional optical
lattice. The exotic nature of Bose-Einstein condensation in the presence of
spin-orbit coupling is an interesting study by itself. Additionally, when the
optical lattice is introduced, the system provides a highly controllable
experimental testing ground for numerous condensed matter physics phenomena.
Five phases of the system are considered, and their excitation spectra,
critical superfluid velocities and free energies are found. In obtaining the
free energy, the effects of terms in the Hamiltonian that are linear in
excitation operators are included, and such terms have not been studied
previously in this context. Minimization of the free energy at zero temperature
is used to confirm the phase diagrams reported in the literature, where it has
usually been obtained by neglecting the effect of excitations. The plane and
stripe wave phases in the phase diagram are bosonic analogues of
Fulde-Ferrell-Larkin-Ovchinnikov states in superconductors involving nonzero
condensate momenta.",2011.10999v1
2021-06-22,Effects of spin-orbit coupling and magnetic field on electronic properties of Germanene structure,"In this paper, we present a Kane-Mele model in the presence of magnetic field
and next nearest neighbors hopping amplitudes for investigations the electronic
and optical properties of monolayer Germanene. Specially, we address the
dynamical conductivity of the structure as a function of photon frequency and
in the presence of magnetic field and spin-orbit coupling at finite
temperature. Using linear response theory and Green's function approach, the
frequency dependence of optical conductivity has been obtained in the context
of Kane-Mele model Hamiltonian. Our results show a finite Drude response at low
frequency at non zero value for magnetic field in the presence of spin-orbit
coupling. However Drude weight gets remarkable amount in the presence of
electron doping. The thermal conductivity and specific heat increase with
increasing the temperature at low amounts of temperature due to the increasing
of thermal energy of charge carriers and excitation of them to the conduction
bands. The results for Seebeck coefficient show the sign of thermopower is
negative in the presence of spin-orbit coupling. Also we have studied the
temperature dependence of electrical conductivity of Germanene monolayer due to
both spin orbit coupling and magnetic field factors in details.",2106.11967v1
2021-12-03,Solar System Dynamics and Multiyear Droughts of the Western USA,"The recent addition of orbit-spin coupling torques to atmospheric global
circulation models has enabled successful years-in-advance forecasts of global
and regional-scale dust storms on Mars. Here we explore the applicability of
the orbit-spin coupling mechanism for understanding and forecasting anomalous
weather and climate events on Earth. We calculate the time history of
orbit-spin coupling torques on the Earth system for the interval from
1860-2040. The torque exhibits substantial variability on decadal to bidecadal
timescales. Deep minima recur at intervals from 15-26 years; eight such
episodes are documented within the study period prior to 2020. Each of the
identified torque minima corresponds in time to an episode of widespread
drought in the Western USA extending over several years. The multiyear droughts
of the 1930s, the 1950s, the mid-1970s, the early 1990s, and of 2011-2015 were
each coincident in time with orbit-spin coupling torque minima. The upcoming
torque minimum of 2030 is the deepest such minimum of the 180-yr study
interval. A multiyear episode of widespread drought in the Western USA is
likely to be underway by 2028 plus or minus 4 years (2 standard deviations).
The potential benefits to societies of improved drought predictions justify an
immediate high-priority effort to include forcing by orbit-spin coupling within
state-of-the-art Earth system GCMs. Future targeted numerical modeling
investigations are likely to yield forecasts with considerably lower
uncertainties and with much improved temporal resolution in comparison to that
obtained here.",2112.02186v1
2022-03-06,Superfluidity of a Raman spin-orbit-coupled Bose gas at finite temperature,"We investigate the superfluidity of a three-dimensional weakly interacting
Bose gas with a one-dimensional Raman-type spin-orbit coupling at both zero and
finite temperatures. Using the imaginary-time Green's function within the
Bogoliubov approximation, we explicitly derive analytic expressions of the
current-current response functions in the plane-wave and zero-momentum phases,
from which we extract the superfluid density in the limits of long wavelength
and zero frequency. At zero temperature, we check that the resultant superfluid
density agrees exactly with our previous analytic prediction obtained from a
phase-twist approach. Both results also satisfy a generalized Josephson
relation in the presence of spin-orbit coupling. At finite temperature, we find
a significant non-monotonic temperature dependence of superfluid density near
the transition from the plane-wave phase to the zero-momentum phase. We show
that this non-trivial behavior might be understood from the sound velocity,
which has a similar temperature dependence. The non-monotonic temperature
dependence is also shared by Landau critical velocity, above which the
spin-orbit-coupled Bose gas loses its superfluidity. Our results would be
useful for further theoretical and experimental studies of superfluidity in
exotic spin-orbit coupled quantum gases.",2203.02921v1
2022-03-30,Large Rashba Spin-Orbit Coupling and High-Temperature Quantum Anomalous Hall Effect in Re-Intercalated Graphene/CrI$_3$ Heterostructure,"In 2010, quantum anomalous Hall effect (QAHE) in graphene was proposed in the
presence of Rashba spin-orbit coupling and ferromagnetic exchange field. After
a decade's experimental exploration, the anomalous Hall conductance can only
reach about 0.25 in the units of $2e^2/h$, which was attributed to the tiny
Rashba spin-orbit coupling. Here, we theoretically show that Re-intercalation
in graphene/CrI$_3$ heterostructure can not only induce sizeable Rashba
spin-orbit coupling ($>$ 40~meV), but also open up large band gaps at valleys
$K$ (22.2 meV) and $K' $ (30.3 meV), and a global band gap over 5.5 meV (19.5
meV with random Re distribution) hosting QAHE. A low-energy continuum model is
constructed to explain the underlying physical mechanism. We find that Rashba
spin-orbit coupling is robust against external stress whereas a tensile strain
can increase the global bulk gap. Furthermore, we also show that
Re-intercalated graphene with hexagonal boron-nitride can also realize QAHE
with bulk gap over 40~meV, indicating the tunability of $5d$-intercalated
graphene-based heterostructure. Our finding makes a great leap towards the
experimental realization of graphene-based QAHE, and will definitely accelerate
the practical application of graphene-based low-power electronics.",2203.16429v1
2022-07-18,Multifractally-enhanced superconductivity in two-dimensional systems with spin-orbit coupling,"The interplay of Anderson localization and electron-electron interactions is
known to lead to enhancement of superconductivity due to multifractality of
electron wave functions. We develop the theory of multifractally-enhanced
superconducting states in two-dimensional systems in the presence of spin-orbit
coupling. Using the Finkel'stein nonlinear sigma model, we derive the modified
Usadel and gap equations that take into account renormalizations caused by the
interplay of disorder and interactions. Multifractal correlations induce energy
dependence of the superconducting spectral gap. We determine the
superconducting transition temperature and the superconducting spectral gap in
the case of Ising and strong spin orbit couplings. In the latter case the
energy dependence of superconducting spectral gap is convex whereas in the
former case (as well as in the absence of spin-orbit coupling) it is concave.
Multifractality enhances not only the transition temperature but, in the same
way, the spectral gap at zero temperature. Also we study mesoscopic
fluctuations of the local density of states in the superconducting state.
Similarly to the case of normal metal, spin-orbit coupling reduce the amplitude
of fluctuations.",2207.08594v2
2022-11-02,Spin-orbit coupling-enhanced valley ordering of malleable bands in twisted bilayer graphene on WSe2,"New phases of matter can be stabilized by a combination of diverging
electronic density of states, strong interactions, and spin-orbit coupling.
Recent experiments in magic-angle twisted bilayer graphene (TBG) have uncovered
a wealth of novel phases as a result of interaction-driven spin-valley flavour
polarization. In this work, we explore correlated phases appearing due to the
combined effect of spin-orbit coupling-enhanced valley polarization and large
density of states below half filling ($\nu \lesssim 2$) of the moir\'e band in
a TBG coupled to tungsten diselenide. We observe anomalous Hall effect,
accompanied by a series of Lifshitz transitions, that are highly tunable with
carrier density and magnetic field. Strikingly, the magnetization shows an
abrupt sign change in the vicinity of half-filling, confirming its orbital
nature. The coercive fields reported are about an order of magnitude higher
than previous studies in graphene-based moir\'e systems, presumably aided by a
Stoner instability favoured by the van Hove singularities in the malleable
bands. While the Hall resistance is not quantized at zero magnetic fields,
indicative of a ground state with partial valley polarization, perfect
quantization and complete valley polarization are observed at finite fields.
Our findings illustrate that singularities in the flat bands in the presence of
spin-orbit coupling can stabilize ordered phases even at non-integer moir\'e
band fillings.",2211.01251v1
2001-01-31,Spin-orbit induced anisotropy in the magnetoconductance of two-dimensional metals,"It is shown that the spin-orbit coupling due to structure inversion asymmetry
leads to a characteristic anisotropy in the magnetoconductance of
two-dimensional metals. Relevance for recent experiments is discussed.",0101473v1
1995-06-02,Spin-rotor Interpretation of Identical Bands and Quantized Alignment in Superdeformed A $\approx$ 190 Nuclei,"The ``identical'' bands in superdeformed mercury, thallium, and lead nuclei
are interpreted as examples of orbital angular momentum rotors with the weak
spin-orbit coupling of pseudo-$SU(3)$ symmetries and supersymmetries.",9506001v1
2017-03-08,Electron Spin Relaxation in a Transition-Metal Dichalcogenide Quantum Dot,"We study the relaxation of a single electron spin in a circular quantum dot
in a transition-metal dichalcogenide monolayer defined by electrostatic gating.
Transition-metal dichalcogenides provide an interesting and promising arena for
quantum dot nano-structures due to the combination of a band gap, spin-valley
physics and strong spin-orbit coupling. First we will discuss which bound state
solutions in different B-field regimes can be used as the basis for qubits
states. We find that at low B-fields combined spin-valley Kramers qubits to be
suitable, while at large magnetic fields pure spin or valley qubits can be
envisioned. Then we present a discussion of the relaxation of a single electron
spin mediated by electron-phonon interaction via various different relaxation
channels. In the low B-field regime we consider the spin-valley Kramers qubits
and include impurity mediated valley mixing which will arise in disordered
quantum dots. Rashba spin-orbit admixture mechanisms allows for relaxation by
in-plane phonons either via the deformation potential or by piezoelectric
coupling, additionally direct spin-phonon mechanisms involving out-of-plane
phonons give rise to relaxation. We find that the relaxation rates scale as
$\propto B^6$ for both in-plane phonons coupling via deformation potential and
the piezoelectric effect, while relaxation due to the direct spin-phonon
coupling scales independant to B-field to lowest order but scales strongly on
device mechanical tension. We will also discuss the relaxation mechanisms for
pure spin or valley qubits formed in the large B-field regime.",1703.02751v1
2017-12-20,Magnetic field effects on a nanowire with inhomogeneous Rashba spin-orbit coupling: Spin properties at equilibrium,"By modeling a Rashba nanowire contacted to leads via an inhomogeneous
spin-orbit coupling profile, we investigate the equilibrium properties of the
spin sector when a uniform magnetic field is applied along the nanowire axis.
We find that the interplay between magnetic field and Rashba coupling generates
a spin current, polarised perpendicularly to the applied field and flowing
through the nanowire even at equilibrium. In the nanowire bulk such effect
persists far beyond the regime where the nanowire mimics the helical states of
a quantum spin Hall system, while in the leads the spin current is suppressed.
Furthermore, despite the nanowire not being proximized by superconductors, at
the interfaces with the leads we predict the appearance of localized spin
torques and spin polarizations, orthogonal to the magnetic field and partially
penetrating into the leads. This feature, due to the inhomogeneity of the
Rashba coupling, suggests to use caution in interpreting spin polarization as
signatures of Majorana fermions. When the magnetic field has a component also
along the Rashba field, its collinearity with the spin polarization and
orthogonality to the spin current are violated in the nanowire bulk too. We
analyze these quantities in terms of the magnetic field and chemical potential
for both long and short nanowires in experimentally realistic regimes.",1712.07536v2
2018-10-15,Spin current generation and relaxation in a quenched spin-orbit-coupled Bose-Einstein condensate,"Understanding the effects of spin-orbit coupling (SOC) and many-body
interactions on spin transport is important in condensed matter physics and
spintronics. This topic has been intensively studied for spin carriers such as
electrons but barely explored for charge-neutral bosonic quasiparticles
(including their condensates), which hold promises for coherent spin transport
over macroscopic distances. Here, we explore the effects of synthetic SOC
(induced by optical Raman coupling) and atomic interactions on the spin
transport in an atomic Bose-Einstein condensate (BEC), where the spin-dipole
mode (SDM, actuated by quenching the Raman coupling) of two interacting spin
components constitutes an alternating spin current. We experimentally observe
that SOC significantly enhances the SDM damping while reducing the
thermalization (the reduction of the condensate fraction). We also observe
generation of BEC collective excitations such as shape oscillations. Our theory
reveals that the SOC-modified interference, immiscibility, and interaction
between the spin components can play crucial roles in spin transport.",1810.06504v2
2014-08-05,Tuning spin orbit interaction in high quality gate-defined InAs one-dimensional channels,"Spin-orbit coupling in solids describes an interaction between an electron's
spin, an internal quantum-mechanical degree of freedom, with its linear
momentum, an external property. Spin-orbit interaction, due to its relativistic
nature, is typically small in solids, and is often taken into account
perturbatively. It has been recently realized, however, that materials with
strong spin-orbit coupling can lead to novel states of matter such as
topological insulators and superconductors. This exciting development might
lead to a number of useful applications ranging from spintronics to quantum
computing. In particular, theory predicts that narrow band gap semiconductors
with strong spin-obit coupling are a suitable platform for the realization of
Majorana zero-energy modes, predicted to obey exotic non-Abelian braiding
statistics. The pursuit for realizing Majorana modes in condensed matter
systems and investigating their exotic properties has been a subject of
intensive experimental research recently. Here, we demonstrate the first
realization of gate-defined wires where one-dimensional confinement is created
using electrostatic potentials, on large area InAs two dimensional electron
systems (2DESs). The electronic properties of the parent 2DES are fully
characterized in the region that wires are formed. The strength of the
spin-orbit interaction has been measured and tuned while the high mobility of
the 2DES is maintained in the wire. We show that this scheme could provide new
prospective solutions for scalable and complex wire networks.",1408.1122v1
2019-03-16,Induced exchange and spin-orbit effects by proximity in graphene on Ni and Co,"The induced-proximity effects of nearly commensurate lattice structure of a
graphene layer on Ni(111) and Co(0001) substrates in the AC stacking
configuration are addressed through an analytical tight-binding approach within
the Slater-Koster method. A minimal Hamiltonian is constructed by considering
the hybridizations of the magnetic $3d$-orbitals of Ni(Co) atoms with the
$p_z$-orbitals of graphene, in addition to the atomic spin-orbit coupling and
the magnetization of the Ni(Co) atoms. A low-energy effective Hamiltonian for
graphene/Ni(Co) describing the perturbed $\pi$-bands in the vicinity of the
Dirac points is derived which enable us to get further insight on the physical
nature of the induced-effective couplings to the graphene layer. It is shown
that a magneto-spin-orbit type effect may emerge through two competing
mechanisms simultaneously present, namely the proximity induced exchange and
Rashba spin-orbit interaction. Such effects results in giant exchange
splittings and robust Rashba spin-orbit coupling transferred to the graphene
layer in agreement with recent density functional theory calculations and
experimental observations. We further analyze the physical conditions for the
appearance of intact Dirac cones in the minority spin bands as observed by
recent photoemission measurements with spin resolution.",1903.06959v1
2021-07-20,"Magnetic topology in coupled binaries, spin-orbital resonances, and flares","We consider topological configurations of the magnetically coupled spinning
stellar binaries (e.g., merging neutron stars or interacting star-planet
systems). We discuss conditions when the stellar spins and the orbital motion
nearly `compensate' each other, leading to very {\it slow} overall winding of
the coupled magnetic fields; slowly winding configurations allow gradual
accumulation of magnetic energy, that is eventually released in a flare when
the instability threshold is reached. We find that this slow winding can be
global and/or local. We describe the topology of the relevant space
$\mathbb{F}=T^1S^2$ as the unit tangent bundle of the two-sphere and find
conditions for slowly winding configurations in terms of magnetic moments,
spins and orbital momentum. These conditions become ambiguous near the
topological bifurcation points; in certain cases they also depend on the
relative phases of the spin and orbital motions. In the case of merging
magnetized neutron stars, if one of the stars is a millisecond pulsar, spinning
at $\sim$ 10 msec, the global resonance $\omega_1+\omega_2= 2 \Omega$
(spin-plus beat is two times the orbital period) occurs approximately a second
before the merger; the total energy of the flare can be as large as $10\%$ of
the total magnetic energy, producing bursts of luminosity $\sim 10^{44}$ erg
s$^{-1}$. Higher order local resonances may have similar powers, since the
amount of involved magnetic flux tubes may be comparable to the total connected
flux.",2107.09702v3
2007-04-03,Spin-orbit coupling effect on the persistent currents in mesoscopic ring with an Anderson impurity,"Based on the finite $U$ slave boson method, we have investigated the effect
of Rashba spin-orbit(SO) coupling on the persistent charge and spin currents in
mesoscopic ring with an Anderson impurity. It is shown that the Kondo effect
will decrease the magnitude of the persistent charge and spin currents in this
side-coupled Anderson impurity case. In the presence of SO coupling, the
persistent currents change drastically and oscillate with the strength of SO
coupling. The SO coupling will suppress the Kondo effect and restore the abrupt
jumps of the persistent currents. It is also found that a persistent spin
current circulating the ring can exist even without the charge current in this
system.",0704.0319v1
2018-09-12,Topological phases in pseudospin-1 Fermi gases with two-dimensional spin-orbit coupling,"The recent experimental realization of spin-orbit (SO) coupling for ultracold
bosons and fermions opens an exciting avenue for engineering quantum matter
that may be challenging to realize in solid state materials such as SO coupled
spin-1 fermions. While one-dimensional SO coupling for spin-1 bosons has been
experimentally realized, the generation of two-dimensional (2D) SO coupling and
its topological properties are largely unexplored. Here we propose an
experimental scheme for realizing a 2D Dresselhaus-type SO coupling in a square
lattice for spin-1 Fermi gases. Because of the extended spin degree of freedom,
many interesting topological phases could exist without relying on lattice
point group symmetries that are crucial in solid state materials. These exotic
phases include triply-degenerate points, quadratic band touching, a large Chern
number ($C=5$) superfluid with 5 Majorana modes, triple-Weyl fermions, etc. Our
scheme can be generalized to larger spins and provides a new route for
engineering topological quantum matter by utilizing large spin degrees of
freedom, instead of specific lattice symmetries.",1809.04537v2
2006-08-11,Magnetic and orbital correlations in a two-site molecule,"We analyze the role of orbital degeneracy in possible magnetic and orbital
instabilities by solving exactly a two-site molecule with two orbitals of
either $e_g$ or $t_{2g}$ symmetry at quarter-filling. As a generic feature of
both models one finds that the spin and orbital correlations have opposite
signs in the low temperature regime when the orbitals are degenerate, in
agreement with the Goodenough-Kanamori rules. While Hund's exchange coupling
$J_H$ induces ferromagnetic spin correlations in both models, it is more
efficient for $t_{2g}$ orbitals where the orbital quantum number is conserved
along the hopping processes. We show that the ground state and finite
temperature properties may change even qualitatively with increasing Coulomb
interaction when the crystal field splitting of the two orbitals is finite, and
the Goodenough-Kanamori rules may not be followed.",0608271v1
2007-01-22,Orbital order in ZnV$_2$O$_4$,"In view of recent controversy regarding the orbital order in the frustrated
spinel ZnV2O4, we analyze the orbital and magnetic groundstate of this system
within an ab initio density functional theory approach. While LDA+U
calculations in the presence of a cooperative Jahn-Teller distortion stabilize
an A-type staggered orbital order, the consideration of relativistic spin-orbit
effects unquenches the orbital moment and leads to a uniform orbital order with
a net magnetic moment close to the experimental one. Our results show that ab
initio calculations are able to resolve the existing discrepancies in previous
theories and that it is the spin-orbit coupling alongwith electronic
correlations which play a significant role in determining the orbital structure
in these materials.",0701528v2
2023-05-02,Orbital Hall effect in mesoscopic devices,"We investigate the orbital Hall effect through a mesoscopic device with
momentum-space orbital texture that is connected to four semi-infinite
terminals embedded in the Landauer-B\""uttiker configuration for quantum
transport. We present analytical and numerical evidence that the orbital Hall
current exhibits mesoscopic fluctuations, which can be interpreted in the
framework of random matrix theory (RMT) (as with spin Hall current
fluctuations). The mesoscopic fluctuations of orbital Hall current display two
different amplitudes of 0.36 and 0.18 for weak and strong spin-orbit coupling,
respectively. The amplitudes are obtained by analytical calculation via RMT and
are supported by numerical calculations based on the tight-binding model.
Furthermore, the orbital Hall current fluctuations lead to two relationships
between the orbital Hall angle and conductivity. Finally, we confront the two
relations with experimental data of the orbital Hall angle, which shows good
concordance between theory and experiment.",2305.01640v2
2004-11-24,Effect of spin-orbit coupling on zero-conductance resonances in asymmetrically coupled one-dimensional rings,"The influence of Rashba spin-orbit coupling on zero conductance resonances
appearing in one dimensional ring asymmetrically coupled to two leads is
investigated. For this purpose, the transmission function of the corresponding
one-electron scattering problem is derived analytically and analyzed in the
complex energy plane with focus on the zero-pole structure characteristic of
transmission (anti)resonances. The lifting of real conductance zeros due to
spin-orbit coupling in the asymmetric Aharonov-Casher (AC) ring is related to
the breaking of spin reversal symmetry in analogy to the time-reversal symmetry
breaking in the asymmetric Aharonov-Bohm (AB) ring.",0411620v2
2010-04-15,Spin-orbit coupling and anisotropic exchange in two-electron double quantum dots,"The influence of the spin-orbit interactions on the energy spectrum of
two-electron laterally coupled quantum dots is investigated. The effective
Hamiltonian for a spin qubit pair proposed in F. Baruffa et al., Phys. Rev.
Lett. 104, 126401 (2010) is confronted with exact numerical results in single
and double quantum dots in zero and finite magnetic field. The anisotropic
exchange Hamiltonian is found quantitatively reliable in double dots in
general. There are two findings of particular practical importance: i) The
model stays valid even for maximal possible interdot coupling (a single dot),
due to the absence of a coupling to the nearest excited level, a fact following
from the dot symmetry. ii) In a weak coupling regime, the Heitler-London
approximation gives quantitatively correct anisotropic exchange parameters even
in a finite magnetic field, although this method is known to fail for the
isotropic exchange. The small discrepancy between the analytical model (which
employes the linear Dresselhaus and Bychkov-Rashba spin-orbit terms) and the
numerical data for GaAs quantum dots is found to be mostly due to the cubic
Dresselhaus term.",1004.2610v2
2021-03-01,Evolution of Majorona zero-energy edge states in a $T^2 = -1$ symmetry protected 1D topological superconductor with dominant spin-orbit coupling,"We consider a 1D topological superconductor (TSC) constructed by coupling a
pair of Kitaev's Majorana chains with opposite spin configurations. Such a 1D
lattice model is known to be protected by a $T^2 = -1$ time-reversal symmetry.
Furthermore, we consider a modeled Rashba spin-orbit coupling on such a system
of $T^2=-1$ time-reversal symmetric TSC. The Rashba spin-orbit coupling
together with the chemical potential engineered the phase transitions of the
edge states in the system and consequently the number of Majorona's zero-energy
edge modes (MZM's) emerging at the edge of the coupled chains. Correspondingly,
the topological nature of the system is described by a phase diagram consisting
of three different phases. The three phases are characterized by a topological
winding number, $\mathcal{W}=1$, $2$ (with one and two MZM's: topological
phases) and $\mathcal{W}=0$ (devoid of any MZM: trivial insulating phase).",2103.00960v1
2021-04-24,Spin-orbit-coupled fluids of light in bulk nonlinear media,"We show that nonparaxial polarized light beams propagating in a bulk
nonlinear Kerr medium naturally exhibit a coupling between the motional and the
polarization degrees of freedom, realizing a spin-orbit-coupled mixture of
fluids of light. We investigate the impact of this mechanism on the Bogoliubov
modes of the fluid, using a suitable density-phase formalism built upon a
linearization of the exact Helmholtz equation. The Bogoliubov spectrum is found
to be anisotropic, and features both low-frequency gapless branches and
high-frequency gapped ones. We compute the amplitudes of these modes and
propose a couple of experimental protocols to study their excitation
mechanisms. This allows us to highlight a phenomenon of hybridization between
density and spin modes, which is absent in the paraxial description and
represents a typical fingerprint of spin-orbit coupling.",2104.11982v2
2010-04-27,Construction of a Microscopic Model for Yb and Tm Compounds on the Basis of a $\mib{j}$-$\mib{j}$ Coupling Scheme,"We provide a prescription to construct a microscopic model for heavy
lanthanide systems such as Yb and Tm compounds by exploiting a $j$-$j$ coupling
scheme. Here we consider a situation with a large spin-orbit coupling, in which
$j$=5/2 sextet is fully occupied, while $j$=7/2 octet is partially occupied,
where $j$ denotes total angular momentum. We evaluate crystalline electric
field potentials and Coulomb interactions among the states of the $j$=7/2 octet
to construct a local Hamiltonian in the $j$-$j$ coupling scheme. Then, it is
found that the local $f$-electron states composed of the $j$=7/2 octet agree
quite well with those of seven $f$ orbitals even for a realistic value of the
spin-orbit coupling. As an example of the application of the present model, we
discuss low-temperature multipole states of Yb- and Tm-based filled
skutterudites by analyzing multipole susceptibility of the Anderson model in
the $j$-$j$ coupling scheme with the use of a numerical renormalization group
technique. From the comparison with the numerical results of the seven-orbital
Anderson model, it is concluded that the multipole state is also well
reproduced by the $j$-$j$ coupling model, even when we include the
hybridization between conduction and $f$ electrons for the realistic value of
the spin-orbit coupling. Finally, we briefly discuss future applications of the
present prescription for theoretical research on heavy lanthanide compounds.",1004.4707v1
2019-12-06,Synthetic spin-orbit coupling mediated by a bosonic environment,"We study a mobile quantum impurity, possessing internal rotational degrees of
freedom, confined to a ring in the presence of a many-particle bosonic bath. By
considering the recently introduced rotating polaron problem, we define the
Hamiltonian and examine the energy spectrum. The weak-coupling regime is
studied by means of a variational ansatz in the truncated Fock space. The
corresponding spectrum indicates that there emerges a coupling between the
internal and orbital angular momenta of the impurity as a consequence of the
phonon exchange. We interpret the coupling as a phonon-mediated spin-orbit
coupling and quantify it by using a correlation function between the internal
and orbital angular momentum operators. The strong-coupling regime is
investigated within the Pekar approach and it is shown that the correlation
function of the ground state shows a kink at a critical coupling, that is
explained by a sharp transition from the non-interacting state to the states
that exhibit strong interaction with the surroundings. The results might find
applications in such fields as spintronics or topological insulators, where
spin-orbit coupling is of crucial importance.",1912.03092v2
2004-10-24,Spin-Hall conductivity of a disordered 2D electron gas with Dresselhaus spin-orbit interaction,"The spin-Hall conductivity of a disordered 2D electron gas has been
calculated for an arbitrary spin-orbit interaction. We have found that in the
diffusive regime of electron transport, in accordance with previous
calculations, the dc spin-Hall conductivity of a homogeneous system turns to
zero due to impurity scattering when the spin-orbit coupling is represented
only by the Rashba interaction. However, when the Dresselhaus interaction is
taken into account, the spin-Hall current is not zero. We also considered the
spin-Hall currents induced by an inhomogeneous electric field. It is shown that
a time dependent electric charge induces a vortex of spin-Hall currents.",0410607v2
2008-06-02,"Photo-induced, non-equilibrium spin and charge polarization in quantum rings","We investigate the spin-dependent dynamical response of a quantum ring with a
spin-orbit interaction upon the application of linearly polarized, picosecond,
asymmetric electromagnetic pulses. The oscillations of the generated dipole
moment are sensitive to the parity of the occupation number in the ring and to
the strength of the spin-orbit coupling. It is shown how the associated
emission spectrum can be controlled via the pulse strength or a gate voltage.
In addition, we inspect how a static magnetic flux can modify the
non-equilibrium dynamics. In presence of the spin-orbit interaction and for a
paramagnetic ring, the applied pulse results in a spin-split, non-equilibrium
local charge density. The resulting temporal spin polarization is directed
perpendicular to the light-pulse polarization axis and oscillates periodically
with the frequency of the spin-split charge density. The spin-averaged
non-equilibrium charge density possesses a left-right symmetry with respect to
the pulse polarization axis. The calculations presented here are applicable to
nano-meter rings fabricated in heterojuctions of III-V and II-VI semiconductors
containing several hundreds electrons.",0806.0317v1
2012-07-05,Onsager relations in a two-dimensional electron gas with spin-orbit coupling,"Theory predicts for the two-dimensional electrons gas with only Rashba
spin-orbit interaction a vanishing spin Hall conductivity and at the same time
a finite inverse spin Hall effect. We show how these seemingly contradictory
results are compatible with the Onsager relations: the latter do hold for spin
and particle (charge) currents in the two-dimensional electron gas, although
(i) their form depends on the experimental setup and (ii) a vanishing bulk spin
Hall conductivity does not necessarily imply a vanishing spin Hall effect. We
also discuss the situation in which extrinsic spin orbit from impurities is
present and the bulk spin Hall conductivity can be different from zero.",1207.1289v2
2018-11-13,Atomic-scale tailoring of spin susceptibility via non-magnetic spin-orbit impurities,"Following the discovery of topological insulators, there has been a renewed
interest in superconducting systems that have strong spin-orbit (SO) coupling.
Here we address the fundamental question of how the spin properties of a
otherwise spin-singlet superconducting ground state evolve with increasing SO
impurity density. We have mapped out the Zeeman critical field phase diagram of
superconducting Al films that were deposited over random Pb cluster arrays of
varying density. These phase diagrams give a direct measure of the Fermi liquid
spin renormalization, as well as the spin orbit scattering rate. We find that
the spin renormalization is a linear function of the average Pb
cluster-to-cluster separation and that this dependency can be used to tune the
spin susceptibility of the Al over a surprisingly wide range from 0.8$\chi_0$
to 4.0$\chi_0$, where $\chi_0$ is the non-interacting Pauli susceptibility.",1811.05265v1
2010-04-30,Spin-dependent tunneling into an empty lateral quantum dot,"Motivated by the recent experiments of Amasha {\it et al.} [Phys. Rev. B {\bf
78}, 041306(R) (2008)], we investigate single electron tunneling into an empty
quantum dot in presence of a magnetic field. We numerically calculate the
tunneling rate from a laterally confined, few-channel external lead into the
lowest orbital state of a spin-orbit coupled quantum dot. We find two
mechanisms leading to a spin-dependent tunneling rate. The first originates
from different electronic $g$-factors in the lead and in the dot, and favors
the tunneling into the spin ground (excited) state when the $g$-factor
magnitude is larger (smaller) in the lead. The second is triggered by
spin-orbit interactions via the opening of off-diagonal spin-tunneling
channels. It systematically favors the spin excited state. For physical
parameters corresponding to lateral GaAs/AlGaAs heterostructures and the
experimentally reported tunneling rates, both mechanisms lead to a discrepancy
of $\sim$10% in the spin up vs spin down tunneling rates. We conjecture that
the significantly larger discrepancy observed experimentally originates from
the enhancement of the $g$-factor in laterally confined lead.",1005.0024v2
2011-01-03,Sublattice asymmetry and spin-orbit interaction induced out-of-plane spin polarization of photoelectrons,"We study theoretically the effect of spin-orbit coupling and sublattice
asymmetry in graphene on the spin polarization of photoelectrons. We show that
sublattice asymmetry in graphene not only opens a gap in the band structure but
in case of finite spin-orbit interaction it also gives rise to an out-of-plane
spin polarization of electrons close to the Dirac point of the Brillouin zone.
This can be detected by measuring the spin polarization of photoelectrons and
therefore spin resolved photoemission spectroscopy can reveal the presence of a
band gap even if it is too small to be observed directly by angle resolved
photoemission spectroscopy because of the finite resolution of measurements or
because the sample is $p$-doped. We present analytical and numerical
calculations on the energy and linewidth dependence of photoelectron intensity
distribution and spin polarization.",1101.0624v2
2011-09-12,Nonadiabatic generation of spin currents in a quantum ring with Rashba and Dresselhaus spin-orbit interactions,"When subjected to a linearly polarized terahertz pulse, a mesoscopic ring
endowed with spin-orbit interaction (SOI) of the Rashba-Dresselhaus type
exhibits nonuniform azimuthal charge and spin distributions. Both types of SOI
couplings are considered linear in the electron momentum. Our results are
obtained within a formalism based on the equation of motion satisfied by the
density operator which is solved numerically for different values of the angle
$\phi$, the angle determining the polarization direction of the laser pulse.
Solutions thus obtained are later employed in determining the time-dependent
charge and spin currents, whose values are calculated in the stationary limit.
Both these currents exhibit an oscillatory behavior complicated in the case of
the spin current by a beating pattern. We explain this occurrence on account of
the two spin-orbit interactions which force the electron spin to oscillate
between the two spin quantization axes corresponding to Rashba and Dresselhaus
interactions. The oscillation frequencies are explained using the single
particle spectrum.",1109.2572v1
2015-06-15,Giant Spin-Orbit-Induced Spin Splitting in Bi Chains on GaAs(110),"The search for one-dimensional electron systems with a giant Rashba-type spin
splitting is of importance for the application of spin transport. Here we
report, based on a first-principles density-functional-theory calculation, that
Bi zigzag chains formed on a heterogeneous GaAs(110) surface have a giant spin
splitting of surface states. This giant spin splitting is revealed to originate
from spin-orbit coupling (SOC) and electric dipole interaction that are
significantly enhanced by (i) the asymmetric surface charge distribution due to
the strong SOC-induced hybridization of the Bi px , py , and pz orbitals and
(ii) the large out-of-plane and in-plane potential gradients generated by two
geometrically and electronically inequivalent Bi atoms bonding to Ga and As
atoms. The results demonstrate an important implication of the in-plane and
out-of-plane asymmetry of the Bi/GaAs(110) interface system in producing the
giant spin splitting with the in-plane and out-of-plane spin components.",1506.04798v2
2021-03-30,Oxide spin-orbitronics: spin-charge interconversion and topological spin textures,"Quantum oxide materials possess a vast range of properties stemming from the
interplay between the lattice, charge, spin and orbital degrees of freedom, in
which electron correlations often play an important role. Historically, the
spin-orbit coupling was rarely a dominant energy scale in oxides. It however
recently came to the forefront, unleashing various exotic phenomena connected
with real and reciprocal-space topology that may be harnessed in spintronics.
In this article, we review the recent advances in the new field of oxide
spin-orbitronics with a special focus on spin-charge interconversion from the
direct and inverse spin Hall and Edelstein effects, and on the generation and
observation of topological spin textures such as skyrmions. We highlight the
control of spin-orbit-driven effects by ferroelectricity and give perspectives
for the field.",2103.16271v1
2006-08-23,Spin-spin coupling in electrostatically coupled quantum dots,"We study the spin-spin coupling between two single-electron quantum dots due
to the Coulomb and spin-orbit interactions, in the absence of tunneling between
the dots. We find an anisotropic XY spin-spin interaction that is proportional
to the Zeeman splitting produced by the external magnetic field. This
interaction is studied both in the limit of weak and strong Coulomb repulsion
with respect to the level spacing of the dot. The interaction is found to be a
non-monotonic function of inter-dot distance $a_0$ and external magnetic field,
and, moreover, vanishes for some special values of $a_0$ and/or magnetic field
orientation. This mechanism thus provides a new way to generate and tune spin
interaction between quantum dots. We propose a scheme to measure this spin-spin
interaction based on the spin-relaxation-measurement technique.",0608512v1
2017-08-14,Large Proximity-Induced Spin Lifetime Anisotropy in Transition Metal Dichalcogenide/Graphene Heterostructures,"Van-der-Waals heterostructures have become a paradigm for designing new
materials and devices, in which specific functionalities can be tailored by
combining the properties of the individual 2D layers. A single layer of
transition metal dichalcogenide (TMD) is an excellent complement to graphene
(Gr), since the high quality of charge and spin transport in Gr is enriched
with the large spin-orbit coupling of the TMD via proximity effect. The
controllable spin-valley coupling makes these heterostructures particularly
attractive for spintronic and opto-valleytronic applications. In this work, we
study spin precession in a monolayer MoSe2/Gr heterostructure and observe an
unconventional, dramatic modulation of the spin signal, showing one order of
magnitude longer lifetime of out-of-plane spins (40 ps) compared with that of
in-plane spins (3.5 ps). This demonstration of a large spin lifetime anisotropy
in TMD/Gr heterostructures, is a direct evidence of induced spin-valley
coupling in Gr and provides an accessible route for manipulation of spin
dynamics in Gr, interfaced with TMDs.",1708.04067v1
2017-01-06,Spin Analogues of Superconductivity and the Integer Quantum Hall Effect in an Array of Spin Chains,"Motivated by the successful idea of using weakly-coupled quantum electronic
wires to realize the quantum Hall effects and the quantum spin Hall effects, we
theoretically construct two systems composed of weakly-coupled quantum spin
chains, which can exhibit spin analogues of superconductivity and the integer
quantum Hall effect. Specifically, a certain bilayer of two arrays of
interacting spin chains is mapped, via the Jordan-Wigner transformation, to a
negative-$U$ Hubbard model that exhibits superconductivity. In addition, an
array of spin-orbit-coupled spin chains in the presence of an suitable external
magnetic field is transformed to an array of quantum wires that exhibits the
integer quantum Hall effect. The resultant spin superconductivity and spin
integer quantum Hall effect can be characterized by their ability to transport
spin without any resistance.",1701.01509v1
2023-07-31,Generation of charge current by the Inverse Stern-Gerlach Effect and the suppression of spin transport due to spin counter-current exchange in semiconductors,"The spin-orbit interaction is frequently the mechanism by which spin and
charge are coupled for spintronic applications. The discovery of spin, a
century ago, relied on spin-charge coupling by a magnetic field gradient; this
mechanism has received scant attention as a means for generating spin and
charge currents in semiconductors. Through the derivation of a set of coupled
spin-charge drift-diffusion equations, our work shows that magnetic field
gradients can be used to generate charge currents from non-equilibrium spin
polarization, in solid state systems. We predict, in GaAs, an ``Stern-Gerlach""
voltage comparable to what is measured by the inverse spin Hall effect.
Non-intuitively, we find the spin diffusion length is reduced by the magnetic
gradient. This is understood by invoking the idea of co-current and
counter-current exchange which is a concept frequently invoked in fields as
disparate as animal physiology and thermal engineering.",2307.16838v1
2024-03-11,Impact of spin torques and spin pumping phenomena on magnon-plasmon polaritons in antiferromagnetic insulator-semiconductor heterostructures,"We investigate the impact of spin torque and spin pumping on the surface
magnon polariton dispersion in a antiferromagnetic insulator-semiconductor
heterostructure. In the bilayer system, the surface magnon polaritons
conventionally couple to the plasma-oscillations in the semiconductor via
electromagnetic fields. Additionally, magnons in the antiferromagnetic
insulator layer may interact with the semiconductor layer via spin torques and
their reciprocal phenomena of spin pumping. Due to the spin-to-charge
conversion from the spin Hall and inverse spin Hall effects in the
semiconductor layer with a strong spin-orbit coupling, this can couple the
magnons to the plasmons in the semiconductor layer. Our research reveals that
modifications in the mode frequency and the hybridization gap induced by these
phenomena depend on the thickness of the antiferromagnetic layer. In thick
layers, the spin-pumping contribution to the frequency shift and damping is
inversely proportional to the wavelength, while in thin layers it is inversely
proportional to the thickness. Furthermore, hybridization of the surface magnon
polariton and dispersive magnons in the antiferromagnet is shown to depend on
both the thickness and wavelength of the modes.",2403.06934v1
2017-04-25,Unified Treatment of Spin Torques using a Coupled Magnetisation Dynamics and Three-Dimensional Spin Current Solver,"A three-dimensional spin current solver based on a generalised spin
drift-diffusion description, including the spin Hall effect, is integrated with
a magnetisation dynamics solver. The resulting model is shown to simultaneously
reproduce the spin-orbit torques generated using the spin Hall effect, spin
pumping torques generated by magnetisation dynamics in multilayers, as well as
the spin transfer torques acting on magnetisation regions with spatial
gradients, whilst field-like and spin-like torques are reproduced in a spin
valve geometry. Two approaches to modelling interfaces are analysed, one based
on the spin mixing conductance and the other based on continuity of spin
currents where the spin dephasing length governs the absorption of transverse
spin components. In both cases analytical formulas are derived for the
spin-orbit torques in a heavy metal / ferromagnet bilayer geometry, showing in
general both field-like and damping-like torques are generated. The limitations
of the analytical approach are discussed, showing that even in a simple bilayer
geometry, due to the non-uniformity of the spin currents, a full
three-dimensional treatment is required. Finally the model is applied to the
quantitative analysis of the spin Hall angle in Pt by reproducing published
experimental data on the ferromagnetic resonance linewidth in the bilayer
geometry.",1704.07758v2
2012-11-16,Spin thermoelectrics in a disordered Fermi gas,"We study the connection between the spin-heat and spin-charge response in a
disordered Fermi gas with spin-orbit coupling. It is shown that the ratio
between the above responses can be expressed as the thermopower $S=-(\pi
k_B)^2T\sigma'/3e\sigma$ times a number $R_s$ which depends on the strength and
type of the spin-orbit couplings considered. The general results are
illustrated by examining different two-dimensional electron or hole systems
with different and competing spin-orbit mechanisms, and we conclude that a
metallic system could prove much more efficient as a heat-to-spin than as a
heat-to-charge converter.",1211.3839v2
2009-12-06,Resonant all-electric spin pumping with spin-orbit coupling,"All-electric devices for the generation and filtering of spin currents are of
crucial importance for spintronics experiments and applications. Here we
consider a quantum dot between two metallic leads in the presence of spin-orbit
coupling, and we analyze in the frame of a scattering matrix approach the
conditions for generating spin currents in an adiabatically driven two-terminal
device. We then focus on a dot with two resonant orbitals and show by specific
examples that both spin filtering and pure spin current generation can be
achieved. Finally, we discuss the effect of the Coulomb interaction.",0912.1096v2
2020-02-26,Spin-orbit-phonon interaction as an origin of helical-symmetry breaking spin-triplet superconducting state,"The excess increase of the local field distribution width $\Delta
H\equiv\sigma/\gamma_{\mu}$ (with $\gamma_{\mu}=135.5\,$MHz/T being the
gyromagnetic ratio of $\mu^{+}$), and/or the spontaneous magnetic field $H_{\rm
spon}$, have been reported in the superconducting state of a series of
compounds more than 10 by $\mu$SR (muon spin rotation or relaxation)
experiment. Sizes of these quantities are of the order of 1G on the whole. We
propose that the increase of the local field distribution $\Delta H$ in those
compounds, including ions with strong spin-orbit interaction of 5d electrons,
such as La in LaNiGa$_2$ or Re in Re$_6$Zr, is possible through the cooperation
of the spin-orbit coupling between the quasiparticles and ionic vibrations
(phonons) and the conventional quasiparticles-phonon coupling, inducing the
spin-triplet p-wave pairing with helical symmetry breaking superconducting
state with chiral super spin current around stopped $\mu^{+}$ site. The size of
$\Delta H$ is estimated as of the order of 1G, in consistent with experimental
observations.",2002.11344v1
2019-08-23,Momentum-Dependent Spin Splitting by Collinear Antiferromagnetic Ordering,"We clarify the macroscopic symmetry and microscopic model-parameter
conditions for emergence of spin-split electronic band structure in collinear
antiferromagnets without atomic spin-orbit coupling. By using the microscopic
multipole descriptions, we elucidate the fundamental degree of freedom in a
cluster unit of an antiferromagnet giving rise to an effective spin-orbit
interaction through the anisotropic kinetic motions of electrons. We show a
correspondence of the ordering patterns and resultant momentum-dependent spin
splitting for 32 crystallographic point groups after demonstrating two
intuitive examples of four-sublattice pyrochlore and tetragonal systems. Our
study unveils potential features of collinear antiferromagnets with
considerably weak spin-orbit coupling in light-element materials and 3$d$
transition metal oxides, which can be utilized for a spin-current generation by
electric (thermal) current and a magneto-striction effect.",1908.08680v1
2002-08-13,Electron Spin Dynamics in Semiconductors without Inversion Symmetry,"We present a microscopic analysis of electron spin dynamics in the presence
of an external magnetic field for non-centrosymmetric semiconductors in which
the D'yakonov-Perel' spin-orbit interaction is the dominant spin relaxation
mechanism. We implement a fully microscopic two-step calculation, in which the
relaxation of orbital motion due to electron-bath coupling is the first step
and spin relaxation due to spin-orbit coupling is the second step. On this
basis, we derive a set of Bloch equations for spin with the relaxation times
T_1 and T_2 obtained microscopically. We show that in bulk semiconductors
without magnetic field, T_1 = T_2, whereas for a quantum well with a magnetic
field applied along the growth direction T_1 = T_2/2 for any magnetic field
strength.",0208261v1
2007-04-24,Spin-charge filtering through a spin-orbit coupled quantum dot controlled via an Aharonov-Bohm interferometer,"We show that a strongly correlated quantum dot embedded in an Aharonov-Bohm
interferometer can be used to filter both charge and spin at zero voltage bias.
The magnitude with which the Aharonov-Bohm arm is coupled to the system
controls the many-body effects on the quantum dot. When the quantum dot is in
the Kondo regime the flow of charge through the system can be tuned by the
phase of the Aharonov-Bohm arm, $\phi_{AB}$. Furthermore when a spin-orbit
interaction is present on a Kondo quantum dot we can control the flow of spin
by the spin-orbit phase, $\phi_{SO}$. The existence of the Kondo peak at the
Fermi energy makes it possible to control the flow of both charge and spin in
the zero voltage bias limit.",0704.3212v3
2012-09-07,Chiral Spin Waves in Fermi Liquids with Spin-Orbit Coupling,"We predict the existence of chiral spin waves collective modes in a
two-dimensional Fermi liquid with the Rashba or Dresselhaus spin-orbit
coupling. Starting from the phenomenological Landau theory, we show that the
long-wavelength dynamics of magnetization is governed by the Klein- Gordon
equations. The standing-wave solutions of these equations describe ""particles""
with effective masses, whose magnitudes and signs depend on the strength of the
electron-electron interaction. The spectrum of the spin-chiral modes for
arbitrary wavelengths is determined from the Dyson equation for the interaction
vertex. We propose to observe spin-chiral modes via microwave absorption of
standing waves confined by an in-plane profile of the spin-orbit splitting.",1209.1647v1
2014-12-18,Intrinsic Spin Torque Without Spin-Orbit Coupling,"We derive an intrinsic contribution to the non-adiabatic spin torque for
non-uniform magnetic textures. It differs from previously considered
contributions in several ways and can be the dominant contribution in some
models. It does not depend on the change in occupation of the electron states
due to the current flow but rather is due to the perturbation of the electronic
states when an electric field is applied. Therefore it should be viewed as
electric-field-induced rather than current-induced. Unlike previously reported
non-adiabatic spin torques, it does not originate from extrinsic relaxation
mechanisms nor spin-orbit coupling. This intrinsic non-adiabatic spin torque is
related by a chiral connection to the intrinsic spin-orbit torque that has been
calculated from the Berry phase for Rashba systems.",1412.6123v2
2016-11-09,The $3d$-Electron Heisenberg Pyrochlore Mn$_2$Sb$_2$O$_7$,"In frustrated magnetic systems, geometric constraints or the competition
amongst interactions introduce extremely high degeneracy and prevent the system
from readily selecting a low-temperature ground state. The most frustrated
known spin arrangement is on the pyrochlore lattice, but nearly all magnetic
pyrochlores have unquenched orbital angular momentum, constraining the spin
directions through spin-orbit coupling. Pyrochlore Mn$_2$Sb$_2$O$_7$ is an
extremely rare Heisenberg pyrochlore system, with directionally-unconstrained
spins and low chemical disorder. We show that it undergoes a spin-glass
transition at 5.5K, which is suppressed by disorder arising from Mn vacancies,
indicating this ground state to be a direct consequence of the spins'
interactions. The striking similarities to $3d$ transition metal pyrochlores
with unquenched angular momentum suggests that the low spin-orbit coupling in
the $3d$ block makes Heisenberg pyrochlores far more accessible than previously
imagined.",1611.02811v1
2011-11-29,Anomalous Hall effect in superconductors with spin-orbit interaction,"We calculate the anomalous Hall conductance of superconductors with
spin-orbit interaction and with either uniform or local magnetization. In the
first case we consider a uniform ferromagnetic ordering in a spin triplet
superconductor, while in the second case we consider a conventional s-wave spin
singlet superconductor with a magnetic impurity (or a diluted set of magnetic
impurities). In the latter case we show that the anomalous Hall conductance can
be used to track the quantum phase transition, that occurs when the spin
coupling between the impurity and electronic spin density exceeds a certain
critical value. In both cases we find that for large spin-orbit coupling the
superconductivity is destroyed and the Hall conductance oscillates strongly.",1111.6748v1
2014-06-03,Spin-orbital dynamics in a system of polar molecules,"Spin-orbit coupling (SOC) in solids normally originates from the electron
motion in the electric field of the crystal. It is key to understanding a
variety of spin-transport and topological phenomena, such as Majorana fermions
and recently discovered topological insulators. Implementing and controlling
spin-orbit coupling is thus highly desirable and could open untapped
opportunities for the exploration of unique quantum physics. Here, we show that
dipole-dipole interactions can produce an effective SOC in two-dimensional
ultracold polar molecule gases. This SOC generates chiral excitations with a
non-trivial Berry phase $2\pi$. These excitations, which we call
\emph{chirons}, resemble low-energy quasiparticles in bilayer graphene and
emerge regardless of the quantum statistics and for arbitrary ratios of kinetic
to interaction energies. Chirons manifest themselves in the dynamics of the
spin density profile, spin currents, and spin coherences, even for molecules
pinned in a deep optical lattice and should be observable in current
experiments.",1406.0570v2
2015-12-14,Nonlocal Anomalous Hall Effect,"The anomalous Hall effect is deemed to be a unique transport property of
ferromagnetic metals, caused by the concerted action of spin polarization and
spin-orbit coupling. Nevertheless, recent experiments have shown that the
effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic
insulator (yttrium iron garnet (YIG)), even when precautions are taken to
ensure there is no induced magnetization in the metal. We propose a theory of
this effect based on the combined action of spin-dependent scattering from the
magnetic interface and the spin Hall effect in the bulk of the metal. At
variance with previous theories, we predict the effect to be of first order in
the spin-orbit coupling, just as the conventional anomalous Hall effect -- the
only difference being the spatial separation of the spin orbit interaction and
the magnetization. For this reason we name this effect \textit{nonlocal
anomalous Hall effect} and predict that its sign will be determined by the sign
of the spin Hall angle in the metal. The AH conductivity that we calculate from
our theory is in good agreement with the measured values in Pt/YIG structures.",1512.04146v1
2020-05-18,Mechanically modulated spin orbit couplings in oligopeptides,"Recently experiments have shown very significant spin activity in biological
molecules such as DNA, proteins, oligopeptides and aminoacids. Such molecules
have in common their chiral structure, time reversal symmetry and the absence
of magnetic exchange interactions. The spin activity is then assumed to be due
to either the pure Spin-orbit (SO) interaction or SO coupled to the presence of
strong local sources of electric fields. Here we derive an analytical
tight-binding Hamiltonian model for Oligopeptides that contemplates both
intrinsic SO and Rashba interaction induced by hydrogen bond. We use a lowest
order perturbation theory band folding scheme and derive the reciprocal space
intrinsic and Rashba type Hamiltonian terms to evaluate the spin activity of
the oligopeptide and its dependence of molecule uniaxial deformations. SO
strengths in the tens of meV are found and explicit spin active deformation
potentials. We find a rich interplay between responses to deformations both to
enhance and diminish SO strength that allow for experimental testing of the
orbital model. Qualitative consistency with recent experiments shows the role
of hydrogen bonding in spin activity.",2005.08474v1
2024-02-19,Photoelectron Polarization Vortexes in Strong-Field Ionization,"The spin polarization of photoelectrons induced by an intense linearly
polarized laser field is investigated using numerical solutions of the
time-dependent Schr\""odinger equation in companion with our analytic treatment
via the spin-resolved strong-field approximation and classical trajectory Monte
Carlo simulations. We demonstrate that, even though the total polarization
vanishes upon averaging over the photoelectron momentum, momentum-resolved spin
polarization is significant, typically exhibiting a vortex structure relative
to the laser polarization axis. The polarization arises from the transfer of
spin-orbital coupling in the bound state to the spin-correlated quantum orbits
in the continuum. The rescattering of photoelectrons at the atomic core plays
an important role in forming the polarization vortex structure, while there is
no significant effect of the spin-orbit coupling during the continuum dynamics.
Furthermore, spin-polarized electron holography is demonstrated, feasible for
extracting fine structural information about the atom.",2402.11825v1
2006-05-08,"Spin-orbit effects in GaAs quantum wells: Interplay between Rashba, Dresselhaus, and Zeeman interactions","The interplay between Rashba, Dresselhaus and Zeeman interactions in a
quantum well submitted to an external magnetic field is studied by means of an
accurate analytical solution of the Hamiltonian, including electron-electron
interactions in a sum rule approach. This solution allows to discuss the
influence of the spin-orbit coupling on some relevant quantities that have been
measured in inelastic light scattering and electron-spin resonance experiments
on quantum wells. In particular, we have evaluated the spin-orbit contribution
to the spin splitting of the Landau levels and to the splitting of charge- and
spin-density excitations. We also discuss how the spin-orbit effects change if
the applied magnetic field is tilted with respect to the direction
perpendicular to the quantum well.",0605199v1
2014-09-30,Current-induced spin torque resonance of magnetic insulators affected by field-like spin-orbit torques and out-of-plane magnetizations,"The spin-torque ferromagnetic resonance (ST-FMR) in a bilayer system
consisting of a magnetic insulator such as Y3Fe5O12 and a normal metal with
spin-orbit interaction such as Pt is addressed theoretically. We model the
ST-FMR for all magnetization directions and in the presence of field-like
spin-orbit torques based on the drift-diffusion spin model and quantum
mechanical boundary conditions. ST-FMR experiments may expose crucial
information about the spin-orbit coupling between currents and magnetization in
the bilayers.",1409.8406v2
2015-11-03,The role of spin-orbit interaction in the ultrafast demagnetization of small iron clusters,"The ultra-fast demagnetization of small iron clusters initiated by an intense
optical excitation is studied with time-dependent spin density functional
theory (TDSDFT). In particular we investigate the effect of the spin-orbit
interaction on the onset of the demagnetization process. It is found that the
initial rate of coherent spin loss is proportional to the square of the atomic
spin-orbit coupling constant, $\lambda$. A simplified quantum spin model
comprising spin-orbit interaction and a local time-dependent magnetic field is
found to be the minimal model able to reproduce our {\it ab initio} results.
The model predicts the $\lambda^2$ dependence of the onset rate of
demagnetization when it is solved either numerically or analytically in the
linear response limit. Our findings are supported by additional TDSDFT
simulations of clusters made of Co and Ni.",1511.00864v1
2021-11-09,Dynamics of hole singlet triplet qubits with large g-factor differences,"The spin-orbit interaction is the key element for electrically tunable spin
qubits. Here we probe the effect of cubic Rashba spin-orbit interaction on
mixing of the spin states by investigating singlet-triplet oscillations in a
planar Ge hole double quantum dot. By varying the magnetic field direction we
find an intriguing transformation of the funnel into a butterfly-shaped
pattern. Landau-Zener sweeps disentangle the Zeeman mixing effect from the
spin-orbit induced coupling and show that large singlet-triplet avoided
crossings do not imply a strong spin-orbit interaction. Our work emphasizes the
need for a complete knowledge of the energy landscape when working with hole
spin qubits.",2111.05130v1
2018-04-26,Orbital quantum magnetism in spin dynamics of strongly interacting magnetic lanthanide atoms,"Laser cooled lanthanide atoms are ideal candidates with which to study strong
and unconventional quantum magnetism with exotic phases. Here, we use
state-of-the-art closed-coupling simulations to model quantum magnetism for
pairs of ultracold spin-6 erbium lanthanide atoms placed in a deep optical
lattice. In contrast to the widely used single-channel Hubbard model
description of atoms and molecules in an optical lattice, we focus on the
single-site multi-channel spin evolution due to spin-dependent contact,
anisotropic van der Waals, and dipolar forces. This has allowed us to identify
the leading mechanism, orbital anisotropy, that governs molecular spin dynamics
among erbium atoms. The large magnetic moment and combined orbital angular
momentum of the 4f-shell electrons are responsible for these strong anisotropic
interactions and unconventional quantum magnetism. Multi-channel simulations of
magnetic Cr atoms under similar trapping conditions show that their
spin-evolution is controlled by spin-dependent contact interactions that are
distinct in nature from the orbital anisotropy in Er. The role of an external
magnetic field and the aspect ratio of the lattice site on spin dynamics is
also investigated.",1804.10102v1
2013-11-29,Gate Tunable In- and Out-Of-Plane Spin-Orbit Coupling and Spin Splitting Anisotropy at LaAlO3/SrTiO3 (110) Interface,"Manipulating spin-orbit coupling (SOC) is important for devices such as
spin-orbit torque based memory and its understanding is neccessary to answer
several fundamental open questions in triplet state superconductivity,
topological insulators and Majorana fermions. Here we report spin splitting of
25 meV at the LaAlO3/SrTiO3 (110) interface for in-plane spins at a current
density of 1.4x104 A/cm2, which is large compared to that found in
semiconductor heterostructures or the LaAlO3/SrTiO3 (100) interface, and in
addition it is anisotropic. The anisotropy arises from the difference in
electron effective mass along the [001] and [1-10] directions. Our study
predicts a spin splitting energy > 1000 meV at a current density of 107 A/cm2,
which is enormous compared to metallic systems and will be an ideal spin
polarized source. In addition to the in-plane effect, there is an unexpected
gate-tunable out-of-plane SOC at the LaAlO3/SrTiO3 (110) interface when the
spins lie out-of-plane due to broken symmetry in the plane of the interface. We
demonstrate that this can be manipulated by varying the LaAlO3 thickness
showing that this interface can be engineered for spin-orbit torque devices.",1311.7532v3
2014-08-31,Effect of the spin-orbit interaction on flows in heavy-ion collisions at intermediate energies,"The effect of the spin-orbit coupling in heavy ion collisions is investigated
based on an updated version of the ultra-relativistic quantum molecular
dynamics (UrQMD) model, in which the Skyrme potential energy density functional
is employed. And in special, the spin-orbit coupling effects on the directed
and elliptic flows of free nucleons emitted from $^{197}$Au+$^{197}$Au
collisions as functions of both the beam energy and the impact parameter are
studied. Our results show that the net contribution of the spin-orbit term to
flows of nucleons is negligible, whereas a directed flow splitting between
spin-up and spin-down nucleons is visible especially at large impact parameters
and a peak of the splitting is found at the beam energy around 150
MeV$/$nucleon. We also found that the directed flow splitting between spin-up
and spin-down neutrons is comparable with the neutron directed flow difference
calculated by a soft and a stiff symmetry energy, indicating that the directed
flow of neutrons cannot be used to pin down the stiffness of symmetry energy
any more without considering the spin degree of freedom in models in case of
spin polarization.",1409.0188v1
2023-07-10,Spin transport properties of spinel vanadate-based heterostructures,"Spin-orbit coupling and breaking of inversion symmetry are necessary
ingredients to enable a pure spin current-based manipulation of the
magnetization via the spin-orbit torque effect. Currently, magnetic insulator
oxides with non-dissipative characteristics are being explored. When combined
with non-magnetic heavy metals, known for their large spin-orbit coupling, they
offer promising potential for energy-efficient spin-orbitronics applications.
The intrinsic electronic correlations characterizing those strongly correlated
oxides hold the promises to add extra control-knobs to the desired efficient
spin-wave propagation and abrupt magnetization switching phenomena. Spinel
vanadate FeV2O4 (FVO) exhibits several structural phase transitions which are
accompanied by an intricate interplay of magnetic, charge and orbital
orderings. When grown as a thin film onto SrTiO3, the compressive strain state
induces a perpendicular magnetic anisotropy, making FVO-based heterostructures
desirable for spin-orbitronics applications. In this study, we have optimised
the deposition of stoichiometric and epitaxial Pt/FVO heterostructures by
Pulsed Laser Deposition and examined their spin-related phenomena. From
angle-dependent magnetotransport measurements, we observed both Anisotropic
Magnetoresistance (AMR) and Spin Hall Magnetoresistance (SMR) effects. Our
findings show the SMR component as the primary contributor to the overall
magnetoresistance, whose high value of 0.12% is only comparable to properly
optimized oxide-based systems.",2307.04389v1
2014-06-16,Early Excitation of Spin-Orbit Misalignments in Close-in Planetary Systems,"Continued observational characterization of transiting planets that reside in
close proximity to their host stars has shown that a substantial fraction of
such objects posses orbits that are inclined with respect to the spin axes of
their stars. Mounting evidence for the wide-spread nature of this phenomenon
has challenged the conventional notion that large-scale orbital transport
occurs during the early epochs of planet formation and is accomplished via
planet-disk interactions. However, recent work has shown that the excitation of
spin-orbit misalignment between protoplanetary nebulae and their host stars can
naturally arise from gravitational perturbations in multi-stellar systems as
well as magnetic disk-star coupling. In this work, we examine these processes
in tandem. We begin with a thorough exploration of the
gravitationally-facilitated acquisition of spin-orbit misalignment and
analytically show that the entire possible range of misalignments can be
trivially reproduced. Moreover, we demonstrate that the observable spin-orbit
misalignment only depends on the primordial disk-binary orbit inclination.
Subsequently, we augment our treatment by accounting for magnetic torques and
show that more exotic dynamical evolution is possible, provided favorable
conditions for magnetic tilting. Cumulatively, our results suggest that
observed spin-orbit misalignments are fully consistent with disk-driven
migration as a dominant mechanism for the origin of close-in planets.",1406.4183v1
2019-10-01,Complete reversal of the atomic unquenched orbital moment by a single electron,"The orbital angular moment of magnetic atoms adsorbed on surfaces is often
quenched as a result of an anisotropic crystal field. Due to spin-orbit
coupling, what remains of the orbital moment typically delineates the
orientation of the electron spin. These two effects limit the scope of
information processing based on these atoms to essentially only one magnetic
degree of freedom: the spin. In this work, we gain independent access to both
the spin and orbital degrees of freedom of a single atom, inciting and probing
excitations of each moment. By coordinating a single Fe atom atop the nitrogen
site of the Cu$_2$N lattice, we realize a single-atom system with a large
zero-field splitting--the largest reported for Fe atoms on surfaces--and an
unquenched uniaxial orbital moment that closely approaches the free-atom value.
We demonstrate a full reversal of the orbital moment through a single-electron
tunneling event between the tip and Fe atom, a process that is mediated by a
charged virtual state and leaves the spin unchanged. These results, which we
corroborate using density functional theory and first-principles multiplet
calculations, demonstrate independent control over the spin and orbital degrees
of freedom in a single-atom system.",1910.00325v2
1996-06-10,Surprises in the Orbital Magnetic Moment and g-Factor of the Dynamic Jahn-Teller Ion C_{60}^-,"We calculate the magnetic susceptibility and g-factor of the isolated
C_{60}^- ion at zero temperature, with a proper treatment of the dynamical
Jahn-Teller effect, and of the associated orbital angular momentum, Ham-reduced
gyromagnetic ratio, and molecular spin-orbit coupling. A number of surprises
emerge. First, the predicted molecular spin-orbit splitting is two orders of
magnitude smaller than in the bare carbon atom, due to the large radius of
curvature of the molecule. Second, this reduced spin-orbit splitting is
comparable to Zeeman energies, for instance, in X-band EPR at 3.39KGauss, and a
field dependence of the g-factor is predicted. Third, the orbital gyromagnetic
factor is strongly reduced by vibron coupling, and so therefore are the
effective weak-field g-factors of all low-lying states. In particular, the
ground-state doublet of C_{60}^- is predicted to show a negative g-factor of
\sim -0.1.",9606059v1
2014-07-03,A Poor Man's Derivation of Quantum Compass-Heisenberg Interaction: Superexchange Interaction in J-J Coupling Scheme,"The exchange interaction between 5d electrons in t$_{2g}$ orbitals is derived
in the J-J coupling scheme which is the appropriate basis in the case of strong
spin-orbit interaction. From simple calculations, it is found that
ferromagnetic Ising interaction (quantum compass model) occurs due to a
selection rule of hybridization between $\Gamma_7$ and $\Gamma_8$ orbitals,
while antiferromagnetic Heisenberg interaction appears from hybridization
between $\Gamma_7$ orbitals. It is also found that the ferromagnetic Ising
interaction becomes small as the spin-orbit interaction increases. Thus, the
sign of exchange interaction changes from ferromagnetic Ising to
antiferromagnetic Heisenberg interaction as the spin-orbit interaction
increases.",1407.0811v1
2014-05-19,Strain and Spin-Orbit Coupling Induced Orbital-Ordering in Mott Insulator BaCrO3,"Using ab initio calculations, we have investigated an insulating tetragonally
distorted perovskite BaCrO$_3$ with a formal $3d^2$ configuration, the volume
of which is apparently substantially enhanced by a strain due to SrTiO$_3$
substrate. Inclusion of both correlation and spin-orbit coupling (SOC) effects
leads to a metal-insulator transition and in-plane zigzag orbital-ordering (OO)
of alternating singly filled $d_{xz}+id_{yz}$ and $d_{xz}-id_{yz}$ orbitals,
which results in a large orbital moment $M_L$ ~ -0.78 $\mu_B$ antialigned to
the spin moment $M_S$ ~ $2|M_L|$ in Cr ions. Remarkably, this ordering also
induces a considerable $M_L$ for apical oxygens. Our findings show
metal-insulator and OO transitions, driven by an interplay among strain,
correlation, and SOC, which is uncommon in 3d systems.",1405.4593v2
2019-11-05,"Internal magnetic fields, spin-orbit coupling, and orbital period modulation in close binary systems","We introduce a new model to explain the modulation of the orbital period
observed in close stellar binary systems based on an angular momentum exchange
between the spin of the active component and the orbital motion. This
spin-orbit coupling is not due to tides, but is produced by a non-axisymmetric
component of the gravitational quadrupole moment of the active star due to a
persistent non-axisymmetric internal magnetic field. The proposed mechanism
easily satisfies all the energy constraints having an energy budget about
100-1000 times smaller than those of previously proposed models and is
supported by the observations of persistent active longitudes in the active
components of close binary systems. We present preliminary applications to
three well-studied binary systems to illustrate the model. The case of stars
with hot Jupiters is also discussed showing that no significant orbital period
modulation is generally expected on the basis of the proposed model.",1911.01757v3
2021-02-19,Local Observations of Orbital Diamagnetism and Excitation in Three-Dimensional Dirac Fermion Systems Bi$_{1-x}$Sb$_x$,"Dirac fermions display a singular response against magnetic and electric
fields. A distinct manifestation is large diamagnetism originating in the
interband effect of Bloch bands, as observed in bismuth alloys. Through
$^{209}$Bi NMR spectroscopy, we extract diamagnetic orbital susceptibility
inherent to Dirac fermions in the semiconducting bismuth alloys
Bi$_{1-x}$Sb$_x$ ($x = 0.08 - 0.16$). The $^{209}$Bi hyperfine coupling
constant provides an estimate of the effective orbital radius. In addition to
the interband diamagnetism, Knight shift includes an anomalous
temperature-independent term originating in the enhanced intraband diamagnetism
under strong spin-orbit coupling. The nuclear spin-lattice relaxation rate
$1/T_1$ is dominated by orbital excitation and follows cubic temperature
dependence in the extensive temperature range. The result demonstrates the
robust diamagnetism and low-lying orbital excitation against the small gap
opening, whereas $x$-dependent spin excitation appears at low temperatures.",2102.09917v1
2005-10-13,Theory of successive transitions in vanadium spinels and order of orbitals and spins,"We have theoretically studied successive transitions in vanadium spinel
oxides with (t_2g)^2 electron configuration. These compounds show a structural
transition at ~ 50K and an antiferromagnetic transition at ~ 40K. Since
threefold t_2g orbitals of vanadium cations are occupied partially and
vanadiums constitute a geometrically-frustrated pyrochlore lattice, the system
provides a particular example to investigate the interplay among spin, orbital
and lattice degrees of freedom on frustrated lattice. We examine the models
with the Jahn-Teller coupling and/or the spin-orbital superexchange
interaction, and conclude that keen competition between these two contributions
explains the thermodynamics of vanadium spinels. Effects of quantum
fluctuations as well as relativistic spin-orbit coupling are also discussed.",0510331v1
2013-04-08,Origin of the insulating state in honeycomb iridates and rhodates,"A burning question in the emerging field of spin-orbit driven insulating
iridates, such as Na2IrO3 and Li2IrO3 is whether the observed insulating state
should be classified as a Mott-Hubbard insulator derived from a half-filled
relativistic j_eff=1/2 band or as a band insulator where the gap is assisted by
spin-orbit interaction, or Coulomb correlations, or both. The difference
between these two interpretations is that only for the former, strong
spin-orbit coupling (lambda >~ W, where W is the band width) is essential. We
have synthesized the isostructural and isoelectronic Li2RhO3 and report its
electrical resistivity and magnetic susceptibility. Remarkably it shows
insulating behavior together with fluctuating effective S=1/2 moments, similar
to Na2IrO3 and Li2IrO3, although in Rh4+ (4d5) the spin-orbit coupling is
greatly reduced. We show that this behavior has non-relativistic one-electron
origin (although Coulomb correlations assist in opening the gap), and can be
traced down to formation of quasi-molecular orbitals, similar to those in
Na2IrO3.",1304.2258v3
2015-03-04,Gate induced enhancement of spin-orbit coupling in dilute fluorinated graphene,"We analyze the origin of spin-orbit coupling (SOC) in fluorinated graphene
using Density Functional Theory (DFT) and a tight-binding model for the
relevant orbitals. As it turns out, the dominant source of SOC is the atomic
spin-orbit of fluorine adatoms and not the impurity induced SOC based on the
distortion of the graphene plane as in hydrogenated graphene. More
interestingly, our DFT calculations show that SOC is strongly affected by both
the type and concentrations of the graphene's carriers, being enhanced by
electron doping and reduced by hole doping. This effect is due to the charge
transfer to the fluorine adatom and the consequent change in the
fluorine-carbon bonding. Our simple tight-binding model, that includes the SOC
of the $2p$ orbitals of F and effective parameters based on maximally localized
Wannier functions, is able to account for the effect. The strong enhancement of
the SOC induced by graphene doping opens the possibility to tune the spin
relaxation in this material.",1503.01395v1
2015-06-24,Origin of the Spin-Orbit Interaction,"We consider a semi-classical model to describe the origin of the spin-orbit
interaction in a simple system such as the hydrogen atom. The interaction
energy U is calculated in the rest-frame of the nucleus, around which an
electron, having linear velocity v and magnetic dipole-moment mu, travels in a
circular orbit. The interaction energy U is due to the coupling of the induced
electric dipole p=(v/c)x mu with the electric field En of the nucleus. Assuming
the radius of the electron's orbit remains constant during a spin-flip
transition, our model predicts that the energy of the system changes by Delta_E
= U/2, the factor 1/2 emerging naturally as a consequence of equilibrium and
the change of the kinetic energy of the electron. The correct 1/2 factor for
the spin-orbit coupling energy is thus derived without the need to invoke the
well-known Thomas precession in the rest-frame of the electron.",1506.07239v1
2017-06-26,Optically and electrically controllable adatom spin-orbital dynamics in transition metal dichalcogenides,"We analyze the interplay of spin-valley coupling, orbital physics and
magnetic anisotropy taking place at single magnetic atoms adsorbed on
semiconducting transition-metal dichalcogenides, MX$_2$ (M = Mo, W; X = S, Se).
Orbital selection rules turn out to govern the kinetic exchange coupling
between the adatom and charge carriers in the MX$_2$ and lead to highly
orbitally dependent spin-flip scattering rates, as we illustrate for the
example of transition metal adatoms with $d^9$ configuration. Our ab initio
calculations suggest that $d^9$ configurations are realizable by single Co, Rh,
or Ir adatoms on MoS$_2$, which additionally exhibit a sizable magnetic
anisotropy. We find that the interaction of the adatom with carriers in the
MX$_2$ allows to tune its behavior from a quantum regime with full Kondo
screening to a regime of ""Ising spintronics"" where its spin-orbital moment acts
as classical bit, which can be erased and written electronically and optically.",1706.08365v1
2020-08-08,Orbital tunable 0-$π$ transitions in Josephson junctions with noncentrosymmetric topological superconductors,"We investigate the Josephson transport properties in a Josephson junction
consisting of a conventional $s$-wave superconductor coupled to a multi-orbital
noncentrosymmetric superconductor marked by an orbitally driven inversion
asymmetry and isotropic interorbital spin-triplet pairing. Contrary to the
canonical single band noncentrosymmetric superconductor, we demonstrate that
the local interorbital spin-triplet pairing is tied to the occurrence of
sign-changing spin-singlet pair amplitude on different bands with $d$-wave
symmetry. Such multi-band $d^{\pm}$-wave state is a unique superconducting
configuration that drives unexpected Josephson effects with 0-$\pi$ transitions
displaying a high degree of electronic control. Remarkably, we find that the
phase state of a noncentrosymmetric/$s$-wave Josephson junction can be toggled
between 0 and $\pi$ in multiple ways through a variation of electron filling,
strength of the spin-orbital coupling, amplitude of the inversion asymmetry
interaction, and junction transparency. These results highlight an intrinsic
orbital and electrical tunability of the Josephson response and provide unique
paths to unveil the nature of unconventional multiorbital superconductivity as
well as inspire innovative designs of Josephson quantum devices.",2008.03482v2
2022-04-06,Influence of spin-orbit coupling on chemical bonding,"The influence of spin-orbit interaction on chemical bonds in elemental solids
and homonuclear dimers is analyzed by means of density-functional-theory
calculations. Employing highly precise all-electron full-potential methodology,
our results represent benchmark quality. Comparison of the scalar- and
fully-relativistic approaches for elemental solids shows that the spin-orbit
interaction may contract or expand the volume of the considered material. The
largest variation of the volume is obtained for Au, Tl, I, Bi, Po and Hg,
exhibiting changes between 1.0--7.6\%. Using the tight-binding model, we show
for diatomic molecules that the nature of this effect lies in the angular
rearrangement of bonding and antibonding orbitals introduced by spin-orbit
coupling. Such an angular rearrangement appears in partially filled $p$- or
$d$-orbitals in heavy elements. Finally, we discuss the impact of the
relativistic effects on the chemical bonding in single-layer iodides and
transition metal dichalcogenides",2204.02751v1
2011-11-14,Importance of including small body spin effects in the modelling of intermediate mass-ratio inspirals. II Accurate parameter extraction of strong sources using higher-order spin effects,"We improve the numerical kludge waveform model introduced in [1] in two ways.
We extend the equations of motion for spinning black hole binaries derived by
Saijo et al. [2] using spin-orbit and spin-spin couplings taken from
perturbative and post-Newtonian (PN) calculations at the highest order
available. We also include first-order conservative self-force corrections for
spin-orbit and spin-spin couplings, which are derived by comparison to PN
results. We generate the inspiral evolution using fluxes that include the most
recent calculations of small body spin corrections, spin-spin and spin-orbit
couplings and higher-order fits to solutions of the Teukolsky equation. Using a
simplified version of this model in [1], we found that small body spin effects
could be measured through gravitational wave observations from
intermediate-mass ratio inspirals (IMRIs) with mass ratio eta ~ 0.001, when
both binary components are rapidly rotating. In this paper we study in detail
how the spin of the small/big body affects parameter measurement using a
variety of mass and spin combinations for typical IMRIs sources. We find that
for IMRI events of a moderately rotating intermediate mass black hole (IMBH) of
ten thousand solar masses, and a rapidly rotating central supermassive black
hole (SMBH) of one million solar masses, gravitational wave observations made
with LISA at a fixed signal-to-noise ratio (SNR) of 1000 will be able to
determine the inspiralling IMBH mass, the central SMBH mass, the SMBH spin
magnitude, and the IMBH spin magnitude to within fractional errors of ~0.001,
0.001, 0.0001, and 9%, respectively. LISA can also determine the location of
the source in the sky and the SMBH spin orientation to within ~0.0001
steradians. We show that by including conservative corrections up to 2.5PN
order, systematic errors no longer dominate over statistical errors for IMRIs
with typical SNR ~1000.",1111.3243v3
2021-06-01,Spin Hall and inverse spin galvanic effects in graphene with strong interfacial spin-orbit coupling: a quasi-classical Green's function approach,"van der Waals heterostructures assembled from atomically thin crystals are
ideal model systems to study spin-orbital coupled transport because they
exhibit a strong interplay between spin, lattice and valley degrees of freedom
that can be manipulated by strain, electric bias and proximity effects. The
recently predicted spin-helical regime in graphene on transition metal
dichalcogenides, in which spin and pseudospin degrees of freedom are locked
together [M. Offidani et al. Phys. Rev. Lett. 119, 196801 (2017)], suggests
their potential application in spintronics. Here, by deriving an Eilenberger
equation for the quasiclassical Green's function of two-dimensional Dirac
fermions in the presence of} spin-orbit coupling\textcolor{black}{{} (SOC) and
scalar disorder, we obtain analytical expressions for the dc spin galvanic
susceptibility and spin Hall conductivity in the spin-helical regime. Our
results disclose a sign change in the spin Hall angle (SHA) when the Fermi
energy relative to the Dirac point matches the Bychkov-Rashba energy scale,
irrespective of the magnitude of the spin-valley interaction imprinted on the
graphene layer. The behavior of the SHA is connected to a reversal of the total
internal angular momentum of Bloch electrons that reflects the spin-pseudospin
entanglement induced by SOC. We also show that the charge-spin conversion
reaches a maximum when the Fermi level lies at the edge of the spin-minority
band in agreement with previous findings. Both features are fingerprints of
spin-helical Dirac fermions and suggest a direct way to estimate the strength
of proximity-induced SOC from transport data. The relevance of these findings
for interpreting recent spin-charge conversion measurements in nonlocal
spin-valve geometry is also discussed.",2106.00624v1
2023-04-29,Natural orbitals and two-particle correlators as tools for analysis of effective exchange couplings in solids,"Using generalizations of natural orbitals, spin-averaged natural orbitals,
and two-particle charge correlators for solids, we investigate electronic
structure of antiferromagnetic transition-metal oxides with a fully
self-consistent, finite-temperature GW method. Our findings disagree with
Goodenough-Kanamori (GK) rules, commonly used for qualitative interpretation of
such solids. First, we found a strong dependence of natural orbital occupancies
on momenta contradicting GK assumptions. Second, along the momentum path, the
character of natural orbitals changes. In particular, contributions of oxygen
2s orbitals are important, which has not been considered in the GK rules. To
analyze the influence of electronic correlation on the values of effective
exchange coupling constants, we use both natural orbitals and two-particle
correlators and show that electronic screening modulates the degree of
superexchange by stabilizing the charge-transfer contributions, greatly
affecting these coupling constants. Finally, we give a set of predictions and
recommendations regarding the use of density functional, Green's function, and
wave-function methods for evaluating effective magnetic couplings in molecules
and solids.",2305.00325v1
2020-04-15,Interfacial-hybridization-modified Ir Ferromagnetism and Electronic Structure in LaMnO$_3$/SrIrO$_3$ Superlattices,"Artificially fabricated 3$d$/5$d$ superlattices (SLs) involve both strong
electron correlation and spin-orbit coupling in one material by means of
interfacial 3$d$-5$d$ coupling, whose mechanism remains mostly unexplored. In
this work we investigated the mechanism of interfacial coupling in
LaMnO$_3$/SrIrO$_3$ SLs by several spectroscopic approaches. Hard x-ray
absorption, magnetic circular dichroism and photoemission spectra evidence the
systematic change of the Ir ferromagnetism and the electronic structure with
the change of the SL repetition period. First-principles calculations further
reveal the mechanism of the SL-period dependence of the interfacial electronic
structure and the local properties of the Ir moments, confirming that the
formation of Ir-Mn molecular orbital is responsible for the interfacial
coupling effects. The SL-period dependence of the ratio between spin and
orbital components of the Ir magnetic moments can be attributed to the
realignment of electron spin during the formation of the interfacial molecular
orbital. Our results clarify the nature of interfacial coupling in this
prototypical 3$d$/5$d$ SL system and the conclusion will shed light on the
study of other strongly correlated and spin-orbit coupled oxide
hetero-interfaces.",2004.06864v1
2015-04-21,Valley coupling in finite-length metallic single-wall carbon nanotubes,"Degeneracy of discrete energy levels of finite-length, metallic single-wall
carbon nanotubes depends on type of nanotubes, boundary condition, length of
nanotubes and spin-orbit interaction. Metal-1 nanotubes, in which two
non-equivalent valleys in the Brillouin zone have different orbital angular
momenta with respect to the tube axis, exhibits nearly fourfold degeneracy and
small lift of the degeneracy by the spin-orbit interaction reflecting the
decoupling of two valleys in the eigenfunctions. In metal-2 nanotubes, in which
the two valleys have the same orbital angular momentum, vernier-scale-like
spectra appear for boundaries of orthogonal-shaped edge or cap-termination
reflecting the strong valley coupling and the asymmetric velocities of the
Dirac states. Lift of the fourfold degeneracy by parity splitting overcomes the
spin-orbit interaction in shorter nanotubes with a so-called minimal boundary.
Slowly decaying evanescent modes appear in the energy gap induced by the
curvature of nanotube surface. Effective one-dimensional model reveals the role
of boundary on the valley coupling in the eigenfunctions.",1504.05337v1
2016-05-27,Functional renormalization group study of orbital fluctuation mediated superconductivity: Impact of the electron-boson coupling vertex corrections,"In various multiorbital systems, the emergence of the orbital fluctuations
and its role on the pairing mechanism attract increasing attention. To archive
deep understanding on these issues, we perform the
functional-renormalization-group (fRG) study for the two-orbital Hubbard model.
The vertex corrections for the electron-boson coupling ($U$-VC), which are
dropped in the Migdal-Eliashberg gap equation, are obtained by solving the RG
equation. We reveal that the dressed electron-boson coupling for the
charge-channel, $U_{eff}^c$, becomes much larger than the bare Coulomb
interaction, $U^0$, due to the $U$-VC in the presence of moderate spin
fluctuations. For this reason, the attractive pairing interaction due to the
charge or orbital fluctuations is enlarged by the factor $(U_{eff}^c/U^0)^2 >>
1$. In contrast, the spin fluctuation pairing interaction is suppressed by the
spin-channel $U$-VC, because of the relation $U_{eff}^s << U^0$. The present
study demonstrates that the orbital or charge fluctuation pairing mechanism can
be realized in various multiorbital systems thanks to the $U$-VC, such as in
Fe-based superconductors.",1605.08728v2
2020-01-23,Effect of Spin-Orbit Coupling on Decay Widths of Electronic Decay Processes,"Auger-Meitner processes are electronic decay processes of energetically
low-lying vacancies. In these processes, the vacancy is filled by an electron
of an energetically higher lying orbital, while another electron is
simultaneously emitted to the continuum. In low-lying orbitals relativistic
effects can not even be neglected for light elements. At the same time lifetime
calculations are computationally expensive. In this context, we investigate
which effect spin-orbit coupling has on Auger-Meitner decay widths and aim for
a rule of thumb for the relative decay widths of initial states split by
spin-orbit coupling. We base this rule of thumb on Auger-Meitner decay widths
of Sr4$p^{-1}$ and Ra6$p^{-1}$ obtained by relativistic FanoADC-Stieltjes
calculations.",2001.08441v2
2022-03-25,Spin-orbit coupling and crystal-field splitting in Ti-doped Ca2RuO4 studied by ellipsometry,"In Ca2RuO4, the competition of spin-orbit coupling $\zeta$ and tetragonal
crystal field splitting $\Delta_{CF}$ has been discussed controversially for
many years. The orbital occupation depends on $\Delta_{CF}/\zeta$, which allows
us to address this ratio via the optical spectral weights of the lowest
intersite Mott-Hubbard excitations. We study the optical conductivity of
Ca$_2$Ru$_{0.99}$Ti$_{0.01}$O$_4$ in the range of 0.75 - 5 eV by ellipsometry,
using the large single crystals that can be grown for small Ti concentrations.
Based on a local multiplet calculation, our analysis results in $2.4 \leq
\Delta_{CF}/\zeta \leq 4$ at 15 K. The dominant crystal field yields a ground
state close to xy orbital order but spin-orbit coupling is essential for a
quantitative description of the properties. Furthermore, we observe a
pronounced decrease of $\Delta_{CF}$ with increasing temperature, as expected
based on the reduction of octahedral distortions.",2203.13651v1
2021-07-09,Effect of Rashba spin-orbit and Rabi couplings on the excitation spectrum of binary Bose-Einstein condensates,"We present the collective excitation spectrum analysis of binary
Bose-Einstein condensates (BECs) with spin-orbit (SO) and Rabi couplings in a
quasi-two-dimensional system. In particular, we investigate the role of SO and
Rabi coupling strengths in determining the dynamical stability of the coupled
BECs using Bogoliubov-de Gennes (BdG) theory. Using the eigenergy of BdG
spectrum, we confirm the existence of phonon, roton, and maxon modes with weak
repulsive intra- and inter-species contact interactions. The depth of the
minimum corresponding to the roton mode depends strongly on the coupling
strength. We find that the increase of the SO coupling leads to instability,
while the increase in the Rabi coupling stabilizes the system. Also the
eigenvectors of BdG spectrum indicates the presence of density like mode in the
stable regime and spin like modes in unstable regimes. A phase diagram
demonstrating the stability regime in the plane of SO and Rabi coupling
strengths is obtained. Finally, we complement the observation of the excitation
spectrum with the direct numerical simulation results of coupled
Gross-Pitaevskii equations.",2107.04237v1
2013-06-15,The spin Hall effect in a quantum gas,"Electronic properties like current flow are generally independent of the
electron's spin angular momentum, an internal degree of freedom present in
quantum particles. The spin Hall effects (SHEs), first proposed 40 years ago,
are an unusual class of phenomena where flowing particles experience
orthogonally directed spin-dependent Lorentz-like forces, analogous to the
conventional Lorentz force for the Hall effect, but opposite in sign for two
spin states. Such spin Hall effects have been observed for electrons flowing in
spin-orbit coupled materials such as GaAs or InGaAs and for laser light
traversing dielectric junctions. Here we observe the spin Hall effect in a
quantum-degenerate Bose gas, and use the resulting spin-dependent Lorentz
forces to realize a cold-atom spin transistor. By engineering a spatially
inhomogeneous spin-orbit coupling field for our quantum gas, we explicitly
introduce and measure the requisite spin-dependent Lorentz forces, in excellent
agreement with our calculations. This atomtronic circuit element behaves as a
new type of velocity-insensitive adiabatic spin-selector, with potential
application in devices such as magnetic or inertial sensors. In addition, such
techniques --- for both creating and measuring the SHE --- are clear
prerequisites for engineering topological insulators and detecting their
associated quantized spin Hall effects in quantum gases. As implemented, our
system realized a laser-actuated analog to the Datta-Das spin transistor.",1306.3579v2
2013-12-26,Bulk topological insulators as inborn spintronics detectors,"Detection and manipulation of electrons' spins are key prerequisites for
spin-based electronics or spintronics. This is usually achieved by contacting
ferromagnets with metals or semiconductors, in which the relaxation of spins
due to spin-orbit coupling limits both the efficiency and the length scale. In
topological insulator materials, on the contrary, the spin-orbit coupling is so
strong that the spin direction uniquely determines the current direction, which
allows us to conceive a whole new scheme for spin detection and manipulation.
Nevertheless, even the most basic process, the spin injection into a
topological insulator from a ferromagnet, has not yet been demonstrated. Here
we report successful spin injection into the surface states of topological
insulators by using a spin pumping technique. By measuring the voltage that
shows up across the samples as a result of spin pumping, we demonstrate that a
spin-electricity conversion effect takes place in the surface states of
bulk-insulating topological insulators Bi1.5Sb0.5Te1.7Se1.3 and Sn-doped
Bi2Te2Se. In this process, due to the two-dimensional nature of the surface
state, there is no spin current along the perpendicular direction. Hence, the
mechanism of this phenomenon is different from the inverse spin Hall effect and
even predicts perfect conversion between spin and electricity at room
temperature. The present results reveal a great advantage of topological
insulators as inborn spintronics devices.",1312.7091v1
2016-04-07,Spin diffusion in p-type bilayer WSe$_2$,"We investigate the steady-state out-of-plane spin diffusion in p-type bilayer
WSe2 in the presence of the Rashba spin-orbit coupling and Hartree-Fock
effective magnetic field. The out-of-plane components of the Rashba spin-orbit
coupling serve as the opposite Zeeman-like fields in the two valleys. Together
with the identical Hartree-Fock effective magnetic fields, different total
effective magnetic field strengths in the two valleys are obtained. It is
further revealed that due to the valley-dependent total effective magnetic
field strength, similar (different) spin-diffusion lengths in the two valleys
are observed at small (large) spin injection. Nevertheless, it is shown that
the intervalley hole-phonon scattering can suppress the difference in the
spin-diffusion lengths at large spin injection due to the spin-conserving
intervalley charge transfers with the opposite transfer directions between
spin-up and -down holes. Moreover, with a fixed large pure spin injection, we
predict the build-up of a steady-state valley polarization during the spin
diffusion with the maximum along the diffusion direction being capable of
exceeding 1 %. It is revealed that the valley polarization arises from the
induced quasi hot-hole Fermi distributions with different effective hot-hole
temperatures between spin-up and -down holes during the spin diffusion, leading
to the different intervalley charge transfer rates in the opposite transfer
directions. Additionally, it is also shown that by increasing the injected spin
polarization, the hole density or the impurity density, the larger valley
polarization can be obtained.",1604.01892v2
2017-01-21,Stationary states and screening equations in the spin-Hall effect,"The characterization of the stationary states in the spin-Hall effect is
discussed within the framework of the phenomenological two spin-channel model.
It is shown that two different definitions of the stationary states can be
applied in the spin-Hall effect, leading to two different types of state in the
bulk: zero transverse spin-current or non-zero pure spin-current. This
difference is due to the treatment of the region near the edges, in which
electric charge accumulation occurs. The screening equations that describe the
accumulation of electric charges due to spin-orbit coupling are derived. The
spin-accumulation associated to spin-flip scattering and the spin-Hall
accumulation due to spin-orbit coupling are two independent effects if we
assume that the screening length is small with respect to the spin-diffusion
length. The corresponding transport equations are discussed in terms of the
Dyakonov-Perel equations.",1701.06017v3
2009-01-27,What can we learn about the dynamics of transported spins by measuring shot noise in spin-orbit-coupled nanostructures?,"We review recent studies of the shot noise of spin-polarized charge currents
and pure spin currents in multiterminal semiconductor nanostructures, while
focusing on the effects brought by the intrinsic Rashba spin-orbit (SO)
coupling and/or extrinsic SO scattering off impurities in two-dimensional
electron gas (2DEG) based devices. By generalizing the scattering theory of
quantum shot noise to include the full spin-density matrix of electrons
injected from a spin-filtering electrode, we show how decoherence and dephasing
in the course of spin precession can lead to substantial enhancement of the
Fano factor (noise-to-current ratio) of spin-polarized charge currents. In
four-terminal SO-coupled nanostructures, injection of unpolarized charge
current through the longitudinal leads is responsible not only for the pure
spin Hall current in the transverse leads, but also for nonequilibrium random
time-dependent current fluctuations. The analysis of the shot noise of
transverse pure spin Hall current and zero charge current, or transverse spin
current and non-zero charge Hall current, driven by unpolarized or
spin-polarized injected longitudinal charge current, respectively, reveals a
unique experimental tool to differentiate between the intrinsic Rashba and
extrinsic SO mechanisms underlying the spin Hall effect in 2DEG devices.
Finally, we discuss the shot noise of transverse spin and zero charge currents
in the quantum-interference-driven spin Hall effect in ballistic four-terminal
Aharonov-Casher rings realized using high-mobility 2DEG with the Rashba SO
coupling.",0901.4182v2
2020-10-07,Orbital isotropy of magnetic fluctuations in correlated electron materials induced by Hund's exchange coupling,"Characterizing non-local magnetic fluctuations in materials with strong
electronic Coulomb interactions remains one of the major outstanding challenges
of modern condensed matter theory. In this work we address the spatial symmetry
and orbital structure of magnetic fluctuations in perovskite materials. To this
aim, we develop a consistent multi-orbital diagrammatic extension of dynamical
mean field theory, which we apply to an anisotropic three-orbital model of
cubic $t_{2g}$ symmetry. We find that the form of spatial spin fluctuations is
governed by the local Hund's coupling. For small values of the coupling,
magnetic fluctuations are anisotropic in orbital space, which reflects the
symmetry of the considered $t_{2g}$ model. Large Hund's coupling enhances
collective spin excitations, which mixes orbital and spatial degrees of
freedom, and magnetic fluctuations become orbitally isotropic. Remarkably, this
effect can be seen only in two-particle quantities; single-particle observables
remain anisotropic for any value of the Hund's coupling. Importantly, we find
that the orbital isotropy can be induced both, at half-filling and for the case
of $4$ electrons per lattice site, where the magnetic instability is associated
with different, antiferromagnetic and ferromagnetic modes, respectively.",2010.03433v4
2007-03-22,Orbital contribution to the magnetic properties of iron as a function of dimensionality,"The orbital contribution to the magnetic properties of Fe in systems of
decreasing dimensionality (bulk, surfaces, wire and free clusters) is
investigated using a tight-binding hamiltonian in an $s, p,$ and $d$ atomic
orbital basis set including spin-orbit coupling and intra-atomic electronic
interactions in the full Hartree-Fock (HF) scheme, i.e., involving all the
matrix elements of the Coulomb interaction with their exact orbital dependence.
Spin and orbital magnetic moments and the magnetocrystalline anisotropy energy
(MAE) are calculated for several orientations of the magnetization. The results
are systematically compared with those of simplified hamiltonians which give
results close to those obtained from the local spin density approximation. The
full HF decoupling leads to much larger orbital moments and MAE which can reach
values as large as 1$\mu_B$ and several tens of meV, respectively, in the
monatomic wire at the equilibrium distance. The reliability of the results
obtained by adding the so-called Orbital Polarization Ansatz (OPA) to the
simplified hamiltonians is also discussed. It is found that when the spin
magnetization is saturated the OPA results for the orbital moment are in
qualitative agreement with those of the full HF model. However there are large
discrepancies for the MAE, especially in clusters. Thus the full HF scheme must
be used to investigate the orbital magnetism and MAE of low dimensional
systems.",0703576v1
2003-11-13,Theory of Spin-Charge Coupled Transport in a Two-Dimensional Electron Gas with Rashba Spin-Orbit Interactions,"We use microscopic linear response theory to derive a set of equations that
provide a complete description of coupled spin and charge diffusive transport
in a two-dimensional electron gas (2DEG) with the Rashba spin-orbit (SO)
interaction. These equations capture a number of interrelated effects including
spin accumulation and diffusion, Dyakonov-Perel spin relaxation,
magnetoelectric, and spin-galvanic effects. They can be used under very general
circumstances to model transport experiments in 2DEG systems that involve
either electrical or optical spin injection. We comment on the relationship
between these equations and the exact spin and charge density operator
equations of motion. As an example of the application of our equations, we
consider a simple electrical spin injection experiment and show that a voltage
will develop between two ferromagnetic contacts if a spin-polarized current is
injected into a 2DEG, that depends on the relative magnetization orientation of
the contacts. This voltage is present even when the separation between the
contacts is larger than the spin diffusion length.",0311328v3
2020-01-02,Noncollinear Spintronics and Electric-Field Control: A Review,"Our world is composed of various materials with different structures, where
spin structures have been playing a pivotal role in spintronic devices of the
contemporary information technology. Apart from conventional collinear spin
materials such as collinear ferromagnets and collinear antiferromagnetically
coupled materials, noncollinear spintronic materials have emerged as hot spots
of research attention owing to exotic physical phenomena. In this Review, we
firstly introduce two types noncollinear spin structures, i.e., the chiral spin
structure that yields real-space Berry phases and the coplanar noncollinear
spin structure that could generate momentum-space Berry phases, and then move
to relevant novel physical phenomena including topological Hall effect,
anomalous Hall effect, multiferroic, Weyl fermions, spin-polarized current, and
spin Hall effect without spin-orbit coupling in these noncollinear spin
systems. Afterwards, we summarize and elaborate the electric-field control of
the noncollinear spin structure and related physical effects, which could
enable ultralow power spintronic devices in future. In the final outlook part,
we emphasize the importance and possible routes for experimentally detecting
the intriguing theoretically predicted spin-polarized current, verifying the
spin Hall effect in the absence of spin-orbit coupling and exploring the
anisotropic magnetoresistance and domain-wall-related magnetoresistance effects
for noncollinear antiferromagnetic materials.",2001.00321v1
2020-10-26,Spin Insulatronics,"Spin insulatronics covers efforts to generate, detect, control, and utilize
high-fidelity pure spin currents and excitations inside magnetic insulators.
Ultimately, the new findings may open doors for pure spin-based information and
communication technologies. The aim is to replace moving charges with dynamical
entities that utilize low-dissipation coherent and incoherent spin excitations
in antiferromagnetic and ferromagnetic insulators. The ambition is that the new
pure spin-based system will suffer reduced energy losses and operate at high
frequencies. In magnetic insulators, there are no mobile charge carriers that
can dissipate energy. Integration with conventional electronics is possible via
interface exchange interactions and spin-orbit couplings. In this way, the free
electrons in the metals couple to the localized spins in the magnetic
insulators. In turn, these links facilitate spin-transfer torques and
spin-orbit torques across metal-insulator interfaces and the associated
phenomena of spin-pumping and charge-pumping. The interface couplings also
connect the electron motion inside the metals with the spin fluctuations inside
the magnetic insulators. These features imply that the system can enable
unprecedented control of correlations resulting from the electron-magnon
interactions. We review recent developments to realize electric and thermal
generation, manipulation, detection, and control of pure spin information in
insulators.",2010.13512v1
2018-07-24,Microscopic Theory of Spin Relaxation Anisotropy in Graphene with Proximity-Induced Spin-Orbit Coupling,"Inducing sizable spin--orbit interactions in graphene by proximity effect is
establishing as a successful route to harnessing two-dimensional Dirac fermions
for spintronics. Semiconducting transition metal dichalcogenides (TMDs) are an
ideal complement to graphene because of their strong intrinsic spin--orbit
coupling (SOC) and spin/valley-selective light absorption, which allows
all-optical spin injection into graphene. In this study, we present a
microscopic theory of spin dynamics in weakly disordered graphene samples
subject to uniform proximity-induced SOC as realized in graphene/TMD bilayers.
A time-dependent perturbative treatment is employed to derive spin Bloch
equations governing the spin dynamics at high electronic density. Various
scenarios are predicted, depending on a delicate competition between
interface-induced Bychkov-Rashba and spin--valley (Zeeman-type) interactions
and the ratio of intra- to inter-valley scattering rates. For weak SOC compared
to the disorder-induced quasiparticle broadening, the anisotropy ratio of
out-of-plane to in-plane spin lifetimes
$\zeta=\tau_{s}^{\perp}/\tau_{s}^{\parallel}$ agrees qualitatively with a toy
model of spins in a weak fluctuating SOC field recently proposed by Cummings
and co-workers [PRL 119, 206601 (2017)]. In the opposite regime of
well-resolved SOC, qualitatively different formulae are obtained, which can be
tested in ultra-clean heterostructures characterized by uniform
proximity-induced SOC in the graphene layer.",1807.09275v1
2020-08-11,Impact of $\mathcal{T}$-symmetry on spin decoherence and control in a synthetic spin-orbit field,"The electrical control of a spin qubit in a quantum dot relies on spin-orbit
coupling (SOC), which could be either intrinsic to the underlying crystal
lattice or heterostructure, or extrinsic via, for example, a micro-magnet. Here
we show that a key difference between the intrinsic SOC and the synthetic SOC
introduced by a micro-magnet is their symmetry under time reversal.
Specifically, the time-reversal symmetry ($\mathcal{T}$-symmetry) of the
intrinsic SOC leads to not only the traditional van Vleck cancellation known
for spin relaxation, but also vanishing spin dephasing to the lowest order of
SOC, which we term as ""longitudinal spin-orbit field cancellation"". On the
other hand, the synthetic SOC from a micro-magnet breaks the
$\mathcal{T}$-symmetry, therefore eliminates both the ""van Vleck cancellation""
and the ""longitudinal spin-orbit field cancellation"". In other words, the
effective field $\vec\Omega$ experienced by the spin qubit does not depend on
the quantization magnetic field anymore, and a longitudinal component is
allowed for $\vec\Omega$ to the first order of SOC. Consequently, spin
relaxation and dephasing are qualitatively modified compared with the case of
the intrinsic SOC. Furthermore, the fidelity of electric-dipole spin resonance
based on $\vec\Omega$ could be optimized, with potential applications in
spin-based quantum computing.",2008.04671v2
2020-05-11,Photoinduced electronic and spin properties of two-dimensional electron gases with Rashba spin-orbit coupling under perpendicular magnetic fields,"We theoretically investigate photoinduced phenomena induced by time-periodic
driving fields in two-dimensional electron gases under perpendicular magnetic
fields with Rashba spin-orbit coupling. Using perturbation theory, we provide
analytical results for the Floquet-Landau energy spectrum appearing due to THz
radiation. By employing the resulting photo-modulated states, we compute the
dynamical evolution of the spin polarization function for an initially prepared
coherent state. We find that the interplay of the magnetic field, Rashba
spin-orbit interaction and THz radiation can lead to inversion of the spin
polarization. The dynamics also induces fractional revivals and non-trivial
beating patterns in the autocorrelation function due to interference of the
photo-modulated quantum states. We also calculate the transverse photo-assisted
conductivity in the linear response regime using Kubo formalism and analyze the
impact of the radiation field and Rashba spin-orbit interaction. In the static
limit, we find that our results reduce to well-known expressions of the
conductivity in non-relativistic and quasi-relativistic (topological insulator
surfaces) two-dimensional electron gas thoroughly described in the literature.
We discuss the possible experimental detection of our theoretical prediction
and their relevance for spin-orbit physics at high magnetic fields.",2005.05450v2
2021-10-18,Momentum-Space Spin Antivortex and Spin Transport in Monolayer Pb,"Non-trivial momentum-space spin texture of electrons can be induced by
spin-orbit coupling and underpins various spin transport phenomena, such as
current-induced spin polarization and spin Hall effect. In this work, we find a
non-trivial spin texture, spin anti-vortex, can appear at certain momenta on
the $\Gamma-\text K$ line in 2D monolayer Pb on top of SiC. Different from spin
vortex due to the band degeneracy in the Rashba model, the existence of this
spin anti-vortex is guaranteed by Poincare-Hopf theorem and thus topologically
stable. Accompanied with this spin anti-vortex, a Lifshtiz transition of Fermi
surfaces occur at certain momenta on the $\text K- \text M$ line, and both
phenomena are originated from the anti-crossing between the $j=1/2$ and $j=3/2$
bands. A rapid variation of the response coefficients for both the
current-induced spin polarization and spin Hall conductivity is found when the
Fermi energy is tuned around the spin anti-vortex. Our work demonstrates the
monolayer Pb as a potentially appealing platform for spintronic applications.",2110.08968v2
2015-12-10,Robust Zero Energy Bound States Localized at Magnetic Impurities in Iron-based Superconductors,"We investigate the effect of spin-orbit coupling on the in-gap bound states
localized at magnetic impurities in multi-band superconductors with
unconventional (sign-changed) and conventional (sign-unchanged) $s$-wave
pairing symmetry, which may be relevant to iron-based superconductors. Without
spin-orbit coupling, for spin-singlet superconductors it is known that such
bound states cross zero energy at a critical value of the impurity scattering
strength and acquire a finite spin-polarization. Moreover, the degenerate,
spin-polarized, zero energy bound states are unstable to applied Zeeman fields
as well as deviation of the impurity scattering strength away from criticality.
Using a T-matrix formalism as well as analytical arguments, we show that, in
the presence of spin-orbit coupling, the zero-energy bound states localized at
magnetic impurities in unconventional, sign-changed, $s$-wave superconductors
acquire surprising robustness to applied Zeeman fields and variation in the
impurity scattering strength, an effect which is absent in the conventional,
sign-unchanged, $s$-wave superconductors. Given that the iron-based multi-band
superconductors may possess a substantial spin-orbit coupling as seen in recent
experiments, our results may provide one possible explanation to the recent
observation of surprisingly robust zero bias scanning tunneling microscope
peaks localized at magnetic impurities in iron-based superconductors provided
the order parameter symmetry is sign changing $s_{+-}$-wave.",1512.03450v2
2021-07-09,Magnetoelectric torque and edge currents caused by spin-orbit coupling,"Using a tight-biding model, we elaborate that the previously discovered
out-of-plane polarized helical edge spin current caused by Rashba spin-orbit
coupling can be attributed to the fact that in a strip geometry, a positive
momentum eigenstate does not always have the same spin polarization at the edge
as the corresponding negative momentum eigenstate. In addition, in the presence
of a magnetization pointing perpendicular to the edge, an edge charge current
is produced, which can be chiral or nonchiral depending on whether the
magnetization lies in-plane or out-of-plane. The spin polarization near the
edge develops a transverse component orthogonal to the magnetization, which is
antisymmetric between the two edges and tends to cause a noncollinear magnetic
order between the two edges. If the magnetization only occupies a region near
one edge, or in an irregular shaped quantum dot, this transverse component has
a nonzero average, rendering a gate voltage-induced magnetoelectric torque
without the need of a bias voltage. We also argue that other types of
spin-orbit coupling that can be obtained from the Rashba type through a unitary
transformation, such as the Dresselhaus spin-orbit coupling, will have similar
effects too.",2107.04665v2
2023-10-26,Perfect crossed Andreev reflection in the proximitized graphene/superconductor/proximitized graphene junctions,"We study the crossed Andreev reflection and the nonlocal transport in the
proximitized graphene/supercondcutor/proximitized graphene junctions with the
pseudospin staggered potential and the intrinsic spin-orbit coupling. The
crossed Andreev reflection with the local Andreev reflection and the elastic
cotunneling being completely eliminated can be realized for the electrons with
the specific spin-valley index when the intrinsic spin-orbit couplings in the
left graphene and the right graphene possess the opposite sign. The perfect
crossed Andreev reflection with its probability equal to $100\%$ can be
obtained in the space consisting of the incident angle and the energy of the
electrons. The crossed conductance and its oscillation with the superconductor
length are also investigated. The energy ranges for the crossed Andreev
reflection without the local Andreev reflection and the elastic cotunneling are
clarified for the different magnitudes of the pseudospin potential and the
spin-orbit coupling. The spin-valley index of the electrons responsible for the
perfect crossed Andreev reflection can be switched by changing the sign of the
intrinsic spin-orbit coupling or exchanging the biases applied on the left
graphene and the right graphene. Our results are helpful for designing the
flexible and high-efficiency Cooper pair splitter based on the spin-valley
degree of freedom.",2310.17301v1
2005-02-09,Post-Newtonian gravitational radiation and equations of motion via direct integration of the relaxed Einstein equations. III. Radiation reaction for binary systems with spinning bodies,"Using post-Newtonian equations of motion for fluid bodies that include
radiation-reaction terms at 2.5 and 3.5 post-Newtonian (PN) order (O[(v/c)^5]
and O[(v/c)^7] beyond Newtonian order), we derive the equations of motion for
binary systems with spinning bodies. In particular we determine the effects of
radiation-reaction coupled to spin-orbit effects on the two-body equations of
motion, and on the evolution of the spins. For a suitable definition of spin,
we reproduce the standard equations of motion and spin-precession at the first
post-Newtonian order. At 3.5PN order, we determine the spin-orbit induced
reaction effects on the orbital motion, but we find that radiation damping has
no effect on either the magnitude or the direction of the spins. Using the
equations of motion, we find that the loss of total energy and total angular
momentum induced by spin-orbit effects precisely balances the radiative flux of
those quantities calculated by Kidder et al. The equations of motion may be
useful for evolving inspiraling orbits of compact spinning binaries.",0502039v2
2016-06-15,Quantum Computing with Acceptor Spins in Silicon,"The states of a boron acceptor near a Si/SiO2 interface, which bind two
low-energy Kramers pairs, have exceptional properties for encoding quantum
information and, with the aid of strain, both heavy hole and light hole-based
spin qubits can be designed. Whereas a light-hole spin qubit was introduced
recently [Phys. Rev. Lett. 116, 246801 (2016)], here we present analytical and
numerical results proving that a heavy-hole spin qubit can be reliably
initialised, rotated and entangled by electrical means alone. This is due to
strong Rashba-like spin-orbit interaction terms enabled by the interface
inversion asymmetry. Single qubit rotations rely on electric-dipole spin
resonance (EDSR), which is strongly enhanced by interface-induced spin-orbit
terms. Entanglement can be accomplished by Coulomb exchange, coupling to a
resonator, or spin-orbit induced dipole-dipole interactions. By analysing the
qubit sensitivity to charge noise, we demonstrate that interface-induced
spin-orbit terms are responsible for sweet spots in the dephasing time T2* as a
function of the top gate electric field, which are close to maxima in the EDSR
strength, where the EDSR gate has high fidelity. We show that both qubits can
be described using the same starting Hamiltonian, and by comparing their
properties we show that the complex interplay of bulk and interface-induced
spin-orbit terms allows a high degree of electrical control and makes acceptors
potential candidates for scalable quantum computation in Si.",1606.04697v1
2003-08-29,Landau Expansion for the Kugel-Khomskii $t_{2g}$ Hamiltonian,"The Kugel-Khomskii (KK) Hamiltonian for the titanates describes spin and
orbital superexchange interactions between $d^1$ ions in an ideal perovskite
structure in which the three $t_{2g}$ orbitals are degenerate in energy and
electron hopping is constrained by cubic site symmetry. In this paper we
implement a variational approach to mean-field theory in which each site, $i$,
has its own $n \times n$ single-site density matrix $\rhov(i)$, where $n$, the
number of allowed single-particle states, is 6 (3 orbital times 2 spin states).
The variational free energy from this 35 parameter density matrix is shown to
exhibit the unusual symmetries noted previously which lead to a
wavevector-dependent susceptibility for spins in $\alpha$ orbitals which is
dispersionless in the $q_\alpha$-direction. Thus, for the cubic KK model
itself, mean-field theory does not provide wavevector `selection', in agreement
with rigorous symmetry arguments. We consider the effect of including various
perturbations. When spin-orbit interactions are introduced, the susceptibility
has dispersion in all directions in ${\bf q}$-space, but the resulting
antiferromagnetic mean-field state is degenerate with respect to global
rotation of the staggered spin, implying that the spin-wave spectrum is
gapless. This possibly surprising conclusion is also consistent with rigorous
symmetry arguments. When next-nearest-neighbor hopping is included, staggered
moments of all orbitals appear, but the sum of these moments is zero, yielding
an exotic state with long-range order without long-range spin order. The effect
of a Hund's rule coupling of sufficient strength is to produce a state with
orbital order.",0308608v1
1997-10-31,Non-precessional spin-orbit effects on gravitational waves from inspiraling compact binaries to second post-Newtonian order,"We derive all second post-Newtonian (2PN), non-precessional effects of spin-
orbit coupling on the gravitational wave forms emitted by an inspiraling binary
composed of spinning, compact bodies in a quasicircular orbit. Previous post-
Newtonian calculations of spin-orbit effects (at 1.5PN order) relied on a fluid
description of the spinning bodies. We simplify the calculations by introducing
into post-Newtonian theory a delta-function description of the influence of the
spins on the bodies' energy-momentum tensor. This description was recently used
by Mino, Shibata, and Tanaka (MST) in Teukolsky-formalism analyses of particles
orbiting massive black holes, and is based on prior work by Dixon. We compute
the 2PN contributions to the wave forms by combining the MST energy-momentum
tensor with the formalism of Blanchet, Damour, and Iyer for evaluating the
binary's radiative multipoles, and with the well-known 1.5PN order equations of
motion for the binary. Our results contribute at 2PN order only to the
amplitudes of the wave forms. The secular evolution of the wave forms' phase,
the quantity most accurately measurable by LIGO, is not affected by our results
until 2.5PN order, at which point other spin-orbit effects also come into play.
We plan to evaluate the entire 2.5PN spin-orbit contribution to the secular
phase evolution in a future paper, using the techniques of this paper.",9710134v1
2018-08-19,Emergent quantum criticality from spin-orbital entanglement in $d^8$ Mott insulators: the case of a diamond lattice antiferromagnet,"Motivated by the recent activities on the Ni-based diamond lattice
antiferromagnet NiRh$_2$O$_4$, we theoretically explore on a general ground the
unique spin and orbital physics for the Ni$^{2+}$ ions with a $3d^8$ electron
configuration in the tetrahedral crystal field environment and on a diamond
lattice Mott insulator. The superexchange interaction between the local moments
usually favors magnetic orders. Due to the particular electron configuration of
the Ni$^{2+}$ ion with a partially filled upper $t_{2g}$ level and a fully
filled lower $e_g$ level, the atomic spin-orbit coupling becomes active at the
linear order and would favor a spin-orbital-entangled singlet with quenched
local moments in the single-ion limit. Thus, the spin-orbital entanglement
competes with the superexchange and could drive the system to a quantum
critical point that separates the spin-orbital singlet and the magnetic order.
We further explore the effects of magnetic field and uniaxial pressure. The
non-trivial response to the magnetic field is intimately tied to the underlying
spin-orbital structure of the local moments. We discuss the future experiments
such as doping and pressure, and point out the correspondence between different
electron configurations.",1808.06154v1
2023-09-16,Exploring orbital-charge conversion mediated by interfaces with copper through spin-orbital pumping,"We investigated how different materials affect the orbital-charge conversion
in heterostructures with the naturally oxidized cooper capping layer. When we
added a thin layer of $CuOx(3nm)$ onto yttrium iron garnet $(YIG)/W$ stacks, we
observed a significant reduction in the charge current signal measured by means
the spin pumping effect technique. This finding contrasts with the results of a
prior study conducted on YIG/Pt/CuOx, which reported the opposite effect. On
the other hand, when we added the same $CuOx(3nm)$ layer to $YIG/Ti(4nm)$
structures, there was not much change in the spin pumping signal. This occurred
because Ti does not generate much orbital current at the $Ti/CuOx$ interface,
unlike Pt, due to its weaker spin-orbit coupling. Interestingly, when we added
the $CuOx(3nm)$ layer to $SiO_{2}/Py(5nm)/Pt(4nm)$ structures, the spin pumping
signal increased. However, in $SiO_{2}/CuOx(3nm)/Pt(4nm)/Py(5nm)$ structures,
the signal decreased. Finally, we delve into a theoretical analysis of the spin
(orbital) Hall effect in YIG/Heavy-metal systems. These findings have the
potential to advance research in the innovative field of orbitronics and
contribute to the development of new technologies based on spin-orbital
conversion.",2309.08857v2
2023-11-22,Spin-orbit interaction driven terahertz nonlinear dynamics in transition metals,"The interplay of electric charge, spin, and orbital polarizations, coherently
driven by picosecond long oscillations of light fields in spin-orbit coupled
systems, is the foundation of emerging terahertz spintronics and orbitronics.
The essential rules for how terahertz light interacts with these systems in a
nonlinear way are still not understood. In this work, we demonstrate a
universally applicable electronic nonlinearity originating from spin-orbit
interactions in conducting materials, wherein the interplay of light-induced
spin and orbital textures manifests. We utilized terahertz harmonic generation
spectroscopy to investigate the nonlinear dynamics over picosecond timescales
in various transition metal films. We found that the terahertz harmonic
generation efficiency scales with the spin Hall conductivity in the studied
films, while the phase takes two possible values (shifted by {\pi}), depending
on the d-shell filling. These findings elucidate the fundamental mechanisms
governing non-equilibrium spin and orbital polarization dynamics at terahertz
frequencies, which is relevant for potential applications of terahertz spin-
and orbital-based devices.",2311.13272v1
2021-01-06,Analytically solvable model to the spin Hall effect with Rashba and Dresselhaus spin-orbit couplings,"When the Rashba and Dresslhaus spin-orbit coupling are both presented for a
two-dimensional electron in a perpendicular magnetic field, a striking
resemblance to anisotropic quantum Rabi model in quantum optics is found. We
perform a generalized Rashba coupling approximation to obtain a solvable
Hamiltonian by keeping the nearest-mixing terms of Laudau states, which is
reformulated in the similar form to that with only Rashba coupling. Each Landau
state becomes a new displaced-Fock state with a displacement shift instead of
the original Harmonic oscillator Fock state, yielding eigenstates in closed
form. Analytical energies are consistent with numerical ones in a wide range of
coupling strength even for a strong Zeeman splitting. In the presence of an
electric field, the spin conductance and the charge conductance obtained
analytically are in good agreements with the numerical results. As the
component of the Dresselhaus coupling increases, we find that the spin Hall
conductance exhibits a pronounced resonant peak at a larger value of the
inverse of the magnetic field. Meanwhile, the charge conductance exhibits a
series of plateaus as well as a jump at the resonant magnetic field. Our method
provides an easy-to-implement analytical treatment to two-dimensional electron
gas systems with both types of spin-orbit couplings.",2101.01906v1
2018-05-15,Spin-orbit-coupled Bose-Einstein condensates of rotating polar molecules,"An experimental proposal for realizing spin-orbit (SO) coupling of
pseudospin-1 in the ground manifold $^1\Sigma(\upsilon=0)$ of (bosonic)
bialkali polar molecules is presented. The three spin components are composed
of the ground rotational state and two substates from the first excited
rotational level. Using hyperfine resolved Raman processes through two select
excited states resonantly coupled by a microwave, an effective coupling between
the spin tensor and linear momentum is realized. The properties of
Bose-Einstein condensates for such SO-coupled molecules exhibiting dipolar
interactions are further explored. In addition to the SO-coupling-induced
stripe structures, the singly and doubly quantized vortex phases are found to
appear, implicating exciting opportunities for exploring novel quantum physics
using SO-coupled rotating polar molecules with dipolar interactions.",1805.05524v1
1998-12-22,Modified Double Exchange Model with Novel Spin and Orbital Coupling: Phase Diagram of The Manganites,"From a general model of the Mn oxides R_{1-x}A_{x}MnO_3, we derive an
effective Hamiltonian in the low-energy subspace using the projection operator
method, in which a novel coupling between the spin and orbital degrees of
freedom is included. A phase diagram for temperature T versus doping
concentration x is computed by means of Monte Carlo simulation. Our result is
consistent with experimental observations in the Mn oxides with relatively wide
conduction band, such as Pr_{1-x}Sr_{x} MnO_{3} and La_{1-x}Sr_{x}MnO_{3}.
According to the obtained orbital ordering, we also predict that the motion of
charge carriers transforms from three-dimensional to two-dimensional as x is
increased beyond a critical value.",9812374v1
2000-11-15,Numerical Renormalization Group Study of Kondo Effect in Unconventional Superconductors,"Orbital degrees of freedom of a Cooper pair play an important role in the
unconventional superconductivity. To elucidate the orbital effect in the Kondo
problem, we investigated a single magnetic impurity coupled to Cooper pairs
with a $p_x +i p_y$ ($d_{x^2-y^2}+id_{xy}$) symmetry using the numerical
renormalization group method. It is found that the ground state is always a
spin doublet. The analytical solution for the strong coupling limit explicitly
shows that the orbital dynamics of the Cooper pair generates the spin 1/2 of
the ground state.",0011256v2
2004-01-29,"Orbital Ordering, New Phases, and Stripe Formation in Doped Layered Nickelates","Ground-state properties of layered nickelates are investigated based on the
orbital-degenerate Hubbard model coupled with lattice distortions, by using
umerical techniques. The N\'eel state composed of spin S=1 ions is confirmed in
the undoped limit x=0. At x=1/2, novel antiferromagnetic states, called CE- and
E-type phases, are found by increasing the Hund's coupling. (3 x^2 - r^2 / 3
y^2 - r^2)-type orbital ordering is predicted to occur in a checkerboard-type
charge-ordered state. At x=1/3, both Coulombic and phononic interactions are
found to be important, since the former stabilizes the spin stripe, while the
latter leads to the striped charge-order.",0401596v1
2000-12-04,On the pre-RLO spin-orbit couplings in LMXBs,"We investigate the effect of orbital decay caused by nuclear expansion of a
(sub)giant star in synchronous binary system. We compare this effect with the
presence of a magnetic stellar wind and show that the additional transfer of
orbital angular momentum into spin angular momentum is relatively important --
especially since it has been shown that the effect of magnetic braking
saturates at short orbital periods.",0012077v1
2008-06-25,Hidden Orbital Liquid State Within Ferromagnetically Ordered Metallic SrRuO3,"We have experimentally found related anomalies in electrical resistivity, dc
and ac magnetic susceptibility, appearing deeply within ferromagnetically
ordered state in SrRuO3. Lack of Jahn-Teller distortion in this regime rules
out conventional orbital order, forcing one to describe these in terms of an
orbital liquid ground state coexisting with ferromagnetic spin order. We
suggest that weak spin-orbit coupling in such an unusual state underpins the
observed anomalies.",0806.4198v1
2016-03-06,Spin-Orbital Entangled Excitonic Insulators in $(t_{2g})^4$ Correlated Electron Systems,"We employ the multi-orbital dynamical mean-field theory to examine the ground
state of a three-orbital Hubbard model with a relativistic spin-orbit coupling
(SOC) at four electrons per site. We demonstrate that the interplay between the
strong electron correlations and the SOC induces a Van Vleck-type nonmagnetic
insulator and its magnetic exciton condensation. We also find in the moderate
electron correlation regime that the SOC induces another type of a nonmagnetic
excitonic insulator, in addition to a relativistic band insulator. The
characteristic features among these insulators are manifested in the momentum
resolved single-particle excitations, thus accessible by angle-resolved
photoemission spectroscopy experiments.",1603.01800v1
2005-11-11,Periodic-orbit bifurcations as the origin of nuclear deformations,"Semiclassical analysis of shell structures in realistic nuclear potentials
are presented using periodic-orbit theory. We adopted r^alpha potential model
and examined classical-quantum correspondence using Fourier transformation
technique. Spin-orbit coupling is also taken into account in the model
Hamiltonian. Gross shell structure for a certain combination of surface
diffuseness and spin-orbit parameters are investigated and its relation to
pseudospin symmetry is discussed. Analysis of superdeformed shell structure in
realistic model is also presented.",0511032v1
2001-09-27,Spin and orbital effects of Cooper pairs coupled to a single magnetic impurity,"The Kondo effect strongly depends on spin and orbital degrees of freedom of
unconventional superconductivity. We focus on the Kondo effect in the $p_x + i
p_y$-wave and $d_{x^2 - y^2} + i d_{xy}$-wave superconductors to compare the
magnetic properties of the spin-triplet and spin-singlet Cooper pairs. The
difference appears when both of the paired electrons couple to a local spin
directly. For the $p_x + i p_y$-wave, the ground state is always a spin doublet
for a $S_{\rm imp} = 1/2$ local spin, and it is always a spin singlet for
$S_{\rm imp} = 1$. The latter is due to uniaxial spin anisotropy of the triplet
Cooper pair. For the $d_{x^2 - y^2} + i d_{xy}$-wave, the interchange of ground
states occurs, which resembles a competition between the Kondo effect and the
superconducting energy gap in s-wave superconductors. Thus the internal degrees
of freedom of Cooper pairs give a variety to the Kondo effect.",0109513v2
2004-08-13,Spin precession due to spin-orbit coupling in a two-dimensional electron gas with spin injection via ideal quantum point contact,"We present the analytical result of the expectation value of spin resulting
from an injected spin polarized electron into a semi-infinitely extended 2DEG
plane with [001] growth geometry via ideal quantum point contact. Both the
Rashba and Dresselhaus spin-orbit couplings are taken into account. A pictorial
interpretation of the spin precession along certain transport directions is
given. The spin precession due to the Rashba term is found to be especially
interesting since it behaves simply like a windshield wiper which is very
different from the ordinary precession while that due to the Dresselhaus term
is shown to be crystallographic-direction-dependent. Some crystallographic
directions with interesting and handleable behavior of spin precession are
found and may imply certain applicability in spintronic devices.",0408315v2
2005-05-20,Persistent spin current in spin-orbit coupling systems in the absence of an external magnetic field,"The spin-orbit coupling systems with a zero magnetic field is studied under
the equilibrium situation, {\it i.e.}, without a voltage bias. A persistent
spin current is predicted to exist under most circumstances, although the
persistent charge current and the spin accumulation are identically zero. In
particular, a two-dimensional quantum wire is investigated in detail.
Surprisingly, a persistent spin current is found to flow along the confined
direction, due to the spin precession in accompany with the particle motion.
This provides an interesting example of constant spin flowing without inducing
a spin accumulation, contrary to common intuition.",0505517v2
2005-05-24,Current induced local spin polarization due to the spin-orbit coupling in a two dimensional narrow strip,"The current induced local spin polarization due to weak Rashba spin-orbit
coupling in narrow strip is studied. In the presence of longitudinal charge
current, local spin polarizations appear in the sample. The spin polarization
perpendicular to the plane has opposite sign near the two edges. The in-plane
spin polarization in the direction perpendicular to the sample edges also
appears, but does not change sign across the sample. From our scaling analysis
based on increasing the strip width, the out-of-plane spin polarization is
important mainly in a system of mesoscopic size, and thus appears not to be
associated with the spin-Hall effect in bulk samples.",0505576v1
2007-01-15,Spin-Current-Induced Charge Accumulation and Electric Current in Semiconductor Nanostructures with Rashba Spin-Orbit Coupling,"We demonstrate that the flow of a longitudinal spin current with different
spin polarization will induce different patterns of charge accumulation in a
two-terminal strip, or electric current distribution in a four-terminal
Hall-bar structure, of two-dimensional electron gas with Rashba spin-orbit
coupling (RSOC). For an in-plane polarized spin current, charges will
accumulate either by the two lateral edges or around the center of the strip
structure while, for an out-of-plain polarized spin current, charge densities
will show opposite signs by the two lateral edges leading to a Hall voltage.
Our calculation offers a new route to experimentally detect or differentiate
pure spin currents with various spin polarization.",0701344v2
2009-09-02,Spin relaxation and combined resonance in two-dimensional electron systems with spin-orbit disorder,"Disorder in spin-orbit (SO) coupling is an important feature of real
low-dimensional electron structures. We study spin relaxation due to such a
disorder as well as resulting abilities of spin manipulation. The spin
relaxation reveals quantum effects when the spatial scale of the randomness is
smaller than the electron wavelength. Due to the disorder in SO coupling, a
time-dependent external electric field generates a spatially random
spin-dependent perturbation. The resulting electric dipole spin resonance in a
two-dimensional electron gas leads to spin injection in a frequency range of
the order of the Fermi energy. These effects can be important for possible
applications in spintronics.",0909.0352v1
2012-03-12,Spin-filtered edge states in graphene,"Spin orbit coupling changes graphene, in principle, into a two-dimensional
topological insulator, also known as quantum spin Hall insulator. One of the
expected consequences is the existence of spin-filtered edge states that carry
dissipationless spin currents and undergo no back-scattering in the presence of
non-magnetic disorder, leading to quantization of conductance. Whereas, due to
the small size of spin orbit coupling in graphene, the experimental observation
of these remarkable predictions is unlikely, the theoretical understanding of
these spin-filtered states is shedding light on the electronic properties of
edge states in other two-dimensional quantum spin Hall insulators. Here we
review the effect of a variety of perturbations, like curvature, disorder, edge
reconstruction, edge crystallographic orientation, and Coulomb interactions on
the electronic properties of these spin filtered states.",1203.2479v1
2013-03-19,Reading charge transport from spin dynamics on the surface of topological insulator,"Resolving the conductance of the topological surface states (TSSs) from the
bulk contribution has been a great challenge for studying the transport
property of topological insulators. By developing a non-purturbative diffusion
equation that describes fully the spin-charge dynamics in the strong spin-orbit
coupling regime, we present a proposal to read the charge transport information
of TSSs from its spin dynamics which can be isolated from the bulk contribution
by time-resolved second harmonic generation pump-probe measurement. We
demonstrate the qualitatively different Dyaknov-Perel spin relaxation behavior
between the TSSs and the two-dimensional spin-orbit coupling electron gas. The
decay time of both in-plane and out-of-plane spin polarization is naturally
proved to be identical to the charge transport time. The out-of-plane spin
dynamics is shown to be in the experimentally reachable regime of the
femtosecond pump probe spectroscopy and thereby we suggest experiments to
detect the charge transport property of the TSSs from their unique spin
dynamics.",1303.4478v3
2017-01-26,Path to stable quantum spin liquids in spin-orbit coupled correlated materials,"The spin liquid phase is one of the prominent strongly interacting
topological phases of matter whose unambiguous confirmation is yet to be
reached despite intensive experimental efforts on numerous candidate materials.
Recently, a new family of correlated honeycomb materials, in which strong
spin-orbit coupling allows for various bond-dependent spin interactions, have
been promising candidates to realize the Kitaev spin liquid. Here we study a
model with bond-dependent spin interactions and show numerical evidence for the
existence of an extended quantum spin liquid region, which is possibly
connected to the Kitaev spin liquid state. These results are used to provide an
explanation of the scattering continuum seen in neutron scattering on
$\alpha$-RuCl$_3$.",1701.07837v2
2008-07-04,Quantum interference and spin polarization on Rashba double quantum dots,"We report on the quantum interference and spin accumulation on double quantum
dots with Rashba spin-orbit coupling and electron-electron interaction, based
on the Keldysh nonequilibrium Green function formalism. It is shown that Rashba
spin-orbit interaction can strongly affect the conductance spectrum. By
gradually increasing the Rashba parameter from zero, Fano resonances in strong
overlap regime continuously evolve to resolve antiresonances. This transition
is ascribed to the phase shift of couplings between molecular states and the
lead due to spin precession. We also show that both bias and Rashba effect
strengthen the induced spin polarization in this device. For particular energy
position, up- and down-spin electron occupation can intersect to form a
crossing point. Spin polarization on different side of this point has opposite
sign in consequence. The magnitude and direction of spin polarization are
therefore controllable by tuning the dot levels and the Rashba parameter
through gates.",0807.0670v1
2015-12-10,The Elliott-Yafet theory of spin relaxation generalized for large spin-orbit coupling,"We generalize the Elliott-Yafet (EY) theory of spin relaxation in metals with
inversion symmetry for the case of large spin-orbit coupling (SOC). The EY
theory treats the SOC to the lowest order but this approach breaks down for
metals of heavy elements (such as e.g. caesium or gold), where the SOC energy
is comparable to the relevant band-band separation energies. The generalized
theory is presented for a four-band model system without band dispersion, where
analytic formulae are attainable for arbitrary SOC for the relation between the
momentum- and spin-relaxation rates. As an extended description, we also
consider an empirical pseudopotential approximation where SOC is deduced from
the band potential (apart from an empirical scaling constant) and the
spin-relaxation rate can be obtained numerically. Both approaches recover the
usual EY theory for weak SOC and give that the spin-relaxation rate approaches
the momentum-relaxation rate in the limit of strong SOC. We argue that this
limit is realized in gold by analyzing spin relaxation data. A calculation of
the $g$-factor shows that the empirical Elliott-relation, which links the
$g$-factor and spin-relaxation rate, is retained even for strong SOC.",1512.03204v1
2017-07-14,Out-of-plane carrier spin in transition-metal dichalcogenides under electric current,"In a multilayer comprising ferromagnet and heavy metal, in-plane carrier spin
is induced by applied electric current owing to Rashba spin-orbit coupling,
while the out-of-plane component is absent. We propose the out-of-plane carrier
spin can emerge in ferromagnetic transition-metal dichalcogenides monolayer, by
symmetry arguments and first-principles calculations. An intrinsic spin-orbit
coupling in the monolayer provides valley-contrasting Zeeman-type spin
splitting for generating the vertical induced spin. The current direction can
be exploited to tune the induced spin, accompanied with valley polarization.
The exotic spin accumulation paves an accessible way for perpendicular
magnetization switching and electric control of valleys.",1707.04548v2
2017-10-26,Spin dynamics in helical molecules with non-linear interactions,"It is widely admitted that the helical conformation of certain chiral
molecules may induce a sizable spin selectivity observed in experiments. Spin
selectivity arises as a result of the interplay between a helicity-induced
spin-orbit coupling and electric dipole fields in the molecule. From the
theoretical point of view, different phenomena might affect the spin dynamics
in helical molecules, such as quantum dephasing, dissipation and the role of
metallic contacts. Previous studies neglected the local deformation of the
molecule about the carrier thus far, but this assumption seems unrealistic to
describe charge transport in molecular systems. We introduce an effective model
describing the electron spin dynamics in a deformable helical molecule with
weak spin-orbit coupling. We find that the electron-lattice interaction allows
the formation of stable solitons such as bright solitons with well defined spin
projection onto the molecule axis. We present a thorough study of these bright
solitons and analyze their possible impact on the spin dynamics in deformable
helical molecules.",1710.09582v1
2019-06-27,Perspectives of Electrically generated spin currents in ferromagnetic materials,"Spin-orbit coupling enables charge currents to give rise to spin currents and
vice versa, which has applications in non-volatile magnetic memories, miniature
microwave oscillators, thermoelectric converters and Terahertz devices. In the
past two decades, a considerable amount of research has focused on electrical
spin current generation in different types of nonmagnetic materials. However,
electrical spin current generation in ferromagnetic materials has only recently
been actively investigated. Due to the additional symmetry breaking by the
magnetization, ferromagnetic materials generate spin currents with different
orientations of spin direction from those observed in nonmagnetic materials.
Studies centered on ferromagnets where spin-orbit coupling plays an important
role in transport open new possibilities to generate and detect spin currents.
We summarize recent developments on this subject and discuss unanswered
questions in this emerging field.",1906.11772v1
2017-11-04,Hyperfine-phonon spin relaxation in a single-electron GaAs quantum dot,"Understanding and control of the spin relaxation time $T_1$ is among the key
challenges for spin based qubits. A larger $T_1$ is generally favored, setting
the fundamental upper limit to the qubit coherence and spin readout fidelity.
In GaAs quantum dots at low temperatures and high in-plane magnetic fields $B$,
the spin relaxation relies on phonon emission and spin-orbit coupling. The
characteristic dependence $T_1 \propto B^{-5}$ and pronounced $B$-field
anisotropy were already confirmed experimentally. However, it has also been
predicted 15 years ago that at low enough fields, the spin-orbit interaction is
replaced by the coupling to the nuclear spins, where the relaxation becomes
isotropic, and the scaling changes to $T_1 \propto B^{-3}$. We establish these
predictions experimentally, by measuring $T_1$ over an unprecedented range of
magnetic fields -- made possible by lower temperature -- and report a maximum
$T_1 = 57\pm15$ s at the lowest fields, setting a new record for the electron
spin lifetime in a nanostructure.",1711.01474v1
2020-09-11,Spin entanglement via STM current,"We consider a system of two spins under a scanning tunneling microscope bias
and derive its master equation. We find that the tunneling elements to the
electronic contacts (tip and substrate) generate an exchange interaction
between the spins, as well as a Dzyaloshinskii-Moriya interaction in the
presence of spin-orbit coupling. The tunnel current spectrum then shows
additional lines compared to conventional spin resonance experiments. When the
spins have degenerate Larmor frequencies and equal tunneling amplitudes
(without spin-orbit), there is a dark state with vanishing decay rate. The
coupling to the electronic environment generates significant spin-spin
entanglement via the dark state, even if the initial state is non-entangled.",2009.05452v2
2021-06-29,Spin-valley qubits in gated quantum dots in a single layer of transition metal dichalcogenides,"We develop a microscopic and atomistic theory of electron spin-based qubits
in gated quantum dots in a single layer of transition metal dichalcogenides.
The qubits are identified with two degenerate locked spin and valley states in
a gated quantum dot. The two-qubit states are accurately described using a
multi-million atom tight-binding model solved in wavevector space. The
spin-valley locking and strong spin-orbit coupling result in two degenerate
states, one of the qubit states being spin-down located at the $+K$ valley of
the Brillouin zone, and the other state located at the $-K$ valley with spin
up. We describe the qubit operations necessary to rotate the spin-valley qubit
as a combination of the applied vertical electric field, enabling spin-orbit
coupling in a single valley, with a lateral strongly localized valley-mixing
gate.",2106.15090v2
2021-07-22,Spin-orbit effects for compact binaries in scalar-tensor gravity,"Gravitational waves provide us with a new window into our Universe, and have
already been used to place strong constrains on the existence of light scalar
fields, which are a common feature in many alternative theories of gravity.
However, spin effects are still relatively unexplored in this context. In this
work, we construct an effective point-particle action for a generic spinning
body that can couple both conformally and disformally to a real scalar field,
and we show that requiring the existence of a self-consistent solution
automatically implies that if a scalar couples to the mass of a body, then it
must also couple to its spin. We then use well-established effective field
theory techniques to conduct a comprehensive study of spin-orbit effects in
binary systems to leading order in the post-Newtonian (PN) expansion. Focusing
on quasicircular nonprecessing binaries for simplicity, we systematically
compute all key quantities, including the conservative potential, the orbital
binding energy, the radiated power, and the gravitational-wave phase. We show
that depending on how strongly each member of the binary couples to the scalar,
the spin-orbit effects that are due to a conformal coupling first enter into
the phase at either 0.5PN or 1.5PN order, while those that arise from a
disformal coupling start at either 3.5PN or 4.5PN order. This suppression by
additional PN orders notwithstanding, we find that the disformal spin-orbit
terms can actually dominate over their conformal counterparts due to an
enhancement by a large prefactor. Accordingly, our results suggest that
upcoming gravitational-wave detectors could be sensitive to disformal
spin-orbit effects in double neutron star binaries if at least one of the two
bodies is sufficiently scalarised.",2107.10841v2
1997-12-31,Disorder-Induced Broadening of the Density of States for 2D Electrons with Strong Spin-Orbit Coupling,"We study theoretically the disorder-induced smearing of the density of states
in a two-dimensional electron system taking into account a spin-orbit term in
the Hamiltonian of a free electron. We show that the characteristic energy
scale for the smearing increases with increasing the spin-orbit coupling. We
also demonstrate that in the limit of a strong spin-orbit coupling the diagrams
with self-intersections give a parametrically small contribution to the
self-energy. As a result, the coherent potential approximation becomes
asymptotically exact in this limit. The tail of the density of states has the
energy scale which is much smaller than the magnitude of the smearing. We find
the shape of the tail using the instanton approach.",9712328v1
2001-05-10,Weak localization and conductance fluctuations of a chaotic quantum dot with tunable spin-orbit coupling,"In a two-dimensional quantum dot in a GaAs heterostructure, the spin-orbit
scattering rate is substantially reduced below the rate in a bulk
two-dimensional electron gas [B.I. Halperin et al, Phys. Rev. Lett. 86, 2106
(2001)]. Such a reduction can be undone if the spin-orbit coupling parameters
acquire a spatial dependence, which can be achieved, e.g., by a metal gate
covering only a part of the quantum dot. We calculate the effect of such
spatially non-uniform spin-orbit scattering on the weak localization correction
and the universal conductance fluctuations of a chaotic quantum dot coupled to
electron reservoirs by ballistic point contacts, in the presence of a magnetic
field parallel to the plane of the quantum dot.",0105222v3
2006-02-01,Screening properties of the two-dimensional electron gas with spin-orbit coupling,"We study screening properties of the two-dimensional electron gas with Rashba
spin-orbit coupling. Calculating the dielectric function within the random
phase approximation, we describe the new features of screening induced by
spin-orbit coupling, which are the extension of the region of particle-hole
excitations and the spin-orbit-induced suppression of collective modes. The
required polarization operator is calculated in an analytic form without any
approximations. Carefully deriving its static limit, we prove the absence of a
small-$q$ anomaly at zero frequency. On the basis of our results at finite
frequencies we establish the new boundaries of the particle-hole continuum and
calculate the SO-induced lifetime of collective modes such as plasmons and
longitudinal optical phonons. According to our estimates, these effects can be
resolved in inelastic Raman scattering. We evaluate the experimentally
measurable dynamic structure factor and establish the range of parameters where
the described phenomena are mostly pronounced.",0602029v2
2006-03-02,Optical Conductivity of a Two-Dimensional Electron Liquid with Spin-Orbit Interaction,"The interplay of electron-electron interactions and spin-orbit coupling leads
to a new contribution to the homogeneous optical conductivity of the electron
liquid. The latter is known to be insensitive to many-body effects for a
conventional electron system with parabolic dispersion. The parabolic spectrum
has its origin in the Galilean invariance which is broken by spin-orbit
coupling. This opens up a possibility for the optical conductivity to probe
electron-electron interactions. We analyze the interplay of interactions and
spin-orbit coupling and obtain optical conductivity beyond RPA.",0603058v3
2008-01-31,Singlet-Triplet Relaxation in Two-electron Silicon Quantum Dots,"We investigate the singlet-triplet relaxation process of a two electron
silicon quantum dot. In the absence of a perpendicular magnetic field, we find
that spin-orbit coupling is not the main source of singlet-triplet relaxation.
Relaxation in this regime occurs mainly via virtual states and is due to
nuclear hyperfine coupling. In the presence of an external magnetic field
perpendicular to the plane of the dot, the spin-orbit coupling is important and
virtual states are not required. We find that there can be strong anisotropy
for different field directions: parallel magnetic field can increase
substantially the relaxation time due to Zeeman splitting, but when the
magnetic field is applied perpendicular to the plane, the enhancement of the
spin-orbit effect shortens the relaxation time. We find the relaxation to be
orders of magnitude longer than for GaAs quantum dots, due to weaker hyperfine
and spin-orbit effects.",0801.4898v1
2009-11-15,Interplay between Kondo physics and spin-orbit coupling in carbon nanotube quantum dots,"We investigate the influence of spin-orbit coupling on the Kondo effects in
carbon nanotube quantum dots, using the numerical renormalization group
technique. A sufficiently large spin-orbit coupling is shown to destroy the
SU(4) Kondo effects at zero magnetic field, leaving only two SU(2) Kondo
effects in the one- and three-electron Coulomb blockade valleys. On applying a
finite magnetic field, two additional, spin-orbit induced SU(2) Kondo effects
arise in the three- and two-electron valleys. Using physically realistic model
parameters, we calculate the differential conductance over a range of gate
voltages, temperatures and fields. The results agree well with measurements
from two different experimental devices in the literature, and explain a number
of observations that are not described within the standard framework of the
SU(4) Anderson impurity model.",0911.2886v1
2010-11-06,Spin-orbit coupling and phase-coherence in InAs nanowires,"We investigated the magnetotransport of InAs nanowires grown by selective
area metal-organic vapor phase epitaxy. In the temperature range between 0.5
and 30 K reproducible fluctuations in the conductance upon variation of the
magnetic field or the back-gate voltage are observed, which are attributed to
electron interference effects in small disordered conductors. From the
correlation field of the magnetoconductance fluctuations the phase-coherence
length l_phi is determined. At the lowest temperatures l_phi is found to be at
least 300 nm, while for temperatures exceeding 2 K a monotonous decrease of
l_phi with temperature is observed. A direct observation of the weak
antilocalization effect indicating the presence of spin-orbit coupling is
masked by the strong magnetoconductance fluctuations. However, by averaging the
magnetoconductance over a range of gate voltages a clear peak in the
magnetoconductance due to the weak antilocalization effect was resolved. By
comparison of the experimental data to simulations based on a recursive
two-dimensional Green's function approach a spin-orbit scattering length of
approximately 70 nm was extracted, indicating the presence of strong spin-orbit
coupling.",1011.1556v1
2011-01-19,Exact solutions for a type of electron pairing model with spin-orbit interactions and Zeeman coupling,"A type of electron pairing model with spin-orbit interactions or Zeeman
coupling is solved exactly in the framework of Richardson ansatz. Based on the
exact solutions for the case with spin-orbit interactions, it is shown
rigorously that the pairing order parameter has always the $p+ip$-wave symmetry
regardless of the strength of pairing interaction, justifying an important
conclusion obtained by the mean field theory. Analytical results are derived
for two simple systems with respectively spin-orbit interactions and Zeeman
coupling.",1101.3740v4
2011-05-09,"Theoretical Comparison of Rashba Spin-Orbit Coupling in Digitally, Discretely, and Continuously Alloyed Nanostructures","Although most theoretical calculations of quantum wells with non-square
profiles assume that material composition is varied continuously, it is more
common in experiment to grow digital alloys. We compare the Rashba spin-orbit
interaction of triangular wells using continuous, discrete, and digital
alloying profiles in (001)-grown triangular InSb/Al_f(z)In_(1-f(z))Sb, finding
a very large difference between digital alloying and the others, including a
sign change in the Rashba spin-orbit coupling. We find that the interface
contribution to the Rashba spin-orbit coupling is much larger in the
continuously- and discretely-alloyed triangular quantum wells than in the
digitally-alloyed triangular wells, in which it is almost completely absent.
The electric field contribution, however, is quite similar in all three
systems. Due to a much stronger doping dependence in all three systems, the
electric field contribution dominates at higher dopings, although the very
large offset due to the near absence of interface contribution in
digitally-alloyed wells persists.",1105.1804v1
2012-08-10,Acoustic phonon-limited resistivity in spin-orbit coupled 2DEG: Deformation potential and piezoelectric scattering,"We study the interaction between electron and acoustic phonon in a Rashba
spin-orbit coupled two dimensional electron gas using Boltzmann transport
theory. Both deformation potential and piezoelectric scattering mechanisms are
considered in the Bloch-Gruneisen (BG) as well as in the equipartition (EP)
regimes. Effect of the Rashba spin-orbit interaction on the temperature
dependence of resistivity in the BG and EP regimes has been discussed. We find
effective exponent of the temperature dependence of the resistivity in the BG
regime decreases due to spin-orbit coupling.",1208.2151v3
2012-12-06,Phonon-drag thermopower and hot-electron energy-loss rate in a Rashba spin-orbit coupled two-dimensional electron system,"We theoretically study phonon-drag contribution to the thermoelectric power
and hot-electron energy-loss rate in a Rashba spin-orbit coupled
two-dimensional electron system (2DES) in the Bloch-Gruneisen (BG) regime. We
assume that electrons interact with longitudinal acoustic phonons through
deformation potential and with both longitudinal and transverse acoustic
phonons through piezoelectric potential. Effect of the Rashba spin-orbit
interaction on magnitude and temperature dependence of the phonon-drag
thermoelectric power and hot-electron energy-loss rate are discussed. We
numerically extract the exponent of temperature dependence of the phonon-drag
thermopower and the energy-loss rate. We find the exponents are strongly
suppressed due to the presence of the Rashba spin-orbit coupling.",1212.1303v2
2014-11-08,Spin and Orbital Magnetic Response on the Surface of a Topological Insulator,"Coupling of the spin and orbital degrees of freedom on the surface of a
strong three-dimensional insulator, on the one hand, and textured magnetic
configuration in an adjacent ferromagnetic film, on the other, is studied using
a combination of transport and thermodynamic considerations. Expressing
exchange coupling between the localized magnetic moments and Dirac electrons in
terms of the electrons' out-of-plane orbital and spin magnetizations, we relate
the thermodynamic properties of a general ferromagnetic spin texture to the
physics in the zeroth Landau level. Persistent currents carried by Dirac
electrons endow the magnetic texture with a Dzyaloshinski-Moriya interaction,
which exhibits a universal scaling form as a function of electron temperature,
chemical potential, and the time-reversal symmetry breaking gap. In addition,
the orbital motion of electrons establishes a direct magnetoelectric coupling
between the unscreened electric field and local magnetic order, which furnishes
complex long-ranged interactions within the magnetic film.",1411.2070v1
2016-06-11,Spin-Orbit Coupling and Spin Textures in Optical Superlattices,"We proposed and demonstrated a new approach for realizing spin orbit coupling
with ultracold atoms. We use orbital levels in a double well potential as
pseudospin states. Two-photon Raman transitions between left and right wells
induce spin-orbit coupling. This scheme does not require near resonant light,
features adjustable interactions by shaping the double well potential, and does
not depend on special properties of the atoms. A pseudospinor Bose-Einstein
condensate spontaneously acquires an antiferromagnetic pseudospin texture which
breaks the lattice symmetry similar to a supersolid.",1606.03514v2
2016-07-18,J-freezing and Hund's rules in spin-orbit-coupled multiorbital Hubbard models,"We investigate the phase diagram of the spin-orbit-coupled three orbital
Hubbard model at arbitrary filling by means of dynamical mean-field theory
combined with continuous-time quantum Monte Carlo. We find that the
spin-freezing crossover occurring in the metallic phase of the non-relativistic
multiorbital Hubbard model can be generalized to a $\mathbf{J}$-freezing
crossover, with $\mathbf{J}=\mathbf{L}+\mathbf{S}$, in the spin-orbit-coupled
case. In the $\mathbf{J}$-frozen regime the correlated electrons exhibit a
non-trivial flavor selectivity and energy dependence. Furthermore, in the
regions near $n=2$ and $n=4$ the metallic states are qualitatively different
from each other, which reflects the atomic Hund's third rule. Finally, we
explore the appearance of magnetic order from exciton condensation at $n=4$ and
discuss the relevance of our results for real materials.",1607.05196v2
2016-09-21,Brillouin-Wigner Theory for Floquet Topological Phase Transitions in Spin-orbit Coupled Materials,"We develop the high frequency expansion based on the Brillouin-Wigner (B-W)
perturbation theory for driven systems with spin-orbit coupling which is
applicable to the cases of silicene, germanene and stanene. We compute the
effective Hamiltonian in the zero photon subspace not only to order
$O(\omega^{-1})$, but by keeping all the important terms to order
$O(\omega^{-2})$, and obtain the photo-assisted correction terms to both the
hopping and the spin-orbit terms, as well as new longer ranged hopping terms.
We then use the effective static Hamiltonian to compute the phase diagram in
the high frequency limit and compare it with the results of direct numerical
computation of the Chern numbers of the Floquet bands, and show that at
sufficiently large frequencies, the B-W theory high frequency expansion works
well even in the presence of spin-orbit coupling terms.",1609.06504v1
2014-03-26,Parity violation in ferromagnet-superconductor heterostructures with strong spin-orbit coupling,"We study spectroscopic properties of ferromagnetic-superconductor
heterostructures with strong spin-orbit coupling of the Rashba type and in the
presence of exchange fields. The superconducting layer (film) experiences both
an intrinsic spin-orbit field and an exchange field due to the proximity to
ferromagnetic layers (films). We analyse the temperature dependence of the
order parameter for superconductivity at various values of exchange field and
spin-orbit coupling, and describe momentum-dependent properties that exhibit
parity violation. Furthermore, we show that parity violation can be probed in
tunneling experiments of the single-particle density of states and in
photoemission experiments of the momentum distribution.",1403.6858v1
2017-01-28,Appropriate conditions to realize a $p$-wave superfluid state starting from a spin-orbit coupled $s$-wave superfluid Fermi gas,"We theoretically investigate a spin-orbit coupled $s$-wave superfluid Fermi
gas, to examine the time evolution of the system, after an $s$-wave pairing
interaction is replaced by a $p$-wave one at $t=0$. In our recent paper, we
proposed that this manipulation may realize a $p$-wave superfluid Fermi gas,
because the $p$-wave pair amplitude that is induced in the $s$-wave superfluid
state by a parity-broken antisymmetric spin-orbit interaction gives a
non-vanishing $p$-wave superfluid order parameter, immediately after the
$p$-wave interaction is turned on. In this paper, using a time-dependent
Bogoliubov-de Gennes theory, we assess this idea under various conditions with
respect to the $s$-wave and $p$-wave interaction strengths, as well as the
spin-orbit coupling strength. From these, we clarify that the momentum
distribution of Fermi atoms in the initial $s$-wave state ($t<0$) is a key to
produce a large $p$-wave superfluid order parameter. Since the realization of a
$p$-wave superfluid state is one of the most exciting and difficult challenges
in cold Fermi gas physics, our results may provide a possible way to accomplish
this.",1701.08255v1
2014-05-20,High-Chern-number bands and tunable Dirac cones in $β$-graphyne,"Graphynes represent an emerging family of carbon allotropes that recently
attracted much interest due to the tunability of the Dirac cones in the band
structure. Here, we show that the spin-orbit couplings in $\beta$-graphyne
could produce various effects related to the topological properties of its
electronic bands. Intrinsic spin-orbit coupling yields high- and tunable
Chern-number bands, which may host both topological and Chern insulators, in
the presence and absence of time-reversal symmetry, respectively. Furthermore,
Rashba spin-orbit coupling can be used to control the position and the number
of Dirac cones in the Brillouin zone. These findings suggest that
spin-orbit-related physics in $\beta$-graphyne is very rich, and, in
particular, that this system could provide a platform for the realization of a
two-dimensional material with tunable topological properties.",1405.5039v2
2016-08-03,Magnetoanisotropic Josephson effect due to interfacial spin-orbit fields in superconductor/ferromagnet/superconductor junctions,"We study theoretically the effects of interfacial Rashba and Dresselhaus
spin-orbit coupling in superconductor/ferromagnet/superconductor (S/F/S)
Josephson junctions---with allowing for tunneling barriers between the
layers---by solving the Bogoljubov-de Gennes equation for a realistic
heterostructure and applying the Furusaki-Tsukada technique to calculate the
electric current at a finite temperature. The presence of spin-orbit couplings
leads to out- and in-plane magnetoanisotropies of the Josephson current, which
are giant in comparison to current magnetoanisotropies in similar normal-state
ferromagnet/normal metal (F/N) junctions. Especially huge anisotropies appear
in the vicinity of $ 0 $-$ \pi $ transitions, caused by the exchange-split
bands in the ferromagnetic metal layer. We also show that the direction of the
Josephson critical current can be controlled (inducing $ 0 $-$ \pi $
transitions) by the strength of the spin-orbit coupling and, more crucial, by
the orientation of the magnetization. Such a control can bring new
functionalities into Josephson junction devices.",1608.01218v2
2017-06-17,\emph{Ab initio} calculation of spin-orbit coupling for NV center in diamond exhibiting dynamic Jahn-Teller effect,"Point defects in solids may realize solid state quantum bits. The spin-orbit
coupling in these point defects plays a key role in the magneto-optical
properties that determine the conditions of quantum bit operation. However,
experimental data and methods do not directly yield this highly important data,
particularly, for such complex systems where dynamic Jahn-Teller (DJT) effect
damps the spin-orbit interaction. Here, we show for an exemplary quantum bit,
nitrogen-vacancy (NV) center in diamond, that \emph{ab initio} supercell
density functional theory provide quantitative prediction for the spin-orbit
coupling damped by DJT. We show that DJT is responsible for the multiple
intersystem crossing rates of NV center at cryogenic temperatures. Our results
pave the way toward optimizing solid state quantum bits for quantum information
processing and metrology applications.",1706.05523v2
2018-09-04,Experimental realization of a superfluid stripe phase in a spin-orbit-coupled Bose-Einstein condensate enabled by momentum-space hopping,"In the past few decades, the search for supersolid-like phases has attracted
great attention in condensed matter and ultracold atom communities. Here we
experimentally demonstrate a route for realizing a superfluid stripe-phase in a
spin-orbit coupled Bose-Einstein condensate by employing a weak optical lattice
to induce momentum-space hopping between two spin-orbit band minima. We
characterize the striped ground state as a function of lattice coupling
strength and spin-orbit detuning and find good agreement with mean-field
simulations. We observe coherent Rabi oscillations in momentum space between
two band minima and demonstrate a long lifetime of the ground state. Our work
offers an exciting new and stable experimental platform for exploring
superfluid stripe-phases and their exotic excitations, which may shed light on
the properties of supersolid-like states.",1809.01208v1
2000-06-28,"Doped two orbital chains with strong Hund's rule couplings - ferromagnetism, spin gap, singlet and triplet pairings","Different models for doping of two-orbital chains with mobile $S=1/2$
fermions and strong, ferromagnetic (FM) Hund's rule couplings stabilizing the
S=1 spins are investigated by density matrix renormalization group (DMRG)
methods. The competition between antiferromagnetic (AF) and FM order leads to a
rich phase diagram with a narrow FM region for weak AF couplings and strongly
enhanced triplet pairing correlations. Without a level difference between the
orbitals, the spin gap persists upon doping, whereas gapless spin excitations
are generated by interactions among itinerant polarons in the presence of a
level difference. In the charge sector we find dominant singlet pairing
correlations without a level difference, whereas upon the inclusion of a
Coulomb repulsion between the orbitals or with a level difference, charge
density wave (CDW) correlations decay slowest. The string correlation functions
remain finite upon doping for all models.",0006439v1
2017-11-15,"Spin-orbit coupling, minimal model and potential Cooper-pairing from repulsion in BiS$_2$-superconductors","We develop the realistic minimal electronic model for recently discovered
BiS$_2$ superconductors including the spin-orbit coupling based on a
first-principles band structure calculations. Due to strong spin-orbit
coupling, characteristic for the Bi-based systems, the tight-binding low-energy
model necessarily includes $p_x$, $p_y$, and $p_z$ orbitals. We analyze a
potential Cooper-pairing instability from purely repulsive interaction for the
moderate electronic correlations using the so-called leading angular harmonics
approximation (LAHA). For small and intermediate doping concentrations we find
the dominant instabilities to be $d_{x^2-y^2}$-wave, and $s_{\pm}$-wave
symmetries, respectively. At the same time, in the absence of the sizable spin
fluctuations the intra and interband Coulomb repulsion are of the same
strength, which yields the strongly anisotropic behaviour of the
superconducting gaps on the Fermi surface in agreement with recent ARPES
findings. In addition, we find that the Fermi surface topology for BiS$_2$
layered systems at large electron doping can resembles the doped iron-based
pnictide superconductors with electron and hole Fermi surfaces with sufficient
nesting between them. This could provide further boost to increase $T_c$ in
these systems.",1711.05454v1
2018-12-07,Flat bands and dynamical localization of spin-orbit coupled Bose-Einstein condensates,"Flat bands and dynamical localization of binary mixtures of Bose-Einstein
condensates, with spin-orbit coupling subjected to a deep optical lattice which
is shaking in time and to a periodic time modulation of the Zeeman field, are
investigated. In contrast with usual dynamical localization in the absence of
spin-orbit coupling, we find that to fully suppress the tunneling in the system
the optical lattice shaking is not enough, and a proper tuning of the
spin-orbit term, achievable via the Zeeman field modulation, is also required.
This leads to a sequence of Zeeman parameter values where energy bands become
flat, the tunneling in the system is suppressed, and the dynamical localization
phenomenon occurs. Exact wave functions at the dynamical localization points
show that the binary mixture localizes on a dimer with the two components
occupying different sites. This type of localization occurs in exact form also
for the ground state of the system at the dynamical localization points in the
presence of nonlinearity and remains valid, although in approximate form, for a
wide range of the Zeeman parameter around these points. The possibility of
observing the above phenomena in real experiments is also briefly discussed.",1812.03164v1
2018-12-17,Asymmetry and spin-orbit coupling of light scattered from subwavelength particles,"Light scattering and spin-orbit angular momentum coupling phenomena from
subwavelength objects, with electric and magnetic dipolar responses, are
receiving an increasing interest. Under illumination by circularly polarized
light, spin-orbit coupling effects have been shown to lead to significant
shifts between the measured and actual position of particles. Here we show that
the remarkable angular dependence of these ""optical mirages"" and those of the
intensity, degree of circular polarization (DoCP), and spin and orbital angular
momentum of scattered photons, are all linked and fully determined by the
dimensionless ""asymmetry parameter"" g, being independent of the specific
optical properties of the scatterer. Interestingly, for g different from 0, the
maxima of the optical mirage and angular momentum exchange take place at
different scattering angles. In addition we show that the g parameter is
exactly half of the DoCP at a right-angle scattering. This finding opens the
possibility to infer the whole angular properties of the scattered fields by a
single far-field polarization measurement.",1812.06812v1
2019-02-07,Modified spin-orbit couplings in uniaxially strained graphene,"Intrinsic and Rashba spin-orbit interactions in strained graphene is studied
within the tight-binding (TB) approach. Dependence of Slater-Koster (SK)
parameters of graphene on strain are extracted by fitting the \emph{ab initio}
band structure to the TB results. A generalized low-energy effective
Hamiltonian in the presence of spin-orbit couplings is proposed for strained
graphene subjected to an external perpendicular electric field. Dependence of
the modified Rashba strength and other parameters of effective Hamiltonian on
the strain and electric field are calculated. In order to analyze the influence
of the applied strain on the electronic properties of the graphene, one must
take into account the lattice deformation, modifications of the hopping
amplitudes and shift of the Dirac points. We find that using the strain it is
possible to control the strength of Rashba and intrinsic spin-orbit couplings
as well as energy gap at the shifted Dirac points. Meanwhile, the strain
slightly modifies the topology of low-energy dispersion around the Dirac
points. We describe the SOCs induced energy splitting as a function of strain.",1902.02656v1
2020-06-04,The Jahn-Teller effect and spin--orbit coupling: friends or foes?,"The Jahn-Teller effect is one of the most fundamental phenomena important not
only for physics, but also for chemistry and material science. Solving the
Jahn-Teller problem and taking into account strong electron correlations we
show that quantum entanglement of the spin and orbital degrees of freedom via
spin--orbit coupling strongly affects this effect. Depending on the number of
$d$ electrons it may quench (electronic configurations $t_{2g}^2$, $t_{2g}^4$,
and $t_{2g}^5$), partially suppress ($t_{2g}^1$) or in contrast induce
($t_{2g}^3$) Jahn-Teller distortions. Moreover, in certain situations,
interplay between the Jahn-Teller effect and spin--orbit coupling promotes
formation of the ""Mexican hat"" energy surface facilitating various quantum
phenomena.",2006.03097v1
2024-01-11,Josephson Junction of Nodal Superconductors with Rashba and Ising Spin-Orbit coupling,"We study the effect of a Rashba spin-orbit coupling on the nodal
superconducting phase of an Ising superconductor. Such nodal phase was
predicted to occur when applying an in-plane field beyond the Pauli limit to a
superconducting monolayer transition metal dichalcogenides (TMD). Generically,
Rashba spin-orbit is known to lift the chiral symmetry that protects the nodal
points, resulting in a fully gapped phase. However, when the magnetic field is
applied along the $\Gamma -K $ line, a residual vertical mirror symmetry
protects a nodal crystalline phase. We study a single-band tight-binding model
that captures the low energy physics around the $\Gamma $ pocket of monolayer
TMD. We calculate the topological properties, the edge state structure, and the
current phase relation in a Josephson junction geometry of the nodal
crystalline phase. We show that while the nodal crystalline phase is
characterized by localized edge modes on non-self-reflecting boundaries, the
current phase relation exhibits a trivial $2\pi $ periodicity in the presence
of Rashba spin-orbit coupling.",2401.05685v1
2007-08-14,Spin torque contribution to the a.c. spin Hall conductivity,"Using the recently proposed definition of a conserved spin-current operator
[J. Shi et al., Phys. Rev. Lett. 96, 076604 (2006)] we explore the frequency
dependent spin Hall conductivity for a two-dimensional electron gas with Rashba
and Dresselhaus spin-orbit interaction in response to an oscillating electric
field. We show that the optical spectrum of the spin Hall conductivity exhibit
remarkable changes when the new definition of spin current is applied. Such
behavior is mainly due to a significant contribution of the spin torque term
which is absent in the conventional form of the spin current. In addition, it
is observed that the magnitude and direction of the dynamic spin Hall current
strongly depends on the electric field frequency as with the interplay of the
spin-orbit coupling strengths.",0708.1957v2
2007-11-14,Spin-Hall conductivity of a spin-polarized two-dimensional electron gas with Rashba spin-orbit interaction and magnetic impurities,"The Kubo formula is used to calculate the spin-Hall conductivity in a
spin-polarized two-dimensional electron system with Rashba-type spin-orbit
interaction. As in the case of the unpolarized electron system, spin Hall
conductivity is entirely determined by states at the Fermi level, a property
that persists in the presence of magnetic impurities. In the clean limit, the
spin-Hall conductivity decreases monotonically with the Zeeman splitting, a
result of the ordering effect on the electron spins produced by the magnetic
field. In the presence of magnetic impurities, the spin-dependent scattering
determines a finite renormalization of the static part of the fully dressed
vertex correction of the velocity operator that leads to an enhancement of the
\sigma_{sH}, an opposite behaviour to that registered in the presence of
spin-independent disorder. The variation of \sigma_{sH} with the strength of
the Rashba coupling and the Zeeman splitting is studied.",0711.2127v2
2011-01-31,Spontaneous Emergence of Persistent Spin Helix from Homogeneous Spin Polarization,"We demonstrate that a homogeneous spin polarization in one-dimensional
structures of finite length in the presence of Bychkov-Rashba spin-orbit
coupling decays spontaneously toward a persistent spin helix. The analysis of
formation of spin helical state is presented within a novel approach based on a
mapping of spin drift-diffusion equations into a heat equation for a complex
field. Such a strikingly different and simple method allows generating robust
spin structures whose properties can be tuned by the strength of the spin orbit
interaction and/or structure's length. We generalize our results for
two-dimensional case predicting formation of persistent spin helix in
two-dimensional channels from homogeneous spin polarization.",1102.0039v1
2013-11-27,Spin transistor operation driven by the Rashba spin-orbit coupling in the gated nanowire,"The theoretical description has been proposed for the operation of the spin
transistor in the gate-controlled InAs nanowire. The calculated current-voltage
characteristics show that the current flowing from the source (spin injector)
to the drain (spin detector) oscillates as a function of the gate voltage,
which results from the precession of the electron spin caused by the Rashba
spin-orbit interaction in the vicinity of the gate. We have studied two
operation modes of the spin transistor: (A) the ideal operation mode with the
full spin polarization of electrons in the contacts, the zero temperature, and
the single conduction channel corresponding to the lowest-energy subband of the
transverse motion and (B) the more realistic operation mode with the partial
spin polarization of the electrons in the contacts, the room temperature, and
the conduction via many transverse subbands taken into account. For mode (A)
the spin-polarized current can be switched on/off by the suitable tuning of the
gate voltage, for mode (B) the current also exhibits the pronounced
oscillations but with no-zero minimal values. The computational results
obtained for mode (B) have been compared with the recent experimental data and
a good agreement has been found.",1311.7029v1
2014-03-11,Spin Dependent Lifetimes and Spin-orbit Hybridization Points in Heusler Compounds,"We present an ab initio calculation of the k and spin-resolved electronic
lifetimes in the half-metallic Heusler compounds Co(2)MnSi and Co(2)FeSi. We
determine the spin-flip and spin-conserving contributions to the lifetimes and
study in detail the behavior of the lifetimes around states that are strongly
spin-mixed by spin-orbit coupling. We find that, for non-degenerate bands, the
spin mixing alone does not determine the energy dependence of the (spin-flip)
lifetimes. Qualitatively, the lifetimes reflect the lineup of electron and hole
bands. We predict that different excitation conditions lead to drastically
different spin-flip dynamics of excited electrons and may even give rise to an
enhancement of the non-equilibrium spin polarization.",1403.2590v2
2017-06-22,Spin-relaxation time in the impurity band of wurtzite semiconductors,"The spin-relaxation time for electrons in the impurity band of semiconductors
with wurtzite crystal structure is determined. The effective Dresselhaus
spin-orbit interaction Hamiltonian is taken as the source of the spin
relaxation at low temperature and for doping densities corresponding to the
metallic side of the metal-insulator transition. The spin-flip hopping matrix
elements between impurity states are calculated and used to set up a
tight-binding Hamiltonian that incorporates the symmetries of wurtzite
semiconductors. The spin-relaxation time is obtained from a semiclassical model
of spin diffusion, as well as from a microscopic self-consistent diagrammatic
theory of spin and charge diffusion in doped semiconductors. Estimates are
provided for particularly important materials. The theoretical spin-relaxation
times compare favorably with the corresponding low-temperature measurements in
GaN and ZnO. For InN and AlN, we predict that tuning of the spin-orbit coupling
constant induced by an external potential leads to a potentially dramatic
increase of the spin-relaxation time related to the mechanism under study.",1706.07318v1
2021-10-30,"Excitonic Correlations, Spin-State Ordering, and Magnetic-Field Effects in One-Dimensional Two-Orbital Hubbard Model for Spin-Crossover Region","The electronic properties of excitonic insulators have been examined
precisely in recent years. Pictures of exciton condensation may be applied to
the spin-state transition observed in perovskite cobalt oxides. We examine the
crystal-field and magnetic-field dependences of spatial spin structures on the
basis of the density matrix renormalization group method using an effective
model for the one-dimensional two-orbital Hubbard model in strong-coupling
limit. We find an excitonic insulating (EI) phase and a spin-state ordering
(SSO) phase in the intermediate region between low-spin and high-spin phases.
In the EI phase, spin-triplet excitons are spatially fluctuating due to quantum
effects, and an incommensurate spin correlation realizes. The analyses of a
spin gap and degeneracy of entanglement spectra suggest the realization of the
Haldane-like edge state in the EI phase. In the SSO phase, 3-fold or
incommensurate SSO structures realize depending on the crystal-field splitting.
These structures are stabilized as a result of the competition of exchange
interactions between spin states.",2111.00209v4
2018-09-03,Antiferromagnetic spin valve from heterostructure of two-dimensional hexagonal crystals,"Spin valves consisting of heterostructures of single-layer hexagonal crystal
on an antiferromagnetic substrate or of bilayer hexagonal crystal intercalated
between two (anti)ferromagnetic insulators, with the current-in-plane geometry,
are proposed. The two-dimensional hexagonal crystals such as graphene,
silicene, germanene, and stanene are modeled by the tight binding model of
honeycomb lattice. The magnetization orientation of the antiferromagnetic
substrate(s) controls the band gap and topological properties of bulk, which in
turn control the transport of three types of spin valve geometries: (i) the
in-plane transport of bulk; (ii) the transport of topological edge states along
nanoribbon with bulk gap; (iii) the transport of chiral edge state along domain
wall. The heterostructures are investigated by a tight binding model with an
(anti)ferromagnetic exchange field, Hubbard interaction and(or) spin-orbital
coupling. For the first type of spin valve geometry, the Hubbard interaction
could enlarged the effective band gap of bulk, which in turn improve the
sensitivity of the spin valves to the antiferromagnetic exchange field. For the
second and third types of spin valve geometries, the topological phase diagrams
of varying types of heterostructures with spin-orbital coupling serve as
guideline for designing the spin valve. The coexistence of the Hubbard
interaction and the spin-orbital coupling could enlarge the topological gap in
bulk and improve the quality of the chiral edge states at the domain walls
between regions with different topological numbers.",1809.00597v4
2022-04-05,Quantum spin Hall effect in two-dimensional metals without spin-orbit coupling,"The quantum spin Hall effect has been observed in topological insulators
using spin-orbit coupling as the probe, but it has not yet been observed in a
metal. An experiment is proposed to measure the quantum spin Hall effect of an
electron or hole in a two-dimensional (2D) metal by using the previously
unexplored but relativistically generated 2D quantum spin Hall Hamiltonian, but
without using spin-orbit coupling. A long cylindrical solenoid lies normally
through the inner radius of a 2D metallic Corbino disk. The current $I_S$
surrounding the solenoid produces an azimuthal magnetic vector potential but no
magnetic field in the disk. In addition, a radial electric field is generated
across the disk by imposing either (a) a potential difference $\Delta v$ or (b)
a radial charge current ${\bm I}$ across its inner and outer radii. Combined
changes in $I_S$ and in either $\Delta v$ or ${\bm I}$ generate spontaneously
quantized azimuthal charge and spin currents. The experiment is designed to
measure these quantized azimuthal charge and spin currents in the disk
consistently. The quantum Hamiltonians for experiments (a) and (b) are both
solved exactly. A method to control the Joule heating is presented, which could
potentially allow the quantum spin Hall measurements to be made at room
temperature. Extensions of this design to an array of thermally-managed
solenoids, each surrounded by thermally-managed stacks of 2D metallic Corbino
disks, could function as a quantum computer that could potentially operate at
room temperature.",2204.01949v1
2000-02-14,Effect of the Orbital Level Difference in Doped Spin-1 Chains,"Doping of a two-orbital chain with mobile S=1/2 Fermions and strong Hund's
rule couplings stabilizing the S=1 spins strongly depends on the presence of a
level difference among these orbitals. By DMRG methods we find a finite spin
gap upon doping and dominant pairing correlations without level-difference,
whereas the presence of a level difference leads to dominant charge density
wave (CDW) correlations with gapless spin-excitations. The string correlation
function also shows qualitative differences between the two models.",0002193v2
2006-04-01,Temperature effects in a spin-orbital model for manganites,"We study a two-dimensional effective orbital superexchange model derived for
strongly correlated e_g electrons coupled to t_{2g} core spins in layered
manganites. One finds that the ferromagnetic and antiferromagnetic correlations
closely compete, and small changes of parameters can switch the type of
magnetic order. For the same reason, spin order is easily destroyed with rising
temperature, while alternating orbital correlations can persist to temperatures
where FM order has already melted. A scenario for the AF phase observed in
LaSrMnO_4 is presented.",0604016v1
2006-04-07,The Jahn-Teller theorem for 3d ions and their compounds,"In contrary to customarily consideration of the Jahn-Teller theorem for
3d-ion compounds in the orbital space only we point out that it has to be
considered in the spin-orbital space. It is despite the weakness of the
intraatomic spin-orbit coupling. A direct motivation for this paper is an
erroneous claim of a recent Phys. Rev. Lett. 96 (2006) 027201 paper that the
high-spin t2g4eg2 state of the 3d6 configuration is not Jahn-Teller active.",0604207v1
2009-02-21,Extreme spin-orbit coupling in Hermite-Gaussian beams in a uniaxial crystal,"Transformation of the spin and orbital angular momentum of Hermite-Gaussian
beams of a complex and real argument propagating through a uniaxial crystal is
considered. We revealed that the spin and orbital angular momentum of the
complex argument HG beam experience a sharp splashes whereas such an intense
conversion process is not inherent in a real argument HG beams. The reasons and
conditions of the resonance effect are brought to light.",0902.3716v1
2009-06-04,Spin-orbit effects in a graphene bipolar pn junction,"A graphene $pn$ junction is studied theoretically in the presence of both
intrinsic and Rashba spin-orbit couplings. We show that a crossover from
perfect reflection to perfect transmission is achieved at normal incidence by
tuning the perpendicular electric field. By further studying angular dependent
transmission, we demonstrate that perfect reflection at normal incidence can be
clearly distinguished from trivial band gap effects. We also investigate how
spin-orbit effects modify the conductance and the Fano factor associated with a
potential step in both $nn$ and $np$ cases.",0906.0775v2
2012-03-05,Robustness of odd-parity superconductivity with spin-orbit locking against disorder,"Unconventional superconductors host a plethora of interesting physical
phenomena. However, the standard theory of superconductivity suggests that
unconventional pairing is highly sensitive to disorder, and hence can only be
observed in ultraclean systems. We find that due to an emergent chiral
symmetry, spin-orbital locking can parametrically suppress pair decoherence
introduced by impurity scattering in odd-parity superconductors. Our work
demonstrates that disorder is not an obstacle to realize odd-parity
superconductivity in materials with strong spin-orbit coupling.",1203.1055v2
2013-10-10,Asymmetry in effective fields of spin-orbit torques in Pt/Co/Pt stacks,"Measurements of switching via spin-orbit coupling (SOC) mechanisms are
discussed for a pair of inverted Pt/Co/Pt stacks with asymmetrical Pt
thicknesses. Taking into account the planar Hall effect contribution, effective
fields of spin-orbit torques (SOT) are evaluated using lock-in measurements of
the first and second harmonics of the Hall voltage. Reversing the stack
structure leads to significant asymmetries in the switching behavior, including
clear evidence of a nonlinear current dependence of the transverse effective
field. Our results demonstrate potentially complex interplay in devices with
all-metallic interfaces utilizing SOT.",1310.2771v1
2014-08-04,Effect of spin-orbit interactions on the 0.7 anomaly in quantum point contacts,"We study how the conductance of a quantum point contact is affected by
spin-orbit interactions, for systems at zero temperature both with and without
electron-electron interactions. In the presence of spin-orbit coupling, tuning
the strength and direction of an external magnetic field can change the
dispersion relation and hence the local density of states in the point contact
region. This modifies the effect of electron-electron interactions, implying
striking changes in the shape of the 0.7-anomaly and introducing additional
distinctive features in the first conductance step.",1408.0746v2
2017-03-14,Spin-Orbit Dirac Fermions in 2D Systems,"We propose a novel model for including spin-orbit interactions in buckled two
dimensional systems. Our results show that in such systems, intrinsic
spin-orbit coupling leads to a formation of Dirac cones, similar to Rashba
model. We explore the microscopic origins of this behaviour and confirm our
results using DFT calculations.",1703.04713v1
2000-01-29,The g-factors of discrete levels in nanoparticles,"Spin-orbit scattering suppresses Zeeman splitting of individual energy levels
in small metal particles. This suppression becomes significant when the
spin-orbit scattering rate \tau_{so}^{-1} is comparable with the quantum level
spacing \delta. The g-factor exhibits mesoscopic fluctuations; at small
\delta\tau_{so} it is distributed according to the Maxwell distribution. At
\delta\tau_{so}\to 0 the average g-factor levels off at a small value
g\sim(l/L)^{1/2} given by the ratio of the electron mean free path l to the
particle size L. On the contrary, in 2D quantum dots the g-factor is strongly
enhanced by spin-orbit coupling.",0001431v1
2000-07-18,Permanent magnetic moment in mesoscopic metals with spin-orbit interaction,"We argue that at zero temperature an isolated metal particle (or an AB ring)
with spin-orbit interaction and odd number of electrons will have a permanent
magnetic moment, even in zero magnetic field (flux). In a zero-field-cooled
state both the direction and the magnitude of the moment varies from particle
to particle and averages to zero. In a field-cooled state it averages to $\sim
\mu_{B}(k_{F}\ell) ^{1/2}$. We argue that the permanent moment is due to an
uncompensated electron in the last occupied (Fermi) level. We introduce an
effective single-electron Hamiltonian which accounts for spin-orbit coupling.",0007297v1
2000-10-04,Spin orbit effects in a GaAs quantum dot in a parallel magnetic field,"We analyze the effects of spin-orbit coupling on fluctuations of the
conductance of a quantum dot fabricated in a GaAs heterostructure. We argue
that spin-orbit effects may become important in the presence of a large
parallel magnetic field B_{||}, even if they are negligble for B_{||}=0. This
should be manifest in the level repulsion of a closed dot, and in reduced
conductance fluctuations in dots with a small number of open channels in each
lead, for large B_{||}. Our picture is consistent with the experimental
observations of Folk et al.",0010064v1
2004-04-12,Renormalization of spin-orbit coupling in quantum dots due to Zeeman interaction,"We derive analitycally a partial diagonalization of the Hamiltonian
representing a quantum dot including spin-orbit interaction and Zeeman energy
on an equal footing. It is shown that the interplay between these two terms
results in a renormalization of the spin-orbit intensity. The relation between
this feature and experimental observations on conductance fluctuations is
discussed, finding a good agreement between the model predictions and the
experimental behavior.",0404262v2
2004-06-08,Persistent currents in multicomponent Tomonaga-Luttinger liquid: application to mesoscopic semiconductor ring with spin-orbit interaction,"We study persistent currents in semiconductor ballistic rings with spin-orbit
Rashba interaction. We use as a working model the multicomponent
Tomonaga-Luttinger liquid which arises due to the nonparabolic dispersion
relations of electrons in the rings with rather strong spin-orbit coupling.
This approach predicts some new characteristic features of persistent currents,
which may be observed in experimental studies of semiconductor ballistic rings.",0406188v1
2004-12-02,One-Dimensional S=1 Spin-Orbital Model with Uniaxial Single-Ion Anisotropy,"We investigate ground-state properties of a one-dimensional S=1 spin-orbital
model with or without uniaxial single-ion anisotropy. By means of the density
matrix renormalization group method, we compute the ground-state energy, the
magnetization curves and the correlation functions. We discuss how the
ground-state properties depend on the two exchange couplings for orbital and
spin sectors. The phase diagram obtained is compared with that for the S=1/2
model. We also address the effect of uniaxial single-ion anisotropy.",0412067v1
2005-04-26,Fermi liquid parameters in 2D with spin-orbit interaction,"We derive analytical expressions for the quasiparticle lifetime tau, the
effective mass m*, and the Green's function renormalization factor Z for a 2D
Fermi liquid with electron-electron interaction in the presence of the Rashba
spin-orbit interaction. We find that the modifications are independent of the
Rashba band index rho, and occur in second order of the spin-orbit coupling
alpha. In the derivation of these results, we also discuss the screening of the
Coulomb interaction, as well as the susceptibility and the self-energy in small
alpha.",0504661v2
2005-05-04,Landau level mixing by full spin-orbit interactions,"We study a two-dimensional electron gas in a perpendicular magnetic field in
the presence of both Rashba and Dresselhaus spin-orbit interactions. Using a
Bogoliubov transformation we are able to write an approximate formula for the
Landau levels, thanks to the simpler form of the resulting Hamiltonian. The
exact numerical calculation of the energy levels, is also made simpler by our
formulation. The approximate formula and the exact numerical results show
excellent agreement for typical semiconductors, especially at high magnetic
fields. We also show how effective Zeeman coupling is modified by spin-orbit
interactions.",0505090v1
2003-12-12,"An aberrant ""spin-orbit interaction"" persists in the literature since more than thirty years","An expression for the spin-orbit interaction coupling between different
levels, which was shown to be aberrant more than thirty years ago is used in a
recent article [K. Amos, L. Canton, G.Piseni, J. P. Svenne and D. van der
Knijff, Nucl. Phys. A 728, 65 (2003)]. It leads to expressions quite simpler
than they should be. Its behavior is in fact of a character opposite to that of
the spin-orbit interaction used in two-body studies.",0312038v2
2008-05-21,Exchange energy dominated by large orbital spin-currents in $δ$-Pu,"The electronic structure of the anomalous $\delta$-phase of Pu is analyzed by
a general and exact reformulation of the exchange energy of the $f$-shell. It
is found that the dominating contribution to the exchange energy is a
polarization of orbital spin-currents that preserves the time reversal
symmetry, hence a non-magnetic solution in accordance with experiments. The
analysis brings a unifying picture of the role of exchange in the $5f$-shell
with its relatively strong spin-orbit coupling. The results are in good
accordance with recent measurements of the branching ratio for the $d$ to $f$
transition in the actinides.",0805.3241v1
2011-09-20,Violation of a Bell inequality in two-dimensional spin-orbit hypoentangled subspaces,"Based on spin-orbit coupling induced by q-plates, we present a feasible
experimental proposal for preparing two-dimensional spatially inhomogeneous
polarizations of light. We further investigate the quantum correlations between
these inhomogeneous polarizations of photon pairs generated by spontaneous
parametric down-conversion, which in essence describe the so-called
hypoentanglement that is established between composite spin-orbit variables of
photons. The violation of the Clauser-Horne-Shimony-Holt-Bell inequality is
predicted with S=2\sqrt2 to illustrate the entangled nature of the cylindrical
symmetry of spatially inhomogeneous polarizations.",1109.4303v1
2012-07-24,Implementing the Deutsch's algorithm with spin-orbital angular momentum of photon without interferometer,"Deutsch's algorithm is the simplest quantum algorithm which shows the
acceleration of quantum computer. In this paper, we theoretically advance a
scheme to implement quantum Deutsch's algorithm in spin-orbital angular
momentum space. Our scheme exploits a newly developed optical device called
""q-plate"", which can couple and manipulate the spin-orbital angular momentum
simultaneously. This experimental setup is of high stability and efficiency
theoretically for there is no interferometer in it.",1207.5505v1
2013-05-29,Wavefunction Vortex Attachment via Matrix Products: Application to Atomic Fermi Gases in Flat Spin-Orbit Bands,"Variational wavefunctions that introduce zeros (vortices) to screen repulsive
interactions are typically difficult to verify in unbiased microscopic
calculations. An approach is constructed to insert vortices into ansatz
wavefunctions using a matrix product representation. This approach opens the
door to validation of a broad class of Jastrow-based wavefunctions. The
formalism is applied to a model motivated by experiments on ultracold atomic
gases in the presence of synthetic spin-orbit coupling. Validated wavefunctions
show that vortices in atomic Fermi gases with flat Rashba spin-orbit bands
cluster near the system center and should therefore be directly visible in
time-of-flight imaging.",1305.6852v2
2015-04-23,Effects of the interplay between the orbital and spin currents in electroexcitation of light nuclei,"The interplay between the orbital and spin currents in (e,e') excitations of
light nuclei is discussed. The microscopic analysis of E1 and M2 resonances was
performed within the particle-core coupling approximation (PCC) of the shell
model. The comparison of the theoretical results with the available
experimental data has shown that the studies of relative contributions of the
orbital and different spin components of the nuclear current into the
excitation of EJ and MJ resonances could be useful for the identification of
their configurational structure.",1504.06032v1
2015-08-19,Effects of spin-orbit coupling and many-body correlations in STM transport through copper phthalocyanine,"The interplay of exchange correlations and spin-orbit interaction (SOI) on
the many-body spectrum of a copper phtalocyanine (CuPc) molecule and their
signatures in transport are investigated. We first derive a minimal model
Hamiltonian in a basis of frontier orbitals which is able to reproduce
experimentally observed singlet-triplet splittings; in a second step SOI
effects are included perturbatively. Major consequences of the SOI are the
splitting of former degenerate levels and a magnetic anisotropy, which can be
captured by an effective low-energy spin Hamiltonian. We show that STM-based
magnetoconductance measurements can yield clear signatures of both these SOI
induced effects.",1508.04647v1
2011-11-23,Spin-orbit Interaction induced Singlet-Triplet Resonant Raman Transitions in Quantum-dot Helium,"From our theoretical studies of resonant Raman transitions in two-electron
quantum dots (artificial helium atoms) we show that in this system, the
singlet-triplet Raman transitions are allowed (in polarized configuration) only
in the presence of spin-orbit interactions. With an increase of the applied
magnetic field this transition dominates over the singlet-singlet and
triplet-triplet transitions. This intriguing effect can therefore be utilized
to tune Raman transitions as well as the spin-orbit coupling in few-electron
quantum dots.",1111.5460v1
2019-06-23,Quantum Ferromagnetic Transition in Clean Dirac Metals,"The ferromagnetic quantum phase transition in clean metals with a negligible
spin-orbit interaction is known to be first order due to a coupling of the
magnetization to soft fermionic particle-hole excitations. A spin-orbit
interaction gives these excitations a mass, suggesting the existence of a
ferromagnetic quantum critical point in metals with a strong spin-orbit
interaction. We show that this expectation is not borne out in a large class of
materials with a Dirac spectrum, since the chirality degree of freedom leads to
new soft modes that again render the transition first order.",1906.09605v1
2014-08-28,Stable non-Fermi liquid phase of itinerant spin-orbit coupled ferromagnets,"Direct coupling between gapless bosons and a Fermi surface results in the
destruction of Landau quasiparticles and a breakdown of Fermi liquid theory.
Such a non-Fermi liquid phase arises in spin-orbit coupled ferromagnets with
spontaneously broken continuous symmetries due to strong coupling between
rotational Goldstone modes and itinerant electrons. These systems provide an
experimentally accessible context for studying non-Fermi liquid physics.
Possible examples include low-density Rashba coupled electron gases, which have
a natural tendency towards spontaneous ferromagnetism, or topological insulator
surface states with proximity-induced ferromagnetism. Crucially, unlike the
related case of a spontaneous nematic distortion of the Fermi surface, for
which the non-Fermi liquid regime is expected to be masked by a superconducting
dome, we show that the non-Fermi liquid phase in spin-orbit coupled
ferromagnets is stable.",1408.6826v2
2020-12-18,Superradiant phase transition with cavity assisted dynamical spin-orbit coupling,"Superradiant phase transition represents an important quantum phenomenon that
shows the collective excitations based on the coupling between atoms and cavity
modes. The spin-orbit coupling is another quantum effect which induced from the
interaction of the atom internal degrees of freedom and momentum of
center-of-mass. In this work, we consider the cavity assisted dynamical
spin-orbit coupling which comes from the combination of these two effects. It
can induce a series of interesting quantum phenomena, such as the flat spectrum
and the singularity of the excitation energy spectrum around the critical point
of quantum phase transition. We further discuss the influence of atom decay and
nonlinear coupling to the phase diagram. The atom decay suppresses the
singularity of the phase diagram and the nonlinear coupling can break the
symmetric properties of the phase transition. Our work provide the theoretical
methods to research the rich quantum phenomena in this dynamic many-body
systems.",2012.10098v1
2020-10-01,Modeling coupled spin and lattice dynamics,"A unified model of molecular and atomistic spin dynamics is presented
enabling simulations both in microcanonical and canonical ensembles without the
necessity of additional phenomenological spin damping. Transfer of energy and
angular momentum between the lattice and the spin systems is achieved by a
coupling term based upon the spin-orbit interaction. The characteristic spectra
of the spin and phonon systems are analyzed for different coupling strength and
temperatures. The spin spectral density shows magnon modes together with the
uncorrelated noise induced by the coupling to the lattice. The effective
damping parameter is investigated showing an increase with both coupling
strength and temperature. The model paves the way to understanding magnetic
relaxation processes beyond the phenomenological approach of the Gilbert
damping and the dynamics of the energy transfer between lattice and spins.",2010.00642v1
2018-02-14,Spin-lattice Coupling in U(1) Quantum Spin Liquids,"Quantum spin liquids (QSLs) are exotic phases with intrinsic massive
entanglements. Instead of microscopic spins, fractionalized particles and gauge
fluctuations are emergent, revealing QSLs' exotic natures. Quantum spins with
strong spin-orbit coupling on a pyrchlore lattice, for example Pr2Zr2O7, are
suggested to host a U(1) QSL with emergent photons, gapless excitations without
breaking any symmetries, as well as emergent monopoles. One of the key issues
in QSLs is an interplay between emergent degrees of freedom of QSLs and
conventional degrees of freedom, and we investigate the interplay by
constructing a general theory of spin-lattice coupling in U(1) QSLs. We find
that the coupling induces characteristic interplay between phonons and photons.
For example, photons become qualitatively more stable than phonons at low
temperature. We also propose mechanisms to detect emergent photons in
experiments such as sound attenuation and thermal transport relying on
spin-lattice coupling in U(1) QSLs.",1802.05280v2
2019-10-26,Spin-rotation coupling in p-wave Feshbach resonances,"We report evidence for spin-rotation coupling in $p$-wave Feshbach resonances
in an ultracold mixture of fermionic $^6$Li and bosonic $^{133}$Cs lifting the
commonly observed degeneracy of states with equal absolute value of
orbital-angular-momentum projection on the external magnetic field. By
employing magnetic field dependent atom-loss spectroscopy we find triplet
structures in $p$-wave resonances. Comparison with coupled-channel
calculations, including contributions from both spin-spin and spin-rotation
interactions, yields a spin-rotation coupling parameter
$|\gamma|=0.566(50)\times10^{-3}$. Our findings highlight the potential of
Feshbach resonances in revealing subtle molecular couplings and providing
precise information on electronic and nuclear wavefunctions, especially at
short internuclear distance. The existence of a non-negligible spin-rotation
splitting may have consequences for future classifications of $p$-wave
superfluid phases in spin-polarized fermions.",1910.12011v2
2003-05-12,Magnetic transition and orbital degrees of freedom in vanadium spinels,"We propose a scenario for the two phase transitions in $A$V$_2$O$_4$ ($A$=Zn,
Mg, Cd), based on an effective spin-orbital model on the pyrochlore lattice. At
high temperatures, spin correlations are strongly frustrated due to the lattice
structure, and the transition at $\sim$50 [K] is an orbital order, supported by
Jahn-Teller lattice distortion. This orbital order introduces spatial
modulation of spin exchange couplings depending on the bond direction. This
partially releases the frustration, and leads to a spin order at $\sim$40 [K].
We also study the stable spin configuration by taking account of third-neighbor
exchange couplings and quantum fluctuations. The result is consistent with the
experimental results.",0305269v1
2005-11-24,Collective excitation of quantum wires and effect of spin-orbit coupling in the presence of a magnetic field along the wire,"The band structure of a quantum wire with the Rashba spin-orbit coupling
develops a pseudogap in the presence of a magnetic field along the wire. In
such a system spin mixing at the Fermi wavevectors $-k_F$ and $k_F$ can be
different. We have investigated theoretically the collective mode of this
system, and found that the velocity of this collective excitation depends
sensitively on the strength of the Rashba spin-orbit interaction and magnetic
field. Our result suggests that the strength of the spin-orbit interaction can
be determined from the measurement of the velocity.",0511591v1
2007-03-08,Quantum Rings with Rashba spin orbit coupling: a path integral approach,"We employ a path integral real time approach to compute the DC conductance
and spin polarization for electrons transported across a ballistic Quantum Ring
with Rashba spin-orbit interaction. We use a piecewise semiclassical
approximation for the particle orbital motion and solve the spin dynamics
exactly, by accounting for both Zeeman coupling and spin-orbit interaction at
the same time. Within our approach, we are able to study how the interplay
between Berry phase, Ahronov Casher phase, Zeeman interaction and weak
localization corrections influences the quantum interference in the conductance
within a wide range of externally applied fields. Our results are helpful in
inerpreting recent measurements on interferometric rings.",0703216v2
2007-05-31,Insulating state and the importance of the spin-orbit coupling in Ca$_3$CoRhO$_6$,"We have carried out a comparative theoretical study of the electronic
structure of the novel one-dimensional Ca$_3$CoRhO$_6$ and Ca$_3$FeRhO$_6$
systems. The insulating antiferromagnetic state for the Ca$_3$FeRhO$_6$ can be
well explained by band structure calculations with the closed shell high-spin
$d^5$ (Fe$^{3+}$) and low-spin $t_{2g}^{6}$ (Rh$^{3+}$) configurations. We
found for the Ca$_3$CoRhO$_6$ that the Co has a strong tendency to be $d^7$
(Co$^{2+}$) rather than $d^6$ (Co$^{3+}$), and that there is an orbital
degeneracy in the local Co electronic structure. We argue that it is the
spin-orbit coupling which will lift this degeneracy thereby enabling local spin
density approximation + Hubbard U (LSDA+U) band structure calculations to
generate the band gap. We predict that the orbital contribution to the magnetic
moment in Ca$_3$CoRhO$_6$ is substantial, i.e. significantly larger than 1
$\mu_B$ per formula unit. Moreover, we propose a model for the contrasting
intra-chain magnetism in both materials.",0705.4538v1
2010-03-17,Spin-orbit coupling and spectral function of interacting electrons in carbon nanotubes,"The electronic spin-orbit coupling in carbon nanotubes is strongly enhanced
by the curvature of the tube surface and has important effects on the
single-particle spectrum. Here, we include the full spin-orbit interaction in
the formulation of the effective low-energy theory for interacting electrons in
metallic single-wall carbon nanotubes and study its consequences. The resulting
theory is a four-channel Luttinger liquid, where spin and charge modes are
mixed. We show that the analytic structure of the spectral function is strongly
affected by this mixing, which can provide an experimental signature of the
spin-orbit interaction.",1003.3495v2
2011-03-11,Signatures of spin-orbit interaction in transport properties of finite carbon nanotubes in a parallel magnetic field,"The transport properties of finite nanotubes placed in a magnetic field
parallel to their axes are investigated. Upon including spin-orbit coupling and
curvature effects, two main phenomena are analyzed which crucially depend on
the tube's chirality: i) Finite carbon nanotubes in a parallel magnetic field
may present a suppression of current due to the localization at the edges of
otherwise conducting states. This phenomenon occurs due to the magnetic-field
dependent open boundary conditions obeyed by the carbon nanotube's wave
functions. The transport is fully suppressed above threshold values of the
magnetic field which depend on the nanotube chirality, length and on the
spin-orbit coupling. ii) Reversible spin polarized currents can be obtained
upon tuning the magnetic field, exploiting the curvature-induced spin-orbit
splitting.",1103.2308v1
2013-05-16,Phonon-drag magnetothermopower in Rashba spin-split two-dimensional electron systems,"We study phonon-drag contribution to the thermoelectric power in a
quasi-two-dimensional electron system confined in GaAs/AlGaAs heterostructure
in presence of both Rashba spin-orbit interaction and perpendicular magnetic
field at very low temperature. It is observed that the peaks in the phonon-drag
thermopower split into two when the Rashba spin-orbit coupling constant is
strong. This splitting is a direct consequence of the Rashba spin-orbit
interaction. We show the dependence of phonon-drag thermopower on both magnetic
field and temperature numerically. A power-law dependence of phonon-drag
magnetothermopower on the temperature in the Bloch-Gruneisen regime is found.
We also extract the exponent of the temperature dependence of phonon-drag
thermopower for different parameters like electron density, magnetic field, and
the spin-orbit coupling constant.",1305.3745v2
2015-03-14,Orbital magnetic phase and pure persistent spin current in spin-orbit coupling mesoscopic rings,"By solving the Rashba model of mesoscopic rings, we give analytically the
ground-state properties of the ring, including the spin polarization, the
persistent charge and spin currents (PCC and PSC). These ground-state
properties can be given based on four kinds of electron numbers in rings. The
effect of the self-inductance of the ring leads to the self-sustained magnetic
flux (SSMF) and the self-sustained PCC and PSC, which break spontaneously
time-reversal symmetry to form orbital magnetic phase (OMP). To tune the
spin-orbit coupling strength or electron number of the ring can induce the
phase transition between the OMP and non-OMP. For exact one-dimensional rings
we find the coexistence of the pure PSC and SSMF. This property of the pure PSC
may provide a new scheme to measure the pure PSC.",1503.04274v1
2015-06-20,Analysis of Charge-spin-orbital Fluctuations by Ab Initio Calculation and Random Phase Approximation: Application to Non-coplanar Antiferromagnet Cd2Os2O7,"We present a systematic analysis on the basis of ab initio calculations and
many-body perturbation theory for clarifying the dominant fluctuation in
complex charge-spin-orbital coupled systems. For a tight-binding multiband
model obtained from the maximally-localized Wannier function analysis of the
band structure by the local density approximation, we take into account
electron correlations at the level of random phase approximation. To identify
the dominant fluctuation, we carry out the eigenmode analysis of the
generalized susceptibility that includes all the multiple degrees of freedom:
charge, spin, and orbital. We apply this method to the paramagnetic metallic
phase of a pyrochlore oxide Cd$_2$Os$_2$O$_7$, which shows a metal-insulator
transition accompanied by a peculiar noncoplanar antiferromagnetic order of
all-in all-out type. We find that the corresponding spin fluctuation is
dominantly enhanced by the on-site Coulomb repulsions in the presence of strong
spin-orbit coupling and trigonal crystal field splitting. Our results indicate
that the combined method offers an effective tool for the systematic analysis
of potential instabilities in strongly correlated electron materials.",1506.06231v1
2017-03-11,Spin-orbit interaction driven dimerization in one dimensional frustrated magnets,"We study the effect of spin-orbit interaction on one-dimensional
U(1)-invariant frustrated magnets with dominant critical nematic fluctuations.
The spin-orbit coupling explicitly breaks the U(1) symmetry of arbitrary global
spin rotations about the high-symmetry axis down to $Z_2$ (invariance under a
$\pi$-rotation). Given that the nematic order parameter is invariant under a
$\pi$-rotation, it is relevant to ask if other discrete symmetries can be
spontaneously broken. Here we demonstrate that the spin-orbit coupling induces
a bond density wave that spontaneously breaks the translational symmetry and
opens a gap in the excitation spectrum.",1703.03881v2
2019-05-17,Spin-orbit coupling: atom versus semiconductor crystal,"We reconsider a key point in semiconductor physics, the splitting of the
valence band states induced by the spin-orbit interaction, through a novel
approach which uses neither the group theory formalism, nor the usual
$\textbf{L}\cdot\textbf{S}$ formulation valid for atoms but conceptually
incorrect for periodic lattices, the angular momenta $\textbf{L}$ and
$\textbf{J}$ having no meaning due to the absence of spherical symmetry. We
show that for zinc-blende structures, the valence band eigenstates resulting
from spin-orbit coupling are uniquely determined by: (i) the equivalence of the
($x,y,z$) crystal axes, (ii) the three-fold degeneracy of the valence band. The
fact that these two conditions are also fulfilled by atomic $p$ states allows
us to understand why the spin-orbit eigenstates for three-fold atomic and
valence electrons have exactly the same structure, albeit the drastic
differences in the potential and electronic symmetries. We also come back to
the commonly accepted understanding of the exciton-photon interaction in terms
of bright and dark excitons having total angular momenta $J=(1,2)$ respectively
and present a simple derivation of this interaction which only relies on spin
conservation.",1905.07252v1
2020-07-15,Spin-orbit coupling in single layer ferrimagnets: direct observation of spin-orbit torques and chiral spin textures,"We demonstrate that effects of spin-orbit coupling and inversion asymmetry
exist in a single GdFeCo ferrimagnetic layer, even without a heavy metal
interface. We use electric transport measurements to quantify the spin-orbit
torques. We measure the Dzyaloshinskii-Moriya interaction using Brillouin light
scattering measurement technique, and we observe the resulting chiral magnetic
textures using x-ray PEEM microscopy. We attribute these effects to a
composition variation along the thickness, that we observed by scanning
transmission electron microscopy. We show that these effects can be optimized
by varying the GdFeCo thickness or by combining them with interfacial effects.",2007.07569v2
2016-12-26,Magnetic excitations in a three-orbital model for the strongly spin-orbit coupled iridates: Effect of mixing between the J=1/2 and 3/2 sectors,"A three-orbital-model approach for studying spin wave excitations in the
strongly spin-orbit coupled layered perovskite iridates is presented which
provides a unified description of magnetic excitations as well as the
electronic band structure. The calculated spin wave dispersions with realistic
three-band parameters are in excellent agreement with the RIXS data for
iridates, including the strong AF zone boundary dispersion in the single-layer
compound $\rm Sr_2 Ir O_4$ and the large anisotropy gap in the bilayer compound
$\rm Sr_3 Ir_2 O_7$. The RIXS spin wave data is shown to provide evidence of
mixing between the J=1/2 and 3/2 sectors in both compounds.",1612.08360v1
2020-02-12,Exact results relating spin-orbit interactions in two dimensional strongly correlated systems,"A 2D square, two-bands, strongly correlated and non-integrable system is
analysed exactly in the presence of many-body spin-orbit interactions via the
method of Positive Semidefinite Operators. The deduced exact ground states in
the high concentration limit are strongly entangled, and given by the
spin-orbit coupling are ferromagnetic and present an enhanced carrier mobility,
which substantially differs for different spin projections. The described state
emerges in a restricted parameter space region, which however is clearly
accessible experimentally. The exact solutions are provided via the solution of
a matching system of equations containing 74 coupled, non-linear and complex
algebraic equations. In our knowledge, other exact results for 2D interacting
systems with spin-orbit interactions are not present in the literature.",2002.05086v1
2017-09-05,Newton's second law in spin-orbit torque,"Spin-orbit torque (SOT) refers to the excitation of magnetization dynamics
via spin-orbit coupling under the application of a charged current. In this
work, we introduce a simple and intuitive description of the SOT in terms of
spin force. In Rashba spin-orbit coupling system, the damping-like SOT can be
expressed as ${\mathbf T}^\mathrm{so}={\mathbf R}_c\times {\mathbf F}^{{\mathrm
{so}}}$, in analogy to the classical torque-force relation, where $R_c$ is the
effective radius characterizing the Rashba splitting in the momentum space. As
a consequence, the magnetic energy is transferred to the conduction electrons,
which dissipates through Joule heating at a rate of $({\mathbf j}_e\cdot
{\mathbf F}^{\mathrm {so}})$, with $j_e$ being the applied current. Finally, we
propose an experimental verification of our findings via measurement of the
anisotropic magnetoresistance effect.",1709.01302v2
2020-11-13,"Magnetic field-induced ""mirage"" gap in an Ising superconductor","Superconductivity is commonly destroyed by a magnetic field due to orbital or
Zeeman-induced pair breaking. Surprisingly, the spin-valley locking in a
two-dimensional superconductor with spin-orbit interaction makes the
superconducting state resilient to large magnetic fields. We investigate the
spectral properties of such an Ising superconductor in a magnetic field taking
into account disorder. The interplay of the in-plane magnetic field and the
Ising spin-orbit coupling leads to noncollinear effective fields. We find that
the emerging singlet and triplet pairing correlations manifest themselves in
the occurrence of ""mirage"" gaps: at (high) energies of the order of the
spin-orbit coupling strength, a gap-like structure in the spectrum emerges that
mirrors the main superconducting gap. We show that these mirage gaps are
signatures of the equal-spin triplet finite-energy pairing correlations and due
to their odd parity are sensitive to intervalley scattering.",2011.07080v2
2021-11-15,First-principles calculations of spin-orbit torques in Mn$_2$Au/heavy-metal bilayers,"Using the non-equilibrium Green's function technique, we calculate spin-orbit
torques in a Mn$_2$Au/heavy-metal bilayer, where the heavy metal (HM) is W or
Pt. Spin-orbit coupling (SOC) in the bulk of Mn$_2$Au generates strong
fieldlike torquance, which is parallel on the two sublattices and scales
linearly with the conductivity, and a weaker dampinglike torquance that is
antiparallel on the two sublattices. Interfaces with W or Pt generate parallel
dampinglike torques of opposite signs that are similar in magnitude to those in
ferromagnetic bilayers and similarly insensitive to disorder. The dampinglike
torque efficiency depends strongly on the termination of the interface and on
the presence of spin-orbit coupling in Mn$_2$Au, suggesting that the
dampinglike torque is not due solely to the spin-Hall effect in the HM layer.
Interfaces also induce antiparallel fieldlike and dampinglike torques that can
penetrate deep into Mn$_2$Au.",2111.07532v2
2023-01-04,Covariant orbital-spin scheme for any spin based on irreducible tensor,"In hadron spectrum physics, the partial wave analysis is a primary method
used to extract properties of hadronic resonances. The covariant orbital-spin
coupling scheme holds unique advantages over other partial wave methods due to
its Lorentz covariant form and determined orbital-spin quantum numbers. This
paper presents a general form of the covariant orbital-spin coupling scheme
based on the irreducible tensor of the homogeneous proper Lorentz group and its
little groups. A systematic procedure for constructing partial wave amplitude
in a Lorentz covariant way is provided, which can be applied to both massive
and massless particles. Specific examples are also included.",2301.01575v3
2012-04-20,Strong coupling of a spin qubit to a superconducting stripline cavity,"We study electron-spin-photon coupling in a single-spin double quantum dot
embedded in a superconducting stripline cavity. With an external magnetic
field, we show that either a spin-orbit interaction (for InAs) or an
inhomogeneous magnetic field (for Si and GaAs) could produce a strong
spin-photon coupling, with a coupling strength of the order of 1 MHz. With an
isotopically purified Si double dot, which has a very long spin coherence time
for the electron, it is possible to reach the strong-coupling limit between the
spin and the cavity photon, as in cavity quantum electrodynamics. The coupling
strength and relaxation rates are calculated based on parameters of existing
devices, making this proposal experimentally feasible.",1204.4732v2
2022-04-01,Tunable hole spin-photon interaction based on g-matrix modulation,"We consider a spin circuit-QED device where a superconducting microwave
resonator is capacitively coupled to a single hole confined in a semiconductor
quantum dot. Thanks to the strong spin-orbit coupling intrinsic to valence-band
states, the gyromagnetic g-matrix of the hole can be modulated electrically.
This modulation couples the photons in the resonator to the hole spin. We show
that the applied gate voltages and the magnetic-field orientation enable a
versatile control of the spin-photon interaction, whose character can be
switched from fully transverse to fully longitudinal. The longitudinal coupling
is actually maximal when the transverse one vanishes and vice-versa. This
""reciprocal sweetness"" results from geometrical properties of the g-matrix and
protects the spin against dephasing or relaxation. We estimate coupling rates
reaching ~ 10 MHz in realistic settings and discuss potential circuit-QED
applications harnessing either the transverse or the longitudinal spin-photon
interaction. Furthermore, we demonstrate that the g-matrix curvature can be
used to achieve parametric longitudinal coupling with enhanced coherence.",2204.00404v3
2017-12-27,The simple-cubic structure of elemental Polonium and its relation to combined charge and orbital order in other elemental chalcogens,"Polonium is the only element to crystallise into a simple cubic structure at
ambient conditions. Moreover, at high temperatures it undergoes a structural
phase transition into a less symmetric trigonal configuration. It has long been
suspected that the strong spin-orbit coupling in Polonium is involved in both
peculiarities, but the precise mechanism by which it operates remains
controversial. Here, we introduce a single microscopic model capable of
capturing the atomic structure of all chalcogen crystals: Selenium, Tellurium,
and Polonium. We show that the strong spin-orbit coupling in Polonium
suppresses the trigonal charge and orbital ordered state known to be the ground
state configuration of Selenium and Tellurium, and allows the simple cubic
state to prevail instead. We also confirm a recent suggestion based on ab
initio calculations that a small increase in the lattice constant may
effectively decrease the role of spin-orbit coupling, leading to a re-emergence
of the trigonal orbital ordered state at high temperatures. We conclude that
Polonium is a unique element, in which spins, orbitals, electronic charges, and
lattice deformations all cooperate and collectively cause the emergence of the
only elemental crystal structure with the simplest possible, cubic, lattice.",1712.09533v3
2016-07-10,Classification of multipole superconductivity in multi-orbital systems and its implications,"Motivated by a growing interest in multi-orbital superconductors with
spin-orbit interactions, we perform the group-theoretical classification of
various unconventional superconductivity emerging in symmorphic $\rm O$, $\rm
D_4$, and $\rm D_6$ space groups. The generalized Cooper pairs, which we here
call ""multipole"" superconductivity, possess spin-orbital coupled (multipole)
degrees of freedom, instead of the conventional spin singlet/triplet in
single-orbital systems. From the classification, we obtain the following key
consequences, which have been overlooked in the long history of research in
this field: (1) A superconducting gap function with
$\varGamma_9\otimes\varGamma_9$ in $\rm D_6$ possesses nontrivial momentum
dependence, different from the usual spin 1/2 classification. (2)
Unconventional gap structure can be realized in the BCS approximation of purely
local (on-site) interactions irrespective of attractive/repulsive. It implies
the emergence of an electron-phonon (e-ph) driven unconventional
superconductivity. (3) Reflecting symmetry of orbital basis functions, there
appear not symmetry-protected but inevitable line nodes/gap minima, and thus,
anisotropic $s$-wave superconductivity can be naturally explained without any
competitive fluctuations.",1607.02716v1
2013-08-05,Spin and Orbital Contributions to Magnetically Ordered Moments in 5d Layered Perovskite Sr2IrO4,"The ratio of orbital (L) and spin (S) contributions to the magnetically
ordered moments of a 5d transition metal oxide, Sr2IrO4 was evaluated by
non-resonant magnetic x-ray diffraction. We applied a new experimental setting
to minimize the error in which we varied only the linear-polarization of
incident x-ray at a fixed scattering angle. Strong polarization dependence of
the intensity of magnetic diffraction was observed, from which we conclude that
the ordered moments contain substantial contribution from the orbital degree of
freedom with the ratio of <L>/<S> ~5.0, evidencing the pronounce effect of
spin-orbit coupling. The obtained ratio is close to but slightly larger than
the expected value for the ideal J_eff = 1/2 moment of a spin-orbital Mott
insulator, |<J_1/2|L_z|J_1/2>|/|<J_1/2|S_z|J_1/2>| = 4, which cannot be
accounted by the redistribution of orbital components within the t_2g bands
associated with the elongation of the IrO6 octahedra.",1308.0923v1
2019-10-08,Orbital Nernst Effect of Magnons,"In the past, magnons have been shown to mediate thermal transport of spin in
various systems. Here, we reveal that the fundamental coupling of scalar spin
chirality, inherent to magnons, to the electronic degrees of freedom in the
system can result in the generation of sizeable orbital magnetization and
thermal transport of orbital angular momentum. We demonstrate the emergence of
the latter phenomenon of orbital Nernst effect by referring to the spin-wave
Hamiltonian of kagome ferromagnets, predicting that in a wide range of systems
the transverse current of orbital angular momentum carried by magnons in
response to an applied temperature gradient can overshadow the accompanying
spin current. We suggest that the discovered effect fundamentally correlates
with the topological Hall effect of fluctuating magnets, and it can be utilized
in magnonic devices for generating magnonic orbital torques.",1910.03317v2
2003-05-19,Manipulation of spin dephasing in InAs quantum wires,"The spin dephasing due to the Rashba spin-orbit coupling, especially its
dependence on the direction of the electric field is studied in InAs quantum
wire. We find that the spin dephasing is strongly affected by the angle of
Rashba effective magnetic field and the applied magnetic field. The
nonlinearity in spin dephasing time versus the direction of the electric field
shows a potential evenue to manipulate the spin lifetime in spintronic device.
Moreover, we figure out a quantity that can well represent the inhomogeneous
broadening of the system which may help us to understand the many-body spin
dephasing due to the Rashba effect.",0305429v1
2003-10-06,Tunneling spin-galvanic effect,"It has been shown that tunneling of spin-polarized electrons through a
semiconductor barrier is accompanied by generation of an electric current in
the plane of the interfaces. The direction of this interface current is
determined by the spin orientation of the electrons, in particular the current
changes its direction if the spin orientation changes the sign. Microscopic
origin of such a 'tunneling spin-galvanic' effect is the spin-orbit
coupling-induced dependence of the barrier transparency on the spin orientation
and the wavevector of electrons.",0310111v1
2005-03-08,Spin relaxation and decoherence of holes in quantum dots,"We investigate heavy-hole spin relaxation and decoherence in quantum dots in
perpendicular magnetic fields. We show that at low temperatures the spin
decoherence time is two times longer than the spin relaxation time. We find
that the spin relaxation time for heavy holes can be comparable to or even
longer than that for electrons in strongly two-dimensional quantum dots. We
discuss the difference in the magnetic-field dependence of the spin relaxation
rate due to Rashba or Dresselhaus spin-orbit coupling for systems with positive
(i.e., GaAs quantum dots) or negative (i.e., InAs quantum dots) $g$-factor.",0503181v1
2005-12-16,Spin dynamics in a compound semiconductor spintronic structure with a Schottky barrier,"We demonstrate theoretically that spin dynamics of electrons injected into a
GaAs semiconductor structure through a Schottky barrier possesses strong
non-equilibrium features. Electrons injected are redistributed quickly among
several valleys. Spin relaxation driven by the spin-orbital coupling in the
semiconductor is very rapid. At T = 4.2 K, injected spin polarization decays on
a distance of the order of 50 - 100 nm from the interface. This spin
penetration depth reduces approximately by half at room temperature. The spin
scattering length is different for different valleys.",0512414v1
2006-02-17,Spin orientation of a two-dimensional electron gas by a high-frequency electric field,"Coupling of spin states and space motion of conduction electrons due to
spin-orbit interaction opens up possibilities for manipulation of the electron
spins by electrical means. It is shown here that spin orientation of a
two-dimensional electron gas can be achieved by excitation of the carriers with
a linearly polarized high-frequency electric field. In (001)-grown quantum well
structures excitation with in-plane ac electric field induces orientation of
the electron spins along the quantum well normal, with the spin sign and the
magnitude depending on the field polarization.",0602410v1
2006-10-03,Non-diffusive spin dynamics in a two-dimensional electron gas,"We describe measurements of spin dynamics in the two-dimensional electron gas
in GaAs/GaAlAs quantum wells. Optical techniques, including transient
spin-grating spectroscopy, are used to probe the relaxation rates of spin
polarization waves in the wavevector range from zero to $6\times 10^4$
cm$^{-1}$. We find that the spin polarization lifetime is maximal at nonzero
wavevector, in contrast with expectation based on ordinary spin diffusion, but
in quantitative agreement with recent theories that treat diffusion in the
presence of spin-orbit coupling.",0610054v1
2011-03-04,Spin-triplet supercurrent carried by quantum Hall edge states through a Josephson junction,"We show that a spin-polarized Landau level in a two-dimensional electron gas
can carry a spin-triplet supercurrent between two spin-singlet superconductors.
The supercurrent results from the interplay of Andreev reflection and Rashba
spin-orbit coupling at the normal--superconductor (NS) interface. We contrast
the current-phase relationship and the Fraunhofer oscillations of the
spin-triplet and spin-singlet Josephson effect in the lowest Landau level, and
find qualitative differences.",1103.0887v1
2018-06-19,Spin-active devices based on graphene / WSe$_2$ heterostructure,"We consider graphene on monolayer WSe$_2$ and the spin-orbit coupling induced
by the transition-metal dichalcogenide substrate for application to spin-active
devices. We study quantum dots and graphene quantum rings as tunable spin
filters and inverters. We use an atomistic tight-binding model as well as the
Dirac equation to determine stationary states confined in quantum dots and
rings. Next we solve the spin-transport problem for dots and rings connected to
nanoribbon leads. The systems connected to zigzag nanoribbons at low magnetic
fields act as spin filters and provide strongly spin polarized current.",1806.07068v1
2005-03-29,Spin-Forster transfer in optically excited quantum dots,"The mechanisms of energy and spin transfer in quantum dot pairs coupled via
the Coulomb interaction are studied. Exciton transfer can be resonant or
phonon-assisted. In both cases, the transfer rates strongly depend on the
resonance conditions. The spin selection rules in the transfer process come
from the exchange and spin-orbit interactions. The character of energy
dissipation in spin transfer is different than that in the traditional spin
currents. The spin-dependent photon cross-correlation functions reflect the
exciton transfer process. In addition, a mathematical method to calculate
F\""orster transfer in crystalline nanostructures beyond the dipole-dipole
approximation is described.",0503688v1
2005-10-13,Quantum Spin Current Induced Through Optical Fields,"We propose a scheme to generate quantum spin current via optical dipole
transition process. By coupling a three-level system based on the spin states
of charged particles (electrons or holes in semiconductor) to the angular
momentum states of the radiation, we show that a pure quantum spin current can
be generated. No spin-orbit interaction is needed in this scheme. We also
calculate the effect of nonmagnetic impurities on the created spin currents and
show that the vertex correction of the spin hall conductivity in the ladder
approximation is exactly zero.",0510334v2
2006-07-06,Mesoscopic Hall effect driven by chiral spin order,"A Hall effect due to spin chirality in mesoscopic systems is predicted. We
consider a 4-terminal Hall system including local spins with geometry of a
vortex domain wall, where strong spin chirality appears near the center of
vortex. The Fermi energy of the conduction electrons is assumed to be
comparable to the exchange coupling energy where the adiabatic approximation
ceases to be valid. Our results show a Hall effect where a voltage drop and a
spin current arise in the transverse direction. The similarity between this
Hall effect and the conventional spin Hall effect in systems with spin-orbit
interaction is pointed out.",0607159v1
2011-03-30,Theory of spin noise in nanowires,"We develop a theory of spin noise in semiconductor nanowires considered as
prospective elements for spintronics. In these structures spin-orbit coupling
can be realized as a random function of coordinate correlated on the spatial
scale of the order of 10 nm. By analyzing different regimes of electron
transport and spin dynamics, we demonstrate that the spin relaxation can be
very slow and the resulting noise power spectrum increases algebraically as
frequency goes to zero. This effect makes spin effects in nanowires best
suitable for studies by rapidly developing spin-noise spectroscopy.",1103.6040v2
2023-12-22,Tunneling spin Nernst effect for a single quantum dot,"We describe theoretically the spin Nernst effect for electrons tunneling to a
quantum dot from a quantum wire with the heat flowing along it. Such a
tunneling spin Nernst effect is shown to take place due to the spin-dependent
electron tunneling produced by the spin-orbit coupling. The Coulomb interaction
of electrons in the quantum dot is taken into account using nonequilibrium
Green's functions and is shown to increase significantly the accumulated spin
in a single quantum dot. The difference of the temperatures as small as tenth
of Kelvin applied to the ends of the quantum wire can lead to the spin
polarization as large as tens of percent.",2312.14700v1
2018-09-02,Nodal topology in $d$-wave superconducting monolayer FeSe,"A nodeless $d$-wave state is likely in superconducting monolayer FeSe on
SrTiO$_3$. The lack of nodes is surprising but has been shown to be a natural
consequence of the observed small interband spin-orbit coupling. Here we
examine the evolution from a nodeless state to the nodal state as this
spin-orbit coupling is increased from a topological perspective. We show that
this evolution depends strongly on the orbital content of the superconducting
degrees of freedom. In particular, there are two $d$-wave solutions, which we
call orbitally trivial and orbitally nontrivial. In both cases, the nodes carry
a $\pm 2$ topological winding number that originates from a chiral symmetry.
However, the momentum space distribution of the positive and negative charges
is different for the two cases, resulting in a different evolution of these
nodes as they annihilate to form a nodeless superconductor. We further show
that the orbitally trivial and orbitally nontrivial nodal states exhibit
different Andreev flat band spectra at the edge.",1809.00334v2
2018-01-30,Controlled spatial separation of spins and coherent dynamics in spin-orbit-coupled nanostructures,"The spatial separation of electron spins followed by the control of their
individual spin dynamics has recently emerged as an essential ingredient in
many proposals for spin-based technologies because it would enable both of the
two spin species to be simultaneously utilized, distinct from most of the
current spintronic studies and technologies wherein only one spin species could
be handled at a time. Here we demonstrate that the spatial spin splitting of a
coherent beam of electrons can be achieved and controlled using the interplay
between an external magnetic field and Rashba spin-orbit interaction in
semiconductor nanostructures. The technique of transverse magnetic focusing is
used to detect this spin separation. More notably, our ability to engineer the
spin-orbit interactions enables us to simultaneously manipulate and probe the
coherent spin dynamics of both spin species and hence their correlation, which
could open a route towards spintronics and spin-based quantum information
processing.",1801.10148v1
2005-07-20,Astrophysical Unipolar Inductors Powered by Gravitational Wave Emission,"We consider the Unipolar Inductor Model (Goldreich & Lynden-Bell 1969)
applied to Double Degenerate Binaries (DDBs) with ultrashort periods (Wu et al.
2002). In this model a magnetized primary white dwarf has a slight asynchronism
between its spin and orbital motion, so that the (non-magnetic) secondary
experiences a motional electric field when moving through the primary field
lines. This induces a current flow between the two stars and provides an
electric spin-orbit coupling mechanism for the primary. We study the combined
effect of Gravitational Wave emission and electric spin-orbit coupling on the
evolution of the primary degree of asynchronism and the associated rate of
electric current dissipation in such systems, assuming that the primary's spin
is not affected by any other mechanisms. In particular, we show that in
ultrashort period binaries the emission of GW pumps energy in the electric
circuit as to keep it steadily active. This happens despite the fact that
spin-orbit coupling can rapidly synchronize the primary, because GW represent a
slow desynchronizing mechanism steadily substracting orbital angular momentum
to the system. A slightly asynchronous steady-state is thus achieved,
determined by the balance between these two competing effects. This can be
shown to correspond to a condition where the total available electric energy is
conserved, because of GW emission, while dissipation, synchronization and
orbital shrinking continue.",0507474v1
2013-10-29,Wave packet dynamics and zitterbewegung of heavy holes in a quantizing magnetic field,"In this work we study wave packet dynamics and $zitterbewegung$, an
oscillatory quantum motion, of heavy holes in III-V semiconductor quantum wells
in presence of a quantizing magnetic field. It is revealed that a Gaussian
wave-packet describing a heavy hole diffuses asymmetrically along the circular
orbit while performing cyclotron motion. The wave packet splits into two peaks
with unequal amplitudes after a certain time depending on spin-orbit coupling
constant. This unequal splitting of the wave packet is attributed to the cubic
Rashba interaction for heavy holes. The difference in the peak amplitudes
disappears with time. At a certain time the two peaks diffuse almost along the
entire cyclotron orbit. Then tail and head of the diffused wave packet
interfere and as a result a completely randomized pattern of the wave packet is
observed. The diffusion rate of the wave packet increases with increase of the
spin-orbit interaction strength. Also strong spin-orbit coupling expedite the
splitting and the randomization of the wave packet. We also study the
$zitterbewegung$ in various physical observables such as position, charge
current and spin angular momentum of the heavy hole. The $zitterbewegung$
oscillations are very much sensitive to the initial wave vector of the Gaussian
wave packet and the strength of the Rashba spin-orbit coupling.",1310.7749v2
2020-01-06,Highly efficient spin orbit torque in Pt/Co/Ir multilayers with antiferromagnetic interlayer exchange coupling,"We have studied the spin orbit torque (SOT) in Pt/Co/Ir multilayers with 3
repeats of the unit structure. As the system exhibits oscillatory interlayer
exchange coupling (IEC) with varying Ir layer thickness, we compare the SOT of
films when the Co layers are coupled ferromagnetically and
antiferromagnetically. SOT is evaluated using current induced shift of the
anomalous Hall resistance hysteresis loops. A relatively thick Pt layer,
serving as a seed layer to the multilayer, is used to generate spin current via
the spin Hall effect. In the absence of antiferromagnetic coupling, the SOT is
constant against the applied current density and the corresponding spin torque
efficiency (i.e. the effective spin Hall angle) is $\sim$0.09, in agreement
with previous reports. In contrast, for films with antiferromagnetic coupling,
the SOT increases with the applied current density and eventually saturates.
The SOT at saturation is a factor of $\sim$15 larger than that without the
antiferromagnetic coupling. The spin torque efficiency is $\sim$5 times larger
if we assume the net total magnetization is reduced by a factor of 3 due to the
antiferromagnetic coupling. Model calculations based on the Landau Lifshitz
Gilbert equation show that the presence of antiferromagnetic coupling can
increase the SOT but the degree of enhancement is limited, in this case, to a
factor of 1.2-1.4. We thus consider there are other sources of SOT, possibly at
the interfaces, which may account for the highly efficient SOT in the
uncompensated synthetic anti-ferromagnet (SAF) multilayers.",2001.01454v1
2020-02-06,"Effects of transition-metal spacers on the spin-orbit torques, spin Hall magnetoresistance, and magnetic anisotropy of Pt/Co bilayers","We studied the effect of inserting 0.5 nm-thick spacer layers (Ti, V, Cr, Mo,
W) at the Pt/Co interface on the spin-orbit torques, Hall effect,
magnetoresistance, saturation magnetization, and magnetic anisotropy. We find
that the damping-like spin-orbit torque decreases substantially for all samples
with a spacer layer compared to the reference Pt/Co bilayer, consistently with
the opposite sign of the atomic spin-orbit coupling constant of the spacer
elements relative to Pt. The reduction of the damping-like torque is monotonic
with atomic number for the isoelectronic 3d, 4d, and 5d elements, with the
exception of V that has a stronger effect than Cr. The field-like spin-orbit
torque almost vanishes for all spacer layers irrespective of their composition,
suggesting that this torque predominantly originates at the Pt/Co interface.
The anomalous Hall effect, magnetoresistance, and saturation magnetization are
also all reduced substantially, whereas the sheet resistance is increased in
the presence of the spacer layer. Finally, we evidence a correlation between
the amplitude of the spin-orbit torques, the spin Hall-like magnetoresistance,
and the perpendicular magnetic anisotropy. These results highlight the
significant influence of ultrathin spacer layers on the magnetotransport
properties of heavy metal/ferromagnetic systems.",2002.02162v1
2015-09-14,Highly anisotropic magnon dispersion in Ca2RuO4: evidence for strong spin orbit coupling,"The magnon disp ersion in Ca2RuO4 has been determined by inelastic neutron
scattering on single crytals containing 1% of Ti. The dispersion is well
described by a conventional Heisenberg model suggesting a local moment model
with nearest neighbor interaction of J=8 meV. Nearest and next-nearest neighbor
interaction as well as inter-layer coupling parameters are required to properly
describe the entire dispersion. Spin-orbit coupling induces a very large
anisotropy gap in the magnetic excitations in apparent contrast with a simple
planar magnetic model. Orbital ordering breaking tetragonal symmetry, and
strong spin-orbit coupling can thus be identified as important factors in this
system.",1509.03999v2
2018-04-01,Resonance states near a quantum magnetic impurity in single-layer FeSe superconductors with $d$-wave symmetry,"In this work, we investigate the local density of states (LDOS) near a
magnetic impurity in single-layer FeSe superconductors. The two-orbital model
with spin-orbit coupling proposed in Ref. [{\emph{Phys. Rev. Lett.}
\textbf{119}, 267001 (2017)}] is used to describe the FeSe superconductor. In
the strong coupling regime, two impurity resonance peaks appear with opposite
resonance energies in the LDOS spectral function. For a strong spin-orbit
coupling, the superconducting gap in this model is $d$-wave symmetric with
nodes, the spatial distributions of the LDOS at the two resonance energies are
fourfold symmetric, which reveals typical characteristic of $d$-wave pairing.
When the spin-orbit coupling is not strong enough to close the superconducting
gap, we find that the spatial distribution of the LDOS at one of the resonance
energies manifests $s$-wave symmetry, while the pairing potential preserves
$d$-wave symmetry. This result is consistent with previous experimental
investigations.",1804.00258v1
2019-07-25,Alleviating the Sign Problem in Quantum Monte Carlo Simulations of Spin-Orbit-Coupled Multi-Orbital Hubbard Models,"We present a strategy to alleviate the sign problem in continuous-time
quantum Monte Carlo (CTQMC) simulations of the dynamical-mean-field-theory
(DMFT) equations for the spin-orbit-coupled multiorbital Hubbard model. We
first identify the combinations of rotationally invariant Hund coupling terms
present in the relativistic basis which lead to a severe sign problem.
Exploiting the fact that the average sign in CTQMC depends on the choice of
single-particle basis, we propose a bonding-antibonding basis
$V_{j3/2\mathrm{BA}}$ which shows an improved average sign compared to the
widely used relativistic basis for most parameter sets investigated. We then
generalize this procedure by introducing a stochastic optimization algorithm
that exploits the space of single-particle bases and show that
$V_{j3/2\mathrm{BA}}$ is very close to optimal within the parameter space
investigated. Our findings enable more efficient DMFT simulations of materials
with strong spin-orbit coupling.",1907.11298v2
2019-01-30,Thermal transitions of the modulated superfluid for spin-orbit coupled correlated bosons in an optical lattice,"We investigate the thermal physics of a Bose-Hubbard model with Rashba
spin-orbit coupling starting from a strong coupling mean-field ground state.
The essential role of the spin-orbit coupling $\left(\gamma\right)$ is to
promote condensation of the bosons at a finite wavevector ${k}_{0}$. We find
that the bosons display either homogeneous or phase-twisted or orbital ordered
superfluid phases, depending on $\gamma$ and the inter-species interaction
strength $\lambda$. We show that an increase of $\gamma$ leads to suppression
of the critical interaction $U_c$ for the superfluid to Mott insulator
transition in the ground state, and a reduction of the $T_c$ for superfluid to
Bose-liquid transition at a fixed interaction. We capture the thermal
broadening in the momentum distribution function, and the real space profiles
of the thermally disordered magnetic textures, including their homogenization
for $T \gtrsim T_{c}$. We provide a Landau theory based description of the
ground state phase boundaries and thermal transition scales, and discuss
experiments which can test our theory.",1901.10672v1
2017-04-02,Pseudospin Hall effect of light in photonic crystals with Weyl points,"The study of spin-orbit coupling of photons has attracted much attention in
recent years, and leads to many potential applications in optics. In the
recently discovered metamaterial -- photonic crystals with Weyl points, the
pseudospin-orbit coupling of photons bears a resemblance to the spin-orbit
coupling. We study the pseudospin Hall effect of light in such metamaterials
and find that during total reflection, the light beam experiences a transverse
shift that is proportional to the pseudospin (or the monopole charge) of the
Weyl point. As the spin Hall effect has inspired many works to explore the
applications in optics, exploring the coupling between the orbital and
pseudospin degrees of freedom of photons can also be fruitful in the field of
optics, as well as in other fields where Weyl points can be realized.",1704.00305v1
2000-01-03,Spin-Orbit Couplings in X-ray Binaries,"We discuss the influence of tidal spin-orbit interactions on the orbital
dynamics of close intermediate-mass X-ray binaries. In particular we consider
here a process in which spin angular momentum of a contracting RLO donor star,
in a synchronous orbit, is converted into orbital angular momentum and thus
helps to stabilize the mass transfer by widening the orbit. Binaries which
would otherwise suffer from dynamically unstable mass transfer (leading to the
formation of a common envelope and spiral-in evolution) are thus shown to
survive a phase of extreme mass transfer on a sub-thermal timescale.
Furthermore, we discuss the orbital evolution prior to RLO in X-ray binaries
with low-mass donors, caused by the competing effects of wind mass loss and
tidal effects due to expansion of the (sub)giant.",0001014v1
1999-04-20,Birth of resonances in the spin-orbit problem of Celestial Mechanics,"The behaviour of resonances in the spin-orbit coupling in Celestial Mechanics
is investigated. We introduce a Hamiltonian nearly-integrable model describing
an approximation of the spin-orbit interaction. A parametric representation of
periodic orbits is presented. We provide explicit formulae to compute the
Taylor series expansion in the perturbing parameter of the function describing
this parametrization. Then we compute approximately the radius of convergence
providing an indication of the stability of the periodic orbit. This quantity
is used to describe the different probabilities of capture into resonance. In
particular, we notice that for low values of the orbital eccentricity the only
significative resonance is the synchronous one. Higher order resonances
(including 1:2, 3:2, 2:1) appear only as the orbital eccentricity is increased.",9904035v1
2011-03-12,Orbital multicriticality in spin gapped quasi-1D antiferromagnets,"Motivated by the quasi-1D antiferromagnet CaV$_2$O$_4$, we explore
spin-orbital systems in which the spin modes are gapped but orbitals are near a
macroscopically degenerate classical transition. Within a simplified model we
show that gapless orbital liquid phases possessing power-law correlations may
occur without the strict condition of a continuous orbital symmetry. For the
model proposed for CaV$_2$O$_4$, we find that an orbital phase with coexisting
order parameters emerges from a multicritical point. The effective orbital
model consists of zigzag-coupled transverse field Ising chains. The
corresponding global phase diagram is constructed using field theory methods
and analyzed near the multicritical point with the aid of an exact solution of
a zigzag XXZ model.",1103.2473v2
2011-04-10,Interplay of orbital and spin ordering in the iron pnictides,"A number of recent experiments exhibit electronic anisotropy in the iron
pnictides, and there is a growing body of experimental evidence that its origin
is related to orbital ordering in Fe d_{xz} and d_{yz} orbitals. We examine
this problem in the parent compounds of the iron pnictides by a combination of
ab initio band theory calculations, phenomenological Ginzburg-Landau theory of
coupled orbital and magnetic order parameters, and a microscopic mean-field
study of the Kugel-Khomskii model. We find that orbital ordering is sufficient
to explain a number of key experimental observations, in particular a linear
correlation between the orthorhombic lattice distortion and the magnetic
ordered moment. We predict that orbital polarization should scale as a square
of magnetic moment close to T_N. Mediated by orbital polarization, the
effective spin-spin exchange interactions develop anisotropy in the ab-plane,
in accord with recent neutron scattering measurements.",1104.1747v1
2016-05-21,"Spin-Orbit-Induced Spin, Charge, and Energy Transport in Diffusive Superconductors","We consider the spin-orbit-induced spin Hall effect and spin swapping in
diffusive superconductors. By employing the non-equilibrium Keldysh Green's
function technique in the quasiclassical approximation, we derive coupled
transport equations for the spectral spin and particle distributions and for
the energy density in the elastic scattering regime. We compute four
contributions to the spin Hall conductivity, namely, skew scattering,
side-jump, anomalous velocity, and the Yafet contribution. The reduced density
of states in the superconductor causes a renormalization of the spin Hall
angle. We demonstrate that all four of these contributions to the spin Hall
conductivity are renormalized in the same way in the superconducting state. In
its simplest manifestation, spin swapping transforms a primary spin current
into a secondary spin current with swapped current and polarization directions.
We find that the spin-swapping coefficient is not explicitly but only
implicitly affected by superconducting correlations through the renormalized
diffusion coefficients. We discuss experimental consequences for measurements
of the (inverse) spin Hall effect and spin swapping in four-terminal
geometries. In our geometry, below the superconducting transition temperature,
the spin-swapping signal is increased an order of magnitude while changes in
the (inverse) spin Hall signal are moderate.",1605.06611v2
2020-02-26,Spin-orbit quantum impurity in a topological kagome magnet,"Quantum states induced by single-atomic-impurities are the current frontier
of material and information science. Recently the spin-orbit coupled correlated
kagome magnets are emerging as a new class of topological quantum materials,
although the effect of single-atomic impurities remains unexplored. Here we use
state-of-the-art scanning tunneling microscopy/spectroscopy (STM/S) to study
the atomic indium impurity in a topological kagome magnet Co3Sn2S2, which is
designed to support the spin-orbit quantum state. We find each impurity
features a strongly localized bound state. Our systematic
magnetization-polarized tunneling probe reveals its spin-down polarized nature
with an unusual moment of -5uB, indicative of additional orbital magnetization.
As the separation between two impurities progressively shrinks, their
respective bound states interact and form quantized molecular orbital states.
The molecular orbital of three neighboring impurities further exhibits an
intriguing splitting owing to the combination of geometry, magnetism, and
spin-orbit coupling, analogous to the splitting of the topological Weyl fermion
line12,19. Our work demonstrates the quantum-level interplay between magnetism
and spin-orbit coupling at an individual atomic impurity, which provides
insights into the emergent impurity behavior in a topological kagome magnet and
the potential of spin-orbit quantum impurities for information science.",2002.11783v1
2014-03-03,The honeycomb lattice with multi-orbital structure: topological and quantum anomalous Hall insulators with large gaps,"We construct a minimal four-band model for the two-dimensional (2D)
topological insulators and quantum anomalous Hall insulators based on the
$p_x$- and $p_y$-orbital bands in the honeycomb lattice. The multiorbital
structure allows the atomic spin-orbit coupling which lifts the degeneracy
between two sets of on-site Kramers doublets $j_z=\pm\frac{3}{2}$ and
$j_z=\pm\frac{1}{2}$. Because of the orbital angular momentum structure of
Bloch-wave states at $\Gamma$ and $K(K^\prime)$ points, topological gaps are
equal to the atomic spin-orbit coupling strengths, which are much larger than
those based on the mechanism of the $s$-$p$ band inversion. In the weak and
intermediate regime of spin-orbit coupling strength, topological gaps are the
global gap. The energy spectra and eigen wave functions are solved analytically
based on Clifford algebra. The competition among spin-orbit coupling $\lambda$,
sublattice asymmetry $m$ and the N\'eel exchange field $n$ results in band
crossings at $\Gamma$ and $K (K^\prime)$ points, which leads to various
topological band structure transitions. The quantum anomalous Hall state is
reached under the condition that three gap parameters $\lambda$, $m$, and $n$
satisfy the triangle inequality. Flat bands also naturally arise which allow a
local construction of eigenstates. The above mechanism is related to several
classes of solid state semiconducting materials.",1403.0563v6
2017-11-07,Mixing of $t_{2g}$-$e_g$ orbitals in 4d and 5d transition metal oxides,"Using exact diagonalization, we study the spin-orbit coupling and
interaction-induced mixing between $t_{2g}$ and $e_g$ $d$-orbital states in a
cubic crystalline environment, as commonly occurs in transition metal oxides.
We make a direct comparison with the widely used $t_{2g}$ only or $e_g$ only
model, depending on electronic filling. We consider all electron fillings of
the $d$-shell and compute the total magnetic moment, the spin, the occupancy of
each orbital, and the effective spin-orbit coupling strength (renormalized
through interaction effects) in terms of the bare interaction parameters,
spin-orbit coupling, and crystal field splitting, focusing on the parameter
ranges relevant to 4d and 5d transition metal oxides. In various limits we
provide perturbative results consistent with our numerical calculations. We
find that the $t_{2g}$-$e_g$ mixing can be large, with up to 20\% occupation of
orbitals that are nominally ""empty"", which has experimental implications for
the interpretation of the branching ratio in experiments, and can impact the
effective local moment Hamiltonian used to study magnetic phases and magnetic
excitations in transition metal oxides. Our results can aid the theoretical
interpretation of experiments on these materials, which often fall in a regime
of intermediate coupling with respect to electron-electron interactions.",1711.02328v2
2023-06-20,Metallic ruthenium ilmenites: first-principles study of MgRuO$_3$ and CdRuO$_3$,"Ilmenites $AB$O$_3$ provide a platform for electron correlation and magnetism
on alternatively stacked honeycomb layers of edge-sharing $A$O$_6$ or $B$O$_6$
octahedra. When $A$ and $B$ are $3d$ transition metals, strong electron
correlation makes the systems Mott insulators showing various magnetic
properties, while when $B$ is Ir with $5d$ electrons, competition between
electron correlation and spin-orbit coupling realizes a spin-orbital coupled
Mott insulator as a potential candidate for quantum spin liquids. Here we
theoretically investigate intermediate $4d$ ilmenites, $A$RuO$_3$ with $A$=Mg
and Cd, which were recently synthesized and shown to be metallic, unlike the
$3d$ and $5d$ cases. By using first-principles calculations, we optimize the
lattice structures and obtain the electronic band structures. We show that
MgRuO$_3$ exhibits strong dimerization on RuO$_6$ honeycomb layers, leading to
the formation of bonding and anti-bonding bands for one of three $t_{2g}$
orbitals; the lattice symmetry is lowered from $R\bar{3}$ to $P\bar{1}$, and
the Fermi surfaces are composed of the other two $t_{2g}$ orbitals. In
contrast, we find that CdRuO$_3$ has a lattice structure close to $R\bar{3}$,
and all three $t_{2g}$ orbitals contribute almost equally to the Fermi
surfaces. Comparison of our results with other Ru honeycomb materials such as
Li$_2$RuO$_3$ indicates that the metallic ruthenium ilmenites stand on a subtle
balance among electron correlation, spin-orbit coupling, and electron-phonon
coupling.",2306.11542v1
2013-08-01,Rashba-induced spin electromagnetic fields in a strong sd coupling regime,"Spin electromagnetic fields driven by the Rashba spin-orbit interaction, or
Rashba-induced spin Berry's phase, in ferromagnetic metals is theoretically
studied based on the Keldysh Green's function method. Considering a limit of
strong sd coupling without spin relaxation (adiabatic limit), the spin electric
and magnetic fields are determined by calculating transport properties. The
spin electromagnetic fields turn out to be expressed in terms of a
Rashba-induced effective vector potential, and thus they satisfy the Maxwell's
equation. In contrast to the conventional spin Berry's phase, the
Rashba-induced one is linear in the gradient of magnetization profile, and thus
can be extremely large even for slowly varying structures. We show that the
Rashba-induced spin Berry's phase exerts the Lorentz force on spin resulting in
a giant spin Hall effect in magnetic thin films in the presence of
magnetization structures. Rashba-induced spin magnetic field would be useful to
distinguish between topologically equivalent magnetic structures.",1308.0152v1
2016-11-10,Laser-induced ultrafast demagnetization time and spin moment in ferromagnets: First-principles calculation,"When a laser pulse excites a ferromagnet, its spin undergoes a dramatic
change. The initial demagnetization process is very fast. Experimentally, it is
found that the demagnetization time is related to the spin moment in the
sample. In this study, we employ the first-principles method to directly
simulate such a process. We use the fixed spin moment method to change the spin
moment in ferromagnetic nickel, and then we employ the Liouville equation to
couple the laser pulse to the system. We find that in general the dependence of
demagnetization time on the spin moment is nonlinear: It decreases with the
spin moment up to a point, after which an increase with the spin moment is
observed, followed by a second decrease. To understand this, we employ an
extended Heisenberg model, which includes both the exchange interaction and
spin-orbit coupling. The model directly links the demagnetization rate to the
spin moment itself and demonstrates analytically that the spin relaxes more
slowly with a small spin moment. A future experimental test of our predictions
is needed.",1611.03154v1
2016-12-29,Theory of electron transport and magnetization dynamics in metallic ferromagnets,"Magnetic electric effects in ferromagnetic metals are discussed from the
viewpoint of effective spin electromagnetic field that couples to conduction
electron spin. The effective field in the adiabatic limit is the spin Berry's
phase in space and time, and it leads to spin motive force (voltage generated
by magnetization dynamics) and topological Hall effect due to spin chirality.
Its gauge coupling to spin current describes the spin transfer effect, where
magnetization structure is driven by an applied spin current. The idea of
effective gauge field can be extended to include spin relaxation and Rashba
spin-orbit interaction. Voltage generation by the inverse Edelstein effect in
junctions is interpreted as due to the electric component of Rashba-induced
spin gauge field. The spin gauge field arising from the Rashba interaction
turns out to coincides with troidal moment, and causes asymmetric light
propagation (directional dichroism) as a result of the Doppler shift. Rashba
conductor without magnetization is shown to be natural metamaterial exhibiting
negative refraction.",1612.09019v1
2023-06-15,Efficient Spin Seebeck and Spin Nernst Effects of Magnons in Altermagnets,"We report two non-degenerate magnon modes with opposite spins or chiralities
in collinearly antiferromagnetic insulators driven by symmetry-governed
anisotropic exchange couplings. The consequent giant spin splitting contributes
to spin Seebeck and spin Nernst effects generating longitudinal and transverse
spin currents when the temperature gradient applies along and away from the
main crystal axis, without requiring any external magnetic field and spin-orbit
coupling. Based on first-principle calculations, we predict feasible material
candidates holding robust altermagnetic spin configurations and
room-temperature structural stability to efficiently transport spin. The spin
Seebeck conductivity is comparable to the records of antiferromagnets that
require the magnetic field, and the spin Nernst conductivity is two orders in
magnitude larger than that in antiferromagnetic monolayers that need Berry
curvature.",2306.08976v2
2000-02-13,Magnetic impurities in the one-dimensional spin-orbital model,"Using one-dimensional spin-orbital model as a typical example of quantum spin
systems with richer symmetries, we study the effect of an isolated impurity on
its low energy dynamics in the gapless phase through bosonization and
renormalization group methods. In the case of internal impurities, depending on
the symmetry, the boundary fixed points can be either an open chain with a
residual spin or (and) orbital triplet left behind, or a periodic chain.
However, these two fixed points are indistinguishable in the sense that in both
cases, the lead-correction-to-scaling boundary operators (LCBO) only show
Fermi-liquid like corrections to thermodynamical quantities. (Except the
possible Curie-like contributions from the residual moments in the latter
cases.) In the case of external (Kondo) impurities, the boundary fixed points,
depending on the sign of orbital couplings, can be either an open chain with an
isolated orbital doublet due to Kondo screening or it will flow to an
intermediate fixed point with the same LCBO as that of the two-channel Kondo
problem. Comparison with the Kondo effect in one-dimensional (1D) Heisenberg
spin chain and multi-band Hubbard models is also made.",0002184v1
2006-06-20,Intrinsic and Rashba Spin-orbit Interactions in Graphene Sheets,"Starting from a microscopic tight-binding model and using second order
perturbation theory, we derive explicit expressions for the intrinsic and
Rashba spin-orbit interaction induced gaps in the Dirac-like low-energy band
structure of an isolated graphene sheet. The Rashba interaction parameter is
first order in the atomic carbon spin-orbit coupling strength $\xi$ and first
order in the external electric field $E$ perpendicular to the graphene plane,
whereas the intrinsic spin-orbit interaction which survives at E=0 is second
order in $\xi$. The spin-orbit terms in the low-energy effective Hamiltonian
have the form proposed recently by Kane and Mele. \textit{Ab initio} electronic
structure calculations were performed as a partial check on the validity of the
tight-binding model.",0606504v4
2004-07-13,Spin-orbit splitting of 9 Lambda Be excited states studied with the SU_6 quark-model baryon-baryon interactions,"The previous Faddeev calculation of the two-alpha plus Lambda system for 9
Lambda Be is extended to incorporate the spin-orbit components of the SU_6
quark-model baryon-baryon interactions. We employ the Born kernel of the
quark-model Lambda N LS interaction, and generate the spin-orbit component of
the Lambda alpha potential by the alpha-cluster folding. The Faddeev
calculation in the jj-coupling scheme implies that the direct use of the
quark-model Born kernel for the Lambda N LS component is not good enough to
reproduce the small experimental value Delta E^exp_{ls}=43 +- 5 keV for the
5/2^+ - 3/2^+ splitting. This procedure predicts three to five times larger
values in the model FSS and fss2. The spin-orbit contribution from the
effective meson-exchange potentials in fss2 is argued to be unfavorable to the
small ls splitting, through the analysis of the Scheerbaum factors for the
single-particle spin-orbit potentials calculated in the G-matrix formalism.",0407039v1
2011-02-13,Orbital magnetic moment and extrinsic spin Hall effect for iron impurity in gold,"We report electronic structure calculations of an iron impurity in gold host.
The spin, orbital and dipole magnetic moments were investigated using the
LDA+$U$ correlated band theory. We show that the {\em
around-mean-field}-LDA+$U$ reproduces the XMCD experimental data well and does
not lead to formation of a large orbital moment on the Fe atom. Furthermore,
exact diagonalization of the multi-orbital Anderson impurity model with the
full Coulomb interaction matrix and the spin-orbit coupling is performed in
order to estimate the spin Hall angle. The obtained value $\gamma_S \approx
0.025$ suggests that there is no giant extrinsic spin Hall effect due to
scattering on iron impurities in gold.",1102.2614v1
2011-06-28,Theoretical investigation of the evolution of the topological phase of Bi$_{2}$Se$_{3}$ under mechanical strain,"The topological insulating phase results from inversion of the band gap due
to spin-orbit coupling at an odd number of time-reversal symmetric points. In
Bi$_2$Se$_3$, this inversion occurs at the $\Gamma$ point. For bulk
Bi$_2$Se$_3$, we have analyzed the effect of arbitrary strain on the $\Gamma$
point band gap using Density Functional Theory. By computing the band structure
both with and without spin-orbit interactions, we consider the effects of
strain on the gap via Coulombic interaction and spin-orbit interaction
separately. While compressive strain acts to decrease the Coulombic gap, it
also increases the strength of the spin-orbit interaction, increasing the
inverted gap. Comparison with Bi$_2$Te$_3$ supports the conclusion that effects
on both Coulombic and spin-orbit interactions are critical to understanding the
behavior of topological insulators under strain, and we propose that the
topological insulating phase can be effectively manipulated by inducing strain
through chemical substitution.",1106.5556v1
2013-03-19,Highly relativistic circular orbits of spinning particle in the Kerr field,"The Mathisson-Papapetrou equations in Kerr's background are considered. The
region of existence of highly relativistic planar circular orbits of a spinning
particle in this background and dependence of the particle's Lorentz
$\gamma$-factor on its spin and radial coordinate are investigated. It is shown
that in contrast to the highly relativistic circular orbits of a spinless
particle the corresponding orbits of a spinning particle are allowed in much
wider space region. Some of these orbits show the significant attractive action
of the spin-gravity coupling on a particle and others are caused by the
significant repulsive action. Numerical estimates for electrons, protons and
neutrinos in the gravitational field of black holes are presented.",1303.4707v1
2013-12-15,Spin-Orbit Effects in Atomic High-Harmonic Generation,"Spin-orbit interactions lead to small energy gaps between the outer-most
$p_{1/2}$ and $p_{3/2}$ shells of noble gas atoms. Strong-field pulses
tunnel-ionize an electron out of either shell resulting in spin-orbit-driven
hole motion. These hole dynamics affect the HHG yield. However, the spectral
shape as well as the angular distribution of the HHG emission is not influenced
by spin-orbit coupling. We demonstrate the spin-orbit effect on atomic krypton
by solving the multi-electron Schr\""odinger equation with the time-dependent
configuration-interaction singles (TDCIS) approach. We also provide pulse
parameters where this effect can be identified in experiments through an
enhancement in the HHG yield as the wavelength of the strong-field pulse
increases.",1312.4151v1
2014-10-21,Dissipation dynamics and spin-orbit force in time-dependent Hartree-Fock theory,"We investigate the one-body dissipation dynamics in heavy-ion collisions of
$^{16}{\rm O}$+$^{16}{\rm O}$ using a fully three-dimensional time-dependent
Hartree-Fock (TDHF) theory with the modern Skyrme energy functional and without
any symmetry restrictions. The energy dissipation is revealed to decrease in
deep-inelastic collisions of the light systems as the bombarding energy
increases owing to the competition between collective motion and
single-particle degrees of freedom. The role of spin-orbit force is given
particular emphasis in deep-inelastic collisions. The spin-orbit force causes a
significant enhancement of the dissipation. The time-even coupling of
spin-orbit force plays a dominant role at low energies, while the influence of
time-odd terms is notable at high energies. About 40-65\% of the total
dissipation depending on the different parameter sets is predicted to arise
from the spin-orbit force. The theoretical fusion cross section has a
reasonably good agreement with the experimental data, considering that no free
parameters are adjusted to reaction dynamics in the TDHF approach.",1410.5573v1
2020-02-16,Electric-field control of spin-orbit torques in perpendicularly magnetized W/CoFeB/MgO films,"Controlling magnetism by electric fields offers a highly attractive
perspective for designing future generations of energy-efficient information
technologies. Here, we demonstrate that the magnitude of current-induced
spin-orbit torques in thin perpendicularly magnetized CoFeB films can be tuned
and even increased by electric field generated piezoelectric strain. Using
theoretical calculations, we uncover that the subtle interplay of spin-orbit
coupling, crystal symmetry, and orbital polarization is at the core of the
observed strain dependence of spin-orbit torques. Our results open a path to
integrating two energy efficient spin manipulation approaches, the electric
field-induced strain and the current-induced magnetization switching, thereby
enabling novel device concepts.",2002.06578v1
2004-05-18,Spin-other-orbit operator in the tensorial form of second quantization,"The tensorial form of the spin-other-orbit interaction operator in the
formalism of second quantization is presented. Such an expression is needed to
calculate both diagonal and off-diagonal matrix elements according to an
approach, based on a combination of second quantization in the coupled
tensorial form, angular momentum theory in three spaces (orbital, spin and
quasispin), and a generalized graphical technique. One of the basic features of
this approach is the use of tables of standard quantities, without which the
process of obtaining matrix elements of spin-other-orbit interaction operator
between any electron configurations is much more complicated. Some special
cases are shown for which the tensorial structure of the spin-other-orbit
interaction operator reduces to an unusually simple form.",0405092v1
2011-05-02,Relativistic Electron Vortex Beams: Angular Momentum and Spin-Orbit Interaction,"Motivated by the recent discovery of electron vortex beams carrying orbital
angular momentum (AM), we construct exact Bessel-beam solutions of the Dirac
equation. They describe relativistic and nonparaxial corrections to the scalar
electron beams. We describe the spin and orbital AM of the electron with
Berry-phase corrections and predict the intrinsic spin-orbit coupling in free
space. This can be observed as a spin-dependent probability distribution of the
focused electron vortex beams. Moreover, the magnetic moment is calculated,
which shows different $g$-factors for spin and orbital AM and also contains the
Berry-phase correction.",1105.0331v3
2013-11-21,Wave patterns generated by a flow of two-component Bose-Einstein condensate with spin-orbit interaction past a localized obstacle,"It is shown that spin-orbit interaction leads to drastic changes in wave
patterns generated by a flow of two-component Bose-Einstein condensate (BEC)
past an obstacle. The combined Rashba and Dresselhaus spin-orbit interaction
affects in different ways two types of excitations---density and polarization
waves---which can propagate in a two-component BEC. We show that the density
and polarization ""ship wave"" patterns rotate in opposite directions around the
axis located at the obstacle position and the angle of rotation depends on the
strength of spin-orbit interaction. This rotation is accompanied by narrowing
of the Mach cone. The influence of spin-orbit coupling on density solitons and
polarization breathers is studied numerically.",1311.5387v1
2014-10-24,Frustration and Entanglement in Compass and Spin-Orbital Models,"We review the consequences of intrinsic frustration of the orbital
superexchange and of spin-orbital entanglement. While Heisenberg perturbing
interactions remove frustration in the compass model, the lowest columnar
excitations are robust in the nanoscopic compass clusters and might be used for
quantum computations. Entangled spin-orbital states determine the ground states
in some cases, while in others concern excited states and lead to measurable
consequences, as in the $R$VO$_3$ perovskites. On-site entanglement for strong
spin-orbit coupling generates the frustrated Kitaev-Heisenberg model with a
rich magnetic phase diagram on the honeycomb lattice. Frustration is here
reflected in hole propagation which changes from coherent in an antiferromagnet
via hidden quasiparticles in zigzag and stripe phases to entirely incoherent
one in the Kitaev spin liquid.",1410.6722v1
2015-10-06,Anomalous magnetic response of a quasi-periodic mesoscopic ring in presence of Rashba and Dresselhaus spin-orbit interactions,"We investigate the properties of persistent charge current driven by magnetic
flux in a quasi-periodic mesoscopic Fibonacci ring with Rashba and Dresselhaus
spin-orbit interactions. Within a tight-binding framework we work out
individual state currents together with net current based on second-quantized
approach. A significant enhancement of current is observed in presence of
spin-orbit coupling and sometimes it becomes orders of magnitude higher
compared to the spin-orbit interaction free Fibonacci ring. We also establish a
scaling relation of persistent current with ring size, associated with the
Fibonacci generation, from which one can directly estimate current for any
arbitrary flux, even in presence of spin-orbit interaction, without doing
numerical simulation. The present analysis indeed gives a unique opportunity of
determining persistent current and has not been discussed so far.",1510.01438v4
2015-10-08,"Orbital order, spin waves, and doping effects in the $(π,0)$ SDW state --- comparative study of the three band models for iron pnictides","Aimed at identifying the role of microscopic Hamiltonian parameters on spin
wave excitations, orbital order, and magnetic moments in the $(\pi,0)$ SDW
state, two different three band models for iron pnictides are compared --- one
at two-third filling ($n=4$) and another at half filling $(n=3)$ --- both of
which yield qualitatively correct Fermi surface structure in the paramagnetic
state. Spin wave analysis of the model at $n=4$ shows instability of the SDW
state, which is attributed to weakly developed magnetic moments and weak
magnetic couplings due to overfilling, as inferred from the observed
stabilization of the SDW state and enhancement of magnetic excitation energies
upon hole doping. In contrast, the model at $n=3$ (half filling) yields a
gapped SDW state with well developed magnetic moments and the calculated spin
wave excitations are in excellent agreement with INS experiments. The sign of
the orbital order ($n_{xz} - n_{yz} \approx +0.2$) is also in agreement with
experiments. Both the zone boundary spin wave energies in the F and AF
directions as well as the orbital order are shown to peak near half filling,
highlighting the correlation between orbital order and SDW state stabilization.",1510.02276v1
2008-07-15,Single spin asymmetry and five-quark components of the proton,"We examine the single-spin asymmetry (SSA) caused by the five-quark
components of the proton for semi-inclusive electroproduction of charged pions
in deep-inelastic scattering on a transversely polarized hydrogen target. The
large SSA is considered to have close relation with quark orbital motion in the
proton and suggests that the quark orbital angular momentum is nonzero. For the
five-quark $qqqq\bar{q}$ components of the proton, the lowest configurations
with $qqqq$ system orbitally excited and the $\bar{q}$ in the ground state
would give spin-orbit correlations naturally for the quarks in a polarized
proton. We show that based on the basic reaction $\gamma q \to \pi q'$, the
orbital-spin coupling of the probed quarks in the five-quark configuration
leads to the single-spin asymmetry consistent with recent experiment results.",0807.2324v1
2018-10-31,Spin-orbital excitons and their potential condensation in pentavalent iridates,"We investigate magnetic excitations in iridium insulators with pentavalent
Ir$^{5+}$ ($5d^4$) ions with strong spin-orbit coupling. We obtain a
microscopic model based on the local Ir$^{5+}$ multiplets involving $J=0$
(singlet), $J=1$ (triplet), and $J=2$ (quintet) spin-orbital states. We get
effective interactions between these multiplets on square and
face-centered-cubic (fcc) structures of magnetic ions in the
layered-perovskites and the double-perovkites, in particular Ba$_2$YIrO$_6$.
Further, we derive an effective spin-orbital Hamiltonian in terms of bond
bosons and explore possible instabilities towards magnetic and quadrupole
orderings. Additionally, we study charge excitations with help of the
variational cluster perturbation theory and calculate the electronic charge gap
as a function of hopping and Coulomb interactions. Based on both electronic and
magnetic phase diagrams, we verify the possibility of excitonic magnetism due
to condensation of spin-orbital excitons in Ir$^{5+}$ iridates.",1810.13058v2
2023-02-01,Controlled longitudinal spin-orbit separation of complex vector modes,"Complex vector modes, entangled in spin and orbital angular momentum, are
opening burgeoning opportunities for a wide variety of applications.
Importantly, the flexible manipulation the various properties of such beams
will pave the way to novel applications. As such, in this manuscript, we
demonstrate a longitudinal spin-orbit separation of complex vector modes
propagating in free space. To achieve this we employed the recently
demonstrated circular Airy Gaussian vortex vector (CAGVV) modes, which feature
a self-focusing property. More precisely, by properly manipulating the
intrinsic parameters of CAGVV modes, the strong coupling between the two
constituting orthogonal components of CAGVV mode undergo a spin-orbit
separation along the propagation direction namely, while one polarisation
component, focuses at a specific plane, the other focuses at a different plane.
Such spin-orbit separation, which we demonstrated by numerical simulations and
corroborated experimentally, can be adjusted on-demand by simply changing the
initial parameters of CAGVV modes. Our findings will be of great relevance, for
example in optical tweezers, to manipulate micro- or nano-particles at two
different parallel planes.",2302.00241v1
2007-04-01,High-spin to low-spin and orbital polarization transitions in multiorbital Mott systems,"We study the interplay of crystal field splitting and Hund coupling in a
two-orbital model which captures the essential physics of systems with two
electrons or holes in the e_g shell. We use single site dynamical mean field
theory with a recently developed impurity solver which is able to access strong
couplings and low temperatures. The fillings of the orbitals and the location
of phase boundaries are computed as a function of Coulomb repulsion, exchange
coupling and crystal field splitting. We find that the Hund coupling can drive
the system into a novel Mott insulating phase with vanishing orbital
susceptibility. Away from half-filling, the crystal field splitting can induce
an orbital selective Mott state.",0704.0057v2
2006-11-17,Coherent optical manipulation of triplet-singlet states in coupled quantum dots,"We show that spin-orbit coupling in a quantum dot molecule allows for
coherent manipulation of two electron spin states using Raman transitions. Such
two-electron spin states defined by the singlet and triplet states of two
exchange coupled quantum dots can have favorable coherence properties. In
addition, two of the four metastable ground states in this system can be used
as auxiliary states that could facilitate implementation of tasks such as
mapping of spin states to that of a single propagating photon. We find that
even weak spin-orbit effects -- manifesting themselves as slightly different
g-factors for the electron and the hole -- would allow for the coherent Raman
coupling of the singlet-triplet states. We also discuss the possibilities for
implementing quantum optical techniques for spin preparation and manipulation.",0611469v1
2021-01-20,Dynamical preparation of stripe states in spin-orbit coupled gases,"In spinor Bose-Einstein condensates, spin-changing collisions are a
remarkable proxy to coherently realize macroscopic many-body quantum states.
These processes have been, e.g., exploited to generate entanglement, to study
dynamical quantum phase transitions, and proposed for realizing nematic phases
in atomic condensates. In the same systems dressed by Raman beams, the coupling
between spin and momentum induces a spin dependence in the scattering processes
taking place in the gas. Here we show that, at weak couplings, such modulation
of the collisions leads to an effective Hamiltonian which is equivalent to the
one of an artificial spinor gas with spin-changing collisions that are tunable
with the Raman intensity. By exploiting this dressed-basis description, we
propose a robust protocol to coherently drive the spin-orbit coupled condensate
into the ferromagnetic stripe phase via crossing a quantum phase transition of
the effective low-energy model in an excited-state.",2101.08253v3
2018-03-21,Spin-orbital-angular-momentum coupled Bose-Einstein condensates,"We demonstrate coupling between the atomic spin and orbital-angular-momentum
(OAM) of the atom's center-of-mass motion in a Bose-Einstein condensate (BEC).
The coupling is induced by Raman-dressing lasers with a Laguerre-Gaussian beam,
and creates coreless vortices in a $F=1$ $^{87}$Rb spinor BEC. We observe
correlations between spin and OAM in the dressed state and characterize the
spin texture; the result is in good agreement with the theory. In the presence
of the Raman field our dressed state is stable for 0.1~s or longer, and it
decays due to collision-induced relaxation. As we turn off the Raman beams, the
vortex cores in the bare spin $|m_F=1\rangle$ and $|-1\rangle$ split. These
spin-OAM coupled systems with the Raman-dressing approach have great potential
for exploring new topological textures and quantum states.",1803.07860v3
2014-05-21,Spin-orbit coupled Bose-Einstein condensates in a double well,"We study the quantum dynamics of a spin-orbit (SO) coupled Bose-Einstein
condensate (BEC) in a double-well potential inspired by the experimental
protocol recently developed by NIST group. We focus on the regime where the
number of atoms is very large and perform a two-mode approximation. An
analytical solution of the two-site Bose-Hubbard-like Hamiltonian is found for
several limiting cases, which range from a strong Raman coupling to a strong
Josephson coupling, ending with the complete model in the presence of weak
nonlinear interactions. Depending on the particular limit, different approaches
are chosen: a mapping onto an SU(2) spin problem together with a
Holstein-Primakoff transformation in the first two cases and a rotating wave
approximation (RWA) when dealing with the complete model. The quantum evolution
of the number difference of bosons with equal or different spin between the two
wells is investigated in a wide range of parameters; finally the corresponding
total atomic current and the spin current are computed. We show a spin
Josephson effect which could be detected in experiments and employed to build
up realistic devices.",1405.5356v1
2001-09-28,"Spin, spin-orbit, and electron-electron interactions in mesoscopic systems","We review recent theoretical developments about the role of spins,
electron-electron interactions, and spin-orbit coupling in metal nanoparticles
and semiconductor quantum dots. For a closed system, in the absence of
spin-orbit coupling or of an external magnetic field, electron-electron
interactions make it possible to have ground states with spin $S > 1/2$. We
review here a theoretical analysis which makes predictions for the probability
of finding various values of spin $S$ for an irregular particle in the limit
where the number of electron is large but finite. We also present results for
the probability distribution of the spacing between successive groundstate
energies in such a particle. In a metallic particle with strong spin-orbit
interactions, for odd electron number, the groundstate has a Kramers'
degeneracy, which is split linearly by a weak applied magnetic field. The
splitting may be characterized by an effective $g$-tensor whose principal axes
and eigenvalues vary from one level to another. Recent calculations have
addressed the joint probability distribution, including the anisotropy, of the
eigenvalues. The peculiar form of the spin-orbit coupling for a two-dimensional
electron system in a GaAs heterostructure or quantum well leads to a strong
suppression of spin-orbit effects when the electrons are confined in a small
quantum dot. Spin-effects can be enhanced, however, in the presence of an
applied magnetic field parallel to the layer, which may explain recent
observations on fluctuations in the conductances through such dots. We also
discuss possible explanations for the experimental observations by Davidovic
and Tinkham of a multiplet splitting of the lowest resonance in the tunneling
conductance through a gold nano-particle.",0109541v1
2015-07-10,Spin-orbit coupling in methyl functionalized graphene,"We present first-principles calculations of the electronic band structure and
spin-orbit effects in graphene functionalized with methyl molecules in dense
and dilute limits. The dense limit is represented by a 2$\times$2 graphene
supercell functionalized with one methyl admolecule. The calculated spin-orbit
splittings are up to $0.6$ meV. The dilute limit is deduced by investigating a
large, 7$\times$7, supercell with one methyl admolecule. The electronic band
structure of this supercell is fitted to a symmetry-derived effective
Hamiltonian, allowing us to extract specific hopping parameters including
intrinsic, Rashba, and PIA (pseudospin inversion asymmetry) spin-orbit terms.
These proximity-induced spin-orbit parameters have magnitudes of about 1 meV,
giant compared to pristine graphene whose intrinsic spin-orbit coupling is
about 10 $\mu$eV. We find that the origin of this giant local enhancement is
the $sp^3$ corrugation and the breaking of local pseudospin inversion symmetry,
as in the case of hydrogen adatoms. Also similar to hydrogen, methyl acts as a
resonant scatterer, with a narrow resonance peak near the charge neutrality
point. We also calculate STM-like images showing the local charge densities at
different energies around methyl on graphene.",1507.02820v2
2017-11-08,Planet Formation in Disks with Inclined Binary Companions: Can Primordial Spin-Orbit Misalignment be Produced?,"Many hot Jupiter (HJ) systems have been observed to have their stellar spin
axis misaligned with the planet's orbital angular momentum axis. The origin of
this spin-orbit misalignment and the formation mechanism of HJs remain poorly
understood. A number of recent works have suggested that gravitational
interactions between host stars, protoplanetary disks, and inclined binary
companions may tilt the stellar spin axis with respect to the disk's angular
angular momentum axis, producing planetary systems with misaligned orbits.
These previous works considered idealized disk evolution models and neglected
the gravitational influence of newly formed planets. In this paper, we explore
how disk photoevaporation and planet formation and migration affect the
inclination evolution of planet-star-disk-binary systems. We take into account
planet-disk interactions and the gravitational spin-orbit coupling between the
host star and the planet. We find that the rapid depletion of the inner disk
via photoevaporation reduces the excitation of stellar obliquities. Depending
on the formation and migration history of HJs, the spin-orbit coupling between
the star and the planet may reduces and even completely suppress the excitation
of stellar obliquities. Our work constrains the formation/migration history of
HJs. On the other hand, planetary systems with ""cold"" Jupiters or close-in
super-earths may experience excitation of stellar obliquities in the presence
of distant inclined companions.",1711.03138v2
2021-04-25,Staggered spin-orbit interaction in a nanoscale device,"The coupling of the spin and the motion of charge carriers stems directly
from the atomic structure of a conductor. It has become an important ingredient
for the emergence of topological matter, and, in particular, topological
superconductivity which could host non-abelian excitations such as Majorana
modes or parafermions. These modes are sought after mostly in semiconducting
platforms which are made of heavy atoms and therefore exhibit naturally a large
spin-orbit interaction. Creating domain walls in the spin orbit interaction at
the nanoscale may turn out to be a crucial resource for engineering topological
excitations suitable for universal topological quantum computing. For example,
it has been proposed for exploring exotic electronic states or for creating
hinge states. Realizing this in natural platforms remains a challenge. In this
work, we show how this can be alternatively implemented by using a synthetic
spin orbit interaction induced by two lithographically patterned magnetically
textured gates. By using a double quantum dot in a light material -- a carbon
nanotube -- embedded in a microwave cavity, we trigger hopping between two
adjacent orbitals with the microwave photons and directly compare the wave
functions separated by the domain wall via the light-matter coupling. We show
that we can achieve an engineered staggered spin-orbit interaction with a
change of strength larger than the hopping energy between the two sites.",2104.12181v1
2019-02-27,Intertwined spin-orbital coupled orders in the iron-based superconductors,"The underdoped phase diagram of the iron-based superconductors exemplifies
the complexity common to many correlated materials. Indeed, multiple ordered
states that break different symmetries but display comparable transition
temperatures are present. Here, we argue that such a complexity can be
understood within a simple unifying framework. This framework, built to respect
the symmetries of the non-symmorphic space group of the FeAs/Se layer, consists
of primary magnetically-ordered states and their vestigial phases that
intertwine spin and orbital degrees of freedom. All vestigial phases have
Ising-like and zero wave-vector order parameters, described in terms of
composite spin order and exotic orbital-order patterns such as spin-orbital
loop-currents, staggered atomic spin-orbit coupling, and emergent Rashba- and
Dresselhaus-type spin-orbit interactions. Moreover, they host unusual
phenomena, such as the electro-nematic effect, by which electric fields acts as
transverse fields to the nematic order parameter, and the ferro-N\'eel effect,
by which a uniform magnetic field induces N\'eel order. We discuss the
experimental implications of our findings to iron-based superconductors and
possible extensions to other correlated compounds with similar space groups.",1902.10831v2
2008-04-03,Multiple Andreev reflections in a quantum dot coupled to superconductors: Effects of spin-orbit coupling,"We study the out-of-equilibrium current through a multilevel quantum dot
contacted to two superconducting leads and in the presence of Rashba and
Dresselhaus spin-orbit couplings, in the regime of strong dot-lead coupling.
The multiple Andreev reflection (MAR) subgap peaks in the current voltage
characteristics are found to be modified (but not suppressed) by the spin-orbit
interaction, in a way that strongly depends on the shape of the dot confining
potential. In a perfectly isotropic dot the MAR peaks are enhanced when the
strength $\alpha_R$ and $\alpha_D$ of Rashba and Dresselhaus terms are equal.
When the anisotropy of the dot confining potential increases the dependence of
the subgap structure on the spin-orbit angle
$\theta=\arctan(\alpha_D/\alpha_R)$ decreases. Furthermore, when an in-plane
magnetic field is applied to a strongly anisotropic dot, the peaks of the
non-linear conductance oscillate as a function of the magnetic field angle, and
the location of the maxima and minima allows for a straightforward read-out of
the spin-orbit angle $\theta$.",0804.0591v2
2014-04-22,Order-by-disorder and spin-orbital liquids in a distorted Heisenberg-Kitaev model,"The microscopic modeling of spin-orbit entangled $j=1/2$ Mott insulators such
as the layered hexagonal Iridates Na$_2$IrO$_3$ and Li$_2$IrO$_3$ has spurred
an interest in the physics of Heisenberg-Kitaev models. Here we explore the
effect of lattice distortions on the formation of the collective spin-orbital
states which include not only conventionally ordered phases but also gapped and
gapless spin-orbital liquids. In particular, we demonstrate that in the
presence of spatial anisotropies of the exchange couplings conventionally
ordered states are formed through an order-by-disorder selection which is not
only sensitive to the type of exchange anisotropy but also to the relative
strength of the Heisenberg and Kitaev couplings. The spin-orbital liquid phases
of the Kitaev limit -- a gapless phase in the vicinity of spatially isotropic
couplings and a gapped Z$_2$ phase for a dominant spatial anisotropy of the
exchange couplings -- show vastly different sensitivities to the inclusion of a
Heisenberg exchange. While the gapless phase is remarkably stable, the gapped
Z$_2$ phase quickly breaks down in what might be a rather unconventional phase
transition driven by the simultaneous condensation of its elementary
excitations.",1404.5490v2
2021-07-21,Robust propagating in-gap modes due to spin-orbit domain walls in graphene,"Recently, great experimental efforts towards designing topological electronic
states have been invested in layered incommensurate heterostructures which form
various nano- and meso-scale domains. In particular, it has become clear that a
delicate interplay of different spin-orbit terms is induced in graphene on
transition metal dichalcogenide substrates. We therefore theoretically study
various types of domain walls in spin-orbit coupling in graphene looking for
robust one-dimensional propagating electronic states. To do so, we use an
interface Chern number and a spectral flow analysis in the low-energy theory
and contrast our results to the standard arguments based on valley-Chern
numbers or Chern numbers in continuum models. Surprisingly, we find that a
sign-changing domain wall in valley-Zeeman spin-orbit coupling binds two robust
Kramers pairs, within the bulk gap opened due to a simultaneous presence of
Rashba coupling. We also study the robustness to symmetry breaking and lattice
backscattering effects in tight-binding models. We show an explicit mapping of
our valley-Zeeman domain wall to a domain wall in gated spinless bilayer
graphene. We discuss the possible spectroscopic and transport signatures of
various types of spin-orbit coupling domain walls in heterostructures.",2107.10116v2
2010-09-02,On the influence of hidden momentum and hidden energy in the classical analysis of spin-orbit coupling in hydrogenlike atoms,"In a recent article, Kholmetskii, Missevitch and Yarmin [""On the classical
analysis of spin-orbit coupling in hydrogenlike atoms,"" Am. J. Phys. 78(4),
April 2010 (428-432)] examine in detail the spin-orbit coupling in the
semiclassical hydrogenic atom, and identify a need to account for non-Coulomb
forces not included in the standard analysis. Kholmetskii, et al., showed that
the experimentally-measured coupling continues to be obtained when the new
forces are incorporated in the analysis. This requires that the change in
orbital radius due to non-Coulomb forces is also properly accounted for. In
response to a comment, Kholmetskii, et al., showed that the
experimentally-measured coupling continues to be obtained when so-called
""hidden momentum"" forces are also included. However it has been postulated that
when hidden momentum is nonvanishing, a corresponding hidden energy must also
be present, that was not included in the total energy by Kholmetskii, et al.
Hidden energy is postulated necessary to obtaining a relativistically covariant
description. Inclusion of hidden energy leads to disagreement with the
experimentally-determined spin-orbit coupling magnitude if the Bohr postulate,
that orbital angular momentum is quantized in whole multiples of the reduced
Planck constant, is assumed to apply to kinetic momentum alone. The empirical
result may be recovered in the semiclassical picture and using the general
approach developed by Kholmetskii, et al., if the Bohr postulate is
reinterpreted to apply to orbital angular momentum that consists of hidden as
well as kinetic momentum.",1009.0495v4
2008-07-22,Anisotropic tunneling magnetoresistance and tunneling anisotropic magnetoresistance: spin-orbit coupling in magnetic tunnel junctions,"The effects of the spin-orbit interaction on the tunneling magnetoresistance
of ferromagnet/semiconductor/normal metal tunnel junctions are investigated.
Analytical expressions for the tunneling anisotropic magnetoresistance (TAMR)
are derived within an approximation in which the dependence of the
magnetoresistance on the magnetization orientation in the ferromagnet
originates from the interference between Bychkov-Rashba and Dresselhaus
spin-orbit couplings that appear at junction interfaces and in the tunneling
region. We also investigate the transport properties of
ferromagnet/semiconductor/ferromagnet tunnel junctions and show that in such
structures the spin-orbit interaction leads not only to the TAMR effect but
also to the anisotropy of the conventional tunneling magnetoresistance (TMR).
The resulting anisotropic tunneling magnetoresistance (ATMR) depends on the
absolute magnetization directions in the ferromagnets. Within the proposed
model, depending on the magnetization directions in the ferromagnets, the
interplay of Bychkov-Rashba and Dresselhaus spin-orbit couplings produces
differences between the rates of transmitted and reflected spins at the
ferromagnet/seminconductor interfaces, which results in an anisotropic local
density of states at the Fermi surface and in the TAMR and ATMR effects. Model
calculations for Fe/GaAs/Fe tunnel junctions are presented. Furthermore, based
on rather general symmetry considerations, we deduce the form of the
magnetoresistance dependence on the absolute orientations of the magnetizations
in the ferromagnets.",0807.3564v1
2023-06-27,Spin-orbital Jahn-Teller bipolarons,"Polarons and spin-orbit (SO) coupling are distinct quantum effects that play
a critical role in charge transport and spin-orbitronics. Polarons originate
from strong electron-phonon interaction and are ubiquitous in polarizable
materials featuring electron localization, in particular $\mathrm{3d}$
transition metal oxides (TMOs). On the other hand, the relativistic coupling
between the spin and orbital angular momentum is notable in lattices with heavy
atoms and develops in $\mathrm{5d}$ TMOs, where electrons are spatially
delocalized. Here we combine ab initio calculations and magnetic measurements
to show that these two seemingly mutually exclusive interactions are entangled
in the electron-doped SO-coupled Mott insulator
$\mathrm{Ba_2Na_{1-x}Ca_xOsO_6}$ ($0< x < 1$), unveiling the formation of
spin-orbital bipolarons. Polaron charge trapping, favoured by the Jahn-Teller
lattice activity, converts the Os $\mathrm{5d^1}$ spin-orbital
$\mathrm{J_{eff}=3/2}$ levels, characteristic of the parent compound
$\mathrm{Ba_2NaOsO_6}$ (BNOO), into a bipolaron $\mathrm{5d^2}$
$\mathrm{J_{eff}=2}$ manifold, leading to the coexistence of different
J-effective states in a single-phase material. The gradual increase of
bipolarons with increasing doping creates robust in-gap states that prevents
the transition to a metal phase even at ultrahigh doping, thus preserving the
Mott gap across the entire doping range from $\mathrm{d^1}$ BNOO to
$\mathrm{d^2}$ $\mathrm{Ba_2CaOsO_6}$ (BCOO).",2306.15757v1
2023-10-26,Polarization and third-order Hall effect in III-V semiconductor heterojunctions,"We study Berry connection polarizability (BCP) induced electric polarization
and third-order Hall (TOH) effect in a two-dimensional electron/hole gas
(2DEG/2DHG) with Rashba-Dresselhaus (RD) spin-orbit couplings in III-V
semiconductor heterostructures. The electric polarization decreases with the
increase of the Fermi energy and is responsive to the electric field
orientation in the presence of RD spin-orbit couplings for both systems. We
determine the BCP-induced TOH conductivity ($\chi_{\perp}^{\text{I}}$) along
with the TOH conductivity associated with the band velocity
($\chi_{\perp}^{\text{II}}$). We find that the presence of an infinitesimal
amount of Dresselhaus coupling in addition to the dominant Rashba coupling
results in finite TOH responses. These conductivities vanish when the field is
aligned with and/or orthogonal to the symmetry lines $k_x\pm k_y=0$ in both
systems. For typical system parameters in a 2DEG with $k$-linear RD
interactions, the magnitude of $\chi_{\perp}^{\text{I}}$ is smaller than that
of $\chi_{\perp}^{\text{II}}$. On the other hand, when both the SO couplings
are comparable, $\chi_{\perp}^{\text{I}}$ shows a notable increase in
magnitude, owing to the distinctive characteristics of BCP. The TOH
conductivity of 2DEG remains unchanged when Rashba and Dresselhaus spin-orbit
couplings are exchanged. For 2DHG with $k$-cubic RD interactions,
$\chi_{\perp}^{\text{I},h}$ exhibits a larger magnitude compared to
$\chi_{\perp}^{\text{II},h}$. Unlike the electron case, the BCP induced
$\chi_{\perp}^{\text{I},h}$ alters under the exchange of spin-orbit coupling
parameters, whereas $\chi_{\perp}^{\text{II},h}$ remains the same.",2310.17371v2
2021-04-14,"Spin-orbit coupling in organic microcavities: Lower polariton splitting, triplet polaritons, and disorder-induced dark-states relaxation","Using an extended Tavis-Cummings model, we study the effect of the spin-orbit
coupling between the singlet and the triplet molecular excitons in organic
microcavities in the strong coupling regime. The model is solved in the single
excitation space for polaritons, which contains the bright (permutation
symmetric) singlet and triplet excitons, as well as the dark bands consisting
of the nonsymmetric excitons of either type. We find that the spin-orbit
coupling splits the lower polariton into two branches, and also creates a
triplet polariton when the cavity mode is in resonance with the triplet
excitons. The optical absorption spectrum of the system that can reveal this
splitting in experiments is presented and the effect of disorder in exciton
energies and couplings is explored. An important consequence of the disorder in
the spin-orbit coupling -- a weak coupling between the otherwise decoupled
bright and dark sectors -- is explored and detailed calculations of the squared
transition matrix elements between the dark bands and polaritons are presented
along with derivation of some approximate yet quite accurate analytical
expressions. This relaxation channel for the dark states contains an
interference between two transition paths that, for a given polariton state,
suppresses the relaxation of one dark band and enhances it for the other.",2104.07016v3
2019-06-25,Unambiguous Electrical Detection of Spin-Charge Conversion in Lateral Spin-Valves,"Efficient detection of spin-charge conversion is crucial for advancing our
understanding of emergent phenomena in spin-orbit-coupled nanostructures. Here,
we provide proof of principle of an electrical detection scheme of spin-charge
conversion that enables full disentanglement of competing spin-orbit coupling
transport phenomena in diffusive lateral channels i.e. the inverse spin Hall
effect (ISHE) and the spin galvanic effect (SGE). A suitable detection geometry
in an applied oblique magnetic field is shown to provide direct access to
spin-charge transport coefficients through a simple symmetry analysis of the
output non-local resistance. The scheme is robust against tilting of the
spin-injector magnetization, disorder and spurious non-spin related
contributions to the non-local signal, and can be used to probe spin-charge
conversion effects in both spin-valve and hybrid optospintronic devices.",1906.10448v2
2008-05-11,Evolution of Spin-Orbital-Lattice Coupling in the $R$VO$_3$ Perovskites,"We introduce a microscopic model which unravels the physical mechanisms
responsible for the observed phase diagram of the $R$VO$_3$ perovskites. It
reveals a nontrivial interplay between superexchange, the orbital-lattice
coupling due to the GdFeO$_3$-like rotations of the VO$_6$ octahedra, and
orthorhombic lattice distortions. We find that the lattice strain affects the
onset of the magnetic and orbital order by partial suppression of orbital
fluctuations. The present approach provides also a natural explanation of the
observed reduction of magnon energies from LaVO$_3$ to YVO$_3$.",0805.1545v1
2018-07-18,Spin-orbit coupled soliton in a random potential,"We investigate theoretically the dynamics of a spin-orbit coupled soliton
formed by a self- interacting Bose-Einstein condensate immersed in a random
potential, in the presence of an artificial magnetic field. We find that due to
the anomalous spin-dependent velocity, the synthetic Zeeman coupling can play a
critical role in the soliton dynamics by causing its localization or
delocalization, depending on the coupling strength and on the parameters of the
random potential. The observed effects of the Zeeman coupling qualitatively
depend on the type of self-interaction in the condensate since the spin state
and the self-interaction energy of the condensate are mutually related if the
invariance of the latter with respect to the spin rotation is lifted.",1807.06794v2
2023-08-05,Analytical results for a spin-orbit coupled atom held in a non-Hermitian double well under synchronous combined modulation,"We propose a simple method of synchronous combined modulations to generate
the exact analytic solutions for a spin-orbit (SO) coupled ultracold atom held
in a non-Hermitian double-well potential. Based on the obtained analytical
solutions, we mainly study the parity-time ($\mathcal{PT}$) symmetry of this
system and the system stability for both balanced and unbalanced gain-loss
between two wells. Under balanced gain and loss, the effect of the proportional
constants between synchronous combined modulations and the SO-coupling strength
on the $\mathcal{PT}$-symmetry breaking is revealed analytically. Surprisingly,
we find when the Zeeman field is present, the stable spin-flipping tunneling
between two wells can not occur in the non-Hermitian SO-coupled ultracold
atomic system, but the stable spin-conserving tunneling can be performed. Under
unbalanced gain and loss, the unique set of parameter conditions that can cause
the system to stabilize is found. The results may provide a possibility for the
exact control of $\mathcal{PT}$-symmetry breaking and quantum spin dynamics in
a non-Hermitian SO-coupled system.",2308.02848v1
2005-06-14,Spin-wave softening and Hund's coupling in ferromagnetic manganites,"Using one-orbital model of hole-doped manganites, we show with the help of
Holstein-Primakov transformation that finite Hund's coupling is responsible for
the spin-wave softening in the ferromagnetic $B$-phase manganites. We obtain an
analytical result for the spin-wave spectrum for $\JH\gg t$. In the limit of
infinte Hund's coupling, the spectrum is the conventional nearest-neighbor
Heisenberg ferromagnetic spin-wave. The $o(t/\JH)$-order correction is negative
and thus accounts for the softening near the zone boundary.",0506321v1
2020-01-09,Block-Lanczos density-matrix renormalization-group approach to spin transport in Heisenberg chains coupled to leads,"We adapt the block-Lanczos density-matrix renormalization-group technique to
study the spin transport in a spin chain coupled to two non-interacting
fermionic leads. As an example, we consider leads described by two-dimensional
tight-binding models on a square lattice. Although the simulations are carried
out using a chain representation of the leads, observables in the original
two-dimensional lattice can be calculated by reversing the block-Lanczos
transformation. This is demonstrated for leads with Rashba spin-orbit coupling.",2001.02926v2
2017-03-09,Spin-wave excitations in the SDW state of iron pnictides: a comparison between the roles of interaction parameters,"We investigate the role of Hund's coupling in the spin-wave excitations of
the ($\pi, 0$) ordered magnetic state within a five-orbital tight-binding model
for iron pnictides. To differentiate between the roles of intraorbital Coulomb
interaction and Hund's coupling, we focus on the self-consistently obtained
mean-field SDW state with a fixed magnetic moment obtained by using different
sets of interaction parameters. We find that the Hund's coupling is crucial for
the description of various experimentally observed characteristics of the
spin-wave excitations including the anisotropy, energy-dependent behavior, and
spin-wave spectral weight distribution.",1703.03228v2
2012-11-29,Possible Manipulation of Kondo Effect by Transition between Antiferromagnetic and Ferromagnetic s-d Coupling,"Kondo effect originates from antiferromagnetic (AFM) s-d coupling between
magnetic impurity and the conduction electron, while it will be totally
quenched in ferromagnetic (FM) regime due to malfunction of spin-flip. We
investigate the possibility of switching on/off Kondo effect by transition of
AFM/FM s-d coupling using 3d-metal phthalocyanine molecule (MPc) on Au(111) as
a model system. A Hamiltonian model is constructed based on the feature of MPc
molecule to show the condition for AFM/FM s-d coupling. The AFM s-d coupling
could transform to FM s-d coupling if the spin state of the lowest unoccupied
orbital changes.",1211.6955v1
2006-10-25,Spin relaxation of two-dimensional electrons with a hierarchy of spin-orbit couplings,"The density matrix formalism is applied to calculate the spin-relaxation time
for two-dimensional systems with a hierarchy of spin-orbit couplings, such as
Rashba-type, Dresselhaus-type and so on. It is found that the spin-relaxation
time can be infinite if those coupling strengths $\alpha$, $\beta$, $\gamma_1$
and $\gamma_2$ satisfy either condition (i) $\alpha=\beta, \gamma_1=0$ or (ii)
$\alpha=-\beta, \gamma_2=0$, which correspond to the vanishing Yang-Mills
""magnetic"" field. The effect caused by the application of an external magnetic
field is also discussed. It is found that the longitudinal and in-plane spin
components can possess infinite life time when the spin components, the Larmor
precession frequency and the external magnetic field satisfy certain relations.",0610694v1
2013-11-04,Photonic spin Hall effect in topological insulators,"In this paper we theoretically investigate the photonic spin Hall effect
(SHE) of a Gaussian beam reflected from the interface between air and
topological insulators (TIs). The photonic SHE is attributed to spin-orbit
coupling and manifests itself as in-plane and transverse spin-dependent
splitting. We reveal that the spin-orbit coupling effect in TIs can be routed
by adjusting the axion angle variations. Unlike the transverse spin-dependent
splitting, we find that the in-plane one is sensitive to the axion angle. It is
shown that the polarization structure in magneto-optical Kerr effect is
significantly altered due to the spin-dependent splitting in photonic SHE. We
theoretically propose a weak measurement method to determine the strength of
axion coupling by probing the in-plane splitting of photonic SHE.",1311.0556v1
2015-11-17,Do micromagnets expose spin qubits to charge and Johnson noise?,"An ideal quantum dot spin qubit architecture requires a local magnetic field
for one-qubit rotations. Such an inhomogeneous magnetic field, which could be
implemented via a micromagnet, couples the qubit subspace with background
charge fluctuations causing dephasing of spin qubits. In addition, a
micromagnet generates magnetic field evanescent-wave Johnson noise. We derive
an effective Hamiltonian for the combined effect of a slanting magnetic field
and charge noise on a single-spin qubit and estimate the free induction decay
dephasing times T2* for Si and GaAs. The effect of the micromagnet on Si qubits
is comparable in size to that of spin-orbit coupling at an applied field of
B=1T, whilst dephasing in GaAs is expected to be dominated by spin-orbit
coupling. Tailoring the magnetic field gradient can efficiently reduce T2* in
Si. In contrast, the Johnson noise generated by a micromagnet will only be
important for highly coherent spin qubits.",1511.05247v1
2018-04-28,Non-exponential long-range interaction of magnetic impurities in spin-orbit coupled superconductors,"The Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction of magnetic impurities
in a superconductor exponentially decreases when the distance $r$ between them
is larger than the superconductor's coherence length, because this interaction
is mediated by quasiparticles which have a gap in their energy spectrum. At the
same time, the spin-singlet superconducting condensate was always assumed to
stay neutral to magnetic impurities. Due to a spin-orbit coupling (SOC),
however, Cooper pairs gain an admixture of spin-triplet correlated states which
provide for a link between impurity spins and an s-wave condensate. It is shown
that its static Goldstone mode mediates the $1/r^2$ interaction of the spins in
two-dimensional (2D) systems. This effect is considered within two models: of a
clean 2D s-wave superconductor with the strong Rashba SOC and of a bilayer
system combining a 2D Rashba coupled electron gas and an s-wave superconducting
film. The predicted long-range interaction can have a strong effect on a spin
order in superconductor-magnetic impurity systems that are expected to host
Majorana fermions.",1804.10756v2
2020-02-06,Rashba controlled two-electron spin-charge qubits as building blocks of a quantum computer,"The spin-sensitive charge oscillation, controlled by an external magnetic
field, was recently proposed as a mechanism of transformations of qubits,
defined as two-electron spin-charge Wannier molecules in a square quantum dot.
The paper expands this idea by including the effects of Rashba type spin-orbit
coupling. The problem is studied theoretically by mapping the system to an
analytic effective Hamiltonian for 8 low energy states, comprising singlet and
triplet on each dot diagonal. The validity of the mapping is confirmed by
comparing the energy and spin of full and mapped system, and also by the
reproduction of charge-oscillation dynamics in the presence of magnetic flux.
The newly introduced Rashba coupling significantly enriches the system
dynamics, affecting the magnitude of charge oscillations and allowing the
controlled transitions between singlet and triplet states due to the spin
rotations, induced by spin-orbit coupling. The results indicate the possibility
for use of the studied system for quantum information processing, while
possible extensions of the system to serve as a qubit in a universal quantum
computer, fulfilling all five DiVincenzo criteria, are also discussed.",2002.02426v1
2020-03-03,Photoprotected spin Hall effect on graphene with substrate induced Rashba spin-orbit coupling,"We propose an experimental realization of the Spin Hall effect in graphene by
illuminating a graphene sheet on top of a substrate with circularly polarized
monochromatic light. The substrate induces a controllable Rashba type
spin-orbit coupling which breaks the spin-degeneracy of the Dirac cones but it
is gapless. The circularly polarized light induces a gap in the spectrum and
turns graphene into a Floquet topological insulator with spin dependent edge
states. By analyzing the high and intermediate frequency regimes, we find that
in both parameter limits, the spin-Chern number can be tuned by the effective
coupling strength of the charge particles to the radiation field and determine
the condition for the photoinduced topological phase transition.",2003.01779v1
2022-12-20,Spin dynamics in quantum dots on liquid helium,"Liquid He-4 is free from magnetic defects, making it an ideal substrate for
electrons with long-lived spin states. Such states can serve as qubit states.
Here we consider the spin states of electrons electrostatically localized in
quantum dots on a helium surface. Efficient gate operations in this system
require spin-orbit coupling. It can be created by a nonuniform magnetic field
from a current-carrying wire, can be turned on and off, and allows one to
obtain large electro-dipole moment and comparatively fast coupling of spins in
neighboring dots. Of central importance is to understand the spin decay due to
the spin-orbit coupling. We establish the leading mechanism of such decay and
show that the decay is sufficiently slow to enable high-fidelity single- and
two-qubit gate operations",2212.10683v1
2023-01-02,Topological Kondo Superconductors,"Spin-triplet $p$-wave superconductors are promising candidates for
topological superconductors. They have been proposed in various
heterostructures where a material with strong spin-orbit interaction is coupled
to a conventional $s$-wave superconductor by proximity effect. However,
topological superconductors existing in nature and driven purely by strong
electron correlations are yet to be studied. Here we propose a realization of
such a system in a class of Kondo lattice materials in the absence of
spin-orbit coupling and proximity effect. Therein, the odd-parity Kondo
hybridization mediates ferromagnetic spin-spin coupling and leads to
spin-triplet resonant-valence-bond ($t$-RVB) pairing between local moments.
Spin-triplet $p\pm i p^\prime$-wave topological superconductivity is reached
when Kondo effect co-exists with $t$-RVB. We identify the topological nature by
the non-trivial topological invariant and the Majorana fermions at edges. Our
results offer a comprehensive understanding of experimental observations on
UTe$_2$, a U-based ferromagnetic heavy-electron superconductor.",2301.00538v1
2006-10-06,Boundary spin Hall effect in a two-dimensional semiconductor system with Rashba spin-orbit coupling,"We derive boundary conditions for the coupled spin-charge diffusion equations
at a transmitting interface between two-dimensional electron systems with
different strengths of the Rashba spin-orbit (SO) coupling $\alpha$, and an
electric field parallel to the interface. We consider the limit where the
spin-diffusion length l_s is long compared to the electron mean free path l,
and assume that $\alpha$ changes discontinuously on the scale of l_s. We find
that the spin density is also discontinuous on the scale of l_s. In the case
where the electron mobility is constant across the interface, this leads to the
complete suppression of the expected spin injection from a region with
$\alpha\neq0$ into a non-SO region with $\alpha=0$.",0610190v2
2008-03-27,Fano and Dicke effects and spin polarization in a double Rashba-ring system side coupled to a quantum wire,"The electronic transport in a system of two quantum rings side-coupled to a
quantum wire is studied via a single-band tunneling tight-binding Hamiltonian.
We derived analytical expressions for the conductance and spin polarization
when the rings are threaded by magnetic fluxes with Rashba spin-orbit
interaction. We show that by using the Fano and Dicke effects this system can
be used as an efficient spin-filter even for small spin orbit interaction and
small values of magnetic flux. We compare the spin-dependent polarization of
this design and the polarization obtained with one ring side coupled to a
quantum ring. As a main result, we find better spin polarization capabilities
as compared to the one ring design",0803.4014v1
2018-05-10,Designing Rashba-Dresselhaus effect in magnetic insulators,"One of the major strategies to control magnetism in spintronics is to utilize
the coupling between electron spin and its orbital motion. The Rashba and
Dresselhaus spin-orbit couplings induce magnetic textures of band electrons
called spin momentum locking, which produces a spin torque by the injection of
electric current. However, joule heating had been a bottleneck for device
applications. Here, we propose a theory to generate further rich spin textures
in insulating antiferromagnets with broken spatial inversion symmetry (SIS),
which is easily controlled by a small magnetic field. In antiferromagnets, the
ordered moments host two species of magnons that serve as internal degrees of
freedom in analogy with electron spins. The Dzyaloshinskii-Moriya interaction
introduced by the SIS breaking couples the two-magnon-degrees of freedom with
the magnon momentum. We present a systematic way to design such texture and to
detect it via magnonic spin current for the realization of antiferromagnetic
memory.",1805.03925v2
2023-04-21,Magnetic properties of a spin-orbit entangled Jeff = 1/2 honeycomb lattice,"The interplay between spin-orbit coupling, anisotropic magnetic interaction,
frustration-induced quantum fluctuations and spin correlations can lead to
novel quantum states with exotic excitations in rare-earth-based quantum
magnets. Herein, we present the crystal structure, magnetization, electron spin
resonance (ESR), specific heat, and nuclear magnetic resonance (NMR)
experiments on the polycrystalline samples of Ba9Yb2Si6O24, in which Yb3+ ions
form a perfect honeycomb lattice without detectable anti-site disorder. The
magnetization data reveal antiferromagnetically coupled spin-orbit entangled
Jeff = 1/2 degrees of freedom of Yb3+ ions in the Kramers doublet state. The
ESR measurements reveal that the first excited Kramers doublet is 32.3(7) meV
above the ground state. The specific heat results suggest the absence of any
long-range magnetic order in the measured temperature range. Furthermore, the
29Si NMR results do not indicate any signature of magnetic ordering down to 1.6
K, and the spin-lattice relaxation rate reveals the presence of a field-induced
gap that is attributed to the Zeeman splitting of Kramers doublet state in this
quantum material. Our experiments detect neither spin freezing nor long-range
magnetic ordering down to 1.6 K. The current results suggest the presence of
short-range spin correlations in this spin-orbit entangled Jeff =1/2 rare-earth
magnet on a honeycomb lattice.",2304.10890v2
2006-11-24,Spin dynamics in the regime of hopping conductivity,"We consider spin dynamics in the impurity band of a semiconductor with
spin-split spectrum. Due to the splitting, phonon-assisted hops from one
impurity to another are accompanied by rotation of the electron spin, which
leads to spin relaxation. The system is strongly inhomogeneous because of
exponential variation of hopping times. However, at very small couplings an
electron diffuses over a distance exceeding the characteristic scale of the
inhomogeneity during the time of spin relaxation, so one can introduce an
averaged spin relaxation rate. At larger values of coupling the system is
effectively divided into two subsystems: the one where relaxation is very fast
and another one where relaxation is rather slow. In this case, spin decays due
to escape of the electrons from one subsystem to another. As a result, the spin
dynamics is non-exponential and hardly depends on spin-orbit coupling.",0611626v1
2012-02-08,Tuning into the Kitaev spin liquid phase:A spin model on the honeycomb lattice with two types of Heisenberg exchange couplings,"We study a spin model on honeycomb lattice with two types of Heisenberg
exchange couplings, $J$ and $\tilde J$, where $J$ is for the conventional spin
and and $\tilde J$ for rotated spin. When $\tilde J=0$, this is the
conventional Heisenberg model. When J=0, the system is either in a stripy
antiferromagnetic order($\tilde J<0$, ferromagnetic for rotated spin) or a
zig-zag antiferromagnetic order ($\tilde J>0$, antiferromagnetic for rotated
spin). The competition between two ferromagnetic orders or two
antiferromagnetic orders induces Kitaev's spin liquid phase characterized by
the exactly solvable Kitaev model ($J=\tilde J$). Our model can be applied to
layered Mott insulators A$_2$IrO$_3$ (A=Li, Na). For a monolayer of
Li$_2$IrO$_3$, we show that it is possible to tune the controlling parameter
into the Kitaev spin liquid regime by a link-dependent Rashba spin-orbital
coupling.",1202.1610v5
2004-09-02,Black-hole ejecta by frame-dragging along the axis of rotation,"An energy $E=\omega J$ is derived for gravitational spin-orbit coupling by
frame-dragging $\omega$ acting on angular momentum $J$. This interaction
defines a no-boundary mechanism for linear acceleration of magnetized matter
along the axis of rotation of black holes. We explain GRB030329/SN2003dh by
centered nucleation of a high-mass black hole with rapid rotation, producing
baryon-poor ejecta by gravitational spin-orbit coupling. The duration of the
burst is attributed to spin-down in the emission of gravitational-waves by a
surrounding non-axisymmetric torus.",0409062v1
1999-11-22,The role of spin-orbit coupling for the superconducting state in Sr_2RuO_4,"The odd-parity spin-triplet Cooper pairing states show a six-fold degeneracy
for a quasi-two-dimensional electron system. In this article we show how
spin-orbit coupling can lift this degeneracy for Sr_2RuO_4 taking the band
structure based on the three relevant t_{2g}-orbitals of the Ru-ions into
account. The stabilized state depends on the relative strength of the pairing
interaction. We show that under reasonable assumptions the chiral pairing state
d(k) = z(k_x +/- i k_y) is favored against the others.",9911325v1
2000-01-27,Skyrmion Strings and Anomalous Hall Effect in Double Exchange Systems,"We perform Monte Carlo simulations to obtain quantitative results for the
anomalous Hall resistance, R_A, observed in colossal magnetoresistance
manganites. R_A arises from the interaction between the spin magnetization and
topological defects via spin-orbit coupling. We study these defects and how
they are affected by the spin-orbit coupling within the framework of the double
exchange model. The obtained anomalous Hall resistance is, in sign, order of
magnitude and shape, in agreement with experimental data.",0001404v1
2000-12-12,Loss of the magnetism in FeS,"It is argued that the formation of the non-magnetic state of FeS in external
pressures above 6.5 GPa is in agreement with the prediction of the quantum
atomistic solid-state theory, an extension of the crystal-field theory with the
spin-orbit coupling incorporated, and is related with the change of sign of the
off-cubic trigonal distortion marked by the change of the c/a ratio from >1.63
(magnetic) to <1.63 (non-magnetic). Keywords: highly-correlated electron
system, crystal field, low-spin state, Fe2+ ion, spin-orbit coupling",0012196v1
2001-10-17,Spin-orbit coupling and ESR theory for carbon nanotubes,"A theoretical description of ESR in 1D interacting metals is given, with
primary emphasis on carbon nanotubes. The spin-orbit coupling is derived, and
the resulting ESR spectrum is analyzed by field theory and exact
diagonalization. Drastic differences in the ESR spectra of single-wall and
multi-wall nanotubes are found. For single-wall tubes, the predicted double
peak spectrum could reveal spin-charge separation.",0110352v2
2005-01-24,Criterion for weak spin-orbit coupling in heavy-fermion superconductivity: A numerical renormalization-group study,"A criterion for effective irrelevancy of the spin-orbit coupling in the
heavy-fermion superconductivity is discussed on the basis of the impurity
Anderson model with two sets of Kramers doublets. Using Wilson's numerical
renormalization-group method, we demonstrate a formation of the quasiparticle
as well as the renormalization of the rotational symmetry-breaking interaction
in the lower Kramers doublet (quasispin) space. A comparison with the quasispin
conserving interaction exhibits the effective irrelevancy of the
symmetry-breaking interaction for the splitting of two doublets Delta larger
than the characteristic energy of the local spin fluctuation T_K. The formula
for the ratio of two interactions is also determined.",0501560v1
2005-01-26,Conductance Fluctuations and Spin Symmetries in Quantum Dots,"Conductance fluctuations in GaAs quantum dots with spin-orbit and Zeeman
coupling are investigated experimentally and compared to a random matrix theory
formulation that defines a number of regimes of spin symmetry depending on
experimental parameters. Accounting for orbital coupling of the in-plane
magnetic field, which can break time-reversal symmetry, yields excellent
overall agreement between experiment and theory.",0501622v2
2005-08-19,Trapping of Quantized Electrical Charge in Superfluid 3He-B via the Electrodynamics of Spin-orbit Coupled Systems,"Exploiting analogies between spin-orbit coupled spin superfluids and
non-Abelian Yang-Mills theory, we argue that machines can be built capable of
trapping a quantized amount of electric linear charge density, while the line
charge quantum itself is surprisingly large. The required conditions might well
hold in superfluid 3He-B, for which we propose an experimental realization of
this phenomenon.",0508481v1
2006-05-06,Light Induced Hall effect in semiconductors with spin-orbit coupling,"We show that optically excited electrons by a circularly polarized light in a
semiconductor with spin-orbit coupling subject to a weak electric field will
carry a Hall current transverse to the electric field. This light induced Hall
effect is a result of quantum interference of the light and the electric field,
and can be viewed as a physical consequence of the spin current induced by the
electric field. The light induced Hall conductance is calculated for the p-type
GaAs bulk material, and the n-type and p-type quantum well structures.",0605159v1
2006-09-05,Weak localization correction to the density of transmission eigenvalues in the presence of magnetic field and spin-orbit coupling for a chaotic quantum dot,"We calculated the weak localization correction to the density of the
transmission eigenvalues in the case of chaotic quantum dots in the framework
of Random Matrix Theory including the parametric dependence on the magnetic
field and spin-orbit coupling. The result is interpreted in terms of spin
singlet and triplet Cooperon modes of conventional diagrammatic perturbation
theory. As simple applications, we obtained the weak localization correction to
the conductance, the shot noise power and the third cumulant of the
distribution of the transmitted charge.",0609086v1
2007-03-30,Enhanced triplet superconductivity in noncentrosymmetric systems,"We study pairing symmetry of noncentrosymmetric superconductors based on the
extended Hubbard model on square lattice near half-filling, using the random
phase approximation. We show that d+f-wave pairing is favored and the triplet
f-wave state is enhanced by Rashba type spin-orbit coupling originating from
the broken inversion symmetry. The enhanced triplet superconductivity stems
from the increase of the effective interaction for the triplet pairing and the
reduction of the spin susceptibility caused by the Rashba type spin-orbit
coupling which lead to the increase of the triplet component and the
destruction of the singlet one, respectively.",0703809v1
2004-11-17,Solution of a Hamiltonian of quantum dots with Rashba spin-orbit coupling: quasi-exact solution,"We present a method to solve the problem of Rashba spin-orbit coupling in
semiconductor quantum dots, within the context of quasi-exactly solvable
spectral problems. We show that the problem possesses a hidden osp(2,2)
superalgebra. We constructed a general matrix whose determinant provide exact
eigenvalues. Analogous mathematical structures between the Rashba and some of
the other spin-boson physical systems are notified.",0411124v1
2007-08-22,Spin orbit interaction and zitterbewegung in symmetric wells,"Recently, we have introduced a novel inter-subband-induced spin-orbit (s-o)
coupling [Phys. Rev. Lett. 99, 076603 (2007); cond-mat/0607218] arising in
\textit{symmetric} wells with at least two subbands. This new s-o coupling
gives rise to an usual zitterbewegung -- i.e. the semiconductor analog to the
relativistic trembling motion of electrons -- with cycloidal motion without
magnetic fields. Here we complement these findings by explicitly deriving
expressions for the corresponding zitterbewegung in spin space.",0708.3091v1
2007-11-21,Anomalous Hall effect in a two dimensional electron gas with magnetic impurities,"Magnetic impurities play an important role in many spintronics-related
materials. Motivated by this fact, we study the anomalous Hall effect in the
presence of magnetic impurities, focusing on two-dimensional electron systems
with Rashba spin-orbit coupling. We find a highly nonlinear dependence on the
impurity polarization, including possible sign changes. At small impurity
magnetizations, this is a consequence of the remarkable result that the linear
term is independent of the spin-orbit coupling strength. Near saturation of the
impurity spins, the anomalous Hall conductivity can be resonantly enhanced, due
to interference between potential and magnetic scattering.",0711.3415v1
2009-02-12,Kondo effect in transport through Aharonov-Bohm and Aharonov-Casher interferometers,"We derive the extension of the Hubbard model to include Rashba spin-orbit
coupling that correctly describes Aharonov-Bohm and Aharonov-Casher phases in a
ring under applied magnetic and electric fields. When the ring is connected to
conducting leads, we develop a formalism that is able to describe both, Kondo
and interference effects. We find that in the Kondo regime, the spin-orbit
coupling reduces strongly the conductance from the unitary limit. This effect
in combination with the magnetic flux, can be used to produce spin polarized
carriers.",0902.2200v1
2011-10-11,Unconventional superfluidity induced by spin-orbital coupling in a polarized two-dimensional Fermi gas,"We show the spin-orbital coupling induced by an artificial light-induced
gauge field can fully restore superfluidity suppressed by population imbalance
in a two-dimensional (2D) Fermi gas, leading to unconventional superfluid
states either with topological Majorana fermion excitations or showing a novel
mixture of triplet pairing with spin-up (down) components respectively in the
$p_{x}\pm ip_{y}$ pairing channels. We self-consistently calculate the zero
temperature phase diagram at the BCS\ side of Feshbach resonance and show that
the phase transitions between different superfluid states can be revealed
through measurement of the in-situ density profile of the 2D atomic cloud in a
weak global trap.",1110.2241v1
2012-07-25,Magnetotransport effects in polar versus non-polar SrTiO3 based heterostructures,"Anisotropic magnetoresistance and negative magnetoresistance for in-plane
fields are compared for the LaAlO3 /SrTiO3 interface and the symmetric Nb-doped
SrTiO3 heterostructure. Both effects are exceptionally strong in LaAlO3 /SrTiO3
. We analyze their temperature, magnetic field and gate voltage dependencies
and find them to arise from a Rashba type spin-orbit coupling with magnetic
scatterers that have two contributions to their potential: spin exchange and
Coulomb interaction. Atomic spin-orbit coupling is sufficient to explain the
small effects observed in Nb-doped SrTiO3 . These results clarify contradicting
transport interpretations in SrTiO3 -based heterostructures.",1207.6057v1
2012-08-30,Composite fermion state of spin-orbit coupled bosons,"We consider spinor Bose gas with the isotropic Rashba spin-orbit coupling in
2D. We argue that at low density its groundstate is a composite fermion state
with a Chern-Simons gauge field and filling factor one. The chemical potential
of such a state scales with the density as \mu \propto n^{3/2}. This is a lower
energy per particle than \mu \propto n for the earlier suggested groundstate
candidates: a condensate with broken time-reversal symmetry and a spin density
wave state.",1208.6266v1
2013-04-18,Spontaneous ferromagnetism in the spinor Bose gas with Rashba spin-orbit coupling,"We show that in the two-component Bose gas with Rashba spin-orbit coupling an
arbitrarily small attractive interaction between bosons with opposite spin
induces spontaneous ferromagnetism below a finite critical temperature $T_c$.
In the ferromagnetic phase the single-particle spectrum exhibits a unique
minimum in momentum space in the direction of the magnetization. For
sufficiently small temperatures below $T_c$ the bosons eventually condense into
the unique state at the bottom of the spectrum, forming a ferromagnetic
Bose-Einstein condensate.",1304.5103v2
2014-10-13,Topological properties of the bond-modulated honeycomb lattice,"We study the combined effects of lattice deformation, e-e interaction and
spin-orbit coupling in a two-dimensional (2D) honeycomb lattice. We adopt
different kinds of hopping modulation--generalized dimerization and a Kekule
distortion--and calculate topological invariants for the non-interacting system
and for the interacting system. We identify the parameter range (Hubbard U,
hopping modulation, spin-orbit coupling) where the 2D system behaves as a
trivial insulator or Quantum Spin Hall Insulator.",1410.3411v2
2014-12-09,Spin-dependent thermoelectric properties of a Kondo-correlated quantum dot with Rashba spin-orbit coupling,"Thermoelectric transport phenomena in a single-level quantum dot coupled to
ferromagnetic leads are considered theoretically in the Kondo regime. The dot
is described by the Anderson model with Rashba type spin-orbit interaction. The
finite-U mean field slave boson technique is used to describe the transport
characteristics, like heat conductance, thermopower, thermoelectric efficiency
(figure of merit). The role of quantum interference effects in thermoelectric
parameters is also analyzed.",1412.2921v1
2015-03-03,Tuning the Chern number and Berry curvature with spin-orbit coupling and magnetic textures,"We obtain the band structure of a particle moving in a magnetic spin texture,
classified by its chirality and structure factor, in the presence of spin-orbit
coupling. This rich interplay leads to a variety of novel topological phases
characterized by the Berry curvature and their associated Chern numbers. We
suggest methods of experimentally exploring these topological phases by Hall
drift measurements of the Chern number and Berry phase interferometry to map
the Berry curvature.",1503.01164v1
2016-03-07,Spin-orbit coupled correlated metal phase in Kondo lattices: an implementation with alkaline-earth atoms,"We show that an interplay between quantum effects, strong on-site
ferromagnetic exchange interaction and antiferromagnetic correlations in Kondo
lattices can give rise to an exotic spin-orbit coupled metallic state in
regimes where classical treatments predict a trivial insulating behavior. This
phenomenon can be simulated with ultracold alkaline-earth fermionic atoms
subject to a laser-induced magnetic field by observing dynamics of spin-charge
excitations in quench experiments.",1603.01946v4
2016-07-18,Exotic Topological States with Raman-Induced Spin-Orbit Coupling,"We propose a simple experimental scheme to realize simultaneously the
one-dimensional spin-orbit coupling and the staggered spin-flip in ultracold
pseudospin-$1/2$ atomic Fermi gases trapped in square optical lattices. In the
absence of interspecies interactions, the system supports gapped Chern
insulators and gapless topological semimetal states. By turning on the $s$-wave
interactions, a rich variety of gapped and gapless inhomogeneous topological
superfluids can emerge. In particular, a gapped topological Fulde-Ferrell
superfluid, in which the chiral edge states at opposite boundaries possess the
same chirality, is predicted.",1607.05109v2
2017-02-14,Interference effects and Huygens' principle in transverse magnetic focusing of electrons and holes,"Interference effects form a fundamental pillar of quantum mechanics. In this
paper, we examine the interference in spin-orbit coupled transverse magnetic
focusing, where a weak magnetic field is used to focus charge carries over
mesoscopic scales. We determine a semi-classical form for the Green's function
in a weak magnetic field, for the case of both spin-less and spin-orbit coupled
charge carriers. The obtained forms for the Greens' function are independent of
particle dispersion and are thus applicable to a wide variety of systems.",1702.04425v1
2011-11-28,Crystallized merons and inverted merons in the condensation of spin-1 Bose gases with spin-orbit coupling,"The non-equilibrium dynamics of a rapidly quenched spin-1 Bose gas with
spin-orbit coupling is studied. By solving the stochastic projected
Gross-Pitaevskii equation, we show that crystallization of merons can occur in
a spinor condensate of ^{87}Rb. Analytic form and stability of the crystal
structure are given. Likewise, inverted merons can be created in a
spin-polarized spinor condensate of ^{23}Na. Our studies provide a chance to
explore the fundamental properties of meron-like matter.",1111.6338v2
2015-12-02,Two dipolar atoms in a harmonic trap,"Two identical dipolar atoms moving in a harmonic trap without an external
magnetic field are investigated. Using the algebra of angular momentum a semi -
analytical solutions are found. We show that the internal spin - spin
interactions between the atoms couple to the orbital angular momentum causing
an analogue of Einstein - de Haas effect. We show a possibility of
adiabatically pumping our system from the s-wave to the d-wave relative motion.
The effective spin-orbit coupling occurs at anti-crossings of the energy
levels.",1512.00631v2
2017-07-06,"Computation of unitary group for the Rashba spin-orbit coupled operator, with application to point-interactions","We compute an explicit formula for the one-parameter unitary group of the
single-particle Rashba spin-orbit coupled operator in dimension three. As an
application, we derive the formula for the Green function for the two-particle
operator, and then prove that the spin-dependent point-interaction is of class
$\mathcal{H}_{-4}$. The latter is thus the example of a supersingular
perturbation for which no self-adjoint operator can be constructed.",1707.01824v1
2017-10-11,Ultra-cold Collisions between Spin-Orbit-Coupled Dipoles: General Formalism and Universality,"A theoretical study of the low-energy scattering properties of two aligned
identical bosonic and fermionic dipoles in the presence of isotropic spin-orbit
coupling (SOC) is presented. A general treatment of particles with arbitrary
(pseudo-) spin is given in the framework of multi-channel scattering. At
ultracold temperatures and away from shape resonances or closed-channel
dominated resonances, the cross-section can be well described within the Born
approximation to within corrections due to the s-wave scattering. We compare
our findings with numerical calculations and find excellent agreement.",1710.03901v2
2019-08-23,Strong antisymmetric spin-orbit coupling and superconducting properties: The case of noncentrosymmetric LaPtSi,"In this work we aim to analyze the effect of a strong antisymmetric
spin-orbit coupling (ASOC) on superconductivity of noncentrosymmetric LaPtSi.
We study the energy gap structure of polycrystalline LaPtSi by using magnetic
penetration depth measurements down to 0.02$T_c$. We observed a dirty s-wave
behavior, which provides compelling evidence that the spin-singlet component of
the mixed pairing state is highly dominant. This is consistent with previous
results in the sense that the mere presence of a strong ASOC does not lead to
unconventional behaviors. Our result also downplays LaPtSi as a good candidate
for realizing time-reversal invariant topological superconductivity.",1908.08828v1
2020-08-22,Pseudospin resonances reveal synthetic spin-orbit interaction,"We investigate a spin-full double quantum dot (DQD) coupled to the leads in a
pseudospin valve configuration. The interplay of interaction and interference
produces in the stability diagram a rich variety of resonances, modulated by
the system parameters. In presence of ferromagnetic leads and pseudospin
anisotropy, those resonances split, turn into dips and acquire a Fano shape
thus revealing a synthetic spin-orbit coupling induced on the DQD. A set of
rate equations derived for a minimal model captures those features. The model
accurately matches the numerical results obtained for the full system in the
framework of a generalized master equation and calculated within the
cotunneling approximation.",2008.09857v1
2021-11-11,Spin-Orbit Coupling in Transition Metal Dichalcogenide Heterobilayer Flat Bands,"The valence flat bands in transition metal dichalcogenide (TMD)
heterobilayers are shown to exhibit strong intralayer spin-orbit coupling. This
is reflected in a simple tight-binding model with spin-dependent complex
hoppings based on the continuum model. A perpendicular electric field causes
interlayer hybridization, such that the effective model is equivalent to the
Kane-Mele model of topological insulators. The proposed model can be used as a
starting point to understand interactions and the experimentally observed
topological phases.",2111.06208v1
2021-12-07,Bogoliubov spectrum and the dynamic structure factor in a quasi-two-dimensional spin-orbit coupled BEC,"We compute the the Bogoliubov-de-Gennes excitation spectrum in a trapped
two-component spin-orbit-coupled (SOC) Bose-Einstein condensate (BEC) in
quasi-two-dimensions as a function of linear and angular momentum and analyse
them. The excitation spectrum exhibits a minima-like feature at finite momentum
for the immiscible SOC-BEC configuration. We augment these results by computing
the dynamic structure factor in the density and pseudo-spin sector, and discuss
its interesting features that can be experimentally measured through Bragg
spectroscopy of such ultra cold-condensate.",2112.03505v1
2023-08-28,Anomalous Zeeman effect in SrTiO3 and its possible all-electric detection,"We show that the interplay between spin-orbit coupling and cubic symmetry
breaking in SrTiO3 results in a highly anomalous Zeeman effect of conduction
electrons substantially different among the three conduction sub-bands and
strongly dependent on their splitting. This effect can be measured via
electrically-driven spin resonance enabled by the interplay between electron
hopping and spin-orbit coupling, and enhanced by the near-degeneracy of the
conduction sub-bands. The proposed effects can provide a unique insight into
the electronic properties of SrTiO3 and its heterostructures.",2308.14592v2
2004-03-12,Consequences of spin-orbit coupling for the Bose-Einstein condensation of magnons,"In the first part we discuss how the BEC picture for magnons is modified by
anisotropies induced by spin-orbit coupling. In particular we focus on the
effects of antisymmetric spin interactions and/or a staggered component of the
$g$ (gyromagnetic) tensor. Such terms lead to a gapped quasiparticle spectrum
and a nonzero condensate density for all temperatures so that no phase
transition occurs. We contrast this to the effect of crystal field anisotropies
which are also induced by spin-orbit coupling. In the second part we study the
field-induced magnetic ordering in TlCuCl$_3$ on a quantitative level. We show
that the usual BEC picture does not allow for a good description of the
experimental magnetisation data and argue that antisymmetric spin interactions
and/or a staggered $g$ tensor component are still crucial, although both are
expected to be tiny in this compound due to crystal symmetries. Including this
type of interaction we obtain excellent agreement with experimental data.",0403311v2
2006-02-28,Photon-assisted electron transmission resonance through a quantum well with spin-orbit coupling,"Using the effective-mass approximation and Floquet theory, we study the
electron transmission over a quantum well in semiconductor heterostructures
with Dresselhaus spin-orbit coupling and an applied oscillation field. It is
demonstrated by the numerical evaluations that Dresselhaus spin-orbit coupling
eliminates the spin degeneracy and leads to the splitting of asymmetric
Fano-type resonance peaks in the conductivity. In turn, the splitting of
Fano-type resonance induces the spin- polarization-dependent electron-current.
The location and line shape of Fano-type resonance can be controlled by
adjusting the oscillation frequency and the amplitude of external field as
well. These interesting features may be a very useful basis for devising
tunable spin filters.",0602658v1
2007-09-10,Weak antilocalization in high mobility Ga(x)In(1-x)As/InP two-dimensional electron gases with strong spin-orbit coupling,"We have studied the spin-orbit interaction in a high mobility two-dimensional
electron gas in a GaInAs/InP heterostructure as a function of an applied gate
voltage as well as a function of temperature. Highly sensitive magnetotransport
measurements of weak antilocalization as well as measurements of Shubnikov--de
Haas oscillations were performed in a wide range of electron sheet
concentrations. In our samples the electron transport takes place in the strong
spin precession regime in the whole range of applied gate voltages, which is
characterized by the spin precession length being shorter than the elastic mean
free path. The magnitude of the Rashba spin-orbit coupling parameter was
determined by fitting the experimental curves by a simulated quantum
conductance correction according to a model proposed recently by Golub [Phys.
Rev. B 71, 235310 (2005)]. A comparison of the Rashba coupling parameter
extracted using this model with the values estimated from the analysis of the
beating pattern in the Shubnikov--de Haas oscillations showed a good agreement.",0709.1326v1
2009-11-04,Features due to spin-orbit coupling in the optical conductivity of single-layer graphene,"We have calculated the optical conductivity of a disorder-free single
graphene sheet in the presence of spin-orbit coupling, using the Kubo
formalism. Both intrinsic and structural-inversion-asymmetry induced types of
spin splitting are considered within a low-energy continuum theory. Analytical
results are obtained that allow us to identify distinct features arising from
spin-orbit couplings. We point out how optical-conductivity measurements could
offer a way to determine the strengths of spin splitting due to various origins
in graphene.",0911.0754v2
2010-02-16,"Orbital Ordering and Unfrustrated $(π,0)$ Magnetism from Degenerate Double Exchange in the Iron Pnictides","The magnetic excitations of the iron pnictides are explained within a
degenerate double-exchange model. The local-moment spins are coupled by
superexchanges $J_1$ and $J_2$ between nearest and next-nearest neighbors,
respectively, and interact with the itinerant electrons of the degenerate
$d_{xz}$ and $d_{yz}$ orbitals via a ferromagnetic Hund exchange. The latter
stabilizes $(\pi,0)$ stripe antiferromagnetism due to emergent ferro-orbital
order and the resulting kinetic energy gain by hopping preferably along the
ferromagnetic spin direction. Taking the quantum nature of the spins into
account, we calculate the magnetic excitation spectra in the presence of both,
super- and double-exchange. A dramatic increase of the spin-wave energies at
the competing N\'eel ordering wave vector is found, in agreement with recent
neutron scattering data. The spectra are fitted to a spin-only model with a
strong spatial anisotropy and additional longer ranged couplings along the
ferromagnetic chains. Over a realistic parameter range, the effective couplings
along the chains are negative corresponding to unfrustrated stripe
antiferromagnetism.",1002.3165v3
2010-11-16,Development in the Scattering Matrix Theory: From Spin-Orbit-Coupling Affected Shot Noise to Quantum Pumping,"The review chapter starts by a pedagogical introduction to the general
concept of the scattering theory: from the fundamental wave-function picture to
the second-quantization language, with the aim to clear possible ambiguity in
conventional textbooks. Recent progress in applying the method to current
fluctuations and oscillating-parameter driven quantum pumping processes is
presented with inclusion of contributions by B\""{u}ttiker, Brouwer, Moskalets,
Zhu, etc. In particular, the spin-orbit-coupling affected shot noise can be
dealt with by taking into account the spin-dependent scattering processes. A
large shot noise suppression with the Fano factor below 0.5 observed
experimentally can be illustrated by effective repulsion between electrons with
antiparallel spin induced by the Dresselhaus spin-orbit coupling effect. A
Floquet scattering theory for quantum-mechanical pumping in mesoscopic
conductors is developed by Moskalets et al., which gives a general picture of
quantum pumping phenomenon, from adiabatic to non-adiabatic and from weak
pumping to strong pumping.",1011.3603v1
2012-03-28,Interplay of spin-orbit coupling and Zeeman splitting in the absorption lineshape of 2D fermions,"We suggest that electron spin resonance (ESR) experiment can be used as a
probe of spinon excitations of hypothetical spin-liquid state of frustrated
antiferromagnet in the presence of asymmetric Dzyaloshinskii-Moriya (DM)
interaction. We describe assumptions under which the ESR response is reduced to
the response of 2D electron gas with Rashba spin-orbit coupling. Unlike
previous treatments, the spin-orbit coupling, \Delta_{SO}, is not assumed small
compared to the Zeeman splitting, \Delta_Z. We demonstrate that ESR response
diverges at the edges of the absorption spectrum for ac magnetic field
perpendicular to the static field. At the compensation point,
\Delta_{SO}\approx \Delta_Z, the broad absorption spectrum exhibits features
that evolve with temperature, T, even when T is comparable to the Fermi energy.",1203.6118v2
2013-01-07,Parity violating superfluidity in ultra-cold fermions under the influence of artificial non-Abelian gauge fields,"We discuss the creation of parity violating Fermi superfluids in the presence
of non-Abelian gauge fields involving spin-orbit coupling and crossed Zeeman
fields. We focus on spin-orbit coupling with equal Rashba and Dresselhaus (ERD)
strengths which has been realized experimentally in ultra-cold atoms, but we
also discuss the case of arbitrary mixing of Rashba and Dresselhaus (RD) and of
Rashba-only (RO) spin-orbit coupling. To illustrate the emergence of parity
violation in the superfluid, we analyze first the excitation spectrum in the
normal state and show that the generalized helicity bands do not have inversion
symmetry in momentum space when crossed Zeeman fields are present. This is also
reflected in the superfluid phase, where the order parameter tensor in the
generalized helicity basis violates parity. However, the pairing fields in
singlet and triplet channels of the generalized helicity basis are still parity
even and odd, respectively. Parity violation is further reflected on ground
state properties such as the spin-resolved momentum distribution, and in
excitation properties such as the spin-dependent spectral function and density
of states.",1301.1353v1
2013-01-18,Current induced torques and interfacial spin-orbit coupling: Semiclassical Modeling,"In bilayer nanowires consisting of a ferromagnetic layer and a non-magnetic
layer with strong spin-orbit coupling, currents create torques on the
magnetization beyond those found in simple ferromagnetic nanowires. The
resulting magnetic dynamics appear to require torques that can be separated
into two terms, damping-like and field-like. The damping-like torque is
typically derived from models describing the bulk spin Hall effect and the spin
transfer torque, and the field-like torque is typically derived from a Rashba
model describing interfacial spin-orbit coupling. We derive a model based on
the Boltzmann equation that unifies these approaches. We also consider an
approximation to the Boltzmann equation, the drift-diffusion model, that
qualitatively reproduces the behavior, but quantitatively fails to reproduce
the results. We show that the Boltzmann equation with physically reasonable
parameters can match the torques for any particular sample, but in some cases,
it fails to describe the experimentally observed thickness dependences.",1301.4513v1
2013-01-28,Magnetic Impurity Affected by Spin-Orbit Coupling: Behavior near a Topological Phase Transition,"We investigate the effect of spin-orbit coupling on the behavior of magnetic
impurity at the edge of a zigzag graphene ribbon by means of quantum Monte
Carlo simulations. A peculiar interplay of Kane-Mele type spin-orbit and
impurity-host coupling is found to affect local properties such as the impurity
magnetic moment and spectral densities. The special helical nature of the
topological insulator on the edge is found to affect nonlocal quantities, such
as the two-particle and spin-spin correlation functions linking electrons on
the impurity with those in the conduction band.",1301.6501v2
2013-04-09,Ground-state phase diagram and critical temperature of two-component Bose gases with Rashba spin-orbit coupling,"Ground-state phase diagram of two-component Bose gases with Rashba spin-orbit
coupling is determined via a variational approach. A phase in which the fully
polarized condensate occupies zero momentum is identified. This zero-momentum
phase competes with the spin density wave phase when interspecies interaction
is stronger than intraspecies interaction, and the former one is always the
ground state for weak spin-orbit coupling. When the energies of these two
phases are close, there is a phase separation between them. At finite
temperature, such a zero-momentum condensation can be induced by a
ferromagnetic phase transition in normal state. The spontaneous spin
polarization removes the degeneracy of quasiparticles' energy minima, and
consequently the modified density of state accommodates a Bose condensation to
appear below a critical temperature.",1304.2690v2
2013-05-14,Quasiclassical Treatment and Odd-parity/Triplet Correspondence in Topological Superconductors,"We construct a quasiclassical framework for topological superconductors with
the strong spin-orbit coupling such as CuxBi2Se3. In the manner of the
quasiclassical treatment, decomposing the slowly varying component from the
total quasi-particle wave function, the original massive Dirac Bogoliubov-de
Gennes (BdG) Hamiltonian derived from the tight-binding model represented by 8
x 8 matrix is reduced to 4 x 4 one. The resultant equations are equivalent to
Andreev-type equations of singlet or triplet superconductors, in which the
apparent spin-orbit coupling vanishes. Using this formalism, we find a fact
that the odd-parity superconductivity in topological superconductors turns to
the spin-triplet one. % without the spin-orbit coupling through the
quasiclassical treatment. Moreover, in terms of the quasiclassical treatment,
we show that the topologically-protected zero-energy states in topological
superconductors has the correspondence to the Andreev bound states established
in a long history of studies for the unconventional superconductors. This
clearly indicates that low-energy non-trivial superconducting properties in the
topological superconductors can be analyzed by the established theoretical
descriptions on the spin-triplet superconductors.",1305.3025v2
2014-04-03,Three-component Ultracold Fermi Gases with Spin-Orbit Coupling,"We investigate the pairing physics in a three-component Fermi-Fermi mixture,
where a few impurities are immersed in a non-interacting spin-$\frac{1}{2}$
Fermi gas with synthetic spin-orbit coupling (SOC), and interact attractively
with one spin species in the Fermi gas. Due to the interplay of SOC and
spin-selective interaction, the molecular state intrinsically acquires a
non-zero center-of-mass momentum, which results in a new type of Fulde-Ferrell
(FF) pairing in spin-orbit coupled Fermi systems. The existence of the Fermi
sea can also lead to the competition between FF-like molecular states with
different center-of-mass momenta, which corresponds to a first-order transition
between FF phases in the thermodynamic limit. As the interaction strength is
tuned, a polaron-molecule transition occurs in the highly imbalanced system,
where the boundary varies non-monotonically with SOC parameters and gives rise
to the reentrance of polaron states. The rich physics in this system can be
probed using existing experimental techniques.",1404.0756v4
2015-03-11,Giant Triplet Proximity Effect in $π$-biased Josephson Junctions with Spin-Orbit Coupling,"In diffusive Josephson junctions the phase-difference $\phi$ between the
superconductors strongly influences the spectroscopic features of the layer
separating them. The observation of a uniform minigap and its phase modulation
were only recently experimentally reported, demonstrating agreement with
theoretical predictions up to now - a vanishing minigap at $\phi=\pi$.
Remarkably, we find that in the presence of intrinsic spin-orbit coupling a
giant proximity effect due to spin-triplet Cooper pairs can develop at
$\phi=\pi$, in complete contrast to the suppressed proximity effect without
spin-orbit coupling. We here report a combined numerical and analytical study
of this effect, proving its presence solely based on symmetry arguments, which
makes it independent of the specific parameters used in experiments. We show
that the spectroscopic signature of the triplets is present throughout the
entire ferromagnetic layer. Our finding offers a new way to artificially
create, control and isolate spin-triplet superconductivity.",1503.03500v2
2015-11-23,The Sagnac Effect in Optical Lattices with Laser-Assisted Tunneling,"We propose a scheme to realize the rotation sensing using optical lattices
with laser-assisted tunneling. We demonstrate that the competition between the
rotation and the spin-orbit coupling governs the spin-dependent response of the
cyclotron dynamics of the spin-orbit coupled bosons. The Sagnac-type cumulative
phase can be read out from the envelop of a beat-frequency particle current in
the spin-balanced system and enhanced by the cyclotron motion. We also
theoretically show that the sensitivity limit of the spin-orbit-coupled system
to the rotational motion can reach 7*10^-8 rad s^-1 Hz^1/2.",1511.07197v3
2016-03-08,Weak (anti)localization in tubular semiconductor nanowires with spin-orbit coupling,"We compute analytically the weak (anti)localization correction to the Drude
conductivity for electrons in tubular semiconductor systems of zinc blende
type. We include linear Rashba and Dresselhaus spin-orbit coupling (SOC) and
compare wires of standard growth directions $\langle100\rangle$,
$\langle111\rangle$, and $\langle110\rangle$. The motion on the
quasi-two-dimensional surface is considered diffusive in both directions:
transversal as well as along the cylinder axis. It is shown that Dresselhaus
and Rashba SOC similarly affect the spin relaxation rates. For the
$\langle110\rangle$ growth direction, the long-lived spin states are of helical
nature. We detect a crossover from weak localization to weak anti-localization
depending on spin-orbit coupling strength as well as dephasing and scattering
rate. The theory is fitted to experimental data of an undoped
$\langle111\rangle$ InAs nanowire device which exhibits a top-gate-controlled
crossover from positive to negative magnetoconductivity. Thereby, we extract
transport parameters where we quantify the distinct types of SOC individually.",1603.02495v3
2013-09-17,Radical-pair model of magnetoreception with spin-orbit coupling,"The mechanism used by migratory birds to orientate themselves using the
geomagnetic field is still a mystery in many species. The radical pair
mechanism, in which very weak magnetic fields can influence certain types of
spin-dependent chemical reactions, leading to biologically observable signals,
has recently imposed itself as one of the most promising candidates for certain
species. This is thanks both to its extreme sensitivity and its capacity to
reproduce results from behavioral studies. Still, in order to gain a
directional sensitivity, an anisotropic mechanism is needed. Recent proposals
have explored the possibility that such an anisotropy is due to the
electron-nucleus hyperfine interaction. In this work we explore a different
possibility, in which the anisotropy is due to spin-orbit coupling between the
electron spin and its angular momentum. We will show how a
spin-orbit-coupling-based magnetic compass can have performances comparable
with the usually-studied nuclear-hyperfine based mechanism. Our results could
thus help researchers actively looking for candidate biological molecules which
may host magnetoreceptive functions, both to describe magnetoreception in birds
as well as to develop artificial chemical compass systems.",1309.5882v1
2014-06-19,Ring model for trapped condensates with synthetic spin-orbit coupling,"We derive an effective ring model in momentum space for trapped bosons with
synthetic spin-orbit coupling. This effective model is characterized by a
peculiar form of the inter particle interactions, which is crucially modified
by the external confinement. The ring model allows for an intuitive
understanding of the phase diagram of trapped condensates with isotropic
spin-orbit coupling, and in particular for the existence of skyrmion lattice
phases. The model, which may be generally applied for spinor condensates of
arbitrary spin and spin-dependent interactions, is illustrated for the
particular cases of spin-1/2 and spin-1 condensates.",1406.4938v5
2016-12-05,Spatial compression of a particle state in a parabolic potential by spin measurements,"We propose a scheme for engineering compressed spatial states in a
two-dimensional parabolic potential with a spin-orbit coupling by selective
spin measurements. This sequence of measurements results in a
coordinate-dependent density matrix with probability maxima achieved at a set
of lines or at a two dimensional lattice. The resultant probability density
depends on the spin-orbit coupling and the potential parameters and allows one
to obtain a broad class of localized pure states on demand. The proposed scheme
can be realized in spin-orbit coupled Bose-Einstein condensates.",1612.01588v1
2019-10-08,Spatial coherence of spin-orbit-coupled Bose gases,"Spin-orbit-coupled Bose-Einstein condensates (SOBECs) exhibit two new phases
of matter, now known as the stripe and plane-wave phases. When two interacting
spin components of a SOBEC spatially overlap, density modulations with
periodicity given by the spin-orbit coupling strength appear. In equilibrium,
these components fully overlap in the miscible stripe phase, and overlap only
in a domain wall in the immiscible plane-wave phase. Here we probe the density
modulation present in any overlapping region with optical Bragg scattering, and
observe the sudden drop of Bragg scattering as the overlapping region shrinks.
Using an atomic analogue of the Talbot effect, we demonstrate the existence of
long-range coherence between the different spin components in the stripe phase
and surprisingly even in the phase-separated plane-wave phase.",1910.03613v1
2020-01-19,Repulsive Fermi gases in a two-dimensional lattice with non-Abelian gauge fields,"Motivated by the recent experiment realizing bidirectional spin-orbit-coupled
Bose-Einstein condensates (BEC), we theoretically explore the properties of
repulsive fermions in the two-dimensional (2D) optical lattice with such
non-Abelian gauge fields. Within the mean-field level, we find a novel phase of
topological antiferromagnetic (TAFM) order which incorporates both the
non-trivial topology due to spin-flip hopping and spontaneous symmetry breaking
(SSB) for the in-plane spin order. We argue that the appearance of such a phase
is generic for repulsive fermions in Chern bands achieved through spin-orbit
coupling. Our work paves the way for further studies of fermionic
generalization of 2D non-Abelian spin-orbit-coupled quantum gases.",2001.06757v1
2021-01-20,Cubic spin-orbit coupling and anomalous Josephson effect in planar junctions,"Spin-orbit coupling in two-dimensional systems is usually characterized by
Rashba and Dresselhaus spin-orbit coupling (SOC) linear in the wave vector.
However, there is a growing class of materials which instead support dominant
SOC cubic in the wave vector (cSOC), while their superconducting properties
remain unexplored. By focusing on Josephson junctions in Zeeman field with
superconductors separated by a normal cSOC region, we reveal a strongly
anharmonic current-phase relation and complex spin structure. An experimental
cSOC tunability enables both tunable anomalous phase shift and supercurrent,
which flows even at the zero-phase difference in the junction. A fingerprint of
cSOC in Josephson junctions is the f-wave spin-triplet superconducting
correlations, important for superconducting spintronics and supporting Majorana
bound states.",2101.08272v2
2018-03-05,Néel- and Bloch-Type Magnetic Vortices in Rashba Metals,"We theoretically study noncoplanar spin textures in polar magnetic
conductors. Starting from the Kondo lattice model with the Rashba spin-orbit
coupling, we derive an effective spin model with generalized
Ruderman-Kittel-Kasuya-Yosida interactions including the anisotropic and
antisymmetric exchange interactions. By performing simulated annealing for the
effective model, we find that a vortex crystal of N\'eel type is stabilized
even in the absence of a magnetic field. Moreover, we demonstrate that a
Bloch-type vortex crystal, which is usually associated with the Dresselhaus
spin-orbit coupling, can also be realized in our Rashba-based model. A magnetic
field turns the vortex crystals into N\'eel- and Bloch-type skyrmion-like
crystals. Our results underscore that the interplay between the spin-orbit
coupling and itinerant magnetism brings fertile possibilities of noncoplanar
magnetic orderings.",1803.01543v1
2018-03-07,Edge currents as a probe of the strongly spin-polarized topological noncentrosymmetric superconductors,"Recently the influence of antisymmetric spin-orbit coupling has been studied
in novel topological superconductors such as half-Heuslers and artificial
hetero-structures. We investigate the effect of Rashba and/or Dresselhaus
spin-orbit couplings on the band structure and topological properties of a
two-dimensional noncentrosymetric superconductor. For this goal, the
topological helical edge modes are analyzed for different spin-orbit couplings
as well as for several superconducting pairing symmetries. To explore the
transport properties, we examine the response of the spin-polarized edge states
to an exchange field in a superconductor-ferromagnet heterostructure. The
broken chiral symmetry causes the uni-directional currents at opposite edges.",1803.02591v1
2019-12-06,Topological superconducting phases and Josephson effect in curved time-reversal-invariant superconductors,"We consider a Rashba spin-orbit coupled nanowire with anisotropic
spin-singlet superconducting pairing and time-reversal-invariant symmetry. We
explore the evolution of the topological superconducting phases of this system
due to geometric deformations for the representative case of a wire bent in a
semielliptical shape. We find that when the system is in its topological
superconducting phase, strong inhomogeneities in the profile curvature can
produce a pair of localized eigenmodes, which can be attributed to a nonuniform
topological phase. The curved geometric profile also allows to tune the spin
correlations of the superconducting state via the induced inhomogeneity of the
spin-orbit coupling (SOC). The geometric control of the superconducting pair
correlations allows to manipulate the critical current in Josephson junctions
made up of two time reversal invariant topological superconductors separated by
a spin-orbit coupled normal metal. In particular, we find that the curvature
inhomogeneity can be exploited for amplifying the current intensity, but also
to generate a $0-\pi$ transition, and a second harmonic contribution, which
generates, for some specific geometric configurations, a $\varphi$-junction
behavior.",1912.03279v1
2021-02-12,An Antisymmetric Berry Frictional Force At Equilibrium in the Presence of Spin-Orbit Coupling,"We analytically calculate the electronic friction tensor for a molecule near
a metal surface in the case that the electronic Hamiltonian is complex-valued,
e.g. the case that there is spin-orbit coupling and/or an external magnetic
field. In such a case, even at equilibrium, we show that the friction tensor is
not symmetric. Instead, the tensor is the real-valued sum of one positive
definite tensor (corresponding to dissipation) plus one antisymmetric tensor
(corresponding to a Berry pseudomagnetic force). Moreover, we find that this
Berry force can be much larger than the dissipational force, suggesting the
possibility of strongly spin-polarized chemicurrents or strongly spin-dependent
rate constants for systems with spin-orbit coupling.",2102.06596v5
2021-09-26,Spin-orbit-coupled spin-1 Bose-Einstein condensates in a toroidal trap: even-petal-number necklacelike state and persistent flow,"Spin-orbit coupling has novel spin-flip symmetries, a spin-1 spinor
Bose-Einstein condensate owns meaningful interactions, and a toroidal trap is
topologically nontrivial. We incorporate the three together and study the
ground-state phase diagram in a Rashba spin-orbit-coupled spin-1 Bose-Einstein
condensate with a toroidal trap. The spin-flip symmetries give rise to two
different interesting phases: persistent flows with a unit phase winding
difference between three components, and necklace states with even
petal-number. The existing parameter regimes and properties of these phases are
characterized by two-dimension numerical calculations and an azimuthal
analytical one-dimension model.",2109.12529v1
2022-10-04,Dissipative dynamics of an impurity with spin-orbit coupling,"Brownian motion of a mobile impurity in a bath is affected by spin-orbit
coupling (SOC). Here, we discuss a Caldeira-Leggett-type model that can be used
to propose and interpret quantum simulators of this problem in cold Bose gases.
First, we derive a master equation that describes the model and explore it in a
one-dimensional (1D) setting. To validate the standard assumptions needed for
our derivation, we analyze available experimental data without SOC; as a
byproduct, this analysis suggests that the quench dynamics of the impurity is
beyond the 1D Bose-polaron approach at temperatures currently accessible in a
cold-atom laboratory -- motion of the impurity is mainly driven by dissipation.
For systems with SOC, we demonstrate that 1D spin-orbit coupling can be 'gauged
out' even in the presence of dissipation -- the information about SOC is
incorporated in the initial conditions. Observables sensitive to this
information (such as spin densities) can be used to study formation of steady
spin polarization domains during quench dynamics.",2210.01829v2
2023-04-12,Phonon-Induced Collective Modes in Spin-Orbit Coupled Polar Metals,"We study the interplay between collective electronic and lattice modes in
polar metals in an applied magnetic field aligned with the polar axis. Static
spin-orbit coupling leads to the appearance of a particle-hole spin-flip
continuum that is gapped at low energies in a finite field. We find that a weak
spin-orbit assisted coupling between electrons and polar phonons induces the
emergence of electronic collective modes. The strength of the applied magnetic
field tunes the number of modes and their energies, which can lie both above
and below the particle-hole continuum. For a range of field values, we identify
Fano-like interference between the electronic continuum and phonons. We show
that signatures of these collective modes can be observed in electron spin
resonance experiments, and we provide the corresponding theoretical
predictions.",2304.06083v2
2023-08-07,Exciton-spin interactions in antiferromagnetic charge-transfer insulators,"We derive exciton-spin interactions from a microscopic correlated model that
captures important aspects of the physics of charge-transfer (CT) insulators to
address magnetism associated with exciton creation. We present a minimal model
consisting of coupled clusters of transition metal d and ligand p orbitals that
captures the essential features of the local atomic and electronic structure.
First, we identify the lowest-energy state and optically allowed excited states
within a cluster by applying the molecular orbital picture to the ligand p
orbitals. Then, we derive the effective interactions between two clusters
mediated by intercluster hoppings, which include exciton-spin couplings. The
interplay of the correlations and the spatial structure of the CT exciton leads
to strong magnetic exchange couplings with spatial anisotropy. Finally, we
calculate an optical excitation spectrum in our effective model to obtain
insights into magnetic sidebands optically observed in magnetic materials. We
demonstrate that the spin-flip excitation due to the strongly enhanced local
spin interactions around the exciton gives rise to the magnetic sidebands.",2308.03309v2
2005-08-14,Consistency in Formulation of Spin Current and Torque Associated with a Variance of Angular Momentum,"Stimulated generally by recent interest in the novel spin Hall effect, the
nonrelativistic quantum mechanical conserved currents, taken into account of
spin-orbit coupling, are rigorously formulated based on the symmetries of
system and Noether' theorem. The quantum mechanical force on the spin as well
as the torque associated with the variance of angular momentum are obtained.
Consequently, the kinetic interpretation of the variances of spin and orbit
angular momentum currents implies a torque on the ""electric dipole"" associated
with the moving spin. The bearing of the force and the torque on the properties
of spin current in a two-dimensional electron gas with the Rashba spin-orbit
interaction is discussed.",0508340v1
2006-01-06,Coherent spin ratchets: A spin-orbit based quantum ratchet mechanism for spin-polarized currents in ballistic conductors,"We demonstrate that the combined effect of a spatially periodic potential,
lateral confinement and spin-orbit interaction gives rise to a quantum ratchet
mechanism for spin-polarized currents in two-dimensional coherent conductors.
Upon adiabatic ac-driving, in the absence of a static bias, the system
generates a directed spin current while the total charge current is zero. We
analyze the underlying mechanism by employing symmetry properties of the
scattering matrix and numerically verify the effect for different setups of
ballistic conductors. The spin current direction can be changed upon tuning the
Fermi energy or the strength of the Rashba spin-orbit coupling.",0601118v3
2009-06-26,Nonlinear Spin-Charge Dynamics in a Driven Double Quantum Dot,"The coupled nonlinear coordinate and spin dynamics of an electron in a double
quantum dot with spin-orbit interaction is studied semiclassically. The system
is driven by an electric field with the frequency matching the orbital or the
Zeeman resonance in magnetic field. Calculated evolution of the spin state is
crucially sensitive to the irregularities in the spatial motion and the
geometry of the host nanostructure. The resulting spin-flip Rabi frequency has
an unusual dependence on the field amplitude, demonstrating approach to the
chaotic spin motion. In turn, the orbital dynamics depends strongly on the spin
evolution due to the spin-dependent term in the electron velocity.",0906.4854v1
2012-10-13,Spin-flip transitions induced by time-dependent electric fields in surfaces with strong spin-orbit interaction,"We present a comprehensive theoretical investigation of the light absorption
rate at the Pb/Ge(111) surface with strong spin-orbit coupling. Our
calculations show that electron spin-flip transitions cause as much as 6% of
the total light absorption, representing one order of magnitude enhancement
over Rashba-like systems. Thus, it is demonstrated that a substantial part of
the light irradiating this nominally non-magnetic surface is attenuated in spin
flip processes. Remarkably, the spin-flip transition probability is structured
in well defined hot spots within the Brillouin zone where the electron spin
experiences a sudden 90 degree rotation. This mechanism offers the possibility
of an experimental approach to the spin-orbit phenomena by optical means.",1210.4506v1
2013-01-08,Evolution of the persistent spin helix in the presence of Hartree-Fock fields,"We derive a spin diffusion equation for a spin-orbit coupled two-dimensional
electron gas including the Hartree-Fock field resulting from 1st order
electron-electron interactions. We find that the lifetime of the persistent
spin helix, which emerges for equal linear Rashba- and Dresselhaus spin-orbit
interactions, can be enhanced considerably for large initial spin polarizations
due to the Hartree-Fock field. The reason is a reduction of the
symmetry-breaking cubic Dresselhaus scattering rate by the Hartree-Fock field.
Also higher harmonics are generated and the polarization of the persistent spin
helix rotates out of the (Sy,Sz)-plane acquiring a finite Sx-component. This
effect becomes more pronounced, when the cubic Dresselhaus spin-orbit
interaction is large.",1301.1662v1
2013-04-28,Extrinsic spin Hall effect induced by resonant skew scattering in graphene,"We show that the extrinsic spin Hall effect can be engineered in monolayer
graphene by decoration with small doses of adatoms, molecules, or nanoparticles
originating local spin-orbit perturbations. The analysis of the single impurity
scattering problem shows that intrinsic and Rashba spin-orbit local couplings
enhance the spin Hall effect via skew scattering of charge carriers in the
resonant regime. The solution of the transport equations for a random ensemble
of spin-orbit impurities reveals that giant spin Hall currents are within the
reach of the current state of the art in device fabrication. The spin Hall
effect is robust with respect to thermal fluctuations and disorder averaging.",1304.7511v3
2015-08-18,Charge-insensitive single-atom spin-orbit qubit in silicon,"High fidelity entanglement of an on-chip array of spin qubits poses many
challenges. Spin-orbit coupling (SOC) can ease some of these challenges by
enabling long-ranged entanglement via electric dipole-dipole interactions,
microwave photons, or phonons. However, SOC exposes conventional spin qubits to
decoherence from electrical noise. Here we propose an acceptor-based spin-orbit
qubit in silicon offering long-range entanglement at a sweet spot where the
qubit is protected from electrical noise. The qubit relies on quadrupolar SOC
with the interface and gate potentials. As required for surface codes, $10^5$
electrically mediated single-qubit and $10^4$ dipole-dipole mediated two-qubit
gates are possible in the predicted spin lifetime. Moreover, circuit quantum
electrodynamics with single spins is feasible, including dispersive readout,
cavity-mediated entanglement, and spin-photon entanglement. An industrially
relevant silicon-based platform is employed.",1508.04259v4
2019-09-27,Observation of spin-orbit magnetoresistance in CoFeB/heavy metal/MgO with existence of both spin Hall effect and Edelstein effect,"In this paper, we report the observation of spin-orbit magnetoresistance
(SOMR) in ferromagnetic metal/heavy metal/MgO system. We measure the
magnetoresistance as the function of the thickness of heavy metal (HM) for
CoFeB/HM/MgO and CoFeB/HM films where HM = Pt and Ta. Besides the conventional
spin Hall magnetoresistance (SMR) peak, the evidence of the SOMR is indicated
by another peak of the MR ratio when the thickness of HM is around 1 ~ 2 nm for
CoFeB/HM/MgO films, which is absent for CoFeB/HM films. We speculate the SOMR
observed in our experiment originates from the spin-orbit coupling at the
HM/MgO interface. We give the boundary conditions of our samples and calculate
the theoretical magnetoresistance based on spin diffusion equation. Based on
the theoretical results, we can explain the two peaks we observe separately
comes from the spin current generated by spin Hall effect and by Edelstein
effect.",1909.12811v3
2022-12-13,Josephson current via spin and orbital states of a tunable double quantum dot,"Supercurrent transport is experimentally studied in a Josephson junction
hosting a double quantum dot (DQD) with tunable symmetries. The QDs are
parallel-coupled to two superconducting contacts and can be tuned between
strong inter-dot hybridization and a ring geometry where hybridization is
suppressed. In both cases, we observe supercurrents when the two interacting
orbitals are either empty or filled with spins, or a combination. However, when
each QD hosts an unpaired spin, the supercurrent depends on the spin ground
state. It is strongly suppressed for the ring geometry with a spin-triplet
ground state at zero external magnetic field. By increasing the QD
hybridization, we find that a supercurrent appears when the ground state
changes to spin-singlet. In general, supercurrents are suppressed in cases of
spin doublet ground state, but an exception occurs at orbital degeneracy when
the system hosts one additional spin, as opposed to three, pointing to a broken
particle-hole symmetry.",2212.06484v1
2023-06-14,Multipolar spin liquid in an exactly solvable model for $j_\mathrm{eff} = \frac{3}{2}$ moments,"We study an exactly solvable model with bond-directional quadrupolar and
octupolar interactions between spin-orbital entangled $j_{\mathrm{eff}} =
\frac{3}{2}$ moments on the honeycomb lattice. We show that this model features
a multipolar spin liquid phase with gapless fermionic excitations. In the
presence of perturbations that break time-reversal and rotation symmetries, we
find Abelian and non-Abelian topological phases in which the Chern number
evaluates to $0$, $\pm 1$, and $\pm 2$. We also investigate quantum phase
transitions out of the multipolar spin liquid using a parton mean-field
approach and orbital wave theory. In the regime of strong
integrability-breaking interactions, the multipolar spin liquid gives way to
ferroquadrupolar-vortex and antiferro-octupolar ordered phases that harbor a
hidden spin-$\frac{1}{2}$ Kitaev spin liquid. Our work unveils mechanisms for
unusual multipolar orders and quantum spin liquids in Mott insulators with
strong spin-orbit coupling.",2306.08624v2
2022-02-23,Spin-orbit enabled all-electrical readout of chiral spin-textures,"Chirality and topology are intimately related fundamental concepts, which are
heavily explored to establish spin-textures as potential magnetic bits in
information technology. However, this ambition is inhibited since electrical
reading of chiral attributes is highly non-trivial with conventional current
perpendicular-to-plane (CPP) sensing devices. Here we demonstrate from
extensive first-principles simulations and multiple scattering expansion the
emergence of the chiral spin-mixing magnetoresistance (C-XMR) enabling highly
efficient all-electrical readout of the chirality and helicity of respectively
one- and two-dimensional magnetic states of matter. It is linear with
spin-orbit coupling in contrast to the quadratic dependence associated with the
newly unveiled non-local spin-mixing anisotropic MR (X-AMR). Such transport
effects are systematised on various non-collinear magnetic states --
spin-spirals and skyrmions -- and compared to the uncovered
spin-orbit-independent multi-site magnetoresistances. Owing to their simple
implementation in readily available reading devices, the proposed
magnetoresistances offer exciting and decisive ingredients to explore with
all-electrical means the rich physics of topological and chiral magnetic
objects.",2202.11637v1
2014-10-22,Spin dynamics of Mn impurities and their bound acceptors in GaAs,"We present results of tight-binding spin-dynamics simulations of individual
and pairs of substitutional Mn impurities in GaAs. Our approach is based on the
mixed quantum-classical scheme for spin dynamics, with coupled equations of
motions for the quantum subsystem, representing the host, and the localized
spins of magnetic dopants, which are treated classically. In the case of a
single Mn impurity, we calculate explicitly the time evolution of the Mn spin
and the spins of nearest-neighbors As atoms, where the acceptor (hole) state
introduced by the Mn dopant resides. We relate the characteristic frequencies
in the dynamical spectra to the two dominant energy scales of the system,
namely the spin-orbit interaction strength and the value of the p-d exchange
coupling between the impurity spin and the host carriers. For a pair of Mn
impurities, we find signatures of the indirect (carrier-mediated) exchange
interaction in the time evolution of the impurity spins. Finally, we examine
temporal correlations between the two Mn spins and their dependence on the
exchange coupling and spin-orbit interaction strength, as well as on the
initial spin-configuration and separation between the impurities. Our results
provide insight into the dynamic interaction between localized magnetic
impurities in a nano-scaled magnetic-semiconductor sample, in the extremely
dilute (solotronics) regime.",1410.5978v1
2015-01-20,Spinning gravitating objects in the effective field theory in the post-Newtonian scheme,"We introduce a formulation for spinning gravitating objects in the effective
field theory in the post-Newtonian scheme in the context of the binary inspiral
problem. We aim at an effective action, where all field modes below the orbital
scale are integrated out. We spell out the relevant degrees of freedom, in
particular the rotational ones, and the associated symmetries. Building on
these symmetries, we introduce the minimal coupling part of the point particle
action in terms of gauge rotational variables, and construct the spin-induced
nonminimal couplings, where we obtain the leading order couplings to all orders
in spin. We specify the gauge for the rotational variables, where the
unphysical degrees of freedom are eliminated already from the Feynman rules,
and all the orbital field modes are integrated out. The equations of motion of
the spin can be directly obtained via a proper variation of the action, and
Hamiltonians may be straightforwardly derived. We implement this effective
field theory for spin to derive all spin dependent potentials up to
next-to-leading order to quadratic level in spin, namely up to the third
post-Newtonian order for rapidly rotating compact objects. In particular, the
proper next-to-leading order spin-squared potential and Hamiltonian for generic
compact objects are also derived. For the implementations we use the
nonrelativistic gravitational field decomposition, which is found here to
eliminate higher-loop Feynman diagrams also in spin dependent sectors, and
facilitates derivations. This formulation for spin is thus ideal for treatment
of higher order spin dependent sectors.",1501.04956v3
2021-09-09,Spin Texture in Doped Mott Insulators with Spin-Orbit Coupling,"A hole injected into a Mott insulator will gain an internal structure as
recently identified by exact numerics, which is characterized by a nontrivial
quantum number whose nature is of central importance in understanding the Mott
physics. In this work, we show that a spin texture associated with such an
internal degree of freedom can explicitly manifest after the spin degeneracy is
lifted by a \emph{weak} Rashba spin-orbit coupling (SOC). It is described by an
emergent angular momentum $J_{z}=\pm3/2$ as shown by both exact diagonalization
(ED) and variational Monte Carlo (VMC) calculations, which are in good
agreement with each other at a finite size. In particular, as the internal
structure such a spin texture is generally present in the hole composite even
at high excited energies, such that a corresponding texture in momentum space,
extending deep inside the Brillouin zone, can be directly probed by the
spin-polarized angle-resolved photoemission spectroscopy (ARPES). This is in
contrast to a Landau quasiparticle under the SOC, in which the spin texture
induced by SOC will not be protected once the excited energy is larger than the
weak SOC coupling strength, away from the Fermi energy. We point out that the
spin texture due to the SOC should be monotonically enhanced 1with reducing
spin-spin correlation length in the superconducting/pseudogap phase at finite
doping. A brief discussion of a recent experiment of the spin-polarized ARPES
will be made.",2109.04492v2
2021-12-14,Charge-spin interconversion in graphene-based systems from density functional theory,"We present a methodology to address, from first principles, charge-spin
interconversion in two-dimensional materials with spin-orbit coupling. Our
study relies on an implementation of density functional theory based quantum
transport formalism adapted to such purpose. We show how an analysis of the
$k$-resolved spin polarization gives the necessary insight to understand the
different charge-spin interconversion mechanisms. We have tested it in the
simplest scenario of isolated graphene in a perpendicular electric field where
effective tight-binding models are available to compare with. Our results show
that the flow of an unpolarized current across a single layer of graphene
produces, as expected, a spin separation perpendicular to the current for two
of the three spin components (out-of-plane and longitudinal), which is the
signature of the spin Hall effect. Additionally, it also yields an overall spin
accumulation for the third spin component (perpendicular to the current), which
is the signature of the Rashba-Edelstein effect. Even in this simple example,
our results reveal an unexpected competition between the Rashba and the
intrinsic spin-orbit coupling. Remarkably, the sign of the accumulated spin
density does not depend on the electron or hole nature of the injected current
for realistic values of the Rashba coupling.",2112.07559v1
2013-12-10,Rashba spin orbit coupling in the Kane-Mele-Hubbard model,"Spin-orbit (SO) coupling is the crucial parameter to drive topological
insulating phases in electronic band models. In particular, the generic
emergence of SO coupling involves the Rashba term which fully breaks the SU(2)
spin symmetry. As soon as interactions are taken into account, however, many
theoretical studies have to content themselves with the analysis of a
simplified U(1) conserving SO term without Rashba coupling. We intend to fill
this gap by studying the Kane-Mele-Hubbard (KMH) model in the presence of
Rashba SO coupling and present the first systematic analysis of the effect of
Rashba SO coupling in a correlated two-dimensional topological insulator. We
apply the variational cluster approach (VCA) to determine the interacting phase
diagram by computing local density of states, magnetization, single particle
spectral function, and edge states. Preceded by a detailed VCA analysis of the
KMH model in the presence of U(1) conserving SO coupling, we find that the
additional Rashba SO coupling drives new electronic phases such as a metallic
regime and a direct-gap only topological insulating phase which persist in the
presence of interactions.",1312.2934v2
2006-01-14,Spin Hall effect in two-dimensional $p$-type semiconductors in a magnetic field,"We calculate the spin Hall conductivity driven by Rashba spin-orbit
interaction in $p$-type two-dimensional semiconductors in the presence of a
perpendicular magnetic field. For a highly confined quantum well, the system is
described by a $k$-cubic Rashba term for two-dimensional heavy holes.
  The eigenstates of the system can be described by
  Landau spinor states. First we consider the conventional spin Hall
conductivity. The contribution of the interband transitions to the
Kubo-Greenwood formula gives the density dependent intrinsic spin Hall
conductivity, which approaches its universal value $\sigma^z_{xy}=9e/8\pi$ for
weak spin-orbit coupling and low Fermi energies, in agreement with previous
work.
  However two intraband contribution terms cancel this effect leading to zero
conventional spin Hall conductivity. Adding the torque dipole contribution to
the definition of spin current, we also study the {\it effective} spin
conductivity. This is shown to be proportional to the total magnetization plus
surface terms which exactly cancel it for small spin-orbit coupling. If in low
magnetic field the intraband transitions evolve to vertex corrections, the fact
that both {effective} and conventional spin Hall conductivities vanish is
unexpected. This suggests that the zero magnetic field limit of the model is
singular.",0601315v2
2019-05-03,Effective spin-mixing conductance of topological-insulator/ferromagnet and heavy-metal/ferromagnet spin-orbit-coupled interfaces: A first-principles Floquet-nonequilibrium-Green-function approach,"The spin mixing conductance (SMC) is a key quantity determining efficiency of
spin transport across interfaces. Thus, knowledge of its precise value is
required for accurate measurement of parameters quantifying numerous effects in
spintronics, such as spin-orbit torque, spin Hall magnetoresistance, spin Hall
effect and spin pumping. However, the standard expression for SMC, provided by
the scattering theory in terms of the reflection probability amplitudes, is
inapplicable when strong spin-orbit coupling (SOC) is present directly at the
interface. This is the precisely the case of topological-insulator/ferromagnet
and heavy-metal/ferromagnet interfaces of great contemporary interest. We
introduce an approach where first-principles Hamiltonian of these interfaces,
obtained from noncollinear density functional theory (ncDFT) calculations, is
combined with charge conserving Floquet-nonequilibrium-Green-function formalism
to compute {\em directly} the pumped spin current $I^{S_z}$ into semi-infinite
left lead of two-terminal heterostructures Cu/X/Co/Cu or Y/Co/Cu---where
X=Bi$_2$Se$_3$ and Y=Pt or W---due to microwave-driven steadily precessing
magnetization of the Co layer. This allows us extract an effective SMC as a
prefactor in $I^{S_z}$ vs. precession cone angle $\theta$ dependence, as long
as it remains the same, $I^{S_z} \propto \sin^2 \theta$, as in the case where
SOC is absent. By comparing calculations where SOC in switched off vs. switched
on in ncDFT calculations, we find that SOC consistently reduces the pumped spin
current and, therefore, the effective SMC.",1905.01299v2
2015-05-05,Large spin Hall magnetoresistance and its correlation to the spin-orbit torque in W/CoFeB/MgO structures,"The spin-orbit interaction in heavy metal/ferromagnet/oxide structures has
been extensively investigated because it can be employed in manipulation of the
magnetization direction by in-plane current. This implies the existence of an
inverse effect, in which the conductivity in such structures should depend on
the magnetization orientation. In this work, we report a systematic study of
the magnetoresistance (MR) of the W/CoFeB/MgO structures and its correlation to
the current-induced torque to the magnetization. We observe that the MR is
independent of the angle between magnetization and current direction, but is
determined by the relative magnetization orientation with respect to the spin
direction accumulated by spin Hall effect, which is the same symmetry of
so-called spin Hall magnetoresistance. The MR of ~1% in W/CoFeB/MgO samples is
considerably larger than those in other structures of Ta/CoFeB/MgO or
Pt/Co/AlOx, which indicates a larger spin Hall angle of W. Moreover, the
similar W thickness dependence of the MR and the current-induced magnetization
switching efficiency demonstrates that they share the same underlying physics,
which allows one to utilize the MR in non-magnet/ferromagnet structure in order
to understand closely related other spin-orbit coupling effects such as inverse
spin Hall effect, spin-orbit spin transfer torques, etc.",1505.00899v1
2015-08-31,Spin Response to Localized Pumps: Exciton Polaritons Versus Electrons and Holes,"Polariton polarization can be described in terms of a pseudospin which can be
oriented along the $x,\,y,$ or $z$ axis, similarly to electron and hole spin.
Unlike electrons and holes where time-reversal symmetry requires that the
spin-orbit interaction be odd in the momentum, the analogue of the spin-orbit
interaction for polaritons, the so-called TE-TM splitting, is even in the
momentum. We calculate and compare spin transport of polariton, electron, and
hole systems, in the diffusive regime of many scatterings. After dimensional
rescaling diffusive systems with spatially uniform particle densities have
identical dynamics, regardless of the particle type. Differences between the
three particles appear in spatially non-uniform systems, with pumps at a
specific localized point. We consider both oscillating pumps and transient
(delta-function) pumps. In such systems each particle type produces distinctive
spin patterns. The particles can be distinguished by their differing spatial
multipole character, their response and resonances in a perpendicular magnetic
field, and their relative magnitude which is largest for electrons and weakest
for holes. These patterns are manifested both in response to unpolarized pumps
which produce in-plane and perpendicular spin signals, and to polarized pumps
where the spin precesses from in-plane to out-of-plane and vice versa. These
results will be useful for designing systems with large spin polarization
signals, for identifying the dominant spin-orbit interaction and measuring
subdominant terms in experimental devices, and for measuring the scattering
time and the spin-orbit coupling's magnitude.",1508.07863v2
2022-10-28,Field-free-switching state diagram of perpendicular magnetization subjected to conventional and unconventional spin-orbit torques,"The lack of certain crystalline symmetries in strong spin-orbit-coupled
non-magnetic materials allows for the existence of uncoventional spin Hall
responses, with electrically generated transverse spin currents possessing
collinear flow and spin directions. The injection of such spin currents into an
adjacent ferromagnetic layer can excite magnetization dynamics via
unconventional spin-orbit torques, leading to deterministic switching in
ferromagnets with perpendicular magnetic anisotropy. We study the interplay
between conventional and unconventional spin-orbit torques on the magnetization
dynamics of a perpendicular ferromagnet in the small intrinsic damping limit,
and identify a rich set of dynamical regimes that includes deterministic and
probabilistic switching, precessional and pinning states. Contrary to common
belief, we found that there exists a critical conventional spin Hall angle,
beyond which deterministic magnetization switching transitions to a
precessional or pinned state. Conversely, we showed that larger unconventional
spin Hall angle is generally beneficial for deterministic switching. We derive
an approximate expression that qualitatively describes the state diagram
boundary between the full deterministic switching and precessional states and
discuss a criterion for searching symmetry-broken spin Hall materials in order
to maximize switching efficiency. Our work offers a roadmap towards energy
efficient spintronic devices, which might opens doors for applications in
advanced in-memory computing technologies.",2210.16344v1
2020-08-25,Bottom-up design of spin-split and reshaped electronic band structures in spin-orbit-coupling free antiferromagnets: Procedure on the basis of augmented multipoles,"We propose an efficient microscopic design procedure of electronic band
structures having intrinsic spin and momentum dependences in
spin-orbit-coupling free antiferromagnets. Our bottom-up design approach to
creating desired spin-split and reshaped band structures could result in
further findings of practical spin-orbit-coupling free materials exhibiting a
giant spin-dependent and/or nonreciprocal transport, magneto-electric and
elastic responses as a consequence of such band structures. We establish a
systematic guideline to construct symmetric/antisymmetric spin-split and
antisymmetrically deformed spin-independent band structures in
spin-orbit-coupling free systems by using two polar multipole degrees of
freedom, electric and magnetic toroidal multipoles. The two polar multipoles
describe arbitrary degrees of freedom in the hopping Hamiltonian, whose onsite
and offsite degrees of freedom in a cluster are described as the cluster and
bond multipoles, respectively, and another degree of freedom connecting between
clusters is expressed as momentum multipoles. By using these multipole
descriptions, we elucidate simple microscopic conditions to realize intrinsic
band deformations in magnetically ordered states: The symmetric spin splitting
is realized in collinear magnets when cluster and bond multipoles contain the
same symmetry of multipoles. The antisymmetric spin splitting occurs in
noncollinear antiferromagnets when a bond-type magnetic toroidal multipole is
present. Furthermore, the antisymmetric band deformation with spin degeneracy
is realized in noncoplanar antiferromagnets. We exemplify three lattice systems
in order to demonstrate the band deformations under the magnetic ordering. On
the basis of the proposed procedure, we list up various candidate materials
showing intrinsic band deformations in accordance with MAGNDATA, magnetic
structures database.",2008.10815v2
2013-10-07,Spin Splitting Induced by a Competition between Quantum Spin Hall Edge States and Valley Edge States,"Strained graphene with lattice deformations has been demonstrated to give
rise to large pseudomagnetic fields and host many exotic properties. Here, we
propose a non-magnetic approach to realize a momentum-dependent out-of-plane
spin splitting in strained graphene nanoribbons with a moderate spin-orbit
coupling. This unique spin splitting distincts from the well-known Zeeman-type
spin splitting and the Rashba-type spin splitting. Our analysis indicates that
the competition between quantum spin Hall edge states and valley edge states in
the nanoribbon leads to the unique spin splitting. The quantum spin Hall states
at one edge of the nanoribbon are suppressed by the counterpropagating edge
modes induced by the pseudomagnetic field. At the opposite edge, the quantum
spin Hall states are not affected at all. Therefore, the degenerate quantum
spin Hall states of opposite spin orientation, which propagate at the two
opposite edges of the nanoribbon, are lifted. This result reveals a new method
to manipulate the spin degrees of freedom of electrons.",1310.1671v2
2020-10-28,Fast spin-valley-based quantum gates in Si with micromagnets,"An electron spin qubit in silicon quantum dots holds promise for quantum
information processing due to the scalability and long coherence. An essential
ingredient to recent progress is the employment of micromagnets. They generate
a synthetic spin-orbit coupling (SOC), which allows high-fidelity spin
manipulation and strong interaction between an electron spin and cavity
photons. To scaled-up quantum computing, multiple technical challenges remain
to be overcome, including controlling the valley degree of freedom, which is
usually considered detrimental to a spin qubit. Here, we show that it is
possible to significantly enhance the electrical manipulation of a spin qubit
through the effect of constructive interference and the large spin-valley
mixing. To characterize the quality of spin control, we also studied spin
dephasing due to charge noise through spin-valley mixing. The competition
between the increased control strength and spin dephasing produces two
sweet-spots, where the quality factor of the spin qubit can be high. Finally,
we reveal that the synthetic SOC leads to distinctive spin relaxation in
silicon, which explains recent experiments.",2010.14844v3
2004-02-10,Magnetism in semiconductors: A dynamical mean field study of ferromagnetism in Ga_{1-x}Mn_xAs,"We employ the dynamical mean field approximation to perform a systematic
study of magnetism in Ga_{1-x}Mn_xAs. Our model incorporates the effects of the
strong spin-orbit coupling on the J=3/2 GaAs valence bands and of the exchange
interaction between the randomly distributed magnetic ions and the itinerant
holes. The ferromagnetic phase transition temperature T_c is obtained for
different values of the impurity-hole coupling J_c and of the hole
concentration n_h at the Mn doping of x=0.05. We also investigate the
temperature dependence of the local magnetization and spin polarization of the
holes. By comparing our results with those for a single band Hamiltonian in
which the spin-orbit coupling is switched off, we conclude that the spin-orbit
coupling in Ga_{1-x}Mn_xAs gives rise to frustration in the ferromagnetic
order, strengthening recent findings by Zarand and Janko (Phys. Rev. Lett. 89,
047201 (2002)).",0402289v1
2005-07-14,Role of spin-orbit coupling on the spin triplet pairing in Na_{x}CoO_{2}yH_{2}O II: Multiple phase diagram under the magnetic field,"The possibility of multiple phase diagram in the novel superconductor
Na_{x}CoO_{2}yH_{2}O is analyzed on the basis of the multi-orbital Hubbard
model including the atomic spin-orbit coupling. We have shown that the spin
triplet pairing state is stable in this model. The p-wave (f-wave) state is
stabilized when the Hund's rule coupling is large (small). In the precedent
paper, we have determined the direction of d-vector at T=Tc and H=0 within the
linearized Dyson-Gorkov equation. In this paper, the pairing state below Tc and
under the magnetic field is determined within the weak coupling approximation
including the paramagnetic effect. We find that the p+f coexistent state is
stabilized at low temperatures in a part of parameter range. We point out that
the phase diagram in the H-T plane is quite different between the p-wave,
f-wave and p+f-wave superconductivities. The characteristics of each phase are
clarified by showing the magnetic susceptibility and specific heat. We discuss
the comparison with experimental results and suggest some future experiments to
detect the multiple phase transition.",0507327v1
2006-03-08,Tunneling conductance of a mesoscopic ring with spin-orbit coupling and Tomonaga-Luttinger interaction,"We study the tunneling current through a mesoscopic two-terminal ring with
spin-orbit coupling, which is threaded by a magnetic flux. The
electron-electron interaction in the ring is described in terms of a
Tomonaga-Luttinger model which also allows us to account for a capacitive
coupling between the ring and the gate electrode. In the regime of weak
tunneling, we describe how, at temperatures lower than the mean level spacing,
the peak positions of the conductance depend on magnetic flux, spin-orbit
coupling strength, gate voltage, charging energy, and interaction parameters
(charge and spin velocity and stiffness).",0603211v2
2014-04-26,Kondo effect in graphene with Rashba spin-orbit coupling,"We study the Kondo screening of a magnetic impurity adsorbed in graphene in
the presence of Rashba spin-orbit interaction. The system is described by an
effective single-channel Anderson impurity model, which we analyze using the
numerical renormalization group. The nontrivial energy dependence of the host
density of states gives rise to interesting behaviors under variation of the
chemical potential or the spin-orbit coupling. Varying the Rashba coupling
produces strong changes in the Kondo temperature characterizing the many-body
screening of the impurity spin, and at half filling allows approach to a
quantum phase transition separating the strong-coupling Kondo phase from a
free-moment phase. Tuning the chemical potential close to sharp features of the
hybridization function results in striking features in the temperature
dependences of thermodynamic quantities and in the frequency dependence of the
impurity spectral function.",1404.6669v2
2015-01-29,Electron Correlation Effects in Non-Centrosymmetric Metals in the Weak Coupling Regime,"The two-dimensional Rashba-Hubbard model is investigated in order to clarify
the electron correlation effects in non-centrosymmetric metals. The
renormalization effect on Rashba spin-orbit coupling (RSOC) is calculated on
the basis of second-order and third-order perturbation theories. We show that
RSOC is enhanced by the electron correlation. On the other hand, the
spin-splitting of the Fermi momentum (SFM) is robust against the electron
correlation effect because the enhancement of RSOC is cancelled by the $k$-mass
renormalization. The cancellation is almost perfect in often adopted models in
which the momentum dependence of RSOC is linear in the quasiparticle velocity.
A small correction to the SFM appears otherwise. We show that the same results
are obtained for other antisymmetric spin-orbit couplings in
non-centrosymmetric systems, such as the synthetic spin-orbit coupling in cold
atoms.",1501.07367v3
2016-01-18,Spin-orbit coupling and odd-parity superconductivity in the quasi-one-dimensional compound Li$_{0.9}$Mo$_6$O$_{17}$,"Previous theoretical studies [W. Cho, C. Platt, R. H. McKenzie, and S. Raghu,
Phys. Rev. B 92, 134514 (2015); N. Lera and J. V. Alvarez, Phys. Rev. B 92,
174523 (2015)] have suggested that Li$_{0.9}$Mo$_6$O$_{17}$, a quasi-one
dimensional ""purple bronze"" compound, exhibits spin-triplet superconductivity
and that the gap function changes sign across the two nearly degenerate Fermi
surface sheets. We investigate the role of spin-orbit coupling (SOC) in
determining the symmetry and orientation of the $d$-vector associated with the
superconducting order parameter. We propose that the lack of local inversion
symmetry within the four-atom unit cell leads to a staggered spin-orbit
coupling analogous to that proposed for graphene, MoS$_2$, or SrPtAs. In
addition, from a weak-coupling renormalization group treatment of an effective
model Hamiltonian, we find that SOC favors the odd parity $A_{1u}$ state with
$S_z = \pm 1$ over the $B$ states with $S_z=0$, where $z$ denotes the
least-conducting direction. We discuss possible definitive experimental
signatures of this superconducting state.",1601.04757v1
2017-08-30,Quantum Phases of Two-Component Bosons with Spin-Orbit Coupling in Optical Lattices,"Ultracold bosons in optical lattices are one of the few systems where bosonic
matter is known to exhibit strong correlations. Here we push the frontier of
our understanding of interacting bosons in optical lattices by adding synthetic
spin-orbit coupling, and show that new kinds of density- and chiral-orders
develop. The competition between the optical lattice period and the spin-orbit
coupling length -- which can be made comparable in experiments -- along with
the spin hybridization induced by a transverse field (i.e., Rabi coupling) and
interparticle interactions create a rich variety of quantum phases including
uniform, non-uniform and phase-separated superfluids, as well as Mott
insulators. The spontaneous symmetry breaking phenomena at the transitions
between them are explained by a two-order-parameter Ginzburg-Landau model with
multiparticle umklapp processes. Finally, in order to characterize each phase,
we calculated their experimentally measurable crystal momentum distributions.",1708.09186v1
2014-06-02,Anisotropic Multipolar Exchange Interactions in Systems with Strong Spin-Orbit Coupling,"We introduce a theoretical framework for computaions of anisotropic
multipolar exchange interactions found in many spin--orbit coupled magnetic
systems and propose a method to extract these coupling constants using a
density functional total energy calculation. This method is developed using a
multipolar expansion of local density matrices for correlated orbitals that are
responsible for magnetic degrees of freedom. Within the mean--field
approximation, we show that each coupling constant can be recovered from a
series of total energy calculations via what we call the ``pair--flip''
technique. This technique flips the relative phase of a pair of multipoles and
computes corresponding total energy cost associated with the given exchange
constant. To test it, we apply our method to Uranium Dioxide, which is a system
known to have pseudospin $J=1$ superexchange induced dipolar, and superexchange
plus spin--lattice induced quadrupolar orderings. Our calculation reveals that
the superexchange and spin--lattice contributions to the quadrupolar exchange
interactions are about the same order with ferro-- and antiferro--magnetic
contributions, respectively. This highlights a competition rather than a
cooperation between them. Our method could be a promising tool to explore
magnetic properties of rare--earth compounds and hidden--order materials.",1406.0221v1
2020-04-20,The three body first post-Newtonian effects on the secular dynamics of a compact binary near a spinning supermassive black hole,"The binary black holes (BBHs) formed near the supermassive black holes
(SMBHs) in the galactic nuclei would undergo eccentricity excitation due to the
gravitational perturbations from the SMBH and therefore merger more
efficiently. In this paper, we study the coupling of the three body 1st
post-Newtonian (PN) effects with the spin effects from the SMBH in the
hierarchical triple system. We extend previous work by including the coupling
between the de Sitter precession and the Lense-Thirring precession from the
SMBH spin. This coupling includes both the precessions of the inner orbit
angular momentum and the Runge-Lenz vector around the outer orbit angular
momentum in a general reference frame. We find the change of the (maximal)
eccentricity in the neighboring Kozai-Lidov cycles due to spin effects is
detectable by LISA in the future. Our general argument on the coupling of the
three body 1PN effects in three body systems could be extended to any other
situation as long as the outer orbital plane evolves.",2004.09390v2
2020-12-24,Van der Waals Heterostructure Pt$_{2}$HgSe$_{3}$/CrI$_3$ for Topological Valleytronics,"We identify a valley-polarized Chern insulator in the van der Waals
heterostructure, Pt$_{2}$HgSe$_{3}$/CrI$_3$, for potential applications with
interplay between electric, magnetic, optical, and mechanical effects. The
interlayer proximity magnetic coupling nearly closes the band gap of
Pt$_{2}$HgSe$_{3}$ and the strong intra-layer spin-orbit coupling further lifts
the valley degeneracy by over 100 meV leading to positive and negative band
gaps at opposite valleys. In the valley with negative gap, the interfacial
Rashba spin-orbit coupling opens a topological band gap of 17.8 meV, which is
enlarged to 30.8 meV by adding an $h$-BN layer. We find large orbital
magnetization in Pt$_{2}$HgSe$_{3}$ layer that is much larger than spin, which
can induce measurable optical Kerr effect. The valley polarization and Chern
number are coupled to the magnetic order of the nearest neighboring CrI$_3$
layer, which is switchable by electric, magnetic, and mechanical means in
experiments. The presence of $h$-BN protects the topological phase allowing the
construction of superlattices with valley, spin, and layer degrees of freedoms.",2012.13298v1
2017-11-28,Interplay of spin-orbit coupling and hybridization in Ca3LiOsO6 and Ca3LiRuO6,"The electronic ground state of Ca3LiOsO6 was recently considered within an
intermediate coupling regime that revealed J=3/2 spin-orbit entangled magnetic
moments. Through inelastic neutron scattering and density functional theory we
investigate the magnetic interactions and probe how the magnetism is influenced
by the change in hierarchy of interactions as we move from Ca3LiOsO6 (5d3) to
Ca3LiRuO6 (4d3). An alteration of the spin-gap and ordered local moment is
observed, however the magnetic structure, Neel temperature and exchange
interactions are unaltered. To explain this behavior it is necessary to include
both spin-orbit coupling and hybridization, indicating the importance of an
intermediate coupling approach when describing 5$d$ oxides.",1711.10393v1
2019-04-07,Tuning Rashba spin-orbit coupling at LaAlO3/SrTiO3 interfaces by band filling,"The electric-field tunable Rashba spin-orbit coupling at the LaAlO3/SrTiO3
interface shows potential applications in spintronic devices. However,
different gate dependence of the coupling strength has been reported in
experiments. On the theoretical side, it has been predicted that the largest
Rashba effect appears at the crossing point of the $d_{xy}$ and $d_{xz,yz}$
bands. In this work, we study the tuneability of the Rashba effect in
LaAlO3/SrTiO3 by means of back-gating. The Lifshitz transition was crossed
multiple times by tuning the gate voltage so that the Fermi energy is tuned to
approach or depart from the band crossing. By analyzing the weak
antilocalization behavior in the magnetoresistance, we find that the maximum
spin-orbit coupling effect occurs when the Fermi energy is near the Lifshitz
point. Moreover, we find strong evidence for a single spin winding at the Fermi
surface.",1904.03731v1
2021-10-19,"Ab initio Calculations in Atoms, Molecules, and Solids, Treating Spin-Orbit Coupling and Electron Interaction on Equal Footing","We incorporate explicit, non-perturbative treatment of spin-orbit coupling
into ab initio auxiliary-field quantum Monte Carlo (AFQMC) calculations. The
approach allows a general computational framework for molecular and bulk
systems in which materials specificity, electron correlation, and spin-orbit
coupling effects can be captured accurately and on equal footing, with
favorable computational scaling versus system size. We adopt relativistic
effective-core potentials which have been obtained by fitting to fully
relativistic data and which have demonstrated a high degree of reliability and
transferability in molecular systems. This results in a 2-component
spin-coupled Hamiltonian, which is then treated by generalizing the ab initio
AFQMC approach. We demonstrate the method by computing the electron affinity in
Pb, the bond dissociation energy in Br$_2$ and I$_2$, and solid Bi.",2110.10201v1
1999-02-09,Spin liquid ground state in a two dimensional non-frustrated spin model,"We consider an exchange model describing two isotropic spin-1/2 Heisenberg
antiferromagnets coupled by a quartic term on the square lattice. The model is
relevant for systems with orbital degeneracy and strong electron-vibron
coupling in the large Hubbard repulsion limit, and is known to show a
spin-Peierls-like dimerization in one dimension. In two dimensions we calculate
energy gaps, susceptibilities, and correlation functions with a Green's
Function Monte Carlo. We find a finite spin gap and no evidence of any kind of
order. We conclude that the ground state is, most likely, a spin liquid of
resonating valence bonds.",9902116v1
2006-01-16,Transport Equations and Spin-Charge Propagating Mode in the Two Dimensional Hole Gas,"We find that the spin-charge motion in a strongly confined two-dimensional
hole gas (2DHG) supports a propagating mode of cubic dispersion apart from the
diffusive mode due to momentum scattering. Propagating modes seem to be a
generic property of systems with spin-orbit coupling. Through a rigorous
Keldysh approach, we obtain the transport equations for the 2DHG, we analyze
the behavior of the hole spin relaxation time, the diffusion coefficients, and
the spin-charge coupled motion.",0601353v1
2006-05-23,Spin currents in the Rashba model in the presence of non-uniform fields,"Spin currents in a two dimensional electron gas with Rashba-type spin orbit
coupling are derived from a spin connection. Using a functional integral
method, we recover the result derived by Sinova {\em et al.}$[
\mathrm{Phys.Rev. Lett.
  92, 126603 (2004)}]$ for a uniform electric field and in the absence of
impurities. We extend this result to inhomogeneous electric and magnetic
fields. We find that non-uniform magnetic fields can give rise to spin currents
that are independent of the Rashba coupling and hence are less susceptible to
impurities than in the case of uniform electric fields.",0605582v1
2006-04-26,Spin-Excitation Mechanisms in Skyrme-Force Time-Dependent Hartree-Fock,"We investigate the role of odd-odd (with respect to time inversion) couplings
in the Skyrme force on collisions of light nuclei, employing a fully
three-dimensional numerical treatment without any symmetry restrictions and
with modern Skyrme functionals. We demonstrate the necessity of these couplings
to suppress spurious spin excitations owing to the spin-orbit force in free
translational motion of a nucleus but show that in a collision situation there
is a strong spin excitation even in spin-saturated systems which persists in
the departing fragments. The energy loss is considerably increased by the
odd-odd terms.",0604070v1
2024-01-16,Classical 'spin' filtering with two degrees of freedom and dissipation,"Coupling of angular motion to a spin degree of freedom gives rise to various
transport phenomena in quantum systems that are beyond the standard paradigms
of classical physics. Here, we discuss features of spin-orbit dynamics that can
be visualized using a classical model with two coupled angular degrees of
freedom. Specifically, we demonstrate classical 'spin' filtering through our
model and show that the interplay between angular degrees of freedom and
dissipation can lead to asymmetric 'spin' transport.",2401.08454v1
2021-02-24,Spin texture in a bilayer high-temperature cuprate superconductor,"We investigate the possibility of spin texture in the bilayer cuprate
superconductor $\rm Bi_2Sr_2CaCu_2O_{8+\delta}$ using cluster dynamical mean
field theory (CDMFT). The one-band Hubbard model with a small interlayer
hopping and a Rashba spin-orbit coupling is used to describe the material. The
$d$-wave order parameter is not much affected by the presence of the Rashba
coupling, but a small triplet component appears. We find a spin texture
circulating in the same direction around $\mathbf{k}=(0,0)$ and
$\mathbf{k}=(\pi,\pi)$ and stable against the superconducting phase. The
amplitude of the spin structure, however, is strongly affected by the pseudogap
phenomenon, more so than the spectral function itself.",2102.12015v1
2011-01-04,"Density functional theory analysis of the interplay between Jahn-Teller instability, uniaxial magnetism, spin arrangement, metal-metal interaction and spin-orbit coupling in Ca3CoMO6 (M = Co, Rh, Ir)","In the isostructural oxides Ca3CoMO6 (M = Co, Rh, Ir), the CoMO6 chains made
up of face-sharing CoO6 trigonal prisms and MO6 octahedra are separated by Ca
atoms. We analyzed the magnetic and electronic properties of these oxides on
the basis of density functional theory calculations including on-site repulsion
and spin-orbit coupling, and examined the essential one-electron pictures
hidden behind results of these calculations. Our analysis reveals an intimate
interplay between Jahn-Teller instability, uniaxial magnetism, spin
arrangement, metal-metal interaction, and spin-orbit coupling in governing the
magnetic and electronic properties of these oxides. These oxides undergo a
Jahn-Teller distortion but their distortions are weak, so that their
trigonal-prism Con+ (n = 2, 3) ions still give rise to strong easy-axis
anisotropy along the chain direction. As for the d-state split pattern of these
ions, the electronic and magnetic properties of Ca3CoMO6 (M = Co, Rh, Ir) are
consistent with d0 < (d2, d-2) < (d1, d-1), but not with (d2, d-2) < d0 < (d1,
d-1). The trigonal-prism Co3+ ion in Ca3Co2O6 has the L = 2 configuration
(d0)1(d2, d-2)3(d1, d-1)2 because of the metal-metal interaction between
adjacent Co3+ ions in each Co2O6 chain, which is mediated by their z2 orbitals,
and the spin-orbit coupling of the trigonal-prism Co3+ ion. The spins in each
CoMO6 chain of Ca3CoMO6 prefer the ferromagnetic arrangement for M = Co and Rh,
but the antiferromagnetic arrangement for M = Ir. The octahedral M4+ ion of
Ca3CoMO6 has the (1a)1(1e)4 configuration for M = Rh but the (1a)2(1e)3
configuration for M = Ir, which arises from the difference in the spin-orbit
coupling of the M4+ ions and the Co...M metal-metal interactions.",1101.0644v1
2015-03-06,Ultrafast spin dynamics in II-VI diluted magnetic semiconductors with spin-orbit interaction,"We study theoretically the ultrafast spin dynamics of II-VI diluted magnetic
semiconductors in the presence of spin-orbit interaction. Our goal is to
explore the interplay or competition between the exchange $sd$-coupling and the
spin-orbit interaction in both bulk and quantum well systems. For bulk
materials we concentrate on Zn$_{1-x}$Mn$_x$Se and take into account the
Dresselhaus interaction, while for quantum wells we examine
Hg$_{1-x-y}$Mn$_x$Cd$_y$Te systems with a strong Rashba coupling. Our
calculations were performed with a recently developed formalism which
incorporates electronic correlations beyond mean-field theory originated from
the exchange $sd$-coupling. For both bulk and quasi-two-dimensional systems we
find that, by varying the system parameters within realistic ranges, both
interactions can be chosen to play a dominant role or to compete on an equal
footing with each other. The most notable effect of the spin-orbit interaction
in both types of systems is the appearance of strong oscillations where the
exchange $sd$-coupling by itself only causes an exponential decay of the mean
electronic spin components. The mean-field approximation is also studied and it
is interpreted analytically why it shows a strong suppression of the
spin-orbit-induced dephasing of the spin component parallel to the Mn magnetic
field.",1503.01937v2
2016-01-07,Hubbard model with Rashba or Dresselhaus spin-orbit coupling and Rotated Anti-ferromagnetic Heisenberg Model,"In this work, we investigate the possible dramatic effects of Rashba or
Dresselhaus spin-orbit coupling (SOC) on fermionic Hubbard model in a 2d square
lattice. In the strong coupling limit, it leads to the Rotated
Anti-ferromagnetic Heisenberg model which is a new class of quantum spin model.
For a special equivalent class, we identify a new spin-orbital entangled
commensurate ground ( Y-y ) state subject to strong quantum fluctuations at
$T=0$. We evaluate the quantum fluctuations by the spin wave expansion up to
order $ 1/S^2 $. In some SOC parameter regime, the Y-y state supports a massive
relativistic in-commensurate magnon ( C-IC ) with its two gap minima positions
continuously tuned by the SOC parameters. The C-IC magnons dominate all the low
temperature thermodynamic quantities and also lead to the separation of the
peak positions between the longitudinal and the transverse spin structure
factors. In the weak coupling limit, any weak repulsive interaction also leads
to a weak Y-y state. There is only a crossover from the weak to the strong
coupling. High temperature expansions of the specific heats in both weak and
strong coupling are presented. The dramatic roles to be played by these C-IC
magnons at generic SOC parameters or under various external probes are hinted.
Experimental applications to both layered noncentrosymmetric materials and cold
atom are discussed.",1601.01642v2
2001-11-14,"Magnetic Ordering, Orbital Ordering and Resonant X-ray Scattering in Perovskite Titanates","The effective Hamiltonian for perovskite titanates is derived by taking into
account the three-fold degeneracy of $t_{2g}$ orbitals and the strong
electron-electron interactions. The magnetic and orbital ordered phases are
studied in the mean-field approximation applied to the effective Hamiltonian. A
large degeneracy of the orbital states in the ferromagnetic phase is found in
contrast to the case of the doubly degenerate $e_g$ orbitals. Lifting of this
orbital degeneracy due to lattice distortions and spin-orbit coupling is
examined. A general form for the scattering cross section of the resonant x-ray
scattering is derived and is applied to the recent experimental results in
YTiO$_3$. The spin wave dispersion relation in the orbital ordered YTiO$_3$ is
also studied.",0111249v1
2020-12-16,Adiabatically Induced Orbital Magnetization,"A semiclassical theory for the orbital magnetization due to adiabatic
evolutions of Bloch electronic states is proposed. It renders a unified theory
for the periodic-evolution pumped orbital magnetization and the orbital
magnetoelectric response in insulators by revealing that these two phenomena
are the only instances where the induced magnetization is gauge invariant. This
theory also accounts for the electric-field induced intrinsic orbital
magnetization in two-dimensional metals and Chern insulators. We illustrate the
orbital magnetization pumped by microscopic local rotations of atoms, which
correspond to phonon modes with angular momentum, in toy models based on
honeycomb lattice, and the results are comparable to the pumped spin
magnetization via strong Rashba spin orbit coupling. We also show the vital
role of the orbital magnetoelectricity in validating the Mott relation between
the intrinsic nonlinear anomalous Hall and Ettingshausen effects.",2012.08750v3
2020-11-15,Orbital gyrotropic magneto-electric effect and its strain engineering in monolayer Nb$X_2$,"Electrical control of the orbital degrees of freedom is an important area of
research in the emerging field of ""orbitronics."" Orbital {\it gyrotropic}
magneto-electric effect (OGME) is the generation of an orbital magnetization in
a nonmagnetic metal by an applied electric field. Here, we show that strain
induces a large GME in the monolayer Nb$X_2$ ($X =$ S, Se) normal to the plane,
primarily driven by the orbital moments of the Bloch bands as opposed to the
conventional spin magnetization, without any need for spin-orbit coupling. The
key physics is captured within an effective two-band valley-orbital model and
it is shown to be driven by three key ingredients: the intrinsic valley orbital
moment, broken $C_{3z}$ symmetry, and strain-induced Fermi surface changes. The
effect can be furthermore switched by changing the strain condition, with
potential for future device applications.",2011.07508v1
2024-03-18,Spin-Orbital Ordering in Alkali Superoxides,"Akali superoxides AO2 (A=Na, K, Rb, Cs), due to an open p shell of the oxygen
ion O2^- with degenerate pi orbitals, have spin and orbital degrees of freedom.
The complex magnetic, orbital, and structural phase transitions observed
experimentally in this family of materials are only partially understood. Based
on density functional theory, we derive a strong-coupling effective model for
the isostructural compounds AO2 (A=K, Rb, Cs) from a two-orbital Hubbard model.
We find that CsO2 has highly frustrated exchange interactions in the a-b plane,
while the frustration is weaker for smaller alkali ions. We solve the resulting
Kugel-Khomskii model in the mean-field approximation. We show that CsO2
exhibits an antiferro-orbital (AFO) order with the ordering vector q=(1,0,0)
and a stripe antiferromagnetic order with q=(1/2,0,0), which is consistent with
recent neutron scattering experiments. We discuss the role of the pi-orbital
degrees of freedom for the experimentally observed magnetic transitions and
interpret the as-yet-unidentified T_s2=70K transition in CsO2 as an orbital
ordering transition.",2403.11698v2
2019-04-17,Two-orbital effective model for magnetic Weyl semimetal in Kagome-lattice shandite,"We construct a two-orbital effective model for a ferromagnetic Kagome-lattice
shandite, $\rm{{Co}_3{Sn}_2{S}_2}$, a candidate material of magnetic Weyl
semimetals, by considering one $d$ orbital from Co, and one $p$ orbital from
interlayer Sn. The energy spectrum near the Fermi level, and the configurations
of the Weyl points, computed by using our model, are similar to those obtained
by first principle calculations. We show also that nodal rings appear even with
spin-orbit coupling when the magnetization points in-plane direction.
Additionally, magnetic properties of $\rm{{Co}_3{Sn}_2{S}_2}$ and other
shandite materials are discussed.",1904.08148v1
2004-07-25,The dynamics of precessing binary black holes using the post-Newtonian approximation,"We investigate the (conservative) dynamics of binary black holes using the
Hamiltonian formulation of the post-Newtonian (PN) equations of motion. The
Hamiltonian we use includes spin-orbit coupling, spin-spin coupling, and mass
monopole/spin-induced quadrupole interaction terms. In the case of both
quasi-circular and eccentric orbits, we search for the presence of chaos (using
the method of Lyapunov exponents) for a large variety of initial conditions.
For quasi-circular orbits, we find no chaotic behavior for black holes with
total mass 10 - 40 solar masses when initially at a separation corresponding to
a Newtonian gravitational-wave frequency less than 150 Hz. Only for rather
small initial radial distances, for which spin-spin induced oscillations in the
radial separation are rather important, do we find chaotic solutions, and even
then they are rare. Moreover, these chaotic quasi-circular orbits are of
questionable astrophysical significance, since they originate from direct
parametrization of the equations of motion rather than from widely separated
binaries evolving to small separations under gravitational radiation reaction.
In the case of highly eccentric orbits, which for ground-based interferometers
are not astrophysically favored, we again find chaotic solutions, but only at
pericenters so small that higher order PN corrections, especially higher spin
PN corrections, should also be taken into account.",0407091v2
2012-08-21,Graphene for spintronics: giant Rashba splitting due to hybridization with Au,"Graphene in spintronics has so far primarily meant spin current leads of high
performance because the intrinsic spin-orbit coupling of its pi-electrons is
very weak. If a large spin-orbit coupling could be created by a proximity
effect, the material could also form active elements of a spintronic device
such as the Das-Datta spin field-effect transistor, however, metal interfaces
often compromise the band dispersion of massless Dirac fermions. Our
measurements show that Au intercalation at the graphene-Ni interface creates a
giant spin-orbit splitting (~100 meV) in the graphene Dirac cone up to the
Fermi energy. Photoelectron spectroscopy reveals hybridization with Au-5d
states as the source for the giant spin-orbit splitting. An ab initio model of
the system shows a Rashba-split dispersion with the analytically predicted
gapless band topology around the Dirac point of graphene and indicates that a
sharp graphene-Au interface at equilibrium distance will account for only ~10
meV spin-orbit splitting. The ab initio calculations suggest an enhancement due
to Au atoms that get closer to the graphene and do not violate the sublattice
symmetry.",1208.4265v1
2014-11-24,Manipulating Femtosecond Spin--Orbit Torques with Laser Pulse Sequences to Control Magnetic Memory States and Ringing,"Femtosecond (fs) coherent control of collective order parameters is important
for non--equilibrium phase dynamics in correlated materials. Here we propose a
possible scheme for fs control of a ferromagnetic order parameter based on
non--adiabatic optical manipulation of electron--hole ($e$--$h$)
photoexcitations between spin--orbit--coupled bands that are exchange--split by
magnetic interaction with local spins. We photoexcite fs carrier spin--pulses
with controllable direction and time profile without using
circularly--polarized light, via time--reversal symmetry--breaking by
non--perturbative interplay between spin--orbit and magnetic exchange coupling
of coherent photocarriers. We manipulate photoexcited {\em fs spin--orbit
torques} to control complex switching pathways of the magnetization between
multiple magnetic memory states. We calculate the photoinduced fs magnetic
anisotropy in the time domain by using density matrix equations of motion
rather than the quasi--equilibrium free energy. By comparing to pump--probe
experiments, we identify a ""sudden"" magnetization canting induced by laser
excitation, which displays magnetic hysteresis absent in static
magneto--optical measurements and agrees with switchings measured by Hall
magnetoresistivity. The fs magnetization canting switches direction with
magnetic state and laser frequency, which distinguishes it from nonlinear
optical and demagnetization longitudinal effects. By shaping two--color
laser--pulse sequences analogous to multi--dimensional Nuclear Magnetic
Resonance (NMR) spectroscopy, we show that sequences of clockwise or
counter--clockwise fs spin--orbit torques can enhance or suppress magnetic
ringing and switching rotation at any desired time. We propose protocols that
can provide controlled access to four magnetic states via consequative 90$^{o}$
switchings.",1411.6662v1
2017-03-05,Response to Comment on 'Spin-Orbit Logic with Magnetoelectric Nodes: A Scalable Charge Mediated Nonvolatile Spintronic Logic' (arXiv:1607.06690),"In this technical note, we address the comments on the energy estimates for
Magnetoelectric Spin-orbit (MESO) Logic, a new logic device proposed by the
authors. We provide an analytical derivation of the switching energy, and
support it with time-domain circuit simulations using a self-consistent
ferroelectric (FE) compact model. While the energy to charge a capacitor is
dissipated in the interconnect and transistor resistance, we note that the
energy to switch a capacitor and a FE is independent of the interconnect
resistance value to the first order. Also device design can mitigate the
parasitic energy losses. We further show the circuit simulations for a sub 10
aJ switching operation of a MESO logic device comprehending: a) Energy stored
in multiferroic; b) Energy dissipation in the resistance of the interconnect,
Ric ; c) Energy dissipation in the inverse spin-orbit coupling (ISOC) spin to
charge converter Risoc; d) Supply, ground resistance, and transistor losses. We
also identify the requirements for the resistivity of the spin-orbit coupling
materials and address the effect of internal resistance of the spin to charge
conversion layer. We provide the material parameter space where MESO (with a
fan-out of 1 and interconnect) achieves sub 10 aJ switching energy with path
for scaling via ferroelectric/magnetoelectric/spin-orbit materials development.",1703.01559v1
2017-09-15,Emergent $\mathrm{SU}(4)$ Symmetry in $α$-ZrCl$_3$ and Crystalline Spin-Orbital Liquids,"While the enhancement of the spin-space symmetry from the usual
$\mathrm{SU}(2)$ to $\mathrm{SU}(N)$ is promising for finding nontrivial
quantum spin liquids, its realization in magnetic materials remains
challenging. Here we propose a new mechanism by which the $\mathrm{SU}(4)$
symmetry emerges in the strong spin-orbit coupling limit. In $d^1$ transition
metal compounds with edge-sharing anion octahedra, the spin-orbit coupling
gives rise to strongly bond-dependent and apparently $\mathrm{SU}(4)$-breaking
hopping between the $J_\textrm{eff}=3/2$ quartets. However, in the honeycomb
structure, a gauge transformation maps the system to an
$\mathrm{SU}(4)$-symmetric Hubbard model. In the strong repulsion limit at
quarter filling, as realized in $\alpha$-ZrCl$_3,$ the low-energy effective
model is the $\mathrm{SU}(4)$ Heisenberg model on the honeycomb lattice, which
cannot have a trivial gapped ground state and is expected to host a gapless
spin-orbital liquid. By generalizing this model to other three-dimensional
lattices, we also propose crystalline spin-orbital liquids protected by this
emergent $\mathrm{SU}(4)$ symmetry and space group symmetries.",1709.05252v3
2021-02-25,Unidirectional magnetoresistance and spin-orbit torque in NiMnSb,"Spin-dependent transport phenomena due to relativistic spin-orbit coupling
and broken space-inversion symmetry are often difficult to interpret
microscopically, in particular when occurring at surfaces or interfaces. Here
we present a theoretical and experimental study of spin-orbit torque and
unidirectional magnetoresistance in a model room-temperature ferromagnet NiMnSb
with inversion asymmetry in the bulk of this half-heusler crystal. Besides the
angular dependence on magnetization, the competition of Rashba and
Dresselhaus-like spin-orbit couplings results in the dependence of these
effects on the crystal direction of the applied electric field. The
phenomenology that we observe highlights potential inapplicability of commonly
considered approaches for interpreting experiments. We point out that, in
general, there is no direct link between the current-induced non-equilibrium
spin polarization inferred from the measured spin-orbit torque and the
unidirectional magnetiresistance. We also emphasize that the unidirectional
magnetoresistance has not only longitudinal but also transverse components in
the electric field -- current indices which complicates its separation from the
thermoelectric contributions to the detected signals in common experimental
techniques. We use the theoretical results to analyze our measurements of the
on-resonance and off-resonance mixing signals in microbar devices fabricated
from an epitaxial NiMnSb film along different crystal directions. Based on the
analysis we extract an experimental estimate of the unidirectional
magnetoresistance in NiMnSb.",2102.12838v1
2013-04-18,A Primordial Origin for Misalignments Between Stellar Spin Axes and Planetary Orbits,"The presence of gaseous giant planets whose orbits lie in extreme proximity
to their host stars (""hot Jupiters""), can largely be accounted for by planetary
migration, associated with viscous evolution of proto-planetary nebulae.
Recently, observations of the Rossiter-McLaughlin effect during planetary
transits have revealed that a considerable fraction of detected hot Jupiters
reside on orbits that are misaligned with respect to the spin-axes of their
host stars. This observational fact has cast significant doubts on the
importance of disk-driven migration as a mechanism for production of hot
Jupiters, thereby reestablishing the origins of close-in planetary orbits as an
open question. Here we show that misaligned orbits can be a natural consequence
of disk migration. Our argument rests on an enhanced abundance of binary
stellar companions in star formation environments, whose orbital plane is
uncorrelated with the spin axes of the individual stars. We analyze the
dynamical evolution of idealized proto-planetary disks under perturbations from
massive distant bodies and demonstrate that the resulting gravitational torques
act to misalign the orbital planes of the disks relative to the spin poles of
their host stars. As a result, we predict that in the absence of strong
disk-host star angular momentum coupling or sufficient dissipation that acts to
realign the stellar spin axis and the planetary orbits, the fraction of
planetary systems (including systems of hot Neptunes and Super-Earths), whose
angular momentum vectors are misaligned with respect to their host-stars should
be commensurate with the rate of primordial stellar multiplicity.",1304.5166v1
2016-10-19,Interplay of non-symmorphic symmetry and spin-orbit coupling in hyperkagome spin liquids: Applications to Na$_4$Ir$_3$O$_8$,"Na$_4$Ir$_3$O$_8$ provides a material platform to study three-dimensional
quantum spin liquids in the geometrically frustrated hyperkagome lattice of
Ir$^{4+}$ ions. In this work, we consider quantum spin liquids on hyperkagome
lattice for generic spin models, focusing on the effects of anisotropic spin
interactions. In particular, we classify possible $\mathbb{Z}_2$ and $U(1)$
spin liquid states, following the projective symmetry group analysis in the
slave-fermion representation. There are only three distinct $\mathbb{Z}_2$ spin
liquids, together with 2 different $U(1)$ spin liquids. The non-symmorphic
space group symmetry of hyperkagome lattice plays a vital role in simplifying
the classification, forbidding ""$\pi$-flux"" or ""staggered-flux"" phases in
contrast to symmorphic space groups. We further prove that both $U(1)$ states
and one $Z_2$ state among all 3 are symmetry-protected gapless spin liquids,
robust against any symmetry-preserving perturbations. Motivated by the
""spin-freezing"" behavior recently observed in Na$_4$Ir$_3$O$_8$ at low
temperatures, we further investigate the nearest-neighbor spin model with
dominant Heisenberg interaction subject to all possible anisotropic
perturbations from spin-orbit couplings. We found a $U(1)$ spin liquid ground
state with spinon fermi surfaces is energetically favored over $Z_2$ states.
Among all spin-orbit coupling terms, we show that only Dzyaloshinskii-Moriya
(DM) interaction can induce spin anisotropy in the ground state when perturbing
from the isotropic Heisenberg limit. Our work paves the way for a systematic
study of quantum spin liquids in various materials with a hyperkagome crystal
structure.",1610.06191v3
2003-05-16,Spin-orbit coupling and electron spin resonance for interacting electrons in carbon nanotubes,"We review the theoretical description of spin-orbit scattering and electron
spin resonance in carbon nanotubes. Particular emphasis is laid on the effects
of electron-electron interactions. The spin-orbit coupling is derived, and the
resulting ESR spectrum is analyzed both using the effective low-energy field
theory and numerical studies of finite-size Hubbard chains and two-leg Hubbard
ladders. For single-wall tubes, the field theoretical description predicts a
double peak spectrum linked to the existence of spin-charge separation. The
numerical analysis basically confirms this picture, but also predicts
additional features in finite-size samples.",0305388v2
2004-05-04,Bosonization of Luttinger liquids: spin flipping interactions and spin-orbit coupling,"In this thesis we present contributions in the field of the applications of
quantum field theories techniques to condensed matter models. In chapter 3 we
investigate on the non covariant fermionic determinant and its connection to
Luttinger liquids. We address the problem of the regularization of the theory.
In chapter 4 we treat spin flipping interactions in the non local Thirring
model and we obtain an effective bosonic actions that describe separated spin
and charge degrees of freedom. In chapter 4 we apply the self consistent
harmonic approximation to previously derived bosonic action and we obtain
potential depending equations for the spectrum gap. In chapter 5 we include
spin-orbit couplings and compute correlations functions. We show that the spin
orbit interactions modify the exponents and the phase diagram of the system and
makes new susceptibilities diverge for low temperature. Finally in chapter 6 we
summarize the main results and the conclusions.",0405054v1
2005-10-31,Longitudinal and spin-Hall conductance of a two-dimensional Rashba system with arbitrary disorder,"We calculate the longitudinal and spin-Hall conductances in four-lead bridges
with Rashba - Dresselhaus spin-orbit interactions. Numerical results are
obtained both within Landauer-Buttiker formalism and by the direct evaluation
of the Kubo formula. The microscopic Hamiltonian is obtained in the
tight-binding approximation in terms of the neareast-neighbor hopping integral
$t$, the Rashba spin-orbit coupling $V_R$, the Dresselhaus spin-orbit coupling
$V_D$ and an Anderson-like, on-site disorder energy strength $W$. We reconfirm
that below a critical disorder threshold, the spin-Hall effect is present.
Further, we study the effect on the two conductivities of the Fermi energy,
Rashba/Dresselhaus coefficient ratio, and system size.",0510842v1
2006-12-04,Quenching of Spin Hall Effect in Ballistic nano-junctions,"We show that a nanometric four-probe ballistic junction can be used to check
the presence of a transverse spin Hall current in a system with a Spin Orbit
coupling not of the Rashba type, but rather due to the in-plane electric field.
Indeed, the spin Hall effect is due to the presence of an effective small
transverse magnetic field corresponding to the Spin Orbit coupling generated by
the confining potential. The strength of the field and the junction shape
characterize the quenching Hall regime, usually studied by applying
semi-classical approaches. We discuss how a quantum mechanical relativistic
effect, such as the Spin Orbit one, can be observed in a low energy system and
explained by using classical mechanics techniques.",0612074v1
2007-05-24,Local spin dynamic arising from the non-perturbative SU(2) gauge field of the spin orbit effect,"We use the non-perturbative gauge field approach to study the effects of spin
orbit coupling on the dynamic of magnetic moment. We present a general equation
of motion (EOM) which unifies i) the spin orbit coupling effect derived from
the SU(2) spin gauge field, and ii) the moment chirality effect previously
derived from the topological U(1)xU(1) rotation gauge under the adiabatic
condition. We present a modified Landau-Liftshitz-Gilbert equation and discuss
the implication of the modified EOM in various technological applications, such
as current-induced switching and trajectory of magnetic moments in spin-valve
multilayers, magnetic memory and diluted magnetic semiconductor.",0705.3502v1
2009-07-23,Spin Hall effect due to intersubband-induced spin-orbit interaction in symmetric quantum wells,"We investigate the intrinsic spin Hall effect in two-dimensional electron
gases in quantum wells with two subbands, where a new intersubband-induced
spin-orbit coupling is operative. The bulk spin Hall conductivity
$\sigma^z_{xy}$ is calculated in the ballistic limit within the standard Kubo
formalism in the presence of a magnetic field $B$ and is found to remain finite
in the B=0 limit, as long as only the lowest subband is occupied. Our
calculated $\sigma^z_{xy}$ exhibits a nonmonotonic behavior and can change its
sign as the Fermi energy (the carrier areal density $n_{2D}$) is varied between
the subband edges. We determine the magnitude of $\sigma^z_{xy}$ for realistic
InSb quantum wells by performing a self-consistent calculation of the
intersubband-induced spin-orbit coupling.",0907.4078v2
2010-11-29,Interplay between Lattice Distortion and Spin-Orbit Coupling in Double Perovskites,"We develop anisotropic pseudo-spin antiferromagnetic Heisenberg models for
monoclinically distorted double perovskites. We focus on these A$_2$BB'O$_6$
materials that have magnetic moments on the 4d or 5d transition metal B' ions,
which form a face-centered cubic lattice. In these models, we consider local
z-axis distortion of B'-O octahedra, affecting relative occupancy of $t_{2g}$
orbitals, along with geometric effects of the monoclinic distortion, and
spin-orbit coupling. The resulting pseudo-spin-1/2 models are solved in the
saddle-point limit of the Sp(N) generalization of the Heisenberg model. The
spin S in the SU(2) case generalizes as a parameter $\kappa$ controlling
quantum fluctuation in the Sp(N) case. We consider two different models that
may be appropriate for these systems. In particular, using Heisenberg exchange
parameters for La$_2$LiMoO$_6$ from a spin-dimer calculation, we conclude that
this pseudo-spin-1/2 system may order, but must be very close to a disordered
spin liquid state.",1011.6389v2
2012-12-07,Strongly spin-orbit coupled two-dimensional electron gas emerging near the surface of polar semiconductors,"We investigate the two-dimensional (2D) highly spin-polarized electron
accumulation layers commonly appearing near the surface of n-type polar
semiconductors BiTeX (X = I, Br, and Cl) by angular-resolved photoemission
spectroscopy. Due to the polarity and the strong spin-orbit interaction built
in the bulk atomic configurations, the quantized conduction-band subbands show
giant Rashba-type spin-splitting. The characteristic 2D confinement effect is
clearly observed also in the valence-bands down to the binding energy of 4 eV.
The X-dependent Rashba spin-orbit coupling is directly estimated from the
observed spin-split subbands, which roughly scales with the inverse of the
band-gap size in BiTeX.",1212.1552v1
2014-04-17,Effect of spin-orbit interaction on the critical temperature of an ideal Bose gas,"We consider Bose-Einstein condensation of an ideal bose gas with an equal
mixture of `Rashba' and `Dresselhaus' spin-orbit interactions and study its
effect on the critical temperature.
  In uniform bose gas a `cusp' and a sharp drop in the critical temperature
occurs due to the change in the density of states at a critical Raman coupling
where the degeneracy of the ground states is lifted. Relative drop in the
critical temperature depends on the diluteness of the gas as well as on the
spin-orbit coupling strength. In the presence of a harmonic trap, the cusp in
the critical temperature smoothened out and a minimum appears. Both the drop in
the critical temperature and lifting of `quasi-degeneracy' of the ground states
exhibit crossover phenomena which is controlled by the trap frequency. By
considering a 'Dicke' like model we extend our calculation to bosons with large
spin and observe a similar minimum in the critical temperature near the
critical Raman frequency, which becomes deeper for larger spin. Finally in the
limit of infinite spin, the critical temperature vanishes at the critical
frequency, which is a manifestation of Dicke type quantum phase transition.",1404.4500v1
2015-01-30,Intrinsic Damping of Collective Spin Modes in a Two-Dimensional Fermi Liquid with Spin-Orbit Coupling,"A Fermi liquid with spin-orbit coupling (SOC) is expected to support a new
kind of collective modes: oscillations of magnetization in the absence of the
magnetic field. We show that these modes are damped by the electron-electron
interaction even in the limit of an infinitely long wavelength (q = 0). The
linewidth of the collective mode is on the order of {\Delta}^2=E_F , where
{\Delta} is a characteristic spin-orbit energy splitting and E_F is the Fermi
energy. Such damping is in a stark contrast to known damping mechanisms of both
charge and spin collective modes in the absence of SOC, all of which disappear
at q = 0, and arises because none of the components of total spin is conserved
in the presence of SOC.",1502.00027v1
2015-06-30,Graphene on transition-metal dichalcogenides: a platform for proximity spin-orbit physics and optospintronics,"Hybrids of graphene and two dimensional transition metal dichalcogenides
(TMDC) have the potential to bring graphene spintronics to the next level. As
we show here by performing first-principles calculations of graphene on
monolayer MoS$_2$, there are several advantages of such hybrids over pristine
graphene. First, Dirac electrons in graphene exhibit a giant global proximity
spin-orbit coupling, without compromising the semimetallic character of the
whole system at zero field. Remarkably, these spin-orbit effects can be very
accurately described by a simple effective Hamiltonian. Second, the Fermi level
can be tuned by a transverse electric field to cross the MoS$_2$ conduction
band, creating a system of coupled massive and massles electron gases. Both
charge and spin transport in such systems should be unique. Finally, we propose
to use graphene/TMDC structures as a platform for optospintronics, in
particular for optical spin injection into graphene and for studying spin
transfer between TMDC and graphene.",1506.08954v1
2015-08-03,Spin-Spin Coupling in the Solar System,"The richness of dynamical behavior exhibited by the rotational states of
various solar system objects has driven significant advances in the theoretical
understanding of their evolutionary histories. An important factor that
determines whether a given object is prone to exhibiting non-trivial rotational
evolution is the extent to which such an object can maintain a permanent
aspheroidal shape, meaning that exotic behavior is far more common among the
small body populations of the solar system. Gravitationally bound binary
objects constitute a substantial fraction of asteroidal and TNO populations,
comprising systems of triaxial satellites that orbit permanently deformed
central bodies. In this work, we explore the rotational evolution of such
systems with specific emphasis on quadrupole-quadrupole interactions, and show
that for closely orbiting, highly deformed objects, both prograde and
retrograde spin-spin resonances naturally arise. Subsequently, we derive
capture probabilities for leading order commensurabilities and apply our
results to the illustrative examples of (87) Sylvia and (216) Kleopatra
asteroid systems. Cumulatively, our results suggest that spin-spin coupling may
be consequential for highly elongated, tightly orbiting binary objects.",1508.00616v1
2015-08-27,"Symmetry, distorted bandstructure, and spin-orbit coupling of (group-III) metal-monochalcogenide monolayers","The electronic structure of (group-III) metal-monochalcogenide monolayers
exhibits many unusual features. Some, such as the unusually distorted upper
valence band dispersion we describe as a 'caldera', are primarily the result of
purely orbital interactions. Others, including spin splitting and wavefunction
spin-mixing, are directly driven by spin-orbit coupling. We employ elementary
group theory to explain the origins of these properties, and use a
tight-binding model to calculate the phenomena enabled by them, such as
band-edge carrier effective g-factors, optical absorption spectrum, conduction
electron spin orientation, and a relaxation-induced upper valence band
population inversion and spin polarization mechanism.",1508.06963v5
2014-05-09,Magnetic excitations and anomalous spin wave broadening in multiferroic FeV2O4,"We report on the different roles of two orbital-active Fe$^{2+}$ at the A
site and V$^{3+}$ at the B site in the magnetic excitations and on the
anomalous spin wave broadening in FeV$_{2}$O$_{4}$. FeV$_{2}$O$_{4}$ exhibits
three structural transitions and successive paramagnetic (PM)-collinear
ferrimagnetic (CFI)-noncollinear ferrimagnetic (NCFI) transitions. The
high-temperature tetragonal/PM -orthorhombic/CFI transition is accompanied by
the appearance of an energy gap with a high magnitude in the magnetic
excitations due to strong spin-orbit coupling induced anisotropy at the
Fe$^{2+}$ site. While there is no measurable increase in the energy gap from
the orbital ordering of V$^{3+}$ at the orthorhombic/CFI-tetragonal/NCFI
transition, anomalous spin wave broadening is observed in the orthorhombic/CFI
state due to V$^{3+}$ spin fluctuations at the B site. The spin wave broadening
is also observed at the zone boundary without softening, which is discussed in
terms of magnon-phonon coupling.",1405.2272v2
2019-10-24,Algebraic decay of the nonadiabaticity arising through chiral spin transfer torque in magnetic domain walls with Rashba spin-orbit interaction,"Spin transfer torque in a two dimensional electron gas system without space
inversion symmetry was theoretically investigated by solving the
Pauli-Schr\""{o}dinger equation for the itinerant electrons inside magnetic
domain walls. Due to the presence of the Rashba spin-orbit coupling induced by
the broken inversion symmetry, the spin transfer torque is chiral and the
nonadiabaticity, which is defined to measure the relative importance of the
nonadiabatic, field-like torque to the adiabatic, damping-like torque, exhibits
an inverse power law decay as the domain wall width is increased. This
algebraic decay is much slower than the exponential decay observed for systems
without the Rashba spin-orbit coupling, and may find applications in innovative
design of spintronic devices utilising magnetic topological textures such as
magnetic domain walls and skyrmions.",1910.11031v3
2020-04-16,Exchange interaction of hole-spin qubits in double quantum dots in highly anisotropic semiconductors,"We study the exchange interaction between two hole-spin qubits in a double
quantum dot setup in a silicon nanowire in the presence of magnetic and
electric fields. Based on symmetry arguments we show that there exists an
effective spin that is conserved even in highly anisotropic semiconductors,
provided that the system has a twofold symmetry with respect to the direction
of the applied magnetic field. This finding facilitates the definition of qubit
basis states and simplifies the form of exchange interaction for two-qubit
gates in coupled quantum dots. If the magnetic field is applied along a generic
direction, cubic anisotropy terms act as an effective spin-orbit interaction
introducing novel exchange couplings even for an inversion symmetric setup.
Considering the example of a silicon nanowire double dot, we present the
relative strength of these anisotropic exchange interaction terms and calculate
the fidelity of the $\sqrt{\text{SWAP}}$ gate. Furthermore, we show that the
anisotropy-induced spin-orbit effects can be comparable to that of the direct
Rashba spin-orbit interaction for experimentally feasible electric field
strengths.",2004.07658v1
2018-06-28,Electrical control of the Zeeman spin splitting in two-dimensional hole systems,"Semiconductor holes with strong spin-orbit coupling allow all-electrical spin
control, with broad applications ranging from spintronics to quantum
computation. Using a two-dimensional hole system in a GaAs quantum well, we
demonstrate a new mechanism of electrically controlling the Zeeman splitting,
which is achieved through altering the hole wave vector $k$. We find a
threefold enhancement of the in-plane $g-$factor $g_{\parallel}(k)$. We
introduce a new method for quantifying the Zeeman splitting from
magnetoresistance measurements, since the conventional tilted field approach
fails for two-dimensional systems with strong spin-orbit coupling. Finally, we
show that the Rashba spin-orbit interaction suppresses the in-plane Zeeman
interaction at low magnetic fields. The ability to control the Zeeman splitting
with electric fields opens up new possibilities for future quantum spin-based
devices, manipulating non-Abelian geometric phases, and realising Majorana
systems in $p-$type superconductor systems.",1806.10817v1
2021-11-12,Dissipationless Circulating Currents and Fringe Magnetic Fields Near a Single Spin Embedded in a Two-Dimensional Electron Gas,"Theoretical calculations predict the dissipationless circulating current
induced by a spin defect in a two-dimensional electron gas with spin-orbit
coupling. The shape and spatial extent of these dissipationless circulating
currents depend dramatically on the relative strengths of spin-orbit fields
with differing spatial symmetry, offering the potential to use an electric gate
to manipulate nanoscale magnetic fields and couple magnetic defects. The
spatial structure of the magnetic field produced by this current is calculated
and provides a direct way to measure the spin-orbit fields of the host, as well
as the defect spin orientation, \textit{e.g.} through scanning nanoscale
magnetometry.",2111.06770v1
2022-06-08,Gate-Tunable Spin-Orbit Coupling in a Germanium Hole Double Quantum Dot,"Hole spins confined in semiconductor quantum dot systems have gained
considerable interest for their strong spin-orbit interactions (SOIs) and
relatively weak hyperfine interactions. Here we experimentally demonstrate a
tunable SOI in a double quantum dot in a Germanium (Ge) hut wire (HW), which
could help enable fast all-electric spin manipulations while suppressing
unwanted decoherence. Specifically, we measure the transport spectra in the
Pauli spin blockade regime in the double quantum dot device.By adjusting the
interdot tunnel coupling, we obtain an electric field tuned spin-orbit length
lso = 2.0 - 48.9 nm. This tunability of the SOI could pave the way toward the
realization of high-fidelity qubits in Ge HW systems.",2206.03653v1
2024-01-10,Self-generated spin-orbit torque driven by anomalous Hall current,"Spin-orbit torques enable energy-efficient manipulation of magnetization by
electric current and hold promise for applications ranging from nonvolatile
memory to neuromorphic computing. Here we report the discovery of a giant
spin-orbit torque induced by anomalous Hall current in ferromagnetic
conductors. This anomalous Hall torque is self-generated as it acts on
magnetization of the ferromagnet that engenders the torque. The magnitude of
the anomalous Hall torque is sufficiently large to fully negate magnetic
damping of the ferromagnet, which allows us to implement a microwave spin
torque nano-oscillator driven by this torque. The peculiar angular symmetry of
the anomalous Hall torque favors its use over the conventional spin Hall torque
in coupled nano-oscillator arrays. The universal character of the anomalous
Hall torque makes it an integral part of the description of coupled spin
transport and magnetization dynamics in magnetic nanostructures.",2401.05006v1
1993-01-06,Spin-Orbit Scattering and Pair Breaking in a Structurally Disordered Copper-Oxide Layer,"To leading order in displacement size, the scattering of electrons in a Cu-O
plane from O displacements perpendicular to that plane is due to spin-orbit
coupling. This scattering is investigated with the following results: (1) As a
consequence of time-reversal symmetry, spin fluctuations, which can strongly
enhance scattering from a spin impurity, do not enhance spin-orbit scattering;
and (2) for a superconductor with a $d_{x^2-y^2}$ gap function, pair-breaking
from spin-orbit scattering can be strong, particularly in a structurally
disordered phase in which locally CuO$_6$ octahedra tilt as in the orthorhombic
phase of La$_2$CuO$_4$, but globally the average structure is tetragonal. These
results are discussed in the context of the (La,Nd)-(Sr,Ba)-Cu-O system where
certain structural transitions are observed to suppress superconductivity.",9301003v2
2002-03-09,Semiclassical theory of spin-orbit interactions using spin coherent states,"We formulate a semiclassical theory for systems with spin-orbit interactions.
Using spin coherent states, we start from the path integral in an extended
phase space, formulate the classical dynamics of the coupled orbital and spin
degrees of freedom, and calculate the ingredients of Gutzwiller's trace formula
for the density of states. For a two-dimensional quantum dot with a spin-orbit
interaction of Rashba type, we obtain satisfactory agreement with fully
quantum-mechanical calculations. The mode-conversion problem, which arose in an
earlier semiclassical approach, has hereby been overcome.",0203015v2
2010-02-10,Disentangling the effects of spin-orbit and hyperfine interactions on spin blockade,"We have achieved the few-electron regime in InAs nanowire double quantum
dots. Spin blockade is observed for the first two half-filled orbitals, where
the transport cycle is interrupted by forbidden transitions between triplet and
singlet states. Partial lifting of spin blockade is explained by spin-orbit and
hyperfine mechanisms that enable triplet to singlet transitions. The
measurements over a wide range of interdot coupling and tunneling rates to the
leads are well reproduced by a simple transport model. This allows us to
separate and quantify the contributions of the spin-orbit and hyperfine
interactions.",1002.2120v2
2012-10-23,Impact of the various spin and orbital ordering processes on multiferroic properties of orthovanadate DyVO3,"The orthovanadate DyVO3 crystal, known to exhibit multiple structural, spin
and orbital ordering transitions, is presently investigated on the basis of
magnetization, heat capacity, resistivity, dielectric and polarization
measurements. Our main result is experimental evidence for the existence of
multiferroicity below a high TC of 108 K over a wide temperature range
including different spin-orbital ordered states. The onset of ferroelectricity
is found to coincide with the antiferromagnetic C-type spin ordering transition
taking place at 108 K, which indicates that DyVO3 belongs to type II
multiferroics exhibiting a coupling between magnetism and ferroelectricity.
Some anomalies detected on the temperature dependence of electric polarization
are discussed with respect to the nature of the spin-orbital ordered states of
the V sublattice and the degree of spin alignment in the Dy sublattice. The
orthovanadates RVO3 (R = rare earth or Y) form an important new category for
searching for high-TC multiferroics.",1210.6373v3
2018-04-05,Spin dynamics of the block orbital-selective Mott phase,"Iron-based superconductors display a variety of magnetic phases originating
in the competition between electronic, orbital, and spin degrees of freedom.
Previous theoretical investigations of the multi-orbital Hubbard model in one
dimension revealed the existence of an orbital-selective Mott phase (OSMP) with
block spin order. Recent inelastic neutron scattering (INS) experiments on the
BaFe$_2$Se$_3$ ladder compound confirmed the relevance of the block-OSMP.
Moreover, the powder INS spectrum reveled an unexpected structure, containing
both low-energy acoustic and high-energy optical modes. Here we present the
theoretical prediction for the dynamical spin structure factor within a
block-OSMP regime using the density-matrix renormalization group method. In
agreement with experiments we find two dominant features: low-energy dispersive
and high-energy dispersionless modes. We argue that the former represents the
spin-wave-like dynamics of the block ferromagnetic islands, while the latter is
attributed to a novel type of local on-site spin excitations controlled by the
Hund coupling.",1804.01959v2
2018-05-31,Spin-orbit torque induced dipole skyrmion motion at room temperature,"We demonstrate deterministic control of dipole-field-stabilized skyrmions by
means of spin-orbit torques arising from heavy transition-metal seed layers.
Experiments are performed on amorphous Fe/Gd multilayers that are patterned
into wires and exhibit stripe domains and dipole skyrmions at room temperature.
We show that while the domain walls and skyrmions are achiral on average due to
lack of Dzyaloshinskii-Moriya interactions, the N\'eel-like closure domain
walls at each surface are chiral and can couple to spin-orbit torques. The
current-induced domain evolutions are reported for different magnetic phases,
including disordered stripe domains, coexisting stripes and dipole skyrmions
and a closed packed dipole skyrmion lattice. The magnetic textures exhibit
motion under current excitations with a current density ~10^8 A/m2. By
comparing the motion resulting from magnetic spin textures in Fe/Gd films with
different heavy transition-metal interfaces, we confirm spin currents can be
used to manipulate achiral dipole skyrmions via spin-orbit torques.",1805.12517v1
2012-01-18,Crossover from coherent to incoherent scattering in spin-orbit dominated Sr2IrO4,"Strong spin-orbit interaction in the two dimensional compound Sr2IrO4 leads
to the formation of Jeff=1/2 isospins with unprecedented dynamics. In Raman
scattering a continuum attributed to double spin scattering is observed. With
higher excitation energy of the incident Laser this signal crosses over to an
incoherent background. The characteristic energy scale of this cross over is
identical to that of intensity resonance effects in phonon scattering. It is
related to exciton-like orbital excitations that are also evident in resonant
X-Ray scattering. The crossover and evolution of incoherent excitations are
proposed to be due to their coupling to spin excitations. This signals a
spin-orbit induced entanglement of spin, lattice and charge degrees of freedoms
in Sr2IrO4.",1201.3841v1
2017-12-20,Understanding the mechanism stabilizing intermediate spin states in Fe(II)-Porphyrin,"Spin fluctuations in Fe(II)-porphyrins are at the heart of heme-proteins
functionality. Despite significant progress in porphyrin chemistry, the
mechanisms that rule spin state stabilisation remain elusive. Here, it is
demonstrated by using multiconfigurational quantum chemical approaches,
including the novel Stochastic-CASSCF method, that electron delocalization
between the metal centre and the pi system of the macrocycle differentially
stabilises the triplet spin states over the quintet. This delocalisation takes
place via charge-transfer excitations, involving the out-of-plane iron d
orbitals, key linking orbitals between metal and macrocycle. Through a
correlated breathing mechanism, the 3d electrons can make transitions towards
the pi orbitals of the macrocycle. This guarantees a strong coupling between
the on-site radial correlation on the metal and electron delocalization.
Opposite-spin 3d electrons of the triplet can effectively reduce electron
repulsion in this manner. Constraining the out-of-plane orbitals from breathing
hinders delocalization and reverses the spin ordering. Our results find a
qualitative analogue in Kekul\'e resonance structures involving also the metal
centre.",1712.07710v1
2019-09-30,Highly frustrated magnetism in relativistic $\boldsymbol{d}^\mathbf{4}$ Mott insulators: Bosonic analog of Kitaev honeycomb model,"We study the orbitally frustrated singlet-triplet models that emerge in the
context of spin-orbit coupled Mott insulators with $t_{2g}^4$ electronic
configuration. In these compounds, low-energy magnetic degrees of freedom can
be cast in terms of three-flavor ""triplon"" operators describing the transitions
between spin-orbit entangled $J=0$ ionic ground state and excited $J=1$ levels.
In contrast to a conventional, flavor-isotropic O(3) singlet-triplet models,
spin-orbit entangled triplon interactions are flavor-and-bond selective and
thus highly frustrated. In a honeycomb lattice, we find close analogies with
the Kitaev spin model -- an infinite number of conserved quantities, no
magnetic condensation, and spin correlations being strictly short-ranged.
However, due to the bosonic nature of triplons, there are no emergent gapless
excitations within the spin gap, and ground state is a strongly correlated
paramagnet of dense triplon pairs with no long-range entanglement. Using exact
diagonalization, we study the bosonic Kitaev model and its various extensions,
which break exact symmetries of the model and allow magnetic condensation of
triplons. Possible implications for magnetism of ruthenium oxides are
discussed.",1910.00074v2
2020-03-24,Spinning test particle in four-dimensional Einstein-Gauss-Bonnet Black Hole,"In this paper, we investigate the motion of a classical spinning test
particle orbiting around a static spherically symmetric black hole in a novel
four-dimensional Einstein-Gauss-Bonnet gravity [D. Glavan and C. Lin, Phys.
Rev. Lett. 124, 081301 (2020)]. We find that the effective potential of a
spinning test particle in the background of the black hole has two minima when
the Gauss-Bonnet coupling parameter $\alpha$ is nearly in a special range
$-6.1<\alpha/M^2<-2$ ($M$ is the mass of the black hole), which means such
particle can be in two separate orbits with the same spin angular momentum and
orbital angular momentum. We also investigate the innermost stable circular
orbits of the spinning test particle and find that the effect of the particle
spin on the the innermost stable circular is similar to the case of the
four-dimensional black hole in general relativity.",2003.10960v3
2021-06-30,Magnetoelectric effects in superconductors due to spin-orbit scattering: a non-linear $σ$-model description,"We suggest a generalization of nonlinear $\sigma$-model for diffusive
superconducting systems to account for magnetoelectric effects due to
spin-orbit scattering. In the leading orders of spin-orbit strength and
gradient expansion it includes two additional terms responsible for the
spin-Hall effect and the spin-current swapping. First, assuming a
delta-correlated disorder we derive the new terms from the Keldysh path
integral representation of the generating functional. Then we argue
phenomenologically that they exhaust all invariants allowed in the effective
action to the leading order in the spin-orbit coupling (SOC). Finally, the
results are confirmed by a direct derivation of the saddle-point (Usadel)
equation from the quantum kinetic equations in the presence of randomly
distributed impurities with SOC. At this point we correct a recent derivation
of the Usadel equation that includes magneto-electric effects and does not
resort to the Born approximation.",2106.15859v1
2023-10-25,Spin-eccentricity interplay in merging binary black holes,"Orbital eccentricity and spin precession are precious observables to infer
the formation history of binary black holes with gravitational-wave data. We
present a post-Newtonian, multi-timescale analysis of the binary dynamics able
to capture both precession and eccentricity over long inspirals. We show that
the evolution of an eccentric binary can be reduced that of effective source on
quasi-circular orbits, coupled to a post-Newtonian prescription for the secular
evolution of the eccentricity. Our findings unveil an interplay between
precession and eccentricity: the spins of eccentric binaries precess on shorter
timescales and their nutation amplitude is altered compared to black holes on
quasi-circular orbits, consequently affecting the so-called spin morphology.
Even if binaries circularize by the time they enter the sensitivity window of
our detectors, their spin orientations retain some memory of the past evolution
on eccentric orbits, thus providing a new link between gravitational-wave
detection and astrophysical formation. At the same time, we point out that
residual eccentricity should be considered a source of systematics when
reconstructing the past history of black-hole binaries using the spin
orientations.",2310.16893v2
2024-03-31,Chiral Spin Textures Driven by Emergent Spin-Orbit Interaction: A Numerical Study,"We explore numerically the intricate interplay between Berry phases in both
real and momentum spaces within itinerant magnets. This interplay manifests as
an emergent spin-orbit coupling, where charge carriers occupying a Berry-curved
band generate an orbital magnetization, inducing a pseudo-magnetic field
originating in chiral spin textures. Using density-matrix-renormalization-group
techniques, we demonstrate that switching on a band Berry curvature in a
metallic ferromagnetic phase results in chiral magnetic textures. Furthermore,
employing a two-leg strip geometry, we establish a connection between charge
and spin chirality, further supporting this emergent spin-orbit interaction.",2404.00706v3
2011-09-26,Engineering Dresselhaus spin-orbit coupling for cold atoms in a double tripod configuration,"We study laser induced spin-orbit (SO) coupling in cold atom systems where
lasers couple three internal states to a pair of excited states, in a double
tripod topology. Proper choice of laser amplitudes and phases produces a
Hamiltonian with a doubly degenerate ground state separated from the remaining
""excited"" eigenstates by gaps determined by the Rabi frequencies of the
atom-light coupling. After eliminating the excited states with a Born-
Oppenheimer approximation, the Hamiltonian of the remaining two states includes
Dresselhaus (or equivalently Rashba) SO coupling. Unlike earlier proposals,
here the SO coupled states are the two lowest energy ""dressed"" spin states and
are thus immune to collisional relaxation. Finally, we discuss a specific
implementation of our system using Raman transitions between different
hyperfine states within the electronic ground state manifold of nuclear spin I
= 3/2 alkali atoms.",1109.5481v1
2022-03-21,Molecular state in a spin-orbital-angular-momentum coupled Fermi gas,"We study the two-body bound states in a spin-orbital-angular-momentum (SOAM)
coupled quantum gas of fermions. Two different configurations are considered:
an attractive $s$-wave interaction exists between two spin species that are
SOAM coupled; and an atom with SOAM coupled internal spins interacts
state-selectively with another atom. For both cases, we identify the condition
for the emergence of molecular states with finite total angular momenta.These
molecular states with quantized total angular momenta correspond to the
SOAM-coupling-induced vortices in the corresponding Fermi superfluid. We
propose to detect the molecules through Raman spectroscopy with
Laguerre-Gaussian lasers. As the molecular states can form above the superfluid
temperature, they offer an experimentally more accessible route toward the
study of the underlying pairing mechanism under SOAM coupling.",2203.10834v1
2022-10-17,Supersolid-like solitons in two-dimensional nonmagnetic spin-orbit coupled spin-1 and spin-2 condensates,"We demonstrate spontaneous generation of spatially-periodic supersolid-like
super-lattice and stripe solitons in Rashba spin-orbit (SO) coupled spin-1 and
spin-2 quasi-two-dimensional nonmagnetic Bose-Einstein condensates (BECs). The
solitons in a weakly SO-coupled spin-1 BEC are circularly-symmetric of $(-1, 0,
+1)$ and $(0, +1, +2)$ types and have inherent vorticity; the numbers in the
parentheses are the winding numbers in hyper-spin components $+1, 0, -1$,
respectively. The circularly-symmetric solitons in an SO-coupled spin-2 BEC are
of types $(-2, -1, 0, +1, +2)$ and $(-1, 0, +1, +2, +3)$ with the former being
the ground state, where the winding numbers correspond to spin components $+2,
+1, 0, -1, -2$, respectively. For stronger SO-coupling strengths, these
solitons acquire a multiring structure while preserving the winding numbers.
Quasi-degenerate stripe and super-lattice solitons, besides a
circularly-asymmetric soliton, also emerge as excited stationary states for
stronger SO-coupling strengths in spin-1 and spin-2 BECs. pla-cl.tex",2210.08947v1
2017-10-31,Kitaev-Heisenberg Hamiltonian for High-Spin $d^7$ Mott Insulators,"In the search for quantum spin liquids, candidate materials for the Kitaev
model and its extensions have been intensively explored during the past decade,
as the models realize the exact quantum spin liquids in the ground state. Thus
far, insulating magnets in the low-spin $d^5$ electron configuration under the
strong spin-orbit coupling have been studied for realizing the Kitaev-type
bond-dependent anisotropic interactions between the spin-orbital entangled
Kramers doublets. To extend the candidates, here we investigate the systems in
a high-spin $d^7$ electron configuration, whose ground state is described by
the spin-orbital entangled Kramers doublet. By the second- order perturbation
in terms of the $t_{2g}$-$t_{2g}$ and $t_{2g}$-$e_g$ hoppings, we show that the
effective spin model possesses the anisotropic Kitaev interactions as well as
the isotropic Heisenberg ones. While the Kitaev interaction is always
ferromagnetic, the Heisenberg interaction can become either ferromagnetic or
antiferromagnetic depending on the Coulomb interactions and the crystalline
electric fields. We also derive the effective model for the low-spin $d^5$
electron configuration within the same perturbation scheme, in which the Kitaev
interaction becomes both ferromagnetic and antiferromagnetic, while the
Heisenberg one always ferromagnetic. Referring to the previous study for the
Kitaev-Heisenberg model, we find that the quantum spin liquid phase exists in
the reasonable parameter region in both $d^7$ and $d^5$ cases, while the former
has a richer structure of the phase diagram. We discuss the advantages of the
$d^7$ case in comparison with the $d^5$ case. Our results indicate that the
high-spin $d^7$ state provides another platform for the Kitaev-type quantum
spin liquid.",1710.11357v2
2017-08-29,The translational side of topological band insulators,"Spin-orbit coupled materials have attracted revived prominent research
interest as of late, especially due their direct connection with topological
notions. Arguably, a hallmark of this pursuit is formed by the concept of the
topological band insulator (TBI). In these incompressible systems band
inversions, often driven by strong spin-orbit coupling, result in a state that
is topologically distinct from the usual insulator as long as time reversal
symmetry is maintained. More generally, topological states that arise by virtue
of a protecting symmetry have resulted in a flourishing research field on both
the experimental as well as theoretical side of the condensed matter agenda. As
a prime signature topological band insulators can exhibit protected spin
filtered edge states, whose time reversal invariant partner is spatially
separated on the other edge. While these edge states have resultantly been
identified with many exotic physical phenomena, we here wish to provide a
perspective on the equally rich, although far less explored, aspects of the
bulk. That is, we will focus on the role of lattice defects, dislocations in
particular, and their relation with the topological nature of the bulk.",1708.08886v1
2017-04-03,Fulde-Ferrell-Larkin-Ovchinnikov state in spin-orbit-coupled superconductors,"We show that in the presence of magnetic field, two superconducting phases
with the center-of-mass momentum of Cooper pair parallel to the magnetic field
are induced in spin-orbit-coupled superconductor Li$_2$Pd$_3$B. Specifically,
at small magnetic field, the center-of-mass momentum is induced due to the
energy-spectrum distortion and no unpairing region with vanishing singlet
correlation appears. We refer to this superconducting state as the drift-BCS
state. By further increasing the magnetic field, the superconducting state
falls into the Fulde-Ferrell-Larkin-Ovchinnikov state with the emergence of the
unpairing regions. The observed abrupt enhancement of the center-of-mass
momenta and suppression on the order parameters during the crossover indicate
the first-order phase transition. Enhanced Pauli limit and hence enlarged
magnetic-field regime of the Fulde-Ferrell-Larkin-Ovchinnikov state, due to the
spin-flip terms of the spin-orbit coupling, are revealed. We also address the
triplet correlations induced by the spin-orbit coupling, and show that the
Cooper-pair spin polarizations, generated by the magnetic field and
center-of-mass momentum with the triplet correlations, exhibit totally
different magnetic-field dependences between the drift-BCS and
Fulde-Ferrell-Larkin-Ovchinnikov states.",1704.00409v1
2022-11-03,Spin-orbit and exchange proximity couplings in graphene/1T-TaS$_2$ heterostructure triggered by a charge density wave,"Proximity-induced fine features and spin-textures of the electronic bands in
graphene-based van der Waals heterostructures can be explored from the point of
tailoring a twist angle. Here we study spin-orbit coupling and exchange
coupling engineering of graphene states in the proximity of 1T-TaS$_2$ not
triggering the twist, but a charge density wave in 1T-TaS$_2$-a realistic
low-temperature phase. Using density functional theory and effective model we
found that the emergence of the charge density wave in 1T-TaS$_2$ significantly
enhances Rashba spin-orbit splitting in graphene and tilts the spin texture by
a significant Rashba angle-in a very similar way as in the conventional
twist-angle scenarios. Moreover, the partially filled Ta $d$-band in the charge
density wave phase leads to the spontaneous emergence of the in-plane magnetic
order that transgresses via proximity from 1T-TaS$_2$ to graphene, hence,
simultaneously superimposing along the spin-orbit also the exchange coupling
proximity effect. To describe this intricate proximity landscape we have
developed an effective model Hamiltonian and provided a minimal set of
parameters that excellently reproduces all the spectral features predicted by
the first-principles calculations. Conceptually, the charge density wave
provides a highly interesting knob to control the fine features of electronic
states and to tailor the superimposed proximity effects-a sort of twistronics
without twist.",2211.02153v2
2019-05-20,Orbitally Dominated Rashba-Edelstein Effect in Noncentrosymmetric Antiferromagnets,"Efficient manipulation of magnetic order with electric current pulses is
desirable for achieving fast spintronic devices. The Rashba-Edelstein effect,
wherein a spin polarization is electrically induced in noncentrosymmetric
systems, provides a mean to achieve current-induced staggered spin-orbit
torques. Initially predicted for spin, the orbital counterpart of this effect
has been disregarded up to now. Here, we present a generalized Rashba-Edelstein
effect, which generates not only spin polarization but also orbital
polarization, which we find to be far from being negligible and could play a
crucial role in the magnetization dynamics. We show that the orbital
Rashba-Edelstein effect does not require spin-orbit coupling to exist. We
present first-principles calculations of the frequency-dependent spin and
orbital Rashba-Edelstein susceptibility tensors for the noncentrosymmetric
antiferromagnets CuMnAs and Mn2Au. We show that the electrically induced local
magnetization has both staggered in-plane components and non-staggered
out-of-plane components, and can exhibit Rashba-like or Dresselhaus-like
symmetries, depending on the magnetic configuration. Furthermore, there is an
induced local magnetization on the nonmagnetic atoms as well, that is smaller
in Mn2Au than in CuMnAs. We compute sizable induced magnetizations at optical
frequencies, which suggest that electric-field driven switching could be
achieved at much higher frequencies.",1905.08279v1
2017-05-12,Orbital-selective Mott phase in multiorbital models for iron pnictides and chalcogenides,"There is increasing recognition that the multiorbital nature of the 3d
electrons is important to the proper description of the electronic states in
the normal state of the iron-based superconductors. Earlier studies of the
pertinent multiorbital Hubbard models identified an orbital-selective Mott
phase, which anchors the orbital-selective behavior seen in the overall phase
diagram. An important characteristics of the models is that the orbitals are
kinetically coupled -- i.e. hybridized -- to each other, which makes the
orbital-selective Mott phase especially nontrivial. A U(1) slave-spin method
was used to analyze the model with nonzero orbital-level splittings. Here we
develop a Landau free-energy functional to shed further light on this issue. We
put the microscopic analysis from the U(1) slave-spin approach in this
perspective, and show that the intersite spin correlations are crucial to the
renormalization of the bare hybridization amplitude towards zero and the
concomitant realization of the orbital-selective Mott transition. Based on this
insight, we discuss additional ways to study the orbital-selective Mott physics
from a dynamical competition between the interorbital hybridization and
collective spin correlations. Our results demonstrate the robustness of the
orbital-selective Mott phase in the multiorbital models appropriate for the
iron-based superconductors.",1705.04541v1
2013-04-11,Intrinsic Spin Hall Effect at Oxide Interfaces: a Simple Model,"An asymmetric triangular potential well provides the simplest model for the
confinement of mobile electrons at the interface between two insulating oxides,
such as LaAlO_3 and SrTiO_3 (LAO/STO). These electrons have been recently shown
to exhibit a large spin-orbit coupling of the Rashba type, i.e., linear in the
in-plane momentum. In this paper we study the intrinsic spin Hall effect due to
Rashba coupling in an asymmetric triangular potential well. Besides splitting
each subband into two branches of opposite helicity, the spin-orbit interaction
causes the wave function in the direction perpendicular to the plane of the
quantum well (the z direction) to depend on the in-plane wave vector k. In
contrast to the extreme asymmetric case, i.e., the wedge-shaped quantum well,
for which the intrinsic spin Hall effect vanishes due to vertex corrections, we
find that the asymmetric well supports a non-vanishing intrinsic spin Hall
conductivity, which increases in magnitude as the well becomes more symmetric.
The spin Hall conductivity is found to be proportional to the square of the
spin-orbit coupling constant and, in the limit of low carrier density, depends
only on the effective mass renormalization associated with the k-dependence of
the wave functions in the z direction. Its origin lies in the non-vanishing
matrix elements of the spin current between subbands corresponding to different
states of quantized motion perpendicular to the plane of the well.",1304.3476v2
2014-11-11,Magnonic Charge Pumping via Spin-Orbit Coupling,"The interplay between spin, charge, and orbital degrees of freedom has led to
the development of spintronic devices like spin-torque oscillators, spin-logic
devices, and spin-transfer torque magnetic random-access memories. In this
development spin pumping, the process where pure spin-currents are generated
from magnetisation precession, has proved to be a powerful method for probing
spin physics and magnetisation dynamics. The effect originates from direct
conversion of low energy quantised spin-waves in the magnet, known as magnons,
into a flow of spins from the precessing magnet to adjacent normal metal leads.
The spin-pumping phenomenon represents a convenient way to electrically detect
magnetisation dynamics, however, precessing magnets have been limited so far to
pump pure spin currents, which require a secondary spin-charge conversion
element such as heavy metals with large spin Hall angle or multi-layer layouts
to be detectable. Here, we report the experimental observation of charge
pumping in which a precessing ferromagnet pumps a charge current, demonstrating
direct conversion of magnons into high-frequency currents via the relativistic
spin-orbit interaction. The generated electric current, differently from spin
currents generated by spin-pumping, can be directly detected without the need
of any additional spin to charge conversion mechanism and amplitude and phase
information about the relativistic current-driven magnetisation dynamics. The
charge-pumping phenomenon is generic and gives a deeper understanding of the
recently observed spin-orbit torques, of which it is the reciprocal effect and
which currently attract interest for their potential in manipulating magnetic
information. Furthermore, charge pumping provides a novel link between
magnetism and electricity and may find application in sourcing alternating
electric currents.",1411.2779v1
2004-01-29,Rashba spin-orbit coupling and spin relaxation in silicon quantum wells,"Silicon is a leading candidate material for spin-based devices, and
two-dimensional electron gases (2DEGs) formed in silicon heterostructures have
been proposed for both spin transport and quantum dot quantum computing
applications. The key parameter for these applications is the spin relaxation
time. Here we apply the theory of D'yakonov and Perel' (DP) to calculate the
electron spin resonance linewidth of a silicon 2DEG due to structural inversion
asymmetry for arbitrary static magnetic field direction at low temperatures. We
estimate the Rashba spin-orbit coupling coefficient in silicon quantum wells
and find the $T_{1}$ and $T_{2}$ times of the spins from this mechanism as a
function of momentum scattering time, magnetic field, and device-specific
parameters. We obtain agreement with existing data for the angular dependence
of the relaxation times and show that the magnitudes are consistent with the DP
mechanism. We suggest how to increase the relaxation times by appropriate
device design.",0401615v2
2006-10-04,Mesoscopic Spin Hall Effect,"We investigate the spin Hall effect in ballistic chaotic quantum dots with
spin-orbit coupling. We show that a longitudinal charge current can generate a
pure transverse spin current. While this transverse spin current is generically
nonzero for a fixed sample, we show that when the spin-orbit coupling time is
large compared to the mean dwell time inside the dot, it fluctuates universally
from sample to sample or upon variation of the chemical potential with a
vanishing average. For a fixed sample configuration, the transverse spin
current has a finite typical value ~e^2 V/h, proportional to the longitudinal
bias V on the sample, and corresponding to about one excess open channel for
one of the two spin species. Our analytical results are in agreement with
numerical results in a diffusive system [W. Ren et al., Phys. Rev. Lett. 97,
066603 (2006)] and are further confirmed by numerical simulation in a chaotic
cavity.",0610109v1
2008-05-28,Electric field-induced spin textures in a superlattice with Rashba and Dresselhaus spin-orbit coupling,"The DC charge current, field-induced spin polarization and spin textures are
studied in the 1D gated superlattice with both fixed and varying Rashba and
Dresselhaus contributions to spin-orbit coupling. It is found that a spin
component with zero mean value can demonstrate non-vanishing field-induced spin
texture in a superlattice cell which can be probed experimentally, with the
highest amplitudes achievable in an interval of comparable Rashba and
Dresselhaus terms. The consideration of the finite parameters for collision
rate and temperature is found to be non-destructive for the calculated current
and spin characteristics depending on all states below the Fermi level.",0805.4284v3
2009-05-26,Infinite spin diffusion length of any spin polarization along direction perpendicular to effective magnetic field from Dresselhaus and Rashba spin-orbit couplings with identical strengths in (001) GaAs quantum wells,"In this note, we show that the latest spin grating measurement of spin helix
by Koralek {\em et al.} [Nature {\bf 458}, 610 (2009)] provides strong evidence
of the infinite spin diffusion length of any spin polarization along the
direction perpendicular to the effective magnetic field from the
  Dresselhaus and Rashba spin-orbit couplings with identical strengths in
$(001)$ GaAs quantum wells, predicted by Cheng {\em et al.} [Phys. Rev. B {\bf
75}, 205328 (2007)].",0905.4207v2
2009-11-18,Strong electron spin-Hall effect by a coherent optical potential,"We demonstrate theoretically that a coherent manipulation of electron spins
in low-dimensional semiconductor structures with spin-orbit coupling by
infrared radiation is possible. The proposed approach is based on using a
dipole force acting on a two-level system in a nonuniform optical field,
similar to that employed in the design of the cold atoms diode. For ballistic
electrons the spin-dependent force, proportional to the intensity of external
radiation, leads to a spin-Hall effect and resulting spin separation even if
the spin-orbit coupling itself does not allow for these effects. Achievable
spatial separation of electrons with opposite spins can be of the order of
several tenth of a micron, an order of magnitude larger than can be produced by
the charged impurity scattering in the diffusive regime.",0911.3577v2
2010-03-10,Effective time-reversal symmetry breaking in the spin relaxation in a graphene quantum dot,"We study the relaxation of a single electron spin in a circular gate-tunbable
quantum dot in gapped graphene. Direct coupling of the electron spin to
out-of-plane phonons via the intrinsic spin-orbit coupling leads to a
relaxation time T_1 which is independent of the B-field at low fields. We also
find that Rashba spin-orbit induced admixture of opposite spin states in
combination with the emission of in-plane phonons provides various further
relaxation channels via deformation potential and bond-length change. In the
absence of valley mixing, spin relaxation takes place within each valley
separately and thus time-reversal symmetry is effectively broken, thus
inhibiting the van Vleck cancellation at B=0 known from GaAs quantum dots. Both
the absence of the van Vleck cancellation as well as the out-of-plane phonons
lead to a behavior of the spin relaxation rate at low magnetic fields which is
markedly different from the known results for GaAs. For low B-fields, we find
that the rate is constant in B and then crosses over to ~B^2 or ~B^4 at higher
fields.",1003.2088v1
2010-10-27,Coupling molecular spin states by photon-assisted tunneling,"Artificial molecules containing just one or two electrons provide a powerful
platform for studies of orbital and spin quantum dynamics in nanoscale devices.
A well-known example of these dynamics is tunneling of electrons between two
coupled quantum dots triggered by microwave irradiation. So far, these
tunneling processes have been treated as electric dipole-allowed
spin-conserving events. Here we report that microwaves can also excite
tunneling transitions between states with different spin. In this work, the
dominant mechanism responsible for violation of spin conservation is the
spin-orbit interaction. These transitions make it possible to perform detailed
microwave spectroscopy of the molecular spin states of an artificial hydrogen
molecule and open up the possibility of realizing full quantum control of a two
spin system via microwave excitation.",1010.5682v1
2011-08-09,Selective probing of photo-induced charge and spin dynamics in the bulk and surface of a topological insulator,"Topological insulators possess completely different spin-orbit coupled bulk
and surface electronic spectra that are each predicted to exhibit exotic
responses to light. Here we report time-resolved fundamental and second
harmonic optical pump-probe measurements on the topological insulator Bi2Se3 to
independently measure its photo-induced charge and spin dynamics with bulk and
surface selectivity. Our results show that a transient net spin density can be
optically induced in both the bulk and surface, which may drive spin transport
in topological insulators. By utilizing a novel rotational anisotropy analysis
we are able to separately resolve the spin de-polarization, intraband cooling
and interband recombination processes following photo-excitation, which reveal
that spin and charge degrees of freedom relax on very different time scales
owing to strong spin-orbit coupling.",1108.1848v1
2011-10-24,Readout of carbon nanotube vibrations based on spin-phonon coupling,"We propose a scheme for spin-based detection of the bending motion in
suspended carbon-nanotubes, using the curvature-induced spin-orbit interaction.
We show that the resulting effective spin-phonon coupling can be used to
down-convert the high-frequency vibration-modulated spin-orbit field to
spin-flip processes at a much lower frequency. This vibration-induced
spin-resonance can be controlled with an axial magnetic field. We propose a
Pauli spin blockade readout scheme and predict that the leakage current shows
pronounced peaks as a function of the external magnetic field. Whereas the
resonant peaks allow for frequency readout, the slightly off-resonant current
is sensitive to the vibration amplitude.",1110.5165v1
2012-11-05,A unified theory of spin-relaxation due to spin-orbit coupling in metals and semiconductors,"Spintronics is an emerging paradigm with the aim to replace conventional
electronics by using electron spins as information carriers. Its utility relies
on the magnitude of the spin-relaxation, which is dominated by spin- orbit
coupling (SOC). Yet, SOC induced spin-relaxation in metals and semiconductors
is discussed for the seemingly orthogonal cases when inversion symmetry is
retained or broken by the so-called Elliott-Yafet and Dyakonov-Perel
spin-relaxation mechanisms, respectively. We unify the two theories on general
grounds for a generic two-band system containing intra- and inter-band SOC.
While the previously known limiting cases are recovered, we also identify
parameter domains when a crossover occurs between them, i.e. when an inversion
symmetry broken state evolves from a Dyakonov-Perel to an Elliott-Yafet type of
spin-relaxation and conversely for a state with inversional symmetry. This
provides an ultimate link between the two mechanisms of spin-relaxation.",1211.0826v2
2014-02-17,Effects of Rashba spin-orbit coupling and a magnetic field on a polygonal quantum ring,"Using standard quantum network method, we analytically investigate the effect
of Rashba spin-orbit coupling (RSOC) and a magnetic field on the spin transport
properties of a polygonal quantum ring. Using Landauer-Buttiker formula, we
have found that the polarization direction and phase of transmitted electrons
can be controlled by both the magnetic field and RSOC. A device to generate a
spin-polarized conductance in a polygon with an arbitrary number of sides is
discussed. This device would permit precise control of spin and selectively
provide spin filtering for either spin up or spin down simply by interchanging
the source and drain.",1402.3868v1
2014-11-03,Experimental Demonstration of the Co-existence of the Spin Hall and Rashba Effects in beta-Tantalum/Ferromagnet Bilayers,"We have measured the spin torques of beta-Tantalum / Co20Fe60B20 bilayers
versus Ta thickness at room temperature using an FMR technique. The spin Hall
coefficient was calculated both from the observed change in damping coefficient
of the ferromagnet with Ta thickness, and from the ratio of the symmetric and
anti-symmetric components of the FMR signal. Results from these two methods
yielded values for the spin Hall coefficient of -0.090+/-0.005 and
-0.11+/-0.01, respectively. We have also identified a significant out-of-plane
spin torque originating from Ta, which is constant with Ta thickness. We
ascribe this to an interface spin orbit coupling, or Rashba effect, due to the
strength and constancy of the torque with Ta thickness. From fitting measured
data to a model including interface spin orbit coupling, we have determined the
spin diffusion length for beta-Tantalum to be ~2.5 nm.",1411.0601v1
2015-03-18,Signatures of pairing and spin-orbit coupling in correlation functions of Fermi gases,"We derive expressions for spin and density correlation functions in the
(greatly enhanced) pseudogap phase of spin-orbit coupled Fermi superfluids.
Density-density correlation functions are found to be relatively insensitive to
the presence of these Rashba effects. To arrive at spin-spin correlation
functions we derive new $f$-sum rules, valid even in the absence of a spin
conservation law. Our spin-spin correlation functions are shown to be fully
consistent with these $f$-sum rules. Importantly, they provide a clear
signature of the Rashba band-structure and separately help to establish the
presence of a pseudogap.",1503.05454v1
2015-04-06,Incomplete Protection of the Surface Weyl Cones of the Kondo Insulator SmB$_6$: Spin Exciton Scattering,"The compound SmB$_6$ is a Kondo Insulator, where the lowest-energy bulk
electronic excitations are spin excitons. It also has surface states that are
subjected to strong spin-orbit coupling. It has been suggested that SmB$_6$ is
also a topological insulator. Here we show that, despite the absence of
time-reversal symmetry breaking and the presence of strong spin-orbit coupling,
the chiral spin texture of the Weyl cone is not completely protected. In
particular, we show that the spin-exciton mediated scattering produces features
in the surface electronic spectrum at energies separated from the surface Fermi
energy by the spin-exciton energy. Despite the features being far removed from
the surface Fermi energy, they are extremely temperature dependent. The
temperature variation occurs over a characteristic scale determined by the
dispersion of the spin exciton. The structures may be observed by electron
spectroscopy at low temperatures.",1504.01179v1
2015-11-14,Dynamics of spin-orbit coupled Bose-Einstein condensates in a random potential,"Disorder plays a crucial role in spin dynamics in solids and condensed matter
systems. We demonstrate that for a spin-orbit coupled Bose-Einstein condensate
in a random potential two mechanisms of spin evolution, that can be
characterized as ""precessional"" and ""anomalous"", are at work simultaneously.
The precessional mechanism, typical for solids, is due to the condensate
displacement. The unconventional ""anomalous"" mechanism is due to the
spin-dependent velocity producing the distribution of the condensate spin
polarization. The condensate expansion is accompanied by a random displacement
and fragmentation, where it becomes sparse, as clearly revealed in the spin
dynamics. Thus, different stages of the evolution can be characterized by
looking at the condensate spin.",1511.04588v1
2015-11-24,Inverse Spin Hall Effect from pulsed Spin Current in Organic Semiconductors with Tunable Spin-Orbit Coupling,"Exploration of spin-currents in organic semiconductors (OSECs) induced by
resonant microwave absorption in ferromagnetic substrates has been of great
interest for potential spintronics applications. Due to the inherently weak
spin-orbit coupling (SOC) of OSECs, their inverse spin Hall effect (ISHE)
response is very subtle; limited by the microwave power applicable under
continuous-wave (cw) excitation. Here we introduce a novel approach for
generating significant ISHE signals using pulsed ferromagnetic resonance, where
the ISHE is ~2-3 orders of magnitude larger compared to cw excitation. This
strong ISHE enables us to investigate a variety of OSECs ranging from
pi-conjugated polymers with strong SOC that contain intrachain platinum atoms,
to weak SOC polymers, to C60 films, where the SOC is predominantly caused by
the molecule surface curvature. The pulsed-ISHE technique offers a robust route
for efficient injection and detection schemes of spin-currents at room
temperature, and paves the way for spin-orbitronics in plastic materials.",1511.07848v1
2016-03-10,Spin Hall Effect in a Spinor Dipolar Bose-Einstein Condensate,"We theoretically show that the spin Hall effect arises in a Bose-Einstein
condensate (BEC) of neutral atoms interacting via the magnetic dipole-dipole
interactions (MDDIs). Since the MDDI couples the total spin angular momentum
and the relative orbital angular momentum of two colliding atoms, it works as a
spin-orbit coupling. Thus, when we prepare a BEC in a magnetic sublevel $m=0$,
thermally and quantum-mechanically excited atoms in the $m=1$ and $-1$ states
feel the Lorentz-like foces in the opposite directions. This is the origin for
the emergence of the the spin Hall effect. We define the mass-current and
spin-current operators from the equations of continuity and calculate the spin
Hall conductivity from the off-diagonal current-current correlation function
within the Bogoliubov approximation. We find that the correction of the current
operators due to the MDDI significantly contributes to the spin Hall
conductivity. Possible experimental situation is also discussed.",1603.03202v1
2018-01-17,Spin-Orbit Coupling and Topological States in $F=\frac{3}{2}$ Cold Fermi Gas,"In this work we study the possible occurrence of topological insulators for
2D fermions of high spin. They can be realized in cold fermion systems with
ground-state atomic spin $F>\tfrac{1}{2}$, if the optical potential is properly
designed, and spin-orbit coupling is relevant. The latter is shown to be
induced by letting the fermions interact with a specially tuned arrangement of
polarized laser beams. When the system is subject to a perpendicular magnetic
field, time reversal symmetry is broken but the ensuing Hamiltonian is still
endowed with a mirror symmetry.
  Topological insulators for fermions of higher spins are fundamentally
distinct from those pertaining to spin $\frac{1}{2}$. The underlying physics
reveals a plethora of positive and negative mirror Chern numbers, respectively
corresponding to chiral and anti-chiral edge states. Here, for simplicity, we
concentrate on the case $F=\tfrac{3}{2}$ (which is suitable for $^{6}$Li or
$^2$H atoms) but extension to higher spins (such as $^{40}$K whose ground-state
spin is $F=\tfrac{9}{2}$), is straightforward.",1801.05646v4
2019-06-06,Charge noise induced spin dephasing in a nanowire double quantum dot with spin-orbit coupling,"Unexpected fluctuating charge field near a semiconductor quantum dot has
severely limited the coherence time of the localized spin qubit. It is the
interplay between the spin-orbit coupling and the asymmetrical confining
potential in a quantum dot, that mediates the longitudinal interaction between
the spin qubit and the fluctuating charge field. Here, we study the $1/f$
charge noise induced spin dephasing in a nanowire double quantum dot via
exactly solving its eigen-energies and eigenfunctions. Our calculations
demonstrate that the spin dephasing has a nonmonotonic dependence on the
asymmetry of the double quantum dot confining potential. With the increase of
the potential asymmetry, the dephasing rate first becomes stronger very sharply
before reaching to a maximum, after that it becomes weaker softly. Also, we
find that the applied external magnetic field contributes to the spin
dephasing, the dephasing rate is strongest at the anti-crossing point $B_{0}$
in the double quantum dot.",1906.02378v3
2019-07-02,Non-linear spin filter for non-magnetic materials at zero magnetic field,"The ability to convert spin accumulation to charge currents is essential for
applications in spintronics. In semiconductors, spin-to-charge conversion is
typically achieved using the inverse spin Hall effect or using a large magnetic
field. Here we demonstrate a general method that exploits the non-linear
interactions between spin and charge currents to perform all-electrical, rapid
and non-invasive detection of spin accumulation without the need for a magnetic
field. We demonstrate the operation of this technique with ballistic GaAs holes
as a model system with strong spin-orbit coupling, in which a quantum point
contact provides the non-linear energy filter. This approach is generally
applicable to electron and hole systems with strong spin orbit coupling.",1907.01312v3
2012-05-09,Full electrostatic control over polarized currents through spin-orbital Kondo effect,"Numerical calculations indicate that by suitably controlling the individual
gate voltages of a capacitively coupled parallel double quantum dot, with each
quantum dot coupled to one of two independent non-magnetic channels, this
system can be set into a spin-orbital Kondo state by applying a magnetic field.
This Kondo regime, closely related to the SU(4) Kondo, flips spin from one to
zero through cotunneling processes that generate almost totally spin-polarized
currents with opposite spin orientation along the two channels. Moreover, by
appropriately changing the gate voltages of both quantum dots, one can
simultaneously flip the spin polarization of the currents in each channel. As a
similar zero magnetic field Kondo effect has been recently observed by Y.
Okazaki {\it et al.} [Phys. Rev. B {\bf 84}, (R)161305 (2011)], we analyze a
range of magnetic field values where this polarization effect seems robust,
suggesting that the setup may be used as an efficient bipolar spin filter,
which can generate electrostatically reversible spatially separated spin
currents with opposite polarizations.",1205.2115v1
2019-01-23,Correspondence between bulk equilibrium spin-currents and edge spin accumulation in wires with spin-orbit coupling,"We demonstrate that the interplay of Zeeman and spin-orbit coupling fields in
a 1D wire leads to an equilibrium spin current that manifests itself in a spin
accumulation at the wire ends with a polarization perpendicular to both fields.
This is a universal property that occurs in the normal and superconducting
state independently of the degree of disorder. We find that the edge spin
polarization transverse to the Zeeman field is strongly enhanced in the
superconducting state when the Zeeman energy is of the order of the
superconducting gap. By calculating the space resolved magnetization response
of the wire we demonstrate that the transverse component of the spin at the
wire edges can be much larger than the one parallel to the field. This result
generalizes the well established theory of the Knight-shift in superconductors
to the case of finite systems.",1901.07890v1
2020-11-19,Spin Structure and Resonant Driving of Spin-1/2 Defects in SiC,"Transition metal (TM) defects in silicon carbide have favorable spin
coherence properties and are suitable as quantum memory for quantum
communication. To characterize TM defects as quantum spin-photon interfaces, we
model defects that have one active electron with spin 1/2 in the atomic $D$
shell. The spin structure, as well as the magnetic and optical resonance
properties of the active electron emerge from the interplay of the crystal
potential and spin-orbit coupling and are described by a general model derived
using group theory. We find that the spin-orbit coupling leads to additional
allowed transitions and a modification of the $g$-tensor. To describe the
dependence of the Rabi frequency on the magnitude and direction of the static
and driving fields, we derive an effective Hamiltonian. This theoretical
description can also be instrumental to perform and optimize spin control in TM
defects.",2011.09987v1
2021-03-29,Photonic spin lattices: symmetry constraints for skyrmion and meron topologies,"Symmetry governs many electronic and photonic phenomena in optics and
condensed matter physics. Skyrmions and merons are prominent topological
structures in magnetic materials, with the topological features determined by
the interplay between anisotropy of a material and its magnetization. Here we
theoretically show and experimentally demonstrate that the symmetry of the
electromagnetic field determines the spin topological properties of the guided
modes via spin-orbit coupling and may only result in either hexagonal
spin-skyrmion or square spin-meron lattices. We also show that in the absence
of spin-orbit coupling these spin topologies are degenerated in dynamic
field-skyrmions, unifying description of electromagnetic field topologies. The
results provide new understanding of electromagnetic field topology and its
transformations as well as new opportunities for applications in quantum
optics, spin-optics and topological photonics.",2103.15366v1
2021-06-28,The emergent linear Rashba spin-orbit coupling offering the fast manipulation of hole-spin qubits in germanium,"The electric dipole spin resonance (EDSR) combining strong spin-orbit
coupling (SOC) and electric-dipole transitions facilitates fast spin control in
a scalable way, which is the critical aspect of the rapid progress made
recently in germanium (Ge) hole-spin qubits. However, a puzzle is raised
because centrosymmetric Ge lacks the Dresselhaus SOC, a key element in the
initial proposal of the hole-based EDSR. Here, we demonstrate that the recently
uncovered finite k-linear Rashba SOC of 2D holes offers fast hole spin control
via EDSR with Rabi frequencies in excellent agreement with experimental results
over a wide range of driving fields. We also suggest that the Rabi frequency
can reach 500 MHz under a higher gate electric field or multiple GHz in a
replacement by [110]oriented wells. These findings bring a deeper understanding
for hole-spin qubit manipulation and offer design principles to boost the gate
speed.",2106.14684v2
2021-11-05,Relativistic first-order spin hydrodynamics via the Chapman-Enskog expansion,"In this paper, we present a detailed derivation of relativistic first-order
spin hydrodynamics using the Chapman-Enskog method to linearize the nonlocal
collision term for massive fermions proposed in \cite{Weickgenannt:2021cuo},
which well describes spin-orbit coupling in the collision process and is
relevant for the research on local spin polarization. Based on this collisional
term, we provide a formal discussion about first-order spin hydrodynamics and
determine the motion equations of fluid variables and nonequilibrium
corrections to the energy-momentum and spin tensors. The results indicate that
the motion equations show no differences compared to spinless first-order
hydrodynamics and the energy-momentum tensor receives no corrections from spin
as far as first-order theory is concerned, which calls for the construction of
second-order theory of fluids naturally incorporating the effect of spin-orbit
coupling.",2111.03571v2
2023-05-29,Higher-dimensional spin selectivity in chiral crystals,"This study aims to investigate the interplay between chiral-induced
spin-orbit coupling along the screw axis and antisymmetric spin-orbit coupling
(ASOC) in the normal plane within a chiral crystal, using both general model
analysis and first-principles simulations of InSeI, a chiral van der Waals
crystal. While chiral molecules of light atoms typically exhibit spin
selectivity only along the screw axis, chiral crystals with heavier atoms can
have strong ASOC effects that influence spin-momentum locking in all
directions. The resulting phase diagram of spin texture shows the potential for
controlling phase transition and flipping spin by reducing symmetry through
surface cleavage, thickness reduction or strain. We also experimentally
synthesized high-quality InSeI crystals of the thermodynamically stable achiral
analogue which showed exposed (110) facets corresponding to single-handed
helices to demonstrate the potential of material realization for
higher-dimensional spin selectivity in the development of spintronic devices.",2305.18637v1
2023-07-03,Spin model for the Honeycomb $\rm NiPS_3$,"In the Van der Waal material $\rm NiPS_3$, Ni atoms have spin S=1 and realize
a honeycomb lattice. Six sulfur atoms surround each Ni and split their d
manifold into three filled and two unfilled bands. Aimed to determine the spin
Hamiltonian of $\rm NiPS_3$, we study its exchange mechanisms using a two-band
half-filled Hubbard model. Hopping between d orbitals is mediated by p orbitals
of sulfur and gives rise to bilinear and biquadratic spin couplings in the
limit of strong electronic correlations. The microscopic model exposed a
ferromagnetic biquadratic spin interaction $\rm K_1$ allowing the completion of
a minimal $\rm J_1-J_3-K_1$ spin Hamiltonian for $\rm NiPS_3$. In bulk, a
ferromagnetic first nearest neighbor $\rm J_1$ and a more significant
antiferromagnetic third nearest neighbor spin coupling $\rm J_3$ agreed with
the literature, while in monolayer $\rm J_1$ is positive and very small in
comparison. Using a variational scheme we found that a zig-zag
antiferromagnetic order is the ground state of bulk samples. The zig-zag
pattern is adjacent to commensurate and incommensurate spin spirals, which
could hint at the puzzling results reported in $\rm NiPS_3$ monolayers.",2307.01133v2
2018-02-21,Quantum field theory of nematic transitions in spin orbit coupled spin-1 polar bosons,"We theoretically study an ultra-cold gas of spin-1 polar bosons in a one
dimensional continuum which are subject to linear and quadratic Zeeman fields
and a Raman induced spin-orbit coupling. Concentrating on the regime in which
the background fields can be treated perturbatively we analytically solve the
model in its low-energy sector, i.e. we characterize the relevant phases and
the quantum phase transitions between them. Depending on the sign of the
effective quadratic Zeeman field $\epsilon$, two superfluid phases with
distinct nematic order appear. In addition, we uncover a spin-disordered
superfluid phase at strong coupling. We employ a combination of renormalization
group calculations and duality transformations to access the nature of the
phase transitions. At $\epsilon = 0$, a line of spin-charge separated pairs of
Luttinger liquids divides the two nematic phases and the transition to the spin
disordered state at strong coupling is of the Berezinskii-Kosterlitz-Thouless
type. In contrast, at $\epsilon \neq 0$, the quantum critical theory separating
nematic and strong coupling spin disordered phases contains a Luttinger liquid
in the charge sector that is coupled to a Majorana fermion in the spin sector
(i.e. the critical theory at finite $\epsilon$ maps to a quantum critical Ising
model that is coupled to the charge Luttinger liquid). Due to an emergent
Lorentz symmetry, both have the same, logarithmically diverging velocity. We
discuss the experimental signatures of our findings that are relevant to
ongoing experiments in ultra-cold atomic gases of $^{23}$Na.",1802.07736v2
2002-06-19,Magnetic-field dependence of energy levels in ultrasmall metal grains,"We present a theory of mesoscopic fluctuations of g tensors and avoided
crossing energies in a small metal grain. The model, based on random matrix
theory, contains both the orbital and spin contributions to the g tensor. The
two contributions can be experimentally separated for weak spin-orbit coupling
while they merge in the strong coupling limit. For intermediate coupling,
substantial correlations are found between g factors of neighboring levels.",0206377v1
2006-05-13,Scattering wave function approach to multi-terminal mesoscopic system with spin-orbit coupling,"In this paper,we present a detailed formulation to solve the scattering wave
function for a multi-terminal mesoscopic system with spin-orbit coupling. In
addition to terminal currents, all local quantities can be calculated
explicitly by taking proper ensemble average in the Landauer-Buttiker's spirit
using the scattering wave functions. Based on this formulation, we derive some
rigorous results for equilibrium state. Furthermore, some new symmetry
relations are found for the typical two terminal structure in which a
semiconductor bar with Rashba or/and Dresselhaus SO coupling is sandwiched
symmetrically between two leads. These symmetry property can provide accuracy
tests for experimental measurements and numerical calculations.",0605361v1
2011-03-15,Quantum transport in oxide nanostructures,"We describe magnetotransport experiments performed on Hall crosses made from
quantum wires at LaAlO3/SrTiO3 interfaces. Shubnikov-de Haas oscillations
measured in a 14-nm wide structure exhibit modulations that are consistent with
spin-orbit coupling or valley degeneracies. Hall measurements performed on the
6 nm-wide Hall cross reveal dissipative coupling to magnetic phases. Hall
plateaus are observed that deviate significantly from two-dimensional quantum
Hall counterparts. Non-monotonic dips in the Hall resistance are attributed to
one-dimensional confinement and spin-orbit coupling.",1103.3036v1
2014-10-17,Quantum plateau of Andreev reflection induced by spin-orbit coupling,"In this work we uncover an interesting quantum plateau behavior for the
Andreev reflection between a one-dimensional quantum wire and superconductor.
The quantum plateau is achieved by properly tuning the interplay of the
spin-orbit coupling within the quantum wire and its tunnel coupling to the
superconductor. This plateau behavior is justified to be unique by excluding
possible existences in the cases associated with multi-channel quantum wire,
the Blonder-Tinkham-Klapwijk continuous model with a barrier, and lattice
system with on-site impurity at the interface.",1410.4642v1
2015-04-22,Novel energy level structure of Dirac oscillator in magnetic field,"We have presented an elegant high energy quantum problem, namely, the full
Dirac oscillator under axial magnetic field with its full solution. We have
found the energy spectrum which is rich and at the same time has a novel
structure. The quantized energy levels show coupling of the oscillator
frequency with the Larmor frequency in the 2D surface where the electrons under
consideration follow a 2D oscillator. The axis in which magnetic field is
pointed, the electrons follow a 1D oscillator. There is also coupling between
spin and orbital motion and also a coupling between a resultant effect of
orbital and spin motion with Larmor precession.",1504.05660v2
2015-06-19,Coherent manipulation of a Majorana qubit by a mechanical resonator,"We propose a hybrid system composed of a Majorana qubit and a nanomechanical
resonator, implemented by a spin-orbit-coupled superconducting nanowire, using
a set of static and oscillating ferromagnetic gates. The ferromagnetic gates
induce Majorana bound states in the nanowire, which hybridize and constitute a
Majorana qubit. Due to the oscillation of one of these gates, the Majorana
qubit can be coherently rotated. By tuning the gate voltage to modulate the
local spin-orbit coupling, it is possible to reach the resonance of the
qubit-oscillator system for relatively strong couplings.",1506.05879v2
2015-09-24,Fractional Local Moment and High Temperature Kondo Effect in Rashba-Fermi Gases,"We investigate the new physics that arises when a correlated quantum impurity
hybridizes with Fermi gas with a generalized Rashba spin-orbit coupling
produced via a uniform synthetic non-Abelian gauge field. We show that the
impurity develops a {\it fractional} local moment which couples
anti-ferromagnetically to the Rashba-Fermi gas. This results in a concomitant
{\it Kondo effect with a high temperature scale} that can be tuned by the
strength of the Rashba spin-orbit coupling.",1509.07328v2
2016-04-01,Unconventional low-field magnetic response of a diffusive ring with spin-orbit coupling,"We report an unconventional behavior of electron transport in the limit of
zero magnetic flux in a one-dimensional disordered ring, be it completely
random or any correlated one, subjected to Rashba spin-orbit (SO) coupling. It
exhibits much higher circulating current compared to a fully perfect ring for a
wide range of SO coupling yielding larger electrical conductivity which is
clearly verified from our Drude weight analysis.",1604.00165v2
2018-02-19,Spin-Orbit Coupling Induced Resonance in an Ultracold Bose Gas,"We study a two-component Bose gas with artificial spin-orbit coupling (SOC)
which couples the center-of-mass momentum of atom to its internal states. We
show that in this system resonance can be induced by tuning SOC strength. With
a two-dimensional SOC, resonances in two scattering channels can be induced by
tuning the aspect ratio of SOC strengths. With a three-dimensional SOC,
resonance in all scattering channels can be induced by tuning the appropriate
SOC strength. Similarly, we also find that in a Fermi gas with two- or
three-dimensional SOC resonance can be induced by tuning SOC strength.",1802.06522v2
2018-11-13,Quench Dynamics in a Trapped Bose-Einstein Condensate with Spin-Orbit Coupling,"We consider the phase transition dynamics of a trapped Bose-Einstein
condensate subject to Raman-type spin-orbit coupling (SOC). By tuning the
coupling strength the condensate is taken through a second order phase
transition into an immiscible phase. We observe the domain wall defects
produced by a finite speed quench is described by the Kibble-Zurek mechanism
(KZM), and quantify a power law behavior for the scaling of domain number and
formation time with the quench speed.",1811.05327v2
2014-03-14,Mott-Superfluid Transition for Spin-Orbit Coupled Bosons in One-Dimensional Optical Lattices,"We study the effects of spin-orbit coupling on the Mott-superfluid transition
of bosons in a one-dimensional optical lattice. We determine the strong
coupling magnetic phase diagram by a combination of exact analytic and
numerical means. Smooth evolution of the magnetic structure into the superfluid
phases are investigated with the density matrix renormalization group
technique. Novel magnetic phases are uncovered and phase transitions between
them within the superfluid regime are discussed. Possible experimental
detection are discussed.",1403.3491v2
2012-04-04,Intrinsic instability of electronic interfaces with strong Rashba coupling,"We consider a model for the two-dimensional electron gas formed at the
interface of oxide heterostructures, which includes a Rashba spin-orbit
coupling proportional to the electric field perpendicular to the interface.
Based on the standard mechanism of polarity catastrophe, we assume that the
electric field is proportional to the electron density. Under these simple and
general assumptions, we show that a phase separation instability occurs for
realistic values of the spin-orbit coupling and of the band parameters. This
could provide an intrinsic mechanism for the recently observed inhomogeneous
phases at the LaAlO_3/SrTiO_3 or LaTiO_3/SrTiO_3 interfaces.",1204.0962v3
2013-09-17,Cavity-Assisted Dynamical Spin-Orbit Coupling in Cold Atoms,"We consider ultracold atoms subjected to a cavity-assisted two-photon Raman
transition. The Raman coupling gives rise to effective spin-orbit interaction
which couples atom's center-of-mass motion to its pseudospin degrees of
freedom. Meanwhile, the cavity photon is dynamically affected by the atom. This
feedback between atom and photon leads to a dramatic modification of the atomic
dispersion relation, and further leads to dynamical instability of the system.
We propose to detect the change of cavity photon number as a direct way to
demonstrate dynamical instability.",1309.4369v2
2020-10-30,Microscopic Theory of Ultrafast Skyrmion Excitation by Light,"We propose a microscopic mechanism for ultrafast skyrmion photo-excitation
via a two-orbital electronic model. In the strong correlation limit the
$d$-electrons are described by an effective spin Hamiltonian, coupled to
itinerant $s$-electrons via $s-d$ exchange. Laser-exciting the system by a
direct coupling to the electric charge leads to skyrmion nucleation on a 100 fs
timescale. The coupling between photo-induced electronic currents and magnetic
moments, mediated via Rashba spin-orbit interactions, is identified as the
microscopic mechanism behind the ultrafast optical skyrmion excitation.",2010.16125v1
2023-01-23,"Charge localization, frustration relief, and spin-orbit coupling in U$_3$O$_8$","Research efforts on the low temperature magnetic order and electronic
properties of U$_3$O$_8$ have been inconclusive so far. Reinterpreting neutron
scattering results, we use group representation theory to show that the ground
state presents collinear out-of-plane magnetic moments, with antiferromagnetic
coupling both in-layer and between layers. Charge localization relieves the
initial geometric frustration, generating a slightly distorted honeycomb
sublattice with N\'eel order. We show, furthermore, that spin-orbit coupling
has a giant effect on the conduction band states and band gap value. Our
results allow a reinterpretation of recent optical absorption measurements.",2301.09343v1
2023-07-01,Coupling of acoustic phonon to a spin-orbit entangled pseudospin,"We consider coupling of acoustic phonon to pseudospins consisting of
electronic spins locked to orbital angular momentum states. We show that a
Berry phase term arises from projection onto the time-dependent lowest energy
manifold. We examine consequences on the phonon modes, in particular mode
splitting, induced chirality and Berry curvatures under an external magnetic
field which Zeeman couples to the pseudospin.",2307.00208v2
1997-05-07,Spin Precession and Time-Reversal Symmetry Breaking in Quantum Transport of Electrons Through Mesoscopic Rings,"We consider the motion of electrons through a mesoscopic ring in the presence
of spin-orbit interaction, Zeeman coupling, and magnetic flux. The coupling
between the spin and the orbital degrees of freedom results in the geometric
and the dynamical phases associated with a cyclic evolution of spin state.
Using a non-adiabatic Aharonov-Anandan phase approach, we obtain the exact
solution of the system and identify the geometric and the dynamical phases for
the energy eigenstates. Spin precession of electrons encircling the ring can
lead to various interference phenomena such as oscillating persistent current
and conductance. We investigate the transport properties of the ring connected
to current leads to explore the roles of the time-reversal symmetry and its
breaking therein with the spin degree of freedom being fully taken into
account. We derive an exact expression for the transmission probability through
the ring. We point out that the time-reversal symmetry breaking due to Zeeman
coupling can totally invalidate the picture that spin precession results in
effective, spin-dependent Aharonov-Bohm flux for interfering electrons.
Actually, such a picture is only valid in the Aharonov-Casher effect induced by
spin-orbit interaction only. Unfortunately, this point has not been realized in
prior works on the transmission probability in the presence of both SO
interaction and Zeeman coupling. We carry out numerical computation to
illustrate the joint effects of spin-orbit interaction, Zeeman coupling and
magnetic flux. By examining the resonant tunneling of electrons in the weak
coupling limit, we establish a connection between the observable time-reversal
symmetry breaking effects manifested by the persistent current and by the
transmission probability. For a ring formed by two-dimensional electron gas, we",9705054v1
2005-08-22,Edge spin accumulation in semiconductor two-dimensional hole gases,"The controlled generation of localized spin densities is a key enabler of
semiconductor spintronics In this work, we study spin Hall effect induced edge
spin accumulation in a two-dimensional hole gas with strong spin orbit
interactions. We argue that it is an intrinsic property, in the sense that it
is independent of the strength of disorder scattering. We show numerically that
the spin polarization near the edge induced by this mechanism can be large, and
that it becomes larger and more strongly localized as the spin-orbit coupling
strength increases, and is independent of the width of the conducting strip
once this exceeds the elastic scattering mean-free-path. Our experiments in
two-dimensional hole gas microdevices confirm this remarkable spin Hall effect
phenomenology. Achieving comparable levels of spin polarization by external
magnetic fields would require laboratory equipment whose physical dimensions
and operating electrical currents are million times larger than those of our
spin Hall effect devices.",0508532v2
2023-04-15,Unlocking Hidden Spins in Centrosymmetric SnSe2 by Vacancy-Controlled Spin-Orbit Scattering,"Spin current generation and manipulation remain the key challenge of
spintronics, in which relativistic spinorbit coupling (SOC) play a ubiquitous
role. In this letter, we demonstrate that hidden Rashba spins in the
non-magnetic, centrosymmetric lattice of multilayer SnSe2 can be efficiently
activated by spin-orbit scattering introduced by Se vacancies. Via vacancy
scattering, conduction electrons with hidden spin-momentum locked polarizations
acquire out-of-plane magnetization components, which effectively break the
chiral symmetry between the two Se sublattices of an SnSe2 monolayer when
electron spins start precession in the strong built-in Rashba SOC field. The
resulting spin separations are manifested in quantum transport as vacancy
concentrationand temperature-dependent crossovers from weak antilocalization
(WAL) to weak localization (WL), with the distinctive spin relaxation mechanism
of the Dyakonov-Perel type. Our study shows the great potential of
twodimensional systems with hidden-spin textures for spintronics.",2304.07448v1
2004-05-11,Spin relaxation dynamics of quasiclassical electrons in ballistic quantum dots with strong spin-orbit coupling,"We performed path integral simulations of spin evolution controlled by the
Rashba spin-orbit interaction in the semiclassical regime for chaotic and
regular quantum dots. The spin polarization dynamics have been found to be
strikingly different from the D'yakonov-Perel' (DP) spin relaxation in bulk
systems. Also an important distinction have been found between long time spin
evolutions in classically chaotic and regular systems. In the former case the
spin polarization relaxes to zero within relaxation time much larger than the
DP relaxation, while in the latter case it evolves to a time independent
residual value. The quantum mechanical analysis of the spin evolution based on
the exact solution of the Schroedinger equation with Rashba SOI has confirmed
the results of the classical simulations for the circular dot, which is
expected to be valid in general regular systems. In contrast, the spin
relaxation down to zero in chaotic dots contradicts to what have to be expected
from quantum mechanics. This signals on importance at long time of the
mesoscopic echo effect missed in the semiclassical simulations.",0405212v1
2006-05-31,Persistent spin current in a spin-orbit coupling/normal hybrid ring,"We investigate the equilibrium property of a mesoscopic ring with spin orbit
(SO) interaction. It is well known that for a normal mesoscopic ring threaded
by a magnetic flux, the electron acquires a Berry phase that induces the
persistent (charge) current. Similarly, the spin of electron acquires a spin
Berry phase traversing the ring with SO interaction. It is this spin Berry
phase that induces a persistent spin current. To demonstrate its existence, we
calculate the persistent spin current without accompanying charge current in
the normal region in a hybrid mesoscopic ring. We point out that this
persistent spin current describes the real spin motion and can be observed
experimentally.",0605748v1
2010-05-21,Spin injection and perpendicular spin transport in graphite nanostructures,"Organic and carbon-based materials are attractive for spintronics because
their small spin-orbit coupling and low hyperfine interaction is expected to
give rise to large spin-relaxation times. However, the corresponding
spin-relaxation length is not necessarily large when transport is via weakly
interacting molecular orbitals. Here we use graphite as a model system and
study spin transport in the direction perpendicular to the weakly bonded
graphene sheets. We achieve injection of highly (75%) spin-polarized electrons
into graphite nanostructures of 300-500 nm across and up to 17 nm thick, and
observe transport without any measurable loss of spin information. Direct
visualization of local spin transport in graphite-based spin-valve sandwiches
also shows spatially uniform and near-unity transmission for electrons at 1.8
eV above the Fermi level.",1005.3991v1
2021-05-07,Optical induced Spin Current in Monolayer NbSe$_2$,"Monolayer NbSe2 is a metallic two-dimensional (2D) transition-metal
dichalcogenide material. Owing to the lattice structure and the strong atomic
spin-orbit coupling (SOC) field, monolayer NbSe2 possesses Ising-type SOC which
acts as effective Zeeman field, leading to the unconventional topological spin
properties. In this paper, we numerically calculate spin-dependent optical
conductivity of monolayer NbSe2 using Kubo formula based on an effective
tight-binding model which includes $d_{z^2}$, $d_{x^2-y^2}$ and $d_{xy}$
orbitals of Nb atom. Numerical calculation indicates that the up- and down-spin
have opposite sign of Hall current, so the pure spin Hall current can be
generated in monolayer NbSe2 under light irradiation, owing to the topological
nature of monolayer NbSe2, i.e., finite spin Berry curvature. The spin Hall
angle is also evaluated. The optical induced spin Hall current can be enhanced
by the electron doping and persists even at room temperature. Our results will
serve to design opt-spintronics devices such as spin current harvesting by
light irradiation on the basis of 2D materials.",2105.03021v1
2023-10-20,Exchange-driven spin Hall effect in anisotropic ferromagnets,"Crystallographic anisotropy of the spin-dependent conductivity tensor can be
exploited to generate transverse spin-polarized current in a ferromagnetic
film. This ferromagnetic spin Hall effect is analogous to the spin-splitting
effect in altermagnets and does not require spin-orbit coupling.
First-principles screening of 41 non-cubic ferromagnets revealed that many of
them, when grown as a single crystal with tilted crystallographic axes, can
exhibit large spin Hall angles comparable with the best available
spin-orbit-driven spin Hall sources. Macroscopic spin Hall effect is possible
for uniformly magnetized ferromagnetic films grown on some low-symmetry
substrates with epitaxial relations that prevent cancellation of contributions
from different orientation domains. Macroscopic response is also possible for
any substrate if magnetocrystalline anisotropy is strong enough to lock the
magnetization to the crystallographic axes in different orientation domains.",2310.13688v2
2015-04-20,Three-component Fulde-Ferrell superfluids in a two-dimensional Fermi gas with spin-orbit coupling,"We investigate the pairing physics of a three-component spin-orbit coupled
Fermi gas in two spatial dimensions. The three atomic hyperfine states of the
system are coupled by the recently realized synthetic spin-orbit coupling
(SOC), which mixes different hyperfine states into helicity branches in a
momentum-dependent manner. As a consequence, the interplay of spin-orbit
coupling and the hyperfine-state dependent interactions leads to the emergence
of Fulde-Ferrell (FF) pairing states with finite center-of-mass momenta even in
the absence of the Fermi-surface asymmetry that is usually mandatory to
stabilize an SOC-induced FF state. We show that, for different combinations of
spin-dependent interactions, the ground state of the system can either be the
conventional Bardeen-Cooper-Schrieffer pairing state with zero center-of-mass
momentum or be the FF pairing states. Of particular interest here is the
existence of a three-component FF pairing state in which every two out of the
three components form FF pairing. We map out the phase diagram of the system
and characterize the properties of the three-component FF state, such as the
order parameters, the gapless contours and the momentum distributions. Based on
these results, we discuss possible experimental detection schemes for the
interesting pairing states in the system.",1504.05047v2
2015-11-22,Review of Spin Orbit Coupled Semimetal SrIrO3 in thin film form,"Spin orbit coupling provides a mechanism to lock the momentum of electron to
its spin degree, recent years was revealed to be essential in arousing many
novel physical behaviors. SrIrO3 is a typical metallic member of the strong
spin orbit coupling iridate family. Its orthorhombic phase was confirmed as a
particular spin orbit coupling assistant electron correlated semimetal with
small electron and hole pockets, and was supposed to host versatile topological
phases, with prospect of opening a new topological matter field based on
oxides. The existing experiments have demonstrated that orthorhombic SrIrO3 can
be easily synthesized at two dimensional scale films under the substrate
lattice constraint, and the films display Fermi-liquid behavior in high
temperature and generally two dimensional weak localization resulted metal
insulator transition. The properties of orthorhombic SrIrO3 film are sensitive
to the rotation and tilting angle, as well as the interlayer coupling of the
IrO6 octahedras, consequently can be tuned through substrate strain engineering
and size scale. For example, the film was approached a state similar to Sr2IrO4
at the ultrathin limit to several unit cell, becoming a canted
antiferromagnetic semiconductor/insulator. The existing knowledges suggest
urgent demands of researches on the superlattices constructed with orthorhombic
SrIrO3, for further understanding the evolution mechanism of the electron
structure, and so the relevant magnetic state and topological phases in the
orthorhombic SrIrO3 and its family.",1511.06979v2
2018-09-05,Nonlinear gap modes and compactons in a lattice model for spin-orbit coupled exciton-polaritons in zigzag chains,"We consider a system of generalized coupled Discrete Nonlinear
Schr\""{o}dinger (DNLS) equations, derived as a tight-binding model from the
Gross-Pitaevskii-type equations describing a zigzag chain of weakly coupled
condensates of exciton-polaritons with spin-orbit (TE-TM) coupling. We focus on
the simplest case when the angles for the links in the zigzag chain are $\pm
\pi/4$ with respect to the chain axis, and the basis (Wannier) functions are
cylindrically symmetric (zero orbital angular momenta). We analyze the
properties of the fundamental nonlinear localized solutions, with particular
interest in the discrete gap solitons appearing due to the simultaneous
presence of spin-orbit coupling and zigzag geometry, opening a gap in the
linear dispersion relation. In particular, their linear stability is analyzed.
We also find that the linear dispersion relation becomes exactly flat at
particular parameter values, and obtain corresponding compact solutions
localized on two neighboring sites, with spin-up and spin-down parts $\pi/2$
out of phase at each site. The continuation of these compact modes into
exponentially decaying gap modes for generic parameter values is studied
numerically, and regions of stability are found to exist in the lower or upper
half of the gap, depending on the type of gap modes.",1809.01623v2
2016-09-30,Spin-orbit coupling in a hexagonal ring of pendula,"We consider the mechanical motion of a system of six macroscopic pendula
which are connected with springs and arranged in a hexagonal geometry. When the
springs are pre-tensioned, the coupling between neighbouring pendula along the
longitudinal (L) and the transverse (T) directions are different: identifying
the motion along the L and T directions as a spin-like degree of freedom, we
theoretically and experimentally verify that the pre-tensioned springs result
in a tunable spin-orbit coupling. We elucidate the structure of such a
spin-orbit coupling in the extended two-dimensional honeycomb lattice, making
connections to physics of graphene. The experimental frequencies and the
oscillation patterns of the eigenmodes for the hexagonal ring of pendula are
extracted from a spectral analysis of the motion of the pendula in response to
an external excitation and are found to be in good agreement with our
theoretical predictions. We anticipate that extending this classical analogue
of quantum mechanical spin-orbit coupling to two-dimensional lattices will lead
to exciting new topological phenomena in classical mechanics.",1609.09651v2
2019-11-29,Observation of the spin-orbit gap in bilayer graphene by one-dimensional ballistic transport,"We report on measurements of quantized conductance in gate-defined quantum
point contacts in bilayer graphene that allow the observation of subband
splittings due to spin-orbit coupling. The size of this splitting can be tuned
from 40 to 80 $\mu$eV by the displacement field. We assign this gate-tunable
subband-splitting to a gap induced by spin-orbit coupling of Kane-Mele type,
enhanced by proximity effects due to the substrate. We show that this
spin-orbit coupling gives rise to a complex pattern in low perpendicular
magnetic fields, increasing the Zeeman splitting in one valley and suppressing
it in the other one. In addition, we observe the existence of a spin-polarized
channel of 6 e$^2$/h at high in-plane magnetic field and of signatures of
interaction effects at the crossings of spin-split subbands of opposite spins
at finite magnetic field.",1911.13176v4
2022-10-17,Experimental observation of spin-split energy dispersion in high-mobility single-layer graphene/WSe2 heterostructures,"Proximity-induced spin-orbit coupling in graphene has led to the observation
of intriguing phenomena like time-reversal invariant $\mathbb{Z}_2$ topological
phase and spin-orbital filtering effects. An understanding of the effect of
spin-orbit coupling on the band structure of graphene is essential if these
exciting observations are to be transformed into real-world applications. In
this research article, we report the experimental determination of the band
structure of single-layer graphene (SLG) in the presence of strong
proximity-induced spin-orbit coupling. We achieve this in high-mobility
hBN-encapsulated SLG/WSe2 heterostructures through measurements of quantum
oscillations. We observe clear spin-splitting of the graphene bands along with
a substantial increase in the Fermi velocity. Using a theoretical model with
realistic parameters to fit our experimental data, we uncover evidence of a
band gap opening and band inversion in the SLG. Further, we establish that the
deviation of the low-energy band structure from pristine SLG is determined
primarily by the valley-Zeeman SOC and Rashba SOC, with the Kane-Mele SOC being
inconsequential. Despite robust theoretical predictions and observations of
band-splitting, a quantitative measure of the spin-splitting of the valence and
the conduction bands and the consequent low-energy dispersion relation in SLG
was missing -- our combined experimental and theoretical study fills this
lacuna.",2210.08926v1
2021-08-14,Dissipation-relaxation dynamics of a spin-1/2 particle with a Rashba-type spin-orbit coupling in an ohmic heat bath,"Spin-orbit coupling (SOC), which is inherent to a Dirac particle that moves
under the influence of electromagnetic fields, manifests itself in a variety of
physical systems including non-relativistic ones. For instance, it plays an
essential role in spintronics developed in the past few decades, particularly
by controlling spin current generation and relaxation. In the present work, by
using an extended Caldeira-Leggett model, we elucidate how the interplay
between spin relaxation and momentum dissipation of an open system of a single
spin-$1/2$ particle with a Rashba type SOC is induced by the interactions with
a spinless, three-dimensional environment. Staring from the path integral
formulation for the reduced density matrix of the system, we have derived a set
of coupled nonlinear equations that consists of a quasi-classical Langevin
equation for the momentum with a frictional term and a spin precession
equation. The spin precesses around the effective magnetic field generated by
both the SOC and the frictional term. It is found from analytical and numerical
solutions to these equations that a spin torque effect included in the
effective magnetic field causes a spin relaxation and that the spin and
momentum orientations after a long time evolution are largely controlled by the
Rashba coupling strength. Such a spin relaxation mechanism is qualitatively
different from, e.g., the one encountered in semiconductors where essentially
no momentum dissipation occurs due to the Pauli blocking.",2108.06465v1
2006-12-31,Local spin density in two-dimensional electron gas with hexagonal boundary,"The intrinsic spin-Hall effect in hexagon-shaped samples is investigated. To
take into account the spin-orbit couplings and to fit the hexagon edges, we
derive the triangular version of the tight-binding model for the linear Rashba
[Sov. Phys. Solid State 2, 1109 (1960)] and Dresselhaus [Phys. Rev. 100, 580
(1955)] [001] Hamiltonians, which allow direct application of the
Landauer-Keldysh non-equilibrium Green function formalism to calculating the
local spin density within the hexagonal sample. Focusing on the out-of-plane
component of spin, we obtain the geometry-dependent spin-Hall accumulation
patterns, which are sensitive to not only the sample size, the spin-orbit
coupling strength, the bias strength, but also the lead configurations.
Contrary to the rectangular samples, the accumulation pattern can be very
different in our hexagonal samples. Our present work provides a fundamental
description of the geometry effect on the intrinsic spin-Hall effect, taking
the hexagon as the specific case. Moreover, broken spin-Hall symmetry due to
the coexistence of the Rashba and Dresselhaus couplings is also discussed. Upon
exchanging the two coupling strengths, the accumulation pattern is reversed,
confirming the earlier predicted sign change in spin-Hall conductivity.",0701019v2
2017-07-23,Topological spinon bands and vison excitations in spin-orbit coupled quantum spin liquids,"Spin liquids are exotic quantum states characterized by the existence of
fractional and deconfined quasiparticle excitations, referred to as spinons and
visons. Their fractional nature establishes topological properties such as a
protected ground-state degeneracy. This work investigates spin-orbit coupled
spin liquids where, additionally, topology enters via non-trivial band
structures of the spinons. We revisit the $Z_2$ spin-liquid phases that have
recently been identified in a projective symmetry-group analysis on the square
lattice when spin-rotation symmetry is maximally lifted [Phys. Rev. B 90,
174417 (2014)]. We find that in the case of nearest neighbor couplings only,
$Z_2$ spin liquids on the square lattice always exhibit trivial spinon bands.
Adding second neighbor terms, the simplest projective symmetry-group solution
closely resembles the Bernevig-Hughes-Zhang model for topological insulators.
Assuming that the emergent gauge fields are static we investigate vison
excitations, which we confirm to be deconfined in all investigated spin phases.
Particularly, if the spinon bands are topological, the spinons and visons form
bound states consisting of several spinon-Majorana zero modes coupling to one
vison. The existence of such zero modes follows from an exact mapping between
these spin phases and topological $p+ip$ superconductors with vortices. We
propose experimental probes to detect such states in real materials.",1707.07306v1
2016-07-09,Electrical spin injection into graphene from a topological insulator in a van der Waals heterostructure,"All-electrical (magnetic-material-free) spin injection is one of the
outstanding goals in spintronics. Topological insulators (TIs) have been
recognized as a promising electrically controlled spin source thanks to the
strong spin-orbit coupling and in particular, the spin-momentum locked
topological surface states (TSS) supporting helically spin polarized currents.
Many TI materials such as Bi-based chalcogenides are also layered 2D materials
and can be incorporated into van der Waals (vdW) coupled heterostructures,
opening the possibility of the utilization of TIs for electrical spin injection
into other 2D materials. Here, we demonstrate electrical injection of helically
spin-polarized current into graphene through a 3D TI in a mechanically stacked
heterostructure between Bi2Te2Se (a TI) and chemical vapor deposition
(CVD)-grown graphene, using the spin potentiometric measurement. When a dc
current is flowing from the TI to graphene, we detect a striking step-like
voltage change (spin signal) in both the TI and graphene using ferromagnetic
(FM) probes. The sign of the spin signal can be reversed by reversing the
direction of the dc bias current, and the corresponding amplitude of the spin
signal increases linearly with the bias current, indicative of a
current-induced helical spin polarization in both TI and graphene. In contrast,
the graphene itself exhibits usual nonlocal spin valve signal when the spins
are injected using an FM electrode. We discuss possible origins of the helical
spin polarization injected into the graphene in our TI/graphene heterostructure
that may include TSS as well as the spin-orbit coupled Rashba states. Our
findings show electrical injection of a spin helical current into graphene
through a TI and demonstrate TIs as potential spin sources for future
spintronic devices wherein spin manipulation is achieved electrically.",1607.02651v1
2002-05-19,Adiabatic spin pumping through a quantum dot with a single orbital level,"We investigate an adiabatic spin pumping through a quantum dot with a single
orbital energy level under the Zeeman effect. Electron pumping is produced by
two periodic time dependent parameters, a magnetic field and a difference of
the dot-lead coupling between the left and right barriers of the dot. The
maximum charge transfer per cycle is found to be $e$, the unit charge in the
absence of a localized moment in the dot. Pumped charge and spin are different,
and spin pumping is possible without charge pumping in a certain situation.
They are tunable by changing the minimum and maximum value of the magnetic
field.",0205395v2
2003-06-02,Comments on `Rashba precession in quantum wire with interaction',"In a recent Rapid Communication (Phys. Rev. B {\bf 63}, 121210(R) (2001)),
Ha\""usler showed that the interaction between electrons in quantum wires may
enhance the persistent spin current arising from Rashba spin-orbital coupling.
In this Comments, we would like to point out that this 'enhancement' comes from
a misunderstanding to the boosting persistent current in the Luttinger liquid
theory. A correct calculation will not give such an enhancement of the
persistent spin current. Meanwhile, we provide a Luttinger liquid theory with
Rashba spin-orbital interaction by bosonization, which may show how the Rashba
precession is in a Luttinger liquid.",0306019v1
2005-10-04,Quantum splitter controlled by Rashba spin-orbit interaction,"We propose the mesoscopic device based on the Rashba spin orbit interaction
(SOI) that contains a gated ballistic Aharonov-Bohm (AB) ring with incoming
lead and two asymmetrically situated outgoing leads. The variations of the
Rashba coupling parameter induced by the gate voltage applied to the AB ring is
shown to cause the redistribution of the carrier flux between the outgoing
leads and spin polarization of the outgoing currents, thus allowing the system
to manifest the properties of the quantum splitter and spin filter.",0510069v1
2006-09-05,Out-of-plane spin polarization from in-plane electric and magnetic fields,"We show that the joint effect of spin-orbit and magnetic fields leads to a
spin polarization perpendicular to the plane of a two-dimensional electron
system with Rashba spin-orbit coupling and in-plane parallel dc magnetic and
electric fields, for angle-dependent impurity scattering or nonparabolic energy
spectrum, while only in-plane polarization persists for simplified models. We
derive Bloch equations, describing the main features of recent experiments,
including the magnetic field dependence of static and dynamic responses.",0609078v1
2011-08-15,Spin superstructure and noncoplanar ordering in metallic pyrochlore magnets with degenerate orbitals,"We study double-exchange models with itinerant t2g electrons in spinel and
pyrochlore crystals. In both cases the localized spins form a network of
corner-sharing tetrahedra. We show that the strong directional dependence of
t2g orbitals leads to unusual Fermi surfaces that induce spin superstructures
and noncoplanar orderings for a weak coupling between itinerant electrons and
localized spins. Implications of our results to ZnV2O4 and Cd2Os2O7 are also
discussed.",1108.3066v1
2013-07-31,Relativistic symmetries in Rosen-Morse potential and tensor interaction using the Nikiforov-Uvarov method,"Approximate analytical bound-state solutions of the Dirac particle in the
field of both attractive and repulsive RM potentials including Coulomb-like
tensor (CLT) potential are obtained for arbitrary spin-orbit quantum number The
Pekeris approximation is used to deal with the spin-orbit coupling terms In the
presence of exact spin and pseudospin (p-spin) symmetries, the energy
eigenvalues and the corresponding normalized two-component wave functions are
found by using the parametric generalization of the Nikiforov-Uvarov (NU)
method. The numerical results show that the CLT interaction removes
degeneracies between spin and p-spin state doublets.",1307.8311v1
2018-09-20,Highly Efficient Induction of Spin Polarization by Circularly-Polarized Electromagnetic Waves in the Rashba Spin-Orbit Systems,"We theoretically demonstrate that a rotating electric-field component of
circularly polarized microwave or terahertz light can induce electron-spin
polarization within a few picoseconds in a two-dimensional electron system with
the Rashba spin-orbit interaction by taking advantage of the magnetoelectric
coupling. The efficiency turns out to be several orders of magnitude greater
than that of conventional methods, indicating high potential of this technique
for future spintronics.",1809.07513v1
2020-04-01,Entropy and specific heat of the infinite-dimensional three-orbital Hubbard model,"The Hund coupling in multiorbital Hubbard systems induces spin freezing and
associated Hund metal behavior. Using dynamical mean field theory, we explore
the effect of local moment formation, spin and charge excitations on the
entropy and specific heat of the three-orbital model. In particular, we
demonstrate a substantial enhancement of the entropy in the spin-frozen metal
phase at low temperatures, and peaks in the specific heat associated with the
activation of spin and charge fluctuations at high temperature. We also clarify
how these temperature scales depend on the interaction parameters and filling.",2004.00471v1
2010-02-01,Tunneling Anisotropic Magnetoresistance of Helimagnet Tunnel Junctions,"We theoretically investigate the angular and spin dependent transport in
normal-metal/helical-multiferroic/ferromagnetic heterojunctions. We find a
tunneling anisotropic magnetoresistance (TAMR) effect due to the spiral
magnetic order in the tunnel junction and to an effective spin-orbit coupling
induced by the topology of the localized magnetic moments in the multiferroic
spacer.
  The predicted TAMR effect is efficiently controllable by an external electric
field due to the magnetoelectric coupling.",1002.0221v1
2013-10-31,A Non-Centrosymmetric Superconductor with a Bulk 3D Dirac Cone Gapped by Strong Spin Orbit Coupling,"Layered, non-centrosymmetric, heavy element PbTaSe2 is found to be
superconducting. We report its electronic properties accompanied by electronic
structure calculations. Specific heat, electrical resistivity and magnetic
susceptibility measurements indicate that PbTaSe2 is a moderately coupled,
type-II BCS superconductor (Tc = 3.72 K, Ginzburg-Landau parameter Kappa = 14)
with an electronphonon coupling constant of Lambda_ep = 0.74. Electronic
structure calculations reveal a single bulk 3D Dirac cone at the K point of the
Brillouin Zone derived exclusively from its hexagonal Pb layer; it is similar
to the feature found in graphene except there is a 0.8 eV gap opened by
spin-orbit coupling. The combination of large spin-orbit coupling and lack of
inversion symmetry also results in large Rashba splitting on the order of
tenths of eV.",1310.8368v1
2015-09-14,Itinerant chiral ferromagnetism in a trapped Rashba spin-orbit coupled Fermi gas,"How ferromagnetic phases emerge in itinerant systems is an outstanding
problem in quantum magnetism. Here we consider a repulsive two-component Fermi
gas confined in a two dimensional isotropic harmonic potential and subject to a
large Rashba spin-orbit (SO) coupling, whose single-particle dispersion can be
tailored by adjusting the SO coupling strength. We show that the interplay
among SO coupling, correlation effects and mean-field repulsion leads to a
competition between ferromagnetic and non-magnetic phases. At intermediate
interaction strengths, ferromagnetic phase emerges which can be well described
by the mean-field Hartree-Fock theory; whereas at strong interaction strengths,
a strongly correlated non-magnetic phase is favored due to the
beyond-mean-field quantum correlation effects. Furthermore, the ferromagnetic
phase of this system possesses a chiral current density induced by the Rashba
spin-orbit coupling, whose experimental signature is investigated.",1509.04095v1
2014-06-19,A criterion of the non-existence of surface states in a semi-infinite crystal,"An infinite crystal can be constructed by an infinite number of parallel
two-dimensional (hkl) crystal planes coupled to each other. For crystals with
negligible spin-orbit coupling, we report a rigorous proof of a criterion on
the non-existence of surface states in a semi-infinite crystal with the crystal
symmetry. The forward transfer to be the same as the backward one, called as
F-B dynamical symmetry, is key to realize the criterion. Based on lattice model
Hamiltonian with coupling between the nearest neighbor crystal planes only, we
prove that a cut crystal will not be able to accommodate any surface states if
the original infinite crystal has reflection symmetry about every crystal plane
which results in F-B symmetry. The criterion provide a platform to simply
conclude whether surface states exist or not in a cut crystal. For any such
crystals, the non-existence or existence of surface states depends on the cut
direction of the crystal plane. Since the spin-orbit coupling breaks the chiral
symmetry, resulting in the F-B asymmetry, surface states can emerge in the
(hkl) cut crystal with spin-orbit coupling.",1406.5010v2
2018-06-18,From Klein to anti-Klein tunneling in graphene tuning the Rashba spin-orbit interaction or the bilayer coupling,"We calculate the transmission coefficient for a particle crossing a potential
barrier in monolayer graphene with Rashba spin-orbit coupling and in bilayer
graphene. We show that in both the cases one can go from Klein tunneling
regime, characterized by perfect normal transmission, to anti-Klein tunneling
regime, with perfect normal reflection, by tuning the Rashba spin-orbit
coupling for a monolayer or the interplane coupling for a bilayer graphene. We
show that the intermediate regime is characterized by a non-monotonic behavior
with oscillations and resonances in the normal transmission amplitude as a
function of the coupling and of the potential parameters.",1806.06962v2
2019-03-20,High Landau levels of 2D electrons near the topological transition caused by interplay of spin-orbit and Zeeman energy shifts,"In the presence of spin-orbit coupling two branches of the energy spectrum of
2D electrons get shifted in the momentum space. Application of in-plane
magnetic field causes the splitting of the branches in energy. When both,
spin-orbit coupling and Zeeman splitting are present, the branches of energy
spectrum cross at certain energy. Near this energy, the Landau quantization
becomes peculiar since semiclassical trajectories, corresponding to individual
branches, get coupled. We study this coupling as a function of proximity to the
topological transition. Remarkably, the dependence on the proximity is strongly
asymmetric reflecting the specifics of the behavior of the trajectories near
the crossing. Equally remarkable, on one side of the transition, the magnitude
of coupling is an oscillating function of this proximity. These oscillations
can be interpreted in terms of the St{\""u}ckelberg interference. Scaling of
characteristic detuning with magnetic length is also unusual. This unusual
behavior cannot be captured by simply linearizing the Fermi contours near the
crossing point.",1903.08315v1
2019-03-30,Disentangling spin-orbit coupling and local magnetism in a quasi-two-dimensional electron system,"Quantum interference between time-reversed electron paths in two dimensions
leads to the well-known weak localization correction to resistance. If
spin-orbit coupling is present, the resistance correction is negative, termed
weak anti-localization (WAL). Here we report the observation of WAL coexisting
with exchange coupling between itinerant electrons and localized magnetic
moments. We use low-temperature magneto-transport measurements to investigate
the quasi-two-dimensional, high-electron-density interface formed between
SrTiO$_3$ (STO) and the anti-ferromagnetic Mott insulator NdTiO$_3$ (NTO). As
the magnetic field angle is gradually tilted away from the sample normal, the
data reveals the interplay between strong $k$-cubic Rashba-type spin-orbit
coupling and a substantial magnetic exchange interaction from local magnetic
regions. The resulting quantum corrections to the conduction are in excellent
agreement with existing models and allow sensitive determination of the small
magnetic moments (22 $\mu_B$ on average), their magnetic anisotropy and mutual
coupling strength. This effect is expected to arise in other 2D magnetic
materials systems.",1904.00295v2
2023-07-14,Hydrodynamic Navier-Stokes equations in two-dimensional systems with Rashba spin-orbit coupling,"We study a two-dimensional (2D) electron system with a linear spectrum in the
presence of Rashba spin-orbit (RSO) coupling in the hydrodynamic regime. We
derive a semiclassical Boltzmann equation with a collision integral due to
Coulomb interactions in the basis of the eigenstates of the system with RSO
coupling. Using the local equilibrium distribution functions, we obtain a
generalized hydrodynamic Navier-Stokes equation for electronic systems with RSO
coupling. In particular, we discuss the influence of the spin-orbit coupling on
the viscosity and the enthalpy of the system and present some of its observable
effects in hydrodynamic transport.",2307.07408v3
2024-01-31,Stability of vortices in exciton-polariton condensates with spin-orbital-angular-momentum coupling,"The existence and dynamics of stable quantized vortices is an important
subject of quantum many-body physics. Spin-orbital-angular-momentum coupling
(SOAMC), a special type of spin-orbit coupling, has been experimentally
achieved to create vortices in atomic Bose-Einstein condensate (BEC). Here, we
generalize the concept of SOAMC to a two-component polariton BEC and analyze
the emergence and configuration of vortices under a finite-size circular
pumping. We discover that the regular configuration of vortex lattices induced
by a finite-size circular pump is significantly distorted by the spatially
dependent Raman coupling of SOAMC. Meanwhile, a vortex induced by SOAMC located
at the center of the polariton cloud remains stable and pinned in place. When
the Raman coupling is sufficiently strong, the polariton BEC with SOAMC is torn
apart to become fragmented.",2401.17927v1
2011-10-21,Spin Relaxation in Ge/Si Core-Shell Nanowire Qubits,"Controlling decoherence is the most challenging task in realizing quantum
information hardware. Single electron spins in gallium arsenide are a leading
candidate among solid- state implementations, however strong coupling to
nuclear spins in the substrate hinders this approach. To realize spin qubits in
a nuclear-spin-free system, intensive studies based on group-IV semiconductor
are being pursued. In this case, the challenge is primarily control of
materials and interfaces, and device nanofabrication. We report important steps
toward implementing spin qubits in a predominantly nuclear-spin-free system by
demonstrating state preparation, pulsed gate control, and charge-sensing spin
readout of confined hole spins in a one-dimensional Ge/Si nanowire. With fast
gating, we measure T1 spin relaxation times in coupled quantum dots approaching
1 ms, increasing with lower magnetic field, consistent with a spin-orbit
mechanism that is usually masked by hyperfine contributions.",1110.4742v1
2003-10-16,Spin Hall effect and Berry phase in two dimensional electron gas,"The spin Hall effect is investigated in a high mobility two dimensional
electron system with the spin-orbital coupling of both the Rashba and the
Dresselhaus types. A spin current perpendicular to the electric field is
generated by either the Rashba or the Dresselhaus coupling. The spin Hall
conductance is independent of the stength of the coupling, but its sign is
determined by the relative ratio of the two couplings. The direction of spin
current is controllable by tuning the magnitude of the surface electric field
perpendicular to the two dimensional plane via adjusting the Rashba coupling.
It is observed that the spin Hall conductance has a close relation to the Berry
phase of conduction electrons.",0310368v3
2009-07-09,Spin-lattice coupling in frustrated antiferromagnets,"We review the mechanism of spin-lattice coupling in relieving the geometrical
frustration of pyrochlore antiferromagnets, in particular spinel oxides. The
tetrahedral unit, which is the building block of the pyrochlore lattice,
undergoes a spin-driven Jahn-Teller instability when lattice degrees of freedom
are coupled to the antiferromagnetism. By restricting our considerations to
distortions which preserve the translational symmetries of the lattice, we
present a general theory of the collective spin-Jahn-Teller effect in the
pyrochlore lattice. One of the predicted lattice distortions breaks the
inversion symmetry and gives rise to a chiral pyrochlore lattice, in which
frustrated bonds form helices with a definite handedness. The chirality is
transferred to the spin system through spin-orbit coupling, resulting in a
long-period spiral state, as observed in spinel CdCr2O4. We discuss explicit
models of spin-lattice coupling using local phonon modes, and their
applications in other frustrated magnets.",0907.1693v1
2015-02-13,Antiferromagnet-Mediated Spin Transfer Between Metal and Ferromagnet,"We develop a theory for spin transported by coherent Neel dynamics through an
antiferromagnetic insulator coupled to a ferromagnetic insulator on one side
and a current-carrying normal metal with strong spin-orbit coupling on the
other. The ferromagnet is considered within the mono-domain limit and we assume
its coupling to the local antiferromagnet Neel order at the
ferromagnet|antiferromagnet interface through exchange coupling. Coupling
between the charge current and the local Neel order at the other interface is
described using spin Hall phenomenology. Spin transport through the
antiferromagnet, assumed to possess an easy-axis magnetic anisotropy, is solved
within the adiabatic approximation and the effect of spin current flowing into
the ferromagnet on its resonance linewidth is evaluated. Onsager reciprocity is
used to evaluate the inverse spin Hall voltage generated across the metal by a
dynamic ferromagnet as a function the antiferromagnet thickness.",1502.04128v1
2015-02-28,Electron-spin to Phonon Coupling in Graphene Decorated with Heavy Adatoms,"The naturally weak spin-orbit coupling in Graphene can be largely enhanced by
adatom deposition (e.g. Weeks et al. Phys. Rev. X 1, 021001 (2011)). However,
the dynamics of the adatoms also induces a coupling between phonons and the
electron spin. Using group theory and a tight-binding model, we systematically
investigate the coupling between the low-energy in-plane phonons and the
electron spin in single-layer graphene uniformly decorated with heavy adatoms.
Our results provide the foundation for future investigations of spin transport
and superconductivity in this system. In order to quantify the effect of the
coupling to the lattice on the electronic spin dynamics, we compute the
spin-flip rate of electrons and holes. We show that the latter exhibits a
strong dependence on the quasi-particle energy and system temperature.",1503.00092v1
2011-11-29,Accelerated Orbital Expansion And Secular Spin Down of the Accreting Millisecond Pulsar SAX J1808.4-3658,"The accreting millisecond pulsar SAX J1808.4-3658 has shown a peculiar
orbital evolution in the past with an orbital expansion much faster than
expected from standard binary evolutionary scenarios. Previous limits on the
pulsar spin frequency derivative during transient accretion outbursts were
smaller than predicted by standard magnetic accretion torque theory, while the
spin evolution between outbursts was consistent with magnetic dipole spin-down.
In this paper we present the results of a coherent timing analysis of the 2011
outburst observed by the Rossi X-ray Timing Explorer and extend our previous
long-term measurements of the orbital and spin evolution over a baseline of
thirteen years. We find that the expansion of the 2 hr orbit is accelerating at
a rate 1.6E-20 s/s^2 and we interpret this as the effect of short-term angular
momentum exchange between the mass donor and the orbit. The gravitational
quadrupole coupling due to variations in the oblateness of the companion can be
a viable mechanism for explaining the observations. No significant spin
frequency derivatives are detected during the 2011 outburst (<4E-13 Hz/s) and
the long term spin down remains stable over thirteen years with a rate of
approximately -1E-15 Hz/s.",1111.6967v2
2019-10-30,Global phase diagram of a spin-orbital Kondo impurity model and the suppression of Fermi-liquid scale,"Many correlated metallic materials are described by Landau Fermi-liquid
theory at low energies, but for Hund metals the Fermi-liquid coherence scale
$T_{\text{FL}}$ is found to be surprisingly small. In this Letter, we study the
simplest impurity model relevant for Hund metals, the three-channel
spin-orbital Kondo model, using the numerical renormalization group (NRG)
method and compute its global phase diagram. In this framework, $T_{\text{FL}}$
becomes arbitrarily small close to two new quantum critical points (QCPs) which
we identify by tuning the spin or spin-orbital Kondo couplings into the
ferromagnetic regimes. We find quantum phase transitions to a singular
Fermi-liquid or a novel non-Fermi-liquid phase. The new non-Fermi-liquid phase
shows frustrated behavior involving alternating overscreenings in spin and
orbital sectors, with universal power laws in the spin ($\omega^{-1/5}$),
orbital ($\omega^{1/5}$) and spin-orbital ($\omega^1$) dynamical
susceptibilities. These power laws, and the NRG eigenlevel spectra, can be
fully understood using conformal field theory arguments, which also clarify the
nature of the non-Fermi-liquid phase.",1910.13643v2
2023-12-07,Unusual Sign Reversal of Field-like Spin-Orbit Torque in Pt/Ni/Py with an Ultrathin Ni Spacer,"The magnetization manipulation by spin-orbit torques (SOTs) in
nonmagnetic-metal (NM)/ferromagnet (FM) heterostructures has provided great
opportunities for spin devices. Besides the conventional spin Hall effect (SHE)
in heavy metals with strong spin-orbit coupling, the orbital currents have been
proposed to be another promising approach to generate strong SOTs. Here, we
systematically study the SOTs efficiency and its dependence on the FM thickness
and different NM/FM interfaces in two prototypical Pt/Py and Ta/Py systems by
inserting an ultrathin magnetic layer (0.4 nm thick ML = Co, Fe, Gd, and Ni).
The dampinglike (DL) torque efficiency $\xi_{DL}$ is significantly enhanced by
inserting ultrathin Co, Fe, and Ni layers and is noticeably suppressed for the
Gd insertion. Moreover, the Ni insertion results in a sign change of the
field-like (FL) torque in Pt/Py and substantially reduces $\xi_{DL}$ in Ta/Py.
These results are likely related to the additional spin currents generated by
combining the orbital Hall effect (OHE) in the NM and orbital-to-spin
conversion in the ML insertion layer and/or their interfaces, especially for
the Ni insertion. Our results demonstrate that inserting ultrathin ML can
effectively manipulate the strength and sign of the SOTs, which would be
helpful for spintronics applications.",2312.04276v2
2017-10-31,Strongly anisotropic spin relaxation in graphene/transition metal dichalcogenide heterostructures at room temperature,"Graphene has emerged as the foremost material for future two-dimensional
spintronics due to its tuneable electronic properties. In graphene, spin
information can be transported over long distances and, in principle, be
manipulated by using magnetic correlations or large spin-orbit coupling (SOC)
induced by proximity effects. In particular, a dramatic SOC enhancement has
been predicted when interfacing graphene with a semiconducting transition metal
dechalcogenide, such as tungsten disulphide (WS$_2$). Signatures of such an
enhancement have recently been reported but the nature of the spin relaxation
in these systems remains unknown. Here, we unambiguously demonstrate
anisotropic spin dynamics in bilayer heterostructures comprising graphene and
WS$_2$. By using out-of-plane spin precession, we show that the spin lifetime
is largest when the spins point out of the graphene plane. Moreover, we observe
that the spin lifetime varies over one order of magnitude depending on the spin
orientation, indicating that the strong spin-valley coupling in WS$_2$ is
imprinted in the bilayer and felt by the propagating spins. These findings
provide a rich platform to explore coupled spin-valley phenomena and offer
novel spin manipulation strategies based on spin relaxation anisotropy in
two-dimensional materials.",1710.11568v3
2013-07-08,5d transition metal oxide IrO2 as a material for spin current detection,"Devices based on a pure spin current (a flow of spin angular momentum) have
been attracting increasing attention as key ingredients for low-dissipation
electronics. To integrate such spintronics devices into charge-based
technologies, an electric detection of spin current is essential. Inverse spin
Hall effect converts a spin current into an electric voltage through spin-orbit
coupling. Noble metals such as Pt and Pd, and also Cu-based alloys, owing to
the large direct spin Hall effect, have been regarded as potential materials
for a spin-current injector. Those materials, however, are not promising as a
spin-current detector based on inverse spin Hall effect. Their spin Hall
resistivity rho_SH, representing the performance as a detector, is not large
enough mainly due to their low charge resistivity. Here we demonstrate that
heavy transition metal oxides can overcome such limitations inherent to
metal-based spintronics materials. A binary 5d transition metal oxide IrO2,
owing to its large resistivity as well as a large spin-orbit coupling
associated with 5d character of conduction electrons, was found to show a
gigantic rho_SH ~ 38 microohm cm at room temperature, one order of magnitude
larger than those of noble metals and Cu-based alloys and even comparable to
those of atomic layer thin film of W and Ta.",1307.2121v1
2014-07-15,Classification of spin liquids on the square lattice with strong spin-orbit coupling,"Spin liquids represent exotic types of quantum matter that evade conventional
symmetry-breaking order even at zero temperature. Exhaustive classifications of
spin liquids have been carried out in several systems, particularly in the
presence of full SU(2) spin-rotation symmetry. Real magnetic compounds,
however, generically break SU(2) spin symmetry as a result of spin-orbit
coupling - which in many materials provides an `order one' effect. We
generalize previous works by using the projective symmetry group method to
classify $Z_2$ spin liquids on the square lattice when SU(2) spin symmetry is
maximally lifted. We find that, counterintuitively, the lifting of spin
symmetry actually results in vastly more spin liquid phases compared to
SU(2)-invariant systems. A generic feature of the SU(2)-broken case is that the
spinons naturally undergo $p+ip$ pairing; consequently, many of these $Z_2$
spin liquids feature a topologically nontrivial spinon band structure
supporting gapless Majorana edge states. We study in detail several spin-liquid
phases with varying numbers of gapless edge states and discuss their
topological protection. The edge states are often protected by a combination of
time reversal and lattice symmetries and hence resemble recently proposed
topological crystalline superconductors.",1407.4124v1
2016-11-10,Spin-charge coupled dynamics driven by a time-dependent magnetization,"The spin-charge coupled dynamics in a thin, magnetized metallic system are
investigated. The effective driving force acting on the charge carriers is
generated by a dynamical magnetic texture, which can be induced, e.g., by a
magnetic material in contact with a normal-metal system. We consider a general
inversion-asymmetric substrate/normal-metal/magnet structure, which, by
specifying the precise nature of each layer, can mimick various experimentally
employed setups. Inversion symmetry breaking gives rise to an effective Rashba
spin-orbit interaction. We derive general spin-charge kinetic equations which
show that such spin-orbit interaction, together with anisotropic Elliott-Yafet
spin relaxation, yields significant corrections to the magnetization-induced
dynamics. In particular, we present a consistent treatment of the spin density
and spin current contributions to the equations of motion, inter alia
identifying a novel term in the effective force which appears due to a spin
current polarized parallel to the magnetization. This ""inverse spin filter""
contribution depends markedly on the parameter which describes the anisotropy
in spin relaxation. To further highlight the physical meaning of the different
contributions, the spin pumping configuration of typical experimental setups is
analyzed in detail. In the two-dimensional limit the build-up of a DC voltage
is dominated by the spin galvanic (inverse Edelstein) effect. A measuring
scheme that could isolate this contribution is discussed.",1611.03378v3
2019-07-26,Nonlocal magnetolectric effects in diffusive conductors with spatially inhomogeneous spin-orbit coupling,"We present a theoretical study of nonlocal magnetoelectric effects in
diffusive hybrid structures with an intrinsic linear-in-momentum spin-orbit
coupling (SOC) which is assumed to be spatially inhomogeneous. Our analysis is
based on the SU(2)-covariant drift-diffusion equations from which we derive the
BC at hybrid interfaces. Within this formulation, the spin current is
covariantly conserved when the spin relaxation is only due to the intrinsic
SOC. This conservation leads to the absence of spin Hall (SH) currents in
homogeneous systems. We also consider extrinsic sources of relaxation (ESR), as
magnetic impurities, which break the covariant spin conservation, and may lead
to SH currents. We apply our model to describe nonlocal transport in a system
with an interface separating two regions: one normal region without intrinsic
SOC and one with a Rashba SOC. We first explore the inverse spin-galvanic
effect, i.e., a spin polarization induced by an electric field. We demonstrate
how the spatial behavior of such spin density depends on both, the direction of
the electric field and the strength of the ESR rate. We also study the
spin-to-charge conversion, and compute the charge current and the distribution
of electrochemical potential in the Rashba region induced by a spin current
injected into the normal region. In systems with an inhomogeneous SOC varying
in one spatial direction, we find an interesting nonlocal reciprocity between
the spin density induced by a charge current at a given point in space, and the
spatially integrated current induced by a spin density injected at the same
point.",1907.11688v2
2021-03-16,Large Spin-to-Charge Conversion in Ultrathin Gold-Silicon Multilayers,"Investigation of the spin Hall effect in gold has triggered increasing
interest over the past decade, since gold combines the properties of a large
bulk spin diffusion length and strong interfacial spin-orbit coupling. However,
discrepancies between the values of the spin Hall angle of gold reported in the
literature have brought into question the microscopic origin of the spin Hall
effect in Au. Here, we investigate the thickness dependence of the spin-charge
conversion efficiency in single Au films and ultrathin Au/Si multilayers by
non-local transport and spin-torque ferromagnetic resonance measurements. We
show that the spin-charge conversion efficiency is strongly enhanced in
ultrathin Au/Si multilayers, reaching exceedingly large values of 0.99 +/- 0.34
when the thickness of the individual Au layers is scaled down to 2 nm. These
findings reveal the coexistence of a strong interfacial spin-orbit coupling
effect which becomes dominant in ultrathin Au, and bulk spin Hall effect with a
relatively low bulk spin Hall angle of 0.012 +/- 0.005. Our experimental
results suggest the key role of the Rashba-Edelstein effect in the
spin-to-charge conversion in ultrathin Au.",2103.08876v1
2023-07-24,The Spin Point Groups and their Representations,"The spin point groups are finite groups whose elements act on both real space
and spin space. Among these groups are the magnetic point groups in the case
where the real and spin space operations are locked to one another. The
magnetic point groups are central to magnetic crystallography for strong
spin-orbit coupled systems and the spin point groups generalize these to the
intermediate and weak spin-orbit coupled cases. The spin point groups were
introduced in the 1960's and enumerated shortly thereafter. In this paper, we
complete the theory of spin point groups by presenting an account of these
groups and their representation theory. Our main findings are that the
so-called nontrivial spin point groups (numbering 598 groups) have co-irreps
corresponding exactly to the (co-)irreps of regular or black and white groups
and we tabulate this correspondence for each nontrivial group. However a total
spin group, comprising the product of a nontrivial group and a spin-only group,
has new co-irreps in cases where there is continuous rotational freedom. We
provide explicit co-irrep tables for all these instances. We also discuss new
forms of spin-only group extending the Litvin-Opechowski classes. To exhibit
the usefulness of these groups to physically relevant problems we discuss a
number of examples from electronic band structures of altermagnets to magnons.",2307.12784v2
2005-10-27,Spin Decay in a Quantum Dot Coupled to a Quantum Point Contact,"We consider a mechanism of spin decay for an electron spin in a quantum dot
due to coupling to a nearby quantum point contact (QPC) with and without an
applied bias voltage. The coupling of spin to charge is induced by the
spin-orbit interaction in the presence of a magnetic field. We perform a
microscopic calculation of the effective Hamiltonian coupling constants to
obtain the QPC-induced spin relaxation and decoherence rates in a realistic
system. This rate is shown to be proportional to the shot noise of the QPC in
the regime of large bias voltage and scales as $a^{-6}$ where $a$ is the
distance between the quantum dot and the QPC. We find that, for some specific
orientations of the setup with respect to the crystallographic axes, the
QPC-induced spin relaxation and decoherence rates vanish, while the charge
sensitivity of the QPC is not changed. This result can be used in experiments
to minimize QPC-induced spin decay in read-out schemes.",0510758v1
2017-12-13,Coupled spin and electron-phonon dynamics at the relativistic Tl/Si(111) surface,"We investigate the role played by the electron spin and the spin-orbit
interaction on the exceptional electronphonon coupling at the Tl/Si(111)
surface. Our first-principles calculations demonstrate that the particular spin
pattern of this system dominates the whole low-energy electron-phonon physics,
which is remarkably explained by forbidden spin-spin scattering channels. In
particular, we show that the strength of the electron-phonon coupling appears
drastically weakened for surface states close to the K and K' valleys, which is
unambiguously attributed to the spin polarization through the associated
modulation due to the spinor overlaps. However, close to the {\Gamma} point,
the particular spin pattern in this area is less effective in damping the
electron-phonon matrix elements, and the result is an exceptional strength of
electron-phonon coupling parameter {\lambda} ~ 1.4. These results are
rationalized by a simple model for the electron-phonon matrix elements
including the spinor terms.",1712.04868v3
2022-03-30,Angular momentum transfer via relativistic spin-lattice coupling from first principles,"The transfer and control of angular momentum is a key aspect for spintronic
applications. Only recently, it was shown that it is possible to transfer
angular momentum from the spin system to the lattice on ultrashort time scales.
In an attempt to contribute to the understanding of angular momentum transfer
between spin and lattice degrees of freedom we present a scheme to calculate
fully-relativistic spin-lattice coupling parameters from first-principles. By
treating changes in the spin configuration and atomic positions at the same
level, closed expressions for the atomic spin-lattice coupling parameters can
be derived in a coherent manner up to any order. Analyzing the properties of
these parameters, in particular their dependence on spin-orbit coupling, we
find that even in bcc Fe the leading term for the angular momentum exchange
between the spin system and the lattice is a Dzyaloshiskii-Moriya-type
interaction, which is due to the symmetry breaking distortion of the lattice.",2203.16144v1
2024-01-20,Phonon-mediated spin transport in quantum paraelectric metals,"The concept of ferroelectricity is now often extended to include continuous
inversion symmetry-breaking transitions in various metals and doped
semiconductors. Paraelectric metals near ferroelectric quantum criticality,
which we term `quantum paraelectric metals,' typically possess soft transverse
optical phonons that have Rashba-type coupling to itinerant electrons in the
presence of spin-orbit coupling. We find through the Kubo formula calculation
that such Rashba electron-phonon coupling has a profound impact on electron
spin transport. While the spin Hall effect arising from non-trivial electronic
band structures has been studied extensively, we find here the presence of the
Rashba electron-phonon coupling can give rise to spin current, including spin
Hall current, in response to an inhomogeneous electric field even with a
completely trivial band structure. Furthermore, this spin conductivity displays
unconventional characteristics, such as quadrupolar symmetry associated with
the wave vector of the electric field and a thermal activation behavior
characterized by scaling laws dependent on the phonon frequency to temperature
ratio. These findings shed light on exotic electronic transport phenomena
originating from ferroelectric quantum criticality, highlighting the intricate
interplay of charge and spin degrees of freedom.",2401.11164v1
2014-03-31,Orbital-dependent singlet dimers and orbital-selective Peierls transitions in transition metal compounds,"We show that in transition metal compounds containing structural metal dimers
there may exist in the presence of different orbitals a special state with
partial formation of singlets by electrons on one orbital, while others are
effectively decoupled and may give e.g. long-range magnetic order or stay
paramagnetic. Similar situation can be realized in dimers spontaneously formed
at structural phase transitions, which can be called orbital-selective Peierls
transition. This can occur in case of strongly nonuniform hopping integrals for
different orbitals and small intra-atomic Hund's rule coupling JH. Yet another
consequence of this picture is that for odd number of electrons per dimer there
exist competition between double exchange mechanism of ferromagnetism, and the
formation of singlet dimer by electron on one orbital, with remaining electrons
giving a net spin of a dimer. The first case is realized for strong Hund's rule
coupling, typical for 3d compounds, whereas the second is more plausible for
4d-5d compounds. We discuss some implications of these phenomena, and consider
examples of real systems, in which orbital-selective phase seems to be
realized.",1403.7871v2
2016-08-18,Non-local correlations in the orbital selective Mott phase of a one dimensional multi-orbital Hubbard model,"We study non-local correlations in a three-orbital Hubbard model defined on
an extended one-dimensional chain using determinant quantum Monte Carlo and
density matrix renormalization group methods. We focus on a parameter with
robust Hund's coupling, which produces an orbital selective Mott phase (OSMP)
at intermediate values of the Hubbard U, as well as an orbitally ordered
ferromagnetic insulating state at stronger coupling. An examination of the
orbital and spin-correlation functions indicates that the orbital ordering
occurs before the onset of magnetic correlations in this parameter regime as a
function of temperature. In the OSMP, we find that the self-energy for the
itinerant electrons is momentum dependent, indicating a degree of non-local
correlations while the localized electrons have largely momentum independent
self-energies. These non-local correlations also produce relative shifts of the
hole-like and electron-like bands within our model. The overall momentum
dependence of these quantities is strongly suppressed in the orbitally-ordered
insulating phase.",1608.05297v1
2023-08-18,Correlation Effects and Concomitant Two-Orbital $s_\pm$-Wave Superconductivity in La$_3$Ni$_2$O$_7$ under High Pressure,"Possible high-$T_c$ superconductivity (SC) has been found experimentally in
the bilayer material La$_3$Ni$_2$O$_7$ under high pressure recently, in which
the Ni-$3d_{3z^2-r^2}$ and $3d_{x^2-y^2}$ orbitals are expected to play a key
role in the electronic structure and the SC. Here we study the two-orbital
electron correlations and the nature of the SC using the bilayer two-orbital
Hubbard model downfolded from the band structure of La3Ni2O7 in the framework
of the dynamical mean-field theory. We find that each of the two orbitals forms
$s_\pm$-wave SC pairing. Because of the nonlocal inter-orbital hoppings, the
two-orbital SCs are concomitant and they transition to Mott insulating states
simultaneously when tuning the system to half filling. The Hund's coupling
induced local inter-orbital spin coupling enhances the electron correlations
pronouncedly and is crucial to the SC.",2308.09698v1
2009-01-28,Variational Monte Carlo study of ferromagnetism in the two-orbital Hubbard model on a square lattice,"To understand effects of orbital degeneracy on magnetism, in particular
effects of Hund's rule coupling, we study the two-orbital Hubbard model on a
square lattice by a variational Monte Carlo method. As a variational wave
function, we consider a Gutzwiller projected wave function for a staggered spin
and/or orbital ordered state. We find a ferromagnetic phase with staggered
orbital order around quarter-filling, i.e., electron number n=1 per site, and
an antiferromagnetic phase without orbital order around half-filling n=2. In
addition, we find that another ferromagnetic phase without orbital order
realizes in a wide filling region for large Hund's rule coupling. These two
ferromagnetic states are metallic except for quarter filling. We show that
orbital degeneracy and strong correlation effects stabilize the ferromagnetic
states.",0901.4415v1
2013-11-26,Spin-orbit coupling and chaotic rotation for coorbital bodies in quasi-circular orbits,"Coorbital bodies are observed around the Sun sharing their orbits with the
planets, but also in some pairs of satellites around Saturn. The existence of
coorbital planets around other stars has also been proposed. For close-in
planets and satellites, the rotation slowly evolves due to dissipative tidal
effects until some kind of equilibrium is reached. When the orbits are nearly
circular, the rotation period is believed to always end synchronous with the
orbital period. Here we demonstrate that for coorbital bodies in quasi-circular
orbits, stable non-synchronous rotation is possible for a wide range of mass
ratios and body shapes. We show the existence of an entirely new family of
spin-orbit resonances at the frequencies $n\pm k\nu/2$, where $n$ is the
orbital mean motion, $\nu$ the orbital libration frequency, and $k$ an integer.
In addition, when the natural rotational libration frequency due to the axial
asymmetry, $\sigma$, has the same magnitude as $\nu$, the rotation becomes
chaotic. Saturn coorbital satellites are synchronous since $\nu\ll\sigma$, but
coorbital exoplanets may present non-synchronous or chaotic rotation. Our
results prove that the spin dynamics of a body cannot be dissociated from its
orbital environment. We further anticipate that a similar mechanism may affect
the rotation of bodies in any mean-motion resonance.",1311.6750v2
1993-03-23,Relativistic Dynamics of Spin in Strong External Fields,"The dynamics of relativistic spinning particles in strong external
electromagnetic or gravitational fields is discussed. Spin-orbit coupling is
shown to affect such relativistic phenomena as time-dilation and perihelion
shift. Possible applications include muon decay in a magnetic field and the
dynamics of neutron stars in binary systems.",9303124v1
1995-08-02,Spin-dependent resonant tunneling through semimetallic ErAs quantum wells,"Resonant tunneling through semimetallic ErAs quantum wells embedded in GaAs
structures with AlAs barriers was recently found to exhibit an intriguing
behavior in magnetic fields which is explained in terms of tunneling selection
rules and the spin-polarized band structure including spin-orbit coupling.",9508003v1
2010-01-11,The quantum spin Hall effect and topological insulators,"In topological insulators, spin-orbit coupling and time-reversal symmetry
combine to form a novel state of matter predicted to have exotic physical
properties.",1001.1602v1
1999-10-07,Spin interactions and switching in vertically tunnel-coupled quantum dots,"We determine the spin exchange coupling J between two electrons located in
two vertically tunnel-coupled quantum dots, and its variation when magnetic (B)
and electric (E) fields (both in-plane and perpendicular) are applied. We
predict a strong decrease of J as the in-plane B field is increased, mainly due
to orbital compression. Combined with the Zeeman splitting, this leads to a
singlet-triplet crossing, which can be observed as a pronounced jump in the
magnetization at in-plane fields of a few Tesla, and perpendicular fields of
the order of 10 Tesla for typical self-assembled dots. We use harmonic
potentials to model the confining of electrons, and calculate the exchange J
using the Heitler-London and Hund-Mulliken technique, including the long-range
Coulomb interaction. With our results we provide experimental criteria for the
distinction of singlet and triplet states and therefore for microscopic spin
measurements. In the case where dots of different sizes are coupled, we present
a simple method to switch on and off the spin coupling with exponential
sensitivity using an in-plane electric field. Switching the spin coupling is
essential for quantum computation using electronic spins as qubits.",9910105v1
2018-07-15,K-matrix formulation of two-particle scattering in a wave guide in the presence of one-dimensional spin-orbit coupling,"The creation of artificial gauge fields in neutral ultracold atom systems has
opened the possibility to study the effects of spin-orbit coupling terms in
clean environments. This work considers the multi-channel scattering properties
of two atoms confined by a wave guide in the presence of spin-orbit coupling
terms within a K-matrix scattering framework. The tunability of resonances,
induced by the interplay of the external wave guide geometry, the interactions,
and the spin-orbit coupling terms, is demonstrated. Our results for the
K-matrix elements as well as partial and total reflection coefficients for two
identical fermions interacting through a finite-range interaction potential in
the singlet channel only are compared with those obtained for a strictly
one-dimensional effective low- energy Hamiltonian, which uses the effective
coupling constant derived in Zhang et al. [Scientific Reports 4, 1 (2014)] and
Zhang et al. [Phys. Rev. A 88, 053605 (2013)] as input. In the regime where the
effective Hamiltonian is applicable, good agreement is obtained, provided the
energy- dependence of the coupling constant is accounted for. Our approach
naturally describes the energy regime in which the bands associated with
excited transverse modes lie below a subset of the bands associated with the
lowest transverse modes. The threshold behavior is discussed and scattering
observables are linked to bound state properties.",1807.05564v2
2003-09-19,Spin-orbit origin of large reduction of the effective moment in Na2V3O7*,"We have shown that the observed large reduction of the effective moment and
the drastic violation of the Curie-Weiss law in Na2V3O7 (Phys. Rev. Lett. 90
(2003) 167202) is caused by conventional crystal-field interactions and the
intra-atomic spin-orbit coupling of the V4+ ion. The fine discrete electronic
structure of the 3d1 configuration with the weakly-magnetic Kramers-doublet
ground state, caused by the large orbital moment, is the reason for anomalous
properties of Na2V3O7. Moreover, according to the Quantum Atomistic Solid-State
Theory (QUASST) Na2V3O7 is expected to exhibit pronounced heavy-fermion
phenomena at low temperatures.
  PACS: 71.70.E, 75.10.D
  Keywords: crystal-field interactions, spin-orbit coupling, orbital moment,
Na2V3O7",0309460v2
2005-03-16,The atomic-start description of NiO,"We have calculated magnetic properties and the electronic structure of NiO
both in the paramagnetic and in magnetically-ordered state as well as
zero-temperature properties and thermodynamics within the strongly-correlated
crystal-field approach. It is in agreement with a Mott's suggestion that NiO is
an insulator due to strong electron correlations. We have quantified
crystal-field, spin-orbit and magnetic interactions of the Ni2+ ion in NiO. We
have obtained that E_dd >> E_CF(=2.0 eV) >> E_{s-o}(=0.29 eV) > E_mag(=0.07
eV). The orbital moment of 0.54 mu_B amounts at 0 K, in the
magnetically-ordered state, to about 20% of the total moment (2.53 mu_B). Our
studies indicate that it is the highest time to ""unquench"" orbital magnetic
moment in 3d solid-state physics and the necessity to take always into account
strong intra-atomic correlations among d electrons and the intra-atomic
spin-orbit coupling.
  Pacs: 75.25.+z, 75.10.Dg
  Keywords: Crystalline Electric Field, 3d oxides, magnetism, spin-orbit
coupling NiO",0503407v1
2006-01-16,Fermi arc in doped high-Tc cuprates,"We propose a $d$-density wave induced by the spin-orbit coupling in the CuO
plane. The spectral function of high-temperature superconductors in the under
doped and lightly doped regions is calculated in order to explain the Fermi arc
spectra observed recently by angle-resolved photoemission spectroscopy. We take
into account the tilting of CuO octahedra as well as the on-site
Coulombrepulsive interaction; the tilted octahedra induce the staggered
transfer integral between $p_{x,y}$ orbitals and Cu $t_{2g}$ orbitals, and
bring about nontrivial effects of spin-orbit coupling for the $d$ electrons in
the CuO plane. The spectral weight shows a peak at around ($\pi/2$,$\pi/2$) for
light doping and extends around this point forming an arc as the carrier
density increases, where the spectra for light doping grow continuously to be
the spectra in the optimally doped region. This behavior significantly agrees
with that of the angle-resolved photoemissionspectroscopy spectra. Furthermore,
the spin-orbit term and staggered transfer effectively induce a flux state, a
pseudo-gap with time-reversal symmetry breaking. We have a nodal metallic state
in the light-doping case since the pseudogap has a $d_{x^2-y^2}$ symmetry.",0601329v1
2008-10-14,Mott insulating state in a quarter-filled two-orbital Hubbard chain with different bandwidths,"We investigate the ground-state properties of the one-dimensional two-band
Hubbard model with different bandwidths. The density-matrix renormalization
group method is applied to calculate the averaged electron occupancies $n$ as a
function of the chemical potential $\mu$. Both at quarter and half fillings,
""charge plateaux"" appear in the $n$-$\mu$ plot, where $d\mu/dn$ diverges and
the Mott insulating states are realized. To see how the orbital polarization in
the one-quarter charge plateau develops, we apply the second-order perturbation
theory from the strong-coupling limit at quarter filling. The resultant
Kugel-Khomskii spin-orbital model includes a $magnetic$ field coupled to
orbital pseudo-spins. This field originates from the discrepancy between the
two bandwidths and leads to a finite orbital pseudo-spin magnetization.",0810.2539v1
2009-11-30,Antiferromagnetic and structural transitions in the superoxide KO2 from first principles: A 2p-electron system with spin-orbital-lattice coupling,"KO2 exhibits concomitant antiferromagnetic (AFM) and structural transitions,
both of which originate from the open-shell 2p electrons of O$_{2}^{-}$
molecules. The structural transition is accompanied by the coherent tilting of
O$_{2}^{-}$ molecular axes. The interplay among the spin-orbital-lattice
degrees of freedom in KO2 is investigated by employing the first-principles
electronic structure theory and the kinetic-exchange interaction scheme. We
have shown that the insulating nature of the high symmetry phase of KO2 at high
temperature (T) arises from the combined effect of the spin-orbit coupling and
the strong Coulomb correlation of O 2p electrons. In contrast, for the low
symmetry phase of KO2 at low T with the tilted O$_{2}^{-}$ molecular axes, the
band gap and the orbital ordering are driven by the combined effects of the
crystal-field and the strong Coulomb correlation. We have verified that the
emergence of the O 2p ferro-orbital ordering is essential to achieve the
observed AFM structure for KO2.",0911.5677v2
2010-09-02,Spin and Orbital Order of the Vanadium Spinel MgV2O4,"We present a unique study of the frustrated spinel MgV2O4 which possesses
highly coupled spin, lattice and orbital degrees of freedom. Using large
single-crystal and powder samples, we find a distortion from spinel at room
temperature (space group F-43m) which allows for a greater trigonal distortion
of the VO6 octahedra and a low temperature space group (I-4m2) that maintains
the mirror plane symmetry. The magnetic structure that develops below 42 K
consists of antiferromagnetic chains with a strongly reduced moment while
inelastic neutron scattering reveals one-dimensional behavior and a single band
of excitations. The implications of these results are discussed in terms of
various orbital ordering scenarios. We conclude that although spin-orbit
coupling must be significant to maintain the mirror plane symmetry, the
trigonal distortion is large enough to mix the 3d levels leading to a wave
function of mixed real and complex orbitals.",1009.0429v2
2012-09-17,Spin-Fluctuation-Driven Orbital Nematic Order in Ru-Oxides: Self-Consistent Vertex Correction Analysis for Two-Orbital Model,"To reveal the origin of the ""nematic electronic fluid phase"" in
Sr$_3$Ru$_2$O$_7$, we apply the self-consistent vertex correction analysis to
the ($d_{xz},d_{yz}$)-orbital Hubbard model. It is found that the
Aslamazov-Larkin type vertex correction causes the strong coupling between spin
and orbital fluctuations, which corresponds to the Kugel-Khomskii spin-orbital
coupling in the local picture. Due to this mechanism, orbital nematic order
with $C_2$ symmetry is induced by the magnetic quantum criticality in
multiorbital systems, while this mechanism is ignored in the
random-phase-approximation. The present study naturally explains the intimate
relation between the magnetic quantum criticality and the nematic state in
Sr$_3$Ru$_2$O$_7$ and Fe-based superconductors.",1209.3629v2
2015-08-06,Molecular orbital polarization in Na2Ti2Sb2O: microscopic route to metal-metal transition without spontaneous symmetry breaking,"Ordered phases such as charge- and spin-density wave state accompany either
full or partial gapping of Fermi surface (FS) leading a metal-insulator or
metal-metal transition (MMT). However, there are examples of MMT without any
signatures of symmetry breaking. One example is Na$_2$Ti$_2$Sb$_2$O, where a
partial gapping of FS is observed but a density wave ordering has not been
found. Here we propose a microscopic mechanism of such a MMT which occurs due
to a momentum dependent spin-orbit coupled molecular orbital polarization.
Since a molecular $d$ orbital polarization is present due to a small spin-orbit
coupling of Ti, there is no spontaneous symmetry breaking involved. However, a
sharp increase of polarization happens above a critical electron interaction
which gaps out the $d$ orbtial FS and reduces the density of states
significantly, while the rest of FS associated with Sb $p$ orbtials is almost
intact across MMT. Experimental implications to test our proposal and
applications to other systems are also discussed.",1508.01519v1
2016-03-28,Orbital-FFLO state in a chain of high spin ultracold atoms,"Recent experiments with Yb-173 and Sr-87 isotopes provide new possibilities
to study high spin two-orbital systems. Within these experiments part of the
atoms are excited to a higher energy metastable electronic state mimicking an
additional internal (orbital) degree of freedom. The interaction between the
atoms depends on the orbital states, therefore four different scattering
channels can be identified in the system characterized by four independent
couplings. When the system is confined into a one-dimensional chain the
scattering lengths can be tuned by changing the transverse confinement, and
driven through four resonances. Using the new available experimental data of
the scattering lengths we analyze the phase diagram of the one-dimensional
system as the couplings are tuned via transverse confinement, and the
populations of the two orbital states are changed. We found that three orders
compete showing power law decay: a state with dominant density wave
fluctuations, another one with spin density fluctuations, and a third one
characterized by exotic Fulde-Ferrell-Larkin-Ovchinnikov-like pairs consisting
one atom in the electronic ground state and one in the excited state. We also
show that sufficiently close to the resonances the compressibility of the
system starts to diverge indicating that the emerging order is unstable and
collapses to a phase separated state with a first order phase transition.",1603.08505v1
2018-03-10,Optical control of competing exchange interactions and coherent spin-charge coupling in two-orbital Mott insulators,"In order to have a better understanding of ultrafast electrical control of
exchange interactions in multi-orbital systems, we study a two-orbital Hubbard
model at half filling under the action of a time-periodic electric field. Using
suitable projection operators and a generalized time-dependent canonical
transformation, we derive an effective Hamiltonian which describes two
different regimes. First, for a wide range of non-resonant frequencies, we find
a change of the bilinear Heisenberg exchange $J_{\textrm{ex}}$ that is
analogous to the single-orbital case. Moreover we demonstrate that also the
additional biquadratic exchange interaction $B_{\textrm{ex}}$ can be enhanced,
reduced and even change sign depending on the electric field. Second, for
special driving frequencies, we demonstrate a novel spin-charge coupling
phenomenon enabling coherent transfer between spin and charge degrees of
freedom of doubly ionized states. These results are confirmed by an exact
time-evolution of the full two-orbital Mott-Hubbard Hamiltonian.",1803.03796v2
2019-03-12,Time-reversal symmetry breaking superconductivity in hole-doped monolayer MoS$_{2}$,"We investigate the nature of the time-reversal breaking pairing state in the
hole-doped monolayer MoS$_{2}$ on the basis of the realistic three-orbital
attractive Hubbard-like model with the atomic spin-orbit coupling. Due to the
multi-band features arising from the Mo $d$ orbitals in the noncentrosymmetric
crystal structure, the Lifshitz transition takes place upon hole doping. Across
the Lifshitz transition point, the sign of the relative phase between the
Cooper-pair components drastically changes, leading to the emergence of the
time-reversal breaking phase with complex gap functions. It is shown that this
intriguing pairing state is characterized by the finite momentum-space
distributions of the orbital and spin angular momentum with three-fold
rotational symmetry on the Fermi-surface pockets around K and K$'$ points. The
present mechanism for the time-reversal breaking superconductivity can
ubiquitously be applied to spin-orbit-coupled metals in noncentrosymmetric
crystal structures.",1903.04830v2
2014-02-05,Signatures of Rashba Spin-Orbit Interaction in Charge and Spin Properties of Quantum Hall Systems,"We study the local equilibrium properties of two-dimensional electron gases
at high magnetic fields in the presence of random smooth electrostatic
disorder, Rashba spin-orbit coupling, and the Zeeman interaction. Using a
systematic magnetic length ($l_B$) expansion within a Green's function
framework we derive quantum functionals for the local spin-resolved particle
and current densities which can be useful for future studies combining disorder
and mean-field electron-electron interaction in the quantum Hall regime. We
point out that the spin polarization presents a peculiar spatial dependence
which can be used to determine the strength of the Rashba coupling by local
probes. The spatial structure of the current density, consisting of both
compressible and incompressible contributions, also essentially reflects the
effects of Rashba spin-orbit interaction on the energy spectrum. We show that
in the semiclassical limit $l_B \rightarrow 0$ the local Hall conductivity
remains, however, still quantized in units of $e^2/h$ for any finite strength
of the spin-orbit interaction. In contrast, it becomes half-integer quantized
when the latter is infinite, a situation which corresponds to a disordered
topological insulator surface consisting of a single Dirac cone. Finally, we
argue how to define at high magnetic fields a spin Hall conductivity related to
a dissipationless angular momentum flow, which is characterized by a sequence
of plateaus as a function of the inverse magnetic field (thus free of
resonances).",1402.1090v2
2018-12-01,Rectification in Spin-Orbit Materials Using Low Energy Barrier Magnets,"The coupling of spin-orbit materials to high energy barrier ($\sim$40-60
$k_BT$) nano-magnets has attracted growing interest for exciting new physics
and various spintronic applications. We predict that a coupling between the
spin-momentum locking (SML) observed in spin-orbit materials and low-energy
barrier magnets (LBM) should exhibit a unique multi-terminal rectification for
arbitrarily small amplitude channel currents. The basic idea is to measure the
charge current induced spin accumulation in the SML channel in the form of a
magnetization dependent voltage using an LBM, either with an in-plane or
perpendicular anisotropy (IMA or PMA). The LBM feels an instantaneous
spin-orbit torque due to the accumulated spins in the channel which causes the
average magnetization to follow the current, leading to the non-linear
rectification. We discuss the frequency band of this multi-terminal
rectification which can be understood in terms of the angular momentum
conservation in the LBM. For a fixed spin-current from the SML channel, the
frequency band is same for LBMs with IMA and PMA, as long as they have the same
total magnetic moment in a given volume. The proposed all-metallic structure
could find application as highly sensitive passive rf detectors and as energy
harvesters from weak ambient sources where standard technologies may not
operate.",1812.00286v2
2019-08-29,Gate-tunable Rashba spin-orbit coupling and spin polarization at diluted oxide interfaces,"Diluted oxide interface of LaAl1-xMnxO/SrTiO3 (LAMO/STO) provides a new way
of tuning the ground states of the interface between the two band insulators of
LAO and STO from metallic/superconducting to highly insulating. Increasing the
Mn doping level (x) leads to a delicate control of the carrier density as well
as a raise in the electron mobility and spin polarization. Herein, we
demonstrate a tunable Rashba spin-orbit coupling (SOC) and spin polarization of
LAMO/STO (0.2 <= x <= 0.3) by applying a back gate. The presence of SOC causes
the splitting of energy band into two branches by a spin splitting energy. The
maximum spin splitting energy depends on the Mn doping and decreases with the
increasing Mn content and then vanishes at x = 0.3. The carrier density
dependence of the spin splitting energy for different compositions shows a
dome-shaped behavior with a maximum at different normalized carrier density.
These findings have not yet been observed in LAO/STO interfaces. A fully
back-gate-tunable spin-polarized 2DEL is observed at the interface with x = 0.3
where only dxy orbits are populated (5.3E12 cm-2 <= ns <= 1.0E13 cm-2). The
present results shed light on unexplored territory in SOC at STO-base oxide
heterostructures and make LAMO/STO an intriguing platform for spin-related
phenomena in 3d-electron systems.",1908.11167v1
2017-08-15,Electron g-factor of valley states in realistic silicon quantum dots,"We theoretically model the spin-orbit interaction in silicon quantum dot
devices, relevant for quantum computation and spintronics. Our model is based
on a modified effective mass approach with spin-valley boundary conditions,
derived from the interface symmetry under presence of perpendicular to the
interface electric field. The g-factor renormalization in the two lowest valley
states is explained by the interface-induced spin-orbit 2D (3D) interaction,
favoring intervalley spin-flip tunneling over intravalley processes. We show
that the quantum dot level structure makes only negligible higher order effects
to the g-factor. We calculate the g-factor as a function of the magnetic field
direction, which is sensitive to the interface symmetry. We identify spin-qubit
dephasing sweet spots at certain directions of the magnetic field, where the
g-factor renormalization is zeroed: these include perpendicular to the
interface magnetic field, and also in-plain directions, the latter being
defined by the interface-induced spin-orbit constants. The g-factor dependence
on electric field opens the possibility for fast all-electric manipulation of
an encoded, few electron spin-qubit, without the need of a nanomagnet or a
nuclear spin-background. Our approach of an almost fully analytic theory allows
for a deeper physical understanding of the importance of spin-orbit coupling to
silicon spin qubits.",1708.04555v2
2019-09-16,"Test black holes, scattering amplitudes and perturbations of Kerr spacetime","It has been suggested that amplitudes for quantum higher-spin massive
particles exchanging gravitons lead, via a classical limit, to results for
scattering of spinning black holes in general relativity, when the massive
particles are in a certain way minimally coupled to gravity. Such limits of
such amplitudes suggest, at least at lower orders in spin, up to second order
in the gravitational constant $G$, that the classical aligned-spin scattering
function for an arbitrary-mass-ratio two-spinning-black-hole system can be
obtained by a simple kinematical mapping from that for a spinning test black
hole scattering off a stationary background Kerr black hole. Here we test these
suggestions, at orders beyond the reach of the post-Newtonian and
post-Minkowskian results used in their initial partial verifications, by
confronting them with results from general-relativistic ""self-force""
calculations of the linear perturbations of a Kerr spacetime sourced by a small
orbiting body, here considering only results for circular orbits in the
equatorial plane. We translate between scattering and circular-orbit results by
assuming the existence of a local-in-time canonical Hamiltonian governing the
conservative dynamics of generic (bound and unbound) aligned-spin orbits, while
employing the associated first law of spinning binary mechanics. We confirm,
through linear order in the mass ratio, some previous conjectures which would
begin to fill in the spin-dependent parts of the conservative dynamics for
arbitrary-mass-ratio aligned-spin binary black holes at the fourth-and-a-half
and fifth post-Newtonian orders.",1909.07361v1
2011-08-01,Entangled spin-orbital phases in the bilayer Kugel-Khomskii model,"We derive the Kugel-Khomskii spin-orbital (SO) model for a bilayer and
investigate its phase diagram depending on Hund's exchange $J_H$ and the $e_g$
orbital splitting $E_z$. In the (classical) mean-field approach with on-site
spin $<S_i^z>$ and orbital $<\tau_i^z>$ order parameters and factorized
spin-and-orbital degrees of freedom, we demonstrate a competition between the
phases with either $G$-type or $A$-type antiferromagnetic (AF) or ferromagnetic
long-range order. Next we develop a Bethe-Peierls-Weiss method with a Lanczos
exact diagonalization of a cube coupled to its neighbors in $ab$ planes by the
mean-field terms --- this approach captures quantum fluctuations on the bonds
which decide about the nature of disordered phases in the highly frustrated
regime near the orbital degeneracy. We show that the long-range spin order is
unstable in a large part of the phase diagram which contains then six phases,
including also the valence-bond phase with interlayer spin singlets stabilized
by holes in $3z^2-r^2$ orbitals (VB$z$ phase), a disordered plaquette
valence-bond (PVB) phase and a crossover phase between the VB$z$ and the
$A$-type AF phase. When on-site SO coupling is also included by the
$<S_i^z\tau_i^z>$ order parameter, we discover in addition two entangled phases
which compete with $A$-type AF phase and another crossover phase in between the
$G$-AF phase with occupied $x^2-y^2$ orbitals and the PVB phase. Thus, the
present bilayer model provides an example of SO entanglement which generates
novel disordered phases. We analyze the order parameters in all phases and
identify situations where SO entanglement is crucial and factorization of the
spins and orbitals leads to qualitatively incorrect results. We point out that
SO entanglement may play a role in a bilayer fluoride K$_3$Cu$_2$F$_7$ which is
a realization of the VB$z$ phase.",1108.0279v1
2004-05-21,Spintronics: Fundamentals and applications,"Spintronics, or spin electronics, involves the study of active control and
manipulation of spin degrees of freedom in solid-state systems. This article
reviews the current status of this subject, including both recent advances and
well-established results. The primary focus is on the basic physical principles
underlying the generation of carrier spin polarization, spin dynamics, and
spin-polarized transport in semiconductors and metals. Spin transport differs
from charge transport in that spin is a nonconserved quantity in solids due to
spin-orbit and hyperfine coupling. The authors discuss in detail spin
decoherence mechanisms in metals and semiconductors. Various theories of spin
injection and spin-polarized transport are applied to hybrid structures
relevant to spin-based devices and fundamental studies of materials properties.
Experimental work is reviewed with the emphasis on projected applications, in
which external electric and magnetic fields and illumination by light will be
used to control spin and charge dynamics to create new functionalities not
feasible or ineffective with conventional electronics.",0405528v1
2005-07-10,Coulomb corrections to the extrinsic spin-Hall effect of a two-dimensional electron gas,"We develop the microscopic theory of the extrinsic spin Hall conductivity of
a two-dimensional electron gas, including skew-scattering, side-jump, and
Coulomb interaction effects. We find that while the spin-Hall conductivity
connected with the side-jump is independent of the strength of
electron-electron interactions, the skew-scattering term is reduced by the
spin-Coulomb drag, so the total spin current and the total spin-Hall
conductivity are reduced for typical experimental mobilities. Further, we
predict that in paramagnetic systems the spin-Coulomb drag reduces the spin
accumulations in two different ways: (i) directly through the reduction of the
skew-scattering contribution (ii) indirectly through the reduction of the spin
diffusion length. Explicit expressions for the various contributions to the
spin Hall conductivity are obtained using an exactly solvable model of the
skew-scattering.",0507228v4
2006-10-16,Spin-Hall interface resistance in terms of Landauer type spin dipoles,"We considered the nonequlibrium spin dipoles induced around spin independent
elastic scatterers by the intrinsic spin-Hall effect associated with the Rashba
spin-orbit coupling. The normal to 2DEG spin polarization has been calculated
in the diffusion range around the scatterer. We found that although around each
impurity this polarization is finite, the corresponding macroscopic spin
density, obtained via averaging of individual spin dipole distributions over
impurity positions is zero in the bulk. At the same time, the spin density is
finite near the boundary of 2DEG, except for a special case of a hard wall
boundary. The boundary value of the spin polarization can be associated with
the interface spin-Hall resistance determining the additional energy
dissipation due to spin accumulation.",0610423v2
2013-05-18,Spin force and the generation of sustained spin current in time-dependent Rashba and Dresselhauss systems,"The generation of spin current and spin polarization in a 2DEG structure is
studied in the presence of Dresselhaus and Rashba spin-orbit couplings (SOC),
the strength of the latter being modulated in time by an ac gate voltage. By
means of the non-Abelian gauge field approach, we established the relation
between the Lorentz spin force and the spin current in the SOC system, and
showed that the longitudinal component of the spin force induces a transverse
spin current. For a constant (time-invariant) Rashba system, we recover the
universal spin Hall conductivity of $\frac e{8\pi}$, derived previously via the
Berry phase and semiclassical methods. In the case of a time-dependent SOC
system, the spin current is sustained even under strong impurity scattering. We
evaluated the ac spin current generated by a time-modulated Rashba SOC in the
absence of any dc electric field. The magnitude of the spin current reaches a
maximum when the modulation frequency matches the Larmor frequency of the
electrons.",1305.4221v1
2016-03-21,Rashba semiconductor as spin Hall material: Experimental demonstration of spin pumping in wurtzite $n$-GaN:Si,"Pure spin currents in semiconductors are essential for implementation in the
next generation of spintronic elements. Heterostructures of III- nitride
semiconductors are currently employed as central building-blocks for lighting
and high-power devices. Moreover, the long relaxation times and the spin-orbit
coupling (SOC) in these materials indicate them as privileged hosts for spin
currents and related phenomena. Spin pumping is an efficient mechanism for the
inception of spin current and its conversion into charge current in
non-magnetic metals and semiconductors with Rashba SOC $via$ spin Hall effects.
We report on the generation in $n$-GaN:Si\,--\,at room temperature and through
spin pumping\,--\,of pure spin current, fundamental for the understanding of
the spin dynamics in these non-centrosymmetric Rashba systems. We find for
$n$-GaN:Si a spin Hall angle $\theta_{\mathrm{SH}}$=$3.03\times10^{-3}$,
exceeding by one order of magnitude those reported for other semiconductors,
pointing at III-nitrides as particularly efficient spin current generators.",1603.06471v1
2017-01-26,Wurtzite spin lasers,"Semiconductor lasers are strongly altered by adding spin-polarized carriers.
Such spin lasers could overcome many limitations of their conventional
(spin-unpolarized) counterparts. While the vast majority of experiments in spin
lasers employed zinc-blende semiconductors, the room temperature electrical
manipulation was first demonstrated in wurtzite GaN-based lasers. However, the
underlying theoretical description of wurtzite spin lasers is still missing. To
address this situation, focusing on (In,Ga)N-based wurtzite quantum wells, we
develop a theoretical framework in which the calculated microscopic
spin-dependent gain is combined with a simple rate equation model. A small
spin-orbit coupling in these wurtzites supports simultaneous spin polarizations
of electrons and holes, providing unexplored opportunities to control spin
lasers. For example, the gain asymmetry, as one of the key figures of merit
related to spin amplification, can change the sign by simply increasing the
carrier density. The lasing threshold reduction has a nonmonotonic depenedence
on electron spin polarization, even for a nonvanishing hole spin polarization.",1701.07793v1
2020-06-02,Spin pumping and inverse spin Hall effect in iridium oxide,"Large charge-to-spin conversion (spin Hall angle) and spin Hall conductivity
are prerequisites for development of next generation power efficient spintronic
devices. In this context, heavy metals (e.g. Pt, W etc.), topological
insulators, antiferromagnets are usually considered because they exhibit high
spin-orbit coupling (SOC). In addition to the above materials, 5d transition
metal oxide e.g. Iridium Oxide (IrO 2 ) is a potential candidate which exhibits
high SOC strength. Here we report a study of spin pumping and inverse spin Hall
effect (ISHE), via ferromagnetic resonance (FMR), in IrO 2 /CoFeB system. We
identify the individual contribution of spin pumping and other spin
rectification effects in the magnetic layer, by investigating the in-plane
angular dependence of ISHE signal. Our analysis shows significant contribution
of spin pumping effect to the ISHE signal. We show that polycrystalline IrO 2
thin film exhibits high spin Hall conductivity and spin Hall angle which are
comparable to the values of Pt.",2006.01865v2
2023-09-20,Giant interfacial spin-Hall angle from Rashba-Edelstein effect revealed by the spin-Hall Hanle processes,"The Rashba-Edelstein effect (REE), which generates interfacial spin
polarization and subsequent spin current, is a compelling spin-charge
conversion mechanism for spintronics applications, since it is not limited by
the elemental spin-orbit coupling. In this work, we demonstrate REE at
Pt/ferroelectric interfaces using the recently elucidated spin-Hall Hanle
effects (SHHE), in which a Larmor precession of spin polarization in a
diffusion process from the interface manifest as magnetoresistance and Hall
effect. We show that REE leads to a three-fold enhancement of the effective
spin Hall angle in ferroelectric interface Pt/h-LuFeO3 compared to that of Pt
/Al2O3, although the difference in the spin relaxation time is negligible.
Modeling using SHHEs involving REE as an additional source of interfacial
polarization suggests that REE can lead to an interfacial spin Hall angle
(~0.3) that is one order of magnitude larger than the bulk value of Pt. Our
results demonstrate that a ferroelectric interface can produce large
spin-charge conversion and that SHHEs are a sensitive tool for characterizing
interfacial spin transport properties.",2309.10985v1
2010-07-06,Radial Spin Helix in Two-Dimensional Electron Systems with Rashba Spin-Orbit Coupling,"We suggest a long-lived spin polarization structure, a radial spin helix, and
study its relaxation dynamics. For this purpose, starting with a simple and
physically clear consideration of spin transport, we derive a system of
equations for spin polarization density and find its general solution in the
axially symmetric case. It is demonstrated that the radial spin helix of a
certain period relaxes slower than homogeneous spin polarization and plain spin
helix. Importantly, the spin polarization at the center of the radial spin
helix stays almost unchanged at short times. At longer times, when the initial
non-exponential relaxation region ends, the relaxation of the radial spin helix
occurs with the same time constant as that describing the relaxation of the
plain spin helix.",1007.0853v1
2020-01-23,Universal intrinsic higher-rank spin Hall effect,"Spin Hall effect (SHE), a fundamental transport phenomenon with non-zero spin
current but vanishing charge current, has important applications in spintronics
for the electrical control of spins. Owing to the half-spin nature of
electrons, the rank of spin current (determined by the rank of spin tensors)
has been restricted to 0 and 1 for charge and spin Hall effects. Motivated by
recent studies of pseudospin-1 fermions in solid state and cold atomic systems,
here we introduce and characterize higher-rank ($\geq 2$) SHEs in large spin
($\geq 1$) systems. We find a universal rank-2 spin Hall conductivity $e/{8}\pi
$, with zero rank-0 and 1 conductivities, for a spin-1 model with intrinsic
spin-orbit coupling. Similar rank-2 SHEs can also be found in a spin-3/2
system. An experimental scheme is proposed to realize and measure rank-2 SHEs
with pseudospin-1 ultracold fermionic atoms. Our results reveal novel spin
transport phenomena in large spin systems and may find important applications
in designing innovative spintronic devices.",2001.08675v2
2000-11-01,"Magnetism, Spin-Orbit Coupling, and Superconducting Pairing in UGe$_2$","A consistent picture on the mean-field level of the magnetic properties and
electronic structure of the superconducting itinerant ferromagnet UGe$_2$ is
shown to require inclusion of correlation effects beyond the local density
approximation (LDA). The ""LDA+U"" approach reproduces both the magnitude of the
observed moment, composed of strongly opposing spin and orbital parts, and the
magnetocrystalline anisotropy. The largest Fermi surface sheet is comprised
primarily of spin majority states with orbital projection $m_{\ell}$=0,
suggesting a much simpler picture of the pairing than is possible for general
strong spin-orbit coupled materials. This occurrence, and the
quasi-two-dimensional geometry of the Fermi surface, support the likelihood of
magnetically mediated p-wave triplet pairing.",0011026v1
2002-04-12,Spin-orbit scattering effect on critical current in SFIFS tunnel structures,"The spin-orbit scattering effect on critical current through
superconductor/ferromagnet (SF) bilayers separated by an insulator (SFIFS
tunnel junction) have been investigated for the case of absence of the
superconducting order parameter oscillations (thin F layers). The analysis is
based on a microscopic theory for proximity coupled SF bilayer for different
bilayer parameters (boundary transparency, proximity effect strength, relative
orientation and value of the F layers exchange field). We find that the
spin-orbit scattering considerably modifies dc Josephson current in SFIFS
tunnel junction. In contrast to a simple physical picture, the reduction of the
exchange field effects is nonlinear in character getting its maximum in the
field's region where the critical current enhancement or the transition to the
\pi-state take place. Hence, for understanding the various experimental results
on tunnel structures with thin F layers, the coupled effects of the exchange
interaction and spin-orbit scattering must be considered.",0204273v1
2003-09-30,Effect of one-ion L-S coupling on magnetic properties of a correlated spin-orbit system,"By introducing a basis for a novel realization of the SU(4) Lie algebra, we
exactly solve a spin-orbital chain with one-ion $L$-$S$ coupling (OILSC) via
the Bethe ansatz (BA) approach. In the context of different Land\'e $g$ factors
of the spin and orbital sectors, the OILSC results in rich and novel quantum
phase transitions. Some accurate analytical expressions for the critical fields
are obtained. Both spin ordering and orbital ordering are found in a gapped
singlet phase. The system exhibits many interesting phenomena such as
nonvanishing magnetization of the singlet phase, multi-entrance of the singlet
in the ground state when the field varies, unsymmetric magnetization in
two-component phase and magnetization crossover for different OILSC.",0309718v1
2004-07-30,Spin-orbit coupling in nuclei and realistic nucleon-nucleon potentials,"We analyze the spin-orbit coupling term in the nuclear energy density
functional in terms of a zero-range NN-contact interaction and finite-range
contributions from two-pion exchange. We show that the strength of the
spin-orbit contact interaction as extracted from high-precision nucleon-nucleon
potentials is in perfect agreement with that of phenomenological Skyrme forces
employed in non-relativistic nuclear structure calculations. Additional
long-range contributions from chiral two-pion exchange turn out to be
relatively small. These explicitly density-dependent contributions reduce the
ratio of the isovector to the isoscalar spin-orbit strength significantly below
the Skyrme value 1/3. We perform a similar analysis for the strength function
of the $(\vec \nabla \rho)^2$-term and find values not far from those of
phenomenological Skyrme parameterizations.",0407116v1
2007-04-20,Application of energy and angular momentum balance to gravitational radiation reaction for binary systems with spin-orbit coupling,"We study gravitational radiation reaction in the equations of motion for
binary systems with spin-orbit coupling, at order (v/c)^7 beyond Newtonian
gravity, or O(v/c)^2 beyond the leading radiation reaction effects for
non-spinning bodies. We use expressions for the energy and angular momentum
flux at infinity that include spin-orbit corrections, together with an
assumption of energy and angular momentum balance, to derive equations of
motion that are valid for general orbits and for a class of coordinate gauges.
We show that the equations of motion are compatible with those derived earlier
by a direct calculation.",0704.2720v1
2009-09-17,Enhanced Rashba effect for hole states in a quantum dot,"The effect of Rashba spin-orbit (SO) interaction on the hole states in a
quantum dot is studied in the presence of an external magnetic field. We
demonstrate here that the Rashba SO coupling has a profound effect on the
energy spectrum of the holes revealing level repulsions between the states with
the same total momentum. We also show that the resulting spin-orbit gap is much
larger than the corresponding one for the electron energy levels in a quantum
dot. Inter-hole interactions only marginally reduce the spin-orbit gap. This
enhanced Rashba effect would manifest itself in the tuneling current which
depends on the spin-orbit coupling strength.",0909.3318v2
2010-09-17,Microscopic study of spin-orbit-induced Mott insulator in Ir oxides,"Motivated by recent experiments of a novel 5$d$ Mott insulator in
Sr$_2$IrO$_4$, we have studied the two-dimensional three-orbital Hubbard model
with a spin-orbit coupling $\lambda$. The variational Monte Carlo method is
used to obtain the ground state phase diagram with varying a on-site Coulomb
interaction $U$ as well as $\lambda$. It is found that the transition from a
paramagnetic metal to an antiferromagnetic (AF) insulator occurs at a finite
$U=U_{\mathrm{MI}}$, which is greatly reduced by a large $\lambda$,
characteristic of 5$d$ electrons, and leads to the ""spin-orbit-induced"" Mott
insulator. It is also found that the Hund's coupling induces the anisotropic
spin exchange and stabilizes the in-plane AF order. We have further studied the
one-particle excitations using the variational cluster approximation, and
revealed the internal electronic structure of this novel Mott insulator. These
findings are in agreement with experimental observations on Sr$_2$IrO$_4$, and
qualitatively different from those of extensively studied 3$d$ Mott insulators.",1009.3311v2
2011-02-04,Tuning of the spin-orbit interaction in a quantum dot by an in-plane magnetic field,"Using an exact diagonalization approach we show that one- and two-electron
InAs quantum dots exhibit avoided crossing in the energy spectra that are
induced by the spin-orbit coupling in the presence of an in-plane external
magnetic field. The width of the avoided crossings depends strongly on the
orientation of the magnetic field which reveals the intrinsic anisotropy of the
spin-orbit coupling interactions. We find that for specific orientations of the
magnetic field avoided crossings vanish. Value of this orientation can be used
to extract the ratio of the strength of Rashba and Dresselhaus interactions.
The spin-orbit anisotropy effects for various geometries and orientations of
the confinement potential are discussed. Our analysis explains the physics
behind the recent measurements performed on a gated self-assembled quantum dot
[S. Takahashi et al. Phys. Rev. Lett. 104, 246801 (2010)].",1102.1002v2
2011-08-23,Resonant X-Ray Diffraction Study of Strongly Spin-Orbit-Coupled Mott Insulator CaIrO3,"We performed resonant x-ray diffraction experiments at the $L$ absorption
edges for the post-perovskite-type compound CaIrO$_{3}$ with $(t_{2g})^5$
electronic configuration. By observing the magnetic signals, we could clearly
see that the magnetic structure was a striped order with an antiferromagnetic
moment along the c-axis and that the wavefunction of a $t_{2g}$ hole is
strongly spin-orbit entangled, the $J_{\rm eff} =1/2$ state. The observed spin
arrangement is consistent with theoretical work predicting a unique
superexchange interaction in the $J_{\rm eff} =1/2$ state and points to the
universal importance of the spin-orbit coupling in Ir oxides, irrespective of
the local coordination and lattice topology. We also propose that the
non-magnetic resonant scattering is a powerful tool for unraveling an orbital
state even in a metallic iridate.",1108.4523v1
2011-10-04,Two-orbital quantum spin model of magnetism in the iron pnictides,"We study a two-orbital spin model to describe (pi,0) stripe
antiferromagnetism in the iron pnictides. The ""double-spin"" model has an
on-site Hunds's coupling and inter-site interactions extending to second
neighbors (inter- and intra-orbital) on the square lattice. Using a variational
method based on a cluster decomposition, we optimize wave functions with up to
8 cluster sites (up to 2^16 variational parameters). We focus on the
anomalously small ordered moments in the stripe state of the pnictides. To
account for it, and large variations among different compounds, we show that
the second-neighbor cross-orbital exchange constant should be ferromagnetic,
which leads to ""partially hidden"" stripe order, with a moment that can be
varied over a large range by small changes in the coupling constants. In a
different parameter region, we confirm the existence of a canted state
previously found in spin-wave theory. We also identify several other phases of
the model.",1110.0761v2
2012-03-09,Two-dimensional Heisenberg behavior of Jeff = 1/2 isospins in the paramagnetic state of spin-orbital Mott insulator Sr2IrO4,"Dynamical correlations of Jeff = 1/2 isospins in the paramagnetic state of
spin-orbital Mott insu- lator Sr2IrO4 was revealed by resonant magnetic x-ray
diffuse scattering. We found two-dimensional antiferromagnetic fluctuation with
a large in-plane correlation length exceeding 100 lattice spacings at even 20 K
above the mangnetic ordering temperature. In marked contrast to the naive
expecta- tion of strong magnetic anisotropy associated with an enhanced
spin-orbit coupling, we discovered isotropic isospin correlation that is well
described by the two-dimensional S = 1/2 quantum Heisen- berg model. The
estimated antiferromagnetic coupling constant as large as J ~ 0.1 eV that is
comparable to the small Mott gap (< 0.5 eV) points the weak and marginal Mott
character of this spin-orbital entangled system.",1203.1983v1
2012-07-26,Magnetoelectric effects in superconducting nanowires with Rashba spin-orbit coupling,"Recent experiments in semiconductor nanowires with a spin-orbit coupling and
proximity-induced superconductivity exhibit signatures of Majorana bound states
predicted to exist in the topological phase. In this work we predict that these
nanowire systems exhibit unconventional magnetoelectric effects showing a sharp
crossover behavior at the topological phase transition. We find that magnetic
fields with a component parallel to the spin-orbit field can give rise to
currents in equilibrium. Surprisingly, also fields perpendicular to the
spin-orbit field may induce currents and can be employed in adiabatic charge
pumping. The perpendicular field magnetoelectric effect may be regarded as a
manifestation of the anomalous Hall effect in one dimension. We discuss how the
predicted phenomena could be observed in experiments and employed in probing
the topological phase transition.",1207.6311v1
2013-12-28,"Impact of spin-orbit coupling on the magnetism of Sr3MIrO6 (M = Ni, Co)","Using density functional calculations, we demonstrate that the spin-orbit
coupling (SOC) of the Ir4+ ion plays an essential role in determining the
antiferromagnetism of the hexagonal spin-chain system Sr3MIrO6 (M = Ni, Co) by
tuning the crystal-field level sequence and altering the Ir-M inter-orbital
interactions. The SOC splits the e'_{g} doublet of the octahedral Ir4+ ion
(t_{2g}^5) in a trigonal crystal field, and the single t_{2g} hole resides on
the e'_{g} upper branch and gives rise to the antiferromagnetic superexchange.
In absence of the SOC, however, the single t_{2g} hole would occupy the a_{1g}
singlet instead, which would mediate an unreal ferromagnetic exchange due to a
direct a_{1g} hopping along the Ir-M chain. We also find that the Ni2+ and Co2+
ions are both in a high-spin state and moreover the Co2+ ion carries a huge
orbital moment. This work well accounts for the recent experiments and
magnifies again the significance of the SOC in iridates.",1312.7411v1
2015-04-07,Fractal butterflies in buckled graphene-like materials,"We study theoretically the properties of buckled graphene-like materials,
such as silicene and germanene, in a strong perpendicular magnetic field and a
periodic potential. We analyze how the spin-orbit interaction and the
perpendicular electric field influences the energy spectra of these systems.
When the magnetic flux through a unit cell of the periodic potential measured
in magnetic flux quantum is a rational number, ? = p/q, then in each Landau
level the energy spectra have a band structure, which is characterized by the
corresponding gaps. We study the dependence of those gaps on the parameters of
the buckled graphene-like materials. Although some gaps have weak dependence on
the magnitude of the spin-orbit coupling and the external electric field, there
are gaps that show strong nonomonotic dependence on these parameters. For ? =
1/2, the spin-orbit interaction also opens up a gap at one of the Landau
levels. The magnitude of the gap increases with spin-orbit coupling and
decreases with the applied electric field.",1504.01749v1
2015-08-06,Odd-parity superconductivity by competing spin-orbit coupling and orbital effect in artificial heterostructures,"We show that odd-parity superconductivity occurs in multilayer Rashba systems
without requiring spin-triplet Cooper pairs. A pairing interaction in the
spin-singlet channel stabilizes the odd-parity pair-density-wave (PDW) state in
the magnetic field parallel to the two-dimensional conducting plane. It is
shown that the layer-dependent Rashba spin-orbit coupling and the orbital
effect play essential roles for the PDW state in binary and tricolor
heterostructures. We demonstrate that the odd-parity PDW state is a
symmetry-protected topological superconducting state characterized by the
one-dimensional winding number in the symmetry class BDI. The superconductivity
in the artificial heavy-fermion superlattice CeCoIn_5/YbCoIn_5 and bilayer
interface SrTiO_3/LaAlO_3 is discussed.",1508.01333v2
2016-07-28,A spin-freezing perspective on cuprates,"The high-temperature superconducting state in cuprates appears if charge
carriers are doped into a Mott insulating parent compound. An unresolved puzzle
is the unconventional nature of the normal state above the superconducting
dome, and its connection to the superconducting instability. At weak
hole-doping, a ""pseudo-gap"" metal state with signatures of time-reversal
symmetry breaking is observed, which near optimal doping changes into a
""strange metal"" with non-Fermi liquid properties. Qualitatively similar phase
diagrams are found in multi-orbital systems, such as pnictides, where the
unconventional metal states arise from a Hund coupling induced spin-freezing.
Here, we show that the relevant model for cuprates, the single-orbital Hubbard
model on the square lattice, can be mapped onto an effective multi-orbital
problem with strong ferromagnetic Hund coupling. The spin-freezing physics of
this multi-orbital system explains the phenomenology of cuprates, including the
pseudo-gap, the strange metal, and the d-wave superconducting instability. Our
analysis suggests that spin-freezing is the universal mechanism which controls
the properties of unconventional superconductors.",1607.08573v1
2014-03-05,Statistical properties of spectra in harmonically trapped spin-orbit coupled systems,"We compute single-particle energy spectra for a one-body hamiltonian
consisting of a two-dimensional deformed harmonic oscillator potential, the
Rashba spin-orbit coupling and the Zeeman term. To investigate the statistical
properties of the obtained spectra as functions of deformation, spin-orbit and
Zeeman strengths we examine the distributions of the nearest neighbor spacings.
We find that the shapes of these distributions depend strongly on the three
potential parameters. We show that the obtained shapes in some cases can be
well approximated with the standard Poisson, Brody and Wigner distributions.
The Brody and Wigner distributions characterize irregular motion and help
identify quantum chaotic systems. We present a special choices of deformation
and spin-orbit strengths without the Zeeman term which provide a fair
reproduction of the fourth-power repelling Wigner distribution. By adding the
Zeeman field we can reproduce a Brody distribution, which is known to describe
a transition between the Poisson and linear Wigner distributions.",1403.1205v2
2013-09-09,Wigner crystal of a two-dimensional electron gas with a strong spin-orbit interaction,"The Wigner-crystal phase of two-dimensional electrons interacting via the
Coulomb repulsion and subject to a strong Rashba spin-orbit coupling is
investigated. For low enough electronic densities the spin-orbit band splitting
can be larger than the zero-point energy of the lattice vibrations. Then the
degeneracy of the lower subband results in a spontaneous symmetry breaking of
the vibrational ground state. The $60^{\circ}-$rotational symmetry of the
triangular (spin-orbit coupling free) structure is lost, and the unit cell of
the new lattice contains two electrons. Breaking the rotational symmetry also
leads to a (slight) squeezing of the underlying triangular lattice.",1309.2307v2
2016-08-24,Anisotropic spin fluctuations in Sr$_2$RuO$_4$: role of spin-orbit coupling and induced strain,"We analyze the spin anisotropy of the magnetic susceptibility of Sr$_2$RuO$4$
in presence of spin-orbit coupling and anisotropic strain using
quasi-two-dimensional tight-binding parametrization fitted to the ARPES
results. Similar to the previous observations we find the in-plane polarization
of the low ${\bf q}$ magnetic fluctuations and the out-of-plane polarization of
the incommensurate magnetic fluctuation at the nesting wave vector ${\bf Q}_1 =
(2/3 \pi ,2/3 \pi)$ but also nearly isotropic fluctuations near ${\bf
Q}_2=(\pi/6,\pi/6)$. Furthermore, one finds that apart from the high-symmetry
direction of the tetragonal Brillouin zone the magnetic anisotropy is maximal,
i.e. $\chi^{xx} \neq \chi^{yy} \neq \chi^{zz}$. This is the consequence of the
orbital anisotropy of the $xz$ and $yz$ orbitals in the momentum space. We also
study how the magnetic anisotropy evolves in the presence of the strain and
find strong Ising-like ferromagnetic fluctuations near the Lifshitz transition
for the $xy$-band.",1608.06786v1
2018-10-22,First-principles studies of spin-orbital physics in pyrochlore oxides,"The pyrochlore oxides $A_2B_2$O$_7$ exhibit a complex interplay between
geometrical frustration, electronic correlations, and spin-orbit coupling, due
to the lattice structure and active charge, spin, and orbital degrees of
freedom. Understanding the properties of these materials is a theoretical
chalenge, because their intricate nature depends on material-specific details
and quantum many-body effects. Here we review our recent studies based on
first-principles calculations and quantum many-body theories for 4$d$ and 5$d$
pyrochlore oxides with $B$=Mo, Os, and Ir. In these studies, the spin-orbit
coupling and local electron correlations are treated within the LDA+$U$ and
LDA+dynamical mean-field theory formalisms. We also discuss the technical
aspects of these calculations.",1810.09596v2
2019-09-05,Spin-orbit related power-law dependence of the diffusive conductivity on the carrier density in disordered Rashba two-dimensional electron systems,"By using the momentum-space Lanczos recursive method which considers
rigorously all multiple-scattering events, we unveil that the non-perturbative
disorder effect has dramatic impact on the charge transport of a
two-dimensional electron system with Rashba spin-orbit coupling in the
low-density region. Our simulations find a power-law dependence of the dc
longitudinal conductivity on the carrier density, with the exponent linearly
dependent on the Rashba spin-orbit strength but independent of the disorder
strength. Therefore, the classical charge transport influenced by complicated
multiple-scattering processes also shows the characteristic feature of the
spin-orbit coupling. This highly unconventional behavior is argued to be
observable in systems with tunable carrier density and Rashba splitting, such
as the LaAlO$_{3}$/SrTiO$_{3}$ interface, the heterostructure of Rashba
semiconductors bismuth tellurohalides and the surface alloy
Bi$_x$Pb$_y$Sb$_{1-x-y}$/Ag(111).",1909.02186v3
2019-10-06,Spin-orbit coupling effects on the electronic properties of the pressure-induced superconductor CrAs,"We present the effects of spin-orbit coupling on the low-energy bands and
Fermi surface of the recently discovered pressure-induced superconductor CrAs.
We apply the L\""owdin down-folding procedure to a tight-binding hamiltonian
that includes the intrinsic spin-orbit interaction, originating from the Cr 3d
electrons as well as from As 4p ones. Our results indicate that As
contributions have negligible effects, whereas the modifications to the band
structure and the Fermi surface can be mainly ascribed to the Cr contribution.
We show that the inclusion of the spin-orbit interaction allows for a selective
removal of the band degeneracy due to the crystal symmetries, along specific
high symmetry lines. Such release of the band degeneracy naturally determines a
reconstruction of the Fermi surface, including the possibility of changing the
number of pockets.",1910.02407v1
2020-04-09,First-Principles Calculation of Spin and Orbital Contributions to Magnetically Ordered Moments in Sr$_{2}$IrO$_{4}$,"We show how an accurate first-principles treatment of the
canted-antiferromagnetic ground state of Sr$_2$IrO$_4$, a prototypical $5d$
correlated spin-orbit coupled material, can be obtained without invoking any
free parameters such as the Hubbard U or tuning the spin-orbit coupling
strength. Our theoretically predicted iridium magnetic moment of 0.250 $\mu_B$,
canted by 12.6$^{\circ}$ off the a-axis, is in accord with experimental
results. By resolving the magnetic moments into their spin and orbital
components, we show that our theoretically obtained variation of the magnetic
scattering amplitude $<M_{m}>$ as a function of the polarization angle is
consistent with recent non-resonant magnetic x-ray scattering measurements. The
computed value of the band gap (55 meV) is also in line with the corresponding
experimental values. A comparison of the band structure to that of the cuprates
suggests the presence of incommensurate charge-density wave phases in
Sr$_{2}$IrO$_{4}$.",2004.04759v1
2019-03-15,Type-II Ising superconductivity in two-dimensional materials with strong spin-orbit coupling,"Recent discovery of Ising superconductivity protected against in-plane
magnetic field by spin-orbit coupling (SOC) has stimulated intensive research
interests. The effect, however, was only expected to appear in two-dimensional
(2D) noncentrosymmetric materials with spin-valley locking. In this work, we
proposed a new type of Ising superconductivity in 2D materials with $C_{nz}$
rotational symmetry ($n=3,4,6$). This mechanism, dubbed as type-II Ising
superconductivity, is applicable for centrosymmetric materials. Type-II Ising
superconductivity relies on the SOC-induced spin-orbital locking characterized
by Ising-type Zeeman-like fields displaying opposite signs for opposing
orbitals. We found that type-II Ising superconductivity are most prominent
around time-reversal invariant momenta and is not sensitive to inversion
symmetry breaking. By performing high-throughput first-principles calculations,
about one hundred candidate materials were identified. Our work significantly
enriches the physics and materials of Ising superconductor, opening new
opportunities for fundamental research and practical applications of 2D
materials.",1903.06660v3
2020-11-04,Level attraction and exceptional points in a resonant spin-orbit torque system,"Level attraction can appear in driven systems where instead of repulsion two
modes coalesce in a region separated by two exceptional points. This behavior
was proposed for optomechanical and optomagnonic systems, and recently observed
for dissipative cavity magnon-polaritons. We demonstrate that such a regime
exists in a spin-orbit torque system where a magnetic oscillator is resonantly
coupled to an electron reservoir. An instability mechanism necessary for mode
attraction can be provided by applying an electric field. The field excites
interband transitions between spin-orbit split bands leading to an instability
of the magnetic oscillator. Two exceptional points then appear in the
oscillator energy spectrum and the region of instability. We discuss conditions
under which this can occur and estimate the electric field strength necessary
for reaching the attraction region for a spin-orbit torque oscillator with
Rashba coupling. A proposal for experimental detection is made using magnetic
susceptibility measurements.",2011.02520v1
2021-03-23,GRIT: a package for structure-preserving simulations of gravitationally interacting rigid-bodies,"Spin-orbit coupling of planetary systems plays an important role in the
dynamics and habitability of planets. However, symplectic integrators that can
accurately simulate not only how orbit affects spin but also how spin affects
orbit have not been constructed for general systems. Thus, we develop
symplectic Lie-group integrators to simulate systems consisting gravitationally
interacting rigid bodies. A user friendly package (GRIT
\url{https://github.com/GRIT-RBSim/GRIT}) is provided and external forcings
such as tidal interactions are also included. As a demonstration, this package
is applied to Trappist-I. It shows that the differences in transit timing
variations due to spin-orbit coupling could reach a few min in ten year
measurements, and strong planetary perturbations can push Trappist-I f, g and h
out of the synchronized states.",2103.12767v2
2021-07-18,Statistical correlation between quantum entanglement and spin-orbit coupling in crossed beam molecular dynamics,"Non-classical features like interference is already being harnessed to
control the output of chemical reactions. However quantum entanglement which is
an equally enigmatic many-body quantum correlation can also be used as a
powerful resource yet have eluded explicit attention. In this report, we
propose an experimental scheme under the crossed beam molecular dynamical
setup, with the F+HD reaction, aiming to study the possible influence of
entanglement within reactant pairs on the angular features of the product
distribution. The aforesaid reaction has garnered interest recently as an
unusual horseshoe shape pattern in the product (HF) distribution was observed,
which has been attributed to the coupling of spin and orbital degrees of
freedom. We propose an experimental scheme aiming to study the possible
influence of entanglement on the necessity for the inclusion of such spin-orbit
characteristics, under circumstances wherein the existence of entanglement and
spin-orbit interaction is simultaneously detectable. We further numerically
simulate the attainable results highlighting specific patterns corresponding to
various possibilities. Such studies if extended can provide unforeseen
mechanistic insight in analogous reactions too from the lens of quantum
information.",2107.08483v1
2022-01-21,Frequency-dependent Inter-pseudospin Solutions to Superconducting Strontium Ruthenate,"The lasting puzzle of the superconducting order parameter of Sr$_2$RuO$_4$
calls for theoretical studies that include seldom-considered effects. Here we
include spin-orbit coupling effects on the electronic structure and then solve
the linearized Eliashberg equation in a pseudospin basis, including the
possibility that spin and charge fluctuations induce frequency-dependent
superconducting order parameters. We find that spin-orbit coupling mixes even
and odd contributions in orbital, spin and frequency spaces and that leading
inter-pseudospin symmetries, B$_{1g}^+$ and A$_{2g}^-$, have intra-orbital
components respectively even and odd in Matsubara frequency. An accidental
degeneracy between these could resolve apparent experimental contradictions.",2201.08917v2
2022-04-29,Rydberg Atomic Antenna in Strongly Driven Multi-Electron Atoms,"We study the role of intermediate excitations of Rydberg states as an example
of Kuchiev's ""atomic antenna"" in above-threshold ionization of xenon, in
particular their effect on the coherence between the spin-orbit-split states of
the ion. We focus on the case of a laser frequency close to resonant with the
spin-orbit splitting, where a symmetry (parity) argument would preclude any
coherence being directly generated by strong-field ionization. Using ab initio
simulations of coupled multielectron spin-orbit dynamics in strong laser
fields, we show how field-driven rescattering of the trapped Rydberg electrons
introduces efficient coupling between the spin-orbit-split channels, leading to
substantial coherences, exceeding 10 % for some photon energies.",2204.14082v2
2022-08-06,Tunable two-dimensional superconductivity and spin-orbit coupling at the EuO/KTaO3(110) interface,"Unconventional quantum states, most notably the two-dimensional (2D)
superconductivity, have been realized at the interfaces of oxide
heterostructures where they can be effectively tuned by the gate voltage
($V_G$). Here we report that the interface between high-quality EuO (111) thin
film and KTaO3 (KTO) (110) substrate shows superconductivity with onset
transition temperature $T_c^{onset}$ = 1.35 K. The 2D nature of
superconductivity is verified by the large anisotropy of the upper critical
field and the characteristics of a Berezinskii-Kosterlitz-Thouless transition.
By applying $V_G$, $T_c^{onset}$ can be tuned from ~ 1 to 1.7 K; such an
enhancement can be possibly associated with a boosted spin-orbit energy
${\epsilon}_{so}$ = $\hbar$ / ${\tau}_{so}$, where ${\tau}_{so}$ is the
spin-orbit relaxation time. Further analysis of ${\tau}_{so}$ based on the
upper critical field ($H_{c2}$) and magnetoconductance reveals complex nature
of spin-orbit coupling (SOC) at the EuO/KTO(110) interface with different
mechanisms dominate the influence of SOC effects for the superconductivity and
the magnetotransport in the normal state. Our results demonstrate that the SOC
should be considered as an important factor determining the 2D
superconductivity at oxide interfaces.",2208.03507v1
2022-09-06,High-spin orbital interactions across van der Waals gaps controlling the interlayer ferromagnetism in van der Waals ferromagnets,"We examined what interactions control the sign and strength of the interlayer
coupling in van der Waals ferromagnets such as Fe3-xGeTe2, Cr2Ge2Te6, CrI3 and
VI3, to find that high-spin orbital interaction across the van der Waals gaps
are a key to understanding their ferromagnetism. Interlayer ferromagnetic
coupling in Fe3-xGeTe2 Cr2Ge2Te6, and CrI3 is governed by the high-spin
two-orbital two-electron destabilization, but that in VI3 by the high-spin
four-orbital two-electron stabilization. These interactions explain a number of
seemingly puzzling observations in van der Waals fer-romagnets.",2209.02233v1
2023-07-29,Swapping exchange and spin-orbit induced correlated phases in ex-so-tic van der Waals heterostructures,"Ex-so-tic van der Waals heterostructures take advantage of the electrically
tunable layer polarization to swap proximity exchange and spin-orbit coupling
in the electronically active region. Perhaps the simplest example is Bernal
bilayer graphene (BBG) encapsulated by a layered magnet from one side and a
strong spin-orbit material from the other. Taking WS$_2$/BBG/Cr$_2$Ge$_2$Te$_6$
as a representative ex-so-tronic device, we employ realistic \emph{ab
initio}-inspired Hamiltonians and effective electron-electron interactions to
investigate the emergence of correlated phases within the random phase
approximation. We find that for a given doping level, exchange and spin-orbit
coupling induced Stoner and intervalley coherence instabilities can be swapped,
allowing to explore the full spectrum of correlated phases within a single
device.",2307.16025v1
2023-10-10,Non-relativistic torque and Edelstein effect in noncollinear magnets,"The Edelstein effect is the origin of the spin-orbit torque: a
current-induced torque that is used for the electrical control of ferromagnetic
and antiferromagnetic materials. This effect originates from the relativistic
spin-orbit coupling, which necessitates utilizing materials with heavy
elements. Here we show that in magnetic materials with non-collinear magnetic
order, the Edelstein effect and consequently also a current-induced torque can
exist even in the absence of the spin-orbit coupling. Using group symmetry
analysis, model calculations, and realistic simulations on selected compounds,
we identify large classes of non-collinear magnet candidates and demonstrate
that the current-driven torque is of similar magnitude as the celebrated
spin-orbit torque in conventional transition metal structures. We also show
that this torque can exist in an insulating material, which could allow for
highly efficient electrical control of magnetic order.",2310.06499v1
2007-08-15,Spin dynamics in InAs-nanowire quantum-dots coupled to a transmission line,"We study theoretically electron spins in nanowire quantum dots placed inside
a transmission line resonator. Because of the spin-orbit interaction, the spins
couple to the electric component of the resonator electromagnetic field and
enable coherent manipulation, storage, and read-out of quantum information in
an all-electrical fashion. Coupling between distant quantum-dot spins, in one
and the same or different nanowires, can be efficiently performed via the
resonator mode either in real time or through virtual processes. For the latter
case we derive an effective spin-entangling interaction and suggest means to
turn it on and off. We consider both transverse and longitudinal types of
nanowire quantum-dots and compare their manipulation timescales against the
spin relaxation times. For this, we evaluate the rates for spin relaxation
induced by the nanowire vibrations (phonons) and show that, as a result of
phonon confinement in the nanowire, this rate is a strongly varying function of
the spin operation frequency and thus can be drastically reduced compared to
lateral quantum dots in GaAs. Our scheme is a step forward to the formation of
hybrid structures where qubits of different nature can be integrated in a
single device.",0708.2091v1
2007-08-23,Control of spin coherence in semiconductor double quantum dots,"We propose a scheme to manipulate the spin coherence in vertically coupled
GaAs double quantum dots. Up to {\em ten} orders of magnitude variation of the
spin relaxation and {\em two} orders of magnitude variation of the spin
dephasing can be achieved by a small gate voltage applied vertically on the
double dot. Specially, large variation of spin relaxation still exists at 0 K.
In the calculation, the equation-of-motion approach is applied to obtain the
electron decoherence time and all the relevant spin decoherence mechanisms,
such as the spin-orbit coupling together with the electron--bulk-phonon
scattering, the direct spin-phonon coupling due to the phonon-induced strain,
the hyperfine interaction and the second-order process of electron-phonon
scattering combined with the hyperfine interaction, are included. The condition
to obtain the large variations of spin coherence is also addressed.",0708.3125v2
2014-09-09,Electron-spin dynamics in elliptically polarized light waves,"We investigate the coupling of the spin angular momentum of light beams with
elliptical polarization to the spin degree of freedom of free electrons. It is
shown that this coupling, which is of similar origin as the well-known
spin-orbit coupling, can lead to spin precession. The spin-precession frequency
is proportional to the product of the laser-field's intensity and its spin
density. The electron-spin dynamics is analyzed by employing exact numerical
methods as well as time-dependent perturbation theory based on the fully
relativistic Dirac equation and on the nonrelativistic Pauli equation that is
amended by a relativistic correction that accounts for the light's spin
density.",1409.2647v2
2016-04-28,Ballistic Josephson junctions in the presence of generic spin dependent fields,"Ballistic Josephson junctions are studied in the presence of a spin-splitting
field and spin-orbit coupling. A generic expression for the quasi-classical
Green's function is obtained and with its help we analyze several aspects of
the proximity effect between a spin-textured normal metal (N) and singlet
superconductors (S). In particular, we show that the density of states may show
a zero-energy peak which is a generic consequence of the spin-dependent
couplings in heterostructures. In addition we also obtain the spin current and
the induced magnetic moment in a SNS structure and discuss possible coherent
manipulation of the magnetization which results from the coupling between the
superconducting phase and the spin degree of freedom. Our theory predicts a
spin accumulation at the S/N interfaces, and transverse spin currents flowing
perpendicular to the junction interfaces. Some of these findings can be
understood in the light of a non-Abelian electrostatics.",1604.08455v2
2008-07-16,Theory of electric dipole spin resonance in quantum dots: Mean field theory with Gaussian fluctuations and beyond,"Very recently, the electric dipole spin resonance (EDSR) of single electrons
in quantum dots was discovered by three independent experimental groups.
Remarkably, these observations revealed three different mechanisms of EDSR:
coupling of electron spin to its momentum (spin-orbit), to the operator of its
position (inhomogeneous Zeeman coupling), and to the hyperfine Overhauser field
of nuclear spins. In this paper, I present a unified microscopic theory of
these resonances in quantum dots. A mean field theory, derived for all three
mechanisms and based on retaining only two-spin correlators, justifies applying
macroscopic description of nuclear polarization to the EDSR theory. In the
framework of the mean field theory, a fundamental difference in the time
dependence of EDSR inherent of these mechanisms is revealed; it changes from
the Rabi-type oscillations to a nearly monotonic growth. The theory provides a
regular procedure to account for the higher nuclear-spin correlators that
become of importance for a wider time span and can change the asymptotic
behavior of EDSR. It also allows revealing the effect of electron spin dynamics
on the effective coupling between nuclear spins.",0807.2624v1
2017-05-29,Optospintronics in graphene via proximity coupling,"The observation of micron size spin relaxation makes graphene a promising
material for applications in spintronics requiring long distance spin
communication. However, spin dependent scatterings at the contact/graphene
interfaces affect the spin injection efficiencies and hence prevent the
material from achieving its full potential. While this major issue could be
eliminated by nondestructive direct optical spin injection schemes, graphenes
intrinsically low spin orbit coupling strength and optical absorption place an
obstacle in their realization. We overcome this challenge by creating sharp
artificial interfaces between graphene and WSe2 monolayers. Application of a
circularly polarized light activates the spin polarized charge carriers in the
WSe2 layer due to its spin coupled valley selective absorption. These carriers
diffuse into the superjacent graphene layer, transport over a 3.5 um distance,
and are finally detected electrically using BN/Co contacts in a non local
geometry. Polarization dependent measurements confirm the spin origin of the
non local signal.",1705.10267v1
2018-10-15,Ferromagnetic and Antiferromagnetic Coupling of Spin Molecular Interfaces with High Thermal Stability,"We report an advanced organic spin-interface architecture with magnetic
remanence at room temperature, constituted by metal phthalocyanine molecules
magnetically coupled with Co layer(s), mediated by graphene. Fe- and
Cu-phthalocyanines assembled on graphene/Co have identical structural
configurations, but FePc couples antiferromagnetically with Co up to room
temperature, while CuPc couples ferromagnetically with weaker coupling and
thermal stability, as deduced by element-selective X-ray magnetic circular
dichroic signals. The robust antiferromagnetic coupling is stabilized by a
superexchange interaction, driven by the out-of-plane molecular orbitals
responsible of the magnetic ground state and electronically decoupled from the
underlying metal via the graphene layer, as confirmed by ab initio theoretical
predictions. These archetypal spin interfaces can be prototypes to demonstrate
how antiferromagnetic and/or ferromagnetic coupling can be optimized by
selecting the molecular orbital symmetry.",1810.06317v1
2021-08-16,Coherently Coupled Mixtures of Bose-Einstein Condensed Gases,"This paper summarizes some of the relevant features exhibited by bi-nary
mixtures of Bose-Einstein condensates in the presence of coherent coupling at
zero temperature. The coupling, which is experimentally produced by proper
photon transitions, can either involve negligible momentum transfer from the
electromagnetic radiation (Rabi coupling) or large momentum transfer (Raman
coupling) associated with spin-orbit effects.The nature of the quantum phases
exhibited by coherently coupled mixtures is discussed in detail, including
their paramagnetic, ferromagnetic, and, in the case of spin-orbit coupling,
supersolid phases.The behavior of the corresponding elementary excitations is
discussed, with explicit emphasis on the novel features caused by the spin-like
degree of freedom. Focus is further given to the topological excitations
(solitons, vortices) as well as to the superfluid properties. The paper also
points out relevant open questions which deserve more systematic theoretical
and experimental investigations.",2108.10159v1
2005-05-23,Spin-orbit coupling induced magnetism in the $d$-density wave phase of La$_{2-x}$Ba$_x$CuO$_4$ superconductors,"We study the effects of spin-orbit coupling in the $d$-density wave (DDW)
phase. In the low-temperature orthorhombic phase of La$_{2-x}$Ba$_x$CuO$_4$, we
find that spin-orbit coupling induces a ferromagnetic moment in the DDW phase,
which is polarized along the [110] direction with a considerable magnitude.
This effect does not exist in the superconducting phase. On the other hand, if
the $d$-density wave order does not exist at zero field, a magnetic field along
the [110] direction always induces such a staggered orbital current. We discuss
experimental constraints on the DDW states in light of our theoretical
predictions.",0505544v3
2009-04-21,Band-structure topologies of graphene: spin-orbit coupling effects from first principles,"The electronic band structure of graphene in the presence of spin-orbit
coupling and transverse electric field is investigated from first principles
using the linearized augmented plane-wave method. The spin-orbit coupling opens
a gap at the $K(K')$-point of the magnitude of 24 $\mu$eV (0.28 K). This
intrinsic splitting comes 96% from the usually neglected $d$ and higher
orbitals. The electric field induces an additional (extrinsic)
Bychkov-Rashba-type splitting of 10 $\mu$eV (0.11 K) per V/nm, coming from the
$\sigma$-$\pi$ mixing. A 'mini-ripple' configuration with every other atom is
shifted out of the sheet by less than 1% differs little from the intrinsic
case.",0904.3315v2
2013-12-10,"Pairing Symmetry, Phase diagram and Edge Modes in Topological Fulde-Ferrell-Larkin-Ovchinnikov Phase","The realizations of spin-orbit coupling in cold atoms lead to a burst of
research activities in the searching of topological matters in ultracold atom
systems. The very recent theoretical predictions show that topological
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superfluids can be realized with proper
spin-orbit coupling and Zeeman fields. In this work, a comprehensive
understanding of the pairing symmetry, phase diagram and the edge modes in this
new topological matter are presented. The momentum of the Cooper pairs plays
the role of renormalizing the in-plane Zeeman field and chemical potential. The
in-plane Zeeman field and finite momentum pairing induce asymmetry to the
effective $p$-wave pairing, apart from a small fraction of higher orbital
components. The phase diagram is composed by different phases, which are
determined by the topology and band gap nature of the superfluids. Especially,
the gapped and gapless topological FFLO phase have totally different finite
size effect. These novel features show that the spin-orbit coupled cold atoms
provides an important platform in realizing topological matters which may not
be materialized with solids.",1312.3000v1
2015-10-06,"Interplay between Spin-Orbit Coupling and Strong Correlation Effects: Comparison of Three Osmate Double Perovskites: Ba$_{2}A$OsO$_{6}$ ($A=$Na, Ca, Y)","High formal valence Os-based double perovskites are a focus of current
interest because they display strong interplay of large spin orbit coupling and
strong electronic correlation. Here we present the electronic and magnetic
characteristics of a sequence of three cubic Os based double perovskites
Ba$_{2}$$A$OsO$_{6}$, ($A=$Na, Ca, Y), with formal valences (charge states) of
Os$^{+7}~(d^{1})$, Os$^{+6}(d^{2})$, Os$^{+5}(d^{3})$. For these first
principles based calculations we apply an ``exact exchange for correlated
electrons'' functional, with exact exchange applied in a hybrid fashion solely
to the Os($5d$) states. While Ba$_{2}$NaOsO$_{6}$ is a ferromagnetic Dirac-Mott
insulator studied previously, the other two show antiferromagnetic ordering
while all retain the cubic (undistorted) structure. For comparison purposes we
have investigated only the ferromagnetic ordered phase. A metal-insulator
transition is predicted to occur upon rotating the direction of magnetization
in all three materials, reflecting the central role of spin orbit coupling in
these small gap osmates. Surprises arising from comparing formal charge states
with the radial charge densities are discussed. Chemical shielding factors and
orbital susceptibilities are provided for comparison with future nuclear
magnetic resonance data.",1510.01719v1
2014-06-14,Quantum anomalous Hall phase in (001) double-perovskite monolayers via intersite spin-orbit coupling,"Using tight-binding models and first-principles calculations, we demonstrate
the possibility to achieve a quantum anomalous Hall (QAH) phase on a
two-dimensional square lattice, which can be realized in monolayers of double
perovskites. We show that effective intersite spin-orbit coupling between eg
orbitals can be induced perturbatively, giving rise to a QAH state. Moreover,
the effective spin-orbit coupling can be enhanced by octahedral rotations.
Based on first-principles calculations, we propose that this type of QAH state
could be realized in La2MnIrO6 monolayers, with the size of the gap as large as
26 meV in the ideal case. We observe that the electronic structure is sensitive
to structural distortions, and that an enhanced Hubbard U tends to stabilize
the nontrivial gap.",1406.4437v1
2016-08-01,Phase Transition in IrTe$_2$ induced by spin-orbit coupling,"IrTe$_2$ has been renewed as an interesting system showing competing
phenomenon between a questionable density-wave transition near 270 K followed
by superconductivity with doping of high atomic number materials. Higher atomic
numbers of Te and Ir supports strong spin-orbital coupling in this system.
Using dynamical mean field theory with LDA band structure I have introduced
Rashba spin orbit coupling in this system to get the interpretation for
anomalous resistivity and related transition in this system. While no
considerable changes are observed in DMFT results of Ir-5d band other than
orbital selective pseudogap pinned to Fermi level, Te-p band shows a van Hove
singularity at the Fermi level except low temperature. Finally I discuss the
implications of these results in theoretical understanding of ordering in
IrTe$_2$.",1608.00467v1
2019-10-16,Anisotropic superexchange through nonmagnetic anions with spin-orbit coupling,"Anisotropic superexchange interaction is one of the most important
interactions in realizing exotic quantum magnetism, which is traditionally
regarded to originate from magnetic ions and has no relation with the
nonmagnetic ions. In our work, by studying a multi-orbital Hubbard model with
spin-orbit coupling on both magnetic cations and nonmagnetic anions, we
analytically demonstrate that the spin-orbit coupling on nonmagnetic anions
alone can induce antisymmetric Dzyaloshinskii-Moriya interaction, symmetric
anisotropic exchange and single ion anisotropy on the magnetic ions and thus it
actually contributes to anisotropic superexchange on an equal footing as that
of magnetic ions. Our results promise one more route to realize versatile
exotic phases in condensed matter systems, long-range orders in low dimensional
materials and switchable single molecule magnetic devices for recording and
manipulating quantum information through nonmagnetic anions.",1910.07118v3
2018-03-22,Carrier dynamics in doped bilayer iridates near magnetic quantum criticality,"Motivated by experiments on the carrier-doped bilayer iridate
$(\text{Sr}_{1-x}\text{La}_x)_3\text{Ir}_2\text{O}_7$, we study the dynamics of
a single doped electron in a bilayer magnet in the presence of spin-orbit
coupling, taking into account the spatially staggered rotation of IrO$_6$
octahedra. We employ an effective single-orbital bilayer $t$-$J$ model,
concentrating on the quantum paramagnetic phase near the magnetic quantum
critical point. We determine the carrier dispersion using a combination of
self-consistent Born and bond-operator techniques. Extrapolating to finite
small carrier density we find that, for experimentally relevant parameters, the
combination of octahedral rotation and spin-orbit coupling induces a band
folding which results in a Fermi surface of small double electron pockets, in
striking agreement with experimental observations. We also determine the
influence of spin-orbit coupling on the location of the quantum critical point
in the undoped case, and discuss aspects of the global phase diagram of doped
bilayer Mott insulators.",1803.08516v3
2021-07-10,Anisotropic Berry phase in the Dirac nodal-line semimetal ZrSiS: The effect of spin-orbit coupling,"The topological nodal-line semimetals (NLSMs) possess a loop of Dirac nodes
in the k space with linear dispersion, different from the point nodes in
Dirac/Weyl semimetals. While the quantum transport associated with the
topologically nontrivial Dirac fermions has been investigated extensively,
features uniquely associated with the extended nodal lines remain to be
demonstrated. Here, we investigate the quantum oscillations (QOs) in the
nodal-line semimetal ZrSiS, with the electron transport along the c axis, and
magnetic field rotating in the ab plane. The extremal orbits identified through
the field orientation dependence of the QOs interlock with the nodal line,
leading to a nonzero Berry phase. Most importantly, the Berry phase shows a
significant dependence on the magnetic field orientation, which we argue to be
due to the finite spin-orbit coupling gap. Our results demonstrate the
importance of the spin-orbit coupling and the nodal-line dispersion in
understanding the quantum transport of NLSMs.",2107.04786v1
2024-03-19,Electrical readout of spins in the absence of spin blockade,"In semiconductor nanostructures, spin blockade (SB) is the most scalable
mechanism for electrical spin readout requiring only two bound spins for its
implementation which, in conjunction with charge sensing techniques, has led to
high-fidelity readout of spins in semiconductor-based quantum processors.
However, various mechanisms may lift SB, such as strong spin-orbit coupling
(SOC) or low-lying excited states, hence posing challenges to perform spin
readout at scale and with high fidelity in such systems. Here, we present a
method, based on the dependence of the two-spin system polarizability on energy
detuning, to perform spin state readout even when SB lifting mechanisms are
dominant. It leverages SB lifting as a resource to detect different spin
measurement outcomes selectively and positively. We demonstrate the method
using a hybrid system formed by a quantum dot (QD) and a Boron acceptor in a
silicon p-type transistor and show spin selective and positive readout of
different spin states under SB lifting conditions due to (i) SOC and (ii)
low-lying orbital states in the QD. We further use the method to determine the
detuning-dependent spin relaxation time of 0.1-8~$\mu$s. Our method should help
perform high-fidelity projective spin measurements in systems subject to strong
SOC and may facilitate quantum tomography and state leakage studies.",2403.12888v1
2023-02-06,Twist-angle dependent proximity induced spin-orbit coupling in graphene/topological insulator heterostructures,"The proximity-induced spin-orbit coupling (SOC) in heterostructures of
twisted graphene and topological insulators (TIs) Bi$_2$Se$_3$ and Bi$_2$Te$_3$
is investigated from first principles. To build commensurate supercells, we
strain graphene and correct thus resulting band offsets by applying a
transverse electric field. We then fit the low-energy electronic spectrum to an
effective Hamiltonian that comprises orbital and spin-orbit terms. For twist
angles 0$^\circ\leq\Theta \lessapprox 20^\circ$, we find the dominant
spin-orbit couplings to be of the valley-Zeeman and Rashba types, both a few
meV strong. We also observe a sign change in the induced valley-Zeeman SOC at
$\Theta\approx 10^\circ$. Additionally, the in-plane spin structure resulting
from the Rashba SOC acquires a non-zero radial component, except at $0^\circ$
or $30^\circ$. At $30^\circ$ the graphene Dirac cone interacts directly with
the TI surface state. We therefore explore this twist angle in more detail,
studying the effects of gating, TI thicknesses, and lateral shifts on the SOC
parameters. We find, in agreement with previous results, the emergence of the
proximitized Kane-Mele SOC, with a change in sign possible by electrically
tuning the Dirac cone within the TI bulk band gap.",2302.03102v2
2019-05-05,Dipole coupling of a tunable hole double quantum dot in germanium hut wire to a microwave resonator,"The germanium (Ge) hut wire system has strong spin-orbit coupling, a long
coherence time due to a very large heavy-light hole splitting, and the
advantage of site-controlled large-scale hut wire positioning. These properties
make the Ge hut wire a promising candidate for the realization of strong
coupling of spin to superconducting resonators and scalability for multiple
qubit coupling. We have coupled a reflection line resonator to a hole double
quantum dot (DQD) formed in Ge hut wire. The amplitude and phase responses of
the microwave resonator revealed that the charge stability diagrams of the DQD
are in good agreement with those obtained from transport measurements. The DQD
interdot tunneling rate is shown to be tunable from 6.2 GHz to 8.5 GHz, which
demonstrates the ability to adjust the frequency detuning between the qubit and
the resonator. Furthermore, we achieved a hole-resonator coupling strength of
up to 15 MHz, with a charge qubit decoherence rate of 0.28 GHz. Meanwhile the
hole spin-resonator coupling rate was estimated to be 3 MHz. These results
suggest that holes of a DQD in a Ge hut wire are dipole coupled to microwave
photons, potentially enabling tunable hole spin-photon interactions in Ge with
an inherent spin-orbit coupling.",1905.01586v2
1999-07-23,Spin relaxation in semiconductor quantum dots,"We have studied the physical processes responsible for the spin -flip in GaAs
quantum dots. We have calculated the rates for different mechanisms which are
related to spin-orbit coupling and cause a spin-flip during the inelastic
relaxation of the electron in the dot both with and without a magnetic field.
We have shown that the zero-dimensional character of the problem when electron
wave functions are localized in all directions leads to freezing out of the
most effective spin-flip mechanisms related to the absence of the inversion
centers in the elementary crystal cell and at the heterointerface and, as a
result, to unusually low spin-flip rates.",9907367v1
2002-09-12,Electron Spin Relaxation in a Semiconductor Quantum Well,"A fully microscopic theory of electron spin relaxation by the
D'yakonov-Perel' type spin-orbit coupling is developed for a semiconductor
quantum well with a magnetic field applied in the growth direction of the well.
We derive the Bloch equations for an electron spin in the well and define
microscopic expressions for the spin relaxation times. The dependencies of the
electron spin relaxation rate on the lowest quantum well subband energy,
magnetic field and temperature are analyzed.",0209296v2
2003-06-16,All-Electrical Quantum Computation with Mobile Spin Qubits,"We describe and discuss a solid state proposal for quantum computation with
mobile spin qubits in one-dimensional systems, based on recent advances in
spintronics. Static electric fields are used to implement a universal set of
quantum gates, via the spin-orbit and exchange couplings. Initialization and
measurement can be performed either by spin injection from/to ferromagnets, or
by using spin filters and mesoscopic spin polarizing beam-splitters. The
vulnerability of this proposal to various sources of error is estimated by
numerical simulations. We also assess the suitability of various materials
currently used in nanotechnology for an actual implementation of our model.",0306401v1
2003-11-27,Drift-Diffusion Approach to Spin-Polarized Transport,"We develop a drift-diffusion equation that describes electron spin
polarization density in two-dimensional electron systems. In our approach,
superpositions of spin-up and spin-down states are taken into account, what
distinguishes our model from the traditional two-component drift-diffusion
approximation. The Dresselhaus and Rashba spin-orbit coupling mechanisms are
incorporated into consideration, as well as an applied electric field. The
derived equation is applied to the modelling of relaxation of homogeneous spin
polarization. Our results are consistent with previous studies.",0311633v3
2004-04-02,Splitting electronic spins with a Kondo double dot device,"We present a simple device made of two small capacitively coupled quantum
dots in parallel. This set-up can be used as an efficient ""Stern-Gerlach"" spin
filter, able to simultaneously produce, from a normal metallic lead, two
oppositely spin-polarized currents when submitted to a local magnetic field.
Our proposal is based on the realization of a Kondo effect where spin and
orbital degrees of freedom are entangled, allowing a spatial separation between
the two spin polarized currents. In the low temperature Kondo regime, the
efficiency is very high and the device conductance reaches the unitary limit,
$\frac{e^2}{h}$ per spin branch.",0404037v2
2004-09-22,Rashba spin precession in quantum Hall edge channels,"Quasi--one dimensional edge channels are formed at the boundary of a
two-dimensional electron system subject to a strong perpendicular magnetic
field. We consider the effect of Rashba spin--orbit coupling, induced by
structural inversion asymmetry, on their electronic and transport properties.
Both our analytical and numerical results show that spin--split quantum--Hall
edge channels exhibit properties analogous to that of Rashba--split quantum
wires. Suppressed backscattering and a long spin life time render these edge
channels an ideal system for observing voltage--controlled spin precession.
Based on the latter, we propose a magnet--less spin--dependent electron
interferometer.",0409580v1
2004-10-08,Spin-dependent resonant tunneling in symmetrical double-barrier structure,"A theory of resonant spin-dependent tunneling has been developed for
symmetrical double-barrier structures grown of non-centrosymmetrical
semiconductors. The dependence of the tunneling transparency on the spin
orientation and the wave vector of electrons leads to (i) spin polarization of
the transmitted carriers in an in-plane electric field, (ii) generation of an
in-plane electric current under tunneling of spin-polarized carriers. These
effects originated from spin-orbit coupling-induced splitting of the resonant
level have been considered for double-barrier tunneling structures.",0410198v1
2004-12-20,Intrinsic Spin-Hall Effect in n-Doped Bulk GaAs,"We show that the bulk Dresselhauss ($k^3$) spin-orbit coupling term leads to
an intrinsic spin-Hall effect in n-doped bulk GaAs, but without the appearance
of uniform magnetization. The spin-Hall effect in strained and unstrained bulk
GaAs has been recently observed experimentally by Kato {\emph{et. al.}}
\cite{kato2004A}. We show that the experimental result is quantitatively
consistent with the intrinsic spin-Hall effect due to the Dresselhauss term,
when lifetime broadening is taken into account. On the other hand, extrinsic
contribution to the spin-Hall effect is several orders of magnitude smaller
than the observed effect.",0412550v1
2005-01-31,Spin Polarization and Dichroism Effects by Electric Field,"We show that electric field can induce spin polarization and dichroism
effects in angle resolved photoemission spectroscopy (ARPES) in spin orbit
coupling systems. The physical origin behind the effects essentially is the
same as the spin Hall effect induced by the electric field. Since the ARPES
experiments have both energy and momentum resolutions, the spin Hall effect can
be directly verified by the ARPES experiments for individual band even if there
is no net spin current.",0502005v1
2005-01-31,Spin current injection by intersubband transitions in quantum wells,"We show that a pure spin current can be injected in quantum wells by the
absorption of linearly polarized infrared radiation, leading to transitions
between subbands. The magnitude and the direction of the spin current depend on
the Dresselhaus and Rashba spin-orbit coupling constants and light frequency
and, therefore, can be manipulated by changing the light frequency and/or
applying an external bias across the quantum well. The injected spin current
should be observable either as a voltage generated via the anomalous spin-Hall
effect, or by spatially resolved pump-probe optical spectroscopy.",0502007v2
2005-03-20,Charge and spin density modulations in semiconductor quantum wires,"We investigate static charge and spin density modulation patterns along a
ferromagnet/semiconductor single junction quantum wire in the presence of
spin-orbit coupling. Coherent scattering theory is used to calculate the charge
and spin densities in the ballistic regime. The observed oscillatory behavior
is explained in terms of the symmetry of the charge and spin distributions of
eigenstates in the semiconductor quantum wire. Also, we discuss the condition
that these charge and spin density oscillations can be observed experimentally.",0503513v1
2005-04-14,Intrinsic Spin Hall Effect,"A brief review is given on the spin Hall effect, where an external electric
field induces a transverse spin current. It has been recognized over 30 years
that such effect occurs due to impurities in the presence of spin-orbit
coupling. Meanwhile, it was proposed recently that there is also an intrinsic
contribution for this effect. We explain the mechanism for this intrinsic spin
Hall effect. We also discuss recent experimental observations of the spin Hall
effect.",0504353v2
2006-01-09,Spin transverse force and intrinsic quantum transverse transport,"The spin-orbit coupling may generate spin transverse force on moving electron
spin, which gives a heuristic picture for the quantum transverse transport of
electron. A relation between the spin and anomalous Hall conductance and spin
force was established, and applied to several systems. It was predicted that
the sign change of anomalous Hall conductance can occur in diluted magnetic
semiconductors of narrow band and can be applied to identify intrinsic
mechanism experimentally.",0601152v2
2006-06-08,Spin relaxation in narrow wires of a two-dimensional electron gas,"How does an initially homogeneous spin-polarization in a confined
two-dimensional electron gas with Rashba spin-orbit coupling evolve in time?
How does the relaxation time depend on system size? We study these questions
for systems of a size that is much larger than the Fermi wavelength, but
comparable and even shorter than the spin relaxation length. Depending on the
confinement spin-relaxation may become faster or slower than in the bulk. An
initially homogeneously polarized spin system evolves into a spiral pattern.",0606209v1
2007-01-25,Current-induced spin polarization and the spin Hall effect: a quasiclassical approach,"The quasiclassical Green function formalism is used to describe charge and
spin dynamics in the presence of spin-orbit coupling. We review the results
obtained for the spin Hall effect on restricted geometries. The role of
boundaries is discussed in the framework of spin diffusion equations.",0701629v1
2008-05-15,Spin polarizations and spin Hall currents in a two-dimensional electron gas with magnetic impurities,"We consider a two-dimensional electron gas in the presence of Rashba
spin-orbit coupling, and study the effects of magnetic s-wave impurities and
long-range non-magnetic disorder on the spin-charge dynamics of the system. We
focus on voltage induced spin polarizations and their relation to spin Hall
currents. Our results are obtained using the quasiclassical Green function
technique, and hold in the full range of the disorder parameter $\alpha
p_F\tau$.",0805.2346v2
2008-09-29,Spin-dependent electron transport through a parallel double-quantum-dot structure,"Electron transport properties in a parallel double-quantum-dot structure with
three-terminals are theoretically studied. By introducing a local Rashba
spin-orbit coupling, we find that an incident electron from one terminal can
select a specific terminal to depart from the quantum dots according to its
spin state. As a result, spin polarization and spin separation can be
simultaneously realized in this structure. And spin polarizations in different
terminals can be inverted by tuning the structure parameters. The underlying
quantum interference that gives rise to such a result is analyzed in the
language of Feynman paths for the electron transmission.",0809.4913v1
2009-04-07,Spin angular impulse due to spin-dependent reflection off a barrier,"The spin-dependent elastic reflection of quasi two-dimensional electrons from
a lateral impenetrable barrier in the presence of band-structure spin-orbit
coupling results in a spin angular impulse exerted on the electrons which is
proportional to the nontrivial difference between the electrons' momentum and
velocity. Even for an unpolarized incoming beam we find that the spin angular
impulse is nonzero when averaged over all components of the reflected beam. We
present a detailed analysis of the kinematics of this process.",0904.1228v2
2009-05-04,Electron spin relaxation in graphene: the role of the substrate,"Theory of the electron spin relaxation in graphene on the SiO$_2$ substrate
is developed. Charged impurities and polar optical surface phonons in the
substrate induce an effective random Bychkov-Rashba-like spin-orbit coupling
field which leads to spin relaxation by the D'yakonov-Perel' mechanism.
Analytical estimates and Monte Carlo simulations show that the corresponding
spin relaxation times are between micro- to milliseconds, being only weakly
temperature dependent. It is also argued that the presence of adatoms on
graphene can lead to spin lifetimes shorter than nanoseconds.",0905.0424v2
2009-06-20,Wavevector-dependent spin filtering and spin transport through magnetic barriers in graphene,"We study the spin-resolved transport through magnetic nanostructures in
monolayer and bilayer graphene. We take into account both the orbital effect of
the inhomogeneous perpendicular magnetic field as well as the in-plane spin
splitting due to the Zeeman interaction and to the exchange coupling possibly
induced by the proximity of a ferromagnetic insulator. We find that a single
barrier exhibits a wavevector-dependent spin filtering effect at energies close
to the transmission threshold. This effect is significantly enhanced in a
resonant double barrier configuration, where the spin polarization of the
outgoing current can be increased up to 100% by increasing the distance between
the barriers.",0906.3809v1
2010-11-03,Voltage controlled spin precession in InAs quantum wells,"In this work we investigate spin diffusion in InAs quantum wells with the
Rashba spin-orbit coupling modulated by a gate voltage. The gate voltage
dependence of the spin diffusion under different temperatures is studied with
all the scattering explicitly included. Our result partially supports the claim
of the realization of the Datta-Das spin-injected field effect transistor by
Koo {\it et al.} [Science {\bf 325}, 1515 (2009)]. We also show that the
scattering plays an important role in spin diffusion in such a system.",1011.0813v2
2011-04-08,Zero temperature geometric spin dephasing on a ring in presence of an Ohmic environment,"We study zero temperature spin dynamics of a particle confined to a ring in
presence of spin orbit coupling and Ohmic electromagnetic fluctuations. We show
that the dynamics of the angular position $\theta(t)$ are decoupled from the
spin dynamics and that the latter is mapped to certain correlations of a
spinless particle. We find that the spin correlations in the $z$ direction
(perpendicular to the ring) are finite at long times, i.e. do not dephase. The
parallel (in plane) components for spin $\half$ do not dephase at weak
dissipation but they probably decay as a power law with time at strong
dissipation.",1104.1637v1
2011-06-15,Spin Scissors Mode and the Fine Structure of M1 States in Nuclei,"The coupled dynamics of low lying modes, including the scissors mode, and
various giant quadrupole resonances are studied with the help of the Wigner
Function Moments method generalized to take into account spin degrees of
freedom. Equations of motion for collective variables are derived on the basis
of Time Dependent Hartree-Fock equations in the model of harmonic oscillator
with spin orbital mean field potential plus quadrupole-quadrupole residual
interaction. Introducing spin allows one to consider new types of nuclear
collective motion where the nucleons with spin 'up' oscillate against nucleons
with spin 'down'.",1106.2963v1
2013-03-26,Current-driven domain wall motion with spin Hall effect: Reduction of threshold current density,"We theoretically study the current-driven domain wall motion in the presence
of both the spin Hall effect and an extrinsic pinning potential. The spin Hall
effect mainly affects the damping ratio of the domain wall precession in the
pinning potential. When the pinning potential is not too strong, this results
in a significant reduction of a threshold current density for the depinning of
a domain wall with certain polarity. We also propose one way to distinguish the
spin Hall effect induced spin-transfer torque from the one induced by the
Rashba spin-orbit coupling experimentally.",1303.6458v1
2013-07-12,Fermi liquid theory of resonant spin pumping,"We study resonant all-electric adiabatic spin pumping through a quantum dot
with two nearby levels by using a Fermi liquid approach in the strongly
interacting regime, combined with a projective numerical renormalization group
(NRG) theory. Due to spin-orbit coupling, a strong spin pumping resonance
emerges at every charging transition, which allows for the transfer of a spin
$~ \hbar/2$ through the device in a single pumping cycle. Depending on the
precise geometry of the device, controlled pure spin pumping is also possible.",1307.3416v2
2015-03-10,Graphene Spintronics,"The isolation of graphene has triggered an avalanche of studies into the
spin-dependent physical properties of this material, as well as graphene-based
spintronic devices. Here we review the experimental and theoretical
state-of-art concerning spin injection and transport, defect-induced magnetic
moments, spin-orbit coupling and spin relaxation in graphene. Future research
in graphene spintronics will need to address the development of applications
such as spin transistors and spin logic devices, as well as exotic physical
properties including topological states and proximity-induced phenomena in
graphene and other 2D materials.",1503.02743v1
2015-08-27,Kane model parameters and stochastic spin current,"The spin current and spin conductivity is computed through thermally driven
stochastic process. By evaluating the Kramers equation and with the help of
$\vec{k}.\vec{p}$ method we have studied the spin Hall scenario. Due to the
thermal assistance, the Kane model parameters get modified, which consequently
modulate the spin orbit coupling(SOC). This modified SOC causes the spin
current to change in a finite amount.",1508.06764v1
2008-07-27,Tunneling spin current and spin diode behavior in bilayer system,"The coherent tunneling spin current in the bilayer system with spin-orbit
coupling is investigated. Based on the continuity-like equations, we discuss
the definition of the tunneling current and show that the overlaps between
wavefunctions for different layers contribute to the tunneling current. We
study the linear response of the tunneling spin current to an in-plane electric
field in the presence of nonmagnetic impurities. The tunneling spin
conductivity we obtained presents a feature asymmetrical with respect to the
gate voltage when the strengthes of impurity potentials are different in each
layer.",0807.4296v1
2009-12-16,Universality of Anderson transition in two-dimensional systems of symplectic symmetry class,"We investigate localization of noninteracting particles with spins higher
than 1/2 in a two-dimensional random potential in presence of spin-orbit
coupling. We consider an integer spin ($s=1$) and a half-integer spin ($s=3/2$)
belonging to orthogonal and symplectic symmetry classes, respectively. We show
that particles with integer spin are localized and those with half-integer spin
exhibit Anderson transition. The transition belongs to universality class of
conventional symplectic model for spin-1/2 particles.",0912.3084v2
2013-09-02,Proposal for a local heating driven spin current generator,"We propose a two-terminal spin-orbit interferometer with a hot molecule
inserted in one of its arms to generate pure spin currents. Local heating is
achieved by coupling the vibrational modes of the molecule to a third
(phononic) reservoir. We show that this spin calorimetric effect is due to the
combined influence of spin-dependent wave interference and inelastic
scattering. Remarkably, the device converts heat flow into spin-polarized
current even without applying any voltage or temperature difference to the
electronic terminals.",1309.0366v1
2018-12-17,Intrinsic Spin Hall Conductivity of MoTe2 and WTe2 Semimetals,"We report a comprehensive study on the intrinsic spin Hall conductivity (SHC)
of semimetals MoTe2 and WTe2 by ab initio calculation. Large SHC and desirable
spin Hall angles have been discovered, due to the strong spin orbit coupling
effect and low charge conductivity in semimetals. Diverse anisotropic SHC
values, attributed to the unusual reduced-symmetry crystalline structure, have
been revealed. We report an effective method on SHC optimization by electron
doping, and exhibit the mechanism of SHC variation respect to the energy
shifting by the spin Berry curvature. Our work provides insights into the
realization of strong spin Hall effects in 2D systems.",1812.06910v1
2019-08-20,Spin-selective Aharonov-Casher caging in a topological quantum network,"A periodic network of connected rhombii, mimicking a spintronic device, is
shown to exhibit an intriguing spin selective extreme localization, when
submerged in a uniform out of plane electric field. The topological Aharonov
Casher phase acquired by a travelling spin is seen to induce a complete caging,
triggered at a special strength of the spin orbit coupling, for half odd
integer spins s \ge n\hbar/2, with n odd, sparing the integer spins. The
observation finds exciting experimental parallels in recent literature on
caged, extreme localized modes in analogous photonic lattices. Our results are
exact.",1908.07175v1
2019-12-24,Large spin Hall angle and spin mixing conductance in highly resistive antiferromagnetic Mn2Au,"Antiferromagnetic (AFM) materials recently have shown interest in the
research in spintronics due to its zero stray magnetic field, high anisotropy,
and spin orbit coupling. In this context, the bi-metallic AFM Mn2Au has drawn
attention because it exhibits unique properties and its Neel temperature is
very high. Here, we report spin pumping and inverse spin Hall effect
investigations in Mn2Au and CoFeB bilayer system using ferromagnetic resonance.
We found large spin Hall angle {\theta}_SH = 0.22",1912.11522v2
2023-12-30,Ultrafast X-ray Diffraction Probe of Coherent Spin-state Dynamics in Molecules,"We propose an approach to probe coherent spin-state dynamics of molecules
using circularly polarized hard x-ray pulses. For the dynamically aligned
nitric oxide molecules in a coherent superposition spin-orbit coupled
electronic state that can be prepared through stimulated Raman scattering, we
demonstrate the capability of ultrafast x-ray diffraction to not only reveal
the quantum beating of the coherent spin-state wave packet, but also image the
spatial spin density of the molecule. With circularly polarized ultrafast x-ray
diffraction signal, we show that the electronic density matrix can be
retrieved. The spatio-temporal resolving power of ultrafast x-ray diffraction
paves the way for tracking transient spatial wave function in molecular
dynamics involving spin degree of freedom.",2401.00259v1
2024-03-21,Efecto Hall de espin inverso en peliculas de Nb Mo y Bi por bombeo de espin,"The inverse spin Hall effect used for detection of spin currents was observed
by voltage measurements in bilayers of normal metal (NM)/ferromagnetic metal
(FM), using Nb, Mo and Bi as normal metal and Permalloy (Py,
Ni$_{81}$Fe$_{19}$) as ferromagnetic metal. The spin current was generated by
the spin pumping effect with ferromagnetic resonance. The samples were
deposited by dc magnetron sputtering at room temperature on Si (001)
substrates. The three bilayers of Nb/Py, Mo/Py and Bi/Py had a spin-orbit
coupling large enough to observe the voltage generation by spin Hall effect",2403.17976v1
2003-09-25,Strong-coupling theory of superconductivity in a degenerate Hubbard model,"In order to discuss superconductivity in orbital degenerate systems, a
microscopic Hamiltonian is introduced. Based on the degenerate model, a
strong-coupling theory of superconductivity is developed within the fluctuation
exchange (FLEX) approximation where spin and orbital fluctuations, spectra of
electron, and superconducting gap function are self-consistently determined.
Applying the FLEX approximation to the orbital degenerate model, it is shown
that the $d_{x^2-y^2}$-wave superconducting phase is induced by increasing the
orbital splitting energy which leads to the development and suppression of the
spin and orbital fluctuations, respectively. It is proposed that the orbital
splitting energy is a controlling parameter changing from the paramagnetic to
the antiferromagnetic phase with the $d_{x^2-y^2}$-wave superconducting phase
in between.",0309575v1
2004-07-05,Ferromagnetic fluctuation and possible triplet superconductivity in Na_xCoO_2*yH_2O: Fluctuation-exchange study of multi-orbital Hubbard model,"Spin and charge fluctuations and superconductivity in a recently discovered
superconductor Na_xCoO_2*yH_2O are studied based on a multi-orbital Hubbard
model. Tight-binding parameters are determined to reproduce the LDA band
dispersions with the Fermi surface, which consist of a large cylindrical one
around the Gamma-point and six hole pockets near the K-points. By applying the
fluctuation-exchange (FLEX) approximation, we show that the Hund's-rule
coupling between the Co t2g orbitals causes ferromagnetic (FM) spin
fluctuation. Triplet f_{y(y^2-3x^2)}-wave and p-wave pairings are favored by
this FM fluctuation on the hole-pocket band. We propose that, in
Na_xCoO_2*yH_2O, the Co t2g orbitals and inter-orbital Hund's-rule coupling
play important roles on the triplet pairing, and this compound can be a first
example of the triplet superconductor in which the orbital degrees of freedom
play substantial roles.",0407094v3
2012-10-05,Orbital phases of fermions in an asymmetric optical ladder,"We study a quantum ladder of interacting fermions with coupled s and p
orbitals. Such a model describes dipolar molecules or atoms loaded into a
double-well optical lattice, dipole moments being aligned by an external field.
The two orbital components have distinct hoppings. The tunneling between them
is equivalent to a partial Rashba spin-orbital coupling when the orbital space
(s, p) is identified as spanned by pseudo-spin 1/2 states. A rich phase
diagram, including incommensurate orbital density wave, pair density wave and
other exotic superconducting phases, is proposed with bosonization analysis. In
particular, superconductivity is found in the repulsive regime.",1210.1859v2
2019-08-24,SU(4) Heisenberg model on the honeycomb lattice with exchange-frustrated perturbations: implications for twistronics and Mott insulators,"The SU(4)-symmetric spin-orbital model on the honeycomb lattice was recently
studied in connection to correlated insulators such as the $e_{g}$ Mott
insulator Ba$_{3}$CuSb$_{2}$O$_{9}$ and the insulating phase of magic-angle
twisted bilayer graphene at quarter filling. Here we provide a unified
discussion of these systems by investigating an extended model that includes
the effects of Hund's coupling and anisotropic, orbital-dependent exchange
interactions. Using a combination of mean-field theory, linear flavor-wave
theory, and variational Monte Carlo, we show that this model harbors a quantum
spin-orbital liquid over a wide parameter regime around the SU(4)-symmetric
point. For large Hund's coupling, a ferromagnetic antiferro-orbital ordered
state appears, while a valence-bond crystal combined with a vortex orbital
state is stabilized by dominant orbital-dependent exchange interactions.",1908.09224v2
2016-02-25,Phase diagram and collective excitation in excitonic insulator: from the orbital physics viewpoint,"Excitonic insulating system is studied from the viewpoints of the orbital
physics in strongly correlated electron systems. An effective model Hamiltonian
for low-energy electronic states is derived from the two-orbital Hubbard model
with a finite energy difference corresponding to the crystalline field
splitting. The effective model is represented by the spin operators and the
pseudo-spin operators for the spin-state degrees of freedom. The ground state
phase diagram is analyzed by the mean-field approximation. In addition to the
low-spin state and high-spin state phases, two kinds of the excitonic
insulating phases emerge as a consequence of the competition between the
crystalline field effect and the Hund coupling. The excitonic transition is
classified to be an Ising-like transition reflecting a spontaneous breaking of
the $Z_2$ symmetry. Magnetic structures in the two excitonic insulating phases
are different from each other; an antiferromagnetic order and a spin nematic
order. Collective excitations in each phase are examined by using the
generalized spin-wave method. The Goldstone modes in the excitonic insulating
phases appear in the dynamical correlation functions for the spins and
pseudo-spin operators. Both the transverse and longitudinal spin excitation
modes are active in the two excitonic insulating phases in contrast to the
low-spin state and high-spin state phases. Connections of the present results
to the perovskite cobalt oxides are discussed.",1602.07831v2
2021-10-07,Relativistic scattering of a fast spinning neutron star by a massive black hole,"The orbital dynamics of fast spinning neutron stars encountering a massive
Black Hole (BH) with unbounded orbits are investigated using the
quadratic-in-spin Mathisson-Papapetrou- Dixon (MPD) formulation. We consider
the motion of the spinning neutron stars with astrophysically relevant speed in
the gravity field of the BH. For such slow-speed scattering, the hyperbolic
orbits followed by these neutron stars all have near the e = 1 eccentricity,
and have distinct properties compared with those of e >> 1. We have found that
compared with geodesic motion, the spin-orbit and spin-spin coupling will lead
to a variation of scattering angles at spatial infinity, and this variation is
more prominent for slow-speed scattering than fast-speed scattering. Such a
variation leads to an observable difference in pulse-arrival-time within a few
hours of observation, and up to a few days or months for larger BH masses or
longer spinning periods. Such a relativistic pulsar-BH system also emits a
burst of gravitational waves (GWs) in the sensitivity band of LISA, and for
optimal settings, can be seen up to 100 Mpc away. A radio follow up of such a
GW burst with SKA or FAST will allow for measuring the orbital parameters with
high accuracy and testing the predictions of General Relativity (GR).",2110.03494v1
2015-08-07,Spin reorientation driven by the interplay between spin-orbit coupling and Hund's rule coupling in iron pnictides,"In most magnetically-ordered iron pnictides, the magnetic moments lie in the
FeAs planes, parallel to the modulation direction of the spin stripes. However,
recent experiments in hole-doped iron pnictides have observed a reorientation
of the magnetic moments from in-plane to out-of-plane. Interestingly, this
reorientation is accompanied by a change in the magnetic ground state from a
stripe antiferromagnet to a tetragonal non-uniform magnetic configuration.
Motivated by these recent observations, here we investigate the origin of the
spin anisotropy in iron pnictides using an itinerant microscopic electronic
model that respects all the symmetry properties of a single FeAs plane. We find
that the interplay between the spin-orbit coupling and the Hund's rule coupling
can account for the observed spin anisotropies, including the spin
reorientation in hole-doped pnictides, without the need to invoke orbital or
nematic order. Our calculations also reveal an asymmetry between the magnetic
ground states of electron- and hole-doped compounds, with only the latter
displaying tetragonal magnetic states.",1508.01763v4
2018-05-03,Post-Newtonian spin-tidal couplings for compact binaries,"We compute the spin-tidal couplings that affect the dynamics of two orbiting
bodies at the leading order in the post-Newtonian (PN) framework and to linear
order in the spin. These corrections belong to two classes: (i) terms arising
from the coupling between the ordinary tidal terms and the point-particle
terms, which depend on the standard tidal Love numbers of order $l$ and affect
the gravitational-wave (GW) phase at $(2l+5/2)$PN order and (ii) terms
depending on the rotational tidal Love numbers, recently introduced in previous
work, that affect the GW phase at $(2l+1/2+\delta_{2l})$PN order. For circular
orbits and spins orthogonal to the orbital plane, all leading-order spin-tidal
terms enter the GW phase at $1.5$PN order relative to the standard,
quadrupolar, tidal deformability term (and, thus, before the standard octupolar
tidal deformability terms). We present the GW phase that includes all tidal
terms up to $6.5$PN order and to linear order in the spin. We comment on a
conceptual issue related to the inclusion of the rotational tidal Love numbers
in a Lagrangian formulation and on the relevance of spin-tidal couplings for
parameter estimation in coalescing neutron-star binaries and for tests of
gravity.",1805.01487v3
2020-01-26,Electronically driven spin-reorientation transition of the correlated polar metal Ca$_3$Ru$_2$O$_7$,"Polar distortions in solids give rise to the well-known functionality of
switchable macroscopic polarisation in ferroelectrics and, when combined with
strong spin-orbit coupling, can mediate giant spin splittings of electronic
states. While typically found in insulators, ferroelectric-like distortions can
remain robust against increasing itineracy, giving rise to so-called ""polar
metals"". Here, we investigate the temperature-dependent electronic structure of
Ca$_3$Ru$_2$O$_7$, a correlated oxide metal in which octahedral tilts and
rotations combine to mediate pronounced polar distortions. Our angle-resolved
photoemission measurements reveal the destruction of a large hole-like Fermi
surface upon cooling through a coupled structural and spin-reorientation
transition at 48 K, accompanied by a sudden onset of quasiparticle coherence.
We demonstrate how these result from band hybridisation mediated by a hidden
Rashba-type spin-orbit coupling. This is enabled by the bulk structural
distortions and unlocked when the spin reorients perpendicular to the local
symmetry-breaking potential at the Ru sites. We argue that the electronic
energy gain associated with the band hybridisation is actually the key driver
for the phase transition, reflecting a delicate interplay between spin-orbit
coupling and strong electronic correlations, and revealing a new route to
control magnetic ordering in solids.",2001.09499v1
2004-12-28,Magnetic state of plutonium ion in metallic Pu and its compounds,"By LDA+U method with spin-orbit coupling (LDA+U+SO) the magnetic state and
electronic structure have been investigated for plutonium in \delta and \alpha
phases and for Pu compounds: PuN, PuCoGa5, PuRh2, PuSi2, PuTe, and PuSb. For
metallic plutonium in both phases in agreement with experiment a nonmagnetic
ground state was found with Pu ions in f^6 configuration with zero values of
spin, orbital, and total moments. This result is determined by a strong
spin-orbit coupling in 5f shell that gives in LDA calculation a pronounced
splitting of 5f states on f^{5/2} and f^{7/2} subbands. A Fermi level is in a
pseudogap between them, so that f^{5/2} subshell is already nearly completely
filled with six electrons before Coulomb correlation effects were taken into
account. The competition between spin-orbit coupling and exchange (Hund)
interaction (favoring magnetic ground state) in 5f shell is so delicately
balanced, that a small increase (less than 15%) of exchange interaction
parameter value from J_H=0.48eV obtained in constrain LDA calculation would
result in a magnetic ground state with nonzero spin and orbital moment values.
For Pu compounds investigated in the present work, predominantly f^6
configuration with nonzero magnetic moments was found in PuCoGa5, PuSi2, and
PuTe, while PuN, PuRh2, and PuSb have f^5 configuration with sizeable magnetic
moment values. Whereas pure jj coupling scheme was found to be valid for
metallic plutonium, intermediate coupling scheme is needed to describe 5f shell
in Pu compounds. The results of our calculations show that both spin-orbit
coupling and exchange interaction terms in the Hamiltonian must be treated in a
general matrix form for Pu and its compounds.",0412724v2
2006-08-07,Polarization-induced Rashba spin-orbit coupling in structurally symmetric III-Nitride quantum wells,"The effective linear coupling coefficient and the total spin-splitting are
calculated in Ga- and N- face InGaN quantum wells. Alloy content, geometry, and
gate voltage affect an internal field and an electron density distribution in
the growth direction that has direct effect on a spin-splitting. The sign of
structural inversion asymmetry (SIA) spin-orbit coupling coefficient depends on
an internal electric field in the well that results in different signs for
Ga-face and N-face III-Nitride structures. The effective linear coupling
coefficient is always positive because of the Dresselhaus-type contribution
that is a major one in quantum wells under consideration. The magnitude of the
spin-splitting is comparable with that experimentally observed in III-Nitrides
and III-V zinc-blende structures.",0608179v1
2019-04-17,Dynamical spin-orbit coupling of a quantum gas,"We realize the dynamical 1D spin-orbit-coupling (SOC) of a Bose-Einstein
condensate confined within an optical cavity. The SOC emerges through
spin-correlated momentum impulses delivered to the atoms via Raman transitions.
These are effected by classical pump fields acting in concert with the quantum
dynamical cavity field. Above a critical pump power, the Raman coupling emerges
as the atoms superradiantly populate the cavity mode with photons.
Concomitantly, these photons cause a back-action onto the atoms, forcing them
to order their spin-spatial state. This SOC-inducing superradiant Dicke phase
transition results in a spinor-helix polariton condensate. We observe emergent
SOC through spin-resolved atomic momentum imaging. Dynamical SOC in quantum gas
cavity QED, and the extension to dynamical gauge fields, may enable the
creation of Meissner-like effects, topological superfluids, and exotic quantum
Hall states in coupled light-matter systems.",1904.08388v1
2012-02-14,Quantum tri-criticality and phase transitions in spin-orbit coupled Bose-Einstein condensates,"We consider a spin-orbit coupled configuration of spin-1/2 interacting bosons
with equal Rashba and Dresselhaus couplings. The phase diagram of the system is
discussed with special emphasis to the role of the interaction treated in the
mean-field approximation. For a critical value of the density and of the Raman
coupling we predict the occurrence of a characteristic tri-critical point
separating the spin mixed, the phase separated and the single minimum states of
the Bose gas. The corresponding quantum phases are investigated analyzing the
momentum distribution, the longitudinal and transverse spin-polarization and
the emergence of density fringes. The effect of harmonic trapping as well as
the role of the breaking of spin symmetry in the interaction Hamiltonian are
also discussed.",1202.3036v2
2012-06-28,Theory of Spin Relaxation in Two-Electron Lateral Coupled Si/SiGe Quantum Dots,"Highly accurate numerical results of phonon-induced two-electron spin
relaxation in silicon double quantum dots are presented. The relaxation,
enabled by spin-orbit coupling and the nuclei of $^{29}$Si (natural or purified
abundance), are investigated for experimentally relevant parameters, the
interdot coupling, the magnetic field magnitude and orientation, and the
detuning. We calculate relaxation rates for zero and finite temperatures (100
mK), concluding that our findings for zero temperature remain qualitatively
valid also for 100 mK. We confirm the same anisotropic switch of the axis of
prolonged spin lifetime with varying detuning as recently predicted in GaAs.
Conditions for possibly hyperfine-dominated relaxation are much more stringent
in Si than in GaAs. For experimentally relevant regimes, the spin-orbit
coupling, although weak, is the dominant contribution, yielding anisotropic
relaxation rates of at least two order of magnitude lower than in GaAs.",1206.6906v2
2020-11-25,Non-tidal Coupling of the Orbital and Rotational Motions of Extended Bodies,"The orbital motions and spin-axis rotations of extended bodies are
traditionally considered to be coupled only by tidal mechanisms. The orbit-spin
coupling hypothesis supplies an additional mechanism. A reversing torque on
rotating extended bodies is identified. The torque effects an exchange of
angular momentum between the reservoirs of the orbital and rotational motions.
The axis of the torque is constrained to lie within the equatorial plane of the
subject body. Hypothesis testing to date has focused on the response to the
putative torque of the Martian atmosphere. Atmospheric global circulation model
simulations reveal that an episodic strengthening and weakening of meridional
overturning circulations should be observable and is diagnostic in connection
with the triggering of Martian planet-encircling dust storms. Spacecraft
observations obtained during the earliest days of the 2018 Martian global dust
storm document a strong intensification of atmospheric meridional motions as
predicted under this hypothesis. We review implications for atmospheric
physics, for investigations of planetary orbital evolution with rotational
energy dissipation, and for theories of gravitation.",2011.13053v1
2023-06-19,Superconductivity from polar fluctuations in multi-orbital systems,"Motivated by the superconductivity near paraelectric (PE) to ferroelectric
(FE) quantum critical point (QCP) in polar metals, we study polar fluctuation
mediated superconductivity in multi-orbital systems. The PE to FE QCP is
approached by softening of a transverse optical (TO) phonon that is odd under
inversion ($\mathcal{I}$). We show that the necessary and sufficient condition
for the linear coupling between electron-TO phonon is the presence of multiple
orbitals on the Fermi-surface, irrespective of the spin-orbital (SO) coupling,
multiple electronic bands, or the vicinity to band crossings. We show that the
linear coupling to the polar fluctuations (such as TO modes) can generally lead
to superconductivity. We also show that irrespective of the strong $\vec{k}$
dependence of the effective electron-electron interaction in the BCS channel,
quite generally the even-parity channel leads to the highest critical
temperature. In the presence of additional repulsive electron-electron
interactions, an odd-parity spin-triplet channel can become the leading BCS
instability. Finally, we discuss our results in the context of the
superconductivity in $\text{SrTiO}_3$ and $\text{KTaO}_3$ that highlights the
importance of the underlying multi-orbital physics if the superconductivity is
mediated by the polar fluctuations.",2306.11063v1
2010-12-14,Chiral Rashba spin textures in ultra-cold Fermi gases,"Spin-orbit coupling is an important ingredient in many recently discovered
phenomena such as the spin-Hall effect and topological insulators. Of
particular interest is topological superconductivity, with its potential
application in topological quantum computation. The absence of disorder in
ultra-cold atomic systems makes them ideal for quantum computation
applications, however, the spin-orbit (SO) coupling schemes proposed thus far
are experimentally impractical owing to large spontaneous emission rates in the
alkali fermions. In this paper, we develop a scheme to generate Rashba SO
coupling with a low spontaneous emission extension to a recent experiment. We
show that this scheme generates a Fermi surface spin texture for $^{40}\rm{K}$
atoms, which is observable in time-of-flight measurements. The chiral spin
texture, together with conventional $s$-wave interactions leads to topological
superconductivity and non-Abelian Majorana quasiparticles.",1012.3170v2
2011-10-29,High-temperature Aharonov-Bohm-Casher interferometer,"We study theoretically the combined effect of the spin-orbit and Zeeman
interactions on the tunneling electron transport through a single-channel
quantum ring threaded by magnetic flux. We focus on the high temperature case
(temperature is much higher than the level spacing in the ring) and demonstrate
that spin-interference effects are not suppressed by thermal averaging. In the
absence of the Zeeman coupling the high-temperature tunneling conductance of
the ring exhibits two types of oscillations: Aharonov-Bohm oscillations with
magnetic flux and Aharonov-Casher oscillations with the strength of the
spin-orbit interaction. For weak tunneling coupling both oscillations have the
form of sharp periodic antiresonances. In the vicinity of the antiresonances
the tunneling electrons acquire spin polarization, so that the ring serves as a
spin polarizer. We also demonstrate that the Zeeman coupling leads to
appearance of two additional peaks both in the tunneling conductance and in the
spin polarization.",1110.6520v1
2014-09-06,Buckled honeycomb lattice and unconventional magnetic response,"We study the magnetic response of buckled honeycomb-lattice materials. The
buckling breaks the sublattice symmetry, enhances the spin-orbit coupling, and
allows the tuning of a topological quantum phase transition. As a result, there
are two doubly degenerate spin-valley coupled massive Dirac bands, which
exhibit an unconventional Hall plateau sequence under strong magnetic fields.
We show how to externally control the splitting of anomalous zeroth Landau
levels, the prominent Landau level crossing effects, and the polarizations of
spin, valley, and sublattice degrees of freedom. In particular, we reveal that
in a p-n junction, spin-resolved fractionally quantized conductance appears in
a two-terminal measurement with a spin-polarized current propagating along the
interface. In the low-field regime where the Landau quantization is not
applicable, we provide a semiclassical description for the anomalous Hall
transport. We comment briefly on the effects of electron-electron interactions
and Zeeman couplings to electron spins and to atomic orbitals.",1409.1977v1
2015-02-16,Hanle Magnetoresistance in Thin Metal Films with Strong Spin-Orbit Coupling,"We report measurements of a new type of magnetoresistance in Pt and Ta thin
films. The spin accumulation created at the surfaces of the film by the spin
Hall effect decreases in a magnetic field because of the Hanle effect,
resulting in an increase of the electrical resistance as predicted by Dyakonov
[PRL 99, 126601 (2007)]. The angular dependence of this magnetoresistance
resembles the recently discovered spin Hall magnetoresistance in Pt/Y3Fe5O12
bilayers, although the presence of a ferromagnetic insulator is not required.
We show that this Hanle magnetoresistance is an alternative, simple way to
quantitatively study the coupling between charge and spin currents in metals
with strong spin-orbit coupling.",1502.04624v2
2015-03-06,Spin-Motive Forces and Current-Induced Torques in Ferromagnets,"In metallic ferromagnets, the spin-transfer torque and spin-motive force are
known to exhibit a reciprocal relationship. Recent experiments on ferromagnets
with strong spin-orbit coupling have revealed a rich complexity in the
interaction between itinerant charge carriers and magnetization, but a full
understanding of this coupled dynamics is lacking. Here, we develop a general
phenomenology of the two reciprocal processes of charge pumping by spin-motive
forces and current-driven magnetization dynamics. The formalism is valid for
spin-orbit coupling of any strength and presents a systematic scheme for
deriving all possible torque and charge-pumping terms that obey the symmetry
requirements imposed by the point group of the system. We demonstrate how the
different charge pumping and torque contributions are connected via the Onsager
reciprocal relations. The formalism is applied to two important classes of
systems: isotropic ferromagnets with non-uniform magnetization and homogeneous
ferromagnets described by the point group $C_{2v}$.",1503.01899v2
2016-02-02,Pseudospin induced chirality with Staggered Optical Graphene,"Pseudospin plays a very important role in understanding various interesting
physical phenomena associated with 2D materials such as graphene. It has been
proposed that pseudospin is directly related to angular momentum, and it was
recently experimentally demonstrated that orbit angular momentum is an
intrinsic property of pseudospin in a photonic honeycomb lattice. However, in
photonics, the interaction between spin and pseudospin for light has never been
investigated. In this Letter, we propose that, in an optical analogue of
staggered graphene, i.e. a photonic honeycomb lattice waveguide with in-plane
inversion symmetry breaking, the pseudospin mode can strongly couple to the
spin of an optical beam incident along certain directions. The spin-pseudospin
coupling, caused by the spin-orbit conversion in the scattering process,
induces a strong optical chiral effect for the transmitted optical beam.
Spin-pseudospin coupling of light opens door to the design of
pseudospin-mediated spin or valley selective photonic devices.",1602.01014v1
2020-07-13,Quenching dynamics of the bright solitons and other localized states in spin-orbit coupled Bose-Einstein condensates,"We study the dynamics of binary Bose-Einstein condensates made of ultracold
and dilute alkali-metal atoms in a quasi-one-dimensional setting. Numerically
solving the two coupled Gross-Pitaevskii equations which accurately describe
the system dynamics, we demonstrate that the spin transport can be controlled
by suitably quenching spin-orbit (SO) and Rabi coupling strengths. Moreover, we
predict a variety of dynamical features induced by quenching: broken
oscillations, breathers-like oscillating patterns, spin-mixing-demixing,
miscible-immiscible transition, emerging dark-bright states, dark solitons, and
spin-trapping dynamics. We also outline the experimental relevance of the
present study in manipulating the spin states in $^{39}$K condensates.",2007.06171v1
2017-04-21,Usadel equation in the presence of intrinsic spin-orbit coupling: A unified theory of magneto-electric effects in normal and superconducting systems,"The Usadel equation is the standard theoretical tool for the description of
superconducting structures in the diffusive limit. Here I derive the Usadel
equation for gyrotropic materials with a generic linear in momentum spin-orbit
coupling. It accounts for the spin-charge/singlet-triplet coupling and in the
normal state reduces to the system of spin-charge diffusion equations
describing various magneto-electric effects, such as the spin Hall effect
(SHE), the spin-galvanic effect (SGE) and their inverses. Therefore the derived
Usadel equation establishes a direct connection of these effects to their
superconducting counterparts. The working power of the present formalism is
illustrated on the example of the bulk SGE.",1704.06451v1
2017-11-09,"Spin-orbit coupling, optical transitions, and spin pumping in mono- and few-layer InSe","We show that spin-orbit coupling (SOC) in InSe enables the optical transition
across the principal band gap to couple with in-plane polarized light. This
transition, enabled by $p_{x,y}\leftrightarrow p_z$ hybridization due to
intra-atomic SOC in both In and Se, can be viewed as a transition between two
dominantly $s$- and $p_z$-orbital based bands, accompanied by an electron
spin-flip. Having parametrized $\mathbf{k\cdot p}$ theory using first
principles density functional theory we estimate the absorption for
$\sigma^{\pm}$ circularly polarized photons in the monolayer as $\sim 1.5\%$,
which saturates to $\sim 0.3\%$ in thicker films ($3-5$ layers). Circularly
polarized light can be used to selectively excite electrons into spin-polarized
states in the conduction band, which permits optical pumping of the spin
polarization of In nuclei through the hyperfine interaction.",1711.03402v1
2019-12-12,Strongly interacting spin-orbit coupled Bose-Einstein condensates in one dimension,"We theoretically study dilute superfluidity of spin-1 bosons with
antiferromagnetic interactions and synthetic spin-orbit coupling (SOC) in a
one-dimensional lattice. Employing a combination of density matrix
renormalization group and quantum field theoretical techniques we demonstrate
the appearance of a robust superfluid spin-liquid phase in which the
spin-sector of this spinor Bose-Einstein condensate remains quantum disordered
even after introducing quadratic Zeeman and helical magnetic fields. Despite
remaining disordered, the presence of these symmetry breaking fields lifts the
perfect spin-charge separation and thus the nematic correlators obey power-law
behavior. We demonstrate that, at strong coupling, the SOC induces a charge
density wave state that is not accessible in the presence of linear and
quadratic Zeeman fields alone. In addition, the SOC induces oscillations in the
spin and nematic expectation values as well as the bosonic Green's function.
These non-trivial effects of a SOC are suppressed under the application of a
large quadratic Zeeman field. We discuss how our results could be observed in
experiments on ultracold gases of $^{23}$Na in an optical lattice.",1912.06142v1
2020-05-21,Chemical Reaction Rates for Systems with Spin-Orbit Coupling and an Odd Number of Electrons: Does Berry's Phase Lead to Meaningful Spin-Dependent Nuclear Dynamics for a Two State Crossing?,"Within the context of very simple avoided crossing, we investigate the
investigate the effect of a complex diabatic coupling in determining
spin-dependent rate constants and scattering states. We find that, if the
molecular geometry is not linear and the Berry force is not zero, one can find
significant spin polarization of the products. This study emphasizes that, when
analyzing nonadiabatic reactions with spin orbit coupling (and a complex
Hamiltonian), one must consider how Berry force affects nuclear motion -- at
least in the context of gas phase reactions. Work is currently ongoing as far
as extrapolating these conclusions to the condensed phase where interesting
spin selection has been observed in recent years.",2005.10424v1
2020-06-10,Controlling spin without magnetic fields -- the Bloch-Rashba rotator,"We consider the dynamics of a quantum particle held in a lattice potential,
and subjected to a time-dependent spin-orbit coupling. Tilting the lattice
causes the particle to perform Bloch oscillations, and by suitably changing the
Rashba interaction during its motion, the spin of the particle can be gradually
rotated. Even if the Rashba coupling can only be altered by a small amount,
large spin-rotations can be obtained by accumulating the rotation from
successive oscillations. We show how the time-dependence of the spin-orbit
coupling can be chosen to maximize the rotation per cycle, and thus how this
method can be used to produce a precise and controllable spin-rotator, the
Bloch-Rashba rotator, without requiring an applied magnetic field.",2006.06046v2
2021-09-22,Engineering infinite-range SU($n$) interactions with spin-orbit-coupled fermions in an optical lattice,"We study multilevel fermions in an optical lattice described by the Hubbard
model with on site SU($n$)-symmetric interactions. We show that in an
appropriate parameter regime this system can be mapped onto a spin model with
all-to-all SU($n$)-symmetric couplings. Raman pulses that address internal spin
states modify the atomic dispersion relation and induce spin-orbit coupling,
which can act as a synthetic inhomogeneous magnetic field that competes with
the SU($n$) exchange interactions. We investigate the mean-field dynamical
phase diagram of the resulting model as a function of $n$ and different initial
configurations that are accessible with Raman pulses. Consistent with previous
studies for $n=2$, we find that for some initial states the spin model exhibits
two distinct dynamical phases that obey simple scaling relations with $n$.
Moreover, for $n>2$ we find that dynamical behavior can be highly sensitive to
initial intra-spin coherences. Our predictions are readily testable in current
experiments with ultracold alkaline-earth(-like) atoms.",2109.11019v1
2022-08-04,Giant chirality-induced spin-selectivity of polarons,"The chirality-induced spin selectivity (CISS) effect gives rise to strongly
spin-dependent transport through many organic molecules and structures. Its
discovery raises fascinating fundamental questions as well as the prospect of
possible applications. The basic phenomenology, a strongly asymmetric
magnetoresistance despite the absence of magnetism, is now understood to result
from the combination of spin-orbit coupling and chiral geometry. However,
experimental signatures of electronic helicity were observed at room
temperature, i.e., at an energy scale that exceeds the typical spin-orbit
coupling in organic systems by several orders of magnitude. This work shows
that a new energy scale for CISS emerges for currents carried by polarons,
i.e., in the presence of strong electron-phonon coupling. In particular, we
found that polaron fluctuations play a crucial role in the two manifestations
of CISS in transport measurements -- the spin-dependent transmission
probability through the system and asymmetric magnetoresistance.",2208.02530v1
2022-10-25,Exact solutions for a spin-orbit coupled bosonic double-well system,"Exact solutions for spin-orbit (SO) coupled cold atomic systems are very
important and rare in physics. In this paper, we propose a simple method of
combined modulations to generate the analytic exact solutions for an SO-coupled
boson held in a driven double well. For the cases of synchronous combined
modulations and the spin-conserving tunneling, we obtain the general analytical
accurate solutions of the system respectively. For the case of spin-flipping
tunneling under asynchronous combined modulations, we get the special exact
solutions in simple form when the driving parameters satisfy certain
conditions. Based on these obtained exact solutions, we reveal some intriguing
quantum spin dynamical phenomena, for instance, the arbitrary population
transfer (APT) with and/or without spin-flipping, the controlled coherent
population conservation (CCPC), and the controlled coherent population
inversion (CCPI). The results may have potential applications in the
preparation of accurate quantum entangled states and quantum information
processing.",2210.13724v1
2023-05-02,i-SPin 2: An integrator for general spin-s Gross-Pitaevskii systems,"We provide an algorithm for evolving general spin-$s$ Gross-Pitaevskii /
non-linear Schr\""odinger systems carrying a variety of interactions, where the
$2s+1$ components of the `spinor' field represent the different
spin-multiplicity states. We consider many nonrelativistic interactions up to
quartic order in the Schr\""odinger field (both short and long-range, and
spin-dependent and spin-independent interactions), including explicit
spin-orbit couplings. The algorithm allows for spatially varying external
and/or self-generated vector potentials that couple to the spin density of the
field. Our work can be used for scenarios ranging from laboratory systems such
as spinor Bose-Einstein condensates (BECs), to cosmological/astrophysical
systems such as self-interacting bosonic dark matter. As examples, we provide
results for two different setups of spin-$1$ BECs that employ a varying
magnetic field and spin-orbit coupling, respectively, and also collisions of
spin-$1$ solitons in dark matter. Our symplectic algorithm is second-order
accurate in time, and is extensible to the known higher-order accurate methods.",2305.01675v1
2023-10-12,Time-resolved Broadband Spectroscopy of Coherent Lattice Dynamics in a Rashba Material,"Spintronics aims at establishing an information technology relying on the
spins of electrons. Key to this vision is the spin-to-charge conversion (and
vice versa) enabled by spin-orbit coupling, which represents the intimate bond
between spins and charges. Here, we set the foundations to manipulate the
spin-orbit coupling in Rashba systems in a coherent way at THz frequencies
without parasitic electronic dissipation. Our approach relies on the generation
of coherent lattice dynamics in BiTeI. Using ultrashort laser pulses ranging
from the visible to the mid-infrared spectral range we establish quantitatively
the conditions for an effective generation of coherent THz phonons, with the
required symmetry for a manipulation of the Rashba coupling. Furthermore, we
conclude an open discussion on the possibility of photoinducing of a spin
current in BiTeI, proving that this is not the case. We envision a direct
application of our pumping scheme in a photoemission experiment, which can
directly disclose the THz dynamics of the Rashba splitting.",2310.08411v1
2007-09-07,Spin-orbit coupling effects in one-dimensional ballistic quantum wires,"We study the spin-dependent electronic transport through a one-dimensional
ballistic quantum wire in the presence of Rashba spin-orbit interaction. In
particular, we consider the effect of the spin-orbit interaction resulting from
the lateral confinement of the two-dimensional electron gas to the
one-dimensional wire geometry. We generalize a situation suggested earlier [P.
Streda and P. Seba, Phys. Rev. Lett. 90, 256601 (2003)] which allows for
spin-polarized electron transport. As a result of the lateral confinement, the
spin is rotated out of the plane of the two-dimensional system. We furthermore
investigate the spin-dependent transmission and the polarization of an electron
current at a potential barrier. Finally, we construct a lattice model which
shows similar low-energy physics. In the future, this lattice model will allow
us to study how the electron-electron interaction affects the transport
properties of the present setup.",0709.1057v2
2008-06-24,Spin polarization control via magnetic barriers and spin-orbit effects,"We investigate the spin-dependent transport properties of two-dimensional
electron gas (2DEG) systems formed in diluted magnetic semiconductors and in
the presence of Rashba spin-orbit interaction in the framework of the
scattering matrix approach. We focus on nanostructures consisting of realistic
magnetic barriers produced by the deposition of ferromagnetic strips on
heterostructures. We calculate spin-dependente conductance of such barrier
systems and show that the magnetization pattern of the strips, the tunable
spin-orbit coupling, and the enhanced Zeeman splitting have a strong effect on
the conductance of the structure. We describe how these effects can be employed
in the efficient control of spin polarization via the application of moderate
fields.",0806.3967v1
2009-06-11,The influence of the discretized Rashba spin-orbit interaction on the Harper model,"The movement of the electrons under the simultaneous influence of a scalar
periodic potential and of a uniform transversal magnetic field is described by
the well-known second order discrete Harper equation. This equation originates
from a two-dimensional energy dispersion law under the minimal substitution.
Here one deals with the Harper model under the additional influence of the
discretized spin orbit interaction. Converting the spin-orbit interaction in
terms of discrete derivatives opens the way for analytical and numerical
studies. One finds coupled equations for the spin dependent wave functions,
which leads to an appreciable alteration of the nested energy subbands
characterizing the self-similar structure of the usual Harper spectrum. To this
aim the transfer matrix method has been applied to selected spin-up and
spin-down wavefunctions. Accordingly, very manifestations of spinfiltering and
of spin correlations are accounted for. Our energy-bands calculations show that
the splitting effect implemented by such wavefunctions is appreciable.",0906.2054v1
2009-08-07,Lateral spin-orbit interaction and spin polarization in quantum point contacts,"We study ballistic transport through semiconductor quantum point contact
systems under different confinement geometries and applied fields. In
particular, we investigate how the {\em lateral} spin-orbit coupling,
introduced by asymmetric lateral confinement potentials, affects the spin
polarization of the current. We find that even in the absence of external
magnetic fields, a variable {\em non-zero spin polarization} can be obtained by
controlling the asymmetric shape of the confinement potential. These results
suggest a new approach to produce spin polarized electron sources and we study
the dependence of this phenomenon on structural parameters and applied magnetic
fields. This asymmetry-induced polarization provides also a plausible
explanation of our recent observations of a 0.5 conductance plateau (in units
of $2e^2/h$) in quantum point contacts made on InAs quantum-well structures.
Although our estimates of the required spin-orbit interaction strength in these
systems do not support this explanation, they likely play a role in the effects
enhanced by electron-electron interactions.",0908.1080v1
2010-12-01,Spin orbit in curved graphene ribbons,"We study the electronic properties of electrons in flat and curved zigzag
graphene ribbons using a tight-binding model within the Slater Koster
approximation.
  We find that curvature dramatically enhances the action of spin orbit effects
in graphene ribbons and has a strong effect on the spin orientation of the edge
states: whereas spins are normal to the surface in the case of flat ribbons,
this is no longer the case in the case of curved ribbons. We find that for the
edge states, the spin density lies always in the plane perpendicular to the
ribbon axis, and deviate strongly from the normal to the ribbon, even for very
small curvature and the small spin orbit coupling of carbon. We find that
curvature results also in an effective second neighbor hopping that modifies
the electronic properties of zigzag graphene ribbons. We discuss the
implications of our finding in the spin Hall phase of curved graphene Ribbons.",1012.0228v1
2012-08-30,Generation of spin-polarized current using multi-terminated quantum dot with spin-orbit interaction,"We theoretically examine generation of spin-polarized current using
multi-terminated quantum dot with spin-orbit interaction. First, a two-level
quantum dot is analyzed as a minimal model, which is connected to $N$ ($\ge 2$)
external leads via tunnel barriers. When an unpolarized current is injected to
the quantum dot from a lead, a polarized current is ejected to others,
similarly to the spin Hall effect. In the absence of magnetic field, the
generation of spin-polarized current requires $N \ge 3$. The polarization is
markedly enhanced by resonant tunneling when the level spacing in the quantum
dot is smaller than the level broadening due to the tunnel coupling to the
leads. In a weak magnetic field, the orbital magnetization creates a
spin-polarized current even in the two-terminal geometry (N=2). The numerical
study for generalized situations confirms our analytical result using the
two-level model.",1208.6084v1
2012-10-24,Spin Current Generation as a Nonequilibrium Kondo Effect in a Spin-orbit Mesoscopic Interferometer,"We study nonequilibrium generation of spin-dependent transport through a
single-level quantum dot embedded in a ring with the Rashba spin-orbit
coupling. We consider nonmagnetic systems, involving no magnetic field nor
ferromagnetic leads. It is theoretically predicted that large spin-dependent
current occurs as a combined effect of the Rashba spin-orbit interaction, the
Kondo effect, and nonequilibrium effect, without using magnetic field or
material. The phenomenon is viewed as a new nonequilibrium correlation effect
that disappears when either interaction or finite bias is absent. We show how
the Kondo physics is connected with such emergent spin phenomenon by employing
the finite interaction slave-boson approach.",1210.6428v1
2017-03-22,Quantum spin Hall density wave insulator of correlated fermions,"We present the theory of a new type of topological quantum order which is
driven by the spin-orbit density wave order parameter, and distinguished by
$Z_2$ topological invariant. We show that when two oppositely polarized chiral
bands [resulting from the Rashba-type spin-orbit coupling $\alpha_k$, $k$ is
crystal momentum] are significantly nested by a special wavevector ${\bf
Q}\sim(\pi,0)/(0,\pi)$, it induces a spatially modulated inversion of the
chirality ($\alpha_{k+Q}=\alpha_k^*$) between different sublattices. The
resulting quantum order parameters break translational symmetry, but preserve
time-reversal symmetry. It is inherently associated with a $Z_2$-topological
invariant along each density wave propagation direction. Hence it gives a weak
topological insulator in two dimensions, with even number of spin-polarized
boundary states. This phase is analogous to the quantum spin-Hall state, except
here the time-reversal polarization is spatially modulated, and thus it is
dubbed quantum spin-Hall density wave (QSHDW) state. This order parameter can
be realized or engineered in quantum wires, or quasi-2D systems, by tuning the
spin-orbit couping strength and chemical potential to achieve the special
nesting condition.",1703.07629v1
2017-08-23,Spin-orbit torques induced by interface-generated spin currents,"Magnetic torques generated through spin-orbit coupling promise
energy-efficient spintronic devices. It is important for applications to
control these torques so that they switch films with perpendicular
magnetizations without an external magnetic field. One suggested approach uses
magnetic trilayers in which the torque on the top magnetic layer can be
manipulated by changing the magnetization of the bottom layer. Spin currents
generated in the bottom magnetic layer or its interfaces transit the spacer
layer and exert a torque on the top magnetization. Here we demonstrate
field-free switching in such structures and attribute it to a novel spin
current generated at the interface between the bottom layer and the spacer
layer. The measured torque has a distinct dependence on the bottom layer
magnetization which is consistent with this interface-generated spin current
but not the anticipated bulk effects. This other interface-generated spin-orbit
torque will enable energy-efficient control of spintronic devices.",1708.06864v1
2017-06-20,Theory of non-collinear interactions beyond Heisenberg exchange; applications to bcc Fe,"We show for a simple non-collinear configuration of the atomistic spins (in
particular, where one spin is rotated by a finite angle in a ferromagnetic
background) that the pairwise energy variation computed in terms of multiple
scattering formalism cannot be fully mapped onto a bilinear Heisen- berg spin
model even in the lack of spin-orbit coupling. The non-Heisenberg terms induced
by the spin-polarized host appear in leading orders in the expansion of the
infinitesimal angle variations. However, an Eg-T2g symmetry analysis based on
the orbital decomposition of the exchange param- eters in bcc Fe leads to the
conclusion that the nearest neighbor exchange parameters related to the T2g
orbitals are essentially Heisenberg-like: they do not depend on the spin
configuration, and can in this case be mapped onto a Heisenberg spin model even
in extreme non-collinear cases.",1706.06560v1
2017-10-24,Electrical spin driving by $g$-matrix modulation in spin-orbit qubits,"In a semiconductor spin qubit with sizable spin-orbit coupling, coherent spin
rotations can be driven by a resonant gate-voltage modulation. Recently, we
have exploited this opportunity in the experimental demonstration of a hole
spin qubit in a silicon device. Here we investigate the underlying physical
mechanisms by measuring the full angular dependence of the Rabi frequency as
well as the gate-voltage dependence and anisotropy of the hole $g$-factors. We
show that a $g$-matrix formalism can simultaneously capture and discriminate
the contributions of two mechanisms so far independently discussed in the
literature: one associated with the modulation of the $g$ factors, and
measurable by Zeeman energy spectroscopy, the other not. Our approach has a
general validity and can be applied to the analysis of other types of
spin-orbit qubits.",1710.08690v2
2019-09-30,Magnetic circular dichroism in hard x-ray Raman scattering as a probe of local spin polarization,"We argue that the magnetic circular dichroism (MCD) of the hard x-ray Raman
scattering (XRS) could be used as an element selective probe of local spin
polarization. The magnitude of the XRS-MCD signal is directly proportional to
the local spin polarization when the angle between the incident wavevector and
the magnetization vector is $135^{\circ}$ or $-45^{\circ}$. By comparing the
experimental observation and the configuration interaction calculation at the
$L_{2,3}$ and $M_{2,3}$ edges of ferromagnetic iron, we suggest that the
integrated MCD signal in terms of the transferred energy could be used to
estimate the local spin moment even in the case where the application of the
spin sum-rule in X-ray absorption is questionable. We also point out that
XRS-MCD signal could be observed at the $M_{1}$ edge with a magnitude
comparable to that at the $M_{2,3}$ edge, although the spin-orbit coupling is
absent in the core orbital. By combining the XRS-MCD at various edges, spin
polarization distribution depending on the orbital magnetic quantum number
would be determined.",1909.13490v1
2019-01-24,Non-equilibrium spin density and spin-orbit torque in three dimensional topological insulators - antiferromagnet heterostructure,"We study the behavior of non-equilibrium spin density and spin-orbit torque
in a topological insulator - antiferromagnet heterostructure. Unlike
ferromagnetic heterostructures where Dirac cone is gapped due to time-reversal
symmetry breaking, here the Dirac cone is preserved. We demonstrate the
existence of a staggered spin density corresponding to a damping like torque,
which is quite robust against the scalar impurity, when the transport energy is
in the topological insulator surface energy regime. We show the contribution to
the non-equilibrium spin density due to both surface and bulk topological
insulator bands. Finally, we show that the torques in topological
insulator-antiferromagnet heterostructure exhibit an angular dependence that is
consistent with the standard spin-orbit torque obtained in Rashba system with
some additional nonlinear effects arising from the interfacial coupling.",1901.08314v1
2019-08-15,Natural orbital functional for multiplets,"A natural orbital functional for electronic systems with any value of the
spin is proposed. This energy functional is based on a new reconstruction for
the two-particle reduced density matrix (2RDM) of the multiplet, that is, of
the mixed quantum state that allows all possible spin projections. The mixed
states of maximum spin multiplicity are considered. This approach differs from
the methods routinely used in electronic structure calculations that focus on
the high-spin component or break the spin symmetry. In the ensemble, there are
no interactions between electrons with opposite spins in singly occupied
orbitals, as well as new inter-pair alpha-beta-contributions are proposed in
the 2RDM. The proposed 2RDM fulfills (2,2)-positivity necessary
N-representability conditions and guarantees the conservation of the total
spin. The NOF for multiplets is able to recover the non-dynamic and the
intrapair dynamic electron correlation. The missing dynamic correlation is
recovered by the NOF-MP2 method. Calculation of ionization potentials of the
first-row transition-metal atoms is presented as test case. The values obtained
agree with those reported at the coupled cluster singles and doubles level of
theory with perturbative triples and experimental data.",1908.05501v1
2020-10-02,Gravitational spin-orbit and aligned spin$_1$-spin$_2$ couplings through third-subleading post-Newtonian orders,"The study of scattering encounters continues to provide new insights into the
general relativistic two-body problem. The local-in-time conservative dynamics
of an aligned-spin binary, for both unbound and bound orbits, is fully encoded
in the gauge-invariant scattering-angle function, which is most naturally
expressed in a post-Minkowskian (PM) expansion, and which exhibits a remarkably
simple dependence on the masses of the two bodies (in terms of appropriate
geometric variables). This dependence links the PM and small-mass-ratio
approximations, allowing gravitational self-force results to determine new
post-Newtonian (PN) information to all orders in the mass ratio. In this paper,
we exploit this interplay between relativistic scattering and self-force theory
to obtain the third-subleading (4.5PN) spin-orbit dynamics for generic spins,
and the third-subleading (5PN) spin$_1$-spin$_2$ dynamics for aligned spins. We
further implement these novel PN results in an effective-one-body framework,
and demonstrate the improvement in accuracy by comparing against
numerical-relativity simulations.",2010.02018v2
2022-03-20,Rashba spin-orbit coupling and quantum-interference effect for a pair of spin-correlated electrons in their tunneling and reflection under a step potential,"We present both theory and numerical-computation results for the transmission
and reflection probability currents of a charged particle across a potential
step in the presence of a Rashba spin-orbit interaction. By varying kinetic
energy and angle of incident electrons or barrier height, different features
associated with tunneling and reflection of electrons are revealed by
inter-spin-channel electron tunnelings and reflections. These unique properties
are further accompanied by spin-state quantum interference of either a
reflected or transmitted pairs of spin-correlated electrons with the same
kinetic energy but in different spin-orbital states. Such distinctive features
are expected to give rise to a lot of applications in both spintronics and
quantum-computation devices.",2203.10606v1
2019-12-11,Magnetic field effects on electron transport in nanoring with orbital Rashba coupling,"We study the effects of a Zeeman magnetic field on the electron transport of
one-dimensional quantum rings which are marked by electronic states with
$d-$orbital symmetry in the presence of spin-orbit and orbital Rashba
couplings. By considering phase-coherent propagation, we analyse the geometric
Aharonov-Anandan (AA) phase of the channels which is acquired in a closed path,
by demonstrating that the orbital polarization can influence the electronic
transport when amplitude and magnetic field directions are varied. We explore
all the possible cases for the injection of electrons at various energies in
the regime of low electron filling. The magnetic field can allow the selection
of only one channel where the transmission is uniquely affected by the AA
phase. Conversely, when more orbital channels are involved there is also a
dynamical contribution that lead to oscillations in the transmission as the
magnetic field is varied. In particular, the transmission is chiral when the
energy states are close to the absolute minimum of the energy bands. Instead,
when an interference between the channels occurs the orbital and spin
contributions tend to balance each other with the increasing of the magnetic
field amplitude resulting in a trivial AA phase. This saturation effect does
not occur in the high magnetic field regime when orbital and spin properties of
the channels exhibit sharp variations with direct consequences on the
transport.",1912.05602v1
2021-07-06,Comparing the effective enhancement of local and non-local spin-orbit couplings on honeycomb lattices due to strong electronic correlations,"We investigate the interplay of electronic correlations and spin-orbit
coupling (SOC) for a one-band and a two-band honeycomb lattice model. The main
difference between the two models concerning SOC is that in the one-band case
the SOC is a purely non-local term in the basis of the $p_z$ orbitals, whereas
in the two-band case with $p_x$ and $p_y$ as basis functions it is purely
local. In order to grasp the correlation effects on non-local spin-orbit
coupling, we apply the TRILEX approach that allows to calculate non-local
contributions to the self-energy approximatively. For the two-band case we
apply dynamical mean-field theory. In agreement with previous studies, we find
that for all parameter values in our study, the effect of correlations on the
spin-orbit coupling strength is that the bare effective SOC parameter is
increased. However, this increase is much weaker in the non-local than in the
local SOC case. Concerning the TRILEX method, we introduce the necessary
formulas for calculations with broken SU(2) symmetry.",2107.02576v2
2001-10-10,Charge and Orbital Ordering in the Triangular-Lattice t_{2g}-Orbital System in One Dimension: A Possible Ground State of Bi_xV_8O_{16},"We consider the possible charge and orbital ordering in a Hollandite compound
Bi_xV_8O_{16}, which is a new one-dimensional triangular-lattice t_{2g}-orbital
system. Using the strong-coupling perturbation theory, we derive the effective
spin-orbit Hamiltonian in the approximation neglecting the small off-diagonal
hopping parameters or orbital fluctuation, whereby we obtain the spin
Hamiltonians in the partial space of each orbital-ordering pattern. We then
apply an exact-diagonalization technique on small clusters to these spin
Hamiltonians and calculate the ground-state phase diagram. We find that a
variety of orbital-ordering patterns appear in the parameter space, which
include the state characterized by the partial singlet formation consistent
with recent NMR experiment.",0110197v1
2020-01-02,Emergence of Superconductivity in Doped Multiorbital Hubbard Chains,"We introduce a variational state for one-dimensional two-orbital Hubbard
models that intuitively explains the recent computational discovery of pairing
in these systems when hole doped. Our Ansatz is an optimized linear
superposition of Affleck-Kennedy-Lieb-Tasaki valence bond states, rendering the
combination a valence bond liquid dubbed Orbital Resonant Valence Bond. We show
that the undoped (one electron/orbital) quantum state of two sites coupled into
a global spin singlet is exactly written employing only spin-1/2 singlets
linking orbitals at nearest-neighbor sites. Generalizing to longer chains
defines our variational state visualized geometrically expressing our chain as
a two-leg ladder, with one orbital per leg. As in Anderson's resonating
valence-bond state, our undoped variational state contains preformed singlet
pairs that via doping become mobile leading to superconductivity. Doped real
materials with one-dimensional substructures, two near-degenerate orbitals, and
intermediate Hubbard U/W strengths -- W the carrier's bandwidth -- could
realize spin-singlet pairing if on-site anisotropies are small. If these
anisotropies are robust, spin-triplet pairing emerges.",2001.00589v2
2015-03-05,Spin-Orbit-Induced Orbital Excitations in Sr2RuO4 and Ca2RuO4: A Resonant Inelastic X-ray Scattering Study,"High-resolution resonant inelastic X-ray scattering (RIXS) at the oxygen
K-edge has been used to study the orbital excitations of Ca2RuO4 and Sr2RuO4.
In combination with linear dichroism X-ray absorption spectroscopy, the
ruthenium 4d-orbital occupation and excitations were probed through their
hybridization with the oxygen p-orbitals. These results are described within a
minimal model, taking into account crystal field splitting and a spin-orbit
coupling \lambda_{so}=200~meV. The effects of spin-orbit interaction on the
electronic structure and implications for the Mott and superconducting ground
states of (Ca,Sr)2RuO4 are discussed.",1503.01574v2
2009-12-11,"Orbital order, stacking defects and spin-fluctuations in the $p$-electron molecular solid RbO$_2$","We examine magnon and orbiton behavior in localized O$_2$ anti-bonding
molecular $\pi^*$ orbitals using an effective Kugel-Khomskii Hamiltonian
derived from a two band Hubbard model with hopping parameters taken from {\em
ab initio} density functional calculations. The considerable difference between
intraband and interband hoppings leads to a strong coupling between the spin
wave dispersion and the orbital ground state, providing a straightforward way
of experimentally determining the orbital ground state from the measured magnon
dispersion. The near degeneracy of different orbital ordered states leads to
stacking defects which further modulate spin-fluctuation spectra. Proliferation
of orbital domains disrupts long-range magnetic order, thus causing a
significant reduction in the observed N\'eel temperature.",0912.2334v2
2017-06-30,Photoinduced Hund excitons in the breakdown of a two-orbital Mott insulator,"We study the photoinduced breakdown of a two-orbital Mott insulator and
resulting metallic state. Using time-dependent density matrix renormalization
group, we scrutinize the real-time dynamics of the half-filled two-orbital
Hubbard model interacting with a resonant radiation field pulse. The breakdown,
caused by production of doublon-holon pairs, is enhanced by Hund's exchange,
which dynamically activates large orbital fluctuations. The melting of the Mott
insulator is accompanied by a high to low spin transition with a concomitant
reduction of antiferromagnetic spin fluctuations. Most notably, the overall
time response is driven by the photogeneration of excitons with orbital
character that are stabilized by Hund's coupling. These unconventional ""Hund
excitons"" correspond to bound spin-singlet orbital-triplet doublon-holon pairs.
We study exciton properties such as bandwidth, binding potential, and size
within a semiclassical approach. The photometallic state results from a
coexistence of Hund excitons and doublon-holon plasma.",1706.10247v2
2017-04-29,Resonant inelastic x-ray scattering operators for $t_{2g}$ orbital systems,"We derive general expressions for resonant inelastic x-ray scattering (RIXS)
operators for $t_{2g}$ orbital systems, which exhibit a rich array of
unconventional magnetism arising from unquenched orbital moments. Within the
fast collision approximation, which is valid especially for 4$d$ and 5$d$
transition metal compounds with short core-hole lifetimes, the RIXS operators
are expressed in terms of total spin and orbital angular momenta of the
constituent ions. We then map these operators onto pseudospins that represent
spin-orbit entangled magnetic moments in systems with strong spin-orbit
coupling. Applications of our theory to such systems as iridates and ruthenates
are discussed, with a particular focus on compounds based on $d^4$ ions with
Van Vleck-type nonmagnetic ground state.",1705.00215v2
2008-08-22,"Lattice Properties of PbX (X = S, Se, Te): Experimental Studies and ab initio Calculations Including Spin-Orbit Effects","During the past five years the low temperature heat capacity of simple
semiconductors and insulators has received renewed attention. Of particular
interest has been its dependence on isotopic masses and the effect of spin-
orbit coupling in ab initio calculations. Here we concentrate on the lead
chalcogenides PbS, PbSe and PbTe. These materials, with rock salt structure,
have different natural isotopes for both cations and anions, a fact that allows
a systematic experimental and theoretical study of isotopic effects e.g. on the
specific heat. Also, the large spin-orbit splitting of the 6p electrons of Pb
and the 5p of Te allows, using a computer code which includes spin-orbit
interaction, an investigation of the effect of this interaction on the phonon
dispersion relations and the temperature dependence of the specific heat and on
the lattice parameter. It is shown that agreement between measurements and
calculations significantly improves when spin-orbit interaction is included.",0808.3152v1
2011-07-15,Orbital degeneracy and Mott transition in Mo pyrochlore oxides,"We present our theoretical results on an effective two-band double-exchange
model on a pyrochlore lattice for understanding intricate phase competition in
Mo pyrochlore oxides. The model includes the twofold degeneracy of $e_g'$
orbitals under trigonal field splitting, the interorbital Coulomb repulsion,
the Hund's-rule coupling between itinerant $e_g'$ electrons and localized
$a_{1g}$ spins, and the superexchange antiferromagnetic interaction between the
$a_{1g}$ spins. By Monte Carlo simulation with treating the Coulomb repulsion
at an unrestricted-type mean-field level, we obtain the low-temperature phase
diagram as functions of the Coulomb repulsion and the superexchange
interaction. The results include four dominant phases with characteristic spin
and orbital orders and the metal-insulator transitions among them. The
insulating region is characterized by a `ferro'-type orbital ordering of the
$e_g'$ orbitals along the local $<111>$ axis, irrespective of the spin
ordering.",1107.2986v1
2016-04-26,Modulated spin helicity stabilized by incommensurate orbital density waves in a quadruple perovskite manganite,"Through a combination of neutron diffraction and Landau theory we describe
the spin ordering in the ground state of the quadruple perovskite manganite
CaMn7O12 - a magnetic multiferroic supporting an incommensurate orbital density
wave that onsets above the magnetic ordering temperature, TN1 = 90 K. The
multi-k magnetic structure in the ground state was found to be a
nearly-constant-moment helix with modulated spin helicity, which oscillates in
phase with the orbital occupancies on the Mn3+ sites via trilinear
magneto-orbital coupling. Our phenomenological model also shows that, above TN2
= 48 K, the primary magnetic order parameter is locked into the orbital wave by
an admixture of helical and collinear spin density wave structures.
Furthermore, our model naturally explains the lack of a sharp dielectric
anomaly at TN1 and the unusual temperature dependence of the electrical
polarisation.",1604.07747v1
2016-06-07,Full Stark Control of Polariton States on a Spin-Orbit Hypersphere,"The orbital angular momentum and the polarisation of light are physical
quantities widely investigated for classical and quantum information
processing. In this work we propose to take advantage of strong light-matter
coupling, circular-symmetric confinement, and transverse-electric
transverse-magnetic splitting to exploit states where these two degrees of
freedom are combined. To this end we develop a model based on a spin-orbit
Poincar\'{e} hypersphere. Then we consider the example of semiconductor
polariton systems and demonstrate full ultrafast Stark control of spin-orbit
states. Moreover, by controlling states on three different spin-orbit spheres
and switching from one sphere to another we demonstrate the control of
different logic bits within one single physical system.",1606.02335v2
2017-07-31,Orbital-selective thermalization plateau in the mass imbalanced Hubbard model,"We use time-dependent non-equilibrium dynamical mean-field theory with
weak-coupling auxiliary-field continuous time quantum Monte Carlo as an
impurity solver to study the thermalization behavior of the mass-imbalanced
single-band Hubbard model after a quench of the Coulomb interaction from the
non-interacting limit to a finite positive value. By contrast, when the Coulomb
interaction in our model is increased under equilibrium conditions, the
quasi-particle weight for spin-up and spin-down (the mass imbalance) electrons
approach zero simultaneously, indicating the absence of an orbital selective
Mott transition. Our out-of-equilibrium study suggests that there exists a time
window where an orbital selective dynamical phase transition occurs. The
dynamical phase transition is characterized by the relaxation behavior of
energy (kinetic and Coulomb interaction) and the spin-resolved
momentum-dependent occupation. To make connection with possible experiments, we
calculate the spin-resolved two-time optical conductivity, which confirms the
orbital-selective thermalization plateau. We find the time window for the
orbital selective dynamical phase transition grows as the mass imbalance
increases.",1707.09692v2
2018-01-26,Enhancement of Superconducting $T_c$ due to the Spin-orbit Interaction,"We calculate the superconducting $T_c$ for a system which experiences Rashba
spin-orbit interactions. Contrary to the usual case where the electron-electron
interaction is assumed to be wave vector-independent, where superconductivity
is suppressed by the spin-orbit interaction (except for a small region at low
electron or hole densities), we find an enhancement of the superconducting
transition temperature when we include a correlated hopping interaction between
electrons. This interaction originates in the expansion of atomic orbitals due
to electron-electron repulsion and gives rise to superconductivity only at high
electron (low hole) densities. When superconductivity results from this
interaction it is enhanced by spin-orbit coupling, in spite of a suppression of
the density of states. The degree of electron-hole asymmetry about the Fermi
surface is also enhanced.",1801.08988v2
2021-02-03,Spatiotemporal Vortex Pulses: Angular Momenta and Spin-Orbit Interaction,"Recently, spatiotemporal optical vortex pulses carrying a purely transverse
intrinsic orbital angular momentum were generated experimentally [{\it Optica}
{\bf 6}, 1547 (2019); {\it Nat. Photon.} {\bf 14}, 350 (2020)]. However, an
accurate theoretical analysis of such states and their angular-momentum
properties remains elusive. Here we provide such analysis, including scalar and
vector spatiotemporal Bessel-type solutions as well as descrption of their
propagational, polarization, and angular-momentum properties. Most importantly,
we calculate both local densities and integral values of the spin and orbital
angular momenta, and predict observable spin-orbit interaction phenomena
related to the coupling between the trasnverse spin and orbital angular
momentum. Our analysis is readily extended to spatiotemporal vortex pulses of
other natures (e.g., acoustic).",2102.02180v2
2013-07-23,Microscopic origin of spin-orbital separation in Sr2CuO3,"Recently performed resonant inelastic x-ray scattering experiment (RIXS) at
the copper L3 edge in the quasi-1D Mott insulator Sr2CuO3 has revealed a
significant dispersion of a single orbital excitation (orbiton). This large and
unexpected orbiton dispersion has been explained using the concept of
spin-orbital fractionalization in which orbiton, which is intrinsically coupled
to the spinon in this material, liberates itself from the spinon due to the
strictly 1D nature of its motion. Here we investigate this mechanism in detail
by: (i) deriving the microscopic spin-orbital superexchange model from the
charge transfer model for the CuO3 chains in Sr2CuO3, (ii) mapping the orbiton
motion in the obtained spin-orbital model into a problem of a single hole
moving in an effective half-filled antiferromagnetic chain t-J model, and (iii)
solving the latter model using the exact diagonalization and obtaining the
orbiton spectral function. Finally, the RIXS cross section is calculated based
on the obtained orbiton spectral function and compared with the RIXS
experiment.",1307.6180v3
2015-04-13,Insensitivity of spin dynamics to the orbital angular momentum transferred from twisted light to extended semiconductors,"We study the spin dynamics of carriers due to the Rashba interaction in
semiconductor quantum disks and wells after excitation with light with orbital
angular momentum. We find that although twisted light transfers orbital angular
momentum to the excited carriers and the Rashba interaction conserves their
total angular momentum, the resulting electronic spin dynamics is essentially
the same for excitation with light with orbital angular momentum $l=+|l|$ and
$l=-|l|$. The differences between cases with different values of $|l|$ are due
to the excitation of states with slightly different energies and not to the
different angular momenta per se, and vanish for samples with large radii where
a $k$-space quasi-continuum limit can be established. These findings apply not
only to the Rashba interaction but also to all other envelope-function
approximation spin-orbit Hamiltonians like the Dresselhaus coupling.",1504.03098v1
2018-02-08,Manipulating Anomalous Hall Antiferromagnets with Magnetic Fields,"The symmetry considerations that imply a non-zero anomalous Hall effect (AHE)
in certain non-collinear antiferromagnets also imply both non-zero orbital
magnetization and a net spin magnetization. We have explicitly evaluated the
orbital magnetizations of several anomalous Hall effect antiferromagnets and
find that they tend to dominate over spin magnetizations, especially so when
spin-orbit interactions are weak. Because of the greater relative importance of
orbital magnetization the coupling between magnetic order and an external
magnetic field is unusual. We explain how magnetic fields can be used to
manipulate magnetic configurations in these systems, pointing in particular to
the important role played by the response of orbital magnetization to the
Zeeman-like spin exchange fields.",1802.03044v2
2023-09-26,Spin-orbit excitons in a correlated metal: Raman scattering study of Sr2RhO4,"Using Raman spectroscopy to study the correlated 4$d$-electron metal
Sr$_2$RhO$_4$, we observe pronounced excitations at 220 meV and 240 meV with
$A_\mathrm{1g}$ and $B_\mathrm{1g}$ symmetries, respectively. We identify them
as transitions between the spin-orbit multiplets of the Rh ions, in close
analogy to the spin-orbit excitons in the Mott insulators Sr$_2$IrO$_4$ and
$\alpha$-RuCl$_3$. This observation provides direct evidence for the unquenched
spin-orbit coupling in Sr$_2$RhO$_4$. A quantitative analysis of the data
reveals that the tetragonal crystal field $\Delta$ in Sr$_2$RhO$_4$ has a sign
opposite to that in insulating Sr$_2$IrO$_4$, which enhances the planar $xy$
orbital character of the effective $J=1/2$ wave function. This supports a
metallic ground state, and suggests that $c$-axis compression of Sr$_2$RhO$_4$
may transform it into a quasi-two-dimensional antiferromagnetic insulator.",2309.15299v2
2016-06-27,Effect of the inter-subband spin-orbit interaction on the spin transistor operation,"We consider the electron transport in the Datta-Das spin transistor within
the two-subband model taking into account the intra- and inter-subband
spin-orbit (SO) interaction and study the influence of the inter-subband SO
coupling on the spin-transistor operation. Starting from the model, in which
the SO coupling constants are treated as parameters, we show that the
inter-subband SO interaction strongly affects the ordinary conductance
oscillations predicted for the transistor with the single occupancy.
Interestingly, we find that even in the absence of the intra-subband SO
interaction, the conductance oscillates as a function of the inter-subband SO
coupling constant. This phenomenon is explained as resulting from the
inter-subband transition with spin-flip. Next, we consider the realistic spin
transistor model based on the gated
Al$_{0.48}$In$_{0.52}$As/Ga$_{0.47}$In$_{0.53}$As double quantum well, for
which the SO coupling constants are determined by the Schr\""{o}dinger-Poisson
approach. We show that the SO coupling constants rapidly change around $V_g=0$,
which is desirable for the spin transistor operation. We demonstrate that for
high electron densities the inter-subband SO interaction starts to play the
dominant role. The strong evidence of this interaction is the reduction of the
conductance for gate voltage $V_g=0$, which leads to the reduction of the
on/off conductance ratio.",1606.08202v1
2023-10-10,Self-induced inverse spin Hall effect in La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ films,"The efficient generation of spin currents and spin torques via spin-orbit
coupling is an important goal of spintronics research. One crucial metric for
spin current generation is the spin Hall angle, which is the ratio of the spin
Hall current to the transversely flowing charge current. A typical approach to
measure the spin Hall angle in nonmagnetic materials is to generate spin
currents via spin pumping in an adjacent ferromagnetic layer and measure the
transverse voltage from the inverse spin Hall effect in the nonmagnetic layer.
However, given that the spin Hall effect also occurs in ferromagnets, single
ferromagnetic layers could generate a self-induced transverse voltage during
spin pumping as well. Here we show that manganite based
La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ (LSMO) films deposited by pulsed laser
deposition exhibit a significant self-induced inverse spin Hall voltage while
undergoing spin pumping. We observe efficient spin to charge conversion in the
LSMO films via the inverse spin Hall effect. A spin pumping voltage of 1.86
$\mu$V is observed in the LSMO (12 nm) film. Using density functional theory
and the Kubo formalism, we calculate the intrinsic spin current conductivities
of these films and show that they are in reasonable agreement with the
experimental measurements.",2310.06967v1
2014-04-09,"Spin-orbit coupling in octamers in a spinel sulfide CuIr$_2$S$_4$: Competition between spin-singlet and quadrupolar states, and its relevance to remnant paramagnetism","We theoretically investigate magnetic properties in the low-temperature phase
with the formation of eight-site clusters, octamers, in the spinel compound
CuIr$_2$S$_4$. The octamer state was considered to be a spin-singlet state
induced by a Peieirls instability through the strong anisotropy of $d$
orbitals, the so-called orbital Peierls state. We reexamine this picture by
taking into account the spin-orbit coupling which was ignored in the previous
study. We derive a low-energy effective model between $j_{\rm eff}=1/2$
quasispins on Ir$^{4+}$ cations in an octamer from the multiorbital Hubbard
model with the strong spin-orbit coupling by performing the perturbation
expansion from the strong correlation limit. The effective Hamiltonian is in
the form of the Kitaev-Heisenberg model but with an additional interaction, a
symmetric off-diagonal exchange interaction originating from the perturbation
process including both d-d and d-p-d hopping. Analyzing the effective
Hamiltonian on two sites and the octamer by the exact diagonalization, we find
that there is a competition between a spin-singlet state and a quadrupolar
state. The former singlet state is a conventional one, adiabatically connected
to the orbital-Peierls state. On the other hand, the latter quadrupolar state
is stabilized by the additional interaction, which consists of a linear
combination of different total spin momenta along the spin quantization axis.
In the competing region, the model exhibits paramagnetic behavior with a
renormalized small effective moment at low temperature. This peculiar remnant
paramagnetism is not obtained in the Kitaev-Heisenberg model without the
additional interaction. Our results renew the picture of the octamer state and
provide a scenario for the intrinsic paramagnetic behavior recently observed in
a muon spin rotation experiment [K. M. Kojima et al., Phys. Rev. Lett. 112,
087203 (2014)].",1404.2426v1
2023-07-03,Effects of spin-orbit coupling on gravitational waveforms from a triaxial non-aligned neutron star in a binary system,"Spinning neutron stars (NSs) can emit continuous gravitational waves (GWs)
that carry a wealth of information about the compact object. If such a signal
is detected, it will provide us with new insight into the physical properties
of matter under extreme conditions. Future space-based GW detectors, such as
LISA and TianQin, can potentially detect some double NSs in tight binaries with
orbital periods shorter than 10 minutes. The possibility of a successful
directed search for continuous GWs from the spinning NS in such a binary system
identified by LISA/TianQin will be significantly increased with the proposed
next-generation ground-based GW observatories, such as Cosmic Explorer and
Einstein Telescope. Searching for continuous GWs from such a tight binary
system requires highly accurate waveform templates that account for the
interaction of the NS with its companion. In this spirit, we derive analytic
approximations that describe the GWs emitted by a triaxial non-aligned NS in a
binary system in which the effects of spin-orbit coupling have been
incorporated. The difference with the widely used waveform for the isolated NS
is estimated and the parameter estimation accuracy of an example signal using
Cosmic Explorer is calculated. For a typical tight double NS system with a
6~min orbital period, the angular frequency correction of the spinning NS in
this binary due to spin precession is $\sim 10^{-6}~{\rm Hz}$, which is in the
same order of magnitude as the angular frequency of orbital precession. The
fitting factor between the waveforms with and without spin precession will drop
to less than 0.97 after a few days ($\sim 10^5~{\rm s}$). We find that
spin-orbit coupling has the potential to improve the accuracy of parameter
estimation, especially for the binary inclination angle and spin precession
cone opening angle, by up to 3 orders of magnitude. (Abridged)",2307.01055v2
2020-04-01,Interlayer exchange coupling through Ir-doped Cu spin Hall material,"Metallic superlattices where the magnetization vectors in the adjacent
ferromagnetic layers are antiferromagnetically coupled by the interlayer
exchange coupling through nonmagnetic spacer layers are systems available for
the systematic study on antiferromagnetic (AF) spintronics. As a candidate of
nonmagnetic spacer layer material exhibiting remarkable spin Hall effect, which
is essential to achieve spin-orbit torque switching, we selected the Ir-doped
Cu in this study. The AF-coupling for the Co / Cu$_{95}$Ir$_{5}$ / Co was
investigated, and was compared with those for the Co / Cu / Co and Co / Ir /
Co. The maximum magnitude of AF-coupling strength was obtained to be 0.39
mJ/m$^{2}$ at the Cu$_{95}$Ir$_{5}$ thickness of about 0.75 nm. Furthermore, we
found a large spin Hall angle of Cu$_{95}$Ir$_{5}$ in Co / Cu$_{95}$Ir$_{5}$
bilayers by carrying out spin Hall magnetoresistance and harmonic Hall voltage
measurements, which are estimated to be 3 ~ 4 %. Our experimental results
clearly indicate that Cu$_{95}$Ir$_{5}$ is a nonmagnetic spacer layer allowing
us to achieve moderately strong AF-coupling and to generate appreciable
spin-orbit torque via the spin Hall effect.",2004.00739v1
2012-05-08,Properties of edge states in spin-triplet two-band superconductor,"Motivated by Sr2RuO4 the magnetic properties of edge states in a two-band
spin-triplet superconductor with electron- and hole-like Fermi surfaces are
investigated assuming chiral p-wave pairing symmetry. The two bands correspond
to the alpha-beta-bands of Sr2RuO4 and are modeled within a tight-binding model
including inter-orbital hybridization and spin-orbit coupling effects.
Including superconductivity the quasiparticle spectrum is determined by means
of a self-consistent Bogolyubov-de Gennes calculation. While a full
quasiparticle excitation gap appears in the bulk, gapless states form at the
edges which produce spontaneous spin and/or charge currents. The spin current
is the result of the specific band structure while the charge current
originates from the superconducting condensate. Together they induce a small
spin polarization at the edge. Furthermore onsite Coulomb repulsion is included
to show that the edge states are unstable against the formation of a
Stoner-like spin polarization of the edge states. Through spin-orbit coupling
the current- and the correlation-induced magnetism are coupled to the
orientation of the chirality of the superconducting condensate. We speculate
that this type of phenomenon could yield a compensation of the magnetic fields
induced by currents and also explain the negative result in the recent
experimental search for chiral edge currents.",1205.1591v1
2005-06-18,Quadratic response theory for spin-orbit coupling in semiconductor heterostructures,"This paper examines the properties of the self-energy operator in
lattice-matched semiconductor heterostructures, focusing on nonanalytic
behavior at small values of the crystal momentum, which gives rise to
long-range Coulomb potentials. A nonlinear response theory is developed for
nonlocal spin-dependent perturbing potentials. The ionic pseudopotential of the
heterostructure is treated as a perturbation of a bulk reference crystal, and
the self-energy is derived to second order in the perturbation. If spin-orbit
coupling is neglected outside the atomic cores, the problem can be analyzed as
if the perturbation were a local spin scalar, since the nonlocal spin-dependent
part of the pseudopotential merely renormalizes the results obtained from a
local perturbation. The spin-dependent terms in the self-energy therefore fall
into two classes: short-range potentials that are analytic in momentum space,
and long-range nonanalytic terms that arise from the screened Coulomb potential
multiplied by a spin-dependent vertex function. For an insulator at zero
temperature, it is shown that the electronic charge induced by a given
perturbation is exactly linearly proportional to the charge of the perturbing
potential. These results are used in a subsequent paper to develop a
first-principles effective-mass theory with generalized Rashba spin-orbit
coupling.",0506465v2
2010-04-28,Spin-orbit coupling and broken spin degeneracy in multilayer graphene,"Since the lattices of ABA-stacked graphene multilayers with an even number of
layers, as well as that of monolayer graphene, satisfy spatial-inversion
symmetry, their electronic bands must be spin degenerate in the presence of
time-inversion symmetry. In intrinsic monolayer and bilayer graphene, when
symmetry is not broken by external fields, the only spin-orbit coupling present
at low energy near the corner of the Brillouin zone is the Kane-Mele term, that
opens a bulk energy gap but does not break the spin degeneracy of the energy
bands [C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95, 226801 (2005)]. However,
spin splitting is allowed in multilayers with an odd number of layers (greater
than or equal to 3) because their lattices do not satisfy spatial inversion
symmetry. We show that, in trilayer graphene, in addition to the Kane-Mele
term, there is a second type of intrinsic spin-orbit coupling present at low
energy near the corner of the Brillouin zone. It introduces a Zeeman-like spin
splitting of the energy bands at each valley, with an opposite sign of the
effective magnetic field in the two valleys. We estimate the magnitude of the
effective field to be ~2T.",1004.5083v1
2012-06-05,Effective theory of fractional topological insulators in two spatial dimensions,"Electrons subjected to a strong spin-orbit coupling in two spatial dimensions
could form fractional incompressible quantum liquids without violating the
time-reversal symmetry. Here we construct a Lagrangian description of such
fractional topological insulators by combining the available experimental
information on potential host materials and the fundamental principles of
quantum field theory. This Lagrangian is a Landau-Ginzburg theory of spinor
fields, enhanced by a topological term that implements a state-dependent
fractional statistics of excitations whenever both particles and vortices are
incompressible. The spin-orbit coupling is captured by an external static SU(2)
gauge field. The presence of spin conservation or emergent U(1) symmetries
would reduce the topological term to the Chern-Simons effective theory tailored
to the ensuing quantum Hall state. However, the Rashba spin-orbit coupling in
solid-state materials does not conserve spin. We predict that it can
nevertheless produce incompressible quantum liquids with topological order but
without a quantized Hall conductivity. We discuss two examples of such liquids
whose description requires a generalization of the Chern-Simons theory. One is
an Abelian Laughlin-like state, while the other has a new kind of non-Abelian
many-body entanglement. Their quasiparticles exhibit fractional spin-dependent
exchange statistics, and have fractional quantum numbers derived from the
electron's charge and spin according to their transformations under
time-reversal. In addition to conventional phases of matter, the proposed
topological Lagrangian can capture a broad class of hierarchical Abelian and
non-Abelian topological states, involving particles with arbitrary spin or
general emergent SU(N) charges.",1206.1055v2
2019-11-04,Spin-helix driven insulating phase in two dimensional lattice,"Motivated by emergent $SU(2)$ symmetry in the spin orbit coupled system, we
study the spin helix driven insulating phase in two dimensional lattice. When
both Rashba and Dresselhaus spin orbit couplings are present, the perfect Fermi
surface nesting occurs at a special condition depending on the lattice
geometry. In this case, the energies of spin up at any wave vector $\vec{k}$
are equivalent to the ones of spin down at $\vec{k}\!+\!\vec{Q}$ with so-called
the \textit{shifting wave vector} $\vec{Q}$. Thus, the system stabilizes
magnetic insulator with spiral like magnetic ordering even in the presence of
tiny electron-electron interaction where the magnetic ordering wave vector is
proportional to $\vec{Q}$. We first show the condition for existence of the
\textit{shifting wave vector} in general lattice model and emergent $SU(2)$
symmetry in the spin orbit coupled system. Then, we exemplify this in square
lattice at half filling and discuss the insulating phase with (non-) coplanar
spin density wave and charge order. Our study emphasizes possible new types of
two dimensional magnetic materials and can be applicable to various van-der
Waals materials and their heterostructures with the control of electric field,
strain and pressure.",1911.01440v1
2021-06-14,Spin-pure Stochastic-CASSCF via GUGA-FCIQMC applied to Iron Sulfur Clusters,"In this work we demonstrate how to compute the one- and two-body reduced
density matrices within the spin-adapted full configuration interaction quantum
Monte Carlo (FCIQMC) method, which is based on the graphical unitary group
approach (GUGA). This allows us to use GUGA-FCIQMC as a spin-pure configuration
interaction (CI) eigensolver within the complete active space self-consistent
field (CASSCF) procedure, and hence to stochastically treat active spaces far
larger than conventional CI solvers whilst variationally relaxing orbitals for
specific spin-pure states. We apply the method to investigate the spin-ladder
in iron-sulfur dimer and tetramer model systems. We demonstrate the importance
of the orbital relaxation by comparing the Heisenberg model magnetic coupling
parameters from the CASSCF procedure to those from a CI-only procedure based on
restricted open-shell Hartree-Fock orbitals. We show that orbital relaxation
differentially stabilizes the lower spin states, thus enlarging the coupling
parameters with respect to the values predicted by ignoring orbital relaxation
effects. Moreover, we find that while CI eigenvalues are well fit by a simple
bilinear Heisenberg Hamiltonian, the CASSCF eigenvalues exhibits deviations
that necessitate the inclusion of biquadratic terms in the model Hamiltonian.",2106.07775v1
2019-02-20,Synthetic spin orbit interaction for Majorana devices,"The interplay of superconductivity with a non-trivial spin texture holds
promises for the engineering of non-abelian Majorana quasi-particles. A wide
class of systems expected to exhibit exotic correlations are based on nanoscale
conductors with strong spin-orbit interaction, subject to a strong external
magnetic field. The strength of the spin-orbit coupling is a crucial parameter
for the topological protection of Majorana modes as it forbids other trivial
excitations at low energy. The spin-orbit interaction is in principle intrinsic
to a material. As a consequence, experimental efforts have been recently
focused on semiconducting nano-conductors or spin-active atomic chains
contacted to a superconductor. Alternatively, we show how both a spin-orbit and
a Zeeman effect can be autonomously induced by using a magnetic texture coupled
to any low dimensional conductor, here a carbon nanotube. Transport
spectroscopy through superconducting contacts reveals oscillations of Andreev
like states under a change of the magnetic texture. These oscillations are well
accounted for by a scattering theory and are absent in a control device with no
magnetic texture. A large synthetic spin-orbit energy of about 1.1 meV, larger
than the intrinsic spin orbit energy in many other platforms, is directly
derived from the number of oscillations. Furthermore, a robust zero energy
state, the hallmark of devices hosting localized Majorana modes, emerges at
zero magnetic field. Our findings synthetize all the features for the emergence
of Majorana modes at zero magnetic field in a controlled, local and autonomous
fashion. It could be used for advanced experiments, including microwave
spectroscopy and braiding operations, which are at the heart of new schemes of
topological quantum computation.",1902.07479v1
2018-01-25,Synthetic spin-orbit coupling and topological polaritons in Janeys-Cummings lattices,"The interaction between a photon and a qubit in the Janeys-Cummings (JC)
model generates a kind of quasiparticle called polariton. While they are widely
used in quantum optics, difficulties in engineering controllable coupling of
them severely limit their applications to simulate spinful quantum systems.
Here we show that, in the superconducting quantum circuit context, polariton
states in the single-excitation manifold of a JC lattice can be used to
simulate a spin-1/2 system, based on which tunable synthetic spin-orbit
coupling and novel topological polaritons can be generated and explored. The
lattice is formed by a sequence of coupled transmission line resonators, each
of which is connected to a transmon qubit. Synthetic spin-orbit coupling and
effective Zeeman field of the polariton can both be tuned by modulating the
coupling strength between neighbouring resonators, allowing for the realization
of a large variety of polaritonic topological semimetal bands. Methods for
detecting the polaritonic topological edge states and topological invariants
are also proposed. Therefore, our work suggests that the JC lattice is a
versatile platform for exploring spinful topological states of matter, which
may inspire developments of topologically protected quantum optical and
information processing devices.",1801.08426v4
2015-07-03,Persistent Skyrmion Lattice of Noninteracting Electrons with Spin-Orbit Coupling,"A persistent spin helix (PSH) is a robust helical spin-density pattern
arising in disordered 2D electron gases with Rashba $\alpha$ and Dresselhaus
$\beta$ spin-orbit (SO) tuned couplings, i.e., $\alpha=\pm\beta$. Here we
investigate the emergence of a Persistent Skyrmion Lattice (PSL) resulting from
the coherent superposition of PSHs along orthogonal directions -- crossed PSHs
-- in wells with two occupied subbands $\nu=1,2$. For realistic GaAs wells we
show that the Rashba $\alpha_\nu$ and Dresselhaus $\beta_\nu$ couplings can be
simultaneously tuned to equal strengths but opposite signs, e.g., $\alpha_1=
\beta_1$ and $\alpha_2=-\beta_2$. In this regime and away from band
anticrossings, our {\it non-interacting} electron gas sustains a topologically
non-trivial skyrmion-lattice spin-density excitation, which inherits the
robustness against spin-independent disorder and interactions from its
underlying crossed PSHs. We find that the spin relaxation rate due to the
interband SO coupling is comparable to that of the cubic Dresselhaus term as a
mechanism of the PSL decay. Near anticrossings, the interband-induced spin
mixing leads to unusual spin textures along the energy contours beyond those of
the Rahsba-Dresselhaus bands. Our PSL opens up the unique possibility of
observing topological phenomena, e.g., topological and skyrmion Hall effects,
in ordinary GaAs wells with non-interacting electrons.",1507.00811v2
2020-12-22,Orbital Rotations induced by Charges of Polarons and Defects in Doped Vanadates,"We explore the competiton of doped holes and defects that leads to the loss
of orbital order in vanadate perovskites. In compounds such as La$_{1-{\sf
x}}$Ca$_{\,\sf x}$VO$_3$ spin and orbital order result from super-exchange
interactions described by an extended three-orbital degenerate Hubbard-Hund
model for the vanadium $t_{2g}$ electrons. Long-range Coulomb potentials of
charged Ca$^{2+}$ defects and $e$-$e$ interactions control the emergence of
defect states inside the Mott gap. The quadrupolar components of the Coulomb
fields of doped holes induce anisotropic orbital rotations of degenerate
orbitals. These rotations modify the spin-orbital polaron clouds and compete
with orbital rotations induced by defects. Both mechanisms lead to a mixing of
orbitals, and cause the suppression of the asymmetry of kinetic energy in the
$C$-type magnetic phase. We find that the gradual decline of orbital order with
doping, a characteristic feature of the vanadates, however, has its origin not
predominantly in the charge carriers, but in the off-diagonal couplings of
orbital rotations induced by the charges of the doped ions.",2012.11919v1
2015-07-01,Dynamical spin-density waves in a spin-orbit-coupled Bose-Einstein condensate,"Synthetic spin-orbit (SO) coupling, an important ingredient for quantum
simulation of many exotic condensed matter physics, has recently attracted
considerable attention. The static and dynamic properties of a SO coupled
Bose-Einstein condensate (BEC) have been extensively studied in both theory and
experiment. Here we numerically investigate the generation and propagation of a
\textit{dynamical} spin-density wave (SDW) in a SO coupled BEC using a fast
moving Gaussian-shaped barrier. We find that the SDW wavelength is sensitive to
the barrier's velocity while varies slightly with the barrier's peak potential
or width. We qualitatively explain the generation of SDW by considering a
rectangular barrier in a one dimensional system. Our results may motivate
future experimental and theoretical investigations of rich dynamics in the SO
coupled BEC induced by a moving barrier.",1507.00318v1
2017-10-05,Magnetic Skyrmionic Polarons,"We study a two-dimensional electron gas exchanged-coupled to a system of
classical magnetic ions. For large Rashba spin-orbit coupling a single electron
can become self-trapped in a skyrmion spin texture self-induced in the magnetic
ions system. This new quasiparticle carries electrical and topological charge
as well as a large spin, and we named it as magnetic skyrmionic polaron. We
study the range of parameters; temperature, exchange coupling, Rashba coupling
and magnetic field, for which the magnetic skyrmionic polaron is the
fundamental state in the system. The dynamics of this quasiparticle is studied
using the collective coordinate approximation, and we obtain that in presence
of an electric field the new quasiparticle shows, because the chirality of the
skyrmion, a Hall effect. Finally we argue that the magnetic skyrmionic polarons
can be found in large Rashba spin-orbit coupling semiconductors as GeMnTe.",1710.02182v1
2021-12-16,Semiconductor Spin Qubits,"The spin degree of freedom of an electron or a nucleus is one of the most
basic properties of nature and functions as an excellent qubit, as it provides
a natural two-level system that is insensitive to electric fields, leading to
long quantum coherence times. We review the physics of semiconductor spin
qubits, focusing not only on the early achievements of spin initialization,
control, and readout in GaAs quantum dots, but also on recent advances in Si
and Ge spin qubits, including improved charge control and readout, coupling to
other quantum degrees of freedom, and scaling to larger system sizes. We begin
by introducing the four major types of spin qubits: single spin qubits, donor
spin qubits, singlet-triplet spin qubits, and exchange-only spin qubits. We
then review the mesoscopic physics of quantum dots, including single-electron
charging, valleys, and spin-orbit coupling. We next give a comprehensive
overview of the physics of exchange interactions, a crucial resource for
single- and two-qubit control in spin qubits. The bulk of this review is
centered on the presentation of results from each major spin qubit type, the
present limits of fidelity, and a brief overview of alternative spin qubit
platforms. We then give a physical description of the impact of noise on
semiconductor spin qubits, aided in large part by an introduction to the filter
function formalism. Lastly, we review recent efforts to hybridize spin qubits
with superconducting systems, including charge-photon coupling, spin-photon
coupling, and long-range cavity-mediated spin-spin interactions. Cavity-based
readout approaches are also discussed. This review is intended to give an
appreciation for the future prospects of semiconductor spin qubits, while
highlighting the key advances in mesoscopic physics over the past two decades
that underlie the operation of modern quantum-dot and donor spin qubits.",2112.08863v1
2016-08-26,Non-collinear antiferromagnetism of coupled spins and pseudospins in the double perovskite La2CuIrO6,"We report the structural, magnetic and thermodynamic properties of the double
perovskite compound La2CuIrO6 from X-ray, neutron diffraction, neutron
depolarization, dc magnetization, ac susceptibility, specific heat,
muon-spin-relaxation (uSR), electron-spin-resonance (ESR) and nuclear magnetic
resonance (NMR) measurements. Below ~113 K, short-range spin-spin correlations
occur within the Cu2+ sublattice. With decreasing temperature, the Ir4+
sublattice progressively involves in the correlation process. Below T = 74 K,
the magnetic sublattices of Cu (spin s = 1/2) and Ir (pseudospin j = 1/2) in
La2CuIrO6 are strongly coupled and exhibit an antiferromagnetic phase
transition into a non-collinear magnetic structure accompanied by a small
uncompensated transverse moment. A weak anomaly in ac-susceptibility as well as
in the NMR and {\mu}SR spin lattice relaxation rates at 54 K is interpreted as
a cooperative ordering of the transverse moments which is influenced by the
strong spin-orbit coupled 5d ion Ir4+. We argue that the rich magnetic
behaviour observed in La2CuIrO6 is related to complex magnetic interactions
between the strongly correlated spin-only 3d ions with the strongly spin-orbit
coupled 5d transition ions where a combination of the spin-orbit coupling and
the low-symmetry of the crystal lattice plays a special role for the spin
structure in the magnetically ordered state.",1608.07513v2
2014-10-09,Leading order finite size effects with spins for inspiralling compact binaries,"The leading order finite size effects due to spin, namely that of the cubic
and quartic in spin interactions, are derived for the first time for generic
compact binaries via the effective field theory for gravitating spinning
objects. These corrections enter at the third and a half and fourth
post-Newtonian orders, respectively, for rapidly rotating compact objects.
Hence, we complete the leading order finite size effects with spin up to the
fourth post-Newtonian accuracy. We arrive at this by augmenting the point
particle effective action with new higher dimensional nonminimal coupling
worldline operators, involving higher-order derivatives of the gravitational
field, and introducing new Wilson coefficients, corresponding to constants,
which describe the octupole and hexadecapole deformations of the object due to
spin. These Wilson coefficients are fixed to unity in the black hole case. The
nonminimal coupling worldline operators enter the action with the electric and
magnetic components of the Weyl tensor of even and odd parity, coupled to even
and odd worldline spin tensors, respectively. Moreover, the non relativistic
gravitational field decomposition, which we employ, demonstrates a coupling
hierarchy of the gravito-magnetic vector and the Newtonian scalar, to the odd
and even in spin operators, respectively, which extends that of minimal
coupling. This observation is useful for the construction of the Feynman
diagrams, and provides an instructive analogy between the leading order
spin-orbit and cubic in spin interactions, and between the leading order
quadratic and quartic in spin interactions.",1410.2601v3
2007-10-23,Silicon in the Quantum Limit: Quantum Computing and Decoherence in Silicon Architectures,"Semiconductor architectures hold promise for quantum information processing
(QIP) applications due to their large industrial base and perceived scalability
potential. Electron spins in silicon in particular may be an excellent
architecture for QIP and also for spin electronics (spintronics) applications.
While the charge of an electron is easily manipulated by charged gates, the
spin degree of freedom is well isolated from charge fluctuations. Inherently
small spin-orbit coupling and the existence of a spin-zero Si isotope
facilitate long single spin qubit coherence times. Here we consider the
relaxation properties of localized electronic states in silicon due to donors,
quantum wells, and quantum dots, including effects due to phonons and Rashba
spin-orbit coupling. Our analysis is impeded by the complicated, many-valley
band structure of silicon and previously unaddressed physics in silicon quantum
wells. We find that electron spins in silicon and especially strained silicon
have excellent decoherence properties. Where possible we compare with
experiment to test our theories. We go beyond issues of coherence in a quantum
computer to problems of control and measurement. Precisely what makes spin
relaxation so long in semiconductor architectures makes spin measurement so
difficult. To address this, we propose a new scheme for spin readout which has
the added benefit of automatic spin initialization, a vital component of
quantum computing and quantum error correction. Our results represent important
practical milestones on the way to the design and construction of a
silicon-based quantum computer.",0710.4263v1
2008-05-21,Kinetics of spin coherence of electrons in $n$-type InAs quantum wells under intense terahertz laser fields,"Spin kinetics in $n$-type InAs quantum wells under intense terahertz laser
fields is investigated by developing fully microscopic kinetic spin Bloch
equations via the Floquet-Markov theory and the nonequilibrium Green's function
approach, with all the relevant scattering, such as the electron-impurity,
electron-phonon, and electron-electron Coulomb scattering explicitly included.
We find that a {\em finite} steady-state terahertz spin polarization induced by
the terahertz laser field, first predicted by Cheng and Wu [Appl. Phys. Lett.
{\bf 86}, 032107 (2005)] in the absence of dissipation, exists even in the
presence of all the scattering. We further discuss the effects of the terahertz
laser fields on the spin relaxation and the steady-state spin polarization. It
is found that the terahertz laser fields can {\em strongly} affect the spin
relaxation via hot-electron effect and the terahertz-field-induced effective
magnetic field in the presence of spin-orbit coupling. The two effects compete
with each other, giving rise to {\em non-monotonic} dependence of the spin
relaxation time as well as the amplitude of the steady state spin polarization
on the terahertz field strength and frequency. The terahertz field dependences
of these quantities are investigated for various impurity densities, lattice
temperatures, and strengths of the spin-orbit coupling. Finally, the importance
of the electron-electron Coulomb scattering on spin kinetics is also addressed.",0805.3280v3
2022-05-01,"Computational Insights into Electronic Excitations, Spin-Orbit Coupling Effects, and Spin Decoherence in Cr(IV)-based Molecular Qubits","The great success of point defects and dopants in semiconductors for quantum
information processing has invigorated a search for molecules with analogous
properties. Flexibility and tunability of desired properties in a large
chemical space have great advantages over solid-state systems. The properties
analogous to point defects were demonstrated in Cr(IV)-based molecular family,
Cr(IV)(aryl)$_4$, where the electronic spin states were optically initialized,
read out, and controlled. Despite this kick-start, there is still a large room
for enhancing properties crucial for molecular qubits. Here we provide
computational insights into key properties of the Cr(IV)-based molecules aimed
at assisting chemical design of efficient molecular qubits. Using the
multireference ab-initio methods, we investigate the electronic states of
Cr(IV)(aryl)$_4$ molecules with slightly different ligands, showing that the
zero-phonon line energies agree with the experiment, and that the excited
spin-triplet and spin-singlet states are highly sensitive to small chemical
perturbations. By adding spin-orbit interaction, we find that the sign of the
uniaxial zero-field splitting (ZFS) parameter is negative for all considered
molecules, and discuss optically-induced spin initialization via non-radiative
intersystem crossing. We quantify (super)hyperfine coupling to the $^{53}$Cr
nuclear spin and to the $^{13}$C and $^1$H nuclear spins, and we discuss
electron spin decoherence. We show that the splitting or broadening of the
electronic spin sub-levels due to superhyperfine interaction with $^1$H nuclear
spins decreases by an order of magnitude when the molecules have a substantial
transverse ZFS parameter.",2205.00375v2
2023-03-22,Giant spin Hall effect in AB-stacked MoTe2/WSe2 bilayers,"The spin Hall effect (SHE), in which electrical current generates transverse
spin current, plays an important role in spintronics for the generation and
manipulation of spin-polarized electrons. The phenomenon originates from
spin-orbit coupling. In general, stronger spin-orbit coupling favors larger
SHEs but shorter spin relaxation times and diffusion lengths. To achieve both
large SHEs and long-range spin transport in a single material has remained a
challenge. Here we demonstrate a giant intrinsic SHE in AB-stacked MoTe2/WSe2
moir\'e bilayers by direct magneto optical imaging. Under moderate electrical
currents with density < 1 A/m, we observe spin accumulation on transverse
sample edges that nearly saturates the spin density. We also demonstrate
long-range spin Hall transport and efficient non-local spin accumulation
limited only by the device size (about 10 um). The gate dependence shows that
the giant SHE occurs only near the Chern insulating state, and at low
temperatures, it emerges after the quantum anomalous Hall breakdown. Our
results demonstrate moir\'e engineering of Berry curvature and large SHEs for
potential spintronics applications.",2303.12881v1
2005-11-24,"Microscopic Model for High-spin vs. Low-spin ground state in $[Ni_2{M(CN)_8]}$ ($M=Mo^V, W^V, Nb^{IV}$) magnetic clusters","Conventional superexchange rules predict ferromagnetic exchange interaction
between Ni(II) and M (M=Mo(V), W(V), Nb(IV)). Recent experiments show that in
some systems this superexchange is antiferromagnetic. To understand this
feature, in this paper we develop a microscopic model for Ni(II)-M systems and
solve it exactly using a valence bond approach. We identify the direct exchange
coupling, the splitting of the magnetic orbitals and the inter-orbital electron
repulsions, on the M site as the parameters which control the ground state spin
of various clusters of the Ni(II)-M system. We present quantum phase diagrams
which delineate the high-spin and low-spin ground states in the parameter
space. We fit the spin gap to a spin Hamiltonian and extract the effective
exchange constant within the experimentally observed range, for reasonable
parameter values. We also find a region in the parameter space where an
intermediate spin state is the ground state. These results indicate that the
spin spectrum of the microscopic model cannot be reproduced by a simple
Heisenberg exchange Hamiltonian.",0511594v1
2005-12-19,Equilibrium spin current through the tunnelling junctions,"We study equilibrium pure spin current through tunnelling junctions at zero
bias. The two leads of the junctions connected via a thin insulator barrier,
can be either a ferromagnetic metal (FM) or a nonmagnetic high-mobility
two-dimensional electron gas (2DEG) with Rashba spin orbital interaction (RSOI)
or Dresselhaus spin orbital interaction (DSOI). As a lead of a tunnelling
junction, the isotropic RSOI or DSOI in 2DEG can give rise to an average
effective planar magnetic field orthogonal or parallel to the current
direction. It is found by the linear response theory that equilibrium spin
current $\vec{J}$ can flow in the following three junctions, 2DEG/2DEG,
2DEG/FM, and FM/FM junctions, as a result of the exchange coupling between the
magnetic moments, $\vec{h}_{l}$ and $\vec{h}_{r}$, in the two electrodes of the
junction, i.e., $\vec{J}\sim\vec{h}_{l}\times\vec{h}_{r}$. An important
distinction between the FM and 2DEG with RSOI (DSOI) lead is that in a strict
one-dimensional case RSOI (DSOI) cannot lead to equilibrium spin current in the
junction since the two spin bands are not spin-polarized as in a FM lead where
Zeeman spin splitting occurs.",0512430v1
2008-01-13,Phonon modulation of the spin-orbit interaction as a spin relaxation mechanism in InSb quantum dots,"We calculate the spin relaxation rates in a parabolic InSb quantum dots due
to the spin interaction with acoustical phonons. We considered the deformation
potential mechanism as the dominant electron-phonon coupling in the
Pavlov-Firsov spin-phonon Hamiltonian. By studying suitable choices of magnetic
field and lateral dot size, we determine regions where the spin relaxation
rates can be practically suppressed. We analyze the behavior of the spin
relaxation rates as a function of an external magnetic field and mean quantum
dot radius. Effects of the spin admixture due to Dresselhaus contribution to
spin-orbit interaction are also discussed.",0801.1952v1
2008-03-25,Quantum dissipative Rashba spin ratchets,"We predict the possibility to generate a finite stationary spin current by
applying an unbiased ac driving to a quasi-one-dimensional asymmetric periodic
structure with Rashba spin-orbit interaction and strong dissipation. We show
that under a finite coupling strength between the orbital degrees of freedom
the electron dynamics at low temperatures exhibits a pure spin ratchet
behavior, {\it i.e.} a finite spin current and the absence of charge transport
in spatially asymmetric structures. It is also found that the equilibrium spin
currents are not destroyed by the presence of strong dissipation.",0803.3526v2
2009-06-07,Do Spinors Frame-Drag?,"We investigate the effect of the intrinsic spin of a fundamental spinor field
on the surrounding spacetime geometry. We show that despite the lack of a
rotating stress-energy source (and despite claims to the contrary) the
intrinsic spin of a spin-half fermion gives rise to a frame-dragging effect
analogous to that of orbital angular momentum, even in Einstein-Hilbert gravity
where torsion is constrained to be zero. This resolves a paradox regarding the
counter-force needed to restore Newton's third law in the well known spin-orbit
interaction. In addition, the frame-dragging effect gives rise to a {\it
long-range} gravitationally mediated spin-spin dipole interaction coupling the
{\it internal} spins of two sources. We argue that despite the weakness of the
interaction, the spin-spin interaction will dominate over the ordinary inverse
square Newtonian interaction in any process of sufficiently high-energy for
quantum field theoretical effects to be non-negligible.",0906.1385v2
2010-08-17,Spin projection and spin current density within relativistic electronic transport calculations,"A spin projection scheme is presented which allows the decomposition of the
electric conductivity into two different spin channels within fully
relativistic $ab$ $initio$ transport calculations that account for the impact
of spin-orbit coupling. This is demonstrated by calculations of the
spin-resolved conductivity of Fe$_{1-x}$Cr$_x$ and Co$_{1-x}$Pt$_x$ disordered
alloys on the basis of the corresponding Kubo-Greenwood equation implemented
using the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA)
band structure method. In addition, results for the residual resistivity of
diluted Ni-based alloys are presented that are compared to theoretical and
experimental ones that rely on Mott's two-current model for spin-polarized
systems. The application of the scheme to deal with the spin-orbit induced spin
Hall effect is discussed in addition.",1008.2900v1
2012-09-11,Enhancement of spin relaxation time in hydrogenated graphene spin valve devices,"Hydrogen adsorbates in graphene are interesting as they are not only strong
Coulomb scatterers but they also induce a change in orbital hybridization of
the carbon network from sp^2 into sp^3. This change increases the spin-orbit
coupling and is expected to largely modify spin relaxation. In this work we
report the change in spin transport properties of graphene due to plasma
hydrogenation. We observe an up to three-fold increase of spin relaxation time
tau_S after moderate hydrogen exposure. This increase of tau_S is accompanied
by the decrease of charge and spin diffusion coefficients, resulting in a minor
change in spin relaxation length lambda_S. At high carrier density we obtain
lambda_S of 7 microns, which allows for spin detection over a distance of 11
microns. After hydrogenation a value of tau_S as high as 2.7 ns is measured at
room temperature.",1209.2365v1
2014-01-15,Extrinsic spin Hall effects measured with lateral spin valve structures,"The spin Hall effect (SHE), induced by spin-orbit interaction in nonmagnetic
materials, is one of the promising phenomena for conversion between charge and
spin currents in spintronic devices. The spin Hall (SH) angle is the
characteristic parameter of this conversion. We have performed experiments of
the conversion from spin into charge currents by the SHE in lateral spin valve
structures. We present experimental results on the extrinsic SHEs induced by
doping nonmagnetic metals, Cu or Ag, with impurities having a large spin-orbit
coupling, Bi or Pb, as well as results on the intrinsic SHE of Au. The SH angle
induced by Bi in Cu or Ag is negative and particularly large for Bi in Cu, 10
times larger than the intrinsic SH angle in Au. We also observed a large SH
angle for CuPb but the SHE signal disappeared in a few days. Such an aging
effect could be related to a fast mobility of Pb in Cu and has not been
observed in CuBi alloys.",1401.3445v2
2014-07-20,Spintronic magnetic anisotropy,"An attractive feature of magnetic adatoms and molecules for nanoscale
applications is their superparamagnetism, the preferred alignment of their spin
along an easy axis preventing undesired spin reversal. The underlying magnetic
anisotropy barrier --a quadrupolar energy splitting-- is internally generated
by spin-orbit interaction and can nowadays be probed by electronic transport.
Here we predict that in a much broader class of quantum-dot systems with spin
larger than one-half, superparamagnetism may arise without spin-orbit
interaction: by attaching ferromagnets a spintronic exchange field of
quadrupolar nature is generated locally. It can be observed in conductance
measurements and surprisingly leads to enhanced spin filtering even in a state
with zero average spin. Analogously to the spintronic dipolar exchange field,
responsible for a local spin torque, the effect is susceptible to electric
control and increases with tunnel coupling as well as with spin polarization.",1407.5273v1
2014-09-17,Arbitrary Spin Galilean Oscillator,"The so-called Dirac oscillator was proposed as a modification of the free
Dirac equation which reproduces many of the properties of the simple harmonic
oscillator but accompanied by a strong spin-orbit coupling term. It has yet to
be extended successfully to the arbitrary spin S case primarily because of the
unwieldiness of general spin Lorentz invariant wave equations. It is shown here
using the formalism of totally symmetric multispinors that the Dirac oscillator
can, however, be made to accommodate spin by incorporating it into the
framework of Galilean relativity. This is done explicitly for spin zero and
spin one as special cases of the arbitrary spin result. For the general case it
is shown that the coefficient of the spin-orbit term has a 1/S behavior by
techniques which are virtually identical to those employed in the derivation of
the g-factor carried out over four decades ago.",1409.5101v1
2019-06-26,Fermi Level Dependent Spin Pumping from a Magnetic Insulator into a Topological Insulator,"Topological spintronics aims to exploit the spin-momentum locking in the
helical surface states of topological insulators for spin-orbit torque devices.
We address a fundamental question that still remains unresolved in this
context: does the topological surface state alone produce the largest values of
spin-charge conversion efficiency or can the strongly spin-orbit coupled bulk
states also contribute significantly? By studying the Fermi level dependence of
spin pumping in topological insulator/ferrimagnetic insulator bilayers, we show
that the spin Hall conductivity is constant when the Fermi level is tuned
across the bulk band gap, consistent with a full bulk band calculation. The
results suggest a new perspective, wherein ""bulk-surface correspondence"" allows
spin-charge conversion to be simultaneously viewed either as coming from the
full bulk band, or from spin-momentum locking of the surface state.",1906.11116v1
2018-03-04,Systematic derivation of realistic spin-models for beyond-Heisenberg solids,"We present a systematic derivation of effective lattice spin Hamiltonians
derived from a rotationally invariant multi-orbital Hubbard model including a
term ensuring Hund's rule coupling. The Hamiltonians are derived down-folding
the fermionic degrees of freedom of the Hubbard model into the proper
low-energy spin sector using L\""owdin partitioning, which will be outlined in
detail for the case of two sites and two orbitals at each site. Correcting the
ground state systematically up to fourth order in the hopping of electrons, we
find for spin $S\geq 1$ a biquadratic, three-spin and four-spin interaction
beyond the conventional Heisenberg term. Comparing the puzzling energy spectrum
of the magnetic states for a single Fe monolayer on Ru(0001), obtained from
density functional theory, with the spin Hamiltonians taken at the limit of
classical spins, we show that the previously ignored three-spin interaction can
be comparable in size to the conventional Heisenberg exchange.",1803.01315v3
2021-03-09,Self-induced spin-orbit torques in metallic ferromagnets,"We present a phenomenological theory of spin-orbit torques in a metallic
ferromagnet with spin-relaxing boundaries. The model is rooted in the coupled
diffusion of charge and spin in the bulk of the ferromagnet, where we account
for the anomalous Hall effects as well as the anisotropic magnetoresistance in
the corresponding constitutive relations for both charge and spin sectors. The
diffusion equations are supplemented with suitable boundary conditions
reflecting the spin-sink capacity of the environment. In inversion-asymmetric
heterostructures, the uncompensated spin accumulation exerts a dissipative
torque on the order parameter, giving rise to a current-dependent linewidth in
the ferromagnetic resonance with a characteristic angular dependence. We
compare our model to recent spin-torque ferromagnetic resonance measurements,
illustrating how rich self-induced spin-torque phenomenology can arise even in
simple magnetic structures.",2103.05743v2
2023-06-15,Characteristic THz-emissions induced by optically excited collective orbital modes,"We study the generation of collective orbital modes, their evolution, and the
characteristic non-linear optical response induced by them in a photoinduced
orbital-ordered correlated oxide using real-time simulations based on an
interacting multiband tight-binding (TB) model. The d-d optical transitions
under femtoseconds light-pulse in a orbital-ordered state excite collective
orbital modes, also known as ""orbitons"". The consistent inclusion of electronic
interactions and the coupling between charge, spin, and lattice degrees of
freedom in the TB-model provide a better understanding of the underlying
mechanisms of the collective orbital modes. The dynamics of Jahn-Teller
vibrational modes in the photoinduced state modify the intersite orbital
interaction, which further amplifies these orbital modes. In the presence of
weak ferroelectricity, the excitation of collective orbital modes induces a
strong THz oscillatory photocurrent which is long-lived. This suggests an
alternative way to experimentally detect quasiparticles describing such
collective modes through THz-emission studies in the photoinduced state. Our
study also elucidates that quasiparticle dynamics in improper ferroelectric
oxides can be exploited to achieve highly interesting and non-trivial
optoelectronic properties.",2306.09107v1
2003-06-20,Anisotropic transport in the two-dimensional electron gas in the presence of spin-orbit coupling,"In a two-dimensional electron gas as realized by a semiconductor quantum
well, the presence of spin-orbit coupling of both the Rashba and Dresselhaus
type leads to anisotropic dispersion relations and Fermi contours. We study the
effect of this anisotropy on the electrical conductivity in the presence of
fixed impurity scatterers. The conductivity also shows in general an anisotropy
which can be tuned by varying the Rashba coefficient. This effect provides a
method of detecting and investigating spin-orbit coupling by measuring
spin-unpolarized electrical currents in the diffusive regime. Our approach is
based on an exact solution of the two-dimensional Boltzmann equation and
provides also a natural framework for investigating other transport effects
including the anomalous Hall effect.",0306528v2
2004-11-06,Spin-Orbit Coupling and Symmetry of the Order Parameter in Strontium Ruthenate,"Determination of the orbital symmetry of a state in spin triplet
Sr$_2$RuO$_4$ superconductor is a challenge of considerable importance. Most of
the experiments show that the chiral state of the $\hat{z} (k_x \pm ik_y)$ type
is realized and remains stable on lowering the temperature. Here we have
studied the stability of various superconducting states of Sr$_2$RuO$_4$ in the
presence of spin-orbit coupling.
  Numerically we found that the chiral state is never the minimum energy. Alone
among the five states studied it has $<{\bf \hat L}.{\bf \hat S} >=0$ and is
therefore not affected to linear order in the coupling parameter $\lambda$. We
found that stability of the chiral state requires spin dependent pairing
interactions. This imposes strong constraint on the pairing mechanism.",0411169v1
2005-07-22,Multiple Scattering Theory for Two-dimensional Electron Gases in the Presence of Spin-Orbit Coupling,"In order to model the phase-coherent scattering of electrons in
two-dimensional electron gases in the presence of Rashba spin-orbit coupling, a
general partial-wave expansion is developed for scattering from a cylindrically
symmetric potential. The theory is applied to possible electron flow imaging
experiments using a moveable scanning probe microscope tip. In such
experiments, it is demonstrated theoretically that the Rashba spin-orbit
coupling can give rise to spin interference effects, even for unpolarized
electrons at nonzero temperature and no magnetic field.",0507528v2
2005-09-14,Interface Spin-Orbit Coupling in a Non-centrosymmetric Thin-Film Superconductor,"We present a detailed study of the effects of interface spin-orbit coupling
(ISOC) on the critical field behavior of non-centrosymmetric (NCS), ultra-thin
superconducting Be/Au bilayers. Parallel field measurements were made in
bilayers with Be thicknesses in the range of 2 - 10 nm and Au coverages of 0.5
nm. Though the Au had no significant effect on the superconducting gap, it
produced profound changes in the spin states of the system. In particular, the
parallel critical field exceeded the Clogston limit by an order of magnitude in
the thinnest films studied. In addition, the parallel critical field
unexpectedly scaled as Hc||/\Delta ~ 1/d suggesting that the spin-orbit
coupling energy was proportional to Delta/d^2. Tilted field measurements showed
that contrary to recent theory, the ISOC induces a large in-plane
superconducting susceptibility but only a very small transverse susceptibility.",0509385v2
2006-10-18,Triplet-Singlet Spin Relaxation in Quantum Dots with Spin-Orbit Coupling,"We estimate the triplet-singlet relaxation rate due to spin-orbit coupling
assisted by phonon emission in weakly-confined quantum dots. Our results for
two and four electrons show that the different triplet-singlet relaxation
trends observed in recent experiments under magnetic fields can be understood
within a unified theoretical description, as the result of the competition
between spin-orbit coupling and phonon emission efficiency. Moreover, we show
that both effects are greatly affected by the strength of the confinement and
the external magnetic field, which may give access to very long-lived triplet
states as well as to selective population of the triplet Zeeman sublevels.",0610509v2
2007-12-14,Spin-orbit coupled Bose-Einstein condensates,"We consider a many-body system of pseudo-spin-1/2 bosons with spin-orbit
interactions, which couple the momentum and the internal pseudo-spin degree of
freedom created by spatially varying laser fields. The corresponding single-
particle spectrum is generally anisotropic and contains two degenerate minima
at finite momenta. At low temperatures, the many-body system condenses into
these minima generating a new type of entangled Bose-Einstein condensate. We
show that in the presence of weak density-density interactions the many-body
ground state is characterized by a twofold degeneracy. The corresponding
many-body wave function describes a condensate of ``left-'' and
``right-moving'' bosons. By fine-tuning the parameters of the laser field, one
can obtain a bosonic version of the spin-orbit coupled Rashba model. In this
symmetric case, the degeneracy of the ground state is very large, which may
lead to phases with nontrivial topological properties. We argue that the
predicted new type of Bose-Einstein condensates can be observed experimentally
via time-of-flight imaging, which will show characteristic multipeak structures
in momentum distribution.",0712.2256v3
2008-10-07,Nontrivial interplay between superconductivity and spin-orbit coupling in non-centrosymmetric ferromagnets,"Motivated by the recent discoveries of ferromagnetic and non-centrosymmetric
superconductors, we present a mean-field theory for a superconductor that
\textit{both} lacks inversion symmetry and displays ferromagnetism, a scenario
which is believed to be realized in UIr. We study the interplay between the
order parameters to clarify how superconductivity is affected by the presence
of ferromagnetism and spin-orbit coupling. One of our key findings is that the
spin-orbit coupling seems to enhance both ferromagnetism and superconductivity
in all spin channels. We discuss our results in the context of the heavy
fermion superconductor UIr and analyze possible symmetries of the order
parameter by the group theory method.",0810.1281v1
2010-06-26,Spin-Orbit Coupled Spinor Bose-Einstein Condensates,"An effective spin-orbit coupling can be generated in cold atom system by
engineering atom-light interactions. In this letter we study spin-1/2 and
spin-1 Bose-Einstein condensates with Rashba spin-orbit coupling, and find that
the condensate wave function will develop non-trivial structures. From
numerical simulation we have identified two different phases. In one phase the
ground state is a single plane wave, and often we find the system splits into
domains and an array of vortices plays the role as domain wall. In this phase,
time-reversal symmetry is broken. In the other phase the condensate wave
function is a standing wave and it forms spin stripe. The transition between
them is driven by interactions between bosons. We also provide an analytical
understanding of these results and determines the transition point between the
two phases.",1006.5148v4
2010-10-25,Plasmon mass and Drude weight in strongly spin-orbit-coupled 2D electron gases,"Spin-orbit-coupled two-dimensional electron gases (2DEGs) are a textbook
example of helical Fermi liquids, i.e. quantum liquids in which spin (or
pseudospin) and momentum degrees-of-freedom at the Fermi surface have a
well-defined correlation. Here we study the long-wavelength plasmon dispersion
and the Drude weight of archetypical spin-orbit-coupled 2DEGs. We first show
that these measurable quantities are sensitive to electron-electron
interactions due to broken Galileian invariance and then discuss in detail why
the popular random phase approximation is not capable of describing the
collective dynamics of these systems even at very long wavelengths. This work
is focussed on presenting approximate microscopic calculations of these
quantities based on the minimal theoretical scheme that captures the basic
physics correctly, i.e. the time-dependent Hartree-Fock approximation. We find
that interactions enhance the ""plasmon mass"" and suppress the Drude weight. Our
findings can be tested by inelastic light scattering, electron energy loss, and
far-infrared optical-absorption measurements.",1010.5169v1
2012-07-16,Higgs-like Excitations of Cold Atom System with Spin-orbit Coupling,"The Higgs-like excitations, which distinguish from the Higgs amplitude mode
in many-body system, are single-particle excitations in system with non-Abelian
gauge potential. We investigate the Higgs-like excitations of cold atom system
in artificial non-Abelian gauge potential. We demonstrate that when a
non-Abelian gauge potential is reduced to Abelian potential, its Abelian part
constructs spin-orbit coupling, and its non-Abelian part emerges Higgs-like
excitations. The Higgs-like excitations induce a mass of the non-Abelian gauge
field, which offsets the defect of massless of the gauge theories. We show that
the mass of gauge field can affect the spin Hall currents which are produced by
the spin-orbit coupling. We also discuss the observation of these phenomena in
real experiment.",1207.3707v3
2012-07-26,Spin-orbit-coupling induced domain-wall resistance in diffusive ferromagnets,"We investigate diffusive transport through a number of domain wall (DW)
profiles of the important magnetic alloy Permalloy taking into account
simultaneously noncollinearity, alloy disorder, and spin-orbit coupling fully
quantum mechanically, from first principles. In addition to observing the known
effects of magnetization mistracking and anisotropic magnetoresistance, we
discover a not-previously identified contribution to the resistance of a DW
that comes from spin-orbit-coupling-mediated spin-flip scattering in a textured
diffusive ferromagnet. This adiabatic DW resistance, which should exist in all
diffusive DWs, can be observed by varying the DW width in a systematic fashion
in suitably designed nanowires.",1207.6277v2
2012-07-31,Effects of Magnetovolume and Spin-orbit Coupling in the Ferromagnetic Cubic Perovskite BaRuO3,"BaRuO3 having five different crystal structures has been synthesized by
varying the pressure while sintering. Contrary to the other phases being
nonmagnetic, the cubic perovskite phase synthesized recently shows an itinerant
ferromagnetic character. We investigated this ferromagnetic BaRuO3 using first
principles calculations. A few van Hove singularities appear around the Fermi
energy, causing unusually high magnetovolume effects of $\Delta M/\Delta a$ ~
4.3 $\mu_B$/\AA as well as a Stoner instability [IN(0) ~ 1.2]. At the optimized
lattice parameter a, the magnetic moment M is 1.01 $\mu_B$ in the local spin
density approximation. When spin-orbit coupling is included, the topologies of
some Fermi surfaces are altered, and the net moment is reduced by 10% to a
value very close to the experimentally observed value of ~ 0.8 $\mu_B$. Our
results indicate that this ferromagnetism is induced by the Stoner instability,
but the combined effects of the p-d hybridization, the magnetovolume, and the
spin-orbit coupling determine the net moment. In addition, we briefly discuss
the results of the tight-binding Wannier function technique.",1207.7145v2
2012-08-09,Route to Observable Fulde-Ferrell-Larkin-Ovchinnikov Phases in 3D Spin-Orbit Coupled Degenerate Fermi Gases,"The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase was first predicted in 2D
superconductors about 50 years ago, but so far unambiguous experimental
evidences are still lacked. The recently experimentally realized
spin-imbalanced Fermi gases may potentially unveil this elusive state, but
require very stringent experimental conditions. In this Letter, we show that
FFLO phases may be observed even in a 3D degenerate Fermi gas with spin-orbit
coupling and in-plane Zeeman field. The FFLO phase is driven by the interplay
between asymmetry of Fermi surface and superfluid order, instead of the
interplay between magnetic and superconducting order in solid materials. The
predicted FFLO phase exists in a giant parameter region, possesses a stable
long-range superfluid order due to the 3D geometry, and can be observed with
experimentally already achieved temperature ($T\sim 0.05E_{F}$), thus opens a
new fascinating avenue for exploring FFLO physics.",1208.2029v2
2012-08-28,Spin-orbit coupling induced separation and hidden spin textures in spin-1 Bose-Einstein condensates,"We analytically and numerically investigate the ground state of the
spin-orbit coupled spin-1 Bose-Einstein condensates in an external parabolic
potential. When the spin-orbit coupling strength $\kappa$ is comparable with
that of the trapping potential, the density distribution centers of different
components of the spinor condensate deviate evidently from the trap center in
the plane wave and stripe phases. When $\kappa\gg1$, the magnitude of this
deviation decreases as $\kappa$ is getting larger and larger. Correspondingly,
periphery half-skyrmions textures arise. This deviation can be reflected by the
non-uniform magnetic moment in the $z$ direction, $\mathcal{F}_z$. With the
manipulation of the external trap, the local magnitude of $\mathcal{F}_z$ can
be increased evidently. This kind of increase of $\mathcal{F}_z$ is also
observed in the square vortex lattice phase of the condensate.",1208.5591v3
2012-10-01,Pair-density wave states through spin-orbit coupling in multilayer superconductors,"Spin singlet superconductors with quasi-two dimensional multilayer structure
are studied in high magnetic fields. Specifically we concentrate on bi- and
tri-layer systems whose layers by symmetry are subject Rashba-type spin-orbit
coupling. The combination of magnetic field and spin-orbit coupling leads to a
first order phase transition between different states of layer-dependent
superconducting order parameters upon rising the magnetic field. In this
context we distinguish the low-field Bardeen-Cooper-Schrieffer state where all
layers have order parameters of the same sign and the high-field pair-density
wave state where the layer-dependent order parameters change the sign at the
center layer. We also show that progressive paramagnetic limiting effects yield
additional features in the H-T phase diagram. As possible realizations of such
unusual superconducting phases we consider artificial superlattices of
CeCoIn_5, as well as some multilayer high-T_c cuprates.",1210.0315v1
2012-11-21,Quantum Degenerate Fermi Gas with Spin-orbit Coupling and Crossed Zeeman Fields,"We study quantum degenerate ultra-cold Fermi gases in the presence of
artificial spin-orbit coupling and crossed Zeeman fields. We emphasize the case
where parity is violated in the excitation spectrum and compare it with the
simpler situation where parity is preserved. We investigate in detail
spectroscopic properties such as the excitation spectrum, the spectral
function, momentum distribution and density of states for the cases where
parity is preserved or violated. Similarly, we show that thermodynamic
properties such as pressure, chemical potential, entropy, specific heat,
isothermal compressibility and induced spin polarization become anisotropic as
a function of Zeeman field components, when parity is violated. Lastly, we
discuss the effects of interactions and present results for the pairing
temperature as the precursor for the transition to a superfluid state. In
particular, we find that the pairing temperature is dramatically reduced in the
weak interaction regime as parity violation gets stronger, and that the
momentum dependence of the order parameter for superfluidity violates parity
when crossed Zeeman fields are present for finite spin-orbit coupling.",1211.5133v1
2013-02-19,Engineering three-dimensional topological insulators in Rashba-type spin-orbit coupled heterostructures,"Topological insulators represent a new class of quantum phase defined by
invariant symmetries and spin-orbit coupling that guarantees metallic Dirac
excitations at its surface. The discoveries of these states have sparked the
hope of realizing nontrivial excitations and novel effects such as a
magnetoelectric effect and topological Majorana excitations. Here we develop a
theoretical formalism to show that a three dimensional topological insulator
can be designed artificially via stacking bilayers of two-dimensional Fermi
gases with opposite Rashba-type spin-orbit coupling on adjacent layers, and
with inter-layer quantum tunneling. We demonstrate that in the stack of
bilayers grown along a (001)-direction, a nontrivial topological phase
transition occurs above a critical number of Rashba-bilayers. In the
topological phase we find the formation of a single spin-polarized Dirac cone
at the $\Gamma$-point. This approach offers an accessible way to design
artificial topological insulators in a set up that takes full advantage of the
atomic layer deposition approach. This design principle is tunable and also
allows us to bypass limitations imposed by bulk crystal geometry.",1302.4514v2
2013-04-08,Phase diagrams and Thomas-Fermi estimates for spin-orbit coupled Bose-Einstein Condensates under rotation,"We provide complete phase diagrams describing the ground state of a trapped
spinor BEC under the combined effects of rotation and a Rashba spin-orbit
coupling. The interplay between the different parameters (magnitude of
rotation, strength of the spin-orbit coupling and interaction) leads to a rich
ground state physics that we classify. We explain some features analytically in
the Thomas-Fermi approximation, writing the problem in terms of the total
density, total phase and spin. In particular, we analyze the giant skyrmion,
and find that it is of degree 1 in the strong segregation case. In some regions
of the phase diagrams, we relate the patterns to a ferromagnetic energy.",1304.2178v2
2014-02-18,The role of spin-orbit coupling in topologically protected interface states in Dirac materials,"We highlight the fact that two-dimensional materials with Dirac-like low
energy band structures and spin-orbit coupling will produce linearly dispersing
topologically protected Jackiw-Rebbi modes at interfaces where the Dirac mass
changes sign. These modes may support persistent spin or valley currents
parallel to the interface, and the exact arrangement of such topologically
protected currents depends crucially on the details of the spin-orbit coupling
in the material. As examples, we discuss buckled two-dimensional hexagonal
lattices such as silicene or germanene, and transition metal dichalcogenides
such as MoS$_2$.",1402.4347v2
2014-11-13,Exact solitons and manifold mixing dynamics in the spin-orbit-coupled spinor condensates,"We derive exact static as well as moving solitonic solutions to the
one-dimensional spin-orbit-coupled F=1 Bose-Einstein condensates. The static
polar soliton is shown to be the ground state by the imaginary-time evolution
method. It shows a helical modulation of the order parameter due to the
spin-orbit coupling. In particular, the moving soliton exhibits a periodic
oscillation among the particle numbers of the hyperfine states. We further
explore the temporal evolution of the static polar soliton and find that the
spin-polarization exhibits dynamical oscillations. This disappearance and
re-emergence of the ferromagnetic state indicates the mixing of the
ferromagnetic and the antiferromagnetic manifolds.",1411.3420v1
2015-08-19,Chiral Magnetic Effect and Anomalous Hall Effect in Antiferromagnetic Insulators with Spin-Orbit Coupling,"We search for dynamical magnetoelectric phenomena in three-dimensional
correlated systems with spin-orbit coupling. We focus on the antiferromagnetic
insulator phases where the dynamical axion field is realized by the fluctuation
of the antiferromagnetic order parameter. It is shown that the dynamical chiral
magnetic effect, an alternating current generation by magnetic fields, emerges
due to the time dependences of the order parameter such as antiferromagnetic
resonance. It is also shown that the anomalous Hall effect arises due to the
spatial variations of the order parameter such as antiferromagnetic domain
walls. Our study indicates that spin excitations in antiferromagnetic
insulators with spin-orbit coupling can result in nontrivial charge responses.
Moreover, observing the chiral magnetic effect and anomalous Hall effect in our
system is equivalent to detecting the dynamical axion field in condensed
matter.",1508.04590v2
2016-03-01,Evidence for correlated states in a cluster of bosons with Rashba spin-orbit coupling,"We study the ground state properties of spin-half bosons subjected to the
Rashba spin-orbit coupling in two dimensions. Due to the enhancement of the low
energy density of states, it is expected that the effect of interaction becomes
more important. After reviewing several possible ideal condensed states, we
carry out an exact diagonalization calculation for a cluster of the bosons in
the presence of strong spin-orbit coupling on a two-dimensional disk and reveal
strong correlations in its ground state. We derive a low-energy effective
Hamiltonian to understand how states with strong correlations become
energetically more favorable than the ideal condensed states.",1603.00163v1
2019-05-24,The microscopic Einstein-de Haas effect,"The Einstein-de Haas (EdH) effect, where the spin angular momentum of
electrons is transferred to the mechanical angular momentum of atoms, was
established experimentally in 1915. While a semi-classical explanation of the
effect exists, modern electronic structure methods have not yet been applied to
modelling the phenomenon. In this paper we investigate its microscopic origins
by means of a non-collinear tight-binding model of an $\textrm{O}_2$ dimer,
which includes the effects of spin-orbit coupling, coupling to an external
magnetic field, and vector Stoner exchange. By varying an external magnetic
field in the presence of spin-orbit coupling, a torque can be generated on the
dimer, validating the presence of the EdH effect. Avoided energy level
crossings and the rate of change of magnetic field determine the evolution of
the spin. We find also that the torque exerted on the nuclei by the electrons
in a time-varying $B$ field is not only due to the EdH effect. Other
contributions arise from field-induced changes in the electronic orbital
angular momentum and from the direct action of the Faraday electric field
associated with the time-varying magnetic field.",1905.10449v1
2020-07-01,First-principles Dzyaloshinskii-Moriya interaction in a non-collinear framework,"We have derived an expression of the Dzyaloshinskii-Moriya (DM) interaction,
where all the three components of the DM vector can be calculated
independently, for a general, non-collinear magnetic configuration. The
formalism is implemented in a real space - linear muffin-tin orbital - atomic
sphere approximation (RS-LMTO-ASA) method. We have chosen the Cr triangular
trimer on Au(111) and Mn triangular trimers on Ag(111) and Au(111) surfaces as
numerical examples. The results show that the DM interaction (module and
direction) is drastically different for collinear and non-collinear states.
Based on the relation between the spin and charge currents flowing in the
system and their coupling to the non-collinear magnetic configuration of the
triangular trimer, we demonstrate that the DM interaction can be significant,
even in the absence of spin-orbit coupling. This is shown to emanate from the
non-collinear magnetic structure, that can induce significant spin and charge
currents even with spin-orbit coupling is ignored.",2007.00358v2
2020-07-23,Laser-induced topological $s$-wave superconductivity in bilayer transition metal dichalcogenides,"In this paper, we propose a way to realize topological $s$-wave
superconductivity with application of circularly polarized laser light in
two-dimensional bilayer transition metal dichalcogenides (TMDs). Using Floquet
theory, we analyze a tight-binding model of bilayer TMDs with time-periodic
electric fields. After deriving an effective Hamiltonian, we investigate
topological properties of the $s$-wave superconducting state. The laser light
induces valley-dependent layer polarization and makes the system to be a
topologically nontrivial superconducting state characterized by the Chern
number. We show topological phase diagrams in the absence and presence of the
Kane-Mele spin-orbit coupling which causes hidden spin polarization in bilayer
TMDs. Although the topological phase diagram is affected by the spin-orbit
coupling, topological superconductivity can be realized without relying on the
spin-orbit coupling in sharp contrast to a previous proposal of laser-induced
topological superconductivity [K. Takasan, \textit{et al.}, Phys. Rev. B
\textbf{95}, 134508 (2017)]. We also discuss experimental setups to detect the
topological phase.",2007.11812v1
2020-07-28,Dynamic modulation of phonon-assisted transitions in quantum defects in monolayer transition-metal dichalcogenide semiconductors,"Quantum localization via atomic point defects in semiconductors is of
significant fundamental and technological importance. Quantum defects in
monolayer transition-metal dichalcogenide semiconductors have been proposed as
stable and scalable optically-addressable spin qubits. Yet, the impact of
strong spin-orbit coupling on their dynamical response, for example under
optical excitation, has remained elusive. In this context, we study the effect
of spin-orbit coupling on the electron-phonon interaction in a single chalcogen
vacancy defect in monolayer transition metal dichalcogenides, molybdenum
disulfide (MoS$_2$) and tungsten disulfide (WS$_2$). From ab initio electronic
structure theory calculations, we find that spin-orbit interactions tune the
magnitude of the electron-phonon coupling in both optical and charge-state
transitions of the defect, modulating their respective efficiencies. This
observation opens up a promising scheme of dynamically modulating material
properties to tune the local behavior of a quantum defect.",2007.14399v1
2014-03-05,Random Rashba spin-orbit coupling at the quantum spin Hall edge,"We study a one-dimensional helical system with random Rashba spin-orbit
coupling. Using renor- malization group methods, we derive a consistent set of
flow equations governing the important con- trol parameters of the
backscattering process. Thereby, we prove the existence of disorder-induced
two-particle backscattering that can even be non-local in space. This analysis
allows us to derive the scaling form of the conductance at low temperatures. We
find that two-particle backscattering due to random spin-orbit coupling differs
from the one off a single Rashba impurity by both the scaling of the
conductance with the temperature and the relevance of the backscattering
operators.",1403.1082v2
2018-05-07,Revealing Controllable Anisotropic Magnetoresistance in Spin Orbit Coupled Antiferromagnet Sr2IrO4,"Antiferromagnetic spintronics actively introduces new principles of magnetic
memory, in which the most fundamental spin-dependent phenomena, i.e.
anisotropic magnetoresistance effects, are governed by an antiferromagnet
instead of a ferromagnet. A general scenario of the antiferromagnetic
anisotropic magnetoresistance effects mainly stems from the magnetocrystalline
anisotropy related to spin-orbit coupling. Here we demonstrate magnetic field
driven contour rotation of the fourfold anisotropic magnetoresistance in bare
antiferromagnetic Sr2IrO4/SrTiO3 (001) thin films hosting a strong spin-orbit
coupling induced Jeff=1/2 Mott state. Concurrently, an intriguing minimal in
the magnetoresistance emerges. Through first principles calculations, the
band-gap engineering due to rotation of the Ir isospins is revealed to be
responsible for these emergent phenomena, different from the traditional
scenario where relatively more conductive state was obtained usually when
magnetic field was applied along the magnetic easy axis. Our findings
demonstrate a new efficient route, i.e. via the novel Jeff=1/2 state, to
realize controllable anisotropic magnetoresistance in antiferromagnetic
materials.",1805.02394v1
2012-04-10,Topological phases in a two-dimensional lattice: Magnetic field versus spin-orbit coupling,"In this work, we explore the rich variety of topological states that arise in
two-dimensional systems, by considering the competing effects of spin-orbit
couplings and a perpendicular magnetic field on a honeycomb lattice. Unlike
earlier approaches, we investigate minimal models in order to clarify the
effects of the intrinsic and Rashba spin-orbit couplings, and also of the
Zeeman splitting, on the quantum Hall states generated by the magnetic field.
In this sense, our work provides an interesting path connecting quantum Hall
and quantum spin Hall physics. First, we consider the properties of each term
individually and we analyze their similarities and differences. Secondly, we
investigate the subtle competitions that arise when these effects are combined.
We finally explore the various possible experimental realizations of our model.",1204.2212v2
2015-12-02,Synthesizing Majorana zero-energy modes in a periodically gated quantum wire,"We explore a scheme for engineering a one-dimensional spinless p-wave
superconductor hosting unpaired Majorana zero-energy modes, using an
all-electric setup with a spin-orbit coupled quantum wire in proximity to an
s-wave superconductor. The required crossing of the Fermi level by a single
spin-split energy band is ensured by employing a periodically modulated Rashba
interaction, which, assisted by electron-electron interactions and a uniform
Dresselhaus interaction, opens a gap at two of the spin-orbit shifted Fermi
points. While an implementation in a hybrid superconductor-semiconductor device
requires improvements upon present-day capabilities, a variant of our scheme
where spin-orbit-coupled cold fermions are effectively proximity-coupled to a
BEC reservoir of Feshbach molecules may provide a ready-to-use platform.",1512.00827v3
2017-07-10,"Ultracold atoms in a square lattice with spin-orbit coupling: Charge order, superfluidity, and topological signatures","We present an $\textit{ab initio}$, numerically exact study of attractive
fermions in square lattices with Rashba spin-orbit coupling. The ground state
of this system is a supersolid, with co-existing charge and superfluid order.
The superfluid is composed of both singlet and triplet pairs induced by
spin-orbit coupling. We perform large-scale calculations using auxiliary-field
quantum Monte Carlo to provide the first full, quantitative description of the
charge, spin, and pairing properties of the system. In addition to
characterizing the exotic physics, our results will serve as essential
high-accuracy benchmarks for the intense theoretical and especially
experimental efforts in ultracold atoms to realize and understand an expanding
variety of quantum Hall and topological superconductor systems.",1707.02994v1
2017-07-19,Odd-parity superconductivity in bilayer transition metal dichalcogenides,"Spin-orbit coupling in transition metal dichalcogenides (TMDCs) causes
spin-valley locking giving rise to unconventional optical, transport, and
superconducting properties. In this paper, we propose exotic superconductivity
in bilayer group-IV TMDCs by symmetry control. The sublattice-dependent hidden
spin-orbit coupling arising from local inversion symmetry breaking in the
crystal structure may stabilize the odd-parity superconductivity by purely
$s$-wave local pairing interaction. The stability of the odd-parity
superconducting state depends on the bilayer stacking. The 2H$_b$ stacking in
MoX$_2$ and WX$_2$ (X =S, Se) favors the odd-parity superconductivity due to
interlayer quantum interference. On the other hand, the odd-parity
superconductivity is suppressed by the 2H$_a$ stacking of NbSe$_2$. Calculating
the phase diagram of the tight-binding model derived from first principles band
calculations, we conclude that the intercalated bilayer MoS$_2$ and WS$_2$ are
candidates for a new class of odd-parity superconductors by spin-orbit
coupling.",1707.05964v1
2020-01-26,Topological properties of a generalized spin-orbit-coupled Su-Schrieffer-Heeger model,"We explore theoretically the effect of inter and intra cell spin-orbit
couplings on topological properties of a generalized Su-Schrieffer-Heeger model
with multipartite lattice structure containing even number of sites per unit
cell. We show that the spin-orbit couplings enrich topological phase diagrams
so that nontrivial topological regions in the space of parameters extend
significantly which is suitable for potential applications. We present an
analytical formula for winding number in terms of sublattice number signaling
that there are two nontrivial topological phases in the space of parameters
hosting twofold/fourfold degenerate zero-mode boundary states. We also find
that by increasing the number of sublattices within unit cell, the nontrivial
regions of topological phase diagram including twofold degenerate zero-mode
edge states extend dramatically. Our symmetry investigation shows that U(1)
spin rotational symmetry around the lattice direction is the crucial ingredient
for the appearance of fourfold degenerate zero-mode boundary states.",2001.09491v1
2017-09-02,"Gravitational spin-orbit coupling in binary systems, post-Minkowskian approximation and effective one-body theory","A novel approach for extracting gauge-invariant information about spin-orbit
coupling in gravitationally interacting binary systems is introduced. This
approach is based on the ""scattering holonomy"", i.e. the integration (from the
infinite past to the infinite future) of the differential spin evolution along
the two worldlines of a binary system in hyperboliclike motion. We apply this
approach to the computation, at the first post-Minkowskian approximation (i.e.
first order in $G$ and all orders in $v/c$), of the values of the two
gyrogravitomagnetic ratios describing spin-orbit coupling in the Effective
One-Body formalism. These gyrogravitomagnetic ratios are found to tend to zero
in the ultrarelativistic limit.",1709.00590v1
2017-11-13,Quantum Hall Effect in Graphene with Interface-Induced Spin-Orbit Coupling,"We consider an effective model for graphene with interface-induced spin-orbit
coupling and calculate the quantum Hall effect in the low-energy limit. We
perform a systematic analysis of the contribution of the different terms of the
effective Hamiltonian to the quantum Hall effect (QHE). By analysing the
spin-splitting of the quantum Hall states as a function of magnetic field and
gate-voltage, we obtain different scaling laws that can be used to characterise
the spin-orbit coupling in experiments. Furthermore, we employ a real-space
quantum transport approach to calculate the quantum Hall conductivity and
investigate the robustness of the QHE to disorder introduced by hydrogen
impurities. For that purpose, we combine first-principles calculations and a
genetic algorithm strategy to obtain a graphene-only Hamiltonian that models
the impurity.",1711.04811v2
2017-11-15,Spin-orbit coupled bosons in one dimension: emergent gauge field and Lifshitz transition,"In the presence of strong spin-independent interactions and spin-orbit
coupling, we show that the spinor Bose liquid confined to one spatial dimension
undergoes an interaction- or density-tuned quantum phase transition similar to
one theoretically proposed for itinerant magnetic solid-state systems. The
order parameter describes broken $Z_2$ inversion symmetry, with the ordered
phase accompanied by non-vanishing momentum which is generated by fluctuations
of an emergent dynamical gauge field at the phase transition. This quantum
phase transition has dynamical critical exponent $z \simeq 2$, typical of a
Lifshitz transition, but is described by a nontrivial interacting fixed point.
From direct numerical simulation of the microscopic model, we extract
previously unknown critical exponents for this fixed point. Our model describes
a realistic situation of 1D ultracold atoms with Raman-induced spin-orbit
coupling, establishing this system as a platform for studying exotic critical
behavior of the Hertz-Millis type.",1711.05794v2
2018-03-16,Revealing weak spin-orbit coupling effects on charge carriers in a $π$-conjugated polymer,"We measure electrically detected magnetic resonance (EDMR) on organic
light-emitting diodes (OLEDs) made of the polymer
poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) at room
temperature and high magnetic fields, where spectral broadening of the
resonance due to spin-orbit coupling (SOC) exceeds that due to the local
hyperfine fields. Density-functional-theory calculations on an open-shell model
of the material reveal g-tensors of charge-carrier spins in the lowest
unoccupied (electron) and highest occupied (hole) molecular orbitals. These
tensors are used for simulations of magnetic resonance line-shapes. Besides
providing the first quantification and direct observation of SOC effects on
charge-carrier states in these weakly SO-coupled hydrocarbons, this procedure
demonstrates that spin-related phenomena in these materials are fundamentally
monomolecular in nature.",1803.06052v1
2018-03-28,Split Fermi Surfaces of the Spin-Orbit-Coupled Metal Cd2Re2O7 Probed by de Haas-van Alphen Effect,"The superconducting pyrochlore oxide Cd2Re2O7 shows a structural transition
with inversion symmetry breaking (ISB) at Ts1 = 200 K. A recent theory [L. Fu,
Phys. Rev. Lett. 115, 026401 (2015)] suggests that the origin is an electronic
instability that leads to a multipolar order in the spin-orbit-coupled metal.
To observe the Fermi surface of the low-temperature phase of Cd2Re2O7, we
perform de Haas-van Alphen effect measurements by means of magnetic torque. In
reference to a calculated band structure, the spin-split Fermi surfaces with
large cyclotron masses of 5-9m0 are revealed. The splitting is suggested to be
due to an antisymmetric spin-orbit coupling induced by ISB, the strength of
which is estimated to be approximately 67 K, which is rather smaller than those
of typical non-centrosymmetric metals.",1803.10472v1
2019-11-08,Ground states of dipolar spin-orbit-coupled Bose-Einstein condensates in a toroidal trap,"We investigate the ground-state structures of dipolar spin-orbit-coupled
Bose-Einstein condensates in a toroidal trap. Combined effects of dipole-dipole
interaction (DDI) and spin-orbit coupling (SOC) on the ground states of the
system are discussed. A ground-state phase diagram is obtained as a function of
the SOC and DDI strengths. As two new degrees of freedom, the DDI and SOC can
be used to obtain the desired ground-state phases and to control the phase
transition between various ground states. In particular, the system displays
exotic topological structures and spin textures, such as half-quantum vortex,
vortex string, vortex necklace, complex vortex lattice including giant vortex
and hidden antivortex chains, different skyrmions, meron
(half-skyrmion)-antimeron (half-antiskyrmion) necklace, and composite
meron-antimeron lattice.",1911.03303v1
2020-09-30,Tunable critical field in Rashba superconductor thin-films,"The upper critical field in type II superconductors is limited by the Pauli
paramagnetic limit. In superconductors with strong Rashba spin-orbit coupling
this limit can be overcome by forming a helical state. Here we quantitatively
study the magnetic field-temperature phase diagram of finite-size
superconductors with Rashba spin-orbit coupling. We discuss the effect of
finite size and shape anisotropy. We demonstrate that the critical field is
controllable by intrinsic parameters such as spin-orbit coupling strength and
tunable parameters such as sample geometry and applied field direction. Our
study opens new avenues for the design of superconducting spin-valves.",2009.14592v1
2020-11-01,Fermi polaron in a dissipative bath with spin-orbit coupling,"We study the polaron problem of an impurity immersed in a dissipative
spin-orbit coupled Fermi gas via a non-self-consistent T-matrix method. We
first propose an experimental scheme to realize a spin-orbit coupled Fermi bath
with dissipation, and show that such a system can be described by a
non-Hermitian Hamiltonian that contains an imaginary spin-flip term and an
imaginary constant shift term. We find that the non-Hermiticity will change the
single particle dispersion of the bath gas, and modify the properties of
attractive and repulsive polarons such as energy, quasi-particle residue,
effective mass, and decay rate. We also investigate the Thouless criteria
corresponding to the instability of the polaron molecule transition, which
suggests a molecule state is more facilitated with stronger bath dissipation.
Finally, we consider the case with finite impurity density and calculate the
interaction between polarons. Our result extends the study of polaron physics
to non-Hermitian systems and may be realized in future experiment.",2011.00461v1
2021-09-10,Topological superfluids in two-dimensional Fermi gas with Rashba spin-orbit coupling,"The realization of spin-orbit coupling (SOC) in ultracold atoms has triggered
an intensive exploring of topological superfluids in the degenerate Fermi gases
based on mean-field theory, which has not yet been reported in experiments.
Here, we demonstrate the topological phase transitions in the system via the
numerically exact quantum Monte Carlo method. Without prior assumptions, our
unbiased real-space calculation shows that spin-orbit coupling can stabilize an
unconventional pairing in the weak SOC regime, in which the
Fulde-Ferrell-Larkin-Ovchinnikov pairing coexists with the
Bardeen-Cooper-Schrieffer pairing. Furthermore, we use the jumps in the spin
polarization at the time-reversal invariant momenta to qualify the topological
phase transition, where we find the critical exponent deviated from the
mean-field theory. Our results pave the way for the searching of unconventional
pairing and topological superfluids with degenerate Fermi gases.",2109.04670v1
2021-12-28,Topological viewpoint of two-dimensional group III-V and IV-IV compounds in the presence of electric field and spin-orbit coupling by density functional theory and tight-binding model,"Using the tight-binding model and density functional theory, the topological
invariant of the two-dimensional (2D) group III-V and IV-IV compounds are
studied in the absence and the presence of an external perpendicular electric
field and spin-orbit coupling. It will be recognized that a critical value of
these parameters changes the topological invariant of 2D graphene-like
compounds. The significant effects of an external electric field and spin-orbit
coupling are considered to the two-center overlap integrals of the
Slater-Koster model involved in band structures, changing band-gap, and tuning
the topological phase transition between ordinary and quantum spin Hall regime.
These declare the good consistency between two theories: tight-binding and
density functional. So, this study reveals topological phase transition in
these materials. Our finding paves a way to extend an effective Hamiltonian,
and may instantly clear some computation aspects of the study in the field of
spintronic based on the first-principles methods.",2112.14155v2
2022-01-14,Supersolid Devil's Staircases of Spin-Orbit-Coupled Bosons in Optical Lattices,"We study the emergence of supersolid Devil's staircases of spin-orbit coupled
bosons loaded in optical lattices. We consider two- and three-dimensional
systems of pseudo-spin-$1/2$ bosons interacting via local spin-dependent
interactions. These interactions together with spin-orbit coupling produce
length scales that are commensurate to the lattice spacing. This
commensurability leads to Devil's staircases of supersolids, with fractal
Hausdorff dimensions, which arise from uniform superfluid phases. We show that
umklapp processes are essential for the existence of commensurate supersolids,
and that without them the Devil's staircase does not exist. Lastly, we
emphasize the generality of our results, suggest experiments that can unveil
these unusual predictions, and discuss potential applications to the case of
$^{87}$Rb.",2201.05372v1
2022-10-17,Rashba spin-orbit coupling in the square lattice Hubbard model: A truncated-unity functional renormalization group study,"The Rashba-Hubbard model on the square lattice is the paradigmatic case for
studying the effect of spin-orbit coupling, which breaks spin and inversion
symmetry, in a correlated electron system. We employ a truncated-unity variant
of the functional renormalization group which allows us to analyze magnetic and
superconducting instabilities on equal footing. We derive phase diagrams
depending on the strengths of Rasbha spin-orbit coupling, real second-neighbor
hopping and electron filling. We find commensurate and incommensurate magnetic
phases which compete with d-wave superconductivity. Due to the breaking of
inversion symmetry, singlet and triplet components mix; we quantify the mixing
of d-wave singlet pairing with f-wave triplet pairing.",2210.09384v2
2022-11-18,Skew scattering by magnetic monopoles and anomalous Hall effect in spin-orbit coupled systems,"Magnetic textures like skyrmions and domain walls coupled to itinerant
electrons give rise to rich transport phenomena such as anomalous Hall effect
and nonreciprocal current. An interesting case is when the transport
coefficient is related to the global (or topological) property of the magnetic
texture, e.g., skyrmion and domain wall numbers. Such phenomena are also
interesting from applications, in which the transport phenomena are potential
probes for electrically detecting magnetic textures in nano-scale devices.
Here, we show that an anomalous Hall effect proportional to the net magnetic
monopole charge occurs from skew scattering when the magnetic texture couples
to itinerant electrons in a non-centrosymmetric system with spin-orbit
interaction. This mechanism gives rise to a finite anomalous Hall effect in a
ferromagnetic domain wall whose spins rotate in the $xy$ plane, despite no
out-of-plane magnetic moment. We also discuss the relation between the magnetic
texture contributing to the anomalous Hall effect and the crystal symmetry. The
results demonstrate rich features arising from the interplay of spin-orbit
interaction and magnetic textures and their potential for detecting various
magnetic textures in nanoscale devices.",2211.10180v1
2023-01-11,Correlated Zak insulator in organic antiferromagnets,"Searching for topological insulators in solids is one of the main issues of
modern condensed matter physics since robust gapless edge or surface states of
the topological insulators can be used as building blocks of next-generation
devices. Enhancing spin-orbit couplings is a promising way to realize
topological insulators in solids, whereas the amplitude of the spin-orbit
couplings is not sufficiently large in most materials. Here we show a way to
realize a topological state characterized by the quantized Zak phase, termed
the Zak insulator, with spin-polarized edges in organic antiferromagnetic Mott
insulators without relying on the spin-orbit coupling. The obtained Zak
insulator can have a large charge gap compared to the conventional topological
insulators, since Coulomb interactions mainly govern the amplitude of the
charge gap in the antiferromagnetic Mott insulators. Besides the mean-field
analysis, we demonstrate that the Zak insulator survives against electron
correlation effects by calculating the many-body Zak phase. Our finding
provides an unprecedented way to realize a topological state in strongly
correlated electron systems.",2301.04490v2
2023-04-17,Spin-orbit coupled Hubbard skyrmions,"When the material phases exhibit topological quantum numbers, they host
defects protected by the nontrivial topology. Magnetic skyrmions are such
``quantized"" objects and although many of them are metals they had been most
likely treated in theories as purely classical spin states. Here, we show that
the electrons described by the Hubbard model with strong spin-orbit couplings
can exhibit various nano- or flake-size skyrmions in their ground state.
Importantly, the conducting electrons forming Fermi pockets themselves carry
textured magnetic moments in both real and momentum space and on that top,
possess Chern numbers in their energy bands. This quantum and conducting
skyrmion is related to small skyrmions observed in atomic-layered compounds. We
clarify how the effective magnetic interactions and magnetic anisotropies are
tied to the spin-orbit coupling, and how they influence the stability of
skyrmions beyond the phenomenology.",2304.08199v2
2023-10-12,Weyl points and spin-orbit coupling in copper-substituted lead phosphate apatite,"We study the impact of spin-orbit coupling on the topological band-properties
of copper-substituted lead phosphate apatite using a combination of
group-theoretical analysis and full-relativistic density-functional theory
calculations. We characterize Weyl points at time-reversal invariant momenta
and find that a band-inversion due to spin-orbit coupling leads to additional
Weyl points close to the Fermi-edge at general momenta. To determine the
position of the altogether 66 Weyl points in the Brilouin-zone, we develop an
algorithm that follows a Berry-curvature-derived vector field to its monopole:
the Weyl point. The emerging surface Fermi-arcs and their spin-polarization
reveal avoided crossings and a Fermi-loop detached from the Weyl points.",2310.09310v1
2024-03-15,Effects of spin-orbit coupling in a valley chiral kagomé network,"Valley chiral kagom\'e networks can arise in various situations, like for
example, in double-aligned graphene-hexagonal boron nitride and periodically
strained graphene. Here, we construct a phenomenological scattering model based
on the symmetries of the network to investigate the energy spectrum and
magnetotransport in this system. Additionally, we consider the effects of a
finite Rashba spin-orbit coupling on the transport properties of the kagom\'e
network. We identify conditions where the interplay of the Rashba spin-orbit
coupling and the geometry of the lattice results in a reduction of the
periodicity of the magnetoconductance and characteristic sharp resonances.
Moreover, we find a finite spin-polarization of the conductance, which could be
exploited in spintronic devices.",2403.10181v1
2014-02-27,Enhanced Stability of Skyrmions in Two-Dimensional Chiral Magnets with Rashba Spin-Orbit Coupling,"Recent developments have led to an explosion of activity on skyrmions in
three-dimensional (3D) chiral magnets. Experiments have directly probed these
topological spin textures, revealed their nontrivial properties, and led to
suggestions for novel applications. However, in 3D the skyrmion crystal phase
is observed only in a narrow region of the temperature-field phase diagram. We
show here, using a general analysis based on symmetry, that skyrmions are much
more readily stabilized in two-dimensional (2D) systems with Rashba spin-orbit
coupling. This enhanced stability arises from the competition between field and
easy-plane magnetic anisotropy and results in a nontrivial structure in the
topological charge density in the core of the skyrmions. We further show that,
in a variety of microscopic models for magnetic exchange, the required
easy-plane anisotropy naturally arises from the same spin-orbit coupling that
is responsible for the chiral Dzyaloshinskii-Moriya interactions. Our results
are of particular interest for 2D materials like thin films, surfaces, and
oxide interfaces, where broken surface-inversion symmetry and Rashba spin-orbit
coupling naturally lead to chiral exchange and easy-plane compass anisotropy.
Our theory gives a clear direction for experimental studies of 2D magnetic
materials to stabilize skyrmions over a large range of magnetic fields down to
T=0.",1402.7082v2
2012-01-06,Half-quantum vortex state in a spin-orbit coupled Bose-Einstein condensate,"We investigate theoretically the condensate state and collective excitations
of a two-component Bose gas in two-dimensional harmonic traps subject to
isotropic Rashba spin-orbit coupling. In the weakly interacting regime when the
inter-species interaction is larger than the intra-species interaction
($g_{\uparrow\downarrow}>g$), we find that the condensate ground state has a
half-quantum-angular-momentum vortex configuration with spatial rotational
symmetry and skyrmion-type spin texture. Upon increasing the interatomic
interaction beyond a threshold $g_{c}$, the ground state starts to involve
higher-order angular momentum components and thus breaks the rotational
symmetry. In the case of $g_{\uparrow\downarrow}<g$, the condensate becomes
unstable towards the superposition of two degenerate half-quantum vortex
states. Both instabilities (at $g>g_{c}$ and $g_{\uparrow\downarrow}<g$) can be
determined by solving the Bogoliubov equations for collective density
oscillations of the half-quantum vortex state, and by analyzing the softening
of mode frequencies. We present the phase diagram as functions of the
interatomic interactions and the spin-orbit coupling. In addition, we directly
simulate the time-dependent Gross-Pitaevskii equation to examine the dynamical
properties of the system. Finally, we investigate the stability of the
half-quantum vortex state against both the trap anisotropy and anisotropy in
the spin-orbit coupling term.",1201.1471v1
2012-01-29,Collective Dipole Oscillation of a Spin-Orbit Coupled Bose-Einstein Condensate,"We present an experimental study of the collective dipole oscillation of a
spin-orbit coupled Bose-Einstein condensate in a harmonic trap. Dynamics of the
center-of-mass dipole oscillation is studied in a broad parameter region, as a
function of spin-orbit coupling parameters as well as oscillation amplitude.
Anharmonic properties beyond effective-mass approximation are revealed, such as
amplitude-dependent frequency and finite oscillation frequency at place with
divergent effective mass. These anharmonic behaviors agree quantitatively with
variational wave-function calculations. Moreover, we experimentally demonstrate
a unique feature of spin-orbit coupled system predicted by a sum-rule approach,
stating that spin polarization susceptibility--a static physical quantity--can
be measured via dynamics of dipole oscillation. The divergence of polarization
susceptibility is observed at the quantum phase transition that separates
magnetic nonzero-momentum condensate from nonmagnetic zero-momentum phase. The
good agreement between the experimental and theoretical results provides a
bench mark for recently developed theoretical approaches.",1201.6018v2
2019-09-25,Van der Waals heterostructures with spin-orbit coupling,"In this article we review recent work on van der Waals (vdW) systems in which
at least one of the components has strong spin-orbit coupling. We focus on a
selection of vdW heterostructures to exemplify the type of interesting
electronic properties that can arise in these systems. We first present a
general effective model to describe the low energy electronic degrees of
freedom in these systems. We apply the model to study the case of (vdW) systems
formed by a graphene sheet and a topological insulator. We discuss the
electronic transport properties of such systems and show how they exhibit much
stronger spin-dependent transport effects than isolated topological insulators.
We then consider vdW systems in which the layer with strong spin-orbit coupling
is a monolayer transition metal dichalcogenide (TMD) and briefly discuss
graphene-TMD systems. In the second part of the article we discuss the case in
which the vdW system includes a superconducting layer in addition to the layer
with strong spin-orbit coupling. We show in detail how these systems can be
designed to realize odd-frequency superconducting pair correlations. Finally,
we discuss twisted graphene-NbSe2 bilayer systems as an example in which the
strength of the proximity-induced superconducting pairing in the normal layer,
and its Ising character, can be tuned via the relative twist angle between the
two layers forming the heterostructure.",1909.11674v2
2021-06-26,Role of line defect in the bandgap and transport properties of silicene nanoribbons,"By using the tight-binding model and non-equilibrium Green's function method
(NEGF), we study the band structures and transport properties of a silicene
nanoribbon with a line defect where a bulk energy gap is opened due to the
sublattice symmetry breaking. The flat subband bends downwards or upwards due
to the effect of the line defect. The spin-orbit coupling induces quantum spin
Hall states. Especially, the energy band depends on the distance between the
line defect and the edge of the nanoribbon. The effects of the on-site energies
on the band spectra of the two defect configurations are different. There
always exists one band gap for different on-site energies for the defect
configuration of case 1. However, a gapless state and a band gap can be
modulated by changing the on-site energy, the sublattice potential and
spin-orbit couplings for the defect configuration of case 2. Accordingly, the
variation trends of the conductance including zero conductance can be well
understood in terms of the combined effect of the sublattice potential, the
on-site energy and spin-orbit couplings on the band structures. Thus it is easy
and effective to modulate the transport property of the silicene nanoribbon
with the defect configuration of case 2 by utilizing the sublattice potential,
the on-site energy and spin-orbit couplings. This study is of great
significance for the fabrication and the modulation of the transport property
of silicene-based devices.",2106.14062v1
2009-02-26,Effects of Magnetic Braking and Tidal Friction on Hot Jupiters,"Tidal friction is thought to be important in determining the long-term
spin-orbit evolution of short-period extrasolar planetary systems. Using a
simple model of the orbit-averaged effects of tidal friction Eggleton, Kiseleva
& Hut (1998), we analyse the effects of the inclusion of stellar magnetic
braking on the evolution of such systems. A phase-plane analysis of a
simplified system of equations, including only the stellar tide together with a
model of the braking torque proposed by Verbunt & Zwaan (1981), is presented.
The inclusion of stellar magnetic braking is found to be extremely important in
determining the secular evolution of such systems, and its neglect results in a
very different orbital history. We then show the results of numerical
integrations of the full tidal evolution equations, using the misaligned spin
and orbit of the XO-3 system as an example, to study the accuracy of simple
timescale estimates of tidal evolution. We find that it is essential to
consider coupled evolution of the orbit and the stellar spin in order to model
the behaviour accurately. In addition, we find that for typical Hot Jupiters
the stellar spin-orbit alignment timescale is of the same order as the inspiral
time, which tells us that if a planet is observed to be aligned, then it
probably formed coplanar. This reinforces the importance of Rossiter-McLaughlin
effect observations in determining the degree of spin-orbit alignment in
transiting systems.",0902.4554v1
2004-10-26,Orbital Physics in the Perovskite Ti Oxides,"In the perovskite Ti oxide RTiO3 (R=rare-earth ions), the Ti t2g orbitals and
spins in the 3d^1 state couple each other through the strong electron
correlations, resulting in a rich variety of orbital-spin phases. The origin
and nature of orbital-spin states of these Mott insulators have been
intensively studied. In this article, we review the studies on orbital physics
in the perovskite titanates. We focus on the following three topics: (1) the
origin and nature of the ferromagnetism as well as the orbital ordering in the
compounds with relatively small R ions such as GdTiO3 and YTiO3, (2) the origin
of the G-type antiferromagnetism and the orbital state in LaTiO3, and (3) the
orbital-spin structures in other AFM(G) compounds with relatively large R ions
(R=Ce, Pr, Nd and Sm). On the basis of these discussions, we discuss the whole
phase diagram together with mechanisms of the magnetic phase transition. We
also show that the Ti t2g degeneracy is inherently lifted in the titanates,
which allows the single-band descriptions of the ground-state and low-energy
electronic structures as a good starting point. Our analyses indicate that
these compounds offer touchstone materials described by the single-band Hubbard
model on the cubic lattice. From this insight, we also reanalyze the hole-doped
titanates. Experimentally revealed filling-dependent and bandwidth-dependent
properties and the critical behavior of the metal-insulator transitions are
discussed in the light of theories based on the single-band Hubbard models.",0410650v1
2013-01-17,Defect states and spin-orbital physics in doped vanadates Y1-xCaxVO3,"We present a model for typical charged defects in weakly doped Y1-xCaxVO3
perovskites and study how they influence the magnetic and orbital order.
Starting from a multiband Hubbard model, we show that the charge carriers
introduced by doping are bound to the Ca defects with large binding energy of
about 1 eV at small doping, and give rise to the in-gap absorption band
observed in the optical spectroscopy. The central position of a generic Ca
defect with eight equidistant vanadium neighbors implies a partly filled defect
band and permits activated transport due to Coulomb disorder. We explore the
effect of bound charge carriers on the dynamics of the (yz,zx) orbital and spin
degrees of freedom in the context of a spin-orbital t-J model. After deriving
the superexchange interactions around the doped hole, we show that the
transition from G-type to C-type antiferromagnetic (AF) order is triggered by
the kinetic energy of doped holes via the double-exchange mechanism. The defect
states lead to local modification of orbital correlations within ferromagnetic
chains along the c axis; some of them contain hole defects, while the
charge-orbital coupling suppresses locally (yz,zx) orbital fluctuations in the
others. Thereby, Ca defects provide a physical mechanism for spin-orbital
dimerization along the ferromagnetic bonds, suggesting that, in the C-AF phase
of weakly doped Y1-xCaxVO3, dimerization increases with doping.",1301.4026v1
2004-11-25,Spin Hall Effect in a Diffusive Rashba Two-dimensional Electron Gas,"A nonequilibrium Green's functions approach to spin-Hall effect is developed
in a diffusive two-dimensional electron system with Rashba spin-orbit
interaction. In the presence of long-range impurities, the coupled quantum
kinetic equations are solved analytically in the self-consistent Born
approximation. It is shown that the intrinsic spin-Hall effect stems from the
dc-field-induced perturbation of the density of states. In addition, there is
an additional disorder-mediated process, which involves the transition of
nonequilibrium electrons between two spin-orbit-coupled bands. It results in an
additional collision-independent spin-Hall conductivity and leads to the
vanishing of the total spin-Hall current even at nonzero temperature.",0411629v2
2006-02-27,Intrinsic Spin Hall Effect in the presence of Extrinsic Spin-Orbit Scattering,"Intrinsic and extrinsic spin Hall effects are considered together on an equal
theoretical footing for the Rashba spin-orbit coupling in two-dimensional (2D)
electron and hole systems, using the diagrammatic method for calculating the
spin Hall conductivity. Our analytic theory for the 2D holes shows the expected
lowest-order additive result for the spin Hall conductivity. But, the 2D
electrons manifest a very surprising result, exhibiting a non-analyticity in
the Rashba coupling strength $\alpha$ where the strictly extrinsic spin Hall
conductivity (for $\alpha = 0$) cannot be recovered from the $\alpha \to 0$
limit of the combined theory. The theoretical results are discussed in the
context of existing experimental results.",0602607v1
2006-10-11,Spin relaxation in an InAs quantum dot in the presence of terahertz driving fields,"The spin relaxation in a 1D InAs quantum dot with the Rashba spin-orbit
coupling under driving THz magnetic fields is investigated by developing the
kinetic equation with the help of the Floquet-Markov theory, which is
generalized to the system with the spin-orbit coupling, to include both the
strong driving field and the electron-phonon scattering. The spin relaxation
time can be effectively prolonged or shortened by the terahertz magnetic field
depending on the frequency and strength of the terahertz magnetic field. The
effect can be understood as the sideband-modulated spin-phonon scattering. This
offers an additional way to manipulate the spin relaxation time.",0610300v2
2007-01-10,Electron Density Dependence of in-plane Spin Relaxation Anisotropy in GaAs/AlGaAs Two-Dimensional Electron Gas,"We investigated the spin dynamics of two-dimensional electrons in (001)
GaAs/AlGaAs heterostructure using the time resolved Kerr rotation technique
under a transverse magnetic field. The in-plane spin lifetime is found to be
anisotropic below 150k due to the interference of Rashba and Dresselhaus
spin-orbit coupling and D'yakonov-Perel' spin relaxation. The ratio of in-plane
spin lifetimes is measured directly as a function of temperature and pump
power, showing that the electron density in 2DEG channel strongly affects the
Rashba spin-orbit coupling.",0701195v2
2008-01-17,Spin polarized current generation from quantum dots without magnetic fields,"An unpolarized charge current passing through a chaotic quantum dot with
spin-orbit coupling can produce a spin polarized exit current without magnetic
fields or ferromagnets. We use random matrix theory to estimate the typical
spin polarization as a function of the number of channels in each lead in the
limit of large spin-orbit coupling. We find rms spin polarizations up to 45%
with one input channel and two output channels. Finite temperature and
dephasing both suppress the effect, and we include dephasing effects using a
new variation of the third lead model. If there is only one channel in the
output lead, no spin polarization can be produced, but we show that dephasing
lifts this restriction.",0801.2592v2
2008-02-04,Current-induced spin polarization in spin-orbit-coupled two-dimensional electron systems,"Current-induced spin polarization (CISP) is rederived in ballistic
spin-orbit-coupled electron systems, based on equilibrium statistical
mechanics. A simple and useful picture is correspondingly proposed to help
understand the CISP and predict the polarization direction. Nonequilibrium
Landauer-Keldysh formalism is applied to demonstrate the validity of the
statistical picture, taking the linear Rashba-Dresselhaus [001] two-dimensional
system as a specific example. Spin densities induced by the CISP in
semiconductor heterostructures and in metallic surface states are compared,
showing that the CISP increases with the spin splitting strength and hence
suggesting that the CISP should be more observable on metal and semimetal
surfaces due to the discovered strong Rashba splitting. An application of the
CISP designed to generate a spin-Hall pattern in the inplane, instead of the
out-of-plane, component is also proposed.",0802.0366v3
2008-03-07,Conservation and persistence of spin currents and their relation to the Lieb-Schulz-Mattis twist operators,"Systems with spin-orbit coupling do not conserve ""bare"" spin current
$\bf{j}$. A recent proposal for a conserved spin current $\bf{J}$ [J. Shi {\it
et.al} Phys. Rev. Lett. {\bf 96}, 076604 (2006)] does not flow persistently in
equilibrium. We suggest another conserved spin current $\bar{\bf{J}}$ that may
flow persistently in equilibrium. We give two arguments for the instability of
persistent current of the form $\bf{J}$: one based on the equations of motions
and another based on a variational construction using Lieb-Schulz-Mattis twist
operators. In the absence of spin-orbit coupling, the three forms of spin
current coincide.",0803.0984v2
2008-04-15,Surface bound states and spin currents in non-centrosymmetric superconductors,"We investigate the influence of spin-orbit coupling in a non-centrosymmetric
superconductor on its ground state properties near a surface. We determine the
spectrum of Andreev bound states due to surface-induced mixing of bands with
opposite spin helicities for a Rashba-type spin-orbit coupling. We find a
qualitative change of the Andreev spectrum when we account for the suppression
of the order parameter near the surface, leading to clear signatures in the
surface density of states. We also compute the spin current at the surface,
which has spin polarization normal to that of the bulk current. The magnitude
of the current at the surface is enhanced in the normal state compared to the
bulk, and even further enlarged in the superconducting phase. The particle and
hole coherence amplitudes show Faraday-like rotations of the spin along
quasiparticle trajectories.",0804.2464v1
2008-06-16,Density dependence of spin relaxation in GaAs quantum well at room temperature,"Carrier density dependence of electron spin relaxation in an intrinsic GaAs
quantum well is investigated at room temperature using time-resolved circularly
polarized pump-probe spectroscopy. It is revealed that the spin relaxation time
first increases with density in the relatively low density regime where the
linear D'yakonov-Perel' spin-orbit coupling terms are dominant, and then tends
to decrease when the density is large and the cubic D'yakonov-Perel' spin-orbit
coupling terms become important. These features are in good agreement with
theoritical predictions by L\""u {\em et al.} [Phys. Rev. B {\bf 73}, 125314
(2006)]. A fully microscopic calculation based on numerically solving the
kinetic spin Bloch equations with both the D'yakonov-Perel' and the
Bir-Aronov-Pikus mechanisms included, reproduces the density dependence of spin
relaxation very well.",0806.2577v2
2010-07-27,Simulating and Detecting the Quantum Spin Hall Effect in Kagomé Optical Lattice,"We propose a model which includes a nearest-neighbor intrinsic spin-orbit
coupling and a dimer Hamiltonian in the Kagom\'{e} lattice and promises to host
the transition from the quantum spin Hall insulator to the normal insulator. In
addition, we design an experimental scheme to simulate and detect this
transition in the ultracold atom system. The lattice intrinsic spin-orbit
coupling is generated via the laser-induced-gauge-field method. Furthermore, we
establish the connection between the spin Chern number and the spin-atomic
density which enables us to detect the topological quantum spin Hall insulator
directly by the standard density-profile technique used in the atomic systems.",1007.4637v2
2011-02-23,Spin relaxation near the metal-insulator transition: dominance of the Dresselhaus spin-orbit coupling,"We identify the Dresselhaus spin-orbit coupling as the source of the dominant
spin-relaxation mechanism in the impurity band of doped semiconductors. The
Dresselhaus-type (i.e. allowed by bulk-inversion asymmetry) hopping terms are
derived and incorporated into a tight-binding model of impurity sites, and they
are shown to unexpectedly dominate the spin relaxation, leading to
spin-relaxation times in good agreement with experimental values. This
conclusion is drawn from two complementary approaches employed to extract the
spin-relaxation time from the effective Hamiltonian: an analytical
diffusive-evolution calculation and a numerical finite-size scaling.",1102.4753v1
2011-03-24,Novel Spin-texture on the warped Dirac-cone surface states in topological insulators,"We have investigated the nature of surface states in the Bi2Te3 family of
three-dimensional topological insulators using first-principles calculations as
well as model Hamiltonians. When the surface Dirac cone is warped due to
Dresselhaus spin-orbit coupling in rhombohedral structures, the spin acquires a
finite out-of-plane component. We predict a novel in-plane spin-texture of the
warped surface Dirac cone with spins not perpendicular to the electron
momentum. Our k.p model calculation reveals that this novel in-plane
spin-texture requires high order Dresselhaus spin-orbit coupling terms.",1103.4675v1
2013-03-31,Electrical current and coupled electron-nuclear spin dynamics in double quantum dots,"We examine electronic transport in a spin-blockaded double quantum dot. We
show that by tuning the strength of the spin-orbit interaction the current
flowing through the double dot exhibits a dip at zero magnetic field or a peak
at a magnetic field for which the two-electron energy levels anticross. This
behaviour is due to the dependence of the singlet-triplet mixing on the field
and spin-orbit amplitude. We derive approximate expressions for the current as
a function of the amplitudes of the states involved in the transport. We also
consider an alternative model that takes into account a finite number of
nuclear spins and study the resulting coupled dynamics between electron and
nuclear spins. We show that if the spin ensemble is in a thermal state there
are regular oscillations in the transient current followed by quasi-chaotic
revivals akin to those seen in a thermal Jaynes-Cummings model.",1304.0169v1
2013-04-16,Gauge-spin-space rotation invariant vortices in spin-orbit coupled Bose-Einstein condensates,"We revisit ground states of spinor Bose-Einstein condensates with a Rashba
spin-orbit coupling, and find that votices show up as a direct consequence of
spontaneous symmetry breaking into a combined gauge, spin, and space rotation
symmetry, which determines the vortex-core spin state at the rotating center.
For the continuous combined symmetry, the total spin rotation about the
rotating axis is restricted to $2\pi$, whereas for the discrete combined
symmetry, we further need 2F quantum numbers to characterize the total spin
rotation for the spin-$F$ system. For lattice phases we find that in the ground
state the topological charge for each unit cell vanishes. However, we find two
types of highly symmetric lattices with a nontrivial topological charge in the
spin-$\frac{1}{2}$ system based on the symmetry classification, and show that
they are skyrmion crystals.",1304.4340v1
2013-04-17,Angular dependence and symmetry of Rashba spin torque in ferromagnetic heterostructures,"In a ferromagnetic heterostructure, the interplay between a Rashba spin-orbit
coupling and an exchange field gives rise to a current-driven spin torque. In a
realistic device setup, we investigate the Rashba spin torque in the diffusive
regime and report two major findings: (i) a nonvanishing torque exists at the
edges of the device even when the magnetization and effective Rashba field are
aligned; (ii) anisotropic spin relaxation rates driven by the Rashba spin-orbit
coupling assign the spin torque a general expression ${\bm
T}=T^y_{\para}(\theta){\bm m}\times(\hat{\bm y}\times{\bm
m})+T^y_{\bot}(\theta)\hat{\bm y}\times{\bm m}+T^z_{\para}(\theta){\bm
m}\times(\hat{\bm z}\times{\bm m})+T^z_{\bot}(\theta)\hat{\bm z}\times{\bm m}$,
where the coefficients $T_{\para,\bot}^{y,z}$ depend on the magnetization
direction. Our results agree with recent experiments.",1304.4823v1
2013-12-30,Indirect control of spin precession by electric field via spin-orbit coupling,"The spin-orbit coupling (SOC) can mediate electric-dipole spin resonance
(EDSR) in an a.c. electric field. In this letter, the EDSR is essentially
understood as an spin precession under an effective a.c. magnetic field induced
by the SOC in the reference frame, which is exactly following the classical
trajectory of the electron and obtained by applying a quantum linear coordinate
transformation. With this observation for one-dimensional (1D) case, we find a
upper limit for the spin-flipping speed in the EDSR-based control of spin,
which is given by the accessible data from the current experiment. For
two-dimensional case, the azimuthal dependence of the effective magnetic field
can be used to measure the ratio of the Rashba and Dresselhause SOC strengths.",1312.7635v3
2014-10-24,Spin-orbit coupled transport in a curved quantum wire,"We study the interplay of both Rashba and Dresselhaus spin-orbit couplings
(SOCs) and a uniform perpendicular magnetic field $\textbf{B}$ on the transport
of a spin-polarized electron along a curved quantum wire. Eigenenergies and
eigenfunctions of the system were analytically solved in the presence of both
SOCs for a confinement radius $R$. From the transmission coefficients, the spin
transport properties such as spin polarization, probability current density and
spin conductance were computed numerically to determine their dependence on the
SOCs, $\textbf{B}$ and $R$. We find the condition for $\textbf{B}$ that if it
is beyond $R^{1/3}$, no spin reversal will occur. Our results show that for a
sufficiently large SOC strength, regardless of its inversion asymmetry origin,
the effect of the external magnetic field is reduced. Finding the optimal
effective SOC strength is essential in achieving suitable magneto-transport
properties for possible spintronic device applications.",1410.6595v1
2014-12-22,Transport Theory of Metallic B20 Helimagnets,"B20 compounds are a class of cubic helimagnets harboring nontrivial spin
textures such as spin helices and skyrmions. It has been well understood that
the Dzyaloshinskii-Moriya (DM) interaction is the origin of these textures, and
the physics behind the DM interaction is the spin-orbital coupling (SOC).
However the SOC shows its effect not only on the spins, but also on the
electrons. In this paper, we will discuss effects of the SOC on the electron
and spin transports in B20 compounds. An effective Hamiltonian is presented
from symmetry analysis, and the spin-orbital coupling therein shows anomalous
behaviors in anisotropic magnetoresistance (AMR) and helical resistance. New
effects such as inverse spin-galvanic effect is proposed, and the origin of the
DM interaction is discussed.",1412.7177v1
2015-04-09,Spin Textures of Polariton Condensates in a Tunable Microcavity with Strong Spin-Orbit Interaction,"We report an extended family of spin textures in coexisting modes of
zero-dimensional polariton condensates spatially confined in tunable open
microcavity structures. The coupling between photon spin and angular momentum,
which is enhanced in the open cavity structures, leads to new eigenstates of
the polariton condensates carrying quantised spin vortices. Depending on the
strength and anisotropy of the cavity confinement potential and the strength of
the spin-orbit coupling, which can be tuned via the excitonic/photonic
fractions, the condensate emissions exhibit either spin-vortex-like patterns or
linear polarization, in good agreement with theoretical modelling.",1504.02341v1
2017-04-05,Tuning the effective spin-orbit coupling in molecular semiconductors,"The control of spins and spin to charge conversion in organics requires
understanding the molecular spin-orbit coupling (SOC), and a means to tune its
strength. However, quantifying SOC strengths indirectly through spin relaxation
effects has proven diffi- cult due to competing relaxation mechanisms. Here we
present a systematic study of the g-tensor shift in molecular semiconductors
and link it directly to the SOC strength in a series of high mobility molecular
semiconductors with strong potential for future devices. The results
demonstrate a rich variability of the molecular g-shifts with the effective
SOC, depending on subtle aspects of molecular composition and structure. We
correlate the above g -shifts to spin-lattice relaxation times over four orders
of magnitude, from 200 {\mu}s to 0.15 {\mu}s, for isolated molecules in
solution and relate our findings for isolated molecules in solution to the spin
relaxation mechanisms that are likely to be relevant in solid state systems.",1704.01371v2
2019-07-16,Current-driven Rashba Field in a Magnetic Quantum Well,"In materials lacking inversion symmetry, the spin-orbit coupling enables the
direct connection between the electron's spin and its linear momentum, a
phenomenon called inverse spin galvanic effect. In magnetic materials, this
effect promotes current-driven torques that can be used to control the
magnetization direction electrically. In this work, we investigate the
current-driven inverse spin galvanic effect in a quantum well consisting in a
magnetic material embedded between dissimilar insulators. Assuming the presence
of Rashba spin-orbit coupling at the interfaces, we investigate the nature of
the non-equilibrium spin density and the influence of the quantum well
parameters. We find that the torque is governed by the interplay between the
number of states participating to the transport and their spin chirality, the
penetration of the wave function into the tunnel barriers, and the strength of
the Rashba term.",1907.07116v1
2017-11-16,Phonon-assisted spin splitting in centrosymmetric crystals,"For static crystals it is well known that electronic states are doubly
degenerate in their spin degree of freedom in the presence of time reversal and
inversion symmetries. This degeneracy can only be lifted by either (i) breaking
time reversal symmetry, for example in a ferromagnet, or (ii) breaking
inversion symmetry and having spin orbit coupling, for example in the Rashba
effect. We propose that spin degeneracy can be lifted in time reversal and
inversion symmetric crystals with a combination of lattice vibrations and
spin-orbit coupling. We demonstrate this effect in the cubic perovskite
CsPbCl$_3$ by performing first principles calculations of the finite
temperature band structure, which, in accordance with our prediction, undergoes
spin splitting. We also suggest optical and photoemission experiments to
examine our predictions. This new understanding dramatically expands the range
of materials that can exhibit spin splitting, with potential applications in a
variety of technologies such as spintronics and photovoltaics.",1711.06274v1
2018-08-01,Synthesizing and Controlling Helical Indirect Exchange Interactions at Nonequilibrium,"We study the nonequilibrium effects of spin and/or electric currents on the
helical indirect exchange interactions of local spins that embedded in general
open electronic systems. Especially, besides the synthesized anisotropic
Heisenberg interactions, we find that the synthetic helical indirect exchange
interactions possess two parts: antisymmetric (Dzyaloshinskii-Moriya
interaction) and symmetric (Kaplan-Shekhtman-Entin-Wohlman-Aharony
interaction), which are all formulated in terms of Keldysh nonequilibrium
Green's functions. The presence of either spin-orbit coupling or spin polarized
currents alone is able to synthesize and control the antisymmetric
Dzyaloshinskii-Moriya exchange interactions, as the same direction as spin
splitting. However, the appearance of symmetric
Kaplan-Shekhtman-Entin-Wohlman-Aharony interactions requires both, i.e., the
spin-orbit coupling and spin polarized currents with different splitting
directions. Our results show the detailed scheme of controlling the sign,
magnitude, and direction of indirect Dzyaloshinskii-Moriya vectors and
Kaplan-Shekhtman-Entin-Wohlman-Aharony interactions at nonequilibrium in open
quantum devices.",1808.00187v1
2020-03-30,Adiabatic spin-dependent momentum transfer in an SU(N) degenerate Fermi gas,"We introduce a spin-orbit coupling scheme, where a retro-reflected laser beam
selectively diffracts two spin components in opposite directions. Spin
sensitivity is provided by sweeping through a magnetic-field sensitive
transition while dark states ensure that spontaneous emission remains low. The
scheme is adiabatic and thus inherently robust. This tailored spin-orbit
coupling allows simultaneous measurements of the spin and momentum
distributions of a strontium degenerate Fermi gas, and thus opens the path to
momentum-resolved spin correlation measurements on SU(N) quantum magnets.",2003.13444v3
2020-10-21,Spontaneous Chiral-Spin Ordering in Spin-Orbit Coupled Honeycomb Magnets,"Frustrated magnets with highly degenerate ground states are at the heart of
hunting exotic states of matter. Recent studies in spin-orbit coupled honeycomb
magnets have generated immense interest in bond-dependent interactions,
appreciating a symmetric off-diagonal $\Gamma$ interaction which exhibits a
macroscopic degeneracy in the classical limit. Here, we study a generic spin
model and discover a novel chiral-spin ordering with spontaneously broken
time-reversal symmetry near the dominant $\Gamma$ region. The chiral-spin phase
is demonstrated to possess a staggered chirality relation in different
sublattices, and it exhibits gapless excitations as revealed by the vanishing
energy gap and the finite central charge on cylinders. Although there is a
vestige of a tiny peak in the corner of the second Brillouin zone, the magnetic
order is likely to vanish as the system size increases. Finally, we also
attempt to gain insight into the possible topological signature of the
chiral-spin phase by calculating the dynamic structure factor and the modular
$\mathcal{S}$ matrix.",2010.11233v2
2021-03-10,Spin response and topology of a staggered Rashba superconductor,"Inversion symmetry is a key symmetry in unconventional superconductors and
even its local breaking can have profound implications. For inversion-symmetric
systems, there is a competition on a microscopic level between the spin-orbit
coupling associated with the local lack of inversion and hybridizing terms that
`restore' inversion. Investigating a layered system with alternating
mirror-symmetry breaking, we study this competition considering the spin
response of different superconducting order parameters for the case of strong
spin-orbit coupling. We find that signatures of the local non-centrosymmetry,
such as an increased spin susceptibility in spin-singlet superconductors for
$T\rightarrow 0$, persist even into the quasi-three-dimensional regime. This
leads to a direction dependent spin response which allows to distinguish
different superconducting order parameters. Furthermore, we identify several
regimes with possible topological superconducting phases within a
symmetry-indicator analysis. Our results may have direct relevance for the
recently reported Ce-based superconductor CeRh$_2$As$_2$ and beyond.",2103.06282v1
2021-04-19,Old experiments in new light: Young's double-slit and Stern-Gerlach experiments in liquid crystal microcavities,"Spin-orbit interactions which couple spin of a particle with its momentum
degrees of freedom lie at the center of spintronic applications. Of special
interest in semiconductor physics are Rashba and Dresselhaus spin-orbit
coupling (SOC). When equal in strength, the Rashba and Dresselhaus fields
result in SU(2) spin rotation symmetry and emergence of the persistent spin
helix (PSH) only investigated for charge carriers in semiconductor quantum
wells. Recently, a synthetic Rashba-Dresselhaus Hamiltonian was shown to
describe cavity photons confined in a microcavity filled with optically
anisotropic liquid crystal. In this work, we present a purely optical
realisation of two types of spin patterns corresponding to PSH and the
Stern-Gerlach experiment in such a cavity. We show how the symmetry of the
Hamiltonian results in spatial oscillations of the spin orientation of photons
travelling in the plane of the cavity.",2104.09674v1
2021-07-11,Electronic and magnetic properties of honeycomb zigzag nanoribbons in the in-plane transverse electric field using Kane-Mele-Hubbard model,"Using the Kane-Mele-Hubbard model in the unrestricted mean field
approximation, the effect of spin-orbit coupling, as an intrinsic parameter,
and an in-plane transverse electric field, as an external parameter, on the
electronic and magnetic properties of honeycomb zigzag nanoribbons are
investigated in the presence of electron-electron interaction. Our calculations
show that each of these parameters has significant effects on the physical
properties of nanoribbons, and each of them independently transitions the
nanoribbon from a magnetic to non-magnetic state. The process of change in some
aspect of physical properties, such as symmetry breaking, separation of spin up
and spin down energy bands, reduction of magnetic order, change of electric
dipole moment and spin current of nanoribbons, which are due to change of these
two parameters are investigated. we will see that spin-orbit coupling in the
competition with the transverse electric field determines the basic physical
properties of the nanoribbon. This research, can provide a better understanding
of two types of topological and non-topological transitions. In addition, the
separation of spin-up and spin-down energy bands and their tuning by these
parameters can be considered as a candidate for use in spintronic instruments.",2107.05120v1
2023-12-14,Giant chirality-induced spin polarization in twisted transition metal dichalcogenides,"Chirality-induced spin selectivity (CISS) is an effect that has recently
attracted a great deal of attention in chiral chemistry and that remains to be
understood. In the CISS effect, electrons passing through chiral molecules
acquire a large degree of spin polarization. In this work we study the case of
atomically-thin chiral crystals created by van der Waals assembly. We show that
this effect can be spectacularly large in systems containing just two
monolayers, provided they are spin-orbit coupled. Its origin stems from the
combined effects of structural chirality and spin-flipping spin-orbit coupling.
We present detailed calculations for twisted homobilayer transition metal
dichalcogenides, showing that the chirality-induced spin polarization can be
giant, e.g. easily exceeding $50\%$ for ${\rm MoTe}_2$. Our results clearly
indicate that twisted quantum materials can operate as a fully tunable platform
for the study and control of the CISS effect in condensed matter physics and
chiral chemistry.",2312.09169v2
2002-02-04,Electronic theory for the normal state spin dynamics in Sr$_2$RuO$_4$: anisotropy due to spin-orbit coupling,"Using a three-band Hubbard Hamiltonian we calculate within the
random-phase-approximation the spin susceptibility, $\chi({\bf q},\omega)$, and
NMR spin-lattice relaxation rate, 1/T$_1$, in the normal state of the triplet
superconductor Sr$_2$RuO$_4$ and obtain quantitative agreement with
experimental data. Most importantly, we find that due to spin-orbit coupling
the out-of-plane component of the spin susceptibility $\chi^{zz}$ becomes at
low temperatures two times larger than the in-plane one. As a consequence
strong incommensurate antiferromagnetic fluctuations of the
quasi-one-dimensional $xz$- and $yz$-bands point into the $z$-direction. Our
results provide further evidence for the importance of spin fluctuations for
triplet superconductivity in Sr$_2$RuO$_4$.",0202051v2
2005-01-04,Anisotropy of spin splitting and spin relaxation in lateral quantum dots,"Inelastic spin relaxation and spin splitting $\epsilon_{\mathrm{s}}$ in
lateral quantum dots are studied in the regime of strong in-plane magnetic
field. Due to both g-factor energy dependence and spin-orbit coupling
$\epsilon_{\mathrm{s}}$ demonstrates a substantial non-linear magnetic field
dependence similar to that observed by R.Hanson \textit{et al} [Phys. Rev.
Lett. \textbf{91}, 196802 (2003)]. It also varies with the in-plane orientation
of magnetic field due to crystalline anisotropy of spin-orbit coupling. Spin
relaxation rate is also anisotropic, the anisotropy increasing with the field.
When the magnetic length is less than the 'thickness' of GaAs dot, the
relaxation can be order of magnitude faster for $\mathbf{B}% \Vert\lbrack100]$
than for $\mathbf{B\Vert}[110]$.",0501046v1
2006-04-18,Spin precession in inversion-asymmetric two-dimensional systems,"We present a theoretical method to calculate the expectation value of spin in
an inversion-asymmetric two-dimensional (2D) system with respect to an
arbitrarily spin-polarized electron state, injected via an ideal point contact.
The 2D system is confined in a [001]-grown quantum well, where both the Rashba
and the Dresselhaus spin-orbit couplings are taken into account. The obtained
analytical results allow more concrete description of the spatial behaviors of
the spin precession caused by individually the Rashba and the Dresselhaus
terms. Applying the calculation on the Datta-Das spin-FET, whose original
design considers only the Rashba effect inside the channel, we investigate the
possible influence due to the Dresselhaus spin-orbit coupling. Concluded
solution is the choice of +-[1+-10], in particular [110], as the channel
direction.",0604406v1
2011-09-05,Nucleon resonances in the fourth resonance region,"Nucleon and $\Delta$ resonances in the fourth resonance region are studied in
a multichannel partial-wave analysis which includes nearly all available data
on pion- and photo-induced reactions off protons. In the high-mass range, above
1850\,MeV, several alternative solutions yield a good description of the data.
For these solutions, masses, widths, pole residues and photo-couplings are
given. In particular, we find evidence for nucleon resonances with
spin-parities $J^P=1/2^+...7/2^+$. For one set of solutions, there are four
resonances forming naturally a spin-quartet of resonances with orbital angular
momentum L=2 and spin S=3/2 coupling to $J=1/2,...,7/2$. Just below 1.9\,GeV we
find a spin doublet of resonances with $J^P=1/2^-$ and $3/2^-$. Since a spin
partner with $J^P=5/2^-$ is missing at this mass, the two resonances form a
spin doublet which must have a symmetric orbital-angular-momentum wave function
with L=1. For another set of solutions, the four positive-parity resonances are
accompanied by mass-degenerate negative-parity partners -- as suggested by the
conjecture of chiral symmetry restoration. The possibility of a $J^P=1/2^+,
3/2^+$ spin doublet at 1900\,MeV belonging to a 20-plet is discussed.",1109.0970v1
2013-06-02,Interband spin-orbit coupling between anti-parallel spin states in Pb quantum well states,"Using spin and angle-resolved photoemission spectroscopy we investigate a
momentum region in Pb quantum well states on Si(111) where hybridization
between Rashba-split bands alters the band structure significantly. Starting
from the Rashba regime where the dispersion of the quasi-free two-dimensional
electron gas is well described by two spin-polarized parabolas, we find a
breakdown of the Rashba behavior which manifests itself (i) in a spin splitting
that is no longer proportional to the in-plane momentum and (ii) in a reversal
of the sign of the momentum splitting. Our experimental findings are well
explained by including interband spin-orbit coupling that mixes Rashba-split
states with anti-parallel rather than parallel spins. Similar results for
Pb/Cu(111) reveal that the proposed hybridization scenario is independent on
the supporting substrate.",1306.0245v1
2013-11-19,Parity-Mixed Superconductivity in Locally Non-centrosymmetric System,"We study the parity-mixed superconductivity in locally non-centrosymmetric
systems. In multilayer systems an inhomogeneous Rashba spin-orbit coupling is
induced by the local violation of inversion symmetry. Our previous study
revealed that a pair-density wave (PDW) phase, with a sign-modulated order
parameter, is stabilized in the spin-singlet multilayer superconductors owing
to the spin-orbit coupling. In this letter, we show that the uniform
spin-triplet superconductivity emerges through parity mixing in the PDW phase,
taking into account a weak interaction in the spin-triplet channel, which was
neglected in our previous study. The spin-triplet superconducting phase is
nonunitary owing to field-induced parity mixing. The critical magnetic field is
markedly increased by the emergence of spin-triplet superconductivity. We
calculate the density of states and analyze the signature specific to this
phase.",1311.4660v1
2014-10-01,Near-Earth Asteroid Satellite Spins Under Spin-Orbit Coupling,"We develop a fourth-order numerical integrator to simulate the coupled spin
and orbital motions of two rigid bodies having arbitrary mass distributions
under the influence of their mutual gravitational potential. We simulate the
dynamics of components in well-characterized binary and triple near-Earth
asteroid systems and use surface of section plots to map the possible spin
configurations of the satellites. For asynchronous satellites, the analysis
reveals large regions of phase space where the spin state of the satellite is
chaotic. For synchronous satellites, we show that libration amplitudes can
reach detectable values even for moderately elongated shapes. The presence of
chaotic regions in the phase space has important consequences for the evolution
of binary asteroids. It may substantially increase spin synchronization
timescales, explain the observed fraction of asynchronous binaries, delay
BYORP-type evolution, and extend the lifetime of binaries. The variations in
spin rate due to large librations also affect the analysis and interpretation
of lightcurve and radar observations.",1410.0082v3
2016-06-03,Enhanced spin-orbit coupling in core/shell nanowires,"The spin-orbit coupling (SOC) in semiconductors is strongly influenced by
structural asymmetries, as prominently observed in bulk crystal structures that
lack inversion symmetry. Here, we study an additional effect on the SOC: the
asymmetry induced by the large interface area between a nanowire core and its
surrounding shell. Our experiments on purely wurtzite GaAs/AlGaAs core/shell
nanowires demonstrate optical spin injection into a single free-standing
nanowire and determine the effective electron g-factor of the hexagonal GaAs
wurtzite phase. The spin relaxation is highly anisotropic in time-resolved
micro-photoluminescence measurements on single nanowires, showing a significant
increase of spin relaxation in external magnetic fields. This behavior is
counterintuitive compared to bulk wurtzite crystals. We present a model for the
observed electron spin dynamics highlighting the dominant role of the
interface-induced SOC in these core/shell nanowires. This enhanced SOC may
represent an interesting tuning parameter for the implementation of
spin-orbitronic concepts in semiconductor-based structures.",1606.01135v1
2016-06-17,Designing exotic many-body states of atomic spin and motion in photonic crystals,"Cold atoms coupled to photonic crystals constitute an exciting platform for
exploring quantum many-body physics. Here we investigate the strong coupling
between atomic internal (""spin"") degrees of freedom and motion, which arises
from spin-dependent forces associated with the exchange of guided photons. We
show that this system can realize a remarkable and extreme limit of quantum
spin-orbital systems, where both the direct spin exchange between neighboring
sites and the kinetic energy of the orbital motion vanish. We find that this
previously unexplored system has a rich phase diagram of emergent orders,
including spatially dimerized spin-entangled pairs, a fluid of composite
particles comprised of joint spin-phonon excitations, phonon-induced N\'eel
ordering, and a fractional magnetization plateau associated with trimer
formation.",1606.05582v1
2008-07-10,Spin rotations induced by electron running on closed trajectories in gated semiconductor nanodevices,"A design for a quantum gate performing transformations of a single electron
spin is presented. The spin rotations are performed by the electron going
around the closed loops in a gated semiconductor device. We demonstrate the
operation of NOT, phase-flip and Hadamard quantum gates, i.e. the single-qubit
gates which are most commonly used in the algorithms. The proposed devices
employ the self-focusing effect for the electron wave packet interacting with
the electron gas on the electrodes and the Rashba spin-orbit coupling. Due to
the self-focusing effect the electron moves in a compact wave packet. The
spin-orbit coupling translates the spatial motion of the electron into the
rotations of the spin. The device does not require microwave radiation and
operates using low constant voltages. It is therefore suitable for selective
single-spin rotations in larger registers.",0807.1627v2
2012-05-29,"Sum rules, dipole oscillation and spin polarizability of a spin-orbit coupled quantum gas","Using a sum rule approach we investigate the dipole oscillation of a
spin-orbit coupled Bose-Einstein condensate confined in a harmonic trap. The
crucial role played by the spin polarizability of the gas is pointed out. We
show that the lowest dipole frequency exhibits a characteristic jump at the
transition between the stripe and spin-polarized phase. Near the second order
transition between the spin-polarized and the single minimum phase the lowest
frequency is vanishingly small for large condensates, reflecting the divergent
behavior of the spin polarizability. We compare our results with recent
experimental measurements as well as with the predictions of effective mass
approximation.",1205.6398v2
2017-05-25,Semiclassical Boltzmann theory of spin Hall effects in giant Rashba systems,"For the spin Hall effect arising from strong band-structure spin-orbit
coupling, a semiclassical Boltzmann theory reasonably addressing the intriguing
disorder effect called side-jump is still absent. In this paper we describe
such a theory of which the key ingredient is the spin-current-counterpart of
the semiclassical side-jump velocity (introduced in the context of the
anomalous Hall effect). Applying this theory to spin Hall effects in a
two-dimensional electron gas with giant Rashba spin-orbit coupling, we find
largely enhanced spin Hall angle in the presence of magnetic impurities when
only the lower Rashba band is partially occupied.",1705.09399v3
2021-07-14,Current Induced Hole Spin Polarization in Quantum Dot via Chiral Quasi Bound State,"We put forward a mechanism for current induced spin polarization for a hole
in a quantum dot side-coupled to a quantum wire, that is based on the
spin-orbit splitting of the valence band. We predict that in a stark contrast
with the traditional mechanisms based on the linear in momentum spin-orbit
coupling, an exponentially small bias applied to the quantum wire with heavy
holes is enough to create the 100% spin polarization of a localized light hole.
Microscopically, the effect is related with the formation of chiral quasi bound
states and the spin dependent tunneling of holes from the quantum wire to the
quantum dot. This novel current induced spin polarization mechanism is equally
relevant for the GaAs, Si and Ge based semiconductor nanostructures.",2107.06741v1
2022-01-25,Spin splitting in low-symmetry quantum wells beyond Rashba and Dresselhaus terms,"Spin-orbit interaction in semiconductor structures with broken space
inversion symmetry leads to spin splitting of electron and hole states even in
the absence of magnetic field. We discover that, beyond the Rashba and
Dresselhaus contributions, there is an additional type of the zero-field spin
splitting which is caused by the interplay of the cubic shape of crystal unit
cell and macroscopic structure asymmetry. In quantum wells grown along
low-symmetry crystallographic axes, this type of spin-orbit interaction couples
the out-of-plane component of carrier's spin with the in-plane momentum while
the coupling strength is controlled by structure inversion asymmetry. We carry
out numerical calculations and develop an analytical theory, which demonstrate
that this interaction can dominate $\boldsymbol{k}$-linear spin splitting of
heavy-hole subbands.",2201.10388v1
2023-09-02,Chirality-dependent persistent spin current in single circular helix molecules,"Since the chiral-induced spin selectivity (CISS) was first observed
experimentally, its microscopic mechanism has been continuously explored by the
scientific community. Among these investigations, the non-equilibrium effects
and the unknown origins of spin-orbit coupling (SOC) have been the central
issues discussed in recent years. Here, we have achieved a persistent spin
current in different circular single-helix molecule driven by a magnetic field,
which is inherently linked to the equilibrium state associated with chirality.
Due to its measurement method being different from the transport currents
observed in previous experiments, the origin of its spin-orbit coupling can be
explored by modifying the substrate with different light and heavy metal
elements. Our results demonstrate that a persistent spin current can be
observed regardless of whether the SOC originates from the chiral molecule or
the substrate. Furthermore, by tuning the direction of the magnetic field, we
can achieve a phase transition between trivial and non-trivial chiral
persistent spin currents. Our work provides a new perspective and platform for
exploring the nature of CISS and controlling the effects of CISS.",2309.00812v2
2022-09-06,Enhancement of spin-orbit torque efficiency by tailoring interfacial spin-orbit coupling in Pt-based magnetic multilayers,"We study inserting Co layer thickness-dependent spin transport and spin-orbit
torques (SOTs) in the Pt/Co/Py trilayers by spin-torque ferromagnetic
resonance. The interfacial perpendicular magnetic anisotropy energy density
($K_s = 2.7~erg/cm^2$), which is dominated by interfacial spin-orbit coupling
(ISOC) in the Pt/Co interface, total effective spin-mixing conductance
($G_{eff,tot} = 0.42 {\times} 10^{15}~{\Omega}^{-1} m^{-2}$) and two-magnon
scattering (${\beta}_{TMS} = 0.46~nm^2$) are first characterized, and the
damping-like torque (${\xi}_{DL}$ = 0.103) and field-like torque (${\xi}_{FL}$
= -0.017) efficiencies are also calculated quantitatively by varying the
thickness of the inserting Co layer. The significant enhancement of
${\xi}_{DL}$ and ${\xi}_{FL}$ in Pt/Co/Py than Pt/Py bilayer system originates
from the interfacial Rashba-Edelstein effect due to the strong ISOC between
Co-3d and Pt-5d orbitals at the Pt/Co interface. Additionally, we find a
considerable out-of-plane spin polarization SOT, which is ascribed to the spin
anomalous Hall effect and possible spin precession effect due to IPMA-induced
perpendicular magnetization at the Pt/Co interface. Our results demonstrate
that the ISOC of the Pt/Co interface plays a vital role in spin transport and
SOTs-generation. Our finds offer an alternative approach to improve the
conventional SOTs efficiencies and generate unconventional SOTs with
out-of-plane spin polarization to develop low power Pt-based spintronic via
tailoring the Pt/FM interface.",2209.02282v1
2013-05-24,Effective-one-body Hamiltonian with next-to-leading order spin-spin coupling for two nonprecessing black holes with aligned spins,"The canonical Arnowitt-Deser-Misner (ADM) Hamiltonian with next-to-leading
order spin-spin coupling [J. Steinhoff, S. Hergt, and G. Sch\""afer] is
converted into the EOB formalism of T. Damour, P. Jaranowski, and G. Sch\""afer
for the special case of spinning black hole binaries whose spins are aligned
with the angular momentum. In particular, we propose to include the new terms
by adding a dynamical term of next-to-leading order to the Kerr parameter
squared entering the effective metric. The modified EOB Hamiltonian
consistently reduces to the Kerr Hamiltonian as the mass ratio tends to zero;
moreover, it predicts the existence of an Innermost Stable Circular Orbit. We
also derive, for the general case of arbitrarily oriented spins but in the
vanishing mass-ratio limit, a coordinate transformation that maps the
next-to-leading order spin-spin contribution of the ADM Hamiltonian to the EOB
Hamiltonian.",1305.5674v3
2016-01-07,Majorana bound states in a disordered quantum dot chain,"We study Majorana bound states in a disordered chain of semiconductor quantum
dots proximity-coupled to an s-wave superconductor. By calculating its
topological quantum number, based on the scattering-matrix method and a
tight-binding model, we can identify the topological property of such an
inhomogeneous one-dimensional system. We study the robustness of Majorana bound
states against disorder in both the spin-independent terms (including the
chemical potential and the regular spin-conserving hopping) and the
spin-dependent term, i.e., the spin-flip hopping due to the Rashba spin-orbit
coupling. We find that the Majorana bound states are not completely immune to
the spin-independent disorder, especially when the latter is strong. Meanwhile,
the Majorana bound states are relatively robust against spin-dependent
disorder, as long as the spin-flip hopping is of uniform sign (i.e., the
varying spin-flip hopping term does not change its sign along the chain).
Nevertheless, when the disorder induces sign-flip in spin-flip hopping, the
topological-nontopological phase transition takes place in the
low-chemical-potential region.",1601.01402v2
2023-02-06,Inverse Ising effect and Ising magnetoresistance,"Ising (Zeeman-type) spin-orbit coupling (SOC) generated by in-plane inverse
asymmetry has attracted considerable attention, especially in Ising
superconductors and spin-valley coupling physics. However, many unconventional
observations and emerging physical phenomena remain to be elucidated. Here, we
theoretically study the spin texture of {\sigma}_z (spin angular momentum
projection along z) induced by Ising SOC in 1Td WTe2, and propose an
unconventional spin-to-charge conversion named inverse Ising effect, in which
the directions of the spin current, spin polarization and charge current are
not orthogonal. In particular, we predict the Ising magnetoresistance, whose
resistance depends on the out-of-plane magnetic momentum in WTe2/ferromagnetic
heterostructure. The Ising magnetoresistance is believed to be an interesting
counterpart to the well studied spin Hall magnetoresistance. Our predictions
provide promising way to spin-momentum locking and spin-charge conversion based
on emerging Ising SOC.",2302.02745v1
2023-11-02,Controllable single spin evolution at sub-harmonics of electric dipole spin resonance enhanced by four-level Landau-Zener-St{ü}ckelberg-Majorana interference,"Sub-harmonics of electric dipole spin resonance (EDSR) mediated by
Landau-Zener-St{\""u}ckelberg-Majorana (LZSM) tunneling transitions are studied
numerically and analytically in a Zeeman-split four level system with strong
spin-orbit coupling that can be realized, for example, in a GaAs-based double
quantum dot in a single-hole regime. The spin qubit is formed in one of the
dots and the second dot is used as an auxiliary element to enhance
functionality of the spin qubit. In particular, it is found that the spin
rotation rate can be essentially enhanced due to the tunnel coupling with the
auxiliary dot on both the main EDSR frequency and at its high sub-harmonics
allowing the coherent spin $\pi$-rotations on a 10-ns time scale. Spin
manipulation on high sub-harmonics is promising for new time-efficient schemes
of the spin control and readout in qubit devices operating at high magnetic
fields where the main harmonic is inaccessible due to hardware limitations.",2311.01607v1
2003-10-05,Dynamical Symmetry Enlargement Versus Spin-Charge Decoupling in the One-Dimensional SU(4) Hubbard Model,"We investigate dynamical symmetry enlargement in the half-filled SU(4)
Hubbard chain using non-perturbative renormalization group and Quantum Monte
Carlo techniques. A spectral gap is shown to open for arbitrary Coulombic
repulsion $U$. At weak coupling, $U \lesssim 3t$, a SO(8) symmetry between
charge and spin-orbital excitations is found to be dynamically enlarged at low
energy. At strong coupling, $U \gtrsim 6t$, the charge degrees of freedom
dynamically decouple and the resulting effective theory in the spin-orbital
sector is that of the SO(6) antiferromagnetic Heisenberg model. Both regimes
exhibit spin-Peierls order. However, although spin-orbital excitations are
$incoherent$ in the SO(6) regime they are $coherent$ in the SO(8) one. The
cross-over between these regimes is discussed.",0310090v1
2004-07-22,Strongly correlated crystal-field approach to Mott insulator LaCoO3,"Our success in description of recent electron-spin-resonance results on Mott
insulator LaCoO3, Phys. Rev. B 67 (2003) 172401, lies in taking into account
strong electron correlations among d electrons and the relativistic spin-orbit
coupling. In the developed by us Quantum Atomistic Solid State Theory (QUASST)
we assume that the atomic-like integrity of the 3d^6 system is preserved in the
Co^3+ ion in LaCoO3 and that intra-atomic correlations are much stronger than
crystal field interactions. We conclude that in LaCoO3 there is no intermediate
spin state as came out from band-structure calculations. The excited states
originate from the high-spin 5T2g term, being 12 meV above the ground 1A1
state. We are convinced that many-electron CEF approach with strong
correlations and the atomic-scale orbital magnetism is physically adequate
approach to 3d oxides.
  Keywords: Mott insulator, crystal field, spin-orbit coupling, LaCoO3",0407580v2
2006-08-31,Coulomb Drag and Spin Coulomb Drag in the presence of Spin-orbit Coupling,"Employing diagrammatic perturbation theory, we calculate the (charge) Coulomb
drag resistivity $\rho_D$ and spin Coulomb drag resistivity
$\rho_{\uparrow\downarrow}$ in the presence of Rashba spin-orbit coupling.
Analytical expressions for $\rho_D$ and $\rho_{\uparrow\downarrow}$ are
derived, and it is found that spin-orbit interaction produces a small
enhancement to $\rho_D$ and $\rho_{\uparrow\downarrow}$ in the ballistic regime
while $\rho_D$ is unchanged in the diffusive regime. This enhancement in the
ballistic regime is attributed to the enhancement of the nonlinear
susceptibility (i.e. current produced through the rectification of the thermal
electric potential fluctuations in the passive layer) while the lack of
enhancement in the diffusive regime is due to the suppression by disorder.",0608728v1
2006-11-03,Anisotropic spin relaxation in quantum dots,"We study theoretically phonon-assisted spin relaxation of an electron
confined in an elliptical quantum dot (QD) subjected to a tilted magnetic
field. In the presence of both Rashba and Dresselhaus spin-orbit terms, the
relaxation rate is anisotropic with respect to the in-plane field orientation.
This anisotropy originates from the interference, at nonzero tilt angle,
between the two spin-orbit terms. We show that, in a narrow range of magnetic
field orientations, the relaxation rate exhibits anomalous sensitivity to
variations of the QD parameters. In this range, the relative change in the
relaxation rate with in-plane field orientation is determined {\em solely} by
the spin-orbit coupling strengths and by the dot geometry. This allows
simultaneous determination of both Rashba and Dresselhaus coupling parameters
and the dot ellipticity from analysis of the angular dependence of the
relaxation rate.",0611065v2
2007-04-23,Spin dephasing due to a random Berry phase,"We investigate relaxation and dephasing of an electron spin confined in a
semiconductor quantum dot and subject to spin-orbit coupling. Even in vanishing
magnetic field, B = 0, slow noise coupling to the electron's orbital degree of
freedom leads to dephasing of the spin due to a random, in general non-Abelian
Berry phase acquired by the spin. For illustration we first present a simple
quasiclassical description, then consider a model with 2 orbital states only,
and finally present a perturbative quantum treatment appropriate for an
electron in a realistic (roughly parabolic, not too strongly confining) quantum
dot. We further compare the effect of different sources of noise. While at
large magnetic fields phonons dominate the relaxation processes, at low fields
electron-hole excitations and possibly 1/f noise may dominate.",0704.2974v1
2008-03-21,Intrinsic electric polarization in spin-orbit coupled semiconductor heterostructures,"We present Maxwell equations with source terms for the electromagnetic field
interacting with a moving electron in a spin-orbit coupled semiconductor
heterostructure. We start with the eight--band ${\bm k}{\bm p}$ model and
derive the electric and magnetic polarization vectors using the Gordon--like
decomposition method. Next, we present the ${\bm k}{\bm p}$ effective
Lagrangian for the nonparabolic conduction band electrons interacting with
electromagnetic field in semiconductor heterostructures with abrupt interfaces.
This Lagrangian gives rise to the Maxwell equations with source terms and
boundary conditions at heterointerfaces as well as equations for the electron
envelope wave function in the external electromagnetic field together with
appropriate boundary conditions. As an example, we consider spin--orbit effects
caused by the structure inversion asymmetry for the conduction electron states.
We compute the intrinsic contribution to the electric polarization of the
steady state electron gas in asymmetric quantum well in equilibrium and in the
spin Hall regime. We argue that this contribution, as well as the intrinsic
spin Hall current, are not cancelled by the elastic scattering processes.",0803.3193v1
2009-02-08,Magnetization in two-dimensional electron gas in a perpendicular magnetic field: the roles of edge states and spin-orbit coupling,"We study the de Haas--van Alphen (dHvA) oscillations in the magnetization of
a two-dimensional electron gas (2DEG) under the influence of the edge states
and/or the Rashba spin-orbit interaction (SOI). The boundaries of the systems
lift partially the degeneracies of Landau levels (LL's) and the resulting edge
states lead to the changes of both the center and the amplitude of the
sawtoothlike magnetization oscillation. The SOI mixes the spin-up and spin-down
states of neighboring LL's into two unequally spaced energy branches. The
inclusion of SOI changes the well-defined sawtooth pattern of the dHvA
oscillations in the magnetization. The weaker the magnetic field is, the larger
is the change of the dHvA oscillations due to the edge effect and/or the
spin-orbit coupling. Some theoretical results are compared with the
experimental data.",0902.1298v1
2010-09-28,Role of linear and cubic terms for the drift-induced Dresselhaus spin-orbit splitting in a two-dimensional electron gas,"The Dresselhaus spin-orbit interaction (SOI) of a series of two-dimensional
electron gases (2DEGs) hosted in GaAs/AlGaAs and InGaAs/GaAs (001) quantum
wells (QWs) is measured by monitoring the precession frequency of the spins as
a function of an in-plane electric field. The measured spin-orbit-induced
spin-splitting is linear in the drift velocity, even in the regime where the
cubic Dresselhaus SOI is important. We relate the measured splitting to the
Dresselhaus coupling parameter, the QW confinement, the Fermi wavenumber and to
strain effects. From this, the coupling parameter is determined quantitatively,
including its sign.",1009.5596v2
2013-12-27,Exact Nonadiabatic Holonomic Transformations of Spin-Orbit Qubits,"An exact analytical solution is derived for the wavefunction of an electron
in a one-dimensional moving quantum dot in a nanowire, in the presence of
time-dependent spin-orbit coupling. For cyclic evolutions we show that the spin
of the electron is rotated by an angle proportional to the area of a closed
loop in the parameter space of the time-dependent quantum dot position and the
amplitude of a fictitious classical oscillator driven by the time-dependent
spin-orbit coupling. By appropriate choice of parameters, we show that
arbitrary spin rotations may be performed on the Bloch sphere. Exact
expressions for dynamical and geometrical phases are also derived.",1312.7254v3
2014-01-05,Magnon-Mediated Dzyaloshinskii-Moriya Torque in Homogeneous Ferromagnets,"In thin magnetic layers with structural inversion asymmetry and spin-orbit
coupling, a Dzyaloshinskii-Moriya interaction arises at the interface. When a
spin wave current ${\bf j}_m$ flows in a system with a homogeneous
magnetization {\bf m}, this interaction produces an effective field-like torque
on the form ${\bf T}_{\rm FL}\propto{\bf m}\times({\bf z}\times{\bf j}_m)$ as
well as a damping-like torque, ${\bf T}_{\rm DL}\propto{\bf m}\times[({\bf
z}\times{\bf j}_m)\times{\bf m}]$ in the presence of spin-wave relaxation
(${\bf z}$ is normal to the interface). These torques mediated by the magnon
flow can reorient the time-averaged magnetization direction and display a
number of similarities with the torques arising from the electron flow in a
magnetic two dimensional electron gas with Rashba spin-orbit coupling. This
magnon-mediated spin-orbit torque can be efficient in the case of magnons
driven by a thermal gradient.",1401.0883v2
2015-05-15,Rashba Spin-Orbit Coupling Enhanced Carrier Lifetime in Organometal Halide Perovskites,"Organometal halide perovskites are promising solar-cell materials for
next-generation photovoltaic applications. The long carrier lifetime and
diffusion length of these materials make them very attractive for use in light
absorbers and carrier transporters. While these aspects of organometal halide
perovskites have attracted the most attention, the consequences of the Rashba
effect, driven by strong spin-orbit coupling, on the photovoltaic properties of
these materials are largely unexplored. In this work, taking the electronic
structure of methylammonium lead iodide as an example, we propose an intrinsic
mechanism for enhanced carrier lifetime in 3D Rashba materials. Based on
first-principles calculations and a Rashba spin-orbit model, we demonstrate
that the recombination rate is reduced due to the spin-forbidden transition.
These results are important for understanding the fundamental physics of
organometal halide perovskites and for optimizing and designing the materials
with better performance. The proposed mechanism including spin degrees of
freedom offers a new paradigm of using 3D Rashba materials for photovoltaic
applications.",1505.04212v1
2015-12-02,Enhanced spin-orbit coupling in dilute fluorinated graphene,"The preservation and manipulation of a spin state mainly depends on the
strength of the spin-orbit interaction. For pristine graphene, the intrinsic
spin-orbit coupling (SOC) is only in the order of few ueV, which makes it
almost impossible to be used as an active element in future electric field
controlled spintronics devices. This stimulates the development of a systematic
method for extrinsically enhancing the SOC of graphene. In this letter, we
study the strength of SOC in weakly fluorinated graphene devices. We observe
high non-local signals even without applying any external magnetic field. The
magnitude of the signal increases with increasing fluorine adatom coverage.
From the length dependence of the non-local transport measurements, we obtain
SOC values of ~ 5.1 meV and ~ 9.1 meV for the devices with ~ 0.005% and ~ 0.06%
fluorination, respectively. Such a large enhancement, together with the high
charge mobility of fluorinated samples (u~4300 cm2/Vs - 2700 cm2/Vs), enables
the detection of the spin Hall effect even at room temperature.",1512.00642v1
2018-10-24,A systematic study of the local minima in L(S)DA+U,"We have performed a systematic study of the emergence of meta-stable states
in density functional theory plus Hubbard U (DFT+U ) simulations of NiO, CoO,
FeO. Particular attention is given to the spin-polarization of the
exchange-correlation functional and the double counting term, and the role of
the spin-orbit coupling. The method of occupation matrix control is extended to
use constrained random density matrices to map out the local minima in the
total energy landscape. The extended scheme, random density matrix control, is
successfully benchmarked against UO2, one of the most investigated systems in
the field. When applied to the transition metal oxides it yields several meta-
stable states which are well-characterized by their local spin and orbital
moments. We find that the addition of spin-orbit coupling helps the simulations
to converge to the global high-spin energy minimum. The random density matrix
control scheme combined with LDA+U yields accurate magnetic moments for all the
studied AFM transition metal oxides.",1810.10393v1
2019-10-02,Valley- and spin-dependent quantum Hall states in bilayer silicene,"The Hall conductivity $\sigma_{xy}$ of many condensed matter systems presents
a step structure when a uniform perpendicular magnetic field is applied. We
report the quantum Hall effect in buckled AB-bottom-top bilayer silicene and
its robust dependence on the electronic valley and spin-orbit coupling. With
the unique multi-valley electronic structure and the lack of spin degeneracy,
the quantization of the Hall conductivity in this system is unlike the
conventional sequence as reported for graphene. Furthermore, the conductivity
plateaux take different step values for conduction ($2e^2/h$) and valence
($6e^2/h$) bands since their originating valleys present inequivalent
degeneracy. We also report the emergence of fractions under significant effect
of a uniform external electric field on the quantum Hall step structure by the
separation of orbital distributions and the mixing of Landau levels from
distinct valleys. The valley- and spin-dependent quantum Hall conductivity
arises from the interplay of lattice geometry, atomic interaction, spin-orbit
coupling, and external magnetic and electric fields.",1910.00786v1
2019-10-24,Microscopic model for the hidden Rashba effect in YBa$_2$Cu$_3$O$_{6+x}$,"Each unit cell in YBa$_2$Cu$_3$O$_{6+x}$ contains a pair of two-dimensional
CuO$_2$ layers. While the crystal structure is globally inversion symmetric,
the individual layers are not. This leads, necessarily, to a nonvanishing
Rashba spin-orbit coupling (SOC) in the CuO$_2$ layers, with opposite signs of
the coupling constant in each layer. These so-called Rashba bilayers generate
hidden spin textures, with a vansishing net spin at each $k$-point in the
Brillouin zone, but nonvanishing spin textures in each layer separately. Here,
we trace the microscopic origin of the Rashba splitting through the orbital
structure of the CuO$_2$ conduction bands, obtain a generic three-orbital model
Hamiltonian, and show that the magnitude of the spin-splitting predicted by
density functional theory is $\sim 10$~meV.",1910.11444v1
2020-01-02,Origin of Strong Two-Magnon Scattering in Heavy Metal/Ferromagnet/Oxide Heterostructures,"We experimentally investigate the origin of the two-magnon scattering (TMS)
in heavy-metal (HM)/ferromagnet (FM)/oxide heterostructures (FM = Co, Ni81Fe19,
or Fe60Co20B20) by varying the materials located above and below the FM layers.
We show that strong TMS in HM/FM/oxide systems arises primarily at the HM/FM
interface and increases with the strength of interfacial spin-orbit coupling
and magnetic roughness at this interface. TMS at the FM/oxide interface is
relatively weak, even in systems where spin-orbit coupling at this interface
generates strong interfacial magnetic anisotropy. We also suggest that the
spin-current-induced excitation of non-uniform short-wavelength magnon at the
HM/FM interface may function as a mechanism of spin memory loss for the
spin-orbit torque exerted on the uniform mode.",2001.00300v1
2019-01-30,Van Hove scenario of anisotropic transport in a two-dimensional spin-orbit coupled electron gas in an in-plane magnetic field,"We study electronic transport in two-dimensional spin-orbit coupled electron
gas subjected to an in-plane magnetic field. The interplay of the spin-orbit
interaction and the magnetic field leads to the Van Hove singularity of the
density of states and strong anisotropy of Fermi contours. We develop a method
that allows one to exactly calculate the nonequilibrium distribution function
for these conditions within the framework of the semiclassical Boltzmann
equation without using the scattering time approximation. The method is applied
to calculate the conductivity tensor and the tensor of spin polarization
induced by the electric field (Aronov-Lyanda-Geller-Edelstein effect). It is
found that both the conductivity and the spin polarization have a sharp
singularity as functions of the Fermi level or magnetic field, which occurs
when the Fermi level passes through the Van Hove singularity. In addition, the
transport anisotropy dramatically changes near the singularity.",1901.10823v1
2020-06-07,Sublattice symmetry breaking and ultra low energy excitations in Graphene-on-hBN Heterostructures,"The low-lying states of graphene contain exciting topological properties that
depend on the interplay of different symmetry breaking terms. The corresponding
energy gaps remained unexplored until recently, owing to the low energy scale
of the terms involved (few tens of ueV). These low energy terms include
sublattice splitting, the Rashba and the intrinsic spin-orbit coupling, whose
balance determines the topological properties. In this work, we unravel the
contributions arising from the sublattice and the intrinsic spin orbit
splitting in graphene on hexagonal boron-nitride. Employing
resistively-detected electron spin resonance, we measure a sublattice splitting
of the order of 20E-6 eV, and confirm an intrinsic spin orbit coupling of
approximately 45E-6 eV. The dominance of the latter suggests a topologically
non-trivial state, involving fascinating properties. Electron spin resonance is
a promising route towards unveiling the intriguing band structure at low energy
scales.",2006.04190v1
2021-10-26,Ultra-Strong Spin-Orbit Coupling and Topological Moiré Engineering in Twisted ZrS2 Bilayers,"We predict that twisted bilayers of 1T-ZrS$_2$ realize a novel and tunable
platform to engineer two-dimensional topological quantum phases dominated by
strong spin-orbit interactions. At small twist angles, ZrS$_2$ heterostructures
give rise to an emergent and twist-controlled moir\'e Kagom\'e lattice,
combining geometric frustration and strong spin-orbit coupling to give rise to
a moir\'e quantum spin Hall insulator with highly controllable and
nearly-dispersionless bands. We devise a generic pseudo-spin theory for
group-IV transition metal dichalcogenides that relies on the two-component
character of the valence band maximum of the 1T structure at $\Gamma$, and
study the emergence of a robust quantum anomalous Hall phase as well as
possible fractional Chern insulating states from strong Coulomb repulsion at
fractional fillings of the topological moir\'e Kagom\'e bands. Our results
establish group-IV transition metal dichalcogenide bilayers as a novel moir\'e
platform to realize strongly-correlated topological phases in a twist-tunable
setting.",2110.13370v1
2022-10-24,Effects of spin-orbit coupling and in-plane Zeeman fields on the critical current in two-dimensional hole gas SNS junctions,"Superconductor--semiconductor hybrid devices are currently attracting much
attention, fueled by the fact that strong spin--orbit interaction in
combination with induced superconductivity can lead to exotic physics with
potential applications in fault-tolerant quantum computation. The detailed
nature of the spin dynamics in such systems is, however, often strongly
dependent on device details and hard to access in experiment. In this paper we
theoretically investigate a superconductor--normal--superconductor junction
based on a two-dimensional hole gas with additional Rashba spin
orbit--coupling, and we focus on the dependence of the critical current on the
direction and magnitude of an applied in-plane magnetic field. We present a
simple model, which allows us to systematically investigate different parameter
regimes and obtain both numerical results and analytical expressions for all
limiting cases. Our results could serve as a tool for extracting more
information about the detailed spin physics in a two-dimensional hole gas based
on a measured pattern of critical currents.",2210.13266v2
2001-05-09,Phase Diagram of the Spin-Orbital model on the Square Lattice,"We study the phase diagram of the spin-orbital model in both the weak and
strong limits of the quartic spin-orbital exchange interaction. This allows us
to study quantum phase transitions in the model and to approach from both sides
the most interesting intermediate-coupling regime and in particular the
SU(4)-symmetric point of the Hamiltonian. It was suggested earlier by Li et al
[Phys.Rev.Lett. vol. 81, 3527 (1999)] that at this point the ground state of
the system is a plaquette spin-orbital liquid. We argue that the state is more
complex. There is plaquette order, but it is anisotropic: bonds in one
direction are stronger than those in the perpendicular direction. This order is
somewhat similar to that found recently in the frustrated J_1-J_2 Heisenberg
spin model.",0105178v1
2001-07-25,Ruling Out Chaos in Compact Binary Systems,"We investigate the orbits of compact binary systems during the final inspiral
period before coalescence by integrating numerically the second-order
post-Newtonian equations of motion. We include spin-orbit and spin-spin
coupling terms, which, according to a recent study by Levin [J. Levin, Phys.
Rev. Lett. 84, 3515 (2000)], may cause the orbits to become chaotic. To examine
this claim, we study the divergence of initially nearby phase-space
trajectories and attempt to measure the Lyapunov exponent gamma. Even for
systems with maximally spinning objects and large spin-orbit misalignment
angles, we find no chaotic behavior. For all the systems we consider, we can
place a strict lower limit on the divergence time t_L=1/gamma that is many
times greater than the typical inspiral time, suggesting that chaos should not
adversely affect the detection of inspiral events by upcoming
gravitational-wave detectors.",0107082v1
2009-05-28,Large-J approach to strongly coupled spin-orbital systems,"We present a novel approach to study the ground state and elementary
excitations in compounds where spins and orbitals are entangled by on-site
relativistic spin-orbit interaction. The appropriate degrees of freedom are
localized states with an effective angular momentum J. We generalize J to
arbitrary large values while maintaining the delicate spin-orbital
entanglement. After projecting the inter-site exchange interaction to the
manifold of effective spins, a systematic 1/J expansion of the effective
Hamiltonian is realized using the Holstein-Primakoff transformation.
Applications to representative compounds Sr2IrO4 and particularly vanadium
spinels AV2O4 are discussed.",0905.4728v3
2016-05-04,Giant spin-orbit splitting in inverted InAs/GaSb double quantum wells,"Transport measurements in inverted InAs/GaSb quantum wells reveal a giant
spin-orbit splitting of the energy bands close to the hybridization gap. The
splitting results from the interplay of electron-hole mixing and spin-orbit
coupling, and can exceed the hybridization gap. We experimentally investigate
the band splitting as a function of top gate voltage for both electron-like and
hole-like states. Unlike conventional, noninverted two-dimensional electron
gases, the Fermi energy in InAs/GaSb can cross a single spin-resolved band,
resulting in full spin-orbit polarization. In the fully polarized regime we
observe exotic transport phenomena such as quantum Hall plateaus evolving in
$e^2/h$ steps and a non-trivial Berry phase.",1605.01241v2
2019-07-01,Spin Diffusion Equations for Magnetized or Orbital Polarized Systems,"Charge and spin transport in spintronics devices can be described by a spin
diffusion equation suitable for modelling scales much larger than the
scattering and atomic scales. This work concerns the coarse graining procedure
used to compute the coefficients of the diffusion equation, which are sensitive
the details of individual atoms and impurities. We show with two simple
examples that in spintronics devices which have both a spin-orbit interaction
and magnetization, standard coarse graining can easily obtain diffusion
equations which fail to conserve electronic charge. The same failure can occur
in systems with both a spin-orbit interaction and orbital polarization. We show
that linear response theory, coupled with the self-consistent Born
approximation and ladder diagrams, offers an improved way of calculating
diffusion equations. We show that the resulting equations satisfy a
Ward-Takahashi identity that guarantees charge conservation.",1907.00948v1
2019-11-08,Giant anisotropy of Gilbert damping in a Rashba honeycomb antiferromagnet,"Giant Gilbert damping anisotropy is identified as a signature of strong
Rashba spin-orbit coupling in a two-dimensional antiferromagnet on a honeycomb
lattice. The phenomenon originates in spin-orbit induced splitting of
conduction electron subbands that strongly suppresses certain spin-flip
processes. As a result, the spin-orbit interaction is shown to support an
undamped non-equilibrium dynamical mode that corresponds to an ultrafast
in-plane N\'eel vector precession and a constant perpendicular-to-the-plane
magnetization. The phenomenon is illustrated on the basis of a two dimensional
$s$-$d$ like model. Spin-orbit torques and conductivity are also computed
microscopically for this model. Unlike Gilbert damping these quantities are
shown to reveal only a weak anisotropy that is limited to the semiconductor
regime corresponding to the Fermi energy staying in a close vicinity of
antiferromagnetic gap.",1911.03408v1
2020-06-16,Spin texture driven spintronic enhancement at the LaAlO$_3$/SrTiO$_3$ interface,"Recent experiments have shown that transition metal oxide heterostructures
such as SrTiO$_3$-based interfaces, exhibit large, gate tunable, spintronic
responses. Our theoretical study showcases key factors controlling the
magnitude of the conversion, measured by the inverse Edelstein and Spin Hall
effects, and their evolution with respect to an electrostatic doping. The
origin of the response can be linked to spin-orbital textures. These stem from
the broken inversion symmetry at the interface which produces an unusual form
of the interfacial spin-orbit coupling, provided a bulk atomic spin-orbit
contribution is present. The amplitudes and variations of these observables are
direct consequences of the multi-orbital subband structure of these materials,
featuring avoided and topological crossings. Interband contributions to the
coefficients lead to enhanced responses and non-monotonic evolution with
doping. We highlight these effects using analytical approaches and low energy
modeling.",2006.09037v1
2021-04-23,"Radiation-reaction force and multipolar waveforms for eccentric, spin-aligned binaries in the effective-one-body formalism","While most binary inspirals are expected to have circularized before they
enter the LIGO/Virgo frequency band, a small fraction of those binaries could
have non-negligible orbital eccentricity depending on their formation channel.
Hence, it is important to accurately model eccentricity effects in waveform
models used to detect those binaries, infer their properties, and shed light on
their astrophysical environment. We develop a multipolar effective-one-body
(EOB) eccentric waveform model for compact binaries whose components have spins
aligned or anti-aligned with the orbital angular momentum. The waveform model
contains eccentricity effects in the radiation-reaction force and gravitational
modes through second post-Newtonian (PN) order, including tail effects, and
spin-orbit and spin-spin couplings. We recast the PN-expanded, eccentric
radiation-reaction force and modes in factorized form so that the newly derived
terms can be directly included in the state-of-the-art, quasi-circular--orbit
EOB model currently used in LIGO/Virgo analyses (i.e., the SEOBNRv4HM model).",2104.11705v2
2021-12-28,Spin-orbit coupling for close-in planets,"We study the spin evolution of close-in planets in multi-body systems and
present a very general formulation of the spin-orbit problem. This includes a
simple way to probe the spin dynamics from the orbital perturbations, a new
method for computing forced librations and tidal deformation, and general
expressions for the tidal torque and capture probabilities in resonance. We
show that planet-planet perturbations can drive the spin of Earth-size planets
into asynchronous or chaotic states, even for nearly circular orbits. We apply
our results to Mercury and to the KOI-1599 system of two super-Earths in a 3/2
mean motion resonance.",2112.14335v1
2023-03-01,Rashba spin-orbit coupling in infinite-layer nickelate films on SrTiO3(001) and KTaO3(001),"The impact of spin-orbit interactions in NdNiO2/SrTiO3(001) and
NdNiO2/KTaO3(001) is explored by performing density functional theory
simulations including a Coulomb repulsion term. Polarity mismatch drives the
emergence of an interfacial two-dimensional electron gas in NdNiO2/KTaO3(001)
involving the occupation of Ta $5d$ conduction-band states, which is twice as
pronounced as in NdNiO2/SrTiO3(001). We identify a significant anisotropic
$k^3$ Rashba spin splitting of the respective $d_{xy}$ states in both systems
that results from the broken inversion symmetry at the nickelate-substrate
interface and exceeds the width of the superconducting gap. In
NdNiO2/KTaO3(001), the splitting reaches 210 meV, which is comparable to
Bi(111) surface states. At the surface, the Ni $3d_{x^2-y^2}$-derived states
exhibit a linear Rashba effect with $\alpha_\text{R} \sim$ 125 meV \r{A},
exemplifying its orbital selectivity. The corresponding Fermi sheets present a
reconstructed circular shape due to the electrostatic doping, but undergo a
Lifshitz transition towards a cuprate-like topology deeper in the film that
coincides with a realignment of their spin texture. These results promote
surface and interface polarity as interesting design parameters to control
spin-orbit physics in infinite-layer nickelate heterostructures.",2303.00717v1
2023-12-08,Beyond spin models in orbitally-degenerate open-shell nanographenes,"The study of open-shell nanographenes has relied on a paradigm where spins
are the only low-energy degrees of freedom. Here we show that some
nanographenes can host low-energy excitations that include strongly coupled
spin and orbital degrees of freedom. The key ingredient is the existence of
orbital degeneracy, as a consequence of leaving the benzenoid/half-filling
scenario. We analyze the case of nitrogen-doped triangulenes, using both
density-functional theory and Hubbard model multiconfigurational and
random-phase approximation calculations. We find a rich interplay between
orbital and spin degrees of freedom that confirms the need to go beyond the
spin-only paradigm, opening a new venue in this field of research.",2312.04938v1
2006-06-16,Orbitally driven spin-singlet dimerization in $S$=1 La$_{4}$Ru$_{2}$O$_{10}$,"Using x-ray absorption spectroscopy at the Ru-$L_{2,3}$ edge we reveal that
the Ru$^{4+}$ ions remain in the $S$=1 spin state across the rare 4d-orbital
ordering transition and spin-gap formation. We find using local spin density
approximation + Hubbard U (LSDA+U) band structure calculations that the crystal
fields in the low temperature phase are not strong enough to stabilize the
$S$=0 state. Instead, we identify a distinct orbital ordering with a
significant anisotropy of the antiferromagnetic exchange couplings. We conclude
that La$_{4}$Ru$_{2}$O$_{10}$ appears to be a novel material in which the
orbital physics drives the formation of spin-singlet dimers in a quasi
2-dimensional $S$=1 system.",0606445v2
2018-04-02,Importance of orbital fluctuations for the magnetic dynamics in heavy-fermion compound SmB$_6$,"The emergent dynamical processes associated with magnetic excitations in
heavy-fermion SmB$_6$ are investigated. By imposing multiorbital interactions
on a first-principles model, we find the interplay between spin and orbital
fluctuations in the $f$ manifold is highly sensitive to local correlations. The
magnetic phase diagram constructed at zero temperature reveals quantum critical
features with the existence of several competing phases. Within the random
phase approximation, we perform a comprehensive study of the spin-spin
correlation function, and our results agree with neutron scattering
experiments. Spectral weight analysis shows the low energy spin excitations are
selectively accompanied by orbital fluctuations, indicating a non-trivial
entanglement between the spin and orbital degree of freedom driven by
relativistic couplings.",1804.00674v2
2016-05-31,Spin-Orbit Torques in ferrimagnetic GdFeCo Alloys,"The spin-orbit torque switching of ferrimagnetic
Gd$_x$(Fe$_{90}$Co$_{10}$)$_{100-x}$ films was studied for both transition
metal (TM)-rich and rare earth (RE)-rich configurations. The spin-orbit torque
driven magnetization switching follows the same handedness in TM-rich and
RE-rich samples with respect to the total magnetization, but the handedness of
the switching is reversed with respect to the TM magnetization. This indicates
that the sign of the spin-orbit-torque-driven magnetic switching follows the
total magnetization, although transport based techniques such as anomalous Hall
effect are only sensitive to the transition metal magnetization. These results
provide important insight into the physics of spin angular momentum transfer in
materials with antiferromagnetically coupled sublattices.",1605.09498v1
2022-04-27,Quantifying and reducing spin contamination in algebraic diagrammatic construction theory of charged excitations,"Algebraic diagrammatic construction (ADC) theory is a computationally
efficient and accurate approach for simulating electronic excitations in
chemical systems. However, for the simulations of excited states in molecules
with unpaired electrons the performance of ADC methods can be affected by the
spin contamination in unrestricted Hartree-Fock (UHF) reference wavefunctions.
In this work, we benchmark the accuracy of ADC methods for electron attachment
and ionization of open-shell molecules with the UHF reference orbitals
(EA/IP-ADC/UHF) and develop an approach to quantify the spin contamination in
the charged excited states. Following this assessment, we demonstrate that the
spin contamination can be reduced by combining EA/IP-ADC with the reference
orbitals from restricted open-shell Hartree-Fock (ROHF) or orbital-optimized
M{\o}ller-Plesset perturbation (OMP) theories. Our numerical results
demonstrate that for open-shell systems with strong spin contamination in the
UHF reference the third-order EA/IP-ADC methods with the ROHF or OMP reference
orbitals are similar in accuracy to equation-of-motion coupled cluster theory
with single and double excitations.",2204.13164v2
2013-10-18,Weyl spin-orbit-coupling-induced interactions in uniform and trapped atomic quantum fluids,"We establish through analytical and numerical studies of thermodynamic
quantities for noninteracting atomic gases that the isotropic three-dimensional
spin-orbit coupling, the Weyl coupling, induces interaction which counters
""effective"" attraction (repulsion) of the exchange symmetry present in
zero-coupling Bose (Fermi) gas. The exact analytical expressions for the grand
potential and hence for several thermodynamic quantities have been obtained for
this purpose in both uniform and trapped cases. It is enunciated that many
interesting features of spin-orbit coupled systems revealed theoretically can
be understood in terms of coupling-induced modifications in statistical
interparticle potential. The temperature-dependence of the chemical potential,
specific heat and isothermal compressibility for a uniform Bose gas is found to
have signature of the incipient Bose-Einstein condensation in very weak
coupling regime although the system does not really go in the Bose-condensed
phase. The transition temperature in harmonically trapped case decreases with
increase of coupling strength consistent with the weakening of the statistical
attractive interaction. Anomalous behavior of some thermodynamic quantities,
partly akin to that in dimensions less than two, appears for uniform fermions
as soon as the Fermi level goes down the Dirac point on increasing the coupling
strength. It is suggested that the fluctuation-dissipation theorem can be
utilized to verify anomalous behaviors from studies of long-wavelength
fluctuations in bunching and antibunching effects.",1310.5180v1
2016-11-17,"Hund interaction, spin-orbit coupling and the mechanism of superconductivity in strongly hole-doped iron pnictides","We present a novel mechanism of s-wave pairing in Fe-based superconductors.
The mechanism involves holes near dxz/dyz pockets only and is applicable
primarily to strongly hole doped materials. We argue that as long as the
renormalized Hund's coupling J exceeds the renormalized inter-orbital Hubbard
repulsion U', any finite spin-orbit coupling gives rise to s-wave
superconductivity. This holds even at weak coupling and regardless of the
strength of the intra-orbital Hubbard repulsion U. The transition temperature
grows as the hole density decreases. The pairing gaps are four-fold symmetric,
but anisotropic, with the possibility of eight accidental nodes along the
larger pocket. The resulting state is consistent with the experiments on
KFe2As2.",1611.05802v1
2014-04-08,Odd-parity triplet superconductivity in multi-orbital materials with strong spin-orbit coupling: applications to doped Sr2IrO4,"We explore possible superconducting states in $t_{2g}$ multi-orbital
correlated electron systems with strong spin-orbit coupling (SOC). In order to
study such systems in a controlled manner, we employ large-scale dynamical
mean-field theory (DMFT) simulations with the hybridization expansion
continuous-time Quantum Monte Carlo (CTQMC) impurity solver. To determine the
pairing symmetry, we go beyond the local DMFT formalism using parquet equations
to introduce the momentum dependence in the two-particle vertex and correlation
functions. In the strong SOC limit, a singlet, $d$-wave pairing state in the
electron-doped side of the phase diagram is observed at weak Hund's coupling,
which is triggered by antiferromagnetic fluctuations. When the Hund's coupling
is comparable to SOC, a two-fold degenerate, triplet $p$-wave pairing state
with relatively high $T_c$ emerges in the hole-doped side of the phase diagram,
which is associated with enhanced charge fluctuations. Experimental
implications to doped Sr$_{2}$IrO$_{4}$ are discussed.",1404.2290v2
2013-09-03,Spin relaxation in ultracold spin-orbit coupled $^{40}$K gas,"We report the anomalous Dyakonov-Perel' spin relaxation in ultracold
spin-orbit coupled $^{40}$K gas when the coupling between $|9/2,9/2\ >$ and
$|9/2,7/2\ >$ states (atcing as the effective Zeeman magnetic field) is much
stronger than the spin-orbit coupled field. Both the transverse and
longitudinal spin relaxations are investigated with small and large spin
polarizations. It is found that with small spin polarization, the transverse
(longitudinal) spin relaxation is divided into four (two) regimes: the normal
weak scattering regime, the anomalous Dyakonov-Perel'-like regime, the
anomalous Elliott-Yafet-like regime and the normal strong scattering regime
(the anomalous Elliott-Yafet-like regime and the normal strong scattering
regime), with only the normal weak scattering regime being in the weak
scattering limit. This is very different from the conventional situation under
the weak magnetic field, which is divided into the weak and strong scattering
regimes according to the weak/strong scattering limit. With large spin
polarization, we find that the Hartree-Fock self-energy, which acts as an
effective magnetic field, can markedly suppress the transverse spin relaxation
in both weak and strong scattering limits. Moreover, by noting that as both the
momentum relaxation time and the Hartree-Fock effective magnetic field vary
with the scattering length in cold atoms, the anomalous Dyakonov-Perel'-like
regime is suppressed and the transverse spin relaxation is hence divided into
three regimes in the scattering length dependence: the normal weak scattering
regime, the anomalous Elliott-Yafet-like regime and the strong scattering
regime. On the other hand, the longitudinal spin relaxation is again divided
into the anomalous EY-like and normal strong scattering regimes. ...",1309.0727v3
2010-04-26,Orbital Order and Spontaneous Orthorhombicity in Iron Pnictides,"A growing list of experiments show orthorhombic electronic anisotropy in the
iron pnictides, in some cases at temperatures well above the spin density wave
transition. These experiments include neutron scattering, resistivity and
magnetoresistance measurements, and a variety of spectroscopies. We explore the
idea that these anisotropies stem from a common underlying cause: orbital order
manifest in an unequal occupation of $d_{xz}$ and $d_{yz}$ orbitals, arising
from the coupled spin-orbital degrees of freedom. We emphasize the distinction
between the total orbital occupation (the integrated density of states), where
the order parameter may be small, and the orbital polarization near the Fermi
level which can be more pronounced. We also discuss light-polarization studies
of angle-resolved photoemission, and demonstrate how x-ray absorption linear
dichroism may be used as a method to detect an orbital order parameter.",1004.4611v2
2018-05-07,Anatomy of interfacial spin-orbit coupling in Co/Pd multilayers using X-ray magnetic circular dichroism and first-principles calculations,"Element-specific orbital magnetic moments and their anisotropies in
perpendicularly magnetised Co/Pd multilayers are investigated using Co L-edge
and Pd M-edge angle-dependent x-ray magnetic circular dichroism. We show that
the orbital magnetic moments in Co are anisotropic, whereas those in Pd are
isotropic. The first-principles density-functional-theory calculations also
suggest that the Co/Pd interfacial orbital magnetic moments in Co are
anisotropic and contribute to the perpendicular magnetic anisotropy (PMA), and
that the isotropic ones in Pd manipulates the Co orbitals at the interface
through proximity effects. Orbital-resolved anatomy of Co/Pd interfaces reveals
that the orbital moment anisotropy in Co and spin-flipped transition related to
the magnetic dipoles in Pd are essential for the appearance of PMA.",1805.02416v1
2019-07-09,Orbital pseudospin-momentum locking in two-dimensional chiral borophene,"Recently, orbital-textures have been found in Rashba and topological
insulator (TI) surface states as a result of the spin-orbit coupling (SOC).
Here, we predict a $p_x/p_y$ orbital texture, in linear dispersive Dirac bands,
arising at the K/K' points of $\chi$-$h_0$ borophene chiral monolayer.
Combining first-principles calculations with effective hamiltonians, we show
that the orbital pseudospin has its direction locked with the momentum in a
similar way as TIs' spin-textures. Additionally, considering a layer pseudospin
degree of freedom, this lattice allows stackings of layers with equivalent or
opposite chiralities. In turn, we show a control of the orbital textures and
layer localization through the designed stacking and external electric field.
For instance, for the opposite chirality stacking, the electric field allows
for an on/off switch of the orbital-textured Dirac cone.",1907.04351v2
2019-12-17,Tuning Crystal Field Potential by Orbital Dilution in $d^4$ Oxides,"We investigate the interplay between Coulomb driven orbital order and
octahedral distortions in strongly correlated Mott insulators due to orbital
dilution, i.e., doping by metal ions without an orbital degree of freedom. In
particular, we focus on layered transition metal oxides and study the effective
spin-orbital exchange due to $d^3$ substitution at $d^4$ sites. The structure
of the $d^3-d^4$ spin-orbital coupling between the impurity and the host in the
presence of octahedral rotations favors a distinct type of orbital polarization
pointing towards the impurity and outside the impurity--host plane. This yields
an effective lattice potential that generally competes with that associated
with flat octahedra and, in turn, can drive an inversion of the crystal field
interaction.",1912.07975v1
2014-02-17,Persistent charge and spin currents in the long wavelength regime for graphene rings,"We address the problem of persistent charge and spin currents on a Corbino
disk built from a graphene sheet. We consistently derive the Hamiltonian
including kinetic, intrinsic (ISO) and Rashba spin-orbit interactions in
cylindrical coordinates. The Hamiltonian is carefully considered to reflect
hermiticity and covariance. We compute the energy spectrum and the
corresponding eigenfunctions separately for the intrinsic and Rashba spin-orbit
interactions. In order to determine the charge persistent currents we use the
spectrum equilibrium linear response definition. We also determine the spin and
pseudo spin polarizations associated with such equilibrium currents. For the
intrinsic case one can also compute the correct currents by applying the bare
velocity operator to the ISO wavefunctions or alternatively the ISO group
velocity operator to the free wavefunctions. Charge currents for both SO
couplings are maximal in the vicinity of half integer flux quanta. Such maximal
currents are protected from thermal effects because contributing levels plunge
($\sim$1K) into the Fermi sea at half integer flux values. Such a mechanism,
makes them observable at readily accessible temperatures. Spin currents only
arise for the Rashba coupling, due to the spin symmetry of the ISO spectrum.
For the Rashba coupling, spin currents are cancelled at half integer fluxes but
they remain finite in the vicinity, and the same scenario above protects spin
currents.",1402.4103v1
2023-07-28,Spin Hall conductivity in the Kane-Mele-Hubbard model at finite temperature,"The Kane-Mele model is known to show a quantized spin Hall conductivity at
zero temperature. Including Hubbard interactions at each site leads to a
quantum phase transition to an XY antiferromagnet at sufficiently high
interaction strength. Here, we use the two-particle self-consistent approach
(TPSC), which we extend to include spin-orbit coupling, to investigate the
Kane-Mele-Hubbard model at finite temperature and half-filling. TPSC is a weak
to intermediate coupling approach capable of calculating a frequency- and
momentum-dependent self-energy from spin and charge fluctuations. We present
results for the spin Hall conductivity and correlation lengths for
antiferromagnetic spin fluctuations for different values of temperature,
spin-orbit coupling and Hubbard interaction. The vertex corrections, which here
are analogues of Maki-Thompson contributions, show a strong momentum dependence
and give a large contribution in the vicinity of the phase transition at all
temperatures. Their inclusion is necessary to observe the quantization of the
spin Hall conductivity for the interacting system in the zero temperature
limit. At finite temperature, increasing the Hubbard interaction leads to a
decrease of the spin Hall conductivity. This decrease can be explained by
band-gap renormalization from scattering of electrons on antiferromagnetic spin
fluctuations.",2307.15652v2
2006-03-06,Magnetism of iron: from the bulk to the monoatomic wire,"The magnetic properties of iron (spin and orbital magnetic moments,
magnetocrystalline anisotropy energy) in various geometries and
dimensionalities are investigated by using a parametrized tight-binding model
in an $s$, $p$ and $d$ atomic orbital basis set including spin polarization and
the effect of spin-orbit coupling. The validity of this model is well
established by comparing the results with those obtained by using an ab-initio
code. This model is applied to the study of iron in bulk bcc and fcc phases,
$(110)$ and $(001)$ surfaces and to the monatomic wire, at several interatomic
distances. New results are derived. The variation of the component of the
orbital magnetic moment on the spin quantization axis has been studied as a
function of depth, revealing a significant enhancement in the first two layers,
especially for the $(001)$ surface. It is found that the magnetic anisotropy
energy is drastically increased in the wire and can reach several meV. This is
also true for the orbital moment, which in addition is highly anisotropic.
Furthermore it is shown that when the spin quantization axis is neither
parallel nor perpendicular to the wire the average orbital moment is not
aligned with the spin quantization axis. At equilibrium distance the easy
magnetization axis is along the wire but switches to the perpendicular
direction under compression. The success of this model opens up the possibility
of obtaining accurate results on other elements and systems with much more
complex geometries.",0603121v1
2005-01-12,"Valence-Bond Crystal, and Lattice Distortions in a Pyrochlore Antiferromagnet with Orbital Degeneracy","We discuss the ground state properties of a spin 1/2 magnetic ion with
threefold $t_{2g}$ orbital degeneracy on a highly frustrated pyrochlore
lattice, like Ti$^{3+}$ ion in B-spinel MgTi$_2$O$_4$. We formulate an
effective spin-orbital Hamiltonian and study its low energy sector by
constructing several exact-eigenstates in the limit of vanishing Hund's
coupling. We find that orbital degrees of freedom modulate the spin-exchange
energies, release the infinite spin-degeneracy of pyrochlore structure, and
drive the system to a non-magnetic spin-singlet manifold. The latter is a
collection of spin-singlet dimers and is, however, highly degenerate with
respect of dimer orientations. This ``orientational'' degeneracy is then lifted
by a magneto-elastic interaction that optimizes the previous energy gain by
distorting the bonds in suitable directions and leading to a tetragonal phase.
In this way a valence bond crystal state is formed, through the condensation of
dimers along helical chains running around the tetragonal c-axis, as actually
observed in MgTi$_2$O$_4$. The orbitally ordered pattern in the dimerized phase
is predicted to be of ferro-type along the helices and of antiferro-type
between them. Finally, through analytical considerations as well as numerical
ab-initio simulations, we predict a possible experimental tool for the
observation of such an orbital ordering, through resonant x-ray scattering.",0501289v1
2021-07-01,Charge disproportionation and Hund's insulating behavior in a five-orbital Hubbard model applicable to $d^4$ perovskites,"We explore the transition to a charge-disproportionated insulating phase in a
five-orbital cubic tight-binding model applicable to transition-metal
perovskites with a formal $d^4$ occupation of the transition-metal cation, such
as ferrates or manganites. We use dynamical mean-field theory to obtain the
phase diagram as a function of the average local Coulomb repulsion $U$ and the
Hund's coupling $J$. The main structure of the phase diagram follows from the
zero band-width (atomic) limit and represents the competition between high-spin
and low-spin homogeneous and an inhomogeneous charge-disproportionated state.
This results in two distinct insulating phases: the standard homogeneous Mott
insulator and the inhomogeneous charge-disproportionated insulator, recently
also termed Hund's insulator. We characterize the unconventional nature of this
Hund's insulating state. Our results are consistent with previous studies of
two- and three-orbital models applicable to isolated $t_{2g}$ and $e_g$
subshells, respectively, with the added complexity of the low-spin/high-spin
transition. We also test the applicability of an effective two-orbital
($e_g$-only) model with disordered $S=3/2$ $t_{2g}$ core spins. Our results
show that the overall features of the phase diagram in the high-spin region are
well described by this simplified two-orbital model but also that the spectral
features exhibit pronounced differences compared to the full five-orbital
description.",2107.00348v2
2017-09-21,Orbital loop currents in iron-based superconductors,"We show that the antiferromagnetic state commonly observed in the phase
diagrams of the iron-based superconductors necessarily triggers loop currents
characterized by charge transfer between different Fe $ 3d $ orbitals. This
effect is rooted on the glide-plane symmetry of these materials and on the
existence of an atomic spin-orbit coupling that couples states at the $X$ and
$Y$ points of the 1-Fe Brillouin zone. In the particular case in which the
magnetic moments are aligned parallel to the magnetic ordering vector direction
which is the moment configuration most commonly found in the iron-based
superconductors these loop currents involve the $d_{xy}$ orbital and either the
$d_{yz}$ orbital (if the moments point along the $y$ axis) or the $d_{xz}$
orbitals (if the moments point along the $x$ axis). We show that the two main
manifestations of the orbital loop currents are the emergence of magnetic
moments in the pnictide/chalcogen site and an orbital-selective band splitting
in the magnetically ordered state, both of which could be detected
experimentally. Our results highlight the unique intertwining between orbital
and spin degrees of freedom in the iron-based superconductors, and reveal the
emergence of an unusual correlated phase that may impact the normal state and
superconducting properties of these materials.",1709.07266v2
2013-03-18,BCS-BEC crossover at finite temperature in spin-orbit coupled Fermi gases,"By adopting a $T$-matrix-based method within the $G_0G$ approximation for the
pair susceptibility, we study the effects of the pairing fluctuation on the
three-dimensional spin-orbit coupled Fermi gases at finite temperature. The
critical temperatures of the superfluid/normal phase transition are determined
for three different types of spin-orbit coupling (SOC): (1) the extreme oblate
(EO) or Rashba SOC, (2) the extreme prolate (EP) or equal Rashba-Dresselhaus
SOC, and (3) the spherical (S) SOC. For EO- and S-type SOC, the SOC dependence
of the critical temperature signals a crossover from BCS to BEC state; at
strong SOC limit, the critical temperature recover those of ideal BEC of
rashbons. The pairing fluctuation induces a pseudogap in the fermionic
excitation spectrum in both superfluid and normal phases. We find that, for EO-
and S-type SOC, even at weak coupling, sufficiently strong SOC can induce
sizable pseudogap. Our research suggests that the spin-orbit coupled Fermi
gases may open new means to the study of the pseudogap formation in fermionic
systems.",1303.4136v2
2016-07-19,Kondo effect in a quantum wire with spin-orbit coupling,"The influence of spin-orbit interactions on the Kondo effect has been under
debate recently. Studies conducted recently on a system composed by an Anderson
impurity on a 2DEG with Rashba spin-orbit have been shown that it can enhance
or suppress the Kondo temperature ($T_{\rm K}$), depending on the relative
energy level position of the impurity with respect to the particle-hole
symmetric point. Here we investigate a system composed by a single Anderson
impurity side-coupled to a quantum wire with spin-orbit coupling (SOC). We
derive an effective Hamiltonian in which the Kondo coupling is modified by the
SOC. In addition, the Hamiltonian contains two other scattering terms, the so
called Dzaloshinskyi-Moriya interaction, know to appear in these systems, and a
new one describing processes similar to the Elliott-Yafet scattering
mechanisms. By performing a renormalization group analysis on the effective
Hamiltonian, we find that the correction on the Kondo coupling due to the SOC
favors and enhancement of the Kondo temperature even in the particle-hole
symmetric point of the Anderson model, agreeing with the NRG results. Moreover,
away from the particle-hole symmetric point, $T_{\rm K}$ always increases with
the SOC, accordingly with the previous renormalization group analysis.",1607.05684v1
2020-11-30,"Graphene on two-dimensional hexagonal BN, AlN, and GaN: Electronic, spin-orbit, and spin relaxation properties","We investigate the electronic structure of graphene on a series of 2D
hexagonal nitride insulators hXN, X = B, Al, and Ga, with DFT calculations. A
symmetry-based model Hamiltonian is employed to extract orbital parameters and
spin-orbit coupling (SOC) from the low-energy Dirac bands of proximitized
graphene. While commensurate hBN induces a staggered potential of about 10 meV
into the Dirac bands, less lattice-matched hAlN and hGaN disrupt the Dirac
point much less, giving a staggered gap below 100 $\mu$eV. Proximitized
intrinsic SOC surprisingly does not increase much above the pristine graphene
value of 12 $\mu$eV; it stays in the window of (1-16) $\mu$eV, depending
strongly on stacking. However, Rashba SOC increases sharply when increasing the
atomic number of the boron group, with calculated maximal values of 8, 15, and
65 $\mu$eV for B, Al, and Ga-based nitrides, respectively. The individual
Rashba couplings also depend strongly on stacking, vanishing in
symmetrically-sandwiched structures, and can be tuned by a transverse electric
field. The extracted spin-orbit parameters were used as input for spin
transport simulations based on Chebyshev expansion of the time-evolution of the
spin expectation values, yielding interesting predictions for the electron spin
relaxation. Spin lifetime magnitudes and anisotropies depend strongly on the
specific (hXN)/graphene/hXN system, and they can be efficiently tuned by an
applied external electric field as well as the carrier density in the graphene
layer. A particularly interesting case for experiments is graphene/hGaN, in
which the giant Rashba coupling is predicted to induce spin lifetimes of 1-10
ns, short enough to dominate over other mechanisms, and lead to the same spin
relaxation anisotropy as observed in conventional semiconductor
heterostructures: 50\%, meaning that out-of-plane spins relax twice as fast as
in-plane spins.",2011.14588v2
2011-04-23,Nuclear Dynamics During Landau-Zener Singlet-Triplet Transitions in Double Quantum Dots,"We consider nuclear spin dynamics in a two-electron double dot system near
the intersection of the electron spin singlet $S$ and the lower energy
component $T_{+}$ of the spin triplet. The electron spin interacts with nuclear
spins and is influenced by the spin-orbit coupling. Our approach is based on a
quantum description of the electron spin in combination with the coherent
semiclassical dynamics of nuclear spins. We consider single and double
Landau-Zener passages across the $S$-$T_{+}$ anticrossings. For linear sweeps,
the electron dynamics is expressed in terms of parabolic cylinder functions.
The dynamical nuclear polarization is described by two complex conjugate
functions $\Lambda ^{\pm}$ related to the integrals of the products of the
singlet and triplet amplitudes ${\tilde{c}}_{S}^{\ast}{\tilde{c}}_{T_{+}}$
along the sweep. The real part $P$ of $\Lambda ^{\pm}$ is related to the
$S$-$T_{+}$ spin-transition probability, accumulates in the vicinity of the
anticrossing, and for long linear passages coincides with the Landau-Zener
probability $P_{LZ}=1-e^{-2\pi \gamma}$, where $\gamma $ is the Landau-Zener
parameter. The imaginary part $Q$ of $\Lambda^{+}$ is specific for the nuclear
spin dynamics, accumulates during the whole sweep, and for $\gamma \gtrsim 1$
is typically an order of magnitude larger than $P$. $Q$ has a profound effect
on the nuclear spin dynamics, by (i) causing intensive shake-up processes among
the nuclear spins and (ii) producing a high nuclear spin generation rate when
the hyperfine and spin-orbit interactions are comparable in magnitude. We find
analytical expressions for the back-action of the nuclear reservoir represented
via the change in the Overhauser fields the electron subsystem experiences.",1104.4591v1
2021-11-07,A correctly scaling rigorously spin-adapted and spin-complete open-shell CCSD implementation for arbitrary high-spin states,"In this paper, we report on a correctly scaling novel coupled cluster singles
and doubles (CCSD) implementation for arbitrary high-spin open-shell states.
The chosen cluster operator is completely spin-free, i.e. employs spatial
substitutions only. It is composed of our recently developed L\""owdin-type
operators (doi: 10.1063/5.0026762), which ensure (1) spin completeness and (2)
spin adaption i.e. spin purity of the CC wave function. In contrast to the
proof-of-concept matrix-representation-based implementation presented there,
the present implementation relies on second quantization and factorized tensor
contractions. The generated singles and doubles operators are embedded in an
equation generation engine. In the latter, Wick's theorem is used to derive
prefactors arising from spin integration directly from the spin-free full
contraction patterns. The obtained Wick terms composed of products of Kronecker
deltas are represented by special non-antisymmetrized Goldstone diagrams.
Identical (redundant) diagrams are identified by solving the underlying graph
isomorphism problem. All non-redundant graphs are then automatically translated
to locally -- one term at a time -- factorized tensor contractions. Finally,
the spin-adapted and spin-complete (SASC) CCS and CCSD variants are applied to
a set of small molecular test systems. Both correlation energies and amplitude
norms hint towards a reasonable convergence of the SASC-CCSD method for a BCH
series truncation of order four. In comparison to spin orbital CCSD, SASC-CCSD
leads to slightly improved correlation energies with differences of up to 0.886
mE_H (0.98% w.r.t. spin orbital CCSD(T)).",2111.04186v1
2007-10-15,Significant g-factor values of a two-electron ground state in quantum dots with spin-orbit coupling,"The magnetization of semiconductor quantum dots in the presence of spin-orbit
coupling and interactions is investigated numerically. When the dot is occupied
by two electrons we find that a level crossing between the two lowest many-body
eigenstates may occur as a function of the spin-orbit coupling strength. This
level crossing is accompanied by a non-vanishing magnetization of the
ground-state. Using first order perturbation theory as well as exact numerical
diagonalization of small clusters we show that the tendency of interactions to
cause Stoner-like instability is enhanced by the SO coupling. The resulting
g-factor can have a significant value, and thus may influence g-factor
measurements. Finally we propose an experimental method by which the predicted
phenomenon can be observed.",0710.2772v2
2015-07-09,Trion-polaritons : How strong coupling to a cavity changes the orbital and spin properties of trions,"The elementary optical excitations of a two-dimensional electron system
strongly coupled to a microcavity are trion-polaritons. Using a variational
approach, we demonstrate that the competition between Coulomb interaction and
light-matter coupling plays a crucial role in determining the lowest-energy
orbital and spin properties of trion-polaritons. When the light-matter
interaction exceeds the bare trion binding, singlet and triplet trion states
are mixed due to a cavity-mediated spin-orbit effect, which in turn results in
a strong increase of the outer electron Bohr radius. In this strong cavity
coupling regime, the trion-polariton consists of an exciton-polariton
surrounded by a weakly bound electron and is reminiscent of a coherent Rydberg
excitation.",1507.02480v2
2018-04-25,Energy levels repulsion by spin-orbit coupling in two-dimensional Rydberg excitons,"We study the effects of Rashba spin-orbit coupling on two-dimensional Rydberg
exciton systems. Using analytical and numerical arguments we demonstrate that
this coupling considerably modifies the wave functions and leads to a level
repulsion that results in a deviation from the Poissonian statistics of the
adjacent level distance distribution. This signifies the crossover to
non-integrability of the system and hints on the possibility of quantum chaos
emerging. Such a behavior strongly differs from the classical realization,
where spin-orbit coupling produces highly entangled, chaotic electron
trajectories in an exciton. We also calculate the oscillator strengths and show
that randomization appears in the transitions between states with different
total momenta.",1804.09545v1
2018-11-27,Cavity-induced spin-orbit coupling in an interacting bosonic wire,"We consider theoretically ultra-cold interacting bosonic atoms confined to a
wire geometry and coupled to the field of an optical cavity. A spin-orbit
coupling is induced via Raman transitions employing a cavity mode and a
transverse running wave pump beam, the transition imprints a spatial dependent
phase onto the atomic wavefunction. Adiabatic elimination of the cavity field
leads to an effective Hamiltonian for the atomic degrees of freedom, with a
self-consistency condition. We map the spin-orbit coupled bosonic wire to a
bosonic ladder in a magnetic field, by discretizing the spatial dimension.
Using the numerical density matrix renormalization group method, we show that
in the continuum limit the dynamical stabilization of a Meissner superfluid is
possible, for parameters achievable by nowadays experiments.",1811.11045v2
2015-12-09,General conditions for proximity-induced odd-frequency superconductivity in two-dimensional electronic systems,"We obtain the general conditions for the emergence of odd-frequency
superconducting pairing in a two-dimensional (2D) electronic system
proximity-coupled to a superconductor, making minimal assumptions about both
the 2D system and the superconductor. Using our general results we show that a
simple heterostructure formed by a monolayer of a group VI transition metal
dichalcogenide, such as molybdenum disulfide, and an s-wave superconductor with
Rashba spin-orbit coupling will exhibit odd-frequency superconducting pairing.
Furthermore, we show that in such a heterostructure the odd-frequency pairing
amplitude will be proportional to the product of the Rashba spin-orbit coupling
in the substrate and the spin-orbit coupling in the dichalcogenide layer.",1512.03068v2
2019-07-19,A cryogenic memory element based on an anomalous Josephson junction,"We propose a non-volatile memory element based on a lateral ferromagnetic
Josephson junction with spin-orbit coupling and out-of-plane magnetization. The
interplay between the latter and the intrinsic exchange field of the
ferromagnet leads to a magnetoelectric effect that couples the charge current
through the junction and its magnetization, such that by applying a current
pulse the direction of the magnetic moment in F can be switched. The two memory
states are encoded in the direction of the out-of-plane magnetization. With the
aim to determine the optimal working temperature for the memory element, we
explore the noise-induced effects on the averaged stationary magnetization by
taking into account thermal fluctuations affecting both the Josephson phase and
the magnetic moment dynamics. We investigate the switching process as a
function of intrinsic parameters of the ferromagnet, such as the Gilbert
damping and strength of the spin-orbit coupling, and proposed a non-destructive
readout scheme based on a dc-SQUID. Additionally, we analyze a way to protect
the memory state from external perturbations by voltage gating in systems with
a both linear-in-momentum Rashba and Dresselhaus spin-orbit coupling.",1907.08454v2
2022-05-17,Magnetism and metal-insulator transitions in the Rashba-Hubbard model,"The nature of metal-insulator and magnetic transitions is still a subject
under intense debate in condensed matter physics. Amongst the many possible
mechanisms, the interplay between electronic correlations and spin-orbit
couplings is an issue of a great deal of interest, in particular when dealing
with quasi-2D compounds. In view of this, here we use a Hartree-Fock approach
to investigate how the Rashba spin-orbit coupling, $V_\text{SO}$, affects the
magnetic ordering provided by a Hubbard interaction, $U$, on a square lattice.
At half-filling, we have found a sequence of transitions for increasing
$V_\text{SO}$: from a Mott insulator to a metallic antiferromagnet, and then to
a paramagnetic Rashba metal. Also, our results indicate that the Rashba
coupling favors magnetic striped phases in the doped regime. By analyzing
spectral properties, we associate the rearrangement of the magnetic ordering
with the emerging chirality created by the spin-orbit coupling. Our findings
provide insights towards clarifying the competition between these tendencies.",2205.08651v1
2022-06-20,Enhanced superconductivity through virtual tunneling in Bernal bilayer graphene coupled to WSe$_2$,"Motivated by a recent experiment [arXiv:2205.05087], we investigate a
possible mechanism that enhances superconductivity in hole-doped Bernal bilayer
graphene due to a proximate WSe$_2$ monolayer. We show that the virtual
tunneling between WSe$_2$ and Bernal bilayer graphene, which is known to induce
Ising spin-orbit coupling, can generate an additional attraction between two
holes, providing a potential explanation for enhancing superconductivity in
Bernal bilayer graphene. Using microscopic interlayer tunneling, we derive the
Ising spin-orbit coupling and the effective attraction as functions of the
twist angle between Bernal bilayer graphene and the WSe$_2$ monolayer. Our
theory provides an intuitive and physical explanation for the intertwined
relation between Ising spin-orbit coupling and superconductivity enhancement,
which should motivate future studies.",2206.09922v3
2003-05-27,The nonrelativistic limit of the relativistic point coupling model,"We relate the relativistic finite range mean-field model (RMF-FR) to the
point-coupling variant and compare the nonlinear density dependence. From this,
the effective Hamiltonian of the nonlinear point-coupling model in the
nonrelativistic limit is derived. Different from the nonrelativistic models,
the nonlinearity in the relativistic models automatically yields contributions
in the form of a weak density dependence not only in the central potential but
also in the spin-orbit potential. The central potential affects the bulk and
surface properties while the spin-orbit potential is crucial for the shell
structure of finite nuclei. A modification in the Skyrme-Hartree-Fock model
with a density-dependent spin-orbit potential inspired by the point-coupling
model is suggested.",0305078v1
2009-02-25,Low-energy theory and RKKY interaction for interacting quantum wires with Rashba spin-orbit coupling,"We present the effective low-energy theory for interacting 1D quantum wires
subject to Rashba spin-orbit coupling. Under a one-loop renormalization group
scheme including all allowed interaction processes for not too weak Rashba
coupling, we show that electron-electron backscattering is an irrelevant
perturbation. Therefore no gap arises and electronic transport is described by
a modified Luttinger liquid theory. As an application of the theory, we discuss
the RKKY interaction between two magnetic impurities. Interactions are shown to
induce a slower power-law decay of the RKKY range function than the usual 1D
noninteracting $\cos(2k_F x)/|x|$ law. Moreover, in the noninteracting Rashba
wire, the spin-orbit coupling causes a twisted (anisotropic) range function
with several different spatial oscillation periods. In the interacting case, we
show that one special oscillation period leads to the slowest decay, and
therefore dominates the RKKY interaction for large separation.",0902.4402v2
2012-07-29,Anisotropic dynamics of a spin-orbit coupled Bose-Einstein condensate,"By calculating the density response function we identify the excitation
spectrum of a Bose-Einstein condensate with equal Rashba and Dresselhaus
spin-orbit coupling. We find that the velocity of sound along the direction of
spin-orbit coupling is deeply quenched and vanishes when one approaches the
second-order phase transition between the plane wave and the zero momentum
quantum phases. We also point out the emergence of a roton minimum in the
excitation spectrum for small values of the Raman coupling, providing the onset
of the transition to the stripe phase. Our findings point out the occurrence of
a strong anisotropy in the dynamic behavior of the gas. A hydrodynamic
description accounting for the collective oscillations in both uniform and
harmonically trapped gases is also derived.",1207.6804v2
2012-11-01,Matter-wave bright solitons in spin-orbit coupled Bose-Einstein condensates,"We study matter-wave bright solitons in spin-orbit (SO) coupled Bose-Einstein
condensates (BECs) with attractive interatomic interactions. We use a
multiscale expansion method to identify solution families for chemical
potentials in the semi-infinite gap of the linear energy spectrum. Depending on
the linear and spin-orbit coupling strengths, the solitons may resemble either
standard bright nonlinear Schr\""{o}dinger solitons or exhibit a modulated
density profile, reminiscent of the stripe phase of SO-coupled repulsive BECs.
Our numerical results are in excellent agreement with our analytical findings,
and demonstrate the potential robustness of such solitons for experimentally
relevant conditions through stability analysis and direct numerical
simulations.",1211.0199v1
2016-04-12,Hybridization and spin-orbit coupling effects in quasi-one-dimensional spin-1/2 magnet Ba3Cu3Sc4O12,"We study electronic and magnetic properties of the quasi-one-dimensional
spin-1/2 magnet Ba3Cu3Sc4O12 with a distinct orthogonal connectivity of CuO4
plaquettes. An effective low-energy model taking into account spin-orbit
coupling was constructed by means of first-principles calculations. On this
basis a complete microscopic magnetic model of Ba3Cu3Sc4O12, including
symmetric and antisymmetric anisotropic exchange interactions, is derived. The
anisotropic exchanges are obtained from a distinct first-principles numerical
scheme combining, on one hand, the local density approximation taking into
account spin-orbit coupling, and, on the other hand, projection procedure along
with the microscopic theory by Toru Moriya. The resulting tensors of the
symmetric anisotropy favor collinear magnetic order along the structural chains
with the leading ferromagnetic coupling J1 = -9.88 meV. The interchain
interactions J8 = 0.21 meV and J5 = 0.093 meV are antiferromagnetic. Quantum
Monte Carlo simulations demonstrated that the proposed model reproduces the
experimental Neel temperature, magnetization and magnetic susceptibility data.
The modeling of neutron diffraction data reveals an important role of the
covalent Cu-O bonding in Ba3Cu3Sc4O12.",1604.03333v1
2019-05-02,Analytical solution of narrow quantum rings with general Rashba and Dresselhaus spin-orbit couplings,"We solve analytically the energy eigenvalue problem of narrow semiconductor
quantum rings with a general spin-orbit term that includes as a special case
the Rashba and Dresselhaus interactions acting simultaneously. The eigenstates
and eigenenergies of the system are found for arbitrary values of the
spin-orbit coupling constants without making use of approximations. The general
eigenstates are expressed as products of a scalar Mathieu function and a spinor
factor which is periodic or pseudo-periodic on the ring. Our general solution
reduces to the previously found solutions for particular combinations of the
Rashba and Dresselhaus couplings, like the well-studied cases of Rashba-only
and of equal coupling constants.",1905.00878v1
2014-06-27,Energy spectrum of a harmonically trapped two-atom system with spin-orbit coupling,"Ultracold atomic gases provide a novel platform with which to study
spin-orbit coupling, a mechanism that plays a central role in the nuclear shell
model, atomic fine structure and two-dimensional electron gases. This paper
introduces a theoretical framework that allows for the efficient determination
of the eigenenergies and eigenstates of a harmonically trapped two-atom system
with short-range interaction subject to an equal mixture of Rashba and
Dresselhaus spin-orbit coupling created through Raman coupling of atomic
hyperfine states. Energy spectra for experimentally relevant parameter
combinations are presented and future extensions of the approach are discussed.",1406.7177v1
2019-08-19,Energetics and structural properties of two- and three-boson systems in the presence of 1D spin-orbit coupling,"It was shown recently that the discrete scaling symmetry, which underlies the
Efimov effect in the three identical boson system with two-body short-range
interactions, survives when single-particle 1D spin-orbit coupling terms are
added to the Hamiltonian. Each three-body energy level in the ordinary Efimov
scenario turns into an energy manifold that contains four energy levels in the
presence of 1D spin-orbit coupling (equal mixture of Rashba-Dresselhaus
coupling). This work provides a detailed characterization of the energy levels
in these manifolds. The two-boson energies, which enter into the three-boson
scattering threshold, are analyzed in detail. Moreover, the structural
properties, e.g., momentum distributions of the two- and three-boson systems,
are analyzed for various parameter combinations.",1908.06918v1
2015-11-25,Interplay of Rashba spin orbit coupling and disorder in the conductance properties of a four terminal junction device,"We report a thorough theoretical investigation on the quantum transport of a
disordered four terminal device in the presence of Rashba spin orbit coupling
(RSOC) in two dimensions. Specifically we compute the behaviour of the
longitudinal (charge) conductance, spin Hall conductance and spin Hall
conductance fluctuation as a function of the strength of disorder and Rashba
spin orbit interaction using the Landauer Buttiker formalism via Green's
function technique. Our numerical calculations reveal that both the
conductances diminish with disorder. At smaller values of the RSOC parameter,
the longitudinal and spin Hall conductances increase, while both vanish in the
strong RSOC limit. The spin current is more drastically affected by both
disorder and RSOC than its charge counterpart. The spin Hall conductance
fluctuation does not show any universality in terms of its value and it depends
on both disorder as well as on the RSOC strength. Thus the spin Hall
conductance fluctuation has a distinct character compared to the fluctuation in
the longitudinal conductance. Further one parameter scaling theory is studied
to assess the transition to a metallic regime as claimed in literature and we
find no confirmation about the emergence of a metallic state induced by RSOC.",1511.07966v3
2017-11-28,Spin transport in high-mobility graphene on WS$_2$ substrate with electric-field tunable proximity spin-orbit interaction,"Graphene supported on a transition metal dichalcogenide substrate offers a
novel platform to study the spin transport in graphene in presence of a
substrate induced spin-orbit coupling, while preserving its intrinsic charge
transport properties. We report the first non-local spin transport measurements
in graphene completely supported on a 3.5 nm thick tungsten disulfide (WS$_2$)
substrate, and encapsulated from the top with a 8 nm thick hexagonal boron
nitride layer. For graphene, having mobility up to 16,000
cm$^2$V$^{-1}$s$^{-1}$, we measure almost constant spin-signals both in
electron and hole-doped regimes, independent of the conducting state of the
underlying WS$_2$ substrate, which rules out the role of spin-absorption by
WS$_2$. The spin-relaxation time $\tau_{\text{s}}$ for the electrons in
graphene-on-WS$_2$ is drastically reduced down to~10 ps than $\tau_{\text{s}}$
~ 800 ps in graphene-on-SiO$_2$ on the same chip. The strong suppression of
$\tau_{\text{s}}$ along with a detectable weak anti-localization signature in
the quantum magneto-resistance measurements is a clear effect of the WS$_2$
induced spin-orbit coupling (SOC) in graphene. Via the top-gate voltage
application in the encapsulated region, we modulate the electric field by 1
V/nm, changing $\tau_{\text{s}}$ almost by a factor of four which suggests the
electric-field control of the in-plane Rashba SOC. Further, via carrier-density
dependence of $\tau_{\text{s}}$ we also identify the fingerprints of the
D'yakonov-Perel' type mechanism in the hole-doped regime at the graphene-WS$_2$
interface.",1711.10293v1
2021-08-08,Origin of Rashba spin-splitting and strain tunability in ferroelectric bulk CsPbF$_3$,"Spin-orbit coupling (SOC) in conjunction with broken inversion symmetry acts
as a key ingredient for several intriguing quantum phenomena viz. persistent
spin textures, topological surface states and Rashba-Dresselhaus (RD) effects.
The coexistence of spontaneous polarization and the RD effect in ferroelectric
materials enables the electrical control of spin degree of freedom. In light of
this, we explore here the ferroelectric lead halide perovskite viz. CsPbF$_3$
as a potential candidate in the field of spintronics by employing
state-of-the-art first-principles based methodologies viz. density functional
theory (DFT) with semi-local and hybrid functional (HSE06) combined with
spin-orbit coupling (SOC) and many-body perturbation theory (G$_0$W$_0$). For a
deeper understanding of the observed spin-splitting, we have analyzed the spin
textures within the combined framework of DFT and $\textbf{k.p}$ model
Hamiltonian. The latter confirms that there is no out of plane spin component
indicating that the Rashba splitting dominates over Dresselhaus splitting in
this system. Owing to the presence of Pb-6$p$ orbital in conduction band, the
large value of Rashba coefficient ($\alpha_R$) at conduction band minimum (CBm)
is noticed in comparison to that of at the valence band maximum (VBM). Notably,
we also observe that strength of Rashba spin-splitting can be substancially
tuned on application of uniaxial strain ($\pm5\%$). This finding will further
pave the path for perovskite-based spintronics devices.",2108.03683v2
2021-11-02,Evidence for anisotropic spin-triplet Andreev reflection at the 2D van der Waals ferromagnet/superconductor interface,"Fundamental symmetry breaking and relativistic spin-orbit coupling give rise
to fascinating phenomena in quantum materials. Of particular interest are the
interfaces between ferromagnets and common s-wave superconductors, where the
emergent spin-orbit fields support elusive spin-triplet superconductivity,
crucial for superconducting spintronics and topologically-protected Majorana
bound states. Here, we report the observation of large magnetoresistances at
the interface between a quasi-two-dimensional van der Waals ferromagnet
Fe0.29TaS2 and a conventional s-wave superconductor NbN, which provides the
possible experimental evidence for the spin triplet Andreev reflection and
induced spin-triplet superconductivity at ferromagnet/superconductor interface
arising from Rashba spin-orbit coupling. The temperature, voltage, and
interfacial barrier dependences of the magnetoresistance further support the
induced spin-triplet superconductivity and spin-triplet Andreev reflection.
This discovery, together with the impressive advances in two-dimensional van
der Waals ferromagnets, opens an important opportunity to design and probe
superconducting interfaces with exotic properties.",2111.01360v2
2023-05-24,Flat band separation and robust spin-Berry curvature in bilayer kagome metals,"Kagome materials have emerged as a setting for emergent electronic phenomena
that encompass different aspects of symmetry and topology. It is debated
whether the XV$_6$Sn$_6$ kagome family (where X is a rare earth element), a
recently discovered family of bilayer kagome metals, hosts a topologically
non-trivial ground state resulting from the opening of spin-orbit coupling
gaps. These states would carry a finite spin-Berry curvature, and topological
surface states. Here, we investigate the spin and electronic structure of the
XV$_6$Sn$_6$ kagome family. We obtain evidence for a finite spin-Berry
curvature contribution at the center of the Brillouin zone, where the nearly
flat band detaches from the dispersing Dirac band because of spin-orbit
coupling. In addition, the spin-Berry curvature is further investigated in the
charge density wave regime of ScV$_6$Sn$_6$, and it is found to be robust
against the onset of the temperature-driven ordered phase. Utilizing the
sensitivity of angle resolved photoemission spectroscopy to the spin and
orbital angular momentum, our work unveils the spin-Berry curvature of
topological kagome metals, and helps to define its spectroscopic fingerprint.",2305.15345v1
2018-12-03,"Heterostructures of graphene and hBN: electronic, spin-orbit, and spin relaxation properties from first principles","We perform extensive first-principles calculations for heterostructures
composed of monolayer graphene and hexagonal boron nitride (hBN). Employing a
symmetry-derived minimal tight-binding model, we extract orbital and spin-orbit
coupling (SOC) parameters for graphene on hBN, as well as for hBN encapsulated
graphene. Our calculations show that the parameters depend on the specific
stacking configuration of graphene on hBN. We also perform an interlayer
distance study for the different graphene/hBN stacks to find the corresponding
lowest energy distances. For very large interlayer distances, one can recover
the pristine graphene properties, as we find from the dependence of the
parameters on the interlayer distance. Furthermore, we find that orbital and
SOC parameters, especially the Rashba one, depend strongly on an applied
transverse electric field, giving a rich playground for spin physics. Armed
with the model parameters, we employ the Dyakonov-Perel formalism to calculate
the spin relaxation in graphene/hBN heterostructures. We find spin lifetimes in
the nanosecond range, in agreement with recent measurements. The spin
relaxation anisotropy, being the ratio of out-of-plane to in-plane spin
lifetimes, is found to be giant close to the charge neutrality point,
decreasing with increasing doping, and being highly tunable by an external
transverse electric field. This is in contrast to bilayer graphene in which an
external field saturates the spin relaxation anisotropy.",1812.00866v2
2015-06-09,Universal chiral-triggered magnetization switching in confined nanodots,"Spin orbit interactions are rapidly emerging as the key for enabling
efficient current-controlled spintronic devices. Much work has focused on the
role of spin-orbit coupling at heavy metal/ferromagnet interfaces in generating
current-induced spin-orbit torques. However, the strong influence of the
spin-orbit-derived Dzyaloshinskii-Moriya interaction (DMI) on spin textures in
these materials is now becoming apparent. Recent reports suggest DMI-stabilized
homochiral domain walls (DWs) can be driven with high efficiency by spin torque
from the spin Hall effect. However, the influence of the DMI on the
current-induced magnetization switching has not been explored nor is yet
well-understood, due in part to the difficulty of disentangling spin torques
and spin textures in nano-sized confined samples. Here we study the
magnetization reversal of perpendicular magnetized ultrathin dots, and show
that the switching mechanism is strongly influenced by the DMI, which promotes
a universal chiral non-uniform reversal, even for small samples at the
nanoscale. We show that ultrafast current-induced and field-induced
magnetization switching consists on local magnetization reversal with domain
wall nucleation followed by its propagation along the sample. These findings,
not seen in conventional materials, provide essential insights for
understanding and exploiting chiral magnetism for emerging spintronics
applications.",1506.02893v1
2022-09-07,Hidden spin-orbital texture at the $\barΓ$-located valence band maximum of a transition metal dichalcogenide semiconductor,"Finding stimuli capable of driving an imbalance of spin-polarised electrons
within a solid is the central challenge in the development of spintronic
devices. However, without the aid of magnetism, routes towards this goal are
highly constrained with only a few suitable pairings of compounds and driving
mechanisms found to date. Here, through spin- and angle-resolved photoemission
along with density functional theory, we establish how the $p$-derived bulk
valence bands of semiconducting 1T-HfSe$_2$ possess a local, ground-state spin
texture spatially confined within each Se-sublayer due to strong
sublayer-localised electric dipoles orientated along the $c$-axis. This hidden
spin-polarisation manifests in a `coupled spin-orbital texture' with
in-equivalent contributions from the constituent $p$-orbitals. While the
overall spin-orbital texture for each Se sublayer is in strict adherence to
time-reversal symmetry (TRS), spin-orbital mixing terms with net polarisations
at time-reversal invariant momenta are locally maintained. These apparent
TRS-breaking contributions dominate, and can be selectively tuned between with
a choice of linear light polarisation, facilitating the observation of
pronounced spin-polarisations at the Brillouin zone centre for all $k_z$. We
discuss the implications for the generation of spin-polarised populations from
1T-structured transition metal dichalcogenides using a fixed energy, linearly
polarised light source.",2209.03110v1
2002-10-18,Coherent spin valve phenomena and electrical spin injection in ferromagnetic/semiconductor/ferromagnetic junctions,"Coherent quantum transport in ferromagnetic/ semiconductor/ ferromagnetic
junctions is studied theoretically within the Landauer framework of ballistic
transport. We show that quantum coherence can have unexpected implications for
spin injection and that some intuitive spintronic concepts which are founded in
semi-classical physics no longer apply: A quantum spin-valve (QSV) effect
occurs even in the absence of a net spin polarized current flowing through the
device, unlike in the classical regime. The converse effect also arises, i.e. a
zero spin-valve signal for a non-vanishing spin-current. We introduce new
criteria useful for analyzing quantum and classical spin transport phenomena
and the relationships between them. The effects on QSV behavior of
spin-dependent electron transmission at the interfaces, interface Schottky
barriers, Rashba spin-orbit coupling and temperature, are systematically
investigated. While the signature of the QSV is found to be sensitive to
temperature, interestingly, that of its converse is not. We argue that the QSV
phenomenon can have important implications for the interpretation of
spin-injection in quantum spintronic experiments with spin-valve geometries.",0210391v1
2005-07-06,Co-planar spin-polarized light emitting diode,"Studies of spin manipulation in semiconductors has benefited from the
possibility to grow these materials in high quality on top of optically active
III-V systems. The induced electroluminescence in these layered semiconductor
heterostructures has been used for a reliable spin detection. In semiconductors
with strong spin-orbit interaction, the sensitivity of vertical devices may be
insufficient, however, because of the sepration of the spin aligner part and
the spin detection region by one or more heterointerfaces and becuse of the
short spin coherence length. Here we demostrate that higly sensitive spin
detection can be achieved using a lateral arrangement of the spin polarized and
optically active regions. Using our co-planar spin-polarized light emitting
diodes we detect electrical field induced spin generation in a semiconductor
heterojunction two-dimensional hole gas. The polarization results from spin
asymmetric recombination of injected electrons with strongly SO coupled
two-dimensional holes. The possibility to detect magnetized Co particles
deposited on the co-planar diode structure is also demonstrated.",0507143v1
2006-12-21,Deduction of Pure Spin Current from Spin Linear and Circular Photogalvanic Effect in Semiconductor Quantum Wells,"We study the spin photogalvanic effect in two-dimensional electron system
with structure inversion asymmetry by means of the solution of semiconductor
optical Bloch equations. It is shown that a linearly polarized light may inject
a pure spin current in spin-splitting conduction bands due to Rashba spin-orbit
coupling, while a circularly polarized light may inject spin-dependent
photocurrent. We establish an explicit relation between the photocurrent by
oblique incidence of a circularly polarized light and the pure spin current by
normal incidence of a linearly polarized light such that we can deduce the
amplitude of spin current from the measured spin photocurrent experimentally.
This method may provide a source of spin current to study spin transport in
semiconductors quantitatively.",0612542v1
2014-10-07,Y3Fe5O12 Spin Pumping for Quantitative Understanding of Pure Spin Transport and Spin Hall Effect in a Broad Range of Materials,"Using Y3Fe5O12 (YIG) thin films grown by our sputtering technique, we study
dynamic spin transport in nonmagnetic (NM), ferromagnetic (FM) and
antiferromagnetic (AF) materials by ferromagnetic resonance (FMR) spin pumping.
From both inverse spin Hall effect (ISHE) and damping enhancement, we determine
the spin mixing conductance and spin Hall angle in many metals. Surprisingly,
we observe robust spin conduction in AF insulators excited by an adjacent YIG
at resonance. This demonstrates that YIG spin pumping is a powerful and
versatile tool for understanding spin Hall physics, spin-orbit coupling (SOC),
and magnetization dynamics in a broad range of materials.",1410.1597v1
2014-10-10,Spin Hall effect associated with SU(2) gauge field,"In this paper, we focus on the connection between spin Hall effect and spin
force. Here we investigate that the spin force due to spin-orbit coupling,
which in two-dimensional system is equivalent to forces of Hirsch and
Chudnovsky besides constant factors 3 and 3/2 respectively, is a part of
classic Anandan force, and that the spin Hall effect is an anomalous Hall
effect. Furthermore, we develop the method of AC phase to derive the formula
for the spin force, and find that the most basic spin Hall effect originates
from the AC phase and is therefore an intrinsic quantum mechanical property of
spin. This method differs from approach of Berry phase in the study of
anomalous Hall effect, which is the intrinsic property of the perfect crystal.
On the other hand, we use an elegant skill to show that the Chudnovsky-Drude
model is reasonable, and further have improved the theoretical values of spin
Hall conductivity of Chudnovsky. Compared to the theoretical values of spin
Hall conductivity in the Chudnovsky-Drude model, ours are in better agreement
with experimentation. Finally, we discuss the relation between spin Hall effect
and fractional statistics.",1410.3429v1
2014-11-11,Spin Relaxation Mechanism in a Highly Doped Organic Polymer Film,"We report the systematic studies of spin current transport and relaxation
mechanism in highly doped organic polymer film. In this study, we have
determined spin diffusion length (SDL), spin lifetime, and spin diffusion
constant by using different experimental techniques. The spin lifetime
estimated from the electron paramagnetic resonance experiment is much shorter
than the previous expectation beyond the experimental ambiguity. This suggests
that significantly large spin diffusion constant, which is reasonably explained
by the hopping transport mechanism in degenerate semiconductors, exists in
highly doped organic semiconductors. The calculated SDL using the spin lifetime
and spin diffusion constant estimated from our experiment is comparable to the
experimentally obtained SDL of the order of one hundred nanometers. Moreover,
the present study revealed that the spin angular momentum is almost preserved
in the hopping events. In other words, the spin relaxation mainly occurs due to
the spin-orbit coupling at the nanoscale crystalline grains.",1411.2740v1
2019-05-04,Skyrmion quantum spin Hall effect,"The quantum spin Hall effect is conventionally thought to require a strong
spin-orbit coupling, producing an effective spin-dependent magnetic field.
However, spin currents can also be present without transport of spins, for
example, in spin-waves or skyrmions. In this paper, we show that topological
skyrmionic spin textures can be used to realize a quantum spin Hall effect.
From basic arguments relating to the single-valuedness of the wave function, we
deduce that loop integrals of the derivative of the Hamiltonian must have a
spectrum that is integer multiples of $ 2 \pi $. By relating this to the spin
current, we form a new quantity called the quantized spin current which obeys a
precise quantization rule. This allows us to derive a quantum spin Hall effect,
which we illustrate with an example of a spin-1 Bose-Einstein condensate.",1905.01459v2
2017-03-06,Spin circuit representation of spin pumping,"Circuit theory has been tremendously successful in translating physical
equations into circuit elements in organized form for further analysis and
proposing creative designs for applications. With the advent of new materials
and phenomena in the field of spintronics and nanomagnetics, it is imperative
to construct the spin circuit representations for different materials and
phenomena. Spin pumping is a phenomenon by which a pure spin current can be
injected into the adjacent layers. If the adjacent layer is a material with a
high spin orbit coupling, a considerable amount of charge voltage can be
generated via inverse spin Hall effect, allowing spin detection. Here we
develop the spin circuit representation of spin pumping. We then combine it
with the spin circuit representation for the materials having spin Hall effect
to show that it reproduces the standard results in literature. We further show
how complex multilayers can be analyzed by simply writing a netlist.",1704.02338v1
2022-01-04,A comprehensive theory of second-order spin photocurrents,"The spin photocurrents, direct currents induced by light, hold great promise
for introducing new elements to spintronics. However, a general theory for spin
photocurrents in real materials which is applicable to systems with spin-orbit
coupling or noncollinear magnetism is absent. Here, we develop such a general
theory of second-order spin photocurrents. We find that the secondorder spin
photocurrents can be classified into Drude, Berry curvature dipole, shift,
injection, and rectification currents, which have different physical origins
and symmetry properties. Surprisingly, our theory predicts a direct pure spin
rectification current in an insulator induced by photons with energies lower
than the material band gap. This phenomenon is absent in the case of the charge
photocurrent. We find that the pure spin current of BiTeI induced by subgap
light is large enough to be observable in experiments. Moreover, the subgap
pure spin photocurrent is highly tunable with the polarization of light and the
flowing direction of the spin photocurrent. This study lays the groundwork for
the study of nonlinear spin photocurrents in real materials and provides a
route to engineer light-controlled spin currents.",2201.01301v1
2023-07-23,Algorithm for spin symmetry operation search,"A spin space group provides a suitable way to fully exploit the symmetry of a
spin arrangement with a negligible spin-orbit coupling. There has been a
growing interest in applying spin symmetry analysis with the spin space group
in the field of magnetism. However, there is no established algorithm to search
for spin symmetry operations of the spin space group. This paper presents an
exhaustive algorithm for determining spin symmetry operations of commensurate
spin arrangements. The present algorithm searches for spin symmetry operations
from the symmetry operations of a corresponding nonmagnetic crystal structure
and determines their spin-rotation parts by solving a Procrustes problem. An
implementation is distributed under a permissive free software license in
spinspg v0.1.1: https://github.com/spglib/spinspg.",2307.12228v2
2017-12-10,Effective gauge field theory of spintronics,"The aim of this paper is to present a comprehensive theory of spintronics
phenomena based on the concept of effective gauge field, the spin gauge field.
An effective gauge field generally arises when we change a basis to describe
system and describes low energy properties of the system. In the case of
ferromagnetic metals we consider, it arises from structures of localized spin
(magnetization) and couples to spin current of conduction electron. The first
half of the paper is devoted to quantum mechanical arguments and phenomenology.
We show that the spin gauge field has adiabatic and nonadiabatic (off-diagonal)
components, consisting an SU(2) gauge field. The adiabatic component gives rise
to spin Berry's phase, topological Hall effect and spin motive force, while
nonadiabatic components are essential for spin-transfer torque and spin pumping
effects by inducing nonequilibrium spin accumulation. In the latter part of the
paper, field theoretic approaches are described. Dynamics of localized spins in
the presence of applied spin-polarized current is studied in a microscopic
viewpoint, and current-driven domain wall motion is discussed. Recent
developments on interface spin-orbit interaction is also mentioned.",1712.03489v2
2019-12-27,Extrinsic spin Hall effect in inhomogeneous systems,"Charge-to-spin conversion in inhomogeneous systems is studied theoretically.
  We consider free electrons subject to impurities with spin-orbit interaction
and with spatially modulated distribution, and calculate spin accumulation and
spin current induced by an external electric field.
  It is found that the spin accumulation is induced by the vorticity of
electron flow through the side-jump and skew-scattering processes, and the
differences of the two processes are discussed.
  The results can be put in a form of generalized spin diffusion equation with
a spin source term given by the divergence of the spin Hall current.
  This spin source term reduces to the form of spin-vorticity coupling when the
spin Hall angle is independent of impurity concentration. We also study the
effects of long-range Coulomb interaction, which is indispensable when the
process involves charge inhomogeneity and accumulation as in the present
problem.",1912.12077v2
2023-03-08,Spin selective charge recombination in chiral donor-bridge-acceptor triads,"In this paper we outline a physically motivated framework for describing
spin-selective recombination processes in chiral systems, from which we derive
spin-selective reaction operators for recombination reactions of
donor-bridge-acceptor molecules, where the electron transfer is mediated by
chirality and spin-orbit coupling. In general the recombination process is
selective only for spin-coherence between singlet and triplet states, and it is
not in general selective for spin polarisation. We find that spin polarisation
selectivity only arises in hopping mediated electron transfer. We describe how
this effective spin-polarisation selectivity is a consequence of
spin-polarisation generated transiently in the intermediate state. The
recombination process also augments the coherent spin dynamics of the charge
separated state, which is found to have a significant effect on recombination
dynamics and to destroy any long-lived spin polarisation. Although we only
consider a simple donor-bridge-acceptor system, the framework we present here
can be straightforwardly extended to describe spin-selective recombination
processes in more complex systems.",2303.04742v1
2023-10-06,Spin-vibronic dynamics in open-shell systems beyond the spin Hamiltonian formalism,"Vibronic coupling has a dramatic influence over a large number of molecular
processes, ranging from photo-chemistry, to spin relaxation and electronic
transport. The simulation of vibronic coupling with multi-reference
wavefunction methods has been largely applied to organic compounds, and only
early efforts are available for open-shell systems such as transition metal and
lanthanide complexes. In this work, we derive a numerical strategy to
differentiate the molecular electronic Hamiltonian in the context of
multi-reference ab initio methods and inclusive of spin-orbit coupling effects.
We then provide a formulation of open quantum system dynamics able to predict
the time evolution of the electrons' density matrix under the influence of a
Markovian phonon bath up to fourth-order perturbation theory. We apply our
method to Co(II) and Dy(III) molecular complexes exhibiting long spin
relaxation times and successfully validate our strategy against the use of an
effective spin Hamiltonian. Our study shed light on the nature of vibronic
coupling, the importance of electronic excited states in spin relaxation, and
the need for high-level computational chemistry to quantify it.",2310.04278v2
2020-12-17,Superconducting Orbital Magnetoelectric Effect and its Evolution across the Superconductivity Normal Metal Phase Transition,"Superconducting magnetoelectric effect, which is the current-induced
magnetization in a superconductor, mainly focused on the spin magnetization in
previous studies, but ignore the effect of the orbital magnetic moments carried
by the paired Bloch electrons. In this work, we show that orbital magnetic
moments in superconductors can induce large orbital magnetization in the
presence of a current. We constructed a unified description for the
current-induced spin and orbital magnetization across the superconductivity
normal metal phase transition. We find that in a superconductor with uniform
pairing, the current-induced magnetization at a given current density is the
same as that in its normal metal state, while with the nonuniform
superconducting pairing, the current-induced magnetization exhibits an abrupt
change in magnitude near the superconductivity normal metal phase transition.
Importantly, our theory predicts the orbital magnetoelectric effect in
superconducting twisted bilayer graphene which has paired Bloch electrons with
large orbital magnetic moments and negligible spin-orbit coupling. We propose
that the measurement of the current-induced orbital magnetoelectric effect can
be used to detect the possible nonuniform pairings in twisted bilayer graphene
and other newly discovered superconductors with non-trivial Berry curvatures.",2012.09896v3
1996-04-09,Chaos in Schwarzschild Spacetime : The Motion of a Spinning Particle,"We study the motion of a spinning test particle in Schwarzschild spacetime,
analyzing the Poincar\'e map and the Lyapunov exponent. We find chaotic
behavior for a particle with spin higher than some critical value (e.g. $S_{cr}
\sim 0.64 \mu M$ for the total angular momentum $J=4 \mu M$), where $\mu$ and
$M$ are the masses of a particle and of a black hole, respectively. The inverse
of the Lyapunov exponent in the most chaotic case is about three orbital
periods, which suggests that chaos of a spinning particle may become important
in some relativistic astrophysical phenomena. The ``effective potential""
analysis enables us to classify the particle orbits into four types as follows.
When the total angular momentum $J$ is large, some orbits are bounded and the
``effective potential""s are classified into two types: (B1) one saddle point
(unstable circular orbit) and one minimal point (stable circular orbit) on the
equatorial plane exist for small spin; and (B2) two saddle points bifurcate
from the equatorial plane and one minimal point remains on the equatorial plane
for large spin. When $J$ is small, no bound orbits exist and the potentials are
classified into another two types: (U1) no extremal point is found for small
spin; and (U2) one saddle point appears on the equatorial plane, which is
unstable in the direction perpendicular to the equatorial plane, for large
spin. The types (B1) and (U1) are the same as those for a spinless particle,
but the potentials (B2) and (U2) are new types caused by spin-orbit coupling.
The chaotic behavior is found only in the type (B2) potential. The
``heteroclinic orbit'', which could cause chaos, is also observed in type (B2).",9604020v1
2018-03-12,Rotation-symmetry-enforced coupling of spin and angular momentum for p-orbital bosons,"Intrinsic spin angular-momentum coupling of an electron has a relativistic
quantum origin with the coupling arising from charged-orbits, which does not
carry over to charge-neutral atoms. Here we propose a mechanism of spontaneous
generation of spin angular-momentum coupling with spinor atomic bosons loaded
into $p$-orbital bands of a two-dimensional optical-lattice. This spin
angular-momentum coupling originates from many-body correlations and
spontaneous symmetry breaking in a superfluid, with the key ingredients
attributed to spin-channel quantum fluctuations and an approximate rotation
symmetry. The resultant spin angular-momentum intertwined superfluid has Dirac
excitations. In presence of a chemical potential difference for adjacent sites,
it provides a bosonic analogue of a symmetry-protected-topological insulator.
Through a dynamical mean-field calculation, this novel superfluid is found to
be a generic low-temperature phase, and it gives way to Mott localization only
at strong interactions and even-integer fillings. We show the temperature to
reach this order is accessible with present experiments.",1803.04429v2
2010-03-31,Quantum transport in a curved one-dimensional quantum wire with spin-orbit interactions,"The one-dimensional effective Hamiltonian for a planar curvilinear quantum
wire with arbitrary shape is proposed in the presence of the Rashba spin-orbit
interaction. Single electron propagation through a device of two straight lines
conjugated with an arc has been investigated and the analytic expressions of
the reflection and transmission probabilities have been derived. The effects of
the device geometry and the spin-orbit coupling strength $\alpha$ on the
reflection and transmission probabilities and the conductance are investigated
in the case of spin polarized electron incidence. We find that no spin-flip
exists in the reflection of the first junction. The reflection probabilities
are mainly influenced by the arc angle and the radius, while the transmission
probabilities are affected by both spin-orbit coupling and the device geometry.
The probabilities and the conductance take the general behavior of oscillation
versus the device geometry parameters and $\alpha $. Especially the electron
transportation varies periodically versus the arc angle $\theta_{w}$. We also
investigate the relationship between the conductance and the electron energy,
and find that electron resonant transmission occurs for certain energy.
Finally, the electron transmission for the incoming electron with arbitrary
state is considered. For the outgoing electron, the polarization ratio is
obtained and the effects of the incoming electron state are discussed. We find
that the outgoing electron state can be spin polarization and reveal the
polarized conditions.",1003.5972v1
2010-06-03,Spin-Orbit Effects in Carbon-Nanotube Double Quantum Dots,"We study the energy spectrum of symmetric double quantum dots in narrow-gap
carbon nanotubes with one and two electrostatically confined electrons in the
presence of spin-orbit and Coulomb interactions. Compared to GaAs quantum dots,
the spectrum exhibits a much richer structure because of the spin-orbit
interaction that couples the electron's isospin to its real spin through two
independent coupling constants. In a single dot, both constants combine to
split the spectrum into two Kramers doublets, while the antisymmetric constant
solely controls the difference in the tunneling rates of the Kramers doublets
between the dots. For the two-electron regime, the detailed structure of the
spin-orbit split energy spectrum is investigated as a function of detuning
between the quantum dots in a 22-dimensional Hilbert space within the framework
of a single-longitudinal-mode model. We find a competing effect of the
tunneling and Coulomb interaction. The former favors a left-right symmetric
two-particle ground state, while in the regime where the Coulomb interaction
dominates over tunneling, a left-right antisymmetric ground state is found. As
a result, ground states on both sides of the $(11)$-$(02)$ degeneracy point may
possess opposite left-right symmetry, and the electron dynamics when tuning the
system from one side of the $(11)$-$(02)$ degeneracy point to the other is
controlled by three selection rules (in spin, isospin, and left-right
symmetry). We discuss implications for the spin-dephasing and Pauli blockade
experiments.",1006.0724v2
2010-09-26,Exotic phases induced by strong spin-orbit coupling in ordered double perovskites,"We construct and analyze a microscopic model for insulating rock salt ordered
double perovskites, with the chemical formula A$_2$BB'O$_6$, where the B' atom
has a 4d$^1$ or 5d$^1$ electronic configuration and forms a face centered cubic
(fcc) lattice. The combination of the triply-degenerate $t_{2g}$ orbital and
strong spin-orbit coupling forms local quadruplets with an effective spin
moment $j=3/2$. Moreover, due to strongly orbital-dependent exchange, the
effective spins have substantial biquadratic and bicubic interactions (fourth
and sixth order in the spins, respectively). This leads, at the mean field
level, to three main phases: an unusual antiferromagnet with dominant octupolar
order, a ferromagnetic phase with magnetization along the $[110]$ direction,
and a non-magnetic but quadrupolar ordered phase, which is stabilized by
thermal fluctuations and intermediate temperatures. All these phases have a two
sublattice structure described by the ordering wavevector ${\boldsymbol Q}
=2\pi (001)$. We consider quantum fluctuations and argue that in the regime of
dominant antiferromagnetic exchange, a non-magnetic valence bond solid or
quantum spin liquid state may be favored instead. Candidate quantum spin liquid
states and their basic properties are described. We also address the effect of
single-site anisotropy driven by lattice distortions. Existing and possible
future experiments are discussed in light of these results.",1009.5115v1
2012-07-02,Experimental observation of the optical spin-orbit torque,"Spin polarized carriers electrically injected into a magnet from an external
polarizer can exert a spin transfer torque (STT) on the magnetization. The phe-
nomenon belongs to the area of spintronics research focusing on manipulating
magnetic moments by electric fields and is the basis of the emerging
technologies for scalable magnetoresistive random access memories. In our
previous work we have reported experimental observation of the optical
counterpart of STT in which a circularly polarized pump laser pulse acts as the
external polarizer, allowing to study and utilize the phenomenon on several
orders of magnitude shorter timescales than in the electric current induced
STT. Recently it has been theoretically proposed and experimentally
demonstrated that in the absence of an external polarizer, carriers in a magnet
under applied electric field can develop a non-equilibrium spin polarization
due to the relativistic spin-orbit coupling, resulting in a current induced
spin-orbit torque (SOT) acting on the magnetization. In this paper we report
the observation of the optical counterpart of SOT. At picosecond time-scales,
we detect excitations of magnetization of a ferromagnetic semiconductor
(Ga,Mn)As which are independent of the polarization of the pump laser pulses
and are induced by non-equilibrium spin-orbit coupled photo-holes.",1207.0307v1
2020-11-27,Few-electron Single and Double Quantum Dots in an InAs Two-Dimensional Electron Gas,"Most proof-of-principle experiments for spin qubits have been performed using
GaAs-based quantum dots because of the excellent control they offer over
tunneling barriers and the orbital and spin degrees of freedom. Here, we
present the first realization of high-quality single and double quantum dots
hosted in an InAs two-dimensional electron gas (2DEG), demonstrating accurate
control down to the few-electron regime, where we observe a clear Kondo effect
and singlet-triplet spin blockade. We measure an electronic $g$-factor of $16$
and a typical magnitude of the random hyperfine fields on the dots of $\sim
0.6\, \mathrm{mT}$. We estimate the spin-orbit length in the system to be $\sim
5-10\, \mu \mathrm{m}$, which is almost two orders of magnitude longer than
typically measured in InAs nanostructures, achieved by a very symmetric design
of the quantum well. These favorable properties put the InAs 2DEG on the map as
a compelling host for studying fundamental aspects of spin qubits. Furthermore,
having weak spin-orbit coupling in a material with a large Rashba coefficient
potentially opens up avenues for engineering structures with spin-orbit
coupling that can be controlled locally in space and/or time.",2011.13865v1
2023-07-29,Charge-Spin Conversion in Two-Subband Quantum Wells with Conventional and Unconventional Rashba Spin-Orbit Coupling,"The reciprocal interconversion between spin polarization and charge current
(CSC) is the focus of intensive theoretical and experimental investigation in
spintronics research. Its physical origin stems from the Rashba spin-orbit
coupling (SOC) induced by the breaking of the structure inversion symmetry. The
steady-state interconversion efficiency is the result of the non-trivial spin
textures of the electric-field distorted Fermi surface. Its full understanding
and evaluation requires the consideration of disorder-induced relaxation
effects in the presence of spin-orbit induced band splitting. In this paper the
additional effect of the orbital degree of freedom is analyzed in a two-subband
quantum well with both conventional and unconventional Rashba SOC in the
presence of disorder impurity scattering. The latter is treated at the level of
the Born approximation in the Green's function self-energy and with the
inclusion of vertex corrections in the linear response functions for the charge
current and the spin polarization. By explicitly considering the symmetry
properties of the Hamiltonian the matrix structure of the correlation functions
is shown to decompose in independent blocks of symmetry-related physical
observables. We find that the inclusion of vertex corrections is important for
the correct estimate of the CSC efficiency, which also depends on the position
of the Fermi level. We also find that the relative sign of the Rashba SOC in
the two subbands plays a key role in determining the behavior of the CSC.
Finally, we point out how the two-subband model compares with the standard
single-band two-dimensional electron gas.",2307.15923v1
2021-05-24,Role of two-dimensional Ising superconductivity in the non-equilibrium quasiparticle spin-to-charge conversion efficiency,"Non-equilibrium studies of two-dimensional (2D) superconductors (SCs) with
Ising spin-orbit coupling are prerequisite for their successful application to
equilibrium spin-triplet Cooper pairs and, potentially, Majorana fermions. By
taking advantage of the recent discoveries of 2D SCs and their compatibility
with any other materials, we fabricate here non-local magnon devices to examine
how such 2D Ising superconductivity affects the conversion efficiency of magnon
spin to quasiparticle charge in superconducting flakes of 2H-NbSe2 transferred
onto ferrimagnetic insulating Y3Fe5O12. Comparison with a reference device
based on a conventionally paired superconductor shows that the Y3Fe5O12-induced
in-plane (IP) exchange spin-splitting in the NbSe2 flake is hindered by its
inherent out-of-plane (OOP) spin-orbit-field, which, in turn, limits the
transition-state enhancement of the spin-to-charge conversion efficiency. Our
out-of-equilibrium study highlights the significance of symmetry matching
between underlying Cooper pairs and exchange-induced spin-splitting for the
giant transition-state spin-to-charge conversion and may have implications
towards proximity-engineered spin-polarized triplet pairing via tuning the
relative strength of IP exchange and OOP spin-orbit fields in ferromagnetic
insulator/2D Ising SC bilayers.",2105.11159v4
2018-08-20,Anisotropic spin-orbit torque generation in epitaxial SrIrO3 by symmetry design,"Spin-orbit coupling (SOC), the interaction between the electron spin and the
orbital angular momentum, can unlock rich phenomena at interfaces, in
particular interconverting spin and charge currents. Conventional heavy metals
have been extensively explored due to their strong SOC of conduction electrons.
However, spin-orbit effects in classes of materials such as epitaxial
5d-electron transition metal complex oxides, which also host strong SOC, remain
largely unreported. In addition to strong SOC, these complex oxides can also
provide the additional tuning knob of epitaxy to control the electronic
structure and the engineering of spin-to-charge conversion by crystalline
symmetry. Here, we demonstrate room-temperature generation of spin-orbit torque
on a ferromagnet with extremely high efficiency via the spin-Hall effect in
epitaxial metastable perovskite SrIrO3. We first predict a large intrinsic
spin-Hall conductivity in orthorhombic bulk SrIrO3 arising from the Berry
curvature in the electronic band structure. By manipulating the intricate
interplay between SOC and crystalline symmetry, we control the spin-Hall torque
ratio by engineering the tilt of the corner-sharing oxygen octahedra in
perovskite SrIrO3 through epitaxial strain. This allows the presence of an
anisotropic spin-Hall effect due to a characteristic structural anisotropy in
SrIrO3 with orthorhombic symmetry. Our experimental findings demonstrate the
heteroepitaxial symmetry design approach to engineer spin-orbit effects. We
therefore anticipate that these epitaxial 5d transition-metal oxide thin films
can be an ideal building block for low-power spintronics.",1808.06650v1
2015-04-06,Vortex Dynamics in a Spin-Orbit Coupled Bose-Einstein Condensate,"Vortices in a one-component dilute atomic ultracold Bose-Einstein condensate
(BEC) usually arise as a response to externally driven rotation. Apart from a
few special situations, these vortices are singly quantized with unit
circulation. Recently, the NIST group has constructed a two-component BEC with
a spin-orbit coupled Hamiltonian involving Pauli matrices, and I here study the
dynamics of a two-component vortex in such a spin-orbit coupled condensate.
These spin-orbit coupled BECs use an applied magnetic field to split the
hyperfine levels. Hence they rely on a focused laser beam to trap the atoms. In
addition, two Raman laser beams create an effective (or synthetic) gauge
potential. The resulting spin-orbit Hamiltonian is discussed in some detail.
The various laser beams are fixed in the laboratory, so that it is not feasible
to nucleate a vortex by an applied rotation that would need to rotate all the
laser beams and the magnetic field. In a one-component BEC, a vortex can also
be created by a thermal quench, starting from the normal state and suddenly
cooling deep into the condensed state. I propose that a similar method would
work for a vortex in a spin-orbit coupled BEC. Such a vortex has two
components, and each has its own circulation quantum number. If both components
have the same circulation, I find that the composite vortex should execute
uniform precession, like that observed in a single-component BEC. In contrast,
if one component has unit circulation and the other has zero circulation, then
some fraction of the dynamical vortex trajectories should eventually leave the
condensate, providing clear experimental evidence for this unusual vortex
structure. In the context of exciton-polariton condensates, such a vortex is
known as a ""half-quantum vortex"".",1504.01314v1
2015-12-16,Spin-orbit transitions in $α$ and $γ$-CoV$_{2}$O$_{6}$,"$\gamma$-triclinic and $\alpha$-monoclinic polymorphs of CoV$_{2}$O$_{6}$ are
two of the few known transition metal ion based materials that display stepped
$1/3$ magnetization plateaus at low temperatures. Neutron diffraction [M.
Markkula et al. Phys. Rev. B 86, 134401 (2012)], x-ray dichroism [N. Hollmann
et al. Phys. Rev. B 89, 201101(R) (2014)], and dielectric measurements [K.
Singh et al. J. Mater. Chem. 22, 6436 (2012)] have shown a coupling between
orbital, magnetic and structural orders in CoV$_{2}$O$_{6}$. We apply neutron
inelastic scattering to investigate this coupling by measuring the spin-orbit
transitions in both $\alpha$ and $\gamma$ polymorphs. We find the spin-exchange
and anisotropy in monoclinic $\alpha$-CoV$_{2}$O$_{6}$ to be weak in comparison
with the spin-orbit coupling $\lambda$ and estimate an upper limit of
$|J/\lambda| \sim$ 0.05. However, the spin exchange is larger in the triclinic
polymorph and we suggest the excitations are predominately two dimensional. The
local compression of the octahedra surrounding the Co$^{2+}$ ion results in a
direct coupling between higher energy orbital levels, the magnetic ground
state, and elastic strain. CoV$_{2}$O$_{6}$ is therefore an example where the
local distortion along with the spin-orbit coupling provides a means of
intertwining structural and magnetic properties. We finish the paper by
investigating the low-energy magnetic fluctuations within the ground state
doublet and report a magnetic excitation that is independent of the local
crystalline electric field. We characterize the temperature and momentum
dependence of these excitations and discuss possible connections to the
magnetization plateaus.",1512.05071v1
2009-10-08,Three orbital model for the iron-based superconductors,"The theoretical need to study the properties of the Fe-based high-T_c
superconductors with reliable many-body techniques requires us to determine the
minimum number of orbital degrees of freedom that will capture the physics of
these materials. While the shape of the Fermi surface (FS) obtained with the
local density approximation (LDA) can be reproduced by a two-orbital model, it
has been argued that the bands that cross the chemical potential result from
the strong hybridization of three of the Fe 3d orbitals. For this reason, a
three-orbital Hamiltonian obtained with the Slater-Koster formalism by
considering the hybridization of the As p orbitals with the Fe d_xz,d_yz, and
d_xy orbitals is discussed here. This model reproduces qualitatively the FS
shape and orbital composition obtained by LDA calculations for undoped
pnictides when four electrons per Fe are considered. Within a mean-field
approximation, its magnetic and orbital properties in the undoped case are
described. With increasing Coulomb repulsion, four regimes are obtained: (1)
paramagnetic, (2) magnetic (pi,0) spin order, (3) the same (pi,0) spin order
but now including orbital order, and finally (4) a magnetic and orbital ordered
insulator. The spin-singlet pairing operators allowed by the lattice and
orbital symmetries are also constructed. It is found that for pairs of
electrons involving up to diagonal nearest-neighbors sites, the only fully
gapped and purely intraband spin-singlet pairing operator is given by
Delta(k)=f(k)\sum_{alpha} d_{k,alpha,up}d_{-k,alpha,down} with f(k)=1 or
f(k)=cos(k_x)cos(k_y) which would arise only if the electrons in all different
orbitals couple with equal strength to the source of pairing.",0910.1573v3
2005-04-29,Strain-Induced Coupling of Spin Current to Nanomechanical Oscillations,"We propose a setup which allows to couple the electron spin degree of freedom
to the mechanical motions of a nanomechanical system not involving any of the
ferromagnetic components. The proposed method employs the strain induced
spin-orbit interaction of electrons in narrow gap semiconductors. We have shown
how this method can be used for detection and manipulation of the spin flow
through a suspended rod in a nanomechanical device.",0504773v2
2007-01-09,Electron scattering from a mesoscopic disk in Rashba system,"Electrons with spin-orbit coupling moving in mesoscopic structures can often
exhibit local spin polarization. In this paper, we study the influence of the
Rashba coupling on the scattering of two-dimensional electrons from a circular
disk. It is observed that spin-polarized regions exist, even if the incident
electrons are unpolarized. In addition to the distributions of charge and spin
current in the near-field region, we also analyze the symmetry and the
differential cross-section of the scattering.",0701162v1
2006-11-18,Axial exchange currents and nucleon spin,"We calculate the hypercharge and flavor singlet axial couplings related to
the spin of the nucleon in a constituent quark model. In addition to the
standard one-body axial currents, the model includes two-body axial exchange
currents. The latter are necessary to satisfy the Partial Conservation of Axial
Current (PCAC) condition. For both axial couplings we find significant
corrections to the standard quark model prediction. Exchange currents reduce
the valence quark contribution to the nucleon spin and afford an interpretation
of the missing nucleon spin as orbital angular momentum carried by nonvalence
quark degrees of freedom.",0611248v1
2021-10-13,Spin elastodynamic motive force,"The spin-motive force (SMF) in a simple ferromagnetic monolayer caused by a
surface acoustic wave is studied theoretically via spin-vorticity coupling
(SVC). The SMF has two mechanisms. The first is the SVC-driven SMF, which
produces the first harmonic electromotive force, and the second is the
interplay between the SVC and the magentoelastic coupling, which produces the
d.c. and second harmonic electromotive forces. We show that these electric
voltages induced by a Rayleigh-type surface acoustic wave can be detected in
polycrystalline nickel. No sophisticated device structures, non-collinear
magnetic structures, or strong spin-orbit materials are used in our approach.
Consequently, it is intended to broaden the spectrum of SMF applications
considerably.",2110.06552v1
2024-03-15,General-order open-shell coupled-cluster method with partial spin adaptation I: formulations,"A general-order open-shell coupled-cluster method based on spatial orbitals
is formulated. The method is an extension of the partial-spin adaptation (PSA)
scheme from Janssen and Schaefer (Theor. Chim. Acta, 79, 1-42, 1991). By
increasing the order of excitation operator and spin adaptation, the full
configuration interaction (CI) limit is expected to be achieved. In the
meanwhile, the advantages of spin-free approach in closed-shell systems:
fourth-order truncation of the Baker-Campbell-Hausdorff (BCH) expansion and
only $HT$-type connected terms are conserved.",2403.10128v1
2002-04-04,Chirality driven anomalous Hall effect in weak coupling regime,"Anomalous Hall effect arising from non-trivial spin configuration (chirality)
is studied based on the $s$-$d$ model. Considering a weak coupling case, the
interaction is treated perturbatively. Scattering by normal impurities is
included. Chirality is shown to drive locally Hall current and leads to overall
Hall effect if there is a finite uniform chirality. This contribution is
independent of the conventional spin-orbit contribution and shows distinct low
temperature behavior. In mesoscopic spin glasses, chirality-induced anomalous
Hall effect is expected below the spin-glass transition temperature.
Measurement of Hall coefficient would be useful in experimentally confirming
the chirality ordering.",0204096v1
2010-08-11,"Chirality, charge and spin-density wave instabilities of a two-dimensional electron gas in the presence of Rashba spin-orbit coupling","We show that a result equivalent to Overhauser's famous Hartree-Fock
instability theorem can be established for the case of a two-dimensional
electron gas in the presence of Rashba spin-obit coupling. In this case it is
the spatially homogeneous paramagnetic chiral ground state that is shown to be
differentially unstable with respect to a certain class of distortions of the
spin-density-wave and charge-density-wave type. The result holds for all
densities. Basic properties of these inhomogeneous states are analyzed.",1008.1816v1
2011-06-07,Goldstone Mode Relaxation in a Quantum Hall Ferromagnet due to Hyperfine Interaction with Nuclei,"Spin relaxation in quantum Hall ferromagnet regimes is studied. As the
initial non-equilibrium state, a coherent deviation of the spin system from the
${\vec B}$ direction is considered and the breakdown of this Goldstone-mode
state due to hyperfine coupling to nuclei is analyzed. The relaxation occurring
non-exponentially with time is studied in terms of annihilation processes in
the ""Goldstone condensate"" formed by ""zero spin excitons"". The relaxation rate
is calculated analytically even if the initial deviation is not small. This
relaxation channel competes with the relaxation mechanisms due to spin-orbit
coupling, and at strong magnetic fields it becomes dominating.",1106.1386v1
2012-12-17,Quantum Anomalous Hall Effect in Kagome Ice,"An anomalous Hall insulator without magnetic long-range ordering is
theoretically reported in the absence of the relativistic spin-orbit coupling.
It is realized in itinerant electrons coupled with the Ising spins on a <111>
kagome plane of pyrochlore spin ice in applied magnetic field. We find that the
kagome-ice type local spin correlation in the magnetization plateau state opens
a charge gap without magnetic ordering, which results in quantization of the
Hall conductivity. By Monte Carlo simulation, we identify the anomalous Hall
insulating region in the magnetic phase diagram, in addition to another
anomalous Hall insulator in a fully-saturated state.",1212.3855v1
1998-03-28,Anomalous Hall Effect in Double Exchange Magnets,"We investigate the possible origin of anomalous Hall effect in the CMR
(colossal magnetoresistance) materials - the doped rare earth manganites -
observed recently by Matl et al. It is demonstrated that the spin-orbit
interaction in the double exchange model couples magnetization to the Berry
phase associated with three dimensional spin textures and induces a non-zero
average topological flux which in turn generates an anomalous contribution to
transverse resistivity. The same effect, but involving the orbital Berry phase,
occurs in the model with orbital degeneracy and Coulomb repulsion.",9803350v1
1999-04-29,Spin and orbital ordering in double-layered manganites,"We study theoretically the phase diagram of the double-layered perovskite
manganites taking into account the orbital degeneracy, the strong Coulombic
repulsion, and the coupling with the lattice deformation. Observed spin
structural changes as the increased doping are explained in terms of the
orbital ordering and the bond-length dependence of the hopping integral along
$c$-axis. Temperature dependence of the neutron diffraction peak corresponding
to the canting structure is also explained. Comparison with the 3D cubic system
is made.",9904427v1
2002-07-28,Anisotropy of Mott-Hubbard gap transitions due to spin and orbital ordering in LaVO3 and YVO3,"Anisotropic optical spectra coupled with antiferromagnetic spin ordering (SO)
and orbital ordering (OO) have been investigated for single crystals of
LaVO_{3} and YVO_{3}. The orbital-dependent Mott-Hubbard gap transitions are
observed around 2 eV. The transitions composed of the two peaks show distinct
anisotropy and selection rules, reflecting the respective SO and OO patterns.
The temperature dependence of the anisotropic transitions clearly indicates the
SO/OO correlation and the evolution of the order parameters.",0207664v1
2005-10-05,Orbital Polarization in Itinerant Magnets,"We propose a parameter-free scheme of calculation of the orbital polarization
(OP) in metals, which starts with the strong-coupling limit for the screened
Coulomb interactions in the random-phase approximation (RPA). For itinerant
magnets, RPA can be further improved by restoring the spin polarization of the
local-spin-density approximation (LSDA) through the local-field corrections.
The OP is then computed in the static GW approach, which systematically
improves the orbital magnetization and the magnetic anisotropy energies in
transition-metal and actinide compounds.",0510100v1
2005-11-30,Evidence for electronic phase separation between orbital orderings in SmVO3,"We report evidence for phase coexistence of orbital orderings of different
symmetry in SmVO$_3$ by high resolution X-Ray powder diffraction. The phase
coexistence is triggered by an antiferromagnetic ordering of the vanadium spins
near 130K, below an initial orbital ordering near 200K. The phase coexistence
is the result of the intermediate ionic size of samarium coupled to exchange
striction at the vanadium spin ordering.",0511744v1
2018-04-12,Spinon-orbiton repulsion and attraction mediated by Hund's rule,"We study the impact of Hund's-rule coupling on orbital excitations, as e.g.
measured in inelastic resonant x-ray scattering. We find that the
interpretation in terms of spin-orbit separation, which has been derived for
one-dimensional systems without Hund's rule, remains robust in its presence.
Depending on whether or not the orbital excitation includes a spin excitation,
Hund's rule leads to an attractive or repulsive interaction between spinon and
orbiton. Attraction and repulsion leave clear signatures through a transfer of
spectral weight to the lower resp. upper edge of the spectrum.",1804.04462v1
2000-10-09,Almost Non-Magnetic Ground State of the V4+ Ion: The case of BaVS3,"We have shown that the V4+ ion with 1 d electron can have almost non-magnetic
ground state under the action of the octahedral crystal field in the presence
of the spin-orbit coupling and off-cubic distortions. Such the situation occurs
in the hexagonal BaVS3. The fine discrete electronic structure with the
weakly-magnetic Kramers-doublet ground state is the reason for anomalous
properties of BaVS3.
  Keywords: crystal-field, spin-orbit, orbital moment. PACS: 71.70.E, 75.10.D",0010135v1
2007-06-22,Orbital and Spin Excitations in Cobalt Oxide,"By means of neutron scattering we have determined new branches of magnetic
excitations in orbitally active CoO (TN=290 K) up to 15 THz and for
temperatures from 6 K to 450 K. Data were taken in the (111) direction in six
single-crystal zones. From the dependence on temperature and Q we have
identified several branches of magnetic excitation. We describe a model for the
coupled orbital and spin states of Co2+ subject to a crystal field and
tetragonal distortion.",0706.3345v1
2020-07-07,Twisting Neutral Particles with Electric Fields,"We demonstrate that spin-orbit coupled states are generated in neutral
magnetic spin 1/2 particles travelling through an electric field. The
quantization axis of the orbital angular momentum is parallel to the electric
field, hence both longitudinal and transverse orbital angular momentum can be
created. Furthermore we show that the total angular momentum of the particle is
conserved. Finally we propose a neutron optical experiment to measure the
transverse effect.",2007.03345v3
2014-09-22,Phase separation in a spin-orbit coupled Bose-Einstein condensate,"We study a spin-orbit (SO) coupled hyperfine spin-1 Bose-Einstein condensate
(BEC) in a quasi-one-dimensional trap. For a SO-coupled BEC in a
one-dimensional box, we show that in the absence of the Rabi term, any non-zero
value of SO coupling will result in a phase separation among the components for
a ferromagnetic BEC, like $^{87}$Rb. On the other hand, SO coupling favors
miscibility in a polar BEC, like $^{23}$Na. In the presence of a harmonic trap,
which favors miscibility, a ferromagnetic BEC phase separates, provided the
SO-coupling strength and number of atoms are greater than some critical value.
The Rabi term favors miscibility irrespective of the nature of the spin
interaction: ferromagnetic or polar.",1409.6211v2
2020-12-01,"Multi-ring, stripe, and super-lattice solitons in a spin-orbit coupled spin-1 condensate","We demonstrate exotic stable quasi-two-dimensional solitons in a Rashba or a
Dresselhaus spin-orbit (SO) coupled hyperfine spin-1 ($F=1$) trap-less
antiferromagnetic Bose-Einstein condensate using the mean-field
Gross-Pitaevskii equation. For weak SO coupling, the solitons are of the
$(-1,0,+1)$ or $(+1,0,-1)$ type with intrinsic vorticity, for Rashba or
Dresselhaus SO coupling, where the numbers in the parentheses denote angular
momentum in spin components $F_z= +1,0,-1$, respectively. For intermediate SO
coupling, the solitons have multi-ring structure maintaining the
above-mentioned vortices in respective components. For larger SO coupling,
superlattice solitons with a square-lattice structure in total density are
found in addition to stripe solitons with stripe pattern in component densities
with no periodic modulation in total density.",2012.00872v2
2004-01-07,Spin-triplet s-wave local pairing induced by Hund's rule coupling,"We show within the dynamical mean field theory that local multiplet
interactions such as Hund's rule coupling produce local pairing
superconductivity in the strongly correlated regime. Spin-triplet
superconductivity driven by the Hund's rule coupling emerges from the pairing
mediated by local fluctuations in pair exchange. In contrast to the
conventional spin-triplet theories, the local orbital degrees of freedom has
the anti-symmetric part of the exchange symmetry, leaving the spatial part as
fully gapped and symmetric s-wave.",0401104v1
2016-12-11,Electronic origin of spin-phonon coupling effect in transition-metal perovskites,"By applying Wannier-based extended Kugel-Khomskii model, we carry out
first-principles calculations and electronic structure analysis to understand
the spin-phonon coupling effect in transition-metal perovskites. We demonstrate
the successful application of our approach to SrMnO$_3$ and BiFeO$_3$. We show
that both the electron orbitals under crystal field splitting and the
electronic configuration should be taken into account in order to understand
the large variances of spin-phonon coupling effects among various phonon modes
as well as in different materials.",1612.03436v1
2021-05-21,OpenMP solver for rotating spin-one spin-orbit- and Rabi-coupled Bose-Einstein condensates,"We present OpenMP version of a Fortran program for solving the
Gross-Pitaevskii equation for a harmonically trapped three-component rotating
spin-1 spinor Bose-Einstein condensate (BEC) in two spatial dimensions with or
without spin-orbit (SO) and Rabi couplings. The program uses either Rashba or
Dresselhaus SO coupling. We use the split-step Crank-Nicolson discretization
scheme for imaginary- and real-time propagation to calculate stationary states
and BEC dynamics, respectively.",2105.10517v1
2009-05-15,Polarized DIS in N=4 SYM: Where is spin at strong coupling?,"Using the AdS/CFT correspondence, we calculate the polarized structure
functions in strongly coupled N=4 supersymmetric Yang-Mills theory deformed in
the infrared. We find that the flavor singlet contribution to the g_1 structure
function is vanishingly small, while the flavor non-singlet contribution shows
the Regge behavior at small-x with an intercept slightly less than 1. We
explicitly check that the latter satisfies the moment sum rule. We discuss the
`spin crisis' problem and suggest that at strong coupling the spin of a hadron
entirely comes from the orbital angular momentum.",0905.2493v1
2012-05-15,Magnetic softness in iron-based superconductors,"We examine the relevance of several major material-dependent parameters to
the magnetic softness in iron-base superconductors by first-principles
electronic structure analysis of their parent compounds. The results are
explained in the spin-fermion model where localized spins and orbitally
degenerate itinerant electrons coexist and are coupled by Hund's rule coupling.
We found that the difference in the strength of the Hund's rule coupling term
is the major material-dependent microscopic parameter for determining the
ground-state spin pattern. The magnetic softness in iron-based superconductors
is essentially driven by the competition between the double-exchange
ferromagnetism and the superexchange antiferromagnetism.",1205.3509v1
2021-08-07,Dynamic electron-phonon and spin-phonon interactions due to inertia,"THz radiation allows for the controlled excitation of vibrational modes in
molecules and crystals. We show that the circular motion of ions introduces
inertial effects on electrons. In analogy to the classical Coriolis and
centrifugal forces, these effects are the spin-rotation coupling, the
centrifugal field coupling, the centrifugal spin-orbit coupling, and the
centrifugal redshift. Depending on the phonon decay, these effects persist for
various picoseconds after excitation. Potential boosting of the effects would
make it a promising platform for vibration-based control of localized quantum
states or chemical reaction barriers.",2108.03473v2
2011-02-19,Realistic Rashba and Dressehaus spin-orbit coupling for neutral atoms,"We describe a new class of atom-laser coupling schemes which lead to
spin-orbit coupled Hamiltonians for ultra-cold neutral atoms. By properly
setting the optical phases, a pair of degenerate pseudospin states emerge as
the lowest energy states in the spectrum, and are thus immune to collisionally
induced decay. These schemes use $N$ cyclically coupled ground or metastable
internal states. We specialize to two situations: a three level case giving
fixed Rashba coupling, and a four-level case that adds a controllable
Dresselhaus contribution. We describe an implementation of the four level
scheme for $\Rb87$ and analyze the sensitivity of our approach to realistic
experimental limitations and imperfections. Lastly, we argue that no laser
coupling scheme can give pure Rashba or Dresselhaus coupling: akin to condensed
matter systems, higher order terms spoil the symmetry of these couplings.
However, for sufficiently intense laser fields the continuous rotational
symmetry approximately holds, making the Rashba Hamiltonian applicable for cold
atoms.",1102.3945v2
2014-11-27,Efimov physics and universal trimer in spin-orbit coupled ultracold atomic mixtures,"We study the two-body and three-body bound states in ultracold atomic
mixtures with one of the atoms subjected to an isotropic spin-orbit (SO)
coupling. We consider a system of two identical fermions interacting with one
SO coupled atom. It is found that there can exist two types of three-body bound
states, Efimov trimers and universal trimers. The Efimov trimers are
energetically less favored by the SO coupling, which will finally merge into
the atom-dimer threshold as increasing the SO coupling strength. Nevertheless,
these trimers exhibit a new kind of discrete scaling law incorporating the SO
coupling effect. On the other hand, the universal trimers are more favored by
the SO coupling. They can be induced at negative s-wave scattering lengths and
with smaller mass ratios than those without SO coupling. These results are
obtained by both the Born-Oppenheimer approximation and exact solutions from
three-body equations.",1411.7488v1
2013-09-04,"Excitons in quantum dot molecules: Coulomb coupling, spin-orbit effects and phonon-induced line broadening","Excitonic states and the line shape of optical transitions in coupled quantum
dots (quantum dot molecules) are studied theoretically. For a pair of
electrically tunable, vertically aligned quantum dots we investigate the
coupling between spatially direct and indirect excitons caused by different
mechanisms such as tunnel coupling, Coulomb coupling, coupling due to the
spin-orbit interaction and coupling induced by a structural asymmetry. The
peculiarities of the different types of couplings are reflected in the
appearance of either crossings or avoided crossings between direct and indirect
excitons, the latter ones being directly visible in the absorption spectrum. We
analyze the influence of the phonon environment on the spectrum by calculating
the line shape of the various optical transitions including contributions due
to both pure dephasing and phonon-induced transitions between different exciton
states. The line width enhancement due to phonon-induced transitions is
particularly pronounced in the region of an anticrossing and it strongly
depends on the energy splitting between the two exciton branches.",1309.1032v2
2015-06-15,Hole spin relaxation in bilayer WSe$_2$,"We investigate the hole spin relaxation due to the Rashba spin-orbit coupling
induced by an external perpendicular electric field in bilayer WSe$_2$. The
Rashba spin-orbit coupling coefficients in bilayer WSe$_2$ are constructed from
the corresponding monolayer ones. In contrast to monolayer WSe$_2$, the
out-of-plane component of the bilayer Rashba spin-orbit coupling acts as a
Zeeman-like field with opposite directions but identical values in the two
valleys. For in-plane spins, this Zeeman-like field, together with the
intervalley hole-phonon scattering, opens an intervalley spin relaxation
channel, which is found to dominate the in-plane spin relaxation in bilayer
WSe$_2$ even at low temperature. For out-of-plane spins, this Zeeman-like field
is superimposed by the identical Hartree-Fock effective magnetic fields in the
two valleys, and hence different total effective magnetic fields between two
valleys are obtained. Owing to the large difference of the total fields at
large spin polarization, different out-of-plane spin relaxation times in the
two valleys are obtained when the intervalley hole-phonon scattering is weak at
low temperature and low hole density. This difference in the spin relaxation
times can be suppressed by enhancing the intervalley hole-phonon scattering
through increasing temperature or hole density. Moreover, at large spin
polarization and low temperature, due to the weak intravalley hole-phonon
scattering but relatively strong hole-hole Coulomb scattering, the fast spin
precessions are found to result in a quasi hot-hole Fermi distribution
characterized by an effective hot-hole temperature larger than the temperature,
which also enhances the intervalley scattering. During this process, it is
interesting to discover that the initially equal hole densities in the two
valleys are broken in the temporal evolution, and a valley polarization is
built up. ....",1506.04482v1
2015-11-17,"Spin Dynamics of Complex Oxides, Bismuth-Antimony Alloys, and Bismuth Chalcogenides","This thesis predicts that two types of material families could be a solution
to the challenges in spintronics: complex oxides and bismuth based materials.
We derive a general approach for constructing an effective spin-orbit
Hamiltonian, which applies to all nonmagnetic materials. We also verify this
formalism through comparisons with other approaches for III-V semiconductors.
Its general applicability is illustrated by deriving the spin-orbit interaction
and predicting spin lifetimes for strained SrTiO$_3$ and a two-dimensional
electron gas (such as at the LaAlO$_3$/SrTiO$_3$ interface). Our results
suggest robust spin coherence and spin transport properties in SrTiO$_3$
related materials. In the second part, we calculate intrinsic spin Hall
conductivities for Bi$_{1-x}$Sb$_x$ semimetals with strong spin-orbit
couplings, from the Kubo formula and using Berry curvatures evaluated from a
tight-binding Hamiltonian. Nearly crossing bands with strong spin-orbit
interaction generate giant spin Hall conductivities in these materials, ranging
from 474 ($\hbar/e)( \Omega^{-1}cm^{-1}$) for bismuth to 96($\hbar/e)(
\Omega^{-1}cm^{-1}$) for antimony; the value for bismuth is more than twice
that of platinum. The large spin Hall conductivities persist for alloy
compositions corresponding to a three-dimensional topological insulator state,
such as Bi$_{0.83}$Sb$_{0.17}$. The spin Hall conductivity could be changed by
a factor of 5 for doped Bi, or for Bi$_{0.83}$Sb$_{0.17}$, by changing the
chemical potential, suggesting the potential for doping or voltage tuned spin
Hall current. We also calculate intrinsic spin Hall conductivities of
Bi$_2$Se$_3$ and Bi$_2$Te$_3$ topological insulators from an effective
tight-binding Hamiltonian. We conclude that bismuth-antimony alloys and bismuth
chalcogenides are primary candidates for efficiently generating spin currents
through the spin Hall effect.",1511.05276v1
2001-05-03,Ballistic spin-polarized transport and Rashba spin precession in semiconductor nanowires,"We present numerical calculations of the ballistic spin-transport properties
of quasi-one-dimensional wires in the presence of the spin-orbit (Rashba)
interaction. A tight-binding analog of the Rashba Hamiltonian which models the
Rashba effect is used. By varying the robustness of the Rashba coupling and the
width of the wire, weak and strong coupling regimes are identified. Perfect
electron spin-modulation is found for the former regime, regardless of the
incident Fermi energy and mode number. In the latter however, the
spin-conductance has a strong energy dependence due to a nontrivial subband
intermixing induced by the strong Rashba coupling. This would imply a strong
suppression of the spin-modulation at higher temperatures and source-drain
voltages. The results may be of relevance for the implementation of
quasi-one-dimensional spin transistor devices.",0105049v1
2007-03-01,Driven dissipative dynamics of spins in quantum dots,"We have studied the dissipative dynamics of a driven electronic spin trapped
in a quantum dot. We consider the dissipative mechanism as due to the indirect
coupling of the electronic spin to acoustic phonons via the
spin-orbit/electron-phonon couplings. Using an effective spectral function of
the dissipative phonon bath, we evaluated the expectation values of the spin
components through the Bloch-Redfield theory. We show that due to a sharp bath
resonance present in the effective spectral function, with typical energy much
smaller than the electronic confinement energy, the dissipative spin has a rich
dynamical behavior that helps us to determine some features of the spin-bath
coupling. We also quantify the effects produced by the sharp bath resonance,
and thus indicate the best regimes of operation in order to achieve the longest
relaxation times for the spin.",0703009v1
2018-12-03,Two-dimensional spin-valley-coupled Dirac semimetals in functionalized SbAs monolayers,"In the presence of spin-orbit coupling (SOC), achieving both spin and valley
polarized Dirac state is significant to promote the fantastic integration of
Dirac physics, spintronics and valleytronics. Based on ab initio calculations,
here we demonstrate that a class of spin-valley-coupled Dirac semimetals
(svc-DSMs) in the functionalized SbAs monolayers (MLs) can host such desired
state. Distinguished from the graphene-like 2D Dirac materials, the Dirac cones
in svc-DSMs hold giant spin-splitting induced by strong SOC under inversion
symmetry breaking. In the 2.3% strained SbAsH2 ML, the Dirac fermions in
inequivalent valleys have opposite Berry curvature and spin moment, giving rise
to Dirac spin-valley Hall effect with constant spin Hall conductivity as well
as massless and dissipationless transport. Topological analysis reveals that
the svc-DSM emerges at the boundary between trivial and 2D topological
insulators, which provides a promising platform for realizing the flexible and
controllable tuning among different quantum states.",1812.00867v1
2021-10-11,Monte Carlo simulations of spin transport in nanoscale In$_{0.7}$Ga$_{0.3}$As transistors: Temperature and size effects,"Spin-based metal-oxide-semiconductor field-effect transistors (MOSFET) with a
high-mobility III-V channel are studied using self-consistent quantum corrected
ensemble Monte Carlo device simulations of charge and spin transport. The
simulations including spin-orbit coupling mechanisms (Dresselhaus and Rashba
coupling) examine the electron spin transport in the 25 nm gate length
In$_{0.7}$Ga$_{0.3}$As MOSFET. The transistor lateral dimensions (the gate
length, the source-to-gate, and the gate-to-drain spacers) are increased to
investigate the spin-dependent drain current modulation induced by the gate
from room temperature of 300 K down to 77 K. This modulation increases with
increasing temperature due to increased Rashba coupling. Finally, an increase
of up to 20 nm in the gate length, source-to-gate, or the gate-to-drain spacers
increases the spin polarization and enhances the spin-dependent drain current
modulation at the drain due to polarization-refocusing effects.",2110.05366v2
2022-07-14,Dzyaloshinskii-Moriya spin density by skew scattering,"Anisotropic exchange couplings, such as the Dzyaloshinskii-Moriya interaction
(DMI), have played a vital role in the formation and dynamics of spin textures.
This work predicts an anisotropic conduction electron spin density in metals
with heavy magnetic impurities. The polarization of this
$Dzyaloshinskii$-$Moriya$ $spin$ $density$ (DM-SD) is not collinear to the
localized magnetic moments but rotated by the spin-dependent skew scattering of
heavy atoms. The DM-SD induces the DMI between magnetic moments in metals and,
therefore, it is the anisotropic extension of the
Rutherman-Kittel-Kasuya-Yoshida spin density. Our model consists of two
localized magnetic moments, one with a large spin-orbit coupling (a lanthanide
or rare earth), in a free electron gas. The lanthanide spin controls the DM-SD
strength and polarization, promising a flexible control mechanism for
anisotropic couplings.",2207.06842v2
2009-09-22,Spin Hall and longitudinal conductivity of a conserved spin current in two dimensional heavy-hole gases,"The spin Hall and longitudinal conductivity of a 2D heavy-hole gas with {\it
k}-cubic Rashba and Dresselhaus spin-orbit interaction is studied in the ac
frequency domain. Using Kubo linear-response theory and a recently proposed
definition for the (conserved) spin current operator suitable for spin-3/2
holes, it is shown that the spin conductivity tensor exhibit very
distinguishable features from those obtained with the standard definition of
the spin current. This is due to a significant contribution of the spin-torque
term arisen from the alternative definition of spin current which strongly
affects the magnitude and the sign of the dynamic spin current. In the dc (free
of disorder) limit, the spin Hall conductivity for only (or dominant) {\it
k}-cubic Rashba coupling is $\sigma^{s,z}_{xy}(0)=-9e/8\pi$, whereas
$\sigma^{s,z}_{xy}(0)=-3e/8\pi$ for only (or dominant) {\it k}-cubic
Dresselhaus coupling. Such anisotropic response is understood in terms of the
absence of mapping the {\it k}-cubic Rashba $\leftrightarrow$ Dresselhaus
Hamiltonians. This asymmetry is also responsible for the non-vanishing dc spin
Hall conductivity ($\sigma^{s,z}_{xy}(0)=-6e/8\pi$) when the Rashba and
Dresselhaus parameters have the same strength, in contrast with its
corresponding case for electrons. These results are of relevance to validate
the alternative definition of spin-current through measurements in the
frequency domain of the spin accumulation and/or spin currents in 2D hole
gases.",0909.4045v3
2011-04-23,Orbital density wave induced by electron-lattice coupling in orthorhombic iron pnictides,"In this paper we explore the magnetic and orbital properties closely related
to a tetragonal-orthorhombic structural phase transition in iron pnictides
based on both two- and five-orbital Hubbard models. The electron-lattice
coupling, which interplays with electronic interaction, is self-consistently
treated. Our results reveal that the orbital polarization stabilizes the spin
density wave (SDW) order in both tetragonal and orthorhombic phases. However,
the ferro-orbital density wave (F-ODW) only occurs in the orthorhombic phase
rather than in the tetragonal one. Magnetic moments of Fe are small in the
intermediate Coulomb interaction region for the striped antiferromangnetic
phase in the realistic five orbital model. The anisotropic Fermi surface in the
SDW/ODW orthorhombic phase is well in agreement with the recent angle-resolved
photoemission spectroscopy experiments. These results suggest a scenario that
the magnetic phase transition is driven by the ODW order mainly arising from
the electron-lattice coupling.",1104.4575v1
2023-05-23,Metamagnetic transition in the two $f$ orbitals Kondo lattice model,"In this work, we study the effects of a transverse magnetic field in a Kondo
lattice model with two $f$ orbitals interacting with the conduction electrons.
The $f$ electrons that are present on the same site interact through Hund's
coupling, while on neighboring sites they interact through intersite exchange.
We consider here that part of $f$ electrons are localized (orbital 1) while
another part (orbital 2) are delocalized, as it is frequent in uranium systems.
Then, only electrons in the localized orbital 1 interact through exchange
interaction with the neighboring ones, while electrons in orbital 2 are coupled
with conduction electrons through a Kondo interaction. We obtain a solution
where ferromagnetism and Kondo effect coexist for small values of an applied
transverse magnetic field for $T\rightarrow0$. Increasing the transverse field,
two situations can be obtained when Kondo coupling vanishes: first, a
metamagnetic transition occurs just before or at the same time of the fully
polarized state, and second, a metamagnetic transition occurs when the spins
are already pointing out along the magnetic field.",2305.13559v1
2006-05-09,Circular orbits and spin in black-hole initial data,"The construction of initial data for black-hole binaries usually involves the
choice of free parameters that define the spins of the black holes and
essentially the eccentricity of the orbit. Such parameters must be chosen
carefully to yield initial data with the desired physical properties. In this
paper, we examine these choices in detail for the quasiequilibrium method
coupled to apparent-horizon/quasiequilibrium boundary conditions. First, we
compare two independent criteria for choosing the orbital frequency, the
""Komar-mass condition"" and the ""effective-potential method,"" and find excellent
agreement. Second, we implement quasi-local measures of the spin of the
individual holes, calibrate these with corotating binaries, and revisit the
construction of non-spinning black hole binaries. Higher-order effects, beyond
those considered in earlier work, turn out to be important. Without those,
supposedly non-spinning black holes have appreciable quasi-local spin;
furthermore, the Komar-mass condition and effective potential method agree only
when these higher-order effects are taken into account. We compute a new
sequence of quasi-circular orbits for non-spinning black-hole binaries, and
determine the innermost stable circular orbit of this sequence.",0605053v3
2023-08-29,RKKY interaction in triplet superconductors: Dzyaloshinskii-Moriya-type interaction mediated by spin-polarized Cooper pairs,"The Ruderman--Kittel--Kasuya--Yosida (RKKY) interaction governs the coupling
between localized spins and is strongly affected by the environment in which
these spins reside. In superconductors, this interaction becomes long-ranged
and provides information about the orbital symmetry of the superconducting
order parameter. In this work, we consider the RKKY interaction between
localized spins mediated by $p$-wave triplet superconductors. In contrast to
the well-studied RKKY interaction in $d$-wave superconductors, we find that the
spin of the Cooper pair in a triplet state also modulates the spin--spin
coupling. We consider several different types of $p$-wave triplet states, and
find that the form of the RKKY interaction changes significantly with the
symmetries of the order parameter. For non-unitary superconducting states, two
new terms appear in the RKKY interaction: a background spin magnetization
coupling to the individual spins and, more interestingly, an effective
Dzyaloshinskii--Moriya term. The latter term oscillates with the separation
distance between the impurity spins. Finally, we find that the finite spin
expectation value in non-unitary superconductors in concert with the
conventional RKKY interaction can lead to non-collinear magnetic ground states
even when the Dzyaloshinskii--Moriya term is negligible. The RKKY interaction
in $p$-wave triplet superconductors thus offers a way to achieve new ground
state spin configurations of impurity spins and simultaneously provides
information about the underlying superconducting state.",2308.15523v2
2015-06-02,Long-lived nanosecond spin relaxation and spin coherence of electrons in monolayer MoS_2 and WS_2,"The recently-discovered monolayer transition metal dichalcogenides (TMDCs)
provide a fertile playground to explore new coupled spin-valley physics.
Although robust spin and valley degrees of freedom are inferred from polarized
photoluminescence (PL) experiments, PL timescales are necessarily constrained
by short-lived (3-100ps) electron-hole recombination. Direct probes of
spin/valley polarization dynamics of resident carriers in electron (or hole)
doped TMDCs, which may persist long after recombination ceases, are at an early
stage. Here we directly measure the coupled spin-valley dynamics in
electron-doped MoS_2 and WS_2 monolayers using optical Kerr spectroscopy, and
unambiguously reveal very long electron spin lifetimes exceeding 3ns at 5K (2-3
orders of magnitude longer than typical exciton recombination times). In
contrast with conventional III-V or II-VI semiconductors, spin relaxation
accelerates rapidly in small transverse magnetic fields. Supported by a model
of coupled spin-valley dynamics, these results indicate a novel mechanism of
itinerant electron spin dephasing in the rapidly-fluctuating internal
spin-orbit field in TMDCs, driven by fast intervalley scattering. Additionally,
a long-lived spin coherence is observed at lower energies, commensurate with
localized states. These studies provide crucial insight into the physics
underpinning spin and valley dynamics of resident electrons in atomically-thin
TMDCs.",1506.00996v1
2017-05-22,Quantum Transport in Weyl Semimetal Thin Films in the Presence of Spin-Orbit Coupled Impurities,"Topological semimetals have been at the forefront of experimental and
theoretical attention in condensed matter physics. Among these, recently
discovered Weyl semimetals have a dispersion described by a three-dimensional
Dirac cone, which is at the root of exotic physics such as the chiral anomaly
in magnetotransport. In a time reversal symmetric (TRS) Weyl semimetal film,
the confinement gap gives the quasiparticles a mass, while TRS is preserved by
having an even number of valleys with opposite masses. The film can be tuned
through a topological phase transition by a gate electric field. In this work,
we present a theoretical study of the quantum corrections to the conductivity
of a topological semimetal thin film, which is governed by the complex
interplay of the chiral band structure, mass term, and scalar and spin-orbit
scattering. We study scalar and spin-orbit scattering mechanisms on the same
footing, demonstrating that they have a strong qualitative and quantitative
impact on the conductivity correction. We show that, due to the spin structure
of the matrix Green's functions, terms linear in the extrinsic spin-orbit
scattering are present in the Bloch and momentum relaxation times, whereas
previous works had identified corrections starting from the second order. In
the limit of small quasiparticle mass, the terms linear in the impurity
spin-orbit coupling lead to a potentially observable density dependence in the
weak antilocalization correction. Moreover, when the mass term is around 30
percent of the linear Dirac terms, the system is in the unitary symmetry class
with zero quantum correction and switching the extrinsic spin-orbit scattering
drives the system to the weak antilocalization. We discuss the crossover
between the weak localization and weak antilocalization regimes in terms of the
singlet and triplet Cooperon channels, tuning the spin-orbit scattering
strength.",1705.07612v1
2012-07-24,Sequential Landau-Zener transitions in spin-orbit coupled systems,"We investigate the Landau-Zener (LZ) process in spin-orbit coupled systems of
single or multiple two-level (spin-$\frac{1}{2}$) particles. The coupling
between internal spin states and external vibrational states, a simple
spin-orbit coupling (SOC), is induced by applying a spin-dependent harmonic
trap. Because of the SOC, the single-particle energy-level structures are
modified by the Franck-Condon (FC) effects, in which some avoided
energy-level-crossings (ELCs) are almost closed and some ELCs are opened. The
close of avoided ELCs and the open of ELCs result in the FC blockade and the
vibrational transitions, respectively. For a given low sweeping rate, the
sequential LZ transitions of ladder-like population transition can be induced
by strong SOC. We derive an analytical formula for the final population which
is well consistent with the numerical results. For a given strong SOC, the
sequential LZ transitions are submerged in the non-adiabatic transitions if the
sweeping rate is sufficiently high. Further, we study LZ transitions of
multiple interacting two-level Bose particles in a spin-dependent harmonic
trap. The interplay between the SOC effects and the interaction effects is
explored.",1207.5585v4
2014-05-18,Effect of disorder in the transition from topological insulator to valley-spin polarized state in silicene and Germanene,"We start with the silicene or germanene single-particle Hamiltonian in
buckled 2D hexagonal lattices expressed in terms of Dirac matrices in the Weyl
basis. The Hamiltonian of these systems comprises of the Dirac kinetic energy,
a mass gap term, and the spin-orbit coupling. The second term breaks the
sub-lattice symmetry of the honey-comb lattice structure and generates a gap.
The buckled structure generates a staggered sub-lattice potential between
silicon atoms at A sites and B sites for an applied electric field
perpendicular to its plane. Tuning of the electric field, allows for rich
behavior varying from a topological insulator to a band insulator with a valley
spin-polarized metal at a critical value in between. Thus, the mobile electrons
in silicene or germanene are coupled differently compared to graphene to an
external electric field. Our preliminary investigation have shown that, as long
as the non-magnetic impurity scattering strength is moderate, i.e. the strength
is of the same order as the intrinsic spin-orbit coupling of 4 meV, valley-spin
polarized metal phase is protected. The effective ""two-component Dirac physics""
remains valid in this phase. The increase in the electric field beyond the
critical value leads to the valley magnetic moment reversal. The enhancement in
the impurity scattering strength, however, leads to the disappearance of the
polarized metal phase due to accentuated intra- and inter-valley scattering
processes. This disappearance does not occur due to the increase in Rashba
spin-orbit coupling effect.",1405.4521v1
2020-05-07,Strong enhancement of magnetic susceptibility induced by spin-nematic fluctuations in an excitonic insulating system with spin-orbit coupling,"Effects of the spin-orbit coupling (SOC) and magnetic field on excitonic
insulating (EI) states are investigated. We introduce the two-orbital Hubbard
model with the crystalline field splitting, which is a minimal model for
discussing the exciton condensation in strongly correlated electron systems,
and analyze its effective Hamiltonian in the strong correlation limit by using
the mean-field theory. In the absence of the SOC and magnetic field, the ground
state changes from the nonmagnetic band-insulating state to the EI state by
increasing the Hund coupling. In an applied magnetic field, the magnetic moment
appears in the EI state, which is continuously connected to the forced
ferromagnetic state. On the other hand, in the presence of the SOC, they are
separated by a phase boundary. We find that the magnetic susceptibility is
strongly enhanced in the EI phase near the boundary with a small SOC. This
peculiar behavior is attributed to the low-energy fluctuation of the spin
nematicity inherent in the high-spin local state stabilized by the Hund
coupling. The present study not only reveals the impact of the SOC for the EI
state but also sheds light on the role of quantum fluctuations of the spin
nematicity for the EI state.",2005.03290v1
2023-01-13,Search for large topological gaps in atomic spin chains on proximitized superconducting heavy metal layers,"One-dimensional systems comprising s-wave superconductivity with meticulously
tuned magnetism and spin-orbit coupling can realize topologically gapped
superconductors hosting Majorana edge modes whose stability is determined by
the gap's size. The ongoing quest for larger topological gaps evolved into a
material science issue. However, for atomic spin chains on superconductor
surfaces, the effect of the substrate's spin-orbit coupling on the system's
topological gap size is largely unexplored. Here, we introduce an atomic layer
of the heavy metal Au on Nb(110) which combines strong spin-orbit coupling and
a large superconducting gap with a high crystallographic quality enabling the
assembly of defect-free Fe chains using a scanning tunneling microscope tip.
Scanning tunneling spectroscopy experiments and density functional theory
calculations reveal ferromagnetic coupling and ungapped YSR bands in the chain
despite of the heavy substrate. By artificially imposing a spin spiral state
our calculations indicate a minigap opening and zero-energy edge state
formation. The presented methodology paves the way towards a material screening
of heavy metal layers on elemental superconductors for ideal systems hosting
Majorana edge modes protected by large topological gaps.",2301.05622v1
2018-08-02,Generation of pure superconducting spin current in magnetic heterostructures via non-locally induced magnetism due to Landau Fermi-liquid effects,"We propose a mechanism for the generation of pure superconducting
spin-current carried by equal-spin triplet Cooper pairs in a superconductor (S)
sandwiched between a ferromagnet (F) and a normal metal (N$_{\rm so}$) with
intrinsic spin-orbit coupling. We show that in the presence of Landau
Fermi-liquid interactions the superconducting proximity effect can induce
non-locally a ferromagnetic exchange field in the normal layer, which
disappears above the superconducting transition temperature of the structure.
The internal Landau Fermi-liquid exchange field leads to the onset of a spin
supercurrent associated with the generation of long-range spin-triplet
superconducting correlations in the trilayer. We demonstrate that the magnitude
of the spin supercurrent as well as the induced magnetic order in the N$_{\rm
so}$ layer depends critically on the superconducting proximity effect between
the S layer and the F and N$_{\rm so}$ layers and the magnitude of the relevant
Landau Fermi-liquid interaction parameter. We investigate the effect of spin
flip processes on this mechanism. Our results demonstrate the crucial role of
Landau Fermi-liquid interaction in combination with spin-orbit coupling for the
creation of spin supercurrent in superconducting spintronics, and give a
possible explanation of a recent experiment utilizing spin-pumping via
ferromagnetic resonance [Jeon $\it{ et}$ $\it{al.}$, Nat. Mat. ${\bf 17}$, 499
(2018)].",1808.01045v1
2023-02-28,Linear and nonlinear spin current response in anisotropic spin-orbit coupled systems,"We calculate the linear and the second harmonic (SH) spin current response of
two anisotropic systems with spin orbit (SO) interaction. The first system is a
two-dimensional (2D) electron gas in the presence of Rashba and k-linear
Dresselhaus SO couplings. The dependence of the anisotropic spin splitting on
the sample growth direction introduces an additional path to modify the linear
and nonlinear spectra. In particular, vanishing linear and second order spin
conductivity tensors are achievable under SU(2) symmetry conditions,
characterized by a collinear SO vector field. Additional conditions under which
specific tensor components vanish are posible, without having such
collinearity. Thus, a proper choice of the growth direction and SO strengths
allows to select the polarization of the linear and SH spin currents according
to the direction of flowing. The second system is an anisotropic 2D free
electron gas with anisotropic Rashba interaction, which has been employed to
study the optical conductivity of 2D puckered structures with anisotropic
energy bands. The presence of mass anisotropy and an energy gap open several
distinct scenarios for the allowed optical interband transitions, which
manifest in the linear and SH response contrastingly. The linear response
displays only out-of-plane spin polarized currents, while the SH spin currents
flow with spin orientation lying parallel to the plane of the system strictly.
The models illustrate the possibility of the nonlinear spin Hall effect in
systems with SO interaction, under the presence or absence of time-reversal
symmetry. The results suggest different ways to manipulate the linear",2302.14238v1
2017-10-30,Quantum Spin-Hall Effect of Light at Bound States in the Continuum,"The discovery of the topological nature of free-space light and its quantum
chiral behavior has recently raised large attention. This important scientific
endeavor features spin-based integrated quantum technologies. Herein, we
discuss a novel phenomenon based on a resonantly-enhanced quantum spin-Hall
transport of light observed in a dielectric resonator operating near the
bound-state-in-continuum (BIC) regime. The BIC mode is characterized by a
transverse photonic spin angular momentum density extended on a macroscopic
area. As such, the experimental excited mode in near-BIC regime generates
resonant surface waves characterized by spin-momentum locking and that
propagate along the symmetry axes of the structure. In addition, the generated
side waves are interpreted as an abrupt nonparaxial redirection of the exciting
far field light, which is responsible for the spin-to-orbital angular momentum
conversion evidenced in the spin-orbit asymmetry measured in the intensity of
the side waves. The experimental results are in excellent agreement with a
model that combines geometric parallel transport of light polarization and
spin-momentum locking. In addition, breaking the excitation symmetry leads to a
total spin-directive coupling. Our results reveal the possibility of a
BIC-enhanced macroscopic spin-directive coupling, a novel fundamental mechanism
of light-spin manipulation that will have strong impact on emerging quantum
technologies.",1710.10862v1
2022-07-26,Switching modulation of spin transport in ferromagnetic tetragonal silicene,"We study the band structure and transport properties of ferromagnetic
tetragonal silicene nanoribbons by using the non-equilibrium Green's function
method. The band structure and spin-dependent conductance are discussed under
the combined effect of the external electric field, potential energy, exchange
field and the spin-orbit coupling. One can easily realize a phase transition
from a semimetallic to a semiconducting state by changing the transverse width
of the nanoribbon. Separation of spin-dependent conductances arises from the
effect of exchange field and the spin-orbit coupling, while zero-conductance
behaviors exhibit spin-dependent band gaps induced by the electric field. We
propose a device configuration of four-terminal tetragonal silicene nanoribbon
with two central channels. It is found that spin current can be controlled by
utilizing two switches. The switch with a high potential barrier can block
electrons flowing from the central scattering region into other terminals.
Interestingly, applying only one switch can realize spin-dependent zero
conductance and large spin polarization. Two switches can provide multiple
operations for controlling spin-dependent transport properties. The two-channel
ferromagnetic tetragonal silicene nanoribbon can realize an effective
separation of spin current, which may be a potential candidate for spintronic
devices.",2207.12676v2
2019-07-22,Spin-lattice and electron-phonon coupling in 3$d$/5$d$ hybrid Sr$_3$NiIrO$_6$,"While 3$d$-containing materials display strong electron correlations, narrow
band widths, and robust magnetism, 5$d$ systems are recognized for strong
spin-orbit coupling, increased hybridization, and more diffuse orbitals.
Combining these properties leads to novel behavior. Sr$_3$NiIrO$_6$, for
example, displays complex magnetism and ultra-high coercive fields - up to an
incredible 55~T. Here, we combine infrared and optical spectroscopies with
high-field magnetization and first principles calculations to explore the
fundamental excitations of the lattice and related coupling processes including
spin-lattice and electron-phonon mechanisms. Magneto-infrared spectroscopy
reveals spin-lattice coupling of three phonons that modulate the Ir environment
to reduce the energy required to modify the spin arrangement. While these modes
primarily affect exchange within the chains, analysis also uncovers important
inter-chain motion. This provides a mechanism by which inter-chain interactions
can occur in the developing model for ultra-high coercivity. At the same time,
analysis of the on-site Ir$^{4+}$ excitations reveals vibronic coupling and
extremely large crystal field parameters that lead to a t$_{2g}$-derived
low-spin state for Ir. These findings highlight the spin-charge-lattice
entanglement in Sr$_3$NiIrO$_6$ and suggest that similar interactions may take
place in other 3$d$/5$d$ hybrids.",1907.09392v1
2022-06-01,Signatures of spin precession and nutation in isolated black-hole binaries,"The spin precession of binary black holes (BBHs) that originate from isolated
high-mass binary stars is determined by the interplay of phenomena such as
tides, winds, accretion, common-envelope evolution, natal kicks, and stellar
core-envelope coupling. In previous work, we identified regions of the
parameter space that may produce BBHs with large misalignments from natal kicks
and high spin magnitudes from three mechanisms - tides, accretion, or
inheritance via minimal core-envelope coupling. Here, we explore the spin
precession of such BBHs using five parameters that describe the amplitude and
frequency with which the orbital angular momentum precesses and nutates about
the total angular momentum, modulating the gravitational-wave emission.
Precession is generally possible for sufficiently strong natal kicks provided
at least one of the black holes is spinning. Nutation is a consequence of
spin-spin coupling and depends on the three spin-up mechanisms. Tidal
synchronization can leave a distinct correlation between the aligned effective
spin and the nutation frequency, but does not produce large nutations. When a
black hole accretes $\gtrsim 20\%$ of its companion's envelope, the precession
frequency and amplitude are large. A much smaller amount of accretion, e.g.,
$\approx 2\%$, is needed to provide a large precession frequency and amplitude
when the accretor is a Wolf-Rayet (WR) star. The inheritance of high natal WR
spins ($\gtrsim 5\%$ of their maximum breakup value) via minimal core-envelope
coupling is the most promising mechanism for producing nutating BBHs, implying
that a measurement of nutation from gravitational-wave observations may suggest
isolated-binary origin with minimal core-envelope coupling.",2206.00391v2
2020-01-13,Deconfinement of Mott Localized Electrons into Topological and Spin-Orbit Coupled Dirac Fermions,"The interplay of electronic correlations, spin-orbit coupling and topology
holds promise for the realization of exotic states of quantum matter. Models of
strongly interacting electrons on honeycomb lattices have revealed rich phase
diagrams featuring unconventional quantum states including chiral
superconductivity and correlated quantum spin Hall insulators intertwining with
complex magnetic order. Material realizations of these electronic states are
however scarce or inexistent. In this work, we propose and show that stacking
1T-TaSe$_{2}$ into bilayers can deconfine electrons from a deep Mott insulating
state in the monolayer to a system of correlated Dirac fermions subject to
sizable spin-orbit coupling in the bilayer. 1T-TaSe$_{2}$ develops a
Star-of-David (SoD) charge density wave pattern in each layer. When the SoD
centers belonging to two adyacent layers are stacked in a honeycomb pattern,
the system realizes a generalized Kane-Mele-Hubbard model in a regime where
Dirac semimetallic states are subject to significant Mott-Hubbard interactions
and spin-orbit coupling. At charge neutrality, the system is close to a quantum
phase transition between a quantum spin Hall and an antiferromagnetic
insulator. We identify a perpendicular electric field and the twisting angle as
two knobs to control topology and spin-orbit coupling in the system. Their
combination can drive it across hitherto unexplored grounds of correlated
electron physics including a quantum tricritical point and an exotic
first-order topological phase transition.",2001.04102v2
2017-04-19,Exploring a proximity-coupled Co chain on Pb(110) as a possible Majorana platform,"Linear, suspended chains of magnetic atoms proximity coupled to an s-wave
superconductor are predicted to host Majorana zero modes at the chain ends in
the presence of strong spin-orbit coupling. Specifically, iron (Fe) chains on
Pb(110) have been explored as a possible system to exhibit topological
superconductivity and host Majorana zero-modes [Nadj-Perge, et al., Science
346, 602 (2014)]. Here, we study chains of the transition metal cobalt (Co) on
Pb(110) and check for topological signatures. Using spin-polarized scanning
tunneling spectroscopy, we resolve ferromagnetic order in the $d$ bands of the
chains. Interestingly, also the subgap Yu-Shiba-Rusinov (YSR) bands carry a
spin polarization as was predicted decades ago. Superconducting tips allow us
to resolve further details of the YSR bands and in particular resonances at
zero energy. We map the spatial distribution of the zero-energy signal and find
it delocalized along the chain. Hence, despite of the ferromagnetic coupling
within the chains and the strong-spin orbit coupling in the superconductor, we
do not find clear evidence of Majorana modes. Simple tight-binding calculations
suggest that the spin-orbit-split bands may cross the Fermi level four times
which suppresses the zero-energy modes.",1704.05756v1
2021-11-09,Spin-lattice couplings in two-dimensional CrI$_3$ from first-principles study,"Since thermal fluctuations become more important as dimensions shrink, it is
expected that low-dimensional magnets are more sensitive to lattice distortions
and phonons than bulk systems are. Here we present a fully relativistic
first-principles study on the spin-lattice coupling, i.e. how the magnetic
interactions depend on local lattice distortions, of the prototypical
two-dimensional ferromagnet CrI$_3$. We extract an effective measure of the
spin-lattice coupling in CrI$_3$ which is up to ten times larger than what is
found for bcc Fe. The magnetic exchange interactions, including Heisenberg and
relativistic Dzyaloshinskii-Moriya interactions, are sensitive both to the
in-plane motion of Cr atoms and out-of-plane motion of ligand atoms. We find
that significant magnetic pair interactions change sign from ferromagnetic (FM)
to anti-ferromagnetic (AFM) for atomic displacements larger than 0.16 {\AA}. We
explain the observed strong spin-lattice coupling by analyzing the orbital
decomposition of isotropic exchange interactions, involving different
crystal-field-split Cr$-3d$ orbitals. The competition between the AFM t$_{2g}$
- t$_{2g}$ and FM t$_{2g}$ - e$_{g}$ contributions depends on the bond angle
formed by Cr and I atoms as well as Cr-Cr distance. In particular, if a Cr atom
is displaced, the FM-AFM sign change when the I-Cr-I bond angle approaches
90$^\circ$. The obtained spin-lattice coupling constants, along with the
microscopic orbital analysis can act as a guiding principle for further studies
of the thermodynamic properties and combined magnon-phonon excitations in
two-dimensional magnets.",2111.05382v1
2002-07-04,"Dynamics, Selection Rules and Dzyaloshinsky-Moriya interactions in Strongly Frustrated Magnets","Anisotropic spin-spin interactions of the symmetry described by Dzyaloshinsky
and Moriya are generally considered weak, as they depend on the spin-orbit
couplings. In frustrated spin systems with singlet ground states they can,
however, have rather strong effects. We discuss recent results related to two
gapped spin systems: $\rm CuGeO_3$ and $\rm SrCu_2(BO_3)_2$ in particular. In
the first compound the Dzyaloshinsky-Moriya interactions effectively lower the
symmetry of the magnetic unit cell and this leads to doubling of the low
frequency mode. In the second case, the Dzyaloshinsky-Moriya interactions also
split the lowest magnon mode linearly in the spin-orbit coupling. In addition,
the relatively weak Dzyaloshinsky-Moriya interactions can dominate the
dispersion.
  Consideration of the selection rules for optical transitions show that while
the Dzyaloshinsky-Moriya interactions can explain much of the dynamics, they do
not explain the observed transition amplitudes. This leads to a review of
recent calculations of anisotropic spin-phonon couplings. We discuss how this
leads to a novel mechanism to explain the ESR intensities in the spin gap
systems discussed. Selection rules for this novel mechanism involving coupling
to the electric field of the resonant probe are discussed and relation to
polarised neutron experiments briefly mentioned.",0207116v1
2015-09-21,Isotropic and Anisotropic Regimes of the Field-Dependent Spin Dynamics in Sr2IrO4: Raman Scattering Studies,"A major focus of experimental interest in Sr2IrO4 has been to clarify how the
magnetic excitations of this strongly spin-orbit coupled system differ from the
predictions of anisotropic 2D spin-1/2 Heisenberg model and to explore the
extent to which strong spin-orbit coupling affects the magnetic properties of
iridates. Here, we present a high-resolution inelastic light (Raman) scattering
study of the low energy magnetic excitation spectrum of Sr2IrO4 and doped
Eu-doped Sr2IrO4 as functions of both temperature and applied magnetic field.
We show that the high-field (H>1.5 T) in-plane spin dynamics of Sr2IrO4 are
isotropic and governed by the interplay between the applied field and the small
in-plane ferromagnetic spin components induced by the Dzyaloshinskii-Moriya
interaction. However, the spin dynamics of Sr2IrO4 at lower fields (H<1.5 T)
exhibit important effects associated with interlayer coupling and in-plane
anisotropy, including a spin-flop transition at Hc in Sr2IrO4 that occurs
either discontinuously or via a continuous rotation of the spins, depending
upon the in-plane orientation of the applied field. These results show that
in-plane anisotropy and interlayer coupling effects play important roles in the
low-field magnetic and dynamical properties of Sr2IrO4.",1509.06409v1
2012-11-28,Competing topological phases in few-layer graphene,"We investigate the effect of spin-orbit coupling on the band structure of
graphene-based two-dimensional Dirac fermion gases in the quantum Hall regime.
Taking monolayer graphene as our first candidate, we show that a quantum phase
transition between two distinct topological states -- the quantum Hall and the
quantum spin Hall phases -- can be driven by simply tuning the Fermi level with
a gate voltage. This transition is characterized by the existence of a chiral
spin-polarized edge state propagating along the interface separating the two
topological phases. We then apply our analysis to the more difficult case of
bilayer graphene. Unlike in monolayer graphene, spin-orbit coupling by itself
has indeed been predicted to be unsuccessful in driving bilayer graphene into a
topological phase, due to the existence of an even number of pairs of
spin-polarized edge states. While we show that this remains the case in the
quantum Hall regime, we point out that by additionally breaking the layer
inversion symmetry, a non-trivial quantum spin Hall phase can re-emerge in
bilayer graphene at low energy. We consider two different symmetry-breaking
mechanisms: inducing spin-orbit coupling only in the upper layer, and applying
a perpendicular electric field. In both cases, the presence at low energy of an
odd number of pairs of edge states can be driven by an exchange field. The
related situation in trilayer graphene is also discussed.",1211.6628v1
2014-07-08,Dynamical competition between Quantum Hall and Quantum Spin Hall effects,"In this paper we investigate the occurrence of quantum phase transitions in
topological systems out of equi- librium. More specifically, we consider
graphene with a sizable spin-orbit coupling, irradiated by circularly-
polarized light. In the absence of light, the spin-orbit coupling drives a
quantum spin Hall phase where edge currents with opposite spins
counter-propagate. On the other hand, the light generates a time-dependent
vector potential, which leads to a hopping parameter with staggered
time-dependent phases around the benzene ring. The model is a dynamical version
of the Haldane model, which considers a static staggered flux with zero total
flux through each plaquette. Since the light breaks time-reversal symmetry, a
quantum Hall phase protected by an integer topological invariant arises. By
numerically solving the complete problem, with spin-orbit coupling and light,
and investigating different values of the driving frequency {\omega}, we show
that the spectrum exhibits non-trivial gaps not only at zero energy, but also
at {\omega}/2. This additional gap is created by photon resonances between the
valence and conduction band of graphene, and the symmetry of the spectrum
forces it to lie at {\omega}/2. By increasing the intensity of the irradiation,
the topological state in the zero energy gap undergoes a dynamical phase
transition from a quantum spin Hall to a quantum Hall phase, whereas the gap
around {\omega}/2 remains in the quantum Hall regime.",1407.2152v3
2016-06-01,Entanglement and manipulation of the magnetic and spin-orbit order in multiferroic Rashba semiconductors,"The interplay between electronic eigenstates, spin, and orbital degrees of
freedom, combined with fundamental breaking of symmetries is currently one of
the most exciting fields of research. Multiferroics such as (GeMn)Te fulfill
these requirements providing unusual physical properties due to the coexistence
and coupling between ferromagnetic and ferroelectric order in one and the same
system. Here we show that multiferroic (GeMn)Te inherits from its parent
ferroelectric {\alpha}-GeTe compound a giant Rashba splitting of
three-dimensional bulk states which competes with the Zeeman spin splitting
induced by the magnetic exchange interactions. The collinear alignment of
ferroelectric and ferromagnetic polarization leads to an opening of a tunable
Zeeman gap of up to 100 meV around the Dirac point of the Rashba bands, coupled
with a change in spin texture by entanglement of magnetic and spin-orbit order.
Through applications of magnetic fields, we demonstrate manipulation of spin-
texture by spin resolved photoemission experiments, which is also expected for
electric fields based on the multiferroic coupling. The control of spin
helicity of the bands and its locking to ferromagnetic and ferroelectric order
opens fascinating new avenues for highly multifunctional multiferroic Rashba
devices suited for reprogrammable logic and/or nonvolatile memory applications.",1606.00241v2
2018-09-13,"Spin Susceptibility, Upper Critical Field and Disorder Effect in $j=\frac{3}{2}$ Superconductors with Singlet-Quintet Mixing","Recently, a new pairing state with the mixing between s-wave singlet channel
and isotropic d-wave quintet channel induced by centrosymmetric spin-orbit
coupling has been theoretically proposed in the superconducting materials with
$j=\frac{3}{2}$ electrons. In this work, we derive the expressions of the
zero-temperature spin susceptibility, the upper critical field close to the
zero-field critical temperature $T_c$ and the critical temperature with weak
random non-magnetic disorders for the singlet-quintet mixed state based on the
Luttinger model. Our study revealed the following features of the
singlet-quintet mixing. (1) The zero-temperature spin susceptibility remains
zero for the singlet-quintet mixed state if only the centrosymmetric spin-orbit
coupling is taken into account, and will deviate from zero when the
non-centrosymmetric spin-orbit coupling is introduced. (2) The singlet-quintet
mixing can help enhance the upper critical field roughly because it can
increase $T_c$. (3) Although the quintet channel is generally suppressed by the
non-magnetic disorder scattering, we find the strong mixing between singlet and
quintet channels can help to stabilize the quintet channel. As a result, we
still find a sizable quintet component mixed into the singlet channel in the
presence of weak random non-magnetic disorders. Our work provides the guidance
for future experiments on spin susceptibility and upper critical field of the
singlet-quintet mixed superconducting states, and illustrates the stability of
the singlet-quintet mixing against the weak random non-magnetic disorder.",1809.04736v1
2020-12-22,Quantum Anomalous Hall Effect in Magnetic Doped Topological Insulators and Ferromagnetic Spin-Gapless Semiconductors -- A Perspective Review,"Quantum anomalous Hall effect, with a trademark of dissipationless chiral
edge states for electronics/spintronics transport applications, can be realized
in materials with large spin-orbit coupling and strong intrinsic magnetization.
After Haldane seminal proposal, several models have been presented to
control/enhance the spin-orbit coupling and intrinsic magnetic exchange
interaction. After brief introduction of Haldane model for spineless fermions,
following three fundamental quantum anomalous Hall models are discussed in this
perspective review: (i) low-energy effective four band model for magnetic-doped
topological insulator (Bi,Sb)2Te3 thin films, (ii) four band tight-binding
model for graphene with magnetic adatoms, and (iii) two (three) band spinfull
tight-binding model for ferromagnetic spin-gapless semiconductors with
honeycomb (kagome) lattice where ground state is intrinsically ferromagnetic.
These models cover two-dimensional Dirac materials hosting spinless, spinful
and spin-degenerate Dirac points where various mass terms open a band gap and
lead to quantum anomalous Hall effect. With emphasize on the topological phase
transition driven by ferromagnetic exchange interaction and its interplay with
spin-orbit-coupling, we discuss various symmetry constraints on the nature of
mass term and the materialization of these models. We hope this study will shed
light on the fundamental theoretical perspectives of quantum anomalous Hall
materials.",2101.01074v1
2019-11-08,Ground-state properties of spin-orbit-coupled dipolar Bose-Einstein condensates with in-plane gradient magnetic field,"We investigate the ground-state properties of spin-orbit-coupled
pseudo-spin-1/2 dipolar Bose-Einstein condensates (BECs) in a two-dimensional
harmonic trap and an in-plane quadrupole field. The effects of spin-orbit
coupling (SOC), dipole-dipole interaction (DDI) and the in-plane quadrupole
field on the ground-state structures and spin textures of the system are
systematically analyzed and discussed. For fixed SOC and DDI strengths, the
system shows a quadrupole stripe phase with a half-quantum vortex, or a
quadrupole Thomas-Fermi phase with a half-quantum antivortex for small
quadrupole field strength, depending on the ratio between inter- and
intraspecies interaction. As the quadrupole field strength enhances, the system
realizes a ring mixed phase with a hidden vortex-antivortex cluster rather than
an ordinary giant vortex in each component. Of particular interest, when the
strengths of DDI and quadrupole field are fixed, strong SOC leads to the
formation of criss-crossed vortex string structure. For given SOC and
quadrupole field, the system for strong DDI displays a sandwich-like structure,
or a special delaminated structure with a prolate antivortex in the spin-up
component. In addition, typical spin textures for the ground states of the
system are analyzed. It is shown that the system sustains exotic topological
structures, such as a hyperbolic spin domain wall,
skyrmion-half-antiskyrmion-antiskyrmion lattice,
half-skyrmion-skyrmion-half-antiskyrmion lattice, and a drum-shaped antimeron.",1911.03269v1
2021-03-12,Magnetoelectric torque and edge currents in spin-orbit coupled graphene nanoribbons,"For graphene nanoribbons with Rashba spin-orbit coupling, the peculiar
magnetic response due to the presence of a magnetization and geometric
confinement are analyzed within a tight-binding model. We observe a sizable
transverse susceptibility that can be considered as a gate voltage-induced
magnetoelectric torque without the need of a bias voltage, with different
directions for zigzag and armchair ribbons. The local torque generates
non-collinear spin polarization between the two edges and/or along the ribbon,
and the net torque averages to zero if the magnetization is homogeneous.
Nevertheless, a nonzero net torque can appear in partially magnetized
nanoribbons or in nanoflakes of irregular shapes. The equilibrium spin current
produced by the spin-orbit coupling also appears in nanoribbons, but the
component flowing in the direction of confinement is strongly suppressed. Even
without the magnetization, an out-of-plane polarized chiral edge spin current
is produced, resembling that in the quantum spin Hall effect. Moreover, a
magnetization pointing perpendicular to the edge produces a laminar flow of
edge charge currents, whose flow direction is symmetric (non chiral) or
antisymmetric (chiral) between the two edges depends on whether the
magnetization points in-plane or out-of-plane.",2103.07426v1
2022-08-28,Spin Josephson effects of spin-orbit-coupled Bose-Einstein condensates in a non-Hermitian double well,"In this paper, we investigate the spin and tunneling dynamics of a
spin-orbit-coupled noninteracting Bose-Einstein condensate in a periodically
driven non-Hermitian double-well potential. Under high-frequency driving, we
obtain the effective time-averaged Hamiltonian by using the standard
time-averaging method, and analytically calculate the Floquet quasienergies,
revealing that the parity-time (PT)-breaking phase transition appears even for
arbitrarily small non-Hermitian parameters when the spin-orbit coupling
strength takes half-integer value, irrespective of the values of other
parameters used. When the system is PT-symmetric with balanced gain and loss,
we find numerically and analytically that in the broken PT-symmetric regions,
there will exist the net spin current together with a vanishing atomic current,
if we drop the contribution of the exponential growth of the norm to the
current behaviors. When the system is non-PT-symmetric, though the
quasienergies are partial complex, a stable net spin current can be generated
by controlling the periodic driving field, which is accompanied by a spatial
localization of the condensate in the well with gain. The results deepen the
understanding of non-Hermitian physics and could be useful for engineering a
variety of devices for spintronics.",2208.13198v1
2022-10-06,Direct probing of a large spin-orbit coupling in the FeSe superconducting monolayer on STO: Evidence for nontrivial topological states,"In condensed-matter physics spin-orbit coupling (SOC) is a fundamental
physical interaction, which describes how the electrons' spin couples to their
orbital motion. It is the source of a vast variety of fascinating phenomena in
solids such as topological phases of matter, quantum spin Hall states, and many
other exotic quantum states. Although in most theoretical descriptions of the
phenomenon of high-temperature superconductivity SOC has been neglected,
including this interaction can, in principle, revise the microscopic picture of
superconductivity in these compounds. Not only the interaction leading to
Cooper pairing but also the symmetry of the order parameter and the topological
character of the involved states can be determined by SOC. Here by preforming
energy-, momentum-, and spin-resolved spectroscopy experiments with an
unprecedented resolution we demonstrate that while probing the dynamic charge
response of the FeSe monolayer on strontium titanate, a prototype two
dimensional high-temperature superconductor using slow electrons, the
scattering cross-section shows a considerable spin asymmetry. We unravel the
origin of the observed spin asymmetry by developing a model in which SOC is
taken into consideration. Our analysis indicates that SOC in this two
dimensional superconductor is rather strong. We anticipate that such a strong
SOC can have several serious consequences on the electronic structures and can
lead to the formation of topological states. Moreover, a sizable SOC can
compete with other pairing scenarios and is crucial for the mechanism of
high-temperature superconductivity.",2210.02810v1
2023-02-04,Multi-Stability in Cavity QED with Spin-Orbit Coupled Bose-Einstein Condensate,"We investigate the occurrence of steady-state multi-stability in a cavity
system containing spin-orbit coupled Bose-Einstein condensate and driven by a
strong pump laser. The applied magnetic field splits the Bose-Einstein
condensate into pseudo-spin states, which then became momentum sensitive with
two counter propagating Raman lasers directly interacting with ultra-cold
atoms. After governing the steady-state dynamics for all associated subsystems,
we show the emergence of multi-stable behavior of cavity photon number, which
is unlike with previous investigation on cavity-atom systems. However, this
multi-stability can be tuned with associated system parameters. Further, we
illustrate the occurrence of mixed-stability behavior for atomic population of
the pseudo spin-$\uparrow$ amd spin-$\downarrow$ states, which are appearing in
so-called bi-unstable form. The collective behavior of these atomic number
states interestingly possesses a transitional interface among the population of
both spin states, which can be enhance and controlled by spin-orbit coupling
and Zeeman field effects. Furthermore, we illustrate the emergence of secondary
interface mediated by increasing the mechanical dissipation rate of the
pseudo-spin states. These interfaces could be cause by the non-trivial behavior
of synthetic spin state mediated by cavity. Our findings are not only crucial
for the subject of optical switching, but also could provide foundation for
future studies on mechanical aspect of synthetic atomic states with cavity
quantum electrodynamics.",2302.02147v1
2019-05-23,Spin-orbit coupling and crystal-field distortions for a low-spin $3d^5$ state in BaCoO$_{3}$,"We have studied the electronic structure of BaCoO$_3$ using soft x-ray
absorption spectroscopy at the Co-$L_{2,3}$ and O-$K$ edges, magnetic circular
dichroism at the Co-$L_{2,3}$ edges, as well as valence band hard x-ray
photoelectron spectroscopy. The quantitative analysis of the spectra
established that the Co ions are in the formal low-spin tetravalent 3$d^5$
state and that the system is a negative charge transfer Mott insulator. The
spin-orbit coupling plays also an important role for the magnetism of the
system. At the same time, a trigonal crystal field is present with sufficient
strength to bring the 3$d^5$ ion away from the $J_{eff} = 1/2$ state. The sign
of this crystal field is such that the $a_{1g}$ orbital is doubly occupied,
explaining the absence of a Peierl's transition in this system which consists
of chains of face-sharing CoO$_6$ octahedra. Moreover, with one hole residing
in the $e_g^{\pi}$, the presence of an orbital moment and strong
magneto-crystalline anisotropy can be understood. Yet, we also infer that
crystal fields with lower symmetry must be present to reproduce the measured
orbital moment quantitatively, thereby suggesting the possibility for orbital
ordering to occur in BaCoO$_3$.",1905.09549v1
2016-03-01,"Spin orientations of the spin-half Ir4+ ions in Sr3NiIrO6, Sr2IrO4 and Na2IrO3: Density functional, perturbation theory and Madelung potential analyses","The spins of the low-spin Ir4+ (S = 1/2, d5) ions at the octahedral sites of
the oxides Sr3NiIrO6, Sr2IrO4 and Na2IrO3 exhibit preferred orientations with
respect to their IrO6 octahedra. We evaluated the magnetic anisotropies of
these S = 1/2 ions on the basis of DFT calculations including spin-orbit
coupling (SOC), and probed their origin by performing perturbation theory
analyses with SOC as perturbation within the LS coupling scheme. The observed
spin orientations of Sr3NiIrO6 and Sr2IrO4 are correctly predicted by DFT
calculations, and are accounted for by the perturbation theory analysis. As for
the spin orientation of Na2IrO3, both experimental studies and DFT calculations
have not been unequivocal. Our analysis reveals that the Ir4+ spin orientation
of Na2IrO3 should have nonzero components along the c- and a-axes directions.
The spin orientations determined by DFT calculations are sensitive to the
accuracy of the crystal structures employed, which is explained by perturbation
theory analyses when interactions between adjacent Ir4+ ions are taken into
consideration. There are indications implying that the 5d electrons of Na2IrO3
are less strongly localized compared with those of Sr3NiIrO6 and Sr2IrO4. This
implication was confirmed by showing that the Madelung potentials of the Ir4+
ions are less negative in Na2IrO3 than in Sr3NiIrO6, Sr2IrO4. Most
transition-metal S = 1/2 ions do have magnetic anisotropies because the SOC
induces interactions among their crystal-field split d-states, and the
associated mixing of the states modifies only the orbital parts of the states.
This finding cannot be mimicked by a spin Hamiltonian because this model
Hamiltonian lacks the orbital degree of freedom, thereby leading to the
spin-half syndrome. The spin-orbital entanglement for the 5d spin-half ions
Ir4+ is not as strong as has been assumed lately.",1603.00523v2
2023-03-25,Natural orbitals renormalization group approach to a spin-1/2 impurity interacting with two helical liquids,"Using the natural orbitals renormalization group, we studied the problem of a
localized spin- 1/2 impurity coupled to two helical liquids via the Kondo
interaction in a quantum spin Hall insulator, based on the Kane-Mele model
defined in a finite zigzag graphene nanoribbon. We investigated the influence
of the Kondo couplings with the helical liquids on both the static and dynamic
properties of the ground state. The number and distinct spatial structures of
the active natural orbitals (ANOs), which play essential roles in constructing
the ground-state wave function, were first analyzed. Our numerical results
indicate that two ANOs emerge, equal to the number of helical liquids.
Specifically, at the coupling symmetry point, both ANOs are fully active with
their spatial structures being respectively constituted by the different
helical liquids. In comparison, when deviating from the symmetry point, only
one ANO remains fully active, which is dominantly constructed by the helical
liquid with the larger Kondo coupling. Local screening of the impurity,
described by the impurity spin polarization and susceptibility, was further
studied. It shows that at the coupling symmetry point, the impurity is
maximally polarized and the spin susceptibility reaches the maximum. On the
contrary, the impurity tends to be screened without polarization when the Kondo
couplings deviate well from the symmetry point. The Kondo screening cloud,
manifested by the spin correlation between the impurity and the conduction
electrons, was finally explored. It is demonstrated that the Kondo cloud is
mainly formed by the helical liquid with the larger Kondo coupling to the
impurity. On the other hand, the spin-orbital coupling breaks the symmetry in
spatial distribution of the spin correlation, leading to anisotropy in the
Kondo cloud.",2303.14331v1
2015-01-31,Spin-orbit-induced exotic insulators in a three-orbital Hubbard model with $(t_{2g})^5$ electrons,"On the basis of the multi-orbital dynamical mean field theory, a
three-orbital Hubbard model with a relativistic spin-orbit coupling (SOC) is
studied at five electrons per site. The numerical calculations are performed by
employing the continuous-time quantum Monte Carlo (CTQMC) method based on the
strong coupling expansion. We find that appropriately choosing bases, i.e., the
maximally spin-orbit-entangled bases, drastically improve the sign problem in
the CTQMC calculations, which enables us to treat exactly the full Hund's
coupling and pair hopping terms. This improvement is also essential to reach at
low temperatures for a large SOC region where the SOC most significantly
affects the electronic structure. We show that a metal-insulator transition is
induced by the SOC for fixed Coulomb interactions. The insulating state for
smaller Coulomb interactions is antiferromagnetically ordered with the local
effective total angular momentum $j=1/2$, in which the $j=1/2$ based band is
essentially half-filled while the $j=3/2$ based bands are completely occupied.
More interestingly, for larger Coulomb interactions, we find that an excitonic
insulating state emerges, where the condensation of an electron-hole pair in
the $j=1/2$ and $j=3/2$ based bands occurs. The origin of the excitonic
insulator as well as the experimental implication is discussed.",1502.00108v1
2016-02-08,Tight-binding theory of NMR shifts in topological insulators Bi2Se3 and Bi2Te3,"Motivated by recent nuclear magnetic resonance (NMR) experiments, we present
a microscopic sp3 tight-binding model calculation of the NMR shifts in bulk
Bi2Se3, and Bi2Te3. We compute the contact, dipolar, orbital and core
polarization contributions to the carrier-density-dependent part of the NMR
shifts in Bi209, Te125 and Se77. The spin-orbit coupling and the layered
crystal structure result in a contact Knight shift with strong uniaxial
anisotropy. Likewise, because of spin-orbit coupling, dipolar interactions make
a significant contribution to the isotropic part of the NMR shift. The contact
interaction dominates the isotropic Knight shift in Bi209 NMR, even though the
electronic states at the Fermi level have a rather weak s-orbital character. In
contrast, the contribution from the contact hyperfine interaction to the NMR
shift of Se77 and Te125 is weak compared to the dipolar and orbital shifts
therein. In all cases, the orbital shift is at least comparable to the contact
and dipolar shifts, while the shift due to core polarization is subdominant
(except for Te nuclei located at the inversion centers). By artificially
varying the strength of spin-orbit coupling, we evaluate the evolution of the
NMR shift across a band inversion but find no clear signature of the
topological transition.",1602.02649v2
2017-05-04,103-Compound Band Structure Benchmark of Post-SCF Spin-Orbit Coupling Treatments in Density-Functional Theory,"We quantify the accuracy of different non-self-consistent and self-consistent
spin-orbit coupling (SOC) treatments in Kohn-Sham and hybrid density-functional
theory by providing a band structure benchmark set for the valence and
low-lying conduction energy bands of 103 inorganic compounds, covering chemical
elements up to Po. Reference energy band structures for the PBE density
functional are obtained using the full-potential (linearized) augmented plane
wave code Wien2k, employing its self-consistent treatment of SOC including
Dirac-like p$^{1/2}$ orbitals in the basis set. We use this benchmark set to
benchmark a computationally simpler, non-self-consistent all-electron treatment
of SOC based on scalar-relativistic orbitals and numeric atom-centered orbital
basis functions. For elements up to Z$\approx$50, both treatments agree
virtually exactly. For the heaviest elements considered (Tl, Pb, Bi, Po), the
band structure changes due to SOC are captured with a relative deviation of 11%
or less. For different density functionals (PBE vs. the hybrid HSE06), we show
that the effect of spin-orbit coupling is usually similar but can be dissimilar
if the qualitative features of the predicted underlying scalar-relativistic
band structures do not agree. All band structures considered in this work are
available online via the NOMAD Repository to aid in future benchmark studies
and methods development.",1705.01804v2
2009-10-17,Density functional study of the actinide nitrides,"The full potential all electron linearized augmented plane wave plus local
orbitals (FP-LAPW + lo) method, as implemented in the suite of software WIEN2K,
has been used to systematically investigate the structural, electronic, and
magnetic properties of the actinide compounds AnN (An = Ac, Th, Pa, U, Np, Pu,
Am). The theoretical formalism used is the generalized gradient approximation
to density functional theory (GGA-DFT) with the Perdew-Burke-Ernzerhof (PBE)
exchange-correlation functional. Each compound has been studied at six levels
of theory: non-magnetic (NM), non-magnetic with spin-orbit coupling (NM+SOC),
ferromagnetic (FM), ferromagnetic with spin-orbit coupling (FM+SOC),
anti-ferromagnetic (AFM), and anti-ferromagnetic with spin-orbit coupling
(AFM+SOC). The structural parameters, bulk moduli, densities of states, and
charge distributions have been computed and compared to available experimental
data and other theoretical calculations published in the literature. The total
energy calculations indicate that the lowest energy structures of AcN, ThN, and
PaN are degenerate at the NM+SOC, FM+SOC, and AFM+SOC levels of theory with
vanishing total magnetic moments in the FM+SOC and AFM+SOC cases, making the
ground states essentially non-magnetic with spin-orbit interaction. The ground
states of UN, NpN, PuN, and AmN are found to be FM+SOC at the level of theory
used in the present computations. The nature of the interactions between the
actinide metals and nitrogen atom, and the implications on 5f electron
delocalization and localization are discussed in detail.",0910.3337v1
2018-08-21,Pseudospin-lattice coupling in the spin-orbit Mott insulator Sr2IrO4,"Spin-orbit entangled magnetic dipoles, often referred to as pseudospins,
provide a new avenue to explore novel magnetism inconceivable in the weak
spin-orbit coupling limit, but the nature of their low-energy interactions
remains to be understood. We present a comprehensive study of the static
magnetism and low-energy pseudospin dynamics in the archetypal spin-orbit Mott
insulator Sr2IrO4. We find that in order to understand even basic magnetization
measurements, a formerly overlooked in-plane anisotropy is fundamental. In
addition to magnetometry, we use neutron diffraction, inelastic neutron
scattering and resonant elastic and inelastic x-ray scattering to identify and
quantify the interactions that determine the global symmetry of the system and
govern the linear responses of pseudospins to external magnetic felds and their
low-energy dynamics. We find that a pseudospin-only Hamiltonian is insufficient
for an accurate description of the magnetism in Sr2IrO4 and that
pseudospin-lattice coupling is essential. This finding should be generally
applicable to other pseudospin systems with sizable orbital moments sensitive
to anisotropic crystalline environments.",1808.06920v2
2001-07-02,Spin-1 effective Hamiltonian with three degenerate orbitals: An application to the case of V_2O_3,"Motivated by recent neutron and x-ray observations in V_2O_3, we derive the
effective Hamiltonian in the strong coupling limit of an Hubbard model with
three degenerate t_{2g} states containing two electrons coupled to spin S = 1,
and use it to re-examine the low-temperature ground-state properties of this
compound. An axial trigonal distortion of the cubic states is also taken into
account. Since there are no assumptions about the symmetry properties of the
hopping integrals involved, the resulting spin-orbital Hamiltonian can be
generally applied to any crystallographic configuration of the transition metal
ion giving rise to degenerate t_{2g} orbitals. Specializing to the case of
V_2O_3 we consider the antiferromagnetic insulating phase. We find two
variational regimes, depending on the relative size of the correlation energy
of the vertical pairs and the in-plane interaction energy. The former favors
the formation of stable molecules throughout the crystal, while the latter
tends to break this correlated state. We determine in both cases the minimizing
orbital solutions for various spin configurations, and draw the corresponding
phase diagrams. We find that none of the symmetry-breaking stable phases with
the real spin structure presents an orbital ordering compatible with the
magnetic space group indicated by very recent observations of non-reciprocal
x-ray gyrotropy in V_2O_3. We do however find a compatible solution with very
small excitation energy in two distinct regions of the phase space, which might
turn into the true ground state of V_2O_3 due to the favorable coupling with
the lattice. We illustrate merits and drawbacks of the various solutions and
discuss them in relation to the present experimental evidence.",0107026v1
2022-08-18,Dynamics of quantum soliton in Lee-Huang-Yang spin-orbit coupled Bose-Einstein condensates,"We present the numerical results of the structure and dynamics of the
self-bound ground state arising solely because of the presence of beyond mean
field quantum fluctuation in spin-orbit coupled binary Bose-Einstein
condensates in one dimension. Depending upon spin-obit (SO) and Rabi couplings,
we observe that the ground state exhibits either quantum-bright (plane) or
quantum-stripe soliton nature. We find an analytical soliton solution for
non-zero SO coupling that matches quite well with the numerical results.
Further, we investigate the dynamical stability of these solitons by adopting
three protocols, such as (i) adding initial velocity to each component, (ii)
quenching the SO and Rabi coupling parameters at initial and finite time, and
(iii) allowing collision between the two spin-components by giving equal and
opposite direction velocity to them. Many interesting dynamical features of the
solitons, like, multi-fragmented, repelling, and breathing in time and
space-time, are observed. For given Rabi coupling frequency, the breathing
frequency of the soliton increases upon the increase in SO coupling, attaining
a maximum at the critical SO coupling where the phase transition from the
bright to stripe soliton occurs. We observe that the maximum breathing
frequency exhibits power law dependence on the Rabi coupling frequency with an
exponent $\sim 0.16$.",2208.08777v2
2008-12-15,Magnetic and Metallic State at Intermediate Hubbard U Coupling in Multiorbital Models for Undoped Fe Pnictides,"Multi-orbital Hubbard model Hamiltonians for the undoped parent compounds of
the Fe-pnictide superconductors are here investigated using mean-field
techniques. For a realistic four-orbital model, our results show the existence
of an intermediate Hubbard U coupling regime where the mean-field ground state
has spin stripe magnetic order, as in neutron scattering experiments, while
remaining metallic, due to the phenomenon of band overlaps. The angle-resolved
photoemission intensity and Fermi surface of this magnetic and metallic state
are discussed. Other models are also investigated, including a two orbital
model where not only the mean-field technique can be used, but also Exact
Diagonalization in small clusters and the Variational Cluster Approximation in
the bulk. The combined results of the three techniques point toward the
existence of an intermediate-coupling magnetic and metallic state in the
two-orbital model, similar to the intermediate coupling mean-field state of the
four-orbital model. We conclude that the state discussed here is compatible
with the experimentally known properties of the undoped Fe-pnictides.",0812.2894v1
2010-01-13,Cooperative Effect of Coulomb Interaction and Electron-Phonon Coupling on the Heavy Fermion State in the Two-Orbital Periodic Anderson Model,"We investigate the two-orbital periodic Anderson model, where the local
orbital fluctuations of f-electrons couple with a two-fold degenerate
Jahn-Teller phonon, by using the dynamical mean-field theory. It is found that
the heavy fermion state caused by the Coulomb interaction between f-electrons U
is largely enhanced due to the electron-phonon coupling g, in contrast to the
case with the single-orbital periodic Anderson model where the effects of U and
g compete to each other. In the heavy fermion state for large $U$ and g, both
the orbital and lattice fluctuations are enhanced, while the charge (valence)
and spin fluctuations are suppressed. In the strong coupling regime, a sharp
soft phonon mode with a large spectral weight is observed for small U, while a
broad soft phonon mode with a small spectral weight is observed for large U.
The cooperative effect of U and g for half-filling with two f-electrons per
atom $n_f=2$ is more pronounced than that for quarter-filling with $n_f=1$.",1001.2065v2
2006-05-27,Higher-order spin effects in the dynamics of compact binaries I. Equations of motion,"We derive the equations of motion of spinning compact binaries including the
spin-orbit (SO) coupling terms one post-Newtonian (PN) order beyond the
leading-order effect. For black holes maximally spinning this corresponds to
2.5PN order. Our result for the equations of motion essentially confirms the
previous result by Tagoshi, Ohashi and Owen. We also compute the spin-orbit
effects up to 2.5PN order in the conserved (Noetherian) integrals of motion,
namely the energy, the total angular momentum, the linear momentum and the
center-of-mass integral. We obtain the spin precession equations at 1PN order
beyond the leading term, as well. Those results will be used in a future paper
to derive the time evolution of the binary orbital phase, providing more
accurate templates for LIGO-Virgo-LISA type interferometric detectors.",0605139v4
2012-09-29,Probing in-medium spin-orbit potential with intermediate-energy heavy-ion collisions,"Incorporating for the first time both the spin and isospin degrees of freedom
explicitly in transport model simulations of intermediate-energy heavy-ion
collisions, we observe that a local spin polarization appears during collision
process. Most interestingly, it is found that the nucleon spin up-down
differential transverse flow is a sensitive probe of the spin-orbit
interaction, providing a novel approach to probe both the density and isospin
dependence of the in-medium spin-orbit coupling that is important for
understanding the structure of rare isotopes and synthesis of superheavy
elements.",1210.0158v2
2013-02-01,Electronic Properties and Persistent Spin Currents of Nanospring under Static Magnetic Field,"Relativistic electronic properties of a nanospring under a static magnetic
field are theoretically investigated in the present study. The wave equation
accounting for the spin-orbit interaction is derived for the nanospring as a
special case of the Pauli equation for a spin-1/2 particle confined to a curved
surface under an electromagnetic field. We define the helical momentum operator
and show that it commutes with the Hamiltonian owing to the helical geometry of
the nanospring. The energy eigenstates are hence also the eigenstates of the
helical momentum. We solve the equation numerically to obtain the surface wave
functions and the energy spectra. The electronic properties are systematically
examined by varying the parameters that characterize the system. It is
demonstrated that either the nonzero spin-orbit interaction or the nonzero
external magnetic field suffices for the occurrence of the persistent spin
current on the nanospring. Two different mechanisms are shown to generate the
persistent spin current. One employs the spin-orbit interaction coming from the
local inversion asymmetry on the surface, while the other employs the curvature
coupling with the external magnetic field.",1302.0066v1
2017-01-22,Novel Magnetism and Local Symmetry Breaking in a Mott Insulator with Strong Spin Orbit Interactions,"Study of the combined effects of strong electronic correlations with
spin-orbit coupling (SOC) represents a central issue in quantum materials
research. Predicting emergent properties represents a huge theoretical problem
since the presence of SOC implies that the spin is not a good quantum number.
Existing theories propose the emergence of a multitude of exotic quantum
phases, distinguishable by either local point symmetry breaking or local spin
expectation values, even in materials with simple cubic crystal structure such
as Ba$_2$NaOsO$_6$. Experimental tests of such theories by local probes are
highly sought for. Here, we report on local measurements designed to
concurrently probe spin and orbital/lattice degrees of freedom of
Ba$_2$NaOsO$_6$. We find that a novel canted ferromagnetic phase which is
preceded by local point symmetry breaking is stabilized at low temperatures, as
predicted by quantum theories involving multipolar spin interactions.",1701.06117v1
2018-01-17,Discovery of new magnetic orders on pyrochlore spinels,"Frustration in spin system can give rise to unique ordered states and as a
consequence several physical phenomena are expected such as multiferroics, high
temperature superconductors and anomalous hall effect. Here we report the ""new
magnetic orders"" induced by anisotropic spin exchanges on pyrochlore spinels as
the interplay of spin orbit coupling and geometrical frustration. Due to
complicated superexchange paths of B-site spinels, we claim that anisotropic
interaction between next-nearest neighbors play an important role. Based on the
systematic studies of generic spin model, we argue that several classical spin
states can be explored in spinel systems; local XY state, all-in all-out state,
Palmer-Chalker state and coplanar spiral state. In addition, we reveal new
types of magnetic phases with finite ordering wavevectors, labeled as
'octagonal (prism)' state and '(distorted) cubic' states. When the 'octagonal
prism' state is stabilized, non-zero scalar spin chirality induces alternating
net current in addition to finite orbital current and orbital magnetization
even in Mott insulators. Finally, we also discuss the relevance of 'distorted
cubic' state to the magnetic order of spinel compound GeCo2O4.",1801.05820v1
2020-02-13,Thermal effects on a nonadiabatic spin-flip protocol of spin-orbit qubits,"We study the influence of a thermal environment on a non-adiabatic spin-flip
driving protocol of spin-orbit qubits. The driving protocol operates by moving
the qubit, trapped in a harmonic potential, along a nanowire in the presence of
a time-dependent spin-orbit interaction. We consider the harmonic degrees of
freedom to be weakly coupled to a thermal bath. We find an analytical
expression for the Floquet states and derive the Lindblad equation for a
strongly non-adiabatically driven qubit. The Lindblad equation corrects the
dynamics of an isolated qubit with Lamb shift terms and a dissipative
behaviour. Using the Lindblad equation, the influence of a thermal environment
on the spin-flip protocol is analysed.",2002.05548v1
2017-11-13,On-Demand Spin-Orbit Interaction from Which-Layer Tunability in Bilayer Graphene,"Spin-orbit interaction (SOI) that is gate-tunable over a broad range is
essential to exploiting novel spin phenomena. Achieving this regime has
remained elusive because of the weakness of the underlying relativistic
coupling and lack of its tunability in solids. Here we outline a general
strategy that enables exceptionally high tunability of SOI through creating a
which-layer spin-orbit field inhomogeneity in graphene multilayers. An external
transverse electric field is applied to shift carriers between the layers with
strong and weak SOI. Because graphene layers are separated by sub-nm scales,
exceptionally high tunability of SOI can be achieved through a minute carrier
displacement. A detailed analysis of the experimentally relevant case of
bilayer graphene on a semiconducting transition metal dichalchogenide substrate
is presented. In this system, a complete tunability of SOI amounting to its
ON/OFF switching can be achieved. New opportunities for spin control are
exemplified with electrically driven spin resonance and topological phases with
different quantized intrinsic valley Hall conductivities.",1711.04407v1
2018-07-21,Diffusion Monte Carlo methods for Spin-Orbit-Coupled ultracold Bose gases,"We present two Diffusion Monte Carlo (DMC) algorithms for systems of
ultracold quantum gases featuring synthetic spin-orbit interactions. The first
one is a discrete spin generalization of the T- moves spin-orbit DMC, which
provides an upper bound to the fixed-phase energy. The second is a
spin-integrated DMC method which recovers the fixed-phase property by avoiding
the definition of the effective Hamiltonian involved in the T-moves approach.
The latter is a more accurate method but it is restricted to spin-independent
two-body interactions. We report a comparison between both algorithms for
different systems. As a check of the efficiency of both methods, we compare the
DMC energies with results obtained with other numerical methods, finding
agreement between both estimation",1807.08123v2
2020-03-16,Probing the singlet-triplet splitting in double quantum dots: Implications of the ac field amplitude,"We consider a double quantum dot whose energy detuning is controlled by an ac
electric field. We demonstrate an energy configuration for which the ac-induced
current flowing through the double dot directly probes the spin-orbit
anticrossing point for small ac field amplitudes. On the contrary, as the ac
amplitude increases a current antiresonance is formed, and the direct
information about the spin-orbit interaction is lost. This result indicates
that a large ac amplitude is not necessarily advantageous for the spectroscopy
of spin-orbit coupled two-spin states. Moreover, we investigate the ac-induced
current peaks versus the ac amplitude and show a current suppression when the
ac field forms spin blocked states. This effect gives rise to a characteristic
pattern for the current which can be controlled at will by tuning the ac
amplitude. Our results can be explored by performing electronic transport
measurements in the spin blockade regime.",2003.07056v1
2020-03-25,Gravitational spin-orbit coupling through third-subleading post-Newtonian order: from first-order self-force to arbitrary mass ratios,"Exploiting simple yet remarkable properties of relativistic gravitational
scattering, we use first-order self-force (linear-in-mass-ratio) results to
obtain arbitrary-mass-ratio results for the complete third-subleading
post-Newtonian (4.5PN) corrections to the spin-orbit sector of spinning-binary
conservative dynamics, for generic (bound or unbound) orbits and spin
orientations. We thereby improve important ingredients of models of
gravitational waves from spinning binaries, and we demonstrate the improvement
in accuracy by comparing against aligned-spin numerical simulations of binary
black holes.",2003.11391v2
2021-12-30,Majorana chiral spin liquid in Mott insulating cuprates,"The large thermal Hall conductivity recently detected in Mott insulating
cuprates has been attributed to chiral neutral spin excitations. A quantum spin
liquid with Majorana excitations, Chern number +/-4 and large thermal Hall
conductivity is found to be an excited state of a frustrated Heisenberg model
on the square lattice. Using a Majorana mean-field theory and exact
diagonalizations, we explore two possible routes to achieve this chiral quantum
spin liquid, an orbital effect of an applied magnetic field and spin orbit
couplings as present in cuprates. In particular, we show how only the orbital
magnetic field allows this topological phase to be the ground state, while it
remains an excited state of the Majorana mean field under the
Dzyaloshinskii-Moriya terms. We interpret the large thermal Hall effect
observed in Mott cuprates from their close proximity to a transition to a
Majorana chiral quantum spin liquid which can be induced by an external
magnetic field.",2112.14991v1
2022-10-05,Spin current and chirality degrees of freedom inherent in localized electron orbitals,"In solid state physics, any phase transition is commonly observed as a change
in the microscopic distribution of charge, spin, or current. Here we report the
nature of an exotic order parameter inherent in the localized electron orbitals
that cannot be primarily captured by these three fundamental quantities. This
order parameter is described as the electric toroidal multipoles connecting
different total angular momenta under the spin-orbit coupling. The
corresponding microscopic physical quantity is the spin current tensor on an
atomic scale, which induces spin-derived electric polarization and the
chirality of the Dirac equation. We stress that the chirality intrinsic to the
elementary particle is the essence of electric toroidal multipoles. These
findings link microscopic spin currents and chirality in the Dirac theory to
the concept of multipoles and provide a new perspective for quantum states of
matter.",2210.02148v1
2017-09-21,Current-induced magnetization switching using electrically-insulating spin-torque generator,"Current-induced magnetization switching through spin-orbit torques (SOTs) is
the fundamental building block of spin-orbitronics. The SOTs generally arise
from the spin-orbit coupling of heavy metals. However, even in a
heterostructure where a metallic magnet is sandwiched by two different
insulators, a nonzero current-induced SOT is expected because of the broken
inversion symmetry; an electrical insulator can be a spin-torque generator.
Here, we demonstrate current-induced magnetization switching using an
insulator. We show that oxygen incorporation into the most widely used
spintronic material, Pt, turns the heavy metal into an electrically-insulating
generator of the SOTs, enabling the electrical switching of perpendicular
magnetization in a ferrimagnet sandwiched by electrically-insulating oxides. We
further found that the SOTs generated from the Pt oxide can be controlled
electrically through voltage-driven oxygen migration. These findings open a
route towards energy-efficient, voltage-programmable spin-orbit devices based
on solid-state switching of heavy metal oxidation.",1709.07127v1
2014-07-22,Ground states and dynamics of spin-orbit-coupled Bose-Einstein condensates,"We study analytically and asymptotically as well as numerically ground states
and dynamics of two-component spin-orbit-coupled Bose-Einstein condensates
(BECs) modeled by the coupled Gross-Pitaevskii equations (CGPEs). In fact, due
to the appearance of the spin-orbit (SO) coupling in the two-component BEC with
a Raman coupling, the ground state structures and dynamical properties become
very rich and complicated. For the ground states, we establish the existence
and non-existence results under different parameter regimes, and obtain their
limiting behaviors and/or structures with different combinations of the SO and
Raman coupling strengths. For the dynamics, we show that the motion of the
center-of-mass is either non-periodic or with different frequency to the
trapping frequency when the external trapping potential is taken as harmonic
and the initial data is chosen as a stationary state (e.g. ground state) with a
shift, which is completely different from the case of a two-component BEC
without the SO coupling, and obtain the semiclassical limit of the CGPEs in the
linear case via the Wigner transform method. Efficient and accurate numerical
methods are proposed for computing the ground states and dynamics, especially
for the case of box potentials. Numerical results are reported to demonstrate
the efficiency and accuracy of the numerical methods and show the rich
phenomenon in the SO-coupled BECs.",1407.5815v1
2023-11-05,Topological spin-orbit-coupled fermions beyond rotating wave approximation,"The realization of spin-orbit-coupled ultracold gases has driven a wide range
of researches and is typically based on the rotating wave approximation (RWA).
By neglecting the counter-rotating terms, RWA characterizes a single
near-resonant spin-orbit (SO) coupling in a two-level system. Here, we propose
and experimentally realize a new scheme for achieving a pair of two-dimensional
(2D) SO couplings for ultracold fermions beyond RWA. This work not only
realizes the first anomalous Floquet topological Fermi gas beyond RWA, but also
significantly improves the lifetime of the 2D-SO-coupled Fermi gas. Based on
pump-probe quench measurements, we observe a deterministic phase relation
between two sets of SO couplings, which is characteristic for our beyond-RWA
scheme and enables the two SO couplings to be simultaneously tuned to the
optimum 2D configurations. We observe intriguing band topology by measuring
two-ring band-inversion surfaces, quantitatively consistent with a Floquet
topological Fermi gas in the regime of high Chern numbers. Our study can open
an avenue to explore exotic SO physics and anomalous topological states based
on long-lived SO-coupled ultracold fermions.",2311.02584v1
2005-12-09,Molecular orbital calculations of two-electron states for P donor solid-state spin qubits,"We theoretically study the Hilbert space structure of two neighbouring P
donor electrons in silicon-based quantum computer architectures. To use
electron spins as qubits, a crucial condition is the isolation of the electron
spins from their environment, including the electronic orbital degrees of
freedom. We provide detailed electronic structure calculations of both the
single donor electron wave function and the two-electron pair wave function. We
adopted a molecular orbital method for the two-electron problem, forming a
basis with the calculated single donor electron orbitals. Our two-electron
basis contains many singlet and triplet orbital excited states, in addition to
the two simple ground state singlet and triplet orbitals usually used in the
Heitler-London approximation to describe the two-electron donor pair wave
function. We determined the excitation spectrum of the two-donor system, and
study its dependence on strain, lattice position and inter donor separation.
This allows us to determine how isolated the ground state singlet and triplet
orbitals are from the rest of the excited state Hilbert space. In addition to
calculating the energy spectrum, we are also able to evaluate the exchange
coupling between the two donor electrons, and the double occupancy probability
that both electrons will reside on the same P donor. These two quantities are
very important for logical operations in solid-state quantum computing devices,
as a large exchange coupling achieves faster gating times, whilst the magnitude
of the double occupancy probability can affect the error rate.",0512200v1
2004-01-09,The precession of orbital plane and the significant variabilities of binary pulsars,"There are two kinds of expressions on the precession of orbital plane of a
binary pulsar system, which are given by Barker $&$ O'Connell (1975) and
Apostolatos et al. (1994), Kidder (1995) respectively. This paper points out
that these two kinds of orbital precession velocities are actually obtained by
the same Lagrangian under different degrees of freedom. Correspondingly the
former expression is not consistent with the conservation of the total angular
momentum vector; whereas the latter one is. Damour $&$ Sch\""afer (1988) and Wex
$&$ Kopeikin (1999) have applied Barker $&$ O'Connell's orbital precession
velocity in pulsar timing measurement. This paper applies Apostolatos et al.
$&$ Kidder's orbital precession velocity in pulsar timing measurement. We
analyze that Damour $&$ Sch\""afer's treatment corresponds to negligible
Spin-Orbit induced precession of periastron. Whereas the effects corresponding
to Wex $&$ Kopeikin and this paper are both significant (however they are not
equivalent). The observational data of two typical binary pulsars, PSR
J2051-0827 and PSR J1713+0747 apparently support significant Spin-Orbit
coupling effect. Further more, the discrepancies between Wex $&$ Kopeikin and
this paper can be tested on specific binary pulsars with orbital plane nearly
edge on. If the orbital period derivative of double-pulsar system PSRs
J0737-3039 A and B, with orbital inclination angle $i=87.7_{-29}^{+17}$deg, is
much larger than that of the gravitational radiation induced one, then the
expression of this paper is supported, otherwise Wex $&$ Kopeikin's expression
is supported.",0401152v8
2023-07-08,Ultrathin films of black phosphorus as suitable platforms for unambiguous observation of the orbital Hall effect,"Phosphorene, a monolayer of black phosphorus, is a two-dimensional material
that lacks a multivalley structure in the Brillouin zone and has negligible
spin-orbit coupling. This makes it a promising candidate for investigating the
orbital Hall effect independently of the valley or spin Hall effects. To model
phosphorene, we utilized a DFT-derived tight-binding Hamiltonian, which is
constructed with the pseudo atomic orbital projection method. For that purpose,
we use the PAOFLOW code with a newly implemented internal basis that provides a
fairly good description of the phosphorene conduction bands. By employing
linear response theory, we show that phosphorene exhibits a sizable orbital
Hall effect with strong anisotropy in the orbital Hall conductivity for the
out-of-plane orbital angular momentum component. The magnitude and sign of the
conductivity depend upon the in-plane direction of the applied electric field.
These distinctive features enable the observation of the orbital Hall effect in
this material unambiguously. The effects of strain and of a perpendicularly
applied electric field on the phosphorene orbital-Hall response are also
explored. We show that a supplementary electric field applied perpendicular to
the phosphorene layer in its conductive regime gives rise to an induced
in-plane orbital magnetization.",2307.03866v2
1996-09-17,A topological characterization of delocalization in a spin-orbit coupling system,"We show that wavefunctions in a two-dimensional (2D) electron system with
spin-orbit coupling can be characterized by a topological quantity--the Chern
integer due to the existence of the intrinsic Kramers degeneracy. The
localization-delocalization transition in such a system is studied in terms of
such a Chern number description, which reproduces the known metal-insulator
transition point. The present work suggests a unified picture for various known
2D delocalization phenomena based on the same topological characterization.",9609147v1
1999-06-06,Level statistics in a two-dimensional system with strong spin-orbit coupling,"We study level correlations in a two-dimensional system with a long-range
random potential and strong spin-orbit (SO) splitting of the spectrum. The
level correlations for sufficiently large splitting are shown to be described
by orthogonal Wigner-Dyson statistics, in contrast to the common point of view
that a system with the strong SO coupling belongs to the symplectic statistical
ensemble. We demonstrate also that in a wide energy interval the level
statistics is completely determined by transitions between two branches of the
split spectrum. A sharp resonance is obtained in the two-level correlation
function at energy equal to the value of SO splitting.",9906086v1
1999-08-31,Critical Quantum Chaos in 2D Disordered Systems with Spin-Orbit Coupling,"We examine the validity of the recently proposed semi-Poisson level spacing
distribution function P(S), which characterizes `critical quantum chaos', in 2D
disordered systems with spin-orbit coupling. At the Anderson transition we show
that the semi-Poisson P(S) can describe closely the critical distribution
obtained with averaged boundary conditions, over Dirichlet in one direction
with periodic in the other and Dirichlet in both directions. We also obtain a
sub-Poisson linear number variance $\Sigma_{2}(E)\approx \chi_{0}+ \chi E$,
with asymptotic value $\chi\approx0.07$. The obtained critical statistics,
intermediate between Wigner and Poisson, is relevant for disordered systems and
chaotic models.",9908484v1
2002-04-25,The Anderson Transition in Two-Dimensional Systems with Spin-Orbit Coupling,"We report a numerical investigation of the Anderson transition in
two-dimensional systems with spin-orbit coupling. An accurate estimate of the
critical exponent $\nu$ for the divergence of the localization length in this
universality class has to our knowledge not been reported in the literature.
Here we analyse the SU(2) model. We find that for this model corrections to
scaling due to irrelevant scaling variables may be neglected permitting an
accurate estimate of the exponent $\nu=2.73 \pm 0.02$.",0204544v3
2003-03-11,Electronic structure of the V3+ ion in V2O3,"We have attributed magnetism and electronic structure of V2O3 to the V3+
ions. We claim that the V3+ ion in V2O3 should be considered as described by
the quantum numbers S=1 and L=3. Such quantum numbers result from two Hund's
rules. The resulting electronic structure is much more complex than considered
up to now, but it describes, e.g. the insulating ground state and the lowered
magnetic moment, of 1.2 \muB. It turns out that the intra-atomic spin-orbit
coupling is indispensable for the physically adequate description of electronic
and magnetic properties of V2O3.
  Keywords: highly-correlated electron system, crystal field, V3+ ion,
spin-orbit coupling, Mott insulators
  PACS: 71.70.E, 75.10.D, 75.30.Gw",0303194v1
2004-04-27,Numerical estimation of the $β$-function in 2D systems with spin-orbit coupling,"We report a numerical study of Anderson localization in a 2D system of
non-interacting electrons with spin-orbit coupling. We analyze the scaling of
the renormalized localization length for the 2D SU(2) model and estimate its
$\beta$-function over the full range from the localized to the metallic limits.",0404630v2
2005-12-26,Current in a Spin-orbit-coupling System,"The formulae of particle current as well as spin- and angular momentum
currents are studied for most spin-orbit coupling (SOC) systems. It is shown
that the conventional expression of currents in some literatures are not
complete for some SOC systems. The particle current in Dresselhaus system must
have extra terms in additional to the conventional one, but no extra term for
Rashba, Luttinger model. Further more, we also prove that the extra terms of
total angular momentum appear in Rashba current in addition to conventional
one.",0512655v2
2006-05-15,Charge transport in two dimensional electron gas/superconductor junctions with Rashba spin-orbit coupling,"We have studied the tunneling conductance in two dimensional electron gas /
insulator / superconductor junctions in the presence of Rashba spin-orbit
coupling (RSOC). It is found that for low insulating barrier the tunneling
conductance is suppressed by the RSOC while for high insulating barrier it is
almost independent of the RSOC. We also find the reentrant behavior of the
conductance at zero voltage as a function of RSOC for intermediate insulating
barrier strength. The results are essentially different from those predicted in
ferromagnet / superconductor junctions. The present derivation of the
conductance is applicable to arbitrary velocity operator with off-diagonal
components.",0605372v1
2006-09-22,Josephson current through a quantum dot with spin-orbit coupling,"The equilibrium Josephson current through a nanoscale multi-level quantum dot
with Rashba or Dresselhaus spin-orbit coupling $\alpha$ has been computed. The
critical current can be drastically modified already by moderate $\alpha$. In
the presence of a Zeeman field, Datta-Das-like oscillatory dependencies on
$\alpha$ are predicted.",0609577v2
2006-11-14,Ideal switching effect in periodic spin-orbit coupling structures,"An ideal switching effect is discovered in a semiconductor nanowire with a
spatially-periodic Rashba structure. Bistable `ON' and `OFF' states can be
realized by tuning the gate voltage applied on the Rashba regions. The energy
range and position of `OFF' states can be manipulated effectively by varying
the strength of the spin-orbit coupling (SOC) and the unit length of the
periodic structure, respectively. The switching effect of the nanowire is found
to be tolerant of small random fluctuations of SOC strength in the periodic
structure. This ideal switching effect might be applicable in future spintronic
devices.",0611362v1
2006-11-15,Tunneling anisotropic magnetoresistance and spin-orbit coupling in Fe/GaAs/Au tunnel junctions,"We report the observation of tunneling anisotropic magnetoresistance effect
(TAMR) in the epitaxial metal-semiconductor system Fe/GaAs/Au. The observed
two-fold anisotropy of the resistance can be switched by reversing the bias
voltage, suggesting that the effect originates from the interference of the
spin-orbit coupling at the interfaces. Corresponding model calculations
reproduce the experimental findings very well.",0611406v1
2007-02-22,Triplet pairing and upper critical field in the mixed state of d-wave superconductors,"We show that an additional triplet component of the order parameter is
generated in the vortex phase of the d-wave superconductor. Spatial variations
of the triplet component are analyzed for a strong spin-orbit coupling.
Corrections to the London equation and an unusual temperature dependence of the
upper critical field, are obtained in the case of the weak spin-orbit coupling.",0702523v2
1993-04-08,BRS Cohomology of the Supertranslations in D=4,"Supersymmetry transformations are a kind of square root of spacetime
translations. The corresponding Lie superalgebra always contains the
supertranslation operator $ \delta = c^{\alpha} \sigma^{\mu}_{\alpha \dot
\beta} {\overline c}^{\dot \beta} (\epsilon^{\mu})^{\dag} $. We find that the
cohomology of this operator depends on a spin-orbit coupling in an SU(2) group
and has a quite complicated structure. This spin-orbit type coupling will turn
out to be basic in the cohomology of supersymmetric field theories in general.",9304035v1
1999-01-28,Eleven-dimensional massless superparticles and matrix theory spin-orbit couplings revisited,"The classical probe dynamics of the eleven-dimensional massless
superparticles in the background geometry produced by N source M-momenta is
investigated in the framework of N-sector DLCQ supergravity. We expand the
probe action up to the two fermion terms and find that the fermionic
contributions are the spin-orbit couplings, which precisely agree with the
matrix theory calculations. We comment on the lack of non-perturbative
corrections in the one-loop matrix quantum mechanics effective action and its
compatibility with the supergravity analysis.",9901152v1
2007-04-17,Impact of spin-orbit coupling on quantum Hall nematic phases,"Anisotropic charge transport is observed in a two-dimensional (2D) hole
system in a perpendicular magnetic field at filling factors nu=7/2, nu=11/2,
and nu=13/2 at low temperature. In stark contrast, the transport at nu=9/2 is
isotropic for all temperatures. Isotropic hole transport at nu=7/2 is restored
for sufficiently low 2D densities or an asymmetric confining potential. The
density and symmetry dependences of the observed anisotropies suggest that
strong spin-orbit coupling in the hole system contributes to the unusual
transport behavior.",0704.2215v1
2007-05-07,Microscopic origin of Magnetic Ferroelectrics in Nonlinear Multiferroics,"A simple but general microscopic mechanism to understand the interplay
between the electric and magnetic degrees of freedom is developed. Within this
mechanism, the magnetic structure generates an electric current which induce an
counterbalance electric current from the spin orbital coupling. When the
magnetic structure is described by a single order parameter, the electric
polarization is determined by the single spin orbital coupling parameter, and
the material is predicted to be a half insulator. This mechanism provides a
simple estimation of the value of ferroelectricity and sets a physical
limitation as well.",0705.0955v3
2007-05-10,Evanescent states in quantum wires with Rashba spin-orbit coupling,"We discuss the calculation of evanescent states in quasi-one-dimensional
quantum wires in the presence of Rashba spin-orbit interaction. We suggest a
computational algorithm devised for cases in which longitudinal and transverse
motions are coupled. The dispersion relations are given for some selected
cases, illustrating the feasibility of the proposed computational method. As a
practical application, we discuss the solutions for a wire containing a
potential step.",0705.1506v1
2008-04-14,Spin-orbit coupling in ferromagnetic Nickel,"We use the Gutzwiller variational theory to investigate the electronic and
the magnetic properties of fcc-Nickel. Our particular focus is on the effects
of the spin-orbit coupling. Unlike standard relativistic band-structure
theories, we reproduce the experimental magnetic moment direction and we
explain the change of the Fermi-surface topology that occurs when the magnetic
moment direction is rotated by an external magnetic field. The Fermi surface in
our calculation deviates from early de-Haas--van-Alphen (dHvA) results. We
attribute these discrepancies to an incorrect interpretation of the raw dHvA
data.",0804.2211v1
2008-05-03,Kramers degeneracy in a magnetic field and Zeeman spin-orbit coupling in antiferromagnetic conductors,"In this article, I study magnetic response of electron wavefunctions in a
commensurate collinear antiferromagnet. I show that, at a special set of
momenta, hidden anti-unitary symmetry protects Kramers degeneracy of Bloch
eigenstates against a magnetic field, pointing transversely to staggered
magnetization. Hence a substantial momentum dependence of the transverse
g-factor in the Zeeman term, turning the latter into a spin-orbit coupling,
that may be present in materials from chromium to borocarbides, cuprates,
pnictides, as well as organic and heavy fermion conductors.",0805.0378v2
2008-05-12,Spin orbit coupling in bulk ZnO and GaN,"Using group theory and Kane-like $\mathbf{k\cdot p}$ model together with the
L\""owdining partition method, we derive the expressions of spin-orbit coupling
of electrons and holes, including the linear-$k$ Rashba term due to the
intrinsic structure inversion asymmetry and the cubic-$k$ Dresselhaus term due
to the bulk inversion asymmetry in wurtzite semiconductors. The coefficients of
the electron and hole Dresselhaus terms of ZnO and GaN in wurtzite structure
and GaN in zinc-blende structure are calculated using the nearest-neighbor
$sp^3$ and $sp^3s^\ast$ tight-binding models separately.",0805.1577v2
2008-08-03,Direct coupling between magnetism and superconducting current in Josephson Phi junction,"We study the proximity effect between conventional superconductor and
magnetic normal metal with a spin-orbit interaction of the Rashba type. Using
the phenomenological Ginzburg-Landau theory and the quasiclassical Eilenberger
approach it is demonstrated that the Josephson junction with such a metal as a
weak link has a special non-sinusoidal current-phase relation. The ground state
of this junction is caracterized by the finite phase difference Phi, which is
proportional to the strength of the spin-orbit interaction and the exchange
field in the normal metal. The proposed mechanism of the Phi junction formation
gives a direct coupling between the superconducting current and the magnetic
moment in the weak link. Therefore the Phi junctions open interesting
perspectives for the superconducting spintronics.",0808.0299v1
2009-09-16,Anomalous Josephson current through a spin-orbit coupled quantum dot,"For a general model of a mesoscopic multi-level quantum dot, we determine the
necessary conditions for the existence of an anomalous Josephson current with
spontaneously broken time-reversal symmetry. They correspond to a finite
spin-orbit coupling, a suitably oriented Zeeman field, and the dot being a
chiral conductor. We provide analytical expressions for the anomalous
supercurrent covering a wide parameter regime.",0909.3036v1
2010-01-08,Spin-orbit coupling induced by a mass gradient,"The existence of a spin-orbit coupling (SOC) induced by the gradient of the
effective mass in low-dimensional heterostructures is revealed. In structurally
asymmetric quasi-two-dimensional semiconductor heterostructures the presence of
a mass gradient across the interfaces results in a SOC which competes with the
SOC created by the electric field in the valence band. However, in graded
quantum wells subjected to an external electric field, the mass-gradient
induced SOC can be finite even when the electric field in the valence band
vanishes.",1001.1235v1
2010-02-10,Spin-orbit coupling induced anisotropy effects in bimetallic antiferromagnets: A route towards antiferromagnetic spintronics,"Magnetic anisotropy phenomena in bimetallic antiferromagnets Mn$_2$Au and
MnIr are studied by first-principles density functional theory calculations. We
find strong and lattice-parameter dependent magnetic anisotropies of the ground
state energy, chemical potential, and density of states, and attribute these
anisotropies to combined effects of large moment on the Mn 3$d$ shell and large
spin-orbit coupling on the 5$d$ shell of the noble metal. Large magnitudes of
the proposed effects can open a route towards spintronics in compensated
antiferromagnets without involving ferromagnetic elements.",1002.2151v1
2010-04-05,Non-monotonic variation of anomalous Hall effect with spin orbit coupling strength,"For L1(0) FePt films, the anomalous Hall resistivity is found to be
proportional to spontaneous magnetization $M_{\mathrm{S}}$. After the
$M_{\mathrm{S}}$ temperature effect is eliminated, $\rho_{\mathrm{xyo}}$ can be
fitted by $\rho_{\mathrm{xyo}}=a_{\mathrm{o}}\rho_{\mathrm{xx}}+
b_{\mathrm{o}}\rho_{\mathrm{xx}}^{\mathrm{2}}$. $a_{\mathrm{o}}$ and
$b_{\mathrm{o}}$ change non-monotonically with chemical long range ordering
degree $S$. Accordingly, it is indicated that for L1(0) FePt films the spin
orbit coupling strength increases monotonically with increasing $S$.",1004.0548v4
2011-03-14,Topological superconducting phases in disordered quantum wires with strong spin-orbit coupling,"Zeeman fields can drive semiconductor quantum wires with strong spin-orbit
coupling and in proximity to s-wave superconductors into a topological phase
which supports end Majorana fermions and offers an attractive platform for
realizing topological quantum information processing. Here, we investigate how
potential disorder affects the topological phase by a combination of analytical
and numerical approaches. Most prominently, we find that the robustness of the
topological phase against disorder depends sensitively and non-monotonously on
the Zeeman field applied to the wire.",1103.2746v2
2011-04-21,Textures of Spin-Orbit Coupled F=2 Spinor Bose Einstein Condensates,"We study the textures of F=2 spinor Bose-Einstein condensates (BECs) with
spin-orbit coupling (SOC) induced by a synthetic non-Abelian gauge field. On
the basis of the analysis of the SOC energy and the numerical calculation of
the Gross-Pitaevskii equation, we demonstrate that the textures originate from
the helical modulation of the order parameter (OP) due to the SOC. In
particular, the cyclic OP consists of two-dimensional lattice textures, such as
the hexagonal lattice and the 1/3-vortex lattice, commonly understandable as
the two-dimensional network of the helical modulations.",1104.4179v2
2011-05-10,Spin-orbit coupling induced enhancement of superconductivity in a two-dimensional repulsive gas of fermions,"We study a model of a two-dimensional repulsive Fermi gas with Rashba
spin-orbit coupling $\alpha_R$, and investigate the superconducting instability
using renormalization group approach. We find that in general superconductivity
is enhanced as the dimensionless ratio 1/2m\alpha_R^2/E_F$ increases, resulting
in unconventional superconducting states which break time reversal symmetry.",1105.2041v2
2011-06-09,Majorana fermions in spin-orbit coupled ferromagnetic Josephson junctions,"We study all possible Majorana modes in two-dimensional spin-orbit coupled
ferromagnetic superconductor-normal state-superconductor (SNS) Josephson
junctions and propose experiments to detect them. With the S region in a
non-trivial topological phase and a superconducting phase difference $\phi =
\pi$ across the junction, two delocalized Majorana fermions with no excitation
gap appear in the N region. In addition, if S and N belong to different
topological phases and have well-separated the Fermi surfaces, localized
Majorana fermions with a finite excitation gap also emerge at both SN
interfaces for all $\phi$.",1106.1801v2
2012-03-03,Scaling of intrinsic Gilbert damping with spin-orbital coupling strength,"We have experimentally and theoretically investigated the dependence of the
intrinsic Gilbert damping parameter $\alpha_0$ on the spin-orbital coupling
strength $\xi$ by using L1$_{\mathrm{0}}$ ordered
FePd$_{\mathrm{1-x}}$Pt$_{\mathrm{x}}$ ternary alloy films with perpendicular
magnetic anisotropy. With the time-resolved magneto-optical Kerr effect,
$\alpha_0$ is found to increase by more than a factor of ten when $x$ varies
from 0 to 1.0. Since changes of other leading parameters are found to be
neglected, the $\alpha_0$ has for the first time been proven to be proportional
to $\xi^2$.",1203.0607v1
2012-08-08,"Electronic band structure, Fermi surface and effect of spin-orbit coupling for tetragonal low-temperature superconductor Bi2Pd from first principles","We have examined theoretically the electronic band structure and Fermi
surface of tetragonal low-temperature superconductor Bi2Pd. Our main results
are that (i) the Pd 4d and Bi 6p states determine the main peculiarities of the
multiple-sheets FS topology, thus for this material the complicated
superconducting gap structure with different energy gaps on different FS sheets
should be assumed; (ii) the effect of the spin-orbit coupling is of minor
importance for the distributions of the near-Fermi electronic states; and (iii)
this phase adopts 3D-like type owing to the directional bonds between the
adjacent atomic sheets.",1208.1633v1
2012-09-14,An electronic model for self-assembled hybrid organic/perovskite semiconductors: reverse band edge electronic states ordering and spin-orbit coupling,"Based on density functional theory, the electronic and optical properties of
hybrid organic/perovskite crystals are thoroughly investigated. We consider the
mono-crystalline 4FPEPI as material model and demonstrate the optical process
is governed by three active Bloch states at the {\Gamma} point of the reduced
Brillouin zone with a reverse ordering compared to tetrahedrally bonded
semiconductors. Giant spin-orbit coupling effects and optical activities are
subsequently inferred from symmetry analysis.",1209.3195v1
2012-11-22,Observation of Phonon-Assisted Magnon Absorption in Spin-Orbit Coupling Induced Mott Insulator Sr$_{2}$IrO$_{4}$,"The infrared transmission measurement was performed for a two-dimensional
spin-orbit coupling induced Mott insulator Sr$_{2}$IrO$_{4}$ with a
layered-perovskite structure. A phonon-assisted magnon mode was observed at
around 1870 cm$^{-1}$ in the absorption spectrum below 180 K. The
nearest-neighbor superexchange interaction $J$ was estimated to be 57 meV,
which is about a half of the $J$ value of a copper oxide La$_{2}$CuO$_{4}$. Our
results indicate the possibility that nontrivial properties such as
superconductivity are realized at rather high temperature in iridium oxides.",1211.5241v2
2012-12-14,Single-branch theory of ultracold Fermi gases with artificial Rashba spin-orbit coupling,"We consider interacting ultracold fermions subject to Rashba spin-orbit
coupling. We construct a single-branch interacting theory for the Fermi gas
when the system is dilute enough so that the positive helicity branch is not
occupied at all in the non-interacting ground state. We show that the theory is
renormalizable in perturbation theory and therefore yields a model of polarized
fermions that avoids a multi-channel treatment of the problem. Our results open
the path towards a much more straightforward approach to the many-body physics
of cold atoms subject to artificial vector potentials.",1212.3565v1
2012-12-26,Electron Correlation Induced Spontaneous Symmetry Breaking and Weyl Semimetal Phase in a Strongly Spin-Orbit Coupled System,"We study theoretically the electron correlation effect in a three-dimensional
Dirac fermion system which describes a topologically nontrivial state. It is
shown within the mean-field approximation that time-reversal and inversion
symmetries of the system are spontaneously broken in the region where both
spin-orbit coupling and electron correlation are strong. This phase is
considered as an analog of that in the lattice quantum chromodynamics. It is
also shown that in the presence of magnetic impurities, electron correlation
enhances the appearance of the Weyl semimetal phase between the topological
insulator phase and the normal insulator phase.",1212.6218v1
2013-02-05,Fulde-Ferrell Pairing instability in Spin-Orbit Coupled Fermi Gas,"We consider finite-momentum pairing of superfluid phase in ultracold Fermi
gas with spin-orbit coupling when subjected to an effective Zeeman field. Based
on our two body and mean field many body calculations, we show that the
Fulde-Ferrell type superfluid dominates in zero and finite temperature phase
diagram. We examine the origin and properties of this novel phase
systematically.",1302.1189v2
2013-03-14,Spin-orbit interactions in a helical Luttinger liquid with a Kondo impurity,"The combined effect of Rashba and Dresselhaus spin-orbit interactions on the
physics of a helical Luttinger liquid coupled to a Kondo impurity is studied. A
Rashba coupling can potentially destroy the Kondo singlet formation in certain
parameter regimes [Phys. Rev. B 86, 161103(R) (2012)]. This effect is here
shown to vanish for sufficiently strong Dresselhaus interaction. The transport
properties of the system are investigated by calculating electrical
conductance, current and current fluctuations, and thermal conductance.",1303.3558v3
2013-04-01,Fulde-Ferrell superfluidity in ultracold Fermi gases with Rashba spin-orbit coupling,"We theoretically investigate the inhomogeneous Fulde-Ferrell (FF)
superfluidity in a three dimensional atomic Fermi gas with Rashba spin-orbit
coupling near a broad Feshbach resonance. We show that within mean-field theory
the FF superfluid state is always more favorable than the standard
Bardeen-Cooper-Schrieffer (BCS) superfluid state when an in-plane Zeeman field
is applied. We present a qualitative finite-temperature phase diagram near
resonance and argue that the predicted FF superfluid is observable with
experimentally attainable temperatures (i.e., $T\sim0.2T_{F}$, where $T_{F}$ is
the characteristic Fermi degenerate temperature).",1304.0387v2
2013-04-04,Spin-orbit coupling induced Fulde-Ferrell-Larkin-Ovchinnikov-like Cooper pairing and skyrmion-like polarization textures in trapped optical lattices,"We study the interplay between the Zeeman field and spin-orbit coupling (SOC)
in harmonically trapped Fermi gases loaded into a two-dimensional single-band
tight-binding optical lattice. Using the Bogoliubov-de Gennes theory, we find
that the Zeeman field combined with a Rashba SOC gives rise to $(i)$
Fulde-Ferrell-like superfluidity and $(ii)$ skyrmion-like polarization textures
near the edges of the system. We also discussed the effects of interaction,
temperature, SOC anisotropy and Zeeman field anisotropy on the superfluid
ground state and polarization textures.",1304.1473v2
2013-04-27,Valley-Polarized Quantum Anomalous-Hall Effects in Silicene,"We demonstrate a new quantum state of matter---valley-polarized quantum
anomalous Hall effect in monolayer silicene. In the presence of extrinsic
Rashba spin-orbit coupling and exchange field, monolayer silicene can host a
quantum anomalous-Hall state with Chern number C=2. We find that through tuning
Rashba spin-orbit coupling, a topological phase transition gives rise to a
valley polarized quantum anomalous Hall state, i.e. a quantum state which
exhibits electronic properties of both quantum valley-Hall effect (valley Chern
number C_V=3) and quantum anomalous Hall effect with C=-1.",1304.8076v1
2013-12-23,"Reply to Comment on ""Quantum quasicrystals of spin-orbit coupled dipolar bosons''","In a recent Letter [Phys. Rev. Lett. 111, 185304 (2013)], we proposed a
scheme for realizing quantum quasicrystals using spin-orbit coupled dipolar
bosons. We remarked that these quantum quasicrystals have additional
``phason''-like modes compared with their classical counterparts. A recent
comment by Lifshitz [arXiv:1312.1388] contests this claim. We argue here that
our enumeration of gapless modes is indeed the physically relevant one; whether
the additional modes are ``phasons'' is, however, a matter of definition.",1312.6452v1
2014-01-23,Spin-Orbit Coupling in Deformed Harmonic Traps,"We consider a two-dimensional system of harmonically trapped particles with
pseudo-spin-$\frac{1}{2}$ degree of freedom. This degree of freedom is coupled
to the particle's momentum via the so-called Rashba spin-orbit interaction. We
present our numerical results for a single-particle and few-particle systems,
assuming the repulsive interparticle interaction to be of zero range.",1401.5914v1
2014-08-18,Spin Orbit coupling and Anomalous Josephson effect in Nanowires,"A superconductor-semiconducting nanowire-superconductor heterostructure in
the presence of spin orbit coupling and magnetic field can support a
supercurrent even in the absence of phase difference between the
superconducting electrodes. We investigate this phenomenon, the anomalous
Josephson effect, employing a model capable of describing many bands in the
normal region. We discuss geometrical and symmetry conditions required to have
finite anomalous supercurrent and in particular we show that this phenomenon is
enhanced when the Fermi level is located close to a band opening in the normal
region.",1408.3953v2
2014-11-12,Antiferromagnetic Order in a Spin-Orbit Coupled Bose-Einstein Condensate,"Spin-orbit coupling related new physics and quantum magnetism are two
branches of great interest both in condensed matter physics and in cold atomic
physics. With the introduction of a Rashba-like SOC into a Bose-Einstein
condensate (BEC) loaded in a two-dimensional bipartite optical square lattice,
we find that the ground state of the BEC always favors a coherent condensate
than a fragmented condensate and always exhibits very large degeneracy, and
most importantly, an antiferromagnetic order of quantum nature emerges when
parameters satisfy certain condition. This provides an ideal platform to study
the interplay of antiferromagnetic phase and superfluid phase.",1411.3216v1
2014-11-17,Chiral zero modes in superconducting nanowires with Dresselhaus spin-orbit coupling,"Using chiral decomposition, we are able to find analytically the zero modes
and the conditions for such modes to exist in the Kitaev ladder model and
superconducting nanowires with Dresselhaus spin-orbit coupling. As a result, we
are able to calculate the number of zero modes in these systems for arbitrary
given parameters in the semi-infinite limit. Moreover, we find that when
suitable resonance condition is satisfied exact zero modes exist even in finite
systems contrary to the common belief.",1411.4393v1
2014-11-22,Fidelity Approach in Topological Superconductors with Disorders,"We apply the fidelity approach to study the topological superconductivity in
a spin-orbit coupled nanowire system. The wire is modeled as a one layer
lattice chain with Zeeman energy and spin-orbit coupling, which is in proximity
to a multi layer superconductor. In particular, we study the effects of
disorders and find that the fidelity susceptibility show multiple peaks. It is
revealed that the major peak indicates the topological quantum phase
transition, while other peaks signal the pining of the Majorana bound states by
disorders.",1411.6101v1
2015-01-06,Spontaneous symmetry breaking in a spin-orbit coupled $f=2$ spinor condensate,"We study the ground-state density profile of a spin-orbit coupled $f=2$
spinor condensate in a quasi-one-dimensional trap. The Hamiltonian of the
system is invariant under time reversal but not under parity. We identify
different parity- and time-reversal-symmetry-breaking states. The
time-reversal-symmetry breaking is possible for degenerate states. A phase
separation among densities of different components is possible in the domain of
time-reversal-symmetry breaking. Different types of parity- and
time-reversal-symmetry-breaking states are predicted analytically and studied
numerically. We employ numerical and approximate analytic solutions of a
mean-field model in this investigation to illustrate our findings.",1501.01164v1
2015-02-16,Quasiclassical theory of disordered Rashba superconductors,"We derive the quasiclassical equations that describe two-dimensional
superconductors with a large Rashba spin-orbit coupling and in the presence of
impurities. These equations account for the helical phase induced by an
in-plane magnetic field, with a superconducting order parameter that is
spatially modulated along a direction perpendicular to the field. We also
derive the generalized Ginzburg-Landau functional, which includes a
linear-in-gradient term corresponding to the helical phase. This theory paves
the way for studies of the proximity effect in two-dimensional electron gases
with large spin-orbit coupling.",1502.04504v2
2015-02-17,Magnetotransport in disordered two-dimensional topological insulators: signatures of charge puddles,"In this numerical study we investigate the influence and interplay of
disorder, spin-orbit coupling and magnetic field on the edge-transport in
HgTe/CdTe quantum wells in the framework of coherent elastic scattering. We
show that the edge states remain unaffected by the combined effect of moderate
disorder and a weak magnetic field at realistic spin-orbit coupling strengths.
Agreement with the experimentally observed linear magnetic field dependence for
the conductance of long samples is obtained when considering the existence of
charge puddles.",1502.04919v1
2015-04-03,Quantum mechanics of a spin-orbit coupled electron constrained to a space curve,"We derive the effective one-dimensional Schrodinger-Pauli equation for
electrons constrained to move on a space curve. The electrons are confined
using a double thin-wall quantization procedure with adiabatic separation of
fast and slow quantum degrees of freedom. This procedure is capable of yielding
a correct Hermitian one-dimensional Schrodinger-Pauli operator. We find that
the torsion of the space curve generates an additional quantum geometric
potential, adding to the well-known curvature-induced one. Finally, we derive
an analytic form of the one-dimensional Hamiltonian for spin-orbit coupled
electrons in a nanoscale helical wire.",1504.00840v1
2015-04-23,Fluctuation Theory of Rashba Fermi Gases,"Fermi gases with generalized Rashba spin orbit coupling inducedby a synthetic
gauge field have the potential of realizing many interesting states such as
rashbon condensates and topological phases. Here we develop a fluctuation
theory of such systems and demonstrate that beyond-Gaussian effects are
essential to capture the physics of such systems. We obtain their phase diagram
by constructing an approximate non-Gaussian theory. We conclusively establish
that spin-orbit coupling can enhance the exponentially small transition
temperature ($T_c$) of a weakly attracting superfluid to the order of Fermi
temperature, paving a pathway towards high $T_c$ superfluids.",1504.06022v1
2015-04-28,"""Switching"" of Magnetic Anisotropy in a fcc Antiferromagnet with Direction-Dependent Interactions","Direction-dependent anisotropic exchange is a common feature of magnetic
systems with strong spin-orbit coupling. Here we study the effect of such
exchange upon macroscopic magnetic anisotropy for a face-centered-cubic model.
By several theoretical techniques, we show that, both in the paramagnetic and
ordered phases, the magnetic anisotropy is induced by fluctuations. Moreover,
the magnetic anisotropy differs in the paramagnetic and ordered phases: in the
paramagnetic phase the susceptibility is maximum along the $\langle111\rangle$
directions, while the magnetic moments orient along $\langle110\rangle$ or
$\langle100\rangle$ in the ordered phase. We suggest that such ""anisotropy
switching"" can be a common feature of strongly spin-orbit coupled magnets.",1504.07607v1
2015-11-13,Spin-Orbit Coupling Parameters of sp2 Nanocarbons,"The paper presents a new approach to the determination of standard spin-orbit
coupling parameters, such as the SOC constant a_SO and the Lande parameter g,
by using peculiarities of UHF results for open-shell systems. The approach is
convincingly approved for stretched ethylene and fullerene C60 as examples,
thus justifying at once a high efficacy of the UHF formalism to disclose SOC
features.",1511.04327v1
2016-01-20,Quantum Transport of Dirac fermions in graphene with a spatially varying Rashba spin-orbit coupling,"We theoretically study electronic transport through a region with
inhomogeneous Rashba spin-orbit (RSO) coupling placed between two normal
regions in a monolayer graphene. The inhomogeneous RSO region is characterized
by linearly varying RSO strength within its borders and constant RSO strength
in the central region. We calculate the transmission properties within the
transfer matrix approach. It is shown that the amplitude of conductance
oscillations reduces and at the same time the magnitude of conductance
increases with increasing border thickness. We also investigate how the Fano
factor can be modified by the border thickness of RSO region.",1601.05276v1
2019-05-23,First order Fermi surface topological (Lifshitz) transition in an interacting two-dimensional Rashba Fermi liquid,"We study the Fermi surface topological transition of the pocket-opening type
in a two dimensional Fermi liquid with spin-orbit coupling of Rashba type. We
find that the interactions, far from instabilities, drive the transition first
order at zero temperature surprisingly in a more pronounced way than in the
case of interacting Fermi liquid without spin-orbit coupling. We first gain
insight from second order perturbation theory in the self-energy. We then
extend the results to stronger interaction, using the self-consistent
fluctuation approximation. We discuss existing experimental work on the system
BiTeI and suggest further experiments in the light of these results .",1905.09941v2
2010-05-03,Effects of interface spin-orbit coupling on tunneling between normal metal and chiral p-wave superconductor,"We study the tunneling conductance of a clean normal metal/chiral p-wave
superconductor junction using the extended Blonder-Tinkham-Klapwijk formalism.
It is shown that the spin-orbit coupling of the Rashba type that is present
near the interface causes the subgap conductance peaks associated with the
Andreev surface bound states to shift to a nonzero bias. We also investigate
the effect of the Fermi wavevector mismatch between the normal metal and the
superconductor.",1005.0370v1
2013-08-19,Spirals and skyrmions in two dimensional oxide heterostructures,"We construct the general free energy governing long-wavelength magnetism in
two-dimensional oxide heterostructures, which applies irrespective of the
microscopic mechanism for magnetism. This leads, in the relevant regime of weak
but non-negligible spin-orbit coupling, to a rich phase diagram containing
in-plane ferromagnetic, spiral, cone, and skyrmion lattice phases, as well as a
nematic state stabilized by thermal fluctuations. The general conclusions are
vetted by a microscopic derivation for a simple model with Rashba spin-orbit
coupling.",1308.4179v2
2017-04-13,Spontaneous currents in superconducting systems with strong spin-orbit coupling,"We show that Rashba spin-orbit coupling at the interface between a
superconductor and a ferromagnet should produce a spontaneous current in the
atomic thickness region near the interface. This current is counter-balanced by
the superconducting screening current flowing in the region of the width of the
London penetration depth near the interface. Such current carrying state
creates a magnetic field near the superconductor surface, generates a stray
magnetic field outside the sample edges, changes the slope of the temperature
dependence of the critical field $H_{c3}$ and may generate the spontaneous
Abrikosov vortices near the interface.",1704.04123v1
2008-07-11,Breakdown of half-metallic ferromagnetism in zinc-blende II-V compounds,"We investigated the electronic and magnetic properties of a series of
zinc-blend II-V compounds by carrying out density-functional-theory
calculations including spin-orbit couplings. Contrary to the case of CaN and
CaP, the half-metallic characteristics of the II-V compounds such as CaSb and
CaBi were found to be destroyed. Our analysis of the valence band structures of
CaAs, CaSb, and CaBi revealed a critical role of the spin-orbit coupling
interactions on the exchange-split band structure, thereby leading to breakdown
of the half-metallic ferromagnetism for the systems with heavier group V
elements in the zinc-blend II-V compounds.",0807.1778v1
2012-04-15,Stabilizing topological phases in graphene via random adsorption,"We study the possibility of realizing topological phases in graphene with
randomly distributed adsorbates. When graphene is subjected to periodically
distributed adatoms, the enhanced spin-orbit couplings can result in various
topological phases. However, at certain adatom coverages, the intervalley
scattering renders the system a trivial insulator. By employing a finite-size
scaling approach and Landauer-B\""{u}ttiker formula, we show that the
randomization of adatom distribution greatly weakens the intervalley
scattering, but plays a negligible role in spin-orbit couplings. Consequently,
such a randomization turns graphene from a trivial insulator into a topological
state.",1204.3276v1
2013-09-03,Bose-Einstein Condensates with Cavity-Mediated Spin-Orbit Coupling,"We propose a novel scheme to generate the spin-orbit coupling for a
condensate placed inside an optical cavity by using a standing wave and a
traveling wave. It is shown that the interplay of the laser lights and the
cavity gives rise to rich quantum phases. Our scheme also generates an
nontrivial lattice of the magnetic flux, which may facilitate the study of the
exotic quantum phases.",1309.0606v1
2016-05-23,Large magnetic anisotropy in Fe_{0.25}TaS_2,"We present a first-principles study of the large magneto-crystalline
anisotropy in the intercalated di-chalcogenide material \ce{Fe_{0.25}TaS_2},
investigated with the DFT+U approach. We verify a uniaxial magnetocrystalline
anisotropy energy(MAE) of 15meV/Fe. in the material. We further analyze the
dependence of MAE on the constituent elements and the effect of spin-orbit
coupling. Contrary to conventional intuition, we find a small contribution to
MAE due to strong spin-orbit coupling in the heavier element, Ta. We show that
the electronic configuration, crystal field environment and correlational
effects of the magnetic ion are more important.",1605.07141v1
2017-06-29,Three-Dimensional Fractional Topological Insulators in Coupled Rashba Layers,"We propose a model of three-dimensional topological insulators consisting of
weakly coupled electron- and hole-gas layers with Rashba spin-orbit interaction
stacked along a given axis. We show that in the presence of strong
electron-electron interactions the system realizes a fractional strong
topological insulator, where the rotational symmetry and condensation energy
arguments still allow us to treat the problem as quasi-one-dimensional with
bosonization techniques. We also show that if Rashba and Dresselhaus spin-orbit
interaction terms are equally strong, by doping the system with magnetic
impurities, one can bring it into the Weyl semimetal phase.",1706.09863v1
2018-09-22,Modulation instability associated nonlinear dynamics of spin-orbit coupled Bose-Einstein condensates,"We study pattern-forming nonlinear dynamics starting from a continuous wave
state of quasi-one-dimensional two-component Bose-Einstein condensates with
synthetic spin-orbit coupling induced by Raman lasers. Modulation instability
can occur even when the miscibility condition due to the interatomic
interactions is satisfied. We find that the initial stage of the nonlinear
development is consistent with the prediction of modulation instability, where
the two primary and secondary instability bands lead to the spontaneous growth
of the modulation and the subsequent complicated dynamics of pattern formation.
At later stages of the evolution, the wave functions undergo clear separation
in the momentum space, reflected in the dispersion of the single particle
Hamiltonian.",1809.08491v2
2018-10-17,Interface enhanced magnetic anisotropy in Pt/EuO films,"We report proximity effects of spin-orbit coupling in EuO$_{1-x}$ films
capped with a Pt overlayer. Transport measurements suggest that current flows
along a conducting channel at the interface between the Pt and EuO. The
temperature dependence of the resistivity picks up the critical behaviors of
EuO, i.e., the metal-to-insulator transition. We also find an unusual
enhancement of the magnetic anisotropy in this structure from its bulk value
which results from strong spin-orbit coupling across the Pt/EuO interface.",1810.07336v1
2019-10-01,Collective excitations of two-dimensional Bose-Einstein Condensate in liquid phase with spin-orbit coupling,"We have studied the collective excitation of Bose-Einstein condensate of
short range weak interacting atoms with spin-orbit coupling (SOC) in two
dimension in liquid phase. In our study, we have included Rashba, Dresselhaus
SOC as well as Raman SOC. The study of Bogoliubov excitation shows that in
small interaction case only phonon modes are present and for higher
interactions roton modes start to appear. Energy spectra contain two roton
modes in the system relatively strong interacting atomic system.",1910.00264v2
2019-10-21,In-plane Hall effect in two-dimensional helical electron systems,"We study Berry curvature driven and Zeeman magnetic field dependent electric
current responses of two-dimensional electron system with spin-orbit coupling.
New non-dissipative component of the electric current occurring in the applied
in-plane magnetic field is described. This component is transverse to the
electric field, odd in the magnetic field, and depends only on one particular
direction of the magnetic field defined by the spin-orbit coupling. We show
that the effect can be observed in a number of systems with $C_{3v}$ symmetry.",1910.09511v3
2017-09-29,Critical temperature of pair condensation in a dilute Bose gas with spin-orbit coupling,"We study the Bardeen-Cooper-Shrieffer (BCS) pairing state of a two-component
Bose gas with a symmetric spin-orbit coupling. In the dilute limit at low
temperatures, this system is essentially a dilute gas of diatomic molecules. We
compute the effective mass of the molecule and find that it is anisotropic in
momentum space. The critical temperature of the pairing state is about eight
times smaller than the Bose-Einstein condensation (BEC) transition temperature
of an ideal Bose gas with the same density.",1709.10239v1
2017-11-20,Electron paramagnetic resonance g-tensors from state interaction spin-orbit coupling density matrix renormalization group,"We present a state interaction spin-orbit coupling method to calculate
electron paramagnetic resonance (EPR) $g$-tensors from density matrix
renormalization group wavefunctions. We apply the technique to compute
$g$-tensors for the \ce{TiF3} and \ce{CuCl4^2-} complexes, a [2Fe-2S] model of
the active center of ferredoxins, and a \ce{Mn4CaO5} model of the S2 state of
the oxygen evolving complex. These calculations raise the prospects of
determining $g$-tensors in multireference calculations with a large number of
open shells.",1711.07195v3
2018-03-15,Accurate projective two-band description of topological superfluidity in spin-orbit-coupled Fermi gases,"The interplay of spin-orbit coupling and Zeeman splitting in ultracold Fermi
gases gives rise to a topological superfluid phase in two spatial dimensions
that can host exotic Majorana excitations. Theoretical models have so far been
based on a four-band Bogoliubov-de Gennes formalism for the combined spin-1/2
and particle-hole degrees of freedom. Here we present a simpler, yet accurate,
two-band description based on a well-controlled projection technique that
provides a new platform for exploring analogies with chiral p-wave
superfluidity and detailed future studies of spatially non-uniform situations.",1803.05579v2
2018-03-26,Ground-state properties of dilute Bose systems with synthetic dispersion laws,"Experimental advances in synthesizing spin-orbit couplings in cold atomic
Bose gases promise to create single-particle dispersion laws featuring energy
minima that are degenerate on a ring or a sphere in momentum space. We show
that for arbitrary space dimensionality the ground-state properties of a dilute
system of spin-orbit coupled Bose particles with such dispersion and
short-range repulsive interactions are universal: the chemical potential
exhibits a quadratic dependence on the particle density as found in a
one-dimensional free Fermi gas.",1803.09732v2
2018-12-17,Majorana zero modes in a quantum wire platform without Rashba spin-orbit coupling,"We propose a platform for engineering helical fermions in a hybridized
double-quantum-wire setup. When our setup is proximity coupled to an $s$-wave
superconductor it can become a class $D$ topological superconductor exhibiting
Majorana zero modes. The goal of this proposal is to expand the group of
available Hamiltonians to those without strong Rashba spin-orbit interactions
which are essential to many other approaches. Furthermore, we show that there
exist electron-electron interactions that stabilize fractional excitations
which obey $\mathbb{Z}^{\,}_{3}$ parafermionic algebra.",1812.06633v2
2019-12-09,Engineering Topological Nodal Line Semimetals in Rashba Spin-Orbit Coupled Atomic Chains,"We study an atomic chain in the presence of modulated charge potential and
modulated Rashba spin-orbit coupling (RSOC) of equal period. We show that for
commensurate periodicities $\lambda=4 n$ with integer $n$, the
three-dimensional synthetic space obtained by sliding the two phases of the
charge potential and RSOC features a topological nodal line semimetal protected
by an antiunitary particle-hole symmetry. The location and shape of the nodal
lines strongly depend on the relative amplitude between the charge potential
and RSOC.",1912.04059v1
2020-03-19,Two-dimensional square lattice polonium stabilized by the spin-orbit coupling,"Polonium is known as the only simple metal that has the simple cubic (SC)
lattice in three dimension. There is a debate about whether the stabilized SC
structure is attributed to the scalar relativistic effect or the spin-orbit
coupling (SOC). Here, we study another phase, two-dimensional (2D) polonium
(poloniumene), by performing density-functional theory calculations. We show
that the 2D polonium has the square lattice structure as its ground state and
demonstrate that the SOC (beyond the scalar relativistic approximation)
suppresses the Peierls instability and is necessary to obtain no imaginary
phonon frequencies over the Brillouin zone.",2003.08535v1
2020-09-08,Topological metals and finite-momentum superconductors,"We show that Zeeman field can induce a topological transition in
two-dimensional spin-orbit coupled metals, and concomitantly, a first-order
phase transition in the superconducting state involving a discontinuous change
of Cooper pair momentum. Depending on the spin-orbit coupling strength, we find
different phase diagrams of 2D superconductors under in-plane magnetic field.",2009.03848v2
2021-11-30,Majorana Zero Modes in Ferromagnetic Wires without Spin-Orbit Coupling,"We present a novel controllable platform for engineering Majorana zero modes.
The platform consists of a ferromagnetic metallic wire placed among
conventional superconductors, which are in proximity to ferromagnetic
insulators. We demonstrate that Majorana zero modes emerge localised at the
edges of the ferromagnetic wire, due to the interplay of the applied
supercurrents and the induced by proximity exchange fields with conventional
superconductivity. Our mechanism does not rely on the pairing of helical
fermions by combining conventional superconductivity with spin-orbit coupling,
but rather exploits the misalignment between the magnetization of the
ferromagnetic insulators and that of the ferromagnetic wire.",2111.15260v1
2022-02-15,Anisotropic magneto-resistance in MgO-based magnetic tunnel junctions induced by spin-orbit coupling,"We performed a first-principles study of the tunneling anisotropic
magneto-resistance (TAMR) in Ag(Ir,Pt)$/$MgO$/$Fe junctions. Enhanced TAMR with
ideal and skewed fourfold angular dependence is found in-plane and out-of-plane
TAMR of the system, respectively, which shows simple barrier thickness
dependency with number around 10\% in some junctions. The complex angular
dependency of the interfacial resonant states due to the spin-orbit coupling
should be responsible to the complex and enhanced TAMR found in these
junctions.",2202.07264v1
2022-03-11,Self-interfering dynamics in Bose-Einstein condensates with engineered dispersions,"Optical lattice and spin-orbit coupling are typical experimental approaches
to engineer dispersion. We reveal a self-interfering dynamics in a
noninteracting Bose-Einstein condensate with the engineered dispersion by
optical lattice or spin-orbit coupling. The self-interference results from the
co-occupation of positive and negative effect mass regimes in the engineered
dispersion. The physical origination of the self-interference is explained by
the Wigner distribution function of the self-interfering wave-packet. We
characterize detail features of the self-interference pattern.",2203.05722v1
2022-04-08,In situ controllable magnetic phases in doped twisted bilayer transition-metal dichalcogenides,"We study the electronic structure of hole-doped transition metal
dichalcogenides for small twist-angels, where the onsite repulsion is extremely
strong. Using unbiased diagrammatic Monte Carlo simulations, we find evidence
for magnetic correlations which are driven by delocalization and can be
controlled in situ via the dielectric environment. For weak spin-orbit
coupling, we find that the moderately doped system becomes anti-ferromagnetic,
whilst the regime of strong spin-orbit coupling features ferromagnetic
correlations. We show that this behavior is accurately predicted by an
analytical theory based on moment expansion of the Hamiltonian, and analysis of
corresponding particle trajectories.",2204.03917v1
2022-04-21,Detection of roton and phonon excitations in a spin-orbit coupled Bose-Einstein condensate with a moving barrier,"We propose to detect phonon and roton excitations in a two-dimensional
Bose-Einstein condensate with Raman-induced spin-orbit coupling by perturbing
the atomic cloud with a weak barrier. The two excitation modes can be observed
by moving the barrier along different directions in appropriate parameter
regimes. Phonon excitations are identified by the appearance of solitary waves,
while roton excitations lead to distinctive spatial density modulations. We
show that this method can also be used to determine the anisotropic critical
velocities of superfluid.",2204.09865v2
2022-07-22,Spin-orbit coupling induced by ascorbic acid crystals,"Some anisotropic materials form semicristalline structures, called
spherulites, which observed in a polarisation microscope, exhibit a
characteristic ``maltese-cross""-like pattern. While this observation has been
hitherto considered as a tool to characterize these materials, we show that
these patterns are associated with a strong light's spin-orbit coupling induced
by the spherulite structures. We experimentally demonstrate these effects using
samples of crystallized ascorbic acid and observing the creation of optical
vortices in transmitted laser beams, as well as the formation of inhomogeneous
polarisation patterns. Our findings suggest the use of spherulites in frequency
ranges, e.g. in the THz domain, where polarisation and spatial shaping of
electromagnetic radiation is still a challenging task.",2207.11340v1
2022-07-23,"Nonreciprocal Transport in Noncoplanar Magnetic Systems without Spin-Orbit Coupling, Net Scalar Chirality, or Magnetization","We propose a new mechanism of nonlinear nonreciprocal transport in magnetic
systems. By considering a noncoplanar magnetic ordering on a bilayer triangular
lattice, we clarify that a local scalar chirality degree of freedom is a source
of nonreciprocal transport, which does not require any relativistic spin-orbit
coupling, net scalar chirality, and net magnetization. We show a close
relationship between the asymmetric band modulation and the nonreciprocal
transport under the noncoplanar magnetic ordering based on the model-parameter
dependences in the real-space picture.",2207.11420v1
2023-05-19,Josephson-type oscillations in spin-orbit coupled Bose-Einstein condensates with nonlinear optical lattices,"We consider spin-orbit coupled Bose Einstein Condensate in presence of linear
and nonlinear optical lattices within the framework of quasi-one-dimensional
Gross-Pitaevskii equation. The population imbalance between the states changes
periodically with time and the oscillation amplitude depends sensitively on the
initial phase. The optical lattice is found to change phase velocity of the
oscillation of population imbalance. This oscillation can also be arrested
beyond critical values of parameters. We find that the optical lattice can
efficiently be used to control the critical point.",2305.11628v2
2023-05-21,Electrically controllable exchange bias via interface magnetoelectric effect,"Exchange bias is a unidirectional magnetic anisotropy that often arise from
interfacial interaction of a ferromagnetic and antiferromagnetic layers. In
this article, we show that a metallic layer with spin-orbit coupling can
induces an exchange bias via an interface magnetoelectric effect. In linear
response regime, the interface magnetoelectric effect is induced by spin-orbit
couplings that arises from the broken symmetry of the system. Furthermore, we
demonstrate that the exchange bias can be controlled by electric field.",2305.12395v2
2023-06-08,Magnetic anisotropy of superconducting transition in S/AF heterostructures with spin-orbit coupling,"The influence of Rashba spin-orbit coupling (SOC) on superconducting
correlations in thin-film superconductor/antiferromagnet (S/AF) structures with
compensated interfaces is studied. A unique effect of anisotropic enhancement
of proximity-induced triplet correlations by the SOC is predicted. It manifests
itself in the anisotropy of the superconducting critical temperature Tc with
respect to orientation of the Neel vector relative to the S/AF interface, which
is opposite to the behaviour of Tc in superconductor/ferromagnet structures. We
show that the anisotropy is controlled by the chemical potential of the
superconductor and, therefore, can be adjusted in (quasi)2D structures.",2306.05055v1
2023-07-05,Lifshitz model in the presence of spin-orbit coupling,"Wave function of a localized state created by a short-range impurity in two
dimensions falls off with distance, r, from the impurity as r^{-1/2}exp(-r/a),
where ""a"" is the localization radius. With randomly positioned identical
impurities with low concentration, n<<a^{-2}, the level smears into a band due
to the overlap of the impurity wave functions. This is the essence of the
Lifshitz model. We demonstrate that, upon incorporation of the spin-orbit
coupling, the impurity wave functions acquire oscillating factors which,
subsequently, modify their overlap. As a result of such modification, the
density of states develops singularities at certain energies.",2307.01971v1
2023-10-17,Reactive Hall and Edelstein effects in a tight-binding model with spin-orbit coupling,"The reactive Hall constant R_H, described by reactive (nondissipative)
conductivities, is analyzed within linear response theory in the presence of
spin-orbit interaction. Within a two dimensional tight-binding model the effect
of van Hove singularities is studied. Along the same line a formulation of the
Edelstein constant is proposed and studied as a function of coupling parameters
and fermion filling.",2310.11253v2
2023-11-23,Bulk-edge correspondence for the nonlinear eigenvalues problem of the Haldane model,"Recently, there is an interest in studying the bulk-edge correspondence for
nonlinear eigenvalues problems in a two-dimensional topological system with
spin-orbit coupling. By introducing auxiliary eigenvalues, the nonlinear
bulk-edge correspondence was established. In this paper, taking the Haldane
model as an example, we address that such a correspondence will appear in two
dimensional topological system without spin-orbit coupling. The resulting edge
states are characterized by the Chern number of the auxiliary energy band. A
full phase diagram containing topological nontrivial phase, topological trivial
phase, and metallic phase is obtained. Our work generalizes the study of the
bulk-edge correspondence for nonlinear eigenvalue problems in two-dimensional
system.",2311.14229v1
2022-10-18,Coherent spin dynamics of hyperfine-coupled vanadium impurities in silicon carbide,"Progress with quantum technology has for a large part been realized with the
nitrogen-vacancy centre in diamond. Part of its properties, however, are
nonideal and this drives research into other spin-active crystal defects.
Several of these come with much stronger energy scales for spin-orbit and
hyperfine coupling, but how this affects their spin coherence is little
explored. Vanadium in silicon carbide is such a system, with technological
interest for its optical emission at a telecom wavelength and compatibility
with semiconductor industry. Here we show coherent spin dynamics of an ensemble
of vanadium defects around a clock-transition, studied while isolated from, or
coupled to neighbouring nuclear spins. We find spin dephasing times up to 7.2
$\mu$s, and via spin-echo studies coherence lifetimes that go well beyond tens
of microseconds. We demonstrate operation points where strong coupling to
neighbouring nuclear spins does not compromise the coherence of the central
vanadium spin, which identifies how these can be applied as a coherent spin
register. Our findings are relevant for understanding a wide class of defects
with similar energy scales and crystal symmetries, that are currently explored
in diamond, silicon carbide, and hexagonal boron nitride.",2210.09942v1
2019-06-04,Hopping induced ground-state magnetism in 6H perovskite iridates,"Investigation of elementary excitations has advanced our understanding of
many-body physics governing most physical properties of matter. Recently
spin-orbit excitons have drawn much attention, whose condensates near phase
transitions exhibit Higgs mode oscillations, a long-sought physical phenomenon
[Nat. Phys. {\bf 13}, 633 (2017)]. These critical transition points resulting
from competing spin-orbit coupling (SOC), local crystalline symmetry and
exchange interactions, are not obvious in Iridium based materials, where SOC
prevails in general. Here, we present results of resonant inelastic x-ray
scattering on a spin-orbital liquid Ba$_3$ZnIr$_2$O$_9$ and three other
6H-hexagonal perovskite iridates which show magnetism, contrary to non-magnetic
singlet ground state expected due to strong SOC. Our results show that
substantial hopping between closely placed Ir$^{5+}$ ions within Ir$_2$O$_9$
dimers in these 6H-iridates, modifies spin-orbit coupled states and reduces
spin-orbit excitation energies. Here, we are forced to use at least a two-site
model, to match the excitation spectrum going in line with the strong
intra-dimer hopping. Apart from SOC, low energy physics of iridates is thus
critically dependent on hopping, and may not be ignored even for systems having
moderate hopping, where the excitation spectra can be explained using an atomic
model. SOC which is generally found to be 0.4-0.5~eV in iridates, is scaled in
effect down to $\sim$0.26~eV for the 6H-systems, sustaining the hope to achieve
quantum criticality by tuning Ir-Ir separation.",1906.01262v1
2013-10-31,Large spin splitting in the conduction band of transition metal dichalcogenide monolayers,"We study the conduction band spin splitting that arises in transition metal
dichalcogenide (TMD) semiconductor monolayers such as MoS$_2$, MoSe$_2$, WS$_2$
and WSe$_2$ due to the combination of spin-orbit coupling and lack of inversion
symmetry. Two types of calculation are done. First, density functional theory
(DFT) calculations based on plane waves and pseudo potentials that yield large
splittings, between 3 and 30 meV. Second, we derive a tight-binding model, that
permits to address the atomic origin of the splitting. The basis set of the
model is provided by the maximally localized Wannier orbitals, obtained from
the DFT calculation, and formed by 11 atomic-like orbitals corresponding to
5$d$ and 3$p$ orbitals of the transition metal (W,Mo) and chalcogenide (S,Se)
atoms respectively. In the resulting Hamiltonian we can independently change
the atomic spin-orbit coupling constant of the two atomic species at the unit
cell, which permits to analyse their contribution to the spin splitting at the
high symmetry points. We find that ---in contrast to the valence band--- both
atoms give comparable contributions to the conduction band splittings. Given
that these materials are most often $n-$doped, our findings are important for
developments in TMD spintronics.",1311.0049v2
2020-11-27,Shell evolution in neutron-rich nuclei: the single particle perspective,"The shell evolution has been studied extensively within the framework of
interacting shell model, while the studies from the single particle viewpoint
is relatively lacking or neglected. In particular, the isospin dependence of
spin-orbit splitting has become increasingly important as $N/Z$ increases in
neutron-rich nuclei. Following the initial independent-particle strategy
towards explaining the occurrence of magic numbers, we have systematically
investigated the isospin effect on the shell evolution of neutron-rich nuclei
within the Woods-Saxon (WS) mean-field potential plus the spin-orbit term. It
is found that new magic numbers $N = 14$ and $N =16$ may emerge in neutron-rich
nuclei if one changes the sign of the isospin-dependent term in the spin-orbit
coupling while the traditional magic number $N = 20$ may disappear. The magic
number $N = 28$ is expected to be destroyed despite the sign choice of the
isospin part in spin-orbit splitting, while $N = 50$ may disappear and $N = 82$
persists within the single particle scheme. Besides, an appreciable amount of
energy gap appears at $N = 32$ and 34 in neutron-rich Ca isotopes. All these
results are more consistent with those of the interacting shell model, when the
sign of the isospin term of the WS potential is different from that of the
corresponding spin-orbit coupling part. The present study may provide a more
reasonable starting point for not only the interacting shell but also other
nuclear many-body calculations towards the neutron-dripline.",2011.13540v1
2023-11-02,"Spin-orbit-lattice entangled state in A$_2$MgReO$_6$ (A = Ca, Sr, Ba) revealed by resonant inelastic X-ray scattering","The $5d^1$ ordered double perovskites present an exotic playground for
studying novel multi-polar physics due to large spin-orbit coupling. We present
Re L3 edge resonant inelastic X-ray scattering (RIXS) results that reveal the
presence of the dynamic Jahn-Teller effect in the A$_2$MgReO$_6$ (A = Ca, Sr,
Ba) family of $5d^1$ double perovskites. The spin-orbit excitations in these
materials show a strongly asymmetric lineshape and exhibit substantial
temperature dependence, indicating that they are dressed with lattice
vibrations. Our experimental results are explained quantitatively through a
RIXS calculation based on a spin-orbit-lattice entangled electronic ground
state with the dynamic Jahn-Teller effect taken into consideration. We find
that the spin-orbit-lattice entangled state is robust against magnetic and
structural phase transitions as well as against significant static Jahn-Teller
distortions. Our results illustrate the importance of including vibronic
coupling for a complete description of the ground state physics of $5d^1$
double perovskites. Usage: Secondary publications and information retrieval
purposes.",2311.01621v1
2006-02-10,Theory of Electric Dipole Spin Resonance in a Parabolic Quantum Well,"A theory of Electric Dipole Spin Resonance (EDSR), that is caused by various
mechanisms of spin-orbit coupling, is developed as applied to free electrons in
a parabolic quantum well. Choosing a parabolic shape of the well has allowed us
to find explicit expressions for the EDSR intensity and its dependence on the
magnetic field direction in terms of the basic parameters of the Hamiltonian.
By using these expressions, we have investigated and compared the effect of
specific mechanisms of spin orbit (SO) coupling and different polarizations of
ac electric field on the intensity of EDSR. Angular dependences of the EDSR
intensity are indicative of the relative contributions of the competing
mechanisms of SO coupling. Our results show that electrical manipulating
electron spins in quantum wells is generally highly efficient, especially by an
in-plane ac electric field.",0602264v1
2006-12-21,Zero-conductance resonances and spin-filtering effects in ring conductors subject to Rashba coupling,"We investigate the effect of Rashba spin-orbit coupling and of a tunnel
barrier on the zero conduc- tance resonances appearing in a one-dimensional
conducting Aharonov-Bohm (AB) ring symmet- rically coupled to two leads. The
transmission function of the corresponding one-electron problem is derived
within the scattering matrix approach and analyzed in the complex energy plane
with focus on the role of the tunnel barrier strength on the zero-pole
structure characteristic of trans- mission (anti)resonances. The lifting of the
real conductance zeros is related to the breaking of the spin-reversal symmetry
and time-reversal symmetry of Aharonov-Casher (AC)and AB rings, as well as to
rotational symmetry breaking in presence of a tunnel barrier. We show that the
polarization direction of transmitted electrons can be controlled via the
tunnel barrier strength and discuss a novel spin-filtering design in
one-dimensional rings with tunable spin-orbit interaction.",0612560v1
2010-12-22,Rashba field in GaN,"We discuss problem of Rashba field in bulk GaN and in GaN/AlGaN
two-dimensional electron gas, basing on results of X-band microwave resonance
experiments. We point at large difference in spin-orbit coupling between bulk
material and heterostructures. We observe coupled plasmon-cyclotron resonance
from the two-dimensional electron gas, but no spin resonance, being consistent
with large zero-field spin splitting due to the Rashba field reported in
literature. In contrast, small anisotropy of g-factor of GaN effective mass
donors indicates rather weak Rashba spin-orbit coupling in bulk material, not
exceed 400 Gauss, alpha_BIA < 4*10^-13 eVcm. Furthermore, we observe new kind
of electron spin resonance in GaN, which we attribute to surface electron
accumulation layer. We conclude that the sizable Rashba field in GaN/AlGaN
heterostructures originates from properties of the interface.",1012.4999v1
2011-01-28,Observation of a warped helical spin-texture in Bi$_2$Se$_3$ from circular dichroism angle-resolved photoemission spectroscopy,"A differential coupling of topological surface states to left- versus
right-circularly polarized light is the basis of many opto-spintronics
applications of topological insulators. Here we report direct evidence of
circular dichroism from the surface states of Bi$_2$Se$_3$ using a laser-based
time-of-flight angle-resolved photoemission spectroscopy. By employing a novel
sample rotational analysis, we resolve unusual modulations in the circular
dichroism photoemission pattern as a function of both energy and momentum,
which perfectly mimic the predicted but hitherto un-observed three-dimensional
warped spin-texture of the surface states. By developing a microscopic theory
of photoemission from topological surface states, we show that this correlation
is a natural consequence of spin-orbit coupling. These results suggest that our
technique may be a powerful probe of the spin-texture of spin-orbit coupled
materials in general.",1101.5636v2
2014-04-18,Oscillation of the counterpropagating spin-currents of cold atoms on a ring due to light-induced spin-orbit coupling,"The evolution of two-component cold atoms on a ring with quasispin-orbit
(qSO) coupling and spin-flip has been studied analytically (for arbitrary
particle number $ N $ without interaction) and numerically (for a few-body
system with interaction). Counter-propagating and oscillating persistent
spin-currents have been found. The regularity governing the period and
amplitude of oscillation has been clarified. When the strengths for the qSO
coupling and spin-flip are fixed, the frequency of oscillation can be
effectively tuned by the Raman detuning, while the amplitude can be tuned by
either changing the initial status and/or the Raman detuning. When the initial
numbers of atoms of the two-components $N_{1}$ and $N_{2}$ are close to each
other, the oscillation will be seriously suppressed. The condition for
maximizing the amplitude of oscillation is given.",1404.4710v2
2014-11-24,Kitaev magnetism in honeycomb RuCl3 with intermediate spin-orbit coupling,"Intensive studies of the interplay between spin-orbit coupling (SOC) and
electronic correlations in transition metal compounds have recently been
undertaken. In particular, $j_{\rm eff}$ = 1/2 bands on a honeycomb lattice
provide a pathway to realize Kitaev's exactly solvable spin model. However,
since current wisdom requires strong atomic SOC to make $j_{\rm eff}=1/2$
bands, studies have been limited to iridium oxides. Contrary to this
expectation, we demonstrate how Kitaev interactions arise in 4$d$-orbital
honeycomb $\alpha$-RuCl$_3$, despite having significantly weaker SOC than the
iridium oxides, via assistance from electron correlations. A strong coupling
spin model for these correlation-assisted $j_{\rm eff}$ = 1/2 bands is derived,
in which large antiferromagnetic Kitaev interactions emerge along with
ferromagnetic Heisenberg interactions. Our analyses suggest that the ground
state is a zigzag-ordered phase lying close to the antiferromagnetic Kitaev
spin liquid. Experimental implications for angle resolved photoemission
spectroscopy, neutron scattering, and optical conductivities are discussed.",1411.6623v3
2015-04-20,Scattering Continuum and Possible Fractionalized Excitations in $α$-RuCl$_3$,"The combination of electronic correlation and spin-orbit coupling is thought
to precipitate a variety of highly unusual electronic phases in solids,
including topological and quantum spin liquid states. We report a Raman
scattering study that provides evidence for unconventional excitations in
$\alpha$-RuCl$_3$, a spin-orbit coupled Mott insulator on the honeycomb
lattice. In particular, our measurements reveal unusual magnetic scattering,
typified by a broad continuum. The temperature dependence of this continuum is
evident over a large scale compared to the magnetic ordering temperature,
suggestive of frustrated magnetic interactions. This is confirmed through an
analysis of the phonon linewidths, which show a related anomaly due to
spin-phonon coupling. These observations are in line with theoretical
expectations for the Heisenberg-Kitaev model and suggest that $\alpha$-RuCl$_3$
may be close to a quantum spin liquid ground state.",1504.05202v1
2016-09-24,"Spin-orbit coupling and magnetic interactions in Si(111):{C,Si,Sn,Pb}","We study the magnetic properties of the adatom systems on a semiconductor
surface Si(111):\{C,Si,Sn,Pb\} - ($\sqrt{3} \times \sqrt{3}$). On the basis of
all-electron density functional theory calculations we construct effective
low-energy models taking into account spin-orbit coupling and electronic
correlations. In the ground state the surface nanostructures are found to be
insulators with the non-collinear 120$^{\circ}$ N\'eel (for C, Si, Sn monolayer
coverages) and 120$^{\circ}$ row-wise (for Pb adatom) antiferromagnetic
orderings. The corresponding spin Hamiltonians with anisotropic exchange
interactions are derived by means of the superexchange theory and the
calculated Dzyaloshinskii-Moriya interactions are revealed to be very strong
and compatible with the isotropic exchange couplings in the systems with Sn and
Pb adatoms. To simulate the excited magnetic states we solve the constructed
spin models by means of the Monte Carlo method. At low temperatures and zero
magnetic field we observe complex spin spiral patterns in Sn/Si(111) and
Pb/Si(111). On this basis the formation of antiferromagnetic skyrmion lattice
states in adatom $sp$ electron systems in strong magnetic fields is discussed.",1609.07648v1
2017-04-17,A novel design to realize deterministic switching of perpendicularly magnetic layers by spin orbital torque through antiferromagnetic coupling,"We proposed a novel and simple multilayer structure to realize the
deterministic switching of perpendicularly magnetized layers (Co in our work)
by spin orbital torque from the spin Hall Effect in this paper. A pinned layer
is introduced, antiferromagnetically coupled to the magnetic Co layer. We have
confirmed the deterministic switching of perpendicularly magnetized layers from
perspectives of switching loops, trajectories and switching properties under
periodic spin currents through micromagnetic simulation. The antiferromagnetic
interaction accounts for the deterministic switching exhibited in the structure
and the reversal ultimate state of the magnetic layer is predictable when the
applied spin current density is above 60MA/cm2. In our design, the
antiferromagnetic coupling is easily tunable and no external magnetic field is
needed.",1704.04835v2
2017-07-13,Andreev spin qubits in multichannel Rashba nanowires,"We theoretically analyze the Andreev bound states and their coupling to
external radiation in superconductor-nanowire-superconductor Josephson
junctions. We provide an effective Hamiltonian for the junction projected onto
the Andreev level subspace and incorporating the effects of nanowire
multichannel structure, Rashba spin-orbit coupling, and Zeeman field. Based on
this effective model, we investigate the dependence of the Andreev levels and
the matrix elements of the current operator on system parameters such as
chemical potential, nanowire dimensions, and normal transmission. We show that
the combined effect of the multichannel structure and the spin-orbit coupling
gives rise to finite current matrix elements between odd states having
different spin polarizations. Moreover, our analytical results allow to
determine the appropriate parameters range for the detection of transitions
between even as well as odd states in circuit QED like experiments, which may
provide a way for the Andreev spin qubit manipulation.",1707.04273v1
2020-02-13,Geometric spin-orbit coupling and chirality-induced spin selectivity,"We report a new type of spin-orbit coupling (SOC) called geometric SOC.
Starting from the relativistic theory in curved space, we derive an effective
nonrelativistic Hamiltonian in a generic curve embedded into flat three
dimensions. The geometric SOC is $O(m^{-1})$, in which $m$ is the electron
mass, and hence much larger than the conventional SOC of $O(m^{-2})$. The
energy scale is estimated to be a hundred meV for a nanoscale helix. We
calculate the current-induced spin polarization in a coupled-helix model as a
representative of the chirality-induced spin selectivity. We find that it
depends on the chirality of the helix and is of the order of $0.01 \hbar$ per
${\rm nm}$ when a charge current of $1~{\rm \mu A}$ is applied.",2002.05371v2
2017-05-04,Mechanism for unconventional superconductivity in the hole-doped Rashba-Hubbard model,"Motivated by the recent resurgence of interest in topological
superconductivity, we study in this paper superconducting pairing instabilities
of the hole-doped Rashba-Hubbard model on the square lattice with first- and
second-neighbor hopping. Within a weak-coupling approach based on the random
phase approximation, we compute the spin-fluctuation mediated paring
interactions as a function of spin-orbit coupling and hole doping. Rashba
spin-orbit coupling splits the spin degeneracies of the bands, which leads to
two van Hove singularities at two different fillings. We find that for a broad
doping region in between these two van Hove fillings the spin fluctuations
exhibit a strong ferromagnetic contribution. Because of these ferromagnetic
fluctuations, the triplet $f$-wave pairing channel is dominant within this
filling region, resulting in a topologically nontrival phase. We discuss
possible experimental realizations of this phase in heavy-fermion hybrid
structures.",1705.01904v2
2017-05-10,Spin-tensor--momentum-coupled Bose-Einstein condensates,"The recent experimental realization of spin-orbit coupling for ultracold
atomic gases provides a powerful platform for exploring many interesting
quantum phenomena. In these studies, spin represents spin vector (spin-1/2 or
spin-1) and orbit represents linear momentum. Here we propose a scheme to
realize a new type of spin-tensor--momentum coupling (STMC) in spin-1 ultracold
atomic gases. We study the ground state properties of interacting Bose-Einstein
condensates (BECs) with STMC and find interesting new types of stripe
superfluid phases and multicritical points for phase transitions. Furthermore,
STMC makes it possible to study quantum states with dynamical stripe orders
that display density modulation with a long tunable period and high visibility,
paving the way for direct experimental observation of a new dynamical
supersolid-like state.. Our scheme for generating STMC can be generalized to
other systems and may open the door for exploring novel quantum physics and
device applications.",1705.03920v3
2019-01-28,Simple model for electrical hole spin manipulation in semiconductor quantum dots: Impact of dot material and orientation,"We analyze a prototypical particle-in-a-box model for a hole spin qubit. This
quantum dot is subjected to static magnetic and electric fields, and to a
radio-frequency electric field that drives Rabi oscillations owing to
spin-orbit coupling. We derive the equations for the Rabi frequency in a regime
where the Rabi oscillations mostly result from the coupling between the qubit
states and a single nearby excited state. This regime has been shown to prevail
in, e.g., hole spin qubits in thin silicon-on-insulator nanowires. The
equations for the Rabi frequency highlight the parameters that control the Rabi
oscillations. We show, in particular, that [110]-oriented dots on (001)
substrates perform much better than [001]-oriented dots because they take best
advantage of the anisotropy of the valence band of the host material. We also
conclude that silicon provides the best opportunities for fast Rabi
oscillations in this regime despite small spin-orbit coupling.",1901.09563v2
2019-04-02,Deriving models for the Kitaev spin-liquid candidate material $α$-RuCl$_3$ from first principles,"We use the constrained random phase approximation (cRPA) to derive from first
principles the Ru-$t_{2g}$ Wannier function based model for the Kitaev
spin-liquid candidate material $\alpha$-RuCl$_3$. We find the non-local Coulomb
repulsion to be sizable compared to the local one. In addition we obtain the
contribution to the Hamiltonian from the spin-orbit coupling and find it to
also contain non-negligible non-local terms. We invoke strong coupling
perturbation theory to investigate the influence of these non-local elements of
the Coulomb repulsion and the spin-orbit coupling on the magnetic interactions.
We find that the non-local Coulomb repulsions cause a strong enhancement of the
magnetic interactions, which deviate from experimental fits reported in the
literature. Our results contribute to the understanding and design of quantum
spin liquid materials via first principles calculations.",1904.01523v2
2019-11-04,Spin-orbit coupling and spin-triplet pairing symmetry in $\mathrm{Sr_2 Ru O_4}$,"Spin-orbit coupling (SOC) plays a crucial role in determining the spin
structure of an odd parity psedospin-triplet Cooper pairing state. Here, we
present a thorough study of how SOC lifts the degeneracy among different p-wave
pseudospin-triplet pairing states in a widely used microscopic model for
$\mathrm{Sr_2 Ru O_4}$, combining a Ginzburg-Landau (GL) free energy expansion,
a symmetry analysis of the model, and numerical weak-coupling renormalization
group (RG) and random phase approximation (RPA) calculations. These analyses
are then used to critically re-examine previous numerical results on the
stability of chiral p-wave pairing. The symmetry analysis can serve as a guide
for future studies, especially numerical calculations, on the pairing
instability in $\mathrm{Sr_2 Ru O_4}$ and can be useful for studying other
multi-band spin-triplet superconductors where SOC plays an important role.",1911.01446v2
2019-12-05,Enhanced spin-orbit coupling in a heavy metal via molecular coupling,"Heavy metals are key to spintronics because of their high spin-orbit coupling
(SOC) leading to efficient spin conversion and strong magnetic interactions.
When C60 is deposited on Pt, the molecular interface is metallised and the spin
Hall angle in YIG/Pt increased, leading to an enhancement of up to 600% in the
spin Hall magnetoresistance and 700% for the anisotropic magnetoresistance.
This correlates with Density Functional Theory simulations showing changes of
0.46 eV/C60 in the SOC of Pt. This effect opens the possibility of gating the
molecular hybridisation and SOC of metals.",1912.02712v2
2021-02-15,Antiferromagnetic Skyrmion Crystals in the Rashba Hund's Model on Triangular Lattice,"Motivated by the importance of antiferromagnetic skyrmions as building blocks
of next-generation data storage and processing devices, we report theoretical
and computational analysis of a model for a spin-orbit coupled correlated
magnet on a triangular lattice. We find that two distinct antiferromagnetic
skyrmion crystal (AF-SkX) states can be stabilized at low temperatures in the
presence of external magnetic field. The results are obtained via Monte Carlo
simulations on an effective magnetic model derived from the microscopic
electronic Hamiltonian consisting of Rashba spin-orbit coupling, as well as the
Hund's rule coupling of electrons to large classical spins. The two AF-SkX
phases are understood to originate from a classical spin liquid state that
exists at low but finite temperatures. These AF-SkX states can be easily
distinguished from each other in experiments as they are characterized by peaks
at distinct momenta in the spin structure factor which is directly measured in
neutron scattering experiments. We also discuss examples of materials where the
model as well as the two AF-SkX states can be realized.",2102.07563v1
2021-09-04,Inverse Faraday effect in Mott insulators,"The inverse Faraday effect (IFE), where a static magnetization is induced by
circularly polarized light, offers a promising route to ultrafast control of
spin states. Here we study the IFE in Mott insulators using the Floquet theory.
We find two distinct IFE behavior governed by the inversion symmetry. In the
Mott insulators with inversion symmetry, we find that the effective magnetic
field induced by the IFE couples ferromagnetically to the neighboring spins.
While for the Mott insulators without inversion symmetry, the effective
magnetic field due to IFE couples antiferromagnetically to the neighboring
spins. We apply the theory to the spin-orbit coupled single- and multi-orbital
Hubbard model that is relevant for the Kitaev quantum spin liquid material and
demonstrate that the magnetic interactions can be tuned by light.",2109.01940v4
2022-05-27,Nonlinear $σ$-model for disordered systems with intrinsic spin-orbit coupling,"We derive the nonlinear $\sigma$-model to describe diffusive transport in
normal metals and superconductors with intrinsic spin-orbit coupling (SOC). The
SOC is described via an SU(2) gauge field, and we expand the model to the
fourth order in gradients to find the leading non-Abelian field-strength
contribution. This contribution generates the spin-charge coupling that is
responsible for the spin-Hall effect. We discuss how its symmetry differs from
the leading quasiclassical higher-order gradient terms. We also derive the
corresponding Usadel equation describing the diffusive spin-charge dynamics in
superconducting systems. As an example, we apply the obtained equations to
describe the anomalous supercurrent in dirty Rashba superconductors at
arbitrary temperatures.",2205.14075v1
2023-05-17,Quantum disordered ground state in the spin-orbit coupled Jeff = 1/2 distorted honeycomb magnet BiYbGeO5,"We delineate quantum magnetism in the strongly spin-orbit coupled, distorted
honeycomb-lattice antiferromagnet BiYbGeO$_{5}$. Our magnetization and heat
capacity measurements reveal that its low-temperature behavior is well
described by an effective $J_{\rm eff}=1/2$ Kramers doublet of Yb$^{3+}$. The
ground state is nonmagnetic with a tiny spin gap. Temperature-dependent
magnetic susceptibility, magnetization isotherm, and heat capacity could be
modeled well assuming isolated spin dimers with anisotropic exchange
interactions $J_{\rm Z} \simeq 2.6$~K and $J_{\rm XY} \simeq 1.3$~K. Heat
capacity measurements backed by muon spin relaxation suggest the absence of
magnetic long-range order down to at least 80\,mK both in zero field and in
applied fields. This sets BiYbGeO$_5$ apart from Yb$_2$Si$_2$O$_7$ with its
unusual regime of magnon Bose-Einstein condensation and suggests negligible
interdimer couplings, despite only a weak structural deformation of the
honeycomb lattice.",2305.10221v1
2023-07-07,Spectral properties of a mixed singlet-triplet Ising superconductor,"Conventional two-dimensional superconductivity is destroyed when the critical
in-plane magnetic field exceeds the so-called Pauli limit. Some monolayer
transition-metal dichalcogenides lack inversion symmetry and the strong
spin-orbit coupling leads to a valley-dependent Zeeman-like spin splitting. The
resulting spin-valley locking lifts the valley degeneracy and results in a
strong enhancement of the in-plane critical magnetic field. In these systems,
it was predicted that the density of states in an in-plane field exhibits
distinct mirage gaps at finite energies of about the spin-orbit coupling
strength, which arise from a coupling of the electron and hole bands at energy
larger than the superconducting gap. In this study, we investigate the impact
of a triplet pairing channel on the spectral properties, primarily the mirage
gap and the superconducting gap, in the clean limit. Notably, in the presence
of the triplet pairing channel, the mirage-gap width is reduced for the low
magnetic fields. Furthermore, when the temperature is lower than the triplet
critical temperature, the mirage gaps survive even in the strong-field limit
due to the finite singlet and triplet order parameters. Our work provides
insights into controlling and understanding the properties of spin-triplet
Cooper pairs.",2307.03456v1
2024-01-28,Magnetic interactions and excitations in SrMnSb$_2$,"The magnetic interactions in the antiferromagnetic (AFM) Dirac semimetal
candidate SrMnSb$_2$ are investigated using \textit{ab initio} linear response
theory and inelastic neutron scattering (INS). Our calculations reveal that the
first two nearest in-plane couplings ($J_1$ and $J_2$) are both AFM in nature,
indicating a significant degree of spin frustration, which aligns with
experimental observations. The orbital resolution of exchange interactions
shows that $J_1$ and $J_2$ are dominated by direct and superexchange,
respectively. In a broader context, a rigid-band model suggests that electron
doping fills the minority spin channel and results in a decrease in the AFM
coupling strength for both $J_1$ and $J_2$. To better compare with INS
experiments, we calculate the spin wave spectra within a linear spin wave
theory framework, utilizing the computed exchange parameters. The calculated
spin wave spectra exhibit overall good agreement with measurements from INS
experiments, although with a larger magnon bandwidth. Introducing additional
electron correlation within the Mn-$3d$ orbitals can promote electron
localization and reduce the magnetic coupling, further improving the agreement
with experiments.",2401.15572v1
2022-10-31,How Spin Relaxes and Dephases in Bulk Halide Perovskites,"Spintronics in halide perovskites has drawn significant attention in recent
years, due to highly tunable spin-orbit fields and intriguing interplay with
lattice symmetry. Spin lifetime -- a key parameter that determines the
applicability of materials for spintronics and spin-based quantum information
applications -- has been extensively measured in halide perovskites, but not
yet assessed from first-principles calculations. Here, we leverage our
recently-developed \emph{ab initio} density-matrix dynamics framework to
compute the spin relaxation time ($T_{1}$) and ensemble spin dephasing time
($T_{2}^{*}$) in a prototype halide perovskite, namely CsPbBr$_{3}$ with
self-consistent spin-orbit coupling (SOC) and quantum descriptions of the
electron scattering processes. We also implement the Land\'e $g$-factor for
solids from first principles and take it into account in our dynamics, which is
required to accurately capture spin dephasing at external magnetic fields. We
thereby predict intrinsic spin lifetimes as an upper bound for experiments,
identify the dominant spin relaxation pathways, and evaluate the dependence on
temperature, external fields, carrier density,and impurities. Importantly, we
find that the Fr{\""o}hlich interaction that dominates carrier relaxation
contributes negligibly to spin relaxation, consistent with the spin-conserving
nature of this interaction. We investigated the effect of spin-orbit field with
inversion asymmetry on spin lifetime, and we demonstrated from our calculation,
persistent spin helix can enhance spin lifetime when the spin-split is large,
but it can not be realized by Rashba SOC. Our theoretical approach may lead to
new strategies to optimize spin and carrier transport properties in spintronics
and quantum information applications.",2210.17074v3
2016-05-30,A two-dimensional spin field-effect transistor,"The integration of the spin degree of freedom in charge-based electronic
devices has revolutionised both sensing and memory capability in
microelectronics. Further development in spintronic devices requires electrical
manipulation of spin current for logic operations. The approach followed so
far, inspired by the seminal proposal of the Datta and Das spin modulator, has
relied on the spin-orbit field as a medium for electrical control of the spin
state. However, the still standing challenge is to find a material whose
spin-orbit-coupling (SOC) is weak enough to transport spins over long
distances, while also being strong enough to allow their electrical
manipulation. Here we demonstrate a radically different approach by engineering
a heterostructure from atomically thin crystals, which are ""glued"" by weak van
der Waals (vdW) forces and which combine the superior spin transport properties
of graphene with the strong SOC of the semiconducting MoS$_{2}$. The spin
transport in the graphene channel is modulated between ON and OFF states by
tuning the spin absorption into the MoS$_{2}$ layer with a gate electrode. Our
demonstration of a spin field-effect transistor using two-dimensional (2D)
materials identifies a new route towards spin logic operations for beyond CMOS
technology.",1605.09159v1
2018-12-05,Observation of Spin Hall Effect in Weyl Semimetal WTe2 at Room Temperature,"Discovery of topological Weyl semimetals has revealed the opportunities to
realize several extraordinary physical phenomena in condensed matter physics.
Specifically, these semimetals with strong spin-orbit coupling, broken
inversion symmetry and novel spin texture are predicted to exhibit a large spin
Hall effect that can efficiently convert the charge current to a spin current.
Here we report the direct experimental observation of a large spin Hall and
inverse spin Hall effects in Weyl semimetal WTe2 at room temperature obeying
Onsager reciprocity relation. We demonstrate the detection of the pure spin
current generated by spin Hall phenomenon in WTe2 by making van der Waals
heterostructures with graphene, taking advantage of its long spin coherence
length and spin transmission at the heterostructure interface. These
experimental findings well supported by ab initio calculations show a large
charge-spin conversion efficiency in WTe2; which can pave the way for
utilization of spin-orbit induced phenomena in spintronic memory and logic
circuit architectures.",1812.02113v2
2001-12-21,Theory of single spin detection with STM,"We propose a mechanism for detection of a single spin center on a
non-magnetic substrate. In the detection scheme, the STM tunnel current is
correlated with the spin orientation. In the presence of magnetic field, the
spin precesses and the tunnel current is modulated at the Larmor frequency. The
mechanism relies on the effective spin-orbit interaction between the injected
unpolarized STM current and the local spin center, which leads to the nodal
structure of the spatial signal profile. Based on the proposed mechanism, the
strongest spin-related signal can be expected for the systems with large
spin-orbit coupling and low carrier concentration.",0112407v2
2007-09-05,Topological spin-Hall current in waveguided zinc-blende semiconductors with Dresselhaus spin-orbit coupling,"We describe an intrinsic spin-Hall effect in $n$-type bulk zinc-blende
semiconductors with topological origin. When electron transport is confined to
a waveguide structure, and the applied electric field is such that the spins of
electrons remain as eigenstates of the Dresselhaus spin-orbit field with
negligible subband mixing, a gauge structure appears in the momentum space of
the system. In particular, the momentum space exhibits a non-trivial Berry
curvature which affects the transverse motion of electrons anisotropically in
spin, thereby producing a finite spin-Hall effect. The effect should be
detectable using standard techniques in the literature such as Kerr rotation,
and be readily distinguishable from other mechanisms of the spin-Hall effect.",0709.0609v2
2010-07-31,Random walk approach to spin dynamics in a two-dimensional electron gas with spin-orbit coupling,"We introduce and solve a semi-classical random walk (RW) model that describes
the dynamics of spin polarization waves in zinc-blende semiconductor quantum
wells. We derive the dispersion relations for these waves, including the
Rashba, linear and cubic Dresselhaus spin-orbit interactions, as well as the
effects of an electric field applied parallel to the spin polarization
wavevector. In agreement with fully quantum mechanical calculations [Kleinert
and Bryksin, Phys. Rev. B \textbf{76}, 205326 (2007)], the RW approach predicts
that spin waves acquire a phase velocity in the presence of the field that
crosses zero at a nonzero wavevector, $q_0$. In addition, we show that the
spin-wave decay rate is independent of field at $q_0$ but increases as
$(q-q_0)^2$ for $q\neq q_0$. These predictions can be tested experimentally by
suitable transient spin grating experiments.",1008.0132v2
2011-10-18,Two-orbital Schwinger Boson Representation of Spin-One: Application to a Non-abelian Spin Liquid with Quaternion Gauge Field,"A non-abelian spin liquid in triangular lattice spin-1 systems was recently
formulated in the form of continuum field theory [T. Grover, and T. Senthil,
Phys. Rev. Lett. 107, 077203 (2011); Cenke Xu, A.W.W. Ludwig, arXiv:1012.5671].
It has spin-1/2 bosonic spinons coupled to emergent quaternion gauge fields,
and can be obtained by quantum disordering a non-collinear spin nematic order
hypothesized to describe NiGa_2S_4 [H. Tsunetsugu, and M. Arikawa, J. Phys.
Soc. Jpn. 75, 083701 (2006)], However a microscopic lattice description, e.g.
the lattice spinon (mean-field) Hamiltonian and the spin wavefunction, has been
missing, and it has been noted that the standard Schwinger boson or bosonic
triplon representations of spin-1 cannot describe this spin liquid. In this
paper a two-orbital Schwinger boson representation for spin-1 systems is
developed and used to construct a mean-field description of this quaternion
spin liquid. Projecting the mean-field state produces a prototype wavefunction,
which is a superposition of close-packed AKLT loop configurations with
nontrivial amplitudes. This new formalism and related wavefunctions may be
generalized to higher spin systems and can possibly produce spin liquid states
with even richer emergent gauge structures.",1110.4091v1
2012-08-20,Reversal and Termination of Current-Induced Domain Wall Motion via Magnonic Spin-Transfer Torque,"We investigate the domain wall dynamics of a ferromagnetic wire under the
combined influence of a spin-polarized current and magnonic spin-transfer
torque generated by an external field, taking also into account Rashba
spin-orbit coupling interactions. It is demonstrated that current-induced
motion of the domain wall may be completely reversed in an oscillatory fashion
by applying a magnonic spin-transfer torque as long as the spin-wave velocity
is sufficiently high. Moreover, we show that the motion of the domain wall may
be fully terminated by means of the generation of spin-waves, suggesting the
possibility to pin the domain-walls to predetermined locations. We also discuss
how strong spin-orbit interactions modify these results.",1208.4108v1
2013-11-12,Leggett's Modes in Magnetic Systems with Jahn-Teller distortion,"Leggett's mode is a collective excitation corresponding to the oscillation of
the relative phase of the order parameters in a two band superconductor, with
frequency proportional to interband coupling. We report on the existence of
modes, similar to Leggett's mode, in magnetic systems with Jahn-Teller
distortion. The minimal Kugel-Khomskii model, which describes simultaneously
both the spin and the orbital order, is studied. The dynamical degrees of
freedom are spin-$s$ operators of localized spins and pseudospin-$\tau$
operators, which respond to the orbital degeneracy and satisfy the similar
commutation relation with those of the spin operators. In the case of
""antiferro"" spin and pseudospin order the system possesses two
antiferromagnetic magnons with equal spin-wave velocities and two Leggett's
modes with equal gaps proportional to the square root of the spin-pseudospin
interaction constant. In the case of ""ferro"" spin and pseudospin order the
system possesses one ferromagnetic magnon and one Leggett's mode with gap
proportional to the spin-pseudospin interaction constant.",1311.2733v3
2014-01-02,Topological Spin Texture in a Quantum Anomalous Hall Insulator,"The quantum anomalous Hall (QAH) effect has been recently discovered in
experiment using thin-film topological insulator with ferromagnetic ordering
and strong spin-orbit coupling. Here we investigate the spin degree of freedom
of a QAH insulator and uncover a fundamental phenomenon that the edge states
exhibit topologically stable spin texture in the boundary when a chiral-like
symmetry is present. This result shows that edge states are chiral in both the
orbital and spin degrees of freedom, and the chiral edge spin texture
corresponds to the bulk topological states of the QAH insulator. We also study
the potential applications of the edge spin texture in designing
topological-state-based spin devices which might be applicable to future
spintronic technologies.",1401.0415v3
2015-02-02,Theory of spin polarization in mesoscopic spin-orbit coupling systems,"We establish a general formalism of the bulk spin polarization (BSP) and the
current-based spin polarization (CSP) for mesoscopic ferromagnetic and
spin-orbit interaction (SOI) semiconducting systems. Based on this formalism,
we reveal the basic properties of BSP and CSP and their relationships. The BSP
describes the intrinsic spin polarized properties of devices. The CSP depends
on both intrinsic parameters of device and the incident current. For the
non-spin-polarized incident current with the inphase spin-phase coherence, CSP
equals to BSP. We give analytically the BSP and CSP of several typical
nanodevice models, ferromagnetic nanowire, Rashba nanowire and rings. These
results provide basic physical behaviors of BSP and CSP and their
relationships.",1502.00476v1
2016-04-07,Persistent Spin Textures in Semiconductor Nanostructures,"Device concepts in semiconductor spintronics make long spin lifetimes
desirable, and the requirements put on spin control by schemes of quantum
information processing are even more demanding. Unfortunately, due to
spin-orbit coupling electron spins in semiconductors are generically subject to
rather fast decoherence. In two-dimensional quantum wells made of zinc-blende
semiconductors, however, the spin-orbit interaction can be engineered in such a
way that persistent spin structures with extraordinarily long spin lifetimes
arise even in the presence of disorder and imperfections. We review
experimental and theoretical developments on this subject both for $n$-doped
and $p$-doped structures, and we discuss possible device applications.",1604.02026v2
2016-06-28,Spin-multipole effects in binary black holes and the test-body limit,"We discuss the effects of the black holes' spin-multipole structure in the
orbital dynamics of binary black holes according to general relativity,
focusing on the leading-post-Newtonian-order couplings at each order in an
expansion in the black holes' spins. We first review previous widely confirmed
results up through fourth order in spin, observe suggestive patterns therein,
and discuss how the results can be extrapolated to all orders in spin with
minimal information from the test-body limit. We then justify this
extrapolation by providing a complete derivation within the post-Newtonian
framework of a canonical Hamiltonian for a binary black hole, for generic
orbits and spin orientations, which encompasses the leading post-Newtonian
orders at all orders in spin. At the considered orders, the results reveal a
precise equivalence between arbitrary-mass-ratio two-spinning-black-hole
dynamics and the motion of a test black hole in a Kerr spacetime, as well as an
intriguing relationship to geodesic motion in a Kerr spacetime.",1606.08832v3
2011-11-22,Nonuniversality of the intrinsic inverse spin-Hall effect in diffusive systems,"We studied the electric current induced in a two-dimensional electron gas by
the spin current, in the presence of Rashba and cubic Dresselhaus spin-orbit
interactions. We found out that the factor relating these currents is not
universal, but rather depends on the origin of the spin current. Drastic
distinction has been found between two cases: the spin current created by
diffusion of an inhomogeneous spin density, and the pure homogeneous spin
current. We found out that in the former case the ISHE electric current is
finite, while it turns to zero in the latter case, if the spin-orbit coupling
is represented by Rashba interaction.",1111.5082v2
2019-07-18,Tunning Spin Hall conductivities in GeTe by Ferroelectric Polarization,"Controlling charge-spin current conversion by electric fields is crucial in
spintronic devices, which can be realized in diatom ferroelectric semiconductor
GeTe where it is established that ferroelectricity can change the spin texture.
We demonstrated that the spin Hall conductivity (SHC) can be further tuned by
ferroelectricity based on the density functional theory calculations. The spin
texture variation driven by the electric fields was elucidated from the
symmetry point of view, highlighting the interlocked spin and orbital degrees
of freedom. We observed that the origin of SHC can be attributed to the Rashba
effect and the intrinsic spin-orbit coupling. The magnitude of one component of
SHC {\sigma}_xy^z can reach as large as 100 {\hbar}/e/({\Omega}cm) in the
vicinity of the band edge, which is promising for engineering spintronic
devices. Our work on tunable spin transport properties via the ferroelectric
polarization brings novel assets into the field of spintronics.",1907.07919v2
2017-11-09,Room Temperature Giant Charge-to-Spin Conversion at SrTiO3/LaAlO3 Oxide Interface,"Two-dimensional electron gas (2DEG) formed at the interface between SrTiO3
(STO) and LaAlO3 (LAO) insulating layer is supposed to possess strong Rashba
spin-orbit coupling. To date, the inverse Edelstein effect (i.e. spin-to-charge
conversion) in the 2DEG layer is reported. However, the direct effect of
charge-to-spin conversion, an essential ingredient for spintronic devices in a
current induced spin-orbit torque scheme, has not been demonstrated yet. Here
we show, for the first time, a highly efficient spin generation with the
efficiency of ~6.3 in the STO/LAO/CoFeB structure at room temperature by using
spin torque ferromagnetic resonance. In addition, we suggest that the spin
transmission through the LAO layer at high temperature range is attributed to
the inelastic tunneling via localized states in the LAO band gap. Our findings
may lead to potential applications in the oxide insulator based spintronic
devices.",1711.03268v1
2020-08-24,Enhancement of Spin-charge Conversion in Dilute Magnetic Alloys by Kondo Screening,"We derive a kinetic theory capable of dealing both with large spin-orbit
coupling and Kondo screening in dilute magnetic alloys. We obtain the collision
integral non-perturbatively and uncover a contribution proportional to the
momentum derivative of the impurity scattering S-matrix. The latter yields an
important correction to the spin diffusion and spin-charge conversion
coefficients, and fully captures the so-called side-jump process without
resorting to the Born approximation (which fails for resonant scattering), or
to otherwise heuristic derivations. We apply our kinetic theory to a quantum
impurity model with strong spin-orbit, which captures the most important
features of Kondo-screened Cerium impurities in alloys such as
La$_{1-x}$Cu$_6$. We find 1) a large zero-temperature spin Hall conductivity
that depends solely on the Fermi wave number and 2) a transverse spin diffusion
mechanism that modifies the standard Fick's diffusion law. Our predictions can
be readily verified by standard spin-transport measurements in metal alloys
with Kondo impurities.",2008.10185v2
2020-11-29,Spin Seebeck Effect in Nonmagnetic Excitonic Insulators,"We propose a mechanism of the spin Seebeck effect attributed to excitonic
condensation in a nonmagnetic insulator. We analyze a half-filled two-orbital
Hubbard model with a crystalline field splitting in the strong coupling limit.
In this model, the competition between the crystalline field and electron
correlations brings about an excitonic insulating state, where the two orbitals
are spontaneously hybridized. Using the generalized spin-wave theory and
Boltzmann transport equation, we find that a spin current generated by a
thermal gradient is observed in the excitonic insulating state without magnetic
fields. The spin Seebeck effect originates from spin-split collective
excitation modes although the ground state does not exhibit any magnetic
orderings. This peculiar phenomenon is inherent in the excitonic insulating
state, whose order parameter is time-reversal odd and yields a spin splitting
for the collective excitation modes. We also find that the spin current is
strongly enhanced and its direction is inverted in the vicinity of the phase
transition to another magnetically ordered phase. We suggest that the present
phenomenon is possibly observed in perovskite cobaltites with the
GdFeO$_3$-type lattice distortion.",2011.14337v1
2005-10-25,Non-equilibrium spin polarization effects in spin-orbit coupling system and contacting metallic leads,"We study theoretically the current-induced spin polarization effect in a
two-terminal mesoscopic structure which is composed of a semiconductor
two-dimensional electron gas (2DEG) bar with Rashba spin-orbit (SO) interaction
and two attached ideal leads. The nonequilibrium spin density is calculated by
solving the scattering wave functions explicitly within the ballistic transport
regime. We found that for a Rashba SO system the electrical current can induce
spin polarization in the SO system as well as in the ideal leads. The induced
polarization in the 2DEG shows some qualitative features of the intrinsic spin
Hall effect. On the other hand, the nonequilibrium spin density in the ideal
leads, after being averaged in the transversal direction, is independent of the
distance measured from the lead/SO system interface, except in the vicinity of
the interface. Such a lead polarization effect can even be enhanced by the
presence of weak impurity scattering in the SO system and may be detectable in
real experiments.",0510664v2
2014-12-09,Spin excitations in the nematic phase and the metallic stripe spin-density wave phase of iron pnictides,"We present a general study of the magnetic excitations within a weak-coupling
five-orbital model relevant to itinerant iron pnictides. As a function of
enhanced electronic correlations, the spin excitations in the symmetry broken
spin-density wave phase evolve from broad low-energy modes in the limit of weak
interactions to sharply dispersing spin wave prevailing to higher energies at
larger interaction strengths. We show how the resulting spin response at high
energies depends qualitatively on the magnitude of the interactions. We also
calculate the magnetic excitations in the nematic phase by including an orbital
splitting, and find a pronounced C_2 symmetric excitation spectrum right above
the transition to long-range magnetic order. Finally, we discuss the C_2 versus
C_4 symmetry of the spin excitations as a function of energy for both the
nematic and the spin-density wave phase.",1412.2912v1
2015-05-12,Spin-Orbit Coupling Fluctuations as a Mechanism of Spin Decoherence,"We discuss a general framework to address spin decoherence resulting from
fluctuations in a spin Hamiltonian. We performed a systematic study on spin
decoherence in the compound K$_6$[V$_{15}$As$_6$O$_{42}$(D$_2$O)] $\cdot$
8D$_2$O, using high-field Electron Spin Resonance (ESR). By analyzing the
anisotropy of resonance linewidths as a function of orientation, temperature
and field, we find that the spin-orbit term is a major decoherence source. The
demonstrated mechanism can alter the lifetime of any spin qubit and we discuss
how to mitigate it by sample design and field orientation.",1505.03177v2
2018-03-30,Gate-controlled anisotropy in Aharonov-Casher spin interference: signatures of Dresselhaus spin-orbit inversion and spin phases,"The coexistence of Rashba and Dresselhaus spin-orbit interactions (SOIs) in
semiconductor quantum wells leads to an anisotropic effective field coupled to
carriers' spins. We demonstrate a gate-controlled anisotropy in Aharonov-Casher
(AC) spin interferometry experiments with InGaAs mesoscopic rings by using an
in-plane magnetic field as a probe. Supported by a perturbation-theory
approach, we find that the Rashba SOI strength controls the AC resistance
anisotropy via spin dynamic and geometric phases and establish ways to
manipulate them by employing electric and magnetic tunings. Moreover, assisted
by two-dimensional numerical simulations, we identify a remarkable anisotropy
inversion in our experiments attributed to a sign change in the renormalized
linear Dresselhaus SOI controlled by electrical means, which would open a door
to new possibilities for spin manipulation.",1803.11371v2
2010-01-07,Scattering Theory of Current-Induced Spin Polarization,"We construct a novel scattering theory to investigate magnetoelectrically
induced spin polarizations. Local spin polarizations generated by electric
currents passing through a spin-orbit coupled mesoscopic system are measured by
an external probe. The electrochemical and spin-dependent chemical potentials
on the probe are controllable and tuned to values ensuring that neither charge
nor spin current flow between the system and the probe, on time-average. For
the relevant case of a single-channel probe, we find that the resulting
potentials are exactly independent of the transparency of the contact between
the probe and the system. Assuming that spin relaxation processes are absent in
the probe, we therefore identify the local spin-dependent potentials in the
sample at the probe position, and hence the local current-induced spin
polarization, with the spin-dependent potentials in the probe itself. The
statistics of these local chemical potentials is calculated within random
matrix theory. While they vanish on spatial and mesoscopic average, they
exhibit large fluctuations, and we show that single systems typically have spin
polarizations exceeding all known current-induced spin polarizations by a
parametrically large factor. Our theory allows to calculate quantum
correlations between spin polarizations inside the sample and spin currents
flowing out of it. We show that these large polarizations correlate only weakly
with spin currents in external leads, and that only a fraction of them can be
converted into a spin current in the linear regime of transport, which is
consistent with the mesoscopic universality of spin conductance fluctuations.
We numerically confirm the theory.",1001.1125v2
2013-03-14,Spin polarization in the Hubbard model with Rashba spin-orbit coupling on a ladder,"The competition between on-site Coulomb repulsion and Rashba spin-orbit
coupling (RSOC) is studied on two-leg ladders by numerical techniques. By
studying persistent currents in closed rings by exact diagonalization, it is
found that the contribution to the current due to the RSOC V_{SO}, for a fixed
value of the Hubbard repulsion U reaches a maximum at intermediate values of
V_{SO}. By increasing the repulsive Hubbard coupling U, this spin-flipping
current is suppressed and eventually it becomes opposite to the spin-conserving
current. The main result is that the spin accumulation defined as the relative
spin polarization between the two legs of the ladder is enhanced by U. Similar
results for this Hubbard-Rashba model are observed for a completely different
setup in which two halves of the ladders are connected to a voltage bias and
the ensuing time-dependent regime is studied by the density
matrix-renormalization group technique. It is also interesting a combined
effect between V_{SO} and U leading to a strong enhancement of
antiferromagnetic order which in turn may explain the observed behavior of the
spin-flipping current. The implications of this enhancement of the spin-Hall
effect with electron correlations for spintronic devices is discussed.",1303.3613v3
2024-04-09,Excited-State Dynamics and Optically Detected Magnetic Resonance of Solid-State Spin Defects from First Principles,"Optically detected magnetic resonance (ODMR) is an efficient and reliable
method that enables initialization and readout of spin states through
spin-photon interface. In general, high quantum efficiency and large
spin-dependent photoluminescence (PL) contrast are desirable for reliable
quantum information readout. However, reliable prediction of the ODMR contrast
from first-principles requires accurate description of complex spin
polarization mechanisms of spin defects. These mechanisms often include
multiple radiative and nonradiative processes in particular intersystem
crossing (ISC) among multiple excited electronic states. In this work we
present our implementation of the first-principles ODMR contrast, by solving
kinetic master equation with calculated rates from ab initio electronic
structure methods then benchmark the implementation on the case of the
negatively-charged nitrogen vacancy (NV) center in diamond. We show the
importance of correct description of multi-reference electronic states for
accurate prediction of excitation energy, spin-orbit coupling, and the rate of
ISC. Moreover, we underscore the importance of pseudo Jahn-Teller effect for
the spin-orbit coupling, and the dynamical Jahn-Teller effect for
electron-phonon coupling, key factors determining ISC rates and ODMR contrast.
We show good agreement between our first-principles calculations and the
experimental ODMR contrast under magnetic field. We then demonstrate reliable
predictions of magnetic field direction, pump power, and microwave frequency
dependency, as important parameters for ODMR experiments. Our work clarifies
the important excited-state relaxation mechanisms determining ODMR contrast and
provides a predictive computational platform for spin polarization and optical
readout of solid-state quantum defects from first principles.",2404.05917v1
2000-01-18,Octupole Moment as a Hidden Order Parameter in Orbitally Degenerate f-Electron Systems,"Possibility of a novel pseudo-scalar (octupole) order is studied
theoretically for orbitally degenerate systems with strong spin-orbit coupling
such as Ce$_x$La$_{1-x}$B$_6$. It is discussed that coexistence of an octupole
order parameter and antiferromagnetic fluctuation should lead to drastic
softening of the elastic constant by a mode-mixing effect. Nonlinear coupling
between dipole, quadrupole and octupole fluctuations is taken into account in
terms of a Ginzburg-Landau-type functional which is derived microscopically
through path integral.",0001238v1
2007-05-21,Dimer phases in quantum antiferromagnets with orbital degeneracy,"We study and solve the ground-state problem of a microscopic model for a
family of orbitally degenerate quantum magnets. The orbital degrees of freedom
are assumed to have directional character and are represented by static
Potts-like variables. In the limit of vanishing Hund's coupling, the
ground-state manifold of such a model is spanned by the hard-core dimer (spin
singlet) coverings of the lattice. The extensive degeneracy of dimer coverings
is lifted at a finite Hund's coupling through an order-out-of-disorder
mechanism by virtual triplet excitations. The relevance of our results to
several experimentally studied systems is discussed.",0705.2990v2
2007-09-22,Orbital Domain Dynamics in a Doped Manganite,"The coupling of multiple degrees of freedom - charge, spin, and lattice - in
manganites has mostly been considered at the microscopic level. However, on
larger length scales, these correlations may be affected by strain and
disorder, which can lead to short range order in these phases and affect the
coupling between them. To better understand these effects, we explore the
dynamics of orbitally ordered domains in a half-doped manganite near the
orbital ordering phase transition. Our results suggest that the domains are
largely static, and exhibit only slow fluctuations near domain boundaries.",0709.3558v1
2000-10-02,"Large Orbital Magnetic Moment in Feo, Fes and Febr2","Magnetic moment of the Fe2+ ion in FeO, FeS and FeBr2 has been calculated
within the quantum atomistic solid-state theory to substantially exceed a value
of 4 muB in the magnetically-ordered state at 0 K. In all compounds the large
orbital moment, of 0.7 - 1.1 muB, has been revealed. Our calculations show that
for the meaningful analysis of electronic and magnetic properties of FeO, FeS
and FeBr2 the intra-atomic spin-orbit coupling is essentially important and
that the orbital moment is largely unquenched in 3d- ion containing compounds.",0010032v1
2000-12-14,"Comment on ""Orbitally degenerate spin-1 model for insulating V2O3""","We criticize the model proposed by Mila et al. (Phys.Rev.Lett. 85 (2000)
1714) for the description of the V3+ ion in V2O3 by pointing out that it is
completely artificial because the condition about the degenerate (doublet)
orbital ground state required for the authors' model cannot be realized in the
reality. We claim that the V3+ ion should be considered as described by the
quantum numbers S=1 and L=3 and with taking into account the orbital moment and
the intra-atomic spin-orbit coupling. PACS: 71.70.E, 75.10.D",0012257v1
2002-09-02,One-Dimensional Confinement and Enhanced Jahn-Teller Instability in LaVO$_3$,"Ordering and quantum fluctuations of orbital degrees of freedom are studied
theoretically for LaVO$_3$ in spin-C-type antiferromagnetic state. The
effective Hamiltonian for the orbital pseudospin shows strong one-dimensional
anisotropy due to the negative interference among various exchange processes.
This significantly enhances the instability toward lattice distortions for the
realistic estimate of the Jahn-Teller coupling by first-principle LDA+$U$
calculations, instead of favoring the orbital singlet formation. This explains
well the experimental results on the anisotropic optical spectra as well as the
proximity of the two transition temperatures for spin and orbital orderings.",0209021v2
2005-02-06,Interplay of orbitally polarized and magnetically ordered phases in doped transition metal oxides,"We investigate the magnetic instabilities of the two-dimensional model of
interacting e_g electrons for hole doping away from two electrons per site in
the mean-field approximation. In particular, we address the occurrence of
orbitally polarized states due to the inequivalent orbitals, and their
interplay with ferromagnetic and antiferromagnetic spin order. The role played
by the Hund's exchange coupling J_H and by the crystal field orbital splitting
E_z in stabilizing one of the competing phases is discussed in detail.",0502158v1
2006-02-08,Orbital evolution of a test particle around a black hole: Indirect determination of the self force in the post Newtonian approximation,"Comparing the corrections to Kepler's law with orbital evolution under a self
force, we extract the finite, already regularized part of the latter in a
specific gauge. We apply this method to a quasi-circular orbit around a
Schwarzschild black hole of an extreme mass ratio binary, and determine the
first- and second-order conservative gravitational self force in a post
Newtonian expansion. We use these results in the construction of the
gravitational waveform, and revisit the question of the relative contribution
of the self force and spin-orbit coupling.",0602032v2
2008-08-08,Orbital ordering in undoped manganites via a generalized Peierls instability,"We study the ground state orbital ordering of $LaMnO_3$, at weak
electron-phonon coupling, when the spin state is A-type antiferromagnet. We
determine the orbital ordering by extending to our Jahn-Teller system a
recently developed Peierls instability framework for the Holstein model [1]. By
using two-dimensional dynamic response functions corresponding to a mixed
Jahn-Teller mode, we establish that the $Q_2$ mode determines the orbital
order.",0808.1174v3
2009-10-13,Size-dependent orbital symmetry of hole ground states in CdS nanocrystals,"Using time-resolved photoluminescence spectroscopy, we studied the electronic
levels of semiconductor nanocrystals (NCs) with small spin-orbit coupling such
as CdS. Low temperature radiative rates indicate that the lowest energy
transition changes from orbital allowed to orbital forbidden with decreasing NC
size. Our results are well explained by a size-dependent hierarchy of s- and
p-orbital hole levels that is in agreement with theoretical predictions. Around
the critical NC radius of ~2 nm, we observe an anti-crossing of s- and
p-orbital hole levels and large changes in transition rates.",0910.2481v1
2015-05-25,Highly Accurate Measurement of the Electron Orbital Magnetic Moment,"We propose to accurately determine the orbital magnetic moment of the
electron by measuring, in a Magneto-Optical or Ion trap, the ratio of the Lande
g-factors in two atomic states. From the measurement of (gJ1/gJ2), the quantity
A, which depends on the corrections to the electron g-factors can be extracted,
if the states are LS coupled. Given that highly accurate values of the
correction to the spin g-factor are currently available, accurate values of the
correction to the orbital g-factor may also be determined. At present, (-1.8
+/- 0.4) x 10-4 has been determined as a correction to the electron orbital
g-factor, by using earlier measurements of the ratio gJ1/gJ2, made on the
Indium 2P1/2 and 2P3/2 states.",1505.08140v1
2019-07-31,Multi-orbital tight binding model for cavity-polariton lattices,"In this work we present a tight-binding model that allows to describe with a
minimal amount of parameters the band structure of exciton-polariton lattices.
This model based on $s$ and $p$ non-orthogonal photonic orbitals faithfully
reproduces experimental results reported for polariton graphene ribbons. We
analyze in particular the influence of the non-orthogonality, the
inter-orbitals interaction and the photonic spin-orbit coupling on the
polarization and dispersion of bulk bands and edge states.",1907.13621v1
2004-09-11,Controlling Spin Qubits in Quantum Dots,"We review progress on the spintronics proposal for quantum computing where
the quantum bits (qubits) are implemented with electron spins. We calculate the
exchange interaction of coupled quantum dots and present experiments, where the
exchange coupling is measured via transport. Then, experiments on single spins
on dots are described, where long spin relaxation times, on the order of a
millisecond, are observed. We consider spin-orbit interaction as sources of
spin decoherence and find theoretically that also long decoherence times are
expected. Further, we describe the concept of spin filtering using quantum dots
and show data of successful experiments. We also show an implementation of a
read out scheme for spin qubits and define how qubits can be measured with high
precision. Then, we propose new experiments, where the spin decoherence time
and the Rabi oscillations of single electrons can be measured via charge
transport through quantum dots. Finally, all these achievements have promising
applications both in conventional and quantum information processing.",0409294v1
2005-03-24,Edge Spin Current and Spin Polarization in Quantum Hall Regime,"We study the edge spin current and spin polarization in a two-dimensional
electron gas with spin-orbit coupling in the presence of a perpendicular
magnetic field. The edge effect removes the degeneracy of Landau levels due to
the competition between the Rashba coupling and the Zeeman splitting, which
exists in the bulk. Large spin edge current and non-linear response to an
electric field are found when the two levels are degenerated in the bulk. It is
found that he spin current is proportional to spin polarization along the
y-direction in an finite magnetic field, which provides a way to extract the
spin current in the system.",0503592v2
2006-07-10,Boltzmann Equations for Spin and Charge Relaxations in Superconductors,"In a superconductor coupled with a ferromagnetic metal, spin and charge
imbalances can be induced by injecting spin-polarized electron current from the
ferromagnetic metal. We theoretically study a nonequilibrium distribution of
quasiparticles in the presence of spin and charge imbalances. We show that four
distribution functions are needed to characterize such a nonequilibrium
situation, and derive a set of linearized Boltzmann equations for them by
extending the argument by Schmid and Sch\""{o}n based on the quasiclassical
Green's function method. Using the Boltzmann equations, we analyze the spin
imbalance in a thin superconducting wire weakly coupled with a ferromagnetic
electrode. The spin imbalance induces a shift $\delta\mu$ ($- \delta \mu$) of
the chemical potential for up-spin (down-spin) quasiparticles. We discuss how
$\delta \mu$ is relaxed by spin-orbit impurity scattering.",0607227v1
2010-04-25,Single Spin Detection with a Carbon Nanotube Double Quantum Dot,"Spin qubits defined in carbon nanotube quantum dots are of considerable
interest for encoding and manipulating quantum information because of the long
electron spin coherence times expected. However, before carbon nanotubes can
find applications in quantum information processing schemes, we need to
understand and control the coupling between individual electron spins and the
interaction between the electron spins and their environment. Here we make use
of spin selection rules to directly measure - and demonstrate control of - the
singlet-triplet exchange coupling between two carbon nanotube quantum dots. We
furthermore elucidate the effects of spin-orbit interaction on the electron
transitions and investigate the interaction of the quantum dot system with a
single impurity spin - the ultimate limit in spin sensitivity.",1004.4377v1
2014-04-09,Spin Transport in non-inertial frame,"The influence of acceleration and rotation on spintronic applications is
theoretically investigated. In our formulation, considering a Dirac particle in
a non-inertial frame, different spin related aspects are studied. The spin
current appearing due to the inertial spin-orbit coupling (SOC) is enhanced by
the interband mixing of the conduction and valence band states. Importantly,
one can achieve a large spin current through the $\vec{k}. \vec{p}$ method in
this non-inertial frame. Furthermore, apart from the inertial SOC term due to
acceleration, for a particular choice of the rotation frequency, a new kind of
SOC term can be obtained from the spin rotation coupling (SRC). This new kind
of SOC is of Dresselhaus type and controllable through the rotation frequency.
In the field of spintronic applications, utilizing the inertial SOC and SRC
induced SOC term, theoretical proposals for the inertial spin filter, inertial
spin galvanic effect are demonstrated. Finally, one can tune the spin
relaxation time in semiconductors by tuning the non-inertial parameters.",1404.2376v1
2020-01-07,Flexoelectric effect mediated spin-to-charge conversion at amorphous-Si thin film interfaces,"Interfacial spin to charge conversion arises due to an electric potential
perpendicular to the interface. The electric potential can be artificially
induced, for example, using ferroelectric and piezoelectric thin films at the
interface. An alternate way to induce the electric potential could be
flexoelectric field. The flexoelectricity can be observed in all the material
that either have or lack inversion symmetry, additionally no large gate bias is
needed. In this experimental study, we report large spin to charge conversion
(spin-Hall angle- 0.578) at Ni80Fe20/amorphous-Si interfaces attributed to
flexoelectricity mediated Rashba spin-orbit coupling. The flexoelectricity at
the interface also gave rise to interlayer spin-acoustic phonon or
flexo-magnetoelastic coupling. In addition to spin-charge conversion, the
strained interfaces also led to almost three-fold increase in anomalous Nernst
effect. This strain engineering for spin dependent thermoelectric behavior at
room temperature opens a new window to the realization of spintronics and
spin-caloritronics devices.",2001.01822v2
2019-02-28,Microscopic mechanism for higher-spin Kitaev model,"The spin S=$\frac{1}{2}$ Kitaev honeycomb model has attracted significant
attention, since emerging candidate materials have provided a playground to
test non-Abelian anyons. The Kitaev model with higher spins has also been
theoretically studied, as it may offer another path to a quantum spin liquid.
However, a microscopic route to achieve higher spin Kitaev models in solid
state materials has not been rigorously derived. Here we present a theory of
the spin S=1 Kitaev interaction in two-dimensional edge-shared octahedral
systems. Essential ingredients are strong spin-orbit coupling in anions and
strong Hund's coupling in transition metal cations. The S=1 Kitaev and
ferromagnetic Heisenberg interactions are generated from superexchange paths.
Taking into account the antiferromagnetic Heisenberg term from direct-exchange
paths, the Kitaev interaction dominates the physics of S=1 system. Using exact
diagonalization technique, we show a finite regime of S=1 spin liquid in the
presence of the Heisenberg interaction. Candidate materials are proposed, and
generalization to higher spins is discussed.",1903.00011v1
2020-06-18,Intrinsic Spin Photogalvanic Effect in Nonmagnetic Insulator,"We show that with the help of spin-orbit coupling, nonlinear light-matter
interactions can efficiently couple with spin and valley degrees of freedom.
This revealed spin photogalvanic effect can generate the long-time pursued
intrinsic pure spin current (PSC) in non-centrosymmetric nonmagnetic
insulators. Different from the spin and valley Hall effect, such a photo-driven
spin current is universal and can be generated without external bias field.
Using first-principles simulation, we study monolayer transition metal
dichalcogenides (TMDs) to demonstrate this effect and confirm an enhanced PSC
under linearly polarized photoexcitation. The amplitude of the PSC is one order
larger than that of the charge current observed in monolayer TMDs. This exotic
nonlinear light-spin interaction indicates that light can be utilized as a
rapid fashion to manipulate the spin-polarized current, which is crucial for
future low-dissipation nanodevices.",2006.10690v1
2021-03-17,Spin/valley coupled dynamics of electrons and holes at the ${\text{MoS}_{2}-\text{MoSe}_{2}}$ interface,"The coupled spin and valley degrees of freedom in transition metal
dichalcogenides (TMDs) are considered a promising platform for information
processing. Here, we use a TMD heterostructure
${\text{MoS}_{2}-\text{MoSe}_{2}}$ to study optical pumping of spin/valley
polarized carriers across the interface and to elucidate the mechanisms
governing their subsequent relaxation. By applying time-resolved Kerr and
reflectivity spectroscopies, we find that the photoexcited carriers conserve
their spin for both tunneling directions across the interface. Following this,
we measure dramatically different spin/valley depolarization rates for
electrons and holes, $\sim 30\,{\text{ns}}^{-1}$ and $< 1\,{\text{ns}}^{-1}$,
respectively and show that this difference relates to the disparity in the
spin-orbit splitting in conduction and valence bands of TMDs. Our work provides
insights into the spin/valley dynamics of free carriers unaffected by complex
excitonic processes and establishes TMD heterostructures as generators of spin
currents in spin/valleytronic devices.",2103.09934v2
2008-05-05,"Orbital degeneracy, Hund's coupling, and band ferromagnetism: effective quantum parameter, suppression of quantum corrections, and enhanced stability","An effective quantum parameter is obtained for the band ferromagnet in terms
of orbital degeneracy and Hund's coupling. This quantum parameter determines,
in analogy with 1/N for the generalized Hubbard model and 1/S for quantum spin
systems, the strength of quantum corrections to spin stiffness and spin-wave
energies. Quantum corrections are obtained by incorporating correlation effects
in the form of self-energy and vertex corrections within a
spin-rotationally-symmetric approach in which the Goldstone mode is explicitly
preserved order by order. It is shown that even a relatively small Hund's
coupling is rather efficient in strongly suppressing quantum corrections,
especially for large N, resulting in strongly enhanced stability of the
ferromagnetic state. This mechanism for the enhancement of ferromagnetism by
Hund's coupling implicitly involves a subtle interplay of lattice,
dimensionality, band dispersion, spectral distribution, and band filling
effects.",0805.0470v1
2015-02-16,Stueckelberg interferometry using periodically driven spin-orbit coupled Bose-Einstein condensates,"We study the single-particle dispersion of a spin-orbit coupled (SOC)
Bose-Einstein condensate (BEC) under the periodical modulation of the Raman
coupling. This modulation introduces a further coupling of the SOC dressed
eigenlevels, thus creating a second generation of modulation-dressed
eigenlevels. Theoretical calculations show that these modulation-dressed
eigenlevels feature a pair of avoided crossings and a richer spin-momentum
locking, which we observe using BEC transport measurements. Furthermore, we use
the pair of avoided crossings to engineer a tunable Stueckelberg interferometer
that gives interference fringes in the spin polarization of BECs.",1502.04722v2
2015-03-23,Anisotropic Magnetic Couplings and Structure-Driven Canted to Collinear Transitions in Spin-orbit Coupled Sr2IrO4,"We put forward a scheme to study the anisotropic magnetic couplings in
Sr2IrO4 by mapping fully relativistic constrained noncollinear density
functional theory including an on-site Hubbard U correction onto a general spin
model Hamiltonian. This procedure allows for the simultaneous account and
direct control of the lattice, spin and orbital interactions within a fully ab
initio scheme. We compute the isotropic, single site anisotropy and
Dzyaloshinskii-Moriya (DM) coupling parameters, and clarify that the origin of
the canted magnetic state in Sr2IrO4 arises from the interplay between
structural distortions and the competition between isotropic exchange and DM
interactions. A complete magnetic phase diagram with respect to the tetragonal
distortion and the rotation of IrO6 octahedra is constructed, revealing the
presence of two types of canted to collinear magnetic transitions: a spin-flop
transition with increasing tetragonal distortion and a complete quenching of
the basal weak ferromagnetic moment below a critical octahedral rotation.",1503.06753v2
2015-11-30,Tricriticalities and Quantum Phases in Spin-Orbit-Coupled Spin-$1$ Bose Gases,"We study the zero-temperature phase diagram of a spin-orbit-coupled
Bose-Einstein condensate of spin $1$, with equally weighted Rashba and
Dresselhaus couplings. Depending on the antiferromagnetic or ferromagnetic
nature of the interactions, we find three kinds of striped phases with
qualitatively different behaviors in the modulations of the density profiles.
Phase transitions to the zero-momentum and the plane-wave phases can be induced
in experiments by independently varying the Raman coupling strength and the
quadratic Zeeman field. The properties of these transitions are investigated in
detail, and the emergence of tricritical points, which are the direct
consequence of the spin-dependent interactions, is explicitly discussed.",1511.09225v2
2017-02-15,Bosons with incommensurate potential and spin-orbit coupling,"We chart out the phase diagram of ultracold `spin-half' bosons in a
one-dimensional optical lattice in the presence of Aubry-Andr\'e (AA) potential
and with spin-orbit (SO) and Raman couplings investigating the transition from
superfluid (SF) to localized phases and the existence of density wave phase for
nearest-neighbor interaction (NNI). We show that the presence of SO coupling
and AA potential leads to a novel spin-split momentum distribution of the
bosons in the localized phase near the boundary with the SF phase, which can
act as a signature of such a transition. We also obtain the level statistics of
the bosons in the superfluid phase with finite NNI and demonstrate its change
from Gaussian Unitary Ensemble (GUE) to Gaussian Orthogonal Ensemble (GOE) as a
function of the Raman coupling. We discuss experiments which can test our
theory.",1702.04714v1
2018-11-01,Performance of trajectory surface hopping method in the treatment of ultrafast intersystem crossing dynamics,"We carried out extensive studies to examine the performance of the
fewest-switches surface hopping method in the description of the ultrafast
intersystem crossing dynamic of various singlet-triplet (S-T) models by
comparison with the results of the exact full quantum dynamics. Different
implementation details and some derivative approaches were examined. As
expected, it is better to perform the trajectory surface hopping calculations
in the spin-adiabatic representation or by the local diabatization approach,
instead of in the spin-diabatic representation. The surface hopping method
provides reasonable results for the short-time dynamics in the S-T model with
weak spin-orbital coupling (diabatic coupling), although it does not perform
well in the models with strong spin-orbital coupling (diabatic coupling). When
the system accesses the S-T potential energy crossing with rather high kinetic
energy, the trajectory surface hopping method tends to produce the good
description of the nonadiabatic intersystem crossing dynamics. The impact of
the decoherence correction on the performance of the trajectory surface hopping
is system dependent. It improves the result accuracy in many cases, while its
influence may also be minor for other cases.",1811.00254v2
2010-05-27,Renormalized parameters and perturbation theory for an n-channel Anderson model with Hund's rule coupling,"We extend the renormalized perturbation theory for the single impurity
Anderson model to the n-channel model with a Hund's rule coupling, and show
that the exact results for the spin, orbital and charge susceptibilities, as
well as the leading low temperature dependence for the resistivity, are
obtained by working to second order in the renormalized couplings. A universal
relation is obtained between the renormalized parameters, independent of n, in
the Kondo regime. An expression for the dynamic spin susceptibility is also
derived by taking into account repeated quasiparticle scattering, which is
asymptotically exact in the low frequency regime and satisfies the
Korringa-Shiba relation. The renormalized parameters, including the
renormalized Hund's rule coupling, are deduced from numerical renormalization
group calculations for the model for the case n=2. The results confirm
explicitly the universal relations between the parameters in the Kondo regime.
Using these results we evaluate the spin, orbital and charge susceptibilities,
temperature dependence of the low temperature resistivity and dynamic spin
susceptibility for the particle-hole symmetric n=2 model.",1005.5113v1
2019-07-04,Topological spinor vortex matter on spherical surface induced by non-Abelian spin-orbital-angular-momentum coupling,"We provide an explicit way to implement non-Abelian
spin-orbital-angular-momentum (SOAM) coupling in spinor Bose-Einstein
condensates using magnetic gradient coupling. For a spherical surface trap
addressable using high-order Hermite-Gaussian beams, we show that this system
supports various degenerate ground states carrying different total angular
momenta $\mathbf{J}$, and the degeneracy can be tuned by changing the strength
of SOAM coupling. For weakly interacting spinor condensates with $f=1$, the
system supports various meta-ferromagnetic phases and meta-polar states
described by quantized total mean angular momentum $|\langle \mathbf{J}
\rangle|$. Polar states with $Z_2$ symmetry and Thomson lattices formed by
defects of spin vortices are also discussed. The system can be used to prepare
various stable spin vortex states with nontrivial topology, and serve as a
platform to investigate strong-correlated physics of neutral atoms with tunable
ground-state degeneracy.",1907.02216v1
2012-05-14,Magnetic phases of bosons with synthetic spin-orbit coupling in optical lattices,"We investigate magnetic properties in the superfluid and Mott-insulating
states of two-component bosons with spin-orbit (SO) coupling in 2D square
optical lattices. The spin-independent hopping integral $t$ and SO coupled one
$\lambda $are fitted from band structure calculations in the continuum, which
exhibit oscillations as increasing SO coupling strength. The magnetic
superexchange model is derived in the Mott-insulating state with one-particle
per-site, characterized by the Dzyaloshinsky-Moriya (DM) interaction. In the
limit of $|\lambda|\ll |t|$, we find a spin spiral Mott state whose pitch value
is the same as that in the incommensurate superfluid state, while in the
opposite limit $|t| \ll |\lambda|$, the ground state can be found by a dual
transformation to the $|\lambda|\ll|t|$ limit.",1205.3116v3
2020-10-06,Interplay of spin-orbit coupling and Coulomb interaction in ZnO-based electron system,"Spin-orbit coupling (SOC) is pivotal for various fundamental spin-dependent
phenomena in solids and their technological applications. In semiconductors,
these phenomena have been so far studied in relatively weak electron-electron
interaction regimes, where the single electron picture holds. However, SOC can
profoundly compete against Coulomb interaction, which could lead to the
emergence of unconventional electronic phases. Since SOC depends on the
electric field in the crystal including contributions of itinerant electrons,
electron-electron interactions can modify this coupling. Here we demonstrate
the emergence of SOC effect in a high-mobility two-dimensional electron system
in a simple band structure MgZnO/ZnO semiconductor. This electron system
features also strong electron-electron interaction effects. By changing the
carrier density with Mg-content, we tune the SOC strength and achieve its
interplay with electron-electron interaction. These systems pave a way to
emergent spintronic phenomena in strong electron correlation regime and to the
formation of novel quasiparticles with the electron spin strongly coupled to
the density.",2010.02461v1
2022-02-24,Spin-Orbit Interaction of Light Enabled by Negative Coupling in High Quality Factor Optical Metasurfaces,"We study the negative couplings amid local resonances of photonic
metasurfaces. In our analysis, we discover pseudo-spin-orbit coupled bulk modes
leading to lines of circularly polarized radiation eigenstates in
two-dimensional momentum space which were considered to exist only in
three-dimensions. Our theoretical model is exemplified via a guided resonance
dielectric metasurface that possesses Type-II Non-Hermitian diabolical points,
from where the circular polarization lines emanate. The designed metasurface
carries circular polarized radiation eigenstates in both the 0th and the 1st
diffraction orders, allowing spin-selective light deflections. The high quality
factor nature and field enhancement of the designed metasurface could lead to
applications for spin-selective sensing, beam control and nonlinear optics. Our
findings open a gateway for the design of near-field couplings assisted
metasurfaces.",2202.11980v1
2023-06-26,Quantum phases and spectrum of collective modes in a spin-1 BEC with spin-orbital-angular-momentum coupling,"Motivated by the recent experiments [Chen et al., Phys. Rev. Lett 121, 113204
(2018), Chen et al., Phys. Rev. Lett. 121, 250401 (2018)], we investigate the
low-lying excitation spectrum of the ground-state phases of
spin-orbital-angular-momentum-coupled (SOAM-coupled) spin-1 condensates.At
vanishing detuning, a ferromagnetic SOAM-coupled spin-1 BEC can have two
ground-state phases, namely coreless and polar-core vortex states, whereas an
antiferromagnetic BEC supports only polar-core vortex solution. The angular
momentum per particle, longitudinal magnetization, and excitation frequencies
display discontinuities across the phase boundary between the coreless vortex
and polar-core vortex phases. The low-lying excitation spectrum evaluated by
solving the Bogoliubov-de-Gennes equations is marked by avoided crossings and
hence the hybridization of the spin and density channels. The spectrum is
further confirmed by the dynamical evolution of the ground state subjected to a
perturbation suitable to excite a density or a spin mode and a variational
analysis for the density-breathing mode.",2306.14669v2
2023-12-11,Non-constant geometric curvature for tailored spin-orbit coupling and chirality in superconductor-magnet heterostructures,"We show that tailoring the geometric curvature profile of magnets can be used
for bespoke design of an effective non-relativistic spin-orbit coupling, which
may be used to control proximity effects if the magnet is coupled to a
superconductor. We consider proximity-coupled one-dimensional magnetic wires
with variable curvatures, specifically three distinct shapes classified as J-,
C-, and S-type. We demonstrate a chirality-dependent spin polarization of the
superconducting correlations, and show the role of curvature in determining the
ground state of mixed-chirality junctions. We speculate on how this may be
implemented in novel device design, and include analysis of its usage in a
spin-triplet SQUID",2312.06774v2
1995-03-01,Quantum Hall effect in spin-degenerate Landau levels: Spin-orbit enhancement of the conductivity,"The quantum Hall regime in a smooth random potential is considered when two
disorder-broadened Zeeman levels overlap strongly. Spin-orbit coupling is found
to cause a drastic change in the percolation network which leads to a strong
enhancement of the dissipative conductivity at finite temperature, provided the
Fermi level $E_F$ lies between the energies of two delocalized states
$E=\pm\Delta$, $2\Delta$ being the Zeeman splitting. The conductivity is shown
to exhibit a box-like behavior with changing magnetic field: $\sigma_{xx}$ is
$\sim e^2/h$ at $|E_F|<\Delta$ and exponentially small otherwise. Two peaks of
$\sigma_{xx}$ arising as $T\to 0$ are found to be strongly asymmetric.",9503005v1
1998-01-12,Quantum interference and electron-electron interactions at strong spin-orbit coupling in disordered systems,"Transport and thermodynamic properties of disordered conductors are
considerably modified when the angle through which the electron spin precesses
due to spin-orbit interaction (SOI) during the mean free time becomes
significant. Cooperon and Diffusion equations are solved for the entire range
of strength of SOI. The implications of SOI for the electron-electron
interaction and interference effects in various experimental settings are
discussed.",9801095v1
1998-09-30,Josephson Current between Triplet and Singlet Superconductors,"The Josephson effect between triplet and singlet superconductors is studied.
Josephson current can flow between triplet and singlet superconductors due to
the spin-orbit coupling in the spin-triplet superconductor but it is finite
only when triplet superconductor has $L_z=-S_z=\pm 1$, where $L_z$ and $S_z$
are the perpendicular components of orbital angular momentum and spin angular
momentum of the triplet Cooper pairs, respectively. The recently observed
temperature and orientational dependence of the critical current through a
Josephson junction between UPt$_3$ and Nb is investigated by considering a
non-unitary triplet state.",9809403v1
2004-08-10,Key Role of Orbital Anisotropy in Geometrically Frustrated Electron System,"By using the density matrix renormalization group method, we investigate
ground- and excited-state properties of the e_g-orbital degenerate Hubbard
model at quarter filling for two kinds of lattices, zigzag chain and ladder. In
the zigzag chain, the system is effectively regarded as a decoupled double
chain of the S=1/2 antiferromagnetic Heisenberg model, and the spin gap is
approximately zero, similar to the case of weakly coupled Heisenberg chains. On
the other hand, in the ladder, the spin correlation on the rung remains robust
and the spin gap exists.",0408197v1
2006-10-23,Magnetic properties and the electronic structure of LiCoO_2,"We have described properties of LiCoO_2 within the Quantum Atomistic Solid
State (QUASST) theory taking into account very strong electron correlations,
predominantly of the intra-atomic origin, spin-orbit coupling and the detailed
local crystallographic surroundings and its symmetry. Properties of LiCoO_2 are
consistently explained together with NaCoO_2 and LaCoO_3 - in all of these
compounds the Co^3+ ions occur in the low-spin state. This low-spin state is
the effect of the relatively strong crystal-field interactions (B_4^z = +320 K
<=> 10Dq = 3.3 eV) and is a manifestation of the very large orbital moment of
the Co^3+ ion.",0610611v1
2006-11-20,Crossover from diffusive to non-diffusive dynamics in the two-dimensional electron gas with Rashba spin-orbit coupling,"We present the calculation of the density matrix response function of the
two-dimensional electron gas with Rashba spin-orbit interaction, which is
applicable in a wide range of parameters covering the diffusive and
non-diffusive, the dirty and the clean limits. A description of the crossover
between the different regimes is thus provided as well. On the basis of the
derived microscopic expressions we study the propagating charge and
spin-polarization modes in the clean, non-diffusive regime, which is accessible
in the modern experiments.",0611523v2
1999-05-20,Phenomenological spin-orbit three-body force,"In order to improve the description of the N-d vector analyzing powers Ay and
iT11 (the so-called Ay puzzle) a spin-orbit three-body force has been
introduced. The L.S term in the NN potential has been modified including a
two-parameter three-body function depending on the hyperradius \rho. The
modification has been performed in channels where the pair nucleons (i,j) are
coupled to spin Sij=1 and isospin Tij=1. Calculations have been done in the
energy region from Elab=648 keV up to Elab=10 MeV. A noticeable improvement in
the description of the polarization observables has been obtained",9905045v1
2007-07-03,Spin-orbit-assisted electron-phonon interaction and the magnetophonon resonance in semiconductor quantum wells,"We introduce a spin-orbit assisted electron-phonon (e-ph) coupling mechanism
for carriers in semiconductor quantum wells and predict qualitatively the form
and shape of anticrossings between the cyclotron resonance (CR) and optical (LO
and TO) phonons. Since this e-ph interaction involves the electron spin it
makes the predicted TO-CR anticrossing dependent on the filling factor and
therefore on the polarization of the 2D electron gas in the quantum well.",0707.0342v2
2008-02-21,Coherent Control of spin-orbit precession with shaped laser pulses,"Spin precession in Rubidium atoms is investigated through a pump-probe
technique. The excited wave packet corresponds to a precession of spin and
orbital angular momentum around the total angular momentum. We show that using
shaped laser pulses allows us to control this dynamics. With a Fourier
transform limited pulse, the wave packet is initially prepared in the bright
state (coupled to the initial state) whereas a pulse presenting a $\pi $ step
in the spectral phase prepares the wave packet in the dark state (uncoupled to
the initial state).",0802.2986v1
2008-03-31,Anomalous Rashba spin-orbit interaction in InAs/GaSb quantum wells,"We investigate theoretically the Rashba spin-orbit interaction in InAs/GaSb
quantum wells(QWs). We find that the Rashba spin-splitting (RSS) depends
sensitively on the thickness of the InAs layer. The RSS exhibits nonlinear
behavior for narrow InAs/GaSb QWs and the oscillating feature for wide
InAs/GaSb QWs. The nonlinear and oscillating behaviors arise from the weakened
and enhanced interband coupling. The RSS also show asymmetric features respect
to the direction of the external electric field.",0803.4310v1
2008-04-21,Quantum Hall ferromagnetic states and spin-orbit interactions in the fractional regime,"The competition between the Zeeman energy and the Rashba and Dresselhaus
spin-orbit couplings is studied for fractional quantum Hall states by including
correlation effects. A transition of the direction of the spin-polarization is
predicted at specific values of the Zeeman energy. We show that these values
can be expressed in terms of the pair-correlation function, and thus provide
information about the microscopic ground state. We examine the particular
examples of the Laughlin wavefunctions and the 5/2-Pfaffian state. We also
include effects of the nuclear bath.",0804.3332v3
2008-04-25,Side jump contribution to spin-orbit mediated Hall effects and Berry curvature,"Anomalous Hall effect and spin Hall effect originate due to spin-orbit
coupling that in the Kohn-Luttinger ${\bf k}\cdot{\bf p}$ formalism is
represented by anomalous terms in the coordinate and velocity operators.
Relation of these operators to the Berry curvature in the momentum space is
presented for electrons in GaAs type semiconductors. For centrosymmetric
semiconductors, transformational properties of Berry curvature are discussed.",0804.4181v1
2008-10-11,Quantum Criticality and the Alpha/Delta Puzzle,"In this paper we suggest a novel explanation for the alpha-delta transition
in plutonium based on an analogy between the evolution of the actinide ground
state as a function of spin orbit coupling and the behaviour of thin film
superconductors in a magnetic field. The key point is that in metals with a low
carrier density spin-orbit interactions give rise to low energy monopole-like
solitons with quantized spin currents, which play much the same role as
Abrikosov vortices in thin film superconductors. In alpha-plutonium these
solitons form an ordered solid, while in impurity stabilized delta-plutonium
they form a pair condensate.",0810.1984v1
2009-05-29,Field Induced Orbital Antiferromagnetism in Mott Insulators,"We report on a new electromagnetic phenomenon that emerges in Mott
insulators, i.e., materials that do not conduct electricity because of strong
electronic Coulomb repulsion. The phenomenon manifests as antiferromagnetic
ordering due to orbital electric currents which are spontaneously generated
from the coupling between spin currents and an external homogenous magnetic
field. This novel spin-charge current effect provides the mechanism to detect
the so far elusive spin currents by means of unpolarized neutron scattering,
nuclear magnetic resonance or muon spectroscopy. We illustrate this mechanism
by solving a half-filled Hubbard model on a frustrated ladder, a simple but
nontrivial case of strongly interacting electrons.",0905.4871v1
2011-01-04,Spin-orbit coupling inactivity of Co$^{2+}$ ion in geometrically frustrated magnet GeCo$_2$O$_4$,"We report single-crystal neutron diffraction studies on a spinel
antiferromagnet GeCo$_2$O$_4$, which exhibits magnetic order with a trigonal
propagation vector and tetragonal lattice expansion ($c/a\simeq1.001$) below
$T_{\rm N}=21$ K. For this inconsistency between spin and lattice in symmetry,
magnetic Bragg reflections with a tetragonal propagation vector were discovered
below $T_{\rm N}$. We discuss spin and orbital states of Co$^{2+}$ ion
underlying the new magnetic component.",1101.0685v1
2011-05-12,Probing anisotropic superfluidity of rashbons in atomic Fermi gases,"Motivated by the prospect of realizing a Fermi gas of $^{40}$K atoms with a
synthetic non-Abelian gauge field, we investigate theoretically a strongly
interacting Fermi gas in the presence of a Rashba spin-orbit coupling. As the
two-fold spin degeneracy is lifted by spin-orbit interaction, bound pairs with
mixed singlet and triplet pairings (referred to as rashbons) emerge, leading to
an anisotropic superfluid. We show that this anisotropic superfluidity can be
probed via measuring the momentum distribution and single-particle spectral
function in a trapped atomic $^{40}$K cloud near a Feshbach resonance.",1105.2488v1
2011-12-20,Magnetization of a homogeneous two dimensional fermion gas with repulsive contact interaction and Rashba spin-orbit potential,"The z axis magnetization of a two dimensional electron gas with contact
repulsive interaction and in presence of a Rashba potential is computed by
means of quantum field theory at second order. A striking effect of the pure
Rashba interaction is that of hindering spin alignment along the z direction.
Evidence of transition at critical repulsive interaction coupling constant is
still found. The degree of magnetization, however, shows a clear dependence on
the spin-orbit interaction strength. Furthermore, the transition to magnetized
state appears to be smoothed by the presence of the Rashba interaction.",1112.4731v1
2013-10-23,Dynamics of the Dicke model close to the classical limit,"We study the dynamical properties of the Dicke model for increasing spin
length, as the system approaches the limit of a classical spin. First, we
describe the emergence of collective excitations above the groundstate that
converge to the coupled spin-oscillator oscillations found in the classical
limit. The corresponding Green functions reveal quantum dynamical signatures
close to the superradiant quantum phase transition. Second, we identify
signatures of classical quasi-periodic orbits in the quantum time evolution
using numerical time-propagation of the wave function. The resulting phase
space plots are compared to the classical trajectories. We complete our study
with the analysis of individual eigenstates close to the quasi-periodic orbits.",1310.6140v1
2014-09-05,Induced p-wave Superfluidity in Imbalanced Fermi Gases in a Synthetic Gauge Field,"We study pairing formation and the appearance of induced spin-triplet p-wave
superfluidity in dilute three-dimensional imbalanced Fermi gases in the
presence of a uniform non-Abelian gauge field. This gauge field generates a
synthetic Rashba-type spin-orbit interaction which has remarkable consequences
in the induced p-wave pairing gaps. Without the synthetic gauge field, the
p-wave pairing occurs in one of the components due to the induced
(second-order) interaction via an exchange of density fluctuations in the other
component. We show that this p-wave superfluid gap induced by density
fluctuations is greatly enhanced due to the Rashba-type spin-orbit coupling.",1409.1955v1
2015-03-27,Polaron states in a CuO chain,"We introduce a one-dimensional model for a CuO chain, with holes and $S=1/2$
spins localized in $3d_{x^2-y^2}$ orbitals, and $p_\sigma$ oxygen orbitals
without holes in the ground state. We consider a single hole doped at an oxygen
site and study its propagation by spin-flip processes. We develop the Green's
function method and treat the hole-spin coupling in the self-consistent Born
approximation, similar to that successfully used to study polarons in the
regular $t$-$J$ model. We present an analytical solution of the problem and
investigate whether the numerical integration is a good approximation to this
solution.",1503.08201v1
2012-04-12,Spin-orbit coupled cold exciton condensates,"We analyze theoretically the dynamics of degenerate condensate of cold
indirect excitons. We account for both linear spin dependent terms arising from
spin-orbit interaction of Rashba and Dresselhaus types and non-linear terms
transforming a pair of bright excitons into a pair of dark ones. We show that
both terms should lead to the qualitative changes in the dynamics of cold
exciton droplets in the real space and time.",1204.2721v1
2012-04-12,Magnetoelectric effect due to local noncentrosymmetry,"Magnetoelectrics often possess ions located in noncentrosymmetric
surroundings. Based on this fact we suggest a microscopic model of
magnetoelectric interaction and show that the spin-orbit coupling leads to
spin-dependent electric dipole moments of the electron orbitals of these ions,
which results in non-vanishing polarization for certain spin configurations.
The approach accounts for the macroscopic symmetry of the unit cell and is
valid both for commensurate and complex incommensurate magnetic structures. The
model is illustrated by the examples of MnWO4, MnPS3 and LiNiPO4. Application
to other magnetoelectrics is discussed.",1204.2771v1
2017-07-11,Yu-Shiba-Rusinov states of impurities in a triangular lattice of NbSe$_{2}$ with spin orbit coupling,"We study topography of the spin-polarized bound states of magnetic impurities
embedded in triangular lattice of a superconducting host. Such states have been
observed experimentally in 2H-NbSe$_{2}$ crystal [G. C. M'enard et al.,
Nat.Phys. 11, 1013 (2015)] and revealed the oscillating particle-hole asymmetry
extending to tens of nanometers. Using the Bogoliubov-de Gennes approach we
explore the Yu-Shiba-Rusinov states in presence of spin-orbit interaction. We
also study the bound states of double impurities for several relative positions
in a triangular lattice.",1707.03257v2
2017-12-30,"Electronic, magnetic and ferroelectric properties of rhombohedral AgFeO2: an ab initio study","Using first principle calculations under the framework of density functional
theory we have investigated the electronic structure, magnetism and
ferroelectric polarization in the triangular lattice antiferromagnet AgFeO2,
and its comparison to the isostructural system CuFeO2. Our calculations reveal
that spin orbit interaction plays an important role in determining the magnetic
property of AgFeO2 and is possibly responsible for its different magnetic
ground state in comparison to CuFeO2. Calculations of ferroelectric
polarization of AgFeO2 suggest that the spontaneous polarization arises from
noncollinear spin arrangement via spin-orbit coupling. Our calculations also
indicate that in addition to electronic contribution, the lattice mediated
contribution to the polarization are also important for AgFeO2.",1801.00093v1
2019-07-05,Topological states,"Topological phases are characterised by a topological invariant that remains
unchanged by deformations in the Hamiltonian. Materials exhibiting topological
phases include topological insulators, superconductors exhibiting strong
spin-orbit coupling, transition metal dichalcogenides, which can be made
atomically thin and have direct band gaps, as well as high mobility Weyl and
Dirac semimetals. Devices harnessing topological electron states include
topological (spin) transistors, spin-orbit torque devices, non-linear
electrical and optical systems, and topological quantum bits.",1907.02625v1
2012-05-25,Emergence of a common energy scale close to the orbital-selective Mott transition,"We calculate the spectra and spin susceptibilities of a Hubbard model with
two bands having different bandwidths but the same on-site interaction, with
parameters close to the orbital-selective Mott transition, using dynamical
mean-field theory. If the Hund's rule coupling is sufficiently strong, one
common energy scale emerges which characterizes both the location of kinks in
the self-energy and extrema of the diagonal spin susceptibilities. A physical
explanation of this energy scale is derived from a Kondo-type model. We infer
that for multi-band systems local spin dynamics rather than spectral functions
determine the location of kinks in the effective band structure.",1205.5782v1
2019-01-17,Secular evolution of compact binaries revolving around a spinning massive black hole,"The leading order effect of the spin of a distant supermassive black hole
(SMBH) on the orbit of compact binary revolving around it appears at the 1.5
post Newtonian (PN) expansion through coupling with the inner and outer orbital
angular momenta, and makes an oscillating characteristic contribution to the
secular evolution of the compact binary eccentricity over a long time scale
compared to the Kozai-Lidov dynamics caused by a non-spinning SMBH.",1901.05591v1
2020-10-24,Large spin Hall effect in 5d-transition metal anti-perovskites,"The spin Hall effect (SHE) is highly promising for spintronic applications,
and the design of materials with large SHE can enable ultra-low power memory
technology. Recently, 5d-transition metal oxides have been shown to demonstrate
a large SHE. Here we report large values of SHE in four 5d-transition metal
anti-perovskites which makes these anti-perovskites promising spintronic
materials. We demonstrate that these effects originate in the mixing of dx2-y2
and dxy orbitals caused by spin orbit coupling.",2010.12942v1
2023-10-10,Emerging Spin-Orbit Torques in Low Dimensional Dirac Materials,"We report a theoretical description of novel spin-orbit torque components
emerging in two-dimensional Dirac materials with broken inversion symmetry. In
contrast to usual metallic interfaces where field-like and damping-like torque
components are competing, we find that an intrinsic damping-like torque which
derives from all Fermi-sea electrons can be simultaneously enhanced along with
the field-like component. Additionally, hitherto overlooked torque components
unique to Dirac materials, emerge from the coupling between spin and pseudospin
degrees of freedom. These torques are found to be resilient to disorder and
could enhance the magnetic switching performance of nearby magnets.",2310.06447v1
2019-11-08,Phase-separation of vector solitons in spin-orbit coupled spin-1 condensates,"We study the phase-separation in three-component bright vector solitons in a
quasi-one-dimensional spin-orbit-coupled hyper-fine spin $F=1$ ferromagnetic
Bose-Einstein condensate upon an increase of the strength of spin-orbit (SO)
coupling $p_x \Sigma_z$ above a critical value, where $p_x$ is the linear
momentum and $\Sigma_z$ is the $z$-component of the spin-1 matrix. The bright
vector solitons are demonstrated to be mobile and dynamically stable. The
collision between two such vector solitons is found to be elastic at all
velocities with the conservation of density of each vector soliton. The two
colliding vector solitons repel at small separation and at very small colliding
velocity, they come close and bounce back with the same velocity without ever
encountering each other. This repulsion produced by SO coupling is responsible
for the phase separation in a vector soliton for large strengths of SO
coupling. { The collision dynamics is found to be completely insensitive to the
relative phase of the colliding solitons.} However, in the absence of SO
coupling, at very small velocity, the two colliding vector solitons attract
each other and form a vector soliton molecule and the collision dynamics is
sensitive to the relative phase as in scalar solitons. The present
investigation is carried out through a numerical solution and an analytic
variational approximation of the underlying mean-field Gross-Pitaevskii
equation.",1911.03498v1
2023-04-22,Phase biasing of a Josephson junction using Rashba-Edelstein effect,"Manifestation of orbital coupling of spin degree of freedom in condensed
matter systems has opened up a new dimension for the field of spintronics. The
most appealing aspect of the spin-orbit coupling is the apparent Magnus force
sensed by a spin system which locks the Fermi momentum with electron spin in a
fascinating manner. In the current carrying state, the resulting macroscopic
spin polarization becomes directly accessible in the form of spin current or
spin density. At a Rashba interface, for example, a charge current shifts the
spin-locked Fermi surface, leading to a non-equilibrium spin density at the
interface, commonly known as the Rashba-Edelstein effect. Since the
Rashba-Edelstein effect is an intrinsically interface property, direct
detection of the spin moment is harder to set-up. Here we demonstrate that a
simple planar Josephson Junction geometry, realized by placing two closely
spaced superconducting electrodes on such a Rashba interface, allows a direct
estimation of strength of the non-equilibrium spin moment. Measurements of
Fraunhofer patterns of Nb-(Pt/Cu)-Nb planar Josephson junctions in a
perpendicular magnetic field showed a shift of the center of the Fraunhofer
pattern to a non-zero field value. By performing extensive control
measurements, we argue that the screening currents in the junction effectively
lock the external field with the spin moment of the Rashba-Edelstein effect
induced spin-density, leading to the observed shift in the Fraunhofer patterns.
This simple experiment offers a fresh perspective on direct detection of spin
polarization induced by various spin-orbit effects. Very interestingly, this
device platform also offers the possibility of retaining a controllable phase
at zero field in the junction without using any magnetic material, and thereby
useful as phase batteries for superconducting quantum circuits.",2304.11457v2
2006-07-05,Effect of Hund's rule coupling on SU(4) spin-orbital system,"We investigate the ground-state property of a one-dimensional two-orbital
Hubbard model at quarter filling by numerical techniques such as the
density-matrix renormalization group method and the exact diagonalization. When
the Hund's rule coupling $J$ is zero, the model is SU(4) symmetric. In fact,
both spin and orbital correlations have a peak at $q=\pi/2$, indicating an
SU(4) singlet state with a four-site periodicity. On the other hand, with
increasing $J$, it is found that the peak position of the orbital correlation
changes to $q=\pi$, while that of the spin correlation remains at $q=\pi/2$. We
briefly discuss how the SU(4) symmetry is broken by $J$.",0607104v1
2011-02-15,Magnetic Field Probing of an SU(4) Kondo Resonance in a Single Atom Transistor,"Semiconductor nano-devices have been scaled to the level that transport can
be dominated by a single dopant atom. In the strong coupling case a Kondo
effect is observed when one electron is bound to the atom. Here, we report on
the spin as well as orbital Kondo ground state. We experimentally as well than
theoretically show how we can tune a symmetry transition from a SU(4) ground
state, a many body state that forms a spin as well as orbital singlet by
virtual exchange with the leads, to a pure SU(2) orbital ground state, as a
function of magnetic field. The small size and the s-like orbital symmetry of
the ground state of the dopant, make it a model system in which the magnetic
field only couples to the spin degree of freedom and allows for observation of
this SU(4) to SU(2) transition.",1102.2977v2
2013-05-08,"Nematic State of the Pnictides Stabilized by the Interplay Between Spin, Orbital, and Lattice Degrees of Freedom","The nematic state of the iron-based superconductors is studied in the undoped
limit of the three-orbital ($xz$, $yz$, $xy$) spin-fermion model via the
introduction of lattice degrees of freedom. Monte Carlo simulations show that
in order to stabilize the experimentally observed lattice distortion and
nematic order, and to reproduce photoemission experiments, {\it both} the
spin-lattice and orbital-lattice couplings are needed. The interplay between
their respective coupling strengths regulates the separation between the
structural and N\'eel transition temperatures. Experimental results for the
temperature dependence of the resistivity anisotropy and the angle-resolved
photoemission (ARPES) orbital spectral weight are reproduced by the present
numerical simulations.",1305.1879v1
2015-05-19,Pair breaking in multi-orbital superconductors: an application to oxide interfaces,"We investigate the impact of impurity scattering on superconductivity in an
anisotropic multi-orbital model with spin-orbit coupling which describes the
electron fluid at two-dimensional oxide interfaces. As the pairing mechanism is
under debate, both conventional and unconventional superconducting states are
analyzed. We consider magnetic and nonmagnetic spin-dependent intra- and
interorbital scattering and discuss possible microscopic realizations leading
to these processes. It is found that, for magnetic disorder, the unconventional
superconductor is protected against interband scattering and, thus, more robust
than the conventional condensate. In case of nonmagnetic impurities, the
conventional superconductor is protected as expected from the Anderson theorem
and the critical scattering rate of the unconventional state is enhanced by a
factor of four due to the spin-orbit coupling and anisotropic masses in oxide
interfaces.",1505.04919v1
2017-02-03,Geometric influences of a particle confined to a curved surface embedded in three-dimensional Euclidean space,"In the spirit of the thin-layer quantization approach, we give the formula of
the geometric influences of a particle confined to a curved surface embedded in
three-dimensional Euclidean space. The geometric contributions can result from
the reduced commutation relation between the acted function depending on normal
variable and the normal derivative. According to the formula, we obtain the
geometric potential, geometric momentum, geometric orbital angular momentum,
geometric linear Rashba and cubic Dresselhaus spin-orbit couplings. As an
example, a truncated cone surface is considered. We find that the geometric
orbital angular momentum can provide an azimuthal polarization for spin, and
the sign of the geometric Dresselhaus spin-orbit coupling can be flipped
through the inclination angle of generatrix.",1702.00893v2
2019-06-20,"Crystal structure and the magnetic properties of the 5d transition metal oxide AOsO4 (A = K, Rb, Cs)","We synthesized the 5d1-transition metal oxides AOsO4 (A = K, Rb, Cs) by
solid-state reaction, and performed structure determination and magnetic and
heat capacity measurements. It was found that they crystallize in a scheelite
(A = K and Rb) or a quasi-scheelite structure (A = Cs) comprising of distorted
diamond lattices of septivalent Os (d1) ions tetrahedrally coordinated by four
oxide ions without local inversion symmetry; hence an antisymmetric spin-orbit
coupling is expected in the crystals. The K and Rb compounds have Weiss
temperatures of theta = -66 and -18 K, effective magnetic moments of mu_eff =
1.44 and 1.45 mu_B/Os, and antiferromagnetic transition temperatures of T_N =
36.9 and 21.0 K, respectively. In contrast, the Cs compound has theta = 12 K
and mu_eff = 0.8 mu_B/Os without magnetic transition above 2 K, instead
exhibiting a first-order structural transition at T_s = 152.5 K. The decline of
the Os moment from 1.73 mu_B/Os for the simple d1 spin, particularly for Cs, is
likely to originate from the antiparallel orbital moment, although the
spin-orbit coupling is generally quenched in the low-lying e orbitals.",1906.08519v1
2020-01-24,Anisotropic magnetoresistance in spin-orbit semimetal SrIrO3,"SrIrO3, the three-dimensional member of the Ruddlesden-Popper iridates, is a
paramagnetic semimetal characterised by a the delicate interplay between
spin-orbit coupling and Coulomb repulsion. In this work, we study the
anisotropic magnetoresistance (AMR) of SrIrO3 thin films, which is closely
linked to spin-orbit coupling and probes correlations between electronic
transport, magnetic order and orbital states. We show that the low-temperature
negative magnetoresistance is anisotropic with respect to the magnetic field
orientation, and its angular dependence reveals the appearance of a fourfold
symmetric component above a critical magnetic field. We show that this AMR
component is of magnetocrystalline origin, and attribute the observed
transition to a field-induced magnetic state in SrIrO3.",2001.08939v1
2018-06-19,Rolling Skyrmions and the Nuclear Spin-Orbit Force,"We compute the nuclear spin-orbit coupling from the Skyrme model. Previous
attempts to do this were based on the product ansatz, and as such were limited
to a system of two well-separated nuclei. Our calculation utilises a new
method, and is applicable to the phenomenologically important situation of a
single nucleon orbiting a large nucleus. We find that, to second order in
perturbation theory, the coefficient of the spin-orbit coupling induced by pion
field interactions has the wrong sign, but as the strength of the pion-nucleon
interactions increases the correct sign is recovered non-perturbatively.",1806.07330v2
2021-03-09,Tree tensor-network real-time multiorbital impurity solver: Spin-orbit coupling and correlation functions in Sr$_2$RuO$_4$,"We present a tree tensor-network impurity solver suited for general
multiorbital systems. The network is constructed to efficiently capture the
entanglement structure and symmetry of an impurity problem. The solver works
directly on the real-time/frequency axis and generates spectral functions with
energy-independent resolution of the order of one percent of the correlated
bandwidth. Combined with an optimized representation of the impurity bath, it
efficiently solves self-consistent dynamical mean-field equations and
calculates various dynamical correlation functions for systems with
off-diagonal Green's functions. For the archetypal correlated Hund's metal
Sr$_2$RuO$_4$, we show that both the low-energy quasiparticle spectra related
to the van Hove singularity and the high-energy atomic multiplet excitations
can be faithfully resolved. In particular, we show that while the spin-orbit
coupling has only minor effects on the orbital-diagonal one-particle spectral
functions, it has a more profound impact on the low-energy spin and orbital
response functions.",2103.05545v2
2021-08-13,Twist-angle dependent proximity induced spin-orbit coupling in graphene/transition-metal dichalcogenide heterostructures,"We investigate the proximity-induced spin-orbit coupling in heterostructures
of twisted graphene and monolayers of transition-metal dichalcogenides (TMDCs)
MoS$_2$, WS$_2$, MoSe$_2$, and WSe$_2$ from first principles. We identify
strain, which is necessary to define commensurate supercells, as the key factor
affecting the band offsets and thus magnitudes of the proximity couplings. We
establish that for biaxially strained graphene the band offsets between the
Dirac point and conduction (valence) TMDC bands vary linearly with strain,
regardless of the twist angle. This relation allows to identify the apparent
zero-strain band offsets and find a compensating transverse electric field
correcting for the strain. The resulting corrected band structure is then
fitted around the Dirac point to an established spin-orbit Hamiltonian. This
procedure yields the dominant, valley-Zeeman and Rashba spin-orbit couplings.
The magnitudes of these couplings do not vary much with the twist angle,
although the valley-Zeeman coupling vanishes for 30$^{\circ}$ and Mo-based
heterostructures exhibit a maximum of the coupling at around 20$^{\circ}$. The
maximum for W-based stacks is at 0$^{\circ}$. The Rashba coupling is in general
weaker than the valley-Zeeman coupling, except at angles close to 30$^{\circ}$.
We also identify the Rashba phase angle which measures the deviation of the
in-plane spin texture from tangential, and find that this angle is very
sensitive to the applied transverse electric field. We further discuss the
reliability of the supercell approach with respect to atomic relaxation
(rippling of graphene), relative lateral shifts of the atomic layers, and
transverse electric field.",2108.06126v3
2017-03-03,Spin orbit coupling and Lorentz force enhanced efficiency of TiO2 based dye sensitized solar cells,"We report on the effect of the strong spin orbit coupling and the Lorentz
force on the efficiency of TiO2 based dye sensitized solar cells. Upon
inclusion of Ho2O3, due to the strong spin orbit coupling of the rare earth
Ho3+ ion, we do see 13 percent enhancement in the efficiency. We attribute such
an enhancement in power conversion efficiency to the increased lifetime of the
photo-excited excitons. Essentially, a Ho3+ ion accelerates the phenomenon of
the spin rephasing or the intersystem crossing of the excitons in a
photosensitizer. Increase in the absorbance and decrease in the
photoluminescence intensity suggests a decrease in the recombination rate,
hinting an enhanced charge transport and is in accordance with our
electrochemical impedance spectra and the J V characteristics. From the above
we strongly believe that enhanced efficiency of the device is due to increased
intersystem crossing which would accelerate the exciton dissociation. On top of
spin orbit interaction, a configuration where the electric and magnetic fields
are perpendicular to each other helped in enhancing the efficiency by 16
percent, suggesting that the Lorentz force also plays a dominant role in
controlling the charge transport of the photo-generated charge carriers. We
strongly believe that this simple and novel strategy of improving the
efficiency may pave the way for realizing higher efficiency dye sensitized
solar cells.",1703.01099v1
2020-09-08,Spin-Orbit Torques in Transition Metal Dichalcogenide/Ferromagnet Heterostructures,"In recent years, there has been a growing interest in spin-orbit torques
(SOTs) for manipulating the magnetization in nonvolatile magnetic memory
devices. SOTs rely on the spin-orbit coupling of a nonmagnetic material coupled
to a ferromagnetic layer to convert an applied charge current into a torque on
the magnetization of the ferromagnet (FM). Transition metal dichalcogenides
(TMDs) are promising candidates for generating these torques with both high
charge-to-spin conversion ratios, and symmetries and directions which are
efficient for magnetization manipulation. Moreover, TMDs offer a wide range of
attractive properties, such as large spin-orbit coupling, high crystalline
quality and diverse crystalline symmetries. Although numerous studies were
published on SOTs using TMD/FM heterostructures, we lack clear understanding of
the observed SOT symmetries, directions, and strengths. In order to shine some
light on the differences and similarities among the works in literature, in
this mini-review we compare the results for various TMD/FM devices,
highlighting the experimental techniques used to fabricate the devices and to
quantify the SOTs, discussing their potential effect on the interface quality
and resulting SOTs. This enables us to both identify the impact of particular
fabrication steps on the observed SOT symmetries and directions, and give
suggestions for their underlying microscopic mechanisms. Furthermore, we
highlight recent progress of the theoretical work on SOTs using TMD
heterostructures and propose future research directions.",2009.03710v2
2020-09-18,Shadowed triplet pairings in Hund's metals with spin-orbit coupling,"Hund's coupling in multiorbital systems allows for the possibility of
even-parity orbital-antisymmetric spin-triplet pairing, which can be stabilized
by spin-orbit coupling (SOC). While this pairing expressed in the orbital basis
is uniform and spin-triplet, it appears in the band basis as a
pseudospin-singlet, with the momentum dependence determined by the SOC and the
underlying triplet character remaining in the form of interband pairing active
away from the Fermi energy. Here, we examine the role of momentum-dependent SOC
in generating nontrivial pairing symmetries, as well as the hidden triplet
nature associated with this interorbital pairing, which we dub a ""shadowed
triplet"". Applying this concept to Sr$_{2}$RuO$_{4}$, we first derive several
forms of SOC with $d$-wave form factors from a microscopic model, and
subsequently we show that for a range of SOC parameters, a pairing state with
$s+id_{xy}$ symmetry can be stabilized. Such a pairing state is distinct from
pure spin-singlet and -triplet pairings due to its unique character of
pseudospin-energy locking. We discuss experimental probes to differentiate the
shadowed triplet pairing from conventional pseudospin-triplet and -singlet
pairings.",2009.08597v2
2022-04-29,Anomalous Josephson Coupling and High-Harmonics in Non-Centrosymmetric Superconductors with $S$-wave Spin-Triplet Pairing,"We study the Josephson effects arising in junctions made of
non-centrosymmetric superconductors with spin-triplet pairing having $s$-wave
orbital-singlet symmetry. We demonstrate that the orbital dependent character
of the spin-triplet order parameter determines its non-trivial texture in the
momentum space due to the inversion symmetry breaking and spin-orbit
interactions. The emergence of this pattern is responsible for the occurrence
of an anomalous Josephson coupling and a dominance of high-harmonics in the
current phase relation. Remarkably, due to the spin-orbital couplings,
variations in the electronic structure across the heterostructure can generally
turn the ground state of the junction from 0- to a generic value of the
Josephson phase, thus realizing the so-called $\varphi$-junction. Hallmarks of
the resulting Josephson behavior, apart from non-standard current-phase
relation, are provided by an unconventional temperature and magnetic field
dependence of the critical current. These findings indicate the path for the
design of superconducting orbitronics devices and account for several observed
anomalies of the supercurrent in oxide interface superconductors.",2204.14083v2
2021-01-23,Experimental demonstration of cylindrical vector spatiotemporal optical vortex,"We experimentally generate cylindrically polarized wavepackets with
transverse orbital angular momentum, demonstrating the coexistence of
spatiotemporal optical vortex with spatial polarization singularity. The
results in this paper extend the study of spatiotemporal wavepackets to a
broader scope, paving the way for its applications in various areas such as
light-matter interaction, optical tweezers, spatiotemporal spin-orbit angular
momentum coupling, etc.",2101.09452v1
2004-05-13,Modulating Unpolarized Current in Quantum Spintronics: Visibility of Spin-Interference Effects in Multichannel Aharonov-Casher Mesoscopic Rings,"The conventional unpolarized current injected into a {\em quantum-coherent}
semiconductor ring attached to two external leads can be modulated from perfect
conductor to perfect insulator limit via Rashba spin-orbit (SO) coupling. This
requires that ballistic propagation of electrons, whose spin precession is
induced by the Aharonov-Casher phase, takes place through a single conducting
channel ensuring that electronic quantum state remains a pure separable one in
the course of transport. We study the fate of such spin interference effects as
more than one orbital conducting channel becomes available for quantum
transport. Although the conductance of multichannel rings, in general, does not
go all the way to zero at any value of the SO coupling, some degree of current
modulation survives. We analyze possible scenarios that can lead to reduced
visibility of spin interference effects that are responsible for the zero
conductance at particular values of the Rashba interaction: (i) the transmitted
spin states remain fully coherent, but conditions for destructive interference
are different in different channels; (ii) the transmitted spins end up in
partially coherent quantum state arising from entanglement to the environment
composed of orbital degrees of freedom of the same particle to which the spin
is attached.",0405300v1
2012-12-03,Spin polarization via decoherence in spin-orbit active media coupled to an electron reservoir,"We study the spin polarization of mixed and entangled electron states in a
four probe/beam splitter geometry with local Rashba and Dresselhaus
interactions. A pair of maximally entangled electrons collides with the beam
splitter and enters into two perpendicular branches of length L, composed of
spin-orbit active materials (gate confined 2D electron gas). One of the
branches is connected to an electron reservoir that acts as a source of
decoherence by either behaving as a voltage probe or as a controlled source or
sink of current at fixed voltage. Such decoherence source is used to modify the
entropy of an unpolarized incoming state in order to generate electron
polarization at one or both output branches. The degree of entanglement of the
global state and the spin polarization is computed for the outgoing electrons
as a function of the coupling to the electron reservoir. Experimentally
available spin-orbit strength at the beam splitter arms, for arm lengths of a
few micrometers, is able to modulate spin polarization up to 80% in particular
spin axes proportional to the decoherence current. The Dresselhaus and Rashba
coefficients play a symmetric role in modulating the polarization.
Significantly less polarization is achieved for incoming mixed states due to
the local operation of the reservoir.",1212.0497v1
2013-10-29,"Spin-orbit coupling, quantum dots, and qubits in monolayer transition metal dichalcogenides","We derive an effective Hamiltonian which describes the dynamics of electrons
in the conduction band of transition metal dichalcogenides (TMDC) in the
presence of perpendicular electric and magnetic fields. We discuss in detail
both the intrinsic and the Bychkov-Rashba spin-orbit coupling (SOC) induced by
an external electric field.
  We point out interesting differences in the spin-split conduction band
between different TMDC compounds. An important consequence of the strong
intrinsic SOC is an effective out-of-plane $g$-factor for the electrons which
differs from the free-electron g-factor $g\simeq 2$. We identify a new term in
the Hamiltonian of the Bychkov-Rashba SOC which does not exist in III-V
semiconductors. Using first-principles calculations, we give estimates of the
various parameters appearing in the theory.
  Finally, we consider quantum dots (QDs) formed in TMDC materials and derive
an effective Hamiltonian which allows us to calculate the magnetic field
dependence of the bound states in the QDs. We find that all states are both
valley and spin split, which suggests that these QDs could be used as
valley-spin filters.
  We explore the possibility of using spin and valley states in TMDCs as
quantum bits, and conclude that, due to the relatively strong intrinsic
spin-orbit splitting in the conduction band, the most realistic option appears
to be a combined spin-valley (Kramers) qubit at low magnetic fields.",1310.7720v3
2021-04-26,Emergence of spin-orbit coupled ferromagnetic surface state derived from Zak phase in a nonmagnetic insulator FeSi,"A chiral compound FeSi is a nonmagnetic narrow-gap insulator, exhibiting
peculiar charge and spin dynamics beyond a simple band-structure picture. Those
unusual features have been attracting renewed attention from topological
aspects. Although a signature of surface conduction was indicated according to
size-dependent resistivity in bulk crystals, its existence and topological
properties remain elusive. Here we demonstrate an inherent surface
ferromagnetic-metal state of FeSi thin films and its strong spin-orbit-coupling
(SOC) properties through multiple characterizations of the two-dimensional (2D)
conductance, magnetization and spintronic functionality. Terminated
covalent-bonding orbitals constitute the polar surface state with
momentum-dependent spin textures due to Rashba-type spin splitting, as
corroborated by unidirectional magnetoresistance measurements and
first-principles calculations. As a consequence of the spin-momentum locking,
non-equilibrium spin accumulation causes magnetization switching. These surface
properties are closely related to the Zak phase of the bulk band topology. Our
findings propose another route to explore noble-metal-free materials for
SOC-based spin manipulation.",2104.12438v1
2022-04-21,Spin-momentum locking from topological quantum chemistry: applications to multifold fermions,"In spin-orbit coupled crystals, symmetries can protect multifold degeneracies
with large Chern numbers and Brillouin zone spanning topological surface
states. In this work, we explore the extent to which the nontrivial topology of
chiral multifold fermions impacts the spin texture of bulk states. To do so, we
formulate a definition of spin-momentum locking in terms of reduced density
matrices. Using tools from the theory of topological quantum chemistry, we show
how the reduced density matrix can be determined from the knowledge of the
basis orbitals and band representation forming the multifold fermion. We show
how on-site spin orbit coupling, crystal field splitting, and Wyckoff position
multiplicity compete to determine the spin texture of states near chiral
fermions. We compute the spin texture of multifold fermions in several
representative examples from space groups $P432$ (207) and $P2_13$ (198). We
show that the winding number of the spin around the Fermi surface can take many
different integer values, from zero all the way to $\pm 7$. Finally, we
conclude by showing how to apply our theory to real materials using the example
of PtGa in space group $P2_13$.",2204.10113v1
2010-06-21,Next-to-leading order gravitational spin-orbit coupling in an effective field theory approach,"We use an effective field theory (EFT) approach to calculate the next to
leading order (NLO) gravitational spin-orbit interaction between two spinning
compact objects. The NLO spin-orbit interaction provides the most
computationally complex sector of the NLO spin effects, previously derived
within the EFT approach. In particular, it requires the inclusion of
non-stationary cubic self-gravitational interaction, as well as the
implementation of a spin supplementary condition (SSC) at higher orders. The
EFT calculation is carried out in terms of the non-relativistic gravitational
field parametrization, making the calculation more efficient with no need to
rely on automated computations, and illustrating the coupling hierarchy of the
different gravitational field components to the spin and mass sources. Finally,
we show explicitly how to relate the EFT derived spin results to the canonical
results obtained with the ADM Hamiltonian formalism. This is done using
non-canonical transformations, required due to the implementation of covariant
SSC, as well as canonical transformations at the level of the Hamiltonian, with
no need to resort to the equations of motion or the Dirac brackets.",1006.4139v3
2011-01-20,Theory of Single Electron Spin Relaxation in Si/SiGe Lateral Coupled Quantum Dots,"We investigate the spin relaxation induced by acoustic phonons in the
presence of spin-orbit interactions in single electron Si/SiGe lateral coupled
quantum dots. The relaxation rates are computed numerically in single and
double quantum dots, in in-plane and perpendicular magnetic fields. The
deformation potential of acoustic phonons is taken into account for both
transverse and longitudinal polarizations and their contributions to the total
relaxation rate are discussed with respect to the dilatation and shear
potential constants. We find that in single dots the spin relaxation rate
scales approximately with the seventh power of the magnetic field, in line with
a recent experiment. In double dots the relaxation rate is much more sensitive
to the dot spectrum structure, as it is often dominated by a spin hot spot. The
anisotropy of the spin-orbit interactions gives rise to easy passages, special
directions of the magnetic field for which the relaxation is strongly
suppressed. Quantitatively, the spin relaxation rates in Si are typically 2
orders of magnitude smaller than in GaAs due to the absence of the
piezoelectric phonon potential and generally weaker spin-orbit interactions.",1101.3858v3
2011-03-30,Spin and charge transport in U-shaped one-dimensional channels with spin-orbit couplings,"A general form of the Hamiltonian for electrons confined to a curved
one-dimensional (1D) channel with spin-orbit coupling (SOC) linear in momentum
is rederived and is applied to a U-shaped channel. Discretizing the derived
continuous 1D Hamiltonian to a tight-binding version, the Landauer-Keldysh
formalism (LKF) for nonequilibrium transport can be applied. Spin transport
through the U-channel based on the LKF is compared with previous quantum
mechanical approaches. The role of a curvature-induced geometric potential
which was previously neglected in the literature of the ring issue is also
revisited. Transport regimes between nonadiabatic, corresponding to weak SOC or
sharp turn, and adiabatic, corresponding to strong SOC or smooth turn, is
discussed. Based on the LKF, interesting charge and spin transport properties
are further revealed. For the charge transport, the interplay between the
Rashba and the linear Dresselhaus (001) SOCs leads to an additional modulation
to the local charge density in the half-ring part of the U-channel, which is
shown to originate from the angle-dependent spin-orbit potential. For the spin
transport, theoretically predicted eigenstates of the Rashba rings, Dresselhaus
rings, and the persistent spin-helix state are numerically tested by the
present quantum transport calculation.",1103.5926v3
2020-12-23,Nagaoka spin-valley ordering in silicene quantum dots,"We study a cluster of quantum dots defined within silicene that host confined
electron states with spin and valley degrees of freedom. Atomistic
tight-binding and continuum Dirac approximation are applied for few-electron
system in quest for spontaneous valley polarization driven by inter-dot
tunneling and electron-electron interaction, i.e. a valley counterpart of
itinerary Nagaoka ferromagnetic ordering recently identified in GaAs square
cluster of quantum dots with three excess electrons [P. Dehollain, {\it et
al.}, Nature {\bf 579}, 528 (2020)]. We find that for Hamiltonian without
intrinsic-spin orbit coupling -- similar to the one of graphene with staggered
potential -- the valley polarization in the ground-state can be observed in a
range of inter-dot spacing provided that the spin of the system is frozen by
external magnetic field. The inter-valley scattering effects are negligible for
cluster geometry that supports the valley polarized ground-state. In presence
of a strong intrinsic spin-orbit coupling that is characteristic to graphene no
external magnetic field is necessary for observation of ground-state that is
polarized in both spin and valley. The effective magnetic field due to the
spin-orbit interaction produces a perfect anticorrelation of the spin and
valley isospin components in the degenerate ground-state.",2012.12524v2
2007-07-17,Quarkonium and hydrogen spectra with spin dependent relativistic wave equation,"A non-linear non-perturbative relativistic atomic theory introduces spin in
the dynamics of particle motion. The resulting energy levels of Hydrogen atom
are exactly same as the Dirac theory. The theory accounts for the energy due to
spin-orbit interaction and for the additional potential energy due to spin and
spin-orbit coupling. Spin angular momentum operator is integrated into the
equation of motion. This requires modification to classical Laplacian operator.
Consequently the Dirac matrices and the k operator of Dirac's theory are
dispensed with. The theory points out that the curvature of the orbit draws on
certain amount of kinetic and potential energies affecting the momentum of
electron and the spin-orbit interaction energy constitutes a part of this
energy. The theory is developed for spin 1/2 bound state single electron in
Coulomb potential and then further extended to quarkonium physics by
introducing the linear confining potential. The unique feature of this
quarkonium model is that the radial distance can be exactly determined and does
not have a statistical interpretation. The established radial distance is then
used to determine the wave function. The observed energy levels are used as the
input parameters and the radial distance and the string tension are predicted.
This ensures 100% conformance to all observed energy levels for the heavy
quarkonium.",0707.2431v7
2009-10-29,Dual black holes in merger remnants. II: spin evolution and gravitational recoil,"Using high resolution hydrodynamical simulations, we explore the spin
evolution of massive dual black holes orbiting inside a circumnuclear disc,
relic of a gas-rich galaxy merger. The black holes spiral inwards from
initially eccentric co or counter-rotating coplanar orbits relative to the
disc's rotation, and accrete gas that is carrying a net angular momentum. As
the black hole mass grows, its spin changes in strength and direction due to
its gravito-magnetic coupling with the small-scale accretion disc. We find that
the black hole spins loose memory of their initial orientation, as accretion
torques suffice to align the spins with the angular momentum of their orbit on
a short timescale (<1-2 Myr). A residual off-set in the spin direction relative
to the orbital angular momentum remains, at the level of <10 degrees for the
case of a cold disc, and <30 degrees for a warmer disc. Alignment in a cooler
disc is more effective due to the higher coherence of the accretion flow near
each black hole that reflects the large-scale coherence of the disc's rotation.
If the massive black holes coalesce preserving the spin directions set after
formation of a Keplerian binary, the relic black hole resulting from their
coalescence receives a relatively small gravitational recoil. The distribution
of recoil velocities inferred from a simulated sample of massive black hole
binaries has median <70 km/s much smaller than the median resulting from an
isotropic distribution of spins.",0910.5729v2
2013-01-14,Anomalous enhancement of Wilson ratio in a quantum spin liquid with strong spin-orbital entanglement: the case of Na4Ir3O8,"We present a theory for the metal-insulator transition (MIT) in the
quantum-spin-liquid candidate material Na4Ir3O8. We consider an extended
Hubbard model on the hyperkagome lattice, which incorporates atomic spin-orbit
coupling (SOC) and multi-orbital interactions of iridium 5d electrons. This
model is analyzed using the slave-rotor mean-field theory and thermodynamic
properties across the MIT are studied. The ground state in the insulating side
is a U(1) quantum spin liquid with spinon Fermi surfaces that consist of
multiple particle-like and hole-like pockets. It is shown that the Wilson ratio
in the quantum spin liquid phase is highly enhanced compared to the metallic
state. This originates from the fact that the magnetic susceptibility in the
quantum spin liquid phase acquires multiple enhancements due to the strong SOC,
reduced band-width and on-site spin-orbital exchange, while the heat capacity
does not change much across MIT. This explains the large Wilson ratio of the
insulating phase observed in the previous experiment on Na4Ir3O8. Possible
connections to other existing and future experiments, in particular on the
metallic phase, are discussed.",1301.3107v2
2019-06-18,Long-ranged triplet supercurrent in a single in-plane ferromagnet with spin-orbit coupled contacts to superconductors,"By converting conventional spin-singlet Cooper pairs to polarized
spin-triplet pairs, it is possible to sustain long-ranged spin-polarized
supercurrents flowing through strongly polarized ferromagnets. Obtaining such a
conversion via spin-orbit interactions, rather than magnetic inhomogeneities,
has recently been explored in the literature. A challenging aspect with regard
to experimental detection has been that in order for Rashba spin-orbit
interactions, present e.g. at interfaces due to inversion symmetry breaking, to
generate such long-ranged supercurrents, an out-of-plane component of the
magnetization is required. This limits the choice of materials and can induce
vortices in the superconducting region complicating the interpretation of
measurements. Therefore, it would be desirable to identify a way in which
Rashba spin-orbit interactions can induce long-ranged supercurrents for purely
in-plane rotations of the magnetization. Here, we show that this is possible in
a lateral Josephson junction where two superconducting electrodes are placed in
contact with a ferromagnetic film via two thin, heavy normal metals. The
magnitude of the supercurrent in such a setup becomes tunable by the in-plane
magnetization angle when using only a single magnetic layer. These results
could provide a new and simpler way to generate controllable spin-polarized
supercurrents than previous experiments which utilized complicated magnetically
textured Josephson junctions.",1906.07725v2
2019-11-25,"Optimal operation points for ultrafast, highly coherent Ge hole spin-orbit qubits","Strong spin-orbit interactions make hole quantum dots central to the quest
for electrical spin qubit manipulation enabling fast, low-power, scalable
quantum computation. Yet it is important to establish to what extent spin-orbit
coupling exposes qubits to electrical noise, facilitating decoherence. Here,
taking Ge as an example, we show that group IV gate-defined hole spin qubits
generically exhibit optimal operation points, defined by the top gate electric
field, at which they are both fast and long-lived: the dephasing rate vanishes
to first order in electric field noise along all directions in space, the
electron dipole spin resonance strength is maximised, while relaxation is
drastically reduced at small magnetic fields. The existence of optimal
operation points is traced to group IV crystal symmetry and properties of the
Rashba spin-orbit interaction unique to spin-3/2 systems. Our results overturn
the conventional wisdom that fast operation implies reduced lifetimes, and
suggest group IV hole spin qubits as ideal platforms for ultra-fast, highly
coherent scalable quantum computing.",1911.11143v2
2020-03-16,Spin-orbit torques originating from bulk and interface in Pt-based structures,"We investigated spin-orbit torques in prototypical Pt-based spintronic
devices. We found that, in Pt/Ni and Pt/Fe bilayers, the damping-like torque
efficiency depends on the thickness of the Pt layer. We also found that the
damping-like torque efficiency is almost identical in the Pt/Ni and Pt/Fe
bilayers despite the stronger spin memory loss at the Pt/Fe interface. These
results suggest that although the dominant source of the damping-like torque is
the bulk spin Hall effect in the Pt layer, a sizable damping-like torque is
generated by the interface in the Pt/Fe bilayer due to the stronger interfacial
spin-orbit coupling. In contrast to the damping-like torque, whose magnitude
and sign are almost identical in the Pt/Ni and Pt/Fe bilayers, the field-like
torque strongly depends on the choice of the ferromagnetic layer. The sign of
the field-like torque originating from the bulk spin Hall effect in the Pt
layer is opposite between the Pt/Ni and Pt/Fe bilayers, which can be attributed
to the opposite sign of the imaginary part of the spin-mixing conductance.
These results demonstrate that the spin-orbit torques are quite sensitive to
the electronic structure of the FM layer.",2003.07271v2
2022-10-21,Calculation of molecular g-tensors by sampling spin orientations of generalised Hartree-Fock states,"The variational inclusion of spin-orbit coupling in self-consistent field
(SCF) calculations requires a generalised two-component framework, which
permits the single-determinant wave function to completely break spin symmetry.
The individual components of the molecular g-tensor are commonly obtained from
separate SCF solutions that align the magnetic moment along one of the three
principal tensor axes. However, this strategy raises the question if energy
differences between solutions are relevant, or how convergence is achieved if
the principal axis system is not determined by molecular symmetry. The present
work resolves these issues by a simple two-step procedure akin to the generator
coordinate method (GCM). First, a few generalised Hartree Fock (GHF) solutions
are converged, applying, where needed, a constraint to the orientation of the
magnetic-moment or spin vector. Then, superpositions of GHF determinants are
formed through non-orthogonal configuration interaction. This procedure yields
a Kramers doublet for the calculation of the complete g-tensor. Alternatively,
for systems with weak spin-orbit effects, diagonalisation in a basis spanned by
spin rotations of a single GHF determinant affords qualitatively correct
g-tensors by eliminating errors related to spin contamination. For small
first-row molecules, these approaches are evaluated against experimental data
and full configuration interaction results. It is further demonstrated for two
systems (a fictitious tetrahedral CH4+ species, and a CuF4(2-) complex) that a
GCM strategy, in contrast to alternative mean-field methods, can correctly
describe the spin-orbit splitting of orbitally-degenerate ground states, which
causes large g-shifts and may lead to negative g-values.",2210.12009v1
2007-07-31,Photon-assisted spin transport in a two-dimensional electron gas,"We study spin-dependent transport in a two-dimensional electron gas subject
to an external step-like potential $V(x)$ and irradiated by an electromagnetic
field (EF). In the absence of EF the electronic spectrum splits into spin
sub-bands originating from the ""Rashba"" spin-orbit coupling. We show that the
resonant interaction of propagating electrons with the component EF parallel to
the barrier induces a \textit{% non-equilibrium dynamic gap} $(2\Delta_{R})$
between the spin sub-bands. Existence of this gap results in coherent spin-flip
processes that lead to a spin-polarized current and a large magnetoresistance,
i.e the spin valve effect. These effects may be used for controlling spin
transport in semiconducting nanostructures, e.g. spin transistors,
spin-blockade devices etc., by variation of the intensity S and frequency
$\omega $ of the external radiation.",0707.4571v2
2008-12-18,Mesoscopic Spin-Hall Effect in 2D electron systems with smooth boundaries,"Spin-Hall effect in ballistic 2D electron gas with Rashba-type spin-orbit
coupling and smooth edge confinement is studied. We predict that the interplay
of semiclassical electron motion and quantum dynamics of spins leads to several
distinct features in spin density along the edge that originate from
accumulation of turning points from many classical trajectories. Strong peak is
found near a point of the vanishing of electron Fermi velocity in the lower
spin-split subband. It is followed by a strip of negative spin density that
extends until the crossing of the local Fermi energy with the degeneracy point
where the two spin subbands intersect. Beyond this crossing there is a wide
region of a smooth positive spin density. The total amount of spin accumulated
in each of these features exceeds greatly the net spin across the entire edge.
The features become more pronounced for shallower boundary potentials,
controlled by gating in typical experimental setups.",0812.3609v2
2012-02-04,Non-equilibrium spatial distribution of Rashba spin torque in ferromagnetic metal layer,"We study the spatial distribution of spin torque induced by a strong Rashba
spin-orbit coupling (RSOC) in a ferromagnetic (FM) metal layer, using the
Keldysh non-equilibrium Green's function method. In the presence of the s-d
interaction between the non-equilibrium conduction electrons and the local
magnetic moments, the RSOC effect induces a torque on the moments, which we
term as the Rashba spin torque.
  A correlation between the Rashba spin torque and the spatial spin current is
presented in this work, clearly mapping the spatial distribution of Rashba Spin
torque in a nano-sized ferromagnetic device. When local magnetism is turned on,
the out-of-plane (Sz) Spin Hall effect (SHE) is disrupted, but rather
unexpectedly an in-plane (Sy) SHE is detected. We also study the effect of
Rashba strength (\alpha_R) and splitting exchange (\Delta) on the
non-equilibrium Rashba spin torque averaged over the device. Rashba spin torque
allows an efficient transfer of spin momentum such that a typical switching
field of 20 mT can be attained with a low current density of less than 10^6
A/cm^2.",1202.0890v2
2012-07-21,Spin-torque efficiency enhanced by Rashba spin splitting in three dimensions,"We examine a spin torque induced by the Rashba spin-orbit coupling in three
dimensions within the Boltzmann transport theory. We analytically calculate the
spin torque and show how its behavior is related with the spin topology in the
Fermi surfaces by studying the Fermi-energy dependence of the spin torque.
Moreover we discuss the spin-torque efficiency which is the spin torque divided
by the applied electric current in association with the current-induced
magnetization reversal. It is found that high spin-torque efficiency is
achieved when the Fermi energy lies on only the lower band and there exists an
optimal value for the Rashba parameter, where the spin-torque efficiency
becomes maximum.",1207.5094v1
2012-11-13,Decay of Persistent Spin Helix due to the Spin Relaxation at Boundaries,"We study electron spin relaxation in one-dimensional structures of finite
length in the presence of Bychkov-Rashba spin-orbit coupling and boundary spin
relaxation. Using a spin kinetic equation approach, we formulate boundary
conditions for the case of a partial spin polarization loss at the boundaries.
These boundary conditions are used to derive corresponding boundary conditions
for spin drift-diffusion equation. The later is solved analytically for the
case of relaxation of a homogeneous spin polarization in 1D finite length
structures. It is found that the spin relaxation consists of three stages (in
some cases, two) -- an initial D'yakonov-Perel' relaxation is followed by spin
helix formation and its subsequent decay. Analytical expressions for the decay
time are found. We support our analytical results by results of Monte Carlo
simulations.",1211.3139v1
2014-09-30,Origin of inverse Rashba-Edelstein effect at Cu/Bi interface using lateral spin valves,"The spin transport and spin-to-charge current conversion properties of
bismuth are investigated using permalloy/copper/bismuth (Py/Cu/Bi)lateral spin
valve structures. The spin current is strongly absorbed at the surface of Bi,
leading to ultra-short spin diffusion lengths. A spin-to-charge current
conversion is measured, which is attributed to the inverse Rashba-Edelstein
effect at the Cu/Bi interface. The spin-current-induced charge current is found
to change direction with increasing temperature. A theoretical analysis relates
this behavior to the complex spin structure and dispersion of the surface
states at the Fermi energy. The understanding of this phenomenon opens novel
possibilities to exploit spin-orbit coupling to create, manipulate, and detect
spin currents in 2D systems.",1409.8540v2
2016-01-15,Optical Spintronics in Organic-Inorganic Perovskite Photovoltaics,"Organic-inorganic halide CH$_3$NH$_3$PbI$_3$ solar cells have attracted
enormous attention in recent years due to their remarkable power conversion
efficiency. When inversion symmetry is broken, these materials should exhibit
interesting spin-dependent properties as well, owing to their strong spin-orbit
coupling. In this work, we consider the spin-dependent optical response of
CH$_3$NH$_3$PbI$_3$. We first use density functional theory to compute the
ballistic spin current generated by absorption of unpolarized light. We then
consider diffusive transport of photogenerated charge and spin for a thin
CH$_3$NH$_3$PbI$_3$ layer with a passivated surface and an Ohmic, non-selective
contact. The spin density and spin current are evaluated by solving the
drift-diffusion equations for a simplified 3-dimensional Rashba model of the
electronic structure of the valence and conduction bands. We provide analytic
expressions for the photon flux required to induce measurable spin densities,
and propose that these spin densities can provide useful information about the
role of grain boundaries in the photovoltaic behavior of these materials. We
also discuss the prospects for measuring the optically generated spin current
with the inverse spin Hall effect.",1601.04003v2
2016-03-15,Designing Electron Spin Textures and Spin Interferometers by Shape Deformations,"We demonstrate that the spin orientation of an electron propagating in a
one-dimensional nanostructure with Rashba spin-orbit (SO) coupling can be
manipulated on demand by changing the geometry of the nanosystem. Shape
deformations that result in a non-uniform curvature give rise to complex
three-dimensional spin textures in space. We employ the paradigmatic example of
an elliptically deformed quantum ring to unveil the way to get an
all-geometrical and all-electrical control of the spin orientation. The
resulting spin textures exhibit a tunable topological character with windings
around the radial and the out-of-plane directions. We show that these
topologically non trivial spin patterns affect the spin interference effect in
the deformed ring, thereby resulting in different geometry-driven ballistic
electronic transport behaviors. Our results establish a deep connection between
electronic spin textures, spin transport and the nanoscale shape of the system.",1603.04655v2
2016-06-30,Impurity-driven intervalley spin-flip scattering-induced 2D spin relaxation in silicon,"Through the theoretical study of electron spin lifetime in the 2DEG of doped
Si, we highlight a dominant spin relaxation mechanism induced by the impurity
central-cell potential near an interface via intervalley electron scattering.
At low temperatures and with modest doping, this Yafet spin flip mechanism can
become much more important than the Dyakonov-Perel spin relaxation indcued by
the structural Rashba spin-orbit coupling field. As the leading-order
impurity-induced spin flip happens only between two non-opposite valleys in Si,
two-dimensional electron gas (2DEG) systems in Si MOSFETs or SiGe
heterostructures are a natural platform to test and utilize this spin
relaxation mechanism due to the valley splitting near the interface and its
tunability by electrical gating or applied stress. Our proposed new spin
relaxation mechanism may explain a part of the spin relaxation contribution to
Si-based 2DEG systems.",1606.09578v2
2019-05-19,Persistent spin helix in Rashba-Dresselhaus ferroelectric CsBiNb2O7,"Ferroelectric Rashba semiconductors (FERSC) are a novel class of
multifunctional materials showing a giant Rashba spin splitting which can be
reversed by switching the electric polarization. Although they are excellent
candidates as channels in spin field effect transistors, the experimental
research has been limited so far to semiconducting GeTe, in which ferroelectric
switching is often prevented by heavy doping and/or large leakage currents.
Here, we report that CsBiNb2O7, a layered perovskite of Dion-Jacobson type, is
a robust ferroelectric with sufficiently strong spin-orbit coupling and spin
texture reversible by electric field. Moreover, we reveal that its topmost
valence band's spin texture is quasi-independent from the momentum, as a result
of the low symmetry of its ferroelectric phase. The peculiar spin polarization
pattern in the momentum space may yield the so-called ""persistent spin helix"",
a specific spin-wave mode which protects the spin from decoherence in diffusive
transport regime, potentially ensuring a very long spin lifetime in this
material.",1905.07744v2
2017-01-24,Spin mediated enhanced negative magnetoresistance in Ni80Fe20 and p-silicon bilayer,"In this work, we present an experimental study of spin mediated enhanced
negative magnetoresistance in Ni80Fe20 (50 nm)/p-Si (350 nm) bilayer. The
resistance measurement shows a reduction of ~2.5% for the bilayer specimen as
compared to 1.3% for Ni80Fe20 (50 nm) on oxide specimen for an out-of-plane
applied magnetic field of 3T. In the Ni80Fe20-only film, the negative
magnetoresistance behavior is attributed to anisotropic magnetoresistance. We
propose that spin polarization due to spin-Hall effect is the underlying cause
of the enhanced negative magnetoresistance observed in the bilayer. Silicon has
weak spin orbit coupling so spin Hall magnetoresistance measurement is not
feasible. We use V2{\omega} and V3{\omega} measurement as a function of
magnetic field and angular rotation of magnetic field in direction normal to
electric current to elucidate the spin-Hall effect. The angular rotation of
magnetic field shows a sinusoidal behavior for both V2{\omega} and V3{\omega},
which is attributed to the spin phonon interactions resulting from the
spin-Hall effect mediated spin polarization. We propose that the spin
polarization leads to a decrease in hole-phonon scattering resulting in
enhanced negative magnetoresistance.",1701.07049v1
2014-05-28,Photoinduced pure spin current injection in graphene with Rashba spin-orbit interaction,"We propose a photoexcitation scheme for pure spin current generation in
graphene subject to a Rashba spinorbit coupling. Although excitation using
circularly-polarized light does not result in optical orientation of spins in
graphene unless an additional magnetic field is present, we show that
excitation with linearly-polarized light at normal incidence yields spin
current injection without magnetic field. Spins are polarized within the
graphene plane and are displaced in opposite directions, with no net charge
displacement. The direction of the spin current is determined by the linear
polarization axis of the light, and the injection rate is proportional to the
intensity. The technique is tunable via an applied bias voltage and is
accessible over a wide frequency range. We predict a spin current polarization
as high as 75% for photon frequencies comparable to the Rashba frequency. Spin
current injection via optical methods removes the need for ferromagnetic
contacts, which have been identified as a possible source of spin scattering in
electrical spin injection in graphene.",1405.7174v2
2018-06-06,Control of magnetization dynamics by spin Nernst torque,"Control of magnetization dynamics is one of the primary goals in spintronics.
It has been demonstrated using spin Hall effect i.e charge current to spin
current conversion in non-magnetic metal which has large spin-orbit coupling
such as Pt, W etc. Recently different groups have shown generation of spin
current in Pt, W while thermal gradient is created by virtue of spin Nernst
effect. In this work we show the evidence of magnetization control by spin
Nernst torque in Pt/Py bi-layer. We compared relative strength of spin Nernst
Torque and spin Hall torque by measuring the systematic variation of magnetic
linewidth on application of constant heat or charge current. Spin-torque
ferromagnetic resonance (ST-FMR) technique is adopted to excite the magnet and
to measure line-width precisely from the symmetric and anti-symmetric voltage
component. Control of magnetization dynamics by spin Nernst torque will emerge
as an alternative way to manipulate nano-magnets.",1806.01978v1
2019-12-19,Spin rotation by resonant electric field in few-level quantum dots: Floquet dynamics and tunneling,"We study electric dipole spin resonance caused by sub-terahertz (THz)
radiation in a multilevel finite-size quantum dot formed in a nanowire focusing
on the range of driving electric fields amplitudes where a strong interplay
between the Rabi spin oscillations and tunneling from the dot to continuum
states can occur. A strong effect of the tunneling on the spin evolution in
this regime occurs due to formation of mixed spin states. As a result, the
tunneling strongly limits possible spin manipulations time. We demonstrate a
backaction of the spin dynamics on the tunneling and position of the electron.
The analysis of the efficiency of the spin manipulation in terms of the system
energy shows that tunneling decreases this efficiency. Fourier spectra of the
time-dependent expectation value of the electron position show a strong effect
of the spin-orbit coupling on their low-frequency components. This results can
be applied to operational properties of spin-based nanodevices and extending
the range of possible spin resonance frequencies to the THz domain.",1912.09054v2
2020-05-18,Spin-Nematic Vortex States in Cold Atoms,"The (pseudo-)spin degrees of freedom greatly enriches the physics of cold
atoms. This is particularly so for systems with high spins (i.e., spin quantum
number larger than 1/2). For example, one can construct not only the rank-1
spin vector, but also the rank-2 spin tensor in high spin systems. Here we
propose a simple scheme to couple the spin tensor and the center-of-mass
orbital angular momentum in a spin-1 cold atom system, and show that this leads
to a new quantum phase of the matter: the spin-nematic vortex state that
features vorticity in an SU(2) spin-nematic tensor subspace. Under proper
conditions, such states are characterized by quantized topological numbers. Our
work opens up new avenues of research in topological quantum matter with high
spins.",2005.08498v2
2020-09-16,Plasmon to exciton spin conversion in semiconductor-metal hybrid structures,"Optical control of electronic spins is the basis for ultrafast spintronics:
circularly polarized light in combination with spin-orbit coupling of the
electronic states allows for spin manipulation in condensed matter. However,
the conventional approach is limited to spin orientation along one particular
orientation that is dictated by the direction of photon propagation. Plasmonics
opens new capabilities, allowing one to tailor the light polarization at the
nanoscale. Here, we demonstrate ultrafast optical excitation of electron spin
on femtosecond time scales via plasmon to exciton spin conversion. By
time-resolving the THz spin dynamics in a hybrid (Cd,Mn)Te quantum well
structure covered with a metallic grating, we unambiguously determine the
orientation of the photoexcited electron spins which is locked to the
propagation direction of surface plasmon-polaritons. Using the spin of the
incident photons as additional degree of freedom, one can orient the
photoexcited electron spin at will in a two-dimensional plane.",2009.07658v1
2020-10-01,A roadmap for the design of four-terminal spin valves and the extraction of spin diffusion length,"Graphene is a promising substrate for future spintronics devices owing to its
remarkable electronic mobility and low spin-orbit coupling. Hanle precession in
spin valve devices is commonly used to evaluate the spin diffusion and spin
lifetime properties. In this work, we demonstrate that this method is no longer
accurate when the distance between inner and outer electrodes is smaller than
six times the spin diffusion length, leading to errors as large as 50% for the
calculations of the spin figures of merit of graphene. We suggest simple but
efficient approaches to circumvent this limitation by addressing a revised
version of the Hanle fit function. Complementarily, we provide clear guidelines
for the design of four-terminal spin valves able to yield flawless estimations
of the spin lifetime and the spin diffusion coefficient.",2010.00669v1
2022-08-20,Many-body theory of phonon-induced spin relaxation and decoherence,"First-principles calculations enable accurate predictions of electronic
interactions and dynamics. However, computing the electron spin dynamics
remains challenging. The spin-orbit interaction causes various dynamical
phenomena that couple with phonons, such as spin precession and spin-flip e-ph
scattering, which are difficult to describe with current first-principles
calculations. In this work, we show a rigorous framework to study
phonon-induced spin relaxation and decoherence, by computing the spin-spin
correlation function and its vertex corrections due to e-ph interactions. We
apply this approach to a model system and develop corresponding
first-principles calculations of spin relaxation in GaAs. Our vertex-correction
formalism is shown to capture the Elliott-Yafet, Dyakonov-Perel, and
strong-precession mechanisms - three independent spin decoherence regimes with
distinct physical origins - thereby unifying their theoretical treatment and
calculation. Our method is general and enables quantitative studies of spin
relaxation, decoherence, and transport in a wide range of materials and
devices.",2208.09575v1
2022-09-27,Spin-charge separation and quantum spin Hall effect of $β$-bismuthene,"Field theory arguments suggest the possibility of $\mathbb{Z}$-classification
of quantum spin Hall effect with magnetic flux tubes, that cause separation of
spin and charge degrees of freedom, and pumping of spin or Kramers pair.
However, the \emph{proof of principle} demonstration of spin-charge separation
is yet to be accomplished for realistic, \emph{ab initio} band structures of
spin-orbit-coupled materials, lacking spin-conservation law. In this work, we
perform thought experiments with magnetic flux tubes on $\beta$-bismuthene to
demonstrate spin-charge separation, and quantized pumping of spin for three
insulating states that can be accessed by tuning filling fractions. With a
combined analysis of momentum-space topology and real-space response, we
identify important role of topologically non-trivial bands, supporting even
integer winding numbers, which cannot be inferred from symmetry-based
indicators. Our work sets a new standard for prediction of two-dimensional,
quantum spin-Hall materials, based on precise bulk invariant and universal
topological response.",2209.13582v1
2005-02-09,"SU(2)xU(1) unified theory for charge, orbit and spin currents","Spin and charge currents in systems with Rashba or Dresselhaus spin-orbit
couplings are formulated in a unified version of four-dimensional
SU(2)$\times$U(1) gauge theory, with U(1) the Maxwell field and SU(2) the
Yang-Mills field. While the bare spin current is non-conserved, it is
compensated by a contribution from the SU(2) gauge field, which gives rise to a
spin torque in the spin transport, consistent with the semi-classical theory of
Culcer et al. Orbit current is shown to be non-conserved in the presence of
electromagnetic fields. Similar to the Maxwell field inducing forces on charge
and charge current, we derive forces acting on spin and spin current induced by
the Yang Mills fields such as the Rashba and Dresselhaus fields and the sheer
strain field. The spin density and spin current may be considered as a source
generating Yang-Mills field in certain condensed matter systems.",0502231v4
2012-03-02,Three-Dimensional Spin Rotations at the Fermi Surface of a Strongly Spin-Orbit Coupled Surface System,"The spin texture of the metallic two-dimensional electron system (root3 x
root3)-Au/Ge(111) is revealed by fully three-dimensional spin-resolved
photoemission, as well as by density functional calculations. The large
hexagonal Fermi surface, generated by the Au atoms, shows a significant
splitting due to spin-orbit interactions. The planar components of the spin
exhibit helical character, accompanied by a strong out-of-plane spin component
with alternating signs along the six Fermi surface sections. Moreover, in-plane
spin rotations towards a radial direction are observed close to the hexagon
corners. Such a threefold-symmetric spin pattern is not described by the
conventional Rashba model. Instead, it reveals an interplay with
Dresselhaus-like spin-orbit effects as a result of the crystalline
anisotropies.",1203.0520v1
2019-01-28,Strong damping-like spin-orbit torque and tunable Dzyaloshinskii-Moriya interaction generated by low-resistivity Pd$_{1-x}$Pt$_x$ alloys,"Despite their great promise for providing a pathway for very efficient and
fast manipulation of magnetization at the nanoscale, spin-orbit torque (SOT)
operations are currently energy inefficient due to a low damping-like SOT
efficiency per unit current bias, and/or the very high resistivity of the spin
Hall materials. Here, we report an advantageous spin Hall material, Pd1-xPtx,
which combines a low resistivity with a giant spin Hall effect as evidenced
through the use of three independent SOT ferromagnetic detectors. The optimal
Pd0.25Pt0.75 alloy has a giant internal spin Hall ratio of >0.47 (damping-like
SOT efficiency of ~ 0.26 for all three ferromagnets) and a low resistivity of
~57.5 {\mu}{\Omega} cm at 4 nm thickness. Moreover, we find the
Dzyaloshinskii-Moriya interaction (DMI), the key ingredient for the
manipulation of chiral spin arrangements (e.g. magnetic skyrmions and chiral
domain walls), is considerably strong at the Pd1-xPtx/Fe0.6Co0.2B0.2 interface
when compared to that at Ta/Fe0.6Co0.2B0.2 or W/Fe0.6Co0.2B0.2 interfaces and
can be tuned by a factor of 5 through control of the interfacial spin-orbital
coupling via the heavy metal composition. This work establishes a very
effective spin current generator that combines a notably high energy efficiency
with a very strong and tunable DMI for advanced chiral spintronics and spin
torque applications.",1901.09954v1
2022-01-21,A single hole spin with enhanced coherence in natural silicon,"Semiconductor spin qubits based on spin-orbit states are responsive to
electric field excitation allowing for practical, fast and potentially scalable
qubit control. Spin-electric susceptibility, however, renders these qubits
generally vulnerable to electrical noise, which limits their coherence time.
Here we report on a spin-orbit qubit consisting of a single hole
electrostatically confined in a natural silicon metal-oxide-semiconductor
device. By varying the magnetic field orientation, we reveal the existence of
operation sweet spots where the impact of charge noise is minimized while
preserving an efficient electric-dipole spin control. We correspondingly
observe an extension of the Hahn-echo coherence time up to 88 $\mu$s, exceeding
by an order of magnitude the best reported values for hole-spin qubits, and
approaching the state-of-the-art for electron spin qubits with synthetic
spin-orbit coupling in isotopically-purified silicon. This finding largely
enhances the prospects of silicon-based hole spin qubits for scalable quantum
information processing.",2201.08637v2
2022-06-11,Chirality as Generalized Spin-Orbit Interaction in Spintronics,"This review focuses on the chirality observed in the excited states of the
magnetic order, dielectrics, and conductors that hold transverse spins when
they are evanescent. Even without any relativistic effect, the transverse spin
of the evanescent waves are locked to the momentum and the surface normal of
their propagation plane. This chirality thereby acts as a generalized
spin-orbit interaction, which leads to the discovery of various chiral
interactions between magnetic, phononic, electronic, photonic, and plasmonic
excitations in spintronics that mediate the excitation of quasiparticles into a
single direction, leading to phenomena such as chiral spin and phonon pumping,
chiral spin Seebeck, spin skin, magnonic trap, magnon Doppler, and spin diode
effects. Intriguing analogies with electric counterparts in the nano-optics and
plasmonics exist. After a brief review of the concepts of chirality that
characterize the ground state chiral magnetic textures and chirally coupled
magnets in spintronics, we turn to the chiral phenomena of excited states. We
present a unified electrodynamic picture for dynamical chirality in spintronics
in terms of generalized spin-orbit interaction and compare it with that in
nano-optics and plasmonics. Based on the general theory, we subsequently review
the theoretical progress and experimental evidence of chiral interaction, as
well as the near-field transfer of the transverse spins, between various
excitations in magnetic, photonic, electronic and phononic nanostructures at
GHz time scales. We provide a perspective for future research before concluding
this article.",2206.05535v2
2023-05-24,Charged spinning and magnetized test particles orbiting quantum improved charged black holes,"In the present work, we aimed to investigate the dynamics of spinning charged
and magnetized test particles around both electrically and magnetically charged
quantum-improved black holes. We derive the equations of motion for charged
spinning test particles using the Mathisson-Papapetrou-Dixon equations with the
Lorentz coupling term. The radius of innermost stable circular orbits (ISCOs),
specific angular momentum, and energy for charged spinless, uncharged spinning,
and charged spinning test particles around the charged and non-charged
quantum-improved black holes are analyzed separately. We found that the quantum
parameter increases the maximum spin value, $s_\text{max}$, which leads to the
nonphysical motion (superluminal motion) of the charged spinning test particle,
whereas the black hole charge decreases its value. We also found that, in
contrast to the Reissner Nordstr\""om black hole, spinning charged test
particles in the quantum-improved charged black hole have higher
$s_\text{max}$; moreover, positively charged spinning particles can have higher
values of $s_\text{max}$ near the extreme black hole cases when compared with
uncharged spinning particles. Finally, we investigate the magnetized test
particle's dynamics around a quantum-improved magnetically charged black hole
in Quantum Einstein Gravity using the Hamilton-Jacobi equation. We show that
the presence of $\omega$ increases the maximum value of the effective potential
and decreases the minimum energy and angular momentum of magnetized particles
at their circular orbits. We found an upper constraint in the black hole charge
at the ISCO.",2305.15350v1
1997-09-24,Ultrafast Spin Dynamics in Nickel,"The spin dynamics in Ni is studied by an exact diagonalization method on the
ultrafast time scale. It is shown that the femtosecond relaxation of the
magneto-optical response results from exchange interaction and spin-orbit
coupling. Each of the two mechanisms affects the relaxation process
differently. We find that the intrinsic spin dynamics occurs during about 10 fs
while extrinsic effects such as laser-pulse duration and spectral width can
slow down the observed dynamics considerably. Thus, our theory indicates that
there is still room to accelerate the spin dynamics in experiments.",9709264v1
2001-07-04,Chiral Correction to the Spin Fluctuation Feedback in two-dimensional p-wave Superconductors,"We consider the stability of the superconducting phase for spin-triplet
p-wave pairing in a quasi-two-dimensional system. We show that in the absence
of spin-orbit coupling there is a chiral contribution to spin fluctuation
feedback which is related to spin quantum Hall effect in a chiral
superconducting phase. We show that this mechanism supports the stability of a
chiral p-wave state.",0107096v2
2002-11-11,Pumping spin with electrical fields,"Spin currents can be obtained through adiabatic pumping by means of
electrical gating only. This is possible by making use of the tunability of the
Rashba spin-orbit coupling in semiconductor heterostructures. We demonstrate
the principles of this effect by considering a single-channel wire with a
constriction. We also consider realistic structures, consisting of several open
channels where subband spin-mixing and disorder are present, and we confirm our
predictions. Two different ways to detect the spin-pumping effect, either using
ferromagnetic leads or applying a magnetic field, are discussed.",0211211v2
2003-01-06,The Effect of Ramsauer Type Transmission Resonances on the Conductance Modulation of Spin Interferometers,"We use a mean field approach to study the conductance modulation of gate
controlled semiconductor spin interferometers based on the Rashba spin-orbit
coupling effect. The conductance modulation is found to be mostly due to
Ramsauer type transmission resonances rather than the Rashba effect in typical
structures. This is because of significant reflections at the interferometer's
contacts due to large potential barriers and effective mass mismatch between
the contact material and the semiconductor. Thus, unless particular care is
taken to eliminate these reflections, any observed conductance modulation of
spin interferometers may have its origin in the Ramsauer resonances (which is
unrelated to spin) rather than the Rashba effect.",0301052v1
2003-04-17,Spin Readout and Initialization in a Semiconductor Quantum Dot,"Electron spin qubits in semiconductors are attractive from the viewpoint of
long coherence times. However, single spin measurement is challenging. Several
promising schemes incorporate ancillary tunnel couplings that may provide
unwanted channels for decoherence. Here, we propose a novel spin-charge
transduction scheme, converting spin information to orbital information within
a single quantum dot by microwave excitation. The same quantum dot can be used
for rapid initialization, gating, and readout. We present detailed modeling of
such a device in silicon to confirm its feasibility.",0304422v2
2003-09-05,Spinning Holes in Semiconductors,"The electron spin is emerging as a new powerful tool in the electronics and
optics industries. Many proposed applications involve the creation of spin
currents, which so far have proven to be difficult to produce in semiconductor
environments. A new theoretical analysis shows this might be achieved using
holes rather than electrons in semiconductors with significant spin-orbit
coupling.",0309154v1
2003-10-02,Spin relaxations in semiconductor quantum dots,"The spin relaxation time due to the electron-acoustic phonon scattering in
GaAs quantum dots is studied after the exact diagonalization of the electron
Hamiltonian with the spin-orbit coupling. Different effects such as the
magnetic field, the quantum dot size, the temperature as well as the electric
field on the spin relaxation time are investigated in detail. Moreover, we show
that the perturbation method widely used in the literature is inadequate in
accounting for the electron structure and therefore the spin relaxation time.",0310039v2
2004-11-18,"Imaging spin flows in semiconductors subject to electric, magnetic, and strain fields","Using scanning Kerr microscopy, we directly acquire two-dimensional images of
spin-polarized electrons flowing laterally in bulk epilayers of n:GaAs. Optical
injection provides a local dc source of polarized electrons, whose subsequent
drift and/or diffusion is controlled with electric, magnetic, and - in
particular - strain fields. Spin precession induced by controlled uniaxial
stress along the <110> axes demonstrates the direct k-linear spin-orbit
coupling of electron spin to the shear (off-diagonal) components of the strain
tensor.",0411461v1
2004-12-15,Control of spin coherence in $n$-type GaAs quantum wells using strain,"We show that the bulk-inversion-asymmetry-type strain-induced spin-orbit
coupling can be used to effectively modify the Dresselhaus spin splitting in
(001) GaAs quantum wells with small well width and the resulting spin lifetime
can be increased by two orders of magnitude to nanoseconds under right
conditions. The efficiency of this strain manipulation of the spin dephasing
time under different conditions such as temperature, electric field and
electron density is investigated in detail.",0412385v2
2005-04-02,General Electrical Manipulations of Electron Spin,"Traditionally, the interactions related to the 3D spatial angular momentum
have been studied completely, while the ones related to the generators of
Lorentz boost are always ignored. In this paper we show that the generators of
Lorentz boost have a nontrivial physical significance in quantum mechanics, and
try to propose a most general theory about electrical manipulations of electron
spin, where a new treatment and interpretation for the traditional Darwin term
and spin-orbit coupling is given via the concept of electron's induced electric
moment. Some electrostatic fields can even affect the spin quantum states of a
resting electron, and parallel electric and magnetic fields can be
simultaneously applied to fix on the spin orientation of electron.",0504049v1
2005-05-21,Theory of Spin Hall conductivity in n-doped GaAs,"We develop a theory of extrinsic spin currents in semiconductors, resulting
from spin-orbit coupling at charged scatterers, which leads to skew scattering
and side jump contributions to the spin Hall conductance. Applying the theory
to bulk n-GaAs, without any free parameters, we find spin currents that are in
reasonable agreement with recent experiments by Kato et al. [Science 306, 1910
(2004)].",0505535v1
2005-07-20,Spin-lattice relaxation phenomena in manganite La0.7Sr0.3MnO3 thin films,"Time-resolved magneto-optics was used to study spin-lattice relaxation
dynamics in thin epitaxial La0.7Sr0.3MnO3 films. Two distinct recovery regimes
of the ferromagnetic order can be resolved upon photoexcitation, which manifest
themselves by two different relaxation times. A pump pulse energy independent
spin-lattice relaxation time can be deduced. Due to a weak spin-orbit coupling
in manganites this spin-lattice relaxation time is much longer than in
ferromagnetic metals. Heat flow into the substrate sets the ultimate recovery
speed of the ferromagnetic order and allows for a determination of heat
diffusion properties of manganite films.",0507481v1
2005-07-26,Resonant intrinsic spin Hall effect in p-type GaAs quantum well structure,"We study intrinsic spin Hall effect in p-type GaAs quantum well structure
described by Luttinger Hamiltonian and a Rashba spin-orbit coupling arising
from the structural inversion symmetry breaking. The Rashba term induces an
energy level crossing in the lowest heavy hole subband, which gives rise to a
resonant spin Hall conductance. The resonance may be used to identify the
intrinsic spin Hall effect in experiments.",0507603v1
2007-03-08,Spin transverse force and quantum transverse transport,"We present a brief review on spin transverse force, which exerts on the spin
as the electron is moving in an electric field. This force, analogue to the
Lorentz force on electron charge, is perpendicular to the electric field and
spin current carried by the electron. The force stems from the spin-orbit
coupling of electrons as a relativistic quantum effect, and could be used to
understand the Zitterbewegung of electron wave packet and the quantum
transverse transport of electron in a heuristic way.",0703196v1
2007-11-13,Intrinsic Spin Hall Effect Induced by Quantum Phase Transition in HgCdTe Quantum Wells,"Spin Hall effect can be induced both by the extrinsic impurity scattering and
by the intrinsic spin-orbit coupling in the electronic structure. The HgTe/CdTe
quantum well has a quantum phase transition where the electronic structure
changes from normal to inverted. We show that the intrinsic spin Hall effect of
the conduction band vanishes on the normal side, while it is finite on the
inverted side. This difference gives a direct mechanism to experimentally
distinguish the intrinsic spin Hall effect from the extrinsic one.",0711.1900v1
2008-02-10,Equilibrium spin currents: Non-Abelian gauge invariance and color diamagnetism in condensed matter,"The spin-orbit (SO) interaction in condensed matter can be described in terms
of a non-Abelian potential known in high-energy physics as a color field. I
show that a magnetic component of this color field inevitably generates
diamagnetic color currents which are just the equilibrium spin currents
discussed in a condensed matter context. These dissipationless spin currents
thus represent a universal property of systems with SO interaction. In
semiconductors with linear SO coupling the spin currents are related to the
effective non-Abelian field via Yang-Mills magnetostatics equation.",0802.1350v1
2008-08-28,Electric excitation of spin resonance in antiferromagnetic conductors,"Antiferromagnetism couples electron spin to its orbital motion, thus allowing
excitation of electron-spin transitions by an ac electric rather than magnetic
field - with absorption, exceeding that of common electron spin resonance at
least by four orders of magnitude. In addition to potential applications in
spin electronics, this phenomenon may be used as a spectroscopy to study
antiferromagnetic materials of interest - from chromium to borocarbides,
cuprates, iron pnictides, and organic and heavy fermion conductors.",0808.3946v2
2008-09-24,Gated combo nanodevice for sequential operations on single electron spin,"An idea for a nanodevice in which an arbitrary sequence of three basic
quantum single qubit gates - negation, Hadamard and phase shift - can be
performed on a single electron spin. The spin state is manipulated using the
spin-orbit coupling and the electron trajectory is controlled by the electron
wave function self-focusing mechanism due to the electron interaction with the
charge induced on metal gates. We present results of simulations based on
iterative solution of the time dependent Schr\""odinger equation in which the
subsequent operations on the electron spin can be followed and controlled.
Description of the moving electron wave packet requires evaluation of the
electric field within the entire nanodevice in each time step.",0809.4195v1
2009-07-24,Electrical measurement of a two-electron spin state in a double quantum dot,"We propose a scheme for electrical measurement of two-electron spin states in
a semiconductor double quantum dot. We calculated the adiabatic charge transfer
when surface gates are modulated in time. Because of spin-orbit coupling in the
semiconductor, spatial displacement of the electrons causes a total spin
rotation. It follows that the expectation value of the transferred charge
reflects the relative phase as well as the total spin population of a prepared
singlet-triplet superposition state. The precise detection of the charge
transfer serves to identify the quantum superposition.",0907.4191v1
2009-08-20,Superconducting state in the non-centrosymmetric Mg_{9.3}Ir_{19}B_{16.7} and Mg_{10.5}Ir_{19}B_{17.1} revealed by NMR,"We report ^{11}B NMR measurements in non-centrosymmetric superconductors
Mg_{9.3}Ir_{19}B_{16.7} (T_c=5.8 K) and Mg_{10.5}Ir_{19}B_{17.1} (T_c=4.8 K).
The spin lattice relaxation rate and the Knight shift indicate that the Cooper
pairs are predominantly in the spin-singlet state with an isotropic gap.
However, Mg_{10.5}Ir_{19}B_{17.1} is found to have more defects and the spin
susceptibility remains finite even in the zero-temperature limit. We interpret
this result as that the defects enhance the spin-orbit coupling and bring about
more spin-triplet component.",0908.2894v1
2010-01-05,Edge-induced spin polarization in two-dimensional electron gas,"We characterize the role of the spin-orbit coupling between electrons and the
confining potential of the edge in nonequilibrium 2D homogeneous electronic
gas. We derive a simple analytical result for the magnitude of the current
induced spin polarization at the edge and prove that it is independent of the
details of the confinement edge potential and the electronic density within
realistic values of the parameters of the considered models. While the
amplitude of the spin accumulation is comparable to the experimental values of
extrinsic spin Hall effect in similar samples, the spatial extent of edge
induced effect is restricted to the distances of the order of Fermi wavelength
($\sim$ 10nm).",1001.0720v1
2012-08-24,Fast and robust spin manipulation in a quantum dot by electric fields,"We apply an invariant-based inverse engineering method to control by
time-dependent electric fields electron spin dynamics in a quantum dot with
spin-orbit coupling in a weak magnetic field. The designed electric fields
provide a shortcut to adiabatic processes that flips the spin rapidly, thus
avoiding decoherence effects. This approach, being robust with respect to the
device-dependent noise, can open new possibilities for the spin-based quantum
information processing.",1208.4890v2
2012-09-09,Neutron Brillouin scattering with pulsed spallation neutron source - spin-wave excitations from ferromagnetic powder samples -,"Neutron Brillouin scattering (NBS) method was developed using a pulsed
spallation neutron source, and the feasibility of NBS was demonstrated by
observing ferromagnetic spin waves in La$_{0.8}$Sr$_{0.2}$MnO$_3$ and SrRuO$_3$
powders. Gapless spin-wave excitations were observed in
La$_{0.8}$Sr$_{0.2}$MnO$_3$, which were continuously extended to the lower
scattering vector $Q$ from previous results using single crystals. The novel
result is a well-defined quadratic $Q$ dependence in the spin-wave dispersion
curve with a large energy gap in SrRuO$_3$ indicating robust spin-orbit
coupling.",1209.1780v1
2012-11-22,Spin Hall effect in graphene due to random Rashba field,"Spin Hall effect due to random Rashba spin-orbit coupling in the
two-dimensional honeycomb lattice of carbon atoms (graphene) is considered
theoretically. Using the Green function method and diagrammatic technique we
show that fluctuations of the Rashba interaction around zero average value give
rise to nonzero spin Hall conductivity. Generally, the conductivity is not
universal, but depends on the ratio of the total momentum and spin-flip
relaxation rates.",1211.5222v1
2012-12-08,Tensor coupling and relativistic spin and pseudospin symmetries with the Hellmann potential,"The Hellmann potential is a superposition potential that consists of an
attractive Coulomb potential and a Yukawa potential. By using the generalized
parametric Nikiforov-Uvarov (NU) method, we have studied the approximate
analytical solutions of the Dirac equation with the Hellmann potential
including a Coulomb-like tensor potential for arbitrary spin-orbit quantum
number k under the presence of exact spin and pseudo-spin (p-spin) symmetries.
We show that tensor interaction removes degeneracies between spin and
pseudospin doublets. As particular cases, we found the energy levels of
non-relativistic case and also the pure Coulomb potential energy levels.",1212.1830v1
2013-10-10,Effect of gate-driven spin resonance on the conductance of a one-dimensional quantum wire,"We consider quasiballistic electron transmission in a one-dimensional quantum
wire subject to both time-independent and periodic potentials of a finger gate
that results in a coordinate- and time-dependent Rashba-type spin-orbit
coupling. A spin-dependent conductance is calculated as a function of external
constant magnetic field, the electric field frequency, and the potential
strength. The results demonstrate the effect of the gate-driven electric dipole
spin resonance in a transport phenomenon such as spin-flip electron
transmission.",1310.2914v1
2014-07-14,Intrinsic magnetoresistance in metal films on ferromagnetic insulators,"We predict a magnetoresistance induced by the interfacial Rashba spin-orbit
coupling in normal metal|ferromagnetic insulator bilayer. It depends on the
angle between current and magnetization directions identically to the ""spin
Hall magnetoresistance"" mechanism caused by a combined action of spin Hall and
inverse spin Hall effects. Due to the identical phenomenology it is not obvious
whether the magnetoresistance reported by Nakayama et al. is a bulk metal or
interface effect. The interfacial Rashba induced magnetoresistance may be
distinguished from the bulk metal spin Hall magnetoresistance by its dependence
on the metal film thickness.",1407.3571v1
2015-09-08,Anomalous Hall effect driven by dipolar spin waves in uniform ferromagnets,"A new type of anomalous Hall effect is shown to arise from the interaction of
conduction electrons with dipolar spin waves in ferromagnets. This effect
exists even in homogeneous ferromagnets without relativistic spin-orbit
coupling. The leading contribution to the Hall conductivity is proportional to
the chiral spin correlation of dynamical spin textures and is physically
understood in terms of the skew scattering by dipolar magnons.",1509.02284v1
2016-01-07,A novel method to evaluate spin diffusion length of Pt,"Spin diffusion length of Pt is evaluated via proximity effect of spin orbit
coupling (SOC) and anomalous Hall effect (AHE) in Pt/Co2FeAl bilayers. By
varying the thicknesses of Pt and Co2FeAl layer, the thickness dependences of
AHE parameters can be obtained, which are theoretically predicted to be
proportional to the square of the SOC strength. According to the physical image
of the SOC proximity effect, the spin diffusion length of Pt can easily be
identified from these thickness dependences. This work provides a novel method
to evaluate spin diffusion length in a material with a small value.",1601.01371v1
2016-02-23,Spontaneous Spin Textures in Multiorbital Mott Systems,"Spin textures in k-space arising from spin-orbit coupling in
non-centrosymmetric crystals find numerous applications in spintronics. We
present a mechanism that leads to appearance of k-space spin texture due to
spontaneous symmetry breaking driven by electronic correlations. Using
dynamical mean-field theory we show that doping a spin-triplet excitonic
insulator provides a means of creating new thermodynamic phases with unique
properties. The numerical results are interpreted using analytic calculations
within a generalized double-exchange framework.",1602.07122v3
2016-11-22,Electron spin dynamics of two-dimensional layered materials,"The growing library of two-dimensional layered materials is providing
researchers with a wealth of opportunity to explore and tune physical phenomena
at the nanoscale. Here, we review the experimental and theoretical state-of-art
concerning the electron spin dynamics in graphene, silicene, phosphorene,
transition metal dichalcogenides, covalent heterostructures of organic
molecules and topological materials. The spin transport, chemical and defect
induced magnetic moments, and the effect of spin-orbit coupling and spin
relaxation, are also discussed in relation to the field of spintronics.",1611.07208v1
2013-09-13,Skyrmion spin texture in ferromagnetic semiconductor-superconductor heterostructures,"We provide a derivation of a spin Skyrmion number classification for
two-dimensional topological superconductors constructed from ferromagnetic and
Rashba spin-orbit coupled semiconductor-superconductor heterostructures. We
show that in the non-trivial topological phase, characterized by a non-zero
Chern number, there is always a topological spin texture in the occupied bands
represented by a Skyrmion number. The Skyrmion number has the advantage of
being both physically intuitive and directly measurable using spin-sensitive
band structure imaging techniques. In addition, we show that the Skyrmion
classification can be extended to the equivalent one-dimensional topological
superconductors.",1309.3411v2
2015-12-03,Unconventional superconductivity and anomalous response in hole-doped transition metal dichalcogenides,"Two-dimensional transition metal dichalcogenides entwine interaction,
spin-orbit coupling, and topology. Hole-doped systems lack spin degeneracy:
states are indexed with spin and valley specificity. This unique structure
offers new possibilities for correlated phases and phenomena. We realize an
unconventional superconducting pairing phase which is an equal mixture of a
spin singlet and the $m = 0$ spin triplet. It is stable against large in-plane
magnetic fields, and its topology allows quasiparticle excitations of net
nonzero Berry curvature via pair-breaking circularly polarized light.",1512.01261v3
2016-05-21,Electrically tunable quantum interfaces between photons and spin qubits in carbon nanotube quantum dots,"We present a new scheme for quantum interfaces to accomplish the
interconversion of photonic qubits and spin qubits based on optomechanical
resonators and the spin-orbit-induced interactions in suspended carbon nanotube
quantum dots. This interface implements quantum spin transducers and further
enables electrical manipulation of local electron spin qubits, which lays the
foundation for all-electrical control of state transfer protocols between two
distant quantum nodes in a quantum network. We numerically evaluate the state
transfer processes and proceed to estimate the effect of each coupling strength
on the operation fidelities.",1605.06649v1
2016-08-03,Nuclear spin-lattice relaxation rate in noncentrosymmetric superconductor Y$_2$C$_3$,"For a noncentrosymmetric superconductor such as Y$_2$C$_3$, we consider a
parity-mixing model composed of spin-singlet s-wave and spin-triplet f-wave
pairing components.
  The $d$-vector in f-wave state is chosen to be parallel to the Dresselhaus
asymmetric spin-orbit coupling vector.
  It is found that, the quasiparticle excitation spectrum exhibits distinct
nodal structure as a consequence of parity-mixing. Our calculation predict
anomalous noninteger power laws for low-temperature nuclear spin-lattice
relaxation rate $T_{1}^{-1}$.
  We demonstrate particularly that such a model can qualitatively account for
the existing experimental results of the temperature dependence of $T_{1}^{-1}$
in Y$_2$C$_3$.",1608.01190v1
2017-06-16,Conservation of spin supercurrents in superconductors,"We demonstrate that spin supercurrents are conserved upon transmission
through a conventional superconductor, even in the presence of spin-dependent
scattering by impurities with magnetic moments or spin-orbit coupling. This is
fundamentally different from conventional spin currents, which decay in the
presence of such scattering, and this has important implications for the usage
of superconducting materials in spintronic hybrid structures.",1706.05377v3
2018-09-24,Qubit gates with simultaneous transport in double quantum dots,"A single electron spin in a double quantum dot in a magnetic field is
considered in terms of a four-level system. By describing the electron motion
between the potential minima by spin-conserving tunneling and spin flip caused
by a spin-orbit coupling, we inversely engineer faster-than-adiabatic state
manipulation operations based on the geometry of four-dimensional (4D)
rotations. In particular, we show how to transport a qubit among the quantum
dots performing simultaneously a required spin rotation.",1809.08952v1
2021-01-21,Kubo formulae for first-order spin hydrodynamics,"We derive Kubo formulae for first-order spin hydrodynamics based on
non-equilibrium statistical operators method. In first-order spin
hydrodynamics, there are two new transport coefficients besides the ordinary
ones appearing in first-order viscous hydrodynamics. They emerge due to the
incorporation of the spin degree of freedom into fluids and the spin-orbital
coupling. Zubarev's non-equilibrium statistical operator method can be well
applied to investigate these quantum effects in fluids. The Kubo formulae,
based on the method of non-equilibrium statistical operators, are related to
equilibrium (imaginary-time) infrared Green's functions, and all the transport
coefficients can be determined when the microscopic theory is specified.",2101.08440v2
2017-09-26,Probing chiral edge states in topological superconductors through spin-polarized local density of state measurements,"We show that spin-polarized local density of states (LDOS) measurements can
uniquely determine the chiral nature of topologically protected edge states
surrounding a ferromagnetic island embedded in a conventional superconductor
with spin-orbit coupling. The spin-polarized LDOS show a strong
spin-polarization directly tied to the normal direction of the edge, with
opposite polarizations on opposite sides of the island, and with a distinct
oscillatory pattern in energy.",1709.09061v1
2022-05-30,Fledgling quantum spin Hall effect in pseudo gap phase of Bi2212,"We study the emergence of the quantum spin Hall (QSH) states for the
pseudo-gap (PG) phase of Bi2212 bilayer system, assumed to be D-density
wave(DDW) ordered, starting with a strong Rashba spin-orbit coupling(SOC)
armed, and the time reversal symmetry (TRS) complaint Bloch Hamiltonian. The
presence of strong SOC gives rise to non-trivial, spin-momentum locked spin
texture tunable by electric field. The emergence of quantum anomalous Hall
effect with TRS broken Chiral DDW Hamiltonian of Das Sarma et al. is found to
be possible.",2205.15010v1
2022-07-12,Generation of polarized spin-triplet Cooper pairings by magnetic barriers in superconducting junctions,"We investigate the proximity effect in an s-wave superconductor/ferromagnetic
metal with a Rashba spin-orbit coupling/diffusive normal metal junction and an
s-wave superconductor/noncollinear magnetic metal/diffusive normal metal
junction. We show the generation of equal spin-triplet pairings in the
diffusive normal metal due to spin-flip scattering in the intermediate magnetic
regions. The emergence of the spin-triplet odd-frequency Cooper pairings can
generate a zero-energy peak in the quasiparticle density of states in the
diffusive normal metal.",2207.05400v2
2022-12-21,Spin susceptibility of nonunitary spin-triplet superconductors,"The spin susceptibility is an important probe to characterize the symmetry of
the order parameter in unconventional superconductors. Among them, nonunitary
triplet superconductors have attracted a lot of attention recently in the
context of the search for topological superconductivity. Here, we derive a
general formula for the spin susceptibility of nonunitary triplet
superconductors within a single-band model of non-magnetic, centrosymmetric
materials with strong spin-orbit coupling. We use it to critically assess
experimental claims of nonunitary triplet superconductivity in some materials.",2212.11226v1
2016-06-15,Coupling a single electron spin to a microwave resonator: Controlling transverse and longitudinal couplings,"Microwave-frequency superconducting resonators are ideally suited to perform
dispersive qubit readout, to mediate two-qubit gates, and to shuttle states
between distant quantum systems. A prerequisite for these applications is a
strong qubit-resonator coupling. Strong coupling between an electron-spin qubit
and a microwave resonator can be achieved by correlating spin- and orbital
degrees of freedom. This correlation can be achieved through the Zeeman
coupling of a single electron in a double quantum dot to a spatially
inhomogeneous magnetic field generated by a nearby nanomagnet. In this paper,
we consider such a device and estimate spin-resonator couplings of order ~ 1
MHz with realistic parameters. Further, through realistic simulations, we show
that precise placement of the double dot relative to the nanomagnet allows to
select between a purely longitudinal coupling (commuting with the bare spin
Hamiltonian) and a purely transverse (spin non-conserving) coupling.
Additionally, we suggest methods to mitigate dephasing and relaxation channels
that are introduced in this coupling scheme. This analysis gives a clear route
toward the realization of coherent state transfer between a microwave resonator
and a single electron spin in a GaAs double quantum dot with a fidelity above
90%. Improved dynamical decoupling sequences, low-noise environments, and
longer-lived microwave cavity modes may lead to substantially higher fidelities
in the near future.",1606.04736v3
2007-09-16,Orbital-quenching-induced magnetism in Ba_2NaOsO_6,"The double perovskite \bnoo with heptavalent Os ($d^1$) is observed to remain
in the ideal cubic structure ({\it i.e.} without orbital ordering) despite
single occupation of the $t_{2g}$ orbitals, even in the ferromagnetically
ordered phase below 6.8 K. Analysis based on the {\it ab initio} dispersion
expressed in terms of an Os $t_{2g}$-based Wannier function picture, spin-orbit
coupling, Hund's coupling, and strong Coulomb repulsion shows that the magnetic
OsO$_6$ cluster is near a moment-less condition due to spin and orbital
compensation. Quenching (hybridization) then drives the emergence of the small
moment. This compensation, unprecedented in transition metals, arises in a
unified picture that accounts for the observed Mott insulating behavior.",0709.2520v1
2024-02-24,Role of strong correlation and spin-orbit coupling in $\textrm{LuB}_{4}$: a first principle study,"The recent observation of magnetization plateaus in rare-earth metallic
tetraborides has drawn a lot of attention to this class of materials. In this
work, we investigate the electronic structure of one such canonical system
$\textrm{LuB}_{4}$, using first-principle density functional theory, together
with strong Coulomb correlation and spin-orbit coupling (SOC) effects. The
electronic band structures show that $\textrm{LuB}_{4}$ is a non-magnetic
correlated metal with completely filled $4f$ shell. The projected density of
states (DOS) shows a continuum at the Fermi level (FL), arising mainly from
hybridized Lu $d$ and B $p$ orbitals, along with some discrete peaks, well
separated from the continuum. These peaks arise mainly due to core-level Lu
$s$, $p$ and $4f$ atomic orbitals. Upon inclusion of SOC, the discrete peak
arising due to Lu $p$ is split into two peaks with $j = 1/2$, $j = 3/2$ while
the peak arising due to Lu $4f$ orbitals splits into two peaks with $j = 5/2$
and $j = 7/2$. These peaks will give rise to multiplet structure in core level
X-ray photo-emission spectroscopy. Inclusion of strong correlation effects
pushes the Lu $4f$ peak away from the FL while the qualitative features remain
intact.",2402.15822v1
2001-01-23,Spin versus Lattice Polaron: Prediction for Electron-Doped CaMnO3,"CaMnO3 is a simple bi-partite antiferromagnet(AF) which can be continuously
electron-doped up to LaMnO3. Electrons enter the doubly degenerate E_g subshell
with spins aligned to the S=3/2 core of Mn^4+ (T_2g^3)$. We take the Hubbard
and Hund energies to be effectively infinite. Our model Hamiltonian has two E_g
orbitals per Mn atom, nearest neighbor hopping, nearest neighbor exchange
coupling of the S=3/2 cores, and electron-phonon coupling of Mn orbitals to
adjacent oxygen atoms. We solve this model for light doping. Electrons are
confined in local ferromagnetic (FM) regions (spin polarons) where there
proceeds an interesting competition between spin polarization (spin polarons)
which enlarges the polaron, and lattice polarization (Jahn-Teller polarons)
which makes it smaller. A symmetric 7-atom ferromagnetic cluster (Mn_7^27+) is
the stable result, with net spin S=2 relative to the undoped AF. The distorted
oxygen positions around the electron are predicted. The model also predicts a
critical doping x_c=0.045 where the polaronic insulator becomes unstable
relative to a FM metal.",0101354v1
2002-04-30,Rashba spin-orbit interaction and shot noise for spin-polarized and entangled electrons,"We study shot noise for spin-polarized currents and entangled electron pairs
in a four-probe (beam splitter) geometry with a local Rashba spin-orbit (s-o)
interaction in the incoming leads. Within the scattering formalism we find that
shot noise exhibits Rashba-induced oscillations with continuous bunching and
antibunching. We show that entangled states and triplet states can be
identified via their Rashba phase in noise measurements. For two-channel leads
we find an additional spin rotation due to s-o induced interband coupling which
provides enhanced spin control. We show that the s-o interaction determines the
Fano factor which provides a direct way to measure the Rashba coupling constant
via noise.",0204639v2
2004-05-04,Spin Accumulation and Equilibrium Currents at the Edge of 2DEGs with Spin-Orbit Coupling,"We show that in a two dimensional electron gas (2DEG) the interplay between
the Rashba spin-orbit coupling and a potential barrier (eg., the sample edge)
generates interesting spin effects. In the presence of an external charge
current, a spin accumulation is built up near the barrier while in equilibrium
there is an inhomogeneous spin current which is localized at the barrier and
flows parallel to it. When an in-plane magnetic field perpendicular to the
barrier is applied, the system also develops an inhomogeneous charge current
density. These effects originate purely from the structure of the eigenstates
near the boundary.",0405065v3
2004-05-09,Spin susceptibility in superconductors without inversion symmetry,"In materials without spatial inversion symmetry the spin degeneracy of the
conduction electrons can be lifted by an antisymmetric spin-orbit coupling. We
discuss the influence of this spin-orbit coupling on the spin susceptibility of
such superconductors, with a particular emphasis on the recently discovered
heavy Fermion superconductor CePt3Si. We find that, for this compound (with
tetragonal crystal symmetry,) irrespective of the pairing symmetry, the stable
superconducting phases would give a very weak change of the spin susceptibility
for fields along the c-axis and an intermediate reduction for fields in the
basal plane. We also comment on the consequences for the paramagnetic limiting
in this material.",0405179v2
2004-11-27,A Theoretical Investigation of Relativistic Spintronics,"Spintronics directly based on relativistic quantum mechanics is called as
relativistic spintronics, which involves the study of active control and
manipulation of 4D spin-tensor degrees of freedom via the electromagnetic field
tensor. For future potential electronic devices with smaller size, the study of
relativistic spintronics would be valuable. In this paper, we try to establish
a general theoretical basis for relativistic spintronics, from which we have:
1) in relativistic spintronics, there have more plentiful contents for
relativistic effects, e.g. the usual 3D spatial spin-orbit coupling is extended
to the 4D spin-orbit-tensor coupling; 2) via the spin and like-spin degrees of
freedom we can simultaneously make use of electric and magnetic field strengths
to orientate an electron; 3) not only the spin quantum states of a moving
electron but also those of a motionless electron can be affected by some
particular electrostatic fields.",0411689v1
2005-02-19,Orbital ac spin-Hall effect in the hopping regime,"The Rashba and Dresselhaus spin-orbit interactions are both shown to yield
the low temperature spin-Hall effect for strongly localized electrons coupled
to phonons. A frequency-dependent electric field ${\bf E}(\omega)$ generates a
spin-polarization current, normal to ${\bf E}$, due to interference of hopping
paths. At zero temperature the corresponding spin-Hall conductivity is real and
is proportional to $\omega^{2}$. At non-zero temperatures the coupling to the
phonons yields an imaginary term proportional to $\omega$. The interference
also yields persistent spin currents at thermal equilibrium, at ${\bf E}=0$.
The contributions from the Dresselhaus and Rashba interactions to the
interference oppose each other.",0502478v1
2005-12-21,Integer Spin Hall Effect in Ballistic Quantum Wires,"We investigate the ballistic electron transport in a two dimensional Quantum
Wire under the action of an electric field ($E_y$). We demonstrate how the
presence of a Spin Orbit coupling, due to the uniform electric confinement
field gives a non-commutative effect as in the presence of a transverse
magnetic field.
  We discuss how the non commutation implies an edge localization of the
currents depending on the electron spins also giving a semi-classical spin
dependent Hall current.
  We also discuss how it is possible obtain a quantized Spin Hall conductance
in the ballistic transport regime by developing the Landauer formalism and show
the coupling between the spin magnetic momentum and the orbital one due to the
presence of a circulating current.",0512543v1
2005-12-23,S-wave/spin-triplet order in superconductors without inversion symmetry: Li$_2$Pd$_3$B and Li$_2$Pt$_3$B,"We investigate the order parameter of noncentrosymmetric superconductors
Li$_2$Pd$_3$B and Li$_2$Pt$_3$B via the behavior of the penetration depth
$\lambda(T)$. The low-temperature penetration depth shows BCS-like behavior in
Li$_2$Pd$_3$B, while in Li$_2$Pt$_3$B it follows a linear temperature
dependence. We propose that broken inversion symmetry and the accompanying
antisymmetric spin-orbit coupling, which admix spin-singlet and spin-triplet
pairing, are responsible for this behavior. The triplet contribution is weak in
Li$_2$Pd$_3$B, leading to a wholly open but anisotropic gap. The significantly
larger spin-orbit coupling in Li$_2$Pt$_3$B allows the spin-triplet component
to be larger in Li$_2$Pt$_3$B, producing line nodes in the energy gap as
evidenced by the linear temperature dependence of $\lambda(T)$. The
experimental data are in quantitative agreement with theory.",0512601v2
2006-05-09,Dimensional Control of Antilocalisation and Spin Relaxation in Quantum Wires,"The spin relaxation rate $1/\tau_s (W)$ in disordered quantum wires with
Rashba and Dresselhaus spin-orbit coupling is derived analytically as a
function of wire width $W$. It is found to be diminished when $W$ is smaller
than the bulk spin-orbit length $L_{\rm SO}$. Only a small spin relaxation rate
due to cubic Dresselhaus coupling $\gamma$ is found to remain in this limit. As
a result, when reducing the wire width $W$ the quantum conductivity correction
changes from weak anti- to weak localization and from negative to positive
magnetoconductivity.",0605243v4
2007-02-24,Disorder Enhanced Spin Polarization in Diluted Magnetic Semiconductors,"We present a theoretical study of diluted magnetic semiconductors that
includes spin-orbit coupling within a realistic host band structure and treats
explicitly the effects of disorder due to randomly substituted Mn ions. While
spin-orbit coupling reduces the spin polarization by mixing different spin
states in the valence bands, we find that disorder from Mn ions enhances the
spin polarization due to formation of ferromagnetic impurity clusters and
impurity bound states. The disorder leads to large effects on the hole carriers
which form impurity bands as well as hybridizing with the valence band. For Mn
doping 0.01 < x < 0.04, the system is metallic with a large effective mass and
low mobility.",0702567v1
2009-06-08,"Electronic properties of graphene and graphene nanoribbons with ""pseudo-Rashba"" spin-orbit coupling","We discuss the electronic properties of graphene and graphene nanoribbons
including ""pseudo-Rashba"" spin-orbit coupling. After summarizing the bulk
properties, we first analyze the scattering behavior close to an infinite mass
and zigzag boundary. For low energies, we observe strong deviations from the
usual spin-conserving behavior at high energies such as reflection acting as
spin polarizer or switch. This results in a spin polarization along the
direction of the boundary due to the appearance of evanescent modes in the case
of non-equilibrium or when there is no coherence between the two one-particle
branches. We then discuss the spin and density distribution of graphene
nanoribbons.",0906.1371v2
2009-06-09,Giant spin rotation under quasiparticle-photoelectron conversion: Joint effect of sublattice interference and spin-orbit coupling,"Spin- and angular-resolved photoemission spectroscopy is a basic experimental
tool for unveiling spin polarization of electron eigenstates in crystals. We
prove, by using spin-orbit coupled graphene as a model, that photoconversion of
a quasiparticle inside a crystal into a photoelectron can be accompanied with a
dramatic change in its spin polarization, up to a total spin flip. This
phenomenon is typical of quasiparticles residing away from the Brillouin zone
center and described by higher rank spinors, and results in exotic patterns in
the angular distribution of photoelectrons.",0906.1812v2
2009-09-24,Spin-orbit coupling in the metallic and spin-liquid phases of Na4Ir3O8,"It has recently been proposed that Na4Ir3O8 is a weak Mott insulator at
ambient pressure, supporting a three-dimensional spin liquid phase with a
spinon Fermi surface. This proposal is consistent with recent experimental
findings that the material becomes a metal upon increasing pressure or doping.
In this work, we investigate the effect of the spin-orbit coupling arising from
5d Ir moments both in the metallic and spin liquid phases of Na4Ir3O8. The
effective Hubbard model in terms of pseudospin j=1/2 Ir states is derived and
its consequences to both metallic and spin liquid phases are studied. In
particular, the model leads to enhanced Wilson ratio and strong temperature
dependence of the Hall coefficient.",0909.4546v2
2009-10-01,Spin relaxation due to random Rashba spin-orbit coupling in GaAs (110) quantum wells,"We investigate the spin relaxation due to the random Rashba spin-orbit
coupling in symmetric GaAs (110) quantum wells from the fully microscopic
kinetic spin Bloch equation approach. All relevant scatterings, such as the
electron-impurity, electron--longitudinal-optical-phonon,
electron--acoustic-phonon, as well as electron-electron Coulomb scatterings are
explicitly included. It is shown that our calculation reproduces the
experimental data by M\""uller {\em et al.} [Phys. Rev. Lett. {\bf 101}, 206601
(2008)] for a reasonable choice of parameter values. We also predict that the
temperature dependence of spin relaxation time presents a peak in the case with
low impurity density, which originates from the electron-electron Coulomb
scattering.",0910.0066v2
2011-05-31,Topological Insulators and Quantum Spin Liquids,"In this paper we review some connections recently discovered between
topological insulators and certain classes of quantum spin liquids, focusing on
two and three spatial dimensions. In two dimensions we show the integer quantum
Hall effect plays a key role in relating topological insulators and chiral spin
liquids described by fermionic excitations, and we describe a procedure for
""generating"" a certain class of topological states. In three dimensions we
discuss interesting relationships between certain quantum spin liquids and
interacting ""exotic"" variants of topological insulators. We focus attention on
better understanding interactions in topological insulators, and the phases
nearby in parameter space that might result from moderate to strong
interactions in the presence of strong spin-orbit coupling. We stress that
oxides with heavy transition metal ions, which often host a competition between
electron interactions and spin-orbit coupling, are an excellent place to search
for unusual topological phenomena and other unconventional phases.",1106.0013v2
2013-07-16,Nonequilibrium spin noise spectroscopy,"Spin Noise Spectroscopy (SNS) is an experimental approach to obtain
correlators of mesoscopic spin fluctuations in time by purely optical means. We
explore the information that this technique can provide when it is applied to a
weakly non-equilibrium regime when an electric current is driven through a
sample by an electric field. We find that the noise power spectrum of
conducting electrons experiences a shift, which is proportional to the strength
of the spin-orbit coupling for electrons moving along the electric field
direction. We propose applications of this effect to measurements of spin orbit
coupling anisotropy and separation of spin noise of conducting and localized
electrons.",1307.4426v1
2014-04-08,Spin-singlet superconductivity with a full gap in locally non-centrosymmetric SrPtAs,"We report $^{195}$Pt-NMR and $^{75}$As-NQR measurements for the locally
non-centrosymmetric superconductor SrPtAs where the As-Pt layer breaks
inversion symmetry while globally the compound is centrosymmetric. The nuclear
spin lattice relaxation rate $1/T_1$ shows a well-defined coherence peak below
$T_c$ and decreases exponentially at low temperatures. The spin susceptibility
measured by the Knight shift also decreases below $T_c$ down to $T<T_c/6$.
These data together with the penetration depth obtained from the NMR spectra
can be consistently explained by assuming a spin-singlet superconducting state
with a full gap. Our results suggest that the spin-orbit coupling due to the
local inversion-breaking is not large enough to bring about an exotic
superconducting state, or the inter-layer hopping interaction is larger than
the spin-orbit coupling.",1404.2154v1
2014-10-23,Ultrafast single electron spin manipulation in 2D semiconductor quantum dots with optimally controlled time-dependent electric fields through spin-orbit coupling,"We have studied theoretically the possibility of ultra-fast manipulation of a
single electron spin in 2D semiconductor quantum dots, by means of
high-frequency time-dependent electric fields. The electron spin degree of
freedom is excited through spin-orbit coupling, and the procedure may be
enhanced by the presence of a static magnetic field. We use quantum optimal
control theory to tailor the temporal profile of the electric field in order to
achieve the most effective manipulation. The scheme predicts significant
control over spin operations in times of the order of picoseconds -- an
ultrafast time scale that permits to avoid the effects of decoherence if this
scheme is to be used as a tool for quantum information processing.",1410.6344v1
2014-11-19,Seebeck effects in two-dimensional spin transistors,"We consider a spin-orbit-coupled two-dimensional electron system under the
influence of a thermal gradient externally applied to two attached reservoirs.
We discuss the generated voltage bias (charge Seebeck effect), spin bias (spin
Seebeck effect) and magnetization-dependent thermopower (magneto-Seebeck
effect) in the ballistic regime of transport at linear response. We find that
the charge thermopower is an oscillating function of both the spin-orbit
strength and the quantum well width. We also observe that it is always negative
for normal leads. We carefully compare the exact results for the linear
response coefficients and a Sommerfeld approximation. When the contacts are
ferromagnetic, we calculate the spin-resolved Seebeck coefficient for parallel
and antiparallel magnetization configuration. Remarkably, the thermopower can
change its sign by tuning the Fermi energy. This effect disappears when the
Rashba coupling is absent. Additionally, we determine the magneto-Seebeck
ratio, which shows dramatic changes in the presence of a the Rashba potential.",1411.5138v2
2015-06-08,Helical Majorana fermions in d_{x^2-y^2} + i d_{xy}-wave topological superconductivity of doped correlated quantum spin Hall insulators,"Large Hubbard U limit of the Kane-Mele model on a zigzag ribbon of honeycomb
lattice near half-filling is studied via a renormalized mean-field theory. The
ground state exhibits time-reversal symmetry (TRS) breaking d + i d'-wave
superconductivity. At large spin-orbit coupling, the Z2 phase with non-trivial
spin Chern number in the pure Kane-Mele model is persistent into the TRS broken
state (called spin-Chern phase), and has two pairs of counter-propagating
helical Majorana modes at the edges. As the spin-orbit coupling is reduced, the
system undergoes a topological quantum phase transition from the spin-Chern to
chiral superconducting states. Possible relevance of our results to
adatom-doped graphene and irridate compounds is discussed.",1506.02584v1
2016-07-08,Semiclassical ground-state phase diagram and multi-Q phase of a spin-orbit coupled model on triangular lattice,"Motivated by recent experiments on the frustrated quantum magnetic compound
YbMgGaO4, we study an effective spin model on triangular lattice taking into
account the effects of the spin-orbit coupling. We determine the classical
ground-state phase diagram of this model, which includes a 120 degree Neel and
two collinear antiferromagnetic phases. In the vicinity of the phase boundary
between the Neel and collinear phases, we identify three intermediate
non-collinear antiferromagnetic phases. In each of them the magnetic moments
are ordered at multiple incommensurate wave vector Q values. We further study
the effects of quantum fluctuations in this model via a linear spin-wave
theory. We find that the spin excitation gap of the non-collinear multi-Q
antiferromagnetic state is finite but can be vanishingly small, and this state
is unstable to a spin liquid phase under strong quantum fluctuations in some
large J_{z+-} regime.",1607.02295v1
2016-07-08,Supercurrent-induced Skyrmion dynamics and Tunable Weyl points in Chiral Magnet with Superconductivity,"Recent studies show superconductivity provides new perspectives on
spintronics. We study a heterostructure composed of an s-wave superconductor
and a cubic chiral-magnet that can stabilize a topological spin texture, a
skyrmion. We propose a supercurrent-induced spin torque that originates from
the spin-orbit coupling, and we show that the spin torque can drive a skyrmion
in an efficient way that reduces Joule heating. We also study the band
structure of Bogoliubov quasiparticles and show the existence of Weyl points,
whose positions can be controlled by the direction of the magnetization. This
results in an effective magnetic field acting on the quasiparticles in the
presence spin textures. Furthermore, the tilt of the Weyl cones can also be
tuned by the strength of the spin-orbit coupling, and we propose a possible
realization of type-II Weyl points.",1607.02336v4
2016-10-07,Spin blockade as a probe of Zeeman interactions in hole quantum dots,"Spin-orbit coupling is key to all-electrical control of quantum-dot spin
qubits, and is frequently stronger for holes than for electrons. Here we
investigate Pauli spin blockade for two heavy holes in a gated double quantum
dot in an in-plane magnetic field. The interplay of the complex Zeeman and
spin-orbit couplings causes a blockade leakage current anisotropic in the field
direction. The period of the anisotropic leakage is critically dependent on the
relative magnitude of Zeeman interaction terms linear and cubic in the magnetic
field. The current and singlet-triplet exchange splitting can be effectively
adjusted by an appropriate choice of field direction, providing a simple
control variable for quantum information processing and a way of tailoring
magnetic interactions in hole spin qubits.",1610.02119v1
2018-11-11,Closed-form weak localization magnetoconductivity in quantum wells with arbitrary Rashba and Dresselhaus spin-orbit interactions,"We derive a closed-form expression for the weak localization (WL) corrections
to the magnetoconductivity of a 2D electron system with arbitrary Rashba
$\alpha$ and Dresselhaus $\beta$ (linear) and $\beta_3$ (cubic) spin-orbit
interaction couplings, in a perpendicular magnetic field geometry. In a system
of reference with an in-plane $\hat{z}$ axis chosen as the high spin-symmetry
direction at $\alpha = \beta$, we formulate a new algorithm to calculate the
three independent contributions that lead to WL. The antilocalization is
counterbalanced by the term associated with the spin-relaxation along
$\hat{z}$, dependent only on $\alpha - \beta$. The other term is generated by
two identical scattering modes characterized by spin-relaxation rates which are
explicit functions of the orientation of the scattered momentum. Excellent
agreement is found with data from GaAs quantum wells, where in particular our
theory correctly captures the shift of the minima of the WL curves as a
function of $\alpha/\beta$. This suggests that the anisotropy of the effective
spin relaxation rates is fundamental to understanding the effect of the SO
coupling in transport.",1811.04488v1
2010-05-26,Phase Transitions in Dissipative Quantum Transport and Mesoscopic Nuclear Spin Pumping,"Topological phase transitions can occur in the dissipative dynamics of a
quantum system when the ratio of matrix elements for competing transport
channels is varied. Here we establish a relation between such behavior in a
class of non-Hermitian quantum walk problems [M. S. Rudner and L. S. Levitov,
Phys. Rev. Lett. 102, 065703 (2009)] and nuclear spin pumping in double quantum
dots, which is mediated by the decay of a spin-blockaded electron triplet state
in the presence of spin-orbit and hyperfine interactions. The transition occurs
when the strength of spin-orbit coupling exceeds the strength of the net
hyperfine coupling, and results in the complete suppression of nuclear spin
pumping. Below the transition point, nuclear pumping is accompanied by a strong
reduction in current due to the presence of non-decaying ""dark states"" in this
regime. Due to its topological character, the transition is expected to be
robust against dephasing of the electronic degrees of freedom.",1005.4809v1
2016-11-29,Emergent Phenomena Induced by Spin-Orbit Coupling at Surfaces and Interfaces,"Spin-orbit coupling (SOC) describes the relativistic interaction between the
spin and momentum degrees of freedom of electrons, and is central to the rich
phenomena observed in condensed matter systems. In recent years, new phases of
matter have emerged from the interplay between SOC and low dimensionality, such
as chiral spin textures and spin-polarized surface and interface states. These
low-dimensional SOC-based realizations are typically robust and can be
exploited at room temperature. Here we discuss SOC as a means of producing such
fundamentally new physical phenomena in thin films and heterostructures. We put
into context the technological promise of these material classes for developing
spin-based device applications at room temperature.",1611.09521v1
2018-05-15,Spin-orbit coupling and electric-dipole spin resonance in a nanowire double quantum dot,"We study the electric-dipole transitions for a single electron in a double
quantum dot located in a semiconductor nanowire. Enabled by spin-orbit coupling
(SOC), electric-dipole spin resonance (EDSR) for such an electron can be
generated via two mechanisms: the SOC-induced intradot pseudospin states mixing
and the interdot spin-flipped tunneling. The EDSR frequency and strength are
determined by these mechanisms together. For both mechanisms the
electric-dipole transition rates are strongly dependent on the external
magnetic field. Their competition can be revealed by increasing the magnetic
field and/or the interdot distance for the double dot. To clarify whether the
strong SOC significantly impact the electron state coherence, we also calculate
relaxations from excited levels via phonon emission. We show that spin-flip
relaxations can be effectively suppressed by the phonon bottleneck effect even
at relatively low magnetic fields because of the very large $g$-factor of
strong SOC materials such as InSb.",1805.05541v1
2016-08-17,Ultrafast spin-flip dynamics in transition metal complexes triggered by soft X-ray light,"Recent advances in attosecond physics provide access to the correlated motion
of valence and core electrons on their intrinsic timescales. For valence
excitations, processes related to the electron spin are usually driven by
nuclear motion. For core-excited states, where the core hole has a nonzero
angular momentum, spin-orbit coupling is strong enough to drive spin-flips on a
much shorter time scale. Here, unprecedented short spin-crossover driven by
spin-orbit coupling is demonstrated for L-edge (2p$\rightarrow$3d) excited
states of a prototypical Fe(II) complex. It occurs on a time scale, which is
faster than the core hole lifetime of about 4~fs. A detailed analysis of such
phenomena will",1608.04979v1
2017-10-02,Nonlocal Andreev Entanglements and Triplet Correlations in Graphene with Spin Orbit Coupling,"Using a wavefunction Dirac Bogoliubov-de Gennes method, we demonstrate that
the tunable Fermi level of a graphene layer in the presence of Rashba spin
orbit coupling (RSOC) allows for producing an anomalous nonlocal Andreev
reflection and equal spin superconducting triplet pairing. We consider a
graphene junction of a ferromagnet-RSOC-superconductor-ferromagnet
configuration and study scattering processes, the appearance of spin triplet
correlations, and charge conductance in this structure. We show that the
anomalous crossed Andreev reflection is linked to the equal spin triplet
pairing. Moreover, by calculating current cross-correlations, our results
reveal that this phenomenon causes negative charge conductance at weak voltages
and can be revealed in a spectroscopy experiment, and may provide a tool for
detecting the entanglement of the equal spin superconducting pair correlations
in hybrid structures.",1710.00840v2
2018-01-27,Ubiquitous Ideal Spin-Orbit Coupling in a Screw Dislocation in Semiconductors,"We theoretically demonstrate that screw dislocation (SD), a 1D topological
defect widely present in semiconductors, exhibits ubiquitously a new form of
spin-orbit coupling (SOC) effect. Differing from the widely known conventional
2D Rashba-Dresselhaus (RD) SOC effect that typically exists at
surfaces/interfaces, the deep-level nature of SD-SOC states in semiconductors
readily makes it an ideal SOC. Remarkably, the spin texture of 1D SD-SOC,
pertaining to the inherent symmetry of SD, exhibits a significantly higher
degree of spin coherency than the 2D RD-SOC. Moreover, the 1D SD-SOC can be
tuned by ionicity in compound semiconductors to ideally suppress spin
relaxation, as demonstrated by comparative first-principles calculations of SDs
in Si/Ge, GaAs, and SiC. Our findings therefore open a new door to manipulating
spin transport in semiconductors by taking advantage of an otherwise
detrimental topological defect.",1801.09025v1
2018-01-29,First-Principles Evaluation of the Dzyaloshinskii--Moriya Interaction,"We review recent developments of formulations to calculate the
Dzyaloshinskii--Moriya (DM) interaction from first principles. In particular,
we focus on three approaches. The first one evaluates the energy change due to
the spin twisting by directly calculating the helical spin structure. The
second one employs the spin gauge field technique to perform the derivative
expansion with respect to the magnetic moment. This gives a clear picture that
the DM interaction can be represented as the spin current in the equilibrium
within the first order of the spin-orbit couplings. The third one is the
perturbation expansion with respect to the exchange couplings and can be
understood as the extension of the Ruderman--Kittel--Kasuya--Yosida (RKKY)
interaction to the noncentrosymmetric spin-orbit systems. By calculating the DM
interaction for the typical chiral ferromagnets Mn$_{1-x}$Fe$_x$Ge and
Fe$_{1-x}$Co$_x$Ge, we discuss how these approaches work in actual systems.",1801.09439v1
2019-10-16,Acoustic spin-Chern insulator induced by synthetic spin-orbit coupling with spin conservation breaking,"Topologically protected surface modes of classical waves hold the promise to
enable a variety of applications ranging from robust transport of energy to
reliable information processing networks. The integer quantum Hall effect has
delivered on that promise in the electronic realm through high-precision
metrology devices. However, both the route of implementing an analogue of the
quantum Hall effect as well as the quantum spin Hall effect are obstructed for
acoustics by the requirement of a magnetic field, or the presence of fermionic
quantum statistics, respectively. Here, we use a two-dimensional acoustic
crystal with two layers to mimic spin-orbit coupling, a crucial ingredient of
topological insulators. In particular, our setup allows us to free ourselves of
symmetry constraints as we rely on the concept of a non-vanishing ""spin"" Chern
number. We experimentally characterize the emerging boundary states which we
show to be gapless and helical. Moreover, in an H-shaped device we demonstrate
how the transport path can be selected by tuning the geometry, enabling the
construction of complex networks.",1910.07196v1
2021-01-13,Interplay between friction and spin-orbit coupling as a source of spin polarization,"We study an effective one-dimensional quantum model that includes friction
and spin-orbit coupling (SOC), and show that the model exhibits spin
polarization when both terms are finite. Most important, strong spin
polarization can be observed even for moderate SOC, provided that friction is
strong. Our findings might help to explain the pronounced effect of chirality
on spin distribution and transport in chiral molecules. In particular, our
model implies static magnetic properties of a chiral molecule, which lead to
Shiba-like states when a molecule is placed on a superconductor, in accordance
with recent experimental data.",2101.05173v3
2017-09-18,Tunable Anomalous Andreev Reflection and Triplet Pairings in Spin Orbit Coupled Graphene,"We theoretically study scattering process and superconducting triplet
correlations in a graphene junction comprised of ferromagnet-RSO-superconductor
in which RSO stands for a region with Rashba spin orbit interaction. Our
results reveal spin-polarized subgap transport through the system due to an
anomalous equal-spin Andreev reflection in addition to conventional back
scatterings. We calculate equal- and opposite-spin pair correlations near the
F-RSO interface and demonstrate direct link of the anomalous Andreev reflection
and equal-spin pairings arised due to the proximity effect in the presence of
RSO interaction. Moreover, we show that the amplitude of anomalous Andreev
reflection, and thus the triplet pairings, are experimentally controllable when
incorporating the influences of both tunable strain and Fermi level in the
nonsuperconducting region. Our findings can be confirmed by a conductance
spectroscopy experiment and provide better insights into the proximity-induced
RSO coupling in graphene layers reported in recent experiments.",1709.06150v2
2017-11-07,Room temperature magneto-optic effect in silicon light-emitting diodes,"In weakly spin-orbit coupled materials, the spin-selective nature of
recombination can give rise to large magnetic-field effects, for example on
electro-luminescence from molecular semiconductors. While silicon has weak
spin-orbit coupling, observing spin-dependent recombination through
magneto-electroluminescence is challenging due to the inefficiency of emission
due to silicon's indirect band-gap, and to the difficulty in separating
spin-dependent phenomena from classical magneto-resistance effects. Here we
overcome these challenges to measure magneto-electroluminescence in silicon
light-emitting diodes fabricated via gas immersion laser doping. These devices
allow us to achieve efficient emission while retaining a well-defined geometry
thus suppressing classical magnetoresistance effects to a few percent. We find
that electroluminescence can be enhanced by up to 300\% near room temperature
in a seven Tesla magnetic field showing that the control of the spin degree of
freedom can have a strong impact on the efficiency of silicon LEDs.",1711.02451v1
2018-06-19,Evidence for a quantum-spin-Hall phase in graphene decorated with Bi2Te3 nanoparticles,"Realization of the quantum-spin-Hall effect in graphene devices has remained
an outstanding challenge dating back to the inception of the field of
topological insulators. Graphene's exceptionally weak spin-orbit coupling
-stemming from carbon's low mass- poses the primary obstacle. We experimentally
and theoretically study artificially enhanced spin-orbit coupling in graphene
via random decoration with dilute Bi2Te3 nanoparticles. Remarkably,
multi-terminal resistance measurements suggest the presence of helical edge
states characteristic of a quantum-spin-Hall phase; the magnetic-field and
temperature dependence of the resistance peaks, X-ray photoelectron spectra,
scanning tunneling spectroscopy, and first-principles calculations further
support this scenario. These observations highlight a pathway to spintronics
and quantum-information applications in graphene-based quantum-spin-Hall
platforms.",1806.07027v4
2019-02-17,Experimental realization of a non-magnetic one-way spin switch,"Controlling magnetism through non-magnetic means is highly desirable for
future electronic devices, as such means typically have ultra-low power
requirements and can provide coherent control. In recent years, great
experimental progress has been made in the field of electrical manipulation of
magnetism in numerous material systems. These studies generally do not consider
the directionality of the applied non-magnetic potentials and/or magnetism
switching. Here, we theoretically conceive and experimentally demonstrate a
non-magnetic one-way spin switch device using a spin-orbit coupled
Bose-Einstein condensate subjected to a moving spin-independent dipole
potential. The physical foundation of this unidirectional device is based on
the breakdown of Galilean invariance in the presence of spin-orbit coupling.
Such a one-way spin switch opens an avenue for designing novel quantum devices
with unique functionalities and may facilitate further experimental
investigations of other one-way spintronic and atomtronic devices.",1902.06321v1
2019-02-25,Spin-orbit-induced hole spin relaxation in a quantum dot molecule: the effect of $s$-$p$ coupling,"We study the effect of the coupling between the hole $s$ shell of one quantum
dot and the $p$ shell in the other dot forming a quantum dot molecule on the
spin relaxation between the sublevels of the hole $s$ state. Using an effective
model that captures the spin-orbit effects in the $p$ shell irrespective of
their origin, we show that the strong spin mixing in the $p$ shell can be
transferred to the $s$ shell of the other dot, leading to enhanced spin
relaxation in a certain energy range around the $s$-$p$ resonance if the dots
are misaligned and the magnetic field is tilted from the sample plane.",1902.09161v1
2019-04-19,A microscopic description for polarization in particle scatterings,"We propose a microscopic description for the polarization from the first
principle through the spin-orbit coupling in particle collisions. The model is
different from previous ones based on local equilibrium assumptions for the
spin degree of freedom. It is based on scatterings of particles as wave
packets, an effective method to deal with particle scatterings at specified
impact parameters. The polarization is then the consequence of particle
collisions in a non-equilibrium state of spins. The spin-vorticity coupling
naturally emerges from the spin-orbit one encoded in polarized scattering
amplitudes of collisional integrals when one assumes local equilibrium in
momentum but not in spin.",1904.09152v1
2021-04-28,Spin and anomalous Hall effects emerging from topological degeneracy in Dirac fermion system CuMnAs,"Orthorhombic CuMnAs has been proposed as an antiferromagnetic semimetal
hosting nodal line and Dirac points around the Fermi level. We investigate
relations between the topological bands and transport phenomena, i.e. spin Hall
effect and anomalous Hall effect, in orthorhombic CuMnAs with first-principles
calculations combined with symmetry analysis of magnetic structures and of
(spin) Berry curvature. We show the nodal line gapped with spin-orbit coupling
in CuMnAs dominantly generates large spin Hall conductivity in the ground
state. Although the magnetic symmetry in the ground state of CuMnAs forbids the
finite anomalous Hall effect, applied magnetic fields produce a significant
anomalous component of the Hall conductivity with the magnetic symmetry
breaking. We identify that the dominant contribution to anomalous Hall
components comes from further lifting of band degeneracy under external
magnetic fields for the Bloch states generated with splitting of nodal lines by
spin-orbit coupling near Fermi energy.",2104.13704v1
2021-07-06,Spin-valley Silin modes in graphene with substrate-induced spin-orbit coupling,"In the presence of external magnetic field the Fermi-liquid state supports
oscillatory spin modes known as Silin modes. We predict the existence of the
generalized Silin modes in a multivalley system, monolayer graphene. A gauge-
and Berry-gauge- invariant kinetic equation for a multivalley Fermi liquid is
developed and applied to the case of graphene with extrinsic spin-orbit
coupling (SOC). The interplay of SOC and Berry curvature allows for the
excitation of generalized Silin modes in the spin and valley-staggered-spin
channels via an AC electric field. The resonant contributions from these modes
to the optical conductivity are calculated.",2107.02819v1
2021-09-15,Lasing in the Rashba-Dresselhaus spin-orbit coupling regime in a dye-filled liquid crystal optical microcavity,"In the presence of Rashba-Dresselhaus coupling, strong spin-orbit
interactions in liquid crystal optical cavities result in a distinctive
spin-split entangled dispersion. Spin coherence between such modes give rise to
an optical persistent-spin-helix. In this letter, we introduce optical gain in
such a system, by dispersing a molecular dye in a liquid-crystal microcavity.
We demonstrate both lasing in the Rashba-Dresselhaus regime and the emergence
of an optical persistent spin helix.",2109.07338v1
2022-03-01,turboMagnon -- A code for the simulation of spin-wave spectra using the Liouville-Lanczos approach to time-dependent density-functional perturbation theory,"We introduce turboMagnon, an implementation of the Liouville-Lanczos approach
to linearized time-dependent density-functional theory, designed to simulate
spin-wave spectra in solid-state materials. The code is based on the
noncollinear spin-polarized framework and the self-consistent inclusion of
spin-orbit coupling that allow to model complex magnetic excitations. The spin
susceptibility matrix is computed using the Lanczos recursion algorithm that is
implemented in two flavors - the non-Hermitian and the pseudo-Hermitian one.
turboMagnon is open-source software distributed under the terms of the GPL as a
component of Quantum ESPRESSO. As with other components, turboMagnon is
optimized to run on massively parallel architectures using native mathematical
libraries (LAPACK and FFTW) and a hierarchy of custom parallelization layers
built on top of MPI. The effectiveness of the code is showcased by computing
magnon dispersions for the CrI$_3$ monolayer, and the importance of the
spin-orbit coupling is discussed.",2203.01120v2
2022-11-17,Uncovering hidden spin polarization of energy bands in antiferromagnets,"Many textbook physical effects in crystals are enabled by some specific
symmetries. In contrast to such ""apparent effects"", ""hidden effect X"" refers to
the general condition where the nominal global system symmetry would disallow
the effect X, whereas the symmetry of local sectors within the crystal would
enable effect X. Known examples include the hidden Rashba and/or hidden
Dresselhaus spin polarization that require spin orbit coupling, but (unlike the
apparent Rashba and Dresselhaus counterparts) can exist even in
inversion-symmetric non-magnetic crystals. Here we point out that the spin
splitting effect that does not require spin-orbit coupling (SOC) can have a
hidden spin polarization counterpart in antiferromagnets. We show that such
hidden, SOC-independent effects reflect intrinsic properties of the perfect
crystal rather than an effect due to imperfections, opening the possibility for
experimental realization, and offering a potential way to switch
antiferromagnetic ordering.",2211.09921v1
2023-05-17,Emergence of a spin microemulsion in spin-orbit coupled Bose-Einstein condensates,"We report the first numerical prediction of a ""spin microemulsion"" -- a phase
with undulating spin domains resembling classical bicontinuous
oil-water-surfactant emulsions -- in two-dimensional systems of spinor
Bose-Einstein condensates with isotropic Rashba spin-orbit coupling. Using
field-theoretic numerical simulations, we investigated the melting of a
low-temperature stripe phase with supersolid character and find that the
stripes lose their superfluidity at elevated temperature and undergo a
Kosterlitz--Thouless-like transition into a spin microemulsion. Momentum
distribution calculations highlight a thermally broadened occupation of the
Rashba circle of low-energy states with macroscopic and isotropic occupation
around the ring. We provide a finite-temperature phase diagram that positions
the emulsion as an intermediate, structured isotropic phase with residual
quantum character before transitioning at higher temperature into a
structureless normal fluid.",2305.10390v3
2023-06-07,Structural Relaxation of Materials with Spin-Orbit Coupling: Analytical Forces in Spin-Current DFT,"Analytical gradients of the total energy are provided for local density and
generalized-gradient hybrid approximations to generalized Kohn-Sham
spin-current density functional theory (SCDFT). It is shown that gradients may
be determined analytically, in a two-component framework, including spin-orbit
coupling (SOC), with high accuracy. We demonstrate that renormalization of the
electron-electron potential by SOC-induced spin-currents can account for
considerable modification of crystal structures. In the case of Iodine-based
molecular crystals, the effect may amount to more than half of the total
modification of the structure by SOC. Such effects necessitate an SCDFT, rather
than DFT, formulation, in which exchange-correlation functionals are endowed
with an explicit dependence on spin-current densities. An implementation is
presented in the \textsc{Crystal} program.",2306.04309v2
2023-10-02,Spin-orbit enabled unconventional Stoner magnetism,"The Stoner instability remains a cornerstone for understanding metallic
ferromagnets. This instability captures the interplay of Coulomb repulsion,
Pauli exclusion, and two-fold fermionic spin degeneracy. In materials with
spin-orbit coupling, this fermionic spin is generalized to a two-fold
degenerate pseudospin which is typically believed to have symmetry properties
as spin. Here we identify a distinct symmetry of this pseudospin that forbids
it to couple to a Zeeman field. This `spinless' property is required to exist
in five non-symmorphic space groups and has non-trivial implications for
superconductivity and magnetism. With Coulomb repulsion, Fermi surfaces
composed primarily of this spinless pseudospin feature give rise to Stoner
instabilities into magnetic states that are qualitatively different than
ferromagnets. These spinless-pseudospin ferromagnets break time-reversal
symmetry, have a vanishing magnetization, are non-collinear, and exhibit
altermagnetic-like energy band spin-splittings. In superconductors, for all
pairing symmetries and field orientations, this spinless pseudospin
extinguishes paramagnetic limiting. We discuss applications to superconducting
UCoGe and magnetic NiS$_{2-x}$Se$_x$.",2310.00838v2
2023-10-18,Chiral topological metals with multiple types of quasiparticle fermions and large spin Hall effect in the SrGePt family materials,"We present a prediction of chiral topological metals with several classes of
unconventional quasiparticle fermions in a family of SrGePt-type materials in
terms of first-principles calculations. In these materials, fourfold spin-3/2
Rarita-Schwinger-Weyl (RSW) fermion, sixfold excitation, and Weyl fermions
coexist around the Fermi level as spin-orbit coupling is considered, and the
Chern number for the first two kinds of fermions is the maximal value four. We
found that large Fermi arcs from spin-3/2 RSW fermion emerge on the
(010)-surface, spanning the whole surface Brillouin zone. Moreover, there exist
Fermi arcs originating from Weyl points, which further overlap with trivial
bulk bands. In addition, we revealed that the large spin Hall conductivity can
be obtained, which attributed to the remarkable spin Berry curvature around the
degenerate nodes and band-splitting induced by spin-orbit coupling. Our
findings indicate that the SrGePt family of compounds provide an excellent
platform for studying on topological electronic states and the intrinsic spin
Hall effect.",2310.11668v1
2019-03-12,Anomalous spin Nernst effect in Weyl semimetals,"The spin Nernst effect describes a transverse spin current induced by the
longitudinal thermal gradient in a system with the spin-orbit coupling. Here we
study the spin Nernst effect in a mesoscopic four-terminal cross-bar Weyl
semimetal device under a perpendicular magnetic field. By using the
tight-binding Hamiltonian combining with the nonequilibrium Green's function
method, the three elements of the spin current in the transverse leads and then
spin Nernst coefficients are obtained. The results show that the spin Nernst
effect in the Weyl semimetal has the essential difference with the traditional
one: The z direction spin currents is zero without the magnetic field while it
appears under the magnetic field, and the x and y direction spin currents in
the two transverse leads flows out or flows in together, in contrary to the
traditional spin Nernst effect, in which the spin current is induced by the
spin-orbit coupling and flows out from one lead and flows in on the other. So
we call it the anomalous spin Nernst effect. In addition, we show that the Weyl
semimetals have the center-reversal-type symmetry, the mirror-reversal-type
symmetry and the electron-hole-type symmetry, which lead to the spin Nernst
coefficients being odd function or even function of the Fermi energy, the
magnetic field and the transverse terminals. Moreover, the spin Nernst effect
in the Weyl semimetals are strongly anisotropic and its coefficients are
strongly dependent on both the direction of thermal gradient and the direction
of the transverse lead connection. Three non-equivalent connection modes (x-z,
z-x and x-y modes) are studied in detail, and the spin Nernst coefficients for
three different modes exhibit very different behaviors. These strongly
anisotropic behaviors of the spin Nernst effect can be used as the
characterization of magnetic Weyl semimetals.",1903.04848v1
2012-07-11,Superfluidity and collective modes in Rashba spin-orbit coupled Fermi gases,"We present a theoretical study of the superfluidity and the corresponding
collective modes in two-component atomic Fermi gases with s-wave attraction and
synthetic Rashba spin-orbit coupling. The general effective action for the
collective modes is derived from the functional path integral formalism. By
tuning the spin-orbit coupling from weak to strong, the system undergoes a
crossover from an ordinary BCS/BEC superfluid to a Bose-Einstein condensate of
rashbons. We show that the properties of the superfluid density and the
Anderson-Bogoliubov mode manifest this crossover. At large spin-orbit coupling,
the superfluid density and the sound velocity become independent of the
strength of the s-wave attraction. The two-body interaction among the rashbons
is also determined. When a Zeeman field is turned on, the system undergoes
quantum phase transitions to some exotic superfluid phases which are
topologically nontrivial. For the two-dimensional system, the nonanalyticities
of the thermodynamic functions and the sound velocity across the phase
transition are related to the bulk gapless fermionic excitation which causes
infrared singularities. The superfluid density and the sound velocity behave
nonmonotonically: they are suppressed by the Zeeman field in the normal
superfluid phase, but get enhanced in the topological superfluid phase. The
three-dimensional system is also studied.",1207.2810v4
2012-07-24,Unusual Zeeman-field effects in two-dimensional spin-orbit-coupled Fermi superfluids,"We investigate the Zeeman field effects on the bulk superfluid properties and
the collective modes in two-dimensional (2D) attractive atomic Fermi gases with
Rashba-type spin-orbit coupling. In the presence of a large spin-orbit
coupling, the system undergoes a quantum phase transition to a topological
superfluid state at a critical Zeeman field. We show that the nonanalyticities
of the thermodynamic functions as well as other physical quantities at the
quantum phase transition originate from the infrared singularities caused by
the gapless fermionic spectrum. The same argument applies also to the BCS-BEC
evolution in 2D fermionic superfluids with $p$- or d-wave pairing. The
superfluid density $n_s$ and the velocity of the Goldstone sound mode $c_s$
behave oppositely in the normal and the topological superfluid phases: they are
suppressed by the Zeeman field in the normal superfluid phase, but get enhanced
in the topological superfluid phase. The velocity of the Goldstone sound mode
also shows nonanalyticity at the quantum phase transition. For large Zeeman
field, we find $n_s\rightarrow n$ and $c_s\rightarrow \upsilon_{\rm F}$, where
$n$ is the total fermion density and $\upsilon_{\rm F}$ is the Fermi velocity
of noninteracting system. The unusual behavior of the superfluid density and
the collective modes can be understood by the fact that the spin-orbit-coupled
superfluid state at large Zeeman field can be mapped to the $p_x+ip_y$
superfluid state of spinless fermions.",1207.5685v2
2014-10-13,Topological Fulde-Ferrell Superfluids of a Spin-Orbit Coupled Fermi Gas,"Topological Fermi superfluids have played the central role in various fields
of physics. However, all previous studies focus on the cases where Cooper pairs
have zero center-of-mass momenta (i.e. normal superfluids). The topology of
Fulde-Ferrell superfluids with nonzero momentum pairings have never been
explored until recent findings that Fulde-Ferrell superfluids in a spin-orbit
coupled Fermi gas can accommodate Majorana fermions in real space in low
dimensions and Weyl fermions in momentum space in three dimension. In this
review, we first discuss the mechanism of pairings in spin-orbit coupled Fermi
gases in optical lattices subject to Zeeman fields, showing that spin-orbit
coupling as well as Zeeman fields enhance Fulde-Ferrell states while suppress
Larkin-Ovchinnikov states. We then present the low temperature phase diagram
including both FF superfluids and topological FF superfluids phases in both two
dimension and three dimension. In one dimension, Majorana fermions as well as
phase dependent order parameter are visualized. In three dimension, we show the
properties of Weyl fermions in momentum space such as anisotropic linear
dispersion, Fermi arch, and gaplessness away from $k_{\perp}=0$. Finally, we
discuss some possible methods to probe FF superfluids and topological FF
superfluids in cold atom systems.",1410.3497v2
2014-10-16,Impurity-induced bound states in superconductors with spin-orbit coupling,"We study the effect of strong spin-orbit coupling (SOC) on bound states
induced by impurities in superconductors. The presence of spin-orbit coupling
breaks the $\mathbb{SU}(2)$-spin symmetry and causes the superconducting order
parameter to have generically both singlet (s-wave) and triplet (p-wave)
components. We find that in the presence of SOC the spectrum of
Yu-Shiba-Rusinov (YSR) states is qualitatively different in s-wave and p-wave
superconductor, a fact that can be used to identify the superconducting pairing
symmetry of the host system. We also predict that in the presence of SOC the
spectrum of the impurity-induced bound states depends on the orientation of the
magnetic moment $\bf{S}$ of the impurity and, in particular, that by changing
the orientation of $\bf{S}$ the fermion-parity of the lowest energy bound state
can be tuned. We then study the case of a dimer of magnetic impurities and show
that in this case the YSR spectrum for a p-wave superconductor is qualitatively
very different from the one for an s-wave superconductor even in the limit of
vanishing SOC. Our predictions can be used to distinguish the symmetry of the
order parameter and have implications for the Majorana proposals based on
chains of magnetic atoms placed on the surface of superconductors with strong
spin-orbit coupling.",1410.4558v3
2015-12-01,Quench dynamics of a Bose-Einstein condensate under synthetic spin-orbit coupling,"We study the quench dynamics of a Bose-Einstein condensate under a
Raman-assisted synthetic spin-orbit coupling. To model the dynamical process,
we adopt a self-consistent Bogoliubov approach, which is equivalent to applying
the time-dependent Bogoliubov-de-Gennes equations. We investigate the dynamics
of the condensate fraction as well as the momentum distribution of the Bose gas
following a sudden change of system parameters. Typically, the system evolves
into a steady state in the long-time limit, which features an oscillating
momentum distribution and a stationary condensate fraction which is dependent
on the quench parameters. We investigate how different quench parameters such
as the inter- and intra-species interactions and the spin-orbit-coupling
parameters affect the condensate fraction in the steady state. Furthermore, we
find that the time average of the oscillatory momentum distribution in the
long-time limit can be described by a generalized Gibbs ensemble with two
branches of momentum-dependent Gibbs temperatures. Our study is relevant to the
experimental investigation of dynamical processes in a spin-orbit coupled
Bose-Einstein condensate.",1512.00160v3
2020-01-23,First- and Second-Order Topological Superconductivity and Temperature-Driven Topological Phase Transitions in the Extended Hubbard Model with Spin-Orbit Coupling,"The combination of spin-orbit coupling with interactions results in many
exotic phases of matter. In this Letter, we investigate the superconducting
pairing instability of the two-dimensional extended Hubbard model with both
Rashba and Dresselhaus spin-orbit coupling within the mean-field level at both
zero and finite temperature. We find that both first- and second-order
time-reversal symmetry breaking topological gapped phases can be achieved under
appropriate parameters and temperature regimes due to the presence of a favored
even-parity $s+id$-wave pairing even in the absence of an external magnetic
field or intrinsic magnetism. This results in two branches of chiral Majorana
edge states on each edge or a single zero-energy Majorana corner state at each
corner of the sample. Interestingly, we also find that not only does tuning the
doping level lead to a direct topological phase transition between these two
distinct topological gapped phases, but also using the temperature as a highly
controllable and reversible tuning knob leads to different direct
temperature-driven topological phase transitions between gapped and gapless
topological superconducting phases. Our findings suggest new possibilities in
interacting spin-orbit coupled systems by unifying both first- and higher-order
topological superconductors in a simple but realistic microscopic model.",2001.08739v2
2021-12-26,Information theoretic approach to effects of spin-orbit coupling in Bose-Einstein condensates,"We make use of Shannon entropy ($S$) and Fisher information ($I$) to study
the response of atomic density profiles of a spin-orbit coupled Bose-Einstein
condensate to changes in the wave number ($\kappa_L$) of the Raman laser that
couples two hyperfine states of atoms in the condensate. The choice for values
of $\kappa_L$, the so-called spin-orbit parameter, and Rabi frequency
($\Omega$) leads to two distinct regions in the system's energy spectrum with
different order parameters and/or probability densities. In addition, we can
have a spatially modulated density profile, reminiscent of the so called stripe
phase. Our numbers for $S$ and $I$ demonstrate that for $\kappa_L^2<\Omega$
(region 1) the density profile becomes localized as $\kappa_L$ increases while
we observe delocalization in the density distribution for $\kappa_L^2>\Omega$
(region 2) for increasing values of $\kappa_L$. In the stripe phase the nature
of $S$ and $I$ to changes in $\kappa_L$ is similar to that found for the
condensate in region 2. The results for information theoretic quantities in the
stripe phase are, in general, augmented compared to those of region 2. In
particular, the highly enhanced values of position-space Fisher information
imply an extremely concentrated atomic density distribution to provide an
evidence for supersolid properties of Bose-Einstein condensates in the presence
of spin-orbit coupling.",2112.13417v1
2023-03-29,The Mott transition in the 5d$^1$ compound Ba$_2$NaOsO$_6:$ a DFT+DMFT study with PAW spinor projectors,"Spin-orbit coupling has been reported to be responsible for the insulating
nature of the 5d$^1$ osmate double perovskite Ba$_2$NaOsO$_6$ (BNOO). However,
whether spin-orbit coupling indeed drives the metal-to-insulator transition
(MIT) in this compound is an open question. In this work we investigate the
impact of relativistic effects on the electronic properties of BNOO via density
functional theory plus dynamical mean-field theory calculations in the
paramagnetic regime, where the insulating phase is experimentally observed. The
correlated subspace is modeled with spinor projectors of the projector
augumented wave method (PAW) employed in the Vienna Ab Initio Simulation
Package (VASP), suitably interfaced with the TRIQS package. The inclusion of
PAW spinor projectors in TRIQS enables the treatment of spin-orbit coupling
effects fully ab-initio within the dynamical mean-field theory framework. In
the present work, we show that spin-orbit coupling, although assisting the MIT
in BNOO, is not the main driving force for its gapped spectra, placing this
material in the Mott insulator regime. Relativistic effects primarily impact
the correlated states' character, excitations, and magnetic ground-state
properties.",2303.16560v2
2023-08-09,Magnetic Properties and Spin-orbit Coupling induced Semiconductivity in LK-99,"Recent reports of a possible room-temperature superconductor called LK-99
have generated a lot of attention worldwide. In just a few days, a large amount
of experimental works attempted to reproduce this sample and verify its
properties. At the same time a large amount of theoretical works have also been
reported. However, many experiments have drawn different conclusions, and many
theoretical results are not consistent with experimental results. For one of
the structures of LK-99 with the chemical formula as Pb9Cu(PO4)6O, many
first-principles calculations did not consider spin-orbit coupling and
concluded that it is a flat band metal. However, spin-orbit coupling is often
not negligible in systems with heavy elements, and LK-99 contains a large
amount of heavy element Pb. We performed calculations of electronic structure
of Pb9Cu(PO4)6O with spin-orbit coupling, and the results show that it's not a
metal but a semiconductor. This is consistent with many experimental results.
In the ferromagnetic state Pb9Cu(PO4)6O is an indirect-bandgap semiconductor
with a bandgap of 292 meV. Moreover, its conduction band is a flat band. At an
electron doping level of 0.5 e/unit cell, Pb9Cu(PO4)6O becomes metallic and has
a flat band with a width of only 25 meV at the Fermi level in the ferromagnetic
state. While in the antiferromagnetic-A state, Pb9Cu(PO4)6O is a direct-bandgap
semiconductor with a bandgap of 300 meV. As a magnetic narrowband
semiconductor, Pb9Cu(PO4)6O may have potential application value in the field
of optoelectronic device, photocatalytic, photodetector and spintronics device.",2308.05134v2
2012-06-10,Topological Superconductivity without Proximity Effect,"Majorana Fermions, strange particles that are their own antiparticles, were
predicted in 1937 and have been sought after ever since. In condensed matter
they are predicted to exist as vortex core or edge excitations in certain
exotic superconductors. These are topological superconductors whose order
parameter phase winds non-trivially in momentum space. In recent years, a new
and promising route for realizing topological superconductors has opened due to
advances in the field of topological insulators. Current proposals are based on
semiconductor heterostructures, where spin-orbit coupled bands are split by a
band gap or Zeeman field and superconductivity is induced by proximity to a
conventional superconductor. Topological superconductivity is obtained in the
interface layer. The proposed heterostructures typically include two or three
layers of different materials. In the current work we propose a device based on
materials with inherent spin-orbit coupling and an intrinsic tendency for
superconductivity, eliminating the need for a separate superconducting layer.
We study a lattice model that includes spin-orbit coupling as well as on-site
and nearest neighbor interaction. Within this model we show that topological
superconductivity is possible in certain regions of parameter space. These
regions of non-trivial topology can be understood as a nodeless superconductor
with d-wave symmetry which, due to the spin-orbit coupling, acquires an extra
phase twist of $2\pi$.",1206.2028v2
2013-12-29,Artificial Gauge Fields and Spin-Orbit Couplings in Cold Atom Systems,"This article is a report of Projet bibliographique of M1 at \'Ecole Normale
Sup\'erieure. In this article we reviewed the historical developments in
artificial gauge fields and spin-orbit couplings in cold atom systems. We
resorted to origins of literatures to trace the ideas of the developments. For
pedagogical purposes, we tried to work out examples carefully and clearly, to
verified the validity of various approximations and arguments in detail, and to
give clear physical and mathematical pictures of the problems that we
discussed. The first part of this article introduced the fundamental concepts
of Berry phase and Jaynes-Cummings model. The second part reviewed two schemes
to generate artificial gauge fields with N-pod scheme in cold atom systems. The
first one is based on dressed-atom picture which provide a method to generate
non-Abelian gauge fields with dark states. The second one is about rotating
scheme which is achieved earlier historically. Non-Abelian gauge field
inevitably leads to spin-orbit coupling. We reviewed some developments in
achieve spin-orbital coupling theoretically and experimentally. The fourth part
was devoted to recently developed idea of optical flux lattice that provides a
possibility to reach the strongly correlated regime in cold atom systems. We
developed a geometrical interpretation based on Cooper's theory. Some useful
formulae and their proofs were listed in the Appendix.",1312.7486v1
2014-11-16,Distinguishing spin-orbit coupling and nematic order in the electronic spectrum of iron-based superconductors,"The low-energy electronic states of the iron-based superconductors are
strongly affected by both spin-orbit coupling and, when present, by the nematic
order. These two effects have different physical origins, yet they can lead to
similar gap features in the electronic spectrum. Here we show how to
disentangle them experimentally in the iron superconductors with one Fe plane
per unit cell. Although the splitting of the low energy doublet at the
Brillouin zone center ($\Gamma$-point) can be due to either the spin-orbit
coupling or the nematic order, or both, the degeneracy of each of the doublet
states at the zone corner ($M$-point) is protected by the space group symmetry
even when spin-orbit coupling is taken into account. Therefore, any splitting
at $M$ must be due to lowering of the crystal symmetry, such as due to the
nematic order. We further analyze a microscopic tight-binding model with two
different contributions to the nematic order: $d_{xz}/d_{yz}$ onsite energy
anisotropy and the $d_{xy}$ hopping anisotropy. We find that a precise
determination of the former, which has been widely used to characterize the
nematic phase, requires a simultaneous measurement of the splittings of the
$\Gamma$-point doublet and at the two low-energy $M$-point doublets. We also
discuss the impact of twin domains and show how our results shed new light on
ARPES measurements in the normal state of these materials.",1411.4303v1
2014-03-04,Universal Borromean Binding in Spin-Orbit Coupled Ultracold Fermi Gases,"Borromean rings and Borromean binding, a class of intriguing phenomena as
three objects are linked (bound) together while any two of them are unlinked
(unbound), widely exist in nature and have been found in systems of biology,
chemistry and physics. Previous studies have suggested that the occurrence of
such a binding in physical systems typically relies on the microscopic details
of pairwise interaction potentials at short-range, and is therefore
non-universal. Here, we report a new type of Borromean binding in ultracold
Fermi gases with Rashba spin-orbit coupling, which is {\it universal} against
short-range interaction details, with its binding energy only dependent on the
s-wave scattering length and the spin-orbit coupling strength. We show that the
occurrence of this universal Borromean binding is facilitated by the symmetry
of the single-particle dispersion under spin-orbit coupling, and is therefore
{\it symmetry-selective} rather than interaction-selective. The state is robust
over a wide range of mass ratio between composing fermions, which are
accessible by Li-Li, K-K and K-Li mixtures in cold atoms experiments. Our
results reveal the importance of symmetry factor in few-body physics, and shed
light on the emergence of new quantum phases in a many-body system with exotic
few-body correlations.",1403.0649v2
2016-11-09,Perturbational treatment of spin-orbit coupling for generally applicable high-level multi-reference methods,"An efficient perturbational treatment of spin-orbit coupling within the
framework of high-level multi-reference techniques has been implemented in the
most recent version of the COLUMBUS quantum chemistry package, extending the
existing fully variational two-component (2c) multi-reference configuration
interaction singles and doubles (MRCISD) method. The proposed scheme follows
related implementations of quasi-degenerate perturbation theory (QDPT) model
space techniques. Our model space is built either from uncontracted,
large-scale scalar relativistic MRCISD wavefunctions or based on the
scalar-relativistic solutions of the linear-response-theory-based
multi-configurational averaged quadratic coupled cluster method (LRT-MRAQCC).
The latter approach allows for a consistent, approximatively size-consistent
and size-extensive treatment of spin-orbit coupling. The approach is described
in detail and compared to a number of related techniques. The inherent accuracy
of the QDPT approach is validated by comparing cuts of the potential energy
surfaces of acrolein and its S, Se, and Te analoga with the corresponding data
obtained from matching fully variational spin-orbit MRCISD calculations. The
conceptual availability of approximate analytic gradients with respect to
geometrical displacements is an attractive feature of the 2c-QDPT-MRCISD and
2c-QDPT-LRT-MRAQCC methods for structure optimization and ab inito molecular
dynamics simulations.",1611.02884v1
2018-05-31,Drag force and superfluidity in the supersolid stripe phase of a spin-orbit-coupled Bose-Einstein condensate,"The phase diagram of a spin-orbit-coupled two-component Bose gas includes a
supersolid stripe phase, which is featuring density modulations along the
direction of the spin-orbit coupling. This phase has been recently found
experimentally [J.~Li \textit{et al.}, Nature (London) \textbf{543}, 91
(2017)]. In the present work we characterize the superfluid behavior of the
stripe phase by calculating the drag force acting on a moving impurity. Because
of the gapless band structure of the excitation spectrum, the Landau critical
velocity vanishes if the motion is not strictly parallel to the stripes, and
energy dissipation takes place at any speed. Moreover, due to the spin-orbit
coupling, the drag force can develop a component perpendicular to the velocity
of the impurity. Finally, by estimating the time over which the energy
dissipation occurs, we find that for slow impurities the effects of friction
are negligible on a time scale up to several seconds, which is comparable with
the duration of a typical experiment.",1805.12552v3
2013-09-26,Spectral Properties and Local Density of States of Disordered Quantum Hall Systems with Rashba Spin-Orbit Coupling,"We theoretically investigate the spectral properties and the spatial
dependence of the local density of states (LDoS) in disordered two-dimensional
electron gases (2DEG) in the quantum Hall regime, taking into account the
combined presence of electrostatic disorder, random Rashba spin-orbit in-
teraction, and finite Zeeman coupling. To this purpose, we extend a
coherent-state Green's function formalism previously proposed for spinless 2DEG
in the presence of smooth arbitrary disorder, that here incorporates the
nontrivial coupling between the orbital and spin degrees of freedom into the
electronic drift states. The formalism allows us to obtain analytical and
controlled nonperturbative expressions of the energy spectrum in arbitrary
locally flat disorder potentials with both random electric fields and Rashba
coupling. As an illustration of this theory, we derive analytical microscopic
expressions for the LDoS in different temperature regimes which can be used as
a starting point to interpret scanning tunneling spectroscopy data at high
magnetic fields. In this context, we study the spatial dependence and linewidth
of the LDoS peaks and explain an experimentally-noticed correlation between the
spatial dispersion of the spin-orbit splitting and the local extrema of the
potential landscape.",1309.6977v2
2016-12-06,Thermal conductivity of local moment models with strong spin-orbit coupling,"We study the magnetic and lattice contributions to the thermal conductivity
of electrically insulating strongly spin-orbit coupled magnetically ordered
phases on a two-dimensional honeycomb lattice using the Kitaev-Heisenberg
model. Depending on model parameters, such as the relative strength of the
spin-orbit induced anisotropic coupling, a number of magnetically ordered
phases are possible. In this work, we study two distinct regimes of thermal
transport depending on whether the characteristic energy of the phonons or the
magnons dominates, and focus on two different relaxation mechanisms, boundary
scattering and magnon-phonon scattering. For spatially anisotropic magnetic
phases, the thermal conductivity tensor can be highly anisotropic when the
magnetic energy scale dominates, since the magnetic degrees of freedom dominate
the thermal transport for temperatures well below the magnetic transition
temperature. In the opposite limit in which the phonon energy scale dominates,
the thermal conductivity will be nearly isotropic, reflecting the isotropic (at
low temperatures) phonon dispersion assumed for the honeycomb lattice. We
further discuss the extent to which thermal transport properties are influenced
by strong spin-orbit induced anisotropic coupling in the local moment regime of
insulating magnetic phases. The developed methodology can be applied to any 2D
magnon-phonon system, and more importantly to systems where an analytical
Bogoliubov transformation cannot be found and magnon bands are not necessarily
isotropic.",1612.01658v1
2018-10-11,(2+1)$-dimensional sonic black hole from spin-orbit coupled Bose-Einstein condensate and its analogue Hawking radiation,"We study the properties of a $2+1$ dimensional Sonic black hole (SBH) that
can be realised, in a quasi-two-dimensional two-component spin-orbit coupled
Bose-Einstein condensate (BEC). The corresponding equation for phase
fluctuations in the total density mode that describes phonon field in the
hydrodynamic approximation is described by a scalar field equation in $2+1$
dimension whose space-time metric is significantly different from that of the
SBH realised from a single component BEC that was studied experimentally, and,
theoretically meticulously in literature. Given the breakdown of the
irrotationality constraint of the velocity field in such spin-orbit coupled
BEC, we study in detail how the time evolution of such condensate impacts the
various properties of the resulting SBH. By time evolving the condensate in a
suitably created laser-induced potential, we show that such a sonic black hole
is formed, in an annular region bounded by inner and outer event horizon as
well as elliptical ergo-surfaces. We observe amplifying density modulation due
to the formation of such sonic horizons and show how they change the nature of
analogue Hawking radiation emitted from such sonic black hole by evaluating the
density-density correlation at different times, using the truncated Wigner
approximation (TWA) for different values of spin-orbit coupling parameters. We
finally investigate the thermal nature of such analogue Hawking radiation.",1810.04860v3
2019-07-31,Spin-orbit coupled bosons interacting in a two-dimensional harmonic trap,"A system of bosons in a two-dimensional harmonic trap in the presence of
Rashba-type spin-orbit coupling is investigated. An analytic treatment of the
ground state of a single atom in the weak-coupling regime is presented and used
as a basis for a perturbation theory in the interacting two-boson system. The
numerical diagonalization of both the single-particle and the two-boson
Hamiltonian matrices allows us to go beyond those approximations and obtain not
only the ground state, but also the low-energy spectra and the different energy
contributions separately. We show that the expectation value of the spin-orbit
term is related to the expectation value of $\hat{\sigma}_z \hat{L}_z$ for the
eigenstates of the system, regardless of the trapping potential. The low-energy
states of the repulsively interacting two-boson system are characterized. With
the presence of a sufficiently strong interaction and spin-orbit coupling
strength, there is a direct energy-level crossing in the ground state of the
system between states of different $J_z$, the third component of the total
angular momentum, that changes its structure. This is reflected in a
discontinuity in the different energy terms and it is signaled in the spatial
density of the system.",1907.13355v2
2000-06-14,The Jahn-Teller theorem for the 3d magnetic ions,"We argue that the Jahn-Teller theorem, if applied to 3d-ion compounds, has to
be considered in the orbital+spin space. It is despite of the weakness of the
intraatomic spin-orbit coupling.",0006231v1
2021-11-15,Microscopic origin of multiferroic order in monolayer NiI$_2$,"The discovery of multiferroic behavior in monolayer NiI$_2$ provides a new
symmetry-broken state in van der Waals monolayers, featuring the simultaneous
emergence of helimagnetic order and ferroelectric order at a critical
temperature of $T=21$ K. However, the microscopic origin of multiferroic order
in NiI$_2$ monolayer has not been established, and in particular, the role of
non-colinear magnetism and spin-orbit coupling in this compound remains an open
problem. Here we reveal the origin of the two-dimensional multiferroicity in
NiI$_2$ using first-principles electronic structure methods. We show that the
helimagnetic state appears as a consequence of the long-range magnetic exchange
interactions, featuring sizable magnetic moments in the iodine atoms. We
demonstrate that the electronic density reconstruction accounting for the
ferroelectric order emerges from the interplay of non-collinear magnetism and
spin-orbit coupling. We demonstrate that the ferroelectric order is controlled
by the iodine spin-orbit coupling, and leads to an associated
electronically-driven distortion in the lattice. Our results establish the
microscopic origin of the multiferroic behavior in monolayer NiI$_2$, putting
forward the coexistence of helical magnetic order and ligand spin-orbit
coupling as driving forces for multiferroic behavior in two-dimensional
materials.",2111.07909v2
2022-01-05,Controllable nonreciprocal optical response and handedness-switching in magnetized spin orbit coupled graphene,"Starting from a low-energy effective Hamiltonian model, we theoretically
calculate the dynamical optical conductivity and permittivity tensor of a
magnetized graphene layer with Rashba spin orbit coupling (SOC). Our results
reveal a transverse Hall conductivity correlated with the usual nonreciprocal
longitudinal conductivity. Further analysis illustrates that for intermediate
magnetization strengths, the relative magnitudes of the magnetization and SOC
can be identified experimentally by two well-separated peaks in the dynamical
optical response (both the longitudinal and transverse components) as a
function of photon frequency. Moreover, the frequency dependent permittivity
tensor is obtained for a wide range of chemical potentials and magnetization
strengths. Employing experimentally realistic parameter values, we calculate
the circular dichroism of a representative device consisting of magnetized spin
orbit coupled graphene and a dielectric insulator layer, backed by a metallic
plate. The results reveal that this device has different relative
absorptivities for right-handed and left-handed circularly polarized
electromagnetic waves. It is found that the magnetized spin orbit coupled
graphene supports strong handedness-switchings, effectively controlled by
varying the chemical potential and magnetization strength with respect to the
SOC strength.",2201.01779v2
2022-05-23,Effect of spin-orbit coupling in one-dimensional quasicrystals with power-law hopping,"In the one-dimensional quasiperiodic Aubry-Andr\'{e}-Harper Hamiltonian with
nearest-neighbor hopping, all single-particle eigenstates undergo a phase
transition from ergodic to localized states at a critical disorder strength
$W_c/t = 2.0$. There is no mobility edge in this system. However, in the
presence of power-law hopping having the form $1/r^a$, beyond a critical
disorder strength mobility edge appears for $a > 1$, while, for $0< a\leq 1$, a
multifractal edge separates the extended and the multifractal states. In both
these limits, depending on the strength of the disorder, lowest $\beta^s L$
states are delocalized. We have found that, in the presence of the spin-orbit
coupling, the critical disorder strength is always larger irrespective of the
value of the parameter $a$. Furthermore, we demonstrate that for $a\leq 1$, in
the presence of spin-orbit coupling, there exists multiple multifractal edges,
and the energy spectrum splits up into alternative bands of delocalized and
multifractal states. Moreover, the location of the multifractal edges are
generally given by the fraction $(\beta^s \pm \beta^m)$. The qualitative
behavior of the energy spectrum remains unaffected for $a > 1$. However, in
contrast to the previously reported results, we find that in this limit,
similar to the other case, multiple mobility edges can exist with or without
the spin-orbit coupling.",2205.11305v1
2005-04-22,Rashba interaction in quantum wires with in-plane magnetic fields,"We analyze the spectral and transport properties of ballistic quasi
one-dimensional systems in the presence of spin-orbit coupling and in-plane
agnetic fields. Our results demonstrate that Rashba precession and intersubband
coupling must be treated on equal footing for wavevectors near the magnetic
field induced gaps. We find that intersubband coupling limits the occurrence of
negative effective masses at the gap edges and modifies the linear conductance
curves in the strong coupling limit. The effect of the magnetic field on the
spin textured orientation of the wire magnetization is discussed.",0504578v2
2014-07-21,Optical spin-to-orbital angular momentum conversion in ultra-thin metasurfaces with arbitrary topological charges,"Orbital angular momentum associated with the helical phase-front of optical
beams provides an unbounded \qo{space} for both classical and quantum
communications. Among the different approaches to generate and manipulate
orbital angular momentum states of light, coupling between spin and orbital
angular momentum allows a faster manipulation of orbital angular momentum
states because it depends on manipulating the polarisation state of light,
which is simpler and generally faster than manipulating conventional orbital
angular momentum generators. In this work, we design and fabricate an
ultra-thin spin-to-orbital angular momentum converter, based on plasmonic
nano-antennas and operating in the visible wavelength range that is capable of
converting spin to an arbitrary value of OAM $\ell$. The nano-antennas are
arranged in an array with a well-defined geometry in the transverse plane of
the beam, possessing a specific integer or half-integer topological charge $q$.
When a circularly polarised light beam traverses this metasurface, the output
beam polarisation switches handedness and the OAM changes in value by $\ell =
\pm2q\hbar$ per photon. We experimentally demonstrate $\ell$ values ranging
from $\pm 1$ to $\pm 25$ with conversion efficiencies of $8.6\pm0.4~\%$. Our
ultra-thin devices are integratable and thus suitable for applications in
quantum communications, quantum computations and nano-scale sensing.",1407.5491v1
2015-06-03,Large orbital moment and spin-orbit enabled Mott transition in the Ising Fe honeycomb lattice BaFe2(PO4)2,"BaFe2(PO4)2 is an unusual Ising insulating ferromagnet based on the Fe$^{2+}$
spin $S$ = 2 ion, the susceptibility of which suggests a large orbital
component to the Fe local moment. We apply density functional theory based
methods to obtain a microscopic picture of the competing interactions and the
critical role of spin-orbit coupling (SOC) in this honeycomb lattice system.
The low-temperature ferromagnetic phase displays a half-semimetallic Dirac
point pinning the Fermi level and preventing gap opening before consideration
of SOC, presenting a case in which correlation effects modeled by a repulsive
Hubbard $U$ fail to open a gap. Simultaneous inclusion of both correlation and
SOC drives a large orbital moment in excess of 0.7 $\mu_B$ (essentially $L$ =
1) for spin aligned along the $\hat{c}$ axis, with a gap comparable with the
inferred experimental value. The large orbital moment accounts for the large
Ising anisotropy, in spite of the small magnitude of the SOC strength on the
3$d$ (Fe) ion. Ultimately, the Mott-Hubbard gap is enabled by degeneracy
lifting by SOC and the large Fe moments, rather than by standard Hubbard
interactions alone. We suggest that competing orbital occupations are
responsible for the structural transitions involved in the observed re-entrant
rhombohedral-triclinic-rhombohedral sequence.",1506.01413v2
2018-02-23,Nonlocal orbital magnetism of 3d adatoms deposited on the Pt(111) surface,"The orbital magnetic moment is still surprisingly not well understood, in
contrast to the spin part. Its description in finite systems, such as isolated
atoms and molecules, is not problematic, but it was only recently that a
rigorous picture was provided for extended systems. Here we focus on an
intermediate class of systems: magnetic adatoms placed on a non-magnetic
surface. We show that the essential quantity is the ground-state charge current
density, in the presence of spin-orbit coupling, and set out its
first-principles description. This is illustrated by studying the magnetism of
the surface Pt electrons, induced by the presence of Cr, Mn, Fe, Co and Ni
adatoms. A physically appealing partition of the charge current is introduced.
This reveals that there is an important nonlocal contribution to the orbital
moments of the Pt atoms, extending three times as far from each magnetic adatom
as the induced spin and local orbital moments. We find that it is as sizable as
the latter, and attribute its origin to a spin-orbital susceptibility of the Pt
surface, different from the one responsible for the formation of the local
orbital moments.",1802.08609v1
2020-06-14,Intrinsic orbital and spin Hall effects in monolayer transition metal dichalcogenides,"Orbital Hall effect (OHE) is the phenomenon of transverse flow of orbital
moment in presence of an applied electric field. Solids with broken inversion
symmetry are expected to exhibit a strong OHE due to the presence of an
intrinsic orbital moment at individual momentum points in the Brillouin zone,
which in presence of an applied electric field, flows in different directions
causing a net orbital Hall current. Here we provide a comprehensive
understanding of the effect and its tunability in the monolayer 2D transition
metal dichalcogenides (TMDCs). Both metallic and insulating TMDCs are
investigated from full density-functional calculations, effective $d$-band
tight-binding models, as well as a minimal four-band model for the valley
points that captures the key physics of the system. For the tuning of the OHE,
we examine the role of hole doping as well as the change in the band
parameters, which, e. g., can be controlled by strain. We demonstrate that the
OHE is a more fundamental effect than the spin Hall effect (SHE), with the
momentum-space orbital moments inducing a spin moment in the presence of the
spin-orbit coupling, leading to the SHE. The physics of the OHE, described
here, is relevant for 2D materials with broken inversion symmetry in general,
even beyond the TMDCs, providing a broad platform for future research.",2006.07754v2
2010-12-10,Density functional study of orbital-selective magnetism in FeAs-based superconductors,"We performed spin-polarized density functional calculations of
lanthanide-series (Ln) iron oxypnictides LnFeAsO (Ln=La, Ce, Pr, Nd, Sm, and
Gd) with constrained Fe magnetic moments, finding that in-plane dxy and
out-of-plane dyz orbital characters are preferred for small Fe magnetic
moments. Comparison of LnFeAsO compounds shows that the antiferromagnetism
(AFM) from the Fe dxy orbital is itinerantly driven by orbital-dependent
Fermi-surface nesting while AFM from the Fe dyz orbital is driven by
superexchange mechanism. The Fe magnetic moments of the two orbital characters
show different coupling strengths to Fermi-surface electrons
orbital-selectively, suggesting that they may play different roles in
superconductivity and in AFM, and making d orbital characters of the magnetic
moment resolvable by measuring the electronic structures.",1012.2224v2
2018-11-08,Magnetically-driven orbital-selective insulator-metal transition in double perovskite oxides,"Interaction-driven metal-insulator transitions or Mott transitions
  are widely observed in condensed-matter systems. In multi-orbital
  systems, many-body physics is richer in which an orbital-selective
  metal-insulator transition is an intriguing and unique
  phenomenon. Here we use first-principles calculations to show that a
  magnetic transition (from paramagnetic to long-range magnetically
  ordered) can simultaneously induce an orbital-selective
  insulator-metal transition in rock-salt ordered double perovskite
  oxides $A_2BB'$O$_6$ where $B$ is a non-magnetic ion (Y$^{3+}$ and
  Sc$^{3+}$) and $B'$ a
  magnetic ion with a $d^3$ electronic configuration (Ru$^{5+}$ and
  Os$^{5+}$). The orbital selectivity originates from
  geometrical frustration of a face-centered-cubic lattice on which
  the magnetic ions $B'$ reside. Including realistic structural
  distortions and spin-orbit interaction do
  not affect the transition. The predicted orbital-selective transition
  naturally explains the anomaly observed in the electric resistivity
  of Sr$_2$YRuO$_6$. Implications of other available experimental data
  are also discussed. Our work shows that by exploiting
  geometrical frustration on non-bipartite lattices, novel
  electronic/magnetic/orbital-coupled phase transitions can occur in
  correlated materials that are in the vicinity of metal-insulator phase
  boundary.",1811.03465v1
2014-01-16,Effect of core--mantle and tidal torques on Mercury's spin axis orientation,"The rotational evolution of Mercury's mantle and its core under conservative
and dissipative torques is important for understanding the planet's spin state.
Dissipation results from tides and viscous, magnetic and topographic
core--mantle interactions. The dissipative core--mantle torques take the system
to an equilibrium state wherein both spins are fixed in the frame precessing
with the orbit, and in which the mantle and core are differentially rotating.
This equilibrium exhibits a mantle spin axis that is offset from the Cassini
state by larger amounts for weaker core--mantle coupling for all three
dissipative core--mantle coupling mechanisms, and the spin axis of the core is
separated farther from that of the mantle, leading to larger differential
rotation. The relatively strong core--mantle coupling necessary to bring the
mantle spin axis to its observed position close to the Cassini state is not
obtained by any of the three dissipative core--mantle coupling mechanisms. For
a hydrostatic ellipsoidal core--mantle boundary, pressure coupling dominates
the dissipative effects on the mantle and core positions, and dissipation
together with pressure coupling brings the mantle spin solidly to the Cassini
state. The core spin goes to a position displaced from that of the mantle by
about 3.55 arcmin nearly in the plane containing the Cassini state. With the
maximum viscosity considered of $\nu\sim 15.0\,{\rm cm^2/s}$ if the coupling is
by the circulation through an Ekman boundary layer or $\nu\sim 8.75\times
10^5\,{\rm cm^2/s}$ for purely viscous coupling, the core spin lags the
precessing Cassini plane by 23 arcsec, whereas the mantle spin lags by only
0.055 arcsec. Larger, non hydrostatic values of the CMB ellipticity also result
in the mantle spin at the Cassini state, but the core spin is moved closer to
the mantle spin.",1401.4131v1
2014-09-15,Magnetic anisotropy of FePt nanoparticles,"We carry out a systematic theoretical investigation of Magneto Crystalline
Anisotropy (MCA) of L10 FePt clusters with alternating Fe and Pt planes along
the (001) direction. We calculate the structural relaxation and magnetic moment
of each cluster by using ab initio spin-polarized density functional theory
(DFT), and the MCA with both spin-polarized DFT (including spin-orbit coupling
self-consistently) and the torque method. We find that the MCA of any composite
structure of a given size is enhanced with respect to that of the same-sized
pure Pt or pure Fe cluster as well as to that of any pair of Fe and Pt atoms in
bulk L10 FePt. This enhancement results from the hybridization we observe
between the 3d orbital of the Fe atoms and the 5d orbital of their Pt
neighbors. This hybridization, however, affects the electronic properties of
the component atoms in significantly different ways. While it somewhat
increases the spin moment of the Fe atoms, it has little effect on their
orbital moment; at the same time, it greatly increases both the spin and
orbital moment of the Pt atoms. Given the fact that the spin-orbit coupling
(SOC) constant of Pt is about 7 times greater than that of Fe, this Fe-induced
jump in the orbital moment of the Pt atoms produces the increase in MCA of the
composite structures over that of their pure counterparts. That any composite
structure exhibits higher MCA than bulk L10 FePt results from the lower
coordination of Pt atoms in the cluster, whether Fe or Pt predominates within
it. We also find that bipyramidal clusters whose central layer is Pt have
higher MCA than their same-sized counterparts whose central layer is Fe. This
results from the fact that Pt atoms in such configurations are coordinated with
more Fe atoms than in the latter. By thus participating in more instances of
hybridization, they contribute higher orbital moments to the overall MCA of the
unit.",1409.4318v3
2003-07-17,Mercury's spin-orbit model and signature of its dynamical parameters,"The 3:2 spin-orbit resonance between the rotational and orbital motions of
Mercury results from a functional dependance on a tidal friction adding to a
non-zero eccentricity with a permanent asymmetry in the equatorial plane of the
planet. The upcoming space missions, MESSENGER and BepiColombo with onboard
instrumentation capable of measuring the Mercury's rotational parameters,
stimulate the objective to attempt to an accurate theory of the planet's
rotation. We have used our BJV relativistic model of solar system integration
including the spin-orbit motion of the Moon. This model had been previously
built in accordance with the requirements of the Lunar Laser Ranging
observational accuracy. We extended this model to the spin-orbit couplings of
the terrestrial planets including Mercury; the updated model is called SONYR
(acronym of Spin-Orbit N-BodY Relativistic model). An accurate rotation of
Mercury has been then obtained. Moreover, the conception of the SONYR model is
suitable for analyzing the different families of hermean rotational librations.
We accurately identify the non-linear relations between the rotation of Mercury
and its dynamical figure (\cmr2, $C_{20}$, and $C_{22}$). Notably, for a
variation of 1% on the \cmr2 value, signatures in the $\phi$ hermean libration
in longitude as well as in the $\eta$ obliquity of the planet are respectively
0.45 arcseconds (as) and 2.4 milliarcseconds (mas). These determinations
provide new constraints on the internal structure of Mercury to be discussed
with the expected accuracy forecasted in the BepiColombo mission (respectively
3.2 and 3.7 as according to Milani et al 2001).",0307328v1
2004-06-02,Orbital and magnetic transitions in geometrically-frustrated vanadium spinels -- Monte Carlo study of an effective spin-orbital-lattice coupled model --,"We present our theoretical and numerical results on thermodynamic properties
and the microscopic mechanism of two successive transitions in vanadium spinel
oxides $A$V$_2$O$_4$ ($A$=Zn, Mg, or Cd) obtained by Monte Carlo calculations
of an effective spin-orbital-lattice model in the strong correlation limit.
Geometrical frustration in the pyrochlore lattice structure of V cations
suppresses development of spin and orbital correlations, however, we find that
the model exhibits two transitions at low temperatures. First, a discontinuous
transition occurs with an orbital ordering assisted by the tetragonal
Jahn-Teller distortion. The orbital order reduces the frustration in spin
exchange interactions, and induces antiferromagnetic correlations in
one-dimensional chains lying in the perpendicular planes to the tetragonal
distortion. Secondly, at a lower temperature, a three-dimensional
antiferromagnetic order sets in continuously, which is stabilized by the
third-neighbor interaction among the one-dimensional antiferromagnetic chains.
Thermal fluctuations are crucial to stabilize the collinear magnetic state by
the order-by-disorder mechanism. The results well reproduce the experimental
data such as transition temperatures, temperature dependence of the magnetic
susceptibility, changes of the entropy at the transitions, and the magnetic
ordering structure at low temperatures. Quantum fluctuation effect is also
examined by the linear spin wave theory at zero temperature. The staggered
moment in the ground state is found to be considerably reduced from saturated
value, and reasonably agrees with the experimental data.",0406039v1
2010-09-13,"Inspiral of Generic Black Hole Binaries: Spin, Precession, and Eccentricity","Given the absence of observations of black hole binaries, it is critical that
the full range of accessible parameter space be explored in anticipation of
future observation with gravitational wave detectors. To this end, we compile
the Hamiltonian equations of motion describing the conservative dynamics of the
most general black hole binaries, as computed by Will and collaborators, and
incorporate an effective treatment of dissipation through gravitational
radiation. We evolve these equations for systems with orbital eccentricity and
precessing spins. We find that, while spin-spin coupling corrections can
destroy constant radius orbits in principle, the effect is so small that orbits
will reliably tend to quasi-spherical orbits as angular momentum and energy are
lost to gravitational radiation. Still, binaries that are initially highly
eccentric may retain eccentricity as they pass into the detectable bandwidth of
ground-based gravitational wave detectors. We also show that a useful set of
natural frequencies for an orbit demonstrating both spin precession and
periastron precession is comprised of (1) the frequency of angular motion in
the orbital plane, (2) the frequency of the plane precession, and (3) the
frequency of radial oscillations. These three natural harmonics shape the
observed waveform.",1009.2533v3
2012-09-07,Spin-orbit coupling for tidally evolving super-Earths,"We investigate the spin behavior of close-in rocky planets and the
implications for their orbital evolution. Considering that the planet rotation
evolves under simultaneous actions of the torque due to the equatorial
deformation and the tidal torque, both raised by the central star, we analyze
the possibility of temporary captures in spin-orbit resonances. The results of
the numerical simulations of the exact equations of motions indicate that,
whenever the planet rotation is trapped in a resonant motion, the orbital decay
and the eccentricity damping are faster than the ones in which the rotation
follows the so-called pseudo-synchronization. Analytical results obtained
through the averaged equations of the spin-orbit problem show a good agreement
with the numerical simulations. We apply the analysis to the cases of the
recently discovered hot super-Earths Kepler-10 b, GJ 3634 b and 55 Cnc e. The
simulated dynamical history of these systems indicates the possibility of
capture in several spin-orbit resonances; particularly, GJ 3634 b and 55 Cnc e
can currently evolve under a non-synchronous resonant motion for suitable
values of the parameters. Moreover, 55 Cnc e may avoid a chaotic rotation
behavior by evolving towards synchronization through successive temporary
resonant trappings.",1209.1580v1
2013-11-05,Important Roles of Te 5p and Ir 5d Spin-orbit Interactions on the Multi-band Electronic Structure of Triangular Lattice Superconductor Ir1-xPtxTe2,"We report an angle-resolved photoemission spectroscopy (ARPES) study on a
triangular lattice superconductor Ir$_{1-x}$Pt$_{x}$Te$_2$ in which the Ir-Ir
or Te-Te bond formation, the band Jahn-Teller effect, and the spin-orbit
interaction are cooperating and competing with one another. The Fermi surfaces
of the substituted system are qualitatively similar to the band structure
calculations for the undistorted IrTe$_2$ with an upward chemical potential
shift due to electron doping. A combination of the ARPES and the band structure
calculations indicates that the Te $5p$ spin-orbit interaction removes the
$p_x/p_y$ orbital degeneracy and induces $p_x \pm ip_y$ type spin-orbit
coupling near the A point. The inner and outer Fermi surfaces are entangled by
the Te $5p$ and Ir $5d$ spin-orbit interactions which may provide exotic
superconductivity with singlet-triplet mixing.",1311.1199v2
2009-07-10,Dimensional Dependence of Weak Localization Corrections and Spin Relaxation in Quantum Wires with Rashba Spin-Orbit Coupling,"The quantum correction to the conductivity in disordered quantum wires with
linear Rashba spin-orbit coupling is obtained. For quantum wires with
spin-conserving boundary conditions, we find a crossover from weak anti- to
weak localization as the wire width W is reduced using exact diagonalization of
the Cooperon equation. This crossover is due to the dimensional dependence of
the spin relaxation rate of conduction electrons, which becomes diminished,
when the wire width is smaller than the bulk spin precession length $L_{SO}$.
We thus confirm previous results for small wire width, $W/L_{SO}<= 1$
[PRL98,176808(2007)], where only the transverse 0-modes of the Cooperon
equation had been taken into account. We find that spin helix solutions become
stable for arbitrary ratios of linear Rashba and Dresselhaus coupling in narrow
wires. For wider wires, the spin relaxation rate is found to be not monotonous
as function of wire width: it becomes first enhanced for W on the order of the
bulk $L_{SO}$ before it becomes diminished for smaller wire widths. In
addition, we find that the spin relaxation is smallest at the edge of the wire
for wide wires. The effect of the Zeeman coupling to the magnetic field
perpendicular to the 2D electron system is studied and found that it shifts the
crossover from weak anti- to weak localization to larger wire widths $W_c$.
When the transverse confinement potential of the quantum wire is smooth
(adiabatic), the spin relaxation rate is found to be enhanced as W is reduced.
We find that only a spin polarized state retains a finite spin relaxation rate
in such narrow wires. Thus, we conclude that the injection of polarized spins
into nonmagnetic quantum wires should be favorable in wires with smooth
confinement potential. Finally, in wires with tubular shape, corresponding to
transverse periodic boundary conditions, we find no reduction of the spin
relaxation rate.",0907.1819v2
2012-02-14,Low-Energy Effective Hamiltonian and the Surface States of Ca_3PbO,"The band structure of Ca_3PbO, which possesses a three-dimensional massive
Dirac electron at the Fermi energy, is investigated in detail. Analysis of the
orbital weight distributions on the bands obtained in the first-principles
calculation reveals that the bands crossing the Fermi energy originate from the
three Pb-p orbitals and three Ca-dx2y2 orbitals. Taking these Pb-p and Ca-dx2y2
orbitals as basis wave functions, a tight-binding model is constructed. With
the appropriate choice of the hopping integrals and the strength of the
spin-orbit coupling, the constructed model sucessfully captures important
features of the band structure around the Fermi energy obtained in the
first-principles calculation. By applying the suitable basis transformation and
expanding the matrix elements in the series of the momentum measured from a
Dirac point, the low-energy effective Hamiltonian of this model is explicitely
derived and proved to be a Dirac Hamiltonain. The origin of the mass term is
also discussed. It is shown that the spin-orbit coupling and the orbitals other
than Pb-p and Ca-dx2y2 orbitals play important roles in making the mass term
finite. Finally, the surface band structures of Ca_3PbO for several types of
surfaces are investigated using the constructed tight-binding model. We find
that there appear nontrivial surface states that cannot be explained as the
bulk bands projected on the surface Brillouin zone. The relation to the
topological insulator is also discussed.",1202.2909v1
2017-06-01,Spin-orbit precession along eccentric orbits for extreme mass ratio black hole binaries and its effective-one-body transcription,"In this work we present an analytical gravitational self-force calculation of
the spin-orbit precession along an eccentric orbit around a Schwarzschild black
hole, following closely the recent prescription of Akcay, Dempsey, and Dolan.
We then transcribe this quantity within the Effective-One-Body (EOB) formalism,
thereby determining several new, linear-in-mass-ratio, contributions in the
post-Newtonian expansion of the spin-orbit couplings entering the EOB
Hamiltonian. Namely, we determine the second gyro-gravitomagnetic ratio
$g_{S_*}(r,p_r,p_{\phi})$ up to order $p_r^2/r^4$ included.",1706.00459v1
2023-01-22,Violation of the orbital depairing limit in a non-unitary state --on the high field phase in the heavy Fermion superconductor UTe$_2$--,"A theoretical study is reported on the origin of extremely high upper
critical field $\sim$70T observed in UTe$_2$ with the transition temperature
T$_{\rm c}$=1.6K-2K, far exceeding the conventional orbital depairing limit set
by the Fermi velocity and T$_{\rm c}$ for a superconductor (SC) in the clean
limit. We investigate possible violation of the orbital limit in terms of a
spin-triplet nonunitary state, which is effectively coupled to the underlying
magnetization induced by external field. This in turn produces the reduced
internal field by cancelling it via magnetization. We formulate a theory within
Ginzburg-Landau framework to describe this orbital limit violation and analyze
experimental data on the upper critical fields for various field orientations
in UTe$_2$. It is pointed out that the orbital limit violation for a
spin-triplet SC together with the Pauli-Clogston limit violation for a
spin-singlet SC constitutes a complete and useful framework to examine the high
field physics in superconductors in the clean limit.",2301.09035v1
2003-02-14,An effective spin-orbital Hamiltonian for the double perovskite Sr$_2$FeW O$_6$: Derivation of the phase diagram,"We formulate a superexchange theory of insulating double-perovskite compounds
such as Sr$_2$FeWO$_6$. An effective spin-orbital Hamiltonian is derived in the
strong coupling limit of Hubbard model for d-electrons on Fe and W ions. The
relevant degrees of freedom are the spins S=2 and the three-fold orbital
degeneracy of Fe$^{2+}$-ions. W-sites are integrated out by means of a
fourth-order perturbative expansion. The magnetically and orbitally ordered
ground states of the effective Hamiltonia n are discussed as a function of the
model parameters. We show that for realistic values of such parameters the
ground state is antiferromagnetic, as experimentally observed. The order found
is of type-II, consisting of \{111\} ferromagnetic planes stac ked
antiferromagnetically. The orbital order energy scale found is one order of
magnitude less than the spi n one.",0302293v1
2012-10-26,Intrinsic and substrate induced spin-orbit interaction in chirally stacked trilayer graphene,"We present a combined group-theoretical and tight-binding approach to
calculate the intrinsic spin-orbit coupling (SOC) in ABC stacked trilayer
graphene. We find that compared to monolayer graphene, a larger set of d
orbitals (in particular the d_{z^2} orbital) needs to be taken into account. We
also consider the intrinsic SOC in bilayer graphene, because the comparison
between our tight-binding bilayer results and the density functional
computations of Ref.[40] allows us to estimate the values of the trilayer SOC
parameters as well. We also discuss the situation when a substrate or adatoms
induce strong SOC in only one of the layers of bilayer or ABC trilayer
graphene. Both for the case of intrinsic and externally induced SOC we derive
effective Hamiltonians which describe the low-energy spin-orbit physics. We
find that at the K point of the Brillouin zone the effect of Bychkov-Rashba
type SOC is suppressed in bilayer and ABC trilayer graphene compared to
monolayer graphene.",1210.7158v2
2013-03-26,Initial data for neutron star binaries with arbitrary spins,"The starting point of any general relativistic numerical simulation is a
solution of the Hamiltonian and momentum constraints that (ideally) represents
an astrophysically realistic scenario. We present a new method to produce
initial data sets for binary neutron stars with arbitrary spins and orbital
eccentricities. The method only provides approximate solutions to the
constraints. However, we show that the corresponding constraint violations
subside after a couple of orbits, becoming comparable to those found in
evolutions of standard conformally flat, helically symmetric binary initial
data. We evolve in time three data sets, corresponding to binaries with spins
aligned, zero and anti-aligned with the orbital angular momentum. These
simulations show the orbital ""hang-up"" effect previously seen in binary black
holes. Additionally, all three show orbital eccentricities up to one order of
magnitude smaller than those found in helically symmetric initial sets
evolutions.",1303.6692v2
2018-02-12,Electromagnetic wave propagating along a space curve,"Using the thin-layer approach, we derive the effective equation for the
electromagnetic wave propagating along a space curve. We find intrinsic
spin-orbit, extrinsic spin-orbit and extrinsic orbital angular momentum and
intrinsic orbital angular momentum couplings induced by torsion, which can lead
to geometric phase, spin and orbital Hall effects. And we show the helicity
inversion induced by curvature that can convert the right-handed circularly
polarized electromagnetic wave into left-handed polarized one, vice verse.
Finally, we demonstrate that the gauge invariance of the effective dynamics is
protected by the geometrically induced gauge potential.",1802.04059v1
2012-04-17,Calibration of Equilibrium Tide Theory for Extrasolar Planet Systems II,"We present a new empirical calibration of equilibrium tidal theory for
extrasolar planet systems, extending a prior study by incorporating detailed
physical models for the internal structure of planets and host stars. The
resulting strength of the stellar tide produces a coupling that is strong
enough to reorient the spins of some host stars without causing catastrophic
orbital evolution, thereby potentially explaining the observed trend in
alignment between stellar spin and planetary orbital angular momentum. By
isolating the sample whose spins should not have been altered in this model, we
also show evidence for two different processes that contribute to the
population of planets with short orbital periods.
  We apply our results to estimate the remaining lifetimes for short period
planets, examine the survival of planets around evolving stars, and determine
the limits for circularisation of planets with highly eccentric orbits. Our
analysis suggests that the survival of circularised planets is strongly
affected by the amount of heat dissipated, which is often large enough to lead
to runaway orbital inflation and Roche lobe overflow.",1204.3903v1
2016-05-20,"Long-range orders, spin- and orbital-freezing in the two-band Hubbard model","We solve the orbitally degenerate two-band Hubbard model within dynamical
mean field theory and map out the instabilities to various symmetry-broken
phases based on an analysis of the corresponding lattice susceptibilities.
Phase diagrams as a function of the Hund coupling parameter J are obtained both
for the model with rotationally invariant interaction and for the model with
Ising-type anisotropy. For negative J, an intra-orbital spin-singlet
superconducting phase appears at low temperatures, while the normal state
properties are characterized by an orbital freezing phenomenon. This is the
negative-J analogue of the recently discovered fluctuating-moment induced
s-wave spin-triplet superconductivity in the spin-freezing regime of
multi-orbital models with J>0.",1605.06410v1
2020-06-22,Imprinting and driving electronic orbital magnetism using magnons,"Magnons, as the most elementary excitations of magnetic materials, have
recently emerged as a prominent tool in electrical and thermal manipulation and
transport of spin, and magnonics as a field is considered as one of the pillars
of modern spintronics. On the other hand, orbitronics, which exploits the
orbital degree of freedom of electrons rather than their spin, emerges as a
powerful platform in efficient design of currents and redistribution of angular
momentum in structurally complex materials. Here, we uncover a way to bridge
the worlds of magnonics and electronic orbital magnetism, which originates in
the fundamental coupling of scalar spin chirality, inherent to magnons, to the
orbital degree of freedom in solids. We show that this can result in efficient
generation and transport of electronic orbital angular momentum by magnons,
thus opening the road to combining the functionalities of magnonics and
orbitronics to their mutual benefit in the realm of spintronics applications.",2006.13033v2
2023-07-20,Enhanced photo-excitation and angular-momentum imprint of gray excitons in WSe$_{2}$ monolayers by spin-orbit-coupled vector vortex beams,"A light beam can be spatially structured in the complex amplitude to possess
orbital angular momentum (OAM), which introduces a new degree of freedom
alongside the intrinsic spin angular momentum (SAM) associated with circular
polarization. Moreover, super-imposing two twisted lights with distinct SAM and
OAM produces a vector vortex beam (VVB) in non-separable states where not only
complex amplitude but also polarization are spatially structured and entangled
with each other. In addition to the non-separability, the SAM and OAM in a VVB
are intrinsically coupled by the optical spin-orbit interaction and constitute
the profound spin-orbit physics in photonics. In this work, we present a
comprehensive theoretical investigation, implemented on the first-principles
base, of the intriguing light-matter interaction between VVBs and WSe$_{2}$
monolayers (WSe$_{2}$-MLs), one of the best-known and promising two-dimensional
(2D) materials in optoelectronics dictated by excitons, encompassing bright
exciton (BX) as well as various dark excitons (DXs). One of the key findings of
our study is the substantial enhancement of the photo-excitation of gray
excitons (GXs), a type of spin-forbidden dark exciton, in a WSe$_2$-ML through
the utilization of a twisted light that possesses a longitudinal field
associated with the optical spin-orbit interaction. Our research demonstrates
that a spin-orbit-coupled VVB surprisingly allows for the imprinting of the
carried optical information onto gray excitons in 2D materials, which is robust
against the decoherence mechanisms in materials. This observation suggests a
promising method for deciphering the transferred angular momentum from
structured lights to excitons.",2307.10916v1
2016-01-20,Strongly enhanced Rashba splittings in oxide heterostructure: a tantalite monolayer on BaHfO$_3$,"In the two-dimensional electron gas (2DEG) emerging at the transition metal
oxide surface and interface, it has been pointed out that the Rashba spin-orbit
interaction, the momentum-dependent spin splitting due to broken inversion
symmetry and atomic spin-orbit coupling, can have profound effects on
electronic ordering in the spin, orbit, and charge channels, and may help give
rise to exotic phenomena such as ferromagnetism-superconductivity coexistence
and topological superconductivity. Although a large Rashba splitting is
expected to improve experimental accessibility of such phenomena, it has not
been understood how we can maximally enhance this splitting. Here, we present a
promising route to realize significant Rashba-type band splitting using a thin
film heterostructure. Based on first-principles methods and analytic model
analyses, a tantalate monolayer on BaHfO$_3$ is shown to host two-dimensional
bands originating from Ta $t_{2g}$ states with strong Rashba spin splittings -
up to nearly 10% of the bandwidth - at both the band minima and saddle points
due to the maximal breaking of the inversion symmetry. Such 2DEG band structure
makes this oxide heterostructure a promising platform for realizing both a
topological superconductor which hosts Majorana fermions and the electron
correlation physics with strong spin-orbit coupling.",1601.05443v1
2020-04-21,Role of interfacial oxidation in generation of spin-orbit torques,"We report that current-induced spin-orbit torques (SOTs) in
heavy-metal/ferromagnetic-metal bilayers are strongly altered by the oxidation
of the ferromagnetic layer near the interface. We measured damping-like (DL)
and field-like (FL) SOTs for Pt/Co and Pt/Ni$_{81}$Fe$_{19}$ (Pt/Py) films
using spin-torque ferromagnetic resonance. In the Pt/Co film, we found that the
oxidation of the Co layer near the interface enhances both DL and FL SOTs in
spite of the insulating nature of the CoO$_x$ layer. The enhancement of the
SOTs disappears by inserting a thin Ti layer at the Pt/CoO$_x$ interface,
indicating that the dominant source of the SOTs in the Pt/CoO$_x$/Co film is
the spin-orbit coupling at the Pt/CoO$_x$ interface. In contrast to the
Pt/CoO$_x$/Co film, the SOTs in the Pt/PyO$_x$/Py film are dominated by the
bulk spin-orbit coupling. Our result shows that the interfacial oxidation of
the Pt/Py film suppresses the DL-SOT and reverses the sign of the FL-SOT. The
change of the SOTs can be attributed to the change of the real and imaginary
parts of the spin mixing conductance induced by the insertion of the insulating
PyO$_x$ layer. These results show that the interfacial oxidation provides an
effective way to manipulate the strength and sign of the SOTs.",2004.09837v1
2022-01-26,SOiCI and iCISO: Combining iterative configuration interaction with spin-orbit coupling in two ways,"The near-exact iCIPT2 approach for strongly correlated systems of electrons,
which stems from the combination of iterative configuration interaction (iCI,
an exact solver of full CI) with configuration selection for static correlation
and second-order perturbation theory (PT2) for dynamic correlation, is extended
to the relativistic domain. In the spirit of spin separation, relativistic
effects are treated in two steps: scalar relativity is treated by the
infinite-order, spin-free part of the exact two-component (X2C) relativistic
Hamiltonian, whereas spin-orbit coupling (SOC) is treated by the first-order,
Douglas-Kroll-Hess-like SOC operator derived from the same X2C Hamiltonian. Two
possible combinations of iCIPT2 with SOC are considered, i.e., SOiCI and iCISO.
The former treats SOC and electron correlation on an equal footing, whereas the
latter treats SOC in the spirit of state interaction, by constructing and
diagonalizing an effective spin-orbit Hamiltonian matrix in a small number of
correlated scalar states. Both double group and time reversal symmetries are
incorporated to simplify the computation. Pilot applications reveal that SOiCI
is very accurate for the spin-orbit splitting (SOS) of heavy atoms, whereas the
computationally very cheap iCISO can safely be applied to the SOS of light
atoms and even of systems containing heavy atoms when SOC is largely quenched
by ligand fields.",2201.10783v1
2022-07-05,Revisiting Stellar Orbits and the Sgr A$^*$ Quadrupole Moment,"The ""no-hair"" theorem can, in principle, be tested at the center of the Milky
Way by measuring the spin and the quadrupole moment of Sgr A$^*$ with the
orbital precession of S-stars, measured over their full periods. Contrary to
the original method, we show why it is possible to test the no-hair theorem
using observations from only a single star, by measuring precession angles over
a half-orbit. There are observational and theoretical reasons to expect S-stars
to spin rapidly, and we have quantified the effect of stellar spin, via
spin-curvature coupling (the leading-order manifestation of the
Mathisson-Papapetrou-Dixon equations), on future quadrupole measurements. We
find that they will typically suffer from errors of order a few percentage
points, but for some orbital parameters, the error can be much higher. We
re-examine the more general problem of astrophysical noise sources that may
impede future quadrupole measurements, and find that a judicious choice of
measurable precession angles can often eliminate individual noise sources. We
have derived optimal combinations of observables to eliminate the large noise
source of mass precession, the novel noise of spin-curvature coupling due to
stellar spin, and the more complicated noise source arising from transient
quadrupole moments in the stellar potential.",2207.02226v2
2012-08-29,Modified Bethe-Peierls boundary condition for ultracold atoms with Spin-Orbit coupling,"We show that the Bethe-Peierls (BP) boundary condition should be modified for
ultracold atoms with spin-orbit (SO) coupling. Moreover, we derive a general
form of the modified BP boundary condition, which is applicable to a system
with arbitrary kind of SO coupling. In the modified BP condition, an
anisotropic term appears and the inter-atomic scattering length is normally
SO-coupling dependent. For the special system in the current experiments,
however, it can be proved that the scattering length is SO-coupling
independent, and takes the same value as in the case without SO coupling. Our
result is helpful for the study of both few-body and many-body physics in
SO-coupled ultracold gases.",1208.5976v4
2018-01-16,Harmonically trapped attractive and repulsive spin-orbit and Rabi coupled Bose-Einstein condensates,"Numerically we investigate the ground state of effective one-dimensional
spin-orbit (SO) and Rabi coupled two pseudo-spinor Bose-Einstein condensates
(BECs) under the effect of harmonic traps. For both signs of the interaction,
density profiles of SO and Rabi coupled BECs in harmonic potentials, which
simulate a real experimental situation are obtained. The harmonic trap causes a
strong reduction of the multi-peak nature of the condensate and it increases
its density. For repulsive interactions, the increase of SO coupling results in
an uncompressed less dense condensate and with increased multi-peak nature of
the density. The increase of Rabi coupling leads to a density increase with an
almost constant number of multi-peaks. For both signs of the interaction and
negative values of Rabi coupling, the condensate develops a notch in the
central point and it seems to a dark-in-bright soliton. In the case of the
attractive nonlinearity, an interesting result is the increase of the collapse
threshold under the action of the SO and Rabi couplings.",1801.05321v1
2021-04-06,Supersolid-like states in a two-dimensional trapped spin-orbit-coupled spin-1 condensate,"We study supersolid-like states in a quasi-two-dimensional trapped Rashba and
Dresselhaus spin-orbit (SO) coupled spin-1 condensate. For small strengths of
SO coupling $\gamma$ ($\gamma \lessapprox 0.75$), in the ferromagnetic phase,
circularly-symmetric $(0,\pm 1, \pm 2)$- and $(\mp 1, 0,\pm 1)$-type states are
formed where the numbers in the parentheses denote the angular momentum of the
vortex at the center of the components and where the upper (lower) sign
correspond to Rashba (Dresselhaus) coupling; in the antiferromagnetic phase,
only $(\mp 1, 0,\pm 1)$-type states are formed. For large strengths of SO
coupling, supersolid-like superlattice and superstripe states are formed in the
ferromagnetic phase. In the antiferromagnetic phase, for large strengths of SO
coupling, supersolid-like superstripe and multi-ring states are formed. For an
equal mixture of Rashba and Dresselhaus SO couplings, only a superstripe state
is found. All these states are found to be dynamically stable and hence
accessible in an experiment and will enhance the fundamental understanding of
crystallization onto spatially periodic states in solids.",2104.02197v1
2015-12-29,Prediction of spin orientations in terms of HOMO-LUMO interactions using spin-orbit coupling as perturbation,"The preferred spin orientation of a magnetic ion can be predicted on the
basis of density functional theory (DFT) calculations including electron
correlation and spin-orbit coupling (SOC). However, most chemists and
physicists are unaware of how the observed and/or calculated spin orientations
are related to the local electronic structures of the magnetic ions. The
objective of this article is to provide a conceptual framework of thinking
about and predicting the preferred spin orientation of a magnetic ion by
examining the relationship between the spin orientation and the local
electronic structure of the ion. In general, a magnetic ion (i.e., an ion
possessing unpaired spins) in a solid or a molecule is surrounded with
main-group ligand atoms to form a polyhedron, and the d-states of the
polyhedron are split because the antibonding interactions of the metal
d-orbitals with the p orbitals of the surrounding ligands depend on the
symmetries of the orbitals involved. The magnetic ion of the polyhedron has a
certain preferred spin direction because its split d-states interact among
themselves under SOC and because the energy lowering associated with the
SOC-induced interactions depends on spin orientation. The preferred spin
direction can be readily predicted on the basis of perturbation theory, in
which the SOC is taken as perturbation and the split d-states as unperturbed
states, by inspecting the magnetic quantum numbers of its d-orbitals present in
the HOMO and LUMO of the polyhedron. Experimentally, the determination of the
preferred spin orientations of magnetic ions requires a sophisticated level of
experiments. Theoretically, it requires an elaborate level of DFT electronic
structure calculations. We show that the outcomes of such experimental
measurements and theoretical calculations can be predicted by a simple
perturbation theory analysis.",1512.08573v1
2012-11-12,An orbital-selective spin liquid in a frustrated heavy fermion spinel LiV$_2$O$_4$,"The pronounced enhancement of the effective mass is the primary phenomenon
associated with strongly correlated electrons. In the presence of local
moments, the large effective mass is thought to arise from Kondo coupling, the
interaction between itinerant and localised electrons. However, in d electron
systems, the origin is not clear because of the competing Hund's rule coupling.
Here we experimentally address the microscopic origin for the heaviest d
fermion in a vanadium spinel LiV2O4 having geometrical frustration. Utilising
orbital-selective 51V NMR, we elucidate the orbital-dependent local moment that
exhibits no long-range magnetic order despite persistent antiferromagnetic
correlations. A frustrated spin liquid, Hund-coupled to itinerant electrons,
has a crucial role in forming heavy fermions with large residual entropy. Our
method is important for the microscopic observation of the orbital-selective
localisation in a wide range of materials including iron pnictides, cobaltates,
manganites, and ruthnates.",1211.2844v1
2014-02-05,Theoretical study of insulating mechanism in multi-orbital Hubbard models with a large spin-orbit coupling: Slater versus Mott scenario in Sr$_2$IrO$_4$,"To examine the insulating mechanism of 5$d$ transition metal oxide
Sr$_2$IrO$_4$, we study the ground state properties of a three-orbital Hubbard
model with a large relativistic spin-orbit coupling on a square lattice. Using
a variational Monte Carlo method, we find that the insulating state appearing
in the ground state phase diagram for one hole per site varies from a weakly
correlated to a strongly correlated antiferromagnetic (AF) state with
increasing Coulomb interactions. This crossover is characterized by the
different energy gain mechanisms of the AF insulating state, i.e., from an
interaction-energy driven Slater-type insulator to a band-energy driven
Mott-type insulator with increasing Coulomb interactions. Our calculations
reveal that Sr$_2$IrO$_4$ is a ""moderately correlated"" AF insulator located in
the intermediate coupling region between a Slater-type and a Mott-type
insulators.",1402.0935v2
2015-09-04,Slope-Reversed Mott Transition in Multiorbital Systems,"We examine finite-temperature phase transitions in the two-orbital Hubbard
model with different bandwidths by means of the dynamical mean-field theory
combined with the continuous-time quantum Monte Carlo method. It is found that
there emerges a peculiar slope-reversed first-order Mott transition between the
orbital-selective Mott phase and the Mott insulator phase in the presence of
Ising-type Hund's coupling. The origin of the slope-reversed phase transition
is clarified by the analysis of the temperature dependence of the energy
density. It turns out that the increase of Hund's coupling lowers the critical
temperature of the slope-reversed Mott transition. Beyond a certain critical
value of Hund's coupling the first-order transition turns into a
finite-temperature crossover. We also reveal that the orbital-selective Mott
phase exhibits frozen local moments in the wide orbital, which is demonstrated
by the spin-spin correlation functions.",1509.01415v1
2014-05-12,Orbital ferromagnetism in interacting few-electron dots with strong spin-orbit coupling,"We study the ground state of $N$ weakly interacting electrons (with $N\le
10$) in a two-dimensional parabolic quantum dot with strong Rashba spin-orbit
coupling. Using dimensionless parameters for the Coulomb interaction,
$\lambda\lesssim 1$, and the Rashba coupling, $\alpha\gg 1$, the low-energy
physics is characterized by an almost flat single-particle dispersion. From an
analytical approach for $\alpha\to \infty$ and $N=2$, and from numerical exact
diagonalization and Hartree-Fock calculations, we find a transition from a
conventional unmagnetized ground state (for $\lambda<\lambda_c$) to an orbital
ferromagnet (for $\lambda>\lambda_c$), with a large magnetization and a
circulating charge current. We show that the critical interaction strength,
$\lambda_c=\lambda_c(\alpha,N)$, vanishes in the limit $\alpha\to \infty$.",1405.2675v2
2024-02-10,A spin-torque nano-oscillator based on interlayer-coupled meron-skyrmion pairs with a fixed orbit,"In recent years, magnetic skyrmion-based spin-torque nano-oscillators (STNOs)
attract considerable interest for their prospect in future-generation
communication and spintronic technologies. However, some critical issues, which
hamper their practical applications, e.g., the long start-up time and variable
skyrmion gyration orbit, remain to be resolved. Here, we numerically
demonstrate a realization of a fixed-orbit STNO, which is based on an
interlayer-coupled meron-skyrmion (MS) pair other than a magnetic skyrmion. In
this STNO, the MS pair possesses a structurally defined, fixed orbit within a
broad range of driving current, even in the presence of random defects. The
output frequency range of the STNO based on an MS pair far exceeds that of the
STNO typically based on a single skyrmion. Moreover, the output frequency of
this STNO can be further elevated if more MS pairs are incorporated. Our
results reveal the nontrivial dynamics of the interlayer-coupled MS pair,
opening perspectives for the design and optimization of fundamental spintronic
devices.",2402.06865v1
2014-08-19,Quantum Spin Dimers from Chiral Dissipation in Cold-Atom Chains,"We consider the non-equilibrium dynamics of a driven dissipative spin chain
with chiral coupling to a 1D bosonic bath, and its atomic implementation with a
two-species mixture of cold quantum gases. The reservoir is represented by a
spin-orbit coupled 1D quasi-condensate of atoms in a magnetized phase, while
the spins are identified with motional states of a separate species of atoms in
an optical lattice. The chirality of reservoir excitations allows the spins to
couple differently to left and right moving modes, which in our atomic setup
can be tuned from bidirectional to purely unidirectional. Remarkably, this
leads to a pure steady state in which pairs of neighboring spins form dimers
that decouple from the remainder of the chain. Our results also apply to
current experiments with two-level emitters coupled to photonic waveguides.",1408.4357v3
2016-09-12,Anomalous hyperfine coupling and nuclear magnetic relaxation in Weyl semimetals,"The electron-nuclear hyperfine interaction shows up in a variety of phenomena
including e.g. NMR studies of correlated states and spin decoherence effects in
quantum dots. Here we focus on the hyperfine coupling and the NMR spin
relaxation time, $T_1$ in Weyl semimetals. Since the density of states in Weyl
semimetals varies with the square of the energy around the Weyl point, a naive
power counting predicts a $1/T_1T\sim E^4$ scaling with $E$ the maximum of
temperature ($T$) and chemical potential. By carefully investigating the
hyperfine interaction between nuclear spins and Weyl fermions, we find that
while its spin part behaves conventionally, its orbital part diverges unusually
with the inverse of energy around the Weyl point. Consequently, the nuclear
spin relaxation rate scales in a graphene like manner as $1/T_1T\sim
E^2\ln(E/\omega_0)$ with $\omega_0$ the nuclear Larmor frequency. This allows
us to identify an effective hyperfine coupling constant, which is tunable by
gating or doping, which is relevant for decoherence effect in spintronics
devices and double quantum dots where hyperfine coupling is the dominant source
of spin-blockade lifting.",1609.03370v1
2010-08-06,First-principle studies of spin-electric coupling in a $\{Cu_3\}$ single molecular magnet,"We report on a study of the electronic and magnetic properties of the
triangular antiferromagnetic $\{Cu_3\}$ single-molecule magnet, based on spin
density functional theory. Our calculations show that the low-energy magnetic
properties are correctly described by an effective three-site spin $s=1/2$
Heisenberg model, with an antiferromagnetic exchange coupling $J \approx 5$
meV. The ground state manifold of the model is composed of two degenerate spin
$S=1/2$ doublets of opposite chirality. Due to lack of inversion symmetry in
the molecule these two states are coupled by an external electric field, even
when spin-orbit interaction is absent. The spin-electric coupling can be viewed
as originating from a modified exchange constant $\delta J$ induced by the
electric field. We find that the calculated transition rate between the chiral
states yields an effective electric dipole moment $d = 3.38\times 10^{-33} {\rm
C\ m} \approx e 10^{-4}a$, where $a$ is the Cu separation. For external
electric fields ${{\varepsilon}} \approx 10^8$ V/m this value corresponds to a
Rabi time $\tau \approx 1$ ns and to a $\delta J$ of the order of a few
$\mu$eV.",1008.1139v1
2009-12-18,"""Nonmagnetic"" Dimer Mott insulator induced by the coupling of spin with quantum electric dipoles","We present an effective dipolar-spin model based on the strong coupling
analysis, which may explain the possible origin of the ""spin liquid Mott
insulator"". The issue is related to the dimer Mott insulator reminiscent of the
organic triangular lattice system, $\kappa$-ET$_2$Cu$_2$(CN)$_3$, whose gapless
spin liquid state had been discussed in the context of geometrical frustration
of exchange coupling, $J$, between spins on dimer orbitals. It turns out that
another degrees of freedom within the insulator, {\it quantum electric-dipoles}
on dimers, interacts with each other by the Coulomb interaction and brings
about a significant suppression of $J$ through the dipolar-spin coupling.",0912.3674v3
2017-09-03,Nanoscale chiral valley-photon interface through optical spin-orbit coupling,"The emergence of two-dimensional transition metal chalcogenide materials has
sparked an intense activity in valleytronics since their valley information can
be directly encoded and detected by using the spin angular momentum of light.
For their practical applications such as on-chip valley logic gates and
chip-to-chip valley transport, the encoding and processing of valley pseudospin
using light should be extended to an integrated, on-chip nanophotonic system.
Here, we successfully demonstrate, at room temperature, the valley-dependent
directional coupling of light using a plasmonic nanowire-WS2 layers system. Our
calculations show that the local transverse spin angular momentum of the mode
of the plasmonic nanowire provides robust optical spin-path locking of up to 91
%. Experimentally we demonstrate that valley pseudospin in WS2 is coupled with
optical spin of the same handedness and exhibits a high directional coupling
efficiency up to 90 % to the plasmonic guided mode. The result opens up new
avenues of controlling, detecting and processing valley and spin information
with precise optical control at the nanoscale.",1709.00762v1
2021-05-25,Robust exceptional point of arbitrary order in coupled spinning cylinders,"Exceptional points (EPs), i.e., non-Hermitian degeneracies at which
eigenvalues and eigenvectors coalesce, can be realized by tuning the gain/loss
contrast of different modes in non-Hermitian systems or by engineering the
asymmetric coupling of modes. Here we demonstrate a mechanism that can achieve
EPs of arbitrary order by employing the non-reciprocal coupling of spinning
cylinders sitting on a dielectric waveguide. The spinning motion breaks the
time-reversal symmetry and removes the degeneracy of opposite chiral modes of
the cylinders. Under the excitation of a linearly polarized plane wave, the
chiral mode of one cylinder can unidirectionally couple to the same mode of the
other cylinder via the spin-orbit interaction associated with the evanescent
wave of the waveguide. The structure can give rise to arbitrary-order EPs that
are robust against spin-flipping perturbations, in contrast to conventional
systems relying on spin-selective excitations. In addition, we show that
higher-order EPs in the proposed system are accompanied by enhanced optical
isolation, which may find applications in designing novel optical isolators,
nonreciprocal optical devices, and topological photonics.",2105.11629v1
2001-07-01,Coupling and Dissociation in Artificial Molecules,"We show that the spin-and-space unrestricted Hartree-Fock method, in
conjunction with the companion step of the restoration of spin and space
symmetries via Projection Techniques (when such symmetries are broken), is able
to describe the full range of couplings in two-dimensional double quantum dots,
from the strong-coupling regime exhibiting delocalized molecular orbitals to
the weak-coupling and dissociation regimes associated with a Generalized
Valence Bond combination of atomic-type orbitals localized on the individual
dots. The weak-coupling regime is always accompanied by an antiferromagnetic
ordering of the spins of the individual dots. The cases of dihydrogen (H$_2$,
$2e$) and dilithium (Li$_2$, $6e$) quantum dot molecules are discussed in
detail.",0107014v1
2013-03-24,Synthetic Gauge Field with Highly Magnetic Lanthanide Atoms,"We present a scheme for generating a synthetic magnetic field and spin-orbit
coupling via Raman coupling in highly magnetic lanthanide atoms such as
dysprosium. Employing these atoms offer several advantages for realizing
strongly correlated states and exotic spinor phases. The large spin and narrow
optical transitions of these atoms allow the generation of synthetic magnetic
fields an order of magnitude larger than those in the alkalis, but with
considerable reduction of the heating rate for equal Raman coupling. The
effective hamiltonian of these systems differs from that of the alkalis' by an
additional nematic coupling term, which leads to a phase transition in the
dressed states as detuning varies. For \text{high-spin} condensates, spin-orbit
coupling leads to a spatially periodic structure, which is described in
Majorana representation by a set of points moving periodically on a unit
sphere. We name this a ""Majorana spinor helix"" in analogy to the persistent
spin-1/2 helix observed in electronic systems.",1303.6004v1
2019-10-14,Intrinsic Rashba coupling due to Hydrogen bonding in DNA,"We present an analytical model for the role of hydrogen bonding on the
spin-orbit coupling of model DNA molecule. Here we analyze in detail the
electric fields due to the polarization of the Hydrogen bond on the DNA base
pairs and derive, within tight binding analytical band folding approach, an
intrinsic Rashba coupling which should dictate the order of the spin active
effects in the Chiral-Induced Spin Selectivity (CISS) effect. The coupling
found is ten times larger than the intrinsic coupling estimated previously and
points to the predominant role of hydrogen bonding in addition to chirality in
the case of biological molecules. We expect similar dominant effects in
oligopeptides, where the chiral structure is supported by hydrogen-bonding and
bears on orbital carrying transport electrons.",1910.05985v1
2020-12-02,Spontaneous spatial order in two-dimensional ferromagnetic spin-orbit coupled uniform spin-1 condensate solitons,"We demonstrate spontaneous spatial order in stripe and super-lattice solitons
in a Rashba spin-orbit (SO) coupled spin-1 uniform quasi-two-dimensional
(quasi-2D) ferromagnetic Bose-Einstein condensate. For weak SO coupling, the
solitons are of the $(- 1,0,+ 1)$ or $(0,+ 1,+ 2)$ type with intrinsic
vorticity, where the numbers in the parentheses denote angular momentum in spin
components $F_z=+1,0,-1$, respectively. For intermediate SO coupling, three
types of solitons are found: (a) circularly-asymmetric solitons, (b)
circularly-symmetric $(- 1,0,+ 1)$- and (c) $(0,+ 1,+ 2)$-type multi-ring
solitons maintaining the above-mentioned vortices in respective components. For
large SO coupling, quasi-degenerate stripe and super-lattice solitons are found
in addition to the circularly-asymmetric solitons. A super-lattice soliton
forms a 2D square lattice structure in the total density as in a super-solid;
in component densities it may have either (i) a 1D stripe pattern or (ii) a 2D
square lattice structure.",2012.01197v1
2010-12-21,Kondo effects and shot noise enhancement in a laterally coupled double quantum dot,"The spin and orbital Kondo effects and the related shot noise for a laterally
coupled double quantum dot are studied taking account of coherent indirect
coupling via a reservoir. We calculate the linear conductance and shot noise
for various charge states to distinguish between the spin and orbital Kondo
effects. We find that a novel antiferromagnetic exchange coupling can be
generated by the coherent indirect coupling, and it works to suppress the spin
Kondo effect when each quantum dot holds just one electron. We also show that
we can capture the feature of the pseudospin Kondo effect from the shot noise
measurement.",1012.4838v1
2012-11-29,Scattering and effective interactions of ultracold atoms with spin-orbit coupling,"We derive an analytical expression for the scattering amplitude of two
ultracold atoms of arbitrary spin and with general spin-orbit (SO) coupling, on
the basis of our recent work (Phys. Rev. A \textbf{86}, 053608 (2012)). As an
application, we demonstrate that SO coupling can induce scattering resonance in
the case with finite scattering length. The same approach can be applied to
calculate the two-body bound state of SO-coupled ultracold atoms. For the
ultracold spin-1/2 fermi gases in three- or two- dimensional systems with SO
coupling, we also obtain the renormalization relation of effective contact
interaction with momentum cutoff, as well as the applicability of Huang-Yang
pseudo-potential.",1211.6919v7
2023-04-18,Dispersion engineering in spin-orbit coupled spinor $F=1$ condensates driven by negative masses,"In this paper, we bring out several potential signatures of negative mass
regimes while investigating an expanding spin-orbit (SO) coupled spinor $F=1$
Bose-Einstein condensates by analyzing the dispersion relation of the
single-particle quantum system. In SO-coupled spinor condensates, a negative
mass parameter generates a wave packet that propagates in the opposite
direction of the momentum. We analyze the dynamics of spin waves analytically
and present a simple approach to investigate the expansion of spinor
condensates. In particular, we examine the dynamics when both masses are
negative, which results in the spinor condensates splitting into two
counter-propagating self-interfering packets (SIPs). Using numerical
simulations of the coupled Gross-Pitaevskii equations, we demonstrate the
density expansion and self-interference patterns with and without magnetization
for repulsive and attractive interactions with different coupling parameters.
The highlight of our investigation is that we are able to unearth several
phenomena observed in experiments, such as self-interfering packets, pileup,
modulation instability, slow down, self-trapping, and gap solitons. In
particular, the gap soliton exists at the gap created by the intersection of
two negative masses.",2304.08844v2
2009-05-13,Exciting the Scissors Mode in crystals with strong spin-orbit coupling as in Bose-Einstein Condensates,"In a recent study of the magnetic properties of rare-earth systems the two
extreme situations have been considered in which the crystalline electrostatic
field is large or small with respect to the spin-orbit interaction. In the
first case the orbitals of localized electrons are firmly coupled to the
lattice so that while an applied magnetic field rotates the spin, the charge
profile remains fixed to the lattice. In the second case an applied magnetic
field rotates both spin and density profile, even though through a very small
angle. We show that in this second case we have, in addition to the use of
photons or electrons, the possibility of exciting and observing the Scissors
Mode in crystals in a way analogous to that used in Bose-Einstein Condensates.",0905.2100v2
2010-03-11,Spin-orbit excitations of quantum wells,"Confinement asymmetry effects on the photoabsorption of a quantum well are
discussed by means of a sum-rules approach using a Hamiltonian including a
Rashba spin-orbt coupling. We show that while the strength of the excitation is
zero when the spin-orbit coupling is neglected, the inclusion of the spin-orbit
interaction gives rise to a non zero strength and mean excitation energy in the
far-infrared region. A simple expression for these quantities up to the second
order in the Rashba parameter was derived. The effect of two-body Coulomb
interaction is then studied by means of a Quantum Monte Carlo calculation,
showing that electron-electron correlations induce only a small deviation from
the independent particle model result.",1003.2433v1
2010-06-11,Exchange cotunneling through quantum dots with spin-orbit coupling,"We investigate the effects of spin-orbit interaction (SOI) on the exchange
cotunneling through a spinful Coulomb blockaded quantum dot. In the case of
zero magnetic field, Kondo effect is shown to take place via a Kramers doublet
and the SOI will merely affect the Kondo temperature. In contrast, we find that
the breaking of time-reversal symmetry in a finite field has a marked influence
on the effective Anderson, and Kondo models for a single level. The nonlinear
conductance can now be asymmetric in bias voltage and may depend strongly on
direction of the magnetic field. A measurement of the angle dependence of
finite-field cotunneling spectroscopy thus provides valuable information about
orbital, and spin degrees of freedom and their mutual coupling.",1006.2371v1
2010-09-28,Singlet-triplet avoided crossings and effective $g$ factor versus spatial orientation of spin-orbit-coupled quantum dots,"We study avoided crossings opened by spin-orbit interaction in the energy
spectra of one- and two-electron anisotropic quantum dots in perpendicular
magnetic field. We find that for simultaneously present Rashba and Dresselhaus
interactions the width of avoided crossings and the effective $g$ factor depend
on the dot orientation within (001) crystal plane. The extreme values of these
quantities are obtained for [110] and [1$\bar{1}$0] orientations of the dot.
The width of singlet-triplet avoided crossing changes between these two
orientations by as much as two orders of magnitude. The discussed modulation
results from orientation-dependent strength of the Zeeman interaction which
tends to polarize the spins in the direction of the external magnetic field and
thus remove the spin-orbit coupling effects.",1009.5637v1
2011-08-04,Condensate fraction of a resonant Fermi gas with spin-orbit coupling in three and two dimensions,"We study the effects of laser-induced Rashba-like spin-orbit coupling along
the BCS-BEC crossover of a Feshbach resonance for a two-spin-component Fermi
gas. We calculate the condensate fraction in three and two dimensions and find
that this quantity characterizes the crossover better than other quantities,
like the chemical potential or the pairing gap. By considering both the singlet
and the triplet pairings, we calculate the condensate fraction and show that a
large enough spin-orbit interaction enhances the singlet condensate fraction in
the BCS side while suppressing it on the BEC side.",1108.1132v3
2011-10-04,Rashba spin-orbit coupled atomic Fermi gases,"We investigate theoretically BEC-BCS crossover physics in the presence of a
Rashba spin-orbit coupling in a system of two-component Fermi gas with and
without a Zeeman field that breaks the population balance between the two
components. A new bound state (Rashba pair) emerges because of the spin-orbit
interaction. We study the properties of Rashba pairs using a standard pair
fluctuation theory. At zero temperature, the Rashba pairs condense into a
macroscopic mixed spin state. We discuss in detail the experimental signatures
for observing the condensation of Rashba pairs by calculating various physical
observables which characterize the properties of the system and can be measured
in experiment.",1110.0805v1
2012-09-13,The Hubbard model with spin orbit coupling: a lattice gauge theory approach,"We study the symmetry properties of the Hubbard model with spin-orbit
interactions of Rashba and Dresselhaus type. These interactions break the
rotational symmetry in spin space, so that the magnetic order cannot be
excluded by using the Bogoliubov inequality method. Nevertheless, we rigorously
show that the existence of the magnetic long-range orders may be ruled out when
the Rashba and Dresselhaus coupling constants are equal in modulus, whereas the
eta-pairing can be always ruled out, regardless of the microscopic parameters
of the model. These results are obtained by imposing locally the SU(2) gauge
symmetry on the lattice, and rewriting the spin-orbit interactions in such a
way that they are included in the path ordered of the gauge field on lattice.",1209.2844v1
2012-09-28,Theory of spin-orbit enhanced electric-field control of magnetism in multiferroic BiFeO3,"We present a microscopic theory that shows the importance of spin-orbit
coupling in perovskite compounds with heavy ions. In BiFeO3 (BFO) the
spin-orbit coupling at the bismuth ion sites results in a special kind of
magnetic anisotropy that is linear in the applied E-field. This interaction can
convert the cycloid ground state into a homogeneous antiferromagnet, with a
weak ferromagnetic moment whose orientation can be controlled by the E-field
direction. Remarkably, the E-field control of magnetism occurs without poling
the ferroelectric moment, providing a pathway for reduced energy dissipation in
spin-based devices made of insulators.",1209.6612v4
2013-06-05,Chiral Ladders and the Edges of Chern Insulators,"The realization and detection of topological phases with ultracold atomic
gases is at the frontier of current theoretical and experimental research.
Here, we identify cold atoms in optical ladders subjected to synthetic magnetic
fields as readily realizable bridges between one-dimensional spin-orbit (time
reversal) topological insulators and two-dimensional Chern insulators. We
reveal three instances of their promising potential: i) they realize spin-orbit
coupling, with the left-right leg degree of freedom playing the role of an
effective spin, ii) their energy bands and eigenstates exactly reproduce the
topological chiral edge modes of two-dimensional Chern insulators, and iii)
they can be tailored to realize a topological phase transition from a trivial
to a topological insulating phase. We propose realistic schemes to observe the
chiral and topological properties of ladder systems with current optical
lattice-based experiments. Our findings open a door to the exploration of the
physics of the edges of Chern insulators and to the realization of spin-orbit
coupling and topological superfluid phases with ultracold atomic gases.",1306.1190v1
2013-10-28,Interaction-Tuned Dynamical Transitions in a Rashba Spin-Orbit Coupled Fermi Gas,"We consider the time evolution of the magnetization in a Rashba
spin-orbit-coupled Fermi gas, starting from a fully-polarized initial state. We
model the dynamics using a Boltzmann equation, which we solve in the
Hartree-Fock approximation. The resulting non-linear system of equations gives
rise to three distinct dynamical regimes with qualitatively different
asymptotic behaviors of the magnetization at long times. The distinct regimes
and the transitions between them are controlled by the interaction strength:
for weakly interacting fermions, the magnetization decays to zero. For
intermediate interactions, it displays undamped oscillations about zero and for
strong interactions, a partially magnetized state is dynamically stabilized.
The dynamics we find is a spin analog of interaction induced self-trapping in
double-well Bose Einstein condensates. The predicted phenomena can be realized
in trapped Fermi gases with synthetic spin-orbit interactions.",1310.7639v1
2014-04-23,Effect of spin orbit coupling and Hubbard $U$ on the electronic structure of IrO$_2$,"We have studied in detail the electronic structure of IrO$_2$ including
spin-orbit coupling (SOC) and electron-electron interaction, both within the
GGA+U and GGA+DMFT approximations. Our calculations reveal that the Ir t$_{2g}$
states at the Fermi level largely retain the J$_{\rm eff}$ = $\frac{1}{2}$
character, suggesting that this complex spin-orbit entangled state may be
robust even in metallic IrO$_2$. We have calculated the phase diagram for the
ground state of IrO$_2$ as a function of $U$ and find a metal insulator
transition that coincides with a magnetic phase change, where the effect of SOC
is only to reduce the critical values of $U$ necessary for the transition. We
also find that dynamic correlations, as given by the GGA+DMFT calculations,
tend to suppress the spin-splitting, yielding a Pauli paramagnetic metal for
moderate values of the Hubbard $U$. Our calculated optical spectra and
photoemission spectra including SOC are in good agreement with experiment
demonstrating the importance of SOC in IrO$_2$.",1404.5991v1
2015-11-10,Electronic structure and spin-orbit driven novel magnetism in d4.5 insulator Ba3YIr2O9,"We have carried out a detailed first-principles study of a d$^{4.5}$
quaternary iridate Ba$_3$YIr$_2$O$_9$ both in its 6H-perovskite-type ambient
pressure (AP) phase and also for the high pressure (HP) cubic phase. Our
analysis reveals that the AP phase belongs to the intermediate spin-orbit
coupling (SOC) regime. This is further supported by the identification of the
spin moment as the primary order parameter (POP) obtained from a magnetic
multipolar analysis. The large $t_{2g}$ band width renormalizes the strength of
SOC and the Ir intersite exchange interaction dominates resulting in long range
magnetic order in the AP phase. In addition to SOC and Hubbard $U$, strong
intradimer coupling is found to be crucial for the realization of the
insulating state. At high pressure (HP) the system undergoes a structural
transformation to the disordered cubic phase. In sharp contrast to the AP
phase, the calculated exchange interactions in the HP phase are found to be
much weaker and SOC dominates leading to a quantum spin orbital liquid (SOL)
state.",1511.03112v1
2010-05-07,Tuning independently Fermi energy and spin splitting in Rashba systems: Ternary surface alloys on Ag(111),"By detailed first-principles calculations we show that the Fermi energy and
the Rashba splitting in disordered ternary surface alloys (BiPbSb)/Ag(111) can
be independently tuned by choosing the concentrations of Bi and Pb. The
findings are explained by three fundamental mechanisms, namely the relaxation
of the adatoms, the strength of the atomic spin-orbit coupling, and band
filling. By mapping the Rashba characteristics,i.e.the splitting and the Rashba
energy, and the Fermi energy of the surface states in the complete range of
concentrations. Our results suggest to investigate experimentally effects which
rely on the Rashba spin-orbit coupling in dependence on spin-orbit splitting
and band filling.",1005.1162v1
2017-01-02,Rashba spin-orbit interaction enhanced by graphene in-plane deformations,"Graphene consists in a single-layer carbon crystal where 2$p_z$ electrons
display a linear dispersion relation in the vicinity of the Fermi level,
conveniently described by a massless Dirac equation in $2+1$ spacetime.
Spin-orbit effects open a gap in the band structure and offer perspectives for
the manipulation of the conducting electrons spin. Ways to manipulate
spin-orbit couplings in graphene have been generally assessed by proximity
effects to metals that do not compromise the mobility of the unperturbed system
and are likely to induce strain in the graphene layer. In this work we explore
the $\rm{U(1)}\times SU(2)$ gauge fields that result from the uniform
stretching of a graphene sheet under a perpendicular electric field.
Considering such deformations is particularly relevant due to the
counter-intuitive enhancement of the Rashba coupling between 30-50% for small
bond deformations well known from tight-binding and DFT calculations. We report
the accessible changes that can be operated in the band structure in the
vicinity of the K points as a function of the deformation strength and
direction.",1701.00363v2
2018-05-25,"Calculating the transport properties of magnetic materials from first-principles including thermal and alloy disorder, non-collinearity and spin-orbit coupling","A density functional theory based two-terminal scattering formalism that
includes spin-orbit coupling and spin non-collinearity is described. An
implementation using tight-binding muffin-tin orbitals combined with extensive
use of sparse matrix techniques allows a wide variety of inhomogeneous
structures to be flexibly modelled with various types of disorder including
temperature induced lattice and spin disorder. The methodology is illustrated
with calculations of the temperature dependent resistivity and magnetization
damping for the important substitutional disordered magnetic alloy Permalloy
(Py), Ni$_{80}$Fe$_{20}$. Comparison of calculated results with recent
experimental measurements of the damping (including its temperature dependence)
indicates that the scattering approach captures the most important
contributions to this important property.",1805.10062v1
2013-09-24,Noncompact dynamical symmetry of a spin-orbit coupled oscillator,"We explain the finite as well as infinite degeneracy in the spectrum of a
particular system of spin-1/2 fermions with spin-orbit coupling in three
spatial dimensions. Starting from a generalized Runge-Lenz vector, we
explicitly construct a complete set of symmetry operators, which span a
noncompact SO(3,2) algebra. The degeneracy of the physical spectrum only
involves a particular, infinite, so called singleton representation. In the
branch where orbital and spin angular momentum are aligned the full
representation appears, constituting a 3D analogue of Landau levels.
Anti-aligning the spin leads to a finite degeneracy due to a truncation of the
singleton representation. We conclude the paper by constructing the spectrum
generating algebra of the problem.",1309.6128v2
2014-05-06,Magnetic and transport signatures of Rashba spin-orbit coupling on the ferromagnetic Kondo lattice model in two dimensions,"Motivated by emergent phenomena at oxide surfaces and interfaces,
particularly those involving transition metal oxides with perovskite crystal
structure such as LaTiO3/SrTiO3, we examine the ferromagnetic Kondo lattice
model (FKLM) in the presence of a Rashba spin-orbit coupling (RSOC). Using
numerical techniques, under the assumption that the electrons on localized
orbitals may be treated as classical continuum spins, we compute various
charge, spin and transport properties on square clusters at zero temperature.
We find that the main effect of the RSOC is the destruction of the
ferromagnetic state present in the FKLM at low electron fillings, with the
consequent suppression of conductivity. In addition, near half-filling the RSOC
leads to a departure of the antiferromagnetic state of the FKLM with a
consequent reduction to the intrinsic tendency to electronic phase separation.
The interplay between phase separation on one side, and magnetic and transport
properties on the other, is carefully analyzed as a function of the
RSOC/hopping ratio.",1405.1240v2
2017-10-10,Magnetic spin-orbit interaction directs Bloch surface waves,"We study the directional excitation of optical surface waves controlled by
the magnetic field of light. We theoretically predict that a spinning magnetic
dipole develops a tunable unidirectional coupling of light to TE-polarized
Bloch surface waves (BSWs). Experimentally, we show that the helicity of light
projected onto a subwavelength groove milled in the top layer of a 1D photonic
crystal (PC) controls the power distribution between two TE-polarized BSWs
excited on both sides of the groove. Such a phenomenon is shown to be mediated
solely by the helicity of the magnetic field of light, thus revealing a
magnetic spin-orbit interaction. Remarkably, this magnetic optical effect is
clearly observed with a near-field coupler governed by an electric dipole
moment: it is of the same order of magnitude as the electric optical effects
involved in the coupling. The magnetic spin-orbit interaction opens new degrees
of freedom in the manipulation of light and offers appealing novel
opportunities in the development of integrated optical functionalities.",1710.03584v2
2018-01-11,Designing Nanomagnet Arrays for Topological Nanowires in Si,"Recent interest in topological quantum computing has driven research into
topological nanowires, one-dimensional quantum wires that support topological
modes including Majorana fermions. Most topological nanowire designs rely on
materials with strong spin-orbit coupling, such as InAs or InSb, used in
combination with superconductors. It would be advantageous to fabricate
topological nanowires using Si owing to its mature technology. However, the
intrinsic spin-orbit coupling in Si is weak. One approach that could circumvent
this material deficiency is to rotate the electron spins using nanomagnets.
Here, we perform detailed simulations of realistic Si/SiGe systems with an
artificial spin-orbit gap induced by a nanomagnet array. Most of our results
are also generalizable to other nanomagnet-based topological nanowire designs.
By studying several concrete examples, we gain insight into the effects of
nanomagnet arrays, leading to design rules and guidelines. Finally, we present
an experimentally realizable design using magnets with a single polarization.",1801.03676v1
2018-01-30,Quantum ring with the Rashba spin-orbit interaction in the regime of strong light-matter coupling,"We developed the theory of electronic properties of semiconductor quantum
rings with the Rashba spin-orbit interaction irradiated by an off-resonant
high-frequency electromagnetic field (dressing field). Within the Floquet
theory of periodically driven quantum systems, it is demonstrated that the
dressing field drastically modifies all electronic characteristics of the
rings, including spin-orbit coupling, effective electron mass and optical
response. Particularly, the present effect paves the way to controlling the
spin polarization of electrons with light in prospective ring-shaped spintronic
devices.",1801.10250v3
2020-12-11,Dirac imprints on the $g$-factor anisotropy in graphene,"Dirac electrons in graphene are to lowest order spin 1/2 particles, owing to
the orbital symmetries at the Fermi level. However, anisotropic corrections in
the $g$-factor appear due to the intricate spin-valley-orbit coupling of chiral
electrons. We resolve experimentally the $g$-factor along the three orthogonal
directions in a large-scale graphene sample. We employ a Hall bar structure
with an external magnetic field of arbitrary direction, and extract the
effective $g$-tensor via resistively-detected electron spin resonance. We
employ a theoretical perturbative approach to identify the intrinsic and
extrinsic spin orbit coupling and obtain a fundamental parameter inherent to
the atomic structure of $^{12}$C, commonly used in ab-initio models.",2012.06324v1
2018-08-17,Distinct Nature of Orbital Selective Mott Phases Dominated by the Low-energy Local Spin Fluctuations,"Quantum orbital selective Mott (OSM) transitions are investigated within
dynamical mean-field theory based on a two-orbital Hubbard model with different
bandwidth at half filling. We find two distinct OSM phases both showing
coexistence of itinerant electrons and localized spins, dependent on whether
the Hund's coupling is full or of Ising type. The critical values and the
nature of the OSM transitions are efficiently determined by entanglement
entropy. We reveal that vanishing of the Kondo energy scale evidenced by
absence of local spin fluctuations at low frequency in local dynamical spin
susceptibility is responsible for the appearance of non-Fermi-liquid OSM phase
in Ising Hund's coupling case. We argue that this scenario can also be applied
to account for emergent quantum non-Fermi liquid in one-band Hubbard model when
short-range antiferromagnetic order is considered.",1808.05786v1
2021-09-16,Infrared to terahertz optical conductivity of $n$-type and $p$-type monolayer MoS$_2$ in the presence of Rashba spin-orbit coupling,"We investigate the effect of Rashba spin-orbit coupling (SOC) on the
optoelectronic properties of n- and p-type monolayer MoS2. The optical
conductivity is calculated within the Kubo formalism. We find that the
spin-flip transitions enabled by the Rashba SOC result in a wide absorption
window in the optical spectrum. Furthermore, we evaluate the effects of the
polarization direction of the radiation, temperature, carrier density, and the
strength of the Rashba spin-orbit parameter on the optical conductivity. We
find that the position, width, and shape of the absorption peak or absorption
window can be tuned by varying these parameters. This study shows that
monolayer MoS2 can be a promising tunable optical and optoelectronic material
that is active in the infrared to terahertz spectral range.",2109.08054v1
2021-09-23,Strain-induced topological phase transition at (111) SrTiO$_3$-based heterostructures,"The quasi-two-dimensional electronic gas at the (111) SrTiO$_3$-based
heterostructure interfaces is described by a multi-band tight-binding model
providing electronic bands in agreement at low energies with photoemission
experiments. We analyze both the roles of the spin-orbit coupling and of the
trigonal crystal field effects. We point out the presence of a regime with
sizable strain where the band structure exhibits a Dirac cone whose features
are consistent with \textit{ab-initio} approaches. The combined effect of
spin-orbit coupling and trigonal strain gives rise to non-trivial spin and
orbital angular momenta patterns in the Brillouin zone and to quantum spin Hall
effect by opening a gap at the Dirac cone. The system can switch from a
conducting to a topological insulating state \textit{via} modification of
trigonal strain within a parameter range which is estimated to be
experimentally achievable.",2109.11563v1
2024-02-08,Understanding electronic excited states in BiFeO$_3$ via ab initio calculations and symmetry analysis,"BiFeO$_3$ is a technologically relevant multiferroic perovskite featuring
ferroelectricity and antiferromagnetism. Its lattice, magnetic, and
ferroelectric degrees of freedoms are coupled to its optically active
excitations and thus hold the potential to be reversible probed and controlled
by light. In this work, we combine ab initio density functional and many-body
perturbation theory methods with an extensive symmetry and atomic-orbital
analysis to describe and understand the electronic excited states spectrum and
its imprint on the optical absorption spectrum with quantitative accuracy and
qualitative insights. We find that the optical absorption spectrum of BiFeO$_3$
contain several strongly bound and spatially localized electronic transitions
in which the spin-degree of freedom is almost fully flipped. With our analysis
we thoroughly characterize these localized spin-flip transitions in terms of
the unusual crystal field splitting of Fe-$3d$ single-electron orbitals. Our
symmetry analysis further allows us to thoroughly explain how the spin content
and the energetic fine structure of these strongly bound excitons are dictated
by the interplay between crystal symmetry, electron-hole attraction, and the
spin-orbit coupling.",2402.05542v2
2024-02-12,Tuning proximity spin-orbit coupling in graphene/NbSe$_2$ heterostructures via twist angle,"We investigate the effect of the twist angle on the proximity spin-orbit
coupling (SOC) in graphene/NbSe$_2$ heterostructures from first principles. The
low-energy Dirac bands of several different commensurate twisted supercells are
fitted to a model Hamiltonian, allowing us to study the twist-angle dependency
of the SOC in detail. We predict that the magnitude of the Rashba SOC can
triple, when going from $\Theta=0^\circ$ to $\Theta=30^\circ$ twist angle.
Furthermore, at a twist angle of $\Theta\approx23^\circ$ the in-plane spin
texture acquires a large radial component, corresponding to a Rashba angle of
up to $\Phi=25^\circ$. The twist-angle dependence of the extracted proximity
SOC is explained by analyzing the orbital decomposition of the Dirac states to
reveal with which NbSe$_2$ bands they hybridize strongest. Finally, we employ a
Kubo formula to evaluate the efficiency of conventional and unconventional
charge-to-spin conversion in the studied heterostructures.",2402.07533v1
2024-02-22,Dominant 1/3-filling Correlated Insulator States and Orbital Geometric Frustration in Twisted Bilayer Graphene,"Geometric frustration is a phenomenon in a lattice system where not all
interactions can be satisfied, the simplest example being antiferromagnetically
coupled spins on a triangular lattice. Frustrated systems are characterized by
their many nearly degenerate ground states, leading to non-trivial phases such
as spin ice and spin liquids. To date most studies are on geometric frustration
of spins; much less explored is orbital geometric frustration. For electrons in
twisted bilayer graphene (tBLG) at denominator 3 fractional filling, Coulomb
interactions and the Wannier orbital shapes are predicted to strongly constrain
spatial charge ordering, leading to geometrically frustrated ground states that
produce a new class of correlated insulators (CIs). Here we report the
observation of dominant denominator 3 fractional filling insulating states in
large angle tBLG; these states persist in magnetic fields and display magnetic
ordering signatures and tripled unit cell reconstruction. These results are in
agreement with a strong-coupling theory of symmetry-breaking of geometrically
frustrated fractional states.",2402.14774v1
2005-06-23,"Interplay among Spin, Orbital and Lattice Degrees of Freedom in $t_{2g}$ Electron Systems with Edge-Sharing Network of Octahedra","Transition metal oxides whose lattice structure has edge-sharing network of
octahedra constitute a diverse group of intriguing materials besides compounds
with corner-sharing octahedra such as perovskites. We present a theoretical
investigation of the interplay among spin, orbital and lattice degrees of
freedom in these materials. We focus on $t_{2g}$ electron systems where a keen
competition among those degrees of freedom is expected to emerge under a
relatively weak Jahn-Teller coupling. We study the interplay between spin and
orbital degrees of freedom in vanadium spinels and titanium pyroxenes. We
clarify the important role of the strong anisotropy in the orbital interactions
due to the edge-sharing geometry. We also discuss the interplay between spin
and lattice in chromium spinels focusing on the magnetization process under the
external magnetic field.",0506598v1
2005-08-26,Infrared absorption in a quantum wire in the presence of spin-orbit coupling: a technique to measure different types of spin-orbit interaction strengths,"We show that the dominant absorption peak due to inter-subband transition in
a gated quantum wire, with two occupied subbands, will split into a main peak
and two satellite peaks if both Rashba and Dresselhaus spin-orbit interactions
are present. One satellite peak will be red-shifted, and the other
blue-shifted. From the relative intensity of either satellite peak, and the
magnitude of the red- or blue-shift, we can determine both Rashba and
Dresselhaus interaction strengths separately, if we also carry out a Hall
measurement to determine the carrier concentration and a quantized conductance
step measurement to determine the energy separation between subbands. This
method may be a convenient alternative to usual magneto-transport measurements
used to measure spin orbit interaction strengths. It is also more powerful
because it allows us to measure the strengths of the two types of interactions
separately.",0508638v2
2005-10-07,2D SNS junction with Rashba spin-orbit interaction,"The effect of Rashba spin-orbital interaction upon supercurrent in S-2DEG-S
proximity junctions is investigated in the clean limit. Generalization of
Beenakker's formula for Andreev levels to the case of spin-orbital scattering
is presented. Spin-orbit - induced splitting of Andreev bound-states is
predicted for a junction of infinite width, and with non-vanishing normal
backscattering at S/N interfaces. Semiclassical average of the Josephson
current is however insensitive to the Rashba coupling as long as
electron-electron interaction in 2DEG is neglected.",0510182v2
2005-11-22,Spin-Orbit Berry Phase in a Quantum Loop,"We have found a manifestation of spin-orbit Berry phase in the conductance of
a mesoscopic loop with Rashba spin-orbit coupling placed in an external
magnetic field perpendicular to the loop plane. In detail, the transmission
probabilities for a straight quantum wire and for a quantum loop made of the
same wire have been calculated and compared with each other. The difference
between them has been investigated and identified with a manifestation of
spin-orbit Berry phase. The non-adiabaticity effects at small radii of the loop
have been found as well.",0511549v2
2002-06-05,A mass formula for baryon resonances,"Light-baryon resonances with u,d, and s quarks only can be classified using
the non-relativistic quark model. When we assign to baryon resonances with
total angular momenta J intrinsic orbital angular momenta L and spin S we make
the following observations: plotting the squared masses of the light-baryon
resonances against these intrinsic orbital angular momenta L, Delta's with even
and odd parity can be described by the same Regge trajectory. For a given L,
nucleon resonances with spin S=3/2 are approximately degenerate in mass with
Delta resonances of same total orbital momentum L. To which total angular
momentum L and S couple has no significant impact on the baryon mass. Nucleons
with spin 1/2 are shifted in mass; the shift is - in units of squared masses -
proportional to the component in the wave function which is antisymmetric in
spin and flavor. Sequential resonances in the same partial wave are separated
in mass square by the same spacing as observed in orbital angular momentum
excitations. Based on these observations, a new baryon mass formula is proposed
which reproduces nearly all known baryon masses.",0206012v1
1997-09-28,The Nuclear Spin-Orbit Force in Chiral Effective Field Theories,"A compelling feature of relativistic mean-field phenomenology has been the
reproduction of spin-orbit splittings in finite nuclei after fitting only to
equilibrium properties of infinite nuclear matter. This successful result
occurs when the velocity dependence of the equivalent central potential that
leads to saturation arises primarily because of a reduced nucleon effective
mass. The spin-orbit interaction is then also specified when one works in a
four-component Dirac framework. Here the nature of the spin-orbit force in more
general chiral effective field theories of nuclei is examined, with an emphasis
on the role of the tensor coupling of the isoscalar vector meson (omega) to the
nucleon.",9709064v1
2003-11-20,Spin-orbit correlation energy in neutron matter,"We study the relevance of the energy correlation produced by the two-body
spin-orbit coupling present in realistic nucleon-nucleon potentials. To this
purpose, the neutron matter Equation of State (EoS) is calculated with the
realistic two-body Argonne $v_8'$ potential. The shift occuring in the EoS when
spin-orbit terms are removed is taken as an estimate of the spin-orbit
correlation energy. Results obtained within the Bethe-Brueckner-Goldstone
expansion, extended up to three hole-line diagrams, are compared with other
many-body calculations recently presented in the literature. In particular,
excellent agreement is found with the Green's function Monte-Carlo method. This
agreement indicates the present theoretical accuracy in the calculation of the
neutron matter EoS.",0311070v1
2011-02-23,Influence of the spin-orbit interaction in the impurity-band states of n-doped semiconductors,"We study numerically the effects of the Rashba spin-orbit interaction on the
model of electrons in n-doped semiconductors of Matsubara and Toyozawa (MT). We
focus on the analysis of the density of states (DOS) and the inverse
participation ratio (IPR) of the spin-orbit perturbed states in the MT set of
energy eigenstates in order to characterize the eigenstates with respect to
their extended or localized nature. The finite sizes that we are able to
consider necessitate an enhancement of the spin-orbit coupling strength in
order to obtain a meaningful perturbation. The IPR and DOS are then studied as
a function of the enhancement parameter.",1102.4760v1
2013-10-31,Dilute Magnetism and Spin-Orbital Percolation Effects in Rh-doped Sr2IrO4,"We have used a combination of resonant magnetic x-ray scattering (RMXS) and
x-ray absorption spectroscopy (XAS) to investigate the properties of the doped
spin-orbital Mott insulator Sr2Ir(1-x)Rh(x)O4 (0.07 < x < 0.70). We show that
Sr2Ir(1-x)Rh(x)O4 represents a unique model system for the study of dilute
magnetism in the presence of strong spin-orbit coupling, and provide evidence
of a doping-induced change in magnetic structure and a suppression of magnetic
order at x_c ~ 0.17. We demonstrate that Rh-doping introduces Rh3+/Ir5+ ions
which effectively hole-dope this material. We propose that the magnetic phase
diagram for this material can be understood in terms of a novel spin-orbital
percolation picture.",1311.0039v2
2014-07-08,Quantum oscillation signatures of nodal spin-orbit coupling in underdoped bilayer high Tc cuprates,"The highest superconducting transition temperatures in the cuprates are
achieved in bilayer and trilayer systems, highlighting the importance of
intralayer interactions for high Tc. It has been argued that interlayer
hybridization vanishes along the nodal directions by way of a specific pattern
of orbital overlap. Recent quantum oscillation measurements in bilayer cuprates
have provided evidence for a residual bilayer-splitting at the nodes that is
sufficiently small to enable magnetic breakdown tunneling at the nodes. Here we
show that several key features of the experimental data can be understood in
terms weak spin-orbit interactions naturally present in bilayer systems, whose
primary effect is to cause the magnetic breakdown to be accompanied by a spin
flip. These features can now be understood include the equidistant set of three
quantum oscillation frequencies, the asymmetry of the quantum oscillation
amplitudes in c-axis transport compared to ab-plane transport, and the
anomalous magnetic field angle dependence of the amplitude of side frequencies
suggestive of small effective g-factors. We suggest that spin-orbit
interactions in bilayer systems can further affect the structure of the nodal
quasiparticle spectrum in the superconducting phase.",1407.2291v2
2016-11-02,Spin-Orbit Dimers and Non-Collinear Phases in $d^1$ Cubic Double Perovskites,"We formulate and study a spin-orbital model for a family of cubic double
perovskites with $d^1$ ions occupying a frustrated fcc sublattice. A
variational approach and a complimentary analytical analysis reveal a rich
variety of phases emerging from the interplay of Hund's and spin-orbit
couplings (SOC). The phase digram includes non-collinear ordered states, with
or without net moment, and, remarkably, a large window of a non-magnetic
disordered spin-orbit dimer phase. The present theory uncovers the physical
origin of the unusual amorphous valence bond state experimentally suggested for
Ba$_2B$MoO$_6$ ($B$=Y,Lu), and predicts possible ordered patterns in
Ba$_2B$OsO$_6$ ($B$=Na,Li) compounds.",1611.00646v3
2012-04-12,Magnetic order and ice rules in the multiferroic spinel FeV2O4,"We present a neutron diffraction study of FeV2O4, which is rare in exhibiting
spin and orbital degrees of freedom on both cation sublattices of the spinel
structure. Our data confirm the existence of three structural phase transitions
previously identified with x-ray powder diffraction, and reveal that the lower
two transitions are associated with sequential collinear and canted
ferrimagnetic transitions involving both cation sites. Through consideration of
local crystal and spin symmetry, we further conclude that Fe2+ cations are
ferro-orbitally ordered below 135K and V3+ orbitals order at 60K in accordance
with predictions for vanadium spinels with large trigonal distortions and
strong spin-orbit coupling. Intriguingly, the direction of ordered vanadium
spins at low temperatures obey `ice rules' more commonly associated with the
frustrated rare-earth pyrochlore systems.",1204.2812v3
2017-09-30,The impacts of the quantum-dot confining potential on the spin-orbit effect,"For a nanowire quantum dot with the confining potential modeled by both the
infinite and the finite square wells, we obtain exactly the energy spectrum and
the wave functions in the strong spin-orbit coupling regime. We find that
regardless of how small the well height is, there are at least two bound states
in the finite square well: one has the $\sigma^{x}\mathcal{P}=-1$ symmetry and
the other has the $\sigma^{x}\mathcal{P}=1$ symmetry. When the well height is
slowly tuned from large to small, the position of the maximal probability
density of the first excited state moves from the center to $x\ne0$, while the
position of the maximal probability density of the ground state is always at
the center. A strong enhancement of the spin-orbit effect is demonstrated by
tuning the well height. In particular, there exists a critical height
$V^{c}_{0}$, at which the spin-orbit effect is enhanced to maximal.",1710.00816v3
2017-12-29,Symmetry Preservation and Critical Fluctuations in a Pseudospin Crossover Perovskite LaCoO$_3$,"Spin-state crossover beyond a conventional ligand-field theory has been a
fundamental issue in condensed matter physics. Here, we report microscopic
observations of spin states and low-energy dynamics through orbital-resolved
NMR spectroscopy in the prototype compound LaCoO$_3$. The $^{59}$Co NMR
spectrum shows the preserved crystal symmetry across the crossover,
inconsistent with $d$ orbital ordering due to the Jahn-Teller distortion. The
orbital degeneracy results in a pseudospin ($\tilde{J} = 1$) excited state with
an orbital moment observed as $^{59}$Co hyperfine coupling tensors. We found
that the population of the excited state evolves above the heart crossover
temperature. The crossover involves critical spin-state fluctuations emerging
under the magnetic field. These results suggest that the spin-state crossover
can be mapped into a statistical problem, analogous to the supercritical liquid
in liquid-gas transition.",1712.10137v1
2018-09-03,Manipulation of magnetizations by spin-orbit torques,"The control of magnetization by electric current is a rapidly developing area
motivated by a strong synergy between breakthrough basic research discoveries
and industrial applications in the fields of magnetic recording, magnetic field
sensors, spintronics and nonvolatile memories. In recent years, the discovery
of the spin-orbit torque has opened a spectrum of opportunities to manipulate
the magnetization efficiently. This article presents a review of the historical
background and recent literature focusing on spin-orbit torques (SOTs),
highlighting the most exciting new scientific results and suggesting promising
future research directions. It starts with an introduction and overview of the
underlying physics of spin-orbit coupling effects in bulk and at interfaces,
then describes the use of SOTs to control ferromagnets and antiferromagnets.
Finally, we summarize the prospects for the future developments of spintronics
devices based on SOTs.",1809.00546v1
2018-09-24,Spin-orbit proximity effect in graphene on metallic substrates: decoration vs intercalation with metal adatoms,"The so-called spin-orbit proximity effect experimentally realized in graphene
(G) on several different heavy metal surfaces opens a new perspective to
engineer the spin-orbit coupling (SOC) for new generation spintronics devices.
Here, via large-scale density functional theory (DFT) calculations performed
for two distinct graphene/metal models, G/Pt(111) and G/Au/Ni(111), we show
that the spin-orbit splitting of the Dirac cones (DCs) in these stuctures might
be enhanced by either adsorption of adatoms on top of graphene (decoration) or
between the graphene and the metal (intercalation). While the decoration by
inducing strong graphene-adatom interaction suppresses the linearity of the G's
$\pi$ bands, the intercalated structures reveal a weaker adatom-mediated
graphene/substrate hybridization which preserves well-defined although
broadened DCs. Remarkably, the intercalated G/Pt(111) structure exhibits
splittings considerably larger than the defect-free case.",1809.08773v2
2012-05-07,Josephson current through interacting double quantum dots with spin-orbit coupling,"We study the effect of Rashba spin-orbit interaction on the Josephson current
through a double quantum dot in presence of Coulomb repulsion. In particular,
we describe the characteristic effects on the magnetic-field induced
singlet-triplet transition in the molecular regime. Exploring the whole
parameter space, we analyze the effects of the device asymmetry, the
orientation of the applied magnetic field with respect to the spin-orbit
interaction, and finite temperatures. We find that at finite temperatures the
orthogonal component of the spin-orbit interaction exhibits a similar effect as
the Coulomb interaction inducing the occurrence of a {\pi}-phase at
particle-hole symmetry. This provides a new route to the experimental
observability of the {\pi}-phase in multi-level quantum dots.",1205.1291v2
2017-05-18,Classical Emergence of Intrinsic Spin-Orbit Interaction of Light at the Nanoscale,"Traditionally, in macroscopic geometrical optics intrinsic polarization and
spatial degrees of freedom of light can be treated independently. However, at
the subwavelength scale these properties appear to be coupled together, giving
rise to the spin-orbit interaction (SOI) of light. In this work we address
theoretically the classical emergence of the optical SOI at the nanoscale. By
means of a full-vector analysis involving spherical vector waves we show that
the spin-orbit factorizability condition, accounting the mutual influence
between the amplitude (spin) and phase (orbit), is fulfilled only in the
far-field limit. On the other side, in the near-field region, an additional
relative phase introduces an extra term that hinders the factorization and
reveals an intricate dynamical behavior according to the SOI regime. As a
result, we find a suitable theoretical framework able to capture analytically
the main features of intrinsic SOI of light. Besides allowing for a better
understanding into the mechanism leading to its classical emergence at the
nanoscale, our approach may be useful in order to design experimental setups
that enhance the response of SOI-based effects.",1705.06501v3
2019-12-25,Materials Relevant to Realizing a Field-Effect Transistor based on Spin-Orbit Torques,"Spin-orbit torque is a promising mechanism for writing magnetic memories,
while field-effect transistors are the gold-standard device for logic
operation. The spin-orbit torque field effect transistor (SOTFET) is a proposed
device that couples a spin-orbit-torque-controlled ferromagnet to a
semiconducting transistor channel via the transduction in a magnetoelectric
multiferroic. This allows the SOTFET to operate as both a memory and a logic
device, but its realization depends on the choice of appropriate materials. In
this report, we discuss and parametrize the types of materials that can lead to
a SOTFET heterostructure.",1912.11715v1
2021-04-29,Discreteness of Space from Anisotropic Spin-Orbit Interaction,"Various approaches to Quantum Gravity suggest an existence of a minimal
measurable length. The cost to have such minimal length could be modified
uncertainty principle, modified dispersion relation, non-commutative geometry
or breaking of continuous Lorentz symmetry. In this paper, we propose that
minimal length can be obtained naturally through spin-orbit interaction. We
consider Dresselhaus anisotropic spin-orbit interaction as the perturbative
Hamiltonian. When applied to a particle, it implies that the space, which
seizes this particle, should be quantized in terms of units that depend on
particle's mass. This suggests that all measurable lengths in the space are
quantized in units depending on existent mass and the Dresselhaus coupling
constant. On one side, this indicates a breakdown of the space continuum
picture near the scale of tabletop experiments, and on the other side, it
proposes that spin-orbit interaction is a possible quantum gravity effect at
low energy scale that leads naturally to space quantization.",2104.14563v1
2022-11-17,Flat Band Induced Metal-Insulator Transitions for Weak Magnetic Flux and Spin-Orbit Disorder,"We consider manifolds of tunable all-band flat (ABF) lattices in dimensions d
= 1, 2, parametrized by a manifold angle parameter {\theta}. We study
localization properties of eigenstates in the presence of weak magnetic flux
disorder and weak spin-orbit disorder. We demonstrate that weakly disordered
ABF lattices are described by effective scale-free models where the disorder
strength is scaled out. For weak magnetic flux disorder we observe
sub-exponential localization at flatband energies in d = 1, which differs from
the usual Anderson localization. We also find diverging localisation length at
flatband energies for weak flux values in d = 2, however the character of the
eigenstates at these energies is less clear. For weak spin-orbit coupling
disorder in d = 2 we identify a tunable metal-insulator transition with
mobility edges. We also consider the case of mixed spin-orbit and diagonal
disorder and obtain the metal-insulator transition driven by the manifold
parameter {\theta}.",2211.09410v2
2011-03-21,Spin-orbit hybrid entanglement of photons and quantum contextuality,"We demonstrate electromagnetic quantum states of single photons and of
correlated photon pairs exhibiting ""hybrid"" entanglement between spin and
orbital angular momentum. These states are obtained from entangled photon pairs
emitted by spontaneous parametric down conversion, by employing a $q$-plate for
coupling the spin and orbital degrees of freedom of a photon. Entanglement and
contextual quantum behavior (that is also non-local, in the case of photon
pairs) is demonstrated by the reported violation of the
Clauser-Horne-Shimony-Holt inequality. In addition a classical analog of the
hybrid spin-orbit photonic entanglement is reported and discussed.",1103.3962v1
2014-04-28,Nature of Orbital and Spin Rashba Coupling in the Surface Bands of SrTiO3 and KTaO3,"Tight-binding models for the recently observed surface electronic bands of
SrTiO3 and KTaO3 are analyzed with a view to bringing out the relevance of
momentum-space chiral angular momentum structures of both orbital and spin
origins. Depending on the strength of electric field associated with inversion
symmetry breaking at the surface, the orbital and the accompanying spin angular
momentum structures reveal complex linear and cubic dependencies in the
momentum k (linear and cubic Rashba effects, respectively) in a band-specific
manner. Analytical expressions for the cubic orbital and spin Rashba effects
are derived by way of unitary transformation technique we developed, and
compared to numerical calculations. Due to the C4v symmetry of the perovskite
structure the cubic Rashba effect appears as in-plane modulations.",1404.6858v1
2016-02-22,Staggering antiferromagnetic domain wall velocity in a staggered spin-orbit field,"We demonstrate the possibility to drive an antiferromagnet domain-wall at
high velocities by field-like N\'{e}el spin-orbit torques. Such torques arise
from current-induced local fields that alternate their orientation on each
sub-lattice of the antiferromagnet and whose orientation depend primarily on
the current direction, giving them their field-like character. The domain-wall
velocities that can be achieved by this mechanism are two orders of magnitude
greater than the ones in ferromagnets. This arises from the efficiency of the
staggered spin-orbit fields to couple to the order parameter and from the
exchange-enhanced phenomena in antiferromagnetic texture dynamics, which leads
to a low domain-wall effective mass and the absence of a Walker break-down
limit. In addition, because of its nature, the staggered spin-orbit field can
lift the degeneracy between two 180$^\circ$ rotated states in a collinear
antiferromagnet and provides a force that can move such walls and control the
switching of the states.",1602.06766v2
2016-10-28,Spin-Orbit Torque Efficiency in Compensated Ferrimagnetic Cobalt-Terbium Alloys,"Despite the potential advantages of information storage in
antiferromagnetically coupled materials, it remains unclear whether one can
control the magnetic moment orientation efficiently because of the cancelled
magnetic moment. Here, we report spin-orbit torque induced magnetization
switching of ferrimagnetic Co1-xTbx films with perpendicular magnetic
anisotropy. Current induced switching is demonstrated in all of the studied
film compositions, including those near the magnetization compensation point.
The spin-orbit torque induced effective field is further quantified in the
domain wall motion regime. A divergent behavior that scales with the inverse of
magnetic moment is confirmed close to the compensation point, which is
consistent with angular momentum conservation. Moreover, we also quantify the
Dzyaloshinskii-Moriya interaction energy in the Ta/Co1-xTbx system and we find
that the energy density increases as a function of the Tb concentration. The
demonstrated spin-orbit torque switching, in combination with the fast magnetic
dynamics and minimal net magnetization of ferrimagnetic alloys, promises
spintronic devices that are faster and with higher density than traditional
ferromagnetic systems.",1610.09200v1
2017-02-14,Metal-Insulator Transition and Jeff = 1/2 Spin-Orbit Insulating State in Rutile-based IrO2/TiO2 Superlattices,"By combining 5d transition-metal oxides showing pronounced spin-orbit
interactions and oxide-based heterostructures, we propose rutile-based
IrO2/TiO2 superlattices as promising candidates for unconventional electronic
properties. By means of density-functional-theory simulations complemented with
Hubbard-like corrections, we focus on the evolution of the electronic structure
as a function of the IrO2 layer thickness and predict the heterostructures to
exhibit a thickness-controlled metal-to-insulator transition, crucially related
to the connectivity among IrO6 octahedra. The subtle interplay between electron
correlation and spin-orbit coupling leads to an almost pure Jeff = 1/2
spin-orbit insulating state at the level of atomically-thin IrO2 monolayer with
almost isolated IrO6 octahedra, leading to a predicted emerging state awaiting
for experimental confirmation.",1702.04408v1
2017-01-27,Mixed Weyl semimetals and dissipationless magnetization control in insulators by spin-orbit torques,"Reliable and energy efficient magnetization switching by electrically-induced
spin-orbit torques is of crucial technological relevance for spintronic devices
implementing memory and logic functionality. Here we predict that the strength
of spin-orbit torques and the related Dzyaloshinskii-Moriya interaction in
topologically non-trivial magnetic insulators can exceed by far that of
conventional metallic magnets. In analogy to the quantum anomalous Hall effect,
we explain this extraordinary response in absence of longitudinal currents as a
hallmark of magnetic monopoles in the electronic structure of systems that are
interpreted most naturally within the framework of mixed Weyl semimetals. We
thereby launch the effect of spin-orbit torque into the field of topology and
reveal its crucial role in mediating the topological phase transitions arising
due to the complex interplay between magnetization direction and momentum-space
topology. The concepts presented here may be exploited to understand and
utilize magneto-electric coupling phenomena in insulating ferromagnets and
antiferromagnets.",1701.08050v2
2020-08-12,Prediction of Tunable Spin-Orbit Gapped Materials for Dark Matter Detection,"New ideas for low-mass dark matter direct detection suggest that narrow band
gap materials, such as Dirac semiconductors, are sensitive to the absorption of
meV dark matter or the scattering of keV dark matter. Here we propose
spin-orbit semiconductors - materials whose band gap arises due to spin-orbit
coupling - as low-mass dark matter targets owing to their ~10 meV band gaps. We
present three material families that are predicted to be spin-orbit
semiconductors using Density Functional Theory (DFT), assess their electronic
and topological features, and evaluate their use as low-mass dark matter
targets. In particular, we find that that the tin pnictide compounds are
especially suitable having a tunable range of meV-scale band gaps with
anisotropic Fermi velocities allowing directional detection. Finally, we
address the pitfalls in the DFT methods that must be considered in the ab
initio prediction of narrow-gapped materials, including those close to the
topological critical point.",2008.05062v1
2021-06-18,Electrical tuning of the spin-orbit interaction in nanowire by transparent ZnO gate grown by atomic layer deposition,"We develop an InAs nanowire gate-all-around field-effect transistor using a
transparent conductive zinc oxide (ZnO) gate electrode, which is in-situ atomic
layer deposited after growth of gate insulator of Al2O3. We perform
magneto-transport measurements and find a crossover from weak localization to
weak antilocalization effect with increasing gate voltage, which demonstrates
that the Rashba spin-orbit coupling is tuned by the gate electrode. The
efficiency of the gate tuning of the spin-orbit interaction is higher than
those obtained for two-dimensional electron gas, and as high as that for a
gate-all-around nanowire metal-oxide-semiconductor field-effect transistor that
was previously reported. The spin-orbit interaction is discussed in line with
not only conventionally used one-dimensional model but also recently proposed
model that considers effects of microscopic band structures of materials.",2106.10036v1
2011-12-20,Ferromagnetic order of nuclear spins coupled to conduction electrons: a combined effect of the electron-electron and spin-orbit interactions,"We analyze the ordered state of nuclear spins embedded in an interacting
two-dimensional electron gas (2DEG) with Rashba spin-orbit interaction (SOI).
Stability of the ferromagnetic nuclear-spin phase is governed by nonanalytic
dependences of the electron spin susceptibility $\chi^{ij}$ on the momentum
($\tilde{\mathbf{q}}$) and on the SOI coupling constant ($\alpha$). The uniform
($\tq=0$) spin susceptibility is anisotropic (with the out-of-plane component,
$\chi^{zz}$, being larger than the in-plane one, $\chi^{xx}$, by a term
proportional to $U^2(2k_F)|\alpha|$, where $U(q)$ is the electron-electron
interaction). For $\tq \leq 2m^*|\alpha|$, corrections to the leading,
$U^2(2k_F)|\alpha|$, term scale linearly with $\tq$ for $\chi^{xx}$ and are
absent for $\chi^{zz}$. This anisotropy has important consequences for the
ferromagnetic nuclear-spin phase: $(i)$ the ordered state--if achieved--is of
an Ising type and $(ii)$ the spin-wave dispersion is gapped at $\tq=0$. To
second order in $U(q)$, the dispersion a decreasing function of $\tq$, and
anisotropy is not sufficient to stabilize long-range order. However,
renormalization in the Cooper channel for $\tq\ll2m^*|\alpha|$ is capable of
reversing the sign of the $\tq$-dependence of $\chi^{xx}$ and thus stabilizing
the ordered state. We also show that a combination of the electron-electron and
SO interactions leads to a new effect: long-wavelength Friedel oscillations in
the spin (but not charge) electron density induced by local magnetic moments.
The period of these oscillations is given by the SO length $\pi/m^*|\alpha|$.",1112.4786v2
2015-06-23,Dynamical effects of spin-dependent interactions in low- and intermediate-energy heavy-ion reactions,"It is well known that non-central nuclear forces, such as the spin-orbital
coupling and the tensor force, play important roles in understanding many
interesting features of nuclear structures. However, their dynamical effects in
nuclear reactions are poorly known since only the spin-averaged observables are
normally studied both experimentally and theoretically. Realizing that
spin-sensitive observables in nuclear reactions may carry useful information
about the in-medium properties of non-central nuclear interactions, besides
earlier studies using the time-dependent Hartree-Fock approach to understand
effects of spin-orbital coupling on the threshold energy and spin polarization
in fusion reactions, some efforts have been made recently to explore dynamical
effects of non-central nuclear forces in intermediate-energy heavy-ion
collisions using transport models. The focuses of these studies have been on
investigating signatures of the density and isospin dependence of the form
factor in the spin-dependent single-nucleon potential. Interestingly, some
useful probes were identified in the model studies while so far there is still
no data to compare with. In this brief review, we summarize the main physics
motivations as well as the recent progress in understanding the spin dynamics
and identifying spin-sensitive observables in heavy-ion reactions at
intermediate energies. We hope the interesting, important, and new physics
potentials identified in the spin dynamics of heavy-ion collisions will
stimulate more experimental work in this direction.",1506.06860v2
2014-03-14,Electrical spin protection and manipulation via gate-locked spin-orbit fields,"The spin-orbit (SO) interaction couples electron spin and momentum via a
relativistic, effective magnetic field. While conveniently facilitating
coherent spin manipulation in semiconductors, the SO interaction also
inherently causes spin relaxation. A unique situation arises when the Rashba
and Dresselhaus SO fields are matched, strongly protecting spins from
relaxation, as recently demonstrated. Quantum computation and spintronics
devices such as the paradigmatic spin transistor could vastly benefit if such
spin protection could be expanded from a single point into a broad range
accessible with in-situ gate-control, making possible tunable SO rotations
under protection from relaxation. Here, we demonstrate broad, independent
control of all relevant SO fields in GaAs quantum wells, allowing us to tune
the Rashba and Dresselhaus SO fields while keeping both locked to each other
using gate voltages. Thus, we can electrically control and simultaneously
protect the spin. Our experiments employ quantum interference corrections to
electrical conductivity as a sensitive probe of SO coupling. Finally, we
combine transport data with numerical SO simulations to precisely quantify all
SO terms.",1403.3518v1
2016-05-16,A new and simple model for magneto-optics uncovers an unexpected spin switching,"In magneto-optics the spin angular momentum $S_z$ of a sample is indirectly
probed by the rotation angle and ellipticity, which are mainly determined by
the off-diagonal susceptibility $\chi^{(1)}_{xy}$. A direct and analytic
relation between $S_z$ and $\chi^{(1)}_{xy}$ is necessary and of paramount
importance to the success of magneto-optics, but is often difficult to acquire
since quantum mechanically the relation is hidden in the sum-over-states. Here
we propose a new and simple model to establish such a much needed relation. Our
model is based on the Hookean model, but includes spin-orbit coupling. Under cw
excitation, we show that $\chi^{(1)}_{xy}(\omega)$ is indeed directly
proportional to $S_z$ for a fixed photon frequency $\omega$. Such an elegant
relation is encouraging, and we wonder whether our model can describe spin
dynamics as well. By allowing the spin to change dynamically, to our surprise,
our model predicts that an ultrafast laser pulse can induce a spin precession;
with appropriate parameters, the laser can even reverse spin from one direction
to another. This works for both the circularly and linearly polarized light.
The spin reversal window is narrow. These unexpected results closely resemble
all-optical helicity-dependent magnetic switching found in much more
complicated ferrimagnetic rare earth compounds. Therefore, we believe that our
spin-orbit coupled model may find some important applications in spin switching
processes, a hot topic in femtomagnetism.",1605.04847v1
2020-12-11,The semiclassical theory for spin dynamics in a disordered system,"We investigate the Drude model of spin dynamics in two-dimensional spin-orbit
coupled systems. In the absence of an applied electric field, the spin aligns
with the k-dependent effective magnetic field. The influence of disorder (the
momentum relaxation time $\tau$) on the system is considered. In the presence
of an electric field, the change in momentum causes a change in the effective
magnetic field. The in-plane spin can precess around the successive change in
the orientation of the effective magnetic field. We find that up to the linear
order of the electric field, the spin orientation undergoes Larmor-like and
non-Larmor like precession. Furthermore, we find that the non-Larmor motion
over a very short time ($t\ll\tau$) exactly equals the result obtained from the
Kubo formula. This means that the Kubo formula only captures the system's
response over a very short evolution. The spin-Hall conductivity for Larmor and
non-Larmor precession in the Rashba system is analytically calculated. We find
that the intrinsic spin-Hall current is not a universal constant and correctly
drops to zero when the Rashba spin-orbit coupling drops to zero. We also
calculate the time-averaged Larmor and non-Larmor spin-Hall conductivities
(SHCs) for the k-cubic Rashba system and compare them to experimental values.
The time-averaged Larmor SHC vanishes and the non-Larmor SHC is given by
$2.1(q/8\pi)$ which is very close to the experimental value $2.2(q/8\pi)$ by
Wunderlich et al. [Phys. Rev. Lett. {\bf 94}, 047204 (2005)].",2012.06053v1
2018-03-02,Coherent electron transport in silicon quantum dots,"With silicon being the go-to material for spin qubits, and motivated by the
demand of a scalable quantum computer architecture for fast and reliable
quantum information transfer on-chip, we study coherent electron transport in a
silicon double quantum dot. We first examine the valley-orbital dynamics in a
silicon double dot, and discuss how to properly measure the tunnel couplings as
well as the valley phase difference between two quantum dots. We then focus on
possible phase and spin flip errors during spin transport across a silicon
double dot. In particular, we clarify correction on the effective $g$-factor
for the electron spin from the double dot confinement potential, and quantify
the resulting phase error. We then study spin fidelity loss due to spin-valley
mixing, which is a unique feature of silicon quantum dots. We show that a small
phase correction between valleys can cause a significant coherence loss. We
also investigate spin flip errors caused by either an external inhomogeneous
magnetic field or the intrinsic spin-orbit coupling. We show that the presence
of valleys makes it possible to have much broader (in terms of interdot
detuning) level anti-crossings compared to typical anti-crossings in, for
example, a GaAs double dot, and such broad anti-crossings lead to amplification
of spin flip errors. Lastly, we design a pulse sequence to suppress various
possible spin flip errors by taking advantage of the multiple level
anti-crossings in a silicon double dot and employing Landau-Zener transitions.",1803.00749v3
2021-09-09,Reliability of spin-to-charge conversion measurements in graphene-based lateral spin valves,"Understanding spin physics in graphene is crucial for developing future
two-dimensional spintronic devices. Recent studies show that efficient
spin-to-charge conversions via either the inverse spin Hall effect or the
inverse Rashba-Edelstein effect can be achieved in graphene by proximity with
an adjacent spin-orbit coupling material. Lateral spin valve devices, made up
of a graphene Hall bar and ferromagnets, are best suited for such studies.
Here, we report that signals mimicking the inverse Rashba-Edelstein effect can
be measured in pristine graphene possessing negligible spin-orbit coupling,
confirming that these signals are unrelated to spin-to-charge conversion. We
identify either the anomalous Hall effect in the ferromagnet or the ordinary
Hall effect in graphene induced by stray fields as the possible sources of this
artefact. By quantitatively comparing these options with finite-element-method
simulations, we conclude the latter better explains our results. Our study
deepens the understanding of spin-to-charge conversion measurement schemes in
graphene, which should be taken into account when designing future experiments.",2109.04170v2
2022-07-12,Quantum phase transition in magnetic nanographenes on a lead superconductor,"Quantum spins, referred to the spin operator preserved by full SU(2) symmetry
in the absence of the magnetic anistropy, have been proposed to host exotic
interactions with superconductivity4. However, spin orbit coupling and crystal
field splitting normally cause a significant magnetic anisotropy for d/f-shell
spins on surfaces6,9, breaking SU(2) symmetry and fabricating the spins with
Ising properties10. Recently, magnetic nanographenes have been proven to host
intrinsic quantum magnetism due to their negligible spin orbital coupling and
crystal field splitting. Here, we fabricate three atomically precise
nanographenes with the same magnetic ground state of spin S=1/2 on Pb(111)
through engineering sublattice imbalance in graphene honeycomb lattice.
Scanning tunneling spectroscopy reveals the coexistence of magnetic bound
states and Kondo screening in such hybridized system. Through engineering the
magnetic exchange strength between the unpaired spin in nanographenes and
cooper pairs, quantum phase transition from the singlet to the doublet state
has been observed, in consistent with quantum models of spins on
superconductors. Our work demonstrates delocalized graphene magnetism host
highly tunable magnetic bound states with cooper pairs, which can be further
developed to study the Majorana bound states and other rich quantum physics of
low-dimensional quantum spins on superconductors.",2207.05313v1
2022-09-01,Large spin-to-charge conversion at the two-dimensional interface of transition metal dichalcogenides and permalloy,"Spin-to-charge conversion is an essential requirement for the implementation
of spintronic devices. Recently, monolayers of semiconducting transition metal
dichalcogenides (TMDs) have attracted considerable interest for spin-to-charge
conversion due to their high spin-orbit coupling and lack of inversion symmetry
in their crystal structure. However, reports of direct measurement of
spin-to-charge conversion at TMD-based interfaces are very much limited. Here,
we report on the room temperature observation of a large spin-to-charge
conversion arising from the interface of Ni$_{80}$Fe$_{20}$ (Py) and four
distinct large area ($\sim 5\times2$~mm$^2$) monolayer (ML) TMDs namely,
MoS$_2$, MoSe$_2$, WS$_2$, and WSe$_2$. We show that both spin mixing
conductance and the Rashba efficiency parameter ($\lambda_{IREE}$) scales with
the spin-orbit coupling strength of the ML TMD layers. The $\lambda_{IREE}$
parameter is found to range between $-0.54$ and $-0.76$ nm for the four
monolayer TMDs, demonstrating a large spin-to-charge conversion. Our findings
reveal that TMD/ferromagnet interface can be used for efficient generation and
detection of spin current, opening new opportunities for novel spintronic
devices.",2209.00332v1
2022-10-07,Colloquium: Spin-orbit effects in superconducting hybrid structures,"Spin-orbit coupling (SOC) describes the interaction between an electron's
motion and its spin, and is ubiquitous in condensed matter systems. The
interplay of SOC with superconductivity has attracted significant interest over
the past decade and understanding has substantially progressed, both
experimentally and theoretically. Even with well-understood materials,
conventional $s$-wave superconducting hybrid structures with SOC provide a
platform for realizing exotic phenomena and counterparts in the normal state.
Understanding the emergent phenomena in such systems is an important aim in
condensed matter physics. One such area relates to the generation and interplay
of spin-polarized spin-triplet Cooper pairs in superconducting structures with
magnetic interfaces. It is established that certain forms of magnetic
inhomogeneity at an $s$-wave superconductor interface with a ferromagnet can
transform spin-singlet Cooper pairs into a spin-polarized spin-triplet Cooper
pairs, enabling transformative concepts for cryogenic computing. Recently,
theory and experiments have demonstrated singlet-to-triplet pair conversion via
SOC in $s$-wave superconducting structures with or without magnetic layers.
Moreover, the spin-dependent properties of quasiparticles and their
non-equilibrium behavior also change in the presence of SOC. These
breakthroughs create the potential for energy-efficient control of static and
dynamic spin phenomena in superconducting structures and devices. This article
reviews progress in superconducting spintronics with a focus on the coupling of
superconductivity and SOC in hybrid structures and devices, and outlines
directions that are critical for future device development and fundamental
understanding.",2210.03549v1
2017-06-06,Time-dependent theory of solar meridional flows,"We explore consequences for the solar dynamo of a newly-developed physical
hypothesis describing a weak coupling of the orbital and rotational motions of
extended bodies. The coupling is given by - c ((dL/dt) x omega sub alpha) x r,
where dL/dt represents the rate of change of barycentric orbital angular
momentum, omega sub alpha is the angular velocity of rotation, r is a position
vector identifying a particular location in a coordinate system rotating with
the Sun, and c is a coupling efficiency coefficient. This form of coupling has
no dependence on tides. The coupling expression defines a non-axisymmetric
global-scale acceleration field that varies both in space and with time.
Meridional components of acceleration typically dominate in equatorial and
middle latitudes, while zonal accelerations become increasingly significant at
higher latitudes. A comparison of the waveform of the putative dynamical
forcing function with the time series for measured solar meridional flow speeds
from Sunspot Cycle 23 yields correlations significant at the 99.9% level. We
introduce the possibility of a destructive interaction between the predicted
large-scale flows (due to orbit-spin coupling) and the dynamo mechanism(s) of
the 22-year magnetic activity cycle; observations in recent cycles of higher
meridional flow speeds during episodes of reduced solar sunspot activity may be
explained as a consequence of differences between the phasing of the magnetic
cycle and the phase of the forcing function. Algorithms are provided for
calculating meridional and zonal orbit-spin coupling accelerations within the
Sun as a function of latitude, longitude, depth, and time.",1706.01854v1
2013-05-30,Experimental Determination of the Finite-Temperature Phase Diagram of a Spin-Orbit Coupled Bose Gas,"Spin-orbit (SO) coupling has led to numerously exciting phenomena in electron
systems, for instance, the recently discovered topological insulator. The
synthesized SO coupling with ultracold neutral atoms opens a new avenue of
quantum simulation, and gives us an opportunity to study SO coupling in bosonic
systems. Indeed, SO coupling leads to many new phenomena of boson superfluidity
and various condensate phases that spontaneously break different symmetries. A
richer structure of symmetry breaking always results in a nontrivial
finite-temperature phase diagram. While the thermodynamics of the SO coupled
Bose gas at finite temperature is still unknown either in theory or experiment.
In this work, we experimentally generate the SO coupling in ultracold Rb-87 gas
to explore in a large temperature range and get most key features. We discover
a novel phase transition between the stripe ordered phase and the magnetized
phase, which is reminiscent of temperature-driven transition from the B phase
to the A phase in super- fluid Helium-3 and from spin-density-wave to spin
nematic transition in iron pnictide. We also observe that the magnetic phase
transition and the Bose condensate transition occur simultaneously as
temperature decreases. Our work determines the entire finite-temperature phase
diagram of SO coupled Bose gas and further demonstrate the power of quantum
simulation.",1305.7054v2
1998-12-04,Interaction-Induced Enhancement of Spin-Orbit Coupling in Two-Dimensional Electronic System,"We study theoretically the renormalization of the spin-orbit coupling
constant of two-dimensional electrons by electron-electron interactions. We
demonstrate that, similarly to the $g$ factor, the renormalization corresponds
to the enhancement, although the magnitude of the enhancement is weaker than
that for the $g$ factor. For high electron concentrations (small interaction
parameter $r_s$) the enhancement factor is evaluated analytically within the
static random phase approximation. For large $r_s\sim 10$ we use an approximate
expression for effective electron-electron interaction, which takes into
account the local field factor, and calculate the enhancement numerically. We
also study the interplay between the interaction-enhanced Zeeman splitting and
interaction-enhanced spin-orbit coupling.",9812083v1
1999-07-09,Anomalous temperature dependences of the susceptibility for the one-3d- electron cation,"We have studied properties of the one-3d-electron cation (Ti 3+, V 4+ ions)
under the action of the low-symmetry crystal field in the presence of the spin-
orbit coupling. Very anomalous temperature dependences of the magnetic
susceptibility chi (T) have been obtained as resulting from the off-cubic
lattice distortion provided the intra-atomic spin-orbit coupling is taken into
account. It indicates that, despite of the weakness of the spin-orbit coupling,
the one 3d electron in a solid cannot be treated as a free S=1/2 spin. The same
holds for compounds containing the Ti 3+ and V4+ ions.",9907141v1
2006-04-29,Tunneling between 2D electron layers with correlated disorder: anomalous sensitivity to spin-orbit coupling,"Tunneling between two-dimensional electron layers with mutually correlated
disorder potentials is studied theoretically. Due to this correlation, the
diffusive eigenstates in different layers are almost orthogonal to each other.
As a result, a peak in the tunnel I-V characteristics shifts towards small
bias, V. This ""protects"" the peak against the interaction-induced smearing,
since the relaxation rate near the Fermi level is low. If the correlation in
disorder potentials is complete, the peak position and width are governed by
the spin-orbit coupling in the layers; this coupling lifts the orthogonality of
the eigenstates. Possibility to use inter-layer tunneling for experimental
determination of weak intrinsic spin-orbit splitting of the Fermi surface is
discussed.",0605019v2
2008-09-10,Kramers degeneracy in a magnetic field and Zeeman spin-orbit coupling in antiferromagnets,"In this article, I analyze the symmetries and degeneracies of electron
eigenstates in a commensurate collinear antiferromagnet. In a magnetic field
transverse to the staggered magnetization, a hidden anti-unitary symmetry
protects double degeneracy of the Bloch eigenstates at a special set of
momenta. In addition to this `Kramers degeneracy' subset, the manifold of
momenta, labeling the doubly degenerate Bloch states in the Brillouin zone, may
also contain an `accidental degeneracy' subset, that is not protected by
symmetry and that may change its shape under perturbation. These degeneracies
give rise to a substantial momentum dependence of the transverse g-factor in
the Zeeman coupling, turning the latter into a spin-orbit interaction.
  I discuss a number of materials, where Zeeman spin-orbit coupling is likely
to be present, and outline the simplest properties and experimental
consequences of this interaction, that may be relevant to systems from chromium
to borocarbides, cuprates, hexaborides, iron pnictides, as well as organic and
heavy fermion conductors.",0809.1893v3
2010-02-12,Spin-Orbit Coupling and Anomalous Angular-Dependent Magnetoresistance in the Quantum Transport Regime of PbS,"We measured magnetotransport properties of PbS single crystals which exhibit
the quantum linear magnetoresistance (MR) as well as the static skin effect
that creates a surface layer of additional conductivity. The Shubnikov-de Haas
oscillations in the longitudinal MR signify the peculiar role of spin-orbit
coupling. In the angular-dependent MR, sharp peaks are observed when the
magnetic field is slightly inclined from the longitudinal configuration, which
is totally unexpected for a system with nearly spherical Fermi surface and
points to an intricate interplay between the spin-orbit coupling and the
conducting surface layer in the quantum transport regime.",1002.2481v1
2011-04-04,Macroscopic Klein Tunneling in spin-orbit coupled Bose-Einstein Condensates,"We propose an experimental scheme to detect macroscopic Klein tunneling with
spin-orbit coupled Bose-Einstein condensates (BECs). We show that a nonlinear
Dirac equation with tunable parameters can be realized with such BECs. %in a
simple configuration to generate the artificial spin-orbit coupling. Through
numerical calculations, we demonstrate that macroscopic Klein tunneling can be
clearly detected under realistic conditions. Macroscopic quantum coherence in
such relativistic tunneling is clarified and a BEC with a negative energy is
shown to be able to transmit transparently through a wide Gaussian potential
barrier.",1104.0444v2
2011-05-18,Enhancement of the Kondo effect through Rashba spin-orbit interactions,"We analyze the physics of a one-orbital Anderson impurity model in a
two-dimensional electron gas in the presence of Rashba spin-orbit (RSO)
interactions in the Kondo regime. The spin SU(2) symmetry breaking results in
an effective two-band electron gas coupled to the impurity. The Kondo regime is
obtained by a Schrieffer-Wolff transformation revealing the existence of a
parity breaking term with the form of the Dzyaloshinsky-Moriya (DM)
interaction. The DM term vanishes at the particle-hole symmetric point of the
system, but it has important effects otherwise. Performing a renormalization
group (RG) analysis we find that the model describes a two-channel Kondo system
with ferro- and anti-ferromagnetic couplings. Furthermore, the DM term
renormalizes the antiferromagnetic Kondo coupling producing an exponential
enhancement of the Kondo temperature. We suggest that these effects can be
observed in semiconducting systems, as well as in graphene and topological
insulators.",1105.3522v2
2011-06-29,From Anderson to anomalous localization in cold atomic gases with effective spin-orbit coupling,"We study the dynamics of a one-dimensional spin-orbit coupled Schrodinger
particle with two internal components moving in a random potential. We show
that this model can be implemented by the interaction of cold atoms with
external lasers and additional Zeeman and Stark shifts. By direct numerical
simulations a crossover from an exponential Anderson-type localization to an
anomalous power-law behavior of the intensity correlation is found when the
spin-orbit coupling becomes large. The power-law behavior is connected to a
Dyson singularity in the density of states emerging at zero energy when the
system approaches the quasi-relativistic limit of the random mass Dirac model.
We discuss conditions under which the crossover is observable in an experiment
with ultracold atoms and construct explicitly the zero-energy state, thus
proving its existence under proper conditions.",1106.5925v2
2011-10-11,Topological superfluid in a trapped two-dimensional polarized Fermi gas with spin-orbit coupling,"We study the stability region of the topological superfluid phase in a
trapped two-dimensional polarized Fermi gas with spin-orbit coupling and across
a BCS-BEC crossover. Due to the competition between polarization, pairing
interaction and spin-orbit coupling, the Fermi gas typically phase separates in
the trap. Employing a mean field approach that guarantees the ground state
solution, we systematically study the structure of the phase separation and
investigate in detail the optimal parameter region for the preparation of the
topologically non-trivial superfluid phase. We then calculate the momentum
space density distribution of the topological superfluid state and demonstrate
that the existence of the phase leaves a unique signature in the trap
integrated momentum space density distribution which can survive the
time-of-flight imaging process.",1110.2285v2
2012-09-24,Testing the validity of the strong spin-orbit-coupling limit for octahedrally coordinated iridates in a model system Sr$_3$CuIrO$_6$,"The electronic structure of Sr$_3$CuIrO$_6$, a model system for the 5d Ir ion
in an octahedral environment, is studied through a combination of resonant
inelastic x-ray scattering (RIXS) and theoretical calculations. RIXS spectra at
the Ir L$_3$-edge reveal an Ir $t_{2g}$ manifold that is split into three
levels, in contrast to the expectations of the strong spin-orbit-coupling
limit. Effective Hamiltonian and $ab inito$ quantum chemistry calculations find
a strikingly large non-cubic crystal field splitting comparable to the
spin-orbit coupling, which results in a strong mixing of the
$j_{\mathsf{eff}}=1/2$ and $j_{\mathsf{eff}}=3/2$ states and modifies the
isotropic wavefunctions on which many theoretical models are based.",1209.5294v1
2013-03-09,Radio-frequency spectroscopy of a strongly interacting spin-orbit coupled Fermi gas,"We investigate experimentally and theoretically radio-frequency spectroscopy
and pairing of a spin-orbit-coupled Fermi gas of $^{40}$K atoms near a Feshbach
resonance at $B_{0}=202.2$ G. Experimentally, the integrated spectroscopy is
measured, showing characteristic blue and red shifts in the atomic and
molecular responses, respectively, with increasing spin-orbit coupling.
Theoretically, a smooth transition from atomic to molecular responses in the
momentum-resolved spectroscopy is predicted, with a clear signature of
anisotropic pairing at and below resonance. Our many-body prediction agrees
qualitatively well with the observed spectroscopy near the Feshbach resonance.",1303.2212v1
2013-05-24,Andreev reflection at the edge of a two-dimensional electron system with strong spin-orbit coupling,"We experimentally investigate transport properties of a single planar
junction between the niobium superconductor and the edge of a two-dimensional
electron system in a narrow $In_{0.75}Ga_{0.25}As$ quantum well with strong
Rashba-type spin-orbit coupling. We experimentally demonstrate suppression of
Andreev reflection at low biases at ultra low temperatures. From the analysis
of temperature and magnetic field behavior, we interpret the observed
suppression as a result of a spin-orbit coupling. There is also an experimental
sign of the topological superconductivity realization in the present structure.",1305.5685v5
2013-07-09,Topological Fulde-Ferrel-Larkin-Ovchinnikov states in Spin-orbit Coupled Fermi Gases,"Pairing in an attractively interacting two-component Fermi gas in the absence
of the inversion symmetry and/or the time-reversal symmetry may give rise to
exotic superfluid states. Notable examples range from the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state with a finite center-of-mass
momentum in a polarized Fermi gas, to the topological superfluid state in a
two-dimensional Fermi gas under Rashba spin-orbit coupling and an out-of-plane
Zeeman field. Here, we show that a topological FFLO state can be stabilized in
a two-dimensional Fermi gas with Rashba spin-orbit coupling and both in-plane
and out-of-plane Zeeman fields. We characterize the topological FFLO state by a
non-trivial Berry phase, and demonstrate the stability region of the state on
the zero-temperature phase diagram. Given its unique properties in both the
quasi-particle dispersion spectra and the momentum distribution, signatures of
the topological FFLO state can be detected using existing experimental
techniques.",1307.2439v1
2014-04-12,Drag force on a moving impurity in a spin-orbit coupled Bose-Einstein condensate,"We investigate the drag force on a moving impurity in a spin-orbit coupled
Bose-Einstein condensate. We prove rigorously that the superfluid critical
velocity is zero when the impurity moves in all but one directions, in contrast
to the case of liquid helium and superconductor where it is finite in all
directions. We also find that when the impurity moves in all directions except
two special ones, the drag force has nonzero transverse component at small
velocity. When the velocity becomes large and the states of the upper band are
also excited, the transverse force becomes very small due to opposite
contributions of the two bands. The characteristics of the superfluid critical
velocity and the transverse force are results of the order by disorder
mechanism in spin-orbit coupled boson systems.",1404.3252v1
2014-04-24,Spin-orbit-coupled topological Fulde-Ferrell states of fermions in a harmonic trap,"Motivated by recent experimental breakthroughs in generating spin-orbit
coupling in ultracold Fermi gases using Raman laser beams, we present a
systematic study of spin-orbit-coupled Fermi gases confined in a
quasi-one-dimensional trap in the presence of an in-plane Zeeman field (which
can be realized using a finite two-photon Raman detuning). We find that a
topological Fulde-Ferrell state will emerge, featuring finite-momentum Cooper
pairing and zero-energy Majorana excitations localized near the edge of the
trap based on the self-consistent Bogoliubov-de Genes (BdG) equations. We find
analytically the wavefunctions of the Majorana modes. Finally using the
time-dependent BdG we show how the finite-momentum pairing field manifests
itself in the expansion dynamics of the atomic cloud.",1404.6211v1
2014-09-18,Measurement of collective excitations in a spin-orbit-coupled Bose-Einstein condensate,"We measure the collective excitation spectrum of a spin-orbit coupled
Bose-Einstein condensate using Bragg spectroscopy. The spin-orbit coupling is
generated by Raman dressing of atomic hyperfine states. When the Raman detuning
is reduced, mode softening at a finite momentum is revealed, which provides
insight towards a supersolid-like phase transition. We find that for the
parameters of our system, this softening stops at a finite excitation gap and
is symmetric under a sign change of the Raman detuning. Finally, using a moving
barrier that is swept through the BEC, we also show the effect of the
collective excitation on the fluid dynamics.",1409.5387v2
2014-11-27,The in-plane gradient magnetic field induced vortex lattices in spin-orbit coupled Bose-Einstein condensations,"We consider the ground-state properties of the two-component spin-orbit
coupled ultracold bosons subject to a rotationally symmetric in-plane gradient
magnetic field. In the non-interacting case, the ground state supports
giant-vortices carrying large angular momenta without rotating the trap. The
vorticity is highly tunable by varying the amplitudes and orientations of the
magnetic field. Interactions drive the system from a giant-vortex state to
various configurations of vortex lattice states along a ring. Vortices exhibit
ellipse-shaped envelops with the major and minor axes determined by the
spin-orbit coupling and healing lengths, respectively. Phase diagrams of vortex
lattice configurations are constructed and their stabilities are analyzed.",1411.7584v1
2015-02-04,Persistent semi-metal-like nature of epitaxial perovskite CaIrO3 thin films,"Strong spin-orbit coupled 5d transition metal based ABO3 oxides, especially
iridates, allow tuning parameters in the phase diagram and may demonstrate
important functionalities, for example, by means of strain effects and
symmetry-breaking, because of the interplay between the Coulomb interactions
and strong spin-orbit coupling. Here, we have epitaxially stabilized high
quality thin films of perovskite (Pv) CaIrO3. Film on the best lattice-matched
substrate shows semi-metal-like characteristics. Intriguingly, imposing tensile
or compressive strain on the film by altering the underlying lattice-mismatched
substrates still maintains semi-metallicity with minute modification of the
effective correlation as tensile (compressive) strain results in tiny increases
(decreases) of the electronic bandwidth. In addition, magnetoresistance remains
positive with a quadratic field dependence. This persistent semi-metal-like
nature of Pv-CaIrO3 thin films with minute changes in the effective correlation
by strain may provide new wisdom into strong spin-orbit coupled 5d based oxide
physics.",1502.01261v3
2015-03-03,Field-effect control of superconductivity and Rashba spin-orbit coupling in top-gated LaAlO3/SrTiO3 devices,"The recent development in the fabrication of artificial oxide
heterostructures opens new avenues in the field of quantum materials by
enabling the manipulation of the charge, spin and orbital degrees of freedom.
In this context, the discovery of two-dimensional electron gases (2-DEGs) at
LAlO3/SrTiO3 interfaces, which exhibit both superconductivity and strong Rashba
spin-orbit coupling (SOC), represents a major breakthrough. Here, we report on
the realisation of a field-effect LaAlO3/SrTiO3 device, whose physical
properties, including superconductivity and SOC, can be tuned over a wide range
by a top-gate voltage. We derive a phase diagram, which emphasises a
field-effect-induced superconductor-to-insulator quantum phase transition.
Magneto-transport measurements indicate that the Rashba coupling constant
increases linearly with electrostatic doping. Our results pave the way for the
realisation of mesoscopic devices, where these two properties can be
manipulated on a local scale by means of top-gates.",1503.00967v1
2015-08-25,Absence of spin-orbit-coupling-induced effects on lattice dynamics in CePt3Si,"Motivated by model calculations for the heavy fermion superconductor CePt3Si
predicting phonon anomalies because of anti-symmetric spin-orbit coupling we
performed a detailed experimental study of the lattice dynamical properties of
CePt3Si. In particular, we investigated the dispersion of transverse acoustic
and low energy optic phonon branches along the [110] direction using inelastic
neutron scattering. In these branches, we found deviations from our ab-initio
lattice dynamical calculations, which overall give a good description of the
phonon dispersion in CePt3Si. However, the agreement for the [110] transverse
modes can be improved if we neglect the Ce 4f states, done in an additional
calculation. We conclude that the lattice dynamics of CePt3Si are conventional
and that the observed deviations are not related to effects of anti-symmetric
spin-orbit-coupling. More likely, ab-initio calculations overestimate the
exchange between different phonon branches, particularly in the presence of 4f
electron states. Our results imply that the ASOC plays less a role in
non-centrosymmetric superconductors than commonly believed.",1508.06048v1
2015-09-06,Traveling Majorana solitons in a one-dimensional spin-orbit coupled Fermi superfluid,"We investigate traveling solitons of a one-dimensional spin-orbit coupled
Fermi superfluid in both topologically trivial and non-trivial regimes by
solving the static and time-dependent Bogoliubov-de Gennes equations. We find a
critical velocity $v_{h}$ for traveling solitons that is much smaller than the
value predicted using the Landau criterion due to the presence of spin-orbit
coupling, which strongly upshifts the energy level of the soliton-induced
Andreev bound states towards the quasi-particle scattering continuum. Above
$v_{h}$, our time-dependent simulations in harmonic traps indicate that
traveling solitons decay by radiating sound waves. In the topological phase, we
predict the existence of peculiar Majorana solitons, which host two Majorana
fermions and feature a phase jump of $\pi$ across the soliton, irrespective of
the velocity of travel. These unusual properties of Majorana solitons may open
an alternative way to manipulate Majorana fermions for fault-tolerant
topological quantum computations.",1509.01803v1
2015-10-18,Effects of spin-orbit coupling and spatial symmetries on the Josephson current in SNS junctions,"We present an analysis of the symmetries of the interference pattern of
critical currents through a two-dimensional
superconductor-semiconductor-superconductor junction, taking into account
Rashba and Dresselhaus spin-orbit interaction, an arbitrarily oriented magnetic
field, disorder, and structural asymmetries. We relate the symmetries of the
pattern to the absence or presence of symmetries in the Hamiltonian, which
provides a qualitative connection between easily measurable quantities and the
spin-orbit coupling and other symmetries of the junction. We support our
analysis with numerical calculations of the Josephson current based on a
perturbative expansion up to eighth order in tunnel coupling between the normal
region and the superconductors.",1510.05251v2
2015-11-03,Motion of an Impurity in a Bose-Einstein Condensate with Weyl Spin-Orbit Coupling: Non-collinear Drag Force and Anisotropic Critical Velocity,"We consider the motion of a point-like impurity through a three-dimensional
two-component Bose-Einstein condensate subject to Weyl spin-orbit coupling.
Using linear-response theory, we calculate the drag force felt by the impurity
and the associated anisotropic critical velocity from the spectrum of
elementary excitations. The drag force is shown to be generally not collinear
with the velocity of the impurity. This unusual behavior is a consequence of
condensation into a finite-momentum state due to the spin-orbit coupling.",1511.00886v2
2015-11-27,Multidimensional Josephson vortices in spin-orbit coupled Bose-Einstein condensates: snake instability and decay through vortex dipoles,"We analyze the dynamics of Josephson vortex states in two-component
Bose-Einstein condensates with Rashba-Dresselhaus spin-orbit coupling by using
the Gross-Pitaevskii equation. In 1D, both in homogeneous and harmonically
trapped systems, we report on stationary states containing doubly charged,
static Josephson vortices. In multidimensional systems, we find stable
Josephson vortices in a regime of parameters typical of current experiments
with $^{87}$Rb atoms. In addition, we discuss the instability regime of
Josephson vortices in disk-shaped condensates, where the snake instability
operates and vortex dipoles emerge. We study the rich dynamics that they
exhibit in different regimes of the spin-orbit coupled condensate depending on
the orientation of the Josephson vortices.",1511.08685v2
2016-03-10,Zeeman-field-induced nontrivial topological phases in a one-dimensional spin-orbit-coupled dimerized lattice,"We study theoretically the interplay effect of Zeeman field and modulated
spin-orbit coupling on topological properties of a one-dimensional dimerized
lattice, known as Su-Schrieffer-Heeger model. We find that in the weak (strong)
modulated spin-orbit coupling regime, trivial regions or nontrivial ones with
two pairs of zero-energy states can be turned into nontrivial regions by
applying a uniform (staggered) perpendicular Zeeman field through a topological
phase transition. Furthermore, the resulting nontrivial phase hosting a pair of
zero-energy boundary states can survive within a certain range of the
perpendicular Zeeman field magnitude. Due to the effective time-reversal,
particle-hole, chiral, and inversion symmetries, in the presence of either
uniform or staggered perpendicular Zeeman field, the topological class of the
system is BDI which can be characterized by $\mathbbm{Z}$ index. We also
examine the robustness of the nontrivial phase by breaking the underlying
symmetries giving rise that inversion symmetry plays an important role.",1603.03282v2
2016-07-13,Universal trimers emerging from a spin-orbit coupled Fermi sea,"We report the existence of a universal trimer state induced by an impurity
interacting with a two-component spin-orbit coupled Fermi gas in two
dimensions. In the zero-density limit with a vanishing Fermi sea, the trimer is
stabilized by the symmetry of the single-particle spectrum under spin-orbit
coupling, and is therefore {\it universal} against the short-range details of
the interaction potential. When the Fermi energy increases, we show that the
trimer is further stabilized by particle-hole fluctuations over a considerable
parameter region. We map out the phase diagram consisting of trimers, dimers,
and polarons, and discuss the detection of these states using radio-frequency
spectroscopy. The universal trimer revealed in our work is a direct
manifestation of intriguing three-body correlations emerging from a many-body
environment, which, in our case, is cooperatively supported by the
single-particle spectral symmetry and the collective particle-hole excitations.",1607.03580v2
2016-07-27,Anderson transition of cold atoms with synthetic spin-orbit coupling in two-dimensional speckle potentials,"We investigate the metal-insulator transition occurring in two-dimensional
(2D) systems of noninteracting atoms in the presence of artificial spin-orbit
interactions and a spatially correlated disorder generated by laser speckles.
Based on a high order discretization scheme, we calculate the precise position
of the mobility edge and verify that the transition belongs to the symplectic
universality class. We show that the mobility edge depends strongly on the
mixing angle between Rashba and Dresselhaus spin-orbit couplings. For equal
couplings a non-power-law divergence is found, signaling the crossing to the
orthogonal class, where such a 2D transition is forbidden.",1607.08164v2
2016-09-15,Synthetic dimensions and spin-orbit coupling with an optical clock transition,"We demonstrate a novel way of synthesizing spin-orbit interactions in
ultracold quantum gases, based on a single-photon optical clock transition
coupling two long-lived electronic states of two-electron $^{173}$Yb atoms. By
mapping the electronic states onto effective sites along a synthetic
""electronic"" dimension, we have engineered synthetic fermionic ladders with
tunable magnetic fluxes. We have detected the spin-orbit coupling with
fiber-link-enhanced clock spectroscopy and directly measured the emergence of
chiral edge currents, probing them as a function of the magnetic field flux.
These results open new directions for the investigation of topological states
of matter with ultracold atomic gases.",1609.04800v2
2016-09-18,Hidden long-range order in a spin-orbit coupled two-dimensional Bose gas,"A spin-orbit coupled two-dimensional (2D) Bose gas is shown to simultaneously
possess quasi and true long-range order in the total and relative phase
sectors, respectively. The total phase undergoes a Berenzinskii-
Kosterlitz-Thouless transition to a low temperature phase with quasi long-range
order, as expected for a two- dimensional quantum gas. Additionally, the
relative phase undergoes an Ising-type transition building up true long-range
order, which is induced by the anisotropic spin-orbit coupling. Based on the
Bogoliubov approach, expressions for the total- and relative-phase fluctuations
are derived analytically for the low temperature regime. Numerical simulations
of the stochastic projected Gross-Pitaevskii equation (SPGPE) give a good
agreement with the analytical predictions.",1609.05464v2
2016-09-30,BCS pairing state of a Dilute Bose Gas with Spin-Orbit Coupling,"We study a two-component Bose gas with a symmetric spin-orbit coupling, and
find that two atoms can form a bound state with any intra- or inter-species
scattering length. Consequently, in the dilute limit, the
Bardeen-Cooper-Shrieffer (BCS) pairing state of bosons can be formed with
weakly-attractive inter-species and repulsive intra-species interactions. The
quasiparticle excitation energies are anisotropic due to spin-orbit coupling.
This BCS paring state is energetically favored over Bose-Einstein condensation
(BEC) of atoms at low densities. As the density increases, there is a
first-order transition from the BCS to BEC states.",1609.09691v3
2016-10-17,Two-dimensional lattice solitons in polariton condensates with spin-orbit coupling,"We study two-dimensional fundamental and vortex solitons in polariton
condensates with spin-orbit coupling and Zeeman splitting evolving in square
arrays of microcavity pillars. Due to repulsive excitonic nonlinearity such
states are encountered in finite gaps in the spectrum of the periodic array.
Spin-orbit coupling between two polarization components stemming from TE-TM
energy splitting of the cavity photons acting together with Zeeman splitting
lifts the degeneracy between vortex solitons with opposite topological charges
and makes their density profiles different for a fixed energy. This results in
formation of four distinct families of vortex solitons with topological charges
m=+-1, all of which can be stable. At the same time, only two stable families
of fundamental gap solitons characterized by domination of different
polarization components are encountered.",1610.05286v1
2017-02-15,Majorana Quasi-Particles Protected by $\mathbb{Z}_2$ Angular Momentum Conservation,"We show how angular momentum conservation can stabilise a symmetry-protected
quasi-topological phase of matter supporting Majorana quasi-particles as edge
modes in one-dimensional cold atom gases. We investigate a number-conserving
four-species Hubbard model in the presence of spin-orbit coupling. The latter
reduces the global spin symmetry to an angular momentum parity symmetry, which
provides an extremely robust protection mechanism that does not rely on any
coupling to additional reservoirs. The emergence of Majorana edge modes is
elucidated using field theory techniques, and corroborated by
density-matrix-renormalization-group simulations. Our results pave the way
toward the observation of Majorana edge modes with alkaline-earth-like fermions
in optical lattices, where all basic ingredients for our recipe - spin-orbit
coupling and strong inter-orbital interactions - have been experimentally
realized over the last two years.",1702.04733v2
2017-08-08,Magnetic Chern Insulators in a monolayer of Transition Metal Trichalcogenides,"A monolayer of transition metal trichalcogenides has received a lot of
attention as potential two dimensional magnetic materials. The system has a
honeycomb structure of transition metal ions, where both spin-orbit coupling
and electron correlation effect play an important role. Here, motivated by
these transition metal series with effective doping or mixed valence case, we
propose the possible realization of magnetic Chern insulators at quarter filled
honeycomb lattice. We show that the interplay of intrinsic spin-orbit coupling
and electron correlation opens a wide region of ferromagnetic Chern insulating
phases in between metals and normal insulators. Within the mean field
approximation, we present the phase diagram of a quarter filled Kane-Mele
Hubbard model and also discuss the effects of Rashba spin-orbit coupling and
nearest neighbor interactions on it.",1708.02493v1
2018-02-28,Absence of Dirac states in BaZnBi$_{2}$ induced by spin-orbit coupling,"We report magnetotransport properties of BaZnBi$_{2}$ single crystals.
Whereas electronic structure features Dirac states, such states are removed
from the Fermi level by spin-orbit coupling (SOC) and consequently electronic
transport is dominated by the small hole and electron pockets. Our results are
consistent with three dimensional (3D) but also with quasi two dimensional (2D)
portions of the Fermi surface. The spin-orbit coupling-induced gap in Dirac
states is much larger when compared to isostructural SrMnBi$_{2}$. This
suggests that not only long range magnetic order but also mass of the alkaline
earth atoms A in ABX$_{2}$ (A = alkaine earth, B = transition metal and
X=Bi/Sb) are important for the presence of low-energy states obeying the
relativistic Dirac equation at the Fermi surface",1802.10593v1
2018-04-03,Searching for Supersolidity in Ultracold Atomic Bose Condensates with Rashba Spin-Orbit Coupling,"We developed functional integral formulation for the stripe phase of a spinor
Bose-Einstein condensates with Rashba spin-orbit coupling. The excitation
spectrum is found to exhibit double gapless band structures, identified to be
two Goldstone modes resulting from spontaneously broken internal gauge symmetry
and translational invariance symmetry. The sound velocities display anisotropic
behaviors with the lower branch vanishes in the direction perpendicular to the
stripe in the x-y plane. At the transition point between the plane wave phase
and the stripe phase, physical quantities such as fluctuation correction to the
ground state energy and quantum depletion of the condensates exhibit
discontinuity, characteristic of the first order phase transition. Despite
strong quantum fluctuations induced by Rashba spin-orbit coupling, we show that
the supersolid phase is stable against quantum depletion. Finally we extend our
formulation to finite temperatures to account for interactions between
excitations.",1804.01163v1
2018-04-13,Dzyaloshinskii-Moriya Interaction between Multipolar Moments in $5d^1$ Systems,"We propose a new type of Dzyaloshinskii-Moriya (DM) interactions which act on
high-rank multipolar moments such as quadrupolar and octupolar moments. Here we
consider 5d1 systems with broken spatial inversion symmetry, where the
interplay of electron correlation, the spin-orbit coupling, and inversion
symmetry breaking plays a crucial role. Using a numerical diagonalization on a
two-site multiorbital Hubbard model, we reveal that anti-symmetric products of
multipole operators have finite expectation values, indicating the existence of
DM interactions for multipoles. We also find that the spin-orbit coupling
dependences of DM interactions for multipoles are significantly different
depending on the lattice structure. Finally, we discuss the numerical results
for small and large spin-orbit coupling region by using perturbative analysis.",1804.04874v2
2018-04-30,Analytic and numeric computation of edge states and conductivity of a Kane-Mele nanoribbon,"We compute analytic expressions for the edge states in a zigzag Kane-Mele
nanoribbon (KMNR) by solving the eigenvalue equations in presence of intrinsic
and Rashba spin-orbit couplings. Owing to the P-T symmetry of the Hamiltonian
the edge states are protected by topological invariance and hence are found to
be robust. We have done a systematic study for each of the above cases, for
example, a pristine graphene, graphene with an intrinsic spin-orbit coupling,
graphene with a Rashba spin-orbit coupling, a Kane-Mele nanoribbon and
supported our results on the robustness of the edge states by analytic
computation of the electronic probability amplitudes, the local density of
states (LDOS), band structures and the conductance spectra.",1804.11076v3
2020-07-22,Tomography of zero-energy end modes in topological superconducting wires,"We characterize the Majorana zero modes in topological hybrid
superconductor-semiconductor wires with spin-orbit coupling and magnetic field,
in terms of generalized Bloch coordinates $\varphi, \theta, \delta$, and
analyze their transformation under SU(2) rotations. We show that, when the
spin-orbit coupling and the magnetic field are perpendicular, $\varphi$ and
$\delta$ are universal in an appropriate coordinate system. We use these
geometric properties to explain the behavior of the Josephson current in
junctions of two wires with different orientations of the magnetic field and/or
the spin-orbit coupling. We show how to extract from there, the angle $\theta$,
hence providing a full description of the Majorana modes.",2007.11619v4
2020-07-30,Electron-electron scattering and transport properties of spin-orbit coupled electron gas,"We calculate the electrical and thermal conductivity of a two-dimensional
electron gas with strong spin--orbit coupling in which the scattering is
dominated by electron--electron collisions. Despite the apparent absence of
Galilean invariance in the system, the two-particle scattering does not affect
the electrical conductivity above the band-crossing point where both helicity
bands are filled. Below the band-crossing point where one helicity band is
empty, switching on the electron--electron scattering leads only to a limited
decrease of the electrical conductivity, so that its high-temperature value is
independent of the scattering intensity. In contrast to this, thermal
conductivity is not strongly affected by the spin-orbit coupling and exhibits
only a kink as the Fermi level passes through the band-crossing point.",2007.15612v2
2017-04-24,A parity-breaking electronic nematic phase transition in the spin-orbit coupled metal Cd$_2$Re$_2$O$_7$,"Strong electron interactions can drive metallic systems toward a variety of
well-known symmetry-broken phases, but the instabilities of correlated metals
with strong spin-orbit coupling have only recently begun to be explored. We
uncovered a multipolar nematic phase of matter in the metallic pyrochlore
Cd$_2$Re$_2$O$_7$ using spatially resolved second-harmonic optical anisotropy
measurements. Like previously discovered electronic nematic phases, this
multipolar phase spontaneously breaks rotational symmetry while preserving
translational invariance. However, it has the distinguishing property of being
odd under spatial inversion, which is allowed only in the presence of
spin-orbit coupling. By examining the critical behavior of the multipolar
nematic order parameter, we show that it drives the thermal phase transition
near 200 kelvin in Cd$_2$Re$_2$O$_7$ and induces a parity-breaking lattice
distortion as a secondary order.",1704.07399v1
2011-11-08,Topological Superfluid in one-dimensional Ultracold Atomic System with Spin-Orbit Coupling,"We propose a one-dimensional Hamiltonian $H_{1D}$ which supports Majorana
fermions when $d_{x^{2}-y^{2}}$-wave superfluid appears in the ultracold atomic
system and obtain the phase-separation diagrams both for the
time-reversal-invariant case and time-reversal-symmetry-breaking case. From the
phase-separation diagrams, we find that the single Majorana fermions exist in
the topological superfluid region, and we can reach this region by tuning the
chemical potential $\mu$ and spin-orbit coupling $\alpha_{R}$. Importantly, the
spin-orbit coupling has realized in ultracold atoms by the recent experimental
achievement of synthetic gauge field, therefore, our one-dimensional ultra-cold
atomic system described by $H_{1D}$ is a promising platform to find the
mysterious Majorana fermions.",1111.1952v2
2011-11-09,Majorana fermions in superconducting nanowires without spin-orbit coupling,"We show that confined Majorana fermions can exist in nanowires with proximity
induced s-wave superconducting pairing if the direction of an external magnetic
field rotates along the wire. The system is equivalent to nanowires with
Rashba-type spin-orbit coupling, with strength proportional to the derivative
of the field angle. For realistic parameters, we demonstrate that a set of
permanent magnets can bring a nearby nanowire into the topologically
non-trivial phase with localized Majorana modes at its ends. Without the
requirement of spin-orbit coupling this opens up for a new route for
demonstration and design of Majorana fermion systems.",1111.2129v4
2014-05-04,Three-component topological superfluid in one-dimensional Fermi gases with spin-orbit coupling,"We theoretically investigate one-dimensional three-component
spin-orbit-coupled Fermi gases in the presence of Zeeman field. By solving the
Bogoliubov-de-Gennes equations, we obtain the phase diagram at given chemical
potential and order parameter. We show that the system undergoes a phase
transition from Bardeen-Cooper-Schrieffer superfluid to topological superfluid
as increasing the intensity of Zeeman field. By comparing to the two-component
system, we find, besides the topological phase transition from the trivial
superfluid to nontrivial topological superfluid, the system can always be in a
nontrivial topological superfluid, and there are two Majorana zero energy
regions while increasing the magnetic field. We find the three-component
spin-orbit-coupled Fermi gases in certain parameter range is more optimizing
for experimental realization due to the smaller magnetic field needed. We
therefore propose a promising candidate for realizing topological superfluid.",1405.0709v2
2014-06-09,Chiral nanophotonic waveguide interface based on spin-orbit coupling of light,"Controlling the flow of light by means of nanophotonic waveguides has the
potential of transforming integrated information processing much in the same
way that conventional glass fibers have revolutionized global communication.
Owing to the strong transverse confinement of the light, such waveguides give
rise to a coupling between the internal spin of the guided photons and their
orbital angular momentum. Here, we employ this spin-orbit coupling of light to
break the mirror symmetry of the scattering of light by a single gold
nanoparticle on the surface of a nanophotonic waveguide. We thereby realize a
chiral waveguide coupler in which the handedness of the incident light
determines the direction of propagation in the waveguide. Using this effect, we
control the directionality of the scattering process and direct up to 94% of
the incoupled light into a given direction. This enables novel ways for
controlling and manipulating light in optical waveguides and nanophotonic
structures as well as for the design of integrated optical sensors.",1406.2184v1
2015-12-19,Spin-orbit-angular-momentum coupling in a spin-1 Bose-Einstein condensate,"We propose a simple model with spin and orbit angular momentum coupling in a
spin-1 Bose- Einstein condensate, where three internal atomic states are Raman
coupled by a pair of co- propagating Laguerre-Gaussian beams. The resulting
Raman transition imposes a transfer of orbital angular momentum between photons
and the condensate in a spin-dependent way. Focusing on a regime where the
single-particle ground state is nearly three-fold degenerate, we show that the
weak interatomic interaction in the condensate produces a rich phase diagram,
and that a many-body Rabi oscillation between two quantum phases can be induced
by a sudden quench of the quadratic Zeeman shift. We carried out our
calculations using both a variational method and a full numerical method, and
found excellent agreement.",1512.06276v1
2017-10-17,Momentum-space Aharonov-Bohm interferometry in Rashba spin-orbit coupled Bose-Einstein condensates,"Since the recent experimental realization of synthetic Rashba spin-orbit
coupling paved a new avenue for exploring and engineering topological phases in
ultracold atoms, a precise, solid detection of Berry phase has been desired for
unequivocal characterization of system topology. Here, we propose a scheme to
conduct momentum-space Aharonov-Bohm interferometry in a Rashba spin-orbit
coupled Bose-Einstein condensate with a sudden change of in-plane Zeeman field,
capable of measuring the Berry phase of Rashba energy bands. We find that the
Berry phase with the presence of a Dirac point is directly revealed by a robust
dark interference fringe, and that as a function of external Zeeman field is
characterized by the contrast of fringes. We also build a variational model
describing the interference process with semiclassical equations of motion of
essential dynamical quantities, which lead to agreeable trajectories and
geometric phases with the real-time simulation of Gross-Pitaevskii equation.
Our study would provide timely guidance for the experimental detection of Berry
phase in ultracold atomic systems and help further investigation on their
interference dynamics in momentum space.",1710.06403v1
2017-12-23,Three-dimensional vortex-bright solitons in a spin-orbit coupled spin-$1$ condensate,"We demonstrate stable and metastable vortex-bright solitons in a
three-dimensional spin-orbit-coupled three-component hyperfine spin-1
Bose-Einstein condensate (BEC) using numerical solution and variational
approximation of a mean-field model. The spin-orbit coupling provides
attraction to form vortex-bright solitons in both attractive and repulsive
spinor BECs. The ground state of these vortex-bright solitons is axially
symmetric for weak polar interaction. For a sufficiently strong ferromagnetic
interaction, we observe the emergence of a fully asymmetric vortex-bright
soliton as the ground state. We also numerically investigate moving solitons.
The present mean-field model is not Galilean invariant, and we use a
Galilean-transformed mean-field model for generating the moving solitons.",1712.09337v1
2018-01-15,Negative-mass effects in spin-orbit coupled Bose-Einstein condensates,"Negative effective masses can be realised by engineering the dispersion
relation in a variety of quantum systems. A recent experiment with spin-orbit
coupled Bose-Einstein condensates has shown that a negative effective mass can
halt the free expansion of the condensate and produce fringes in the density
[M. Khamehchi et al., Phys. Rev. Lett. 118, 155301 (2017)]. Here, we show that
the observed fringes are due to the negativity of only one of the two effective
mass parameters that characterise the dispersion, which leads to previously
predicted self-interference of the wave packet. We show how confgurations are
nevertheless accessible to spin-orbit coupled Bose-Einstein condensates where
both mass parameters controlling the propagation and diffusion of the
condensate are negative, resulting in the novel phenomenon of
counter-propagating self-interfering packets.",1801.04779v2
2018-09-15,Artificial $SU(3)$ Spin-Orbit Coupling and Exotic Mott Insulators,"Motivated by recent progress in the realization of artificial gauge fields
and $SU(N)$ Mott insulators using alkaline-earth-like atoms in optical
lattices, we develop an unbiased $SU(N)$ real-space dynamical mean-field theory
(DMFT) approach to study the effect of spin-orbit coupling and onsite Hubbard
interaction $U$ on $SU(3)$ fermionic systems. We investigate the behavior of
the local magnetization, double occupancies, and the triple occupancy versus
the Hubbard interaction across the metal to Mott insulator transition. We map
out the magnetic phase diagram in the large-$U$ limit and show that the
spin-orbit coupling can stabilize long-range orders such as ferromagnet,
spiral, and stripes with different orientations in $SU(3)$ Mott insulators.",1809.05704v2
2018-10-03,Possible origin of the absence of magnetic order in LiOsO$_3$: Spin-orbit coupling controlled ground state,"LiOsO$_3$ is the first experimentally confirmed polar metal with
ferroelectric-like distortion. One puzzling experimental fact is its
paramagnetic state down to very low temperature with negligible magnetic
moment, which is anomalous considering its $5d^3$ electron configuration since
other osmium oxides (e.g. NaOsO$_3$) with $5d^3$ Os ions are magnetic. Here the
magnetic and electronic properties of LiOsO$_3$ are re-investigated carefully
using the first-principles density functional theory. Our calculations reveal
that the magnetic state of LiOsO$_3$ can be completely suppressed by the
spin-orbit coupling. The subtle balance between significant spin-orbit coupling
and weak Hubbard $U$ of $5d$ electrons can explain both the nonmagnetic
LiOsO$_3$ and magnetic NaOsO$_3$. Our work provides a reasonable understanding
of the long-standing puzzle of magnetism in some osmium oxides.",1810.01639v1
2019-06-10,Successive Symmetry Breaking in a Jeff = 3/2 Quartet in the Spin-Orbit Coupled Insulator Ba2MgReO6,"We report on the cubic double perovskite Ba2MgReO6 containing Re6+ ions with
the 5d1 electron configuration. Resistivity, magnetization, and heat capacity
measurements using single crystals show that the compound is a Mott insulator
with a magnetic transition at Tm = 18 K, which is accompanied by a weak
ferromagnetic moment with [110] anisotropy. Another transition is observed at
Tq = 33 K in heat capacity, where the inverse of magnetic susceptibility
changes its slope, indicating a substantial change in the electronic state. The
significance of spin-orbit coupling is revealed by the reduced effective
magnetic moment of ~0.68{\mu}B at high temperature above Tq and the total
electronic entropy close to Rln4. These features indicate that Ba2MgReO6 is a
spin-orbit coupled Mott insulator possessing a Jeff = 3/2 quartet state, which
exhibits quadrupolar and dipolar orders at Tq and Tm, respectively.",1906.03802v1
2019-09-24,Bogoliubov Fermi surfaces stabilized by spin-orbit coupling,"It was recently understood that centrosymmetric multiband superconductors
that break time-reversal symmetry generically show Fermi surfaces of Bogoliubov
quasiparticles. We investigate the thermodynamic stability of these Bogoliubov
Fermi surfaces in a paradigmatic model. To that end, we construct the
mean-field phase diagram as a function of spin-orbit coupling and temperature.
It confirms the prediction that a pairing state with Bogoliubov Fermi surfaces
can be stabilized at moderate spin-orbit coupling strengths. The multiband
nature of the model also gives rise to a first-order phase transition, which
can be explained by the competition of intra- and interband pairing and is
strongly affected by cubic anisotropy. For the state with Bogoliubov Fermi
surfaces, we also discuss experimental signatures in terms of the residual
density of states and the induced magnetic order. Our results show that
Bogoliubov Fermi surfaces of experimentally relevant size can be
thermodynamically stable.",1909.10956v2
2019-10-20,Dissipation-facilitated molecules in a Fermi gas with non-Hermitian spin-orbit coupling,"We study the impact of non-Hermiticity on the molecule formation in a
two-component spin-orbit-coupled Fermi gas near a wide Feshbach resonance.
Under an experimentally feasible configuration where the two-photon Raman
process is dissipative, the Raman-induced synthetic spin-orbit coupling
acquires a complex strength. Remarkably, dissipation of the system facilitates
the formation and binding of molecules, which, despite their dissipative nature
and finite lifetime, exist over a wider parameter regime than in the
corresponding Hermitian system. These dissipation-facilitated molecules can be
probed by the inverse radio-frequency (rf) spectroscopy, provided the Raman
lasers are blue detuned to the excited state. The effects of dissipation
manifest in the rf spectra as shifted peaks with broadened widths, which serve
as a clear experimental signature. Our results, readily observable in current
cold-atom experiments, shed light on the fascinating interplay of
non-Hermiticity and interaction in few- and many-body open quantum systems.",1910.08890v3
2012-05-15,"Magnetic couplings, optical spectra, and spin-orbit exciton in 5d electron Mott insulator Sr2IrO4","Based on the microscopic model including strong spin-orbit coupling, on-site
Coulomb and Hund's interactions, as well as crystal field effects, we have
investigated magnetic and optical properties of Sr2IrO4. Taking into account
all possible intermediate state multiplets generated by virtual hoppings of
electrons, we calculated the isotropic Heisenberg, pseudodipolar, and
Dzyaloshinsky-Moriya coupling constants, which describe the experiment quite
well. We have also evaluated the optical conductivity {\sigma}({\omega}) by
employing the exact diagonalization method on small clusters, and obtained two
peaks at \sim 0.5 and \sim 1.0 eV in agreement with experiment. The two peak
structure of {\sigma}({\omega}) arises from the unusual Fano-type overlap
between electron-hole continuum of the Jeff = 1/2 band and the intrasite
spin-orbit exciton observed recently in Sr2IrO4 by resonant x-ray scattering.",1205.3289v3
2017-05-24,Ferromagnetic transition in a one-dimensional spin-orbit-coupled metal and its mapping to a critical point in smectic liquid crystals,"We study the quantum phase transition between a paramagnetic and
ferromagnetic metal in the presence of Rashba spin-orbit coupling in one
dimension. Using bosonization, we analyze the transition by means of
renormalization group, controlled by an $\varepsilon$-expansion around the
upper critical dimension of two. We show that the presence of Rashba spin-orbit
coupling allows for a new nonlinear term in the bosonized action, which
generically leads to a fluctuation driven first-order transition. We further
demonstrate that the Euclidean action of this system maps onto a classical
smectic-A -- C phase transition in a magnetic field in two dimensions. We show
that the smectic transition is second-order and is controlled by a new critical
point.",1705.08890v3
2018-06-04,Spin-Orbit induced phase-shift in Bi$_{2}$Se$_{3}$ Josephson junctions,"The transmission of Cooper pairs between two weakly coupled superconductors
produces a superfluid current and a phase difference; the celebrated Josephson
effect. Because of time-reversal and parity symmetries, there is no Josephson
current without a phase difference between two superconductors. Reciprocally,
when those two symmetries are broken, an anomalous supercurrent can exist in
the absence of phase bias or, equivalently, an anomalous phase shift
$\varphi_0$ can exist in the absence of a superfluid current. We report on the
observation of an anomalous phase shift $\varphi_0$ in hybrid Josephson
junctions fabricated with the topological insulator Bi$_2$Se$_3$ submitted to
an in-plane magnetic field. This anomalous phase shift $\varphi_0$ is observed
directly through measurements of the current-phase relationship in a Josephson
interferometer. This result provides a direct measurement of the spin-orbit
coupling strength and open new possibilities for phase-controlled Josephson
devices made from materials with strong spin-orbit coupling.",1806.01406v2
2019-03-27,Stable multi-ring and rotating solitons in two-dimensional spin-orbit coupled Bose-Einstein condensates with a radially-periodic potential,"We consider two-dimensional spin-orbit coupled atomic Bose-Einstein
condensate in a radially-periodic potential. The system supports different
types of stable self-sustained states including radially-symmetric
vorticity-carrying modes with different topological charges in two spinor
components that may have multiring profiles and at the same time remain
remarkably stable for repulsive interactions. Solitons of the second type show
persistent rotation with constant angular frequency. They can be stable for
both repulsive and attractive interatomic interactions. Due to inequivalence
between clockwise and counterclockwise rotation directions introduced by
spin-orbit coupling, the properties of such solitons strongly differ for
positive and negative rotation frequencies. Collision of solitons located in
the same or different rings is accompanied by change of the rotation frequency
that depends on the phase difference between colliding solitons.",1903.11453v1
2019-08-02,Geometric contribution to the Goldstone mode in spin-orbit coupled Fermi superfluids,"The so-called quantum metric tensor is a band-structure invariant whose
measure corresponds to the quantum distance between nearby states in the
Hilbert space, characterizing the geometry of the underlying quantum states. In
the context of spin-orbit coupled Fermi gases, we recently proposed that the
quantum metric has a partial control over all those superfluid properties that
depend explicitly on the mass of the superfluid carriers, i.e., the
effective-mass tensor of the corresponding (two- or many-body) bound state.
Here we scrutinize this finding by analyzing the collective phase and amplitude
excitations at zero temperature. In particular to the Goldstone mode, we
present extensive numerical calculations for the Weyl and Rashba spin-orbit
couplings, revealing that, despite being small, the geometric contribution is
solely responsible for the nonmonotonic evolution of the sound velocity in the
BCS-BEC crossover.",1908.00818v2
2020-10-22,Effects of optical lattices on bright solitons in spin-orbit coupled Bose-Einstein condensates,"The stationary bright solitons that appear in the ground state of the
spin-orbit coupled Bose-Einstein condensate (SOC-BEC) exhibit nodes. We
consider SOC-BEC in combined linear and nonlinear optical lattices and study
their effects on the matter-wave bright soliton and find that the parameters of
the nonlinear lattice or atomic scattering length can be judiciously
manipulated to have useful control over the nodes of the soliton. It is seen
that the soliton with large number of nodes is less stable compared to one
having fewer number of nodes. We infer that that the synthetic spin-orbit
coupling induces instability in the ordinary matter-wave soliton.",2010.11888v2
2020-11-12,"Optical Hall response in spin-orbit coupled metals: Comparative study of magnetic cluster monopole, quadrupole, and toroidal orders","The optical Hall response is theoretically studied for spin-orbit coupled
metals with ferroic orders of cluster-type magnetic multipoles. We find that
different magnetic multipoles give rise to distinct spectra in the optical Hall
conductivity. In the cases of monopole and quadrupole orders, the optical Hall
response appears predominantly in high- and low-energy regions, which
correspond to the energy scales of electron correlation and kinetic energy,
respectively, while the response is dispersed and rather weak in the case of
toroidal order. By decomposing the spectra into different interband
contributions, we reveal selection rules stemming from the interplay between
the antisymmetric spin-orbit coupling and the underlying multipoles. Our
results suggest that the optical Hall measurement is useful to detect and
distinguish the cluster-type magnetic multipole orders.",2011.06267v1
2021-03-16,Floquet engineering of Mott insulators with strong spin-orbit coupling,"We propose a method for controlling the exchange interactions of Mott
insulators with strong spin-orbit coupling. We consider a multiorbital system
with strong spin-orbit coupling and a circularly polarized light field and
derive its effective Hamiltonian in the strong-interaction limit. Applying this
theory to a minimal model of $\alpha$-RuCl$_{3}$, we show that the magnitudes
and signs of three exchange interactions, $J$, $K$, and $\Gamma$, can be
changed simultaneously. Then, considering another case in which one of the
hopping integrals has a different value and the other parameters are the same
as those for $\alpha$-RuCl$_{3}$, we show that the Heisenberg interaction $J$
can be made much smaller than the anisotropic exchange interactions $K$ and
$\Gamma$.",2103.08941v1
2021-08-09,Interfacial control of vortex-limited critical current in type II superconductor films,"In a small subset of type II superconductor films, the critical current is
determined by a weakened Bean-Livingston barrier posed by the film surfaces to
vortex penetration into the sample. A film property thus depends sensitively on
the surface or interface to an adjacent material. We theoretically investigate
the dependence of vortex barrier and critical current in such films on the
Rashba spin-orbit coupling at their interfaces with adjacent materials.
Considering an interface with a magnetic insulator, we find the spontaneous
supercurrent resulting from the exchange field and interfacial spin-orbit
coupling to substantially modify the vortex surface barrier, consistent with a
previous prediction. Thus, we show that the critical currents in
superconductor-magnet heterostructures can be controlled, and even enhanced,
via the interfacial spin-orbit coupling. Since the latter can be controlled via
a gate voltage, our analysis predicts a class of heterostructures amenable to
gate-voltage modulation of superconducting critical currents. It also sheds
light on the recently observed gate-voltage enhancement of critical current in
NbN superconducting films.",2108.04263v2
2021-10-08,Two types of dark solitons in a spin-orbit-coupled Fermi gas,"Dark solitons in quantum fluids are well known nonlinear excitations that are
usually characterized by a single length scale associated with the underlying
background fluid. We show that in the presence of spin-orbit coupling and a
linear Zeeman field, superfluid Fermi gases support two different types of
nonlinear excitations featured by corresponding length scales related to the
existence of two Fermi surfaces. Only one of these types, which occurs for
finite spin-orbit coupling and a Zeeman field, survives to the topological
phase transition, and is therefore capable to sustain Majorana zero modes. At
the point of the emergence of this soliton for varying the Zeeman field, the
associated Andreev bound states present a minigap that vanishes for practical
purposes, in spite of lacking the reality condition of Majorana modes.",2110.03972v2
2022-01-05,Non-Hermitian skin effect in a spin-orbit-coupled Bose-Einstein condensate,"We study a Bose-Einstein condensate of ultracold atoms subject to a
non-Hermitian spin-orbit coupling, where the system acquires non-Hermitian skin
effect under the interplay of spin-orbit coupling and laser-induced atom loss.
The presence of the non-Hermitian skin effect is confirmed through its key
signatures in term of the spectral winding under the periodic boundary
condition, the accumulation of eigen wavefunctions at boundaries under an open
boundary condition, as well as bulk dynamics signaled by a directional flow. We
show that the bulk dynamics in particular serves as a convenient signal for
experimental detection. The impact of interaction and trapping potentials are
also discussed based on non-Hermitian Gross-Pitaevskii equations. Our work
demonstrates that the non-Hermitian skin effect and its rich implications in
topology, dynamics and beyond are well within reach of current cold-atom
experiments.",2201.01580v2
2022-06-23,Time Translation Symmetry Breaking in an Isolated Spin-Orbit-Coupled Fluid of Light,"We study the interplay between intrinsic spin-orbit coupling and nonlinear
photon-photon interactions in a nonparaxial, elliptically polarized fluid of
light propagating in a bulk Kerr medium. We find that in situations where the
nonlinear interactions induce birefringence, i.e., a polarization-dependent
nonlinear refractive index, their interplay with spin-orbit coupling results in
an interference between the two polarization components of the fluid traveling
at different wave vectors, which entails the breaking of translation symmetry
along the propagation direction. This phenomenon leads to a Floquet band
structure in the Bogoliubov spectrum of the fluid, and to characteristic
oscillations of its intensity correlations. We characterize these oscillations
in detail and point out their exponential growth at large propagation
distances, revealing the presence of parametric resonances.",2206.11714v2
2022-10-29,Spin-orbital effect on polariton state in traps,"I discuss similitude and differences of spin-orbital effects for electrons in
quantum wells with the Rashba coupling and for polaritons in semiconductor
microcavities with TE-TM splitting. Contrary to the case of electron, the
ground state of polariton in the trap can be non-degenerate and can possess
specific polarization structure. For the case of azimuthally symmetric trap and
sufficiently strong spin-orbital coupling, the ground state is either radial or
azimuthal vortex, depending on the sign of the coupling constant. The effect is
strongly enhanced for polaritons trapped in a ring, where even weak TE-TM
splitting results in formation of vorticity and definite polarization of the
ground state. The Hamiltonian for quasi-1D motion of polaritons in the ring is
derived and it is shown the the dispersion of polaritons depend qualitatively
on the curvature of the ring.",2210.16700v1
2022-11-18,Squeezing and overcoming the Heisenberg scaling with spin-orbit coupled quantum gases,"We predict that exploiting spin-orbit coupling in a harmonically trapped
spinor quantum gas can lead to scaling of the optimal measurement precision
beyond the Heisenberg scaling. We show that quadratic scaling with the number
of atoms can be facilitated via squeezed center-of-mass excitations of the
atomic motion using a 1D spin-orbit coupled fermions or strongly interacting
bosons (Tonks-Girardeau gas). Based on predictions derived from analytic
calculations of the corresponding quantum Fisher information, we then introduce
a protocol which overcomes the Heisenberg scaling (and limit) with help of a
tailored excited and entangled many-body state of a non-interacting
Bose-Einstein condensate. We identify corresponding optimal measurements and
argue that even finite temperature as a source of decoherence is, in principle,
rather favorable for the obtainable precision scaling.",2211.10436v1
2022-11-28,Intrinsic anomalous Hall effect across the magnetic phase transition of a spin-orbit-coupled Bose-Einstein condensate,"We study theoretically the zero temperature intrinsic anomalous Hall effect
in an experimentally realized 2D spin-orbit coupled Bose gas. For anisotropic
atomic interactions and as the spin-orbit coupling strength increases, the
system undergoes a ground state phase transition from states exhibiting a total
in-plane magnetization to those with a perpendicular magnetization along the
$z$ direction. We show that finite frequency, or ac, Hall responses exist in
both phases in the absence of an artificial magnetic field, as a result of
finite inter-band transitions. However, the characteristics of the anomalous
Hall responses are drastically different in these two phases because of the
different symmetries preserved by the corresponding ground states. In
particular, we find a finite dc Hall conductivity in one phase but not the
other. The underlying physical reasons for this are analyzed further by
exploring relations of the dc Hall conductivity to the system's chirality and
Berry curvatures of the Bloch bands. Finally, we discuss an experimental method
of probing the anomalous Hall effect in trapped systems.",2211.15511v1
2023-05-29,Stationary and moving bright solitons in Bose-Einstein condensates with spin-orbit coupling in a Zeeman field,"With the discovery of various matter wave solitons in spin-orbit-coupled
Bose-Einstein condensates (BECs), exploring their properties has become
increasingly significant. We mainly study stationary and moving bright solitons
in spin-orbit-coupled spin-1 BECs with or without a Zeeman field. The bright
solitons correspond to the plane wave (PW) and standing wave (SW) phases. With
the assistance of single-particle energy spectrum, we obtain the existence
domains of PW and SW solitons by analytical and numerical methods. The results
indicate that the interaction between atoms is also a key factor determining
the existence of solitons. In addition, we systematically discuss the stability
domains of PW and SW solitons, and investigate the impact of different
parameters on the stability domains. We find that PW solitons are unstable when
the linear Zeeman effect reaches a certain threshold, and the threshold is
determined by other parameters. The linear Zeeman effect also leads to the
alternating distribution of stable and unstable areas of SW solitons, and makes
SW solitons stably exist in the area with stronger ferromagnetism. Finally, we
analyze the collision dynamics of different types of stable solitons.",2305.17950v1
2023-09-19,Revival of superconductivity in a one-dimensional dimerized diamond lattice,"We study an s-wave superconductivity in a one-dimensional dimerized diamond
lattice in the presence of spin-orbit coupling and Zeeman field. The considered
diamond lattice, comprising of three sublattices per unitcell and having flat
band, has two dimerization patterns; the intra unitcell hoppings have the same
(opposite) dimerization pattern as the corresponding inter unitcell hoppings,
namely, neighboring (facing) dimerization. Using the mean-field theory, we
calculate the superconducting order parameter self-consistently and examine the
stability of the superconducting phase against the spin-orbit coupling, and
Zeeman splitting, dimerization, and temperature. We find that the spin-orbit
coupling or Zeeman splitting individually has a detrimental effect on the
superconductivity, mostly for the facing dimerization. But their mutual effect
revives the superconductivity at charge neutrality point for the facing
dimerization.",2309.10637v1
2023-10-05,Manipulating Vortices with Domain Walls in Superconductor-Ferromagnet Heterostructures,"Vortices are point-like topological defects in superconductors whose motion
dictates superconducting properties and controls device performance. In
superconductor-ferromagnet heterostructures, vortices interact with topological
defects in the ferromagnet such as line-like domain walls. While in previous
heterostructure generations, vortex-domain wall interactions were mediated by
stray fields; in new heterostructure families, more important become exchange
fields and spin-orbit coupling. However, spin-orbit coupling's role in
vortex-domain wall interactions remains unexplored. Here we uncover, via
numerical simulations and Ginzburg-Landau theory, that Rashba spin-orbit
coupling induces magnetoelectric interactions between vortices and domain walls
that crucially depend on the wall's winding direction$-$its helicity. The
wall's helicity controls whether vortices are pushed or dragged by N\'eel
walls, and their gliding direction along Bloch walls. Our work capitalizes on
interactions between topological defects from different order parameters and of
different dimensionality to engineer enhanced functionality.",2310.06866v1
2024-03-19,Large Rashba spin-orbit coupling in metallic SrTaO$_3$ thin films,"Epitaxial thin films of SrTaO$_3$ with thickness ($t$) smaller than 74 nm
were successfully fabricated on an insulator
(LaAlO$_3$)$_{0.3}$(Sr$_2$AlTaO$_6$)$_{0.7}$ substrate. Films with $t$ above
8.6 nm showed metallic conduction. Both conductivity and a mobility showed a
decrease with increasing $t$ above 42 nm, suggesting the instability of thick
SrTaO$_3$ films. This instability was also supported by TEM image and XRD
intensity. For the metallic films with $t$ below 25 nm, energy band splitting
due to spin-orbit coupling ($\Delta$$_{so}$) and Rashba parameter
($\alpha$$_R$) were deduced from an analysis of a magnetoresistance using
two-dimensional weak antilocalization theory. The values of $\Delta$$_{so}$
ranged from 26 to 120 meV, which were the largest among other metallic oxide
films, such as SrNbO$_3$, SrIrO$_3$, and La$_{2/3}$Sr$_{1/3}$MnO$_3$ thin
films, indicating that spin-orbit coupling in SrTaO$_3$ was the largest among
the metallic perovskite oxides reported so far. The values of $\alpha$$_R$ for
our SrTaO$_3$ films ranged from $8.8 \times$10$^{-13}$ to $1.7
\times$10$^{-12}$ eV m, which were much larger than those reported for other
metallic oxide thin films.",2403.12612v1
2024-04-08,Many-body quantum dynamics of spin-orbit coupled Andreev states in a Zeeman field,"We provide a theoretical framework to describe the quantum many-body dynamics
of Andreev states in Josephson junctions with spin-orbit coupling and a
magnetic Zeeman field. In such cases, employing a doubled Nambu spinor
description is technically advantageous but one then has to be careful to avoid
double-counting problems. By deriving the Lindblad master equation in the
socalled excitation picture, we show that a physically consistent many-body
theory free from doublecounting problems follows. We apply our formalism to a
study of dynamical parity stabilization of the Andreev sector at intermediate
times after an initial microwave pulse, in particular addressing the combined
effects of spin-orbit coupling and Zeeman field.",2404.05485v1
1997-09-01,Nonlinear Magneto-Optics of Fe Monolayers from first principles: Structural dependence and spin-orbit coupling strength,"We calculate the nonlinear magneto-optical response of free-standing fcc
(001), (110) and (111) oriented Fe monolayers. The bandstructures are
determined from first principles using a full-potential LAPW method with the
additional implementation of spin-orbit coupling. The variation of the
spin-orbit coupling strength and the nonlinear magneto-optical spectra upon
layer orientation are investigated. We find characteristic differences which
indicate an enhanced sensitivity of nonlinear magneto-optics to surface
orientation and variation of the in-plane lattice constants. In particular the
crossover from onedimensional stripe structures to twodimensional films of
(111) layers exhibits a clean signature in the nonlinear Kerr-spectra and
demonstrates the versatility of nonlinear magneto-optics as a tool for in situ
thin-film analysis.",9709006v1
2008-01-08,Spin-orbital coupling effect on Josephson current through a superconductor heterojunction,"We study spin-orbital coupling effect on the Josephson current through a
superconductor (SC) heterojunction, consisting of two s-wave superconductors
and a two-dimensional electron gas (2DEG) layer between them. The Rashba-type
(RSOC) and/or Dresselhaus-type (DSOC) of spin-orbital coupling are considered
in the 2DEG region. By using the lattice Bogoliubov-de Gennes equation and the
Keldysh formalism, we calculate the DC supercurrent flowing through the
junction and find that the critical current $I_c$ exhibits a damped oscillation
with both the strength of SOC and the layer length of 2DEG; especially, the
strength ratio between RSOC and DSOC can also induce switching between the $0$
state and the $\pi$ state of the SC/2DEG/SC junction as well. This $0$-$\pi$
transition results from the fact that SOC in a two-dimension system can lead to
a pseudo-magnetic effect on the flowing electrons like the effect of a
ferromagnet, since the time reversal symmetry of the system has already been
broken by two SC leads with different macroscopic phases.",0801.1145v1
2009-09-29,Effect of a staggered spin-orbit coupling on the occurrence of a nematic phase in Sr$_3$Ru$_2$O$_7$,"Ultra-clean crystals of Sr$_3$Ru$_2$O$_7$ undergo a metamagnetic transition
at low temperatures. This transition shows a strong anisotropy in the applied
field direction with the critical field $H_c$ ranging from $\sim 5.1$T for
$H\perp c$ to $\sim 8$T for $H\parallel c$. In addition, studies on ultra-pure
samples revealed a bifurcation of the metamagnetic line for fields in
$c$-direction and it is argued that a nematic phase emerges between the
magnetization jumps. The aim of this study is to explain the field-direction
anisotropy of these phenomena. Based on a microscopic tight-binding model, we
introduce the metamagnetic transition by means of a van Hove singularity
scenario. We show that the rotation of the O-octahedra around the c-axis
expected for this material introduces a staggered spin-orbit coupling within
the planes and naturally leads to an anisotropy of the magnetic response. We
describe the low-temperature phase as a nematic state favored by forward
scattering processes. The spin-orbit coupling shows an influence on both, the
critical field $H_c$ and the occurrence of the nematic phase.",0909.5392v2
2011-07-12,Mass-imbalanced Fermi gases with spin-orbit coupling,"We use the mean-field theory to analyze the ground-state phase diagrams of
spin-orbit coupled mass-imbalanced Fermi gases throughout the BCS-BEC
evolution, including both the population-balanced and -imbalanced systems. Our
calculations show that the competition between the mass and population
imbalance and the Rashba-type spin-orbit coupling (SOC) gives rise to very rich
phase diagrams, involving normal, superfluid and phase separated regions. In
addition, we find quantum phase transitions between the topologically trivial
gapped superfluid and the nontrivial gapless superfluid phases, opening the way
for the experimental observation of exotic phenomena with cold atom systems.",1107.2376v2
2011-08-01,Majorana fermions emerging from magnetic nanoparticles on a superconductor without spin-orbit coupling,"There exists a variety of proposals to transform a conventional s-wave
superconductor into a topological superconductor, supporting Majorana fermion
mid-gap states. A necessary ingredient of these proposals is strong spin-orbit
coupling. Here we propose an alternative system consisting of a one-dimensional
chain of magnetic nanoparticles on a superconducting substrate. No spin-orbit
coupling in the superconductor is needed. We calculate the topological quantum
number of a chain of finite length, including the competing effects of disorder
in the orientation of the magnetic moments and in the hopping energies, to
identify the transition into the topologically nontrivial state (with Majorana
fermions at the end points of the chain).",1108.0419v1
2011-10-03,First-principles study of the electronic structure and magnetism of CaIrO$_3$,"I study the electronic structure and magnetism of postperovskite CaIrO$_3$
using first-principles calculations. The density functional calculations within
the local density approximation without the combined effect of spin-orbit
coupling and on-site Coulomb repulsion show the system to be metallic, which is
in disagreement with the recent experimental evidences that show CaIrO$_3$ to
be an antiferromagnetic Mott insulator in the $J_\textrm{eff}$ = 1/2 state.
However, when spin-orbit coupling is taken into account, the Ir $t_{2g}$ bands
split into fully filled $J_\textrm{eff}$ = 3/2 bands and half-filled
$J_\textrm{eff}$ = 1/2 bands. I find that spin-orbit coupling along with a
modest on-site Coulomb repulsion opens a gap leading to a Mott insulating
state. The ordering is antiferromagnetic along the c axis with total moments
aligned antiparallel along the c axis and canted along the b axis.",1110.0386v2
2012-06-25,Particle number fractionalization of a one-dimensional atomic Fermi gas with synthetic spin-orbit coupling,"We propose an experimental scheme to simulate the fractionalization of
particle number by using a one-dimensional spin-orbit coupled ultracold
fermionic gas. The wanted spin-orbit coupling, a kink-like potential, and a
conjugation-symmetry-breaking mass term are properly constructed by laser-atom
interactions, leading to an effective low-energy relativistic Dirac Hamiltonian
with a topologically nontrivial background field. The designed system supports
a localized soliton excitation with a fractional particle number that is
generally irrational and experimentally tunable, providing a direct realization
of the celebrated generalized-Su-Schrieffer-Heeger model. In addition, we
elaborate on how to detect the induced soliton mode with the FPN in the system.",1206.5614v2
2012-08-13,Ground state of spin-1 Bose-Einstein condensates with spin-orbit coupling in a Zeeman field,"We systematically investigate the weakly trapped spin-1 Bose-Einstein
condensates with spin-orbit coupling in an external Zeeman field. We find that
the mean-field ground state favors either a magnetized standing wave phase or
plane wave phase when the strength of Zeeman field is below a critical value
related to the strength of spin-orbit coupling. Zeeman field can induce the
phase transition between standing wave and plane wave phases, and we determine
the phase boundary analytically and numerically. The magnetization of these two
phases responds to the external magnetic field in a very unique manner, the
linear Zeeman effect magnetizes the standing wave phase along the direction of
the magnetic field, but the quadratic one demagnetizes the plane wave phase.
When the strength of Zeeman field surpasses the critical value, the system is
completely polarized to a ferromagnetic state or polar state with zero
momentum.",1208.2514v1
2012-09-03,Thermodynamics of spin-orbit-coupled Bose-Einstein condensates,"In this paper we develop a quantum field approach to reveal the thermodynamic
properties of the trapped BEC with the equal Rashba and Dresselhaus spin-orbit
couplings. In the experimentally-feasible regime, the phase transition from the
separate phase to the single minimum phase can be well driven by the tunable
temperature. Moreover, the critical temperature, which is independent of the
trapped potential, can be derived exactly. At the critical point, the specific
heat has a large jump and can be thus regarded as a promising candidate to
detect this temperature-driven phase transition. In addition, we obtain the
analytical expressions for the specific heat and the entropy in the different
phases. In the single minimum phase, the specific heat as well as the entropy
are governed only by the Rabi frequency. However, in the separate phase with
lower temperature, we find that they are determined only by the strength of
spin-orbit coupling. Finally, the effect of the effective atom interaction is
also addressed. In the separate phase, this effective atom interaction affects
dramatically on the critical temperature and the corresponding thermodynamic
properties.",1209.0346v1
2012-09-19,Nodeless superconductivity in Ir$_{1-x}$Pt$_x$Te$_2$ with strong spin-orbital coupling,"The thermal conductivity $\kappa$ of superconductor Ir$_{1-x}$Pt$_{x}$Te$_2$
($x$ = 0.05) single crystal with strong spin-orbital coupling was measured down
to 50 mK. The residual linear term $\kappa_0/T$ is negligible in zero magnetic
field. In low magnetic field, $\kappa_0/T$ shows a slow field dependence. These
results demonstrate that the superconducting gap of Ir$_{1-x}$Pt$_{x}$Te$_2$ is
nodeless, and the pairing symmetry is likely conventional s-wave, despite the
existence of strong spin-orbital coupling and a quantum critical point.",1209.4229v3
2013-04-16,Spin-orbit Coupling Effects on the Superfluidity of Fermi Gas in an Optical Lattice,"We investigate the superfluidity of attractive Fermi gas in a square optical
lattice with spin-orbit coupling (SOC). We show that the system displays a
variety of new filling-dependent features. At half filling, a quantum phase
transition from a semimetal to a superfluid is found for large SOC. Close to
half filling where the emerging Dirac cones governs the behaviors of the
system, SOC tends to suppress the BCS superfluidity. Conversely, SOC can
significantly enhance both the pairing gap and condensate fraction and lead to
a new BCS-BEC crossover for small fillings. Moreover, we demonstrate that the
superfluid fraction also exhibits many interesting phenomena compared with the
spin-orbit coupled Fermi gas without lattice.",1304.4511v2
2013-06-25,Inhomogeneous Topological Superfluidity in One-Dimensional Spin-Orbit-Coupled Fermi Gases,"We theoretically predict an exotic topological superfluid state with
spatially modulated pairing gap in one-dimensional spin-orbit-coupled Fermi
gases. This inhomogeneous topological superfluidity is induced by applying
simultaneously a perpendicular Zeeman magnetic field and an equally weighted
Rashba and Dresselhaus spin-orbit coupling in one-dimensional optical lattices.
Based on the self-consistent Bogoliubov--de Gennes theory, we confirm that this
novel topological phase is a unique condensation of Cooper pairs, which
manifests the interplay between the inhomogeneity of superfluid and its
nontrivial topological structure. The properties of the emergent Majorana bound
states are investigated in detail by examining the associated $\mathbb{Z}_{2}$
topological number, the eigenenergy and density of states spectra, as well as
the wave functions of the localized Majorana end modes. Experimental
feasibility of observing this new topological state of matter is also
discussed.",1306.5934v2
2013-07-14,Topological Fulde-Ferrell superfluid in spin-orbit coupled atomic Fermi gases,"We theoretically predict a new topological matter - topological inhomogeneous
Fulde-Ferrell superfluid - in one-dimensional atomic Fermi gases with equal
Rashba and Dresselhaus spin-orbit coupling near s-wave Feshbach resonances. The
realization of such a spin-orbit coupled Fermi system has already been
demonstrated recently by using a two-photon Raman process and the extra
one-dimensional confinement is easy to achieve using a tight two-dimensional
optical lattice. The topological Fulde-Ferrell superfluid phase is
characterized by a nonzero center-of-mass momentum and a non-trivial Berry
phase. By tuning the Rabi frequency and the detuning of Raman laser beams, we
show that such an exotic topological phase occupies a significant part of
parameter space and therefore it could be easily observed experimentally, by
using, for example, momentum-resolved and spatially resolved radio-frequency
spectroscopy.",1307.3744v2
2013-10-16,Engineering the Quantum Anomalous Hall Effect in Graphene with Uniaxial Strains,"We theoretically investigate the manipulation of the quantum anomalous Hall
effect (QAHE) in graphene by means of the uniaxial strain. The values of Chern
number and Hall conductance demonstrate that the strained graphene in presence
of Rashba spin-orbit coupling and exchange field, for vanishing intrinsic
spin-orbit coupling, possesses non-trivial topological phase which is robust
against the direction and modulus of the strain. Besides, we also find that the
interplay between Rashba and intrinsic spin-orbit couplings results in a
topological phase transition in the strained graphene. Remarkably, as the
strain strength is increased beyond approximately 7%, the critical parameters
of the exchange field for triggering the quantum anomalous Hall phase
transition show distinct behaviors - decrease (increase) for strains along
zigzag (armchair) direction. Our findings open up a new platform for
manipulation of the QAHE by an experimentally accessible strain deformation of
the graphene structure, with promising application on novel quantum electronic
devices with high energy efficiency performance.",1310.4468v2
2014-02-09,Study on the tunneling spectroscopy of $N-pS$ junction and $N-hS$ junction,"We study the complete tunneling spectroscopy of a normal metal/$p$-wave
superconductor junction ($N-pS$) and normal metal/heterostructure
superconductor junction ($N-hS$) by Blonder-Tinkham-Klapwijk (BTK) method. We
find that, for $p$-wave superconductor with non-trivial topology, there exists
a quantized zero-bias conductance peak stably, for heterostructure
superconductor with non-trivial topology, the emerging zero-bias conductance
peak is non-quantized and usually has a considerable gap to the quantized
value. Furthermore, it is sensitive to parameters, especially to spin-orbit
coupling and the $s$-wave pairing potential. Results obtained suggest that the
observation of a small zero-bias conductance peak, instead of a quantized
zero-bias conductance peak, in current tunneling experiments can be a natural
result if the spin-orbit coupling turns out to be several times smaller than
the reported one. Results obtained also suggest that both a stronger spin-orbit
coupling and proximity $s$-wave superconductor with relative weaker pairing
potential can produce a much more striking zero-bias conductance peak (compared
to the experiments), even an almost quantized one. As $s$-wave superconductors
are common in nature, the prediction can be verified within current experiment
ability.",1402.1964v1
2014-02-27,Gapless topological Fulde-Ferrell superfluidity in spin-orbit coupled Fermi gases,"Topological superfluids usually refer to a superfluid state which is gapped
in the bulk but metallic at the boundary. Here we report that a gapless,
topologically non-trivial superfluid with inhomogeneous Fulde-Ferrell pairing
order parameter can emerge in a two-dimensional spin-orbit coupled Fermi gas,
in the presence of both in-plane and out-of-plane Zeeman fields. The
Fulde-Ferrell pairing - induced by the spin-orbit coupling and in-plane Zeeman
field - is responsible for this gapless feature. This exotic superfluid has a
significant Berezinskii-Kosterlitz-Thouless (BKT) transition temperature and
has robust Majorana edge modes against disorder owing to its topological
nature.",1402.6832v2
2014-02-28,Anisotropic optical properties of Fe/GaAs(001) nanolayers from first principles,"We investigate the anisotropy of the optical properties of thin Fe films on
GaAs(001) from first-principles calculations. Both intrinsic and
magnetization-induced anisotropy are covered by studying the system in the
presence of spin-orbit coupling and external magnetic fields. We use the
linearized augmented plane wave method, as implemented in the WIEN2k density
functional theory code, to show that the $C_{2v}$ symmetric anisotropy of the
spin-orbit coupling fields at the Fe/GaAs(001) interface manifests itself in
the corresponding anisotropy of the optical conductivity and the polar
magneto-optical Kerr effect. While their magnetization-induced anisotropy is
negligible, the intrinsic anisotropy of the optical properties is significant
and reflects the underlying $C_{2v}$ symmetry of the Fe/GaAs(001) interface.
This suggests that the effects of anisotropic spin-orbit coupling fields in
experimentally relevant Fe/GaAs(001) slabs can be studied by purely optical
means.",1402.7370v1
2014-09-01,Tight-binding theory of spin-orbit coupling in graphynes,"We investigate the effects of Rashba and intrinsic spin-orbit couplings in
graphynes. First, we develop a general method to address spin-orbit couplings
within the tight-binding theory. Then, we apply this method to $\alpha$,
$\beta$, and $\gamma$-graphyne, and determine the SOC parameters in terms of
the microscopic hopping and on-site energies. We find that for
$\alpha$-graphyne, as in graphene, the intrinsic SOC opens a non-trivial gap,
whereas the Rashba SOC splits each Dirac cone into four. In $\beta$ and
$\gamma$ graphyne, the Rashba SOC can lead to a Lifshitz phase transition, thus
transforming the zero-gap semiconductor into a gapped system or vice versa,
when pairs of Dirac cones annihilate or emerge. The existence of internal
(within the benzene ring) and external SOC in these compounds allow us to
explore a myriad of phases not available in graphene.",1409.0388v2
2015-01-28,Discrete solitons of spin-orbit coupled Bose-Einstein condensates in optical lattices,"We study localized nonlinear excitations of a dilute Bose-Einstein condensate
(BEC) with spin-orbit coupling in a deep optical lattice (OL). We use Wannier
functions to derive a tight-binding model that includes the spin-orbit coupling
(SOC) at the discrete level in the form of a generalized discrete nonlinear
Sch\""odinger equation. Spectral properties are investigated and the existence
and stability of discrete solitons and breathers with different symmetry
properties with respect to the OL is demonstrated. We show that the symmetry of
the modes can be changed from on-site to inter-site and to asymmetric modes
simply by changing the interspecies interaction. Asymmetric modes appear to be
novel modes intrinsic of the SOC.",1501.07296v1
2015-04-24,Bright solitons in a 2D spin-orbit-coupled dipolar Bose-Einstein condensate,"We study a two-dimensional spin-orbit-coupled dipolar Bose-Einstein
condensate with repulsive contact interactions by both the variational method
and the imaginary time evolution of the Gross-Pitaevskii equation. The dipoles
are completely polarized along one direction in the 2D plane so as to provide
an effective attractive dipole-dipole interaction. We find two types of
solitons as the ground states arising from such attractive interactions: a
plane wave soliton with a spatially varying phase and a stripe soliton with a
spatially oscillating density for each component. Both types of solitons
possess smaller size and higher anisotropy than the soliton without spin-orbit
coupling. Finally, we discuss the properties of moving solitons, which are
nontrivial because of the violation of Galilean invariance.",1504.06575v2
2015-06-11,Simulating Chiral Magnetic and Separation Effects with Spin-Orbit Coupled Atomic Gases,"The chiral magnetic and chiral separation effects---quantum-anomaly-induced
electric current and chiral current along an external magnetic field in
parity-odd quark-gluon plasma---have received intense studies in the community
of heavy-ion collision physics. We show that analogous effects occur in
rotating trapped Fermi gases with Weyl-Zeeman spin-orbit coupling where the
rotation plays the role of an external magnetic field. These effects can induce
a mass quadrupole in the atomic cloud along the rotation axis which may be
tested in future experiments. Our results suggest that the spin-orbit coupled
atomic gases are potential simulators of the chiral magnetic and separation
effects.",1506.03590v2
2016-01-06,Influence of structural distortions on the Ir magnetism in Ba2-xSrxYIrO6 double perovskites,"We explore the relative strengths of spin orbit coupling and crystal field
splitting in the Ir5+ compounds Ba2-xSrxYIrO6. In the case of strong spin orbit
coupling and regular Ir5+ octahedra, one expects a nonmagnetic J = 0 state; in
the case of distorted octahedra where crystal field effects dominate, the t2g
manifold splits into a magnetic ground state. We report the results of
continuously transitioning from the cubic Ba2YIrO6 double perovskite with ideal
octahedra to the monoclinic Sr2YIrO6 double perovskite with distorted
octahedra. We see no emergence of an enhanced Ir5+ magnetic moment in the
series on increasing the structural distortions, as would have been the case
for significant crystal field splitting. The near-constant magnetic moment
observed through the Ba2-xSrxYIrO6 series reinforces the notion that spin-orbit
coupling is the dominant force in determining the magnetism of iridium-oxygen
octahedra in perovskite-like structures",1601.01198v1
2019-05-31,Orbital Magnetic Field Effects in Mott Insulators with Strong Spin-Orbit Coupling,"We study the effect of a magnetic field on the low energy description of Mott
insulators with strong spin-orbit (SO) coupling. In contrast to the standard
case of the Hubbard model without SO coupling, we show that Peierls phases can
modulate the magnetic exchange at leading order in the interaction. Our
mechanism crucially depends on the existence of distinct exchange paths between
neighboring magnetic ions enclosing a well-defined area. Thus it will
generically be present in any solid state realisation of the Kitaev model and
its extensions. We explicitly calculate the variation of the exchange constants
of the so-called $JK\Gamma$ model as a function of the magnetic flux. We
discuss experimental implications of our findings for various settings of
candidate Kitaev spin liquids.",1905.13683v3
2010-05-20,"Comment on ""On the classical analysis of spin-orbit coupling in hydrogenlike atoms,"" [Am. J. Phys. 78 (4) 428-432, April 2010]","In their recent paper, Kholmetskii, Missevitch, and Yarman ""reanalyze the
usual classical derivation of spin-orbit coupling in hydrogenlike atoms"" and
find a result ""in qualitative agreement with the solution of the Dirac-Coulomb
equation for hydrogenlike atoms."" However, the authors' result is based on an
equation of translational motion of the electron that omits any contribution
due to the existence of ""hidden"" momentum of the electron intrinsic magnetic
dipole moment in the electric field of the nucleus. Accounting for hidden
momentum is necessary to obtaining conservation of linear momentum in the
interaction of a magnetic dipole with a point charge. If hidden momentum is
omitted from the description, the force on the nucleus due to the electron will
differ from the force on the electron due to the nucleus. Thus, omitting the
hidden momentum contribution, the binding energy including the spin-orbit
coupling cannot be consistently calculated, while including hidden momentum,
the value obtained is in disagreement with experiment.",1005.3841v2
2013-08-21,Effective Hamiltonians for quasi-one-dimensional Fermi gases with spin-orbit coupling,"We derive one-dimensional effective Hamiltonians for spin-orbit coupled Fermi
gases confined in quasi-one-dimensional trapping potentials. For energy regime
around the two-body bound state energy, the effective Hamiltonian takes a
two-channel form, where the population in transverse excited levels are
described by dressed molecules in the closed channel. For energy regime
slightly above the continuum threshold, the effective Hamiltonian takes a
single-channel form, where low-energy physics is governed by the
one-dimensional interacting strength determined by three-dimensional scattering
length and transverse confinement. We further discuss the effect of spin-orbit
coupling and effective Zeeman field on the position of confinement-induced
resonances, and show that these resonances can be understood as Feshbach
resonances between the threshold of the transverse ground state and the
two-body bound state associated with the transverse excited states. We expect
that the shift of confinement-induced resonances can be observed under present
experimental technology at attainable temperatures.",1308.4511v1
2012-01-10,Full counting statistics for orbital-degenerate impurity Anderson model with Hund's rule exchange coupling,"We study non-equilibrium current fluctuations through a quantum dot, which
includes a ferromagnetic Hund's rule coupling $J$, in the low-energy Fermi
liquid regime using the renormalized perturbation theory. The resulting
cumulant for the current distribution in the particle-hole symmetric case,
shows that spin-triplet and spin-singlet pairs of quasiparticles are formed in
the current due to the Hund's rule coupling and these pairs enhance the current
fluctuations. In the fully screened higher-spin Kondo limit, the Fano factor
takes a value $F_b = (9M+6)/ (5M+4)$ determined by the orbital degeneracy $M$.
We also investigate crossover between the small and large $J$ limits in the
two-orbital case M=2, using the numerical renormalization group approach.",1201.1957v2
2012-04-11,Shiba impurity bound states as a probe of topological superconductivity and Fermion parity changing quantum phase transitions,"Spin-orbit coupled superconductors are potentially interesting candidates for
realizing topological and potentially non-Abelian states with Majorana
Fermions. We argue that time-reversal broken spin-orbit coupled superconductors
generically can be characterized as having sub-gap states that are bound to
localized non-magnetic impurities. Such bound states, which are referred to as
Shiba states, can be detected as sharp resonances in the tunneling spectrum of
the spin-orbit coupled superconductors. The Shiba state resonance can be tuned
using a gate-voltage or a magnetic field from being at the edge of the gap at
zero magnetic fields to crossing zero energy when the Zeeman splitting is tuned
into the topological superconducting regime. The zero-crossing signifies a
Fermion parity changing first order quantum phase transition, which is
characterized by a Pfaffian topological invariant.
  These zero-crossings of the impurity level can be used to locally
characterize the topological superconducting state from tunneling experiments.",1204.2537v2
2014-06-20,Zeeman field induced non-trivial topology in a spin-orbit coupled superconductor,"The hope to realize Majorana fermions at the vortex core of a two dimensional
topological superconductor has led to a variety of proposals for devices which
exhibit topological superconductivity. Many of these include superconductivity
through the proximity effect and therefore require a layer of a conventional
superconductor deposited on top of another system, which lends its topological
properties\cite{Fu,Sau,Alicea}. The necessity of the superconducting layer
poses some technical complications and, in particular, makes it harder to probe
the Majorana state. In this work we propose to replace the proximity effect
pairing by an innate tendency for pairing, mediated by interactions. We use a
model system with spin orbit coupling and on-site repulsion and apply
renormalization group to the interaction vertex. Without a Zeeman field this
model exhibits pairing instabilities in different channels depending on the
tuning of parameters. Once a Zeeman field is introduced the model favors
topological superconductivity where the order parameter winds an odd number of
times around the Fermi surface. This suggests that certain superconductors,
with strong spin-orbit coupling, may go through a topological phase transition
as a function of applied magnetic field.",1406.5552v1
2015-12-06,Absence of Localization in Disordered Two Dimensional Electron Gas at Weak Magnetic Field and Strong Spin-Orbit Coupling,"The one-parameter scaling theory of localization predicts that all states in
a disordered two-dimensional system with broken time reversal symmetry are
localized even in the presence of strong spin-orbit coupling. While at constant
strong magnetic fields this paradigm fails (recall quantum Hall effect), it is
believed to hold at weak magnetic fields. Here we explore the nature of quantum
states at weak magnetic field and strongly fluctuating spin-orbit coupling,
employing highly accurate numerical procedure based on level spacing
distribution and transfer matrix technique combined with finite-size
one-parameter scaling hypothesis. Remarkably, the metallic phase, (known to
exist at zero magnetic field), persists also at finite (albeit weak) magnetic
fields, and eventually crosses over into a critical phase, which has already
been confirmed at high magnetic fields. A schematic phase diagram drawn in the
energy-magnetic field plane elucidates the occurrence of localized, metallic
and critical phases. In addition, it is shown that nearest-level statistics is
determined solely by the symmetry parameter $\beta$ and follows the Wigner
surmise irrespective of whether states are metallic or critical.",1512.01733v1
2015-12-13,Zitterbewegung with spin-orbit coupled ultracold atoms in a fluctuating optical lattice,"Dynamics of non-interacting ultracold atoms with artificial spin-orbit
coupling is considered. Spin-orbit coupling is created using two moving optical
lattices with orthogonal polarizations. Our main goal is to study influence of
lattice noise on Rabi oscillations. Special attention is paid to the phenomenon
of the Zitterbewegung being trembling motion caused by Rabi transitions between
states with different velocities. Phase and amplitude fluctuations of lattices
are modelled by means of the two-dimensional stochastic Ornstein-Uhlenbeck
process, also known as harmonic noise. In the the noiseless case the problem is
solved analytically in terms of the momentum representation. It is shown that
lattice noise significantly extends duration of the Zitterbewegung as compared
to the noiseless case. This effect originates from noise-induced decoherence of
Rabi oscillations.",1512.04007v2
2016-05-13,"Topological nodal-line semimetals in alkaline-earth stannides, germanides and silicides","Based on first-principles calculations and an effective Hamiltonian analysis,
we systematically investigate the electronic and topological properties of
alkaline-earth compounds $AX_2$ ($A$=Ca, Sr, Ba; $X$=Si, Ge, Sn). Taking
BaSn$_2$ as an example, we find that when spin-orbit coupling is ignored, these
materials are three-dimensional topological nodal-line semimetals characterized
by a snake-like nodal loop in three-dimensional momentum space. Drumhead-like
surface states emerge either inside or outside the loop circle on the (001)
surface depending on surface termination, while complicated
double-drumhead-like surface states appear on the (010) surface. When
spin-orbit coupling is included, the nodal line is gapped and the system
becomes a topological insulator with Z$_2$ topological invariants (1;001).
Since spin-orbit coupling effects are weak in light elements, the nodal-line
semimetal phase is expected to be achievable in some alkaline-earth germanides
and silicides.",1605.04050v2
2016-12-13,Negative mass hydrodynamics in a Spin-Orbit--Coupled Bose-Einstein Condensate,"A negative effective mass can be realized in quantum systems by engineering
the dispersion relation. A powerful method is provided by spin-orbit coupling,
which is currently at the center of intense research efforts. Here we measure
an expanding spin-orbit coupled Bose-Einstein condensate whose dispersion
features a region of negative effective mass. We observe a range of dynamical
phenomena, including the breaking of parity and of Galilean covariance,
dynamical instabilities, and self-trapping. The experimental findings are
reproduced by a single-band Gross-Pitaevskii simulation, demonstrating that the
emerging features - shockwaves, soliton trains, self-trapping, etc. - originate
from a modified dispersion. Our work also sheds new light on related phenomena
in optical lattices, where the underlying periodic structure often complicates
their interpretation.",1612.04055v2
2017-10-08,$SU(3)$ Topological Insulators in the Honeycomb Lattice,"We investigate realizations of topological insulators with spin-1 bosons
loaded in a honeycomb optical lattice and subjected to a $SU(3)$ spin-orbit
coupling - a situation which can be realized experimentally using cold atomic
gases. In this paper, we focus on the topological properties of the
single-particle band structure, namely Chern numbers (lattice with periodic
boundary conditions) and edge states (lattice with strip geometry). While
$SU(2)$ spin-orbit couplings always lead to time-reversal symmetric Hubbard
models, and thereby to topologically trivial band structures, suitable $SU(3)$
spin-orbit couplings can break time reversal symmetry and lead to topologically
non-trivial bulk band structures and to edge states in the strip geometry. In
addition, we show that one can trigger a series of topological transitions
(i.e. integer changes of the Chern numbers) that are specific to the geometry
of the honeycomb lattice by varying a single parameter in the Hamiltonian.",1710.02788v2
2018-06-07,Bloch bound state of spin-orbit-coupled fermions in an optical lattice,"Understanding fundamentals of few-body physics provides an interesting
bottom-up approach for the clarification of many-body properties. The
remarkable experimental progress in realizing spin-orbit coupling (SOC) in
optical Raman lattices offers a renewed thrust towards discovering novel
few-body features induced by the interplay between SOC and optical lattices.
Using the Wilson renormalization method to account for high-band effects, we
study the low-energy two-body scattering processes of spin-$1/2$ fermions in
spin-orbit coupled optical lattices. We demonstrate that, under weak SOC,
adding a small lattice potential would destabilize shallow two-body bound
states, contrary to conventional wisdom. On the other hand, when lattice is
sufficiently deep, two-body bound states are always stabilized by increasing
the lattice depth. This intriguing non-monotonic behavior of the bound-state
stability derives from the competition between SOC and optical lattices, and
can be explained by analyzing the low-energy density of states. We also discuss
the impact of high-band effects on such a behavior, as well as potential
experimental detections.",1806.02478v2
2018-12-20,Nonlinear dynamics of a spin-orbit-coupled Bose-Einstein condensate,"Single-particle dynamics of a spin-orbit-coupled Bose-Einstein condensate has
recently been investigated in experiments that explore the physics of
Landau-Zener tunneling and of the Zitterbewegung. In this paper, we study the
influence of a nonlinearity due to interactions on these dynamics and show that
the dispersion relation develops interesting loop strucures. The atoms can move
along the nonlinear dispersion curve in the presence of a weak acceleration
force and we show that the loops lead to straightforward nonlinear Landau-Zener
tunneling. However, we find that for the Zitterbewegung, induced by a sudden
quench in the spin-orbit coupling parameters, the nonlinear dispersion is
irrelevant.",1812.08303v2
2019-02-22,Roton-induced Bose polaron in the presence of synthetic spin-orbit coupling,"We theoretically investigate the quasiparticle (polaron) properties of an
impurity immersing in a Bose-Einstein condensate with equal Rashba and
Dresselhaus spin-orbit coupling at zero temperature. In the presence of
spin-orbit coupling, all bosons can condense into a single plane-wave state
with finite momentum, and the corresponding excitation spectrum shows an
intriguing roton minimum. We find that the polaron properties are strongly
modified by this roton minimum, where the ground state of attractive polaron
acquires a nonzero momentum and anisotropic effective mass. Across the
resonance of the interaction between impurity and atoms, the polaron evolves
into a tight-binding dimer. We show that the evolution is not smooth when the
roton structure of the condensate becomes apparent, and a first-order phase
transition from a phonon-induced polaron to a roton-induced polaron is observed
at a critical interaction strength.",1902.08333v1
2019-11-09,Interplay of Coulomb repulsion and spin-orbit coupling in superconducting 3D quadratic band touching Luttinger semimetals,"We investigate the superconductivity of 3D Luttinger semimetals, such as
YPtBi, where Cooper pairs are constituted of spin-3/2 quasiparticles. Various
pairing mechanisms have already been considered for these semimetals, such as
from polar phonons modes, and in this work we explore pairing from the screened
electron-electron Coulomb repulsion. In these materials, the small Fermi energy
and the spin-orbit coupling strongly influence how charge fluctuations can
mediate pairing. We find the superconducting critical temperature as a function
of doping for an s-wave order parameter, and determine its sensitivity to
changes in the dielectric permittivity. Also, we discuss how order parameters
other than s-wave may lead to a larger critical temperature, due to spin-orbit
coupling.",1911.03712v1
2020-06-08,Pressure Induced Topological Superconductivity in the Spin-Orbit Mott Insulator GaTa4Se8,"Lacunar spinel GaTa$_4$Se$_8$ is a unique example of spin-orbit coupled Mott
insulator described by molecular $j_{\text{eff}}\!=\!3/2$ states. It becomes
superconducting at T$_c$=5.8K under pressure without doping. In this work, we
show, this pressure-induced superconductivity is a realization of a new type
topological phase characterized by spin-2 Cooper pairs. Starting from
first-principles density functional calculations and random phase
approximation, we construct the microscopic model and perform the detailed
analysis. Applying pressure is found to trigger the virtual interband tunneling
processes assisted by strong Hund coupling, thereby stabilizing a particular
$d$-wave quintet channel. Furthermore, we show that its Bogoliubov
quasiparticles and their surface states exhibit novel topological nature. To
verify our theory, we propose unique experimental signatures that can be
measured by Josephson junction transport and scanning tunneling microscope. Our
findings open up new directions searching for exotic superconductivity in
spin-orbit coupled materials.",2006.04782v1
2020-06-21,Spin-orbit coupled spin-1 Bose-Einstein condensate flow past an obstacle in the presence of a Zeeman field,"We study the dynamics of a Rashba spin-orbit coupled spin-1 ferromagnetic
Bose-Einstein condensate under a linear Zeeman magnetic field(ZF) disturbed by
a moving obstacle. The Bogoliubov excitation spectrums and corresponding
critical excitations in different situations are analyzed. The structure of the
coreless vortex or antivortex generated by the moving obstacle has been
investigated. When the ZF is applied along x direction, the vortex cores for
the three components of a(an) vortex(antivortex) could be arranged into a
vertical line, and their order would be reversed as the spin-orbit coupling
increases. When the ZF is parallel to z direction, a skyrmion-like vortex
ground state could be induced even by a static obstacle. This topological
structure is also found to be dynamically stable if the obstacle is moving at a
relatively small velocity.",2006.11832v1
2020-11-29,Dynamical generation of solitons in one-dimensional Fermi superfluids with and without spin-orbit coupling,"We theoretically generalize a systematic language to describe the
phase-imprinting technique to investigate the dynamical generation of solitons
in a one-dimensional Raman-type spin-orbit-coupled Fermi superfluid. We check
our method with the simulation of time-dependent Bogoliubov-de Gennes equations
and find that our method not only can generate stable dark and even gray
solitons in a conventional Fermi superfluid by controlling the transferred
phase jump but also is feasible to create a stable dark soliton in both BCS and
topological states of a spin-orbit-coupled Fermi superfluid. We also discuss
the physical implication of our method.",2011.14245v3
2021-03-13,Nonlinear dynamics of topological Dirac fermions in 2D spin-orbit coupled materials,"The graphene family materials are two-dimensional staggered monolayers with a
gapped energy band structure due to intrinsic spin-orbit coupling. The mass
gaps in these materials can be manipulated on-demand via biasing with a static
electric field, an off-resonance circularly polarized laser, or an exchange
interaction field, allowing the monolayer to be driven through a multitude of
topological phase transitions. We investigate the dynamics of spin-orbit
coupled graphene family materials to unveil topological phase transition
fingerprints embedded in the nonlinear regime and show how these signatures
manifest in the nonlinear Kerr effect and in third-harmonic generation
processes. We show that the resonant nonlinear spectral response of topological
fermions can be traced to specific Dirac cones in these materials, enabling
characterization of topological invariants in any phase by detecting the
cross-polarized component of the electromagnetic field. By shedding light on
the unique processes involved in harmonic generation via topological phenomena
our findings open an encouraging path towards the development of novel
nonlinear systems based on two-dimensional semiconductors of the graphene
family.",2103.07632v2
2021-03-14,Topological Mott transition in a two band model of spinless fermions with on-site Coulomb repulsion,"In the framework of mean field approach, we study topological Mott transition
in a two band model of spinless fermions on a square lattice at half filling.
We consider the combined effect of the on-site Coulomb repulsion and the
spin-orbit Rashba coupling. The ground state phase diagram is calculated as a
function of the strength of the spin-orbit Rashba coupling and the Coulomb
repulsion. The spin-orbit Rashba coupling leads to a distinct phase of matter,
the topological semimetal. We study a new type of phase transition between the
non-topological insulator and topological semimetal states. Topological phase
state is characterized by the zero energy Majorana states, which there are in
defined region of the wave vectors and are localized at the boundaries of the
sample. The region of existence of the zero energy Majorana states tends to
zero at the point of the Mott phase transition. The zero energy Majorana states
are dispersionless (they can be considered as flat bands), the Chern number and
Hall conductance are equal to zero (note in two dimensional model",2103.07916v2
2022-03-06,Probing two Higgs oscillations in a one-dimensional Fermi superfluid with Raman-type spin-orbit coupling,"We theoretically investigate the Higgs oscillation in a one-dimensional
Raman-type spin-orbit-coupled Fermi superfluid with the time-dependent
Bogoliubov-de Gennes equations. By linearly ramping or abruptly changing the
effective Zeeman field in both the Bardeen-Cooper-Schrieffer state and the
topological superfluid state, we find the amplitude of the order parameter
exhibits an oscillating behaviour over time with two different frequencies
(i.e., two Higgs oscillations) in contrast to the single one in a conventional
Fermi superfluid. The observed period of oscillations has a great agreement
with the one calculated using the previous prediction [Volkov and Kogan, J.
Exp. Theor. Phys. 38, 1018 (1974)], where the oscillating periods are now
determined by the minimums of two quasi-particle spectrum in this system. We
further verify the existence of two Higgs oscillations using a periodic ramp
strategy with theoretically calculated driving frequency. Our predictions would
be useful for further theoretical and experimental studies of these Higgs
oscillations in spin-orbit-coupled systems.",2203.02919v1
2022-03-21,Hydrodynamic spin-orbit coupling in asynchronous optically driven micro-rotors,"Vortical flows of rotating particles describe interactions ranging from
molecular machines to atmospheric dynamics. Yet to date, direct observation of
the hydrodynamic coupling between artificial micro-rotors has been restricted
by the details of the chosen drive, either through synchronization (using
external magnetic fields) or confinement (using optical tweezers). Here we
present a new active system that illuminates the interplay of rotation and
translation in free rotors. We developed a non-tweezing circularly polarized
beam that simultaneously rotates hundreds of silica-coated birefringent
colloids. The particles rotate asynchronously in the optical torque field while
freely diffusing in the plane. We observe that neighboring particles orbit each
other with an angular velocity that depends on their spins. We derive an
analytical model in the Stokes limit for pairs of spheres that quantitatively
explains the observed dynamics. We then find that the geometrical nature of the
low Reynolds fluid results in a universal hydrodynamic spin-orbit coupling. Our
findings are of significance for the understanding and development of
far-from-equilibrium materials.",2203.11051v2
2023-03-15,The Dynamical Stripes in Spin-Orbit Coupled Bose-Einstein Condensates with Josephson Junctions,"The Josephson dynamics of the Bose-Einstein condensation with Raman-induced
spin-orbit coupling is investigated. A quasi-1D trap is divided into two
reservoirs by an optical barrier. Before the tunneling between the reservoirs
is turned on, the system stays in its equilibrium ground state. For different
spin-orbit coupling parameters and interaction strengthes, the ground state
displays a rich phase diagram. In this work we focus on the plane wave phase
and the stripe phase. Our calculation shows that, when the tunneling is turned
on, the plane wave phase evolves into a dynamical stripe phase, that is, the
density of the particle changes from uniform to periodically modulated.
Basically, this stripe is described by a sine function and the wave length, the
amplitude and the initial phase of the function are all varying with time. If
the system stays in stripe phase initially, the stripes become ``sliding"" when
the tunneling is turned on, which reflects the running of one of the phases of
the wave function.",2303.08585v1
2021-03-11,Tunable spin-valley coupling in layered polar Dirac metals,"In non-centrosymmetric metals, spin-orbit coupling (SOC) induces
momentum-dependent spin polarization at the Fermi surfaces. This is exemplified
by the valley-contrasting spin polarization in monolayer transition metal
dichalcogenides (TMDCs) with in-plane inversion asymmetry. However, the valley
configuration of massive Dirac fermions in TMDCs is fixed by the graphene-like
structure, which limits the variety of spin-valley coupling. Here, we show that
the layered polar metal BaMn$X_2$ ($X =$Bi, Sb) hosts tunable
spin-valley-coupled Dirac fermions, which originate from the distorted $X$
square net with in-plane lattice polarization. We found that in spite of the
larger SOC, BaMnBi$_2$ has approximately one-tenth the lattice distortion of
BaMnSb$_2$, from which a different configuration of spin-polarized Dirac
valleys is theoretically predicted. This was experimentally observed as a clear
difference in the Shubnikov-de Haas oscillation at high fields between the two
materials. The chemically tunable spin-valley coupling in BaMn$X_2$ makes it a
promising material for various spin-valleytronic devices.",2103.06765v2
2023-10-19,Coherence of a field-gradient-driven singlet-triplet qubit coupled to many-electron spin states in 28Si/SiGe,"Engineered spin-electric coupling enables spin qubits in semiconductor
nanostructures to be manipulated efficiently and addressed individually. While
synthetic spin-orbit coupling using a micromagnet is widely used for driving
qubits based on single spins in silicon, corresponding demonstration for
encoded spin qubits is so far limited to natural silicon. Here, we demonstrate
fast singlet-triplet qubit oscillation (~100 MHz) in a gate-defined double
quantum dot in $^{28}$Si/SiGe with an on-chip micromagnet with which we show
the oscillation quality factor of an encoded spin qubit exceeding 580. The
coherence time $\textit{T}_{2}$* is analyzed as a function of potential
detuning and an external magnetic field. In weak magnetic fields, the coherence
is limited by fast noise compared to the data acquisition time, which limits
$\textit{T}_{2}$* < 1 ${\mu}$s in the ergodic limit. We present evidence of
sizable and coherent coupling of the qubit with the spin states of a nearby
quantum dot, demonstrating that appropriate spin-electric coupling may enable a
charge-based two-qubit gate in a (1,1) charge configuration.",2310.12603v2
2018-12-26,Soliton lattices in the Gross-Pitaevskii equation with nonlocal and repulsive coupling,"Spatially-periodic patterns are studied in nonlocally coupled
Gross-Pitaevskii equation. We show first that spatially periodic patterns
appear in a model with the dipole-dipole interaction. Next, we study a model
with a finite-range coupling, and show that a repulsively coupled system is
closely related with an attractively coupled system and its soliton solution
becomes a building block of the spatially-periodic structure. That is, the
spatially-periodic structure can be interpreted as a soliton lattice. An
approximate form of the soliton is given by a variational method. Furthermore,
the effects of the rotating harmonic potential and spin-orbit coupling are
numerically studied.",1812.10218v1
2013-01-18,Engineering quantum anomalous Hall phases with orbital and spin degrees of freedom,"Combining tight-binding models and first principles calculations, we
investigate the quantum anomalous Hall (QAH) effect induced by intrinsic
spin-orbit coupling (SOC) in buckled honeycomb lattice with sp orbitals in an
external exchange field. Detailed analysis reveals that nontrivial topological
properties can arise utilizing not only spin but also orbital degrees of
freedom in the strong SOC limit, when the bands acquire non-zero Chern numbers
upon undergoing the so-called orbital purification. As a prototype of a buckled
honeycomb lattice with strong SOC we choose the Bi(111) bilayer, analyzing its
topological properties in detail. In particular, we show the emergence of
several QAH phases upon spin exchange of the Chern numbers as a function of SOC
strength and magnitude of the exchange field. Interestingly, we observe that in
one of such phases, namely, in the quantum spin Chern insulator phase, the
quantized charge and spin Hall conductivities co-exist. We consider the
possibility of tuning the SOC strength in Bi bilayer via alloying with
isoelectronic Sb, and speculate that exotic properties could be expected in
such an alloyed system owing to the competition of the topological properties
of its constituents. Finally, we demonstrate that 3d dopants can be used to
induce a sizeable exchange field in Bi(111) bilayer, resulting in non-trivial
Chern insulator properties.",1301.4426v1
2016-04-26,Spin-orbit torques in locally and globally non-centrosymmetric crystals: Antiferromagnets and ferromagnets,"One of the main obstacles that prevents practical applications of
antiferromagnets is the difficulty of manipulating the magnetic order
parameter. Recently, following the theoretical prediction [J. \v{Z}elezn\'y et
al., PRL 113, 157201 (2014)], the electrical switching of magnetic moments in
an antiferromagnet has been demonstrated [P. Wadley et al., Science 351, 587
(2016)]. The switching is due to the so-called spin-orbit torque, which has
been extensively studied in ferromagnets. In this phenomena a non-equilibrium
spin-polarization exchange coupled to the ordered local moments is induced by
current, hence exerting a torque on the order parameter. Here we give a general
systematic analysis of the symmetry of the spin-orbit torque in locally and
globally non-centrosymmetric crystals. We study when the symmetry allows for a
nonzero torque, when is the torque effective, and its dependence on the applied
current direction and orientation of magnetic moments. For comparison, we
consider both antiferromagnetic and ferromagnetic orders. In two representative
model crystals we perform microscopic calculations of the spin-orbit torque to
illustrate its symmetry properties and to highlight conditions under which the
spin-orbit torque can be efficient for manipulating antiferromagnetic moments.",1604.07590v1
2014-06-20,Spin-orbit density wave: A new phase of matter applicable to the hidden order state of URu2Si2,"We provide a brief review and detailed analysis of the spin-orbit density
wave (SODW), proposed as a possible explanation to the `hidden order' phase of
URu2Si2. Due to the interplay between inter-orbital Coulomb interaction and
spin-orbit coupling (SOC) in this compound, the SODW is shown to arise from
Fermi surface nesting instability between two spin-orbit split bands. An
effective low-energy Hamiltonian including single-particle SOC and two-particle
SODW is derived, while numerical results are calculated by using
density-functional theory (DFT) based band structure input. Computed gapped
quasiparticle spectrum, entropy loss and spin-excitation spectrum are in
detailed agreement with experiments. Interestingly, despite the fact that SODW
governs dynamical spin-excitations, the static magnetic moment is calculated to
be zero, owing to the time-reversal invariance imposed by SOC. As a
consequence, SODW can be destroyed by finite magnetic field even at zero
temperature. Our estimation of the location of the quantum critical point is
close to the experimental value of Bc ~ 35 T. Finally, we extend the idea of
SODW to other SOC systems including iridium oxides (iridates) and
two-dimensional electronic systems such as BiAg2 surface and LaAlO3/SrTiO3
interface. We show hints of quasiparticle gapping, reduction of preexisting
magnetic moment, large magneto-resistance etc. in these systems which can be
explained consistently within the SODW theory.",1406.5271v2
2021-11-24,"Spin-orbit-entangled nature of magnetic moments and Kitaev magnetism in layered halides $α$-RuX$_3$ (X = Cl, Br, I)","$\alpha$-RuCl$_3$ has been extensively studied recently because of potential
bond-dependent Kitaev magnetic exchange interactions and the resulting quantum
spin liquid phase that can be realized therein. It has been known that the
covalency between Ru 4$d$- and Cl $p$-orbitals is crucial to induce large
Kitaev interactions in this compound, therefore replacing Cl into heavier
halogen elements such as Br or I can be a promising way to promote the Kitaev
interaction even further. In a timely manner, there have been reports on
synthesis of $\alpha$-RuBr$_3$ and $\alpha$-RuI$_3$, which are expected to host
the same spin-orbit-entangled orbitals and Kitaev exchange interactions with
$\alpha$-RuCl$_3$. Here in this work we investigate electronic structures of
$\alpha$-RuCl$_3$, $\alpha$-RuBr$_3$, and $\alpha$-RuI$_3$ in a comparative
fashion, focusing on the cooperation of the spin-orbit coupling and on-site
Coulomb repulsions to realize the spin-orbit-entangled pseudospin-1/2 at Ru
sites. We further estimate magnetic exchange interactions of all three
compounds, showing that $\alpha$-RuBr$_3$ can be promising candidates to
realize Kitaev spin liquid phases in solid-state systems.",2111.12291v2
2022-08-21,Efficient generation of spin currents by the Orbital Hall effect in pure Cu and Al and their measurement by a Ferris-wheel ferromagnetic resonance technique at the wafer level,"We present a new ferromagnetic resonance (FMR) method that we term the Ferris
FMR. It is wideband, has significantly higher sensitivity as compared to
conventional FMR systems, and measures the absorption line rather than its
derivative. It is based on large-amplitude modulation of the externally applied
magnetic field that effectively magnifies signatures of the spin-transfer
torque making its measurement possible even at the wafer-level. Using the
Ferris FMR, we report on the generation of spin currents from the orbital Hall
effect taking place in pure Cu and Al. To this end, we use the spin-orbit
coupling of a thin Pt layer introduced at the interface that converts the
orbital current to a measurable spin current. While Cu reveals a large
effective spin Hall angle exceeding that of Pt, Al possesses an orbital Hall
effect of opposite polarity in agreement with the theoretical predictions. Our
results demonstrate additional spin- and orbit- functionality for two important
metals in the semiconductor industry beyond their primary use as interconnects
with all the advantages in power, scaling, and cost.",2208.09802v1
2019-11-21,Multiple Spin-Orbit Excitons and the Electronic Structure of $α$-RuCl$_3$,"The honeycomb compound $\alpha$-RuCl$_3$ is widely discussed as a proximate
Kitaev spin-liquid material. This scenario builds on spin-orbit entangled $j =
1/2$ moments arising for a $t_{2g}^5$ electron configuration with strong
spin-orbit coupling $\lambda$ and a large cubic crystal field. The low-energy
electronic structure of $\alpha$-RuCl$_3$, however, is still puzzling. In
particular infrared absorption features at 0.30 eV, 0.53 eV, and 0.75 eV seem
to be at odds with theory. Also the energy of the spin-orbit exciton, the
excitation from $j = 1/2$ to 3/2, and thus the value of $\lambda$ are
controversial. Combining infrared and Raman data, we show that the infrared
features can be attributed to single, double, and triple spin-orbit excitons.
We find $\lambda$ = 0.16 eV and $\Delta$ =42(4) meV for the observed non-cubic
crystal-field splitting, supporting the validity of the $j= 1/2$ picture for
$\alpha$-RuCl$_3$. The unusual strength of the double excitation is related to
the underlying hopping interactions which form the basis for dominant Kitaev
exchange.",1911.09337v1
2016-05-30,Spin Josephson effects in Exchange coupled Anti-ferromagnets,"The energy of exchange coupled antiferromagnetic insulators (AFMIs) is a
periodic function of the relative in-plane orientation of the N\'{e}el vector
fields. We show that this leads to oscillations in the relative magnetization
of exchange coupled AFMIs separated by a thin metallic barrier. These
oscillations pump a spin current ($I_{S}$) through the metallic spacer that is
proportional to the rate of change of the relative in-plane orientation of the
N\'{e}el vector fields. By considering spin-transfer torque induced by a spin
chemical potential ($V_{S}$) at one of the interfaces, we predict non-Ohmic
$I_{S}$-$V_{S}$ characteristics of AFMI exchange coupled hetero-structures,
which leads to a non-local voltage across a spin-orbit coupled metallic spacer.",1605.09427v1
2020-09-30,Rashba coupling and spin switching through surface states of Dirac semimetals,"We study the effect of the Rashba spin-orbit coupling on the Fermi arcs of
topological Dirac semimetals. The Rashba coupling is induced by breaking the
inversion symmetry at the surface. Remarkably, this coupling could be enhanced
by the interaction with the substrate and controlled by an external electric
field. We study analytically and numerically the rotation of the spin of the
surface states as a function of the electron's momentum and the coupling
strength. Furthermore, a detailed analysis of the spin-dependent two-terminal
conductance is presented in the clean limit and with the addition of a random
distribution of impurities. Depending on the magnitude of the quadratic terms
in the Hamiltonian, the spin-flip conductance may become dominant, thus showing
the potential of the system for spintronic applications, since the effect is
robust even in the presence of disorder.",2009.14753v2
2003-10-07,Electron-phonon induced spin relaxation in InAs quantum dots,"We have calculated spin relaxation rates in parabolic quantum dots due to the
phonon modulation of the spin-orbit interaction in presence of an external
magnetic field. Both, deformation potential and piezoelectric electron-phonon
coupling mechanisms are included within the Pavlov-Firsov spin-phonon
Hamiltonian. Our results have demonstrated that, in narrow gap materials, the
electron-phonon deformation potential and piezoelectric coupling give
comparable contributions as spin relaxation processes. For large dots, the
deformation potential interaction becomes dominant. This behavior is not
observed in wide or intermediate gap semiconductors, where the piezoelectric
coupling, in general, governs the spin relaxation processes. We also have
demonstrated that spin relaxation rates are particularly sensitive to the
Land\'e $g$-factor.",0310146v1
2010-10-07,Electrical manipulation and measurement of spin properties of quantum spin Hall edge states,"We study effects of a gate-controlled Rashba spin-orbit coupling to quantum
spin-Hall edge states in HgTe quantum wells. A uniform Rashba coupling can be
employed in tuning the spin orientation of the edge states while preserving the
time-reversal symmetry. We introduce a sample geometry where the Rashba
coupling can be used in probing helicity by purely electrical means without
requiring spin detection, application of magnetic materials or magnetic fields.
In the considered setup a tilt of the spin orientation with respect to the
normal of the sample leads to a reduction in the two-terminal conductance with
current-voltage characteristics and temperature dependence typical of Luttinger
liquid constrictions.",1010.1353v2
2011-09-20,Leakage-current lineshapes from inelastic cotunneling in the Pauli spin blockade regime,"We find the leakage current through a double quantum dot in the Pauli spin
blockade regime accounting for inelastic (spin-flip) cotunneling processes.
Taking the energy-dependence of this spin-flip mechanism into account allows
for an accurate description of the current as a function of applied magnetic
fields, gate voltages, and an inter-dot tunnel coupling. In the presence of an
additional local dephasing process or nonuniform magnetic field, we obtain a
simple closed-form analytical expression for the leakage current giving the
full dependence on an applied magnetic field and energy detuning. This work is
important for understanding the nature of leakage, especially in systems where
other spin-flip mechanisms (due, e.g., to hyperfine coupling to nuclear spins
or spin-orbit coupling) are weak, including silicon and carbon-nanotube or
graphene quantum dots.",1109.4445v2
2011-12-19,Nonequilibrium Spin Magnetization Quantum Transport Equations: Spin and Charge Coupling,"The classical Bloch equations of spin magnetization transport is extended to
fully time-dependent and highly-nonlinear nonequilibrium spin magnetization
quantum distribution function transport (SMQDFT) equations. The relevant
variables are the spinor correlation functions which separate into charge and
spin magnetization distributions that becomes highly coupled in SMQDFT equa-
tions. The leading terms consist of the Boltzmann kinetic equation with
spin-orbit coupling in a magnetic eld together with spin-dependent scattering
terms which contribute to the torque. These do not have analogue within the
classical relaxation-dephasing picture, but are inherently quantum many-body
effects. These should incorporate the spatiotemporal-dependent phase-space
dynam- ics of Elliot-Yafet and Dyakonov-Perel scatterings. The resulting SMQDFT
equations should serve as a theoretical foundation for computational spintronic
and nanomagnetic device applications, in ultrafast-switching-speed/low-power
performance and reliability analyses.",1112.4220v2
2014-03-11,Generation and Electric Control of Spin-Coupled Valley Current in WSe2,"The valley degree of freedom in layered transition-metal dichalcogenides
(MX2) provides the opportunity to extend functionalities of novel spintronics
and valleytronics devices. Due to spin splitting induced by spin-orbital
coupling (SOC), the non-equilibrium charge carrier imbalance between two
degenerate and inequivalent valleys to realize valley/spin polarization has
been successfully demonstrated theoretically and supported by optical
experiments. However, the generation of a valley/spin current by the valley
polarization in MX2 remains elusive and a great challenge. Here, within an
electric-double-layer transistor based on WSe2, we demonstrated a spin-coupled
valley photocurrent whose direction and magnitude depend on the degree of
circular polarization of the incident radiation and can be further greatly
modulated with an external electric field. Such room temperature generation and
electric control of valley/spin photocurrent provides a new property of
electrons in MX2 systems, thereby enabling new degrees of control for
quantum-confined spintronics devices.",1403.2696v1
2024-02-01,Spin wave-driven variable-phase mutual synchronization in spin Hall nano-oscillators,"Spin-orbit torque can drive auto-oscillations of propagating spin wave (PSW)
modes in nano-constriction spin Hall nano-oscillators (SHNOs). These modes
allow both long-range coupling and the potential of controlling its phase --
critical aspect for nano-magnonics, spin wave logic, and Ising machines. Here,
we demonstrate PSW-driven variable-phase coupling between two nano-constriction
SHNOs and study how their separation and the PSW wave vector impact their
mutual synchronization. In addition to ordinary in-phase mutual
synchronization, we observe, using both electrical measurements and
phase-resolved $\mu-$Brillouin Light Scattering microscopy, mutual
synchronization with a phase that can be tuned from 0 to $\pi$ using the drive
current or the applied field. Micromagnetic simulations corroborate the
experiments and visualize how the PSW patterns in the bridge connecting the two
nano-constrictions govern the coupling. These results advance the capabilities
of mutually synchronized SHNOs and open up new possibilities for applications
in spin wave logic, unconventional computing, and Ising Machines.",2402.00586v1
2016-11-17,Dynamic localization in optical and Zeeman lattices in the presence of spin-orbit coupling,"The dynamic localization of a two-level atom in a periodic potential under
the action of spin-orbit coupling and a weak harmonically-varying linear force
is studied. We consider optical and Zeeman potentials that are either in-phase
or out-of-phase in two spinor components, respectively. The expectation value
for the position of the atom after one oscillation period of the linear force
is recovered in authentic resonances or in pseudo-resonances. The frequencies
of the linear force corresponding to authentic resonances are determined by the
band structure of the periodic potential and are affected by the spin-orbit
coupling. The width/dispersion of the wavepacket in authentic resonances is
usually minimal. The frequencies corresponding to pseudo-resonances do not
depend on the type of potential and on the strength of the spin-orbit coupling,
while the evolution of excitations at the corresponding frequencies is usually
accompanied by significant dispersion. Pseudo-resonances are determined by the
initial phase of the linear force and by the quasi-momentum of the wavepacket.
Due to the spinor nature of the system, the motion of the atom is accompanied
by periodic, but not harmonic, spin oscillations. Under the action of
spin-orbit coupling the oscillations of the wavepacket can be nearly completely
suppressed in optical lattices. Dynamic localization in Zeeman lattices is
characterized by doubling of the resonant oscillation periods due to band
crossing at the boundary of the Brillouin zone. We also show that higher
harmonics in the Fourier expansion of the energy band lead to effective
dispersion, which can be strong enough to prevent dynamic localization of the
Bloch wavepacket.",1611.05745v1
2015-12-07,Recent progress on correlated electron systems with strong spin-orbit coupling,"Emergence of novel quantum ground states in correlated electron systems with
strong spin-orbit coupling has been a recent subject of intensive studies.
While it has been realized that spin-orbit coupling can provide non-trivial
band topology in weakly interacting electron systems, as in topological
insulators and semi-metals, the role of electron-electron interaction in
strongly spin-orbit coupled systems has not been fully understood. The
availability of new materials with significant electron correlation and strong
spin-orbit coupling now makes such investigations possible. Many of these
materials contain 5d or 4d transition metal elements; the prominent examples
are iridium oxides or iridates. In this review, we succinctly discuss recent
theoretical and experimental progress on this subject. After providing a brief
overview, we focus on pyrochlore iridates and three-dimensional honeycomb
iridates. In pyrochlore iridates, we discuss the quantum criticality of the
bulk and surface states, and the relevance of the surface/boundary states in a
number of topological and magnetic ground states, both in the bulk and thin
film configurations. Experimental signatures of these boundary and bulk states
are discussed. Domain wall formation and strongly-direction-dependent
magneto-transport are also discussed. Regarding the three-dimensional honeycomb
iridates, we consider possible quantum spin liquid phases and unusual magnetic
orders in theoretical models with strongly bond-dependent interactions. These
theoretical ideas and results are discussed in light of recent resonant X-ray
scattering experiments on three-dimensional honeycomb iridates. We also
contrast these results with the situation in two-dimensional honeycomb
iridates. We conclude with the outlook on other related systems.",1512.02224v1
2019-04-03,Possible superconductivity induced by a large spin-orbit coupling in carrier doped iridium oxide insulators: A weak coupling approach,"We study possible superconductivity in a carrier-doped iridium oxide
insulator Sr$_{2}$IrO$_{4}$ based on an effective $t_{2g}$ three-orbital
Hubbard model on the square lattice with a large spin-orbit coupling (SOC).
Numerically solving the linearized Eliashberg equation for the superconducting
(SC) gap function with the random phase approximation, we systematically
examine both singlet and triplet SC gap functions with possible pairing
symmetries and the parameter dependence of the superconductivity. For the
realistic SOC $\lambda$ and Hund's coupling $J/U$ relevant to
Sr$_{2}$IrO$_{4}$, namely, for a large $\lambda$ and small $J/U$ region, we
find that the intra-band antiferromagnetic (AF) pseudospin $\bm{j}_{\text{eff}}
= -\bm{l}+\bm{s}$ fluctuations favor a $d_{x^{2}-y^{2}}$-wave pseudospin
$j_{\text{eff}}=1/2$ singlet pairing in the electron-doping. We also find that
the $d_{x^{2}-y^{2}}$-wave pairing is more stabilized with increasing the SOC
and decreasing the Hund's coupling. Furthermore, we show for a small $\lambda$
and large $J/U$ region that an $s_{\pm}$-wave singlet pairing is favored in the
hole-doped region. The origin of the $s_{\pm}$-wave pairing is due to the
inter-band pair scattering arising from the intra-orbital AF spin $\bm s$
fluctuations. Although the possibility of a pseudospin triplet pairing is
considered, we find it always unfavorable for all parameters studied here. The
experimental consequences for other strongly correlated materials with a large
SOC are also discussed.",1904.01812v1
2003-01-20,A proposal of an orbital-dependent correlation energy functional for energy-band calculations,"An explicitly orbital-dependent correlation energy functional is proposed,
which is to be used in combination with the orbital-dependent exchange energy
functional in energy-band calculations. It bears a close resemblance to the
second-order direct and exchange perturbation terms calculated with Kohn-Sham
orbitals and Kohn-Sham energies except that one of the two Coulomb interactions
entering each term is replaced by an effective interaction which contains
information about long-, intermediate-, and short-range correlations beyond
second-order perturbation theory. Such an effective interaction can rigorously
be defined for the correlation energy of the uniform electron liquid and is
evaluated with high accuracy in order to apply to the orbital-dependent
correlation energy functional. The coupling-constant-averaged spin-parallel and
spin-antiparallel pair correlation functions are also evaluated with high
accuracy for the electron liquid. The present orbital-dependent correlation
energy functional with the effective interaction borrowed from the electron
liquid is valid for tightly-binding electrons as well as for nearly-free
electrons in marked contrast with the conventional local density approximation.",0301344v2
2012-07-12,Linear Magnetoelectric Effect by Orbital Magnetism,"We use symmetry analysis and first principles calculations to show that the
linear magnetoelectric effect can originate from the response of orbital
magnetic moments to the polar distortions induced by an applied electric field.
Using LiFePO4 as a model compound we show that spin-orbit coupling partially
lifts the quenching of the 3d orbitals and causes small orbital magnetic
moments ($\mu_{(L)}\approx 0.3 \mu_B$) parallel to the spins of the Fe$^{2+}$
ions. An applied electric field $\mathbf{E}$ modifies the size of these orbital
magnetic moments inducing a net magnetization linear in $\mathbf{E}$.",1207.2916v2
2004-08-23,Orbital-controlled magnetic transition between gapful and gapless phases in the Haldane system with t2g-orbital degeneracy,"In order to clarify a key role of orbital degree of freedom in the spin S=1
Haldane system, we investigate ground-state properties of the t2g-orbital
degenerate Hubbard model on the linear chain by using numerical techniques.
Increasing the Hund's rule coupling in multi-orbital systems, in general, there
occurs a transition from an antiferromagnetic to a ferromagnetic phase. We find
that the antiferromagnetic phase is described as the Haldane system with spin
gap, while in the ferromagnetic phase, there exists the gapless excitation with
respect to orbital degree of freedom. Possible relevance of the present results
to actual systems is also discussed.",0408479v1
2012-03-23,Complete phase diagram for three-band Hubbard model with orbital degeneracy lifted by crystal field splitting,"Motivated by the unexplored complexity of the phase diagrams for
multi-orbital Hubbard models, a three-band Hubbard model at integer fillings
(N=4) with orbital degeneracy lifted partially by crystal field splitting is
analyzed systematically in this work. By using single site dynamical mean-field
theory and rotationally invariant Gutzwiller approximation, we have computed
the full phase diagram with Coulomb interaction strength $U$ and crystal field
splitting $\Delta$. We find a large region in the phase diagram, where an
orbital selective Mott phase will be stabilized by the positive crystal field
lifting the orbital degeneracy. Further analysis indicates that the Hund's rule
coupling is essential for the orbital selective Mott phase and the transition
toward this phase is accompanied by a high-spin to low-spin transition. Such a
model may be relevant for the recently discovered pnictides and ruthenates
correlated materials.",1203.5159v1
2023-06-02,Zeeman and Orbital Driven Phase Transitions in Planar Josephson Junctions,"We perform supercurrent and tunneling spectroscopy measurements on
gate-tunable InAs/Al Josephson junctions (JJs) in an in-plane magnetic field,
and report on phase shifts in the current-phase relation measured with respect
to an absolute phase reference. The impact of orbital effects is investigated
by studying multiple devices with different superconducting lead sizes. At low
fields, we observe gate-dependent phase shifts of up to ${\varphi_{0}=0.5\pi}$
which are consistent with a Zeeman field coupling to highly-transmissive
Andreev bound states via Rashba spin-orbit interaction. A distinct phase shift
emerges at larger fields, concomitant with a switching current minimum and the
closing and reopening of the superconducting gap. These signatures of an
induced phase transition, which might resemble a topological transition, scale
with the superconducting lead size, demonstrating the crucial role of orbital
effects. Our results elucidate the interplay of Zeeman, spin-orbit and orbital
effects in InAs/Al JJs, giving new understanding to phase transitions in hybrid
JJs and their applications in quantum computing and superconducting
electronics.",2306.01514v2
2013-08-24,Spin Dynamics in Graphene and Graphene like Nanocarbon Doped with Nitrogen the ESR Analysis,"Nano engineered spin degree of freedom in carbon system may offer desired
exchange coupling with optimum spin orbit interaction which is essential, to
construct solid state qubits, for fault tolerant quantum computation. The
purpose of this communication is to analyze spin dynamics of, basically, four
types of systems, (i) Graphene (system with inversion symmetry), (ii) Graphene
like nanocarbons (GNCs, broken inversion symmetry and heterostructure, sp2 and
sp3, environment), and (iii) their nitrogen doped derivatives. The spin
transport data was obtained using the electron spin resonance spectroscopy
(ESR) technique, carried out over 123 to 473K temperature range. Analysis of
shape, linewidths of dispersion derivatives,, and g factor anisotropy has been
carried out. Spin parameters such as, spin spin relaxation time, spin lattice
relaxation time, spin flip parameter,spin relaxation rate,spin, momentum
relaxation rate,pseudo chemical potential, density of states, effective
magnetic moment, spin concentration, defect concentration, and Pauli
susceptibility, has been estimated, and examined for their temperature as well
as interdependence. Details of the analysis are presented. The quantitative
study underlined the following facts: (i) by and large, spin dynamics in
Graphene and GNCs is significantly different, (ii) transport of spin behaves in
opposite fashion, after doping nitrogen, in both the systems, (iii) reduction
in the magnetization has been observed for both GNCs and Graphene, after doping
nitrogen, (iv) hyperfine interactions have been observed in all classes of
systems except in GNCs, (v) nitrogen doped GNCs seems to be appropriate for
qubit designing.",1308.5291v1
2023-07-30,"Ab-initio predictions of spin relaxation, dephasing and diffusion in solids","Spin relaxation, dephasing and diffusion are at the heart of spin-based
information technology. Accurate theoretical approaches to simulate spin
lifetimes ($\tau_s$), determining how fast the spin polarization and phase
information will be lost, are important to the understandings of underlying
mechanism of these spin processes, and invaluable to search for promising
candidates of spintronic materials. Recently, we develop a first-principles
real-time density-matrix (FPDM) approach to simulate spin dynamics for general
solid-state systems. Through the complete first-principles' descriptions of
light-matter interaction and scattering processes including electron-phonon,
electronimpurity and electron-electron scatterings with self-consistent
spin-orbit coupling, as well as ab initio Land'e g-factor, our method can
predict $\tau_s$ at various conditions as a function of carrier density and
temperature, under electric and magnetic fields. By employing this method, we
successfully reproduce experimental results of disparate materials and identify
the key factors affecting spin relaxation, dephasing, and diffusion in
different materials. Specifically, we predict that germanene has long $\tau_s$
(~100 ns at 50 K), a giant spin lifetime anisotropy and spin-valley locking
effect under electric fields, making it advantageous for spin-valleytronic
applications. Based on our theoretical derivations and ab initio simulations,
we propose a new useful electronic quantity, named spin-flip angle
$\theta^{\uparrow\downarrow}$, for the understanding of spin relaxation through
intervalley spin-flip scattering processes. Our method can be further applied
to other emerging materials and extended to simulate exciton spin dynamics and
steady-state photocurrents due to photogalvanic effect.",2307.16311v1
2008-12-08,Spin diffusion in Si/SiGe quantum wells: spin relaxation in the absence of D'yakonov-Perel' relaxation mechanism,"In this work, the spin relaxation accompanying the spin diffusion in
symmetric Si/SiGe quantum wells without the D'yakonov-Perel' spin-relaxation
mechanism is calculated from a fully microscopic approach. The spin relaxation
is caused by the inhomogeneous broadening from the momentum-dependent spin
precessions in spatial domain under a magnetic field in the Voigt
configuration. In fact, this inhomogeneous broadening together with the
scattering lead to an irreversible spin relaxation along the spin diffusion.
The effects of scattering, magnetic field and electron density on spin
diffusion are investigated. Unlike the case of spin diffusion in the system
with the D'yakonov-Perel' spin-orbit coupling such as GaAs quantum wells where
the scattering can either enhance or reduce spin diffusion depending on whether
the system is in strong or weak scattering limit, the scattering in the present
system has no counter-effect on the inhomogeneous broadening and suppresses the
spin diffusion monotonically. The increase of magnetic field reduces the spin
diffusion, while the increase of electron density enhances the spin diffusion
when the electrons are degenerate but has marginal effect when the electrons
are nondegenerate.",0812.1477v2
2011-07-06,Addressing the spin question in gravitational-wave searches: Waveform templates for inspiralling compact binaries with nonprecessing spins,"This paper presents a post-Newtonian (PN) template family of gravitational
waveforms from inspiralling compact binaries with non-precessing spins, where
the spin effects are described by a single ""reduced-spin"" parameter. This
template family, which reparametrizes all the spin-dependent PN terms in terms
of the leading-order (1.5PN) spin-orbit coupling term \emph{in an approximate
way}, has very high overlaps (fitting factor > 0.99) with non-precessing
binaries with arbitrary mass ratios and spins. We also show that this template
family is ""effectual"" for the detection of a significant fraction of generic
spinning binaries in the comparable-mass regime (m_2/m_1 <~ 10), providing an
attractive and feasible way of searching for gravitational waves (GWs) from
spinning low-mass binaries. We also show that the secular (non-oscillatory)
spin-dependent effects in the phase evolution (which are taken into account by
the non-precessing templates) are more important than the oscillatory effects
of precession in the comparable-mass (m_1 ~= m_2) regime. Hence the
effectualness of non-spinning templates is particularly poor in this case, as
compared to non-precessing-spin templates. For the case of binary neutron stars
observable by Advanced LIGO, even moderate spins (L . S/m^2 ~= 0.015 - 0.1)
will cause considerable mismatches (~ 3% - 25%) with non-spinning templates.
This is contrary to the expectation that neutron-star spins may not be relevant
for GW detection.",1107.1267v2
2014-11-12,Spin Hall effect,"Spin Hall effects are a collection of relativistic spin-orbit coupling
phenomena in which electrical currents can generate transverse spin currents
and vice versa. Although first observed only a decade ago, these effects are
already ubiquitous within spintronics as standard spin-current generators and
detectors. Here we review the experimental and theoretical results that have
established this sub-field of spintronics. We focus on the results that have
converged to give us a clear understanding of the phenomena and how they have
evolved from a qualitative to a more quantitative measurement of spin-currents
and their associated spin-accumulation. Within the experimental framework, we
review optical, transport, and magnetization-dynamics based measurements and
link them to both phenomenological and microscopic theories of the effect.
Within the theoretical framework, we review the basic mechanisms in both the
extrinsic and intrinsic regime which are linked to the mechanisms present in
their closely related phenomenon in ferromagnets, the anomalous Hall effect. We
also review the connection to the phenomenological treatment based on
spin-diffusion equations applicable to certain regimes, as well as the
spin-pumping theory of spin-generation which has proven important in the
measurements of the spin Hall angle. We further connect the spin-current
generating spin Hall effect to the inverse spin galvanic effect, which often
accompanies the SHE, in which an electrical current induces a non-equilibrium
spin polarization. These effects share common microscopic origins and can
exhibit similar symmetries when present in ferromagnetic/non-magnetic
structures through their induced current-driven spin torques. Although we give
a short chronological overview, the main body is structured from a pedagogical
point of view, focusing on well-established and accepted physics.",1411.3249v1
2016-07-22,The Spin Nernst effect in Tungsten,"The spin Hall effect allows generation of spin current when charge current is
passed along materials with large spin orbit coupling. It has been recently
predicted that heat current in a non-magnetic metal can be converted into spin
current via a process referred to as the spin Nernst effect. Here we report the
observation of the spin Nernst effect in W. In W/CoFeB/MgO heterostructures, we
find changes in the longitudinal and transverse voltages with magnetic field
when temperature gradient is applied across the film. The field-dependence of
the voltage resembles that of the spin Hall magnetoresistance. A comparison of
the temperature gradient induced voltage and the spin Hall magnetoresistance
allows direct estimation of the spin Nernst angle. We find the spin Nernst
angle of W to be similar in magnitude but opposite in sign with its spin Hall
angle. Interestingly, under an open circuit condition, such sign difference
results in spin current generation larger than otherwise. These results
highlight the distinct characteristics of the spin Nernst and spin Hall
effects, providing pathways to explore materials with unique band structures
that may generate large spin current with high efficiency.",1607.06594v2
2019-03-03,Non-Kitaev spin liquids in Kitaev materials,"We point out that the Kitaev materials may not necessarily support Kitaev
spin liquid. It is well-known that having a Kitaev term in the spin interaction
is not the sufficient condition for the Kitaev spin liquid ground state. Many
other spin liquids may be stabilized by the competing spin interactions of the
systems. We thus explore the possibilities of non-Kitaev spin liquids in the
honeycomb Kitaev materials. We carry out a systematic classification of gapped
$\mathbb{Z}_2$ spin liquids using the Schwinger boson representation for the
spin variables. The presence of strong spin-orbit coupling in the Kitaev
materials brings new ingredients into the projective symmetry group
classification of the non-Kitaev spin liquid. We predict the spectroscopic
properties of these gapped non-Kitaev spin liquids. Moreover, among the gapped
spin liquids that we discover, we identify the spin liquid whose spinon
condensation leads to the magnetic Bragg peak structure of the zig-zag magnetic
order that was observed in Na$_2$IrO$_3$ and $\alpha$-RuCl$_3$. We further
discuss the possibility of gapped $\mathbb{Z}_2$ spin liquid and the deconfined
quantum criticality from the zig-zag magnetic order to spin dimerization in
pressurized $\alpha$-RuCl$_3$.",1903.00895v2
2018-02-12,Influence of multiplet structure on photoemission spectra of spin-orbit driven Mott insulators: application to $\bf{Sr_2IrO_4}$,"Most of the low-energy effective descriptions of spin-orbit driven Mott
insulators consider spin orbit coupling (SOC) as a second order perturbation to
electron-electron interactions. However, when SOC is comparable to anisotropic
Hund's coupling, such as in Ir, validity of this formally weak-SOC approach is
not a priori known. Depending on the relative strength of SOC and anisotropic
Hund's coupling, different descriptions of the multiplet structure should be
employed in the weak and strong SOC limits, \textit{viz.} \textit{LS} and
\textit{jj} coupling schemes, respectively. We investigate the implications of
both the coupling schemes on the low-energy effective $t-J$ model and calculate
the angle resolved photoemission (ARPES) spectra using self-consistent Born
approximation. In particular, we obtain the ARPES spectra of
quasi-two-dimensional square-lattice iridate ${\rm Sr_2IrO_4}$ in both weak and
strong SOC limits. The differences in the limiting cases are understood in
terms of the composition and relative energy splittings of the multiplet
structure. Our results indicate that the LS coupling scheme yields better
agreement with the experiment, thus providing an indirect evidence for the
validity of LS coupling scheme for iridates. We also discuss the implications
for other metal ions with strong SOC.",1802.04158v3
2020-02-12,Interplay between spin-orbit coupling and van Hove singularity in the Hund's metallicity of Sr$_2$RuO$_4$,"We investigate the dynamical properties of Sr$_2$RuO$_4$ at zero and very low
temperature using density functional theory plus dynamical mean-field theory
with an exact diagonalization solver. By considering rotationally invariant
local interaction, we examine how Hund's coupling and spin-orbit coupling
affect the correlated nature of the system. In the absence of Hund's coupling,
the system shows a Fermi liquid behavior over the entire range of temperatures
we consider. We confirm that the Fermi liquid persists at zero temperature even
with nonzero Hund's coupling; however, at sufficient temperatures Hund's
coupling significantly reduces the Fermi liquid regime and the system evolves
into a typical Hund's metal. At the bare electronic occupancy of Sr$_2$RuO$_4$
($t_{2g}^4$), a stronger Hund's metallicity accompanies a larger long-time
correlator. Remarkably, electron doping further destabilizes the Fermi liquid
even though the long-time correlator and magnetic fluctuations decrease upon
doping. This suppression of the Fermi liquid is driven by the van Hove
singularity above the Fermi level in Sr$_2$RuO$_4$, combined with an enhanced
Van Vleck susceptibility by spin-orbit coupling. Such findings point to the
important role that electronic structure plays in the behavior of Hund's
metals, in addition to magnetic fluctuations.",2002.04825v2
2012-02-28,Anisotropic intrinsic spin relaxation in graphene due to flexural distortions,"We propose an intrinsic spin scattering mechanism in graphene originated by
the interplay of atomic spin-orbit interaction and the local curvature induced
by flexural distortions of the atomic lattice. Starting from a multiorbital
tight-binding Hamiltonian with spin-orbit coupling considered
non-perturbatively, we derive an effective Hamiltonian for the spin scattering
of the Dirac electrons due to flexural distortions. We compute the spin
lifetime due to both flexural phonons and ripples and we find values in the
microsecond range at room temperature. Interestingly, this mechanism is
anisotropic on two counts. First, the relaxation rate is different for
off-plane and in-plane spin quantization axis. Second, the spin relaxation rate
depends on the angle formed by the crystal momentum with the carbon-carbon
bond. In addition, the spin lifetime is also valley dependent. The proposed
mechanism sets an upper limit for spin lifetimes in graphene and will be
relevant when samples of high quality can be fabricated free of extrinsic
sources of spin relaxation.",1202.6216v2
2014-06-24,Real-time dynamics of spin-dependent transport through a double-quantum-dot Aharonov-Bohm interferometer with spin-orbit interaction,"The spin-resolved non-equilibrium real-time electron transport through a
double-quantum-dot (DQD) Aharonov-Bohm (AB) interferometer with spin-orbit
interaction (SOI) is explored. The SOI and AB interference in the real-time
dynamics of spin transport is expressed by effective magnetic fluxes.
Analytical formulae for the time-dependent currents, for initially unpolarized
spins, are presented. In many cases, there appear spin currents in the
electrodes, for which the spins in each electrode are polarized along
characteristic directions, pre-determined by the SOI parameters and by the
geometry of the system. Special choices of the system parameters yield
steady-state currents in which the spins are fully polarized along these
characteristic directions. The time required to reach this steady state depends
on the couplings of the DQD to the leads. The magnitudes of the currents depend
strongly on the SOI-induced effective fluxes. Without the magnetic flux, the
spin-polarized current cannot be sustained to the steady states, due to the
phase rigidity for this system. For a non-degenerate DQD, transient spin
transport can be produced by the sole effects of SOI. We also show that one can
extract the spin-resolved currents from measurements of the total charge
current.",1406.6258v2
2017-06-22,Observation of anomalous spin-torque generated by a ferromagnet,"In this work we report observation of in-plane current induced out-of-plane
magnetic field driven torque in spin valve structure. Since ferromagnet has
high spin orbit coupling it is expected to be the source of spin-orbit-torque
as it possesses anomalous-Hall-effect (AHE: equivalent to spin Hall effect in
heavy metal). So we have carried out spin-torque ferromagnetic resonance
(ST-FMR) experiment in a spin valve (consists of a fixed magnet and a free
magnet which are separated by Cu spacer), passing in-plane radio frequency
current and measuring DC voltage. Our experimental results eventually indicate
that spin torque exerted on the free magnet is not caused due to the spin
current injection by the fixed magnet owing to its AHE, but it is originated
from in-plane current driven out-of plane effective magnetic field. This is new
class of spin torque which is completely different from Slonczewski-spin
transfer torque and Rashba like field like torque. The effective out-of plane
magnetic field depends on the direction of current (in-plane) and magnetization
(in-plane) of the pinned layer. One possible mechanism behind this
unconventional torque could be intefacial spin-scattering which is also origin
of current in-plane GMR effect. Most importantly this effective out-of plane
torque can be useful to switch out-of plane magnetic bits in spintronic memory
application.",1706.07245v1
2022-08-26,Anisotropic linear and nonlinear charge-spin conversion in topological semimetal SrIrO3,"Over the past decade, utilizing spin currents in the linear response of
electric field to manipulate magnetization states via spin-orbit torques (SOTs)
is one of the core concepts for realizing a multitude of spintronic devices.
Besides the linear regime, recently, nonlinear charge-spin conversion under the
square of electric field has been recognized in a wide variety of materials
with nontrivial spin textures, opening an emerging field of nonlinear
spintronics. Here, we report the investigation of both linear and nonlinear
charge-spin conversion in one single topological semimetal SrIrO3(110) thin
film that hosts strong spin-orbit coupling and nontrivial spin textures in the
momentum space. In the nonlinear regime, the observation of crystalline
direction dependent response indicates the presence of anisotropic surface
states induced spin-momentum locking near the Fermi level. Such anisotropic
spin textures also give rise to spin currents in the linear response regime,
which mainly contributes to the fieldlike SOT component. Our work demonstrates
the power of combination of linear and nonlinear approaches in understanding
and utilizing charge-spin conversion in topological materials.",2208.12499v1
2023-09-01,Breakdown of the drift-diffusion model for transverse spin transport in a disordered Pt film,"Spin accumulation and spin current profiles are calculated for a disordered
Pt film subjected to an in-plane electric current within the nonequilibrium
Green function approach. In the bulklike region of the sample, this approach
captures the intrinsic spin Hall effect found in other calculations. Near the
surfaces, the results reveal qualitative differences with the results of the
widely used spin-diffusion model, even when the boundary conditions are
modified to try to account for them. One difference is that the effective
spin-diffusion length for transverse spin transport is significantly different
from its longitudinal counterpart and is instead similar to the mean-free path.
This feature may be generic for spin currents generated via the intrinsic
spin-Hall mechanism because of the differences in transport mechanisms compared
to longitudinal spin transport. Orbital accumulation in the Pt film is only
significant in the immediate vicinity of the surfaces and has a small component
penetrating into the bulk only in the presence of spin-orbit coupling, as a
secondary effect induced by the spin accumulation.",2309.00183v2
2023-10-05,Spin-orbit torques and spin Hall magnetoresistance generated by twin-free and amorphous Bi0.9Sb0.1 topological insulator films,"Topological insulators have attracted great interest as generators of
spin-orbit torques (SOTs) in spintronic devices.
Bi\textsubscript{1-x}Sb\textsubscript{x} is a prominent topological insulator
that has a high charge-to-spin conversion efficiency. However, the origin and
magnitude of the SOTs induced by current-injection in
Bi\textsubscript{1-x}Sb\textsubscript{x} remain controversial. Here we report
the investigation of the SOTs and spin Hall magnetoresistance resulting from
charge-to-spin conversion in twin-free epitaxial layers of
Bi\textsubscript{0.9}Sb\textsubscript{0.1}(0001) coupled to FeCo, and compare
it with that of amorphous Bi\textsubscript{0.9}Sb\textsubscript{0.1}. We find a
large charge-to-spin conversion efficiency of 1 in the first case and less than
0.1 in the second, confirming crystalline
Bi\textsubscript{0.9}Sb\textsubscript{0.1} as a strong spin injector material.
The SOTs and spin Hall magnetoresistance are independent of the direction of
the electric current, indicating that charge-to-spin conversion in
single-crystal Bi\textsubscript{0.9}Sb\textsubscript{0.1}(0001) is isotropic
despite the strong anisotropy of the topological surface states. Further, we
find that the damping-like SOT has a non-monotonic temperature dependence with
a minimum at 20~K. By correlating the SOT with resistivity and weak
antilocalization measurements, we conclude that charge-spin conversion occurs
via thermally-excited holes from the bulk states above 20~K, and conduction
through the isotropic surface states with increasing spin polarization due to
decreasing electron-electron scattering below 20~K.",2310.03487v1
2016-03-31,Dynamical spin properties of confined Fermi and Bose systems in presence of spin-orbit coupling,"Due to the recent experimental progress, tunable spin-orbit (SO) interactions
represent ideal candidates for the control of polarization and dynamical spin
properties in both quantum wells and cold atomic systems. A detailed
understanding of spin properties in SO coupled systems is thus a compelling
prerequisite for possible novel applications or improvements in the context of
spintronics and quantum computers. Here we analyze the case of equal Rashba and
Dresselhaus couplings in both homogeneous and laterally confined
two-dimensional systems. Starting from the single-particle picture and
subsequently introducing two-body interactions we observe that periodic spin
fluctuations can be induced and maintained in the system. Through an analytical
derivation we show that the two-body interaction does not involve decoherence
effects in the bosonic dimer, and, in the repulsive homogeneous Fermi gas it
may be even exploited in combination with the SO coupling to induce and tune
standing currents. By further studying the effects of a harmonic lateral
confinement --a particularly interesting case for Bose condensates-- we
evidence the possible appearance of non-trivial {\it spin textures}, whereas
the further application of a small Zeeman-type interaction can be exploited to
fine-tune the system polarizability.",1603.09604v1
2023-11-19,Spin-orbit coupling in a half-filled $t_{2g}$ shell: the case of $5d^3$ K$_2$ReCl$_6$,"The half-filled $t_{2g}$ shell of the $t_{2g}^3$ configuration usually, in LS
coupling, hosts a S = 3/2 ground state with quenched orbital moment. This state
is not Jahn-Teller active. Sufficiently large spin-orbit coupling $\zeta$ has
been predicted to change this picture by mixing in orbital moment, giving rise
to a sizable Jahn-Teller distortion. In $5d^3$ K$_2$ReCl$_6$ we study the
electronic excitations using resonant inelastic x-ray scattering (RIXS) and
optical spectroscopy. We observe on-site intra-$t_{2g}$ excitations below 2 eV
and corresponding overtones with two intra-$t_{2g}$ excitations on adjacent
sites, the Mott gap at 2.7 eV, $t_{2g}$-to-$e_g$ excitations above 3 eV, and
charge-transfer excitations at still higher energy. The intra-$t_{2g}$
excitation energies are a sensitive measure of $\zeta$ and Hund's coupling
$J_H$. The sizable value of $\zeta \approx$ 0.29 eV places K$_2$ReCl$_6$ into
the intermediate coupling regime, but $\zeta/J_H \approx 0.6$ is not
sufficiently large to drive a pronounced Jahn-Teller effect. We discuss the
ground state wavefunction in a Kanamori picture and find that the S = 3/2
multiplet still carries about 97 % of the weight. However, the finite admixture
of orbital moment allows for subtle effects. We discuss small
temperature-induced changes of the optical data and find evidence for a
lowering of the ground state by about 3 meV below the structural phase
transitions.",2311.11419v1
2015-07-28,Observation of intervalley quantum interference in epitaxial monolayer WSe2,"Monolayer (ML) transition metal dichalcogenides (TMDs) have been attracting
great research attentions lately for their extraordinary properties, in
particular the exotic spin-valley coupled electronic structures that promise
future spintronic and valleytronic applications1-3. The energy bands of ML TMDs
have well separated valleys that constitute effectively an extra internal
degree of freedom for low energy carriers3-12. The large spin-orbit coupling in
the TMDs makes the spin index locked to the valley index, which has some
interesting consequences such as the magnetoelectric effects in 2H bilayers13.
A direct experimental characterization of the spin-valley coupled electronic
structure can be of great interests for both fundamental physics and device
applications. In this work, we report the first experimental observation of the
quasi-particle interference (QPI) patterns in ML WSe2 using low-temperature
(LT) scanning tunneling microscopy/spectroscopy (STM/S). We observe intervalley
quantum interference involving the Q-valleys in the conduction band due to
spin-conserved scattering processes, while spin-flip intervalley scattering is
absent. This experiment establishes unequivocally the presence of spin-valley
coupling and affirms the large spin-splitting at the Q valleys. Importantly,
the inefficient spin-flip intervalley scattering implies long valley and spin
lifetime in ML WSe2, which represents a key figure of merit for
valley-spintronic applications.",1507.07637v1
2021-08-11,Charge density waves in multiple-$Q$ spin states,"Coupling between spin and charge degrees of freedom in electrons is a source
of various electronic and magnetic properties of solids. We theoretically study
charge density waves induced by the spin-charge coupling in the presence of
magnetic orderings in itinerant magnets. By performing a perturbative
calculation in the weak-coupling limit of the Kondo lattice model, we derive a
useful formula for the relationship between charge and spin density waves,
which can be applied to any magnetic orderings, including noncollinear and
noncoplanar ones composed of multiple spin density waves called multiple-$Q$
magnetic orderings. We demonstrate the predictive power for single-$Q$ and
double-$Q$ states including skyrmion and meron-antimeron crystals on a square
lattice, in comparison with the numerical calculations. Moreover, we show that
the charge density waves contain richer information than the spin density
waves, and are indeed useful in distinguishing the spin textures with similar
spin structure factors. We discuss the relation to bond modulation in terms of
the kinetic bond energy and the vector spin chirality. We also perform
numerical calculations beyond the perturbative regime and find that the charge
density waves can be enhanced when the electron filling is commensurate.
Furthermore, we investigate the effect of the spin-orbit coupling, which can
lead to additional charge density waves owing to effective anisotropic magnetic
interactions in momentum space. Our result will provide a way to identify
complex magnetic orderings and their origins from the charge modulations.",2108.04997v2
2022-11-18,Acceptor-based qubit in silicon with tunable strain,"Long coherence time and compatibility with semiconductor fabrication make
spin qubits in silicon an attractive platform for quantum computing. In recent
years, hole spin qubits are being developed as they have the advantages of weak
coupling to nuclear spin noise and strong spin-orbit coupling (SOC), in
constructing high-fidelity quantum gates. However, there are relatively few
studies on the hole spin qubits in a single acceptor, which requires only low
density of the metallic gates. In particular, the investigation of flexible
tunability using controllable strain for fault-tolerant quantum gates of
acceptor-based qubits is still lacking. Here, we study the tunability of
electric dipole spin resonance (EDSR) of acceptor-based hole spin qubits with
controllable strain. The flexible tunability of LH-HH splitting and spin-hole
coupling (SHC) with the two kinds of strain can avoid high electric field at
the ""sweet spot"", and the operation performance of the acceptor qubits could be
optimized. Longer relaxation time or stronger EDSR coupling at low electric
field can be obtained. Moreover, with asymmetric strain, two ""sweet spots"" are
induced and may merge together, and form a second-order ""sweet spot"". As a
result, the quality factor $Q$ can reach $10^{4}$ for single-qubit operation,
with high tolerance for the electric field variation. Furthermore, the
two-qubit operation of acceptor qubits based on dipole-dipole interaction is
discussed for high-fidelity two-qubit gates. The tunability of spin qubit
properties in acceptor via strain could provide promising routes for spin-based
quantum computing.",2211.10019v1
2019-08-25,Electric field manipulation enhanced by strong spin-orbit coupling: promoting rare-earth ions as qubits,"Quantum information processing based on magnetic ions are considered
potential candidates for applications because they can be modified and scaled
up by a variety of chemical methods. For these systems to achieve individual
spin addressability and high energy efficiency, we exploited the electric field
as a tool to manipulate their quantum behaviours, functioning via spin-orbit
coupling. A Ce:YAG single crystal was employed due to that rare-earth ions have
strong spin-orbit coupling and with considerations regarding the dynamics and
the symmetry requirements. The Stark effect of the Ce3+ ion was observed and
measured. When demonstrated as a quantum phase gate, the electric field
manipulation exhibited high efficiency which allowed up to 57 {\pi}/2
operations before decoherence with optimized field directions. It was also
utilized to carry out quantum bang-bang control, as a method of dynamic
decoupling, and the refined Deutsch-Jozsa algorithm. Our experiments
highlighted rare-earth ions as potentially applicable qubits since they offer
enhanced spin-electric coupling which enables high-efficiency quantum
manipulation.",1908.09274v2
2013-06-17,Energy spectra of three electrons in SiGe/Si/SiGe laterally coupled triple quantum dots,"We investigate the energy spectra of three electrons in SiGe/Si/SiGe
equilateral triangular and symmetric linear triple quantum dots in the presence
of magnetic (in either Faraday or Voigt configuration) and electric fields with
single valley approximation by using the real-space configuration interaction
method. The strong electron-electron Coulomb interaction, which is crucial to
the energy spectra, is explicitly calculated whereas the weak spin-orbit
coupling is treated perturbatively. In both equilateral triangular and
symmetric linear triple quantum dots, we find doublet-quartet transition of
ground-state spin configuration by varying dot size or interdot distance in the
absence of external fields. This transition has not been reported in the
literature on triple quantum dots. In the magnetic-field (Faraday
configuration) dependence of energy spectra, we find anticrossings with large
energy splittings between the energy levels with the same spin state in the
absence of the spin-orbit coupling. This anticrossing behavior originates from
the triple quantum dot confinement potential. In addition, with the inclusion
of the spin-orbit coupling, we find that all the intersections shown in the
equilateral triangular case become anticrossing whereas only part of the
intersections in symmetric linear case show anticrossing behavior in the
presence of magnetic field in either the Faraday or Voigt configuration. All
the anticrossing behaviors are analyzed based on symmetry consideration.
Moreover, we show that the electric field can effectively influence the energy
levels and the charge configurations.",1306.3719v1
2013-10-07,Tunable Landau-Zener transitions in a spin-orbit coupled Bose-Einstein condensate,"The Landau-Zener (LZ) transition is one of the most fundamental phenomena in
quantum dynamics. It describes nonadiabatic transitions between quantum states
near an avoided crossing that can occur in diverse physical systems. Here we
report experimental measurements and tuning of LZ transitions between the
dressed eigenlevels of a Bose-Einstein condensate (BEC) that is synthetically
spin-orbit (SO) coupled. We measure the transition probability as the BEC is
accelerated through the SO avoided crossing and study its dependence on the
coupling between the diabatic (bare) states, eigenlevel slope, and eigenstate
velocity--the three parameters of the LZ model that are independently
controlled in our experiments. Furthermore, we performed time-resolved
measurements to demonstrate the breaking down of the spin-momentum locking of
the spin-orbit-coupled BEC in the nonadiabatic regime, and we determined the
diabatic switching time of the LZ transitions. Our observations show
quantitative agreement with the LZ model and numerical simulations of the
quantum dynamics in the quasimomentum space. The tunable LZ transition may be
exploited to enable a spin-dependent atomtronic transistor.",1310.1818v2
2015-02-28,Symmetry protected skyrmions in 3D spin-orbit coupled Bose gases,"We present a variational study of pseudo-spin $1/2$ Bose gases in a harmonic
trap with weak 3D spin-orbit coupling of $\bmsigma\cdot\mathbf{p}$ type. This
spin-orbit coupling mixes states with different parities, which inspires us to
approximate the single particle state with the eigenstates of the total angular
momentum, i.e. superposition of harmonic $s$-wave and $p$-wave states. As the
time reversal symmetry is protected by two-body interaction, we set the
variational order parameter as the combination of two mutually time reversal
symmetric eigenstates of the total angular momentum. The variational results
essentially reproduce the 3D skyrmion-like ground state recently identified by
Kawakami {\it et al.}. We show that these skyrmion-like ground states emerging
in this model are primarily caused by $p$ wave spatial mode involving in the
variational order parameter that drives two spin components spatially
separated. We find the ground state of this system falls into two phases with
different density distribution symmetries depending on the relative magnitude
of intraspecies and interspecies interaction: Phase I has parity symmetric and
axisymmetric density distributions, while Phase II is featured with special
joint symmetries of discrete rotational and time reversal symmetry. With the
increasing interaction strength the transition occurs between two phases with
distinct density distributions, while the topological 3D skyrmion-like spin
texture is symmetry protected.",1503.00128v1
2016-01-16,Gauge Covariance and Spin Current Conservation in the Gauge Field Formulation of Systems with Spin-Orbit Coupling,"The question of gauge-covariance in the non-Abelian gauge-field formulation
of two space-dimensional systems with spin-orbit coupling relevant to
spintronics is investigated. Although, these are generally gauge-fixed models,
it is found that for the class of gauge fields that are space-time independent
and satisfy a U(1) algebra, thus having a vanishing field strength, there is a
residual gauge freedom in the Hamiltonian. The gauge transformations assume the
form of a space-dependent rotation of the transformed wave functions with
rotation angles and axes determined by the specific form of the gauge-field,
i.e., the spin-orbit coupling. The fields can be gauged away, reducing the
Hamiltonian to one which is isospectral to the free-particle Hamiltonian, and
giving rise to the phenomenon of persistent spin helix reported first by
B.~A.~Bernevig \emph{et al.} [Phys.~Rev.~Lett. \textbf{97}, 236601 (2006)]. The
investigation of the global gauge transformations leads to the derivation of a
continuity equation where the component of the spin-density along given
directions, again fixed by the specific form of the gauge field, is conserved.",1601.04158v1
2017-03-04,Vortex states and spin textures of rotating spin-orbit-coupled Bose-Einstein condensates in a toroidal trap,"We consider the ground-state properties of Rashba spin-orbit-coupled
pseudo-spin-1/2 Bose-Einstein condensates (BECs) in a rotating two-dimensional
(2D) toroidal trap. In the absence of spin-orbit coupling (SOC), the increasing
rotation frequency enhances the creation of giant vortices for the initially
miscible BECs, while it can lead to the formation of semiring density patterns
with irregular hidden vortex structures for the initially immiscible BECs.
Without rotation, strong 2D isotropic SOC yields a heliciform-stripe phase for
the initially immiscible BECs. Combined effects of rotation, SOC, and
interatomic interactions on the vortex structures and typical spin textures of
the ground state of the system are discussed systematically. In particular, for
fixed rotation frequency above the critical value, the increasing isotropic SOC
favors a visible vortex ring in each component which is accompanied by a hidden
giant vortex plus a (several) hidden vortex ring(s) in the central region. In
the case of 1D anisotropic SOC, large SOC strength results in the generation of
hidden linear vortex string and the transition from initial phase separation
(phase mixing) to phase mixing (phase separation). Furthermore, the peculiar
spin textures including skyrmion lattice, skyrmion pair and skyrmion string are
revealed in this system.",1703.01411v1
2011-11-18,Locally Non-centrosymmetric Superconductivity in Multilayer Systems,"Although multilayer systems possess global inversion symmetry, some of the
layers lack local inversion symmetry because no global inversion centers are
present on such layers. Such locally non-centrosymmetric systems exhibit
spatially modulated Rashba spin-orbit coupling. In this study, the
superconductivity in multilayer models exhibiting inhomogeneous Rashba
spin-orbit coupling is investigated. We study the electronic structure,
superconducting gap, and spin susceptibility in the superconducting state with
mixed parity order parameters. We show the enhancement of the spin
susceptibility by Rashba spin-orbit coupling and interpret it on the basis of
the crossover from a centrosymmetric superconductor to a non-centrosymmetric
superconductor. It is also shown that the spin susceptibility is determined by
the phase difference of the order parameter between layers and is nearly
independent of the parity mixing of order parameters. An intuitive
understanding is given on the basis of the analytic expression of
superconducting order parameters in the band basis. The results indicate that
not only a broken global inversion symmetry but also a broken local inversion
symmetry leads to unique properties of superconductivity. We discuss the
superconductivity in artificial superlattices involving CeCoIn5 and multilayer
high-Tc cuprates.",1111.4293v2
2017-06-20,Symmetry-enriched Bose-Einstein condensates in spin-orbit coupled bilayer system,"We consider the fate of Bose-Einstein condensation (BEC) with time-reversal
symmetry and inversion symmetry in a spin-orbit coupled bilayer system. When
these two symmetry operators commute, all the single particle bands are exactly
two-fold degenerate in the momentum space. The scattering in the two-fold
degenerate rings can relax the spin-momentum locking effect resulting from
spin-orbit coupling, thus we can realize the spin polarized plane wave phase
even when the inter-particle interaction dominates. When these two operators
anti-commute, the lowest two bands may have the same minimal energy, which have
totally different spin structures. As a result, the competition between
different condensates in these two energetically degenerate rings can give rise
to interesting stripe phases with atoms condensed at two or four colinear
momenta. We find that the crossover between these two cases is accompanied by
the excited band condensation when the interference energy can overcome the
increased single particle energy in the excited band. This effect is not based
on strong interaction, thus can be realized even with moderate interaction
strength.",1706.06234v1
2018-01-03,Discovery of highly spin-polarized conducting surface states in the strong spin-orbit coupling semiconductor Sb$_2$Se$_3$,"Majority of the A$_2$B$_3$ type chalcogenide systems with strong spin-orbit
coupling, like Bi$_2$Se$_3$, Bi$_2$Te$_3$ and Sb$_2$Te$_3$ etc., are
topological insulators. One important exception is Sb$_2$Se$_3$, where a
topological non-trivial phase was argued to be possible under ambient
conditions, but such a phase could be detected to exist only under pressure. In
this Letter, we show that like Bi$_2$Se$_3$, Sb$_2$Se$_3$, displays generation
of highly spin-polarized current under mesoscopic superconducting point
contacts as measured by point contact Andreev reflection spectroscopy. In
addition, we observe a large negative and anisotropic magnetoresistance in
Sb$_2$Se$_3$, when the field is rotated in the basal plane. However, unlike in
Bi$_2$Se$_3$, in case of Sb$_2$Se$_3$ a prominent quasiparticle interference
(QPI) pattern around the defects could be obtained in STM conductance imaging.
Thus, our experiments indicate that Sb$_2$Se$_3$ is a regular band insulator
under ambient conditions, but due to it's high spin-orbit coupling, non-trivial
spin-texture exists on the surface and the system could be on the verge of a
topological insulator phase.",1801.00929v1
2019-04-18,Supercurrent in ferromagnetic Josephson junctions with heavy metal interlayers. II. Canted magnetization,"It has been suggested by theoretical works that equal spin-triplet Cooper
pairs can be generated in Josephson junctions containing both a ferromagnet and
a source of spin-orbit coupling. Our recent experimental work suggested that
spin-triplet Cooper pairs were not generated by a Pt spin-orbit coupling layer
when the ferromagnetic weak link had entirely in-plane anisotropy (N. Satchell
and N.O. Birge, Phys. Rev. B 97, 214509 (2018)). Here, we revisit the
experiment using Pt again as a source for spin-orbit coupling and a [Co(0.4
nm)/Ni(0.4 nm)]$_{\times8}$/Co(0.4 nm) ferromagnetic weak link with both
in-plane and out-of-plane magnetization components (canted magnetization). The
canted magnetization more closely matches theoretical predictions than our
previous experimental work. Our results suggest that there is no supercurrent
contribution in our junctions from equal spin-triplets. In addition, this work
includes the first systematic study of supercurrent dependence on Cu interlayer
thickness, a common additional layer used to buffer the growth of the
ferromagnet and which for Co may significantly improve the growth morphology.
We report that the supercurrent in the [Co(0.4 nm)/Ni(0.4
nm)]$_{\times8}$/Co(0.4 nm) ferromagnetic weak links can be enhanced by over
two orders of magnitude by tuning the Cu interlayer thickness. This result has
important application in superconducting spintronics, where large critical
currents are desirable for devices.",1904.08798v2
2021-02-08,Generating and detecting topological phases with higher Chern number,"Topological phases with broken time-reversal symmetry and Chern number |C|>=2
are of fundamental interest, but it remains unclear how to engineer the desired
topological Hamiltonian within the paradigm of spin-orbit-coupled particles
hopping only between nearest neighbours of a static lattice. We show that
phases with higher Chern number arise when the spin-orbit coupling satisfies a
combination of spin and spatial rotation symmetries. We leverage this result
both to construct minimal two-band tight binding Hamiltonians that exhibit
|C|=2,3 phases, and to show that the Chern number of one of the energy bands
can be inferred from the particle spin polarization at the high-symmetry
crystal momenta in the Brillouin zone. Using these insights, we provide a
detailed experimental scheme for the specific realization of a
time-reversal-breaking topological phase with |C|=2 for ultracold atomic gases
on a triangular lattice subject to spin-orbit coupling. The Chern number can be
directly measured using Zeeman spectroscopy; for fermions the spin amplitudes
can be measured directly via time of flight, while for bosons this is preceded
by a short Bloch oscillation. Our results provide a pathway to the realization
and detection of novel topological phases with higher Chern number in ultracold
atomic gases.",2102.04468v2
2022-01-04,Gain/loss effects on spin-orbit coupled ultracold atoms in two-dimensional optical lattices,"Due to the fundamental position of spin-orbit coupled ultracold atoms in the
simulation of topological insulators, the gain/loss effects on these systems
should be evaluated when considering the measurement or the coupling to the
environment. Here, incorporating the mature gain/loss techniques into the
experimentally realized spin-orbit coupled ultracold atoms in two-dimensional
optical lattices, we investigate the corresponding non-Hermitian tight-binding
model and evaluate the gain/loss effects on various properties of the system,
revealing the interplay of the non-Hermiticity and the spin-orbit coupling.
Under periodic boundary conditions, we analytically obtain the topological
phase diagram, which undergoes a non-Hermitian gapless interval instead of a
point that the Hermitian counterpart encounters for a topological phase
transition. We also unveil that the band inversion is just a necessary but not
sufficient condition for a topological phase in two-level spin-orbit coupled
non-Hermitian systems. Because the nodal loops of the upper or lower two
dressed bands of the Hermitian counterpart can be split into exceptional loops
in this non-Hermitian model, a gauge-independent Wilson-loop method is
developed for numerically calculating the Chern number of multiple degenerate
complex bands. Under open boundary conditions, we find that the conventional
bulk-boundary correspondence does not break down with only on-site gain/loss
due to the lack of non-Hermitian skin effect, but the dissipation of chiral
edge states depends on the boundary selection, which may be used in the control
of edge-state dynamics. Given the technical accessibility of state-dependent
atom loss, this model could be realized in current cold-atom experiments.",2201.01216v3
2015-05-05,Spin-orbit coupling and operation of multi-valley spin qubits,"Spin qubits composed of either one or three electrons are realized in a
quantum dot formed at a Si/SiO_2-interface in isotopically enriched silicon.
Using pulsed electron spin resonance, we perform coherent control of both types
of qubits, addressing them via an electric field dependent g-factor. We perform
randomized benchmarking and find that both qubits can be operated with high
fidelity. Surprisingly, we find that the g-factors of the one-electron and
three-electron qubits have an approximately linear but opposite dependence as a
function of the applied dc electric field. We develop a theory to explain this
g-factor behavior based on the spin-valley coupling that results from the sharp
interface. The outer ""shell"" electron in the three-electron qubit exists in the
higher of the two available conduction-band valley states, in contrast with the
one-electron case, where the electron is in the lower valley. We formulate a
modified effective mass theory and propose that inter-valley spin-flip
tunneling dominates over intra-valley spin-flips in this system, leading to a
direct correlation between the spin-orbit coupling parameters and the g-factors
in the two valleys. In addition to offering all-electrical tuning for
single-qubit gates, the g-factor physics revealed here for one-electron and
three-electron qubits offers potential opportunities for new qubit control
approaches.",1505.01213v1
2020-06-30,Spin-orbit coupling suppression and singlet-state blocking of spin-triplet Cooper pairs,"An inhomogeneous magnetic exchange field at a superconductor/ferromagnet
interface converts spin-singlet Cooper pairs to a spin-aligned (i.e.
spin-polarized) triplet state. Although the decay envelope of such triplet
pairs within ferromagnetic materials is well studied, little is known about
their decay in non-magnetic metals and superconductors, and in particular in
the presence of spin-orbit coupling (SOC). Here we investigate devices in which
triplet supercurrents are injected into the s-wave superconductor Nb. In the
normal state of Nb, triplet supercurrents decay over a distance of 5 nm, which
is an order of magnitude smaller than the decay of spin singlet pairs due to
the SOC interacting with the spin associated with triplet pairs. In the
superconducting state of Nb, triplet supercurrents are not able to couple with
the singlet wavefunction and thus blocked by the absence of available
equilibrium states in the singlet gap. The results offer new insight into the
dynamics between s-wave singlet and s-wave triplet states.",2006.16654v3
2022-05-24,Competing spin-orbital singlet states in the 4$d^4$ honeycomb ruthenate Ag$_3$LiRu$_2$O$_6$,"When spin-orbit-entangled $d$-electrons reside on a honeycomb lattice, rich
quantum states are anticipated to emerge, as exemplified by the $d^5$ Kitaev
materials. Distinct yet equally intriguing physics may be realized with a
$d$-electron count other than $d^5$. We found that the layered ruthenate
Ag$_3$LiRu$_2$O$_6$ with $d^4$ Ru$^{4+}$ ions at ambient pressure forms a
honeycomb lattice of spin-orbit-entangled singlets, which is a playground for
frustrated excitonic magnetism. Under pressure, the singlet state does not
develop the expected excitonic magnetism but experiences two successive
transitions to other nonmagnetic phases, first to an intermediate phase with
moderate distortion of honeycomb lattice, and eventually to a high-pressure
phase with very short Ru-Ru dimer bonds. While the strong dimerization in the
high-pressure phase originates from a molecular orbital formation as in the
sister compound Li$_2$RuO$_3$, the intermediate phase represents a
spin-orbit-coupled $J$-dimer state which is stabilized by the admixture of
upper-lying $J_{\rm eff} = 1$-derived states. We argue that the $J$-dimer state
is induced by a pseudo-Jahn-Teller effect associated with the low-lying
spin-orbital excited states and is unique to spin-orbit-entangled $d^4$
systems. The discovery of competing singlet phases demonstrates rich
spin-orbital physics of $d^4$ honeycomb compounds and paves the way for
realization of unconventional magnetism.",2205.12123v1
2019-09-11,Discovering momentum-dependent magnon spin texture in insulating antiferromagnets: Role of the Kitaev interaction,"We theoretically show that the Kitaev interaction generates a novel class of
spin texture in the excitation spectrum of the antiferromagnetic insulator
found in the Kitaev-Heisenberg-$\Gamma$ model. In conducting electronic
systems, there is a series of vortex type of spin texture along the Fermi
surface induced by Rashba and Dresselhaus spin-orbit coupling. Such spin
textures are rarely found in magnetic insulators, since there had been no
systematic ways to control the kinetics of its quasi-particle called magnon
using a magnetic field or spacially asymmetric exchange couplings. Here, we
propose a general framework to explore such spin textures in arbitrary
insulating antiferromagnets. We introduce an analytical method to transform any
complicated Hamiltonian to the simple representation based on pseudo-spin
degrees of freedom. The direction of the pseudo-spin on a Bloch sphere
describes the degree of contributions from the two magnetic sublattices to the
spin moment carried by the magnon. The momentum dependent fictitious ""Zeeman
field"" determines the direction of the pseudo-spin and thus becomes the control
parameter of the spin texture, which is explicitly described by the original
model parameters. The framework enabled us to clarify the uncovered aspect of
the Kitaev interaction, and further provides a tool to easily design or explore
materials with intriguing magnetic properties. Since these spin textures can be
a source of a pure spin current, the Kitaev materials $A_{2}$PrO$_{3}$ ($A$
=Li, Na) shall become a potential platform of power-saving spintronics devices.",1909.05174v2
2016-10-28,Longitudinal optical and spin-Hall conductivities of Rashba conducting strips coupled to ferro- and antiferromagnetic layers,"A system composed of a conducting planar strip with Rashba spin-orbit
coupling (RSOC), magnetically coupled to a layer of localized magnetic moments,
at equilibrium, is studied within a microscopic Hamiltonian with numerical
techniques at zero temperature in the clean limit. In particular, transport
properties for the cases of ferromagnetic (FM) and antiferromagnetic (AFM)
coupled layers are computed in linear response on strips of varying width. Some
behaviors observed for these properties are consistent with the ones observed
for the corresponding Rashba helical currents. The case of uncoupled Rashba
strips is also studied for comparison. In the case of Rashba strips coupled to
an AFM localized order, results for the longitudinal dc conductivity, for small
strip widths, suggest the proximity to a metal-insulator transition. More
interesting, in the proximity of this transition, and in general at
intermediate values of the RSOC, it is observed a large spin-Hall conductivity
that is two orders of magnitude larger than the one for the FM order for the
same values of the RSOC and strip widths. There are clearly two different
regimes for small and for large RSOC, which is also present in the behavior of
Rashba helical currents. Different contributions to the optical and the
spin-Hall conductivities, according to a new classification of inter- or
intra-band origin proposed for planar strips in the clean limit, or coming from
the hopping or spin-orbit terms of the Hamiltonian, are examined. Finally, the
effects of different orientation of the coupled magnetic moments will be also
studied.",1610.09399v2
2011-11-03,Energy spectra of three electrons in Si/SiGe single and vertically coupled double quantum dots,"We study three-electron energy spectra in Si/SiGe single and vertically
coupled double quantum dots where all the relevant effects, such as, the Zeeman
splitting, spin-orbit coupling, valley coupling and electron-electron Coulomb
interaction are explicitly included. In the absence of magnetic field, our
results in single quantum dots agree well with the experiment by Borselli {\em
et al.} [Appl. Phys. Lett. {\bf 98}, 123118 (2011)]. We identify the spin and
valley configurations of the ground state in the experimental cases and give a
complete phase-diagram-like picture of the ground state configuration with
respect to the dot size and valley splitting. We also explicitly investigate
the three-electron energy spectra of the pure and mixed valley configurations
with magnetic fields in both Faraday and Voigt configurations. We find that the
ground state can be switched between doublet and quartet by tuning the magnetic
field and/or dot size. The three-electron energy spectra present many
anticrossing points between different spin states due to the spin-orbit
coupling, which are expected to benefit the spin manipulation. We show that the
negligibly small intervalley Coulomb interaction can result in magnetic-field
independent quartet-doublet degeneracy in the three-electron energy spectrum of
the mixed valley configuration. Furthermore, we study the barrier-width and
barrier-height dependences in vertically coupled double quantum dots with both
pure and mixed valley configurations. Similar to the single quantum dot case,
anticrossing behavior and quartet-doublet degeneracy are observed.",1111.0717v1
2001-11-15,Resonant X-ray Scattering in Manganites - Study of Orbital Degree of Freedom -,"Orbital degree of freedom of electrons and its interplay with spin, charge
and lattice degrees of freedom are one of the central issues in colossal
magnetoresistive manganites. The orbital degree of freedom has until recently
remained hidden, since it does not couple directly to most of experimental
probes. Development of synchrotron light sources has changed the situation; by
the resonant x-ray scattering (RXS) technique the orbital ordering has
successfully been observed . In this article, we review progress in the recent
studies of RXS in manganites. We start with a detailed review of the RXS
experiments applied to the orbital ordered manganites and other correlated
electron systems. We derive the scattering cross section of RXS where the
tensor character of the atomic scattering factor (ASF) with respect to the
x-ray polarization is stressed. Microscopic mechanisms of the anisotropic
tensor character of ASF is introduced and numerical results of ASF and the
scattering intensity are presented. The azimuthal angle scan is a unique
experimental method to identify RXS from the orbital degree of freedom. A
theory of the azimuthal angle and polarization dependence of the RXS intensity
is presented. The theoretical results show good agreement with the experiments
in manganites. Apart from the microscopic description of ASF, a theoretical
framework of RXS to relate directly to the 3d orbital is presented. The
scattering cross section is represented by the correlation function of the
pseudo-spin operator for the orbital degree of freedom. A theory is extended to
the resonant inelastic x-ray scattering and methods to observe excitations of
the orbital degree of freedom are proposed.",0111269v1
2014-04-10,Two-body gravitational spin-orbit interaction at linear order in the mass ratio,"We analytically compute, to linear order in the mass-ratio, the ""geodetic""
spin precession frequency of a small spinning body orbiting a large
(non-spinning) body to the eight-and-a-half post-Newtonian order, thereby
extending previous analytical knowledge which was limited to the third
post-Newtonian level. These results are obtained applying analytical
gravitational self-force theory to the first-derivative level generalization of
Detweiler's gauge-invariant redshift variable. We compare our analytic results
with strong-field numerical data recently obtained by S.~R.~Dolan et al.
[Phys.\ Rev.\ D {\bf 89}, 064011 (2014)]. Our new, high-post-Newtonian-order
results capture the strong-field features exhibited by the numerical data. We
argue that the spin-precession will diverge as $\approx -0.14/(1-3y)$ as the
light-ring is approached. We transcribe our kinematical spin-precession results
into a corresponding improved analytic knowledge of one of the two
(gauge-invariant) effective gyro-gravitomagnetic ratios characterizing
spin-orbit couplings within the effective-one-body formalism. We provide
simple, accurate analytic fits both for spin-precession and the effective
gyro-gravitomagnetic ratio. The latter fit predicts that the
linear-in-mass-ratio correction to the gyro-gravitomagnetic ratio changes sign
before reaching the light-ring. This strong-field prediction might be important
for improving the analytic modeling of coalescing spinning binaries.",1404.2747v1
2019-03-04,Rashba spin-splitting in ferroelectric oxides: from rationalizing to engineering,"Ferroelectric Rashba semiconductors (FERSC), in which Rashba spin-splitting
can be controlled and reversed by an electric field, have recently emerged as a
new class of functional materials useful for spintronic applications. The
development of concrete devices based on such materials is, however, still
hampered by the lack of robust FERSC compounds. Here, we show that the
coexistence of large spontaneous polarisation and sizeable spin-orbit coupling
is not sufficient to have strong Rashba effects and clarify why simple
ferroelectric oxide perovskites with transition metal at the B-site are
typically not suitable FERSC candidates. By rationalizing how this limitation
can be by-passed through band engineering of the electronic structure in
layered perovskites, we identify the Bi$_2$WO$_6$ Aurivillius crystal as the
first robust ferroelectric with large and reversible Rashba spin-splitting,
that can even be substantially doped without losing its ferroelectric
properties. Importantly, we highlight that a unidirectional spin-orbit field
arises in layered Bi$_2$WO$_6$, resulting in a protection against
spin-decoherence.We highlight moreover that a unidirectional spin-orbit field
arises in Bi$_2$WO$_6$, in which the spin-texture is so protected against
spin-decoherence.",1903.01241v3
2019-03-14,Band Structure and Spin-Orbital Texture of the (111)-KTaO3 Two-Dimensional Electron Gas,"Two-dimensional electron gases (2DEGs) in oxides show great potential for
discovering new physical phenomena and at the same time hold promise for
electronic applications. In this work we use angle resolved photoemission to
determine the electronic structure of a 2DEG stabilized in the (111)-oriented
surface of the strong spin orbit coupling material KTaO3. Our measurements
reveal multiple sub-bands that emerge as a consequence of quantum confinement
and form a six-fold symmetric Fermi surface. This electronic structure is well
reproduced by self-consistent tight-binding supercell calculations. Based on
these calculations we determine the spin and orbital texture of the 2DEG. We
show that the 2DEG Fermi surface is derived from bulk J = 3/2 states and
exhibits an unconventional anisotropic Rashba-like lifting of the
spin-degeneracy. Spin-momentum locking holds only for high symmetry directions
and a strong out-of-plane spin component renders the spin-texture three-fold
symmetric. We find that the average spin-splitting on the Fermi surface is an
order of magnitude larger than in SrTiO3, which should translate into an
enhancement in the spin-orbitronic response of (111)-KTaO3 2DEG based devices.",1903.06077v1
2021-10-05,Spin-orbit torque generation in NiFe/IrO2 bilayers,"The 5d transition-metal oxides have a unique electronic structure dominated
by strong spin-orbit coupling and hence they can be an intriguing platform to
explore spin-current physics. Here, we report on room-temperature generation of
spin-orbit torque (SOT) from a conductive 5d iridium oxide, IrO2. By measuring
second-harmonic Hall resistance of Ni81Fe19/IrO2 bilayers, we find both
dampinglike and fieldlike SOTs. The former is larger than the latter, enabling
easier control of magnetization. We also observe that the dampinglike SOT
efficiency has a significant dependence on IrO2 thickness, which is well
described by the drift-diffusion model based on the bulk spin Hall effect. We
deduce the effective spin Hall angle of +0.093 +- 0.003 and the spin-diffusion
length of 1.7 +- 0.2 nm. By comparison with control samples Pt and Ir, we show
that the effective spin Hall angle of IrO2 is comparable to that of Pt and
seven times higher than that of Ir. The fieldlike SOT efficiency has a negative
sign without appreciable dependence on the thickness, in contrast to the
dampinglike SOT. This suggests that the fieldlike SOT likely stems from the
interface. These experimental findings suggest that the uniqueness of the
electronic structure of 5d transition-metal oxides is crucial for highly
efficient charge to spin-current conversion.",2110.01801v1
2023-11-03,Magnetic properties and spin dynamics in a spin-orbit driven Jeff= 1/2 triangular lattice antiferromagnet,"Frustration-induced strong quantum fluctuations accompanied by spin-orbit
coupling and crystal electric field can give rise to rich and diverse magnetic
phenomena associated with unconventional low-energy excitations in rare-earth
based quantum magnets. Herein, we present crystal structure, magnetic
susceptibility, specific heat, muon spin relaxation(muSR), and electron spin
resonance (ESR) studies on the polycrystalline samples of Ba6Yb2Ti4O17 in which
Yb3+ ions constitute a perfect triangular lattice in ab-plane without
detectable anti-site disorder between atomic sites. The Curie-Weiss fit of
low-temperature magnetic susceptibility data suggest the spin-orbit entangled
Jeff = 1/2 degrees of freedom of Yb3+ spin with weak antiferromagnetic exchange
interactions in the Kramers doublet ground state. The zero-field specific heat
data reveal the presence of long-range magnetic order at TN = 77 mK which is
suppressed in a magnetic field 1 T. The broad maximum in specific heat is
attributed to the Schottky anomaly implying the Zeeman splitting of the Kramers
doublet ground state. The ESR measurements suggest the presence of anisotropic
exchange interaction between the moments of Yb3+ spins and the well separated
Kramers doublet state. muSR experiments reveal a fluctuating state of Yb3+
spins in the temperature range 0.1 K-100 K owing to depopulation of crystal
electric field levels, which suggests that the Kramers doublets are well
separated consistent with thermodynamic and ESR results. In addition to the
intraplane nearest-neighbor superexchange interaction, the interplane exchange
interaction and anisotropy are expected to stabilize the long-range ordered
state in this triangular lattice antiferromagnet.",2311.01858v1
2021-12-01,Libration-induced Orbit Period Variations Following the DART Impact,"The Double Asteroid Redirection Test (DART) mission will be the first test of
a kinetic impactor as a means of planetary defense. In late 2022, DART will
collide with Dimorphos, the secondary in the Didymos binary asteroid system.
The impact will cause a momentum transfer from the spacecraft to the binary
asteroid, changing the orbit period of Dimorphos and forcing it to librate in
its orbit. Owing to the coupled dynamics in binary asteroid systems, the orbit
and libration state of Dimorphos are intertwined. Thus, as the secondary
librates, it also experiences fluctuations in its orbit period. These
variations in the orbit period are dependent on the magnitude of the impact
perturbation, as well as the system's state at impact and the moments of
inertia of the secondary. In general, any binary asteroid system whose
secondary is librating will have a non-constant orbit period on account of the
secondary's fluctuating spin rate. The orbit period variations are typically
driven by two modes: a long-period and short-period, each with significant
amplitudes on the order of tens of seconds to several minutes. The fluctuating
orbit period offers both a challenge and an opportunity in the context of the
DART mission. Orbit period oscillations will make determining the post-impact
orbit period more difficult, but can also provide information about the
system's libration state and the DART impact.",2112.00634v1
2024-03-16,Coherent Acoustic Control of Defect Orbital States in the Strong-Driving Limit,"We use a bulk acoustic wave resonator to demonstrate coherent control of the
excited orbital states in a diamond nitrogen-vacancy (NV) center at cryogenic
temperature. Coherent quantum control is an essential tool for understanding
and mitigating decoherence. Moreover, characterizing and controlling orbital
states is a central challenge for quantum networking, where optical coherence
is tied to orbital coherence. We study resonant multi-phonon orbital Rabi
oscillations in both the frequency and time domain, extracting the strength of
the orbital-phonon interactions and the coherence of the acoustically driven
orbital states. We reach the strong-driving limit, where the physics is
dominated by the coupling induced by the acoustic waves. We find agreement
between our measurements, quantum master equation simulations, and a
Landau-Zener transition model in the strong-driving limit. Using perturbation
theory, we derive an expression for the orbital Rabi frequency versus acoustic
drive strength that is non-perturbative in the drive strength and agrees well
with our measurements for all acoustic powers. Motivated by continuous wave
spin resonance-based decoherence protection schemes, we model the orbital
decoherence and find good agreement between our model and our measured
few-to-several nanoseconds orbital decoherence times. We discuss the outlook
for orbital decoherence protection.",2403.10989v1
2004-11-29,Quantum Spin Hall Effect in Graphene,"We study the effects of spin orbit interactions on the low energy electronic
structure of a single plane of graphene. We find that in an experimentally
accessible low temperature regime the symmetry allowed spin orbit potential
converts graphene from an ideal two dimensional semimetallic state to a quantum
spin Hall insulator. This novel electronic state of matter is gapped in the
bulk and supports the quantized transport of spin and charge in gapless edge
states that propagate at the sample boundaries. The edge states are non chiral,
but they are insensitive to disorder because their directionality is correlated
with spin. The spin and charge conductances in these edge states are calculated
and the effects of temperature, chemical potential, Rashba coupling, disorder
and symmetry breaking fields are discussed.",0411737v2
2006-01-12,Observation of Spin Relaxation Anisotropy in Semiconductor Quantum Wells,"Spin relaxation of two-dimensional electrons in asymmetrical (001) AlGaAs
quantum wells are measured by means of Hanle effect. Three different spin
relaxation times for spins oriented along [110], [1-10] and [001]
crystallographic directions are extracted demonstrating anisotropy of
D'yakonov-Perel' spin relaxation mechanism. The relative strengths of Rashba
and Dresselhaus terms describing the spin-orbit coupling in semiconductor
quantum well structures. It is shown that the Rashba spin-orbit splitting is
about four times stronger than the Dresselhaus splitting in the studied
structure.",0601252v1
2008-12-31,Spin Hall effect in the kagome lattice with Rashba spin-orbit interaction,"We study the spin Hall effect in the kagom\'{e} lattice with Rashba
spin-orbit coupling. The conserved spin Hall conductance $\sigma_{xy}^{s}$ (see
text) and its two components, i.e., the conventional term $\sigma_{xy}^{s0}$
and the spin-torque-dipole term $\sigma_{xy}^{s\tau}$, are numerically
calculated, which show a series of plateaus as a function of the electron Fermi
energy $\epsilon_{F}$. A consistent two-band analysis, as well as a Berry-phase
interpretation, is also given. We show that these plateaus are a consequence of
the various Fermi-surface topologies when tuning $\epsilon_{F}$. In particular,
we predict that compared to the case with the Fermi surface encircling the
$\mathbf{\Gamma}$ point in the Brillouin zone, the amplitude of the spin Hall
conductance with the Fermi surface encircling the $\mathbf{K}$ points is twice
enhanced, which makes it highly meaningful in the future to systematically
carry out studies of the $\mathbf{K}$-valley spintronics.",0901.0053v1
2010-11-23,Correlation Effects in Quantum Spin-Hall Insulators: A Quantum Monte Carlo Study,"We consider the Kane-Mele model with spin-orbit coupling supplemented by a
Hubbard U term. On the basis of projective auxiliary field quantum Monte Carlo
simulations on lattice sizes up to 15 x 15, we map out the phase diagram. The
quantum spin-liquid state found in the Hubbard model is shown to be robust
against weak spin-orbit interaction, and is not adiabatically connected to the
spin-Hall insulating state. Beyond a critical value of U > U_c both states are
unstable toward magnetic ordering. Within the quantum spin-Hall state we study
the spin, charge and single-particle dynamics of the helical Luttinger liquid
by retaining the Hubbard interaction only on the edge of a ribbon. The Hubbard
interaction greatly suppresses charge currents along the edge, promotes edge
magnetism, but leaves the single-particle signatures of the helical liquid
intact.",1011.5063v3
2011-12-22,The universal definition of spin current,"The spin current $J_{S}$, orbit angular momentum current $J_{L}$ and total
angular momentum current $J_{J}$ in a dyad form have been universally defined
according to quantum electrodynamics. Their conservation quantities and the
continuity equations have been discussed in different cases. Non-relativistic
approximation forms are deduced in order to explain their physical meanings,
and to analyze some experiment results. The spin current of helical edge states
in HgTe/CdTe quantum wells is calculated to demonstrate the properties of spin
current on the two dimensional quantum spin-Hall system. A generalized
spin-orbit coupling term in the semiconductoring media is deduced based on the
theory of the electrodynamics in the moving media. We recommend to use the
effective total angular momentum current instead of the pure spin current to
describe the polarizing distribution and transport phenomena in spintronic
media.",1112.5320v2
2012-06-01,Dynamical Self-Quenching of Spin Pumping into Double Quantum Dots,"Nuclear spin polarization can be pumped into spin-blocked quantum dots by
multiple Landau- Zener passages through singlet-triplet anticrossings. By
numerical simulations of realistic systems including approximately $10^7$
nuclear spins during $10^5$ sweeps, we uncover a mechanism of dynamical
self-quenching which results in a fast saturation of the nuclear polarization
under stationary pumping. This is caused by screening of the field of the
nuclear spins. In systems with moderate spin-orbit coupling, self-quenching
also screens the spin-orbit interaction. The mechanism is generic and remains
robust under a moderate noise. Our finding explains low polarization levels
achieved experimentally and calls for developing new protocols that break the
self-quenching limitations.",1206.0100v3
2012-07-05,Unconventional Quantum Hall Effect and Tunable Spin Hall Effect in MoS2 Trilayers,"We analyze the Landau level (LL) structure and spin Hall effect in a MoS2
trilayer. Due to orbital asymmetry, the low-energy Dirac fermions become
heavily massive and the LL energies grow linearly with $B$, rather than with
$\sqrt{B}$. Spin-orbital couplings break spin and valley degenerate LL's into
two time reversal invariant groups, with LL crossing effects present in the
valence bands. We find a field-dependent unconventional Hall plateau sequence
$\nu=...$ $-2M-6$, $-2M-4$, $-2M-2$, $-2M-1$, ..., -5, -3, -1, 0, 2, 4 .... In
a p-n junction, spin-resolved fractionally quantized conductance appears in
two-terminal measurements with a controllable spin-polarized current that can
be probed at the interface. We also show the tunability of zero-field spin Hall
conductivity.",1207.1205v1
2015-08-06,Interface-driven spin-torque ferromagnetic resonance by Rashba coupling at the interface between non-magnetic materials,"The Rashba-Edelstein effect stems from the interaction between the electron's
spin and its momentum induced by spin-orbit interaction at an interface or a
surface. It was shown that the inverse Rashba-Edelstein effect can be used to
convert a spin- into a charge current. Here, we demonstrate that a Bi/Ag Rashba
interface can even drive an adjacent ferromagnet to resonance. We employ a
spin-torque ferromagnetic resonance excitation/detection scheme which was
developed originally for a bulk spin-orbital effect, the spin Hall effect. In
our experiment, the direct Rashba-Edelstein effect generates an oscillating
spin current from an alternating charge current driving the magnetization
precession in a neighboring permalloy (Py, Ni80Fe20) layer. Electrical
detection of the magnetization dynamics is achieved by a rectification
mechanism of the time dependent multilayer resistance arising from the
anisotropic magnetoresistance.",1508.01410v1
2016-07-12,Spin Hall conductance in a Y-shaped junction device in presence of tunable spin-orbit coupling,"We study spin Hall effect in a three terminal Y-shaped device in presence of
tunable spin-orbit (SO) interactions via Landauer-B\""{u}ttiker formalism. We
have evolved a fabrication technique for creating different angular separation
between the two arms of the Y-shaped device so as to investigate the effect of
angular width on the spin Hall conductance (SHC). A smaller angular separation
yields a larger conductance. Also arbitrary orientation of the spin
quantization axes yields interesting three dimensional contour maps for the SHC
corresponding to different angular separation of the Y-shaped device. The
results explicitly show breaking of the spin rotational symmetry. Further a
systematic study is carried out to compare and contrast between the different
SO terms, such as Rashba and Dresselhaus SO interactions and the interplay of
the angular separation therein.",1607.03352v1
2016-07-12,Controlling the optical spin Hall effect with light,"The optical spin Hall effect (OSHE) is a transport phenomenon of exciton
polaritons in semiconductor microcavities, caused by the polaritonic spin-orbit
interaction, that leads to the formation of spin textures. In the semiconductor
cavity, the physical basis of the spin orbit coupling is an effective magnetic
field caused by the splitting of transverse-electric and transverse-magnetic
(TE-TM) modes. The spin textures can be observed in the near field (local spin
distribution of polaritons), and as light polarization patterns in the more
readily observable far field. For future applications in spinoptronic devices,
a simple and robust control mechanism, which establishes a one-to-one
correspondence between stationary incident light intensity and far-field
polarization pattern, is needed. We present such a control scheme, which is
made possible by a specific double-microcavity design.",1607.03530v1
2014-03-27,Tight-binding simulations of electrically driven spin-valley transitions in carbon nanotube quantum dots,"We describe dynamics of spin and valley transitions driven by alternating
electric fields in quantum dots defined electrostatically within semiconducting
carbon nanotubes (CNT). We use the tight-binding approach to describe the
states localized within a quantum dot taking into account the circumferential
spin-orbit interaction due to the s-p hybridization and external fields. The
basis of eigenstates localized in the quantum dot is used in the solution of
the time-dependent Schroedinger equation for description of spin flips and
inter-valley transitions that are driven by periodic perturbation in the
presence of coupling between the spin, valley and orbital degrees of freedom.
Besides the first order transitions we find also fractional resonances. We
discuss the transition rates with selection rules that are lifted by atomic
disorder and the bend of the tube. We demonstrate that the electric field
component perpendicular to the axis of the CNT activates spin transitions which
are otherwise absent and that the resonant spin-flip time scales with the
inverse of the electric field.",1403.6970v3
2017-01-23,Unidirectional spin Hall magnetoresistance in topological insulator/ferromagnetic layer heterostructures,"The large spin orbit coupling in topological insulators results in helical
spin-textured Dirac surface states that are attractive for topological
spintronics. These states generate an efficient spin-orbit torque on proximal
magnetic moments at room temperature. However, memory or logic spin devices
based upon such switching require a non-optimal three terminal geometry, with
two terminals for the writing current and one for reading the state of the
device. An alternative two terminal device geometry is now possible by
exploiting the recent discovery of a unidirectional spin Hall magnetoresistance
in heavy metal/ferromagnet bilayers and (at low temperature) in magnetically
doped topological insulator heterostructures. We report the observation of
unidirectional spin Hall magnetoresistance in a technologically relevant device
geometry that combines a topological insulator with a conventional
ferromagnetic metal. Our devices show a figure-of-merit (magnetoresistance per
current density per total resistance) that is comparable to the highest
reported values in all-metal Ta/Co bilayers.",1701.06505v1
2022-02-03,Element Doping Enhanced Charge-to-Spin Conversion Efficiency in Amorphous PtSn4 Dirac Semimetal,"Topological semimetals (TSs) are promising candidates for low-power
spin-orbit torque (SOT) devices due to their large charge-to-spin conversion
efficiency. Here, we investigated the charge-to-spin conversion efficiency of
amorphous PtSn4 (5 nm)/CoFeB (2.5-12.5 nm) layered structures prepared by a
magnetron sputtering method at room temperature. The charge-to-spin ratio of
PtSn4/CoFeB bilayers was 0.08, characterized by a spin torque ferromagnetic
resonance (ST-FMR) technique. This ratio can further increase to 0.14 by
inducing dopants, like Al and CoSi, into PtSn4. The dopants can also decrease
(Al doping) or increase (CoSi doping) the resistivity of PtSn4. The work
proposed a way to enhance the spin-orbit coupling (SOC) in amorphous TSs with
dopants.",2202.01384v1
2022-03-08,Enhancement of thermal spin pumping by orbital angular momentum of rare earth iron garnet,"In a bilayer of ferromagnetic and non-magnetic metal, spin pumping can be
generated by a thermal gradient. The spin current generation depends on the
spin mixing conductance of the interface and the magnetic properties of the
ferromagnetic layer. Due to its low intrinsic damping, rare earth iron garnet
is often used for the ferromagnetic layer in the spin Seebeck experiment.
However, it is actually a ferrimagnetic with antiferromagnetically coupled
magnetic lattices and the contribution of rare earth magnetic lattice of rare
earth iron garnet on thermal spin pumping is not well understand. Here we focus
on the effect of magnetic properties of lanthanide and show that the orbital
angular momentum of rare earth iron garnet enhances thermal spin current
generation of lanthanide substituted yttrium iron garnet.",2203.03915v2
2022-06-08,Quarkonium in a spin dependent quark anti-quark potential at finite temperature,"We study the states of $c\bar{c}$ and $b\bar{b}$ system in a non-relativistic
a spin dependent potential model at finite temperature. The potential
incorporate color screening effect through a parameter $\mu$. The parameter
$\mu$ along with strong coupling constant $\alpha_s$ and string tension
$\sigma$ are taken temperature dependent and their values are fitted to the
Lattice data of quark anti-quark potential available at different values of
temperature. The applied potential include spin-spin, spin-orbital, tensor
interactions which allow us to study spin singlet and triplet states of
quarkonia. By solving non-relativistic Schr{\""o}dinger equation, we find the
spectrum of quarkonium states at different temperature and also determine the
critical temperature at which each state is dissolved. We find the critical
temperature is decreased with orbital and radial excitations, however, for spin
singlet and triplet states it remains same.",2206.04169v1
2004-12-10,Spin-orbit induced mixed-spin ground state in $R$NiO$_3$ perovskites probed by XAS: new insight into the metal to insulator transition,"We report on a Ni L$_{2,3}$ edges x-ray absorption spectroscopy (XAS) study
in $R$NiO$_3$ perovskites. These compounds exhibit a metal to insulator ($MI$)
transition as temperature decreases. The L$_{3}$ edge presents a clear
splitting in the insulating state, associated to a less hybridized ground
state. Using charge transfer multiplet calculations, we establish the
importance of the crystal field and 3d spin-orbit coupling to create a
mixed-spin ground state. We explain the $MI$ transition in $R$NiO$_3$
perovskites in terms of modifications in the Ni$^{3+}$ crystal field splitting
that induces a spin transition from an essentially low-spin (LS) to a
mixed-spin state.",0412276v1
2007-07-26,Spin separation in a T ballistic nanojunction due to lateral-confinement-induced spin-orbit-coupling,"We propose a new scheme of spin filtering employing ballistic nanostructures
in two dimensional electron gases (2DEGs). The proposal is essentially based on
the spin-orbit (SO) interaction arising from the lateral confining electric
field. This sets the basic difference with other works employing ballistic
crosses and T junctions with the conventional SO term arising from 2DEG
confinement. We discuss the consequences of this different approach on
magnetotransport properties of the device, showing that the filter can in
principle be used not only to generate a spin polarized current but also to
perform an electric measurement of the spin polarization of a charge current.
We focus on single-channel transport and investigate numerically the spin
polarization of the current.",0707.3918v1
2009-11-06,Spin-polarized electric currents in quantum transport through tubular two-dimensional electron gases,"Scattering theory is employed to derive a Landauer-type formula for the spin
and the charge currents, through a finite region where spin-orbit interactions
are effective. It is shown that the transmission matrix yields the spatial
direction and the magnitude of the spin polarization. This formula is used to
study the currents through a tubular two-dimensional electron gas. In this
cylindrical geometry, which may be realized in experiment, the transverse
conduction channels are not mixed (provided that the spin-orbit coupling is
uniform). It is then found that for modest boundary scattering, each step in
the quantized conductance is split into two, and the new steps have a non-zero
spin conductance, with the spin polarization perpendicular to the direction of
the current.",0911.1347v4
2010-11-11,Anomalous spin-resolved point-contact transmission of holes due to cubic Rashba spin-orbit coupling,"Evidence is presented for the finite wave vector crossing of the two lowest
one-dimensional spin-split subbands in quantum point contacts fabricated from
two-dimensional hole gases with strong spin-orbit interaction. This phenomenon
offers an elegant explanation for the anomalous sign of the spin polarization
filtered by a point contact, as observed in magnetic focusing experiments.
Anticrossing is introduced by a magnetic field parallel to the channel or an
asymmetric potential transverse to it. Controlling the magnitude of the
spin-splitting affords a novel mechanism for inverting the sign of the spin
polarization.",1011.2676v2
2011-02-15,Spin dynamics in the strong spin-orbit coupling regime,"We study the spin dynamics in a high-mobility two dimensional electron gas
(2DEG) with generic spin-orbit interactions (SOIs). We derive a set of spin
dynamic equations which capture the purely exponential to the damped
oscillatory spin evolution modes observed in different regimes of SOI strength.
Hence we provide a full treatment of the D'yakonov-Perel's mechanism by using
the microscopic linear response theory from the weak to the strong SOI limit.
We show that the damped oscillatory modes appear when the electron scattering
time is larger than half of the spin precession time due to the SOI, in
agreement with recent observations. We propose a new way to measure the
scattering time and the relative strength of Rashba and linear Dresselhaus SOIs
based on these modes and optical grating experiments. We discuss the physical
interpretation of each of these modes in the context of Rabi oscillation.",1102.3170v1
2015-07-31,Evidence of Ising pairing in superconducting NbSe$_2$ atomic layers,"Two-dimensional transition metal dichalcogenides with strong spin-orbit
interactions and valley-dependent Berry curvature effects have attracted
tremendous recent interests. Although novel single-particle and excitonic
phenomena related to spin-valley coupling have been extensively studied,
effects of spin-momentum locking on collective quantum phenomena remain
unexplored. Here we report an observation of superconducting monolayer NbSe$_2$
with an in-plane upper critical field over six times of the Pauli paramagnetic
limit by magneto-transport measurements. The effect can be understood in terms
of the competing Zeeman effect and large intrinsic spin-orbit interactions in
non-centrosymmetric NbSe$_2$ monolayers, where the electronic spin is locked to
the out-of-plane direction. Our results provide a strong evidence of
unconventional Ising pairing protected by spin-momentum locking and open up a
new avenue for studies of non-centrosymmetric superconductivity with unique
spin and valley degrees of freedom in the exact two-dimensional limit.",1507.08731v1
2015-09-02,Pauli Spin Blockade of Heavy Holes in a Silicon Double Quantum Dot,"In this work, we study hole transport in a planar silicon
metal-oxide-semiconductor based double quantum dot. We demonstrate Pauli spin
blockade in the few hole regime and map the spin relaxation induced leakage
current as a function of inter-dot level spacing and magnetic field. With
varied inter-dot tunnel coupling we can identify different dominant spin
relaxation mechanisms. Applying a strong out-of-plane magnetic field causes an
avoided singlet-triplet level crossing, from which the heavy hole g-factor
$\sim$ 0.93, and the strength of spin-orbit interaction $\sim$ 110 $\mu$eV, can
be obtained. The demonstrated strong spin-orbit interaction of heavy hole
promises fast local spin manipulation using only electrical fields, which is of
great interest for quantum information processing.",1509.00553v1
2016-01-13,Lifshitz transition driven by spin fluctuations and spin-orbit renormalization in NaOsO$_3$,"In systems where electrons form both dispersive bands and small local spins,
we show that changes of the spin configuration can tune the bands through a
Lifshitz transition, resulting in a continuous metal-insulator transition
associated with a progressive change of the Fermi surface topology. In contrast
to a Mott-Hubbard and Slater pictures, this spin-driven Lifshitz transition
appears in systems with small electron-electron correlation and large
hybridization. We show that this situation is realized in 5$d$ distorted
perovskites with an half-filled $t_{2g}$ bands such as NaOsO$_3$, where the
strong $p-d$ hybridization reduces the local moment, and spin-orbit coupling
causes a large renormalization of the electronic mobility. This weakens the
role of electronic correlations and drives the system towards an itinerant
magnetic regime which enables spin-fluctuations.",1601.03310v3
2016-09-26,Elastic Spin Hall effect in Mechanical Graphene,"We show that spin-orbit interaction and elastic spin-Hall effect can exist in
a classical mechanical system consisting of a two-dimensional honeycomb lattice
of masses and springs. The band structure shows the presence of splitting at K
point induced by the difference of longitudinal and transverse elastic
constant, and this splitting can be regarded as an effective Dresselhaus-type
spin-orbit coupling. Interestingly, as an initial displacement away from the
equilibrium is applied, the time evolution simulation shows that waves of
different spin polarization propagates along different directions at the Gamma
and K point, which is characteristic of spin-Hall effect. Several cases for
spin-Hall effect are also discussed.",1609.08061v1
2017-03-14,A Novel Spin-Orbit Torque due to Conduction Electrons,"The anomalous Hall effect is mainly used to probe the magnetization
orientation in ferromagnetic materials. A less explored aspect is the torque
acting back on magnetization, an effect that can be important at high currents.
The spin-orbit coupling of the conduction electrons causes spin-up and
spin-down electrons to scatter to opposite sides when a charge current flows in
the sample. This is equivalent to a spin current with orientation and flow
perpendicular to the driving charge current, leading to a non-equilibrium spin
accumulation that exerts a torque on the bulk magnetization through the s-d
exchange interaction. The symmetry of this toque is that of an uniaxial
anisotropy along the driving current. The large screening currents generated
with laser pulses in all-optical magnetic switching experiments make for
practical uses of this torque.",1703.04724v2
2017-03-31,"Comment on ""Spin-Orbit Coupling Induced Gap in Graphene on Pt(111) with Intercalated Pb Monolayer""","Recently a paper of Klimovskikh et al. was published presenting experimental
and theoretical analysis of the graphene/Pb/Pt(111) system. The authors
investigate the crystallographic and electronic structure of this
graphene-based system by means of LEED, ARPES, and spin-resolved PES of the
graphene $\pi$ states in the vicinity of the Dirac point of graphene. The
authors of this paper demonstrate that an energy gap of approx. 200 meV is
opened in the spectral function of graphene directly at the Dirac point of
graphene and spin-splitting of 100 meV is detected for the upper part of the
Dirac cone. On the basis of the spin-resolved photoelectron spectroscopy
measurements of the region around the gap the authors claim that these
splittings are of a spin-orbit nature and that the observed spin structure
confirms the observation of the quantum spin Hall state in graphene, proposed
in earlier theoretical works. Here we will show that careful systematic
analysis of the experimental data presented in this manuscript is needed and
their interpretation require more critical consideration for making such
conclusions. Our analysis demonstrates that the proposed effects and
interpretations are questionable and require further more careful experiments.",1704.00034v1
2014-05-07,Organic Magnetoelectroluminescence for Room Temperature Transduction between Magnetic and Optical Information,"Magnetic and spin-based technologies for data storage and processing pose
unique challenges for information transduction to light because of magnetic
metals' optical loss, and the inefficiency and resistivity of semiconductor
spin-based emitters at room temperature. Transduction between magnetic and
optical information in typical organic semiconductors poses additional
challenges as the Faraday and Kerr magnetooptical effects rely on the
electronic spin-orbit interaction, and the spin-orbit interaction in organics
is weak. Other methods of coupling light and spin have emerged in organics,
however, as the spin-dependent character of exciton recombination, with spin
injection from magnetic electrodes, provides magnetization-sensitive light
emission, although such approaches have been limited to low temperature and low
polarization efficiency. Here we demonstrate room temperature information
transduction between a magnet and an organic light emitting diode that does not
require electrical current, based on control via the magnet's remanent field of
the exciton recombination process in the organic semiconductor.",1405.1664v1
2016-05-16,Spin-polarization in the vicinity of quantum point contact with spin-orbit interaction,"We have developed a novel technique for detection of spin polarization with a
quantum dot weakly coupled to the objective device. The disturbance to the
object in this technique is very small since the detection is performed through
sampling of single electrons in the object with very slow rate. We have applied
the method to a quantum point contact (QPC) under a spin-orbit interaction. A
high degree of spin polarization in the vicinity of the QPC was detected when
the conductance stayed on a plateau at a half of the unit conductance quantum
($G_{\rm q}/2\equiv e^2/h$), and also on another plateau at $2e^2/h$. On the
half-quantum plateau, the degree of polarization $P$ decreased with the bias
source-drain voltage of the QPC while $P$ increased on the single-quantum
plateau, manifesting that different mechanisms of polarization were working on
these plateaus. Very long spin relaxation times in the detector quantum dot
probably due to dynamical nuclear spin polarization were observed. Anomalous
decrease of $P$ around zero-bias was observed at a Kondo-like resonance peak.",1605.04685v1
2016-07-30,Anisotropic Pauli spin blockade in hole quantum dots,"We present measurements on gate-defined double quantum dots in Ge-Si
core-shell nanowires, which we tune to a regime with visible shell filling in
both dots. We observe a Pauli spin blockade and can assign the measured leakage
current at low magnetic fields to spin-flip cotunneling, for which we measure a
strong anisotropy related to an anisotropic g-factor. At higher magnetic fields
we see signatures for leakage current caused by spin-orbit coupling between
(1,1)-singlet and (2,0)-triplet states. Taking into account these anisotropic
spin-flip mechanisms, we can choose the magnetic field direction with the
longest spin lifetime for improved spin-orbit qubits.",1608.00111v1
2016-12-05,Spin-dependent thermoelectric effects in graphene based superconductor junctions,"Using the Bogoliubov de-Gennes formalism, we investigate the charge and
spin-dependent thermoelectric effects in superconductor graphene junctions.
Results demonstrate that despite normal-superconductor junctions, there is a
temperature-dependent spin thermopower both in the graphene-based
ferromagnetic-superconductor (F-S) and ferromagnetic-Rashba spin-orbit
region-superconductor (F-RSO-S) junctions. It is also shown that in the
presence of Rashba spin-orbit interaction, the charge and spin-dependent
Seebeck coefficients can reach to their maximum up to 3.5$k_B/e$ and
2.5$k_B/e$, respectively. Remarkably, these coefficients have a zero-point
critical value with respect to magnetic exchange field and chemical potential.
This effect disappears when the Rashba coupling is absent. These results
suggest that graphene-based superconductors can be used in spin-caloritronics
devices.",1612.01461v1
2016-12-21,Spin transitions driven by electric dipole spin resonance in fluorinated single- and bilayer-graphene quantum dots,"Spin transitions driven by a periodically varying electric potential in
dilute fluorinated graphene quantum dots are investigated. Flakes of monolayer
graphene are considered as well as electrostatic electron traps induced in
bilayer graphene. The stationary states are obtained within the tight-binding
approach and are used to the basis of eigenstates to describe the system
dynamics. The dilute fluorination of the top layer lifts the valley degeneracy
of the confined states and attenuates the orbital magnetic dipole moments due
to current circulation within the flake. Moreover, the spin-orbit coupling
introduced by the surface deformation of the top layer induced by the adatoms
allows spin flips to be driven by the AC electric field. For the bilayer
quantum dots the spin flip times is substantially shorter than the experimental
spin relaxation. Dynamical effects including many-photon and multilevel
transitions are also discussed.",1612.07001v1
2018-10-16,On-chip detection of spin-selective routing in plasmonic nanocircuits,"On-chip manipulating and controlling the temporal and spatial evolution of
light is of crucial importance for information processing in future planar
integrated nanophotonics. The spin and orbital angular momentum of light, which
can be treated independently in classical macroscopic geometrical optics,
appear to be coupled on subwavelength scales. We use spin-orbit interactions in
a plasmonic achiral nano-coupler to unidirectionally excite surface plasmon
polariton modes propagating in seamlessly integrated plasmonic slot waveguides.
The spin-dependent flow of light in the proposed nanophotonic circuit allows
on-chip electrical detection of the spin state of incident photons by
integrating two germanium-based plasmonic-waveguide photodetectors.
Consequently, our device serves as a compact ($\sim$ 6 $\times$ 18 $\mu$m$^2$)
electrical sensor for photonic spin Hall dynamics. The demonstrated
configuration opens new avenues for developing highly-integrated
polarization-controlled optical devices that would exploit the spin-degree of
freedom for manipulating and controlling subwavelength optical modes in
nanophotonic systems.",1810.06922v1
2017-09-23,Spin precession in spin-orbit coupled weak links: Coulomb repulsion and Pauli quenching,"A simple model for the transmission of pairs of electrons through a weak
electric link in the form of a nanowire made of a material with strong electron
spin-orbit interaction (SOI) is presented, with emphasis on the effects of
Coulomb interactions and the Pauli exclusion principle. The constraints due to
the Pauli principle are shown to ""quench"" the coherent SOI-induced precession
of the spins when the spatial wave packets of the two electrons overlap
significantly. The quenching, which results from the projection of the pair's
spin states onto spin-up and spin-down states on the link, breaks up the
coherent propagation in the link into a sequence of coherent hops that add
incoherently. Applying the model to the transmission of Cooper pairs between
two superconductors, we find that in spite of Pauli quenching, the Josephson
current oscillates with the strength of the SOI, and may even change its sign.
Conditions for an experimental detection of these features are discussed.",1709.08022v2
2018-08-12,Tunable magnetoresistance in spin-orbit coupled graphene junctions,"Using the Landauer-B\""utikker formalism, we study the graphene
magneto-transport in the presence of Rashba spin-orbit interaction (RSOI). We
show that the angle resolved transmission probability in the proposed
structures can be tuned by the RSOI strength. The transmission spectrum show
Klein tunneling in the parallel (P) magnetization configuration which can be
blocked by the RSOI. This effect is also observable for the anti-parallel (AP)
magnetization configuration in different incident angle. The numerical results
shows that the spin-polarized conductance strongly depends on the strength of
the RSOI and can be generated by tuning the magnetic exchange field and RSOI
strength. This spin-polarized conductance is a sensitive oscillatory function
of the thickness of the RSO region. Because of the spin-flip effect, the
junction shows a spin-valve effect with large and negative magnetoresistance
(MR) and spin-magnetoresistance (SMR) in the presence of RSOI. When the RSOI is
on, the frequency and amplitude of shot-noise and Fano factor's oscillations
are also increased. These results can provide a way to extending the
application of graphene-based junctions in spintronics.",1808.03957v1
2023-01-01,Spin Hall Induced Magnetization Dynamics in Multiferroic Tunnel Junction,"The combination of spin-orbit coupling driven effects and multiferroic
tunneling properties was explored experimentally in thin Pt/Co/BTO/LSMO
multilayers. The presence of a Pt heavy metal allows for the spin
current-induced magnetization precession of Co upon radio-frequency charge
current injection. The utilization of a BTO ferroelectric tunnel barrier
separating the Co and LSMO ferromagnetic electrodes gives rise to both
tunneling-magnetoresistance and electroresistance. Using the spin-orbit torque
ferromagnetic resonance, the maganetization dynamics of the Co/Pt bilayers was
studied at room temperature. Unexpectedly the magnetization dynamics study in
the same geometry performed at low temperature reveals the existence of both Co
and LSMO resonance peaks indicating efficient spin current generation both
using the spin Hall effect in Pt and spin pumping in LSMO that tunnel via the
BTO barrier.",2301.00459v1
2023-02-15,Approximate SU(4) spin models on triangular and honeycomb lattices in twisted AB-Stacked WSe$_2$ homo-bilayer,"In this paper, we derive lattice models for the narrow moir\'e bands of the
AB-stacked twisted WSe$_2$ homobilayer through continuum model and Wannier
orbital construction. Previous work has shown that an approximate SU(4) Hubbard
model may be realized by combining spin and layer because inter-layer tunneling
is suppressed due to spin $S_z$ conservation. However, Rashba spin-orbit
coupling (SOC) was ignored in the previous analysis. Here, we show that a
Rashba SOC of reasonable magnitude can induce a finite but very small
inter-layer hopping in the final lattice Hubbard model. At total filling $n=1$,
we derive a spin-layer model on a triangular lattice in the large-U limit where
the inter-layer tunneling contributes as a sublattice-dependent transverse
Ising field for the layer pseudospin. We then show that the $n=2$ Mott
insulator is also captured by an approximate SU(4) spin model, but now on
honeycomb lattice. We comment on the possibility of a Dirac spin liquid (DSL)
and competing phases due to SU(4) anisotropy terms.",2302.07750v1
2003-09-24,Magnetic susceptibilities of diluted magnetic semiconductors and anomalous Hall-voltage noise,"The carrier spin and impurity spin densities in diluted magnetic
semiconductors are considered using a semiclassical approach. Equations of
motions for the spin densities and the carrier spin current density in the
paramagnetic phase are derived, exhibiting their coupled diffusive dynamics.
The dynamical spin susceptibilities are obtained from these equations. The
theory holds for p-type and n-type semiconductors doped with magnetic ions of
arbitrary spin quantum number. Spin-orbit coupling in the valence band is shown
to lead to anisotropic spin diffusion and to a suppression of the Curie
temperature in p-type materials. As an application we derive the Hall-voltage
noise in the paramagnetic phase. This quantity is critically enhanced close to
the Curie temperature due to the contribution from the anomalous Hall effect.",0309547v1
2011-02-17,SU(2)-invariant spin liquids on the triangular lattice with spinful Majorana excitations,"We describe a new class of spin liquids with global SU(2) spin rotation
symmetry in spin 1/2 systems on the triangular lattice, which have real
Majorana fermion excitations carrying spin S = 1. The simplest
translationally-invariant mean-field state on the triangular lattice breaks
time-reversal symmetry and is stable to fluctuations. It generically possesses
gapless excitations along 3 Fermi lines in the Brillouin zone. These intersect
at a single point where the excitations scale with a dynamic exponent z = 3. An
external magnetic field has no orbital coupling to the SU(2) spin
rotation-invariant fermion bilinears that can give rise to a transverse thermal
conductivity, thus leading to the absence of a thermal Hall effect. The Zeeman
coupling is found to gap out two-thirds of the z = 3 excitations near the
intersection point and this leads to a suppression of the low temperature
specific heat, the spin susceptibility and the Wilson ratio. We also compute
physical properties in the presence of weak disorder and discuss possible
connections to recent experiments on organic insulators.",1102.3690v2
2016-03-26,Direct coupling between charge current and spin polarization by extrinsic mechanisms in graphene,"Spintronics---the all-electrical control of the electron spin for quantum or
classical information storage and processing---is one of the most promising
applications of the two-dimensional material graphene. Although pristine
graphene has negligible spin-orbit coupling (SOC), both theory and experiment
suggest that SOC in graphene can be substantially enhanced by extrinsic means,
such as functionalization by adatom impurities. We present a theory of
transport in graphene that accounts for the full spin-coherent dynamics of the
carriers, including hitherto-neglected spin precession processes during
resonant scattering with dilute impurities. We identify a novel ""anisotropic
spin precession scattering"" process, specific to two dimensions and extrinsic
SOC, which contributes to a large current-induced spin polarization in
graphene. The theory also yields a comprehensive description of the spin
relaxation mechanisms in impurity-decorated graphene: the Elliot-Yafet and
Dyakonov-Perel relaxation rates are both present, and we find that the latter
can dominate for some choices of carrier density and impurity strength. This
provides theoretical foundations for designing future graphene-based integrated
spintronic devices.",1603.08107v2
2014-05-06,Mechanically induced spin resonance in a carbon nanotube,"The electron spin is a promising qubit candidate for quantum computation and
quantum information. Here we propose and analyze a mechanically-induced single
electron spin resonance, which amounts to a rotation of the spin about the
$x$-axis in a suspended carbon nanotube. The effect is based on the coupling
between the spin and the mechanical degree of freedom due to the intrinsic
curvature-induced spin-orbit coupling. A rotation about the $z$-axis is
obtained by the off-resonant external electric driving field. Arbitrary-angle
rotations of the single electron spin about any axis in the $x$-$z$ plane can
be obtained with a single operation by varying the frequency and the strength
of the external electric driving field. With multiple steps combining the
rotations about the $x$- and $z$-axes, arbitrary-angle rotations about
arbitrary axes can be constructed, which implies that any single-qubit gate of
the electron spin qubit can be performed. We simulate the system numerically
using a master equation with realistic parameters.",1405.1347v1
2019-07-03,Anisotropy of spin-transfer torques and Gilbert damping induced by Rashba coupling,"Spin-transfer torques (STT), Gilbert damping (GD), and effective spin
renormalization (ESR) are investigated microscopically in a 2D Rashba
ferromagnet with spin-independent Gaussian white-noise disorder. Rashba
spin-orbit coupling induced anisotropy of these phenomena is thoroughly
analysed. For the case of two partly filled spin subbands, a remarkable
relation between the anisotropic STT, GD, and ESR is established. In the
absence of magnetic field and other torques on magnetization, this relation
corresponds to a current-induced motion of a magnetic texture with the
classical drift velocity of conduction electrons. Finally, we compute spin
susceptibility of the system and generalize the notion of spin-polarized
current.",1907.02041v3
2020-12-08,Spin emitters beyond the point dipole approximation in nanomagnonic cavities,"Control over transition rates between spin states of emitters is crucial in a
wide variety of fields ranging from quantum information science to the
nanochemistry of free radicals. We present an approach to drive a both electric
and magnetic dipole-forbidden transition of a spin emitter by placing it in a
nanomagnonic cavity, requiring a description of both the spin emitter beyond
the point dipole approximation and the vacuum magnetic fields of the
nanomagnonic cavity with a large spatial gradient over the volume of the spin
emitter. We specifically study the SiV$^-$ defect in diamond, whose
Zeeman-split ground states comprise a logical qubit for solid-state quantum
information processing, coupled to a magnetic nanoparticle serving as a model
nanomagnonic cavity capable of concentrating microwave magnetic fields into
deeply subwavelength volumes. Through first principles modeling of the SiV$^-$
spin orbitals, we calculate the spin transition densities of magnetic
dipole-allowed and -forbidden transitions and calculate their coupling rates to
various multipolar modes of the nanomagnonic cavity. We envision using such a
framework for quantum state transduction and state preparation of spin qubits
at GHz frequency scales.",2012.04662v1
2018-06-07,Spin accumulation and dynamics in inversion-symmetric van der Waals crystals,"Inversion symmetric materials are forbidden to show an overall spin texture
in their band structure in the presence of time-reversal symmetry. However, in
van der Waals materials which lack inversion symmetry within a single layer, it
has been proposed that a layer-dependent spin texture can arise leading to a
coupled spin-layer degree of freedom. Here we use time-resolved Kerr rotation
in inversion symmetric WSe$_{2}$ and MoSe$_{2}$ bulk crystals to study this
spin-layer polarization and unveil its dynamics. Our measurements show that the
spin-layer relaxation time in WSe$_2$ is limited by phonon-scattering at high
temperatures and that the inter-layer hopping can be tunned by a small in-plane
magnetic field at low temperatures, enhancing the relaxation rates. We find a
significantly lower lifetime for MoSe$_{2}$ which agrees with theoretical
expectations of a spin-layer polarization stabilized by the larger spin-orbit
coupling in WSe$_2$.",1806.02558v1
2020-03-03,Spin Hall Effects in Antiferromagnets,"Recent experiments demonstrate that antiferromagnets exhibit the spin Hall
effect. We study a tight-binding model of an antiferromagnet on a square
lattice with Rashba spin-orbit coupling and disorder. By exact diagonalization
of a finite system connected to reservoirs within the
Landauer-B$\ddot{\text{u}}$ttiker formalism, we compute the transverse spin
Hall current in response to a longitudinal voltage difference. Surprisingly,
the spin Hall conductance can be considerably larger in antiferromagnets than
in normal metals. We compare our results to the Berry-phase-induced spin Hall
effect governed by the intrinsic contribution in the Kubo formula. The
Berry-phase-induced intrinsic spin Hall conductivity in bulk systems shows the
opposite behavior: large exchange couplings in AFs drastically reduce the spin
Hall current.",2003.01714v2
2022-06-23,Valley spin-acoustic resonance in MoS${\bf _2}$ monolayers,"The band structure of a monolayer MoS$_2$ comprises of spin-split subbands,
owing to the mutual presence of broken inversion symmetry and strong spin-orbit
coupling. In the conduction band, spin-valley coupled subbands cross each other
at finite momenta, and they are valley-degenerate. When exposed to surface
acoustic waves, the emerging strain-induced effective magnetic field can give
rise to spin-flip transitions between the spin-split subbands in the vicinity
of subbands crossing point, resulting in the emergence of a spin-acoustic
resonance and the acoustoelectric current. An external magnetic field breaks
the valley degeneracy resulting in the valley-selective splitting of
spin-acoustic resonances both in surface acoustic wave absorption and
acoustoelectric current.",2206.11551v1
2023-05-10,Collisionless dynamics of superconducting gap excited by spin-splitting field,"We study the coherent dynamic interaction of a time-dependent spin-splitting
field with the homogeneous superconducting order parameter $\Delta(t)$ mediated
by spin-orbit coupling using the time-dependent Bogoliubov-de Gennes theory. In
the first part of the work we show that linear response of the superconductor
is strongly affected by the Zeeman field and spin-flip processes, giving rise
to multiple resonant frequencies of the superconducting Higgs modes. These
modes can be excited either by a quench, or by an additional non-stationary
component of the spin-splitting field, which couples linearly to the Higgs
modes. In the second part, we analyze the nonadiabatic dynamics of
quasiparticle states arising from the intersection of spectral branches from
different spin subbands, which can be provoked by a linearly growing Zeeman
field. We provide insights into the dependence of the order parameter
$\Delta(t)$ on this field and interference effects caused by tunneling of
states at the avoided crossing points. We also show that since the nonadiabatic
tunneling is related to spin-flip processes, the quasiparticle gas experiences
a dynamic magnetization that contributes to its spin susceptibility.",2305.06201v1
2023-12-22,Opportunities for the direct manipulation of a phase-driven Andreev spin qubit,"In a Josephson junction, the transfer of Cooper pairs from one superconductor
to the other one can be associated with the formation of Andreev bound states.
In a Josephson junction made with a semiconducting nanowire, the spin
degeneracy of these Andreev states can be broken thanks to the presence of
spin-orbit coupling and a finite phase difference between the two
superconducting electrodes. The lifting of the spin degeneracy opened the way
to the realization of Andreev spin qubits that do not require the application
of a large magnetic field. So far the operation of these qubits relied on a
Raman process involving two microwave tones and a third Andreev state [M. Hays
et al., Science 373, 430 (2021)]. Still, time-reversal preserving impurities in
the nanowire allow for spin-flip scattering processes. Here, using the
formalism of scattering matrices, we show that these processes generically
couple Andreev states with opposite spins. In particular, the non-vanishing
current matrix element between them allows for the direct manipulation of
phase-driven Andreev spin qubits, thereby circumventing the use of the
above-mentioned Raman process.",2312.14865v1
2024-01-27,Dragging of the particle spin and spin-spin coupling effect on its periapsis shift,"The periapsis shift (PS) of spinning test particles in the equatorial plane
of arbitrary stationary and axisymmetric spacetime is studied using the
post-Newtonian method. The result is expressed as a half-integer power series
of $M/p$ where $M$ is the spacetime mass and $p$ is the semilatus rectum. The
coefficients of the series are polynomials of the particle spin, the asymptotic
expansion coefficients of the metric functions and the eccentricity of the
orbit. The particle spin is shown to have a similar effect as the
Lense-Thirring (LT) effect on the PS, and both of them appear from the
$(M/p)^{-3/2}$ order in the PS. The coupling between the spacetime and particle
spins will increase (or decrease) the PS if they are parallel (or
antiparallel). For Jupiter and Saturn rotating around the Sun and exceptionally
designed satellites around Mercury and Moon, the particle spin effect can be
comparable to the LT one in size. The PS in other spacetime studied are not
distinguishable from that in the Kerr spacetime to the $(M/p)^{-3/2}$ order.",2401.15342v1
2004-01-12,Spin Transport in Two Dimensional Hopping Systems,"A two dimensional hopping system with Rashba spin-orbit interaction is
considered. Our main interest is concerned with the evolution of the spin
degree of freedom of the electrons. We derive the rate equations governing the
evolution of the charge density and spin polarization of this system in the
Markovian limit in one-particle approximation. If only two-site hopping events
are taken into account, the evolution of the charge density and of the spin
polarization is found to be decoupled. A critical electric field is found,
above which oscillations are superimposed on the temporal decay of the total
polarization. A coupling between charge density and spin polarization occurs on
the level of three-site hopping events. The coupling terms are identified as
the anomalous Hall effect and the recently proposed spin Hall effect. Thus, an
unpolarized charge current through a sheet of finite width leads to a
transversal spin accumulation in our model system.",0401171v1
2004-09-13,DC Spin Current Generation in a Rashba-type Quantum Channel,"We propose and demonstrate theoretically that resonant inelastic scattering
(RIS) can play an important role in dc spin current generation. The RIS makes
it possible to generate dc spin current via a simple gate configuration: a
single finger-gate that locates atop and orients transversely to a quantum
channel in the presence of Rashba spin-orbit interaction. The ac biased
finger-gate gives rise to a time-variation in the Rashba coupling parameter,
which causes spin-resolved RIS, and subsequently contributes to the dc spin
current. The spin current depends on both the static and the dynamic parts in
the Rashba coupling parameter, $\alpha_0$ and $\alpha_1$, respectively, and is
proportional to $\alpha_0 \alpha_1^2$. The proposed gate configuration has the
added advantage that no dc charge current is generated. Our study also shows
that the spin current generation can be enhanced significantly in a double
finger-gate configuration.",0409291v3
2007-06-17,Spin magnetotransport in two-dimensional hole systems,"Spin current of two-dimensional holes occupying the ground-state subband in
an asymmetric quantum well and interacting with static disorder potential is
calculated in the presence of a weak magnetic field H perpendicular to the well
plane. Both spin-orbit coupling and Zeeman coupling are taken into account. It
is shown that the applied electric field excites both the transverse
(spin-Hall) and diagonal spin currents, the latter changes its sign at a finite
H and becomes greater than the spin-Hall current as H increases. The effective
spin-Hall conductivity introduced to describe the spin response in Hall bars is
considerably enhanced by the magnetic field in the case of weak disorder and
demonstrates a non-monotonic dependence on H.",0706.2468v1
2014-08-27,Control of vibrational states by spin-polarized transport in a carbon nanotube resonator,"We study spin-dependent transport in a suspended carbon nanotube quantum dot
in contact with two ferromagnetic leads and with the dot's spin coupled to the
flexural mechanical modes. The spin-vibration interaction induces spin-flip
processes between the two energy levels of the dot. This interaction arises
from the spin-orbit coupling or a magnetic field gradient. The inelastic
vibration-assisted spin flips give rise to a mechanical damping and, for an
applied bias voltage, to a steady nonequilibrium occupation of the harmonic
oscillator. We analyze these effects as function of the energy-level separation
of the dot and the magnetic polarization of the leads. Depending on the
magnetic configuration and the bias-voltage polarity, we can strongly cool a
single mode or pump energy into it. In the latter case, we find that within our
approximation, the system approaches eventually a regime of mechanical
instability. Furthermore, owing to the sensitivity of the electron transport to
the spin orientation, we find signatures of the nanomechanical motion in the
current-voltage characteristic. Hence, the vibrational state can be read out in
transport measurements.",1408.6357v3
2015-06-26,One-dimensional spin texture of Bi(441); Quantum Spin Hall properties without a topological insulator,"The high index (441) surface of bismuth has been studied using Scanning
Tunnelling Microscopy (STM), Angle Resolved Photoemission Spectroscopy (APRES)
and spin-resolved ARPES. The surface is strongly corrugated, exposing a regular
array of (110)-like terraces. Two surface localised states are observed, both
of which are linearly dispersing in one in-plane direction ($k_x$), and
dispersionless in the orthogonal in-plane direction ($k_y$), and both of which
have a Dirac-like crossing at $k_x$=0. Spin ARPES reveals a strong in-plane
polarisation, consistent with Rashba-like spin-orbit coupling. One state has a
strong out-of-plane spin component, which matches with the miscut angle,
suggesting its {possible} origin as an edge-state. The electronic structure of
Bi(441) has significant similarities with topological insulator surface states
and is expected to support one dimensional Quantum Spin Hall-like coupled
spin-charge transport properties with inhibited backscattering, without
requiring a topological insulator bulk.",1506.08017v1
2016-02-25,Majorana spintronics,"We propose a systematic magnetic-flux-free approach to detect, manipulate and
braid Majorana fermions in a semiconductor nanowire-based topological Josephson
junction by utilizing the Majorana spin degree of freedom. We find an intrinsic
$\pi$-phase difference between spin-triplet pairings enforced by the Majorana
zeros modes (MZMs) at the two ends of a one-dimensional spinful topological
superconductor. This $\pi$-phase is identified to be a spin-dependent
superconducting phase, referred to as the spin-phase, which we show to be
tunable by controlling spin-orbit coupling strength via electric gates. This
electric controllable spin-phase not only affects the coupling energy between
MZMs but also leads to a fractional Josephson effect in the absence of any
applied magnetic flux, which enables the efficient topological qubit readout.
We thus propose an all-electrically controlled superconductor-semiconductor
hybrid circuit to manipulate MZMs and to detect their non-Abelian braiding
statistics properties. Our work on spin properties of topological Josephson
effects potentially opens up a new thrust for spintronic applications with
Majorana-based semiconductor quantum circuits.",1602.08093v2
2018-05-31,Observation of spin-valley coupling induced large spin lifetime anisotropy in bilayer graphene,"We report the first observation of a large spin lifetime anisotropy in
bilayer graphene (BLG) fully encapsulated between hexagonal boron nitride. We
characterize the out-of-plane ($\tau_\perp$) and in-plane ($\tau_\parallel$)
spin lifetimes by oblique Hanle spin precession. At 75~K and the charge
neutrality point (CNP) we observe a strong anisotropy of
$\tau_\perp/\tau_\parallel$ = 8 $\pm$ 2. This value is comparable to
graphene/TMD heterostructures, whereas our high quality BLG provides with
$\tau_\perp$ up to 9~ns, a more than two orders of magnitude larger spin
lifetime. The anisotropy decreases to 3.5 $\pm$ 1 at a carrier density of n =
$6\times 10^{11}~$cm$^{-2}$. Temperature dependent measurements show above 75~K
a decrease of $\tau_\perp/\tau_\parallel$ with increasing temperature, reaching
the isotropic case close to room temperature. We explain our findings with
electric field induced spin-valley coupling arising from the small intrinsic
spin orbit fields in BLG of 12~$\mu$eV at the CNP.",1805.12420v1
2023-03-21,Kondo enhancement of current induced spin accumulation in a quantum dot,"Weak spin-orbit coupling produces very limited current induced spin
accumulation in semiconductor nanostructures. We demonstrate a possibility to
increase parametrically the spin polarization using the Kondo effect. As a
model object we consider a quantum dot side coupled to a quantum wire taking
into account the spin dependent electron tunneling from the wire to the dot.
Using the nonequilibrium Green's functions, we show that the many body
correlations between the quantum dot and the quantum wire can increase the
current induced spin accumulation at low temperatures by almost two orders of
magnitude for the moderate system parameters. The enhancement is related to the
Kondo peak formation in the density of states and the spin instability due to
the strong Coulomb interaction. This effect may be useful to electrically
manipulate the localized electron spins in quantum dots for their quantum
applications.",2303.11778v1
2021-11-25,Chirality-Induced Spin Filtering in Pseudo Jahn-Teller Molecules,"Chirality-induced spin selectivity (CISS) refers to an ability to induce a
spin polarization of an electron transmitted through chiral materials. An
important experimental observation is that incredibly large spin polarization
is realized at room temperature even for organic molecules that have weak
spin-orbit coupling (SOC), although SOC is the only interaction that can
manipulate the electrons' spins in the setups. Therefore, the mechanism of the
CISS needs to be constructed in a way insensitive to or enhancing the magnitude
of the SOC strength. In this paper, we describe a theoretical study of CISS
with a model chiral molecule that belongs to the point group $\mathrm{C}_3$. In
this molecule, electronic translational and rotational degrees of freedom for
an injected electron are coupled to one another via the nuclear vibrational
mode with a pseudo Jahn-Teller effect. By properly taking the molecular
symmetry as well as the time-reversal symmetry into account and classifying the
molecular ground states by their angular- and spin-momentum quantum numbers, we
show that the chiral molecule can act as an efficient spin filter. The
efficiency of this spin filtering can be nearly independent of the SOC strength
in this model, while it well exceeds the spin polarization relying solely on
the SOC. The nuclear vibrations turned out to have the role of not only
mediating the translation-rotation coupling, but also enhancing the
spin-filtering efficiency.",2111.12917v2
2016-09-01,Coupled orbital and spin evolution of the CoRoT-7 two-planet system using a Maxwell viscoelastic rheology,"We investigate the orbital and rotational evolution of the CoRoT-7 two-planet
system, assuming that the innermost planet behaves like a Maxwell body. We
numerically resolve the coupled differential equations governing the
instantaneous deformation of the inner planet together with the orbital motion
of the system. We show that, depending on the relaxation time for the
deformation of the planet, the orbital evolution has two distinct behaviours:
for relaxation times shorter than the orbital period, we reproduce the results
from classic tidal theories, for which the eccentricity is always damped.
However, for longer relaxation times, the eccentricity of the inner orbit is
secularly excited and can grow to high values. This mechanism provides an
explanation for the present high eccentricity observed for CoRoT-7 b, as well
as for other close-in super-Earths in multiple planetary systems.",1609.00319v1
2018-01-08,Stability of the Nagaoka-type Ferromagnetic State in a $t_{2g}$ Orbital System on a Cubic Lattice,"We generalize the previous exact results of the Nagaoka-type itinerant
ferromagnetic states in a three dimensional $t_{2g}$-orbital system to allow
for multiple holes. The system is a simple cubic lattice with each site
possessing $d_{xy}$, $d_{yz}$, and $d_{xz}$ orbitals, which allow
two-dimensional hopping within each orbital plane. In the strong coupling limit
of $U\to \infty$, the orbital-generalized Nagaoka ferromagnetic states are
proved degenerate with the ground state in the thermodynamic limit when the
hole number per orbital layer scales slower than $L^{\frac{1}{2}}$. This result
is valid for arbitrary values of the ferromagnetic Hund's coupling $J>0$ and
inter-orbital repulsion $V\ge 0$. The stability of the Nagaoka-type state at
finite electron densities with respect to a single spin-flip is investigated.
These results provide helpful guidance for studying the mechanism of itinerant
ferromagnetism for the $t_{2g}$-orbital materials.",1801.02583v2
2020-11-03,Controlling directed atomic motion and second-order tunneling of a spin-orbit-coupled atom in optical lattices,"We theoretically explore the tunneling dynamics for the tight-binding (TB)
model of a single spin-orbit-coupled atom trapped in an optical lattice
subjected to lattice shaking and to time-periodic Zeeman field. By means of
analytical and numerical methods, we demonstrate that the spin-orbit (SO)
coupling adds some new results to the tunneling dynamics in both multiphoton
resonance and far-off-resonance parameter regimes. When the driving frequency
is resonant with the static Zeeman field (multi-photon resonances), we obtain
an unexpected new dynamical localization (DL) phenomenon where the single
SO-coupled atom is restricted to making perfect two-site Rabi oscillation
accompanied by spin flipping.By using the unconventional DL phenomenon, we are
able to generate a ratchetlike effect which enables directed atomic motion
towards different directions and accompanies periodic spin-flipping under the
action of SO coupling. For the far-off-resonance case, we show that by
suppressing the usual inter-site tunneling alone, it is possible to realize a
type of spin-conserving second-order tunneling between next-nearest-neighboring
sites, which is not accessible in the conventional lattice system without SO
coupling. We also show that simultaneous controls of the usual inter-site
tunneling and the SO-coupling-related second-order-tunneling are necessary for
quasienergies flatness (collapse) and completely frozen dynamics to exist.
These results may be relevant to potential applications such as spin-based
quantum information processing and design of novel spintronics devices.",2011.01399v2
2002-12-03,Tunneling measurement of quantum spin oscillations,"We consider the problem of tunneling between two leads via a localized spin
1/2 or any other microscopic system which can be modeled by a two-level
Hamiltonian. We assume that a constant magnetic field ${\bf B}_0$ acts on the
spin, that electrons in the leads are in the thermal equilibrium and that the
tunneling electrons are coupled to the spin through exchange and spin-orbit
interactions. Using the non-equilibrium Keldysh formalism we find the
dependence of the spin-spin and current-current correlation functions on the
applied voltage between leads $V$, temperature $T$, ${\bf B}_0$, and on the
degree and orientation ${\bf m}_{\alpha}$ of spin polarization of the electrons
in the right ($\alpha=$R) and left ($\alpha=$L) leads. We compare our results
of a full quantum-mechanical treatment of the tunneling-via-spin model with
those previously obtained in the quasi-classical approach, and discuss the
experimental results observed using STM dynamic probes of the localized spin.",0212049v3
2004-07-01,Rashba spin splitting in quantum wires,"This article presents an overview of results pertaining to electronic
structure, transport properties, and interaction effects in ballistic quantum
wires with Rashba spin splitting. Limits of weak and strong spin--orbit
coupling are distinguished, and spin properties of the electronic states
elucidated. The case of strong Rashba spin splitting where the spin--precession
length is comparable to the wire width turns out to be particularly
interesting. Hybridization of spin--split quantum--wire subbands leads to an
unusual spin structure where the direction of motion for electrons can fix
their spin state. This peculiar property has important ramifications for linear
transport in the quantum wire, giving rise to spin accumulation without
magnetic fields or ferromagnetic contacts. A description for interacting
Rashba--split quantum wires is developed, which is based on a generalization of
the Tomonaga--Luttinger model.",0407036v1
2011-04-13,Spin diffusion in $n$-type (111) GaAs quantum wells,"We utilize the kinetic spin Bloch equation approach to investigate the
steady-state spin diffusion in $n$-type (111) GaAs quantum wells, where the
in-plane components of the Dresselhaus spin-orbit coupling term and the Rashba
term can be partially canceled by each other. A peak of the spin diffusion
length due to the cancellation is predicted in the perpendicular electric field
dependence. It is shown that the spin diffusion length around the peak can be
markedly controlled via temperature and doping. When the electron gas enters
into the degenerate regime, the electron density also leads to observable
influence on the spin diffusion in the strong cancellation regime. Furthermore,
we find that the spin diffusion always presents strong anisotropy with respect
to the direction of the injected spin polarization. The anisotropic spin
diffusion depends on whether the electric field is far away from or in the
strong cancellation regime.",1104.2496v2
2011-04-21,Switching spin and charge between edge states in topological insulator constrictions,"Since the prediction of a new topological state of matter in graphene,
materials acting as topological insulators have attracted wide attention.
Shortly after the theoretical proposal for a mercury telluride (HgTe)-based
two-dimensional topological insulator, the observation of the quantum spin Hall
effect and non-local edge transport brought compelling experimental evidence
for quantized conductance due to edges states. The spin orientation and
propagation direction of such helical edge states are inherently connected,
providing protection against backscattering. However, these features conversely
render controlled spin operations such as spin switching difficult. Here we
therefore propose constrictions as connectors between opposite edge (and spin)
states in HgTe. We demonstrate how the coupling between edge states, which
overlap in the constriction, can be employed both for steering the charge flow
into different edge modes and for controlled spin switching. This gives rise to
a three-state charge and spin transistor function. Unlike in a conventional
spin transistor, the switching does not rely on a tunable Rashba spin-orbit
interaction, but on the energy dependence of the edge state wavefunctions.
Based on this mechanism, and supported by numerical transport calculations, we
present two different ways to control spin- and charge-currents depending on
the gating of the constriction.",1104.4284v1
2011-07-30,Electron spin dephasing in two-dimensional systems with anisotropic scattering,"We develop a microscopic theory of spin relaxation of a two-dimensional
electron gas in quantum wells with anisotropic electron scattering. Both
precessional and collision-dominated regimes of spin dynamics are studied. It
is shown that, in quantum wells with noncentrosymmetric scatterers, the
in-plane and out-of-plane spin components are coupled: spin dephasing of
carriers initially polarized along the quantum well normal leads to the
emergence of an in-plane spin component even in the case of isotropic
spin-orbit splitting. In the collision-dominated regime, the
spin-relaxation-rate tensor is expressed in terms of the electric conductivity
tensor. We also study the effect of an in-plane and out-of-plane external
magnetic field on spin dephasing and show that the field dependence of electron
spin can be very intricate.",1108.0107v1
2013-02-11,Electrical control over single hole spins in nanowire quantum dots,"Single electron spins in semiconductor quantum dots (QDs) are a versatile
platform for quantum information processing, however controlling decoherence
remains a considerable challenge. Recently, hole spins have emerged as a
promising alternative. Holes in III-V semiconductors have unique properties,
such as strong spin-orbit interaction and weak coupling to nuclear spins, and
therefore have potential for enhanced spin control and longer coherence times.
Weaker hyperfine interaction has already been reported in self-assembled
quantum dots using quantum optics techniques. However, challenging fabrication
has so far kept the promise of hole-spin-based electronic devices out of reach
in conventional III-V heterostructures. Here, we report gate-tuneable hole
quantum dots formed in InSb nanowires. Using these devices we demonstrate Pauli
spin blockade and electrical control of single hole spins. The devices are
fully tuneable between hole and electron QDs, enabling direct comparison
between the hyperfine interaction strengths, g-factors and spin blockade
anisotropies in the two regimes.",1302.2648v1
2014-02-20,Rashba-Zeeman-effect-induced spin filtering energy windows in a quantum wire,"We perform a numerical study on the spin-resolved transport in a quantum wire
(QW) under the modulation of both Rashba spin-orbit coupling (SOC) and a
perpendicular magnetic field (MF) by adopting the developed Usuki
transfer-matrix method in combination with the Landauer-Buttiker formalism.
Wide spin filtering energy windows can be achieved in this system for a
spin-unpolarized injection. In addition, both the width of these energy windows
and the magnitude of the spin conductance within these energy widows can be
tuned by varying the Rashba SOC strength, which can be apprehended by analyzing
the energy dispersions and the spin-polarized density distributions inside the
QW, respectively. Further study also demonstrates that these
Rashba-SOC-controlled spin filtering energy windows show a strong robustness
against disorders. These findings may not only benefit to further understand
the spin-dependent transport properties of the QW in the presence of external
fields but also provide a theoretical instruction to design a spin filter
device.",1402.4909v1
2014-07-30,Room Temperature Spin Pumping in Topological Insulator Bi2Se3,"Three-dimensional (3D) topological insulators are known for their strong
spin-orbit coupling and the existence of spin-textured topological surface
states which could be potentially exploited for spintronics. Here, we
investigate spin pumping from a metallic ferromagnet (CoFeB) into a 3D
topological insulator (Bi2Se3) and demonstrate successful spin injection from
CoFeB into Bi2Se3 and the direct detection of the electromotive force generated
by the inverse spin Hal effect (ISHE) at room temperature. The spin pumping,
driven by the magnetization dynamics of the metallic ferromagnet, introduces a
spin current into the topological insulator layer, resulting in a broadening of
the ferromagnetic resonance (FMR) linewidth. We find that the FMR linewidth
more than quintuples, the spin mixing conductance can be as large as
3.4*10^20m^-2 and the spin Hall angle can be as large as 0.23 in the Bi2Se3
layer.",1407.7940v1
2015-09-03,Nanomechanical detection of the spin Hall effect,"The spin Hall effect creates a spin current in response to a charge current
in a material that has strong spin-orbit coupling. The size of the spin Hall
effect in many materials is disputed, requiring independent measurements of the
effect. We develop a novel mechanical method to measure the size of the spin
Hall effect, relying on the equivalence between spin and angular momentum. The
spin current carries angular momentum, so the flow of angular momentum will
result in a mechanical torque on the material. We determine the size and
geometry of this torque and demonstrate that it can be measured using a
nanomechanical device. Our results show that measurement of the spin Hall
effect in this manner is possible and also opens possibilities for actuating
nanomechanical systems with spin currents.",1509.01269v3
2016-01-06,Spin helical states and spin transport of the line defect in silicene lattice,"We investigated the electronic structure of a silicene-like lattice with a
line defect under the consideration of spin-orbit coupling. In the bulk energy
gap, there are defect related bands corresponding to spin helical states
localized beside the defect line: spin-up electrons flow forward on one side
near to the line defect and move backward on the other side, and vice verse for
spin-down electrons. When the system is subjected to random distribution of
spin-flipping scatterers, electrons suffer much less spin-flipped scattering
when they transport along the line defect than in the bulk. An electric gate
above the line defect can tune the spin-flipped transmission, which makes the
line defect as a spin-controllable waveguide.",1601.01277v1
2016-02-01,Equations of motion of test particles for solving the spin-dependent Boltzmann-Vlasov equation,"A consistent derivation of the equations of motion (EOMs) of test particles
for solving the spin-dependent Boltzmann-Vlasov equation is presented. The
resulting EOMs in phase space are similar to the canonical equations in
Hamiltonian dynamics, and the EOM of spin is the same as that in the Heisenburg
picture of quantum mechanics. Considering further the quantum nature of spin
and choosing the direction of total angular momentum in heavy-ion reactions as
a reference of measuring nucleon spin, the EOMs of spin-up and spin-down
nucleons are given separately. The key elements affecting the spin dynamics in
heavy-ion collisions are identified. The resulting EOMs provide a solid
foundation for using the test-particle approach in studying spin dynamics in
heavy-ion collisions at intermediate energies. Future comparisons of model
simulations with experimental data will help constrain the poorly known
in-medium nucleon spin-orbit coupling relevant for understanding properties of
rare isotopes and their astrophysical impacts.",1602.00404v2
2018-04-27,Pseudospin-driven spin relaxation mechanism in graphene,"The possibility of transporting spin information over long distances in
graphene, owing to its small intrinsic spin-orbit coupling (SOC) and the
absence of hyperfine interaction, has led to intense research into spintronic
applications. However, measured spin relaxation times are orders of magnitude
smaller than initially predicted, while the main physical process for spin
dephasing and its charge-density and disorder dependences remain unconvincingly
described by conventional mechanisms. Here, we unravel a spin relaxation
mechanism for nonmagnetic samples that follows from an entanglement between
spin and pseudospin driven by random SOC, which makes it unique to graphene.
The mixing between spin and pseudospin-related Berry's phases results in fast
spin dephasing even when approaching the ballistic limit, with increasing
relaxation times away from the Dirac point, as observed experimentally. The SOC
can be caused by adatoms, ripples or even the substrate, suggesting novel spin
manipulation strategies based on the pseudospin degree of freedom.",1804.10682v1
2016-08-02,Spintronics of Organometal Trihalide Perovskites,"The family of organometal trihalide perovskite (OTP), CH3NH3PbX3 (where X is
halogen) has recently revolutionized the photovoltaics field and shows promise
in a variety of optoelectronic applications. The characteristic spin properties
of charge and neutral excitations in OTPs are influenced by the large
spin-orbit coupling of the Pb atoms, which may lead to spin-based device
applications. Here we report the first studies of pure spin-current and
spin-aligned carrier injection in OTP spintronics devices using spin-pumping
and spin-injection, respectively. We measure a relatively large
inverse-spin-Hall effect using pulsed microwave excitation in OTP devices at
resonance with a ferromagnetic substrate, from which we derive room temperature
spin diffusion length, lambda_sd~9nm; and low-temperature giant
magnetoresistance in OTP-based spin-valves from which we estimate
lambda_sd~85nm.",1608.00993v1
2012-05-16,Spin transport and spin dephasing in zinc oxide,"The wide bandgap semiconductor ZnO is interesting for spintronic applications
because of its small spin-orbit coupling implying a large spin coherence
length. Utilizing vertical spin valve devices with ferromagnetic electrodes
(TiN/Co/ZnO/Ni/Au), we study the spin-polarized transport across ZnO in
all-electrical experiments. The measured magnetoresistance agrees well with the
prediction of a two spin channel model with spin-dependent interface
resistance. Fitting the data yields spin diffusion lengths of 10.8nm (2K),
10.7nm (10K), and 6.2nm (200K) in ZnO, corresponding to spin lifetimes of 2.6ns
(2K), 2.0ns (10K), and 31ps (200K).",1205.3666v3
2018-03-29,Detecting End-States of Topological Quantum Paramagnets via Spin Hall Noise Spectroscopy,"We theoretically study the equilibrium spin current fluctuations and the
corresponding charge noise generated by inverse spin Hall effect (ISHE) in a
metal with strong spin-orbit coupling deposited on top of a quantum paramagnet.
It is shown that the charge noise power spectra measured along different
spatial axes can directly probe the different spin components of the boundary
dynamic spin correlations of the quantum paramagnet. We report the utility of
this ISHE-facilitated spin noise probe as a tool to unambiguously detect
topological phase transitions in an S=1/2 quantum spin ladder that hosts a
trivial ground state of singlet product states, but topologically-protected
fractional spin excitations localized at its ends. Our work demonstrates the
general usefulness of the ISHE-mediated spin noise spectroscopy for the
detection of topological phases in quantum paramagnets.",1803.11239v1
2018-07-13,Free-Layer-Thickness-dependence of the Spin Galvanic Effect with Spin Rotation Symmetry,"Spin-orbit coupling near the surface of a ferromagnetic metal gives rises to
spin-to-charge conversion with symmetry different from the conventional inverse
spin Hall effect. We have previously observed this spin galvanic effect with
spin rotation symmetry (SGE-SR) in a spin valve under a temperature gradient.
Here we show there are two processes that contribute to the SGE-SR, one of
which is sensitive to the free magnetic layer thickness, while the other only
depends on the interface of the free layer. Based on the
free-layer-thickness-dependent study, we extrapolate the spin diffusion length
of Py to be 3.9+/-0.2 nm. We also propose that the SGE-SR can help to
quantitatively study the spin Seebeck effect in metallic magnetic films.",1807.04918v2
2019-11-04,The generic phase diagram of spin relaxation in solids and the Loschmidt echo,"The spin relaxation time in solids is determined by several competing energy
scales and processes and distinct methods are called for to analyze the various
regimes. We present a stochastic model for the spin dynamics in solids which is
equivalent to solving the spin Boltzmann equation and takes the relevant
processes into account on equal footing. The calculations reveal yet unknown
parts of the spin-relaxation phase diagram, where strong spin-dephasing occurs
in addition to spin-relaxation. Spin-relaxation times are obtained for this
regime by introducing the numerical Loschmidt echo. This allows us to construct
a generic approximate formula for the spin-relaxation time, $\tau_{\text{s}}$,
for the entire phase diagram, involving the quasiparticle scattering rate,
$\Gamma$, spin-orbit coupling strength, $\mathcal{L}$, and a magnetic term,
$\Delta_{\text{Z}}$ due to the Zeeman effect. The generic expression reads as
$\hbar/\tau_{\text{s}}\approx \Gamma\cdot \mathcal{L}^2
/(\Gamma^2+\mathcal{L}^2+\Delta_{\text{Z}}^2)$.",1911.01482v1
2020-06-14,"MoS2 thin-film transistors spin-states, of conduction electrons and vacancies, distinguished by operando electron spin resonance","Transition metal dichalcogenide MoS2 is a two-dimensional material,
attracting much attention for next-generation applications thanks to rich
functionalities stemmed from the crystal structure. Many experimental and
theoretical works have focused on the spin-orbit interaction which couples the
valley and spin degree of freedom so that the spin-states can be electrically
controllable. However, the spin-states of charge carriers and vacancies have
not been yet elucidated directly from a microscopic viewpoint. We report the
spin-states in thin-film electric double-layer transistors using operando
electron spin resonance (ESR) spectroscopy. We have observed clearly different
ESR signals of the conduction electrons and vacancies, and distinguished the
corresponding spin-states from the signals and theoretical calculations,
evaluating the gate-voltage dependence and spin-susceptibility and g-factor
temperature dependence. This analysis gives deep insight into the MoS2
magnetism and clearly indicates the lower charge mobilities compared to
graphene, which would be useful for improvements of the device characteristics
and new applications.",2006.07842v1
2021-04-07,Spin-helical detection in a semiconductor quantum device with ferromagnetic contacts,"Spin-helical states, which arise in quasi-one-dimensional (1D) channels with
spin-orbital (SO) coupling, underpin efforts to realize topologically-protected
quantum bits based on Majorana modes in semiconductor nanowires. Detecting
helical states is challenging due to non-idealities present in real devices.
Here we show by means of tight-binding calculations that by using ferromagnetic
contacts it is possible to detect helical modes with high sensitivity even in
the presence of realistic device effects, such as quantum interference. This is
possible because of the spin-selective transmission properties of helical
modes. In addition, we show that spin-polarized contacts provide a unique path
to investigate the spin texture and spin-momentum locking properties of helical
states. Our results are of interest not only for the ongoing development of
Majorana qubits, but also as for realizing possible spin-based quantum devices,
such as quantum spin modulators and interconnects based on spin-helical
channels.",2104.02884v1
2021-04-27,Symmetry-protected photonic chiral spin textures by spin-orbit coupling,"Chiral spin textures are researched widely in condensed matter systems and
show potential for spintronics and storage applications. Along with extensive
condensed-matter studies of chiral spin textures, photonic counterparts of
these textures have been observed in various optical systems with broken
inversion symmetry. Unfortunately, the resemblances are only phenomenological.
This work proposes a theoretical framework based on the variational theorem to
show that the formation of photonic chiral spin textures in an optical
interface is derived from the system's symmetry and relativity. Analysis of the
optical system's rotational symmetry indicates that conservation of the total
angular momentum is preserved from the local variations of spin vectors.
Specifically, although the integral spin momentum does not carry net energy,
the local spin momentum distribution, which determines the local subluminal
energy transport and minimization variation of the square of total angular
momentum, results in the chiral twisting of the spin vectors. The findings here
deepen the understanding of the symmetries, conservative laws and energy
transportation in optical system, construct the comparability in the formation
mechanisms and geometries of photonic and condensed-matter chiral spin
textures, and suggest applications to optical manipulation and chiral
photonics.",2104.12982v1
2021-05-18,Chiral Phonon Activated Spin Seebeck Effect,"Efficient generation of spin polarization is the central focus of
spintronics. In magnetic materials, spin currents can arise from heat currents
by the conventional spin Seebeck effect. Recently, chiral phonons with definite
handedness and angular momenta have also produced profound impacts on multiple
research fields. In this paper, starting with nonequilibrium distribution of
chiral phonons under temperature gradient, we find a new spin selectivity
effect - chiral phonon activated spin Seebeck (CPASS) effect, in chiral
materials without magnetic order nor spin-orbit coupling. With both phonon-drag
and band transport contributions, the CPASS coefficients are computed based on
the Boltzmann transport theory. The spin accumulations by the CPASS effect
quadratically increase with temperature gradient, and vary with the chemical
potential modulation, thus enabling highly efficient and tunable spin
generation. The CPASS effect provides a promising explanation on the
chiral-induced spin selectivity effect and opportunities for designing advanced
spintronic devices based on nonmagnetic chiral materials.",2105.08485v2
2023-03-10,Phonon-mediated spin dynamics in a two-electron double quantum dot under a phonon temperature gradient,"We have theoretically studied phonon-mediated spin-flip processes of
electrons in a GaAs double quantum dot (DQD) holding two spins, under a phonon
temperature gradient over the DQD. Transition rates of inter-dot
phonon-assisted tunnel processes and intra-dot spin-flip processes involving
spin triplet states are formalized by the electron-phonon interaction
accompanied with the spin-orbit interaction. The calculations of the spin-flip
rates and the occupation probabilities of the spin-states in the two-electron
DQD with respect to the phonon temperature difference between the dots are
quantitatively consistent with our previous experiment. This theoretical study
on the temperature gradient effect onto spins in coupled QDs would be essential
for understanding spin-related thermodynamic physics.",2303.05700v1
2023-06-23,Spin-valley locking for in-gap quantum dots in a MoS2 transistor,"Spins confined to atomically-thin semiconductors are being actively explored
as quantum information carriers. In transition metal dichalcogenides (TMDCs),
the hexagonal crystal lattice gives rise to an additional valley degree of
freedom with spin-valley locking and potentially enhanced spin life- and
coherence times. However, realizing well-separated single-particle levels, and
achieving transparent electrical contact to address them has remained
challenging. Here, we report well-defined spin states in a few-layer MoS$ _2$
transistor, characterized with a spectral resolution of $\sim{50~\mu}$eV at
${T_\textrm{el} = 150}$~mK. Ground state magnetospectroscopy confirms a finite
Berry-curvature induced coupling of spin and valley, reflected in a pronounced
Zeeman anisotropy, with a large out-of-plane $g$-factor of ${g_\perp \simeq
8}$. A finite in-plane $g$-factor (${g_\parallel \simeq 0.55-0.8}$) allows us
to quantify spin-valley locking and estimate the spin-orbit splitting
${2\Delta_{\rm SO} \sim 100~\mu}$eV. The demonstration of spin-valley locking
is an important milestone towards realizing spin-valley quantum bits.",2306.13542v1
2017-08-01,Spin Hall photoconductance in a 3D topological insulator at room temperature,"Three-dimensional topological insulators are a class of Dirac materials,
wherein strong spin-orbit coupling leads to two-dimensional surface states. The
latter feature spin-momentum locking, i.e., each momentum vector is associated
with a spin locked perpendicularly to it in the surface plane. While the
principal spin generation capability of topological insulators is well
established, comparatively little is known about the interaction of the spins
with external stimuli like polarized light. We observe a helical,
bias-dependent photoconductance at the lateral edges of topological Bi2Te2Se
platelets for perpendicular incidence of light. The same edges exhibit also a
finite bias-dependent Kerr angle, indicative of spin accumulation induced by a
transversal spin Hall effect in the bulk states of the Bi2Te2Se platelets. A
symmetry analysis shows that the helical photoconductance is distinct to common
longitudinal photoconductance and photocurrent phenomena, but consistent with
the accumulated spins being transported in the side facets of the platelets.
Our findings demonstrate that spin effects in the facets of 3D topological
insulators can be addressed and read-out in optoelectronic devices even at room
temperatures.",1708.00283v1
2018-03-05,Single-shot readout of hole spins in Ge,"The strong atomistic spin orbit coupling of holes makes single-shot spin
readout measurements difficult because it reduces the spin lifetimes. By
integrating the charge sensor into a high bandwidth radio-frequency
reflectometry setup we were able to demonstrate single-shot readout of a
germanium quantum dot hole spin and measure the spin lifetime. Hole spin
relaxation times of about 90 $\mu$s at 500\,mT are reported. By analysing
separately the spin-to-charge conversion and charge readout fidelities insight
into the processes limiting the visibilities of hole spins has been obtained.
The analyses suggest that very high hole visibilities are feasible at realistic
experimental conditions underlying the potential of hole spins for the
realization of viable qubit devices.",1803.01775v4
2018-06-21,Bulk and surface spin conductivity in topological insulators with hexagonal warping,"We investigate the spin conductivity of topological insulators taking into
account both the surface and quasi-two-dimensional bulk states. We apply a
low-energy expansion of the Hamiltonian up to the third order in momentum and
take into account the vertex corrections arising due to the short range
disorder. Hexagonal warping gives rise to the additional anisotropic components
in the spin conductivity tensor. Typically, isotropic part of the spin
conductivity is larger than anisotropic one. The helical regime for the bulk
states, in which the electrons in the Fermi level have the same projection of
the spin on the direction of momentum, have been studied in a more detail. In
this regime, a substantial increase of the spin conductivity contribution from
the bulk states at the Fermi level is observed. We find that the bulk spin
conductivity is insensitive to disorder if Rashba spin-orbit coupling is larger
than disorder strength, otherwise, it is strongly suppressed. The contribution
to the spin conductivity from the surface states is almost independent of the
chemical potential, robust to disorder and its value is comparable to the spin
conductivity contribution from the bulk states per layer. The obtained results
are in agreement with experimental data.",1806.08257v1
2021-10-28,Magnus spin Hall and spin Nernst effects in gapped 2D Rashba systems,"We study the Magnus transport in a gapped 2D electron gas with Rashba
spin-orbit coupling using semiclassical Boltzmann transport formalism. Apart
from its signature in the charge transport coefficients, the inclusion of
Magnus velocity in the spin current operator enables us to study Magnus spin
transport in the system. In particular, we study the roles of mass gap and
Fermi surface topology on the behavior of Magnus Hall and Nernst conductivities
and their spin counterparts. We find that the Magnus spin Hall conductivity
vanishes in the limit of zero gap, unlike the universal spin Hall conductivity
$\sigma_s=e/(8\pi)$. The Magnus spin currents with spin polarization
perpendicular to the applied bias (electrical/thermal) are finite while with
polarization along the bias vanishes. Each Magnus conductivity displays a
plateau as Fermi energy sweeps through the gap and has peaks (whose magnitudes
decrease with the gap) when the Fermi energy is at the gap edges.",2110.15282v3
2017-02-01,Two-Center Gaussian potential well for studying light nucleus in cluster structure,"The clustering phenomena is very important to determine structure of light
nuclei and deformation of spherical shape is inevitable. Hence, we calculated
the energy levels of two-center Gaussian potential well including spin-orbit
coupling by solving the Schr\""odinger equation in the cylindrical coordinates.
This model could predict the spin and parity of the light nucleus that have
cluster structure consist of two identical clusters.",1702.00390v1
1998-05-23,On T-violation signals originating from magnetic orders through double exchange mechanism,"The photon self energy tensor in a crystal with double exchange and
ferromagnetic or canting magnetic orders is analyzed at zero temperature with
emphasis on the signal of the time-reversal invariance breaking. Three
comparable contributions, spin susceptibility, local magnetic field and
spin-orbit coupling are estimated and the prospect of their experimental
detection is discussed.",9805303v1
2010-02-17,Anomalous Hall effects and electron polarizability,"A theory of the anomalous and spin Hall effects, based on the space
distribution of the current densities, is presented. Spin-orbit coupling gives
rise to a space separation of the mass centers, as well as a current density
separation of the quasiparticle states having opposite group velocities. It is
shown that this microscopic property is essential for existence of both Hall
effects.",1002.3212v1
2016-11-22,Relativistic Stern-Gerlach Deflection: Hamiltonian Formulation,"A Hamiltonian formalism is employed to elucidate the effects of the
Stern-Gerlach force on beams of relativistic spin-polarized particles, for
passage through a localized region with a static magnetic or electric field
gradient. The problem of the spin-orbit coupling for nonrelativistic bounded
motion in a central potential (hydrogen-like atoms, in particular) is also
briefly studied.",1611.07326v1
2020-03-12,MagGene: A genetic evolution program for magnetic structure prediction,"We have developed a software MagGene to predict magnetic structures by using
genetic algorithm. Starting from an atom structure, MagGene repeatedly
generates new magnetic structures and calls first-principles calculation engine
to get the most stable structure. This software is applicable to both collinear
and noncollinear systems. It is particularly convenient for predicting the
magnetic structures of atomic systems with strong spin-orbit couplings and/or
strong spin frustrations.",2003.05650v1
2006-05-09,Electron energy spectrum and density of states for non-symmetric heterostructures in an in-plane magnetic field,"Modifications of spin-splitting dispersion relations and density of states
for electrons in non-symmetric heterostructures under in-plane magnetic field
are studied within the envelope function formalism. Spin-orbit interactions,
caused by both a slow potential and the heterojunction potentials (which are
described by the boundary conditions) are taken into account. The interplay
between these contributions and the magnetic field contribution to the
spin-splitting term in the Hamiltonian is essential when energy amount
resulting from the Zeeman and spin-orbit coupling are of the same order. Such
modifications of the energy spectra allow us to separate the spin-orbit
splitting contributions due to a slow potential and due to the heterojunctions.
Numerical estimates for selectively-doped heterojunction and quantum well with
narrow-gap region of electron localization are performed.",0605222v1
2002-07-23,Classical Mechanics of a Three Spin Cluster,"A cluster of three spins coupled by single-axis anisotropic exchange exhibits
classical behaviors ranging from regular motion at low and high energies, to
chaotic motion at intermediate energies. A change of variable, taking advantage
of the conserved z-angular momentum, combined with a 3-d graphical presentation
(described in the Appendix), produce Poincare sections that manifest all
symmetries of the system and clearly illustrate the transition to chaos as
energy is increased.
  The three-spin system has four families of periodic orbits. Linearization
around stationary points predicts orbit periods in the low energy
(antiferromagnetic) and high energy (ferromagnetic) limits and also determines
the stability properties of certain orbits at a special intermediate energy.
The energy surface undergoes interesting changes of topology as energy is
varied. We describe the similiarities of our three spin system with the
Anisotropic Kepler Problem and the Henon-Heiles Hamiltonian. An appendix
discusses numerical integration techniques for spin systems.",0207040v1
2005-11-05,The spectral form factor for quantum graphs,"We consider quantum graphs with spin-orbit couplings at the vertices.
Time-reversal invariance implies that the bond S-matrix is in the orthogonal or
symplectic symmetry class, depending on spin quantum number s being integer or
half-integer, respectively. The periodic-orbit expansion of the spectral form
factor is shown to acquire additional weights from spin rotations along orbits.
We determine the spin contribution to the coefficients in an expansion of the
form factor from properties of the representation of the group of spin
transformations on the graph. Consistency with the Circular Orthogonal and
Circular Symplectic Ensemble, respectively, of random matrices is obtained.",0511011v1
2011-04-07,Quantum Spin Hall Effect in Silicene,"Recent years have witnessed great interest in the quantum spin Hall effect
(QSHE) which is a new quantum state of matter with nontrivial topological
property due to the scientific importance as a novel quantum state and the
technological applications in spintronics. Taking account of Si, Ge significant
importance as semiconductor material and intense interest in the realization of
QSHE for spintronics, here we investigate the spin-orbit opened energy gap and
the band topology in recently synthesized silicene using first-principles
calculations. We demonstrate that silicene with topologically nontrivial
electronic structures can realize QSHE by exploiting adiabatic continuity and
direct calculation of the Z2 topological invariant. We predict that QSHE in
silicene can be observed in an experimentally accessible low temperature regime
with the spin-orbit band gap of 1.55 meV, much higher than that of graphene due
to large spin-orbit coupling and the low-buckled structure. Furthermore, we
find that the gap will increase to 2.90 meV under certain pressure strain.
Finally, we also study germanium with similar low buckled stable structure, and
predict that SOC opens a band gap of 23.9 meV, much higher than the liquid
nitrogen temperature.",1104.1290v1
2011-12-15,Quantitative modeling of spin relaxation in quantum dots,"We use numerically exact diagonalization to calculate the spin-orbit and
phonon-induced triplet-singlet relaxation rate in a two-electron quantum dot
exposed to a tilted magnetic field. Our scheme includes a three-dimensional
description of the quantum dot, the Rashba and the linear and cubic Dresselhaus
spin-orbit coupling, the ellipticity of the quantum dot, and the full angular
description of the magnetic field. We are able to find reasonable agreement
with the experimental results of Meunier et al. [Phys. Rev. Lett. 98, 126601
(2007)] in terms of the singlet-triplet energy splitting and the spin
relaxation rate, respectively. We analyze in detail the effects of the
spin-orbit factors, magnetic-field angles, and the dimensionality, and discuss
the origins of the remaining deviations from the experimental data.",1112.3562v1
2015-04-09,Spin responses and effective Hamiltonian for the two dimensional electron gas at oxide interface {LaAlO}$_3$/{SrTiO}$_3$,"Strong Rashba spin-orbit coupling (SOC) of the two-dimensional electron gas
(2DEG) at the oxide interface $\mathrm{LaAlO_{3}/SrTiO_{3}}$ underlies a
variety of exotic physics, but its nature is still under debate. We derive an
effective Hamiltonian for the 2DEG at the oxide interface
$\mathrm{LaAlO_{3}/SrTiO_{3}}$ and find a different anisotropic Rashba SOC for
the $d_{xz}$ and $d_{yz}$ orbitals. This anisotropic Rashba SOC leads to
anisotropic static spin susceptibilities and also distinctive behavior of the
spin Hall conductivity. These unique spin responses may be used to determine
the nature of the Rashba SOC experimentally and shed light on the orbital
origin of the 2DEG.",1504.02177v3
2015-05-22,Chiral spin-orbital liquids with nodal lines,"Strongly correlated materials with strong spin-orbit coupling hold promise
for realizing topological phases with fractionalized excitations. Here we
propose a chiral spin-orbital liquid as a stable phase of a realistic model for
heavy-element double perovskites. This spin liquid state has Majorana fermion
excitations with a gapless spectrum characterized by nodal lines along the
edges of the Brillouin zone. We show that the nodal lines are topological
defects of a non-Abelian Berry connection and that the system exhibits
dispersing surface states. We discuss some experimental signatures of this
state and compare them with properties of the spin liquid candidate Ba_2YMoO_6.",1505.06171v3
2016-09-15,Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry,"Spin-orbit interactions are known to have drastic effects on the band
structure of heavy-element-based materials. Celebrated examples are the
recently identified 3D and 2D topological insulators. In those systems
transport takes place at surfaces or along edges, and spin-momentum locking
provides protection against (non-magnetic) impurity scattering, favoring
spin-polarized ballistic transport. We have used the measurement of the current
phase relation of a micrometer-long single crystal bismuth nanowire connected
to superconducting electrodes, to demonstrate that transport occurs
ballistically along two edges of this high-spin-orbit material. In addition, we
show that a magnetic field can induce to 0-pi transitions and phi0-junction
behavior, thanks to the extraordinarily high g-factor and spin orbit coupling
in this system, providing a way to manipulate the phase of the
supercurrent-carrying edge states.",1609.04848v1
2017-03-21,Room temperature spin-orbit torque switching induced by a topological insulator,"Recent studies on the magneto-transport properties of topological insulators
(TI) have attracted great attention due to the rich spin-orbit physics and
promising applications in spintronic devices. Particularly the strongly
spin-moment coupled electronic states have been extensively pursued to realize
efficient spin-orbit torque (SOT) switching. However, so far current-induced
magnetic switching with TI has only been observed at cryogenic temperatures. It
remains a controversial issue whether the topologically protected electronic
states in TI could benefit spintronic applications at room temperature. In this
work, we report full SOT switching in a TI/ferromagnet bilayer heterostructure
with perpendicular magnetic anisotropy at room temperature. The low switching
current density provides a definitive proof on the high SOT efficiency from TI.
The effective spin Hall angle of TI is determined to be several times larger
than commonly used heavy metals. Our results demonstrate the robustness of TI
as an SOT switching material and provide a direct avenue towards applicable
TI-based spintronic devices.",1703.07470v1
2018-02-05,First-principles theory of giant Rashba-like spin-splitting in bulk ferroelectrics,"Recently large Rashba-like spin splitting has been observed in certain bulk
ferroelectrics. In contrast with the relativistic Rashba effect, the chiral
spin texture and large spin-splitting of the electronic bands depend strongly
on the character of the band and atomic spin-orbit coupling. We establish that
this can be traced back to the so-called orbital Rashba effect, also in the
bulk. This leads to an additional dependence on the orbital composition of the
bands, which is crucial for a complete picture of the effect. Results from
first-principles calculations on ferroelectic GeTe verify the key predictions
of the model.",1802.01546v3
2014-03-24,Spin-orbit and impurity scattering in an integrable electron model: Exact results for dynamic correlations,"We introduce an integrable model of spin-polarized interacting electrons
subject to a spin-conserving spin-orbit interaction. Using Bethe Ansatz and
conformal field theory we calculate the exact large-time single-electron and
density correlations and find that while the spin-orbit interaction enhances
the single-electron Green's function, the density correlations get suppressed.
Adding a localized impurity and coupling it to the electrons so that
integrability is preserved, the dynamic correlations are found to change
significantly after a quantum quench with the impurity interaction switched on
suddenly. When the electrons are confined to a periodic structure, the
correlations are indifferent to the location of the impurity and only carry an
imprint of its intrinsic properties. We conjecture that this unusual feature
originates from the integrability of the model.",1403.6091v2
2017-06-15,The low-temperature highly correlated quantum phase in the charge-density-wave 1T-TaS_2 compound,"A prototypical quasi-2D metallic compound, 1T-TaS_2 has been extensively
studied due to an intricate interplay between a Mott-insulating ground state
and a charge density-wave (CDW) order. In the low-temperature phase, 12 out of
13 Ta_{4+} 5\textit{d}-electrons form molecular orbitals in hexagonal
star-of-David patterns, leaving one 5\textit{d}-electron with \textit{S} = 1/2
spin free. This orphan quantum spin with a large spin-orbit interaction is
expected to form a highly correlated phase of its own. And it is most likely
that they will form some kind of a short-range order out of a strongly
spin-orbit coupled Hilbert space. In order to investigate the low-temperature
magnetic properties, we performed a series of measurements including neutron
scattering and muon experiments. The obtained data clearly indicate the
presence of the short-ranged phase and put the upper bound on ~ 0.4
\textit{\mu}_B for the size of the magnetic moment, consistent with the
orphan-spin scenario.",1706.04735v1
2018-06-05,Multi-orbital nature of the spin fluctuations in Sr$_2$RuO$_4$,"The spin susceptibility of strongly correlated Sr$_2$RuO$_4$ is known to
display a rich structure in reciprocal space, with a prominent peak at ${\bf
Q}_i$=$(0.3,0.3,0)$. It is still debated if the resulting incommensurate
spin-density-wave fluctuations foster unconventional superconductivity at low
temperature or compete therewith. By means of density functional theory
combined with dynamical mean-field theory, we reveal the realistic
multi-orbital signature of the (dynamic) spin susceptibility beyond existing
weak-coupling approaches. The experimental fluctuation spectrum up to 80 meV is
confirmed by theory. Furthermore, the peak at ${\bf Q}_i$ is shown to carry
nearly equal contributions from each of the Ru$(4d)$-$t_\mathrm{2g}$ orbitals,
pointing to a cooperative effect resulting in the dominant spin fluctuations.",1806.01511v2
2018-08-02,Orbital- and spin-driven lattice instabilities in quasi-one-dimensional CaV$_2$O$_4$,"Calcium vanadate CaV$_2$O$_4$ has a crystal structure of
quasi-one-dimensional zigzag chains composed of orbital-active V$^{3+}$ ions
and undergoes successive structural and antiferromagnetic phase transitions at
$T_s\sim 140$ K and $T_N \sim 70$ K, respectively. We perform ultrasound
velocity measurements on a single crystal of CaV$_2$O$_4$. The temperature
dependence of its shear elastic moduli exhibits huge Curie-type softening upon
cooling that emerges above and below $T_s$ depending on the elastic mode. The
softening above $T_s$ suggests the presence of either onsite Jahn-Teller-type
or intersite ferro-type orbital fluctuations in the two inequivalent V$^{3+}$
zigzag chains. The softening below $T_s$ suggests the occurrence of a
dimensional spin-state crossover, from quasi-one to three, that is driven by
the spin-lattice coupling along the inter-zigzag-chain orthogonal direction.
The successive emergence of the orbital- and spin-driven lattice instabilities
above and below $T_s$, respectively, is unique to the orbital-spin zigzag chain
system of CaV$_2$O$_4$.",1808.00642v1
2022-08-30,Spinor superfluid currents of exciton-polaritons on a split-ring,"Recently, split-ring bosonic condensates of exciton polaritons have been
proposed for realisation of qubits. We formulate an analytical model of a
polariton condensate in a one-dimensional ring split by a delta-function
potential. The persistent current is stopped by the potential defect embedded
in a scalar condensate of non-interacting particles, however, it reappears in
the presence of an up-critical non-linearity. The nonlinear supercurrents are
characterised by fractional orbital momenta while their eigenfunctions may
feature grey or dark solitons. The coupling between the spin and the orbital
angular momentum of a spinor condensate affects persistent currents crucially.
We show that the spin-orbit interaction (SOI) induces the net superfluid
current in the condensate with a spatially uniform spin polarisation. We also
find solutions where the SOI-induced currents of two spin components of the
condensate propagate in opposite directions. The corresponding states of spinor
condensates obey a combined mirror reflection and the spin-flip symmetry.",2208.14094v2
2023-10-09,Ordered phases and superconductivity in two-dimensional electron systems subject to pair spin-orbit interaction,"Pair spin-orbit interaction can emerge in strongly-interacting systems
characterized by a large spin-orbit coupling. Here we study the role of this
interaction in stabilizing ordered and unconventional superconducting phases.
We find that, if the system avoids superconductivity, the order realized is a
combination of charge-density and spin-vorticity waves. The latter is
reminiscent of a loop-current state, albeit in the spin, rather in the charge,
channel. If the system becomes superconducting, the order parameter assumes the
form of a paired density wave, i.e. pairing occurs at finite momentum.
Intriguingly, one of the possible pairings acquires a form analogous to
Amperean superconductivity. However, the order parameter here is always a blend
of paired density wave and Amperean pairing, rather than being purely one or
the other.",2310.06190v1
2024-02-09,g-factor symmetry and topology in semiconductor band states,"The $\bf{g}$ tensor, which determines the reaction of Kramers-degenerate
states to an applied magnetic field, is of increasing importance in the current
design of spin qubits. It is affected by details of heterostructure
composition, disorder, and electric fields, but it inherits much of its
structure from the effect of the spin-orbit interaction working at the
crystal-lattice level. Here we uncover new symmetry and topological features of
$\bf{g}=\bf{g}_L+\bf{g}_S$ for important valence and conduction bands in
silicon, germanium, and gallium arsenide. For all crystals with high (cubic)
symmetry, we show that large departures from the nonrelativistic value $g=2$
are {\em guaranteed} by symmetry. In particular, considering the spin part
$\bf{g}_S(\bf{k})$, we prove that the scalar function $det(\bf{g}_S(\bf{k}))$
must go to zero on closed surfaces in the Brillouin zone, no matter how weak
the spin-orbit coupling is. We also prove that for wave vectors $\bf{k}$ on
these surfaces, the Bloch states $|u_{n\bf{k}}\rangle$ have maximal
spin-orbital entanglement. Using tight-binding calculations, we observe that
the surfaces $det(\bf{g}(\bf{k}))=0$ exhibit many interesting topological
features, exhibiting Lifshitz critical points as understood in Fermi-surface
theory.",2402.06310v1
2003-05-14,Orbital order in the low-dimensional quantum spin system TiOCl probed by ESR,"We present electron spin resonance data of Ti$^{3+}$ (3$d^1$) ions in single
crystals of the novel layered quantum spin magnet TiOCl. The analysis of the g
tensor yields direct evidence that the d_{xy} orbital from the t_{2g} set is
predominantly occupied and owing to the occurrence of orbital order a linear
spin chain forms along the crystallographic b axis. This result corroborates
recent theoretical LDA+U calculations of the band structure. The temperature
dependence of the parameters of the resonance signal suggests a strong coupling
between spin and lattice degrees of freedom and gives evidence for a transition
to a nonmagnetic ground state at 67 K.",0305317v2
2007-10-04,From spin and orbital SU(4) to spin SU(2) Kondo effect in double quantum dot,"We consider spin and orbital Kondo effect in a parallel arrangement of two
strongly electrostatically coupled quantum dots. Increasing the exchange of
electrons between the dots through the attached leads induces a smooth
crossover between SU(4) spin- and orbital Kondo effect and SU(2) spin Kondo
effect. Being the same for the SU(4) and SU(2) symmetry points, the Kondo
temperature drops slightly in the intermediate regime. Experimentally, two
kinds of Kondo effect can be discriminated by the sensitivity to the
suppression of the spin Kondo effect by Zeeman field. The dependence of the
Kondo temperature and of the differential conductance on the strength of
electronic exchange through the leads and Zeeman field is analyzed in detail.",0710.0950v2
2008-08-22,Perturbation Method for Classical Spinning Particle Motion: II. Vaidya Space-Time,"This paper describes an application of the Mathisson-Papapetrou-Dixon (MPD)
equations in analytic perturbation form to the case of circular motion around a
radially accreting or radiating black hole described by the Vaidya metric.
Based on the formalism presented earlier, this paper explores the effects of
mass accretion or loss of the central body on the overall dynamics of the
orbiting spinning particle. This includes changes to its squared mass and spin
magnitude due to the classical analog of radiative corrections from
spin-curvature coupling. Various quantitative consequences are explored when
considering orbital motion near the black hole's event horizon. An analysis on
the orbital stability properties due to spin-curvature interactions is examined
briefly, with conclusions in general agreement with previous work performed for
the case of circular motion around a Kerr black hole.",0808.3006v3
2012-08-13,Magnetic Dipole and Electric Quadrupole Transitions in the Trivalent Lanthanide Series: Calculated Emission Rates and Oscillator Strengths,"Given growing interest in optical-frequency magnetic dipole transitions, we
use intermediate coupling calculations to identify strong magnetic dipole
emission lines that are well suited for experimental study. The energy levels
for all trivalent lanthanide ions in the 4fn configuration are calculated using
a detailed free ion Hamiltonian, including electrostatic and spin-orbit terms
as well as two-body, three-body, spin-spin, spin-other-orbit, and
electrostatically correlated spin-orbit interactions. These free ion energy
levels and eigenstates are then used to calculate the oscillator strengths for
all ground-state magnetic dipole absorption lines and the spontaneous emission
rates for all magnetic dipole emission lines including transitions between
excited states. A large number of strong magnetic dipole transitions are
predicted throughout the visible and near-infrared spectrum, including many at
longer wavelengths that would be ideal for experimental investigation of
magnetic light-matter interactions with optical metamaterials and plasmonic
antennas.",1208.2642v2
2018-12-08,Competing superconducting phases in interacting two-dimensional electron gas with strong Rashba spin-orbit coupling,"In this work we study interacting electrons on square lattice in the presence
of strong Rashba spin-orbit interaction. The spin-orbit term forces the
time-reversal electron states to be paired in even Cooper channels. For
concreteness, we only consider the repulsive onsite Hubbard and
nearest-neighbor coulomb interactions, the so called extended Hubbard model. To
examine the superconducting instability we obtain the effective interaction
between electrons within the random phase approximation and treat the pairing
instabilities driven by charge and spin fluctuations and their combined
effects. We mapped out the phase diagram of the model in terms of interactions
and electron fillings, and found that while the $d_{xy}$ and $d_{x^2-y^2}$
symmetries are the most likely pairing symmetries driven by charge and spin
fluctuations, respectively, the strong effect of both fluctuations yields
higher angular momentum Cooper instability. The possibility of topological
superconductivity and triplet pairing is also discussed.",1812.03316v1
2019-07-09,Tunneling anisotropic magnetoresistance of Pb and Bi adatoms and dimers on Mn/W(110): A first-principles study,"We show that Pb and Bi adatoms and dimers have a large tunneling anisotropic
magnetoresistance (TAMR) of up to 60% when adsorbed on a magnetic
transition-metal surface due to strong spin-orbit coupling and the
hybridization of 6p orbitals with 3d states of the magnetic layer. Using
density functional theory, we have explored the TAMR effect of Pb and Bi
adatoms and dimers adsorbed on a Mn monolayer on W(110). This surface exhibits
a noncollinear cycloidal spin spiral ground state with an angle of 173$^\circ$
between neighboring spins which allows to rotate the spin quantization axis of
an adatom or dimer quasi-continuously and is ideally suited to explore the
angular dependence of TAMR using scanning tunneling microscopy (STM). We find
that the induced magnetic moments of Pb and Bi adatoms and dimers are small,
however, the spin-polarization of the local density of states (LDOS) is still
very large. The TAMR obtained from the anisotropy of the vacuum LDOS is up to
50-60 % for adatoms. For dimers the TAMR depends sensitively on the dimer
orientation with respect to the crystallographic directions of the surface due
to the formation of bonds between the adatoms with the Mn surface atoms and the
symmetry of the spin-orbit coupling induced mixing. Dimers oriented along the
spin spiral direction of the Mn monolayer display the largest TAMR of 60 %
which is due to hybrid 6p-3d states of the dimers and the Mn layer",1907.04363v1
2019-09-23,Josephson junctions with spin-orbit and spin-flip interactions,"In this thesis we study short Josephson junctions which include a region with
Rashba spin-orbit coupling effect. Our junctions consists of two
superconductors (S) and a 2-dimensional electron gas (2DEG) layer between them:
S/2DEG/S junction. We also include two thin insulating interfaces between the
superconductors and the 2DEG, which are capable of both normal and spin-flip
scattering. The junctions we study are assumed to be in the ballistic limit and
so, we do not consider the effects of impurities. The basic equations we use
for our model are the Bogoliubov-de Gennes equations. We give particular
emphasis in the relation between the supercurrent of the junction as a function
of difference of the phase parameters of the two superconductors. We study
thoroughly how this relation differs to the change of the junction's length,
the spin-orbit coupling constant, the normal scattering strength and the
spin-flip scattering strength and direction. We are also interested in the
0-$\pi$ transition and the second harmonic appearance, as well as the
symmetries which occur in the current-phase relation, for different geometries
of the two spin-flip interfaces. In addition, we show how the Critical current
of our junction is affected to the change of the above parameters and under
which conditions it is optimized. Finally, we study the supercurrent flowing at
zero phase difference (ZPC) of the two superconductors. We emphasize the
conditions under which it is non-zero and also examine the cases it becomes
maximized.",1909.10617v2
2020-06-16,Block orbital-selective Mott insulators: a spin excitation analysis,"We present a comprehensive study of the spin excitations - as measured by the
dynamical spin structure factor $S(q,\omega)$ - of the so-called block-magnetic
state of low-dimensional orbital-selective Mott insulators. We realize this
state via both a multi-orbital Hubbard model and a generalized Kondo-Heisenberg
Hamiltonian. Due to various competing energy scales present in the models, the
system develops periodic ferromagnetic islands of various shapes and sizes,
which are antiferromagnetically coupled. The 2$\times$2 particular case was
already found experimentally in the ladder material BaFe$_2$Se$_3$ that becomes
superconducting under pressure. Here we discuss the electronic density as well
as Hubbard and Hund coupling dependence of $S(q,\omega)$ using density matrix
renormalization group method. Several interesting features were identified: (1)
An acoustic (dispersive spin-wave) mode develops. (2) The spin-wave bandwidth
establishes a new energy scale that is strongly dependent on the size of the
magnetic island and becomes abnormally small for large clusters. (3) Optical
(dispersionless spin excitation) modes are present for all block states studied
here. In addition, a variety of phenomenological spin Hamiltonians have been
investigated but none matches entirely our results that were obtained primarily
at intermediate Hubbard $U$ strengths. Our comprehensive analysis provides
theoretical guidance and motivation to crystal growers to search for
appropriate candidate materials to realize the block states, and to neutron
scattering experimentalists to confirm the exotic dynamical magnetic properties
unveiled here, with a rich mixture of acoustic and optical features.",2006.09495v2
2020-11-23,Response of a strongly interacting spin-orbit coupling system to a Zeeman field,"A strongly spin-orbital coupled systems could be in a magnetic ordered phase
at zero field. However, a Zeeman field could drive it into different quantum or
topological phases. In this work, starting from general symmetry principle, we
construct various effective actions to study all these quantum phases and phase
transitions which take different forms depending on the condensation momenta
are commensurate or in-commensurate.
  We not only recover all these quantum phases and their excitations achieved
by the microscopic calculations, but also discover several novel classes of
quantum phase transitions with dynamic exponents $ z=1, z=2 $ and anisotropic
ones $ (z_x=3/2, z_y=3) $ respectively. We determine the relations between the
quantum spin and the order parameters of the effective actions which display
rich spin-orbital structures. We find a new type of dangerously irrelevant
operator we name type-II, in distinction from the known one we name type-I. We
explore a new phenomena called order parameter fractionization where one
complex order parameter split into two which is different than quantum spin
fractionization into a spinon and a $ Z_2 $ flux. Finite temperature
transitions are presented. The dynamic spin-spin correlation functions are
evaluated. Thermal Hall conductivities are discussed. The cases with the $
U(1)_{soc} $ symmetry explicitly broken are briefly outlined. In view of recent
experimental advances in generating 2d SOC for cold atoms in optical lattices,
these new many-body phenomena can be explored in the near future cold atom
experiments. Implications to various SOC materials such as MnSi,
Fe$_{0.5}$Co$_{0.5}$Si, especially 4d Kitaev materials $\alpha$-RuCl$_3$ in a
Zeeman field are outlined.",2011.11287v2
2021-11-22,Ensemble spin relaxation of shallow donor qubits in ZnO,"We present an experimental and theoretical study of the longitudinal electron
spin relaxation ($T_1$) of shallow donors in the direct band-gap semiconductor
ZnO. $T_1$ is measured via resonant excitation of the Ga donor-bound exciton.
$T_1$ exhibits an inverse-power dependence on magnetic field $T_1\propto
B^{-n}$, with $4\leq n\leq 5$, over a field range of 1.75 T to 7 T. We derive
an analytic expression for the donor spin-relaxation rate due to spin-orbit
(admixture mechanism) and electron-phonon (piezoelectric) coupling for the
wurtzite crystal symmetry. Excellent quantitative agreement is found between
experiment and theory suggesting the admixture spin-orbit mechanism is the
dominant contribution to $T_1$ in the measured magnetic field range.
Temperature and excitation-energy dependent measurements indicate a donor
density dependent interaction may contribute to small deviations between
experiment and theory. The longest $T_1$ measured is 480 ms at 1.75 T with
increasing $T_1$ at smaller fields theoretically expected. This work highlights
the extremely long longitudinal spin-relaxation time for ZnO donors due to
their small spin-orbit coupling.",2111.11564v3
2019-08-28,Tilting Ice Giants with a Spin-Orbit Resonance,"Giant collisions can account for Uranus's and Neptune's large obliquities,
yet generating two planets with widely different tilts and strikingly similar
spin rates is a low-probability event. Trapping into a secular spin-orbit
resonance, a coupling between spin and orbit precession frequencies, is a
promising alternative, as it can tilt the planet without altering its spin
period. We show with numerical integrations that if Uranus harbored a massive
circumplanetary disk at least three times the mass of its satellite system
while it was accreting its gaseous atmosphere, then its spin precession rate
would increase enough to resonate with its own orbit, potentially driving the
planet's obliquity to 70${^\circ}$. We find that the presence of a massive disk
moves the Laplace radius significantly outward from its classical value,
resulting in more of the disk contributing to the planet's pole precession.
Although we can generate tilts greater than 70${^\circ}$ only rarely and cannot
drive tilts beyond 90${^\circ}$, a subsequent collision with an object about
$0.5\,M_{\oplus}$ could tilt Uranus from 70${^\circ}$ to 98${^\circ}$.
Minimizing the masses and number of giant impactors from two or more to just
one increases the likelihood of producing Uranus's spin states by about an
order of magnitude. Neptune, by contrast, needs a less massive disk to explain
its 30${^\circ}$ tilt, eliminating the need for giant collisions altogether.",1908.10969v4
2022-09-21,Ferroaxial moment induced by vortex spin texture,"The nature of an electric ferro-axial moment characterizing a
time-reversal-even axial-vector quantity is theoretically investigated under
magnetic orderings. We clarify that a vortex spin texture results in the
emergence of the ferro-axial moment depending on the helicity. By introducing a
multipole description, we show that the ferro-axial nature appears when two
types of odd-parity magnetic multipoles become active under the vortex spin
texture: One is the magnetic monopole and the other is the magnetic toroidal
dipole. We present all the magnetic point groups to possess the ferro-axial
moment in the presence of the magnetic orderings with the magnetic monopole and
magnetic toroidal dipole. Moreover, we specifically consider a multi-orbital
model in a four-sublattice tetragonal system to demonstrate the ferro-axial
moment induced by the vortex spin texture. We show that the ferro-axial moment
is microscopically characterized by both the cluster-scale and atomic-scale
axial-vector quantities: The former is described by the vortex of the local
electric dipole and the latter is represented by the outer product of the local
orbital and spin angular momenta. Moreover, we find that the atomic-spin orbit
coupling and the hybridization between orbitals with different parity are key
ingredients to induce the ferro-axial moment. We also apply the result to a
magnetic skyrmion with a topologically-nontrivial spin texture and discuss
candidate materials.",2209.10657v2
2023-01-24,Orbital antiferroelectricity and higher dimensional magnetoelectric order in the spin-$1/2$ XX chain extended with three-spin interactions,"We study the spin-1/2 XX model extended with three-spin interactions of the
XZX+YZY and XZY-YZX types. We solve the model exactly and obtain the ground
state phase diagram as a function of the two three-spin coupling strengths. We
show that even in absence of external electric and magnetic fields there is a
phase which exhibits spontaneous magnetoelectric order when both XZX+YZY and
XZY-YZX interactions are present. Specifically, in this regime, we show that
there exists not only a non-zero magnetization and a scalar chirality but also
a vector chiral order. Further, we show the existence of a plaquette vector
chirality, or circulating chiral spin current loops, in the plaquettes n, n+1,
n+2 with the sense of the current being opposite in adjacent plaquettes.
Analogous to charge current loops giving rise to orbital magnetic dipole
moments, the circulating spin current loops give rise to orbital electric
dipole moments - a novel orbital antiferroelectricity. We characterize this
phase by a higher-dimensional scalar and vector toroidal order. Such a novel
phase with higher dimensional order arises because of the non-trivial
topological connectivity resulting from the presence of both the three-spin
interactions. We also study the combined effect of both types of three-spin
interactions on the entanglement entropy.",2301.10138v1
2019-08-12,Uncovering Non-Fermi-Liquid Behavior in Hund Metals: Conformal Field Theory Analysis of an SU(2)$\times$SU(3) Spin-Orbital Kondo Model,"Hund metals have attracted attention in recent years due to their
unconventional superconductivity, which supposedly originates from
non-Fermi-liquid (NFL) properties of the normal state. When studying Hund
metals using dynamical mean-field theory, one arrives at a self-consistent
""Hund impurity problem"" involving a multiorbital quantum impurity with nonzero
Hund coupling interacting with a metallic bath. If its spin and orbital degrees
of freedom are screened at different energy scales, $T_\mathrm{sp} <
T_\mathrm{orb}$, the intermediate energy window is governed by a novel NFL
fixed point, whose nature had not yet been clarified. We resolve this problem
by providing an analytical solution of a paradigmatic example of a Hund
impurity problem, involving two spin and three orbital degrees of freedom. To
this end, we combine a state-of-the-art implementation of the numerical
renormalization group, capable of exploiting non-Abelian symmetries, with a
generalization of Affleck and Ludwig's conformal field theory (CFT) approach
for multichannel Kondo models. We characterize the NFL fixed point of Hund
metals in detail for a Kondo model with an impurity forming an
SU(2)$\times$SU(3) spin-orbital multiplet, tuned such that the NFL energy
window is very wide. The impurity's spin and orbital susceptibilities then
exhibit striking power-law behavior, which we explain using CFT arguments. We
find excellent agreement between CFT predictions and numerical renormalization
group results. Our main physical conclusion is that the regime of spin-orbital
separation, where orbital degrees of freedom have been screened but spin
degrees of freedom have not, features anomalously strong local spin
fluctuations: the impurity susceptibility increases as
$\chi_\mathrm{sp}^\mathrm{imp} \sim \omega^{-\gamma}$, with $\gamma > 1$.",1908.04362v2
2022-09-19,Andreev bound states at boundaries of polarized 2D Fermi superfluids with s-wave pairing and spin-orbit coupling,"A topological superfluid phase characterized by an emergent chiral-p-wave
pair potential is expected to form in a two-dimensional Fermi superfluid
subject to s-wave pairing, spin-orbit coupling and a large-enough Zeeman
splitting. Andreev bound states appear at phase boundaries, including Majorana
zero modes whose existence is assured by the bulk-boundary correspondence
principle. Here we study the physical properties of these subgap-energy bound
states at step-like interfaces using the spin-resolved Bogoliubov-deGennes
mean-field formalism and assuming small spin-orbit coupling. Extending a
recently developed spin-projection technique based on Feshbach partitioning
[SciPost Phys. 5, 016 (2018)] combined with the Andreev approximation allows us
to obtain remarkably simple analytical expressions for the bound-state energies
as well as the majority and minority spin components of their wave functions.
Besides the vacuum boundary, where a majority-spin Majorana excitation is
encountered, we also consider the boundary between the topological and a
nontopological superfluid phase that can appear in a coexistence scenario due
to the first-order topological phase transition predicted for this system. At
this superfluid-superfluid interface, we find a localized chiral Majorana mode
hosted by the minority-spin sector. Our theory further predicts majority-spin
subgap-energy bound states similar to those found at a Josephson junction
between same-chirality p-wave superfluids. Their presence affects the Majorana
mode due to a coupling of minority and majority spin sectors only in the small
energy range where their spectra overlap. Our results may inform experimental
efforts aimed at realizing and characterizing unconventional Majorana
quasiparticles.",2209.08766v2
2008-12-21,Spatial fluctuations of spin and orbital in two-orbital Hubbard model,"We investigate the quasiparticle dynamics in the two-orbital Hubbard model on
the square lattice at quarter filling by means of the cellular dynamical mean
field theory. We show that the Fermi-liquid state is stabilized up to the large
Hubbard interactions in the symmetric case without the Hund's coupling, and
find the heavy quasiparticles around the metal-insulator boundary. It is
elucidated that the Hund's coupling enhances the antiferro-orbital
correlations, which give rise to the pseudo gap behavior in the single-particle
excitations. We also find the nonmonotonic temperature dependence in the
quasiparticle dynamics for intermediate strength of the Hund's coupling, and
clarify that it is caused by the competition between the Fermi-liquid formation
and the antiferro-orbital fluctuations.",0812.4019v2
2009-02-04,Theory of valley-orbit coupling in a Si/SiGe quantum dot,"Electron states are studied for quantum dots in a strained Si quantum well,
taking into account both valley and orbital physics. Realistic geometries are
considered, including circular and elliptical dot shapes, parallel and
perpendicular magnetic fields, and (most importantly for valley coupling) the
small local tilt of the quantum well interface away from the crystallographic
axes. In absence of a tilt, valley splitting occurs only between pairs of
states with the same orbital quantum numbers. However, tilting is ubiquitous in
conventional silicon heterostructures, leading to valley-orbit coupling. In
this context, ""valley splitting"" is no longer a well defined concept, and the
quantity of merit for qubit applications becomes the ground state gap. For
typical dots used as qubits, a rich energy spectrum emerges, as a function of
magnetic field, tilt angle, and orbital quantum number. Numerical and
analytical solutions are obtained for the ground state gap and for the mixing
fraction between the ground and excited states. This mixing can lead to valley
scattering, decoherence, and leakage for Si spin qubits.",0902.0777v3
2019-08-22,Nonequilibrium Orbital Transitions via Applied Electrical Current in Calcium Ruthenate,"Simultaneous control of structural and physical properties via applied
electrical current poses a key, new research topic and technological
significance. Studying the spin-orbit-coupled antiferromagnet Ca2RuO4, with 3%
Mn doping to weaken the violent first-order transition at 357 K for more robust
measurements, we find that a small applied electrical current couples to the
lattice by significantly reducing its orthorhombicity and octahedral rotations,
concurrently diminishing the 125 K- antiferromagnetic transition and inducing a
new, orbital order below 80 K. Our effort to establish a phase diagram reveals
a critical regime near a current density of 0.15 A/cm2 that separates the
vanishing antiferromagnetic order and the new orbital order. Further increasing
current density (> 1 A/cm2) enhances competitions between relevant interactions
in a metastable manner, leading to a peculiar glassy behavior above 80 K. The
coupling between the lattice and nonequilibrium driven current is interpreted
theoretically in terms of t2g orbital occupancies. The current-controlled
lattice is the driving force of the observed novel phenomena.",1908.08571v3
2020-07-23,Coupled Yu-Shiba-Rusinov states induced by a many-body molecular spin on a superconductor,"A magnetic impurity on a superconductor induces Yu-Shiba-Rusinov (YSR) bound
states, detected by tunneling spectroscopy as long-lived quasiparticle
excitations inside the superconducting gap. Coupled YSR states constitute basic
elements to engineer artificial superconducting states, but their
substrate-mediated interactions are generally weak. In this paper, we report
that intramolecular (Hund's like) exchange interactions produce coupled YSR
states across a molecular platform. We measured YSR spectra along a magnetic
iron-porphyrin on Pb(111) and found evidences of two orbital interaction
channels, which invert their particle-hole asymmetry across the molecule.
Numerical calculations show that the identical YSR asymmetry pattern of the two
channels is caused by two spin-hosting orbitals with opposite potential
scattering and coupled strongly. Both channels can be similarly excited by
tunneling electrons into each orbital, depicting a new scenario for entangled
superconducting bound states using molecular platforms.",2007.12091v2
2017-01-23,Determination of Hund's coupling in 5d Oxides using Resonant Inelastic X-ray Scattering,"We report resonant inelastic X-ray scattering (RIXS) measurements on ordered
double perovskite samples containing Re$^{5+}$ and Ir$^{5+}$ with $5d^2$ and
$5d^4$ electronic configurations respectively. In particular, the observed RIXS
spectra of Ba$_2$YReO$_6$ and Sr$_2$MIrO$_6$ (M=Y, Gd) show sharp
intra-t$_{2g}$ transitions, which can be quantitatively understood using a
minimal `atomic' Hamiltonian incorporating spin-orbit coupling ($\lambda$) and
Hund's coupling ($J_H$). Our analysis yields $\lambda=0.38(2)$eV with
$J_H=0.26(2)$eV for Re$^{5+}$, and $\lambda=0.42(2)$eV with $J_H=0.25(4)$eV for
Ir$^{5+}$. Our results provide the first sharp estimates for the Hund's
coupling in $5d$ oxides, and suggest that it should be treated on equal footing
with spin-orbit interaction in multi-orbital $5d$ transition metal compounds.",1701.06584v3
2019-10-02,Proximity induced spin orbit effects in graphene on Au,"We introduce a $p_{z}-d$ coupling model Hamiltonian for the $\pi$-graphene/Au
bands that predicts a rather large intrinsic spin-orbit (SO) coupling as are
being reported in recent experiments and DFT studies. Working within the
analytical Slater-Koster tight-binding approach we were able to identify the
overlapping orbitals of relevance in the enhancement of the SO coupling for
both, the sublattice symmetric (BC), and the ATOP (AC) stacking configurations.
Our model effective Hamiltonian reproduces quite well the experimental spectrum
for the two registries, and in addition, its shows that the hollow site
configuration (BC), in which the A/B sites remain symmetric, yields the larger
increase of the SO coupling. We also explore the Au-diluted case keeping the BC
configuration and showed that it renders the preservation of the SO-gap with a
similar SO interaction enhancement as the undiluted case but with a smaller
graphene-gold distance.",1910.01110v1
2011-08-30,Orbital ordering in the geometrically frustrated MgV$_2$O$_4$: \emph{Ab initio} electronic structure calculations,"In the light of recent interesting experimental work on MgV$_2$O$_4$ we
employ the density functional theory to investigate the crucial role played by
different interaction parameters in deciding its electronic and magnetic
properties. The strong Coulomb correlation in presence of antiferromagnetic
(AFM) coupling is responsible for the insulating ground state. In the ground
state the $d_{xz}$ and $d_{yz}$ orbitals are ordered and intra-chain vanadium
ions are antiferromagnetically coupled. The calculation gives small spin-orbit
coupling (SOC), which provides a tilt of $\sim11.3^0$ to the magnetic moment
from the z-axis. In the presence of weak SOC and strong exchange coupling, the
experimentally observed small magnetic moment and low AFM transition
temperature appear to arise from spin fluctuation due to activeness of
geometrical frustration.",1108.5907v2
2017-05-24,Pairing Tendencies in a Two-orbital Hubbard Model in One Dimension,"The recent discovery of superconductivity under high pressure in the ladder
compound BaFe$_2$S$_3$ has opened a new field of research in iron-based
superconductors with focus on quasi one-dimensional geometries. In this
publication, using the Density Matrix Renormalization Group technique, we study
a two-orbital Hubbard model defined in one dimensional chains. Our main result
is the presence of hole binding tendencies at intermediate Hubbard $U$
repulsion and robust Hund coupling $J_H/U=0.25$. Binding does not occur neither
in weak coupling nor at very strong coupling. The pair-pair correlations that
are dominant near half-filling, or of similar strength as the charge and spin
correlation channels, involve hole-pair operators that are spin singlets, use
nearest-neighbor sites, and employ different orbitals for each hole. The Hund
coupling strength, presence of robust magnetic moments, and antiferromagnetic
correlations among them are important for the binding tendencies found here.",1705.08780v2
2016-01-29,Weak-coupling superconductivity in a strongly correlated iron pnictide,"Iron-based superconductors have been found to exhibit an intimate interplay
of orbital, spin, and lattice degrees of freedom, dramatically affecting their
low-energy electronic properties, including superconductivity. Albeit the
precise pairing mechanism remains unidentified, several candidate interactions
have been suggested to mediate the superconducting pairing, both in the orbital
and in the spin channel. Here, we employ optical spectroscopy (OS),
angle-resolved photoemission spectroscopy (ARPES), ab initio band-structure,
and Eliashberg calculations to show that nearly optimally doped
NaFe$_{0.978}$Co$_{0.022}$As exhibits some of the strongest orbitally selective
electronic correlations in the family of iron pnictides. Unexpectedly, we find
that the mass enhancement of itinerant charge carriers in the strongly
correlated band is dramatically reduced near the $\Gamma$ point and attribute
this effect to orbital mixing induced by pronounced spin-orbit coupling.
Embracing the true band structure allows us to describe all low-energy
electronic properties obtained in our experiments with remarkable consistency
and demonstrate that superconductivity in this material is rather weak and
mediated by spin fluctuations.",1601.08195v1
2023-04-07,Electron confinement in chain-doped TMDs: A platform for spin-orbit coupled 1D physics,"The state-of-the-art defect engineering techniques have paved the way to
realize novel quantum phases out of pristine materials. Here, through
density-functional calculations and model studies, we show that the chain-doped
monolayer transition metal dichalcogenides (TMDs), where M atoms on a single
the zigzag chains are replaced by a higher-valence transition-metal element
M$^\prime$ (MX$_2$/M$^\prime$), exhibit one-dimensional (1D) bands. These 1D
bands, occurring in the fundamental gap of the pristine material, are
dispersive along the doped chain but are strongly confined along the lateral
direction. This confinement occurs as the bare potential of the dopant chain
formed by the positively charged M$^\prime$ ions resembles the potential well
of a uniformly charged wire. These bands could show novel 1D physics, including
a new type of Tomonaga-Luttinger liquid behavior, multi-orbital Mott insulator
physics, and an unusual optical absorption, due to the simultaneous presence of
the spin-orbit coupling, strong correlation, multiple orbitals, Rashba spin
splitting, and broken symmetry. For the half-filled 1D bands, we find, quite
surprisingly, a broadening of the 1D bands due to correlation, as opposed to
the expected band narrowing. This is interpreted to be due to multiple orbitals
forming the single Hubbard band at different points of the Brillouin zone.
Furthermore, due to the presence of an intrinsic electric field along the
lateral direction, the 1D bands are Rashba spin-split and provide a new
mechanism for tuning the valley dependent optical transitions.",2304.03620v1
2012-11-29,Microscopic theory of magnetism in Sr3Ir2O7,"An intriguing idea of spin-orbit Mott insulator has been proposed to explain
magnetic insulating behavior in various iridates. This scenario relies on the
strength of the spin-orbit coupling being comparable to electronic
correlations, and it is not a priori obvious whether this picture is valid for
all iridates. In particular, Sr3Ir2O7 exhibits a small charge gap and magnetic
moment compared to Sr2IrO4, questioning the validity of such hypothesis. To
understand the microscopic mechanism for magnetism in Sr3Ir2O7, we construct a
tight binding model taking into account the full t2g- orbitals, the staggered
rotation of the local octahedra, and the bilayer structure. The bands near the
Fermi level are mainly characterized by the total angular momentum Jeff = 1/2,
except below the {\Gamma} point, supporting a reasonably strong spin-orbit
coupling picture. A first order transition to a collinear antiferromagnet via
multi-orbital Hubbard interactions is found within the mean field
approximation. The magnetic moment jump at the transition is consistently
smaller than Sr2IrO4, originated from the underlying band structure of a barely
band insulator. Given the small charge gap and moment observed in Sr3Ir2O7, the
system is close to a magnetic transition. A comparison to a spin-model is
presented and connection to the Mott insulator is also discussed.",1211.7067v1
2011-07-14,"Role of Degeneracy, Hybridization, and Nesting in the Properties of Multi-Orbital Systems","To understand the role that degeneracy, hybridization, and nesting play in
the magnetic and pairing properties of multiorbital Hubbard models we here
study numerically two types of two- orbital models, both with hole-like and
electron-like Fermi surfaces (FS's) that are related by nesting vectors ({\pi},
0) and (0, {\pi}). In one case the bands that determine the FS's arise from
strongly hybridized degenerate dxz and dyz orbitals, while in the other the two
bands are determined by non-degenerate and non-hybridized s-like orbitals.
Using a variety of techniques, in the weak coupling regime it is shown that
only the model with hybridized bands develops metallic magnetic order, while
the other model exhibits an ordered excitonic orbital-transverse spin state
that is insulating and does not have a local magnetization. However, both
models display similar insulating magnetic stripe ordering in the strong
coupling limit. These results indicate that nesting is a necessary but not
sufficient condition for the development of ordered states with finite local
magnetization in multiorbital Hubbard systems; the additional ingredient
appears to be that the nested portions of the bands need to have the same
orbital flavor. This condition can be achieved via strong hybridization of the
orbitals in weak coupling or via the FS reconstruction induced by the Coulomb
interactions in the strong coupling regime. This effect also impacts the
pairing symmetry as demonstrated by the study of the dominant pairing channels
for the two models.",1107.2962v1
2021-09-01,Influence of Rashba spin-orbit and Rabi couplings on the miscibility and ground state phases of binary Bose-Einstein condensates,"We study the miscibility properties and ground state phases of two-component
spin-orbit (SO) coupled Bose-Einstein condensates (BECs) in a harmonic trap
with strong axial confinement. By numerically solving the coupled
Gross-Pitaevskii equations in the two-dimensional setting, we analyze the
SO-coupled BECs for two possible permutations of the intra- and interspecies
interactions, namely (i) weak intra- and weak interspecies interactions (W-W)
and (ii) weak intra- and strong interspecies interactions (W-S). Considering
the density overlap integral as a miscibility order parameter, we investigate
the miscible-immiscible transition by varying the coupling parameters. We
obtain various ground state phases, including plane wave, half quantum vortex,
elongated plane wave, and different stripe wave patterns for W-W interactions.
For finite Rabi coupling, an increase in SO coupling strength leads to the
transition from the fully miscible to the partially miscible state. We also
characterize different ground states in the coupling parameter space using the
root mean square sizes of the condensate. The spin density vector for the
ground state phases exhibits density, quadrupole and dipole like spin
polarizations. For the W-S interaction, in addition to that observed in the W-W
case, we witness semi vortex, mixed mode, and shell-like immiscible phases. We
notice a wide variety of spin polarizations, such as density, dipole,
quadrupole, symbiotic, necklace, and stripe-like patterns for the W-S case. A
detailed investigation in the coupling parameter space indicates immiscible to
miscible state phase transition upon varying the Rabi coupling for a fixed
Rashba SO coupling. The critical Rabi coupling for the immiscible-miscible
phase transition decreases upon increasing the SO coupling strength.",2109.00491v1
2022-09-15,Spin-orbital-angular-momentum-coupled quantum gases,"We briefly review the recent progress of theories and experiments on
spin-orbital-angular-momentum (SOAM)-coupled quantum gases. The coupling
between the intrinsic degree of freedom of particles and their external orbital
motions widely exists in universe, and leads to a broad variety of fundamental
phenomena both in the classical physics and quantum mechanics. Recent
realization of synthetic SOAM coupling in cold atoms has attracted a great deal
of attention, and stimulates a large amount of considerations on exotic quantum
phases in both Bose and Fermi gases. In this review, we present a basic idea of
engineering SOAM coupling in neutral atoms, starting from a semiclassical
description of atom-light interaction. Unique features of the single-particle
physics in the presence of SOAM coupling are discussed. The intriguing
ground-state quantum phases of weakly interacting Bose gases are introduced,
with emphasis on a so-called angular stripe phase, which has yet been observed
at present. It is demonstrated how to generate a stable giant vortex in a
SOAM-coupled Fermi superfluid. We also discuss topological characters of a
Fermi superfluid in the presence of SOAM coupling. We then introduce the
experimental achievement of SOAM coupling in $^{87}$Rb Bose gases and its first
observation of phase transitions. The most recent development of SOAM-coupled
Bose gases in experiments is also summarized. Regarding the controllability of
ultracold quantum gases, it opens a new era, on the quantum simulation point of
view, to study the fundamental physics resulted from SOAM coupling as well as
newly emergent quantum phases.",2209.07051v2
2016-10-20,All-Electrical Spin Field Effect Transistor in van der Waals Heterostructures at Room Temperature,"Spintronics aims to exploit the spin degree of freedom in solid state devices
for data storage and information processing technologies. The fundamental
spintronic device concepts such as creation, manipulation and detection of spin
polarization has been demonstrated in semiconductors and spin transistor
structures using both the electrical and optical methods. However, an unsolved
challenge in the field is the realization of all electrical methods to control
the spin polarization and spin transistor operation at ambient temperature. For
this purpose, two-dimensional (2D) crystals offer a unique platform due to
their remarkable and contrasting spintronic properties, such as weak spin-orbit
coupling (SOC) in graphene and strong SOC in molybdenum disulfide (MoS$_2$).
Here we combine graphene and MoS$_2$ in a van der Waals heterostructure to
realize the electric control of the spin polarization and spin lifetime, and
demonstrated a spin field-effect transistor (spin-FET) at room temperature in a
non-local measurement geometry. We observe electrical gate control of the spin
valve signal due to pure spin transport and Hanle spin precession signals in
the graphene channel in proximity with MoS$_2$ at room temperature. We show
that this unprecedented control over the spin polarization and lifetime stems
from the gate-tuning of the Schottky barrier at the MoS$_2$/graphene interface
and MoS$_2$ channel conductivity leading to spin interaction with high SOC
material. The all-electrical creation, transport and control of the spin
polarization in a spin-FET device at room temperature is a substantial step in
the field of spintronics. It opens a new platform for the interplay of spin,
charge and orbital degrees of freedom for testing a plethora of exotic physical
phenomena, which can be key building blocks in future device architectures.",1610.06326v1
2015-04-17,"Electrically Engineered Band Gap in Two-Dimensional Ge, Sn, and Pb: A First-Principles and Tight-Binding Approach","First-principles calculations were performed to investigate the electronic
structure of two-dimensional (2-D) Ge, Sn, and Pb without and with the presence
of an external electric field in combination with spin-orbit coupling.
Tight-binding calculations based on four orbitals per atom and an effective
single orbital are presented to match with the results obtained from
first-principles calculations. In particular, the electronic band structure and
the band splitting are investigated with both models. Moreover, the simple
$k\cdot p$ model is also considered in order to understand the band splitting
in the presence of an external electric field and spin-orbit coupling. A large
splitting is obtained, which is expected to be useful for spintronic devices.
The fair agreement between the first-principle, $k\cdot p$ model, and
tight-binding approaches leads to a table of parameters for future
tight-binding studies on hexagonal 2-D nanostructures. By using the tight
binding parameters, the transport properties of typical 0-D triangular quantum
dots between two semi-infinite electrodes in the presence of spin-orbit
coupling are addressed.",1504.04601v1
2021-06-18,Magnetic response of metallic nanoparticles: Geometric and weakly relativistic effects,"While the large paramagnetic response measured in certain ensembles of
metallic nanoparticles has been assigned to orbital effects of conduction
electrons, the spin-orbit coupling has been pointed out as a possible origin of
the anomalously large diamagnetic response observed in other cases. Such a
relativistic effect, arising from the inhomogeneous electrostatic potential
seen by the conduction electrons, might originate from the host ionic lattice,
impurities, or the self-consistent confining potential. Here we theoretically
investigate the effect of the spin-orbit coupling arising from the confining
potential, quantifying its contribution to the zero-field magnetic
susceptibility and gauging it against the ones generated by other
weakly-relativistic corrections. Two ideal geometries are considered in detail,
the sphere and the half-sphere, focusing on the expected increased role of the
spin-orbit coupling upon a symmetry reduction, and the application of these
results to actual metallic nanoparticles is discussed. The matrix elements of
the different weakly-relativistic corrections are obtained and incorporated in
a perturbative treatment of the magnetic field, leading to tractable
semi-analytical and semiclassical expressions for the case of the sphere, while
a numerical treatment becomes necessary for the half-sphere. The correction to
the zero-field susceptibility arising from the spin-orbit coupling in a single
sphere is quite small, and it is dominated by the weakly-relativistic kinetic
energy correction, which in turn remains considerably smaller than the typical
values of the nonrelativistic zero-field susceptibility. Moreover, the
spin-orbit contribution to the average response for ensembles of nanoparticles
with a large size dispersion is shown to vanish. The symmetry reduction in
going from the single sphere to the half-sphere does not translate into a
significant (...)",2106.10113v3
2023-12-07,Colossal orbital Zeeman effect driven by tunable spin-Berry curvature in a kagome metal,"Berry phase and the related concept of Berry curvature can give rise to many
unconventional phenomena in solids. In this work, we discover colossal orbital
Zeeman effect of topological origin in a newly synthesized bilayer kagome metal
TbV6Sn6. We use spectroscopic-imaging scanning tunneling microscopy to study
the magnetic field induced renormalization of the electronic band structure.
The nonmagnetic vanadium d-orbitals form Dirac crossings at the K point with a
small mass gap and strong Berry curvature induced by the spin-orbit coupling.
We reveal that the magnetic field leads to the splitting of gapped Dirac
dispersion into two branches with giant momentum-dependent g factors, resulting
in the substantial renormalization of the Dirac band. These measurements
provide a direct observation of the magnetic field controlled orbital Zeeman
coupling to the enormous orbital magnetic moments of up to 200 Bohr magnetons
near the gapped Dirac points. Interestingly, the effect is increasingly
non-linear, and becomes gradually suppressed at higher magnetic fields.
Theoretical modeling further confirms the existence of orbital magnetic moments
in TbV6Sn6 produced by the non-trivial spin-Berry curvature of the Bloch wave
functions. Our work provides the first direct insight into the
momentum-dependent nature of topological orbital moments and their tunability
by magnetic field concomitant with the evolution of the spin-Berry curvature.
Significantly large orbital magnetic moments driven by the Berry curvature can
also be generated by other quantum numbers beyond spin, such as the valley in
certain graphene-based structures, which may be unveiled using the same tools
highlighted in our work.",2312.04445v1
2015-04-13,Transverse and longitudinal angular momenta of light,"We review basic physics and novel types of optical angular momentum. We start
with a theoretical overview of momentum and angular momentum properties of
generic optical fields, and discuss methods for their experimental
measurements. In particular, we describe the well-known longitudinal (i.e.,
aligned with the mean momentum) spin and orbital angular momenta in polarized
vortex beams. Then, we focus on the transverse (i.e., orthogonal to the mean
momentum) spin and orbital angular momenta, which were recently actively
discussed in theory and observed in experiments. First, the recently-discovered
transverse spin angular momenta appear in various structured fields: evanescent
waves, interference fields, and focused beams. We show that there are several
kinds of transverse spin angular momentum, which differ strongly in their
origins and physical properties. We describe extraordinary features of the
transverse optical spins and overview recent experiments. In particular, the
helicity-independent transverse spin inherent in edge evanescent waves offers
robust spin-direction coupling at optical interfaces (the quantum spin Hall
effect of light). Second, we overview the transverse orbital angular momenta of
light, which can be both extrinsic and intrinsic. These two types of the
transverse orbital angular momentum are produced by spatial shifts of the
optical beams (e.g., in the spin Hall effect of light) and their Lorentz
boosts, respectively. Our review is underpinned by a unified theory of the
angular momentum of light based on the canonical momentum and spin densities,
which avoids complications associated with the separation of spin and orbital
angular momenta in the Poynting picture. It allows us to construct
comprehensive classification of all known optical angular momenta based on
their key parameters and main physical properties.",1504.03113v2
2022-09-16,"Interplay of Structural Chirality, Electron Spin and Topological Orbital in Chiral Molecular Spin Valves","Chirality has been a property of central importance in chemistry and biology
for more than a century, and is now taking on increasing relevance in condensed
matter physics. Recently, electrons were found to become spin polarized after
transmitting through chiral molecules, crystals, and their hybrids. This
phenomenon, called chirality-induced spin selectivity (CISS), presents broad
application potentials and far-reaching fundamental implications involving
intricate interplays among structural chirality, topological states, and
electronic spin and orbitals. However, the microscopic picture of how chiral
geometry influences electronic spin remains elusive. In this work, via a direct
comparison of magnetoconductance (MC) measurements on magnetic
semiconductor-based chiral molecular spin valves with normal metal electrodes
of contrasting strengths of spin-orbit coupling (SOC), we unambiguously
identified the origin of the SOC, a necessity for the CISS effect, given the
negligible SOC in organic molecules. The experiments revealed that a
heavy-metal electrode provides SOC to convert the orbital polarization induced
by the chiral molecular structure to spin polarization. Our results evidence
the essential role of SOC in the metal electrode for engendering the CISS spin
valve effect. A tunneling model with a magnetochiral modulation of the
potential barrier is shown to quantitatively account for the unusual transport
behavior. This work hence produces critical new insights on the microscopic
mechanism of CISS, and more broadly, reveals a fundamental relation between
structure chirality, electron spin, and orbital.",2209.08117v1
2017-07-06,The role of spin-orbit coupling in the electronic structure of IrO$_2$,"The delicate interplay of electronic charge, spin, and orbital degrees of
freedom is in the heart of many novel phenomena across the transition metal
oxide family. Here, by combining high- resolution angle resolved photoemission
spectroscopy and first principles calculations (with and without spin-orbit
coupling), the electronic structure of the rutile binary iridate, IrO$_2$ is
investigated. The detailed study of electronic bands measured on a high-quality
single crystalline sample, and use of a wide range of photon energy provide a
huge improvement over the previous studies. The excellent agreement between
theory and experimental results shows that the single-particle DFT description
of IrO$_2$ band structure is adequate, without the need of invoking any
treatment of correlation effects. Although many observed features point to a 3D
nature of the electronic structure, clear surface effects are revealed. The
discussion of the orbital character of the relevant bands crossing the Fermi
level sheds light on spin orbit coupling-driven phenomena in this material,
unveiling a spin-orbit induced avoided crossing, a property likely to play key
role in its large spin Hall effect.",1707.01624v3
2016-01-21,Detection of spin pumping from YIG by spin-charge conversion in a Au/Ni$_{80}$Fe$_{20}$ spin-valve structure,"Many experiments have shown the detection of spin-currents driven by
radio-frequency spin pumping from yttrium iron garnet (YIG), by making use of
the inverse spin-Hall effect, which is present in materials with strong
spin-orbit coupling, such as Pt. Here we show that it is also possible to
directly detect the resonance-driven spin-current using Au/permalloy (Py,
Ni$_{80}$Fe$_{20}$) devices, where Py is used as a detector for the spins
pumped across the YIG/Au interface. This detection mechanism is equivalent to
the spin-current detection in metallic non-local spin-valve devices. By finite
element modeling we compare the pumped spin-current from a reference Pt strip
with the detected signals from the Au/Py devices. We find that for one series
of Au/Py devices the calculated spin pumping signals mostly match the
measurements, within 20%, whereas for a second series of devices additional
signals are present which are up to a factor 10 higher than the calculated
signals from spin pumping. We also identify contributions from thermoelectric
effects caused by the resonant (spin-related) and non-resonant heating of the
YIG. Thermocouples are used to investigate the presence of these thermal
effects and to quantify the magnitude of the Spin-(dependent-)Seebeck effect.
Several additional features are observed, which are also discussed.",1601.05605v1
2016-05-23,Direct comparison of current-induced spin polarization in topological insulator Bi2Se3 and InAs Rashba states,"Three-dimensional topological insulators (TIs) exhibit time-reversal symmetry
protected, linearly dispersing Dirac surface states. Band bending at the TI
surface may also lead to coexisting trivial two-dimensional electron gas (2DEG)
states with parabolic energy dispersion that exist as spin-split pairs due to
Rashba spin-orbit coupling (SOC). A bias current is expected to generate spin
polarization in both systems arising from their helical spin-momentum locking.
However, their induced spin polarization is expected to be different in both
magnitude and sign. Here, we compare spin potentiometric measurements of bias
current-generated spin polarization in Bi2Se3(111) films where Dirac surface
states coexist with trivial 2DEG states, with identical measurements on
InAs(001) samples where only trivial 2DEG states are present. We observe spin
polarization arising from spin-momentum locking in both cases, with opposite
signs of the spin voltage. We present a model based on spin dependent
electrochemical potentials to directly derive the signs expected for the TI
surface states, and unambiguously show that the dominant contribution to the
current-generated spin polarization measured in the TI is from the Dirac
surface states. This direct electrical access of the helical spin texture of
Dirac and Rashba 2DEG states is an enabling step towards the electrical
manipulation of spins in next generation TI and SOC based quantum devices.",1605.07155v1
2017-12-30,Spin-Hall effect and emergent antiferromagnetic phase transition in n-Si,"Spin current experiences minimal dephasing and scattering in Si due to small
spin-orbit coupling and spin-lattice interactions is the primary source of spin
relaxation. We hypothesize that if the specimen dimension is of the same order
as the spin diffusion length then spin polarization will lead to
non-equilibrium spin accumulation and emergent phase transition. In n-Si, spin
diffusion length has been reported up to 6 {\mu}m. The spin accumulation in Si
will modify the thermal transport behavior of Si, which can be detected with
thermal characterization. In this study, we report observation of spin-Hall
effect and emergent antiferromagnetic phase transition behavior using
magneto-electro-thermal transport characterization. The freestanding Pd (1 nm)/
Ni80Fe20 (75 nm)/ MgO (1 nm)/ n-Si (2 micron) thin film specimen exhibits a
magnetic field dependent thermal transport and spin-Hall magnetoresistance
behavior attributed to Rashba effect. An emergent phase transition is
discovered using self-heating 3omega method, which shows a diverging behavior
at 270 K as a function of temperature similar to a second order phase
transition. We propose that spin-Hall effect leads to the spin accumulation and
resulting emergent antiferromagnetic phase transition. We propose that the
length scale for Rashba effect can be equal to the spin diffusion length and
two-dimensional electron gas is not essential for it. The emergent
antiferromagnetic phase transition is attributed to the site inversion
asymmetry in diamond cubic Si lattice.",1801.00073v1
2019-10-10,Large multi-directional spin-to-charge conversion in low symmetry semimetal MoTe$_2$ at room temperature,"Efficient and versatile spin-to-charge current conversion is crucial for the
development of spintronic applications, which strongly rely on the ability to
electrically generate and detect spin currents. In this context, the spin Hall
effect has been widely studied in heavy metals with strong spin-orbit coupling.
While the high crystal symmetry in these materials limits the conversion to the
orthogonal configuration, unusual configurations are expected in low symmetry
transition metal dichalcogenide semimetals, which could add flexibility to the
electrical injection and detection of pure spin currents. Here, we report the
observation of spin-to-charge conversion in MoTe$_2$ flakes, which are stacked
in graphene lateral spin valves. We detect two distinct contributions arising
from the conversion of two different spin orientations. In addition to the
conventional conversion where the spin polarization is orthogonal to the charge
current, we also detect a conversion where the spin polarization and the charge
current are parallel. Both contributions, which could arise either from bulk
spin Hall effect or surface Edelstein effect, show large efficiencies
comparable to the best spin Hall metals and topological insulators. Our finding
enables the simultaneous conversion of spin currents with any in-plane spin
polarization in one single experimental configuration.",1910.04642v1
2019-04-02,Spin pumping and spin torque in interfacial tailored Co2FeAl/\b{eta}-Ta layers,"The Heusler ferromagnetic (FM) compound Co2FeAl interfaced with a high-spin
orbit coupling non-magnetic (NM) layer is a promising candidate for energy
efficient spin logic circuits. The circuit potential depends on the strength of
angular momentum transfer across the FM/NM interface; hence, requiring low spin
memory loss and high spin-mixing conductance. To highlight this issue, spin
pumping and spin-transfer torque ferromagnetic resonance measurements have been
performed on Co_2FeAl/\beta-Ta heterostructures tailored with Cu interfacial
layers. The interface tailored structure yields an enhancement of the effective
spin-mixing conductance. The interface transparency and spin memory loss
corrected values of the spin-mixing conductance, spin Hall angle and spin
diffusion length are found to be 3.40 \pm 0.01 \times 10^{19} m^{-2}, 0.029 \pm
0.003, and 2.3 \pm 0.5 nm, respectively. Furthermore, a high current modulation
of the effective damping of around 2.1 % has been achieved at an applied
current density of 1 \times 10^9 A/m^2 , which clearly indicates the potential
of using this heterostructure for energy efficient control in spin devices",1904.01506v3
2022-03-11,Full-plane persistent spin textures with cubic order intrinsic and anisotropic band splitting in bulk Lead-free materials,"Spin-orbit coupling (SOC) effects occurring in noncentrosymmetric materials
are known to be responsible for nontrivial spin configurations and a number of
emergent physical phenomena such as electrical control of spin degrees of
freedom and spin-to-charge conversion. The materials preserving a uniform spin
configuration in the momentum-space, known as persistent spin texture (PST),
provide long carrier spin lifetimes through persistent spin helix (PSH)
mechanism. However, most of the PST studied till now are attributed to the
linear in \textbf{\textit{k}} splitting and cease to exist locally around
certain high-symmetry-point of first Brillouin Zone (FBZ). The persistent spin
textures with purely cubic spin splittings have drawn attention owing to unique
benefits in spin transport. Here, by using the relativistic first-principles
calculations supplemented with \textbf{\textit{k.p}} analysis, we report the
emergence of purely cubic splitting (PCS) belonging to $D_{3h}$ point group,
which is enforced by in-plane mirror and three-fold rotation operations. In
addition, the in-plane mirror symmetry operation sustains the PST in larger
region (i.e. full planes) of FBZ alongside giant spin splitting. Our results
also demonstrate how application of uniaxial strain could be envisaged to tune
the magnitude of the PCS, preserving the PST. The observed PSTs provide a route
to non-dephasing spin transport with larger spin-Hall conductivity, thus
offering a promising platform for future spintronics devices.",2203.05978v1
1997-06-10,A timing formula for main-sequence star binary pulsars,"In binary radio pulsars with a main-sequence star companion, the spin-induced
quadrupole moment of the companion gives rise to a precession of the binary
orbit. As a first approximation one can model the secular evolution caused by
this classical spin-orbit coupling by linear-in-time changes of the longitude
of periastron and the projected semi-major axis of the pulsar orbit. This
simple representation of the precession of the orbit neglects two important
aspects of the orbital dynamics of a binary pulsar with an oblate companion.
First, the quasiperiodic effects along the orbit, due to the anisotropic
$1/r^3$ nature of the quadrupole potential. Secondly, the long-term secular
evolution of the binary orbit which leads to an evolution of the longitude of
periastron and the projected semi-major axis which is non-linear in time.
  In this paper a simple timing formula for binary radio pulsars with a
main-sequence star companion is presented which models the short-term secular
and most of the short-term periodic effects caused by the classical spin-orbit
coupling. I also give extensions of the timing formula which account for
long-term secular changes in the binary pulsar motion. It is shown that the
short-term periodic effects are important for the timing observations of the
binary pulsar PSR B1259--63. The long-term secular effects are likely to become
important in the next few years of timing observations of the binary pulsar PSR
J0045--7319. They could help to restrict or even determine the moments of
inertia of the companion star and thus probe its internal structure.
  Finally, I reinvestigate the spin-orbit precession of the binary pulsar PSR
J0045--7319 since the analysis given in the literature is based on an incorrect
expression for the precession of the longitude of periastron.",9706086v2
2014-02-05,Spin-orbit coupling as a source of long-range triplet proximity effect in superconductor-ferromagnet hybrid structures,"We investigate the proximity effect in diffusive superconducting hybrid
structures with a spin-orbit (SO) coupling. Our study is focused on the
singlet-triplet conversion and the generation of long-range superconducting
correlations in ferromagnetic elements. We derive the quasiclassical equations
for the Green's functions including the SO coupling terms in form of a
background SU(2) field. With the help of these equations, we first present a
complete analogy between the spin diffusion process in normal metals and the
generation of the triplet components of the condensate in a diffusive
superconducting structure in the presence of SO coupling. From this analogy it
turns out naturally that the SO coupling is an additional source of the
long-range triplet component (LRTC) besides the magnetic inhomogeneities
studied in the past. We demonstrate an explicit connection between an
inhomogeneous exchange field and SO coupling mechanisms for the generation of
the LRTC and establish the conditions for the appearance of the LRTC in
different geometries. We also consider a S/F bilayer in contact with normal
metal with SO coupling and show that the latter can be used as a source for the
LRTC. Our work gives a global description of the singlet-triplet conversion in
hybrids structures in terms of generic spin-fields and our results are
particularly important for the understanding of the physics underlying
spintronics devices with superconductor elements.",1402.1025v3
2023-11-10,Strong-coupling superconductivity of the Heusler-type compound ScAu2Al: Ab-initio studies,"The ScAu$_2$Al superconducting Heusler-type compound was recently
characterized to have the highest critical temperature of $T_c = 5.12$ K and
the strongest electron-phonon coupling among the Heusler family. In this work,
the electronic structure, phonons, electron-phonon coupling, and
superconductivity of ScAu$_2$Al are studied using \textit{ab initio}
calculations. The spin-orbit coupling significantly changes the electronic
structure removing the van Hove singularity from the vicinity of the Fermi
level. In the phonon spectrum, low frequency acoustic modes, additionally
softened by the spin-orbit interaction, strongly couple with electrons, leading
to the electron-phonon coupling constant $\lambda=1.25$, a record high among
Heuslers. The density functional theory for superconductors is then used to
analyze superconducting {state in this two-band superconductor}. The effect of
spin fluctuations (SF) on superconductivity is also analyzed. The calculated
critical temperatures of $T_c = 5.16$ K (4.79 K with SF) agree very well with
the experiment, confirming the electron-phonon mechanism of superconductivity
and showing a weak spin-fluctuations effect. The superconducting gaps formed on
two Fermi surface sheets exhibit moderate anisotropy. Their magnitudes confirm
the strong coupling regime, as the reduced average values are $2\Delta_1/k_BT_c
\simeq 4.1$ and $2\Delta_2/k_BT_c \simeq 4.3$. Anisotropy of the gaps and large
spread in their values significantly affect the calculated quasiparticle
density of states.",2311.06075v3
2006-10-24,Scattering on the lateral one-dimensional superlattice with spin-orbit coupling,"The problem of scattering of the two-dimensional electron gas on the lateral
one-dimensional superlattice both having different strengths of Rashba
spin-orbit coupling is investigated. The scattering is considered for all the
electron states on a given Fermi level. The distribution of spin density
components along the superlattice is studied for the transmitted states where
the formation of standing waves is observed. It is found that the shape of spin
density distribution is robust against the variations of the Rashba coupling
constants, the superlattice potential strength, and the Fermi level in the
electron gas.",0610657v3
2007-10-02,Microscopic mechanisms of spin-dependent electric polarization in 3d oxides,"We address a systematic microscopic theory of spin-dependent electric
polarization in 3d oxides starting with a generic three-site two-hole cluster.
A perturbation scheme realistic for 3d oxides is applied which implies the
quenching of orbital moments by low-symmetry crystal field, strong intra-atomic
correlations, the dp-transfer effects, and rather small spin-orbital coupling.
An effective spin operator of the electric dipole moment is deduced
incorporating both nonrelativistic and relativistic terms. The nonrelativistic
electronic polarization mechanism related with the effects of the
redistribution of the local on-site charge density due to $pd$ covalency and
exchange coupling is believed to govern the multiferroic behaviour in 3d
oxides. The relativistic exchange-dipole moment is mainly stems from the
nonrelativistic one due to the perturbation effect of Dzyaloshinsky-Moriya
coupling and is estimated to be a weak contributor to the electric polarization
observed in the most of 3d multiferroics.",0710.0496v1
2009-04-13,Metal-insulator transition in a quantum wire driven by a modulated Rashba spin-orbit coupling,"We study the ground-state properties of electrons confined to a quantum wire
and subject to a smoothly modulated Rashba spin-orbit coupling. When the period
of the modulation becomes commensurate with the band filling, the Rashba
coupling drives a quantum phase transition to a nonmagnetic insulating state.
Using bosonization and a perturbative renormalization group approach, we find
that this state is robust against electron-electron interactions. The gaps to
charge- and spin excitations scale with the amplitude of the Rashba modulation
with a common interaction-dependent exponent. An estimate of the expected size
of the charge gap, using data for a gated InAs heterostructure, suggests that
the effect can be put to practical use in a future spin transistor design.",0904.1846v2
2014-01-01,Analytic theory of Hund's metals: a renormalization group perspective,"We study the emergence of quasiparticles in Hund's metals with an
SU($M$)$\times$SU($N$)-symmetric Kondo impurity model carrying both spin and
orbital degrees of freedom. We show that the coupling of the impurity spin to
the conduction electrons can be \emph{ferromagnetic}, notably for hole-doped
iron pnictides. We derive the weak-coupling renormalization group (RG)
equations for arbitrary representations of SU($M$)$\times$SU($N$). A
ferromagnetic spin coupling results in a protracted RG flow, accounting for the
surprising particle-hole asymmetry that is observed in the iron-pnictide
systems. We establish the low coherence scale $T_{\rm K}$ which depends on the
filling through the impurity representation. We also discuss the temperature
dependence of the spin and orbital susceptibilities. Finally, we argue that
this mechanism explains the strong valence dependence of the coherence scale
observed in dilute transition-metal magnetic alloys.",1401.0331v3
2015-05-07,Currents induced by magnetic impurities in superconductors with spin-orbit coupling,"We show that superconducting currents are generated around magnetic
impurities and ferromagnetic islands proximity-coupled to superconductors with
finite spin-orbit coupling. Using the Ginzburg-Landau theory, T-matrix
calculation, as well as self-consistent numerical simulation on a lattice, we
find a strong dependence of the current on the direction and magnitude of the
magnetic moment. We establish that in the case of point magnetic impurities,
the current is carried by the induced Yu-Shiba-Rusinov (YSR) subgap states. In
the vicinity of the phase transition, where the YSR states cross at zero
energy, the current increases dramatically. Furthermore, we show that the
currents are orthogonal to the local spin polarization and, thus, can be probed
by measuring the spin-polarized local density of states.",1505.01672v2
2015-05-08,Visibility and stability of superstripes in a spin-orbit-coupled Bose-Einstein condensate,"We consider a spin-$1/2$ Bose-Einstein condensate with equal Rashba and
Dresselhaus spin-orbit coupling. After reviewing some relevant features of the
quantum phases of the system, we present a short study on how their properties
are changed by the presence of non-zero magnetic detunings and spin-asymmetric
interactions. At small values of the Raman coupling and of the magnetic field
the so-called stripe phase occurs, which displays both superfluidity and
periodic density modulations, in analogy with supersolids. We finally review a
recent proposal (Phys. Rev. A 90, 041604) to improve the visibility of the
fringes, based on the space separation of the two spin components into a 2D
bi-layer configuration and on the application of a $\pi/2$ Bragg pulse, and we
show that this new configuration also yields a sizable increase of the
stability of the stripe phase against magnetic fluctuations.",1505.02088v2
2015-11-04,S=1/2 quantum critical spin ladders produced by orbital ordering in Ba2CuTeO6,"The ordered hexagonal perovskite Ba2CuTeO6 hosts weakly coupled S=1/2 spin
ladders produced by an orbital ordering of Cu2+. The magnetic susceptibility
chi(T) of Ba2CuTeO6 is well described by that expected for isolated spin
ladders with exchange coupling of J~86 K but shows a deviation from the
expected thermally activated behavior at low temperatures below T*~25 K. An
anomaly in chi(T), indicative of magnetic ordering, is observed at T_mag=16 K.
No clear signature of long-range ordering, however, is captured in NMR,
specific heat or neutron diffraction measurements at and below T_mag. The
marginal magnetic transition, indicative of strong quantum fluctuations, is
evidence that Ba2CuTeO6 is in very close proximity to a quantum critical point
between a magnetically ordered phase and a gapped spin liquid controlled by
inter-ladder couplings.",1511.01477v1
2017-03-22,Spin-orbit coupling induced two-electron relaxation in silicon donor pairs,"We unravel theoretically a key intrinsic relaxation mechanism among the
low-lying singlet and triplet donor-pair states in silicon, an important
element in the fast-developing field of spintronics and quantum computation.
Despite the perceived weak spin-orbit coupling (SOC) in Si, we find that our
discovered relaxation mechanism, combined with the electron-phonon and
inter-donor interactions, dominantly drives the transitions in the two-electron
states over a large range of donor coupling regime. The scaling of the
relaxation rate with inter-donor exchange interaction $J$ goes from $J^5$ to
$J^4$ at the low to high temperature limits. Our analytical study draws on the
symmetry analysis over combined band, donor envelope and valley configurations.
It uncovers naturally the dependence on the donor-alignment direction and
triplet spin orientation, and especially on the dominant SOC source from donor
impurities. While a magnetic field is not necessary for this relaxation, unlike
in the single-donor spin relaxation, we discuss the crossover behavior with
increasing Zeeman energy in order to facilitate comparison with experiments.",1703.07788v2
2017-04-05,Collective excitation of a trapped Bose-Einstein condensate with spin-orbit coupling,"We investigate the collective excitations of a Raman-induced spin-orbit
coupled Bose-Einstein condensate confined in a quasi one-dimension harmonic
trap using the Bogoliubov method. By tuning the Raman coupling strength, three
phases of the system can be identified. By calculating the transition strength,
we are able to classify various excitation modes that are experimentally
relevant. We show that the three quantum phases possess distinct features in
their collective excitation properties. In particular, the spin dipole and the
spin breathing modes can be used to clearly map out the phase boundaries. We
confirm these predictions by direct numerical simulations of the quench
dynamics that excites the relevant collective modes.",1704.01242v1
2017-10-19,Moiré excitons: from programmable quantum emitter arrays to spin-orbit coupled artificial lattices,"Highly uniform and ordered nanodot arrays are crucial for high performance
quantum optoelectronics including new semiconductor lasers and single photon
emitters, and for synthesizing artificial lattices of interacting
quasiparticles towards quantum information processing and simulation of
many-body physics. Van der Waals heterostructures of 2D semiconductors are
naturally endowed with an ordered nanoscale landscape, i.e. the moir\'e pattern
that laterally modulates electronic and topographic structures. Here we find
these moir\'e effects realize superstructures of nanodot confinements for
long-lived interlayer excitons, which can be either electrically or strain
tuned from perfect arrays of quantum emitters to excitonic superlattices with
giant spin-orbit coupling (SOC). Besides the wide range tuning of emission
wavelength, the electric field can also invert the spin optical selection rule
of the emitter arrays. This unprecedented control arises from the gauge
structure imprinted on exciton wavefunctions by the moir\'e, which underlies
the SOC when hopping couples nanodots into superlattices. We show that the
moir\'e hosts complex-hopping honeycomb superlattices, where exciton bands
feature a Dirac node and two Weyl nodes, connected by spin-momentum locked
topological edge modes.",1710.07015v1
2018-05-16,Extended Creutz ladder with spin-orbit coupling: a one-dimensional analog of the Kane-Mele model,"We construct a topological ladder model, one-dimensional, following the steps
which lead to the Kane-Mele model in two dimensions. Starting with a Creutz
ladder we modify it so that the gap closure points can occur at either $k = \pi
/ 2$ or $-\pi/2$. We then couple two such models, one for each spin channel, in
such a way that time-reversal invariance is restored. We also add a Rashba
spin-orbit coupling term. The model falls in the CII symmetry class. We derive
the relevant $2\mathbb{Z}$ topological index, calculate the phase diagram and
demonstrate the existence of edge states. We also give the thermodynamic
derivation of the quantum spin Hall conductance (St\v{r}eda-Widom). Approximate
implementation of this result indicates that this quantity is sensitive to the
topological behavior of the model.",1806.01111v1
2020-05-09,Chaotic cyclotron and Hall trajectories due to spin-orbit coupling,"We demonstrate that the synergistic effect of a gauge field, Rashba
spin-orbit coupling (SOC), and Zeeman splitting can generate chaotic cyclotron
and Hall trajectories of particles. The physical origin of the chaotic behavior
is that the SOC produces a spin-dependent (so-called anomalous) contribution to
the particle velocity and the presence of Zeeman field reduces the number of
integrals of motion. By using analytical and numerical arguments, we study the
conditions of chaos emergence and report the dynamics both in the regular and
chaotic regimes. {We observe the critical dependence of the dynamic patterns
(such as the chaotic regime onset) on small variations in the initial
conditions and problem parameters, that is the SOC and/or Zeeman constants. The
transition to chaotic regime is further verified by the analysis of phase
portraits as well as Lyapunov exponents spectrum.} The considered chaotic
behavior can occur in solid state systems, weakly-relativistic plasmas, and
cold atomic gases with synthetic gauge fields and spin-related couplings.",2005.04468v1
2020-09-09,Magnetic Anisotropy in Spin-3/2 with Heavy Ligand in Honeycomb Mott Insulators: Application to CrI$_3$,"Ferromagnetism in the two-dimensional CrI$_3$ has generated a lot of
excitement, and it was recently proposed that the spin-orbit coupling (SOC) in
Iodine may generate bond-dependent spin interactions leading to magnetic
anisotropy. Here we derive a microscopic spin model of S=3/2 on transition
metals surrounded by heavy ligands in honeycomb Mott insulators using a
strong-coupling perturbation theory. For ideal octahedra we find Heisenberg and
Kitaev interactions, which favor the magnetic moment along the cubic axis via
quantum fluctuations. When a slight trigonal distortion of the octahedra is
present together with the SOC, three additional interactions arise, comprised
of the off-diagonal symmetric $\Gamma$ and $\Gamma^\prime$, and single-ion
anisotropy. The resulting magnetic anisotropy pins the moment perpendicular to
the honeycomb plane as observed in a single-layer of CrI$_3$, suggesting the
significance of SOC and trigonal distortion in understanding magnetism of two
dimensional Mott insulators. Comparison to the spin-orbit coupled $J_{\rm
eff}$= 1/2 and S=1 models is also presented.",2009.04475v2
2020-09-28,Spin-orbit coupling and linear crossings of dipolar magnons in van der Waals antiferromagnets,"A magnon spin-orbit coupling, induced by the dipole-dipole interaction, is
derived in monoclinic-stacked bilayer honeycomb spin lattice with perpendicular
magnetic anisotropy and antiferromagnetic interlayer coupling. Linear crossings
are predicted in the magnon spectrum around the band minimum in G valley, as
well as in the high frequency range around the zone boundary. The linear
crossings in K and K' valleys, which connect the acoustic and optical bands,
can be gapped when the intralayer dipole-dipole or Kitaev interactions exceed
the interlayer dipole-dipole interaction, resulting in a phase transition from
semimetal to insulator. Our results are useful for analyzing the magnon spin
dynamics and transport properties in van der Waals antiferromagnet.",2009.13660v1
2021-01-19,Tunable Rashba spin-orbit coupling and its interplay with multiorbital effect and magnetic ordering at oxide interfaces,"The complex oxide heterostructures such as LaAlO3/SrTiO3 (LAO/STO) interface
are paradigmatic platforms to explore emerging multi-degrees of freedom
coupling and the associated exotic phenomena. In this study, we reveal the
effects of multiorbital and magnetic ordering on Rashba spin-orbit coupling
(SOC) at the LAO/STO (001) interface. Based on first-principles calculations,
we show that the Rashba spin splitting near the conduction band edge can be
tuned substantially by the interfacial insulator-metal transition due to the
multiorbital effect of the lowest t_2g bands. We further unravel a competition
between Rashba SOC and intrinsic magnetism, in which the Rashba SOC induced
spin polarization is suppressed by the interfacial magnetic ordering. These
results deepen our understanding of intricate electronic and magnetic
reconstruction at the perovskite oxide interfaces and shed light on the
engineering of oxide heterostructures for all-oxides-based spintronic devices.",2101.07586v1
2021-02-03,Exciting the Goldstone Modes of a Supersolid Spin-Orbit-Coupled Bose Gas,"Supersolidity is deeply connected with the emergence of Goldstone modes,
reflecting the spontaneous breaking of both phase and translational symmetry.
Here, we propose accessible signatures of these modes in harmonically trapped
spin-orbit-coupled Bose-Einstein condensates, where supersolidity appears in
the form of stripes. By suddenly changing the trapping frequency, an axial
breathing oscillation is generated, whose behavior changes drastically at the
critical Raman coupling. Above the transition, a single mode of hybridized
density and spin nature is excited, while below it, we predict a beating effect
signaling the excitation of a Goldstone spin-dipole mode. We further provide
evidence for the Goldstone mode associated with the translational motion of
stripes. Our results open up new perspectives for probing supersolid properties
in experimentally relevant configurations with both symmetric as well as highly
asymmetric intraspecies interactions.",2102.02221v2
2022-02-15,Electron Transfer and Spin-Orbit Coupling: How Strong are Berry Force Effects In and Out of Equilibrium in the Presence of Nuclear Friction?,"We investigate a spin-boson inspired model of electron transfer, where the
diabatic coupling is given by a position-dependent phase, exp(iWx). We consider
both equilibrium and nonequilibrium initial conditions. We show that, for this
model, all equilibrium results are completely invariant to the sign of W(to
infinite order). However, the nonequilibrium results do depend on the sign of
W, suggesting that photo-induced electron transfer dynamics are meaningfully
affected by Berry forces even in the presence of nuclear friction; furthermore,
whenever there is spin-orbit coupling, electronic spin polarization can emerge
(at least for some time).",2202.07204v1
2022-02-27,"Layered Opposite Rashba Spin-Orbit Coupling in Bilayer Graphene: Loss of Spin Chirality, Symmetry Breaking and Topological Transition","Inversion symmetry in bilayer graphene allows for layered opposite Rashba
spin-orbit coupling (LO-RSOC) -- the situation when the RSOC has the same
magnitude but the opposite sign in two coupled spatially separated layers. We
show that the LO-RSOC results in the loss of spin chirality in the momentum
space, in contrast to the common uniform RSOC. This chirality loss makes it
difficult to experimentally establish whether the LO-RSOC (on the scale of 10
meV) exists, because the band structure is insensitive to it. To solve this
problem, we propose to identify the LO-RSOC either by gating to break the
inversion symmetry or by magnetic field to break the time-reversal symmetry.
Remarkably, we observe the transition between trivial and non-trivial band
topology as the system deviates from the LO Rashba state. Ab inito calculations
suggest that bilayer graphene encapsulated by two monolayers of Au is a
candidate to be a LO Rashba system.",2202.13267v2
2023-07-10,Weyl Semimetallic State in the Rashba-Hubbard Model,"We investigate the Hubbard model with the Rashba spin-orbit coupling on a
square lattice. The Rashba spin-orbit coupling generates two-dimensional Weyl
points in the band dispersion. In a system with edges along [11] direction,
zero-energy edge states appear, while no edge state exists for a system with
edges along an axis direction. The zero-energy edge states with a certain
momentum along the edges are predominantly in the up-spin state on the right
edge, while they are predominantly in the down-spin state on the left edge.
Thus, the zero-energy edge states are helical. By using a variational Monte
Carlo method for finite Coulomb interaction cases, we find that the Weyl points
can move toward the Fermi level by the correlation effects. We also investigate
the magnetism of the model by the Hartree-Fock approximation and discuss weak
magnetic order in the weak-coupling region.",2307.04307v2
2011-03-10,Engineering a p+ip Superconductor: Comparison of Topological Insulator and Rashba Spin-Orbit Coupled Materials,"We compare topological insulator materials and Rashba coupled surfaces as
candidates for engineering p+ip superconductivity. Specifically, in each type
of material we examine 1) the limitations to inducing superconductivity by
proximity to an ordinary s-wave superconductor, and 2) the robustness of the
resulting superconductivity against disorder. We find that topological
insulators have strong advantages in both regards: there are no fundamental
barriers to inducing superconductivity, and the induced superconductivity is
immune to disorder. In contrast, for Rashba coupled quantum wires or surface
states, the the achievable gap from induced superconductivity is limited unless
the Rashba coupling is large. Furthermore, for small Rashba coupling the
induced superconductivity is strongly susceptible to disorder. These features
pose serious difficulties for realizing p+ip superconductors in semiconductor
materials due to their weak spin-orbit coupling, and suggest the need to seek
alternatives. Some candidate materials are discussed.",1103.2129v2
2011-12-05,Mixed partial-wave scattering with spin-orbit coupling and validity of pseudo-potentials,"We present exact solutions of two-body problem for spin-1/2 fermions with
isotropic spin-orbit(SO) coupling and interacting with an arbitrary short-range
potential. We find that in each partial-wave scattering channel, the
parametrization of two-body wavefunction at short inter-particle distance
depends on the scattering amplitudes of all channels. This reveals the mixed
partial-wave scattering induced by SO couplings. By comparing with results from
a square-well potential, we investigate the validity of original
pseudo-potential models in the presence of SO coupling. We find the s-wave
pseudo-potential provides a good approximation for low-energy solutions near
s-wave resonances, given the length scale of SO coupling much longer than the
potential range. However, near p-wave resonance the p-wave pseudo-potential
gives low-energy solutions that are qualitatively different from exact ones,
based on which we conclude that the p-wave model can not be applied to the
fermion system if the SO coupling strength is larger or comparable to the Fermi
momentum.",1112.1122v2
2012-03-12,Bose-Einstein Condensates in Spin-Orbit Coupled Optical Lattices: Flat Bands and Superfluidity,"Recently spin-orbit (SO) coupled superfluids in free space or harmonic traps
have been extensively studied, motivated by the recent experimental realization
of SO coupling for Bose-Einstein condensates (BEC). However, the rich physics
of SO coupled BEC in optical lattices has been largely unexplored. In this
paper, we show that in suitable parameter region the lowest Bloch state forms
an isolated flat band in a one dimensional (1D) SO coupled optical lattice,
which thus provides an experimentally feasible platform for exploring the
recently celebrated topological flat band physics in lattice systems. We show
that the flat band is preserved even with the mean field interaction in BEC. We
investigate the superfluidity of the BEC in SO coupled lattices through
dynamical and Landau stability analysis, and show that the BEC is stable on the
whole flat band.",1203.2389v2
2015-04-08,Dissociation of Feshbach molecules via spin-orbit coupling in ultracold Fermi gases,"We study the dissociation of Feshbach molecules in ultracold Fermi gases with
spin-orbit (SO) coupling. Since SO coupling can induce quantum transition
between the Feshbach molecules and the fully polarized Fermi gas, the Feshbach
molecules can be dissociated by the SO coupling. We experimentally realized
this new type of dissociation in ultracold gases of 40K atoms with SO coupling
created by Raman beams, and observed that the dissociation rate is highly
non-monotonic on both the positive and negative Raman-detuning sides. Our
results show that the dissociation of Feshbach molecules can be controlled by
new degrees of freedoms, i.e., the SO-coupling intensity or the momenta of the
Raman beams, as well as the detuning of the Raman beams.",1504.02021v1
2017-03-27,Bright soliton dynamics in Spin Orbit-Rabi coupled Bose-Einstein condensates,"We investigate the dynamics of a spin-orbit (SO) coupled BECs in a time
dependent harmonic trap and show the dynamical system to be completely
integrable by constructing the Lax pair. We then employ gauge transformation
approach to witness the rapid oscillations of the condensates for a relatively
smaller value of SO coupling in a time independent harmonic trap compared to
their counterparts in a transient trap. Keeping track of the evolution of the
condensates in a transient trap during its transition from confining to
expulsive trap, we notice that they collapse in the expulsive trap. We further
show that one can manipulate the scattering length through Feshbach resonance
to stretch the lifetime of the confining trap and revive the condensate.
Considering a SO coupled state as the initial state, the numerical simulation
indicates that the reinforcement of Rabi coupling on SO coupled BECs generates
the striped phase of the bright solitons and does not impact the stability of
the condensates despite destroying the integrability of the dynamical system.",1703.09119v1
2013-09-08,Universal Trimers induced by Spin-Orbit Coupling in Ultracold Fermi Gases,"In this letter we address the issue how synthetic spin-orbit (SO) coupling
can strongly affect three-body physics in ultracold atomic gases. We consider a
system which consists of three fermionic atoms, including two spinless heavy
atoms and one spin-1/2 light atom subjected to an isotropic SO coupling. We
find that SO coupling can induce universal three-body bound states with
negative s-wave scattering length at a smaller mass ratio, where no trimer
bound state can exist if in the absence of SO coupling. The energies of these
trimers are independent of high-energy cutoff, and therefore they are universal
ones. Moreover, the resulting atom-dimer resonance can be effectively
controlled by SO coupling strength. Our results can be applied to systems like
${}^6$Li and ${}^{40}$K mixture.",1309.1925v1
2022-01-19,Supersolid-like solitons in spin-orbit coupled spin-2 condensate,"We study supersolid-like crystalline structures emerging in the stationary
states of a quasi-two-dimensional spin-orbit (SO)-coupled spin-2 condensate in
the ferromagnetic, cyclic, and antiferro-magnetic phases by solving a
mean-field model.Interplay of different strengths of SO coupling and
interatomic interactions gives rise to a variety of non-trivial density
patterns in the emergent solutions. For small SO-coupling strengths $\gamma$
($\gamma \approx 0.5$), the ground state is an axisymmetric multi-ring soliton
for polar, cyclic and weakly-ferromagnetic interactions, whereas for
stronger-ferromagnetic interactions a circularly-asymmetric soliton emerges as
the ground state.Depending on the values of interaction parameters, with an
increase in SO-coupling strength, a stripe phase may also emerge as the ground
state for polar and cyclic interactions. For intermediate values of SO-coupling
strength ($\gamma \approx 1$), in addition to these solitons, one could have a
quasi-degenerate triangular-lattice soliton in all magnetic phases. On further
increasing the SO-coupling strength ($\gamma \gtrapprox 4$), a square-lattice
and a superstripe soliton emerge as quasi-degenerate states. The emergence of
all these solitons can be inferred from a study of solutions of the
single-particle Hamiltonian.",2201.07500v1
2023-11-17,Electron-phonon interaction and electronic correlations in transport through electrostatically and tunnel coupled quantum dots,"We investigate two equivalent capacitively and tunnel coupled quantum dots,
each coupled to its own pair of leads. Local Holstein type electron-phonon
coupling at the dots is assumed. To study many-body effects we use the finite-U
mean-field slave boson approach. For vanishing interdot interaction, weak e-ph
coupling and finite tunneling, molecular orbital spin Kondo effects occur for
single electron or single hole occupations. Phonons influence both correlations
and tunneling and additionally they shift the energies of the dots. Depending
on the dot energies and the strength of electron-phonon coupling, the system is
occupied by a different number of electrons that effectively interact with each
other repulsively or attractively leading to a number of different ground
states of DQD. Among them are Kondo-like states with spin, orbital or charge
correlations resulting from polaron cotunneling processes and states with
magnetic intersite correlations.",2311.10509v1
2012-12-31,Properties of Bose Gases with Raman-Induced Spin-Orbit Coupling,"In this paper we investigate the properties of Bose gases with Raman-induced
spin-orbit(SO) coupling. It is found that the SO coupling can greatly modify
the single particle density-of-state, and thus lead to non-monotonic behavior
of the condensate depletion, the Lee-Huang-Yang correction of ground-state
energy and the transition temperature of a non-interacting Bose-Einstein
condensate. The presence of the SO coupling also breaks the Galilean
invariance, and this gives two different critical velocities, corresponding to
the movement of the condensate and the impurity respectively. Finally, we show
that with SO coupling, the interactions modify the BEC transition temperature
even at Hartree-Fock level, in contrast to the ordinary Bose gas without SO
coupling. All results presented here can be directly verified in the current
cold atom experiments using Raman laser-induced gauge field.",1212.6832v1
2019-09-18,Influence of Rashba spin-orbit coupling on the 0-$π$ transition and Kondo temperature in 1D superconductors,"Using the framework of the density-matrix renormalization group (DMRG), we
study a quantum dot coupled to a superconducting nanowire with strong Rashba
spin-orbit coupling. Regarding the singlet-to-doublet ""0-$\pi$"" transition that
takes place when the Kondo effect is overcome by the superconducting gap, we
show that the Rashba coupling modifies the critical values at which the
transition occurs, favouring the doublet phase. In addition, using a
generalized Haldane's formula for the Kondo temperature $T_K$, we show that it
is lowered by the Rashba coupling. We benchmark our DMRG results comparing them
with previous numerical renormalization group (NRG) results. The excellent
agreement obtained opens the possibility of studying chains or clusters of
impurities coupled to superconductors by the means of DMRG.",1909.08486v1
2021-10-01,Modulational Instabity of Spin-Orbit Coupled Bose-Einstein Condensates in Discrete Media,"We address the impact of intra-site spin-orbit (SO) coupling and associated
inter-component Rabi coupling on the modulational instability (MI) of
plane-wave states in two-component discrete Bose-Einstein condensates (BECs).
Conditions for the onset of the MI and the respective instability are found
analytically. SO coupling allows us to produce the MI even for a small initial
wavenumber (q < {\pi}/2) for miscible states. In particular, SO coupling
introduces MI even in the absence of hopping coefficient, a concept which may
have wider ramifications in heavy atomic BECs. Our investigations predict that
the impact of Rabi coupling is more pronounced compared to the other system
parameters. We have also shown how our results of the linear stability analysis
can be corroborated numerically. The fact that we have brought out the
stability criteria in different domains of system parameters means that our
model is tailor made experiments.",2110.00288v1
2023-06-28,Domain formation of modulation instability in spin-orbit-Rabi coupled Gross-Pitaevskii equation with cubic-quintic interactions,"The effect of two- and three-body interactions on the modulation instability
(MI) domain formation of a spin-orbit (SO) and Rabi-coupled Bose-Einstein
condensate is studied within a quasi-one-dimensional model. To this aim, we
perform numerical and analytical investigations of the associated dispersion
relations derived from the corresponding coupled Gross-Pitaevskii equation. The
interplay between the linear (SO and Rabi) couplings with the nonlinear
cubic-quintic interactions are explored in the mixture, considering miscible
and immiscible configurations, with a focus on the impact in the analysis of
experimental realizations with general binary coupled systems, in which
nonlinear interactions can be widely varied together with linear couplings.",2306.16599v1
2011-12-11,Spin-to-charge conversion in lateral and vertical topological-insulator/ferromagnet heterostructures with microwave-driven precessing magnetization,"Using the charge-conserving Floquet-Green function approach to open quantum
systems driven by external time periodic potential, we analyze how spin current
pumped (in the absence of any dc bias voltage) by the precessing magnetization
of a ferromagnetic (F) layer is injected {\em laterally} into the interface
with strong spin-orbit coupling (SOC) and converted into charge current flowing
in the same direction. In the case of metallic interface with the Rashba SOC
used in experiments [Nature Comm. {\bf 4}, 2944 (2013)], both spin
$I^{S_\alpha}$ and charge $I$ current flow within it where $I/I^{S_\alpha}
\simeq$ 2--8\% (depending on the precession cone angle), while for
F/topological-insulator (F/TI) interface employed in related experiments
(arXiv:1312.7091) the conversion efficiency is greatly enhanced $I/I^{S_\alpha}
\simeq$ 40--60\% due to perfect spin-momentum locking on the surface of TI. The
spin-to-charge conversion occurs also when spin current is pumped {\em
vertically} through the F/TI interface with smaller efficiency $I/I^{S_\alpha}
\sim 0.001\%$, but with charge current signal being sensitive to whether the
Dirac fermions at the interface are massive or massless.",1112.2314v2
2014-01-27,Helical order in one-dimensional magnetic atom chains and possible emergence of Majorana bound states,"We theoretically obtain the phase diagram of localized magnetic impurity
spins arranged in a one-dimensional chain on top of a one- or two-dimensional
electron gas with Rashba spin-orbit coupling. The interactions between the
spins are mediated by the Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism
through the electron gas. Recent work predicts that such a system may
intrinsically support topological superconductivity when a helical spin-density
wave is formed in the spins, and superconductivity is induced in the electron
gas. We analyze, using both analytical and numerical techniques, the conditions
under which such a helical spin state is stable in a realistic situation in the
presence of disorder. We show that it becomes unstable towards the formation of
(anti) ferromagnetic domains if the disorder in the impurity spin positions
$\delta R$ becomes comparable with the Fermi wave length. We also examine the
stability of the helical state against Gaussian potential disorder in the
electronic system using a diagrammatic approach. Our results suggest that in
order to stabilize the helical spin state, and thus the emergent topological
superconductivity, a sufficiently strong Rashba spin-orbit coupling, giving
rise to Dzyaloshinskii-Moriya interactions, is required.",1401.7048v2
2015-04-07,Spin Transport in Hydrogenated Graphene,"In this review we discuss the multifaceted problem of spin transport in
hydrogenated graphene from a theoretical perspective. The current experimental
findings suggest that hydrogenation can either increase or decrease spin
lifetimes, which calls for clarification. We first discuss the spin-orbit
coupling induced by local $\sigma-\pi$ re-hybridization and ${\bf sp}^{3}$ C-H
defect formation together with the formation of a local magnetic moment.
First-principles calculations of hydrogenated graphene unravel the strong
interplay of spin-orbit and exchange couplings. The concept of magnetic
scattering resonances, recently introduced \cite{Kochan2014} is revisited by
describing the local magnetism through the self-consistent Hubbard model in the
mean field approximation in the dilute limit, while spin relaxation lengths and
transport times are computed using an efficient real space order N wavepacket
propagation method. Typical spin lifetimes on the order of 1 nanosecond are
obtained for 1 ppm of hydrogen impurities (corresponding to transport time
about 50 ps), and the scaling of spin lifetimes with impurity density is
described by the Elliott-Yafet mechanism. This reinforces the statement that
magnetism is the origin of the substantial spin polarization loss in the
ultraclean graphene limit.",1504.01591v1
2017-02-16,Theory of current-induced spin polarizations in an electron gas,"We derive the Bloch equations for the spin dynamics of a two-dimensional
electron gas in the presence of spin-orbit coupling. For the latter we consider
both the intrinsic mechanisms of structure inversion asymmetry (Rashba) and
bulk inversion asymmetry (Dresselhaus), and the extrinsic ones arising from the
scattering from impurities. The derivation is based on the SU(2) gauge-field
formulation of the Rashba-Dresselhaus spin-orbit coupling. Our main result is
the identification of a new spin-generation torque arising from the
Elliot-Yafet process, which opposes a similar term arising from the
Dyakonov-Perel process. The new spin-generation torque contributes to the
current-induced spin polarization (CISP) -- also known as the Edelstein or
inverse spin-galvanic effect. As a result, the behavior of the CISP turns out
to be more complex than one would surmise from consideration of the internal
Rashba-Dresselhaus fields alone. In particular, the symmetry of the
current-induced spin polarization does not necessarily coincide with that of
the internal Rashba-Dresselhaus field, and an out-of-plane component of the
CISP is generally predicted, as observed in recent experiments. We also discuss
the extension to the three-dimensional electron gas, which may be relevant for
the interpretation of experiments in thin films.",1702.04887v1
2022-07-18,Switchable large-gap quantum spin Hall state in two-dimensional MSi$_2$Z$_4$ materials class,"Quantum spin Hall (QSH) insulators exhibit spin-polarized conducting edge
states that are topologically protected from backscattering and offer unique
opportunities for addressing fundamental science questions and device
applications. Finding viable materials that host such topological states,
however, remains a challenge. Here by using in-depth first-principles
theoretical modeling, we predict large bandgap QSH insulators in recently
bottom-up synthesized two-dimensional (2D) MSi$_2$Z$_4$ (M = Mo or W and Z = P
or As) materials family with $1T^\prime$ structure. A structural distortion in
the $2H$ phase drives a band inversion between the metal (Mo/W) $d$ and $p$
states of P/As to realize spinless Dirac cone states without spin-orbit
coupling. When spin-orbit coupling is included, a hybridization gap as large as
$\sim 204$ meV opens up at the band crossing points, realizing spin-polarized
conducting edge states with nearly quantized spin Hall conductivity. We also
show that the inverted band gap is tunable with a vertical electric field which
drives a topological phase transition from the QSH to a trivial insulator with
Rashba-like edge states. Our study identifies 2D MSi$_2$Z$_4$ materials family
with $1T^\prime$ structure as large bandgap, tunable QSH insulators with
protected spin-polarized edge states and large spin-Hall conductivity.",2207.08407v1
2023-09-23,Strong unidirectional Rashba state induced by extended vacancy line defects in a $1T'$-WTe$_{2}$ monolayer,"The correlation between spin-orbit coupling and low crystal symmetry in the
$1T'$ phase of the tungsten ditellurides (WTe$_{2}$) monolayer (ML) plays a
significant role in its electronic and topological properties. However, the
centrosymmetric nature of the crystal maintains Kramer's spin degeneracy in its
electronic states, which limits its functionality in spintronics. In this
paper, through a systematic study using first-principles calculations, we show
that significant spin splitting can be induced in the $1T'$-WTe$_{2}$ ML by
introducing one dimensional (1D) vacancy line defect (VLD). We examine six
configurations of the 1D VLD, which consist of three VLDs extended in the
armchair direction including a Te$_{1}$ armchair-VLD ($ACV_{\texttt{Te}_{1}}$),
Te$_{2}$ armchair-VLD ($ACV_{\texttt{Te}_{2}}$), and W armchair-VLD
($ACV_{\texttt{W}}$); and three VLDs elongated along the zigzag direction
comprising a Te$_{1}$ zigzag-VLD ($ZZV_{\texttt{Te}_{1}}$), Te$_{2}$ zigzag-VLD
($ZZV_{\texttt{Te}_{2}}$), and W zigzag-VLD ($ZZV_{\texttt{W}}$), where
Te$_{1}$ and Te$_{2}$ are two nonequivalent Te atoms located at the lower and
higher sites in the top layer, respectively. We find that both the
$ACV_{\texttt{Te}_{1}}$ and $ACV_{\texttt{W}}$ systems have the lowest
formation energy. Concerning these two most stable VLD systems, we identify
large spin splitting in the defect states near the Fermi level driven by a
strong coupling of the in-plane $p-d$ orbitals, displaying highly
unidirectional Rashba states with perfectly collinear spin configurations in
the momentum space. This unique spin configuration gives rise to a specific
spin mode that protects the spin from decoherence and leads to an exceptionally
long spin lifetime...........",2309.13234v2
2020-05-18,Confinement versus interface bound states in spin-orbit coupled nanowires,"Semiconductor nanowires with strong Rashba spin-orbit coupling are currently
on the spotlight of several research fields such as spintronics, topological
materials and quantum computation. While most theoretical models assume an
infinitely long nanowire, in actual experimental setups the nanowire has a
finite length, is contacted to metallic electrodes and is partly covered by
gates. By taking these effects into account through an inhomogeneous spin-orbit
coupling profile, we show that in general two types of bound states arise in
the nanowire, namely confinement bound states and interface bound states. The
appearance of confinement bound states, related to the finite length of the
nanowire, is favoured by a mismatch of the bulk band bottoms characterizing the
lead and the nanowire, and occurs even in the absence of magnetic field. In
contrast, an interface bound states may only appear if a magnetic field applied
perpendicularly to the spin-orbit field direction overcomes a critical value,
and is favoured by an alignment of the band bottoms of the two regions across
the interface. We describe in details the emergence of these two types of bound
states, pointing out their differences. Furthermore, we show that when a
nanowire portion is covered by a gate the application of a magnetic field can
change the nature of the electronic ground state from a confinement to an
interface bound state, determining a redistribution of the electron charge.",2005.08587v2
2022-07-05,Spin-orbit coupling and electron scattering in high-quality InSb$_{1-x}$As$_{x}$ quantum wells,"InSb$_{1-x}$As$_{x}$ is a promising material system for exploration of
topological superconductivity in hybrid superconductor/semiconductor devices
due to large effective g-factor and enhanced spin-orbit coupling when compared
to binary InSb and InAs. Much remains to be understood concerning the
fundamental properties of the two-dimensional electron gas (2DEG) in InSbAs
quantum wells. We report on the electrical properties of a series of 30 nm
InSb$_{1-x}$As$_{x}$ quantum wells grown 40 nm below the surface with three
different arsenic mole fractions, x = 0.05, 0.13 and 0.19. The dependencies of
mobility on 2DEG density and arsenic mole fraction are analyzed. For the x =
0.05 sample, the 2DEG displays a peak mobility $\mu$ = 2.4 $\times$ 10$^5$
cm$^2$/Vs at a density of n = 2.5 $\times$ 10$^{11}$ cm$^{-2}$. High mobility,
small effective mass, and strong spin-orbit coupling result in beating in the
Shubnikov de Hass oscillations at low magnetic field. Fourier analysis of the
Shubnikov de Haas oscillations facilitates extraction of the Rashba spin-orbit
parameter ${\alpha}$ as a function of 2DEG density and quantum well mole
fraction. For x = 0.19 at n = 3.1 $\times$ 10$^{11}$ cm$^{-2}$, ${\alpha}$
$\approx$ 300 meV$\r{A}$, among the highest reported values in III-V materials.",2207.02006v1
2022-08-02,Spin-Orbital States and Strong Antiferromagnetism of Layered Eu$_2$SrFe$_2$O$_6$ and Sr$_3$Fe$_2$O$_4$Cl$_2$,"The insulating iron compounds Eu$_2$SrFe$_2$O$_6$ and Sr$_3$Fe$_2$O$_4$Cl$_2$
have high-temperature antiferromagnetic (AF) order despite their different
layered structures. Here we carry out density functional calculations and Monte
Carlo simulations to study their electronic structures and magnetic properties
aided with analyses of the crystal field, magnetic anisotropy, and
superexchange. We find that both compounds are Mott insulators and in the
high-spin (HS) Fe$^{2+}$ state ($S$ = 2) accompanied by the weakened crystal
field. Although they have different local coordination and crystal fields, the
Fe$^{2+}$ ions have the same level sequence and ground-state configuration
$(3z^2-r^2)^2(xz,yz)^2(xy)^1(x^2-y^2)^1$. Then, the multiorbital superexchange
produces strong AF couplings, and the $(3z^2-r^2)/(xz,yz)$ mixing via the
spin-orbit coupling (SOC) yields a small in-plane orbital moment and
anisotropy. Indeed, by tracing a set of different spin-orbital states, our
density functional calculations confirm the strong AF couplings and the easy
planar magnetization for both compounds. Moreover, using the derived magnetic
parameters, our Monte Carlo simulations give the N\'eel temperature $T_{\rm N}$
= 420 K (372 K) for the former (the latter), which well reproduce the
experimental results. Therefore, the present study provides a unified picture
for Eu$_2$SrFe$_2$O$_6$ and Sr$_3$Fe$_2$O$_4$Cl$_2$ concerning their electronic
and magnetic properties.",2208.01318v1
2016-06-15,Spin-orbit coupling and strong electronic correlations in cyclic molecules,"In atoms spin-orbit coupling (SOC) cannot raise the angular momentum above a
maximum value or lower it below a minimum. Here we show that this need not be
the case in materials built from nanoscale structures including multi-nuclear
coordination complexes, materials with decorated lattices, or atoms on
surfaces. In such cyclic molecules the electronic spin couples to currents
running around the molecule. For odd-fold symmetric molecules (e.g., odd
membered rings) the SOC is highly analogous to the atomic case; but for
even-fold symmetric molecules every angular momentum state can be both raised
and lowered. These differences arise because for odd-fold symmetric molecules
the maximum and minimum molecular orbital angular momentum states are time
reversal conjugates, whereas for even-fold symmetric molecules they are aliases
of the same single state. We show, from first principles calculations, that in
suitable molecules this molecular SOC is large, compared to the energy
differences between frontier molecular orbitals. Finally, we show that, when
electronic correlations are strong, molecular SOC can cause highly anisotropic
exchange interactions and discuss how this can lead to effective spin models
with compass Hamiltonians.",1606.04605v4
2017-05-06,Electrical and thermoelectric transport properties of two-dimensional fermionic systems with $k$-cubic spin-orbit coupling,"We investigate the effect of $k$-cubic spin-orbit interaction on electrical
and thermoelectric transport properties of two-dimensional fermionic systems.
We obtain exact analytical expressions of the inverse relaxation time (IRT) and
the Drude conductivity for long-range Coulomb and short-range delta scattering
potentials. The IRT reveals that the scattering is completely suppressed along
the three directions $\theta^\prime = (2n+1)\pi/3 $ with $ n=1,2,3$. We also
obtain analytical results of the thermopower and thermal conductivity at low
temperature. The thermoelectric transport coefficients obey the Wiedemann-Franz
law, even in the presence of $k$-cubic Rashba spin-orbit coupling (RSOC) at low
temperature. In the presence of quantizing magnetic field, the signature of the
RSOC is revealed through the appearance of the beating pattern in the
Shubnikov-de Haas (SdH) oscillations of thermopower and thermal conductivity in
low magnetic field regime. The empirical formulae for the SdH oscillation
frequencies accurately describe the locations of the beating nodes. The beating
pattern in magnetothermoelectric measurement can be used to extract the
spin-orbit coupling constant.",1705.02483v2
2021-11-14,Intrinsic first and higher-order topological superconductivity in a doped topological insulator,"We explore higher order topological superconductivity in an artificial Dirac
material with intrinsic spin-orbit coupling, which is a doped $\mathbb{Z}_2$
topological insulator in the normal state. A mechanism for superconductivity
due to repulsive interactions -- $\mathit{pseudospin}$ $\mathit{pairing}$ --
has recently been shown to naturally result in higher-order topology in Dirac
systems past a minimum chemical potential \cite{Li2021}. Here we apply this
theory through microscopic modeling of a superlattice potential imposed on an
inversion symmetric hole-doped semiconductor heterostructure, known as
hole-based semiconductor artificial graphene, and extend previous work to
include the effects of spin-orbit coupling. We find that spin-orbit coupling
enhances interaction effects, providing an experimental handle to increase the
efficiency of the superconducting mechanism. We show that the phase diagram of
these systems, as a function of chemical potential and interaction strength,
contains three superconducting states -- a first-order topological $p+ip$
state, a second-order topological spatially modulated $p+i\tau p$ state, and a
second-order topological extended $s$-wave state, $s_\tau$. We calculate the
symmetry-based indicators for the $p+i\tau p$ and $s_\tau$ states, which prove
these states possess second-order topology. Exact diagonalisation results are
presented which illustrate the interplay between the boundary physics and spin
orbit interaction. We argue that this class of systems offer an experimental
platform to engineer and explore first and higher-order topological
superconducting states.",2111.07252v4
2023-05-25,Delving into the anisotropic interlayer exchange in bilayer CrI$_3$,"Bilayer CrI$_3$ attracted much attention owing to peculiar switching between
the layered ferromagnetic and antiferromagnetic order upon stacking
alternation. This finding pointed out the importance of the apparently small
interlayer exchange, yet, existing literature addresses only its isotropic
part. To fill this gap, we combine the density functional theory with
Hamiltonian modeling to examine the anisotropic interlayer exchange in bilayer
CrI$_3$ - Dzyaloshinskii-Moriya (DMI) and the Kitaev interaction (KI). We
develop and apply a novel computational procedure that yields the off-diagonal
exchange matrix elements with $\mu$eV accuracy. Inspecting two types of bilayer
stacking, we found a weak interlayer KI and much stronger DMI between the
sublattices of monoclinic bilayer and their complete absence in rhombohedral
bilayer. We show how these anisotropic interactions depend on the interlayer
distance, stacking sequence, and the spin-orbit coupling strength and suggest
the dominant superexchange processes at play. In addition, we demonstrate that
the single-ion anisotropy largely depends on stacking, increasing by 50% from
monoclinic to rhombohedral structure. Remarkably, our findings prove that
iodines, owing to their spatially extended 5p orbitals featuring strong
spin-orbit coupling, are extremely efficient in mediating DMI across the van
der Waals gap in two-dimensional magnetic heterostructures. Given that similar
findings were previously demonstrated only in metallic multilayers where the
DMI shows a much longer range, our study gives promise that the chiral control
of spin textures can be achieved in two-dimensional semiconducting magnetic
bilayers whose ligands feature strong spin-orbit coupling.",2305.16142v1
2024-03-04,BAGELS: A General Method for Minimizing the Rate of Radiative Depolarization in Electron Storage Rings,"We present a novel method for minimizing the effects of radiative
depolarization in electron storage rings by use of vertical orbit bumps in the
arcs. Electron polarization is directly characterized by the RMS of the
so-called spin orbit coupling function in the bends. In the Electron Storage
Ring (ESR) of the Electron-Ion Collider (EIC), as was the case in HERA, this
function is excited by the spin rotators. Individual vertical corrector coils
in the arcs can have varying impacts on this function globally. In this method,
we use a singular value decomposition of the response matrix of the spin-orbit
coupling function with each coil to define a minimal number of most effective
groups of coils, motivating the name ""Best Adjustment Groups for ELectron Spin""
(BAGELS) method. The BAGELS method can be used to minimize the depolarizing
effects in an ideal lattice, and to obtain fine-tuning knobs to restore the
minimization in rings with realistic closed orbit distortions. Furthermore, the
least effective groups can instead be chosen for other applications where no
impact on polarization is desirable, e.g. global coupling compensation or
vertical emittance creation. Application of the BAGELS method has significantly
increased the polarization in simulations of the 18 GeV ESR, beyond achievable
with conventional methods.",2403.02103v1
2020-02-21,Magnetic field effects on the quantum spin liquid behaviors of NaYbS$_2$,"Spin-orbit coupling is an important ingredient to regulate the many-body
physics, especially for many spin liquid candidate materials such as rare-earth
magnets and Kitaev materials. The rare-earth chalcogenides NaYbCh$_2$ (Ch = O,
S, Se) is a congenital frustrating system to exhibit the intrinsic landmark of
spin liquid by eliminating both the site disorders between Na$^{+}$ and
Yb$^{3+}$ ions with the big ionic size difference and the Dzyaloshinskii-Moriya
interaction with the perfect triangular lattice of the Yb$^{3+}$ ions. The
temperature versus magnetic-field phase diagram is established by the
magnetization, specific heat, and neutron-scattering measurements. Notably, the
neutron diffraction spectra and the magnetization curve might provide
microscopic evidence for a series of spin configuration for in-plane fields,
which include the disordered spin liquid state, 120$^{o}$ antiferromagnet, and
one-half magnetization state. Furthermore, the ground state is suggested to be
a gapless spin liquid from inelastic neutron scattering, and the magnetic field
adjusts the spin orbit coupling. Therefore, the strong spin-orbit coupling in
the frustrated quantum magnet substantially enriches low-energy spin physics.
This rare-earth family could offer a good platform for exploring the quantum
spin liquid ground state and quantum magnetic transitions.",2002.09224v2
2004-08-30,Magnetically-controlled impurities in quantum wires with strong Rashba coupling,"We investigate the effect of strong spin-orbit interaction on the electronic
transport through non-magnetic impurities in one-dimensional systems. When a
perpendicular magnetic field is applied, the electron spin polarization becomes
momentum-dependent and spin-flip scattering appears, to first order in the
applied field, in addition to the usual potential scattering. We analyze a
situation in which, by tuning the Fermi level and the Rashba coupling, the
magnetic field can suppress the potential scattering. This mechanism should
give rise to a significant negative magnetoresistance in the limit of large
barriers.",0408656v2
2002-10-08,Quark spin coupling in baryons - revisited,"A direct connection can be made between mixing angles in negative parity
baryons and the spin coupling of constituent quarks. The mixing angles do not
depend on spectral data. These angles are recalculated for gluon exchange and
pion exchange between quarks. For pion exchange the results of Glozman and
Riska are corrected. The experimental data on mixing are very similar to those
derived from gluon exchange but substantially different from the values
obtained for pion exchange.",0210126v2
1993-01-11,On the Electromagnetic Interactions of Anyons,"Using the appropriate representation of the Poincare group and a definition
of minimal coupling, we discuss some aspects of the electromagnetic
interactions of charged anyons. In a nonrelativistic expansion, we derive a
Schrodinger-type equation for the anyon wave function which includes
spin-magnetic field and spin-orbit couplings. In particular, the gyromagnetic
ratio for charged anyons is shown to be 2; this last result is essentially a
reflection of the fact that the spin is parallel to the momentum in (2+1)
dimensions.",9301037v1
1996-10-03,Low-energy interaction of composite spin-half systems with scalar and vector fields,"We consider a composite spin-half particle moving in spatially-varying scalar
and vector fields. The vector field is assumed to couple to a conserved charge,
but no assumption is made about either the structure of the composite or its
coupling to the scalar field. A general form for the piece of the spin-orbit
interaction of the composite with the scalar and vector fields which is
first-order in momentum transfer ${\bf Q}$ and second-order in the fields is
derived.",9610007v1
2001-06-28,Anisotropic Spin Exchange in Pulsed Quantum Gates,"We show how to eliminate the first-order effects of the spin-orbit
interaction in the performance of a two-qubit quantum gate. Our procedure
involves tailoring the time dependence of the coupling between neighboring
spins. We derive an effective Hamiltonian which permits a systematic analysis
of this tailoring. Time-symmetric pulsing of the coupling automatically
eliminates several undesirable terms in this Hamiltonian. Well chosen pulse
shapes can produce an effectively isotropic exchange gate, which can be used in
universal quantum computation with appropriate coding.",0106161v1
2003-05-15,Quantum Mechanics in a Rotating Frame,"The rotating frame is considered in quantum mechanics on the basis of the
position dependent boost relating this frame to the non rotating inertial
frame. We derive the Sagnac phase shift and the spin coupling with the rotation
in the non relativistic limit by a simple treatment. By taking the low energy
limit of the Dirac equation with a spin connection, we obtain the Hamiltonian
for the rotating frame, which gives rise to all the phase shifts discussed
before. Furthermore, we obtain a new phase shift due to the spin-orbit
coupling.",0305081v2
2008-03-05,Fano-Rashba effect in quantum dots,"We consider the electronic transport through a Rashba quantum dot coupled to
ferromagnetic leads. We show that the interference of localized electron states
with resonant electron states leads to the appearance of the Fano-Rashba
effect. This effect occurs due to the interference of bound levels of
spin-polarized electrons with the continuum of electronic states with an
opposite spin polarization. We investigate this Fano-Rashba effect as a
function of the applied magnetic field and Rashba spin-orbit coupling.",0803.0671v1
2009-11-03,Dzyaloshinskii-Moriya interaction in transport through single molecule transistors,"The Dzyaloshinskii-Moriya interaction is shown to result in a canting of
spins in a single molecule transistor. We predict non-linear transport
signatures of this effect induced by spin-orbit coupling for the generic case
of a molecular dimer. The conductance is calculated using a master equation and
is found to exhibit a non-trivial dependence on the magnitude and direction of
an external magnetic field. We show how three-terminal transport measurements
allow for a determination of the coupling-vector characterizing the
Dzyaloshinskii-Moriya interaction. In particular, we show how its orientation,
defining the intramolecular spin chirality, can be probed with ferromagnetic
electrodes.",0911.0571v1
2011-10-27,Superconductivity without Local Inversion Symmetry; Multi-layer Systems,"While multi-layer systems can possess global inversion centers, they can have
regions with locally broken inversion symmetry. This can modify the
superconducting properties of such a system. Here we analyze two dimensional
multi-layer systems yielding spatially modulated antisymmetric spin-orbit
coupling (ASOC) and discuss superconductivity with mixed parity order
parameters. In particular, the influence of ASOC on the spin susceptibility is
investigated at zero temperature. For weak inter-layer coupling we find an
enhanced spin susceptibility induced by ASOC, which hints the potential
importance of this aspect for superconducting phase in specially structured
superlattices.",1110.6000v1
2013-07-31,Approximate relativistic bound states of a particle in Yukawa field with Coulomb tensor interaction,"We obtain the approximate relativistic bound state of a spin-1/2 particle in
the field of the Yukawa potential and a Coulomb-like tensor interaction with
arbitrary spin-orbit coupling number k under the spin and pseudospin (p-spin)
symmetries. The asymptotic iteration method is used to obtain energy
eigenvalues and corresponding wave functions in their closed forms. Our
numerical results show that the tensor interaction removes degeneracies between
the spin and p-spin doublets and creates new degenerate doublets for various
strengths of tensor coupling.",1307.8326v1
2016-09-29,Phase space methods for the spin dynamics in condensed matter systems,"Using the phase-space formulation of quantum mechanics, we derive a
four-component Wigner equation for a system composed of spin-1/2 fermions
(typically, electrons) including the Zeeman effect and the spin-orbit coupling.
This Wigner equation is coupled to the appropriate Maxwell equations to form a
self-consistent mean-field model. A set of semiclassical Vlasov equations with
spin effects is obtained by expanding the full quantum model to first order in
the Planck constant. The corresponding hydrodynamic equations are derived by
taking velocity moments of the phase-space distribution function. A simple
closure relation is proposed to obtain a closed set of hydrodynamic equations.",1609.09472v1
2014-03-19,Renormalization group study of interaction-driven quantum anomalous Hall and quantum spin Hall phases in quadratic band crossing systems,"It is shown that topological insulating phases driven by interactions can be
realized without the need for spin-orbit coupling or large intersite
interaction in a two-dimensional system of spin-1/2 fermions with a single pair
of parabolically touching bands. Using a weak-coupling, Wilsonian
renormalization group procedure, we show that a quantum anomalous Hall phase is
realized for Hubbard interaction, while a quantum spin Hall phase is favored
for longer-ranged interactions.",1403.4957v2
2017-06-21,Quantum kinetic equations and anomalous non-equilibrium Cooper pair spin accumulation in Rashba wires with Zeeman splitting,"We derive the theoretical and numerical framework for investigating
nonequilibrium properties of spin-orbit coupled wires with Zeeman splitting
proximized by a superconductor in the non-linear diffusive regime. We
demonstrate that the anisotropic behaviour of triplet Cooper pairs in this
system leads to novel spin accumulation profiles tunable by the magnetic field
and strength of applied voltage bias. This paves the way for enhanced
manipulation of superconducting spintronic devices, and enables further
investigation of nonequilibrium effects in proximity-coupled superconducting
structures more generally.",1706.07058v2
2018-09-18,Spin-triplet $f$-wave pairing in twisted bilayer graphene near 1/4 filling,"We investigate the twisted bilayer graphene by a two-orbital Hubbard model on
the honeycomb lattice. The model is studied near 1/4 band filling by using the
singular-mode functional renormalization group theory. Spin-triplet $f$-wave
pairing is found from weak to moderate coupling limit of the local
interactions, and is associated with the Hund's rule coupling and
incommensurate spin fluctuations at moderate momenta.",1809.06772v1
2021-04-15,Spin susceptibility of superconductors with strong spin-orbit coupling,"We show that in some trigonal and hexagonal crystals the Zeeman coupling of
band electrons with an external magnetic field is strongly anisotropic and
necessarily vanishes along the main symmetry axis. This leads to qualitative
changes in the temperature dependence of the electron spin susceptibility in
the superconducting state. In particular, the power-law exponents at low
temperatures due to the contribution of the nodal quasiparticles are
considerably modified compared to their textbook values.",2104.07734v1
2013-02-20,Multiplet effects in orbital and spin ordering phenomena: A hybridization-expansion quantum impurity solver study,"Orbital and spin ordering phenomena in strongly correlated systems are
commonly studied using the local-density approximation + dynamical mean-field
theory approach. Typically, however, such simulations are restricted to
simplified models (density-density Coulomb interactions, high symmetry
couplings and few-band models). In this work we implement an efficient general
hybridization-expansion continuous-time quantum Monte Carlo impurity solver
(Krylov approach) which allows us to investigate orbital and spin ordering in a
more realistic setting, including interactions that are often neglected (e.g.,
spin-flip and pair-hopping terms), enlarged basis sets (full d versus eg),
low-symmetry distortions, and reaching the very low-temperature (experimental)
regime. We use this solver to study ordering phenomena in a selection of
exemplary low-symmetry transition-metal oxides: LaMnO3 and rare-earth
manganites as well as the perovskites CaVO3 and YTiO3. We show that spin-flip
and pair hopping terms do not affect the Kugel-Khomskii orbital-order melting
transition in rare-earth manganites, or the suppression of orbital fluctuations
driven by crystal field and Coulomb repulsion. For the Mott insulator YTiO3 we
find a ferromagnetic transition temperature 50 K, in remarkably good agreement
with experiments. For LaMnO3 we show that the classical t2g-spin approximation,
commonly adopted for studying manganites, yields indeed an occupied eg orbital
in very good agreement with that obtained for the full d 5-orbital Hubbard
model, while the spin-spin e_g-t_{2g} correlation function calculated from the
full d model is 0.74, very close to the value expected for aligned eg and t2g
spins; the eg spectral function matrix is also well reproduced. Finally, we
show that the t2g screening reduces the eg-eg Coulomb repulsion by about 10%",1302.5068v1
2006-05-28,Spin Hall effect in infinitely large and finite-size diffusive Rashba two-dimensional electron systems: A helicity-basis nonequilibrium Green's function approach,"A nonequilibrium Green's function approach is employed to investigate the
spin-Hall effect in diffusive two-dimensional electron systems with Rashba
spin-orbit interaction. Considering a long-range electron-impurity scattering
potential in the self-consistent Born approximation, we find that the spin-Hall
effect arises from two distinct interband polarizations in helicity basis: a
disorder-unrelated polarization directly induced by the electric field and a
polarization mediated by electron-impurity scattering. The disorder-unrelated
polarization is associated with all electron states below the Fermi surface and
produces the original intrinsic spin-Hall current, while the disorder-mediated
polarization emerges with contribution from the electron states near the Fermi
surface and gives rise to an additional contribution to the spin-Hall current.
Within the diffusive regime, the total spin-Hall conductivity vanishes in {\it
infinitely large} samples, independently of temperature, of the spin-orbit
coupling constant, of the impurity density, and of the specific form of the
electron-impurity scattering potential. However, in a {\it finite-size} Rashba
two-dimensional semiconductor, the spin-Hall conductivity no longer always
vanishes. Depending on the sample size in the micrometer range, it can be
positive, zero or negative with a maximum absolute value reaching as large as
$e/8\pi$ order of magnitude at low temperatures. As the sample size increases,
the total spin-Hall conductivity oscillates with a decreasing amplitude. We
also discuss the temperature dependence of the spin-Hall conductivity for
different sample sizes.",0605687v1
1999-03-11,Ordering and Fluctuation of Orbital and Lattice Distortion in Perovskite Manganese Oxides,"Roles of orbital and lattice degrees of freedom in strongly correlated
systems are investigated to understand electronic properties of perovskite Mn
oxides such as La_{1-x}Sr_{x}MnO_{3}. An extended double-exchange model
containing Coulomb interaction, doubly degenerate orbitals and Jahn-Teller
coupling is derived under full polarization of spins with two-dimensional
anisotropy. Quantum fluctuation effects of Coulomb interaction and orbital
degrees of freedom are investigated by using the quantum Monte Carlo method. In
undoped states, it is crucial to consider both the Coulomb interaction and the
Jahn-Teller coupling in reproducing characteristic hierarchy of energy scales
among charge, orbital-lattice and spin degrees of freedom in experiments. Our
numerical results quantitatively reproduce the charge gap amplitude as well as
the stabilization energy and the amplitude of the cooperative Jahn-Teller
distortion in undoped compounds. Upon doping of carriers, in the absence of the
Jahn-Teller distortion, critical enhancement of both charge compressibility and
orbital correlation length is found with decreasing doping concentration. These
are discussed as origins of strong incoherence in charge dynamics. With the
Jahn-Teller coupling in the doped region, collapse of the Jahn-Teller
distortion and instability to phase separation are obtained and favorably
compared with experiments. These provide a possible way to understand the
complicated properties of lightly doped manganites.",9903183v2
2002-11-21,Construction of microscopic model for f-electron systems on the basis of j-j coupling scheme,"We construct a microscopic model for f-electron systems, composed of
f-electron hopping, Coulomb interaction, and crystalline electric field (CEF)
terms. In order to clarify the meaning of one f-electron state, here the j-j
coupling scheme is considered, since the spin-orbit interaction is generally
large in f-electron systems. Thus, the f-electron state at each site is
labelled by $\mu$, namely, the z-component of total angular momentum j. By
paying due attention to f-orbital symmetry, the hopping amplitudes between
f-electron states are expressed using Slater's integrals. The Coulomb
interaction terms among the $\mu$-states are written by Slater-Condon or Racah
parameters. Finally, the CEF terms are obtained from the table of Hutchings.
The constructed Hamiltonian is regarded as an orbital degenerate Hubbard model,
since it includes two pseudo-spin and three pseudo-orbital degrees of freedom.
For practical purposes, it is further simplified into a couple of two-orbital
models by discarding one of the three orbitals. One of those simplified models
is here analyzed using the exact diagonalization method to clarify ground-state
properties by evaluating several kinds of correlation functions. Especially,
the superconducting pair correlation function in orbital degenerate systems is
carefully calculated based on the concept of off-diagonal long-range order. We
attempt to discuss a possible relation of the present results with experimental
observations for recently discovered heavy fermion superconductors CeMIn$_5$
(M=Ir, Co, and Rh), and a comprehensive scenario to understand superconducting
and antiferromagnetic tendencies in the so-called ``115'' materials such as
CeMIn$_5$, UMGa$_5$, and PuCoGa$_5$ from the microscopic viewpoint.",0211467v1
2014-12-14,General ultracold scattering formalism with isotropic spin orbit coupling,"A general treatment of ultracold two-body scattering in the presence of
isotropic spin-orbit coupling (SOC) is presented. Owing to the mixing of
different partial wave channels, scattering with SOC is in general a coupled
multichannel problem. A systematic method is introduced to analytically solve a
class of coupled differential equations by recasting the coupled channel
problem as a simple eigenvalue problem. The exact Green's matrix in the
presence of SOC is found, which readily gives the scattering solutions for any
two identical particles in any total angular momentum subspace having
negligible center of mass momentum. Application of this formalism to two spin-1
bosons shows the ubiquitous low energy threshold behavior for systems with
isotropic SOC. A modified threshold behavior shows up, which does not occur for
the spin-orbit coupled spin-1/2 system. We also confirm the parity-breaking
mechanism for the spontaneous emergency of handedness, that has been proposed
by Duan et. al. [1]. Additionally, a two-body bound state is found for any
arbitrarily small and negative scattering length. Our study sheds light on the
few-body side of SOC physics and provides one step towards understanding
ultracold scattering in a non-Abelian gauge field.",1412.4420v1
2003-06-20,Experimental Separation of Rashba and Dresselhaus Spin-Splittings in Semiconductor Quantum Wells,"The relative strengths of Rashba and Dresselhaus terms describing the
spin-orbit coupling in semiconductor quantum well (QW) structures are extracted
from photocurrent measurements on n-type InAs QWs containing a two-dimensional
electron gas (2DEG). This novel technique makes use of the angular distribution
of the spin-galvanic effect at certain directions of spin orientation in the
plane of a QW. The ratio of the relevant Rashba and Dresselhaus coefficients
can be deduced directly from experiment and does not relay on theoretically
obtained quantities. Thus our experiments open a new way to determine the
different contributions to spin-orbit coupling.",0306521v1
2003-11-03,Rashba effect in 2D mesoscopic systems with transverse magnetic field,"We present semiclassical and quantum mechanical results for the effects of a
strong magnetic field in Quantum Wires in the presence of Rashba Spin Orbit
coupling. Analytical and numerical results show how the perturbation acts in
the presence of a transverse magnetic field in the ballistic regime and we
assume a strong reduction of the backward scattering interaction which could
have some consequences for the Tomonaga-Luttinger transport. We analyze the
spin texture due to the action of Spin Orbit coupling and magnetic field often
referring to the semiclassical solutions that magnify the singular spin
polarization: results are obtained for free electrons in a twodimensional
electron gas and for electrons in a Quantum Wire.
  We propose the systems as possible devices for the spin filtering at various
regimes.",0311051v1
2004-06-02,"Positional Disorder, Spin-Orbit Coupling and Frustration in GaMnAs","We study the magnetic properties of metallic GaMnAs. We calculate the
effective RKKY interaction between Mn spins using several realistic models for
the valence band structure of GaAs. We also study the effect of positional
disorder of the Mn on the magnetic properties. We find that the interaction
between two Mn spins is anisotropic due to spin-orbit coupling within both the
so-called spherical approximation and in the more realistic six band model. The
spherical approximation strongly overestimates this anistropy, especially for
short distances between Mn ions. Using the obtained effective Hamiltonian we
carry out Monte Carlo simulations of finite and zero temperature magnetization
and find that, due to orientational frustration of the spins, non-collinear
states appear in both valence band approximations for disordered, uncorrelated
Mn impurities in the small concentration regime. Introducing correlations among
the substitutional Mn positions or increasing the Mn concentration leads to an
increase in the remnant magnetization at zero temperature and an almost fully
polarized ferromagnetic state.",0406068v1
2005-05-31,Signatures of spin-related phases in transport through regular polygons,"We address the subject of transport in one-dimensional ballistic polygon
loops subject to Rashba spin-orbit coupling. We identify the role played by the
polygon vertices in the accumulation of spin-related phases by studying
interference effects as a function of the spin-orbit coupling strength. We find
that the vertices act as strong spin-scattering centers that hinder the
developing of Aharovov-Casher and Berry phases. In particular, we show that the
oscillation frequency of interference pattern can be doubled by modifying the
shape of the loop from a square to a circle.",0505750v2
2005-09-26,Spin-orbit coupling in a Quantum Dot at high magnetic field,"We describe the simultaneous effects of the spin-orbit (SO) perturbation and
a magnetic field $B$ on a disk shaped quantum dot (QD). {As it is known the}
combination of electrostatic forces among the $N$ electrons confined in the QD
and the Pauli principle can induce a spin polarization when $B$ (applied in the
direction orthogonal to the QD) is above a threshold value. In the presence of
an electric field parallel to $B$, coupled to the spin $ S $ by a Rashba term,
we demonstrate that a symmetry breaking takes place: we can observe it by
analyzing the splitting of the levels belonging to an unperturbed multiplet. We
also discuss the competitive effects of the magnetic field, the SO perturbation
and the electron electron interaction, in order to define the hierarchy of the
states belonging to a multiplet. We demonstrate how this hierarchy depends on
the QD's size. We show the spin texture due to the combined effects of the
Rashba effect and the interaction responsible for the polarization.",0509654v1
2006-10-27,Nonvanishing spin Hall currents in the presence of magnetic impurities,"The intrinsic spin Hall conductivity in a two dimensional electron gas with
Rashba spin-orbit coupling is evaluated by taking account of anisotropic
coupling between magnetic impurities and itinerant electrons. In our
calculation Kubo's linear response formalism is employed and the vertex
correction is considered. In the semiclassical limit $\mu \gg 1/\tau$, a
non-vanishing spin Hall conductivity $\sigma^{}_{sH}$ is found to depend on the
momentum relaxation time $\tau$, spin-orbit splitting $\Delta$ and the
anisotropic coefficient of interaction between itinerant electrons and magnetic
impurities. The clean limit of $\sigma^{}_{sH}$ is in the region of $e/8\pi
\sim e/6\pi$, depending on the anisotropic coefficient.",0610776v2
2007-08-08,Spin-orbital Kondo decoherence by environmental effects in capacitively coupled quantum dot devices,"Strong correlation effects in a capacitively coupled double quantum-dot setup
were previously shown to provide the possibility of both entangling spin-charge
degrees of freedom and realizing efficient spin-filtering operations by static
gate-voltage manipulations. Motivated by the use of such a device for quantum
computing, we study the influence of electromagnetic noise on a general
spin-orbital Kondo model, and investigate the conditions for observing
coherent, unitary transport, crucial to warrant efficient spin manipulations.
We find a rich phase diagram, where low-energy properties sensitively depend on
the impedance of the external environment and geometric parameters of the
system. Relevant energy scales related to the Kondo temperature are also
computed in a renormalization-group treatment, allowing to assess the
robustness of the device against environmental effects.",0708.1092v2
2008-02-14,Coriolis Effect in Optics: Unified Geometric Phase and Spin-Hall Effect,"We examine the spin-orbit coupling effects that appear when a wave carrying
intrinsic angular momentum interacts with a medium. The Berry phase is shown to
be a manifestation of the Coriolis effect in a non-inertial reference frame
attached to the wave. In the most general case, when both the direction of
propagation and the state of the wave are varied, the phase is given by a
simple expression that unifies the spin redirection Berry phase and the
Pancharatnam--Berry phase. The theory is supported by the experiment
demonstrating the spin-orbit coupling of electromagnetic waves via a surface
plasmon nano-structure. The measurements verify the unified geometric phase,
demonstrated by the observed polarization-dependent shift (spin-Hall effect) of
the waves.",0802.2114v2
2009-04-20,Introduction to superconductivity in metals without inversion center,"This Chapter gives a brief introduction to some basic aspects metals and
superconductors in crystal without inversion symmetry. In a first part we
analyze some normal state properties which arise through antisymmetric
spin-orbit coupling existing in non-centrosymmetric materials and show its
influence on the de Haas-van Alphen effect. For the superconducting phase we
introduce a multi-band formulation which naturally arises due the spin
splitting of the bands by spin-orbit coupling. It will then be shown how the
states can be symmetry classified and their relation to the original
classification in even-parity spin-singlet and odd-parity spin-triplet pairing
states. The general Ginzburg-Landau functional will be derived and applied to
the nucleation of superconductivity in a magnetic field. It will be shown that
magneto-electric effects can modify the standard paramagnetic limiting behavior
drastically.",0904.2962v2
2009-07-02,Tuning Molecule-Mediated Spin Coupling in Bottom-Up Fabricated Vanadium-TCNE Nanostructures,"We have fabricated hybrid magnetic complexes from V atoms and
tetracyanoethylene (TCNE) ligands via atomic manipulation with a cryogenic
scanning tunneling microscope. Using tunneling spectroscopy we observe
spin-polarized molecular orbitals as well as Kondo behavior. For complexes
having two V atoms, the Kondo behavior can be quenched for different molecular
arrangements, even as the spin-polarized orbitals remain unchanged. This is
explained by variable spin-spin (i.e., V-V) ferromagnetic coupling through a
single TCNE molecule, as supported by density functional calculations.",0907.0490v1
2010-07-28,Band topology and quantum spin Hall effect in bilayer graphene,"We consider bilayer graphene in the presence of spin orbit coupling, to
assess its behavior as a topological insulator. The first Chern number $n$ for
the energy bands of single and bilayer graphene is computed and compared. It is
shown that for a given valley and spin, $n$ in a bilayer is doubled with
respect to the monolayer. This implies that bilayer graphene will have twice as
many edge states as single layer graphene, which we confirm with numerical
calculations and analytically in the case of an armchair terminated surface.
Bilayer graphene is a weak topological insulator, whose surface spectrum is
susceptible to gap opening under spin-mixing perturbations. We also assess the
stability of the associated topological bulk state of bilayer graphene under
various perturbations. Finally, we consider an intermediate situation in which
only one of the two layers has spin orbit coupling, and find that although
individual valleys have non-trivial Chern numbers, the spectrum as a whole is
not gapped, so that the system is not a topological insulator.",1007.4910v1
2012-12-19,Quantum spin Hall effect induced by electric field in silicene,"We investigate the transport properties in a zigzag silicene nanoribbon in
the presence of an external electric field. The staggered sublattice potential
and two kinds of Rashba spin-orbit couplings can be induced by the external
electric field due to the buckled structure of the silicene. A bulk gap is
opened by the staggered potential and gapless edge states appear in the gap by
tuning the two kinds of Rashba spin-orbit couplings properly. Furthermore, the
gapless edge states are spin-filtered and are insensitive to the non-magnetic
disorder. These results prove that the quantum spin Hall effect can be induced
by an external electric field in silicene, which may have certain practical
significance in applications for future spintronics device.",1212.4577v1
2014-02-28,Simulating systems of itinerant spin-carrying particles using arrays of superconducting qubits and resonators,"We propose possible approaches for the quantum simulation of itinerant
spin-carrying particles in a superconducting qubit-resonator array. The
standard Jaynes-Cummings-Hubbard setup considered in several recent studies can
readily be used as a quantum simulator for a number of relevant phenomena,
including the interaction with external magnetic fields and spin-orbit
coupling. A more complex setup where multiple qubits and multiple resonator
modes are utilized in the simulation gives a higher level of complexity,
including the simulation of particles with high spin values and allowing more
direct control on processes related to spin-orbit coupling. This proposal could
be implemented in state-of-the-art superconducting circuits in the near future.",1402.7185v2
2014-07-10,Supersolid with nontrivial topological spin textures in spin-orbit-coupled Bose gases,"Supersolid is a long-sought exotic phase of matter, which is characterized by
the coexistence of a diagonal long-range order of solid and an off-diagonal
long-range order of superfluid. Possible candidates to realize such a phase
have been previously considered, including hard-core bosons with long-range
interaction and soft-core bosons. Here we demonstrate that an ultracold atomic
condensate of hard-core bosons with contact interaction can establish a
supersolid phase when simultaneously subjected to spin-orbit coupling and a
spin-dependent periodic potential. This supersolid phase is accompanied by
topologically nontrivial spin textures, and is signaled by the separation of
momentum distribution peaks, which can be detected via time-of-flight
measurements. We also discuss possibilities to produce and observe the
supersolid phase for realistic experimental situations.",1407.2972v2
2014-07-12,Possible Half Metallic Antiferromagnetism in a Double Perovskite Material with Strong Spin-Orbit Couplings,"Using the first-principles density functional approach, we investigate a
material Pr$_2$MgIrO$_6$ (PMIO) of double perovskite structure synthesized
recently. According to the calculations, PMIO is a magnetic Mott-Hubbard
insulator influenced by the cooperative effect of spin-orbit coupling (SOC) and
Coulomb interactions of Ir-5$d$ and Pr-4$f$ electrons, as well as the crystal
field. When Pr is replaced with Sr gradually, the system exhibits half metallic
(HM) states desirable for spintronics applications. In
[Pr$_{2-x}$Sr$_x$MgIrO$_6$]$_2$, HM antiferromagnetism (HMAFM) with zero spin
magnetization in the unit cell is obtained for $x=1$, whereas for $x=0.5$ and
1.5 HM ferrimagnetism (HMFiM) is observed with $\mu_{\rm tot}=3\mu_{\rm B}$ and
$\mu_{\rm tot}=-3\mu_{\rm B}$ per unit cell respectively. It is emphasized that
the large exchange splitting between spin-up and spin-down bands at the Fermi
level makes the half metallicity possible even with strong SOC.",1407.3408v1
2014-10-13,Spin-polarized dynamic transport in tubular two-dimensional electron gases,"The ac conductance of a finite tubular two-dimensional electron gas is
studied in the presence of the Rashba spin-orbit interaction. When the tube is
coupled to two reservoirs, that interaction splits the steps in the dc current,
introducing energy ranges with spin-polarized currents. For this setup, we
calculate the current-current correlations (the noise spectrum) and show that
the existence of these dc spin-polarized currents can be deduced from the shot
noise. We also find that the Wigner-Smith time delay is almost unaffected by
the spin-orbit interaction. When the tube is coupled to a single reservoir, we
calculate the quantum capacitance and the charge-relaxation resistance, and
find that they exhibit singularities near the openings of new channels.",1410.3262v1
2014-12-03,Valley Zeeman effect and spin-valley polarized conductance in monolayer MoS$_2$ in a perpendicular magnetic field,"We study the effect of a perpendicular magnetic field on the electronic
structure and charge transport of a monolayer MoS$_2$ nanoribbon at zero
temperature. We particularly explore the induced valley Zeeman effect through
the coupling between the magnetic field, $B$, and the orbital magnetic moment.
We show that the effective two-band Hamiltonian provides a mismatch between the
valley Zeeman coupling in the conduction and valence bands due to the effective
mass asymmetry and it is proportional to $B^2$ similar to the diamagnetic shift
of exciton binding energies. However, the dominant term which evolves with $B$
linearly, originates from the multi-orbital and multi-band structures of the
system. Besides, we investigate the transport properties of the system by
calculating the spin-valley resolved conductance and show that, in a low-hole
doped case, the transport channels at the edge are chiral for one of the spin
components. This leads to a localization of the non-chiral spin component in
the presence of disorder and thus provides a spin-valley polarized transport
induced by disorder.",1412.1459v3
2015-02-16,Cyclotron Dynamics of a Kondo Singlet in a Spin-Orbit-Coupled Alkaline-Earth Atomic Gas,"We propose a scheme to investigate the interplay between Kondo-exchange
interaction and quantum spin Hall effect with ultracold fermionic
alkaline-earth atoms trapped in two-dimensional optical lattices using
ultracold collision and laser-assisted tunneling. In the strong Kondo-coupling
regime, though the loop trajectory of the mobile atom disappears, collective
dynamics of an atom pair in two clock states can exhibit an unexpected
spin-dependent cyclotron orbit in a plaquette, realizing the quantum spin Hall
effect of the Kondo singlet. We demonstrate that the collective cyclotron
dynamics of the spin-zero Kondo singlet is governed by an effective
Harper-Hofstadter model in addition to second-order diagonal tunneling.",1502.04422v1
2015-02-16,Effect of non-uniform exchange field in ferromagnetic graphene,"We have presented here the consequences of the non-uniform exchange field on
the spin transport issues in spin chiral configuration of ferromagnetic
graphene. Taking resort to the spin orbit coupling (SOC) term and non-uniform
exchange coupling term we are successful to express the expression of Hall
conductivity in terms of the exchange field and SOC parameters through the Kubo
formula approach. However, for a specific configuration of the exchange
parameter we have evaluated the Berry curvature of the system. We also have
paid attention to the study of SU(2) gauge theory of ferromagnetic graphene.
The generation of anti damping spin orbit torque in spin chiral magnetic
graphene is also briefly discussed.",1502.04453v1
2015-03-12,Emergence of Quantum Nonmagnetic Insulating Phase in Spin-Orbit Coupled Square Lattices,"We investigate the metal-insulator transition (MIT) and phase diagram of the
half-filled Fermi Hubbard model with Rashba-type spin-orbit coupling (SOC) on a
square optical lattice. The interplay between the atomic interactions and SOC
results in distinctive features of the MIT. Significantly, in addition to the
diverse spin ordered phases, a nonmagnetic insulating phase emerges in a
considerably large regime of parameters near the Mott transition. This phase
has a finite single-particle gap but vanishing magnetization and spin
correlation exhibits a power-law scaling, suggesting a potential algebraic
spin-liquid ground state. These results are confirmed by the non-perturbative
cluster dynamical mean-field theory.",1503.03545v1
2015-06-09,Experimental realization of a two-dimensional synthetic spin-orbit coupling in ultracold Fermi gases,"Spin-orbit coupling (SOC) is central to many physical phenomena, including
fine structures of atomic spectra and quantum topological matters. Whereas SOC
is in general fixed in a physical system, atom-laser interaction provides
physicists a unique means to create and control synthetic SOC for ultracold
atoms \cite{Dalibard}. Though significant experimental progresses have been
made, a bottleneck in current studies is the lack of a two-dimensional (2D)
synthetic SOC, which is crucial for realizing high-dimensional topological
matters. Here, we report the experimental realization of 2D SOC in ultracold
$^{40}$K Fermi gases using three lasers, each of which dresses one atomic
hyperfine spin state. Through spin injection radio-frequency (rf) spectroscopy,
we probe the spin-resolved energy dispersions of dressed atoms, and observe a
highly controllable Dirac point created by the 2D SOC. Our work paves the way
for exploring high-dimensional topological matters in ultracold atoms using
Raman schemes.",1506.02861v1
2015-06-23,BCS-BEC crossover of Spin Polarized Fermi Gases with Rashba Spin-Orbit Coupling,"We study the BCS-Bose Einstein Condensation (BEC) crossover of a three
dimensional spin polarized Fermi gas with Rashba spin-orbital-coupling (SOC).
At finite temperature, the effects of non-condensed pairs due to the thermal
excitation are considered based on the $G_0G$ pair fluctuation theory. These
fluctuations generate a pseudogap even persistent above $T_c$. Within this
framework, the Sarma state or the spin polarized superfluid state and polarized
pseudogap state are explored in detail. The resulting $T_c$ curves show that
the enhancement of pairing due to the SOC roughly cancels out the suppression
of pairing due to the population imbalance. Thus we observed that in a large
portion of the parameter space, the polarized superfluid state are stabilized
by the SOC.",1506.07064v1
2015-06-25,Conserved Spin Quantity in Strained Hole Systems with Rashba and Dresselhaus Spin-Orbit Coupling,"We derive an effective Hamiltonian for a (001)-confined quasi-two-dimensional
hole gas in a strained zincblende semiconductor heterostructure including both
Rashba and Dresselhaus spin-orbit coupling. In the presence of uniaxial strain
along the $\left\langle110\right\rangle$ axes, we find a conserved spin
quantity in the vicinity of the Fermi contours in the lowest valence subband.
In contrast to previous works, this quantity meets realistic requirements for
the Luttinger parameters. For more restrictive conditions, we even find a
conserved spin quantity for vanishing strain, restricted to the vicinity of the
Fermi surface.",1506.07639v3
2015-07-09,New Perspectives for Rashba Spin-Orbit Coupling,"In 1984, Bychkov and Rashba introduced a simple form of spin-orbit coupling
to explain certain peculiarities in the electron spin resonance of
two-dimensional semiconductors. Over the past thirty years, similar ideas have
been leading to a vast number of predictions, discoveries, and innovative
concepts far beyond semiconductors. The past decade has been particularly
creative with the realizations of means to manipulate spin orientation by
moving electrons in space, controlling electron trajectories using spin as a
steering wheel, and with the discovery of new topological classes of materials.
These developments reinvigorated the interest of physicists and materials
scientists in the development of inversion asymmetric structures ranging from
layered graphene-like materials to cold atoms. This review presents the most
remarkable recent and ongoing realizations of Rashba physics in condensed
matter and beyond.",1507.02408v2
2015-07-14,U(1) symmetry of the spin-orbit coupled Hubbard model on the Kagome lattice,"We study the symmetry properties of the single-band Hubbard model with
general spin-orbit coupling (SOC) on the Kagome lattice. We show that the
global U(1) spin-rotational symmetry is present in the Hubbard Hamiltonian
owing to the inversion symmetry centered at sites. The corresponding spin
Hamiltonian has, therefore, the SO(2) spin-rotational symmetry, which can be
captured by including SOC non-perturbatively. The exact classical groundstates,
which we obtain for arbitrary SOC, are governed by the SU(2) fluxes associated
with SOC threading the constituent triangles. The groundstates break the SO(2)
symmetry, and the associated Berezinsky-Kosterlitz-Thouless transition
temperature is determined by the SU(2) fluxes through the triangles, which we
confirm by finite temperature classical Monte Carlo simulation.",1507.03963v3
2015-10-09,Electron Spin Resonance in a Two-Dimensional Fermi Liquid with Spin-Orbit Coupling,"Electron spin resonance (ESR) is usually interpreted as a single-particle
phenomenon protected from the effect of many-body correlations. We show that
this is not the case in a two-dimensional Fermi liquid (FL) with spin-orbit
coupling (SOC). Depending on whether the magnetic field is below or above some
critical value, ESR in such a system probes up to three collective chiral-spin
modes, augmented by the presence of the field, or the Larmor mode, augmented
both by SOC and FL renormalizations. We argue that ESR can be used as a probe
not only for SOC but also for many-body physics.",1510.02534v2
2016-01-10,"Interfacial Dzyaloshinskii-Moriya interaction, surface anisotropy energy,and spin pumping at spin orbit coupled Ir/Co interface","The interfacial Dzyaloshinskii-Moriya interaction (iDMI), surface anisotropy
energy, and spin pumping at the Ir/Co interface are experimentally investigated
by performing Brillouin light scattering. Contrary to previous reports, we
suggest that the sign of the iDMI at the Ir/Co interface is the same as in the
case of the Pt/Co interface. We also find that the magnitude of the iDMI energy
density is relatively smaller than in the case of the Pt/Co interface, despite
the large strong spin-orbit coupling (SOC) of Ir. The saturation magnetization
and the perpendicular magnetic anisotropy (PMA) energy are significantly
improved due to a strong SOC. Our findings suggest that an SOC in an Ir/Co
system behaves in different ways for iDMI and PMA. Finally, we determine the
spin pumping effect at the Ir/Co interface, and it increases the Gilbert
damping constant from 0.012 to 0.024 for 1.5 nmthick Co.",1601.02210v3
2016-02-22,Spin-orbit-coupling induced torque in ballistic domain walls: equivalence of charge-pumping and nonequilibrium magnetization formalisms,"To study the effect of spin-orbit coupling (SOC) on spin-transfer torque in
magnetic materials, we have implemented two theoretical formalisms that can
accommodate SOC. Using the ""charge-pumping"" formalism, we find two
contributions to the out-of-plane spin-transfer torque parameter $\beta$ in
ballistic Ni domain walls (DWs). For short DWs, the nonadiabatic reflection of
conduction electrons caused by the rapid spatial variation of the exchange
potential results in an out-of-plane torque that increases rapidly with
decreasing DW length. For long DWs, the Fermi level conduction channel
anisotropy that gives rise to an intrinsic DW resistance in the presence of SOC
leads to a linear dependence of $\beta$ on the DW length. To understand this
counterintuitive divergence of $\beta$ in the long DW limit, we use the
""nonequilibrium magnetization"" formalism to examine the spatially resolved
spin-transfer torque. The SOC-induced out-of-plane torque in ballistic DWs is
found to be quantitatively consistent with the values obtained using the
charge-pumping calculations indicating the equivalence of the two theoretical
methods.",1602.06676v1
2016-02-26,Generation of spin-dependent coherent states in a quantum wire,"We propose an all-electrically controlled nanodevice - a gated semiconductor
nanowire - capable of generating a coherent state of a single electron trapped
in a harmonic oscillator or superposition of such coherent states - the
Schr\""odinger cat state. In the proposed scheme, electron in the ground state
of the harmonic potential is driven by resonantly oscillating Rashba spin-orbit
coupling. This allows for the creation of the Schr\""odinger cat state with
superposition amplitudes depending on the initial electron spin state. Such a
method can be used for initialization of a single spin qubit defined in a
coherent state. The harmonic confinement potential along the InSb nanowire and
the modulation of the Rashba spin-orbit coupling is obtained by proper gating.
The results are supported by realistic three-dimensional time-dependent self
consistent Poisson-Schr\""odinger calculations.",1602.08531v2
2016-07-20,Magnetoelectric Andreev effect due to proximity-induced non-unitary triplet superconductivity in helical metals,"Non-centrosymmetric superconductors exhibit the magnetoelectric effect which
manifests itself in the appearance of the magnetic spin polarization in
response to a dissipationless electric current (supercurrent). While much
attention has been dedicated to the thermodynamic version of this phenomenon
(Edelstein effect), non-equilibrium transport magnetoelectric effects have not
been explored yet. We propose the magnetoelectric Andreev effect (MAE) which
consists in the generation of spin-polarized triplet Andreev conductance by an
electric supercurrent. The MAE stems from the spin polarization of the
Cooper-pair condensate due to a supercurrent-induced non-unitary triplet
pairing. We propose the realization of such non-unitary pairing and MAE in
superconducting proximity structures based on two-dimensional helical metals --
strongly spin-orbit-coupled electronic systems with the Dirac spectrum such as
the topological surface states. Our results uncover an unexplored route towards
electrically controlled superconducting spintronics and are a smoking gun for
induced unconventional superconductivity in spin-orbit-coupled materials.",1607.05880v2
2017-08-25,Surface magnetism in a chiral d-wave superconductor with hexagonal symmetry,"Surface properties are examined in a chiral d-wave superconductor with
hexagonal symmetry, whose one-body Hamiltonian possesses the intrinsic
spin-orbit coupling identical to the one characterizing the topological nature
of the Kane-Mele honeycomb insulator. In the normal state spin-orbit coupling
gives rise to spontaneous surface spin currents, whereas in the superconducting
state there exist besides the spin currents also charge surface currents, due
to the chiral pairing symmetry. Interestingly, the combination of these two
currents results in a surface spin polarization, whose spatial dependence is
markedly different on the zigzag and armchair surfaces. We discuss various
potential candidate materials, such as SrPtAs, which may exhibit these surface
properties.",1708.07640v2
2018-04-19,{\emph{Ab initio} magneto-optical spectrum of Group-IV -- Vacancy color centers in diamond,"Group-IV -- Vacancy color centers in diamond are fast emerging qubits that
can be harnessed in quantum communication and sensor applications. There is an
immediate quest for understanding their magneto-optical properties, in order to
select the appropriate qubits for varying needs of particular quantum
applications. Here we present results from cutting edge \emph{ab initio}
calculations about the charge state stability, zero-phonon-line energies,
spin-orbit and electron-phonon couplings for Group-IV -- Vacancy color centers.
Based on the analysis of our results, we develop a novel spin Hamiltonian for
these qubits which incorporates the interaction of the electron spin and orbit
coupled with phonons beyond perturbation theory. Our results are in good
agreement with previous data and predict a new defect for qubit applications
with thermally initialized ground state spin and long spin coherence time.",1804.07004v1
2018-04-30,Superfluid weight and Berezinskii-Kosterlitz-Thouless temperature of spin-imbalanced and spin-orbit-coupled Fulde-Ferrell phases in lattice systems,"We study the superfluid weight $D^s$ and Berezinskii-Kosterlitz-Thouless
(BKT) transition temperatures $T_{BKT}$ in case of exotic Fulde-Ferrell (FF)
superfluid states in lattice systems. We consider spin-imbalanced systems with
and without spin-orbit coupling (SOC) accompanied with in-plane Zeeman field.
By applying mean-field theory, we derive general equations for $D^s$ and
$T_{BKT}$ in the presence of SOC and the Zeeman fields for 2D Fermi-Hubbard
lattice models, and apply our results to a 2D square lattice. We show that
conventional spin-imbalanced FF states without SOC can be observed at finite
temperatures and that FF phases are further stabilized against thermal
fluctuations by introducing SOC. We also propose how topologically non-trivial
SOC-induced FF phases could be identified experimentally by studying the total
density profiles. Furthermore, the relative behavior of transverse and
longitudinal superfluid weight components and the role of the geometric
superfluid contribution are discussed.",1804.11063v2
2018-11-06,Chiral-induced switching of antiferromagnet spins in a confined nanowire,"In the development of spin-based electronic devices, a particular challenge
is the manipulation of the magnetic state with high speed and low power
consumption. Although research has focused on the current-induced spin-orbit
torque based on strong spin-orbit coupling, the charge-based and the
torque-driven devices have fundamental limitations: Joule heating, phase
mismatching and overshooting. In this work, we investigate numerically and
theoretically alternative switching scenario of antiferromagnetic insulator in
one-dimensional confined nanowire sandwiched with two electrodes. As the
electric field could break inversion symmetry and induce Dzyaloshinskii-Moriya
interaction and pseudo-dipole anisotropy, the resulting spiral texture takes
symmetric or antisymmetric configuration due to additional coupling with the
crystalline anisotropy. Therefore, by competing two spiral states, we show that
the magnetization reversal of antiferromagnets is realized, which is valid in
ferromagnetic counterpart. Our finding provides promising opportunities to
realize the rapid and energy-efficient electrical manipulation of magnetization
for future spin-based electronic devices.",1811.02200v2
2018-11-06,Superconductivity from the Condensation of Topological Defects in a Quantum Spin-Hall Insulator,"The discovery that spin-orbit coupling can generate a new state of matter in
the form of quantum spin-Hall (QSH) insulators has brought topology to the
forefront of condensed matter physics. While QSH states from spin-orbit
coupling can be fully understood in terms of band theory, fascinating many-body
effects are expected if the state instead results from interaction-generated
symmetry breaking. In particular, topological defects of the corresponding
order parameter provide a route to exotic quantum phase transitions. Here, we
introduce a model in which the condensation of skyrmion defects in an
interaction-generated QSH insulator produces a superconducting (SC) phase.
Because vortex excitations of the latter carry a spin-$1/2$ degree of freedom
numbers, the SC order may be understood as emerging from a gapless spin liquid
normal state. The QSH-SC transition is an example of a deconfined quantum
critical point (DQCP), for which we provide an improved model with only a
single length scale that is accessible to large-scale quantum Monte Carlo
simulations.",1811.02583v1
2017-01-26,Exotic Spin Phases in Two Dimensional Spin-orbit Coupled Models: Importance of Quantum Fluctuation Effects,"We investigate the phase diagrams of the effective spin models derived from
Fermi-Hubbard and Bose-Hubbard models with Rashba spin-orbit coupling, using
string bond states, one of the quantum tensor network states methods. We focus
on the role of quantum fluctuation effect in stabilizing the exotic spin phases
in these models. For boson systems, and when the ratio between inter-particle
and intra-particle interaction $\lambda > 1$, the out-of-plane ferromagnetic
(FM) and antiferromagnetic (AFM) phases obtained from quantum simulations are
the same to those obtained from classic model. However, the quantum
order-by-disorder effect reduces the classical in-plane XY-FM and XY-vortex
phases to the quantum X/Y-FM and X/Y-stripe phase when $\lambda < 1$. The
spiral phase and skyrmion phase can be realized in the presence of quantum
fluctuation. For the Fermi-Hubbard model, the quantum fluctuation energies are
always important in the whole parameter regime. %, which are much larger than
those of the Bose model. A general picture to understand the phase diagrams
from symmetry point of view is also presented.",1701.07722v1
2018-05-31,Spin-orbit coupling and resonances in the conductance of quantum wires,"We investigate a possibility of pair electron-electron e-e collisions in a
ballistic wire with spin-orbit coupling and only one populated mode. Unlike in
a spin-degenerate system, a combination of spin-splitting in momentum space
with a momentum-dependent spin-precession opens up a finite phase space for
pair e-e collisions around three distinct positions of the wire's chemical
potential. For a short wire, we calculate corresponding resonant contributions
to the conductance, which have different power-law temperature dependencies,
and, in some cases, vanish if the wire's transverse confinement potential is
symmetric. Our results may explain the recently observed feature at the lower
conductance plateau in InAs wires.",1805.12385v2
2015-12-04,Kondo screening in two-dimensional $p$-type transition-metal dichalcogenides,"Systems with strong spin orbit coupling support a number of new phases of
matter and novel phenomena. This work focuses on the interplay of spin orbit
coupling and interactions in yielding correlated phenomena in two dimensional
transition metal dichalcogenides. In particular we explore the physics of Kondo
screening resulting from the lack of centro-symmetry, large spin splitting and
spin valley locking in hole doped systems. The key ingredients are i) valley
dependent spin-momentum locking perpendicular to the two dimensional crystal;
ii) single nondegenerate Fermi surface per valley, and iii) nontrivial Berry
curvature associated with the low energy bands. The resulting Kondo resonance
has a finite triplet component and nontrivial momentum space structure which
facilitates new approaches to both probe and manipulate the correlated state.
Using a variational wave function and the numerical renormalization group
approaches we study the nature of the Kondo resonance both in the absence and
presence of circularly polarized light. The latter induces an imbalance in the
population of the two valleys leading to novel magnetic phenomena in the
correlated state.",1512.01590v2
2017-12-16,Bulk-edge correspondence and new topological phases in periodically driven spin-orbit coupled materials in the low frequency limit,"We study the topological phase transitions induced in spin-orbit coupled
materials with buckling like silicene, germanene, stanene, etc, by circularly
polarised light, beyond the high frequency regime, and unearth many new
topological phases. These phases are characterised by the spin-resolved
topological invariants, $C_0^\uparrow$, $C_0^\downarrow$, $C_\pi^\uparrow$ and
$C_\pi^\downarrow$, which specify the spin-resolved edge states traversing the
gaps at zero quasi-energy and the Floquet zone boundaries respectively. We show
that for each phase boundary, and independently for each spin sector, the gap
closure in the Brillouin zone occurs at a high symmetry point.",1712.05916v2
2020-01-10,Bound fermion states in pinned vortices in the surface states of a superconducting topological insulator: The Majorana bound state,"By analytically solving the Bogoliubov-de Gennes equations we study the
fermion bound states at the center of the core of a vortex in a two-dimensional
superconductor. We consider three kinds of 2D superconducting models: (a) a
standard type II superconductor in the mixed state with low density of vortex
lines, (b) a superconductor with strong spin-orbit coupling locking the spin
parallel to the momentum and (c) a superconductor with strong spin-orbit
coupling locking the spin perpendicular to the momentum. The 2D superconducting
states are induced via proximity effect between an $s$-wave superconductor and
the surface states of a strong topological insulator. In case (a) the energy
gap for the excitations is of order $\Delta_{\infty}^2/(2E_F)$, while for cases
(b) and (c) a zero-energy Majorana state arises together with an equally spaced
($\Delta^2_{\infty}/E_F$) sequence of fermion excitations. The spin-momentum
locking is key to the formation of the Majorana state. We present analytical
expressions for the energy spectrum and the wave functions.",2001.03666v2
2018-03-02,Rashba proximity states in superconducting tunnel junctions,"We consider a new kind of superconducting proximity effect created by the
tunneling of ""spin split"" Cooper pairs between two conventional superconductors
connected by a normal conductor containing a quantum dot. The difference
compared to the usual superconducting proximity effect is that the spin states
of the tunneling Cooper pairs are split into singlet and triplet components by
the electron spin-orbit coupling, which is assumed to be active in the normal
conductor only. We demonstrate that the supercurrent carried by the spin-split
Cooper pairs can be manipulated both mechanically and electrically for
strengths of the spin-orbit coupling that can realistically be achieved by
electrostatic gates.",1803.01725v1
2018-12-12,Spin-Splitting and Rashba-Effect at Mono-Layer GaTe in the Presence of Strain,"In this paper, spintronic properties of the mono-layer GaTe under biaxial and
uniaxial strain is investigated. Here, spin properties of two structures of
GaTe, one with mirror symmetry and the other with inversion symmetry, is
studied. We have also calculated the band structure of GaTe with and without
spin-orbit coupling to find out the importance of spinorbit interaction (SOI)
on its band structure. We find band gap can be modified by applying spin-orbit
coupling in the presence of strain. We explore Mexican-hat dispersion for
different structures and different strain. We find Mexican-hat can be tuned
however some cases shows any Mexican-hat. We calculate spin-splitting in
conduction and valence band in the presence of strain where the structure with
inversion symmetry doesn't show any splitting. We find in some cases, GaTe
indicates Rashba dispersion that can be adjusted by strain. The amount of
Rashba parameters may be in the order of other reported two-dimensional
materials.",1812.04820v3
2019-02-02,Effects of strong magnetic fields on neutron $^{3}P_{2}$ superfluidity with spin-orbit interactions,"We discuss neutron $^{3}P_{2}$ phases in the core of neutron stars in strong
magnetic field (magnetars). The neutron $^{3}P_{2}$ pairing provides a wide
variety of condensates, such as the uniaxial nematic and (D$_{2}$ and D$_{4}$)
biaxial nematic, with different symmetries stemming from the combinations of
spin and momentum. Based on the spin-orbital angular momentum coupling and the
spin-magnetic field coupling of the neutrons, we derive the Ginzburg-Landau
equation containing higher order terms of the magnetic field. We investigate
the phase diagram of the neutron $^{3}P_{2}$ superfluidity, and find that the
D$_{2}$ biaxial nematic phase is extended by the higher order terms of the
magnetic field. We also discuss the thermodynamic properties, the heat capacity
and the spin susceptibility.",1902.00674v2
2019-02-25,Influences of spin-orbit coupling on Fermi surfaces and Dirac cones in ferroelectric-like polar metals,"Based on first-principles calculations and k .p effective models, we report
physical properties of ferroelectric-like hexagonal polar metals with P63mc
symmetry, which are distinct from those of conventional metals with spatial
inversion symmetry. Spin textures exist on the Fermi surface of polar metals
(e.g. ternary LiGaGe and elemental polar metal of Bi) and spin-momentum locking
exist on accidental Dirac cones on the sixfold rotational axis, due to the
spin-orbit coupling and lack of inversion symmetry in polar space group. This
effect has potential applications in spin-orbitronics. Dirac points are also
predicted in LiGaGe.",1902.09052v1
2019-03-14,Quasiparticle Interference and Symmetry of Superconducting Order Parameter in Strongly Electron-Doped Iron-based Superconductors,"Motivated by recent experimental reports of significant spin-orbit coupling
(SOC) and a sign-changing order-parameter in the
Li$_{1-x}$Fe$_x$(OHFe)$_{1-y}$Zn$_y$Se superconductor with only electron
pockets present, we study the possible Cooper-pairing symmetries and their
quasiparticle interference (QPI) signatures. We find that each of the resulting
states - $s$-wave, $d$-wave and helical $p$-wave - can have a fully gapped
density of states (DOS) consistent with angle-resolved photoemission
spectroscopy (ARPES) experiments and, due to spin-orbit coupling, are a mixture
of spin singlet and triplet components leading to intra- and inter-band
features in the QPI signal. Analyzing predicted QPI patterns we find that only
the spin-triplet dominated even parity $A_{1g}$ (s-wave) and $B_{2g}$ (d-wave)
pairing states are consistent with the experimental data. Additionally, we show
that these states can indeed be realized in a microscopic model with
atomic-like interactions and study their possible signatures in spin-resolved
STM experiments.",1903.05935v3
2019-12-29,Emergent chiral spin ordering and anomalous Hall effect of kagome lattice at 1/3 filling,"The study of electronic and magnetic properties of kagome lattice has been an
active research area searching for topological phases of matters. In
particular, the kagome system with transition metal stannides and etc exhibit
interesting anomalous Hall effects driven by ferromagnetic or non-collinear
magnetic ordering. In this paper, motivated by these pioneer works, we study
strongly correlated spin-orbit coupled electrons in kagome lattice at 1/3
filling. Using both Hartree-Fock approach and effective model analysis, we
report quantum phase transitions accompanied with distinct charge and magnetic
ordered phases. Especially, for strongly interacting limit, we discover new
types of 1(2)-pinned metallic states which are understood by effective
localized electron models. Furthermore, when spin-orbit coupling is present, it
turns out that such pinned metallic states open a wide region of Chern
insulating phase with chiral spin ordering. Thus, quantum anomalous Hall effect
is expected with emergent scalar spin chirality. Our theory provides a
theoretical platform of strongly interacting kagome metal which is applicable
to transition metal stannides.",1912.12621v1
2019-12-31,Spin-polarized electron transmission in DNA-like systems,"The helical distribution of the electronic density in chiral molecules, such
as DNA and bacteriorhodopsin, has been suggested to induce a spin-orbit
coupling interaction that may lead to the so-called chirality-induced spin
selectivity (CISS) effect. Key ingredients for the theoretical modelling are,
in this context, the helically shaped potential of the molecule and,
concomitantly, a Rashba-like spin-orbit coupling due to the appearance of a
magnetic field in the electron reference frame. Symmetries of these models
clearly play a crucial role in explaining the observed effect, but a thorough
analysis has been largely ignored in the literature. In this work, we present a
study of these symmetries and how they can be exploited to enhance
chiral-induced spin selectivity in helical molecular systems.",1912.13271v1
2020-11-18,Hole spin qubits in Si FinFETs with fully tunable spin-orbit coupling and sweet spots for charge noise,"The strong spin-orbit coupling in hole spin qubits enables fast and
electrically tunable gates, but at the same time enhances the susceptibility of
the qubit to charge noise. Suppressing this noise is a significant challenge in
semiconductor quantum computing. Here, we show theoretically that hole Si
FinFETs are not only very compatible with modern CMOS technology, but they
present operational sweet spots where the charge noise is completely removed.
The presence of these sweet spots is a result of the interplay between the
anisotropy of the material and the triangular shape of the FinFET
cross-section, and it does not require an extreme fine-tuning of the
electrostatics of the device. We present how the sweet spots appear in FinFETs
grown along different crystallographic axes and we study in detail how the
behaviour of these devices change when the cross-section area and aspect ratio
are varied. We identify designs that maximize the qubit performance and could
pave the way towards a scalable spin-based quantum computer.",2011.09417v2
2016-03-31,Rashba scattering in the low-energy limit,"We study potential scattering in a two-dimensional electron gas with Rashba
spin-orbit coupling in the limit that the energy of the scattering electron
approaches the bottom of the lower spin-split band. Focusing on two
spin-independent circularly symmetric potentials, an infinite barrier and a
delta-function shell, we show that scattering in this limit is qualitatively
different from both scattering in the higher spin-split band and scattering of
electrons without spin-orbit coupling. The scattering matrix is purely
off-diagonal with both off-diagonal elements equal to one, and all angular
momentum channels contribute equally; the differential cross section becomes
increasingly peaked in the forward and backward scattering directions; the
total cross section exhibits quantized plateaus. These features are independent
of the details of the scattering potentials, and we conjecture them to be
universal. Our results suggest that Rashba scattering in the low-energy limit
becomes effectively one-dimensional.",1603.09456v3
2016-10-14,Magnetic Field Evolution of Spin Blockade in Ge/Si Nanowire Double Quantum Dots,"We perform transport measurements on double quantum dots defined in Ge/Si
core/shell nanowires and focus on Pauli spin blockade in the regime where tens
of holes occupy each dot. We identify spin blockade through the magnetic field
dependence of leakage current. We find both a dip and a peak in the leakage
current at zero field. We analyze this behavior in terms of the quantum dot
parameters such as coupling to the leads, interdot tunnel coupling as well as
spin-orbit interaction. We find a lower bound for spin-orbit interaction with
$l_{\rm so}=500$ nm. We also extract large and anisotropic effective Land$\rm
\acute{e}$ g-factors, with larger g-factors in the direction perpendicular to
the nanowire axis in agreement with previous studies and experiments but with
larger values reported here.",1610.04596v1
2016-10-17,Spin-orbit coupling in quasi-one-dimensional Wigner crystals,"We study the effect of Rashba spin-orbit coupling (SOC) on the charge and
spin degrees of freedom of a quasi-one-dimensional (quasi-1D) Wigner crystal.
As electrons in a quasi-1D Wigner crystal can move in the transverse direction,
SOC cannot be gauged away in contrast to the pure 1D case. We show that for
weak SOC, a partial gap in the spectrum opens at certain ratios between density
of electrons and the inverse Rashba length. We present how the low-energy
branch of charge degrees of freedom deviates due to SOC from its usual linear
dependence at small wave vectors. In the case of strong SOC, we show that spin
sector of a Wigner crystal cannot be described by an isotropic
antiferromagnetic Heisenberg Hamiltonian any more, and that instead the ground
state of neighboring electrons is mostly a triplet state. We present a new spin
sector Hamiltonian and discuss the spectrum of Wigner crystal in this limit.",1610.05241v2
2018-10-24,Nearly isotropic spin-pumping related Gilbert damping in Pt/Ni$_{81}$Fe$_{19}$/Pt,"A recent theory by Chen and Zhang [Phys. Rev. Lett. 114, 126602 (2015)]
predicts strongly anisotropic damping due to interfacial spin-orbit coupling in
ultrathin magnetic films. Interfacial Gilbert-type relaxation, due to the spin
pumping effect, is predicted to be significantly larger for magnetization
oriented parallel to compared with perpendicular to the film plane. Here, we
have measured the anisotropy in the Pt/Ni$_{81}$Fe$_{19}$/Pt system via
variable-frequency, swept-field ferromagnetic resonance (FMR). We find a very
small anisotropy of enhanced Gilbert damping with sign opposite to the
prediction from the Rashba effect at the FM/Pt interface. The results are
contrary to the predicted anisotropy and suggest that a mechanism separate from
Rashba spin-orbit coupling causes the rapid onset of spin-current absorption in
Pt.",1810.10595v4
2020-09-21,Impurity induced magnetic ordering in Sr$_2$RuO$_4$,"Ti substituting Ru in Sr$_2$RuO$_4$ in small concentrations induces
incommensurate spin density wave order with a wave vector $\boldsymbol{Q}
\simeq (2 \pi /3, 2 \pi /3)$ corresponding to the nesting vector of two out of
three Fermi surface sheets. We consider a microscopic model for these two bands
and analyze the correlation effects leading to magnetic order through
non-magnetic Ti-doping. For this purpose we use a position dependent mean field
approximation for the microscopic model and a phenomenological Ginzburg-Landau
approach, which both deliver consistent results and allow us to examine the
inhomogeneous magnetic order. Spin-orbit coupling additionally leads to spin
currents around each impurity, which in combination with the magnetic
polarization produce a charge current pattern. This is also discussed within a
gauge field theory in both charge and spin channel. This spin-orbit coupling
effect causes an interesting modification of the magnetic structure, if
currents run through the system. Our findings allow a more detailed analysis of
the experimental data for Sr$_{2}$Ru$_{1-x}$Ti$_{x}$O$_{4}$. In particular, we
find that the available measurements are consistent with our theoretical
predictions.",2009.10086v2
2020-09-24,Stückelberg interferometry using spin-orbit-coupled cold atoms in an optical lattice,"Time evolution of spin-orbit-coupled cold atoms in an optical lattice is
studied, with a two-band energy spectrum having two avoided crossings. A force
is applied such that the atoms experience two consecutive Landau-Zener
tunnelings while transversing the avoided crossings. St\""uckelberg interference
arises from the phase accumulated during the adiabatic evolution between the
two tunnelings. This phase is gauge field-dependent and thus provides new
opportunities to measure the synthetic gauge field, which is verified via
calculation of spin transition probabilities after a double passage process.
Time-dependent and time-averaged spin probabilities are derived, in which
resonances are found. We also demonstrate chiral Bloch oscillation and rich
spin-momentum locking behavior in this system.",2009.11438v1
2021-03-04,Intrinsic and extrinsic tunability of Rashba spin-orbit coupled emergent inductors,"The emergent induction of spiral magnets that was proposed [Jpn. J. Appl.
Phys. 58, 120909 (2019)] and recently demonstrated [Nature 586, 232 (2020)] is
shown to be further extended by a comprehensive treatment of the Rashba
spin-orbit coupling and the electron spin relaxation that affect the underlying
processes of spin-transfer torque and spinmotive force. Within adiabatic
approximation, we show that the output voltages are widely altered
intrinsically via the Rashba effect whereas extrinsically via the nonadiabatic
correction due to the spin relaxation and sample disorder. The findings
respectively clarify the origins for the amplitude modulation and sign change
of the emergent inductance with tunability by electrical gating and careful
sample preparation.",2103.02859v1
2021-09-02,Terahertz Nonlinear Optics in Two-dimensional Semi-Hydrogenated SiB,"Phase transition and current of planar clusters with loops of Josephson $\pi$
junction is of great importance for application in the adiabatic quantum
computation devices (AQC). Each $\pi$-ring possesses an orbital moment with a
current. The orientation of these orbital moments is altered by
self-interactions and controlled with a bias current. In the current research,
we construct the phase diagram of semi-hydrogenated SiB (H-SiB) semiconductor
using a two-dimensional (2D) Ising model with considering nearest-neighbor and
diagonal interactions of spin planes on the on the hexagonal lattice. Our
findings reveal that by decreasing temperature, two phase transitions of order
and disorder occur and at low temperatures a glassy state appears, where this
model maps to spin qubit. We theoretically study the magnetostriction effect by
considering of laser electromagnetic field coupled to the spin planes of
electric polarization of magnetic insulator for both unstrained and strained
H-SiB monolayers. The dynamic of laser-spin coupling and spin current shows
nonlinear optical effects and high-harmonic generation (HHG) under both
terahertz (THz) and gigahertz (GHz) electromagnetic waves. The findings of this
research open an avenue for experimentalists how to detect HHG in the
topological insulators, Dirac systems, Mott insulators, and superconducting
memories.",2109.00858v1
2021-09-29,Graphene bilayer and trilayer Moiré lattice with Rashba spin-orbit coupling,"We consider twisted bilayer and trilayer graphene in the presence of Rashba
spin-orbit coupling and explore the physics of Moir\'e spintronics. The
electronic charge density has a sharp step right at the magic angles
$\theta_m$. As a result, local spin observables (polarization and equilibrium
spin currents) have sharp peaks (of width about a small fraction of 1$^\circ$)
as a function of the twist angle $\theta$, and abrupt sign reversals at
$\theta_m$. Thereby, the magic angle can be determined in an unprecedented
accuracy. In the first chiral limit, the spin currents vanish, but the peculiar
pattern of the polarization at $\theta_m$ persists. Major differences result in
spintronics of twisted bilayer graphene at magic angles as compared with the
spintronics of single and/or {\it un-twisted} bilayer graphene. Thus, in
addition to the numerous spectacular physical phenomena already reported in
twisted bilayer graphene at magic angles, new phenomena also occur in
twistronic spintronics.",2109.14308v3
2022-10-21,Spin-Dependent High-Order Topological Insulator and Two Types of Distinct Corner Modes in Monolayer FeSe/GdClO Heterostructure,"We propose that a spin-dependent second-order topological insulator can be
realized in monolayer FeSe/GdClO heterostructure, in which substrate GdClO
helps to stabilize and enhance the antiferromagnetic order in FeSe. The
second-order topological insulator is free from spin-orbit coupling and
in-plane magnetic field. We also find that there exist two types of distinct
corner modes residing in intersections of two ferromagnetic edges and two
antiferromagnetic edges, respectively. The underlying physics for ferromagnetic
corner mode follows a sublattice-chirality-kink picture. More interestingly,
ferromagnetic corner mode shows spin-dependent property, which is also robust
against spin-orbit coupling. Unexpectedly, antiferromagnetic corner mode can be
taken as a typical emergent and hierarchical phenomenon from an array of
ferromagnetic corner modes. Remarkably, antiferromagnetic corner modes violate
general kink picture and can be understood as bound states of a one-dimensional
Schrodinger equation under a connected potential well. Our findings not only
provide a promising second-order topological insulator in electronic materials,
but uncover some new properties of corner modes in high-order topological
insulator.",2210.11813v1
2022-12-13,Spin-orbit amplitudes for decays with arbitrary spin,"In this paper, we propose a method to construct the decay amplitudes in the
orbital ($L$) and spin ($S$) coupling scheme for particles with arbitrary
spins. For the $1\to 2$ decay with only massive particles involved, the angular
dependence is completely encoded in the angular momentum part, and the spins of
daughter particles are coupled in the rest frame of the mother particle, which
contributes only a constant factor. For the sequential decay, the total
amplitude is constructed by the two $1\to2$ amplitudes evaluated in the rest
frame of their own mother particles, and then they are transformed to the
common frame, usually chosen as the laboratory frame, by certain Lorentz
transformations. In this way, it is easy to add the amplitudes of possible
different decay chains coherently. If massless particles show up in the final
states, the polarizations are expressed in helicity basis and the amplitudes
are modified correspondingly.",2212.06417v2
2023-01-02,Spin Hall and Edelstein Effects in pseudospin-1 systems: significant contribution of vertex corrections,"Edelstein and spin Hall effect response functions for a two-dimensional (2D)
system of pseudospin-1 particles is investigated. These two response functions
denoted by $ \sigma_{SH} $ and $ \sigma_{EE} $ have been analyzed in a
pseudospin-1 particle system in the presence of the Rashba-type spin-orbit
interaction using the Kubo-Streda technique and vertex corrections with
non-magnetic impurities. Then, for a given range of the Rashba coupling,
response functions of the spin Hall effect (SHE) and Edelstein effect (EE) have
been estimated at various energy gaps and Fermi energies. Results indicate that
in this type of the two-dimensional materials, SHE and EE are essentially
induced by the vertex corrections and without considering these corrections the
amount of these effects are really negligible. It has also been realized that
SHE and EE conductivities can be modulated by the Rashba coupling strength at
low and intermediate level of this spin-orbit type interaction.",2301.00550v1
2023-08-08,Landau Theory of Altermagnetism,"We formulate a Landau theory for altermagnets, a class of colinear
compensated magnets with spin-split bands. Starting from the non-relativistic
limit, this Landau theory goes beyond a conventional analysis by including
spin-space symmetries, providing a simple framework for understanding the key
features of this family of materials. We find a set of multipolar secondary
order parameters connecting existing ideas about the spin symmetries of these
systems, their order parameters and the effect of non-zero spin-orbit coupling.
We account for several features of canonical altermagnets such as RuO$_2$, MnTe
and CuF$_2$ that go beyond symmetry alone, relating the order parameter to key
observables such as magnetization, anomalous Hall conductivity and
magneto-elastic and magneto-optical probes. Finally, we comment on
generalizations of our framework to a wider family of exotic magnetic systems
deriving from the zero spin-orbit coupled limit.",2308.04484v1
2023-11-02,Weak localization at arbitrary disorder in systems with generic spin-dependent fields,"We present a theory of weak localization (WL) in the presence of generic
spin-dependent fields, including any type of spin-orbit coupling, Zeeman
fields, and non-homogeneous magnetic textures. We go beyond the usual diffusive
approximation, considering systems with arbitrary disorder, and obtain a
compact expression for the weak localization (WL) correction to the
conductivity in terms of the singlet-triplet polarization operator in momentum
space. The latter can be directly related to the solution of the quasiclassical
Eilenberger equation for superconducting systems. This formulation presents an
intuitive framework to explore how the interplay of various spin-dependent
fields drives weak (anti) localization. We apply our results to study in-plane
magnetoconductivity in systems with spin-orbit coupling, and in newly
discovered altermagnets. Our results enable straightforward calculation of the
WL conductivity at arbitrary disorder, which can be particularly useful for
interpreting experiments on high-mobility samples.",2311.01148v1
2023-11-08,Time evolution of coherent wave propagation and spin relaxation in spin-orbit coupled systems,"We investigate, both numerically and analytically, the time evolution of a
particle in an initial plane wave state as it is subject to elastic scattering
in a two-dimensional disordered system with Rashba spin-orbit coupling (SOC).
In the analytic calculation, we treat the SOC non-perturbatively, and the
disorder perturbatively using the Diffuson and the Cooperon. We calculate the
time dependence of coherent backscattering (CBS) as a function of the strength
of the SOC. We identify weak and strong SOC regimes, and give the relevant time
and energy scales in each case. By studying the time dependence of the
anisotropy of the disorder-averaged momentum distribution we identify the spin
relaxation time. We find a crossover from D'yakonov-Perel' spin relaxation for
weak SOC to Elliot-Yafet like behaviour for strong SOC.",2311.04613v2
2011-06-20,Spin-orbit coupling in $d^{2}$ ordered double perovskites,"We construct and analyze a microscopic model for insulating rock salt ordered
double perovskites, with the chemical formula A$_2$BB'O$_6$, where the magnetic
ion B' has a 4d$^2$ or 5d$^2$ electronic configuration and forms a face
centered cubic (fcc) lattice. For these B' ions, the combination of the
triply-degenerate antisymmetric two-electron orbital states and strong
spin-orbit coupling forms local quintuplets with an effective spin moment
$j=2$. Moreover, due to strongly orbital-dependent exchange, the effective
spins have substantial biquadratic and bicubic interactions (fourth and sixth
order in the spins, respectively). This leads, at the mean field level, to a
rich ground state phase diagram which includes seven different phases: a
uniform ferromagnetic phase with an ordering wavevector ${\bf p} = {\bf 0}$ and
uniform magnetization along $[111]$ direction, four two-sublattice phases with
an ordering wavevector ${\bf p} = 2\pi(001)$ and two four-sublattice
antiferromagnetic phases. Amongst the two-sublattice phases there is a
quadrupolar ordered phase which preserves time reversal symmetry. Extending the
mean field theory to finite temperatures, we find ten different magnetization
processes with different magnetic thermal transitions. In particular, we find
that thermal fluctuations stabilize the two-sublattice quadrupolar ordered
phase in a large portion of phase diagram. Existing and possible future
experiments are discussed in light of these theoretical predictions.",1106.3993v1
2011-11-12,Half-metallic Ferrimagnetism Driven by Coulomb Enhanced Spin-Orbit Coupling in PdCrO3,"Recently, in the seemingly narrow gap insulating NiCrO$_3$ with the
trigonally distorted (R-3c) perovskite-like structure, a compensated half-metal
(CHM) is predicted, as applying a modest pressure. Using ab initio calculations
including both Coulomb correlations and spin-orbit coupling (SOC), we
investigate the as-yet-unsynthesized PdCrO$_3$, isostructural and isovalent to
NiCrO$_3$. Upon applying the on-site Coulomb repulsion $U$ to both Pd and Cr
ions, the Cr spin moment is precisely compensated with the antialigned spin
moments of Pd and oxygens. Coincidentally only one spin channel remains
metallic due to the twice larger width of the Pd 4d bands than the Ni 3d bands
in NiCrO$_3$, indicating CHM in ambient pressure. Inclusion of SOC as well as
correlation effects (LDA+U+SOC) produces a SOC constant enhanced twice over the
value of LDA+SOC, leading to unusually large orbital moment of --0.25 $\mu_B$
on Pd. However, the half-metallicity still survives, so that a transition of
CHM to a half-metallic ferrimagnet occurs due to Coulomb enhanced SOC. On the
other hand, an isovalent, but presumed cubic double perovskite La$_2$PdCrO$_6$
is expected to be a half-metal ferromagnet with tiny orbital moments.",1111.2911v1
2016-03-01,Generic model for hyperkagome iridate in the local moment regime,"Hyperkagome iridate, Na$_4$Ir$_3$O$_8$, has been regarded as a promising
candidate material for a three-dimensional quantum spin liquid. Here the
three-dimensional network of corner-sharing triangles forms the hyperkagome
lattice of Ir$^{4+}$ ions. Due to strong spin-orbit coupling, the local moments
of Ir$^{4+}$ ions are described by the pseudospin $j_{\rm eff} = 1/2$ Kramers
doublet. The Heisenberg model on this lattice is highly frustrated and
quantum/classical versions have been studied in earlier literature. In this
work, we derive a generic local-moment model beyond the Heisenberg limit for
the hyperkagome iridate by considering multi-orbital interactions for all the
$t_{2g}$ orbitals and spin-orbit coupling. The lifting of massive classical
degeneracy in the Heisenberg model by various spin-anisotropy terms is
investigated at the classical level and the resulting phase diagram is
presented. We find that different anisotropy terms prefer distinct classes of
magnetically ordered phases, often with various discrete degeneracy. The
implications of our results for recent $\mu$SR and NMR experiments on this
material and possible quantum spin liquid phases are discussed.",1603.00469v3
2022-04-15,First demonstration of tuning between the Kitaev and Ising limits in a honeycomb lattice,"Recent observations of novel spin-orbit coupled states have generated
tremendous interest in $4d/5d$ transition metal systems. A prime example is the
$J_{\text{eff}}=\frac{1}{2}$ state in iridate materials and $\alpha$-RuCl$_{3}$
that drives Kitaev interactions. Here, by tuning the competition between
spin-orbit interaction ($\lambda_{\text{SOC}}$) and trigonal crystal field
splitting ($\Delta_\text{T}$), we restructure the spin-orbital wave functions
into a novel $\mu=\frac{1}{2}$ state that drives Ising interactions. This is
done via a topochemical reaction that converts Li$_{2}$RhO$_{3}$ to
Ag$_{3}$LiRh$_{2}$O$_{6}$, leading to an enhanced trigonal distortion and a
diminished spin-orbit coupling in the latter compound. Using perturbation
theory, we present an explicit expression for the new $\mu=\frac{1}{2}$ state
in the limit $\Delta_\text{T}\gg \lambda_{\text{SOC}}$ realized in
Ag$_{3}$LiRh$_{2}$O$_{6}$, different from the conventional
$J_\text{eff}=\frac{1}{2}$ state in the limit $\lambda_{\text{SOC}}\gg
\Delta_\text{T}$ realized in Li$_{2}$RhO$_{3}$. The change of ground state is
followed by a dramatic change of magnetism from a 6 K spin-glass in
Li$_{2}$RhO$_{3}$ to a 94 K antiferromagnet in Ag$_{3}$LiRh$_{2}$O$_{6}$. These
results open a pathway for tuning materials between the two limits and creating
a rich magnetic phase diagram.",2204.07591v1
2023-12-15,Geometry of the dephasing sweet spots of spin-orbit qubits,"The dephasing time of spin-orbit qubits is limited by the coupling with
electrical and charge noise. However, there may exist ""dephasing sweet spots""
where the qubit decouples (to first order) from the noise so that the dephasing
time reaches a maximum. Here we discuss the nature of the dephasing sweet spots
of a spin-orbit qubit electrically coupled to some fluctuator. We characterize
the Zeeman energy $E_\mathrm{Z}$ of this qubit by the tensor $G$ such that
$E_\mathrm{Z}=\mu_B\sqrt{\vec{B}^\mathrm{T}G\vec{B}}$ (with $\mu_B$ the Bohr
magneton and $\vec{B}$ the magnetic field), and its response to the fluctuator
by the derivative $G^\prime$ of $G$ with respect to the fluctuating field. The
geometrical nature of the sweet spots on the unit sphere describing the
magnetic field orientation depends on the sign of the eigenvalues of
$G^\prime$. We show that sweet spots usually draw lines on this sphere. We then
discuss how to characterize the electrical susceptibility of a spin-orbit qubit
with test modulations on the gates. We apply these considerations to a Ge/GeSi
spin qubit heterostructure, and discuss the prospects for the engineering of
sweet spots.",2312.09840v2
2020-11-13,"Eigenspectrum, Chern Numbers and Phase Diagrams of Ultracold Color-orbit Coupled SU(3) Fermions in Optical Lattices","We study ultracold color fermions with three internal states Red, Green and
Blue with ${\rm SU(3)}$ symmetry in optical lattices, when color-orbit coupling
and color-flip fields are present. This system corresponds to a generalization
of two-internal state fermions with ${\rm SU(2)}$ symmetry in the presence of
spin-orbit coupling and spin-flipping Zeeman fields. We investigate the
eigenspectrum and Chern numbers to describe different topological phases that
emerge in the phase diagrams of color-orbit coupled fermions in optical
lattices. We obtain the phases as a function of artificial magnetic,
color-orbit and color-flip fields that can be independently controlled. For
fixed artificial magnetic flux ratio, we identify topological quantum phases
and phase transitions in the phase diagrams of chemical potential versus
color-flip fields or color-orbit coupling, where the chirality and number of
midgap edge states changes. The topologically non-trivial phases are classified
in three groups: the first group has total non-zero chirality and exhibit only
the quantum charge Hall effect; the second group has total non-zero chirality
and exhibit both quantum charge and quantum color Hall effects; and the third
group has total zero chirality, but exhibit the quantum color Hall effect.
These phases are generalizations of the quantum Hall and quantum spin Hall
phases for charged spin-$1/2$ fermions. Lastly, we also describe the color
density of states and a staircase structure in the total and color filling
factors versus chemical potential for fixed color-orbit, color-flip and
magnetic flux ratio. We show the existence of incompressible states at rational
filling factors precisely given by a gap-labelling theorem that relates the
filling factors to the magnetic flux ratio and topological quantum numbers.",2011.07139v1
2021-04-13,Collective P-Wave Orbital Dynamics of Ultracold Fermions,"We consider the non-equilibrium orbital dynamics of spin-polarized ultracold
fermions in the first excited band of an optical lattice. A specific lattice
depth and filling configuration is designed to allow the $p_x$ and $p_y$
excited orbital degrees of freedom to act as a pseudo-spin. Starting from the
full Hamiltonian for p-wave interactions in a periodic potential, we derive an
extended Hubbard-type model that describes the anisotropic lattice dynamics of
the excited orbitals at low energy. We then show how dispersion engineering can
provide a viable route to realizing collective behavior driven by p-wave
interactions. In particular, Bragg dressing and lattice depth can reduce
single-particle dispersion rates, such that a collective many-body gap is
opened with only moderate Feshbach enhancement of p-wave interactions. Physical
insight into the emergent gap-protected collective dynamics is gained by
projecting the Hamiltonian into the Dicke manifold, yielding a one-axis
twisting model for the orbital pseudo-spin that can be probed using
conventional Ramsey-style interferometry. Experimentally realistic protocols to
prepare and measure the many-body dynamics are discussed, including the effects
of band relaxation, particle loss, spin-orbit coupling, and doping.",2104.06480v3
2018-12-07,Effects of paramagnetic pair-breaking and spin-orbital coupling on multi-band superconductivity,"The BCS picture of superconductivity describes pairing between electrons
originating from a single band. A generalization of this picture occurs in
multi-band superconductors, where electrons from two or more bands contribute
to superconductivity. The contributions of the different bands can result in an
overall enhancement of the critical field and can lead to qualitative changes
in the temperature dependence of the upper critical field when compared to the
single-band case. While the role of orbital pair-breaking on the critical field
of multi-band superconductors has been explored extensively, paramagnetic and
spin-orbital scattering effects have received comparatively little attention.
Here we investigate this problem using thin films of Nd-doped SrTiO$_3$. We
furthermore propose a model for analyzing the temperature-dependence of the
critical field in the presence of orbital, paramagnetic and spin-orbital
effects, and find a very good agreement with our data. Interestingly, we also
observe a dramatic enhancement in the out-of-plane critical field to values
well in excess of the Chandrasekhar-Clogston (Pauli) paramagnetic limit, which
can be understood as a consequence of multi-band effects in the presence of
spin-orbital scattering.",1812.02875v2
2022-11-18,Coupled cluster theory: Towards an algebraic geometry formulation,"Coupled cluster theory produced arguably the most widely used high-accuracy
computational quantum chemistry methods. Despite the approach's overall great
computational success, its mathematical understanding is so far limited to
results within the realm of functional analysis. The coupled cluster
amplitudes, which are the targeted objects in coupled cluster theory,
correspond to solutions to the coupled cluster equations, which is a system of
polynomial equations of at most degree four. The high dimensionality of the
electronic Schr\""odinger equation and the non-linearity of the coupled cluster
ansatz have so far stalled a formal analysis of this polynomial system. In this
article, we present algebraic investigations that shed light on the coupled
cluster equations and the root structure of this ansatz. This is of importance
for the a posteriori evaluation of coupled cluster calculations. To that end,
we investigate the root structure by means of Newton polytopes. We derive a
general v-description, which is subsequently turned into an h-description for
explicit examples. This perspective reveals an apparent connection between
Pauli's exclusion principle and the geometrical structure of the Newton
polytopes. We also propose an alternative characterization of the coupled
cluster equations projected onto singles and doubles as cubic polynomials on an
algebraic variety with certain sparsity patterns. Moreover, we provide
numerical simulations of two computationally tractable systems, namely, the two
electrons in four spin-orbitals system and the three electrons in six
spin-orbitals system. These simulations provide novel insight into the root
structure of the coupled cluster solutions when the coupled cluster ansatz is
truncated.",2211.10389v3
2023-08-17,Orbital Multiferroicity in Pentalayer Rhombohedral Graphene,"Ferroic orders describe spontaneous polarization of spin, charge, and lattice
degrees of freedom in materials. Materials featuring multiple ferroic orders,
known as multiferroics, play important roles in multi-functional electrical and
magnetic device applications. 2D materials with honeycomb lattices offer
exciting opportunities to engineer unconventional multiferroicity, where the
ferroic orders are driven purely by the orbital degrees of freedom but not
electron spin. These include ferro-valleytricity corresponding to the electron
valley and ferro-orbital-magnetism supported by quantum geometric effects. Such
orbital multiferroics could offer strong valley-magnetic couplings and large
responses to external fields-enabling device applications such as
multiple-state memory elements, and electric control of valley and magnetic
states. Here we report orbital multiferroicity in pentalayer rhombohedral
graphene using low temperature magneto-transport measurements. We observed
anomalous Hall signals Rxy with an exceptionally large Hall angle (tan{\Theta}H
> 0.6) and orbital magnetic hysteresis at hole doping. There are four such
states with different valley polarizations and orbital magnetizations, forming
a valley-magnetic quartet. By sweeping the gate electric field E we observed a
butterfly-shaped hysteresis of Rxy connecting the quartet. This hysteresis
indicates a ferro-valleytronic order that couples to the composite field E\cdot
B, but not the individual fields. Tuning E would switch each ferroic order
independently, and achieve non-volatile switching of them together. Our
observations demonstrate a new type of multiferroics and point to electrically
tunable ultra-low power valleytronic and magnetic devices.",2308.08837v2
2010-11-30,Topologically non-trivial superconductivity in spin-orbit coupled systems: Bulk phases and quantum phase transitions,"Topologically non-trivial superconductivity has been predicted to occur in
superconductors with a sizable spin-orbit coupling in the presence of an
external Zeeman splitting. Two such systems have been proposed: (a) s-wave
superconductor pair potential is proximity induced on a semiconductor, and (b)
pair potential naturally arises from an intrinsic s-wave pairing interaction.
As is now well known, such systems in the form of a 2D film or 1D nano-wires in
a wire-network can be used for topological quantum computation. When the
external Zeeman splitting $\Gamma$ crosses a critical value $\Gamma_c$, the
system passes from a regular superconducting phase to a non-Abelian topological
superconducting phase. In both cases (a) and (b) we consider in this paper the
pair potential $\Delta$ is strictly s-wave in both the ordinary and the
topological superconducting phases, which are separated by a topological
quantum critical point at $\Gamma_c = \sqrt{\Delta^2 + \mu^2}$, where $\mu (>>
\Delta)$ is the chemical potential. On the other hand, since $\Gamma_c >>
\Delta$, the Zeeman splitting required for the topological phase ($\Gamma >
\Gamma_c$) far exceeds the value ($\Gamma \sim \Delta$) above which an s-wave
pair potential is expected to vanish (and the system to become
non-superconducting) in the absence of spin-orbit coupling. We are thus led to
a situation that the topological superconducting phase appears to set in a
parameter regime at which the system actually is non-superconducting in the
absence of spin-orbit coupling. In this paper we address the question of how a
pure s-wave pair potential can survive a strong Zeeman field to give rise to a
topological superconducting phase. We show that the spin-orbit coupling is the
crucial parameter for the quantum transition into and the robustness of the
topologically non-trivial superconducting phase realized for $\Gamma >>
\Delta$.",1012.0057v3
2015-08-11,Quantum phase transitions and Berezinskii-Kosterlitz-Thouless temperature in a two-dimensional spin-orbit-coupled Fermi gas,"We study the effect of spin-orbit coupling on both the zero-temperature and
non-zero temperature behavior of a two-dimensional (2D) Fermi gas. We include a
generic combination of Rashba and Dresselhaus terms into the system
Hamiltonian, which allows us to study both the experimentally relevant
equal-Rashba-Dresselhaus (ERD) limit and the Rashba-only (RO) limit. At zero
temperature, we derive the phase diagram as a function of the two-body binding
energy and Zeeman field. In the ERD case, this phase diagram reveals several
topologically distinct uniform superfluid phases, classified according to the
nodal structure of the quasiparticle excitation energies. Furthermore, we use a
momentum dependent SU(2)-rotation to transform the system into a generalized
helicity basis, revealing that spin-orbit coupling induces a triplet pairing
component of the order parameter. At non-zero temperature, we study the
Berezinskii-Kosterlitz-Thouless (BKT) phase transition by including phase
fluctuations of the order parameter up to second order. We show that the
superfluid density becomes anisotropic due to the presence of spin-orbit
coupling (except in the RO case). This leads both to elliptic vortices and
antivortices, and to anisotropic sound velocities. The latter prove to be
sensitive to quantum phase transitions between topologically distinct phases.
We show further that at a fixed non-zero Zeeman field, the BKT critical
temperature is increased by the presence of ERD spin-orbit coupling.
Subsequently, we demonstrate that the Clogston limit becomes infinite:
$T_{\rm{BKT}}$ remains non-zero at all finite values of the Zeeman field. We
conclude by extending the quantum phase transition lines to non-zero
temperature, using the nodal structure of the quasiparticle spectrum, thus
connecting the BKT critical temperature with the zero-temperature results.",1508.02545v2
2019-08-01,Spin-Orbit Excitons in CoO,"CoO has an odd number of electrons in its unit cell, and therefore is
expected to be metallic. Yet, CoO is strongly insulating owing to significant
electronic correlations, thus classifying it as a Mott insulator. We
investigate the magnetic fluctuations in CoO using neutron spectroscopy. The
strong and spatially far-reaching exchange constants reported in [Sarte et al.
Phys. Rev. B 98 024415 (2018)], combined with the single-ion spin-orbit
coupling of similar magnitude [Cowley et al. Phys. Rev. B 88, 205117 (2013)]
results in significant mixing between $j_{eff}$ spin-orbit levels in the low
temperature magnetically ordered phase. The high degree of entanglement,
combined with the structural domains originating from the Jahn-Teller
structural distortion at $\sim$ 300 K, make the magnetic excitation spectrum
highly structured in both energy and momentum. We extend previous theoretical
work on PrTl$_{3}$ [Buyers et al. Phys. Rev. B 11, 266 (1975)] to construct a
mean-field and multi-level spin exciton model employing the aforementioned spin
exchange and spin-orbit coupling parameters for coupled Co$^{2+}$ ions on a
rocksalt lattice. This parameterization, based on a tetragonally distorted
type-II antiferromagnetic unit cell, captures both the sharp low energy
excitations at the magnetic zone center, and the energy broadened peaks at the
zone boundary. However, the model fails to describe the momentum dependence of
the excitations at high energy transfers, where the neutron response decays
faster with momentum than the Co$^{2+}$ form factor. We discuss such a failure
in terms of a possible breakdown of localized spin-orbit excitons at high
energy transfers.",1908.00459v2
2004-10-07,Resonant spin Hall conductance in quantum Hall systems lacking bulk and structural inversion symmetry,"Following a previous work [Shen, Ma, Xie and Zhang, Phys. Rev. Lett. 92,
256603 (2004)] on the resonant spin Hall effect, we present detailed
calculations of the spin Hall conductance in two-dimensional quantum wells in a
strong perpendicular magnetic field. The Rashba coupling, generated by
spin-orbit interaction in wells lacking bulk inversion symmetry, introduces a
degeneracy of Zeeman-split Landau levels at certain magnetic fields. This
degeneracy, if occuring at the Fermi energy, will induce a resonance in the
spin Hall conductance below a characteristic temperature of order of the Zeeman
energy. At very low temperatures, the spin Hall current is highly non-ohmic.
The Dresselhaus coupling due to the lack of structure inversion symmetry
partially or completely suppresses the spin Hall resonance. The condition for
the resonant spin Hall conductance in the presence of both Rashba and
Dresselhaus couplings is derived using a perturbation method. In the presence
of disorder, we argue that the resonant spin Hall conductance occurs when the
two Zeeman split extended states near the Fermi level becomes degenerate due to
the Rashba coupling and that the the quantized charge Hall conductance changes
by 2e^2/h instead of e^2/h as the magnetic field changes through the resonant
field.",0410169v1
2013-08-13,Coulomb interaction and valley-orbit coupling in Si quantum dots,"The valley-orbit coupling in a few-electron Si quantum dot is expected to be
a function of its occupation number N. We study the spectrum of multivalley Si
quantum dots for 2 <= N <= 4, showing that, counterintuitively,
electron-electron interaction effects on the valley-orbit coupling are
negligible. For N=2 they are suppressed by valley interference, for N=3 they
vanish due to spinor overlaps, and for N = 4 they cancel between different
pairs of electrons. To corroborate our theoretical findings, we examine the
experimental energy spectrum of a few-electron metal-oxide-semiconductor
quantum dot. The measured spin-valley state filling sequence in a magnetic
field reveals that the valley-orbit coupling is definitively unaffected by the
occupation number.",1308.2728v1
2016-07-29,Spectroscopic signatures of molecular orbitals on a honeycomb lattice,"A tendency to form benzene-like molecular orbitals has been recently shown to
be a common feature of the $4d$ and $5d$ transition metal oxides with a
honeycomb lattice. This tendency competes with other interactions such as the
spin-orbit coupling and Hubbard correlations, and can be partially or
completely suppressed. In the calculations, SrRu$_{2}$O$_{6}$ presents the
cleanest, so far, case of well-formed molecular orbitals, however, direct
experimental evidence for or against this proposition has been missing. In this
paper, we show that combined photoemission and optical studies can be used to
identify molecular orbitals in SrRu$_{2}$O$_{6}$. Symmetry-driven election
selection rules suppress optical transitions between certain molecular
orbitals, while photoemission and inverse photoemission measurements are
insensitive to them. Comparing the photoemission and optical conductivity
spectra one should be able to observe clear signatures of molecular orbitals.",1607.08847v1
2023-05-30,Orbital effect on intrinsic superconducting diode effect,"Much ink has recently been spilled on nonreciprocal phenomena in
superconductors, especially the superconducting diode effect (SDE)
characterized by the nonreciprocity of the critical current $\Delta J_c$.
Contrary to the fundamental and practical significance of the SDE, the precise
underlying mechanism remains unclear. In this paper, we investigate the impact
of an orbital effect on the intrinsic SDE in a bilayer superconductor with
Rashba spin-orbit coupling and an in-plane magnetic field. We show that a small
orbital effect leads to the sign reversal of $\Delta J_c$ and a crossover of
the helical superconducting state at a lower magnetic field than the monolayer
superconductor. On the other hand, a large orbital effect induces a decoupling
transition, stabilizing a finite momentum Cooper pairing state called the
orbital Fulde-Ferrell-Larkin-Ovchinnikov state, and results in the drastic
change of the SDE. Owing to the orbital effect, the field dependence of the SDE
may show oscillations several times. The results shed light on the mechanism of
the SDE in atomically-thin multilayer superconductors.",2305.19317v1
2023-11-24,Rashba splitting in polar-nonpolar sandwich heterostructure : A DFT Study,"In this study, we employ density functional theory (DFT) based
first-principles calculations to investigate the spin-orbit effects in the
electronic structure of a polar-nonpolar sandwich heterostructure namely
LAO$_{2.5}$/STO$_{5.5}$/LAO$_{2.5}$. Our focus on the Ti-3d bands reveals an
inverted ordering of the STO-$\rm t_{2g}$ orbital near the n-type interface,
consistent with earlier experimental work. In contrast, toward the p-type
interface, the orbital ordering aligns with the natural ordering of STO
orbitals, influenced by crystal field splitting. Interestingly, we have found a
strong inter-orbital coupling between $t_{2g}$ and $e_g$ orbital, which has not
been reported earlier in $\rm SrTiO_3$ based 2D system. Additionally, our
observations highlight that the cubic Rashba splitting in this system surpasses
the linear Rashba splitting, contrary to experimental findings. This
comprehensive analysis contributes to a refined understanding of the role of
orbital mixing in Rashba splitting in the sandwich oxide heterostructures.",2311.14787v1
2016-02-29,Numerical Modeling of Orbit-Spin Coupling Accelerations in a Mars General Circulation Model: Implications for Global Dust Storm Activity,"We employ the MarsWRF general circulation model (GCM) to test the predictions
of a new physical hypothesis: a weak coupling of the orbital and rotational
angular momenta of extended bodies is predicted to give rise to cycles of
intensification and relaxation of circulatory flows within atmospheres. The
dynamical core of the GCM has been modified to include the orbit-spin coupling
accelerations due to solar system dynamics for the years 1920-2030. The
modified GCM is first subjected to extensive testing and validation. We compare
forced and unforced model outcomes for large-scale zonal and meridional flows,
and for near-surface wind velocities and surface wind stresses. The predicted
cycles of circulatory intensification and relaxation within the modified GCM
are observed. Most remarkably, the modified GCM reproduces conditions favorable
for the occurrence of perihelion-season global-scale dust storms on Mars in
years in which such storms were observed. A strengthening of the meridional
overturning (Hadley) circulation during the dust storm season occurs in the GCM
in all previously known years with perihelion-season global-scale dust storms.
The increased upwelling produced in the southern hemisphere in southern summer
may facilitate the transport of dust to high altitudes in the Mars atmosphere
during the dust storm season, where radiative heating may further strengthen
the circulation. Significantly increased surface winds and surface wind
stresses are also obtained. These may locally facilitate saltation and dust
lifting from the surface. The numerical simulations constitute proof of concept
for the orbit-spin coupling hypothesis under evaluation.",1602.09137v1
2016-10-03,Spin-orbital liquids and insulator-metal transitions on the pyrochlore lattice,"The two orbital Hubbard model, with the electrons additionally coupled to a
complex magnetic background, arises in the pyrochlore molybdates. The
background involves local moments Hund's coupled to the electrons, driving
double exchange ferromagnetism, and antiferromagnetic (AF) tendency arising
from competing superexchange. The key scales include the Hubbard repulsion and
the superexchange, both of which can be tuned in these materials. They control
the phase transition from a ferromagnetic metal to a spin glass metal and then
to a spin glass (Mott) insulator. We provide a comprehensive description of the
ground state of this model using an unrestricted Hartree-Fock scheme
implemented via a simulated annealing procedure and establish the
metal-insulator transition line for varying Hubbard interaction and
superexchange. The electrons see an effective disorder, due to orbital
frustration, already in the ferromagnetic phase. The disorder is further
enhanced by antiferromagnetic coupling and the resulting magnetic disorder. As
a result, increasing AF coupling shifts the metal-insulator transition to lower
Hubbard interaction and gives it an additional ""Anderson"" character. We provide
detailed results on the magnetic and orbital correlations, the density of
states, and the optical conductivity.",1610.00695v3
2020-06-01,Vortex-lattice formation in a spin-orbit coupled rotating spin-1 condensate,"We study the vortex-lattice formation in a rotating {Rashba} spin-orbit (SO)
coupled quasi-two-dimensional (quasi-2D) hyper-fine spin-1 spinor Bose-Einstein
condensate (BEC) in the $x-y$ plane using a numerical solution of the
underlying mean-field Gross-Pitaevskii equation. % The wave function for this
system %has three components corresponding to the three projections of
hyper-fine spin $F_z= +1,0,-1$. In this case, the non-rotating {Rashba}
SO-coupled spinor BEC can have topological excitation in the form of vortices
of different angular momenta in the three components, e.g. the $(0,+1,+2)$- and
$(-1,0,+1)$-type states in ferromagnetic and anti-ferromagnetic spinor BEC: the
numbers in the parenthesis denote the intrinsic angular momentum of the vortex
states of the three components with the negative sign denoting an anti-vortex.
The presence of these states with intrinsic vorticity breaks the symmetry
between rotation with vorticity along the $z$ and $-z$ axes and thus generates
a rich variety of vortex-lattice and anti-vortex-lattice states in a rotating
quasi-2D spin-1 spinor ferromagnetic and anti-ferromagnetic BEC, not possible
in a scalar BEC. {For weak SO coupling, } we find two types of symmetries of
these states $-$ hexagonal and ""square"". The hexagonal (square) symmetry state
has vortices arranged in closed concentric orbits with a maximum of $6, 12,
18...$ ($8,12,16...$) vortices in successive orbits. Of these two symmetries,
the square vortex-lattice state is found to have the smaller energy.",2006.00646v3
2023-10-06,Electronic structure of MoS$_2$ revisited: a comprehensive assessment of $G_0W_0$ calculations,"Two-dimensional MoS$_2$ combines many interesting properties that make the
material a top candidate for a variety of applications. It exhibits a high
electron mobility comparable to graphene, a direct fundamental band gap,
relatively strongly bound excitons, and moderate spin-orbit coupling. For a
thorough understanding of all these properties, an accurate description of the
electronic structure is mandatory. Surprisingly, published band gaps of MoS$_2$
obtained with $GW$, the state-of-the-art in electronic-structure calculations,
are quite scattered, ranging from 2.31 to 2.97 eV. The details of $G_0W_0$
calculations, such as the underlying geometry, the starting point, the
inclusion of spin-orbit coupling, and the treatment of the Coulomb potential
can critically determine how accurate the results are. In this manuscript, we
employ the linearized augmented planewave + local orbital method to
systematically investigate how all these aspects affect the quality of $G_0W_0$
calculations, and also provide a summary of literature data. We conclude that
the best overall agreement with experiments and coupled-cluster calculations is
found for $G_0W_0$ results with HSE06 as a starting point including spin-orbit
coupling, a truncated Coulomb potential, and an analytical treatment of the
singularity at $q=0$.",2310.04198v1
2010-05-14,"Electron Confinement, Orbital Ordering, and Orbital Moments in $d^0$-$d^1$ Oxide Heterostructures","The (SrTiO$_3$)$_m$/(SrVO$_3$)$_n$ $d^0-d^1$ multilayer system is studied
with first principles methods through the observed insulator-to-metal
transition with increasing thickness of the SrVO$_3$ layer. When correlation
effects with reasonable magnitude are included, crystal field splittings from
the structural relaxations together with spin-orbit coupling (SOC) determines
the behavior of the electronic and magnetic structures. These confined slabs of
SrVO$_3$ prefer $Q_{orb}$=($\pi,\pi$) orbital ordering of $\ell_z = 0$ and
$\ell_z = -1$ ($j_z=-1/2$) orbitals within the plane, accompanied by
$Q_{spin}$=(0,0) spin order (ferromagnetic alignment). The result is a
SOC-driven ferromagnetic Mott insulator. The orbital moment of 0.75 $\mu_B$
strongly compensates the spin moment on the $\ell_z = -1$ sublattice. The
insulator-metal transition for $n = 1 \to 5$ (occurring between $n$=4 and
$n$=5) is reproduced. Unlike in the isoelectronic $d^0-d^1$ TiO$_2$/VO$_2$
(rutile structure) system and in spite of some similarities in orbital
ordering, no semi-Dirac point [{\it Phys. Rev. Lett.} {\bf 102}, 166803 (2009)]
is encountered, but the insulator-to-metal transition occurs through a
different type of unusual phase. For n=5 this system is very near (or at) a
unique semimetallic state in which the Fermi energy is topologically determined
and the Fermi surface consists of identical electron and hole Fermi circles
centered at $k$=0. The dispersion consists of what can be regarded as a
continuum of radially-directed Dirac points, forming a ""Dirac circle"".",1005.2484v1
2019-08-07,Evolution of topological superconductivity by orbital selective confinement in oxide nanowires,"We determine the optimal conditions to achieve topological superconducting
phases having spin-singlet pairing for a planar nanowire with finite lateral
width in the presence of an in-plane external magnetic field. We employ a
microscopic description that is based on a three-band electronic model
including both the atomic spin-orbit coupling and the inversion asymmetric
potential at the interface between oxide band-gap insulators. We consider
amplitudes of the pairing gap, spin-orbit interactions and electronic
parameters that are directly applicable to nanowires of LaAlO$_3$-SrTiO$_3$.
The lateral confinement introduces a splitting of the $d$-orbitals that alters
the orbital energy hierarchy and significantly affects the electron filling
dependence of the topological phase diagram. Due to the orbital directionality
of the $t_{2g}$-states, we find that in the regime of strong confinement the
onset of topological phases is pinned at electron filling where the quasi flat
heavy bands start to get populated. The increase of the nanowire thickness
leads to a changeover from sparse-to-dense distribution of topologically
non-trivial domains which occurs at the cross-over associated to the orbital
population inversion. These findings are corroborated by a detailed analysis of
the most favorable topological superconducting phases in the electron
doping-magnetic field plane highlighting the role of orbital selective
confinement.",1908.02857v1
2003-09-30,Effect of Hund coupling in the one-dimensional SU(4) Hubbard model,"The one-dimensional SU(4) Hubbard model perturbed by Hund coupling is
studied, away from half-filling, by means of renormalization group and
bosonization methods. A spectral gap is always present in the spin-orbital
sector irrespective of the magnitude of the Coulomb repulsion. We further
distinguish between two qualitatively different regimes. At small Hund
coupling, we find that the symmetry of the system is dynamically enlarged to
SU(4) at low energy with the result of {\it coherent} spin-orbital excitations.
When the charge sector is not gapped, a superconducting instability is shown to
exist. At large Hund coupling, the symmetry is no longer enlarged to SU(4) and
the excitations in the spin sector become {\it incoherent}. Furthermore, the
superconductivity can be suppressed in favor of the conventional charge density
wave state.",0310003v1
2013-06-03,Nonrelativistic Limit of the Dirac-Schwarzschild Hamiltonian: Gravitational Zitterbewegung and Gravitational Spin-Orbit Coupling,"We investigate the nonrelativistic limit of the gravitationally coupled Dirac
Equation via a Foldy-Wouthuysen transformation. The relativistic correction
terms have immediate and obvious physical interpretations in terms of a
gravitational zitterbewegung, and a gravitational spin-orbit coupling. We find
no direct coupling of the spin vector to the gravitational force, which would
otherwise violate parity. The particle-antiparticle symmetry described recently
by one of us in [Phys.Rev.A 87 (2013) 032101] is verified on the level of the
perturbative corrections accessed by the Foldy-Wouthuysen transformation. The
gravitational corrections to the electromagnetic transition current are
calculated.",1306.0479v2
2013-06-24,Density profiles and collective modes of a Bose-Einstein condensate with light-induced spin-orbit coupling,"The phases of a Bose-Einstein condensate (BEC) with light-induced spin-orbit
coupling (SOC) are studied within the mean-field approximation. The mixed BEC
phase, in which the system condenses in a superposition of two plane wave
states, is found to be stable for sufficiently small light-atom coupling,
becoming unstable in a continuous fashion with increasing light-atom coupling.
The structure of the phase diagram at fixed chemical potential for bosons with
SOC is shown to imply an unusual density dependence for a trapped mixed BEC
phase, with the density of one dressed spin state increasing with increasing
radius, providing a unique experimental signature of this state. The collective
Bogoliubov sound mode is shown to also provide a signature of the mixed BEC
state, vanishing as the boundary to the regime of phase separation is
approached.",1306.5717v2
2015-02-02,Carbon-dioxide-like Skyrmion controlled by spin-orbit coupling in atomic-molecular Bose-Einstein condensates,"Atomic-molecular Bose-Einstein condensates (BECs) offer brand new
opportunities to revolutionize quantum gases and probe the variation of
fundamental constants with unprecedented sensitivity. The recent realization of
spin-orbit coupling (SOC) in BECs provides a new platform for exploring
completely new phenomena unrealizable elsewhere. However, there is no study of
SOC atomic-molecular BECs so far. Here, we find a novel way of creating a
Rashba-Dresselhaus SOC in atomic-molecular BECs by combining the spin dependent
photoassociation and Raman coupling, which can control the formation and
distribution of a new type of topological excitation -- carbon-dioxide-like
Skyrmion. This Skyrmion is formed by two half-Skyrmions of molecular BECs
coupling with one Skyrmion of atomic BECs, where the two half-Skyrmions locates
at both sides of one Skyrmion, which can be detected by measuring the vortices
structures using the time-of-flight absorption imaging technique in real
experiments.",1502.00489v2
2017-02-15,Fulde-Ferrell-Larkin-Ovchinnikov state to topological superfluidity transition in bilayer spin-orbit coupled degenerate Fermi gas,"Recently a scheme has been proposed for generating the 2D Rashba-type
spin-orbit coupling (SOC) for ultracold atomic bosons in a bilayer geometry
[S.-W. Su et al, Phys. Rev. A \textbf{93}, 053630 (2016)]. Here we investigate
the superfluidity properties of a degenerate Fermi gas affected by the SOC in
such a bilayer system. We demonstrate that a Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) state appears in the regime of small to moderate atom-light coupling. In
contrast to the ordinary SOC, the FFLO state emerges in the bilayer system
without adding any external fields or spin polarization. As the atom-light
coupling increases, the system can transit from the FFLO state to a topological
superfluid state. These findings are also confirmed by the BdG simulations with
a weak harmonic trap added.",1702.04735v2
2018-03-01,Tuning the two-electron hybridization and spin states in parallel-coupled InAs quantum dots,"We study spin transport in the one- and two-electron regimes of
parallel-coupled double quantum dots (DQDs). The DQDs are formed in InAs
nanowires by a combination of crystal-phase engineering and electrostatic
gating, with an interdot tunnel coupling ($t$) tunable by one order of
magnitude. Large single-particle energy separations (up to 10 meV) and $|g^*|$
factors ($\sim$10) enable detailed studies of the $B$-field-induced transition
from a singlet-to-triplet ground state as a function of $t$. In particular, we
investigate how the magnitude of the spin-orbit-induced singlet-triplet
anticrossing depends on $t$. For cases of strong coupling, we find values of
230 $\mu$eV for the anticrossing using excited-state spectroscopy. Experimental
results are reproduced by calculations based on rate equations and a DQD model
including a single orbital in each dot.",1803.00326v2
2019-04-07,Polarity and spin-orbit coupling induced large interfacial exchange coupling an asymmetric charge transfer in iridate-manganite heterostructure,"Charge transfer is of particular importance in manipulating the interface
physics in transition-metal oxide heterostructures. In this work, we have
fabricated epitaxial bilayers composed of polar 3d LaMnO3 and nonpolar 5d
SrIrO3. Systematic magnetic measurements reveal an unexpectedly large exchange
bias effect in the bilayer, together with a dramatic enhancement of the
coercivity of LaMnO3. Based on first-principles calculations and x-ray
absorption spectroscopy measurements, such a strong interfacial magnetic
coupling is found closely associated with the polar nature of LaMnO3 and the
strong spin-orbit interaction in SrIrO3, which collectively drives an
asymmetric interfacial charge transfer and leads to the emergence of an
interfacial spin glass state. Our study provides new insight into the charge
transfer in transition-metal oxide heterostructures and offers a novel means to
tune the interfacial exchange coupling for a variety of device applications.",1904.03613v2
2022-09-16,The electronic system $(2)^2Σ^+$ and $(1)^2Π$ of LiCa,"High resolution Fourier transform spectroscopy and Laser induced fluorescence
has been performed on LiCa in the infrared spectral range. We analyze
rovibrational transitions of the $(2)^2\Sigma^+$--$X(1)^2\Sigma^+$ system of
LiCa and find the $(2)^2\Sigma^+$ state to be perturbed by spin-orbit coupling
to the $(1)^2\Pi$ state. We study the coupled system obtaining molecular
parameters for the $(2)^2\Sigma^+$ and the $(1)^2\Pi$ state together with
effective spin-orbit and spin-rotation coupling constants. The coupled system
has also been evaluated by applying a potential function instead of
rovibrational molecular parameters for the state $(2)^2\Sigma^+$. An improved
analytic potential function of the $X(1)^2\Sigma^+$ state is derived, due to
the extension of the observed rotational ladder.",2209.07853v1
2020-07-30,Electrical and Thermal Generation of Spin Currents by Magnetic Graphene,"The demand for compact, high-speed and energy-saving circuitry urges higher
efficiency of spintronic devices that can offer a viable alternative for the
current electronics. The route towards this goal suggests implementing
two-dimensional (2D) materials that provide large spin polarization of charge
current together with the long-distance transfer of the spin information. Here,
for the first time, we experimentally demonstrate a large spin polarization of
the graphene conductivity ($\approx 14\%$) arising from a strong induced
exchange interaction in proximity to a 2D layered antiferromagnetic. The strong
coupling of charge and spin currents in graphene with high efficiency of spin
current generation, comparable to that of metallic ferromagnets, together with
the observation of spin-dependent Seebeck and anomalous Hall effects, all
consistently confirm the magnetic nature of graphene. The high sensitivity of
spin transport in graphene to the magnetization of the outermost layer of the
adjacent interlayer antiferromagnet, also provides a tool to read out a single
magnetic sub-lattice. The first time observations of the electrical and thermal
generation of spin currents by magnetic graphene suggest it as the ultimate
building block for ultra-thin magnetic memory and sensory devices, combining
gate tunable spin-dependent conductivity, long-distance spin transport and
spin-orbit coupling all in a single 2D material.",2007.15597v1
2020-12-16,Ab initio Ultrafast Spin Dynamics in Solids,"Spin relaxation and decoherence is at the heart of spintronics and spin-based
quantum information science. Currently, theoretical approaches that can
accurately predict spin relaxation of general solids including necessary
scattering pathways and capable for ns to ms simulation time are urgently
needed. We present a first-principles real-time density-matrix approach based
on Lindblad dynamics to simulate ultrafast spin dynamics for general
solid-state systems. Through the complete first-principles descriptions of
pump, probe and scattering processes including electron-phonon,
electron-impurity and electron-electron scatterings with self-consistent
electronic spin-orbit couplings, our method can directly simulate the ultrafast
pump-probe measurements for coupled spin and electron dynamics over ns at any
temperatures and doping levels. We first apply this method to a prototypical
system GaAs and obtain excellent agreement with experiments. We find that the
relative contributions of different scattering mechanisms and phonon modes
differ considerably between spin and carrier relaxation processes. In sharp
contrast to previous work based on model Hamiltonians, we point out that the
electron-electron scattering is negligible at room temperature but becomes
dominant at low temperatures for spin relaxation in n-type GaAs. We further
examine ultrafast dynamics in novel spin-valleytronic materials - monolayer and
bilayer WSe2 with realistic defects. We find that spin relaxation is highly
sensitive to local symmetry and chemical bonds around defects. Our work
provides a predictive computational platform for spin dynamics in solids, which
has unprecedented potentials for designing new materials ideal for spintronics
and quantum information technology.",2012.08711v3
2021-03-26,Tuning interactions between spins in a superconductor,"Novel many-body and topological electronic phases can be created in
assemblies of interacting spins coupled to a superconductor, such as
one-dimensional topological superconductors with Majorana zero modes (MZMs) at
their ends. Understanding and controlling interactions between spins and the
emergent band structure of the in-gap Yu-Shiba-Rusinov (YSR) states they induce
in a superconductor are fundamental for engineering such phases. Here, by
precisely positioning magnetic adatoms with a scanning tunneling microscope
(STM), we demonstrate both the tunability of exchange interaction between spins
and precise control of the hybridization of YSR states they induce on the
surface of a bismuth (Bi) thin film that is made superconducting with the
proximity effect. In this platform, depending on the separation of spins, the
interplay between Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, spin-orbit
coupling, and surface magnetic anisotropy stabilizes different types of spin
alignments. Using high-resolution STM spectroscopy at millikelvin temperatures,
we probe these spin alignments through monitoring the spin-induced YSR states
and their energy splitting. Such measurements also reveal a quantum phase
transition between the ground states with different electron number parity for
a pair of spins in a superconductor tuned by their separation. Experiments on
larger assemblies show that spin-spin interactions can be mediated in a
superconductor over long distances. Our results show that controlling
hybridization of the YSR states in this platform provides the possibility of
engineering the band structure of such states for creating topological phases.",2103.14656v1
2008-03-12,Analysis of spin precession in binary black hole systems including quadrupole-monopole interaction,"We analyze in detail the spin precession equations in binary black hole
systems, when the tidal torque on a Kerr black hole due to quadrupole-monopole
coupling is taken into account. We show that completing the precession
equations with this term reveals the existence of a conserved quantity at 2PN
order when averaging over orbital motion. This quantity allows one to solve the
(orbit-averaged) precession equations exactly in the case of equal masses and
arbitrary spins, neglecting radiation reaction. For unequal masses, an exact
solution does not exist in closed form, but we are still able to derive
accurate approximate analytic solutions. We also show how to incorporate
radiation reaction effects into our analytic solutions adiabatically, and
compare the results to solutions obtained numerically. For various
configurations of the binary, the relative difference in the accumulated
orbital phase computed using our analytic solutions versus a full numerical
solution vary from about 0.3% to 1.8% over the 80 - 140 orbital cycles
accumulated while sweeping over the orbital frequency range 20 - 300 Hz. This
typically corresponds to a discrepancy of order 5-6 radians. While this may not
be accurate enough for implementation in LIGO template banks, we still believe
that our new solutions are potentially quite useful for comparing numerical
relativity simulations of spinning binary black hole systems with
post-Newtonian theory. They can also be used to gain more understanding of
precession effects, with potential application to the gravitational recoil
problem, and to provide semi-analytical templates for spinning, precessing
binaries.",0803.1820v3
2015-09-03,Nematicity and magnetism in FeSe and other families of Fe-based superconductors,"Nematicity and magnetism are two key features in Fe-based superconductors,
and their interplay is one of the most important unsolved problems. In FeSe,
the magnetic order is absent below the structural transition temperature
$T_{str}=90$K, in stark contrast that the magnetism emerges slightly below
$T_{str}$ in other families. To understand such amazing material dependence, we
investigate the spin-fluctuation-mediated orbital order ($n_{xz}\neq n_{yz}$)
by focusing on the orbital-spin interplay driven by the strong-coupling effect,
called the vertex correction. This orbital-spin interplay is very strong in
FeSe because of the small ratio between the Hund's and Coulomb interactions
($\bar{J}/\bar{U}$) and large $d_{xz},d_{yz}$-orbitals weight at the Fermi
level. For this reason, in the FeSe model, the orbital order is established
irrespective that the spin fluctuations are very weak, so the magnetism is
absent below $T_{str}$. In contrast, in the LaFeAsO model, the magnetic order
appears just below $T_{str}$ both experimentally and theoretically. Thus, the
orbital-spin interplay due to the vertex correction is the key ingredient in
understanding the rich phase diagram with nematicity and magnetism in Fe-based
superconductors in a unified way.",1509.01161v2
2016-05-20,Elementary specific spin and orbital moments of ultrathin CoFeB amorphous films on GaAs(100),"Nanoscale CoFeB amorphous films have been synthesized on GaAs(100) and
studied with X-ray magnetic circular dichroism (XMCD) and transmission electron
microscopy (TEM). We have found that the ratios of the orbital to spin magnetic
moments of both the Co and Fe in the ultrathin amorphous film have been
enhanced by more than 300% compared with those of the bulk crystalline Co and
Fe, and in specifically, a large orbital moment of 0.56*10^-6 B from the Co
atoms has been observed and at the same time the spin moment of the Co atoms
remains comparable to that of the bulk hcp Co. The results indicate that the
large uniaxial magnetic anisotropy (UMA) observed in the ultrathin CoFeB film
on GaAs(100) is related to the enhanced spin-orbital coupling of the Co atoms
in the CoFeB. This work offers experimental evidences of the correlation
between the UMA and the elementary specific spin and orbital moments in the
CoFeB amorphous film on the GaAs(100) substrate, which is significant for
spintronics applications.",1605.06358v1
2021-02-21,Role of exchange splitting and ligand field splitting in tuning the magnetic anisotropy of an individual iridium atom on TaS2 substrate,"In this work, using first-principle calculation we investigate the magnetic
anisotropy (MA) of single-atom iridium (Ir) on TaS2 substrate. We find that the
strength and direction of MA in the Ir adatom can be tuned by strain. The MA
arises from two sources, namely spin-conservation term and spin-flip term. The
spin-conservation term is generated by spin-orbit coupling (SOC) interaction on
dxy/dx2-y2 orbitals and is contributed to the out-of-plane MA. The spin-flip
term is caused by SOC interaction on dxz/dyz and px/py orbitals and is
responsible for the in-plane MA. We further find that strain-tuned MA is mainly
determined by exchange splitting and ligand field splitting. Increase of strain
will enhance the exchange splitting and reduce the ligand field splitting,
resulting in the enhancement of the in-plane MA from dxy/dx2-y2 orbitals and
the reduction of the out-of-plane MA from dxz/dyz and px/py orbitals, and hence
leading to the change of the strength and direction of the total MA. Our study
provides a way for tuning the MA of single-atoms magnet on 2D transition metal
dichalcogenides substrate by control of the exchange splitting and the ligand
field splitting.",2102.10548v2
2021-05-10,Observation of the Orbital Rashba-Edelstein Magnetoresistance,"We report the observation of magnetoresistance (MR) originating from the
orbital angular momentum transport (OAM) in a Permalloy (Py) / oxidized Cu
(Cu*) heterostructure: the orbital Rashba-Edelstein magnetoresistance. The
angular dependence of the MR depends on the relative angle between the induced
OAM and the magnetization in a similar fashion as the spin Hall
magnetoresistance (SMR). Despite the absence of elements with large spin-orbit
coupling, we find a sizable MR ratio, which is in contrast to the conventional
SMR which requires heavy elements. By varying the thickness of the Cu* layer,
we confirm that the interface is responsible for the MR, suggesting that the
orbital Rashba-Edelstein effect is responsible for the generation of the OAM.
Through Py thickness-dependence studies, we find that the effective values for
the spin diffusion and spin dephasing lengths of Py are significantly larger
than the values measured in Py / Pt bilayers, approximately by the factor of 2
and 4, respectively. This implies that another mechanism beyond the
conventional spin-based scenario is responsible for the MR observed in Py / Cu*
structures originated in a sizeable transport of OAM. Our findings not only
unambiguously demonstrate the current-induced torque without using any heavy
element via the OAM channel but also provide an important clue towards the
microscopic understanding of the role that OAM transport can play for
magnetization dynamics.",2105.04495v2
2023-06-04,Efficient method to calculate energy spectra for analysing magneto-oscillations,"Magneto-oscillations in two-dimensional systems with spin-orbit interaction
are typically characterized by fast Shubnikov-de~Haas (SdH) oscillations and
slower spin-orbit-related beatings. The characterization of the full SdH
oscillatory behavior in systems with both spin-orbit interaction and Zeeman
coupling requires a time consuming diagonalization of large matrices for many
magnetic field values. By using the Poisson summation formula we can explicitly
separate the density of states into, fast and slow oscillations, which
determine the corresponding fast and slow parts of the magneto-oscillations. We
introduce an efficient scheme of partial diagonalization of our Hamiltonian,
where only states close to the Fermi energy are needed to obtain the SdH
oscillations, thus reducing the required computational time. This allows an
efficient method for fitting numerically the SdH data, using the inherent
separation of the fast and slow oscillations. We compare systems with only
Rashba spin-orbit interaction (SOI) and both Rashba and Dresselhaus SOI with,
and without, an in-plane magnetic field. The energy spectra are characterized
in terms of symmetries, which have direct and visible consequences in the
magneto-oscillations. To highlight the benefits of our methodology, we use it
to extract the spin-orbit parameters by fitting realistic transport data.",2306.02503v1
2023-04-10,"Spin-phonon interactions and magnetoelectric coupling in Co$_4$$B_2$O$_9$ ($B$ = Nb, Ta)","In order to explore the consequences of spin-orbit coupling on spin-phonon
interactions in a set of chemically-similar mixed metal oxides, we measured the
infrared vibrational properties of Co$_4B_2$O$_9$ ($B$ = Nb, Ta) as a function
of temperature and compared our findings with lattice dynamics calculations and
several different models of spin-phonon coupling. Frequency vs. temperature
trends for the Co$^{2+}$ shearing mode near 150 cm$^{-1}$ reveal significant
shifts across the magnetic ordering temperature that are especially large in
relative terms. Bringing these results together and accounting for
noncollinearity, we obtain spin-phonon coupling constants of -3.4 and -4.3
cm$^{-1}$ for Co$_4$Nb$_2$O$_9$ and the Ta analog, respectively. Analysis
reveals that these coupling constants derive from interlayer (rather than
intralayer) exchange interactions and that the interlayer interactions contain
competing antiferromagnetic and ferromagnetic contributions. At the same time,
beyond-Heisenberg terms are minimized due to fortuitous symmetry
considerations, different than most other 4$d$- and 5$d$-containing oxides.
Comparison with other contemporary oxides shows that spin-phonon coupling in
this family of materials is among the strongest ever reported, suggesting an
origin for magnetoelectric coupling.",2304.04865v1
2011-03-21,High Chern number quantum anomalous Hall phases in graphene ribbons with Haldane orbital coupling,"We investigate possible phase transitions among the different quantum
anomalous Hall (QAH) phases in a zigzag graphene ribbon under the influence of
the exchange field. The effective tight-binding Hamiltonian for graphene is
made up of the hopping term, the Kane-Mele and Rashba spin-orbit couplings as
well as the Haldane orbital term. We find that the variation of the exchange
field results in bulk gap-closing phenomena and phase transitions occur in the
graphene system. If the Haldane orbital coupling is absent, the phase
transition between the chiral (anti-chiral) edge state $\nu=+2$ ($\nu=-2$) and
the pseudo-quantum spin Hall state ($\nu=0$) takes place. Surprisingly, when
the Haldane orbital coupling is taken into account, an intermediate QSH phase
with two additional edge modes appears in between phases $\nu=+2$ and $\nu=-2$.
This intermediate phase is therefore either the hyper-chiral edge state of high
Chern number $\nu=+4$ or anti-hyper-chiral edge state of $\nu=-4$ when the
direction of exchange field is reversed. We present the band structures, edge
state wave functions and current distributions of the different QAH phases in
the system. We also report the critical exchange field values for the QAH phase
transitions.",1103.4083v1
2023-07-27,Interlayer Coupling Driven High-Temperature Superconductivity in La$_3$Ni$_2$O$_7$ Under Pressure,"The newly discovered high-temperature superconductivity in La$_3$Ni$_2$O$_7$
under pressure has attracted a great deal of attentions. The essential
ingredient characterizing the electronic properties is the bilayer NiO$_2$
planes coupled by the interlayer bonding of $3d_{z^2}$ orbitals through the
intermediate oxygen-atoms. In the strong coupling limit, the low energy physics
is described by an intralayer antiferromagnetic spin-exchange interaction
$J_{\parallel}$ between $3d_{x^2-y^2}$ orbitals and an interlayer one
$J_{\perp}$ between $3d_{z^2}$ orbitals. Taking into account Hund's rule on
each site and integrating out the $3d_{z^2}$ spin degree of freedom, the system
reduces to a single-orbital bilayer $t$-$J$ model based on the $3d_{x^2-y^2}$
orbital. By employing the slave-boson approach, the self-consistent equations
for the bonding and pairing order parameters are solved. Near the physically
relevant $\frac{1}{4}$-filling regime (doping $\delta=0.3\sim 0.5$), the
interlayer coupling $J_{\perp}$ tunes the conventional single-layer $d$-wave
superconducting state to the $s$-wave one. A strong $J_{\perp}$ could enhance
the inter-layer superconducting order, leading to a dramatically increased
$T_c$. Interestingly, there could exist a finite regime in which an $s+id$
state emerges.",2307.14965v3
2018-06-17,Interactions and magnetotransport through spin-valley coupled Landau levels in monolayer MoS$_{2}$,"The strong spin-orbit coupling and the broken inversion symmetry in monolayer
transition metal dichalcogenides (TMDs) results in spin-valley coupled band
structures. Such a band structure leads to novel applications in the fields of
electronics and optoelectronics. Density functional theory calculations as well
as optical experiments have focused on spin-valley coupling in the valence
band. Here we present magnetotransport experiments on high-quality n-type
monolayer molybdenum disulphide (MoS$_{2}$) samples, displaying highly resolved
Shubnikov-de Haas oscillations at magnetic fields as low as $2~T$. We find the
effective mass $0.7~m_{e}$, about twice as large as theoretically predicted and
almost independent of magnetic field and carrier density. We further detect the
occupation of the second spin-orbit split band at an energy of about $15~meV$,
i.e. about a factor $5$ larger than predicted. In addition, we demonstrate an
intricate Landau level spectrum arising from a complex interplay between a
density-dependent Zeeman splitting and spin and valley-split Landau levels.
These observations, enabled by the high electronic quality of our samples,
testify to the importance of interaction effects in the conduction band of
monolayer MoS$_{2}$.",1806.06402v2
1998-08-03,Coupled quantum dots as quantum gates,"We consider a new quantum gate mechanism based on electron spins in coupled
semiconductor quantum dots. Such gates provide a general source of spin
entanglement and can be used for quantum computers. We determine the exchange
coupling J in the effective Heisenberg model as a function of magnetic (B) and
electric fields, and of the inter-dot distance (a) within the Heitler-London
approximation of molecular physics. This result is refined by using
sp-hybridization, and by the Hund-Mulliken molecular-orbit approach which leads
to an extended Hubbard description for the two-dot system that shows a
remarkable dependence on B and a due to the long-range Coulomb interaction. We
find that the exchange J changes sign at a finite field (leading to a
pronounced jump in the magnetization) and then decays exponentially. The
magnetization and the spin susceptibilities of the coupled dots are calculated.
We show that the dephasing due to nuclear spins in GaAs can be strongly
suppressed by dynamical nuclear spin polarization and/or by magnetic fields.",9808026v2
2019-05-02,"Phonon dispersion, Raman spectra and evidence for spin-phonon coupling in MnV$_2$O$_4$ from first-principles","MnV$_2$O$_4$ in the spinel structure is known to exhibit coupled orbital and
spin ordering, and its Raman spectra show interesting anomalies in its
low-temperature phase. With a goal to explain this behavior involving coupled
spins and phonons, we determine here the spin-phonon couplings in MnV$_2$O$_4$
from a theoretical analysis of its phonon spectra and their dependence on
spin-ordering and electron correlations, obtained from first-principles density
functional theoretical calculations. Using these in an analysis based on a
Landau-like theory, we uncover the mechanism governing the Raman anomalies
observed in its low-temperature phase.",1905.00551v1
2022-12-12,Magnon-Plasmon Hybridization Mediated by Spin-Orbit Interaction in Magnetic Materials,"We propose a mechanism for magnon-plasmon coupling and hybridization in
ferromagnetic (FM) and antiferromagnetic (AFM) systems. The electric field
associated with plasmon oscillations creates a non-equilibrium spin density via
the inverse spin galvanic effect. This plasmon-induced spin density couples to
magnons by an exchange interaction. The strength of magnon-plasmon coupling
depends on the magneto-electric susceptibility of the system and the wavevector
at which the level repulsion is happened. This wavevector may be tuned by an
applied magnetic field. In AFM systems, the degeneracy of two chiral magnons is
broken in the presence of a magnetic field, and we find two separate hybrid
modes for left-handed and right-handed AFM magnons. Furthermore, we show that
magnon-plasmon coupling in AFM systems is enhanced because of strong
intra-sublattice spin dynamics. We argue that the recently discovered
two-dimensional magnetic systems are ideal platforms to investigate proposed
magnon-plasmon hybrid modes.",2212.06105v1
2003-09-09,Spin interference effects in ring conductors subject to Rashba coupling,"Quantum interference effects in rings provide suitable means for controlling
spin at mesoscopic scales. Here we apply such control mechanisms to coherent
spin-dependent transport in one- and two-dimensional rings subject to Rashba
spin-orbit coupling. We first study the spin-induced modulation of unpolarized
currents as a function of the Rashba coupling strength. The results suggest the
possibility of all-electrical spintronic devices. Moreover, we find signatures
of Berry phases in the conductance previously unnoticed. Second, we show that
the polarization direction of initially polarized, transmitted spins can be
tuned via an additional small magnetic control flux. In particular, this
enables to precisely reverse the polarization direction at half a flux quantum.
We present full numerical calculations for realistic two-dimensional ballistic
microstructures and explain our findings in a simple analytical model for
one-dimensional rings.",0309228v2
2013-03-08,Electron Spin Relaxation in Graphene Nanoribbon Quantum Dots,"Graphene is promising as a host material for electron spin qubits because of
its predicted potential for long coherence times. In armchair graphene
nanoribbons (aGNRs) a small bandgap is opened, allowing for electrically gated
quantum dots, and furthermore the valley degeneracy is lifted. The spin
lifetime T_1 is limited by spin relaxation, where the Zeeman energy is absorbed
by lattice vibrations, mediated by spin-orbit and electron-phonon coupling. We
have calculated T_1 by treating all couplings analytically and find that T_1
can be in the range of seconds for several reasons: (i) low phonon density of
states away from Van Hove singularities; (ii) destructive interference between
two relaxation mechanisms; (iii) Van Vleck cancellation at low magnetic fields;
(iv) vanishing coupling to out-of-plane modes in lowest order due to the
electronic structure of aGNRs. Owing to the vanishing nuclear spin of 12C, T_1
may be a good measure for overall coherence. These results and recent advances
in the controlled production of graphene nanoribbons make this system
interesting for spintronics applications.",1303.2027v2
2015-04-14,Magnetic charges and magnetoelectricity in hexagonal rare-earth manganites and ferrites,"Magnetoelectric (ME) materials are of fundamental interest and show broad
potential for technological applications. Commonly the dominant contribution to
the ME response is the lattice-mediated one, which is proportional to both the
Born electric charge $Z^{\rm e}$ and its analogue, the dynamical magnetic
charge $Z^{\rm m}$. Our previous study has shown that exchange striction acting
on noncollinear spins induces much larger magnetic charges than those that
depend on spin-orbit coupling. The hexagonal manganites $R$MnO$_3$ and ferrites
$R$FeO$_3$ ($R$ = Sc, Y, In, Ho-Lu) exhibit strong couplings between electric,
magnetic and structural degrees of freedom, with the transition-metal ions in
the basal plane antiferromagnetically coupled through super-exchange so as to
form a 120$^\circ$ noncollinear spin arrangement. Here we present a theoretical
study of the magnetic charges, and of the spin-lattice and spin-electronic ME
constants, in these hexagonal manganites and ferrites, clarifying the
conditions under which exchange striction leads to an enhanced $Z^{\rm m}$
values and anomalously large in-plane spin-lattice ME effects.",1504.03405v1
2017-01-13,Zeeman splitting via spin-valley-layer coupling in bilayer MoTe2,"Atomically thin transition metal dichalcogenides (TMDs) possess coupling of
spin and valley degrees of freedom, making them promising for
spin-valleytronics. ln monolayer TMDs, the emission helicity is locked to the
valleys as a consequence of spin-orbit coupling and inversion symmetry
breaking, leading to a valley analog of Zeeman effect in presence of
out-of-plane magnetic field. As inversion symmetry is recovered in bilayers,
the emission helicity should no longer be locked to the valleys. Here we show
that Zeeman splitting, however, still persists in bilayers, as a result of an
additional degree of freedom viz., the layer pseudospin and spin-valley-layer
locking. In contrast to monolayer, Zeeman splitting here exists without lifting
valley degeneracy. The degree of circularly polarized photoluminescence can be
tuned with magnetic field from $-27\%$ to $27\%$. Our results demonstrate the
control of degree of freedom in bilayer with magnetic field, which, together
with previous electric field control, makes bilayer a promising platform for
spin-valley quantum gates based on magnetoelectric effects.",1701.03583v1
2012-04-02,The Spin of Holographic Electrons at Nonzero Density and Temperature,"We study the Green's function of a gauge invariant fermionic operator in a
strongly coupled field theory at nonzero temperature and density using a dual
gravity description. The gravity model contains a charged black hole in four
dimensional anti-de Sitter space and probe charged fermions. In particular, we
consider the effects of the spin of these probe fermions on the properties of
the Green's function. There exists a spin-orbit coupling between the spin of an
electron and the electric field of a Reissner-Nordstrom black hole. On the
field theory side, this coupling leads to a Rashba like dispersion relation. We
also study the effects of spin on the damping term in the dispersion relation
by considering how the spin affects the placement of the fermionic quasinormal
modes in the complex frequency plane in a WKB limit. An appendix contains some
exact solutions of the Dirac equation in terms of Heun polynomials.",1204.0518v2
2014-05-20,Electron-electron interaction mediated indirect coupling of electron and magnetic ion or nuclear spins in self-assembled quantum dots,"We show here the existence of the indirect coupling of electron and magnetic
or nuclear ion spins in self-assembled quantum dots mediated by
electron-electron interactions. With a single localized spin placed in the
center of the dot, only the spins of electrons occupying the zero angular
momentum states couple directly to the localized spin. We show that when the
electron-electron interactions are included, the electrons occupying finite
angular momentum orbitals interact with the localized spin. This effective
interaction is obtained using exact diagonalization of the microscopic
Hamiltonian as a function of the number of electronic shells, shell spacing,
and anisotropy of the electron-Mn exchange interaction. The effective
interaction can be engineered to be either ferromagnetic or antiferromagnetic
by tuning the parameters of the quantum dot.",1405.4983v1
2016-05-23,Cooling a Mechanical Resonator with a Nitrogen-Vacancy Center Ensemble Using a Room Temperature Excited State Spin-Strain Interaction,"We propose a protocol to dissipatively cool a room temperature mechanical
resonator using a nitrogen-vacancy (NV) center ensemble. The spin ensemble is
coupled to the resonator through its orbitally-averaged excited state, which
has a spin-strain interaction that has not been previously characterized. We
experimentally demonstrate that the spin-strain coupling in the excited state
is $13.5\pm0.5$ times stronger than the ground state spin-strain coupling. We
then theoretically show that this interaction combined with a high-density spin
ensemble enables the cooling of a mechanical resonator from room temperature to
a fraction of its thermal phonon occupancy.",1605.07131v2
2017-10-06,Supercurrent as a Probe for Topological Superconductivity in Magnetic Adatom Chains,"A magnetic adatom chain, proximity coupled to a conventional superconductor
with spin-orbit coupling, exhibits locally an odd-parity, spin-triplet pairing
amplitude. We show that the singlet-triplet junction, thus formed, leads to a
net spin accumulation in the near vicinity of the chain. The accumulated spins
are polarized along the direction of the local $\mathbf{d}$-vector for triplet
pairing and generate an enhanced persistent current flowing around the chain.
The spin polarization and the ""supercurrent"" reverse their directions beyond a
critical exchange coupling strength at which the singlet superconducting order
changes its sign on the chain. The current is strongly enhanced in the
topological superconducting regime where Majorana bound states appear at the
chain ends. The current and the spin profile offer alternative routes to
characterize the topological superconducting state in adatom chains and
islands.",1710.02331v1
2019-01-16,Spin and Quadrupole Couplings for High Spin Equatorial Intermediate Mass-ratio Coalescences,"Intermediate mass-ratio coalescences are potential signals of ground-based
and space-based gravitational observatories. Accurate modeling of their
waveforms within general relativity can be achieved within black hole
perturbation theory including self-force and finite size effects. In this
paper, we present analytic results to the Teukolsky perturbation of equatorial
orbits in the near-horizon region of an extremely high spin black hole
including spin coupling and finite size effects at leading order in the high
spin limit while neglecting the self-force. We detail the critical behavior
occuring close to the smallest specific angular momentum, and we discuss
features of spin and quadrupole couplings.",1901.05370v2
2019-02-25,Phonon-assisted carrier tunneling in coupled quantum dot systems with hyperfine-induced spin flip,"We calculate the rates of phonon-assisted hyperfine spin flips during
electron and hole tunneling between quantum dots in a self-assembled quantum
dot molecule. We show that the hyperfine process dominates over the
spin-orbit-induced spin relaxation in magnetic fields up to a few Tesla for
electrons, while for holes this cross-over takes place at field magnitudes of a
fraction of Tesla, upon the assumption of a large $d$-shell admixture to the
valence band state, resulting in a strong transverse hyperfine coupling. The
interplay of the two spin-flip mechanisms leads to a minimum of the spin-flip
probability, which is in principle experimentally measurable and can be used as
a test for the presence of substantial transverse hyperfine couplings in the
valence band.",1902.09515v2
2019-11-28,Coupled Spin-Charge-Phonon Fluctuation in the All-In/All-Out Antiferromagnet Cd$_2$Os$_2$O$_7$,"We report on a novel spin-charge fluctuation in the all-in-all-out pyrochlore
magnet Cd$_2$Os$_2$O$_7$, where the spin fluctuation is driven by the
conduction of thermally excited electrons/holes and associated fluctuation of
Os valence. The fluctuation exhibits an activation energy significantly greater
than the spin-charge excitation gap and a peculiar frequency range of
$10^{6}$--$10^{10}$ s$^{-1}$. These features are attributed to the hopping
motion of carriers as small polarons in the insulating phase, where the polaron
state is presumably induced by the magnetoelastic coupling via the strong
spin-orbit interaction. Such a coupled spin-charge-phonon fluctuation manifests
as a part of the metal-insulator transition that is extended over a wide
temperature range due to the modest electron correlation comparable with other
interactions characteristic for 5$d$-subshell systems.",1911.12500v1
2015-08-10,Mechanically induced two-qubit gates and maximally entangled states for single electron spins in a carbon nanotube,"We theoretically analyze a system where two electrons are trapped separately
in two quantum dots on a suspended carbon nanotube (CNT), subject to external
ac electric driving. An indirect mechanically-induced coupling of two distant
single electron spins is induced by the interaction between the spins and the
mechanical motion of the CNT. We show that a two-qubit iSWAP gate and arbitrary
single-qubit gates can be obtained from the intrinsic spin-orbit coupling.
Combining the iSWAP gate and single-qubit gates, maximally entangled states of
two spins can be generated in a single step by varying the frequency and the
strength of the external electric driving field. The spin-phonon coupling can
be turned off by electrostatically shifting the electron wave function on the
nanotube.",1508.02107v1
2021-10-31,Electron-Spin-Resonance in a proximity-coupled MoS2/Graphene van-der-Waals heterostructure,"Coupling graphene's excellent electron and spin transport properties with
higher spin-orbit coupling material allows tackling the hurdle of spin
manipulation in graphene, due to the proximity to van-der-Waals layers. Here we
use magneto transport measurements to study the electron spin resonance on a
combined system of graphene and MoS2 at 1.5K. The electron spin resonance
measurements are performed in the frequency range of 18-33GHz, which allows us
to determine the g-factor in the system. We measure average g-factor of 1.91
for our hybrid system which is a considerable shift compared to what is
observed in graphene on SiO2. This is a clear indication of proximity induced
SOC in graphene in accordance with theoretical predictions.",2111.00530v2
2023-11-28,Disordered ground state in the spin-orbit coupled $J_{\rm eff}= 1/2$ cobalt-based metal-organic framework magnet with orthogonal spin dimers,"We present the magnetic properties of a strongly spin-orbit coupled quantum
dimer magnet based on Co$^{2+}$. The metal-organic framework compound
Co$_2$(BDC)$_2$(DPTTZ)$_2$$\cdot$DMF features Co$^{2+}$ dimers arranged nearly
orthogonal to each other, similar to the Shastry-Sutherland lattice. Our
assessment based on the magnetization and heat capacity experiments reveals
that the magnetic properties at low temperatures can be described by an
effective $J_{\rm eff} = 1/2$ Kramers doublet and the ground state is a singlet
with a tiny spin gap. Although the magnetic susceptibility could be analyzed in
terms of the interacting dimer model with an isotropic intradimer coupling
$J_0/k_{\rm B} \simeq 7.6$ K, this model fails to reproduce the shape of
magnetization isotherm and heat capacity data. A model of isolated spin dimers
with the anisotropic exchange couplings $J_{xy} \simeq 3.5$ K and $J_{z} \simeq
11$ K provides an adequate description to the magnetic susceptibility,
magnetization isotherm, and heat capacity data at low temperatures.
Interestingly, no field-induced quantum phase phase is detected down to 100~mK
around the critical field of gap closing, suggesting the absence of
Bose-Einstein condensation of triplons and establishing isolated dimers with a
negligible interdimer coupling.",2311.16890v1
2011-09-19,Doping a spin-orbit Mott Insulator: Topological Superconductivity from the Kitaev-Heisenberg Model and possible application to (Na2/Li2)IrO3,"We study the effects of doping a Mott insulator on the honeycomb lattice
where spins interact via direction dependent Kitaev couplings J_K, and weak
antiferromagnetic Heisenberg couplings J. This model is known to have a spin
liquid ground state and may potentially be realized in correlated insulators
with strong spin orbit coupling. The effect of hole doping is studied within a
t-J-J_K model, treated using the SU(2) slave boson formulation, which correctly
captures the parent spin liquid. We find superconductor ground states with spin
triplet pairing that spontaneously break time reversal symmetry. Interestingly,
the pairing is qualitatively different at low and high dopings, and undergoes a
first order transition with doping. At high dopings, it is smoothly connected
to a paired state of electrons propagating with the underlying free particle
dispersion. However, at low dopings the dispersion is strongly influenced by
the magnetic exchange, and is entirely different from the free particle band
structure. Here the superconductivity is fully gapped and topological,
analogous to spin polarized electrons with px+ipy pairing. These results may be
relevant to honeycomb lattice iridates such as A2IrO3 (A=Li or Na) on doping.",1109.4155v3
2012-11-06,Optical Signatures of the Tunable Band Gap and Valley-Spin Coupling in Silicene,"We investigate the optical response of the silicene and similar materials,
such as germanene, in the presence of an electrically tunable band gap for
variable doping. The interplay of spin orbit coupling, due to the buckled
structure of these materials, and a perpendicular electric field gives rise to
a rich variety of phases: a topological or quantum spin Hall insulator, a
valley-spin-polarized metal and a band insulator. We show that the dynamical
conductivity should reveal signatures of these different phases which would
allow for their identification along with the determination of parameters such
as the spin orbit energy gap. We find an interesting feature where the electric
field tuning of the band gap might be used to switch on and off the Drude
intraband response. Furthermore, in the presence of spin-valley coupling, the
response to circularly polarized light as a function of frequency and electric
field tuning of the band gap is examined. Using right- and left-handed circular
polarization it is possible to select a particular combination of spin and
valley index. The frequency for this effect can be varied by tuning the band
gap.",1211.1336v1
2013-01-14,Superfluid and magnetic states of an ultracold Bose gas with synthetic three-dimensional spin-orbit coupling in an optical lattice,"We study ultracold bosonic atoms with the synthetic three-dimensional
spin-orbit (SO) coupling in a cubic optical lattice. In the superfluidity
phase, the lowest energy band exhibits one, two or four pairs of degenerate
single-particle ground states depending on the SO-coupling strengths, which can
give rise to the condensate states with spin-stripes for the weak atomic
interactions. In the deep Mott-insulator regime, the effective spin Hamiltonian
of the system combines three-dimensional Heisenberg exchange interactions,
anisotropy interactions and Dzyaloshinskii-Moriya interactions. Based on Monte
Carlo simulations, we numerically demonstrate that the resulting Hamiltonian
with an additional Zeeman field has a rich phase diagram with spiral, stripe,
vortex crystal, and especially Skyrmion crystal spin-textures in each xy-plane
layer. The obtained Skyrmion crystals can be tunable with square and hexagonal
symmetries in a columnar manner along the z axis, and moreover are stable
against the inter-layer spin-spin interactions in a large parameter region.",1301.2869v2
2011-11-12,Persistent charge and spin currents in a 1D ring with Rashba and Dresselhaus spin-orbit interactions by excitation with a terahertz pulse,"Persistent, oscillatory charge and spin currents are shown to be driven by a
two-component terahertz laser pulse in a one-dimensional mesoscopic ring with
Rashba-Dresselhaus spin orbit interactions (SOI) linear in the electron
momentum. The characteristic interference effects result from the opposite
precession directions imposed on the electron spin by the two SOI couplings.
The time dependence of the currents is obtained by solving numerically the
equation of motion for the density operator, which is later employed in
calculating statistical averages of quantum operators on few electron
eigenstates. The parameterization of the problem is done in terms of the SOI
coupling constants and of the phase difference between the two laser
components. Our results indicate that the amplitude of the oscillations is
controlled by the relative strength of the two SOI's, while their frequency is
determined by the difference between the excitation energies of the electron
states. Furthermore, the oscillations of the spin current acquire a beating
pattern of higher frequency that we associate with the nutation of the electron
spin between the quantization axes of the two SOI couplings. This phenomenon
disappears at equal SOI strengths, whereby the opposite precessions occur with
the same probability.",1111.2949v1
2018-03-27,Theory of Hole-Spin Qubits in Strained Germanium Quantum Dots,"We theoretically investigate the properties of holes in a
Si$_{x}$Ge$_{1-x}$/Ge/ Si$_{x}$Ge$_{1-x}$ quantum well in a perpendicular
magnetic field that make them advantageous as qubits, including a large
($>$100~meV) intrinsic splitting between the light and heavy hole bands, a very
light ($\sim$0.05$\, m_0$) in-plane effective mass, consistent with higher
mobilities and tunnel rates, and larger dot sizes that could ameliorate
constraints on device fabrication. Compared to electrons in quantum dots, hole
qubits do not suffer from the presence of nearby quantum levels (e.g., valley
states) that can compete with spins as qubits. The strong spin-orbit coupling
in Ge quantum wells may be harnessed to implement electric-dipole spin
resonance, leading to gate times of several nanoseconds for single-qubit
rotations. The microscopic mechanism of this spin-orbit coupling is discussed,
along with its implications for quantum gates based on electric-dipole spin
resonance, stressing the importance of coupling terms that arise from the
underlying cubic crystal field. Our results provide a theoretical foundation
for recent experimental advances in Ge hole-spin qubits.",1803.10320v5
2018-06-15,Entangled end states with fractionalized spin projection in a time-reversal-invariant topological superconducting wire,"We study the ground state and low-energy subgap excitations of a finite wire
of a time-reversal-invariant topological superconductor (TRITOPS) with
spin-orbit coupling. We solve the problem analytically for a long chain of a
specific one-dimensional lattice model in the electron-hole symmetric
configuration and numerically for other cases of the same model. We present
results for the spin density of excitations in long chains with an odd number
of particles. The total spin projection along the axis of the spin-orbit
coupling $S_z= \pm 1/2$ is distributed with fractions $\pm 1/4$ localized at
both ends, and shows even-odd alternation along the sites of the chain. We
calculate the localization length of these excitations and find that it can be
well approximated by a simple analytical expression. We show that the energy
$E$ of the lowest subgap excitations of the finite chain defines tunneling and
entanglement between end states.We discuss the effect of a Zeeman coupling
$\Delta_Z$ on one of the ends of the chain only. For $\Delta_Z<E$, the energy
difference of excitations with opposite spin orientation is $\Delta_Z/2$,
consistent with a spin projection $\pm 1/4$. We argue that these physical
features are not model dependent and can be experimentally observed in TRITOPS
wires under appropriate conditions.",1806.06104v4
2019-11-25,Quantum field theory of topological spin dynamics,"We develop a field theory of quantum magnets and magnetic (semi)metals, which
is suitable for the analysis of their universal and topological properties. The
systems of interest include collinear, coplanar and general non-coplanar
magnets. At the basic level, we describe the dynamics of magnetic moments using
smooth vector fields in the continuum limit. Dzyaloshinskii-Moriya interaction
is captured by a non-Abelian vector gauge field, and chiral spin couplings
related to topological defects appear as higher-rank antisymmetric tensor gauge
fields. We distinguish type-I and type-II magnets by their equilibrium response
to the non-Abelian gauge flux, and characterize the resulting lattices of
skyrmions and hedgehogs, the spectra of spin waves, and the chiral response to
external perturbations. The general spin-orbit coupling of electrons is
similarly described by non-Abelian gauge fields, including higher-rank tensors
related to the electronic Berry flux. Itinerant electrons and local moments
exchange their gauge fluxes through Kondo and Hund interactions. Hence, by
utilizing gauge fields, this theory provides a unifying physical picture of
``intrinsic'' and ``topological'' anomalous Hall effects, spin-Hall effects,
and other correlations between the topological properties of electrons and
moments. We predict ``topological'' magnetoelectric effect in materials prone
to hosting hedgehogs. Links to experiments and model calculations are provided
by deriving the couplings and gauge fields from generic microscopic models,
including the Hubbard model with spin-orbit interactions. We establish the
possible existence of novel quantum spin liquids that exhibit a fractional
magnetoelectric effect, and discuss a few applications to topological magnetic
conductors like Mn$_3$Sn and Pr$_2$Ir$_2$O$_7$.",1911.11155v2
2011-08-05,Ferromagnetic spin coupling of 2p-impurities in band insulators stabilized by intersite Coulomb interaction: Nitrogen-doped MgO,"For a nitrogen dimer in insulating MgO, a ferromagnetic coupling between
spin-polarized $2p$-holes is revealed by calculations based on the density
functional theory amended by an on-site Coulomb interaction and corroborated by
the Hubbard model. It is shown that the ferromagnetic coupling is facilitated
by a T-shaped orbital arrangement of the $2p$-holes, which is in its turn
controlled by an intersite Coulomb interaction due to the directionality of the
$p$-orbitals. We thus conjecture that this interaction is an important
ingredient of ferromagnetism in band insulators with $2p$ dopants.",1108.1294v1
2019-10-18,Probing quantum spin liquids in equilibrium using the inverse spin Hall effect,"We propose an experimental method utilizing a strongly spin-orbit coupled
metal to quantum magnet bilayer that will probe quantum magnets lacking long
range magnetic order, e.g., quantum spin liquids, via examination of the
voltage noise spectrum in the metal layer. The bilayer is held in thermal and
chemical equilibrium, and spin fluctuations arising across the single interface
are converted into voltage fluctuations in the metal as a result of the inverse
spin Hall effect. We elucidate the theoretical workings of the proposed bilayer
system, and provide precise predictions for the frequency characteristics of
the enhancement to the ac electrical resistance measured in the metal layer for
three candidate quantum spin liquid models. Application to the Heisenberg
spin-$1/2$ kagom{\'e} lattice model should allow for the extraction of any
spinon gap present. A quantum spin liquid consisting of fermionic spinons
coupled to a $U(1)$ gauge field should cause subdominant $\W^{4/3}$ scaling of
the resistance of the coupled metal. Finally, if the magnet is well-captured by
the Kitaev model in the gapless spin liquid phase, then the proposed bilayer
can extract the two-flux gap which arises in spite of the gapless spectrum of
the fermions. We therefore show that spectral analysis of the ac resistance in
the metal in a single interface, equilibrium bilayer can test the relevance of
a quantum spin liquid model to a given candidate material.",1910.08610v2
2023-07-29,Comparative $^{181}$Ta-NQR Study of Weyl Monopnictides TaAs and TaP: Relevance of Weyl Fermion Excitations,"Based on our first detailed $^{181}$Ta nuclear quadrupole resonance (NQR)
studies from 2017 on the Weyl semimetal TaP, we now extended our NQR studies to
another Ta-based monopnictide TaAs. In the present work, we have determined the
temperature-dependent $^{181}$Ta-NQR spectra, the spin-lattice relaxation time
$T_{1}$, and the spin-spin relaxation time $T_{2}$. We found the following
characteristic features that showed great contrast to what was found in TaP:
(1) The quadrupole coupling constant and asymmetry parameter of EFG, extracted
from three NQR frequencies, have a strong temperature dependence above $\sim$80
K that cannot be explained by the density functional theory calculation
incorporating the thermal expansion of the lattice. (2) The temperature
dependence of the spin-lattice relaxation rate, $1/T_{1} T$, shows a $T^{4}$
power law behavior above $\sim$30 K. This is a great contrast with the $1/T_{1}
T \propto T^{2}$ behavior found in TaP, which was ascribed to the magnetic
excitations at the Weyl nodes with a temperature-dependent orbital hyperfine
coupling. (3) Regarding the nuclear spin-spin interaction, we found the
spin-echo signal decays with the pulse separation simply by a Lorentzian
function in TaAs, but we have observed spin-echo modulations in TaP that is
most likely due to the indirect nuclear spin-spin coupling via virtually
excited Weyl fermions. From our experimental findings, we conclude that the
present NQR results do not show dominant contributions from Weyl fermion
excitations in TaAs.",2307.16009v1
2010-12-29,Competing Exotic Topological Insulator Phases in Transition Metal Oxides on the Pyrochlore Lattice with Distortion,"In this work we investigate the phase diagram of heavy (4d and 5d) transition
metal oxides on the pyrochlore lattice, such as those of the form
$\mathrm{A_2M_2O_7}$, where A is a rare earth element and M is a transition
metal element. We focus on the competition between Coulomb interaction,
spin-orbit coupling, and lattice distortion when these energy scales are
comparable. Strong spin-orbit coupling entangles the spin and the $t_{2g}$
$d$-orbitals giving rise to doublet $j=1/2$ and quadruplet $j=3/2$ states. In
contrast to previous works which focused on the doublet manifold, we also
discuss the quadruplet manifold which is relevant for several pyrochlore
oxides. The Coulomb interaction is taken into account by use of the slave-rotor
mean field theory and different classes of lattice distortions which further
split the levels of the quadruplet $j=3/2$ manifold are studied. Various
topological phases are predicted, including exotic strong and weak topological
Mott insulating phases. We discuss the general structure of the phase diagram
for several values of $d$-shell filling and various symmetry classes of lattice
distortions. Our results are relevant to the search for exotic topological
insulators and quantum spin liquids in strongly correlated materials with
strong spin-orbit coupling.",1101.0007v2
2014-05-11,Controllable Spin-Charge Transport in Strained Graphene Nanoribbon Devices,"We theoretically investigate the spin-charge transport in two-terminal device
of graphene nanoribbons in the presence of an uniform uniaxial strain,
spin-orbit coupling, exchange field and smooth staggered potential. We show
that the direction of applied strain can efficiently tune strain-strength
induced oscillation of band-gap of armchair graphene nanoribbon (AGNR). It is
also found that electronic conductance in both AGNR and zigzag graphene
nanoribbons (ZGNRs) oscillates with Rashba spin-orbit coupling akin to the
Datta-Das field effect transistor. Two distinct strain response regimes of
electronic conductance as function of spin-orbit couplings (SOC) magnitude are
found. In the regime of small strain, conductance of ZGNR presents stronger
strain dependence along the longitudinal direction of strain. Whereas for high
values of strain shows larger effect for the transversal direction.
Furthermore, the local density of states (LDOS) shows that depending on the
smoothness of the staggered potential, the edge state of AGNR can either emerge
or be suppressed. These emerging states can be determined experimentally by
performing spatially scanning tunneling microscope or by scanning tunneling
spectroscopy. Our findings open up new paradigms of manipulation and control of
strained graphene based nanostructure for application on novel topological
quantum devices.",1405.2497v1
2018-09-26,Phase transitions of the Kane-Mele-Hubbard model with a long-range hopping,"The interacting Kane-Mele model with a long-range hopping is studied using
analytical method. The original Kane-Mele model is defined on a honeycomb
lattice. In the work, we introduce a four-lattice-constant range hopping and
the on-site Hubbard interaction into the model and keep its lattice structure
unchanged. From the single-particle energy spectrum, we obtain the critical
strength of the long-range hopping $t_L$ at which the topological transition
occurs in the non-interacting limit of the model and our results show that it
is independent of the spin-orbit coupling. After introducing the Hubbard
interaction, we investigate the Mott transition and the magnetic transition of
the generalized strongly correlated Kane-Mele model using the slave-rotor mean
field theory and Hartree-Fock mean field theory respectively. In the small
long-range hopping region, it is a correlated quantum spin Hall state below the
Mott transition, while a topological Mott insulator above the Mott transition.
By comparing the energy band of spin degree of freedom with the one of
electrons in non-interacting limit, we find a condition for the $t_L$-driven
topological transition. Under the condition, critical values of $t_L$ at which
the topological transition occurs are obtain numerically from seven
self-consistency equations in both regions below and above the Mott transition.
Influences of the interaction and the spin-orbit coupling on the topological
transition are discussed in this work. Finally, we show complete phase diagrams
of the generalized interacting topological model at some strength of
spin-orbital coupling.",1809.09903v3
2020-12-29,Controlling Synthetic Spin-Orbit Coupling in a Silicon Quantum Dot with Magnetic Field,"Tunable synthetic spin-orbit coupling (s-SOC) is one of the key challenges in
various quantum systems, such as ultracold atomic gases, topological
superconductors, and semiconductor quantum dots. Here we experimentally
demonstrate controlling the s-SOC by investigating the anisotropy of
spin-valley resonance in a silicon quantum dot. As we rotate the applied
magnetic field in-plane, we find a striking nonsinusoidal behavior of resonance
amplitude that distinguishes s-SOC from the intrinsic spin-orbit coupling
(i-SOC), and associate this behavior with the previously overlooked in-plane
transverse magnetic field gradient. Moreover, by theoretically analyzing the
experimentally measured s-SOC field, we predict the quality factor of the spin
qubit could be optimized if the orientation of the in-plane magnetic field is
rotated away from the traditional working point.",2012.14636v2
2018-07-23,Proximity-Induced Mixed Odd and Even Frequency Pairings in Monolayer NbSe$_2$,"Monolayer superconducting transition metal dichalcogenide NbSe$_2$ is a
candidate for a nodal topological superconductor by magnetic field. Because of
the so-called Ising spin-orbit coupling that strongly pins the electron spins
to the out-of-plane direction, Cooper pairs in monolayer superconductor
NbSe$_2$ are protected against an applied in-plane magnetic field much larger
than the Pauli limit. In monolayer NbSe$_2$, in addition to the Fermi pockets
at the corners of Brillouin zone with opposite crystal momentum similar to
other semiconducting transition metal dichalcogenides, there is an extra Fermi
pocket around the $\Gamma$ point with much smaller spin splitting, which could
lead to an alternative strategy for pairing possibilities that are manipulable
by a smaller magnetic field. By considering a monolayer NbSe$_2$-ferromagnet
substrate junction, we explore the modified pairing correlations on the pocket
at $\Gamma$ point in hole-doped monolayer NbSe$_2$. The underlying physics is
fascinating as there is a delicate interplay of the induced exchange field and
the Ising spin-orbit coupling. We realize a mixed singlet-triplet
superconductivity, s+f, due to the Ising spin-orbit coupling. Moreover, our
results reveal the admixture state including both odd- and even-frequency
components, associated with the ferromagnetic proximity effect. Different
frequency symmetries of the induced pairing correlations can be realized by
manipulating the magnitude and direction of the induced magnetization.",1807.08470v1
2020-11-15,Van Vleck excitons in Ca$_{2}$RuO$_{4}$,"A framework is presented for modeling and understanding magnetic excitations
in localized, intermediate coupling magnets where the interplay between
spin-orbit coupling, magnetic exchange, and crystal field effects are known to
create a complex landscape of unconventional magnetic behaviors and ground
states. A spin-orbit exciton approach for modeling these excitations is
developed based upon a Hamiltonian which explicitly incorporates single-ion
crystalline electric field and spin exchange terms. This framework is then
leveraged to understand a canonical Van Vleck $j\rm{_{eff}}=0$ singlet ground
state whose excitations are coupled spin and crystalline electric field levels.
Specifically, the anomalous Higgs mode [Jain et al. Nat. Phys. 13, 633 (2017)],
spin-waves [S. Kunkem\""{o}ller et al. Phys. Rev. Lett. 115, 247201 (2015)], and
orbital excitations [L. Das et al. Phys. Rev. X 8, 011048 (2018)] in the
multiorbital Mott insulator Ca$_2$RuO$_4$ are captured and good agreement is
found with previous neutron and inelastic x-ray spectroscopic measurements.
Furthermore, our results illustrate how a crystalline electric field-induced
singlet ground state can support coherent longitudinal, or amplitude
excitations, and transverse wavelike dynamics. We use this description to
discuss mechanisms for accessing a nearby critical point.",2011.07425v1
2020-03-09,Effective triangular ladders with staggered flux from spin-orbit coupling in 1D optical lattices,"Light-induced spin-orbit coupling is a flexible tool to study quantum
magnetism with ultracold atoms. In this work we show that spin-orbit coupled
Bose gases in a one-dimensional optical lattice can be mapped into a two-leg
triangular ladder with staggered flux following a lowest-band truncation of the
Hamiltonian. The effective flux and the ratio of the tunneling strengths can be
independently adjusted to a wide range of values. We identify a certain regime
of parameters where a hard-core boson approximation holds and the system
realizes a frustrated triangular spin ladder with tunable flux. We study the
properties of the effective spin Hamiltonian using the density-matrix
renormalization-group method and determine the phase diagram at half-filling.
It displays two phases: a uniform superfluid and a bond-ordered insulator. The
latter can be stabilized only for low Raman detuning. Finally, we provide
experimentally feasible trajectories across the parameter space of the SOC
system that cross the predicted phase transition.",2003.04154v3
2022-03-30,Realization of the topological Hopf term in two-dimensional lattice models,"It is known that a two-dimensional spin system can acquire a topological Hopf
term by coupling to massless Dirac fermions whose energy spectrum has a single
cone. But it is challenging to realize the Hopf term in condensed matter
physics due to the fermion-doubling in the low-energy spectrum. In this work we
propose a scenario to realize the Hopf term in lattice models. The central aim
is tuning the coupling between the spins and the Dirac fermions such that the
topological terms contributed by the two cones do not cancel each other. To
this end, we consider $p_x$ and $p_y$ orbitals for the Dirac fermions on the
honeycomb lattice such that there are totally four bands. By utilizing the
orbital degrees of freedom, a $\theta=2\pi$ Hopf term is successfully generated
for the spin system after integrating out the Dirac fermions. If the fermions
have a small gap $m_0$ or if the spin-orbit coupling is considered, then
$\theta$ is no longer quantized, but it may flow to multiple of $2\pi$ under
renormalization. The ground state and the physical response of a spin system
having the Hopf term are discussed.",2203.16480v3
2010-02-22,Spin fluctuations and superconductivity in noncentrosymmetric heavy fermion systems CeRhSi$_3$ and CeIrSi$_3$,"We study the normal and the superconducting properties in noncentrosymmetric
heavy fermion superconductors CeRhSi$_3$ and CeIrSi$_3$. For the normal state,
we show that experimentally observed linear temperature dependence of the
resistivity is understood through the antiferromagnetic spin fluctuations near
the quantum critical point (QCP) in three dimensions. For the superconducting
state, we derive a general formula to calculate the upper critical field
$H_{c2}$, with which we can treat the Pauli and the orbital depairing effect on
an equal footing. The strong coupling effect for general electronic structures
is also taken into account. We show that the experimentally observed features
in $H_{c2}\parallel \hat{z}$, the huge value up to 30(T), the downward
curvatures, and the strong pressure dependence, are naturally understood as an
interplay of the Rashba spin-orbit interaction due to the lack of inversion
symmetry and the spin fluctuations near the QCP. The large anisotropy between
$H_{c2}\parallel \hat{z}$ and $H_{c2}\perp \hat{z}$ is explained in terms of
the spin-orbit interaction. Furthermore, a possible realization of the
Fulde-Ferrell- Larkin-Ovchinnikov state for $H\perp \hat{z}$ is studied. We
also examine effects of spin-flip scattering processes in the pairing
interaction and those of the applied magnetic field on the spin fluctuations.
We find that the above mentioned results are robust against these effects. The
consistency of our results strongly supports the scenario that the
superconductivity in CeRhSi$_3$ and CeIrSi$_3$ is mediated by the spin
fluctuations near the QCP.",1002.4031v1
2014-04-25,"Orbit- and Atom-Resolved Spin Textures of Intrinsic, Extrinsic and Hybridized Dirac Cone States","Combining first-principles calculations and spin- and angle-resolved
photoemission spectroscopy measurements, we identify the helical spin textures
for three different Dirac cone states in the interfaced systems of a 2D
topological insulator (TI) of Bi(111) bilayer and a 3D TI Bi2Se3 or Bi2Te3. The
spin texture is found to be the same for the intrinsic Dirac cone of Bi2Se3 or
Bi2Te3 surface state, the extrinsic Dirac cone of Bi bilayer state induced by
Rashba effect, and the hybridized Dirac cone between the former two states.
Further orbit- and atom-resolved analysis shows that s and pz orbits have a
clockwise (counterclockwise) spin rotation tangent to the iso-energy contour of
upper (lower) Dirac cone, while px and py orbits have an additional radial spin
component. The Dirac cone states may reside on different atomic layers, but
have the same spin texture. Our results suggest that the unique spin texture of
Dirac cone states is a signature property of spin-orbit coupling, independent
of topology.",1404.6306v1
2016-12-04,Anisotropic Pauli Spin Blockade of Holes in a GaAs Double Quantum Dot,"Electrically defined semiconductor quantum dots are attractive systems for
spin manipulation and quantum information processing. Heavy-holes in both Si
and GaAs are promising candidates for all-electrical spin manipulation, owing
to the weak hyperfine interaction and strong spin-orbit interaction. However,
it has only recently become possible to make stable quantum dots in these
systems, mainly due to difficulties in device fabrication and stability. Here
we present electrical transport measurements on holes in a gate-defined double
quantum dot in a $\mathrm{GaAs/Al_xGa_{1-x}As}$ heterostructure. We observe
clear Pauli spin blockade and demonstrate that the lifting of this spin
blockade by an external magnetic field is highly anisotropic. Numerical
calculations of heavy-hole transport through a double quantum dot in the
presence of strong spin-orbit coupling show quantitative agreement with
experimental results and suggest that the observed anisotropy can be explained
by both the anisotropic effective hole g-factor and the surface Dresselhaus
spin-orbit interaction.",1612.01062v1
2021-10-06,"Stacking-order effect on spin-orbit torque, spin-Hall magnetoresistance, and magnetic anisotropy in Ni$_{81}$Fe$_{19}$-IrO$_2$ bilayers","The 5d transition-metal oxides have been an intriguing platform to
demonstrate efficient charge to spin current conversion due to a unique
electronic structure dominated by strong spin-orbit coupling. Here, we report
on stacking-order effect of spin-orbit torque (SOT), spin-Hall
magnetoresistance, and magnetic anisotropy in bilayer Ni$_{81}$Fe$_{19}$-5d
iridium oxide, IrO$_2$. While all the IrO$_2$ and Pt control samples exhibit
large dampinglike-SOT generation stemming from the efficient charge to spin
current conversion, the magnitude of the SOT is larger in the IrO$_2$
(Pt)-bottom sample than in the IrO$_2$ (Pt)-top one. The fieldlike-SOT has even
more significant stack order effect, resulting in an opposite sign in the
IrO$_2$ samples in contrast to the same sign in the Pt samples. Furthermore, we
observe that the magnetic anisotropy energy density and the anomalous Hall
effect are increased in the IrO$_2$ (Pt)-bottom sample, suggesting enhanced
interfacial perpendicular magnetic anisotropy. Our findings highlight the
significant influence of the stack order on spin transport and magnetotransport
properties of Ir oxide/ferromagnet systems, providing useful information on
design of SOT devices including 5d transition-metal oxides.",2110.02517v1
2010-01-27,Quantum dot spin qubits in Silicon: Multivalley physics,"Research on Si quantum dot spin qubits is motivated by the long spin
coherence times measured in Si, yet the orbital spectrum of Si dots is
increased as a result of the valley degree of freedom. The valley degeneracy
may be lifted by the interface potential, which gives rise to a valley-orbit
coupling, but the latter depends on the detailed structure of the interface and
is generally unknown a priori. These facts motivate us to provide an extensive
study of spin qubits in Si double quantum dots, accounting fully for the valley
degree of freedom and assuming no prior knowledge of the valley-orbit coupling.
For single-spin qubits we analyze the spectrum of a multivalley double quantum
dot, discuss the initialization of one qubit, identify the conditions for the
lowest energy two-electron states to be a singlet and a triplet well separated
from other states, and determine analytical expressions for the exchange
splitting. For singlet-triplet qubits we analyze the single-dot spectrum and
initialization process, the double-dot spectrum, singlet-triplet mixing in an
inhomogeneous magnetic field and the peculiarities of spin blockade in
multivalley qubits. We review briefly the hyperfine interaction in Si and
discuss its role in spin blockade in natural Si, including intravalley and
intervalley effects. We study the evolution of the double-dot spectrum as a
function of magnetic field. We address briefly the situation in which the
valley-orbit coupling is different in each dot due to interface roughness. We
propose a new experiment for measuring the valley splitting in a single quantum
dot. We discuss the possibility of devising other types of qubits in Si QDs,
and the size of the intervaley coupling due to the Coulomb interaction.",1001.5040v2
2010-06-14,Evidence of Possible Spin-Orbit Misalignment Along the Line of Sight in Transiting Exoplanet Systems,"Of the 26 transiting exoplanet systems with measurements of the
Rossiter-McLaughlin (RM) effect, eight have now been found to be significantly
spin-orbit misaligned in the plane of the sky. Unfortunately, the RM effect
only measures the angle between the orbit of a transiting exoplanet and the
spin of its host star projected in the plane of sky, leaving unconstrained the
compliment misalignment angle between the orbit of the planet and the spin of
its host star along the line of sight. I use a simple model of stellar rotation
benchmarked with observational data to statistically identify ten exoplanet
systems from a sample of 75 for which there is likely a significant degree of
misalignment along the line of sight between the orbit of the planet and the
spin of its host star. I find that HAT-P-7, HAT-P-14, HAT-P-16, HD 17156,
Kepler-5, Kepler-7, TrES-4, WASP-1, WASP-12, and WASP-14 are likely spin-orbit
misaligned along the line of sight. All ten systems have host stellar masses
M_star in the range 1.2 M_sun <= M_star <= 1.5 M_sun, and the probability of
this occurrence by chance is less than one in ten thousand. In addition, the
planets in the candidate misaligned systems are preferentially massive and
eccentric. The coupled distribution of misalignment from the RM effect and from
this anaylsis suggests that transiting exoplanets are more likely to be
spin-orbit aligned than expected given predictions for a transiting planet
population produced entirely by planet-planet scattering or Kozai cycles and
tidal friction. For that reason, there are likely two populations of close-in
exoplanet systems: a population of aligned systems and a population of
apparently misaligned systems in which the processes that lead to misalignment
or to the survival of misaligned systems operate more efficiently in systems
with massive stars and planets. (abridged)",1006.2851v1
2020-07-26,Spin-orbit quantum impurity and quantization in a topological magnet,"Quantum states induced by single-atomic impurities are at the frontier of
physics and material science. While such states have been reported in
high-temperature superconductors and dilute magnetic semiconductors, they are
unexplored in topological magnets which can feature spin-orbit tunability. Here
we use spin-polarized scanning tunneling microscopy/spectroscopy (STM/S) to
study the engineered quantum impurity in a topological magnet Co3Sn2S2. We find
that each substituted In impurity introduces a striking localized bound state.
Our systematic magnetization-polarized probe reveals that this bound state is
spin-down polarized, in lock with a negative orbital magnetization. Moreover,
the magnetic bound states of neighboring impurities interact to form quantized
orbitals, exhibiting an intriguing spin-orbit splitting, analogous to the
splitting of the topological fermion line. Our work collectively demonstrates
the strong spin-orbit effect of the single-atomic impurity at the quantum
level, suggesting that a nonmagnetic impurity can introduce spin-orbit coupled
magnetic resonance in topological magnets.",2007.13738v1
2016-10-09,Eccentricity and Spin-Orbit Misalignment in Short-Period Stellar Binaries as a Signpost of Hidden Tertiary Companions,"Eclipsing binaries are observed to have a range of eccentricities and
spin-orbit misalignments (stellar obliquities). Whether such properties are
primordial, or arise from post-formation dynamical interactions remains
uncertain. This paper considers the scenario in which the binary is the inner
component of a hierarchical triple stellar system, and derives the requirements
that the tertiary companion must satisfy in order to raise the eccentricity and
obliquity of the inner binary. Through numerical integrations of the secular
octupole-order equations of motion of stellar triples, coupled with the spin
precession of the oblate primary star due to the torque from the secondary, we
obtain a simple, robust condition for producing spin-orbit misalignment in the
inner binary: In order to excite appreciable obliquity, the precession rate of
the stellar spin axis must be smaller than the orbital precession rate due to
the tertiary companion. This yields quantitative requirements on the mass and
orbit of the tertiary. We also present new analytic expressions for the maximum
eccentricity and range of inclinations allowing eccentricity excitation
(Lidov-Kozai window), for stellar triples with arbitrary masses and including
the non-Keplerian potentials introduced by general relativity, stellar tides
and rotational bulges. The results of this paper can be used to place
constraints on unobserved tertiary companions in binaries that exhibit high
eccentricity and/or spin-orbit misalignment, and will be helpful in guiding
efforts to detect external companions around stellar binaries. As an
application, we consider the eclipsing binary DI Herculis, and identify the
requirements that a tertiary companion must satisfy to produce the observed
spin-orbit misalignment.",1610.02626v2
2019-05-01,Black Hole and Neutron Star Binary Mergers in Triple Systems: II. Merger Eccentricity and Spin-Orbit Misalignment,"We study the dynamical signatures of black hole (BH) and neutron star (NS)
binary mergers via Lidov-Kozai oscillations induced by tertiary companions in
hierarchical triple systems. For each type of binaries (BH-BH and BH-NS), we
explore a wide range of binary/triple parameters that lead to binary mergers,
and determine the distributions of eccentricity ($e_\mathrm{m}$) and spin-orbit
misalignment angle ($\theta_\rm {sl}^\rm f$) when the binary enters the
LIGO/VIRGO band. We use the double-averaged (over both orbits) and
single-averaged (over the inner orbit) secular equations, as well as N-body
integration, to evolve systems with different hierarchy levels, including the
leading-order post-Newtonian effect, spin-orbit coupling and gravitational
radiation. We find that for merging BH-BH binaries with comparable masses,
about $7\%$ have $e_\mathrm{m}>0.1$ and $0.7\%$ have $e_{\rm m}>0.9$. The
majority of the mergers have significant eccentricities in the LISA band. The
BH spin evolution and $\theta_\rm {sl}^\rm f$ are correlated with the orbital
evolution and $e_{\rm m}$. Mergers with $e_{\rm m} \lesssim 10^{-3}$ have a
distribution of $\theta_\rm {sl}^\rm f$ that peaks around $90^\circ$ (and thus
favoring a projected binary spin parameter $\chi_{\rm eff}\sim 0$), while
mergers with larger $e_{\rm m}$ have a more isotropic spin-orbit misalignments.
For typical BH-NS binaries, strong octuple effects lead to more mergers with
non-negligible $e_\mathrm{m}$ (with $\sim 18\%$ having $e_\mathrm{m}>0.1$ and
$2.5\%$ having $e_\mathrm{m}>0.9$), and the final BH spin axis tends to be
randomly orientated. Measurements or constraints on eccentric mergers and
$\theta_\rm {sl}^\rm f$ from LIGO/VIRGO and LISA would provide useful
diagnostics on the dynamical formation of merging BH or NS binaries in triples.",1905.00427v2
2023-03-02,A protected spin-orbit induced absorption divergence in distorted Landau levels,"The effect of spin-orbit (and Darwin) interaction on a 2D electron gas
subject to a radial symmetric, inhomogeneous $1/r$-magnetic field is discussed
analytically in a perturbative and non-perturbative manner. For this purpose,
we investigate the radial Hall conductivity that emerges from an additional
homogeneous electric field perturbation perpendicular to the 2D electron gas,
which solely interacts via spin-orbit coupling. Numerical calculations of the
absorptive spin-orbit spectra show for an ideal InSb electron gas a behaviour
that is dominated by the localized (atomic) part of the distorted Landau
levels. In contrast, however, we also find analytically that a (non-local)
divergent static response emerges for Fermi energies close to the ionization
energy in the thermodynamic limit. The divergent linear response implies that
the external electric field is entirely absorbed outside the 2D electron gas by
induced radial spin-orbit currents, as it would be the case inside a perfect
conductor. This spin-orbit induced polarization mechanism depends on the
effective $g^*$-factor of the material for which it shows a critical behaviour
at $g^*_c=2$, where it abruptly switches direction. The diverging absorption
relies on the presence of degenerate energies with allowed selection rules that
are imposed by the radial symmetry of our inhomogeneous setup. We show
analytically the presence of a discrete Rydberg-like band structure that obeys
these symmetry properties. In a last step, we investigate the robustness of the
spectra by solving analytically the Dirac equation expanded up to order
$1/(mc)^2$. We find that the distorted Landau-levels, and thus the divergent
spin-orbit polarization, remain protected with respect to slow changes of the
applied $1/r$-magnetic field.",2303.01286v2
1999-12-15,Spin-1 chain doped with mobile S=1/2 fermions,"We investigate doping of a two-orbital chain with mobile $S=1/2$ fermions as
a valid model for $\rm Y_{2-x}Ca_xBaNiO_5$. The S=1 spins are stabilized by
strong, ferromagnetic (fm) Hund's rule couplings. We calculate correlation
functions and thermodynamic quantities by DMRG methods and find a new hierarchy
of energy scales in the spin sector upon doping. Gapless spin-excitations are
generated at a lower energy scale by interactions among itinerant polarons
created by each hole and coexist with the larger scale of the gapful
spin-liquid background of the S=1 chain accompanied by a finite string-order
parameter.",9912273v1
2001-08-29,Magnetic Semiconductors are Frustrated Ferromagnets,"Starting from microscopic and symmetry considerations, we derive the
Hamiltonian describing the exchange interaction between the localized Mn spins
and the valence band holes in $Ga_{1-x}Mn_x As$. We find that due to the strong
spin-orbit coupling in the valence band, this exchange interaction has a rather
complex structure and generates a highly anisotropic effective interaction
between the Mn spins. The corresponding ground state has a finite ferromagnetic
magnetization but is intrinsically spin-disordered even at zero temperature.",0108477v1
2003-03-26,Chern Numbers for Spin Models of Transition Metal Nanomagnets,"We argue that ferromagnetic transition metal nanoparticles with fewer than
approximately 100 atoms can be described by an effective Hamiltonian with a
single giant spin degree of freedom. The total spin $S$ of the effective
Hamiltonian is specified by a Berry curvature Chern number that characterizes
the topologically non-trivial dependence of a nanoparticle's many-electron
wavefunction on magnetization orientation. The Berry curvatures and associated
Chern numbers have a complex dependence on spin-orbit coupling in the
nanoparticle and influence the semiclassical Landau-Liftshitz equations that
describe magnetization orientation dynamics.",0303555v1
2003-10-06,Dissipation effects in spin-Hall transport of electrons and holes,"We investigate the spin-Hall effect of both electrons and holes in
semiconductors using the Kubo formula in the correct zero-frequency limit
taking into account the finite momentum relaxation time of carriers in real
semiconductors. This approach allows to analyze the range of validity of recent
theoretical findings. In particular, the spin-Hall conductivity vanishes for
vanishing spin-orbit coupling if the correct zero-frequency limit is performed.",0310108v3
2003-11-04,Quantum dots based on spin properties of semiconductor heterostructures,"The possibility of a novel type of semiconductor quantum dots obtained by
spatially modulating the spin-orbit coupling intensity in III-V
heterostructures is discussed. Using the effective mass model we predict
confined one-electron states having peculiar spin properties. Furthermore, from
mean field calculations (local-spin-density and Hartree-Fock) we find that even
two electrons could form a bound state in these dots.",0311077v2
2003-12-14,Theory of spin waves in diluted-magnetic-semiconductor quantum wells,"We present a theory of collective spin excitations in
diluted-magnetic-semiconductor quantum wells in which local magnetic moments
are coupled via a quasi-two-dimensional gas of electrons or holes. In the case
of a ferromagnetic state with partly spin-polarized electrons, we find that the
Goldstone collective mode has anomalous $k^4$ dispersion and that for symmetric
quantum wells odd parity modes do not disperse at all. We discuss the gap in
the collective excitation spectrum which appears when spin-orbit interactions
are included.",0312347v2
2004-07-09,Electronic and spin properties of Rashba billiards,"Ballistic electrons confined to a billiard and subject to spin--orbit
coupling of the Rashba type are investigated, using both approximate
semiclassical and exact quantum--mechanical methods. We focus on the
low--energy part of the spectrum that has negative eigenvalues. When the spin
precession length is smaller than the radius of the billiard, the low--lying
energy eigenvalues turn out to be well described semiclassically. Corresponding
eigenspinors are found to have a finite spin polarization in the direction
perpendicular to the billiard plane.",0407247v1
2004-11-27,Geometric spin dephasing of carriers with strong spin-orbit coupling,"It has been shown that the geometric Berry-phase shift acquired by the
components of the light hole (LH) spinor during an adiabatic collision is equal
to the angular distance traveled by the wave vector. For LH, geometric
dephasing leads to equality between angular and crystal momentum relaxation
time. I will show that the same mechanism is completely ineffective for heavy
and split-off holes in bulk crystals, and in electron QSLs in spherical
nanostructures. This non-model result suggests that these carriers may be
considered as the stern candidates for implementation of dissipationless spin
currents (Spin Hall effect) and fault-tolerant qubits.",0411683v1
2004-12-19,Oscillatory spin relaxation rates in quantum dots,"Phonon-induced spin relaxation rates in quantum dots are studied as function
of in-plane and perpendicular magnetic fields, temperature and electric field,
for different dot sizes. We consider Rashba and Dresselhaus spin-orbit mixing
in diferent materials, and show how Zeeman sublevels can relax via
piezoelectric and deformation potential coupling to acoustic phonons. We find
that strong lateral and vertical confinements may induce minima in the rates at
particular values of the magnetic field, where spin relaxation times can reach
even seconds. We obtain good agreement with experimental findings in GaAs
quantum dots.",0412520v1
2005-04-07,Quantum Spin Hall Effect,"The quantum Hall liquid is a novel state of matter with profound emergent
properties such as fractional charge and statistics. Existence of the quantum
Hall effect requires breaking of the time reversal symmetry caused by an
external magnetic field. In this work, we predict a quantized spin Hall effect
in the absence of any magnetic field, where the intrinsic spin Hall conductance
is quantized in units of $2 \frac{e}{4\pi}$. The degenerate quantum Landau
levels are created by the spin-orbit coupling in conventional semiconductors in
the presence of a strain gradient. This new state of matter has many profound
correlated properties described by a topological field theory.",0504147v1
2006-05-29,Nuclear spin effect in metallic spin valve,"We study electronic transport through a ferromagnet normal-metal ferromagnet
system and we investigate the effect of hyperfine interaction between electrons
and nuclei in the normal-metal part. A switching of the magnetization
directions of the ferromagnets causes nuclear spins to precess. We show that
the effect of this precession on the current through the system is large enough
to be observed in experiment.",0605703v2
2006-09-16,Anomalous k-dependent spin splitting in wurtzite AlxGa1-xN/GaN heterostructures,"We have confirmed the k-dependent spin splitting in wurtzite AlxGa1-xN/GaN
heterostructures. Anomalous beating pattern in Shubnikov-de Haas measurements
arises from the interference of Rashba and Dresselhaus spin-orbit interactions.
The dominant mechanism for the k-dependent spin splitting at high values of k
is attributed to Dresselhaus term which is enhanced by the Delta C1-Delta C3
coupling of wurtzite band folding effect.",0609396v2
2007-01-29,"Comment on ""Nonexistence of ""Spin Transverse Force"" for a Relativistic Electron"" by Wlodek Zawadzki (cond-mat/0701387)","This is a reply to W. Zawadzki's paper (arXiv: cond-mat/0701378) on
non-exietence of spin transverse force for a relativistic electron. The force
was first proposed by the present author that the spin current will experience
a transverse force in an electric field as a relativistic quantum mechanical
effect, and in semiconductor with Rahsba spin-orbit coupling. Zawadzki's
approach is based on an incorrect relation between the velocity and canonical
momentum, and his conclusion is not true.",0701700v1
2007-03-07,Theory of resonant spin Hall effect,"A biref review is presented on resonant spin Hall effect, where a tiny
external electric field induces a saturated spin Hall current in a
2-dimensional electron or hole gas in a perpendicular magnetic field. The
phenomenon is attributted to the energy level crossing associated with the
spin-orbit coupling and the Zeeman splitting. We summarize recent theoretical
development of the effect in various systems and discuss possible experiments
to observe the effect.",0703176v1
2007-03-12,Transit-Time Spin Field-Effect-Transistor,"We propose and analyze a four-terminal metal-semiconductor device that uses
hot-electron transport through thin ferromagnetic films to inject and detect a
charge-coupled spin current transported through the conduction band of an
arbitrary semiconductor. This provides the possibility of realizing a spin
field-effect-transistor in Si, using electrostatic transit-time control in a
perpendicular magnetic field, rather than Rashba effect with spin-orbit
interaction.",0703300v1
2004-11-19,Spinning particles in the vacuum C metric,"The motion of a spinning test particle given by the Mathisson-Papapetrou
equations is studied on an exterior vacuum C metric background spacetime
describing the accelerated motion of a spherically symmetric gravitational
source. We consider circular orbits of the particle around the direction of
acceleration of the source. The symmetries of this configuration lead to the
reduction of the differential equations of motion to algebraic relations. The
spin supplementary conditions as well as the coupling between the spin of the
particle and the acceleration of the source are discussed.",0411098v1
1997-02-06,How Much of the Nucleon Spin is Carried by Glue?,"We estimate in the QCD sum rule approach the amount of the nucleon spin
carried by the gluon angular momentum: the sum of the gluon spin and orbital
angular momenta. The result indicates that gluons contribute at least one half
of the nucleon spin at scale of 1 GeV^2.",9702277v2
2007-04-06,Spin accumulation from the non-Abelian Aharonov-Bohm effect,"Recently, it has been shown that the spin-orbit coupling (SOC) of the
Dresselhaus type in $[110]$ quantum wells can be mathematically removed by a
non-Abelian gauge transformation. In the presence of an additional uniform
magnetic field, such a non-Abelian gauge flux leads to a spin accumulation at
the edges of the sample, where the relative sign of the spin accumulation
between the edges can be tuned by the sign of the Dresselhaus SOC constant. Our
prediction can be tested by Kerr measurements within the available experimental
sensitivities.",0704.0830v1
2007-07-27,Spin-triplet pairing instability of the spinon Fermi surface in a U(1) spin liquid,"Recent experiments on the organic compound \kappa-(ET)_2Cu_2(CN)_3 have
provided a promising example of a two dimensional spin liquid state. This phase
is described by a two-dimensional spinon Fermi sea coupled to a U(1) gauge
field. We study Kohn-Luttinger-like pairing instabilities of the spinon Fermi
surface due to singular interaction processes with twice-the-Fermi-momentum
transfer. We find that under certain circumstances the pairing instability
occurs in odd-orbital-angular-momentum/spin-triplet channels. Implications to
experiments are discussed.",0707.4031v1
2008-05-06,Spin-Hall Effect in A Symmetric Quantum Wells by A Random Rashba Field,"Changes dopant ion concentrations in the sides of a symmetric quantum well
are known to create a random Rashba-type spin-orbit coupling. Here we
demonstrate that, as a consequence, a finite size spin-Hall effect is also
present. Our numerical algorithm estimates the result of the Kubo formula for
the spin-Hall conductivity, by using a tight-binding approximation of the
Hamiltonian in the framework of a time-dependent Green's function formalism,
well suited for very large systems.",0805.0678v1
2008-06-05,Thermally Assisted Spin Hall Effect,"The spin polarized charge transport is systematically analyzed as a thermally
driven stochastic process. The approach is based on Kramers' equation
describing the semiclassical motion under the inclusion of stochastic and
damping forces. Due to the relativistic spin-orbit coupling the damping
experiences a relativistic correction leading to an additional contribution
within the spin Hall conductivity. A further contribution to the conductivity
is originated from the averaged underlying crystal potential, the mean value of
which depends significantly on the electric field. We derive an exact
expression for the electrical conductivity. All corrections are estimated in
lowest order of a relativistic approach and in the linear response regime.",0806.0948v1
2008-06-19,Dirac particle in gravitational field,"Classical dynamics of spinning zero-size objects in an external gravitational
field is derived from the conservation law of the stress-energy and spin
tensors. The resulting world line equations differ from those in the existing
literature. In particular, the spin of the Dirac particle does not couple to
the background curvature. As a check of consistency, the wave packet solution
of the free Dirac equation is considered. The resulting equations are shown to
include a constraint that relates the wave packet spin to its orbital angular
momentum. In the zero-size limit, both contributions to the total angular
momentum disappear simultaneously.",0806.3228v1
2008-11-19,Excitation of spin waves on a cylindrical semiconductor heterostructure with Rashba spin-orbit interaction,"Elementary excitations in a paramagnetic semiconductor quantum well confined
to a cylindrical surface are theoretically studied on the basis of coupled
spin-charge drift-diffusion equations. The electric-field-mediated eigenmodes
are optically excited by an oscillating interference pattern, which induces a
current in the outer circuit. For a cylinder with a given radius, sharp
resonances are predicted to occur in the steady-state current response, which
are due to weakly damped spin remagnetization waves.",0811.3070v1
2010-03-08,Theory of Spin-Dependent Phonon-Assisted Optical Transitions in Silicon,"A theory for the relation between the spin polarization and luminescence in
silicon is presented. The theory provides intuitive relations for
phonon-assisted optical transitions between the conduction and valence band
edges. It is shown that an opposite behavior of longitudinal and transverse
optical phonon-assisted transitions is responsible to recent experimental
results of spin injection into silicon. The effects of spin-orbit coupling and
doping are studied in detail.",1003.1709v2
2010-09-28,Effects of mechanical rotation on spin currents,"We study the Pauli--Schr\""odinger equation in a uniformly rotating frame of
reference to describe a coupling of spins and mechanical rotations. The
explicit form of the spin-orbit interaction (SOI) with the inertial effects due
to the mechanical rotation is presented. We derive equations of motion for a
wavepacket of electrons in two-dimensional planes subject to the SOI. The
solution is a superposition of two cyclotron motions with different frequencies
and a circular spin current is created by the mechanical rotation.",1009.5424v2
2011-06-03,Effective transition operators for resonant inelastic X-ray scattering,"Effective symmetry-based transition operators for resonant inelastic X-ray
scattering (RIXS) are derived that show how the scattering between different
states depends on the polarization of the incoming and outgoing X-rays. In
spherical symmetry, the effective operators can be rewritten in terms of spin
operators, although the expressions depend on the nature of the ground state.
For lower symmetries, the combined action of the crystal field and the
spin-orbit interaction breaks up the spin space and spin operators are no
longer appropiate operators. By taking iridium compounds as an example, it is
demonstrated that effective scattering operators can still be obtained. These
effective transition operators facilitate our understanding how RIXS couples to
elementary excitations.",1106.0640v1
2011-12-20,Decoherence-avoiding spin qubits in optically active quantum dot molecules,"In semiconductors, the T2* coherence time of a single confined spin is
limited either by the fluctuating magnetic environment (via the hyperfine
interaction), or by charge fluctuations (via the spin-orbit interaction). We
demonstrate that both limitations can be overcome simultaneously by using two
exchange-coupled electron spins that realize a single decoherence-avoiding
qubit. Using coherent population trapping, we generate a coherent superposition
of the singlet and triplet states of an optically active quantum-dot molecule,
and show that the corresponding T2* may exceed 200 nanoseconds.",1112.4710v2
2012-03-30,Approximate spin and pseudospin solutions of the Dirac equation for the inversely quadratic Yukawa potential and tensor interaction,"We approximately solve the Dirac equation for the inversely quadratic Yukawa
(IQY) potential including a Coulomb-like tensor potential with arbitrary
spin-orbit coupling quantum number . In the framework of the spin and
pseudospin (pspin) symmetry, we obtain the energy eigenvalue equation and the
corresponding eigenfunctions in closed form by using the Nikiforov-Uvarov
method. The numerical results show that the Coulomb-like tensor interaction
removes degeneracies between spin and pspin state doublets.",1203.6769v1
2012-06-14,DFT Calculations as a Tool to Analyse Quadrupole Splittings of Spin Crossover Fe(II) complexes,"Density functional methods have been applied to calculate the quadrupole
splitting of a series of iron(II) spin crossover complexes. Experimental and
calculated values are in reasonable agreement. In one case spin-orbit coupling
is necessary to explain the very small quadrupole splitting value of 0.77 mm/s
at 293 K for a high-spin isomer.",1206.3036v1
2013-04-24,Antiferromagnetic crystalline topological insulators,"The gapless surface Dirac cone of time reversal invariant topological
insulators is protected by time reversal symmetry due to the Kramers' theorem.
Spin degree of freedom is usually required since Kramers' theorem only
guarantees double degeneracy for spinful fermions, but not for spinless
fermions. In this paper, we present an antiferromagnetic spinless model, which
breaks time reversal symmetry. Similar to time reversal invariant topological
insulators, this model possesses a topologically non-trivial phase with a
single surface Dirac cone, which is protected by the combination of time
reversal and translation operation. Our results show that in magnetic crystals,
a single Dirac cone can exist on the surface even without any spin degree of
freedom and spin-orbit coupling.",1304.6455v1
2013-06-10,Spin Transfer of Quantum Information between Majorana Modes and a Resonator,"We show that resonant coupling and entanglement between a mechanical
resonator and majorana bound states can be achieved via spin currents in a 1D
quantum wire with strong spin-orbit interactions. The bound states induced by
vibrating and stationary magnets can hybridize thus resulting in spin-current
induced $4\pi$-periodic torque, as a function of the relative field angle,
acting on the resonator. We study the feasibility of detecting and manipulating
majorana bound states with the use of magnetic resonance force microscopy
techniques.",1306.2339v1
2013-07-30,Spin-dependent shot noise enhancement in a quantum dot,"The spin-dependent dynamical blockade was investigated in a lateral quantum
dot in a magnetic field. Spin-polarized edge channels in the two-dimensional
leads and the spatial distribution of Landau orbitals in the dot modulate the
tunnel coupling of the quantum dot level spectrum. In a measurement of the
electron shot noise we observe a pattern of super-Poissonian noise which is
correlated to the spin-dependent competition between different transport
channels.",1307.8165v1
2014-08-09,Spin-valley relaxation and quantum transport regimes in two-dimensional transition metal dichalcogenides,"Quantum transport and spintronics regimes are studied in p- and n-doped
atomic layers of hexagonal transition metal dichalcogenides (TMDCs), subject to
the interplay between the valley structure and spin-orbit coupling. We find how
spin relaxation of carriers depends on their areal density and show that it
vanishes for holes near the band edge, leading to the density-independent spin
diffusion length, and we develop a theory of weak
localisation/antilocalisation, describing the crossovers between the
orthogonal, double-unitary and symplectic regimes of quantum transport in
TMDCs.",1408.2121v2
2014-11-10,Classical and quantum chaotic angular-momentum pumps,"We study directed transport of charge and intrinsic angular momentum by
periodically driven scattering in the regime of fast and strong driving. A
spin-orbit coupling through a kicked magnetic field confined to a compact
region in space leads to irregular scattering and triggers spin flips in a
spatially asymmetric manner which allows to generate polarized currents. The
dynamical mechanisms responsible for the spin separation carry over to the
quantum level and give rise to spin pumping. Our theory, based on the Floquet
formalism, is confirmed by numerical solutions of the time-dependent
inhomogeneous Schr\""{o}dinger equation with a continuous source term.",1411.2659v2
2014-12-28,Majorana Edge States and Braiding in an Exactly Solvable One-dimensional Spin Model,"We derive an exactly solvable one-dimensional (1D) spin model from the
three-band Hubbard model with a strong spin-orbit coupling by introducing U(1)
gauge fields to the isospin states. We find that it has a topological
nontrivial phase characterized by Majorana end modes which are protected by a
new Z_2 topological invariant related to the parity of the lattice sites (odd
or even number of sites) in the spin chain. With the protection of this Z_2
topological invariant, a novel braiding of two Majorana edge states in this
strictly geometric 1D chain is realized. We also discuss the possible
realization of the gauge fields.",1412.8183v1
2016-07-24,Consequences of the thermal dependence of spin orbit coupling in semiconductors,"The $\vec{k}.\vec{p}$ perturbation theory in semiconductor modifies some spin
related parameters of the semi-conducting system. Furthermore, renormalization
of the Kane model parameters occurs when temperature appears in the scenario.
In this paper, we have analysed the consequences of this renormalized Kane
parameters on some spin transport issues. It is noteworthy to study that the
temperature corrected scenario, explained here can open up a new direction
towards the spin calorimetric applications in semiconductors.",1607.07026v1
2017-03-10,A microscopic formulation of dynamical spin injection in ferromagnetic-nonmagnetic heterostructures,"We develop a microscopic formulation of dynamical spin injection in
heterostructure comprising nonmagnetic metals in contact with ferromagnets. The
spin pumping current is expressed in terms of Green's function of the
nonmagnetic metal attached to the ferromagnet where a precessing magnetization
is induced. The formulation allows for the inclusion of spin-orbit coupling and
disorder. The Green's functions involved in the expression for the current are
expressed in real-space lattice coordinates and can thus be efficiently
computed using recursive methods.",1703.03775v2
2013-09-07,Fast spin control in a two-electron double quantum dot by dynamical invariants,"Inverse engineering of electric fields has been recently proposed to achieve
fast and robust spin control in a single-electron quantum dot with spin-orbit
coupling. In this paper we design, by inverse engineering based on
Lewis-Riesenfeld invariants, time-dependent electric fields to realize fast
transitions in the selected singlet-triplet subspace of a two-electron double
quantum dot. We apply two-mode driving schemes, directly employing the
Lewis-Riesenfeld phases, to minimize the electric field necessary to design
flexible protocols and perform spin manipulation on the chosen timescale.",1309.1916v1
2015-12-11,Electrically controlled spin-transistor operation in helical magnetic field,"A proposal of electrically controlled spin transistor in helical magnetic
field is presented. In the proposed device, the transistor action is driven by
the Landau-Zener transitions that lead to a backscattering of spin polarized
electrons and switching the transistor into the high-resistance state (off
state). The on/off state of the transistor can be controlled by the
all-electric means using Rashba spin-orbit coupling that can be tuned by the
voltages applied to the side electrodes.",1512.03653v1
2015-12-18,Origin of Lattice Spin in Graphitic Systems,"Lattice spin, in planar condensed matter system with emergent Dirac
dispersion, is shown to emerge from the inherent SU(2) symmetry, arising
through Schwingers angular momentum construction from anti-commuting Heisenberg
operators of the sub-lattices. The presence of a mass term in the emergent
Dirac dispersion is essential for the existence of this spin. The usual hopping
term, that entangles the two sub-lattices, leads to the orbital counterpart.
Relative sub-lattice displacements, that couple to the effective Dirac fermions
like U(1) gauge fields, do not effect the lattice spin.",1512.06037v1
2019-09-03,Quasiclassical expressions for the free energy of superconducting systems,"In the seminal work by G. Eilenberger [Z. Phys. 214, 195 (1968)], the
quasiclassical expression for the free energy of spin-singlet superconductor
has been suggested. Starting from the Luttinger-Ward formulation we derive the
Eilenberger free energy and find its generalization for superconductor or
superfluid with spin-triplet correlations. Besides ordinary superconductors
with various scattering mechanisms, the obtained free energy functional can be
used for systems with spin-triplet pairing such as superfluid $^3$He and
superconducting systems with spatially-inhomogeneous exchange field or
spin-orbit coupling. Using this general result we derive the simplified
expression for the free energy in the diffusive limit in terms of the
momentum-averaged propagators.",1909.00992v1
2018-03-15,Non-centrosymmetric superconductors on honeycomb lattice,"We study non-centrosymmetric topological superconductivity in correlated
doped quantum spin-Hall insulators (QSHI) on honeycomb lattice without
inversion symmetry where the intrinsic (Kane-Mele) and Rashba spin-orbit
couplings can in general exist. We explore the generic topologically
non-trivial superconducting phase diagram of the model system. Over a certain
parameter space, the parity-mixing superconducting state with co-existing
spin-singlet $d$+$id$ and spin-triplet $p$+$ip$-wave pairing is found. On a
zigzag nanoribbon, the parity-mixing superconducting state shows co-existing
helical and chiral Majorana fermions at edges. Relevance of our results for
experiments is discussed.",1803.05751v1
2019-04-10,Spin-momentum locking and Majorana fermions in charge carrier hole epitaxial wires,"Epitaxial semiconductor nanowires with charge carrier holes can exhibit an
infinite mass of holes and spin-locking due to chiral spectrum linear in
momentum and spin. The criterion for emergence of topological superconductivity
and Majorana fermions in these wires coupled to an s-type superconductors is
the same as in topological insulators, and opposite to the criterion of onset
of Majorana modes in quantum wires with parabolic spectrum in the presence of
spin-orbit interactions.",1904.05088v2
2020-11-20,Presence of x-ray magnetic circular dichroism effect for zero-magnetization state in antiferromagnetism,"X-ray magnetic circular dichroism (XMCD) is generally not observed for
antiferromagnetic (AFM) states because XMCD signals from the antiparallelly
coupled spins cancel each other. In this letter, we theoretically show the
presence of an XMCD signal from compensated two-dimensional triangle AFM
structures on a Kagome lattice. The calculation reveals the complete
correspondence between the XMCD spectra and the sign of the spin chirality: the
XMCD signal only appears when the spin chirality is negative. This XMCD signal
originates from the different absorption coefficients of the three sublattices
reflecting different charge density anisotropies and directions of spin and
orbital magnetic moments.",2011.12773v1
2021-04-26,Hyperfine Structure of Transition Metal Defects in SiC,"Transition metal (TM) defects in silicon carbide (SiC) are a promising
platform in quantum technology, especially because some TM defects emit in the
telecom band. We develop a theory for the interaction of an active electron in
the $D$-shell of a TM defect in SiC with the TM nuclear spin and derive the
effective hyperfine tensor within the Kramers doublets formed by the spin-orbit
coupling. Based on our theory we discuss the possibility to exchange the
nuclear and electron states with potential applications for nuclear spin
manipulation and long-lived nunclear-spin based quantum memories.",2104.12351v1
2020-03-04,Crossover of spin Hall to quantum anomalous Hall effect in PbC/MnSe heterostructures,"In this paper, we study topological properties and Hall conductivities in
PbC/MnSe heterostructure under the illumination of a circularly polarized
light. At high frequency regime, energy gap, Chern numbers, and Hall
conductivities are studied based on the Floquet theory and Green's function
formalism, respectively. The interplay between spin orbit coupling and light
leads to topological phase transition between anomalous Hall states and spin
Hall states, which is related to the emission and absorption of two virtual
photons. The anomalous Hall conductivities are dependent on polarization of
light, while the spin Hall conductivity is independent.",2003.02072v1
2023-10-27,Resilient Intraparticle Entanglement and its Manifestation in Spin Dynamics of Disordered Dirac Matter,"Topological quantum matter exhibits novel transport phenomena driven by
entanglement between internal degrees of freedom, as for instance generated by
spin-orbit coupling effects. Here we report on a direct connection between the
mechanism driving spin relaxation and the intertwined dynamics between spin and
sublattice degrees of freedom in disordered graphene. Beyond having a direct
observable consequence, such intraparticle entanglement is shown to be
resilient to disorder, pointing towards a novel resource for quantum
information processing.",2310.17950v1
2023-12-22,Hyperbolic Spin Waves in Magnetic Polar Metals,"We demonstrate the emergence of collective spin modes with hyperbolic
dispersion in three-dimensional spin-orbit coupled polar metals magnetized by
intrinsic ordering or applied fields. These particle-hole bound states exist
for arbitrarily weak repulsive interactions; they are optically accessible and
can be used to generate pure spin current when magnetization is tilted away
from the polar axis. We suggest material hosts for these excitations and
discuss their potential relevance to nanoscale spintronic and polaritonic
applications.",2312.14377v2
2015-06-22,All-electric all-semiconductor spin field effect transistors,"The spin field effect transistor envisioned by Datta and Das opens a gateway
to spin information processing. Although the coherent manipulation of electron
spins in semiconductors is now possible, the realization of a functional spin
field effect transistor for information processing has yet to be achieved,
owing to several fundamental challenges such as the low spin-injection
efficiency due to resistance mismatch, spin relaxation, and the spread of spin
precession angles. Alternative spin transistor designs have therefore been
proposed, but these differ from the field effect transistor concept and require
the use of optical or magnetic elements, which pose difficulties for the
incorporation into integrated circuits. Here, we present an all-electric and
all-semiconductor spin field effect transistor, in which these obstacles are
overcome by employing two quantum point contacts as spin injectors and
detectors. Distinct engineering architectures of spin-orbit coupling are
exploited for the quantum point contacts and the central semiconductor channel
to achieve complete control of the electron spins -- spin injection,
manipulation, and detection -- in a purely electrical manner. Such a device is
compatible with large-scale integration and hold promise for future spintronic
devices for information processing.",1506.06507v1
2019-07-07,"Spin-1 Dirac half-metal, spin-gapless semiconductor, and spin-polarized massive Dirac dispersion in transition metal dihalide monolayers","Spin-1 condensed matter systems characterized by the combination of a
Dirac-like dispersion and flat bands are ideal for realizing high-temperature
electronics and spintronic technologies in the absence of external magnetic
field. In this study, we propose a three-band tight binding model, with
spin-polarized Haldane-like next-nearest-neighbour tunnelling, on dice lattice
and show that spin-1 Dirac half-metal, spin-1 Dirac spin-gapless semiconductor,
and spin-polarized spin-1 massive Dirac dispersion with nontrivial topology can
exist in two-dimensional ferromagnetic condensed matter systems with electron
spin polarization P = 1. The proposed spin-polarized spin-1 phases can be
realized in ferromagnetic transition metal dihalides MX2 monolayers
effectively. By using first principle calculations, we show that a small
compressive strain leads MX2 monolayers to be spin-one Dirac half-metal for M =
Fe and X = Br, Cl while spin-one Dirac spin-gapless semiconductor for M = Co
and X = Br, Cl. Spin-one Dirac spin-gapless semiconductors CoBr2 and CoCl2
embeds flat band ferromagnetism where spin-orbit coupling opens a topologically
non-trivial Dirac gap between dispersing valance and conduction band while
leaving flat band unaffected. The intrinsic flat-band ferromagnetism in
spin-polarized spin-1 massive Dirac dispersion plays key role in materializing
quantum anomalous Hall state with Chern number C = -2.",1907.07756v1
2020-01-14,Spin splitting with persistent spin textures induced by the line defect in 1T-phase of monolayer transition metal dichalcogenides,"The spin splitting driven by spin-orbit coupling in monolayer (ML) transition
metal dichalcogenides (TMDCs) family has been widely studied only for the
1H-phase structure, while it is not profound for the 1T-phase structure due to
the centrosymmetric of the crystal. Based on first-principles calculations, we
show that significant spin splitting can be induced in the ML 1T-TMDCs by
introducing the line defect. Taking the ML PtSe2 as a representative example,
we considered the most stable form of the line defects, namely Se-vacancy line
defect (Se-VLD). We find that large spin splitting is observed in the defect
states of the Se-VLD, exhibiting a highly unidirectional spin configuration in
the momentum space. This peculiar spin configuration may yield the so-called
persistent spin textures (PST), a specific spin structure resulting in
protection against spin-decoherence and supporting an extraordinarily long spin
lifetime. Moreover, by using k.p perturbation theory supplemented with symmetry
analysis, we clarified that the emerging of the spin splitting maintaining the
PST in the defect states is originated from the inversion symmetry breaking
together with one-dimensional nature of the Se-VLD engineered ML PtSe2. Our
findings pave a possible way to induce the significant spin splitting in the ML
1T-TMDCs, which could be highly important for designing spintronic devices.",2001.04613v2
2019-08-21,Ordering phenomena of spin trimers accompanied by large geometrical Hall effect,"The wavefuntion of conduction electrons moving in the background of a
non-coplanar spin structure can gain a quantal phase - Berry phase - as if the
electrons were moving in a strong fictitious magnetic field. Such an emergent
magnetic field effect is approximately proportional to the solid angle
subtended by the spin moments on three neighbouring spin sites, termed the
scalar spin chirality. The entire spin chirality of the crystal, unless
macroscopically canceled, causes the geometrical Hall effect of real-space
Berry-phase origin, whereas the intrinsic anomalous Hall effect (AHE) in a
conventional metallic ferromagnet is of the momentum-space Berry-phase origin
induced by relativistic spin-orbit coupling (SOC). Here, we report the ordering
phenomena of the spin-trimer scalar spin chirality and the consequent large
geometrical Hall effect in the breathing kagom\'e lattice compound
Dy$_3$Ru$_4$Al$_{12}$, where the Dy$^{3+}$ moments form non-coplanar spin
trimers with local spin chirality. Using neutron diffraction, we show that the
local spin chirality of the spin trimers as well as its ferroic/antiferroic
orders can be switched by an external magnetic field, accompanying large
changes in the geometrical Hall effect. Our finding reveals that systems
composed of tunable spin trimers can be a fertile field to explore large
emergent electromagnetic responses arising from real-space topological magnetic
orders.",1908.07728v1
2018-10-30,Room temperature spin Hall effect in graphene/MoS$_2$ van der Waals heterostructures,"Graphene is an excellent material for long distance spin transport but allows
little spin manipulation. Transition metal dichalcogenides imprint their strong
spin-orbit coupling into graphene via proximity effect, and it has been
predicted that efficient spin-to-charge conversion due to spin Hall and
Rashba-Edelstein effects could be achieved. Here, by combining Hall probes with
ferromagnetic electrodes, we unambiguously demonstrate experimentally spin Hall
effect in graphene induced by MoS$_2$ proximity and for varying temperature up
to room temperature. The fact that spin transport and spin Hall effect occur in
different parts of the same material gives rise to a hitherto unreported
efficiency for the spin-to-charge voltage output. Remarkably for a single
graphene/MoS$_2$ heterostructure-based device, we evidence a superimposed
spin-to-charge current conversion that can be indistinguishably associated with
either the proximity-induced Rashba-Edelstein effect in graphene or the spin
Hall effect in MoS$_2$. By comparing our results to theoretical calculations,
the latter scenario is found the most plausible one. Our findings pave the way
towards the combination of spin information transport and spin-to-charge
conversion in two-dimensional materials, opening exciting opportunities in a
variety of future spintronic applications.",1810.12481v1
2021-02-06,Spin pumping and inverse spin Hall effect in CoFeB/IrMn heterostructures,"High spin to charge conversion efficiency is the requirement for the
spintronics devices which is governed by spin pumping and inverse spin Hall
effect (ISHE). In last one decade, ISHE and spin pumping are heavily
investigated in ferromagnet/ heavy metal (HM) heterostructures. Recently
antiferromagnetic (AFM) materials are found to be good replacement of HMs
because AFMs exhibit terahertz spin dynamics, high spin-orbit coupling, and
absence of stray field. In this context we have performed the ISHE in CoFeB/
IrMn heterostructures. Spin pumping study is carried out for
$Co_{40}Fe_{40}B_{20} (12\ nm)/ Cu (3\ nm)/ Ir_{50}Mn_{50} (t\ nm)/ AlO_{x} (3\
nm)$ samples where \textit{t} value varies from 0 to 10 nm. Damping of all the
samples are higher than the single layer CoFeB which indicates that spin
pumping due to IrMn is the underneath mechanism. Further the spin pumping in
the samples are confirmed by angle dependent ISHE measurements. We have also
disentangled other spin rectifications effects and found that the spin pumping
is dominant in all the samples. From the ISHE analysis the real part of spin
mixing conductance (\textit{$g_{r}^{\uparrow \downarrow}$}) is found to be
0.704 $\pm$ 0.003 $\times$ $10^{18}$ $m^{-2}$.",2102.03624v2
2023-10-23,Microscopic theory of spin Seebeck effect in antiferromagnets,"We develop a microscopic theory for the spin Seebeck effect (SSE) in N\'eel
and canted phases of antiferromagnetic insulators. We calculate the DC spin
current tunneling from the antiferromagnet to an attached metal, incorporating
the spin-wave theory and the non-equilibrium Green's function approach. Our
result shows a sign change of the spin current at the spin-flop phase
transition between N\'eel and canted phases, which is in agreement with a
recent experiment for the SSE of $\rm Cr_2O_3$ in a semi-quantitative level.
The sign change can be interpreted from the argument based on the density of
states of up- and down-spin magnons, which is related to the polarized-neutron
scattering spectra. The theory also demonstrates that the spin current in the
N\'eel phase is governed by the magnon correlation, while that in the canted
phase consists of two parts: Contributions from not only the magnon dynamics
but also the static transverse magnetization. This result leads to a prediction
that at sufficiently low temperatures, the spin current non-monotonically
changes as a function of magnetic field in the canted phase. Towards a more
unified understanding of the SSE in antiferromagnets, we further discuss some
missing links of theories of SSE: Interface properties, effects of the
transverse spin moment in the canted phase, the spin-orbit coupling in the
metal, etc. Finally, we compare the SSE of antiferromagnets with those of
different magnetic phases such as ferromagnets, ferrimagnets, an
one-dimensional spin liquid, a spin-nematic liquid, and a spin-Peierls
(dimerized) phase.",2310.15292v2
2003-02-14,Microscopic Identification of the D-vector in Triplet Superconductor Sr_2RuO_4,"Triplet superconductivity in Sr_2RuO_4 is investigated with main interest on
its internal degree of freedom. We perform a microscopic calculation to
investigate how the chiral state d(k) = (k_x \pm ik_y)z is realized among the
underlying six degenerate states. Starting from the three band Hubbard model
with spin-orbit interaction, we use a perturbation theory in order to calculate
the pairing interaction. The p-wave superconductivity with T_c \sim 1.5K is
obtained in the moderately weak coupling region. It is shown that the orbital
dependent superconductivity (ODS) robustly appears in Sr_2RuO_4. We determine
the stabilized state by solving the Eliashberg equations. It is found that the
Hund coupling term as well as the spin-orbit interaction is necessary for the
``symmetry breaking interaction''. The main result is that the chiral state is
stabilized in case of the p-wave symmetry with the main \gamma-band, which is
obtained in the perturbation theory. When we assume the other pairing symmetry
including the f-wave state, the symmetry breaking interaction gives the other
D-vector. The electronic structure constructed from the t_2g-orbitals is
essential for this result.",0302299v1
2004-06-21,"Orbital ordering and one-dimensional magnetic correlation in vanadium spinel oxides AV2O4 (A = Zn, Mg, or Cd)","We present our theoretical results on the mechanism of two transitions in
vanadium spinel oxides $A$V$_2$O$_4$ ($A$=Zn, Mg, or Cd) in which magnetic V
cations constitute a geometrically-frustrated pyrochlore structure. We have
derived an effective spin-orbital-lattice coupled model in the strong
correlation limit of the multiorbital Hubbard model, and applied Monte Carlo
simulation to the model. The results reveal that the higher-temperature
transition is a layered antiferro-type orbital ordering accompanied by
tetragonal Jahn-Teller distortion, and the lower-temperature transition is an
antiferromagnetic spin ordering. The orbital order lifts the magnetic
frustration partially, and induces spatial anisotropy in magnetic exchange
interactions. In the intermediate phase, the system can be considered to
consist of weakly-coupled antiferromagnetic chains lying in the perpendicular
planes to the tetragonal distortion.",0406462v1
2008-04-18,Antibonding ground states in semiconductor artificial molecules,"The spin-orbit interaction is a crucial element of many semiconductor
spintronic technologies. Here we report the first experimental observation, by
magneto-optical spectroscopy, of a remarkable consequence of the spin-orbit
interaction for holes confined in the molecular states of coupled quantum dots.
As the thickness of the barrier separating two coupled quantum dots is
increased, the molecular ground state changes character from a bonding orbital
to an antibonding orbital. This result is counterintuitive, and antibonding
molecular ground states are never observed in natural diatomic molecules. We
explain the origin of the reversal using a four band k.p model that has been
validated by numerical calculations that account for strain. The discovery of
antibonding molecular ground states provides new opportunities for the design
of artificially structured materials with complex molecular properties that
cannot be achieved in natural systems.",0804.3097v1
2010-09-22,Local symmetry and magnetic anisotropy in multiferroic MnWO4 and antiferromagnetic CoWO4 studied by soft x-ray absorption spectroscopy,"Soft x-ray absorption experiments on the transition metal L2,3 edge of
multiferroic MnWO4 and antiferromagnetic CoWO4 are presented. The observed
linear polarization dependence, analyzed by full-multiplet calculations, is
used to determine the ground state wave function of the magnetic Mn2+ and Co2+
ions. The impact of the local structure and the spin-orbit coupling on the
orbital moment is discussed in terms of the single-ion anisotropy. It is shown
that the orbital moment in CoWO4 is responsible for the collinear
antiferromagnetism, while the small size of spin-orbit coupling effects make
spiral magnetic order in MnWO4 possible, enabling the material to be
multiferroic.",1009.4338v1
2012-06-30,Microscopic Theory of Rashba Interaction in Magnetic Metal,"Theory of Rashba spin-orbit coupling in magnetic metals is worked out from
microscopic Hamiltonian describing d-orbitals. When structural inversion
symmetry is broken, electron hopping between $d$-orbitals generates chiral
ordering of orbital angular momentum, which combines with atomic spin-orbit
coupling to result in the Rashba interaction. Rashba parameter characterizing
the interaction is band-specific, even reversing its sign from band to band.
Large enhancement of the Rashba parameter found in recent experiments is
attributed to the orbital mixing of 3d magnetic atoms with non-magnetic heavy
elements as we demonstrate by first-principles and tight-binding calculations.",1207.0089v1
2017-03-01,Topological Fulde-Ferrell states in alkaline-earth-metal-like atoms near an orbital Feshbach resonance,"We study the effects of synthetic spin-orbit coupling on the pairing physics
in quasi-one-dimensional ultracold Fermi gases of alkaline-earth-metal-like
atoms near an orbital Feshbach resonance (OFR). The interplay between
spin-orbit coupling and pairing interactions near the OFR leads to an
interesting topological Fulde-Ferrell state, where the nontrivial topology of
the state is solely encoded in the closed channel with a topologically trivial
Fulde-Ferrell pairing in the open channel. We confirm the topological property
of the system by characterizing the Zak phase and the edge states. The
topological Fulde-Ferrell state can be identified by the momentum-space density
distribution obtained from time-of-flight images.",1703.00138v2
2014-05-12,Multiple lattice instabilities resolved by magnetic-field and disorder sensitivities in cubic paramagnetic phase of the orbital-degenerate frustrated spinel MgV$_2$O$_4$,"Ultrasound velocity measurements of the orbital-degenerate frustrated spinel
MgV$_2$O$_4$ are performed in the high-purity single crystal which exhibits
successive structural and antiferromagnetic phase transitions, and in the
disorder-introduced single crystal which exhibits spin-glass-like behavior. The
measurements reveal that two-types of unusual temperature dependence of the
elastic moduli coexist in the cubic paramagnetic phase, which are resolved by
magnetic-field and disorder sensitivities: huge Curie-type softening with
decreasing temperature, and concave temperature dependence with a
characteristic minimum. These elastic anomalies suggest the coupling of lattice
to coexisting orbital fluctuations and orbital-spin-coupled excitations.",1405.2802v1
2015-12-22,(C$_{4}$H$_{12}$N$_{2}$)[CoCl$_{4}$] -tetrahedrally coordinated Co$^{2+}$ without the orbital degeneracy,"We report on the synthesis, crystal structure, and magnetic properties of a
previously unreported Co$^{2+}$ $S={3 \over 2}$ compound,
(C$_{4}$H$_{12}$N$_{2}$)[CoCl$_{4}$], based upon a tetrahedral crystalline
environment. The $S={3 \over 2}$ magnetic ground state of Co$^{2+}$, measured
with magnetization, implies an absence of spin-orbit coupling and orbital
degeneracy. This contrasts with compounds based upon an octrahedral and even
known tetrahedral Co$^{2+}$ based systems where a sizable spin-orbit coupling
is measured. The compound is characterized with single crystal x-ray
diffraction, magnetic susceptibility, infrared, and ultraviolet/visible
spectroscopy. Magnetic susceptibility measurements find no magnetic ordering
above 2 K. The results are also compared with the previously known monoclinic
hydrated analogue.",1512.07124v1
2014-06-15,Dynamical topological phases in quenched spin-orbit coupled degenerate Fermi gas,"The spin-orbit coupled degenerate Fermi gas provides a totally new platform
to realize topological superfluids and related topological excitations.
Previous studies have mainly focused on the properties of the ground state.
Here we consider a two-dimensional Fermi gas with Rashba spin-orbit coupling
subject to a perpendicular Zeeman field. For this system, we have found that
its ground state topological structure is captured by the spin texture, which
is readily measurable in experiments. We show that, when the Zeeman field is
suddenly quenched, dynamical topological phases can be realized. More
specifically, three post-quench dynamical phases can be identified according to
the asymptotic behavior of the order parameter. In the undamped phase, a
persistent oscillation of the order parameter may support a topological Floquet
state with multiple edge states. In the Landau damped phase, the magnitude of
the order parameter approaches a constant via a power-law decay, and this
system can support a dynamical topological phase with a pair of edge states at
the boundary. In the over-damped phase, the order parameter decays to zero
exponentially although the condensate fraction remains finite. These
predictions can be observed in the strong coupling regime of ultracold Fermi
gas.",1406.3821v2
2021-03-08,Kondo effect and spin-orbit coupling in graphene quantum dots,"The Kondo effect is a cornerstone in the study of strongly correlated
fermions. The coherent exchange coupling of conduction electrons to local
magnetic moments gives rise to a Kondo cloud that screens the impurity spin.
Whereas complete Kondo screening has been explored widely, realizations of the
underscreened scenario - where only some of several Kondo channels participate
in the screening - remain rare. Here we report the observation of fully
screened and underscreened Kondo effects in quantum dots in bilayer graphene.
More generally, we introduce a unique platform for studying Kondo physics. In
contrast to carbon nanotubes, whose curved surfaces give rise to strong
spin-orbit coupling breaking the SU(4) symmetry of the electronic states
relevant for the Kondo effect, we study a nominally flat carbon material with
small spin-orbit coupling. Moreover, the unusual two-electron triplet ground
state in bilayer graphene dots provides a route to exploring the underscreened
spin-1 Kondo effect.",2103.04864v1
2021-10-06,Anomalously small superconducting gap in the strong spin-orbit coupled superconductor: $ β- $Tungsten,"Thin films of $ \beta- $tungsten host superconductivity in the presence of
strong spin-orbit coupling. This non-equilibrium crystalline phase of tungsten
has attracted considerable attention in recent years due to its giant spin Hall
effect and the potential promise of exotic superconductivity. However, more
than 60 years after its discovery, superconductivity in this material is still
not well understood. Using time-domain THz spectroscopy, we measure the
frequency response of the complex optical conductivity of $ \beta- $tungsten
thin film with a T$_c$ of 3.7 K in its superconducting state. At temperatures
down to 1.6 K, we find that both the superconducting gap and the superfluid
spectral weight are much smaller than that expected for a weakly coupled
superconductor given the T$_c$. The conclusion of a small gap holds up even
when accounting for possible inhomogeneities in the system, which could come
from other crystalline forms of tungsten (that are not superconducting at these
temperatures) or surface states on $ \beta- $tungsten grains. Using detailed
X-ray diffraction measurements, we preclude the possibility of significant
amount of other tungsten allotropes, strongly suggesting the topological
surface states of $ \beta- $tungsten play the role of inhomogeneity in these
films. Our observations pose a challenge and opportunity for a theory of
strongly anisotropic normal metals with strong spin-orbit coupling to describe.",2110.02464v1
2007-09-10,Spin-gap behaviour in the 2-leg spin-ladder BiCu2PO6,"We present magnetic suscceptibility and heat capacity data on a new S=1/2
two-leg spin ladder compound BiCu2PO6. From our susceptibility analysis, we
find that the leg coupling J1/k_B is ~ 80 K and the ratio of the rung to leg
coupling J2/J1 ~ 0.9. We present the magnetic contribution to the heat capacity
of a two-leg ladder. The spin-gap Delta/k_B =3 4 K obtained from the heat
capacity agrees very well with that obtained from the magnetic susceptibility.
Significant inter-ladder coupling is suggested from the susceptibility
analysis. The hopping integrals determined using Nth order muffin tin orbital
(NMTO) based downfolding method lead to ratios of various exchange couplings in
agreement with our experimental data. Based on our band structure analysis, we
find the inter-ladder coupling in the bc-plane J2 to be about 0.75J1 placing
the compound presumably close to the quantum critical limit.",0709.1338v1
2017-06-28,Electric control of the edge magnetization in zigzag stanene nanoribbon,"There has been tremendous interest in manipulating electron and hole-spin
states in low-dimensional structures for electronic and spintronic
applications. We study the edge magnetic coupling and anisotropy in zigzag
stanene nanoribbons, by first-principles calculations. Taking into account
considerable spin-orbit coupling and ferromagnetism at each edge, zigzag
stanene nanoribbon is insulating and its band gap depends on the inter-edge
magnetic coupling and the magnetization direction. Especially for nanoribbon
edges with out-of-plane antiferromagnetic coupling, two non-degenerate valleys
of edge states emerge and the spin degeneracy is tunable by a transverse
electric field, which give full play to spin and valley degrees of freedom.
More importantly, both the magnetic order and anisotropy can be selectively
controlled by electron and hole doping, demonstrating a readily accessible
gate-induced modulation of magnetism. These intriguing features offer a
practical avenue for designing energy-efficient devices based on multiple
degrees of freedom of electron and magneto-electric couplings.",1706.09098v1
2022-12-19,NaRuO$_2$: Kitaev-Heisenberg exchange in triangular-lattice setting,"Kitaev exchange, a new paradigm in quantum magnetism research, occurs for
90$^{\circ}$ metal-ligand-metal links, $t_{2g}^5$ transition ions, and sizable
spin-orbit coupling. It is being studied in honeycomb compounds but also on
triangular lattices. While for the former it is known by now that the Kitaev
intersite couplings are ferromagnetic, for the latter the situation is unclear.
Here we pin down the exchange mechanisms and determine the effective coupling
constants in the $t_{2g}^5$ triangular-lattice material NaRuO$_2$, recently
found to host a quantum spin liquid ground state. We show that, compared to
honeycomb compounds, the characteristic triangular-lattice cation surroundings
dramatically affect exchange paths and effective coupling parameters, changing
the Kitaev interactions to antiferromagnetic. The quantum chemical analysis and
subsequent effective spin model computations provide perspective onto the
nature of the experimentally observed quantum spin liquid -- it seemingly
implies finite longer-range exchange, and the atypical proximity to
ferromagnetic order is related to sizable ferromagnetic Heisenberg
nearest-neighbor couplings.",2212.09365v2
2005-03-04,Can the interface between a non-ideal ferromagnet and a semiconductor quantum wire acts as an ideal spin filter?,"The problem of spin injection across the interface between a non-ideal
ferromagnet (less than 100% spin polarization) and a semiconductor
(paramagnetic) quantum wire is examined in the presence of Rashba spin orbit
coupling and an axial magnetic field along the wire axis. The field is caused
by the ferromagnet magnetized along the wire axis. At low temperatures and for
certain injection energies, the interface can act as an ideal spin filter
allowing injection only from the majority spin band of the ferromagnet. Thus,
100% spin filtering can take place even if the ferromagnet itself is less than
100% spin polarized. Below a critical value of the magnetic field, there are
two injection energies for which ideal (100%) spin filtering is possible; above
this critical field, there is only one such injection energy.",0503112v1
2005-06-27,Spin transverse force on spin current in an electric field,"As a relativistic quantum mechanical effect, it is shown that the electric
field exerting a transverse force on an electron spin 1/2 only if the electron
is moving and the spin is polarized along the electric field. The spin force,
analogue to the Lorentz for on an electron charge in a magnetic field, is
perpendicular to the electric field and the spin current polarized anong the
electric field. This spin-dependent force can be used to understand the
zitterbewegung of electron wave packet with spin-orbit coupling and is relevant
to the generation of the charge Hall effect driven by the spin current in
semiconductors.",0506676v2
2006-03-01,Spin precession and alternating spin polarization in spin-3/2 hole systems,"The spin density matrix for spin-3/2 hole systems can be decomposed into a
sequence of multipoles which has important higher-order contributions beyond
the ones known for electron systems [R. Winkler, Phys. Rev. B \textbf{70},
125301 (2004)]. We show here that the hole spin polarization and the
higher-order multipoles can precess due to the spin-orbit coupling in the
valence band, yet in the absence of external or effective magnetic fields. Hole
spin precession is important in the context of spin relaxation and offers the
possibility of new device applications. We discuss this precession in the
context of recent experiments and suggest a related experimental setup in which
hole spin precession gives rise to an alternating spin polarization.",0603025v2
2006-12-08,Spin transport in Heisenberg antiferromagnets,"We analyze spin transport in insulating antiferromagnets described by the XXZ
Heisenberg model in two and three dimensions. Spin currents can be generated by
a magnetic-field gradient or, in systems with spin-orbit coupling,
perpendicular to a time-dependent electric field. The Kubo formula for the
longitudinal spin conductivity is derived analogously to the Kubo formula for
the optical conductivity of electronic systems. The spin conductivity is
calculated within interacting spin-wave theory. In the Ising regime, the XXZ
magnet is a spin insulator. For the isotropic Heisenberg model, the
dimensionality of the system plays a crucial role: In d=3 the regular part of
the spin conductivity vanishes linearly in the zero frequency limit, whereas in
d=2 it approaches a finite zero frequency value.",0612215v1
2007-02-19,Spin relaxation times in disordered graphene,"We consider two mechanisms of spin relaxation in disordered graphene. i) Spin
relaxation due to curvature spin orbit coupling caused by ripples. ii) Spin
relaxation due to the interaction of the electronic spin with localized
magnetic moments at the edges. We obtain analytical expressions for the spin
relaxation times, tau_SO and tau_J due to both mechanisms and estimate their
values for realistic parameters of graphene samples. We obtain that spin
relaxation originating from these mechanisms is very weak and spin coherence is
expected in disordered graphene up to samples of length L ~ 1 micron.",0702433v2
2007-07-19,Spin injection and relaxation in a mesoscopic superconductor,"We study spin accumulation and spin relaxation in a superconducting nanowire.
Spins are injected and detected by using a set of magnetic tunnel contact
electrodes, closely spaced along the nanowire. We observe a giant enhancement
of the spin accumulation of up to five orders of magnitude on transition into
the superconducting state, consistent with the expected changes in the density
of states. The spin relaxation length decreases by an order of magnitude from
its value in the normal state. These measurements combined with our theoretical
model, allow us to distinguish the individual spin flip mechanisms present in
the transport channel. Our conclusion is that magnetic impurities rather than
spin-orbit coupling dominate spin-flip scattering in the superconducting state.",0707.2879v3
2008-04-14,Spin and Charge Shot Noise in Mesoscopic Spin Hall Systems,"Injection of unpolarized charge current through the longitudinal leads of a
four-terminal two-dimensional electron gas with the Rashba spin-orbit (SO)
coupling and/or SO scattering off extrinsic impurities is responsible not only
for the pure spin Hall current in the transverse leads, but also for random
time-dependent current fluctuations. We employ the scattering approach to
current-current correlations in multiterminal nanoscale conductors to analyze
the shot noise of transverse pure spin Hall and zero charge current, or
transverse spin current and non-zero charge Hall current, driven by unpolarized
or spin-polarized longitudinal current, respectively. Since any spin-flip acts
as an additional source of noise, we argue that these shot noises offer a
unique tool to differentiate between intrinsic and extrinsic SO mechanisms
underlying the spin Hall effect in paramagnetic devices.",0804.2076v1
2009-03-27,Comment on recent papers regarding next-to-leading order spin-spin effects in gravitational interaction,"It is argued that the tetrad in a recent paper by Porto and Rothstein on
gravitational spin-spin coupling should not have the given form. The fixation
of that tetrad was suggested by Steinhoff, Hergt, and Schaefer as a possible
source for the disagreement found in the spin-squared dynamics. However, this
inconsistency will only show up in the next-to-leading order spin-orbit
dynamics and not in the spin-squared dynamics. Instead, the disagreement found
at the next-to-leading order spin-squared level is due to a sign typo in the
spin-squared paper by Porto and Rothstein.",0903.4772v2
2009-05-18,Bulk Spin-Hall Effect,"We show that a two-dimensional spin-orbit-coupled system in the presence of a
charge/spin-density wave with a wave-vector perpendicular to an applied
electric field supports bulk manifestations of the direct/inverse spin-Hall
effect. We develop a theory of this phenomenon in the framework of the spin
diffusion equation formalism and show that, due to the inhomogeneity created by
a spin-grating, an anomalous bulk charge-density wave is induced away from
sample boundaries. The optimal conditions for the observation of the effect are
determined. The main experimental manifestation of the bulk spin-Hall effect,
the induced charge/spin-density-wave, is characterized by a pi/2-phase shift
relative to the initial non-homogeneous spin/charge-polarization profile and
has a non-monotonic time-varying amplitude.",0905.2771v1
2010-10-29,Temperature and Electron Density Dependence of Spin Relaxation in GaAs/AlGaAs Quantum Well,"Temperature and carrier density dependent spin dynamics for GaAs/AlGaAs
quantum wells (QWs) with different structural symmetry has been studied by
using time-resolved Kerr rotation technique. The spin relaxation time is
measured to be much longer for the symmetrically-designed GaAs quantum well
comparing with the asymmetrical one, indicating the strong influence of Rashba
spin-orbit coupling on spin relaxation. D'yakonov-Perel' (DP) mechanism has
been revealed to be the dominant contribution for spin relaxation in
GaAs/AlGaAs QWs. The spin relaxation time exhibits non-monotonic dependent
behavior on both temperature and photo-excited carrier density, revealing the
important role of non-monotonic temperature and density dependence of
electron-electron Coulomb scattering. Our experimental observations demonstrate
good agreement with recently developed spin relaxation theory based on
microscopic kinetic spin Bloch equation approach.",1010.6144v1
2010-11-10,Detection of spin injection into a double quantum dot: Violation of magnetic-field-inversion symmetry of nuclear polarization instabilities,"In mesoscopic systems with spin-orbit coupling, spin-injection into quantum
dots at zero magnetic field is expected under a wide range of conditions.
However, up to now, a viable approach for experimentally identifying such
injection has been lacking. We show that electron spin injection into a
spin-blockaded double quantum dot is dramatically manifested in the breaking of
magnetic- field-inversion symmetry of nuclear polarization instabilities. Over
a wide range of parameters, the asymmetry between positive and negative
instability fields is extremely sensitive to the injected electron spin
polarization and allows for the detection of even very weak spin injection.
This phenomenon may be used to investigate the mechanisms of spin transport,
and may hold implications for spin-based information processing.",1011.2247v1
2010-11-20,Spin precession and modulation in ballistic cylindrical nanowires due to the Rashba effect,"The spin precession in a cylindrical semiconductor nanowire due to Rashba
spin-orbit coupling has been investigated theoretically using an InAs nanowire
containing a surface two-dimensional electron gas as a model. The eigenstates,
energy-momentum dispersion, and the energy-magnetic field dispersion relation
are determined by solving the Schr\""odinger equation in a cylindrical symmetry
The combination of states with the same total angular momentum but opposite
spin orientation results in a periodic modulation of the axial spin component
along the axis of the wire. Spin-precession about the wires axis is achieved by
interference of two states with different total angular momentum. Because a
superposition state with exact opposite spin precession exists at zero magnetic
field, an oscillation of the spin orientation can be obtained. If an axially
oriented magnetic field is applied, the spin gains an additional precessing
component.",1011.4557v2
2010-12-08,Spin-to-Charge Conversion of Mesoscopic Spin Currents,"Recent theoretical investigations have shown that spin currents can be
generated by passing electric currents through spin-orbit coupled mesoscopic
systems. Measuring these spin currents has however not been achieved to date.
We show how mesoscopic spin currents in lateral heterostructures can be
measured with a single-channel voltage probe. In the presence of a spin
current, the charge current $I_{\rm qpc}$ through the quantum point contact
connecting the probe is odd in an externally applied Zeeman field $B$, while it
is even in the absence of spin current. Furthermore, the zero field derivative
$\partial_B I_{\rm qpc}$ is proportional to the magnitude of the spin current,
with a proportionality coefficient that can be determined in an independent
measurement. We confirm these findings numerically.",1012.1831v2
2011-04-04,Electric Control of Spin Currents and Spin-Wave Logic,"Spin waves in insulating magnets are ideal carriers for spin currents with
low energy dissipation. An electric field can modify the dispersion of spin
waves, by directly affecting, via spin-orbit coupling, the electrons that
mediate the interaction between magnetic ions. Our microscopic calculations
based on the super-exchange model indicate that this effect of the electric
field is sufficiently large to be used to effectively control spin currents. We
apply these findings to the design of a spin-wave interferometric device, which
acts as a logic inverter and can be used as a building block for
room-temperature, low-dissipation logic circuits.",1104.0657v2
2014-04-11,Effect of contacts on spin lifetime measurements in graphene,"Injection, transmission, and detection of spins in a conducting channel are
the basic ingredients of spintronic devices. Long spin lifetimes during transit
are an important ingredient in realizing this technology. An attractive
platform for this purpose is graphene, which has high mobilities and low
spin-orbit coupling. Unfortunately, measured spin lifetimes are orders of
magnitude smaller than theoretically expected. A source of spin loss is the
resistance mismatch between the ferromagnetic electrodes and graphene. While
this has been studied numerically, here we provide a closed form expression for
Hanle spin precession which is the standard method of measuring spin lifetimes.
This allows for a detailed characterization of the nonlocal spin valve device.",1404.3211v2
2014-04-23,Semiclassical spin-spin dynamics and feedback control in transport through a quantum dot,"We present a theory of magnetotransport through an electronic orbital, where
the electron spin interacts with a (sufficiently) large external spin via an
exchange interaction. Using a semiclassical approximation, we derive a set of
equations of motions for the electron density matrix and the mean value of the
external spin that turns out to be highly nonlinear. The dissipation via the
electronic leads is implemented in terms of a quantum master equation that is
combined with the nonlinear terms of the spin-spin interaction. With an
anisotropic exchange coupling a variety of dynamics is generated, such as
self-sustained oscillations with parametric resonances or even chaotic
behavior. Within our theory we can integrate a Maxwell-demon-like closed-loop
feedback scheme that is capable of transporting particles against an applied
bias voltage and that can be used to implement a spin filter to generate
spin-dependent oscillating currents of opposite directions.",1404.5831v3
2015-06-08,Coherent ultrafast spin-dynamics probed in three dimensional topological insulators,"Topological insulators are candidates to open up a novel route in spin based
electronics. Different to traditional ferromagnetic materials, where the
carrier spin-polarization and magnetization are based on the exchange
interaction, the spin properties in topological insulators are based on the
coupling of spin- and orbit interaction connected to its momentum. Specific
ways to control the spin-polarization with light have been demonstrated: the
energy momentum landscape of the Dirac cone provides spin-momentum locking of
the charge current and its spin. The directionality of spin and momentum, as
well as control with light has been demonstrated. Here we demonstrate a
coherent femtosecond control of spin-polarization for states in the valence
band at around the Dirac cone.",1506.02692v1
2015-07-21,Spin Gating of Mesoscopic Devices,"Inefficient screening of electric fields in nanoconductors makes electric
manipulation of electronic transport in nanodevices possible. Accordingly,
electrostatic (charge) gating is routinely used to affect and control the
Coulomb electrostatics and quantum interference in modern nanodevices. Besides
their charge, another (quantum mechanical) property of electrons - their spin -
is at the heart of modern spintronics, a term implying that a number of
magnetic and electrical properties of small systems are simultaneously
harvested for device applications. In this review the possibility to achieve
""spin gating"" of mesoscopic devices, i.e. the possibility of an external spin
control of the electronic properties of nanodevices is discussed. Rather than
the Coulomb interaction, which is responsible for electric-charge gating, we
consider two other mechanisms for spin gating. These are on the one hand the
magnetic exchange interaction in magnetic devices and on the other hand the
spin-orbit coupling (""Rashba effect""), which is prominent in low dimensional
conductors. A number of different phenomena demonstrating the spin gating
phenomenon will be discussed, including the spintro-mechanics of magnetic
shuttling, Rashba spin splitting, and spin-gated weak superconductivity.",1507.05822v1
2016-04-25,Giant intrinsic spin Hall effect in the TaAs family of Weyl semimetals,"Since their discovery, topological insulators have been expected to be ideal
spintronic materials owing to the spin currents carried by surface states with
spin--momentum locking. However, the bulk doping problem remains an obstacle
that hinders such application. In this work, we predict that a newly discovered
family of topological materials, the Weyl semimetals, exhibits large intrinsic
spin Hall effects that can be utilized to generate and detect spin currents.
Our $ab~initio$ calculations reveal a large spin Hall conductivity that is
comparable to that of $4d$ and $5d$ transition metals. The spin Hall effect
originates intrinsically from the bulk band structure of Weyl semimetals, which
exhibit a large Berry curvature and spin--orbit coupling, so the bulk carrier
problem in the topological insulators is naturally avoided. Our work not only
paves the way for employing Weyl semimetals in spintronics, but also proposes a
new guideline for searching for the spin Hall effect in various topological
materials.",1604.07167v2
2018-02-13,All-electrical manipulation of silicon spin qubits with tunable spin-valley mixing,"We show that the mixing between spin and valley degrees of freedom in a
silicon quantum bit (qubit) can be controlled by a static electric field acting
on the valley splitting $\Delta$. Thanks to spin-orbit coupling, the qubit can
be continuously switched between a spin mode (where the quantum information is
encoded into the spin) and a valley mode (where the the quantum information is
encoded into the valley). In the spin mode, the qubit is more robust with
respect to inelastic relaxation and decoherence, but is hardly addressable
electrically. It can however be brought into the valley mode then back to the
spin mode for electrical manipulation. This opens new perspectives for the
development of robust and scalable, electrically addressable spin qubits on
silicon. We illustrate this with tight-binding simulations on a so-called
""corner dot"" in a silicon-on-insulator device where the confinement and valley
splitting can be independently tailored by a front and a back gate.",1802.04693v1
2013-08-26,Spin Hall effect in AA-stacked bilayer graphene,"Intrinsic spin Hall effect in the AA-stacked bilayer graphene is studied
theoretically. The low-energy electronic spectrum for states in the vicinity of
the Dirac points is obtained from the corresponding $\mathbf{k}\cdot\mathbf{p}$
Hamiltonian. The spin Hall conductivity in the linear response regime is
determined within the Green function formalism. Conditions for the existence of
spin Hall insulator phase are also analyzed, and it is shown that the spin Hall
insulator phase can exist for a sufficiently large spin-orbit coupling, which
opens a gap in the spectrum. The electric field perpendicular to the graphene
plane leads then to reduction of the gap width and suppression of the spin Hall
insulator phase. The low temperature spin Nernst effect is also calculated from
the zero temperature spin Hall conductivity.",1308.5549v1
2014-06-18,Controlling spin relaxation in hexagonal BN-encapsulated graphene with a transverse electric field,"We experimentally study the electronic spin transport in hBN encapsulated
single layer graphene nonlocal spin valves. The use of top and bottom gates
allows us to control the carrier density and the electric field independently.
The spin relaxation times in our devices range up to 2 ns with spin relaxation
lengths exceeding 12 $\mu$m even at room temperature. We obtain that the ratio
of the spin relaxation time for spins pointing out-of-plane to spins in-plane
is $\tau_{\bot} / \tau_{||} \approx$ 0.75 for zero applied perpendicular
electric field. By tuning the electric field this anisotropy changes to
$\approx$0.65 at 0.7 V/nm, in agreement with an electric field tunable in-plane
Rashba spin-orbit coupling.",1406.4656v2
2017-06-14,Spin inversion in fluorinated graphene n-p junction,"We consider a dilute fluorinated graphene nanoribbon as a spin-active
element. The fluorine adatoms introduce a local spin-orbit Rashba interaction
that induces spin-precession for electron passing by. In the absence of the
external magnetic field the transport is dominated by multiple scattering by
adatoms which cancels the spin precession effects, since the direction of the
spin precession depends on the electron momentum. Accumulation of the spin
precession effects is possible provided that the Fermi level electron passes
many times near the same adatom with the same momentum. In order to arrange for
these conditions a circular n-p junction can be introduced to the ribbon by
e.g. potential of the tip of an atomic force microscope. In the quantum Hall
conditions the electron current gets confined along the junction. The electron
spin interaction with the local Rashba field changes with the lifetime of the
quasi-bound states that is controlled with the coupling of the junction to the
edge of the ribbon. We demonstrate that the spin-flip probability can be
increased in this manner by as much as three orders of magnitude.",1706.04490v2
2017-06-26,Spin excitation anisotropy in the paramagnetic tetragonal phase of BaFe2 As2,"We use neutron polarization analysis to study temperature dependence of the
spin excitation anisotropy in BaFe$_2$As$_2$, which has a
tetragonal-to-orthorhombic structural distortion at $T_s$ and antiferromagnetic
(AF) phase transition at $T_N$ with ordered moments along the orthorhombic
$a$-axis below $T_s\approx T_N\approx 136$ K. In the paramagnetic tetragonal
state at 160 K, spin excitations are isotropic in spin space with
$M_a=M_b=M_c$, where $M_a$, $M_b$, and $M_c$ are spin excitations polarized
along the $a$, $b$, and $c$-axis directions of the orthorhombic lattice,
respectively. On cooling towards $T_N$, significant spin excitation anisotropy
with $M_a>M_b\approx M_c$ develops below 3 meV with a diverging $M_a$ at $T_N$.
The in-plane spin excitation anisotropy in the tetragonal phase of
BaFe$_2$As$_2$ is similar to those seen in the tetragonal phase of its electron
and hole-doped superconductors, suggesting that spin excitation anisotropy is a
direct probe of doping dependence of spin-orbit coupling and its connection to
superconductivity in iron pnictides.",1706.08258v1
2018-09-09,Spin transfer torques and spin-dependent transport in a metallic F/AF/N tunneling junction,"We study spin-dependent electron transport through a
ferromagnetic-antiferromagnetic-normal metal tunneling junction subject to a
voltage or temperature bias, in the absence of spin-orbit coupling. We derive
microscopic formulas for various types of spin torque acting on the
antiferromagnet as well as for charge and spin currents flowing through the
junction. The obtained results are applicable in the limit of slow
magnetization dynamics. We identify a parameter regime in which an
unconventional damping-like torque can become comparable in magnitude to the
equivalent of the conventional Slonczewski's torque generalized to
antiferromagnets. Moreover, we show that the antiferromagnetic sublattice
structure opens up a channel of electron transport which does not have a
ferromagnetic analogue and that this mechanism leads to a pronounced field-like
torque. Both charge conductance and spin current transmission through the
junction depend on the relative orientation of the ferromagnetic and the
antiferromagnetic vectors (order parameters). The obtained formulas for charge
and spin currents allow us to identify the microscopic mechanisms responsible
for this angular dependence and to assess the efficiency of an
antiferromagnetic metal acting as a spin current polarizer.",1809.02950v1
2019-07-17,Transverse photon spin beyond interfaces,"Photons possess spin degree of freedom, corresponding to clockwise and
counter clockwise rotating direction of the fields. Photon spin plays an
important role in various applications such as optical communications,
information processing and sensing. In conventional isotropic media, photon
spin is aligned with the propagation direction of light, obeying spin momentum
locking. Interestingly, at certain interfaces, the surface waves decaying away
from the interface possess a photon spin transverse to its propagation, opening
exciting opportunities for observation of spin dependent unidirectional
excitation in confined systems. Here we propose and realize transverse photon
spin (T-spin) in the interior of a bulk medium, without relying on the presence
of any interfaces. We show the complete mapping of the T-spin of surface modes
to that of the bulk modes by introducing the coupling between electric and
magnetic responses along orthogonal directions, i.e., the bianisotropy, into
the medium. We further discover that an interface formed by two bianisotropic
media of opposite orientations supports edge-dependent propagating modes with
tunable cutoff frequencies. Our results provide a new platform for manipulating
the spin orbit interaction of electromagnetic waves.",1907.07654v1
2020-04-03,Spin-Excitations Anisotropy in the Bilayer Iron-Based Superconductor CaKFe$_4$As$_4$,"We use polarized inelastic neutron scattering to study the spin-excitations
anisotropy in the bilayer iron-based superconductor CaKFe$_4$As$_4$ ($T_c$ = 35
K). In the superconducting state, both odd and even $L-$modulations of spin
resonance have been observed in our previous unpolarized neutron scattering
experiments (T. Xie {\it et al.} Phys. Rev. Lett. {\bf 120}, 267003 (2018)).
Here we find that the high-energy even mode ($\sim 18$ meV) is isotropic in
spin space, but the low-energy odd modes consist of a $c-$axis polarized mode
around 9 meV along with another partially overlapped in-plane mode around 12
meV. We argue that such spin anisotropy is induced by the spin-orbit coupling
in the spin-vortex-type fluctuations of this unique compound. The spin
anisotropy is strongly affected by the superconductivity, where it is weak
below 6 meV in the normal state and then transferred to higher energy and
further enhanced in the odd mode of spin resonance below $T_c$.",2004.01405v1
2017-05-09,Determination of spin relaxation times in heavy metals via 2nd harmonic spin injection magnetoresistance,"In tunnel junctions between ferromagnets and heavy elements with strong spin
orbit coupling the magnetoresistance is often dominated by tunneling
anisotropic magnetoresistance (TAMR). This makes conventional DC spin injection
techniques impractical for determining the spin relaxation time ($\tau_s$).
Here, we show that this obstacle for measurements of $\tau_s$ can be overcome
by 2nd harmonic spin-injection-magnetoresistance (SIMR). In the 2nd harmonic
signal the SIMR is comparable in magnitude to TAMR, thus enabling Hanle-induced
SIMR as a powerful tool to directly determine $\tau_s$. Using this approach we
determined the spin relaxation time of Pt and Ta and their temperature
dependences. The spin relaxation in Pt seems to be governed by Elliott-Yafet
mechanism due to a constant resistivity $\times$spin relaxation time product
over a wide temperature range.",1705.03149v1
2018-03-04,Spin Hall effects without spin currents in magnetic insulators,"The spin Hall effect (SHE) is normally discussed in terms of a spin current,
which is ill-defined in strongly spin-orbit-coupled systems because of spin
non-conservation. In this work we propose an alternative view of SHE phenomena
by relating them to a spin analog of charge polarization induced by an electric
field. The spin density polarization is most conveniently defined in
insulators, which can have a SHE if they break time-reversal symmetry, i.e. if
they are magnetic. The reciprocal of this SHE is a counterpart of the inverse
SHE (ISHE), and is manifested in magnetic insulators as a charge polarization
induced by a Zeeman field gradient. We use a modified Kane-Mele model to
illustrate the magnetic spin Hall effect, and to discuss its bulk-boundary
relationship.",1803.01294v2
2018-03-06,Electron spin inversion in gated silicene nanoribbons,"We study locally gated silicene nanoribbons as spin active devices. We find
that the gated segments of nanoribbons with zigzag edge can be used to perform
a spin inversion for the electron spins injected with an in-plane orientation.
The strong intrinsic spin-orbit coupling for low Fermi energy in presence of an
external vertical electric field provides a fast spin precession around the
axis perpendicular to the silicene plane. The spin inversion length can be as
small as 10 nm. On the other hand in the armchair nanoribbons the spin
inversion occurs via the Rashba effect which is weak and the spin inversion
lengths are of the order of $\mu$m.",1803.02131v2
2019-03-19,Nonlinear Inverse Spin Galvanic Effect in Anisotropic Disorder-free Systems,"Spin transport phenomena in solid materials suffer limitations from spin
relaxation associated to disorder or lack of translational invariance.
Ultracold atoms, free of that disorder, can provide a platform to observe
phenomena beyond the usual two-dimensional electron gas. By generalizing the
approach used for isotropic two-dimensional electron gases, we theoretically
investigate the inverse spin galvanic effect in the two-level atomic system in
the presence of anisotropic Rashba-Dresselhaus spin-orbit couplings (SOC) and
external magnetic field. We show that the combination of the SOC results in an
asymmetric case: the total spin polarization considered for a small momentum
has a longer spin state than in a two-dimensional electron gas when the SOC
field prevails over the external electric field. Our results can be relevant
for advancing experimental and theoretical investigations in spin dynamics as a
basic approach for studying spin state control.",1903.08269v1
2019-06-26,Electric Dipole Spin Resonance of 2D Semiconductor Spin Qubits,"Monolayer transition metal dichalcogenides (TMDs) offer a novel
two-dimensional platform for semiconductor devices. One such application,
whereby the added low dimensional crystal physics (i.e. optical spin selection
rules) may prove TMDs a competitive candidate, are quantum dots as qubits. The
band structure of TMD monolayers offers a number of different degrees of
freedom and combinations thereof as potential qubit bases, primarily electron
spin, valley isospin and the combination of the two due to the strong spin
orbit coupling known as a Kramers qubit. Pure spin qubits in monolayer MoX$_2$
(where X=S or Se) can be achieved by energetically isolating a single valley
and tuning to a spin degenerate regime within that valley by a combination of a
sufficiently small quantum dot radius and large perpendicular magnetic field.
Within such a TMD spin qubit, we theoretically analyse single qubit rotations
induced by electric dipole spin resonance. We employ a rotating wave
approximation within a second order time dependent Schrieffer-Wolf effective
Hamiltonian to derive analytic expressions for the Rabi frequency of single
qubit oscilations, and optimise the mechanism or the parameters to show
oscilations up to $250\,{\rm MHz}$.",1906.11350v1
2021-05-22,Spin Seebeck effect of correlated magnetic molecules,"In this paper we investigate the spin-resolved thermoelectric properties of
strongly correlated molecular junctions in the linear response regime. The
magnetic molecule is modeled by a single orbital level to which the molecular
core spin is attached by an exchange interaction. Using the numerical
renormalization group method we analyze the behavior of the (spin) Seebeck
effect, heat conductance and figure of merit for different model parameters of
the molecule. We show that the thermopower strongly depends on the strength and
type of the exchange interaction as well as the molecule's magnetic anisotropy.
When the molecule is coupled to ferromagnetic leads, the thermoelectric
properties reveal an interplay between the spin-resolved tunneling processes
and intrinsic magnetic properties of the molecule. Moreover, in the case of
finite spin accumulation in the leads, the system exhibits the spin Seebeck
effect. We demonstrate that a considerable spin Seebeck effect can develop when
the molecule exhibits an easy-plane magnetic anisotropy, while the sign of the
spin thermopower depends on the type and magnitude of the molecule's exchange
interaction.",2105.10713v1
2021-12-21,Spin accumulation without spin current,"The spin Hall (SH) effect is a phenomenon in which the spin current flows
perpendicular to an applied electric field and causes the spin accumulation at
the boundaries. However, in the presence of spin-orbit couplings, the spin
current is not well defined. Here, we calculate the spin response to an
electric-field gradient, which naturally appears at the boundaries. We derive a
generic formula using the Bloch wave functions and the phenomenological
relaxation time. We also calculate the response for the uniform Rashba model
with $\delta$-function nonmagnetic disorder within the first-order Born
approximation and corresponding vertex corrections. We find the nonzero spin
accumulation, although the SH conductivity exactly vanishes.",2112.11043v3
2022-03-10,Long-range current-induced spin accumulation in chiral crystals,"Chiral materials, similarly to human hands, have distinguishable right-handed
and left-handed enantiomers which may behave differently in response to
external stimuli. Here, we use for the first time an approach based on the
density functional theory (DFT)+PAOFLOW calculations to quantitatively estimate
the so-called collinear Rashba-Edelstein effect (REE) that generates spin
accumulation parallel to charge current and can manifest as chirality-dependent
charge-to-spin conversion in chiral crystals. Importantly, we reveal that the
spin accumulation induced in the bulk by an electric current is intrinsically
protected by the quasi-persistent spin helix arising from the crystal
symmetries present in chiral systems with the Weyl spin-orbit coupling. In
contrast to conventional REE, spin transport can be preserved over large
distances, in agreement with the recent observations for some chiral materials.
This allows, for example, the generation of spin currents from spin
accumulation, opening novel routes for the design of solid-state spintronics
devices.",2203.05518v2
2022-04-07,The chirality-dependent second-order spin current in systems with time-reversal symmetry,"Spin currents proportional to the first- and second-order of the electric
field are calculated in a specific tight-binding model with time-reversal
symmetry. Specifically, a tight-binding model with time-reversal symmetry is
constructed with chiral hopping and spin-orbit coupling. The spin conductivity
of the model is calculated using the Boltzmann equation. As a result, it is
clarified that the first-order spin current of the electric field vanishes,
while the second-order spin current can be finite. Furthermore, the spin
current changes its sign by reversing the chirality of the model. The present
results reveal the existence of spin currents in systems with time-reversal
symmetry depending on the chirality of the system. They may provide useful
information for understanding the chirality-dependent spin polarization
phenomena in systems with time-reversal symmetry.",2204.03263v1
2022-10-12,Perfect optical spin-filtering in antiferromagnetic stanene nanoribbons induced by band bending and uniaxial strain,"Non-equilibrium spin-polarized transport properties of antiferromagnetic
stanene nanoribbons are theoretically studied under the combining effect of a
normal electric field and linearly polarized irradiation based on the
tight-binding model at room temperature. Due to the existence of spin-orbit
coupling in stanene lattice, applying normal electric field leads to splitting
of band degeneracy of spin-resolved energy levels in conduction and valence
bands. Furthermore, unequivalent absorption of the polarized photons at two
valleys which is attributed to an antiferromagnetic exchange field results in
unequal spin-polarized photocurrent for spin-up and spin-down components.
Interestingly, in the presence of band bending which has been induced by edge
potentials, an allowable quantum efficiency occurs over a wider wavelength
region of the incident light. It is especially important that the variation of
an exchange magnetic field generates spin semi-conducting behavior in the
bended band structure. Moreover, it is shown that optical spin-filtering effect
is obtained under the simultaneous effect of uniaxial strain and narrow edge
potential.",2210.06037v1
2023-04-26,Spin-dependent Destructive Quantum Interference Associated with Chirality-induced Spin Selectivity in Circular Single Helix Molecules,"Theoretical studies on spin-dependent transport through helical molecules
with straight spiral geometry have received intense research interest in the
past decade, however, the physics in circular helical molecules has still less
been explored. In this work, we theoretically construct a circular single helix
(CSH) possessing the chirality-induced spin-orbit coupling and contacting with
two non-magnetic electrodes. Our theoretical calculations demonstrate that the
spin-related transport in CSH exhibits the so-called chiral-induced spin
selectivity (CISS) effect and more importantly, the CISS-reduced spin-dependent
destructive quantum interference (DQI) also occurs in the CSH, without any
external magnetic field or magnetic electrodes. Moreover, the changing of CSH
length or the electrode positions exhibits specific patterns in the
spin-polarized conductance. Particularly, the dephasing magnitude can adjust
effectively these two spin-dependent effects to realize their coexistence.
Additionally, the phase transition between the CISS-dependent constructive
quantum interference (CQI) and DQI is also observed in the CSH. Our theoretical
work puts forwards a new material plateau to explore the CISS and to exhibit
the novel CISS-dependent CQI effect.",2304.13305v1
2023-08-08,Chirality-induced spin splitting in 1D InSeI,"Spin-orbit coupling in chiral materials can induce chirality-dependent spin
splitting, enabling electrical manipulation of spin polarization. Here, we use
first-principles calculations to investigate the electronic states of chiral
one-dimensional (1D) semiconductor InSeI, which has two enantiomorphic
configurations with left- and right-handedness. We find that opposite spin
states exist in the left- and right-handed 1D InSeI with significant spin
splitting and spin-momentum collinear locking. Although the spin states at the
conduction band minimum (CBM) and valence band maximum (VBM) of 1D InSeI are
both nearly degenerate, a direct-to-indirect bandgap transition occurs when a
moderate tensile strain ($\sim$4%) is applied along the 1D chain direction,
leading to a sizable spin splitting ($\sim$0.11 eV) at the CBM. These findings
indicate that 1D InSeI is a promising material for chiral spintronics.",2308.04350v2
2023-08-14,Converting a triplet Cooper pair supercurrent into a spin-signal,"Superconductivity with spin-polarized Cooper pairs is known to emerge by
combining conventional spinless superconductors with materials that have
spin-dependent interactions, such as magnetism and spin-orbit coupling. This
enables a dissipationless and conserved flow of spin. However, actually
utilizing the spin-polarization of such supercurrents have proven challenging.
Here, we predict an experimental signature of current-carrying triplet Cooper
pairs in the form of an induced spin-signal. We show that a supercurrent
carried only by triplet Cooper pairs induces a non-local magnetization that is
controlled by the polarization direction of the triplet Cooper pairs. This
provides a measurement protocol to directly use the spin-polarization of the
triplet Cooper pairs in supercurrents to transfer spin information in a
dissipationless manner.",2308.07226v1
2023-08-26,Non-equilibrium spin polarisation via interfacial exchange-field spin filtering,"A key phenomenon that enables nanoscale spintronic devices is the efficient
inter-conversion between spin and charge degrees of freedom. Here, we
experimentally demonstrate a pathway to generate current-induced spin
polarization at the interface between an insulating ferromagnet and a
non-magnetic metal using interfacial exchange-field spin filtering. Measuring
current-in-plane giant magnetoresistance in Py$|$Cu$|$EuS trilayer Hall cross
devices, we induce a non-equilibrium spin polarization of
$P_\text{neq}^\text{Cu|EuS}$=0.6% at a low charge current density of
1.88$\times$10$^3$ A/cm$^2$. This efficiency is comparable to that of
conventional charge-to-spin conversion of spin-Hall or Rashba-Edelstein effects
enabled by relativistic spin-orbit coupling. Interfacial exchange field
filtering allows operation with largely reduced power consumption and magnetic
reconfigurability, opening new pathways to nanoscale low-power insulator
spintronics.",2308.13855v1
2023-09-05,Strong and nearly 100$\%$ spin-polarized second-harmonic generation from ferrimagnet Mn$_{2}$RuGa,"Second-harmonic generation (SHG) has emerged as a promising tool for
detecting electronic and magnetic structures in noncentrosymmetric materials,
but 100$\%$ spin-polarized SHG has not been reported. In this work, we
demonstrate nearly 100$\%$ spin-polarized SHG from half-metallic ferrimagnet
Mn$_{2}$RuGa. A band gap in the spin-down channel suppresses SHG, so the
spin-up channel contributes nearly all the signal, as large as 3614 pm/V about
10 times larger than that of GaAs. In the spin-up channel, $\chi_{xyz}^{(2)}$
is dominated by the large intraband current in three highly dispersed bands
near the Fermi level. With the spin-orbit coupling (SOC), the reduced magnetic
point group allows additional SHG components, where the interband contribution
is enhanced. Our finding is important as it predicts a large and complete
spin-polarized SHG in a all-optical spin switching ferrimagnet. This opens the
door for future applications.",2309.01965v1
2020-10-23,Current-induced orbital magnetization in systems without inversion symmetry,"In systems with time-reversal symmetry, the orbital magnetization is zero in
equilibrium. Recently, it has been proposed that the orbital magnetization can
be induced by an electric current in a helical crystal structure in the same
manner as that in a classical solenoid. In this paper, we extend this theory
and study the current-induced orbital magnetization in a broader class of
systems without inversion symmetry. First, we consider polar metals which have
no inversion symmetry. We find that the current-induced orbital magnetization
appears in a direction perpendicular to the electric current even without
spin-orbit coupling. Using the perturbation method, we physically clarify how
the current-induced orbital magnetization appears in polar metals. As an
example, we calculate the current-induced orbital magnetization in SnP, and
find that it might be sufficiently large for measurement. Next, we consider a
two-dimensional system without inversion symmetry. We establish a method to
calculate the current-induced orbital magnetization in the in-plane direction
by using real-space coordinates in the thickness direction. By applying this
theory to surfaces and interfaces of insulators, we find that an electric
current along surfaces and interfaces induces an orbital magnetization
perpendicular to the electric current.",2010.12159v1
2023-08-09,Complexity reduction in self-interaction-free density functional calculations using the Fermi-Löwdin self-interaction correction method,"Fermi-L\""owdin (FLO) self-interaction-correction (SIC) (FLOSIC) method uses
symmetric orthogonalized Fermi orbitals as localized orbitals in one-electron
SIC schemes resulting in a formal reduction in the scaling of SIC methods (e.g.
Perdew-Zunger SIC (PZSIC) method) but requires a set of Fermi orbital
descriptors used to define the FLOs which can be computationally taxing. Here,
we propose to simplify the SIC calculations using a selective orbital scaling
self-interaction correction (SOSIC) by removing SIE from a select set of
orbitals that are of interest. We illustrate the approach by choosing a valence
set of orbitals as active orbitals in the SOSIC approach. The results obtained
using the vSOSIC scheme are compared with those obtained with PZSIC which
corrects for SIE of all orbitals. The comparison is made for atomization
energies, barrier heights, ionization energies (absolute highest occupied
orbital [HOO] eigenvalues), exchange coupling constant and spin densities of
Cu-containing complexes, and vertical detachment energies (VDE) of water
cluster anions. The agreement between the two methods is within a few percent
for the majority of the properties. The MAE in the VDE (absolute HOO
eigenvalue) of water cluster anions with vSOSIC-PBE with respect to benchmark
CCSD(T) results is only 15 meV making vSOSIC-PBE an excellent alternative to
the CCSD(T) to obtain the VDE of water cluster anions. The vSOSIC calculation
on [Cu$_2$Cl$_6$]$^{2-}$ complex demonstrates that, in addition to the cost
savings from using fewer orbitals to account for SIC, the FOD optimization in
vSOSIC is also substantially smoother and faster.",2308.04664v1
2010-06-14,Non-Abelian quantum order in spin-orbit-coupled semiconductors: The search for topological Majorana particles in solid state systems,"We show that an ordinary semiconducting thin film with spin-orbit coupling
can, under ap- propriate circumstances, be in a quantum topologically ordered
state supporting exotic Majorana excitations which follow non-Abelian
statistics. The key to the quantum topological order is the coexistence of
spin-orbit coupling with proximity-induced s-wave superconductivity and an
externally-induced Zeeman coupling of the spins. For the Zeeman coupling below
a critical value, the system is a non-topological (proximity-induced) s-wave
superconductor. However, for a range of Zeeman coupling above the critical
value, the lowest energy excited state inside a vortex is a zero-energy
Majorana fermion state. The system, thus, has entered into a non-Abelian s-wave
superconducting state via a topological quantum phase transition (TQPT) tuned
by the Zeeman coupling. In the one-dimensional version of the same structure
and for the Zeeman coupling above the critical value, there are localized
Majorana zero-energy modes at the two ends of a semiconducting quantum
nanowire. In this case, the Zeeman coupling can be induced more easily by an
external magnetic field parallel to the wire, obviating the need for a magnetic
insulator. We show that, despite the fact that the superconducting pair
potential in the nanowire is explicitly s-wave, tunneling of electrons to the
ends of the wire reveals a pronounced zero-bias peak. Such a peak is absent
when the Zeeman coupling is below its critical value, i.e., the nanowire is in
the non-topological s-wave superconducting state. We argue that the observation
of this zero-bias tunneling peak in the semiconductor nanowire is possibly the
simplest and clearest experiment proposed so far to unambiguously detect a
Majorana fermion mode in a condensed matter system.",1006.2829v2
1996-05-16,Orbital Decay of the PSR J0045-7319/B Star Binary System: Age of Radio Pulsar and Initial Spin of Neutron Star,"Recent timing observations of PSR J0045-7319 reveal that the neutron star/B
star binary orbit is decaying on a time scale of $|\Porb/\dot\Porb|=0.5$ Myr,
shorter than the characteristic age ($\tau_c=3$ Myr) of the pulsar (Kaspi et
al.~1996a). We study mechanisms for the orbital decay. The standard weak
friction theory based on static tide requires far too short a viscous time to
explain the observed $\dot\Porb$. We show that dynamical tidal excitation of
g-modes in the B star can be responsible for the orbital decay. However, to
explain the observed short decay timescale, the B star must have some
significant retrograde rotation with respect to the orbit --- The retrograde
rotation brings lower-order g-modes, which couple much more strongly to the
tidal potential, into closer ``resonances'' with the orbital motion, thus
significantly enhancing the dynamical tide. A much less likely possibility is
that the g-mode damping time is much shorter than the ordinary radiative
damping time. The observed orbital decay timescale combined with a generic
orbital evolution model based on dynamical tide can be used as a ``timer'',
giving an upper limit of $1.4$ Myr for the age of the binary system since the
neutron star formation. Thus the characteristic age of the pulsar is not a good
age indicator. Assuming standard magnetic dipole braking for the pulsar and no
significant magnetic field decay on a timescale $\lo 1$ Myr, the upper limit
for the age implies that the initial spin of the neutron star at birth was
close to its current value.",9605096v1
2021-03-29,Bilayer graphene encapsulated within monolayers of WS$_2$ or Cr$_2$Ge$_2$Te$_6$: Tunable proximity spin-orbit or exchange coupling,"Van der Waals (vdW) heterostructures consisting of bilayer graphene (BLG)
encapsulated within monolayers of strong spin-orbit semiconductor WS$_2$ or
ferromagnetic semiconductor Cr$_2$Ge$_2$Te$_6$ (CGT), are investigated. By
performing realistic first-principles calculations we capture the essential BLG
band structure features, including layer- and sublattice-resolved proximity
spin-orbit or exchange couplings. For different relative twist angles (0 or
60$^{\circ}$) of the WS$_2$ layers, and the magnetizations (parallel or
antiparallel) of the CGT layers, with respect to BLG, the low energy bands are
found and characterized by a series of fit parameters of model Hamiltonians.
These effective models are then employed to investigate the tunability of the
relevant energy dispersions by a gate field. For WS$_2$/BLG/WS$_2$
encapsulation we find that twisting allows to turn off the spin splittings away
from the $K$ points, due to opposite proximity-induced valley-Zeeman couplings
in the two sheets of BLG. Close to the $K$ points the electron spins are
polarized out of the plane. This polarization can be flipped by applying a gate
field. As for magnetic CGT/BLG/CGT structures, we realize the recently proposed
spin-valve effect, whereby a gap opens for antiparallel magnetizations of the
CGT layers. Furthermore, we find that for the antiferromagnetic orientation the
electron states away from $K$ have vanishingly weak proximity exchange, while
the states close to $K$ remain spin polarized in the presence of an electric
field. The induced magnetization can be flipped by changing the gate field.
These findings should be useful for spin transport, spin filtering, and spin
relaxation anisotropy studies of BLG-based vdW heterostructures.",2103.15378v2
2001-11-29,Zeeman effects on the impurity-induced resonances in d-wave superconductors,"It is shown how the resonant states induced by a single spinless impurity in
a d-wave superconductor evolve under the effect of an applied Zeeman magnetic
field. Moreover, it is demonstrated that the spin-orbit coupling to the
impurity potential can have important and characteristic effects on the
resonant states and their response to the Zeeman field, especially when the
impurity is close to the unitary limit. For zero or very small spin-orbit
interaction, the resonant states becomes Zeeman splitted by the magnetic field
while when the spin-orbit coupling is important, new low-lying resonances arise
which do not show any Zeeman splitting.",0111554v2
2004-06-11,Weak spin-orbit interactions induce exponentially flat mini-bands in magnetic metals without inversion symmetry,"In metallic magnets like MnSi the interplay of two very weak spin-orbit
coupling effects can strongly modify the Fermi surface. In the absence of
inversion symmetry even a very small Dzyaloshinsky-Moriya interaction of
strength delta<<1 distorts a ferromagnetic state into a chiral helix with a
long pitch of order 1/delta. We show that additional small spin-orbit coupling
terms of order delta in the band structure lead to the formation of
exponentially flat minibands with a bandwidth of order exp(-1/sqrt(delta))
parallel to the direction of the helix. These flat minibands cover a rather
broad belt of width sqrt(delta) on the Fermi surface where electron motion
parallel to the helix practically stops. We argue that these peculiar
band-structure effects lead to pronounced features in the anomalous skin
effect.",0406259v2
2006-02-22,Single electron control in n-type semiconductor quantum dots using non-Abelian holonomies generated by spin orbit coupling,"We propose that n-type semiconductor quantum dots with the Rashba and
Dresselhaus spin orbit interactions may be used for single electron
manipulation through adiabatic transformations between degenerate states. All
the energy levels are discrete in quantum dots and possess a double degeneracy
due to time reversal symmetryin the presence of the Rashba and/or Dresselhaus
spin orbit coupling terms. We find that the presence of double degeneracy does
not necessarily give rise to a finite non-Abelian (matrix) Berry phase. We show
that a distorted two-dimensional harmonic potential may give rise to
non-Abelian Berry phases. The presence of the non-Abelian Berry phase may be
tested experimentally by measuring the optical dipole transitions.",0602512v1
2008-08-05,P-wave Lambda N - Sigma N coupling and the spin-orbit splitting of 9 Lambda Be,"We reexamine the spin-orbit splitting of 9 Lambda Be excited states in terms
of the SU_6 quark-model baryon-baryon interaction. The previous folding
procedure to generate the Lambda alpha spin-orbit potential from the
quark-model Lambda N LS interaction kernel predicted three to five times larger
values for Delta E_{ell s}=E_x(3/2^+)-E_x(5/2^+) in the model FSS and fss2.
This time, we calculate Lambda alpha LS Born kernel, starting from the LS
components of the nuclear-matter G-matrix for the Lambda hyperon. This
framework makes it possible to take full account of an important P-wave Lambda
N - Sigma N coupling through the antisymmetric LS^{(-)} force involved in the
Fermi-Breit interaction. We find that the experimental value, Delta
E^{exp}_{ell s}=43 pm 5 keV, is reproduced by the quark-model G-matrix LS
interaction with a Fermi-momentum around k_F=1.0 fm^{-1}, when the model FSS is
used in the energy-independent renormalized RGM formalism.",0808.0628v1
2008-09-05,"Optical Spectroscopy in CoO: Phonons, Electric, and Magnetic Excitations","The reflectivity of single-crystalline CoO has been studied by optical
spectroscopy for wave numbers ranging from 100 to 28,000\wn and for
temperatures 8 $< T <$ 325 K\@. A splitting of the cubic IR-active phonon mode
on passing the antiferromagnetic phase transition at $T_N$ = 289 K has been
observed. At low temperatures the splitting amounts to 15.0\wn. In addition, we
studied the splitting of the cubic crystal field ground state of the Co$^{2+}$
ions due to spin-orbit coupling, a tetragonal crystal field, and exchange
interaction. Below $T_N$, magnetic dipole transitions between the
exchange-split levels are identified and the energy-level scheme can be well
described with a spin-orbit coupling $\lambda = 151.1\wn$, an exchange constant
$J = 17.5\wn$, and a tetragonal crystal-field parameter $D = -47.8\wn$. Already
in the paramagnetic state electric quadrupole transitions between the
spin-orbit split level have been observed. At high frequencies, two electronic
levels of the crystal-field-split $d$-manifold were identified at 8,000 and
18,500\wn.",0809.0997v1
2009-02-09,Microscopic theory of the nematic phase in Sr$_3$Ru$_2$O$_7$,"In an externally applied magnetic field, ultra-pure crystals of the bilayer
compound Sr$_3$Ru$_2$O$_7$ undergo a metamagnetic transition below a critical
temperature, $T^*$, which varies as a function of the angle between the
magnetic field $H$ and the Ru-O planes. Moreover, $T^*$ approaches zero when
$H$ is perpendicular to the planes. This putative ""metamagnetic quantum
critical point"", however, is preempted by a nematic fluid phase with order one
resistive anisotropy in the {\it ab} plane. In a ""realistic"" bilayer model with
moderate strength local Coulomb interactions, the existence of a sharp
divergence of the electronic density of states near a van Hove singularity of
the quasi-one-dimensional bands, and the spin-orbit couplings permitted by the
presence of multiple orbitals result in a mean-field phase diagram which
accounts for many of these experimentally observed phenomena. Although the
spin-orbit coupling is not overly strong, it destroys the otherwise near
perfect Fermi surface nesting and hence suppresses spin-density-wave (SDW)
ordering.",0902.1336v2
2010-06-16,The degree of 5f electron localization in URu2Si2: electron energy-loss spectroscopy and spin-orbit sum rule analysis,"We examine the degree of 5f electron localization in URu2Si2 using spin-orbit
sum rule analysis of the U N4,5 (4d \to 5f) edge. When compared to {\alpha}-U
metal, US, USe, and UTe, which have increasing localization of the 5f states,
we find that the 5f states of URu2Si2 are more localized, although not
entirely. Spin-orbit analysis shows that intermediate coupling is the correct
angular momentum coupling mechanism for URu2Si2 when the 5f electron count is
between 2.6 and 2.8. These results have direct ramifications for theoretical
assessment of the hidden order state of URu2Si2, where the degree of
localization of the 5f electrons and their contribution to the Fermi surface
are critical.",1006.3111v1
2011-04-04,Unconventional Fulde-Ferrel-Larkin-Ovchinnikov states in spin-orbit coupled condensates: exact results,"We find that a model Hamiltonian of s-wave superconductors in the presence of
spin-orbit interactions and a Zeeman field is exactly solvable. Most
intriguingly, based on the exact solutions, an unconventional type of
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) ground state is rigorously revealed, in
which the center-of-mass momentum of the fermion pair is proportional to the
Zeeman field. We also elaborate on the drifting effect of the Zeeman field on
the spin-orbit-coupled Bose-Einstein condensate.",1104.0614v3
2012-06-21,"Dielectric function, screening, and plasmons of graphene in the presence of spin-orbit interactions","We study the dielectric properties of graphene in the presence of Rashba and
intrinsic spin-orbit interactions in their most general form, i.e., for
arbitrary frequency, wave vector, doping, and spin-orbit coupling (SOC)
parameters. The main result consists in the derivation of closed analytical
expressions for the imaginary as well as for the real part of the polarization
function. Several limiting cases, e.g., the case of purely Rashba or purely
intrinsic SOC, and the case of equally large Rashba and intrinsic coupling
parameters are discussed. In the static limit the asymptotic behavior of the
screened potential due to charged impurities is derived. In the opposite limit
($q=0$, $\omega\to0$), an analytical expression for the plasmon dispersion is
obtained and afterwards compared to the numerical result. Our result can also
be applied to related systems such as bilayer graphene or topological
insulators.",1206.4849v2
2012-10-08,Doped Mott Insulators in (111) Bilayers of Perovskite Transition-Metal Oxides with a Strong Spin-Orbit Coupling,"The electronic properties of Mott insulators realized in (111) bilayers of
perovskite transition-metal oxides are studied. The low-energy effective
Hamiltonians for such Mott insulators are derived in the presence of a strong
spin-orbit coupling. These models are characterized by the antiferromagnetic
Heisenberg interaction and the anisotropic interaction whose form depends on
the $d$ orbital occupancy. From exact diagonalization analyses on finite
clusters, the ground state phase diagrams are derived, including a Kitaev spin
liquid phase in a narrow parameter regime for $t_{2g}$ systems. Slave-boson
mean-field analyses indicate the possibility of novel superconducting states
induced by carrier doping into the Mott-insulating parent systems, suggesting
the present model systems as unique playgrounds for studying
correlation-induced novel phenomena. Possible experimental realizations are
also discussed.",1210.2290v3
2013-06-03,"Dy-V magnetic interaction and local structure bias on the complex spin and orbital ordering in Dy$_{1-x}$Tb$_{x}$VO$_3$ (x\,=\,0 and 0.2)","The spin and orbital ordering in Dy$_{1-x}$Tb$_{x}$VO$_3$ (x\,=\,0 and 0.2)
was studied by measuring x-ray powder diffraction, magnetization, specific
heat, and neutron single crystal diffraction. The results show that G-OO/C-AF
and C-OO/G-AF phases coexist in Dy$_{0.8}$Tb$_{0.20}$VO$_3$ in the temperature
range 2\,K$\sim$60\,K and the volume fraction of each phase is temperature and
field dependent. The ordering of Dy moments at T*\,=\,12\,K induces a
transition from G-OO/C-AF to a C-OO/G-AF phase. Magnetic fields suppress the
long range order of Dy moments and thus the C-OO/G-AF phase below T*. The
polarized moments induced at the Dy sublattice by external magnetic fields
couple to the V 3d moments and this coupling favors the G-OO/C-AF state. Also
discussed is the effect of the Dy-V magnetic interaction and local structure
distortion on the spin and orbital ordering in Dy$_{1-x}$Tb$_{x}$VO$_3$.",1306.0513v1
2013-10-03,Synthetic spin-orbit interactions and magnetic fields in ring-cavity QED,"The interactions between light and matter are strongly enhanced when atoms
are placed in high-finesse quantum cavities, offering tantalizing opportunities
for generating exotic new quantum phases. In this work we show that both
spin-orbit interactions and strong synthetic magnetic fields result when a
neutral atom is confined within a ring cavity, whenever the internal atomic
states are coupled to two off-resonant counter-propagating modes. We
diagonalize the resulting cavity polariton Hamiltonian and find characteristic
spin-orbit dispersion relations for a wide range of parameters. An adjustable
uniform gauge potential is also generated, which can be converted into a
synthetic magnetic field for neutral atoms by applying an external magnetic
field gradient. Very large synthetic magnetic fields are possible as the
strength is proportional to the (average) number of photons in each of the
cavity modes. The results suggest that strong-coupling cavity quantum
electrodynamics can be a useful environment for the formation of topological
states in atomic systems.",1310.0884v1
2013-12-18,Vortex dynamics in spin-orbit coupled Bose-Einstein condensates,"I use a time-dependent Lagrangian formalism and a variational trial function
to study the dynamics of a two-component vortex in a spin-orbit coupled
Bose-Einstein condensate (BEC). For a single-component BEC, various experiments
have validated this theoretical approach, for example a thermal quench that
yields a quantized vortex in roughly 25% of trials. To be definite, I assume
the specific spin-orbit form used in recent NIST experiments, which introduces
a spatial asymmetry because of the external Raman laser beams. I here
generalize this formalism to include a two-component order parameter that has
quantized circulation in each component but not necessarily with the same
circulation. For example a singly quantized vortex in just one component yields
a BEC analog of the half-quantum vortex familiar in $^3$He-A and in $p$-wave
chiral superconductors. This and other unusual two-component vortices have both
periodic trajectories and unbounded trajectories that leave the condensate,
depending on the initial conditions. The optimized phase of the order parameter
induces a term in the particle current that cancels the contribution from the
vector potential, leaving pure circulating current around the vortex.",1312.5289v2
2014-02-04,CaIrO3: a Spin-Orbit Mott Insulator Beyond the jeff = 1/2 Ground State,"In CaIrO3 electronic correlation, spin-orbit coupling, and tetragonal crystal
field splitting are predicted to be of comparable strength. However, the nature
of its ground state is still object of debate, with contradictory experimental
and theoretical results. We probe the ground state of CaIrO3 and assess the
effective tetragonal crystal field splitting and spin-orbit coupling at play in
this system by means of resonant inelastic x-ray scattering. We conclude that
insulating CaIrO3 is not a jeff = 1/2 iridate and discuss the consequences of
our finding to the interpretation of previous experiments. In particular, we
clarify how the Mott insulating state in iridates can be readily extended
beyond the jeff = 1/2 ground state.",1402.0893v1
2014-02-28,Probing anisotropy in a new noncentrosymmetric superconductor BiPd,"Strength of Rashba type antisymmetric spin orbit coupling has the crucial
effect on superconducting and normal state properties in noncentrosymmetric
(NCS) superconductors. This can be seen on various anisotropic properties of
the system. For a system with lowered crystalline symmetry as in
noncentrosymmetric crystals, the superconducting pairing state can have
correlation to the normal state properties. In our earlier work we have shown
that alfa-BiPd which has a monoclinic (P_21) structure with the absence of the
centre of inversion exhibits bulk superconductivity at 3.8 K. In order to
understand the role of spin-orbit scattering, we have studied the anisotropic
properties of high quality single crystal (RRR 170) of NCS BiPd by measuring
magnetic susceptibility, electrical transport from 1.8 K to 300 K and
isothermal M_H loop (1.8 K to 3.8 K) in the superconducting state for <010> and
<100> crystallographic directions respectively. Moderate anisotropy up to 30 %
has been found in the electrical transport possibly indicating significant
Rashba type antisymmetric spin orbit coupling present in alfa-BiPd.",1402.7232v1
2014-07-16,Phase separation and long wave-length charge instabilities in spin-orbit coupled systems,"We investigate a two-dimensional electron model with Rashba spin-orbit
interaction where the coupling constant $g=g(n)$ depends on the electronic
density. It is shown that this dependence may drive the system unstable towards
a long-wave length charge density wave (CDW) where the associated second order
instability occurs in close vicinity to global phase separation. For very low
electron densities the CDW instability is nesting-induced and the modulation
follows the Fermi momentum $k_F$. At higher density the instability criterion
becomes independent of $k_F$ and the system may become unstable in a broad
momentum range. Finally, upon filling the upper spin-orbit split band, finite
momentum instabilities disappear in favor of phase separation alone. We discuss
our results with regard to the inhomogeneous phases observed at the
LaAlO$_3$/SrTiO$_3$ or LaTiO$_3$/SrTiO$_3$ interfaces.",1407.4280v1
2015-01-14,Intraband and interband spin-orbit torques in non-centrosymmetric ferromagnets,"Intraband and interband contributions to the current-driven spin-orbit torque
in magnetic materials lacking inversion symmetry are theoretically studied
using Kubo formula. In addition to the current-driven field-like torque ${\bf
T}_{\rm FL}= \tau_{\rm FL}{\bf m}\times{\bf u}_{\rm so}$ (${\bf u}_{\rm so}$
being a unit vector determined by the symmetry of the spin-orbit coupling), we
explore the intrinsic contribution arising from impurity-independent interband
transitions and producing an anti-damping-like torque of the form ${\bf T}_{\rm
DL}= \tau_{\rm DL}{\bf m}\times({\bf u}_{\rm so}\times{\bf m})$. Analytical
expressions are obtained in the model case of a magnetic Rashba two-dimensional
electron gas, while numerical calculations have been performed on a dilute
magnetic semiconductor (Ga,Mn)As modeled by the Kohn-Luttinger Hamiltonian
exchanged coupled to the Mn moments. Parametric dependences of the different
torque components and similarities to the analytical results of the Rashba
two-dimensional electron gas in the weak disorder limit are described.",1501.03292v1
2015-06-05,Multi-reference approach to the calculation of photoelectron spectra including spin-orbit coupling,"X-ray photoelectron spectra provide a wealth of information on the electronic
structure. The extraction of molecular details requires adequate theoretical
methods, which in case of transition metal complexes has to account for effects
due to the multi-configurational and spin-mixed nature of the many-electron
wave function. Here, the Restricted Active Space Self-Consistent Field method
including spin-orbit coupling is used to cope with this challenge and to
calculate valence and core photoelectron spectra. The intensities are estimated
within the frameworks of the Dyson orbital formalism and the sudden
approximation. Thereby, we utilize an efficient computational algorithm that is
based on a biorthonormal basis transformation. The approach is applied to the
valence photoionization of the gas phase water molecule and to the core
ionization spectrum of the $\text{[Fe(H}_2\text{O)}_6\text{]}^{2+}$ complex.
The results show good agreement with the experimental data obtained in this
work, whereas the sudden approximation demonstrates distinct deviations from
experiments.",1506.01826v1
2015-06-30,Finite-size effects on the minimal conductivity in graphene with Rashba spin-orbit coupling,"We study theoretically the minimal conductivity of monolayer graphene in the
presence of Rashba spin-orbit coupling. The Rashba spin-orbit interaction
causes the low-energy bands to undergo trigonal-warping deformation and for
energies smaller than the Lifshitz energy, the Fermi circle breaks up into
parts, forming four separate Dirac cones. We calculate the minimal conductivity
for an ideal strip of length $L$ and width $W$ within the Landauer--B\""uttiker
formalism in a continuum and in a tight binding model. We show that the minimal
conductivity depends on the relative orientation of the sample and the probing
electrodes due to the interference of states related to different Dirac cones.
We also explore the effects of finite system size and find that the minimal
conductivity can be lowered compared to that of an infinitely wide sample.",1507.00022v1
2016-04-08,Topological Mirror Insulators in One Dimension,"We demonstrate the existence of topological insulators in one dimension
protected by mirror and time-reversal symmetries. They are characterized by a
nontrivial $\mathbb{Z}_2$ topological invariant defined in terms of the
""partial"" polarizations, which we show to be quantized in presence of a 1D
mirror point. The topological invariant determines the generic presence or
absence of integer boundary charges at the mirror-symmetric boundaries of the
system. We check our findings against spin-orbit coupled Aubry-Andr\'e-Harper
models that can be realized, e.g. in cold-atomic Fermi gases loaded in
one-dimensional optical lattices or in density- and Rashba spin-orbit-modulated
semiconductor nanowires. In this setup, in-gap end-mode Kramers doublets
appearing in the topologically non-trivial state effectively constitute a
double-quantum-dot with spin-orbit coupling.",1604.02427v2
2017-02-22,Prediction of High Temperature Quantum Anomalous Hall Effect in Two Dimensional Transition-Metal Oxides,"Quantum anomalous Hall (QAH) insulator is a topological phase which exhibits
chiral edge states in the absence of magnetic field. The celebrated Haldane
model is the first example of QAH effect, but difficult to realize. Here, we
predict the two-dimensional single-atomic-layer V2O3 with a honeycomb-Kagome
structure is a QAH insulator with a large band gap (large than 0.1 eV) and a
high ferromagnetic Curie temperature (about 900 K). Combining the
first-principle calculations with the effective Hamiltonian analysis, we find
that the spin-majority dxy and dyz orbitals of V atoms on the honeycomb lattice
form a massless Dirac cone near the Fermi level which becomes massive when the
on-site spin-orbit coupling is included. Interestingly, we find that the large
band gap is caused by a cooperative effect of electron correlation and
spin-orbit coupling. Both first-principle calculations and the effective
Hamiltonian analysis confirm that 2D V2O3 has a non-zero Chern number (i.e.,
one). Our work paves a new direction towards realizing the QAH effect at room
temperature.",1702.07022v1
2017-03-28,A general method to describe intersystem crossing dynamics in trajectory surface hopping,"Intersystem crossing is a radiationless process that can take place in a
molecule irradiated by UV-Vis light, thereby playing an important role in many
environmental, biological and technological processes. This paper reviews
different methods to describe intersystem crossing dynamics, paying attention
to semiclassical trajectory theories, which are especially interesting because
they can be applied to large systems with many degrees of freedom. In
particular, a general trajectory surface hopping methodology recently developed
by the authors, which is able to include non-adiabatic and spin-orbit couplings
in excited-state dynamics simulations, is explained in detail. This method,
termed SHARC, can in principle include any arbitrary coupling, what makes it
generally applicable to photophysical and photochemical problems, also those
including explicit laser fields. A step-by-step derivation of the main
equations of motion employed in surface hopping based on the fewest-switches
method of Tully, adapted for the inclusion of spin-orbit interactions, is
provided. Special emphasis is put on describing the different possible choices
of the electronic bases in which spin-orbit can be included in surface hopping,
highlighting the advantages and inconsistencies of the different approaches.",1703.09456v1
2018-02-26,Drumhead surface states and their signatures in quasiparticle scattering interference,"We consider a two-orbital tight-binding model defined on a layered
three-dimensional hexagonal lattice to investigate the properties of
topological nodal lines and their associated drumhead surface states. We
examine these surface states in centrosymmetric systems, where the bulk nodal
lines are of Dirac type (i.e., four-fold degenerate), as well as in
non-centrosymmetric systems with strong Rashba and/or Dresselhaus spin-orbit
coupling, where the bulk nodal lines are of Weyl type (i.e., two-fold
degenerate). We find that in non-centrosymmetric systems the nodal lines and
their corresponding drumhead surface states are fully spin polarized due to
spin-orbit coupling. We show that unique signatures of the topologically
nontrivial drumhead surface states can be measured by means of quasiparticle
scattering interference, which we compute for both Dirac and Weyl nodal line
semimetals. At the end, we analyze the possible crystal structures with a
symmetry that supports flat surface states which are effectively ringlike.",1802.09139v2
2017-04-11,Spin-orbit coupling and rovibrational structure in the iododiacetylene radical cation by PFI-ZEKE photoelectron spectroscopy,"The photoelectron spectrum of the $\textrm{X}^{+}\,{}^{2}\Pi \leftarrow
\textrm{X}\,{}^{1}\Sigma^{+}$ photoionising transition in iododiacetylene,
HC$_4$I, has been recorded using pulsed-field-ionisation zero-kinetic-energy
(PFI-ZEKE) photoelectron spectroscopy with partial resolution of the rotational
structure. The first adiabatic ionisation energy of HC$_4$I and the spin-orbit
splitting of the X$^{+}\,{}^{2}\Pi$ state of HC$_4$I$^+$ are determined as
$E^{\textrm{ad}}_{\textrm{I}}/(hc) = 74470.7(2)$ cm$^{-1}$ and
$\Delta\tilde{\nu}_{\textrm{so}} = 1916.7(4)$ cm$^{-1}$, respectively. Several
vibrational levels of the X$^{+}\,{}^{2}\Pi$ electronic ground state of the
HC$_4$I$^+$ cation have been observed. The experimental data are discussed in
the realm of a simple three-state charge-transfer model without adjustable
parameters which allows for a qualitative description of the electronic
structure and spin-orbit coupling in HC$_4$I$^+$ and of the change in bond
lengths upon ionisation of HC$_4$I.",1704.03280v1
2018-05-06,Quantum Anomalous Hall Effect and Giant Rashba Spin-Orbit Splitting in Compensated n-p--Codoped Graphene,"Quantum anomalous Hall effect (QAHE) is a fundamental quantum transport
phenomenon in condensed matter physics. Until now, the only experimental
realization of the QAHE has been observed for Cr/V-doped (Bi,Sb)$_2$Te$_3$ but
at extremely low observational temperature, thereby limiting its potential
application in dissipationless quantum electronics. Employing first-principles
calculations, we study the electronic structures of graphene codoped with
5\textit{d} transition metal and boron (B) atoms based on a compensated
\textit{n}--\textit{p} codoping scheme. Our findings are as follows. 1) The
electrostatic attraction between the \textit{n}- and \textit{p}-type dopants
effectively enhances the adsorption of metal adatoms and suppresses their
undesirable clustering. 2) Hf--B and Os--B codoped graphene systems can
establish long-range ferromagnetic order and open nontrivial band gaps because
of the spin-orbit coupling with the non-vanishing Berry curvatures to host the
QAHE. 3) The calculated Rashba splitting energy in Re--B and Pt--B codoped
graphene systems can reach up to 158 and 85~meV, respectively, which is several
orders of magnitude higher than the reported intrinsic spin-orbit coupling
strength.",1805.02230v1
2012-01-18,Electronic structure of LaBr3 from quasi-particle self-consistent GW calculations,"Rare-earth based scintillators in general and lanthanum bromide (LaBr_3) in
particular represent a challenging class of materials due to pronounced
spin-orbit coupling and subtle interactions between d and f states that cannot
be reproduced by standard density functional theory (DFT). Here a detailed
investigation of the electronic band structure of LaBr_3 using the
quasi-particle self-consistent GW (QPscGW) method is presented. This
parameter-free approach is shown to yield an excellent description of the
electronic structure of LaBr_3. Specifically it is able to reproduce the band
gap, the correct level ordering and spacing of the 4f and 5d states, as well as
the spin-orbit splitting of La-derived states. The QPscGW results are
subsequently used to benchmark several computationally less demanding
techniques including DFT+U, hybrid exchange-correlation functionals, and the
G_0W_0 method. Spin-orbit coupling is included self-consistently at each QPscGW
iteration and maximally localized Wannier functions are used to interpolate
quasi-particle energies. The QPscGW results provide an excellent starting point
for investigating the electronic structure of excited states, charge
self-trapping, and activator ions in LaBr_3 and related materials.",1201.3860v1
2014-05-23,Magnetic Excitations in Spin-Orbit Coupled $d^4$ Mott Insulator on Square Lattice,"We study the magnetic order and excitations in strong spin-orbit coupled, Van
Vleck-type, $d^4$ Mott insulators on a square lattice. Extending the previous
work, we include the tetragonal crystal field splitting and explore its effects
on magnetic phase diagram and magnon spectra. Two different ordered phases,
with in-plane and out-of-plane orientation of the staggered moments, are found
for the higher and lower values of the crystal field splitting, respectively.
The magnetic excitation spectra for paramagnetic and magnetically ordered
phases are calculated and discussed in the context of a candidate spin-orbit
$d^4$ Mott insulator Ca$_2$RuO$_4$.",1405.6062v2
2017-10-02,Accurate computations of Rashba spin-orbit coupling in interacting systems: from the Fermi gas to real materials,"We describe the treatment of Rashba spin-orbit coupling (SOC) in interacting
many-fermion systems within the auxiliary-field quantum Monte Carlo framework,
and present a set of illustrative results. These include numerically exact
calculations on the ground-state properties of the spin-balanced, attractive
two-dimensional Fermi gas, as well as a study of a tight-binding Hamiltonian
with repulsive interaction. These systems are formally connected via the
Hubbard Hamiltonian with SOC, but cover different physics ranging from
superfluidity and triplet pairing to SOC in real materials in the presence of
strong interactions in localized orbitals. We carry out detailed benchmark
studies of the method in the latter case when an approximation is needed to
control the sign problem for repulsive Coulomb interactions. The methods
presented here provide an approach for predictive computations in materials to
study the interplay of SOC and strong correlation.",1710.00887v1
2018-09-10,Unified low-energy effective Hamiltonian and the band topology of $p$-block square-net layer derivatives,"In recent years, low-dimensional materials with tetragonal $P4/nmm$
(orthorhombic $Pnma$) space group having square-net (chain-like) substructure
of $p$-block elements have been studied extensively. By using a
first-principles calculation and a two-sites $\otimes$ two-orbitals
tight-binding model, we construct the unified low-energy effective Hamiltonian
and the $\mathbb{Z}_{2}$ topological phase diagram for such materials with
different filling factors. Near the chemical potential, we show that the
staggered arrangement of ions at 2c (4c) site yields the virtual hopping that
have the same form with the second nearest-neighbor hopping between the
square-net (chain-like) ions. We show that this hybridization and low-symmetry
of the chain-like structure protects the quantum spin Hall insulator phase.
Finally, the second order spin-orbit coupling on top of the atomic spin-orbit
coupling is considered to clarify the origin of the non-zero Berry phase
signals reported in recent quantum oscillation experiments.",1809.03086v1
2019-09-11,"Brightening odd-parity excitons in transition-metal dichalcogenides: Rashba spin-orbit interaction, skyrmions, and cavity polaritons","Odd-angular momentum exciton states are dark to light in monolayers of
transition-metal dichalcogenides and can be addressed only by two-photon
probes. Besides, $2p$ excitons states are expected to show a fine splitting
that arises from the peculiar electronic band structure of the material,
characterized by a finite Berry curvature around each valley. In this work we
study in detail the coupling of photons to $p$ exciton states and we find that
the Rashba spin-orbit interaction or a Skyrmion in the transition-metal
dichalcogenide substrate can be exploited to engineer finite optical selection
rules. The basis mechanism relies on a matching of the exciton angular momentum
with the winding of the Rashba spin-orbit interaction or the Skyrmion
topological charge. In a photonic cavity, the coupling is enhanced due to
photon confinement and the resulting polaritonic branches acquire a mixing with
$2p^\pm$ excitons, thus providing a useful tool to detect exciton
fine-splitting and and enable novel uses of odd-parity dark excitons.",1909.05297v2
2020-04-03,Interface Dark Excitons at Sharp Lateral Two-Dimensional Heterostructures,"We study the dark excitons at the interface of sharp lateral heterostructure
of two-dimensional transition metal dichalcogenides. By introducing a
low-energy effective Hamiltonian model, we find the energy dispersion relation
of exciton and show how it depends on the onsite energy of composed materials
and their spin-orbit coupling strengths. It is shown that the effect of
geometrical structure of interface, as a deformation gauge field
(pseudo-spin-orbit coupling), should be considered in calculating the binding
energy of exciton. By discretization of real-space version of the dispersion
relation on a triangular lattice, we show that the binding energy of exciton
depends on its distance from the interface line. For exciton near the interface
the binding energy is equal to 0.36 eV, while for the exciton enough far from
the interface it is equal to 0.26 eV. Also, it has been shown that for zigzag
interface the binding energy increases by 0.34 meV in comparison with the
armchair interface due to the pseudo-spin-orbit interaction (gauge filed). The
results can be used for designing the two-dimensional lateral heterostructure
based optoelectronic devices and improving their characteristics.",2004.01381v3
2018-07-05,Spin-Orbit Protection of Induced Superconductivity in Majorana Nanowires,"Spin-orbit interaction (SOI) plays a key role in creating Majorana zero modes
in semiconductor nanowires proximity coupled to a superconductor. We track the
evolution of the induced superconducting gap in InSb nanowires coupled to a
NbTiN superconductor in a large range of magnetic field strengths and
orientations. Based on realistic simulations of our devices, we reveal SOI with
a strength of 0.15-0.35 eV$\require{mediawiki-texvc}\AA$. Our approach
identifies the direction of the spin-orbit field, which is strongly affected by
the superconductor geometry and electrostatic gates.",1807.01940v2
2019-02-01,Two dimensional electron gas in the $δ$-doped iridates with strong spin-orbit coupling: La$_δ$Sr$_2$IrO$_4$,"Iridates are of considerable current interest because of the strong
spin-orbit coupling that leads to a variety of new phenomena. Using
density-functional studies, we predict the formation of a spin-orbital
entangled two-dimensional electron gas (2DEG) in the $\delta$-doped iridate
La$_\delta$Sr$_2$IrO$_4$, where a single SrO layer is replaced by a LaO layer.
The extra La electron resides close to the $\delta$-doped layer, partially
occupying the $J_{\rm eff}= 1/2 $ upper Hubbard band and thereby making the
interface metallic. The magnetic structure of the bulk is destroyed near the
interface, with the Ir$_0$ layer closest to the interface becoming
non-magnetic, while the next layer (Ir$_1$) continues to maintain the AFM
structure of the bulk, but with a reduced magnetic moment. The Fermi surface
consists of a hole pocket and an electron pocket, located in two different Ir
layers (Ir$_0$ and Ir$_1$), with both carriers derived from the $J_{\rm eff}=
1/2 $ upper Hubbard band. The presence of both electrons and holes at the
$\delta$-doped interface suggests unusual transport properties, leading to
possible device applications.",1902.00578v1
2019-02-14,Competing phases of interacting electrons on triangular lattices in moiré heterostructures,"We study the quantum many-body instabilities of interacting electrons with
SU(2)$\times$SU(2) symmetry in spin and orbital degrees of freedom on the
triangular lattice near van-Hove filling. Our work is motivated by effective
models for the flat bands in hexagonal moir\'e heterostructures like twisted
bilayer boron nitride and trilayer graphene-boron nitride systems. We consider
an extended Hubbard model including onsite Hubbard and Hund's couplings, as
well as nearest-neighbor exchange interactions and analyze the different
ordering tendencies with the help of an unbiased functional renormalization
group approach. We find three classes of instabilities controlled by the
filling and bare interactions. For a nested Fermi surface at van-Hove filling,
Hund-like couplings induce a weak instability towards spin or orbital density
wave phases. An SU(4) exchange interaction moves the system towards a Chern
insulator, which is robust with respect to perturbations from Hund-like
interactions or deviations from perfect nesting. Further, in an extended range
of fillings and interactions, we find topological $d\pm id$ and
(spin-singlet)-(orbital-singlet) $f$-wave superconductivity.",1902.05350v1
2019-04-04,Emergent non-Fermi-liquid phenomena in multipolar quantum impurity systems,"Discovery of novel spin-orbital entangled quantum ground states paves an
important avenue for controllable quantum materials via unique couplings to the
lattice and other external perturbations. In this work, motivated by recent
experiments on cubic heavy fermion materials with multipolar local moments, we
theoretically investigate strongly-interacting spin-orbital entangled quantum
ground states in multipolar quantum impurity systems. Here itinerant electrons
are interacting with the local moments carrying quadrupolar and octupolar
moments, in contrast to the conventional Kondo problem with dipolar local
moment. Using perturbative renormalization group methods, we uncover a number
of non-Fermi liquid ground states, which are characterized by an absence of
well-defined quasiparticles and singular power-law behaviours in physical
properties. We show that the non-Fermi liquid states found here are outside the
known categories of non-Fermi liquid states in the conventional multi-channel
Kondo problem. This work lays a novel ground for the identification of
unexpected non-Fermi liquid phases in many strongly spin-orbital-coupled
quantum materials.",1904.02717v2
2019-04-12,Optimized micromagnet geometries for Majorana zero modes in low g-factor materials,"Solid-state experimental realizations of Majorana bound states are based on
materials with strong intrinsic spin-orbit interactions. In this paper, we
explore an alternative approach where spin-orbit coupling is induced
artificially through a nonuniform magnetic field that originates from an array
of micromagnets. Using a recently developed optimization algorithm, we find
suitable magnet geometries for the emergence of topological superconductivity
in wires without intrinsic spin-orbit coupling. We confirm the robustness of
Majorana bound states against disorder and periodic potentials whose amplitudes
do not exceed the Zeeman energy. Furthermore, we identify low g-factor
materials commonly used in mesoscopic physics experiments as viable candidates
for Majorana devices.",1904.06275v2
2019-11-09,Levitons in helical liquids with Rashba spin-orbit coupling probed by a superconducting contact,"We consider transport properties of a single edge of a two-dimensional
topological insulators, in presence of Rashba spin-orbit coupling, driven by
two external time-dependent voltages and connected to a thin superconductor. We
focus on the case of a train of Lorentzian-shaped pulses, which are known to
generate coherent single-electron excitations in two-dimensional electron gas,
and prove that they are minimal excitations for charge transport also in
helical edge states, even in the presence of spin-orbit interaction.
Importantly, these properties of Lorentzian-shaped pulses can be tested
computing charge noise generated by the scattering of particles at the thin
superconductor. This represents a novel setup where electron quantum optics
experiments with helical states can be implemented, with the superconducting
contact as an effective beamsplitter. By elaborating on this configuration, we
also evaluate charge noise in a collisional Hong-Ou-Mandel configuration,
showing that, due to the peculiar effects induced by Rashba interaction, a
non-vanishing dip at zero delay appears.",1911.03697v1
2020-05-20,"Hubbard-Kanamori model: spectral functions, negative electron compressibility, and susceptibilities","The two-orbital Hubbard-Kanamori model is studied using the strong coupling
diagram technique. This approach allows one to take into account the
interactions of electrons with spin, charge, and orbital fluctuations of all
ranges. It was found that, at low temperatures, the model has four regions of
the negative electron compressibility, which can lead to charge inhomogeneities
with the assistance of phonons. For half-filling, the phase diagram of the
model contains regions of the Mott and Slater insulators, bad-metal, and states
with spin-polaron peaks. These sharp peaks at the Fermi level are seen in doped
states also. A finite Hund coupling leads to a large increase of
antiferromagnetic spin correlations with strong suppression of charge and
orbital fluctuations near half-filling. For moderate doping, all types of
correlations become comparable. They peak at the antiferromagnetic wave vector
except for a narrow region with an incommensurate response. Stronger doping
destroys all correlations.",2005.09901v1
2020-05-28,Multi-ultraflatbands tunability and effect of spin-orbit coupling in twisted bilayer transition metal dichalcogenides,"Ultraflatbands that have been theoretically and experimentally detected in a
bunch of van der Waals stacked materials showing some peculiar properties, for
instance, highly localized electronic states and enhanced electron-electron
interactions. In this Letter, using an accurate tight-binding model, we study
the formation and evolution of ultraflatbands in transition metal
dichalcogenides (TMDCs) under low rotation angles. We find that, unlike in
twisted bilayer graphene, ultraflatbands exist in TMDCs for almost any small
twist angles and their wave function becomes more localized when the rotation
angle decreases. Lattice relaxation, pressure and local deformation can tune
the width of the flatbands, as well as their localization. Furthermore, we
investigate the effect of spin-orbit coupling on the flatbands and discover
spin/orbital/valley locking at the minimum of the conduction band at the K
point of the Brillouin zone. The ultraflatbands found in TMDCs with a range of
rotation angle below $7^\circ$, may provide an ideal platform to study strongly
correlated states.",2005.13868v2
2016-03-11,Atomic-scale control of magnetic anisotropy via novel spin-orbit coupling effect in La2/3Sr1/3MnO3/SrIrO3 superlattices,"Magnetic anisotropy (MA) is one of the most important material properties for
modern spintronic devices. Conventional manipulation of the intrinsic MA, i.e.
magnetocrystalline anisotropy (MCA), typically depends upon crystal symmetry.
Extrinsic control over the MA is usually achieved by introducing shape
anisotropy or exchange bias from another magnetically ordered material. Here we
demonstrate a pathway to manipulate MA of 3d transition metal oxides (TMOs) by
digitally inserting non-magnetic 5d TMOs with pronounced spin-orbit coupling
(SOC). High quality superlattices comprised of ferromagnetic La2/3Sr1/3MnO3
(LSMO) and paramagnetic SrIrO3 (SIO) are synthesized with the precise control
of thickness at atomic scale. Magnetic easy axis reorientation is observed by
controlling the dimensionality of SIO, mediated through the emergence of a
novel spin-orbit state within the nominally paramagnetic SIO.",1603.03794v2
2016-10-31,La-doping effect on spin-orbit coupled Sr2IrO4 probed by x-ray absorption spectroscopy,"Sr2IrO4 was predicted to be an unconventional superconductor upon carrier
doping since it highly resembles the high-temperature cuprates. Here, to
understand carrier doping effect on spin-orbit coupled Mott insulator Sr2IrO4,
the electronic structure and local structure distortion for Sr2-xLaxIrO4 system
have been investigated by x-ray absorption spectroscopy (XAS). By comparing the
intensity of white-line features at the Ir L2,3 absorption edges, we observe
remarkably large branching ratios in La-doped compounds, greater than that of
the parent material Sr2IrO4, suggesting a strong spin-orbit interaction (SOI)
for Sr2IrO4-based system. Moreover, extended x-ray absorption fine structure
(EXAFS) spectra demonstrate more regular IrO6 octahedra, i.e. the weakened
crystal electric field (CEF) versus La-doping. By theoretical calculations, the
synergistic effect of regular IrO6 octahedra and electron doping is
established, which accounts for the transition from a Mott insulator to a
conductive state in Sr2-xLaxIrO4-based system.",1610.09839v1
2016-12-07,Quantum phases of interacting three-component fermions under the influence of spin-orbit coupling and Zeeman fields,"We describe the quantum phases of interacting three component fermions in the
presence of spin-orbit coupling, as well as linear and quadratic Zeeman fields.
We classify the emerging superfluid phases in terms of the loci of zeros of
their quasi-particle excitation spectrum in momentum space, and we identify
several Lifshitz-type topological transitions. In the particular case of
vanishing quadratic Zeeman field, a quintuple point exists where four gapless
superfluid phases with surface and line nodes converge into a fully gapped
superfluid phase. Lastly, we also show that the simultaneous presence of
spin-orbit and Zeeman fields transforms a momentum-independent scalar order
parameter into an explicitly momentum-dependent tensor in the generalized
helicity basis.",1612.02365v1
2017-07-05,Nuclear Structure Features of Gamow-Teller Excitations,"It is widely accepted that nuclear Gamow-Teller transitions are quenched;
shell-model calculations also showed a clear anticorrelation between the
Gamow-Teller strength and the transition rate of the collective quadrupole
excitation from the ground state. We discuss the physics beyond this
observation. It is based on the existence of spin-orbit coupling that is
responsible for the non-zero probabilities of Gamow-Teller transitions in
self-conjugate nuclei (N = Z). The shell-model calculations in the f p-space
demonstrate the effects of the gradual artificial removal of the spin-orbit
coupling that influences Gamow-Teller and quadrupole modes in opposite way. The
realistic spin-orbit splitting moves the cumulative Gamow-Teller strength up
and leads to stronger fragmentation; both trends are discussed in terms of
simple symmetry arguments. Along with this process, the Gamow-Teller operator
excites, in addition to the main line of L = 0 states, states with L = 2 which
should be added, with the interference terms, to account for the total
strength.",1707.01293v1
2017-11-21,An efficient method for hybrid density functional calculation with spin-orbit coupling,"In first-principles calculations, hybrid functional is often used to improve
accuracy from local exchange correlation functionals. A drawback is that
evaluating the hybrid functional needs significantly more computing effort.
When spin-orbit coupling (SOC) is taken into account, the non-collinear spin
structure increases computing effort by at least eight times. As a result,
hybrid functional calculations with SOC are intractable in most cases. In this
paper, we present an approximate solution to this problem by developing an
efficient method based on a mixed linear combination of atomic orbital (LCAO)
scheme. We demonstrate the power of this method using several examples and we
show that the results compare very well with those of direct hybrid functional
calculations with SOC, yet the method only requires a computing effort similar
to that without SOC. The presented technique provides a good balance between
computing efficiency and accuracy, and it can be extended to magnetic
materials.",1711.07640v2
2017-11-29,p-wave superconductivity in weakly repulsive 2D Hubbard model with Zeeman splitting and weak Rashba spin-orbit coupling,"We study the superconducting order in a two-dimensional square lattice
Hubbard model with weak repulsive interactions, subject to a Zeeman field and
weak Rashba spin-orbit interactions. Diagonalizing the non-interacting
Hamiltonian leads to two separate bands, and by deriving an effective
low-energy interaction we find the mean field gap equations for the
superconducting order parameter on the bands. Solving the gap equations just
below the critical temperature, we find that superconductivity is caused by
Kohn-Luttinger type interaction, while the pairing symmetry of the bands are
indirectly affected by the spin-orbit coupling. The dominating attractive
momentum channel of the Kohn-Luttinger term depends on the filling fraction $n$
of the system, and it is therefore possible to change the momentum dependence
of the order parameter by tuning $n$. Moreover, $n$ also determines which band
has the highest critical temperature. Rotating the magnetic field changes the
momentum dependence from states that for small momenta reduce to a chiral $p_x
\pm i p_y$ type state for out-of-plane fields, to a nodal p-wave type state for
purely in-plane fields.",1711.11047v2
2019-06-07,Field-free switching of a Spin-orbit torque device aided by interlayer-coupling induced domain walls,"The spin-orbit torque device is promising as a candidate for next generation
magnetic memory, while the static in-plane field needed to induce deterministic
switching is a main obstacle for its application in highly integrated circuits.
Instead of introducing effective field into the device, in this work we present
an alternative way to achieve the field-free current-driven magnetization
switching. By adding Tb/Co multilayers at two ends of the current channel,
assisting domain wall is created by interlayer exchange coupling. The
field-free deterministic switching is achieved by the movement of the domain
wall driven by current. By loop shift measurement we find the driven force
exerted on the domain wall is determined by the direction of the in-plane
moment in the domain wall. Finally, we modify the device into a synthetic
antiferromagnetic structure to solve the problem of reading out signal. The
present work broadens the choice of field-free spin-orbit torque device design
and clearly depicts the difference between two different switching mechanism.",1906.02938v1
2020-03-20,Spin-orbit-coupled metal candidate PbRe2O6,"We study the lead rhenium oxide PbRe2O6 as a candidate spin-orbit-coupled
metal (SOCM), which has attracted much attention as a testing ground for
studying unconventional Fermi liquid instability associated with a large
spin-orbit interaction. The compound comprises a stack of modulated honeycomb
lattices made of Re5+ (5d2) ions in a centrosymmetric R-3m structure at room
temperature. Resistivity, magnetic susceptibility, and heat capacity
measurements using single crystals reveal two successive first-order phase
transitions at Ts1 = 265 K and Ts2 = 123 K. At Ts1, the magnetic susceptibility
is enormously reduced and a structural transition to a monoclinic structure
takes place, while relatively small changes are observed at Ts2. Surprisingly,
PbRe2O6 bears a close resemblance to another SOCM candidate Cd2Re2O7 despite
crucial differences in the crystal structure and probably in the electronic
structure, suggesting that PbRe2O6 is an SOCM.",2003.09051v1
2021-01-14,Observation of Symmetry-Protected Dirac States in Nonsymmorphic $α$-Antimonene,"Two-dimensional (2D) Dirac states with linear band dispersion have attracted
enormous interest since the discovery of graphene. However, to date, 2D Dirac
semimetals are still very rare due to the fact that 2D Dirac states are
generally fragile against perturbations such as spin-orbit couplings.
Nonsymmorphic crystal symmetries can enforce the formation of Dirac nodes,
providing a new route to establishing symmetry-protected Dirac states in 2D
materials. Here we report the symmetry-protected Dirac states in nonsymmorphic
alpha-antimonene. The antimonene was synthesized by the method of molecular
beam epitaxy. Two Dirac cones with large anisotropy were observed by
angle-resolved photoemission spectroscopy. The Dirac state in alpha-antimonene
is of spin-orbit type in contrast to the spinless Dirac states in graphene. The
result extends the 'graphene' physics into a new family of 2D materials where
spin-orbit coupling is present.",2101.05793v3
2021-05-25,Hartree-Fock study of the moiré Hubbard model for twisted bilayer transition metal dichalcogenides,"Twisted bilayer transition metal dichalcogenides have emerged as important
model systems for the investigation of correlated electron physics because
their interaction strength, carrier concentration, band structure, and
inversion symmetry breaking are controllable by device fabrication, twist
angle, and most importantly, gate voltage, which can be varied in situ. The low
energy physics of some of these materials has been shown to be described by a
""moir\'e Hubbard model"" generalized from the usual Hubbard model by the
addition of strong, tunable spin orbit coupling and inversion symmetry
breaking. In this work, we use a Hartree-Fock approximation to reach a
comprehensive understanding of the moir\'e Hubbard model on the mean field
level. We determine the magnetic and metal-insulator phase diagrams, and assess
the effects of spin orbit coupling, inversion symmetry breaking, and the
tunable van Hove singularity. We also consider the spin and orbital effects of
applied magnetic fields. This work provides guidance for experiments and sets
the stage for beyond mean-field calculations.",2105.11883v2
2021-07-09,Two-dimensional ferromagnetic spin-orbital excitations in the honeycomb VI$_{3}$,"VI$_{3}$ is a ferromagnet with planar honeycomb sheets of bonded V$^{3+}$
ions held together by van der Waals forces. We apply neutron spectroscopy to
measure the two dimensional ($J/J_{c} \approx 17$) magnetic excitations in the
ferromagnetic phase, finding two energetically gapped ($\Delta \approx k_{B}
T_{c} \approx$ 55 K) and dispersive excitations. We apply a multi-level spin
wave formalism to describe the spectra in terms of two coexisting domains
hosting differing V$^{3+}$ orbital ground states built from contrasting
distorted octahedral environments. This analysis fits a common nearest neighbor
in-plane exchange coupling ($J$=-8.6 $\pm$ 0.3 meV) between V$^{3+}$ sites. The
distorted local crystalline electric field combined with spin-orbit coupling
provides the needed magnetic anisotropy for spatially long-ranged
two-dimensional ferromagnetism in VI$_{3}$.",2107.04311v1
2022-01-24,Hund's coupling and electronic anisotropy in the spin-density wave state of iron pnictides,"In the multiband systems, Hund's coupling ($J$) plays a significant role in
the spin and charge excitations. We study the dependence of electronic
anisotropy on $J$ in terms of Drude-weight along different directions as well
as the orbital order in the four-fold symmetry broken spin-density wave state
of iron pnictides. A robust behavior of the Drude-weight anisotropy within a
small window around $J \sim 0.25U$ with $U$ as intraorbital Coulomb interaction
is described in terms of orbital-weight distribution along the reconstructed
Fermi surfaces. We also find that the ferro-orbital order increases with $J$ in
the widely accepted regime for the latter, which is explained as a consequence
of rising exchange field with an increase in magnetization.",2201.09808v1
2022-03-14,Noncollinear antiferromagnetic textures driven high harmonic generation from magnetic dynamics in the absence of spin-orbit coupling,"We demonstrate the generation of high order harmonics in carrier pumping from
precessing ferromagnetic or antiferromagnetic orders, excited via magnetic
resonance, in the presence of topological antiferromagnetic textures. This
results in an enhancement of the carrier dynamics by orders of magnitude.
Interestingly, the generation process occurs in an intrinsic manner, and is
solely governed by the interplay between the s-d exchange coupling underlying
the noncollinear antiferromagnetic order and the dynamical s-d exchange
parameter of the magnetic drive. Therefore, the relativistic spin-orbit
interaction is not required for the emergence of high harmonics in the pumped
currents. Accordingly, the noncollinear topological antiferromagnetic order is
presented as an alternative to spin-orbit interaction for the purpose of
harnessing high harmonic emission in carrier pumping. Our proposal initiates a
tantalizing perspective for the exploitation of topological magnetic textures
in the context of the highly active domain of ultrafast spintronics.",2203.07310v2
2022-08-05,Field-controlled quantum anomalous Hall effect in electron-doped CrSiTe$_{ 3 }$ monolayer: a first-principles prediction,"We report Chern insulating phases emerging from a single layer of layered
chalcogenide CrSiTe$_{3}$, a transition metal trichacogenides (TMTC) material,
in the presence of charge doping. Due to strong hybridization with Te $p$
orbitals, the spin-orbit coupling effect opens a finite band gap, leading to a
nontrivial topology of the Cr $e_{\mathrm{g}}$ conduction band manifold with
higher Chern numbers. Our calculations show that quantum anomalous Hall effects
can be realized by adding one electron in a formula unit cell of
Cr$_{2}$Si$_{2}$Te$_{6}$, equivalent to electron doping by
2.36$\times$10$^{14}$ cm$^{-2}$ carrier density. Furthermore, the
doping-induced anomalous Hall conductivity can be controlled by an external
magnetic field via spin-orientation-dependent tuning of the spin-orbit
coupling. In addition, we find distinct quantum anomalous Hall phases employing
tight-binding model analysis, suggesting that CrSiTe$_{3}$ can be a fascinating
new platform to realize Chern insulating systems with higher Chern numbers.",2208.02997v2
2022-09-14,Optimization of the Femtosecond Laser Impulse for Excitation and the Spin-Orbit Mediated Dissociation in the NaRb Dimer,"We study the dynamics of multiple coupled states under the influence of an
arbitrary time-dependent external field to investigate the femtosecond
laser-driven excitation and the spin-orbit mediated dissociation in the NaRb
dimer. In this process, the dimer is excited from the ground triplet state
$1^3\Sigma^+$ to the $1^3\Pi$ state using the femtosecond laser impulse and the
spin-orbit coupling between the $1^3\Pi$ and $2^1\Sigma^+$ states results in
the singlet-triplet transition. The laser impulse parameters are optimised to
obtain maximum yield in electronic states correlating with the first excited
atomic asymptote. We observe the detailed population statistics and power-law
decay of these states. Finally, the analysis of the population oscillations
allows us to determine the optimal time delay for dumping the molecule to its
absolute ground state.",2209.06863v3
2022-12-21,Lattice vibrational modes in changchengite from Raman spectroscopy and first principles electronic structure,"We measured room-temperature phonon Raman spectra of changchengite (IrBiS)
and compared the experimental phonon wavenumbers to the theoretical ones
obtained by means of the \emph{ab initio} density-functional-theory
calculations in the presence and absence of the spin-orbit coupling effects.
Combining two different excitation photon energies all the symmetry predicted
Raman modes are experimentally observed. The electronic properties of IrBiS are
found to be similar to the recently studied isostructural compound IrBiSe
showing a large Dresselhaus spin-orbit valence band splitting. A good agreement
between the experimental and theoretically predicted Raman phonon wavenumbers
is found only when the lattice parameter is constrained to the experimental
value. The inclusion of the spin orbit coupling does not significantly affect
the phonon wavenumbers.",2212.11349v1
2023-01-25,Slave-spin mean field for broken-symmetry states: Néel antiferromagnetism and its phase separation in multi-orbital Hubbard models,"We introduce the generalization of the Slave-Spin Mean-Field method to
broken-symmetry phases. Through a variational approach we derive the
single-particle energy shift in the mean-field equations which generates the
appropriate self-consistent field responsible for the stabilization of the
broken symmetry. With this correction the different flavours of the slave-spin
mean-field are actually the same method and they give identical results to
Kotliar-Ruckenstein slave-bosons and to the Gutzwiller approximation. We apply
our formalism to the N\'eel antiferromagnetic state and study it in
multi-orbital models as a function of the number of orbitals and Hund's
coupling strength, providing phase diagrams in the interaction-doping plane. We
show that the doped antiferromagnet in proximity of half-filling is typically
unstable towards insulator-metal and magnetic-non magnetic phase separation.
Hund's coupling extends the range of this antiferromagnet, and favors its phase
separation.",2301.10726v2
2024-03-15,Thermoelectric performance of nano junctions subjected to microwave driven spin-orbit coupling,"Coherent charge and heat transport through periodically driven nanodevices
provide a platform for studying thermoelectric effects on the nanoscale. Here
we study a junction comprising a quantum dot connected to two fermionic
terminals by two weak links. An AC electric field induces time-dependent
spin-orbit interaction in the weak links. We show that this setup supports DC
charge and heat currents and that thermoelectric performance can be improved,
as reflected by the effect of the spin-orbit coupling on the Seebeck
coefficient and the electronic thermal conductance. Our analysis is based on
the nonequilibrium Keldysh Green's function formalism in the time domain and
reveals an interesting distribution of the power supply from the AC source
among the various components of the device, apparently not realized before.",2403.10264v1
2024-03-21,Current density functional framework for spin-orbit coupling: Extension to periodic systems,"Spin-orbit coupling induces a current density in the ground state, which
consequently requires a generalization for meta-generalized gradient
approximations. That is, the exchange-correlation energy has to be constructed
as an explicit functional of the current density and a generalized kinetic
energy density has to be formed to satisfy theoretical constraints. Herein, we
generalize our previously presented formalism of spin-orbit current density
functional theory [Holzer et al., J. Chem. Phys. 157, 204102 (2022)] to
non-magnetic and magnetic periodic systems of arbitrary dimension. Besides the
ground-state exchange-correlation potential, analytical derivatives such as
geometry gradients and stress tensors are implemented. The importance of the
current density is assessed for band gaps, lattice constants, magnetic
transitions, and Rashba splittings. For the latter, the impact of the current
density may be larger than the deviation between different density functional
approximations.",2403.14420v1
2003-12-17,A Post-Newtonian diagnostic of quasi-equilibrium binary configurations of compact objects,"Using equations of motion accurate to the third post-Newtonian (3PN) order
(O(v/c)^6 beyond Newtonian gravity), we derive expressions for the total energy
E and angular momentum J of the orbits of compact binary systems (black holes
or neutron stars) for arbitrary orbital eccentricity. We also incorporate
finite-size contributions such as spin-orbit and spin-spin coupling, and
rotational and tidal distortions, calculated to the lowest order of
approximation, but we exclude the effects of gravitational radiation damping.
We describe how these formulae may be used as an accurate diagnostic of the
physical content of quasi-equilibrium configurations of compact binary systems
of black holes and neutron stars generated using numerical relativity. As an
example, we show that quasi-equilibrium configurations of corotating neutron
stars recently reported by Miller et al. can be fit by our diagnostic to better
than one per cent with a circular orbit and with physically reasonable tidal
coefficients.",0312082v3
2015-12-07,Novel Magnetic Quantization of sp$^{3}$ Bonding in Monolayer Tinene,"A generalized tight-binding model, which is based on the subenvelope
functions of the different sublattices, is developed to explore the novel
magnetic quantization in monolayer gray tin. The effects due to the $sp^{3}$
bonding, the spin-orbital coupling, the magnetic field and the electric field
are simultaneously taken into consideration. The unique magneto-electronic
properties lie in two groups of low-lying Landau levels, with different orbital
components, localization centers, state degeneracy, spin configurations, and
magnetic- and electric-field dependences. The first and second groups mainly
come from the $5p_{z}$ and ($5p_{x}$,$5p_{y}$) orbitals, respectively. Their
Landau-level splittings are, respectively, induced by the electric field and
spin-orbital interactions. The intragroup anti-crossings are only revealed in
the former. The unique tinene Landau levels are absent in graphene, silicene
and germanene.",1512.02129v1
2022-12-06,Multipolar interactions and magnetic excitation gap in d$^3$ spin-orbit Mott insulators,"In Mott insulators with a half-filled $t_{2g}$ shell the Hund's rule coupling
induces a spin-3/2 orbital-singlet ground state. The spin-orbit interaction is
not expected to qualitatively impact low-energy degrees of freedom in such
systems. Indeed, $d^3$ cubic double perovskites (DP) of heavy transition metals
are believed to exhibit conventional collinear magnetic orders. However, their
inelastic neutron scattering spectra feature large gaps of unclear origin. Here
we derive first-principles low-energy Hamiltonians for the cubic DP
Ba$_2$Y$B'$O$_6$ ($B'=$ Os, Ru) and show that they include significant
multipolar - dipole-octupolar - intersite exchange terms. These terms break
continuous symmetry of the spin-3/2 Hamiltonian opening an excitation gap. The
calculated gap magnitudes are in good agreement with experiment. The
dipole-octupolar intersite exchange is induced due to excited states of the
$t_{2g}^3$ manifold that are admixed by the spin-orbit interaction into the
spin-3/2 ground state.",2212.03358v3
1999-12-29,"Competition between ferromagnetic and charge-orbital ordered phases in Pr$_{1-x}$Ca$_{x}$MnO$_3$ for $x$=1/4, 3/8, and 1/2","Spin, charge, and orbital structures in models for doped manganites are
studied by a combination of analytic mean-field and numerical relaxation
techniques. At realistic values for the electron-phonon and antiferromagnetic
$t_{2g}$ spin couplings, a competition between a ferromagnetic (FM) phase and a
charge-orbital ordered (COO) insulating state is found for $x$=1/4, 3/8, and
1/2, as experimentally observed in Pr$_{1-x}$Ca$_{x}$MnO$_3$ for
$x$=0.3$\sim$0.5. The theoretical predictions for the spin-charge-orbital
ordering pattern are compared with experiments. The FM-COO energy difference is
surprisingly small for the densities studied, result compatible with the
presence of a robust colossal-magnetoresistive effect in
Pr$_{1-x}$Ca$_{x}$MnO$_3$ in a large density interval.",9912469v1
2004-03-25,XMCD characterization of rare-earth dopants in Ni$_{81}$Fe$_{19}$(50nm): microscopic basis of engineered damping,"We present direct evidence for the contribution of local orbital moments to
the damping of magnetization precession in magnetic thin films. Using x-ray
magnetic circular dichroism (XMCD) characterization of rare-earth (RE)
M$_{4,5}$ edges in Ni$_{81}$Fe$_{19}$ doped with $<$ 2% Gd and Tb, we show that
the enhancement of GHz precessional relaxation is accompanied by a significant
orbital moment fraction on the RE site. Tb impurities, which enhance the
Landau-Lifshitz(-Gilbert) LL(-G) damping $\lambda(\alpha)$, show a spin to
orbital number ratio of 1.5$\pm$0.3; Gd impurities, which have no effect on
damping, show a spin to orbital number ratio of zero within experimental error.
The results indicate that the dopant-based control of magnetization damping in
RE-doped ferromagnets is an atomistic effect, arising from spin-lattice
coupling, and thus scalable to nanometer dimensions.",0403627v1
2004-09-12,Quantum Versus Jahn-Teller Orbital Physics in YVO$_3$ and LaVO$_3$,"We argue that the large Jahn-Teller (JT) distortions in YVO$_3$ and LaVO$_3$
should suppress the quantum orbital fluctuation. The unusual magnetic
properties can be well explained based on LDA+$U$ calculations using
experimental structures, in terms of the JT orbital. The observed splitting of
the spin-wave dispersions for YVO$_3$ in C-type antiferromagnetic state is
attributed to the inequivalent VO$_2$ layers in the crystal structure, instead
of the ``orbital Peierls state''. Alternative stacking of $ab$-plane exchange
couplings produces the c-axis spin-wave splitting, thus the spin system is
highly three dimensional rather than quasi-one-dimensional. Similar splitting
is also predicted for LaVO$_3$, although it is weak.",0409299v1
2006-01-05,On-site approximation for spin-orbit coupling in LCAO density functional methods,"We propose a computational method that simplifies drastically the inclusion
of spin-orbit interaction in density functional theory implemented on localised
atomic orbital basis sets. Our method is based on a well-known procedure for
obtaining pseudopotentials from atomic relativistic 'ab initio' calculations
and on an on-site approximation for the spin-orbit matrix elements. We have
implemented the technique in the SIESTA code, and we show that it provides
accurate results for the overall band structure and splittings of group IV and
III-IV semiconductors as well as for 5d metals.",0601093v3
2009-01-11,"Unconventional Bose-Einstein Condensations Beyond the ""No-node"" Theorem","Feynman's ""no-node"" theorem states that the conventional many-body
ground-state wavefunctions of bosons in the coordinate representation is
positive-definite. This implies that time-reversal symmetry cannot be
spontaneously broken. In this article, we review our progress in studying a
class of new states of unconventional Bose-Einstein condensations beyond this
paradigm. These states can either be the long-lived metal-stable states of
ultra-cold bosons in high orbital bands in optical lattices as a result of the
""orbital-Hund's rule"" interaction, or the ground states of spinful bosons with
spin-orbit coupling linearly dependent on momentum. In both cases, Feynman's
argument does not apply. The resultant many-body wavefunctions are
complex-valued and thus break time-reversal symmetry spontaneously. Exotic
phenomena in these states include the Bose-Einstein condensation at non-zero
momentum, the ordering of orbital angular momentum moments, the half-quantum
vortex, and the spin texture of skyrmions.",0901.1415v2
2011-05-12,Coupled spin-lattice fluctuations in a compound with orbital degrees of freedom: the Cr based dimer system Sr3Cr2O8,"We report on an extended fluctuation regime in the spin dimer system Sr3Cr2O8
based on anomalies in Raman active phonons and magnetic scattering. The
compound has two characteristic temperatures, TS = 275 K, related to a
Jahn-Teller transition with structural distortions and orbital ordering and a
second, T*= 150 K, which is due to further changes in the orbital sector. Below
TS quasielastic scattering marks strong fluctuations and in addition phonon
anomalies are observed. For temperatures below T* we observe an exponential
decrease of one phonon linewidth and determine a gap of the orbital
excitations. At low temperatures the observation of two- and three-magnon
scattering allows the determination of the spin excitation gap.",1105.2369v1
2016-09-12,Hund's rule-driven Dzyaloshinskii-Moriya interaction at 3d-5d interfaces,"Using relativistic first-principles calculations, we show that the chemical
trend of Dzyaloshinskii-Moriya interaction (DMI) in 3d-5d ultrathin films
follows Hund's first rule with a tendency similar to their magnetic moments in
either the unsupported 3d monolayers or 3d-5d interfaces. We demonstrate that,
besides the spin-orbit coupling (SOC) effect in inversion asymmetric
noncollinear magnetic systems, the driving force is the 3d orbital occupation
and their spin flip/mixing processes with the spin-orbit active 5d states
control directly the sign and magnitude of the DMI. The magnetic chirality
changes are discussed in the light of the interplay between SOC, Hund's first
rule, and the crystal field splitting of d orbitals.",1609.04004v1
2017-10-09,Generation of a lattice of spin-orbit beams via coherent averaging,"We describe a highly robust method, applicable to both electromagnetic and
matter-wave beams, that can produce a beam consisting of a lattice of orbital
angular momentum (OAM) states coupled to a two-level system. We also define
efficient protocols for controlling and manipulating the lattice
characteristics. These protocols are applied in an experimental realization of
a lattice of optical spin-orbit beams. The novel passive devices we demonstrate
here are also a natural alternative to existing methods for producing
single-axis OAM and spin-orbit beams. Our techniques provide new tools for
investigations of chiral and topological materials with light and particle
beams.",1710.03169v1
2018-07-22,Ordering of hidden multipoles in spin-orbital entangled 5$d^{1}$ Ta chlorides,"Spin-orbit coupling of as large as a half eV for electrons in 5$d$ orbitals
often gives rise to the formation of spin-orbital entangled objects,
characterized by the effective total angular momentum $J_{eff}$. Of particular
interest are the $J_{eff}$ = 3/2 states realized in 5$d^{1}$ transition metal
ions surrounded by an anion octahedron. The pure $J_{eff}$ = 3/2 quartet does
not have any magnetic dipolar moment (<$M$> = 0) but hosts hidden
pseudo-dipolar moments accompanied by charge quadrupoles and magnetic
octupoles. Cs$_2$TaCl$_6$ and Rb$_2$TaCl$_6$ are correlated insulators with
5$d^{1}$ Ta$^{4+}$ ions in a regular Cl octahedron. Here we demonstrate that
these Ta chlorides have a substantially suppressed effective magnetic dipolar
moment of ~ 0.2 ${\mu}_B$. Two phase transitions are observed at low
temperatures that are not pronounced in the magnetization but accompanied with
large electronic entropy of $R$ln4. We ascribe the two transitions to the
ordering of hidden multipoles.",1807.08311v2
2020-05-04,Quantum Magnetism in Wannier-Obstructed Mott Insulators,"We develop a strong coupling approach towards quantum magnetism in Mott
insulators for Wannier obstructed bands. Despite the lack of Wannier orbitals,
electrons can still singly occupy a set of exponentially-localized but
nonorthogonal orbitals to minimize the repulsive interaction energy. We develop
a systematic method to establish an effective spin model from the electron
Hamiltonian using a diagrammatic approach. The nonorthogonality of the Mott
basis gives rise to multiple new channels of spin-exchange (or permutation)
interactions beyond Hartree-Fock and superexchange terms. We apply this
approach to a Kagome lattice model of interacting electrons in Wannier
obstructed bands (including both Chern bands and fragile topological bands).
Due to the orbital nonorthogonality, as parameterized by the nearest neighbor
orbital overlap $g$, this model exhibits stable ferromagnetism up to a finite
bandwidth $W\sim U g$, where $U$ is the interaction strength. This provides an
explanation for the experimentally observed robust ferromagnetism in Wannier
obstructed bands. The effective spin model constructed through our approach
also opens up the possibility for frustrated quantum magnetism around the
ferromagnet-antiferromagnet crossover in Wannier obstructed bands.",2005.01439v1
2019-05-27,The Curious Case of NiRh$_2$O$_4$: A Spin-Orbit Entangled Diamond Lattice Paramagnet,"Motivated by the interest in topological quantum paramagnets in candidate
spin-$1$ magnets, we investigate the diamond lattice compound NiRh$_2$O$_4$
using {\it ab initio} theory and model Hamiltonian approaches. Our density
functional study, taking into account the unquenched orbital degrees of
freedom, shows stabilization of $S=1$ and $L=1$ state. We highlight the
importance of spin-orbit coupling, in addition to Coulomb correlations, in
driving the insulating gap, and uncover frustrating large second-neighbor
exchange mediated by Ni-Rh covalency. A single-site model Hamiltonian
incorporating the large tetragonal distortion is shown to give rise to a
spin-orbit entangled non-magnetic ground state, largely accounting for the
entropy, magnetic susceptibility, and inelastic neutron scattering results.
Incorporating inter-site exchange within a slave-boson theory, we show that
exchange frustration can suppress exciton condensation. We capture the
dispersive gapped magnetic modes, uncover `dark states' invisible to neutrons,
and make predictions for future experiments.",1905.11403v1
2022-08-25,Anomalous Hall effect in antiferromagnetic perovskites,"We theoretically study the anomalous Hall effect (AHE) in perovskites with
antiferromagnetic (AFM) orderings. By studying the multiorbital Hubbard model
for $d$ electrons in perovskite transition metal oxides under the
GdFeO$_3$-type distortion within the Hartree-Fock approximation, we investigate
the behavior of intrinsic AHE owing to the atomic spin-orbit coupling via the
linear response theory. We consider the cases where there exist two ($d^2$) and
three ($d^3$) electrons in the $t_{2g}$ orbitals, and show that AFM ordered
states can exhibit AHE. In the $d^2$ case, $C$-type AFM states give rise to dc
AHE in metals and optical (finite-$\omega$) AHE in insulators accompanying
orbital ordering, while in the $d^3$ case, a $G$-type AFM insulating state
supports the optical AHE. By resolving the components in the spin patterns
compatible with the space group symmetry, we specify the collinear AFM
component to be responsible for the AHE, rather than the small ferromagnetic
component. We discuss the microscopic origin of the AHE: the collinear AFM spin
structure produces a nonzero Berry phase from the triangular units of the
lattice, activated by the complex orbital mixing terms owing to the
GdFeO$_3$-type distortion, and results in the microscopic Lorentz force.",2208.11823v1
2020-01-21,Strong Spin-Orbit Quenching via the Product Jahn-Teller Effect in Neutral Group IV Artificial Atom Qubits in Diamond,"Artificial atom qubits in diamond have emerged as leading candidates for a
range of solid-state quantum systems, from quantum sensors to repeater nodes in
memory-enhanced quantum communication. Inversion-symmetric group IV vacancy
centers, comprised of Si, Ge, Sn and Pb dopants, hold particular promise as
their neutrally charged electronic configuration results in a ground-state spin
triplet, enabling long spin coherence above cryogenic temperatures. However,
despite the tremendous interest in these defects, a theoretical understanding
of the electronic and spin structure of these centers remains elusive. In this
context, we predict the ground- and excited-state properties of the neutral
group IV color centers from first principles. We capture the product
Jahn-Teller effect found in the excited state manifold to second order in
electron-phonon coupling, and present a non-perturbative treatment of the
effect of spin-orbit coupling. Importantly, we find that spin-orbit splitting
is strongly quenched due to the dominant Jahn-Teller effect, with the lowest
optically-active $^3E_u$ state weakly split into $m_s$-resolved states. The
predicted complex vibronic spectra of the neutral group IV color centers are
essential for their experimental identification and have key implications for
use of these systems in quantum information science.",2001.07743v1
2020-12-10,Counterintuitive gate dependence of weak antilocalization in bilayer graphene/WSe$_2$ heterostructures,"Strong gate control of proximity-induced spin-orbit coupling was recently
predicted in bilayer graphene/transition metal dichalcogenides (BLG/TMDC)
heterostructures, as charge carriers can easily be shifted between the two
graphene layers, and only one of them is in close contact to the TMDC. The
presence of spin-orbit coupling can be probed by weak antilocalization (WAL) in
low field magnetotransport measurements. When the spin-orbit splitting in such
a heterostructure increases with the out of plane electric displacement field
$\bar D$, one intuitively expects a concomitant increase of WAL visibility. Our
experiments show that this is not the case. Instead, we observe a maximum of
WAL visibility around $\bar D=0$. This counterintuitive behaviour originates in
the intricate dependence of WAL in graphene on symmetric and antisymmetric spin
lifetimes, caused by the valley-Zeeman and Rashba terms, respectively. Our
observations are confirmed by calculating spin precession and spin lifetimes
from an $8\times 8$ model Hamiltonian of BLG/TMDC.",2012.05718v4
2021-05-04,Topologically-driven three-spin chiral exchange interactions treated from first principles,"The mechanism behind the three-spin chiral interaction (TCI) included in the
extended Heisenberg Hamiltonian and represented by an expression worked out
recently (Phys.\ Rev.\ B, {\bf 101}, 174401 (2020)) is discussed. It is
stressed that this approach provides a unique set of the multispin exchange
parameters which are independent of each other either due to their different
order of perturbation or due to different symmetry. This ensures in particular
the specific properties of the TCI that were demonstrated previously via fully
relativistic first principles calculations, and that result from the common
influence of several issues not explicitly seen from the expression for the TCI
parameters. Therefore, an interpretation of the TCI is suggested, showing
explicitly its dependence on the relativistic spin-orbit coupling and on the
topological orbital susceptibility (TOS). This is based on an expression for
the TOS that is worked out on the same footing as the expression for the TCI.
Using first-principles calculations we demonstrate in addition numerically the
common topological properties of the TCI and TOS. To demonstrate the role of
the relativistic spin-orbit coupling (SOC) for the TCI, a so-called
topological' spin susceptibility (TSS) is introduced. This quantity
characterizes the SOC induced spin magnetic moment on the atom in the presence
of non-collinear magnetic structure, giving a connection between the TOS and
TCI. Numerical results again support our conclusions.",2105.01653v2
2023-05-25,Dzyaloshinskii-Moriya interaction in strongly spin-orbit-coupled systems: General formula and application to topological and Rashba materials,"We theoretically study the Dzyaloshinskii-Moriya interaction (DMI) mediated
by band electrons with strong spin-orbit coupling (SOC). We first derive a
general formula for the coefficient ${\bm D}_i$ of the DMI in free energy in
terms of Green's functions, and examine its variations in relation to physical
quantities. In general, the DMI coefficient can vary depending on physical
quantities, i.e., whether one is looking at equilibrium spin structure (${\bm
D}_i$) or spin-wave dispersion (${\bm D}_i^{(2)}$), and the obtained formula
helps to elucidate their relations. By explicit evaluations for a magnetic
topological insulator and a Rashba ferromagnet with perpendicular
magnetization, we observe ${\bm D}_i^{(2)} \ne {\bm D}_i$ in general. In the
latter model, or more generally, when the magnetization and the spin-orbit
field are mutually orthogonal, ${\bm D}_i$ is exactly related to the
equilibrium spin current for arbitrary strength of SOC, generalizing the
similar relation for systems with weak SOC. Among various systems with strong
SOC, magnetic Weyl semimetals are special in that ${\bm D}_i^{(2)} = {\bm
D}_i$, and in fact, the DMI in this system arises as the chiral anomaly.",2305.16083v2
1995-07-11,Quantum interference and the spin orbit interaction in mesoscopic normal-superconducting junctions,"We calculate the quantum correction to the classical conductance of a
disordered mesoscopic normal-superconducting (NS) junction in which the
electron spatial and spin degrees of freedom are coupled by an appreciable spin
orbit interaction. We use random matrix theory to describe the scattering in
the normal part of the junction and consider both quasi-ballistic and diffusive
junctions. The dependence of the junction conductance on the Schottky barrier
transparency at the NS interface is also considered. We find that the quantum
correction is sensitive to the breaking of spin rotation symmetry even when the
junction is in a magnetic field and time reversal symmetry is broken. We
demonstrate that this sensitivity is due to quantum interference between
scattering processes which involve electrons and holes traversing closed loops
in the same direction. We explain why such processes are sensitive to the spin
orbit interaction but not to a magnetic field. Finally we consider the effect
of the spin orbit interaction on the phenomenon of ``reflectionless
tunnelling.''",9507028v2
2003-06-17,Relativistic Models for Binary Neutron Stars with Arbitrary Spins,"We introduce a new numerical scheme for solving the initial value problem for
quasiequilibrium binary neutron stars allowing for arbitrary spins. The coupled
Einstein field equations and equations of relativistic hydrodynamics are solved
in the Wilson-Mathews conformal thin sandwich formalism. We construct sequences
of circular-orbit binaries of varying separation, keeping the rest mass and
circulation constant along each sequence. Solutions are presented for
configurations obeying an n=1 polytropic equation of state and spinning
parallel and antiparallel to the orbital angular momentum. We treat stars with
moderate compaction ((m/R) = 0.14) and high compaction ((m/R) = 0.19). For all
but the highest circulation sequences, the spins of the neutron stars increase
as the binary separation decreases. Our zero-circulation cases approximate
irrotational sequences, for which the spin angular frequencies of the stars
increases by 13% (11%) of the orbital frequency for (m/R) = 0.14 ((m/R) = 0.19)
by the time the innermost circular orbit is reached. In addition to leaving an
imprint on the inspiral gravitational waveform, this spin effect is measurable
in the electromagnetic signal if one of the stars is a pulsar visible from
Earth.",0306075v2
2018-07-28,Electronic transport and the related anomalous effects in silicene-like hexagonal lattice,"We investigate the anomalous effects due to the Berry correction and the
considerable perturbations in the silicene-like hexagonal lattice system. The
Berry curvature in periodic Bloch band system which related to the
electromagnetic field is explored, the induced transverse anomalous velocity
gives rise to the intrinsic Hall conductivity (without the vertex correction)
expecially in the quantum anomalous Hall phase. The quantum anomalous Hall
effect which related to the anomalous velocity term is detected, including the
band avoided corssing effect and the generated special band gap. %{Enlarged
Galilean symmetry of anyons and the Hall effect} The topological spin transport
is affected by the Berry curvature %{Topological spin transport of a
relativistic electron} %{Anomalous direction for skyrmion bubble motion} and
the spin-current-induced Skyrmion spin texture motion is contrasted between the
quantum spin Hall effect and quantum anomalous Hall effect. Since silicene
involving the orbital degree of freedom, the orbital magnetic moment and
orbital magnetization contributes significantly to the electronic transport
properties of silicene %{Photoinduced quantum spin and valley Hall effects, and
orbital magnetization in monolayer MoS2} as explored in this article. We also
investigate the electronic tunneling properties of silicene in Josephon
junction with the electric-field-induced Rashba-coupling, the anomalous effect
due to the Berry phase is mentioned. Our results is meaningful to the
application of the spintronics and valleytronics base on the silicene-like
topological insulators.",1807.10898v1
2020-05-19,Skew-scattering-induced giant antidamping spin-orbit torques: Collinear and out-of-plane Edelstein effects at two-dimensional material/ferromagnet interfaces,"Heavy metal/ferromagnet interfaces feature emergent spin-orbit effects absent
in the bulk materials. Because of their inherent strong coupling between spin,
charge and orbital degrees of freedom, such systems provide a platform for
technologically sought-after spin-orbit torques (SOTs). However, the
microscopic origin of purely interfacial antidamping SOT, especially in the
ultimate atomically thin limit, has proven elusive. Here, using two-dimensional
(2D) van der Waals materials as a testbed for interfacial phenomena, we address
this problem by means of a microscopic framework accounting for band structure
effects and impurity scattering on equal footing and nonperturbatively. A
number of unconventional and measurable effects are predicted, the most
remarkable of which is a giant enhancement of antidamping SOT in the dilute
disorder limit induced by a robust skew scattering mechanism, which is
operative in realistic interfaces and does not require magnetic impurities. The
newly unveiled skew scattering mechanism activates rich semiclassical
spin-charge conversion effects that have gone unnoticed in the literature,
including a collinear Edelstein effect with nonequilibrium spin polarization
aligned with the direction of the applied current.",2005.09670v2
2019-08-13,Orbital transmutation and the electronic spectrum of FeSe in the nematic phase,"We consider the electronic spectrum near $M=(\pi,\pi)$ in the nematic phase
of FeSe ($T<T_{{\rm nem}}$) and make a detailed comparison with recent ARPES
and STM experiments. Our main focus is the unexpected temperature dependence of
the excitations at the $M$ point. These have been identified as having $xz$ and
$yz$ orbital character well below $T_{{\rm nem}}$, but remain split at
$T>T_{{\rm nem}}$, in apparent contradiction to the fact that in the tetragonal
phase the $xz$ and $yz$ orbitals are degenerate. Here we present two scenarios
which can describe the data. In both scenarios, hybridization terms present in
the tetragonal phase leads to an orbital transmutation, a change in the
dominant orbital character of some of the bands, between $T > T_{\rm nem}$ and
$T \ll T_{\rm nem}$. The first scenario relies on the spin-orbit coupling at
the $M$ point. We show that a finite spin-orbit coupling gives rise to orbital
transmutation, in which one of the modes, identified as $xz$ ($yz)$ at $T \ll
T_{{\rm nem}}$, becomes predominantly $xy$ at $T > T_{{\rm nem}}$ and hence
does not merge with the predominantly $yz$ ($xz$) mode. The second scenario,
complementary to the first, takes into consideration the fact that both ARPES
and STM are surface probes. In the bulk, a direct hybridization between the
$xz$ and $yz$ orbitals is not allowed at the $M$ point, however, it is
permitted on the surface. In the presence of a direct $xz/yz$ hybridization,
the orbital character of the $xz/yz$ modes changes from pure $xz$ and pure $yz$
at $T \ll T_{{\rm nem}}$ to $xz \pm yz$ at $T > T_{{\rm nem}}$, i.e., the two
modes again have mono-orbital character at low $T$, but do not merge at
$T_{{\rm nem}}$. We discuss how these scenarios can be distinguished in
polarized ARPES experiments.",1908.04889v2
2003-07-01,Spin Exciton in quantum dot with spin orbit coupling in high magnetic field,"Coulomb interactions of few ($ N $) electrons confined in a disk shaped
quantum dot, with a large magnetic field $B=B^*$ applied in the z-direction
(orthogonal to the dot), produce a fully spin polarized ground state. We
numerically study the splitting of the levels corresponding to the multiplet of
total spin $S=N/2$ (each labeled by a different total angular momentum $ J_z $)
in presence of an electric field parallel to $ B $, coupled to $ S $ by a
Rashba term. We find that the first excited state is a spin exciton with a
reversed spin at the origin. This is reminiscent of the Quantum Hall
Ferromagnet at filling one which has the skyrmion-like state as its first
excited state. The spin exciton level can be tuned with the electric field and
infrared radiation can provide energy and angular momentum to excite it.",0307016v2
2006-03-02,Quantum Spin Hall Effect and Topologically Invariant Chern Numbers,"We present a topological description of quantum spin Hall effect (QSHE) in a
two-dimensional electron system on honeycomb lattice with both intrinsic and
Rashba spin-orbit couplings. We show that the topology of the band insulator
can be characterized by a $2\times 2$ traceless matrix of first Chern integers.
The nontrivial QSHE phase is identified by the nonzero diagonal matrix elements
of the Chern number matrix (CNM). A spin Chern number is derived from the CNM,
which is conserved in the presence of finite disorder scattering and spin
nonconserving Rashba coupling. By using the Laughlin's gedanken experiment, we
numerically calculate the spin polarization and spin transfer rate of the
conducting edge states, and determine a phase diagram for the QSHE.",0603054v1
2007-02-20,Magnification of spin Hall effect in bilayer electron gas,"Spin transport properties of a coupled bilayer electron gas with Rashba
spin-orbit coupling are studied. The definition of the spin currents in each
layer as well as the corresponding continuity-like equations in the bilayer
system are given. The curves of the spin Hall conductivities obtained in each
layer exhibit sharp cusps around a particular value of the tunnelling strength
and the conductivities undergo sign changes across this point. Our
investigation on the impurity effect manifests that an arbitrarily small
concentration of nonmagnetic impurities does not suppress the spin Hall
conductivity to zero in the bilayer system. Based on these features, an
experimental scheme is suggested to detect a magnification of the spin Hall
effect.",0702456v2
2008-03-04,Magneto-Dielectric phenomena in charge and spin frustrated system of layered iron oxide,"Dielectric and magnetic phenomena in spin and charge frustrated system RFe2O4
(R is a rare-earth metal ion) are studied. An electronic model for charge, spin
and orbital degrees in a pair of triangular-lattice planes is derived. We
analyze this model by utilizing the mean-field approximation and the
Monte-Carlo simulation in a finite size cluster. A three fold-type charge
ordered structure with charge imbalance between the planes is stabilized in
finite temperatures. This polar charge order is reinforced by spin ordering of
Fe ions. This novel magneto-dielectric phenomenon is caused by spin frustration
and charge-spin coupling in the exchange interaction. We show cross-correlation
effect in magnetic- and electric-field responses. Oxygen deficiency effect as
an impurity effect in a frustrated charge-spin coupled system is also examined.",0803.0394v1
2008-03-07,Understanding spin transport from the motion in SU(2)$\times$U(1) fields,"Starting from a continuum constituted by charged tops, we formulate the
classical counterpart of a previously obtained covariant continuity-like
equation for the spin current. Such a formulism provides an intuitive picture
to elucidate the non-conservation of the spin current and to interpret the
condition for the emergence of an infinite spin relaxation time. It also
facilitates the discussion on the spin precession in a one-dimensional quantum
wire with Dresselhaus and Rashba spin-orbit couplings. Furthermore, we derive
the diffusion equations for both the charge and spin densities and find that
they couple to each other due to the Zitterbewegung.",0803.1101v1
2013-05-02,Coupled Spin and Pseudo-magnetic Field in Graphene Nanoribbons,"Pseudo-magnetic field becomes an experimental reality after the observation
of zero-field Landau level-like quantization in strained graphene, but it is
not expected that the time-reversal symmetric pseudo-magnetic fields will have
any effect on the spin degree of freedom of the charge carriers. Here, we
demonstrate that spin-orbit coupling (SOC) could act as a bridge between
pseudo-magnetic field and spin. In quantum spin Hall (QSH) states, the
direction of the spin of edge states is tied to their direction of motion
because of the SOC. The pseudo-magnetic field affects the clockwise and
counter-clock-wise edge currents of the QSH states, and consequently lifts the
degenerate edge states of opposite spin orientation. Because of opposite signs
of the pseudo-magnetic field in two valleys of graphene, the one-dimensional
charge carriers at the two opposite edges have different group velocities, and
in some special cases the edge states can only propagate at one edge of the
nanoribbon and the group velocity at the other edge becomes zero.",1305.0335v2
2013-05-27,Collinear and non-collinear spin ground state of wurtzite CoO,"Collinear and non-collinear spin structures of wurtzite phase CoO often
appearing in nano-sized samples are investigated using first-principles density
functional theory calculations. We examined the total energy of several
different spin configurations, electronic structure and the effective magnetic
coupling strengths. It is shown that the AF3-type antiferromagnetic ordering is
energetically most stable among possible collinear configurations. Further, we
found that a novel spiral spin order can be stabilized by including the
relativistic spin-orbit coupling and the non-collinearity of spin direction.
Our result suggests that a non-collinear spin ground state can be observed in
the transition-metal-oxide nanostructures which adds an interesting new aspect
to the nano-magnetism study.",1305.6496v1
2014-07-16,Spin dynamics and magneto-optical response in charge-neutral tunnel-coupled quantum dots,"We model the electron and hole spin dynamics in an undoped double quantum dot
structure, considering the carrier tunneling between quantum dots. Taking into
account also the presence of an in-plane or tilted magnetic field, we provide
the simulation of magneto-optical experiments, like the time resolved Kerr
rotation measurement, which are performed currently on such structures to probe
the temporal spin dynamics. With our model, we reproduce the experimentally
observed effect of the extension of the spin polarization life time caused by
the spatial charge separation, which may occur in structures of this type.
Moreover, we provide a number of qualitative predictions concerning the
necessary conditions for observation of this effect as well as about possible
channels of its suppression, including the spin-orbit coupling, which leads to
tunneling of carriers accompanied by a spin-flip. We consider also the impact
of the magnetic field tilting, which results in an interesting spin
polarization dynamics.",1407.4529v4
2014-09-16,Phonon-modulated magnetic interactions and spin Tomonaga-Luttinger liquid in the p-orbital antiferromagnet CsO2,"The magnetic response of antiferromagnetic CsO2, coming from the p-orbital
S=1/2 spins of anionic O2- molecules, is followed by 133Cs nuclear magnetic
resonance across the structural phase transition occuring at Ts1=61 K on
cooling. Above Ts1, where spins form a square magnetic lattice, we observe a
huge, nonmonotonic temperature dependence of the exchange coupling originating
from thermal librations of O2- molecules. Below Ts1, where antiferromagnetic
spin chains are formed as a result of p-orbital ordering, we observe a spin
Tomonaga-Luttinger-liquid behavior of spin dynamics. These two interesting
phenomena, which provide rare simple manifestations of the coupling between
spin, lattice and orbital degrees of freedom, establish CsO2 as a model system
for molecular solids.",1409.4818v2
2014-09-22,Donor Spin Qubits in Ge-based Phononic Crystals,"We propose qubits based on shallow donor electron spins in germanium.
Spin-orbit interaction for donor spins in germanium is in many orders of
magnitude stronger than in silicon. In a uniform bulk material it leads to very
short spin lifetimes. However the lifetime increases dramatically when the
donor is placed into a quasi-2D phononic crystal and the energy of the Zeeman
splitting is tuned to lie within a phonon bandgap. In this situation single
phonon processes are suppressed by energy conservation. The remaining
two-phonon decay channel is very slow. The Zeeman splitting within the gap can
be fine tuned to induce a strong, long-range coupling between the spins of
remote donors via exchange by virtual phonons. This, in turn, opens a very
efficient way to manipulate the quits. We explore various geometries of
phononic crystals in order to maximize the coherent qubit-qubit coupling while
keeping the decay rate minimal. We find that phononic crystals with unit cell
sizes of 100-150 nm are viable candidates for quantum computing applications
and suggest several spin-resonance experiments to verify our theoretical
predictions.",1409.6285v1
2015-01-25,Continuum model for chiral induced spin selectivity in helical molecules,"A minimal model is exactly solved for electron spin transport on a helix.
Electron transport is assumed to be supported by well oriented $p_z$ type
orbitals on base molecules forming a staircase of definite chirality. In a
tight binding interpretation, the SOC opens up an effective $\pi_z-\pi_z$
coupling via interbase $p_{x,y}-p_z$ hopping, introducing spin coupled
transport. The resulting continuum model spectrum shows two Kramers doublet
transport channels with a gap proportional to the SOC. Each doubly degenerate
channel satisfies time reversal symmetry, nevertheless, a bias chooses a
transport direction and thus selects for spin orientation. The model predicts
which spin orientation is selected depending on chirality and bias, changes in
spin preference as a function of input Fermi level and scattering suppression
protected by the SO gap. We compute the spin current with a definite helicity
and find it to be proportional to the torsion of the chiral structure and the
non-adiabatic Aharonov- Anandan phase. To describe room temperature transport
we assume that the total transmission is the result of a product of coherent
steps limited by the coherence length.",1501.06201v1
2015-03-12,Gate-control of spin-motive force and spin-torque in Rashba SOC systems,"The introduction of a strong Rashba spin orbit coupling (SOC) had been
predicted to enhance the spin motive force (SMF) [see Phys. Rev. Lett. {\bf
108}, 217202 (2012)]. In this work, we predict further enhancement of the SMF
by time modulation of the Rashba coupling $\alpha_R$, which induces an
additional electric field $E^R_d={\dot \alpha_R} m_e/e\hbar({\hat z}\times
{\mathbf m})$. When the modulation frequency is higher than the magnetization
precessing frequency, the amplitude of this field is significantly larger than
previously predicted results. Correspondingly, the spin torque on the
magnetization is also effectively enhanced. Additionally, the nature of SOC
induced spin torque in the system can be transformed from damping to
antidamping-like by modulating ${\dot \alpha_R}$. We also suggest a biasing
scheme to achieve rectification of SMF, {\it i.e.}, by application of a square
wave voltage at the resonant frequency. Finally, we numerically estimate the
resulting spin torque field arising from a Gaussian pulse time modulation of
$\alpha_R$.",1503.03651v2
2016-01-20,Enhanced photonic spin Hall effect with subwavelength topological edge states,"Photonic structures offer unique opportunities for controlling light-matter
interaction, including the photonic spin Hall effect associated with the
transverse spin-dependent displacement of light that propagates in specially
designed optical media. However, due to small spin-orbit coupling, the photonic
spin Hall effect is usually weak at the nanoscale. Here we suggest
theoretically and demonstrate experimentally, in both optics and microwave
experiments, the photonic spin Hall effect enhanced by topologically protected
edge states in subwavelength arrays of resonant dielectric particles. Based on
direct near-field measurements, we observe the selective excitation of the
topological edge states controlled by the handedness of the incident light.
Additionally, we reveal the main requirements to the symmetry of photonic
structures to achieve a topology-enhanced spin Hall effect, and also analyse
the robustness of the photonic edge states against the long-ranged coupling.",1601.05264v1
2017-08-14,Spin-resolved electronic structure of ferroelectric α-GeTe and multiferroic Ge1-xMnxTe,"Germanium telluride features special spin-electric effects originating from
spin-orbit coupling and symmetry breaking by the ferroelectric lattice
polarization, which opens up many prospectives for electrically tunable and
switchable spin electronic devices. By Mn doping of the {\alpha}-GeTe host
lattice, the system becomes a multiferroic semiconductor possessing
magnetoelectric properties in which the electric polarization, magnetization
and spin texture are coupled to each other. Employing spin- and angle-resolved
photoemission spectroscopy in bulk- and surface-sensitive energy ranges and by
varying dipole transition matrix elements, we disentangle the bulk, surface and
surface-resonance states of the electronic structure and determine the spin
textures for selected parameters. From our results, we derive a comprehensive
model of the {\alpha}-GeTe surface electronic structure which fits experimental
data and first principle theoretical predictions and we discuss the
unconventional evolution of the Rashba-type spin splitting upon manipulation by
external B- and E-fields.",1708.04104v1
2019-09-23,Band splitting with vanishing spin polarizations in noncentrosymmetric crystals,"The Dresselhaus and Rashba effects are well-known phenomena in solid-state
physics, in which spin-orbit coupling (SOC) splits spin-up and spin-down energy
bands of nonmagnetic non-centrosymmetric crystals. Here, we discover a new
phenomenon, dubbed as band splitting with vanishing spin polarizations (BSVSP),
in which, as usual, SOC splits the energy bands in nonmagnetic
non-centrosymmetric systems; surprisingly, however, both split bands show no
net spin polarization along certain high-symmetry lines in the Brillouin zone.
In order to rationalize this phenomenon, we propose a new classification of
point groups into pseudo-polar and non-pseudo-polar groups. By means of
first-principles simulations, we demonstrate that BSVSP can take place in both
symmorphic (e.g., bulk GaAs) and non-symmorphic systems (e.g., two dimensional
ferroelectric SnTe). Furthermore, we propose a novel linear magnetoelectric
coupling in reciprocal space, which could be employed to tune the spin
polarization with an external electric field. The BSVSP effect and its
manipulation could therefore pave a new way to novel spintronic devices.",1909.10365v1
2020-01-10,Transport-induced suppression of nuclear field fluctuations in multi-quantum-dot systems,"Magnetic noise from randomly fluctuating nuclear spin ensembles is the
dominating source of decoherence for many multi-quantum-dot multielectron spin
qubits. Here we investigate in detail the effect of a DC electric current on
the coupled electron-nuclear spin dynamics in double and triple quantum dots
tuned to the regime of Pauli spin blockade. We consider both systems with and
without significant spin-orbit coupling and find that in all cases the flow of
electrons can induce a process of dynamical nuclear spin polarization that
effectively suppresses the nuclear polarization gradients over neighboring
dots. Since exactly these gradients are the components of the nuclear fields
that act harmfully in the qubit subspace, we believe that this presents a
straightforward way to extend coherence times in multielectron spin qubits by
at least one order of magnitude.",2001.03481v1
2022-03-30,On the Origins of Life's Homochirality: Inducing Enantiomeric Excess with Spin-Polarized Electrons,"Life as we know it is homochiral, but the origins of biological homochirality
on early Earth remain elusive. Shallow closed-basin lakes are a plausible
prebiotic environment on early Earth, and most are expected to have significant
sedimentary magnetite deposits. We hypothesize that UV (200-300nm) irradiation
of magnetite deposits could generate hydrated spin-polarized electrons
sufficient to induce chirally selective prebiotic chemistry. Such electrons are
potent reducing agents that drive reduction reactions where the spin
polarization direction can alter enantioselectively the reaction kinetics. Our
estimate of this chiral bias is based on the strong effective spin-orbit
coupling observed in the chiral-induced spin selectivity (CISS) effect, as
applied to energy differences in reduction reactions for different isomers. In
the original CISS experiments, spin selective electron transmission through a
monolayer of dsDNA molecules is observed at room temperature - indicating a
strong coupling between molecular chirality and electron spin. We propose that
the chiral symmetry breaking due to the CISS effect, when applied to reduction
chemistry, can induce enantioselective synthesis on the prebiotic Earth and
thus facilitate the homochiral assembly of life's building blocks.",2203.16011v1
2023-03-03,Impact of the $p$-cubic Dresselhaus term on the spin Hall effect,"It is well known that the Dresselhaus spin-orbit coupling (SOC) in
semiconductor two dimensional electron gases (2DEGs) possesses both linear and
cubic in momentum contributions. Nevertheless, the latter is usually neglected
in most theoretical studies. However, recent Kerr rotation experiments have
revealed a significant enhancement of the cubic Dresselhaus interaction by
increasing the drift velocities in 2DEGs hosted in GaAs quantum wells. Here, we
present a study of the optical spin Hall conductivity in 2DEGs under the
simultaneous presence of Rashba and (linear plus cubic) Dresselhaus SOC. The
work was done within the Kubo formalism in linear response. We show that the
coexistence of the Rashba and cubic Dresselhaus SOC in 2DEGs promotes a strong
anisotropy of the band spin splitting which in turn leads to a very
characteristic frequency dependence of the spin Hall conductivity. We find that
the spin Hall conductivity response could be very sensible to sizeable
cubic-Dresselhaus coupling strength. This may be of relevance for the optical
control of spin currents in 2DEGs with non-negligible cubic-Dresselhaus SOC.",2303.01941v1
2023-06-08,Spin squeezing in mixed-dimensional anisotropic lattice models,"We describe a theoretical scheme for generating scalable spin squeezing with
nearest-neighbour interactions between spin-1/2 particles in a 3D lattice,
which are naturally present in state-of-the-art 3D optical lattice clocks. We
propose to use strong isotropic Heisenberg interactions within individual
planes of the lattice, forcing the constituent spin-1/2s to behave as large
collective spins. These large spins are then coupled with XXZ anisotropic
interactions along a third direction of the lattice. This system can be
realized via superexchange interactions in a 3D optical lattice subject to an
external linear potential, such as gravity, and in the presence of spin-orbit
coupling (SOC) to generate spin anisotropic interactions. We show there is a
wide range of parameters in this setting where the spin squeezing improves with
increasing system size even in the presence of holes.",2306.05313v1
2023-06-27,Spin-Polarized Photoelectrons in the Vicinity of Spectral Features,"We investigate the spin polarization of photoelectrons emitted from noble
gases, in the vicinity of spectral features such as Fano resonances, Cooper
minima, and giant resonances. Since these features all exhibit spatio-spectral
coupling, they are intrinsically linked to the spin polarization through the
spin-orbit coupling.
  In contrast to c{\ae}sium, as originally proposed by Fano (1969)
https://doi.org/10.1103/PhysRev.178.131, the rare gases do not provide large
spin polarization in the vicinity of the Cooper minimum. However, the Fano
resonances yield much higher spin polarization ($\ge40\%$). Furthermore, if the
photoelectron is measured in coincidence with the photoion, 100\% spin
polarization is possible, also close to the Cooper minimum.",2306.15665v1
2022-06-20,Spin transfer torques due to the bulk states of topological insulators,"Spin torques at topological insulator (TI)/ferromagnet interfaces have
received considerable attention in recent years with a view towards achieving
full electrical manipulation of magnetic degrees of freedom. The most important
question in this field concerns the relative contributions of bulk and surface
states to the spin torque, a matter that remains incompletely understood.
Whereas the surface state contribution has been extensively studied, the
contribution due to the bulk states has received comparatively little
attention. Here we study spin torques due to TI bulk states and show that: (i)
There is no spin-orbit torque due to the bulk states on a homogeneous
magnetisation, in contrast to the surface states, which give rise to a
spin-orbit torque via the well-known Edelstein effect. (ii) The bulk states
give rise to a spin transfer torque (STT) due to the inhomogeneity of the
magnetisation in the vicinity of the interface. This spin transfer torque,
which has not been considered in TIs in the past, is somewhat unconventional
since it arises from the interplay of the bulk TI spin-orbit coupling and the
gradient of the monotonically decaying magnetisation inside the TI. Whereas we
consider an idealised model in which the magnetisation gradient is small and
the spin transfer torque is correspondingly small, we argue that in real
samples the spin transfer torque should be sizable and may provide the dominant
contribution due to the bulk states. We show that an experimental smoking gun
for identifying the bulk states is the fact that the field-like component of
the spin transfer torque generates a spin density with the same size but
opposite sign for in-plane and out-of-plane magnetisations. This distinguishes
them from the surface states, which are expected to give a spin density of a
similar size and the same sign for both an in-plane and out-of-plane
magnetisations.",2206.09939v2
2013-12-03,Orbital occupancies and the putative jeff = 1/2 groundstate in Ba2IrO4: a combined oxygen K edge XAS and RIXS study,"The nature of the electronic groundstate of Ba2IrO4 has been addressed using
soft X-ray absorption and inelastic scattering techniques in the vicinity of
the oxygen K edge. From the polarization and angular dependence of XAS we
deduce an approximately equal superposition of xy, yz and zx Ir4+ 5d orbitals.
By combining the measured orbital occupancies, with the value of the spin-orbit
coupling provided by RIXS, we estimate the crystal field splitting associated
with the tetragonal distortion of the IrO6 octahedra to be small, \Delta=50(50)
meV. We thus conclude definitively that Ba2IrO4 is a close realization of a
spin-orbit Mott insulator with a jeff = 1/2 groundstate, thereby overcoming
ambiguities in this assignment associated with the interpretation of X-ray
resonant scattering experiments.",1312.0857v1
2016-11-28,Optical Properties of Monolayer Tinene in Electric Fields,"Monolayer tinene presents rich absorption spectra in electric fields. There
are three kinds of special structures, namely shoulders, logarithmically
symmetric peaks and asymmetric peaks in the square-root form, corresponding to
the optical excitations of the extreme points, saddle points and
constant-energy loops. With the increasing field strength, two splitting
shoulder structures, which are dominated by the parabolic bands of ${5p_z}$
orbitals, come to exist because of the spin-split energy bands. The frequency
of threshold shoulder declines to zero and then linearly grows. The third
shoulder at ${0.75 \sim 0.85}$ eV mainly comes from (${5p_x,5p_y}$) orbitals.
The former and the latter orbitals, respectively, create the saddle-point
symmetric peaks near the M point, while they hybridize with one another to
generate the loop-related asymmetric peaks. Tinene quite differs from graphene,
silicene, and germanene. The special relationship among the multi-orbital
chemical bondings, spin-orbital couplings and Coulomb potentials accounts for
the feature-rich optical properties.",1611.08999v1
2023-04-19,Optoelectronic manifestation of orbital angular momentum driven by chiral hopping in helical Se chains,"Chiral materials have garnered significant attention in the field of
condensed matter physics. Nevertheless, the magnetic moment induced by the
chiral spatial motion of electrons in helical materials, such as elemental Te
and Se, remains inadequately understood. In this work, we investigate the
development of quantum angular momentum enforced by chirality using static and
time-dependent density functional theory calculations for an elemental Se
chain. Our findings reveal the emergence of an unconventional orbital texture
driven by the chiral geometry, giving rise to a non-vanishing current-induced
orbital moment. By incorporating spin-orbit coupling, we demonstrate that a
current-induced spin accumulation arises in the chiral chain, which
fundamentally differs from the conventional Edelstein effect. Furthermore, we
demonstrate the optoelectronic detection of the orbital angular momentum in the
chiral Se chain, providing a conceptually novel alternative to the interband
Berry curvature, which is ill-defined in low dimensions.",2304.09364v3
1999-05-14,Crossover Phenomena in the One-Dimensional SU(4) Spin-Orbit Model under Magnetic Fields,"We study the one-dimensional SU(4) exchange model under magnetic fields,
which is the simplest effective Hamiltonian in order to investigate the quantum
fluctuations concerned with the orbital degrees of freedom in coupled
spin-orbit systems. The Bethe ansatz approaches and numerical calculations
using the density matrix renormalization group method are employed. The main
concern of the paper is how the system changes from the SU(4) to the SU(2)
symmetric limit as the magnetic field is increased. For this model the
conformal field theory predicts an usual behavior: there is a jump of the
critical exponents just before the SU(2) limit. For a finite-size system,
however, the orbital-orbital correlation functions approach continuously to the
SU(2) limit after interesting crossover phenomena. The crossover takes place in
the magnetization range of 1/3 $\sim$ 1/2 for the system with 72 sites studied
in this paper.",9905211v1
2009-01-14,Falling Transiting Extrasolar Giant Planets,"We revisit the tidal stability of extrasolar systems harboring a transiting
planet and demonstrate that, independently of any tidal model, none but one
(HAT-P-2b) of these planets has a tidal equilibrium state, which implies
ultimately a collision of these objects with their host star. Consequently,
conventional circularization and synchronization timescales cannot be defined
because the corresponding states do not represent the endpoint of the tidal
evolution. Using numerical simulations of the coupled tidal equations for the
spin and orbital parameters of each transiting planetary system, we confirm
these predictions and show that the orbital eccentricity and the stellar
obliquity do not follow the usually assumed exponential relaxation but instead
decrease significantly, reaching eventually a zero value, only during the final
runaway merging of the planet with the star. The only characteristic evolution
timescale of {\it all} rotational and orbital parameters is the lifetime of the
system, which crucially depends on the magnitude of tidal dissipation within
the star. These results imply that the nearly circular orbits of transiting
planets and the alignment between the stellar spin axis and the planetary orbit
are unlikely to be due to tidal dissipation. Other dissipative mechanisms, for
instance interactions with the protoplanetary disk, must be invoked to explain
these properties.",0901.2048v1
2009-05-26,Compensated magnetism by design in double perovskite oxides,"Taking into account Goodenough's superexchange rules, including both full
structural relaxation and spin-orbit coupling, and checking strong correlation
effects, we look for compensated half metals within the class of oxide double
perovskites materials. Identifying likely half metallic (or half semimetallic)
antiferromagnets, the full complications including orbital magnetism are
included in order to arrive at realistic predictions of designed magnetic
compounds with (near) vanishing net moment. After sorting through several
candidates that have not been considered previously, two materials,
K$_2$MnRhO$_6$ and La$_2$CrWO$_6$, remain as viable candidates. An important
factor is obtaining compounds either with very small induced orbital moment
(helped by closed subshells) or with an orbital moment that compensates the
spin-orbit driven degradation of half metallic character. While thermodynamic
stability of these materials cannot be ensured, the development of
layer-by-layer oxide deposition techniques does not require that materials be
thermodynamically stable to be synthesized.",0905.4199v1
2013-02-25,Quantized magnetic flux through the orbits of hydrogen-like atoms within the atomic model of Sommerfeld,"Within the Sommerfeld atomic model the quantization of magnetic flux through
the electronic orbits is investigated together with its dependency on
additional sources of magnetic fields. These sources alter the magnetic flux
through the atomic orbits and in consequence are causing energy shifts. This
effect is investigated for the cases, where the source is an external magnetic
field, the magnetic moment of the nucleus or the magnetic moment of the
electron. The energy shifts due to external magnetic fields, the magnetic
dipole contribution of the hyperfine splitting and the spin-orbit coupling can
be reproduced very well. The meaning of 'spin', however, changes within this
approach drastically. The unusual Land\'e g-factor of 2 for the electron is a
result of the orbital motion and the magnetic moment of the electron rather
than it is an intrinsic property of the electron.",1302.6163v1
2020-12-14,"Berry curvature, orbital magnetization, and Nernst effect in biased bilayer WSe$_2$","A valley-contrasting Berry curvature in bilayer transition metal
dichalcogenides with spin-orbit coupling can generate valley magnetization when
the inversion symmetry is broken, for example, by an electric field, regardless
of time-reversal symmetry. A nontrivial Berry curvature can also lead to
anomalous transport responses, such as the anomalous Hall effect and the
anomalous Nernst effect. Applied to a bilayer WSe$_2$, an electric field can
tune the Berry curvature and orbital magnetic moment, which has important
consequences for the orbital magnetization and the anomalous Nernst responses.
The orbital magnetization and its two contributions, one due to the magnetic
moment and one due to the Berry curvature, are calculated and interpreted in
terms of opposite circulating currents of the bands in the two layers. The
valley anomalous Nernst coefficient and spin Nernst coefficient are also
calculated. We find that a finite electric field leads to peaks and dips in the
Nernst responses that have the signs of the Berry curvatures of the bands and
are proportional to their magnitudes; it also enhances the valley Nernst
responses. These experimentally verifiable findings may be promising for
caloritronic applications.",2101.03185v1
2021-02-11,Orbital Frustration and Emergent Flat Bands,"We expand the concept of frustration in Mott insulators and quantum spin
liquids to metals with flat bands. We show that when inter-orbital hopping
$t_2$ dominates over intra-orbital hopping $t_1$, in a multiband system with
strong spin-orbit coupling $\lambda$, electronic states with a narrow bandwidth
$W\sim t_2^2/\lambda$ are formed compared to a bandwidth of order $t_1$ for
intra-orbital hopping. We demonstrate the evolution of the electronic
structure, Berry phase distributions for time-reversal and inversion breaking
cases, and their imprint on the optical absorption, in a tight binding model of
$d$-orbital hopping on a honeycomb lattice. Going beyond quantum Hall effect
and twisted bilayer graphene, we provide an alternative mechanism and a richer
materials platform for achieving flat bands poised at the brink of
instabilities toward novel correlated and fractionalized metallic phases.",2102.06302v2
2022-03-29,Orbital Angular Momentum of Magnons in Collinear Magnets,"We study the orbital angular momentum of magnons for collinear ferromagnet
(FM) and antiferromagnetic (AF) systems with nontrivial networks of exchange
interactions. The orbital angular momentum of magnons for AF and FM zig-zag and
honeycomb lattices becomes nonzero when the lattice contains two inequivalent
sites and is largest at the avoided-crossing points or extremum of the
frequency bands. Hence, the arrangement of exchange interactions may play a
more important role at producing the orbital angular momentum of magnons than
the spin-orbit coupling energy and the resulting non-collinear arrangement of
spins.",2203.15677v3
2024-03-08,Damping Obliquities of Hot Jupiter Hosts by Resonance Locking,"When orbiting hotter stars, hot Jupiters are often highly inclined relative
to their host star equator planes. By contrast, hot Jupiters orbiting cooler
stars are more aligned. Prior attempts to explain this correlation between
stellar obliquity and effective temperature have proven problematic. We show
how resonance locking -- the coupling of the planet's orbit to a stellar
gravity mode (g mode) -- can solve this mystery. Cooler stars with their
radiative cores are more likely to be found with g-mode frequencies increased
substantially by core hydrogen burning. Strong frequency evolution in resonance
lock drives strong tidal evolution; locking to an axisymmetric g mode damps
semi-major axes, eccentricities, and as we show for the first time,
obliquities. Around cooler stars, hot Jupiters evolve into spin-orbit alignment
and avoid engulfment. Hotter stars lack radiative cores, and therefore preserve
congenital spin-orbit misalignments. We focus on resonance locks with
axisymmetric modes, supplementing our technical results with simple physical
interpretations, and show that non-axisymmetric modes also damp obliquity.",2403.05616v1
2007-08-30,Further insight into gravitational recoil,"We test the accuracy of our recently proposed empirical formula to model the
recoil velocity imparted to the merger remnant of spinning, unequal-mass
black-hole binaries. We study three families of black-hole binary
configurations, all with mass ratio q=3/8 (to maximize the unequal-mass
contribution to the kick) and spins aligned (or counter aligned) with the
orbital angular momentum, two with spin configurations chosen to minimize the
spin-induced tangential and radial accelerations of the trajectories
respectively, and a third family where the trajectories are significantly
altered by spin-orbit coupling. We find good agreement between the measured and
predicted recoil velocities for the first two families, and reasonable
agreement for the third. We also re-examine our original generic binary
configuration that led to the discovery of extremely large spin-driven recoil
velocities and inspired our empirical formula, and find reasonable agreement
between the predicted and measured recoil speeds.",0708.4048v3
2008-01-11,Magneto-spin Hall conductivity of a two-dimensional electron gas,"It is shown that the interplay of long-range disorder and in-plane magnetic
field gives rise to an out-of-plane spin polarization and a finite spin Hall
conductivity of the two-dimensional electron gas in the presence of Rashba
spin-orbit coupling. A key aspect is provided by the electric-field induced
in-plane spin polarization. Our results are obtained first in the
\textit{clean} limit where the spin-orbit splitting is much larger than the
disorder broadening of the energy levels via the diagrammatic evaluation of the
Kubo-formula. Then the results are shown to hold in the full range of the
disorder parameter $\alpha p_F \tau$ by means of the quasiclassical Green
function technique.",0801.1786v1
2010-04-26,Spin transfer in a ferromagnet-quantum dot and tunnel barrier coupled Aharonov-Bohm ring system with Rashba spin-orbit interactions,"The spin transfer effect in ferromagnet-quantum dot (insulator)-ferromagnet
Aharonov-Bohm (AB) ring system with Rashba spin-orbit (SO) interactions is
investigated by means of Keldysh nonequilibrium Green function method. It is
found that both the magnitude and direction of the spin transfer torque (STT)
acting on the right ferromagnet electrode can be effectively controlled by
changing the magnetic flux threading the AB ring or the gate voltage on the
quantum dot. The STT can be greatly augmented by matching a proper magnetic
flux and an SO interaction at a cost of low electrical current. The STT,
electrical current, and spin current are uncovered to oscillate with the
magnetic flux. The present results are expected to be useful for information
storage in nanospintronics.",1004.4507v1
2015-01-30,Predominance of the Kitaev interaction in a three-dimensional honeycomb iridate: from ab-initio to spin model,"The recently discovered three-dimensional hyperhoneycomb iridate,
$\beta$-Li$_2$IrO$_3$, has raised hopes for the realization of dominant Kitaev
interaction between spin-orbit entangled local moments due to its near-ideal
lattice structure. If true, this material may lie close to the sought-after
quantum spin liquid phase in three dimensions. Utilizing ab-initio electronic
structure calculations, we first show that the spin-orbit entangled basis,
$j_{\rm eff}$=1/2, correctly captures the low energy electronic structure. The
effective spin model derived in the strong coupling limit supplemented by the
ab-initio results is shown to be dominated by the Kitaev interaction. We
demonstrated that the possible range of parameters is consistent with a
non-coplanar spiral magnetic order found in a recent experiment. All of these
analyses suggest that $\beta$-Li$_2$IrO$_3$ may be the closest among known
materials to the Kitaev spin liquid regime.",1502.00006v2
2015-09-16,Charge-Induced Spin Torque in Anomalous Hall Ferromagnets,"We demonstrate that spin-orbit coupled electrons in a magnetically doped
system exert a spin torque on the local magnetization, without a flowing
current, when the chemical potential is modulated in a magnetic field. The spin
torque is proportional to the anomalous Hall conductivity, and its effective
field strength may overcome the Zeeman field. Using this effect, the direction
of the local magnetization is switched by gate control in a thin film. This
charge-induced spin torque is essentially an equilibrium effect, in contrast to
the conventional current-induced spin-orbit torque, and, thus, devices using
this operating principle possibly have higher efficiency than the conventional
ones. In addition to a comprehensive phenomenological derivation, we present a
physical understanding based on a model of a Dirac-Weyl semimetal, possibly
realized in a magnetically doped topological insulator. The effect might be
realized also in nanoscale transition materials, complex oxide ferromagnets,
and dilute magnetic semiconductors.",1509.04799v1
2015-10-15,Shaped electric fields for fast optimal manipulation of electron spin and position in a double quantum dot,"We use quantum optimal control theory algorithms to design external electric
fields that drive the coupled spin and orbital dynamics of an electron in a
double quantum dot, subject to the spin-orbit interaction and Zeeman magnetic
fields. We obtain time-profiles of multi-frequency electric pulses which
increase the rate of spin-flip transitions by several orders of magnitude in
comparison with monochromatic fields, where the spin Rabi oscillations were
predicted to be very slow. This precise, with the accuracy higher than
$10^{-4}$, and fast, at the timescale of the order of 0.1 ns, simultaneous
control of the electron spin orientation and position is achieved while keeping
the electron in the four lowest tunneling- and Zeeman-split levels through the
duration of the pulse, facilitating high fidelity and suggesting useful
applications in spintronics and quantum information devices.",1510.04502v2
2016-01-12,Improper magnetic ferroelectricity of nearly pure electronic nature in cycloidal spiral CaMn$_{7}$O$_{12}$,"The noncollinear cycloidal magnetic order breaks the inversion symmetry in
CaMn$_{7}$O$_{12}$, generating one of the largest spin-orbit driven
ferroelectric polarizations measured to date. In this Letter, the microscopic
origin of the polarization, including its direction, charge density
redistribution, magnetic exchange interactions, and its coupling to the spin
helicity, is explored via first principles calculations. The Berry phase
computed polarization exhibits almost pure electronic behavior, as the Mn
displacements are negligible, $\approx$~0.7~m\textrm{\AA}. The polarization
magnitude and direction are both determined by the Mn spin current, where the
\emph{p}-\emph{d} orbital mixing is driven by the inequivalent exchange
interactions within the \emph{B}-site Mn cycloidal spiral chains along each
Cartesian direction. We employ the generalized spin-current model with
Heisenberg-exchange Dzyaloshinskii-Moriya interaction energetics to provide
insight into the underlying physics of this spin-driven polarization.
Persistent electronic polarization induced by helical spin order in nearly
inversion-symmetric ionic crystal lattices suggests opportunities for ultrafast
magnetoelectric response.",1601.03020v1
2016-06-17,Gate-voltage response of a one-dimensional ballistic spin valve without spin-orbit interaction,"We show that engineering of tunnel barriers forming at the interfaces of a
one-dimensional spin valve provides a viable path to a strong gate-voltage
tunability of the magnetoresistance effect. In particular, we investigate
theoretically a carbon nanotube (CNT) spin valve in terms of the influence of
the CNT-contact interface on the performance of the device. The focus is on the
strength and the spin selectivity of the tunnel barriers that are modelled as
Dirac-delta potentials. The scattering matrix approach is used to derive the
transmission coefficient that yields the tunneling magnetoresistance (TMR). We
find a strong non-trivial gate-voltage response of the TMR in the absence of
spin-orbit coupling when the energy of the incident electrons matches the
potential energy of the barrier. Analytic expressions for the TMR in various
limiting cases are derived. These are used to explain previous experimental
results, but also to predict parameters for device optimization with respect to
size and tunability of the TMR effect in the ballistic transport regime.",1606.05571v2
2016-06-28,Control of Spin Helix Symmetry in Semiconductor Quantum Wells by Crystal Orientation,"We investigate the possibility of spin-preserving symmetries due to the
interplay of Rashba and Dresselhaus spin-orbit coupling in n-doped zinc-blende
semiconductor quantum wells of general crystal orientation. It is shown that a
conserved spin operator can be realized if and only if at least two
growth-direction Miller indices agree in modulus. The according spin-orbit
field has in general both in-plane and out-of-plane components and is always
perpendicular to the shift vector of the corresponding persistent spin helix.
We also analyze higher-order effects arising from the Dresselhaus term, and the
impact of our results on weak (anti)localization corrections.",1606.08774v2
2016-09-21,Creating spin-one fermions in the presence of artificial spin-orbit fields: Emergent spinor physics and spectroscopic properties,"We propose the creation and investigation of a system of spin-one fermions in
the presence of artificial spin-orbit coupling, via the interaction of three
hyperfine states of fermionic atoms to Raman laser fields. We explore the
emergence of spinor physics in the Hamiltonian described by the interaction
between light and atoms, and analyze spectroscopic properties such as
dispersion relation, Fermi surfaces, spectral functions, spin-dependent
momentum distributions and density of states. Connections to spin-one bosons
and SU(3) systems is made, as well relations to the Lifshitz transition and
Pomeranchuk instability are presented.",1609.06607v1
2018-04-11,Theory of proximity effect in two-dimensional unconventional superconductor with Rashba spin-orbit interaction,"We study the anomalous proximity effect in diffusive normal metal
(DN)/unconventional superconductor junctions, where the local density of states
(LDOS) in the DN has a zero-energy peak due to the penetration of the
odd-frequency spin-triplet $s$-wave pairing. In this study, we consider a
two-dimensional unconventional superconductor on the substrate in the presence
of a Rashba spin-orbit coupling (RSOC) $\lambda$, where the Rashba vector is
parallel to the $z$-direction. The anomalous proximity effect, originally
predicted in spin-triplet $p$-wave superconductor junctions, is sensitive to
the RSOC. It disappears with the increase of $\lambda$. On the other hand, the
anomalous proximity effect can be switched on by the large $\lambda$ values in
the spin-singlet $d_{xy}$-wave superconductor junctions. The resulting
zero-energy LDOS and the magnitude of the odd-frequency spin-triplet $s$-wave
pair amplitude increase with the increase of $\lambda$.",1804.04018v3
2018-11-01,Inversion-induced orbital and exchange disorders in antiferromagnetic A-site spinel CoAl2O4,"The inversion and volume effects on magnetism in a spinel-type magnetically
frustrated compound, CoAl2O4, and its gallium-substituted system, CoAl2-xGaxO4,
were investigated. Magnetically frustrated Co2+ with spin S = 3/2 on the
tetrahedral site formed a diamond lattice in CoAl2O4 located in the vicinity of
the magnetic phase boundary between Neel and spin-spiral states. In the
Ga-substituted system, the number of Co ions, the so-called inversion h
dominating the octahedral site, increased with increasing x. From comprehensive
crystallographic, magnetic, and thermal measurements, increments of both volume
and inversion strongly reduced the Neel point, while the latter also induced a
spin-glass state above the critical value of hc = 0.09. In the spin glass
state, h > hc, the orbital degree of freedom of Co2+ ions in the octahedral
site appeared in the magnetic entropy, which couples strongly with that of
spin, even above the magnetic transitions. Above h ~ hc, the field-induced
quenched magnetic moment appeared above the transitions. Therefore, a short
range ordered state emerged among the paramagnetic, antiferromganetic, and
spin-glass states in the magnetic phase diagram.",1811.00186v1
2018-05-15,Emergence of a Field-Driven U(1) Spin Liquid in the Kitaev Honeycomb Model,"In the field of quantum magnetism, the exactly solvable Kitaev honeycomb
model serves as a paradigm for the fractionalization of spin degrees of freedom
and the formation of $\mathbb{Z}_2$ quantum spin liquids. An intense
experimental search has led to the discovery of a number of spin-orbit
entangled Mott insulators that realize its characteristic bond-directional
interactions and, in the presence of magnetic fields, exhibit no indications of
long-range order. Here, we map out the complete phase diagram of the Kitaev
model in tilted magnetic fields and report the emergence of a distinct gapless
quantum spin liquid at intermediate field strengths. Analyzing a number of
static, dynamical, and finite temperature quantities using numerical exact
diagonalization techniques, we find strong evidence that this phase exhibits
gapless fermions coupled to a massless $U(1)$ gauge field. We discuss its
stability in the presence of perturbations that naturally arise in spin-orbit
entangled candidate materials.",1805.05953v4
2017-10-21,Spin interferometry in anisotropic spin-orbit fields,"Electron spins in a two-dimensional electron gas (2DEG) can be manipulated by
spin-orbit (SO) fields originating from either Rashba or Dresselhaus
interactions with independent isotropic characteristics. Together, though, they
produce anisotropic SO fields with consequences on quantum transport through
spin interference. Here we study the transport properties of modelled
mesoscopic rings subject to Rashba and Dresselhaus [001] SO couplings in the
presence of an additional in-plane Zeeman field acting as a probe. By means of
1D and 2D quantum transport simulations we show that this setting presents
anisotropies in the quantum resistance as a function of the Zeeman field
direction. Moreover, the anisotropic resistance can be tuned by the Rashba
strength up to the point to invert its response to the Zeeman field. We also
find that a topological transition in the field texture that is associated with
a geometric phase switching is imprinted in the anisotropy pattern. We conclude
that resistance anisotropy measurements can reveal signatures of SO textures
and geometric phases in spin carriers.",1710.07810v2
2018-06-13,Deep-subwavelength features of photonic skyrmions in a confined electromagnetic field with orbital angular momentum,"In magnetic materials, skyrmions are nanoscale regions where the orientation
of electron spin changes in a vortex-type manner. Here we show that spin-orbit
coupling in a focused vector beam results in a skyrmion-like photonic spin
distribution of the excited waveguided fields. While diffraction limits the
spatial size of intensity distributions, the direction of the field, defining
photonic spin, is not subject to this limitation. We demonstrate that the
skyrmion spin structure varies on the deep-subwavelength scales down to 1/60 of
light wavelength, which corresponds to about 10 nanometre lengthscale. The
application of photonic skyrmions may range from high-resolution imaging and
precision metrology to quantum technologies and data storage where the spin
structure of the field, not its intensity, can be applied to achieve
deep-subwavelength optical patterns.",1806.04827v1
2020-10-21,Strong tuning of magnetism and electronic structure by spin orientation,"To efficiently manipulate magnetism is a key physical issue for modern
condensed matter physics, which is also crucial for magnetic functional
applications. Most previous relevant studies rely on the tuning of spin
texture, while the spin orientation is often negligible. As an exception,
spin-orbit coupled $J_{\rm eff}$ states of $4d$/$5d$ electrons provide an ideal
platform for emergent quantum effects. However, many expectations have not been
realized due to the complexities of real materials. Thus the pursuit for more
ideal $J_{\rm eff}$ states remains ongoing. Here a near-ideal $J_{\rm
eff}$=$3/2$ Mott insulating phase is predicted in the family of hexachloro
niobates, which avoid some common drawbacks of perovskite oxides. The local
magnetic moment is nearly compensated between spin and orbital components,
rendering exotic recessive magnetism. More interestingly, the electronic
structure and magnetism can be strongly tuned by rotating spin axis, which is
rare but crucial for spintronic applications.",2010.10741v1
2021-04-06,Spin-orbit enabled quantum transport channels in a two-hole double quantum dot,"We analyze experimentally and theoretically the transport spectra of a gated
lateral GaAs double quantum dot containing two holes. The strong spin-orbit
interaction present in the hole subband lifts the Pauli spin blockade and
allows to map out the complete spectra of the two-hole system. By performing
measurements in both source-drain voltage directions, at different detunings
and magnetic fields, we carry out quantitative fitting to a Hubbard two-site
model accounting for the tunnel coupling to the leads and the spin-flip
relaxation process. We extract the singlet-triplet gap and the magnetic field
corresponding to the singlet-triplet transition in the double-hole ground
state. Additionally, at the singlet-triplet transition we find a resonant
enhancement (in the blockaded direction) and suppression of current (in the
conduction direction). The current enhancement stems from the multiple
resonance of two-hole levels, opening several conduction channels at once. The
current suppression arises from the quantum interference of spin-conserving and
spin flipping tunneling processes.",2104.02568v1
2021-05-24,Spin pumping of two-dimensional electron gas with Rashba and Dresselhaus spin-orbit interactions,"We theoretically consider spin pumping in a junction between a ferromagnetic
insulator (FI) and a two-dimensional electron gas (2DEG) in which the Rashba
and Dresselhaus spin-orbit interactions coexist. Using second-order
perturbation theory, we derive an increase in linewidth in the case of an
interfacial exchange coupling in a ferromagnetic resonance (FMR) experiment. We
clarify how the enhancement of Gilbert damping depends on the resonant
frequency and spin orientation of the FI. We show that this setup of an FMR
experiment can provide information on the spin texture of 2DEG at the Fermi
surface.",2105.11193v3
2021-11-24,Spin Polarization through A Molecular Junction Based on Nuclear Berry Curvature Effects,"We explore the effects of spin-orbit coupling on nuclear wave packet motion
near an out-of-equilibrium molecular junction, where nonzero Berry curvature
emerges as the antisymmetric part of the electronic friction tensor. The
existence of nonzero Berry curvature mandates that different nuclear wave
packets (associated with different electronic spin states) experience different
nuclear Berry curvatures, i.e. different pseudo-magnetic fields. Furthermore,
for a generic, two-orbital two-lead model (representing the simplest molecular
junction), we report significant spin polarization of the {\em electronic}
current with decaying and oscillating signatures in the large voltage limit --
all as a result of {\em nuclear} motion. These results are consistent with
magnetic AFM chiral-induced spin selectivity experiments. Altogether, our
results highlight an essential role for Berry curvature in condensed phase
dynamics, where spin separation survives dissipation to electron-hole pair
creation and emerges as one manifestation of nuclear Berry curvature.",2111.12815v2
2022-05-26,Symmetry-resolved elastic anomalies in spin-crossover cobaltite LaCoO$_3$,"Ultrasound velocity measurements of the pseudo-cubic spin-crossover cobaltite
LaCoO$_3$ and the lightly Ni-substituted La(Co$_{0.99}$Ni$_{0.01}$)O$_3$ reveal
two types of symmetry-resolved elastic anomaly in the insulating paramagnetic
state that are commonly observed in these compounds. The temperature dependence
of the bulk modulus exhibits Curie-type softening upon cooling below 300 K down
to $\sim$70 K, indicating the presence of isostructural lattice instability
arising from orbital fluctuations. The temperature dependence of the tetragonal
and trigonal shear moduli exhibits unusual hardening upon cooling below 300 K,
indicating the occurrence of elasticity crossover arising from the spin
crossover. The present study also reveals that the isostructural lattice
instability in LaCoO$_3$ is sensitively suppressed with the Ni substitution,
indicating the suppression of orbital fluctuations with the light Ni
substitution. This Ni substitution effect in LaCoO$_3$ can be explained on the
basis that the isostructural lattice instability arises from the coupling of
the lattice to the Co spin state fluctuating between the high-spin state and
intermediate-spin state.",2205.13228v3
2007-01-18,Finite-size Effects in a Two-Dimensional Electron Gas with Rashba Spin-Orbit Interaction,"Within the Kubo formalism, we estimate the spin-Hall conductivity in a
two-dimensional electron gas with Rashba spin-orbit interaction and study its
variation as a function of disorder strength and system size. The numerical
algorithm employed in the calculation is based on the direct numerical
integration of the time-dependent Schrodinger equation in a spin-dependent
variant of the particle source method. We find that the spin-precession length,
L_s controlled by the strength of the Rashba coupling, establishes the critical
lengthscale that marks the significant reduction of the spin-Hall conductivity
in bulk systems. In contrast, the electron mean free path, inversely
proportional to the strength of disorder, appears to have only a minor effect.",0701451v1
2009-10-16,Anderson Impurity in Helical Metal,"We use a trial wave function to study the spin-1/2 Kondo effect of a helical
metal on the surface of a three-dimensional topological insulator. While the
impurity spin is quenched by conduction electrons, the spin-spin correlation of
the conduction electron and impurity is strongly anisotropic in both spin and
spatial spaces. As a result of strong spin-orbit coupling, the out-of-plane
component of the impurity spin is found to be fully screened by the orbital
angular momentum of the conduction electrons.",0910.3031v5
2012-06-20,Spin Hall Conductivity on the Anisotropic Triangular Lattice,"We present a detailed study of the spin Hall conductivity on a
two-dimensional triangular lattice in the presence of Rashba spin-orbit
coupling. In particular, we focus part of our attention on the effect of the
anisotropy of the nearest neighbor hopping amplitude. It is found that the
presence of anisotropy has drastic effects on the spin Hall conductivity,
especially in the hole doped regime where a significant increase or/and
reversed sign of the spin Hall conductivity has been obtained. We also provide
a systematic analysis of the numerical results in terms of Berry phases. The
changes of signs observed at particular density of carriers appear to be a
consequence of both Fermi surface topology and change of sign of electron
velocity. In addition, in contrast to the two-dimensional square lattice, it is
shown that the tight binding spin-orbit Hamiltonian should be derived carefully
from the continuous model on the triangular lattice.",1206.4537v1
2012-12-12,Spin-orbit induced chirality of Andreev states in Josephson junctions,"We study Josephson junctions (JJs) in which the region between the two
superconductors is a multichannel system with Rashba spin-orbit coupling (SOC)
where a barrier or a quantum point contact (QPC) is present. These systems
might present unconventional Josephson effects such as Josephson currents for
zero phase difference or critical currents that \textit{depend on} the current
direction. Here, we discuss how the spin polarizing properties of the system in
the normal state affect the spin characteristic of the Andreev bound states
inside the junction. This results in a strong correlation between the spin of
the Andreev states and the direction in which they transport Cooper pairs.
While the current-phase relation for the JJ at zero magnetic field is
qualitatively unchanged by SOC, in the presence of a weak magnetic field a
strongly anisotropic behavior and the mentioned anomalous Josephson effects
follow. We show that the situation is not restricted to barriers based on
constrictions such as QPCs and should generically arise if in the normal system
the direction of the carrier's spin is linked to its direction of motion.",1212.2786v1
2018-05-28,Gravitational spin-orbit coupling in binary systems at the second post-Minkowskian approximation,"We compute the rotations, during a scattering encounter, of the spins of two
gravitationally interacting particles at second-order in the gravitational
constant (second post-Minkowskian order). Following a strategy introduced in
Phys. Rev. D {\bf 96}, 104038 (2017), we transcribe our result into a
correspondingly improved knowledge of the spin-orbit sector of the Effective
One-Body (EOB) Hamiltonian description of the dynamics of spinning binary
systems. We indicate ways of resumming our results for defining improved
versions of spinning EOB codes which might help in providing a better
analytical description of the dynamics of coalescing spinning binary black
holes.",1805.10809v1
2019-06-24,Octahedral tilting induced isospin reorientation transition in iridate heterostructures,"Iridate heterostructures are gaining interest as their magnetic properties
are much more sensitive to structural distortion compared to pure spin systems
due to spin-orbital entanglement induced by strong spin-orbit coupling. While
bulk monolayer and bilayer iridates show $ab$-plane canted and $c$-axis
antiferromagnetic (AFM) order, recent experiments on layered iridate
superlattices (SL) have revealed striking properties, especially in the bilayer
SL. A spin model is presented including the tilting induced Kitaev type
interactions, which illustrates the proclivity towards $ab$-plane canted AFM
order. A realistic Hubbard model including spin-dependent hopping terms arising
from octahedral rotation and tilting is constructed for the bilayer SL in
isospin space, and magnetic excitations are investigated in the
self-consistently determined magnetic state. The Hubbard model analysis
confirms the spin model results and shows strongly reduced magnon energy gap
and an isospin reorientation transition from $c$-axis to $ab$-plane canted AFM
order with increasing tilting.",1906.09879v2
2022-08-03,Ultrafast Demagnetization Dynamics Due to Electron-Electron Scattering and Its Relation to Momentum Relaxation in Ferromagnets,"We analyze theoretically the demagnetization dynamics in a ferromagnetic
model system due to the interplay of spin-orbit coupling and electron-electron
Coulomb scattering. We compute the $k$-resolved electronic reduced spin-density
matrix including precessional dynamics around internal spin-orbit and exchange
fields as well as the electron-electron Coulomb scattering for densities and
spin coherences. Based on a comparison with numerical solutions of the full
Boltzmann scattering integrals, we establish that the $k$-resolved reduced
spin-density matrix dynamics are well described using a simpler generalized
relaxation-time ansatz for the reduced spin-density matrix. This ansatz allows
one to relate the complicated scattering dynamics underlying the
demagnetization dynamics to a physically meaningful momentum relaxation time
$\tau$. Our approach reproduces the behaviors of the demagnetization time
$\tau_{m} \propto 1/\tau$ and $\tau_{m} \propto \tau$ for the limits of short
and long $\tau$, respectively, and is also valid for the intermediate regime.
The ansatz thus provides a tool to include the correct demagnetization behavior
in approaches that treat other contributions to the magnetization dynamics such
as transport or magnon/phonon dynamics.",2208.02356v1
2007-05-21,Non-Abelian hydrodynamics and the flow of spin in spin-orbit coupled substances,"Motivated by heavy ion collision experiments, we study the hydrodynamic
properties of non-Abelian systems. These issues arise in condensed matter
physics in the context of transport of spins in the presence of spin orbit
coupling: the Pauli Hamiltonian governing the leading relativistic corrections
in condensed matter systems can be rewritten in a language of SU(2) covariant
derivatives, where the role of the non-Abelian gauge fields is taken by the
physical electromagnetic fields. Taking a similar perspective as Jackiw and
coworkers, we show that non-abelian hydrodynamical currents can be factored in
a non-coherent 'classical' part, and a coherent part requiring macroscopic
non-abelian quantum entanglement. Non-abelian flow being thus a much richer
affair than familiar hydrodynamics, permits us to classify the various spin
transport phenomena in in condensed matter physics in a unifying framework.In
semiconductor spintronics, the absence of hydrodynamics is well known, but in
our formulation it is directly associated with the fact that non-abelian
currents are only covariantly conserved.We analyze the quantum mechanical
single particle currents of relevance to mesoscopic transport with as highlight
the Aharonov-Casher effect, where we demonstrate that the non-abelian transport
structure renders it much more fragile than its abelian counterpart, the
Aharonov-Bohm effect. We subsequently focus on spin flows protected by order
parameters, of which the spin-spiral magnets and the spin superfluids are
important examples. The surprising bonus is that the presence of an order
parameter, being single-valued, restores hydrodynamics. We demonstrate a new
effect: the trapping of electrical line charge, being the 'fixed frame'
non-Abelian analogue of the familiar magnetic flux trapping by superconductors.",0705.2953v1
2008-08-27,Torque and conventional spin-Hall currents in two-dimensional spin-orbit coupled systems: Universal relation and hyper-selection rule,"We investigate torque and also conventionally defined spin-Hall currents in
two-dimensional (2D) spin-orbit coupled systems of spin-1/2 particles within
the linear response Kubo formalism. We obtain some interesting relations
between the conventional and torque spin-Hall conductivities for the generic
effective Hamiltonian $H_0=\epsilon_k^0+A(k)\sigma_x-B(k)\sigma_y$, where
$A(k)=\eta^A_ik_i+\eta^A_{ij}k_ik_j+\eta^A_{ijl}k_ik_jk_l+...$,
$B(k)=\eta^B_ik_i+\eta^B_{ij}k_ik_j+\eta^B_{ijl}k_ik_jk_l+...$, and $\eta$'s
are the specific system-dependent coefficients. Specifically, we find that in
the intrinsic case the magnitude of torque spin-Hall conductivity
$\sigma^{\tau_z}_{xy}(0)$ is always twice larger than the conventional
spin-Hall conductivity $\sigma^{s_z}_{xy}(0)$, and the two conductivities have
the opposite signs, i.e., $\sigma^{\tau_z}_{xy}(0)=-2\sigma^{s_z}_{xy}(0)$.
This universal relation also holds in the presence of an uniform in-plane
magnetic field. We also find that if the energy dispersion is rotationally
invariant, there exists a hyper-angular momentum $I_z = (k\times
\partial\theta/\partial k)_z s_z + L_z$ which is conserved. Furthermore, the
hyper-angular momentum current $<{1/2}\{I_z,v_x\}>$ vanishes, and this leads to
a hyper selection rule for the conventional spin-Hall current.",0808.3625v2
2009-06-16,Hole spin relaxation in [001] strained asymmetric Si/SiGe and Ge/SiGe quantum wells,"Hole spin relaxation in [001] strained asymmetric Si/Si$_{0.7}$Ge$_{0.3}$
(Ge/Si$_{0.3}$Ge$_{0.7}$) quantum wells is investigated in the situation with
only the lowest hole subband being relevant. The effective Hamiltonian of the
lowest hole subband is obtained by the subband L\""owdin perturbation method in
the framework of the six-band Luttinger ${\bf k}\cdot{\bf p}$ model, with
sufficient basis functions included. The lowest hole subband in Si/SiGe quantum
wells is light-hole like with the Rashba spin-orbit coupling term depending on
momentum both linearly and cubically, while that in Ge/SiGe quantum wells is a
heavy hole state with the Rashba spin-orbit coupling term depending on momentum
only cubically. The hole spin relaxation is investigated by means of the fully
microscopic kinetic spin Bloch equation approach, with all the relevant
scatterings considered. It is found that the hole-phonon scattering is very
weak, which makes the hole-hole Coulomb scattering become very important. The
hole system in Si/SiGe quantum wells is generally in the strong scattering
limit, while that in Ge/SiGe quantum wells can be in either the strong or the
weak scattering limit. The Coulomb scattering leads to a peak in both the
temperature and hole density dependences of spin relaxation time in Si/SiGe
quantum wells, located around the crossover between the degenerate and
nondegenerate regimes. Nevertheless, the Coulomb scattering leads to not only a
peak but also a valley in the temperature dependence of spin relaxation time in
Ge/SiGe quantum wells.... (The remaining is omitted due to the limit of space).",0906.2865v2
2017-08-09,Electrically driven electron spin resonance mediated by spin-valley-orbit coupling in a silicon quantum dot,"The ability to manipulate electron spins with voltage-dependent electric
fields is key to the operation of quantum spintronics devices, such as
spin-based semiconductor qubits. A natural approach to electrical spin control
exploits the spin-orbit coupling (SOC) inherently present in all materials. So
far, this approach could not be applied to electrons in silicon, due to their
extremely weak SOC. Here we report an experimental realization of electrically
driven electron-spin resonance in a silicon-on-insulator (SOI) nanowire quantum
dot device. The underlying driving mechanism results from an interplay between
SOC and the multi-valley structure of the silicon conduction band, which is
enhanced in the investigated nanowire geometry. We present a simple model
capturing the essential physics and use tight-binding simulations for a more
quantitative analysis. We discuss the relevance of our findings to the
development of compact and scalable electron-spin qubits in silicon.",1708.02903v2
2017-08-23,Spin-memory loss due to spin-orbit coupling at ferromagnet/heavy-metal interfaces: Ab initio spin-density matrix approach,"Spin-memory loss (SML) of electrons traversing
ferromagnetic-metal/heavy-metal (FM/HM), FM/normal-metal (FM/NM) and HM/NM
interfaces is a fundamental phenomenon that must be invoked to explain
consistently large number of spintronic experiments. However, its strength
extracted by fitting experimental data to phenomenological semiclassical
theory, which replaces each interface by a fictitious bulk diffusive layer, is
poorly understood from a microscopic quantum framework and/or materials
properties. Here we describe an ensemble of flowing spin quantum states using
spin-density matrix, so that SML is measured like any decoherence process by
the decay of its off-diagonal elements or, equivalently, by the reduction of
the magnitude of polarization vector. By combining this framework with density
functional theory (DFT), we examine how all three components of the
polarization vector change at Co/Ta, Co/Pt, Co/Cu, Pt/Cu and Pt/Au interfaces
embedded within Cu/FM/HM/Cu vertical heterostructures. In addition, we use ab
initio Green's functions to compute spectral functions and spin textures over
FM, HM and NM monolayers around these interfaces which quantify interfacial
spin-orbit coupling and explain the microscopic origin of SML in long-standing
puzzles, such as why it is nonzero at Co/Cu interface; why it is very large at
Pt/Cu interface; and why it occurs even in the absence of disorder, intermixing
and magnons at the interface.",1708.07105v3
2018-02-28,Spin-dependent magneto-thermopower of narrow-gap lead chalcogenide quantum wells,"A semi-classical analysis of magneto-thermopower behaviour, namely, the
\textit{Seebeck} and \textit{Nernst} effect (NE) in quantum wells of IV-VI lead
salts with significant extrinsic Rashba spin-orbit coupling (RSOC) is performed
in this report. In addition to the spin-dependent Seebeck effect that has been
observed before, we also theoretically predict a similar spin-delineated
behaviour for its thermal analog, the spin-dependent NE. The choice of lead
salts follows from a two-fold advantage they offer, in part, to their superior
thermoelectric properties, especially PbTe, while their low band gaps and high
spin-orbit coupling make them ideal candidates to study \textit{RSOC} in
nanostructures. The calculations show a larger longitudinal magneto-thermopower
for the spin-up electrons while the transverse components are nearly identical.
In contrast, for a magnetic field free case, the related power factor
calculations reveal a significantly higher contribution from the spin-down
ensemble and suffer a reduction with an increase in the electron density. We
also discuss qualitatively the limitations of the semi-classical approach for
the extreme case of a high magnetic field and allude to the observed
thermopower behaviour when the quantum Hall regime is operational. Finally,
techniques to modulate the thermopower are briefly outlined.",1802.10350v1
2018-11-30,Dynamical precession of spin in the two-dimensional spin-orbit coupled systems,"We investigate the spin dynamics in the two-dimensional spin-orbit coupled
system subject to an in-plane ($x$-$y$ plane) constant electric field, which is
assumed to be turned on at the moment $t=0$. The equation of spin precession in
linear response to the switch-on of the electric field is derived in terms of
Heisenberg's equation by the perturbation method up to the first order of the
electric field. The dissipative effect, which is responsible for bringing the
dynamical response to an asymptotic result, is phenomenologically implemented
\`{a} la the Landau-Lifshitz-Gilbert equation by introducing damping terms upon
the equation of spin dynamics. Mediated by the dissipative effect, the
resulting spin dynamics asymptotes to a stationary state, where the spin and
the momentum-dependent effective magnetic field are aligned again and have
nonzero components in the out-of-plane ($z$) direction. In the linear response
regime, the asymptotic response obtained by the dynamical treatment is in full
agreement with the stationary response as calculated in the Kubo formula, which
is a time-independent approach treating the applied electric field as
completely time-independent. Our method provides a new perspective on the
connection between the dynamical and stationary responses.",1811.12626v2
2016-08-18,Spin drift and diffusion in one- and two-subband helical systems,"The theory of spin drift and diffusion in two-dimensional electron gases is
developed in terms of a random walk model incorporating Rashba, linear and
cubic Dresselhaus, and intersubband spin-orbit couplings. The additional
subband degree of freedom introduces new characteristics to the persistent spin
helix (PSH) dynamics. As has been described before, for negligible intersubband
scattering rates, the sum of the magnetization of independent subbands leads to
a checkerboard pattern of crossed PSHs with long spin lifetime. For strong
intersubband scattering we model the fast subband dynamics as a new random
variable, yielding a dynamics set by averaged spin-orbit couplings of both
subbands. In this case the crossed PSH becomes isotropic, rendering circular
(Bessel) patterns with short spin lifetime. Additionally, a finite drift
velocity breaks the symmetry between parallel and transverse directions,
distorting and dragging the patterns. We find that the maximum spin lifetime
shifts away from the PSH regime with increasing drift velocity. We present
approximate analytical solutions for these cases and define their domain of
validity. Effects of magnetic fields and initial package broadening are also
discussed.",1608.05437v2
2020-09-30,Pathways for producing binary black holes with large misaligned spins in the isolated formation channel,"Binary black holes (BBHs) can form from the collapsed cores of isolated
high-mass binary stars. The masses and spins of these BBHs are determined by
the complicated interplay of phenomena such as tides, winds, accretion,
common-envelope evolution (CEE), supernova natal kicks, and stellar
core-envelope coupling. The gravitational waves emitted during the mergers of
BBHs depend on their masses and spins and can thus constrain these phenomena.
We present a simplified model of binary stellar evolution and identify regions
of the parameter space that produce BBHs with large spins misaligned with their
orbital angular momentum. In Scenario A (B) of our model, stable mass transfer
(SMT) occurs after Roche-lobe overflow (RLOF) of the more (less) massive star,
while CEE follows RLOF of the less (more) massive star. Each scenario is
further divided into Pathways 1 and 2 depending on whether the core of the more
massive star collapses before or after RLOF of the less massive star,
respectively. If the stellar cores are coupled weakly to their envelopes,
highly spinning BBHs can be produced if natal spins greater than $10\%$ of the
breakup value are inherited from the stellar progenitors. BBHs can
alternatively acquire large spins by tidal synchronization during the
Wolf-Rayet stage in Scenario A or by accretion onto the initially more massive
star during SMT in Scenario B. BBH spins can be highly misaligned if the kicks
are comparable to the orbital velocity, which is more easily achieved in
Pathway A1 where the kick of the more massive star precedes CEE.",2010.00078v2
2022-02-20,Effective spin model in momentum space: Toward a systematic understanding of multiple-$Q$ instability by momentum-resolved anisotropic exchange interactions,"Multiple-$Q$ magnetic states, such as a skyrmion crystal, become a source of
unusual transport phenomena and dynamics. Recent theoretical and experimental
studies clarify that such multiple-$Q$ states ubiquitously appear under
different crystal structures in metals and insulators. Toward a systematic
understanding of the formation of the multiple-$Q$ states in various crystal
systems, in this theoretical study, we present a low-energy effective spin
model with anisotropic exchange interactions in momentum space. We summarize
specific six symmetry rules for nonzero symmetric and antisymmetric anisotropic
exchange interactions in momentum space, which are regarded as an extension of
Moriya's rule. According to the rules, we construct the effective spin model
for tetragonal, hexagonal, and trigonal magnets with crystal- and
momentum-dependent anisotropic exchange interactions based on magnetic
representation analysis. Furthermore, we describe the origin of the effective
anisotropic exchange interactions in itinerant magnets by perturbatively
analyzing a multi-band periodic Anderson model with the spin-orbit coupling. We
apply the effective spin model to an itinerant magnet in a $P6/mmm$ crystal and
find various multiple-$Q$ states with a spin scalar chirality in the ground
state. Our results provide a foundation of constructing effective
phenomenological spin models for any crystal systems hosting the multiple-$Q$
states, which will stimulate further exploration of exotic multiple-$Q$ states
in materials with the spin-orbit coupling.",2202.09744v1
2022-09-13,Theory of transverse magnetization in spin-orbit coupled antiferromagnets,"Some antiferromagnets under a magnetic field develop magnetization
perpendicular to the field as well as more conventional ones parallel to the
field. So far, the transverse magnetization (TM) has been attributed to either
spin canting effect or the presence of cluster magnetic multipolar ordering.
However, a general theory of TM based on microscopic understanding is still
missing. Here, we construct a general microscopic theory of TM in
antiferromagnets with cluster magnetic multipolar ordering by considering
classical spin Hamiltonians with spin anisotropy that arises from the
spin-orbit coupling. First, from general symmetry analysis, we show that TM can
appear only when all crystalline symmetries are broken other than the
antiunitary mirror, antiunitary two-fold rotation, and inversion symmetries.
Moreover, by analyzing spin Hamiltonians, we show that TM always appears when
the degenerate ground state manifold of the spin Hamiltonian is discrete. On
the other hand, when the degenerate ground state manifold is continuous, TM
generally does not appear except when the magnetic field direction and the spin
configuration satisfy specific geometric conditions under single-ion
anisotropy. Finally, we show that TM can induce anomalous planar Hall Effect, a
unique transport phenomenon that can be used to probe multipolar
antiferromagnetic structures. We believe that our theory provides a useful
guideline for understanding the anomalous magnetic responses of the
antiferromagnets with complex magnetic structures.",2209.05702v1
2017-02-07,Large room temperature spin-to-charge conversion signals in a few-layer graphene/Pt lateral heterostructure,"Electrical generation and detection of pure spin currents without the need of
magnetic materials are key elements for the realization of full electrically
controlled spintronic devices. In this framework, achieving a large
spin-to-charge conversion signal is crucial, since considerable outputs are
needed for plausible applications. Unfortunately, the values obtained so far
have been rather low. Here we exploit the spin Hall effect by using Pt, a
non-magnetic metal with strong spin-orbit coupling, to generate and detect pure
spin currents in a few-layer graphene channel. Furthermore, the outstanding
properties of graphene, with long distance spin transport and higher electrical
resistivity than metals, allows us to achieve in our graphene/Pt lateral
heterostructures the largest spin-to-charge voltage signal at room temperature
reported so far in the literature. Our approach opens up exciting opportunities
towards the implementation of spin-orbit-based logic circuits and all
electrical control of spin information without magnetic field.",1702.01971v2
2022-10-24,Spin State Evolution of (99942) Apophis during its 2029 Earth Encounter,"We explore the effects of the 2029 Earth encounter on asteroid (99942)
Apophis' non-principal axis spin state, leveraging refined orbit, spin state,
and inertia information provided by more recent optical and radar observations.
Propagating the asteroids' coupled orbit and rigid body attitude dynamics
through the flyby, we present the range of possible post-flyby spin states.
These spin state distributions will be valuable for planning Apophis
observation campaigns and spacecraft missions, most notably OSIRIS-APEX. The
simulations indicate that gravitationally induced changes to the asteroid's
tumbling periods and rotational angular momentum direction (pole) will likely
be significant and measurable. For the current spin state and inertia estimates
and their uncertainties, Apophis is likely to remain in a short axis mode (SAM)
tumbling state but its effective spin rate could halve or double. Its pole is
likely to shift by 10 degrees or more and increase in longitude while moving
closer to the ecliptic plane. These spin state changes are very sensitive to
the asteroid's close approach attitude and mass distribution. With ground-based
tracking of the asteroid's spin state through the encounter, this sensitivity
will help refine mass distribution knowledge. We also discuss the implications
of this abrupt spin state alteration for Apophis' Yarkovsky acceleration and
geophysical properties, identifying possible pathways for surface and internal
changes, most notably if Apophis is a contact binary. Comparison of the pre and
post-flyby inertia estimates obtained from the ground-based observations will
help assess the extent of possible geophysical changes.",2210.13365v1
2023-05-15,Tidal Spin-up of Black Hole Progenitor Stars,"Gravitational wave observations indicate the existence of merging black holes
(BHs) with high spin ($a\gtrsim0.3$), whose formation pathways are still an
open question. A possible way to form those binaries is through the tidal
spin-up of a Wolf-Rayet (WR) star by its BH companion. In this work, we
investigate this scenario by directly calculating the tidal excitation of
oscillation modes in WR star models, determining the tidal spin-up rate, and
integrating the coupled spin-orbit evolution for WR-BH binaries. We find that,
for short-period orbits and massive WR stars, the tidal interaction is mostly
contributed by standing gravity modes, in contrast to Zahn's model of traveling
waves which is frequently assumed in the literature. The standing modes are
less efficiently damped than traveling waves, meaning that prior estimates of
tidal spin-up may be overestimated. We show that tidal synchronization is
rarely reached in WR-BH binaries, and the resulting BH spins have $a \lesssim
0.4$ for all but the shortest-period ($P_{\rm orb} \! \lesssim 0.5 \, {\rm d}$)
binaries. Tidal spin-up in lower-mass systems is more efficient, providing an
anticorrelation between the mass and spin of the BHs, which could be tested in
future gravitational wave data. Nonlinear damping processes are poorly
understood but may allow for more efficient tidal spin-up. We also discuss a
new class of gravito-thermal modes that appear in our calculations.",2305.08356v2
2017-08-30,Gate-Control of Anisotropic Spin Transport and Spin Helix Dynamics in a Modulation-Doped GaAs Quantum Well,"Electron spin transport and dynamics are investigated in a single,
high-mobility, modulation-doped, GaAs quantum well using ultrafast two-color
Kerr-rotation micro-spectroscopy, supported by qualitative kinetic theory
simulations of spin diffusion and transport. Evolution of the spins is governed
by the Dresselhaus bulk and Rashba structural inversion asymmetries, which
manifest as an effective magnetic field that can be extracted directly from the
experimental coherent spin precession. A spin precession length L-SOI is
defined as one complete precession in the effective magnetic field. It is
observed that application of (a) an out-of-plane electric field changes the
spin decay time and L-SOI through the Rashba component of the spin-orbit
coupling, (b) an in-plane magnetic field allows for extraction of the
Dresselhaus and Rashba parameters, and (c) an in-plane electric field markedly
modifies both the L-SOI and diffusion coefficient. While simulations reproduce
the main features of the experiments, the latter results exceed the
corresponding simulations and extend previous studies of
drift-current-dependent spin-orbit interactions.",1708.09150v2
2019-04-01,Electron-phonon superconductivity in CaBi2 and the role of spin-orbit interaction,"CaBi$_2$ is a recently discovered type-I superconductor with $T_c=2$~K and a
layered crystal structure. In this work electronic structure, lattice dynamics
and electron-phonon interaction are studied, with a special attention paid to
the influence of the spin-orbit coupling (SOC) on above-mentioned quantities.
We find, that in the scalar-relativistic case (without SOC), electronic
structure and electron-phonon interaction show the quasi-two dimensional
character. Strong Fermi surface nesting is present, which leads to appearance
of the Kohn anomaly in the phonon spectrum and enhanced electron-phonon
coupling for the phonons propagating in the Ca-Bi atomic layers. However,
strong spin-orbit coupling in this material changes the topology of the Fermi
surface, reduces the nesting and the electron-phonon coupling becomes weaker
and more isotropic. The electron-phonon coupling parameter $\lambda$ is reduced
by SOC almost twice, from 0.94 to 0.54, giving even stronger effect on the
superconducting critical temperature $T_c$, which drops from 5.2~K (without
SOC) to 1.3~K (with SOC). Relativistic values of $\lambda$ and $T_c$ remain in
a good agreement with experimental findings, confirming the general need for
including SOC in analysis of the electron-phonon interaction in materials
containing heavy elements.",1904.00650v1
2022-03-10,Electrically tunable Berry curvature and strong light-matter coupling in birefringent perovskite microcavities at room temperature,"The field of spinoptronics is underpinned by good control over photonic
spin-orbit coupling in devices that possess strong optical nonlinearities. Such
devices might hold the key to a new era of optoelectronics where momentum and
polarization degrees-of-freedom of light are interwoven and interfaced with
electronics. However, manipulating photons through electrical means is a
daunting task given their charge neutrality and requires complex electro-optic
modulation of their medium. In this work, we present electrically tunable
microcavity exciton-polariton resonances in a Rashba-Dresselhaus spin-orbit
coupling field at room temperature. We show that a combination of different
spin orbit coupling fields and the reduced cavity symmetry leads to tunable
formation of Berry curvature, the hallmark of quantum geometrical effects. For
this, we have implemented a novel architecture of a hybrid photonic structure
with a two-dimensional perovskite layer incorporated into a microcavity filled
with nematic liquid crystal. Our work interfaces spinoptronic devices with
electronics by combining electrical control over both the strong light-matter
coupling conditions and artificial gauge fields.",2203.05289v1
2009-03-05,Quantum critical behavior driven by Hund's rule coupling in quantum antiferromagnets,"When localized spins on different d orbitals prefer different types of
antiferromagnetic ordering, the Hund's rule coupling creates frustration. Using
spin-wave theory we study the case of two such orbitals on a square lattice
coupled through Hund's rule, such that the first one couples
antiferromagnetically (AF) more strongly to its nearest neighbors, while the
second couples more strongly to its next nearest neighbors. We find that the
zero temperature phase diagram has four regions, one characterized by the
familiar $(\pi,\pi)$ AF order, a second by the columnar $(\pi,0)$ order, a
third by a {\it canted} order and a fourth region where a quantum-disordered
state emerges. We comment on the possible relevance of these findings for the
case of Fe-pnictide based antiferromagnets.",0903.0983v1
2020-02-11,FORTRESS: FORTRAN programs for solving coupled Gross-Pitaevskii equations for spin-orbit coupled spin-1 Bose-Einstein condensate,"Here, we present simple and efficient numerical scheme to study static and
dynamic properties of spin-1 Bose-Einstein condensates (BECs) with spin-orbit
(SO) coupling by solving three coupled Gross-Pitaevskii equations (CGPEs) in
three-, quasi-two and quasi-one dimensional systems. We provide a set of three
codes developed in FORTRAN 90/95 programming language with user defined '{\em
option}' of imaginary and real-time propagation. We present the numerical
results for energy, chemical potentials, and component densities for the ground
state and compare with the available results from the literature. The results
are presented for both the ferromagnetic and antiferromagnetic spin-1 BECs with
and without SO coupling. To improve the computational speed, all the codes have
the option of OpenMP parallelization. We have also presented the results for
speedup and efficiency of OpenMP parallelization for the three codes with both
imaginary and real-time propagation.",2002.04365v2
2019-01-09,Effect of spin-orbit coupling on tunnelling escape of Bose-Einstein condensate,"We theoretically investigate quantum tunnelling escape of a spin-orbit (SO)
coupled Bose-Einstein condensate (BEC) from a trapping well. The condensate is
initially prepared in a quasi-one-dimensional harmonic trap. Depending on the
system parameters, the ground state can fall in different phases --- single
minimum, separated or stripe. Then, suddenly the trapping well is opened at one
side. The subsequent dynamics of the condensate is studied by solving nonlinear
Schr\""{o}dinger equations. We found that the diverse phases will greatly change
the tunneling escape behavior of SO coupled BECs. In single minimum and
separated phases, the condensate escapes the trapping well continuously, while
in stripe phase it escapes the well as an array of pulses. We also found that
SO coupling has a suppressing effect on the tunnelling escape of atoms.
Especially, for BECs without inter-atom interaction, the tunnelling escape can
be almost completely eliminated when the system is tuned near the transition
point between single minimum and stripe phase. Our work thus suggests that SO
coupling may be a useful tool to control the tunnelling dynamic of BECs, and
potentially be applied in realization of atom lasers and matter wave switches.",1901.02621v1
2022-03-22,Superradiant Quantum Phase transition for Landau Polaritons with Rashba and Zeeman couplings,"We develop a theory of cavity quantum electrodynamics for a two-dimensional
electron gas in the presence of Rashba spin-orbit and Zeeman couplings and
perpendicular magnetic field, coupled to a spatially nonuniform quantum photon
field. We show that the superradiant quantum phase transition (SQPT), also
known as photon condensation, can in principle occur through a pure in-plane
Zeeman coupling, but it requires extremely small (unrealistic) quantum well
widths or extremely fine tuning of the effective Land\'e factor which makes two
Landau levels coincide. Landau level crossings can also be induced by the
Rashba spin-orbit coupling and they promote the SQPT which can be obtained for
certain values of the effective Land\'e factor and filling factors.",2203.11850v2
2011-07-25,Spin-Orbit Coupled Bose-Einstein Condensate under Rotation,"We examine the combined effects of Rashba spin-orbit (SO) coupling and
rotation on trapped spinor Bose-Einstein condensates (BECs). Nature of single
particle states is thoroughly examined in the Landau level basis and is shown
to support the formation of half-quantum vortex. In the presence of weak s-wave
interactions, the ground state at strong SO coupling develops ring-like
structures with domains whose number shows step behavior with increasing
rotation. For fast rotation case, the vortex pattern favors triangular lattice,
accompanied by the density depletion in the central region and weakened
Skyrmionic character as the SO coupling is enhanced. Giant vortex formation is
facilitated when SO coupling and rotation are both strong.",1107.4845v2
2013-06-14,Localized modes in dense repulsive and attractive Bose-Einstein condensates with spin-orbit and Rabi couplings,"We consider a binary Bose-Einstein condensate with linear and nonlinear
interactions between its components, which emulate the spinor system with
spin-orbit (SO) and Rabi couplings. For a relatively dense condensate, 1D
coupled equations with the nonpolynomial nonlinearity of both repulsive and
attractive signs are derived from the 3D Gross-Pitaevskii equations. Profiles
of modes confined in an external potential under the action of the
self-repulsion, and self-trapped solitons in the case of the self-attraction,
are found in a numerical form and by means of analytical approximations. In the
former case, the interplay of the SO and Rabi couplings with the repulsive
nonlinearity strongly distorts shapes of the trapped modes, adding conspicuous
side lobes to them. In the case of the attractive nonlinearity, the most
essential result is reduction of the collapse threshold under the action of the
SO and Rabi couplings.",1306.3402v1
2017-10-02,High Controllable and Robust 2D Spin-Orbit Coupling for Quantum Gases,"We report the realization of a robust and highly controllable two-dimensional
(2D) spin-orbit (SO) coupling with topological non-trivial band structure. By
applying a retro-reflected 2D optical lattice, phase tunable Raman couplings
are formed into the anti-symmetric Raman lattice structure, and generate the 2D
SO coupling with precise inversion and $C_4$ symmetries, leading to
considerably enlarged topological regions. The life time of the 2D SO coupled
Bose-Einstein condensate reaches several seconds, which enables the exploring
of fine tuning interaction effects. These essential advantages of the present
new realization open the door to explore exotic quantum many-body effects and
non-equilibrium dynamics with novel topology.",1710.00717v3
2018-01-16,Matter-waves in Bose-Einstein condensates with spin-orbit and Rabi couplings,"We investigate the one-dimensional (1D) and two-dimensional (2D)reduction of
a quantum field theory starting from the three-dimensional (3D) many-body
Hamiltonian of interacting bosons with spin-orbit (SO) and Rabi couplings. We
obtain the effective time-dependent 1D and 2D nonpolynomial Heisenberg
equations for both repulsive and attractive signs of the inter-atomic
interaction. Our findings show that in case in which the many-body state
coincides with the Glauber coherent state,the 1D and 2D Heisenberg equations
become 1D and 2D nonpolynomial Schr\""odinger equations (NPSEs). These models
were derived in a mean-field approximation from 3D Gross-Pitaevskii equation
(GPE), describing a Bose-Einstein condensate (BEC)with SO and Rabi couplings.
In the present work self-repulsive and self-attractive localized solutions of
the 1D NPSE and the 1D GPE are obtained in a numerical form. The combined
action of SO and Rabi couplings produces conspicuous sidelobes on the density
profile, for both signs of the interaction. In the case of the attractive
nonlinearity, an essential result is the possibility of getting an unstable
condensate by increasing of SO coupling.",1801.05314v1
2021-12-27,Screening nearest-neighbor interactions in networks of exciton-polariton condensates through spin orbit coupling,"We study the modification of the spatial coupling parameter between
interacting ballistic exciton-polariton condensates in the presence of photonic
spin orbit coupling appearing from TE-TM splitting in planar semiconductor
microcavities. We propose a strategy to make the coupling strength between
next-nearest-neighbours stronger than between nearest-neighbour, which inverts
the conventional idea of the spatial coupling hierarchy between sites. Our
strategy relies on the dominantly populated high-momentum components in the
ballistic condensates which, in the presence of TE-TM splitting, lead to rapid
radial precession of the polariton pseudospin. As a consequence, condensate
pairs experience distance-periodic screening of their interaction strength,
severely modifying their synchronization and condensation threshold solutions.",2112.13601v2
2023-07-21,Electronic and Spin-Orbit Properties of hBN Encapsulated Bilayer Graphene,"Van der Waals (vdW) heterostructures consisting of Bernal bilayer graphene
(BLG) and hexagonal boron nitride (hBN) are investigated. By performing
first-principles calculations we capture the essential BLG band structure
features for several stacking and encapsulation scenarios. A low-energy model
Hamiltonian, comprising orbital and spin-orbit coupling (SOC) terms, is
employed to reproduce the hBN-modified BLG dispersion, spin splittings, and
spin expectation values. Most important, the hBN layers open an orbital gap in
the BLG spectrum, which can range from zero to tens of meV, depending on the
precise stacking arrangement of the individual atoms. Therefore, large local
band gap variations may arise in experimentally relevant moir\'{e} structures.
Moreover, the SOC parameters are small (few to tens of $\mu$eV), just as in
bare BLG, but are markedly proximity modified by the hBN layers. Especially
when BLG is encapsulated by monolayers of hBN, such that inversion symmetry is
restored, the orbital gap and spin splittings of the bands vanish. In addition,
we show that a transverse electric field mainly modifies the potential
difference between the graphene layers, which perfectly correlates with the
orbital gap for fields up to about 1~V/nm. Moreover, the layer-resolved Rashba
couplings are tunable by $\sim 5~\mu$eV per V/nm. Finally, by investigating
twisted BLG/hBN structures, with twist angles between 6$^{\circ}$ --
20$^{\circ}$, we find that the global band gap increases linearly with the
twist angle. The extrapolated $0^{\circ}$ band gap is about 23~meV and results
roughly from the average of the stacking-dependent local band gaps. Our
investigations give new insights into proximity spin physics of hBN/BLG
heterostructures, which should be useful for interpreting experiments on
extended as well as confined (quantum dot) systems.",2307.11697v2
1995-06-16,Critical level spacing distribution of two-dimensional disordered systems with spin-orbit coupling,"The energy level statistics of 2D electrons with spin-orbit scattering are
considered near the disorder induced metal-insulator transition. Using the Ando
model, the nearest-level-spacing distribution is calculated numerically at the
critical point. It is shown that the critical spacing distribution is size
independent and has a Poisson-like decay at large spacings as distinct from the
Gaussian asymptotic form obtained by the random-matrix theory.",9506072v1
2001-01-22,"Possibility of two-channel orbital Kondo ""spin"" 1/2 conductance in a quantum dot","We propose that two-channel orbital Kondo ``spin'' 1/2 conductance can be
measured in a quantum dot at Coulomb Blockade with an odd number of electrons
with contacts in a pillar configuration, if an orthogonal magnetic field
induces an appropriate level crossing. At the zero-temperature strong coupling
fixed point the conductance reaches the unitarity limit with a non-Fermi liquid
sqrt(T)-law.",0101341v2
2002-12-10,Quantum Phase Transition in the SU(4) Spin-Orbital Model on the Triangular Lattice,"Motivated by the absence of cooperative Jahn-Teller effect in LiNiO2 and
BaVS3, two layered oxides with triangular planes, we study the SU(4) symmetric
spin-orbital model on the triangular lattice. Upon reducing the next-nearest
neighbour coupling, we show that the system undergoes a quantum phase
transition to a liquid phase. A variational approach to this liquid phase shows
that simple types of long-range correlations are suppressed, suggesting that it
is stable against lattice distortions.",0212211v1
2004-09-14,Antilocalization and spin-orbit coupling in hole strained GaAs/InGaAs/GaAs quantum well heterostructures,"Low-field magnetoresistance in p-type strained quantum wells is studied. It
is shown that the Rashba mechanism leads to the cubic in quasimomentum
spin-orbit splitting of the hole energy spectrum and the antilocalization
behavior of low-field magnetoresistance is well described by the
Hikami-Larkin-Nagaoka expression.",0409342v1
2004-11-02,Anisotropic electron g-factor in quantum dots with spin-orbit interaction,"g-factor tuning of electrons in quantum dots is studied as function of
in-plane and perpendicular magnetic fields for different confinements. Rashba
and Dresselhaus effects are considered, and comparison is made between wide-
and narrow-gap materials. The interplay between magnetic fields and intrinsic
spin-orbit coupling is analyzed, with two distinct phases found in the spectrum
for GaAs in perpendicular field. The anisotropy of the g-factor is reported,
and good agreement with available experimental findings is obtained.",0411071v1
2005-10-03,Low energy electronic states and triplet pairing in layered cobaltates,"The structure of the low-energy electronic states in layered cobaltates is
considered starting from the Mott insulating limit. We argue that the coherent
part of the wave-functions and the Fermi-surface topology at low doping are
strongly influenced by spin-orbit coupling of the correlated electrons on the
$t_{2g}$ level. An effective t-J model based on mixed spin-orbital states is
radically different from that for the cuprates, and supports unconventional,
pseudospin-triplet pairing.",0510051v1
2005-12-07,Zitterbewegung of electrons and holes in III-V semiconductor quantum wells,"The notion of zitterbewegung is a long-standing prediction of relativistic
quantum mechanics. Here we extend earlier theoretical studies on this
phenomenon for the case of III-V zinc-blende semiconductors which exhibit
particularly strong spin-orbit coupling. This property makes nanostructures
made of these materials very favorable systems for possible experimental
observations of zitterbewegung. Our investigations include electrons in n-doped
quantum wells under the influence of both Rashba and Dresselhaus spin-orbit
interaction, and also the two-dimensional hole gas. Moreover, we give a
detailed anaysis of electron zitterbewegung in quantum wires which appear to be
particularly suited for experimentally observing this effect.",0512148v1
2005-12-07,Effect of spin-orbit interaction on a magnetic impurity in the vicinity of a surface,"We propose a new mechanism for surface-induced magnetic anisotropy to explain
the thickness-dependence of the Kondo resistivity of thin films of dilute
magnetic alloys. The surface anisotropy energy, generated by spin-orbit
coupling on the magnetic impurity itself, is an oscillating function of the
distance d from the surface and decays as 1/d^2. Numerical estimates based on
simple models suggest that this mechanism, unlike its alternatives, gives rise
to an effect of the desired order of magnitude.",0512154v1
2006-08-16,Degenerate states of narrow semiconductor rings in the presence of spin orbit coupling: Role of time-reversal and large gauge transformations,"The electron Hamiltonian of narrow semiconductor rings with the Rashba and
Dresselhaus spin orbit terms is invariant under time-reversal operation
followed by a large gauge transformation. We find that all the eigenstates are
doubly degenerate when integer or half-integer quantum fluxes thread the
quantum ring. The wavefunctions of a degenerate pair are related to each other
by the symmetry operation. These results are valid even in the presence of a
disorder potential. When the Zeeman term is present only some of these
degenerate levels anticross.",0608347v1
2007-01-15,Exchange energy and generalized polarization in the presence of spin-orbit coupling in two dimensions,"We discuss a general form of the exchange energy for a homogeneous system of
interacting electrons in two spatial dimensions which is particularly suited in
the presence of a generic spin-orbit interaction. The theory is best formulated
in terms of a generalized fractional electronic polarization. Remarkably we
find that a net generalized polarization does not necessarily translate into an
increase in the magnitude of the exchange energy, a fact that in turn favors
unpolarized states. Our results account qualitatively for the findings of
recent experimental investigations.",0701355v2
2007-02-05,"Theory of Layered Iron Oxide on Frustrated Geometry: Electric Polarization, Magnetoelectric Effect and Orbital State","A layered iron oxide \rfeo ($R$: rare-earth elements) is an exotic dielectric
material with charge-order (CO) driven electric polarization and
magnetoelectric effect caused by spin-charge coupling. In this paper, a theory
of electronic structure and dielectric property in \rfeo is presented. Charge
frustration in paired-triangular lattices allows a charge imbalance without
inversion symmetry. Spin frustration induces reinforcement of this polar CO by
a magnetic ordering. We also analyze an orbital model for the Fe ion which does
not show a conventional long-range order.",0702087v2
2000-08-17,Effects of Instantons on the YN Interaction,"We investigate the symmetric and anti-symmetric spin-orbit forces (SLS and
ALS) of the effective $\Lambda$N interaction derived from a quark cluster model
with the instanton-induced interaction (\III), which can reproduce the observed
YN cross sections as well as the observed NN scattering data.
  It is found that coupling to the $\Sigma$N channel enhances $\Lambda$N ALS,
and therefore that the cancellation between SLS and ALS in the $\Lambda$N
channel becomes more complete. This may be one of the major reasons why the
single-particle spin-orbit force of $\Lambda$ in nuclei is weak.",0008178v1
1998-04-28,Accelerated Electrons and the Unruh Effect,"Quantum effects for electrons in a storage ring are studied in a co-moving,
accelerated frame. The polarization effect due to spin flip synchrotron
radiation is examined by treating the electron as a simple quantum mechanical
two-level system coupled to the orbital motion and to the radiation field. The
excitations of the spin system are related to the Unruh effect, i.e. the effect
that an accelerated radiation detector is thermally excited by vacuum
fluctuations. The importance of orbital fluctuations is pointed out and the
vertical fluctuations are examined.",9804179v1
1999-03-18,Hamiltonian Methods for the Study of Polarized Proton Beam Dynamics in Accelerators and Storage Rings,"The equations of classical spin-orbit motion can be extended to a Hamiltonian
system in 9-dimensional phase space by introducing a coupled spin-orbit Poisson
bracket and a Hamiltonian function. After this extension and by establishing
connections between initial and extended systems it becomes possible to apply
the methods of the theory of Hamiltonian systems to the study of polarized
particle beam dynamics in circular accelerators and storage rings. Some of
those methods have been implemented in the computer code FORGET-ME-NOT.",9903032v1
2004-10-26,An estimate of the inter-system crossing time in light-emitting polymers,"The reported enhanced singlet-exciton yields in light-emitting polymers over
the statistical limit of 25% has attracted wide experimental and theoretical
attention. Most theoretical estimates of the singlet-exciton yield depend
crucially on estimates of the inter-system crossing rates induced by spin-orbit
coupling. In this paper we use the experimentally determined phosphorescent
life-time and energy of the lowest-lying triplet state, as well as calculated
values of Huang-Rhys factors to estimate the spin-orbit matrix element and
inter-system crossing time between the lowest-lying singlet and triplet states.",0410253v1
2004-04-01,Representing multiqubit unitary evolutions: spin coherences and infinitesimal coherences,"For the tensor of coherences parametrization of a multiqubit density
operator, we provide an explicit formulation of the corresponding unitary
dynamics at infinitesimal level. The main advantage of this formalism (clearly
reminiscent of the idea of ``coherences'' and ``coupling Hamiltonians'' of spin
systems) is that the pattern of correlation between qubits and the pattern of
infinitesimal correlation are highlighted simultaneously and can be used
constructively for qubit manipulation. For example, it allows to compute
explicitly a Rodrigues' formula for the one-parameter orbits of nonlocal
Hamiltonians. The result is easily generalizable to orbits of Cartan
subalgebras and allows to write the Cartan decomposition of unitary propagators
as a linear action.",0404006v2
2005-05-09,Adiabatic geometric phases in hydrogenlike atoms,"We examine the effect of spin-orbit coupling on geometric phases in
hydrogenlike atoms exposed to a slowly varying magnetic field. The marginal
geometric phases associated with the orbital angular momentum and the intrinsic
spin fulfill a sum rule that explicitly relates them to the corresponding
geometric phase of the whole system. The marginal geometric phases in the
Zeeman and Paschen-Back limit are analyzed. We point out the existence of nodal
points in the marginal phases that may be detected by topological means.",0505058v2
2009-09-04,Approximate Analytical Solutions of the Pseudospin Symmetric Dirac Equation for Exponential-type Potentials,"The solvability of The Dirac equation is studied for the exponential-type
potentials with the pseudospin symmetry by using the parametric generalization
of the Nikiforov-Uvarov method. The energy eigenvalue equation, and the
corresponding Dirac spinors for Morse, Hulthen, and q-deformed Rosen-Morse
potentials are obtained within the framework of an approximation to the
spin-orbit coupling term, so the solutions are given for any value of the
spin-orbit quantum number $\kappa=0$, or $\kappa \neq 0$.",0909.0821v1
2010-08-26,Evidence for charge orbital and spin stripe order in an overdoped manganite,"We present diffraction data on a single-layered manganite
La(0.42)Sr(1.58)MnO4 with hole doping (x>0.5). Overdoped La(0.42)Sr(1.58)MnO4
exhibits a complex ordering of charges, orbitals and spins. Single crystal
neutron diffraction experiments reveal three incommensurate and one
commensurate order parameters to be tightly coupled. The position and the shape
of the distinct superstructure scattering points to a stripe arrangement in
which ferromagnetic zigzag chains are disrupted by additional Mn4+ stripes.",1008.4496v1
2011-06-23,Probing high-energy electronic excitations using inelastic neutron scattering,"High-energy, local multiplet excitations of the d-electrons are revealed in
our inelastic neutron scattering measurements on the prototype magnetic
insulator NiO. These become allowed by the presence of both non-zero crystal
field and spin-orbit coupling. The observed excitations are consistent with
optical, x-ray, and EELS measurements of d-d excitations. This experiment
serves as a proof of principle that high-energy neutron spectroscopy is a
reliable and useful technique for probing electronic excitations in systems
with significant crystal field and spin-orbit interactions.",1106.4634v1
2011-08-02,Spin-orbit-enhanced Wigner localization in quantum dots,"We investigate quantum dots with Rashba spin-orbit coupling in the
strongly-correlated regime. We show that the presence of the Rashba interaction
enhances the Wigner localization in these systems, making it achievable for
higher densities than those at which it is observed in Rashba-free quantum
dots. Recurring shapes in the pair-correlated densities of the yrast spectrum,
which might be associated with rotational and vibrational modes, are also
reported.",1108.0512v3
2011-09-19,Local Quantum Criticality of an Iron-Pnictide Tetrahedron,"Motivated by the close correlation between transition temperature ($T_c$) and
the tetrahedral bond angle of the As-Fe-As layer observed in the iron-based
superconductors, we study the interplay between spin and orbital physics of an
isolated iron-arsenide tetrahedron embedded in a metallic environment. Whereas
the spin Kondo effect is suppressed to low temperatures by Hund's coupling, the
orbital degrees of freedom are expected to quantum mechanically quench at high
temperatures, giving rise to an overscreened, non-Fermi liquid ground-state.
Translated into a dense environment, this critical state may play an important
role in the superconductivity of these materials.",1109.4131v2
2013-01-26,Electronic Structure and magnetism in Ir based double-perovskite Sr$_2$CeIrO$_6$,"The electronic structure and magnetism of Sr$_2$CeIrO$_6$, an Ir-based double
perovskite system has been investigated using first-principles calculations. We
found that a strong spin-orbit coupling dictate the electronic and magnetic
properties of this system. A small value of $U$ along with SOC could open up a
gap at the Fermi level, offering the possibility of novel J$_{eff}$ = 1/2 Mott
quantum state. Our calculations reveal that the magnetic ground state is
antiferromagnetic in agreement with the magnetization data and provide the
value of spin and orbital moment for this system which is in agreement with the
other isostructural Ir-based compound.",1301.6218v1
2013-06-14,Inter-valley scattering induced by Coulomb interaction and disorder in carbon-nanotube quantum dots,"We develop a theory of inter-valley Coulomb scattering in semiconducting
carbon-nanotube quantum dots, taking into account the effects of curvature and
chirality. Starting from the effective-mass description of single-particle
states, we study the two-electron system by fully including Coulomb
interaction, spin-orbit coupling, and short-range disorder. We find that the
energy level splittings associated with inter-valley scattering are nearly
independent of the chiral angle and, while smaller than those due to spin-orbit
interaction, large enough to be measurable.",1306.3502v2
2013-12-31,Tuning Magnetic Properties Polycrystalline of PtCo Alloys Films with Pt,"We experimentally investigated disordered PtxCo1-x (here x: 0.4, 0.5 and 0.6)
alloy thin films magnetic properties which depended on Pt content. The magnetic
properties of PtCo films were described with two effects, one of them is the
hybridization between Co 3d and Pt 5d energy levels and it causes Pt magnetic
polarization. The second one is the high spin orbit coupling constant of Pt
which increases the ratio of magnetic orbital moment to spin moment. We
investigated magnetic properties considering these effects by vibrating sample
magnetometer (VSM) and ferromagnetic resonance (FMR) techniques.",1401.0227v2
2014-09-25,Equivalent spin-orbit interaction in two-polariton Jaynes-Cummings-Hubbard model,"A hybrid quantum system combines two or more distinct quantum components,
exhibiting features not seen in these individual systems. In this work, we
study the one-dimensional Jaynes-Cummings- Hubbard model in the two-excitation
subspace. We find that the center momentum of two-excitation induces a magnetic
ux piercing the 4-leg ladder in the auxiliary space. Furthermore, it is shown
that the system in {\pi}-center-momentum subspace is equivalent to a chain
system for spin-1 particle with spin-orbit coupling. As a simple application,
based on this concise description, a series of bound-pair eigenstates is
presented, which displays long-range correlation.",1409.7161v1
2015-02-07,Majorana Fermion Rides on a Magnetic Domain Wall,"We propose using a mobile magnetic domain wall as a host of zero-energy
Majorana fermions in a spin-orbit coupled nanowire sandwiched by two
ferromagnetic strips and deposited on an $s$-wave superconductor. The ability
to control domain walls by thermal means allows to braid Majorana fermions
nonintrusively, which obey non-Abelian statistics. The analytical solutions of
Majorana fermions inside domain walls are obtained in the strong spin-orbit
regime.",1502.02088v1
2015-11-14,Spin-orbit concept of open-shell systems,"The paper presents a first attempt to look at the peculiarities of open-shell
systems from the viewpoint of spin-orbit coupling. Contrary to common opinion
of a negligible role of the issue for light element molecules, presented in the
paper evidences its governing role in such systems peculiarities on example of
sp2 nanocarbons. A particular attention is given to the justification of the
validity of UHF approach to exhibit the SOC peculiarities of open-shell
systems.",1511.05480v1
2016-01-13,Anisotropic Paramagnetic Meissner Effect by Spin-Orbit Coupling,"Conventional $s$-wave superconductors repel external magnetic flux. However,
a recent experiment [A. Di Bernardo et al., Phys. Rev. X \textbf{5}, 041021
(2015)] has tailored the electromagnetic response of superconducting
correlations via adjacent magnetic materials. We consider another route to
alter the Meissner effect where spin-orbit interactions induce an anisotropic
Meissner response that changes sign depending on the field orientation. The
tunable electromagnetic response opens new paths in the utilization of hybrid
systems comprised of magnets and superconductors.",1601.03404v2
2018-04-25,Topological Insulator State due to Finite Spin-Orbit Interaction in an Organic Dirac Fermion System,"Recently, Valenti et al. pointed out the significance of the spin-orbit
interaction (SOI) in organic materials, and explained the anomalous insulating
behavior of a Dirac semimetal alpha-(BEDT-TTF)2I3 at low temperatures in terms
of the small SOI gap. We propose a lattice model with plausible SOI coupling,
and indicate that the gapped state is a topological insulator. This model is an
organic analogue of the Kane-Mele model for graphene.",1804.09420v1
2018-11-13,Composition and Stacking Dependent Topology in Bilayers from the Graphene Family,"We present a compositional and structural investigation of silicene,
germanene, and stanene bilayers from first-principles. Due to the staggering of
the individual layers, several stacking patterns are possible, most of which
are not available to the bilayer graphene. This structural variety, in
conjunction with the presence of the spin-orbit coupling, unveil a diversity of
the electronic properties, with the appearance of distinct band features,
including orbital hybridization and band inversion. We show that for particular
cases, the intrinsic spin Hall response exhibits signatures of non-trivial
electronic band topology, making these structures promising candidates to probe
Dirac-like physics.",1811.05525v2
2011-11-21,Mapping spin-polarised transitions with atomic resolution,"The coupling between Angstrom-sized electron probes and spin polarised
electronic transitions shows that the inelastically scattered probe is in a
mixed state containing electron vortices with non-zero orbital angular
momentum. These electrons create an asymmetric intensity distribution in energy
filtered diffraction patterns, giving access to maps of the magnetic moments
with atomic resolution. A feasibility experiment shows evidence of the
predicted effect. Potential applications are column-by-column maps of magnetic
ordering, and the creation of Angstrom-sized free electrons with orbital
angular momentum by inelastic scattering in a thin ferromagnetic foil.",1111.4915v2
2012-04-03,Quaternionic vector coherent states for spin-orbit interactions,"This work addresses the study of two-dimensional electron gas in a
perpendicular magnetic field in the presence of both Rashba and Dresselhaus
spin-orbit (SO) interactions, with effective Zeeman coupling. Exact analytical
expressions are found for the eigenvalue problem giving the Landau levels and
the associated eigenstates, thanks to an appropriate method of parametrization
used to quantize the physical system. Such a system exhibits interesting
properties of quaternions for which vector coherent states are built.
Similarity with the Weyl-Heisenberg group and some relevant properties of these
vectors are discussed.",1204.0722v1
2013-09-21,Photovoltaic effect in BiFeO3/TiO2 heterostructures tuned with epitaxial strain and an electric field,"The photovoltaic effect in the BiFeO3/TiO2 heterostructures can be tuned by
epitaxial strain and an electric field in the visible-light region which is
manifested by the enhancement of absorption activity in the heterojunction
under tensile strain and an electric field based on the first-principles
calculations. It is suggested that there are coupling between photon, spin
carrier, charge, orbital, and lattice in the interface of the bilayer film
which makes the heterojunction an intriguing candidate towards fabricating the
multifunctional photoelectric devices based on spintronics. The microscopic
mechanism involved in the heterostruces is related deeply with the spin
transfer and charge rearrangement between the Fe 3d and O 2p orbitals in the
vicinity of the interface.",1309.5432v1
2016-05-02,Majorana fermions at odd junctions in a wire network of ferromagnetic impurities,"We consider a wire network of ferromagnetic impurities on the surface of an
$s$-wave superconductor with strong Rashba spin-orbit interaction. Within the
topological phase, zero-energy Majorana fermions appear at wire end-points as
well as at junctions between an odd number of wire segments, while no
low-energy states are present at junctions between an even number of wire
segments, providing strong experimentally accessible signatures for Majorana
fermions. We also investigate the quasiparticle energy gap with respect to
varying the Rashba spin-orbit coupling and magnetic impurity strength.",1605.00696v1
2016-08-02,Ferromagnetic Damping/Anti-damping in a Periodic 2D Helical surface; A Non-Equilibrium Keldysh Green Function Approach,"In this paper, we investigate theoretically the spin-orbit torque as well as
the Gilbert damping for a two band model of a 2D helical surface state with a
Ferromagnetic (FM) exchange coupling. We decompose the density matrix into the
Fermi sea and Fermi surface components and obtain their contributions to the
electronic transport as well as the spin-orbit torque (SOT). Furthermore, we
obtain the expression for the Gilbert damping due to the surface state of a 3D
Topological Insulator (TI) and predicted its dependence on the direction of the
magnetization precession axis.",1608.00984v2
2019-09-25,Magnetic Quantum Phase Transitions in a Clean Dirac Metal,"We consider clean Dirac metals where the linear band crossing is caused by a
strong spin-orbit interaction, and study the quantum phase transitions from the
paramagnetic phase to various magnetic phases, including homogeneous
ferromagnets, ferrimagnets, canted ferromagnets, and magnetic nematics. We show
that in all of these cases the coupling of fermionic soft modes to the order
parameter generically renders the quantum phase transition first order, with
certain gapless Dirac systems providing a possible exception. These results are
surprising since a strong spin-orbit scattering suppresses the mechanism that
causes the first order transition in ordinary metals. The important role of
chirality in generating a new mechanism for a first-order transition is
stressed.",1909.11642v1
2019-08-03,Resonant inelastic x-ray scattering study of $α$-RuCl$_3$: a progress report,"Ru M$_3$-edge resonant inelastic x-ray scattering (RIXS) measurements of
RuCl$_3$ with 27 meV resolution reveals a spin-orbit exciton without noticeable
splitting. We extract values for the spin-orbit coupling constant
($\lambda=154\pm2$ meV) and trigonal distortion field energy
($\left|\Delta\right|<65$ meV) which support the $j_{\rm eff}=1/2$ nature of
RuCl$_3$. We demonstrate the feasibility of M-edge RIXS for $4d$ systems, which
allows ultra high-resolution RIXS of $4d$ systems until instrumentation for
L-edge RIXS improves.",1908.01190v1
2019-12-17,"Itinerant surfaces with spin-orbit couplings, correlations and external magnetic fields: Exact results","We analyze, in exact terms, multiband 2D itinerant correlated fermionic
systems with many-body spin-orbit interactions, and in-plane external magnetic
fields. Even if such systems with broad applicability in leading technologies
are non-integrable, we set up an exact solution procedure for them, which is
described in detail. Casting the Hamiltonian in positive semidefinite form, the
technique leads to the ground state and also characterizes the low lying
excitation spectrum.",1912.07888v1
2016-10-07,Ballistic Anisotropic Magnetoresistance in Core Shell Nanowires and Rolled-up Nanotubes,"In ferromagnetic nanostructures, the ballistic anisotropic magnetoresistance
(BAMR) is a change in the ballistic conductance with the direction of
magnetization due to spin-orbit interaction. Very recently, a directional
dependent ballistic conductance has been predicted to occur in a number of
newly synthesized nonmagnetic semiconducting nanostructures subject to
externally applied magnetic fields, without necessitating spin-orbit coupling.
In this article, we review past works on the prediction of this BAMR effect in
core-shell nanowires and rolled-up nanotubes. This is complemented by new
results we establish for the transport properties of tubular nanosystems
subject to external magnetic fields.",1610.02337v1
2019-06-19,On the pseudospin description of the electron Bloch bands,"We study the transformation properties of the electron states in crystals
with spin-orbit coupling, focusing primarily on the limitations of the
frequently used pseudospin-1/2 description of twofold degenerate Bloch bands.
Using the language of corepresentations of magnetic point groups, we construct
the Bloch bases across the Brillouin zone in a way which is consistent with all
symmetry requirements. This construction is applied to derive the effective
spin-orbit Hamiltonians in noncentrosymmetric crystals, known as the
generalized Rashba models, in both single-band and multiband cases.",1906.08106v1
2023-03-14,Magnetic and Structural Properties of 5d Osmate Double Perovskites Probed by Nuclear Magnetic Resonance,"The combined effect of electronic correlation and strong
spin-orbit-coupling(SOC) can give rise to a variety of exotic quantum phases.
Double perovskites provide a simple structure to study the spin-orbit-lattice
entangled states. In this thesis, focusing on the 5d osmate double perovskite
system, we conduct a combination of work including theoretical model
simulation, first-principle calculation, and nuclear magnetic resonance
experiments to understand the fundamental physical properties of this material
system.",2303.07573v1
2023-09-04,Spin-orbit coupling and Jahn-Teller effect in $T_d$ symmetry: an \textit{ab initio} study on the substitutional nickel defect in diamond,"We analyze the spin-orbit and Jahn-Teller interactions in $T_d$ symmetry that
are relevant for substitutional transition metal defects in semiconductors. We
apply our theory to the substitutional nickel defect in diamond and compute the
appropriate fine-leve structure and magneto-optical parameters by means of
hybrid density functional theory. Our calculations confirm the intepretations
of previous experimental findings that the 2.56-eV and 2.51-eV optical centres
are associated with this defect. Our analysis of the electronic structure
unravels possible mechanisms behind the observed optical transitions and the
optically detected magnetic resonance signal, too.",2310.08591v1
2021-05-12,Altermagnetism: spin-momentum locked phase protected by non-relativistic symmetries,"The search for novel magnetic quantum phases, phenomena and functional
materials has been guided by relativistic magnetic-symmetry groups in coupled
spin and real space from the dawn of the field in 1950s to the modern era of
topological matter. However, the magnetic groups cannot disentangle
non-relativistic phases and effects, such as the recently reported
unconventional spin physics in collinear antiferromagnets from the typically
weak relativistic spin-orbit coupling phenomena. Here we discover that more
general spin symmetries in decoupled spin and crystal space categorize
non-relativistic collinear magnetism in three phases: conventional ferromagnets
and antiferromagnets, and a third distinct phase combining zero net
magnetization with an alternating spin-momentum locking in energy bands, which
we dub ""altermagnetic"". For this third basic magnetic phase, which is omitted
by the relativistic magnetic groups, we develop a spin-group theory describing
six characteristic types of the altermagnetic spin-momentum locking. We
demonstrate an extraordinary spin-splitting mechanism in altermagnetic bands
originating from a local electric crystal field, which contrasts with the
conventional magnetic or relativistic splitting by global magnetization or
inversion asymmetry. Based on first-principles calculations, we identify
altermagnetic candidates ranging from insulators and metals to a parent crystal
of cuprate superconductor. Our results underpin emerging research of quantum
phases and spintronics in high-temperature magnets with light elements,
vanishing net magnetization, and strong spin-coherence.",2105.05820v2
2017-10-27,"Effect of Cu$^{2+}$ substitution in Spin-Orbit Coupled Sr$_2$Ir$_{1-x}$Cu$_x$O$_4$: Structure, magnetism and electronic properties","Sr$_2$IrO$_4$ is an extensively studied spin-orbit coupling induced insulator
with antiferromagnetic ground state. The delicate balance between competing
energy scales plays crucial role for its low temperature phase, and the route
of chemical substitution has often been used to tune these different energy
scales. Here, we report an evolution of structural, magnetic and electronic
properties in doped Sr$_2$Ir$_{1-x}$Cu$_x$O$_4$ ($x$ $\leq$ 0.2). The
substitution of Cu$^{2+}$ (3$d^9$) for Ir$^{4+}$ (5$d^5$) acts for electron
doping, though it tunes the related parameters such as, spin-orbit coupling,
electron correlation and Ir charge state. Moreover, both Ir$^{4+}$ and
Cu$^{2+}$ has single unpaired spin though it occupies different $d$-orbitals.
With Cu substitution, system retains its original structural symmetry but the
structural parameters show systematic changes. X-ray photoemission spectroscopy
measurements show Ir$^{4+}$ equivalently converts to Ir$^{5+}$ and a
significant enhancement in the density of states has been observed at the Fermi
level due to the contribution from the Cu 3$d$ orbitals, which supports the
observed decrease in the resistivity with Cu substitution. While the long-range
magnetic ordering is much weakened and the highest doped sample shows almost
paramagnetic-like behavior the overall system remains insulator. Analysis of
resistivity data shows mode of charge conduction in whole series follows
2-dimensional variable-range-hopping model but the range of validity varies
with temperature. Whole series of samples exhibit negative magnetoresistance at
low temperature which is considered to be a signature of weak localization
effect in spin-orbit coupled system, and its evolution with Cu appears to
follow the variation of resistivity with $x$.",1710.10281v1
2006-08-23,Spin-orbit interactions and spin-currents from an exact-exchange Kohn-Sham method,"An exact-exchange spin-current Kohn-Sham method to treat non-collinear spin,
magnetic effects, currents, spin-currents, and spin-orbit interactions
self-consistently on equal footing is introduced. Spin-orbit interactions are
shown to induce spin-currents. Results for silicon and germanium are presented.",0608505v1
2006-05-16,Divergence of the orbital nuclear magnetic relaxation rate in metals,"We analyze the nuclear magnetic relaxation rate $(1/T_1)_{orb}$ due to the
coupling of nuclear spin to the orbital moment of itinerant electrons in
metals. In the clean non--interacting case, contributions from large--distance
current fluctuations add up to cause a divergence of $(1/T_1)_{orb}$. When
impurity scattering is present, the elastic mean free time $\tau$ cuts off the
divergence, and the magnitude of the effect at low temperatures is controlled
by the parameter $\ln(\mu \tau)$, where $\mu$ is the chemical potential. The
spin--dipolar hyperfine coupling, while has the same spatial variation $1/r^3$
as the orbital hyperfine coupling, does not produce a divergence in the nuclear
magnetic relaxation rate.",0605420v4
2012-06-29,Magnetic and Superconducting Ordering at LaAlO3/SrTiO3 Interfaces,"We formulate a model for magnetic and superconducting ordering at
LaAlO3/SrTiO3 interfaces containing both localized magnetic moments and
itinerant electrons. Though these both originate in Ti 3d orbitals, the former
may be due to electrons more tightly-bound to the interface while the latter
are extended over several layers. Only the latter contribute significantly to
metallic conduction and superconductivity. In our model, the interplay between
the two types of electrons, which is argued to be ferromagnetic, combined with
strong spin-orbit coupling of the itinerant electrons, leads to magnetic
ordering. Furthermore, we propose a model for interfacial superconductivity,
consisting of random superconducting grains in the bulk STO driven, via
coupling to the interface conduction band, towards long-ranged or
quasi-long-ranged order. Most interestingly, the magnetic order and strong spin
orbit coupling can lead in this manner to unconventional interfacial
superconductivity, yielding a possible realization of Majorana physics.",1206.6959v1
2013-09-16,GW quasiparticle calculations with spin-orbit coupling for the light actinides,"We report on the importance of GW self-energy corrections for the electronic
structure of light actinides in the weak-to-intermediate coupling regime. Our
study is based on calculations of the band structure and total density of
states of Np, U, and Pu using a one-shot GW approximation that includes
spin-orbit coupling within a full potential LAPW framework. We also present RPA
screened effective Coulomb interactions for the f-electron orbitals for
different lattice constants, and show that there is an increased contribution
from electron-electron correlation in these systems for expanded lattices. We
find a significant amount of electronic correlation in these highly localized
electronic systems.",1309.4110v2
2016-05-09,Orbit-spin coupling and the circulation of the Martian atmosphere,"The physical origins of the observed interannual variability of weather and
climate on Mars are poorly understood. In this paper we introduce a
deterministic physical mechanism that may account for much of the variability
of the circulation of the Mars atmosphere on seasonal and longer timescales. We
derive a coupling expression linking orbital and rotational motions that
produces an acceleration field varying with position and with time on and
within a subject body. The spatially and temporally varying accelerations may
interfere constructively or destructively with large-scale flows of geophysical
fluids that are established and maintained by other means. The hypothesis
predicts cycles of intensification and relaxation of circulatory flows of
atmospheres on seasonal and longer timescales that are largely independent of
solar forcing. The predictions of the hypothesis may be tested through
numerical modeling. Examples from investigations of the atmospheric circulation
of Mars are provided to illustrate qualitative features and quantitative
aspects of the mechanism proposed. We briefly discuss the implications and
applicability of the orbit-spin coupling hypothesis for planets other than
Mars.",1605.02707v1
2018-08-21,Pseudo Jahn-Teller Effect and Magnetoelastic Coupling in Spin-Orbit Mott Insulators,"The consequences of the Jahn-Teller (JT) orbital-lattice coupling for
magnetism of pseudospin J_{eff}=1/2 and J_{eff}=0 compounds are addressed. In
the former case, represented by Sr_2IrO_4, this coupling generates, through the
so-called pseudo-JT effect, orthorhombic deformations of a crystal concomitant
with magnetic ordering. The orthorhombicity axis is tied to the magnetization
and rotates with it under magnetic field. The theory resolves a number of
puzzles in Sr_2IrO_4 such as the origin of in-plane magnetic anisotropy and
magnon gaps, metamagnetic transition, etc. In J_{eff}=0 systems, the pseudo-JT
effect leads to spin-nematic transition well above magnetic ordering, which may
explain the origin of `orbital order' in Ca_2RuO_4",1808.06919v2
2019-08-24,Magnetic order and anisotropic interactions induced by mixing between the $J=1/2$ and $3/2$ sectors in spin-orbit coupled honeycomb-lattice compounds,"Novel magnetic ordering on the honeycomb lattice due to emergent weak
anisotropic interactions generated by the mixing between the $J=1/2$ sector and
the magnetically inactive 3/2 sector is investigated in a three-orbital
interacting electron model in the absence of Hund's coupling. Self-consistent
determination of magnetic order yields anisotropic N\'{e}el and zigzag orders
for different parameter regimes, highlighting the effect of the emergent
single-ion anisotropy. Study of magnon excitations shows extremely small magnon
energy scale compared to the hopping energy scale, and enhancement of
anisotropy effects for smaller spin-orbit coupling. These results account for
several features of the honeycomb lattice compounds such as $\rm Na_2 Ir O_3$
and $\rm Ru Cl_3$, where the leading order anisotropic interactions within the
magnetically active $J=1/2$ sector are completely quenched due to the
edge-sharing octahedra.",1908.09130v1
2002-10-22,Shot noise for entangled and spin-polarized electrons,"We review our recent contributions on shot noise for entangled electrons and
spin-polarized currents in novel mesoscopic geometries. We first discuss some
of our recent proposals for electron entanglers involving a superconductor
coupled to a double dot in the Coulomb blockade regime, a superconductor
tunnel-coupled to Luttinger-liquid leads, and a triple-dot setup coupled to
Fermi leads. We calculate current and shot noise for spin-polarized currents
and entangled/unentangled electron pairs in a beam-splitter geometry with a
\textit{local} Rashba spin-orbit (s-o) interaction in the incoming leads. We
find \textit{continuous} bunching and antibunching behaviors for the
\textit{entangled} pairs -- triplet and singlet -- as a function of the Rashba
rotation angle. In addition, we find that unentangled triplets and the
entangled one exhibit distinct shot noise. Shot noise for spin-polarized
currents shows sizable oscillations as a function of the Rashba phase. This
happens only for electrons injected perpendicular to the Rashba rotation axis;
spin-polarized carriers along the Rashba axis are noiseless. We find an
additional spin rotation for electrons with energies near the crossing of the
bands where s-o induced interband coupling is relevant. This gives rise to an
additional modulation of the noise for both electron pairs and spin-polarized
currents. Finally, we briefly discuss shot noise for a double dot near the
Kondo regime.",0210498v1
2021-07-13,Quantum spins and hybridization in artificially-constructed chains of magnetic adatoms on a superconductor,"Magnetic adatom chains on surfaces constitute fascinating quantum spin
systems. Superconducting substrates suppress interactions with bulk electronic
excitations but couple the adatom spins to a chain of subgap Yu-Shiba-Rusinov
(YSR) quasiparticles. Using a scanning tunneling microscope, we investigate
such correlated spin-fermion systems by constructing Fe chains adatom by adatom
on superconducting NbSe$_2$. The adatoms couple entirely via the substrate,
retaining their quantum spin nature. In dimers, we observe that the deepest YSR
state undergoes a quantum phase transition due to Ruderman-Kittel-Kasuya-Yosida
interactions, a distinct signature of quantum spins. Chains exhibit coherent
hybridization and band formation of the YSR excitations, indicating
ferromagnetic coupling. Longer chains develop separate domains due to
coexisting charge-density-wave order of NbSe$_2$. Despite the
spin-orbit-coupled substrate, we find no signatures of Majoranas, possibly
because quantum spins reduce the parameter range for topological
superconductivity. We suggest that adatom chains are versatile systems for
investigating correlated-electron physics and its interplay with topological
superconductivity.",2107.06361v2
2022-06-28,Strong coupling between a photon and a hole spin in silicon,"Spins in semiconductor quantum dots constitute a promising platform for
scalable quantum information processing. Coupling them strongly to the photonic
modes of superconducting microwave resonators would enable fast non-demolition
readout and long-range, on-chip connectivity, well beyond nearest-neighbor
quantum interactions. Here we demonstrate strong coupling between a microwave
photon in a superconducting resonator and a hole spin in a silicon-based double
quantum dot issued from a foundry-compatible MOS fabrication process. By
leveraging the strong spin-orbit interaction intrinsically present in the
valence band of silicon, we achieve a spin-photon coupling rate as high as
330~MHz largely exceeding the combined spin-photon decoherence rate. This
result, together with the recently demonstrated long coherence of hole spins in
silicon, opens a new realistic pathway to the development of circuit quantum
electrodynamics with spins in semiconductor quantum dots.",2206.14082v2
2022-07-06,Anisotropic exchange coupling and ground state phase diagram of Kitaev compound YbOCl,"Rare-earth chalcohalide REChX (RE = rare earth; Ch = O, S, Se, Te; X = F, Cl,
Br, I) is a newly reported family of Kitaev spin liquid candidates. The family
offers a platform where a strong spin-orbit coupling meets a van der Waals
layered and undistorted honeycomb spin lattice, which outputs highly
anisotropic exchange couplings required by the Kitaev model. YbOCl is the first
single crystal of the family we grew, with a size up to ~ 15 mm. We have
performed magnetization and high magnetic field electron spin resonance
measurements from 2 to 300 K. We develop the mean-field scenario for the
anisotropic spin system, with which we are able to well describe the
experiments and reliably determine the fundamental parameters. The
self-consistent simulations give the anisotropic spin-exchange interactions of
$J_{\pm}$ (~ -0.3 K) and $J_{zz}$ (~ 1.6 K), and g factors of $g_{ab}$ (~ 3.4)
and $g_{c}$ (~ 2.9). Based on the spin-exchange interactions, we employ the
exact diagonalization method to work out the ground state phase diagram of
YbOCl in terms of the off-diagonal exchange couplings. The phase diagram
hosting rich magnetic phases including the spin-disordered one, sheds light on
the novel magnetic properties of the family, particularly the Kitaev physics.",2207.02383v1
2024-01-30,Partial tidal disruptions of spinning eccentric white dwarfs by spinning intermediate mass black holes,"Intermediate mass black holes (IMBHs, $\sim 10^2-10^5M_{\odot}$) are often
dubbed as the missing link between stellar mass ($\lesssim 10^2M_{\odot}$) and
super-massive ($\gtrsim 10^{5-6} M_{\odot}$) black holes. Observational
signatures of these can result from tidal disruption of white dwarfs (WDs),
which would otherwise be captured as a whole by super-massive black holes.
Recent observations indicate that IMBHs might be rapidly spinning, while it is
also known that isolated white dwarfs might have large spins, with spin periods
of the order of minutes. Here, we aim to understand the effects of ``coupling''
between black hole and stellar spin, focussing on the tidal disruption of
spinning WDs in the background of spinning IMBHs. Using smoothed particle
hydrodynamics, we perform a suite of numerical simulations of partial tidal
disruptions, where spinning WDs are in eccentric orbits about spinning IMBHs.
We take a hybrid approach, where we integrate the Kerr geodesic equations while
being in a regime where we can treat the internal stellar fluid dynamics in the
Newtonian limit. We find substantial effects of the ``coupling'' between the
black hole spin and the spin of the white dwarf, although the pericenter
distance of the white dwarf is taken to be large enough so that the Newtonian
limit of its fluid dynamics is a robust approximation. In particular, the core
mass, the bound tail mass, and the mass difference between the two tidal tails
strongly depend on such ``coupled'' spin effects. However, the late time
fallback rate of the debris behaves similar to the non-spinning cases. We also
compute gravitational wave amplitudes and find that while the black hole spin
influences the same, there is no evidence of influence of stellar spin on such
amplitudes in our regime of interest.",2401.17031v1
1998-08-12,"Effects of Electron Correlation, Orbital Degeneracy and Jahn-Teller Coupling in Perovskite Manganites","Roles of Coulomb interaction, orbital degeneracy and Jahn-Teller coupling in
double-exchange models are examined for Mn perovskite oxides. We study the
undoped Mott insulator as well as metal-insulator transitions by hole doping,
and especially strong incoherence of ferromagnetic metal. We derive models
where all the spins are fully polarized in two-dimensional planes as in the
experimental indications, and investigate their ground-state properties by
quantum Monte Carlo method. At half filling where the number of $e_{g}$
electron is one per site on average, the Coulomb interaction opens a Mott gap
and induces a staggered orbital ordering. The opening of the Mott gap is,
however, substantially slower than the mean-field results if the Jahn-Teller
coupling is absent. The synergy between the strong correlation and the
Jahn-Teller coupling largely enhances the Mott gap amplitude and reproduces
realistic amplitudes and stabilization energy of the Jahn-Teller distortion.
Upon doping, the orbital ordering stabilized by the Coulomb interaction is
destroyed immediately. Toward the metal-insulator transition, the short-ranged
orbital correlation is critically enhanced in metals, which should be related
to strong incoherence of charge dynamics observed in experiments. Our model,
moreover, exhibits a uniform ordering of $d_{x^{2}-y^{2}}$ orbital in a wide
region of doping in agreement with experimental indications.",9808124v2
2022-11-14,Orbital Fulde-Ferrell pairing state in moiré Ising superconductors,"In this work, we study superconducting moir\'e homobilayer transition metal
dichalcogenides where the Ising spin-orbit coupling (SOC) is much larger than
the moir\'e bandwidth. We call such noncentrosymmetric superconductors, moir\'e
Ising superconductors. Due to the large Ising SOC, the depairing effect caused
by the Zeeman field is negligible and the in-plane upper critical field
($B_{c2}$) is determined by the orbital effects. This allows us to study the
effect of large orbital fields. Interestingly, when the applied in-plane field
is larger than the conventional orbital $B_{c2}$, a finite-momentum pairing
phase would appear which we call the orbital Fulde-Ferrell (FF) state. In this
state, the Cooper pairs acquire a net momentum of $2q_B$ where $2q_B=eBd$ is
the momentum shift caused by the magnetic field $B$ and $d$ denotes the layer
separation. This orbital field-driven FF state is different from the
conventional FF state driven by Zeeman effects in Rashba superconductors.
Remarkably, we predict that the FF pairing would result in a giant
superconducting diode effect under electric gating when layer asymmetry is
induced. An upturn of the $B_{c2}$ as the temperature is lowered, coupled with
the giant superconducting diode effect, would allow the detection of the
orbital FF state.",2211.07406v3
2022-11-14,Orbital Fulde-Ferrell-Larkin-Ovchinnikov state in an Ising superconductor,"The conventional Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state relies on the
Zeeman effect of an external magnetic field to break time-reversal symmetry,
forming a state of finite-momentum Cooper pairing. In superconductors with
broken inversion symmetries, the Rashba or Ising-type spin-orbit coupling (SOC)
can interact with either the Zeeman or the orbital effect of magnetic fields,
extending the range of possible FFLO states, though evidence for these more
exotic forms of FFLO pairing has been lacking. Here we report the discovery of
an unconventional FFLO state induced by coupling the Ising SOC and the orbital
effect in multilayer 2H-NbSe2. Transport measurements show that the
translational and rotational symmetries are broken in the orbital FFLO state,
providing the hallmark signatures of finite momentum cooper pairings. We
establish the entire orbital FFLO phase diagram, consisting of normal metal,
uniform Ising superconducting phase, and a six-fold orbital FFLO state. This
study highlights an alternative route to finite-momentum superconductivity and
provides a universal mechanism to prepare orbital FFLO states in similar
materials with broken inversion symmetries.",2211.07745v2
2003-11-05,Weak antilocalization in a strained InGaAs/InP quantum well structure,"Weak antilocalization (WAL) effect due to the interference corrections to the
conductivity has been studied experimentally in a strained InGaAs/InP quantum
well structure. From measurements in tilted magnetic filed, it was shown that
both weak localization and WAL features depend only on the normal component of
the magnetic field for tilt angles less than 84 degrees. Weak antilocalization
effect showed non-monotonous dependence on the gate voltage which could not be
explained by either Rashba or Dresselhouse mechanisms of the spin-orbit
coupling. To describe magnetic field dependence of the conductivity, it was
necessary to assume that spin-orbit scattering time depends on the external
magnetic field which quenches the spin precession around effective, spin-orbit
related, magnetic fields.",0311116v1
2004-07-01,Effect of an InP/In$_{0.53}$Ga$_{0.47}$As Interface on Spin-orbit Interaction in In$_{0.52}$Al$_{0.48}$As/In$_{0.53}$Ga$_{0.47}$As Heterostructures,"We report the effect of the insertion of an InP/In$_{0.53}$Ga$_{47}$As
Interface on Rashba spin-orbit interaction in
In$_{0.52}$Al$_{0.48}$As/In$_{0.53}$Ga$_{0.47}$As quantum wells. A small spin
split-off energy in InP produces a very intriguing band lineup in the valence
bands in this system. With or without this InP layer above the
In$_{0.53}$Ga$_{47}$As well, the overall values of the spin-orbit coupling
constant $\alpha$ turned out to be enhanced or diminished for samples with the
front- or back-doping position, respectively. These experimental results, using
weak antilocalization analysis, are compared with the results of the
$\mathbf{k\cdot p}$ theory. The actual conditions of the interfaces and
materials should account for the quantitative difference in magnitude between
the measurements and calculations.",0407020v3
2005-04-19,Nature of magnetism in Ca$_3$Co$_2$O$_6$,"We find using LSDA+U band structure calculations that the novel
one-dimensional cobaltate Ca$_3$Co$_2$O$_6$ is not a ferromagnetic half-metal
but a Mott insulator. Both the octahedral and the trigonal Co ions are formally
trivalent, with the octahedral being in the low-spin and the trigonal in the
high-spin state. The inclusion of the spin-orbit coupling leads to the
occupation of the minority-spin $d_{2}$ orbital for the unusually coordinated
trigonal Co, producing a giant orbital moment (1.57 $\mu_{B}$). It also results
in an anomalously large magnetocrystalline anisotropy (of order 70 meV),
elucidating why the magnetism is highly Ising-like. The role of the oxygen
holes, carrying an induced magnetic moment of 0.13 $\mu_{B}$ per oxygen, for
the exchange interactions is discussed.",0504490v2
2004-03-16,Semiclassical propagation of coherent states with spin-orbit interaction,"We study semiclassical approximations to the time evolution of coherent
states for general spin-orbit coupling problems in two different semiclassical
scenarios: The limit \hbar to zero is first taken with fixed spin quantum
number s and then with \hbar*s held constant. In these two cases different
classical spin-orbit dynamics emerge. We prove that a coherent state propagated
with a suitable classical dynamics approximates the quantum time evolution up
to an error of size \sqrt{\hbar} and identify an Ehrenfest time scale.
Subsequently an improvement of the semiclassical error to an arbitray order
\hbar^{N/2} is achieved by a suitable deformation of the state that is
propagated classically.",0403030v1
2012-07-19,Finger-gate manipulated quantum transport in a semiconductor narrow constriction with spin-orbit interactions and Zeeman effect,"The authors investigate quantum transport in a narrow constriction fabricated
by narrow band gap semiconductor materials with spin-orbit (SO) couplings. We
consider the Rashba-Dresselhaus (RD) spin-orbit interactions (SOIs) and the
Zeeman effect induced by an in-plane magnetic field along the transport
direction. The interplay of the RD-SOI and the Zeeman effect may induce a
SOI-Zeeman gap and influence the transport properties. We demonstrate that an
attractive scattering potential may induce electron-like quasi-bound-state
feature and manifest the RD-SOI-Zeeman induced Fano line-shape in conductance.
Furthermore, a repulsive scattering potential may induce hole-like
quasi-bound-state feature on the subband top of the lower spin branch.",1207.4558v2
2013-01-02,Spin-orbital locked magnetic excitations in a half-metallic double perovskite Ba2FeReO6,"We present a powder inelastic neutron scattering study of magnetic
excitations in Ba$_2$FeReO$_6$, a member of the double perovskite family of
materials which exhibit half-metallic behavior and high Curie temperatures. We
find clear evidence of two well-defined dispersing magnetic modes in its low
temperature ferrimagnetic state. We develop a local moment model, which
incorporates the interaction of Fe spins with spin-orbit locked magnetic
moments on Re, and show that this captures our experimental observations. Our
study further opens up double perovskites as model systems to explore the
interplay of strong correlations and spin-orbit coupling in 5d transition metal
oxides.",1301.0327v1
2015-01-22,Anatomy of Dzyaloshinskii-Moriya Interaction at Co/Pt Interfaces,"The Dzyaloshinskii-Moriya Interaction (DMI) between spins is induced by
spin-orbit coupling in magnetic materials lacking inversion symmetry. DMI is
recognized to play a crucial role at the interface between ferromagnetic (FM)
and heavy nonmagnetic (NM) metals to create topological textures called
magnetic skyrmions which are very attractive for ultra-dense information
storage and spintronic devices. DMI also plays an essential role for fast
domain wall (DW) dynamics driven by spin-orbit torques. Here, we present first
principles calculations which clarify the main features and microscopic
mechanisms of DMI in Co/Pt bilayers. DMI is found to be predominantly located
at the interfacial Co layer, originating from spin-orbit energy provided by the
adjacent NM layer. Furthermore, no direct correlation is found between DMI and
proximity induced magnetism in Pt. These results clarify underlying mechanisms
of DMI at FM/NM bilayers and should help optimizing material combinations for
skyrmion- and DW-based storage and memory devices.",1501.05511v1
2016-01-16,Spin-orbit torque in Cr/CoFeAl/MgO and Ru/CoFeAl/MgO epitaxial magnetic heterostructures,"We study the spin-orbit torque (SOT) effective fields in Cr/CoFeAl/MgO and
Ru/CoFeAl/MgO magnetic heterostructures using the adiabatic harmonic Hall
measurement. High-quality perpendicular-magnetic-anisotropy CoFeAl layers were
grown on Cr and Ru layers. The magnitudes of the SOT effective fields were
found to significantly depend on the underlayer material (Cr or Ru) as well as
their thicknesses. The damping-like longitudinal effective field ({\Delta}H_L)
increases with increasing underlayer thickness for all heterostructures. In
contrast, the field-like transverse effective field ({\Delta}H_T) increases
with increasing Ru thickness while it is almost constant or slightly decreases
with increasing Cr thickness. The sign of {\Delta}H_L observed in the
Cr-underlayer devices is opposite from that in the Ru-underlayer devices while
{\Delta}H_T shows the same sign with a small magnitude. The opposite directions
of {\Delta}HL indicate that the signs of spin Hall angle in Cr and Ru are
opposite, which are in good agreement with theoretical predictions. These
results show sizable contribution from SOT even for elements with small spin
orbit coupling such as 3d Cr and 4d Ru.",1601.04164v1
2016-06-03,Non-collinear spin-orbit magnetic fields in a carbon nanotube double quantum dot,"We demonstrate experimentally that non-collinear intrinsic spin-orbit
magnetic fields can be realized in a curved carbon nanotube two-segment device.
Each segment, analyzed in the quantum dot regime, shows near four-fold
degenerate shell structure allowing for identification of the spin-orbit
coupling and the angle between the two segments. Furthermore, we determine the
four unique spin directions of the quantum states for specific shells and
magnetic fields. This class of quantum dot systems is particularly interesting
when combined with induced superconducting correlations as it may facilitate
unconventional superconductivity and detection of Cooper pair entanglement. Our
device comprises the necessary elements.",1606.01065v1
2018-02-15,Tunneling magnetoresistance enhancement by symmetrization in spin-orbit torque magnetic tunnel junction,"Heavy metals with strong spin-orbit coupling (SOC) have been employed to
generate spin current to control the magnetization dynamics by spin-orbit
torque (SOT). Magnetic tunnel junction based on SOT (SOT-MTJ) is a promising
application with efficient writing operation. Unfortunately, SOT-MTJ faces the
low tunneling magnetoresistance (TMR) problem. In this work, we present an ab
initio calculation on the TMR in SOT-MTJ. It is demonstrated that TMR would be
enhanced by SOT-MTJ symmetry structure. The symmetrization induces interfacial
resonant states (IRSs). When IRSs match identical resonances at the opposite
barrier interface, resonant tunneling occurs in SOT-MTJ, which significantly
contributes to the conductance in parallel configuration and improves TMR. We
demonstrate the occurrence of resonant tunneling by transmission spectra,
density of scattering states and differential density of states. We also point
out that the thickness of heavy metal has limited influence on TMR. This work
would benefit the TMR optimization in SOT-MTJ, as well as the SOT spintronics
device.",1802.05787v2
2018-11-12,Site selective spin and orbital excitations in Fe3O4,"$Fe_3O_4$ is a mixed-valence strongly correlated transition metal oxide which
displays the intriguing metal to insulator Verwey transition. Here we
investigate the electronic and magnetic structure of $Fe_3O_4$ by a unique
combination of high-resolution Fe 2p3d resonant inelastic scattering magnetic
circular (RIXS-MCD) and magnetic linear (RIXS-MLD) dichroism. We show that by
coupling the site selectivity of RIXS with the magnetic selectivity imposed by
the incident polarization handedness, we can unambiguously identify spin-flip
excitations and quantify the exchange interaction of the different sublattices.
Furthermore, our RIXS-MLD measurements show spin-orbital excitations that
exhibit strong polarization and magnetic field dependence. Guided by
theoretical simulations, we reveal that the angular dependence arises from a
strong interplay between trigonal crystal-field, magnetic exchange and
spin-orbit interaction at the nominal $Fe^{2+}$ sites. Our results highlight
the capabilities of RIXS magnetic dichroism studies to investigate the ground
state of complex systems where in-equivalent sites and bonds are simultaneously
present.",1811.04836v1
2012-05-21,Designer quantum spin Hall phase transition in molecular graphene,"Graphene was the first material predicted to be a time-reversal-invariant
topological insulator; however, the insulating gap is immeasurably small owing
to the weakness of spin-orbit interactions in graphene. A recent experiment [1]
demonstrated that designer honeycomb lattices with graphene-like ""Dirac"" band
structures can be engineered by depositing a regular array of carbon monoxide
atoms on a metallic substrate. Here, we argue that by growing such designer
lattices on metals or semiconductors with strong spin-orbit interactions, one
can realize an analog of graphene with strong intrinsic spin-orbit coupling,
and hence a highly controllable two-dimensional topological insulator. We
estimate the range of substrate parameters for which the topological phase is
achievable, and consider the experimental feasibility of some candidate
substrates.",1205.4728v1
1999-05-05,Weak localisation in AlGaAs/GaAs p-type quantum wells,"We have for the first time experimentally investigated the weak localisation
magnetoresistance in a AlGaAs/GaAs p-type quantum well. The peculiarity of such
systems is that spin-orbit interaction is strong. On the theoretical side it is
not possible to treat the spin-orbit interaction as a perturbation. This is in
contrast to all prior investigations of weak localisation. In this letter we
compare the experimental results with a newly developed diffusion theory, which
explicitly describes the weak localisation regime when the spin-orbit coupling
is strong. The spin relaxation rates calculated from the fitting parameters was
found to agree with theoretical expectations. Furthermore the fitting
parameters indicate an enhanced phase breaking rate compared to theoretical
predictions.",9905057v2
1999-03-22,The Dirac Oscillator. A relativistic version of the Jaynes--Cummings model,"The dynamics of wave packets in a relativistic Dirac oscillator is compared
to that of the Jaynes-Cummings model. The strong spin-orbit coupling of the
Dirac oscillator produces the entanglement of the spin with the orbital motion
similar to what is observed in the model of quantum optics. The collapses and
revivals of the spin which result extend to a relativistic theory our previous
findings on nonrelativistic oscillator where they were known under the name of
`spin-orbit pendulum'. There are important relativistic effects (lack of
periodicity, zitterbewegung, negative energy states). Many of them disappear
after a Foldy-Wouthuysen transformation.",9903073v1
2008-01-11,Spin-orbit effects on two-electron states in nanowhisker double quantum dots,"We investigate theoretically the combined effects of the electron-electron
and the Rashba spin-orbit interactions on two electrons confined in
quasi-one-dimensional AlInSb-based double quantum dots. We calculate the
two-electron wave functions and explore the interplay between these two
interactions on the energy levels and the spin of the states. The energy
spectrum as a function of an applied magnetic field shows crossings and
anticrossings between triplet and singlet states, associated with level mixing
induced by the spin-orbit coupling. We find that the fields at which these
crossings occur can be naturally controlled by the interdot barrier width,
which controls the exchange integral in the structure.",0801.1808v1
2008-02-19,Classical dimers and dimerized superstructure in orbitally degenerate honeycomb antiferromagnet,"We discuss the ground state of the spin-orbital model for spin-one ions with
partially filled $t_{2g}$ levels on a honeycomb lattice. We find that the
orbital degrees of freedom induce a spontaneous dimerization of spins and drive
them into nonmagnetic manifold spanned by hard-core dimer (spin-singlet)
coverings of the lattice. The cooperative ``dimer Jahn-Teller'' effect is
introduced through a magnetoelastic coupling and is shown to lift the
orientational degeneracy of dimers leading to a peculiar valence bond crystal
pattern. The present theory provides a theoretical explanation of nonmagnetic
dimerized superstructure experimentally seen in Li$_2$RuO$_3$ compound at low
temperatures.",0802.2692v2
2008-10-14,Quantum information transfer from spin to orbital angular momentum of photons,"The optical ""spin-orbit"" coupling occurring in a suitably patterned
nonuniform birefringent plate known as `q-plate' allows entangling the
polarization of a single photon with its orbital angular momentum (OAM). This
process, in turn, can be exploited for building a bidirectional ""spin-OAM
interface"", capable of transposing the quantum information from the spin to the
OAM degree of freedom of photons and \textit{vice versa}. Here, we
experimentally demonstrate this process by single-photon quantum tomographic
analysis. Moreover, we show that two-photon quantum correlations such as those
resulting from coalescence interference can be successfully transferred into
the OAM degree of freedom.",0810.2417v2
2009-11-25,Spin-Orbit Qubits of Rare-Earth-Metal Ions in Axially Symmetric Crystal Fields,"Contrary to the well known spin qubits, rare-earth qubits are characterized
by a strong influence of crystal field due to large spin-orbit coupling. At low
temperature and in the presence of resonance microwaves, it is the magnetic
moment of the crystal-field ground-state which nutates (for several $\mu$s) and
the Rabi frequency $\Omega_R$ is anisotropic. Here, we present a study of the
variations of $\Omega_R(\vec{H}_{0})$ with the magnitude and direction of the
static magnetic field $\vec{H_{0}}$ for the odd $^{167}$Er isotope in a single
crystal CaWO$_4$:Er$^{3+}$. The hyperfine interactions split the
$\Omega_R(\vec{H}_{0})$ curve into eight different curves which are fitted
numerically and described analytically. These ""spin-orbit qubits"" should allow
detailed studies of decoherence mechanisms which become relevant at high
temperature and open new ways for qubit addressing using properly oriented
magnetic fields.",0911.4818v1
2011-07-25,Strong Spin-Orbit Interaction and Helical Hole States in Ge/Si Nanowires,"We study theoretically the low-energy hole states of Ge/Si core/shell
nanowires. The low-energy valence band is quasidegenerate, formed by two
doublets of different orbital angular momenta, and can be controlled via the
relative shell thickness and via external fields. We find that direct (dipolar)
coupling to a moderate electric field leads to an unusually large spin-orbit
interaction of Rashba type on the order of meV which gives rise to pronounced
helical states enabling electrical spin control. The system allows for quantum
dots and spin qubits with energy levels that can vary from nearly zero to
several meV, depending on the relative shell thickness.",1107.4870v2
2013-01-13,Theory of t2g electron-gas Rashba interactions,"The spin-degeneracy of Bloch bands in a crystal can be lifted when spin-orbit
(SO) coupling is present and inversion symmetry is absent. In two-dimensional
electron systems (2DES) spin-degeneracy is lifted by Rashba interaction terms -
symmetry invariants that are scalar products of spin and orbital axial vectors.
Rashba interactions are symmetry allowed whenever a 2DES is not invariant under
reflections through the plane it occupies. In this paper, we use a
tight-binding model informed by ab initio electronic structure calculations to
develop a theory of Rashba splitting in the t2g bands of the two- dimensional
electron systems formed at cubic perovskite crystal surfaces and interfaces. We
find that Rashba splitting in these systems is due to atomic-like on-site SO
interactions combined with processes in which t2g electrons change orbital
character when they hop between metal sites. These processes are absent in a
cubic environment and are due primarily to polar lattice distortions which
alter the metal-oxygen-metal bond angle.",1301.2784v1
2015-05-01,Density functional versus spin-density functional and the choice of correlated subspace in multi-variable effective action theories of electronic structure,"Modern extensions of density functional theory such as the density functional
theory plus U and the density functional theory plus dynamical mean-field
theory require choices, including selection of variable (charge vs spin
density) for the density functional and specification of the correlated
subspace. This paper examines these issues in the context of the ""plus U""
extensions of density functional theory, in which additional correlations on
specified correlated orbitals are treated using a Hartree-Fock approximation.
Differences between using charge-only or spin-density-dependent
exchange-correlation functionals and between Wannier and projector-based
definitions of the correlated orbitals are considered on the formal level and
in the context of the structural energetics of the rare earth nickelates. It is
demonstrated that theories based on spin-dependent exchange-correlation
functionals can lead to large and in some cases unphysical effective on-site
exchange couplings. Wannier and projector-based definitions of the correlated
orbitals lead to similar behavior near ambient pressure, but substantial
differences are observed at large pressures. Implications for other beyond
density functional methods such as the combination of density functional and
dynamical mean field theory are discussed.",1505.00227v1
2015-10-01,"Trivial and inverted Dirac bands, and emergence of quantum spin Hall states in graphene on transition-metal dichalcogenides","Proximity orbital and spin-orbital effects of graphene on monolayer
transition-metal dichalcogenides (TMDCs) are investigated from
first-principles. The Dirac band structure of graphene is found to lie within
the semiconducting gap of TMDCs for sulfides and selenides, while it merges
with the valence band for tellurides. In the former case the proximity-induced
staggered potential gaps and spin-orbit couplings (all on the meV scale) of the
Dirac electrons are established by fitting to a phenomenological effective
Hamiltonian. While graphene on MoS$_2$, MoSe$_2$, and WS$_2$ has a
topologically trivial band structure, graphene on WSe$_2$ exhibits inverted
bands. Using a realistic tight-binding model we find topologically protected
helical edge states for graphene zigzag nanoribbons on WSe$_2$, demonstrating
the quantum spin Hall effect. This model also features ""half-topological
states"", which are protected against time-reversal disorder on one edge only.",1510.00166v1
2016-04-26,Intrinsic spin orbit torque in a single domain nanomagnet,"We present theoretical studies of the intrinsic spin orbit torque (SOT) in a
single domain ferromagnetic layer with Rashba spin-orbit coupling (SOC) using
the non-equilibrium Green's function formalism for a model Hamiltonian. We find
that, to the first order in SOC, the intrinsic SOT has only the field-like
torque symmetry and can be interpreted as the longitudinal spin current induced
by the charge current and Rashba field. We analyze the results in terms of the
material related parameters of the electronic structure, such as band filling,
band width, exchange splitting, as well as the Rashba SOC strength. On the
basis of these numerical and analytical results, we discuss the magnitude and
sign of SOT. Our results show that the different sign of SOT in identical
ferromagnetic layers with different supporting layers, e.g. Co/Pt and Co/Ta,
could be attributed to electrostatic doping of the ferromagnetic layer by the
support.",1604.07885v2
2020-07-13,Spin-orbit interaction of light in three-dimensional microcavities,"We investigate the spin-orbit coupling of light in three-dimensional
cylindrical and tube-like whispering gallery mode resonators. We show that its
origin is the transverse confinement of light in the resonator walls, even in
the absence of inhomogeneities or anisotropies. The spin-orbit interaction
results in elliptical far-field polarization (spin) states and causes spatial
separation of polarization handedness in the far field. The ellipticity and
spatial separation are enhanced for whispering gallery modes with higher
excitation numbers along the resonator height. We analyze the asymmetry of the
ellipticity and the tilt of the polarization orientation in the far field of
cone-like microcavities. Furthermore, we find a direct relationship between the
tilt of the polarization orientation in the far field and the local inclination
of the resonator wall. Our findings are based on FDTD-simulations and are
supported by three-dimensional diffraction theory.",2007.06721v1
2020-04-22,Effect of phonons on the electron spin resonance absorption spectrum,"The unavoidable presence of vibrations in solid-state devices can drastically
modify the expected electron spin resonance (ESR) absorption spectrum in
magnetically active systems. In this work, we model the effect of phonons and
temperature on the ESR signal in molecular systems with strong $E \otimes e$
Jahn-Teller (JT) effect and an electronic spin-$1/2$. Our microscopic model
considers the linear JT interaction with a continuum of phonon modes, the
spin-orbit coupling, the Zeeman effect, and the response of the system under a
weak oscillating magnetic field. We derive a Lindblad master equation for the
orbital and spin degrees of freedom, where one- and two-phonon processes are
considered for the phonon-induced relaxation, and the thermal dependence of Ham
reduction factors is calculated. We find that the suppression of ESR signals is
due to phonon broadening but not based on the common assumption of orbital
quenching. Our results can be applied to explain the experimentally observed
absence of the ESR signal in color centers in diamond, such as the neutral
nitrogen-vacancy and negatively charged silicon-vacancy color centers in
diamond.",2004.10355v2
2020-12-15,Possible Spin-Density Wave on Fermi Arc of Edge State in Single-Component Molecular Conductors [Pt(dmdt)$_2$] and [Ni(dmdt)$_2$],"We construct three-orbital tight-binding models describing single-component
molecular conductors [Pt(dmdt)$_2$] and [Ni(dmdt)$_2$] using first-principles
calculations. We show that [Ni(dmdt)$_2$] is a Dirac nodal line system with
highly one-dimensional edge states at the (001) edge, similar to
[Pt(dmdt)$_2$], as demonstrated in prior studies. To investigate possible edge
magnetism, we calculate longitudinal and transverse spin susceptibilities using
real-space-dependent random-phase approximation (RPA) in three-orbital Hubbard
models in the presence of spin--orbit coupling. We find that the edge
spin-density wave (SDW) is induced by the Coulomb repulsion and incommensurate
nestings of the Fermi arcs. We also find that the magnetic structure of the
edge SDW can be changed via extremely small carrier doping, which is
controllable in molecular conductors.",2012.08132v3
2017-05-26,Photoemission Circular Dichroism and Spin Polarization of the Topological Surface States in Ultrathin Bi2Te3 Films,"Circular dichroism (CD) observed by photoemission, being sensitive to the
orbital and spin angular momenta of the electronic states, is a powerful probe
of the nontrivial surface states of topological insulators, but the
experimental results thus far have eluded a comprehensive description. We
report a study of Bi2Te3 films with thicknesses ranging from one quintuple
layer (two-dimensional limit) to twelve layers (bulk limit) over a wide range
of incident photon energy. The data show complex variations in magnitude and
sign reversals, which are nevertheless well described by a theoretical
calculation including all three photoemission mechanisms: dipole transition,
surface photoemission, and spin-orbit coupling. The results establish the
nontrivial connection between the spin-orbit texture and CD.",1705.09720v1
2019-12-11,Chirality-induced linear response properties in non-coplanar Mn$_3$Ge,"Taking the non-collinear antiferromagnetic hexagonal Heusler compound
Mn$_3$Ge as a reference system, the contributions to linear response phenomena
arising solely from the chiral coplanar and non-coplanar spin configurations
are investigated. Orbital moments, X-ray absorption, anomalous and spin Hall
effects, as well as corresponding spin-orbit torques and Edelstein
polarizations are studied depending on a continuous variation of the polar
angle relative to the Kagome planes of corner-sharing triangles between the
non-collinear antiferromagnetic and the ferromagnetic limits. By scaling the
speed of light from the relativistic Dirac case to the non-relativistic limit
the chirality-induced or topological contributions can be identified by
suppressing the spin-orbit coupling.",1912.05211v1
2020-10-03,Observation of quantum interference conductance fluctuations in metal rings with strong spin-orbit coupling,"We investigated the magnetotransport properties of mesoscopic platinum
nanostructures (wires and rings) with sub-100 nm lateral dimensions at very low
temperatures. Despite the strong spin-orbit interaction in platinum,
oscillations of the conductance as a function of the external magnetic field
due to quantum interference effects was found to appear. The oscillation was
decomposed into Aharonov-Bohm periodic oscillations and aperiodic fluctuations
of the conductance due to a magnetic flux piercing the loop of the ring and the
metal wires forming the nanostructures, respectively. We also investigated the
magnetotransport under different bias currents to explore the interplay between
electron phase coherence and spin accumulation effects in strong spin-orbit
conductors.",2010.01300v1
2016-03-17,Dephasing measurements in InGaAs/AlInAs heterostructures: manifestations of spin-orbit and Zeeman interactions,"We have measured weak antilocalization effects, universal conductance
fluctuations, and Aharonov-Bohm oscillations in the two-dimensional electron
gas formed in InGaAs/AlInAs heterostructures. This system possesses strong
spin-orbit coupling and a high Land\'{e} factor. Phase-coherence lengths of
2$-$4 $\mu$m at 1.5$-$4.2 K are extracted from the magnetoconductance
measurements. The analysis of the coherence-sensitive data reveals that the
temperature dependence of the decoherence rate complies with the dephasing
mechanism originating from electron-electron interactions in all three
experiments. Distinct beating patterns superimposed on the Aharonov-Bohm
oscillations are observed over a wide range of magnetic fields, up to 0.7 Tesla
at the relatively high temperature of 1.5 K. The possibility that these beats
are due to the interplay between the Aharonov-Bohm phase and the Berry one,
different for electrons of opposite spins in the presence of strong spin-orbit
and Zeeman interactions in ring geometries, is carefully investigated. It
appears that our data are not explained by this mechanism; rather, a few
geometrically-different electronic paths within the ring's width can account
for the oscillations' modulations.",1603.05640v2
2019-06-04,Observation of spin-orbit excitations and Hund's multiplets in Ca$_2$RuO$_4$,"We use Ru $L_3$-edge (2838.5 eV) resonant inelastic x-ray scattering (RIXS)
to quantify the electronic structure of Ca$_2$RuO$_4$, a layered $4d$-electron
compound that exhibits a correlation-driven metal-insulator transition and
unconventional antiferromagnetism. We observe a series of Ru intra-ionic
transitions whose energies and intensities are well described by model
calculations. In particular, we find a $\rm{J}=0\rightarrow 2$ spin-orbit
excitation at 320 meV, as well as Hund's-rule driven $\rm{S}=1\rightarrow 0$
spin-state transitions at 750 and 1000 meV. The energy of these three features
uniquely determines the spin-orbit coupling, tetragonal crystal-field energy,
and Hund's rule interaction. The parameters inferred from the RIXS spectra are
in excellent agreement with the picture of excitonic magnetism that has been
devised to explain the collective modes of the antiferromagnetic state.
$L_3$-edge RIXS of Ru compounds and other $4d$-electron materials thus enables
direct measurements of interactions parameters that are essential for realistic
model calculations.",1906.01221v1
2021-10-21,Physics-Based Models for Magneto-Electric Spin-Orbit Logic Circuits,"Spintronic devices are a promising beyond-CMOS device option thanks to their
energy efficiency and compatibility with CMOS. To accurately capture their
multi-physics dynamics, a rigorous treatment of both spin and charge and their
inter-conversion is required. Here we present physics-based device models based
on 4x4 matrices for the spin-orbit coupling part of the magneto-electric
spin-orbit (MESO) device. Also, a more rigorous physics model of ferroelectric
and magnetoelectric switching of ferromagnets, based on Landau-Lifshitz-Gilbert
(LLG) and Landau-Khalatnikov (LK) equations, is presented. With the combined
model implemented in a SPICE circuit simulator environment, simulation results
were obtained which show feasibility of MESO implementation and functional
operation of buffers, oscillators, and majority gates.",2110.10890v1
2023-04-11,Sensitive detection of millimeter wave electric field by driving trapped surface-state electrons,"Sensitive detection of electromagnetic wave electric field plays an important
role for electromagnetic communication and sensing. Here, we propose a quantum
sensor to sensitively detect the electric field of the millimeter (mm) wave.
The quantum sensor consists of many surface-state electrons trapped
individually on liquid helium by a scalable electrode-network at the bottom of
the helium film. On such a chip, each of the trapped electrons can be
manipulated by the biased dc-current to deliver the strong spin-orbit
couplings. The mm wave signal to be detected is applied to non-dispersively
drive the orbital states of the trapped electrons, just resulting in the Stark
shifts of the dressed spin-orbital states. As a consequence, the electric field
of the applied mm wave could be detected sensitively by using the spin-echo
interferometry of the long-lived spin states of the electrons trapped on liquid
helium. The reasonable accuracy of the detection and also the feasibility of
the proposal are discussed.",2304.05154v1
2023-12-21,Andreev bound states and supercurrent in disordered spin-orbit-coupled nanowire SNS-junctions,"We use a single-channel scattering formalism to derive general expressions
for the Andreev bound-state energies and resulting current--phase relationship
in a one-dimensional semiconductor-based SNS-junction, including arbitrarily
oriented effective spin--orbit and Zeeman fields and taking into account
disorder in the junction in by including a single scatterer with transmission
probability $0 \leq T^2 \leq 1$, arbitrarily located in the normal region. We
first corroborate our results by comparing them to the known analytic
limiting-case expressions. Then we simplify our general result in several
additional limits, including the case of the scatterer being at a specific
location and the cases of small and large spin--orbit fields compared to the
Zeeman splitting, assuming low transparency ($T\ll 1$). We believe that our
results could be helpful for disentangling the main spin-mixing processes in
experiments on low-dimensional semiconductor-based SNS-junctions.",2312.13833v1
2003-07-23,A novel approach to the crystal-field theory - the orbital magnetism in 3d-ion compounds,"We point out that the orbital magnetism has to be taken into account in the
description of real 3d-ion compounds. According to the developed by us the
Quantum-Atomistic Solid-State (QUASST) theory in compounds containing open
3d-/4f-/5f-shell atoms there exists a discrete atomic-like low-energy
electronic structure that predominantly determines electronic and magnetic
properties of the whole compound. The relatively weak intra-atomic spin-orbit
coupling is fundamentally important as it governs the low-energy discrete
electronic structure.",0307575v1
2006-11-03,The Orbital Selective Mott Transition in a Three Band Hubbard model: a Slave Boson Mean Field Study,"In the present paper, we systematically studied the possible Orbital
selective Mott transition (OSMT) in the $t_{2g}$ system, which has three
orbital degeneracy. The slave Boson mean field theory is generalized to the
three band systems with full Hund's rule coupling including spin flip and pair
hopping terms. A new type of Mott transition which is driven by the crystal
field splitting or the lattice distortion is found is this model. We argue that
this new type of Mott transition may relate to the puzzling phase in
$Sr_{x}Ca_{2-x}RuO_4$.",0611075v1
2012-12-10,Effect of Gravitational Frame Dragging on Orbiting Qubits,"In this paper we discuss the effect of gravitational frame dragging on
orbiting qubits. In particular, we consider the Kerr spacetime geometry and
spin-1/2 qubits moving in an equatorial radial fall with zero angular momentum
and equatorial circular orbits. We ignore the ${\cal O}(\hbar)$ order effects
due to spin-curvature coupling, which allows us to consider the motion of the
spin-1/2 particles as Kerr geometry geodesics. We derive analytical expressions
for the infinitesimal Wigner rotation and numerical results for their
integration across the length of the particle's trajectory. To this end, we
consider the bounds on the finite Wigner rotation imposed by Penrose's cosmic
censorship hypothesis.",1212.2200v1
2018-05-11,Electrically Protected Valley-Orbit Qubits in Silicon,"Electrons confined in Si quantum dots possess orbital, spin, and valley
degrees of freedom (d.o.f.). We perform Landau-Zener-Stuckelberg-Majorana
(LZSM) interferometry on a Si double quantum dot that is strongly coupled to a
microwave cavity to probe the valley d.o.f. The resulting LZSM interference
pattern is asymmetric as a function of level detuning and persists for drive
periods that are much longer than typical charge decoherence times. By
correlating the LZSM interference pattern with charge noise measurements, we
show that valley-orbit hybridization provides some protection from the
deleterious effects of charge noise. Our work opens the possibility of
harnessing the valley d.o.f. to engineer charge-noise-insensitive qubits in Si.",1805.04545v1
2016-12-14,Analytic gradients for natural orbital functional theory,"The analytic energy gradients with respect to nuclear motion are derived for
natural orbital functional (NOF) theory. The resulting equations do not require
to resort to linear-response theory, so the computation of NOF energy gradients
is analogous to gradient calculations at the Hartree-Fock level of theory. The
structures of 15 spin-compensated systems, composed by first- and second-row
atoms, are optimized employing the conjugate gradient algorithm. As
functionals, two orbital-pairing approaches were used, namely, the fifth and
sixth Piris NOFs (PNOF5 and PNOF6). For the latter, the obtained equilibrium
geometries are compared with coupled cluster singles and doubles (CCSD)
calculations and accurate empirical data.",1612.04673v1
2014-11-06,Electromagnetic coupling of spins and pseudospins in bilayer graphene,"We present a detailed theoretical study of bilayer-graphene's electronic
properties in the presence of electric and magnetic fields. Using
group-theoretical methods, we derive an invariant expansion of the Hamiltonian
for electron states near the K point of the Brillouin zone. In contrast to
known materials, including single-layer graphene, any possible coupling of
physical quantities to components of the external electric (magnetic) field has
a counterpart where the analogous component of the magnetic (electric) field
couples to exactly the same combination of quantities. For example, a purely
electric spin splitting appears as the magneto-electric analogue of the
familiar magnetic Zeeman spin splitting. The measurable thermodynamic response
induced by magnetic and electric fields is thus completely symmetric. The Pauli
magnetization induced by a magnetic field takes exactly the same functional
form as the polarization induced by an electric field. Our findings thus reveal
unconventional behavior of spin and pseudospin degrees of freedom in their
coupling to external fields. We explain how these counterintuitive couplings
are consistent with fundamental principles such as time reversal symmetry. For
example, only a magnetic field can give rise to a macroscopic spin
polarization, whereas only a perpendicular electric field can induce a
macroscopic polarization of the sublattice-related pseudospin degree of freedom
characterizing the intravalley orbital motion in bilayer graphene. These rules
enforced by symmetry for the matter-field interactions clarify the nature of
spins versus pseudospins. We also provide numerical values of prefactors for
relevant coupling terms. While our theoretical arguments use bilayer graphene
as an example, they are generally valid for any material with similar
symmetries.",1411.1720v2
2013-08-02,Cotunneling signatures of Spin-Electric coupling in frustrated triangular molecular magnets,"The ground state of frustrated (antiferromagnetic) triangular molecular
magnets is characterized by two total-spin $S =1/2$ doublets with opposite
chirality. According to a group theory analysis [M. Trif \textit{et al.}, Phys.
Rev. Lett. \textbf{101}, 217201 (2008)] an external electric field can
efficiently couple these two chiral spin states, even when the spin-orbit
interaction (SOI) is absent. The strength of this coupling, $d$, is determined
by an off-diagonal matrix element of the dipole operator, which can be
calculated by \textit{ab-initio} methods [M. F. Islam \textit{et al.}, Phys.
Rev. B \textbf{82}, 155446 (2010)]. In this work we propose that
Coulomb-blockade transport experiments in the cotunneling regime can provide a
direct way to determine the spin-electric coupling strength. Indeed, an
electric field generates a $d$-dependent splitting of the ground state
manifold, which can be detected in the inelastic cotunneling conductance. Our
theoretical analysis is supported by master-equation calculations of quantum
transport in the cotunneling regime. We employ a Hubbard-model approach to
elucidate the relationship between the Hubbard parameters $t$ and $U$, and the
spin-electric coupling constant $d$. This allows us to predict the regime in
which the coupling constant $d$ can be extracted from experiment.",1308.0404v2
2023-03-02,Spin-valley magnetism on the triangular moiré lattice with SU(4) breaking interactions,"The discovery of correlated insulating states in moir\'e heterostructures has
renewed the interest in strongly-coupled electron systems where spin and valley
(or layer) degrees of freedom are intertwined. In the strong-coupling limit,
such systems can be effectively described by SU(4) spin-valley models akin to
Kugel-Khomskii models long studied in the context of spin-orbit coupled
materials. However, typical moir\'e heterostructures also exhibit interactions
that break the SU(4) symmetry down to
SU(2)${}_{\mathrm{spin}}\otimes$U(1)${}_{\mathrm{valley}}$. Here we investigate
the impact of such symmetry-breaking couplings on the magnetic phase diagram
for triangular superlattices considering a filling of two electrons (or holes)
per moir\'e unit cell. We explore a broad regime of couplings -- including XXZ
anisotropies, Dzyaloshinskii-Moriya exchange and on-site Hund's couplings --
using semi-classical Monte Carlo simulations. We find a multitude of
classically ordered phases, including (anti-)ferromagnetic, incommensurate, and
stripe order, manifesting in different sectors of the spin-valley model's
parameter space. Zooming in on the regimes where quantum fluctuations are
likely to have an effect, we employ pseudo-fermion functional renormalization
group (pf-FRG) calculations to resolve quantum disordered ground states such as
spin-valley liquids, which we indeed find for certain parameter regimes. As a
concrete example, we discuss the case of trilayer graphene aligned with
hexagonal boron nitride using material-specific parameters.",2303.01244v2
2017-01-26,Magnetic and electronic properties of La$_3M$O$_7$ and possible polaron formation in hole-doped La$_3M$O$_7$ ($M$=Ru and Os),"Oxides with $4d$/$5d$ transition metal ions are physically interesting for
their particular crystalline structures as well as the spin-orbit coupled
electronic structures. Recent experiments revealed a series of $4d$/$5d$
transition metal oxides $R_3M$O$_7$ ($R$: rare earth; $M$: $4d$/$5d$ transition
metal) with unique quasi-one-dimensional $M$ chains. Here first-principles
calculations have been performed to study the electronic structures of
La$_3$OsO$_7$ and La$_3$RuO$_7$. Our study confirm both of them to be Mott
insulating antiferromagnets with identical magnetic order. The reduced magnetic
moments, which are much smaller than the expected value for ideal high-spin
state ($3$ $t_{2g}$ orbitals occupied), are attributed to the strong $p-d$
hybridization with oxygen ions, instead of the spin-orbit coupling. The
Ca-doping to La$_3$OsO$_7$ and La$_3$RuO$_7$ can not only modulate the nominal
carrier density but also affect the orbital order as well as the local
distortions. The Coulombic attraction and particular orbital order would prefer
to form polarons, which might explain the puzzling insulating behavior of doped
$5d$ transition metal oxides. In addition, our calculation predict that the
Ca-doping can trigger ferromagnetism in La$_3$RuO$_7$ but not in La$_3$OsO$_7$.",1701.07655v1
2019-06-10,Néel and stripe ordering from spin-orbital entanglement in $α$-Sr$_2$CrO$_4$,"The rich phenomenology engendered by the coupling between the spin and
orbital degrees of freedom has become appreciated as a key feature of many
strongly-correlated electron systems. The resulting emergent physics is
particularly prominent in a number of materials, from Fe-based unconventional
superconductors to transition metal oxides, including manganites and vanadates.
Here, we investigate the electronic ground states of $\alpha$-Sr$_2$CrO$_4$, a
compound that is a rare embodiment of the spin-1 Kugel-Khomskii model on the
square lattice -- a paradigmatic platform to capture the physics of coupled
magnetic and orbital electronic orders. We have used resonant X-ray diffraction
at the Cr-$K$ edge to reveal N\'{e}el magnetic order at the in-plane wavevector
$\mathbf{Q}_N = (1/2, 1/2)$ below $T_N = 112$ K, as well as an additional
electronic order at the 'stripe' wavevector $\mathbf{Q}_s = (1/2, 0)$ below
T$_s$ $ \sim 50$ K. These findings are examined within the framework of the
Kugel-Khomskii model by a combination of mean-field and Monte-Carlo approaches,
which supports the stability of the spin N\'{e}el phase with subsequent
lower-temperature stripe orbital ordering, revealing a candidate mechanism for
the experimentally observed peak at $\mathbf{Q}_s$. On the basis of these
findings, we propose that $\alpha$-Sr$_2$CrO$_4$ serves as a new platform in
which to investigate multi-orbital physics and its role in the low-temperature
phases of Mott insulators.",1906.04194v2
2022-11-02,Pressure-induced dimerization and molecular orbitals formation in Na2RuO3 with strong correlation-enhanced spin-orbit coupling effect,"First-principles calculations and simulations are conducted to clarify the
nonmagnetic insulating ground state of the honeycomb lattice compound Na2RuO3
with 4d^4 electronic configuration and explore the evolutions of crystal
structure and electronic property under pressure. We reveal that individual
Coulomb correlation or spin-orbit coupling (SOC) effect cannot reproduce the
experimentally observed nonmagnetic insulating behavior of Na2RuO3, whereas the
Coulomb correlation enhanced SOC interactions give rise to an unusual
spin-orbital-entangled J = 0 nonmagnetic insulating state, which contrasts with
the SOC assisted Mott insulating state in d^5 ruthenates and iridates.
Furthermore, a pressure-induced structural dimerization transition has been
predicted around 15-17.5 GPa. The honeycomb lattice of the high-pressure
dimerized phase features with parallel pattern of the short Ru-Ru dimers
aligning along the crystallographic b direction. Accompanied with the
structural dimerization, the electronic structure shows striking reconstruction
by formation of molecular orbitals. Interestingly, the cooperation of Coulomb
correlation together with SOC can realize a nonmagnetic insulating state in the
high-pressure dimerized phase. The d^4 ruthenate Na2RuO3 with honeycomb lattice
will provide a new platform to explore unusual physics and rich phase diagram
due to the delicate interplay of lattice degree of freedom, electron
correlations, and SOC interactions.",2211.00811v2
2023-12-15,Probing the Mott-insulating behavior of Ba$_2$MgReO$_6$ with DFT+DMFT,"We investigate the interplay of spin-orbit coupling, electronic correlations,
and lattice distortions in the $5d^1$ double perovskite Ba$_2$MgReO$_6$.
Combining density-functional theory (DFT) and dynamical mean-field theory
(DMFT), we establish the Mott-insulating character of Ba$_2$MgReO$_6$ in both
its cubic and tetragonal paramagnetic phases. Despite substantial spin-orbit
coupling, its impact on the formation of the insulating state is minimal,
consistent with theoretical expectations for $d^1$ systems. We further
characterize the electronic properties of the cubic and tetragonal phases by
analyzing spectral functions and local occupations in terms of multipole
moments centered on the Re sites. Our results confirm the presence of
ferroically ordered $z^2$ quadrupoles in addition to the antiferroic
$x^2-y^2$-type order. We compare two equivalent but complementary descriptions
in terms of either effective Re-\ttg frontier orbitals or more localized
atomic-like Re-d and O-p orbitals. The former maps directly on a physically
intuitive picture in terms of nominal $d^1$ Re cations, while the latter
explicitly demonstrates the role of hybridization with the ligands in the
spin-orbit splitting and the formation of the charge quadrupoles around the Re
sites. Finally, we compare our DFT+DMFT results with a previous DFT+$U$ study
of the tetragonal paramagnetic state. We find good qualitative agreement for
the dominant charge quadrupoles, but also notable differences in the
corresponding spectral functions, underscoring the need for more comparative
studies between these two methods.",2312.09839v1
2020-09-25,"A Unified Description of Spin Transport, Weak Antilocalization and Triplet Superconductivity in Systems with Spin-Orbit Coupling","The Eilenberger equation is a standard tool in the description of
superconductors with an arbitrary degree of disorder. It can be generalized to
systems with linear-in-momentum spin-orbit coupling (SOC), by exploiting the
analogy of SOC with a non-abelian background field. Such field mixes singlet
and triplet components and yields the rich physics of magnetoelectric
phenomena. In this work we show that the application of this equation extends
further, beyond superconductivity. In the normal state, the linearized
Eilenberger equation describes the coupled spin-charge dynamics. Moreover, its
resolvent corresponds to the so called Cooperons, and can be used to calculate
the weak localization corrections. Specifically, we show how to solve this
equation for any source term and provide a closed-form solution for the case of
Rashba SOC. We use this solution to address several problems of interest for
spintronics and superconductivity. Firstly, we study spin injection from
ferromagnetic electrodes in the normal state, and describe the spatial
evolution of spin density in the sample, and the complete crossover from the
diffusive to the ballistic limit. Secondly, we address the so-called
superconducting Edelstein effect, and generalize the previously known results
to arbitrary disorder. Thirdly, we study weak localization correction beyond
the diffusive limit, which can be a valuable tool in experimental
characterization of materials with very strong SOC. We also address the
so-called pure gauge case where the persistent spin helices form. Our work
establishes the linearized Eilenberger equation as a powerful and a very
versatile method for the study of materials with spin-orbit coupling, which
often provides a simpler and more intuitive picture compared to alternative
methods.",2009.12321v1
2022-09-28,Temperature Dependent Zero-Field Splittings in Graphene,"Graphene is a quantum spin Hall insulator with a 45 $\mu$eV wide non-trivial
topological gap induced by the intrinsic spin-orbit coupling. Even though this
zero-field spin splitting is weak, it makes graphene an attractive candidate
for applications in quantum technologies, given the resulting long spin
relaxation time. On the other side, the staggered sub-lattice potential,
resulting from the coupling of graphene with its boron nitride substrate,
compensates intrinsic spin-orbit coupling and decreases the non-trivial
topological gap, which may lead to the phase transition into trivial band
insulator state. In this work, we present extensive experimental studies of the
zero-field splittings in monolayer and bilayer graphene in a temperature range
2K-12K by means of sub-Terahertz photoconductivity-based electron spin
resonance technique. Surprisingly, we observe a decrease of the spin splittings
with increasing temperature. We discuss the origin of this phenomenon by
considering possible physical mechanisms likely to induce a temperature
dependence of the spin-orbit coupling. These include the difference in the
expansion coefficients between the graphene and the boron nitride substrate or
the metal contacts, the electron-phonon interactions, and the presence of a
magnetic order at low temperature. Our experimental observation expands
knowledge about the non-trivial topological gap in graphene.",2209.14001v2
2023-12-27,Topological phase transitions induced by the variation of exchange couplings in graphene,"We consider a modified graphene model under exchange couplings. Various
quantum anomalous phases are known to emerge under uniform or staggered
exchange couplings. We introduce the twist between the orientations of two
sublattice exchange couplings, which is useful for examining how such
topologically nontrivial phases under different types of exchange couplings are
connected to one another. The phase diagrams constructed by the variation of
exchange coupling strengths and twist angles exhibit rich structures of
successive topological transitions. We analyze the emergence of peculiar phases
in terms of the evolution of the energy dispersions. Perturbation schemes
applied to the energy levels turn out to reproduce well phase boundary lines up
to moderate values of the twist angle. We also discover two close topological
transitions under uniform exchange couplings, which is attributed to the
interplay of the trigonal-warping deformation due to Rashba spin-orbit coupling
and the staggered sublattice potential. Finally the implications of Berry
curvature structure and topological excitations in real and pseudo spin
textures are discussed.",2312.16625v2
2018-04-05,"Spin-orbit coupled systems in the ""atomic"" limit: rhenates, osmates, iridates","Motivated by RIXS experiments on a wide range of complex heavy oxides,
including rhenates, osmates, and iridates, we discuss the theory of RIXS for
site-localized $t_{2g}$ orbital systems with strong spin-orbit coupling. For
such systems, we present exact diagonalization results for the spectrum at
different electron fillings, showing that it accesses ""single-particle"" and
""multi-particle"" excitations. This leads to a simple picture for the energies
and intensities of the RIXS spectra in Mott insulators such as double
perovskites which feature highly localized electrons, and yields estimates of
the spin-orbit coupling and Hund's coupling in correlated $5d$ oxides. We
present new higher resolution RIXS data at the Re-L$_3$ edge in Ba$_2$YReO$_6$
which finds a previously unresolved peak splitting, providing further
confirmation of our theoretical predictions. Using ab initio electronic
structure calculations on Ba$_2$${\cal M}$ReO$_6$ (with ${\cal M}$=Re, Os, Ir)
we show that while the atomic limit yields a reasonable effective Hamiltonian
description of the experimental observations, effects such as $t_{2g}$-$e_g$
interactions and hybridization with oxygen are important. Our ab initio
estimate for the strength of the intersite exchange coupling shows that,
compared to the osmates, the exchange is one or two orders of magnitude weaker
in the rhenates and iridates, which may partly explain the suppression of
long-range magnetic order in the latter compounds. As a way to interpolate
between the site-localized picture and our electronic structure band
calculations, we discuss the spin-orbital levels of the ${\cal M}$O$_6$
cluster. This suggests a possible role for non-dispersive intra-cluster
excitons in Ba$_2$YIrO$_6$ which may lead to a weak breakdown of the atomic
$J_{\rm eff}=0$ picture and to small magnetic moments.",1804.02006v2
2008-11-20,Metal-Insulator Transition and Orbital Order in PbRuO3,"Anomalous low temperature electronic and structural behaviour has been
discovered in PbRuO3. The structure (space group Pnma, a = 5.56314(1), b =
7.86468(1), c = 5.61430(1) A) and metallic conductivity at 290 K are similar to
those of SrRuO3 and other ruthenate perovskites, but a sharp metal-insulator
transition at which the resistivity increases by four orders of magnitude is
discovered at 90 K. This is accompanied by a first order structural transition
to an Imma phase (a = 5.56962(1), b = 7.74550(1), c = 5.66208(1) A at 25 K)
that shows a coupling of Ru4+ 4d orbital order to distortions from Pb2+ 6s6p
orbital hybridization. The Pnma to Imma transition is an unconventional
reversal of the group-subgroup symmetry relationship. No long range magnetic
order is evident down to 1.5 K. Electronic structure calculations show that
hybridization of Pb 6s6p and Ru 4d orbitals and strong spin-orbit coupling
stabilise this previously hidden ground state for ruthenate perovskites",0811.3378v1
2011-05-29,Trimer Formation and Metal-Insulator Transition in Orbital Degenerate Systems on a Triangular Lattice,"As a prototypical self-organization in the system with orbital degeneracy, we
theoretically investigate trimer formation on a triangular lattice, as observed
in LiVO2. From the analysis of an effective spin-orbital coupled model in the
strong correlation limit, we show that the previously-proposed orbital-ordered
trimer state is not the lowest-energy state for a finite Hund's-rule coupling.
Instead, exploring the ground state in a wide range of parameters for a
multiorbital Hubbard model, we find an instability toward a different
orbital-ordered trimer state in the intermediately correlated regime in the
presence of trigonal crystal field. The trimer phase appears in the competing
region among a paramagnetic metal, band insulator, and Mott insulator. The
underlying mechanism is nesting instability of the Fermi surface by a
synergetic effect of Coulomb interactions and trigonal-field splitting. The
results are compared with experiments in triangularlattice compounds, LiVX2
(X=O, S, Se) and NaVO2.",1105.5757v1
2014-01-16,Functionalized Germanene as a Prototype of Large-Gap Two-Dimensional Topological Insulators,"We propose new two-dimensional (2D) topological insulators (TIs) in
functionalized germanenes (GeX, X=H, F, Cl, Br or I) using first-principles
calculations. We find GeI is a 2D TI with a bulk gap of about 0.3 eV, while
GeH, GeF, GeCl and GeBr can be transformed into TIs with sizeable gaps under
achievable tensile strains. A unique mechanism is revealed to be responsible
for large topologically-nontrivial gap obtained: owing to the
functionalization, the $\sigma$ orbitals with stronger spin-orbit coupling
(SOC) dominate the states around the Fermi level, instead of original $\pi$
orbitals with weaker SOC; thereinto, the coupling of the $p_{xy}$ orbitals of
Ge and heavy halogens in forming the $\sigma$ orbitals also plays a key role in
the further enlargement of the gaps in halogenated germanenes. Our results
suggest a realistic possibility for the utilization of topological effects at
room temperature.",1401.4100v1
2015-05-20,"Orbital Arrangements and Magnetic Interactions in the Quasi-One-Dimensional Cuprates ACuMoO_4(OH) (A = Na, K)","A new spin-1/2 quasi-one-dimensional antiferromagnet KCuMoO_4(OH) is prepared
by the hydrothermal method. The crystal structures of KCuMoO_4(OH) and the
already-known Na-analogue, NaCuMoO_4(OH), are isotypic, comprising chains of
Cu^{2+} ions in edge-sharing CuO_4(OH)_2 octahedra. Despite the structural
similarity, their magnetic properties are quite different because of the
different arrangements of d_{x2-y2} orbitals carrying spins. For NaCuMoO_4(OH),
d_{x2-y2} orbitals are linked by superexchange couplings via two bridging oxide
ions, which gives a ferromagnetic nearest-neighbor interaction J_1 of -51 K and
an antiferromagnetic next-nearest-neighbor interaction J_2 of 36 K in the
chain. In contrast, a staggered d_{x2-y2} orbital arrangement in KCuMoO_4(OH)
results in superexchange couplings via only one bridging oxide ion, which makes
J_1 antiferromagnetic as large as 238 K and J_2 negligible. This comparison
between the two isotypic compounds demonstrates an important role of orbital
arrangements in determining the magnetic properties of cuprates.",1505.05332v1
2020-07-22,Orbital period modulation in hot Jupiter systems,"We introduce a model for the orbital period modulation in systems with
close-by giant planets based on a spin-orbit coupling that transfers angular
momentum from the orbit to the rotation of the planet and viceversa. The
coupling is produced by a permanent non-axisymmetric gravitational quadrupole
moment assumed to be present in the solid core of the planet. We investigate
two regimes of internal planetary rotation, that is, when the planet rotates
rigidly and when the rotation of its deep interior is time dependent as a
consequence of a vacillating or intermittent convection in its outer shell. The
model is applied to a sample of very hot Jupiters predicting maximum
transit-time deviations from a constant-period ephemeris of approximately 50
seconds in the case of rigid rotation. The transit time variations of WASP-12,
currently the only system showing evidence of a non-constant period, cannot be
explained by assuming rigid rotation, but can be modelled in the time-dependent
internal rotation regime, thus providing an alternative to their interpretation
in terms of a tidal decay of the planet orbit.",2007.11264v1
2013-05-01,Ballistic spin transport in exciton gases,"Traditional spintronics relies on spin transport by charge carriers, such as
electrons in semiconductor crystals. This brings several complications: the
Pauli principle prevents the carriers from moving with the same speed; Coulomb
repulsion leads to rapid dephasing of electron flows. Spin-optronics is a
valuable alternative to traditional spintronics. In spin-optronic devices the
spin currents are carried by electrically neutral bosonic quasi-particles:
excitons or exciton-polaritons. They can form highly coherent quantum liquids
and carry spins over macroscopic distances. The price to pay is a finite
life-time of the bosonic spin carriers. We present the theory of exciton
ballistic spin transport which may be applied to a range of systems where
bosonic spin transport has been reported, in particular, to indirect excitons
in coupled GaAs/AlGaAs quantum wells. We describe the effect of spin-orbit
interaction of electrons and holes on the exciton spin, account for the Zeeman
effect induced by external magnetic fields, long range and short range exchange
splittings of the exciton resonances. We also consider exciton transport in the
non-linear regime and discuss the definitions of exciton spin current,
polarization current and spin conductivity.",1305.0133v3
2017-06-11,Transport theory for electrical detection of the spin texture and spin-momentum locking of topological surface states,"The surface states of three-dimensional topological insulators exhibit a
helical spin texture with spin locked to momentum. To date, however, the direct
all-electrical detection of the helical spin texture has remained elusive owing
to the lack of necessary spin-sensitive measurements. We here provide a general
theory for spin polarized transports of helical Dirac electrons through
spin-polarized scanning tunneling microscopy (STM). It is found that different
from conventional magnetic materials, the tunneling conductance through the TI
surface acquires an extra component determined by the in-plane spin texture,
exclusively associated with spin momentum locking. Importantly, this extra
conductance unconventionally depends on the spatial azimuthal angle of the
magnetized STM tip, which is never carried out in previous STM theory. By
magnetically doping to break the symmetry of rotation and time reversal of the
TI surface, we find that the measurement of the spatial resolved conductance
can reconstruct the helical structure of spin texture. Furthermore, one can
extract the SML angle if the in-plane magnetization is induced purely by the
spin-orbit coupling of surface Dirac elections. Our theory offers an
alternative way, rather than using angle resolved photoemission spectroscopy,
to electrical identify the helical spin texture on TI surfaces.",1706.03379v1
2018-07-10,Interfacial spin Hall effect and spin swapping in Fe|Au bilayer from first principles,"The interfaces in hybridized structures could give rise to rich phenomena,
which open the way to novel devices with extraordinary performance. Here, we
investigate the interface-related spin transport properties in Fe|Au bilayer
based on first-principle calculation. We find that the spin Hall current in the
Au side near the interface flows in the opposite direction to the bulk spin
Hall current with the magnitude sensitive to the magnetization direction of Fe.
This negative interfacial contribution is attributed to the spin dependent
transmission within a few atomic layers, where a strong interfacial Rashba
spin-orbit coupling exists. Surprisingly, the interfacial spin Hall currents
are found to be not confined at the interface but extend tens of nanometers at
low temperature, which is limited by momentum scattering and therefore much
shorter than the spin diffusion length. In addition, the interfacial swapping
spin currents, as a consequence of the spin precession under the interfacial
Rashba field, are also obtained from our calculation and complete the full spin
transport picture with all non-vanishing components. Our results suggest the
importance of the interface engineering in spin-related transport in
ferromagnetic|non-magnetic heterostructures and the possibility of manipulating
the interfacial transport by the magnetization orientation of the magnetic
layer.",1807.03433v1
2019-02-01,Photoinduced Rashba spin to charge conversion via interfacial unoccupied state,"At interfaces with inversion symmetry breaking, Rashba effect couples the
motion of electrons to their spin; as a result, spin-charge interconversion
mechanism can occur. These interconversion mechanisms commonly exploit Rashba
spin splitting at the Fermi level by spin pumping or spin torque ferromagnetic
resonance. Here, we report evidence of significant photoinduced spin to charge
conversion via Rashba spin splitting in an unoccupied state above the Fermi
level at the Cu(111)/$\alpha$-Bi$_{2}$O$_{3}$ interface. We predict an average
Rashba coefficient of $1.72\times 10^{-10}eV.m$ at 1.98 eV above the Fermi
level, by fully relativistic first-principles analysis of the interfacial
electronic structure with spin orbit interaction. We find agreement with our
observation of helicity dependent photoinduced spin to charge conversion
excited at 1.96 eV at room temperature, with spin current generation of
$J_{s}=10^{6}A/m^{2}$. The present letter shows evidence of efficient
spin-charge conversion exploiting Rashba spin splitting at excited states,
harvesting light energy without magnetic materials or external magnetic fields.",1902.00237v2
2017-07-14,Spin-momentum locked interaction between guided photons and surface electrons in topological insulators,"The propagation of electrons and photons can respectively have the
spin-momentum locking effect which correlates the spin with the linear
momentum. For the surface electrons in three-dimensional topological insulators
(TIs), their spin is locked to the transport direction. For photons in optical
fibers and photonic waveguides, they carry transverse spin angular momentum
(SAM) which is also locked to the propagation direction. A direct connection
between the electronic and the optical spins occurs in TIs with lifted spin
degeneracy, which leads to spin-dependent selection rules of optical
transitions and results in phenomena such as circular photogalvanic effect
(CPGE). Here, we demonstrate an optoelectronic device that integrates a TI with
a photonic waveguide. Interaction between the photons in the
transverse-magnetic (TM) mode of the waveguide, which carries transverse SAM,
and the surface electrons in a Bi2Se3 layer generates a directional,
spin-polarized photocurrent. Because of optical spin-momentum locking, the
device works in a non-reciprocal way such that changing the light propagation
direction reverses the photon spin and thus the direction of the photocurrent
in the TI. This novel device provides a directional interface that directly
converts the photon propagation path to the direction and spin polarization of
the photo-excited surface current in the TI. It represents a new way of
implementing coupled spin-orbit interaction between electrons and photons and
may lead to significant applications in opto-spintronics and quantum
information processing.",1707.04559v2
2019-05-03,Charge-to-Spin Conversion by the Rashba-Edelstein Effect in 2D van der Waals Heterostructures up to Room Temperature,"The proximity of a transition metal dichalcogenide (TMD) to graphene imprints
a rich spin texture in graphene and complements its high quality charge/spin
transport by inducing spin-orbit coupling (SOC). Rashba and valley-Zeeman SOCs
are the origin of charge-to-spin conversion mechanisms such as Rashba-Edelstein
effect (REE) and spin Hall effect (SHE). In this work, we experimentally
demonstrate for the first time charge-to-spin conversion due to the REE in a
monolayer WS2-graphene van der Waals heterostructure. We measure the
current-induced spin polarization up to room temperature and control it by a
gate electric field. Our observation of the REE and inverse of the effect
(IREE) is accompanied by the SHE which we discriminate by symmetry-resolved
spin precession under oblique magnetic fields. These measurements also allow
for quantification of the efficiencies of charge-to-spin conversion by each of
the two effects. These findings are a clear indication of induced Rashba and
valley-Zeeman SOC in graphene that lead to generation of spin accumulation and
spin current without using ferromagnetic electrodes. These realizations have
considerable significance for spintronic applications, providing accessible
routes towards all-electrical spin generation and manipulation in
two-dimensional materials.",1905.01371v1
2020-09-06,Adiabatic and Nonadiabatic Spin-transfer Torques in Antiferromagnets,"Electron transport in magnetic orders and the magnetic orders dynamics have a
mutual dependence, which provides the key mechanisms in spin-dependent
phenomena. Recently, antiferromagnetic orders are focused on as the magnetic
order, where current-induced spin-transfer torques, a typical effect of
electron transport on the magnetic order, have been debatable mainly because of
the lack of an analytic derivation based on quantum field theory. Here, we
construct the microscopic theory of spin-transfer torques on the slowly-varying
staggered magnetization in antiferromagnets with weak canting. In our theory,
the electron is captured by bonding/antibonding states, each of which is the
eigenstate of the system, doubly degenerates, and spatially spreads to
sublattices because of electron hopping. The spin of the eigenstates depends on
the momentum in general, and a nontrivial spin-momentum locking arises for the
case with no site inversion symmetry, without considering any spin-orbit
couplings. The spin current of the eigenstates includes an anomalous component
proportional to a kind of gauge field defined by derivatives in momentum space
and induces the adiabatic spin-transfer torques on the magnetization.
Unexpectedly, we find that one of the nonadiabatic torques has the same form as
the adiabatic spin-transfer torque, while the obtained forms for the adiabatic
and nonadiabatic spin-transfer torques agree with the phenomenological
derivation based on the symmetry consideration. This finding suggests that the
conventional explanation for the spin-transfer torques in antiferromagnets
should be changed. Our microscopic theory provides a fundamental understanding
of spin-related physics in antiferromagnets.",2009.02686v1
2004-05-20,Optimal Axes of Siberian Snakes for Polarized Proton Acceleration,"Accelerating polarized proton beams and storing them for many turns can lead
to a loss of polarization when accelerating through energies where a spin
rotation frequency is in resonance with orbit oscillation frequencies.
First-order resonance effects can be avoided by installing Siberian Snakes in
the ring, devices which rotate the spin by 180 degrees around the snake axis
while not changing the beam's orbit significantly. For large rings, several
Siberian Snakes are required.
  Here a criterion will be derived that allows to find an optimal choice of the
snake axes. Rings with super-period four are analyzed in detail, and the HERA
proton ring is used as an example for approximate four-fold symmetry. The
proposed arrangement of Siberian Snakes matches their effects so that all
spin-orbit coupling integrals vanish at all energies and therefore there is no
first-order spin-orbit coupling at all for this choice, which I call snakes
matching. It will be shown that in general at least eight Siberian Snakes are
needed and that there are exactly four possibilities to arrange their axes.
When the betatron phase advance between snakes is chosen suitably, four
Siberian Snakes can be sufficient.
  To show that favorable choice of snakes have been found, polarized protons
are tracked for part of HERA-p's acceleration cycle which shows that
polarization is preserved best for the here proposed arrangement of Siberian
Snakes.",0405109v1
2009-06-03,Non-local mean field effect on nuclei near Z=64 sub-shell,"Evolutions of single-particle energies and Z=64 sub-shell along the isotonic
chain of N=82 are investigated in the density dependent relativistic
Hartree-Fock (DDRHF) theory in comparison with other commonly used mean field
models such as Skyrme HF, Gogny HFB and density dependent relativistic Hartree
model (DDRMF). The pairing is treated in the BCS scheme, except for Gogny HFB.
It is pointed out that DDRHF reproduces well characteristic features of
experimental $Z$-dependence of both spin orbital and pseudo-spin orbital
splittings around the sub-shell closure Z=64. Non-local exchange terms of the
isoscalar $\sigma$ and $\omega$ couplings play dominant roles in the
enhancements of the spin-orbit splitting of proton 2d states, which is the key
ingredient to give the Z=64 sub-shell closure properly. On the other hand, the
$\pi$ and $\rho$ tensor contributions for the spin-orbit splitting cancel each
other and the net effect becomes rather small. The enhancement of the sub-shell
gaps towards Z=64 is studied by the DDRHF, for which the local terms of the
scalar and vector meson couplings are found to be important.",0906.0636v1
2013-03-08,Ab initio analysis of the tight-binding parameters and magnetic interactions in Na2IrO3,"By means of density functional theory (DFT) calculations (with and without
inclusion of spin-orbit (SO) coupling) we present a detailed study of the
electronic structure and corresponding microscopic Hamiltonian parameters of
Na2IrO3. In particular, we address the following aspects: (i) We investigate
the role of the various structural distortions and show that the electronic
structure of Na2IrO3 is exceptionally sensitive to structural details. (ii) We
discuss both limiting descriptions for Na2IrO3; quasi-molecular orbitals (small
SO limit, itinerant) versus relativistic orbitals (large SO limit, localized)
and show that the description of Na2IrO3 lies in an intermediate regime. (iii)
We investigate whether the nearest neighbor Kitaev-Heisenberg model is
sufficient to describe the electronic structure and magnetism in Na2IrO3. In
particular, we verify the recent suggestion of an antiferromagnetic Kitaev
interaction and show that it is not consistent with actual or even plausible
electronic parameters. Finally, (iv) we discuss correlation effects in Na2IrO3.
We conclude that while the Kitaev-Heisenberg Hamiltonian is the most general
expression of the quadratic spin-spin interaction in the presence of spin-orbit
coupling (neglecting single-site anisotropy), the itinerant character of the
electrons in Na2IrO3 makes other terms beyond this model (including, but not
limited to 2nd and 3rd neighbor interactions) essential.",1303.2105v2
2013-03-24,Compass and Kitaev models -- Theory and Physical Motivations,"Compass models are theories of matter in which the couplings between the
internal spin (or other relevant field) components are inherently spatially
(typically, direction) dependent. Compass-type interactions appear in diverse
physical systems including Mott insulators with orbital degrees of freedom
(where interactions sensitively depend on the spatial orientation of the
orbitals involved), the low energy effective theories of frustrated quantum
magnets, systems with strong spin-orbit couplings (such as the iridates),
vacancy centers, and cold atomic gases. Kitaev's models, in particular the
compass variant on the honeycomb lattice, realize basic notions of topological
quantum computing. The fundamental inter-dependence between internal (spin,
orbital, or other) and external (i.e., spatial) degrees of freedom which
underlies compass models generally leads to very rich behaviors including the
frustration of (semi-)classical ordered states on non-frustrated lattices and
to enhanced quantum effects prompting, in certain cases, the appearance of zero
temperature quantum spin liquids. As a consequence of these frustrations, new
types of symmetries and their associated degeneracies may appear. These
intermediate symmetries lie midway between the extremes of global symmetries
and local gauge symmetries and lead to effective dimensional reductions. We
review compass models in a unified manner, paying close attention to exact
consequences of these symmetries, and to thermal and quantum fluctuations that
stabilize orders via order out of disorder effects. We review non-trivial
statistics and the appearance of topological quantum orders in compass systems
in which, by virtue of their intermediate symmetry standard orders do not
arise. This is complemented by a survey of numerical results. Where appropriate
theoretical and experimental results are compared.",1303.5922v1
2014-01-15,Formation of quantum spin Hall state on Si surface and energy gap scaling with strength of spin orbit coupling,"For potential applications in spintronics and quantum computing, it is
desirable to place a quantum spin Hall insulator [i.e., a 2D topological
insulator (TI)] on a substrate while maintaining a large energy gap. Here, we
demonstrate a unique approach to create the large-gap 2D TI state on a
semiconductor surface, based on first-principles calculations and effective
Hamiltonian analysis. We show that when heavy elements with strong spin orbit
coupling (SOC) such as Bi and Pb atoms are deposited on a patterned H-Si(111)
surface into a hexagonal lattice, they exhibit a 2D TI state with a large
energy gap of over 0.5 eV. The TI state arises from an intriguing substrate
orbital filtering effect that selects a suitable orbital composition around the
Fermi level, so that the system can be matched onto a four-band effective model
Hamiltonian. Furthermore, it is found that within this model, the SOC gap does
not increase monotonically with the increasing strength of SOC. These
interesting results may shed new light in future design and fabrication of
large-gap topological quantum states.",1401.3392v2
2014-12-02,Interplay of spin-orbit torque and thermoelectric effects in ferromagnet/normal metal bilayers,"We present harmonic transverse voltage measurements of current-induced
thermoelectric and spin-orbit torque (SOT) effects in ferromagnet/normal metal
bilayers, in which thermal gradients produced by Joule heating and SOT coexist
and give rise to ac transverse signals with comparable symmetry and magnitude.
Based on the symmetry and field-dependence of the transverse resistance, we
develop a consistent method to separate thermoelectric and SOT measurements. By
addressing first ferromagnet/light metal bilayers with negligible spin-orbit
coupling, we show that in-plane current injection induces a vertical thermal
gradient whose sign and magnitude are determined by the resistivity difference
and stacking order of the magnetic and nonmagnetic layers. We then study
ferromagnet/heavy metal bilayers with strong spin-orbit coupling, showing that
second harmonic thermoelectric contributions to the transverse voltage may lead
to a significant overestimation of the antidamping SOT. We find that
thermoelectric effects are very strong in Ta(6nm)/Co(2.5nm) and negligible in
Pt(6nm)/Co(2.5nm) bilayers. After including these effects in the analysis of
the transverse voltage, we find that the antidamping SOTs in these bilayers,
after normalization to the magnetization volume, are comparable to those found
in thinner Co layers with perpendicular magnetization, whereas the field-like
SOTs are about an order of magnitude smaller.",1412.0865v1
2015-03-04,Signature of strong spin-orbital coupling in the large non-saturating magnetoresistance material WTe2,"We report the detailed electronic structure of WTe$_2$ by high resolution
angle-resolved photoemission spectroscopy. Unlike the simple one electron plus
one hole pocket type of Fermi surface topology reported before, we resolved a
rather complicated Fermi surface of WTe$_2$. Specifically, there are totally
nine Fermi pockets, including one hole pocket at the Brillouin zone center
$\Gamma$, and two hole pockets and two electron pockets on each side of
$\Gamma$ along the $\Gamma$-$X$ direction. Remarkably, we have observed
circular dichroism in our photoemission spectra, which suggests that the
orbital angular momentum exhibits a rich texture at various sections of the
Fermi surface. As reported previously for topological insulators and Rashiba
systems, such a circular dichroism is a signature for spin-orbital coupling
(SOC). This is further confirmed by our density functional theory calculations,
where the spin texture is qualitatively reproduced as the conjugate consequence
of SOC. Since the backscattering processes are directly involved with the
resistivity, our data suggest that the SOC and the related spin and orbital
angular momentum textures may be considered in the understanding of the
anomalous magnetoresistance of WTe$_2$.",1503.01422v1
2019-10-29,"Giant proximity exchange and valley splitting in transition metal dichalcogenide/$h\mathrm{BN}$/(Co, Ni) heterostructures","We investigate the proximity-induced exchange coupling in transition-metal
dichalcogenides (TMDCs), originating from spin injector geometries composed of
hexagonal boron-nitride (hBN) and ferromagnetic (FM) cobalt (Co) or nickel
(Ni), from first-principles. We employ a minimal tight-binding Hamiltonian that
captures the low energy bands of the TMDCs around K and K' valleys, to extract
orbital, spin-orbit, and exchange parameters. The TMDC/hBN/FM heterostructure
calculations show that due to the hBN buffer layer, the band structure of the
TMDC is preserved, with an additional proximity-induced exchange splitting in
the bands. We extract proximity exchange parameters in the 1--10 meV range,
depending on the FM. The combination of proximity-induced exchange and
intrinsic spin-orbit coupling (SOC) of the TMDCs, leads to a valley
polarization, translating into magnetic exchange fields of tens of Tesla. The
extracted parameters are useful for subsequent exciton calculations of TMDCs in
the presence of a hBN/FM spin injector. Our calculated absorption spectra show
large splittings for the exciton peaks; in the case of MoS$_2$/hBN/Co we find a
value of about 8 meV, corresponding to about 50 Tesla external magnetic field
in bare TMDCs. The reason lies in the band structure, where a hybridization
with Co $d$ orbitals causes a giant valence band exchange splitting of more
than 10 meV. Structures with Ni do not show any $d$ level hybridization
features, but still sizeable proximity exchange and exciton peak splittings of
around 2 meV are present in the TMDCs.",1910.13223v2
2020-02-18,BCS-BEC crossover in a $(t_{2g})^4$ Excitonic Magnet,"The condensation of spin-orbit-induced excitons in $(t_{2g})^4$ electronic
systems is attracting considerable attention. In the large Hubbard U limit,
antiferromagnetism was proposed to emerge from the Bose-Einstein Condensation
(BEC) of triplons ($J_{\textrm{eff}} = 1$). In this publication, we show that
even for the weak and intermediate U regimes, the spin-orbit exciton
condensation is possible leading also to staggered magnetic order. The
canonical electron-hole excitations (excitons) transform into local triplon
excitations at large U , and this BEC strong coupling regime is smoothly
connected to the intermediate U excitonic insulator region. We solved the
degenerate three-orbital Hubbard model with spin-orbit coupling ($\lambda$) in
one-dimensional geometry using the Density Matrix Renormalization Group, while
in two-dimensional square clusters we use the Hartree-Fock approximation (HFA).
Employing these techniques, we provide the full $\lambda$ vs U phase diagrams
for both one- and two- dimensional lattices. Our main result is that at the
intermediate Hubbard U region of our focus, increasing $\lambda$ at fixed U the
system transitions from an incommensurate spin-density-wave metal to a
Bardeen-Cooper-Schrieffer (BCS) excitonic insulator, with coherence length r
coh of O(a) and O(10a) in 1d and 2d, respectively, with a the lattice spacing.
Further increasing $\lambda$, the system eventually crosses over to the BEC
limit (with r coh << a).",2002.07351v1
2020-04-29,Towards Electrical-Current Control of Quantum States in Spin-Orbit-Coupled Matter,"Novel materials, which often exhibit surprising or even revolutionary
physical properties, are necessary for critical advances in technologies.
Simultaneous control of structural and physical properties via a small
electrical current is of great significance both fundamentally and
technologically. Recent studies demonstrate that a combination of strong
spin-orbit interactions and a distorted crystal structure in magnetic Mott
insulators is sufficient to attain this long-desired goal. In this Topical
Review, we highlight underlying properties of this class of materials and
present two representative antiferromagnetic Mott insulators, namely,
4d-electron based Ca2RuO4 and 5d-electron based Sr2IrO4, as model systems. In
essence, a small, applied electrical current engages with the lattice,
critically reducing structural distortions, which in turn readily suppresses
the antiferromagnetic and insulating state and subsequently results in emergent
new states. While details may vary in different materials, at the heart of
these phenomena are current-reduced lattice distortions, which, via spin-orbit
interactions, dictate physical properties. Electrical current, which joins
magnetic field, electric field, pressure, light, etc. as a new external
stimulus, provides a new, key dimension for materials research, and also pose a
series of intriguing questions that may provide the impetus for advancing our
understanding of spin-orbit-coupled matter. This Topical Review provides a
brief introduction, a few hopefully informative examples and some general
remarks. It is by no means an exhaustive report of the current state of studies
on this topic.",2004.14510v2
2017-09-29,CERES: An ab initio code dedicated to the calculation of the electronic structure and magnetic properties of lanthanide complexes,"We have developed and implemented a new ab initio code, CERES (Computational
Emulator of Rare Earth Systems), completely written in C++11, which is
dedicated to the efficient calculation of the electronic structure and magnetic
properties of the crystal field states arising from the splitting of the ground
state spin-orbit multiplet in lanthanide complexes. The new code gains
efficiency via an optimised implementation of a direct configurational averaged
Hartree-Fock (CAHF) algorithm for the determination of $4f$ quasi-atomic active
orbitals common to all multi-electron spin manifolds contributing to the ground
spin-orbit multiplet of the lanthanide ion. The new CAHF implementation is
based on quasi-Newton convergence acceleration techniques coupled to an
efficient library for the direct evaluation of molecular integrals, and
problem-specific density matrix guess strategies. After describing the main
features of the new code, we compare its efficiency with the current
state--of--the--art ab initio strategy to determine crystal field levels and
properties, and show that our methodology, as implemented in CERES, represents
a more time-efficient computational strategy for the evaluation of the magnetic
properties of lanthanide complexes, also allowing a full representation of
non-perturbative spin-orbit coupling effects.",1709.10315v1
2018-10-24,High-throughput Discovery of Topologically Non-trivial Materials using Spin-orbit Spillage,"We present a novel methodology to identify topologically non-trivial
materials based on band inversion induced by spin-orbit coupling (SOC) effect.
Specifically, we compare the density functional theory (DFT) based
wavefunctions with and without spin-orbit coupling and compute the
spin-orbit-spillage as a measure of band-inversion. Due to its ease of
calculation, without any need for symmetry analysis or dense k-point
interpolation, the spillage is an excellent tool for identifying topologically
non-trivial materials. Out of 30000 materials available in the JARVIS-DFT
database, we applied this methodology to more than 4835 non-magnetic materials
consisting of heavy atoms and low bandgaps. We found 1868 candidate materials
with high-spillage (using 0.5 as a threshold). We validated our methodology by
carrying out conventional Wannier-interpolation calculations for 289 candidate
materials. We demonstrate that in addition to Z2 topological insulators, this
screening method successfully identified many semimetals and topological
crystalline insulators. Importantly, our approach is applicable to the
investigation of disordered or distorted as well as magnetic materials, because
it is not based on symmetry considerations. We discuss some individual example
materials, as well as trends throughout our dataset, which is available at the
websites: https://www.ctcms.nist.gov/~knc6/JVASP.html and
https://jarvis.nist.gov/.",1810.10640v2
2001-11-08,Mesoscopics in Spintronics: Quantum Interference Effects in Spin-Polarized Electron Transport,"We generalize a Landauer-type formula, using a real$\otimes$spin-space Green
function technique, to treat spin-dependent transport in quantum-coherent
conductors attached to two ferromagnetic contacts. The formalism is employed to
study the properties of components of an exact zero-temperature conductance
matrix ${\bf G}$, as well as their mesoscopic fluctuations, describing
injection and detection of a spin-polarized current in a two-dimensional system
where electrons exhibit an interplay between Rashba spin-orbit (SO) coupling
and phase-coherent propagation through a disordered medium. Strong Rashba
coupling leads to a dramatic reduction of localization effects on the
conductances and their fluctuations, whose features depend on the
spin-polarization of injected electrons. In the limit of weak Rashba
interaction antilocalization vanishes (i.e., the sum of the matrix elements of
${\bf G}$ is almost independent of the SO coupling), but the partial
spin-resolved conductances can still be non-zero. Besides spin-resolved
conductance fluctuations and antilocalization, unusual quantum interference
effects are revealed in this system leading to a negative difference between
the partial conductances for a parallel and an antiparallel orientation of the
contact magnetization, in a range of disorder strengths and for a particular
spin-polarization of incoming electron with respect to the direction of Rashba
electric field.",0111144v3
2020-11-02,Spin precession as a new window into disformal scalar fields,"We launch a first investigation into how a light scalar field coupled both
conformally and disformally to matter influences the evolution of spinning
point-like bodies. Working directly at the level of the equations of motion, we
derive novel spin-orbit and spin-spin effects accurate to leading order in a
nonrelativistic and weak-field expansion. Crucially, unlike the
spin-independent effects induced by the disformal coupling, which have been
shown to vanish in circular binaries due to rotational symmetry, the
spin-dependent effects we study here persist even in the limit of zero
eccentricity, and so provide a new and qualitatively distinct way of probing
these kinds of interactions. To illustrate their potential, we confront our
predictions with spin-precession measurements from the Gravity Probe B
experiment and find that the resulting constraint improves upon existing bounds
from perihelion precession by over 5 orders of magnitude. Our results therefore
establish spin effects as a promising window into the disformally coupled dark
sector.",2011.01213v2
2021-04-26,Hyperfine-mediated transitions between electronic spin-1/2 levels of transition metal defects in SiC,"Transition metal defects in SiC give rise to localized electronic states that
can be optically addressed in the telecom range in an industrially mature
semiconductor platform. This has led to intense scrutiny of the spin and
optical properties of these defect centers. For spin-1/2 defects, a combination
of the defect symmetry and the strong spin-orbit coupling may restrict the
allowed spin transitions, giving rise to defect spins that are long lived, but
hard to address via microwave spin manipulation. Here, we show via analytical
and numerical results that the presence of a central nuclear spin can lead to a
non-trivial mixing of electronic spin states, while preserving the defect
symmetry. The interplay between a small applied magnetic field and hyperfine
coupling opens up magnetic microwave transitions that are forbidden in the
absence of hyperfine coupling, enabling efficient manipulation of the
electronic spin. We also find that an electric microwave field parallel to the
c-axis can be used to manipulate the electronic spin via modulation of the
relative strength of the dipolar hyperfine term.",2104.12433v2
2022-12-16,Spin excitations in the kagome-lattice metallic antiferromagnet Fe$_{0.89}$Co$_{0.11}$Sn,"Kagome-lattice materials have attracted tremendous interest due to the broad
prospect for seeking superconductivity, quantum spin liquid states, and
topological electronic structures. Among them, the transition-metal kagome
lattices are high-profile objects for the combination of topological
properties, rich magnetism, and multiple-orbital physics. Here we report an
inelastic neutron scattering study on the spin dynamics of a kagome-lattice
antiferromagnetic metal Fe$_{0.89}$Co$_{0.11}$Sn. Although the magnetic
excitations can be observed up to $\sim$250 meV, well-defined spin waves are
only identified below $\sim$90 meV and can be modeled using Heisenberg exchange
with ferromagnetic in-plane nearest-neighbor coupling $J_1$, in-plane
next-nearest-neighbor coupling $J_2$, and antiferromagnetic (AFM) interlayer
coupling $J_c$ under linear spin-wave theory. Above $\sim$90 meV, the spin
waves enter the itinerant Stoner continuum and become highly damped
particle-hole excitations. At the K point of the Brillouin zone, we reveal a
possible band crossing of the spin wave, which indicates a potential Dirac
magnon. Our results uncover the evolution of the spin excitations from the
planar AFM state to the axial AFM state in Fe$_{0.89}$Co$_{0.11}$Sn, solve the
magnetic Hamiltonian for both states, and confirm the significant influence of
the itinerant magnetism on the spin excitations.",2212.08590v2
2005-09-01,Shot noise and spin-orbit coherent control of entangled and spin polarized electrons,"We extend our previous work on shot noise for entangled and spin polarized
electrons in a beam-splitter geometry with spin-orbit (\textit{s-o})
interaction in one of the incoming leads (lead 1). Besides accounting for both
the Dresselhaus and the Rashba spin-orbit terms, we present general formulas
for the shot noise of singlet and triplets states derived within the scattering
approach. We determine the full scattering matrix of the system for the case of
leads with \textit{two} orbital channels coupled via weak \textit{s-o}
interactions inducing channel anticrossings. We show that this interband
coupling coherently transfers electrons between the channels and gives rise to
an additional modulation angle -- dependent on both the Rashba and Dresselhaus
interaction strengths -- which allows for further independent coherent control
of the electrons traversing the incoming leads. We derive explicit shot noise
formulas for a variety of correlated pairs (e.g., Bell states) and lead spin
polarizations. Interestingly, the singlet and \textit{each} of the triplets
defined along the quantization axis perpendicular to lead 1 (with the local
\textit{s-o} interaction) and in the plane of the beam splitter display
distinctive shot noise for injection energies near the channel anticrossings;
hence, one can tell apart all the triplets, in addition to the singlet, through
noise measurements. We also find that spin-orbit induced backscattering within
lead 1 reduces the visibility of the noise oscillations, due to the additional
partition noise in this lead. Finally, we consider injection of two-particle
wavepackets into leads with multiple discrete states and find that two-particle
entanglement can still be observed via noise bunching and antibunching.",0509038v1
2012-04-13,One-dimensional ballistic transport with FLAPW Wannier functions,"We present an implementation of the ballistic Landauer-B\""uttiker transport
scheme in one-dimensional systems based on density functional theory (DFT)
calculations within the full-potential linearized augmented plane-wave (FLAPW)
method. In order to calculate the conductance within the Green's function
method we map the electronic structure from the extended states of the FLAPW
calculation to Wannier functions which constitute a minimal localized basis
set. Our approach benefits from the high accuracy of the underlying FLAPW
calculations allowing us to address the complex interplay of structure,
magnetism, and spin-orbit coupling and is ideally suited to study
spin-dependent electronic transport in one-dimensional magnetic nanostructures.
To illustrate our approach we study ballistic electron transport in
non-magnetic Pt monowires with a single stretched bond including spin-orbit
coupling, and in ferromagnetic Co monowires with different collinear magnetic
alignment of the electrodes with the purpose of analysing the magnetoresistance
when going from tunneling to the contact regime. We further investigate
spin-orbit scattering due to an impurity atom. We consider two configurations:
a Co atom in a Pt monowire and vice versa. In both cases, the spin-orbit
induced band mixing leads to a change of the conductance upon switching the
magnetization direction from along the chain axis to perpendicular to it. The
main contribution stems from ballistic spin-scattering for the magnetic Co
impurity in the non-magnetic Pt monowire and for the Pt scatterer in the
magnetic Co monowire from the band formed from states with $d_{xy}$ and
$d_{x^2-y^2}$ orbital symmetry. We quantify this effect by calculating the
ballistic anisotropic magnetoresistance which displays values up to as much as
7% for ballistic spin-scattering and gigantic values of around 100% for the Pt
impurity in the Co wire.",1204.3002v1
2014-04-04,Toroidal order in metals without local inversion symmetry,"Toroidal order, given by a composite of electric and magnetic orders,
manifests itself not only in the peculiar magnetism but also in anomalous
transport and magnetoelectric effect. We report our theoretical results on the
influence and stability of a toroidal order in metals on the basis of a
microscopic model. We consider an effective single-band Hubbard-type model with
a site-dependent antisymmetric spin-orbit coupling, which is derived from a
four-band tight-binding model including the atomic spin-orbit coupling,
off-site hybridizations between orbitals with different parities, and
odd-parity crystalline electric field. For this single-band model on a layered
honeycomb lattice, we investigate the electronic structure, magnetotransport,
and magnetoelectric effect in the toroidal ordered state with a vortex-like
magnetic structure. The ferroic order of the microscopic toroidal moments acts
as an effective gauge field for electrons, which modulates the electronic band
structure with a shift of the band bottom in the momentum space. In addition,
the site-dependent antisymmetric spin-orbit coupling gives rise to highly
anisotropic Hall responses. The most salient feature is two different types of
magnetoelectric responses: one is a magnetic order with net toroidal
magnetization induced by an electric current perpendicular to the planes, and
the other is a uniform transverse magnetization induced by an electric current
within the planes. We examine the ground state of the effective model by the
mean-field approximation, and show that the toroidal order is stabilized by
strong electron correlations at low electron density. We also discuss the
temperature dependence of the magnetoelectric effects associated with
spontaneous toroidal ordering. Implications to experiments are also presented.",1404.1156v1
2016-11-14,Unusual nodal behaviors of the superconducting gap in the iron-based superconductor Ba(Fe$_{0.65}$Ru$_{0.35}$)$_2$As$_2$: Effects of spin-orbit coupling,"We have investigated the superconducting gap of optimally doped
Ba(Fe$_{0.65}$Ru$_{0.35}$)$_2$As$_2$ by angle-resolved photoemission
spectroscopy (APRES) using bulk-sensitive 7 eV laser and synchrotron radiation.
It was found that the gap is isotropic in the $k_x$-$k_y$ plane both on the
electron and hole Fermi surfaces (FSs). The gap magnitudes of two resolved hole
FSs show similar $k_z$ dependences and decrease as $k_z$ approaches $\sim$
2$\pi$/$c$ (i.e., around the Z point) unlike the other Fe-based superconductors
reported so far, where the superconducting gap of only one hole FS shows a
strong $k_z$ dependence. This unique gap structure can be understood in the
scenario that the $d_{z^2}$ orbital character is mixed into both hole FSs due
to the finite spin-orbit coupling between almost degenerate FSs and is
reproduced by calculations within the random phase approximation including the
spin-orbit coupling.",1611.04266v1
2020-04-29,Magnetized particle motion around magnetized Schwarzschild-MOG black hole,"In this paper, we have presented the studies of the motion of magnetized
particles and energetic processes around Schwarzschild black holes in modified
gravity (MOG). The study of circular stable orbits shows that orbits of
magnetized particles can not be stable for the values of magnetic coupling
parameter $\beta \geq 1$. It was also shown that the range of stable circular
orbits increases with the increase of both MOG and magnetic coupling
parameters, while the effects of magnetic interaction stronger than the
gravity. It was obtained that the increase of the MOG parameter causes the
increase of center-of-mass energy collision of magnetized particles. Moreover,
we have analyzed how to mimic the magnetic interaction with the spin of Kerr
and Schwarzschild-MOG black holes. We have obtained that the magnetic coupling
parameter can mimic the spin parameter $a \leq 0.15$ ($a \leq 0.28$) giving the
same radius of innermost contour(co)-rotating orbits at the values of the
parameter $\beta \in (-1,1)$ and the MOG parameter in the range $\alpha \in
(-0.17,0.28)$ while the MOG parameter $\alpha \in (-0.7, 0.9)$ mimics spin
parameter of the black hole with the range $|a| \in (0,1)$.",2004.14868v2
2016-10-27,Model spin-orbit coupling Hamiltonians for graphene systems,"We present a detailed theoretical study of effective spin-orbit coupling
(SOC) Hamiltonians for graphene based systems, covering global effects such as
proximity to substrates and local SOC effects resulting, for example, from
dilute adsorbate functionalization. Our approach combines group theory and
tight-binding descriptions. We consider structures with global point group
symmetries $D_{6h}$, $D_{3d}$, $D_{3h}$, $C_{6v}$, and $C_{3v}$ that represent,
for example, pristine graphene, graphene mini-ripple, planar boron-nitride,
graphene on a substrate and free standing graphone, respectively. The presence
of certain spin-orbit coupling parameters is correlated with the absence of the
specific point group symmetries. Especially in the case of $C_{6v}$---graphene
on a substrate, or transverse electric field---we point out the presence of a
third SOC parameter, besides the conventional intrinsic and Rashba
contributions, thus far neglected in literature. For all global structures we
provide effective SOC Hamiltonians both in the local atomic and Bloch forms.
Dilute adsorbate coverage results in the local point group symmetries $C_{6v}$,
$C_{3v}$, and $C_{2v}$ which represent the stable adsorption at hollow, top and
bridge positions, respectively. For each configuration we provide effective SOC
Hamiltonians in the atomic orbital basis that respect local symmetries. In
addition to giving specific analytic expressions for model SOC Hamiltonians, we
also present general (no-go) arguments about the absence of certain SOC terms.",1610.08794v1
2023-12-29,Spin-orbit coupling tuned crossover of gaped and gapless topological phases in the chalcopyrite HgSnX 2 (X=N/P): An ab-initio investigation,"The coupling between electron orbital momentum and spin momentum, known as
spin-orbit coupling (SOC), is a fundamental origin of a multitude of
fascinating physical phenomena, especially it holds paramount significance in
the realm of topological materials. In our work, we have predicted the
topological phase in Hg-based chalcopyrite compounds using the first principles
density functional theory. The initial focus was on HgSnN 2 , revealing it to
be a nonmagnetic Weyl semimetal, while HgSnP 2 displayed characteristics of a
strong topological insulator. What makes our work truly unique is that despite
both compounds having the same SOC strength, arises from Hg, they exhibit
distinct topological phases due to the distinct hybridization effect of the
Hg-5d and X-p bands. This finding can address a significant factor, i.e., the
effect of the band hybridization in deriving distinct topological phases,
keeping the symmetry aspect intact. Our results indicate that due to the
presence of band hybridization between the dominant X-np orbitals n=2 and 3 for
X=N and P respectively and a minor contribution from Hg-5d, we can tune the
topological phase by manipulating SOC strength, which equivalently achievable
by chemical substitutions. This investigation stands as a remarkable
illustration of the unique roles that hybridization plays in sculpting the
topological properties of these compounds while simultaneously preserving their
underlying symmetries.",2312.17669v1
2024-02-23,Simulating Transient X-ray Photoelectron Spectra of Fe(CO)5 and Its Photodissociation Products With Multireference Algebraic Diagrammatic Construction Theory,"Accurate simulations of transient X-ray photoelectron spectra (XPS) provide
unique opportunities to bridge the gap between theory and experiment in
understanding the photoactivated dynamics in molecules and materials. However,
simulating X-ray photoelectron spectra along a photochemical reaction pathway
is challenging as it requires accurate description of electronic structure
incorporating core-hole screening, orbital relaxation, electron correlation,
and spin-orbit coupling in excited states or at nonequilibrium ground-state
geometries. In this work, we employ the recently developed multireference
algebraic diagrammatic construction theory (MR-ADC) to investigate the
core-ionized states and X-ray photoelectron spectra of Fe(CO)5 and its
photodissociation products (Fe(CO)4, Fe(CO)3) following excitation with 266 nm
light. The simulated transient Fe 3p and CO 3{\sigma} XPS spectra incorporating
spin-orbit coupling and high-order electron correlation effects are shown to be
in a good agreement with the experimental measurements by Leitner et al. [J.
Chem. Phys. 149, 044307 (2018)]. Our calculations suggest that core-hole
screening, spin-orbit coupling, and ligand-field splitting effects are
similarly important in reproducing the experimentally observed chemical shifts
in transient Fe 3p XPS spectra of iron carbonyl complexes. Our results also
demonstrate that the MR-ADC methods can be very useful in interpreting the
transient XPS spectra of transition metal compounds.",2402.15599v1
2023-07-28,Type II t-J model and shared antiferromagnetic spin coupling from Hund's rule in superconducting La$_3$Ni$_2$O$_7$,"Recently, a 80 K superconductor was discovered in La$_3$Ni$_2$O$_7$ under
high pressure. Density function theory (DFT) calculations identify
$d_{x^2-y^2}$, $d_{z^2}$ as the active orbitals on the bilayer square lattice
with a $d^{8-x}$ configuration of of Ni per site. One naive expectation is to
describe this system in terms of a two-orbital t-J model. However, we emphasize
the importance of Hund's coupling $J_H$ and the $x=0$ limit should be viewed as
a spin-one Mott insulator. Especially, the significant Hund's coupling shares
the inter-layer super-exchange $J_\perp$ of the $d_{z^2}$ orbital to the
$d_{x^2-y^2}$ orbital, an effect that cannot be captured by conventional
perturbation or mean-field approaches. In this study, we first explore the
limit where the $d_{z^2}$ orbital is Mott localized, dealing with a one-orbital
bilayer t-J model focused on the $d_{x^2-y^2}$ orbital. Notably, we find that
strong inter-layer pairing survives up to $x=0.5$ hole doping driven by the
transmitted $J_\perp$, which explains the existence of a high Tc superconductor
in the experiment at this doping level. Next, we uncover the more realistic
situation where the $d_{z^2}$ orbital is slightly hole-doped and cannot be
simply integrated out. We take the $J_H\rightarrow +\infty$ limit and propose a
type II t-J model with four \textit{spin-half} singlon ($d^7$) states and three
\textit{spin-one} doublon ($d^8$) states. Employing a parton mean-field
approach, we recover similar results as in the one-orbital t-J model, but now
with the effect of the $J_\perp$ automatically generated. We propose future
experiments to electron dope the system to further enhance $T_c$.",2307.15706v3
2020-09-28,Effective Field Theory of Dark Matter Direct Detection With Collective Excitations,"We develop a framework for computing light dark matter direct detection rates
through single phonon and magnon excitations via general effective operators.
Our work generalizes previous calculations focused on spin-independent
interactions involving the total nucleon and electron numbers $N$ (the usual
route to excite phonons) and spin-dependent interactions involving the total
electron spin $S$ (the usual route to excite magnons), leading us to identify
new responses involving the orbital angular momenta $L$, as well as spin-orbit
couplings $L\otimes S$ in the target. All four types of responses can excite
phonons, while couplings to electron's $S$ and $L$ can also excite magnons. We
apply the effective field theory approach to a set of well-motivated
relativistic benchmark models, including (pseudo-)scalar mediated interactions,
and models where dark matter interacts via a multipole moment, such as a dark
electric dipole, magnetic dipole or anapole moment. We find that couplings to
point-like degrees of freedom $N$ and $S$ often dominate dark matter detection
rates, implying that exotic materials with orbital $L$ order or large
spin-orbit couplings $L\otimes S$ are not necessary to have strong reach to a
broad class of DM models. We highlight that phonon based crystal experiments in
active R&D (such as SPICE) will probe light dark matter models well beyond
those having a simple spin-independent interaction, including e.g. models with
dipole and anapole interactions. Lastly, we make publicly available a code,
PhonoDark, which computes single phonon production rates in a wide variety of
materials with the effective field theory framework.",2009.13534v2
2021-10-19,Electronic reconstruction and charge transfer in strained Sr$_2$CoIrO$_6$ double perovskite,"The electronic, magnetic and optical properties of the double perovskite
Sr$_2$CoIrO$_6$ (SCIO) under biaxial strain are explored in the framework of
density functional theory (DFT) including a Hubbard $U$ term and spin-orbit
coupling (SOC) in combination with absorption spectroscopy measurements on
epitaxial thin films. While the end member SrIrO$_3$ is a semimetal with a
quenched spin and orbital moment and bulk SrCoO$_3$ is a ferromagnetic (FM)
metal with spin and orbital moment of 2.50 and 0.13 $\mu_{B}$, respectively,
the double perovskite SCIO emerges as an antiferromagnetic Mott insulator with
antiparallel alignment of Co, Ir planes along the [110]-direction. Co exhibits
a spin and enhanced orbital moment of $\sim 2.35-2.45$ and $0.31-$0.45
$\mu_{B}$, respectively. Most remarkably, Ir acquires a significant spin and
orbital moment of 1.21-1.25 and 0.13 $\mu_{B}$, respectively. Analysis of the
orbital occupation indicates an electronic reconstruction due to a substantial
charge transfer from minority to majority spin states in Ir and from Ir to Co,
signaling an Ir$^{4+\delta}$, Co$^{4-\delta}$ configuration. Biaxial strain,
varied from -1.02% ($a_{\rm NdGaO_3}$) through 0% ($a_{\rm SrTiO_3}$) to 1.53%
($a_{\rm GdScO_3}$), influences in partcular the orbital polarization of the
$t_{2g}$ states and leads to a nonmonotonic change of the band gap between 163
and 235 meV. The absorption coefficient reveals a two plateau fearure due to
transitions from the valence to the lower lying narrow $t_{2g}$ and the higher
lying broader $e_{g}$ bands. Inclusion of many body effects, in particular,
excitonic effects by solving the Bethe-Salpeter equation (BSE), increases the
band gap by $\sim0.2$ and improves the agreement with the measured spectrum
concerning the position of the second peak at $\sim 2.6$ eV.",2110.09810v1
2004-08-31,Mesoscopic Spin Hall Effect in Multiprobe Ballistic Spin-Orbit Coupled Semiconductor Bridges,"We predict that unpolarized charge current driven through the longitudinal
leads attached to ballistic quantum-coherent two-dimensional electron gas
(2DEG) in semiconductor heterostructure will induce a {\em pure} spin current,
which is not accompanied by any net charge flow, in the transverse voltage
probes. Its magnitude can be tuned by the Rashba spin-orbit (SO) interaction
and, moreover, it is resilient to weak spin-independent scattering off
impurities within the metallic diffusive regime. While the polarization vector
of the spin transported through the transverse leads is not orthogonal to the
plane of 2DEG, we demonstrate that only two components (out-of-plane and
longitudinal) of the transverse spin current are signatures of the spin Hall
effect in four-probe Rashba spin-split semiconductor nanostructures. The linear
response spin Hall current, obtained from the multiprobe Landauer-B\"" uttiker
scattering formalism generalized for quantum transport of spin, is the
Fermi-surface determined nonequilibrium quantity whose scaling with the 2DEG
size $L$ reveals the importance of processes occurring on the spin precession
{\em mesoscale} $L_{\rm SO}$ (on which spin precesses by an angle $\pi$)--the
out-of-plane component of the transverse spin current exhibits quasioscillatory
behavior for $L \lesssim L_{\rm SO}$ (attaining the maximum value in 2DEGs of
the size $L_{\rm SO} \times L_{\rm SO}$), while it reaches the asymptotic value
in the macroscopic regime $L \gg L_{\rm SO}$. Furthermore, these values of the
spin Hall current can be manipulated by the measuring geometry defined by the
attached leads.",0408693v5
2021-09-08,Spin-orbit induced equilibrium spin currents in materials,"The existence of spin-currents in absence of any driving external fields is
commonly considered an exotic phenomenon appearing only in quantum materials,
such as topological insulators. We demonstrate instead that equilibrium spin
currents are a rather general property of materials with non negligible
spin-orbit coupling (SOC). Equilibrium spin currents can be present at the
surfaces of a slab. Yet, we also propose the existence of global equilibrium
spin currents, which are net bulk spin-currents along specific crystallographic
directions of materials. Equilibrium spin currents are allowed by symmetry in a
very broad class of systems having gyrotropic point groups. The physics behind
equilibrium spin currents is uncovered by making an analogy between electronic
systems with SOC and non-Abelian gauge theories. The electron spin can be seen
as the analogous of the color degree of freedom and equilibrium spin currents
can then be identified with diamagnetic color currents appearing as the
response to an effective non-Abelian magnetic field generated by SOC.
Equilibrium spin currents are not associated with spin transport and
accumulation, but they should nonetheless be carefully taken into account when
computing transport spin currents. We provide quantitative estimates of
equilibrium spin currents for several systems, specifically metallic surfaces
presenting Rashba-like surface states, nitride semiconducting nanostructures
and bulk materials, such as the prototypical gyrotropic medium tellurium. In
doing so, we also point out the limitations of model approaches showing that
first-principles calculations are needed to obtain reliable predictions. We
therefore use Density Functional Theory computing the so-called bond currents,
which represent a powerful tool to understand the relation between equilibrium
currents, electronic structure and crystal point group.",2109.03790v2
2014-07-25,"Strong-field tidal distortions of rotating black holes: Formalism and results for circular, equatorial orbits","Tidal coupling between members of a compact binary system can have an
interesting and important influence on that binary's dynamical inspiral. Tidal
coupling also distorts the binary's members, changing them (at lowest order)
from spheres to ellipsoids. At least in the limit of fluid bodies and Newtonian
gravity, there are simple connections between the geometry of the distorted
ellipsoid and the impact of tides on the orbit's evolution. In this paper, we
develop tools for investigating tidal distortions of rapidly rotating black
holes using techniques that are good for strong-field, fast-motion binary
orbits. We use black hole perturbation theory, so our results assume extreme
mass ratios. We develop tools to compute the distortion to a black hole's
curvature for any spin parameter, and for tidal fields arising from any bound
orbit, in the frequency domain. We also develop tools to visualize the
horizon's distortion for black hole spin $a/M \le \sqrt{3}/2$ (leaving the more
complicated $a/M > \sqrt{3}/2$ case to a future analysis). We then study how a
Kerr black hole's event horizon is distorted by a small body in a circular,
equatorial orbit. We find that the connection between the geometry of tidal
distortion and the orbit's evolution is not as simple as in the Newtonian
limit.",1407.6983v3
2011-02-10,An effective quantum parameter for strongly correlated metallic ferromagnets,"The correlated motion of electrons in multi-orbital metallic ferromagnets is
investigated in terms of a realistic Hubbard model with {\cal N}-fold orbital
degeneracy and arbitrary intra- and inter-orbital Coulomb interactions U and J
using a Goldstone-mode-preserving non-perturbative scheme. An effective quantum
parameter '\hbar'=\frac{U^2+({\cal N}-1)J^2}{(U+({\cal N}-1)J)^2} is obtained
which determines, in analogy with 1/S for quantum spin systems and 1/N for the
N-orbital Hubbard model, the strength of correlation-induced quantum
corrections to magnetic excitations. The rapid suppression of this quantum
parameter with Hund's coupling J, especially for large {\cal N}, provides
fundamental insight into the phenomenon of strong stabilization of metallic
ferromagnetism by orbital degeneracy and Hund's coupling. This approach is
illustrated for the case of ferromagnetic iron and the half metallic Heusler
alloy Co_2 Mn Si. For realistic values for iron, the calculated spin stiffness
and Curie temperature values obtained are in quantitative agreement with
measurements. Significantly, the contribution of long wavelength modes is shown
to yield a nearly ~25% reduction in the calculated Curie temperature. Finally,
an outline is presented for extending the approach to generic multi-band
metallic ferromagnets including realistic band-structure features of
non-degenerate orbitals and inter-orbital hopping as obtained from LDA
calculations.",1102.2115v1
2018-05-31,Investigation into the role of the orbital moment in a series of isostructural weak ferromagnets,"The orbital contribution to the magnetic moment of the transition metal ion
in the isostructural weak ferromagnets ACO$_3$ (A=Mn,Co,Ni) and FeBO$_3$ was
investigated by a combination of first-principles calculations, non-resonant
x-ray magnetic scattering and x-ray magnetic circular dichroism. A non-trivial
evolution of the orbital moment as a function of the $3d$ orbitals filling is
revealed, with an anomalously large value found in the Co member of the family.
Here, the coupling between magnetic and lattice degrees of freedom produced by
the spin-orbit interaction results in a large single-ion anisotropy and a
peculiar magnetic-moment-induced electron cloud distortion, evidenced by the
appearance of a subtle scattering amplitude at space group-forbidden
reflections and significant magnetostrictive effects. Our results, which
complement a previous investigation on the sign of the Dzyaloshinskii$-$Moriya
interaction across the series, highlight the importance of spin-orbit coupling
in the physics of weak ferromagnets and prove the ability of modern
first-principles calculations to predict the properties of materials where the
Dzyaloshinskii$-$Moriya interaction is a fundamental ingredient of the magnetic
Hamiltonian.",1805.12423v2
2019-04-16,Engineering spin squeezing in a 3D optical lattice with interacting spin-orbit-coupled fermions,"One of the most important tasks in modern quantum science is to coherently
control and entangle many-body systems, and to subsequently use these systems
to realize powerful quantum technologies such as quantum-enhanced sensors.
However, many-body entangled states are difficult to prepare and preserve since
internal dynamics and external noise rapidly degrade any useful entanglement.
Here, we introduce a protocol that counterintuitively exploits inhomogeneities,
a typical source of dephasing in a many-body system, in combination with
interactions to generate metrologically useful and robust many-body entangled
states. Motivated by current limitations in state-of-the-art three-dimensional
(3D) optical lattice clocks (OLCs) operating at quantum degeneracy, we use
local interactions in a Hubbard model with spin-orbit coupling to achieve a
spin-locking effect. In addition to prolonging inter-particle spin coherence,
spin-locking transforms the dephasing effect of spin-orbit coupling into a
collective spin-squeezing process that can be further enhanced by applying a
modulated drive. Our protocol is fully compatible with state-of-the-art 3D OLC
interrogation schemes and may be used to improve their sensitivity, which is
currently limited by the intrinsic quantum noise of independent atoms. We
demonstrate that even with realistic experimental imperfections, our protocol
may generate $\sim10$--$14$ dB of spin squeezing in $\sim1$ second with
$\sim10^2$--$10^4$ atoms. This capability allows OLCs to enter a new era of
quantum enhanced sensing using correlated quantum states of driven
non-equilibrium systems.",1904.07866v2
2020-06-19,"Spin-orbit-proximitized ferromagnetic metal by monolayer transition metal dichalcogenide: Atlas of spectral functions, spin textures and spin-orbit torques in Co/MoSe$_2$, Co/WSe$_2$ and Co/TaSe$_2$ heterostructures","The bilayer heterostructures composed of an ultrathin ferromagnetic metal
(FM) and a material hosting strong spin-orbit (SO) coupling are principal
resource for SO torque and spin-to-charge conversion nonequilibrium effects in
spintronics. We demonstrate how hybridization of wavefunctions of Co layer and
a monolayer of transition metal dichalcogenides (TMDs)---such as semiconducting
MoSe$_2$ and WSe$_2$ or metallic TaSe$_2$---can lead to dramatic transmutation
of electronic and spin structure of Co within some distance away from its
interface with TMD, when compared to the bulk of Co or its surface in contact
with vacuum. This is due to proximity induced SO splitting of Co bands encoded
in the spectral functions and spin textures on its monolayers, which we obtain
using noncollinear density functional theory (ncDFT) combined with equilibrium
Green function (GF) calculations. In fact, SO splitting is present due to
structural inversion asymmetry of the bilayer even if SO coupling within TMD
monolayer is artificially switched off in ncDFT calculations, but switching it
on makes the effects associated with proximity SO coupling within Co layer
about five times larger. Injecting spin-unpolarized charge current through
SO-proximitized monolayers of Co generates nonequilibrium spin density over
them, so that its cross product with the magnetization of Co determines SO
torque. The SO torque computed via first-principles quantum transport
methodology, which combines ncDFT with nonequilibrium GF calculations, can be
used as the screening parameter to identify optimal combination of materials
and their interfaces for applications in spintronics. In particular, we
identify heterostructure two-monolayer-Co/monolayer-WSe$_2$ as the most
optimal.",2006.11335v1
2021-04-15,Interacting holes in Si and Ge double quantum dots: from a multiband approach to an effective-spin picture,"The states of two electrons in tunnel-coupled semiconductor quantum dots can
be effectively described in terms of a two-spin Hamiltonian with an isotropic
Heisenberg interaction. A similar description needs to be generalized in the
case of holes due to their multiband character and spin-orbit coupling, which
mixes orbital and spin degrees of freedom, and splits $J=3/2$ and $J = 1/2$
multiplets. Here we investigate two-hole states in prototypical coupled Si and
Ge quantum dots via different theoretical approaches. Multiband
$\boldsymbol{k}\cdot\boldsymbol{p}$ and Configuration-Interaction calculations
are combined with entanglement measures in order to thoroughly characterize the
two-hole states in terms of band mixing and justify the introduction of an
effective spin representation, which we analytically derive a from generalized
Hubbard model. We find that, in the weak interdot regime, the ground state and
first excited multiplet of the two-hole system display -- unlike their
electronic counterparts -- a high degree of $J$-mixing, even in the limit of
purely heavy-hole states. The light-hole component additionally induces
$M$-mixing and a weak coupling between spinors characterized by different
permutational symmetries.",2104.07730v2
2008-06-20,Effective Hamiltonian for FeAs based superconductors,"The recently discovered FeAs-based superconductors show intriguing behavior
and unusual dynamics of electrons and holes which occupy the Fe $d$-orbitals
and As $4s$ and $4p$ orbitals. Starting from the atomic limit, we carry out a
strong coupling expansion to derive an effective hamiltonian that describes the
electron and hole behavior. The hopping and the hybridization parameters
between the Fe $d$ and As $s$ and $p$-orbitals are obtained by fitting the
results of our density-functional-theory calculations to a tight-binding model
with nearest-neighbor interactions and a minimal orbital basis. We find that
the effective hamiltonian, in the strong on-site Coulomb repulsion limit,
operates on three distinct sub-spaces coupled through Hund's rule. The three
sub-spaces describe different components (or subsystems): (a) one spanned by
the $d_{x^2-y^2}$ Fe orbital; (b) one spanned by the degenerate atomic Fe
orbitals $d_{xz}$ and $d_{yz}$; and (c) one spanned by the atomic Fe orbitals
$d_{xy}$ and $d_{z^2}$. Each of these Hamiltonians is an extended t-t'-J-J'
model and is characterized by different coupling constants and filling factors.
For the case of the undoped material the second subspace alone prefers a ground
state characterized by a spin-density-wave order similar to that observed in
recent experimental studies, while the other two subspaces prefer an
antiferromagnetic order. We argue that the observed spin-density-wave order
minimizes the ground state energy of the total hamiltonian.",0806.3432v5
2012-09-02,Tensor-optimized shell model for the Li isotopes with a bare nucleon-nucleon interaction,"We study the Li isotopes systematically in terms of the tensor-optimized
shell model (TOSM) by using a bare nucleon-nucleon interaction as the AV8'
interaction. The short-range correlation is treated in the unitary correlation
operator method (UCOM). Using the TOSM+UCOM approach, we investigate the role
of the tensor force on each spectrum of the Li isotopes. It is found that the
tensor force produces quite a characteristic effect on various states in each
spectrum and those spectra are affected considerably by the tensor force. The
energy difference between the spin-orbit partner, the p1/2 and p3/2 orbits of
the last neutron, in 5Li is caused by opposite roles of the tensor correlation.
In 6Li, the spin-triplet state in the LS coupling configuration is favored
energetically by the tensor force in comparison with jj coupling shell model
states. In 7,8,9Li, the low-lying states containing extra neutrons in the p3/2
orbit are favored energetically due to the large tensor contribution to allow
the excitation from the 0s orbit to the p1/2 orbit by the tensor force. Those
three nuclei show the jj coupling character in their ground states which is
different from 6Li.",1209.0150v1
2005-04-07,"Coriolis force, geometric phase, and spin-electric coupling in semiconductors","We consider the response of an effective spin of a charge carrier to an
adiabatic rotation of its crystal momentum induced by electric field. This
rotation gives rise to Coriolis pseudo-force that is responsible for torque
acting on the orbital momentum of a particle. Mediated by a spin-orbit coupling
in the valence band this perturbation leads to a spin-electric coupling that
may affect the coherent transport properties of a charge carrier and cause a
spin precession in zero magnetic fields. In the static uniform electric field
the derived effective spin-Hamiltonians of the carriers in the conduction and
light hole bands are homologous to the Rashba Hamiltonian. These effects may be
also interpreted as a manifestation of, in general, a non-Abelian gauge
potential and can be described in purely geometric terms as a consequence of
the corresponding holonomy. We demonstrate that in the conduction band the
strength of the associated covariant gauge field is proportional to the
effective electron g-tensor and is controllable by gate fields or a strain
applied to the crystal.",0504183v6
2016-05-17,Spin-lattice coupling mediated multiferroicity in (ND4)2FeCl5D2O,"We report a neutron diffraction study of the multiferroic mechanism in
(ND4)2FeCl5D2O, a molecular compound that exhibits magnetically induced
ferroelectricity. This material exhibits two successive magnetic transitions on
cooling: a long-range order transition to an incommensurate (IC) collinear
sinusoidal spin state at TN=7.3 K, followed by a second transition to an IC
cycloidal spin state at TFE=6.8 K, the later of which is accompanied by
spontaneous ferroelectric polarization. The cycloid structure is strongly
distorted by spin-lattice coupling as evidenced by the observations of both odd
and even higher-order harmonics associated with the cycloid wave vector, and a
weak commensurate phase that coexists with the IC phase. The appearance of the
2nd-order harmonic coincides with the onset of the electric polarization,
thereby providing unambiguous evidence that the induced electric polarization
is mediated by the spin-lattice interaction. Our results for this system, in
which the orbital angular momentum is expected to be quenched, are remarkably
similar to those of the prototypical TbMnO3, in which the magnetoelectric
effect is attributed to spin-orbit coupling.",1605.05214v1
2019-10-17,Scattering-induced and highly tunable by gate damping-like spin-orbit torque in graphene doubly proximitized by two-dimensional magnet Cr$_2$Ge$_2$Te$_6$ and WS$_2$,"Graphene sandwiched between semiconducting monolayers of ferromagnet
Cr$_2$Ge$_2$Te$_6$ and transition-metal dichalcogenide WS$_2$ acquires both
spin-orbit (SO), of valley-Zeeman and Rashba types, and exchange couplings.
Using first-principles combined with quantum transport calculations, we predict
that such doubly proximitized graphene within van der Waals heterostructure
will exhibit SO torque driven by unpolarized charge current. This system
lacking spin Hall current, putatively considered to be necessary for efficient
damping-like (DL) SO torque that plays a key role in magnetization switching,
demonstrates how DL torque component can be generated solely by skew-scattering
off spin-independent potential barrier or impurities in purely two-dimensional
electronic transport due to the presence of proximity SO coupling and its spin
texture tilted out-of-plane. This leads to current-driven nonequilibrium spin
density emerging in all spatial directions, whose cross product with proximity
magnetization yields DL SO torque, unlike the ballistic regime with no
scatterers in which only field-like (FL) SO torque appears. In contrast to SO
torque on conventional metallic ferromagnets in contact with three dimensional
SO-coupled materials, the ratio of FL and DL torque can be tuned by more than
an order of magnitude via combined top and back gates.",1910.08072v3
2006-10-25,Ballistic spin field-effect transistors: Multichannel effects,"We study a ballistic spin field-effect transistor (SFET) with special
attention to the issue of multi-channel effects. The conductance modulation of
the SFET as a function of the Rashba spin-orbit coupling strength is
numerically examined for the number of channels ranging from a few to close to
100. Even with the ideal spin injector and collector, the conductance
modulation ratio, defined as the ratio between the maximum and minimum
conductances, decays rapidly and approaches one with the increase of the
channel number. It turns out that the decay is considerably faster when the
Rashba spin-orbit coupling is larger. Effects of the electronic coherence are
also examined in the multi-channel regime and it is found that the coherent
Fabry-Perot-like interference in the multi-channel regime gives rise to a
nested peak structure. For a nonideal spin injector/collector structure, which
consists of a conventional metallic ferromagnet-thin insulator-2DEG
heterostructure, the Rashba-coupling-induced conductance modulation is strongly
affected by large resonance peaks that arise from the electron confinement
effect of the insulators. Finally scattering effects are briefly addressed and
it is found that in the weakly diffusive regime, the positions of the resonance
peaks fluctuate, making the conductance modulation signal sample-dependent.",0610685v2
2007-12-28,"Half Semimetallic Antiferromagnetism in the Sr$_2$CrTO$_6$ System, T=Os, Ru","Double perovskite Sr$_2$CrOsO$_6$ is (or is very close to) a realization of a
spin-asymmetric semimetallic compensated ferrimagnet, according to first
principles calculations. This type of near-half metallic antiferromagnet is an
unusual occurrence, and more so in this compound because the zero gap is
accidental rather than being symmetry determined. The large spin-orbit coupling
(SOC) of osmium upsets the spin balance (no net spin moment without SOC): it
reduces the Os spin moment by 0.27 $\mu_B$ and induces an Os orbital moment of
0.17 $\mu_B$ in the opposite direction. The effects combine (with small oxygen
contributions) to give a net total moment of 0.54 $\mu_B$ per cell in \scoo,
reflecting a large impact of SOC in this compound. This value is in moderately
good agreement with the measured saturation moment of 0.75 $\mu_B$. The value
of the net moment on the Os ion obtained from neutron diffraction (0.73 $\mu_B$
at low temperature) differs from the calculated value (1.14 $\mu_B$). Rather
surprisingly, in isovalent Sr$_2$CrRuO$_6$ the smaller SOC-induced spin changes
and orbital moments (mostly on Ru) almost exactly cancel. This makes
Sr$_2$CrRuO$_6$ a ""half (semi)metallic antiferromagnet"" (practically vanishing
net total moment) even when SOC is included, with the metallic channel being a
small-band-overlap semimetal. Fixed spin moment (FSM) calculations are
presented for each compound, illustrating how they provide different
information than in the case of a nonmagnetic material. These FSM results
indicate that the Cr moment is an order of magnitude stiffer against
longitudinal fluctuations than is the Os moment.",0712.4308v1
2017-08-08,Spin-orbit-torque driven magnetoimpedance in Pt-layer/magnetic-ribbon heterostructures,"When a flow of electron passes through a paramagnetic layer with strong
spin-orbit-coupling such as platinum (Pt), a net spin current is produced via
spin Hall effect (SHE). This spin current can exert a torque on the
magnetization of an adjacent ferromagnetic layer which can be probed via
magnetization dynamic response, e.g. spin-torque ferromagnetic resonance
(ST-FMR). Nevertheless, that effect in lower frequency magnetization dynamic
regime (MHz) where skin effect occurs in high permeability ferromagnetic
conductors namely the magneto-impedance (MI) effect can be fundamentally
important which has not been studied so far. Here, by utilizing the MI effect
in magnetic-ribbon/Pt heterostructure with high magnetic permeability that
allows the ac current effectively confined at the skin depth of ~100 nm
thickness, the effect of spin-orbit-torque (SOT) induced by the SHE probed via
MI measurement is investigated. We observed a systematic MI frequency shift
that increases by increasing the applied current amplitude and thickness of the
Pt layer (varying from 0 nm to 20 nm). In addition, the role of Pt layer in
ribbon/Pt heterostructure is evaluated with ferromagnetic resonance (FMR)
effect representing standard Gilbert damping increase as the result of presence
of the SHE. Our results unveil the role of SOT in dynamic control of the
transverse magnetic permeability probed with impedance spectroscopy as useful
and valuable technique for detection of future SHE devices.",1708.02402v2
2017-04-11,Uniaxial strain control of spin-polarization in multicomponent nematic order of BaFe$_{2}$As$_{2}$,"The iron-based high temperature superconductors exhibit a rich phase diagram
reflecting a complex interplay between spin, lattice, and orbital degrees of
freedom [1-4]. The nematic state observed in many of these compounds epitomizes
this complexity, by entangling a real-space anisotropy in the spin fluctuation
spectrum with ferro-orbital order and an orthorhombic lattice distortion [5-7].
A more subtle and much less explored facet of the interplay between these
degrees of freedom arises from the sizable spin-orbit coupling present in these
systems, which translates anisotropies in real space into anisotropies in spin
space. Here, we present a new technique enabling nuclear magnetic resonance
under precise tunable strain control, which reveals that upon application of a
tetragonal symmetry-breaking strain field, the magnetic fluctuation spectrum in
the paramagnetic phase of BaFe$_{2}$As$_{2}$ also acquires an anisotropic
response in spin-space. Our results unveil a hitherto uncharted internal spin
structure of the nematic order parameter, indicating that similar to liquid
crystals, electronic nematic materials may offer a novel route to
magneto-mechanical control.",1704.03566v1
2020-10-04,Unified Framework for Charge-Spin Interconversion in Spin-Orbit Materials,"Materials with spin-orbit coupling are of great interest for various
spintronics applications due to the efficient electrical generation and
detection of spin-polarized electrons. Over the past decade, many materials
have been studied, including topological insulators, transition metals, Kondo
insulators, semimetals, semiconductors, and oxides; however, there is no
unifying physical framework for understanding the physics and therefore
designing a material system and devices with the desired properties. We present
a model that binds together the experimental data observed on the wide variety
of materials in a unified manner. We show that in a material with a given
spin-momentum locking, the density of states plays a crucial role in
determining the charge-spin interconversion efficiency, and a simple inverse
relationship can be obtained. Remarkably, experimental data obtained over the
last decade on many different materials closely follow such an inverse
relationship. We further deduce two figure-of-merits of great current interest:
the spin-orbit torque (SOT) efficiency (for the direct effect) and the inverse
Rashba-Edelstein effect length (for the inverse effect), which statistically
show good agreement with the existing experimental data on wide varieties of
materials. Especially, we identify a scaling law for the SOT efficiency with
respect to the carrier concentration in the sample, which agrees with existing
data. Such an agreement is intriguing since our transport model includes only
Fermi surface contributions and fundamentally different from the conventional
views of the SOT efficiency that includes contributions from all the occupied
states.",2010.01484v2
2022-02-15,Cooperative effect of electrons spin polarization in a hybrid nanostructure of a magnetic thin film with adsorbed chiral molecules studied with non-spin-polarized scanning tunneling microscopy,"Polyalanine molecules (PA) with an {\alpha}-helix conformation gathered
recently a lot of interest as the propagation of electrons through the chiral
backbone structure comes along with spin polarization of the transmitted
electrons. By means of scanning tunneling microscopy and spectroscopy at
ambient conditions, PA molecules adsorbed on surfaces of epitaxial magnetic
Al2O3/Pt/Au/Co/Au nanostructures with perpendicular anisotropy were studied.
Thereby, a correlation between the PA molecules ordering at the surface with
the electron tunneling across this hybrid system as a function of the substrate
magnetization orientation as well as the coverage density and helicity of the
was observed. The highest spin polarization values, P, were found for
well-ordered self-assembled monolayers and with a defined chemical coupling of
the molecules to the magnetic substrate surface, showing that the current
induced spin selectivity is a cooperative effect. Thereby, P deduced from the
electron transmission along unoccupied molecular orbitals of the helical
molecules is larger as compared to values derived from the occupied molecular
orbitals. Apparently, the larger orbital overlap is resulting in a higher
electron mobility yielding a higher P value. By switching the magnetization
direction of the Co-layer, it was demonstrated that the non-spin-polarized STM
can be used to study chiral molecules with a sub-molecular resolution, to
detect properties of buried magnetic layers and to detect the spin polarization
of the molecules from the change of the magnetoresistance of such hybrid
structures.",2202.07417v1
2023-06-15,Wegner's Ising gauge spins versus Kitaev's Majorana partons: Mapping and application to anisotropic confinement in spin-orbital liquids,"Emergent gauge theories take a prominent role in the description of quantum
matter, supporting deconfined phases with topological order and fractionalized
excitations. A common construction of $\mathbb{Z}_2$ lattice gauge theories,
first introduced by Wegner, involves Ising gauge spins placed on links and
subject to a discrete $\mathbb{Z}_2$ Gauss law constraint. As shown by Kitaev,
$\mathbb{Z}_2$ lattice gauge theories also emerge in the exact solution of
certain spin systems with bond-dependent interactions. In this context, the
$\mathbb{Z}_2$ gauge field is constructed from Majorana fermions, with gauge
constraints given by the parity of Majorana fermions on each site. In this
work, we provide an explicit Jordan-Wigner transformation that maps between
these two formulations on the square lattice, where the Kitaev-type gauge
theory emerges as the exact solution of a spin-orbital (Kugel-Khomskii)
Hamiltonian. We then apply our mapping to study local perturbations to the
spin-orbital Hamiltonian, which correspond to anisotropic interactions between
electric-field variables in the $\mathbb{Z}_2$ gauge theory. These are shown to
induce anisotropic confinement that is characterized by emergence of
weakly-coupled one-dimensional spin chains. We study the nature of these phases
and corresponding confinement transitions in both absence and presence of
itinerant fermionic matter degrees of freedom. Finally, we discuss how our
mapping can be applied to the Kitaev spin-1/2 model on the honeycomb lattice.",2306.09405v2
2023-12-21,Electric dipole spin resonance in single and two electron quantum dot defined in two-dimensional electron gas at the SrTiO$_3$/LaAlO$_3$ interface,"We investigate the energy spectrum of a single and two electron quantum dot
(QD) embedded in two dimensional electron gas at the interface between
SrTiO$_3$ and LaAlO$_3$, in the presence of the external magnetic field. For
this purpose the three band model of $3d$-electrons defined on the square
lattice of Ti ions was utilized. We demonstrate that, for the weak parabolic
confinement potential, the low energy spectrum is sufficiently well described
by the effective Hamiltonian reduced to the one $d_{xy}$ orbital with the
spin-orbit interaction originating from the coupling to the $d_{xz}$, $d_{yz}$
bands. This is not the case for stronger confinement where contribution of the
states related to the $d_{xz/yz}$ orbital is relevant. Based on the time
depended calculations we discuss in details the manipulation of the electron
spin in QD by external AC voltages, in the context of the electric dipole spin
resonance. The allowed and forbidden transitions are discussed in details with
respect to the parity selection rule. Our calculations show that for a single
electron QD the spin-flip in the ground-state has a character of a Rabi
resonance while for two electrons the singlet-triplet transition is forbidden
by the parity symmetry. For the two electrons QD, we demonstrate that the
spin-flip transition can still be accomplished via a second-order, two-photon
process that has a two-state Rabi character for low AC field amplitude. The
violation of the parity symmetry on the spin-flip transitions is also analyzed.",2312.13862v1
2021-02-24,Theory of the $sp-d$ coupling of transition metal impurities with free carriers in ZnO,"The $s,p-d$ exchange coupling between the spins of band carriers and of
transition metal (TM) dopants ranging from Ti to Cu in ZnO is studied within
the density functional theory. The $+U$ corrections are included to reproduce
the experimental ZnO band gap and the dopant levels. The $p-d$ coupling reveals
unexpectedly complex features. In particular, (i) the $p-d$ coupling constants
$N_0\beta$ vary about 10 times when going from V to Cu, (ii) not only the value
but also the sign of $N_0\beta$ depends on the charge state of the dopant,
(iii) the $p-d$ coupling with the heavy holes and the light holes is not the
same; in the case of Fe, Co and Ni, $N_0\beta$s for the two subbands can differ
twice, and for Cu the opposite sign of the coupling is found for light and
heavy holes. The main features of the $p-d$ coupling are determined by the
$p-d$ hybridization between the $d$(TM) and $p$(O) orbitals. In contrast, the
$s-d$ coupling constant $N_0\alpha$ is almost the same for all TM ions, and
does not depend on the charge state of the dopant. The TM-induced spin
polarization of the $p$(O) orbitals contributes to the $s-d$ coupling,
enhancing $N_0\alpha$.",2102.12338v1
2002-05-09,Coexistence of spin-triplet superconductivity and ferromagnetism induced by the Hund's rule exchange,"We discuss general implications of the local spin-triplet pairing among
correlated fermions that is induced by the Hund's rule coupling in orbitally
degenerate systems. The quasiparticle energies, the magnetic moment, and the
superconducting gap are determined for principal superconducting phases, in the
situation with the exchange field induced by both the local Coulomb and the
Hund's rule exchange interactions. The phase diagram, as well as the evolution
in an applied magnetic field of the spin-triplet paired states near the Stoner
threshold is provided for a model two-band system. The appearance of the
spin-polarized superconducting phase makes the Stoner threshold a hidden
critical point, since the pairing creates a small but detectable uniform
magnetization. The stability of the superconducting state against the
ferromagnetism with an alternant orbital ordering appearing in the
strong-coupling limit is also discussed.",0205203v1
2004-10-08,Intense terahertz laser fields on a two-dimensional electron gas with Rashba spin-orbit coupling,"The spin-dependent density of states and the density of spin polarization of
an InAs-based two-dimensional electron gas with the Rashba spin-orbit coupling
under an intense terahertz laser field are investigated by utilizing the
Floquet states to solve the time-dependent Schr\""odinger equation.
  It is found that both densities are strongly affected by the terahertz laser
field. Especially a terahertz magnetic moment perpendicular to the external
terahertz laser field in the electron gas is induced. This effect can be used
to convert terahertz electric signals into terahertz magnetic ones efficiently.",0410186v2
2005-10-01,Spin-polarized proximity effect in superconducting junctions,"We study spin dependent phonomena in superconducting junctions in both
ballistic and diffusive regimes. For ballistic junctions we study both
ferromagnet / $s$- and d-wave superconductor junctions and two dimensional
electron gas / s-wave superconductor junctions with Rashba spin-orbit coupling.
It is shown that the exchange field alway suppresses the conductance while the
Rashba spin-orbit coupling can enhance it. In the latter part of the article we
study the diffusive ferromagnet / insulator / $s$- and d-wave superconductor
junctions, where the proximity effect can be enhanced by the exchange field in
contrast to common belief. It is shown that the resonant proximity effect
originating from the exchange field strongly influences the tunneling
conductance and density of states.",0510008v2
2006-01-07,Fermi Surface and Anisotropic Spin-Orbit Coupling of Sb(111) studied by Angle-Resolved Photoemission Spectroscopy,"High-resolution angle-resolved photoemission spectroscopy has been performed
on Sb(111) to elucidate the origin of anomalous electronic properties in
group-V semimetal surfaces. The surface was found to be metallic despite the
semimetallic character of bulk. We clearly observed two surface-derived Fermi
surfaces which are likely spin split, demonstrating that the spin-orbit
interaction plays a dominant role in characterising the surface electronic
states of group-V semimetals. Universality/disimilarity of the electronic
structure in Bi and Sb is discussed in relation to the granular
superconductivity, electron-phonon coupling, and surface charge/spin density
wave.",0601133v1
2006-06-14,Electronic structure and transport for a laser-field-irradiated quantum wire with Rashba spin-orbit coupling,"We investigate theoretically the electronic structure and transport for a
two-level quantum wire with Rashba spin-orbit coupling (SOC) under the
irradiation of an external laser field at low temperatures. The photon-induced
transitions between SOC-splitted subbands with the same lateral confinement
quantum numbers and between subbands with different confinement quantum number
are expected. Using the method of equation of motion (EOM) for Keldysh
nonequilibrium Green's functions (NGF), we examine the time-averaged density of
states (DOS) and the spin polarized conductance for the system with photon
polarization perpendicular to the wire direction. Through the analytical
analysis and some numerical examples, the interplay effects of the external
laser field and the Rashba SOC on both the DOS and the conductance of the
system are demonstrated and discussed. It is found that the external laser
field can adjust the spin polarization rate and the transport of the quantum
wire system with some proper Rashba SOC strengths.",0606379v1
2006-07-10,Spin Fine Structure in Optically Excited Quantum Dot Molecules,"The interaction between spins in coupled quantum dots is revealed in distinct
fine structure patterns in the measured optical spectra of InAs/GaAs double
quantum dot molecules containing zero, one, or two excess holes. The fine
structure is explained well in terms of a uniquely molecular interplay of spin
exchange interactions, Pauli exclusion and orbital tunneling. This knowledge is
critical for converting quantum dot molecule tunneling into a means of
optically coupling not just orbitals, but spins.",0607241v4
2006-09-13,Tunneling currents in ferromagnetic systems with multiple broken symmetries,"SHORTENED ABSTRACT: A system exhibiting multiple simultaneously broken
symmetries offers the opportunity to influence physical phenomena such as
tunneling currents by means of external control parameters. In this paper, we
consider the broken SU(2) (internal spin) symmetry of ferromagnetic systems
coexisting with \textit{i)} the broken U(1) symmetry of superconductors and
\textit{ii)} the broken spatial inversion symmetry induced by a Rashba term in
a spin-orbit coupling Hamiltonian. In order to study the effect of these broken
symmetries, we consider tunneling currents that arise in two different systems;
tunneling junctions consisting of non-unitary spin-triplet ferromagnetic
superconductors and junctions consisting of ferromagnets with spin-orbit
coupling.",0609314v2
2007-01-30,Excitonic condensation under spin-orbit coupling and BEC-BCS crossover,"The condensation of electron-hole (e-h) pairs is studied at zero temperature
and in the presence of a weak spin-orbit coupling (SOC) in the inversion-layer
quantum wells. Under realistic conditions, a perturbative SOC can have
observable effects in the order parameter of the experimentally
long-searched-for excitonic condensate. Firstly, the fermion exchange symmetry
is absent for the e-h pairs indicating a counterexample to the known
classification schemes of fermion pairing. With the lack of fermion exchange,
the condensate spin has no definite parity. Additionally, the excitonic SOC
breaks the rotational symmetry yielding a complex order parameter in an
unconventional way, i.e. the phase pattern of the order parameter is a function
of the condensate density. This is manifested through finite off diagonal
components of the static spin susceptibility, suggesting a new experimental
method to confirm an excitonic condensate.",0701751v3
2010-04-26,Fermiology and transport properties of the half-metallic itinerant ferromagnet CoS$_2$: influence of spin orbit coupling,"Electronic structure calculations were performed on the compound CoS$_2$, an
itinerant ferromagnet whose magnetic properties can be understood in terms of
spin fluctuation theory. We have identified nesting features in the Fermi
surface of the compound, active for long wavelength spin fluctuations. The
electronic structure of the material is close to a half-metal. We show the
importance of introducing spin-orbit coupling (SOC) in the calculations, that
partially destroys the half-metallicity of the material. By means of transport
properties calculations, we have quantified the influence of SOC in the
conductivity at room temperature, with an important decrease comparing to the
GGA alone conductivity. SOC also helps to understand the negative 0 of the
material, whose conductivity varies by a few percent with the introduction of
small perturbations in the states around the Fermi level.",1004.4472v1
2011-06-08,Topological Order and Semions in a Strongly Correlated Quantum Spin Hall Insulator,"We provide a self-consistent mean-field framework to study the effect of
strong interactions in a quantum spin Hall insulator on the honeycomb lattice.
We identify an exotic phase for large spin-orbit coupling and intermediate
Hubbard interaction. This phase is gapped in the bulk, has gapless edge states
and does not break any symmetry. Instead, we find a four-fold topological
degeneracy of the ground state on the torus and fractionalized excitations with
semionic mutual braiding statistics. Our work highlights the important theme
that interesting phases arise in the regime of strong spin-orbit coupling and
interactions.",1106.1559v2
2011-12-20,Experimental observation of the spin Hall effect of light on a nano-metal film via weak measurements,"We theorize the spin Hall effect of light (SHEL) on a nano-metal film and
demonstrate it experimentally via weak measurements. A general propagation
model to describe the relationship between the spin-orbit coupling and the
thickness of the metal film is established. It is revealed that the spin-orbit
coupling in the SHEL can be effectively modulated by adjusting the thickness of
the metal film, and the transverse displacement is sensitive to the thickness
of metal film in certain range for horizontal polarization light. Importantly,
a large negative transverse shift can be observed as a consequence of the
combined contribution of the ratio and the phase difference of Fresnel
coefficients.",1112.4560v3
2012-02-26,Quantum Anomalous Hall Effect in Flat Band Ferromagnet,"We proposed a theory of quantum anomalous Hall effect in a flat-band
ferromagnet on a two-dimensional (2D) decorated lattice with spin-orbit
coupling. Free electrons on the lattice have dispersionless flat bands, and the
ground state is highly degenerate when each lattice site is occupied averagely
by one electron, i.e., the system is at half filling. The on-site Coulomb
interaction can remove the degeneracy and give rise to the ferrimagnetism,
which is the coexistence of the ferromagnetic and antiferromagnetic long-range
orders. On the other hand the spin-orbit coupling makes the band structure
topologically non-trivial, and produces the quantum spin Hall effect with a
pair of helical edge states around the system boundary. Based on the rigorous
results for the Hubbard model, we found that the Coulomb interaction can
provide an effective staggered potential and turn the quantum spin Hall phase
into a quantum anomalous Hall phase.",1202.5747v1
2012-03-09,Symmetry classification of spin-orbit coupled spinor Bose-Einstein condensates,"We develop a symmetry classification scheme to find ground states of pseudo
spin-1/2, spin-1, and spin-2 spin-orbit coupled spinor Bose-Einstein
condensates, and show that as the SO(2) symmetry of simultaneous spin and space
rotations is broken into discrete cyclic groups, various types of lattice
structures emerge in the absence of a lattice potential, examples include two
different kagaome lattices for pseudo spin-1/2 condensates and a nematic vortex
lattice in which uniaxial and biaxial spin textures align alternatively for
spin-2 condensates. For the pseudo spin-1/2 system, although mean-field states
always break time-reversal symmetry, there exists a time-reversal invariant
many-body ground state, which is fragmented and expected to be observed in a
micro-condensate.",1203.2005v3
2012-08-09,Superconducting pairing symmetry on the extended Hubbard model in the presence of the Rashba-type spin-orbit coupling,"In order to study the pairing symmetry in non-centrosymmetric
superconductors, we solve the linearized Eliashberg's equation on the
two-dimensional extended Hubbard model in the presence of the Rashba-type
spin-orbit coupling (RSOC) within the random phase approximation. In the
presence of the RSOC, three types of pairing symmetries appear in the phase
diagram with respect to the on-site Coulomb repulsion U and off-site one V.
Each of pairing symmetries is admixture of spin-singlet and -triplet ones. On
the basis of analytical study, it is found that the admixture of spin-singlet
and -triplet components depends on not only the predominant pairing symmetry
but also dispersion relation and pairing interaction.",1208.2190v1
2012-11-13,Gate control of Berry phase in III-V semiconductor quantum dots,"Berry phase in semiconductor quantum dots (QDs) can be induced by moving the
dots adiabatically in a closed loop with the application of the distortion
potential in the lateral direction. We show that the Berry phase is highly
sensitive to the electric fields arising from the interplay between the Rashba
and the Dresselhaus spin-orbit couplings. We report that the accumulated Berry
phase can be induced from other available quantum state that are only differed
by one quantum number of the same spin state. The sign change in the g-factor
due to the penetration of the Bloch wavefunctions into the barrier material can
be reflected in the Berry phase. We solve the time dependent
Schr$\mathrm{\ddot{o}}$dinger equation and investigate the evolution of the
spin dynamics during the adiabatic movement of the QDs in the 2D plane. Our
results might open the possibilities of building a topological quantum dot
quantum computer where the Berry phase can be engineered and can be manipulated
with the application of the spin-orbit couplings through gate controlled
electric fields.",1211.2936v2
2013-04-26,Interplay between symmetry and spin-orbit coupling in graphene nanoribbons,"We study the electronic structure of chiral and achiral graphene nanoribbons
with symmetric edges, including curvature and spin-orbit effects. Curved
ribbons show spin-split bands, whereas flat ribbons present spin-degenerate
bands. We show that this effect is due to the breaking of spatial inversion
symmetry in curved graphene nanoribbons, while flat ribbons with symmetric
edges possess an inversion center, regardless of their having chiral or achiral
edges. We find an enhanced edge-edge coupling and a substantial gap in narrow
chiral nanoribbons, which is not present in zigzag ribbons of similar width. We
attribute these size effects to the mixing of the sublattices imposed by the
edge geometry, yielding a distinct behavior of chiral ribbons from those with
pure zigzag edges.",1304.7137v2
2013-06-11,Topological quantum phase transitions in the spin-singlet superconductor with Rashba and Dresselhaus (110) spin-orbit couplings,"We examine the topological properties of a spin-singlet superconductor with
Rashba and Dresselhaus (110) spin-orbit couplings. We demonstrate that there
are several topological invariants in the Bogoliubov-de Gennes (BdG)
Hamiltonian by symmetry analysis. We use the Pfaffian invariant $\mathcal{P}$
for the particle-hole symmetry to demonstrate all the possible phase diagrams
of the BdG Hamiltonian. We find that the edge spectrum is either Dirac cone or
flat band which supports the emergence of the Majorana fermion in this system.
For the Majorana flat bands, a higher symmetric BdG Hamiltonian is needed to
make them topologically stable. The Pfaffian invariant $\mathcal{P}(k_{y})$ and
the winding number $\mathcal{W}(k_{y})$ are used in determining the location of
the Majorana flat bands.",1306.2436v1
2013-07-01,The Two-Band Luttinger Liquid with Spin-Orbit Coupling: Applications to Monatomic Chains on Surfaces,"Recently, monatomic chains on surfaces have been synthesized which show
evidence of Luttinger liquid physics. The experimental data point to a
dispersion along the chain with four Fermi points. Here we investigate a
general low-energy effective Hamiltonian for such a two-band model where SU(2)
spin symmetry is broken but time reversal symmetry persists, as is expected due
to the surface geometry. Spin-orbit coupling gives rise to a new energy scale
epsilon_{SO} much smaller than the Fermi energy epsilon_F and to spin
non-conserving scattering processes. We derive the generic phase diagram at
zero temperature as well as an effective phase diagram at temperatures
epsilon_{SO} < T << epsilon_F. For the part of the phase diagram where a
Luttinger liquid is found to be stable, the density of states and the spectral
function are calculated and discussed in relation to the experimental data.",1307.0344v2
2013-11-12,Spin-orbit coupling induced semi-metallic state in the 1/3 hole doped hyper-kagome Na3Ir3O8,"The complex iridium oxide Na3Ir3O8 with a B-site ordered spinel structure was
synthesized in single crystalline form, where the chiral hyper-kagome lattice
of Ir atoms, as observed in the spin-liquid candidate Na4Ir3O8, was identified.
The average valence of Ir is 4.33+ and, therefore, Na3Ir3O8 can be viewed as a
doped analogue of the hyper-kagome spin liquid with Ir4+. The transport
measurements showed that Na3Ir3O8 is in fact a semi-metal. The electronic
structure calculation demonstrated that the strong spin-orbit coupling of Ir
yields the semi-metallic state out of an otherwise band insulating state, which
may harbor exotic topological effects embedded in the hyper-kagome lattice.",1311.2885v2
2014-04-04,Topological invariants in interacting Quantum Spin Hall: a Cluster Perturbation Theory approach,"Using Cluster Perturbation Theory we calculate Green's functions,
quasi-particle energies and topological invariants for interacting electrons on
a 2-D honeycomb lattice, with intrinsic spin-orbit coupling and on-site e-e
interaction. This allows to define the parameter range (Hubbard U vs spin-orbit
coupling) where the 2D system behaves as a trivial insulator or Quantum Spin
Hall insulator. This behavior is confirmed by the existence of gapless
quasi-particle states in honeycomb ribbons. We have discussed the importance of
the cluster symmetry and the effects of the lack of full translation symmetry
typical of CPT and of most Quantum Cluster approaches. Comments on the limits
of applicability of the method are also provided.",1404.1287v3
2014-07-01,Weak localization in low-symmetry quantum wells,"Theory of weak localization is developed for electrons in semiconductor
quantum wells grown along [110] and [111] crystallographic axes. Anomalous
conductivity correction caused by weak localization is calculated for
symmetrically doped quantum wells. The theory is valid for both ballistic and
diffusion regimes of weak localization in the whole range of classically weak
magnetic fields. We demonstrate that in the presence of bulk inversion
asymmetry the magnetoresistance is negative: The linear in the electron
momentum spin-orbit interaction has no effect on the conductivity while the
cubic in momentum coupling suppresses weak localization without a change of the
correction sign. Random positions of impurities in the doping layers in
symmetrically doped quantum wells produce electric fields which result in
position-dependent Rashba coupling. This random spin-orbit interaction leads to
spin relaxation which changes the sign of the anomalous magnetoconductivity.
The obtained expressions allow determination of electron spin relaxation times
in (110) and (111) quantum wells from transport measurements.",1407.0182v1
2014-09-16,Theory of diffusive φ0 Josephson junctions in the presence of spin-orbit coupling,"We present a full microscopic theory based on the SU(2) covariant formulation
of the quasiclassical formalism to describe the Josephson current through an
extended superconductor-normal metal- superconductor (SNS) diffusive junction
with an intrinsic spin-orbit coupling (SOC) in the presence of a spin-splitting
field h. We demonstrate that the ground state of the junction corresponds to a
finite intrinsic phase difference 0 < {\phi}0 < 2{\pi} between the
superconductor electrodes provided that both, h and the SOC-induced SU(2)
Lorentz force are finite. In the particular case of a Rashba SOC we present
analytic and numerical results for {\phi}0 as a function of the strengths of
the spin fields, the length of the junction, the temperature and the properties
of SN interfaces.",1409.4563v1
2014-10-16,Superconductivity in cubic noncentrosymmetric PdBiSe Crystal,"Mixing of spin singlet and spin triplet superconducting pairing state is
expected in noncentrosymmetric superconductors (NCS) due to the inherent
presence of Rashba-type antisymmetric spin-orbit coupling. Unlike low symmetry
(tetragonal or monoclinic) NCS, parity is isotropicaly broken in space for
cubic NCS and can additionally lead to the coexistence of magnetic and
superconducting state under certain conditions. Motivated with such enriched
possibility of unconventional superconducting phases in cubic NCS we are
reporting successful formation of single crystalline cubic noncentrosymmetric
PdBiSe with lattice parameter a = 6.4316 {\AA} and space group P2_1 3 (space
group no. 198) which undergoes to superconducting transition state below 1.8 K
as measured by electrical transport and AC susceptibility measurements.
Significant strength of Rashba-type antisymmetric spin-orbit coupling can be
expected for PdBiSe due to the presence of high Z (atomic number) elements
consequently making it potential candidate for unconventional
superconductivity.",1410.4459v1
2014-11-26,Bose-Einstein condensates with localized spin-orbit coupling: soliton complexes and spinor dynamics,"Spin-orbit (SO) coupling can be introduced in a Bose--Einstein condensate
(BEC) as a gauge potential acting only in a localized spatial domain. Effect of
such a SO ""defect"" can be understood by transforming the system to the
integrable vector model. The properties of the SO-BEC change drastically if the
SO defect is accompanied by the Zeeman splitting. In such a non-integrable
system, the SO defect qualitatively changes the character of soliton
interactions and allows for formation of stable nearly scalar soliton complexes
with almost all atoms concentrated in only one dark state. These solitons exist
only if the number of particles exceeds a threshold value. We also report on
the possibility of transmission and reflection of a soliton upon its scattering
on the SO defect. Scattering strongly affects the pseudo-spin polarization and
can induce pseudo-spin precession. The scattering can also result in almost
complete atomic transfer between the dark states.",1411.7322v1
2015-05-10,Oscillation of the spin-currents of cold atoms on a ring due to light-induced spin-orbit coupling,"The evolution of two-component cold atoms on a ring with spin-orbit coupling
has been studied analytically for the case with N noninteracting particles.
Then, the effect of interaction is evaluated numerically via a two-body system.
Two cases are considered: (i) Starting from a ground state the evolution is
induced by a sudden change of the laser field, and (ii) Starting from a
superposition state. Oscillating persistent spin-currents have been found. A
set of formulae have been derived to describe the period and amplitude of the
oscillation. Based on these formulae the oscillation can be well controlled via
adjusting the parameters of the laser beams. In particular, it is predicted
that movable stripes might emerge on the ring.",1505.02401v1
2015-09-16,Antiferromagnetic order in CeCoIn5 oriented by spin-orbital coupling,"An incommensurate spin density wave ($Q$ phase) confined inside the
superconducting state at high basal plane magnetic field is an unique property
of the heavy fermion metal CeCoIn$_5$. The neutron scattering experiments and
the theoretical studies point out that this state come out from the soft mode
condensation of magnetic resonance excitations. We show that the fixation of
direction of antiferromagnetic modulations by a magnetic field reported by
Gerber et al., Nat. Phys. {\bf 10}, 126 (2014) is explained by spin-orbit
coupling. This result, obtained on the basis of quite general phenomenological
arguments, is supported by the microscopic derivation of the $\chi_{zz}$
susceptibility dependence on the mutual orientation of the basal plane magnetic
field and the direction of modulation of spin polarization in a multi-band
metal.",1509.04915v4
2015-09-24,Skyrmions in Chiral Magnets with Rashba and Dresselhaus Spin-Orbit Coupling,"Skyrmions are topological spin textures of interest for fundamental science
and applications. Previous theoretical studies have focused on systems with
broken bulk inversion symmetry, where skyrmions are stabilized by easy-axis
anisotropy. We investigate here systems that break surface inversion symmetry,
in addition to possible broken bulk inversion. This leads to two distinct
Dzyaloshinskii-Moriya (DM) terms with strengths $D_\perp$, arising from Rashba
spin-orbit coupling (SOC), and $D_\parallel$ from Dresselhaus SOC. We show that
skyrmions become progressively more stable with increasing
$D_\perp/D_\parallel$, extending into the regime of easy-plane anisotropy. We
find that the spin texture and topological charge density of skyrmions develops
nontrivial spatial structure, with quantized topological charge in a unit cell
given by a Chern number. Our results give a design principle for tuning Rashba
SOC and magnetic anisotropy to stabilize skyrmions in thin films, surfaces,
interfaces and bulk magnetic materials that break mirror symmetry.",1509.07508v2
2015-10-05,Relativistic ponderomotive Hamiltonian of a Dirac particle in a vacuum laser field,"We report a point-particle ponderomotive model of a Dirac electron
oscillating in a high-frequency field. Starting from the Dirac Lagrangian
density, we derive a reduced phase-space Lagrangian that describes the
relativistic time-averaged dynamics of such a particle in a geometrical-optics
laser pulse propagating in vacuum. The pulse is allowed to have an arbitrarily
large amplitude (provided radiation damping and pair production are negligible)
and a wavelength comparable to the particle de Broglie wavelength. The model
captures the Bargmann-Michel-Telegdi (BMT) spin dynamics, the Stern-Gerlach
spin-orbital coupling, the conventional ponderomotive forces, and the
interaction with large-scale background fields. Agreement with the BMT spin
precesison equation is shown numerically. The commonly known theory in which
ponderomotive effects are incorporated in the particle effective mass is
reproduced as a special case when the spin-orbital coupling is negligible. This
model could be useful for studying laser-plasma interactions in relativistic
spin-$1/2$ plasmas.",1510.01268v2
2015-10-20,Spin-orbital and spin Kondo effects in parallel coupled quantum dots,"Strong electron correlations and interference effects are discussed in
parallel-coupled single-level and orbitally doubly degenerate quantum dots. The
finite-U mean-field slave boson approach is used to study many-body effects.
The analysis is carried out in a wide range of parameter space including both
atomic-like and molecular-like Kondo regimes and taking into account various
perturbations, like interdot tunneling, interdot interaction, mixing of the
electrode channels and exchange interaction. We also discuss the influence of
singularities of electronic structure and the impact of polarization of
electrodes. Special attention is paid to potential spintronic applications of
these systems showing how current polarization can be controlled by adjusting
interference conditions and correlations by gate voltage. Simple proposals of
double dot spin valve and bipolar electrically tunable spin filter are
presented.",1510.05853v1
2017-08-07,Disorder-induced topological phase transitions on Lieb lattices,"Motivated by the very recent experimental realization of electronic Lieb
lattices and research interest on topological states of matter, we study the
topological phase transitions driven by Anderson disorder on spin-orbit coupled
Lieb lattices in the presence of spin-independent and dependent potentials. By
combining the numerical transport and self-consistent Born approximation
methods, we found that both time-reversal invariant and broken Lieb lattices
can host disorder-induced gapful topological phases, including the quantum spin
Hall insulator (QSHI) and quantum anomalous Hall insulator (QAHI) phases. For
the time-reversal invariant case, this disorder can induce a topological phase
transition directly from normal insulator (NI) to the QSHI. While for the
time-reversal broken case, the disorder can induce either a QAHI-QSHI phase
transition or a NI-QAHI-QSHI phase transition. Remarkably, the time-reversal
broken QSHI phase can be induced by Anderson disorder on the spin-orbit coupled
Lieb lattices without time-reversal symmetry.",1708.02121v2
2018-11-26,"Direct Observation of Topological Edge States in Silicon Photonic Crystals: Spin, Dispersion, and Chiral Routing","Topological protection in photonics offers new prospects for guiding and
manipulating classical and quantum information. The mechanism of spin-orbit
coupling promises the emergence of edge states that are helical; exhibiting
unidirectional propagation that is topologically protected against
back-scattering. We directly observe the topological states of a photonic
analogue of electronic materials exhibiting the quantum Spin Hall effect,
living at the interface between two silicon photonic crystals with different
topological order. Through the far-field radiation that is inherent to the
states' existence we characterize their properties, including linear dispersion
and low loss. Importantly, we find that the edge state pseudospin is encoded in
unique circular far-field polarization and linked to unidirectional
propagation, thus revealing a signature of the underlying photonic spin-orbit
coupling. We use this connection to selectively excite different edge states
with polarized light, and directly visualize their routing along sharp chiral
waveguide junctions.",1811.10739v1
2020-07-12,Density Dependent Spin-Orbit Coupling in Degenerate Quantum Gases,"In this letter we propose a method to realize a kind of spin-orbit coupling
in ultracold Bose and Fermi gases whose format and strength depend on density
of atoms. Our method combines two-photon Raman transition and periodical
modulation of spin-dependent interaction, which gives rise to the direct Raman
process and the interaction assisted Raman process, and the latter depends on
density of atoms. These two processes have opposite effects in term of
spin-momentum locking and compete with each other. As the interaction
modulation increases, the system undergoes a crossover from the direct Raman
process dominated regime to the interaction assisted Raman process dominated
regime. For this crossover, we show that for bosons, both the condensate
momentum and the chirality of condensate wave function change sign, and for
fermions, the Fermi surface distortion is inverted. We highlight that there
exists an emergent spatial reflection symmetry in the crossover regime, which
can manifest itself universally in both Bose and Fermi gases. Our method paves
a way to novel phenomena in a non-abelian gauge field with intrinsic dynamics.",2007.05999v2
2017-01-09,2D spin-orbit coupling for ultracold atoms in optical lattices,"Spin-orbit coupling (SOC) is at the heart of many exotic band-structures and
can give rise to many-body states with topological order. Here we present a
general scheme based on a combination of microwave driving and lattice shaking
for the realization of time-reversal invariant 2D SOC with ultracold atoms in
systems with inversion symmetry. We show that the strengths of Rashba and
Dresselhaus SOC can be independently tuned in a spin-dependent square lattice.
More generally, our method can be used to open gaps between different spin
states without breaking time-reversal symmetry. We demonstrate that this allows
for the realization of topological insulators in the presence of SOC, which is
closely related to the Kane-Mele model.",1701.02111v2
2017-04-06,Density inhomogeneities and Rashba spin-orbit coupling interplay in oxide interfaces,"There is steadily increasing evidence that the two-dimensional electron gas
(2DEG) formed at the interface of some insulating oxides like LaAlO3/SrTiO3 and
LaTiO3/SrTiO3 is strongly inhomogeneous. The inhomogeneous distribution of
electron density is accompanied by an inhomogeneous distribution of the
(self-consistent) electric field confining the electrons at the interface. In
turn this inhomogeneous transverse electric field induces an inhomogeneous
Rashba spin-orbit coupling (RSOC). After an introductory summary on two
mechanisms possibly giving rise to an electronic phase separation accounting
for the above inhomogeneity,we introduce a phenomenological model to describe
the density-dependent RSOC and its consequences. Besides being itself a
possible source of inhomogeneity or charge-density waves, the density-dependent
RSOC gives rise to interesting physical effects like the occurrence of
inhomogeneous spin-current distributions and inhomogeneous quantum-Hall states
with chiral ""edge"" states taking place in the bulk of the 2DEG. The
inhomogeneous RSOC can also be exploited for spintronic devices since it can be
used to produce a disorder-robust spin Hall effect.",1704.01852v1
2009-12-16,Coupling of spin and orbital excitations in the iron-based superconductor FeSe(0.5)Te(0.5),"We present a combined analysis of neutron scattering and photoemission
measurements on superconducting FeSe(0.5)Te(0.5). The low-energy magnetic
excitations disperse only in the direction transverse to the characteristic
wave vector (1/2,0,0), whereas the electronic Fermi surface near (1/2,0,0)
appears to consist of four incommensurate pockets. While the spin resonance
occurs at an incommensurate wave vector compatible with nesting, neither
spin-wave nor Fermi-surface-nesting models can describe the magnetic
dispersion. We propose that a coupling of spin and orbital correlations is key
to explaining this behavior. If correct, it follows that these nematic
fluctuations are involved in the resonance and could be relevant to the pairing
mechanism.",0912.3205v2
2019-09-04,Coherent charge and spin oscillations induced by local quenches in nanowires with spin-orbit coupling,"When a local and attractive potential is quenched in a nanowire, the spectrum
changes its topology from a purely continuum to a continuum and discrete
portion. We show that, under appropriate conditions, this quench leads to
stable coherent oscillations in the observables time evolution. In particular,
we demonstrate that ballistic nanowires with spin-orbit coupling (SOC) exposed
to a uniform magnetic field are especially suitable to observe this effect.
Indeed, while in ordinary nanowires the effect occurs only if the strength
$U_0$ of the attractive potential is sufficiently strong, even a weak value of
$U_0$ is sufficient in SOC nanowires. Furthermore, in these systems coherent
oscillations in the spin sector can be generated and controlled electrically by
quenching the gate voltage acting on the charge sector. We interpret the origin
of this phenomenon, analyze the effect of variation of the chemical potential
and the switching time of the quenched attractive potential, and address
possible implementation schemes.",1909.01574v1
2019-10-18,Weak-field induced nonmagnetic state in a Co-based honeycomb,"Layered honeycomb magnets are of interest as potential realizations of the
Kitaev quantum spin liquid (KQSL), a quantum state with long-range spin
entanglement and an exactly solvable Hamiltonian. Conventional magnetically
ordered states are present for all currently known candidate materials,
however, because non-Kitaev terms in the Hamiltonians obscure the Kitaev
physics. Current experimental studies of the KQSL are focused on 4d- or
5d-transition-metal-based honeycombs, in which strong spin-orbit coupling can
be expected, yielding Kitaev interaction that dominate in an applied magnetic
field. In contrast, for 3d-based layered honeycomb magnets, spin orbit coupling
is weak and thus Kitaev-physics should be substantially less accessible. Here
we report our studies on BaCo2(AsO4)2, for which we find that the magnetic
order associated with the non-Kitaev interactions can be fully suppressed by a
relatively low magnetic field, yielding a non-magnetic material and implying
the presence of strong magnetic frustration and weak non-Kitaev interactions.",1910.08577v1
2019-10-31,Ferromagnetic fluctuations in the Rashba-Hubbard model,"We study the occurrence and the origin of ferromagnetic fluctuations in the
longitudinal spin susceptibility of the $t$-$t'$-Rashba-Hubbard model on the
square lattice. The combined effect of the second-neighbor hopping $t'$ and the
spin-orbit coupling leads to ferromagnetic fluctuations in a broad filling
region. The spin-orbit coupling splits the energy bands, leading to two van
Hove fillings, where the sheets of the Fermi surface change their topology.
Between these two van Hove fillings the model shows ferromagnetic fluctuations.
We find that these ferromagnetic fluctuations originate from interband
contributions to the spin susceptibility. These interband contributions only
arise if there is one holelike and one electronlike Fermi surface, which is the
case for fillings in between the two van Hove fillings. We discuss implications
for experimental systems and propose a test on how to identify these types of
ferromagnetic fluctuations in experiments.",1910.14621v2
2020-12-11,Graphene with Rashba spin-orbit interaction and coupling to a magnetic layer: Electron states localized at the domain wall,"Electron states localized at a magnetic domain wall in a graphene caplayer
with Rashba spin-orbit interaction and coupled to a magnetic overlayer are
studied theoretically. It is shown that two one-dimensional bands of edge modes
propagating along the domain wall emerge in the energy gap for each Dirac
point, and the modes associated with different Dirac points K and K' are the
same. The coefficients describing decay of the corresponding wavefunctions with
distance from the domain wall contain generally real and imaginary terms.
Numerical results on the local spin density and on the total spin expected in
the edge states characterized by the wavenumber $k_y$ are presented and
discussed. The Chern number for a single magnetic domain on graphene indicates
that the system is in the quantum anomalous Hall phase, with two chiral modes
at the edges. In turn, the number of modes localized at the domain wall is
determined by the difference in Chern numbers on both sides of the wall. These
numbers are equal to 2 and -2, respectively, so there are four modes localized
at the domain wall.",2012.06357v3
2018-08-26,One-dimensional topological metal,"We propose a new type of topological states of matter exhibiting
topologically nontrivial edge states (ESs) within gapless bulk states (GBSs)
protected by both spin rotational and reflection symmetries. A model presenting
such states is simply comprised of a one-dimensional reflection symmetric
superlattice in the presence of spin-orbit coupling containing odd number of
sublattices per unit cell. We show that the system has a rich phase diagram
including a topological metal (TM) phase where nontrivial ESs coexist with
nontrivial GBSs at Fermi level. Topologically distinct phases can be reached
through subband gap closing-reopening transition depending on the relative
strength of inter and intra unit cell spin-orbit couplings. Moreover,
topological class of the system is AI with an integer topological invariant
called $\mathbb{Z}$ index. The stability of TM states is also analyzed against
Zeeman magnetic fields and on-site potentials resulting in that the spin
rotational symmetry around the lattice direction is a key requirement for the
appearance of such states. Also, possible experimental realizations are
discussed.",1808.08530v2
2019-01-21,Twist-angle dependence of the proximity spin-orbit coupling in graphene on transition-metal dichalcogenides,"We theoretically study the proximity spin-orbit coupling in graphene on
transition-metal dichalcogenides monolayer stacked with arbitrary twist angles.
We find that the relative rotation greatly enhances the spin splitting of
graphene, typically by a few to ten times compared to the non-rotated
geometry,and the maximum splitting is achieved around $20^\circ$. The induced
SOC can be changed from the Zeeman-type to the Rashba-type by rotation. The
spin-splitting is also quite sensitive to the gate-induced potential, and it
sharply rises when the graphene's Dirac point is shifted toward the TMDC band.
The theoretical method does not need the exact lattice matching and it is
applicable to any incommensurate bilayer systems. It is useful for the
twist-angle engineering of a variety of van der Waals proximity effects.",1901.06769v1
2019-08-19,Tuning the Topological Features of Quantum-Dot Hydrogen and Helium by a Magnetic Field,"The topological charge of the spin texture in a quantum dot with spin-orbit
couplings is shown analytically here to be stable against the ellipticity of
the dot. It is directly tunable by a single magnetic field and is related to
the \textit{sign} of the Land\'e $g$ factor. In a quantum-dot helium, the
overall winding number could have different property from that of the
single-electron case (quantum-dot hydrogen), since tuning the number of
electron affects the winding number by the Coulomb interaction and the $z$
component angular momentum $\langle L^{}_z \rangle$. The density profile and
the spin texture influence each other when the Coulomb interaction is present.
When $\langle L^{}_z \rangle$ is biased away from an integer by the spin-orbit
couplings, the rotational symmetry is broken which induces strong density
deformation. The sign of the topological charge may also be reversed with
increasing magnetic field. These findings are of major significance since the
applied magnetic field alone now provides a direct route to control the
topological properties of quantum dots.",1908.06575v1
2020-08-14,Topological Superconductivity in Rashba Spin-Orbital Coupling Suppressed Monolayer \{beta}-Bi2Pd,"The weak interlayer Van Der Waals material \{beta}-Bi2Pd has recently been
established as a strong topological superconductor candidate with
unconventional spin-triplet pairing and Majorana zero modes at vortices. In
this letter, we study the topological characters and the superconducting
pairing, which are still obscure in monolayer \{beta}-Bi2Pd, in light of our
effective theoretical model. We find that the non-Rashba spin-orbital coupling
plays a critical role in realizing and tuning various novel topological
natures. In particular, the spin-triplet p-wave superconducting pairing with
Majorana zero mode is revealed in monolayer \{beta}-Bi2Pd. Our studies deepen
the understanding of topology and superconductivity in monolayer \{beta}-Bi2Pd
and indicate it is a promising platform for achieving low-dimentional
topological superconductivity.",2008.06260v2
2017-07-26,Spin-dependent heat and thermoelectric currents in a Rashba ring coupled to a photon cavity,"Spin-dependent heat and thermoelectric currents in a quantum ring with Rashba
spin-orbit interaction placed in a photon cavity are theoretically calculated.
The quantum ring is coupled to two external leads with different temperatures.
In a resonant regime, with the ring structure in resonance with the photon
field, the heat and the thermoelectric currents can be controlled by the Rashba
spin-orbit interaction. The heat current is suppressed in the presence of the
photon field due to contribution of the two-electron and photon replica states
to the transport while the thermoelectric current is not sensitive to changes
in parameters of the photon field. Our study opens a possibility to use the
proposed interferometric device as a tunable heat current generator in the
cavity photon field.",1707.08416v1
2017-11-17,Influence of Spin Orbit Coupling in the Iron-Based Superconductors,"We report on the influence of spin-orbit coupling (SOC) in the Fe-based
superconductors (FeSCs) via application of circularly-polarized spin and
angle-resolved photoemission spectroscopy. We combine this technique in
representative members of both the Fe-pnictides and Fe-chalcogenides with ab
initio density functional theory and tight-binding calculations to establish an
ubiquitous modification of the electronic structure in these materials imbued
by SOC. The influence of SOC is found to be concentrated on the hole pockets
where the superconducting gap is generally found to be largest. This result
contests descriptions of superconductivity in these materials in terms of pure
spin-singlet eigenstates, raising questions regarding the possible pairing
mechanisms and role of SOC therein.",1711.06686v3
2020-06-17,Exchange-bias controlled correlations in magnetically encapsulated twisted van der Waals dichalcogenides,"Twisted van der Waals materials have become a paradigmatic platform to
realize exotic correlated states of matter. Here, we show that a twisted
dichalcogenide bilayer (WSe$_2$) encapsulated between a magnetic van der Waals
material (CrBr$_3$) features flat bands with tunable valley and spin flavors.
We demonstrate that, when electron-electron interactions are included,
spin-ferromagnetic and valley-ferromagnetic states emerge in the flat bands,
stemming from the interplay between correlations, intrinsic spin-orbit coupling
and exchange proximity effects. We show that the specific symmetry broken state
is controlled by the relative alignment of the magnetization of the
encapsulation, demonstrating the emergence of correlated states controlled by
exchange bias. Our results put forward a new van der Waals heterostructure
where symmetry broken states emerge from a genuine interplay between twist
engineering, spin-orbit coupling and exchange proximity, providing a powerful
starting point to explore exotic collective states of matter.",2006.09953v2
2020-06-22,"Probing nodeless superconductivity in LaMSi (M = Ni, Pt) using muon-spin rotation and relaxation","Systems with strong spin-orbit coupling have been a topic of fundamental
interest in condensed matter physics due to the exotic topological phases and
the unconventional phenomenon they exhibit. In this particular study, we have
investigated the superconductivity in the transition-metal ternary
noncentrosymmetric compounds LaMSi (M = Ni, Pt) with different spin-orbit
coupling strength, using muon-spin rotation and relaxation measurements.
Transverse-field measurements made in the vortex state indicate that the
superconductivity in both materials is fully gapped, with a conventional s-wave
pairing symmetry and BCS-like magnitudes for the zero-temperature gap energies.
Zero field measurements suggest a time-reversal symmetry preserved
superconductivity in both the systems, though a small increase in muon
depolarization is observed upon decreasing temperature. However, this has been
attributed to quasi-static magnetic fluctuations.",2006.12172v1
2021-10-09,Enhancement of spin-orbit coupling and magnetic scattering in hydrogenated graphene,"Spin-orbit coupling (SOC) can provide essential tools to manipulate electron
spins in two-dimensional materials like graphene, which is of great interest
for both fundamental physics and spintronics application. In this paper, we
report the low-field magnetotransport of in situ hydrogenated graphene where
hydrogen atoms are attached to the graphene surface in continuous low
temperature and vacuum environment. Transition from weak localization to weak
antilocalization with increasing hydrogen adatom density is observed,
indicating enhancing Bychkov-Rashba-type SOC in a mirror symmetry broken
system. From the low-temperature saturation of phase breaking scattering rate,
the existence of spin-flip scattering is identified, which corroborates the
existence of magnetic moments in hydrogenated graphene.",2110.04477v1
2022-07-12,Nonlinear nonreciprocal transport in antiferromagnets free from spin-orbit coupling,"We theoretically propose a realization of a nonlinear nonreciprocal transport
in antiferromagnets without relying on the relativistic spin-orbit coupling.
Through the symmetry and microscopic model analyses, we show that a local spin
scalar chirality to induce an asymmetric band modulation becomes a source of a
Drude-type nonlinear transport, while an electric polarization induced by a
collinear spin configuration in a triangle unit leads to a
Berry-curvature-dipole-type nonlinear transport. We demonstrate that
120$^\circ$ antiferromagnetic ordering on a triangular lattice and a breathing
kagome lattice in an external magnetic field are typical examples. Our results
open a new direction of designing and engineering functional materials with
showing rich parity-violating transport phenomena by spontaneous magnetic phase
transitions.",2207.05857v1
2022-10-18,Dynamics of Stripe Patterns in Supersolid Spin-Orbit-Coupled Bose Gases,"Despite ground-breaking observations of supersolidity in spin-orbit-coupled
Bose-Einstein condensates, until now the dynamics of the emerging spatially
periodic density modulations has been vastly unexplored. Here, we demonstrate
the nonrigidity of the density stripes in such a supersolid condensate and
explore their dynamic behavior subject to spin perturbations. We show both
analytically in infinite systems and numerically in the presence of a harmonic
trap how spin waves affect the supersolid's density profile in the form of
crystal waves, inducing oscillations of the periodicity as well as the
orientation of the fringes. Both these features are well within reach of
present-day experiments. Our results show that this system is a paradigmatic
supersolid, featuring superfluidity in conjunction with a fully dynamic
crystalline structure.",2210.10064v2
2022-12-30,"Coexistence of Rashba Effect and Spin-valley Coupling in TiX2 (X= Te, S and Se) based Heterostructures","Spin-orbit coupling (SOC) combined with broken inversion symmetry play key
roles in inducing Rashba effect. The combined spontaneous polarization and
Rashba effect enable controlling a material's spin degrees of freedom
electrically. In this work we investigated the electronic band structure for
several combinations of TiX2 monolayers (X= Te, S and Se): TiTe2/TiSe2,
TiTe2/TiS2, and TiSe2/TiS2. Based on the observed orbital hybridization between
the different monolayers in these hetero-structures (HSs), we conclude that the
most significant Rashba splitting occurs in TiSe2/TiS2. Subsequently, we used
Fluorine (F) as an adatom over the surface of TiSe2/TiS2 at hollow and top
sites of the surface to enhance the Rashba intensity, as the F adatom induces
polarization due to difference in charge distribution. Furthermore, by
increasing the number of F atoms on the surface, we reinforced the band
splitting, i.e., we observe Rashba splitting accompanied by Zeeman splitting at
the valence-band edge states. Berry curvatures at K and K' with equal and
opposite nature confirms the existence of valley polarization. The
computationally observed properties suggest that these HSs are promising
candidates for spin-valley Hall effect devices and other spintronic
applications.",2212.14508v1
2023-03-08,Electrical control of spin and valley in spin-orbit coupled graphene multilayers,"Electrical control of magnetism has been a major techonogical pursuit of the
spintronics community, owing to its far-reaching implications for data storage
and transmission. Here, we propose and analyze a new mechanism for electrical
switching of isospin, using chiral-stacked graphene multilayers, such as bernal
bilayer graphene or rhombohedral trilayer graphene, encapsulated by transition
metal dichalcogenide (TMD) substrates. Leveraging the proximity-induced
spin-orbit coupling from the TMD, we demonstrate electrical switching of
correlation-induced spin and/or valley polarization, by reversing a
perpendicular displacement field or the chemical potential. We substantiate our
proposal with both analytical arguments and self-consistent Hartree-Fock
numerics. Finally, we illustrate how the relative alignment of the TMDs,
together with the top and bottom gate voltages, can be used to selectively
switch distinct isospin flavors, putting forward correlated van der Waals
heterostructures as a promising platform for spintronics and valleytronics.",2303.04855v3
2023-09-14,Photochemical reaction enabling the engineering of photonic spin-orbit coupling in organic-crystal optical microcavities,"The control and active manipulation of spin-orbit coupling (SOC) in photonic
systems is fundamental in the development of modern spin optics and topological
photonic devices. Here, we demonstrate the control of an artificial
Rashba-Dresselhaus (RD) SOC mediated by photochemical reactions in a
microcavity filled with an organic single-crystal of photochromic phase-change
character. Splitting of the circular polarization components of the optical
modes induced by photonic RD SOC is observed experimentally in momentum space.
By applying an ultraviolet light beam, we control the spatial molecular
orientation through a photochemical reaction and with that we control the
energies of the photonic modes. This way we realize a reversible conversion of
spin-splitting of the optical modes with different energies, leading to an
optically controlled switching between circularly and linearly polarized
emission from our device. Our strategy of in situ and reversible engineering of
SOC induced by a light field provides a promising approach to actively design
and manipulate synthetic gauge fields towards future on-chip integration in
photonics and topological photonic devices.",2309.07652v1
2023-10-18,Magnetic eight-fold nodal-point and nodal-network fermions in MnB2,"Realizing topological semimetal states with novel emergent fermions in
magnetic materials is a focus of current research. Based on first-principle
calculations and symmetry analysis, we reveal interesting magnetic emergent
fermions in an existing material MnB2. In the temperature range from 157 K to
760 K, MnB2 is a collinear antiferromagnet. We find the coexistence of
eightfold nodal points and nodal net close to the Fermi level, which are
protected by the spin group in the absence of spin-orbit coupling. Depending on
the Neel vector orientation, consideration of spin-orbit coupling will either
open small gaps at these nodal features, or transform them into magnetic linear
and quadratic Dirac points and nodal rings. Below 157 K, MnB2 acquires weak
ferromagnetism due to spin tilting. We predict that this transition is
accompanied by a drastic change in anomalous Hall response, from zero above 157
K to 200 $\Omega\cdot \text{cm}^{-1}$ below 157 K.",2310.11669v1
2024-02-05,Realizing and detecting Stiefel-Whitney insulators in an optical Raman lattice,"We propose a feasible scheme to realize a four-band Stiefel-Whitney insultor
(SWI) with spin-orbit coupled ultracold atoms in an optical Raman lattice. Four
selected spin states are coupled by carefully designed Raman lasers, to
generate the desired spin-orbit interactions with spacetime inversion symmetry.
We map out a phase diagram with respect to the experimental parameters, where a
large topological phase region exists. We further present two distinct
detection methods to resolve the non-abelian band topology, in both equilibrium
and dynamical ways. The detection relies on the spin textures extracted from
the time-of-flight imaging, showing the tomographic signatures in the ground
states and long-time averaged patterns on certain submanifold via a
bulk-surface duality. Our work paves a realistic way to explore novel real
topology with quantum matters.",2402.02777v1
2024-03-02,Driven charge density modulation by spin density wave and their coexistence interplay in SmFeAsO: A first-principles study,"We use density functional theory to investigate effects of spin-orbit
coupling and single-stripe-type antiferromagnetic (sAFM) ordering on the
crystal structure and electronic properties of SmFeAsO. The results indicate
that AFM ordering causes the crystal structure transition from tetragonal to
orthorhombic, along with increase in the height of As atoms from Fe layer due
to magnetostriction. It also leads to the opening of partial band gaps, the
emergence of a prominent peak near Fermi energy (EF) in the density of states
(DOS) and a reduction in Fermi surface nesting. The study finds a correlation
between the calculated area under the DOS curve, spanning from EF to the first
peak above it, and the optimal electron-doped concentration required for
inducing superconductivity in SmFeAsO. The findings suggest that spin and
charge density waves can play important roles in the superconducting mechanism
of Fe-based superconductors. Our calculations demonstrate that spin-orbit
coupling reduces electronic correlation.",2403.01111v1
2024-04-01,Josephson diode effect in a ballistic single-channel nanowire,"When time-reversal and inversion symmetry are broken, superconducting
circuits may exhibit a so-called diode effect, where the critical currents for
opposite directions of the current flow differ. In recent years, this effect
has been observed in a multitude of systems and the different physical
ingredients that may yield such an effect are well understood. On a microscopic
level, the interplay between spin-orbit coupling and a Zeeman field may give
rise to a diode effect in a single Josephson junction. However, so far there is
no analytical description of the effect within a simple model. Here we study a
single channel nanowire with Rashba spin-orbit coupling and subject to a Zeeman
field. We show that the different Fermi velocities and spin projections of the
two pseudo-spin bands lead to a diode effect. Simple analytical expressions for
the efficiency can be obtained in limiting cases.",2404.01429v1
2000-10-04,Kondo ground state in a quantum dot with an even number of electrons,"Kondo conduction has been observed in a quantum dot with an even number of
electrons at the Triplet-Singlet degeneracy point produced by applying a small
magnetic field $B$ orthogonal to the dot plane.
  At a much larger field $ B \sim B_*$, orbital effects induce the reversed
transition from the Singlet to the Triplet state. We study the newly proposed
Kondo behavior at this point. Here the Zeeman spin splitting cannot be
neglected, what changes the nature of the Kondo coupling. On grounds of exact
diagonalization results in a dot with cylindrical symmetry, we show that, at
odds with what happens at the other crossing point, close to $B_*$, orbital and
spin degrees of freedom are ``locked together'', so that the Kondo coupling
involves a fictitious spin 1/2 only, which is fully compensated by conduction
electrons under suitable conditions. In this sense, spin at the dot is
fractionalized. We derive the scaling equation of the system by means of a
nonperturbative variational approach. The approach is extended to the $B \neq
B_*$-case and the residual magnetization on the dot is discussed.",0010054v1
2007-03-20,Skew scattering due to intrinsic spin-orbit coupling in a two-dimensional electron gas,"We present the generalization of the two-dimensional quantum scattering
formalism to systems with Rashba spin-orbit coupling. Using symmetry
considerations, we show that the differential scattering cross section depends
on the spin state of the incident electron, and skew scattering may arise even
for central spin-independent scattering potentials. The skew scattering effect
is demonstrated by exact results of a simple hard wall impurity model. The
magnitude of the effect for short-range impurities is estimated using the first
Born approximation. The exact formalism we present can serve as a foundation
for further theoretical investigations.",0703516v2
2010-04-16,Edge Dynamics in a Quantum Spin Hall State: Effects from Rashba Spin-Orbit Interaction,"We analyze the dynamics of the helical edge modes of a quantum spin Hall
state in the presence of a spatially non-uniform Rashba spin-orbit (SO)
interaction. A randomly fluctuating Rashba SO coupling is found to open a
scattering channel which causes localization of the edge modes for a weakly
screened electron-electron (e-e) interaction. A periodic modulation of the SO
coupling, with a wave number commensurate with the Fermi momentum, makes the
edge insulating already at intermediate strengths of the e-e interaction. We
discuss implications for experiments on edge state transport in a HgTe quantum
well.",1004.2777v2
2011-09-12,Stabilizing the spiral order with spin-orbit coupling in an anisotropic triangular antiferromagnet,"We study the effects of spin-orbit coupling (SOC) on the large-U Hubbard
model on anisotropic triangular lattice at half-filling using the
Schwinger-boson method. We find that the SOC will in general lead to a zero
temperature condensation of the Schwinger bosons with a single condensation
momentum. As a consequence, the spin-spin correlation vanishes along the z-axis
but develops in the $x$-$y$ plane, with the ordering wave vector being
dramatically dependent on the SOC. Moreover, the phase boundary of the magnetic
ordered state extends to the region of large spatial anisotropy with increased
condensation density, demonstrating that the spiral order is always stabilized
by the SOC.",1109.2364v1
2014-04-03,Bose-Bose Mixtures with Synthetic Spin-Orbit Coupling in Optical Lattices,"We investigate the ground state properties of Bose-Bose mixtures with
Rashba-type spin-orbit (SO) coupling in a square lattice. The system displays
rich physics from the deep Mott-insulator (MI) all the way to the superfluid
(SF) regime. In the deep MI regime, novel spin-ordered phases arise due to the
effective Dzyaloshinskii-Moriya type super-exchange interactions. By employing
the non-perturbative Bosonic Dynamical Mean-Field-Theory (BDMFT), we
numerically study and establish the stability of these magnetic phases against
increasing hopping amplitude. We show that as hopping is increased across the
MI to SF transition, exotic superfluid phases with magnetic textures emerge. In
particular, we identify a new spin-spiral magnetic texture with spatial period
3 in the superfluid close to the MI-SF transition.",1404.0970v2
2014-09-10,Approach for making visible and stable stripes in a spin-orbit-coupled Bose-Einstein superfluid,"The striped phase exhibited by a spin-$1/2$ Bose-Einstein condensate with
spin-orbit coupling is characterized by the spontaneous breaking of two
continuous symmetries: gauge and translational symmetry. This is a peculiar
feature of supersolids and is the consequence of interaction effects. We
propose an approach to produce striped configurations with high-contrast
fringes, making their experimental detection in atomic gases a realistic
perspective. Our approach, whose efficiency is directly confirmed by
three-dimensional Gross-Pitaevskii simulations, is based on the space
separation of the two spin components into a two-dimensional bilayer
configuration, causing the reduction of the effective interspecies interaction
and the increase of the stability of the striped phase. We also explore the
effect of a $\pi/2$ Bragg pulse, causing the increase of the fringe wavelength,
and of a $\pi/2$ rf pulse, revealing the coherent nature of the order parameter
in the spin channel.",1409.3149v3
2015-03-04,Dichroism as a probe for parity-breaking phases of spin-orbit coupled metals,"Recently, a general formalism was presented for gyrotropic, ferroelectric,
and multipolar order in spin-orbit coupled metals induced by spin-spin
interactions. Here, I point out that the resulting order parameters are
equivalent to expectation values of operators that determine natural circular
dichroic signals in optical and x-ray absorption. Some general properties of
these operator equivalents and the resulting dichroisms are mentioned, and I
list several material examples in this connection, including Weyl semimetals.
The particular case of the tensor order in the pyrochlore superconductor
Cd2Re2O7 is treated in more detail, including calculations of the x-ray
absorption and circular dichroism at the O K edge.",1503.01501v3
2016-04-23,Spin Hall Conductivity in the impure two-dimensional Rashba s-wave superconductor,"Based on the Kubo formula approach, the spin Hall conductivity (SHC) of a
two-dimensional (2D) Rashba s-wave superconductor in the presence of
nonmagnetic impurities is calculated. We will show that by increasing the
superconducting gap, the SHC decreases monotonically to zero, while by
decreasing the concentration of impurities at zero gap, the SHC closes to the
clean limit universal value . As a function of the impurity relaxation rate at
and (is the spin-orbit coupling in unit of), we will show that in the dirty
limit () the SHC vanishes, and by increasing the relaxation time () the SHC
depends on the value of superconducting gap (), is changed from zero for full
gap to in zero gap. At low temperatures, the SHC goes to zero exponentially and
near the critical temperature depending on the concentration of the scattering
centers, the SHC will tend to the value of normal state. We will also show that
the SHC is independent of spin-orbit coupling () in the clean limit.",1604.06887v1
2016-07-06,Hyperfine and spin-orbit coupling effects on decay of spin-valley states in a carbon nanotube,"The decay of spin-valley states is studied in a suspended carbon nanotube
double quantum dot via leakage current in Pauli blockade and via dephasing and
decoherence of a qubit. From the magnetic field dependence of the leakage
current, hyperfine and spin-orbit contributions to relaxation from blocked to
unblocked states are identified and explained quantitatively by means of a
simple model. The observed qubit dephasing rate is consistent with the
hyperfine coupling strength extracted from this model and inconsistent with
dephasing from charge noise. However, the qubit coherence time, although longer
than previously achieved, is probably still limited by charge noise in the
device.",1607.01695v2
2017-02-27,Breakdown of Magnons in a Strongly Spin-Orbital Coupled Magnet,"The description of quantized collective excitations stands as a landmark in
the quantum theory of condensed matter. A prominent example occurs in
conventional magnets, which support bosonic magnons - quantized harmonic
fluctuations of the ordered spins. In striking contrast is the recent discovery
that strongly spin-orbital coupled magnets, such as $\alpha$-RuCl$_3$, may
display a broad excitation continuum inconsistent with conventional magnons.
Due to incomplete knowledge of the underlying interactions unraveling the
nature of this continuum remains challenging. The most discussed explanation
refers to a coherent continuum of fractional excitations analogous to the
celebrated Kitaev spin liquid. Here we present a more general scenario. We
propose that the observed continuum represents incoherent excitations
originating from strong magnetic anharmoniticity that naturally occurs in such
materials. This scenario fully explains the observed inelastic magnetic
response of $\alpha$-RuCl$_3$ and reveals the presence of nontrivial
excitations in such materials extending well beyond the Kitaev state.",1702.08466v3
2017-08-02,Flocking from a quantum analogy: Spin-orbit coupling in an active fluid,"Systems composed of strongly interacting self-propelled particles can form a
spontaneously flowing polar active fluid. The study of the connection between
the microscopic dynamics of a single such particle and the macroscopic dynamics
of the fluid can yield insights into experimentally realizable active flows,
but this connection is well understood in only a few select cases. We introduce
a model of self-propelled particles based on an analogy with the motion of
electrons that have strong spin-orbit coupling. We find that, within our model,
self-propelled particles are subject to an analog of the Heisenberg uncertainty
principle that relates translational and rotational noise. Furthermore, by
coarse-graining this microscopic model, we establish expressions for the
coefficients of the Toner-Tu equations---the hydrodynamic equations that
describe an active fluid composed of these ""active spins."" The connection
between self-propelled particles and quantum spins may help realize exotic
phases of matter using active fluids via analogies with systems composed of
strongly correlated electrons.",1708.00937v1
2012-04-23,Interaction Induced Hall Response in a Spin-Orbit Coupled Bose-Einstein Condensate,"In this letter we consider the dynamic behaviors of spin-orbit coupled Bose
condensates realized in recent experiments. We show that there exists an
interaction induced ac Hall response which is absent in a non-interacting
system. This condensate has two distinct equilibrium phases known as the plane
wave phase and the stripe phase. In the plane wave phase, we show that an ac
longitudinal current will induce an ac radial current in the transverse
direction, and vice versa, as a cooperation effect of spin-velocity locking and
spin-dependent interaction. In the stripe phase, we show that the dominant
longitudinal response to a transverse radial current is sliding of the density
stripe, because it is the low-lying excitation mode originated from spontaneous
spatial translational symmetry breaking in this phase.",1204.5121v1
2014-05-25,Spin Hall phenomenology of magnetic dynamics,"We study the role of spin-orbit interactions in the coupled magnetoelectric
dynamics of a ferromagnetic film coated with an electrical conductor. While the
main thrust of this work is phenomenological, several popular simple models are
considered microscopically in some detail, including Rashba and Dirac
two-dimensional electron gases coupled to a magnetic insulator, as well as a
diffusive spin Hall system. We focus on the long-wavelength magnetic dynamics
that experiences current-induced torques and produces fictitious electromotive
forces. Our phenomenology provides a suitable framework for analyzing
experiments on current-induced magnetic dynamics and reciprocal charge pumping,
including the effects of magnetoresistance and Gilbert-damping anisotropies,
without a need to resort to any microscopic considerations or modeling.
Finally, some remarks are made regarding the interplay of spin-orbit
interactions and magnetic textures.",1405.6354v2
2017-06-21,Uniform magnetization dynamics of a submicron ferromagnetic coin driven by the spin-orbit coupled spin torque,"A simple model of magnetization dynamics in a ferromagnet/doped semiconductor
hybrid structure with Rashba spin-orbit interaction (SOI) driven by an applied
pulse of the electric field is proposed. The electric current excited by the
applied field is spin-polarized due to the SOI and therefore it induces the
magnetization rotation in the ferromagnetic layer via s-d exchange coupling.
Magnetization dynamics dependence on the electric pulse shape and magnitude is
analyzed for realistic values of parameters. We show that it is similar to the
dynamics of a damped nonlinear oscillator with the time-dependent frequency
proportional to the square root of the applied electric field. The
magnetization switching properties of an elliptic magnetic element are examined
as a function of the applied field magnitude and direction.",1706.06909v1
2017-06-26,Ferroelectric control of the giant Rashba spin orbit coupling in GeTe(111)/InP(111) superlattice,"GeTe wins the renewed research interest due to its giant bulk Rashba spin
orbit coupling (SOC), and becomes the father of a new multifunctional material,
i.e., ferroelectric Rashba semiconductor. In the present work, we investigate
Rashba SOC at the interface of the ferroelectric semiconductor superlattice
GeTe(111)/InP(111) by using the first principles calculation. Contribution of
the interface electric field and the ferroelectric field to Rashba SOC is
revealed. A large modulation to Rashba SOC and a reversal of the spin
polarization is obtained by switching the ferroelectric polarization. Our
investigation about GeTe(111)/InP(111) superlattice is of great importance in
the application of ferroelectric Rashba semiconductor in the spin field effect
transistor.",1706.08256v1
2018-01-17,Symmetry Breaking of the Persistent Spin Helix in Quantum Transport,"We exploit the high-symmetry spin state obtained for equal Rashba and linear
Dresselhaus interactions to derive a closed-form expression for the weak
localization magnetoconductivity -- the paradigmatic signature of spin-orbit
coupling in quantum transport. The small parameter of the theory is the
deviation from the symmetry state introduced by the mismatch of the linear
terms and by the cubic Dresselhaus term. In this regime, we perform quantum
transport experiments in GaAs quantum wells. Top and back gates allow
independent tuning of the Rashba and Dresselhaus terms in order to explore the
broken-symmetry regime where the formula applies. We present a reliable
two-step method to extract all parameters from fits to the new expression,
obtaining excellent agreement with recent experiments. This provides
experimental confirmation of the new theory, and advances spin-orbit coupling
towards a powerful resource in emerging quantum technologies.",1801.05657v1
2018-03-06,Supercurrent in ferromagnetic Josephson junctions with heavy metal interlayers,"The lengthscale over which supercurrent from conventional BCS, $s$-wave,
superconductors ($S$) can penetrate an adjacent ferromagnetic ($F$) layer
depends on the ability to convert singlet Cooper pairs into triplet Cooper
pairs. Spin aligned triplet Cooper pairs are not dephased by the ferromagnetic
exchange interaction, and can thus penetrate an $F$ layer over much longer
distances than singlet Cooper pairs. These triplet Cooper pairs carry a
dissipationless spin current and are the fundamental building block for the
fledgling field of superspintronics. Singlet-triplet conversion by
inhomogeneous magnetism is well established. Here, we describe an attempt to
use spin orbit coupling as a new mechanism to mediate singlet-triplet
conversion in $S-F-S$ Josephson junctions. We report that the addition of thin
Pt spin-orbit coupling layers in our Josephson junctions significantly
increases supercurrent transmission, however the decay length of the
supercurrent is not found to increase. We attribute the increased supercurrent
transmission to Pt acting as a buffer layer to improve the growth of the Co $F$
layer.",1803.01965v2
2019-11-09,Topological defects of spin-orbit coupled Bose-Einstein condensates in a rotating anharmonic trap,"We investigate the topological defects and spin structures of binary
Bose-Einstein condensates (BECs) with Dresselhaus spin-orbit coupling (D-SOC)
in a rotating anharmonic trap. Our results show that for initially mixed BECs
without SOC the increasing rotation frequency can lead to the structural phase
transition of the system. In the presence of isotropic D-SOC, the system
sustains vortex pair,Anderson--Toulouse coreless vortices, circular vortex
sheets, and combined vortex structures. In particular, when the rotation
frequency is fixed above the radial trapping frequency the strong D-SOC results
in a peculiar topological structure which is comprised of multi-layer visible
vortex necklaces, hidden vortex necklaces and a hidden giant vortex. In
addition, the system exhibits rich spin textures including basic skyrmion,
meron cluster, skyrmion string and various skyrmion lattices. The skyrmions
will be destroyed in the limit of large D-SOC or rotation frequency.
Furthermore, the effects of anisotropic D-SOC and Rashba-Dresselhaus SOC on the
topological structures of the system are discussed.",1911.03650v1
2020-10-24,Impurity in a Fermi gas under non-Hermitian spin-orbit coupling,"We study the fate of an impurity in a two-component, non-interacting Fermi
gas under a non- Hermitian spin-orbit coupling (SOC) which is generated by
dissipative Raman lasers. While SOC mixes the two spin species in the Fermi gas
thus modifies the single-particle dispersions, we consider the case where the
impurity only interacts with one of the spin species. As a result, spectral
properties of the impurity constitute an ideal probe to the dissipative Fermi
gas in the background. In particular, we show that dissipation destabilizes
polarons in favor of molecular formation, consistent with previous few-body
studies. The dissipative nature of the Fermi gas further leads to broadened
peaks in the inverse radio-frequency spectra for both the attractive and
repulsive polaron branches, which could serve as signals for experimental
observation. Our results provides an exemplary scenario where the interplay of
non-Hermiticity and interaction can be probed.",2010.12767v1
2020-11-03,Tunable-spin-model generation with spin-orbit-coupled fermions in optical lattices,"We study the dynamical behaviour of ultracold fermionic atoms loaded into an
optical lattice under the presence of an effective magnetic flux, induced by
spin-orbit coupled laser driving. At half filling, the resulting system can
emulate a variety of iconic spin-1/2 models such as an Ising model, an XY
model, a generic XXZ model with arbitrary anisotropy, or a collective one-axis
twisting model. The validity of these different spin models is examined across
the parameter space of flux and driving strength. In addition, there is a
parameter regime where the system exhibits chiral, persistent features in the
long-time dynamics. We explore these properties and discuss the role played by
the system's symmetries. We also discuss experimentally-viable implementations.",2011.01842v3
2017-11-23,Magnetic and Electronic Properties of Spin-Orbit Coupled Dirac Electrons on a $(001)$ Thin Film of Double Perovskite Sr$_2$FeMoO$_6$,"We present an interacting model for the electronic and magnetic behavior of a
strained $(001)$ atomic layer of Sr$_2$FeMoO$_6,$ which shows room-temperature
ferrimagnetism and magnetoresistance with potential spintronics application in
the bulk. We find that the strong spin-orbit coupling in the molybdenum 4$d$
shell gives rise to a robust ferrimagnetic state with an emergent
spin-polarized electronic structure consisting of flat bands and four massive
or massless Dirac dispersions. Based on the spin-wave theory, we demonstrate
that the magnetic order remains intact for a wide range of doping, leading to
the possibility of exploring flat band physics, such as Wigner crystallization
in electron-doped Sr$_{2-x}$La$_{x}$FeMoO$_6.$",1711.08674v3
2019-06-06,Odd-Parity Superconductivity Driven by Octahedra Rotations in Iridium Oxides,"Iridium oxides have provided a playground to study novel phases originating
from spin-orbit coupling and electron-electron interactions. Among them, the
d-wave singlet superconductor was proposed for electron-doped Sr$_2$IrO$_4$,
containing two Ir atoms in a unit cell due to the staggered rotation of oxygen
octahedra about the c-axis. It was also noted that such oxygen octahedra
rotation affects electronic transports. Here we study the role of octahedra
tilting away from the c-axis, in determining superconducting pairing symmetry.
We show that the octahedra tilting changes the large Fermi surface to a Dirac
point, which strongly suppresses the conventional d-wave pairing. Furthermore,
it also promotes effective spin-triplet interactions in the strong Hubbard
interaction limit, leading to a transition from the even-parity to odd-parity
superconducting phase. Thus, tuning octahedra distortions can be used as a tool
to engineer a spin triplet superconductor in strongly correlated systems with
strong spin-orbit coupling.",1906.02749v1
2022-05-30,Spin-orbit-derived giant magnetoresistance in a layered magnetic semiconductor AgCrSe2,"Two-dimensional magnetic materials have recently attracted great interest due
to their unique functions as the electric field control of a magnetic phase and
the anomalous spin Hall effect. For such remarkable functions, a spin-orbit
coupling (SOC) serves as an essential ingredient. Here we report a giant
positive magnetoresistance in a layered magnetic semiconductor AgCrSe2, which
is a manifestation of the subtle combination of the SOC and Zeeman-type spin
splitting. When the carrier concentration approaches the critical value of
2.5\times10^18 cm^-3, a sizable positive magnetoresistance of ~400 % emerges
upon the application of magnetic fields normal to the conducting layers. Based
on the magneto-Seebeck effect and the first-principles calculations, the
unconventional magnetoresistance is ascribable to the enhancement of effective
carrier mass in the SOC induced J = 3/2 state, which is tuned to the Fermi
level through the Zeeman splitting enhanced by the p-d coupling. This study
demonstrates a new aspect of the SOC-derived magnetotransport in
two-dimensional magnetic semiconductors, paving the way to novel spintronic
functions.",2205.14795v1
2022-06-08,Tunable zero-energy Dirac and Luttinger nodes in a two-dimensional topological superconductor,"Cooper pairing in ultrathin films of topological insulators, induced
intrinsically or by proximity effect, can produce an energetically favorable
spin-triplet superconducting state. The spin-orbit coupling acts as an SU(2)
gauge field and stimulates the formation of a spin-current vortex lattice in
this superconducting state. Here we study the Bogoliubov quasiparticles in such
a state and find that the quasiparticle spectrum consists of a number of Dirac
nodes pinned to zero energy by the particle-hole symmetry. Some nodes are
""accidental"" and move through the first Brillouin zone along high-symmetry
directions as the order parameter magnitude or the strength of the spin-orbit
coupling are varied. At special parameter values, nodes forming neutral
quadruplets merge and become gapped out, temporarily producing a quadratic
band-touching spectrum. All these features are tunable by controlling the order
parameter magnitude via a gate voltage in a heterostructure device. In addition
to analyzing the spectrum at the mean-field level, we briefly discuss a few
experimental signatures of this spectrum.",2206.04065v2
2022-08-15,Emergent chiral symmetry in non-bipartite kagome and pyrochlore lattices with spin-orbit coupling,"Chiral symmetry in energy bands appears as perfectly symmetric anti-bonding
and bonding pairs of energy levels. It has only been observed in a few classes
of models with a bipartite lattice structure or Bogoliubov-de-Gennes systems
having the pairwise basis. We show that the non-bipartite kagome and pyrochlore
lattices can host chiral symmetric bands when the strong spin-orbit coupling is
introduced. There, the electrons hop to their neighbors by always converting
the spin orientation up-side-down, which allows the up and down spin bases to
form fictitious bipartite connections. The gauge invariant Wilson loop operator
defined on a triangular unit serves as a marker to detect the presence of
chiral symmetry, and using this property, the chiral operator is constructed.
This allows us to access their topological symmetry classes that can easily
change with small perturbations.",2208.07171v1
2023-03-07,Impact of gapped spin-orbit excitons on low energy pseudospin exchange interactions,"The quest for exotic quantum magnetic ground states, including the Kitaev
spin liquid and quantum spin-ices, has led to the discovery of several quantum
materials where low energy pseudospin-$1/2$ doublets arise from the splitting
of spin-orbit entangled multiplets with higher degeneracy. Such systems include
$d$-orbital and $f$-orbital Mott insulators. When the gap between the low
energy pseudospin-$1/2$ levels and the excited levels of the multiplet or
`excitons' is not large, the effective low-energy exchange interactions between
the low energy pseudospin-$1/2$ moments can acquire significant corrections
from coupling to the excitons. We extract these corrections using higher order
perturbation theory as well as an exact Schrieffer-Wolff transformation. Such
corrections can impact the exchange matrix for the low energy pseudospin-$1/2$
levels by renormalizing the strength and the sign of Heisenberg exchange or
Ising anisotropies, and potentially even inducing bond-anisotropic couplings
such as Kitaev-$\Gamma$ exchange interactions. We discuss recent experiments on
various cobaltate and osmate materials which hint at the ubiquity and
importance of this physics.",2303.04169v1
2023-06-30,Substrate suppression of oxidation process in pnictogen monolayers,"2D materials present an interesting platform for device designs. However,
oxidation can drastically change the system's properties, which need to be
accounted for. Through {\it ab initio} calculations, we investigated
freestanding and SiC-supported As, Sb, and Bi mono-elemental layers. The
oxidation process occurs through an O$_2$ spin-state transition, accounted for
within the Landau-Zener transition. Additionally, we have investigated the
oxidation barriers and the role of spin-orbit coupling. Our calculations
pointed out that the presence of SiC substrate reduces the oxidation time scale
compared to a freestanding monolayer. We have extracted the energy barrier
transition, compatible with our spin-transition analysis. Besides, spin-orbit
coupling is relevant to the oxidation mechanisms and alters time scales. The
energy barriers decrease as the pnictogen changes from As to Sb to Bi for the
freestanding systems, while for SiC-supported, they increase across the
pnictogen family. Our computed energy barriers confirm the enhanced robustness
against oxidation for the SiC-supported systems.",2307.00138v1
2023-10-22,Properties of an α-T3 Aharonov-Bohm quantum ring: Interplay of Rashba spin-orbit coupling and topological defect,"In this paper we investigate the interplay of the Rashba spin-orbit coupling
(RSOC) and a topological defect, such as a screw dislocation in an {\alpha}-T3
Aharonov-Bohm quantum ring and scrutinized the effect of an external transverse
magnetic field therein. Our study reveals that the energy spectrum follows a
parabolic dependence on the Burgers vector associated with the screw
dislocation. Moreover, its presence results in an effective flux, encompassing
the ramifications due to both the topological flux and that due to the external
magnetic field. Furthermore, we observe periodic oscillations in the persistent
current in both charge and spin sectors, with a period equal to one flux
quantum, which, however suffers a phase shift that is proportional to the
dislocation present in the system. Such tunable oscillations of the spin
persistent current highlights potential application of our system to be used as
spintronic devices. Additionally, we derive and analyse the thermodynamic
properties of the ring via obtaining the canonical partition function through
Euler-Maclaurin formula. In particular, we compute the thermodynamic
potentials, free energies, entropy, and heat capacity and found the latter to
yield the expected Dulong-Petit law at large temperatures.",2310.14169v1
2024-02-03,Weyl semimetallic state with antiferromagnetic order in Rashba-Hubbard model,"We study the phase diagram of Rashba-Hubbard model by employing the
Hartree-Fock meanfield theory, and thereby establish the existence of an
antiferromagnetically ordered Weyl semimetallic state with in-plane magnetic
moments. This phase is found to be sandwiched in between the antiferromagnetic
insulator and Rashba metal in the interaction vs spin-orbit coupling phase
diagram. The antiferromagnetically-ordered topological semimetallic state
exists in the presence of combined time-reversal and inversion symmetry though
individually both are broken. The study of the static magnetic susceptibility
indicates the robustness of the antiferromagnetic order within a realistic
range of interaction and spin-orbit coupling parameters. In addition to the
edge states associated with the Weyl points, we also investigate the
spin-resolved quasiparticle interference, which provides important insight into
the possible spin texture of the bands especially in the vicinity of Weyl
points.",2402.02131v1
2024-03-19,Dielectric response in twisted MoS2 bilayer facilitated by spin-orbit coupling effect,"Twisted van der Waals bilayers provide ideal two-dimensional (2D) platforms
to study the interplay between spin and charge degree of freedom of electron.
An exotic dielectric response behavior in such system is what we find here
through the investigation of twisted bilayer MoS2 with two different stackings
but same size of the commensurate supercell, which forms H-type like and R-type
like stacked bilayer system. Our first-principles calculations show that
applying an out-of-plane electric field gives rise to different response of the
electric polarization, whose susceptibility is suppressed in H-type like case
compared with that of R-type like one. Further analysis shows the dielectric
response to perpendicular electric field is linked to the moire ferroelectric
dipole texture. Their underlying link comes from that, through Rashba
spin-orbit coupling (SOC) effect, the external electric field tends to change
the internal pseudo-spin texture, which further depends on the twist induced
dipole texture. Consequently, the suppression of dielectric response can be
attributed to the topology protection of such ferroelectric dipole structure.",2403.12475v1
2010-10-06,Orbital degrees of freedom as origin of magnetoelectric coupling in magnetite,"A microscopic understanding of magnetoelectricity, i.e. the coupling between
magnetic (electric) properties and external electric (magnetic) fields, is a
crucial milestone for future generations of electrically-controlled spintronic
devices. Here, we focus on the first magnetoelectric known to mankind:
magnetite. By means of a joint approach based on phenomenological Landau theory
and density-functional simulations, we show that magnetoelectricity in
charge-/orbital-ordered Fe3O4 in the non-centrosymmetric Cc structure is driven
by the interplay between a peculiar orbital-order and on-site spin-orbit
coupling. The excellent agreement with available experiments confirms our
theoretical picture, pointing to magnetite as a prototype of a novel category
of magnetoelectrics where ferroelectric polarization can be induced, tuned or
switched via a magnetic field.",1010.1105v2
2004-05-21,A new numerical algorithm for the double-orbital Hubbard model -- Hund-coupled pairing symmetry in the doped case,"In order to numerically study electron correlation effects in multi-orbital
systems, we propose a new type of discrete transformation for the exchange
(Hund's coupling) and pair-hopping interactions to be used in the dynamical
mean field theory + quantum Monte Carlo method. The transformation, which is
real and exact, turns out to suppress the sign problem in a wide parameter
region including non-half-filled bands. This enables us to obtain the dominant
pairing symmetry in the double-orbital Hubbard model, which shows that the
spin-triplet, orbital-antisymmetric pairing that exploits Hund's coupling is
stable in a wide region of the band filling.",0405503v1
2016-06-06,Band gap tuning and orbital mediated electron phonon coupling in $HoFe_{1-x}Cr_xO_3$,"We report on the evidenced orbital mediated electron phonon coupling and band
gap tuning in HoFe1-xCrxO3 compounds. From the room temperature Raman
scattering, it is apparent that the electron-phonon coupling is sensitive to
the presence of both the Fe and Cr at the B-site. Essentially, an Ag like local
oxygen breathing mode is activated due to the charge transfer between Fe3+ -
Cr3+ at around 670 cm-1, this observation is explained on the basis of
Franck-Condon (FC) mechanism. Optical absorption studies infer that there
exists a direct band gap in the HoFe1-xCrxO3 compounds. Decrease in band gap
until x = 0.5 is ascribed to the broadening of the oxygen p orbitals as a
result of the induced spin disorder due to Fe3+ and Cr3+ at B site. In
contrast, the increase in band gap above x = 0.5 is explained on the basis of
the reduction in the available unoccupied d - orbitals of Fe3+ at the
conduction band. We believe that above results would be helpful for the
development of the optoelectronic devices based on the ortho-ferrites.",1606.01698v1
2013-10-23,Neutron scattering measurements of $dd$ and spin-orbit excitations below the Mott-Hubbard gap in CoO,"Neutron scattering is used to investigate the single-ion spin and orbital
excitations below the Mott-Hubbard gap in CoO. Three excitations are reported
at 0.870 $\pm$ 0.009 eV, 1.84 $\pm$ 0.03, and 2.30 $\pm$ 0.15 eV. These were
parameterized within a weak crystal field scheme with an intra-orbital exchange
of $J(dd)$=1.3 $\pm$ 0.2 eV and a crystal field splitting 10Dq=0.94 $\pm$ 0.10
eV. A reduced spin-orbit coupling of \lambda=-0.016 $\pm$ 0.003 eV is derived
from dilute samples of Mg$_{0.97}$Co$_{0.03}$O, measured to remove
complications due to spin exchange and structural distortion parameters which
split the cubic phase degeneracy of the orbital excitations complicating the
inelastic spectrum. The 1.84 eV, while reported using resonant x-ray and
optical techniques, was absent or weak for non resonant x-ray experiments and
overlaps with the expected position of a $^{4}A_{2}$ level. This transition is
absent in the dipolar approximation but expected to have a finite quadrupolar
matrix element that can be observed with neutron scattering techniques at
larger momentum transfers. Our results agree with a crystal field analysis (in
terms of Racah parameters and Tanabe-Sugano diagrams) and with previous
calculations performed using local-density band theory for Mott insulating
transition metal oxides. The results also demonstrate the use of neutron
scattering for measuring dipole forbidden transitions in transition metal oxide
systems.",1310.6207v1
2014-01-20,Momentum dependence of spin-orbit interaction effects in single-layer and multi-layer transition metal dichalcogenides,"One of the main characteristics of the new family of two-dimensional crystals
of semiconducting transition metal dichalcogenides (TMD) is the strong
spin-orbit interaction, which makes them very promising for future applications
in spintronics and valleytronics devices. Here we present a detailed study of
the effect of spin-orbit coupling (SOC) on the band structure of single-layer
and bulk TMDs, including explicitly the role of the chalcogen orbitals and
their hybridization with the transition metal atoms. To this aim, we combine
density functional theory (DFT) calculations with a Slater-Koster tight-binding
model. Whereas most of the previous tight-binding models have been restricted
to the K and K' points of the Brillouin zone (BZ), here we consider the effect
of SOC in the whole BZ, and the results are compared to the band structure
obtained by DFT methods. The tight-binding model is used to analyze the effect
of SOC in the band structure, considering separately the contributions from the
transition metal and the chalcogen atoms. Finally, we present a scenario where,
in the case of strong SOC, the spin/orbital/valley entanglement at the minimum
of the conduction band at Q can be probed and be of experimental interest in
the most common cases of electron-doping reported for this family of compounds.",1401.5009v2
2015-09-23,Tilting Saturn without tilting Jupiter: Constraints on giant planet migration,"The migration and encounter histories of the giant planets in our Solar
System can be constrained by the obliquities of Jupiter and Saturn. We have
performed secular simulations with imposed migration and N-body simulations
with planetesimals to study the expected obliquity distribution of migrating
planets with initial conditions resembling those of the smooth migration model,
the resonant Nice model and two models with five giant planets initially in
resonance (one compact and one loose configuration). For smooth migration, the
secular spin-orbit resonance mechanism can tilt Saturn's spin axis to the
current obliquity if the product of the migration time scale and the orbital
inclinations is sufficiently large (exceeding 30 Myr deg). For the resonant
Nice model with imposed migration, it is difficult to reproduce today's
obliquity values, because the compactness of the initial system raises the
frequency that tilts Saturn above the spin precession frequency of Jupiter,
causing a Jupiter spin-orbit resonance crossing. Migration time scales
sufficiently long to tilt Saturn generally suffice to tilt Jupiter more than is
observed. The full N-body simulations tell a somewhat different story, with
Jupiter generally being tilted as often as Saturn, but on average having a
higher obliquity. The main obstacle is the final orbital spacing of the giant
planets, coupled with the tail of Neptune's migration. The resonant Nice case
is barely able to simultaneously reproduce the {orbital and spin} properties of
the giant planets, with a probability ~0.15%. The loose five planet model is
unable to match all our constraints (probability <0.08%). The compact five
planet model has the highest chance of matching the orbital and obliquity
constraints simultaneously (probability ~0.3%).",1509.06834v1
2018-08-16,Pressure-induced collapse of spin-orbital Mott state in the hyperhoneycomb iridate $β$-Li$_2$IrO$_3$,"Hyperhoneycomb iridate $\beta$-Li$_2$IrO$_3$ is a three-dimensional analogue
of two-dimensional honeycomb iridates, such as $\alpha$-Li$_2$IrO$_3$, which
recently appeared as another playground for the physics of Kitaev-type spin
liquid. $\beta$-Li$_2$IrO$_3$ shows a non-collinear spiral ordering of
spin-orbital-entangled $J_{\rm eff}$ = 1/2 moments at low temperature, which is
known to be suppressed under a pressure of $\sim$2 GPa. With further increase
of pressure, a structural transition is observed at $P_{\rm S}$ $\sim$ 4 GPa at
room temperature. Using the neutron powder diffraction technique, the crystal
structure in the high-pressure phase of $\beta$-Li$_2$IrO$_3$ above $P_{\rm S}$
was refined, which indicates the formation of Ir$_2$ dimers on the zig-zag
chains, with the Ir-Ir distance even shorter than that of metallic Ir. We argue
that the strong dimerization stabilizes the bonding molecular orbital state
comprising the two local $d_{zx}$-orbitals on the Ir-O$_2$-Ir bond plane, which
conflicts with the equal superposition of $d_{xy}$-, $d_{yz}$- and $d_{zx}$-
orbitals in the $J_{\rm eff}$ = 1/2 wave function produced by strong spin-orbit
coupling. The results of resonant inelastic x-ray scattering (RIXS)
measurements and the electronic structure calculations are fully consistent
with the collapse of the $J_{\rm eff}$ = 1/2 state. A subtle competition of
various electronic phases is universal in honeycomb-based Kitaev materials.",1808.05494v1
2022-08-26,Quasiparticle characteristics of the weakly ferromagnetic Hund's metal MnSi,"Hund's metals are multi-orbital systems with $3d$ or $4d$ electrons
exhibiting both itinerant character and local moments, and they feature
Kondo-like screenings of local orbital and spin moments, with suppressed
coherence temperature driven by Hund's coupling $J_H$. They often exhibit
magnetic order at low temperature, but how the interaction between the
Kondo-like screening and long-range magnetic order is manifested in the
quasiparticle spectrum remains an open question. Here we present spectroscopic
signature of such interaction in a Hund's metal candidate MnSi exhibiting weak
ferromagnetism. Our photoemission measurements reveal renormalized
quasiparticle bands near the Fermi level with strong momentum dependence: the
ferromagnetism manifests through possibly exchange-split bands (Q1) below $T_C$
, while the spin/orbital screenings lead to gradual development of
quasiparticles (Q2) upon cooling. Our results demonstrate how the
characteristic spin/orbital coherence in a Hund's metal could coexist and
compete with the magnetic order to form a weak itinerant ferromagnet, via
quasiparticle bands that are well separated in momentum space and exhibit
distinct temperature dependence. Our results imply that the competition between
the spin/orbital screening and the magnetic order in a Hund's metal bears
intriguing similarity to the Kondo lattice systems.",2208.12456v2
2023-04-20,Contrasting electronic states of RuI3 and RuCl3,"The spin-orbital entangled states are of great interest as they hold exotic
phases and intriguing properties. Here we use first-principles calculations to
investigate the electronic and magnetic properties of RuI$_{3}$ and RuCl$_{3}$
in both bulk and monolayer cases. Our results show that RuI$_{3}$ bulk is a
paramagnetic metal, which is in agreement with recent experiments. We find that
the Ru$^{3+}$ ion of RuI$_{3}$ is in the spin-orbital entangled $j_{\rm
eff}=\frac{1}{2}$ state. More interestingly, a metal-insulator transition
occurs from RuI$_{3}$ bulk to monolayer, and this is mainly due to the band
narrowing with the decreasing lattice dimensionality and to the Ru-I
hybridization altered by the I $5p$ spin-orbit coupling. In contrast,
RuCl$_{3}$ bulk and monolayer both show Mott-insulating behavior, the Ru$^{3+}$
ion is in the formal $S=\frac{1}{2}$ and $L=1$ state with a large in-plane
orbital moment, and this result well explains the experimental large effective
magnetic moment of RuCl$_{3}$ and the strong in-plane magnetization. The
present work demonstrates the contrasting spin-orbital states and the varying
properties of RuI$_{3}$ and RuCl$_{3}$.",2304.10090v1
2017-06-12,Optical Signatures of Spin-Orbit Exciton in Bandwidth Controlled Sr$_2$IrO$_4$ Epitaxial Films via High-Concentration Ca and Ba Doping,"We have investigated the electronic and optical properties of
(Sr$_{1-x}$Ca$_{x}$)$_2$IrO$_4$ (x= 0 - 0.375) and
(Sr$_{1-y}$Ba$_y$)$_2$IrO$_4$ (y= 0 - 0.375) epitaxial thin-films, in which the
bandwidth is systematically tuned via chemical substitutions of Sr ions by Ca
and Ba. Transport measurements indicate that the thin-film series exhibits
insulating behavior, similar to the J$_{eff}$= 1/2 spin-orbit Mott insulator
Sr$_2$IrO$_4$. As the average A-site ionic radius increases from
(Sr$_{1-x}$Ca$_{x}$)$_2$IrO$_4$ to (Sr$_{1-y}$Ba$_y$)$_2$IrO$_4$, optical
conductivity spectra in the near-infrared region shift to lower energies, which
cannot be explained by the simple picture of well-separated J$_{eff}$= 1/2 and
J$_{eff}$= 3/2 bands. We suggest that the two-peak-like optical conductivity
spectra of the layered iridates originates from the overlap between the
optically-forbidden spin-orbit exciton and the inter-site optical transitions
within the J$_{eff}$= 1/2 band. Our experimental results are consistent with
this interpretation as implemented by a multi-orbital Hubbard model
calculation: namely, incorporating a strong Fano-like coupling between the
spin-orbit exciton and inter-site d-d transitions within the J$_{eff}$= 1/2
band.",1706.03529v1
1999-10-07,Meson-like Baryons and the Spin-Orbit Puzzle,"I describe a special class of meson-like \Lambda_Q excited states and present
evidence supporting the similarity of their spin-independent spectra to those
of mesons. I then examine spin-dependent forces in these baryons, showing that
predicted effects of spin-orbit forces are small for them for the same reason
they are small for the analogous mesons: a fortuitous cancellation between
large spin-orbit forces due to one-gluon-exchange and equally large inverted
spin-orbit forces due to Thomas precession in the confining potential. In
addition to eliminating the baryon spin-orbit puzzle in these states, this
solution provides a new perspective on spin-orbit forces in all baryons.",9910272v1
2001-02-13,Magnetic and Orbital States and Their Phase Transition of the Perovskite-Type Ti Oxides: Strong Coupling Approach,"The properties and mechanism of the magnetic phase transition of the
perovskite-type Ti oxides, which is driven by the Ti-O-Ti bond angle
distortion, are studied theoretically by using the effective spin and
pseudospin Hamiltonian with strong Coulomb repulsion. It is shown that the
A-type antiferromagnetic (AFM(A)) to ferromagnetic (FM) phase transition occurs
as the Ti-O-Ti bond angle is decreased. Through this phase transition, the
orbital state changes only little whereas the spin-exchange coupling along the
c-axis is expected to change from positive to negative nearly continuously and
approaches zero at the phase boundary. The resultant strong two-dimensionality
in the spin coupling causes rapid suppression of the critical temperature, as
observed experimentally. It may induce large quantum fluctuations in this
region.",0102223v1
2009-06-15,Effect of the spin-orbit interaction and the electron phonon coupling on the electronic state in a silicon vacancy,"The electronic state around a single vacancy in silicon crystal is
investigated by using the Green's function approach. The triply degenerate
charge states are found to be widely extended and account for extremely large
elastic softening at low temperature as observed in recent ultrasonic
experiments. When we include the LS coupling $\lambda_{\rm Si}$ on each Si
atom, the 6-fold spin-orbital degeneracy for the $V^{+}$ state with the valence
+1 and spin 1/2 splits into $\Gamma_{7}$ doublet groundstates and $\Gamma_{8}$
quartet excited states with a reduced excited energy of $O(\lambda_{\rm
Si}/10)$. We also consider the effect of couplings between electrons and
Jahn-Teller phonons in the dangling bonds within the second order perturbation
and find that the groundstate becomes $\Gamma_{8}$ quartet which is responsible
for the magnetic-field suppression of the softening in B-doped silicon.",0906.2596v2
2014-08-26,Ferromagnetic and Nematic Non-Fermi Liquids in Spin-Orbit Coupled Two-Dimensional Fermi Gases,"We study the fate of a two-dimensional system of interacting fermions with
Rashba spin-orbit coupling in the dilute limit. The interactions are strongly
renormalized at low densities, and give rise to various fermionic liquid
crystalline phases, including a spin-density wave, an in-plane ferromagnet, and
a non-magnetic nematic phase, even in the weak coupling limit. The nature of
the ground state in the low-density limit depends on the range of the
interactions: for short range interactions it is the ferromagnet, while for
dipolar interactions the nematic phase is favored. Interestingly, the
ferromagnetic and nematic phases exhibit strong deviations from Fermi liquid
theory, due to the scattering of the Fermionic quasi-particles off
long-wavelength collective modes. Thus, we argue that a system of interacting
fermions with Rashba dispersion is generically a non-Fermi liquid at low
densities.",1408.6250v3
2017-03-29,Magnon dispersion in Ca2RuO4: impact of spin-orbit coupling and oxygen moments,"The magnon dispersion of Ca$_2$RuO$_4$ has been studied by polarized and
unpolarized neutron scattering experiments on crystals containing 0, 1 and 10 %
of Ti. The entire dispersion of transverse magnons can be well described by a
conventional spin-wave model with interaction and anisotropy parameters that
agree with density functional theory calculations. Spin-orbit coupling strongly
influences the magnetic excitations, which is most visible in large energies of
the magnetic zone-center modes arising from magnetic anisotropy. We find
evidence for a low-lying additional mode that exhibits strongest scattering
intensity near the antiferromagnetic zone center. This extra signal can be
explained by a sizable magnetic moment of 0.11 Bohr magnetons on the apical
oxygens parallel to the Ru moment, which is found in the density functional
theory calculations. The energy and the signal strength of the additional
branch are well described by taking into account this oxygen moment with weak
ferromagnetic coupling between Ru and O moments.",1703.10017v1
2020-07-08,Supersolid Striped Droplets in a Raman Spin-Orbit-Coupled System,"We analyze the role played by quantum fluctuations on a Raman Spin-Orbit
Coupled system in the stripe phase. We show that beyond mean-field effects
stabilize the collapse predicted by mean-field theory and induce the emergence
of two phases: a gas and a liquid, which also show spatial periodicity along a
privileged direction. We show that the energetically favored phase is
determined by the Raman coupling and the spin-dependent scattering lengths. We
obtain the ground-state solution of the finite system by solving the extended
Gross-Pitaevskii equation and find self-bound, droplet-like solutions that
feature internal structure through a striped pattern. We estimate the critical
number for binding associated to these droplets and show that their value is
experimentally accessible. We report an approximate energy functional in order
to ease the evaluation of the Lee-Huang-Yang correction in practical terms.",2007.04196v1
2020-01-14,Self-bound supersolid stripe phase in binary Bose-Einstein condensates,"Supersolidity - a coexistence of superfluidity and crystalline or amorphous
density variations - has been vividly debated ever since its conjecture. While
the initial focus was on helium-4, recent experiments uncovered supersolidity
in ultra-cold dipolar quantum gases. Here, we propose a new self-bound
supersolid phase in a binary mixture of Bose gases with short-range
interactions, making use of the non-trivial properties of spin-orbit coupling.
We find that a first-order phase transition from a self-bound supersolid stripe
phase to a zero-minimum droplet state of the Bose gas occurs as a function of
the Rabi coupling strength. These phases are characterized using the momentum
distribution, the transverse spin polarization and the superfluid fraction. The
critical point of the transition is estimated in an analytical framework. The
predicted density-modulated supersolid stripe and zero-minimum droplet phase
should be experimentally observable in a binary mixture of $^{39}$K with
spin-orbit coupling.",2001.04751v1
2020-01-17,Supersolid Stripes Enhanced by Correlations in a Raman Spin-Orbit-Coupled System,"A Bose gas under the effect of Raman Spin-Orbit Coupling (SOC) is analyzed
using the Discrete Spin T-moves Diffusion Monte Carlo method. By computing the
energy as well as the static structure factor and the superfluid fraction of
the system, the emergence of an energetically favorable supersolid stripe state
is observed, which is in agreement with recent observations. A significant
enhancement of the stability of the stripe phase with respect to the mean-field
prediction is observed when the strength of the inter-atomic correlations is
increased. We also quantify and characterize the degree of superfluidity of the
stripes and show that this quantity is mostly determined by the ratio between
the Raman coupling and the square of the momentum difference between the pair
of SOC inducing laser beams.",2001.06394v2
2020-02-12,Spin-orbit coupling in photonic graphene,"We generate experimentally a honeycomb refractive index pattern in an atomic
vapor cell using electromagnetically-induced transparency. We study
experimentally and theoretically the propagation of polarized light beams in
such ""photonic graphene"". We demonstrate that an effective spin-orbit coupling
appears as a correction to the paraxial beam equations because of the strong
spatial gradients of the permittivity. It leads to the coupling of spin and
angular momentum at the Dirac points of the graphene lattice. Our results
suggest that the polarization degree plays an important role in many
configurations where it has been previously neglected.",2002.04927v1
2017-07-16,"Reorientations, relaxations, metastabilities and multidomains of skyrmion lattices","Magnetic skyrmions are nano-sized topologically protected spin textures with
particle-like properties. They can form lattices perpendicular to the magnetic
field and the orientation of these skyrmion lattices with respect to the
crystallographic lattice is governed by spin-orbit coupling. By performing
small angle neutron scattering measurements, we investigate the coupling
between the crystallographic and skyrmion lattices in both Cu$_2$OSeO$_3$ and
the archetype chiral magnet MnSi. The results reveal that the orientation of
the skyrmion lattice is primarily determined by the magnetic field direction
with respect to the crystallographic lattice. In addition, it is also
influenced by the magnetic history of the sample which can induce metastable
lattices. Kinetic measurements show that these metastable skyrmion lattices may
or may not relax to their equilibrium positions under macroscopic relaxation
times. Furthermore, multidomain lattices may form when two or more equivalent
crystallographic directions are favored by spin-orbit coupling and oriented
perpendicular to the magnetic field.",1707.04921v2
2023-07-19,Coupling of the triple-Q state to the atomic lattice by anisotropic symmetric exchange,"We identify the triple-Q (3Q) state as magnetic ground state in Pd/Mn and
Rh/Mn bilayers on Re(0001) using spin-polarized scanning tunneling microscopy
and density functional theory. An atomistic model reveals that in general the
3Q state with tetrahedral magnetic order and zero net spin moment is coupled to
a hexagonal atomic lattice in a highly symmetric orientation via the
anisotropic symmetric exchange interaction, whereas other spin-orbit coupling
terms cancel due to symmetry. Our experiments are in agreement with the
predicted orientation of the 3Q state. A distortion from the ideal tetrahedral
angles leads to other orientations of the 3Q state which, however, results in a
reduced topological orbital magnetization compared to the ideal 3Q state.",2307.09764v1
2009-03-04,Phonon-induced dephasing of singlet-triplet superpositions in double quantum dots without spin-orbit coupling,"We show that singlet-triplet superpositions of two-electron spin states in a
double quantum dot undergo a phonon-induced pure dephasing which relies only on
the tunnel coupling between the dots and on the Pauli exclusion principle. As
such, this dephasing process is independent of spin-orbit coupling or hyperfine
interactions. The physical mechanism behind the dephasing is elastic phonon
scattering, which persists to much lower temperatures than real phonon-induced
transitions. Quantitative calculations performed for a lateral GaAs/AlGaAs
gate-defined double quantum dot yield micro-second dephasing times at
sub-Kelvin temperatures, which is consistent with experimental observations.",0903.0783v2
2011-09-09,Signatures of Rashba spin-orbit interaction in the superconducting proximity effect in helical Luttinger liquids,"We consider the superconducting proximity effect in a helical Luttinger
liquid at the edge of a 2D topological insulator, and derive the low-energy
Hamiltonian for an edge state tunnel-coupled to a s-wave superconductor. In
addition to correlations between the left and right moving modes, the coupling
can induce them inside a single mode, as the spin axis of the edge modes is not
necessarily constant. This can be induced controllably in HgTe/CdTe quantum
wells via the Rashba spin-orbit coupling, and is a consequence of the 2D nature
of the edge state wave function. The distinction of these two features in the
proximity effect is also vital for the use of such helical modes in order to
split Cooper-pairs. We discuss the consequent transport signatures, and point
out a long-ranged feature in a dc conductance measurement that can be used to
distinguish the two types of correlations present and to determine the
magnitude of the Rashba interaction.",1109.2097v2
2013-03-27,Superstripes and the excitation spectrum of a spin-orbit-coupled Bose-Einstein condensate,"Using Bogoliubov theory we calculate the excitation spectrum of a spinor
Bose-Einstein condensed gas with equal Rashba and Dresselhaus spin-orbit
coupling in the stripe phase. The emergence of a double gapless band structure
is pointed out as a key signature of Bose-Einstein condensation and of the
spontaneous breaking of translational invariance symmetry. In the long
wavelength limit the lower and upper branches exhibit, respectively, a clear
spin and density nature. For wave vectors close to the first Brillouin zone,
the lower branch acquires an important density character responsible for the
divergent behavior of the structure factor and of the static response function,
reflecting the occurrence of crystalline order. The sound velocities are
calculated as functions of the Raman coupling for excitations propagating
orthogonal and parallel to the stripes. Our predictions provide new
perspectives for the identification of supersolid phenomena in ultracold atomic
gases.",1303.6903v2
2013-06-26,Finite-temperature conductance of weakly interacting quantum wires with Rashba spin-orbit coupling,"We calculate the finite-temperature conductance of clean, weakly interacting
one-dimensional quantum wires subject to Rashba spin-orbit coupling and a
magnetic field. For chemical potentials near the center of the Zeeman gap ($\mu
= 0$), two-particle scattering causes the leading deviation from the quantized
conductance at finite temperatures. On the other hand, for $|\mu| > 0$,
three-particle scattering processes become more relevant. These deviations are
a consequence of the strongly nonlinear single-particle spectrum, and are thus
not accessible using Luttinger liquid theory. We discuss the observability of
these predictions in current experiments on InSb nanowires and in ""spiral
liquids"", where a spontaneous ordering of the nuclear spins at low temperatures
produces an effective Rashba coupling.",1306.6218v3
2014-02-25,Signatures of the Helical Phase in the Critical Fields at Twin Boundaries of Non-Centrosymmetric Superconductors,"Domains in non-centrosymmetric materials represent regions of different
crystal structure and spin-orbit coupling. Twin boundaries separating such
domains display unusual properties in non-centrosymmetric superconductors
(NCS), where magneto-electric effects influence the local lower and upper
critical magnetic fields. As a model system, we investigate NCS with tetragonal
crystal structure and Rashba spin-orbit coupling (RSOC), and with twin
boundaries parallel to their basal planes. There, we report that there are two
types of such twin boundaries which separate domains of opposite RSOC. In a
magnetic field parallel to the basal plane, magneto-electric coupling between
the spin polarization and supercurrents induces an effective magnetic field at
these twin boundaries. We show this leads to unusual effects in such
superconductors, and in particular to the modification of the upper and lower
critical fields, in ways that depend on the type of twin boundary, as analyzed
in detail, both analytically and numerically. Experimental implications of
these effects are discussed.",1402.6027v1
2015-04-28,"Multicriticality, Metastability, and Roton Feature in Bose-Einstein Condensates with Three-Dimensional Spin-Orbit Coupling","We theoretically study homogeneously trapped atomic Bose-Einstein condensates
where all three momentum components couple to a pseudo-spin-$1/2$ degree of
freedom. Tuning the anisotropies of spin-orbit coupling and the spin-dependent
interactions is shown to provide access to a rich phase diagram with a
tetracritical point, first-order phase transitions, and multiple metastable
phases of stripe and plane-wave character. The elementary excitation spectrum
of the axial plane-wave phase features an anisotropic roton feature and can be
used to probe the phase diagram. In addition to providing a versatile
laboratory for studying fundamental concepts in statistical physics, the
emergence of metastable phases creates new opportunities for observing
false-vacuum decay and bubble nucleation in ultra-cold-atom experiments.",1504.07370v1
2015-11-18,Spin-orbit torque switching without external field with a ferromagnetic exchange-biased coupling layer,"Magnetization reversal of a perpendicular ferromagnetic free layer by
spin-orbit torque (SOT) is an attractive alternative to spin-transfer torque
(STT) switching in magnetic random-access memory (MRAM) where the write process
involves passing a high current across an ultrathin tunnel barrier. A small
symmetry-breaking bias field is usually needed for deterministic SOT switching
but it is impractical to generate the field externally for spintronic
applications. Here, we demonstrate robust zero-field SOT switching of a
perpendicular Co90Fe10 (CoFe) free layer where the symmetry is broken by
magnetic coupling to a second in-plane exchange-biased CoFe layer via a
nonmagnetic Ru spacer. The preferred magnetic state of the free layer is
determined by the current polarity and the nature of the interlayer exchange
coupling (IEC). Our strategy offers a scalable solution to realize
bias-field-free SOT switching that can lead to a generation of SOT-based
devices, that combine high storage density and endurance with potentially low
power consumption.",1511.05773v1
2015-11-26,Experimental observation of a topological band gap opening in ultracold Fermi gases with two-dimensional spin-orbit coupling,"The recent experimental realization of synthetic spin-orbit coupling (SOC)
opens a new avenue for exploring novel quantum states with ultracold atoms.
However, in experiments for generating two-dimensional SOC (e.g., Rashba type),
a perpendicular Zeeman field, which opens a band gap at the Dirac point and
induces many topological phenomena, is still lacking. Here we theoretically
propose and experimentally realize a simple scheme for generating two-dimension
SOC and a perpendicular Zeeman field simultaneously in ultracold Fermi gases by
tuning the polarization of three Raman lasers that couple three hyperfine
ground states of atoms. The resulting band gap opening at the Dirac point is
probed using spin injection radio-frequency spectroscopy. Our observation may
pave the way for exploring topological transport and topological superfluids
with exotic Majorana and Weyl fermion excitations in ultracold atoms.",1511.08492v2
2016-01-28,Two Dimensional Antiferromagnetic Chern Insulator NiRuCl6,"Based on DFT and Berry curvature calculations, we predict that quantum
anomalous hall effect (QAHE) can be realized in two dimensional
anti-ferromagnetic (AFM) NiRuCl6 with zero net magnetic moment. By tuning
spin-orbits coupling (SOC), we find that the topological properties of NiRuCl6
come from its energy band reversal. The results indicate that NiRuCl6 behaves
as AFM Chern insulator and its spin-polarized electronic structure and strong
spin-orbits coupling (SOC) are the origin of QAHE. Considering the
compatibility between AFM and insulator, AFM Chern insulator is more suitable
to realize high temperature QAHE because generally Neel temperature of AFM
systems is more easily improved than Curie temperature of ferromagnetic (FM)
systems. Due to the different magnetic coupling mechanism between FM and AFM
Chern insulator, AFM Chern insulator provides a new way to archive high
temperature QAHE in experiments.",1601.07705v2
2019-09-29,Quantum phases and collective excitations of a spin-orbit-coupled Bose-Einstein condensate in a one-dimensional optical lattice,"The ground state of a spin-orbit-coupled Bose gas in a one-dimensional
optical lattice is known to exhibit a mixed regime, where the condensate wave
function is given by a superposition of multiple Bloch-wave components, and an
unmixed one, in which the atoms occupy a single Bloch state. The unmixed regime
features two unpolarized Bloch-wave phases, having quasimomentum at the center
or at the edge of the first Brillouin zone, and a polarized Bloch-wave phase at
intermediate quasimomenta. By calculating the critical values of the Raman
coupling and of the lattice strength at the transitions among the various
phases, we show the existence of a tricritical point where the mixed, the
polarized and the edge-quasimomentum phases meet, and whose appearance is a
consequence of the spin-dependent interaction. Furthermore, we evaluate the
excitation spectrum in the unmixed regime and we characterize the behavior of
the phonon and the roton modes, pointing out the instabilities occurring when a
phase transition is approached.",1909.13317v1
2020-02-14,Multi-channel scattering mechanism behind the re-entrant conductance feature in nanowires subject to strong spin-orbit coupling,"The characterization of helical states can be performed by checking the
existence of the re-entrant behaviour, which appears as a dip in the
conductance probed in nanowires (NWs) with strong spin-orbit coupling (SOC) and
under perpendicular magnetic field. On the other hand, the experiment described
in Ref. 1 observed the re-entrant behaviour in the absence of a magnetic field,
which was explained through spin-flipping two-particle backscattering. We
theoretically show that the observation of the re-entrant behaviour is due to a
multi-channel scattering mechanism, which causes a reduction of the
transmission when an effective attractive potential and coupling between
different channels are present. Both ingredients are provided by the SOC in the
transport properties of NWs.",2002.06046v1
2020-04-03,Quantum Anomalous Hall Effects in Graphene from Proximity-Induced Uniform and Staggered Spin-Orbit and Exchange Coupling,"We investigate an effective model of proximity modified graphene (or
symmetrylike materials) with broken time-reversal symmetry. We predict the
appearance of quantum anomalous Hall phases by computing bulk band gap and
Chern numbers for benchmark combinations of system parameters. Allowing for
staggered exchange field enables quantum anomalous Hall effect in flat graphene
with Chern number $C=1$. We explicitly show edge states in zigzag and armchair
nanoribbons and explore their localization behavior. Remarkably, the
combination of staggered intrinsic spin-orbit and uniform exchange coupling
gives topologically protected (unlike in time-reversal systems) pseudohelical
states, whose spin is opposite in opposite zigzag edges. Rotating the
magnetization from out of plane to in plane makes the system trivial, allowing
to control topological phase transitions. We also propose, using density
functional theory, a material platform---graphene on Ising antiferromagnet
MnPSe$_3$---to realize staggered exchange (pseudospin Zeeman) coupling.",2004.01760v1
2017-05-18,Strong coupling phases of the spin-orbit-coupled spin-1 Bose-Hubbard chain: odd integer Mott lobes and helical magnetic phases,"We study the odd integer filled Mott phases of a spin-1 Bose-Hubbard chain
and determine their fate in the presence of a Raman induced spin-orbit coupling
which has been achieved in ultracold atomic gases; this system is described by
a quantum spin-1 chain with a spiral magnetic field. The spiral magnetic field
initially induces helical order with either ferromagnetic or dimer order
parameters, giving rise to a spiral paramagnet at large field. The spiral
ferromagnet-to-paramagnet phase transition is in a novel universality class,
with critical exponents associated with the divergence of the correlation
length $\nu \approx 2/3$ and the order parameter susceptibility $\gamma \approx
1/2$. We solve the effective spin model exactly using the density matrix
renormalization group, and compare with both a large-$S$ classical solution and
a phenomenological Landau theory. We discuss how these exotic bosonic magnetic
phases can be produced and probed in ultracold atomic experiments in optical
lattices.",1705.06742v2
2019-01-28,Chern insulator in a ferromagnetic two-dimensional electron system with Dresselhaus spin-orbit coupling,"We propose a Chern insulator in a two-dimensional electron system with
Dresselhaus spin-orbit coupling, ferromagnetism, and spin-dependent effective
mass. The analytically-obtained topological phase diagrams show the topological
phase transitions induced by tuning the magnetization orientation with the
Chern number varying between $1,0,-1$. The magnetization orientation tuning
shown here is a more practical way of triggering the topological phase
transitions than manipulating the exchange coupling that is no longer tunable
after the fabrication of the system. The analytic results are confirmed by the
band structure and transport calculations, showing the feasibility of this
theoretical proposal. With the advanced and mature semiconductor engineering
today, this Chern insulator is very possible to be experimentally realized and
also promising to topological spintronics.",1901.09536v3
2021-04-21,Revealing hidden magneto-electric multipoles using Compton scattering,"Magneto-electric multipoles, which are odd under both space-inversion $\cal
I$ and time-reversal $\cal T$ symmetries, are fundamental in understanding and
characterizing magneto-electric materials. However, the detection of these
magneto-electric multipoles is often not straightforward as they remain
""hidden"" in conventional experiments in part since many magneto-electrics
exhibit combined $\cal IT$ symmetry. In the present work, we show that the
anti-symmetric Compton profile is a unique signature for all the
magneto-electric multipoles, since the asymmetric magnetization density of the
magneto-electric multipoles couples to space via spin-orbit coupling, resulting
in an anti-symmetric Compton profile. We develop the key physics of the
anti-symmetric Compton scattering using symmetry analysis and demonstrate it
using explicit first-principles calculations for two well-known representative
materials with magneto-electric multipoles, insulating LiNiPO$_4$ and metallic
Mn$_2$Au. Our work emphasizes the crucial roles of the orientation of the spin
moments, the spin-orbit coupling, and the band structure in generating the
anti-symmetric Compton profile in magneto-electric materials.",2104.10484v1
2017-11-20,Exposing the quantum geometry of spin-orbit coupled Fermi superfluids,"The coupling between a quantum particle's intrinsic angular momentum and its
center-of-mass motion gives rise to the so-called helicity states that are
characterized by the projection of the spin onto the direction of momentum. In
this paper, by unfolding the superfluid-density tensor into its intra-helicity
and inter-helicity components, we reveal that the latter contribution is
directly linked with the total quantum metric of the helicity bands. We
consider both Rashba and Weyl spin-orbit couplings across the BCS-BEC
crossover, and show that the geometrical inter-helicity contribution is
responsible for up to a quarter of the total superfluid density. We believe
this is one of those elusive effects that may be measured within the
highly-tunable realm of cold Fermi gases.",1711.07262v2
2021-09-15,The Dirac paradox in 1+1 dimensions and its realization with spin-orbit coupled nanowires,"At the interface between two massless Dirac models with opposite helicity a
paradoxical situation arises: A transversally impinging electron can seemingly
neither be transmitted nor reflected, due to the locking between spin and
momentum. Here we investigate this paradox in one spatial dimension where,
differently from higher dimensional realizations, electrons cannot leak along
the interface. We show that models involving only massless Dirac modes lead to
either no solutions or to trivial solutions to the paradox, depending on how
the helicity change across the interface is modeled. However, non trivial
scattering solutions to the paradox are shown to exist when additional massive
Dirac modes are taken into account. Although these modes carry no current for
energies within their gap, their interface coupling with the massless modes can
induce a finite and tunable transmission. Finally, we show that such
massless+massive Dirac model can be realized in suitably gated spin-orbit
coupled nanowires exposed to an external Zeeman field, where the transmission
coefficient can be controlled electrically.",2109.07355v2
2022-07-19,Topological Superconductivity From Forward Phonon Scatterings,"We propose a new Rashba-free mechanism to realize topological
superconductivity with electron-phonon interaction. In the presence of a
magnetic field, electron-phonon interaction with small momentum transfer is
found to favor spin-triplet Cooper pairing. This process facilitates the
formation of chiral topological superconductivity even when Rashba spin-orbital
coupling is absent. As a proof of concept, we propose an experimentally
feasible heterostructure to systematically study the entangled relationship
among forward-phonon scatterings, Rashba spin-orbital couplings, pairing
symmetries, and superconducting topology. Our theory sheds light on the
important role of electron-phonon coupled materials in the pursuit of
non-Abelian Majorana quasiparticles.",2207.09443v2
2023-01-13,Exceptional degeneracies in non-Hermitian Rashba semiconductors,"Exceptional points are spectral degeneracies of non-Hermitian systems where
eigenvalues and eigenvectors coalesce, inducing unique topological phases that
have no counterpart in the Hermitian realm. Here we consider a non-Hermitian
system by coupling a two-dimensional semiconductor with Rashba spin-orbit
coupling to a ferromagnet lead and show the emergence of highly tunable
exceptional points along rings in momentum space. Interestingly, these
exceptional degeneracies are the endpoints of lines formed by the eigenvalue
coalescence at finite real energy, resembling the bulk Fermi arcs commonly
defined at zero real energy. We then show that an in-plane Zeeman field
provides a way to control these exceptional degeneracies although higher values
of non-Hermiticity are required in contrast to the zero Zeeman field regime.
Furthermore, we find that the spin projections also coalescence at the
exceptional degeneracies and can acquire larger values than in the Hermitian
regime. Finally, we demonstrate that the exceptional degeneracies induce large
spectral weights, which can be used as a signature for their detection. Our
results thus reveal the potential of systems with Rashba spin-orbit coupling
for realizing non-Hermitian bulk phenomena.",2301.05337v3
2023-11-28,Linear and Angular Momentum Conservation in Surface Hopping Methods,"We demonstrate that, for systems with spin-orbit coupling and an odd number
of electrons, the standard fewest switches surface hopping (FSSH) algorithm
does not conserve the total linear or angular momentum. This lack of
conservation arises not so much from the hopping direction (which is easily
adjusted) but more generally from propagating adiabatic dynamics along surfaces
that are not time reversible. We show that one solution to this problem is to
run along eigenvalues of phase-space electronic Hamiltonians $H(R,P)$ (i.e.
electronic Hamiltonians that depend on both nuclear position and momentum) with
an electronic nuclear coupling $\Gamma\cdot P$ and we delineate the conditions
that must be satisfied by the operator $\Gamma$. The present results should be
extremely useful as far as developing new semiclassical approaches that can
treat systems where the nuclear, electronic orbital, and electronic spin
degrees of freedom altogether are all coupled together, hopefully including
systems displaying the chiral induced spin selectivity (CISS) effect.",2311.16976v1
1999-07-14,Late evolution of cataclysmic variables: the loss of AM Her systems,"The white dwarf in AM Her systems is strongly magnetic and keeps in
synchronous rotation with the orbit by magnetic coupling to the secondary star.
As the latter evolves through mass loss to a cool, degenerate brown dwarf it
can no longer sustain its own magnetic field and coupling is lost. Angular
momentum accreted then spins up the white dwarf and the system no longer
appears as an AM Her system. Possible consequences are run-away mass transfer
and mass ejection from the system. Some of the unusual cataclysmic variable
systems at low orbital periods may be the outcome of this evolution.",9907190v1
2005-02-23,Entangled microwave photons from quantum dots,"We describe a mechanism for the production of polarisation-entangled
microwaves using intra-band transitions in a pair of quantum dots. This
proposal relies neither on spin-orbit coupling nor on control over
electron-electron interactions. The quantum correlation of microwave
polarisations is obtained from orbital degrees of freedom in an external
magnetic field. We calculate the concurrence of emitted microwave photon pairs,
and show that a maximally entangled Bell pair is obtained in the limit of weak
inter-dot coupling.",0502550v2
2014-07-31,Electronic structure of non-centrosymmetric superconductors Re24(Nb;Ti)5 by ab initio calculations,"Electronic structures of superconducting Re24Nb5 and Re24Ti5 have been
calculated employing the full-potential local-orbital method within the density
functional theory. The investigations were focused on the influence of the
antisymmetric spin-orbit coupling on band structures and Fermi surfaces of
these non-centrosymmetric systems. The predicted here density of states at the
Fermi level for Re24Ti5 is abnormally low with respect to that deduced from
previous heat capacity measurements. This discrepancy suggests an intermediate
coupled superconducting state in Re24Ti5. The differences between electronic
properties of both compounds could explain more robust superconductivity in the
Nb-based material.",1407.8416v1
2020-01-17,Thermal spin transport and spin in thermoelectrics,"This article reviews the principles that govern the combined transport of
spin, heat, and charge. The extensive thermodynamic quantity associated with
spin transport is the magnetization; its Onsager-conjugate force is in general
the derivative of the free energy with respect to the magnetization. Spins are
carried in one of two ways: (1) by spin-polarized free electrons in magnetic
metals and doped semiconductors, or (2) by spin waves (magnons) that reside on
localized electrons on unfilled d- or f-shells of transition metal or
rare-earth elements. The paper covers both cases in separate chapters. In both
cases, it is possible to define a spin chemical potential whose gradient is the
more practical conjugate force to spin transport. The paper further describes
the anomalous Hall, spin Hall, and inverse spin Hall effects in magnetic and
non-magnetic solids with strong spin-orbit coupling because these effects are
used to generate and measure spin fluxes. Spin transport across interfaces is
described next, and includes spin pumping and spin transfer torque. The final
chapter then puts all these concepts together to describe the spin-Seebeck,
spin-Peltier, and magnon-drag effects, which exist in ferromagnetic,
antiferromagnetic, and even paramagnetic solids. Magnon-drag, in particular, is
a high-temperature effect that boosts the thermopower of metals by an order of
magnitude and that of semiconductors by a factor of 2 or 3 above the electronic
diffusion thermopower. This is the only example where a spin-driven effect is
larger than a charge-driven effect. Magnon drag leads a simple binary
paramagnetic semiconductor, MnTe, to have zT > 1 without optimization. This
shows how adding spin as an additional design parameter in thermoelectrics
research is a new and promising approach toward the quest for high-zT
materials.",2001.06366v1
2005-08-12,Spin relaxation rates in quasi-one-dimensional coupled quantum dots,"We study theoretically the spin relaxation rate in quasi-one-dimensional
coupled double semiconductor quantum dots. We consider InSb and GaAs-based
systems in the presence of the Rashba spin-orbit interaction, which causes
mixing of opposite-spin states, and allows phonon-mediated transitions between
energy eigenstates. Contributions from all phonon modes and coupling mechanisms
in zincblende semiconductors are taken into account. The spin relaxation rate
is shown to display a sharp, cusp-like maximum as function of the
interdot-barrier width, at a value of the width which can be controlled by an
external magnetic field. This remarkable behavior is associated with the
symmetric-antisymmetric level splitting in the structure.",0508303v1
2005-09-15,Cotunneling current through quantum dots with phonon-assisted spin-flip processes,"We consider cotunneling through a quantum dot in the presence of spin-flip
processes induced by the coupling to acoustic phonons of the surrounding. An
expression for the phonon-assisted cotunneling current is derived by means of a
generalized Schrieffer-Wolff transformation. The influence of the spin-phonon
coupling on the heating of the dot is considered. The result is evaluated for
the case of a parabolic semiconductor quantum dot with Rashba and Dresselhaus
spin-orbit coupling and a method for the determination of the spin-phonon
relaxation rate is proposed.",0509420v2
2006-06-01,Spin-Hall Conductivity in Electron-Phonon Coupled Systems,"We derive the ac spin-Hall conductivity $\sigma_{\rm sH}(\omega)$ of
two-dimensional spin-orbit coupled systems interacting with dispersionless
phonons of frequency $\omega_0$. For the linear Rashba model we show that the
electron-phonon contribution to the spin-vertex corrections breaks the
universality of $\sigma_{\rm sH}(\omega)$ at low-frequencies and provides a
non-trivial renormalization of the interband resonance. On the contrary, in a
generalized Rashba model for which the spin-vertex contributions are absent,
the coupling to the phonons enters only through the self-energy, leaving the
low frequency behavior of $\sigma_{\rm sH}(\omega)$ unaffected by the
electron-phonon interaction.",0606035v2
2011-10-21,Partially disordered state and spin-lattice coupling in an S=3/2 triangular lattice antiferromagnet Ag2CrO2,"Ag2CrO2 is an S=3/2 frustrated triangular lattice antiferromagnet without
orbital degree of freedom. With decreasing temperature, a 4-sublatice spin
state develops. However, a long-range partially disordered state with 5
sublattices abruptly appears at TN=24 K, accompanied by a structural
distortion, and persists at least down to 2 K. The spin-lattice coupling
stabilizes the anomalous state, which is expected to appear only in limited
ranges of further-neighbor interactions and temperature. It was found that the
spin-lattice coupling is a common feature in triangular lattice
antiferromagnets with multiple-sublattice spin states, since the triangular
lattice is elastic.",1110.4822v2
2013-06-05,Theory of a chiral Fermi liquid: general formalism,"We extend the Fermi-liquid (FL) theory to include spin-orbit (SO) splitting
of the energy bands, focusing on the Rashba SO coupling as an example. We
construct the phenomenological Landau interaction function for such a system
using the symmetry arguments and verify this construction by an explicit
perturbative calculation. The Landau function is used to obtain the effective
mass, compressibility, and stability conditions of the FL. It is shown that
although the charge-sector properties, such as the effective mass and
compressibility, are determined solely by well-defined quasiparticles, the
spin-sector properties, such as the spin susceptibility, contain a contribution
from damped states in between the spin-split Fermi surfaces, and thus cannot be
fully described by the FL theory, except for the case of weak SO coupling. We
derive some specific properties of a chiral FL and show, in particular, that
for contact interaction spin-splitting of the Fermi velocities of Rashba
subbands occurs because of the Kohn anomaly, also modified by SO coupling.",1306.1165v1
2015-05-28,Incommensurate spin density wave at a ferromagnetic quantum critical point in a three-dimensional parabolic semimetal,"We explore the ferromagnetic quantum critical point in a three-dimensional
semimetallic system with upward- and downward-dispersing bands touching at the
Fermi level. Evaluating the static spin susceptibility to leading order in the
coupling between the fermions and the fluctuating ferromagnetic order
parameter, we find that the ferromagnetic quantum critical point is masked by
an incommensurate, longitudinal spin density wave phase. We first analyze an
idealized model which, despite having strong spin-orbit coupling, still
possesses O(3) rotational symmetry generated by the total angular momentum
operator. In this case, the direction of the incommensurate spin density wave
propagation can point anywhere, while the magnetic moment is aligned along the
direction of propagation. Including symmetry-allowed anisotropies in the
fermion dispersion and the coupling to the order parameter field, however, the
ordering wavevector instead breaks a discrete symmetry and aligns along either
the [111] or [100] direction, depending on the signs and magnitudes of these
two types of anisotropy.",1505.07685v1
2016-06-06,Spin-Wave and Electromagnon Dispersions in Multiferroic MnWO4 as Observed by Neutron Spectroscopy: Isotropic Heisenberg Exchange versus Anisotropic Dzyaloshinskii-Moriya Interaction,"High resolution inelastic neutron scattering reveals that the elementary
magnetic excitations in multiferroic MnWO4 consist of low energy dispersive
electromagnons in addition to the well-known spin-wave excitations. The latter
can well be modeled by a Heisenberg Hamiltonian with magnetic exchange coupling
extending to the 12th nearest neighbor. They exhibit a spin-wave gap of 0.61(1)
meV. Two electromagnon branches appear at lower energies of 0.07(1) meV and
0.45(1) meV at the zone center. They reflect the dynamic magnetoelectric
coupling and persist in both, the collinear magnetic and paraelectric AF1
phase, and the spin spiral ferroelectric AF2 phase. These excitations are
associated with the Dzyaloshinskii-Moriya exchange interaction, which is
significant due to the rather large spin-orbit coupling.",1606.01954v1
2012-04-27,Resonant harmonic generation and collective spin rotations in electrically driven quantum dots,"Spin rotations induced by an AC electric field in a two-electron double
quantum dot are studied by an exact numerical solution of the time dependent
Schroedinger equation in the context of recent electric dipole spin resonance
experiments based on the Pauli blockade. We demonstrate that the splitting of
the main resonance line by the spin exchange coupling is accompanied by the
appearance of fractional resonances and that both these effects are triggered
by interdot tunnel coupling. We find that the AC driven system generates
residual but distinct harmonics of the driving frequency which are amplified
when tuned to the main transition frequency. The mechanism is universal for
electron systems in electrically driven potentials and works also in the
absence of electron-electron interaction or spin-orbit coupling.",1204.6208v2
2019-03-25,Quench dynamics of spin in quantum dots coupled to spin-polarized leads,"We investigate the quench dynamics of a quantum dot strongly coupled to
spin-polarized ferromagnetic leads. The real-time evolution is calculated by
means of the time-dependent density-matrix numerical renormalization group
method implemented within the matrix product states framework. We examine the
system's response to a quench in the spin-dependent coupling strength to
ferromagnetic leads as well as in the position of the dot's orbital level. The
spin dynamics is analyzed by calculating the time-dependent expectation values
of the quantum dot's magnetization and occupation. Based on these, we determine
the time-dependence of a ferromagnetic-contact-induced exchange field and
predict its nonmonotonic build-up. In particular, two time scales are
identified, describing the development of the exchange field and the dot's
magnetization sign change. Finally, we study the effects of finite temperature
on the dynamical behavior of the system.",1903.10381v1
2021-01-19,Equal-time kinetic equations in a rotational field,"We investigate quantum kinetic theory for a massive fermion system under a
rotational field. From the Dirac equation in curved space we derive the
complete set of kinetic equations for the spin components of the covariant and
equal-time Wigner functions. While the particles are no longer on a mass shell
in general case due to the rotation-spin coupling, there are always only two
independent components, which can be taken as the number and spin densities.
With the help from the off-shell constraint we obtain the closed transport
equations for the two independent components in classical limit and at quantum
level. The classical rotation-orbital coupling controls the dynamical evolution
of the number density, but the quantum rotation-spin coupling explicitly
changes the spin density.",2101.07596v1
2022-04-23,Nonreciprocal light propagation induced by a subwavelength spinning cylinder,"Nonreciprocal optical devices have broad applications in light manipulations
for communications and sensing. Non-magnetic mechanisms of optical
nonreciprocity are highly desired for high-frequency on-chip applications.
Here, we investigate the nonreciprocal properties of light propagation in a
dielectric waveguide induced by a subwavelength spinning cylinder. We find that
the chiral modes of the cylinder can give rise to unidirectional coupling with
the waveguide via the transverse spin-orbit interaction, leading to different
transmissions for guided wave propagating in opposite directions and thus
optical isolation. We reveal the dependence of the nonreciprocal properties on
various system parameters including mode order, spinning speed, and coupling
distance. The results show that higher-order chiral modes and larger spinning
speed generally give rise to stronger nonreciprocity, and there exists an
optimal cylinder-waveguide coupling distance where the optical isolation
reaches the maximum. Our work contributes to the understanding of
nonreciprocity in subwavelength moving structures and can find applications in
integrated photonic circuits, topological photonics, and novel metasurfaces.",2204.11093v1
2006-09-20,Microscopic theories for cubic and tetrahedral superconductors: application to PrOs_4Sb_{12},"We examine weak-coupling theory for unconventional superconducting states of
cubic or tetrahedral symmetry for arbitrary order parameters and Fermi surfaces
and identify the stable states in zero applied field. We further examine the
possibility of having multiple superconducting transitions arising from the
weak breaking of a higher symmetry group to cubic or tetrahedral symmetry.
Specifically, we consider two higher symmetry groups. The first is a weak
crystal field theory in which the spin-singlet Cooper pairs have an approximate
spherical symmetry. The second is a weak spin orbit coupling theory for which
spin-triplet Cooper pairs have a cubic orbital symmetry and an approximate
spherical spin rotational symmetry. In hexagonal UPt_3, these theories easily
give rise to multiple transitions. However, we find that for cubic materials,
there is only one case in which two superconducting transitions occur within
weak coupling theory. This sequence of transitions does not agree with the
observed properties of PrOs_4Sb_{12}. Consequently, we find that to explain two
transitions in PrOs_4Sb_{12} using approximate higher symmetry groups requires
a strong coupling theory. In view of this, we finally consider a weak coupling
theory for which two singlet representations have accidentally nearly
degenerate transition temperatures (not due to any approximate symmetries). We
provide an example of such a theory that agrees with the observed properties of
PrOs_4Sb_{12}.",0609530v1
2021-09-18,Realization of Qi-Wu-Zhang model in spin-orbit-coupled ultracold fermions,"Based on the optical Raman lattice technique, we experimentally realize the
Qi-Wu-Zhang model for quantum anomalous Hall phase in ultracold fermions with
two-dimensional (2D) spin-orbit (SO) coupling. We develop a novel protocol of
pump-probe quench measurement to probe, with minimal heating, the resonant spin
flipping on particular quasi-momentum subspace called band-inversion surfaces.
With this protocol we demonstrate the first Dirac-type 2D SO coupling in a
fermionic system, and detect non-trivial band topology by observing the change
of band-inversion surfaces as the two-photon detuning varies. The non-trivial
band topology is also observed by slowly loading the atoms into optical Raman
lattices and measuring the spin textures. Our results show solid evidence for
the realization of the minimal SO-coupled quantum anomalous Hall model, which
can provide a feasible platform to investigate novel topological physics
including the correlation effects with SO-coupled ultracold fermions.",2109.08885v2
2001-02-13,Isotopically engineered silicon/silicon-germanium nanostructures as basic elements for a nuclear spin quantum computer,"The idea of quantum computation is the most promising recent developments in
the high-tech domain, while experimental realization of a quantum computer
poses a formidable challenge. Among the proposed models especially attractive
are semiconductor based nuclear spin quantum computer's (S-NSQC), where nuclear
spins are used as quantum bistable elements, ''qubits'', coupled to the
electron spin and orbital dynamics. We propose here a scheme for implementation
of basic elements for S-NSQC's which are realizable within achievements of the
modern nanotechnology. These elements are expected to be based on a
nuclear-spin-controlled isotopically engineered Si/SiGe heterojunction, because
in these semiconductors one can vary the abundance of nuclear spins by
engineering the isotopic composition. A specific device is suggested, which
allows one to model the processes of recording, reading and information
transfer on a quantum level using the technique of electrical detection of the
magnetic state of nuclear spins. Improvement of this technique for a
semiconductor system with a relatively small number of nuclei might be applied
to the manipulation of nuclear spin ''qubits'' in the future S-NSQC.",0102228v1
2002-01-28,Spin Ordering and Quasiparticles in Spin Triplet Superconducting Liquids,"Spin ordering and its effect on low energy quasiparticles in a p-wave
superconducting liquid are investigated. We show that there is a new 2D p-wave
superconducting liquid where the ground state is rotation invariant. In quantum
spin disordered liquids, the low energy quasiparticles are bound states of the
bare Bogolubov- De Gennes (${\em BdeG}$) quasiparticles and zero energy
skyrmions, which are charge neutral bosons at the low energy limit. Further
more, spin collective excitations are fractionalized ones carrying a half spin
and obeying fermionic statistics. In thermally spin disordered limits, the
quasi-particles are bound states of bare ${\em BdeG}$ quasi-particles. The
latter situation can be realized in some layered p-wave superconductors where
the spin-orbit coupling is weak.",0201512v3
2003-07-05,Anisotropic splitting of intersubband spin plasmons in quantum wells with bulk and structural inversion asymmetry,"In semiconductor heterostructures, bulk and structural inversion asymmetry
and spin-orbit coupling induce a k-dependent spin splitting of valence and
conduction subbands, which can be viewed as being caused by momentum-dependent
crystal magnetic fields. This paper studies the influence of these effective
magnetic fields on the intersubband spin dynamics in an asymmetric n-type
GaAs/AlGaAs quantum well. We calculate the dispersions of intersubband spin
plasmons using linear response theory. The so-called D'yakonov-Perel'
decoherence mechanism is inactive for collective intersubband excitations,
i.e., crystal magnetic fields do not lead to decoherence of spin plasmons.
Instead, we predict that the main signature of bulk and structural inversion
asymmetry in intersubband spin dynamics is a three-fold, anisotropic splitting
of the spin plasmon dispersion. The importance of many-body effects is pointed
out, and conditions for experimental observation with inelastic light
scattering are discussed.",0307124v1
2004-07-12,Spin-Orbit Coupling in Diamond and Zincblende Heterostructures,"Spin splittings in III-V materials and heterostructures are of interest
because of potential applications, mainly in spintronic devices. A necessary
condition for the existence of these spin splittings is the absence of
inversion symmetry. In bulk zincblende materials the inversion symmetry is
broken, giving rise to a small spin splitting. The much larger spin splitting
observed in quantum wells is normally attributed to the asymmetry of the
confining potential and explained on the basis of the Rashba effect. For
symmetrically confined wells, where the only source of asymmetry is that of the
underlying crystal potential, the confining potential strongly enhances the
spin splittings. This enhancement does not require the asymmetry of the
confining potential but depends on the interplay between the confinement and
the crystal potential. In this situation the behavior of the spin splittings is
consistent with the Dresselhaus contribution.
  In asymmetrically confined wells both Dresselhaus and Rashba terms
contribute.
  We present a general theory of the spin splittings of these structures based
on the group theory of diamond and zincblende heterostructures.",0407294v1
2004-11-05,Properties and Detection of Spin Nematic Order in Strongly Correlated Electron Systems,"A spin nematic is a state which breaks spin SU(2) symmetry while preserving
translational and time reversal symmetries. Spin nematic order can arise
naturally from charge fluctuations of a spin stripe state. Focusing on the
possible existence of such a state in strongly correlated electron systems, we
build a nematic wave function starting from a t-J type model. The nematic is a
spin-two operator, and therefore does not couple directly to neutrons. However,
we show that neutron scattering and Knight shift experiments can detect the
spin anisotropy of electrons moving in a nematic background. We find the mean
field phase diagram for the nematic taking into account spin-orbit effects.",0411159v2
2004-12-21,Theory of spin-polarized transport in semiconductor heterojunctions: Proposal for spin injection and detection in silicon,"Spin injection and detection in silicon is a difficult problem, in part
because the weak spin-orbit coupling and indirect gap preclude using standard
optical techniques. We propose two ways to overcome this difficulty, and
illustrate their operation by developing a model for spin-polarized transport
across a heterojunction. We find that equilibrium spin polarization of holes
leads to a strong modification of the spin and charge dynamics of electrons,
and we show how the symmetry properties of the charge current can be exploited
to detect spin injection in silicon using currently available techniques.",0412580v2
2006-08-14,Understanding spin Hall effects from the motion in SU(2)XU(1) fields,"We derive the classical counterpart of a previously obtained quantum
mechanical covariant ``continuitylike'' equation for the spin density, and
present an intuitive picture for elucidating the non-conservation of the spin
current. This reveals the equations of motion for a particle with spin under
the Yang-Mills field (in certain semiconductors) as well as the Maxwell field,
from which the condition for an infinite spin relaxation time is drawn out
directly. As a concrete example, we discuss the procession of the spin
orientation in spin Hall effect with the so called ReD field, which undergoes a
circle with the frequency dependent on both the strength of the spin-orbit
coupling and the initial velocity. The anti-commutation of the Pauli matrices
is found to be crucial in simplifying the equations of motion in the view of
quantum mechanism of the same topics.",0608303v1
2006-09-15,Relativistic treatment of spin-currents and spin-transfer torque,"It is shown that a useful relativistic generalization of the conventional
spin density for the case of moving electrons is the expectation value of the
four-component Bargmann-Wigner polarization operator. An exact equation of
motion for this quantity is derived, using the one-particle Dirac equation, and
the relativistic analogues of the non-relativistic concepts of spin-currents
and spin-transfer torques are identified. In the classical limit the time
evolution is governed by the equation of motion first proposed by Bargmann,
Michel and Telegdi generalized to the case of inhomogeneous systems. In the
non-relativistic limit it is found that the spin-current has an intrinsic Hall
contribution and to order 1/c^2 a spin-orbit coupling related torque appears in
the equation of motion. The relevance of these results to the theory of the
intrinsic spin Hall effect and current-induced switching are briefly discussed.",0609376v2
2007-06-01,Conserved spin Hall conductance in two dimensional electron gas in a perpendicular magnetic field,"Using the microscopic theory of the conserved spin current [Phys. Rev. Lett.
\textbf{96}, 076604 (2006)], we investigate the spin Hall effect in the two
dimensional electron gas system with a perpendicular magnetic field. The spin
Hall conductance $\sigma_{\mu\nu}^{s}$ as a response to the electric field
consists of two parts, i.e., the conventional part $\sigma_{\mu\nu}^{s0}$ and
the spin torque dipole correction $\sigma_{\mu\nu}^{s\tau}$. It is shown that
the spin-orbit coupling competes with Zeeman splitting by introducing
additional degeneracies between different Landau levels at certain values of
magnetic field. These degeneracies, if occurring at the Fermi level, turn to
give rise to resonances in both $\sigma_{\mu\nu}^{s0}$ and $\sigma_{\mu\nu
}^{s\tau}$ in spin Hall conductance. Remarkably, both of these two components
have the same sign in the wide range of variation in the magnetic field, which
result in an overall enhancement of the total spin Hall current. In particular,
the magnitude of $\sigma_{\mu\nu}^{s\tau}$ is much larger than that of
$\sigma_{\mu\nu}^{s0}$ around the resonance.",0706.0047v1
2007-06-12,Graphene Spin Transistor,"Graphitic nanostructures, e.g. carbon nanotubes (CNT) and graphene, have been
proposed as ideal materials for spin conduction[1-7]; they have long electronic
mean free paths[8] and small spin-orbit coupling[9], hence are expected to have
very long spin-scattering times. In addition, spin injection and detection in
graphene opens new opportunities to study exotic electronic states such as the
quantum Hall[10,11] and quantum spin Hall[9] states, and spin-polarized edge
states[12] in graphene ribbons. Here we perform the first non-local four-probe
experiments[13] on graphene contacted by ferromagnetic Permalloy electrodes. We
observe sharp switching and often sign-reversal of the non-local resistance at
the coercive field of the electrodes, indicating definitively the presence of a
spin current between injector and detector. The non-local resistance changes
magnitude and sign quasi-periodically with back-gate voltage, and
Fabry-Perot-like oscillations[6,14,15] are observed, consistent with
quantum-coherent transport. The non-local resistance signal can be observed up
to at least T = 300 K.",0706.1597v1
2008-08-08,Hole spin relaxation in $p$-type GaAs quantum wires,"We investigate the spin relaxation of $p$-type GaAs quantum wires by
numerically solving the fully microscopic kinetic spin Bloch equations. We find
that the quantum-wire size influences the spin relaxation time effectively by
modulating the energy spectrum and the heavy-hole--light-hole mixing of wire
states. The effects of quantum-wire size, temperature, hole density, and
initial polarization are investigated in detail. We show that, depending on the
situation, the spin relaxation time can either increase or decrease with hole
density. Due to the different subband structure and effects arising from
spin-orbit coupling, many spin-relaxation properties are quite different from
those of holes in the bulk or in quantum wells, and the inter-subband
scattering makes a marked contribution to the spin relaxation.",0808.1170v2
2008-08-22,Perturbation Method for Classical Spinning Particle Motion: I. Kerr Space-Time,"This paper presents an analytic perturbation approach to the dynamics of a
classical spinning particle, according to the Mathisson-Papapetrou-Dixon (MPD)
equations of motion, with a direct application to circular motion around a Kerr
black hole. The formalism is established in terms of a power series expansion
with respect to the particle's spin magnitude, where the particle's kinematic
and dynamical degrees are expressed in a completely general form that can be
constructed to infinite order in the expansion parameter. It is further shown
that the particle's squared mass and spin magnitude can shift due to a
classical analogue of radiative corrections that arise from spin-curvature
coupling. Explicit expressions are determined for the case of circular motion
near the event horizon a Kerr black hole, where the mass and spin shift
contributions are dependent on the initial conditions of the particle's spin
orientation. A preliminary analysis of the stability properties of the orbital
motion in the Kerr background due to spin-curvature interactions is explored
and briefly discussed.",0808.3005v2
2010-02-05,"Electron spin coherence in metallofullerenes: Y, Sc and La@C82","Endohedral fullerenes encapsulating a spin-active atom or ion within a carbon
cage offer a route to self-assembled arrays such as spin chains. In the case of
metallofullerenes the charge transfer between the atom and the fullerene cage
has been thought to limit the electron spin phase coherence time (T2) to the
order of a few microseconds. We study electron spin relaxation in several
species of metallofullerene as a function of temperature and solvent
environment, yielding a maximum T2 in deuterated o-terphenyl greater than 200
microseconds for Y, Sc and La@C82. The mechanisms governing relaxation (T1, T2)
arise from metal-cage vibrational modes, spin-orbit coupling and the nuclear
spin environment. The T2 times are over 2 orders of magnitude longer than
previously reported and consequently make metallofullerenes of interest in
areas such as spin-labelling, spintronics and quantum computing.",1002.1282v1
2010-04-13,Quantum dots and spin qubits in graphene,"This is a review on graphene quantum dots and their use as a host for spin
qubits. We discuss the advantages but also the challenges to use graphene
quantum dots for spin qubits as compared to the more standard materials like
GaAs. We start with an overview of this young and fascinating field and will
then discuss gate-tunable quantum dots in detail. We calculate the bound states
for three different quantum dot architectures where a bulk gap allows for
confinement via electrostatic fields: (i) graphene nanoribbons with armchair
boundary, (ii) a disc in single-layer graphene, and (iii) a disc in bilayer
graphene. In order for graphene quantum dots to be useful in the context of
spin qubits, one needs to find reliable ways to break the valley-degeneracy.
This is achieved here, either by a specific termination of graphene in (i) or
in (ii) and (iii) by a magnetic field, without the need of a specific boundary.
We further discuss how to manipulate spin in these quantum dots and explain the
mechanism of spin decoherence and relaxation caused by spin-orbit interaction
in combination with electron-phonon coupling, and by hyperfine interaction with
the nuclear spin system.",1004.2136v1
2011-05-28,Relaxation of Electron Spin during High-Field Transport in GaAs Bulk,"A semiclassical Monte Carlo approach is adopted to study the multivalley spin
depolarization of drifting electrons in a doped n-type GaAs bulk semiconductor,
in a wide range of lattice temperature ($40<T_L<300$ K) and doping density
($10^{13}<n<10^{16}$cm$^{-3}$). The decay of the initial non-equilibrium spin
polarization of the conduction electrons is investigated as a function of the
amplitude of the driving static electric field, ranging between 0.1 and 6
kV/cm, by considering the spin dynamics of electrons in both the $\Gamma$ and
the upper valleys of the semiconductor. Doping density considerably affects
spin relaxation at low temperature and weak intensity of the driving electric
field. At high values of the electric field, the strong spin-orbit coupling of
electrons in the $L$-valleys significantly reduces the average spin
polarization lifetime, but, unexpectedly, for field amplitudes greater than 2.5
kV/cm, the spin lifetime increases with the lattice temperature. Our numerical
findings are validated by a good agreement with the available experimental
results and with calculations recently obtained by a different theoretical
approach.",1105.5716v2
2011-12-12,Spin-blockade effect and coherent control of DNA-damage by free radicals: a proposal on bio-spintronics,"Coherent control of OH-free radicals interacting with the spin-triplet state
of a DNA molecule is investigated. A model Hamiltonian for molecular spin
singlet-triplet resonance is developed. We illustrate that the spin-triplet
state in DNA molecules can be efficiently populated, as the spin-injection rate
can be tuned to be orders of magnitudes greater than the decay rate due to
small spin-orbit coupling in organic molecules. Owing to the nano-second
life-time of OH free radicals, a non-equilibrium free energy barrier induced by
the injected spin triplet state that lasts approximately longer than one-micro
second in room temperature can efficiently block the initial Hydrogen
abstraction and DNA damage. For a direct demonstration of the spin-blockade
effect, a molecular simulation based on an {\em ab-initio} Car-Parrinello
molecular dynamics is deployed.",1112.2733v1
2012-03-25,Spin-polarized current separator based on a fork-shaped Rashba nanostructure,"A scheme for a spin-polarized current separator is proposed by studying the
spin-dependent electron transport of a fork-shaped nanostructure with Rashba
spin-orbit coupling (SOC), connected to three leads with the same width. It is
found that two spin-polarized currents are of the same magnitude but opposite
polarizations can be generated simultaneously in the two output leads when the
spin-unpolarized electrons injected from the input lead. The underlying physics
is revealed to originate from the different spin-dependent conductance caused
by the effects of Rashba SOC and the geometrical structure of the system.
Further study shows that the spin-polarized current with strong a robustness
against disorder, demonstrates the feasibility of the proposed nanostructure
for a real application.",1203.5473v1
2012-06-06,Spin-polarized current induced by a local exchange field in a silicene nanoribbon,"A mechanism to generate a spin-polarized current in a two-terminal zigzag
silicene nanoribbon is predicted. As a weak local exchange field that is
parallel to the surface of silicene is applied on one of edges of the silicene
nanoribbon, a gap is opened in the corresponding gapless edge states but
another pair of gapless edge states with opposite spin are still protected by
the time-reversal symmetry. Hence, a spin-polarized current can be induced in
the gap opened by the local exchange field in this two-terminal system. What is
important is that the spin-polarized current can be obtained even in the
absence of Rashba spin-orbit coupling and in the case of the very weak exchange
filed. That is to say, the mechanism to generate the spin-polarized currents
can be easily realized experimentally.We also find that the spin-polarized
current is insensitive to weak disorder.",1206.1114v2
2012-06-29,Spin Relaxation in Single Layer Graphene with Tunable Mobility,"Graphene is an attractive material for spintronics due to theoretical
predictions of long spin lifetimes arising from low spin-orbit and hyperfine
couplings. In experiments, however, spin lifetimes in single layer graphene
(SLG) measured via Hanle effects are much shorter than expected theoretically.
Thus, the origin of spin relaxation in SLG is a major issue for graphene
spintronics. Despite extensive theoretical and experimental work addressing
this question, there is still little clarity on the microscopic origin of spin
relaxation. By using organic ligand-bound nanoparticles as charge reservoirs to
tune mobility between 2700 and 12000 cm2/Vs, we successfully isolate the effect
of charged impurity scattering on spin relaxation in SLG. Our results
demonstrate that while charged impurities can greatly affect mobility, the spin
lifetimes are not affected by charged impurity scattering.",1206.6941v1
2014-01-05,Dynamics of spin-flip photon-assisted tunneling,"We present time-resolved measurements of spin-flip photon-assisted tunneling
and spin-flip relaxation in a doubly occupied double quantum dot. The
photon-assisted excitation rate as a function of magnetic field indicates that
spin-orbit coupling is the dominant mechanism behind the spin-flip under the
present conditions. We are able to extract the resulting effective `spin-flip
tunneling' energy, which is found to be three orders of magnitude smaller than
the regular spin-conserving tunneling energy. We also measure the relaxation
and dephasing times of a qubit formed out of two two-electron states with
different spin and charge configurations.",1401.0881v1
2014-11-14,Spin Correlations in Quantum Wires,"We consider theoretically spin correlations in an 1D quantum wire with
Rashba-Dresselhaus spin-orbit interaction (RDI). The correlations of
non-interacting electrons display electron-spin resonance at a frequency
proportional to the RDI coupling. Interacting electrons on varying the
direction of external magnetic field transit from the state of Luttinger liquid
(LL) to the spin density wave (SDW) state. We show that the two-time total spin
correlations of these states are significantly different. In the LL the
projection of total spin to the direction of the RDI induced field is conserved
and the corresponding correlator is equal to zero. The correlators of two
components perpendicular to the RDI field display a sharp ESR driven by RDI
induced intrinsic field. In contrast, in the SDW state the longitudinal
projection of spin dominates, whereas the transverse components are suppressed.
This prediction indicates a simple way for experimental diagnostic of the SDW
in a quantum wire.",1411.4084v2
2015-01-28,Universal spin-triplet superconducting correlations of Majorana fermions,"We establish that Majorana fermions on the boundary of topological
superconductors have only spin-triplet superconducting correlations independent
of whether the bulk superconducting gap is spin singlet or triplet. This is
universal for time-reversal broken (respected) topological superconductors
(TSCs) with an odd number of (pairs of) Majorana fermions on the boundary.
Consequently, resonant Andreev reflection induced by Majorana fermions only
occurs in spin-triplet channels and always injects spin-triplet Cooper pairs
into the leads. This spin-triplet condensate results in a spin-orbit coupling
(SOC) controlled oscillatory critical current without a $0$-$\pi$ transition in
the TSC/SOC-semiconductor/TSC Josephson junction. The observation of this
unique current-phase relation can serve as the definitive signal for Majorana
fermions. Our study shows a technique for manipulating Majorana fermions based
on their spin-triplet superconducting correlations.",1501.07273v2
2015-03-25,Intercombination Effects in Resonant Energy Transfer,"We investigate the effect of intercombination transitions in excitation
hopping processes such as those found in F\""orster resonance energy transfer.
Taking strontium Rydberg states as our model system, the breakdown of
$LS$-coupling leads to weakly allowed transitions between Rydberg states of
different spin quantum number. We show that the long-range interactions between
two Rydberg atoms can be affected by these weakly allowed spin transitions, and
the effect is greatest when there is a near-degeneracy between the initial
state and a state with a different spin quantum number. We also consider a case
of four atoms in a spin chain, and show that a spin impurity can resonantly hop
along the chain. By engineering the many-body energy levels of the spin-chain,
the breakdown of $LS$ coupling due to inter-electronic effects in individual
atoms can be mapped onto a spatial separation of the total spin and the total
orbital angular momentum along the spin chain.",1503.07417v4
2015-06-17,Cooperative phenomenon in a rippled graphene: Chiral spin guide,"We analyze spin scattering in ballistic transport of electrons through a
ripple at a normal incidence of an electron flow. The model of a ripple
consists of a curved graphene surface in the form of an arc of a circle
connected from the left-hand and right-hand sides to two flat graphene sheets.
At certain conditions the curvature induced spin-orbit coupling creates a
transparent window for incoming electrons with one spin polarization
simultaneously with a backscattering of those with opposite polarization. This
window is equally likely transparent for electrons with spin up and spin down
that move in opposite directions. The spin filtering effect being small in one
ripple becomes prominent with the increase of N consequently connected ripples
that create a graphene sheet of the sinusoidal type. We present the analytical
expressions for spin up (down) transmission probabilities as a function of N
connected ripples.",1506.05409v2
2017-02-05,Chiral Spin Condensation in a One-Dimensional Optical Lattice,"We study a spinor (two-component) Bose gas confined in a one-dimensional
double-valley optical lattice which has a double-well structure in momentum
space. Based on field theory analysis, it is found that spinor bosons in the
double-valley band may form a spin-charge mixed chiral spin quasicondensate
under certain conditions. Our numerical calculations in a concrete $\pi$-flux
triangular ladder system confirm the robustness of the chiral spin order
against interactions and quantum fluctuations. This exotic atomic Bose-Einstein
condensate exhibits spatially staggered spin loop currents without any charge
dynamics despite the complete absence of spin-orbit coupling in the system,
creating an interesting approach to atom spintronics. The entanglement entropy
scaling allows us to extract conformal-field-theory central charge and
establish the low-energy effective field theory for the chiral spin condensate
as a two-component Luttinger liquid. Our predictions should be detectable in
atomic experiments through spin-resolved time-of-flight techniques.",1702.01439v2
2010-05-10,Anisotropy of Magnetic Interactions in the Spin-Ladder Compound (C$_5$H$_{12}$N)$_2$CuBr$_4$,"Magnetic excitations in the spin-ladder material (C$_5$H$_{12}$N)$_2$CuBr$_4$
[BPCB] are probed by high-resolution multi-frequency electron spin resonance
(ESR) spectroscopy. Our experiments provide a direct evidence for a biaxial
anisotropy ($\sim 5\%$ of the dominant exchange interaction), that is in
contrast to a fully isotropic spin-ladder model employed for this system
previously. It is argued that this anisotropy in BPCB is caused by spin-orbit
coupling, which appears to be important for describing magnetic properties of
this compound. The zero-field zone-center gap in the excitation spectrum of
BPCB, $\Delta_0/k_{B}=16.5$ K, is detected directly. Furthermore, an ESR
signature of the inter-ladder exchange interactions is obtained. The detailed
characterization of the anisotropy in BPCB completes the determination of the
full spin hamiltonian of this exceptional spin-ladder material and shows ways
to study anisotropy effects in spin ladders.",1005.1474v1
2016-12-31,Spin Transport and Accumulation in 2D Weyl Fermion System,"In this work, we study the spin Hall effect and Rashba-Edelstein effect of a
2D Weyl fermion system in the clean limit using the Kubo formalism. Spin
transport is solely due to the spin-torque current in this strongly spin-orbit
coupled (SOC) system, and chiral spin-flip scattering off non-SOC scalar
impurities, with potential strength $V$ and size $a$, gives rise to a
skew-scattering mechanism for the spin Hall effect. The key result is that the
resultant spin-Hall angle has a fixed sign, with $\theta^{SH} \sim O
\left(\tfrac{V^2}{v_F^2/a^2} (k_F a)^4 \right)$ being a strongly-dependent
function of $k_F a$, with $k_F$ and $v_F$ being the Fermi wave-vector and Fermi
velocity respectively. This, therefore, allows for the possibility of tuning
the SHE by adjusting the Fermi energy or impurity size.",1701.00074v3
2011-11-15,Dynamical spin Hall conductivity in a magnetic disordered system,"We investigate the intrinsic spin Hall effect in a quantum well semiconductor
doped with magnetic impurities, as a means to manipulate the carriers' spin.
Using a simple Hamiltonian with Rashba spin-orbit coupling and exchange
interactions, we analytically compute the spin Hall conductivity. It is
demonstrated that using the appropriate order of limits, one recovers the
intrinsic universal value. Numerical computations on a tight-binding model, in
the weak disorder regime, confirm that the spin Hall effect is preserved in the
presence of magnetic impurities. The optical spin conductivity shows large
sample to sample fluctuations in the low frequency region. As a consequence,
for weak disorder, the static spin conductivity is found to follow a wide
Gaussian distribution with its mean value near the intrinsic clean value.",1111.3575v1
2011-11-15,Mach-Zehnder Interferometric device for spin filtering in a GaAs/AlGaAs electron gas,"A spin filtering device using quantum spin interference is theoretically
proposed in a GaAs/AlGaAs electron gas that has both Rashba and Dresselhaus
spin-orbit couplings. The device achieves polarized electron currents by
separating spin up and spin down components without a magnetic field gradient.
We find two broad spin filtering regimes, one where the interferometer has
symmetrical arms, where a small magnetic flux is needed to achieve spin
separation, and the other with asymmetric arms where the change in path length
renders an extra phase emulating the effects of a magnetic field. We identify
operating points for the device where optimal electron polarization is achieved
within value ranges found in a 2D electron gas. Both device setups apply for
arbitrary incoming electron polarization and operate at broad energy ranges
within the incoming electron band.",1111.3624v1
2014-05-29,Helical spin texture of surface states in topological superconductors,"Surface states of topological noncentrosymmetric superconductors exhibit
intricate helical spin textures, i.e., the spin orientation of the surface
quasiparticles is coupled to their momentum. Using quasiclassical theory, we
study the spin polarization of the surface states as a function of the
spin-orbit interaction and superconducting pairing symmetry. We focus on two-
and three-dimensional fully gapped and nodal noncentrosymmetric
superconductors. For the case of nodal systems, we show that the spin
polarization of the topological flat bands is controlled by the spin
polarization of the bulk normal states at the bounding gap nodes. We
demonstrate that the zero-bias conductance in a magnetic tunnel junction can be
used as an experimental test of the surface-state spin polarization.",1405.7733v1
2017-06-16,Gate-tunable large magnetoresistance in an all-semiconductor spin-transistor-like device,"A large spin-dependent and electric field-tunable magnetoresistance of a
two-dimensional electron system (2DES) is a key ingredient for the realization
of many novel concepts for spin-based electronic devices. The low
magnetoresistance observed during the last decades in devices with lateral
semiconducting (SC) transport channels between ferromagnetic (FM) source (S)
and drain (D) contacts has been the main obstacle for realizing spin field
effect transistor proposals. Here, we show both, a large two terminal
magnetoresistance in lateral 2DES-based spin valve geometry, with up to 80%
resistance change, and tunability of the magnetoresistance by an electric gate.
The large magnetoresistance is due to finite electric field effects at the
FM/SC interface, which boost spin-to-charge conversion. The gating scheme we
use is based on switching between uni- and bi-directional spin diffusion,
without resorting to the spin-orbit coupling.",1706.05239v1
2017-10-24,Trigonal warping induced terraced spin texture and nearly perfect spin polarization in graphene with Rashba effect,"Electrical tunability of spin polarization has been a focus in spintronics.
Here, we report that the trigonal warping (TW) effect, together with spin-orbit
coupling (SOC), can lead to two distinct magnetoelectric effects in
low-dimensional systems. Taking graphene with Rashba SOC as example, we study
the electronic properties and spin-resolved scattering of system. It is found
that the TW effect gives rise to a terraced spin texture in low-energy bands
and can render significant spin polarization in the scattering, both resulting
in an efficient electric control of spin polarization. Our work unveils not
only SOC but also the TW effect is important for low-dimensional spintronics.",1710.08669v1
2019-07-19,Direct observations of chiral spin textures in van der Waals magnet Fe3GeTe2 nanolayers,"In two-dimensional van der Waals (vdW) magnets, the presence of magnetic
orders, strong spin-orbit coupling and asymmetry at interfaces is the key
ingredient for hosting chiral spin textures. However, experimental evidences
for chiral magnetism in vdW magnets remain elusive. Here we demonstrate
unambiguously the formation of chiral spin textures in thin Fe3GeTe2 nanoflakes
using advanced magnetic electron microscopy and first-principles calculations.
Specifically, electron holography analyses reveal the spin configurations of
N\'eel-type, zero-field-stabilized skyrmions in 20-nm-thick Fe3GeTe2 nanoflakes
at cryogenic temperature. In situ Lorentz transmission electron microscopy
measurements further provide detailed magnetic phase diagrams of chiral spin
textures including spirals and skyrmions in Fe3GeTe2 as a function of
temperature, applied magnetic field and specimen thickness. First-principles
calculations unveil a finite interfacial Dzyaloshinskii-Moriya interaction in
the Te/Fe3Ge/Te slabs that induces the spin chirality in Fe3GeTe2. Our
discovery of spin chirality in the prototypical vdW Fe3GeTe2 opens up new
opportunities for studying chiral magnetism in two-dimensional vdW magnets from
both fundamental and applied perspectives.",1907.08382v1
2019-10-22,Novel chiral quantum spin liquids in Kitaev magnets,"Mott insulators under sufficiently strong spin-orbit coupling can display
quantum spin liquid phases with topological order and fractional excitations.
Quantum magnets with pure Kitaev spin exchange interactions can host a gapped
quantum spin liquid with a single Majorana edge mode propagating in the
counter-clockwise direction when a small positive magnetic field is applied.
Here, we show how under a sufficiently strong positive magnetic field a
topological transition into a gapped quantum spin liquid with two Majorana edge
modes propagating in the clockwise direction occurs. The Dzyaloshinskii-Moriya
interaction is found to turn the non-chiral Kitaev's gapless quantum spin
liquid into a chiral one with equal Berry phases at the two Dirac points.
Thermal Hall conductance experiments can provide evidence of the novel
topologically gapped quantum spin liquid states predicted.",1910.09874v2
2020-02-04,One-way reflection-free exciton-polariton spin filtering channel,"We consider theoretically exciton-polaritons in a strip of honeycomb lattice
with zigzag edges and it is shown that the interplay among the spin-orbit
coupling, Zeeman splitting, and an onsite detuning between sublattices can give
rise to a band structure where all the edge states of the system split in
energy. Within an energy interval, one of the spin polarized edge states
resides with the gap-less bulk having opposite spin. Being surrounded by
opposite spin and the absence of the backward propagating edge state ensures
both reflection free and feedback suppressed one-way flow of polaritons with
one particular spin in the system. The edge states in this system are more
localized than those in the standard topological polariton systems and are
fully spin polarized. This paves the way for feedback free spin-selective
polariton channels for transferring information in polariton networks.",2002.01168v1
2020-02-25,Engineering the molecular structure to optimize the spin Hall signal in organics,"In this study, by engineering the molecular structure, we optimize the spin
Hall conductivity and the spin Hall angle in organics by more than five and
three orders of magnitude, respectively. We identify two important
characteristics of organic molecules, namely substitution of heavy elements and
the torsion angles between constituent units of the polymer, which have
significant effects on the spin Hall signal. These characteristics are directly
related to the spin-orbit coupling and the energetic disorder, both of which
offer a wide scope of chemical tunability in high-mobility polymers. We compute
the spin Hall characteristics for easily synthesized molecules and identify
candidates to exhibit the largest spin Hall signals in organic systems, several
orders of magnitude larger than previously observed. The present study brings
organic spintronics, by introducing polymers with much stronger spin Hall
signal, closer to their inorganic counterparts.",2002.11092v2
2017-09-25,Strain-induced large spin splitting and persistent spin helix at LaAlO$_3$/SrTiO$_3$ interface,"We investigated the effect of the tensile strain on the spin splitting at the
n-type interface in LaAlO$_3$/SrTiO$_3$ in terms of the spin-orbit coupling
coefficient $\alpha$ and spin texture in the momentum space using
first-principles calculations. We found that the $\alpha$ could be controlled
by the tensile strain and be enhanced up to 5 times for the tensile strain of
7%, and the effect of the tensile strain leads to a persistent spin helix,
which has a long spin lifetime. These results support that the strain effect on
LaAlO$_3$/SrTiO$_3$ is important for various applications such as spinFET and
spin-to-charge conversion.",1709.08335v2
2018-03-28,Persistent Spin Helix Manipulation by Optical Doping of a CdTe Quantum Well,"Time-resolved Kerr-rotation microscopy explores the influence of optical
doping on the persistent spin helix in a [001]-grown CdTe quantum well at
cryogenic temperatures. Electron spin diffusion dynamics reveal a
momentum-dependent effective magnetic field providing SU(2) spin-rotation
symmetry, consistent with kinetic theory. The Dresselhaus and Rashba spin-orbit
coupling parameters are extracted independently from rotating the spin helix
with external magnetic fields applied parallel and perpendicular to the
effective magnetic field. Most importantly, a non-uniform spatiotemporal
precession pattern is observed. The kinetic theory framework of spin diffusion
allows for modeling of this finding by incorporating the photocarrier density
into the Rashba ($\alpha$) and the Dresselhaus ($\beta_3$) parameters.
Corresponding calculations are further validated by an excitation-density
dependent measurement. This work shows universality of the persistent spin
helix by its observation in a II-VI compound and the ability to fine-tune it by
optical doping.",1803.10644v1
2018-06-08,Anomalous Hall magnetoresistance in a ferromagnet,"The anomalous Hall effect, observed in conducting ferromagnets with broken
time-reversal symmetry, offers the possibility to couple spin and orbital
degrees of freedom of electrons in ferromagnets. In addition to charge, the
anomalous Hall effect also leads to spin accumulation at the surfaces
perpendicular to both the current and magnetization direction. Here we
experimentally demonstrate that the spin accumulation, subsequent spin
backflow, and spin-charge conversion can give rise to a different type of spin
current related magnetoresistance, dubbed here as the anomalous Hall
magnetoresistance, which has the same angular dependence as the recently
discovered spin Hall magnetoresistance. The anomalous Hall magnetoresistance is
observed in four types of samples: co-sputtered (Fe1-xMnx)0.6Pt0.4, Fe1-xMnx
and Pt multilayer, Fe1-xMnx with x = 0.17 to 0.65 and Fe, and analyzed using
the drift-diffusion model. Our results provide an alternative route to study
charge-spin conversion in ferromagnets and to exploit it for potential
spintronic applications.",1806.03083v1
2018-06-13,Phase-locking between different partial-waves in atom-ion spin-exchange collisions,"We present a joint experimental and theoretical study of spin dynamics of a
single $^{88}$Sr$^+$ ion colliding with an ultracold cloud of Rb atoms in
various hyperfine states. While spin-exchange between the two species occurs
after 9.1(6) Langevin collisions on average, spin-relaxation of the Sr$^+$ ion
Zeeman qubit occurs after 48(7) Langevin collisions which is significantly
slower than in previously studied systems due to a small second-order
spin-orbit coupling. Furthermore, a reduction of the endothermic spin-exchange
rate was observed as the magnetic field was increased. Interestingly, we found
that, while the phases acquired when colliding on the spin singlet and triplet
potentials vary largely between different partial waves, the singlet-triplet
phase difference, which determines the spin-exchange cross-section, remains
locked to a single value over a wide range of partial-waves which leads to
quantum interference effects.",1806.05150v2
2018-12-06,Nonlinear excitonic spin Hall effect in monolayer transition metal dichalcogenides,"We propose and analyze a mechanism for inducing spin Hall currents in
ordinary (1H phase) monolayer transition metal dichalcogenides (TMDs) due to
the nonlinear process of optical rectification. The photo-induced spin current
is proportional to the light intensity, and originates from the intrinsic
spin-orbit coupling in TMDs. The spin current spectrum is strongly influenced
by electron-hole interactions, i.e. excitonic effects, analogous to the optical
absorption. Remarkably, excitons change the temperature dependence of the
induced spin current, to the point that the current direction can even be
reversed by varying the temperature. This peculiar excitonic behavior is shown
to emerge from the relative strength of two distinct mechanisms contributing to
the optical response, i.e. a purely interband part and a mixed inter/intraband
contribution. Furthermore, we investigate the valley dichrosim of
second-harmonic charge and spin currents, and demonstrate different valley
polarization of $s$ and $p$ excitons that stem from their distinct angular
momenta. Our findings pave the path to the generation of dc spin currents in
ordinary TMDs without external static electric or magnetic fields.",1812.02596v1
2018-12-12,Laser-Irradiated CrI$_3$: When Chiral Photons Meet Topological Magnons,"Insulating honeycomb ferromagnet CrI$_3$ has recently attracted considerable
attention due to its potential use for dissipationless spintronics
applications. Recently, topological spin excitations have been observed
experimentally in bulk CrI$_3$ by L. Chen, et al. [Phys. Rev. X ${\bf 8}$,
041028 (2018)] using inelastic neutron scattering. This suggest that bulk
CrI$_3$ has strong spin-orbit coupling and its spin Hamiltonian should include
a next-nearest neighbour Dzyaloshinskii-Moriya (DM) interaction. Inspired by
this experiment, we study non-equilibrium emergent photon-dressed topological
spin and thermal Hall transports in laser-irradiated CrI$_3$ with and without
the DM interaction. We show that the spin excitations can be manipulated into
different topological phases with different Chern numbers. Most importantly, we
show that the emergent photon-dressed spin and thermal Hall response can be
switched to different signs. Hence, the generated magnon spin photocurrents can
be manipulated by the laser field, which is of great interest in ultrafast spin
current generation and could pave the way for future applications of CrI$_3$ to
topological opto-spintronics and opto-magnonics.",1812.05101v2
2019-03-03,Near-Unity Spin Hall Ratio in Ni$_x$Cu$_{1-x}$ Alloys,"We report a large spin Hall effect in the 3$d$ transition metal alloy
Ni$_x$Cu$_{1-x}$ for $x\in\left\{ 0.3,0.75\right\} $, detected via the
ferromagnetic resonance of a Permalloy (Py = Ni$_{80}$Fe$_{20}$) film deposited
in a bilayer with the alloy. A thickness series at $x$ = 0.6, for which the
alloy is paramagnetic at room temperature, allows us to determine the spin Hall
ratio $\theta_{\rm{SH}}\approx1$, spin diffusion length $\lambda_{\rm{s}}$,
spin mixing conductance $G_{\uparrow\downarrow}$, and damping
$\alpha_{\rm{SML}}$ due to spin memory loss . We compare our results with
similar experiments on Py/Pt bilayers measured using the same method. Ab initio
band structure calculations with disorder and spin-orbit coupling suggest an
intrinsic spin Hall effect in Ni$_x$Cu$_{1-x}$ alloys, although the experiments
here cannot distinguish between extrinsic and intrinsic mechanisms.",1903.00910v2
2019-04-09,"Parafermions, induced edge states and domain walls in the fractional quantum Hall effect spin transitions","Search for parafermions and Fibonacci anyons, which are excitations obeying
non-Abelian statistics, is driven both by the quest for deeper understanding of
nature and prospects for universal topological quantum computation. However,
physical systems that can host these exotic excitations are rare and hard to
realize in experiments. Here we study the domain walls and the edge states
formed in spin transitions in the fractional quantum Hall effect. Effective
theory approach and exact diagonalization in a disk and torus geometries proves
the existence of the counter-propagating edge modes with opposite spin
polarizations at the boundary between the two neighboring regions of the
two-dimensional electron liquid in spin-polarized and spin-unpolarized phases.
By analytical and numerical analysis, we argue that these systems can host
parafermions when coupled to an s-wave superconductor and are experimentally
feasible. We investigate settings based on $\nu=\frac{2}{3}$, $\nu=\frac{4}{3}$
and $\nu=\frac{5}{3}$ spin transitions and analyze spin-flipping interactions
that hybridize counter-propagating modes. Finally, we discuss spin-orbit
interactions of composite fermions.",1904.04719v1
2020-05-14,Spin Hall Effect in Bilayer Graphene Combined with an Insulator up to Room Temperature,"Spin-orbit coupling in graphene can be enhanced by chemical
functionalization, adatom decoration or proximity with a van der Waals
material. As it is expected that such enhancement gives rise to a sizeable spin
Hall effect, a spin-to-charge current conversion phenomenon of technological
relevance, it has sparked wide research interest. However, it has only been
measured in graphene/transition metal dichalcogenide van der Waals
heterostructures with limited scalability. Here, we experimentally demonstrate
spin Hall effect up to room temperature in bilayer graphene combined with a
nonmagnetic insulator, an evaporated bismuth oxide layer. The measured spin
Hall effect raises most likely from an extrinsic mechanism. With a large
spin-to-charge conversion efficiency, scalability, and ease of integration to
electronic devices, we show a promising material heterostructure suitable for
spin-based device applications.",2005.07249v1
2020-10-15,Emergent Bloch oscillations in a kinetically constrained Rydberg spin lattice,"We explore the relaxation dynamics of elementary spin clusters of a
kinetically constrained spin system. Inspired by experiments with Rydberg
lattice gases, we focus on the situation in which an excited spin leads to a
""facilitated"" excitation of a neighboring spin. We show that even weak
interactions that extend beyond nearest neighbors can have a dramatic impact on
the relaxation behavior: they generate a linear potential, which under certain
conditions leads to the onset of Bloch oscillations of spin clusters. These
hinder the expansion of a cluster and more generally the relaxation of
many-body states towards equilibrium. This shows that non-ergodic behavior in
kinetically constrained systems may occur as a consequence of the interplay
between reduced connectivity of many-body states and weak interparticle
interactions. We furthermore show that the emergent Bloch oscillations
identified here can be detected in experiment through measurements of the
Rydberg atom density, and discuss how spin-orbit coupling between internal and
external degrees of freedom of spin clusters can be used to control their
relaxation behavior.",2010.07825v2
2020-11-25,Perovskite as a spin current generator,"We theoretically show that materials with perovskite-type crystal structures
provide a platform for spin current generation, taking advantage of a mechanism
requiring neither the spin-orbit coupling nor a ferromagnetic moment, but is
based on spin-split band structures in certain kinds of collinear
antiferromagnetic states. By investigating a multiband Hubbard model for
transition metal compounds by means of the Hartree-Fock approximation and the
Boltzmann transport theory, we find that a pure spin current is induced by an
electric field applied to a C-type antiferromagnetic metallic phase. The spin
current generation originates from a cooperative effect of spatially
anisotropic electron transfer integrals owing to the GdFeO$_3$-type lattice
distortion, which is ubiquitous in many perovskites, and the collinear spin
configuration. We discuss our finding from the symmetry point of view, in
comparison with other spin current generator candidates with collinear
antiferomagnetism. We also propose several ways to detect the phenomenon in
candidate perovskite materials.",2011.12459v1
2021-04-13,Theory of spin-Hall magnetoresistance in the AC (terahertz) regime,"In bilayers consisting of a normal metal (N) with spin-orbit coupling and a
ferromagnet (F), the combination of the spin-Hall effect, the spin-transfer
torque, and the inverse spin-Hall effect gives a small correction to the
in-plane conductivity of N, which is referred to as spin-Hall magnetoresistance
(SMR). We here present a theory of the SMR and the associated off-diagonal
conductivity corrections for frequencies up to the terahertz regime. We show
that the SMR signal has pronounced singularities at the spin-wave frequencies
of F, which identifies it as a potential tool for all-electric spectroscopy of
magnon modes. A systematic change of the magnitude of the SMR at lower
frequencies is associated with the onset of a longitudinal magnonic
contribution to spin transport across the F-N interface.",2104.06518v2
2016-12-20,All-Electrical Generation of Spin-Polarized Currents in Quantum Spin Hall Insulators,"The control and generation of spin-polarized currents (SPCs) without magnetic
materials and external magnetic field is a big challenge in spintronics and
normally requires spin-flip mechanism. In this work, we propose a novel method
to control and generate SPCs in stanene nanoribbons in the quantum spin Hall
(QSH) insulator regime by all electrical means without spin-flip mechanism.
This is achieved with intrinsic spin-orbit coupling in stanene nanoribbons by
tuning the relative phase of spin up and down electrons using a gate voltage,
which creates a time delay between them thereby producing alternative SPCs
driven by ac voltage. The control and generation of SPCs are demonstrated
numerically for ac transport in both transient and ac regime. Our results are
robust against edge imperfections and generally valid for other QSH insulators
such as silicene and germanene, etc. These findings establish a novel route for
generating SPCs by purely electrical means and open the door for new
applications of semiconductor spintronics.",1612.06629v1
2020-03-09,Symmetric spin liquids on the stuffed honeycomb lattice,"We use a projective symmetry group analysis to determine all symmetric spin
liquids on the stuffed honeycomb lattice Heisenberg model. This lattice
interpolates between honeycomb, triangular and dice lattices, always preserving
hexagonal symmetry, and it already has one spin liquid candidate, TbInO$_3$,
albeit with strong spin-orbit coupling not considered here. In addition to the
stuffed honeycomb lattice itself, we gain valuable insight into potential spin
liquids on the honeycomb and triangular lattices, as well as how they might be
connected. For example, the sublattice pairing state proposed on the honeycomb
lattice connects to the uniform spinon Fermi surface that may be relevant for
the triangular lattice with ring exchange, while there are no spin liquids
competitive on both the $J_1-J_2$ honeycomb and triangular lattice limits. In
particular, we find three stuffed honeycomb descendants of the U(1) Dirac spin
liquid widely believed to be found on the $J_1-J_2$ triangular lattice. We also
discuss how spin liquids near the honeycomb limit can potentially explain the
physics of LiZn$_2$Mo$_3$O$_8$.",2003.04269v1
2020-09-18,Spin-momentum locking induced non-local voltage in topological insulator nanowire,"The momentum and spin of charge carriers in the topological insulators are
constrained to be perpendicular to each other due to the strong spin-orbit
coupling. We have investigated this unique spin-momentum locking property in
Sb2Te3 topological insulator nanowires by injecting spin-polarized electrons
through magnetic tunnel junction electrodes. Non-local voltage measurements
exhibit a symmetry with respect to the magnetic field applied perpendicular to
the nanowire channel, which is remarkably different from that of a non-local
measurement in a channel that lacks spin-momentum locking. In stark contrast to
conventional non-local spin valves, simultaneous reversal of magnetic moments
of all magnetic contacts to the Sb2Te3 nanowire alters the non-local voltage.
This unusual symmetry is a clear signature of the spin-momentum locking in the
Sb2Te3 nanowire surface states.",2009.09091v1
2021-01-08,Chirality Induced Spin Coherence in Electron Transfer Reactions,"Recently there has been much interest in the chirality induced spin
selectivity effect, whereby electron spin polarisation, which is dependent on
the molecular chirality, is produced in electrode-molecule electron transfer
processes. Naturally, one might consider if a similar effect can be observed in
simple molecular charge transfer reactions, for example in light-induced
electron transfer from an electron donor to an electron acceptor. In this work
we explore the effect of electron transfer on spins in chiral single radicals
and chiral radical pairs using Nakajima-Zwanzig theory. In these cases
chirality, in conjuction with spin-orbit coupling, does not lead to spin
polarisation, but instead the electron transfer generates quantum coherence
between spins states. In principle, this chirality induced spin coherence could
manifest in a range of experiments, and in particular we demonstrate that the
OOP-ESEEM pulse EPR experiment would be able to detect this effect in oriented
radical pairs.",2101.03104v1
2021-03-01,Electron-induced nuclear magnetic ordering in n-type semiconductors,"Nuclear magnetism in n-doped semiconductors with positive hyperfine constant
is revisited. Two kinds of nuclear magnetic ordering can be induced by resident
electrons in a deeply cooled nuclear spin system. At positive nuclear spin
temperature below a critical value, randomly oriented nuclear spin polarons
similar to that predicted by I. Merkulov [I. Merkulov, Physics of the Solid
State 40, 930 (1998)] should emerge. These polarons are oriented randomly and
within each polaron nuclear and electron spins are aligned
antiferromagnetically. At negative nuclear spin temperature below a critical
value we predict another type of magnetic ordering - dynamically induced
nuclear ferromagnet. This is a long-range ferromagnetically ordered state
involving both electrons and nuclei. It can form if electron spin relaxation is
dominated by the hyperfine coupling, rather than by the spin-orbit interaction.
Application of the theory to the n-doped GaAs suggests that the ferromagnetic
order may be reached at experimentally achievable nuclear spin temperature
$\Theta_N \approx 0.5$ $\mu$K and lattice temperature $T_L \approx 5$ K.",2103.01120v1
2021-06-11,The origin of chirality induced spin selectivity in photo-induced electron transfer,"Here we propose a mechanism by which spin polarization can be generated
dynamically in chiral molecular systems undergoing photo-induced electron
transfer. The proposed mechanism explains how spin polarization emerges in
systems where charge transport is dominated by incoherent hopping, mediated by
spin orbit and electronic exchange couplings through an intermediate charge
transfer state. We derive a simple expression for the spin polarization that
predicts a non-monotonic temperature dependence consistent with recent
experiments. We validate this theory using approximate quantum master equations
and the numerically exact hierarchical equations of motion. The proposed
mechanism of chirality induced spin selectivity should apply to many chiral
systems, and the ideas presented here have implications for the study of spin
transport at temperatures relevant to biology, and provide simple principles
for the molecular control of spins in fluctuating environments.",2106.06554v1
2021-07-07,Acoustic Rashba-Edelstein effect,"We theoretically study the mechanical induction of the spin density via the
Rashba spin--orbit interaction (SOI). The spin density in the linear response
to lattice distortion dynamics is calculated based on the microscopic theory.
We reveal that there are two mechanisms of spin induction: one is the acoustic
Edelstein effect (AEE) from the acceleration of the lattice dynamics and the
other is caused by the Rashba spin--vorticity coupling (RSVC). We find that the
AEE induces a more efficient spin-to-charge conversion in comparison with the
conventional electric Edelstein effect. The induced spin density due to the
RSVC is expressed as a Berry curvature-like quantity; therefore, it can be
attributed to the spatial symmetry breaking due to the Rashba SOI. Our work
demonstrates high-efficiency spin generation in Rashba systems.",2107.03115v1
2021-07-21,Nonmonotonic quantum phase gathering in curved spintronic circuits,"Spin carriers propagating along quantum circuits gather quantum spin phases
depending on the circuit's size, shape, and spin-orbit coupling (SOC) strength.
These phases typically grow monotonically with the SOC strength, as found in
Rashba quantum wires and rings. In this work we show that the spin-phase
gathering can be engineered by geometric means, viz. by the geometric curvature
of the circuits, to be non-monotonic. We demonstrate this peculiar property by
using one-dimensional polygonal models where flat segments alternate with
highly curved vertices. The complex interplay between dynamic and geometric
spin-phase components -- triggered by a series of emergent spin degeneracy
points -- leads to bounded, global spin phases. Moreover, we show that the
particulars of the spin-phase gathering have observable consequences in the
Aharonov-Casher conductance of Rashba loops, a connection that passed unnoticed
in previous works.",2107.10192v4
2021-09-21,Chiral Surface Wave propagation with Anomalous Spin-momentum Locking,"The ability to control the directionality of surface waves by manipulating
its polarization has been of great significance for applications in spintronics
and polarization-based optics. Surface waves with evanescent tails are found to
possess an inherent in-plane transverse spin which is dependent on the
propagation direction while an out-of-plane transverse spin does not naturally
occur for surface waves and requires a specific surface design. Here, we
introduce a new type of surface waves called chiral surface wave which has two
transverse spins, an in-plane one that is inherent to any surface wave and an
out-of-plane spin which is enforced by the design due to strong x-to-y coupling
and broken rotational symmetry. The two transverse spins are locked to the
momentum. Our study opens a new direction for metasurface designs with enhanced
and controlled spin-orbit interaction by adding an extra degree of freedom to
control the propagation direction as well as the transverse spin of surface
waves.",2109.10314v1
2021-12-22,Surface Cooper pair spin waves in triplet superconductors,"We study the electrodynamics of spin triplet superconductors including
dipolar interactions, which give rise to an interplay between the collective
spin dynamics of the condensate and orbital Meissner screening currents. Within
this theory, we identify a class of spin waves that originate from the coupled
dynamics of the spin-symmetry breaking triplet order parameter and the
electromagnetic field. In particular, we study magnetostatic spin wave modes
that are localized to the sample surface. We show that these surface modes can
be excited and detected using experimental techniques such as microwave spin
wave resonance spectroscopy or nitrogen-vacancy magnetometry, and propose that
the detection of these modes offers a means for the identification of spin
triplet superconductivity.",2112.12146v2
2022-01-22,Elasto-Dynamical Induced Spin and Charge Pumping in Bulk Heavy Metals,"Analogous to the Spin-Hall Effect (SHE), {\it ab initio} electronic structure
calculations reveal that acoustic phonons can induce charge (spin) current
flowing along (normal to) its propagation direction. Using Floquet approach we
have calculated the elastodynamical-induced charge and spin pumping in bulk Pt
and demonstrate that: (i) While the longitudinal charge pumping is an intrinsic
observable, the transverse pumped spin-current has an extrinsic origin that
depends strongly on the electronic relaxation time; (ii) The longitudinal
charge current
  is of nonrelativstic origin, while the transverse spin current is a
relativistic effect that to lowest order scales linearly with the spin-orbit
coupling strength; (iii) both charge and spin pumped currents have parabolic
dependence on the amplitude of the elastic wave.",2201.09121v1
2022-03-10,Bulk photospin effect: Calculation of electric spin susceptibility to second order in an electric field,"We compute the electric spin susceptibility of Bloch electrons with
spin-orbit coupling to second order. We find that it is possible to generate a
nonequilibrium spin polarization in the bulk of non-magnetic
inversion-symmetric materials using linearly polarized electric fields, but the
process depends on interband coherence and produces heating. It may be possible
to avoid heating with circular polarization in certain scenarios. The standard
Edelstein effect and spin orientation effects are recovered in appropriate
limits within the formalism. Finally, the electric spin susceptibility of
metals has contributions proportional to spin multipole moments of the Fermi
sea that dominate the low frequency spin response.",2203.05116v3
2022-03-18,Datta-Das transistor for atomtronic circuits using artificial gauge fields,"Spin-dependent electrical injection has found useful applications in storage
devices, but fully operational spin-dependent semiconductor electronics remain
a challenging task because of weak spin-orbit couplings and/or strong spin
relaxations. These limitations are lifted considering atoms instead of
electrons or holes as spin carriers. In this emerging field of atomtronics, we
demonstrate the equivalent of a Datta-Das transistor using a degenerate Fermi
gas of strontium atoms as spin carriers in interaction with a tripod
laser-beams scheme. We explore the dependence of spin rotation, and we identify
two key control parameters which we interpret as equivalent to the gate-source
and drain-source voltages of a field effect transistor. Our finding broadens
the spectrum of atomtronics devices for implementation of operational
spin-sensitive circuits.",2203.13360v2
2022-04-27,Investigation of spin rotators in CEPC at the Z-pole,"Longitudinal polarization is an important design aspect of the future 100
km-scale Circular Electron Position Collider (CEPC). Spin rotators are needed
in CEPC collider rings to make the beam polarization along the longitudinal
direction at the interaction points (IPs). This paper focuses on the design of
spin rotators for CEPC at Z-pole (45.6 GeV). The design of spin rotators in
CEPC at Z-pole is based on solenoid magnets and horizontal bending magnets
sections. The coupling of transverse motion introduced by solenoids is
compensated with quadrupole lenses. Adjustments have been made to the layout to
implement the spin rotators into the collider rings.Longitudinal polarized beam
can be achieved at the IPs with the spin rotators. High degree of polarization
is attainable, while the effect of spin rotators on orbital motion is
acceptable. The detailed simulation results will be presented.A solenoid-based
spin rotator configuration is designed and integrated into the CEPC collider
ring lattice. According to the simulation results, the polarization
requirements can be satisfied.",2204.12664v2
2022-08-10,"Ferrochiral, antiferrochiral, and ferrichiral skyrmion crystals in an itinerant honeycomb magnet","Topological spin textures, such as a skyrmion crystal, are a source of
unusual physical phenomena owing to the interplay between magnetism and
topology. Since physical phenomena depend on the topological property and the
symmetry of underlying spin structures, the search for new topological spin
textures and emergent phenomena is one of the challenges in condensed matter
physics. In this letter, we theoretically explore new topological spin textures
arising from the synergy between spin, charge, and sublattice degrees of
freedom in an itinerant magnet. By performing simulated annealing for an
effective spin model of the honeycomb Kondo lattice model, we find a plethora
of skyrmion crystal instabilities at low temperatures, whose topological spin
textures are classified into three types: ferrochiral, antiferrochiral, and
ferrichiral skyrmion crystals. We show that the obtained skyrmion crystals are
the consequence of the spin-orbit-coupling-free honeycomb structure. Our
results reveal the potential for itinerant honeycomb magnets to host a wide
variety of SkXs and emergent phenomena.",2208.05115v1
2023-05-16,Antiferromagnetic spin fluctuations and unconventional superconductivity in topological superconductor candidate YPtBi revealed by $^{195}$Pt-NMR,"We report $^{195}$Pt nuclear magnetic resonance (NMR) measurements on
topological superconductor candidate YPtBi which has the broken inversion
symmetry and topological non-trivial band structures due to the strong
spin-orbit coupling(SOC). In the normal state, we find that Knight shift $K$ is
field- and temperature-independent, suggesting that the contribution from the
topological bands is very small at low temperatures. However, the spin-lattice
relaxation rate 1/$T_1$ divided by temperature ($T$), 1/$T_1T$, increases with
decreasing $T$, implying the existence of antiferromagnetic spin fluctuations.
In the superconducting state, no Hebel-Slichter coherence peak is seen below
$T_{\rm c}$ and 1/$T_1$ follows $T^{3}$ variation, indicating the
unconventional superconductivity. The finite spin susceptibility at
zero-temperature limit and the anomalous increase of the NMR line width below
$T_{\rm c}$ point to a mixed state of spin-singlet and spin-triplet(or
spin-septet) pairing.",2305.09437v1
2023-06-29,Non-equilibrium spin accumulation and magneto-conductance in chiral nanojunctions from density-functional $\&$ group theory,"It is theoretically well established that a spin-dependent electron
transmission generally appears in chiral systems, even without magnetic
components, as long as a strong spin-orbit coupling is present in some of its
elements. However, how this translates into the so-called chirality-induced
spin selectivity in experiments, where the system is taken out of equilibrium,
is still debated. Aided by non-equilibrium DFT-based quantum transport
calculations, here we show that, when spatial symmetries that forbid a finite
spin polarization in equilibrium are broken, a \textit{net} spin accumulation
appears at finite bias in an arbitrary two-terminal nanojunction. Furthermore,
when a suitably magnetized detector is introduced in the system, the net spin
accumulation, in turn, translates into a finite magneto-conductance. The
symmetry prerequisites are mostly analogous to those for the spin polarization
at any bias, with the vectorial nature given by the direction of magnetization.",2306.17312v1
2023-09-05,Dynamics of anisotropic frustrated antiferromagnet Cs2CoBr4 in a spin-liquid regime,"Cs2CoBr4 is a triangular-lattice antiferromagnet which can be viewed as
weakly interacting spin chains due to spatially anisotropic frustrating
exchange couplings. The spin-orbit interaction in Co(2+) spin-3/2 ions leads to
a strong easy-plane single-ion anisotropy which allows to consider the
low-energy spin dynamics of this system using an anisotropic pseudospin-1/2
model. By means of the electron spin resonance (ESR) technique, we study the
spin dynamics of Cs2CoBr4 in magnetic field in a spin-liquid regime, i.e.,
above the N'eel temperature of 1.3 K but below the temperature of the crossover
to in-chain correlations of pseudospins (6 K). Our experiments reveal two
bright branches of excitations which strongly differ both from excitations in
the low-temperature ordered phases and from high-temperature paramagnetic
resonance of uncorrelated pseudospins and spins. These two branches are
interpreted as excitations with zero momentum of an anisotropic spin-1/2 chain.
Besides, we observe several weak modes of unknown origin which arise mostly as
satellites of one of the bright modes.",2309.02266v1
2024-03-07,A generic model with unconventional Rashba bands and giant spin galvanic effect,"In two-dimensional system, Rashba spin-orbit coupling can lift spin
degeneracy and gives the opposite spin chirality of two split Fermi circles
from two Rashba bands. Here, we propose a generic model which can produce
unconventional Rashba bands. In such a case, the two Fermi circles from two
bands have the same spin chirality. When various interactions are taken into
account, many unique physics can emerge in case of unconventional Rashba bands
in comparison with in case of conventional Rashba bands. For instance, we study
the spin galvanic effect by considering two cases with potential impurity
scattering and magnetic impurity scattering, respectively. In both cases, we
find the efficiency of spin galvanic effect is strongly enhanced in
unconventional Rashba bands in comparison with conventional Rashba bands. More
intriguingly, we find the effeiciency of conventional Rashba bands is
insensitive to potential or magnetic impurity scattering. However, such
efficiency of uncoventional Rashba bands can be further enhanced by the
magnetic impurity scattering in comparison with the potential impurity
scattering. Thus, the unconventional Rashba bands can give giant spin galvanic
effect. These results show that this model is useful to explore abnormal
physics in the systems with unconventional Rashba bands.",2403.04155v1
2020-07-29,Infinite-layer nickelates as Ni-eg Hund's metals,"The recent and exciting discovery of superconductivity in the hole-doped
infinite-layer nickelate Nd 1-{\delta} Sr {\delta} NiO 2 draws strong attention
to correlated quantum materials. From a theoretical view point, this new class
of unconventional superconducting materials provides an opportunity to unveil
new physics in correlated quantum materials. Here we study the temperature and
doping dependence of the local spectrum as well as the charge, spin and orbital
susceptibilities from first principles. By using ab initio LQSGW+DMFT
methodology, we show that onsite Hund's coupling in Ni-d orbitals gives rise to
multiple signatures of Hund's metallic phase in Ni-eg orbitals. The proposed
picture of the nickelates as an eg (two orbital) Hund's metal differs from the
picture of the Fe-based superconductors as a five orbital Hund's metal as well
as the picture of the cuprates as doped charge transfer insulators. Our finding
unveils a new class of the Hunds metals and has potential implications for the
broad range of correlated two orbital systems away from half-filling.",2007.14610v2
2023-05-17,High orbital-moment Cooper pairs by crystalline symmetry breaking,"The pairing structure of superconducting materials is regulated by the point
group symmetries of the crystal. Here, we study spin-singlet multiorbital
superconductivity in materials with unusually low crystalline symmetry content
and unveil the the appearance of even-parity (s-wave) Cooper pairs with high
orbital moment. We show that the lack of mirror and rotation symmetries makes
pairing states with quintet orbital angular momentum symmetry-allowed. A
remarkable fingerprint of this type of pairing state is provided by a
nontrivial superconducting phase texture in momentum space with $\pi$-shifted
domains and walls with anomalous phase winding. The pattern of the quintet
pairing texture is shown to depend on the orientation of the orbital
polarization and the strength of the mirror and/or rotation symmetry breaking
terms. Such momentum dependent phase makes Cooper pairs with net orbital
component suited to design orbitronic Josephson effects. We discuss how an
intrinsic orbital dependent phase can set out anomalous Josephson couplings by
employing superconducting leads with nonequivalent breaking of crystalline
symmetry.",2305.10039v1
2023-11-20,Orbital Hall effect and topology on a two-dimensional triangular lattice: from bulk to edge,"We investigate a generalized multi-orbital tight-binding model on a
triangular lattice, a system prevalent in a wide range of two-dimensional
materials, and particularly relevant for simulating transition metal
dichalcogenide monolayers. We show that the interplay between spin-orbit
coupling and different symmetry-breaking mechanisms leads to the emergence of
four distinct topological phases [Eck, P., \textit{et al.}, Phys. Rev. B, 107
(11), 115130 (2023)]. Remarkably, this interplay also triggers the orbital Hall
effect with distinguished characteristics. Furthermore, by employing the
Landauer-B\""uttiker formula, we establish that in the orbital Hall insulating
phase, the orbital angular momentum is carried by edge states present in
nanoribbons with specific terminations. We also show that, as expected, they do
not have topological protection against the disorder of the edge states
belonging to a first-order topological insulator.",2311.11715v1
2023-11-20,Orbital Kerr effect and terahertz detection via the nonlinear Hall effect,"We investigate the optical response induced by a d.c. current flowing in a
nonmagnetic material that lacks inversion symmetry. In this class of materials,
the flowing current experiences a nonlinear Hall effect and induces a
nonequilibrium orbital magnetization, even in the absence of spin-orbit
coupling. As a result, an orbital-driven Kerr effect arises that can be used to
probe not only the orbital magnetization, but also the nonlinear Hall effect.
In addition, in the long wavelength limit, the nonlinear Hall effect leads to a
rectification current that can be used to detect terahertz radiation. We apply
the theory to selected model systems, such as WTe$_2$ bilayer, as well as to
realistic materials, i.e., bulk Te and metallic superlattices. The
nonequilibrium orbital Kerr efficiencies obtained in these systems are
comparable to the largest values reported experimentally in GaAs and MoS$_2$,
exceeding the values reported in metals and suggesting a large terahertz
current responsivity.",2311.11889v1
2023-03-29,Strong coupling between a microwave photon and a singlet-triplet qubit,"Tremendous progress in few-qubit quantum processing has been achieved lately
using superconducting resonators coupled to gate voltage defined quantum dots.
While the strong coupling regime has been demonstrated recently for odd charge
parity flopping mode spin qubits, first attempts towards coupling a resonator
to even charge parity singlet-triplet spin qubits have resulted only in weak
spin-photon coupling strengths. Here, we integrate a zincblende InAs nanowire
double quantum dot with strong spin-orbit interaction in a magnetic-field
resilient, high-quality resonator. In contrast to conventional strategies, the
quantum confinement is achieved using deterministically grown wurtzite tunnel
barriers without resorting to electrical gating. Our experiments on even charge
parity states and at large magnetic fields, allow to identify the relevant spin
states and to measure the spin decoherence rates and spin-photon coupling
strengths. Most importantly, we find an anti-crossing between the resonator
mode in the single photon limit and a singlet-triplet qubit with an electron
spin-photon coupling strength of $g/2\pi=139\pm4$ MHz. Combined with the
resonator decay rate $\kappa/2\pi=19.8\pm0.2$ MHz and the qubit dephasing rate
$\gamma/2\pi=116\pm7$ MHz, our system achieves the strong coupling regime in
which the coherent coupling exceeds qubit and resonator linewidth. These
results pave the way towards large-scale quantum system based on
singlet-triplet qubits.",2303.16825v2
2021-04-21,Electronic Structure of Mononuclear Cu-based Molecule from Density-Functional Theory with Self-Interaction Correction,"We investigate the electronic structure of a planar mononuclear Cu-based
molecule [Cu(C$_6$H$_4$S$_2$)$_2$]$^z$ in two oxidation states ($z$$=$$-2$,
$-$1) using density-functional theory (DFT) with Fermi-L\""owdin orbital (FLO)
self-interaction correction (SIC). The dianionic Cu-based molecule was proposed
to be a promising qubit candidate. Self-interaction error within approximate
DFT functionals renders severe delocalization of electron and spin densities
arising from 3$d$ orbitals. The FLO-SIC method relies on optimization of
Fermi-L\""owdin orbital descriptors (FODs) with which localized occupied
orbitals are constructed to create the SIC potentials. Starting with many
initial sets of FODs, we employ a frozen-density loop algorithm within the
FLO-SIC method to study the Cu-based molecule. We find that the electronic
structure of the molecule remains unchanged despite somewhat different final
FOD configurations. In the dianionic state (spin $S=1/2$), FLO-SIC spin density
originates from the Cu $d$ and S $p$ orbitals with an approximate ratio of 2:1,
in quantitative agreement with multireference calculations, while in the case
of SIC-free DFT, the orbital ratio is reversed. Overall, FLO-SIC lowers the
energies of the occupied orbitals and in particular the 3$d$ orbitals
unhybridized with the ligands significantly, which substantially increases the
energy gap between the highest occupied molecular orbital (HOMO) and the lowest
unoccupied molecular orbital (LUMO) compared to SIC-free DFT results. The
FLO-SIC HOMO-LUMO gap of the dianionic state is larger than that of the
monoionic state, which is consistent with experiment. Our results suggest a
positive outlook of the FLO-SIC method in the description of magnetic exchange
coupling within 3$d$-element based systems.",2104.10327v1
2007-10-17,The final spin from the coalescence of aligned-spin black-hole binaries,"Determining the final spin of a black-hole (BH) binary is a question of key
importance in astrophysics. Modelling this quantity in general is made
difficult by the fact that it depends on the 7-dimensional space of parameters
characterizing the two initial black holes. However, in special cases, when
symmetries can be exploited, the description can become simpler. For black-hole
binaries with unequal masses but with equal spins which are aligned with the
orbital angular momentum, we show that the use of recent simulations and basic
but exact constraints derived from the extreme mass-ratio limit allow to model
this quantity with a simple analytic expression. Despite the simple dependence,
the expression models very accurately all of the available estimates, with
errors of a couple of percent at most. We also discuss how to use the fit to
predict when a Schwarzschild BH is produced by the merger of two spinning BHs,
when the total angular momentum of the spacetime ``flips'' sign, or under what
conditions the final BH is ``spun-up'' by the merger. Finally, suggest an
extension of the fit to include unequal-spin binaries, thus potentially
providing a complete description of the final spin from the coalescence of
generic black-hole binaries with spins aligned to the orbital angular momentum.",0710.3345v3
2020-02-05,Spin Resonances in Iron-Selenide High-Tc Superconductors by Proximity to Hidden Spin Density Wave,"Recent inelastic neutron scattering studies by Pan et al., Nature
Communications 8, 123 (2017), find evidence for spin excitations at energies
above the quasi-particle gap in an iron-selenide high-Tc superconductor. The
momenta of the spin excitations form a diamond around the checkerboard
wavevector, Q_AF, that is associated with the square lattice of iron atoms that
makes up the system. It has been suggested that such a ""hollowed-out""
spin-excitation spectrum is due to hidden Neel order. We study such a hidden
spin-density wave (hSDW) state that results from nested Fermi surfaces at the
center and at the corner of the unfolded Brillouin zone. It emerges within mean
field theory from an extended Hubbard model over a square lattice of iron atoms
that contain the minimal d_xz and d_yz orbitals. Opposing Neel order exists
over the isotropic d+ = d_xz + i d_yz and d- = d_xz - i d_yz orbitals. The
dynamical spin susceptibility of the hSDW is computed within the random phase
approximation, at perfect nesting. Unobservable Goldstone modes that disperse
acoustically are found at Q_AF. A threshold is found in the spectrum of
observable spin excitations that forms a ""floating ring"" at Q_AF also. The ring
threshold moves down in energy toward zero with increasing Hund's Rule
coupling, while it moves up in energy with increasing magnetic frustration.
Comparison with the normal-state features of the spin-excitation spectrum shown
by electron-doped iron selenide is made. Also, recent predictions of a Lifshitz
transition from the nested Fermi surfaces to Fermi surface pockets at the
corner of the folded Brillouin zone will be discussed.",2002.01732v2
2020-10-20,Determination of the spin axis in quantum spin Hall insulator monolayer WTe2,"Evidence for the quantum spin Hall (QSH) effect has been reported in several
experimental systems in the form of approximately quantized edge conductance.
However, the most fundamental feature of the QSH effect, spin-momentum locking
in the edge channels, has never been demonstrated experimentally. Here, we
report clear evidence for spin-momentum locking in the edge channels of
monolayer WTe2, thought to be a two-dimensional topological insulator (2D TI).
We observe that the edge conductance is controlled by the component of an
applied magnetic field perpendicular to a particular axis, which we identify as
the spin axis. The axis is the same for all edges, situated in the mirror plane
perpendicular to the tungsten chains at 40$\pm$2{\deg} to the layer normal,
implying that the spin-orbit coupling is inherited from the bulk band
structure. We show that this finding is consistent with theory if the band-edge
orbitals are taken to have like parity. We conclude that this parity assignment
is correct and that both edge states and bulk bands in monolayer WTe2 share the
same simple spin structure. Combined with other known features of the edge
states this establishes spin-momentum locking, and therefore that monolayer
WTe2 is truly a natural 2D TI.",2010.09986v2
2022-10-05,Modifications of Tanabe-Sugano d$^6$ diagram induced by radical ligand field: ab initio inspection of a Fe(II)-verdazyl molecular complex,"Quantum entanglement between the spin states of a metal centre and radical
ligands is suggested in an iron(II) [Fe(dipyvd)$_2$]$^{2+}$ compound (dipyvd =
1-isopropyl-3,5-dipyridil-6-oxoverdazyl). Wavefunction \textit{ab initio}
(Difference Dedicated Configuration Interaction, DDCI) inspections were carried
out to stress the versatility of local spin states. We named this phenonmenon
\textit{excited state spinmerism}, in reference to our previous work (see
Roseiro et. al., ChemPhysChem 2022, e202200478) where we introduced the concept
of spinmerism as an extension of mesomerism to spin degrees of freedom. The
construction of localized molecular orbitals allows for a reading of the
wavefunctions and projections onto the local spin states. The low-energy
spectrum is well-depicted by a Heisenberg picture. A 60 cm$^{-1}$ ferromagnetic
interaction is calculated between the radical ligands with the $S_{total} = 0$
and $1$ states largely dominated by a local low-spin $S_{Fe} = 0$. In contrast,
the higher-lying $S_{total} = 2$ states are superpositions of the local $S_{Fe}
= 1$ (17%, 62%) and $S_{Fe} = 2$ (72%, 21%) spin states. Such mixing extends
the traditional picture of a high-field $d^6$ Tanabe-Sugano diagram. Even in
the absence of spin-orbit coupling, the avoided crossing between different
local spin states is triggered by the field generated by radical ligands. This
puzzling scenario emerges from versatile local spin states in compounds which
extend the traditional views in molecular magnetism.",2210.02325v2
2022-11-16,Emergence of large spin-charge interconversion at an oxidized Cu/W interface,"Spin-orbitronic devices can integrate memory and logic by exploiting
spin-charge interconversion (SCI), which is optimized by design and materials
selection. In these devices, such as the magnetoelectric spin-orbit (MESO)
logic, interfaces are crucial elements as they can prohibit or promote spin
flow in a device as well as possess spin-orbit coupling resulting in
interfacial SCI. Here, we study the origin of SCI in a Py/Cu/W lateral spin
valve and quantify its efficiency. An exhaustive characterization of the
interface between Cu and W electrodes uncovers the presence of an oxidized
layer (WO$_x$). We determine that the SCI occurs at the Cu/WO$_x$ interface
with a temperature-independent interfacial spin-loss conductance of $G_{||}
\approx$ 20 $\times$ 10$^{13} \Omega^{-1}m^{-2}$ and an interfacial spin-charge
conductivity $\sigma_{SC}=-$1610 $\Omega^{-1}cm^{-1}$ at 10 K ($-$830
$\Omega^{-1}cm^{-1}$ at 300 K). This corresponds to an efficiency given by the
inverse Edelstein length $\lambda_{IEE}=-$0.76 nm at 10 K ($-$0.4 nm at 300 K),
which is remarkably larger than in metal/metal and metal/oxide interfaces and
bulk heavy metals. The large SCI efficiency at such an oxidized interface is a
promising candidate for the magnetic readout in MESO logic devices.",2211.09250v1
2023-04-28,Interplay of electron-magnon scattering and spin-orbit induced electronic spin-flip fcattering in a two-band Stoner model,"Magnons are one of the carriers of angular momentum that are involved in the
ultrafast magnetization dynamics in ferromagnets, but their contribution to the
electronic dynamics and their interplay with other scattering process that
occur during ultrafast demagnetization has not yet been studied in the
framework of a microscopic dynamical model. The present paper presents such an
investigation of electronic scattering dynamics in itinerant ferromagnets at
the level of Boltzmann scattering integrals for the magnon distributions and
spin-dependent electron distributions. In addition to electron-magnon
scattering, we include spin-conserving and effective Elliott-Yafet like
spin-flip electron-electron scattering processes and the influence of phonons.
In our model system, the creation or annihilation of magnons leads to
transitions between two spin-split electronic bands with energy and momentum
conservation. Due to the presence of spin-orbit coupling, Coulomb scattering
transitions between these bands are also possible, and we describe them on an
equal footing in terms of Boltzmann scattering integrals. For an instantaneous
carrier excitation process we analyze the influence of both interaction
processes on the magnon and spin-dependent electron dynamics, and show that
their interplay gives rise to an efficient creation of magnons at higher
energies and wave vectors accompanied by only a small increase of the
electronic spin polarization. These results present a microscopic dynamical
scenario that shows how non-equilibrium magnons may dominate the magnetic
response of a ferromagnet on ultrafast timescales.",2304.14978v1
2008-11-23,Spectral properties of orbital polarons in Mott insulators,"We address the spectral properties of Mott insulators with orbital degrees of
freedom, and investigate cases where the orbital symmetry leads to Ising-like
superexchange in the orbital sector. The paradigm of a hole propagating by its
coupling to quantum fluctuations, known from the spin t-J model, then no longer
applies. We find instead that when one of the two orbital flavors is immobile,
as in the Falicov-Kimball model, trapped orbital polarons coexist with free
hole propagation emerging from the effective three-site hopping in the regime
of large on-site Coulomb interaction U. The spectral functions are found
analytically in this case within the retraceable path approximation in one and
two dimensions. On the contrary, when both of the orbitals are active, as in
the model for $t_{2g}$ electrons in two dimensions, we find propagating
polarons with incoherent scattering dressing the moving hole and renormalizing
the quasiparticle dispersion. Here, the spectral functions, calculated using
the self-consistent Born approximation, are anisotropic and depend on the
orbital flavor. Unbiased conclusions concerning the spectral properties are
established by comparing the above results for the orbital t-J models with
those obtained using the variational cluster approximation or exact
diagonalization for the corresponding Hubbard models. The present work makes
predictions concerning the essential features of photoemission spectra of
certain fluorides and vanadates.",0811.3763v1
2013-06-07,Orbital-dependent effects of electron correlations in microscopic models for iron-based superconductors,"The bad metal behavior in the normal state of the iron-based superconductors
suggests an intimate connection between the superconductivity and a proximity
to a Mott transition. At the same time, there is strong evidence for the
multi-orbital nature of the electronic excitations. It is then important to
understand the orbital-dependent effects of electron correlations. In this
paper we review the recent theoretical progresses on the metal-to-insulator
transition in multiorbital models for the iron-based superconductors. These
include studies of models that contain at least the 3d xy and 3d xz/yz models,
using a slave-spin technique. For commensurate filling corresponding to that of
the parent iron pnictides and chalcogenideds, a Mott transition generally
exists in all these models. Near the Mott transition, a strongly correlated
metal exhibiting bad metal features and strong orbital selectivity is
stabilized due to the interplay of Hund's coupling and orbital-degeneracy
breaking. Particularly for the alkaline iron selenides, the ordered vacancies
effectively reduce the kinetic energy, thereby pushing the system further into
the Mott-insulating regime; in the metallic state, there exists an
orbital-selective Mott phase in which the iron 3d xy orbital is Mott localized
while the other 3d orbitals are still itinerant. An overall phase diagram for
the alkaline iron selenides has been proposed, in which the orbital-selective
Mott phase connects between the superconducting phase and the Mott-insulating
parent state.",1306.1697v1
2023-03-08,Emergent topological quantum orbits in the charge density wave phase of kagome metal CsV$_3$Sb$_5$,"The recently discovered kagome materials $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs)
attract intense research interest in intertwined topology, superconductivity,
and charge density waves (CDW). Although the in-plane $2\times2$ CDW is well
studied, its out-of-plane structural correlation with the Fermi surface
properties is less understood. In this work, we advance the theoretical
description of quantum oscillations and investigate the Fermi surface
properties in the three-dimensional CDW phase of CsV$_3$Sb$_5$. We derived
Fermi-energy-resolved and layer-resolved quantum orbits that agree
quantitatively with recent experiments in the fundamental frequency, cyclotron
mass, and topology. We reveal a complex Dirac nodal network that would lead to
a $\pi$ Berry phase of a quantum orbit in the spinless case. However, the phase
shift of topological quantum orbits is contributed by the orbital moment and
Zeeman effect besides the Berry phase in the presence of spin-orbital coupling
(SOC). Therefore, we can observe topological quantum orbits with a $\pi$ phase
shift in otherwise trivial orbits without SOC, contrary to common perception.
Our work reveals the rich topological nature of kagome materials and paves a
path to resolve different topological origins of quantum orbits.",2303.04924v1
2012-08-14,Unpaired Floquet Majorana fermions without magnetic fields,"Quantum wires subject to the combined action of spin-orbit and Zeeman
coupling in the presence of \emph{s}-wave pairing potentials (superconducting
proximity effect in semiconductors or superfluidity in cold atoms) are one of
the most promising systems for the developing of topological phases hosting
Majorana fermions. The breaking of time-reversal symmetry is essential for the
appearance of unpaired Majorana fermions. By implementing a
\emph{time-dependent} spin rotation, we show that the standard magnetostatic
model maps into a \emph{non-magnetic} one where the breaking of time-reversal
symmetry is guaranteed by a periodical change of the spin-orbit coupling axis
as a function of time. This suggests the possibility of developing the
topological superconducting state of matter driven by external forces in the
absence of magnetic fields and magnetic elements. From a practical viewpoint,
the scheme avoids the disadvantages of conjugating magnetism and
superconductivity, even though the need of a high-frequency driving of
spin-orbit coupling may represent a technological challenge. We describe the
basic properties of this Floquet system by showing that finite samples host
unpaired Majorana fermions at their edges despite the fact that the bulk
Floquet quasienergies are gapless and that the Hamiltonian at each instant of
time preserves time-reversal symmetry. Remarkably, we identify the mean energy
of the Floquet states as a topological indicator. We additionally show that the
localized Floquet Majorana fermions are robust under local perturbations. Our
results are supported by complementary numerical Floquet simulations.",1208.2742v4
2015-01-28,Very large magnetoresistance in Fe$_{0.28}$TaS$_{2}$ single crystals,"Magnetic moments intercalated into layered transition metal dichalcogenides
are an excellent system for investigating the rich physics associated with
magnetic ordering in a strongly anisotropic, strong spin-orbit coupling
environment. We examine electronic transport and magnetization in
Fe$_{0.28}$TaS$_{2}$, a highly anisotropic ferromagnet with a Curie temperature
$T_{\mathrm{C}} \sim 68.8~$K. We find anomalous Hall data confirming a
dominance of spin-orbit coupling in the magnetotransport properties of this
material, and a remarkably large field-perpendicular-to-plane MR exceeding 60%
at 2 K, much larger than the typical MR for bulk metals, and comparable to
state-of-the-art GMR in thin film heterostructures, and smaller only than CMR
in Mn perovskites or high mobility semiconductors. Even within the
Fe$_x$TaS$_2$ series, for the current $x$ = 0.28 single crystals the MR is
nearly $100\times$ higher than that found previously in the commensurate
compound Fe$_{0.25}$TaS$_{2}$. After considering alternatives, we argue that
the large MR arises from spin disorder scattering in the strong spin-orbit
coupling environment, and suggest that this can be a design principle for
materials with large MR.",1501.07295v1
2015-05-25,Quantum Dynamical Phase Transition in a Spin-Orbit Coupled Bose Condensate,"Spin-orbit coupled bosons can exhibit rich equilibrium phases at low
temperature and in the presence of particle-particle interactions. In the case
with a 1D synthetic spin-orbit interaction, it has been observed that the
ground state of a Bose gas can be a normal phase, stripe phase, or magnetized
phase in different experimentally controllable parameter regimes. The
magnetized states are doubly degenerate and consist of a many-particle
two-state system. In this work, we investigate the nonequilibrium quantum
dynamics by switching on an external perturbation to induce resonant couplings
between the magnetized phases, and predict the novel quantum spin dynamics
which cannot be obtained in the single-particle systems. In particular, due to
particle-particle interactions, the transition of the Bose condensate from one
magnetized phase to the other is forbidden when the strength of external
perturbation is less than a critical value, and a full transition can occur
only when the perturbation exceeds such critical strength. This phenomenon
manifests itself a quantum dynamical phase transition, with the critical point
behavior being exactly solvable. From the numerical simulations and exact
analytic studies we show that the predicted many-body effects can be well
observed with the current experiments.",1505.06687v1
2015-09-28,Influence of Rashba spin-orbit coupling on the Kondo effect,"An Anderson model for a magnetic impurity in a two-dimensional electron gas
with bulk Rashba spin-orbit interaction is solved using the numerical
renormalization group under two different experimental scenarios. For a fixed
Fermi energy, the Kondo temperature T_K varies weakly with Rashba coupling
\alpha, as reported previously. If instead the band filling is low and held
constant, increasing \alpha can drive the system into a helical regime with
exponential enhancement of T_K. Under either scenario, thermodynamic properties
at low temperatures T exhibit the same dependences on T/T_K as are found for
\alpha = 0. Unlike the conventional Kondo effect, however, the impurity
exhibits static spin correlations with conduction electrons of nonzero orbital
angular momentum about the impurity site. We also consider a magnetic field
that Zeeman splits the conduction band but not the impurity level, an effective
picture that arises under a proposed route to access the helical regime in a
driven system. The impurity contribution to the system's ground-state angular
momentum is found to be a universal function of the ratio of the Zeeman energy
to a temperature scale that is not T_K (as would be the case in a magnetic
field that couples directly to the impurity spin), but rather is proportional
to T_K divided by the impurity hybridization width. This universal scaling is
explained via a perturbative treatment of field-induced changes in the
electronic density of states.",1509.08433v2
2016-04-01,"On magnetic monopoles, the anomalous g-factor of the electron and the spin-orbit coupling in the Dirac theory","We discuss the algebra and the interpretation of the anomalous Zeeman effect
and the spin-orbit coupling within the Dirac theory. Whereas the algebra for
the anomalous Zeeman effect is impeccable and therefore in excellent agreement
with experiment, the physical interpretation of that algebra uses images that
are based on macroscopic intuition but do not correspond to the meaning of this
algebra. The interpretation violates the Lorentz symmetry. We give an
alternative intuitive description of the meaning of this effect, which respects
the symmetry and is exact. It can be summarized by stating that a magnetic
field makes any charged particle spin. We show also that the traditional
discussion about magnetic monopoles confuses two issues, viz. the symmetry of
the Maxwell equations and the quantization of charge. These two issues define
each a different concept of magnetic monopole. They cannot be merged together
into a unique all-encompassing issue. We also generalize the minimal
substitution for a charged particle, and provide some intuition for the
magnetic vector potential. We finally explore the algebra of the spin-orbit
coupling, which turns out to be badly wrong. The traditional theory that is
claimed to reproduce the Thomas half is based on a number of errors. An
error-free application of the Dirac theory cannot account for the Thomas
precession, because it only accounts for the instantaneous local boosts, not
for the rotational component of the Lorentz transformation. This runs contrary
to established beliefs, but Thomas precession can be understood in terms of the
Berry phase on a path through the velocity space of the Lorentz group manifold.
These results clearly reveal the limitations of the prevailing working
philosophy to ""shut up and calculate"".",1604.05160v1
2016-09-18,Correlation and transport phenomena in topological nodal-loop semimetals,"We study the unique physical properties of topological nodal-loop semimetals
protected by the coexistence of time-reversal and inversion symmetries with
negligible spin-orbit coupling. We argue that strong correlation effects occur
at the surface of such systems for relatively small Hubbard interaction $U$,
due to the narrow bandwidth of the ""drumhead"" surface states. In the
Hartree-Fock approximation, at small $U$ we obtain a surface ferromagnetic
phase through a continuous quantum phase transition characterized by the
surface-mode divergence of the spin susceptibility, while the bulk states
remain very robust against local interactions and remain non-ordered. At
slightly increased interaction strength, the system quickly changes from a
surface ferromagnetic phase to a surface charge-ordered phase through a
first-order transition. When Rashba-type spin-orbit coupling is applied to the
surface states, a canted ferromagnetic phase occurs at the surface for
intermediate values of $U$. The quantum critical behavior of the surface
ferromagnetic transition is nontrivial in the sense that the surface spin order
parameter couple to Fermi-surface excitations from both surface and bulk
states. This leads to unconventional Landau damping and consequently a na\""ive
dynamical critical exponent $z\!\approx\!1$ when the Fermi level is close to
the bulk nodal energy. We also show that, already without interactions, quantum
oscillations arise due to bulk states, despite the absence of a Fermi surface
when the chemical potential is tuned to the energy of the nodal loop. The bulk
magnetic susceptibility diverges logarithmically whenever the nodal loop
exactly overlaps with a quantized magnetic orbit in the bulk Brillouin zone.
These correlation and transport phenomena are unique signatures of nodal loop
states.",1609.05529v1
2020-07-03,Enhanced transport of spin-orbit coupled Bose gases in disordered potentials,"Anderson localization is a single particle localization phenomena in
disordered media that is accompanied by an absence of diffusion. Spin-orbit
coupling (SOC) describes an interaction between a particle's spin and its
momentum that directly affects its energy dispersion, for example creating
dispersion relations with gaps and multiple local minima. We show theoretically
that combining one-dimensional spin-orbit coupling with a transverse Zeeman
field suppresses the effects of disorder, thereby increasing the localization
length and conductivity. This increase results from a suppression of back
scattering between states in the gap of the SOC dispersion relation. Here, we
focus specifically on the interplay of disorder from an optical speckle
potential and SOC generated by two-photon Raman processes in quasi-1D
Bose-Einstein condensates. We first describe back-scattering using a Fermi's
golden rule approach, and then numerically confirm this picture by solving the
time-dependent 1D Gross Pitaevskii equation for a weakly interacting
Bose-Einstein condensate with SOC and disorder. We find that on the 10's of
millisecond time scale of typical cold atom experiments moving in harmonic
traps, initial states with momentum in the zero-momentum SOC gap evolve with
negligible back-scattering, while without SOC these same states rapidly
localize.",2007.01479v1
2019-01-21,$η$-pairing in correlated fermion models with spin-orbit coupling,"We generalize the $\eta$-pairing theory in Hubbard models to the ones with
spin-orbit coupling (SOC) and obtain the conditions under which the
$\eta$-pairing operator is an eigenoperator of the Hamiltonian. The $\eta$
pairing thus reveals an exact $SU(2)$ pseudospin symmetry in our spin-orbit
coupled Hubbard model, even though the $SU(2)$ spin symmetry is explicitly
broken by the SOC. In particular, these exact results can be applied to a
variety of Hubbard models with SOC on either bipartite or non-bipartite
lattices, whose noninteracting limit can be a Dirac semimetal, a Weyl
semimetal, a nodal-line semimetal, and a Chern insulator. The $\eta$ pairing
conditions also impose constraints on the band topology of these systems. We
then construct and focus on an interacting Dirac-semimetal model, which
exhibits an exact pseudospin symmetry with fine-tuned parameters. The stability
regions for the exact $\eta$-pairing ground states (with momentum $\bm{\pi}$ or
$\bm{0}$) and the exact charge-density-wave ground states are established.
Between these distinct symmetry-breaking phases, there exists an exactly
solvable multicritical line. In the end, we discuss possible experimental
realizations of our results.",1901.06914v4
2019-03-12,Spin-orbit coupled polariton condensates in a radially-periodic potential: Multiring vortices and rotating solitons,"We address evolution of a spinor polariton condensate in radially periodic
potentials. Such potentials allow for the observation of novel nonlinear
excitations and support a variety of dynamically stable soliton states never
demonstrated before in polariton condensates, including ring-like solitons with
density peaks located in different radial minima of the potential and extended
dynamically stable multiring patterns. Among the advantages of the system is
that azimuthal modulational instabilities are suppressed due to dominating
repulsive interactions between polaritons with the same spin, thereby allowing
for the stabilization of radially-symmetric states. The representative feature
of this system is that spin-orbit coupling between different spinor components
requires them to carry different topological charges. Radially-symmetric states
carrying different combinations of topological charges are discussed. Radially
symmetric potentials also support stable rotating multipeaked solitons, whose
properties unexpectedly depend not only on the magnitude of the rotation
velocity, but also on its sign, i.e., on the rotation direction. The latter
property is a consequence of spin-orbit coupling which breaks the equivalence
between clockwise and counterclockwise rotations. The multiring structures are
shown to be robust against unavoidable losses and are therefore amenable to
observations with the presently available experimental techniques.",1903.04885v1
2021-04-27,"Mott transition, magnetic and orbital orders in the ground state of the two-band Hubbard model using variational slave-spin mean field formalism","We study the ground state of the Hubbard model on a square lattice with two
degenerate orbitals per site and at integer fillings as a function of onsite
Hubbard repulsion $U$ and Hund's intra-atomic exchange coupling $J$. We use a
variational slave-spin mean field (VSSMF) method which allows symmetry broken
states to be studied within the computationally less intensive slave-spin mean
field formalism, thus making the method more powerful to study strongly
correlated electron physics. The results show that at half-filling, the ground
state at smaller $U$ is a Slater antiferromagnet (AF) with substantial local
charge fluctuations. As $U$ is increased, the AF state develops a Heisenberg
behavior, finally undergoing a first order transition to a Mott insulating AF
state at a critical interaction $U_c$ which is of the order of the bandwidth.
Introducing the Hund's coupling $J$ correlates the system more and reduces
$U_c$ drastically. At quarter-filling with one electron per site, the ground
state at smaller $U$ is paramagnetic metallic. At finite Hund's coupling $J$,
as interaction is increased above a lower critical value $U_{c1}$, it goes to a
fully spin polarized ferromagnetic state coexisting with an antiferro-orbital
order. The system eventually becomes Mott insulating at a higher critical value
$U_{c2}$. The results as a function of $U$ and $J$ are thoroughly discussed.",2104.13027v1
2015-08-20,Metal-Insulator Transitions and non-Fermi Liquid Behaviors in 5d Perovskite Iridates,"Transition metal oxides, in particular, 3d or 4d perovskites have provided
diverse emergent physics that originates from the coupling of various degrees
of freedom such as spin, lattice, charge, orbital, and also disorder. 5d
perovskites form a distinct class because they have strong spin-orbit coupling
that introduces to the system an additional energy scale that is comparable to
bandwidth and Coulomb correlation. Consequent new physics includes novel Jeff =
1/2 Mott insulators, metal-insulator transitions, spin liquids, and topological
insulators. After highlighting some of the phenomena appearing in
Ruddlesden-Popper iridate series Srn+1IrnO3n+1, we focus on the transport
properties of perovskite SrIrO3. Using epitaxial thin films on various
substrates, we demonstrate that metal-insulator transitions can be induced in
perovskite SrIrO3 by reducing its thickness or by imposing compressive strain.
The metal-insulator transition driven by thickness reduction is due to
disorder, but the metal-insulator transition driven by compressive strain is
accompanied by peculiar non-Fermi liquid behaviors, possibly due to the
delicate interplay between correlation, disorder, and spin-orbit coupling. We
examine various theoretical frameworks to understand the non-Fermi liquid
physics and metal-insulator transition that occurs in SrIrO3 and offer the
Mott-Anderson-Griffiths scenario as a possible solution.",1508.04929v2
2021-10-25,Persistent large anisotropic magnetoresistance and insulator to metal transition in spin-orbit coupled antiferromagnets Sr2(Ir1-xGax)O4,"Antiferromagnetic (AFM) spintronics, where magneto-transport is governed by
an antiferromagnet instead of a ferromagnet, opens fascinating new perspectives
for both fundamental research and device technology, owing to their intrinsic
appealing properties like rigidness to magnetic field, absence of stray field,
and ultrafast spin dynamics. One of the urgent challenges, hindering the
realization of the full potential of AFM spintronics, has been the performance
gap between AFM metals and insulators. Here, we demonstrate the insulator-metal
transition and persistently large anisotropic magnetoresistance (AMR) in single
crystals Sr2(Ir1-xGax)O4 (0<x<0.09) which host the same basal-plane AFM lattice
with strong spin-orbit coupling. The non-doped Sr2IrO4 shows the insulating
transport with the AMR as big as ~16.8% at 50 K. The Ga substitution of Ir
allows a gradual reduction of electrical resistivity, and a clear
insulator-to-metal transition is identified in doped samples with x above 0.05,
while the AMR can still have ~1%, sizable in comparison with those in AFM
metals reported so far. Our experiments reveal that all the samples have the
similar fourfold AMR symmetry, which can be well understood in the scenario of
magnetocrystalline anisotropy. It is suggested that the spin-orbit coupled
antiferromagnets Sr2(Ir1-xGax)O4 are promising candidate materials for AFM
spintronics, providing a rare opportunity to integrate the superior spintronic
functionalities of AFM metals and insulators.",2110.12852v1
2022-04-13,Multiple higher-order topological phases with even and odd pairs of zero-energy corner modes in a $C_3$ symmetry broken model,"The higher-order corner modes for quantum anomalous Hall insulators in $C_3$
symmetry broken honeycomb lattice have been engineered recently. Here we
consider an extended Haldane model in presence of inversion symmetry breaking
sub-lattice mass, time-reversal symmetry breaking Zeeman field and spin-orbit
coupling interaction where we find that only the quantum spin Hall insulator
can host the second-order dipolar phase while the remaining two first-order
topological phases do not morph into the latter. Remarkably, four-fold
degeneracy of zero-energy dipolar states can be reduced to two-fold under the
application (withdrawn) of sub-lattice mass (Zeeman field) term when the
spin-orbit coupling is already present. On the other hand, the sub-lattice mass
and Zeeman field terms compete with each other to pin down the two mid-gap
states at zero-energy in the absence or presence of spin-orbit coupling.
Interestingly, the bulk-polarization can topologically characterize the dipolar
phase irrespective of the energy of the mid-gap states as long as inversion
symmetry is preserved. The effective gap criterion can qualitatively mimic the
extent of SOT phase originated by the interplay between finite Zeeman exchange
field, sub-lattice mass, and SOC interaction.",2204.06641v2
2023-03-01,Ising Superconductivity and Nematicity in Bernal Bilayer Graphene with Strong Spin Orbit Coupling,"Superconductivity is a ubiquitous feature of graphite allotropes, having been
observed in Bernal bilayers, rhombohedral trilayers, and a wide variety of
angle-misaligned multilayers. Despite significant differences in the electronic
structure across these systems, supporting the graphite layer on a WSe$_2$
substrate has been consistently observed to expand the range of
superconductivity in carrier density and temperature. Here, we report the
observation of two distinct superconducting states (denoted SC$_1$ and SC$_2$)
in Bernal bilayer graphene with strong proximity-induced Ising spin-orbit
coupling. Quantum oscillations show that while the normal state of SC$_1$ is
consistent with the single-particle band structure, SC$_2$ emerges from a
nematic normal state with broken rotational symmetry. Both superconductors are
robust to in-plane magnetic fields, violating the paramagnetic limit as
expected for spin-valley locked Ising superconductors. Our results show that
the enhancement of superconductivity in WSe$_2$ supported graphite allotropes
can be directly linked to Ising spin orbit coupling, which favors
valley-balanced ground states with time-reversal symmetric Fermi surfaces
friendly to superconducting pairing.",2303.00742v1
2023-08-06,The Einstein-de Haas Effect in an $\textrm{Fe}_{15}$ Cluster,"Classical models of spin-lattice coupling are at present unable to accurately
reproduce results for numerous properties of ferromagnetic materials, such as
heat transport coefficients or the sudden collapse of the magnetic moment in
hcp-Fe under pressure. This inability has been attributed to the absence of a
proper treatment of effects that are inherently quantum mechanical in nature,
notably spin-orbit coupling. This paper introduces a time-dependent,
non-collinear tight binding model, complete with spin-orbit coupling and vector
Stoner exchange terms, that is capable of simulating the Einstein-de Haas
effect in a ferromagnetic $\textrm{Fe}_{15}$ cluster. The tight binding model
is used to investigate the adiabaticity timescales that determine the response
of the orbital and spin angular momenta to a rotating, externally applied $B$
field, and we show that the qualitative behaviours of our simulations can be
extrapolated to realistic timescales by use of the adiabatic theorem. An
analysis of the trends in the torque contributions with respect to the field
strength demonstrates that SOC is necessary to observe a transfer of angular
momentum from the electrons to the nuclei at experimentally realistic $B$
fields. The simulations presented in this paper demonstrate the Einstein-de
Haas effect from first principles using a Fe cluster.",2308.03130v2
2020-01-29,Single Atom Qubits: Acceptors,"Acceptor dopant atoms in silicon have recently been identified as compelling
candidates for spin-based quantum technologies. Interest in acceptor qubits
ultimately derives from the properties of acceptor bound holes, where
spin-orbit coupling quantizes total angular momentum $J=3/2$ rather than spin,
endowing them with quadrupolar couplings to electric and elastic fields. This
property of single-atom acceptor qubits makes them amenable to electric control
and coupling over long distances using phonon, capacitive, or microwave photon
mediated interactions. Accepted as a contribution within a roadmap for quantum
technologies, this section reviews progress on single-acceptor devices,
observation of ultra-long coherence times of acceptors in isotope purified
silicon, and comments on future challenges in single qubit measurement, long
distance coupling, and scalable acceptor-spin-based technologies.",2001.11119v1
2018-03-05,Formation of a spin texture in a quantum gas coupled to a cavity,"We observe cavity mediated spin-dependent interactions in an off-resonantly
driven multi-level atomic Bose-Einstein condensate that is strongly coupled to
an optical cavity. Applying a driving field with adjustable polarization, we
identify the roles of the scalar and the vectorial components of the atomic
polarizability tensor for single and multi-component condensates. Beyond a
critical strength of the vectorial coupling, we observe a spin texture in a
condensate of two internal states, providing perspectives for global dynamic
gauge fields and self-consistently spin-orbit coupled gases.",1803.01803v4
2010-04-14,Tensor coupling effects on spin symmetry in anti-Lambda spectrum of hypernuclei,"The effects of $\bar\Lambda\bar\Lambda\omega$-tensor coupling on the spin
symmetry of $\bar{\Lambda}$ spectra in $\bar{\Lambda}$-nucleus systems have
been studied with the relativistic mean-field theory. Taking
$^{12}$C+$\bar{\Lambda}$ as an example, it is found that the tensor coupling
enlarges the spin-orbit splittings of $\bar\Lambda$ by an order of magnitude
although its effects on the wave functions of $\bar{\Lambda}$ are negligible.
Similar conclusions has been observed in $\bar{\Lambda}$-nucleus of different
mass regions, including $^{16}$O+$\bar{\Lambda}$, $^{40}$Ca+$\bar{\Lambda}$ and
$^{208}$Pb+$\bar{\Lambda}$. It indicates that the spin symmetry in
anti-lambda-nucleus systems is still good irrespective of the tensor coupling.",1004.2313v1
2013-06-12,Magnon self energy in the correlated ferromagnetic Kondo lattice model: spin-charge coupling effects on magnon excitations in manganites,"Magnon self energy due to spin-charge coupling is calculated for the
correlated ferromagnetic Kondo lattice model using a diagrammatic expansion
scheme. Systematically incorporating correlation effects in the form of
self-energy and vertex corrections, the expansion scheme explicitly preserves
the continuous spin rotation symmetry and hence the Goldstone mode. Due to a
near cancellation of the correlation-induced quantum correction terms at
intermediate coupling and optimal band filling relevant for ferromagnetic
manganites, the renormalized magnon energies for the correlated FKLM are nearly
independent of correlation term. Even at higher band fillings, despite
exhibiting overall non-Heisenberg behavior, magnon dispersion in the \Gamma-X
direction retains nearly Heisenberg form. Therefore, the experimentally
observed doping dependent zone-boundary magnon softening must be ascribed to
spin-orbital coupling effects.",1306.2769v1
2015-12-09,Strong Cavity-Pseudospin Coupling in Monolayer Transition Metal Dichalcogenides: Spontaneous Spin-Oscillations and Magnetometry,"Strong coupling between the electronic states of monolayer transition metal
dichalcogenides (TMDC) such as MoS$_2$, MoSe$_2$, WS$_2$, or WSe$_2$, and a
two-dimensional (2D) photonic cavity gives rise to several exotic effects. The
Dirac type Hamiltonian for a 2D gapped semiconductor with large spin-orbit
coupling facilitates pure Jaynes-Cummings type coupling in the presence of a
single mode electric field. The presence of an additional circularly polarized
beam of light gives rise to valley and spin dependent cavity-QED properties.
The cavity causes the TMDC monolayer to act as an on-chip coherent light source
and a spontaneous spin-oscillator. In addition, a TMDC monolayer in a cavity is
a sensitive magnetic field sensor for an in-plane magnetic field.",1512.02712v1
2019-04-28,Chiral light-matter interactions using spin-valley states in transition metal dichalcogenides,"Chiral light-matter interactions can enable polarization to control the
direction of light emission in a photonic device. Most realizations of chiral
light-matter interactions require external magnetic fields to break
time-reversal symmetry of the emitter. One way to eliminate this requirement is
to utilize strong spin-orbit coupling present in transition metal
dichalcogenides that exhibit a valley dependent polarized emission. Such
interactions were previously reported using plasmonic waveguides, but these
structures exhibit short propagation lengths due to loss. Chiral dielectric
structures exhibit much lower loss levels and could therefore solve this
problem. We demonstrate chiral light-matter interactions using spin-valley
states of transition metal dichalcogenide monolayers coupled to a dielectric
waveguide. We use a photonic crystal glide plane waveguide that exhibits chiral
modes with high field intensity, coupled to monolayer WSe2. We show that the
circularly polarized emission of the monolayer preferentially couples to one
direction of the waveguide, with a directionality as high as 0.35, limited by
the polarization purity of the bare monolayer emission. This system enables
on-chip directional control of light and could provide new ways to control spin
and valley degrees of freedom in a scalable photonic platform.",1904.12349v1
2020-03-26,Experimental realization of spin-tensor momentum coupling in ultracold Fermi gases,"We experimentally realize the spin-tensor momentum coupling (STMC) using the
three ground Zeeman states coupled by three Raman laser beams in ultracold
atomic system of $^{40}$K Fermi atoms. This new type of STMC consists of two
bright-state bands as a regular spin-orbit coupled spin-1/2 system and one
dark-state middle band. Using radio-frequency spin-injection spectroscopy, we
investigate the energy band of STMC. It is demonstrated that the middle state
is a dark state in the STMC system. The realized energy band of STMC may open
the door for further exploring exotic quantum matters.",2003.11829v1
2022-03-08,Coupling between improper ferroelectricity and ferrimagnetism in hexagonal ferrites,"Antisymmetric Dzyaloshinskii-Moriya (DM) interactions generating from the
spin-orbit coupling induce various fascinating properties, like magnetoelectric
(ME) effect, weak ferromagnetism and non-trivial topological spin textures like
skyrmions, in real materials. Compared to their symmetric isotropic exchange
counterpart, these interactions are generally of a weaker order of strength,
creating modest twisting in the spin structure which results in weak
ferromagntism or weak linear ME effect. Our proposed two-sublattice model, in
contrast, predicts a hitherto unobserved, charge ordered non-collinear
ferrimagnetic behavior with a considerably high magnetization $\textbf{M}$
coexisting with a ferroelectric (FE) order with an electric polarization
$\textbf{P}$ and a strong cross coupling between them which is primarily driven
by the inter-sublattice DM interactions. The key to realize these effects is
the coupling between these microscopic interactions and the FE primary order
parameter. We predict microscopic mechanisms to achieve electric field
$\textbf{E}$ induced spin-reorientation transitions and 180$^{\circ}$ switching
of the direction of $\textbf{M}$. This model was realized in the hexagonal
phase of LuFeO$_3$ doped with electrons. This system shows $P \sim$ 15
$\mu$C/cm$^2$, $M \sim$ 1.3 $\mu_B$/Fe and magnetic transition near room
temperature ($\sim$ 290 K). Our theoretical results are expected to stimulate
further quest for energy-efficient routes to control magnetism for spintronics
applications.",2203.03841v1
2018-05-29,Emergence of Weyl metals driven by doped magnetic impurities in spin-orbit coupled semiconductors,"Constructing an effective field theory in terms of doped magnetic impurities
(described by an O(3) vector model with a random mass term), itinerant
electrons of spin-orbit coupled semiconductors (given by a Dirac theory with a
relatively large mass term), and effective interactions between doped magnetic
ions and itinerant electrons (assumed by an effective Zeeman coupling term), we
perform the perturbative renormalization group analysis in the one-loop level
based on the dimensional regularization technique. As a result, we find that
the mass renormalization in dynamics of itinerant electrons acquires negative
feedback effects due to quantum fluctuations involved with the Zeeman coupling
term, in contrast with that of the conventional problem of quantum
electrodynamics, where such interaction effects enhance the fermion mass more
rapidly. Recalling that the applied magnetic field decreases the band gap in
the presence of spin-orbit coupling, this renormalization group analysis shows
that the external magnetic field overcomes the renormalized band gap, allowed
by doped magnetic impurities even without ferromagnetic ordering. In other
words, the Weyl metal physics can be controlled by doping magnetic impurities
into spin-orbit coupled semiconductors, even if the external magnetic field
alone cannot realize the Weyl metal phase due to relatively large band gaps of
semiconductors. Furthermore, we emphasize that quasiparticles do not exist in
this emergent disordered Weyl metal phase due to correlations with strong
magnetic fluctuations. This non-Fermi liquid type Weyl metal state may be
regarded to be a novel metallic phase in the respect that a topologically
nontrivial band structure appears in the vicinity of quantum criticality.",1805.11209v3
2022-03-09,Quenched Λ spin-orbit splitting by relativistic Fock diagram in single-Λ hypernuclei,"We extend the relativistic Hartree-Fock (RHF) theory to study the structure
of single-$\Lambda$ hypernuclei. The density dependence is taken in both
meson-nucleon and meson-hyperon coupling strengths, and the induced
$\Lambda$-nucleon ($\Lambda N$) effective interactions are determined by
fitting $\Lambda$ separation energies to the experimental data for several
single-$\Lambda$ hypernuclei. The equilibrium of nuclear dynamics described by
the RHF model in normal atomic nuclei, namely, the balance between nuclear
attractive and repulsive interactions, is then found to be drastically changed
in single-$\Lambda$ hypernuclei, revealing a different role of Fock terms via
$\Lambda$ hyperon from the nucleon exchange. Since only one hyperon exists in a
single-$\Lambda$ hypernucleus, the overwhelmed $\Lambda N$ and $\Lambda\Lambda$
attractions via the Hartree than the $\Lambda\Lambda$ repulsion from the Fock
terms require an alternation of meson-hyperon coupling strengths in RHF to
rebalance the effective nuclear force with the strangeness degree of freedom,
leading to an improved description of $\Lambda$ Dirac mass and correspondingly
a systematically reduced $\sigma$-$\Lambda$ coupling strength
$g_{\sigma\Lambda}$ in current models as compared to those relativistic
mean-field (RMF) approaches without Fock terms. As a result, the effective
$\Lambda$ spin-orbit coupling potential in the ground state of hypernuclei is
suppressed, and these RHF models predict correspondingly a quenching effect in
$\Lambda$ spin-orbit splitting in comparison with the RMF cases. Furthermore,
the $\Lambda$ spin-orbit splitting could decrease efficiently by evolving the
hyperon-relevant couplings $g_{\sigma\Lambda}$ and $g_{\omega\Lambda}$
simultaneously, where to reconcile with the empirical value the RHF models
address a larger parameter space of meson-hyperon couplings.",2203.04581v2
2023-04-05,Scaling laws of the magnetic dynamics driven high harmonic generation in spin-orbit coupled systems,"The emergence of high order harmonics in carrier pumping from magnetic
dynamics in the presence of spin-orbit coupling has been only recently
predicted [{Phys. Rev. B \textbf{105}, L180415 (2022)}]. In this effect, the
number of the excited high harmonics is found to scale up with the spin-orbit
coupling parameter, the s-d exchange constant of the magnetic system and the
frequency of the driving dynamics. Motivated by the reproduction of the
above-mentioned effect, Nikoli\'{c} and Manjarres [arXiv:2212.06895,
arXiv:2112.14685] confirmed that there is indeed a generation of harmonics as a
result of the interplay between magnetic dynamics and spin-orbit interaction if
the exchange coupling $J$ is taken very small ($J=0.1\gamma$). However, they
claim that the ultrahigh harmonics obtained in the strong $J$ limit can only be
a result of numerical bugs. It turns out that in these works, conclusions built
from numerical simulations performed in the perturbative limit
($J/\hbar\omega\approx 10$) have been applied to criticize results obtained in
the extremely high non-linear regime ($J/\hbar\omega>10^3$). Regarding this
fact, we find it necessary to shed light on many aspects related to the physics
behind the predicted unconventional carrier pumping, in order to enlighten the
readers of the proposed effect and at the same time the authors of the
criticizing works. Here, we present numerical simulations of the scaling laws
underlying the effect. We study the low s-d exchange coupling limit,
corresponding to the regime studied in the above mentioned criticizing works.
And further explore, the high s-d coupling regime where the extremely nonlinear
emission is expected. Furthermore, we provide more insights on the effect and
demonstrate its robustness and reproducibility in both 1D and 2D magnetic
structures.",2304.02619v2
2014-09-22,Unconventional proximity-induced superconductivity in bilayer systems,"We study the proximity-induced superconducting state in a general bilayer --
conventional $s$-wave superconductor hybrid structure. For the bilayer we
include a general parabolic dispersion, Rashba spin-orbit coupling, and finite
layer tunneling as well as the possibility to apply a bias potential and a
magnetic Zeeman field, in order to address experimentally relevant bilayer
systems, ranging from topological insulator thin films to generic double
quantum well systems. By extracting the proximity-induced anomalous Green's
function in the bilayer we show on a very rich structure for the
superconducting pairing, including different spin states and odd-frequency
pairing. Equal-spin spin-triplet $p_x\pm ip_y$-wave pairing is induced in both
layers in the presence of a finite spin-orbit coupling and opposite-spin
spin-triplet $s$-wave pairing with odd-frequency dependence appears for an
applied magnetic Zeeman field. Finite interlayer pairing is also generally
present in the bilayer. The interlayer pairing can be either even or odd in the
layer index, with a complete reciprocity between parity in frequency and in
layer index. We also find that a bilayer offers the possibility of sign
reversal of the superconducting order parameters, both between the two layers
and between multiple Fermi surfaces.",1409.6178v2
2014-10-23,Spectroscopic confirmation of linear relation between Heisenberg- and interfacial Dzyaloshinskii-Moriya-exchange in polycrystalline metal films,"Proposals for novel spin-orbitronic logic1 and memory devices2 are often
predicated on assumptions as to how materials with large spin-orbit coupling
interact with ferromagnets when in contact. Such interactions give rise to a
host of novel phenomena, such as spin-orbit torques3,4 , chiral
spin-structures5,6 and chiral spin-torques. These chiral properties are related
to the anti-symmetric exchange, also referred to as the interfacial
Dzyaloshinskii-Moriya interaction (DMI)9,10. For numerous phenomena, the
relative strengths of the symmetric Heisenberg exchange and the DMI is of great
importance. Here, we use optical spin-wave spectroscopy (Brillouin light
scattering) to directly determine the DMI vector for a series of Ni80Fe20/Pt
samples, and then compare the nearest-neighbor DMI coupling energy with the
independently measured Heisenberg exchange integral. We find that the
Ni80Fe20-thickness-dependencies of both the microscopic symmetric- and
antisymmetric-exchange are identical, consistent with the notion that the basic
mechanisms of the DMI and Heisenberg exchange essentially share the same
underlying physics, as was originally proposed by Moriya11. While of
significant fundamental importance, this result also leads us to a deeper
understanding of DMI and how it could be optimized for spin-orbitronic
applications.",1410.6243v1
2015-03-28,Mimicing the Kane-Mele type spin orbit interaction by spin-flexual phonon coupling in graphene devices,"On the efforts of enhancing the spin orbit interaction (SOI) of graphene for
seeking the dissipationless quantum spin Hall devices, unique Kane-Mele type
SOI and high mobility samples are desired. However, common external decoration
often introduces extrinsic Rashba-type SOI and simultaneous impurity
scattering. Here we show, by the EDTA-Dy molecule decorating, the Kane-Mele
type SOI is mimicked with even improved carrier mobility. It is evidenced by
the suppressed weak localization at equal carrier densities and simultaneous
Elliot-Yafet spin relaxation. The extracted spin scattering time is
monotonically dependent on the carrier elastic scattering time, where the
Elliot-Yafet plot gives the interaction strength of 3.3 meV. Improved quantum
Hall plateaus can be even seen after the external operation. This is attributed
to the spin-flexural phonon coupling induced by the enhanced graphene ripples,
as revealed by the in-plane magnetotransport measurement.",1503.08282v4
2016-07-27,Three-Dimensional Majorana Fermions in Chiral Superconductors,"Through a systematic symmetry and topology analysis we establish that
three-dimensional chiral superconductors with strong spin-orbit coupling and
odd-parity pairing generically host low-energy nodal quasiparticles that are
spin-non-degenerate and realize Majorana fermions in three dimensions. By
examining all types of chiral Cooper pairs with total angular momentum $J$
formed by Bloch electrons with angular momentum $j$ in crystals, we obtain a
comprehensive classification of gapless Majorana quasiparticles in terms of
energy-momentum relation and location on the Fermi surface. We show that the
existence of bulk Majorana fermions in the vicinity of spin-selective point
nodes is rooted in the non-unitary nature of chiral pairing in
spin-orbit-coupled superconductors. We address experimental signatures of
Majorana fermions, and find that the nuclear magnetic resonance (NMR) spin
relaxation rate is significantly suppressed for nuclear spins polarized along
the nodal direction as a consequence of the spin-selective Majorana nature of
nodal quasiparticles. Furthermore, Majorana nodes in the bulk have nontrivial
topology and imply the presence of Majorana bound states on the surface that
form arcs in momentum space. We conclude by proposing the heavy fermion
superconductor PrOs$_4$Sb$_{12}$ and related materials as promising candidates
for non-unitary chiral superconductors hosting three-dimensional Majorana
fermions.",1607.08243v2
2016-08-03,Real space mean-field theory of a spin-1 Bose gas in synthetic dimensions,"The internal degrees of freedom provided by ultracold atoms give a route for
realizing higher dimensional physics in systems with limited spatial
dimensions. Non-spatial degrees of freedom in these systems are dubbed
""synthetic dimensions"". This connection is useful from an experimental
standpoint but complicated by the fact that interactions alter the condensate
ground state. Here we use the Gross-Pitaevskii equation to study ground state
properties of a spin-1 Bose gas under the combined influence of an optical
lattice, spin-orbit coupling, and interactions at the mean field level. The
associated phases depend on the sign of the spin-dependent interaction
parameter and the strength of the optical lattice potential. We find ""charge""
and spin density wave phases which are directly related to helical spin order
in real space and affect the behavior of edge currents in the synthetic
dimension. We determine the resulting phase diagram as a function of the
spin-orbit coupling and spin-dependent interaction strength, considering both
attractive (ferromagnetic) and repulsive (polar) spin-dependent interactions.
Our results are applicable to current and future experiments, specifically with
$^{87}$Rb, $^{7}$Li, $^{41}$K, and $^{23}$Na.",1608.01346v2
2019-09-17,Single spin resonance driven by electric modulation of the g factor anisotropy,"We address the problem of electronic and nuclear spin resonance of an
individual atom on a surface driven by a scanning tunnelling microscope.
Several mechanisms have been proposed so far, some of them based on the
modulation of exchange and crystal field associated to a piezoelectric
displacement of the adatom driven by the RF tip electric field. Here we
consider a new mechanism, where the piezoelectric displacement modulates the g
factor anisotropy, leading both to electronic and nuclear spin flip
transitions. We discuss thoroughly the cases of Ti-H (S = 1/2) and Fe (S = 2)
on MgO, relevant for recent experiments. We model the system using two
approaches. First, an analytical model that includes crystal field, spin orbit
coupling and hyperfine interactions. Second, we carry out density functional
based calculations. We find that the modulation of the anisotropy of the g
tensor due to the piezoelectric displacement of the atom is an additional
mechanism for STM based single spin resonance, that would be effective in S =
1/2 adatoms with large spin orbit coupling. In the case of Ti-H on MgO, we
predict a modulation spin resonance frequency driven by the DC electric field
of the tip.",1909.07942v1
2020-12-20,Chiral tunneling in single layer graphene with Rashba spin-orbit coupling: spin currents,"We study forward scattering of 2D massless Dirac electrons at Fermi energy
{\varepsilon} > 0 in single layer graphene through a 1D rectangular barrier of
height {u_0} in the presence of uniform Rashba spin-orbit coupling (of strength
{\lambda}). The role of the Klein paradox in graphene spintronics is thereby
exposed. It is shown that (1) For {\varepsilon} - 2{\lambda} < {u_0}<
{\varepsilon} + 2{\lambda} there is partial Klein tunneling, wherein the
transmission is bounded by 1 and, quite remarkably, for small {\lambda} >
{\lambda_0} {\approx} 0.1 meV, the transmission nearly vanishes when the
scattering energy equals the barrier height, {\varepsilon}={u_0}. (2) Spin
density and spin-current density are shown to be remarkably different than
these observables predicted in bulk single layer graphene. In particular, they
are sensitive to {\lambda} and {u_0}. (3) Spin current densities are space
dependent, implying the occurrence of non-zero spin torque density. Such a
system may serve as a graphene based spintronic device without the use of an
external magnetic field or magnetic materials.",2012.10971v4
2018-06-07,Dynamics and Spin-Valley Locking Effects in Monolayer Transition Metal Dichalcogenides,"Transition metal dichalcogenides have been the primary materials of interest
in the field of valleytronics for their potential in information storage, yet
the limiting factor has been achieving long valley decoherence times. We
explore the dynamics of four monolayer TMDCs (MoS$_2$, MoSe$_2$, WS$_2$,
WSe$_2$) using ab initio calculations to describe electron-electron and
electron-phonon interactions. By comparing calculations which both omit and
include relativistic effects, we isolate the impact of spin-resolved spin-orbit
coupling on transport properties. In our work, we find that spin-orbit coupling
increases carrier lifetimes at the valence band edge by an order of magnitude
due to spin-valley locking, with a proportional increase in the hole mobility
at room temperature. At temperatures of 50~K, we find intervalley scattering
times on the order of 100 ps, with a maximum value ~140 ps in WSe$_2$. Finally,
we calculate excited-carrier generation profiles which indicate that direct
transitions dominate across optical energies, even for WSe$_2$ which has an
indirect band gap. Our results highlight the intriguing interplay between spin
and valley degrees of freedom critical for valleytronic applications. Further,
our work points towards interesting quantum properties on-demand in transition
metal dichalcogenides that could be leveraged via driving spin, valley and
phonon degrees of freedom.",1806.02673v1
2019-08-18,Electron g-factor engineering for non-reciprocal spin photonics,"We study the interplay of electron and photon spin in non-reciprocal
materials. Traditionally, the primary mechanism to design non-reciprocal
photonic devices has been magnetic fields in conjunction with magnetic oxides,
such as iron garnets. In this work, we present an alternative paradigm that
allows tunability and reconfigurability of the non-reciprocity through
spintronic approaches. The proposed design uses the high-spin-orbit coupling of
a narrow-band gap semiconductor (InSb) with ferromagnetic dopants. A
combination of the intrinsic and a gate-applied electric field gives rise to a
strong external Rashba spin-orbit coupling (RSOC) in a magnetically doped InSb
film. The RSOC which is gate alterable is shown to adjust the magnetic
permeability tensor via the electron g-factor of the medium. We use electronic
band structure calculations (k$\cdot$p theory) to show the gate-adjustable RSOC
manifest itself in the non-reciprocal coefficient of photon fields via shifts
in the Kerr and Faraday rotations. In addition, we show that photon spin
properties of dipolar emitters placed in the vicinity of a non-reciprocal
electromagnetic environment is distinct from reciprocal counterparts. The
Purcell factor (F$_{p}$) of a spin-polarized emitter (right-handed circular
dipole) is significantly enhanced due to a larger g-factor while a left-handed
dipole remains essentially unaffected. Our work can lead to electron spin
controlled reconfigurable non-reciprocal photonic devices.",1908.06393v2
2016-12-01,Spin anisotropy due to spin-orbit coupling in optimally hole-doped Ba$_{0.67}$K$_{0.33}$Fe$_{2}$As$_{2}$,"We use polarized inelastic neutron scattering to study the temperature and
energy dependence of spin space anisotropies in the optimally hole-doped iron
pnictide Ba$_{0.67}$K$_{0.33}$Fe$_{2}$As$_{2}$ ($T_{{\rm c}}=38$ K). In the
superconducting state, while the high-energy part of the magnetic spectrum is
nearly isotropic, the low-energy part displays a pronouced anisotropy,
manifested by a $c$-axis polarized resonance. We also observe that the spin
anisotropy in superconducting Ba$_{0.67}$K$_{0.33}$Fe$_{2}$As$_{2}$ extends to
higher energies compared to electron-doped BaFe$_{2-x}TM_{x}$As$_{2}$ ($TM=$Co,
Ni) and isovalent-doped BaFe$_{2}$As$_{1.4}$P$_{0.6}$, suggesting a connection
between $T_{\rm c}$ and the energy scale of the spin anisotropy. In the normal
state, the low-energy spin anisotropy for optimally hole- and electron-doped
iron pnictides onset at temperatures similar to the temperatures at which the
elastoresistance deviate from Curie-Weiss behavior, pointing to a possible
connection between the two phenomena. Our results highlight the relevance of
the spin-orbit coupling to the superconductivity of the iron pnictides.",1612.00379v2
2018-10-13,Dynamics of spin-orbit-coupled cold atomic gases in a Floquet lattice with an impurity,"In this study, we have studied the quantum tunneling of a single
spin-orbit-coupled atom held in a periodically modulated optical lattice with
an impurity. At the pseudocollapse points of quasienergy bands, where the
dynamical localization takes place globally, two types of local second-order
tunneling processes appear beyond expectation between the two nearest-neighbor
sites of the impurity with the spin unchanged and with impurity site population
negligible all the time, when the impurity potential is far off-resonant with
the driving field. Though tunneling behaviors of the two types seem to be the
same, they are believed to involve two distinct mechanisms: one is related to
spin-independent process, while the other is to spin-dependent tunneling
process. The two types of second-order processes can be identified by means of
resonant tunneling with or without spin-flipping by tuning the impurity
potential to be in resonance with the driving field. In the Floquet picture,
the second-order processes are manifested as subtle and fine avoided crossings
of quasienergy spectrums near the pseudocollapse region. These results are
confirmed analytically on the basis of effective three-site model and
multiple-time-scale asymptotic perturbative method, and may be exploited for
engineering the spin-dependent quantum transport in realistic experiments.",1810.05854v1
2021-03-29,Spin-group symmetry in magnetic materials with negligible spin-orbit coupling,"Symmetry formulated by group theory plays an essential role with respect to
the laws of nature, from fundamental particles to condensed matter systems.
Here, by combining symmetry analysis and tight-binding model calculations, we
elucidate that the crystallographic symmetries of a vast number of magnetic
materials with light elements, in which the neglect of relativistic spin-orbit
coupling (SOC) is an appropriate approximation, are considerably larger than
the conventional magnetic groups. Thus, a symmetry description that involves
partially-decoupled spin and spatial rotations, dubbed as spin group, is
required. Spin group permits more symmetry operations and thus more energy
degeneracies that are disallowed by the magnetic groups. One consequence of the
spin group is the new anti-unitary symmetries that protect SOC-free Z_2
topological phases with unprecedented surface node structures. Our work not
only manifests the physical reality of materials with weak SOC, but also shed
light on the understanding of all solids with and without SOC by a unified
group theory.",2103.15723v4
2021-07-28,Robust all-electrical topological valley filtering using monolayer 2D-Xenes,"We propose a realizable device design for an all-electrical robust valley
filter that utilizes spin protected topological interface states hosted on
monolayer 2D-Xene materials with large intrinsic spin-orbit coupling. In
contrast with conventional quantum spin-Hall edge states localized around the
$X$-points, the interface states appearing at the domain wall between
topologically distinct phases are either from the $K$ or $K^{'}$ points, making
them suitable prospects for serving as valley-polarized channels. We show that
the presence of a large band-gap quantum spin Hall effect enables the spatial
separation of the spin-valley locked helical interface states with the valley
states being protected by spin conservation, leading to a robustness against
short-range non-magnetic disorder. By adopting the scattering matrix formalism
on a suitably designed device structure, valley-resolved transport in the
presence of non-magnetic short-range disorder for different 2D-Xene materials
is also analyzed in detail. Our numerical simulations confirm the role of
spin-orbit coupling in achieving an improved valley filter performance with a
perfect quantum of conductance attributed to the topologically protected
interface states. Our analysis further elaborates clearly the right choice of
material, device geometry and other factors that need to be considered while
designing an optimized valleytronic filter device.",2107.13318v2
2024-02-05,Second-order charge and spin transport in LaO/STO system in the presence of cubic Rashba spin orbit couplings,"Certain non-centrosymmetric materials with broken time-reversal symmetry may
exhibit non-reciprocal transport behavior under an applied electric field in
which the charge and spin currents contain components that are second order in
the electric field. In this study, we investigate the second-order spin
accumulation and charge and spin responses in the LaAlO$_3$/SrTiO$_3$ (LaO/STO)
system with magnetic dopants under the influence of linear and cubic Rashba
spin-orbit coupling (RSOC) terms. We explain the physical origin of the
second-order response and perform a symmetry analysis of the first and
second-order responses for different dopant magnetization directions relative
to the applied electric field. We then numerically solve the Boltzmann
transport equation by extending the approach of Schliemann and Loss [Phys. Rev.
B 68, 165311] to higher orders in the electric field. We show that the sign of
the second-order responses can be switched by varying the magnetization
direction of the magnetic dopants or relative strengths of the two cubic RSOC
terms and explain these trends by considering the Fermi surfaces of the
respective systems. These findings provide insights into the interplay of
multiple SOC effects in a LaO/STO system and how the resulting first- and
second-order charge and spin responses can be engineered by exploiting the
symmetries of the system.",2402.02652v1
2009-07-27,Hamiltonian of a spinning test-particle in curved spacetime,"Using a Legendre transformation, we compute the unconstrained Hamiltonian of
a spinning test-particle in a curved spacetime at linear order in the particle
spin. The equations of motion of this unconstrained Hamiltonian coincide with
the Mathisson-Papapetrou-Pirani equations. We then use the formalism of Dirac
brackets to derive the constrained Hamiltonian and the corresponding
phase-space algebra in the Newton-Wigner spin supplementary condition (SSC),
suitably generalized to curved spacetime, and find that the phase-space algebra
(q,p,S) is canonical at linear order in the particle spin. We provide explicit
expressions for this Hamiltonian in a spherically symmetric spacetime, both in
isotropic and spherical coordinates, and in the Kerr spacetime in
Boyer-Lindquist coordinates. Furthermore, we find that our Hamiltonian, when
expanded in Post-Newtonian (PN) orders, agrees with the Arnowitt-Deser-Misner
(ADM) canonical Hamiltonian computed in PN theory in the test-particle limit.
Notably, we recover the known spin-orbit couplings through 2.5PN order and the
spin-spin couplings of type S_Kerr S (and S_Kerr^2) through 3PN order, S_Kerr
being the spin of the Kerr spacetime. Our method allows one to compute the PN
Hamiltonian at any order, in the test-particle limit and at linear order in the
particle spin. As an application we compute it at 3.5PN order.",0907.4745v3
2019-08-02,Tunable pure spin supercurrents and the demonstration of a superconducting spin-wave device,"Recent ferromagnetic resonance experiments and theory of Pt/Nb/Ni8Fe2
proximity-coupled structures strongly suggest that spin-orbit coupling (SOC) in
Pt in conjunction with a magnetic exchange field in Ni8Fe2 are the essential
ingredients to generate a pure spin supercurrent channel in Nb. Here, by
substituting Pt for a perpendicularly magnetized Pt/Co/Pt spin-sink, we are
able to demonstrate the role of SOC, and show that pure spin supercurrent
pumping efficiency across Nb is tunable by controlling the magnetization
direction of Co. By inserting a Cu spacer with weak SOC between Nb and
Pt/(Co/Pt) spin-sink, we also prove that Rashba type SOC is key for forming and
transmitting pure spin supercurrents across Nb. Finally, by engineering these
properties within a single multilayer structure, we demonstrate a prototype
superconducting spin-wave (SW) device in which lateral SW propagation is
gateable via the opening or closing of a vertical pure spin supercurrent
channel in Nb.",1908.00873v3
2021-02-09,Spin drift-diffusion for two-subband quantum wells,"Controlling the spin dynamics and spin lifetimes is one of the main
challenges in spintronics. To this end, the study of the spin diffusion in
two-dimensional electron gases (2DEGs) shows that when the Rashba and
Dresselhaus spin-orbit couplings (SOC) are balanced, a persistent spin helix
regime arises. There, a striped spin pattern shows a long lifetime, limited
only by the cubic Dresselhaus SOC, and its dynamics can be controlled by
in-plane drift fields. Here, we derive a spin diffusion equation for
non-degenerate two-subbands 2DEGs. We show that the intersubband scattering
rate, which is defined by the overlap of the subband densities, enters as a new
nob to control the spin dynamics, and can be controlled by electric fields,
being maximum for symmetric quantum wells. We find that for large intersubband
couplings the dynamics follow an effective diffusion matrix given by
approximately half of the subband-averaged matrices. This extra 1/2 factor
arises from Matthiessen's rule summing over the intra- and intersubband
scattering rates, and leads to a reduced diffusion constant and larger spin
lifetimes. We illustrate our findings with numerical solutions of the diffusion
equation with parameters extracted from realistic Schr\""odinger-Poisson
calculations.",2102.04831v2
2014-02-13,A new spin-anisotropic harmonic honeycomb iridate,"The physics of Mott insulators underlies diverse phenomena ranging from high
temperature superconductivity to exotic magnetism. Although both the electron
spin and the structure of the local orbitals play a key role in this physics,
in most systems these are connected only indirectly --- via the Pauli exclusion
principle and the Coulomb interaction. Iridium-based oxides (iridates) open a
further dimension to this problem by introducing strong spin-orbit
interactions, such that the Mott physics has a strong orbital character. In the
layered honeycomb iridates this is thought to generate highly spin-anisotropic
interactions, coupling the spin orientation to a given spatial direction of
exchange and leading to strongly frustrated magnetism. The potential for new
physics emerging from such interactions has driven much scientific excitement,
most recently in the search for a new quantum spin liquid, first discussed by
Kitaev \cite{kitaev_anyons_2006}. Here we report a new iridate structure that
has the same local connectivity as the layered honeycomb, but in a
three-dimensional framework. The temperature dependence of the magnetic
susceptibility exhibits a striking reordering of the magnetic anisotropy,
giving evidence for highly spin-anisotropic exchange interactions. Furthermore,
the basic structural units of this material suggest the possibility of a new
family of structures, the `harmonic honeycomb' iridates. This compound thus
provides a unique and exciting glimpse into the physics of a new class of
strongly spin-orbit coupled Mott insulators.",1402.3254v2
2012-12-01,On the half-metallicity of Co2FeSi Heusler alloy: an experimental and ab initio study,"Co2FeSi, a Heusler alloy with the highest magnetic moment per unit cell and
the highest Curie temperature, has largely been described theoretically as a
half-metal. This conclusion, however, disagrees with Point Contact Andreev
Reflection (PCAR) spectroscopy measurements, which give much lower values of
spin polarization, P. Here, we present the spin polarization measurements of
Co2FeSi by the PCAR technique, along with a thorough computational exploration,
within the DFT and a GGA+U approach, of the Coulomb exchange U-parameters for
Co and Fe atoms, taking into account spin-orbit coupling. We find that the
orbital contribution (mo) to the total magnetic moment (mT) is significant,
since it is at least 3 times greater than the experimental uncertainty of mT.
Account of mo radically affects the acceptable values of U. Specifically, we
find no values of U that would simultaneously satisfy the experimental values
of the magnetic moment and result in the half-metallicity of Co2FeSi. On the
other hand, the ranges of U that we report as acceptable are compatible with
spin polarization measurements (ours and the ones found in the literature),
which all are within approximately 40-60% range. Thus, based on reconciling
experimental and computational results, we conclude that: a) spin-orbit
coupling cannot be neglected in calculating Co2FeSi magnetic properties, and b)
Co2FeSi Heusler alloy is not half-metallic. We believe that our approach can be
applied to other Heusler alloys such as Co2FeAl.",1212.0168v1
2014-10-12,"Spin-orbit coupling, strong correlation, and insulator-metal transitions: the J$_{\rm eff}$ =3\2 ferromagnetic Mott insulator Ba$_{2}$NaOsO$_{6}$","The double perovskite Ba$_{2}$NaOsO$_{6}$ (BNOO), an exotic example of a very
high oxidation state (heptavalent) osmium $d^1$ compound and also uncommon by
being a ferromagnetic Mott insulator without Jahn-Teller (JT) distortion, is
modeled using the density functional theory (DFT) hybrid functional based exact
exchange for correlated electrons (oeeHyb) method and including spin-orbit
coupling (SOC). The experimentally observed narrow gap ferromagnetic insulating
ground state is obtained, with easy axis along [110] in accord with experiment,
providing support that this approach provides a realistic method for studying
this system. The predicted spin density for [110] spin orientation is nearly
cubic (unlike for other directions), providing an explanation for the absence
of JT distortion. An orbital moment of -0.4$\mu_B$ strongly compensates the
+0.5$\mu_B$ spin moment on Os, leaving a strongly compensated moment more in
line with experiment. Remarkably, the net moment lies primarily on the oxygen
ions. An insulator-metal transition by rotating the magnetization direction
with an external field under moderate pressure is predicted as one consequence
of strong SOC, and metallization under moderate pressure is predicted.
Comparison is made with the isostructural, isovalent insulator Ba$_2$LiOsO$_6$
which however orders antiferromagnetically.",1410.3167v1
2018-04-13,Tuning Rashba Spin-Orbit Coupling in Gated Multilayer InSe,"Manipulating the electron spin with the aid of spin-orbit coupling (SOC) is
an indispensable element of spintronics. Electrostatically gating a material
with strong SOC results in an effective magnetic field which can in turn be
used to govern the electron spin. In this work, we report the existence and
electrostatic tunability of Rashba SOC in multilayer InSe. We observed a
gate-voltage-tuned crossover from weak localization (WL) to weak
antilocalization (WAL) effect in quantum transport studies of InSe, which
suggests an increasing SOC strength. Quantitative analyses of magneto-transport
studies and energy band diagram calculations provide strong evidence for the
predominance of Rashba SOC in electrostatically gated InSe. Furthermore, we
attribute the tendency of the SOC strength to saturate at high gate voltages to
the increased electronic density of states-induced saturation of the electric
field experienced by the electrons in the InSe layer. This explanation of
nonlinear gate voltage control of Rashba SOC can be generalized to other
electrostatically gated semiconductor nanomaterials in which a similar tendency
of spin-orbit length saturation was observed (e.g. nanowire field effect
transistors), and is thus of broad implications in spintronics. Identifying and
controlling the Rashba SOC in InSe may serve pivotally in devising III-VI
semiconductor-based spintronic devices in the future.",1804.04992v2
2018-06-07,Fractional topological insulator precursors in spin-orbit fermion ladders,"We study precursor states of fractional topological insulators (FTIs) in
interacting fermionic ladders with spin-orbit coupling. Within a
microscopically motivated bosonization approach, we investigate different
competing phases depending on same-spin and interspin interactions at
fractional effective filling $\nu=1/3$ per spin. In the spin-decoupled limit,
we find that strong repulsive interactions of already moderate range may lead
to a partially gapped state with two time-reversed copies of a quasi-one
dimensional Laughlin phase. This FTI precursor competes with an interleg
partially gapped phase displaying quasi long-range density wave order, however
it may be stabilized if interactions have suitable anisotropy, or are
sufficiently near SU($2$) symmetry, in leg space. When the FTI phase is
present, it is moderately robust to small interspin interactions; these
introduce competing partially gapped phases of orbital antiferromagnetic and
bond density wave character. Performing a strong coupling analysis of the FTI
precursor regime, we find that the main effect of interspin interactions is to
induce correlated quasiparticle backscattering between the precursor FTI edge
modes. Although this process competes with the topological phase, we show, by
considering an array of ladders, that its influence may disappear upon
approaching the two dimensional case. Considering time-reversal symmetry
breaking perturbations, we also describe a protocol that adiabatically pumps
$1/6$ charge per half-cycle, thus providing a quantized FTI signature arising
already in the single ladder regime.",1806.02874v3
2018-12-19,Interfacial Spin-Orbit Coupling: New Platform for Superconducting Spintronics,"Spin-orbit coupling (SOC) is a key interaction in spintronics, allowing an
electrical control of spin or magnetization and, vice versa, a magnetic control
of electrical current. However, recent advances have revealed much broader
implications of SOC that is also central to the design of topological states,
including topological insulators, skyrmions, and Majorana fermions, or to
overcome the exclusion of two-dimensional ferro-magnetism expected from the
Mermin-Wagner theorem. SOC and the resulting emergent interfacial spin-orbit
fields are simply realized in junctions through structural inversion asymmetry,
while the anisotropy in magnetoresistance (MR) allows for their experimental
detection. Surprisingly, we demonstrate that an all-epitaxial
ferromagnet/MgO/metal junction with only a negligible MR anisotropy undergoes a
remarkable transformation below the superconducting transition temperature of
the metal. The superconducting junction has a three orders of magnitude higher
MR anisotropy and supports the formation of spin-triplet superconductivity,
crucial for superconducting spintronics, and topologically-protected quantum
computing. Our findings call for revisiting the role of SOC in other systems
which, even when it seems negligible in the normal state, could have a profound
influence on the superconducting response.",1812.08090v2
2022-05-08,Spin interaction and magnetism in cobaltate Kitaev candidate materials: an $ab$ $initio$ and model Hamiltonian approach,"In the quest for materials hosting Kitaev spin liquids, much of the efforts
have been focused on the fourth- and fifth-row transition metal compounds,
which are spin-orbit coupling assisted Mott insulators. Here, we study the
structural and magnetic properties of 3$d$ transition metal oxides,
Na$_2$Co$_2$TeO$_6$ and Na$_3$Co$_2$SbO$_6$. The partial occupancy of sodium in
former compound is addressed using a cluster expansion, and a honeycomb lattice
of sodiums is found to be energetically favored. Starting from the \textit{ab
initio} band structures, a many-body second order perturbation theory leads to
a pseudospin-$\frac{1}{2}$ Hamiltonian with estimated magnetic interactions. We
show that the experimentally observed zigzag magnetic state is stabilized only
when the first neighbor Kitaev coupling dominates over the Heisenberg term,
both of which are highly suppressed due to presence of $e_g$ orbitals. A third
neighbor Heisenberg interaction is found dominant in both these compounds. We
also present a phase diagram for Na$_2$Co$_2$TeO$_6$ by varying the
electron-electron and spin-orbit interactions. The computed spin excitation
spectra are found to capture essential features of recent experimental magnon
spectrum, lending support to our results.",2205.03836v2
2011-12-12,Spin and Orbital Angular Momentum Structures of Cu(111) and Au(111) Surface States,"We performed angle resolved photoemission (ARPES) studies on Cu(111) and
Au(111) surface states with circularly polarized light. Existence of local
orbital angular momentum (OAM) is confirmed as has been predicted to be broadly
present in a system with an inversion symmetry breaking (ISB). The single band
of Cu(111) surface states is found to have chiral OAM in spite of very small
spin-orbit coupling (SOC) in Cu, which is consistent with theoretical
prediction. As for Au(111), we observe split bands for which OAM for the inner
and outer bands are parallel, unlike the Bi2Se3 case. We also performed first
principles calculation and the results are found to be consistent with the
experimental results. Moreover, majority of OAM is found to be from d-orbitals
and a small contribution has p-orbital origin which is anti-aligned to the
spins. We derive an effective Hamiltonian that incorporates the role of OAM and
used it to extract the OAM and spin structures of surface states with various
SOC strength. We discuss the evolution of angular momentum structures from pure
OAM case to a strongly spin-orbit entangled state. We predict that the
transition occurs through reversal of OAM direction at a k-point in the inner
band if the system has a proper SOC strength.",1112.2469v1
2013-12-30,Observation of monolayer valence band spin-orbit effect and induced quantum well states (QWS) in MoX2,"Transition metal dichalcogenides have attracted much attention recently due
to their potential applications in spintronics and photonics as a result of the
indirect to direct band gap transition and the emergence of the spin-valley
coupling phenomenon upon moving from the bulk to monolayer limit. Here, we
report high-resolution angle-resolved photoemission spectroscopy on MoSe2
(molybdenum diselenide) single crystals and monolayer films of MoS2 grown on
Highly Ordered Pyrolytic Graphite substrate. Our experimental results, for the
first time, resolve the two distinct bands at the Brillouin zone corner of the
bulk MoSe2, and provide evidence for the critically important spin-orbit split
bands of the monolayer MoS2. Moreover, by depositing potassium on cleaved
surfaces of these materials, the process through which quantum well states form
on the surfaces of transition metal dichalcogenides is systematically imaged.
We present a theoretical model to account for the observed spin-orbit splitting
and the rich spectrum of the quantum well states observed in our experiments.
Our findings taken together provide important insights into future applications
of transition metal dichalcogenides in nanoelectronics, spintronics, and
photonics devices as they critically depend on the spin-orbit physics of these
materials.",1312.7631v2
2015-10-23,Soft spin-amplitude fluctuations in a Mott-insulating ruthenate,"Magnetism in transition-metal compounds (TMCs) has traditionally been
associated with spin degrees of freedom, because the orbital magnetic moments
are typically largely quenched. On the other hand, magnetic order in 4f- and
5d-electron systems arises from spin and orbital moments that are rigidly tied
together by the large intra-atomic spin-orbit coupling (SOC). Using inelastic
neutron scattering on the archetypal 4d-electron Mott insulator Ca$_2$RuO$_4$,
we report a novel form of excitonic magnetism in the intermediate-strength
regime of the SOC. The magnetic order is characterized by ``soft'' magnetic
moments with large amplitude fluctuations manifested by an intense, low-energy
excitonic mode analogous to the Higgs mode in particle physics. This mode
heralds a proximate quantum critical point separating the soft magnetic order
driven by the superexchange interaction from a quantum-paramagnetic state
driven by the SOC. We further show that this quantum critical point can be
tuned by lattice distortions, and hence may be accessible in epitaxial
thin-film structures. The unconventional spin-orbital-lattice dynamics in
Ca$_2$RuO$_4$ identifies the SOC as a novel source of quantum criticality in
TMCs.",1510.07011v1
2016-06-26,Manipulation of the large Rashba spin splitting in polar two-dimensional transition metal dichalcogenides,"Transition metal dichalcogenide (TMD) monolayers MXY (M=Mo, W, X(not equal
to)Y=S, Se, Te) are two-dimensional polar semiconductors. Setting WSeTe
monolayer as an example and using density functional theory calculations, we
investigate the manipulation of Rashba spin orbit coupling (SOC) in the MXY
monolayer. It is found that the intrinsic out-of-plane electric field due to
the mirror symmetry breaking induces the large Rashba spin splitting around the
Gamma point, which, however, can be easily tuned by applying the in-plane
biaxial strain. Through a relatively small strain (from -2% to 2%), a large
tunability (from around -50% to 50%) of Rashba SOC can be obtained due to the
modified orbital overlap, which can in turn modulate the intrinsic electric
field. The orbital selective external potential method further confirms the
significance of the orbital overlap between W-dz2 and Se-pz in Rashba SOC. In
addition, we also explore the influence of the external electric field on
Rashba SOC in the WSeTe monolayer, which is less effective than strain. The
large Rashba spin splitting, together with the valley spin splitting in MXY
monolayers may make a special contribution to semiconductor spintronics and
valleytronics.",1606.07985v2
2017-06-27,Two-dimensional Spin-Orbit Dirac Point in Monolayer HfGeTe,"Dirac points in two-dimensional (2D) materials have been a fascinating
subject of research, with graphene as the most prominent example. However, the
Dirac points in existing 2D materials, including graphene, are vulnerable
against spin-orbit coupling (SOC). Here, based on first-principles calculations
and theoretical analysis, we propose a new family of stable 2D materials, the
HfGeTe-family monolayers, which represent the first example to host so-called
spin-orbit Dirac points (SDPs) close to the Fermi level. These Dirac points are
special in that they are formed only under significant SOC, hence they are
intrinsically robust against SOC. We show that the existence of a pair of SDPs
are dictated by the nonsymmorphic space group symmetry of the system, which are
very robust under various types of lattice strains. The energy, the dispersion,
and the valley occupation around the Dirac points can be effectively tuned by
strain. We construct a low-energy effective model to characterize the Dirac
fermions around the SDPs. Furthermore, we find that the material is
simultaneously a 2D $\mathbb{Z}_2$ topological metal, which possesses
nontrivial $\mathbb{Z}_2$ invariant in the bulk and spin-helical edge states on
the boundary. From the calculated exfoliation energies and mechanical
properties, we show that these materials can be readily obtained in experiment
from the existing bulk materials. Our result reveals HfGeTe-family monolayers
as a promising platform for exploring spin-orbit Dirac fermions and novel
topological phases in two-dimensions.",1706.08692v2
2018-08-20,Spectroscopy and level detuning of few-electron spin states in parallel InAs quantum dots,"We use tunneling spectroscopy to study the evolution of few-electron spin
states in parallel InAs nanowire double quantum dots (QDs) as a function of
level detuning and applied magnetic field. Compared to the much more studied
serial configuration, parallel coupling of the QDs to source and drain greatly
expands the probing range of excited state transport. Owing to a strong
confinement, we can here isolate transport involving only the very first
interacting single QD orbital pair. For the (2,0)-(1,1) charge transition, with
relevance for spin-based qubits, we investigate the excited (1,1) triplet, and
hybridization of the (2,0) and (1,1) singlets. An applied magnetic field splits
the (1,1) triplet, and due to spin-orbit induced mixing with the (2,0) singlet,
we clearly resolve transport through all triplet states near the avoided
singlet-triplet crossings. Transport calculations, based on a simple model with
one orbital on each QD, fully replicate the experimental data. Finally, we
observe an expected mirrored symmetry between the 1-2 and 2-3 electron
transitions resulting from the two-fold spin degeneracy of the orbitals.",1808.06431v1
2016-03-11,Instability of three-band Tomonaga-Luttinger liquid: renormalization group analysis and possible application to K2Cr3As3,"Motivated by recently discovered quasi-one-dimensional superconductor
K$_{2}$Cr$_{3}$As$_{3}$ with $D_{3h}$ lattice symmetry, we study
one-dimensional three-orbital Hubbard model with generic electron repulsive
interaction described by intra-orbital repulsion $U$, inter-orbital repulsion,
and Hund's coupling $J$. As extracted from density functional theory
calculation, two of the three atomic orbitals are degenerate ($E^{\prime}$
states) and the third one is non-degenerate ($A^{\prime}_1$), and the system is
presumed to be at an incommensurate filling. With the help of bosonization, we
have usual three-band Tomonaga-Luttinger liquid for the normal state. Possible
charge density wave (CDW), spin density wave (SDW) and superconducting (SC)
instabilities are analyzed by renormalization group. The ground state depends
on the ratio $J/U$ and is sensitive to the degeneracy of $E^{\prime}$ bands. At
$0<J<U/3$, spin-singlet SC state is favored, while spin-triplet
superconductivity will be favored in the region $U/3<J<U/2$. The SDW state has
the lowest energy only in the unphysical parameter region $J>U/2$. When the
two-fold degeneracy of $E^{\prime}$ bands is lifted, SDW instability has the
tendency to dominate over the spin-singlet SC state at $0<J<U/3$, while the
order parameter of the spin-triplet SC state will be modulated by a phase
factor $2\Delta k_F x$ at $U/3<J<U/2$. Possible experimental consequences and
applications to K$_{2}$Cr$_{3}$As$_{3}$ are discussed.",1603.03651v3
2021-10-25,Gravitational spin-orbit dynamics at the fifth-and-a-half post-Newtonian order,"Accurate waveform models are crucial for gravitational-wave data analysis,
and since spin has a significant effect on the binary dynamics, it is important
to improve the spin description in these models. In this paper, we derive the
spin-orbit (SO) coupling at the fifth-and-a-half post-Newtonian (5.5PN) order.
The method we use splits the conservative dynamics into local and
nonlocal-in-time parts, then relates the local-in-time part to gravitational
self-force results by exploiting the simple mass-ratio dependence of the
post-Minkowskian expansion of the scattering angle. We calculate the nonlocal
contribution to the 5.5PN SO dynamics to eighth order in the small-eccentricity
expansion for bound orbits, and to leading order in the large-eccentricity
expansion for unbound orbits. For the local contribution, we obtain all the
5.5PN SO coefficients from first-order self-force results for the redshift and
spin-precession invariants, except for one unknown that could be fixed in the
future by second-order self-force results. However, by incorporating our 5.5PN
results in the effective-one-body formalism and comparing its binding energy to
numerical relativity, we find that the remaining unknown has a small effect on
the SO dynamics, demonstrating an improvement in accuracy at that order.",2110.12813v2
2022-08-19,Spin-orbit interactions in noncentrosymmetric plasmonic crystals probed by site-selective cathodoluminescence spectroscopy,"The study of spin-orbit coupling (SOC) of light is crucial to explore the
light-matter interactions in sub-wavelength nanostructures with broken
symmetries. In noncentrosymmetric photonic crystals, the SOC results in the
splitting of the otherwise degenerate energy bands. Herein, we explore the SOC
in a noncentrosymmetric plasmonic crystal, both theoretically and
experimentally. Cathodoluminescence (CL) spectroscopy combined with the
numerically calculated photonic band structure reveals an energy band splitting
that is ascribed to the broken symmetries in the noncentrosymmetric plasmonic
crystal. By shifting the impact position of the electron beam throughout a unit
cell of the plasmonic crystal, we show that the emergence of the energy band
splitting strongly depends on the excitation position of the surface plasmon
(SP) waves on the crystal. Moreover, we exploit angle-resolved CL and
dark-field polarimetry to demonstrate polarization-dependent scattering of SP
waves interacting with the plasmonic crystal. The scattering direction of a
given polarization is determined by the transverse spin angular momentum
inherently carried by the SP wave, which is in turn locked to the direction of
SP propagation. Our study gives insight into the design of novel plasmonic
devices with polarization-dependent directionality of the Bloch plasmons. We
expect spin-orbit plasmonics will find much more scientific interests and
potential applications with the continuous development of nanofabrication
methodologies and uncovering new aspects of spin-orbit interactions.",2208.09238v1
2022-10-25,"Au4Mn, a localized ferromagnet with strong spin-orbit coupling, long-range ferromagnetic exchange and high Curie temperature","Metallic Mn-based alloys with a nearest-neighbor Mn-Mn distance greater than
0.4 nm exhibit large, well-localized magnetic moments. Here we investigate the
magnetism of tetragonal Au4Mn with a Curie temperature of 385 K, where
manganese has a spin moment of 4.1 muB and its orbital moment is quenched.
Since 80% of the atoms are gold, the spin orbit interaction is strong and Au4Mn
exhibits uniaxial magnetocrystalline anisotropy with surface maze domains at
room temperature. The magnetic hardness parameter of 1.0 is sufficient to
maintain the magnetization along the c-axis for a sample of any shape. Au also
reduces the spin moment of Mn through 5d-3d orbital hybridization. An induced
moment of 0.05 muB was found on Au under a pulsed field of 40 T. Density
functional theory calculations indicate that the Mn-Mn exchange is mediated by
spin-polarized gold 5d and 6p electrons. The distance-dependence shows that it
is ferromagnetic or zero for the first ten shells of Mn neighbors out to 1.041
nm (64 atoms), and very weak and oscillatory thereafter.",2210.14069v1
2024-01-12,FeS2 monolayer: a high valence and high-$T_{\rm C}$ Ising ferromagnet,"Two-dimensional (2D) magnetic materials are of current great interest for
their promising applications in spintronics. Strong magnetic coupling and
anisotropy are both highly desirable for the achievement of a high temperature
magnetic order. Here we propose the unusual high valent FeS$_2$ hexagonal
monolayer as such a candidate for a strong Ising 2D ferromagnet (FM), by
spin-orbital state analyses, first-principles calculations, and the
renormalized spin-wave theory (RSWT). We find that very importantly, the high
valent Fe$^{4+}$ ion is in the low-spin state ($t_{2g}^{4}$, $S$=1) with
degenerate $t_{2g}$ orbitals rather than the high-spin state
($t_{2g}^{3}e_g^{1}$, $S$=2). It is the low-spin state that allows to carry a
large perpendicular orbital moment and then produces a huge single ion
anisotropy (SIA) of 25 meV/Fe. Moreover, the negative charge transfer character
associated with the unusual high valence, strong Fe $3d$-S $3p$ hybridization,
wide bands, and a small band gap all help to establish a strong superexchange.
Indeed, our first-principles calculations confirm the strong FM superexchange
and the huge perpendicular SIA, both of which are further enhanced by a
compressive strain. Then, our RSWT calculations predict that the FM $T_{\rm C}$
is 261 K for the pristine FeS$_2$ monolayer and could be increased to 409 K
under the compressive --5\% strain. The high $T_{\rm C}$ is also reproduced by
our Monte Carlo (MC) simulations. Therefore, it is worth exploring the
high-$T_{\rm C}$ Ising FMs in the high valent 2D magnetic materials with
degenerate orbitals.",2401.06357v1
2024-03-11,Spin-orbit correlations in the nucleon in the large-$N_{c}$ limit,"We study the twist-3 spin-orbit correlations of quarks described by the
nucleon matrix elements of the parity-odd rank-2 tensor QCD operator (the
parity-odd partner of the QCD energy-momentum tensor). Our treatment is based
on the effective dynamics emerging from the spontaneous breaking of chiral
symmetry and the mean-field picture of the nucleon in the large-$N_c$ limit.
The twist-3 QCD operators are converted to effective operators, in which the
QCD interactions are replaced by spin-flavor-dependent chiral interactions of
the quarks with the pion field. We compute the nucleon matrix elements of the
twist-3 effective operators and discuss the role of the chiral interactions in
the spin-orbit correlations. We derive the first-quantized representation in
the mean-field picture and develop a quantum-mechanical interpretation. The
chiral interactions give rise to new spin-orbit couplings and qualitatively
change the correlations compared to the quark model picture. We also derive the
twist-3 matrix elements in the topological soliton picture where the quarks are
integrated out (skyrmion). The methods used here can be extended to other QCD
operators describing higher-twist nucleon structure and generalized parton
distributions.",2403.07186v1
2023-12-29,"Effect of Exchange Interaction and Spin-Orbit Coupling on Spin Splitting in CdSnX (X = S, Se and Te) nanoribbons","We have studied the topological properties of free standing Sn doped cadmium
chalcogenide (CdSnX, X = S, Se and Te) nanoribbons of varying widths and three
types of edges viz., distorted armchair, normal armchair and normal zigzag
edges. The unsatisfied bonds of X and Sn atoms at the edges cause non-zero
values of the magnetic moment. This introduces an exchange field leading to
inverted band structure. The electronic band structures of distorted armchair
edge nanoribbons also exhibit different types of spin splitting property for
different X atoms due to the different local orbital angular momentum at
specific X atomic site with the inclusion of spin orbit coupling (SOC). The gap
opening at the band crossings near the Fermi level after inclusion of SOC are
mainly due to SOC of Sn atom and are responsible for the electron and hole
pockets making the system topologically exotic. All the distorted edge
nanoribbons show metallic behaviour with non-zero magnetic moments. Amongst CdX
(X = S, Se and Te) nanoribbons, systems containing S atoms exhibit Weyl-like
semi-metallic behavior and not much change with width, that of Se atoms exhibit
Zeeman-type spin splitting and significant change with varying width, whereas
systems containing Te atoms show signature of Rashba spin splitting along with
Zeeman-type spin splitting and moderate change with varying width. The armchair
edge nanoribbons show wide gap semiconducting behaviour. Zeeman-type spin
splitting is seen in the valence band region for systems containing S atoms and
Rashba spin splitting is visible in the conduction band region for systems
containing Se and Te atoms. For zigzag edge nanoribbons, no such signature of
spin splitting is observed although all the nanoribbons acquire very high
magnetic moments.",2312.17562v1
2005-03-31,Orbital selective Mott transition in multi-band systems: slave-spin representation and dynamical mean-field theory,"We examine whether the Mott transition of a half-filled, two-orbital Hubbard
model with unequal bandwidths occurs simultaneously for both bands or whether
it is a two-stage process in which the orbital with narrower bandwith localizes
first (giving rise to an intermediate `orbital-selective' Mott phase). This
question is addressed using both dynamical mean-field theory, and a
representation of fermion operators in terms of slave quantum spins, followed
by a mean-field approximation (similar in spirit to a Gutzwiller
approximation). In the latter approach, the Mott transition is found to be
orbital-selective for all values of the Coulomb exchange (Hund) coupling J when
the bandwidth ratio is small, and only beyond a critical value of J when the
bandwidth ratio is larger. Dynamical mean-field theory partially confirms these
findings, but the intermediate phase at J=0 is found to differ from a
conventional Mott insulator, with spectral weight extending down to arbitrary
low energy. Finally, the orbital-selective Mott phase is found, at
zero-temperature, to be unstable with respect to an inter-orbital
hybridization, and replaced by a state with a large effective mass (and a low
quasiparticle coherence scale) for the narrower band.",0503764v2
2013-11-04,The kinematics and orbital dynamics of the PSR B1259$-$63/LS 2883 system from 23 years of pulsar timing,"We present an analysis of $23~$yr of pulse arrival times for PSR B1259$-$63.
The pulsar is in a binary orbit about its approximately $20~M_{\odot}$
companion LS$~$2883. Our best-fitting timing solution has none of the
pulse-number ambiguities that have plagued previous attempts to model the
binary orbit. We measure significant first and second time derivatives of the
projected semimajor axis and longitude of the periastron of the orbit. These
variations are found to be consistent with the precession of the orbital plane
due to classical spin-orbit coupling. The derived moment of inertia and spin of
the companion are consistent with the companion rotating at near-breakup
velocity. The system configuration is also consistent with the geometry derived
from both the polarisation of the radio emission and the eclipse of the pulsar
by the equatorial disc of the companion. We find strong evidence for orbital
period decay that can be attributed to mass loss from the companion star. We
also measure a significant proper motion that locates the birth of the system
in the Centaurus OB1 association. By combining proper motion of the pulsar with
radial velocity measurements of the companion, we measure the three-dimensional
velocity of the system. This velocity is used to constrain the masses of the
stars prior to the supernova explosion and the kick the pulsar received at or
immediately after the explosion.",1311.0588v1
2019-01-15,Formation of Hot Jupiters through Secular Chaos and Dynamical Tides,"The population of giant planets on short-period orbits can potentially be
explained by some flavours of high-eccentricity migration. In this paper we
investigate one such mechanism involving ""secular chaos"", in which secular
interactions between at least three giant planets push the inner planet to a
highly eccentric orbit, followed by tidal circularization and orbital decay. In
addition to the equilibrium tidal friction, we incorporate dissipation due to
dynamical tides that are excited inside the giant planet. Using the method of
Gaussian rings to account for planet-planet interactions, we explore the
conditions for extreme eccentricity excitation via secular chaos and the
properties of hot Jupiters formed in this migration channel. Our calculations
show that once the inner planet reaches a sufficiently large eccentricity,
dynamical tides quickly dissipate the orbital energy, producing an eccentric
warm Jupiter, which then decays in semi-major axis through equilibrium tides to
become a hot Jupiter. Dynamical tides help the planet avoid tidal disruption,
increasing the chance of forming a hot Jupiter, although not all planets
survive the process. We find that the final orbital periods generally lie in
the range of 2-3 days, somewhat shorter than those of the observed hot Jupiter
population. We couple the planet migration to the stellar spin evolution to
predict the final spin-orbit misalignments. The distribution of the
misalignment angles we obtain shows a lack of retrograde orbits compared to
observations. Our results suggest that high-eccentricity migration via secular
chaos can only account for a fraction of the observed hot Jupiter population.",1901.05006v1
2004-07-21,Multi-orbital analysis on the Superconductivity in Na_{x}CoO_{2} \cdot y H_{2}O,"We preform a multi-orbital analysis on the novel superconductivity in
Na_{x}CoO_{2} \cdot yH_{2}O. We construct a three-orbital model which
reproduces the band structure expected from the LDA calculation. The effective
interaction leading to the pairing is estimated by means of the perturbation
theory. It is shown that the spin triplet superconductivity is stabilized in
the wide parameter region. This is basically owing to the ferromagnetic
character of spin fluctuation. The p-wave and f-wave superconductivity are
nearly degenerate. The former is realized when the Hund's rule coupling is
large, and vice versa. In a part of the parameter space, the d-wave
superconductivity is also stabilized. We point out that the orbital degeneracy
plays an essential role for these results through the wave function of
quasi-particles. The nearly degeneracy of p-wave and f-wave superconductivity
is explained by analysing the orbital character of each Fermi surface. We
discuss the validity of some reduced models. While the single band Hubbard
model reproducing the Fermi surface is qualitatively inappropriate, we find an
effective two-orbital model appropriate for studying the superconductivity. We
investigate the vertex corrections higher than the third order on the basis of
the two-orbital model. It is shown that the vertex correction induces the
screening effect but does not affect on the qualitative results.",0407563v2
2004-11-18,Intrinsic Spin Hall Effect in the Two Dimensional Hole Gas,"We show that two types of spin-orbit coupling in the 2 dimensional hole gas
(2DHG), with and without inversion symmetry breaking, contribute to the
intrinsic spin Hall effect\cite{murakami2003,sinova2003}. Furthermore, the
vertex correction due to impurity scattering vanishes in both cases, in sharp
contrast to the case of usual Rashba coupling in the electron band. Recently,
the spin Hall effect in a hole doped $GaAs$ semiconductor has been observed
experimentally by Wunderlich \emph{et al}\cite{wunderlich2004}. From the fact
that the life time broadening is smaller than the spin splitting, and the fact
impurity vertex corrections vanish in this system, we argue that the observed
spin Hall effect should be in the intrinsic regime.",0411457v3
2006-06-03,Sign changes and resonance of intrinsic spin Hall effect in two-dimensional hole gas,"The intrinsic spin Hall conductance shows rich sign changes by applying a
perpendicular magnetic field in a two-dimensional hole gas. Especially, a
notable sign changes can be achieved by adjusting the characteristic length of
the Rashba coupling and hole density at moderate magnetic fields. This sign
issue may be easily realized in experiments. The oscillations of the intrinsic
spin Hall conductance as a function of 1/$B$ is nothing else but Shubnikov-de
Haas oscillations, and the additional beatings can be quantitatively related to
the value of the spin-orbit coupling parameter. The Zeeman splitting is too
small to introduce effective degeneracy between different Landau levels in a
two-dimensional hole gas, and the resonant intrinsic spin Hall conductance
appears in high hole density and strong magnetic field due to the transition
between mostly spin-$-{1/2}$ holes and spin-3/2 holes is confirmed. Two likely
ways to establish intrinsic spin Hall effect in experiments and a possible
application are suggested.",0606089v2
2011-07-06,Absence of spontaneous magnetic order of lattice spins coupled to itinerant interacting electrons in one and two dimensions,"We extend the Mermin-Wagner theorem to a system of lattice spins which are
spin-coupled to itinerant and interacting charge carriers. We use the
Bogoliubov inequality to rigorously prove that neither (anti-) ferromagnetic
nor helical long-range order is possible in one and two dimensions at any
finite temperature. Our proof applies to a wide class of models including any
form of electron-electron and single-electron interactions that are independent
of spin. In the presence of Rashba or Dresselhaus spin-orbit interactions (SOI)
magnetic order is allowed and intimately connected to equilibrium spin
currents. However, in the special case when Rashba and Dresselhaus SOIs are
tuned to be equal, magnetic order is excluded again. This opens up a new
possibility to control magnetism in magnetic semiconductors electrically.",1107.1223v2
2012-06-28,Frequency and power dependence of spin-current emission by spin pumping in a thin film YIG/Pt system,"This paper presents the frequency dependence of the spin current emission in
a hybrid ferrimagnetic insulator/normal metal system. The system is based on a
ferrimagnetic insulating thin film of Yttrium Iron Garnet (YIG, 200 nm) grown
by liquid-phase-epitaxy (LPE) coupled with a normal metal with a strong
spin-orbit coupling (Pt, 15 nm). The YIG layer presents an isotropic behaviour
of the magnetization in the plane, a small linewidth, and a roughness lower
than 0.4 nm. Here we discuss how the voltage signal from the spin current
detector depends on the frequency [0.6 - 7 GHz], the microwave power, Pin, [1 -
70 mW], and the in-plane static magnetic field. A strong enhancement of the
spin current emission is observed at low frequencies, showing the appearance of
non-linear phenomena.",1206.6671v2
2013-10-09,Chargeless spin current for switching and coupling of domain walls in magnetic nanowires,"The demonstration of the generation and control of a pure spin current
(without net charge flow) by electric fields and/or temperature gradient has
been an essential leap in the quest for low-power consumption electronics. The
key issue of whether and how such a current can be utilized to drive and
control information stored in magnetic domain walls (DWs) is still outstanding
and is addressed here. We demonstrate that pure spin current acts on DWs in a
magnetic stripe with an effective spin-transfer torque resulting in a mutual
DWs separation dynamics and picosecond magnetization reversal. In addition,
long-range ($\sim$ mm) antiferromagnetic DWs coupling emerges. If one DW is
pinned by geometric constriction, the spin current induces a dynamical spin
orbital interaction that triggers an internal electric field determined by
$\vec{E} \sim \hat{e}_{x} \cdot (\vec{n}_{1} \times \vec{n}_{2})$ where
$\vec{n}_{1/2}$ are the effective DWs orientations and $\hat{e}_{x} $ is their
spatial separation vector. This leads to charge accumulation or persistent
electric current in the wire. As DWs are routinely realizable and tuneable, the
predicted effects bear genuine potential for power-saving spintronics devices.",1310.2331v1
2013-10-14,"Symmetry Protected Topological Charge in Symmetry Broken Phase: Spin-Chern, Spin-Valley-Chern and Mirror-Chern Numbers","The Chern number is a genuine topological number. On the other hand, a
symmetry protected topological (SPT) charge is a topological number only when a
symmetry exists. We propose a formula for the SPT charge as a derivative of the
Chern number in terms of the Green function in such a way that it is valid and
related to the associated Hall current even when the symmetry is broken. We
estimate the amount of deviation from the quantized value as a function of the
strength of the broken symmetry. We present two examples. First, we consider
Dirac electrons with the spin-orbit coupling on honeycomb lattice, where the
SPT charges are given by the spin-Chern, valley-Chern and spin-valley-Chern
numbers. Though the spin-Chern charge is not quantized in the presence of the
Rashba coupling, the deviation is estimated to be $10^{-7}$ in the case of
silicene, a silicon cousin of graphene. Second, we analyze the effect of the
mirror-symmetry breaking of the mirror-Chern number in a thin-film of
topological crystalline insulator.",1310.3536v2
2014-04-02,Ground-state cooling of a carbon nanomechanical resonator by spin-polarized current,"We study the nonequilibrium steady state of a mechanical resonator in the
quantum regime realized by a suspended carbon nanotube quantum dot contacted by
two ferromagnets. Because of the spin-orbit interaction and/or an external
magnetic field gradient, the spin on the dot couples directly to the flexural
eigenmodes. Accordingly, the nanomechanical motion induces inelastic spin flips
of the tunneling electrons. A spin-polarized current at finite bias voltage
causes either heating or active cooling of the mechanical modes. We show that
maximal cooling is achieved at resonant transport when the energy splitting
between two dot levels of opposite spin equals the vibrational frequency. Even
for weak electron-resonator coupling and moderate polarizations we can achieve
ground-state cooling with a temperature of the leads, for instance, of
$T=10\omega$.",1404.0485v3
2014-07-22,Photonic spin Hall effect for precision metrology,"The photonic spin Hall effect (SHE) is generally believed to be a result of
an effective spin-orbit coupling, which describes the mutual influence of the
spin (polarization) and the trajectory of the light beam. The photonic SHE
holds great potential for precision metrology owing to the fact that the
spin-dependent splitting in photonic SHE are sensitive to the physical
parameter variations of different systems. Remarkably, using the weak
measurements, this tiny spin-dependent shifts can be detected with the
desirable accuracy so that the corresponding physical parameters can be
determined. Here, we will review some of our works on using photonic SHE for
precision metrology, such as measuring the thickness of nanometal film,
identifying the graphene layers, detecting the strength of axion coupling in
topological insulators, and determining the magneto-optical constant of
magnetic film.",1407.5721v2
2015-10-21,Spin-dependent two-body interactions from gravitational self-force computations,"We analytically compute, through the eight-and-a-half post-Newtonian order
and the fourth-order in spin, the gravitational self-force correction to
Detweiler's gauge invariant redshift function for a small mass in circular
orbit around a Kerr black hole. Using the first law of mechanics for black hole
binaries with spin [L.~Blanchet, A.~Buonanno and A.~Le Tiec, Phys.\ Rev.\ D
{\bf 87}, 024030 (2013)] we transcribe our results into a knowledge of various
spin-dependent couplings, as encoded within the spinning effective-one-body
model of T.~Damour and A.~Nagar [Phys.\ Rev.\ D {\bf 90}, 044018 (2014)]. We
also compare our analytical results to the (corrected) numerical self-force
results of A.~G.~Shah, J.~L.~Friedman and T.~S.~Keidl [Phys.\ Rev.\ D {\bf 86},
084059 (2012)], from which we show how to directly extract physically relevant
spin-dependent couplings.",1510.06230v2
2018-04-27,All-electric single electron spin-to-charge conversion,"We examine spin-dependent displacement of a single electron, resulting in
separation and relocation of the electron wavefunction components, and thus
charge parts, corresponding to opposite spins. This separation is induced by a
pulse of an electric field which generates varying Rashba type spin-orbit
coupling. This mechanism is next implemented in a nanodevice based on a gated
quantum dot defined within a quantum nanowire. The electric field pulse is
generated by ultrafast changes of voltages, of the order of several hundred mV,
applied to nearby gates. The device is modeled realistically with appropriate
material parameters and voltages applied to the gates, yielding an accurate
confinement potential and Rashba coupling. At the end, we propose a
spin-to-charge conversion device, which with an additional charge detector will
allow for electron spin state measurement.",1804.10595v2
2018-05-15,Heavy quark spin multiplet structure of $\bar{P}^{(*)}Σ_Q^{(*)}$ molecular states,"We study the structure of heavy quark spin (HQS) multiplets for heavy
meson-baryon molecular states in a coupled system of
$\bar{P}^{(*)}\Sigma_{Q}^{(*)}$, with constructing the one-pion exchange
potential with S-wave orbital angular momentum. Using the light cloud spin
basis, we find that there are four types of HQS multiplets classified by the
structure of heavy quark spin and light cloud spin. The multiplets which have
attractive potential are determined by the sign of the coupling constant for
the heavy meson-pion interactions. Furthermore, the difference in the structure
of light cloud spin gives the restrictions of the decay channel, which implies
that the partial decay width has the information for the structure of HQS
multiplets. This behavior is more likely to appear in hidden-bottom sector than
in hidden-charm sector.",1805.05740v1
2009-12-10,Coupled-channel calculation of bound and resonant spectra of Lambda-9Be and Lambda-13C hypernuclei,"A Multi-Channel Algebraic Scattering (MCAS) approach has been used to analyze
the spectra of two hyper-nuclear systems, Lambda-9Be and Lambda-13C. The
splitting of the two odd-parity excited levels (1/2^- and 3/2^-) at 11 MeV
excitation in Lambda-13C is driven mainly by the weak Lambda-nucleus spin-orbit
force, but the splittings of the 3/2^+ and 5/2^+ levels in both Lambda-9Be and
Lambda-13C have a different origin. These cases appear to be dominated by
coupling to the collective 2+ states of the core nuclei. Using simple
phenomenological potentials as input to the MCAS method, the observed splitting
and level ordering in Lambda-9Be is reproduced with the addition of a weak
spin-spin interaction acting between the hyperon and the spin of the excited
target. With no such spin-spin interaction, the level ordering in Lambda-9Be is
inverted with respect to that currently observed. In both hyper-nuclei, our
calculations suggest that there are additional low-lying resonant states in the
Lambda-nucleus continua.",0912.1970v1
2012-05-16,"More about ""short"" spinning quantum strings","We continue investigation of the spectrum of semiclassical quantum strings in
AdS5 x S5 on the examples of folded (S,J) string (with spin S in AdS5 and
orbital momentum J in S5) dual to an sl(2) sector state in gauge theory and its
(J',J) counterpart with spin J' in S5 dual to an su(2) sector state. We study
the limits of small spins and large J at weak and strong coupling, pointing out
that terms linear in spins provide a generalization of ""protected"" coefficients
in the energy that are given by finite polynomials in 't Hooft coupling
\lambda\ (or square of string tension) for any value of \lambda. We propose an
expression for the coefficient of the term linear in spin J' in the (J',J)
string energy which should be the su(2) sector counterpart of the ""slope
function"" in the sl(2) sector suggested by Basso in arXiv:1109.3154.",1205.3656v3
2017-05-23,Spin mixing and protection of ferromagnetism in a spinor dipolar condensate,"We study spin mixing dynamics in a chromium dipolar Bose-Einstein Condensate,
after tilting the atomic spins by an angle $\theta$ with respect to the
magnetic field. Spin mixing is triggered by dipolar coupling, but, once
dynamics has started, it is mostly driven by contact interactions. For the
particular case $\theta=\pi/2$, an external spin-orbit coupling term induced by
a magnetic gradient is required to enable the dynamics. Then the initial
ferromagnetic character of the gas is locally preserved, an unexpected feature
that we attribute to large spin-dependent contact interactions.",1705.08358v1
2018-12-19,Electric dipole spin resonance at shallow donors in quantum wires,"Electric dipole spin resonance is studied theoretically at a shallow donor
formed in a nanowire with spin-orbit coupling in a magnetic field. Such system
may represent a donor-based qubit. The single discrete energy level of the
donor is accompanied by the set of continuum states, which provide a
non-trivial interplay for the picture of electric dipole spin resonance driven
by an external monochromatic field. Strongly nonlinear dependencies of spin
flip time as well as of the coordinate mean values on the electric field
amplitude are observed, demonstrating the significance of coupling to the
continuum for spin-based qubits manipulation in nanostructures.",1812.08048v2
2017-11-20,The electromagnetic instabilities propagation in weak relativistic quantum plasmas,"The electromagnetic instabilities excited by the temperature anisotropy have
been always one of the interesting issues in real high-density physical
systems, where the relativistic and quantum effects due to spin can be
important. This paper discusses the case where plasma is not strongly coupled
but is still in regimes where a classic plasma description is not fully
adequate. The length scale of the plasma can be larger than the de-Broglie
length so that the quantum effects relevance to the spin can be significant. In
addition, the only relativistic effects are due to the electrons spin, for
example the spin-orbit coupling effect (the weak (semi) relativistic effects).
Obtained results imply that these effects can not be important in the ICF
subjects while these can lead to significant results in the astrophysical
subjects because of the strong magnetic fields. It is found that the weakly
relativistic effects can cover the magnetic dipole force and the spin
precession effects so that the growth rate of the instability can increase
compared to the non relativistic spin polarized cases. Indeed, it is expected
that the probability of electron capture in the background magnetic fields and
the particle energy dissipation will be reduced so that there will be a high
portion of free energy in the system.",1711.07200v1
2019-05-02,Spin-valley coupled thermoelectric energy converter with strained honeycomb lattices,"A caloritronic device setup is proposed that harnesses the intrinsic
spin-valley locking of two-dimensional honeycomb lattices with graphene-like
valleys, for instance, silicene and stanene. Combining first-principles and
analytic calculations, we quantitatively show that when sheets of such
materials are placed on a ferromagnetic substrate and held between two contacts
at different temperatures, an interplay between the electron degrees-of-freedom
of charge, spin, and valley arises. A manifestation of this interplay are
finite charge, spin, and valley currents. Uniaxial strain that adjusts the
buckling height in silicene-type of lattices, in conjunction with an applied
electric field, is shown to further modulate the aforementioned currents. We
link these calculations to a Seebeck-like thermopower generator and obtain
expressions (and means to optimize them) for two spin-valley polarized
performance metrics--the thermodynamic efficiency and thermoelectric figure of
merit. A closing summary outlines possible enhancements to presented results
through the inherent topological order and substrate-induced external Rashba
spin-orbit coupling that exists in silicene-type materials.",1905.00984v1
2021-07-20,Intrinsic Magnon Nernst Effects in Pyrochlore Iridate Thin Films,"We theoretically study the magnon spin thermal transport using a strong
coupling approach in pyrochlore iridate trilayer thin films grown along the
[111] direction. As a result of the Dzyaloshinskii-Moriya interaction (DMI),
the spin configuration of the ground state is an all-in/all-out ordering on
neighboring tetrahedra of the pyrochlore lattice. In such a state, the system
has an inversion symmetry and a Nernst-type thermal spin current response is
well defined. We calculate the temperature dependence of the magnon Nernst
response with respect to the magnon band topology controlled by the spin-orbit
coupling parameters and observe topologically protected chiral edge modes over
a range of parameters. Our study complements prior work on the magnon thermal
Hall effect in thin-film pyrochlore iridates and suggests that the [111] grown
thin-film pyrochlore iridates are a promising candidate for thermal spin
transport and spin caloritronic devices.",2107.09613v1
2021-08-03,Optical Rashba effect in a monolithic light-emitting perovskite metasurface,"The Rashba effect, i.e., the splitting of electronic spin-polarized bands in
the momentum space of a crystal with broken inversion symmetry, has enabled the
realization of spin-orbitronic devices, in which spins are manipulated by
spin-orbit coupling. In optics, where the helicity of light polarization
represents the spin degree of freedom for spin-momentum coupling, the optical
Rashba effect is manifested by the splitting of optical states with opposite
chirality in the momentum space. Previous realizations of the optical Rashba
effect relied on passive devices determining either the propagation direction
of surface plasmons or circularly polarized light into nanostructures, or the
directional emission of polarized luminescence from metamaterials hybridized
with light-emitting media. Here we demonstrate an active device underpinned by
the optical Rashba effect, in which a monolithic halide perovskite metasurface
emits highly directional chiral photoluminescence. An all-dielectric
metasurface design with broken in-plane inversion symmetry is directly embossed
into the high refractive index, light-emitting perovskite film, yielding a
degree of circular polarization of photoluminescence of 40% at room temperature
- more than one order of magnitude greater than in state of art chiral
perovskites.",2108.01465v1
2021-08-09,Holographic charm and bottom pentaquarks I: Mass spectra with spin effects,"We revisit the three non-strange pentaquarks $[\frac 12\frac 12^-]_{S=0,1}$
and $[\frac 12\frac 32^-]_{S=1}$
  predicted using the holographic dual description, where chiral and heavy
quark symmetry are manifest in the triple limit of a large number of colors,
large quark mass and strong $^\prime$t Hooft gauge coupling. In the heavy quark
limit, the pentaquarks with internal heavy quark spin $S$ are all degenerate.
The holographic pentaquarks are dual to an instanton bound to heavy mesons in
bulk, without
  the shortcomings related to the nature of the interaction and the choice of
the hard core inherent to the molecular constructions. We explicitly derive the
spin-spin and spin-orbit couplings arising from next to leading order in the
heavy quark mass, and lift totally the internal spin degeneray, in fair
agreement with the newly reported charmed pentaquarks from LHCb. New charm and
bottom pentaquark states are predicted.",2108.04334v1
2021-11-02,Floquet engineering of Kitaev quantum magnets,"In recent years, there has been an intense search for materials realizing the
Kitaev quantum spin liquid model. A number of edge-shared compounds with strong
spin-orbit coupling, such as RuCl$_3$ and iridates, have been proposed to
realize this model. Nevertheless, an effective spin Hamiltonian derived from
the microscopic model relevant to these compounds generally contains terms that
are antagonistic toward the quantum spin liquid. This is consistent with the
fact the zero magnetic field ground state of these materials is generally
magnetically ordered. It is a pressing issue to identify protocols to drive the
system to the limit of the Kitaev quantum spin model. In this work, we propose
Floquet engineering of these Kitaev quantum magnets by coupling materials to a
circularly polarized laser. We demonstrate that all the magnetic interactions
can be tuned in situ by the amplitude and frequency of the laser, hence
providing a route to stabilize the Kitaev quantum spin liquid phase.",2111.01316v1
2021-11-29,Interface-Induced Conservation of Momentum Leads to Chiral-Induced Spin Selectivity,"We study the non-equilibrium dynamics of electron transmission from a
straight waveguide to a helix with spin-orbit coupling. Transmission is found
to be spin-selective and can lead to large spin polarizations of the itinerant
electrons. The degree of spin selectivity depends on the width of the interface
region, and no polarization is found for single-point couplings. We show that
this is due to momentum conservation conditions arising from extended
interfaces. We therefore identify interface structure and conservation of
momentum as crucial ingredients for chiral-induced spin selectivity, and
confirm that this mechanism is robust against static disorder.",2111.14770v1
2022-09-23,A variational model for the hyperfine resolved spectrum of VO in its ground electronic state,"A variational model for the infra-red spectrum of VO is presented which aims
to accurately predict the hyperfine structure within the VO
$\mathrm{X}\,^4\Sigma^-$ electronic ground state. To give the correct electron
spin splitting of the $\mathrm{X}\,^4\Sigma^-$ state, electron spin dipolar
interaction within the ground state and the spin-orbit coupling between
$\mathrm{X}\,^4\Sigma^-$ and two excited states, $\mathrm{A}\,^4\Pi$ and
$\mathrm{1}\,^2\Sigma^+$, are calculated ab initio alongside hyperfine
interaction terms. Four hyperfine coupling terms are explicitly considered:
Fermi-contact interaction, electron spin-nuclear spin dipolar interaction,
nuclear spin-rotation interaction and nuclear electric quadrupole interaction.
These terms are included as part of a full variational solution of the
nuclear-motion Schr\""odinger equation performed using program DUO, which is
used to generate both hyperfine-resolved energy levels and spectra. To improve
the accuracy of the model, ab initio curves are subject to small shifts. The
energy levels generated by this model show good agreement with the recently
derived empirical term values. This and other comparisons validate both our
model and the recently developed hyperfine modules in DUO.",2210.02896v2
2023-08-18,Critical enhancement of the spin Hall effect by spin fluctuations,"The spin Hall (SH) effect, the conversion of the electric current to the spin
current along the transverse direction, relies on the relativistic spin-orbit
coupling (SOC). Here, we develop a microscopic theory on the mechanisms of the
SH effect in magnetic metals, where itinerant electrons are coupled with
localized magnetic moments via the Hund exchange interaction and the SOC. Both
antiferromagnetic metals and ferromagnetic metals are considered. It is shown
that the SH conductivity can be significantly enhanced by the spin fluctuation
when approaching the magnetic transition temperature of both cases. For
antiferromagnetic metals, the pure SH effect appears in the entire temperature
range, while for ferromagnetic metals, the pure SH effect is expected to be
replaced by the anomalous Hall effect below the transition temperature. We
discuss possible experimental realizations and the effect of the quantum
criticality when the antiferromagnetic transition temperature is tuned to zero
temperature.",2308.09636v2
2014-07-23,Magnetic proximity effect at Bi$_2$Se$_3$/EuS interface with broken inversion symmetry,"We investigate a magnetic proximity effect on Dirac surface states of
topological insulator (TI) induced by a Bi$_2$Se$_3$/EuS interface, using
density-functional theory (DFT) and a low-energy effective model, motivated by
a recent experimental realization of the interface. We consider a thin
ferromagnetic insulator EuS film stacked on top of Bi$_2$Se$_3$(111) slabs of
three or five quintuple layers (QLs) with the magnetization of EuS normal to
the interface ($z$ axis), which breaks both time-reversal and inversion
symmetry. It is found that a charge transfer and surface relaxation makes the
Dirac cones electron-doped. For both 3 and 5 QLs, the top-surface Dirac cone
has an energy gap of 9 meV, while the bottom surface Dirac cone remains
gapless. This feature is due to the short-ranged induced magnetic moment of the
EuS film. For the 5 QLs, an additional Dirac cone with an energy gap of 2 meV
is formed right below the bottom-surface Dirac point, while for 3 QLs, there is
no additional Dirac cone. We also examine the spin-orbital texture of the Dirac
surface states with broken inversion symmetry, using DFT and the effective
model. We find that the $p_z$ orbital is coupled to the $z$ component of the
spin moment in the opposite sign to the $p_x$ and $p_y$ orbitals. The $p_z$ and
radial $p$ orbitals are coupled to the in-plane spin texture in the opposite
handedness to the tangential $p$ orbital. The result obtained from the
effective model agrees with our DFT calculations. The calculated spin-orbital
texture may be tested from spin-polarized angle-resolved photoemission
spectroscopy.",1407.6268v1
2013-01-21,"Interatomic potentials, electric properties, and spectroscopy of the ground and excited states of the Rb_2 molecule: Ab initio calculations and effect of a non-resonant field","We formulate the theory for a diatomic molecule in a spatially degenerate
electronic state interacting with a non-resonant laser field and investigate
its rovibrational structure in the presence of the field. We report on
\textit{ab initio} calculations employing the double electron attachment
intermediate Hamiltonian Fock space coupled cluster method restricted to single
and double excitations for all electronic states of the Rb$_2$ molecule up to
$5s+5d$ dissociation limit of about 26.000$\,$cm$^{-1}$. In order to correctly
predict the spectroscopic behavior of Rb$_2$, we have also calculated the
electric transition dipole moments, non-adiabatic coupling and spin-orbit
coupling matrix elements, and static dipole polarizabilities, using the
multireference configuration interaction method. When a molecule is exposed to
strong non-resonant light, its rovibrational levels get hybridized. We study
the spectroscopic signatures of this effect for transitions between the
X$^1\Sigma_g^+$ electronic ground state and the A$^1\Sigma_u^+$ and b$^3\Pi_u$
excited state manifold. The latter is characterized by strong perturbations due
to the spin-orbit interaction. We find that for non-resonant field strengths of
the order $10^9$W/cm$^2$, the spin-orbit interaction and coupling to the
non-resonant field become comparable. The non-resonant field can then be used
to control the singlet-triplet character of a rovibrational level.",1301.4966v2
2013-11-04,Interplay of many-body and single-particle interactions in iridates and rhodates,"Motivated by recent experiments exploring the spin-orbit-coupled magnetism in
$4d$- and $5d$-band transition metal oxides, we study magnetic interactions in
Ir- and Rh-based compounds. In these systems, the comparable strength of
spin-orbit coupling (SOC), crystal field splitting (CF) and Coulomb and Hund's
coupling leads to a rich variety of magnetic exchange interactions, leading to
new types of ground states. Using a strong coupling approach, we derive
effective low-energy super-exchange Hamiltonians from the multi-orbital Hubbard
model by taking full account of the Coulomb and Hund's interactions in the
intermediate states. We find that in the presence of strong SOC and lattice
distortions the super-exchange Hamiltonian contains various kinds of magnetic
anisotropies.
  Here we are primarily interested in the magnetic properties of Sr$_2$IrO$_4$
and Sr$_2$Ir$_{1-x}$Rh$_x$O$_4$ compounds. We perform a systematic study of how
magnetic interactions in these systems depend on the microscopic parameters and
provide a thorough analysis of the resulting magnetic phase diagram. Comparison
of our results with experimental data shows good agreement. Finally, we discuss
the parameter space in which the spin-flop transition in Sr$_2$IrO$_4$,
experimentally observed under pressure, can be realized.",1311.0852v2
2014-07-19,Supersymmetry in quantum optics and in spin-orbit coupled systems,"Light-matter interaction is naturally described by coupled bosonic and
fermionic subsystems. This suggests that a certain Bose-Fermi duality is
naturally present in the fundamental quantum mechanical description of photons
interacting with atoms. We reveal submanifolds in parameter space of a basic
light-matter interacting system where this duality is promoted to a
supersymmetry (SUSY) which remains unbroken. We show that SUSY is robust with
respect to decoherence and dissipation. In particular, a stationary density
matrix at the supersymmetric lines in the parameter space has a degenerate
subspace. A dimension of this subspace is given by the Witten index and thus
topologically protected. As a consequence of this SUSY, dissipative dynamics at
the supersymmetric lines is constrained by an additional conserved quantity
which translates some part of information about an initial state into the
stationary state subspace. We also demonstrate a robustness of this additional
conserved quantity away from the supersymmetric lines. In addition, we
demonstrate that the same SUSY structures are present in condensed matter
systems with spin-orbit couplings of Rashba and Dresselhaus types, and
therefore spin-orbit coupled systems at the SUSY lines should be robust with
respect to various types of disorder and decoherences. Our findings suggest
that optical and condensed matter systems at the SUSY points can be used for
quantum information technology and can open an avenue for quantum simulation of
the SUSY field theories.",1407.5213v1
2015-05-04,Mixing of 0$^+$ and 0$^-$ observed in hyperfine and Zeeman structure of ultracold Rb$_2$ molecules,"We study the combination of hyperfine and Zeeman structure in the spin-orbit
coupled $A^1\Sigma_u^+-b^3\Pi_u$ complex of $^{87}\textrm{Rb}_2$. For this
purpose, absorption spectroscopy at a magnetic field around
$B=1000\:\textrm{G}$ is carried out. We drive optical dipole transitions from
the lowest rotational state of an ultracold Feshbach molecule to various
vibrational levels with $0^+$ symmetry of the $A-b$ complex. In contrast to
previous measurements with rotationally excited alkali-dimers, we do not
observe equal spacings of the hyperfine levels. In addition, the spectra vary
substantially for different vibrational quantum numbers, and exhibit large
splittings of up to $160\:\textrm{MHz}$, unexpected for $0^+$ states. The level
structure is explained to be a result of the repulsion between the states $0^+$
and $0^-$ of $b^3\Pi_u$, coupled via hyperfine and Zeeman interactions. In
general, $0^-$ and $0^+$ have a spin-orbit induced energy spacing $\Delta$,
that is different for the individual vibrational states. From each measured
spectrum we are able to extract $\Delta$, which otherwise is not easily
accessible in conventional spectroscopy schemes. We obtain values of $\Delta$
in the range of $\pm 100\:\textrm{GHz}$ which can be described by coupled
channel calculations if a spin-orbit coupling is introduced that is different
for $0^-$ and $0^+$ of $b^3\Pi_u$.",1505.00682v2
2018-05-07,Theory of electronic magnetoelectric coupling in $d^5$ Mott insulators,"Motivated by recent terahertz (THz) spectroscopy measurements in
$\alpha$-RuCl$_3$, we develop a theory for magnetoelectric (ME) effects in Mott
insulators of $d^5$ transition metal ions in an octahedral crystal field. For
$4d$ and $5d$ compounds, the relatively wide-spread orbitals favor charge
fluctuations of localized electrons to neighboring ions and a significant ME
effect from electronic mechanisms is expected. From a three-orbital Hubbard
model with strong spin-orbit coupling, we derive the mechanisms for the
electric polarization originating from virtual hopping of the localized holes
carrying the spins. We consider the electric polarization generated by pairs of
spin operators on nearest neighbor bonds with either an edge-sharing geometry
(i.e., two ligands are shared) or a corner-sharing geometry (i.e., one ligand
is shared). The allowed couplings are first derived using a symmetry approach.
Then, we explicitly calculate the coupling constants and evaluate the effective
polarization operator in the ground state manifold using perturbation theory
and exact diagonalization. The results are relevant when considering the THz
optical conductivity of magnetic systems such as some perovskite iridates or
Kitaev materials. In particular, they help explain the recent THz optical
measurements of $\alpha$-RuCl$_{3}$ for which the electric-dipole-induced
contribution has been shown to be strong.",1805.02488v2
2018-05-24,Antiferromagnetically assisted electron-phonon coupling and spin-lattice interaction in Fe-based superconductors,"We present a theoretical ab-initio approach that allows us to explicitly
calculate the superconducting transition temperatures (Tc) of the iron-based
superconductors of LaFeAsO1-xFx, SmFeAsO1-xFx, NdFeAsO1-xFx, Ba1-xKxFe2As2,
FeSe and LiFeAs that fit perfectly with the experiments. We consider recent
evidence that electron-phonon coupling may have been underestimated previously,
and a prediction that antiferromagnetism can greatly enhance electron-phonon
coupling through localized iron d orbitals. We then include the contribution of
these localized orbitals in a McMillan formalism. In addition, we take into
account the spin-lattice interaction between the spin-polarized electrons at
the Fermi surface and the iron orbitals in combination with a modified exchange
Hamiltonian involving a ferrimagnetic coupling between Fe and As. With this
approach we can accurately calculate the Tc of FeSe (11 family), LiFeAs (111
family), LaFeAsO0.9F0.1 (1111 family) and BaFe2As2 (122 family) as a function
of pressure. In addition, we also obtain the correct doping dependence of Tc of
LaFeAsO0.9F0.1 (1111 family) and BaFe2As2 (122 family).",1805.09754v5
2020-04-27,Soft and anisotropic local moments in 4$d$ and 5$d$ mixed-valence M$_2$O$_9$ dimers,"We investigate via exact diagonalization of finite clusters the electronic
structure and magnetism of M$_2$O$_9$ dimers in the mixed-valence hexagonal
perovskites A$_3$B'M$_2$O$_9$ for various different fillings of 4$d$ and 5$d$
transition-metal M ions. We find that the magnetic moments of such dimers are
determined by a subtle interplay of spin-orbit coupling, Hund's coupling, and
Coulomb repulsion, as well as the electron filling of the M ions. Most
importantly, the magnetic moments are anisotropic and temperature-dependent.
This behavior is a result of spin-orbit coupling, magnetic field effects, and
the existence of several nearly-degenerate electronic configurations whose
proximity allows occupation of excited states already at room temperature. This
analysis is consistent with experimental susceptibility measurements for a
variety of dimer-based materials. Furthermore, we perform a survey of
A$_3$B'M$_2$O$_9$ materials and propose ground-state phase diagrams for the
experimentally relevant M fillings of $d^{4.5}$, $d^{3.5}$ and $d^{2.5}$.
Finally, our results show that the usually applied Curie-Weiss law with a
constant magnetic moment cannot be used in these spin-orbit-coupled materials.",2004.13050v1
2018-06-16,Observation of quantum phase transition in spin-orbital-angular-momentum coupled Bose-Einstein condensate,"Orbital angular momentum (OAM) of light represents a fundamental optical
freedom that can be exploited to manipulate quantum state of atoms. In
particular, it can be used to realize spin-orbital-angular-momentum (SOAM)
coupling in cold atoms by inducing an atomic Raman transition using two laser
beams with differing OAM. Rich quantum phases are predicted to exist in
many-body systems with SOAM coupling. Their observations in laboratory,
however, are often hampered by the limited control of the system parameters. In
this work we report, for the first time, the experimental observation of the
ground-state quantum phase diagram of the SOAM coupled Bose-Einstein condensate
(BEC). The discontinuous variation of the spin polarization as well as the
vorticity of the atomic wave function across the phase boundaries provides
clear evidence of first-order phase transitions. Our results open up a new way
to the study of phase transitions and exotic quantum phases in quantum gases.",1806.06263v2
2020-06-04,Contribution of the rho meson and quark sub-structure to the nuclear spin-orbit potential,"The microscopic origin of the spin-orbit (SO) potential in terms of
sub-baryonic degrees of freedom is explored and discussed for application to
nuclei and hyper-nuclei. We thus develop a chiral relativistic approach where
the coupling to the scalar- and vector-meson fields are controlled by the quark
substructure. This approach suggests that the isoscalar and isovector density
dependence of the SO potential can be used to test the microscopic ingredients
which are implemented in the relativistic framework: the quark substructure of
the nucleon in its ground-state and its coupling to the rich meson sector where
the $\rho$ meson plays a crucial role. This is also in line with the Vector
Dominance Model (VDM) phenomenology and the known magnetic properties of the
nucleons. We explore predictions based on Hartree and Hartree-Fock mean field,
as well as various scenarios for the $\rho$-nucleon coupling, ranked as weak,
medium and strong, which impacts the isoscalar and isovector density dependence
of the SO potential. We show that a medium to strong $\rho$ coupling is
essential to reproduce Skyrme phenomenology in $N=Z$ nuclei as well as its
isovector dependence. Assuming an SU(6) valence quark model our approach is
extended to hyperons and furnishes a microscopic understanding of the quenching
of the $N\Lambda$ spin-orbit potential in hyper-nuclei. It is also applied to
other hyperons, such as $\Sigma$, $\Xi$ and $\Omega$.",2006.02698v2
2021-10-15,Ground state of Ce$_{3}$Bi$_{4}$Pd$_{3}$ unraveled by hydrostatic pressure,"Noncentrosymmetric Ce$_{3}$Bi$_{4}$Pd$_{3}$ has attracted a lot of attention
as a candidate for strongly correlated topological material, yet its
experimental ground state remains a matter of contention. Two conflicting
scenarios have emerged from a comparison to prototypical Kondo insulator
Ce$_{3}$Bi$_{4}$Pt$_{3}$: either Ce$_{3}$Bi$_{4}$Pd$_{3}$ is a
spin-orbit-driven topological semimetal or a Kondo insulator with smaller Kondo
coupling than its Pt counterpart. Here we determine the ground state of
Ce$_{3}$Bi$_{4}$Pd$_{3}$ via electrical resistivity measurements under
hydrostatic pressure, which is a clean symmetry-preserving tuning parameter
that increases hybridization but virtually preserves spin-orbit coupling.
Ce$_{3}$Bi$_{4}$Pd$_{3}$ becomes more insulating under pressure, which is a
signature of Ce-based Kondo insulating materials. Its small zero-pressure gap
increases quadratically with pressure, similar to the behavior observed in the
series Ce$_{3}$Bi$_{4}$(Pt$_{1-x}$Pd$_{x}$)$_{3}$, which indicates that Pt
substitution and applied pressure have a similar effect. Our result not only
demonstrates that Kondo coupling, rather than spin-orbit coupling, is the main
tuning parameter in this class of materials, but it also establishes that
Ce$_{3}$Bi$_{4}$Pd$_{3}$ has a narrow-gap Kondo insulating ground state.",2110.08230v1
2022-10-13,Spin-orbit coupling controlling the superconducting dome of artificial superlattices of quantum wells,"While it is known that a resonant amplification of Tc in two-gap
superconductors can be driven by using the Fano-Feshbach resonance tuning the
chemical potential near a Lifshitz transition, little is known on tuning the Tc
resonance by cooperative interplay of the Rashba spin-orbit coupling (RSOC)
joint with phonon mediated (e-ph) pairing at selected k-space spots. Here we
present first-principles quantum calculation of superconductivity in an
artificial heterostructure of metallic quantum wells with 3 nm period where
quantum size effects give two-gap superconductivity with RSOC controlled by the
internal electric field at the interface between the nanoscale metallic layers
intercalated by insulating spacer layers. The key results of this work show
that fundamental quantum mechanics effects including RSCO at the nanoscale
(Mazziotti et al Phys. Rev. B, 103, 024523, 2021) provide key tools in applied
physics for quantitative material design of unconventional high temperature
superconductors at ambient pressure. We discuss the superconducting domes where
Tc is a function of either the Lifshitz parameter (?) measuring the distance
from the topological Lifshitz transition for the appearing of a new small Fermi
surface due to quantum size effects with finite spin-orbit coupling and the
variable e-ph coupling g in the appearing second Fermi surface linked with the
softening of the phonon energy cut off.",2211.11547v1
2015-04-15,Proposed method to realize the $p$-wave superfluid state using a $s$-wave superfluid Fermi gas with a synthetic spin-orbit interaction,"We theoretically propose an idea to reach the $p$-wave superfluid phase in an
ultracold Fermi gas. The key of our idea is that the pairing symmetry of a
Fermi superfluid is fully dominated by the symmetry of the superfluid order
parameter, which is essentially given by the product of a pair amplitude and a
pairing interaction. Noting this, in our proposal, we first prepare a $p$-wave
pair amplitude by, not using a $p$-wave interaction, but using the phenomenon
that a $p$-wave pair amplitude is induced in an $s$-wave superfluid Fermi gas
with antisymmetric spin-orbit interaction. In this case, although the system is
still in the $s$-wave superfluid state with the $s$-wave superfluid order
parameter, when one suddenly replaces the $s$-wave interaction by an
appropriate $p$-wave one (which is possible in cold Fermi gases by using a
Feshbach resonance technique), the product of the $p$-wave interaction and the
$p$-wave pair amplitude that has already been prepared in the spin-orbit
coupled $s$-wave superfluid state immediately gives a finite $p$-wave
superfluid order parameter. Thus, at least just after this manipulation, the
system is in the $p$-wave superfluid state, being characterized by the
artificially produced $p$-wave superfluid parameter. In this paper, to assess
our idea, we evaluate the $p$-wave pair amplitude in a spin-orbit coupled
$s$-wave superfluid Fermi gas at $T=0$. We determine the region where a large
$p$-wave pair amplitude is obtained in the phase diagram with respect to the
strengths of the $s$-wave pairing interaction and the spin-orbit coupling. We
also discuss the accessibility of this optimal region on the viewpoint of the
superfluid phase transition temperature. Since the achievement of a $p$-wave
superfluid Fermi gas is one of the most crucial issues in cold atom physics,
our proposal would be useful for this exciting challenge.",1504.03835v1
2016-02-01,$π$ Spin Berry Phase in a Quantum-Spin-Hall-Insulator-Based Interferometer: Evidence for the Helical Spin Texture of the Edge States,"Quantum spin Hall insulator is characterized by the helical edge states, with
the spin polarization of electron being locked to its direction of motion.
Although the edge-state conduction has been observed, unambiguous evidence of
the helical spin texture is still lacking. Here, we investigate the coherent
edge-state transport in an interference loop pinched by two point contacts. Due
to the helical character, the forward inter-edge scattering enforces a $\pi$
spin rotation. Two successive processes can only produce a nontrivial $2\pi$ or
trivial $0$ spin rotation, which can be controlled by the Rashba spin-orbit
coupling. The nontrivial spin rotation results in a geometric $\pi$ Berry
phase, which can be detected by a $\pi$ phase shift of the conductance
oscillation relative to the trivial case. Our results provide a smoking gun
evidence for the helical spin texture of the edge states. Moreover, it also
provides the opportunity to all-electrically explore the trajectory-dependent
spin Berry phase in condensed matter.",1602.00497v2
2019-10-29,Origin of the Magnetic Spin Hall Effect: Spin Current Vorticity in the Fermi Sea,"The interplay of spin-orbit coupling (SOC) and magnetism gives rise to a
plethora of charge-to-spin conversion phenomena that harbor great potential for
spintronics applications. In addition to the spin Hall effect, magnets may
exhibit a magnetic spin Hall effect (MSHE), as was recently discovered [Kimata
\textit{et al.}, Nature \textbf{565}, 627-630 (2019)]. To date, the MSHE is
still awaiting its intuitive explanation. Here we relate the MSHE to the
vorticity of spin currents in the Fermi sea, which explains pictorially the
origin of the MSHE. For all magnetic Laue groups that allow for nonzero spin
current vorticities the related tensor elements of the MSH conductivity are
given. Minimal requirements for the occurrence of a MSHE are compatibility with
either a magnetization or a magnetic toroidal quadrupole. This finding implies
in particular that the MSHE is expected in all ferromagnets with sufficiently
large SOC. To substantiate our symmetry analysis, we present various models, in
particular a two-dimensional magnetized Rashba electron gas, that corroborate
an interpretation by means of spin current vortices. Considering thermally
induced spin transport and the magnetic spin Nernst effect in magnetic
insulators, which are brought about by magnons, our findings for electron
transport can be carried over to the realm of spincaloritronics, heat-to-spin
conversion, and energy harvesting.",1910.13375v1
2020-04-11,Understanding the mechanism of oxygen evolution reaction (OER) with the consideration of spin,"Oxygen evolution reaction (OER) with intractable high overpotential is the
rate-limiting step for rechargeable metal-air battery, water electrolysis
systems, and solar fuels devices. There exists a spin state transition from
spin singlet OH-/H2O reactant to spin triplet O2 product, which has not
received enough attention yet. In this perspective, we attempt to retrospect
electron behaviours during the whole OER process, with the consideration of
spin attribute. Regardless of the adopted mechanisms by different
electrocatalysts, for example, adsorbate evolution mechanism (AEM) or lattice
oxygen mechanism (LOM), the underlying rationale is that active sites have to
extract three in four electrons with the same spin direction before the
formation of O=O. This spin-sensitive nature of OER superimposes additional
high requirements on the electrocatalysts, especially on the spin structure, to
compliment the fast electron transfer in the interface with spin selection and
smoothly delivery afterwards. When optimizing the geometric and electronic
structures catering for the spin-sensitive OER, awareness of the couplings
between spin, charge, orbital and lattice is necessary. Some spin-correlated
physical properties, such as (1) crystal field, (2) coordination, (3)
oxidation, (4) bonding, (5) eg electron number, (6) conductivity and (7)
magnetism, are also discussed briefly. It is hoped that our perspective could
shed lights on the underlying physics of the slow kinetics of OER, providing a
rational guidance for more effective energy conversion electrocatalysts
designs.",2004.05326v1
2018-08-02,Temperature and electric field dependence of spin relaxation in graphene on SrTiO$_3$,"The theoretically predicted intrinsic spin relaxation time of up to 1 $\mu s$
in graphene along with extremely high mobilities makes it a promising material
in spintronics. In spite of extensive experimental studies of spin relaxation
and understanding of its precise mechanism, it is still unclear as to why the
spin lifetime in graphene is three orders of magnitude below the theoretical
predictions. Central to this discrepancy is the role of the local environment
including that of the underlying substrate. In this work, we use the
electronically rich platform SrTiO$_3$ and study its suitability in supporting
spin transport in graphene. We find spin relaxation time and length as large as
1.2 $\pm$ 0.1 ns and 5.6 $\pm$ 0.5 $\mu m$ respectively at 290 K in graphene on
SrTiO$_3$ using a non-local measurement scheme. We analyze the temperature
variation of the spin transport parameters in graphene and attribute the
temperature dependence of the spin transport parameters in graphene to spin
orbit coupling or structural phase transition in SrTiO$_3$. Furthermore, from
the gate dependence of the spin transport parameters, the relation between spin
relaxation time and momentum relaxation time is extracted; the Elliot-Yaffet
and D'Yakonov-Perel' spin relaxation rates are found to be of similar order.",1808.00832v2
2019-11-15,Strain-induced spin-nematic state and nematic susceptibility arising from $2\times2$ Fe clusters in KFe$_{0.8}$Ag$_{1.2}$Te$_2$,"Spin nematics break spin-rotational symmetry while maintaining time-reversal
symmetry, analogous to liquid crystal nematics that break spatial rotational
symmetry while maintaining translational symmetry. Although several candidate
spin nematics have been proposed, the identification and characterization of
such a state remain challenging because the spin-nematic order parameter does
not couple directly to experimental probes. KFe$_{0.8}$Ag$_{1.2}$Te$_2$
(K$_5$Fe$_4$Ag$_6$Te$_{10}$, KFAT) is a local-moment magnet consisting of
well-separated 2$\times$2 Fe clusters, and in its ground state the clusters
order magnetically, breaking both spin-rotational and time-reversal symmetries.
Using uniform magnetic susceptibility and neutron scattering measurements we
find a small strain induces sizable spin anisotropy in the paramagnetic state
of KFAT, manifestly breaking spin-rotational symmetry while retaining
time-reversal symmetry, resulting in a strain-induced spin-nematic state in
which the $2\times2$ clusters act as the spin analogue of molecules in a liquid
crystal nematic. The strain-induced spin anisotropy in KFAT allows us to probe
its nematic susceptibility, revealing a divergent-like increase upon cooling,
indicating the ordered ground state is driven by a spin-orbital entangled
nematic order parameter.",1911.06492v1
2020-11-05,Nanophotonic structures with optical surface modes for tunable spin current generation,"Heat generated by spin currents in spintronics-based devices is typically
much less than that generated by charge current flows in conventional
electronic devices. However, the conventional approaches for excitation of spin
currents based on spin-pumping and spin Hall effect are limited in efficiency
which restricts their application for viable spintronic devices. We propose a
novel type of photonic-crystal (PC) based structures for efficient and tunable
optically-induced spin current generation via the Spin Seebeck and inverse spin
Hall effects. It is experimentally demonstrated that optical surface modes
localized at the PC surface covered by ferromagnetic layer and materials with
giant spin-orbit coupling (SOC) notably increase the efficiency of the
optically-induced spin current generation and provides its tunability by
modifying light wavelength or angle of incidence. Up to 100% of the incident
light power can be transferred to heat within the SOC layer and, therefore, to
spin current. Importantly, high efficiency becomes accessible even for
ultra-thin SOC layers. Moreover, surface patterning of the PC-based spintronic
nanostructure allows local generation of spin currents at the pattern scales
rather than diameter of the laser beam.",2011.02770v2
2021-02-23,Highly persistent spin textures with giant tunable spin splitting in the two-dimensional germanium monochalcogenides,"The ability to control the spin textures in semiconductors is a fundamental
step toward novel spintronic devices, while seeking desirable materials
exhibiting persistent spin texture (PST) remains a key challenge. The PST is
the property of materials preserving a unidirectional spin orientation in the
momentum space, which has been predicted to support an extraordinarily long
spin lifetime of carriers. Herein, by using first-principles density functional
theory calculations, we report the emergence of the PST in the two-dimensional
(2D) germanium monochalcogenides (GeMC). By considering two stable formations
of the 2D GeMC, namely the pure GeX and Janus Ge2XY monolayers (X, Y = S, Se,
and Te), we observed the PST around the valence band maximum where the spin
orientation is enforced by the lower point group symmetry of the crystal. In
the case of the pure GeX monolayers, we found that the PST is characterized by
fully out-of-plane spin orientation protected by C2v point group, while the
canted PST in the y-z plane is observed in the case of the Janus Ge2XY
monolayers due to the lowering symmetry into Cs point group. More importantly,
we find large spin-orbit coupling (SOC) parameter in which the PST sustains,
which could be effectively tuned by in-plane strain. The large SOC parameter
observed in the present systems leads to the small wavelength of the spatially
periodic mode of the spin polarization, which is promising for short spin
channel in the spin Hall transistor devices.",2102.11618v2
2022-06-21,Anisotropic spin Hall and spin Nernst effects in bismuth semimetal,"Bismuth is an archetypal semimetal with gigantic spin-orbit coupling and it
has been a major source material for the discovery of seminal phenomena in
solid state physics for more than a century. In recent years, spin current
transports in bismuth have also attracted considerable attention. In this
paper, we theoretically study both spin Hall effect (SHE) and spin Nernst
effect (SNE) in bismuth, based on relativistic band structure calculations.
First, we find that there are three independent tensor elements of spin Hall
conductivity (SHC) and spin Nernst conductivity (SNC), namely, $Z_{yx}^z$,
$Z_{xz}^y$, and $Z_{zy}^x$. We calculate all the elements as a function of the
Fermi energy. Second, we find that all SHC tensor elements are large, being
$\sim$1000 ($\hbar$/e)(S/cm) and comparable to that of platinum. Furthermore,
because of its low electrical conductivity, the corresponding spin Hall angles
are gigantic, being $\sim$20%. Third, all the calculated SNC tensor elements
are also pronounced, being comparable to that [$\sim$0.13 ($\hbar$/e)(A/m-K)]
of gold, although they are several times smaller than platinum and $\beta$-Ta.
Finally, in contrast to Pt and Au where $Z_{yx}^z = Z_{xz}^y = Z_{zy}^x$, the
SHE and SNE in bismuth are strongly anisotropic, i.e., $Z_{yx}^z$, $Z_{xz}^y$
and $Z_{zy}^x$ differ significantly. Consequently, the Hall voltages due to the
inverse SHE and SNE from the different conductivity elements could cancel each
other and thus result in a small spin Hall angle if polycrystalline samples are
used, which may explain why the measured spin Hall angles ranging from nearly 0
to 25% have been reported. We hope that these interesting findings would
stimulate further spin current experiments on bismuth using highly oriented
single crystal specimens.",2206.10149v2
2022-06-22,Chirality and Rashba-related effects in the spin texture of a 2D centro-symmetric ferromagnet: the case of CrI3 bilayer,"The newly discovered two-dimensional magnetic semiconductors such as CrI$_3$
have triggered a surge of interest stemming from their exotic spin-dependent
properties and potential applications in spintronics and
magneto-optoelectronics. Using first-principle density-functional-theory
calculations, we investigate the properties of the spin-polarization texture in
momentum space in the prototype 2D centrosymmetric ferromagnetic (FM) bilayer
of CrI$_3$, with perpendicular magnetization. The FM bilayer displays a rich
in-plane spin texture in its highest valence bands. We show the existence of
two distinct spin canting effects, which result from the coupling of FM order
with structural chirality and electric polarization, in establishing the
in-plane spin texture. The first effect is generated by the chirality of the
layer stacking and the spin-orbit-polarized nature of the valence states, and
yields the same canting on both layers. The second effect is a Rashba-related
effect, which in a centrosymmetric ferromagnet induces in a single electronic
state two opposite spin-canted components on the two layers. Furthermore, using
the FM bilayer as an example, we provide general rules imposed by
magnetic-space-group symmetries on spin-polarization vectors, serving as
guidelines for the shape of the spin texture in the Brillouin zone of magnetic
crystals. Finally, we show that the above effects can be effectively used to
manipulate the spin texture via compressive strain, which induces in the FM
bilayer valence-band-edge states with canted spins.",2206.10777v2
2022-07-06,Local Symmetry Breaking Drives Picosecond Spin Domain Formation in Polycrystalline Semiconducting Films,"Photoinduced spin-charge interconversion in semiconductors with spin-orbit
coupling could provide a route to optically addressable spintronics without the
use of external magnetic fields. A central question is whether the resulting
spin-associated charge currents are robust to structural disorder, which is
inherent to polycrystalline semiconductors that are desirable for device
applications. Using femtosecond circular polarization-resolved pump-probe
microscopy on polycrystalline halide perovskite thin films, we observe the
photoinduced ultrafast formation of spin-polarized positive and, unexpectedly,
negative spin domains on the micron scale formed through lateral currents.
Further, the polarization of these domains and lateral transport direction is
switched upon switching the polarization of the pump helicity. Micron scale
variations in the intensity of optical second-harmonic generation and vertical
piezoresponse suggest that the spin domain formation is driven by the presence
of strong local inversion symmetry breaking via inter-grain structural
disorder. We propose that this leads to spatially varying Rashba-like spin
textures that drive spin-momentum locked currents, leading to local spin
accumulation. Our results establish ultrafast spin domain formation in
polycrystalline semiconductors as a new optically addressable platform for
nanoscale spin-device physics.",2207.02765v1
2023-05-02,Gate-tunable spin Hall effect in an all-light-element heterostructure: graphene with copper oxide,"Graphene is a light material for long-distance spin transport due to its low
spin-orbit coupling, which at the same time is the main drawback to exhibit a
sizeable spin Hall effect. Decoration by light atoms has been predicted to
enhance the spin Hall angle in graphene while retaining a long spin diffusion
length. Here, we combine a light metal oxide (oxidized Cu) with graphene to
induce the spin Hall effect. Its efficiency, given by the product of the spin
Hall angle and the spin diffusion length, can be tuned with the Fermi level
position, exhibiting a maximum (1.8 $\pm$ 0.6 nm at 100 K) around the charge
neutrality point. This all-light-element heterostructure shows a larger
efficiency than conventional spin Hall materials. The gate-tunable spin Hall
effect is observed up to room temperature. Our experimental demonstration
provides an efficient spin-to-charge conversion system free from heavy metals
and compatible with large-scale fabrication.",2305.01787v2
2023-09-07,Coherent spin dynamics between electron and nucleus within a single atom,"The nuclear spin, being much more isolated from the environment than its
electronic counterpart, enables quantum experiments with prolonged coherence
times and presents a gateway towards uncovering the intricate dynamics within
an atom. These qualities have been demonstrated in a variety of nuclear spin
qubit architectures, albeit with limited control over the direct environment of
the nuclei. As a contrasting approach, the combination of electron spin
resonance (ESR) and scanning tunnelling microscopy (STM) provides a bottom-up
platform to study the fundamental properties of nuclear spins of single atoms
on a surface. However, access to the time evolution of these nuclear spins, as
was recently demonstrated for electron spins, remained a challenge. Here, we
present an experiment resolving the nanosecond coherent dynamics of a
hyperfine-driven flip-flop interaction between the spin of an individual
nucleus and that of an orbiting electron. We use the unique local
controllability of the magnetic field emanating from the STM probe tip to bring
the electron and nuclear spins in tune, as evidenced by a set of avoided level
crossings in ESR-STM. Subsequently, we polarize both spins through scattering
of tunnelling electrons and measure the resulting free evolution of the coupled
spin system using a DC pump-probe scheme. The latter reveals a complex pattern
of multiple interfering coherent oscillations, providing unique insight into
the atom's hyperfine physics. The ability to trace the coherent hyperfine
dynamics with atomic-scale structural control adds a new dimension to the study
of on-surface spins, offering a pathway towards dynamic quantum simulation of
low-dimensional magnonics.",2309.03749v1
2023-11-22,Isotropic spin and inverse spin Hall effect in epitaxial (111)-oriented Pt/Co bilayers,"The spin-to-charge current interconversion in bilayers composed of
ferromagnetic and nonmagnetic layers with strong spin-orbit coupling has
garnered considerable attention due to its exceptional potential in advancing
spintronics devices for data storage and logic applications. Platinum (Pt)
stands out as one of the most effective materials for generating spin current.
While the spin conversion efficiency is isotropic in polycrystalline Pt
samples, an ongoing debate persists regarding its dependence on the crystalline
direction in single crystalline samples. In this study, we aim to
comprehensively evaluate the in-plane anisotropy of spin-charge interconversion
using an array of complementary Spin Hall and inverse Spin Hall techniques with
both incoherent and coherent excitation. Specifically, we investigate the
spin-to-charge interconversion in epitaxial, (111)-oriented, Co/Pt bilayers
with low surface roughness, as resulted from x-ray experiments. By varying the
thickness of the Pt layer, we gain insights into the spin-charge
interconversion in epitaxial Pt and highlight the effects of the interfaces.
Our results demonstrate an isotropic behavior within the limits of our
detection uncertainty. This finding significantly enhances our understanding of
spin conversion in one of the most relevant systems in spintronics and paves
the way for future research in this field.",2311.13400v1
2023-10-12,Extreme mass-ratio inspiral and waveforms for a spinning body into a Kerr black hole via osculating geodesics and near-identity transformations,"Understanding the orbits of spinning bodies in curved spacetime is important
for modeling binary black hole systems with small mass ratios. At zeroth order
in mass ratio, the smaller body moves on a geodesic. Post-geodesic effects are
needed to model the system accurately. One very important post-geodesic effect
is the gravitational self-force, which describes the small body's interaction
with its own contribution to a binary's spacetime. Another post-geodesic
effect, the spin-curvature force, is due to the smaller body's spin coupling to
spacetime curvature. In this paper, we combine the leading orbit-averaged
backreaction of point-particle gravitational-wave emission with the
spin-curvature force to construct the worldline and gravitational waveform for
a spinning body spiraling into a Kerr black hole. We use an osculating geodesic
integrator, which treats the worldline as evolution through a sequence of
geodesic orbits, as well as near-identity transformations, which eliminate
dependence on orbital phases, allowing for fast computation of inspirals. The
resulting inspirals and waveforms include all critical dynamical effects which
govern such systems (orbit and precession frequencies, inspiral, strong-field
gravitational-wave amplitudes), and as such form an effective first model for
the inspiral of spinning bodies into Kerr black holes. We emphasize that our
present calculation is not self consistent, since we neglect effects which
enter at the same order as effects we include. However, our analysis
demonstrates that the impact of spin-curvature forces can be incorporated into
EMRI waveform tools with relative ease. The calculation is sufficiently modular
that it should not be difficult to include neglected post-geodesic effects as
efficient tools for computing them become available. (Abridged)",2310.08438v1
2018-08-29,Fast spin exchange between two distant quantum dots,"The Heisenberg exchange interaction between neighboring quantum dots allows
precise voltage control over spin dynamics, due to the ability to precisely
control the overlap of orbital wavefunctions by gate electrodes. This allows
the study of fundamental electronic phenomena and finds applications in quantum
information processing. Although spin-based quantum circuits based on
short-range exchange interactions are possible, the development of scalable,
longer-range coupling schemes constitutes a critical challenge within the
spin-qubit community. Approaches based on capacitative coupling and
cavity-mediated interactions effectively couple spin qubits to the charge
degree of freedom, making them susceptible to electrically-induced decoherence.
The alternative is to extend the range of the Heisenberg exchange interaction
by means of a quantum mediator. Here, we show that a multielectron quantum dot
with 50-100 electrons serves as an excellent mediator, preserving speed and
coherence of the resulting spin-spin coupling while providing several
functionalities that are of practical importance. These include speed (mediated
two-qubit rates up to several gigahertz), distance (of order of a micrometer),
voltage control, possibility of sweet spot operation (reducing susceptibility
to charge noise), and reversal of the interaction sign (useful for dynamical
decoupling from noise).",1808.09736v1
2007-06-01,Strongly modulated transmission of a spin-split quantum wire with local Rashba interaction,"We investigate the transport properties of ballistic quantum wires in the
presence of Zeeman spin splittings and a spatially inhomogeneous Rashba
interaction. The Zeeman interaction is extended along the wire and produces
gaps in the energy spectrum which allow electron propagation only for spinors
lying along a certain direction. For spins in the opposite direction the waves
are evanescent far away from the Rashba region, which plays the role of the
scattering center. The most interesting case occurs when the magnetic field is
perpendicular to the Rashba field. Then, the spins of the asymptotic
wavefunctions are not eigenfunctions of the Rashba Hamiltonian and the
resulting coupling between spins in the Rashba region gives rise to sudden
changes of the transmission probability when the Fermi energy is swept along
the gap. After briefly examining the energy spectrum and eigenfunctions of a
wire with extended Rashba coupling, we analyze the transmission through a
region of localized Rashba interaction, in which a double interface separates a
region of constant Rashba interaction from wire leads free from spin-orbit
coupling. For energies slightly above the propagation threshold, we find the
ubiquitous occurrence of transmission zeros (antiresonances) which are analyzed
by matching methods in the one-dimensional limit. We find that a a minimal
tight-binding model yields analytical transmission lineshapes of Fano
antiresonance type. More general angular dependences of the external magnetic
field is treated within projected Schroedinger equations with Hamiltonian
matrix elements mixing wavefunction components. Finally, we consider a
realistic quantum wire where the energy subbands are coupled via the Rashba
intersubband coupling term and discuss its effect on the transmission zeros.",0706.0107v1
2011-07-22,Dynamical Tides in Eccentric Binaries and Tidally-Excited Stellar Pulsations in KEPLER KOI-54,"Recent observation of the tidally-excited stellar oscillations in the
main-sequence binary KOI-54 by the KEPLER satellite provides a unique
opportunity for studying dynamical tides in eccentric binary systems. We
develop a general theory of tidal excitation of oscillation modes of rotating
binary stars, and apply our theory to tidally excited gravity modes (g-modes)
in KOI-54. The strongest observed oscillations, which occur at 90 and 91 times
the orbital frequency, are likely due to prograde m=2 modes (relative to the
stellar spin axis) locked in resonance with the orbit. The remaining flux
oscillations with frequencies that are integer multiples of the orbital
frequency are likely due to nearly resonant m=0 g-modes; such axisymmetric
modes generate larger flux variations compared to the m=2 modes, assuming that
the spin inclination angle of the star is comparable to the orbital inclination
angle. We examine the process of resonance mode locking under the combined
effects of dynamical tides on the stellar spin and orbit and the intrinsic
stellar spindown. We show that KOI-54 can naturally evolve into a state in
which at least one m=2 mode is locked in resonance with the orbital frequency.
Our analysis provides an explanation for the fact that only oscillations with
frequencies less than 90-100 times the orbital frequency are observed. We have
also found evidence from the published KEPLER result that three-mode nonlinear
coupling occurs in the KOI-54 system. We suggest that such nonlinear mode
coupling may explain the observed oscillations that are not harmonics of the
orbital frequency.",1107.4594v3
2015-01-20,Anomalous High-Energy Waterfall-Like Electronic Structure in 5d Transition Metal Oxide Sr2IrO4 with a Strong Spin-Orbit Coupling,"The layered 5d transition metal oxides like Sr2IrO4 have attracted
significant interest recently due to a number of exotic and new phenomena
induced by the interplay between the spin-orbit coupling, bandwidth W and
on-site Coulomb correlation U. In contrast to a metallic behavior expected from
the Mott-Hubbard model due to more spatially extended 5d orbitals and moderate
U, an insulating ground state has been observed in Sr2IrO4. Such an insulating
behavior can be understood by an effective J_eff=1/2 Mott insulator model by
incorporating both electron correlation and strong spin-orbital coupling,
although its validity remains under debate at present. In particular, Sr2IrO4
exhibits a number of similarities to the high temperature cuprate
superconductors in the crystal structure, electronic structure, magnetic
structure, and even possible high temperature superconductivity. Here we report
a new observation of the anomalous high energy electronic structure in Sr2IrO4.
By taking high-resolution angle-resolved photoemission measurements on Sr2IrO4
over a wide energy range, we have revealed that the high energy electronic
structures show unusual nearly-vertical bands that extend over a large energy
range. Such anomalous high energy behaviors resemble the high energy waterfall
features observed in the cuprate superconductors, adding one more important
similarity between these two systems. While strong electron correlation plays
an important role in producing high energy waterfall features in the cuprate
superconductors, the revelation of the high energy anomalies in Sr2IrO4 points
to a novel route in generating exotic electronic excitations from the strong
spin-orbit coupling and a moderate electron correlation.",1501.04687v1
1997-03-25,Phase Diagram of the Half-Filled Extended Hubbard Model in Two Dimensions,"We consider an extended Hubbard model of interacting fermions on a lattice.
The fermion kinetic energy corresponds to a tight binding Hamiltonian with
nearest neighbour (-t) and next nearest neighbour (t') hopping matrix elements.
In addition to the onsite Hubbard interaction (U) we also consider a nearest
neighbour repulsion (V). We obtain the zero temperature phase diagram of our
model within the Hartree-Fock approximation. We consider ground states having
charge and spin density wave ordering as well as states with orbital
antiferromagnetism or spin nematic order. The latter two states correspond to
particle-hole binding with $d_{x^2-y^2}$ symmetry in the charge and spin
channels respectively. For $t' = 0$, only the charge density wave and spin
density wave states are energetically stable. For non-zero t', we find that
orbital antiferromagnetism (or spin nematic) order is stable over a finite
portion of the phase diagram at weak coupling. This region of stability is seen
to grow with increasing values of t'.",9703213v1
2003-06-16,Gate control of spin dynamics in III-V semiconductor quantum dots,"We show that the g-factor and the spin-flip time T_{1} of a heterojunction
quantum dot is very sensitive to the band-bending interface electric field even
in the absence of wave function penetration into the barrier. When this
electric field is of the order of 10^{5} V/cm, g and T_{1} show high
sensitivity to dot radius and magnetic field arising from the interplay between
Rashba and Dresselhaus spin-orbit interactions. This result opens new
possibilities for the design of a quantum dot spin quantum computer where
g-factor and T_{1} can be engineered by manipulating the spin-orbit coupling
through external gates.",0306417v2
2005-10-15,Coherent single electron spin control in a slanting Zeeman field,"We consider a single electron in a 1D quantum dot with a static slanting
Zeeman field. By combining the spin and orbital degrees of freedom of the
electron, an effective quantum two-level (qubit) system is defined. This
pseudo-spin can be coherently manipulated by the voltage applied to the gate
electrodes, without the need for an external time-dependent magnetic field or
spin-orbit coupling. Single qubit rotations and the C-NOT operation can be
realized. We estimated relaxation ($T_1$) and coherence ($T_{2}$) times, and
the (tunable) quality factor. This scheme implies important experimental
advantages for single electron spin control.",0510411v1
2005-11-18,"Strangeness spin, magnetic moment and strangeness configurations of the proton","The implications of the empirical signatures for the positivity of the
strangeness magnetic moment $\mu_s$, and the negativity of the strangeness
contribution to the proton spin $\Delta_s$, on the possible $uuds\bar s$
configurations of five quarks in the proton are analyzed. The empirical signs
for the values of these two observables can only be obtained in configurations
where the $uuds$ system is orbitally excited and the $\bar s$ quark is in the
ground state. The configurations, in which the $\bar s$ is orbitally excited,
which include the conventional $K^+\Lambda^0$ congfiguration, with the
exception of that, in which the $uuds$ component has spin 2, yield negative
values for $\mu_s$. Here the strangeness spin $\Delta_s$, the strangeness
magnetic moment $\mu_s$ and the axial coupling constant $G_A^s$ are calculated
for all possible configurations of the $uuds\bar s$ component of the proton. In
the configuration with $[4]_{FS}[22]_F[22]_S$ flavor-spin symmetry, which is
likely to have the lowest energy, $\mu_s$ is positive and $\Delta_s\simeq
G_A^s\simeq -1/3\mu_s$.",0511223v1
2008-04-29,Spin-magnetophonon level splitting in semimagnetic quantum wells,"Spin-magnetophonon level splitting in a quantum well made of a semimagnetic
wide gap semiconductor is considered. The semimagnetic semiconductors are
characterized by a large effective $g$ factor. The resonance conditions
$\hbar\omega_{\rm LO}=\mu_BgB$ for the spin flip between two Zeeman levels due
to interaction with longitudinal optical phonons can be achieved sweeping
magnetic field $B$. This condition is studied in quantum wells. It is shown
that it leads to a level splitting that is dependent on the electron-phonon
coupling strength as well as on the spin-orbit interaction in this structure.
  We treat in detail the Rashba model for the spin-orbit interaction assuming
that the quantum well lacks inversion symmetry and briefly discuss other
models. The resonant transmission and reflection of light by the well is
suggested as a suitable experimental probe of the level splitting.",0804.4654v1
2010-02-08,Coulomb-induced Rashba spin-orbit coupling in semiconductor quantum wells,"In the absence of an external field, the Rashba spin-orbit interaction (SOI)
in a two-dimensional electron gas in a semiconductor quantum well arises
entirely from the screened electrostatic potential of ionized donors. We adjust
the wave functions of a quantum well so that electrons occupying the first
(lowest) subband conserve their spin projection along the growth axis (Sz),
while the electrons occupying the second subband precess due to Rashba SOI.
Such a specially designed quantum well may be used as a spin relaxation
trigger: electrons conserve Sz when the applied voltage (or current) is lower
than a certain threshold V*; higher voltage switches on the Dyakonov-Perel spin
relaxation.",1002.1510v2
2010-04-06,Spin and pseudospin symmetries in the antinucleon spectrum of nuclei,"Spin and pseudospin symmetries in the spectra of nucleons and antinucleons
are studied in a relativistic mean-field theory with scalar and vector
Woods-Saxon potentials, in which the strength of the latter is allowed to
change. We observe that, for nucleons and antinucleons, the spin symmetry is of
perturbative nature and it is almost an exact symmetry in the physical region
for antinucleons. The opposite situation is found in the pseudospin symmetry
case, which is better realized for nucleons than for antinucleons, but is of
dynamical nature and cannot be viewed in a perturbative way both for nucleons
and antinucleons. This is shown by computing the spin-orbit and
pseudospin-orbit couplings for selected spin and pseudospin partners in both
spectra.",1004.0823v1
2011-01-13,Spin transport in higher n-acene molecules,"We investigate the spin transport properties of molecules belonging to the
acenes series by using density functional theory combined with the
non-equilibrium Green's function approach to electronic transport. While short
acenes are found to be non-magnetic, molecules comprising more than nine acene
rings have a spin-polarized ground state. In their gas phase these have a
singlet total spin configuration, since the two unpaired electrons occupying
the doubly degenerate highest molecular orbital are antiferromagnetically
coupled to each other. Such an orbital degeneracy is however lifted once the
molecule is attached asymmetrically to Au electrodes via thiol linkers, leading
to a fractional magnetic moment. In this situation the system Au/n-acene/Au can
act as an efficient spin-filter with interesting applications in the emerging
field of organic spintronics.",1101.2528v1
2011-02-17,"Anomalous optical phonons in FeTe pnictides: spin state, magnetic order, and lattice anharmonicity","Polarized Raman-scattering spectra of non-superconducting, single-crystalline
FeTe are investigated as function of temperature. We have found a relation
between the magnitude of ordered magnetic moments and the linewidth of A1g
phonons at low temperatures. This relation is attributed to the intermediate
spin state (S=1) and the orbital degeneracy of the Fe ions. Spin-phonon
coupling constants have been estimated based on microscopic modeling using
density-functional theory and analysis of the local spin density. Our
observations show the importance of orbital degrees of freedom for the Fe-based
superconductors with large ordered magnetic moments, while small magnetic
moment of Fe ions in some iron pnictides reflects the low spin state of Fe ions
in those systems.",1102.3688v1
2013-01-16,Quantum simulation of a spin polarization device in an electron microscope,"A proposal for an electron-beam device that can act as an efficient
spin-polarization filter has been recently put forward [E. Karimi et al., Phys.
Rev. Lett. 108, 044801 (2012)]. It is based on combining the recently developed
diffraction technology for imposing orbital angular momentum to the beam with a
multipolar Wien filter inducing a sort of artificial non-relativistic
spin-orbit coupling. Here we reconsider the proposed device with a fully
quantum-mechanical simulation of the electron beam propagation, based on the
well established multi-slice method, supplemented with a Pauli term for taking
into account the spin degree of freedom. Using this upgraded numerical tool, we
study the feasibility and practical limitations of the proposed method for
spin-polarizing a free electron beam",1301.3938v2
2013-06-07,The Effective field theory of 2+1 dimensional topological insulator in the presence of Rashba spin-orbit interaction,"2+1 dimensional topological insulator described by the Kane-Mele model in the
presence of Rashba spin-orbit interaction is considered. The effective action
of the external fields coupled to electromagnetic and spin degrees of freedom
is accomplished within this model. The Hamiltonian methods are adopted to
provide the coefficients appearing in the action. It is demonstrated
straightforwardly that the coefficients of the Chern-Simons terms are given by
the first Chern number attained through the related non-Abelian Berry gauge
field. The effective theory which we obtain is in accord with the existence of
the spin Hall phase where the value of the spin Hall conductivity is very close
to the quantized one.",1306.1636v3
2014-02-14,Spin-Precession: Breaking the Black Hole--Neutron Star Degeneracy,"Mergers of compact stellar remnant are prime targets for the LIGO/Virgo
gravitational wave detectors. One hopes that the gravitational wave signals
from these merger events can be used to study the mass and spin distribution of
stellar remnants, and provide information about black hole horizons and the
material properties of neutron stars. However, it has been suggested that
degeneracies in the way that the star's mass and spin are imprinted in the
waveforms may make it impossible to distinguish between black holes and neutron
stars. Here we show that the precession of the orbital plane due to spin-orbit
coupling breaks the mass-spin degeneracy, and allows us to distinguish between
standard neutron stars and alternative possibilities, such as black holes or
exotic neutron stars with large masses and spins.",1402.3581v2
2014-10-30,Relativistic Neel-order fields induced by electrical current in antiferromagnets,"We predict that a lateral electrical current in antiferromagnets can induce
non-equilibrium N\'eel order fields, i.e. fields whose sign alternates between
the spin sublattices, which can trigger ultra-fast spin-axis reorientation.
Based on microscopic transport theory calculations we identify staggered
current-induced fields analogous to the intra-band and to the intrinsic
inter-band spin-orbit fields previously reported in ferromagnets with a broken
inversion-symmetry crystal. To illustrate their rich physics and utility, we
considered bulk Mn2Au with the two spin sublattices forming inversion partners,
and a 2D square-lattice antiferromagnet with broken structural inversion
symmetry modelled by a Rashba spin-orbit coupling. We propose an AFM memory
device with electrical writing and reading.",1410.8296v1
2015-03-24,Anomalous Friedel oscillations in a quasi-helical quantum dot,"The charge and spin patterns of a quantum dot embedded into a spin-orbit
coupled quantum wire subject to a magnetic field are investigated. A Luttinger
liquid theory is developed, taking into account open boundaries and finite
magnetic field. In the quasi-helical regime, when spin-orbit effects dominate
over the Zeeman interaction, peculiar states develop at the Fermi surface of
the dot. Anomalous Friedel oscillations with twice the expected wavelength
develop in the wavefunction of collective excitations of such states,
accompanied by peculiar spin patterns in their magnetization. Both effects are
analyzed in detail and shown possible to be probed in transport experiments.
The stability against electron interactions and magnetic field is investigated.
We also discuss how signatures of such states survive in the total charge and
spin densities.",1503.06957v1
2015-10-05,Resonant Spin and Charge Hall Effects in 2D Electron Gas with Unequal Rashba and Dresselhaus Spin-Orbit Couplings under a Perpendicular Magnetic Field,"We have investigated the complex two-dimensional electron system with unequal
Rashba and Dresselhaus spin-orbit interactions in the presence of a
perpendicular magnetic field. The spin polarizations are obtained in a wide
range of magnetic fields. It is shown that such a system is hard to be
magnetized. We also find that the resonant charge and spin Hall conductances
occurs simultaneously at a certain magnetic field, at which two (nearly)
degenerate Landau levels are filled partly. The resonant Hall effects are
universal in this type of semiconductor materials, and could have potential
application for semiconductor spintronics.",1510.01012v1
2016-02-13,Spin transport in n-type single-layer transition metal dichalcogenides,"Valley asymmetry of the electron spectrum in transition metal dichalcogenides
(TMDs) originates from the spin-orbit coupling. Presence of spin-orbit fields
of opposite signs for electrons in K and K' valleys in combination with
possibility of intervalley scattering result in a nontrivial spin dynamics.
This dynamics is reflected in the dependence of nonlocal resistance on external
magnetic field (the Hanle curve). We calculate theoretically the Hanle shape in
TMDs. It appears that, unlike conventional materials without valley asymmetry,
the Hanle shape in TMDs is different for normal and parallel orientations of
the external field. For normal orientation, it has two peaks for slow
intervalley scattering, while, for fast intervalley scattering the shape is
usual. For parallel orientation, the Hanle curve exhibits a cusp at zero field.
This cusp is a signature of a slow-decaying valley-asymmetric mode of the spin
dynamics.",1602.04276v1
2017-08-15,Coulomb correlations intertwined with spin and orbital excitations in LaCoO$_3$,"We carried out temperature-dependent (20 - 550 K) measurements of resonant
inelastic X-ray scattering on LaCoO$_3$ to investigate the evolution of its
electronic structure across the spin-state crossover. In combination with
charge-transfer multiplet calculations, we accurately quantized the
renormalized crystal-field excitation energies and spin-state populations. We
show that the screening of the on-site Coulomb interaction of 3d electrons is
orbital selective and coupled to the spin-state crossover in LaCoO$_3$. The
results establish that the gradual spin-state crossover is associated with a
relative change of Coulomb energy versus bandwidth, leading to a Mott-type
insulator-to-metal transition.",1708.04417v1
2018-02-07,Excitonic magnet in external field: complex order parameter and spin currents,"We investigate spin-triplet exciton condensation in the two-orbital Hubbard
model close to half filling by means of dynamical mean-field theory. Employing
an impurity solver that handles complex off-diagonal hybridization functions,
we study the behavior of excitonic condensate in stoichiometric and doped
systems subject to external magnetic field. We find a general tendency of the
triplet order parameter to lay perpendicular with the applied field and
identify exceptions from this rule. For solutions exhibiting k-odd spin
textures, we discuss the Bloch theorem which, in the absence of spin-orbit
coupling, forbids the appearance of spontaneous net spin current. We
demonstrate that the Bloch theorem is not obeyed by the dynamical mean-field
theory.",1802.02387v1
2018-11-22,In-gap states of magnetic impurity in quantum spin Hall insulator proximitized to a superconductor,"We study in-gap states of a single magnetic impurity embedded in a honeycomb
monolayer which is deposited on superconducting substrate. The intrinsic
spin-orbit coupling induces the quantum spin Hall insulating (QSHI) phase
gapped around the Fermi energy. Under such circumstances we consider the
emergence of Shiba-like bound states driven by the superconducting proximity
effect. We investigate their topography, spin-polarization and signatures of
the quantum phase transition manifested by reversal of the local currents
circulating around the magnetic impurity. These phenomena might be important
for more exotic in-gap quasiparticles in such complex nanostructures as
magnetic nanowires or islands, where the spin-orbit interaction along with the
proximity induced electron pairing give rise to topological phases hosting the
protected boundary modes.",1811.09295v3
2020-07-30,Silicon quantum dot devices with a self-aligned second gate layer,"We implement silicon quantum dot devices with two layers of gate electrodes
using a self-alignment technique, which allows for ultra-small gate lengths and
intrinsically perfect layer-to-layer alignment. In a double quantum dot system,
we investigate hole transport and observe current rectification due to Pauli
spin blockade. Magnetic field measurements indicate that hole spin relaxation
is dominated by spin-orbit interaction, and enable us to determine the
effective hole $g$-factor $\simeq1.6$. From an avoided singlet-triplet
crossing, occurring at high magnetic field, the spin-orbit coupling strength
$\simeq0.27$meV is obtained, promising fast and all-electrical spin control.",2007.15400v1
2018-05-16,Quantum well structure of a double perovskite superlattice and formation of a spin-polarized two-dimensional electron gas,"Layered oxide heterostructures are the new routes to tailor desired
electronic and magnetic phases emerging from competing interactions involving
strong correlation, orbital hopping, tunnelling and lattice coupling phenomena.
Here, we propose a half-metal/insulator superlattice that intrinsically forms
spin-polarized two-dimensional electron gas (2DEG) following a mechanism very
different from the widely reported 2DEG at the single perovskite polar
interfaces. From DFT$+U$ study on Sr$_2$FeMoO$_6$/La$_2$CoMnO$_6$ (001)
superlattice, we find that a periodic quantum well is created along [001] which
breaks the three-fold $t_{2g}$ degeneracy to separate the doubly degenerate
$xz$ and $yz$ states from the planar $xy$ state. In the spin-down channel, the
dual effect of quantum confinement and strong correlation localizes the
degenerate states, whereas the dispersive $xy$ state forms the 2DEG which is
robust against perturbations to the superlattice symmetry. The spin-up channel
retains the bulk insulating. Both spin polarization and orbital polarization
make the superlattice ideal for spintronic and orbitronic applications. The
suggested 2DEG mechanism widens the scope of fabricating next generation of
oxide heterostructures.",1805.06128v2
2017-06-22,Theory of the spin galvanic effect at oxide interfaces,"The spin galvanic effect (SGE) describes the conversion of a non-equilibrium
spin polarization into a transverse charge current. Recent experiments have
demonstrated a large conversion efficiency for the two-dimensional electron gas
formed at the interface between two insulating oxides, LaAlO$_3$ and SrTiO$_3$.
Here we analyze the SGE for oxide interfaces within a three-band model for the
Ti t$_{2g}$ orbitals which displays an interesting variety of effective
spin-orbit couplings in the individual bands that contribute differently to the
spin-charge conversion. Our analytical approach is supplemented by a numerical
treatment where we also investigate the influence of disorder and temperature,
which turns out to be crucial to provide an appropriate description of the
experimental data.",1706.07243v1
2019-09-10,Kondo effect in a Aharonov-Casher interferometer,"We consider a model describing a spin field-effect transistor based on a
quantum nanowire with a tunable spin-orbit interaction embedded between two
ferromagnetic leads with anticollinear magnetization. We investigate a regime
of a strong interplay between resonance Kondo scattering and interference
associated with the Aharonov-Casher effect. Using the Keldysh technique at weak
coupling regime we calculate perturbatively the charge current. It is predicted
that the effects of the spin-orbit interaction result in a non-vanishing
current for any spin polarization of the leads including the case of fully
polarized anti-collinear contacts. We analyze the influence of the
Aharonov-Casher phase and degree of spin polarization in the leads onto a Kondo
temperature.",1909.04524v2
2019-09-17,Spin-Orbit-Torque Field-Effect Transistor (SOTFET): Proposal for a New Magnetoelectric Memory,"Spin-based memories are attractive for their non-volatility and high
durability but provide modest resistance changes, whereas semiconductor logic
transistors are capable of large resistance changes, but lack memory function
with high durability. The recent availability of multiferroic materials
provides an opportunity to directly couple the change in spin states of a
magnetic memory to a charge change in a semiconductor transistor. In this work,
we propose and analyze the spin-orbit torque field-effect transistor (SOTFET),
a device with the potential to significantly boost the energy efficiency of
spin-based memories, and to simultaneously offer a palette of new
functionalities.",1909.08133v3
2019-04-15,Spin-Orbit-Torque Driven Propagating Spin Waves,"Spin-orbit torque (SOT) can drive sustained spin wave (SW) auto-oscillations
in a class of emerging microwave devices known as spin Hall nano-oscillators
(SHNOs), which have highly non-linear properties governing robust mutual
synchronization at frequencies directly amenable to high-speed neuromorphic
computing. However, all demonstrations have relied on localized SW modes
interacting through dipolar coupling and/or direct exchange. As nanomagnonics
requires propagating SWs for data transfer, and additional computational
functionality can be achieved using SW interference, SOT driven propagating SWs
would be highly advantageous. Here, we demonstrate how perpendicular magnetic
anisotropy can raise the frequency of SOT driven auto-oscillations in magnetic
nano-constrictions well above the SW gap, resulting in the efficient generation
of field and current tunable propagating SWs. Our demonstration greatly extends
the functionality and design freedom of SHNOs enabling long range SOT driven SW
propagation for nanomagnonics, SW logic, and neuro-morphic computing, directly
compatible with CMOS technology.",1904.06945v1
2016-03-15,"Footprints of hyperfine, spin-orbit, and decoherence effects in Pauli spin blockade","We detect in real time inter-dot tunneling events in a weakly coupled two
electron double quantum dot in GaAs. At finite magnetic fields, we observe two
characteristic tunneling times, T_d and T_b, belonging to, respectively, a
direct and a blocked (spin-flip-assisted) tunneling. The latter corresponds to
lifting of a Pauli spin blockade and the tunneling times ratio eta=T_b/T_d
characterizes the blockade efficiency. We find pronounced changes in the
behavior of eta upon increasing the magnetic field, with eta increasing,
saturating and increasing again. We explain this behavior as due to the
crossover of the dominant blockade lifting mechanism from the hyperfine to
spin-orbit interactions and due to a change in the contribution of the charge
decoherence.",1603.04861v1
2017-11-29,Tuning topological surface magnetism by bulk alloying,"Deploying an analytical atomistic model of the bulk band structure of the
IV-VI semiconductors we connect the spin structure of the topological surface
state to the crystal field and spin orbit coupling parameters of the bulk
material. While the Dirac-Weyl (or equivalently, Rashba) type topological
surface state is often assumed universal, we show that the physics of the
surface state is strikingly non-universal. To see this explicitly we calculate
the RKKY interaction, which may be viewed as a probe of this surface state spin
structure, finding its \emph{qualitative form} depends on the values the bulk
spin-orbit and crystal field parameters take. This opens the way to tune the
spin interaction on the surface of a IV-VI topological insulator by, for
instance varying the composition of the IV-VI ternary compounds, as well as
highlighting the importance of the connection between bulk and surface physics
in topological insulators.",1711.10760v1
2019-05-23,Topological Hall Effect and Emergent Skyrmion Crystal in Manganite-Iridate Oxide Interfaces,"Scalar spin chirality is expected to induce a finite contribution to the Hall
response at low temperatures. We study this spin-chirality-driven Hall effect,
known as the topological Hall effect, at the manganite side of the interface
between La$_{1-x}$Sr$_{x}$MnO$_{3}$ and SrIrO$_3$. The ferromagnetic
double-exchange hopping at the manganite layer, in conjunction with the
Dzyaloshinskii-Moriya (DM) interaction which arises at the interface due to
broken inversion symmetry and strong spin-orbit coupling from the iridate
layer, could produce a skyrmion-crystal (SkX) phase in the presence of an
external magnetic field. Using the Monte Carlo technique and a two-orbital
spin-fermion model for manganites, supplemented by an in-plane DM interaction,
we obtain phase diagrams which reveal at low temperatures a clear SkX phase and
also a low-field spin-spiral phase. Increasing temperature, a skyrmion-gas
phase, precursor of the SkX phase upon cooling, was identified. The topological
Hall effect primarily appears in the SkX phase, as observed before in oxide
heterostructures. We conclude that the manganite-iridate superlattices provide
another useful platform to explore a plethora of unconventional magnetic and
transport properties.",1905.09887v2
2021-05-03,Moiré tuning of spin excitations: Individual Fe atoms on MoS$_2$/Au(111),"Magnetic adatoms on surfaces are exchange coupled to their environment,
inducing fast relaxation of excited spin states and decoherence. These
interactions can be suppressed by inserting decoupling layers between the
magnetic adsorbate and the metallic substrate. Using low-temperature scanning
tunneling microscopy and spectroscopy, we investigate the magnetic properties
of single Fe atoms on Au(111) covered by a monolayer of MoS$_2$ and explore the
influence of the moir\'e structure on the spin excitation spectra. Fe adatoms
absorbed at minima of the moir\'e structure exhibit almost pure inelastic spin
excitations. Kondo correlations develop for adsorption sites off the moir\'e
minimum, culminating in fully developed Kondo resonances on moir\'e maxima. The
increase in Kondo correlations is accompanied by a decrease in the single-ion
anisotropy, which we rationalize by poor-person's scaling. Local variations in
the tunneling spectra indicate pronounced interference between tunneling paths
involving the spin-carrying orbitals and a hybrid Fe-S orbital, which forms
despite the nominally inert nature of the terminating S layer.",2105.01176v1
2021-07-21,Spin orbit torque switching of antiferromagnet through the Neel reorientation in rare-earth ferrite,"We suggest coherent switching of canted antiferromagnetic (AFM) spins using
spin-orbit torque (SOT) in small magnet. The magnetic system of orthoferrite
features biaxial easy anisotropy and the Dzyaloshinskii Moriya interaction,
which is perpendicular to the easy axes and therefore creates weak
magnetization (m). A damping-like component of the SOT induces N\'eel
reorientation along one of the easy axes and then exerts torque on m, leading
to tilting of the N\'eel order l. The torque on the magnetization becomes
stronger due to coupling with the induced Oersted field or the field-like
component of the SOT, enhancing the tilting of l. Therefore, l is found to
experience deterministic switching after the SOT is turned off. Based upon both
numerical and analytical analysis of the coherent switching, XOR logic gates
are also found to be implemented in a single magnetic layer. In addition, we
investigate how magnetic parameters affect the critical reorientation angle and
current density in a simple layered structure of platinum and a canted AFM. Our
findings are expected to provide an alternative spin-switching mechanism for
ultrafast applications such as spin logic and electronic devices.",2107.10156v1
2021-10-27,Low-energy effective theory and anomalous Hall effect in monolayer $\mathrm{WTe}_2$,"We develop a symmetry-based low-energy theory for monolayer $\mathrm{WTe}_2$
in its 1T$^{\prime}$ phase, which includes eight bands (four orbitals, two
spins). This model reduces to the conventional four-band spin-degenerate Dirac
model near the Dirac points of the material. We show that measurements of the
spin susceptibility, and of the magnitude and time dependence of the anomalous
Hall conductivity induced by injected or equilibrium spin polarization can be
used to determine the magnitude and form of the spin-orbit coupling
Hamiltonian, as well as the dimensionless tilt of the Dirac bands.",2110.14586v3
2023-04-25,The higher-order magnetic skyrmions in non-uniform magnetic fields,"For 2D Hubbard model with spin-orbit Rashba coupling in external magnetic
field the structure of effective spin interactions is studied in the regime of
strong electron correlations and at half-filling. It is shown that in the third
order of perturbation theory, the scalar and vector chiral spin-spin
interactions of the same order arise. The emergence of the latter is due to
orbital effects of magnetic field. It is shown that for nonuniform fields,
scalar chiral interaction can lead to stabilization of axially symmetric
skyrmion states with arbitrary topological charges. Taking into account the
hierarchy of effective spin interactions, an analytical theory on the optimal
sizes of such states -- the higher-order magnetic skyrmions -- is developed for
axially symmetric magnetic fields of the form $h(r) \sim r^{\beta}$ with $\beta
\in \mathbb{R}$.",2304.12694v1
2023-05-15,Magnetoresistive RAM with n-doped AlGaAs/GaAs writing/reading channels,"We show that the tunable gate voltage in n-doped AlGaAs/GaAs QW (quantum
well) is a key in designing an efficient and ultrafast MRAM (magnetoresistive
random access memory). The Rashba spin-orbit coupling in such QWs can be tuned
appropriately by the gate voltage to create an intense spin-Hall field which in
turns interacts with the ferromagnetic layer of the MRAM through the mechanism
of spin orbit torque. The strong spin-Hall field leads to an infinitesimally
small switching time of the MRAM. Our proposed MRAM is thus a better
alternative to the conventional ferromagnetic/spin-Hall effect bi-layers MRAM
for the reason that the switching time can be varied with ease, which is
unfeasible in the later. Concisely, not only that this work signals a
possibility to design an ultra-fast MRAM, but it also suggests a model to
fabricate a tunable switching time MRAM.",2305.08565v1
2023-12-25,Planar Hall effect from superconducting fluctuations,"We study the planar Hall effect (PHE), and reexamine the Lifshitz invariants
in the spin-orbit coupled superconductors. In the Rashba superconductor, the
PHE is finite as fluctuations are faster along the applied field than
perpendicular to it. We consider spin-orbit splitting that is larger than the
critical temperature. In this regime the Cooper pairs are predominantly
intra-band. The effective two-band interaction matrix elements are not
sensitive enough to the field to affect the PHE. However, in a wide range of
parameters this dependence does modify the Lifshitz invariant, linear in field
and responsible for the spin diode effect. This contribution is a geometrical
effect of the adjustment of the spin texture to the applied field. As such, it
also allows the repulsion or attraction in the spin triplet channel to affect
the Lifshitz invariant. While the PHE can be studied within the effective
two-band superconductor model with an original pairing interaction, the
Lifshitz invariant, in general, cannot. Disorder is shown to only moderately
suppress the PHE.",2312.15688v1
2024-03-01,Decoherence in Andreev spin qubits,"We theoretically study the dephasing of an Andreev spin qubit (ASQ) due to
electric and magnetic noise. Using a tight-binding model, we calculate the
Andreev states formed in a Josephson junction where the link is a semiconductor
with strong spin-orbit interaction. As a result of both the spin-orbit
interaction and induced superconductivity, the local charge and spin of these
states varies as a function of externally controllable parameters: the phase
difference between the superconducting leads, an applied magnetic field, and
filling of the underlying semiconductor. Concomitantly, coupling to
fluctuations of the electric or magnetic environment will vary, which informs
the rate of dephasing. We qualitatively predict the dependence of dephasing on
the nature of the environment, magnetic field, phase difference between the
junction, and filling of the semiconductor. Comparing the simulated electric-
and magnetic-noise-induced dephasing rate to experiment suggests that the
dominant source of noise is magnetic. Moreover, by appropriately tuning these
external parameters, we find sweet-spots at which we predict an enhancement in
ASQ coherence times.",2403.00710v1
2016-04-22,Coherent Coupling of WS_2 Monolayers with Metallic Photonic Nanostructures at Room Temperature,"Room temperature strong coupling of WS_2 monolayer exciton transitions to
metallic Fabry-Perot and plasmonic optical cavities is demonstrated. A Rabi
splitting of 101 meV is observed for the Fabry-Perot cavity, more than double
those reported to date in other 2D materials. The enhanced magnitude and
visibility of WS_2 monolayer strong coupling is attributed to the larger
absorption coefficient, the narrower linewidth of the A exciton transition, and
greater spin-orbit coupling. For WS_2 coupled to plasmonic arrays, the Rabi
splitting still reaches 60 meV despite the less favorable coupling conditions,
and displays interesting photoluminescence features. The unambiguous signature
of WS_2 monolayer strong coupling in easily fabricated metallic resonators at
room temperature suggests many possibilities for combining light-matter
hybridization with spin and valleytronics.",1604.06656v1
2006-01-17,Spin Hot Spots in vertically-coupled Few-electron Quantum Dots,"The effects of spin-orbit (SO) coupling arising from the confinement
potential in single and two vertically-coupled quantum dots have been
investigated. Our work indicates that a dot containing a single electron shows
the lifting of the degeneracy of dipole-allowed transitions at B=0 due to the
SO coupling which disappears for a dot containing two electrons. For coupled
dots with one electron in each dot, the optical spectra is not affected by the
coupling and is the same as the dot containing one electron. However, for the
case of two coupled dots where one partner dot has two interacting electrons
while the other dot has only one electron, a remarkable effect is observed
where the oscillator strength of two out of four dipole-allowed transition
lines disappears as the distance between the dots is decreased.",0601390v1
2014-08-10,Localized modes in quasi-2D Bose-Einstein condensates with spin-orbit and Rabi couplings,"We consider a two-component pancake-shaped, i.e., effectively two-dimensional
(2D), Bose-Einstein condensate (BEC) coupled by the spin-orbit (SO) and Rabi
terms. The SO coupling adopted here is of the mixed Rashba-Dresselhaus type.
For this configuration, we derive a system of two 2D nonpolynomial
Schr\""odinger equations (NPSEs), for both attractive and repulsive interatomic
interactions. In the low- and high-density limits, the system amounts to
previously known models, namely, the usual 2D Gross-Pitaevskii equation, or the
Schr\""odinger equation with the nonlinearity of power 7/3. We present simple
approximate localized solutions, obtained by treating the SO and Rabi terms as
perturbations. Localized solutions of the full NPSE system are obtained in a
numerical form. Remarkably, in the case of the attractive nonlinearity acting
in free space (i.e., without any 2D trapping potential), we find parameter
regions where the SO and Rabi couplings make 2D fundamental solitons
dynamically stable.",1408.2256v2
2015-01-20,Quantum Anomalous Hall Effect in Graphene Proximity Coupled to an Antiferromagnetic Insulator,"We propose realizing the quantum anomalous Hall effect by proximity coupling
graphene to an antiferromagnetic insulator that provides both broken
time-reversal symmetry and spin-orbit coupling. We illustrate our idea by
performing ab initio calculations for graphene adsorbed on the (111) surface of
BiFeO3. In this case, we find that the proximity-induced exchange field in
graphene is about 70 meV, and that a topologically nontrivial band gap is
opened by Rashba spin-orbit coupling. The size of the gap depends on the
separation between the graphene and the thin film substrate, which can be tuned
experimentally by applying external pressure.",1501.04828v1
2015-01-26,Composite localized modes in discretized spin-orbit-coupled Bose-Einstein condensates,"We introduce a discrete model for binary spin-orbit-coupled (SOC)
Bose-Einstein condensates (BEC) trapped in a deep one-dimensional optical
lattice. Two different types of the couplings are considered, with spatial
derivatives acting inside each species, or between the species. The discrete
system with inter-site couplings dominated by the SOC, while the usual hopping
is negligible, \textit{emulates} condensates composed of extremely heavy atoms,
as well as those with opposite signs of the effective atomic masses in the two
components.\ Stable localized composite states of miscible and immiscible types
are constructed. The effect of the SOC on the immiscibility-miscibility
transition in the localized complexes, which emulates the phase transition
between insulating and conducting states in semiconductors, is studied.",1501.06386v1
2015-05-08,Enhanced stripe phases in spin-orbit-coupled Bose-Einstein condensates in ring cavities,"The coupled dynamics of the atom and photon fields in optical ring cavities
with two counter-propagating modes give rise to both spin-orbit interactions as
well as long-ranged interactions between atoms of a many-body system. At zero
temperature, the interplay between the two-body and cavity-mediated
interactions determines the ground state of a Bose-Einstein condensate. In this
work, we find that cavity quantum electrodynamics in the weak-coupling regime
favors a stripe-phase state over a plane-wave phase as the strength of
cavity-mediated interactions increases. Indeed, the stripe phase is
energetically stabilized even for condensates with attractive intra- and
inter-species interactions for sufficiently large cavity interactions. The
elementary excitation spectra in both phases correspond to linear dispersion
relation at long wavelengths, indicating that both phases exhibit
superfluidity, though the plane-wave phase also displays a characteristic
roton-type feature. The results suggest that even in the weak coupling regime
cavities can yield interesting new physics in ultracold quantum gases.",1505.02189v1
2018-02-04,Magnetotransport in Layered Dirac Fermion System Coupled with Magnetic Moments,"We theoretically investigate the magnetotransport of Dirac fermions coupled
with localized moments to understand the physical properties of the Dirac
material EuMnBi$_2$. Using an interlayer hopping form, which simplifies the
complicated interaction between the layers of Dirac fermions and the layers of
magnetic moments in EuMnBi$_2$, the theory reproduces most of the features
observed in this system. The hysteresis observed in EuMnBi$_2$ can be caused by
the valley splitting that is induced by the spin-orbit coupling and the
external magnetic field with the molecular field created by localized moments.
Our theory suggests that the magnetotransport in EuMnBi$_2$ is due to the
interplay among Dirac fermions, localized moments, and spin-orbit coupling.",1802.01060v1
2012-01-11,Searching for Majorana Fermions in 2D Spin-orbit Coupled Fermi Superfluids at Finite Temperature,"Recent experimental breakthrough in realizing spin-orbit (SO) coupling for
cold atoms has spurred considerable interest in the physics of 2D SO coupled
Fermi superfluids, especially topological Majorana fermions (MFs) which were
predicted to exist at zero temperature. However, it is well known that
long-range superfluid order is destroyed in 2D by the phase fluctuation at
finite temperature and the relevant physics is the
Berezinskii-Kosterlitz-Thouless (BKT) transition. In this Letter, we examine
finite temperature effects on SO coupled Fermi gases and show that finite
temperature is indeed necessary for the observation of MFs. MFs are
topologically protected by a quasiparticle energy gap which is found to be much
larger than the temperature. The restrictions to the parameter region for the
observation of MFs have been obtained.",1201.2238v3
2016-08-16,Vortex solitons in two-dimensional spin-orbit coupled Bose-Einstein condensates: effects of the Rashba-Dresselhaus coupling and the Zeeman splitting,"We present an analysis of two-dimensional (2D) matter-wave solitons, governed
by the pseudo-spinor system of Gross-Pitaevskii equations with self- and
cross-attraction, which includes the spin-orbit coupling (SOC) in the general
Rashba-Dresselhaus form, and, separately, the Rashba coupling and the Zeeman
splitting. Families of semi-vortex (SV) and mixed-mode (MM) solitons are
constructed, which exist and are stable in free space, as the SOC terms prevent
the onset of the critical collapse and create the otherwise missing ground
states in the form of the solitons. The Dresselhaus SOC produces a destructive
effect on the vortex solitons, while the Zeeman term tends to convert the MM
states into the SV ones, which eventually suffer delocalization. Existence
domains and stability boundaries are identified for the soliton families. For
physically relevant parameters of the SOC system, the number of atoms in the 2D
solitons is limited by $\sim 1.5\times 10^{4}$. The results are obtained by
means of combined analytical and numerical methods.",1608.04564v1
2017-10-09,Traveling dark-bright solitons in a reduced spin-orbit coupled system: application to Bose-Einstein condensates,"In the present work, we explore the potential of spin-orbit (SO) coupled
Bose-Einstein condensates to support multi-component solitonic states in the
form of dark-bright (DB) solitons. In the case where Raman linear coupling
between components is absent, we use a multiscale expansion method to reduce
the model to the integrable Mel'nikov system. The soliton solutions of the
latter allow us to reconstruct approximate traveling DB solitons for the
reduced SO coupled system. For small values of the formal perturbation
parameter, the resulting waveforms propagate undistorted, while for large
values thereof, they shed some dispersive radiation, and subsequently distill
into a robust propagating structure. After quantifying the relevant radiation
effect, we also study the dynamics of DB solitons in a parabolic trap,
exploring how their oscillation frequency varies as a function of the bright
component mass and the Raman laser wavenumber.",1710.03270v1
2020-05-23,Modulational instability in binary spin-orbit-coupled Bose-Einstein condensates,"We study modulation instability (MI) of flat states in two-component
spin-orbit-coupled (SOC) Bose-Einstein condensates (BECs) in the framework of
coupled Gross-Pitaevskii equations for two components of the pseudospinor wave
function. The analysis is performed for equal densities of the components.
Effects of the interaction parameters, Rabi coupling, and SOC on the MI are
investigated. In particular, the results demonstrate that the SOC strongly
alters the commonly known MI (immiscibility) condition, $g_{12} > g_{1} g_{2}$,
for the binary superfluid with coefficients $g_{1,2}$ and $g_{12}$ of the
intra- and interspecies repulsive interactions. In fact, the binary BEC is
always subject to the MI under the action of the SOC, which implies that the
ground state of the system is plausibly represented by a striped phase.",2005.11505v1
2020-11-17,FORTRESS II: FORTRAN programs for solving coupled Gross-Pitaevskii equations for spin-orbit coupled spin-2 Bose-Einstein condensate,"We provide here a set of three OpenMP parallelized FORTRAN 90/95 programs to
compute the ground states and the dynamics of trapped spin-2 Bose-Einstein
condensates (BECs) with anisotropic spin-orbit (SO) coupling by solving a set
of five coupled Gross-Pitaevskii equations using a time-splitting Fourier
spectral method. Depending on the nature of the problem, without any loss of
generality, we have employed the Cartesian grid spanning either three-, two-,
or one-dimensional space for numerical discretization. To illustrate the
veracity of the package, wherever feasible, we have compared the numerical
ground state solutions of the full mean-field model with those from the
simplified scalar models. The two set of results show excellent agreement, in
particular, through the equilibrium density profiles, energies and chemical
potentials of the ground-states. We have also presented test results for OpenMP
performance parameters like speedup and the efficiency of the three codes.",2011.08892v1
2022-01-31,Fermi surface segmentation in the helical state of a Rashba superconductor,"We investigate the quasiparticle excitations in the FFLO- type helical state
of a superconductor with inversion-symmetry breaking and strong Rashba
spin-orbit coupling. We restrict to a state with single finite momentum of
Cooper pairs in the helical phase that is determined by minimization of the
condensation energy. We derive the dependence of quasiparticle dispersions on
the Rashba coupling strength and external field. It leads to a peculiar
momentum-space segmentation of the corresponding Rashba Fermi surface sheets
which has not yet been observed experimentally. We show that it may be directly
visualized by the method of quasiparticle interference that identifies the
critical points of the segmented sheets and can map their evolution with field
strength, bias voltage and Rashba coupling. We also indicate a strategy how to
determine the finite Cooper-pair momentum from experimental quantities. This
investigation has the potential for a more detailed microscopic understanding
of the helical superconducting state under the influence of Rashba spin-orbit
coupling.",2201.13213v1
2024-02-28,Stabilizing topological superconductivity in disordered spin-orbit coupled semiconductor-superconductor heterostructures,"We investigate theoretically a one-dimensional semiconductor-superconductor
(SM-SC) heterostructure with Rashba spin-orbit coupling and parallel Zeeman
field in the presence of disorder generated by random charged impurities and
identify the optimal regimes for realizing topological superconductivity and
Majorana zero modes. Using a Green's function approach, we show that upon
increasing the disorder strength the stable topological superconducting phase
characterized by robust end-to-end Majorana correlations ""migrates"" toward
larger values of the Zeeman field and can be stabilized by increasing the
effective SM-SC coupling. Based on these findings, we propose a strategy for
accessing a regime characterized by well-separated Majorana zero modes that is
based on (a) enhancing the strength of the effective SM-SC coupling (e.g.,
through interface engineering) and (b) expanding the range of accessible Zeeman
fields (e.g., by enhancing the gyromagnetic ratio or optimizing the parent
superconductor, to enable the application of larger magnetic fields). While
this strategy may still require some reduction of the disorder strength, this
requirement is significantly less strict than the corresponding requirement in
a strategy that focuses exclusively on disorder reduction.",2402.18549v2
2024-03-04,Signature of reentrant localization in collisional inhomogeneous spin-orbit coupled condensates,"We study the localization transition in a spin-orbit (SO) coupled binary
Bose-Einstein condensates (BECs) with collisional inhomogeneous interaction
trapped in a one-dimensional quasiperiodic potential. Our numerical analysis
shows that the competition between the quasiperiodic disorder and inhomogeneous
interaction leads to a reentrant localization transition as the interaction
strength is tuned from attractive to repulsive in nature. Further, we analyse
the combined effect of the SO and Rabi coupling strengths on the localization
transition for different interaction strengths and obtain signatures of
reentrant localization transition as function of SO coupling in the regime of
weak interactions. We complement our numerical observation with the analytical
model using the variational approach. At the end we show how the reentrant
localization is manifested in the quench dynamics of the condensate. Our study
provides an indirect approach to achieve localization transition without tuning
the quasiperiodic potential strength, rather by tuning the inhomogeneous
interaction.",2403.02027v2
1996-05-23,Persistent Current From the Competition Between Zeeman Coupling and Spin-Orbit Interaction,"Applying the non-adiabatic Aharonov-Anandan phase approach to a mesoscopic
ring with non-interacting many electrons in the presence of the spin-orbit
interaction, Zeeman coupling and magnetic flux, we show that the time-reversal
symmetry breaking due to Zeeman coupling is intrinsically different from that
due to magnetic flux. We find that the direction of the persistent currents
induced by the Zeeman coupling changes periodically with the particle number,
while the magnetic flux determines the direction of the induced currents by its
sign alone.",9605144v2
2014-07-03,Equation of state and phase transition in spin-orbit-coupled Bose gases at finite temperature: A perturbation approach,"We study two-component Bose gases with Raman induced spin-orbit coupling via
a perturbation approach at finite temperature. For weak coupling, free energy
is expanded in terms of Raman coupling strength up to the second order, where
the coefficient (referred to as Raman susceptibility) is determined according
to linear response theory. The equation of state for the stripe phase and the
plane-wave phase are obtained in Popov approximation, and the first order
transition between these two phases is investigated. As temperature increases,
we find the phase boundary bends toward the stripe phase side in most
temperature regions, which implies the ferromagnetic order is more robust than
the crystalline order in presence of thermal fluctuations. Our results
qualitatively agree with the recent experimental observation in rubidium atomic
gases. A method to measure the Raman susceptibility through the two-photon
Bragg scattering experiment is also discussed.",1407.0990v2
2014-08-08,Softening of Roton and Phonon Modes in a Bose-Einstein Condensate with Spin-Orbit Coupling,"Roton-type excitations usually emerge from strong correlations or long-range
interactions, as in superfluid helium or dipolar ultracold atoms. However, in
weakly short-range interacting quantum gas, the recently synthesized spin-orbit
(SO) coupling can lead to various unconventional phases of superfluidity, and
give rise to an excitation spectrum of roton-maxon character. Using Bragg
spectroscopy we study a SO coupled Bose-Einstein condensate of $^{87}$Rb atoms,
and show that the excitation spectrum in a ""magnetized"" phase clearly possesses
a two-branch and roton-maxon structure. As Raman coupling strength $\Omega$ is
decreased, a roton-mode softening is observed, as a precursor of the phase
transition to a stripe phase that spontaneously breaks spatially translational
symmetry. The measured roton gaps agree well with theoretical calculations.
Further, we determine sound velocities both in the magnetized and the
non-magnetized phase, and a phonon-mode softening is observed around the phase
transition in between. The validity of the $f$-sum rule is examined.",1408.1755v1
2014-12-02,Dynamical generation of dark solitons in spin-orbit-coupled Bose-Einstein condensates,"We numerically investigate the ground state, the Raman-driving dynamics and
the nonlinear excitations of a realized spin-orbit-coupled Bose-Einstein
condensate in a one-dimensional harmonic trap. Depending on the Raman coupling
and the interatomic interactions, three ground-state phases are identified:
stripe, plane wave and zero-momentum phases. A narrow parameter regime with
coexistence of stripe and zero-momentum or plane wave phases in real space is
found. Several sweep progresses across different phases by driving the Raman
coupling linearly in time is simulated and the non-equilibrium dynamics of the
system in these sweeps are studied. We find kinds of nonlinear excitations,
with the particular dark solitons excited in the sweep from the stripe phase to
the plane wave or zero-momentum phase within the trap. Moreover, the number and
the stability of the dark solitons can be controlled in the driving, which
provide a direct and easy way to generate dark solitons and study their
dynamics and interaction properties.",1412.0800v2
2014-12-11,Biquadratic and ring exchange interactions in orthorhombic perovskite manganites,"We use ab initio electronic structure calculations within the generalized
gradient approximation (GGA+U) to density functional theory (DFT) to determine
the microscopic exchange interactions in the series of orthorhombic rare-earth
manganites, o-$R$MnO$_3$. Our motivation is to construct a model Hamiltonian
(excluding effects due to spin-orbit coupling), which can provide an accurate
description of the magnetism in these materials. First, we consider TbMnO$_3$,
which exhibits a spiral magnetic order at low temperatures. We map the exchange
couplings in this compound onto a Heisenberg Hamiltonian and observe a clear
deviation from the Heisenberg-like behavior. We consider first the coupling
between magnetic and orbital degrees of freedom as a potential source of
non-Heisenberg behavior in TbMnO$_3$, but conclude that it does not explain the
observed deviation. We find that higher order magnetic interactions
(biquadratic and four-spin ring couplings) should be taken into account for a
proper treatment of the magnetism in TbMnO$_3$ as well as in the other
representatives of the o-$R$MnO$_3$ series with small radii of the $R$ cation.",1412.3702v1
2015-10-19,Spin-orbit coupling enhanced superconductivity in Bi-rich compounds ABi$_{3}$ (A=Sr and Ba),"Recently, Bi-based compounds have attracted attentions because of the strong
spin-orbit coupling (SOC). In this work, we figured out the role of SOC in
ABi$_{3}$ (A=Sr and Ba) by theoretical investigation of the band structures,
phonon properties, and electron-phonon coupling. Without SOC, strong Fermi
surface nesting leads to phonon instabilities in ABi$_{3}$. SOC suppresses the
nesting and stabilizes the structure. Moreover, without SOC the calculation
largely underestimates the superconducting transition temperatures ($T_{c}$),
while with SOC the calculated $T_{c}$ are very close to those determined by
measurements on single crystal samples. The SOC enhanced superconductivity in
ABi$_{3}$ is due to not only the SOC induced phonon softening, but also the SOC
related increase of electron-phonon coupling matrix elements. ABi$_{3}$ can be
potential platforms to construct heterostructure of superconductor/topological
insulator to realize topological superconductivity.",1510.05719v1
2016-06-28,Periodic driving control of Raman-induced spin-orbit coupling in Bose-Einstein condensates: the heating mechanisms,"We focus on a technique recently implemented for controlling the magnitude of
synthetic spin-orbit coupling (SOC) in ultra-cold atoms in the Raman-coupling
scenario. This technique uses a periodic modulation of the Raman-coupling
amplitude to tune the SOC. Specifically, it has been shown that the effect of a
high-frequency sinusoidal modulation of the Raman-laser intensity can be
incorporated into the undriven Hamiltonian via effective parameters, whose
adiabatic variation can then be used to steer the SOC. Here, we characterize
the heating mechanisms that can be relevant to this method. We identify the
main mechanism responsible for the heating observed in the experiments as
basically rooted in driving-induced transfer of population to excited states.
Characteristics of that process determined by the harmonic trapping, the decay
of the excited states, and the technique used for preparing the system are
discussed. Additional heating, rooted in departures from adiabaticity in the
variation of the effective parameters, is also described. Our analytical study
provides some clues that may be useful in the design of strategies for curbing
the effects of heating on the efficiency of the control methods.",1606.08800v1
2017-09-20,Solitons in Bose-Einstein Condensates with Helicoidal Spin-Orbit Coupling,"We report on the existence and stability of freely moving solitons in a
spatially inhomogeneous Bose- Einstein condensate with helicoidal spin-orbit
(SO) coupling. In spite of the periodically varying parameters, the system
allows for the existence of stable propagating solitons. Such states are found
in the rotating frame, where the helicoidal SO coupling is reduced to a
homogeneous one. In the absence of the Zeeman splitting, the coupled
Gross-Pitaevskii equations describing localized states feature many properties
of the integrable systems. In particular, four-parametric families of solitons
can be obtained in the exact form. Such solitons interact elastically. Zeeman
splitting still allows for the existence of two families of moving solitons,
but makes collisions of solitons inelastic.",1709.07017v1
2018-06-13,Two-dimensional composite solitons in Bose-Einstein condensates with spatially confined spin-orbit coupling,"It was recently found that the spin-orbit (SO) coupling can help to create
stable matter-wave solitons in spinor Bose-Einstein condensates in the
two-dimensional (2D) free space. Being induced by external laser illumination,
the effective SO coupling can be applied too in a spatially confined area.
Using numerical methods and the variational approximation (VA), we build
families of 2D solitons of the semi-vortex (SV) and mixed-mode (MM) types, and
explore their stability, assuming that the SO-coupling strength is confined in
the radial direction as a Gaussian. The most essential result is
identification, by means of the VA and numerical methods, of the minimum size
of the spatial confinement for which the 2D system maintains stable solitons of
the SV and MM types.",1806.04868v4
2021-11-01,LaIr3Ga2: A Superconductor based on a Kagome Lattice of Ir,"New materials based on Kagome lattices, predicted to host exotic quantum
physics because they can display flat electronic bands, Dirac cones and
topologically nontrivial surface states, are strongly desired. Here we report
the crystal structure and superconducting properties of LaIr3Ga2, a previously
unreported material that is based on a Kagome lattice of the heavy atom Ir.
LaIr3Ga2 is a type II superconductor with Tc ~ 5.2 K, mu0Hc1 (0) ~ 7.1 mT and
mu0Hc2 (0) ~ 4.7 T. The normalized heat capacity jump at the superconducting
transition, (deltaC/gammaTc), 1.41, is within error of the value expected for a
weak coupling BCS superconductor (1.43). Strong electron-electron correlation
is inferred from the superconducting coherence length. Calculations show that
the influence of spin orbit coupling on the electronic structure is
significant, that the 5d states of the Ir in the Kagome planes are dominant
near the Fermi energy (EF), that a nearly flat band is calculated to occur at
about 100 meV below EF, and that two Dirac points are close to EF. This
material is of interest for investigating the coupling between topological
physics and superconductivity in a system with significant spin orbit coupling.",2111.01247v2
2021-06-22,"XY magnetism, Kitaev exchange, and long-range frustration in the $J_{\rm eff}=1/2$ honeycomb cobaltates","The quest for Kitaev quantum spin liquids has led to great interest in
honeycomb quantum magnets with strong spin-orbit coupling. It has been recently
proposed that even Mott insulators with $3d$ transition metal ions, having
nominally weak spin-orbit coupling, can realize such exotic physics. Motivated
by this, we study the rhombohedral honeycomb cobaltates CoTiO$_3$,
BaCo$_2$(PO$_4$)$_2$, and BaCo$_2$(AsO$_4$)$_2$, using $\textit{ab initio}$
density functional theory, which takes into account realistic crystal field
distortions and chemical information, in conjunction with exact diagonalization
numerics. We show that these Co$^{2+}$ magnets host $j_\text{eff}=1/2$ local
moments with highly anisotropic $g$-factors, and we extract their full spin
Hamiltonians including longer-range and anisotropic exchange couplings. For
CoTiO$_3$, we find a nearest-neighbor easy-plane ferromagnetic $XXZ$ model with
additional bond-dependent anisotropies and interlayer exchange, which supports
three-dimensional (3D) Dirac nodal line magnons. In contrast, for
BaCo$_2$(PO$_4$)$_2$ and BaCo$_2$(AsO$_4$)$_2$, we find a strongly suppressed
interlayer coupling, and significant frustration from additional third-neighbor
antiferromagnetic exchange mediated by P/As. Such bond-anisotropic $J_1$-$J_3$
spin models can support collinear zig-zag or coplanar spiral ground states; we
discuss their dynamical spin correlations which reveal a gapped Goldstone mode,
and argue that the effective parameters of these pseudospin-$1/2$ models may be
strongly renormalized by coupling to a low energy spin-exciton. Our results
call for re-examining proposals for realizing Kitaev spin liquids in the
honeycomb cobaltates.",2106.11982v3
2013-05-06,Nonlinear modes in binary bosonic condensates with the pseudo-spin-orbital coupling,"We consider a binary Bose-Einstein condensate (BEC) with nonlinear repulsive
interactions and linear spin-orbit (SO) and Zeeman-splitting couplings. In the
presence of the trapping harmonic-oscillator (HO) potential, we report the
existence of even, odd, and asymmetric spatial modes. They feature alternating
domains with opposite directions of the pseudo-spin, i.e., anti-ferromagnetic
structures, which is explained by the interplay of the linear couplings, HO
confinement, and repulsive self-interaction. The number of the domains is
determined by the strength of the SO coupling. The modes are constructed
analytically in the weakly nonlinear system. The dynamical stability of the
modes is investigated by means of the Bogoliubov-de Gennes equations and direct
simulations. A notable result is that the multi-domain-wall (DW) structures are
stable, alternating between odd and even shapes, while the simplest single-DW
structure is unstable. Thus, the system features a transition to the complex
ground states under the action of the SO coupling. The addition of the Zeeman
splitting transforms the odd modes into asymmetric ones via spontaneous
symmetry breaking. The results suggest possibilities for switching the binary
system between states with opposite (pseudo) magnetization by external fields,
and realization of similar stable states and dynamical effects in solid-state
and nonlinear-optical settings emulated by the SO-coupled BECs.",1305.1147v3
2014-10-27,Spin-orbit interaction in GaAs wells: From one to two subbands,"We investigate the Rashba and Dresselhaus spin-orbit (SO) couplings in GaAs
quantum wells in the range of well widths $w$ allowing for a transition of the
electron occupancy from one to two subbands. By performing a detailed
Poisson-Schr\""odinger self-consistent calculation, we determine all the intra-
and inter-subband Rashba ($\alpha_1$, $\alpha_2$, $\eta$) and Dresselhaus
($\beta_1$, $\beta_2$, $\Gamma$) coupling strengths. For relatively narrow
wells with only one subband occupied, our results are consistent with the data
of Koralek \emph{et al.} [Nature \bfs{48}, 610 (2009)], i.e., the Rashba
coupling $\alpha_1$ is essentially independent of $w$ in contrast to the
decreasing linear Dresselhaus coefficient $\beta_1$. When we widen the well so
that the second subband can also be populated, we observe that $\alpha_2$
decreases and $\alpha_1$ increases, both almost linearly with $w$.
Interestingly, we find that in the parameter range studied (i.e., very
asymmetric wells) $\alpha_2$ can attain zero and change its sign, while
$\alpha_1$ is always positive. In this double-occupancy regime of $w$'s,
$\beta_1$ is mostly constant and $\beta_2$ decreases with $w$ (similarly to
$\beta_1$ for the single-occupancy regime). On the other hand, the intersubband
Rashba coupling strength $\eta$ decreases with $w$ while the intersubband
Dresselhaus $\Gamma$ remains almost constant. We also determine the
persistent-spin-helix symmetry points, at which the Rashba and the renormalized
(due to cubic corrections) linear Dresselhaus couplings in each subband are
equal, as a function of the well width and doping asymmetry. Our results should
stimulate experiments probing SO couplings in multi-subband wells.",1410.7358v2
2021-05-07,"Electronic structure, electron-phonon coupling and superconductivity in noncentrosymmetric ThCoC2 from ab initio calculations","Superconductors without inversion symmetry in their crystal structure are
known to exhibit unconventional properties. Recently, based on the measured
temperature dependence of the magnetic field penetration depth,
superconductivity in noncentrosymmetric $\mathrm{ThCoC_2}$ was proposed to be a
nodal $d$-wave and mediated by the spin fluctuations. Moreover, a non-BCS
behavior of the temperature dependence of the electronic specific heat and the
magnetic upper critical field were reported. In this work, the electronic
structure, phonons and electron-phonon coupling are studied in
$\mathrm{ThCoC_2}$ on the basis of \textit{ab initio} computations. The effect
of the spin-orbit coupling on the electronic structure and electron-phonon
interaction is analyzed, and a large splitting of the electronic band structure
is found. The calculated electron-phonon coupling constant $\lambda = 0.59$
remains in decent agreement with the experimental estimates, suggesting that
the electron-phonon interaction is strong enough to explain superconductivity
with $T_c \simeq 2.5$~K. Nevertheless, we show that the conventional isotropic
Eliashberg formalism is unable to describe the thermodynamic properties of the
superconducting state, as calculated temperature dependence of the electronic
specific heat and magnetic penetration depth deviate from experiments, which is
likely driven by the strong spin-orbit coupling and inversion symmetry
breaking. In addition, to shed more light on the pairing mechanism, we propose
to measure the carbon isotope effect, as our calculations based on the
electron-phonon coupling predict the observation of the isotope effect with an
exponent $\alpha \simeq 0.15$.",2105.03472v2
2022-09-01,Magnon dynamics in parity-time-symmetric dipolarly coupled waveguides and magnonic crystals,"We consider the magnonic properties of two dipolarly coupled magnetic
stripes, both deposited on a normal conductive substrate with strong spin-orbit
coupling. A charge current in the substrate acts on the adjacent magnets with
spin-orbit torques, which result in magnonic damping or antidamping of the spin
waves, and hence a gain-loss coupling of the two magnetic stripes. The whole
setup is demonstrated to exhibit features typical for parity-time (PT)
symmetric systems. Phenomena are demonstrated that can be functionalized in
magnonic devices, including reconfigurable magnonic diodes and logic devices.
Alternative stripes designs and PT-symmetric, periodic, coupled magnonic
textures are studied. Analytical and full numerical analysis identify the
conditions for the appearance of exceptional points (EPs), where magnonic gain
and loss are balanced and evidence nonreciprocal magnon propagation and
enhanced magnon excitation around EPs. Furthermore, the dipolar coupling is
shown to bring in a wave vector-dependent PT-symmetric behavior. Proposing and
simulating a PT-symmetric magnonic crystal, we show how EPs and hence
associated phenomena can be steered to a particular wave vector in a gaped
spectrum via material design. The phenomena offer additional tools for
magnonic-based communication and computational devices.",2209.00180v1
2004-07-21,Orbital magnetism in the half-metallic Heusler alloys,"Using the fully-relativistic screened Korringa-Kohn-Rostoker method I study
the orbital magnetism in the half-metallic Heusler alloys. Orbital moments are
almost completely quenched and they are negligible with respect to the spin
moments. The change in the atomic-resolved orbital moments can be easily
explained in terms of the spin-orbit strength and hybridization effects.
Finally I discuss the orbital and spin moments derived from X-ray magnetic
circular dichroism experiments.",0407560v1
2014-11-11,Quantum Optics of Chiral Spin Networks,"We study the driven-dissipative dynamics of a network of spin-1/2 systems
coupled to one or more chiral 1D bosonic waveguides within the framework of a
Markovian master equation. We determine how the interplay between a coherent
drive and collective decay processes can lead to the formation of pure
multipartite entangled steady states. The key ingredient for the emergence of
these many-body dark states is an asymmetric coupling of the spins to left and
right propagating guided modes. Such systems are motived by experimental
possibilities with internal states of atoms coupled to optical fibers, or
motional states of trapped atoms coupled to a spin-orbit coupled Bose-Einstein
condensate. We discuss the characterization of the emerging multipartite
entanglement in this system in terms of the Fisher information.",1411.2963v2
2019-01-29,Low-impedance superconducting microwave resonators for strong coupling to small magnetic mode volumes,"Recent experiments on strongly coupled microwave and ferromagnetic resonance
modes have focused on large volume bulk crystals such as yttrium iron garnet,
typically of millimeter-scale dimensions. We extend these experiments to lower
volumes of magnetic material by exploiting low-impedance lumped-element
microwave resonators. The low impedance equates to a smaller magnetic mode
volume, which allows us to couple to a smaller number of spins in the
ferromagnet. Compared to previous experiments, we reduce the number of
participating spins by two orders of magnitude, while maintaining the strength
of the coupling rate. Strongly coupled devices with small volumes of magnetic
material may allow the use of spin orbit torques, which require high current
densities incompatible with existing structures.",1901.10395v1
2017-11-16,Yu-Shiba-Rusinov screening of spins in double quantum dots,"A magnetic impurity coupled to a superconductor gives rise to a
Yu-Shiba-Rusinov (YSR) state inside the superconducting energy gap. With
increasing exchange coupling the excitation energy of this state eventually
crosses zero and the system switches to a YSR groundstate with bound
quasiparticles screening the impurity spin by $\hbar/2$. Here we explore InAs
nanowire double quantum dots tunnel coupled to a superconductor and demonstrate
YSR screening of spin-1/2 and spin-1 states. Gating the double dot through 9
different charge states, we show that the honeycomb pattern of zero-bias
conductance peaks, archetypal of double dots coupled to normal leads, is
replaced by lines of zero-energy YSR states. These enclose regions of
YSR-screened dot spins displaying distinctive spectral features, and their
characteristic shape and topology change markedly with tunnel coupling
strengths. We find excellent agreement with a simple zero-bandwidth
approximation, and with numerical renormalization group calculations for the
two-orbital Anderson model.",1711.06081v1
2021-05-18,"Spatial order in a two-dimensional spin-orbit-coupled spin-1/2 condensate: superlattice, multi-ring and stripe formation","We demonstrate the formation of stable spatially-ordered states in a {\it
uniform} and also {\it trapped} quasi-two-dimensional (quasi-2D) Rashba or
Dresselhaus spin-orbit (SO) coupled pseudo spin-1/2 Bose-Einstein condensate
using the mean-field Gross-Pitaevskii equation. For weak SO coupling, one can
have a circularly-symmetric $(0,+1)$- or $(0,-1)$-type multi-ring state with
intrinsic vorticity, for Rashba or Dresselhaus SO coupling, respectively, where
the numbers in the parentheses denote the net angular momentum projection in
the two components, in addition to a circularly-asymmetric degenerate state
with zero net angular momentum projection. For intermediate SO couplings, in
addition to the above two types, one can also have states with stripe pattern
in component densities with no periodic modulation in total density. The stripe
state continues to exist for large SO coupling. In addition, a new
spatially-periodic state appears in the uniform system: a superlattice state,
possessing some properties of a supersolid, with a square-lattice pattern in
component densities and also in total density. In a trapped system the
superlattice state is slightly different with multi-ring pattern in component
density and a square-lattice pattern in total density. For an equal mixture of
Rashba and Dresselhaus SO couplings, in both uniform and trapped systems, only
stripe states are found for all strengths of SO couplings. In a uniform system
all these states are quasi-2D solitonic states.",2105.08849v3
2018-09-11,Neutron Scattering Investigation of Rhenium Orbital Ordering in $3d-5d$ Double Perovskite Ca$_2$FeReO$_6$,"We have carried out inelastic neutron scattering experiments to study
magnetic excitations in ordered double perovskite Ca$_2$FeReO$_6$. We found a
well-defined magnon mode with a bandwidth of $\sim$50meV below the
ferri-magnetic ordering temperature ($T_c\sim$520K), similar to previously
studied Ba$_2$FeReO$_6$. The spin excitation is gapless for most temperatures
within the magnetically ordered phase. However, a spin gap of $\sim$10meV opens
up below $\sim$150K, which is well below the magnetic ordering temperature but
coincides with a previously reported metal-insulator transition and onset of
structural distortion. The observed temperature dependence of spin gap provides
strong evidence for ordering of Re orbitals at $\sim$150~K, in accordance with
earlier proposal put forward by Oikawa $\it{et.\,al}$ based on neutron
diffraction [J. Phys. Soc. Jpn., $\bf{72}$, 1411 (2003)] as well as recent
theoretical work by Lee and Marianetti [Phys. Rev. B, $\bf{97}$, 045102
(2018)]. The presence of separate orbital and magnetic ordering in
Ca$_2$FeReO$_6$ suggests weak coupling between spin and orbital degrees of
freedom and hints towards a sub-dominant role played by spin orbit coupling in
describing its magnetism. In addition, we observed only one well-defined magnon
band near magnetic zone boundary, which is incompatible with simple
ferrimagnetic spin waves arising from Fe and Re local moments, but suggests a
strong damping of Re magnon mode.",1809.03647v2
2018-09-29,Giant and anisotropic many-body spin-orbit tunability in a strongly correlated kagome magnet,"Owing to the unusual geometry of kagome lattices-lattices made of
corner-sharing triangles-their electrons are useful for studying the physics of
frustrated, correlated and topological quantum electronic states. In the
presence of strong spin-orbit coupling, the magnetic and electronic structures
of kagome lattices are further entangled, which can lead to hitherto unknown
spin-orbit phenomena. Here we use a combination of vector-magnetic-field
capability and scanning tunnelling microscopy to elucidate the spin-orbit
nature of the kagome ferromagnet Fe3Sn2 and explore the associated exotic
correlated phenomena. We discover that a many-body electronic state from the
kagome lattice couples strongly to the vector field with three-dimensional
anisotropy, exhibiting a magnetization-driven giant nematic
(two-fold-symmetric) energy shift. Probing the fermionic quasi-particle
interference reveals consistent spontaneous nematicity-a clear indication of
electron correlation-and vector magnetization is capable of altering this
state, thus controlling the many-body electronic symmetry. These spin-driven
giant electronic responses go well beyond Zeeman physics and point to the
realization of an underlying correlated magnetic topological phase. The
tunability of this kagome magnet reveals a strong interplay between an
externally applied field, electronic excitations and nematicity, providing new
ways of controlling spin-orbit properties and exploring emergent phenomena in
topological or quantum materials.",1810.00218v1
2014-12-22,Inverse magneto-refraction as a mechanism for laser modification of spin-spin exchange parameters and subsequent terahertz emission from iron oxides,"Ultrafast non-thermal manipulation of magnetization by light relies on either
indirect coupling of the electric field component of the light with spins via
spin-orbit interaction or direct coupling between the magnetic field component
and spins. Here we propose a novel scenario for coupling between the electric
field of light and spins via optical modification of the exchange interaction,
one of the strongest quantum effects, the strength of which can reach 1000
Tesla. We demonstrate that this isotropic opto-magnetic effect, which can be
called the inverse magneto-refraction, is allowed in a material of any
symmetry. Its existence is corroborated by the experimental observation of THz
emission by magnetic-dipole active spin resonances optically excited in a broad
class of iron oxides with a canted spin configuration. From its strength we
estimate that a sub-picosecond laser pulse with a moderate fluence of ~ 1
mJ/cm^2 acts as a pulsed effective magnetic field of 0.01 Tesla, arising from
the optically perturbed balance between the exchange parameters. Our findings
are supported by a low-energy theory for the microscopic magnetic interactions
between non-equilibrium electrons subjected to an optical field which suggests
a possibility to modify the exchange interactions by light over 1 %.",1412.7094v1
2018-07-09,Cavity-induced emergent topological spin textures in a Bose Einstein condensate,"The coupled nonlinear dynamics of ultracold quantum matter and
electromagnetic field modes in an optical resonator exhibits a wealth of
intriguing collective phenomena. Here we study a $\Lambda$-type,
three-component Bose-Einstein condensate coupled to four dynamical running-wave
modes of a ring cavity, where only two of the modes are externally pumped.
However, the unpumped modes play a crucial role in the dynamics of the system
due to coherent back-scattering of photons. On a mean- field level we identify
three fundamentally different steady-state phases with distinct characteristics
in the density and spatial spin textures: a combined density and spin wave, a
continuous spin spiral with a homogeneous density, and a spin spiral with a
modulated density. The spin-spiral states, which are topological, are
intimately related to cavity-induced spin-orbit coupling emerging beyond a
critical pump power. The topologically trivial density-wave--spin-wave state
has the characteristics of a supersolid with two broken continuous symmetries.
The transitions between different phases are either simultaneously topological
and first order, or second order. The proposed setup allows the simulation of
intriguing many-body quantum phenomena by solely tuning the pump amplitudes and
frequencies, with the cavity output fields serving as a built-in nondestructive
observation tool.",1807.03316v1
2017-11-23,Spin-Interaction Effects for Ultralong-range Rydberg Molecules in a Magnetic Field,"We investigate the fine and spin structure of ultralong-range Rydberg
molecules exposed to a homogeneous magnetic field. Each molecule consists of a
$^{87}$Rb Rydberg atom whose outer electron interacts via spin-dependent $s$-
and p-wave scattering with a polarizable $^{87}$Rb ground state atom. Our model
includes also the hyperfine structure of the ground state atom as well as
spin-orbit couplings of the Rydberg and ground state atom. We focus on
$d$-Rydberg states and principal quantum numbers $n$ in the vicinity of 40. The
electronic structure and vibrational states are determined in the framework of
the Born-Oppenheimer approximation for varying field strengths ranging from a
few up to hundred Gau{\ss}. The results show that the interplay between the
scattering interactions and the spin couplings gives rise to a large variety of
molecular states in different spin configurations as well as in different
spatial arrangements that can be tuned by the magnetic field. This includes
relatively regularly shaped energy surfaces in a regime where the Zeeman
splitting is large compared to the scattering interaction but small compared to
the Rydberg fine structure, as well as more complex structures for both, weaker
and stronger fields. We quantify the impact of spin couplings by comparing the
extended theory to a spin-independent model.",1711.08748v2
2019-06-18,Noninertial and spin effects on the 2D Dirac oscillator in the magnetic cosmic string background,"In this work, we analyze the influence of noninertial and spin effects on the
dynamics of the 2D Dirac oscillator in the magnetic cosmic string background.
To model this background, we consider a uniform magnetic field, the
Aharonov-Bohm effect, and a parameter $\eta$ generated by a cosmic string.
Posteriorly, we determine the bound-state solutions of the system: the Dirac
spinor and the relativistic energy spectrum. We verified that this spinor is
written in terms of the generalized Laguerre polynomials and this spectrum
depends on the effective quantum number $N_r$, angular velocity $\Omega$ and
parameter $s$ associated to the noninertial and spin effects, magnetic flux
$\Phi$, cyclotron frequency $\omega_c$, zero-point energy $E_0$, and on the
deficit angle $\eta$. In particular, we note that besides this spectrum to be a
periodic function and asymmetric, its values infinitely increase when $\eta\to
0$ or $N_r=\omega_c=\Omega\to\infty$. We also note that the energies of the
antiparticle with spin down are larger than of the particle with spin up or
down. In the nonrelativistic limit, we get the Schr\""{o}dinger-Pauli oscillator
with two types of couplings: the spin-orbit coupling and the spin-rotation
coupling, and two Hamiltonians: one quantum harmonic oscillator-type and other
Zeeman-type. Finally, we compare our results with other works, where we
verified that our problem generalizes some particular cases of the literature
when $\Omega$, $\omega_c$, $\Phi$, $s$ or $\eta$ are excluded from the system.",1906.07369v2
2022-07-30,"Coupled spin-valley, Rashba effect and hidden persistent spin polarization in WSi$_2$N$_4$ family","The new two-dimensional materials, MoSi$_2$N$_4$ and WSi$_2$N$_4$ are
experimentally synthesized successfully and various similar structures are
predicted theoretically. Here, we report the electronic properties with a
special focus on the band splitting in WA$_2$Z$_4$ (A=Si, Ge; Z=N, P, As),
using state-of-the-art density functional theory and many-body perturbation
theory (within the framework of G$_0$W$_0$ and BSE). Due to the broken
inversion symmetry and strong spin-orbit coupling effects, we detect coupled
spin-valley effects at the corners of the first Brillouin zone (BZ).
Additionally, we observe cubically and linearly split bands around the $\Gamma$
and M points, respectively. Interestingly, the in-plane mirror symmetry
($\sigma_h$) and the reduced symmetry of arbitrary $k$-point, enforce the
persistent spin textures (PST) to occur in full BZ. We induce the Rashba
splitting by breaking the $\sigma_h$ through an out-of-plane external electric
field (EEF). The inversion asymmetric site point group of the W atom introduces
the hidden spin polarization in centrosymmetric layered bulk counterparts.
Therefore, the spin-layer locking effect, namely, energy degenerate opposite
spins spatially segregated in the top and bottom W layers, has been identified.
Our low energy $k.p$ model demonstrates that the PST along the M-K line is
robust to EEF and layer thickness, making them suitable for applications in
spintronics and valleytronics.",2208.00127v1
2023-01-12,Type II multiferroic order in two-dimensional transition metal halides from first principles spin-spiral calculations,"We present a computational search for spin spiral ground states in
two-dimensional transition metal halides that are experimentally known as van
der Waals bonded bulk materials. Such spin spirals break the rotational
symmetry of the lattice and lead to polar ground states where the axis of
polarization is strongly coupled to the magnetic order (type II multiferroics).
We apply the generalized Bloch theorem in conjunction with non-collinear
density functional theory calculations to find the spiralling vector that
minimizes the energy and then include spin-orbit coupling to calculate the
preferred orientation of the spin plane with respect to the spiral vector. We
find a wide variety of magnetic orders ranging from ferromagnetic, stripy
anti-ferromagnetic, 120$^\circ$ non-collinear structures and incommensurate
spin spirals. The latter two introduce polar axes and are found in the majority
of materials considered here. The spontaneous polarization is calculated for
the incommensurate spin spirals by performing full supercell relaxation
including spinorbit coupling and the induced polarization is shown to be
strongly dependent on the orientation of the spiral planes. We also test the
effect of Hubbard corrections on the results and find that for most materials
LDA+U results agree qualitatively with LDA. An exception is the Mn halides,
which are found to exhibit incommensurate spin spiral ground states if Hubbard
corrections are included whereas bare LDA yields a 120$^\circ$ non-collinear
ground state.",2301.05107v1
2018-09-04,Chiral magnetic interlayer coupling in synthetic antiferromagnets,"The exchange coupling underlies ferroic magnetic coupling and is thus the key
element that governs statics and dynamics of magnetic systems. This fundamental
interaction comes in two flavors - symmetric and antisymmetric coupling. While
symmetric coupling leads to ferro- and antiferromagnetism, antisymmetric
coupling has attracted significant interest owing to its major role in
promoting topologically non-trivial spin textures that promise high-speed and
energy-efficient devices. So far, the antisymmetric exchange coupling rather
short-ranged and limited to a single magnetic layer has been demonstrated,
while the symmetric coupling also leads to long-range interlayer exchange
coupling. Here, we report the missing component of the long-range antisymmetric
interlayer exchange coupling in perpendicularly magnetized synthetic
antiferromagnets with parallel and antiparallel magnetization alignments.
Asymmetric hysteresis loops under an in-plane field unambiguously reveal a
unidirectional and chiral nature of this novel interaction, which cannot be
accounted for by existing coupling mechanisms, resulting in canted
magnetization alignments. This can be explained by spin-orbit coupling combined
with reduced symmetry in multilayers. This new class of chiral interaction
provides an additional degree of freedom for engineering magnetic structures
and promises to enable a new class of three-dimensional topological structures.",1809.01080v2
2017-07-07,"Universal magneto-orbital ordering in the divalent $A$-site quadruple perovskite manganites $A$Mn$_7$O$_{12}$ ($A$ = Ca, Sr, Cd, and Pb)","Through analysis of variable temperature neutron powder diffraction data, we
present solutions for the magnetic structures of SrMn$_7$O$_{12}$,
CdMn$_7$O$_{12}$, and PbMn$_7$O$_{12}$ in all long-range ordered phases. The
three compounds were found to have magnetic structures analogous to that
reported for CaMn$_7$O$_{12}$. They all feature a higher temperature lock-in
phase with \emph{commensurate} magneto-orbital coupling, and a delocked,
multi-\textbf{k} magnetic ground state where \emph{incommensurate}
magneto-orbital coupling gives rise to a constant-moment magnetic helix with
modulated spin helicity. CdMn$_7$O$_{12}$ represents a special case in which
the orbital modulation is commensurate with the crystal lattice and involves
stacking of fully and partially polarized orbital states. Our results provide a
robust confirmation of the phenomenological model for magneto-orbital coupling
previously presented for CaMn$_7$O$_{12}$. Furthermore, we show that the model
is universal to the $A^{2+}$ quadruple perovskite manganites synthesised to
date, and that it is tunable by selection of the $A$-site ionic radius.",1707.02218v1
2019-08-07,"Continuous monitoring of a trapped, superconducting spin","Readout and control of fermionic spins in solid-state systems are key
primitives of quantum information processing and microscopic magnetic sensing.
The highly localized nature of most fermionic spins decouples them from
parasitic degrees of freedom, but makes long-range interoperability difficult
to achieve. In light of this challenge, an active effort is underway to
integrate fermionic spins with circuit quantum electrodynamics (cQED), which
was originally developed in the field of superconducting qubits to achieve
single-shot, quantum-non-demolition (QND) measurements and long-range
couplings. However, single-shot readout of an individual spin with cQED has
remained elusive due to the difficulty of coupling a resonator to a particle
trapped by a charge-confining potential. Here we demonstrate the first
single-shot, cQED readout of a single spin. In our novel implementation, the
spin is that of an individual superconducting quasiparticle trapped in the
Andreev levels of a semiconductor nanowire Josephson element. Due to a
spin-orbit interaction inside the nanowire, this ""superconducting spin""
directly determines the flow of supercurrent through the element. We harnessed
this spin-dependent supercurrent to achieve both a zero-field spin splitting as
well as a long-range interaction between the quasiparticle and a
superconducting microwave resonator. Owing to the strength of this interaction
in our device, measuring the resultant spin-dependent resonator frequency
yielded QND spin readout with 92% fidelity in 1.9 $\mu$s and allowed us to
monitor the quasiparticle's spin in real time. These results pave the way for
new ""fermionic cQED"" devices: superconducting spin qubits operating at zero
magnetic field, devices in which the spin has enhanced governance over the
circuit, and time-domain measurements of Majorana modes.",1908.02800v1
2023-10-31,Strong hole-photon coupling in planar Ge: probing the charge degree and Wigner molecule states,"Semiconductor quantum dots (QDs) in planar germanium (Ge) heterostructures
have emerged as frontrunners for future hole-based quantum processors. Notably,
the large spin-orbit interaction of holes offers rapid, coherent electrical
control of spin states, which can be further beneficial for interfacing hole
spins to microwave photons in superconducting circuits via coherent
charge-photon coupling. Here, we present strong coupling between a hole charge
qubit, defined in a double quantum dot (DQD) in a planar Ge, and microwave
photons in a high-impedance ($Z_\mathrm{r} = 1.3 ~ \mathrm{k}\Omega$)
superconducting quantum interference device (SQUID) array resonator. Our
investigation reveals vacuum-Rabi splittings with coupling strengths up to
$g_{0}/2\pi = 260 ~ \mathrm{MHz}$, and a cooperativity of $C \sim 100$,
dependent on DQD tuning, confirming the strong charge-photon coupling regime
within planar Ge. Furthermore, utilizing the frequency tunability of our
resonator, we explore the quenched energy splitting associated with
strongly-correlated Wigner molecule (WM) states that emerge in Ge QDs. The
observed enhanced coherence of the WM excited state signals the presence of
distinct symmetries within related spin functions, serving as a precursor to
the strong coupling between photons and spin-charge hybrid qubits in planar Ge.
This work paves the way towards coherent quantum connections between remote
hole qubits in planar Ge, required to scale up hole-based quantum processors.",2310.20661v1
2021-06-09,Maximizing Spin-Orbit Torque Generated by the Spin Hall Effect of Pt,"Efficient generation of spin-orbit torques (SOTs) is central for the exciting
field of spin-orbitronics. Platinum, the archetypal spin Hall material, has the
potential to be an outstanding provider for spin-orbit torques due to its giant
spin Hall conductivity, low resistivity, high stabilities, and the ability to
be compatible with CMOS circuits. However, pure clean-limit Pt with low
resistivity still provides a low damping-like spin-orbit torque efficiency,
which limits its practical applications. The efficiency of spin-orbit torque in
Pt-based magnetic heterostructures can be improved considerably by increasing
the spin Hall ratio of Pt and spin transmissivity of the interfaces. Here we
reviews recent advances in understanding the physics of spin current
generation, interfacial spin transport, and the metrology of spin-orbit
torques, and summarize progress towards the goal of Pt-based spin-orbit torque
memories and logic that are fast, efficient, reliable, scalable, and
non-volatile.",2106.04992v2
2023-11-09,Orbital-selective Superconductivity in the Pressurized Bilayer Nickelate La$_3$Ni$_2$O$_7$: An Infinite Projected Entangled-Pair State Study,"The newly discovered high-$T_c$ nickelate superconductor La$_3$Ni$_2$O$_7$
has generated significant research interest. To uncover the pairing mechanism,
it is essential to investigate the intriguing interplay between the two $e_g$,
i.e., $d_{x^2-y^2}$ and $d_{z^2}$ orbitals. Here we perform an infinite
projected entangled-pair state (iPEPS) study of the bilayer $t$-$J$ model,
directly in the thermodynamic limit and with orbitally selective parameters for
$d_{x^2-y^2}$ and $d_{z^2}$ orbitals, respectively. The $d_{x^2-y^2}$ electrons
exhibit significant intralayer hopping $t_\parallel$ and spin couplings
$J_\parallel$, with interlayer $J_\perp$ passed from the $d_{z^2}$ electrons.
However, the interlayer $t_\perp$ is negligible in this case. In contrast, the
$d_{z^2}$ orbital demonstrates strong interlayer $t_\perp$ and $J_\perp$, while
the inherent intralayer $t_\parallel$ and $J_\parallel$ are small. Based on the
iPEPS results, we find clear orbital-selective behaviors in La$_3$Ni$_2$O$_7$.
The $d_{x^2-y^2}$ orbitals exhibit robust superconductive (SC) order driven by
the interlayer coupling $J_\perp$; while the $d_{z^2}$ band shows relatively
weak SC order even if we artificially introduce some $t_\parallel$ to it.
Furthermore, by substituting rare-earth element Pm or Sm with La, we find an
enhanced SC order, which opens up a promising avenue for discovering nickelate
superconductors with even higher $T_c$.",2311.05491v2
2016-07-08,Morphology effects on spin-dependent transport and recombination in polyfluorene thin films,"We have studied the role of spin-dependent processes on conductivity in
polyfluorene (PFO) thin films by conducting continuous wave (c.w.) electrically
detected magnetic resonance (EDMR) spectroscopy at temperatures between 10 K
and 293 K using microwave frequencies between about 100 MHz and 20 GHz as well
as pulsed EDMR at X-band. Variable frequency EDMR allows us to establish the
role of spin-orbit coupling in spin-dependent processes, pulsed EDMR probes
coherent spin motion effects. We used PFO for this study in order to allow for
the investigation of the effects of microscopic morphological ordering since
this material can adopt two distinct intrachain morphologies: an amorphous
(glassy) phase, and an ordered (beta) phase. In thin films of organic
light-emitting diodes (OLEDs) the appearance of a particular phase can be
controlled by deposition parameters, and is verified by electroluminescence
spectroscopy. We conducted multi-frequency c.w. EDMR, electrically detected
Rabi spinbeat experiments, Hahn-echo and inversion-recovery measurements.
Coherent echo spectroscopy reveals electrically detected electron spin-echo
envelope modulation (ESEEM) due to the precession of the carrier spins around
the protons. Our results demonstrate that while conformational disorder can
influence the observed EDMR signals, including the sign of the current changes
on resonance as well as the magnitudes of local hyperfine fields and charge
carrier spin-orbit interactions, it does not qualitatively affect the nature of
spin-dependent transitions in this material. At 293 K and 10 K, polaron-pair
recombination through weakly spin-spin coupled intermediate charge carrier pair
states is dominant, while at low temperatures, additional signatures of
spin-dependent charge transport through the interaction of polarons with
triplet excitons are seen in the half-field resonance of a triplet spin-1
species.",1607.02462v1
2019-12-19,Magnon-driven chiral charge and spin pumping and electron-magnon scattering from time-dependent quantum transport combined with atomistic spin dynamics theory,"Using newly developed quantum-classical hybrid framework, we investigate
interaction between spin-polarized conduction electrons and a single spin wave
(SW) coherently excited within a metallic ferromagnetic nanowire. When the
nanowire hosting SW is attached to two normal metal (NM) leads, with no dc bias
voltage applied between them, the SW pumps chiral electronic charge and spin
currents into the leads---their direction is tied to the direction of SW
propagation and they scale linearly with the frequency of the precession. This
is in contrast to: standard pumping by the uniform precession mode with
identical spin currents flowing in both directions and no accompanying charge
current; or experimentally observed [C.~Ciccarelli et al., Nat. Nanotech. 10,
50 (2014); M.~Evelt et al., Phys. Rev. B 95, 024408 (2017)] magnonic charge
pumping which requires spin-orbit coupling spin-orbit coupling. The mechanism
behind our prediction is nonadiabaticity due to time-retardation
effects---motion of localized magnetic moment affects conduction electron spin
in a retarded way, so that it takes a finite time until the electron spin
reacts to the motion of the classical vector. Upon injecting dc spin-polarized
charge current from the left NM lead, electrons interact with SW where
outflowing charge and spin current into the right NM lead are changed due to
both scattering off time-dependent potential generated by the SW and
superposition with the currents pumped by the SW itself. Using Lorentzian
voltage pulse to excite leviton out of the Fermi sea, which carries one
electron charge with no accompanying electron-hole pairs and behaves as
soliton-like quasiparticle, we describe how a single electron interacts with a
single SW.",1912.09452v2
2018-10-19,Theoretical evidence of spin-orbital-entangled $J_{\mathbf{eff}}$=1/2 state in the 3$d$ transition metal oxide CuAl$_2$O$_4$,"Transition metal oxides exhibit various competing phases and exotic phenomena
depending on how their reaction to the rich degeneracy of the $d$-orbital.
Large spin-orbit coupling (SOC) reduces this degeneracy in a unique way by
providing a spin-orbital-entangled ground state for 4$d$ and 5$d$ transition
metal compounds. In particular, the spin-orbital-entangled Kramers doublet,
known as the $J_{\mathbf{eff}}$=1/2 pseudospin, appears in layered iridates and
$\alpha$-RuCl$_3$, manifesting a relativistic Mott insulating phase. Such
entanglement, however, seems barely attainable in 3$d$ transition metal oxides,
where the SOC is small and the orbital angular momentum is easily quenched.
From experimental and theoretical evidence, here we report on the CuAl$_2$O$_4$
spinel as the first example of a $J_{\mathbf{eff}}$=1/2 Mott insulator in 3$d$
transition metal compounds. Based on the experimental study, including
synthesis of the cubic CuAl$_2$O$_4$ single crystal, density functional theory
and dynamical mean field theory calculations reveal that the
$J_{\mathbf{eff}}$=1/2 state survives the competition with an
orbital-momentum-quenched $S$=1/2 state. The electron-addition spectra probing
unoccupied states are well described by the $j_{\mathbf{eff}}$=1/2 hole state,
whereas electron-removal spectra have a rich multiplet structure. The fully
relativistic entity found in CuAl$_2$O$_4$ provides new insight into the
untapped regime where the spin-orbital-entangled Kramers pair coexists with
strong electron correlation.",1810.08594v3
2016-07-27,"Theory of proximity-induced exchange coupling in graphene on hBN/(Co, Ni)","We perform systematic first-principles calculations of the proximity exchange
coupling, induced by cobalt (Co) and nickel (Ni) in graphene, via a few (up to
three) layers of hexagonal boron nitride (hBN). We find that the induced spin
splitting of the graphene bands is of the order of 10 meV for a monolayer of
hBN, decreasing in magnitude but alternating in sign by adding each new
insulating layer. We find that the proximity exchange can be giant if there is
a resonant $d$ level of the transition metal close to the Dirac point. Our
calculations suggest that this effect could be present in Co heterostructures,
in which a $d$ level strongly hybridizes with the valence-band orbitals of
graphene. Since this hybridization is spin dependent, the proximity spin
splitting is unusually large, about 10 meV even for two layers of hBN. An
external electric field can change the offset of the graphene and
transition-metal orbitals and can lead to a reversal of the sign of the
exchange parameter. This we predict to happen for the case of two monolayers of
hBN, enabling electrical control of proximity spin polarization (but also spin
injection) in graphene/hBN/Co structures. Nickel-based heterostructures show
weaker proximity effects than cobalt heterostructures. We introduce two
phenomenological models to describe the first-principles data. The minimal
model comprises the graphene (effective) $p_z$ orbitals and can be used to
study transport in graphene with proximity exchange, while the $p_z$-$d$ model
also includes hybridization with $d$ orbitals, which is important to capture
the giant proximity exchange. Crucial to both models is the
pseudospin-dependent exchange coupling, needed to describe the different spin
splittings of the valence and conduction bands.",1607.08008v2
2018-10-10,Spin-Orbital Entangled Liquid State in the Copper Oxide Ba$_3$CuSb$_2$O$_9$,"Structure with orbital degeneracy is unstable toward spontaneous distortion.
Such orbital correlation usually has a much higher energy scale than spins, and
therefore, magnetic transition takes place at a much lower temperature, almost
independently from orbital ordering. However, when the energy scales of
orbitals and spins meet, there is a possibility of spin-orbital entanglement
that would stabilize novel ground state such as spin-orbital liquid and random
singlet state. Here we review on such a novel spin-orbital magnetism found in
the hexagonal perovskite oxide Ba$_3$CuSb$_2$O$_9$, which hosts a
self-organized honeycomblike short-range order of a strong Jahn-Teller ion
Cu$^{2+}$. Comprehensive structural and magnetic measurements have revealed
that the system has neither magnetic nor Jahn-Teller transition down to the
lowest temperatures, and Cu spins and orbitals retain the hexagonal symmetry
and paramagnetic state. Various macroscopic and microscopic measurements all
indicate that spins and orbitals remain fluctuating down to low temperatures
without freezing, forming a spin-orbital entangled liquid state.",1810.04346v1
2001-05-11,Spectacular doping dependence of interlayer exchange and other results on spin waves in bilayer manganites,"We report the measurement of spin waves in the bilayer colossal
magnetoresistive manganites La(2-2x)Sr(1+2x)Mn2O7 with x=0.30, 0.35 and 0.40.
For x=0.35 and 0.40 the entire acoustic and optic dispersion relations are
reasonably well described by those for a bilayer Heisenberg Hamiltonian with
nearest neighbour exchange only. The in-plane coupling is only weakly dependent
on x, but the coupling between the planes of a bilayer changes by a factor of
four. The results directly reveal the change from mixed and character of the
orbitals to mostly character with increasing hole concentration.",0105230v1
2002-07-03,Planar spin exchange in LiNiO_2,"We study the planar spin exchange couplings in LiNiO2 using a perturbative
approach. We show that the inclusion of the trigonal crystal field splitting at
the Oxygen sites leads to the appearance of antiferromagnetic exchange
integrals in deviation from the Goodenough-Kanamori-Anderson rules for this 90
degree bond. That gives a microscopic foundation for the recently observed
coexistence of ferromagnetic and antiferromagnetic couplings in the
orbitally-frustrated state of LiNiO2. (F. Reynaud et al, Phys. Rev. Lett. 86,
3638 (2001))",0207104v1
1995-05-02,Mixed Symmetry Solutions of Generalized Three-Particle Bargmann-Wigner Equations in the Strong-Coupling Limit,"Starting from a nonlinear isospinor-spinor field equation, generalized
three-particle Bargmann-Wigner equations are derived. In the strong-coupling
limit, a special class of spin 1/2 bound-states are calculated. These solutions
which are antisymmetric with respect to all indices, have mixed symmetries in
isospin-superspin space and in spin orbit space. As a consequence of this mixed
symmetry, we get three solution manifolds. In appendix \ref{b}, table 2, these
solution manifolds are interpreted as the three generations of leptons and
quarks. This interpretation will be justified in a forthcoming paper.",9505015v1
2004-05-14,The library of subroutines for calculation of matrix elements of two-particle operators for many-electron atoms,"In this paper a library for spin--angular integration in LS-coupling for
many-electron atoms is presented. The software is an implementation of a
methodology based on the second quantization in coupled tensorial form, the
angular momentum theory in 3 spaces (orbital, spin and quasispin), and the
graphical technique of angular momentum. This implementation extends
applications of the relevant methodology to open f- shells and leads to faster
execution of angular integration codes. The possibility of using some library
routines for solving various angular momentum problems in atomic physics is
also discussed.",0405072v1
2004-05-15,Integration over spin-angular variables in atomic physics,"A review of methods for finding general expressions for matrix elements
(non-diagonal with respect to configurations included) of any one- and
two-particle operator for an arbitrary number of shells in an atomic
configuration is given. These methods are compared in various aspects, and the
advantages or shortcomings of each particular method are discussed. Efficient
method to find the abovementioned quantities in LS coupling is presented, based
on the use of symmetry properties of operators and matrix elements in three
spaces (orbital, spin and quasispin), second quantization in coupled tensorial
form, graphical technique and Wick's theorem. This allows to efficiently
account for correlation effects practically for any atom and ion of periodical
table.",0405078v1
2010-06-21,Exact Solution of the Klein-Gordon Equation for the Hydrogen Atom Including Electron Spin,"The term describing the coupling between total angular momentum and
energy-momentum in the hydrogen atom is isolated from the radial Dirac equation
and used to replace the corresponding orbital angular momentum coupling term in
the radial K-G equation. The resulting spin-corrected K-G equation is a second
order differential equation that contains no matrices. It is solved here to
generate the same energy eigenvalues for the hydrogen atom as the Dirac
equation.",1006.3971v1
2010-08-27,Electromagnons in the spin collinear state of a triangular lattice antiferromagnet,"Terahertz time-domain spectroscopy was performed to directly probe the
low-energy (1-5 meV) electrodynamics of triangular lattice antiferromagnets
CuFe1-xGaxO2 (x = 0.00, 0.01, and 0.035). We discovered an electromagnon
(electric-field-active magnon) excitation at 2.3 meV in the paraelectric
up-up-down-down collinear magnetic phase, while this electromagnon vanishes in
the ferroelectric helimagnetic phase. Anti-correlation with noncollinear
magnetism excludes the exchange-striction mechanism as the origin of dynamical
magnetoelectric coupling, and hence evidences the observation of spin-orbit
coupling mediated electromagnon in the present compound.",1008.4709v1
2011-03-16,Theoretical investigation of magnetoelectric effects in Ba2CoGe2O7,"A joint theoretical approach, combining macroscopic symmetry analysis with
microscopic methods (density functional theory and model cluster Hamiltonian),
is employed to shed light on magnetoelectricity in Ba2CoGe2O7. We show that the
recently reported experimental trend of polarization guided by magnetic field
can be predicted on the basis of phenomenological Landau theory. From the
microscopic side, Ba2CoGe2O7 emerges as a prototype of a class of
magnetoelectrics, where the cross coupling between magnetic and dipolar degrees
of freedom needs, as main ingredients, the on-site spin-orbit coupling and the
spin-dependent O p - Co d hybridization, along with structural constraints
related to the noncentrosymmetric structural symmetry and the peculiar
configuration of CoO4 tetrahedrons.",1103.3151v1
2011-07-14,Electrically controlled quantum gates for two-spin qubits in two double quantum dots,"Exchange-coupled singlet-triplet spin qubits in two gate-defined double
quantum dots are considered theoretically. Using charge density operators to
describe the double-dot orbital states, we calculate the Coulomb couplings
between the qubits, and identify optimal bias points for single- and two-qubit
operations, as well as convenient idle positions. The same intuitive
formulation is used to derive dephasing rates of these qubits due to the
fluctuating charge environment, thereby providing the main considerations for a
quantum computation architecture that is within current experimental
capabilities.",1107.2968v1
2014-01-29,Quantum magnetism of ultracold atoms with a dynamical pseudospin degree of freedom,"We consider bosons in a Hubbard lattice with an SU($\cal N$) pseudospin
degree of freedom which is made dynamical via a coherent transfer term. It is
shown that, in the basis which diagonalizes the pseudospin coupling, a generic
hopping process affects the spin state, similar to a spin-orbit coupling. This
results, for the system in the Mott phase, in a ferromagnetic phase with
variable quantization axis. In extreme cases, it can even give rise to
antiferromagnetic order.",1401.7608v1
2019-07-05,Rashba cavity QED: a route towards the superradiant quantum phase transition,"We develop a theory of cavity quantum electrodynamics for a 2D electron gas
in the presence of Rashba spin-orbit coupling and perpendicular static magnetic
field, coupled to spatially nonuniform multimode quantum cavity photon fields.
We demonstrate that the lowest polaritonic frequency of the full Hamiltonian
can vanish for realistic parameters, achieving the Dicke superradiant quantum
phase transition. This singular behaviour originates from soft spin-flip
transitions possessing a non-vanishing dipole moment at non-zero wave vectors
and can be viewed as a magnetostatic instability.",1907.02938v1
2017-09-05,Voltage control of interface rare-earth magnetic moments,"The large spin orbit interaction in rare earth atoms implies a strong
coupling between their charge and spin degrees of freedom. We formulate the
coupling between voltage and the local magnetic moments of rare earth atoms
with partially filled 4f shell at the interface between an insulator and a
metal. The rare earth-mediated torques allow power-efficient control of
spintronic devices by electric field-induced ferromagnetic resonance and
magnetization switching.",1709.01271v1
2018-08-10,Anomalous Josephson Effect in S/SO/F/S heterostructures,"We study the anomalous Josephson effect, as well as the dependence on the
direction of the critical Josephson current, in an S/N/S junction, where the
normal part is realized by alternating spin-orbit coupled and ferromagnetic
layers. We show that to observe these effects it is sufficient to break spin
rotation and time reversal symmetry in spatially separated regions of the
junction. Moreover, we discuss how to further improve these effects by
engineering multilayers structures with more that one couple of alternating
layers.",1808.03475v1
2020-09-26,Majorana Zero Modes in Cylindrical Semiconductor Quantum Wire,"We study Majorana zero modes properties in cylindrical cross-section
semiconductor quantum wires based on the $k \cdot p$ theory and a discretized
lattice model. Within this model, the influence of disorder potentials in the
wire and amplitude and phase fluctuations of the superconducting
order-parameter are discussed. We find that for typical wire geometries,
pairing potentials, and spin-orbit coupling strengths, coupling between
quasi-one-dimensional sub-bands is weak, low-energy quasiparticles near the
Fermi energy are nearly completely spin-polarized, and the number of electrons
in the active sub-bands of topological states is small.",2009.12640v1
2022-02-14,Optimizing the topological properties of stacking semiconductor-ferromagnet-superconductor heterostructures,"We study the electronic properties of a planar semiconductor-superconductor
heterostructure, in which a thin ferromagnetic insulator layer lies in between
and acts as a spin filtering barrier. We find that in such a system one can
simultaneously enhance the strengths of all the three important induced
physical quantities, i.e., Rashba spin-orbit coupling, exchange coupling, and
superconducting pairing potential, for the hybrid mode by external gating. Our
results show specific advantage of this stacked device geometry compared to
conventional devices. We further discuss how to optimize geometrical parameters
for the heterostructure and complement our numerical simulations with analytic
calculations.",2202.06604v1
2023-06-29,Bardasis-Schrieffer-like phase mode in a superconducting bilayer,"We theoretically study the low-lying collective modes of an even-parity
spin-singlet superconducting bilayer, where strong spin-orbit coupling leads to
a closely competing odd-parity pairing state. We develop a gauge-invariant
theory for the coupling of phase fluctuations to an external electromagnetic
field and show that the competing odd-parity pairing instability gives rise to
a Bardasis-Schrieffer-like phase mode within the excitation gap. Accounting for
the long-range Coulomb interaction, however, we find that this mode is
converted into an antisymmetric plasmon and is likely pushed into the
quasiparticle continuum.",2306.16611v2
2015-05-15,Orbital selectivity and emergent superconducting state from quasi-degenerate $s-$ and $d-$wave pairing channels in iron-based superconductors,"A major puzzle about the nature of the iron-based superconductivity appears
in the case of the alkaline iron selenides. Compared to the iron pnictides,
these systems have only electron Fermi pockets (i.e. no hole Fermi pockets) but
comparable superconducting transition temperatures. The challenge lies in
reconciling the two basic experimental features of their superconducting state:
a node-less gap and the existence of a resonance in the spin excitation
spectrum. We propose a mechanism based on reconstructing two quasi-degenerate
pairing states, one in an $s$-wave $A_{1g}$ channel that is fully gapped, and
the other in a $d$-wave $B_{1g}$ channel whose pairing function changes sign
across the electron Fermi pockets at the Brillouin-zone boundary. The resulting
intermediate pairing state, which we call an orbital-selective $s \times
\tau_3$ state, incorporates both of the above two properties. When the leading
spin-singlet pairing is in the $d_{xz}, d_{yz}$ orbital subspace, this state
retains the $s$-wave form factor but has a $B_{1g}$ symmetry due to an internal
$\tau_3$ structure in the orbital space. Within a five-orbital $t-J_{1}-J_{2}$
model with orbital-selective exchange couplings, we show that the proposed
pairing state is energetically competitive over a finite range of control
parameters. We calculate the dynamical spin susceptibility in the
orbital-selective $s \times \tau_3$ superconducting state and show that a spin
resonance arises and has the characteristics of observed by inelastic neutron
experiments in the alkaline iron selenides. More generally, the formation of
the orbital-selective $s \times \tau_3$ state represents a novel means of
relieving the quasi-degeneracy between $s-$ and $d-$wave pairing states, which
is a hitherto unsuspected alternative to the conventional route of linearly
superposing the two into a time-reversal symmetry breaking $s+id$ state.",1505.04170v1
2023-04-24,Strong-coupling theory of quantum dot Josephson junctions: role of the residual quasiparticle,"We consider an interacting quantum dot strongly coupled to two
superconducting leads in a Josephson junction geometry. By defining
symmetry-adapted superpositions of states from the leads, we formulate an
effective Hamiltonian for the strong-hybridisation regime with a single orbital
directly coupled to the dot and three additional indirectly coupled orbitals.
This minimal basis set allows to account for the quasiparticles in the vicinity
of the dot as well as those further away in the leads, and to describe how
their role evolves as a function of coupling strength and phase bias $\phi$.
This formulation also reveals the changing nature of the spin-doublet state for
the experimentally relevant coupling strengths. The binding of a nearly
decoupled quasiparticle in the vicinity of the QD explains the ""doublet
chimney"" in the phase diagram for $\phi \sim \pi$, in contrast to $\phi \sim 0$
where the residual quasiparticle escapes to infinity and plays no active role.",2304.12456v3
2023-04-11,Observation of orbital pumping,"Harnessing spin and orbital angular momentum is a fundamental concept in
condensed matter physics, materials science, and quantum-device applications.
In particular, the search for new phenomena that generate a flow of spin
angular momentum, a spin current, has led to the development of spintronics,
advancing the understanding of angular momentum dynamics at the nanoscale. In
contrast to this success, the generation and detection of orbital currents, the
orbital counterpart of spin currents, remains a significant challenge. Here, we
report the observation of orbital pumping, a phenomenon in which magnetization
dynamics pumps an orbital current, a flow of orbital angular momentum. The
orbital pumping is the orbital counterpart of the spin pumping, which is one of
the most versatile and powerful mechanisms for spin-current generation. We show
that the orbital pumping in Ni/Ti bilayers injects an orbital current into the
Ti layer, which is detected through the inverse orbital Hall effect. Our
findings provide a promising approach for generating orbital currents and pave
the way for exploring the physics of orbital transport in solids.",2304.05266v2
2005-10-23,Orbital magnetic field effects in spin liquid with spinon Fermi sea: Possible application to $κ$-(ET)$_2$Cu$_2$(CN)$_3$,"We consider orbital magnetic field effects in a spin liquid phase of a
half-filled triangular lattice Hubbard system close to the Mott transition,
continuing an earlier exploration of a state with spinon Fermi surface.
Starting from the Hubbard model and focusing on the insulator side, we derive
an effective spin Hamiltonian up to four-spin exchanges in the presence of
magnetic field, and find that the magnetic field couples linearly to spin
chirality on the triangles. The latter corresponds to a flux of an internal
gauge field in a gauge theory description of the spin liquid, and therefore a
static such internal flux is induced. A quantitative estimate of the effect is
obtained using a spinon mean field analysis, where we find that this orbital
field seen by the spinons is comparable to or even larger than the applied
field. We further argue that because the stiffness of the emergent internal
gauge field is very small, such a spinon-gauge system is strongly susceptible
at low temperatures to an instability of the homogeneous state due to strong
Landau level quantization for spinons. This instability is reminiscent of the
so-called strong magnetic interaction regime in metals with the usual
electromagnetic field, but we estimate that the corresponding
temperature--magnetic field range is significantly broader in the spinon-gauge
system.",0510615v2
2007-10-29,Interplay of structure and spin-orbit strength in magnetism of metal-benzene sandwiches: from single molecules to infinite wires,"Based on first-principles density functional theory calculations we explore
electronic and magnetic properties of experimentally producible sandwiches and
infinite wires made of repeating benzene molecules and transition-metal atoms
of V, Nb, and Ta. We describe the bonding mechanism in the molecules and in
particular concentrate on the origin of magnetism in these structures. We find
that all the considered systems have sizable magnetic moments and ferromagnetic
spin-ordering, with the single exception of the V3-Bz4 molecule. By including
the spin-orbit coupling into our calculations we determine the easy and hard
axes of the magnetic moment, the strength of the uniaxial magnetic anisotropy
energy (MAE), relevant for the thermal stability of magnetic orientation, and
the change of the electronic structure with respect to the direction of the
magnetic moment, important for spin-transport properties. While for the V-based
compounds the values of the MAE are only of the order of 0.05-0.5 meV per metal
atom, increasing the spin-orbit strength by substituting V with heavier Nb and
Ta allows to achieve an increase in anisotropy values by one to two orders of
magnitude. The rigid stability of magnetism in these compounds together with
the strong ferromagnetic ordering makes them attractive candidates for
spin-polarized transport applications. For a Nb-benzene infinite wire the
occurrence of ballistic anisotropic magnetoresistance is demonstrated.",0710.5413v1
2013-05-03,Group theoretical and topological analysis of the quantum spin Hall effect in silicene,"Silicene consists of a monolayer of silicon atoms in a buckled honeycomb
structure. It was recently discovered that the symmetry of such a system allows
for interesting Rashba spin-orbit effects. A perpendicular electric field is
able to couple to the sublattice pseudospin, making it possible to electrically
tune and close the band gap. Therefore, external electric fields may generate a
topological phase transition from a topological insulator to a normal insulator
(or semimetal) and vice versa. The contribution of the present article to the
study of silicene is twofold: First, we perform a group theoretical analysis to
systematically construct the Hamiltonian in the vicinity of the $K$ points of
the Brillouin zone and discover a new, but symmetry allowed term. Subsequently,
we identify a tight binding model that corresponds to the group theoretically
derived Hamiltonian near the $K$ points. Second, we start from this tight
binding model to analyze the topological phase diagram of silicene by an
explicit calculation of the $Z_2$ topological invariant of the band structure.
To this end, we calculate the $Z_2$ topological invariant of the honeycomb
lattice in a manifestly gauge invariant way which allows us to include $S_z$
symmetry breaking terms -- like Rashba spin orbit interaction -- into the
topological analysis. Interestingly, we find that the interplay of two Rashba
terms can generate a non-trivial quantum spin Hall phase in silicene. This is
in sharp contrast to the more extensively studied honeycomb system graphene
where Rashba spin orbit interaction is known to compete with the quantum spin
Hall effect in a potentially detrimental way.",1305.0766v2
2016-11-11,Rashba-Dirac cones at the tungsten surface: Insights from a tight-binding model and thin film subband structure,"A tight-binding model of bcc tungsten that includes spin-orbit coupling is
developed and applied to the surface states of (110) tungsten thin films. The
model describes accurately the anisotropic Dirac cone-like dispersion and
Rashba-like spin polarization of the surface states, including the crucial
effect of the relaxation of the surface atomic layer of the tungsten towards
the bulk. It is shown that the surface relaxation affects the tungsten surface
states because it results in increased overlaps between atomic orbitals of the
surface atomic layer and nearby layers whereas electric fields that are due to
charge transfer between the tungsten and the vacuum near the surface or between
the bulk and surface layers do not significantly affect the Rashba-Dirac
surface states. It is found that hybridization with bulk modes has differing
strengths for thin film surface states belonging to the upper and lower
Rashba-Dirac cones and results in $reversal$ of the directions of travel of
spin $\uparrow$ and $\downarrow$ electrons in most of the upper Rashba-Dirac
cone relative to those expected from phenomenology. It is also shown that
intrasite (not intersite) matrix elements of the spin-orbit Hamiltonian are
primarily responsible for the formation of the Rashba-Dirac cones, and their
spin polarization. This finding should be considered when modeling topological
insulators, the spin Hall effect and related phenomena.",1611.03582v1
2017-01-24,Conductance through a helical state in an InSb nanowire,"The motion of an electron and its spin are generally not coupled. However in
a one dimensional material with strong spin-orbit interaction (SOI) a helical
state may emerge at finite magnetic fields, where electrons of opposite spin
will have opposite momentum. The existence of this helical state has
applications for spin filtering and Cooper pair splitter devices and is an
essential ingredient for realizing topologically protected quantum computing
using Majorana zero modes. Here we report electrical conductance measurements
of a quantum point contact (QPC) formed in an indium antimonide nanowire as a
function of magnetic field. At magnetic fields exceeding 3T, the $2e^2/h$
plateau shows a reentrant conductance feature towards $1e^2/h$ which increases
linearly in width with magnetic field before enveloping the $1e^2/h$ plateau.
Rotating the external magnetic field either parallel or perpendicular to the
spin-orbit field allows us to clearly attribute this experimental signature to
SOI. We compare our observations with a model of a QPC incorporating SOI and
extract a spin-orbit energy of ~6.5meV, which is significantly stronger than
the SO energy obtained by other methods.",1701.06878v1
2011-11-14,First-principle studies of the spin-orbit and the Dzyaloshinskii-Moriya interactions in the \{Cu$_3$\} single-molecule magnet,"Frustrated triangular molecule magnets such as \{Cu$_3$\} are characterized
by two degenerate S=1/2 ground-states with opposite chirality. Recently it has
been proposed theoretically [PRL {\bf 101}, 217201 (2008)] and verified by {\it
ab-initio} calculations [PRB {\bf 82}, 155446 (2010)] that an external electric
field can efficiently couple these two chiral spin states, even in the absence
of spin-orbit interaction (SOI). The SOI is nevertheless important, since it
introduces a splitting in the ground-state manifold via the
Dzyaloshinskii-Moriya interaction. In this paper we present a theoretical study
of the effect of the SOI on the chiral states within spin density functional
theory. We employ a recently-introduced Hubbard model approach to elucidate the
connection between the SOI and the Dzyaloshinskii-Moriya interaction. This
allows us to express the Dzyaloshinskii-Moriya interaction constant $D$ in
terms of the microscopic Hubbard model parameters, which we calculate from
first-principles. The small splitting that we find for the \{Cu$_3$\} chiral
state energies ($\Delta \approx 0.02$ meV) is consistent with experimental
results. The Hubbard model approach adopted here also yields a better estimate
of the isotropic exchange constant than the ones obtained by comparing total
energies of different spin configurations. The method used here for calculating
the DM interaction unmasks its simple fundamental origin which is the
off-diagonal spin-orbit interaction between the generally multireference vacuum
state and single-electron excitations out of those states.",1111.3078v1
2016-08-20,"Hybrid excitations due to crystal-field, spin-orbit coupling and spin-waves in LiFePO$_4$","We report on the spin waves and crystal field excitations in single crystal
LiFePO$_4$ by inelastic neutron scattering over a wide range of temperatures,
below and above the antiferromagnetic transition of this system. In particular,
we find extra excitations below $T_N=50$ K that are nearly dispersionless and
are most intense around magnetic zone centers. We show that these excitations
correspond to transitions between thermally occupied excited states of
Fe$^{2+}$ due to splitting of the $S=2$ levels that arise from crystal field
and spin-orbit interaction. These excitations are further amplified by the
highly distorted nature of the oxygen octahedron surrounding the iron atoms.
Above $T_N$, magnetic fluctuations are observed up to at least 720~K, with
additional excitation around 4 meV, likely caused by single-ion splittings
through spin-orbit and crystal field interactions. The latter weakens slightly
at 720~K compared to 100~K, which is consistent with calculated cross-sections
using a single-ion model. Our theoretical analysis, using the MF-RPA model,
provides both detailed spectra of the Fe $d-$ shell and estimates of the
average ordered magnetic moment and $T_N$. By applying the MF-RPA model to a
number of existing spin-wave results from other Li$M$PO$_4$ ($M=$ Mn, Co, and
Ni), we are able to obtain reasonable predictions for the moment sizes and
transition temperatures.",1608.05761v1
2017-12-10,"Tuning the Interfacial Charge, Orbital and Spin Polarization Properties in La0.67Sr0.33MnO3/ La1-xSrxMnO3 Bilayers","The possibility of controlling the interfacial properties of artificial oxide
heterostructures is still attracting researchers in the field of materials
engineering. Here, we used surface sensitive techniques and high-resolution
transmission electron microscopy to investigate the evolution of the surface
spin-polarization and lattice strains across the interfaces between
La0.66Sr0.33MnO3 thin films and low-doped manganites as capping layers. We have
been able to finely tune the interfacial spin-polarization by changing the
capping layer thickness and composition. The spin-polarization was found to be
highest at a critical capping thickness that depends on the Sr doping. We
explain the non-trivial magnetic profile by the combined effect of two
mechanisms. On one hand, the extra carriers supplied by the low-doped
manganites that tend to compensate the overdoped interface, favouring locally a
ferromagnetic double-exchange coupling. On the other hand, the evolution from a
tensile-strained structure of the inner layers to a compressed structure at the
surface that changes gradually the orbital occupation and hybridization of the
3d-Mn orbitals, being detrimental for the spin polarization. The finding of an
intrinsic spin-polarization at the A-site cation observed in XMCD measurements
reveals also the existence of a complex magnetic configuration at the
interface, different from the magnetic phases observed at the inner layers.",1712.03611v1
2023-10-17,RelativisticDynamics.jl: Relativistic Spin-Orbital Dynamics in Julia,"RelativisticDynamics.jl is an open-source Julia package for relativistic
spin-orbital dynamics in the gravitational strong-field of a Kerr spacetime.
Existing codes for modelling the dynamics of spinning objects like pulsars in
the strong-field regime are generally lacking, since such systems occupy an
intermediate regime that is generally overlooked. At the ""low"" end of this
regime there are post-Newtonian descriptions which neglect the influence of the
pulsar spin on the underlying spacetime metric (""spin-curvature"" coupling). At
the ""high"" end there are the full numerical relativity solutions which are
primarily applicable toe two black holes with a mass ratio $\mathcal{O}(1)$,
and are computationally intractable for pulsar systems observed over a large
number of orbital cycles. RelativisticDynamics.jl aims to bridge this gap by
providing a modern, fast code for accurate numerical evolution of spinning
relativistic systems via the Mathisson-Papetrou-Dixon formalism. Julia is a
modern language that solves the ""two language problem"", enabling fast dynamic
typing and JIT compilation on conjunction with petaflop performance, comparable
with numerical languages that are better known in the astrophysics community
such as C or Fortran. RelativisticDynamics.jl is written to be fully type
flexible, being able to support arbitrary number formats, and fully
differentiable via automatic differentiation.",2310.11002v1
2024-01-22,Gravitational spin-orbit coupling through the third-subleading post-Newtonian order: exploring spin-gauge flexibility,"We build upon recent work by Antonelli et al. [Phys. Rev. Lett. 125 (2020) 1,
011103] to obtain, within the effective-one-body (EOB) formalism, and for an
arbitrary choice of gauge, the third-subleading post-Newtonian (4.5PN)
corrections to the spin-orbit conservative dynamics of spin-aligned binaries.
This is then specialized to: (i) the well-known Damour-Jaranowski-Sch\""afer
($\rm DJS$) gauge, where the dependence on the angular momentum of the
gyro-gravitomagnetic functions $(G_S,G_{S_*})$ is removed and (ii) to an
alternative gauge (called anti-$\rm DJS$ gauge, $\overline{\rm DJS}$) that is
chosen so as to precisely reproduce the Hamiltonian of a spinning test-particle
at linear order in the particle spin and keep the full dependence on the radial
and angular momentum in $(G_S,G_{S_*})$. We use these results to extend by one
perturbative order, in PN sense, the analytical knowledge of the periastron
advance. After performing a suitable factorization and resummation of
$(G_S,G_{S_*})$, the $\rm DJS$ and $\overline{\rm DJS}$ performances are
compared via various gauge-invariant quantities at the EOB last stable circular
orbit. We eventually find some indications that the $\overline{\rm DJS}$ gauge
might be advantageous in the description of the inspiral dynamics of
circularized binaries.",2401.12290v1
2024-03-11,Bulk and interface spin-orbit torques in Pt/Co/MgO thin film structures,"We investigate the origin of spin-orbit torques (SOTs) in archetypical
Pt/Co/MgO thin films structures by performing harmonic Hall measurements. The
behaviour of the damping like (DL) effective field ($h_{DL}$) with varying the
Pt layer thickness and the Co layer thickness indicates that bulk spin-Hall
effect (SHE) in Pt is mainly responsible for DL-SOT. The insertion of a Pd
ultrathin layer at the Pt/Co interface leads to a step decrease in $h_{DL}$,
attributed to the modification of interfacial spin transparency. Further
increase in Pd thickness led to a reduction of the interfacial spin-orbit
coupling (iSOC) quantified by the decrease in the surface magnetic anisotropy.
The consistent insensitivity of $h_{DL}$ to variations in iSOC at the bottom
Pt/Co interface and oxidation at the top Co/MgO interface provides additional
evidence for the bulk SHE origin of DL-SOT. The strong reduction in the
field-like (FL) torque effective field ($h_{FL}$) with decreasing iSOC at the
Pt/Co interface points to the interfacial nature of FL-SOT, either due to iSOC
induced interfacial spin-currents or to the Rashba-Edelstein effect at the
Pt/Co interface. Furthermore, we demonstrate that a FL-SOT develops at the top
Co/MgO interface opposing the one generated at the bottom Pt/Co interface,
whose strength increases with Co/MgO interfacial oxidation, and attributed to
the Rashba-Edelstein effect.",2403.06627v1
2012-09-05,In-Plane Orbital Texture Switch at the Dirac Point in the Topological Insulator Bi2Se3,"Topological insulators are novel macroscopic quantum-mechanical phase of
matter, which hold promise for realizing some of the most exotic particles in
physics as well as application towards spintronics and quantum computation. In
all the known topological insulators, strong spin-orbit coupling is critical
for the generation of the protected massless surface states. Consequently, a
complete description of the Dirac state should include both the spin and
orbital (spatial) parts of the wavefunction. For the family of materials with a
single Dirac cone, theories and experiments agree qualitatively, showing the
topological state has a chiral spin texture that changes handedness across the
Dirac point (DP), but they differ quantitatively on how the spin is polarized.
Limited existing theoretical ideas predict chiral local orbital angular
momentum on the two sides of the DP. However, there have been neither direct
measurements nor calculations identifying the global symmetry of the spatial
wavefunction. Here we present the first results from angle-resolved
photoemission experiment and first-principles calculation that both show,
counter to current predictions, the in-plane orbital wavefunctions for the
surface states of Bi2Se3 are asymmetric relative to the DP, switching from
being tangential to the k-space constant energy surfaces above DP, to being
radial to them below the DP. Because the orbital texture switch occurs exactly
at the DP this effect should be intrinsic to the topological physics,
constituting an essential yet missing aspect in the description of the
topological Dirac state. Our results also indicate that the spin texture may be
more complex than previously reported, helping to reconcile earlier conflicting
spin resolved measurements.",1209.1016v1
2015-06-13,Spin-orbital liquid state assisted by singlet-triplet excitation in $J~=~0$ ground state of Ba$_3$ZnIr$_2$O$_9$,"Strong spin-orbit coupling (SOC) effects of heavy $d$-orbital elements have
long been neglected in describing the ground states of their compounds thereby
overlooking a variety of fascinating and yet unexplored magnetic and electronic
states, until recently. The spin-orbit entangled electrons in such compounds
can get stabilized into unusual spin-orbit multiplet $J$-states which warrants
severe investigations. Here we show using detailed magnetic and thermodynamic
studies and theoretical calculations the ground state of Ba$_3$ZnIr$_2$O$_9$, a
6$H$ hexagonal perovskite is a close realisation of the elusive $J$~=~0 state.
However, we find that local Ir moments are spontaneously generated due to the
comparable energy scales of the singlet-triplet splitting driven by SOC and the
superexchange interaction mediated by strong intra-dimer hopping. While the Ir
ions within the structural Ir$_2$O$_9$ dimer prefers to form a spin-orbit
singlet state (SOS) with no resultant moment, substantial interdimer exchange
interactions from a frustrated lattice ensure quantum fluctuations till the
lowest measured temperatures and stabilize a spin-orbital liquid phase.",1506.04312v3
1995-08-16,Spin Dynamics of Hole Doped ${\rm Y_{2-x} Ca_x Ba Ni O_5}$,"We propose an electronic model for the recently discovered hole doped
compound ${\rm Y_{2-x} Ca_x Ba Ni O_5 }$. From a multiband Hamiltonian with
oxygen and nickel orbitals, a one band model is derived. Holes are described
using Zhang-Rice-like S=1/2 states at the nickels propagating on a S=1 spin
chain. Using numerical techniques to calculate the dynamical spin structure
factor ${\rm S(q,\omega)}$ in a realistic regime of couplings, spectral weight
in the Haldane gap is observed in agreement with neutron scattering data. Low
energy states with S=3/2 appear in the model. Several predictions are made to
test these ideas.",9508061v1
1998-02-26,Identification of Non-unitary triplet pairing in a heavy Fermion superconductor UPt_3,"A NMR experiment recently done by Tou et al. on a heavy Fermion
superconductor UPt$_3$ is interpreted in terms of a non-unitary spin-triplet
pairing state which we have been advocating. The proposed state successfully
explains various aspects of the seemingly complicated Knight shift behaviors
probed for major orientations, including a remarkable d-vector rotation under
weak fields. This entitles UPt$_3$ as the first example that a charged many
body system forms a spin-triplet odd-par ity pairing at low temperatures and
demonstrates unambiguously that the putative spin-orbit coupling in UPt$_3$ is
weak.",9802280v1
1998-07-02,Pairing due to Spin Fluctuations in Layered Organic Superconductors,"I show that for a \kappa-type organic (BEDT-TTF)_2-X molecular crystal, a
superconducting state with T_c ~ 10 K and gap nodes on the Fermi surface can be
caused by short-ranged antiferromagnetic spin fluctuations. Using a two-band
description for the anti-bonding orbitals on a BEDT-TTF dimer of the
\kappa-type salt, and an intermediate local Coulomb repulsion between two holes
on one dimer, the magnetic interaction and the superconducting gap-function are
determined self consistently within the fluctuation exchange approximation. The
pairing interaction is predominantly caused by inter-band coupling and
additionally affected by spin excitations of the quasi one-dimensional band.",9807042v1
2000-10-14,d-Wave Superconductivity Induced by Chern-Simons Term in High-$T_c$ Cuprates,"We show that a Chern-Simons term for a gauge field describing a fluctuation
of spins is induced by integrating out hole fields in the presence of
spin-orbit coupling which originates from a buckling of the CuO$_2$ plane.
Through the Chern-Simons term, holes behave like skyrmion excitations in a spin
system and become a superconducting state with $d_{x^2-y^2}$ symmetry after the
antiferromagnetic long-range order is destroyed.",0010199v3
2001-09-10,ESR theory for interacting 1D quantum wires,"We compute the electron spin resonance (ESR) intensity for one-dimensional
quantum wires in semiconductor heterostructures, taking into account
electron-electron interactions and spin-orbit coupling. The ESR spectrum is
shown to be very sensitive to interactions. While in the absence of
interactions, the spectrum is a flat band, characteristic threshold
singularities appear in the interacting limit. This suggests the practical use
of ESR to reveal spin dynamics in a Luttinger liquid.",0109161v1
2002-06-22,Measurements of strongly-anisotropic g-factors for spins in single quantum states,"We have measured the full angular dependence, as a function of the direction
of magnetic field, for the Zeeman splitting of individual energy states in
copper nanoparticles. The g-factors for spin splitting are highly anisotropic,
with angular variations as large as a factor of five. The angular dependence
fits well to ellipsoids. Both the principal-axis directions and g-factor
magnitudes vary between different energy levels within one nanoparticle. The
variations agree quantitatively with random-matrix theory predictions which
incorporate spin-orbit coupling.",0206423v1
2005-10-02,Giant Magneto-Oscillations of Electric-Field-Induced Spin Polarization in 2DEG,"We consider a disordered two-dimensional electron gas with spin-orbit
coupling placed in a perpendicular magnetic field and calculate the magnitude
and direction of the electric-field-induced spin polarization. We find that in
strong magnetic fields the polarization becomes an oscillatory function of the
magnetic field and that the amplitude of these oscillations is parametrically
larger than the polarization at zero magnetic field. We show that the enhanced
amplitude of the polarization is a consequence of strong electron-hole
asymmetry in a quantizing magnetic field.",0510024v1
2005-11-22,Effect of Coulomb interaction on the spin-galvanic mode in a two dimensional electron gas with Rashba spin-orbit interaction,"Recently a new propagating mode of coupled charge and spin oscillations was
predicted in a two dimensional electron gas with a sufficiently strong Rashba
interaction. We show that Coulomb interactions qualitatively modifies the
spectrum and increases the characteristic wavelength of this mode by orders of
magnitude, but does not suppress it. An absorption experiment that can
conclusively detect the presence or absence of such a propagating mode is
proposed.",0511534v1
2006-03-31,Geometrical spin dephasing in quantum dots,"We study spin-orbit mediated relaxation and dephasing of electron spins in
quantum dots. We show that higher order contributions provide a relaxation
mechanism that dominates for low magnetic fields and is of geometrical origin.
In the low-field limit relaxation is dominated by coupling to electron-hole
excitations and possibly $1/f$ noise rather than phonons.",0603847v2
2006-07-24,Kondo Quantum Dots and the Novel Kondo-doublet interaction,"We analyze the interactions between two Kondo Quantum Dots connected to a
Rashba-active Quantum Wire. We find that the Kondo-doublet interaction, at an
inter-dot distance of the order of the wire Fermi length, is over an order of
magnitude greater than the RKKY interaction. The effects induced on the
Kondo-doublet interaction by the wire spin-orbit coupling can be used to
control the Quantum Dots spin-spin correlation. These results imply that the
widely used assumption that the RKKY is the dominant interaction between
Anderson impurities must be revised.",0607620v2
2006-10-16,Exchange-controlled single-electron-spin rotations in quantum dots,"We show theoretically that arbitrary coherent rotations can be performed
quickly (with a gating time ~1 ns) and with high fidelity on the spin of a
single confined electron using control of exchange only, without the need for
spin-orbit coupling or ac fields. We expect that implementations of this scheme
would achieve gate error rates on the order of \eta ~ 10^{-3} in GaAs quantum
dots, within reach of several known error-correction protocols",0610443v2
2004-05-12,Studies of Er ionization energy,"This work is aimed at the multiconfigurational Hartree-Fock calculations of
the Er ionization energy. Authors have used the ATSP MCHF version in which
there are new codes for calculation of spin-angular parts written on the basis
of the methodology Gaigalas, Rudzikas and Froese Fischer, based on the second
quantization in coupled tensorial form, the angular momentum theory in 3 spaces
(orbital, spin and quasispin) and graphical technique of spin-angular
ntegrations. They allow the study of configurations with open f-shells without
any restrictions and lead to fairly accurate values of spectroscopic data.",0405054v1
2008-04-10,Spin-triplet p-wave pairing in a 3-orbital model for iron pnictide superconductors,"We examine the possibility that the superconductivity in the newly discovered
FeAs materials may be caused by the Coulomb interaction between d-electrons of
the iron atoms. We find that when the Hund's rule ferromagnetic interaction is
strong enough, the leading pairing instability is in spin-triplet p-wave
channel in the weak coupling limit. The resulting superconducting gap has nodal
lines on the 3D Fermi surfaces. The k dependent hybridization of several
orbitals around a Fermi pocket is the key for the appearance of the
spin-triplet p-wave pairing.",0804.1739v3
2008-08-09,Gilbert Damping in Conducting Ferromagnets I: Kohn-Sham Theory and Atomic-Scale Inhomogeneity,"We derive an approximate expression for the Gilbert damping coefficient
\alpha_G of itinerant electron ferromagnets which is based on their description
in terms of spin-density-functional-theory (SDFT) and Kohn-Sham quasiparticle
orbitals. We argue for an expression in which the coupling of magnetization
fluctuations to particle-hole transitions is weighted by the spin-dependent
part of the theory's exchange-correlation potential, a quantity which has large
spatial variations on an atomic length scale. Our SDFT result for \alpha_G is
closely related to the previously proposed spin-torque correlation-function
expression.",0808.1373v1
2008-08-11,Anomalous Josephson Current in Junctions with Spin-Polarizing Quantum Point Contacts,"We consider a ballistic Josephson junction with a quantum point contact in a
two-dimensional electron gas with Rashba spin-orbit coupling. The point contact
acts as a spin filter when embedded in a circuit with normal electrodes. We
show that with an in-plane external magnetic field an anomalous supercurrent
appears even for zero phase difference between the superconducting electrodes.
In addition, the external field induces large critical current asymmetries
between the two flow directions, leading to supercurrent rectifying effects.",0808.1516v1
2008-09-03,Aharonov-Casher Effect in Wigner Crystal Exchange Interactions,"We theoretically study the effects of spin-orbit coupling on spin exchange in
a low-density Wigner crystal. In addition to the familiar antiferromagnetic
Heisenberg exchange, we find general anisotropic interactions in spin space if
the exchange paths allowed by the crystal structure form loops in real space.
In particular, it is shown that the two-electron exchange interaction can
acquire ferromagnetic character.",0809.0598v2
2009-07-15,Proposal for Creating a Spin-polarized p_x+ip_y State and Majorana Fermions,"The spin polarized p_x + ip_y superconductor is known to support Majorana
states but so far there has been no example. We propose a simple setup to
create such a state by depositing a ferromagnetic metal on a
non-centrosymmetric superconductor with strong spin-orbit coupling which
contains a Rashba-type term.",0907.2681v2
2009-07-21,Vortex Tiling in a Spin-2 Spinor Bose-Einstein Condensate,"We point out that the internal spin symmetry of the order parameter manifests
itself at the core of a fractional vortex in real space without spin-orbit
coupling. Such symmetry breaking arises from a topological constraint and the
commensurability between spin symmetries of the order parameters inside and
outside the core. Our prediction can be applied to probe the cyclic order
parameter in a rotating spin-2 $^{87}$Rb condensate as a non-circular vortex
core in a biaxial nematic state.",0907.3716v2
2009-11-22,Spin state transition in LaCoO3 by variational cluster approximation,"The variational cluster approximation is applied to the calculation of
thermodynamical quantities and single-particle spectra of LaCoO3. Trial
self-energies and the numerical value of the Luttinger-Ward functional are
obtained by exact diagonalization of a CoO6 cluster. The VCA correctly predicts
LaCoO3 as a paramagnetic insulator and a gradual and relatively smooth increase
of the occupation of high-spin Co3+ ions causes the temperature dependence of
entropy and magnetic susceptibility. The single particle spectral function
agrees well with experiment, the experimentally observed temperature dependence
of photoelectron spectra is reproduced satisfactorily. Remaining discrepancies
with experiment highlight the importance of spin orbit coupling and local
lattice relaxation.",0911.4236v1
2010-11-09,Surface density of states and topological edge states in non-centrosymmetric superconductors,"We study Andreev bound state (ABS) and surface density of state (SDOS) of
non-centrosymmetric superconductor where spin-singlet $d$-wave pairing mixes
with spin-triplet $p$ (or $f)$-wave one by spin-orbit coupling. For $d_{xy} +
p$-wave pairing, ABS appears as a zero energy state. The present ABS is a
Majorana edge mode preserving the time reversal symmetry. We calculate
topological invariant number and discuss the relevance to a single Majorana
edge mode. In the presence of the Majorana edge mode, the SDOS depends strongly
on the direction of the Zeeman field.",1011.2002v1
2011-12-13,Spectral properties of one-dimensional spiral spin density wave states,"We provide a full characterization of the spectral properties of spiral spin
density wave (SSDW) states which emerge in one-dimensional electron systems
coupled to localized magnetic moments or quantum wires with spin-orbit
interactions. We derive analytic results for the spectral function, local
density of states and optical conductivity in the low-energy limit by using
field theory techniques. We identify various collective modes and show that the
spectrum strongly depends on the interaction strength between the electrons.
The results provide characteristic signatures for an experimental detection of
SSDW states.",1112.3045v2
2012-03-13,Monopoles in ferromagnetic metals,"The aim of this short review is to give an introduction to monopoles and to
present theoretical derivation of two particular monopoles in ferromagnetic
metals, a hedgehog monopole and a spin damping monopole. Spin damping monopoles
can be generated in simple systems such as a junction of a ferromagnet and a
heavy element with strong spin-orbit interaction such as Pt. This monopole is
essential in coupling electronics with magnetism, and is thus expected to play
an essential role in spintronics.",1203.2709v1
2012-09-23,On the Origin of Zigzag Magnetic Order in Iridium Oxide Na2IrO3,"We explore the phase diagram of spin-orbit Mott insulators on a honeycomb
lattice, within the Kitaev-Heisenberg model extended to its full parameter
space. Zigzag-type magnetic order is found to occupy a large part of the phase
diagram of the model, and its physical origin is explained as due to
interorbital t2g-eg hopping. Magnetic susceptibility and spin wave spectra are
calculated and compared to the experimental data, obtaining thereby the spin
coupling constants in Na2IrO3 and Li2IrO3.",1209.5100v1
2012-12-08,Relativistic symmetries in the Hulthén scalar-vector-tensor interactions,"In the presence of spin and pseudospin (p-spin) symmetries, the approximate
analytical bound states of the Dirac equation for scalar-vector-tensor
Hulth\'en potentials are obtained with any arbitrary spin-orbit coupling number
using the Pekeris approximation. The Hulth\'en tensor interaction is studied
instead of the commonly used Coulomb or linear terms. The generalized
parametric Nikiforov-Uvarov (NU) method is used to obtain energy eigenvalues
and corresponding wave functions in their closed forms. We show that tensor
interaction removes degeneracies between spin and p-spin doublets. Some
numerical results are also given.",1212.1828v1
2012-12-13,Fast adiabatic-like spin manipulation in a two-electron double quantum dot,"We apply the transitionless quantum driving method to control the electron
spin of a two-electron double quantum dot with spin-orbit coupling by
time-dependent electric fields. The $x$ and $y$ components of applied electric
fields in each dot are designed to achieve fast adiabatic-like passage in the
nanosecond timescale. To simplify the setup, we can further transform
Hamiltonian by z axis to design an alternative speed-up adiabatic passage,
without using the applied electric field in $y$ direction.",1212.3294v1
2013-05-08,Point contacts and localization in generic helical liquids,"We consider two helical liquids on opposite edges of a narrow two-dimensional
topological insulator, which are connected by one or several local tunnel
junctions. In the presence of spatially inhomogeneous Rashba spin-orbit
coupling, the spin textures of the helical states on opposite edges are
different. We demonstrate that this has a strong impact on the electron
transport between the edges. In particular, in the case of many random tunnel
contacts, the localization length depends strongly on the spin textures of the
edge states.",1305.1875v2
2013-05-21,Switching of a single ferromagnetic layer driven by spin Hall effect,"The magnetization switching of a thin ferromagnetic layer placed on top of a
heavy metal (such as Pt, Ta or W) driven by an in-plane current has been
observed in recent experiments. The magnetization dynamics of these processes
is studied in a full micromagnetic framework which takes into account the
transfer-torque from spin Hall effect due to the spin-orbit coupling.
Simulations indicate that the reversal occurs via nucleation of complex
magnetization patterns. In particular, magnetic bubbles appear during the
reversal of the magnetization in the perpendicular configuration while for the
in-plane configuration, nucleation of vortexes are observed.",1305.4806v1
2013-11-27,Statistics of Spin Fluctuations in Quantum Dots with Ising Exchange,"We explore the effect of single-particle level fluctuations on the Stoner
instability in a QD with a strong spin-orbit coupling in the framework of the
universal Hamiltonian with the Ising exchange interaction. We reduce the
problem to studying the statistics of extrema of a certain Gaussian process and
demonstrate that, in spite of the randomness of the single-particle levels, the
longitudinal spin susceptibility and all its moments diverge simultaneously at
the point of the Stoner instability which is determined by the standard
criterion involving the mean level spacing only.",1311.7083v2
2014-08-19,Spinning test particles in Weyl spacetimes,"The motion of spinning test particles along circular orbits in static vacuum
spacetimes belonging to the Weyl class is discussed. Spin alignment and
coupling with background parameters in the case of superimposed Weyl fields,
corresponding to a single Schwarzschild black hole and single Chazy-Curzon
particle as well as to two Schwarzschild black holes and two Chazy-Curzon
particles, are studied in detail for standard choices of supplementary
conditions. Applications to the gravitomagnetic ""clock effect"" are also
discussed.",1408.4273v1
2016-06-10,Chirality in photonic systems,"The optical modes of photonic structures are the so-called TE and TM modes
which bring intrinsic spin-orbit coupling and chirality to these systems. This,
combined with the unique flexibility of design of the photonic potential, and
the possibility to mix photon states with excitonic resonances, sensitive to
magnetic field and interactions, allows to achieve many phenomena, often
analogous to other solid state systems. In this contribution, we review in a
qualitative and comprehensive way several of these realizations, namely the
optical spin Hall effect, the creation of spin currents protected by a
non-trivial geometry, Berry curvature for photons, and the photonic/polaritonic
topological insulator.",1606.03311v1
2017-08-01,Photo-spin voltaic effect and photo-magnetoresistance in proximized platinum,"Spin orbit coupling in heavy metals allows conversion of unpolarized light
into an open-circuit voltage. We experimentally prove that this photo-spin
voltaic effect is due to photo-excitation of carriers in the proximized layer
and can exist for light in the visible range. While carrying out the
experiment, we discovered that, in closed-circuit conditions, the anisotropic
magnetoresistance of the proximized metal is a function of the light intensity.
We name this effect photo-magnetoresistance. A magneto-transport model is
presented that describes the change of magnetoresistance as a function of the
light intensity.",1708.04130v2
2018-04-18,Electronic states and persistent currents in nanowire quantum ring,"The new model of a quantum ring (QR) defined inside a nanowire (NW) is
proposed. The one-particle Hamiltonian for electron in [111]-oriented NW QR is
constructed taking into account both Rashba and Dresselhaus spin-orbit coupling
(SOC). The energy levels as a function of magnetic field are found using the
exact numerical diagonalization. The persistent currents (both charge and spin)
are calculated. The specificity of SOC and arising anticrossings in energy
spectrum lead to unusual features in persistent current behavior. The variation
of magnetic field or carrier concentration by means of gate can lead to pure
spin persistent current with the charge current being zero.",1804.06629v1
2014-03-27,Hyperfine Clock Transitions of Bismuth Donors in Silicon Detected by Spin Dependent Recombination,"Bismuth donors ion-implanted in $^{28}$Si and $^\text{nat}$Si are studied
using magnetic resonance spectroscopy based on spin dependent recombination.
The hyperfine clock transition, at which the linewidth is significantly
narrowed, is observed for the bismuth donors. The experimental results are
modeled quantitatively by molecular orbital theory for a coupled pair
consisting of a bismuth donor and a spin dependent recombination readout
center, including the effect of hyperfine and Zeeman interactions.",1403.6935v2
2012-01-04,Quantum Kinetic Theory of Current-Induced Torques in Rashba Ferromagnets,"Motivated by recent experimental studies of thin-film devices containing a
single ferromagnetic layer, we develop a quantum kinetic theory of
current-induced magnetic torques in Rashba-model ferromagnets. We find that
current-induced spin-densities that are responsible for the switching behavior
are due most essentially to spin-dependent quasiparticle lifetimes and derive
analytic expressions for relevant limits of a simple model. Quantitative model
parameter estimates suggest that spin-orbit coupling in the adjacent metal
normal magnetic layer plays an essential role in the strength of the switching
effect.",1201.0990v1
2017-06-01,Electronic and magnetic properties of low dimensional system Co2TeO3Cl2,"The electronic and magnetic properties of transition metal oxyhalide compound
Co2TeO3Cl2 is investigated using first principle calculations within the
framework of density functional theory. In order to find underlying spin
lattice of this compound, various hopping integrals and exchange interactions
are calculated. The calculations reveal that the dominant inter-chain and
intra-chain interactions are in ab plane. The exchange path is visualised by
Wannier function plotting. The nearest neighbour and next nearest neighbour
exchange interactions are antiferromagnetic, making the system frustrated in
low dimension. The importance of spin orbit coupling in this compound is also
investigated. The spin quantization axis is favoured along the crystallographic
b direction.",1706.00259v1
2000-06-16,Local off-cubic distortion the cause for the low- and high-spin states of the Co3+ ion,"It is pointed out that it is the local symmetry that determines the
realization of the low- and high-spin state of the Co3+ ion. We can rigorously
prove it treating the Co3+ ion as the highly-correlated electron system 3d6,
that fulfiles the Hund's rules with taking into account the spin-orbit
coupling. As the function of the sign of the off-cubic crystal-field distortion
the magnetic or non-magnetic state is realized.",0006269v1
2012-05-07,Electron Number Dependence of Spin Triplet-Singlet Relaxation Time,"In a GaAs single quantum dot, the relaxation time T_{1} between spin triplet
and singlet states has been measured for the last few even number of electrons.
The singlet-triplet energy separation E_{ST} is tuned as a control parameter
for the comparison of T_{1} between different electron numbers. T_{1} shows a
steady decrease from 2-electrons, 4-electrons, to 6-electrons, and we found
this implies an enhancement of the spin-orbital coupling strength in a
multi-electron quantum dot.",1205.1264v1
2017-05-10,Low-Error Operation of Spin Qubits with Superexchange Coupling,"In this theoretical work we investigate superexchange, as a means of indirect
exchange interaction between two single electron spin qubits, each embedded in
a single semiconductor quantum dot (QD). The exchange interaction is mediated
by an intermediate, empty QD. Our findings suggest the existence of first order
""super sweet spots"", in which the qubit operations implemented by superexchange
interaction are simultaneously insensitive to charge noise and errors due to
spin-orbit interaction. We also find that the sign of the superexchange can be
changed by varying the energy detunings between the QDs.",1705.03702v1
2018-06-20,Configuration Interaction Singles with Spin-Orbit Coupling: Constructing Spin-Adiabatic States and Their Analytical Nuclear Gradients,"For future use in modeling photoexcited dynamics and intersystem crossing, we
calculate spin-adiabatic states and their analytical nuclear gradients within
CIS the- ory. These energies and forces should be immediately useful for
surface hopping dynamics, which are natural within an adiabatic framework. The
resulting code has been implemented within the Q-Chem software and preliminary
results suggest that the additional cost of including SOC within the
singles-singles block is not large.",1806.07835v1
2018-07-07,Fully Spin-Polarized Current in Gated Bilayer Silicene,"By applying density functional theory calculations, we predict that the
groundstate of bilayer silicene at certain interlayer distances can be
antiferromagnetic. At small electron or hole doping, it becomes half metallic
under applied out-of-plane electric field, which can be used to produce fully
spin-polarized field-effect-driven current even in the absence of external
magnetic field, ferromagnetic substrates, doped magnetic ions, or spin-orbital
coupling. Our finding points out a new route to overcome the major challenge of
spintronics.",1807.02663v1
2019-02-07,s+if pairing in Ising superconductors,"We show that an in-plane Zeeman field applied to non-centrosymmetric Ising
superconductors converts singlet $s$-wave Cooper pairs to equal-spin triplet
$if$ pairs, leading to an enhancement of the critical transition line beyond
expected from Ising spin-orbit coupling. Singlet to triplet conversion relates
to a phase transformation due to spin rotation by the Zeeman field and has a
geometric origin. The discussion is especially relevant, but not limited to
monolayer transition metal dichalcogenides.",1902.02577v1
2019-04-26,Anti-Localization in Oxides: Effective Spin-3/2 Model,"Weak anti-localization offers an experimental tool to address spin--orbit
coupling of two-dimensional oxide surfaces and interfaces via
magneto-transport. To overcome the shortcomings of the formulation for
single-band spin-1/2 electrons, we consider an effective three-band model that
allows a decomposition into a pseudo-spin representation 1/2+3/2. Whereas the
well-established spin-1/2 transport signature results from the singlet and
triplet sectors in the Cooperon equation, a new structure originates from the
quintet and septet sectors generated by the spin 3/2x3/2 representation.",1904.11770v1
2019-11-14,Zero field splitting of heavy-hole states in quantum dots,"Using inelastic cotunneling spectroscopy, we observe a 55{\mu}eV zero field
splitting in the spin triplet manifold of Ge hut wire quantum dots. The
degeneracy of the heavy hole triplet state is lifted since the interplay of
strong spin orbit coupling and strong confinement leads to a preferred
direction of the heavy-hole pseudospin. The reported effect should be
observable in a broad class of strongly confined hole quantum-dot systems and
needs to be considered when operating hole spin qubits.",1911.06418v2
2016-12-04,Spin- and velocity-dependent non-relativistic potentials in modified electrodynamics,"We investigate the interparticle potential between spin-0, -1/2 and -1
sources interacting in modified electrodynamics in the non-relativistic regime.
By keeping terms of $\mathcal{O}( |{\bf p}|^2/m^2 )$ in the amplitudes, we
obtain spin- and velocity-dependent interaction energies. We find well-known
effects such as spin-orbit couplings, as well as spin-spin (dipole-dipole)
interactions. For concreteness, we consider the cases of electrodynamics with
higher derivatives (Podolsky-Lee-Wick) and hidden photons.",1612.01181v1
2017-11-10,Chiral solitons in a non-linear model of helical molecules,"In this paper an effective integrable non-linear model describing the
electron spin dynamics in a deformable helical molecule with weak spin-orbit
coupling is presented. Non-linearity arises from the electron-lattice
interaction and it enables the formation of a variety of stable solitons such
as bright solitons, breathers and rogue waves, all of them presenting well
defined spin projection onto the molecule axis. A thorough study of the soliton
solutions is presented and discussed.",1711.03794v1
2021-05-27,"Curvature-induced long ranged supercurrents in diffusive SFS Josephson Junctions, with dynamic $0-π$ transition","We report that spin supercurrents can be induced in diffusive SFS Josephson
junctions without any magnetic misalignment or intrinsic spin orbit coupling.
Instead, the pathway to spin triplet generation is provided via geometric
curvature, and results in a long ranged Josephson effect. In addition, the
curvature is shown to induce a dynamically tunable $0-\pi$ transition in the
junction. We provide the analytic framework and discuss potential experimental
and innovation implications.",2105.13372v2
2021-07-08,Antiskyrmions and Bloch Skyrmions in Magnetic Dresselhaus Metals,"We present a microscopic electronic description of how antiskyrmions can be
stabilized in a Dresselhaus spin-orbit coupled magnetic metal. Furthermore, we
show that the antiskyrmions can be tuned into Bloch skyrmions via a change in
sign of hopping integral. The results are based on the state of the art hybrid
Monte Carlo simulations. Origin of such topological textures is understood via
an effective spin-only model. Our results uncover a novel connection between
two very distinct topological spin textures of immense current interest, and
present a microscopic explanation of skyrmion formation reported recently in
certain magnetic Weyl semimetals.",2107.03820v1
2023-07-28,Berezinskii approach to disordered spin systems with asymmetric scattering and application to the quantum boomerang effect,"We extend the Berezinskii diagrammatic technique to one-dimensional
disordered spin systems, in which time-reversal invariance is broken due to a
spin-orbit coupling term inducing left-right asymmetric scattering. We then use
this formalism to theoretically describe the dynamics of the quantum boomerang
effect, a recently discovered manifestation of Anderson localization. The
theoretical results are confirmed by exact numerical simulations of wave-packet
dynamics in a random potential.",2307.15354v1
2023-08-07,Half-quantum flux in spin-triplet superconducting rings with bias current,"Effects of a bias electric current have been theoretically investigated in a
spin-triplet superconducting ring in a magnetic field. Based on the
Ginzburg-Landau theory, we show that the bias current can stabilize a
half-quantum-flux (HQF) state via couplings to the Zeeman field and the
dipole-type spin-orbit interaction, the latter becoming active when the field
is tilted from the ring axis. The emergence of the HQF state is reflected as a
field-induced half-quantum-shift in the Little-Parks (LP) oscillation in the
critical current. Possible relevance to recent LP experiments is also
discussed.",2308.03668v1
2022-03-23,"Relativistic and QED corrections to one-bond indirect nulcear spin-spin couplings in X$_2^{2+}$ and X$_3^{2+}$ ions (X = Zn, Cd, Hg)","The indirect nuclear spin-spin coupling tensor, $\mathbf J$, between mercury
nuclei in Hg-containing systems can be of the order of few kHz and one of the
largest measured. We conduct an analysis of the physics behind the electronic
mechanisms that contribute to the one- and two-bond couplings $^n {\mathbf
J}_{\mathrm{Hg}-\mathrm{Hg}}$ ($n=1, 2$). We performed calculations for
$J$-couplings in X$_2^{2+}$ and $X_3^{2+}$ ions ($X$ = Zn, Cd, Hg), within
polarization propagator theory, using the random phase approximation (RPA) and
the pure zeroth order approximation (PZOA), with Dirac-Hartree-Fock (DHF) and
Dirac-Kohn-Sham (DKS) orbitals, both at four-component and ZORA levels. We show
that the ""paramagnetic-like"" mechanism contribute with more than 99.98\% to the
total isotropic component of the coupling tensor. By means of an analysis of
the molecular and atomic orbitals involved in the total value of the response
function, we find that the $s$-type valence atomic orbitals have a predominant
role in the description of the coupling. This fact allows us to develop an
effective model from which quantum electrodynamics (QED) effects on
$J$-coupling in the aforementioned ions can be estimated. The estimated QED
corrections were found in the interval $(0.7; ~ 1.7)$\% of the total
relativistic effect on isotropic one-bond $^1 {\mathbf J}$ coupling and from
the interval $(-0.2; ~ -0.4)$\%, in Zn-containing ions, to $(-0.8; ~ -1.2)$\%,
in Hg-containing ions, of the total isotropic coupling constant in the studied
systems. We also show that estimated QED corrections cast a visible dependence
on the nuclear charge $Z$ of each atom $X$ in the form of a power-law $\propto
Z^5$.",2203.12356v1
2023-11-06,Quantification of spin-charge interconversion in highly resistive sputtered Bi$_x$Se$_{1-x}$ with non-local spin valves,"The development of spin-orbitronic devices, such as magneto-electric
spin-orbit logic devices, calls for materials with a high resistivity and a
high spin-charge interconversion efficiency. One of the most promising
candidates in this regard is sputtered Bi$_x$Se$_{1-x}$. Although there are
several techniques to quantify spin-charge interconversion, to date reported
values for sputtered Bi$_x$Se$_{1-x}$ have often been overestimated due to
spurious effects related to local currents combined with a lack of
understanding of the effect of the interfaces and the use of approximations for
unknown parameters, such as the spin diffusion length. In the present study,
non-local spin valves are used to inject pure spin currents into
Bi$_x$Se$_{1-x}$, allowing us to directly obtain its spin diffusion length as
well as its spin Hall angle, from 10 K up to 300 K. These values, which are
more accurate than those previously reported in sputtered Bi$_x$Se$_{1-x}$,
evidence that the efficiency of this material is not exceptional. Indeed, the
figure of merit for spin-charge interconversion, given by the product of these
two parameters, is slightly under 1 nm. Our work demonstrates the importance of
considering all material parameters and interfaces when quantifying the spin
transport properties of materials with strong spin-orbit coupling.",2311.03598v1
2017-01-10,Effective lattice model for collective modes in a Fermi liquid with spin-orbit coupling,"A Fermi-liquid (FL) with spin-orbit coupling (SOC) supports a special type of
collective modes--chiral spin waves--which are oscillations of magnetization
even in the absence of the external magnetic field. We study the chiral spin
waves of a two-dimensional FL in the presence of both the Rashba and
Dresselhaus types of SOC and also subject to the in-plane magnetic field. We
map the system of coupled kinetic equations for the angular harmonics of the
occupation number onto an effective one-dimensional tight-binding model, in
which the lattice sites correspond to angular-momentum channels.
Linear-in-momentum SOC ensures that the effective tight-binding model has only
nearest-neighbor hopping on a bipartite lattice. In this language, the
continuum of spin-flip particle-hole excitations becomes a conduction band of
the lattice model, whereas electron-electron interaction, parameterized by the
harmonics of the Landau function, is mapped onto lattice defects of both
on-site and bond type. Collective modes correspond to bound states formed by
such defects. All the features of the collective-mode spectrum receive natural
explanation in the lattice picture as resulting from the competition between
on-site and bond defects.",1701.02781v3
2017-04-11,Synergetic effect of spin-orbit coupling and Zeeman splitting on the optical conductivity in the one-dimensional Hubbard model,"We study how the synergetic effect of spin-orbit coupling (SOC) and Zeeman
splitting (ZS) affects the optical conductivity in the one-dimensional Hubbard
model using the Kubo formula. We focus on two phenomena: (1) the electric
dipole spin resonance (EDSR) in the metallic regime and (2) the optical
conductivity in the Mott-insulating phase above the optical gap. In both cases,
we calculate qualitatively the effects of SOC and ZS and how they depend on the
relative angle between the SOC vector and the magnetic field direction. First,
we investigate the spin resonance without electron correlation (the Hubbard
parameter $U=0$). Although, neither SOC nor ZS causes any resonance by itself
in the optical conductivity, the EDSR becomes possible when both of them exist.
The resulting contribution to the optical conductivity is analyzed
analytically. The effect of $U$ on the spin resonance is also studied with a
numerical method. It is found that at half-filling, the resonance is first
enhanced for small $U$ and then suppressed when the optical gap is large
enough. In the strong coupling limit $U \rightarrow \infty$ at half-filling, we
also refer to the resonance between the lower and upper Hubbard bands appearing
at $\omega \sim U$, above the optical gap. A large magnetic field tends to
suppress the signal while it is recovered thanks to SOC depending on the
relative angle of the magnetic field.",1704.03153v2
2020-11-30,Kitaev interactions in the Co honeycomb antiferromagnets Na$_3$Co$_2$SbO$_6$ and Na$_2$Co$_2$TeO$_6$,"Co$^{2+}$ ions in an octahedral crystal field, stabilise a j$_{eff}$ = 1/2
ground state with an orbital degree of freedom and have been recently put
forward for realising Kitaev interactions, a prediction we have tested by
investigating spin dynamics in two cobalt honeycomb lattice compounds,
Na$_2$Co$_2$TeO$_6$ and Na$_3$Co$_2$SbO$_6$, using inelastic neutron
scattering. We used linear spin wave theory to show that the magnetic spectra
can be reproduced with a spin Hamiltonian including a dominant Kitaev
nearest-neighbour interaction, weaker Heisenberg interactions up to the third
neighbour and bond-dependent off-diagonal exchange interactions. Beyond the
Kitaev interaction that alone would induce a quantum spin liquid state, the
presence of these additional couplings is responsible for the zigzag-type
long-range magnetic ordering observed at low temperature in both compounds.
These results provide evidence for the realization of Kitaev-type coupling in
cobalt-based materials, despite hosting a weaker spin-orbit coupling than their
4d and 5d counterparts.",2012.00006v3
2019-04-23,"$k \cdot p$ theory for phosphorene: Effective g-factors, Landau levels, and excitons","Phosphorene, a single layer of black phosphorus, is a direct-band gap
two-dimensional semiconductor with promising charge and spin transport
properties. The electronic band structure of phosphorene is strongly affected
by the structural anisotropy of the underlying crystal lattice. We describe the
relevant conduction and valence bands close to the $\Gamma$ point by four- and
six-band (with spin) $k \cdot p$ models, including the previously overlooked
interband spin-orbit coupling which is essential for studying anisotropic
crystals. All the $k \cdot p$ parameters are obtained by a robust fit to {\it
ab initio} data, by taking into account the nominal band structure and the
$k$-dependence of the effective mass close to $\Gamma$-point. The inclusion of
interband spin-orbit coupling allows us to determine dipole transitions along
both armchair and zigzag directions. The interband coupling is also key to
determine the effective g-factors and Zeeman splittings of the Landau levels.
We predict the electron and hole g-factor correction of $\approx 0.03$ due to
the intrinsic contributions in phosphorene, which lies within the existing
range of experimental data. Furthermore, we investigate excitonic effects using
the $k \cdot p$ models and find exciton binding energy (0.81 eV) and exciton
diameters consistent with experiments and {\it ab initio} based calculations.
The proposed $k \cdot p$ Hamiltonians should be useful for investigating
magnetic, spin, transport, optical properties and many-body effects in
phosphorene.",1904.10328v3
2020-08-28,Emergence of the strong tunable linear Rashba spin-orbit coupling of two-dimensional hole gases in semiconductor quantum,"Two-dimensional hole gases in semiconductor quantum wells are promising
platforms for spintronics and quantum computation but suffer from the lack of
the $\bf{k}$-linear term in the Rashba spin-orbit coupling (SOC), which is
essential for spin manipulations without magnetism and commonly believed to be
a $\bf{k}$-cubic term as the lowest order. Here, contrary to conventional
wisdom, we uncover a strong and tunable $\bf{k}$-linear Rashba SOC in
two-dimensional hole gases (2DHG) of semiconductor quantum wells by performing
atomistic pseudopotential calculations combined with an effective Hamiltonian
for a model system of Ge/Si quantum wells. Its maximal strength exceeds 120
meV{\AA}, comparable to the highest values reported in narrow bandgap III-V
semiconductor 2D electron gases, which suffers from short spin lifetime due to
the presence of nuclear spin. We also illustrate that this emergent
$\bf{k}$-linear Rashba SOC is a first-order direct Rashba effect, originating
from a combination of heavy-hole-light-hole mixing and direct dipolar
intersubband coupling to the external electric field. These findings confirm
Ge-based 2DHG to be an excellent platform towards large-scale quantum
computation.",2008.12523v2
2023-12-30,Strain induced electronic and magnetic transition in S = 3/2 antiferromagnetic spin chain compound LaCrS3,"Exploring the physics of low-dimensional spin systems and their
pressure-driven electronic and magnetic transitions are thriving research field
in modern condensed matter physics. In this context, recently antiferromagnetic
Cr-based compounds such as CrI3, CrBr3, CrGeTe3 have been investigated
experimentally and theoretically for their possible spintronics applications.
Motivated by the fundamental and industrial importance of these materials, we
theoretically studied the electronic and magnetic properties of a relatively
less explored Cr-based chalcogenide, namely LaCrS3 where 2D layers of magnetic
Cr3+ ions form a rectangular lattice. We employed density functional theory +
Hubbard U approach in conjunction with constrained random-phase approximation
(cRPA) where the later was used to estimate the strength of U. Our findings at
ambient pressure show that the system exhibits semiconducting antiferromagnetic
ground state with a gap of 0.5 eV and large Cr moments that corresponds to
nominal S=3/2 spin-state. The 1st nearest neighbor (NN) interatomic exchange
coupling (J1) is found to be strongly antiferromagnetic (AFM), while 2nd NN
couplings are relatively weaker ferromagnetic (FM), making this system a
candidate for 1D non-frustrated antiferromagnetic spin-chain family of
materials. Based on orbital resolved interactions, we demonstrated the reason
behind two different types of interactions among 1st and 2nd NN despite their
very similar bond lengths. We observe a significant spin-orbit coupling effect,
giving rise to a finite magneto crystalline anisotropy, and
Dzyaloshinskii-Moriya (DM) interaction. Further, we found that by applying
uniaxial tensile strain along crystallographic a and b-axis, LaCrS3 exhibits a
magnetic transition to a semi-conducting FM ground state, while compression
gives rise to the realization of novel gapless semiconducting antiferromagnetic
ground state.",2401.00239v1
2005-05-30,Electronic structure and magnetism of LaVO3 and LaMnO3,"In this contribution we derive and discuss energy levels of the
strongly-correlated d2 configuration of the V3+ ion (LaVO3) and of d4
configuration of the Mn3+ ion (LaMnO3) in the octahedral surroundings in the
presence of the spin-orbit coupling and the resulting magnetic properties. We
take into account very strong correlations among the d electrons and work with
strongly-correlated atomic-like electronic systems, ground term of which is,
also in a solid, described by two Hund's rules quantum numbers. In a solid we
take into account the influence of crystal-field interactions, predominantly of
the cubic (octahedral) symmetry. We describe both paramagnetic state and the
magnetically-ordered state getting a value of 1.3 uB for the V3+ -ion magnetic
moment in the ordered state at 0 K for LaVO3 (3T1g) and of 3.7 uB for LaMnO3
(5Eg). A remarkably consistent description of both zero-temperature properties
and thermodynamic properties indicates on the high physical adequacy of the
applied atomic approach. We point out the necessity to unquench the orbital
moment in 3d-ion compounds. We claim that the intra-atomic spin-orbit coupling
and strong electron correlations are indispensable for the physically adequate
description of electronic and magnetic properties of LaVO3 and LaMnO3.",0505711v1
2008-09-19,Doping a Mott insulator with orbital degrees of freedom,"We study the effects of hole doping on one-dimensional Mott insulators with
orbital degrees of freedom. We describe the system in terms of a generalized
t-J model. At a specific point in parameter space the model becomes integrable
in analogy to the one-band supersymmetric t-J model. We use the Bethe ansatz to
derive a set of nonlinear integral equations which allow us to study the
thermodynamics exactly. Moving away from this special point in parameter space
we use the density-matrix renormalization group applied to transfer matrices to
study the evolution of various phases of the undoped system with doping and
temperature. Finally, we study a one-dimensional version of a realistic model
for cubic titanates which includes the anisotropy of the orbital sector due to
Hund's coupling. We find a transition from a phase with antiferromagnetically
correlated spins to a phase where the spins are fully ferromagnetically
polarized, a strong tendency towards phase separation at large Hund's coupling,
as well as the possibility of an instability towards triplet superconductivity.",0809.3427v1
2011-04-04,Josephson current in carbon nanotubes with spin-orbit interaction,"We demonstrate that curvature-induced spin-orbit (SO) coupling induces a
$0-\pi$ transition in the Josephson current through a carbon nanotube quantum
dot coupled to superconducting leads. In the non-interacting regime, the
transition can be tuned by applying parallel magnetic field near the critical
field where orbital states become degenerate. Moreover, the interplay between
charging and SO effects in the Coulomb Blockade and cotunneling regimes leads
to a rich phase diagram with well-defined (analytical) boundaries in parameter
space. Finally, the 0 phase always prevails in the Kondo regime. Our
calculations are relevant in view of recent experimental advances in transport
through ultra-clean carbon nanotubes.",1104.0513v1
2012-08-29,Spin-orbital coupling in a triplet superconductor-ferromagnet junction,"We study a novel type of coupling between spin and orbital degrees of freedom
which appears at triplet superconductor-ferromagnet interfaces. Using a
self-consistent spatially-dependent mean-field theory, we show that increasing
the angle between the ferromagnetic moment and the triplet vector order
parameter enhances or suppresses the p-wave gap close to the interface,
according as the gap antinodes are parallel or perpendicular to the boundary,
respectively. The associated change in condensation energy establishes an
orbitally-dependent preferred orientation for the magnetization. When both gap
components are present, as in a chiral superconductor, we observe a first-order
transition between different moment orientations as a function of the exchange
field strength.",1208.5871v2
2012-12-24,Fermiology of Strongly Spin-Orbit Coupled Superconductor Sn1-xInxTe and its Implication to Topological Superconductivity,"We have performed angle-resolved photoemission spectroscopy of the strongly
spin-orbit coupled low-carrier density superconductor Sn1-xInxTe (x = 0.045) to
elucidate the electronic states relevant to the possible occurrence of
topological superconductivity recently reported for this compound from
point-contact spectroscopy. The obtained energy-band structure reveals a small
holelike Fermi surface centered at the L point of the bulk Brillouin zone,
together with a signature of a topological surface state which indicates that
this superconductor is essentially a doped topological crystalline insulator
characterized by band inversion and mirror symmetry. A comparison of the
electronic states with a band-non-inverted superconductor possessing a similar
Fermi surface structure, Pb1-xTlxTe, suggests that the anomalous behavior in
the superconducting state of Sn1-xInxTe is likely to be related to the peculiar
orbital characteristics of the bulk valence band and/or the presence of a
topological surface state.",1212.5886v1
2013-03-13,"Ferromagnetic exchange, spin-orbit coupling and spiral magnetism at the LaAlO_3/SrTiO_3 interface","The electronic properties of the polar interface between insulating oxides is
a subject of great current interest. An exciting new development is the
observation of robust magnetism at the interface of two non-magnetic materials
LaAlO_3 (LAO) and SrTiO_3 (STO). Here we present a microscopic theory for the
formation and interaction of local moments, which depends on essential features
of the LAO/STO interface. We show that correlation-induced moments arise due to
interfacial splitting of orbital degeneracy. We find that gate-tunable Rashba
spin-orbit coupling at the interface influences the exchange interaction
mediated by conduction electrons. We predict that the zero-field ground state
is a long-wavelength spiral and show that its evolution in an external field
accounts semi-quantitatively for torque magnetometry data. Our theory describes
qualitative aspects of the scanning SQUID measurements and makes several
testable predictions for future experiments.",1303.3275v2
2013-03-19,Electronic structure of relativistic Mott insulator Li$_2$RhO$_3$,"Motivated by studies of coexisting electron correlation and spin-orbit
coupling effect in Na$_2$IrO$_3$ and a recent experiment of its 4d analogue
Li$_2$RhO$_3$, we performed first-principles calculations of the rhodium oxide
compound. The experimentally observed ground state of Li$_2$RhO$_3$ can be
recovered only if both spin-orbit coupling and on-site Coulomb interaction are
taken into consideration. Within the proper $U$ range for 4d-orbitals
($2\leqslant U\leqslant 4$ eV), the ground state of Li$_2$RhO$_3$ could be
either zigzag-AFM or stripy-AFM, both yielding energy gap close to experimental
observation. Furthermore, the total energy differences between the competing
magnetic phases are $\leqslant 3$ meV/Rh within $2\leqslant U\leqslant 4$ eV,
manifesting strong magnetic frustration in the compound. Finally, the phase
energy of Li$_2$RhO$_3$ cannot be fitted with the two-dimensional
Heisenberg-Kitaev model involving only the nearest neighbor interactions, and
we propose that inter-layer interactions may be responsible for the
discrepancy.",1303.4675v1
2013-03-30,"A generic tight-binding model for monolayer, bilayer and bulk MoS2","Molybdenum disulfide (MoS2) is a layered semiconductor which has become very
important recently as an emerging electronic device material. Being an
intrinsic semiconductor the two-dimensional MoS2 has major advantages as the
channel material in field-effect transistors. In this work we determine the
electronic structure of MoS2 with the highly accurate screened hybrid
functional within the density functional theory (DFT) including the spin-orbit
coupling. Using the DFT electronic structures as target, we have developed a
single generic tight-binding (TB) model that accurately produces the electronic
structures for three different forms of MoS2 - bulk, bilayer and monolayer. Our
TB model is based on the Slater-Koster method with non-orthogonal sp3d5
orbitals, nearest-neighbor interactions and spin-orbit coupling. The TB model
is useful for atomistic modeling of quantum transport in MoS2 based electronic
devices.",1304.0074v1
2013-12-09,Interplay between Hund's coupling and spin-orbit interaction on elementary excitations in Sr2IrO4,"We study the elementary excitations in 5d transition metal oxideSr$_2$IrO$_4$
by calculating the particle-hole Green's function within the random phase
approximation on an antiferromagnetic ground state in the two-dimensional
multi-orbital Hubbard model. The obtained magnetic excitations of bound states
show a characteristic dispersion in consistent with the experiments. In
addition, two new types of excitations are found due to the interplay between
spin-orbit interaction and Hund's coupling: a magnetic excitation as a bound
state, which has energy gap at the $\Gamma$ point, and an exciton as a resonant
mode in the continuum of electron-hole pair creation.",1312.2348v2
2014-09-25,Topological Phases in Oxide Heterostructures with Light and Heavy Transition Metal Ions,"Using a combination of density functional theory, tight-binding models, and
Hartree-Fock theory, we predict topological phases with and without
time-reversal symmetry breaking in oxide heterostructures. We consider both
heterostructures containing light transition metal ions, and those containing
heavy transition metal ions. We find the (111) growth direction naturally leads
to favorable conditions for topological phases in both perovskite structures
and pyrochlore structures. For the case of light transition metal elements,
Hartree-Fock theory predicts the spin-orbit coupling is effectively enhanced by
on-site multiple-orbital interactions and may drive the system through a
topological phase transition, while heavy elements with intrinsically large
spin-orbit coupling require much weaker, or even vanishing electron
interactions to bring about a topological phase.",1409.7148v1
2014-09-25,Spin-orbit decomposition of ab initio wavefunctions,"Although the modern shell-model picture of atomic nuclei is built from
single-particle orbits with good total angular momentum $j$, leading to $j$-$j$
coupling, phenomenological models suggested decades ago that for $0p$-shell
nuclides a simpler picture can be realized via coupling of total spin $S$ and
total orbital angular momentum $L$. I revisit this idea with large-basis,
no-core shell model (NCSM) calculations using modern \textit{ab initio}
two-body interactions, and dissect the resulting wavefunctions into their
component $L$- and $S$-components. Remarkably, there is broad agreement with
calculations using the phenomenological Cohen-Kurath forces, despite a gap of
nearly fifty years and six orders of magnitude in basis dimensions. I suggest
$L$-$S$ may be a useful tool for analyzing \textit{ab initio} wavefunctions of
light nuclei, for example in the case of rotational bands.",1409.7355v2
2015-01-31,Spontaneous multipole ordering by local parity mixing,"Broken spatial inversion symmetry in spin-orbital coupled systems leads to a
mixing between orbitals with different parity, which results in unusual
electronic structures and transport properties. We theoretically investigate
the possibility of multipole ordering induced by a parity mixing. In
particular, we focus on the system in which the parity mixing appears in a
sublattice-dependent form. Starting from the periodic Anderson model with such
a local parity mixing, we derive an extended Kondo lattice model with
sublattice-dependent antisymmetric exchange couplings between itinerant
electrons and localized spins. By the variational calculation, simulated
annealing, and Monte Carlo simulation, we show that the model on a
quasi-one-dimensional zig-zag lattice exhibits an odd-parity multipole order
composed of magnetic toroidal and quadrupole components at and near half
filling. The multipole order causes a band deformation with the band bottom
shift and a magnetoelectric response. The results suggest that unusual
odd-parity multipole orders will be widely observed in multi-orbital systems
with local parity mixing.",1502.00057v1
2016-01-07,Valley Plasmonics in the Dichalcogenides,"The rich phenomenology of plasmonic excitations in the dichalcogenides is
analyzed as a function of doping. The many-body polarization, the dielectric
response function and electron energy loss spectra are calculated using an ab
initio based model involving material-realistic Coulomb interactions, band
structure and spin-orbit coupling. Focusing on the representative case of
MoS$_2$, a plethora of plasmon bands are observed, originating from scattering
processes within and between the conduction or valence band valleys. We discuss
the resulting square-root and linear collective modes, arising from long-range
versus short-range screening of the Coulomb potential. We show that the
multi-orbital nature of the bands and spin-orbit coupling strongly affects
inter-valley scattering processes by gapping certain two-particle modes at
large momentum transfer.",1601.01707v1
2017-03-03,Photo-association of trilobite Rydberg molecules via resonant spin-orbit coupling,"We report on a novel method for photo-association of strongly polar trilobite
Rydberg molecules. This exotic ultralong-range dimer, consisting of a
ground-state atom bound to the Rydberg electron via electron-neutral
scattering, inherits its polar character from the admixture of high angular
momentum electronic orbitals. The absence of low-$L$ character hinders standard
photo-association techniques. Here, we show that for suitable principal quantum
numbers resonant coupling of the orbital motion with the nuclear spin of the
perturber, mediated by electron-neutral scattering, hybridizes the trilobite
molecular potential with the more conventional ${\rm{S}}$-type molecular state.
This provides a general path to associate trilobite molecules with large
electric dipole moments, as demonstrated via high-resolution spectroscopy. We
find a dipole moment of 135(45) D for the trilobite state. Our results are
compared to theoretical predictions based on a Fermi-model.",1703.01096v2
2017-04-11,Possible Bicollinear Nematic State with Monoclinic Lattice Distortions in Iron Telluride Compounds,"Iron telluride FeTe is known to display bicollinear magnetic order at low
temperatures together with a monoclinic lattice distortion. Because the
bicollinear order can involve two different wavevectors $(\pi/2,\pi/2)$ and
$(\pi/2,-\pi/2)$, symmetry considerations allow for the possible stabilization
of a nematic state with short-range bicollinear order coupled to monoclinic
lattice distortions at a $T_S$ higher than the temperature $T_N$ where
long-range bicollinear order fully develops. As a concrete example, the
three-orbitals spin-fermion model for iron telluride is studied with an
additional coupling $\tilde\lambda_{12}$ between the monoclinic lattice strain
and an orbital-nematic order parameter with $B_{2g}$ symmetry. Monte Carlo
simulations show that with increasing $\tilde\lambda_{12}$ the first-order
transition characteristic of FeTe splits and bicollinear nematicity is
stabilized in a (narrow) temperature range. In this new regime the lattice is
monoclinically distorted and short-range spin and orbital order breaks
rotational invariance. A discussion of possible realizations of this exotic
state is provided.",1704.03495v2
2016-08-09,High-temperature large-gap quantum anomalous Hall insulator in ultrathin double perovskite films,"Motivated by the goal of realizing topological phases in thin films and
heterostructures of correlated oxides, we propose here a quantum anomalous Hall
insulator (QAHI) in ultrathin films of double perovskites based on mixed 3d-5d
or 3d-4d transition metal ions, grown along the [111] direction. Considering
the specific case of ultrathin Ba2FeReO6, we present a theoretical analysis of
an effective Hamiltonian derived from first-principles. We establish that a
strong spin-orbit coupling at Re site, t2g symmetry of the low-energy d-bands,
polarity of its [111] orientation of perovskite structure, and mixed 3d-5d
chemistry results in room temperature magnetism with a robust QAHI state of
Chern number C=1 and a large band-gap. We uncover and highlight a
non-relativistic orbital-Rashba-type effect in addition to the spin-orbit
coupling, that governs this QAHI state. Our prediction of a large topological
band-gap of ~100 meV in electronic structure, and a magnetic transition
temperature Tc~300K estimated by Monte Carlo simulations, is expected to
stimulate experimental efforts at synthesis of such films and enable possible
practical applications of its dissipationless edge currents.",1608.02950v1
2017-06-06,In-Plane Magnetization Induced Quantum Anomalous Hall Effect in Atomic Crystals of Group-V Elements,"We theoretically demonstrate that the in-plane magnetization induced quantum
anomalous Hall effect (QAHE) can be realized in atomic crystal layers of
group-V elements with buckled honeycomb lattice. We first construct a general
tight-binding Hamiltonian with $sp^3$ orbitals via Slater-Koster two-center
approximation, and then numerically show that for weak and strong spin-orbit
couplings the systems harbor QAHEs with Chern numbers of $\mathcal{C}=\pm1$ and
$\pm2$ , respectively. For the $\mathcal{C}=\pm1$ phases, we find the critical
phase-transition magnetization from a trivial insulator to QAHE can become
extremely small by tuning the spin-orbit coupling strength. Although the
resulting band gap is small, it can be remarkably enhanced by orders via
tilting the magnetization slightly away from the in-plane orientation. For the
$\mathcal{C}=\pm2$ phases, we find that the band gap is large enough for the
room-temperature observation. Although the critical magnetization is relatively
large, it can be effectively decreased by applying a strain. All these suggest
that it is experimentally feasible to realize high-temperature QAHE from
in-plane magnetization in atomic crystal layers of group-V elements.",1706.01851v1
2018-06-11,Giant perpendicular magnetic anisotropy in Fe/III-V nitride thin films,"Large perpendicular magnetic anisotropy (PMA) in transition metal thin films
provides a pathway for enabling the intriguing physics of nanomagnetism and
developing broad spintronics applications. After decades of searches for
promising materials, the energy scale of PMA of transition metal thin films,
unfortunately, remains only about 1 meV. This limitation has become a major
bottleneck in the development of ultradense storage and memory devices. We
discovered unprecedented PMA in Fe thin-film growth on the $(000\bar{1})$
N-terminated surface of III-V nitrides from first-principles calculations. PMA
ranges from 24.1 meV/u.c. in Fe/BN to 53.7 meV/u.c. in Fe/InN.
Symmetry-protected degeneracy between $x^2-y^2$ and $xy$ orbitals and its lift
by the spin-orbit coupling play a dominant role. As a consequence, PMA in
Fe/III-V nitride thin films is dominated by first-order perturbation of the
spin-orbit coupling, instead of second-order in conventional transition
metal/oxide thin films. This game-changing scenario would also open a new field
of magnetism on transition metal/nitride interfaces.",1806.04162v1
2018-07-07,Topological multiferroic phases in the extended Kane-Mele-Hubbard Model in the Hofstadter regime,"We investigate the new quantum phases on the extended Kane-Mele-Hubbard model
of honeycomb lattice in the Hofstadter regime. In this regime, orbital motion
of the electrons can induce various topological phases with spontaneously
broken symmetries when the spin orbit coupling and electron correlations
coexist. Here, we consider the interaction effects in the Kane-Mele model and
discuss possible phases in the presence of magnetic field at integer fillings
of electrons. In particular, focusing on 2{\pi}/3 magnetic flux per plaquette,
the realization of numerous quantum phases are discussed within the mean field
framework; insulator with coplanar magnetic ordering, ferrimagnetic Chern
insulator with nematic charge order, ferrimagnetic-ferrielectric Chern
insulators etc. Many of these phase transitions are also accompanied with the
change in the topological invariants of the system. Based on our theoretical
study, we propose topological multiferroic phases with a scope of realization
in 2D van-der Waals materials and optical lattice system where the significant
interplay of magnetic field, spin orbit coupling and interactions can be
engineered.",1807.02686v1
2019-08-22,Direct observation of the spin-orbit coupling interaction in ring-core optical fibers,"Ring-core optical fibers have been designed to carry orbital angular momentum
modes. We demonstrate the imaging of these modes, individually identifying
modes separated temporally by only 30~ps. A single-pixel camera operating in
the short-wave infrared detection range is used to image the 1550~nm wavelength
optical modes. With this technique, examination of these optical modes can be
performed with significantly higher temporal resolution than is possible with
conventional imaging systems, such that the imaging of modes separated by
spin-orbit coupling is achieved and evaluated. Deconvolution is required to
separate the instrument response from the optical mode signal, increasing the
clarity and temporal resolution of the measurement system.",1908.08252v1
2020-08-07,Magnetoelastic and Magnetostrictive Properties of Co$_2$XAl Heusler Compounds,"We present a comprehensive first principles electronic structure study of the
magnetoelastic and magnetostrictive properties in the Co-based Co$_2$XAl (X =
V, Ti, Cr, Mn, Fe) full Heusler compounds. In addition to the commonly used
total energy approach, we employ torque method to calculate the magnetoelastic
tensor elements. We show that the torque based methods are in general
computationally more efficient, and allow to unveil the atomic- and
orbital-contributions to the magnetoelastic constants in an exact manner, as
opposed to the conventional approaches based on second order perturbation with
respect to the spin-orbit coupling. The magnetostriction constants are in good
agreement with available experimental data. The results reveal that the main
contribution to the magnetostriction constants, $\lambda_{100}$ and
$\lambda_{111}$, arises primarily from the strained-induced modulation of the
$\langle d_{x^2-y^2}|\hat{L}_z|d_{xy}\rangle$ and $\langle
d_{z^2}|\hat{L}_x|d_{yz}\rangle$ spin orbit coupling matrix elements,
respectively, of the Co atoms.",2008.03005v1
2015-08-01,Non-collinear vs collinear description of the Ir-based one-$t_{2g}$ -hole perovskite-related compounds: SrIrO$_3$ and Sr$_2$IrO$_4$,"We present an analysis of the electronic structure of perovskite-related
iridates, 5d electron compounds where a subtle interplay between spin-orbit
coupling, tetragonal distortions and electron correlations determines the
electronic structure properties. We suggest via electronic structure
calculations that a non-collinear calculation is required to obtain solutions
close to the usually quoted $j_{eff}$ = 1/2 state to describe the $t_{2g}$ hole
in the $Ir^{4+} :d^5$ cation, while a collinear calculation yields a different
solution, the hole is in a simpler xz/yz complex combination with a smaller
$L_z /S_z$ ratio. We describe what the implications of this are in terms of the
electronic structure; surprisingly, both solutions barely differ in terms of
their band structure, and are similar to the one obtained by a tight binding
model involving $t_{2g}$ orbitals with mean field interactions. We also analyze
how the electronic structure and magnetism evolve with strain, with the
spin-orbit coupling strength and with the on-site Coulomb repulsion, suggest
the way the band structure gets modified and draw some comparisons with
available experimental observations.",1508.00107v2
2015-08-18,Transconductance and effective Landé factors for quantum point contacts: spin-orbit coupling and interaction effects,"We analyze the effective $g^*$ factors and their dependence on the
orientation of the external magnetic field for a quantum point contact defined
in the two-dimensional electron gas. The paper simulates the experimental
procedure for evaluation of the effective Land\'e factors from the
transconductance of a biased device in external magnetic field. The
contributions of the orbital effects of the magnetic field, the
electron-electron interaction and spin-orbit (SO) coupling are studied. The
anisotropy of the $g^*$ factors for the in-plane magnetic field orientation,
which seems counterintuitive from the perspective of the effective SO magnetic
field, is explained in an analytical model of the constriction as due to the
SO-induced subband mixing. The asymmetry of the transconductance as a function
of the gate voltage is obtained in agreement with the experimental data and the
results are explained as due to the depletion of the electron gas within the
quantum point contact constriction and the related reduction of the screening
as described within the DFT approach. The results for transconductance and the
$g^*$ factors are in a good agreement with the experimental data [Phys. Rev. B
{\bf 81}, 041303, 2010].",1508.04287v1
2020-06-20,First-principles study of the effective Hamiltonian for Dirac fermions with spin-orbit coupling in two-dimensional molecular conductor $α$-(BETS)$_2$I$_3$,"We employed first-principles density-functional theory (DFT) calculations to
characterize Dirac electrons in quasi-two-dimensional molecular conductor
$\alpha$-(BETS)$_2$I$_3$ [= $\alpha$-(BEDT-TSeF)$_2$I$_3$] at a low temperature
of 30K. We provide a tight-binding model with intermolecular transfer energies
evaluated from maximally localized Wannier functions, where the number of
relevant transfer integrals is relatively large due to the delocalized
character of Se $p$ orbitals. The spin-orbit coupling gives rise to an exotic
insulating state with an indirect band gap of about 2 meV. We analyzed the
energy spectrum with a Dirac cone close to the Fermi level to develop an
effective Hamiltonian with site-potentials, which reproduces the spectrum
obtained by the DFT band structure.",2006.11455v3
2021-06-24,"A first-principles investigation of band inversion in topologically nontrivial Na2AgX (X= As, Sb and Bi) full Heusler compounds","Topological nontrivial nature are the latest phases to be discovered in
condensed matter physics with insulating bulk band gaps and topologically
protected metallic surface states; they are one of the current hot topics
because of their unique properties and potential applications. In this paper,
we have highlighted a first-principles study of the structural stability and
electronic behavior of the Na${}_{2}$AgX (X= As, Sb and Bi) full Heusler
compounds, using the Full-Potential Linear Muffin-Tin Orbital (FP-LMTO) method.
We have originated that the Hg${}_{2}$CuTi structure is appropriate in all
studied materials. The negative values of the calculated formation energies
mean that these compounds are energetically stable. The band structure is
studied for the two cases relating the existence and the absence of
spin-orbital couplings, where all materials are shown to be topologically
non-trivial compounds. Spin orbital couplings were noticed to have no
significant effect on the electronic properties such as the topological order.",2106.13184v1
2021-10-22,Magnetization dynamics fingerprints of an excitonic condensate $t_{2g}^{4}$ magnet,"The competition between spin-orbit coupling $\lambda$ and electron-electron
interaction $U$ leads to a plethora of novel states of matter, extensively
studied in the context of $t_{2g}^4$ and $t_{2g}^5$ materials, such as
ruthenates and iridates. Excitonic magnets -- the antiferromagnetic state of
bounded electron-hole pairs -- is a prominent example of phenomena driven by
those competing energy scales. Interestingly, recent theoretical studies
predicted that excitonic magnets can be found in the ground-state of
spin-orbit-coupled $t_{2g}^4$ Hubbard models. Here, we present a detailed
computational study of the magnetic excitations in that excitonic magnet,
employing one-dimensional chains (via density matrix renormalization group) and
small two-dimensional clusters (via Lanczos). Specifically, first we show that
the low-energy spectrum is dominated by a dispersive (acoustic) magnonic mode,
with extra features arising from the $\lambda=0$ state in the phase diagram.
Second, and more importantly, we found a novel magnetic excitation forming a
high-energy optical mode with the highest intensity at wavevector $q\to 0$. In
the excitonic condensation regime at large $U$, we also have found a novel
high-energy $\pi$-mode composed solely of orbital excitations. These unique
fingerprints of the $t_{2g}^4$ excitonic magnet are important in the analysis
of neutron and RIXS experiments.",2110.11828v1
2021-10-27,Predicting spin orbit coupling effect in the electronic and magnetic properties of cobalt (Co) doped WSe2 monolayer,"The electronic and magnetic properties of cobalt (Co) doped monolayer (ML)
tungsten diselenide (WSe2) are investigated using the density functional theory
with the on-site Hubbard potential correction (DFT+U) for the localized d
orbitals of Co atom taking into account the spin orbit coupling (SOC)
interaction. The results show that the substitution of Co at the W sites of ML
WSe2 is energetically favorable under Se rich environment. We noticed that the
Hund's exchange splitting (\Delta H_{ex}) is dominant over the crystal field
splitting (\Delta_{cf}). The induced magnetic moment due to the Co-doped defect
is ~3.00 \mu_B per Co atom. The magnetic interaction between two Co atoms at
the nearest neighbor separation depends mainly on the concentration of the
impurity atoms. The calculated value of curie temperature (TC) is increasing
with increasing impurity concentration satisfying the Zener model. Based on the
results, it can be proposed that the Co-doped WSe2 monolayer is potential
candidate to apply in spintronics, optoelectronics, and magnetic storage
devices.",2110.14801v2
2022-11-10,Enhanced Spin-Orbit Coupling in a Correlated Metal,"We investigate the correlation effects on spin-orbit coupling (SOC) in a
two-orbital Hubbard model on a square lattice by applying the variational Monte
Carlo method. We consider an effective SOC constant $\lambda_{\text{eff}}$ in
the one-body part of the variational wave function and mainly discuss the cases
of the electron number per site $n=1$, that is, quarter filling. We find that
$\lambda_{\text{eff}}$ is proportional to the bare value $\lambda$ and depends
on the electron-electron interactions through $(U'-J')$ in a relatively wide
parameter range in the paramagnetic (PM) phase, where $U'$ is the interorbital
Coulomb interaction and $J'$ is the pair hopping interaction. Increasing the
electron-electron interactions in the PM phase leads to a transition to an
effective one-band state, in which the upper band becomes empty due to the
enhanced $\lambda_{\text{eff}}$. We also construct phase diagrams considering
magnetic order. The carrier doping effect on $\lambda_{\text{eff}}$ is also
investigated. We find that $\lambda_{\text{eff}}$ enhances in a strongly
correlated region around the Mott transition point and it is necessary to
include the correlation effects beyond the Hartree-Fock approximation to
describe the enhanced SOC properly.",2211.05354v1
2023-10-30,Magnetotransport in spin-orbit coupled noncentrosymmetric and Weyl metals,"Recently, chiral anomaly (CA) has been proposed to occur in spin-orbit
coupled noncentrosymmetric metals (SOC-NCMs), motivating CA to be a Fermi
surface property rather than a Weyl node property. Although the nature of the
anomaly is similar in both SOC-NCMs and Weyl systems, here we point out
significant fundamental differences between the two. We show that the different
nature of the orbital magnetic moment (OMM) in the two systems leads to
non-trivial consequences -- particularly the sign of the longitudinal
magnetoconductance always remains positive in a SOC non-centrosymmetric metal,
unlike a Weyl metal that displays either sign. Furthermore,we investigate the
planar Hall effect and the geometrical contribution to the Hall effect in the
two systems and point out significant differences in the two systems. We
conduct our analysis for magnetic and non-magnetic impurities, making our study
important in light of current and upcoming experiments in both SOC-NCMs and
Weyl metals.",2310.19877v1
2004-11-17,Electronic Transport Spectroscopy of Carbon Nanotubes in a Magnetic Field,"We report magnetic field spectroscopy measurements in carbon nanotube quantum
dots exhibiting four-fold shell structure in the energy level spectrum. The
magnetic field induces a large splitting between the two orbital states of each
shell, demonstrating their opposite magnetic moment and determining transitions
in the spin and orbital configuration of the quantum dot ground state. We use
inelastic cotunneling spectroscopy to accurately resolve the spin and orbital
contributions to the magnetic moment. A small coupling is found between
orbitals with opposite magnetic moment leading to anticrossing behavior at zero
field.",0411440v1
2005-07-20,"Spin, charge, and orbital correlations in the one-dimensional t2g-orbital Hubbard model","We present the zero-temperature phase diagram of the one-dimensional
t2g-orbital Hubbard model, obtained using the density-matrix renormalization
group and Lanczos techniques. Emphasis is given to the case for the electron
density n=5 corresponding to five electrons per site, of relevance for some
Co-based compounds. However, several other cases for electron densities between
n=3 and 6 are also studied. At n=5, our results indicate a first-order
transition between a paramagnetic (PM) insulator phase and a fully-polarized
ferromagnetic (FM) state by tuning the Hund's coupling. The results also
suggest a transition from the n=5 PM insulator phase to a metallic regime by
changing the electron density, either via hole or electron doping. The behavior
of the spin, charge, and orbital correlation functions in the FM and PM states
are also described in the text and discussed. The robustness of these two
states varying parameters suggests that they may be of relevance in more
realistic higher dimensional systems as well.",0507472v1
2008-03-14,Theoretical study of the electronic states of hollandite vanadate K$_2$V$_8$O$_{16}$,"We consider electronic properties of hollandite vanadate K$_2$V$_8$O$_{16}$,
a one-dimensional zigzag-chain system of $t_{2g}$ orbitals in a mixed valent
state. We first calculate the Madelung energy and obtain the relative stability
of several charge-ordering patterns to determine the most stable one that is
consistent with the observed superlattice structure. We then develop the
strong-coupling perturbation theory to derive the effective spin-orbit
Hamiltonian, starting from the triply-degenerate $t_{2g}$ orbitals in the
VO$_6$ octahedral structure. We apply an exact-diagonalization technique on
small clusters of this Hamiltonian and obtain the orbital-ordering pattern and
spin structures in the ground state. We thereby discuss the electronic and
magnetic properties of K$_2$V$_8$O$_{16}$ including predictions on the outcome
of future experimental studies.",0803.2089v1
2011-10-05,Two approximations to the bound states of Dirac-Hulthen problem,"The bound state (energy spectrum and two-spinor wave functions) solutions of
the Dirac equation with the Hulthen potential for all angular momenta based on
the spin and pseudospin symmetry are obtained. The parametric generalization of
the Nikiforov-Uvarov method is used in the calculations. The orbital dependency
(spin-orbit and pseudospin-orbit dependent coupling too singular 1/r^{2}) of
the Dirac equation are included to the solution by introducing a more accurate
approximation scheme to deal with the centrifugal (pseudo-centrifugal) term.
The approximation is also made for the less singular 1/r orbital term in the
Dirac equation for a wider energy spectrum. The nonrelativistic limits are also
obtained on mapping of parameters.",1110.0940v2
2012-03-14,Multi-orbital physics in Fermi liquids prone to magnetic order,"The interplay of spin-orbit-coupling and strong electronic correlations is
studied for the single-layer and the bilayer compound of the strontium
ruthenate Ruddlesden-Popper series by a combination of first-principles
band-structure theory with mean-field rotationally invariant slave bosons. At
equilibrium strongly renormalized (spin-orbit-split) quasiparticle bands are
traced and a thorough description of the low-energy regime for the nearly
ferromagnetic bilayer system in accordance with experimental data is presented.
The metamagnetic response of Sr$_3$Ru$_2$O$_7$ in finite magnetic field $H$ is
verified and a detailed analysis of the underlying correlated electronic
structure provided. Intriguing multi-orbital physics on both local and
itinerant level, such as e.g. competing paramagnetic and diamagnetic
contributions, is observed with important differences depending on the
magnetic-field angle $\theta$ with the crystallographic c axis.",1203.3148v2
2012-03-17,Magnetic Phase Transition and Relaxation Effects in LiFePO4,"We report the observation of para - antiferromagnetic transition at ~ 50 K in
lithium iron phosphate, LiFePO4 through DC magnetization and M\""ossbauer
spectroscopy. The Ferrous ion Fe2+ (3d6, 5D) in LiFePO4 exhibits relaxation
effects with a relaxation frequency ~1.076 \times 10(rise to 7) s-1 at 300 K.
The temperature dependence of the frequency suggests the origin of the
relaxation is spin-lattice type. The quadrupole splitting at low temperatures
indicates the excited orbital states mix strongly to the orbital doublet ground
state via spin-orbit coupling. Modified molecular field model analysis yields a
saturation value for hyperfine field ~125 kOe. The anomaly in magnetization and
M\""ossbauer parameters below 27 K may be ascribed to contribution of orbital
angular momentum. The high value of the asymmetry parameter ({\eta} ~ 0.8) of
the electric field gradient obtained in the antiferromagnetic regime indicates
a strongly distorted octahedral oxygen neighbourhood for the ferrous sites.",1203.3863v2
2013-10-16,Exact Results on Itinerant Ferromagnetism in Multi-orbital Systems on Square and Cubic Lattices,"We study itinerant ferromagnetism in multi-orbital Hubbard models in certain
two-dimensional square and three-dimensional cubic lattices. In the strong
coupling limit where doubly occupied orbitals are not allowed, we prove that
the fully spin-polarized states are the unique ground states, apart from the
trivial spin degeneracies, for a large region of fillings factors. Possible
applications to p-orbital bands with ultra-cold fermions in optical lattices,
and electronic 3d-orbital bands in transition-metal oxides, are discussed.",1310.4391v3
2014-10-13,Isometry Group Orbit Quantization of Spinning Strings in AdS_3 x S^3,"Describing the bosonic AdS_3 x S^3 particle and string in SU(1,1) x SU(2)
group variables, we provide a Hamiltonian treatment of the isometry group
orbits of solutions via analysis of the pre-symplectic form. For the particle
we obtain a one-parameter family of orbits parameterized by
creation-annihilation variables, which leads to the Holstein-Primakoff
realization of the isometry group generators. The scheme is then applied to
spinning string solutions characterized by one winding number in AdS_3 and two
winding numbers in S^3. We find a two-parameter family of orbits, where
quantization again provides the Holstein-Primakoff realization of the symmetry
generators with an oscillator type energy spectrum. Analyzing the minimal
energy at strong coupling we verify the spectrum of short strings at special
values of winding numbers.",1410.3428v2
2015-06-22,Spin-orbit coupling and chaotic rotation for circumbinary bodies. Application to the small satellites of the Pluto-Charon system,"We investigate the resonant rotation of circumbinary bodies in planar
quasi-circular orbits. Denoting $n_b$ and $n$ the orbital mean motion of the
inner binary and of the circumbinary body, respectively, we show that
spin-orbit resonances exist at the frequencies $n\pm k\nu/2$, where $\nu = n_b
- n$, and $k$ is an integer. Moreover, when the libration at natural frequency
has the same magnitude as $\nu$, the resonances overlap and the rotation
becomes chaotic. We apply these results to the small satellites in the
Pluto-Charon system, and conclude that their rotations are likely chaotic.
However, the rotation can also be stable and not synchronous for small axial
asymmetries.",1506.06733v3
2016-06-11,Spin-Orbit Interactions and the Nematicity Observed in the Fe-Based Superconductors,"High-resolution angle-resolved photoelectron spectroscopy is used to examine
the electronic band structure of FeTe$_{0.5}$Se$_{0.5}$ near the Brillouin zone
center. A consistent separation of the $\alpha_{1}$ and $\alpha_{2}$ bands is
observed with little $k_{z}$ dependence of the $\alpha_{1}$ band.
First-principles calculations for bulk and thin films demonstrate that the
antiferromagnetic coupling between the Fe atoms and hybridization-induced
spin-orbit effects lifts the degeneracy of the Fe $d_{xz}$ and $d_{yz}$
orbitals at the zone center leading to orbital ordering. These experimental and
computational results provide a natural microscopic basis for the nematicity
observed in the Fe-based superconductors.",1606.03536v1
2016-07-03,First-Principles Momentum Dependent Local Ansatz Approach to the Ground-State Properties of Iron-Group Transition Metals,"The ground-state properties of iron-group transition metals from Sc to Cu
have been investigated on the basis of the first-principles momentum dependent
local ansatz (MLA) theory. Correlation energy gain is found to show large
values for Mn and Fe: 0.090 Ry (Mn) and 0.094 Ry (Fe). The Hund-rule coupling
energies are found to be 3000 K (Fe), 1400 K (Co), and 300 K (Ni). It is
sugested that these values can resolve the inconsistency in magnetic energy
between the density functional theory and the first-principles dynamical
coherent potential approximation theory at finite temperatures. Charge
fluctuations are shown to be suppressed by the intra-orbital correlations and
inter-orbital charge-charge correlations, so that they show nearly constant
values from V to Fe: 1.57 (V and Cr), 1.52 (Mn), and 1.44 (Fe), which are
roughly twice as large as those obtained by the $d$ band model. The amplitudes
of local moments are enhanced by the intra-orbital and inter-orbital spin-spin
correlations and show large values for Mn and Fe: 2.87 (Mn) and 2.58 (Fe).
These values are in good agreement with the experimental values estimated from
the effective Bohr magneton number and the inner core photoemission data.",1607.00632v1
2016-08-23,Arbitrary optical wavefront shaping via spin-to-orbit coupling,"Converting spin angular momentum to orbital angular momentum has been shown
to be a practical and efficient method for generating optical beams carrying
orbital angular momentum and possessing a space-varying polarized field. Here,
we present novel liquid crystal devices for tailoring the wavefront of optical
beams through the Pancharatnam-Berry phase concept. We demonstrate the
versatility of these devices by generating an extensive range of optical beams
such as beams carrying $\pm200$ units of orbital angular momentum along with
Bessel, Airy and Ince-Gauss beams. We characterize both the phase and the
polarization properties of the generated beams, confirming our devices'
performance.",1608.06603v1
2018-09-25,Two-orbital Hubbard model vs spin $S=1$ Heisenberg model: studies on clusters,"We perform exact numeric calculations for the two-orbital Hubbard model on
the four-site cluster. In the limit of large on-site coupling the model becomes
equivalent to the spin $S=1$ Heisenberg model. By comparing energy spectra of
these two models, we quantified the range of interaction parameters for which
the Heisenberg model satisfactorily reproduces the two-orbital Hubbard model.
Then we examined how the spectrum evolves when we are outside of this region,
focusing especially on checking of how it is modified when various ways of
interatomic hoppings of electrons between different orbitals are taken into
account. We finally show how these modifications affect the dependence of
specific heat on temperature.",1809.09483v1
2020-10-24,Topological bands in two-dimensional orbital-active bipartite lattices,"The search for large gap quantum spin Hall (QSH) and quantum anomalous Hall
(QAH) insulators is important both for fundamental and practical interests. The
degenerate multi-orbitals $p_x,p_y$ in honeycomb lattice provides a paradigm
for QSH state with a boosted topological gap of the first order in atomic
spin-orbit coupling. By using elementary band representation, we explore the
feasibility of this mechanism for QSH in general two-dimensional lattices, and
find that the biparticle lattices with $C_{3v}$ or $C_{4v}$ symmetry and
degenerate multi-orbitals could work. We further provide concrete tight-binding
models on honeycomb, kagome and square lattices to demonstrate the desired
topological physics. By introducing ferromagnetism into QSH state, we extend
the mechanism to QAH state with a boosted gap. The QSH and QAH states can be
achieved when Fermi level is at integer filling only for honeycomb lattice, but
at certain fractional filling for other lattices. We conclude with a brief
discussion on the possible material venues for such mechanism.",2010.12823v1
2016-10-05,"Orbital frustration in the S = 1/2 kagome magnet vesignieite, BaCu3V2O8(OD)2","Here we report crystallographic and magnetic studies on high quality samples
of the magnetically frustrated S = 1/2 kagome antiferromagnet vesignieite,
BaCu3V2O8(OD)2. Powder neutron diffraction data collected from samples obtained
by a new hydrothermal synthetic route reveal a previously unobserved trigonal
P3121 structure, similar to the isoelectronic mineral SrCu3V2O8(OH)2. The
refined structure is consistent with orbital frustration of the eg d-orbitals
in a sublattice of the Cu2+ kagome network due to a dynamic Jahn-Teller effect,
which persists below the magnetic transition at TN = 9K and makes the material
an interesting candidate for exploring concomitant spin and orbital
frustration. A combination of crystallographic strain analysis and
magnetisation measurements indicate strong magnetostructural coupling which may
explain the varied magnetic behaviour between samples of vesignieite in the
literature. The revised orbital structure is similar to that found in
volborthite, rather than the quantum spin liquid herbertsmithite, and provides
a convincing argument for the differing magnetic properties found in these
frustrated magnets.",1610.01436v1
2021-02-08,Evidence of orbital ferromagnetism in twisted bilayer graphene aligned to hexagonal boron nitride,"We have previously reported ferromagnetism evinced by a large hysteretic
anomalous Hall effect in twisted bilayer graphene (tBLG). Subsequent
measurements of a quantized Hall resistance and small longitudinal resistance
confirmed that this magnetic state is a Chern insulator. Here we report that,
when tilting the sample in an external magnetic field, the ferromagnetism is
highly anisotropic. Because spin-orbit coupling is negligible in graphene such
anisotropy is unlikely to come from spin, but rather favors theories in which
the ferromagnetism is orbital. We know of no other case in which ferromagnetism
has a purely orbital origin. For an applied in-plane field larger than $5\
\mathrm{T}$, the out-of-plane magnetization is destroyed, suggesting a
transition to a new phase.",2102.04039v2
2022-01-11,Effects of spin-orbit interaction and electron correlations in strontium titanate,"We show that the Bloch states in the conduction band of SrTiO$_3$ arise from
the interplay between highly anisotropic hopping in sub-bands derived from the
Ti $t_{2g}$ orbitals and spin-orbit coupling that mixes these orbitals. Because
of the nearly flat-band characteristics for one of the principal axes, at
sufficiently high doping these Bloch states become unstable with respect to
electron interactions, resulting in Mott-like singlet correlations. These
findings may be relevant to the anomalous electronic properties of SrTiO$_3$,
including its unusual superconductivity.",2201.04184v5
2022-10-26,Oxygen vacancies at the origin of pinned moments in oxide interfaces: the example of tetragonal CuO/SrTiO$_3$,"Obtaining an accurate theoretical description of the emergent phenomena in
oxide heterostructures is a major challenge. Recently, intriguing paramagnetic
spin and pinned orbital moments have been discovered by x-ray magnetic circular
dichro\""ism measurements at the Cu $L_{2,3}$-edge of a tetragonal CuO/SrTiO$_3$
heterostructure. Using first principles calculations, we propose a scenario
that explains both types of moments, based on the formation of oxygen vacancies
in the TiO$_2$ interface layer. We show the emergence of a paramagnetic 2D
electron gas hosted in the interface CuO layer. It is invisible at the Ti
$L_{2,3}$-edge since the valence of the Ti atoms remains unchanged. Strong
structural distortions breaking both the local and global fourfold rotation
$C_4$ symmetries at the interface lead to the in-plane pinning of the Cu
orbital moment close to the vacancy. Our results, and in particular the pinning
of the orbital moment, may have implications for other systems, especially
monoxide/dioxide interfaces with similar metal-oxygen bond length and weak
spin-orbit coupling.",2210.15084v1
2023-07-10,Quantum oscillations with topological phases in a kagome metal CsTi$_3$Bi$_5$,"Quantum oscillations can reveal Fermi surfaces and their topology in solids
and provide a powerful tool for understanding transport and electronic
properties. It is well established that the oscillation frequency maps the
Fermi surface area by Onsager's relation. However, the topological phase
accumulated along the quantum orbit remains difficult to estimate in
calculations, because it includes multiple contributions from the Berry phase,
orbital and spin moments, and also becomes gauge-sensitive for degenerate
states. In this work, we develop a gauge-independent Wilson loop scheme to
evaluate all topological phase contributions and apply it to CsTi$_3$Bi$_5$, an
emerging kagome metal. We find that the spin-orbit coupling dramatically alters
the topological phase compared to the spinless case. Especially, oscillation
phases of representative quantum orbits demonstrate a strong 3D signature
despite their cylinder-like Fermi surface geometry. Our work reveals the Fermi
surface topology of CsTi$_3$Bi$_5$ and paves the way for the theoretical
investigation of quantum oscillations in realistic materials.",2307.04750v1
2010-07-09,The spin states of Co ions in La1.5Ca0.5CoO4 from first-principles,"The spin states and electronic structure of layered perovskite La1.5Ca0.5CoO4
are investigated using fullpotential linearized augmented plane-wave method.
All the computational results indicate that the Co2+ ion is in a high-spin
state and the Co3+ in a low-spin state. The Co2+ t2g orbitals with a small
crystal-field splitting are mixed by spin-orbit coupling, which accounts for
the observed easy in-plane magnetism. The nonmagnetic LS-Co3+ state, which is
stabilized by a strong crystal field, provides a natural explanation for the
observed low magnetic ordering temperature and a spin-blockade phenomenon of
the electron hopping. Furthermore, we find that the intermediate-spin state of
Co3+ has a large multiplet splitting. But the lowest-lying IS state of Co3+ is
still higher in energy than the LS ground state by a few hundred millielectron
volts and the HS state of Co3+ is even less stable, both in sharp contrast to a
recent experimental study which suggested the HS+IS mixed Co3+ ground state. We
note that either the IS-Co3+ or HS-Co3+ states or their mixture would produce a
wrong out-of-plane magnetic anisotropy and a much higher magneticordering
temperature than observed. Thus, the present work sheds light on this material
concerning its electronic and magnetic structure, and it would stimulate
different experiments to settle this intriguing spin-state issue.",1007.1494v2
2011-10-22,Theory of electronic properties and quantum spin blockade in a gated linear triple quantum dot with one electron spin each,"We present a theory of electronic properties and the spin blockade phenomena
in a gated linear triple quantum dot. Quadruple points where four different
charge configurations are on resonance, particularly involving (1,1,1)
configuration, are considered. In the symmetric case, the central dot is biased
to higher energy and a single electron tunnels through the device when (1,1,1)
configuration is resonant with (1,0,1),(2,0,1),(1,0,2) configurations. The
electronic properties of a triple quantum dot are described by a Hubbard model
containing two orbitals in the two unbiased dots and a single orbital in the
biased dot. The transport through the triple quantum dot molecule involves both
singly and doubly occupied configurations and necessitates the description of
the (1,1,1) configuration beyond the Heisenberg model. Exact eigenstates of the
triple quantum dot molecule with up to three electrons are used to compute
current assuming weak coupling to the leads and non-equilibrium occupation of
quantum molecule states obtained from the rate equation. The intra-molecular
relaxation processes due to acoustic phonons and cotunneling with the leads are
included, and are shown to play a crucial role in the spin blockade effect. We
find a quantum interference-based spin blockade phenomenon at low source-drain
bias and a distinct spin blockade due to a trap state at higher bias. We also
show that, for an asymmetric quadruple point with
(0,1,1),(1,1,1,),(0,2,1),(0,1,2) configurations on resonance, the spin blockade
is analogous to the spin blockade in a double quantum dot.",1110.4982v1
2013-11-02,Quantum-ring spin interference device tuned by quantum point contacts,"We introduce a spin-interference device that comprises a quantum ring (QR)
with three embedded quantum point contacts (QPCs) and study theoretically its
spin transport properties in the presence of Rashba spin-orbit interaction. Two
of the QPCs conform the lead-to-ring junctions while a third one is placed
symmetrically in the upper arm of the QR. Using an appropriate scattering model
for the QPCs and the $\mathbb{S}$-matrix scattering approach, we analyze the
role of the QPCs on the Aharonov-Bohm (AB) and Aharonov-Casher (AC) conductance
oscillations of the QR-device. Exact formulas are obtained for the
spin-resolved conductances of the QR-device as a function of the confinement of
the QPCs and the AB/AC phases. Conditions for the appearance of resonances and
anti-resonances in the spin-conductance are derived and discussed. We predict
very distinctive variations of the QR-conductance oscillations not seen in
previous QR proposals. In particular we find that the interference pattern in
the QR can be manipulated to a large extend by varying electrically the
lead-to-ring topological parameters. The latter can be used to modulate the AB
and AC phases by applying gate voltage only. We have shown also that the
conductance oscillations exhibits a crossover to well-defined resonances as the
lateral QPC confinement strength is increased, mapping the eigenenergies of the
QR. In addition, unique features of the conductance arises by varying the
aperture of the upper-arm QPC and the Rashba spin-orbit coupling. Our results
may be of relevance for promising spin-orbitonics devices based in quantum
interference mechanisms.",1311.0406v1
2016-04-25,Probing variations of the Rashba spin-orbit coupling at the nanometer scale,"The Rashba effect as an electrically tunable spin-orbit interaction is the
base for a multitude of possible applications such as spin filters, spin
transistors, and quantum computing using Majorana states in nanowires.
Moreover, this interaction can determine the spin dephasing and
antilocalization phenomena in two dimensions. However, the real space pattern
of the Rashba parameter has never been probed, albeit it critically influences,
e.g., the more robust spin transistors using the spin helix state and the
otherwise forbidden electron backscattering in topologically protected
channels. Here, we map this pattern down to nanometer length scales by
measuring the spin splitting of the lowest Landau level using scanning
tunnelling spectroscopy. We reveal strong fluctuations correlated with the
local electrostatic potential for an InSb inversion layer with a large Rashba
coefficient (~1 eV{\AA}). The novel type of Rashba field mapping enables a more
comprehensive understanding of the critical fluctuations, which might be
decisive towards robust semiconductor-based spintronic devices.",1604.07326v1
2017-02-21,All-optical Detection of Spin Hall Angle in W/CoFeB/SiO2 Heterostructures by Varying Tungsten Layer Thickness,"The development of advanced spintronics devices hinges on the efficient
generation and utilization of pure spin current. In materials with large
spin-orbit coupling, the spin Hall effect may convert charge current to pure
spin current and a large conversion efficiency, which is quantified by spin
Hall angle (SHA), is desirable for the realization of miniaturized and energy
efficient spintronic devices. Here, we report a giant SHA in beta-tungsten
(\b{eta}-W) thin films in Sub/W(t)/Co20Fe60B20(3 nm)/SiO2(2 nm)
heterostructures with variable W thickness. We employed an all-optical
time-resolved magneto-optical Kerr effect microscope for an unambiguous
determination of SHA using the principle of modulation of Gilbert damping of
the adjacent ferromagnetic layer by the spin-orbit torque from the W layer. A
non-monotonic variation of SHA with W layer thickness (t) is observed with a
maximum of about 0.4 at about t = 3 nm, followed by a sudden reduction to a
very low value at t = 6 nm. This variation of SHA with W-thickness correlates
well with the thickness dependent structural phase transition and resistivity
variation of W above the spin diffusion length of W, while below this length
the interfacial electronic effect at W/CoFeB influences the estimation of SHA.",1702.06258v1
2018-05-22,FMR-related phenomena in spintronic devices,"Spintronic devices, such as non-volatile magnetic random access memories and
logic devices, have attracted considerable attention as potential candidates
for future high efficient data storage and computing technology. In a heavy
metal or other emerging material with strong spin-orbit coupling (SOC), the
charge currents induce spin currents or spin accumulations via SOC. The
generated spin currents can exert spin-orbit torques (SOTs) on an adjacent
ferromagnet, which opens up a new way to realize magnetization dynamics and
switching of the ferromagnetic layer for spintronic devices. In the SOT scheme,
the charge-to-spin interconversion efficiency (SOT efficiency) is an important
figure of merit for applications. For the effective characterization of this
efficiency, the ferromagnetic resonance (FMR) based methods, such as the spin
transfer torque ferromagnetic resonance (ST-FMR) and the spin pumping, are
common utilized in addition to low frequency harmonic or dc measurements. In
this review, we focus on the ST-FMR measurements for the evaluation of the SOT
efficiency. We provide a brief summary of the different ST-FMR setups and data
analysis methods. We then discuss ST-FMR and SOT studies in various materials,
including heavy metals and alloys, topological insulators, two dimensional (2D)
materials, interfaces with strong Rashba effect, antiferromagnetic materials,
two dimensional electron gas (2DEG) in oxide materials and oxidized nonmagnetic
materials.",1805.08496v1
2019-10-15,Bulk Rashba Effect in Multiferroics: a theoretical prediction for BiCoO3,"We put forward the concept of a bulk Rashba effect emerging in a multiferroic
material, such as an antiferromagnetic system with a polar crystal structure.
According to symmetry considerations, while time-reversal and space-inversion
symmetries are both broken, there exist specific spin flipping operations that
relate opposite spin sites in the magnetic crystal structure. As a consequence,
at certain high-symmetry points in the momentum space, the magnetic point group
allows the spin angular momentum to be locked to the linear momentum, a typical
feature of the Rashba effect. In such a case, spin-splitting effects induced by
spin-orbit coupling can arise, similar to what happens in non-magnetic Rashba
systems. As a prototypical example, ab-initio calculations of antiferromagnetic
BiCoO3 in the polar structure reveal that a large Rashba-like band- and spin-
splitting occurs at the conduction band bottom, having a large weight from Bi-p
orbital states. Moreover, we show that the spin texture of such a multiferroic
can be modulated by applying a magnetic field. In particular, an external
in-plane magnetic field is predicted not only to induce spin-canting, but also
a distortion of the energy isocontours and a shift of the spin-vortex (centered
on the high-symmetry point and characteristic of Rashba effect) along a
direction perpendicular to the applied field.",1910.06758v1
2016-03-29,Giant g factor tuning of long-lived electron spins in Ge,"Control of electron spin coherence via external fields is fundamental in
spintronics. Its implementation demands a host material that accommodates the
highly desirable but contrasting requirements of spin robustness to relaxation
mechanisms and sizeable coupling between spin and orbital motion of charge
carriers. Here we focus on Ge, which, by matching those criteria, is rapidly
emerging as a prominent candidate for shuttling spin quantum bits in the mature
framework of Si electronics. So far, however, the intrinsic spin-dependent
phenomena of free electrons in conventional Ge/Si heterojunctions have proved
to be elusive because of epitaxy constraints and an unfavourable band
alignment. We overcome such fundamental limitations by investigating a two
dimensional electron gas (2DEG) confined in quantum wells of pure Ge grown on
SiGe-buffered Si substrates. These epitaxial systems demonstrate exceptionally
long spin relaxation and coherence times, eventually unveiling the potential of
Ge in bridging the gap between spintronic concepts and semiconductor device
physics. In particular, by tuning spin-orbit interaction via quantum
confinement we demonstrate that the electron Land\'e g factor and its
anisotropy can be engineered in our scalable and CMOS-compatible architectures
over a range previously inaccessible for Si spintronics.",1603.08783v1
2020-09-22,Magnon-mediated spin currents in Tm3Fe5O12/Pt with perpendicular magnetic anisotropy,"The control of pure spin currents carried by magnons in magnetic insulator
(MI) garnet films with a robust perpendicular magnetic anisotropy (PMA) is of
great interest to spintronic technology as they can be used to carry, transport
and process information. Garnet films with PMA present labyrinth domain
magnetic structures that enrich the magnetization dynamics, and could be
employed in more efficient wave-based logic and memory computing devices. In
MI/NM bilayers, where NM being a normal metal providing a strong spin-orbit
coupling, the PMA benefits the spin-orbit torque (SOT) driven magnetization's
switching by lowering the needed current and rendering the process faster,
crucial for developing magnetic random-access memories (SOT-MRAM). In this
work, we investigated the magnetic anisotropies in thulium iron garnet (TIG)
films with PMA via ferromagnetic resonance measurements, followed by the
excitation and detection of magnon-mediated pure spin currents in TIG/Pt driven
by microwaves and heat currents. TIG films presented a Gilbert damping constant
{\alpha}~0.01, with resonance fields above 3.5 kOe and half linewidths broader
than 60 Oe, at 300 K and 9.5 GHz. The spin-to-charge current conversion through
TIG/Pt was observed as a micro-voltage generated at the edges of the Pt film.
The obtained spin Seebeck coefficient was 0.54 {\mu}V/K, confirming also the
high interfacial spin transparency.",2009.10299v1
2022-04-18,Hole spin qubits in thin curved quantum wells,"Hole spin qubits are frontrunner platforms for scalable quantum computers
because of their large spin-orbit interaction which enables ultrafast
all-electric qubit control at low power. The fastest spin qubits to date are
defined in long quantum dots with two tight confinement directions, when the
driving field is aligned to the smooth direction. However, in these systems the
lifetime of the qubit is strongly limited by charge noise, a major issue in
hole qubits. We propose here a different, scalable qubit design, compatible
with planar CMOS technology, where the hole is confined in a curved germanium
quantum well surrounded by silicon. This design takes full advantage of the
strong spin-orbit interaction of holes, and at the same time suppresses charge
noise in a wide range of configurations, enabling highly coherent, ultrafast
qubit gates. While here we focus on a Si/Ge/Si curved quantum well, our design
is also applicable to different semiconductors. Strikingly, these devices allow
for ultrafast operations even in short quantum dots by a transversal electric
field. This additional driving mechanism relaxes the demanding design
constraints, and opens up a new way to reliably interface spin qubits in a
single quantum dot to microwave photons. By considering state-of-the-art
high-impedance resonators and realistic qubit designs, we estimate interaction
strengths of a few hundreds of MHz, largely exceeding the decay rate of spins
and photons. Reaching such a strong coupling regime in hole spin qubits will be
a significant step towards high-fidelity entangling operations between distant
qubits, as well as fast single-shot readout, and will pave the way towards the
implementation of a large-scale semiconducting quantum processor.",2204.08212v1
2011-07-13,Coulomb singularities in scattering wave functions of spin-orbit-coupled states,"We report on our analysis of the Coulomb singularity problem in the frame of
the coupled channel scattering theory including spin-orbit interaction. We
assume that the coupling between the partial wave components involves orbital
angular momenta such that $\Delta l = 0, \pm 2$. In these conditions, the two
radial functions, components of a partial wave associated to two values of the
angular momentum $l$, satisfy a system of two second-order ordinary
differential equations. We examine the difficulties arising in the analysis of
the behavior of the regular solutions near the origin because of this coupling.
First, we demonstrate that for a singularity of the first kind in the
potential, one of the solutions is not amenable to a power series expansion.
The use of the Lippmann-Schwinger equations confirms this fact: a logarithmic
divergence arises at the second iteration. To overcome this difficulty, we
introduce two auxilliary functions which, together with the two radial
functions, satisfy a system of four first-order differential equations. The
reduction of the order of the differential system enables us to use a
matrix-based approach, which generalizes the standard Frobenius method. We
illustrate our analysis with numerical calculations of coupled scattering wave
functions in a solid-state system.",1107.2643v1
2023-02-02,Spin waves in a ferromagnetic topological metal,"In most metals, charges and spins can hop rapidly between atoms, yielding
strong dispersion of their energy versus momentum. There are, however, special
arrangements of atoms, such as twisted graphene bilayers or lattices which
resemble woven bamboo ""kagome"" mats, so that particle motion with strong
hopping between neighbours becomes nearly or even completely dispersionless.
Such flat bands are interesting because the interactions between the heavy
particles inhabiting them will become much more important than for strong
dispersion, resulting in novel quantum solid and liquid states, particularly
when topology enters on account of significant spin-orbit coupling for the
underlying electrons. Nonetheless, spectroscopic evidence for flat bands
engendered by lattice geometry rather than weak hopping is rare, particularly
for metallic single crystals. Here we report the discovery, using circularly
polarized X-Rays in resonant absorption and inelastic scattering (RIXS) for the
unambiguous isolation of magnetic signals, of a flat spin wave band and large
orbital moment for the metallic kagome ferromagnet Fe$_3$Sn$_2$, which has a
topologically non-trivial electronic band structure controllable by modest
external magnetic fields. The flat mode energy is consistent with the high
Curie temperature ($T_C$ ~ 640 K) as well as the strong acoustic mode
dispersion, implying, together with the substantial spin-orbit coupling
indicated by the large orbital moment, that the mode is topological. The
measured properties of the spin waves are highly unconventional, and include
very severe damping as well as the flat mode amplitude which is maximized in
the long wavelength limit where it is ordinarily expected to vanish. Our
results open the topic of interactions of topological bosons (spin waves) and
fermions (electrons) with the very specific target of explaining boson
lifetimes and amplitudes.",2302.01457v1
2017-02-24,Thermoelectric unipolar spin battery in a suspended carbon nanotube,"A quantum dot formed in a suspended carbon nanotube exposed to an external
magnetic field is predicted to act as a thermoelectric unipolar spin battery
which generates pure spin current. The built-in spin flip mechanism is a
consequence of the spin-vibration interaction resulting from the interplay
between the intrinsic spin-orbit coupling and the vibrational modes of the
suspended carbon nanotube. On the other hand, utilizing thermoelectric effect,
the temperature difference between the electron and the thermal bath to which
the vibrational modes are coupled provides the driving force. We find that both
magnitude and direction of the generated pure spin current are dependent on the
strength of spin-vibration interaction, the sublevel configuration in dot, the
temperatures of electron and thermal bath, and the tunneling rate between the
dot and the pole. Moreover, in the linear response regime, the kinetic
coefficient is non-monotonic in the temperature $T$ and it reaches its maximum
when $k_BT$ is about one phonon energy. The existence of a strong intradot
Coulomb interaction is irrelevant for our spin battery, provided that
high-order cotunneling processes are suppressed.",1702.07616v1
2018-02-03,Spin Hall effect in Rashba-Dresselhaus planar strips in the presence of electron correlations,"A model with both Rashba and Dresselhaus spin orbit (SO) couplings and
Hubbard electron-electron interaction is studied on planar strips at quarter
filling at zero temperature in the clean limit. In the absence of Hubbard
repulsion and at equilibrium, within linear response theory, a nonmonotonic
behavior of the spin Hall conductivity as a function of the ratio of the Rashba
(alpha) and Dresselhaus (beta) strengths was found for large enough SO
strengths. This behavior is signalled by a peak or a cusp, depending on the
strip width, at intermediate values of beta/alpha in the interval [0,1]. This
behavior of the spin Hall conductivity was correlated with the one for the
longitudinal spin conductivity. This study was then extended to the
out-of-equilibrium regime that arises by imposing a finite voltage bias between
the two ends of an open strip. This system, in the presence of a Hubbard term
with coupling U, was treated with the density matrix renormalization group
technique and with the Landauer-Buttiker formalism. It was found that relevant
properties to the spin Hall effect, such as the transversal spin current and
the spin accumulation, present a similar nonmonotonic behavior as the one found
for the spin conductivities. More importantly, it was also found that these
properties are enhanced by the repulsive Hubbard interaction up to a moderate
value of U.",1802.01035v1
2020-07-20,Tunable spin textures in polar antiferromagnetic hybrid organic inorganic perovskites by electric and magnetic fields,"The hybrid organic inorganic perovskites (HOIPs) have attracted much
attention for their potential applications as novel optoelectronic devices.
Remarkably, the Rashba band splitting, together with specific spin orientations
in k space (i.e., spin texture), has been found to be relevant for the
optoelectronic performances. In this work, by using first principles
calculations and symmetry analyses, we study the electric polarization,
magnetism, and spin texture properties of the antiferromagnetic (AFM) HOIP
ferroelectric TMCM_MnCl3 (TMCM = (CH3)3NCH2Cl, trimethylchloromethyl ammonium).
This recently synthesized compound is a prototype of order disorder and
displacement-type ferroelectric with a large piezoelectric response, high
ferroelectric transition temperature, and excellent photoluminescence
properties [You et al., Science 357, 306 (2017)]. The most interesting result
is that the inversion symmetry breaking coupled to the spin orbit coupling
gives rise to a Rashba-like band splitting and a related robust persistent spin
texture (PST) and/or typical spiral spin texture, which can be manipulated by
tuning the ferroelectric or, surprisingly, also by the AFM magnetic order
parameter. The tunability of spin texture upon switching of AFM order parameter
is largely unexplored and our findings not only provide a platform to
understand the physics of AFM spin texture but also support the AFM HOIP
ferroelectrics as a promising class of optoelectronic materials.",2007.10016v1
2017-04-08,Effect of Frustrated Exchange Interactions and Spin-half Impurity on the Electronic Structure of Strongly Correlated NiFe$_{2}$O$_{4}$,"Spin-polarized density functional calculations, magnetization, and neutron
diffraction measurements are carried out to investigate the magnetic exchange
interactions and strong correlation effects in Yb substituted inverse spinel
nickel ferrite. In the pristine form, the compound is found to be a mixed
insulator under the Zaanen-Sawtazsky-Allen classification scheme as it features
both charge transfer and Mott insulator mechanism. Estimation of magnetic
exchange couplings reveals that both octahedral-octahedral and
octahedral-tetrahedral spin-spin interactions are antiferromagnetic which is
typical of a spin-frustrated triangular lattice. However, the latter is
dominant compared to the former leading to a forced parallel alignment of the
spins at the octahedral site which is in agreement with the results of neutron
diffraction measurements. The substituent Yb is found to be settled in +3
charge state, as confirmed from the XPS measurements, to behave like a
spin-half impurity carried by the localized $f_{z(x^2-y^2)}$ orbital. The
impurity $f$ spin significantly weakens the antiferromagnetic coupling with the
spins at the tetrahedral site, which explains the experimental observation of
fall in Curie temperature with Yb substitution.",1704.02454v2
2019-12-27,Realizing spin-Hamiltonians in nanoscale active photonic lattices,"Spin models arise in the microscopic description of magnetic materials, where
the macroscopic characteristics are governed by exchange interactions among the
constituent magnetic moments. Recently, there has been a growing interest in
complex systems with spin Hamiltonians, largely due to the rich behaviors
exhibited by such interactions at the macroscale. Along these lines, it has
been shown that certain classes of optimization problems involving large
degrees of freedom can be effectively mapped into classical spin models. In
this vein, the respective extremum can be found by identifying the ground state
of the associated spin Hamiltonian. Here, we show both theoretically and
experimentally, that the cooperative interplay among vectorial electromagnetic
modes in coupled metallic nanolasers can be utilized as a means to emulate
certain types of spin-like systems. The ensuing spin exchange interactions are
in general anisotropic, in a way similar to that encountered in magnetic
materials involving spin-orbit coupling. For some topologies, we find that
these active nanophotonic structures are governed by a classical XY Hamiltonian
that exhibits two phases akin to those associated with ferromagnetic (FM) and
antiferromagnetic (AF) materials. In addition, we show that in certain
configurations, the electromagnetic field distribution can undergo geometrical
frustration, depending on the lattice shape and the transverse resonant modes
supported by the individual cavity elements. Our results could pave the way
towards a new scalable nanophotonic platform to study spin exchange
interactions, that can in turn be potentially exploited to investigate more
large-scale networks, emulate some magnetic materials, or to address a variety
of optimization problems.",1912.12075v1
2021-01-27,Response to Comment on: Tunneling in DNA with Spin Orbit coupling,"The comment by O. Entin-Wohlman, A. Aharony, and Y. Utsumi, on our paper S.
Varela, I. Zambrano, B. Berche, V. Mujica, and E. Medina, Phys. Rev. B 101,
241410(R) (2020) makes a few points related to the validity of our model,
especially in the light of the interpretation of Bardarson's theorem: ""in the
presence of time reversal symmetry and for half-integral spin the transmission
eigenvalues of the two terminal scattering matrix come in (Kramers) degenerate
pairs"". The authors of the comment first propose an ansatz for the wave
function in the spin active region and go on to show that the resulting
transmission does not show spin dependence, reasoning that spin dependence
would violate Bardarson's assertion. Here we clearly show that the ansatz
presented assumes spin-momentum independence from the outset and thus just
addresses the spinless particle problem. We then find the appropriate
eigenfunction contemplating spin-momentum coupling and show that the resulting
spectrum obeys Bardarson's theorem. Finally we show that the allowed
wavevectors are the ones assumed in the original paper and thus the original
conclusions follow. We recognize that the Hamiltonian in our paper written in
local coordinates on a helix was deceptively simple and offer the expressions
of how it should be written to more overtly convey the physics involved. The
relation between spin polarization and torque becomes clear, as described in
our paper. This response is a very important clarification in relation to the
implications of Bardarson's theorem concerning the possibility of spin
polarization in one dimensional systems in the linear regime.",2101.11271v1
2021-05-06,Tunable spin polarization and electronic structure of bottom-up synthesized MoSi$_2$N$_4$ materials,"Manipulation of spin-polarized electronic states of two-dimensional (2D)
materials under ambient conditions is necessary for developing new quantum
devices with small physical dimensions. Here, we explore spin-dependent
electronic structures of ultra-thin films of recently introduced 2D synthetic
materials MSi$_2$Z$_4$ (M = Mo or W and Z = N or As) using first-principles
modeling. Stacking of MSi$_2$Z$_4$ monolayers is found to generate dynamically
stable bilayer and bulk materials with thickness-dependent properties. When
spin-orbit coupling (SOC) is included in the computations, MSi$_2$N$_4$
monolayers display indirect bandgaps and large spin-split states at the $K$ and
$K'$ symmetry points at the corners of the Brillouin zone with nearly 100\%
spin polarization. The spins are locked in opposite directions along an
out-of-the-plane direction at $K$ and $K'$, leading to spin-valley coupling
effects. As expected, spin polarization is absent in the pristine bilayers due
to the presence of inversion symmetry, but it can be induced via an external
out-of-plane electric field much like the case of Mo(W)S$_2$ bilayers. A
transition from an indirect to a direct bandgap can be driven by replacing N by
As in MSi$_2$(N, As)$_4$ monolayers. Our study indicates that the MSi$_2$Z$_4$
materials can provide a viable alternative to the MoS$_2$ class of 2D materials
for valleytronics and optoelectronics applications.",2105.02739v2
2022-11-09,Three-carrier spin blockade and coupling in bilayer graphene double quantum dots,"The spin degree of freedom is crucial for the understanding of any condensed
matter system. Knowledge of spin-mixing mechanisms is not only essential for
successful control and manipulation of spin-qubits, but also uncovers
fundamental properties of investigated devices and material. For
electrostatically-defined bilayer graphene quantum dots, in which recent
studies report spin-relaxation times T1 up to 50ms with strong magnetic field
dependence, we study spin-blockade phenomena at charge configuration
$(1,2)\leftrightarrow(0,3)$. We examine the dependence of the spin-blockade
leakage current on interdot tunnel coupling and on the magnitude and
orientation of externally applied magnetic field. In out-of-plane magnetic
field, the observed zero-field current peak could arise from finite-temperature
co-tunneling with the leads; though involvement of additional spin- and
valley-mixing mechanisms are necessary for explaining the persistent sharp side
peaks observed. In in-plane magnetic field, we observe a zero-field current
dip, attributed to the competition between the spin Zeeman effect and the
Kane-Mele spin-orbit interaction. Details of the line shape of this current dip
however, suggest additional underlying mechanisms are at play.",2211.04882v1
2016-05-25,Theory of single and two-qubit operations with donor-bound electron spins in germanium,"The possibility of quantum computing with spins in germanium nanoscale
transistors has recently attracted interest since it promises highly tuneable
qubits that have encouraging coherence times. We here present the first
complete theory of the orbital states of Ge donor electrons, and use it to show
that Ge could have significant advantages over silicon in the implementation of
a donor-based quantum processor architecture. We show that the stronger
spin-orbit interaction and the larger electron donor wave functions for Ge
donors allow for greater tuning of the single qubit energy than for those in Si
crystals, thus enabling a large speedup of selective (local) quantum gates.
Further, exchange coupling between neighboring donor qubits is shown to be much
larger in Ge than in Si, and we show that this greatly relaxes the precision in
donor placement needed for robust two-qubit gates. To do this we compare two
statistical distributions for Ge:P and Si:P pair couplings, corresponding to
realistic donor implantation misplacement, and find that the spin couplings in
Ge:P have a $33\%$ chance of being within an order of magnitude of the largest
coupling, compared with only $10\%$ for the Si:P donors. This allows fast,
parallel and robust architectures for quantum computing with donors in Ge.",1605.07831v1
2017-07-11,Strong electron-hole symmetric Rashba spin-orbit coupling in graphene/monolayer transition metal dichalcogenide heterostructures,"Despite its extremely weak intrinsic spin-orbit coupling (SOC), graphene has
been shown to acquire considerable SOC by proximity coupling with exfoliated
transition metal dichalcogenides (TMDs). Here we demonstrate strong induced
Rashba SOC in graphene that is proximity coupled to a monolayer TMD film, MoS2
or WSe2, grown by chemical vapor deposition with drastically different Fermi
level positions. Graphene/TMD heterostructures are fabricated with a
pickup-transfer technique utilizing hexagonal boron nitride, which serves as a
flat template to promote intimate contact and therefore a strong interfacial
interaction between TMD and graphene as evidenced by quenching of the TMD
photoluminescence. We observe strong induced graphene SOC that manifests itself
in a pronounced weak anti-localization (WAL) effect in the graphene
magnetoconductance. The spin relaxation rate extracted from the WAL analysis
varies linearly with the momentum scattering time and is independent of the
carrier type. This indicates a dominantly Dyakonov-Perel spin relaxation
mechanism caused by the induced Rashba SOC. Our analysis yields a Rashba SOC
energy of ~1.5 meV in graphene/WSe2 and ~0.9 meV in graphene/MoS2,
respectively. The nearly electron-hole symmetric nature of the induced Rashba
SOC provides a clue to possible underlying SOC mechanisms.",1707.03434v1
2022-07-07,"Intensities of KCs $E(4)^1Σ^+\to (a^3Σ^+,X^1Σ^+)$ band system up to dissociation threshold: an interplay between spin-orbit, hyperfine and rovibronic coupling effects","The relative intensity distribution in the rotationally resolved
laser-induced fluorescence spectra belonging to the $E(4)^1\Sigma^+\to
(a^3\Sigma^+_1,X^1\Sigma^+)$ band systems of the KCs molecule was analyzed. The
experimental intensities in doublet $P$,$R$ progressions assigned to
spin-allowed $E\to X$ and spin-forbidden $E\to a$ transitions up to their
common ground dissociation limit were described in the framework of a
coupled-channels (CC) deperturbation model applied for the interacting \Xstate\
and \astate\ states. The CC intensity simulation was based solely on fixed
electronic structure parameters as functions of the internuclear distance $R$,
namely: accurate empirical potential energy curves for all three states,
\emph{ab initio} estimates for matrix elements $A(R)$ of the hyperfine
structure (HFS) , and transition dipole moments $d_{EX}(R)$ and $d_{Ea}(R)$. A
comparison between the measured intensities and their theoretical counterparts
demonstrates a strong competition between different intramolecular
interactions. A weak spin-orbit coupling of the upper \Estate\ state with the
remote $^3\Pi$ states is responsible for appearance of the $E\to a$ vibrational
bands for the intermediate $v_a$-values. In turn, the HFS coupling between
\Xstate\ and \astate\ states leads to peculiarities in $E\to (X,a)$
intensities, which are pronounced for high $v_{X/a}$-values in the vicinity of
K(4$^2S$)+Cs(6$^2S$) dissociation threshold. Both adiabatic ro-vibrational and
non-adiabatic electronic-rotational interactions explain the abrupt deviation
of some observed $P/R$ intensity ratios from the expected H\""{o}nl-London
factors.",2207.03237v1
2002-10-31,Can the Spin-Orbit Interaction Break the Channel Degeneracy of the Two-Channel Orbital Kondo Problem?,"Two-level systems (TLS) interacting with conduction electrons are possibly
described by the two-channel Kondo Hamiltonian. In this case the channel
degeneracy is due to the real spin of the electrons. The possibility of
breaking that degeneracy has interest on his own. In fact, we show that the
interaction of the conduction electrons with a spin-orbit scatterer nearby the
TLS leads to the breaking of the channel degeneracy only in the case of
electron-hole symmetry breaking. The generated channel symmetry breaking
TLS-electron couplings are, however, too weak to result in any observable
effects. Our analysis is also relevant for heavy fermion systems.",0210709v1
2005-02-11,SU(4) versus SU(2) Kondo effect in double quantum dot,"We consider the spin and orbital Kondo effect in a parallel arrangement of
two strongly electrostatically coupled quantum dots. Increasing the exchange of
electrons between the dots through the attached leads induces the transition
between the SU(4) spin- and orbital Kondo effect and SU(2) spin Kondo effect.
Being the same for the SU(4) and SU(2) symmetry points, the Kondo temperature
drops slightly in the intermediate regime. Experimentally, two kinds of Kondo
effects can be discriminated by the sensitivity to the suppression of the spin
Kondo effect by Zeeman field. The dependence of Kondo temperature on Zeeman
field and the strength of electronic exchange mediated by the leads is analyzed
in detail.",0502282v2
2005-12-16,Orbital Ordering and Spin-Ladder Formation in La2RuO5,"The semiconductor-semiconductor transition of La2RuO5 is studied by means of
augmented spherical wave (ASW) electronic structure calculations as based on
density functional theory and the local density approximation. This transition
has lately been reported to lead to orbital ordering and a quenching of the
local spin magnetic moment. Our results hint towards an orbital ordering
scenario which, markedly different from the previously proposed scheme,
preserves the local S = 1 moment at the Ru sites in the low-temperature phase.
The unusual magnetic behaviour is interpreted by the formation of spin-ladders,
which result from the structural changes occurring at the transition and are
characterized by antiferromagnetic coupling along the rungs.",0512409v1
2006-05-22,Quantum Monte Carlo study for multiorbital systems with preserved spin and orbital rotational symmetries,"We propose to combine the Trotter decomposition and a series expansion of the
partition function for Hund's exchange coupling in a quantum Monte Carlo (QMC)
algorithm for multiorbital systems that preserves spin and orbital rotational
symmetries. This enables us to treat the Hund's (spin-flip and pair-hopping)
terms, which is difficult in the conventional QMC method. To demonstrate this,
we first apply the algorithm to study ferromagnetism in the two-orbital Hubbard
model within the dynamical mean-field theory (DMFT). The result reveals that
the preservation of the SU(2) symmetry in Hund's exchange is important, where
the Curie temperature is grossly overestimated when the symmetry is degraded,
as is often done, to Ising (Z$_2$). We then calculate the $t_{2g}$ spectral
functions of Sr$_2$RuO$_4$ by a three-band DMFT calculation with tight-binding
parameters taken from the local density approximation with proper rotational
symmetry.",0605526v2
2004-10-14,Chiral SU(3) dynamics and $Λ$-hyperons in the nuclear medium,"We present a novel approach to the density dependent mean field and the
spin-orbit interaction of a $\Lambda$-hyperon in a nuclear many-body system,
based on flavor-SU(3) in-medium chiral perturbation theory. The leading
long-range $\Lambda N$-interaction arises from kaon exchange and from two-pion
exchange with a $\Sigma$-hyperon in the intermediate state. The empirical
$\Lambda$-nucleus potential depth of about $-28 $MeV is well reproduced with a
single cutoff scale, $\bar \Lambda = 0.7 $GeV, effectively representing all
short-distance (high-momentum) dynamics not resolved at scales characteristic
of the nuclear Fermi momentum. This value of $\bar\Lambda$ is remarkably
consistent with the one required to reproduce the empirical saturation point of
isospin-symmetric nuclear matter in the same framework. The smallness of the
$\Lambda$-nuclear spin-orbit interaction finds a natural (yet novel)
explanation in terms of an almost complete cancellation between short-range
contributions (properly rescaled from the known nucleonic spin-orbit coupling
strength) and long-range terms generated by iterated one-pion exchange with
intermediate $\Sigma$-hyperons. The small $\Sigma\Lambda$-mass difference
figures prominently in this context.",0410062v2
2006-05-03,Critical Survey of Isoscalar and Isovector Contributions to the Spin Orbit Potential in Relativistic Mean Field Theory,"The spin-orbit (SO) interaction, emerging naturally from the Relativistic
Mean Field (RMF) theory is examined critically in the light of the recently
measured excitation energy differences between the terminating states built on
two different configurations for nuclei belonging to the lower pf shell. The
calculations are carried out using the cranked RMF framework. To further probe
the iso-vector dependence of the spin-orbit potential, the energy spacing
between the g_{7/2} and h_{11/2} states in the Sb-chain is compared to
experiment. It is found that the calculation at the quantitative level deviates
strongly from the experiment. In particular the balance of the iso-scalar and
iso-vector strengths of the effective one body SO potential indicates that
additional terms like tensor couplings may be needed to account for the
experimental data.",0605009v4
1999-09-07,Spin-orbit pendulum - Relativistic extension,"We discuss an extension of the theory of {\em spin-orbit pendulum} phenomenon
given in [1] to relativistic approach. It is done within the so called Dirac
Oscillator. Our first results, focusing on circular wave packet motion have
been published recently [2]. The scope of this paper is motion of a linear wave
packet. In relativistic approach we found {\em Zitterbewegung} in spin-orbit
motion (in Dirac representation) due to coupling to negative energy states.
This effect is washed out in the Foldy-Wouthuysen representation. Another
important change with respect to non-relativistic case is the loss of
periodicity. The phenomenon reminds the time evolution of population inversion
in Jaynes-Cummings model.",9909023v1
2007-04-05,The tensor part of the Skyrme energy density functional. I. Spherical nuclei,"We perform a systematic study of the impact of the J^2 tensor term in the
Skyrme energy functional on properties of spherical nuclei. In the Skyrme
energy functional, the tensor terms originate both from zero-range central and
tensor forces. We build a set of 36 parameterizations, which covers a wide
range of the parameter space of the isoscalar and isovector tensor term
coupling constants, with a fit protocol very similar to that of the successful
SLy parameterizations. We analyze the impact of the tensor terms on a large
variety of observables in spherical mean-field calculations, such as the
spin-orbit splittings and single-particle spectra of doubly-magic nuclei, the
evolution of spin-orbit splittings along chains of semi-magic nuclei, mass
residuals of spherical nuclei, and known anomalies of charge radii. Our main
conclusion is that the currently used central and spin-orbit parts of the
Skyrme energy density functional are not flexible enough to allow for the
presence of large tensor terms.",0704.0731v3
2007-04-24,Enhanced spin-orbit scattering length in narrow Al_xGa_{1-x}N/GaN wires,"The magnetotransport in a set of identical parallel AlGaN/GaN quantum wire
structures was investigated. The width of the wires was ranging between 1110 nm
and 340 nm. For all sets of wires clear Shubnikov--de Haas oscillations are
observed. We find that the electron concentration and mobility is approximately
the same for all wires, confirming that the electron gas in the AlGaN/GaN
heterostructure is not deteriorated by the fabrication procedure of the wire
structures. For the wider quantum wires the weak antilocalization effect is
clearly observed, indicating the presence of spin-orbit coupling. For narrow
quantum wires with an effective electrical width below 250 nm the weak
antilocalization effect is suppressed. By comparing the experimental data to a
theoretical model for quasi one-dimensional structures we come to the
conclusion that the spin-orbit scattering length is enhanced in narrow wires.",0704.3146v2
2008-03-03,X-ray absorption and x-ray magnetic dichroism study on Ca3CoRhO6 and Ca3FeRhO6,"Using x-ray absorption spectroscopy at the Rh-L_2,3, Co-L_2,3, and Fe-L_2,3
edges, we find a valence state of Co^2+/Rh^4+ in Ca3CoRhO6 and of Fe^3+/Rh^3+
in Ca3FeRhO6. X-ray magnetic circular dichroism spectroscopy at the Co-L_2,3
edge of Ca3CoRhO6 reveals a giant orbital moment of about 1.7mu_B, which can be
attributed to the occupation of the minority-spin d_0d_2 orbital state of the
high-spin Co^2+ (3d^7) ions in trigonal prismatic coordination. This active
role of the spin-orbit coupling explains the strong magnetocrystalline
anisotropy and Ising-like magnetism of Ca3CoRhO6.",0803.0293v1
2008-05-01,Model for the Magnetic Order and Pairing Channels in Fe Pnictide Superconductors,"A two-orbital model for Fe-pnictide superconductors is investigated using
computational techniques on two-dimensional square clusters. The hopping
amplitudes are derived from orbital overlap integrals, or by band structure
fits, and the spin frustrating effect of the plaquette-diagonal Fe-Fe hopping
is remarked. A spin 'striped' state is stable in a broad range of couplings in
the undoped regime, in agreement with neutron scattering. Adding two electrons
to the undoped ground state of a small cluster, the dominant pairing operators
are found. Depending on parameters, two pairing operators were identified: they
involve inter-xz-yz orbital combinations forming spin singlets or triplets,
transforming according to the B_2g and A_2g representations of the D_4h group,
respectively.",0805.0148v4
2009-01-24,Role of spin orbit coupling and electron correlation in the ground state properties of 5d electronic states,"Electron correlation strength is predicted to be weak in 5d transition metal
oxides and hence, various anomalous electronic properties observed in these
systems are often attributed to the large spin-orbit interaction strength.
Employing first principles approaches, we studied the electronic structure of
Y2Ir2O7, which is insulating and exhibits ferromagnetic phase below 150 K. The
results reveal breakdown of both the above paradigms. The role of spin-orbit
interaction is found to be marginal in determining the ground state properties
of Y2Ir2O7. A large electron correlation strength is required to derive the
experimental bulk spectrum that is consistent with the bulk properties.",0901.3847v2
2009-08-17,Spin-orbit splittings in Si/SiGe quantum wells,"We present a calculation of the wavevector-dependent subband level splitting
from spin-orbit coupling in Si/SiGe quantum wells. We first use the
effective-mass approach, where the splittings are parameterized by separating
contributions from the Rashba and Dresselhaus terms. We then determine the
parameters by fitting tight-binding numerical results obtained using the
quantitative nanoelectronic modeling tool, NEMO-3D. We describe the relevant
parameters as a function of applied electric field and well width in our
numerical simulations. For a silicon membrane, we find the bulk Rashba
parameter to be linear in field, $\alpha = \alpha^1E_z$ with $\alpha^1 \simeq
2\times$ 10 $^{-5}$nm$^{-2}$. The dominant contribution to the spin-orbit
splitting is from Dresselhaus-type terms, and the magnitude for a typical flat
SiGe/Si/SiGe quantum well can be as high as 1$\mu$eV.",0908.2417v1
2009-10-20,Correlated band theory of spin and orbital contributions to Dzyaloshinskii-Moriya interactions,"A new approach for calculations of Dzyaloshinskii-Moriya interactions in
molecules and crystals is proposed. It is based on the exact perturbation
expansion of total energy of weak ferromagnets in the canting angle with the
only assumption of local Hubbard-type interactions. This scheme leads to a
simple and transparent analytical expression for Dzyaloshinskii-Moriya vector
with a natural separation into spin and orbital contributions. The main problem
was transferred to calculations of effective tight-binding parameters in the
properly chosen basis including spin-orbit coupling. Test calculations for
La$_2$CuO$_4$ give the value of canting angle in a good agreement with
experimental data.",0910.3748v2
2010-10-19,Anomalous Cherenkov spin-orbit sound,"The Cherenkov effect is a well known phenomenon in the electrodynamics of
fast charged particles passing through transparent media. If the particle is
faster than the light in a given medium, the medium emits a forward light cone.
This beautiful phenomenon has an acoustic counterpart where the role of photons
is played by phonons and the role of the speed of light is played by the sound
velocity. In this case the medium emits a forward sound cone. Here, we show
that in a system with spin-orbit interactions in addition to this {\it normal}
Cherenkov sound there appears an {\it anomalous} Cherenkov sound with forward
and {\it backward} sound propagation. Furthermore, we demonstrate that the
transition from the normal to anomalous Cherenkov sound happens in a {\it
singular} way at the Cherenkov cone angle. The detection of this acoustic
singularities therefore represents an alternative experimental tool for the
measurement of the spin-orbit coupling strength.",1010.4002v2
2010-12-22,Probing photo-induced melting of antiferromagnetic order in La0.5Sr1.5MnO4 by ultrafast resonant soft X-ray diffraction,"Photo-excitation in complex oxides1 transfers charge across semicovalent
bonds, drastically perturbing spin and orbital orders2. Light may then be used
in compounds like magnetoresistive manganites to control magnetism on nanometre
lengthscales and ultrafast timescales. Here, we show how ultrafast resonant
soft x-ray diffraction can separately probe the photo-induced dynamics of spin
and orbital orders in La0.5Sr1.5MnO4. Ultrafast melting of CE antiferromagnetic
spin order is evidenced by the disappearance of a (1/4,1/4,1/2) diffraction
peak. On the other hand the (1/4,1/4,0) peak, reflecting orbital order, is only
partially reduced. Cluster calculations aid our interpretation by considering
different magnetically ordered states accessible after photo-excitation.
Nonthermal coupling between light and magnetism emerges as a primary aspect of
photo-induced phase transitions in manganites.",1012.4960v2
2011-03-12,Non-Abelian quantum holonomy of hydrogen-like atoms,"We study the Uhlmann holonomy [Rep. Math. Phys. 24, 229 (1986)] of quantum
states for hydrogen-like atoms where the intrinsic spin and orbital angular
momentum are coupled by the spin-orbit interaction and subject to a slowly
varying magnetic field. We show that the holonomy for the orbital angular
momentum and spin subsystems is non-Abelian, while the holonomy of the whole
system is Abelian. Quantum entanglement in the states of the whole system is
crucially related to the non-Abelian gauge structure of the subsystems. We
analyze the phase of the Wilson loop variable associated with the Uhlmann
holonomy, and find a relation between the phase of the whole system with
corresponding marginal phases. Based on the result for the model system we
provide evidence that the phase of the Wilson loop variable and the mixed-state
geometric phase [E. Sj\""oqvist {\it et al.} Phys. Rev. Lett. 85, 2845 (2000)]
are in general inequivalent.",1103.2435v2
2011-03-26,Precision control of charge coherence in parallel double dot systems through spin-orbit interaction,"In terms of the exact quantum master equation solution for open electronic
systems, the coherent dynamics of two charge states described by two parallel
quantum dots with one fully polarized electron on either dot is investigated in
the presence of spin-orbit interaction. We demonstrate that the double dot
system can stay in a dynamically decoherence free space. The coherence between
two double dot charge states can be precisely manipulated through a spin-orbit
coupling. The effects of the temperature, the finite bandwidth of lead, and the
energy deviations during the coherence manipulation are also explored.",1103.5099v2
2011-07-08,Orbital-Angular-Momentum Based Origin of Rashba-Type Surface Band Splitting,"We propose that existence of local orbital angular momentum (OAM) on the
surfaces of high-Z materials play a crucial role in the formation of
Rashba-type surface band splitting. Local OAM state in a Bloch state produces
asymmetric charge distribution (electric dipole). Presence of surface electric
field aligns the electric dipole and results in chiral OAM states and the
relevant Rashba- type splitting. Therefore, the band splitting originates from
electric dipole interaction, not from the Zeeman splitting as proposed in the
original Rashba picture. The characteristic spin chiral structure of Rashba
states is formed through the spin-orbit coupling and thus is a secondary effect
to the chiral OAM. Results from first principles calculations on a single Bi
layer under an external electric field verify the key predictions of the new
model, including the direction of the spin textures which is predicted to be in
opposite direction in the Rashba picture.",1107.1554v2
2011-09-12,Existence of bulk chiral fermions and crystal symmetry,"We consider the existence of bulk chiral fermions around points of symmetry
in the Brillouin zone of nonmagnetic 3D crystals with negligible spin-orbit
interactions. We use group theory to show that this is possible, but only for a
reduced number of space groups and points of symmetry that we tabulate.
Moreover, we show that for a handful of space groups the existence of bulk
chiral fermions is not only possible but unavoidable, irrespective of the
concrete crystal structure. Thus our tables can be used to look for bulk chiral
fermions in a specific class of systems, namely that of nonmagnetic 3D crystals
with sufficiently weak spin-orbit coupling. We also discuss the effects of
spin-orbit interactions and possible extensions of our approach to Weyl
semimetals, crystals with magnetic order, and systems with Dirac points with
pseudospin 1 and 3/2. A simple tight-binding model is used to illustrate some
of the issues.",1109.2581v3
2012-09-06,Giant Anisotropy of Spin-Orbit Splitting at the Bismuth Surface,"We investigate the bismuth (111) surface by means of time and angle resolved
photoelectron spectroscopy. The parallel detection of the surface states below
and above the Fermi level reveals a giant anisotropy of the Spin-Orbit (SO)
spitting. These strong deviations from the Rashba-like coupling cannot be
treated in $\textbf{k}\cdot \textbf{p}$ perturbation theory. Instead, first
principle calculations could accurately reproduce the experimental dispersion
of the electronic states. Our analysis shows that the giant anisotropy of the
SO splitting is due to a large out-of plane buckling of the spin and orbital
texture.",1209.1219v2
2012-09-26,Z_2-vortex lattice in the ground state of the triangular Kitaev-Heisenberg model,"The triangular-lattice Heisenberg antiferromagnet (HAF) is known to carry
topological Z_2 vortex excitations which form a gas at finite temperatures.
Here we show that the spin-orbit interaction, introduced via a Kitaev term in
the exchange Hamiltonian, condenses these vortices into a triangular $Z_2$
vortex crystal at zero temperature. The cores of the Z_2 vortices show abrupt,
soliton-like magnetization modulations and arise by a special intertwining of
three honeycomb superstructures of ferromagnetic domains, one for each of the
three sublattices of the 120-degree state of the pure HAF. This is a new
example of a nucleation transition, analogous to the spontaneous formation of
magnetic domains, Abrikosov vortices in type-II syperconductors, blue phases in
cholesteric liquid crystals, and skyrmions in chiral helimagnets. As the
mechanism relies on the interplay of geometric frustration and spin-orbital
anisotropies, such vortex mesophases can materialize as a ground-state property
in spin-orbit coupled correlated systems with nearly hexagonal topology, as in
triangular or strongly frustrated honeycomb iridates.",1209.5895v3
2013-01-30,Resonance Features of the Conductance of Open Billiards with the Spin-Orbit Interaction,"The transport properties of a circular billiard with attached channels, which
is an open system, have been studied in the presence of the Dresselhaus and
Rashba spin-orbit interactions. It has been shown that this interaction leads
to the appearance of additional Fano resonances in the energy dependence of the
conductance, the width of which is proportional to the fourth power of the
spin-orbit coupling constant.",1301.7219v2
2013-06-18,"Effect of spin-orbit interaction on the excitonic effects in single-layer, double-layer, and bulk MoS2","We present converged ab-initio calculations of the optical absorption spectra
of single-layer, bi-layer, and bulk MoS$_2$. Both the quasiparticle-energy
calculations (on the level of the GW approximation) and the calculation of the
absorption spectra (on the level of the Bethe-Salpeter equation) explicitly
include spin-orbit coupling, using the full spinorial Kohn-Sham wave-functions
as input. Without excitonic effects, the absorption spectra would have the form
of a step-function, corresponding to the joint-density of states of a parabolic
band-dispersion in 2D. This profile is deformed by a pronounced bound excitonic
peak below the continuum onset. The peak is split by spin-orbit interaction in
the case of single-layer and (mostly) by inter-layer interaction in the case of
double-layer and bulk MoS$_2$. The resulting absorption spectra are thus very
similar in the three cases but the interpretation of the spectra is different.
Differences in the spectra can be seen around 3 eV where the spectra of single
and double-layer are dominated by a strongly bound exciton.",1306.4257v2
2014-04-02,Controllable Rashba spin-orbit interaction in artificially engineered superlattices involving the heavy-fermion superconductor CeCoIn5,"By using a molecular beam epitaxy technique, we fabricate a new type of
superconducting superlattices with controlled atomic layer thicknesses of
alternating blocks between heavy fermion superconductor CeCoIn_5, which
exhibits a strong Pauli pair-breaking effect, and nonmagnetic metal YbCoIn_5.
The introduction of the thickness modulation of YbCoIn_5 block layers breaks
the inversion symmetry centered at the superconducting block of CeCoIn_5. This
configuration leads to dramatic changes in the temperature and angular
dependence of the upper critical field, which can be understood by considering
the effect of the Rashba spin-orbit interaction arising from the inversion
symmetry breaking and the associated weakening of the Pauli pair-breaking
effect. Since the degree of thickness modulation is a design feature of this
type of superlattices, the Rashba interaction and the nature of pair-breaking
are largely tunable in these modulated superlattices with strong spin-orbit
coupling.",1404.0482v1
2015-03-31,Formation of Molecular-Orbital Bands in a Twisted Hubbard Tube: Implications for Unconventional Superconductivity in K2Cr3As3,"We study a twisted Hubbard tube modeling the [CrAs] structure of
quasi-one-dimensional superconductors A2Cr3As3 (A = K, Rb, Cs). The
molecular-orbital bands emerging from the quasi-degenerate atomic orbitals are
exactly solved. An effective Hamiltonian is derived for a region where three
partially filled bands intersect the Fermi energy. The deduced local
interactions among these active bands show a significant reduction compared to
the original atomic interactions. The resulting three-channel Luttinger liquid
shows various interaction-induced instabilities including two kinds of
spin-triplet superconducting instabilities due to gapless spin excitations,
with one of them being superseded by the spin-density-wave phase in the
intermediate Hund's coupling regime. The implications of these results for the
alkali chromium arsenides are discussed.",1503.08965v2
2015-10-07,Optimizing spin-orbit splittings in InSb Majorana nanowires,"Semiconductor-superconductor heterostructures represent a promising platform
for the detection of Majorana zero modes and subsequently the processing of
quantum information using their exotic non-Abelian statistics. Theoretical
modeling of such low-dimensional semiconductors is generally based on
phenomenological effective models. However, a more microscopic understanding of
their band structure and, especially, of the spin-orbit coupling of electrons
in these devices is important for optimizing their parameters for applications
in quantum computing. In this paper, we approach this problem by first
obtaining a highly accurate effective tight-binding model from ab initio
calculations in the bulk. This model is symmetrized and correctly reproduces
both the band structure and the wavefunction character. It is then used to
determine Dresselhaus and Rashba spin-orbit splittings induced by finite size
effects and external electric field in zincblende InSb one- and two-dimensional
nanostructures as a function of growth parameters. The method presented here
enables reliable simulations of realistic devices, including those used to
realize exotic topological states.",1510.02025v2
2015-11-16,On the ferromagnetic ground state of SmN,"SmN is a ferromagnetic semiconductor with the unusual property of an
orbital-dominant magnetic moment that is largely cancelled by an antiparallel
spin contribution, resulting in a near-zero net moment. However, there is a
basic gap in the understanding of the ferromagnetic ground state, with existing
density functional theory calculations providing values of the $4f$ magnetic
moments at odds with experimental data. To clarify the situation, we employ an
effective $4f$ Hamiltonian incorporating spin-orbit coupling, exchange, the
crystal field, and $J$-mixing to calculate the ground state $4f$ moments. Our
results are in excellent agreement with experimental data, revealing moderate
quenching of both spin and orbital moments to magnitudes of $\sim 2~\mu_B$ in
bulk SmN, enhanced to an average of $\sim 3~\mu_B$ in SmN layers within a
SmN/GdN superlattice. These calculations provide insight into recent studies of
SmN showing that it is an unconventional superconductor at low temperatures and
displays twisted magnetization phases in magnetic heterostructures.",1511.04820v1
2016-02-25,Mesoscopic Superposition States Generated by Synthetic Spin-orbit Interaction in Fock-state Lattices,"Mesoscopic superposition states of photons can be prepared in three cavities
interacting with the same two-level atom. By periodically modulating the three
cavity frequencies around the transition frequency of the atom with $2\pi/3$
phase difference, the time reversal symmetry is broken and an optical
circulator is generated with chiralities depending on the quantum state of the
atom. A superposition of the atomic states can guide photons from one cavity to
a mesoscopic superposition of the other two cavities. The physics can be
understood in a finite spin-orbit-coupled Fock-state lattice where the atom and
the cavities carry the spin and the orbit degrees of freedom, respectively.
This scheme can be realized in circuit QED architectures and provides a new
platform for exploring quantum information and topological physics in novel
lattices.",1602.08009v3
2018-02-08,Exotic Magnetism and Spin-Orbit Assisted Mott Insulating State in a $3d-5d$ Double Perovskite,"The magnetic structure of Ca$_2$MnReO$_6$ double perovskite is investigated
by neutron powder diffraction and bulk magnetization, showing dominant
non-collinear Mn magnetic moments [$4.35(7)$ $\mu_B$] that are orthogonally
aligned with the small Re moments [$0.22(4)$ $\mu_B$]. $Ab$-initio electronic
structure calculations show that the strong spin-orbit coupling for Re $5d$
electrons combined with a relatively modest on-site Coulomb repulsion
($U_{eff}^{Re} \gtrsim 0.6$ eV) is sufficient to render this material
insulating. This is a rare example of spin-orbit assisted Mott insulator
outside the realm of iridates, with remarkable magnetic properties.",1802.02815v1
2018-11-09,Switching of biaxial synthetic antiferromagnets: a micromagentic study,"We simulate the switching behavior of nanoscale synthetic antiferromagnets
(SAFs), inspired by recent experimental progress in spin-orbit-torque switching
of crystal antiferromagnets. The SAF consists of two ferromagnetic thin films
with in-plane biaxial anisotropy and interlayer exchange coupling. Staggered
field-like Rashba spin-orbit torques from the opposite surfaces of the SAF
induce a canted net magnetization, which triggers an orthogonal torque that
drives 90$^\circ$ switching of the N\'eel vector. Such dynamics driven by the
field-like spin-orbit torque allows for faster switching with increased Gilbert
damping, without a significant detrimental increase of the threshold switching
current density. Our results point to the potential of SAFs as model systems,
based on simple ferromagnetic metals, to mimic antiferromagnetic device
physics.",1811.04094v2
2009-12-18,Tunable Rashba spin-orbit interaction at oxide interfaces,"The quasi-two-dimensional electron gas found at the LaAlO3/SrTiO3 interface
offers exciting new functionalities, such as tunable superconductivity, and has
been proposed as a new nanoelectronics fabrication platform. Here we lay out a
new example of an electronic property arising from the interfacial breaking of
inversion symmetry, namely a large Rashba spin-orbit interaction, whose
magnitude can be modulated by the application of an external electric field. By
means of magnetotransport experiments we explore the evolution of the
spin-orbit coupling across the phase diagram of the system. We uncover a steep
rise in Rashba interaction occurring around the doping level where a quantum
critical point separates the insulating and superconducting ground states of
the system.",0912.3731v1
2011-11-11,Subband structure of a two-dimensional electron gas formed at the polar surface of the strong spin-orbit perovskite KTaO$_3$,"We demonstrate the formation of a two-dimensional electron gas (2DEG) at the
$(100)$ surface of the $5d$ transition-metal oxide KTaO$_3$. From
angle-resolved photoemission, we find that quantum confinement lifts the
orbital degeneracy of the bulk band structure and leads to a 2DEG composed of
ladders of subband states of both light and heavy carriers. Despite the strong
spin-orbit coupling, our measurements provide a direct upper bound for
potential Rashba spin splitting of only $\Delta{k}_\parallel\sim\0.02$
\AA$^{-1}$ at the Fermi level. The polar nature of the KTaO$_3(100)$ surface
appears to help mediate formation of the 2DEG as compared to non-polar
SrTiO$_3(100)$.",1111.2782v1
2012-04-26,"Investigations of the EPR parameters for the tetrahedral [FeX_4]^- clusters in AgX (X=Cl, Br)","The EPR parameters g factors and the superhyperfine parameters for the
tetrahedral [FeX_4]^- clusters in AgX (X=Cl, Br) are theoretically investigated
from the perturbation formulas of these parameters for a 3d^5 ion under
tetrahedra by considering both the crystal-field and charge transfer
contributions. The related model parameters are quantitatively determined from
the cluster approach in a uniform way. The g-shift \Delta g (=g-g_s, where
g_s\approx 2.0023 is the spin only value) from the charge transfer contribution
is opposite (positive) in sign and much larger in magnitude as compared with
that from the crystal-field one. The importance of the charge transfer
contribution increases rapidly with increasing the covalency and the spin-orbit
coupling coefficient of the ligand and thus exhibits the order of AgCl<AgBr.
The unpaired spin densities of the halogen ns, np\sigma\ and np\pi\ orbitals
are quantitatively determined from the related molecular orbital coefficients
based on the cluster approach.",1204.5996v1
2015-12-30,Character of Matter in Holography: Spin-Orbit Interaction,"Gauge/Gravity duality as a theory of matter needs a systematic way to
characterise a system. We suggest a `dimensional lifting' of the least
irrelevant interaction to the bulk theory. As an example, we consider the
spin-orbit interaction, which causes magneto-electric interaction term. We show
that its lifting is an axionic coupling. We present an exact and analytic
solution describing diamagnetic response. Experimental data on annealed
graphite shows a remarkable similarity to our theoretical result. We also find
an analytic formulas of DC transport coefficients, according to which, the
anomalous Hall coefficient interpolates between the coherent metallic regime
with $\rho_{xx}^{2}$ and incoherent metallic regime with $\rho_{xx}$ as we
increase the disorder parameter $\beta$. The strength of the spin-orbit
interaction also interpolates between the two scaling regimes.",1512.08916v1
2016-05-18,Sensitivity of Λ single-particle energies to the ΛN spin-orbit coupling and to nuclear core structure in p-shell and sd-shell hypernuclei,"We introduce a mean field model based on realistic 2-body baryon interactions
and calculate spectra of a set of p-shell and sd-shell {\Lambda} hypernuclei -
13{\Lambda}C, 17{\Lambda}O, 21{\Lambda}Ne, 29{\Lambda}Si and 41{\Lambda}Ca. The
hypernuclear spectra are compared with the results of a relativistic mean field
(RMF) model and available experimental data. The sensitivity of {\Lambda}
single-particle energies to the nuclear core structure is explored. Special
attention is paid to the effect of spin-orbit {\Lambda}N interaction on the
energy splitting of the {\Lambda} single particle levels 0p3/2 and 0p1/2. In
particular, we analyze the contribution of the symmetric (SLS) and the
anti-symmetric (ALS) spin-orbit terms to the energy splitting. We give
qualitative predictions for the calculated hypernuclei.",1605.05646v1
2017-06-08,Writing and Reading antiferromagnetic Mn$_2$Au: Néel spin-orbit torques and large anisotropic magnetoresistance,"Antiferromagnets are magnetically ordered materials which exhibit no net
moment and thus are insensitive to magnetic fields. Antiferromagnetic
spintronics aims to take advantage of this insensitivity for enhanced
stability, while at the same time active manipulation up to the natural THz
dynamic speeds of antiferromagnets is possible, thus combining exceptional
storage density and ultra-fast switching. However, the active manipulation and
read-out of the N\'eel vector (staggered moment) orientation is challenging.
Recent predictions have opened up a path based on a new spin-orbit torque,
which couples directly to the N\'eel order parameter. This N\'eel spin-orbit
torque was first experimentally demonstrated in a pioneering work using
semimetallic CuMnAs. Here we demonstrate for Mn$_2$Au, a good conductor with a
high ordering temperature suitable for applications, reliable and reproducible
switching using current pulses and readout by magnetoresistance measurements.
The symmetry of the torques agrees with theoretical predictions and a large
read-out magnetoresistance effect of more than $\simeq 6$~$\%$ is reproduced by
ab initio transport calculations.",1706.02482v1
2018-09-17,Ultrafast dynamics of spin and orbital correlations in quantum materials: an energy- and momentum-resolved perspective,"Many remarkable properties of quantum materials emerge from states with
intricate coupling between the charge, spin and orbital degrees of freedom.
Ultrafast photo-excitations of these materials hold great promise for
understanding and controlling the properties of these states. Here we introduce
time-resolved resonant inelastic X-ray scattering (trRIXS) as a means of
measuring charge, spin and orbital excitations out of equilibrium. These
excitations encode the correlations and interactions that determine the
detailed properties of the states generated. After outlining the basic
principles and instrumentation of tr-RIXS, we review our first observations of
transient antiferromagnetic correlations in quasi-two dimensions in a
photo-excited Mott insulator and present possible future routes of this
fast-developing technique. The increasing number of X-ray free electron laser
facilities not only enables tackling long-standing fundamental scientific
problems, but also promises to unleash novel inelastic X-ray scattering
spectroscopies",1809.06288v2
2019-07-11,Tuning skyrmion Hall effect via engineering of spin-orbit interaction,"We demonstrate that the Magnus force acting on magnetic skyrmions can be
efficiently tuned via modulation of the spin-orbit interaction strength. We
show that the skyrmion Hall effect, which is a direct consequence of the
non-vanishing Magnus force on the magnetic structure can be suppressed in
certain limits. Our calculations show that the emergent magnetic fields in the
presence of spin-orbit coupling (SOC) renormalize the Lorentz force on
itinerant electrons and thus influence the topological transport. In
particular, we show that for a N\'eel-type skyrmion and Bloch-type
antiskyrmion, the skyrmion Hall effect (SkHE) can vanish by tuning
appropriately the strength of Rashba and Dresselhaus SOCs, respectively. Our
results open up alternative directions to explore in a bid to overcome the
parasitic and undesirable SkHE for spintronic applications.",1907.05196v1
2019-09-13,Hidden spin-orbital order in the Kitaev hyperhoneycomb $β$-Li$_2$IrO$_3$,"We report the existence of a phase transition at high temperature in the 3D
Kitaev candidate material, $\beta$-Li$_2$IrO$_3$. We show that the transition
is bulk, intrinsic and orders a tiny magnetic moment with a spatially
anisotropic saturation moment. We show that even though this transition is
global, it does not freeze the local Ir moments, which order at much lower
temperatures into an incommensurate state. Rather, the ordered moment has an
orbital origin that is coupled to spin correlations, likely of a Kitaev origin.
The separate ordering of spin-correlated orbital moments and of local Ir
moments reveals a novel way in which magnetic frustration in Kitaev systems can
lead to coexisting magnetic states.",1909.06355v1
2017-09-26,Possibility to realize spin-orbit-induced correlated physics in iridium fluorides,"Recent theoretical predictions of ""unprecedented proximity"" of the electronic
ground state of iridium fluorides to the SU(2) symmetric $j_{\mathrm{eff}}=1/2$
limit, relevant for superconductivity in iridates, motivated us to investigate
their crystal and electronic structure. To this aim, we performed
high-resolution x-ray powder diffraction, Ir L$_3$-edge resonant inelastic
x-ray scattering, and quantum chemical calculations on Rb$_2$[IrF$_6$] and
other iridium fluorides. Our results are consistent with the Mott insulating
scenario predicted by Birol and Haule [Phys. Rev. Lett. 114, 096403 (2015)],
but we observe a sizable deviation of the $j_{\mathrm{eff}}=1/2$ state from the
SU(2) symmetric limit. Interactions beyond the first coordination shell of
iridium are negligible, hence the iridium fluorides do not show any magnetic
ordering down to at least 20 K. A larger spin-orbit coupling in iridium
fluorides compared to oxides is ascribed to a reduction of the degree of
covalency, with consequences on the possibility to realize spin-orbit-induced
strongly correlated physics in iridium fluorides.",1709.09027v1
2018-07-03,General relativistic manifestations of orbital angular and intrinsic hyperbolic momentum in electromagnetic radiation,"General relativistic effects in the weak field approximation are calculated
for electromagnetic Laguerre-Gaussian (LG) beams. The current work is an
extension of previous work on the precession of a spinning neutral particle in
the weak gravitational field of an optical vortex. In the current work, the
metric perturbation is extended to all coordinate configurations and includes
gravitational effects from circular polarization and intrinsic hyperbolic
momentum. The final metric reveals frame-dragging effects due to intrinsic spin
angular momentum (SAM), orbital angular momentum (OAM), and spin-orbit (SO)
coupling. When investigating the acceleration of test particles in this metric,
an unreported gravitational phenomenon was found. This effect is analogous to
the motion of charged particles in the magnetic field produced by a current
carrying wire. It was found that the gravitational influence of SAM and OAM
affects test-rays traveling perpendicular to the intense beam and from this a
gravitational Aharonov-Bohm analog is pursued.",1807.00933v1
2018-07-09,Spin-orbit interaction in Pt or Bi2Te3 nanoparticle-decorated graphene realized by a nanoneedle method,"The introduction of spin-orbit interactions (SOIs) and the subsequent
appearance of a two-dimensional (2D) topological phase are crucial for
voltage-controlled and zero-emission energy spintronic devices. In contrast,
graphene basically lacks SOIs due to the small mass of the carbon atom, and
appropriate experimental reports for SOIs are rare. Here, we control
small-amount (cover ratios < 8%) random decoration of heavy nanoparticles
[platinum (Pt) or bismuth telluride (Bi2Te3)] onto mono-layer graphene by
developing an original nanoneedle method. X-ray photoelectron spectra support
low-damage and low-contamination decoration of the nanoparticles, suggesting
the presence of Bi-C and Te-C coupling orbitals. In the samples, we find
particle-density-dependent non-local resistance (RNL) peaks, which are
attributed to the (inverse) spin Hall effect (SHE) arising from SOI with
energies as large as about 30 meV. This is a larger value than in previous
reports and supported by scanning tunneling spectroscopy. The present
observation should lead to topological phases of graphene, which can be
introduced by random decoration with controlled small amounts of heavy
nanoparticles, and their applications.",1807.02984v1
2019-11-25,Application of k . p method on band structure of GaAs obtained through joint density functional theory,"The structural and electronic properties of zinc-blende (ZB) GaAs were
calculated within the framework of plane wave density-functional theory (DFT)
code JDFTx by using Becke 86 in 2D and PBE exchange correlation functionals
from libXC. The standard optimized norm-conserving Vanderbilt pseudopotentials
were used to calculate optimized lattice constant, band gap and spin-orbit
split-off parameter. The calculated values of optimized lattice constant and
direct band gap are in satisfactory agreement with other published theoretical
and experimental findings. By including spin-orbit (SO) coupling, conduction
band and valence bands were studied under parabolicity to calculate effective
masses. The calculated values of effective masses and spin-orbit split-off
parameter are in satisfactory agreement with most recent findings. This work
will be useful for more computational studies related to semiconductor
spintronic devices.",1911.10724v1
2019-12-05,Anomalous Transition Magnetic Moments in two-dimensional Dirac Materials,"We show that the magnetic response of atomically thin materials with Dirac
spectrum and spin-orbit interactions can exhibit strong dependence on
electron-electron interactions. While graphene itself has a very small
spin-orbit coupling, various two-dimensional (2D) compounds ""beyond graphene""
are good candidates to exhibit the strong interplay between spin-orbit and
Coulomb interactions. Materials in this class include dichalcogenides (such as
MoS$_2$ and WSe$_2$), silicene, germanene, as well as 2D topological insulators
described by the Kane-Mele model. We present a unified theory for their
in-plane magnetic field response leading to ""anomalous"", i.e. electron
interaction dependent transition moments. Our predictions can be potentially
used to construct unique magnetic probes with high sensitivity to electron
correlations.",1912.02749v3
2016-03-14,Crystalline spin-orbit interaction and the Zeeman splitting in Pb$_{1-x}$Sn$_x$Te,"The ratio of the Zeeman splitting to the cyclotron energy ($M=\Delta E_Z /
\hbar \omega_c$), which characterizes the relative strength of the spin-orbit
interaction in crystals, is examined for the narrow gap IV-VI semiconductors
PbTe, SnTe, and their alloy Pb$_{1-x}$Sn$_x$Te on the basis of the multiband
$k\cdot p$ theory. The inverse mass $\alpha$, the g-factor $g$, and $M$ are
calculated numerically by employing the relativistic empirical tight-binding
band calculation. On the other hand, a simple but exact formula of $M$ is
obtained for the six-band model based on the group theoretical analysis. It is
shown that $M<1$ for PbTe and $M>1$ for SnTe, which are interpreted in terms of
the relevance of the interband couplings due to the crystalline spin-orbit
interaction. It is clarified both analytically and numerically that $M=1$ just
at the band inversion point, where the transition from trivial to nontrivial
topological crystalline insulator occurs. By using this property, one can
detect the transition point only with the bulk measurements. It is also
proposed that $M$ is useful to evaluate quantitatively a degree of the Dirac
electrons in solids.",1603.04138v1
2018-10-25,First-principles calculation of spin-orbit torque in a Co/Pt bilayer,"The angular dependence of spin-orbit torque in a disordered Co/Pt bilayer is
calculated using a first-principles non-equilibrium Green's function formalism
with an explicit supercell averaging over Anderson disorder. In addition to the
usual dampinglike and fieldlike terms, the odd torque contains a sizeable
planar Hall-like term $(\mathbf{m\cdot
E})\mathbf{m}\times(\mathbf{z}\times\mathbf{m})$ whose contribution to
current-induced damping is consistent with experimental observations. The
dampinglike and planar Hall-like torquances depend weakly on disorder strength,
while the fieldlike torquance declines with increasing disorder. The torques
that contribute to damping are almost entirely due to spin-orbit coupling on
the Pt atoms, but the fieldlike torque does not require it.",1810.11003v2
2020-06-03,Superconductivity-induced change in magnetic anisotropy in epitaxial ferromagnet-superconductor hybrids with spin-orbit interaction,"The interaction between superconductivity and ferromagnetism in thin film
superconductor/ferromagnet heterostructures is usually reflected by a change in
superconductivity of the S layer set by the magnetic state of the F layers.
Here we report the converse effect: transformation of the magnetocrystalline
anisotropy of a single Fe(001) layer, and thus its preferred magnetization
orientation, driven by the superconductivity of an underlying V layer through a
spin-orbit coupled MgO interface. We attribute this to an additional
contribution to the free energy of the ferromagnet arising from the controlled
generation of triplet Cooper pairs, which depends on the relative angle between
the exchange field of the ferromagnet and the spin-orbit field. This is
fundamentally different from the commonly observed magnetic domain modification
by Meissner screening or domain wall-vortex interaction and offers the ability
to fundamentally tune magnetic anisotropies using superconductivity - a key
step in designing future cryogenic magnetic memories.",2006.02118v2
2021-01-01,Stripping the planar Quantum Compass Model to its basics,"We introduce a novel mean-field theory (MFT) around the exactly soluble
two-leg ladder limit for the planar quantum compass model (QCM). In contrast to
usual MFT, our construction respects the stringent constraints imposed by
emergent, lower (here $d=1$) dimensional symmetries of the QCM. Specializing
our construction to the QCM on a periodic four-leg ladder, we find that a
first-order transition separates two mutually dual Ising nematic phases, in
good accord with state-of-the-art numerics for the planar QCM. One
pseudo-spin-flip excitation in the ordered phase turns out to be two
(Jordan-Wigner) fermion bound states, reminiscent of spin waves in spin-$1/2$
Heisenberg chains. We discuss the novel implications of our work on (1) the
emergence of coupled orbital and magnetic ordered and liquidlike disordered
phases, and (2) a rare instance of orbital-spin separation in $d>1$, in the
context of a Kugel-Khomskii view of multi-orbital Mott insulators.",2101.00268v2
2021-08-30,Spin to orbital angular momentum transfer in nonlinear wave mixing,"We demonstrate the spin to orbital angular momentum transfer in the nonlinear
mixing of structured light beams. A vector vortex is coupled to a circularly
polarized Gaussian beam in noncollinear second harmonic generation under
type-II phase match. The second harmonic beam inherits the Hermite-Gaussian
components of the vector vortex, however, the relative phase between them is
determined by the polarization state of the Gaussian beam. This effect creates
an interesting crosstalk between spin and orbital degrees of freedom, allowing
the angular momentum transfer between them. Our experimental results match the
theoretical predictions for the nonlinear optical response.",2108.13190v1
2022-06-09,Spin-orbit excitons and electronic configuration of the $5d^4$ insulator Sr$_3$Ir$_2$O$_7$F$_2$,"Here we report on the low-energy excitations within the paramagnetic
spin-orbit insulator Sr$_3$Ir$_2$O$_7$F$_2$ studied via resonant inelastic
X-ray scattering, \textit{ab initio} quantum chemical calculations, and
model-Hamiltonian simulations. This material is a unique $d^{4}$ Ir$^{5+}$
analog of Sr$_3$Ir$_2$O$_7$ that forms when F ions are intercalated within the
SrO layers spacing the square lattice IrO$_{6}$ bilayers of Sr$_3$Ir$_2$O$_7$.
Due to the large distortions about the Ir$^{5+}$ ions, our computations
demonstrate that a large single-ion anisotropy yields an $S$=1 ($L{\approx}$1,
$J{\approx}$0) ground state wave function. Weakly coupled, excitonic modes out
of the $S_z$=0 ground state are observed and are well-described by a
phenomenological spin-orbit exciton model previously developed for $3d$ and
$4d$ transition metal ions. The implications of our results regarding the
interpretation of previous studies of hole-doped iridates close to $d^{4}$
fillings are discussed.",2206.04721v1
2022-08-22,"Current-induced magnetization reversal in (Ga,Mn)(Bi,As) epitaxial layer with perpendicular magnetic anisotropy","Pulsed current-induced magnetization reversal is investigated in the layer of
(Ga,Mn)(Bi,As) dilute ferromagnetic semiconductor (DFS) epitaxially grown under
tensile misfit strain causing perpendicular magnetic anisotropy in the layer.
The magnetization reversal, recorded through measurements of the anomalous Hall
effect, appearing under assistance of a static magnetic field parallel to the
current, is interpreted in terms of the spin-orbit torque mechanism. Our
results demonstrate that an addition of a small fraction of heavy Bi atoms,
substituting As atoms in the prototype DFS (Ga,Mn)As and increasing the
strength of spin-orbit coupling in the DFS valence band, significantly enhances
the efficiency of current-induced magnetization reversal thus reducing
considerably the threshold current density necessary for the reversal. Our
findings are of technological importance for applications to spin-orbit
torque-driven nonvolatile memory and logic elements.",2208.10318v1
2022-11-17,Vibronic order and emergent magnetism in cubic $d^1$ double perovskites,"The synergistic interplay of different interactions in materials leads to the
emergence of novel quantum phenomena. Spin-orbit and vibronic couplings usually
counteract each other, however, in cubic $d^1$ double perovskites they coexist
and give rise to spin-orbit-lattice entanglement with unquenched dynamic
Jahn-Teller effect on the metal sites. The correlation of these entangled
states induced by intersite interactions was not assessed so far. Here, we
investigate the joint cooperative effect of spin-orbit and vibronic
interactions on the formation of the ordered phases in $d^1$ double
perovskites. We found that the magnetic ordered states in these systems coexist
with a dynamic vibronic order characterized by the ordering of vibronic
quadrupole moments on sites. This treatment allows the rationalization of a
number of unexplained features of experimentally investigated phases.",2211.09577v4
2023-05-04,Quasilinear theory of Brillouin resonances in rotating magnetized plasmas,"Both spin and orbital angular momentum can be exchanged between a rotating
wave and a rotating magnetized plasma. Through resonances the spin and orbital
angular momentum of the wave can be coupled to both the cyclotron rotation and
the drift rotation of the particles. It is however shown that the Landau and
cyclotron resonance conditions which classically describe resonant
energy-momentum exchange between waves and particles are no longer valid in a
rotating magnetized plasma column. In this case a new resonance condition which
involves a resonant matching between the wave frequency, the cyclotron
frequency modified by inertial effects and the harmonics of the guiding center
rotation is identified. A new quasilinear equation describing orbital and spin
angular momentum exchanges through these new Brillouin resonances is then
derived, and used to expose the wave driven radial current responsible for
angular momentum absorption.",2305.02671v1
2023-08-07,Strong coupling of lattice and orbital excitations in quantum magnet Ca$_{10}$Cr$_7$O$_{28}$: Anomalous temperature dependence of Raman phonons,"We report low-temperature Raman signatures of the Heisenberg quantum magnet
Ca$_{10}$Cr$_7$O$_{28}$, showing clear anomalies in phonon mode frequencies and
linewidths below $\sim$100 K. This crossover temperature lies in between the
Jahn-Teller (JT) temperature scale ($>$ room temperature) and the temperature
scale associated with the spin exchange interactions ($<$ 12 K). Our
experimental observation is well captured by a novel secondary JT transition
associated with a cooperative reorientation of the orbitals giving rise to
anomalies in the temperature dependence of Raman frequencies and linewidths.
Such orbital reorganisation, in turn, affects the spin-spin exchange
interactions that decide the fate of the magnet at lower temperatures and hence
provide important clues to understand the energetics of the possible lower
temperature quantum paramagnetic phase.",2308.03237v1
2023-10-11,Electronic States in Helical Materials: General Properties and Application to InSeI,"In this article, we systematically explore several key properties of
electronic states in helical materials systems, including the inheritance of
orbital angular momentum (OAM) from local atomic orbitals to the entire helical
structure, the conservation of helical momentum, and the emergence of
helical-induced spin-orbit coupling (hSOC). We then apply this comprehensive
theoretical framework to elucidate the electronic structure of one-dimensional
(1D) helical crystal InSeI. Our analysis reveals the influence of hSOC, evident
in spin-mixing energy gaps within the electronic band structure, as calculated
through density functional theory. Utilizing a combination of tight-binding
modeling and first-principles calculations, we ascertain the spin-polarized
electric response and the chiral-switchable second-order photocurrent response
of InSeI, characterized as the Landauer-Buttiker ballistic transport and shift
current response. The results highlight the potential of 1D InSeI for
applications in spintronics and optoelectronics. The overarching theoretical
framework established in this work will prove invaluable for the investigation
of other helical electronic systems.",2310.07530v1
2024-02-12,Spin orbit resonance cascade via core shell model. Application to Mercury and Ganymede,"We discuss a model describing the spin orbit resonance cascade. We assume
that the primary has a two-layer (core-shell) structure: it is composed by a
thin solid crust and an inner and heavier solid core that are interacting due
to the presence of a fluid interface. We assume two sources of dissipation: a
viscous one, depending on the relative angular velocity between core and crust
and a tidal one, smaller than the first, due to the viscoelastic structure of
the core. We show how these two sources of dissipation are needful for the
capture in spin-orbit resonance. The crust and the core fall in resonance with
different time scales if the viscous coupling between them is big enough.
Finally, the tidal dissipation of the viscoelastic core, decreasing the
eccentricity, brings the system out of the resonance in a third very long time
scale. This mechanism of entry and exit from resonance ends in the $1:1$ stable
state.",2402.07650v1
1995-12-05,Phase Diagram for Charge Density Waves in a Magnetic Field,"The influence of an external magnetic field on a quasi one-dimensional system
with a charge density wave (CDW) instability is treated within the random phase
approximation which includes both CDW and spin density wave correlations. We
show that the CDW is sensitive to both orbital and Pauli effects of the field.
In the case of perfect nesting, the critical temperature decreases monotonously
with the field, and the wave vector of the instability starts to shift above
some critical value of magnetic field. Depending on the ratio between the spin
and charge coupling constants and on the direction of the applied magnetic
field, the wave vector shift is either parallel ($CDW_x$ order) or
perpendicular ($CDW_y$ order) to the most conducting direction. The $CDW_x$
order is a field dependent linear combination of the charge and spin density
waves and is sensible only to the Pauli effect. The wave vector shift in
$CDW_y$ depends on the interchain coupling, but the critical temperature does
not. This order is affected by the confinement of the electronic orbits. By
increasing the relative strength of the orbital effect with respect to the
Pauli effect, one can destroy the $CDW_y$, establishing either a $CDW_x$, or a
$CDW_0$ (corresponding to perfect nesting wave vector). We also show that by
increasing the imperfect nesting parameter, one passes from the regime where
the critical temperature decreases with the field to the regime where it is
initially enhanced by the orbital effect and eventually suppressed by the Pauli
effect. For a bad nesting, the quantized phases of the field-induced CDW
appear.",9512033v1
2002-09-26,Magnetization orientation dependence of the quasiparticle spectrum and hysteresis in ferromagnetic metal nanoparticles,"We use a microscopic Slater-Koster tight-binding model with short-range
exchange and atomic spin-orbit interactions that realistically captures generic
features of ferromagnetic metal nanoparticles to address the mesoscopic physics
of magnetocrystalline anisotropy and hysteresis in nanoparticle quasiparticle
excitation spectra. Our analysis is based on qualitative arguments supported by
self-consistent Hartree-Fock calculations for nanoparticles containing up to
260 atoms. Calculations of the total energy as a function of magnetization
direction demonstrate that the magnetic anisotropy per atom fluctuates by
several percents when the number of electrons in the particle changes by one,
even for the largest particles we consider. Contributions of individual
orbitals to the magnetic anisotropy are characterized by a broad distribution
with a mean more than two orders of magnitude smaller than its variance and
with no detectable correlations between anisotropy contribution and
quasiparticle energy. We find that the discrete quasiparticle excitation
spectrum of a nanoparticle displays a complex non-monotonic dependence on an
external magnetic field, with abrupt jumps when the magnetization direction is
reversed by the field, explaining recent spectroscopic studies of magnetic
nanoparticles. Our results suggests the existence of a broad cross-over from a
weak spin-orbit coupling to a strong spin-orbit coupling regime, occurring over
the range from approximately 200- to 1000-atom nanoparticles.",0209608v2
2007-10-15,Charge disproportionation and collinear magnetic order in the frustrated triangular antiferromagnet AgNiO2,"We report a high-resolution neutron diffraction study of the crystal and
magnetic structure of the orbitally-degenerate frustrated metallic magnet
AgNiO2. At high temperatures the structure is hexagonal with a single
crystallographic Ni site, low-spin Ni3+ with spin-1/2 and two-fold orbital
degeneracy, arranged in an antiferromagnetic triangular lattice with frustrated
spin and orbital order. A structural transition occurs upon cooling below 365 K
to a tripled hexagonal unit cell containing three crystallographically-distinct
Ni sites with expanded and contracted NiO6 octahedra, naturally explained by
spontaneous charge order on the Ni triangular layers. No Jahn-Teller
distortions occur, suggesting that charge order occurs in order to lift the
orbital degeneracy. Symmetry analysis of the inferred Ni charge order pattern
and the observed oxygen displacement pattern suggests that the transition could
be mediated by charge fluctuations at the Ni sites coupled to a soft oxygen
optical phonon breathing mode. At low temperatures the electron-rich Ni
sublattice (assigned to a valence close to Ni2+ with S = 1) orders magnetically
into a collinear stripe structure of ferromagnetic rows ordered
antiferromagnetically in the triangular planes. We discuss the stability of
this uncommon spin order pattern in the context of an easy-axis triangular
antiferromagnet with additional weak second neighbor interactions and
interlayer couplings.",0710.2811v2
2021-04-16,"Optical, dielectric, and magnetoelectric properties of ferroelectric and antiferroelectric lacunar spinels","Lacunar spinels with a chemical formula of $AM_4X_8$ form a populous family
of narrow-gap semiconductors, which offer a fertile ground to explore
correlation and quantum phenomena, including transition between Mott and
spin-orbit insulator states, ferro/antiferroelectricity driven by cluster
Jahn-Teller effect, and magnetoelectric response of magnetic skyrmions with
polar dressing. The electronic and magnetic properties of lacunar spinels are
determined to a large extent by their molecular-crystal-like structure. The
interplay of electronic correlations with spin-orbit and vibronic couplings
leads to a complex electronic structure already on the single-cluster level,
which -- together with weaker inter-cluster interactions -- gives rise to a
plethora of unconventional correlated states. This review primarily focuses on
recent progresses in the field of optical, dielectric, and magnetoelectric
properties on lacunar spinels. After introducing the main structural aspects,
lattice dynamics and electronic structure of these compounds are discussed on
the basis of optical spectroscopy measurements. Dielectric and polarization
studies reveal the main characteristics of their low-temperature ferro- or
antiferroelectric phases as well as orbital fluctuations in their
high-temperature cubic state. Strong couplings between spin, lattice, and
orbital degrees of freedom are manifested in singlet formation upon
magnetostructural transitions, the emergence of various multiferroic phases,
and exotic domain-wall functionalities.",2104.08019v1
2017-11-10,Transverse acoustic phonon anomalies at intermediate wavevectors in MgV$_{2}$O$_{4}$,"Magnetic spinels (with chemical formula $AX_{2}$O$_{4}$, with $X$ a 3$d$
transition metal ion) that also have an orbital degeneracy are Jahn-Teller
active and hence possess a coupling between spin and lattice degrees of
freedom. At high temperatures, MgV$_{2}$O$_{4}$ is a cubic spinel based on
V$^{3+}$ ions with a spin $S$=1 and a triply degenerate orbital ground state. A
structural transition occurs at T$_{OO}$=63 K to an orbitally ordered phase
with a tetragonal unit cell followed by an antiferromagnetic transition of
T$_{N}$=42 K on cooling. We apply neutron spectroscopy in single crystals of
MgV$_{2}$O$_{4}$ to show an anomaly for intermediate wavevectors at T$_{OO}$
associated with the acoustic phonon sensitive to the shear elastic modulus
$\left(C_{11}-C_{12}\right)/2$. On warming, the shear mode softens for momentum
transfers near close to half the Brillouin zone boundary, but recovers near the
zone centre. High resolution spin-echo measurements further illustrate a
temporal broadening with increased temperature over this intermediate range of
wavevectors, indicative of a reduction in phonon lifetime. A subtle shift in
phonon frequencies over the same range of momentum transfers is observed with
magnetic fields. We discuss this acoustic anomaly in context of coupling to
orbital and charge fluctuations.",1711.03791v1
2021-07-14,Designing light-element materials with large effective spin-orbit coupling,"Spin-orbit coupling (SOC), the core of numerous condensed-matter phenomena
such as nontrivial band gap, magnetocrystalline anisotropy, etc, is generally
considered to be appreciable only in heavy elements, detrimental to the
synthetization and application of functional materials. Therefore, amplifying
the SOC effect in light elements is of great importance. Here, focusing on 3d
and 4d systems, we demonstrate that the interplay between crystal symmetry and
electron correlation can dramatically enhance the SOC effect in certain
partially occupied orbital multiplets, through the self-consistently reinforced
orbital polarization as a pivot. We then provide design principles and
comprehensive databases, in which we list all the Wyckoff positions and site
symmetries, in all two-dimensional (2D) and three-dimensional crystals that
potentially have such enhanced SOC effect. As an important demonstration, we
predict nine material candidates from our selected 2D material pool as
high-temperature quantum anomalous Hall insulators with large nontrivial band
gaps of hundreds of meV. Our work provides an efficient and straightforward way
to predict promising SOC-active materials, releasing the burden of requiring
heavy elements for next-generation spin-orbitronic materials and devices.",2107.06691v2
2022-08-17,Role of spin-orbit coupling effects in rare-earth metallic tetra-borides : a first principle study,"We have investigated the electronic structure of rare-earth tetraborides,
$\textrm{RB}_{4}$, using first-principle electronic structure methods (DFT)
implemented in Quantum Espresso (QE). In this article we have studied
heather-to neglected strong spin-orbit coupling (SOC) effects present in these
systems on the electronic structure of these system in the non-magnetic ground
state. The calculations were done under GGA and GGA+SO approximations using
ultrasoft pseudopotentials and fully relativistic ultrasoft pseudopotentials
(for SOC case). Perdew-Burke-Ernzerhof generalized gradient approximation
(PBE-GGA) exchange-correlation functionals within the linearized plane-wave
(LAPW) method as implemented in QE were used. The projected density of states
consists of 3 distinct spectral peaks well below the Fermi energy and separated
from the continuum density of states around the Fermi energy. The discrete
peaks arises due to rare-earth $s$-orbital, rare-earth $p$ + B $p$ and B
$p$-orbitals while the continuum arises due to hybridized B $p$, rare-earth $d$
orbitals. Upon inclusion of SOC the peak arising due to rare-earth $p$-orbitals
gets split into two peaks corresponding to $j=0.5$ and $j=1.5$ configurations.
In case of $\textrm{LaB}_{4}$, in the presence of SOC, spin-split $4f$ orbitals
contributes to density of states at the Fermi level while the density of states
at the Fermi level largely remains unaffected for all other materials under
consideration.",2208.08381v1
2023-10-28,Varying magnetism in the lattice distorted Y2NiIrO6 and La2NiIrO6,"We investigate the electronic and magnetic properties of the newly
synthesized double perovskites Y$_{2}$NiIrO$_{6}$ and La$_{2}$NiIrO$_{6}$,
using density functional calculations, crystal field theory, superexchange
pictures, and Monte Carlo simulations. We find that both systems are
antiferromagnetic (AFM) Mott insulators, with the high-spin Ni$^{2+}$
$t_{2g}$$^{6}e_{g}$$^{2}$ ($S=1$) and the low-spin Ir$^{4+}$ $t_{2g}$$^{5}$
($S=1/2$) configurations. We address that their lattice distortion induces
$t_{2g}$-$e_{g}$ orbital mixing and thus enables the normal Ni$^{+}$-Ir$^{5+}$
charge excitation with the electron hopping from the Ir `$t_{2g}$' to Ni
`$e_g$' orbitals, which promotes the AFM Ni$^{2+}$-Ir$^{4+}$ coupling.
Therefore, the increasing $t_{2g}$-$e_{g}$ mixing accounts for the enhanced
$T_{\rm N}$ from the less distorted La$_{2}$NiIrO$_{6}$ to the more distorted
Y$_{2}$NiIrO$_{6}$. Moreover, our test calculations find that in the otherwise
ideally cubic Y$_{2}$NiIrO$_{6}$, the Ni$^{+}$-Ir$^{5+}$ charge excitation is
forbidden, and only the abnormal Ni$^{3+}$-Ir$^{3+}$ excitation gives a weakly
ferromagnetic (FM) behavior. Furthermore, we find that owing to the crystal
field splitting, Hund exchange, and broad band formation in the highly
coordinated fcc sublattice, Ir$^{4+}$ ions are not in the $j_{\rm eff}=1/2$
state but in the $S=1/2$ state carrying a finite orbital moment by spin-orbit
coupling (SOC). This work clarifies the varying magnetism in Y$_{2}$NiIrO$_{6}$
and La$_{2}$NiIrO$_{6}$ associated with the lattice distortions.",2310.18641v2
2016-07-13,Dynamics of Stellar Spin Driven by Planets Undergoing Lidov-Kozai Migration: Paths to Spin-Orbit Misalignment,"Many exoplanetary systems containing hot Jupiters (HJs) exhibit significant
misalignment between the spin axes of the host stars and the orbital angular
momentum axes of the planets (""spin-orbit misalignment""). High-eccentricity
migration involving Lidov-Kozai oscillations of the planet's orbit induced by a
distant perturber is a possible channel for producing such misaligned HJ
systems. Previous works have shown that the dynamical evolution of the stellar
spin axis during the high-$e$ migration plays a dominant role in generating the
observed spin-orbit misalignment. Numerical studies have also revealed various
patterns of the evolution of the stellar spin axis leading to the final
misalignment. Here we develop an analytic theory to elucidate the evolution of
spin-orbit misalignment during the Lidov-Kozai migration of planets in stellar
binaries. Secular spin-orbit resonances play a key role in the misalignment
evolution. We include the effects of short-range forces and tidal dissipation,
and categorize the different possible paths to spin-orbit misalignment as a
function of various physical parameters (e.g. planet mass and stellar rotation
period). We identify five distinct spin-orbit evolution paths and outcomes,
only two of which are capable of producing retrograde orbits. We show that
these paths to misalignment and the outcomes depend only on two dimensionless
parameters, which compare the stellar spin precession frequency with the rate
of change of the planet's orbital axis, and the Lidov-Kozai oscillation
frequency. Our analysis reveals a number of novel phenomena for the stellar
spin evolution, ranging from bifurcation, adiabatic advection, to fully chaotic
evolution of spin-orbit angles.",1607.03937v1
2000-10-04,Spin Injection from Ferromagnetic Metals into Gallium Nitride,"The injection of spin polarized electrons from ferromagnetic metals (Fe and
Co) into gallium nitride (GaN) via scanning tunneling microscopy (STM) is
demonstrated. Electrons from STM tips are injected into the semiconductor. Net
circular polarization of the emitted light is observed, which changes sign on
reversal of the magnetization of the tip. The polarization is found to be in
qualitative agreement with that expected from considerations based on the
splitting of the valence bands due to spin-orbit coupling and the crystal field
splitting corresponding to the wurtzite structure, and the magnitude of the
spin polarization from the ferromagnetic metal. We find a lower bound for the
spin injection efficiency of 25%, corresponding to a net spin polarization in
the semiconductor of 10%. This is the largest reported value for a room
temperature measurement of spin injection into semiconductors in air.",0010058v1
2002-04-18,Spin-current modulation and square-wave transmission through periodically stubbed electron waveguides,"Ballistic spin transport through waveguides, with symmetric or asymmetric
double stubs attached to them periodically, is studied systematically in the
presence of a weak spin-orbit coupling that makes the electrons precess. By an
appropriate choice of the waveguide length and of the stub parameters injected
spin-polarized electrons can be blocked completely and the transmission shows a
periodic and nearly square-type behavior, with values 1 and 0, with wide gaps
when only one mode is allowed to propagate in the waveguide. A similar behavior
is possible for a certain range of the stub parameters even when two-modes can
propagate in the waveguide and the conductance is doubled. Such a structure is
a good candidate for establishing a realistic spin transistor. A further
modulation of the spin current can be achieved by inserting defects in a
finite-number stub superlattice. Finite-temperature effects on the spin
conductance are also considered.",0204415v1
2003-10-01,SU(2) Non-Abelian Holonomy and Dissipationless Spin Current in Semiconductors,"Following our previous work [S. Murakami, N. Nagaosa, S. C. Zhang, Science
301, 1348 (2003)] on the dissipationless quantum spin current, we present an
exact quantum mechanical calculation of this novel effect based on the linear
response theory and the Kubo formula. We show that it is possibxle to define an
exactly conserved spin current, even in the presence of the spin-orbit coupling
in the Luttinger Hamiltonian of p-type semiconductors. The light- and the
heavy-hole bands form two Kramers doublets, and an SU(2) non-abelian gauge
field acts naturally on each of the doublets. This quantum holonomy gives rise
to a monopole structure in momentum space, whose curvature tensor directly
leads to the novel dissipationless spin Hall effect, i.e., a transverse spin
current is generated by an electric field. The result obtained in the current
work gives a quantum correction to the spin current obtained in the previous
semiclassical approximation.",0310005v3
2004-07-26,Control of Electron Spin Coherence Using Landau Level Quantization in a Two-Dimensional Electron Gas,"Time-resolved optical measurements of electron spin dynamics in modulation
doped InGaAs quantum wells are used to explore electron spin coherence times
and spin precession frequencies in a regime where an out of plane magnetic
field quantizes the states of a two-dimensional electron gas into Landau
levels. Oscillatory features in the transverse spin coherence time and
effective g-factor as a function of applied magnetic field exhibit a
correspondence with Shubnikov-de Haas oscillations, illustrating a coupling
between spin and orbital eigenstates. We present a theoretical model in which
inhomogeneous dephasing due to the population of different Landau levels limits
the spin coherence time and captures the essential experimental results.",0407681v1
2004-08-29,Precessionless spin transport wire confined in quasi-two-dimensional electron systems,"We demonstrate that in an inversion-asymmetric two-dimensional electron
system 2DES with both Rashba and Dresselhaus spin-orbit couplings taken into
account, certain transport directions on which no spin precession occurs can be
found when the injected spin is properly polarized. By analyzing the
expectation value of spin with respect to the injected electron state on each
space point in the 2DES, we further show that the adjacent regions with
technically reachable widths along these directions exhibit nearly conserved
spin. Hence a possible application in semiconductor spintronics, namely,
precessionless spin transport wire, is proposed.",0408638v2
2004-10-27,Spin Hall Current Driven by Quantum Interferences in Mesoscopic Rashba Rings,"We propose an all-electrical nanoscopic structure where {\em pure} spin
current is induced in the transverse voltage probes attached to {\em
quantum-coherent} one-dimensional ring when conventional unpolarized charge
current is injected through its longitudinal leads. Tuning of the Rashba
spin-orbit coupling in semiconductor heterostructure hosting the ring generates
quasi-periodic oscillations of the predicted spin Hall current due to {\em
spin-sensitive quantum-interference effects} caused by the difference in
Aharonov-Casher phase acquired by opposite spins states traveling clockwise and
counterclockwise. Its amplitude is comparable to the mesoscopic spin Hall
current predicted for finite-size two-dimensional electron gases, while it gets
reduced in wide two-dimensional or disordered rings.",0410716v1
2005-07-21,"Datta-Das transistor: Significance of channel direction, size-dependence of source contacts, and boundary effects","We analyze the spin expectation values for injected spin-polarized electrons
(spin vectors) in a [001]-grown Rashba-Dresselhaus two-dimensional electron gas
(2DEG). We generalize the calculation for point spin injection in semi-infinite
2DEGs to finite-size spin injection in bounded 2DEGs. Using the obtained spin
vector formula, significance of the channel direction for the Datta-Das
transistor is illustrated. Numerical results indicate that the influence due to
the finite-size injection is moderate, while the channel boundary reflection
may bring unexpected changes. Both effects are concluded to decrease when the
spin-orbit coupling strength is strong. Hence [110] is a robust channel
direction and is therefore the best candidate for the design of the Datta-Das
transistor.",0507495v2
2006-08-25,Observation of electric current induced by optically injected spin current,"A normally incident light of linear polarization injects a pure spin current
in a strip of 2-dimensional electron gas with spin-orbit coupling. We report
observation of an electric current with a butterfly-like pattern induced by
such a light shed on the vicinity of a crossbar shaped InGaAs/InAlAs quantum
well. Its light polarization dependence is the same as that of the spin
current. We attribute the observed electric current to be converted from the
optically injected spin current caused by scatterings near the crossing. Our
observation provides a realistic technique to detect spin currents, and opens a
new route to study the spin-related science and engineering in semiconductors.",0608546v1
2003-05-01,Spin effects and baryon resonance dynamics in phi-meson photoproduction at few GeV,"The diffractive $\phi$-meson photoproduction amplitude is dominated by the
Pomeron exchange process and contains the terms that govern the spin-spin and
spin-orbital interactions.
  We show that these terms are responsible for the spin-flip transitions at
forward photoproduction angles and appear in the angular distributions of
$\phi\to K^+K^-$ -decay in reactions with unpolarized and polarized photon
beams.
  At large momentum transfers, the main contribution to the $\phi$-meson
photoproduction is found to be due to the excitation of nucleon resonances.
  Combined analysis of $\omega$ and $\phi$ photoproduction indicates strong
OZI-rule violation in $\phi NN^*$ - couplings.
  We also show that the spin observables are sensitive to the dynamics of
$\phi$-meson photoproduction at large angles and could help distinguish
different theoretical models of nucleon resonances.
  Predictions for spin effects in $\phi$-meson photoproduction are presented
for future experimental tests.",0305002v2
2009-02-02,Gauge-Invariant Formulation of Spin-Current-Density Functional Theory,"Spin-currents and non-abelian gauge potentials in electronic systems can be
treated by spin-current-density functional theory, whose main input is the
exchange-correlation (xc) energy expressed as a functional of spin-currents.
Constructing a functional of spin currents that is invariant under
U(1)$\times$SU(2) transformations is a long-standing challenge. We solve the
problem by expressing the energy as a functional of a new variable we call
""invariant vorticity"". As an illustration we construct the xc energy functional
for a two-dimensional electron gas with linear spin-orbit coupling and show
that it is proportional to the fourth power of the spin current.",0902.0374v2
2009-06-28,Topological winding properties of spin edge states in Kane-Mele graphene model,"We study the spin edge states in the quantum spin-Hall (QSH) effect on a
single-atomic layer graphene ribbon system with both intrinsic and Rashba
spin-orbit couplings. The Harper equation for solving the energies of the spin
edge states is derived. The results show that in the QSH phase, there are
always two pairs of gapless spin-filtered edge states in the bulk energy gap,
corresponding to two pairs of zero points of the Bloch function on the
complex-energy Riemann surface (RS). The topological aspect of the QSH phase
can be distinguished by the difference of the winding numbers of the spin edge
states with different polarized directions cross the holes of the RS, which is
equivalent to the Z2 topological invariance proposed by Kane and Mele [Phys.
Rev. Lett. 95, 146802 (2005)].",0906.5118v1
2009-07-14,Upstanding Rashba spin in honeycomb lattices: Electrically reversible surface spin polarization,"The spin-split states subject to Rashba spin-orbit coupling in
two-dimensional systems have long been accepted as pointing inplane and
perpendicular to the corresponding wave vectors. This is in general true for
free electron model, but exceptions do exist elsewhere. Within the
tight-binding model, we unveil the unusual upstanding behavior of those Rashba
spins around $\bar{K}$ and $\bar{K}^{\prime}$ points in honeycomb lattices. Our
calculation (i) explains the recent experiment of the Tl/Si(111)-$(1\times1)$
surface alloy [Phys. Rev. Lett. \textbf{102}, 096805 (2009)], where abrupt
upstanding spin states near $\bar{K}$ are observed, and (ii) predicts an
electrically reversible out-of-plane surface spin polarization.",0907.2411v3
2009-08-03,Direct Measurement of Quantum Dot Spin Dynamics using Time-Resolved Resonance Fluorescence,"We temporally resolve the resonance fluorescence from an electron spin
confined to a single self-assembled quantum dot to measure directly the spin's
optical initialization and natural relaxation timescales. Our measurements
demonstrate that spin initialization occurs on the order of microseconds in the
Faraday configuration when a laser resonantly drives the quantum dot
transition. We show that the mechanism mediating the optically induced
spin-flip changes from electron-nuclei interaction to hole-mixing interaction
at 0.6 Tesla external magnetic field. Spin relaxation measurements result in
times on the order of milliseconds and suggest that a $B^{-5}$ magnetic field
dependence, due to spin-orbit coupling, is sustained all the way down to 2.2
Tesla.",0908.0292v1
2009-09-28,Is there a dynamical cause of the spin-statistics connection?,"Extant proofs of the spin-statistics connection (SSC) are kinematical. C S
Unnikrishnan has suggested that a dynamical interaction leading to the SSC
would involve spin and perforce gravity, the only known universal force. For
the scattering of two identical particles, he considers [arXiv: gr-qc/0406043]
the interaction of their spins with the gravito-magnetic field generated by
their scattering motion through cosmic matter-energy. There the direct and
particles-exchanged scattering amplitudes accumulate different quantum phases
which provide the relevant bosonic/fermionic sign between them without applying
the ad hoc SSC rule. Here it is shown that the scattering probabilities given
by the standard implementation of SSC in quantum mechanics are actually not
obtained from the above interaction for most initial spin states of the
scattering particles. Instead, an unrealized peculiar dynamical interaction is
required. Further, a spin-gravito-magnetic interaction as above (with caveats)
would result in a large unmeasured spin-orbit coupling type effect on atomic
energy levels. A comparison with a typical rotation based proof is also
provided.",0909.5159v1
2009-11-07,Spin relaxation in multiple (110) quantum wells,"We consider theoretically the relaxation of electron spin component parallel
to the growth direction in multiple (110) GaAs quantum wells. The sources of
spin relaxation are the random Rashba spin-orbit coupling due to the electric
field of donors and spin-flip collisions of electrons from different quantum
wells. We show that the screening of the Coulomb forces at low temperatures
leads to a very strong enhancement of the spin relaxation time. In a degenerate
electron gas the Pauli blocking suppresses the electron-electron collisions,
and the leading spin relaxation mechanism comes from the field of donors. If
the electron gas is nondegenerate the electron-electron collisions and
scattering by the ionized donors give similar contributions to the relaxation
rate.",0911.1444v2
2009-11-25,Semiclassical dynamics and transport of the Dirac spin,"A semiclassical theory of spin dynamics and transport is formulated using the
Dirac electron model. This is done by constructing a wavepacket from the
positive-energy electron band, and studying its structure and center of mass
motion. The wavepacket has a minimal size equal to the Compton wavelength, and
has self-rotation about the average spin angular momentum, which gives rise to
the spin magnetic moment. Geometric gauge structure in the center of mass
motion provides a natural explanation of the spin-orbit coupling and various
Yafet terms. Applications of the spin-Hall and spin-Nernst effects are
discussed.",0911.4760v1
2010-02-17,Spin symmetry in Dirac negative energy spectrum in density-dependent relativistic Hartree-Fock theory,"The spin symmetry in the Dirac negative energy spectrum and its origin are
investigated for the first time within the density-dependent relativistic
Hartree-Fock (DDRHF) theory. Taking the nucleus $^{16}$O as an example, the
spin symmetry in the negative energy spectrum is found to be a good
approximation and the dominant components of the Dirac wave functions for the
spin doublets are nearly identical. In comparison with the relativistic Hartree
approximation where the origin of spin symmetry lies in the equality of the
scalar and vector potentials, in DDRHF the cancellation between the Hartree and
Fock terms is responsible for the better spin symmetry properties and
determines the subtle spin-orbit splitting. These conclusions hold even in the
case when significant deviations from the G-parity values of the
meson-antinucleon couplings occur.",1002.3309v1
2010-12-03,NMR and NQR study of the tetrahedral frustrated quantum spin system Cu2Te2O5Br2 in its paramagnetic phase,"The quantum antiferromagnet Cu2Te2O5Br2 was investigated by NMR and NQR. The
125Te NMR investigation showed that there is a magnetic transition around 10.5K
at 9T, in agreement with previous studies. From the divergence of the
spin-lattice relaxation rate, we ruled out the possibility that the transition
could be governed by a one-dimensional divergence of the spin-spin correlation
function. The observed anisotropy of the 125Te shift was shown to be due to a
spin polarization of the 5s2 ""E"" doublet of the [TeO3E] tetrahedra,
highlighting the importance of tellurium in the exchange paths. In the
paramagnetic state, Br NQR and NMR measurements led to the determination of the
Br hyperfine coupling and the electric field gradient tensor, and to the the
spin polarization of Br p orbitals. The results demonstrate the crucial role of
bromine in the interaction paths between Cu spins.",1012.0611v1
2011-02-22,Spin-Hall current and spin polarization in an electrically biased SNS Josephson junction,"Periodic in time spin-Hall current and spin polarization induced by a dc
electric bias has been calculated in a superconductor-normal
2DEG-superconductor (SNS) Josephson junction. We assumed that the band energies
of electrons in the normal system are splitted due to Rashba spin-orbit
coupling. The transport parameters have been calculated within the diffusion
approximation and using perturbation expansion over a small SN contact
transparency. We found out that in contrast to the stationary Josephson effect,
the spin-Hall current does not turn to zero. Besides a direct proximity effect
caused by Cooper pair's transition into a triplet state, the spin current and
polarization are also driven by a periodic electric field associated with the
charge imbalance.",1102.4446v2
2011-07-20,"Theory of the ground state spin of the NV- center in diamond: I. Fine structure, hyperfine structure, and interactions with electric, magnetic and strain fields","The ground state spin of the negatively charged nitrogen-vacancy center in
diamond has been the platform for the recent rapid expansion of new frontiers
in quantum metrology and solid state quantum information processing. In ambient
conditions, the spin has been demonstrated to be a high precision magnetic and
electric field sensor as well as a solid state qubit capable of coupling with
nearby nuclear and electronic spins. However, in spite of its many outstanding
demonstrations, the theory of the spin has not yet been fully developed and
there does not currently exist thorough explanations for many of its
properties, such as the anisotropy of the electron g-factor and the existence
of Stark effects and strain splittings. In this work, the theory of the ground
state spin is fully developed for the first time using the molecular orbital
theory of the center in order to provide detailed explanations for the spin's
fine and hyperfine structures and its interactions with electric, magnetic and
strain fields.",1107.3868v1
2012-03-23,Spin dynamics in a strongly driven system: very slow Rabi oscillations,"We consider joint effects of tunneling and spin-orbit coupling on driven by
electric field spin dynamics in a double quantum dot with a multi-level
resonance scenario. We demonstrate that tunneling plays the crucial role in the
formation of the Rabi-like spin-flip transitions. In contrast to the linear
behavior for weak electric fields, the spin flip rate becomes much smaller than
expected for the two-level model and shows oscillating dependence on the
driving field amplitude in stronger fields. In addition, the full spin flip is
very difficult to achieve in a multi-level resonant system. These two effects
have a similarity with the Zeno effect of slowing down the dynamics of an
observable by its measurement. As a result, spin manipulation by electric field
becomes much less efficient than expected.",1203.5287v1
2012-03-25,Spin polarization direction switch based on an asymmetrical quantum wire,"A scheme for a spin polarization direction switch is investigated by studying
the spin-dependent electron transport of an asymmetrical quantum wire (QW) with
Rashba spin-orbit coupling (SOC). It is found that the magnitude of the
spin-polarized current in the backward biased case is equal to it in the
forward biased case but their signs are contrary. This results indicate that
the spin polarization direction can be switched by changing the direction of
the external current. The physical mechanism of this device may arise from the
symmetries in the longitudinal and transverse directions are broken but
$C_2$-rotation and time-reversal symmetries are still reserved. Further studies
show that the spin polarization is robust against disorder, displaying the
feasibility of the proposed structure for a potential application.",1203.5472v1
2012-06-12,Magnetic Moment Formation in Graphene Detected by Scattering of Pure Spin Currents,"Hydrogen adatoms are shown to generate magnetic moments inside single layer
graphene. Spin transport measurements on graphene spin valves exhibit a dip in
the non-local spin signal as a function of applied magnetic field, which is due
to scattering (relaxation) of pure spin currents by exchange coupling to the
magnetic moments. Furthermore, Hanle spin precession measurements indicate the
presence of an exchange field generated by the magnetic moments. The entire
experiment including spin transport is performed in an ultrahigh vacuum
chamber, and the characteristic signatures of magnetic moment formation appear
only after hydrogen adatoms are introduced. Lattice vacancies also demonstrate
similar behavior indicating that the magnetic moment formation originates from
pz-orbital defects.",1206.2628v3
2012-06-23,Spin-Valley Optical Selection Rule and Strong Circular Dichroism in Silicene,"Silicene (a monolayer of silicon atoms) is a topological insulator, which
undergoes a topological phase transition to a band insulator under an external
electric field. The spin polarization is unique and opposite at the K and K'
points due to the spin-orbit coupling. Accordingly, silicene exhibits a strong
circular dichroism with respect to optical absorption, obeying a certain
spin-valley selection rule. It is remarkable that this selection rule is
drastically different between these two types of insulators owing to a band
inversion taking place at the phase transition point. Hence we can tell
experimentally whether silicene is in the topological or band insulator phase
by circular dichroism. Furthermore the selection rule enables us to excite
electrons with definite spin and valley indices by optical absorption.
Photo-induced current is spin polarized, where the spin direction is different
between the topological and band insulators. It is useful for future
spintronics applications.",1206.5378v1
2012-09-10,Intrinsic spin Hall effect in monolayers of group-VI dichalcogenides: A first-principles study,"Using first-principles calculations within density functional theory, we
investigate the intrinsic spin Hall effect in monolayers of group-VI
transition-metal dichalcogenides MX2 (M = Mo, W and X = S, Se). MX2 monolayers
are direct band-gap semiconductors with two degenerate valleys located at the
corners of the hexagonal Brillouin zone. Because of the inversion symmetry
breaking and the strong spin-orbit coupling, charge carriers in opposite
valleys carry opposite Berry curvature and spin moment, giving rise to both a
valley- and a spin-Hall effect. The intrinsic spin Hall conductivity (ISHC) in
p-doped samples is found to be much larger than the ISHC in n-doped samples due
to the large spin-splitting at the valence band maximum. We also show that the
ISHC in inversion-symmetric bulk dichalcogenides is an order of magnitude
smaller compared to monolayers. Our result demonstrates monolayer
dichalcogenides as an ideal platform for the integration of valleytronics and
spintronics.",1209.1964v2
2013-03-20,Anomalous D'yakonov-Perel' spin relaxation in semiconductor quantum wells under strong magnetic field in Voigt configuration,"We report an anomalous scaling of the D'yakonov-Perel' spin relaxation with
the momentum relaxation in semiconductor quantum wells under a strong magnetic
field in the Voigt configuration. We focus on the case that the external
magnetic field is perpendicular to the spin-orbit-coupling--induced effective
magnetic field and its magnitude is much larger than the later one. It is found
that the longitudinal spin relaxation time is proportional to the momentum
relaxation time even in the strong scattering limit, indicating that the
D'yakonov-Perel' spin relaxation shows the Elliott-Yafet-like behaviour.
Moreover, the transverse spin relaxation time is inversely proportional
(proportional) to the momentum relaxation time in the weak (strong) scattering
limit, both in the opposite trends against the well-established conventional
D'yakonov-Perel' spin relaxation behaviours. We further demonstrate that all
the above anomalous scaling relations come from the unique form of the
effective inhomogeneous broadening.",1303.4944v3
2013-03-24,Spin-Transfer Torques in Helimagnets,"We theoretically investigate current-induced magnetization dynamics in
chiral-lattice helimagnets. Spin-orbit coupling in non-centrosymmetric crystals
induces a reactive spin-transfer torque that has not been previously
considered. We demonstrate how the torque is governed by the crystal symmetry
and acts as an effective magnetic field along the current direction in cubic
B20-type crystals. The effects of the new torque are computed for
current-induced dynamics of spin-spirals and the Doppler shift of spin waves.
In current-induced spin-spiral motion, the new torque tilts the spiral
structure. The spin waves of the spiral structure are initially displaced by
the new torque, while the dispersion relation is unaffected.",1303.5921v2
2014-02-18,Hidden spin polarization in inversion-symmetric bulk crystals,"Spin-orbit coupling (SOC) can induce spin polarization in nonmagnetic 3D
crystals when the inversion symmetry is broken, as manifested by the bulk
Rashba (R-1) and Dresselhaus (D-1) effects. We determine that these spin
polarization effects originate fundamentally from specific atomic site
asymmetries, rather than from the generally accepted asymmetry of the crystal
space-group. This understanding leads to the recognition that a previously
overlooked hidden form of spin polarization should exist in centrosymmetric
materials. Although all energy bands must be doubly degenerate in
centrosymmetric materials, we find that the two components of such doubly
degenerate bands could have opposite polarizations each spatially localized on
one of the two separate sectors forming the inversion partners. We demonstrate
such hidden spin polarizations in centrosymmetric crystals (denoted as R-2 and
D-2) by first-principles calculations. This new understanding could
considerably broaden the range of currently useful spintronic materials and
enable control of spin polarization via operations on atomic scale.",1402.4446v1
2014-04-28,Spin Texture and Mirror Chern number in Hg-Based Chalcogenides,"The unique feature of surface states in topological insulators is the
so-called ""spin-momentum locking"", which means that electron spin is oriented
along a fixed direction for a given momentum and forms a texture in the
momentum space. In this work, we study spin textures of two typical topological
insulators in Hg-Based Chalcogenides, namely HgTe and HgS, based on both the
first principles calculation and the eight band Kane model. We find opposite
helicities of spin textures between these two materials, originating from the
opposite signs of spin-orbit couplings. Furthermore, we reveal that different
mirror Chern numbers between HgTe and HgS characterize different topological
natures of the systems with opposite spin textures and guarantee the existence
of gapless interface states.",1404.7091v3
2014-08-07,Relation Between the Spin Hall Conductivity and the Spin Chern Number for Dirac-like Systems,"A semiclassical formulation of the spin Hall effect for physical systems
satisfying Dirac-like equation is introduced. We demonstrated that the main
contribution to the spin Hall conductivity is given by the spin Chern number
whether the spin is conserved or not at the quantum level. We illustrated the
formulation within the Kane-Mele model of graphene in the absence and in the
presence of the Rashba spin-orbit coupling term.",1408.1596v3
2014-10-15,Realizing unconventional quantum magnetism with symmetric top molecules,"We demonstrate that ultracold symmetric top molecules loaded into an optical
lattice can realize highly tunable and unconventional models of quantum
magnetism, such as an XYZ Heisenberg spin model. We show that anisotropic
dipole-dipole interactions between molecules can lead to effective spin-spin
interactions which exchange spin and orbital angular momentum. This exchange
produces effective spin models which do not conserve magnetization and feature
tunable degrees of spatial and spin-coupling anisotropy. In addition to
deriving pure spin models when molecules are pinned in a deep optical lattice,
we show that models of itinerant magnetism are possible when molecules can
tunnel through the lattice. Additionally, we demonstrate rich tunability of the
effective models' parameters using only a single microwave frequency, in
contrast to proposals with $^1\Sigma$ diatomic molecules, which often require
many microwave frequencies. Our results are germane not only for experiments
with polyatomic symmetric top molecules, such as methyl fluoride (CH$_3$F), but
also diatomic molecules with an effective symmetric top structure, such as the
hydroxyl radical OH.",1410.4226v1
2014-11-21,Multiple Quantum Phases in Graphene with Enhanced Spin-Orbit Coupling: From the Quantum Spin Hall Regime to the Spin Hall Effect and a Robust Metallic State,"We report an intriguing transition from the quantum spin Hall phase to the
spin Hall effect upon segregation of thallium adatoms adsorbed onto a graphene
surface. Landauer-B\""uttiker and Kubo-Greenwood simulations are used to access
both edge and bulk transport physics in disordered thallium-functionalized
graphene systems of realistic sizes. Our findings not only quantify the
detrimental effects of adatom clustering in the formation of the topological
state, but also provide evidence for the emergence of spin accumulation at
opposite sample edges driven by spin-dependent scattering induced by thallium
islands, which eventually results in a minimum bulk conductivity $\sim
4e^{2}/h$, insensitive to localization effects.",1411.5837v2
2014-12-12,Photon-assisted electronic and spin transport in a junction containing precessing molecular spin,"We study the ac charge and -spin transport through an orbital of a magnetic
molecule with spin precessing in a constant magnetic field. We assume that the
source and drain contacts have time-dependent chemical potentials. We employ
the Keldysh nonequilibrium Green's functions method to calculate the spin and
charge currents to linear order in the time-dependent potentials. The molecular
and electronic spins are coupled via exchange interaction. The time-dependent
molecular spin drives inelastic transitions between the molecular quasienergy
levels, resulting in a rich structure in the transport characteristics. The
time-dependent voltages allow us to reveal the internal precession time scale
(the Larmor frequency) by a dc conductance measurement if the ac frequency
matches the Larmor frequency. In the low-ac-frequency limit the junction
resembles a classical electric circuit. Furthermore, we show that the setup can
be used to generate dc-spin currents, which are controlled by the molecular
magnetization direction and the relative phases between the Larmor precession
and the ac voltage.",1412.3994v2
2015-01-06,Berry-phase effects and electronic dynamics in noncollinear antiferromagnetic texture,"Antiferromagnets (AFMs), in contrast to ferromagnets, show a nontrivial
magnetic structure with zero net magnetization. However, they share a number of
spintronic effects with ferromagnets, including spin-pumping and spin transfer
torques. Both phenomena stem from the coupled dynamics of free carriers and
localized magnetic moments. In the present paper I study the adiabatic dynamics
of a spin-polarized electrons in a metallic AFM exhibiting a noncollinear
120$^\circ$ magnetic structure. I show that the slowly varying AFM spin texture
produces a non-Abelian gauge potential related to the time/space gradients of
the N\'{e}el vectors. Corresponding emergent electric and magnetic fields
induce rotation of spin and influence the orbital dynamics of free electrons. I
discuss both the possibility of a topological spin Hall effect in the vicinity
of topological AFM solitons with nonzero curvature and rotation of the electron
spin traveling through the AFM domain wall.",1501.01189v2
2014-08-26,Post-Newtonian dynamics basing on Mathisson-Papapetrou equations with Corinaldesi-Papapetrou condition in Kerr spacetime,"We derive the post-Newtonian dynamics for a spinning body with
Corinaldesi-Papapetrou spin supplementary condition in Kerr spacetime. Both the
equations of motion for the center-of-mass of body and the spin evolution are
obtained. For the non-relativistic case, our calculations show that the
magnitude of spin measured in the rest frame of the body's center-of-mass does
not change with time, though the center-of-mass does not move along the
geodesic. Moreover, we find that the effects of the spin-orbit and spin-spin
couplings will be suppressed by the Lorentz factor when the body has a
relativistic velocity.",1504.02049v3
2015-05-20,Effect of Transverse Magnetic Field on Dynamics of Current Driven Domain Wall Motion in the Presence of Spin-Hall Effect,"Theoretically, we study the dynamics of a current induced domain wall in the
bi-layer structure consists of a ferromagnetic layer and a non-magnetic metal
layer with strong spin-orbit coupling in the presence of spin-Hall effect. The
analytical expressions for the velocity and width of the domain wall interms of
excitation angle are obtained by solving the Landau-Lifshitz-Gilbert equation
with adiabatic, nonadiabatic and spin Hall effect-spin transfer torques using
Schryers and Walker's method. Numerical results show that the occurance of
polarity switching in the domain wall is observed only above the threshold
current density. The presence of transverse magnetic field along with spin Hall
effect-spin transfer torque enchances the value of the threshold current
density, and the corresponding saturated velocity at the threshold current
density is also increased.",1505.05249v1
2015-09-25,Geometrical spin manipulation in Dirac flakes,"We investigate numerically the spin properties of electrons in flakes made of
materials described by the Dirac equation, at the presence of intrinsic
spin-orbit-coupling(SOC). We show that electrons flowing along the borders of
flakes via edge states, become helically spin-polarized for strong SOC, for
materials with and without a gap at the Fermi energy, corresponding to the
massive and massless Dirac equation respectively. The helically spin-polarized
electrons cause geometrical spin splitting on opposite sides of the flakes,
leading to spin-resolved transport controlled by the flake's geometry in a
multi-terminal device setup. A simple analytical model containing the basic
ingredients of the problem is introduced to get an insight of the helical
mechanism, along with our numerical results which are based on an effective
tight-binding model.",1509.07654v1
2016-01-27,Observation of magnon-mediated current drag in Pt/yttrium iron garnet/Pt(Ta) trilayers,"Pure spin current, a flow of spin angular momentum without flow of any
companying net charge, is generated in two common ways. One makes use of the
spin Hall effect in normal metals (NM) with strong spin-orbit coupling, such as
Pt or Ta. The other utilizes the collective motion of magnetic moments or spin
waves with the quasi-particle excitations called magnons. A popular material
for the latter is yttrium iron garnet, a magnetic insulator (MI). Here we
demonstrate in NM/MI/NM trilayers that these two types of spin currents are
interconvertible across the interfaces, predicated as the magnon-mediated
current drag phenomenon. The transmitted signal scales linearly with the
driving current without a threshold and follows the power-law with n ranging
from 1.5 to 2.5. Our results indicate that the NM/MI/NM trilayer structure can
serve as a scalable pure spin current valve device which is an essential
ingredient in spintronics.",1601.07429v1
2016-02-09,Transporting a single-spin qubit through a double quantum dot,"Coherent spatial transport or shuttling of a single electron spin through
semiconductor nanostructures is an important ingredient in many spintronic and
quantum computing applications. In this work we analyze the possible errors in
solid-state quantum computation due to leakage in transporting a single-spin
qubit through a semiconductor double quantum dot. In particular, we consider
three possible sources of leakage errors associated with such transport: finite
ramping times, spin-dependent tunneling rates between quantum dots induced by
finite spin-orbit couplings, and the presence of multiple valley states. In
each case we present quantitative estimates of the leakage errors, and discuss
how they can be minimized. Moreover, we show that in order to minimize leakage
errors induced by spin-dependent tunnelings, it is necessary to apply pulses to
perform certain carefully designed spin rotations. We further develop a
formalism that allows one to systematically derive constraints on the pulse
shapes and present a few examples to highlight the advantage of such an
approach.",1602.03179v1
2016-04-11,All-Optical Study of Tunable Ultrafast Spin Dynamics in [Co/Pd]-NiFe Systems: The Role of Spin-Twist Structure on Gilbert Damping,"We investigate optically induced ultrafast magnetization dynamics in [Co(0.5
nm)/Pd(1 nm)]x5/NiFe(t) exchange-spring samples with tilted perpendicular
magnetic anisotropy using a time-resolved magneto-optical Kerr effect
magnetometer. The competition between the out-of-plane anisotropy of the hard
layer, the in-plane anisotropy of the soft layer and the applied bias field
reorganizes the spins in the soft layer, which are modified further with the
variation in t. The spin-wave spectrum, the ultrafast demagnetization time, and
the extracted damping coefficient all depend on the spin distribution in the
soft layer, while the latter two also depend on the spin-orbit coupling between
the Co and Pd layers. The spin-wave spectra change from multimode to
single-mode as t increases. At the maximum field reached in this study, H=2.5
kOe, the damping shows a nonmonotonic dependence on t with a minimum at t=7.5
nm. For t<7.5 nm, intrinsic effects dominate, whereas for t>7.5 nm, extrinsic
effects govern the damping mechanisms.",1604.02998v1
2017-08-06,Asymmetric Andreev resonant state with a magnetic exchange field in spin-triplet superconducting monolayer $MoS_2$,"Featuring spin-valley degree of freedom by a magnetic exchange
field-induction to gain transport of charge carriers through a junction based
on superconducting subgap tunneling can provide a new scenario for future
electronics. Transmission of low-energy Dirac-like electron (hole)
quasiparticles through a ferromagnet/superconductor (F/S) interface can be of
noticeable importance due to strong spin-orbit coupling in the valence band of
monolayer $MoS_2$ (ML-MDS). The magnetic exchange field (MEF) of a
ferromagnetic section on top of ML-MDS may affect the electron (hole)
excitations for spin-up and spin-down electrons, differently. Tuning the MEF
enables one to control either electrical properties (such as band gap, SOC and
etc.) or spin-polarized transport. We study the influence of MEF on the
chirality of Andreev resonant state (ARS) appearing at the relating F/S
interface, in which the induced pairing order parameter is chiral $p$-wave
symmetry. The resulting normal conductance is found to be more sensitive to the
magnitude of MEF and doping regime of F region. Unconventional spin-triplet
$p$-wave symmetry features the zero-bias conductance, which strongly depends on
$p$-doping level of F region in the relating NFS junction.",1708.01863v1
2020-07-03,Quantification of interfacial spin-charge conversion in metal/insulator hybrid structures by generalized boundary conditions,"We present and verify experimentally a universal theoretical framework for
the description of spin-charge interconversion in non-magnetic metal/insulator
structures with interfacial spin-orbit coupling (ISOC). Our formulation is
based on drift-diffusion equations supplemented with generalized boundary
conditions. The latter encode the effects of ISOC and relate the electronic
transport in such systems to spin loss and spin-charge interconversion at the
interface, which are parameterized, respectively, by $G_{\parallel/\perp}$ and
$\sigma_{\rm{sc/cs}}$. We demonstrate that the conversion efficiency depends
solely on these interfacial parameters. We apply our formalism to two typical
spintronic devices that exploit ISOC: a lateral spin valve and a multilayer
Hall bar, for which we calculate the non-local resistance and the spin Hall
magnetoresistance, respectively. Finally, we perform measurements on these two
devices with a BiO$_x$/Cu interface and verify that transport properties
related to the ISOC are quantified by the same set of interfacial parameters.",2007.01596v1
2010-05-07,Controlling the spin orientation of photoexcited electrons by symmetry breaking,"We study reflection of optically spin-oriented hot electrons as a means to
probe the semiconductor crystal symmetry and its intimate relation with the
spin-orbit coupling. The symmetry breaking by reflection manifests itself by
tipping the net-spin vector of the photoexcited electrons out of the light
propagation direction. The tipping angle and the pointing direction of the
net-spin vector are set by the crystal-induced spin precession, momentum
alignment and spin-momentum correlation of the initial photoexcited electron
population. We examine non-magnetic semiconductor heterostructures and
semiconductor/ferromagnet systems and show the unique signatures of these
effects.",1005.1280v3
2013-08-15,Spin-Wave Propagation in the Presence of Interfacial Dzyaloshinskii-Moriya Interaction,"In ferromagnetic thin films, broken inversion symmetry and spin-orbit
coupling give rise to interfacial Dzyaloshinskii-Moriya interactions. Analytic
expressions for spin-wave properties show that the interfacial
Dzyaloshinskii-Moriya interaction leads to non-reciprocal spin-wave
propagation, i.e. different properties for spin waves propagating in opposite
directions. In favorable situations, it can increase the spin-wave attenuation
length. Comparing measured spin wave properties in ferromagnet$|$normal metal
bilayers and other artificial layered structures with these calculations can
provide a useful characterization of the interfacial Dzyaloshinskii-Moriya
interactions.",1308.3341v1
2013-08-15,Detection of the microwave spin pumping using the inverse spin Hall effect,"We report electrical detection of the dynamical part of the spin pumping
current emitted during ferromagnetic resonance (FMR) using the inverse Spin
Hall Effect (ISHE). The experiment is performed on a YIG$|$Pt bilayer. The
choice of YIG, a magnetic insulator, ensures that no charge current flows
between the two layers and only pure spin current produced by the magnetization
dynamics are transferred into the adjacent strong spin-orbit Pt layer via spin
pumping. To avoid measuring the parasitic eddy currents induced at the
frequency of the microwave source, a resonance at half the frequency is induced
using parametric excitation in the parallel geometry. Triggering this nonlinear
effect allows to directly detect on a spectrum analyzer the microwave component
of the ISHE voltage. Signals as large as 30 $\mu$V are measured for precession
angles of a couple of degrees. This direct detection provides a novel efficient
means to study magnetization dynamics on a very wide frequency range with great
sensitivity.",1308.3433v2
2016-10-31,Signature of Hanle Precession in Trilayer MoS2: Theory and Experiment,"Valley-spin coupling in transition-metal dichalcogenides (TMDs) can result in
unusual spin transport behaviors under an external magnetic field. Nonlocal
resistance measured from 2D materials such as TMDs via electrical Hanle
experiments are predicted to exhibit nontrivial features, compared with results
from conventional materials due to the presence of intervalley scattering as
well as a strong internal spin-orbit field. Here, for the first time, we report
the all-electrical injection and non-local detection of spin polarized carriers
in trilayer MoS_2 films. We calculate the Hanle curves theoretically when the
separation between spin injector and detector is much larger than spin
diffusion length, \lamda_s. The experimentally observed curve matches the
theoretically-predicted Hanle shape under the regime of slow intervalley
scattering. The estimated spin life-time was found to be around 110 ps at 30 K.",1611.00059v1
2017-01-18,Conversion of electronic to magnonic spin current at heavy-metal magnetic-insulator interface,"Electronic spin current is convertible to magnonic spin current via the
creation or annihilation of thermal magnons at the interface of a magnetic
insulator and a metal with a strong spin-orbital coupling. So far this
phenomenon was evidenced in the linear regime. Based on analytical and
fulledged numerical results for the non-linear regime we demonstrate that the
generated thermal magnons or magnonic spin current in the insulator is
asymmetric with respect to the charge current direction in the metal and
exhibits a nonlinear dependence on the charge current density, which is
explained by the tuning effect of the spin Hall torque and the magnetization
damping. The results are also discussed in light of and are in line with recent
experiments pointing to a new way of non-linear manipulation of spin with
electrical means.",1701.05148v1
2018-05-21,Spin Response and Collective Modes in Simple Metal Dichalcogenides,"Transition metal dichalcogenide (TMD) monolayers are interesting materials in
part because of their strong spin-orbit coupling. This leads to intrinsic
spin-splitting of opposite signs in opposite valleys, so the valleys are
intrinsically spin-polarized when hole-doped. We study spin response in a
simple model of these materials, with an eye to identifying sharp collective
modes (i.e, spin-waves) that are more commonly characteristic of ferromagnets.
We demonstrate that such modes exist for arbitrarily weak repulsive
interactions, even when they are too weak to induce spontaneous ferromagnetism.
The behavior of the spin response is explored for a range of hole dopings and
interaction strengths.",1805.08223v2
2008-07-24,Nonlinear electron and spin transport in semiconductor superlattices,"Nonlinear charge transport in strongly coupled semiconductor superlattices is
described by Wigner-Poisson kinetic equations involving one or two minibands.
Electron-electron collisions are treated within the Hartree approximation
whereas other inelastic collisions are described by a modified BGK
(Bhatnaghar-Gross-Krook) model. The hyperbolic limit is such that the collision
frequencies are of the same order as the Bloch frequencies due to the electric
field and the corresponding terms in the kinetic equation are dominant. In this
limit, spatially nonlocal drift-diffusion balance equations for the miniband
populations and the electric field are derived by means of the Chapman-Enskog
perturbation technique. For a lateral superlattice with spin-orbit interaction,
electrons with spin up or down have different energies and their corresponding
drift-diffusion equations can be used to calculate spin-polarized currents and
electron spin polarization. Numerical solutions show stable self-sustained
oscillations of the current and the spin polarization through a voltage biased
lateral superlattice thereby providing an example of superlattice spin
oscillator.",0807.3900v1
2012-04-22,Spin Hall effect versus Rashba torque: a Diffusive Approach,"Current-driven magnetization dynamics of single ferromagnets in heavy
metal/ferromagnet bilayers has been recently realized. In this work, spin
torque induced by so-called Rashba spin-orbit coupling and spin Hall effect are
considered within a diffusive model. The dependence of the resulting torque as
a function of the thicknesses of the ferromagnet and heavy metal is analyzed.
We show that (i) both torques are on the form ${\bf T}=T_{||}{\bf m}\times{\bf
y}+T_\bot{\bf m}\times({\bf y}\times{\bf m})$, (ii) the ratio $T_{||}/T_\bot$
strongly depends on the thickness of the layers and (iii) the thickness
dependence of the spin torque provides an indication of the origin of the
(Rashba- or spin Hall effect-induced) spin torque .",1204.4869v1
2015-12-17,Graphene-based spin switch device via modulated Rashba field and strain,"We investigate the spin-resolved transport in a two-terminal zigzag graphene
nanoribbon device with two independent gate induced Rashba spin-orbit coupling
regions and in the presence of strain. By employing a recursive Green's
function technique to the tight-binding model for the graphene nanoribbon, we
calculate the spin-resolved conductance of the system. We show that by
switching the sign of one of the gates it is possible to select which spin
component will be transmitted. Moreover, our results show that an uniaxial
strain applied to the nanoribbon plays a significant role in the transport,
providing and additional manner to control the spin-polarized conductance. This
makes the present system a potential candidate for future implementations of
spin-based mechanical strain sensors.",1512.05436v2
2017-06-12,Quantum spin liquid in the semiclassical regime,"Quantum spin liquids have been at the forefront of correlated electron
research ever since their original proposal in 1973, and the realization that
they belong to the broader class of intrinsic topological orders, along with
the fractional quantum Hall states. According to received wisdom, quantum spin
liquids can arise in frustrated magnets with low spin $S$, where strong quantum
fluctuations act to destabilize conventional, magnetically ordered states. Here
we present a magnet that has a $Z_2$ quantum spin liquid ground state already
in the semiclassical, large-$S$ limit. The state has both topological and
symmetry related ground state degeneracy, and two types of gaps, a `magnetic
flux' gap that scales linearly with $S$ and an `electric charge' gap that drops
exponentially in $S$. The magnet is described by the spin-$S$ version of the
spin-1/2 Kitaev honeycomb model, which has been the subject of intense studies
in correlated electron systems with strong spin-orbit coupling, and in optical
lattice realizations with ultracold atoms. The results apply to both integer
and half-integer spins.",1706.03756v2
2017-06-22,The perfect spin injection in silicene FS/NS junction,"We theoretically investigate the spin injection from a ferromagnetic silicene
to a normal silicene (FS/NS), where the magnetization in the FS is assumed from
the magnetic proximity effect. Based on a silicene lattice model, we
demonstrated that the pure spin injection could be obtained by tuning the Fermi
energy of two spin species, where one is in the spin orbit coupling gap and the
other one is outside the gap. Moreover, the valley polarity of the spin species
can be controlled by a perpendicular electric field in the FS region. Our
findings may shed light on making silicene-based spin and valley devices in the
spintronics and valleytronics field.",1706.07278v1
2017-10-26,Itinerant spin fluctuations in iron-based superconductors,"Multiband systems, which possess a wide parameter space, allow to explore a
variety of competing ground states. Bright examples are the Fe-based pnictides
and chalcogenides, which demonstrate metallic, superconducting, and various
magnetic phases. Here I discuss only one of the many interesting topics,
namely, spin fluctuations in metallic multiband systems. I show how to
calculate the effect of itinerant spin excitations on the electronic properties
and formulate a theory of spin fluctuation-induced superconductivity. The
superconducting state is unconventional and thus the system demonstrates
unusual spin response with the spin resonance feature. I discuss its origin,
consequences, and relation to experimental observations. Role of the spin-orbit
coupling is specifically emphasized.",1710.09888v1
2019-07-13,Ab initio modelling of spin relaxation lengths in disordered graphene nanoribbons†,"The spin-dependent transport properties of armchair graphene nanoribbons in
the presence of extrinsic spin-orbit coupling induced by a random distribution
of Nickel adatoms is studied. By combining a recursive Green's function
formalism with density functional theory, we explore the influence of ribbon
length and metal adatom concentration on the conductance. At a given length, we
observed a significant enhancement of the spin-flip channel around resonances
and at energies right above the Fermi level. We also estimate the
spin-relaxation length, finding values on the order of tens of micrometers at
low Ni adatom concentrations. This study is conducted at singular ribbon
lengths entirely from fully ab-initio methods, providing indirectly evidence
that the Dyakonov-Perel spin relaxation mechanism might be the dominant at low
concentrations as well as the observation of oscillations in the
spin-polarization.",1907.05979v1
2020-12-08,Pure spin current injection of single-layer monochalcogenides,"We compute the spectrum of pure spin current injection in ferroelectric
single-layer SnS, SnSe, GeS, and GeSe. The formalism takes into account the
coherent spin dynamics of optically excited conduction states split in energy
by spin orbit coupling. The velocity of spins is calculated as a function of
incoming photon energy and angle of linearly polarized light within a full
electronic band structure scheme using density functional theory. We find peak
speeds of 250, 210, 180 and 154 Km/s for SnS, SnSe, GeS and GeSe, respectively
which are an order of magnitude larger than those found in bulk semiconductors,
e.g., CdSe and GaAs. Interestingly, the spin velocity is independent of the
direction of polarization of light in a range of photon energies. Our results
demonstrate that single-layer SnS, SnSe, GeS and GeSe are candidates to produce
on demand spin-velocity injection for spintronics applications.",2012.04604v1
2017-05-10,Interplay of valley polarization and dynamic nuclear polarization in 2D transition metal dichalcogenides,"The interplay of Ising spin-orbit coupling and non-trivial band topology in
transition metal dichalcogenides (TMDs) produces anomalous transport and
optical properties that are very different from a regular 2D electron gas. The
spin-momentum locking of optically excited carriers near a valley point can
give rise to an anomalous spin-valley Hall current under the application of an
in-plane electric field. TMDs also exhibit strong electron-nuclear hyperfine
interactions, but their effect on spin-valley-locked currents remains unknown.
Here, we show that hyperfine interactions can create a feedback mechanism in
which spin-valley currents generate significant dynamical nuclear polarization
which in turn Zeeman shifts excitonic transitions out of resonance with an
optical driving field, saturating the production of spin-valley polarization.
We propose an experimental signature of dynamic nuclear polarization which can
be detected via measurements of the anomalous Hall current. Our results help to
elucidate the interplay of valley polarization and nuclear spin dynamics in
TMDs.",1705.03909v2
2017-05-24,Covariant conservation laws and the spin Hall effect in Dirac-Rashba systems,"We present a theoretical analysis of two-dimensional Dirac-Rashba systems in
the presence of disorder and external perturbations. We unveil a set of exact
symmetry relations (Ward identities) that impose strong constraints on the spin
dynamics of Dirac fermions subject to proximity-induced interactions. This
allows us to demonstrate that an arbitrary dilute concentration of scalar
impurities results in the total suppression of nonequilibrium spin Hall
currents when only Rashba spin-orbit coupling is present. Remarkably, a finite
spin Hall conductivity is restored when the minimal Dirac-Rashba model is
supplemented with a spin-valley interaction. The Ward identities provide a
systematic way to predict the emergence of the spin Hall effect in a wider
class of Dirac-Rashba systems of experimental relevance and represent an
important benchmark for testing the validity of numerical methodologies.",1705.08898v2
2017-09-22,Multiple odd-frequency superconducting states in buckled quantum spin Hall insulators with time-reversal symmetry,"We consider a buckled quantum spin Hall insulator (QSHI), such as silicene,
proximity-coupled to a conventional spin-singlet, s-wave superconductor. Even
limiting the discussion to the disorder-robust s-wave pairing symmetry, we find
both odd-frequency ($\omega$), spin-singlet and spin-triplet pair amplitudes
and where both preserve time-reversal symmetry. Our results show that there are
two unrelated mechanisms generating these different odd-$\omega$ pair
amplitudes. The spin-singlet state is due to the strong inter-orbital processes
present in the QSHI. It is exists generically at the edges of the QSHI, but
also in the bulk in heavily doped regime if an electric field is applied. The
spin-triplet state requires a finite gradient in the proximity-induced
superconducting order along the edge, which we find is automatically generated
at the atomic scale for armchair edges but not at zigzag edges. In combination
these results make superconducting QSHIs a very exciting venue for
investigating not only the existence of odd-$\omega$ superconductivity, but
also the interplay between different odd-$\omega$ states.",1709.07835v2
2018-03-08,Competing spin transfer and dissipation at Co/Cu(001) interfaces on femtosecond timescales,"By combining interface-sensitive non-linear magneto-optical experiments with
femtosecond time resolution and ab-initio time-dependent density functional
theory, we show that optically excited spin dynamics at Co/Cu(001) interfaces
proceeds via spin-dependent charge transfer and backtransfer between Co and Cu.
This ultrafast spin transfer competes with dissipation of spin angular momentum
mediated by spin-orbit coupling already on sub 100 fs timescales. We thereby
identify the fundamental microscopic processes during laser-induced spin
transfer at a model interface for technologically relevant ferromagnetic
heterostructures.",1803.03090v3
2018-03-27,Magneto-Electric Effect in a Spin-State Transition System,"Magnetic, dielectric, and magnetoelectric properties in a spin-state
transition system are examined, motivated by the recent discovery of a
multiferroic behavior in a cobalt oxide. We construct an effective model
Hamiltonian based on the two-orbital Hubbard model, in which the spin-state
degrees of freedom in magnetic ions couple with ferroelectric-type lattice
distortions. A phase transition occurs from the high-temperature low-spin phase
to the low-temperature high-spin ferroelectric phase with accompanying an
increase of the spin entropy. The calculated results are consistent with the
experimental pressure-temperature phase diagram. We predict the magnetic-field
induced electric polarization in the low-spin paraelectric phase near the
ferroelectric phase boundary.",1803.09881v1
2018-08-28,Theory of charge-spin conversion at oxide interfaces: The inverse spin-galvanic effect,"We evaluate the non-equilibrium spin polarization induced by an applied
electric field for a tight-binding model of electron states at oxides
interfaces in LAO/STO heterostructures. By a combination of analytic and
numerical approaches we investigate how the spin texture of the electron
eigenstates due to the interplay of spin-orbit coupling and inversion asymmetry
determines the sign of the induced spin polarization as a function of the
chemical potential or band filling, both in the absence and presence of local
disorder. With the latter, we find that the induced spin polarization evolves
from a non monotonous behavior at zero temperature to a monotonous one at
higher temperature. Our results may provide a sound framework for the
interpretation of recent experiments.",1808.09157v1
2018-12-11,Semiclassical conservation of spin and large transverse spin current in Dirac systems,"In Dirac materials, the low energy excitations obey the relativistic Dirac
equation. This dependence implies that the electrons are exposed to strong
spin-orbit coupling. Hence, real spin conservation is believed to be violated
in Dirac materials. We show that this point of view needs to be refined in the
semiclassical picture which applies to the case of doped Dirac materials (away
from the nodal point in the spectrum). We derive a novel type of Boltzmann
equation for these systems if they are brought slightly out-of-equilibrium.
Remarkably, spin-momentum locking is softened and a generalized spin
conservation law can be formulated. The most striking observable consequence of
our theory is a large transverse spin current in a nearly ballistic transport
regime.",1812.04493v2
2019-03-03,Theory for spin torque in Weyl semimetal with magnetic texture,"The spin-transfer torque is a fundamental physical quantity to operate the
spintronics devices such as racetrack memory. We theoretically study the
spin-transfer torque and analyze the dynamics of the magnetic domain walls in
magnetic Weyl semimetals. Owing to the strong spin-orbit coupling in Weyl
semimetals, the spin-transfer torque can be significantly enhanced, because of
which they can provide a more efficient means of controlling magnetic textures.
We derive the analytical expression of the spin-transfer torque and find that
the velocity of the domain wall is one order of magnitude greater than that of
conventional ferromagnetic metals. Furthermore, due to the suppression of
longitudinal conductivity in the thin domain-wall configuration, the
dissipation due to Joule heating for the spin-transfer torque becomes much
smaller than that in bulk metallic ferromagnets. Consequently, the fast-control
of the domain wall can be achieved with smaller dissipation from Joule heating
in the Weyl semimetals as required for application to low-energy-consumption
spintronics devices.",1903.00849v1
2019-03-04,Weak localization in boron nitride encapsulated bilayer MoS$_2$,"We present measurements of weak localization on hexagonal boron nitride
encapsulated bilayer MoS$_2$. From the analysis we obtain information regarding
the phase-coherence and the spin diffusion of the electrons. We find that the
encapsulation with boron nitride provides higher mobilities in the samples, and
the phase-coherence shows improvement, while the spin relaxation does not
exhibit any significant enhancement compared to non-encapsulated MoS$_2$. The
spin relaxation time is in the order of a few picoseconds, indicating a fast
intravalley spin-flip rate. Lastly, the spin-flip rate is found to be
independent from electron density in the current range, which can be explained
through counteracting spin-flip scattering processes based on electron-electron
Coulomb scattering and extrinsic Bychkov-Rashba spin-orbit coupling.",1903.01536v1
2019-04-16,Spontaneous generation of spin current from the vacuum by strong electric fields,"We discuss spontaneous spin current generation from the vacuum by strong
electric fields as a result of interplay between the Schwinger mechanism and a
spin-orbit coupling. By considering a homogeneous slow strong electric field
superimposed by a fast weak transverse electric field, we explicitly evaluate
the vacuum expectation value of a spin current (the Bargmann-Wigner spin
current) by numerically solving the Dirac equation. We show that a
non-vanishing spin current polarized in the direction perpendicular to the
electric fields flows mostly in the longitudinal direction. We also find that a
relativistic effect due to the helicity conservation affects
direction/polarization of spin current.",1904.07593v2
2020-08-20,Anisotropic ultrafast spin/valley dynamics in WTe2 films,"WTe2 Weyl semimetal hosts the natural broken inversion symmetry and strong
spin orbit coupling, making it promising for exotic spin/valley dynamics within
a picosecond timescale. Here, we unveil an anisotropic ultrafast spin/valley
dynamics in centimeter-scale, single-crystalline Td-WTe2 films using a
femtosecond pump-probe technique at room temperature. We observe a transient
(~0.8 ps) intra-valley transition and a subsequent polarization duration (~5
ps) during the whole spin/valley relaxation process. Furthermore, the
relaxation exhibits the remarkable anisotropy of approximately six-fold and
two-fold symmetries due to the intrinsic anisotropy along the crystalline
orientation and the extrinsic matrix element effect, respectively. Our results
offer a prospect for the ultrafast manipulation of spin/valleytronics in
topological quantum materials for dissipationless high-speed spin/valleytronic
devices.",2008.08785v2
2020-10-22,Spin-polarized tunable photocurrents,"Harnessing the unique features of topological materials for the development
of a new generation of topological based devices is a challenge of paramount
importance. Using Floquet scattering theory combined with atomistic models we
study the interplay between laser illumination, spin and topology in a
two-dimensional material with spin-orbit coupling. Starting from a topological
phase, we show how laser illumination can selectively disrupt the topological
edge states depending on their spin. This is manifested by the generation of
pure spin currents and spin-polarized charge photocurrents under linearly and
circularly polarized laser-illumination, respectively. Our results open a path
for the generation and control of spin-polarized photocurrents.",2010.11883v2
2020-11-13,Interface enhanced helicity dependent photocurrent in metal/semimetal bilayers,"One of the hallmarks of light-spin interaction in solids is the appearance of
photocurrent that depends on the light helicity. Recent studies have shown that
helicity dependent photocurrent (HDP) emerges due to light induced spin current
and the inverse spin Hall effect of semimetal thin films. We have studied HDP
in metal/semimetal bilayers. Compared to Bi single layer films, we find the HDP
is enhanced in metal/Bi bilayers. For the bilayers, the sign of HDP under back
illumination reverses from that of front illumination. The back illumination
photocurrent is the largest for Ag/Bi bilayers among the bilayers studied.
Using a diffusive spin transport model, we show that the HDP sign reversal
under back illumination is caused by spin absorption and spin to charge
conversion at the interface. Such interfacial effects contribute to the HDP
enhancement under front illumination for the bilayers when the Bi layer
thickness is small. These results show that the HDP can be used to assess
interface states with strong spin orbit coupling.",2011.06786v1
2021-04-09,Strong anomalous proximity effect from spin-singlet superconductors,"The proximity effect from a spin-triplet $p_x$-wave superconductor to a dirty
normal-metal has been shown to result in various unusual electromagnetic
properties, reflecting a cooperative relation between topologically protected
zero-energy quasiparticles and odd-frequency Cooper pairs. However, because of
a lack of candidate materials for spin-triplet $p_x$-wave superconductors,
observing this effect has been difficult. In this paper, we demonstrate that
the anomalous proximity effect, which is essentially equivalent to that of a
spin-triplet $p_x$-wave superconductor, can occur in a semiconductor/high-$T_c$
cuprate superconductor hybrid device in which two potentials coexist: a
spin-singlet $d$-wave pair potential and a spin--orbit coupling potential
sustaining the persistent spin-helix state. As a result, we propose an
alternative and promising route to observe the anomalous proximity effect
related to the profound nature of topologically protected quasiparticles and
odd-frequency Cooper pairs.",2104.04246v2
2016-03-15,A Realization of the Haldane-Kane-Mele Model in a System of Localized Spins,"We theoretically study a spin Hamiltonian for spin-orbit-coupled ferromagnets
on the honeycomb lattice. We find that the effective Hamiltonian for magnons, a
quanta of spin-wave excitations from ordered states, is equivalent to the
Haldane model for electrons in the honeycomb lattice, which indicates the
nontrivial topology of the magnon bands and the existence of the associated
edge state. We also take the Schwinger boson (or bosonic spinon)
representations of spins that are applicable both to ordered and disordered
phases. We show that the spinon bands within the mean-field treatment are
topologically nontrivial, which causes a spin Nernst effect, by adopting the
properties of the Kane-Mele model. A feasible experimental realization of the
spin Hamiltonian is proposed.",1603.04827v2
2016-10-02,Spin galvanic effect at the conducting SrTiO3 surfaces,"The (001) surface of SrTiO3 were transformed from insulating to conducting
after Ar+ irradiation, producing a quasi two-dimensional electron gas (2DEG).
This conducting surface layer can introduce Rashba spin orbital coupling due to
the broken inversion symmetry normal to the plane. The spin splitting of such a
surface has recently been demonstrated by magneto-resistance and angular
resolved photoemission spectra measurements. Here we present experiments
evidencing a large spin-charge conversion at the surface. We use spin pumping
to inject a spin current from NiFe film into the surface, and measure the
resulting charge current. The results indicate that the Rashba effect at the
surface can be used for efficient charge-spin conversion, and the large
efficiency is due to the multi-d-orbitals and surface corrugation. It holds
great promise in oxide spintronics.",1610.00249v1
2017-11-02,Single Magnetic Impurity in Tilted Dirac Surface States,"We utilize variational method to investigate the Kondo screening of a
spin-1/2 magnetic impurity in tilted Dirac surface states with the Dirac cone
tilted along the $k_y$-axis. We mainly study about the effect of the tilting
term on the binding energy and the spin-spin correlation between magnetic
impurity and conduction electrons, and compare the results with the
counterparts in a two dimensional helical metal. The binding energy has a
critical value while the Dirac cone is slightly tilted. However, as the tilting
term increases, the density of states around the Fermi surface becomes
significant, such that the impurity and the host material always favor a bound
state. The diagonal and the off-diagonal terms of the spin-spin correlation
between the magnetic impurity and conduction electrons are also studied. Due to
the spin-orbit coupling and the tilting of the spectra, various components of
spin-spin correlation show very strong anisotropy in coordinate space, and are
of power-law decay with respect to the spatial displacements.",1711.00634v2
2017-11-04,Spin excitation anisotropy in optimal-isovalent-doped superconductor BaFe2(As0.7P0.3)2,"We use neutron polarization analysis to study spin excitation anisotropy in
the optimal-isovalent-doped superconductor BaFe2(As0.7P0.3)2 (Tc = 30 K).
Different from optimally hole and electron-doped BaFe2As2, where there is a
clear spin excitation anisotropy in the paramagnetic tetragonal state well
above Tc, we find no spin excitation anisotropy for energies above 2 meV in the
normal state of BaFe2(As0.7P0.3)2. Upon entering the superconducting state,
significant spin excitation anisotropy develops at the antiferromagnetic (AF)
zone center QAF = (1, 0, L = odd), while magnetic spectrum is isotropy at the
zone boundary Q = (1, 0, L = even). By comparing temperature, wave vector, and
polarization dependence of the spin excitation anisotropy in BaFe2(As0.7P0.3)2
and hole-doped Ba0.67K0.33Fe2As2 (Tc = 38 K), we conclude that such anisotropy
arises from spin-orbit coupling and is associated with the nearby AF order and
superconductivity.",1711.01497v1
2018-10-01,Giant Intrinsic Spin Hall Effect in W$_3$Ta and other A15 Superconductors,"The spin Hall effect (SHE) is the conversion of charge current to spin
current, and non-magnetic metals with large SHEs are extremely sought after for
spintronic applications, but their rarity has stifled widespread use. Here we
predict and explain the large intrinsic SHE in $\beta$-W and the A15 family of
superconductors: W$_3$Ta, Ta$_3$Sb, and Cr$_3$Ir having spin hall
conductivities (SHC) of -2250, -1400, and 1210 $\frac{\hbar}{e}(\Omega
cm)^{-1}$, respectively. Combining concepts from topological physics with the
dependence of the SHE on the spin Berry curvature (SBC) of the electronic
bands, we propose a simple strategy to rapidly search for materials with large
intrinsic SHEs based on the following ideas: high symmetry combined with heavy
atoms gives rise to multiple Dirac-like crossings in the electronic structure,
without sufficient symmetry protection these crossings gap due to spin orbit
coupling (SOC), and gapped Dirac crossings create large spin Berry curvature.",1810.00858v1
2019-05-29,Highly conductive and complete spin filtering of nickel atomic contacts in a nitrogen atmosphere,"Generating efficient and highly spin-polarized currents through nanoscale
junctions is essential in the field of nanoelectronics and spintronics. In this
paper, using $ab$ $initio$ electron transport calculations, we predict highly
conductive and perfect spin filtering of nickel atomic contacts in a nitrogen
environment, where a single N$_2$ molecule sits in parallel (energetically most
favorable) between two nickel electrodes. Such a particular performance is due
to the wave function orthogonality between majority spin $s$-like states of
ferromagnetic electrodes and the lowest unoccupied molecular orbital of the
N$_2$ molecule, and thus, majority spin electrons are completely blocked at the
interface. For the minority spin, on the contrary, two almost saturated
conducting channels were formed due to the effective coupling between
$d_{zx,zy}$ of the Ni atom and $p_{x,y}$ of the N atom, resulting in large
conductance of about 1$G_0$ ($=2e^2/h$). As a consequence, a single N$_2$
molecule acts as a highly conductive and half-metallic conductor. On the other
hand, the CO and NO incorporated molecular junctions exhibit rather low
conductance with a partially spin-polarized current.",1905.12606v1
2020-06-17,Sustainable spin current in the time-dependent Rashba system,"The generation of spin current and spin polarization in 2DEG Rashba system is
considered, in which the spin-orbital coupling (SOC) is modulated by an ac gate
voltage. By using non-Abelian gauge field method, we show the presence of an
additional electric field. This field induces a spin current generated even in
the presence of impurity scattering and is related to the time-modulation of
the Rashba SOC strength. In addition, the spin precession can be controlled by
modulating the modulation frequency of the Rashba SOC strength. It is shown
that at high modulation frequency, the precessional motion is suppressed so
that the electron spin polarization can be sustained in the 2DEG",2006.09644v1
2021-03-16,All-electrical Magnon Transport Experiments in Magnetically Ordered Insulators,"Angular momentum transport is one of the cornerstones of spintronics. Spin
angular momentum is not only transported by mobile charge carriers, but also by
the quantized excitations of the magnetic lattice in magnetically ordered
systems. In this regard, magnetically ordered insulators provide a platform for
magnon spin transport experiments without additional contributions from spin
currents carried by mobile electrons. In combination with charge-to-spin
current conversion processes in conductors with finite spin-orbit coupling it
is possible to realize all-electrical magnon transport schemes in thin film
heterostructures. This review provides an insight into such experiments and
recent breakthroughs achieved. Special attention is given to charge current
based manipulation via an adjacent normal metal of magnon transport in
magnetically ordered insulators in terms of spin-transfer torque. Moreover, the
influence of two magnon modes with opposite spin in antiferromagnetic
insulators on all-electrical magnon transport experiments is discussed.",2103.08996v2
2021-05-15,Neutron--proton spin--spin correlations in the ground states of N=Z nuclei,"We present expressions for the matrix elements of the spin--spin operator
$\vec S_{\rm n}\cdot\vec S_{\rm p}$ in a variety of coupling schemes. These
results are then applied to calculate the expectation value $\langle\vec S_{\rm
n}\cdot\vec S_{\rm p}\rangle$ in eigenstates of a schematic Hamiltonian
describing neutrons and protons interacting in a single-$l$ shell through a
Surface Delta Interaction. The model allows us to trace $\langle\vec S_{\rm
n}\cdot\vec S_{\rm p}\rangle$ as a function of the competition between the
isovector and isoscalar interaction strengths and the spin--orbit splitting of
the $j=l\pm \frac{1}{2}$ shells. We find negative $\langle\vec S_{\rm
n}\cdot\vec S_{\rm p}\rangle$ values in the ground state of all even--even
$N=Z$ nuclei, contrary to what has been observed in hadronic inelastic
scattering at medium energies. We discuss the possible origin of this
discrepancy and indicate directions for future theoretical and experimental
studies related to neutron--proton spin--spin correlations.",2105.07267v1
2021-07-06,Direct X-ray detection of the spin Hall effect in CuBi,"The spin Hall effect and its inverse are important spin-charge conversion
mechanisms. The direct spin Hall effect induces a surface spin accumulation
from a transverse charge current due to spin orbit coupling even in
non-magnetic conductors. However, most detection schemes involve additional
interfaces, leading to large scattering in reported data. Here we perform
interface free x-ray spectroscopy measurements at the Cu L_{3,2} absorption
edges of highly Bi-doped Cu (Cu_{95}Bi_{5}). The detected X-ray magnetic
circular dichroism (XMCD) signal corresponds to an induced magnetic moment of
(2.7 +/- 0.5) x 10-12 {\mu}_{B} A^{-1} cm^{2} per Cu atom averaged over the
probing depth, which is of the same order as for Pt measured by magneto-optics.
The results highlight the importance of interface free measurements to assess
material parameters and the potential of CuBi for spin-charge conversion
applications.",2107.02620v1
2021-12-29,Topological spin texture of chiral edge states in photonic two-dimensional quantum walks,"Topological insulators host topology-linked boundary states, whose spin and
charge degrees of freedom could be exploited to design topological devices with
enhanced functionality. We experimentally observe that dissipationless chiral
edge states in a spin-orbit coupled anomalous Floquet topological phase exhibit
topological spin texture on boundaries, realized via a two-dimensional quantum
walk. Our experiment shows that, for a walker traveling around a closed loop
along the boundary in real space, its spin evolves and winds through a great
circle on the Bloch sphere, which implies that edge-spin texture has nontrivial
winding. This winding is linked to the bulk Dirac Hamiltonian around the
energy-gap opening point. Our experiment confirms that two-dimensional
anomalous Floquet topological systems exhibit topological spin texture on the
boundary, which could inspire novel topology-based spintronic phenomena and
devices.",2112.14563v2
2022-06-19,Charge-to-spin conversion in twisted graphene/WSe$_2$ heterostructures,"We investigate the twist angle dependence of spin-orbit coupling (SOC)
proximity effects and charge-to-spin conversion (CSC) in graphene/WSe$_2$
heterostructures from first principles. The CSC is shown to strongly depend on
the twist angle, with both the spin Hall and standard Rashba-Edelstein
efficiencies optimized at or near 30{\deg} twisting. Symmetry breaking due to
twisting also gives rise to an unconventional Rashba-Edelstein effect, with
electrically generated non-equilibrium spin densities possessing spins
collinear to the applied electric field. We further discuss how the carrier
doping concentration and band broadening control the crossover between the
Fermi-sea and -surface spin response, which reconciles the seemingly disparate
experimental observations of different CSC phenomena.",2206.09478v1
2022-07-19,"Magnetic interactions in AB-stacked kagome lattices: magnetic structure, symmetry, and duality","We present the results of an extensive study of the phase diagram and spin
wave excitations for a general spin model on a hexagonal AB-stacked kagome
system. The boundaries of the magnetic phases are determined via a combination
of numerical (Monte Carlo) and analytical (Luttinger-Tisza) methods. We also
determine the phase coexistence regions by considering the instabilities in the
spin wave spectra. Depending on the strength of the spin-orbit coupling (SOC),
some spin and lattice rotations become decoupled, leading to considerably
larger symmetry groups than typical magnetic groups. Thus, we provide a
detailed symmetry description of the magnetic Hamiltonian with negligible,
weak, and intermediate strength of SOC. The spin symmetry in these three cases
has a strong effect on the splittings observed in the spin excitation spectra.
We further identify a number of self-duality transformations that map the
Hamiltonian onto itself. These transformations describe the symmetry of the
parameter space and provide an exact mapping between the properties of
different magnetic orders and lead to accidental degeneracies. Finally, we
discuss the physical relevance of our findings in the context of
$\mathrm{Mn}_3X$ compounds.",2207.09297v1
2022-08-10,Efficient spin-to-charge interconversion in Weyl semimetal TaP at room temperature,"In this paper we present spin-to-charge current conversion properties in the
Weyl semimetal TaP by means of the inverse Rashba-Edelstein effect (IREE) with
the integration of this quantum material with the ferromagnetic metal Permalloy
$(Py=Ni_{81}Fe_{19})$. The spin currents are generated in the Py layer by the
spin pumping effect (SPE) from microwave-driven ferromagnetic resonance and are
detected by a dc voltage along the TaP crystal, at room temperature. We observe
a field-symmetric voltage signal without the contamination of asymmetrical
lines due to spin rectification effects observed in studies using metallic
ferromagnets. The observed voltage is attributed to spin-to-charge current
conversion based on the IREE, made possible by the spin-orbit coupling induced
intrinsically by the bulk band structure of Weyl semimetals. The measured IREE
coefficient ${\lambda}_{IREE}=(0.30 \pm{0.01})$ nm is two orders of magnitude
larger than in graphene and is comparable to or larger than the values reported
for some metallic interfaces and for several topological insulators.",2208.05151v1
2022-08-19,Spectroscopy of spin-split Andreev levels in a quantum dot with superconducting leads,"We use a hybrid superconductor-semiconductor transmon device to perform
spectroscopy of a quantum dot Josephson junction tuned to be in a spin-1/2
ground state with an unpaired quasiparticle. Due to spin-orbit coupling, we
resolve two flux-sensitive branches in the transmon spectrum, depending on the
spin of the quasi-particle. A finite magnetic field shifts the two branches in
energy, favoring one spin state and resulting in the anomalous Josephson
effect. We demonstrate the excitation of the direct spin-flip transition using
all-electrical control. Manipulation and control of the spin-flip transition
enable the future implementation of charging energy protected Andreev spin
qubits.",2208.09314v2
2022-09-08,Kramers Fulde-Ferrell state and superconducting spin diode effect,"We study a novel Fulde-Ferrell equal-spin pairing state with opposite center
of mass Cooper pair momentum for each spin polarization. This state respects
time-reversal symmetry and is dubbed a Kramers Fulde-Ferrell (KFF) state. It
can be realized in a one-dimensional system with spin-orbit coupling and
nearest neighbor attraction. We find that the KFF state supports nonreciprocal
spin transport for both bulk superconductor and Josephson junctions when
inversion symmetry is broken. In addition to the spin Josephson diode effect,
the charge transport is controlled by intriguing dynamics of bound states whose
transitions can be manipulated by the length of the KFF superconductor. We
discuss the relevance of the effective theory to the novel physics observed in
monolayer Fe-based superconductor along line defects and domain walls, and the
potential for using spins to make dissipationless superconducting spintronics.",2209.03520v3
2023-02-22,Magnetic switching of spin-scattering centers in Dresselhaus [110] circuits,"Spin carriers subject to Dresselhaus [110] (D110) spin-orbit coupling (SOC)
gather null spin phases in closed circuits, contrary to usual Rashba and
Dresselhaus [001] SOC. We show that D110 spin phases can be activated in square
circuits by introducing an in-plane Zeeman field, where localized field
inhomogeneities act as effective spin-scattering centers. Our simulations show
rich interference patterns in the quantum conductance, which work as maps for a
geometric classification of the propagating spin states. We also find that
disorder facilitates low-field implementations.",2302.11271v2
2023-09-13,Spin-valley entangled quantum Hall states in graphene,"We investigate interaction-driven integer quantum Hall states realized in
Landau levels of monolayer graphene when two out of its four nearly degenerate
spin-valley flavors are filled. By employing a model that accounts for
interactions beyond pure delta-functions as well as Zeeman and
substrate-induced valley potentials, we demonstrate the existence of a delicate
competition of several phases with spontaneous generation of spin-valley
entanglement, akin to the spontaneous appearance of spin-orbit coupling driven
by interactions. We encounter a particular phase that we term the
entangled-Kekul\'{e}-antiferromagnet (E-KD-AF) which only becomes spin-valley
entangled under the simultaneous presence of Zeeman and substrate potentials,
because it gains energy by simultaneously canting in the spin and valley
spaces, by combining features of a canted anti-ferromagnet and a canted
Kekul\'{e} state. We quantify the degree of spin-valley entanglement of the
many competing phases by computing their bipartite concurrence.",2309.07217v1
2024-02-08,Modulation of magnetization in BiFeO$_3$ using circularly polarized light,"BiFeO$_3$ is a multiferroic material featuring ferroelectricity and
noncollinear antiferromagnetism, the latter manifested as a cycloid of spin
density. Definitive and efficient control of the characteristic spin texture of
BiFeO$_3$ is attractive for emerging quantum devices. In this regard,
crystal-field $d\rightarrow d$ excitations localized on Fe atomic sites in
BiFeO$_3$ provide an avenue for manipulation of the spin texture as they induce
a complex interplay among the spin, charge, and lattice degrees of freedom. In
this work, the ab initio GW-BSE method is used to characterize these
excitations within an excitonic picture. We find that the $d-d$ transitions
appear as strongly bound, chiral, spin-flip excitons deep within the electronic
band gap as a result of the intricate competition between the lattice
potential, the antiferromagnetic ordering, the spin-orbit coupling, and the
electron-hole interaction. Most crucially, these excitons are composed of
electron-hole pairs with opposite spins that constitute almost all of their
$\pm \hbar$ total angular momentum. These excitons of specific angular momentum
can be selectively excited using circularly polarized light, consequently
modulating the local magnetic moment giving rise to transient ferrimagnetism.",2402.05430v2
2024-02-22,Non-relativistic spin splitting in compensated magnets that are not altermagnets,"The non-relativistic spin-splitting (NRSS) of electronic bands in
""altermagnets"" has sparked renewed interest in antiferromagnets (AFMs) that
have no net magnetization. However, altermagnets with collinear and compensated
magnetism are not the only type of NRSS AFMs. In this study, we identify the
symmetry conditions and characteristic signatures of a distinct group of NRSS
AFMs that go beyond the description of altermagnets. These compounds exhibit a
broken spin-degeneracy among the spin-polarized bands at the $\Gamma$ point in
the absence of spin-orbit coupling (SOC). We use density functional theory
calculations to validate these models in ternary magnetic nitrides,
specifically MnXN$_2$ (X = Si, Ge, Sn), and their cation ordered variants. By
removing the previous NRSS constraint on $\Gamma$, these compounds may
facilitate the generation of spin currents without cancellation arising from
the alternating spin polarizations. Our findings expand the scope of NRSS
eligible materials.",2402.14321v1
2005-03-25,Spin-Hall effect in two-dimensional mesoscopic hole systems,"The spin Hall effect in two dimensional hole systems is studied by using the
four-terminal Landauer-B\""{u}ttiker formula with the help of Green functions.
The spin Hall effect exists even when there are {\em not} any correlations
between the spin-up and -down heavy holes (light holes) and when the
$\Gamma$-point degeneracy of the heavy hole and light hole bands is lifted by
the confinement or recovered by the strain. When only a heavy hole charge
current without any spin polarization is injected through one lead, under right
choice of lead voltages, one can get a pure heavy (light) hole spin current,
combined with a possible impure light (heavy) hole spin current from another
two leads. The spin Hall coefficients of both heavy and light holes depend on
the Fermi energy, devise size and the disorder strength. It is also shown that
the spin Hall effect of two dimensional hole systems is much more robust than
that of electron systems with the Rashba spin-orbit coupling and the spin Hall
coefficients do not decrease with the system size but tend to some nonzero
values when the disorder strength is smaller than some critical value.",0503616v4
2008-04-15,Multi-valley spin relaxation in the presence of high in-plane electric fields in $n$-type GaAs quantum wells,"Multi-valley spin relaxation in $n$-type GaAs quantum wells with in-plane
electric field is investigated at high temperature by means of kinetic spin
Bloch equation approach. The spin relaxation time first increases and then
decreases with electric field, especially when the temperature is relatively
low. We show that $L$ valleys play the role of a ``drain'' of the total spin
polarization due to the large spin-orbit coupling in $L$ valleys and the strong
$\Gamma$-$L$ inter-valley scattering, and thus can enhance spin relaxation of
the total system effectively when the in-plane electric field is high. Under
electric field, spin precession resulting from the electric-field-induced
magnetic field is observed. Meanwhile, due to the strong $\Gamma$-$L$
inter-valley scattering as well as the strong inhomogeneous broadening in $L$
valleys, electron spins in $L$ valleys possess almost the same damping rate and
precession frequency as those in $\Gamma$ valley. This feature still holds when
a finite static magnetic field is applied in Voigt configuration, despite that
the $g$-factor of $L$ valleys is much larger than that of $\Gamma$ valley.
Moreover, it is shown that the property of spin precession of the whole system
is dominated by electrons in $\Gamma$ valley. Temperature, magnetic field, and
impurity can affect spin relaxation in low electric field regime. However, they
are shown to have marginal influence in high electric field regime.",0804.2309v2
2009-08-09,Topological Surface States Protected From Backscattering by Chiral Spin Texture,"Topological insulators are a new class of insulators in which a bulk gap for
electronic excitations is generated by strong spin orbit coupling. These novel
materials are distinguished from ordinary insulators by the presence of gapless
metallic boundary states, akin to the chiral edge modes in quantum Hall
systems, but with unconventional spin textures. Recently, experiments and
theoretical efforts have provided strong evidence for both two- and
three-dimensional topological insulators and their novel edge and surface
states in semiconductor quantum well structures and several Bi-based compounds.
A key characteristic of these spin-textured boundary states is their
insensitivity to spin-independent scattering, which protects them from
backscattering and localization. These chiral states are potentially useful for
spin-based electronics, in which long spin coherence is critical, and also for
quantum computing applications, where topological protection can enable
fault-tolerant information processing. Here we use a scanning tunneling
microscope (STM) to visualize the gapless surface states of the
three-dimensional topological insulator BiSb and to examine their scattering
behavior from disorder caused by random alloying in this compound. Combining
STM and angle-resolved photoemission spectroscopy, we show that despite strong
atomic scale disorder, backscattering between states of opposite momentum and
opposite spin is absent. Our observation of spin-selective scattering
demonstrates that the chiral nature of these states protects the spin of the
carriers; they therefore have the potential to be used for coherent spin
transport in spintronic devices.",0908.1247v1
2010-08-15,Spin relaxation in $n$-type (111) GaAs quantum wells,"We investigate the spin relaxation limited by the D'yakonov-Perel' mechanism
in $n$-type (111) GaAs quantum wells, by means of the kinetic spin Bloch
equation approach. In (111) GaAs quantum wells, the in-plane effective magnetic
field from the D'yakonov-Perel' term can be suppressed to zero on a special
momentum circle under the proper gate voltage, by the cancellation between the
Dresselhaus and Rashba spin-orbit coupling terms. When the spin-polarized
electrons mainly distribute around this special circle, the in-plane
inhomogeneous broadening is small and the spin relaxation can be suppressed,
especially for that along the growth direction of quantum well. This
cancellation effect may cause a peak (the cancellation peak) in the density or
temperature dependence of the spin relaxation time. In the density
(temperature) dependence, the interplay between the cancellation peak and the
ordinary density (Coulomb) peak leads to rich features of the density
(temperature) dependence of the spin relaxation time. The effect of impurities,
with its different weights on the cancellation peak and the Coulomb peak in the
temperature dependence of the spin relaxation, is revealed. We also show the
anisotropy of the spin relaxation with respect to the spin-polarization
direction.",1008.2516v1
2012-08-02,"Importance of exchange-anisotropy and superexchange for the spin-state transitions in LnCoO3 (Ln=La,Y,RE) cobaltates","Spin-state transitions are the hallmark of rare-earth cobaltates. In order to
understand them, it is essential to identify all relevant parameters which
shift the energy balance between spin states, and determine their trends. We
find that \Delta, the eg-t2g crystal-field splitting, increases by ~250 meV
when increasing pressure to 8 GPa and by about 150 meV when cooling from 1000K
to 5K. It changes, however, by less than 100 meV when La is substituted with
another rare earth. Also the Hund's rule coupling J_avg is about the same in
systems with very different spin-state transition temperature, like LaCoO3 and
EuCoO3. Consequently, in addition to \Delta and J_avg, the Coulomb-exchange
anisotropy \Delta J_ avg and the super-exchange energy-gain \Delta E_SE play a
crucial role, and are comparable with spin-state dependent relaxation effects
due to covalency. We show that in the LnCoO3 series, with Ln=Y or a rare earth
(RE), super-exchange progressively stabilizes a low-spin ground state as the
Ln^{3+} ionic radius decreases. We give a simple model to describe spin-state
transitions and show that, at low temperature, the formation of isolated
high-spin/low-spin pairs is favored, while in the high-temperature phase, the
most likely homogeneous state is high-spin, rather than intermediate spin. An
orbital-selective Mott state could be a fingerprint of such a state.",1208.0425v1
2016-07-14,Quantum many-body theory for electron spin decoherence in nanoscale nuclear spin baths,"Decoherence of electron spins in nanoscale systems is important to quantum
technologies such as quantum information processing and magnetometry. It is
also an ideal model problem for studying the crossover between quantum and
classical phenomena. At low temperatures or in light-element materials where
the spin-orbit coupling is weak, the phonon scattering in nanostructures is
less important and the fluctuations of nuclear spins become the dominant
decoherence mechanism for electron spins. Since 1950s, semiclassical noise
theories have been developed for understanding electron spin decoherence. In
spin-based solid-state quantum technologies, the relevant systems are in the
nanometer scale and the nuclear spin baths are quantum objects which require a
quantum description. Recently, quantum pictures have been established to
understand the decoherence and quantum many-body theories have been developed
to quantitatively describe this phenomenon. Anomalous quantum effects have been
predicted and some have been experimentally confirmed. A systematically
truncated cluster correlation expansion theory has been developed to account
for the many-body correlations in nanoscale nuclear spin baths that are built
up during the electron spin decoherence. The theory has successfully predicted
and explained a number of experimental results in a wide range of physical
systems. In this review, we will cover these recent progresses. The limitations
of the present quantum many-body theories and possible directions for future
development will also be discussed.",1607.03993v3
2017-02-20,Valley dependent anisotropic spin splitting in silicon quantum dots,"Spin qubits hosted in silicon (Si) quantum dots (QD) are attractive due to
their exceptionally long coherence times and compatibility with the silicon
transistor platform. To achieve electrical control of spins for qubit
scalability, recent experiments have utilized gradient magnetic fields from
integrated micro-magnets to produce an extrinsic coupling between spin and
charge, thereby electrically driving electron spin resonance (ESR). However,
spins in silicon QDs experience a complex interplay between spin, charge, and
valley degrees of freedom, influenced by the atomic scale details of the
confining interface. Here, we report experimental observation of a valley
dependent anisotropic spin splitting in a Si QD with an integrated micro-magnet
and an external magnetic field. We show by atomistic calculations that the
spin-orbit interaction (SOI), which is often ignored in bulk silicon, plays a
major role in the measured anisotropy. Moreover, inhomogeneities such as
interface steps strongly affect the spin splittings and their valley
dependence. This atomic-scale understanding of the intrinsic and extrinsic
factors controlling the valley dependent spin properties is a key requirement
for successful manipulation of quantum information in Si QDs.",1702.06210v2
2020-07-04,Low-symmetry topological materials for large charge-to-spin interconversion: The case of transition metal dichalcogenide monolayers,"The spin polarization induced by the spin Hall effect (SHE) in thin films
typically points out of the plane. This is rooted on the specific symmetries of
traditionally studied systems, not in a fundamental constraint. Recently,
experiments on few-layer ${\rm MoTe}_2$ and ${\rm WTe}_2$ showed that the
reduced symmetry of these strong spin-orbit coupling materials enables a new
form of {\it canted} spin Hall effect, characterized by concurrent in-plane and
out-of-plane spin polarizations. Here, through quantum transport calculations
on realistic device geometries, including disorder, we predict a very large
gate-tunable SHE figure of merit $\lambda_s\theta_{xy}\sim 1\text{--}50$ nm in
${\rm MoTe}_2$ and ${\rm WTe}_2$ monolayers that significantly exceeds values
of conventional SHE materials. This stems from a concurrent long spin diffusion
length ($\lambda_s$) and charge-to-spin interconversion efficiency as large as
$\theta_{xy} \approx 80$\%, originating from momentum-invariant (persistent)
spin textures together with large spin Berry curvature along the Fermi contour,
respectively. Generalization to other materials and specific guidelines for
unambiguous experimental confirmation are proposed, paving the way towards
exploiting such phenomena in spintronic devices. These findings vividly
emphasize how crystal symmetry and electronic topology can govern the intrinsic
SHE and spin relaxation, and how they may be exploited to broaden the range and
efficiency of spintronic materials and functionalities.",2007.02053v2
2020-08-21,Correlation of interface transmission in THz spintronic emitters with spin mixing conductance in spin pumping experiments,"The field of THz spintronics is a novel direction in the research field of
spintronics that combines magnetism with optical physics and ultrafast
photonics. The experimental scheme of the field involves the use of femtosecond
laser pulses to trigger ultrafast spin and charge dynamics in bilayers composed
of ferromagnetic (FM) and non-magnetic (NM) thin films where the NM layer
features a strong spin-orbit coupling. The key technological and scientific
challenges of THz spintronic emitters is to increase their intensity and
frequency bandwidth. To achieve this the control of the source of the
radiation, namely the transport of the ultrafast spin current is required.
However, the transfer of a spin current from a FM to a NM layer is a highly
interface-sensitive effect. In this work we study the properties of the spin
current transport through the interface measuring the strength of the THz
emission and compare it to the effective spin mixing conductance, one of the
key concepts in the spin current transport through interfaces. The results show
an enhancement of the spin mixing conductance for interfaces with higher degree
of epitaxy similarly to the improvement of the THz emission. The
proportionality between spin mixing conductance and THz emission can define new
directions in engineering the emission of spintronic THz emitters.",2008.09537v1
2020-08-27,Focused linearly-polarized light scattering from a silver nanowire: Experimental characterization of optical spin-Hall effect,"Spin-orbit interactions (SOI) are a set of sub-wavelength optical phenomenon
in which spin and spatial degrees of freedom of light are intrinsically
coupled. One of the unique example of SOI, spin-Hall effect of light (SHEL) has
been an area of extensive research with potential applications in spin
controlled photonic devices as well as emerging fields of spinoptics and
spintronics. Here, we report our experimental study on SHEL due to forward
scattering of focused linearly polarized Gaussian and Hermite-Gaussian
($\textrm{HG}_{10}$) beams from a silver nanowire (AgNW). Spin dependent
anti-symmetric intensity patterns are obtained when the polarization of the
scattered light is analysed. The corresponding spin-Hall signal is obtained by
computing the far-field longitudinal spin density ($s_3$). Furthermore, by
comparing the $s_3$ distributions, significant enhancement of the spin-Hall
signal is found for $\textrm{HG}_{10}$ beam compared to Gaussian beam. The
investigation of the optical fields at the focal plane of the objective lens
reveals the generation of longitudinally spinning fields as the primary reason
for the effects. The experimental results are corroborated by 3-dimensional
numerical simulations. The results lead to better understanding of SOI and can
have direct implications on chip-scale spin assisted photonic devices.",2008.12245v2
2019-06-12,Spin transport and Spin Tunnelling Magneto-Resistance (STMR) of F$|$NCSC$|$F spin valve,"In this work, we study the spin transport at the
Ferromagnet$|$Noncentrosymmetric Superconductor (F$|$NCSC) junction of a
Ferromagnet$|$Noncentrosymmetric Superconductor$|$Ferromagnet (F$|$NCSC$|$F)
spin valve. We investigate the Tunnelling Spin-Conductance (TSC), spin current
and Spin Tunnelling Magneto-Resistance (STMR), and their dependence on various
important parameters like Rashba Spin-Orbit Coupling (RSOC), strength and
orientation of magnetization, an external in-plane magnetic field, barrier
strength and a significant Fermi Wavevector Mismatch (FWM) at the ferromagnetic
and superconducting regions. The study has been carried out for different
singlet-triplet mixing of the NCSC gap parameter. We develop Bogoliubov-de
Gennes (BdG) Hamiltonian and use the extended Blonder - Tinkham - Klapwijk
(BTK) approach along with the scattering matrix formalism to calculate the
scattering coefficients. Our results strongly suggest that the TSC is highly
dependent on RSOC, magnetization strength and its orientation, and
singlet-triplet mixing of the gap parameter. It is observed that NCSC with
moderate RSOC shows maximum conductance for a partially opaque barrier in
presence of low external magnetic field. For a strongly opaque barrier and a
nearly transparent barrier a moderate value and a low value of field
respectively are found to be suitable. Moreover, NCSC with large singlet
component is appeared to be useful. In addition, for NCSC with large RSOC and
low magnetization strength, a giant STMR ($\%$) is observed. We have also seen
that the spin current is strongly magnetization orientation dependent. With the
increase in bias voltage spin current increases in transverse direction, but
the component along the direction of flow is almost independent.",1906.05081v1
2020-06-05,Competing Antiferromagnetic-Ferromagnetic States in $\it{d^7}$ Kitaev Honeycomb Magnet,"The Kitaev model is a rare example of an analytically solvable and physically
instantiable Hamiltonian yielding a topological quantum spin liquid ground
state. Here we report signatures of Kitaev spin liquid physics in the honeycomb
magnet $Li_3Co_2SbO_6$, built of high-spin $\it{d^7}$ ($Co^{2+}$) ions, in
contrast to the more typical low-spin $\it{d^5}$ electron configurations in the
presence of large spin-orbit coupling. Neutron powder diffraction measurements,
heat capacity, and magnetization studies support the development of a
long-range antiferromagnetic order space group of $\it{C_C}2/\it{m}$, below
$\it{T_N}$ = 11 K at $\it{\mu_0H}$ = 0 T. The magnetic entropy recovered
between $\it{T}$ = 2 K and 50 K is estimated to be 0.6Rln2, in good agreement
with the value expected for systems close to a Kitaev quantum spin liquid
state. The temperature-dependent magnetic order parameter demonstrates a
$\beta$ value of 0.19(3), consistent with XY anisotropy and in-plane ordering,
with Ising-like interactions between layers. Further, we observe a spin-flop
driven crossover to ferromagnetic order with space group of $\it{C}2/\it{m}$
under an applied magnetic field of $\it{\mu_0H}$ $\approx$ 0.7 T at $\it{T}$ =
2 K. Magnetic structure analysis demonstrates these magnetic states are
competing at finite applied magnetic fields even below the spin-flop
transition. Both the $\it{d^7}$ compass model, a quantitative comparison of the
specific heat of $Li_3Co_2SbO_6$, and related honeycomb cobaltates to the
anisotropic Kitaev model further support proximity to a Kitaev spin liquid
state. This material demonstrates the rich playground of high-spin $\it{d^7}$
systems for spin liquid candidates, and complements known $\it{d^5}$ Ir- and
Ru-based materials.",2006.03724v1
2021-06-12,Spin pumping and inverse spin Hall effect in CoFeB/C$_{60}$ bilayers,"Pure spin current based research is mostly focused on ferromagnet (FM)/heavy
metal (HM) system. Because of the high spin orbit coupling (SOC) these HMs
exhibit short spin diffusion length and therefore possess challenges for device
application. Low SOC (elements of light weight) and large spin diffusion length
make the organic semiconductors (OSCs) suitable for future spintronic
applications. From theoretical model it is explained that, due to $\pi$ -
$\sigma$ hybridization the curvature of the C$_{60}$ molecules may increase the
SOC strength. Here, we have investigated spin pumping and inverse spin hall
effect (ISHE) in CoFeB/C$_{60}$ bilayer system using coplanar wave guide based
ferromagnetic resonance (CPW-FMR) set-up. We have performed angle dependent
ISHE measurement to disentangle the spin rectification effects for example
anisotropic magnetoresistance, anomalous Hall effect etc. Further, effective
spin mixing conductance (g$_{eff}^{\uparrow\downarrow}$) and spin Hall angle
($\theta_{SH}$) for C$_{60}$ have been reported here. The evaluated value for
$\theta_{SH}$ is 0.055.",2106.06829v2
2022-07-27,Spin-Neutral Tunneling Anomalous Hall Effect,"Anomalous Hall effect (AHE) is a fundamental spin-dependent transport
property that is widely used in spintronics. It is generally expected that
currents carrying net spin polarization are required to drive the AHE. Here we
demonstrate that, in contrast to this common expectation, a spin-neutral
tunneling AHE (TAHE), i.e. a TAHE driven by spin-neutral currents, can be
realized in an antiferromagnetic (AFM) tunnel junction where an AFM electrode
with a non-spin-degenerate Fermi surface and a normal metal electrode are
separated by a non-magnetic barrier with strong spin-orbit coupling (SOC). The
symmetry mismatch between the AFM electrode and the SOC barrier results in an
asymmetric spin-dependent momentum filtering of the spin-neutral longitudinal
current generating the transverse Hall current in each electrode. We predict a
sizable spin-neutral TAHE in an AFM tunnel junction with a RuO$_{2}$-type AFM
electrode and a SnTe-type SOC barrier and show that the Hall currents are
reversible by the N\'eel vector switching. With the Hall angle being comparable
to that in conventional AHE bulk materials, the predicted spin-neutral TAHE can
be used for the N\'eel vector detection in antiferromagnetic spintronics.",2207.13376v1
2023-01-19,RIXS observation of bond-directional nearest-neighbor excitations in the Kitaev material Na$_2$IrO$_3$,"Spin-orbit coupling locks spin direction and spatial orientation and
generates, in semi-classical magnets, a local spin easy-axis and associated
ordering. Quantum spin-1/2's defy this fate: rather than spins becoming locally
anisotropic, the spin-spin interactions do. Consequently interactions become
dependent on the spatial orientation of bonds between spins, prime theoretical
examples of which are Kitaev magnets. Bond-directional interactions imply the
existence of bond-directional magnetic modes, predicted spin excitations that
render crystallographically equivalent bonds magnetically inequivalent, which
yet have remained elusive experimentally. Here we show that resonant inelastic
x-ray scattering allows us to explicitly probe the bond-directional character
of magnetic excitations. To do so, we use a scattering plane spanned by one
bond and the corresponding spin component and scan a range of momentum transfer
that encompasses multiple Brillouin zones. Applying this approach to
Na$_2$IrO$_3$ we establish the different bond-directional characters of
magnetic excitations at 10 meV and 45 meV. Combined with the observation of
spin-spin correlations that are confined to a single bond, this experimentally
validates the Kitaev character of exchange interactions long proposed for this
material.",2301.08340v1
2019-08-04,Experimental observation of coupled valley and spin Hall effect in p-doped WSe2 devices,"Giant spin Hall effect (GSHE) has been observed in heavy metal materials such
as Ta, Pt, and W, where spins are polarized in the surface plane and
perpendicular to the charge current direction. Spins generated in these
materials have successfully switched magnets with in-plane magnetic anisotropy
(IMA) and perpendicular magnetic anisotropy (PMA) through spin orbit torque
(SOT) mechanism. It is generally accepted that PMA magnets are preferred over
IMA magnets in data storage applications owing to their large thermal stability
even at ultra scaled dimensions. However, SOT switching of PMA magnets by
conventional GSHE materials requires either a small external magnetic field, a
local dipolar field, or introducing tilted anisotropy to break the symmetry
with respect to the magnetization. To deterministically switch a PMA without
any additional assistance, nonconventional GSHE materials that can generate
spins with polarization perpendicular to the surfaces are needed. Several
monolayer transition metal dichalcogenides (TMDs) have been predicted to
generate such out of plane spins due to their 2D nature and unique band
structures. Interestingly, opposite spins are locked to their respective
sub-band in each K valley of the TMD valence band with substantially large
energy splitting, which enables polarized spins to be accessible through
electrical gating and spatially separated by electric field through the valley
Hall effect (VHE). Therefore, spatial separation and accumulation of spins in
these 2D TMDs are uniquely referred to as coupled valley and spin Hall effect.
Here, we report an experiment of electrical generation of spin current with out
of plane polarization in monolayer WSe2 and detection of spin signals through a
nonlocal spin valve structure built on a lateral graphene spin diffusion
channel that partially overlaps with WSe2.",1908.01396v1
2004-03-16,Calculated spin-orbit splitting of all diamond-like and zinc-blende semiconductors: Effects of p1/2 local orbitals and chemical trends,"e have calculated the spin-orbit (SO) splitting $\Delta_{SO}=\epsilon
(\Gamma_{8v}) - \epsilon (\Gamma_{7v})$ for all diamond-like group IV and
zinc-blende group III-V, II-VI, and I-VII semiconductors using the full
potential linearized augmented plane wave method within the local density
approximation. The SO coupling is included using the second variation
procedure, including the $p_{1/2}$ local orbitals. The calculated SO splittings
are in very good agreement with available experimental data. The corrections
due to the inclusion of the $p_{1/2}$ local orbital are negligible for lighter
atoms, but can be as large as $\sim$250 meV for 6$p$ anions. We find that (i)
the SO splittings increase monotonically when anion atomic number increases;
(ii) the SO splittings increase with the cation atomic number when the compound
is more covalent such as in most III-V compounds; (iii) the SO splittings
decrease with the cation atomic number when the compound is more ionic, such as
in II-VI and the III-nitride compounds; (iv) the common-anion rule, which
states that the variation of $\Delta_{SO}$ is small for common-anion systems,
is usually obeyed, especially for ionic systems, but can break down if the
compounds contain second-row elements such as BSb;(v) for IB-VII compounds, the
$\Delta_{SO}$ is small and in many cases negative and it does not follow the
rules discussed above. These trends are explained in terms of atomic SO
splitting, volume deformation-induced charge renormalization, and cation-anion
$p$--$d$ couplings.",0403409v2
2015-06-11,Filling-Enforced Quantum Band Insulators in Spin-Orbit Coupled Crystals,"While band insulators are usually described in wavevector space in terms of
fully filled bands, they are sometimes also described in terms of a
complementary Wannier picture in which electrons occupy localized, atom-like
orbitals. Under what conditions does the latter picture break down? The
presence of irremovable quantum entanglement between different sites can
obstruct a localized orbital description, which occurs in systems like Chern
and topological insulators. We collectively refer to such states as Quantum
Band Insulators (QBIs). Here we report the theoretical discovery of a
filling-enforced QBI - that is, a free electron insulator in which the band
filling is smaller than the minimum number dictated by the atomic picture.
Consequently such insulators have no representation in terms of filling
localized orbitals and must be QBIs. This is shown to occur in models of
certain cubic crystals with non-symmorphic space groups. Like topological
insulators, filling-enforced QBIs require spin-orbit coupling. However, in
contrast, they do not typically exhibit protected surface states. Instead their
nontrivial nature is revealed by studying the quantum entanglement of their
ground state wavefunction.",1506.03816v3
2016-09-16,Ab initio calculations to support accurate modelling of the rovibronic spectroscopy calculations of vanadium monoxide (VO),"Accurate knowledge of the rovibronic near-infrared and visible spectra of
vanadium monoxide (VO) is very important for studies of cool stellar and hot
planetary atmospheres. Here, the required ab initio dipole moment and
spin-orbit coupling curves for VO are produced. This data forms the basis of a
new VO line list considering 13 different electronic states and containing over
277 million transitions. Open shell transition, metal diatomics are challenging
species to model through ab initio quantum mechanics due to the large number of
low-lying electronic states, significant spin-orbit coupling and strong static
and dynamic electron correlation. Multi-reference configuration interaction
methodologies using orbitals from a complete active space self-consistent-field
(CASSCF) calculation are the standard technique for these systems. We use
different state-specific or minimal-state CASSCF orbitals for each electronic
state to maximise the calculation accuracy. The off-diagonal dipole moment
controls the intensity of electronic transitions. We test finite-field
off-diagonal dipole moments, but found that (1) the accuracy of the excitation
energies were not sufficient to allow accurate dipole moments to be evaluated
and (2) computer time requirements for perpendicular transitions were
prohibitive. The best off-diagonal dipole moments are calculated using
wavefunctions with different CASSCF orbitals.",1609.05073v1
2004-10-12,Experimental observation of the spin-Hall effect in a two dimensional spin-orbit coupled semiconductor system,"We report the experimental observation of the spin-Hall effect in a
two-dimensional (2D) hole system with Rashba spin-orbit coupling.
  The 2D hole layer is a part of a p-n junction light-emitting diode with a
specially designed co-planar geometry which allows an angle-resolved
polarization detection at opposite edges of the 2D hole system. In equilibrium
the angular momenta of the Rashba split heavy hole states lie in the plane of
the 2D layer. When an electric field is applied across the hole channel a non
zero out-of-plane component of the angular momentum is detected whose sign
depends on the sign of the electric field and is opposite for the two edges.
Microscopic quantum transport calculations show only a weak effect of disorder
suggesting that the clean limit spin-Hall conductance description (intrinsic
spin-Hall effect) might apply to our system.",0410295v3
2011-07-11,Influence of Impurity Scattering on the Conductance Anomalies of Quantum Point Contacts with Lateral Spin-Orbit Coupling,"We have recently shown that asymmetric lateral spin orbit coupling (LSOC)
resulting from the lateral in-plane electric field of the confining potential
of a side-gated quantum point contact (QPC) can be used to create a strongly
spin- polarized current by purely electrical means1 in the absence of applied
magnetic field. Using the non-equilibrium Green function formalism (NEGF)
analysis of a small model QPC2, three ingredients were found to be essential to
generate the strong spin polarization: an asymmetric lateral confinement, a
LSOC induced by the lateral confining potential of the QPC, and a strong
electron-electron (e-e) interaction. In this paper, NEGF is used to study how
the spin polarization is affected by the presence of impurities in the central
portion of the QPC. It is found that the number, location, and shape of the
conductance anomalies, occurring below the first quantized conductance plateau
(G0=2e2/h), are strongly dependent on the nature (attractive or repulsive) and
the locations of the impurities. We show that the maximum of the conductance
spin polarization is affected by the presence of impurities. For QPCs with
impurities off-center, a conductance anomaly appears below the first integer
step even for the case of symmetric bias on the two side gates. These results
are of practical importance if QPCs in series are to be used to fabricate
all-electrical spin valves with large ON/OFF conductance ratio.",1107.1923v1
2012-09-15,Phase diagrams of noncentrosymmetric superconductors,"Noncentrosymmetric superconductors with various types of pairing interactions
are systematically examined with particular focus on phenomena that originate
from the differences between Fermi surfaces split by a strong spin-orbit
coupling. In particular, when the spin-orbit coupling increases and one of the
split Fermi surfaces disappears, the phase diagram and the structure of the gap
function change drastically. For example, we examine the conditions for the
transition from full-gap states to line-node states (FLT), which may explain
the differences in the experimental results between the noncentrosymmetric
superconductors Li2Pd3B and Li2Pt3B discovered recently. The dominant pairing
interactions and gap functions can be predicted to some extent by comparing the
theoretical and experimental results for these compounds. For example, if the
FLT occurs by replacing Pd with Pt, it is most likely that the
superconductivity is mainly induced by charge-charge interactions, and if this
is the case, the superconductivities in Li2Pd3B and Li2Pt3B are an s-wave
nearly spin-triplet state and a d-wave state that has both spin-singlet and
triplet components of comparable weights, respectively. Comparing the
theoretical phase diagrams in simple models, it is found that the FLT occurs in
a wider realistic parameter region for charge-charge interactions, i.e., where
short-range Coulomb repulsion is strong and p-wave and d-wave interactions are
attractive, while it occurs in narrower rather unrealistic parameter regions
for interactions of magnetic origin. It is also found that d-wave spin-triplet
pairing may occur, when pairing interactions are of magnetic origin and
anisotropic in spin space.",1209.3367v4
2020-12-31,Dispersively probed microwave spectroscopy of a silicon hole double quantum dot,"Owing to ever increasing gate fidelities and to a potential transferability
to industrial CMOS technology, silicon spin qubits have become a compelling
option in the strive for quantum computation. In a scalable architecture, each
spin qubit will have to be finely tuned and its operating conditions accurately
determined. In this prospect, spectroscopic tools compatible with a scalable
device layout are of primary importance. Here we report a two-tone spectroscopy
technique providing access to the spin-dependent energy-level spectrum of a
hole double quantum dot defined in a split-gate silicon device. A first
GHz-frequency tone drives electric-dipole spin resonance enabled by the
valence-band spin-orbit coupling. A second lower-frequency tone (approximately
500 MHz) allows for dispersive readout via rf-gate reflectometry. We compare
the measured dispersive response to the linear response calculated in an
extended Jaynes-Cummings model and we obtain characteristic parameters such as
g-factors and tunnel/spin-orbit couplings for both even and odd occupation.",2012.15588v2
2020-10-03,Direct band gap and strong Rashba effect in van der Waals heterostructures of InSe and Sb single layers,"Van der Waals heterostructures formed by stacking different types of 2D
materials are attracting increasing attention due to new emergent physical
properties such as interlayer excitons. Recently synthesized atomically thin
indium selenide (InSe) and antimony (Sb) individually exhibit interesting
electronic properties such as high electron mobility in the former and high
hole mobility in the latter. In this work, we present a first-principles
investigation on the stability and electronic properties of ultrathin bilayer
heterostructures composed of InSe and Sb single layers. The calculated
electronic band structures reveal a direct band gap semiconducting nature of
the InSe/Sb heterostructures independent of stacking pattern. Taking spin-orbit
coupling into account, we find a large Rashba spin splitting at the bottom of
conduction band, which originates from the atomic spin-orbit coupling with the
symmetry breaking in the heterostructure. The strength of the Rashba spin
splitting can be tuned by applying in-plane biaxial strain or an out-of-plane
external electric field. The presence of large Rashba spin splitting together
with a suitable band gap in InSe/Sb bilayer heterostructures make them
promising candidates for spin field-effect transistor and optoelectronic device
applications.",2010.01355v2
2021-04-08,Spin-orbit coupling induced ultra-high harmonic generation from magnetic dynamics,"The recent boost in data transfer rates puts a daring strain on information
technology. Sustaining such a growth rate requires the development of sources,
detectors and systems working in the so-called TeraHertz (THz) gap covering the
frequency window from 0.1 to 10 THz (1 THz = 10$^{12}$~Hz). This gap represents
a challenge for conventional electronic devices due to carrier transit delays
($\sim$1-10ps), as well as for photonic devices due to thermal fluctuations
(300K$\sim$6THz). Nonetheless, designing efficient, room-temperature THz
sources would constitute a key enabler to applications spanning from
high-resolution imaging to extreme wide band wireless communication. Whereas
high-harmonic generation in solid is usually limited to less than ten
harmonics, broadband THz emission has been demonstrated using laser-induced
superdiffusive spin currents in magnetic bilayers composed of a ferromagnet
deposited on top of a noble metal. While promising, this technique presents the
major disadvantage of necessitating optical pumping and hence lacks
scalability. Here, we demonstrate that extremely high harmonic emission can be
achieved by exploiting conventional spin pumping, without the need of optical
excitation. We show that when the spin-orbit coupling strength is close to the
s-d exchange energy, a strongly non linear regime resulting from resonant spin
flip scattering occurs leading to the generation of a thousand of harmonics at
realistic antiferromagnetic precession frequencies, thereby enhancing both spin
and charge dynamics by two orders of magnitude, and allowing for an emission at
frequencies above 300 THz.",2104.04001v1
2016-09-30,Non-collinear Order and Spin-Orbit Coupling in Sr$_3$ZnIrO$_6$,"Sr$_{3}$ZnIrO$_{6}$ is an effective spin one-half Mott insulating iridate
belonging to a family of magnets which includes a number of quasi-one
dimensional systems as well as materials exhibiting three dimensional order.
Here we present the results of an extensive investigation into the magnetism
including heat capacity, a.c. susceptibility, muon spin rotation ($\mu$SR),
neutron diffraction and inelastic neutron scattering on the same sample. It is
established that the material exhibits a transition at about $17$ K into a
three-dimensional antiferromagnetic structure with propagation vector
$\boldsymbol{k}=(0,\frac{1}{2},1)$ in the hexagonal setting of R$\bar{3}$c and
non-collinear moments of $0.87$$\mu_B$ on Ir$^{4+}$ ions. Further we have
observed a well defined powder averaged spin wave spectrum with zone boundary
energy of $\sim 5$ meV at $5$ K. We stress that a theoretical analysis shows
that the observed non-collinear magnetic structure arises from anisotropic
inter- and intra- chain exchange which has its origin in significant spin-orbit
coupling. The model can satisfactorily explain the observed spin wave
excitations.",1610.00038v2
2021-07-29,Superconducting triplet pairings and anisotropic magnetoresistance effects in ferromagnet/superconductor/ferromagnet double-barrier junctions,"Ferromagnetic spin valves offer the key building blocks to integrate giant-
and tunneling-magnetoresistance effects into spintronics devices. Starting from
a generalized Blonder-Tinkham-Klapwijk approach, we theoretically investigate
the impact of interfacial Rashba and Dresselhaus spin-orbit couplings on the
tunneling conductance, and thereby the magnetoresistance characteristics, of
ferromagnet/superconductor/ferromagnet spin-valve junctions embedding thin
superconducting spacers between the either parallel or antiparallel magnetized
ferromagnets. We focus on the unique interplay between usual electron
tunnelings-that fully determine the magnetoresistance in the normal-conducting
state-and the peculiar Andreev reflections in the superconducting state. In the
presence of interfacial spin-orbit couplings, special attention needs to be
paid to the spin-flip (""unconventional"") Andreev-reflection process that is
expected to induce superconducting triplet correlations in proximitized
regions. As a transport signature of these triplet pairings, we detect
conductance double peaks around the singlet-gap energy, reflecting the
competition between the singlet and an additionally emerging triplet gap; the
latter is an effective superconducting gap that can be ascribed to the
formation of triplet Cooper pairs through interfacial spin-flip scatterings
(i.e., to the generation of an effective triplet-pairing term in the order
parameter). We thoroughly analyze the Andreev reflections' role in connection
with superconducting magnetoresistance phenomena, and eventually unravel huge
conductance and magnetoresistance magnetoanisotropies-easily exceeding their
normal-state counterparts by several orders of magnitude-as another
experimentally accessible fingerprint of unconventional Andreev reflections.",2107.13818v2
2022-02-24,Preferred Spin Excitations in the Bilayer Iron-Based Superconductor CaK(Fe$_{0.96}$Ni$_{0.04}$)$_4$As$_4$ with Spin-Vortex Crystal Order,"The spin-orbit coupling (SOC) is a key to understand the magnetically driven
superconductivity in iron-based superconductors, where both local and itinerant
electrons are present and the orbital angular momentum is not completely
quenched. Here, we report a neutron scattering study on the bilayer compound
CaK(Fe$_{0.96}$Ni$_{0.04}$)$_4$As$_4$ with superconductivity coexisting with a
non-collinear spin-vortex crystal magnetic order that preserves the tetragonal
symmetry of Fe-Fe plane. In the superconducting state, two spin resonance modes
with odd and even $L$ symmetries due to the bilayer coupling are found similar
to the undoped compound CaKFe$_4$As$_4$ but at lower energies. Polarization
analysis reveals that the odd mode is $c-$axis polarized, and the low-energy
spin anisotropy can persist to the paramagnetic phase at high temperature,
which closely resembles other systems with in-plane collinear and $c-$axis
biaxial magnetic orders. These results provide the missing piece of the puzzle
on the SOC effect in iron-pnictide superconductors, and also establish a common
picture of $c-$axis preferred magnetic excitations below $T_c$ regardless of
the details of magnetic pattern or lattice symmetry.",2202.11933v1
2023-03-01,Rashba spin-orbit coupling enhanced magnetoresistance in junctions with one ferromagnet,"We explain how Rashba spin-orbit coupling (SOC) in a two-dimensional electron
gas (2DEG), or in a conventional $s$-wave superconductor, can lead to a large
magnetoresistance even with one ferromagnet. However, such enhanced
magnetoresistance is not generic and can be nonmonotonic and change its sign
with Rashba SOC. For an in-plane rotation of magnetization, it is typically
negligibly small for a 2DEG and depends on the perfect transmission which
emerges from a spin-parity-time symmetry of the scattering states, while this
symmetry is generally absent from the Hamiltonian of the system. The key
difference from considering the normal-state magnetoresistance is the presence
of the spin-dependent Andreev reflection at superconducting interfaces. In the
fabricated junctions of quasi-2D van der Waals ferromagnets with conventional
$s$-wave superconductors (Fe$_{0.29}$TaS$_2$/NbN) we find another example of
enhanced magnetoresistance where the presence of Rashba SOC reduces the
effective interfacial strength and is responsible for an equal-spin Andreev
reflection. The observed nonmonotonic trend in the out-of-plane
magnetoresistance with the interfacial barrier is an evidence for the
proximity-induced equal-spin-triplet superconductivity.",2303.00185v1
2023-11-14,Generation of electric current and electromotive force by an antiferromagnetic domain wall,"Dynamic magnetic textures may transfer the angular moment from the varying in
time antiferromagnetic order to spins of conduction electrons. Due to the spin
orbit coupling (SOC) these spin excitations can induce the electric current of
conduction electrons. We calculated the electric current and the electromotive
force (EMF) which are produced by a domain wall (DW) moving parallel to the
magnetically compensated interface between an antiferromagnetic insulator
(AFMI) and a two-dimensional spin orbit coupled metal. Spins of conduction
electrons interact with localized spins of a collinear AFMI through the
interface exchange interaction. The Keldysh formalism of nonequilibrium Green
functions was applied for the analysis of this system. It is shown that a Bloch
DW generates the current perpendicular to the DW motion direction. At the same
time a N\'{e}el DW creates the electric potential which builds up across the
wall. The total charge which is pumped by a Bloch DW can be expressed in terms
of a topologically invariant charge quantum. The latter does not depend on
variations of DW's velocity and shape. These effects increase dramatically when
the Fermi energy approaches the van Hove singularity of the Fermi surface. The
obtained results are important for the electrical detection and control of
dynamic magnetic textures in antiferromagnets.",2311.08067v1
2024-01-15,Meta-generalized-gradient exchange-correlation functionals for spin-orbit coupled electrons,"The prominence of density functional theory (DFT) in the field of electronic
structure computation stems from its ability to usefully balance accuracy and
computational effort. At the base of this ability is a functional of the
electron density: the exchange-correlation (xc) energy. This functional
satisfies known exact conditions that guide the derivation of approximations.
The strongly-constrained-appropriately-normed (SCAN) approximation stands out
as a successful, modern, example. In the presence of spin-orbit coupling,
however, the xc energy must depend not only on the electron density but also on
spin currents -- a fact which is not captured by SCAN or by any mainstream
functional approximation. In this work, we demonstrate how the SU(2)
gauge-invariance of the {\em exact} functional allows us to add the necessary
dependence on spin currents in the SCAN functional (here called JSCAN) -- and
similar meta-generalized-gradient functional approximations -- in a
non-empirical manner. The prescription further ensures that the conjugate
xc-fields of the spin currents have vanishing local torques as in the exact
case. In passing, a spin-current dependent generalization of the electron
localization function (here called JELF) is also derived. The extended forms
are implemented in a developer's version of the \textsc{Crystal23} program.
Applications on molecules and materials confirm the practical relevance of the
extensions.",2401.07581v1
2013-10-08,Magnetic and Gravitational Disk-Star Interactions: An Interdependence of PMS Stellar Rotation Rates and Spin-Orbit Misalignments,"The presence of giant gaseous planets that reside in close proximity to their
host stars may be a consequence of large-scale radial migration through the
proto-planetary nebulae. Within the context of this picture, significant
orbital obliquities characteristic of a substantial fraction of such planets
can be attributed to external torques that perturb the disks out of alignment
with the spin axes of their host stars. Therefore, the acquisition of orbital
obliquity exhibits sensitive dependence on the physics of disk-star
interactions. Here, we analyze the primordial excitation of spin-orbit
misalignment of Sun-like stars, in light of disk-star angular momentum
transfer. We begin by calculating the stellar pre-main sequence rotational
evolution, accounting for spin-up due to gravitational contraction and
accretion as well as spin-down due to magnetic star-disk coupling. We devote
particular attention to angular momentum transfer by accretion, and show that
while generally subdominant to gravitational contraction, this process is
largely controlled by the morphology of the stellar magnetic field (i.e.
specific angular momentum accreted by stars with octupole-dominated surface
fields is smaller than that accreted by dipole-dominated stars by an order of
magnitude). Subsequently, we examine the secular spin-axis dynamics of
disk-bearing stars, accounting for the time-evolution of stellar and disk
properties and demonstrate that misalignments are preferentially excited in
systems where stellar rotation is not overwhelmingly rapid. Moreover, we show
that the excitation of spin-orbit misalignment occurs impulsively, through an
encounter with a resonance between the stellar precession frequency and the
disk-torquing frequency. Cumulatively, the model developed herein opens up a
previously unexplored avenue towards understanding star-disk evolution and its
consequences in a unified manner.",1310.2179v1
2009-04-14,Inverse quantum spin Hall effect generated by spin pumping from precessing magnetization into a graphene-based two-dimensional topological insulator,"We propose a multiterminal nanostructure for electrical probing of the
quantum spin Hall effect (QSHE) in two-dimensional (2D) topological insulators.
The device consists of a ferromagnetic (FM) island with precessing
magnetization that pumps (in the absence of any bias voltage) pure spin current
symmetrically into the left and right adjacent 2D TIs modeled as graphene
nanoribbons with the intrinsic spin-orbit (SO) coupling. The QSH regime of the
six-terminal TI|FM|TI nanodevice, attached to two longitudinal and four
transverse normal metal electrodes, is characterized by the SO-coupling-induced
energy gap, chiral spin-filtered edge states within finite length TI regions,
and quantized spin Hall conductance when longitudinal bias voltage is applied,
despite the presence of the FM island. The same unbiased device, but with
precessing magnetization of the central FM island, blocks completely pumping of
total spin and charge currents into the longitudinal electrodes while
generating DC transverse charge Hall currents. Although these transverse charge
currents are not quantized, their induction together with zero longitudinal
charge current is a unique electrical response of TIs to pumped pure spin
current that cannot be mimicked by SO-coupled but topologically trivial
systems. In the corresponding two-terminal inhomogeneous TI|FM|TI
nanostructures, we image spatial profiles of local spin and charge currents
within TIs which illustrate transport confined to chiral spin-filtered edges
states while revealing concomitantly the existence of interfacial spin and
charge currents flowing around TI|FM interfaces and penetrating into the bulk
of TIs over some short distance.",0904.2192v3
2011-05-18,Modulated Rashba interaction in a quantum wire: Spin and charge dynamics,"It was recently shown that a spatially modulated Rashba spin-orbit coupling
in a quantum wire drives a transition from a metallic to an insulating state
when the wave number of the modulation becomes commensurate with the Fermi wave
length of the electrons in the wire. It was suggested that the effect may be
put to practical use in a future spin transistor design. In the present article
we revisit the problem and present a detailed analysis of the underlying
physics. First, we explore how the build-up of charge density wave correlations
in the quantum wire due to the periodic gate configuration that produces the
Rashba modulation influences the transition to the insulating state. The
interplay between the modulations of the charge density and that of the
spin-orbit coupling turns out to be quite subtle: Depending on the relative
phase between the two modulations, the joint action of the Rashba interaction
and charge density wave correlations may either enhance or reduce the Rashba
current blockade effect. Secondly, we inquire about the role of the Dresselhaus
spin-orbit coupling that is generically present in a quantum wire embedded in
semiconductor heterostructure. While the Dresselhaus coupling is found to work
against the current blockade of the insulating state, the effect is small in
most materials. Using an effective field theory approach, we also carry out an
analysis of effects from electron- electron interactions, and show how the
single-particle gap in the insulating state can be extracted from the more
easily accessible collective charge and spin excitation thresholds. The
smallness of the single-particle gap together with the anti-phase relation
between the Rashba and chemical potential modulations pose serious difficulties
for realizing a Rashba-controlled current switch in an InAs-based device. Some
alternative designs are discussed.",1105.4141v2
2022-04-11,"Spin-orbit coupling controlled ground states in the double perovskite iridates A2BIrO6 (A = Ba, Sr; B = Lu, Sc)","Iridates with the 5$d^4$ electronic configuration have attracted recent
interest due to reports of magnetically-ordered ground states despite
longstanding expectations that their strong spin-orbit coupling would generate
a $J = 0$ electronic ground state for each Ir$^{5+}$ ion. The major focus of
prior research has been on the double perovskite iridates Ba$_2$YIrO$_6$ and
Sr$_2$YIrO$_6$, where the nature of the ground states (i.e. ordered vs
non-magnetic) is still controversial. Here we present neutron powder
diffraction, high energy resolution fluorescence detected x-ray absorption
spectroscopy (HERFD-XAS), resonant inelastic x-ray scattering (RIXS), magnetic
susceptibility, and muon spin relaxation data on the related double perovskite
iridates Ba$_2$LuIrO$_6$, Sr$_2$LuIrO$_6$, Ba$_2$ScIrO$_6$, and Sr$_2$ScIrO$_6$
that enable us to gain a general understanding of the electronic and magnetic
properties for this family of materials. Our HERFD-XAS and RIXS measurements
establish $J = 0$ electronic ground states for the Ir$^{5+}$ ions in all cases,
with similar values for Hund's coupling $J_{\rm H}$ and the spin-orbit coupling
constant $\lambda_{\rm SOC}$. Our bulk susceptibility and muon spin relaxation
data find no evidence for long-range magnetic order or spin freezing, but they
do reveal weak magnetic signals that are consistent with extrinsic local
moments. Our results indicate that the large $\lambda_{\rm SOC}$ is the key
driving force behind the electronic and magnetic ground states realized in the
5$d^4$ double perovskite iridates, which agrees well with conventional wisdom.",2204.05384v2
2016-04-18,"Ferro-deformation at the nuclear system with protons, Z = 20 and neutrons, N = 40: 60Ca","We present a possibility that the system with Z = 20, N = 40, 60Ca, has a
large deformation, even though it has both proton and neutron magic numbers,
symbolizing a spherical nucleus. This large deformation corresponds to the
so-called ferro-deformation that occurs at the particular critical points over
the nuclear chart. By comparisons with the ferra-deformation at the critical
point Z = 40, N = 64 [arXiv:1604.02786], we draw a conclusion that shape phase
transitions should occur at Z = 18 or 20 when N = 36 to 38, which leads to a
ferro-deformation at the critical points of Z = 18 or 20, N = 40; 58Ar, 60Ca.
We explain the shape phase transition in terms of isospin dependent
spin-orbital interactions between neutrons in the f5/2 orbital and protons in
the f7/2 orbital. We find a universal behavior over the nuclear chart for
yielding the ferro-deformation such that; Z = 64, N = 104, Z = 40, N = 64, and
Z = 20, N = 40, respectively. This feature is linked to concept of the
neutron(n)-proton(p)interaction in spin-orbital couplings such that;
nh9/2-ph11/2, ng7/2-pg9/2, and nf5/2-pf7/2, respectively. It is suggested that
triple shape coexistence would be possible in the Z = 20, N = 36, 56Ca, and the
Z = 18, N = 36, 54Ar, where the ferro-deformation is expected to be built on
the second 0+ state. The predicted level schemes for 52Ar, 54Ar, 56Ar, 56Ca,
58Ca, and 60Ca are presented.",1604.05013v1
2014-03-03,Quasiparticle dynamics and spin-orbital texture of the SrTiO3 two-dimensional electron gas,"Two-dimensional electron gases (2DEGs) in SrTiO$_3$ have become model systems
for engineering emergent behaviour in complex transition metal oxides.
Understanding the collective interactions that enable this, however, has thus
far proved elusive. Here we demonstrate that angle-resolved photoemission can
directly image the quasiparticle dynamics of the $d$-electron subband ladder of
this complex-oxide 2DEG. Combined with realistic tight-binding supercell
calculations, we uncover how quantum confinement and inversion symmetry
breaking collectively tune the delicate interplay of charge, spin, orbital, and
lattice degrees of freedom in this system. We reveal how they lead to
pronounced orbital ordering, mediate an orbitally-enhanced Rashba splitting
with complex subband-dependent spin-orbital textures and markedly change the
character of electron-phonon coupling, co-operatively shaping the low-energy
electronic structure of the 2DEG. Our results allow for a unified understanding
of spectroscopic and transport measurements across different classes of
SrTiO$_3$-based 2DEGs, and yield new microscopic insights on their functional
properties.",1403.0520v2
1999-06-08,Orbital symmetry of a triplet pairing in a heavy Fermion superconductor UPt_3,"The orbital symmetry of the superconducting order parameter in UPt_3 is
identified by evaluating the directionally dependent thermalconductivity and
ultrasound attenuation in the clean limit and compared with the existing data
for both basal plane and the c-axis of a hexagonal crystal. The resulting two
component orbital part expressed by (\lambda_x(k), \lambda_y(k)) is combined
with the previously determined triplet spin part, leading to clean limit and
compared with the existing data for both basal plane and the c-axis of a
hexagonal crystal. The resulting two component orbital part expressed by
(\lambda_x(k), \lambda_y(k)) is combined with the previously determined triplet
spin part, leading to the order parameter of either the non-unitary bipolar
state of the form: d(k) = b \lambda_x(k) + i j \lambda_y(k) or the unitary
planar state of the form: d(k) = b \lambda_x(k) + j \lambda_y(k) where b \perp
j = c, or a with the hexagonal unit vectors a, b and c. The d vector is
rotatable in the plane spanned by a and c perpendicular to b under weak applied
c-axis field because of the weak spin orbit coupling. Experiments are proposed
to distinguish between the equally possible these states.",9906105v1
2022-03-11,Variable and orbital-dependent spin-orbit field orientations in a InSb double quantum dot characterized via dispersive gate sensing,"Utilizing dispersive gate sensing (DGS), we investigate the spin-orbit field
($\textbf{B}_{SO}$) orientation in a many-electron double quantum dot (DQD)
defined in an InSb nanowire. While characterizing the inter-dot tunnel
couplings, the measured dispersive signal depends on the electron charge
occupancy, as well as on the amplitude and orientation of the external magnetic
field. The dispersive signal is mostly insensitive to the external field
orientation when a DQD is occupied by a total odd number of electrons. For a
DQD occupied by a total even number of electrons, the dispersive signal is
reduced when the finite external magnetic field aligns with the effective
$\textbf{B}_{SO}$ orientation. This fact enables the identification of
$\textbf{B}_{SO}$ orientations for different DQD electron occupancies. The
$\textbf{B}_{SO}$ orientation varies drastically between charge transitions,
and is generally neither perpendicular to the nanowire nor in the chip plane.
Moreover, $\textbf{B}_{SO}$ is similar for pairs of transitions involving the
same valence orbital, and varies between such pairs. Our work demonstrates the
practicality of DGS in characterizing spin-orbit interactions in quantum dot
systems, without requiring any current flow through the device.",2203.06047v2
2023-12-28,Coupling of structure and magnetism to spin splitting in hybrid organic-inorganic perovskites,"Hybrid organic-inorganic perovskites are famous for the diversity of their
chemical compositions, phases and phase transitions, and associated physical
properties. We use a combination of experimental and computational techniques
to reveal strong coupling between structure, magnetism, and spin splitting in a
representative of the largest family of hybrid organic-inorganic perovskites:
the formates. With the help of first-principles simulations, we find spin
splitting in both conduction and valence bands of [NH$_2$NH$_3$]Co(HCOO)$_3$,
induced by spin-orbit interactions, which can reach up to 14~meV. Our magnetic
measurements reveal that this material exhibits canted antiferromagnetism below
15.5 K. The direction of the associated antiferromagnetic order parameter is
strongly coupled with the spin splitting already in the centrosymmetric phase,
allowing for the creation and annihilation of spin splitting through the
application of a magnetic field. Furthermore, the structural phase transition
into experimentally observed polar Pna2$_1$ phase completely changes the
aforementioned spin splitting and its coupling to magnetic degrees of freedom.
This reveals that in [NH$_2$NH$_3$]Co(HCOO)$_3$, the structure and magnetism
are strongly coupled to spin splitting in a way that allows for its
manipulation through both magnetic and electric fields. As an example, for a
given point inside the Brillouin zone of centrosymmetric Pnma phase of
[NH$_2$NH$_3$]Co(HCOO)$_3$, spin splitting can be turned on/off by aligning the
antiferromagnetic vector along certain crystallographic directions or through
inducing a polar phase by the application of an electric field. We believe that
our findings offer an important step toward fundamental understanding and
practical applications of materials with coupled properties.",2312.17352v1
2012-08-02,Unified theory of spin-dynamics in a two dimensional electron gases with arbitrary spin-orbit coping strength at finite temperature,"We study the spin dynamics in the presence of impurity and electron-electron
(e-e) scattering in a III-V semiconductor quantum well with arbitrary
spin-orbit coupling (SOC) strength and symmetry at finite temperature. We
derive the coupled spin-charge dynamic equations in the presence of inelastic
scattering and provide a new formalism that describes the spin relaxation and
dynamics in both the weak and the strong SOC regime in a unified way. In the
weak SOC regime, as expected, our theory reproduces all previous
zero-temperature results, most of which have focused on impurity-scattering
induced spin-charge dynamics. In the regime where the strength of the Rashba
and linear Dresselhaus SOC match, known as the SU(2) symmetry point,
experiments have observed the spin-helix mode with a large spin-lifetime whose
unexplained non-monotonic temperature dependence peaks at around 75 K. As a key
test of our theory, we are able to naturally explain quantitatively this
non-monotonic dependence and show that it arises as a competition between the
Dyakonov-Perel mechanism, suppressed at the SU(2) point, and the Elliott-Yafet
mechanism. In the strong SOC regime, we show that our theory directly
reproduces the only previous known analytical result at the SU(2) symmetry
point in the ballistic regime. It also explains, as we have shown previously,
the rise of damped oscillating dynamics when the electron scattering time is
larger than half of the spin precession time due to the SOC. Hence, we provide
a unified theory of the spin-dynamics in two dimensional electron gases in the
full phase diagram experimentally accessible.",1208.0379v2
2013-02-24,Electron spin relaxation in bilayer graphene,"Electron spin relaxation due to the D'yakonov-Perel' mechanism is
investigated in bilayer graphene with only the lowest conduction band being
relevant. The spin-orbit coupling is constructed from the symmetry group
analysis with the parameters obtained by fitting to the numerical calculation
according to the latest report by Konschuh {\it et al.} [Phys. Rev. B {\bf 85},
115423 (2012)] from first principles. In contrast to single-layer graphene, the
leading term of the out-of-plane component of the spin-orbit coupling in
bilayer graphene shows a Zeeman-like term with opposite effective magnetic
fields in the two valleys. This Zeeman-like term opens a spin relaxation
channel in the presence of intervalley scattering. It is shown that the
intervalley electron-phonon scattering, which has not been reported in the
previous literature, strongly suppresses the in-plane spin relaxation time at
high temperature whereas the intervalley short-range scattering plays an
important role in the in-plane spin relaxation especially at low temperature. A
marked nonmonotonic dependence of the in-plane spin relaxation time on
temperature with a minimum of several hundred picoseconds is predicted in the
absence of the short-range scatterers. This minimum is comparable to the
experimental data. Moreover, a peak in the electron density dependence of the
in-plane spin relaxation time at low temperature, which is very different from
the one in semiconductors, is predicted. We also find a rapid decrease in the
in-plane spin relaxation time with increasing initial spin polarization at low
temperature, which is opposite to the situation in both semiconductors and
single-layer graphene. ......(The remaining is cut due to the limit of space)",1302.5880v2
2008-07-04,Intersubband-induced spin-orbit interaction in quantum wells,"Recently, we have found an additional spin-orbit (SO) interaction in quantum
wells with two subbands [Phys. Rev. Lett. 99, 076603 (2007)]. This new SO term
is non-zero even in symmetric geometries, as it arises from the intersubband
coupling between confined states of distinct parities, and its strength is
comparable to that of the ordinary Rashba. Starting from the $8 \times 8$ Kane
model, here we present a detailed derivation of this new SO Hamiltonian and the
corresponding SO coupling. In addition, within the self-consistent Hartree
approximation, we calculate the strength of this new SO coupling for realistic
symmetric modulation-doped wells with two subbands. We consider gated
structures with either a constant areal electron density or a constant chemical
potential. In the parameter range studied, both models give similar results. By
considering the effects of an external applied bias, which breaks the
structural inversion symmetry of the wells, we also calculate the strength of
the resulting induced Rashba couplings within each subband. Interestingly, we
find that for double wells the Rashba couplings for the first and second
subbands interchange signs abruptly across the zero bias, while the
intersubband SO coupling exhibits a resonant behavior near this symmetric
configuration. For completeness we also determine the strength of the
Dresselhaus couplings and find them essentially constant as function of the
applied bias.",0807.0771v2
2021-06-15,Cavity magnon-polaritons in cuprate parent compounds,"Cavity control of quantum matter may offer new ways to study and manipulate
many-body systems. A particularly appealing idea is to use cavities to enhance
superconductivity, especially in unconventional or high-$T_c$ systems.
Motivated by this, we propose a scheme for coupling Terahertz resonators to the
antiferromagnetic fluctuations in a cuprate parent compound, which are believed
to provide the glue for Cooper pairs in the superconducting phase. First, we
derive the interaction between magnon excitations of the Ne\'el-order and polar
phonons associated with the planar oxygens. This mode also couples to the
cavity electric field, and in the presence of spin-orbit interactions mediates
a linear coupling between the cavity and magnons, forming hybridized
magnon-polaritons. This hybridization vanishes linearly with photon momentum,
implying the need for near-field optical methods, which we analyze within a
simple model. We then derive a higher-order coupling between the cavity and
magnons which is only present in bilayer systems, but does not rely on
spin-orbit coupling. This interaction is found to be large, but only couples to
the bimagnon operator. As a result we find a strong, but heavily damped,
bimagnon-cavity interaction which produces highly asymmetric cavity line-shapes
in the strong-coupling regime. To conclude, we outline several interesting
extensions of our theory, including applications to carrier-doped cuprates and
other strongly-correlated systems with Terahertz-scale magnetic excitations.",2106.07828v1
2018-06-14,Spin-orbit coupling and topological phases for ultracold atoms,"Cold atoms with laser-induced spin-orbit (SO) interactions provide promising
platforms to explore novel quantum physics, in particular the exotic
topological phases, beyond natural conditions of solids. The past several years
have witnessed important progresses in both theory and experiment in the study
of SO coupling and novel quantum states for ultracold atoms. Here we review the
physics of the SO coupled quantum gases, focusing on the latest theoretical and
experimental progresses of realizing SO couplings beyond one-dimension (1D),
and the further investigation of novel topological quantum phases in such
systems, including the topological insulating phases and topological
superfluids. A pedagogical introduction to the SO coupling for ultracold atoms
and topological quantum phases is presented. We show that the so-called optical
Raman lattice schemes, which combine the creation of the conventional optical
lattice and Raman lattice with topological stability, can provide minimal
methods with high experimental feasibility to realize 1D to 3D SO couplings.
The optical Raman lattices exhibit novel intrinsic symmetries, which enable the
natural realization of topological phases belonging to different symmetry
classes, with the topology being detectable through minimal measurement
strategies. We introduce how the non-Abelian Majorana modes emerge in the SO
coupled superfluid phases which can be topologically nontrivial or trivial, for
which a few fundamental theorems are presented and discussed. The experimental
schemes for achieving non-Abelian superfluid phases are given. Finally, we
point out the future important issues in this rapidly growing research field.",1806.05628v1
2020-05-17,Nonlinear modes in spatially confined spin-orbit-coupled Bose-Einstein condensates with repulsive nonlinearity,"It was found that spatially confined spin-orbit (SO) coupling, which can be
induced by illuminating Bose-Einstein condensates (BECs) with a Gaussian laser
beam, can help trap a spinor Bose gas in multi-dimensional space. Previous
works on this topic were all based on a Boson gas featuring an attractive
interaction. In this paper, we consider the trapping effect in the case in
which the Boson gas features a repulsive interaction. After replacing the
repulsive effect, stable excited modes of semi-vortex (SV) type and mixed-mode
(MM) type, which cannot be created in a boson gas with attractive interactions,
can be found in the current setting. The trapping ability and the capacity of
the confined SO coupling versus the degree of the repulsive strength as well as
the order of the excited mode are systematically discussed firstly through the
paper. Moreover, the stability of the nonlinear mode trapped in this system
with a moving reference frame is also discussed. Unlike the system with
homogeneous SO coupling, two different types of stationary mobility modes can
be stabilized when the SO coupling moves in the x- and y- directions,
respectively. This finding indicates that the system with moving confined SO
coupling features a typical anisotropic character that differs from the system
with moving homogeneous SO coupling.",2005.08268v1
2018-03-20,Anisotropic Pauli spin-blockade effect and spin-orbit interaction field in an InAs nanowire double quantum dot,"We report on experimental detection of the spin-orbit interaction field in an
InAs nanowire double quantum dot device. In the spin blockade regime, leakage
current through the double quantum dot is measured and is used to extract the
effects of spin-orbit interaction and hyperfine interaction on spin state
mixing. At finite magnetic fields, the leakage current arising from the
hyperfine interaction is suppressed and the spin-orbit interaction dominates
spin state mixing. We observe dependence of the leakage current on the applied
magnetic field direction and determine the direction of the spin-orbit
interaction field. We show that the spin-orbit field lies in a direction
perpendicular to the nanowire axis but with a pronounced off-substrate-plane
angle. It is for the first time that such an off-substrate-plane spin-orbit
field in an InAs nanowire has been detected. The results are expected to have
an important implication in employing InAs nanowires to construct spin-orbit
qubits and topological quantum devices.",1803.07277v1
2008-01-31,Zero-field spin-splitting and spin lifetime in n-InSb/In1-xAlxSb asymmetric quantum well heterostructures,"The spin-orbit (SO) coupling parameters for lowest conduction subband due to
structural (SIA) and bulk (BIA) inversion asymmetry are calculated for a range
of carrier densities in [001]-grown delta-doped n-type InSb/In1-xAlxSb
asymmetric quantum wells using the established 8 band k.p formalism [PRB 59,8
R5312 (1999)]. We present calculations for conditions of zero bias at 10 K. It
is shown that both the SIA and BIA parameters scale approximately linearly with
carrier density, and exhibit a marked dependence on well width when alloy
composition is adjusted to allow maximum upper barrier height for a given well
width. In contrast to other material systems the BIA contribution to spin
splitting is found to be of significant and comparable value to the SIA
mechanism in these structures. We calculate the spin lifetime for spins
oriented along [11-0] based on D'yakonov-Perel mechanism using both the theory
of Averkiev et al. [J. Phys.:Condens. Matter 14 (2002)] and also the rate of
precession of spins about the effective magnetic field, taking into account all
three SO couplings, showing good agreement.Spin lifeime for this direction is
largest in the narrow wells over the range of moderate carrier densities
considered, which is attributed to the reduced magnitude of the k-cubic BIA
parameter in narrow wells. The inherently large BIA induced SO coupling in
these systems is shown to have considerable effect on the spin lifetime, which
exhibits significant reduction in the maximum spin lifetime compared to
previous studies which consider systems with relatively weak BIA induced SO
coupling. The relaxation rate of spins oriented in the [001] direction is
dominated by the k-linear SIA and BIA coupling parameters and at least an order
of magnitude greater than in the [11-0] direction.",0801.4849v2
2020-10-21,Spin-orbit coupling effects on spin-phonon coupling in Cd2Os2O7,"Spin-orbit coupling (SOC) is essential in understanding the properties of 5d
transition metal compounds, whose SOC value is large and almost comparable to
other key parameters. Over the past few years, there have been numerous studies
on the SOC-driven effects of the electronic bands, magnetism, and spin-orbit
entanglement for those materials with a large SOC. However, it is less studied
and remains an unsolved problem in how the SOC affects the lattice dynamics.
We, therefore, measured the phonon spectra of 5d pyrochlore Cd2Os2O7 over the
full Brillouin zone to address the question by using inelastic x-ray scattering
(IXS). Our main finding is a visible mode-dependence in the phonon spectra,
measured across the metal-insulator transition at 227 K. We examined the SOC
strength dependence of the lattice dynamics and its spin-phonon (SP) coupling,
with first-principle calculations. Our experimental data taken at 100 K are in
good agreement with the theoretical results obtained with the optimized U = 2.0
eV with SOC. By scaling the SOC strength and the U value in the DFT
calculations, we demonstrate that SOC is more relevant than U to explaining the
observed mode-dependent phonon energy shifts with temperature. Furthermore, the
temperature dependence of the phonon energy can be effectively described by
scaling SOC. Our work provides clear evidence of SOC producing a non-negligible
and essential effect on the lattice dynamics of Cd2Os2O7 and its SP coupling.",2010.10684v1
2023-04-11,Excitation and voltage-gated modulation of single-mode dynamics in a planar nano-gap spin Hall nano-oscillator,"We experimentally study the dynamical modes excited by current-induced
spin-orbit torque and its electrostatic gating effect in a 3-terminal planar
nano-gap spin Hall nano-oscillator (SHNO) with a moderate interfacial
perpendicular magnetic anisotropy (IPMA). Both quasilinear propagating
spin-wave and localized ""bullet"" modes are achieved and controlled by varying
the applied in-plane magnetic field and driving current. The minimum linewidth
shows a linear dependence on the actual temperature of the active area,
confirming single-mode dynamics based on the nonlinear theory of spin-torque
nano-oscillation with a single mode. The observed electrostatic gating tuning
oscillation frequency arises from voltage-controlled magnetic anisotropy and
threshold current of SHNO via modification of the nonlinear damping and/or the
interfacial spin-orbit coupling of the magnetic multilayer. In contrast to
previously observed two-mode coexistence degrading the spectral purity in
Py/Pt-based SHNOs with a negligible IPMA, a single coherent spin-wave mode with
a low driven current can be achieved by selecting the ferromagnet layer with a
suitable IPMA because the nonlinear mode coupling can be diminished by bringing
in the PMA field to compensate the easy-plane shape anisotropy. Moreover, the
simulations demonstrate that the experimentally observed current and
gate-voltage modulation of auto-oscillation modes are also closely associated
with the nonlinear damping and mode coupling, which are determined by the
ellipticity of magnetization precession. The demonstrated nonlinear mode
coupling mechanism and electrical control approach of spin-wave modes could
provide the clue to facilitate the implementation of the mutual synchronization
map for neuromorphic computing applications in SHNO array networks.",2304.05026v1
2016-06-08,Effect of ferromagnetic exchange field on band-gap and spin-polarization of graphene on a TMD substrate,"We calculate the electronic band dispersion of graphene monolayer on a two
dimensional transition metal dichalcogenide substrate (GTMD) (viz., XY2 , X =
Mo, W; Y = S, Se) around K and K prime points taking into account the interplay
of the exchange field due to the ferromagnetic impurities and the substrate
induced, sub-lattice-resolved, strongly enhanced intrinsic spin-orbit
couplings(SOC). There are extrinsic Rashba spin-orbit coupling(RSOC) and the
orbital gap related to the transfer of the electronic charge from graphene to
XY2 as well. The former allows for external tuning of the band gap in GTMD and
connects the nearest neighbors with spin-flip. On account of the strong SOC,
the system acts as a quantum spin Hall insulator. We introduce the exchange
field (M) in the Hamiltonian to take into account the deposition of Fe atoms on
the graphene surface. The cavalcade of the perturbations yield particle-hole
symmetric bands with an effective Zeeman field due to the interplay of the
substrate induced interactions with RSOC as the prime player. Our graphical
analysis with extremely low-lying states strongly suggests the following: The
GTMDs like WY2 exhibit band gap narrowing/widening (Moss-Burs-tein(MB)gap
shift)including the spin-polarization inversion(SPI) at finite but low
temperature (T = 1 K) due to the increase in the exchange field (M) at the
Dirac point K. For graphene on MoY2, on the other hand, the occurrence of the
MB-shift and the SPI at higher temperature (T = 10 K) take place as M is
increased at the Dirac point K prime. Finally, there is anti-crossing of
non-parabolic bands with opposite spins around Dirac points. A direct electric
field control of magnetism at the nano-scale is needed here. The magnetic
multi-ferroics, like BiFeO3 (BFO), are useful for this purpose due to the
coupling between the magnetic and electric order parameters.",1606.02413v2
2021-04-16,"Interplay of spin magnetism, orbital magnetism, and atomic structure in layered van der Waals ferromagnet VI$_3$","Recently discovered ferromagnetism of the layered van der Waals material
VI$_3$ attracts much research attention. Despite substantial progress,in the
following important aspects no consensus has been reached: (i) a possible
deviation of the easy axis from the normal to the VI$_3$ layers, (ii) a
possible inequivalence of the V atoms, (iii) the value of the V magnetic
moments. The theoretical works differ in the conclusions on the conduction
nature of the system,the value and the role of the V orbital moments. To the
best of our knowledge there is no theoretical works addressing issues (i) and
(ii) and only one work dealing with the reduced value of the V moment. By
combining the symmetry arguments with density functional theory (DFT) and
DFT+$U$ calculations we have shown that the antidimerization distortion of the
crystal structure reported in Phys. Rev. B {\bf 99}, 041402(R) (2019) must lead
to the deviation of the easy axis from the normal to the VI$_3$ layers in close
correlation with the experimental results. The antidimerization accompanied by
the breaking the inversion symmetry leads to the inequivalence of the V atoms.
Our DFT+U calculations result in large value 0.8\mu_B$ of the V orbital moments
of the V atoms leading to reduced total V moment in agreement with a number of
experimental results and with the physical picture suggested in Phys. Rev. B bf
101, 100402(R) (2020). We obtained large intraatomic noncollinearity of the V
spin and orbital moments revealing strong competition between effects coursed
by the on-site electron correlation, spin-orbit coupling, and interatomic
hybridization since pure intraatomic effects lead to collinear spin and orbital
moments. Our calculations confirm the experimental results of strong
magnetoelastic coupling revealing itself in the strong dependence of the
magnetic properties on the distortion of the atomic structure.",2104.07992v1
2009-03-05,"Particle Classification and Dynamics in GL(2,C) Gravity","A relatively simple approach to noncommutative gravity utilizes the gauge
theory formulation of general relativity and involves replacing the Lorentz
gauge group by a larger group. This results in additional field degrees of
freedom which either must be constrained to vanish in a nontrivial way, or
require physical interpretation. With the latter in mind, we examine the
coupling of the additional fields to point particles. Nonstandard particle
degrees of freedom should be introduced in order to write down the most general
coupling. The example we study is the $GL(2,C)$ central extension of gravity
given by Chamseddine, which contains two U(1) gauge fields, and a complex
vierbein matrix, along with the usual spin connections. For the general
coupling one should then attach two U(1) charges and a complex momentum vector
to the particle, along with the spin. The momenta span orbits in a
four-dimensional complex vector space, and are classified by $GL(2,C)$
invariants and by their little groups. In addition to orbits associated with
standard massive and massless particles, a number of novel orbits can be
identified. We write down a general action principle for particles associated
with any nontrivial orbit and show that it leads to corrections to geodesic
motion. We also examine the classical and quantum theory of the particle in
flat space-time.",0903.0882v2
2013-04-05,Anisotropic Magneto Resistance and Planar Hall Effect at the LaAlO$_3$/SrTiO$_3$ Heterointerfaces: Effect of Carrier Confinement on Magnetic Interactions,"The confinement of the two dimensional electron gas (2DEG), preferential
occupancy of the Ti 3d orbital and strong spin-orbit coupling at the
LaAlO$_3$/SrTiO$_3$ interface play a significant role in its emerging
properties. Here we report a fourfold oscillation in the anisotropic magneto
resistance (AMR) and the observation of planar Hall effect (PHE) at the
LaAlO$_3$/SrTiO$_3$ heterointerface. We evaluate the carrier confinement
effects on the AMR and find that the fourfold oscillation appears only for the
case of 2DEG system while it is twofold for the 3D system. As the fourfold
oscillation fits well to the phenomenological model for a cubic symmetry
system, we attribute this oscillation to the anisotropy in the magnetic
scattering arising from the interaction of electrons with the localized
magnetic moments coupled to the crystal symmetry. The AMR behavior is further
found to be sensitive to applied gate electric field, emphasizing the
significance of spin-orbit coupling at the interface. These confinement effects
suggest that the magnetic interactions are predominant at the interface, and
the gate electric field modulation of AMR suggest the possible gate tunable
magnetic interactions in these systems. The observed large PHE further
indicates that the in plane nature of magnetic ordering arises from the
in-plane Ti 3dxy orbitals.",1304.1619v1
2014-09-28,Generalized Hund's rule for two-atom systems,"Hund's rule is one of the fundamentals of the correlation physics at the
atomic level, determining the ground state multiplet of the electrons. It
consists of three laws: (i) maximum $S$ (total spin), (ii) maximum $L$ (total
orbital angular momentum) under the constraint of (i), and (iii) the total
angular momentum $J$ is $|L-S|$ for electron number less than half, while
$J=L+S$ for more than half due to the relativistic spin-orbit interaction
(SOI). In real systems, the electrons hop between the atoms and gain the
itinerancy, which is usually described by the band theory. The whole content of
theories on correlation is to provide a reliable way to describe the
intermediate situation between the two limits. Here we propose an approach
toward this goal, i.e., we study the two-atom systems of three $t_{2g}$
orbitals and see how the Hund's rule is modified by the transfer integral $t$
between them. It is found that the competition between $t$ and the Hund's
coupling $J$ at each atom determines the crossover from the molecular orbital
limit to the strong correlation limit. Especially, the focus is on the
generalization of the third rule, i.e., the inter-and intra-atomic SOI's in the
presence of the correlation. We have found that there are cases where the
effective SOI's are appreciably enhanced by the Hund's coupling. The conditions
for the enhancement are the intermediate Hund's coupling and the filling of
four or five electrons.",1409.7858v1
2003-10-01,Spin and orbital structure of uranium compounds on the basis of a j-j coupling scheme,"Key role of orbital degree of freedom to understand the magnetic structure of
uranium compounds is discussed from a microscopic viewpoint by focusing on
typical examples such as UMGa$_5$ (M=Ni and Pt) and the mother compound
UGa$_3$. By analyzing an orbital degenerate Hubbard model constructed from the
$j$-$j$ coupling scheme in the cubic system, we obtain the phase diagram
including several kinds of magnetic states. Especially, in the parameter region
corresponding to actual uranium compounds, the phase diagram suggests
successive transitions among paramagnetic, magnetic metallic, and insulating
N\'eel states, consistent with the experimental results for AuCu$_3$-type
uranium compounds. Furthermore, taking account of tetragonal effects such as
level splitting and reduction of hopping amplitude along the z-axis, an
orbital-based scenario is proposed to understand the change in the magnetic
structure from G- to A-type antiferromagnetic phases, experimentally observed
in UNiGa$_5$ and UPtGa$_5$.",0310008v2
2009-08-27,Magnetic groundstates in a correlated two orbital Hubbard model,"We examine the orbital and magnetic order of the two orbital Hubbard model
within dynamical mean field theory. The model describes the low energy physics
of a partially filled $e_g$-band as can be found in some transition metal
compounds. The model shows antiferromagnetic as well as ferromagnetic phases.
For stabilizing ferromagnetism we find that Hund's coupling is particularly
important. Quarter filling represents a very special situation in the phase
diagram, where the coupling of spin, charge, and orbital degrees of freedom are
involved. Exactly at quarter filling we find a metal insulator transition (MIT)
between two almost fully polarized ferromagnetic states. This MIT can be tuned
by changing the local interaction strength and seems to be a first order
transition at zero temperature. Apart from these ferromagnetic states we were
also able to stabilize antiferromagnetic and charge ordered phases at quarter
filling, depending on the interaction parameters.",0908.3990v2
2019-09-18,Efficient Formulation of Ab Initio Quantum Embedding in Periodic Systems: Dynamical Mean-Field Theory,"We present an efficient ab initio dynamical mean-field theory (DMFT)
implementation for quantitative simulations in solids. Our DMFT scheme employs
ab initio Hamiltonians defined for impurities comprising the full unit cell or
a supercell of atoms and for realistic quantum chemical basis sets. We avoid
double counting errors by using Hartree-Fock as the low-level theory. Intrinsic
and projected atomic orbitals (IAO+PAO) are chosen as the local embedding
basis, facilitating numerical bath truncation. Using an efficient integral
transformation and coupled-cluster Green's function (CCGF) impurity solvers, we
are able to handle embedded impurity problems with several hundred orbitals. We
apply our ab initio DMFT approach to study a hexagonal boron nitride monolayer,
crystalline silicon, and nickel oxide in the antiferromagnetic phase, with up
to 104 and 78 impurity orbitals in spin-restricted and unrestricted cluster
DMFT calculations and over 100 bath orbitals. We show that our scheme produces
accurate spectral functions compared to both benchmark periodic coupled-cluster
computations and experimental spectra.",1909.08592v2
2021-02-07,Berry curvature induced magnetotransport in 3D noncentrosymmetric metals,"We study the magnetoelectric and magnetothermal transport properties of
noncentrosymmetric metals using semiclassical Boltzmann transport formalism by
incorporating the effects of Berry curvature and orbital magnetic moment. These
effects impart quadratic-B dependence to the magnetoelectric and magnetothermal
conductivities, leading to intriguing phenomena such as planar Hall effect,
negative magnetoresistance, planar Nernst effect and negative Seebeck effect.
The transport coefficients associated with these effects show the usual
oscillatory behavior with respect to the angle between the applied electric
field and magnetic field. The bands of noncentrosymmetric metals are split by
Rashba spin-orbit coupling except at a band touching point. For Fermi energy
below (above) the band touching point, giant (diminished) negative
magnetoresistance is observed. This difference in the nature of
magnetoresistance is related to the magnitudes of the velocities, Berry
curvature and orbital magnetic moment on the respective Fermi surfaces, where
the orbital magnetic moment plays the dominant role. The absolute
magnetoresistance and planar Hall conductivity show a decreasing (increasing)
trend with Rashba coupling parameter for Fermi energy below (above) the band
touching point.",2102.03779v2
2022-04-23,Stability analysis of circular orbits around a traversable wormhole with massless conformally coupled scalar field,"We study the stability of circular orbits in the background of a traversable
wormhole (TWH) spacetime obtained as a solution of Einstein's field equations
coupled conformally to a massless scalar field. The Lyapunov stability approach
is employed to determine the stability of circular orbits (timelike and null)
of non-spinning test particles around a TWH spacetime. In the case of timelike
geodesics, the particle is confined to move in four different types of
effective potentials depending on various values of the angular momentum L with
both centrifugal and gravitational part. The effective potential for null
geodesics consists of only a centrifugal part. Further, we characterize each
fixed point according to its Lyapunov stability, and thus classify the circular
orbits at the fixed point into stable center and unstable saddle points by
depicting the corresponding phase-portraits.",2204.10988v1
2023-01-03,Angular Momentum for Black Hole Binaries in Numerical Relativity,"The extensive catalog of waveforms, with details of binary black hole
inspiral and merger, offer an opportunity to understand black hole interactions
beyond the large separation regime. We envision a research program that focuses
on the transfer of angular momentum from spin of the individual holes to the
orbital angular momentum and the role of tidal coupling in the process. That
analysis will require the formulation of an expression for the orbital angular
momentum of a binary, an expression that is useful at small separations, since
that regime is well out of the range of Newtonian approximations and is where
tidal coupling should be most interesting. We report here such an expression, a
binary orbital angular momentum based on numerical relativity results for
quasi-circular orbits, that agrees remarkably well with a similar quantity
constructed with particle-perturbation techniques for the Kerr geometry.",2301.01185v2
1998-12-07,Resonant Tidal Excitations of Rotating Neutron Stars in Coalescing Binaries,"In a coalescing neutron star-neutron star (NS-NS) or neutron star-black hole
(NS-BH) binary, oscillation modes of the NS can be resonantly excited by the
companion during the final minutes of the inspiral. The resonant energy
transfer between the orbit and NS speeds up or slows down the inspiral and
induces a phase change in the emitted gravitational waves from the binary. A
tidal resonance, (jk,m), occurs when the mode frequency equals m times the
orbital frequency. For f-mode resonance to occur before coalescence, the NS
must have rapid rotation, with spin frequency nu_s>710Hz for (22,2)-resonance
and nu_s>570Hz for (33,3)-resonance (M=1.4Mo and R=10km; however, for R=15km,
these spin frequencies become 330Hz and 250Hz). Because of strong tidal
coupling, f-mode resonances induce a large change in the number of orbital
cycles, N_orb, with maximum N_orb~10-1000 for (22,2)-resonance and N_orb~1 for
(33,3)- resonance. Such resonant effects, if present, must be included in
constructing waveform templates used in searching for gravitational wave
signals. Higher order f-mode resonances can occur at slower rotation rates, but
N_orb<0.1. For the dominant g-mode (22,2)-resonance, even modest rotation
(nu_s<100Hz) can enhance the resonant effect on the orbit by shifting resonance
to a smaller orbital frequency. However, because of the weak coupling, N_orb
lies in the range 10^-3-10^-2 (depending on the NS EOS) and is probably
negligible for the purpose of detecting gravitational waves. R-mode resonances
require misaligned spin-orbit inclinations, and the dominant resonances
correspond to (22,3) and (22,1). Since tidal coupling depends strongly on
rotation rate, N_orb<10^-2(R/10km)^(10)(M/1.4Mo)^(-20/3) is negligible for
canonical NS parameters but can be appreciable if the NS radius is larger.",9812116v2
2010-04-28,Scalable quantum register based on coupled electron spins in a room temperature solid,"Realization of devices based on quantum laws might lead to building
processors that outperform their classical analogues and establishing
unconditionally secure communication protocols. Solids do usually present a
serious challenge to quantum coherence. However, owing to their spin-free
lattice and low spin orbit coupling, carbon materials and particularly diamond
are suitable for hosting robust solid state quantum registers. We show that
scalable quantum logic elements can be realized by exploring long range
magnetic dipolar coupling between individually addressable single electron
spins associated with separate color centers in diamond. Strong distance
dependence of coupling was used to characterize the separation of single qubits
98 A with unprecedented accuracy (3 A) close to a crystal lattice spacing. Our
demonstration of coherent control over both electron spins, conditional
dynamics, selective readout as well as switchable interaction, opens the way
towards a room temperature solid state scalable quantum register. Since both
electron spins are optically addressable, this solid state quantum device
operating at ambient conditions provides a degree of control that is currently
available only for atomic systems.",1004.5090v1
2018-04-11,Maximum spin polarization in chromium dimer cations as demonstrated by x-ray magnetic circular dichroism spectroscopy,"X-ray magnetic circular dichroism spectroscopy has been used to characterize
the electronic structure and magnetic moment of Cr$_2^+$. Our results indicate
that the removal of a single electron from the $4s\sigma_g$ bonding orbital of
Cr$_2$ drastically changes the preferred coupling of the $3d$ electronic spins.
While the neutral molecule has a zero-spin ground state with a very short bond
length, the molecular cation exhibits a ferromagnetically coupled ground state
with the highest possible spin of $S=11/2$, and almost twice the bond length of
the neutral molecule. This spin configuration can be interpreted as a result of
indirect exchange coupling between the $3d$ electrons of the two atoms that is
mediated by the single $4s$ electron through a strong intraatomic $3d$-$4s$
exchange interaction. Our finding allows an estimate of the relative energies
of two states that are often discussed as ground-state candidates, the
ferromagnetically coupled $^{12}\Sigma$ and the low-spin $^2\Sigma$ state.",1804.03866v1
2020-09-12,Long-range exchange interaction between spin qubits mediated by a superconducting link at finite magnetic field,"Solid state spin qubits are promising candidates for the realization of a
quantum computer due to their long coherence times and easy electrical
manipulation. However, spin-spin interactions, which are needed for entangling
gates, have only limited range as they generally rely on tunneling between
neighboring quantum dots. This severely constrains scalability. Proposals to
extend the interaction range generally focus on coherent electron transport
between dots or on extending the coupling range. Here, we study a setup where
such an extension is obtained by using a superconductor as a quantum mediator.
Because of its gap, the superconductor effectively acts as a long tunnel
barrier. We analyze the impact of spin-orbit (SO) coupling, external magnetic
fields, and the geometry of the superconductor. We show that while spin
non-conserving tunneling between the dots and the superconductor due to SO
coupling does not affect the exchange interaction, strong SO scattering in the
superconducting bulk is detrimental. Moreover, we find that the addition of an
external magnetic field decreases the strength of the exchange interaction.
Fortunately, the geometry of the superconducting link offers a lot of room to
optimize the interaction range, with gains of over an order of magnitude from a
2D film to a quasi-1D strip. We estimate that for superconductors with weak SO
coupling (\textit{e.g.}, aluminum) exchange rates of up to 100\,MHz over a
micron-scale range can be achieved with this setup in the presence of magnetic
fields of the order of 100\,mT.",2009.05775v1
2022-03-01,Ultrafast enhancement of interfacial exchange coupling in ferromagnetic bilayer,"Fast spin manipulation in magnetic heterostructures, where magnetic
interactions between different materials often define the functionality of
devices, is a key issue in the development of ultrafast spintronics. Although
recently developed optical approaches such as ultrafast spin-transfer and
spin-orbit torques open new pathways to fast spin manipulation, these processes
do not fully utilize the unique possibilities offered by interfacial magnetic
coupling effects in ferromagnetic multilayer systems. Here, we experimentally
demonstrate ultrafast photo-enhanced interfacial exchange interactions in the
ferromagnetic Co$_2$FeAl/(Ga,Mn)As system at low laser fluence levels. The
excitation efficiency of Co$_2$FeAl with the (Ga,Mn)As layer is 30-40 times
higher than the case with the GaAs layer at 5 K due to a photo-enhanced
exchange coupling interaction via photoexcited charge transfer between the two
ferromagnetic layers. In addition, the coherent spin precessions persist to
room temperature, excluding the drive of photo-enhanced magnetization in the
(Ga,Mn)As layer and indicating a proximity-effect-related optical excitation
mechanism. The results highlight the importance of considering the range of
interfacial exchange interactions in ferromagnetic heterostructures and how
these magnetic coupling effects can be utilized for ultrafast, low-power spin
manipulation.",2203.00293v3
1999-05-18,First-Principles Calculations of Hyperfine Interactions in La_2CuO_4,"We present the results of first-principles cluster calculations of the
electronic structure of La_2CuO_4. Several clusters containing up to nine
copper atoms embedded in a background potential were investigated.
Spin-polarized calculations were performed both at the Hartree-Fock level and
with density functional methods with generalized gradient corrections to the
local density approximation. The distinct results for the electronic structure
obtained with these two methods are discussed. The dependence of the
electric-field gradients at the Cu and the O sites on the cluster size is
studied and the results are compared to experiments. The magnetic hyperfine
coupling parameters are carefully examined. Special attention is given to a
quantitative determination of on-site and transferred hyperfine fields. We
provide a detailed analysis that compares the hyperfine fields obtained for
various cluster sizes with results from additional calculations of spin states
with different multiplicities. From this we conclude that hyperfine couplings
are mainly transferred from nearest neighbor Cu^{2+} ions and that
contributions from further distant neighbors are marginal. The mechanisms
giving rise to transfer of spin density are worked out. Assuming conventional
values for the spin-orbit coupling, the total calculated hyperfine interaction
parameters are compared to informations from experiments.",9905246v1
2004-09-13,Manifestation of the spin-Hall effect through transport measurements in the mesoscopic regime,"We study theoretically the manifestation of the spin-Hall effect in a
two-dimensional electronic system with Rashba spin-orbit coupling via
dc-transport measurements in realistic mesoscopic H-shape structures. The
Landauer-Buttiker formalism is used to model samples with mobilities and Rashba
coupling strengths of current experiments and to demonstrate the appearance of
a measurable Rashba-coupling dependent voltage. This type of measurement
requires only metal contacts, i.e., no magnetic elements are present. We also
confirm the robustness of the intrinsic spin-Hall effect against disorder in
the mesoscopic metallic regime in agreement with results of exact
diagonalization studies in the bulk.",0409334v1
2002-03-04,"Gravitomagnetism in Metric Theories: Analysis of Earth Satellites Results, and its Coupling with Spin","Employing the PPN formalism the gravitomagnetic field in different metric
theories is considered in the analysis of the LAGEOS results. It will be shown
that there are several models that predict exactly the same effect that general
relativity comprises. In other words, these Earth satellites results can be
taken as experimental evidence that the orbital angular momentum of a body does
indeed generate space--time geometry, notwithstanding they do not endow general
relativity with an outstanding status among metric theories. Additionally the
coupling spin--gravitomagnetic field is analyzed with the introduction of the
Rabi transitions that this field produces on a quantum system with spin 1/2.
Afterwards, a continuous measurement of the energy of this system is
introduced, and the consequences upon the corresponding probabilities of the
involved gravitomagnetic field will be obtained. Finally, it will be proved
that these proposals allows us, not only to confront against future experiments
the usual assumption of the coupling spin--gravotimagnetism, but also to
measure some PPN parameters and to obtain functional dependences among them.",0203013v1
1999-11-14,Atomic Quantum Computer,"The current proposals for the realization of quantum computer such as NMR,
quantum dots and trapped ions are based on the using of an atom or an ion as
one qubit. In these proposals a quantum computer consists from several atoms
and the coupling between them provides the coupling between qubits necessary
for a quantum gate. We discuss whether a {\it single} atom can be used as a
quantum computer. Internal states of the atom serve to hold the quantum
information and the spin-orbit and spin-spin interaction provides the coupling
between qubits in the atomic quantum computer. In particular one can use the
electron spin resonance (ESR) to process the information encoded in the
hyperfine splitting of atomic energy levels. By using quantum state engineering
one can manipulate the internal states of the natural or artificial (quantum
dot) atom to make quantum computations.",9911062v1
2009-06-26,Exchange coupling in silicon quantum dots: Theoretical considerations for quantum computation,"We study exchange coupling in Si double quantum dots, which have been
proposed as suitable candidates for spin qubits due to their long spin
coherence times. We discuss in detail two alternative schemes which have been
proposed for implementing spin qubits in quantum dots. One scheme uses spin
states in a single dot and the interdot exchange coupling controls interactions
between unbiased dots. The other scheme employs the singlet and triplet states
of a biased double dot as the two-level system making up the qubit and exchange
controls the energy splitting of the levels. Exchange in these two
configurations depends differently on system parameters. Our work relies on the
Heitler-London approximation and the Hund-Mulliken molecular orbital method.
The results we obtain enable us to investigate the sensitivity of the system to
background charge fluctuations and determine the conditions under which optimal
spots, at which the influence of the charge noise is minimized, may exist in Si
double quantum dot structures.",0906.4793v3
2010-01-29,Multichannel effects in Rashba quantum wires,"We investigate intersubband mixing effects in multichannel quantum wires in
the presence of Rashba spin-orbit coupling and attached to two terminals. When
the contacts are ferromagnetic and their magnetization direction is
perpendicular to the Rashba field, the spin-transistor current is expected to
depend in a oscillatory way on the Rashba coupling strength due to spin
coherent oscillations of the travelling electrons. Nevertheless, we find that
the presence of many propagating modes strongly influences the spin precession
effect, leading to (i) a quenching of the oscillations and (ii) strongly
irregular curves for high values of the Rashba coupling. We also observe that
in the case of leads' magnetization parallel to the Rashba field, the
conductance departs from a uniform value as the Rashba strength increases. We
also discuss the Rashba interaction induced current polarization effects when
the contacts are not magnetic and investigate how this mechanism is affected by
the presence of several propagating channels.",1001.5393v1
2011-09-06,Two-Dimensional Topological Insulator State and Topological Phase Transition in Bilayer Graphene,"We show that gated bilayer graphene hosts a strong topological insulator (TI)
phase in the presence of Rashba spin-orbit (SO) coupling. We find that gated
bilayer graphene under preserved time-reversal symmetry is a quantum valley
Hall insulator for small Rashba SO coupling $\lambda_{\mathrm{R}}$, and
transitions to a strong TI when $\lambda_{\mathrm{R}} > \sqrt{U^2+t_\bot^2}$,
where $U$ and $t_\bot$ are respectively the interlayer potential and tunneling
energy. Different from a conventional quantum spin Hall state, the edge modes
of our strong TI phase exhibit both spin and valley filtering, and thus share
the properties of both quantum spin Hall and quantum valley Hall insulators.
The strong TI phase remains robust in the presence of weak graphene intrinsic
SO coupling.",1109.1131v1
2011-10-07,Nonlinear Dynamics in a Magnetic Josephson Junction,"We theoretically consider a Josephson junction formed by a ferromagnetic
spacer with a strong spin-orbit interaction or a magnetic spin valve, i.e., a
bilayer with one static and one free layer. Electron spin transport facilitates
a nonlinear dynamical coupling between the magnetic moment and charge current,
which consists of normal and superfluid components. By phenomenologically
adding reactive and dissipative interactions (guided by structural and Onsager
symmetries), we construct magnetic torques and charge pumping, whose
microscopic origins are also discussed. A stability analysis of our coupled
nonlinear systems generates a rich phase diagram with fixed points, limit
cycles, and quasiperiodic states. Our findings reduce to the known phase
diagrams for current-biased nonmagnetic Josephson junctions, on the one hand,
and spin-torque driven magnetic films, on the other, in the absence of coupling
between the magnetic and superconducting order parameters.",1110.1680v1
2012-10-29,Pure spin decoherence in quantum dots,"We uncover two microscopic physical settings with significant pure spin
decoherence. First, for quantum dots (QD) electrostatically confined in
two-dimensional hole gas, decoherence comes from qubit spin-orbit (SO) coupling
to phonons, whose decay due to free charge carriers in contacts is described by
Ohmic weighted phonon spectral function. We derive significant SO interactions
affecting holes with origin and symmetry distinct from that of conventionally
considered Dresselhaus and Rashba terms. In the second setting of electron or
hole QDs coupled to a linear chain of atoms, decoherence is due to
spin-dependent coupling to phonons, whose decay due to scattering off the free
ends of a chain is described by the weighted phonon spectral function inverse
proportional to frequency. The decoherence rate in both settings is linear in
temperature.",1210.7825v1
2013-11-30,Ferroelectric Rashba Semiconductors as a novel class of multifunctional materials,"The discovery of novel properties, effects or microscopic mechanisms in
modern materials science is often driven by the quest for combining, into a
single compound, several functionalities: not only the juxtaposition of the
latter functionalities, but especially their coupling, can open new horizons in
basic condensed matter physics as well as in technology. Semiconductor
spintronics makes no exception. In this context, we have discovered by means of
density-functional simulations that, when a sizeable spin-orbit coupling is
combined with ferroelectricity, such as in GeTe, one obtains novel
multifunctional materials - called Ferro-Electric Rashba Semi-Conductors
(FERSC) - where, thanks to a giant Rashba spin-splitting, the spin texture is
controllable and switchable via an electric field. This peculiar spin-electric
coupling can find a natural playground in small-gap insulators, such as
chalcogenides, and can bring brand new assets into the field of
electrically-controlled semiconductor spintronics",1312.0095v2
2016-06-02,"Bicollinear Antiferromagnetic Order, Monoclinic Distortion, and Reversed Resistivity Anisotropy in FeTe as a Result of Spin-Lattice Coupling","The bicollinear antiferromagnetic order experimentally observed in FeTe is
shown to be stabilized by the coupling $\tilde g_{12}$ between monoclinic
lattice distortions and the spin-nematic order parameter with $B_{\rm 2g}$
symmetry, within a three-orbital spin-fermion model studied with Monte Carlo
techniques. A finite but small value of $\tilde g_{12}$ is required, with a
concomitant lattice distortion compatible with experiments, and a
tetragonal-monoclinic transition strongly first order. Remarkably, the
bicollinear state found here displays a planar resistivity with the ""reversed""
puzzling anisotropy discovered in transport experiments.Orthorhombic
distortions are also incorporated and phase diagrams interpolating between
pnictides and chalcogenides are presented. We conclude that the spin-lattice
coupling discussed here is sufficient to explain the challenging properties of
FeTe.",1606.00904v1
2017-12-16,High pressure electron spin resonance of the endohedral fullerene $^{15}\mathrm{N@C}_{60}$,"We measure the electron spin resonance spectrum of the endohedral fullerene
molecule $^{15}\mathrm{N@C}_{60}$ at pressures ranging from atmospheric
pressure to 0.25 GPa, and find that the hyperfine coupling increases linearly
with pressure. We present a model based on van der Waals interactions, which
accounts for this increase via compression of the fullerene cage and consequent
admixture of orbitals with a larger hyperfine coupling. Combining this model
with theoretical estimates of the bulk modulus, we predict the pressure shift
and compare it to our experimental results, finding fair agreement given the
spread in estimates of the bulk modulus. The spin resonance linewidth is also
found to depend on pressure. This is explained by considering the
pressure-dependent viscosity of the solvent, which modifies the effect of
dipolar coupling between spins within fullerene clusters.",1712.05991v1
2020-08-21,Cavity Control over Heavy-Hole Spin Qubits in Inversion-Symmetric Crystals,"The pseudospin of heavy-holes (HHs) confined in a semiconductor quantum dot
(QD) represents a promising candidate for a fast and robust qubit. While hole
spin manipulation by a classical electric field utilizing the Dresselhaus
spin-orbit interaction (SOI) has been demonstrated, our work explores
cavity-based qubit manipulation and coupling schemes for inversion-symmetric
crystals forming a planar HH QD. Choosing the exemplary material Germanium
(Ge), we derive an effective cavity-mediated ground state spin coupling that
harnesses the cubic Rashba SOI. In addition, we propose an optimal set of
parameters which allows for Rabi frequencies in the MHz range, thus entering
the strong coupling regime of cavity quantum electrodynamics.",2008.09436v1
2020-08-28,Signatures of nonlinear magnetoelectricity in second harmonic spectra of SU(2) symmetry broken quantum many-body systems,"Quantum mechanical perturbative expressions for second order dynamical
magnetoelectric (ME) susceptibilities have been derived and calculated for a
small molecular system using the Hubbard Hamiltonian with SU(2) symmetry
breaking in the form of spin-orbit coupling (SOC) or spin-phonon coupling.
These susceptibilities will have signatures in second harmonic generation
spectra. We show that SU(2) symmetry breaking is the key to generate these
susceptibilities. We have calculated these ME coefficients by solving the
Hamiltonian for low lying excited states using Lanczos method. Varying the
Hubbard term along with SOC strength, we find spin and charge and both
spin-charge dominated spectra of dynamical ME coefficients. We have shown that
intensities of the peaks in the spectra are highest when the magnitudes of
Hubbard term and SOC coupling term are in similar range.",2008.12521v1
2016-12-21,Superconducting grid-bus surface code architecture for hole-spin qubits,"We present a scalable hybrid architecture for the 2D surface code combining
superconducting resonators and hole-spin qubits in nanowires with tunable
direct Rashba spin-orbit coupling. The back-bone of this architecture is a
square lattice of capacitively coupled coplanar waveguide resonators each of
which hosts a nanowire hole-spin qubit. Both the frequency of the qubits and
their coupling to the microwave field are tunable by a static electric field
applied via the resonator center pin. In the dispersive regime, an entangling
two-qubit gate can be realized via a third order process, whereby a virtual
photon in one resonator is created by a first qubit, coherently transferred to
a neighboring resonator, and absorbed by a second qubit in that resonator.
Numerical simulations with state-of-the-art coherence times yield gate
fidelities approaching the $99\%$ fault tolerance threshold.",1612.07292v1
2021-11-22,Evolution of Interorbital Superconductor to Intraorbital Spin-Density Wave in Layered Ruthenates,"The ruthenate family of layered perovskites has been a topic of intense
interest with much work dedicated to understanding the superconducting state of
the single layer, Sr$_2$RuO$_4$. Another longstanding puzzle is the lack of
superconductivity in its sister compound, Sr$_3$Ru$_2$O$_7$, which constrains
the possible superconducting mechanisms of Sr$_2$RuO$_4$. Here we address a
microscopic mechanism that unifies superconducting and spin-density wave order
in this family of materials. Beginning from a model of Sr$_2$RuO$_4$ featuring
intraband pseudospin-singlet superconductivity originating from interorbital
spin-triplet pairing via Hund's and spin-orbit couplings, the addition of
bilayer coupling and staggered rotations of the oxygen octahedra are
investigated. We find that the bilayer coupling alone enhances
superconductivity, while staggered rotations destroy interorbital
superconductivity, leaving a paramagnetic metal. The magnetic field then shifts
van Hove singularities near the Fermi level, allowing intraorbital SDW order to
form in the bilayer. Our theory predicts that bilayer Sr$_3$Ru$_2$O$_7$ without
staggered rotations exhibits interorbital superconductivity with a possibly
higher transition temperature.",2111.11452v2
2022-12-19,An empirical spectroscopic model for eleven electronic states of VO,"Previously-determined empirical energy levels are used to construct a
rovibronic model for the $\mathrm{X}\,^4\Sigma^-$, $\mathrm{A}'\,^4\Phi$,
$\mathrm{A}\,^4\Pi$, $\mathrm{B}\,^4\Pi$, $\mathrm{C}\,^4\Sigma^-$,
$\mathrm{D}\,^4\Delta$, $\mathrm{1}\,^2\Delta$, $\mathrm{1}\,^2\Sigma^+$,
$\mathrm{1}\,^2\Phi$, $\mathrm{1}\,^2\Pi$ and $\mathrm{2}\,^2\Pi$ electronic
states of vanadium mononoxide. The spectrum of VO is characterized by many
couplings and crossings between the states associated with these curves. The
model is based on the use of potential energy curves, represented as extended
Morse oscillators, and couplings (spin-orbit, spin-spin, angular momentum),
represented by polynomials, which are tuned to the data plus an empirical
allowance for spin-rotation couplings. The curves are used as input for the
variational nuclear motion code \duo. For the $\mathrm{X}\,^4\Sigma^-$,
$\mathrm{1}\,^2\Phi$ and $\mathrm{1}\,^2\Pi$ states the model reproduces the
observed energy to significantly better than 0.1 $\mathrm{cm}^{-1}$. For the
other states the standard deviations are between 0.25 and 1.5
$\mathrm{cm}^{-1}$. Further experimental data and consideration of hyperfine
effects would probably be needed to significantly improve this situation.",2212.09223v1
2023-09-02,Predication of novel effects in rotational nuclei at high speed,"The study of high-speed rotating matter is a crucial research topic in
physics due to the emergence of novel phenomena. In this paper, we combined
cranking covariant density functional theory (CDFT) with a similar
renormalization group approach to decompose the Hamiltonian from the cranking
CDFT into different Hermit components, including the non-relativistic term, the
dynamical term, the spin-orbit coupling, and the Darwin term. Especially, we
obtained the rotational term, the term relating to Zeeman effect-like, and the
spin-rotation coupling due to consideration of rotation and spatial component
of vector potential. By exploring these operators, we aim to identify novel
phenomena that may occur in rotating nuclei. Signature splitting, Zeeman
effect-like, spin-rotation coupling, and spin current are among the potential
novelties that may arise in rotating nuclei. Additionally, we investigated the
observability of these phenomena and their dependence on various factors such
as nuclear deformation, rotational angular velocity, and strength of magnetic
field.",2309.00786v1
2023-10-05,Boosting the Edelstein effect of two-dimensional electron gases by ferromagnetic exchange,"Strontium titanate (SrTiO$_3$) two-dimensional electron gases (2DEGs) have
broken spatial inversion symmetry and possess a finite Rashba spin-orbit
coupling. This enables the interconversion of charge and spin currents through
the direct and inverse Edelstein effects, with record efficiencies at low
temperature, but more modest effects at room temperature. Here, we show that
making these 2DEGs ferromagnetic enhances the conversion efficiency by nearly
one order of magnitude. Starting from the experimental band structure of
non-magnetic SrTiO$_3$ 2DEGs, we mimic magnetic exchange coupling by
introducing an out-of-plane Zeeman term in a tight-binding model. We then
calculate the band structure and spin textures for increasing internal magnetic
fields and compute the Edelstein effect using a semiclassical Boltzmann
approach. We find that the conversion efficiency first increases strongly with
increasing magnetic field, then shows a maximum and finally decreases. This
field dependence is caused by the competition of the exchange coupling with the
effective Rashba interaction. While enhancing the splitting of band pairs
amplifies the Edelstein effect, weakening the in-plane Rashba-type spin texture
reduces it.",2310.03348v1
2019-01-15,Negative flat band magnetism in a spin-orbit coupled correlated kagome magnet,"It has long been speculated that electronic flat band systems can be a
fertile ground for hosting novel emergent phenomena including unconventional
magnetism and superconductivity. Although flat bands are known to exist in a
few systems such as heavy fermion materials and twisted bilayer graphene, their
microscopic roles and underlying mechanisms in generating emergent behavior
remain elusive. Here we use scanning tunneling microscopy to elucidate the
atomically resolved electronic states and their magnetic response in the kagome
magnet Co3Sn2S2. We observe a pronounced peak at the Fermi level, which is
identified to arise from the kinetically frustrated kagome flat band.
Increasing magnetic field up to +-8T, this state exhibits an anomalous
magnetization-polarized Zeeman shift, dominated by an orbital moment in
opposite to the field direction. Such negative magnetism can be understood as
spin-orbit coupling induced quantum phase effects tied to non-trivial flat band
systems. We image the flat band peak, resolve the associated negative
magnetism, and provide its connection to the Berry curvature field, showing
that Co3Sn2S2 is a rare example of kagome magnet where the low energy physics
can be dominated by the spin-orbit coupled flat band. Our methodology of
probing band-resolved ordering phenomena such as spin-orbit magnetism can also
be applied in future experiments to elucidate other exotic phenomena including
flat band superconductivity and anomalous quantum transport.",1901.04822v2
2009-01-28,Spatial trends of non-collinear exchange coupling mediated by itinerant carriers with different Fermi surfaces,"We study the exchange coupling mediated by itinerant carriers with spin-orbit
interaction by both analytic and numeric approaches. The mediated exchange
coupling is non-collinear and its spatial trends depend on the Fermi surface
topology of the itinerant carriers. Taking Rashba interaction as an example,
the exchange coupling is similar to the conventional
Ruderman-Kittel-Kasuya-Yosida type in weak coupling. On the other hand, in the
strong coupling, the spiral interaction dominates. In addition, inclusion of
finite spin relaxation always makes the non-collinear spiral exchange
interaction dominant. Potential applications of our findings are explained and
discussed.",0901.4577v1
2012-09-10,Inelastic Electron Tunneling Spectroscopy for Topological Insulators,"Inelastic Electron Tuneling Spectroscopy (IETS) is a powerful spectroscopy
that allows one to investigate the nature of local excitations and energy
transfer in the system of interest. We study IETS for Topological Insulators
(TI) and investigate the role of inelastic scattering on the Dirac node states
on the surface of TIs. Local inelastic scattering is shown to significantly
modify the Dirac node spectrum. In the weak coupling limit, peaks and steps are
induced in second derivative $d^2I/dV^2$. In the strong coupling limit, the
local negative U centers are formed at impurity sites, and the Dirac cone
structure is fully destroyed locally. At intermediate coupling resonance peaks
emerge. We map out the evolution of the resonance peaks from weak to strong
coupling, which interpolate nicely between the two limits. There is a sudden
qualitative change of behavior at intermediate coupling, indicating the
possible existence of a local quantum phase transition. We also find that even
for a simple local phonon mode the inherent coupling of spin and orbital
degrees in TI leads to the spin polarized texture in inelastic Friedel
oscillations induced by local mode.",1209.2055v1
2023-09-22,Chaotic motion of scalar particle coupling to Chern-Simons invariant in the stationary axisymmetric Einstein-Maxwell dilaton black hole spacetime,"We investigate the motion of a test scalar particle coupling to the
Chern-Simons (CS) invariant in the background of a stationary axisymmetric
black hole in the Einstein-Maxwell-Dilaton-Axion (EMDA) gravity. Comparing with
the case of a Kerr black hole, we observe that the presence of the dilation
parameter makes the CS invariant more complex, and changes the range of the
coupling parameter and the spin parameter where the chaotic motion appears for
the scalar particle. Moreover, we find that the coupling parameter together
with the spin parameter also affects the range of the dilation parameter where
the chaos occurs. We also probe the effects of the dilation parameter on the
chaotic strength of the chaotic orbits for the coupled particle. Our results
indicate that the coupling between the CS invariant and the scalar particle
yields the richer dynamical behavior of the particle in the rotating EMDA black
hole spacetime.",2309.12604v1
2024-01-02,Emergence of unstable avoided crossing in the collective excitations of spin-1 spin-orbit coupled Bose-Einstein condensates,"We present the analytical and numerical results on the collective excitation
spectrum of quasi-one-dimensional spin-orbit (SO) coupled spin-1 Bose-Einstein
condensates. The collective excitation spectrum, using Bogoliubov-de-Gennes
theory, reveals the existence of a diverse range of phases in the SO and Rabi
($k_L-\Omega$) coupling plane. Based on eigenvalue of the excitation spectrum,
we categorize the $k_L-\Omega$ plane into three distinct regions. In region I,
a stable mode with phonon-like excitations is observed. In region IIa, single
and multi-band instabilities are noted with a gapped mode, while multi-band
instability accompanied by a gapless mode between low-lying and first excited
states is realized in region IIb, which also provides evidence of unstable
avoided crossing between low-lying and first excited modes The gap between
low-lying and first-excited states increases upon increasing the Rabi coupling
while decreases upon increase of SO coupling. Using eigenvector analysis, we
confirm the presence of the spin-dipole mode in the spin-like modes in Region
II. We corroborate the nature of the collective excitation through real-time
dynamical evolution of the ground state perturbed with the quench of the trap
using the mean-field Gross-Pitaevskii model. This analysis suggests the
presence of dynamical instability leading to the disappearance of the $0$-th
component of the condensate. In Region III, mainly encompassing $\Omega \sim 0$
and finite $k_L$, we observe phonon-like excitations in both the first excited
and the low-lying state. The eigenvectors in this region reveal alternative in-
and out-of-phase behaviours of the spin components. Numerical analysis reveals
the presence of a super stripe phase for small Rabi coupling in this region,
wherein the eigenvector indicates the presence of more complicated
spin-like-density mixed modes.",2401.01310v1
2015-11-24,Realization of Two-Dimensional Spin-orbit Coupling for Bose-Einstein Condensates,"Cold atoms with laser-induced spin-orbit (SO) interactions provide intriguing
new platforms to explore novel quantum physics beyond natural conditions of
solids. Recent experiments demonstrated the one-dimensional (1D) SO coupling
for boson and fermion gases. However, realization of 2D SO interaction, a much
more important task, remains very challenging. Here we propose and
experimentally realize, for the first time, 2D SO coupling and topological band
with $^{87}$Rb degenerate gas through a minimal optical Raman lattice scheme,
without relying on phase locking or fine tuning of optical potentials. A
controllable crossover between 2D and 1D SO couplings is studied, and the SO
effects and nontrivial band topology are observed by measuring the atomic cloud
distribution and spin texture in the momentum space. Our realization of 2D SO
coupling with advantages of small heating and topological stability opens a
broad avenue in cold atoms to study exotic quantum phases, including the
highly-sought-after topological superfluid phases.",1511.08170v1
2019-07-05,"Fourier transform spectroscopy, relativistic electronic structure calculation, and coupled-channel deperturbation analysis of the fully mixed $A^1Σ^+_u$ and $b^3Π_u$ states of Cs$_2$","The 4503 rovibronic term values belonging to the mutually perturbed
$A^1\Sigma^+_u$ and $b^3\Pi_u$ states of Cs$_2$ were extracted from laser
induced fluorescence (LIF) $A\sim b\rightarrow X^1\Sigma^+_g$ Fourier transform
spectra with the 0.01 cm$^{-1}$ uncertainty. The experimental term values of
the $A^1\Sigma^+_u\sim b^3\Pi_u$ complex covering the rotational levels $J\in
[4,395]$ in the excitation energy range $[9655,13630]$ cm$^{-1}$ were involved
into coupled-channel (CC) deperturbation analysis. The deperturbation model
takes explicitly into account spin-orbit coupling of the
$A^1\Sigma^+_u(A0^+_u)$ and $b^3\Pi^+_{0_u}(b0^+_u)$ states as well as
spin-rotational interaction between the $\Omega=0$, $1$ and $2$ components of
the $b^3\Pi^+_{\Omega_u}$ state. The \emph{ab initio} relativistic calculations
on the low-lying electronic states of Cs$_2$ were accomplished in the framework
of Fock space relativistic coupled cluster (FSRCC) approach to provide the
interatomic potentials of the interacting $A0^+_u$ and $b0^+_u$ states as well
as the relevant $A\sim b$ spin-orbit coupling function. To validate the present
CC deperturbation analysis solely obtained by energy-based data, the $A\sim b
\to X(v^{\prime\prime}_X)$ LIF intensity distributions were measured and
compared with their theoretical counterparts obtained by means of the
non-adiabatic vibrational wave functions of the $A\sim b$ complex and the FSRCC
$A\sim b \to X$ transition dipole moments calculated by the finite-field
method.",1907.02716v1
2019-02-15,Interlayer RKKY Coupling in Bulk Rashba Semiconductors under Topological Phase Transition,"The bulk Rashba semiconductors BiTeX (X=I, Cl and Br) with intrinsically
enhanced Rashba spin-orbit coupling provide a new platform for investigation of
spintronic and magnetic phenomena in materials. We theoretically investigate
the interlayer exchange interaction between two ferromagnets deposited on
opposite surfaces of a bulk Rashba semiconductor BiTeI in its trivial and
topological insulator phases. In the trivial phase BiTeI, we find that for
ferromagnets with a magnetization orthogonal to the interface, the exchange
coupling is reminiscent of that of a conventional three-dimensional metal.
Remarkably, ferromagnets with a magnetization parallel to the interface display
a magnetic exchange qualitatively different from that of conventional
three-dimensional metal due to the spin-orbit coupling. In this case, the
interlayer exchange interaction acquires two periods of oscillations and decays
as the inverse of the thickness of the BiTeI layer. For topological BiTeI, the
magnetic exchange interaction becomes mediated only by the helical surface
states and acts between the one-dimensional spin chains at the edges of the
sample. The surface state-mediated interlayer exchange interaction allows for
the coupling of ferromagnets with non-collinear magnetization and displays a
decay power different from that of trivial BiTeI, allowing the detection of the
topological phase transition in this material. Our work provides insights into
the magnetic properties of these newly discovered materials and their possible
functionalization.",1902.06001v2
1999-10-14,Effect of symmetry breaking perturbations in the one-dimensional SU(4) spin-orbital model,"We study the effect of symmetry breaking perturbations in the one-dimensional
SU(4) spin-orbital model. We allow the exchange in spin ($J_1$) and orbital
($J_2$) channel to be different and thus reduce the symmetry to SU(2) $\otimes$
SU(2). A magnetic field $h$ along the $S^z$ direction is also applied. Using
the formalism developped by Azaria et al we extend their analysis of the
isotropic $J_1=J_2$, h=0 case and obtain the low-energy effective theory near
the SU(4) point in the asymmetric case. An accurate analysis of the
renormalization group flow is presented with a particular emphasis on the
effect of the anisotropy. In zero magnetic field, we retrieve the same
qualitative low-energy physics than in the isotropic case. In particular, the
massless behavior found on the line $J_1=J_2>K/4$ extends in a large
anisotropic region. We discover though that the anisotropy plays its trick in
allowing non trivial scaling behaviors of the physical quantities. When a
magnetic field is present the effect of the anisotropy is striking. In addition
to the usual commensurate-incommensurate phase transition that occurs in the
spin sector of the theory, we find that the field may induce a second
transition of the KT type in the remaining degrees of freedom to which it does
not couple directly. In this sector, we find that the effective theory is that
of an SO(4) Gross-Neveu model with an h-dependent coupling that may change its
sign as h varies.",9910218v2
2010-09-24,First-post-Newtonian quadrupole tidal interactions in binary systems,"We consider tidal coupling in a binary stellar system to first-post-Newtonian
order. We derive the orbital equations of motion for bodies with spins and mass
quadrupole moments and show that they conserve the total linear momentum of the
binary. We note that spin-orbit coupling must be included in a 1PN treatment of
tidal interactions in order to maintain consistency (except in the special case
of adiabatically induced quadrupoles); inclusion of 1PN quadrupolar tidal
effects while omitting spin effects would lead to a failure of momentum
conservation for generic evolution of the quadrupoles. We use momentum
conservation to specialize our analysis to the system's center-of-mass-energy
frame; we find the binary's relative equation of motion in this frame and also
present a generalized Lagrangian from which it can be derived. We then
specialize to the case in which the quadrupole moment is adiabatically induced
by the tidal field (in which case it is consistent to ignore spin effects). We
show how the adiabatic dynamics for the quadrupole can be incorporated into our
action principle and present the simplified orbital equations of motion and
conserved energy for the adiabatic case. These results are relevant to
gravitational wave signals from inspiralling binary neutron stars.",1009.4919v3
2016-09-30,Chiral magnetism of magnetic adatoms generated by Rashba electrons,"We investigate long-range chiral magnetic interactions among adatoms mediated
by surface states spin-splitted by spin-orbit coupling. Using the Rashba model,
the tensor of exchange interactions is extracted wherein a pseudo-dipolar
interaction is found besides the usual isotropic exchange interaction and the
Dzyaloshinskii-Moriya interaction. We find that, despite the latter
interaction, collinear magnetic states can still be stabilized by the
pseudo-dipolar interaction. The inter-adatom distance controls the strength of
these terms, which we exploit to design chiral magnetism in Fe nanostructures
deposited on Au(111) surface. We demonstrate that these magnetic interactions
are related to superpositions of the out-of-plane and in-plane components of
the skyrmionic magnetic waves induced by the adatoms in the surrounding
electron gas. We show that, even if the inter-atomic distance is large, the
size and shape of the nanostructures dramatically impacts on the strength of
the magnetic interactions, thereby affecting the magnetic ground state. We also
derive an appealing connection between the isotropic exchange interaction and
the Dzyaloshinskii-Moriya interaction, which relates the latter to the first
order change of the former with respect to the spin-orbit coupling. This
implies that the chirality defined by the direction of the
Dzyaloshinskii-Moriya vector is driven by the variation of the isotropic
exchange interaction due to the spin-orbit interaction.",1609.09690v1
2020-07-07,Spin-Orbit Exciton in a Honeycomb Lattice Magnet CoTiO$_3$: Revealing Link Between Rare Earth and Transition Metal Magnetism,"We carried out inelastic neutron scattering to study the spin-orbital (SO)
exciton in a single crystal sample of CoTiO$_3$ as a function of temperature.
CoTiO$_3$ is a honeycomb magnet with dominant XY-type magnetic interaction and
an A-type antiferromagnetic order below $\mathrm{T_N} \approx 38$~K. We found
that the SO exciton becomes softer, but acquires a larger bandwidth in the
paramagnetic phase, compared to that in the magnetically ordered phase.
Moreover, an additional mode is only observed in the intermediate temperature
range, as the sample is warmed up above the lowest accessible temperature below
$\mathrm{T_N}$. Such an unusual temperature dependence observed in this
material suggests that its ground states (an $S_{\mathrm{eff}}=\frac{1}{2}$
doublet) and excited states multiplets are strongly coupled, and therefore
cannot be treated independently, as often done in a pseudo-spin model. Our
observations can be explained by a multi-level theory within random phase
approximation that explicitly takes into account both the ground and excited
multiplets. The success of our theory, which is originally developed to explain
temperature dependence of magnetic excitations in the rare-earth magnets,
highlight the similarity between the magnetic excitations in rare-earth systems
and those in transition metal systems with strong spin orbit coupling.",2007.03764v1
2016-08-12,Spin-orbit coupled fermions in an optical lattice clock,"Engineered spin-orbit coupling (SOC) in cold atom systems can aid in the
study of novel synthetic materials and complex condensed matter phenomena.
Despite great advances, alkali atom SOC systems are hindered by heating from
spontaneous emission, which limits the observation of many-body effects,
motivating research into potential alternatives. Here we demonstrate that SOC
can be engineered to occur naturally in a one-dimensional fermionic 87Sr
optical lattice clock (OLC). In contrast to previous SOC experiments, in this
work the SOC is both generated and probed using a direct ultra-narrow optical
clock transition between two electronic orbital states. We use clock
spectroscopy to prepare lattice band populations, internal electronic states,
and quasimomenta, as well as to produce SOC dynamics. The exceptionally long
lifetime of the excited clock state (160 s) eliminates decoherence and atom
loss from spontaneous emission at all relevant experimental timescales,
allowing subsequent momentum- and spin-resolved in situ probing of the SOC band
structure and eigenstates. We utilize these capabilities to study Bloch
oscillations, spin-momentum locking, and Van Hove singularities in the
transition density of states. Our results lay the groundwork for the use of
OLCs to probe novel SOC phases of matter.",1608.03854v2
2019-04-10,Testing the Wave-Particle Duality of Gravitational Wave Using the Spin-Orbital-Hall Effect of Structured Light,"Probing the polarization of gravitational waves (GWs) would provide an
evidence of graviton, indicating the quantization of gravity. Motivated by the
next generation of gravitational wave detectors, we make an attempt to study
the possible helicity coupling of structured lights to GWs. With the analogue
between of gravitational fields and the generic electromagnetic media, we
present a 4-vector optical Dirac equation based on the Maxwell theory under the
paraxial approximation. It is found that twisted lights propagating in a
gravitational field can be viewed as a non-Hermitian system with the
$\mathcal{PT}$ symmetry. We further demonstrate that the coupling effect
between angular momentums of the GWs and twisted lights may make photons
undergo both dipole and quadrupole transitions between different
orbital-angular-momentum(OAM) eigenstates and leads to some measurable optical
features, including the central intensity brightening and macroscopic rotation
of the intensity pattern for twisted lights. The former is spin-independent
while the later is spin dependent phenomena, both of which can be viewed
alternatively as the spin-orbital-Hall effect of structured lights in the GWs
and can serve as an indicator of the particle nature of GWs.",1904.05380v3
2019-11-27,Spin-dimer ground state driven by consecutive charge and orbital ordering transitions in the anionic mixed-valence compound Rb$_4$O$_6$,"Recently, a Verwey-type transition in the mixed-valence alkali sesquioxide
Cs$_4$O$_6$ was deduced from the charge ordering of molecular peroxide
O$_2^{2-}$ and superoxide O$_2^-$ anions accompanied by the structural
transformation and a dramatic change in electronic conductivity [Adler et al,
Sci. Adv 4, eaap7581 (2018)]. Here, we report that in the sister compound
Rb$_4$O$_6$ a similar Verwey-type charge ordering transition is strongly linked
to O$_2^-$ orbital and spin dynamics. On cooling, a powder neutron diffraction
experiment reveals a charge ordering and a cubic-to-tetragonal transition at
$T_{\rm CO}=290$ K, which is followed by a further structural instability at
$T_{\rm s}=92$ K that involves an additional reorientation of magnetic O$_2^-$
anions. Magnetic resonance techniques supported by density functional theory
computations suggest the emergence of a peculiar type of $\pi^*$-orbital
ordering of the magnetically active O$_2^-$ units, which promotes the formation
of a quantum spin state composed of weakly coupled spin dimers. These results
reveal that similarly as in 3$d$ transition metal compounds, also in in the
$\pi^*$ open-shell alkali sesquioxides the interplay between Jahn-Teller-like
electron-lattice coupling and Kugel-Khomskii-type superexchange determines the
nature of orbital ordering and the magnetic ground state.",1911.12049v1
2019-12-19,Stabilizing Even-Parity Chiral Superconductivity in Sr$_2$RuO$_4$,"Strontium ruthenate (Sr$_2$RuO$_4$) has long been thought to host a
spin-triplet chiral $p$-wave superconducting state. However, the singletlike
response observed in recent spin-susceptibility measurements casts serious
doubts on this pairing state. Together with the evidence for broken
time-reversal symmetry and a jump in the shear modulus $c_{66}$ at the
superconducting transition temperature, the available experiments point towards
an even-parity chiral superconductor with $k_z(k_x\pm ik_y)$-like $E_g$
symmetry, which has consistently been dismissed based on the
quasi-two-dimensional electronic structure of Sr$_2$RuO$_4$. Here, we show how
the orbital degree of freedom can encode the two-component nature of the $E_g$
order parameter, allowing for a local orbital-antisymmetric spin-triplet state
that can be stabilized by on-site Hund's coupling. We find that this exotic
$E_g$ state can be energetically stable once a complete, realistic
three-dimensional model is considered, within which momentum-dependent
spin-orbit coupling terms are key. This state naturally gives rise to
Bogoliubov Fermi surfaces.",1912.09525v2
2021-07-21,Chiral Dirac-like fermion in spin-orbit-free antiferromagnetic semimetals,"Dirac semimetal is a phase of matter, whose elementary excitation is
described by the relativistic Dirac equation. In the limit of zero mass, its
parity-time symmetry enforces the Dirac fermion in the momentum space, which is
composed of two Weyl fermions with opposite chirality, to be non-chiral.
Inspired by the flavor symmetry in particle physics, we theoretically propose a
massless Dirac-like equation yet linking two Weyl fields with the identical
chirality by assuming SU(2) isospin symmetry, independent of the space-time
rotation exchanging the two fields. Dramatically, such symmetry is hidden in
certain solid-state spin-1/2 systems with negligible spin-orbit coupling, where
the spin degree of freedom is decoupled with the lattice. Therefore, the
existence of the corresponding quasiparticle, dubbed as flavor Weyl fermion,
cannot be explained by the conventional (magnetic) space group framework. The
four-fold degenerate flavor Weyl fermion manifests linear dispersion and a
Chern number of 2, leading to a robust network of topologically protected Fermi
arcs throughout the Brillouin zone. For material realization, we show that the
transition-metal chalcogenide CoNb3S6 with experimentally confirmed collinear
antiferromagnetic order is ideal for flavor Weyl semimetal under the
approximation of vanishing spin-orbit coupling. Our work reveals a counterpart
of the flavor symmetry in magnetic electronic systems, leading to further
possibilities of emergent phenomena in quantum materials.",2107.09984v3
2023-04-25,Bose-Einstein condensations of magnons in quantum magnets with spin-orbit coupling in a Zeeman field,"We study the response of a quantum magnet with spin-orbit coupling (SOC) to a
Zeeman field by constructing effective actions and performing Renormalization
Group (RG) analysis. There are several novel classes of quantum phase
transitions at a low $ h_{c1} $ and an upper critical field $ h_{c2} $ driven
by magnon condensations at commensurate (C-) or in-commensurate (IC-) momenta $
0 < k_0 < \pi $. The intermediate IC- Skyrmion crystal (IC-SkX) phase is
controlled by a line of fixed points in the RG flows labeled by $ k_0 $. We
derive the relations between the quantum spin and the order parameters of the
effective actions which determine the spin-orbital structures of the IC-SkX
phase. We also analyze the operator contents near $ h_{c1} $ and $ h_{c2} $
which determine the exotic excitation spectra inside the IC-SkX. The intrinsic
differences between the magnon condensations at the C- and IC- momenta are
explored. The two critical fields $ h_{c1} < h_{c2} $ and the intermediate
IC-SkX phase could be a generic feature to any quantum magnets with SOC in a
Zeeman field. Experimental implications to some materials or cold atom systems
with SOC in a Zeeman field are presented.",2304.12612v1
2023-11-07,Revealing the ultra-fast domain wall motion in Manganese Gold through permalloy capping,"Antiferromagnets offer much faster dynamics compared to their ferromagnetic
counterparts but their order parameter is extremely difficult to detect and
control. So far, controlling the N\'eel order parameter electrically is limited
to only very few materials where N\'eel spin-orbit torques are allowed by
symmetry. In this work, we show that coupling a thin ferromagnet (permalloy)
layer on top of an antiferromagnet (Mn$_2$Au) solves a major roadblock -- the
controlled reading, writing, and manipulation of antiferromagnetic domains. We
confirm by atomistic spin dynamics simulations that the domain wall patterns in
the Mn$_2$Au are imprinted on the permalloy, therefore allowing for indirect
imaging of the N\'eel order parameter. Our simulations show that the coupled
domain wall structures in Mn$_2$Au-Py bilayers can be manipulated by either
acting on the N\'eel order parameter via N\'eel spin-orbit torques or by acting
on the magnetisation (the ferromagnetic order parameter) via magnetic fields.
In both cases, we predict ultra-high domain wall speeds on the order of 8.5
km/s. Thus, employing a thin ferromagnetic layer has the potential to easily
control the N\'eel order parameter in antiferromagnets even where N\'eel
spin-orbit torques are forbidden by symmetry. The controlled manipulation of
the antiferromagnetic order parameter provides a promising basis for the
development of high-density storage and efficient computing technologies
working in the THz regime.",2311.04305v1
2024-03-07,Light-induced giant enhancement of nonreciprocal transport at KTaO3-based interfaces,"Nonlinear transport is a unique functionality of noncentrosymmetric systems,
which reflects profound physics, such as spin-orbit interaction,
superconductivity and band geometry. However, it remains highly challenging to
enhance the nonreciprocal transport for promising rectification devices. Here,
we observe a light-induced giant enhancement of nonreciprocal transport at the
superconducting and epitaxial CaZrO3/KTaO3 (111) interfaces. The nonreciprocal
transport coefficient undergoes a giant increase with three orders of magnitude
up to 105 A-1T-1. Furthermore, a strong Rashba spin-orbit coupling effective
field of 14.7 T is achieved with abundant high-mobility photocarriers under
ultraviolet illumination, which accounts for the giant enhancement of
nonreciprocal transport coefficient. Our first-principles calculations further
disclose the stronger Rashba spin-orbit coupling strength and the longer
relaxation time in the photocarrier excitation process, bridging the
light-property quantitative relationship. Our work provides an alternative
pathway to boost nonreciprocal transport in noncentrosymmetric systems and
facilitates the promising applications in opto-rectification devices and
spin-orbitronic devices.",2403.04515v1
2001-04-27,Spin dynamical properties and orbital states of the layered perovskite La_2-2x_Sr_1+2x_Mn_2_O_7 (0.3 <= x < 0.5),"Low-temperature spin dynamics of the double-layered perovskite
La_2-2x_Sr_1+2x_Mn_2_O_7 (LSMO327) was systematically studied in a wide hole
concentration range (0.3 <= x < 0.5). The spin-wave dispersion, which is almost
perfectly 2D, has two branches due to a coupling between layers within a
double-layer. Each branch exhibits a characteristic intensity oscillation along
the out-of-plane direction. We found that the in-plane spin stiffness constant
and the gap between the two branches strongly depend on x. By fitting to
calculated dispersion relations and cross sections assuming Heisenberg models,
we have obtained the in-plane (J_para), intra-bilayer (J_perp) and
inter-bilayer (J') exchange interactions at each x. At x=0.30, J_para=-4meV and
J_perp=-5meV, namely almost isotropic and ferromagnetic. Upon increasing x,
J_perp rapidly approaches zero while |J_para| increases slightly, indicating an
enhancement of the planar magnetic anisotropy. At x=0.48, J_para reaches -9meV,
while J_perp turns to +1meV indicating an antiferromagnetic interaction. Such a
drastic change of the exchange interactions can be ascribed to the change of
the relative stability of the d_x^2-y^2 and d_3z^2-r^2 orbital states upon
doping. However, a simple linear combination of the two states results in an
orbital state with an orthorhombic symmetry, which is inconsistent with the
tetragonal symmetry of the crystal structure. We thus propose that an ``orbital
liquid'' state realizes in LSMO327, where the charge distribution symmetry is
kept tetragonal around each Mn site.",0104535v1
2014-03-17,SeD Radical: A probe for measurement of time variation of Fine Structure Constant($α$) and Proton to Electron Mass Ratio($μ$),"Based on the spectroscopic constants derived from highly accurate potential
energy surfaces, the SeD radical is identified as a spectroscopic probe for
measuring spatial and temporal variation of fundamental physical constants such
as the fine-structure constant (denoted as $\alpha=\frac{e^2}{\hbar c}$) and
the proton-to-electron mass ratio (denoted as $\mu=\frac{m_p}{m_e}$). The
ground state of SeD ($X^2\Pi$), due to spin-orbit coupling, splits into two
fine structure multiplets $^2\Pi_{\frac{3}{2}}$ and $^2\Pi_{\frac{1}{2}}$. The
potential energy surfaces of these spin-orbit components are derived from a
state of the art electronic structure method, MRCI+Q inclusive of scalar
relativistic effects with the spin-orbit effects accounted through the
Breit-Pauli operator. The relevant spectroscopic data are evaluated using
Murrel-Sorbie fit to the potential energy surfaces. The spin-orbit
splitting($\omega_f$) between the two multiplets is similar in magnitude with
the harmonic frequency ($\omega_e$) of the diatomic molecule. The amplification
factor derived from this theoretical method for this particular molecule can be
as large as 350, on the lower side it can be about 34. The significantly large
values of K indicate that SeD radical can be a plaussible experimental
candidate for measuring variation in $\alpha$ and $\mu$.",1403.4061v2
2017-04-20,Mixing of spin and orbital angular momenta via second-harmonic generation in plasmonic and dielectric chiral nanostructures,"We present a theoretical study of the characteristics of the nonlinear
spin-orbital angular momentum coupling induced by second-harmonic generation in
plasmonic and dielectric nanostructures made of centrosymmetric materials. In
particular, the connection between the phase singularities and polarization
helicities in the longitudinal components of the fundamental and
second-harmonic optical fields and the scatterer symmetry properties are
discussed. By in-depth comparison between the interaction of structured optical
beams with plasmonic and dielectric nanostructures, we have found that
all-dielectric and plasmonic nanostructures that exhibit magnetic and electric
resonances have comparable second-harmonic conversion efficiency. In addition,
mechanisms for second-harmonic enhancement for single and chiral clusters of
scatterers are unveiled and the relationships between the content of optical
angular momentum of the incident optical beams and the enhancement of nonlinear
light scattering is discussed. In particular, we formulate a general angular
momenta conservation law for the nonlinear spin-orbital angular momentum
interaction, which includes the quasi-angular-momentum of chiral structures
with different-order rotational symmetry. As a key conclusion of our study
relevant to nanophotonics, we argue that all-dielectric nanostructures provide
a more suitable platform to investigate experimentally the nonlinear
interaction between spin and orbital angular momenta, as compared to plasmonic
ones, chiefly due to their narrower resonance peaks, lower intrinsic losses,
and higher sustainable optical power.",1704.07451v1
2009-12-16,Nuclear energy density functional from chiral pion-nucleon dynamics revisited,"We use a recently improved density-matrix expansion to calculate the nuclear
energy density functional in the framework of in-medium chiral perturbation
theory. Our calculation treats systematically the effects from $1\pi$-exchange,
iterated $1\pi$-exchange, and irreducible $2\pi$-exchange with intermediate
$\Delta$-isobar excitations, including Pauli-blocking corrections up to
three-loop order. We find that the effective nucleon mass $M^*(\rho)$ entering
the energy density functional is identical to the one of Fermi-liquid theory
when employing the improved density-matrix expansion. The strength
$F_\nabla(\rho)$ of the $(\vec\nabla \rho)^2$ surface-term as provided by the
pion-exchange dynamics is in good agreement with that of phenomenological
Skyrme forces in the density region $\rho_0/2 <\rho <\rho_0$. The spin-orbit
coupling strength $F_{so}(\rho)$ receives contributions from iterated
$1\pi$-exchange (of the ``wrong sign'') and from three-nucleon interactions
mediated by $2\pi$-exchange with virtual $\Delta$-excitation (of the ``correct
sign''). In the region around $\rho_0/2 \simeq 0.08 $fm$^{-3}$ where the
spin-orbit interaction in nuclei gains most of its weight these two components
tend to cancel, thus leaving all room for the short-range spin-orbit
interaction. The strength function $F_J(\rho)$ multiplying the square of the
spin-orbit density comes out much larger than in phenomenological Skyrme forces
and it has a pronounced density dependence.",0912.3207v1
2018-07-04,An orbitally derived single-atom magnetic memory,"A single magnetic atom on a surface epitomizes the scaling limit for magnetic
information storage. Indeed, recent work has shown that individual atomic spins
can exhibit magnetic remanence and be read out with spin-based methods,
demonstrating the fundamental requirements for magnetic memory. However, atomic
spin memory has been only realized on thin insulating surfaces to date,
removing potential tunability via electronic gating or distance-dependent
exchange-driven magnetic coupling. Here, we show a novel mechanism for
single-atom magnetic information storage based on bistability in the orbital
population, or so-called valency, of an individual Co atom on semiconducting
black phosphorus (BP). Distance-dependent screening from the BP surface
stabilizes the two distinct valencies and enables us to electronically
manipulate the relative orbital population, total magnetic moment and spatial
charge density of an individual magnetic atom without a spin-dependent readout
mechanism. Furthermore, we show that the strongly anisotropic wavefunction can
be used to locally tailor the switching dynamics between the two valencies.
This orbital memory derives stability from the energetic barrier to atomic
relaxation and demonstrates the potential for high-temperature single-atom
information storage.",1807.01668v1
2019-02-25,Hourglass Weyl loops in two dimensions: Theory and material realization in monolayer GaTeI family,"Nodal loops in two-dimensional (2D) systems are typically vulnerable against
spin-orbit coupling (SOC). Here, we explore 2D systems with a type of doubly
degenerate nodal loops that are robust under SOC and feature an hourglass type
dispersion. We present symmetry conditions for realizing such hourglass Weyl
loops, which involve nonsymmorphic lattice symmetries. Depending on the
symmetry, the loops may exhibit different patterns in the Brillouin zone. Based
on first-principles calculations, we identify the monolayer GaTeI-family
materials as a realistic material platform to realize such loops. These
materials host a single hourglass Weyl loop circling around a high-symmetry
point. Interestingly, there is also a spin-orbit Dirac point enabled by an
additional screw axis. We show that the hourglass Weyl loop and the Dirac point
are robust under a variety of applied strains. By breaking the screw axis, the
Dirac point can be transformed into a second Weyl loop. Furthermore, by
breaking the glide mirror, the hourglass Weyl loop and the spin-orbit Dirac
point can both be transformed into a pair of spin-orbit Weyl points. Our work
offers guidance and realistic material candidates for exploring fascinating
physics of several novel 2D emergent fermions.",1902.09283v2
2020-10-02,Singular magnetic anisotropy in the nematic phase of FeSe,"FeSe is arguably the simplest, yet the most enigmatic, iron-based
superconductor. Its nematic but non-magnetic ground state is unprecedented in
this class of materials and stands out as a current puzzle. Here, our NMR
measurements in the nematic state of mechanically detwinned FeSe reveal that
both the Knight shift and the spin-lattice relaxation rate 1/T_1 possess an
in-plane anisotropy opposite to that of the iron pnictides LaFeAsO and
BaFe2As2. Using a microscopic electron model that includes spin-orbit coupling,
our calculations show that an opposite quasiparticle weight ratio between the
d_xz and d_yz orbitals leads to an opposite anisotropy of the orbital magnetic
susceptibility, which explains our Knight shift results. We attribute this
property to a different nature of nematic order in the two compounds,
predominantly bond-type in FeSe and onsite ferro-orbital in pnictides. The T_1
anisotropy is found to be inconsistent with existing neutron scattering data in
FeSe, showing that the spin fluctuation spectrum reveals surprises at low
energy, possibly from fluctuations that do not break C_4 symmetry. Therefore,
our results reveal that important information is hidden in these anisotropies
and they place stringent constraints on the low-energy spin correlations as
well as on the nature of nematicity in FeSe.",2010.01020v1
2021-01-01,Nuclear charge densities in spherical and deformed nuclei: towards precise calculations of charge radii,"Background: Precise measurements of atomic transitions affected by
electron-nucleus hyperfine interactions offer sensitivity to explore basic
properties of the atomic nucleus and study fundamental symmetries, including
the search for new physics beyond the Standard Model of particle physics. Such
measurements impose higher precision requirements on a theoretical description.
  Purpose: The nuclear charge density is composed of the proton point
distribution folded with the nucleonic charge distributions. The latter induce
subtle relativistic corrections due to the coupling of nucleon magnetic moments
with the nuclear spin-orbit density. We assess the precision of nuclear charge
density calculations by studying the behavior of relativistic corrections.
  Methods: The calculations are performed using Skyrme energy density
functionals and density-dependent pairing force. We used the general expression
for the spin-orbit form factor that is valid for spherical and deformed nuclei.
  Results: We studied the impact of various correction terms on the charge
radii, fourth radial moments, diffraction radii, and surface thickness of
spherical and deformed nuclei. The spin-orbit corrections to charge radial
moments and surface thickness show strong shell fluctuations which impact
high-precision predictions of isotopic shifts.
  Conclusions: To establish reliable constraints on the existence of new forces
from isotope shift measurements,precise calculations of nuclear charge
densities of deformed nuclei are needed. The proper inclusion of the spin-orbit
charge density and other correction terms is essential when aiming at
extraction of subtle effects which become particularly visible in isotopic
trends.",2101.00320v3
2021-06-23,Impact of the spin-orbit interaction on the phase diagram and anisotropy of the in-plane critical magnetic field in superconducting LaAlO$_3$/SrTiO$_3$ interface,"The two-dimensional electron gas at the interface between LaAlO$_3$ and
SrTiO$_3$ (LAO/STO) exhibits gate tunable superconductivity with a
characteristic dome-like shape of the critical temperature ($T_c$) in the phase
diagram. As shown recently [Phys. Rev. B 102, 085420 (2020)], such an effect
can be explained as a consequence of the extended $s-$wave symmetry of the gap
within an intersite real space pairing scenario, leading to a good agreement
between the experiment and theory. In this work, we turn to a detailed analysis
of the influence of spin-orbit coupling on the LAO/STO phase diagram by
considering the atomic and the Rashba components. In particular, we analyze the
optimal carrier concentration for which the maximal $T_c$ is reached relative
to the Lifshitz transition point. We find that the a misalignment between the
two can be significantly enhanced by the spin-orbit splitting of the bands,
combined with the fact that superconductivity sets in when the Fermi level
passes the anticrossing induced by the spin-orbital hybridization. In the
presence of the external in-plane magnetic field, our calculations show
four-fold anisotropy with the paramagnetic limit largely exceeded for $B_{||}$
directed along the high symmetry points [01] and [01]. The obtained electron
concentration dependence of $B_{c||}$ reproduces the characteristic dome-like
shape reported in experiments and the estimated value of $B_{c||}$ corresponds
to that measured experimentally.",2106.12317v1
2021-12-08,Monolayer RhB4: half-auxeticity and almost ideal spin-orbit Dirac point semimetal,"Structural-property relationship, the connection between materials'
structures and their properties, is central to the materials research.
Especially at reduced dimensions, novel structural motifs often generate unique
physical properties.Motivated by a recent work reporting a novel half auxetic
effect in monolayer PdB4 with a hypercoordinated structure, here, we
extensively explore similar 2D transition metal boride structures MB4 with M
covering 3d and 4d elements.Our investigation screens out one stable candidate,
the monolayer RhB4. We find that monolayer RhB4 also shows half auxeticity,
i.e., the material always expands in a lateral in-plane direction in response
to an applied strain in the other direction, regardless of whether the strain
is positive or negative.We show that this special mechanical character is
intimately tied to the hypercoordinated structure with the M\c{opyright}B8
structural motif. Furthermore, regarding electronic properties, monolayer RhB4
is found to be the first example of an almost ideal 2D spin-orbit Dirac point
semimetal.The low-energy band structure is clean, with a pair of fourfold
degenerate Dirac points robust under spin-orbit coupling located close to the
Fermi level. These Dirac points are enforced by the nonsymmorphic space group
symmetry which is also determined by the lattice structure. Our work deepens
the fundamental understanding of structural-property relationship in reduced
dimensions. The half auxeticity and the spin-orbit Dirac points will make
monolayer RhB4 a promising platform for nanomechanics and nanoelectronics
applications.",2112.04157v1
2023-06-19,Formation of spin-orbital entangled 2D electron gas in layer delta-doped bilayer iridate La$_δ$Sr$_3$Ir$_2$O$_7$,"5$d$ transition metal oxides host a variety of exotic phases due to the
comparable strength of Coulomb repulsion and spin-orbit coupling. Herein, by
pursuing density-functional studies on a delta-doped quasi-two-dimensional
iridate Sr$_3$Ir$_2$O$_7$, where a single SrO layer is replaced by LaO layer,
we predict the formation of a spin-orbital entangled two-dimensional electron
gas (2DEG) which is sharply confined on two IrO$_2$ layers close to the LaO
layer. In this bilayer crystal structure, an existing potential well is further
augmented with the inclusion of positively charged LaO layer which results in
confining the extra valence electron made available by the La$^{3+}$ ion. The
confined electron is bound along crystal $a$ direction and is highly mobile in
the $bc$ plane. From the band structure point of view, now the existing
half-filled $J_{eff}$ = 1/2 states are further electron doped to destroy the
antiferromagnetic Mott insulating state of IrO$_2$ layers near to the
delta-doped layer. This leads to partially occupied Ir upper-Hubbard subbands
which host the spin-orbital entangled 2DEG. The IrO$_2$ layers far away from
the interface remain insulating and preserve the collinear G-type magnetic
ordering of pristine Sr$_3$Ir$_2$O$_7$. The conductivity tensors calculated
using semi-classical Boltzmann theory at room temperature reveal that the 2DEG
exhibits large electrical conductivity of the order of 10$^{19}$.",2306.10978v2
1994-06-06,"Van Hove Exciton-Cageons and High-T$_c$ Superconductivity, XA: Role of Spin-Orbit Coupling in Generating a Diabolical Point","Spin-orbit coupling plays a large role in stabilizing the low-temperature
orthorhombic phase of La$_{2-x}$Sr$_x$CuO$_4$. It splits the degeneracy of the
van Hove singularities (thereby stabilizing the distorted phase) and completely
changes the shape of the Fermi surfaces, potentially introducing diabolical
points into the band structure. The present paper gives a detailed account of
the resulting electronic structure.
  A slave boson calculation shows how these results are modified in the
presence of strong correlation effects. A scaling regime, found very close to
the metal-insulator transition, allows an analytical determination of the
crossover, in the limit of zero oxygen-oxygen hopping, $t_{OO}\rightarrow 0$.
Extreme care must exercised in chosing the parameters of the three-band model.
In particular, $t_{OO}$ is renormalized from its LDA value. Furthermore, it is
suggested that the slave boson model be spin-corrected, in which case the
system is close to a metal-insulator transition at half filling.",9406026v1
1998-09-01,Spin gap in low-dimensional Mott insulators with orbital degeneracy,"We consider the exchange Hamiltonian H_ST = -J Sum_{<rr'>} (2 S_r S_r' - 1/2)
(2 T_r T_r' - 1/2) describing two isotropic spin-1/2 Heisenberg
antiferromagnets coupled by a quartic term on equivalent bonds. The model is
relevant for systems with orbital degeneracy and strong electron-vibron
coupling in the large Hubbard repulsion limit. To investigate the ground state
properties we use a Green's Function Monte Carlo, calculating energy gaps and
correlation functions, the latter through the forward walking technique. In one
dimension we find that the ground state is a ``crystal'' of valence bond
dimers. In two dimensions, the spin gap appears to remain finite in the
thermodynamic limit, and, consistently, the staggered magnetization -- signal
of Neel long range order -- seems to vanish. From the analysis of dimer-dimer
correlation functions, however, we find no sign of a valence bond crystal. A
spin liquid appears as a plausible scenario compatible with our findings.",9809013v1
1999-06-23,Spin-orbit coupling effect on quantum Hall ferromagnets with vanishing Zeeman energy,"We present the phase diagram of a ferromagnetic quantum Hall effect liquid in
a narrow quantum well with vanishing single-particle Zeeman splitting,
$\epsilon_{{\rm Z}}$ and pronounced spin-orbit coupling. Upon decreasing
$\epsilon_{{\rm Z}}$, the spin-polarization field of a liquid takes, first, the
easy-axis configuration, followed by the formation of a helical state, which
affects the transport and NMR properties of a liquid and the form of
topological defects in it. The analysis is extended over high odd integer
filling factors.",9906354v2
2004-06-01,Order parameter in superconductors with non-degenerate bands,"In noncentrosymmetric metals, the spin degeneracy of the electronic bands is
lifted by spin-orbit coupling. We consider general symmetry properties of the
pairing function Delta(k) in noncentrosymmetric superconductors with spin-orbit
coupling (NSC), including CePt3Si, UIr and Cd2Re2O7. We find that Delta(k) =
chi(k) t(k), where chi(k) is an even function which transforms according to the
irreducible representations of the crystallographic point group and t(k) is a
model dependent phase factor. We consider tunnelling between a NSC and a
conventional superconductor. It is found that, in terms of thermodynamical
properties as well as the Josephson effect, the state of NSC resembles a
singlet superconducting state with gap function chi(k).",0406003v2
2006-04-13,Realization of arbitrary single-qubit gates through control of spin-orbit couplings in semiconductor nanowires,"We propose a theoretical scheme to realize arbitrary single-qubit gates
through two simple device units: one-dimensional semiconductor wires with
Dresselhaus spin-orbit coupling (SOC) and Rashba SOC, separately. Qubit
information coded by the electron spin can be accurately manipulated by the SOC
when crossing the semiconductor wire. The different manipulative behaviors in
Dresselhaus and Rashba wires enable us to make the diverse quantum logic gates.
Furthermore, by connecting the Dresselhaus and Rashba units in series, we
obtain a universal set of single qubit gates: Hadamard, phase, and $\pi /8$
gates, inferring that an arbitrary single qubit gate can be achieved. Because
the total transmission is satisfied in the two device units, all the logic
gates we have obtained are lossless. In addition, a ballistic spintronic switch
is proposed in the present investigation.",0604346v1
2006-10-03,Tunneling anisotropic magnetoresistance driven by resonant surface states: First-principles calculations of Fe(001) surface,"Fully-relativistic first-principles calculations of the Fe(001) surface
demonstrate that resonant surface (interface) states may produce sizeable
tunneling anisotropic magnetoresistance in magnetic tunnel junctions with a
single magnetic electrode. The effect is driven by the spin-orbit coupling. It
shifts the resonant surface band via the Rashba effect when the magnetization
direction changes. We find that spin-flip scattering at the interface is
controlled not only by the strength of the spin-orbit coupling, but depends
strongly on the intrinsic width of the resonant surface states.",0610061v2
2006-11-28,Distribution of spectral-flow gaps in the Rashba model with disorder: a new universality,"We report a study of disordered electron systems with spin-orbit coupling on
a cylinder using methods of random matrix ensembles. With a threading flux
turned on, the single particle levels will generally avoid, rather than cross,
each other. Our numerical study of the level-avoiding gaps in the disordered
Rashba model demonstrates that the normalized gap distribution is of a
universal form, independent of the random strength and the system size. For
small gaps it exhibits a linear behavior, while for large gaps it decays
exponentially. A framework based on matrix mechanical models is suggested, and
is verified to reproduce the universal linear behavior at small gaps. Thus we
propose to use the distribution of the spectral-flow gaps associated with flux
insertion as a new way to characterize 2d random systems with spin-orbit
coupling. The relevance and qualitative implications for spin (Hall) transport
are also addressed.",0611696v2
2007-11-16,First-principles study of the lattice and electronic structures of TbMn$_2$O$_5$,"The structural, electronic and lattice dielectric properties of multiferroic
TbMn$_2$O$_5$ are investigated using density functional theory within the
generalized gradient approximation (GGA). We use collinear spin approximations
and ignore the spin-orbit coupling. The calculated structural parameters are in
excellent agreement with the experiments. We confirm that the ground state
structure of TbMn$_2$O$_5$ is of space group $Pb2_1m$, allowing polarizations
along the b-axis. The spontaneous electric polarization is calculated to be
1187 $nC\cdot$cm$^{-2}$. The calculated zone-center optical phonons frequencies
and the oscillator strengths of IR phonons agree very well with the
experimental values. We then derive an effective Hamiltonian to explain the
magnetically-induced ferroelectricity in this compound. Our results strongly
suggest that the ferroelectricity in TbMn$_2$O$_5$ is driven by the magnetic
ordering that breaks the the inversion symmetry, without invoking the
spin-orbit coupling.",0711.2539v1
2007-12-19,Coulomb correlation in presence of spin-orbit coupling: application to plutonium,"Attempts to go beyond the local density approximation (LDA) of Density
Functional Theory (DFT) have been increasingly based on the incorporation of
more realistic Coulomb interactions. In their earliest implementations, methods
like LDA+$U$, LDA + DMFT (Dynamical Mean Field Theory), and LDA+Gutzwiller used
a simple model interaction $U$. In this article we generalize the solution of
the full Coulomb matrix involving $F^{(0)}$ to $F^{(6)}$ parameters, which is
usually presented in terms of an $\ell m_\ell$ basis, into a $jm_{j}$ basis of
the total angular momentum, where we also include spin-orbit coupling; this
type of theory is needed for a reliable description of $f$-state elements like
plutonium, which we use as an example of our theory. Close attention will be
paid to spin-flip terms, which are important in multiplet theory but that have
been usually neglected in these kinds of studies. We find that, in a
density-density approximation, the $jm_j$ basis results provide a very good
approximation to the full Coulomb matrix result, in contrast to the much less
accurate results for the more conventional $\ell m_\ell$ basis.",0712.3100v1
2008-03-20,Novel Jeff = 1/2 Mott State Induced by Relativistic Spin-Orbit Coupling in Sr2IrO4,"We investigated electronic structure of 5d transition-metal oxide Sr2IrO4
using angle-resolved photoemission, optical conductivity, and x-ray absorption
measurements and first-principles band calculations. The system was found to be
well described by novel effective total angular momentum Jeff states, in which
relativistic spin-orbit (SO) coupling is fully taken into account under a large
crystal field. Despite of delocalized Ir 5d states, the Jeff-states form so
narrow bands that even a small correlation energy leads to the Jeff = 1/2 Mott
ground state with unique electronic and magnetic behaviors, suggesting a new
class of the Jeff quantum spin driven correlated-electron phenomena.",0803.2927v1
2008-05-21,Friedel oscillations induced surface magnetic anisotropy,"We present detailed numerical studies of the magnetic anisotropy energy of a
magnetic impurity near the surface of metallic hosts (Au and Cu), that we
describe in terms of a realistic tight-binding surface Green's function
technique. We study the case when spin-orbit coupling originates from the
d-band of the host material and we also investigate the case of a strong local
spin-orbit coupling on the impurity itself. The splitting of the impurity's
spin-states is calculated to leading order in the exchange interaction between
the impurity and the host atoms using a diagrammatic Green's function
technique. The magnetic anisotropy constant is an oscillating function of the
separation d from the surface: it asymptotically decays as 1/d2 and its
oscillation period is determined by the extremal vectors of the host's Fermi
Surface. Our results clearly show that the host-induced magnetic anisotropy
energy is by several orders of magnitude smaller than the anisotropy induced by
the local mechanism, which provides sufficiently large anisotropy values to
explain the size dependence of the Kondo resistance observed experimentally.",0805.3275v1
2008-06-10,Pseudo spin-orbit coupling of Dirac particles in graphene spintronics,"We study the pseudo spin-orbital (SO) effects experienced by massive Dirac
particles in graphene, which can potentially be of a larger magnitude compared
to the conventional Rashba SO effects experienced by particles in a 2DEG
semiconductor heterostructure. In order to generate a uniform vertical pseudo
SO field, we propose an artificial atomic structure, consisting of a graphene
ring and a charged nanodot at the center which produces a large radial electric
field. In this structure, a large pseudo SO coupling strength can be achieved
by accelerating the Dirac particles around the ring, due to the small energy
gap in graphene and the large radial electric field emanating from the charged
nanodot. We discuss the theoretical possibility of harnessing the pseudo SO
effects in mesoscopic applications, e.g. pseudo spin relaxation and switching.",0806.1568v1
2008-08-05,Colossal enhancement of upper critical fields in noncentrosymmetric heavy fermion superconductors near quantum criticality: CeRhSi$_3$ and CeIrSi$_3$,"Strong coupling effects on the upper critical fields $H_{c2}$ along the
c-axis in the noncentrosymmetric heavy fermion superconductors near quantum
criticality CeRhSi$_3$ and CeIrSi$_3$ are examined. For sufficiently large
spin-orbit interactions due to the lack of inversion symmetry, $H_{c2}$ is
mainly determined by the orbital depairing effects. From microscopic
calculations taking into account the strong spin fluctuations, we show that
$H_{c2}$ is extremely enhanced as the system approaches the quantum critical
point, resulting in $H_{c2}\sim 30$T even in the case with the low transition
temperature $T_c(H=0)\sim 1$K, which well explains the huge $H_{c2}$ observed
in the recent experiments. Our results reveal intrinsic and universal
properties common to strong coupling superconductivity caused by spin
fluctuations near quantum criticality.",0808.0545v1
2009-07-22,Enhanced spin-orbit coupling in hydrogenated and fluorinated graphenes studied from first principles,"The spin-orbit couplings (SOCs) of hydrogenated and fluorinated graphenes are
calculated from the first principles method. It is found that the SOC-induced
band splittings near their Fermi energies can be significantly enhanced to the
order of 10$^{-2}$ eV from the original about 10$^{-6}$ eV of the pure raphene,
which is comparable to those found in the diamond and even the archetypal
semiconductors. And two different mechanisms are proposed to explain the SOC
enhancements in these two systems. The huge SOC enhancements are found to come
not only from the sp$^3$ hybridization of carbon atoms, but also from the
larger intrinsic SOC of the fluorine atom than the carbon one. We hope many
interesting phenomena caused by the SOCs (e.g. the spin Hall effect) can be
observed experimentally in these systems.",0907.3779v1
2010-10-18,Theory of electric polarization in multi-orbital Mott insulators,"The interaction between the electric field, E, and spins in multi-orbital
Mott insulators is studied theoretically. We find a generic dynamical coupling
mechanism, which works for all crystal lattices and which does not involve
relativistic effects. The general form of the coupling is -T_ab E_a e_b, where
e is the `internal' electric field originating from the dynamical Berry phase
of electrons and T_ab is a tensor determined by lattice symmetry. We discuss
several effects of this interaction: (i) an unusual electron spin resonance
induced by an oscillating electric field, (ii) the displacement of spin
textures in an applied electric field, and (iii) the resonant absorption of
circularly polarized light by Skyrmions, magnetic bubbles, and magnetic
vortices.",1010.3687v1
2011-01-05,Mott Physics and Topological Phase Transition in Correlated Dirac Fermions,"We investigate the interplay between the strong correlation and the
spin-orbital coupling in the Kane-Mele-Hubbard model and obtain the qualitative
phase diagram via the variational cluster approach. We identify, through an
increase of the Hubbard $U$, the transition from the topological band insulator
to either the spin liquid phase or the easy-plane antiferromagnetic insulating
phase, depending on the strength of the spin-orbit coupling. A nontrivial
evolution of the bulk bands in the topological quantum phase transition is also
demonstrated.",1101.0911v1
2011-08-05,Vortex structures of rotating spin-orbit coupled Bose-Einstein condensates,"We consider the quasi-2D two-component Bose-Einstein condensates with Rashba
spin-orbit (SO) coupling in a rotating trap. An external Zeeman term favoring
spin polarization along the radial direction is also considered, which has the
same form as the non-canonical part of the mechanical angular momentum. The
rotating condensate exhibits rich structures as varying the strengths of
trapping potential and interaction. With a strong trapping potential, the
condensate exhibits a half-quantum vortex-lattice configuration. Such a
configuration is driven to the normal one by introducing the external radial
Zeeman field. In the case of a weak trap potential, the condensate exhibits a
multi-domain pattern of plane-wave states under the external radial Zeeman
field.",1108.1238v4
2011-09-27,Exotic superfluidity in spin-orbit coupled Bose-Einstein condensates,"We study the superfluidity of a spin-orbit coupled Bose-Einstein condensate
(BEC) by computing its Bogoliubov excitations, which are found to consist of
two branches: one is gapless and phonon-like at long wavelength; the other is
typically gapped. These excitations imply a superfluidity that has two new
features: ({\it i}) due to the absence of the Galilean invariance, one can no
longer define the critical velocity of superfluidity independent of the
reference frame; ({\it ii}) the superfluidity depends not only on whether the
speed of the BEC exceeds a critical value, but also on {\it cross helicity}
that is defined as the direction of the cross product of the spin and the
kinetic momentum of the BEC.",1109.5811v3
2012-08-13,Possible pairing symmetries in SrPtAs with a local lack of inversion center,"We discuss possible pairing symmetries in the hexagonal pnictide
superconductor SrPtAs. The local lack of inversion symmetry of the two distinct
conducting layers in the unit cell results in a special spin-orbit coupling
with a staggered structure. We classify the pairing symmetry by the global
crystal point group D_3d, and suggest some candidates for the stable state
using a tight-binding model with an in-plane, density-density type pairing
interaction. We may have some unconventional states like s+f-wave and a mixture
of chiral d-wave and chiral p-wave. The spin orbit coupling is larger than the
interlayer hopping, and the mixing between spin-singlet and triplet states can
be seen in spite of the fact that the system has a global inversion center.",1208.2541v1
2013-03-28,Edge states and topological properties of electrons on the bismuth on silicon surface with giant spin-orbit coupling,"We derive a model of localized edge states in the finite width strip for
two-dimensional electron gas formed in the hybrid system of bismuth monolayer
deposited on the silicon interface and described by the nearly-free electron
model with giant spin-orbit splitting. The edge states have the energy
dispersion in the bulk energy gap with the Dirac-like linear dependence on the
quasimomentum and the spin polarization coupled to the direction of
propagation, demonstrating the properties of topological insulator. The
topological stability of edge states is confirmed by the calculations of the
$Z_2$ invariant taken from the structure of the Pfaffian for the time reversal
operator for the filled bulk bands in the surface Brillouin zone which is shown
to have a stable number of zeros with the variations of material parameters.
The proposed properties of the edge states may support future advances in
experimental and technological applications of this new material in
nanoelectronics and spintronics.",1303.7104v3
2013-06-11,Magnetically generated spin-orbit coupling for ultracold atoms,"We present a new technique for producing two- and three-dimensional
Rashba-type spin-orbit couplings for ultracold atoms without involving light.
The method relies on a sequence of pulsed inhomogeneous magnetic fields
imprinting suitable phase gradients on the atoms. For sufficiently short pulse
durations, the time-averaged Hamiltonian well approximates the Rashba
Hamiltonian. Higher order corrections to the energy spectrum are calculated
exactly for spin-1/2 and perturbatively for higher spins. The pulse sequence
does not modify the form of rotationally symmetric atom-atom interactions.
Finally, we present a straightforward implementation of this pulse sequence on
an atom chip.",1306.2606v2
2013-10-31,Gap solitons in the spin-orbit coupled Bose-Einstein condensates,"We report a diversity of stable gap solitons in a spin-orbit coupled
Bose-Einstein condensate subject to a spatially periodic Zeeman field. It is
shown that the solitons, can be classified by the main physical symmetries they
obey, i.e. symmetries with respect to parity (P), time (T), and internal degree
of freedom, i.e. spin, (C) inversions. The conventional gap and gap-stripe
solitons are obtained in lattices with different parameters. It is shown that
solitons of the same type but obeying different symmetries can exist in the
same lattice at different spatial locations. PT and CPT symmetric solitons have
anti-ferromagnetic structure and are characterized respectively by nonzero and
zero total magnetizations.",1310.8517v1
2014-01-22,Current-induced magnetization dynamics at the edge of a two-dimensional electron system with strong spin-orbit coupling,"We experimentally investigate electron transport through the interface
between a permalloy ferromagnet and the edge of a two-dimensional electron
system with strong Rashba-type spin-orbit coupling. We observe strongly
non-linear transport around zero bias at millikelvin temperatures. The observed
nonlinearity is fully suppressed above some critical values of temperature,
magnetic field, and current through the interface. We interpret this behavior
as the result of spin accumulation at the interface and its current-induced
absorption as a magnetization torque.",1401.5719v2
2014-04-22,Constituents of magnetic anisotropy and a screening of spin-orbit coupling in solids,"Using quantum mechanical perturbation theory (PT) we analyze how the energy
of perturbation of different orders is renormalized in solids. We test the
validity of PT analysis by considering a specific case of spin-orbit coupling
as a perturbation. We further compare the relativistic energy and the magnetic
anisotropy from the PT approach with direct density functional calculations in
FePt, CoPt, FePd, MnAl, MnGa, FeNi, and tetragonally strained FeCo. In addition
using decomposition of anisotropy into contributions from individual sites and
different spin components we explain the microscopic origin of high anisotropy
in FePt and CoPt magnets.",1404.5546v2
2014-07-02,Quantum correlations in bulk properties of solids obtained from neutron scattering,"We demonstrate that inelastic neutron scattering technique can be used to
indirectly detect and measure the macroscopic quantum correlations quantified
by both entanglement and discord in a quantum magnetic material, VODPO4 . 1D2O.
The amount of quantum correlations is obtained 2 by analyzing the neutron
scattering data of magnetic excitations in isolated V4+ spin dimers. Our
quantitative analysis shows that the critical temperature of this material can
reach as high as Tc = 82.5 K, where quantum entanglement drops to zero.
Significantly, quantum discord can even survive at Tc = 300 K and may be used
in room temperature quantum devices. Taking into account the spin-orbit (SO)
coupling, we also predict theoretically that entanglement can be significantly
enhanced and the critical temperature Tc increases with the strength of
spin-orbit coupling.",1407.0633v1
2014-07-09,Effective field theory for the bulk-edge correspondence in a two-dimensional Z_2 topological insulator with Rashba interactions,"We determine the effective field theory in (2+1)-dimensional space and time
that captures the long wave length and low-energy limit of fermions hopping on
a honeycomb lattice at half-filling when both a dominant intrinsic and
subdominant Rashba spin-orbit couplings are present. This effective field
theory for a Z_2 topological insulator (the Kane-Mele model at vanishing
uniform and staggered chemical potentials) is a perturbation around a double
Chern-Simons theory, with the U(1) gauge invariance associated to spin
conservation explicitly broken due to the Rashba spin orbit coupling.
Nonetheless, we find that the effective field theory has a BRST symmetry that
allows us to construct the bulk-edge correspondence.",1407.2633v2
2014-09-15,Repulsively interacting fermions in a two-dimensional deformed trap with spin-orbit coupling,"We investigate a two-dimensional system of with two values of the internal
(spin) degree of freedom. It is confined by a deformed harmonic trap and
subject to a Zeeman field, Rashba or Dresselhaus one-body spin-orbit couplings
and two-body short range repulsion. We obtain self-consistent mean-field
$N$-body solutions as functions of the interaction parameters. Single-particle
Spectra and total energies are computed and compared to the results without
interaction. We perform a statistical analysis for the distributions of nearest
neighbor energy level spacings and show that quantum signatures of chaos are
seen in certain parameters regimes. Furthermore, the effects of two-body
repulsion on the nearest neighbor distributions are investigated. This
repulsion can either promote or destroy the signatures of potential chaotic
behavior depending on relative strengths of parameters. Our findings support
the suggestion that cold atoms may be used to study quantum chaos both in the
presence and absence of interactions.",1409.4206v3
2014-09-16,Topological Insulator to Dirac Semimetal Transition Driven by Sign Change of Spin-Orbit Coupling in Thallium Nitride,"Based on the first-principles calculations, we reveal that TlN, a simple
binary compound with Wurtzite structure, is a three-dimensional (3D)
topological insulator (TI) with effectively negative spin-orbit coupling
$\lambda_{eff} < 0$, which makes it distinguished from other TIs by showing
opposite spin-momentum locking effect in its surface states. The sign of
$\lambda_{eff}$ depends on the hybridization between N-$2p$ and Tl-$5d$ states,
and can be tuned from negative to postive by lattice strain or chemical
substitution, which drive the system into a Dirac semimetal with 3D Dirac cones
in its bulk states. Such topological phase transition can be realized by
electronic mechanism without breaking any crystal symmetry.",1409.4534v1
2014-12-11,Artificial Magnetic Fields in Momentum Space in Spin-Orbit Coupled Systems,"The Berry curvature is a geometrical property of an energy band which can act
as a momentum space magnetic field in the effective Hamiltonian of a wide range
of systems. We apply the effective Hamiltonian to a spin-1/2 particle in two
dimensions with spin-orbit coupling, a Zeeman field and an additional harmonic
trap. Depending on the parameter regime, we show how this system can be
described in momentum space as either a Fock-Darwin Hamiltonian or a
one-dimensional ring pierced by a magnetic flux. With this perspective, we
interpret important single-particle properties, and identify analogue magnetic
phenomena in momentum space. Finally we discuss the extension of this work to
higher spin systems, as well as experimental applications in ultracold atomic
gases and photonic systems.",1412.3638v2
2015-01-19,Triangular Spin-Orbit-Coupled Lattice with Strong Coulomb Correlations: Sn Atoms on a SiC(0001) Substrate,"Two-dimensional (2D) atom lattices provide model setups for Coulomb
correlations inducing competing ground states, partly with topological
character. Hexagonal SiC(0001) is an intriguing wide-gap substrate,
spectroscopically separated from the overlayer and hence reduced screening. We
report the first study of an artificial high-Z atom lattice on SiC(0001) by Sn
adatoms, based on combined experimental realization and theoretical modeling.
Density-functional theory of our $\sqrt{3}$-structure model closely reproduces
the scanning tunneling microscopy. Instead of metallic behavior, photoemission
data show a deeply gapped state (~2 eV gap). Based on our calculations
including dynamic mean-field theory, we argue that this reflects a pronounced
Mott insulating scenario. We also find indications that the system is
susceptible to antiferromagnetic superstructures. Such spin-orbit-coupled
correlated heavy atom lattices on SiC(0001) thus form a novel testbed for
peculiar quantum states of matter, with potential bearing for spin liquids and
topological Mott insulators.",1501.04602v1
2015-01-30,"Parity-breaking phases of spin-orbit-coupled metals with gyrotropic, ferroelectric and multipolar orders","We study Fermi liquid instabilities in spin-orbit-coupled metals with
inversion symmetry. By introducing a canonical basis for the doubly degenerate
Bloch bands in momentum space, we derive the general form of interaction
functions. A variety of time-reversal-invariant, parity-breaking phases is
found, whose Fermi surface is spontaneously deformed and spin-split. In terms
of symmetry, these phases possess gyrotropic, ferroelectric and multipolar
orders. The ferroelectric and multipolar phases are accompanied by structural
distortions, from which the electronic orders can be identified. The gyrotropic
phase exhibits a unique nonlinear optical property. Based on recent
experiments, we identify several interesting quantum materials including
pyrochlore oxides, which show evidence of these parity breaking orders.",1502.00015v2
2015-03-13,Entanglement like properties in Spin-Orbit Coupled Ultra Cold Atom and violation of Bell like Inequality,"We show that the general quantum state of synthetically spin-orbit coupled
ultra cold bosonic atom whose condensate was experimentally created recently (
Y. J. Lin {\it et al.}, Nature, {\bf 471}, 83, (2011)), shows entanglement
between motional degrees of freedom ( momentum) and internal degrees of freedom
(hyperfine spin). We demonstrate the violation of Bell-like inequality (CHSH)
for such states that provides a unique opportunity to verify fundamental
principle like quantum non-contextuality for commutating observables which are
not spatially separated. We analyze in detail the Rabi oscillation executed by
such atom-laser system and how that influneces quantities like entanglement
entropy, violation of Bell like Inequality etc. We also discuss the implication
of our result in testing the quantum non-contextuality and Bell's Inequality
vioaltion by macroscopic quantum object like Bose-Einstein Condensate of ultra
cold atoms.",1503.03999v1
2015-04-06,Direct Observation of High-Spin States in Manganese Dimer and Trimer Cations by X-ray Magnetic Circular Dichroism Spectroscopy in an Ion Trap,"The electronic structure and magnetic moments of free Mn$_2^+$ and Mn$_3^+$
are characterized by $2p$ x-ray absorption and x-ray magnetic circular
dichroism spectroscopy in a cryogenic ion trap that is coupled to a synchrotron
radiation beamline. Our results show directly that localized magnetic moments
of 5 $\mu_B$ are created by $3d^5 (^6\mathrm{S})$ states at each ionic core,
which are coupled in parallel to form molecular high-spin states via indirect
exchange that is mediated in both cases by a delocalized valence electron in a
singly-occupied $4s$ derived orbital with an unpaired spin. This leads to total
magnetic moments of 11 $\mu_B$ for Mn$_2^+$ and 16 $\mu_B$ for Mn$_3^+$, with
no contribution of orbital angular momentum.",1504.01411v1
2015-05-22,Mobile vector soliton in a spin-orbit coupled spin-$1$ condensate,"We study the formation of bound states and three-component bright vector
solitons in a quasi-one-dimensional spin-orbit-coupled hyperfine spin $f=1$
Bose-Einstein condensate using numerical solution and variational approximation
of a mean-field model. In the antiferromagnetic domain, the solutions are
time-reversal symmetric, and the component densities have multi-peak structure.
In the ferromagnetic domain, the solutions violate time-reversal symmetry, and
the component densities have single-peak structure. The dynamics of the system
is not Galelian invariant. From an analysis of Galelian invariance, we
establish that the single-peak ferromagnetic vector solitons are true solitons
and can move maintaining constant component densities, whereas the
antiferromagnetic solitons cannot move with constant component densities.",1505.06193v1
2015-05-23,Optical Lattice Modulation Spectroscopy for Spin-orbit Coupled Bosons,"Interacting bosons with two ""spin'' states in a lattice show novel
superfluid-insulator phase transitions in the presence of spin-orbit coupling.
Depending on the parameter regime, bosons in the superfluid phase can condense
to either a zero momentum state or to one or multiple states with finite
momentum, leading to an unconventional superfluid phase. We study the response
of such a system to modulation of the optical lattice potential. We show that
the change in momentum distribution after lattice modulation shows distinct
patterns in the Mott and the superfluid phase and these patterns can be used to
detect these phases and the quantum phase transition between them. Further, the
momentum resolved optical modulation spectroscopy can identify both the gapless
(Goldstone) gapped amplitude (Higgs) mode of the superfluid phase and clearly
distinguish between the superfluid phases with a zero momentum condensate and a
twisted superfluid phase by looking at the location of these modes in the
Brillouin zone. We discuss experiments which can test our theory.",1505.06372v2
2015-09-19,Synthetic spin-orbit coupling in an optical lattice clock,"We propose the use of optical lattice clocks operated with fermionic
alkaline-earth-atoms to study spin-orbit coupling (SOC) in interacting
many-body systems. The SOC emerges naturally during the clock interrogation
when atoms are allowed to tunnel and accumulate a phase set by the ratio of the
""magic"" lattice wavelength to the clock transition wavelength. We demonstrate
how standard protocols such as Rabi and Ramsey spectroscopy, that take
advantage of the sub-Hertz resolution of state-of-the-art clock lasers, can
perform momentum-resolved band tomography and determine SOC-induced $s$-wave
collisions in nuclear spin polarized fermions. By adding a second
counter-propagating clock beam a sliding superlattice can be implemented and
used for controlled atom transport and as a probe of $p$ and $s$-wave
interactions. The proposed spectroscopic probes provide clean and well-resolved
signatures at current clock operating temperatures.",1509.05846v1
2016-01-06,Harmonically Trapped Atoms with Spin-Orbit Coupling,"We study harmonically trapped one-dimensional atoms subjected to an equal
combination of Rashba and Dresselhaus spin-orbit coupling induced by Raman
transition. We first examine the wave function and the degeneracy of the
single-particle ground state, followed by a study of two weakly interacting
bosons or fermions. For the two-particle ground state, we focus on the effects
of the interaction on the degeneracy, the spin density profiles, and the
density-density correlation functions. Finally we show how these studies help
us to understand the many-body properties of the system.",1601.01335v2
2016-02-25,"Rashba spin-orbit coupling, strong interactions, and the BCS-BEC crossover in the ground state of the two-dimensional Fermi Gas","The recent experimental realization of spin-orbit coupled Fermi gases
provides a unique opportunity to study the interplay between strong interaction
and SOC in a tunable, disorder-free system. We present here precision ab initio
numerical results on the two-dimensional, unpolarized, uniform Fermi gas with
attractive interactions and Rashba SOC. Using auxiliary-field quantum Monte
Carlo and incorporating recent algorithmic advances, we carry out exact
calculations on sufficiently large system sizes to provide accurate results
systematically as a function of experimental parameters. We obtain the equation
of state, the momentum distributions, the pseudo-spin correlations and the
pairing wave functions. Our results help illuminate the rich pairing structure
induced by SOC, and provide benchmarks for theory and guidance to future
experimental efforts.",1602.08046v1
2016-04-22,"On the Bargmann-Michel-Telegdi equations, and spin-orbit coupling: a tribute to Raymond Stora","The Bargmann-Michel-Telegdi equations describing the motions of a spinning,
charged, relativistic particle endowed with an anomalous magnetic moment in an
electromagnetic field, are reconsidered. They are shown to duly stem from the
linearization of the characteristic distribution of a pre-symplectic structure
refining the original one of Souriau. In this model, once specialized to the
case of a static electric-like field, the angular momentum and energy given by
the associated moment map now correctly restore the spin-orbit coupling term.
This is the state-of-the-art of unfinished joint work with Raymond Stora.",1604.06550v1
2016-07-09,Phase tunable Josephson junction and spontaneous mass current in a spin-orbit coupled Fermi superfluid,"Atomtronics has the potential for engineering new types of functional
devices, such as Josephson junctions (JJs). Previous studies have mainly
focused on JJs whose ground states have 0 or $\pi $ superconducting phase
difference across the junctions, while arbitrarily tunable phase JJs may have
important applications in superconducting electronics and quantum computation.
Here we show that a phase tunable JJ can be implemented in a spin-orbit coupled
cold atomic gas with the magnetic tunneling barrier generated by a
spin-dependent focused laser beam. We consider the JJ confined in either a
linear harmonic trap or a circular ring trap. In the ring trap, the magnetic
barrier induces a spontaneous mass current for the ground state of the JJ,
demonstrating the magnetoelectric effects of cold atoms.",1607.02599v1
2016-07-12,Electric octupole order in bilayer Rashba system,"The odd-parity multipole is an emergent degree of freedom, leading to
spontaneous inversion symmetry breaking. The odd-parity multipole order may
occur by forming staggered even-parity multipoles in a unit cell. We focus on a
locally noncentrosymmetric bilayer Rashba system, and study an odd-parity
electric octupole order caused by the antiferro stacking of local electric
quadrupoles. Analyzing the forward scattering model, we show that the electric
octupole order is stabilized by a layer-dependent Rashba spin-orbit coupling.
The roles of the spin-orbit coupling are clarified on the basis of the analytic
formula of multipole susceptibility. The spin texture allowed in the D_2d point
group symmetry and its magnetic response are revealed. Furthermore, we show
that the parity-breaking quantum critical point appears in the magnetic field.
The possible realization of the electric octupole order in bilayer high-T_c
cuprate superconductors is discussed.",1607.03283v3
2016-07-22,Influence of spin-orbit coupling on the magnetic dipole term $T_α$,"The influence of the spin-orbit coupling (SOC) on the magnetic dipole term
$T_{\alpha}$ is studied across a range of systems in order to check whether the
$T_{\alpha}$ term can be eliminated from analysis of x-ray magnetic circular
dichroism spectra done via the spin moment sum rule. Fully relativistic
Korringa-Kohn-Rostoker (KKR) Green function calculations for Co monolayers and
adatoms on Cu, Pd, Ag, Pt, and Au (111) surfaces were performed to verify
whether the sum over magnetic dipole terms $T_{x}+T_{y}+T_{z}$ is zero and
whether the angular dependence of the \ta\ term goes as $3\cos^{2}\theta-1$. It
follows that there are circumstances when the influence of the SOC on
$T_{\alpha}$ cannot be neglected even for 3$d$ atoms, where the SOC is
nominally small. The crucial factor appears to be the dimensionality of the
system: for 3$d$ adatoms, the influence of SOC on $T_{\alpha}$ can be
significant while for monolayers it is always practically negligible. Apart
from the dimensionality, hybridization between adatom and substrate states is
also important: small hybridization enhances the importance of the SOC and vice
versa.",1607.06596v1
2016-09-19,Ground states of a Bose-Einstein Condensate in a one-dimensional laser-assisted optical lattice,"We study the ground-state behavior of a Bose-Einstein Condensate (BEC) in a
Raman-laser-assisted one-dimensional (1D) optical lattice potential forming a
multilayer system. We find that, such system can be described by an effective
model with spin-orbit coupling (SOC) of pseudospin $(N-1)/2$, where $N$ is the
number of layers. Due to the intricate interplay between atomic interactions,
SOC and laser-assisted tunnelings, the ground-state phase diagrams generally
consist of three phases -- a stripe, a plane wave and a normal phase with
zero-momentum, touching at a quantum tricritical point. More important, even
though the single-particle states only minimize at zero-momentum for odd $N$,
the many-body ground states may still develop finite momenta. The underlying
mechanisms are elucidated. Our results provide an alternative way to realize an
effective spin-orbit coupling of Bose gas with the Raman-laser-assisted optical
lattice, and would also be beneficial to the studies on SOC effects in spinor
Bose systems with large spin.",1609.05955v2
2017-03-07,Two-Dimensional Large Gap Topological Insulators with Large Rashba Spin-Orbit Coupling in Group-IV films,"Rashba spin orbit coupling in topological insulators has attracted much
interest due to its exotic properties closely related to spintronic devices.
The coexistence of nontrivial topology and giant Rashba splitting, however, has
rare been observed in two-dimensional films, limiting severely its potential
applications at room temperature. Here, we propose a series of inversion
asymmetric group IV films, ABZ2, whose stability are confirmed by phonon
spectrum calculations. The analyses of electronic structures reveal that they
are intrinsic 2D TIs with a bulk gap as large as 0.74 eV, except for GeSiF2,
SnSiCl2, GeSiCl2 and GeSiBr2 monolayers which can transform from normal to
topological phases under appropriate tensile strains. Another prominent
intriguing feature is the giant Rashba spin splitting with a magnitude reaching
0.15 eV, the largest value reported in 2D films. These results present a
platform to explore 2D TIs for room temperature device applications.",1703.02178v1
2018-04-10,Spin-orbit coupling induced quantum droplet in ultracold Bose-Fermi mixtures,"Quantum droplets have intrigued much attention recently in view of their
successful observations in the ultracold homonuclear atoms. In this work, we
demonstrate a new mechanism for the formation of quantum droplet in
heteronuclear atomic systems, i.e., by applying the synthetic spin-orbit
coupling(SOC). Take the Bose-Fermi mixture for example, we show that by
imposing a Rashba SOC between the spin states of fermions, the greatly
suppressed Fermi pressure can enable the formation of Bose-Fermi droplets even
for very weak boson-fermion attractions, which are insufficient to bound a
droplet if without SOC. In such SOC-induced quantum droplets, the boson/fermion
density ratio universally depends on the SOC strength, and they occur in the
mean-field collapsing regime but with a negative fluctuation energy, distinct
from the interaction-induced droplets found in literature. The accessibility of
these Bose-Fermi droplets in ultracold Cs-Li and Rb-K mixtures is also
discussed. Our results shed light on the droplet formation in a vast class of
heteronuclear atomic systems through the manipulation of single-particle
physics.",1804.03278v1
2018-04-24,Rashba and Weyl spin-orbit coupling in an optical lattice clock,"Recent experimental realization of one-dimensional (1D) spin-orbit coupling
(SOC) for ultracold alkaline-earth(-like) atoms in optical lattice clocks opens
a new avenue for exploring exotic quantum matter because of the strongly
suppressed heating of atoms from lasers comparing with alkaline atoms. Here we
propose a scheme to realize two-dimensional (2D) Rashba and three-dimensional
(3D) Weyl types of SOC in a 3D optical lattice clock and explore their
topological phases. With 3D Weyl SOC, the system can support topological phases
with various numbers as well as types (I or II) of Weyl points. The spin
textures of such topological bands for 2D Rashba and 3D Weyl SOC can be
detected using suitably designed spectroscopic sequences. Our proposal may pave
the way for the experimental realization of robust topological quantum matters
and their exotic quasiparticle excitations in ultracold atomic gases.",1804.09282v1
2018-04-25,High-Field Magnetoresistance of Organic Semiconductors,"The magneto-electronic field effects in organic semiconductors at high
magnetic fields are described by field-dependent mixing between singlet and
triplet states of weakly bound charge carrier pairs due to small differences in
their Land\'e g-factors that arise from the weak spin-orbit coupling in the
material. In this work, we corroborate theoretical models for the high-field
magnetoresistance of organic semiconductors, in particular of diodes made of
the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate)
(PEDOT:PSS) at low temperatures, by conducting magnetoresistance measurements
along with multi-frequency continuous-wave electrically detected magnetic
resonance experiments. The measurements were performed on identical devices
under similar conditions in order to independently assess the magnetic
field-dependent spin-mixing mechanism, the so-called {\Delta}g mechanism, which
originates from differences in the charge-carrier g-factors induced by
spin-orbit coupling.",1804.09297v1
2018-11-07,Two-dimensional composite solitons in a spin-orbit-coupled Fermi gas in free space,"We address a possibility of creating soliton states in oblate
binary-fermionic clouds in the framework of the density-functional theory,
which includes the spin-orbit coupling (SOC) and nonlinear attraction between
spin-up and down-polarized components of the spinor wave function. In the limit
when the inter-component attraction is much stronger than the effective
intra-component Pauli repulsion, the resulting model also represents a system
of Gross-Pitaevskii equations for a binary Bose-Einstein condensate including
the SOC effect. We show that the model gives rise to two-dimensional quiescent
composite solitons in free space. A stability region is identified for solitons
of the mixed-mode type (which feature mixtures of zero-vorticity and vortical
terms in both components), while solitons of the other type, semi-vortices
(with the vorticity carried by one component) are unstable. Due to breaking of
the Galilean invariance by SOC, the system supports moving solitons with
velocities up to a specific critical value. Collisions between moving solitons
are briefly considered too. The collisions lead, in particular, to a
quasi-elastic rebound, or an inelastic outcome, which features partial merger
of the solitons.",1811.02718v1
2018-11-14,Topological magneto-optical effects and their quantization in noncoplanar antiferromagnets,"Reflecting the fundamental interactions of polarized light with magnetic
matter, magneto-optical effects are well known since more than a century. The
emergence of these phenomena is commonly attributed to the interplay between
exchange splitting and spin-orbit coupling in the electronic structure of
magnets. Using theoretical arguments, we demonstrate that topological
magneto-optical effects can arise in noncoplanar antiferromagnets due to the
finite scalar spin chirality, without any reference to exchange splitting or
spin-orbit coupling. We propose spectral integrals of certain magneto-optical
quantities that uncover the unique topological nature of the discovered effect.
We also find that the Kerr and Faraday rotation angles can be quantized in
insulating topological antiferromagnets in the low-frequency limit, owing to
nontrivial global properties that manifest in quantum topological
magneto-optical effects. Although the predicted topological and quantum
topological magneto-optical effects are fundamentally distinct from
conventional light-matter interactions, they can be measured by readily
available experimental techniques.",1811.05803v2
2020-07-28,Dynamical Zeeman resonance in spin-orbit-coupled spin-1 Bose gases,"We predict a dynamical resonant effect, which is driven by externally applied
linear and quadratic Zeeman fields, in a spin-orbit-coupled spin-1
Bose-Einstein condensate. The Bose-Einstein condensate is assumed to be
initialized in some superposed state of Zeeman sublevels and subject to a
sudden shift of the trapping potential. It is shown that the time-averaged
center-of-mass oscillation and the spin polarizations of the Bose-Einstein
condensate exhibit remarkable resonant peaks when the Zeeman fields are tuned
to certain strengths. The underlying physics behind this resonance can be
traced back to the out-of-phase interference of the dynamical phases carried by
different spinorbit states. By analyzing the single particle spectrum, the
resonant condition is summarized as a simple algebraic relation, connecting the
strengths of the linear and quadratic Zeeman fields. This property is
potentially applicable in quantum information and quantum precision
measurement.",2007.14131v1
2010-05-16,SU(2) symmetry in a Hubbard model with spin-orbit coupling,"We study the underlying symmetry in a spin-orbit coupled tight-binding model
with Hubbard interaction. It is shown that, in the absence of the on-site
interaction, the system possesses the SU(2) symmetry arising from the
timereversal symmetry. The influence of the on-site interaction on the symmetry
depends on the topology of the networks: The SU(2) symmetry is shown to be the
spin rotation symmetry of a simply-connected lattice, so it still holds in the
presence of the Hubbard correlation. In contrary, the on-site interaction
breaks the SU(2) symmetry of a multi-connected lattice.",1005.2723v2
2014-03-05,Beating dark-dark solitons and Zitterbewegung in spin-orbit coupled Bose-Einstein condensates,"We present families of beating dark-dark solitons in spin-orbit (SO) coupled
Bose-Einstein condensates. These families consist of solitons residing
simultaneously in the two bands of the energy spectrum. The soliton components
are characterized by two different spatial and temporal scales, which are
identified by a multiscale expansion method. The solitons are ""beating"" ones,
as they perform density oscillations with a characteristic frequency, relevant
to Zitterbewegung (ZB). We find that spin oscillations may occur, depending on
the parity of each soliton branch, which consequently lead to ZB oscillations
of the beating dark solitons. Analytical results are corroborated by numerical
simulations, illustrating the robustness of the solitons.",1403.1038v2
2016-11-07,Acceleration of spin-orbit coupled Bose-Einstein condensates: analytical description of the emergence of Landau-Zener transitions,"We analytically study the effect of gravitational and harmonic forces on
ultra-cold atoms with synthetic spin-orbit coupling (SOC). In particular, we
focus on the recently observed transitions between internal states induced by
acceleration of the external modes. Our description corresponds to a
generalized version of the Landau-Zener (LZ) model: the dimensionality is
enlarged to combine the quantum treatment of the external variables with the
internal-state characterization; additionally, atomic-interaction effects are
considered. The emergence of the basic model is analytically traced. Namely, by
using a sequence of unitary transformations and a subsequent reduction to the
spin space, the SOC Hamiltonian, with the gravitational potential incorporated,
is exactly converted into the primary LZ scenario. Moreover, the transitions
induced by harmonic acceleration are approximately cast into the framework of
the basic LZ model through a complete analytical procedure. We evaluate how the
validity of our picture depends on the system preparation and on the magnitude
of atomic-interaction effects. The identification of the regime of
applicability and the rigorous characterization of the parameters of the
effective model provide elements to control the transitions.",1611.02198v1
2017-01-04,Raman Scattering by a Two-Dimensional Fermi Liquid with Spin-Orbit Coupling,"We present a microscopic theory of Raman scattering by a two-dimensional
Fermi liquid (FL) with Rashba and Dresselhaus types of spin-orbit coupling, and
subject to an in-plane magnetic field (B). In the long-wavelength limit, the
Raman spectrum probes the collective modes of such a FL: the chiral spin waves.
The characteristic features of these modes are a linear-in-q term in the
dispersion and the dependence of the mode frequency on the directions of both q
and B. All of these features have been observed in recent Raman experiments on
CdTe quantum wells.",1701.01041v2
2017-01-10,Induced interactions in the BCS-BEC crossover of two-dimensional Fermi gases with Rashba spin-orbit coupling,"We investigate the Gorkov--Melik-Barkhudarov (GM) correction to superfluid
transition temperature in two-dimensional Fermi gases with Rashba spin-orbit
coupling (SOC) across the SOC-driven BCS-BEC crossover. In the calculation of
the induced interaction, we find that the spin-component mixing due to SOC can
induce both of the conventional screening and additional antiscreening
contributions that interplay significantly in the strong SOC regime. While the
GM correction generally lowers the estimate of transition temperature, it turns
out that at a fixed weak interaction, the correction effect exhibits a
crossover behavior where the ratio between the estimates without and with the
correction first decreases with SOC and then becomes insensitive to SOC when it
goes into the strong SOC regime. We demonstrate the applicability of the GM
correction by comparing the zero-temperature condensate fraction with the
recent quantum Monte Carlo results.",1701.02706v2
2017-01-11,Supercurrent Vortex Pinball via a Triplet Cooper Pair Inverse Edelstein Effect,"We consider the Josephson effect through a thin spin-orbit coupled layer in
the presence of an exchange field, and discover a set of supercurrent vortices
appearing in the system which can be controllably moved around in the system by
varying either the direction of the exchange field, its strength, or the
spin-orbit coupling magnitude via a gate voltage. We refer to this phenomenon
as a supercurrent vortex pinball effect and show that its origin is the spin
polarization of the triplet Cooper pairs induced in the system. The
supercurrent vortices thus arise from what resembles a Cooper pair-induced
inverse Edelstein effect. Our results highlight the importance of considering
higher-dimensional models for superconducting hybrid structures which unveils
novel phenomena that are hidden in commonly used effective 1D models.",1701.03108v2
2017-04-01,Observation of Floquet band topology change in driven ultracold Fermi gases,"Periodic driving of a quantum system can significantly alter its energy bands
and even change the band topology, opening a completely new avenue for
engineering novel quantum matter. Although important progress has been made
recently in measuring topological properties of Floquet bands in different
systems, direct experimental measurement of Floquet band dispersions and their
topology change is still demanding. Here we directly measure Floquet band
dispersions in a periodically driven spin-orbit coupled ultracold Fermi gas.
Using spin injection radio-frequency spectroscopy, we observe that the Dirac
point originating from two dimensional spin-orbit coupling can be manipulated
to emerge at the lowest or highest two dressed bands by fast modulating Raman
laser frequencies, demonstrating topological change of Floquet bands. Our work
will provide a powerful tool for understanding fundamental Floquet physics as
well as engineering exotic topological quantum matter.",1704.00132v1
2017-04-10,Hole weak anti-localization in a strained-Ge surface quantum well,"We report a magneto-transport study of a two-dimensional hole gas confined to
a strained Ge quantum well grown on a relaxed Si0.2Ge0.8 virtual substrate. The
conductivity of the hole gas measured as a function of a perpendicular magnetic
field exhibits a zero-field peak resulting from weak anti-localization. The
peak develops and becomes stronger upon increasing the hole density by means of
a top gate electrode. This behavior is consistent with a Rashba-type spin-orbit
coupling whose strength is proportional to the perpendicular electric field,
and hence to the carrier density. By fitting the weak anti-localization peak to
a model including a dominant cubic spin-orbit coupling, we extract the
characteristic transport time scales and a spin splitting energy of ~1 meV.
Finally, we observe a weak anti-localization peak also for magnetic fields
parallel to the quantum well and attribute this finding to a combined effect of
surface roughness, Zeeman splitting, and virtual occupation of higher-energy
hole subbands.",1704.02879v2
2017-04-28,Hanle model of a spin-orbit coupled Bose-Einstein condensate of excitons in semiconductor quantum wells,"We present a theoretical model of a driven-dissipative spin-orbit coupled
Bose-Einstein condensate of indirect excitons in semiconductor quantum wells
(QW's). Our steady-state solution of the problem shares analogies with the
Hanle effect in an optical orientation experiment. The role of the spin pump in
our case is played by boson stimulated scattering into the linearly-polarized
ground state and the depolarization occurs as a result of long-range exchange
interaction between electrons and holes. Our theory agrees with the recent
experiment [A. A. High et al., Phys. Rev. Lett. 110, 246403 (2013)], where
spontaneous emergence of spatial coherence and polarization texture have been
observed. As a complementary test, we discuss a configuration where an external
magnetic field is applied in the structure plane.",1704.08961v2
2018-05-14,Unraveling the nature of magnetism of the 5$\boldsymbol{d^4}$ double perovskite Ba$_2$YIrO$_6$,"We report electron spin resonance (ESR) spectroscopy results on the double
perovskite Ba$_2$YIrO$_6$. On general grounds, this material is expected to be
nonmagnetic due to the strong coupling of the spin and orbital momenta of
Ir$^{5+}$ (5$d^4$) ions. However, controversial experimental reports on either
strong antiferromagnetism with static order at low temperatures or just a
weakly paramagnetic behavior have triggered a discussion on the breakdown of
the generally accepted scenario of the strongly spin-orbit coupled ground
states in the 5$d^4$ iridates and the emergence of a novel exotic magnetic
state. Our data evidence that the magnetism of the studied material is solely
due to a few percent of Ir$^{4+}$ and Ir$^{6+}$ magnetic defects while the
regular Ir$^{5+}$ sites remain nonmagnetic. Remarkably, the defect Ir$^{6+}$
species manifest magnetic correlations in the ESR spectra at $T\lesssim 20$ K
suggesting a long-range character of superexchange in the double prevoskites as
proposed by recent theories.",1805.05243v2
2012-01-27,Quarter-filled Kitaev-Hubbard Model: A Quantum Hall State in an Optical Lattice,"We analyze the Physics of cold atoms in honeycomb optical lattices with
on-site repulsion and spin-orbit couplings that break time reversal symmetry.
Such systems, at half filling and large on-site repulsion, have been proposed
as a possible realization of the Kitaev model. The spin-orbit couplings break
the spin degeneracy and, if strong-enough, lead to four non-overlapping bands
in the non-interacting limit. These bands carry non-zero Chern number and
therefore the non-interacting system has non-zero angular momentum and chiral
edge states at 1/4 and 3/4 filling. We have investigated the effect of
interactions using the variational cluster perturbation theory and conclude
that the chiral edge states exist in finite range of interaction and hopping
parameter space.",1201.5874v2
2013-09-03,The influence of the Rashba spin-orbit coupling on the two-dimensional electron-hole system and magnetoexcitons,"In the review article the influence of the Rashba spin-orbit coupling on the
two-dimensional electrons and holes in a strong perpendicular magnetic field is
described in Landau gauge using the spinor-type two-component wave functions
with different numbers of the Landau quantization levels in different spin
projections, their difference being determined by the order of the chirality
terms. In this representation the two-particle integral operators such as the
electron and hole densities ${{\hat{\rho}}_{e}}(\vec{Q})$, and
${{\hat{\rho}}_{h}}(\vec{Q})$ as well as the magnetoexciton creation and
annihilation operators $\hat{\Psi}_{ex}^{\dagger}({{F}_{n}},\vec{k})$ and
$\hat{\Psi}_{ex}^{{}}({{F}_{n}},\vec{k})$ in different combinations ${{F}_{n}}$
of the electron and hole spinor states were introduced. On this base the
Hamiltonians of the Coulomb electron-electron and electron-radiation
interactions were deduced. The properties of the magnetoexcitons in these
conditions were discussed.",1309.1053v1
2013-09-19,Tuning Magnetotransport in PdPt/Y3Fe5O12: Effects of magnetic proximity and spin orbital coupling,"Anisotropic magnetoresistance (AMR) ratio and anomalous Hall conductivity
(AHC) in PdPt/Y$_3$Fe$_5$O$_{12}$ (YIG) system are tuned significantly by spin
orbital coupling strength $\xi$ through varying the Pt concentration. For both
Pt/YIG and Pd/YIG, the maximal AMR ratio is located at temperatures for the
maximal susceptibility of paramagnetic Pt and Pd metals. The AHC and ordinary
Hall effect both change the sign with temperature for Pt-rich system and vice
versa for Pd-rich system. The present results ambiguously evidence the spin
polarization of Pt and Pd atoms in contact with YIG layers. The global
curvature near the Fermi surface is suggested to change with the Pt
concentration and temperature.",1309.4841v2
2017-09-30,One-step treatment of spin-orbit coupling and electron correlation in large active spaces,"In this work we demonstrate that the heat bath configuration interaction
(HCI) and its semistochastic extension can be used to treat relativistic
effects and electron correlation on an equal footing in large active spaces to
calculate the low energy spectrum of several systems including halogens group
atoms (F, Cl, Br, I), coinage atoms (Cu, Au) and the Neptunyl(VI) dioxide
radical. This work demonstrates that despite a significant increase in the size
of the Hilbert space due to spin symmetry breaking by the spin-orbit coupling
terms, HCI retains the ability to discard large parts of the low importance
Hilbert space to deliver converged absolute and relative energies. For
instance, by using just over $10^7$ determinants we get converged excitation
energies for Au atom in an active space containing (150o,25e) which has over
$10^{30}$ determinants. We also investigate the accuracy of five different
two-component relativistic Hamiltonians in which different levels of
approximations are made in deriving the one-electron and two-electrons
Hamiltonians, ranging from Breit-Pauli (BP) to various flavors of exact
two-component (X2C) theory. The relative accuracy of the different Hamiltonians
are compared on systems that range in atomic number from first row atoms to
actinides.",1710.00259v1
2018-01-22,Finite-temperature behavior of a classical spin-orbit-coupled model for $\textrm{YbMgGaO}_4$ with and without bond disorder,"We present the results of finite-temperature classical Monte Carlo
simulations of a strongly spin-orbit-coupled nearest-neighbor
triangular-lattice model for the candidate $\mathrm{U}(1)$ quantum spin liquid
$\mathrm{YbMgGaO}_4$ at large system sizes. We find a single continuous
finite-temperature stripe-ordering transition with slowly diverging heat
capacity that completely breaks the sixfold ground-state degeneracy, despite
the absence of a known conformal field theory describing such a transition. We
also simulate the effect of random-bond disorder in the model, and find that
even weak bond disorder destroys the transition by fragmenting the system into
very large domains -- possibly explaining the lack of observed ordering in the
real material. The Imry-Ma argument only partially explains this fragility to
disorder, and we extend the argument with a physical explanation for the
preservation of our system's time-reversal symmetry even under a disorder model
that preserves the same symmetry.",1801.06941v3
2019-07-09,Full characterization of spin-orbit coupled photons via spatial-Stokes measurement,"Characterization and analysis of spin-orbit coupled (SOC) states, as a
measurement problem, play a vital role in research on the modern optics and
photonics based on structured light. Here, we demonstrate determination of
photonic SOC states via spatial-Stokes measurement, in which two spatial
complex probability amplitudes of spin-dependent spatial modes within SOC
states and their relative (intramode) phase can be measured directly. Compared
with the standard quantum-state tomography, by avoiding wavefront-flattening
operations, the apparatus can completely record photons' realistic SOC
structure, leading to a more accurate and precise determination of
wavefunction. This simple and general approach for SOC state determination can
provide a powerful toolkit for in-situ measuring photonic SOC state,
characterizing the quality of SOC light source and associated geometric-phase
devices.",1907.04035v1
2020-12-18,Spin and charge order in doped spin-orbit coupled Mott insulators,"We study a two-dimensional single band Hubbard Hamiltonian with antisymmetric
spin-orbit coupling. We argue that this is the minimal model to understand the
electronic properties of locally non-centrosymmetric transition-metal (TM)
oxides such as Sr$_2$IrO$_4$. Based on exact diagonalizations of small clusters
and the random phase approximation, we investigate the correlation effects on
charge and magnetic order as a function of doping and of the TM-oxygen-TM bond
angle $\theta$. For small doping and $\theta$ $\lesssim$ $15^\circ$ we find
dominant commensurate in-plane antiferromagnetic fluctuations while
ferromagnetic fluctuations dominate for $\theta$ $\gtrsim$ $25^\circ$.
Moderately strong nearest-neighbor Hubbard interactions can also stabilize a
charge density wave order. Furthermore, we compare the dispersion of magnetic
excitations for the hole-doped case to resonant inelastic X-ray scattering data
and find good qualitative agreement.",2012.10479v1
2017-05-29,Anisotropic electronic transport of the two-dimensional electron system in Al2O3/SrTiO3 heterostructures,"Transport measurements on the two dimensional electron system in Al2O3 SrTiO3
heterostructures indicate significant noncrystalline anisotropic behavior below
T = 30 K. Lattice dislocations in SrTiO3 and interfacial steps are suggested to
be the main sources for electronic anisotropy. Anisotropic defect scattering
likewise alters magnetoresistance at low temperature remarkably and influences
spin-orbit coupling significantly by the Elliot Yafet mechanism of spin
relaxation resulting in anisotropic weak localization. Applying a magnetic
field parallel to the interface results in an additional field induced
anisotropy of the conductance, which can be attributed to Rashba spin orbit
interaction. Compared to LaAlO3 SrTiO3, Rashba coupling seems to be reduced
indicating a weaker polarity in Al2O3 SrTiO3 heterostructures.",1705.10159v1
2018-07-26,Topological crystalline insulators from stacked graphene layers,"In principle the stacking of different two-dimensional (2D) materials allows
the construction of 3D systems with entirely new electronic properties. Here we
propose to realize topological crystalline insulators (TCI) protected by mirror
symmetry in heterostructures consisting of graphene monolayers separated by
two-dimensional polar spacers. The polar spacers are arranged such that they
can induce an alternating doping and/or spin-orbit coupling in the adjacent
graphene sheets. When spin-orbit coupling dominates, the non-trivial phase
arises due to the fact that each graphene sheet enters a quantum spin-Hall
phase. Instead, when the graphene layers are electron and hole doped in an
alternating fashion, a uniform magnetic field leads to the formation of quantum
Hall phases with opposite Chern numbers. It thus has the remarkable property
that unlike previously proposed and observed TCIs, the non-trivial topology is
generated by an external time-reversal breaking perturbation.",1807.10078v2
2018-08-14,Tuning the topological insulator states of artificial graphene,"We develop a robust, non-perturbative approach to study the band structure of
artificial graphene. Artificial graphene, as considered here, is generated by
imposing a superlattice structure on top of a two dimensional hole gas in a
semiconductor heterostructure, where the hole gas naturally possesses large
spin-orbit coupling. Via tuning of the system parameters we demonstrate how
best to exploit the spin-orbit coupling to generate time reversal
symmetry-protected topological insulator phases. Our major conclusion is the
identification of a second set of topological Dirac bands in the band structure
(with spin Chern number $C=3$), which were not reliably obtainable in previous
perturbative approaches to artificial graphene. Importantly, the second Dirac
bands host more desirable features than the previously studied first set of
Dirac bands (with $C=1$). Moreover, we find that upon tuning of the system
parameters, we can drive the system to the highly desirable regime of the
topological flat band. We discuss the possibilities this opens up for exotic,
strongly correlated phases.",1808.04548v1
2018-12-03,Nontrivial Triplon Topology and Triplon Liquid in Kitaev-Heisenberg-type Excitonic Magnets,"The combination of strong spin-orbit coupling and correlations, e.g. in
ruthenates and iridates, has been proposed as a means to realize quantum
materials with nontrivial topological properties. We discuss here Mott
insulators where onsite spin-orbit coupling favors a local $J_{\textrm{tot}}=0$
singlet ground state. We investigate excitations into a low-lying triplet,
triplons, and find them to acquire nontrivial band topology in a magnetic
field. We also comment on magnetic states resulting from triplon condensation,
where we find, in addition to the same ordered phases known from the
$J_{\textrm{tot}}=\tfrac{1}{2}$ Kitaev-Heisenberg model, a triplon liquid
taking the parameter space of Kitaev's spin liquid.",1812.00833v2
2019-02-06,Spatiotemporal Bloch states of a spin-orbit coupled Bose-Einstein condensate in an optical lattice,"We study the spatiotemporal Bloch states of a high-frequency driven
two-component Bose-Einstein condensate (BEC) with spin-orbit coupling (SOC) in
an optical lattice. By adopting the rotating-wave approximation (RWA) and
applying an exact trial-solution to the corresponding quasistationary system,
we establish a different method for tuning SOC via external field such that the
existence conditions of the exact particular solutions are fitted. Several
novel features related to the exact states are demonstrated, such as SOC leads
to spin-motion entanglement for the spatiotemporal Bloch states, SOC increases
the population imbalance of the two-component BEC and SOC can be applied to
manipulate the stable atomic flow which is conducive to control quantum
transport of the BEC for different application purposes.",1902.02003v1
2019-03-02,Topological band gap in intercalated epitaxial graphene,"Functional manipulation of graphene is an important topic in view of both
fundamental researches and practical applications. In this study, we show that
intercalation of 5$d$ transition metals in epitaxial graphene on SiC is a
promising approach to realize topologically nontrivial phases with a finite
band gap in graphene. Using first-principles calculations based on density
functional theory, we show that the Re- and Ta-intercalated graphene become
two-dimensional topological insulators which exhibit linear Dirac cones and
quadratic bands with topological band gaps, respectively. The appearance of the
topological states is attributed to the strong spin-orbit coupling strength of
the intercalants. We find that topological edge states exist within the finite
bulk band gap in accordance with the bulk-boundary correspondence. We also
discuss the spin splitting of the band structure due to the inversion symmetry
breaking and the spin-orbit coupling. Our results demonstrate that
intercalation of graphene is an effective and viable method to manipulate the
band gap and the topological character of graphene. Such intercalated graphene
systems are potentially useful for spintronics and quantum computing
applications.",1903.00591v1
2019-03-11,Unconventional gate voltage dependence of the charge conductance caused by spin-splitting Fermi surface by Rashba-type spin-orbit coupling,"We calculate the gate voltage (Vg) dependence of charge conductance in a
normal metal (NM)/two dimensional electron gas (2DEG) junction, where Rashba
spin-orbit coupling and ferromagnetism exist in the 2DEG.
  We call this 2DEG as the ferromagnetic Rashba metal (FRM) and the chemical
potential of the FRM is controlled by Vg.
  We clarify the physical origin of the unconventional Vg dependence of charge
conductance in the NM/FRM junction found in our previous work [J. Phys. Soc.
Jpn. 87, 034710 (2018)], in which the charge conductance increases with Vg,
although the number of carries in FRM decreases.
  We calculate the momentum-resolved charge conductance.
  It is clarified that the origin of the unconventional Vg dependence is due to
the non-monotonic change in the size of the inner Fermi surface in FRM as a
function of $V_{g}$.",1903.04346v1
2019-03-25,Stacking sensitive topological phases in a bilayer Kane-Mele-Hubbard model at quarter filling,"Layered quasi two dimensional systems have garnered huge interest both in the
advancement of technology and in understanding emergent physics such as
unconventional superconductivity, topological phases. In particular, the study
of topological properties in some bilayer systems like transition metal
chalcogenides and iridates has been the point of attraction due to
comparatively strong spin orbit coupling of transition metal ions. In this
paper, we analyze the topological phases induced by the interplay of electron
correlation and spin orbit coupling in different stacking orders of bilayer
honeycomb lattice at quarter filling. Considering the two most common stacking
orders, AA and bernel (AB) stacking, we show that the stacking order plays a
crucial role in the topological phase transitions of the bilayer interacting
system. For AA stacking case, the system realizes quantum spin Hall insulator
in the presence (absence) of time reversal symmetry and magnetically ordered
insulator. For bernel stacking case, however, additional phases such as charge
ordered normal insulator or Chern insulator with both charge and magnetic order
can be stabilized. Based on our analysis, we discuss the scope of experimental
realization in bilayers of transition metal chalcogenides.",1903.10124v1
2019-04-03,Non-Abelian Aharonov-Casher Phase Factor in Mesoscopic Systems,"The matrix-valued Aharonov-Casher phase factor $F_{\text{AC}}$ (related to
the c-number Aharonov-Casher phase $\lambda_{\text{AC}}$) plays an important
role in the physics of mesoscopic systems in which spin-orbit coupling is
relevant. Yet, its relation to experimental observables is rather elusive.
Based on the SU(2)-gauge-invariant formulation of the Schroedinger equation, we
relate $F_{\text{AC}}$ to measurable quantities in electronic interferometers
subject to electric fields that generate Rashba or Dresselhaus spin-orbit
coupling. Specifically, we consider electron transmission through (i) a
single-channel ring interferometer and (ii) a two-channel square
interferometer. In both examples, we derive the closed expressions of the
conductance and show them to be simple rational functions of the traceful part
of $F_{\text{AC}}$. In the second case, we also derive a closed expression for
the electron spin polarization vector and find it to be a simple function of
both the traceful and traceless parts of $F_{\text{AC}}$. This analysis then
suggests a direct way for an experimental access to this elusive quantity.",1904.01751v1
2020-11-09,Topological Insulators-Based Magnetic Heterostructure,"The combination of magnetism and topology in magnetic topological insulators
(MTIs) has led to unprecedented advancements of time reversal symmetry-breaking
topological quantum physics in the past decade. Compared with the uniform
films, the MTI heterostructures provide a better framework to manipulate the
spin-orbit coupling and spin properties. In this review, we summarize the
fundamental mechanisms related to the physical orders host in
(Bi,Sb)2(Te,Se)3-based hybrid systems. Besides, we provide an assessment on the
general strategies to enhance the magnetic coupling and spin-orbit torque
strength through different structural engineering approaches and effective
interfacial interactions. Finally, we offer an outlook of MTI
heterostructures-based spintronics applications, particularly in view of their
feasibility to achieve room-temperature operation.",2011.04148v1
2016-10-12,Evidence for topological proximity effect in graphene coupled to topological insulator,"The emergence of topological order in graphene is in great demand for the
realization of quantum spin Hall states. Recently, it is theoretically proposed
that the spin textures of surface states in topological insulator can be
directly transferred to graphene by means of proximity effect. Here we report
the observations of the topological proximity effect in the
graphene-topological insulator Bi2Se3 heterojunctions via magnetotransport
measurements. The coupling between the p_z orbitals of graphene and the p
orbitals of surface states on the Bi2Se3 bottom surface can be enhanced by
applying perpendicular negative magnetic field, resulting in a giant negative
magnetoresistance at the Dirac point up to about -91%. An obvious resistivity
dip in the transfer curve at the Dirac point is also observed in the hybrid
devices, which is consistent with the theoretical predictions of the distorted
Dirac bands with unique spin textures inherited from Bi2Se3 surface states.",1610.03644v1
2016-10-18,Importance of Spin-Orbit Coupling in Organic BEDT-TTF and BEDT-TSF Salts,"We investigate the spin-orbit coupling (SOC) effects in $\alpha$- and
$\kappa$-phase BEDT-TTF and BEDT-TSF organic salts. Contrary to the assumption
that SOC in organics is negligible due to light C, S, H atoms, we show the
relevance of such an interaction in a few representative cases. In the weakly
correlated regime, SOC manifests primarily in the opening of energy gaps at
degenerate band touching points. This effect becomes especially important for
Dirac semimetals such as $\alpha$-(ET)$_2$I$_3$. Furthermore, in the magnetic
insulating phase, SOC results in additional anisotropic exchange interactions,
which provide a compelling explanation for the controversial field-induced
behaviour of the quantum spin-liquid candidate $\kappa$-(ET)$_2$Cu$_2$(CN)$_3$.
We conclude by discussing the importance of SOC for the description of
low-energy properties in organics.",1610.05468v1
2017-11-02,Entanglement and dynamical phase transition in a spin-orbit-coupled Bose-Einstein condensate,"Characterizing quantum phase transitions through quantum correlations has
been deeply developed for a long time, while the connections between dynamical
phase transitions (DPTs) and quantum entanglement is not yet well understood.
In this work, we show that the time-averaged two-mode entanglement in the spin
space reaches a maximal value when it undergoes a DPT induced by external
perturbation in a spin-orbit-coupled Bose-Einstein condensate. We employ the
von Neumann entropy and a correlation-based entanglement criterion as
entanglement measures and find that both of them can infer the existence of
DPT. While the von Neumann entropy works only for a pure state at zero
temperature and requires state tomography to reconstruct, the experimentally
more feasible correlation-based entanglement criterion acts as an excellent
proxy for entropic entanglement and can determine the existence of entanglement
for a mixed state at finite temperature, making itself an excellent indicator
for DPT. Our work provides a deeper understanding about the connection between
DPTs and quantum entanglement, and may allow the detection of DPT via
entanglement become accessible as the examined criterion is suitable for
measuring entanglement.",1711.00766v2
2017-11-14,Single branch of chiral Majorana modes from doubly degenerate Fermi surfaces,"Majorana fermions are often proposed to be realized by first singling out one
Fermi surface without spin degeneracy via spin-orbit coupling, and then
imposing boundaries or defects. In this work, we take a different route
starting with two degenerate Fermi surfaces without spin-orbit coupling, and
show that by the method of ""kink on boundary"", the dispersive chiral Majorana
fermions can be realized in superconducting systems with $p\pm is$ pairings.
The surfaces of these systems develop spontaneous magnetizations whose
directions are determined by the boundary orientations and the phase difference
between the $p$ and $s$-component gap functions. Along the magnetic domain
walls on the surface, there exist chiral Majorana fermions propagating
unidirectionally, which can be conveniently dragged and controlled by external
magnetic fields. Furthermore, the surface magnetization is shown to be a
magnetoelectric effect based on a Ginzburg-Landau free energy analysis. We also
discuss how to use the proximity effects to realize chiral Majorana fermions by
performing the ""kink on boundary"" method.",1711.05241v3
2017-11-15,Transport spectroscopy for Paschen-Back splitting of Landau levels in InAs nanowires,"The coupling of electron orbital motion and spin leads to nontrivial changes
in energy-level structures, leading to various spectroscopies and applications.
In atoms, such spin-orbit coupling (SOC) causes anomalous Zeeman splitting,
known as the Paschen-Back (PB) effect, in the pres-ence of a strong magnetic
field. In solids, SOC generates energy-band inversion or splitting, a
prerequisite for topological phases or Majorana fermions, at zero or weak
magnetic fields. Here, we present the first observation of PB splitting of
Landau levels (LLs) in indium arsenide nan-owires in a strong-field regime. Our
energy-resolved transport spectroscopy results indicated the presence of
LL-dependent anomalous Zeeman splitting in these nanowires, analogous to the
atomic PB effect. This result was found to be in good agreement with a
theoretical analysis based on Rashba SOC. Our findings also suggested a way of
generating spin-resolved electron transport in nanowires.",1711.05432v2
2018-10-19,Ferromagnetic nodal-line metal in monolayer {\em h}-InC,"Based on first-principles calculations, we predict a new two-dimensional
ferromagnetic material that exhibits exotic Fermi surface topology. We show
that monolayer hexagonal indium carbide ({\em h}-InC) is thermodynamically and
dynamically stable, and it energetically favors the ferromagnetic ordering of
spins. The perfectly planar geometry in two dimensions, together with
ferromagnetism, gives rise to a unique opportunity to encounter intriguing
electronic properties, captured in the Fermi surface and band topology. We show
that multiple nodal lines coexist in momentum space, accompanied by the
electron and hole pockets that touch each other linearly at the nodal lines.
Inclusion of spin-orbit coupling enriches the magnetic and electronic
properties of {\em h}-InC. Spin-orbit coupling leads to an easy-plane type
magnetocrystalline anisotropy, and the nodal lines can be tuned into
topological nodal points, contingent upon the magnetization direction. Symmetry
analysis and a tight-binding model are provided to explain the nodal structure
of the bands. Our findings suggest {\em h}-InC as a new venue for supporting
carbon-based magnetism and exotic band topology in two dimensions.",1810.08563v2
2018-10-31,Theory of chiral effects in magnetic textures with spin-orbit coupling,"We present a theoretical study of two-dimensional spatially and temporally
varying magnetic textures in the presence of spin-orbit coupling (SOC) of both
the Rashba and Dresselhaus types. We show that the effective gauge field due to
these SOCs, contributes to the dissipative and reactive spin torques in exactly
the same way as in electromagnetism. Our calculations reveal that Rashba
(Dresselhaus) SOC induces a chiral dissipation in interfacial (bulk) inversion
asymmetric magnetic materials. Furthermore, we show that in addition to chiral
dissipation $\alpha_c$, these SOCs also produce a chiral renormalization of the
gyromagnetic ratio $\tilde{\gamma}_c$, and show that the latter is
intrinsically linked to the former via a simple relation $\alpha_c =
(\tau/\tau_{\rm ex}) \tilde{\gamma}_c$, where $\tau_{\rm ex}$ and $\tau$ are
the exchange time and the electron relaxation time, respectively. Finally, we
propose a theoretical scheme based on the Scattering theory to calculate and
investigate the properties of damping in chiral magnets. Our findings should in
principle provide a guide for material engineering of effects related to chiral
dynamics in magnetic textures with SOC.",1810.13065v1
2018-10-31,Spin molecular-orbit coupling and magnetic properties of the decorated honeycomb layers of Mo3S7(dmit)3 crystals,"We explore the magnetic properties of isolated a-b planes of trinuclear
organometallic crystals, Mo3S7(dmit)3, in which an interplay of strong
electronic correlations and spin molecular-orbital coupling (SMOC) occurs. The
magnetic properties can be described by a XXZ+120, S=1 Heisenberg model on a
honeycomb lattice with single-spin anisotropy, D, which depends strongly on
SMOC. Based on ab initio estimates of SMOC in Mo3S7(dmit)3 crystals, we predict
that the honeycomb layers of Mo3S7(dmit)3 are Neel ordered. However, in
materials with a greater degree of magnetic frustration, Neel order can give
way to the large-D phase.",1810.13399v1
2019-06-17,Robust Weyl points in a 1D superlattice with transverse spin-orbit coupling,"Weyl points, synthetic magnetic monopoles in the 3D momentum space, are the
key features of topological Weyl semimetals. The observation of Weyl points in
ultracold atomic gases usually relies on the realization of high-dimensional
spin-orbit coupling (SOC) for two pseudospin states (% \textit{i.e.,}
spin-1/2), which requires complex laser configurations and precise control of
laser parameters, thus has not been realized in experiment. Here we propose
that robust Wely points can be realized using 1D triple-well superlattices
(spin-1/three-band systems) with 2D transverse SOC achieved by Raman-assisted
tunnelings. The presence of the third band is responsible to the robustness of
the Weyl points against system parameters (e.g., Raman laser polarization,
phase, incident angle, etc.). Different from a spin-1/2 system, the non-trivial
topology of Weyl points in such spin-1 system is characterized by both the spin
vector and tensor textures, which can be probed using momentum-resolved Rabi
spectroscopy. Our proposal provides a simple yet powerful platform for
exploring Weyl physics and related high-dimensional topological phenomena using
high pseudospin ultracold atoms.",1906.06820v3
2020-06-22,Spin-orbit torque induced magnetisation dynamics and switching in CoFeB/Ta/CoFeB system with mixed magnetic anisotropy,"Spin-orbit torque (SOT) induced magnetisation switching in CoFeB/Ta/CoFeB
trilayer with two CoFeB layers exhibiting in-plane magnetic anisotropy (IPMA)
and perpendicular magnetic anisotropy (PMA) is investigated. Interlayer
exchange coupling (IEC), measured using ferromagnetic resonance technique is
modified by varying thickness of Ta spacer. The evolution of the IEC leads to
different orientation of the magnetic anisotropy axes of two CoFeB layers: for
thicker Ta layer where magnetisation prefers antiferromagnetic ordering and for
thinner Ta layer where ferromagnetic coupling exists. Magnetisation state of
the CoFeB layer exhibiting PMA is controlled by the spin-polarized current
originating from SOT in $\mu m$ sized Hall bars. The evolution of the critical
SOT current density with Ta thickness is presented, showing an increase with
decreasing $t_\mathrm{Ta}$, which coincides with the coercive field dependence.
In a narrow range of $t_\mathrm{Ta}$ corresponding to the ferromagnetic IEC,
the field-free SOT-induced switching is achieved.",2006.12068v1
2020-09-01,Effects of Rashba-spin-orbit coupling on superconducting boron-doped nanocrystalline diamond films: evidence of interfacial triplet superconductivity,"Among the many remarkable properties of diamond, the ability to superconduct
when heavily doped with boron has attracted much interest in the carbon
community. When considering the nanocrystalline boron doped system, the reduced
dimensionality and confinement effects have led to several intriguing
observations most notably, signatures of a mixed superconducting phase. Here we
present ultra-high-resolution transmission electron microscopy imaging of the
grain boundary and demonstrate how the complex microstructure leads to enhanced
carrier correlations. We observe hallmark features of spin-orbit coupling (SOC)
manifested as the weak anti-localization effect. The enhanced SOC is believed
to result from a combination of inversion symmetry breaking at the grain
boundary interfaces along with antisymmetric confinement potential between
grains, inducing a Rashba-type SOC. From a pronounced zero bias peak in the
differential conductance, we demonstrate signatures of a triplet component
believed to result from spin mixing caused by tunneling of singlet Cooper pairs
through such Rashba-SOC grain boundary junctions.",2009.00475v1
2021-01-04,NbIr$_2$B$_2$ and TaIr$_2$B$_2$ -- new low symmetry noncentrosymmetric superconductors with strong spin orbit coupling,"Superconductivity was first observed more than a century ago, but the search
for new superconducting materials remains a challenge. The Cooper pairs in
superconductors are ideal embodiments of quantum entanglement. Thus, novel
superconductors can be critical for both learning about electronic systems in
condensed matter and for possible application in future quantum technologies.
Here two previously unreported materials, NbIr$_2$B$_2$ and TaIr$_2$B$_2$, are
presented with superconducting transitions at 7.2 and 5.2 K, respectively. They
display a unique noncentrosymmetric crystal structure, and for both compounds
the magnetic field that destroys the superconductivity at 0 K exceeds one of
the fundamental characteristics of conventional superconductors (the Pauli
limit), suggesting that the superconductivity may be unconventional. Supporting
this experimentally based deduction, first-principle calculations show a spin
split Fermi surface due to the presence of strong spin-orbit coupling. These
materials may thus provide an excellent platform for the study of non-BCS
superconductivity in intermetallic compounds.",2101.00862v1
2021-01-28,Spin-orbit coupling in the kagome lattice with flux and time-reversal symmetry,"We study the topological properties of a spin-orbit coupled Hofstadter model
on the Kagome lattice. The model is time-reversal invariant and realizes a
$\mathbb{Z}_2$ topological insulator as a result of artificial gauge fields. We
develop topological arguments to describe this system showing three
inequivalent sites in a unit cell and a flat band in its energy spectrum in
addition to the topological dispersive energy bands. We show the stability of
the topological phase towards spin-flip processes and different types of
on-site potentials. In particular, we also address the situation where on-site
energies may differ inside a unit cell. Moreover, a staggered potential on the
lattice may realize topological phases for the half-filled situation. Another
interesting result is the occurrence of a topological phase for large on-site
energies. To describe topological properties of the system we use a numerical
approach based on the twisted boundary conditions and we develop a mathematical
approach, related to smooth fields.",2101.12219v2
2021-02-26,On the conservation of the angular momentum in ultrafast spin dynamics,"The total angular momentum of a close system is a conserved quantity, which
should remain constant in time for any excitation experiment once the pumping
signal has extinguished. Such conservation, however, is never satisfied in
practice in any real-time first principles description of the demagnetization
process. Furthermore, there is a growing experimental evidence that the same
takes place in experiments. The missing angular momentum is usually associated
to lattice vibrations, which are not measured experimentally and are never
considered in real-time simulations. Here we critically analyse the issue and
conclude that current state-of-the-art simulations violate angular momentum
conservation already at the electronic level of description. This shortcoming
originates from an oversimplified description of the spin-orbit coupling, which
includes atomic contributions but neglects completely that of itinerant
electrons. We corroborate our findings with time-dependent simulations using
model tight-binding Hamiltonians, and show that indeed such conservation can be
re-introduced by an appropriate choice of spin-orbit coupling. The consequences
of our findings on recent experiments are also discussed.",2102.13255v1
2021-06-08,Tunable spin-orbit coupling in two-dimensional InSe,"We demonstrate that spin-orbit coupling (SOC) strength for electrons near the
conduction band edge in few-layer $\gamma$-InSe films can be tuned over a wide
range. This tunability is the result of a competition between
film-thickness-dependent intrinsic and electric-field-induced SOC, potentially,
allowing for electrically switchable spintronic devices. Using a hybrid
$\mathbf{k\cdot p}$ tight-binding model, fully parameterized with the help of
density functional theory computations, we quantify SOC strength for various
geometries of InSe-based field-effect transistors. The theoretically computed
SOC strengths are compared with the results of weak antilocalization
measurements on dual-gated multilayer InSe films, interpreted in terms of
Dyakonov-Perel spin relaxation due to SOC, showing a good agreement between
theory and experiment.",2106.04719v1
2021-07-03,Moiré flat Chern bands and correlated quantum anomalous Hall states generated by spin-orbit couplings in twisted homobilayer MoS$_2$,"We predict that in a twisted homobilayer of transition-metal dichalcogenide
MoS$_2$, spin-orbit coupling in the conduction band states from $\pm K$ valleys
can give rise to moir\'{e} flat bands with nonzero Chern numbers in each
valley. The nontrivial band topology originates from a unique combination of
angular twist and local mirror symmetry breaking in each individual layer,
which results in unusual skyrmionic spin textures in momentum space with
skyrmion number $\mathcal{S} = \pm 2$. Our Hartree-Fock analysis further
suggests that density-density interactions generically drive the system at
$1/2$-filling into a valley-polarized state, which realizes a correlated
quantum anomalous Hall state with Chern number $\mathcal{C} = \pm 2$. Effects
of displacement fields are discussed with comparison to nontrivial topology
from layer-pseudospin magnetic fields.",2107.01328v3
2021-07-04,Dynamics of rotating spin-orbit-coupled Bose-Einstein condensates in a quasicrystalline optical lattice,"We investigate the dynamics of rotating pseudo-spin-1/2 Bose-Einstein
condensates (BECs) with Rashba spin-orbit coupling (SOC) in a quasicrystalline
optical lattice (QOL). For given parameters, the system evolves from an initial
heliciform-stripe phase into a final visible vortex necklace with a giant
vortex and a hidden vortex necklace. Simultaneously, the corresponding spin
texture undergoes a transition from a meron-antimeron pair to a
half-antiskyrmion necklace. During the dynamic evolution process, the angular
momentum increases gradually, and then approaches to a convergent value.
Furthermore, typical quantum phases of rotating two-component BECs with SOC in
different external potentials are summarized.",2107.01564v1
2021-08-02,A study of all-electric electron spin resonance using Floquet quantum master equations,"We present a theoretical framework to describe experiments directed to
controlling single-atom spin dynamics by electrical means using a scanning
tunneling microscope. We propose a simple model consisting of a quantum
impurity connected to electrodes where an electrical time-dependent bias is
applied. We solve the problem in the limit of weak coupling between the
impurity and the electrodes by means of a quantum master equation that is
derived by the non-equilibrium Green's function formalism. We show results in
two cases. The first case is just a single atomic orbital subjected to a
time-dependent electric field, and the second case consists of a single atomic
orbital coupled to a second spin-1/2. The first case reproduces the main
experimental features Ti atoms on MgO/Ag (100) while the second one directly
addresses the experiments on two Ti atoms. These calculations permit us to
explore the effect of different parameters on the driving of the atomic spins
as well as to reproduce experimental fingerprints.",2108.01011v2
2021-09-10,Controlling magnetism through Ising superconductivity in magnetic van der Waals heterostructures,"Van der Waals heterostructures have risen as a tunable platform to combine
different electronic orders, due to the flexibility in stacking different
materials with competing symmetry broken states. Among them, van der Waals
ferromagnets such as CrI3 and superconductors as NbSe2 provide a natural
platform to engineer novel phenomena at ferromagnet-superconductor interfaces.
In particular, NbSe2 is well known for hosting strong spin-orbit coupling
effects that influence the properties of the superconducting state. Here we put
forward a ferromagnet/NbSe2/ferromagnet heterostructure where the interplay
between Ising superconductivity in NbSe2 and magnetism controls the magnetic
alignment of the heterostructure. In particular, we show that the interplay
between spin-orbit coupling and superconductivity allows controlling magnetic
states in van der Waals materials. Our results show how hybrid van der Waals
ferromagnet/superconductor heterostructure can be used as a tunable materials
platform for superconducting spin-orbitronics.",2109.04788v2
2021-11-17,Proximity-driven ferromagnetism and superconductivity in the triangular Rashba-Hubbard model,"Bilayer Moir\'e structures are a highly tunable laboratory to investigate the
physics of strongly correlated electron systems. Moir\'e transition metal
dichalcogenides at low-energies, in particular, are believed to be described by
a single narrow band Hubbard model on a triangular lattice with spin-orbit
coupling. Motivated by recent experimental evidence for superconductivity in
twisted bilayer materials, we investigate the possible superconducting pairings
in a two-dimensional single band Rashba-Hubbard model. Using a random-phase
approximation in the presence of nearest and next-nearest neighbor hopping, we
analyze the structure of spin fluctuations and the symmetry of the
superconducting gap function. We show that Rashba spin-orbit coupling favors
ferromagnetic fluctuations which strengthen triplet superconductivity. If
parity is violated due to the absence of spatial inversion symmetry, singlet
(d-wave) and triplet (p-wave) channels of superconductivity will be mixed.
Moreover, we show that time-reversal symmetry can be spontaneously broken
leading to a chiral superconducting state. Finally, we consider quasiparticle
interference as a possible experimental technique to observe the
superconducting gap symmetry.",2111.08931v1
2022-01-04,Magnetic-field-induced Anderson localization in orbital selective antiferromagnet BaMn$_2$Bi$_2$,"We report a metal-insulator transition (MIT) in the half-filled multiorbital
antiferromagnet (AF) BaMn$_2$Bi$_2$ that is tunable by a magnetic field
perpendicular to the AF sublattices. Instead of an Anderson-Mott mechanism
usually expected in strongly correlated systems, we find by scaling analyses
that the MIT is driven by an Anderson localization. Electrical and
thermoelectrical transport measurements in combination with electronic band
calculations reveal a strong orbital-dependent correlation effect, where both
weakly and strongly correlated $3d$-derived bands coexist with decoupled charge
excitations. Weakly correlated holelike carriers in the $d_{xy}$-derived band
dominate the transport properties and exhibit the Anderson localization,
whereas other $3d$ bands show clear Mott-like behaviors with their spins
ordered into AF sublattices. The tuning role played by the perpendicular
magnetic field supports a strong spin-spin coupling between itinerant holelike
carriers and the AF fluctuations, which is in sharp contrast to their weak
charge coupling.",2201.01000v3
2022-01-15,Hamiltonian engineering of spin-orbit coupled fermions in a Wannier-Stark optical lattice clock,"Engineering a Hamiltonian system with tunable interactions provides
opportunities to optimize performance for quantum sensing and explore emerging
phenomena of many-body systems. An optical lattice clock based on partially
delocalized Wannier-Stark states in a gravity-tilted shallow lattice supports
superior quantum coherence and adjustable interactions via spin-orbit coupling,
thus presenting a powerful spin model realization. The relative strength of the
on-site and off-site interactions can be tuned to achieve a zero density shift
at a `magic' lattice depth. This mechanism, together with a large number of
atoms, enables the demonstration of the most stable atomic clock while
minimizing a key systematic uncertainty related to atomic density. Interactions
can also be maximized by driving off-site Wannier-Stark transitions, realizing
a ferromagnetic to paramagnetic dynamical phase transition.",2201.05909v1
2022-02-23,Dark Matter Direct Detection in Materials with Spin-Orbit Coupling,"Semiconductors with $\mathcal{O}(\text{meV})$ band gaps have been shown to be
promising targets to search for sub-MeV mass dark matter (DM). In this paper we
focus on a class of materials where such narrow band gaps arise naturally as a
consequence of spin-orbit coupling (SOC). Specifically, we are interested in
computing DM-electron scattering and absorption rates in these materials using
state-of-the-art density functional theory (DFT) techniques. To do this, we
extend the DM interaction rate calculation to include SOC effects which
necessitates a generalization to spin-dependent wave functions. We apply our
new formalism to calculate limits for several DM benchmark models using an
example ZrTe$_{5}$ target and show that the inclusion of SOC can substantially
alter projected constraints.",2202.11716v1
2022-03-10,Interplay of charge and spin fluctuations in a Hund's coupled impurity,"In Hund's metals, the local ferromagnetic interaction between orbitals leads
to an emergence of complex electronic states with large and slowly fluctuating
magnetic moments. Introducing the Hund's coupled mixed valence quantum
impurity, we gain analytic insight into recent numerical renormalization group
studies. We show that valence fluctuations drastically impede the development
of a large fluctuating moment over a wide range of temperatures and energy,
characterized by quenched orbital degrees of freedom and a singular logarithmic
behavior of the spin susceptibility $\chi_{\rm sp}''(\omega) \propto [\omega
\ln(\omega/T_K^{\rm eff})^2]^{-1}$, closely resembling power-law scaling
$\chi_{\rm sp}''(\omega) \sim \omega^{-\gamma}$. Such singular spin
fluctuations are suspected to play an important role in future models of Hund's
driven Cooper pairing.",2203.05172v3
2022-06-28,Simulation and detection of Weyl fermions in ultracold Fermi gases with Raman-assisted spin-orbit coupling,"Weyl fermion, also referred to as pseudo-magnetic monopole in momentum space,
is an undiscovered massless elementary particle with half-integer spin
predicted according to relativistic quantum field theory. Motivated by the
recent experimental observation of Weyl semimetal band in ultracold Bose gases
with Raman-assisted 3D spin-orbit coupling, we investigate the properties and
possible observation of Weyl fermions in the low-energy quasi-particle
excitations of ultracold Fermi gases. Following a previous suggestion that the
existing Raman lattice scheme can be readily generalized to fermionic systems,
here we discuss the movement of the Weyl points in the Brillouin Zone, as well
as the creation and annihilation of Weyl fermions by adjusting the effective
Zeeman field. The relevant topological properties are also demonstrated by
calculating the Chern number. Furthermore, we propose how to experimentally
verify the existence of the Weyl fermions and the associated quantum phase
transition via density profile measurements.",2206.13692v1
2022-06-30,Proximity spin-orbit coupling in graphene on alloyed transition metal dichalcogenides,"The negligible intrinsic spin-orbit coupling (SOC) in graphene can be
enhanced by proximity effects in stacked heterostructures of graphene and
transition metal dichalcogenides (TMDCs). The composition of the TMDC layer
plays a key role in determining the nature and strength of the resultant SOC
induced in the graphene layer. Here, we study the evolution of the
proximity-induced SOC as the TMDC layer is deliberately defected. Alloyed ${\rm
G/W_{\chi}Mo_{1-\chi}Se_2}$ heterostructures with diverse compositions ($\chi$)
and defect distributions are simulated using density functional theory.
Comparison with continuum and tight-binding models allows both local and global
signatures of the metal-atom alloying to be clarified. Our findings show that,
despite some dramatic perturbation of local parameters for individual defects,
the low-energy spin and electronic behaviour follow a simple effective medium
model which depends only on the composition ratio of the metallic species in
the TMDC layer. Furthermore, we demonstrate that the topological state of such
alloyed systems can be feasibly tuned by controlling this ratio.",2206.15313v1
2022-07-30,Bessel Vortices in Spin-Orbit-Coupled Binary Bose-Einstein Condensates with Zeeman Splitting,"We present an analysis of stationary solutions for two-dimensional (2D)
Bose-Einstein condensates (BECs) with the Rashba spin-orbit (SO) coupling and
Zeeman splitting. By introducing the generalized momentum operator, the linear
version of the system can be solved exactly. The solutions are semi-vortices of
the Bessel-vortex (BV) and modified Bessel-vortex (MBV) types, in the presence
of the weak and strong Zeeman splitting, respectively. The ground states (GSs)
of the full nonlinear system are constructed with the help of a specially
designed neural network (NN). The GS of the mixed-mode type appears as
cross-attraction interaction increases. The spin texture of the GS is produced
in detail. It exhibits the Neel skyrmion structure for the semi-vortex GS of
the BV type, and the respective skyrmion number is found in an analytical form.
On the other hand, GSs of the MBV and mixed-mode types do not form skyrmions.",2208.00310v1
2022-10-07,Evidence of linear and cubic Rashba effect in non-magnetic heterostructure,"The LaAlO3/KTaO3 system serves as a prototype to study the electronic
properties that emerge as a result of spin-orbit coupling. In this article, we
have used first-principles calculations to systematically study two types of
defect-free (0 0 1) interfaces, which are termed as Type-I and Type-II. While
the Type-I heterostructure produces a two-dimensional electron gas, the Type-II
heterostructure hosts an oxygen-rich two-dimensional hole gas at the interface.
Furthermore, in the presence of intrinsic spin-orbit coupling, we have found
evidence of both cubic and linear Rashba interactions in the conduction bands
of the Type-I heterostructure. On the contrary, there is spin-splitting of both
the valence and the conduction bands in the Type-II interface, which are found
to be only linear Rashba type. Interestingly, the Type-II interface also
harbours a potential photocurrent transition path, making it an excellent
platform to study the circularly polarized photogalvanic effect.",2210.03722v3
2022-10-19,Dynamic structure factor of one-dimensional Fermi superfluid with spin-orbit coupling,"We theoretically calculate the density dynamic structure factor of
one-dimensional Fermi superfluid with Raman-type spin-orbit coupling, and
analyze its main dynamical character during phase transition between
Bardeen-Cooper-Schrieffer superfluid and topological superfluid. Our
theoretical results display four kinds of single-particle excitations induced
by the two-branch structure of single-particle spectrum, and the cross
single-particle excitation is much easier to be seen in the spin dynamic
structure factor at a small transferred momentum. Also we find a new roton-like
collective mode emerges at a fixed transferred momentum $q \simeq 2k_F$, and it
only appears once the system enters the topological superfluid state. The
occurrence of this roton-like excitation is related to switch of global minimum
in single-particle spectrum from $k=0$ to $k \simeq 2k_F$.",2210.10407v1
2022-11-14,Symmetric Post-Transition-State Bifurcation Reactions with Berry Pseudo-Magnetic Fields,"We investigate how the Berry force (i.e. the pseudo-magnetic force operating
on nuclei as induced by electronic degeneracy and spin-orbit coupling (SOC))
might modify a post-transition state bifurcation (PTSB) reaction path and
affect product selectivity for situations when multiple products share the same
transition state. To estimate the magnitude of this effect, Langevin dynamics
are performed on a model system with a valley-ridge inflection (VRI) point in
the presence of a magnetic field (that mimics the Berry curvature). We also
develop an analytic model for such selectivity that depends on key parameters
such as the surface topology, the magnitude of the Berry force, and the nuclear
friction. Within this dynamical model, static electronic structure calculations
(at the level of generalized Hartree-Fock with spin-orbit coupling (GHF+SOC)
theory) suggest that electronic-spin induced Berry force effects may indeed
lead to noticeable changes in methoxy radical isomerization.",2211.07731v1
2022-12-15,Strain-induced superconductivity in Sr2IrO4,"Multi-orbital quantum materials with strong interactions can host a variety
of novel phases. In this work we study the possibility of interaction-driven
superconductivity in the iridate compound Sr$_2$IrO$_4$ under strain and
doping. We find numerous regimes of strain-induced superconductivity in which
the pairing structure depends on model parameters. Spin-fluctuation mediated
superconductivity is modeled by a Hubbard-Kanamori model with an effective
particle-particle interaction, calculated via the random phase approximation.
Magnetic orders are found using the Stoner criterion. The most likely
superconducting order we find has $d$-wave pairing, predominantly in the total
angular momentum, $J=1/2$ states. Moreover, an $s_{\pm}$-order which mixes
different bands is found at high Hund's coupling, and at high strain
anisotropic $s$- and $d$-wave orders emerge. Finally, we show that in a
fine-tuned region of parameters a spin-triplet $p$-wave order exists. The
combination of strong spin-orbit coupling, interactions, and a sensitivity of
the band structure to strain proves a fruitful avenue for engineering new
quantum phases.",2212.07596v2
2022-12-28,First-principles study of spin orbit coupling contribution to anisotropic magnetic interaction,"Anisotropic magnetic exchange interactions lead to a surprisingly rich
variety of the magnetic properties. Considering the spin orbit coupling (SOC)
as perturbation, we extract the general expression of a bilinear spin
Hamiltonian, including isotropic exchange interaction, antisymmetric
Dzyaloshinskii-Moriya (DM) interaction and symmetric $\Gamma $ term. Though it
is commonly believed that the magnitude of the DM and $\Gamma $ interaction
correspond to the first and second order of SOC strength $% \lambda $
respectively, we clarify that the term proportional to $\lambda ^{2}$ also has
contribution to DM interaction. Based on combining magnetic force theorem and
linear-response approach, we have presented the method of calculating
anisotropic magnetic interactions, which now has been implemented in the open
source software WienJ. Furthermore, we introduce another method which could
calculate the first and second order SOC contribution to the DM interaction
separately, and overcome some shortcomings of previous methods. Our methods are
successfully applied to several typical weak ferromagnets for $3d$, $4d$ and
$5d$ transition metal oxides. We also predict the conditions where the DM
interactions proportional to $\lambda $ are symmetrically forbidden while the
DM interactions proportional to $\lambda ^{2}$ are nonzero, and believe that it
is widespread in certain magnetic materials.",2212.13963v1
2023-01-29,Evidence of The Anomalous Fluctuating Magnetic State by Pressure Driven 4f Valence Change in EuNiGe$_3$,"In rare-earth compounds with valence fluctuation, the proximity of the 4f
level to the Fermi energy leads to instabilities of the charge configuration
and the magnetic moment. Here, we provide direct experimental evidence for an
induced magnetic polarization of the Eu$^{3+}$ atomic shell with J=0, due to
intra-atomic exchange and spin-orbital coupling interactions with Eu$^{2+}$
atomic shell. By applying external pressure, a transition from
antiferromagnetic to a fluctuating behavior in a EuNiGe$_3$ single crystals is
probed. Magnetic polarization is observed for both valence states of Eu$^{2+}$
and Eu$^{3+}$ across the entire pressure range. The anomalous magnetism is
discussed in terms of a homogeneous intermediate valence state where frustrated
Dzyaloshinskii-Moriya couplings are enhanced by the onset of spin-orbital
interaction and engender a chiral spin-liquid-like precursor.",2301.12414v1
2023-03-15,Non-Hermitian skin effect induced by Rashba-Dresselhaus spin-orbit coupling,"1D chains with non-reciprocal tunneling realizing the non-Hermitian skin
effect (NHSE) have attracted considerable interest in the last years whereas
their experimental realization in real space remains limited to a few examples.
In this work, we propose a new generic way of implementing non-reciprocity
based on a combination of the Rashba-Dresshlauss spin-orbit coupling, existing
for electrons, cold atoms, and photons, and a lifetime imbalance between two
spin components. We show that one can realize the Hatano-Nelson model, the
non-Hermitian Su-Schrieffer-Heeger model, and even observe the NHSE in a 1D
potential well without the need for a lattice. We further demonstrate the
practical feasibility of this proposal by considering the specific example of a
photonic liquid crystal microcavity. This platform allows one to switch on and
off the NHSE by applying an external voltage to the microcavity.",2303.08483v1
2023-03-16,Magnetic Real Chern Insulator in 2D Metal-Organic Frameworks,"Real Chern insulators have attracted great interest, but so far, their
material realization is limited to nonmagnetic crystals and to systems without
spin-orbit coupling. Here, we reveal magnetic real Chern insulator (MRCI) state
in a recently synthesized metal-organic framework material Co3(HITP)2. Its
ground state with in-plane ferromagnetic ordering hosts a nontrivial real Chern
number, enabled by the C2zT symmetry and robust against spin-orbit coupling.
Distinct from previous nonmagnetic examples, the topological corner zero-modes
of MRCI are spin-polarized. Furthermore, under small tensile strains, the
material undergoes a topological phase transition from MRCI to a magnetic
double-Weyl semimetal phase, via a pseudospin-1 critical state. Similar physics
can also be found in closely related materials Mn3(HITP)2 and Fe3(HITP)2, which
are also existing. Possible experimental detections and implications of an
emerging magnetic flat band in the system are discussed.",2303.09218v1
2023-04-01,Itinerant ferromagnetism entrenched by the anisotropy of spin-orbit coupling in a dipolar Fermi gas,"We investigate the the itinerant ferromagnetism in a dipolar Fermi atomic
system with the anisotropic spin-orbit coupling (SOC),which is traditionally
explored with isotropic contact interaction.We first study the ferromagnetism
transition boundaries and the properties of the ground states through the
density and spin-flip distribution in momentum space, and we find that both the
anisotropy and the magnitude of the SOC play an important role in this process.
We propose a helpful scheme and a quantum control method which can be applied
to conquering the difficulties of previous experimental observation of
itinerant ferromagnetism. Our further study reveals that exotic Fermi surfaces
and an abnormal phase region can exist in this system by controlling the
anisotropy of SOC, which can provide constructive suggestions for the research
and the application of a dipolar Fermi gas. Furthermore, we also calculate the
ferromagnetism transition temperature and novel distributions in momentum space
at finite temperature beyond the ground states from the perspective of
experiment.",2304.00286v1
2023-04-04,Unidirectional Seebeck effect from Rashba spin-orbit coupling on the subsurface of Ge(111),"A new nonlinear magnetothermal effect, namely unidirectional Seebeck
effect(USE), has been recently reported in magnetic/nonmagnetic topological
insulator (TI) heterostructure and is ascribed to the asymmetry magnon
scattering. Here, we show a new mechanism to generate USE in the Rashba two
dimensional electron gas (2DEG), in which the magnetism or magnetic order is
completely absent. It's found that the USE has a quantum origin from the
spin-momentum locking generated from Rashba spin-orbit coupling. We find that
the USE exhibits a sine dependence on the orientation of the magnetic field
with respect to the direction of the temperature gradient and is dominant from
the states above the Lifshitz point. The USE in the semiconductor Ge(111)
subsurface states has been theoretically and systematically investigated.",2304.01683v1
2023-08-03,Beyond Kitaev physics in strong spin-orbit coupled magnets,"We review the recent advances and current challenges in the field of strong
spin-orbit coupled Kitaev materials, with a particular emphasis on the physics
beyond the exactly-solvable Kitaev spin liquid point. To that end, we give a
comprehensive overview of the most relevant exchange interactions in $d^5$ and
$d^7$ iridates and similar compounds, an exposition of their microscopic
origin, and a systematic attempt to map out the most interesting correlated
regimes of the multi-dimensional parameter space, guided by powerful symmetry
and duality transformations as well as by insights from wide-ranging analytical
and numerical studies. We also survey recent exciting results on quasi-1D
models and discuss their relevance to higher-dimensional models. Finally, we
highlight some of the key questions in the field as well as future directions.",2308.01943v2
2023-09-06,"Tuning flat bands by interlayer interaction, spin-orbital coupling, and external fields in twisted homotrilayer MoS$_2$","Ultraflat bands have already been detected in twisted bilayer graphene and
twisted bilayer transition-metal dichalcogenides, which provide a platform to
investigate strong correlations. In this paper, the electronic properties of
twisted trilayer molybdenum disulfide (TTM) are investigated via an accurate
tight-binding Hamiltonian. We find that the highest valence bands are derived
from the $\Gamma$-point of the constituent monolayer, and they exhibit a
graphenelike dispersion or become isolated flat bands that are dependent on the
starting stacking arrangements. The lattice relaxation, local deformation, and
external fields can significantly tune the electronic structures of TTM. After
introducing the spin-orbital coupling effect, we find a spin-valley-layer
locking effect at the minimum of the conduction band at the $K$- and
$K^\prime$-point of the Brillouin zone, which may provide a platform to study
optical properties and magnetoelectric effects.",2309.03089v2
2023-09-12,Gravitational Radiation from Eccentric Binary Black Hole System in Dynamical Chern-Simons Gravity,"Dynamical Chern-Simons (DCS) gravity, a typical parity-violating
gravitational theory, modifies both the generation and propagation of
gravitational waves from general relativity (GR). In this work, we derive the
gravitational waveform radiated from a binary black hole system with eccentric
orbits under the spin-aligned assumption in the DCS theory. Compared with GR,
DCS modification enters the second-order post-Newtonian (2PN) approximation,
affecting the spin-spin coupling and monopole-quadrupole coupling of binary
motion. This modification produces an extra precession rate of periastron. This
effect modulates the scalar and gravitational waveform through a quite low
frequency. Additionally, the dissipation of conserved quantities results in the
secular evolution of the semimajor axis and the eccentricity of binary orbits.
Finally, the frequency-domain waveform is given in the post-circular scheme,
requiring the initial eccentricity to be $\lesssim0.3$. This ready-to-use
template will benefit the signal searches and improve the future constraint on
DCS theory.",2309.05991v1
2023-10-09,Quantum anomalous Hall state in a fluorinated 1T-MoSe$_2$ monolayer,"The quantum anomalous Hall state with a large band gap and a high Chern
number is significant for practical applications in spintronics. By performing
first-principles calculations, we investigate electronic properties of the
fully fluorinated 1T-MoSe$_{2}$ monolayer. Without considering the spin-orbit
coupling, the band structure demonstrates single-spin semi-metallic properties
and the trigonal warping around $K_{\pm}$ valleys. The introduction of the
spin-orbit coupling opens considerable band gaps of $117.2$ meV around the two
valleys, leading to a nontrivial quantum anomalous Hall state with a Chern
number of $|C|=2$, which provides two chiral dissipationless transport channels
from topological edge states and associated quantized anomalous Hall
conductivity. In addition, an effective model is constructed to describe the
low-energy physics of the monolayer. Our findings in the MoSe$_{2}$F$_{2}$
monolayer sheds light on large-gap quantum anomalous Hall states in
two-dimensional materials with the chemical functionalization, and provides
opportunities in designing low-power and noise-tolerant spintronic devices.",2310.05356v1
2023-10-27,Observation of Chern insulator in crystalline ABCA-tetralayer graphene with spin-orbit coupling,"Degeneracies in multilayer graphene, including spin, valley, and layer
degrees of freedom, are susceptible to Coulomb interactions and can result into
rich broken-symmetry states. In this work, we report a ferromagnetic state in
charge neutral ABCA-tetralayer graphene driven by proximity-induced spin-orbit
coupling from adjacent WSe2. The ferromagnetic state is further identified as a
Chern insulator with Chern number of 4, and its Hall resistance reaches 78% and
100% quantization of h/4e2 at zero and 0.4 tesla, respectively. Three
broken-symmetry insulating states, layer-antiferromagnet, Chern insulator and
layer-polarized insulator and their transitions can be continuously tuned by
the vertical displacement field. Remarkably, the magnetic order of the Chern
insulator can be switched by three knobs, including magnetic field, electrical
doping, and vertical displacement field.",2310.17971v1
2023-11-14,Bright solitons in a spin-orbit-coupled dipolar Bose-Einstein condensate trapped within a double-lattice,"By effectively controlling the dipole-dipole interaction, we investigate the
characteristics of the ground state of bright solitons in a spin-orbit coupled
dipolar Bose-Einstein condensate. The dipolar atoms are trapped within a
double-lattice which consists of a linear and a nonlinear lattice. We derive
the motion equations of the different spin components, taking the controlling
mechanisms of the diolpe-dipole interaction into account. An analytical
expression of dipole-dipole interaction is derived. By adjusting the dipole
polarization angle, the dipole interaction can be adjusted from attraction to
repulsion. On this basis, we study the generation and manipulation of the
bright solitons using both the analytical variational method and numerical
imaginary time evolution. The stability of the bright solitons is also analyzed
and we map out the stability phase diagram. By adjusting the long-range
dipole-dipole interaction, one can achieve manipulation of bright solitons in
all aspects, including the existence, width, nodes, and stability. Considering
the complexity of our system, our results will have enormous potential
applications in quantum simulation of complex systems.",2311.08162v1
2023-12-14,Temperature-induced supersolidity in spin-orbit-coupled Bose gases,"Close to the superfluid plane-wave (PW) - supersolid stripe (ST) phase
transition point of a zero temperature quasi-one-dimensional spin-orbit-coupled
Bose gas, we find that an increase in temperature induces a phase transition to
the supersolid phase with a broken translational symmetry from the superfluid
plane-wave phase. We use the Hartree-Fock-Bogoliubov theory with the Popov
approximation to investigate the effect of thermal fluctuations on the
collective excitation spectrum and investigate the softening of the spin-dipole
mode corresponding to the shift in the quantum critical point. This is in stark
contrast to the PW-ST phase transition in a homogeneous system where non-zero
temperatures facilitate the melting of the stripe phase.",2312.08719v2
2023-12-27,Correlated Quantum Phenomena of Spin-Orbit Coupled Perovskite Oxide Heterostructures: Cases of SrRuO3 and SrIrO3-Based Artificial Superlattices,"Unexpected, yet useful functionalities emerge when two or more materials
merge coherently. Artificial oxide superlattices realize atomic and crystal
structures that are not available in nature, thus providing controllable
correlated quantum phenomena. This review focuses on 4d and 5d oxide
superlattices, in which the spin-orbit coupling plays a significant role
compared with conventional 3d oxide superlattices. Modulations in crystal
structures with octahedral distortion, phonon engineering, electronic
structures, spin orderings, and dimensionality control are discussed for 4d
oxide superlattices. Atomic and magnetic structures, Jeff = 1/2 pseudospin and
charge fluctuations, and the integration of topology and correlation are
discussed for 5d oxide superlattices. This review provides insights into how
correlated quantum phenomena arise from the deliberate design of superlattice
structures that give birth to novel functionalities.",2312.16748v1
2024-01-15,Energy-level inversion for vortex states in spin-orbit coupled Bose-Einstein condensates,"We investigate vortex states in Bose-Einstein condensates under the combined
action of the spin-orbit coupling (SOC), gradient magnetic field, and
harmonic-oscillator trapping potential. The linear version of the system is
solved exactly. Through the linear-spectrum analysis, we find that, varying the
SOC strength and magnetic-field gradient, one can perform energy-level
inversion. With suitable parameters, initial higher-order vortex states can be
made the ground state (GS). The nonlinear system is solved numerically,
revealing that the results are consistent with the linear predictions in the
case of repulsive inter-component interactions. On the other hand,
inter-component attraction creates the GS in the form of mixed-mode states in a
vicinity of the GS phase-transition points. The spin texture of both vortex-
and mixed-mode GSs reveals that they feature the structure of 2D (baby)
skyrmions.",2401.07778v1
2024-01-21,Generation of Entangled Photons via Cooper Pair Recombination in Noncentrosymmetric Quantum Wells,"We theoretically explore the generation of entangled two-photon pairs through
Cooper pair recombination within a noncentrosymmetric [001]-quantum well
superconductor. Superconducting state is induced into the quantum well via
proximity effects, and featuring an admixture of Rashba and Dresselhaus
antisymmetric spin-orbit couplings. Our investigation highlights that the
highest achievable purity of entangled photon pairs emerges within scenarios
involving pure singlet Cooper pairs. Specifically, the conventional $s$-wave
gap function within the singlet pairings achieves the highest purity levels.
Furthermore, our findings underscore the significance of reducing spin-triplet
pairing amplitudes to attain entangled states of superior purity. This
reduction can be achieved by diminishing the amplitude of antisymmetric
spin-orbit couplings. In addition to purity considerations, our study delves
into the population of two-photon states. We observed that states featuring
$s+p$- and $d^{}_{x^2-y^2}+p$-wave Cooper pairings exhibit the highest
population values among the generated entangled two-photon states within a
noncentrosymmetric superconducting quantum well.",2401.11577v1
2024-03-26,Self-consistent quasi-particle $GW$ and hybrid functional calculations for Al/InAs/Al heterojunctions: band offset and spin-orbit coupling effects,"The electronic structure of surfaces and interfaces plays a key role in the
properties of quantum devices. Here, we study the electronic structure of
realistic Al/InAs/Al heterojunctions using a combination of density functional
theory (DFT) with hybrid functionals and state-of-the-art quasi-particle $GW$
(QS$GW$) calculations. We find a good agreement between QS$GW$ calculations and
hybrid functional calculations which themselves compare favourably well with
ARPES experiments. Our study confirm the need of well controlled quality of the
interfaces to obtain the needed properties of InAs/Al heterojunctions. A
detailed analysis of the effects of spin-orbit coupling on the spin-splitting
of the electronic states show a linear scaling in $k$-space, related to the
two-dimensional nature of some interface states. The good agreement by QS$GW$
and hybrid functional calculations open the door towards trust-able use of an
effective approximation to QS$GW$ for studying very large heterojunctions.",2403.17809v2
2007-05-02,Topological insulators beyond the Brillouin zone via Chern parity,"The topological insulator is an electronic phase stabilized by spin-orbit
coupling that supports propagating edge states and is not adiabatically
connected to the ordinary insulator. In several ways it is a spin-orbit-induced
analogue in time-reversal-invariant systems of the integer quantum Hall effect
(IQHE). This paper studies the topological insulator phase in disordered
two-dimensional systems, using a model graphene Hamiltonian introduced by Kane
and Mele as an example. The nonperturbative definition of a topological
insulator given here is distinct from previous efforts in that it involves
boundary phase twists that couple only to charge, does not refer to edge
states, and can be measured by pumping cycles of ordinary charge. In this
definition, the phase of a Slater determinant of electronic states is
determined by a Chern parity analogous to Chern number in the IQHE case.
Numerically we find, in agreement with recent network model studies, that the
direct transition between ordinary and topological insulators that occurs in
band structures is a consequence of the perfect crystalline lattice.
Generically these two phases are separated by a metallic phase, which is
allowed in two dimensions when spin-orbit coupling is present. The same
approach can be used to study three-dimensional topological insulators.",0705.0172v1
2013-02-04,Inhomogeneous Fulde-Ferrell superfluidity in spin-orbit coupled atomic Fermi gases,"Inhomogeneous superfluidity lies at the heart of many intriguing phenomena in
quantum physics. It is believed to play a central role in unconventional
organic or heavy-fermion superconductors, chiral quark matter, and neutron star
glitches. However, so far even the simplest form of inhomogeneous
superfluidity, the Fulde-Ferrell (FF) pairing state with a single
centre-of-mass momentum, is not conclusively observed due to the intrinsic
complexibility of any realistic Fermi systems in nature. Here we theoretically
predict that the controlled setting of ultracold fermionic atoms with synthetic
spin-orbit coupling induced by a two-photon Raman process, demonstrated
recently in cold-atom laboratories, provides a promising route to realize the
long-sought FF superfluidity. At experimentally accessible low temperatures
(i.e., $0.05T_{F}$, where $T_{F}$ is the Fermi temperature), the FF superfluid
state dominates the phase diagram, in sharp contrast to the conventional case
without spin-orbit coupling. We show that the finite centre-of-mass momentum
carried by Cooper pairs is directly measurable via momentum-resolved
radio-frequency spectroscopy. Our work opens the way to direct observation and
characterization of inhomogeneous superfluidity.",1302.0553v2
2013-03-11,X-ray magnetic circular dichroism experiments and theory of transuranium Laves phase compounds,"The actinide cubic Laves compounds NpAl2, NpOs2, NpFe2, and PuFe2 have been
examined by X-ray magnetic circular dichroism (XMCD) at the actinide M4,5
absorption edges and Os L2,3 absorption edges. The XMCD experiments performed
at the M4,5 absorption edges of Np and Pu allow us to determine the
spectroscopic branching ratio, which gives information on the coupling scheme
in these materials. In all materials the intermediate coupling scheme is found
appropriate. Comparison with the SQUID data for NpOs2 and PuFe2 allows a
determination of the individual orbital and spin magnetic moments and the
magnetic dipole contribution mmd. The resulting orbital and spin magnetic
moments are in good agreement with earlier values determined by neutron
diffraction, and the values of mmd are non-negligible, and close to those
predicted for intermediate coupling. There is a comparatively large induced
moment on the Os atom in NpOs2 such that the Os contribution to the total
moment per formula unit is ~30% of the total. The spin and orbital moments at
the Os site are parallel, in contrast to the anti-parallel configuration of Os
impurities in 3d ferromagnetic transition metals. Calculations using the LDA+U
technique are reported. The ab initio computed XMCD spectra show good agreement
with experimental spectra for small values (0-1eV) of the Hubbard U parameter,
which underpins that 5f electrons in these compounds are relatively
delocalized.",1303.2496v1
2014-04-21,Fate of Majorana fermions and Chern numbers after a quantum quench,"The stability of Majorana fermions at the edges of a two-dimensional
topological supercondutor is studied, after quenches to either non-topological
phases or other topological phases. Both instantaneous and slow quenches are
considered. In general, the Majorana modes decay and, in the case of
instantaneous quenches, their revival times scale to infinity as the system
size grows. Considering fast quantum quenches within the same topological
phase, leads, in some cases, to robust edge modes. Quenches to a topological
$Z_2$ phase reveal some robustness of the Majorana fermions. Comparing strong
spin-orbit coupling with weak spin-orbit coupling, it is found that the
Majorana fermions are fairly robust, if the pairing is not aligned with the
spin-orbit Rashba coupling. It is also shown that the Chern number remains
invariant after the quench, until the propagation of the mode along the
transverse direction reaches the middle point, beyond which the Chern number
oscillates between increasing values. In some cases, the time average Chern
number seems to converge to the appropriate value, but often the decay is very
slow. The effect of varying the rate of change in slow quenches is also
analysed. It is found that the defect production is non-universal and does not
follow the Kibble-Zurek scaling with the quench rate, as obtained before for
other systems with topological edge states.",1404.5141v1
2014-10-03,Superfluid density and Berezinskii-Kosterlitz-Thouless transition of a spin-orbit coupled Fulde-Ferrell superfluid,"We theoretically investigate the superfluid density and
Berezinskii-Kosterlitz-Thouless (BKT) transition of a two-dimensional Rashba
spin-orbit coupled atomic Fermi gas with both in-plane and out-of-plane Zeeman
fields. It was recently predicted that, by tuning the two Zeeman fields, the
system may exhibit different exotic Fulde-Ferrell (FF) superfluid phases,
including the gapped FF, gapless FF, gapless topological FF and gapped
topological FF states. Due to the FF paring, we show that the superfluid
density (tensor) of the system becomes anisotropic. When an in-plane Zeeman
field is applied along the \textit{x}-direction, the tensor component along the
\textit{y}-direction $n_{s,yy}$ is generally larger than $n_{s,xx}$ in most
parameter space. At zero temperature, there is always a discontinuity jump in
$n_{s,xx}$ as the system evolves from a gapped FF into a gapless FF state. With
increasing temperature, such a jump is gradually washed out. The critical BKT
temperature has been calculated as functions of the spin-orbit coupling
strength, interatomic interaction strength, in-plane and out-of-plane Zeeman
fields. We predict that the novel FF superfluid phases have a significant
critical BKT temperature, typically at the order of $0.1T_{F}$, where $T_{F}$
is the Fermi degenerate temperature. Therefore, their observation is within the
reach of current experimental techniques in cold-atom laboratories.",1410.0987v1
2015-01-23,Itinerant magnetism in spin-orbit coupled Bose gases,"Phases of matter are conventionally characterized by order parameters
describing the type and degree of order in a system. For example, crystals
consist of spatially ordered arrays of atoms, an order that is lost as the
crystal melts. Like- wise in ferromagnets, the magnetic moments of the
constituent particles align only below the Curie temperature, TC. These two
examples reflect two classes of phase transitions: the melting of a crystal is
a first-order phase transition (the crystalline order vanishes abruptly) and
the onset of magnetism is a second- order phase transition (the magnetization
increases continuously from zero as the temperature falls below TC). Such
magnetism is robust in systems with localized magnetic particles, and yet rare
in model itinerant systems where the particles are free to move about. Here for
the first time, we explore the itinerant magnetic phases present in a spin-1
spin-orbit coupled atomic Bose gas; in this system, itinerant ferromagnetic
order is stabilized by the spin-orbit coupling, vanishing in its absence. We
first located a second-order phase transition that continuously stiffens until,
at a tricritical point, it transforms into a first- order transition (with
observed width as small as h x 4 Hz). We then studied the long-lived metastable
states associated with the first-order transition. These measurements are all
in agreement with theory.",1501.05984v1
2015-07-30,Non-adiabatic dynamics of superfluid spin-orbit coupled degenerate Fermi gas,"We study a problem of non-adiabatic superfluid dynamics of spin-orbit coupled
neutral fermions in two spatial dimensions. We focus on the two cases when the
out-of-equilibrium conditions are initiated either by a sudden change of the
pairing strength or the population imbalance. For the case of zero population
imbalance and within the mean-field approximation, the non-adiabatic evolution
of the pairing amplitude in a collisionless regime can be found exactly by
employing the method of Lax vector construction. Our main finding is that the
presence of the spin-orbit coupling significantly reduces the region in the
parameter space where a steady state with periodically oscillating pairing
amplitude is realized. For the collisionless dynamics initiated by a sudden
disappearance of the population imbalance we obtain an exact expression for the
steady state pairing amplitude. In the general case of quenches to a state with
finite population imbalance we show that there is a region in the steady state
phase diagram where at long times the pairing amplitude dynamics is governed by
the reduced number of the equations of motion in full analogy with exactly
integrable case.",1507.08681v4
2015-11-10,Topological magnetic phase in LaMnO$_3$ (111) bilayer,"Candidates for correlated topological insulators, originated from the
spin-orbit coupling as well as Hubbard type correlation, are expected in the
($111$) bilayer of perovskite-structural transition-metal oxides. Based on the
first-principles calculation and tight-binding model, the electronic structure
of a LaMnO$_3$ ($111$) bilayer sandwiched in LaScO$_3$ barriers has been
investigated. For the ideal undistorted perovskite structure, the Fermi energy
of LaMnO$_3$ ($111$) bilayer just stays at the Dirac point, rendering a
semi-metal (graphene-like) which is also a half-metal (different from graphene
nor previous studied LaNiO$_3$ ($111$) bilayer). The Dirac cone can be opened
by the spin-orbit coupling, giving rise to nontrivial topological bands
corresponding to the (quantized) anomalous Hall effect. For the realistic
orthorhombic distorted lattice, the Dirac point moves with increasing Hubbard
repulsion (or equivalent Jahn-Teller distortion). Finally, a Mott gap opens,
establishing a phase boundary between the Mott insulator and topological
magnetic insulator. Our calculation finds that the gap opened by spin-orbit
coupling is much smaller in the orthorhombic distorted lattice ($\sim$$1.7$
meV) than the undistorted one ($\sim$$11$ meV). Therefore, to suppress the
lattice distortion can be helpful to enhance the robustness of topological
phase in perovskite ($111$) bilayers.",1511.02968v1
2018-05-07,Quantum depletion and superfluid density of a supersolid in Raman spin-orbit coupled Bose gases,"We theoretically investigate a three-dimensional weakly interacting Bose gas
with one-dimensional Raman-type spin-orbit coupling at zero temperature. By
employing an improved ansatz, including high-order harmonics in the stripe
phase, we show that the critical transition from the stripe to the plane-wave
phases is shifted to a relatively larger Rabi frequency compared to the
prediction by previous work [Li $\textit{et al.}$, Phys. Rev. Lett.
$\textbf{108}$, 225301 (2012)] using a first-order stripe ansatz. We also
determine the quantum depletion and superfluid density over a large range of
Rabi frequency in different phases. The depletion exhibits an intriguing
behavior with a discontinuous jump at the transition between the stripe and
plane-wave phases, and a maximum at the transition between the plane-wave and
zero-momentum phases. The superfluid density is derived through a phase-twist
method. In the plane-wave and zero-momentum phases, it is significantly
suppressed along the spin-orbit-coupling direction and vanishes at the
transition, consistent with a recent work [Zhang $\textit{et al.}$, Phys. Rev.
A $\textbf{94}$, 033635 (2016)], while in the stripe phase, it smoothly
decreases with increasing Rabi frequency. Our predictions would be useful for
further theoretical and experimental studies of the exotic supersolid stripe
phase.",1805.02320v2
2015-12-10,Anderson localization of Cooper pairs and Majorana fermions in an ultracold atomic Fermi gas with synthetic spin-orbit coupling,"We theoretically investigate two-particle and many-particle Anderson
localizations of a spin-orbit coupled ultracold atomic Fermi gas trapped in a
quasi-periodic potential and subjected to an out-of-plane Zeeman field. We
solve exactly the two-particle problem in a finite length system by exact
diagonalization and solve approximately the many-particle problem within the
mean-field Bogoliubov-de Gennes approach. At a small Zeeman field, the
localization properties of the system are similar to that of a Fermi gas with
conventional $s$-wave interactions. As the disorder strength increases, the
two-particle binding energy increases and the fermionic superfluidity of many
particles disappears above a threshold. At a large Zeeman field, where the
interatomic interaction behaves effectively like a $p$-wave interaction, the
binding energy decreases with increasing disorder strength and the resulting
topological superfluidity shows a much more robust stability against disorder
than the conventional $s$-wave superfluidity. We also analyze the localization
properties of the emergent Majorana fermions in the topological phase. Our
results could be experimentally examined in future cold-atom experiments, where
the spin-orbit coupling can be induced artificially by using two Raman lasers,
and the quasi-periodic potential can be created by using bichromatic optical
lattices.",1512.03447v1
2017-06-05,Quantum and thermal fluctuations in a Raman spin-orbit coupled Bose gas,"We theoretically study a three-dimensional weakly-interacting Bose gas with
Raman-induced spin-orbit coupling at finite temperature. By employing a
generalized Hartree-Fock-Bogoliubov theory with Popov approximation, we
determine a complete finite-temperature phase diagram of three exotic
condensation phases (i.e., the stripe, plane-wave and zero-momentum phases),
against both quantum and thermal fluctuations. We find that the plane-wave
phase is significantly broadened by thermal fluctuations. The phonon mode and
sound velocity at the transition from the plane-wave phase to the zero-momentum
phase are thoughtfully analyzed. At zero temperature, we find that quantum
fluctuations open an unexpected gap in sound velocity at the phase transition,
in stark contrast to the previous theoretical prediction of a vanishing sound
velocity. At finite temperature, thermal fluctuations continue to significantly
enlarge the gap, and simultaneously shift the critical minimum. For a Bose gas
of $^{87}$Rb atoms at the typical experimental temperature, $T=0.3T_{0}$, where
$T_{0}$ is the critical temperature of an ideal Bose gas without spin-orbit
coupling, our results of gap opening and critical minimum shifting in the sound
velocity, are qualitatively consistent with the recent experimental observation
{[}S.-C. Ji \textit{et al.}, Phys. Rev. Lett. \textbf{114}, 105301 (2015){]}.",1706.01170v1
2017-10-19,Topological Fulde-Ferrell and Larkin-Ovchinnikov states in spin-orbit coupled lattice system,"The spin-orbit coupled lattice system under Zeeman fields provides an ideal
platform to realize exotic pairing states. Notable examples range from the
topological superfluid/superconducting (tSC) state, which is gapped in the bulk
but metallic at the edge, to the Fulde-Ferrell (FF) state (having a
phase-modulated order parameter with a uniform amplitude) and the
Larkin-Ovchinnikov (LO) state (having a spatially varying order parameter
amplitude). Here, we show that the topological FF state with Chern number
($\mathcal{C}=-1$) (tFF$_{1}$) and topological LO state with $\mathcal{C}=2$
(tLO$_{2}$) can be stabilized in Rashba spin-orbit coupled lattice systems in
the presence of both in-plane and out-of-plane Zeeman fields. Besides the
inhomogeneous tSC states, in the presence of a weak in-plane Zeeman field, two
topological BCS phases may emerge with $\mathcal{C}=-1$ (tBCS$_{1}$) far from
half filling and $\mathcal{C}=2$(tBCS$_{2}$) near half filling. We show
intriguing effects such as different spatial profiles of order parameters for
FF and LO states, the topological evolution among inhomogeneous tSC states, and
different non-trivial Chern numbers for the tFF$_{1}$ and tLO$_{1,2}$ states,
which are peculiar to the lattice system. Global phase diagrams for various
topological phases are presented for both half-filling and doped cases. The
edge states as well as local density of states spectra are calculated for tSC
states in a 2D strip.",1710.07169v1
2017-12-25,Gapped topological Fulde-Ferrell-Larkin-Ovchinnikov superfluids with artificial gauge potential and weak interaction,"The topological superfluids with Majorana zero modes have not yet been
realized in ultracold atoms with Rashba spin-orbit coupling. Here we show that
these phases can be realized with an artificial gauge potential, which can be
regarded as a site-dependent rotating Zeeman field. This potential breaks the
inversion symmetry and plays the same role as Rashba spin-orbit coupling. In
the inverted bands, this model can open a proper parameter regime for
topological superfluids. Strikingly, we find that the interaction near the
Fermi surface is dominated by the dispersion scattering in the same band, thus
can realize topological phase with much weaker attractive interaction, as
compared with the model with Rashba spin-orbit coupling. We find a large regime
for the gapped topological Fulde-Ferrell-Larkin-Ovchinnikov superfluids and
unveil the phase diagram with mean-field theory, which should be credible in
the weak interaction regime. In regarding the negligible heating effect in
realizing this potential in alkaline and rare-earth atoms, our model has the
potential to be the first system to realize the long-sought topological FFLO
phase and the associated Majorana zero modes.",1712.09011v1
2020-04-02,Shock Waves in a Superfluid with Higher-Order Dispersion,"Higher-order dispersion can lead to intriguing dynamics that are becoming a
focus of modern hydrodynamics research. Such systems occur naturally, for
example in shallow water waves and nonlinear optics, for which several types of
novel dispersive shocks structures have been identified. Here we introduce
ultracold atoms as a tunable quantum simulations platform for higher-order
systems. Degenerate quantum gases are well controlled model systems for the
experimental study of dispersive hydrodynamics in superfluids and have been
used to investigate phenomena such as vortices, solitons, dispersive shock
waves and quantum turbulence. With the advent of Raman-induced spin-orbit
coupling, the dispersion of a dilute gas Bose-Einstein condensate can be
modified in a flexible way, allowing for detailed investigations of
higher-order dispersion dynamics. Here we present a combined experimental and
theoretical study of shock structures generated in such a system. The breaking
of Galilean invariance by the spin-orbit coupling allows two different types of
shock structures to emerge simultaneously in a single system. Numerical
simulations suggest that the behavior of these shock structures is affected by
interactions with vortices in a manner reminiscent of emerging viscous
hydrodynamics due to an underlying quantum turbulence in the system. This
result suggests that spin-orbit coupling can be used as a powerful means to tun
the effective viscosity in cold-atom experiments serving as quantum simulators
of turbulent hydrodynamics, with applications from condensed matter and optics
to quantum simulations of neutron stars.",2004.00832v1
2012-05-14,Superfluid-Insulator transition of two-species bosons with spin-orbit coupling,"Motivated by recent experiments [Y.J. Lin {\it et al.}, Nature {\bf 471}, 83
(2011)], we study Mott phases and superfluid-insulator (SI) transitions of
two-species ultracold bosonic atoms in a two-dimensional square optical lattice
with nearest neighbor hopping amplitude $t$ in the presence of a spin-orbit
coupling characterized by a tunable strength $\gamma$. Using both
strong-coupling expansion and Gutzwiller mean-field theory, we chart out the
phase diagrams of the bosons in the presence of such spin-orbit interaction. We
compute the momentum distribution of the bosons in the Mott phase near the SI
transition point and show that it displays precursor peaks whose position in
the Brillouin zone can be varied by tuning $\gamma$. Our analysis of the
critical theory of the transition unravels the presence of unconventional
quantum critical points at $t/\gamma=0$ which are accompanied by emergence of
an additional gapless mode in the critical region. We also study the superfluid
phases of the bosons near the SI transition using a Gutzwiller mean-field
theory which reveals the existence of a twisted superfluid phase with an
anisotropic twist angle which depends on $\gamma$. Finally, we compute the
collective modes of the bosons and point out the presence of reentrant SI
transitions as a function of $\gamma$ for non-zero $t$. We propose experiments
to test our theory.",1205.3178v2
2019-04-28,Non-van der Waals honeycomb antiferromagnet SrRu$_2$O$_6$ down to a few layers,"The current family of experimentally realized two-dimensional magnetic
materials consist of 3$d$ transition metals with very weak spin-orbit coupling.
In contrast, we report a new platform in a chemically bonded and layered 4$d$
oxide, with strong electron correlations and competing spin-orbit coupling. We
synthesize ultra-thin sheets of SrRu$_2$O$_6$ using scalable liquid
exfoliation. These exfoliated sheets are characterized by complementary
experimental and theoretical techniques. The thickness of the nano-sheets
varies between three to five monolayers, and within the first-principles
calculations, we show that antiferromagnetism survives in these ultra-thin
layers. Experimental data suggest that exfoliation occurs from the planes
perpendicular to the $c$-axis as the intervening hexagonal Sr-lattice separates
the two-dimensional magnetic honeycomb Ru-layers. The high-resolution
transmission electron microscope images indicate that the average inter-atomic
spacing between the Ru-layers is slightly reduced, which agrees with the
present calculations. The signatures of rotational stacking of the nanosheets
are also observed. Such new two-dimensional platform offers enormous
possibilities to explore emergent properties that appear due to the interplay
between magnetism, strong correlations and spin-orbit coupling. Moreover, these
effects can be further tuned as a function of layer thickness.",1904.12326v2
2015-08-04,Collective modes of a spin-orbit-coupled superfluid Fermi gas in a two-dimensional optical lattice: a comparison between the Gaussian approximation and the Bethe-Salpeter approach,"A functional integral technique and a Legendre transform are used to give a
systematic derivation of the Schwinger-Dyson equations for the generalized
single-particle Green's function and the Bethe-Salpeter equation for the
two-particle Green's function and the associated collective modes of a
population-imbalanced spin-orbit-coupled atomic Fermi gas loaded in a
two-dimensional optical lattice at zero temperature. The collective-mode
excitation energy is calculated within the Gaussian approximation, and from the
Bethe-Salpeter equation in the generalized random phase approximation assuming
the existence of a Sarma superfluid state. It is found that the Gaussian
approximation overestimates the speed of sound of the Goldstone mode. More
interestingly, the Gaussian approximation fails to reproduced the rotonlike
structure of the collective-mode dispersion which appears after the linear part
of the dispersion in the Bethe-Salpeter approach.
  We use the Gaussian approximation and the Bethe-Salpeter approach to
investigate the speed of sound of a balanced spin-orbit-coupled atomic Fermi
gas near the boundary of the topological phase transition driven by an
out-of-plane Zeeman field. It is shown that within both approaches, the minimum
of the speed of sound is located at the topological phase transition boundary,
and this fact can be used to confirm the existence of a topological phase
transition.",1508.00712v2
2017-11-18,Engineering Hybrid Epitaxial InAsSb/Al Nanowire Materials for Stronger Topological Protection,"The combination of strong spin-orbit coupling, large $g$-factors, and the
coupling to a superconductor can be used to create a topologically protected
state in a semiconductor nanowire. Here we report on growth and
characterization of hybrid epitaxial InAsSb/Al nanowires, with varying
composition and crystal structure. We find the strongest spin-orbit interaction
at intermediate compositions in zincblende InAs$_{1-x}$Sb$_{x}$ nanowires,
exceeding that of both InAs and InSb materials, confirming recent theoretical
studies \cite{winkler2016topological}. We show that the epitaxial InAsSb/Al
interfaces allows for a hard induced superconducting gap and 2$e$ transport in
Coulomb charging experiments, similar to experiments on InAs/Al and InSb/Al
materials, and find measurements consistent with topological phase transitions
at low magnetic fields due to large effective $g$-factors. Finally we present a
method to grow pure wurtzite InAsSb nanowires which are predicted to exhibit
even stronger spin-orbit coupling than the zincblende structure.",1711.06864v2
2020-09-22,Relation between transition density and proton inelastic scattering by $^{12}$C target at $E_p =$ 65 and 200 MeV,"We calculate proton elastic and inelastic scatterings with a microscopic
coupled channel (MCC) calculation. The localized diagonal and coupling
potentials including the spin-orbit part are obtained by folding a complex
$G$-matrix effective nucleon-nucleon interaction with a transition density.
This is the first time that the present folding prescription for the spin-orbit
part is applied to the proton inelastic scattering, while for the monopole
transition only. We apply the MCC calculation to the proton elastic and
inelastic (0$^+_2$) scatterings by $^{12}$C target at $E_p$ = 65 and 200 MeV.
The role of diagonal and coupling potentials for the central and spin-orbit
parts is checked. In addition, the relation between the transition density and
the proton inelastic scattering is investigated with the modified wave function
and the modified transition density. Namely, we perform the investigation with
the artificial drastic change rather than fine structural change. The inelastic
cross section is sensitive to the strength and shape of the transition density,
but the inelastic analyzing power is sensitive only to the shape of that.
Finally, we make clear the property of the inelastic analyzing power derived
from the transition density without an ambiguity.",2009.10841v2
2021-03-16,Ferromagnetic helical nodal line and Kane-Mele spin-orbit coupling in kagome metal Fe3Sn2,"The two-dimensional kagome lattice hosts Dirac fermions at its Brillouin zone
corners K and K', analogous to the honeycomb lattice. In the density functional
theory electronic structure of ferromagnetic kagome metal Fe$_3$Sn$_2$, without
spin-orbit coupling we identify two energetically split helical nodal lines
winding along $z$ in the vicinity of K and K' resulting from the trigonal
stacking of the kagome layers. We find that hopping across A-A stacking
introduces a layer splitting in energy while that across A-B stacking controls
the momentum space amplitude of the helical nodal lines. The effect of
spin-orbit coupling is found to resemble that of a Kane-Mele term, where the
nodal lines can either be fully gapped to quasi-two-dimensional massive Dirac
fermions, or remain gapless at discrete Weyl points depending on the
ferromagnetic moment orientation. Aside from numerically establishing
Fe$_3$Sn$_2$ as a model Dirac kagome metal, our results provide insights into
materials design of topological phases from the lattice point of view, where
paradigmatic low dimensional lattice models often find realizations in
crystalline materials with three-dimensional stacking.",2103.08803v1
2021-06-04,Non-Loudon-Fleury Raman scattering in spin-orbit coupled Mott insulators,"We revisit the theory of magnetic Raman scattering in Mott insulators with
strong spin-orbit coupling, with a major focus on Kitaev materials. We show
that Kitaev materials with bond-anisotropic interactions are generally expected
to show both one- and two-magnon responses. It is further shown that, in order
to obtain the correct leading contributions to the Raman vertex operator
$\mc{R}$, one must take into account the precise, photon-assisted microscopic
hopping processes of the electrons and that, in systems with multiple hopping
paths, $\mc{R}$ contains terms beyond those appearing in the traditional
Loudon-Fleury theory. Most saliently, a numerical implementation of the revised
formalism to the case of the three-dimensional hyperhoneycomb Kitaev material
$\beta$-Li$_2$IrO$_3$ reveals that the non-Loudon-Fleury scattering terms
actually dominate the Raman intensity. In addition, they induce a qualitative
modification of the polarization dependence, including, e.g., the emergence of
a sharp one-magnon peak at low energies which is not expected in the
traditional Loudon-Fleury theory. This peak is shown to arise from microscopic
photon-assisted tunneling processes that are of similar type with the ones
leading to the symmetric off-diagonal interaction $\Gamma$ (known to be present
in many Kitaev materials), but take the form of a bond-directional magnetic
dipole term in the Raman vertex. These results are expected to apply across all
Kitaev materials and mark a drastic change of paradigm for the understanding of
Raman scattering in materials with strong spin-orbit coupling and multiple
exchange paths.",2106.02645v2
2021-08-11,Spin-orbital entangled state and realization of Kitaev physics in 3d cobalt compounds: a progress report,"The realization of Kitaev's honeycomb magnetic model in real materials has
become one of the most pursued topics in condensed matter physics and materials
science. If found, it is expected to host exotic quantum phases of matter and
offers potential realizations of fault$-$tolerant quantum computations. Over
the past years, much effort was made on 4d$-$ or 5d$-$ heavy transition metal
compounds because of their intrinsic strong spin$-$orbit coupling. But more
recently, there have been growing shreds of evidence that the Kitaev model
could also be realized in 3d$-$transition metal systems with much weaker
spin$-$orbit coupling. This review intends to serve as a guide to this
fast$-$developing field focusing on systems with d$^7$ transition metal
occupation. It overviews the current theoretical and experimental progress on
realizing the Kitaev model in those systems. We examine the recent experimental
observations of candidate materials with Co$^{2+}$ ions: e.g., CoPS$_3$,
Na$_3$Co$_2$SbO$_6$, and Na$_2$Co$_2$TeO$_6$, followed by a brief review of
theoretical backgrounds. We conclude this article by comparing experimental
observations with density functional theory (DFT) calculations. We stress the
importance of inter$-t_{2g}$ hopping channels and Hund's coupling in the
realization of Kitaev interactions in Co$-$based compounds, which has been
overlooked in previous studies. This review suggests future directions in the
search for Kitaev physics in 3d cobalt compounds and beyond.",2108.05044v3
2021-08-31,Interaction induced topological Bogoliubov excitations in a spin-orbit coupled Bose-Einstein condensate,"We study topologically non-trivial excitations of a weakly interacting,
spin-orbit coupled Bose-Einstein condensate in a two-dimensional square optical
lattice, a system recently realized in experiment [W. Sun et al., Phys. Rev.
Lett. 121, 150401 (2018)]. We focus on situations where the system is not
subjected to a Zeeman field and thus does not exhibit nontrivial
single-particle band topology. Of special interest then is the role of particle
interaction as well as its interplay with the symmetry properties of the system
in producing topologically non-trivial excitations. We find that the
non-interacting system possesses a rich set of symmetries, including the
$\mathcal{PT}$ symmetry, the modified dihedral point group symmetry $\tilde
D_4$ and the nonsymmorphic symmetry. These combined symmetries ensure the
existence of pairs of degenerate Dirac points at the edge of Brillouin zone for
the single-particle energy bands. In the presence of particle interaction and
with sufficient spin-orbit coupling, the atoms condense in a ground state with
net magnetization which spontaneously breaks the $\mathcal{PT}$ and $\tilde
D_4$ symmetry. We demonstrate that this symmetry breaking leads to a gap
opening at the Dirac point for the Bogoliubov spectrum and consequentially
topologically non-trivial excitations. We confirm the non-trivial topology by
calculating the Chern numbers of the lowest excitation bands and show that
gapless edge states form at the interface of systems characterized by different
values of the Chern number.",2108.13784v1
2021-12-30,Non-Fermi liquid behavior in a mixed valent metallic pyrochlore iridate Pb$_2$Ir$_2$O$_{7-δ}$,"Non-Fermi liquid behavior in some fermionic systems have attracted
significant interest in last few decades. Certain pyrochlore iridates with
stronger spin-orbit coupling strength have recently been added to the list.
Here, we provide evidence of such a non-Fermi liquid ground state in another
mixed valent metallic pyrochlore iridate Pb$_2$Ir$_2$O$_{7-\delta}$, through
the combined investigation of electronic, magnetic and thermodynamic properties
as a function of temperature ($T$) and applied magnetic field ($H$).
Resistivity measurement showed a linear temperature dependence down to 15~K
below which it shows $\rho \sim T^{3/2}$ dependence while magnetic
susceptibility diverges as $\chi$(T) $\sim$ $T^{-\alpha}$ ($\alpha < 1$) below
10~K. While a strong negative $\Theta_{CW}$ has been observed from Curie-Weiss
fitting, absence of any long range order down to 80~mK only indicates presence
of strong inherent geometric frustration in the system. Heat capacity data
showed $C_p$ $\sim$ $T\ln(T_0/T)$ + ${\beta}T^3$ dependence below 15~K down to
1.8~K. More importantly spin-orbit coupling strength by x-ray absorption
spectroscopy was found to be weaker in Pb$_2$Ir$_2$O$_{7-\delta}$ compared to
other pyrochlore iridates. In absence of any large moment rare earth magnetic
ion, Pb$_2$Ir$_2$O$_{7-\delta}$ presents a rare example of an irirdate system
showing non-Fermi liquid behaviour due to disordered distribution of Ir$^{4+}$
and Ir$^{5+}$ having markedly different strengths of spin-orbit coupling which
might offer a prescription for achieving new non-Fermi liquid systems.",2112.15070v1
2022-04-28,"Capturing the ground state of uranium dioxide from first principles: crystal distortion, magnetic structure, and phonons","Uranium dioxide (UO$_2$) remains a formidable challenge for first-principles
approaches, due to the complex interplay among spin-orbit coupling, Mott
physics, magnetic ordering, and crystal distortions. Here we use DFT+$U$ to
explore UO$_2$ at zero temperature, incorporating all the aforementioned
phenomena. The technical challenge is to navigate the many metastable
electronic states produced by DFT+$U$, which is acomplished using $f$-orbital
occupation matrix control to search for the ground state. We restrict our
search to the high-symmetry ferromagnetic phase, including spin-orbit coupling,
which produces a previously unreported occupation matrix. This newfound
occupation matrix is then used as an initialization to explore the broken
symmetry phases. We find the oxygen cage distortion of the 3k antiferromagnetic
state to be in excellent agreement with experiments, and both the spin-orbit
coupling and the Hubbard $U$ are critical ingredients. We demonstrate that only
select phonon modes have a strong dependence on the Hubbard $U$, whereas
magnetic ordering has only a small influence overall. We perform measurements
of the phonon dispersion curves using inelastic neutron scattering, and our
calculations show good agreement when using reasonable values of $U$. The
quantitative success of DFT+$U$ warrants exploration of thermal transport and
other observables within this level of theory.",2204.13687v3
2022-06-27,Triple electron-electron-proton excitations and second-order approximations in nuclear-electronic orbital coupled cluster methods,"The accurate description of nuclear quantum effects, such as zero-point
energy, is important for modeling a wide range of chemical and biological
processes. Within the nuclear-electronic orbital (NEO) approach, such effects
are incorporated in a computationally efficient way by treating electrons and
select nuclei, typically protons, quantum mechanically with molecular orbital
techniques. Herein, we implement and test a NEO coupled cluster method that
explicitly includes the triple electron-proton excitations, where two electrons
and one proton are excited simultaneously. Our calculations show that this
NEO-CCSD(eep) method provides highly accurate proton densities and proton
affinities, outperforming any previously studied NEO method. These examples
highlight the importance of the triple electron-electron-proton excitations for
an accurate description of nuclear quantum effects. Additionally, we also
implement and test the second-order approximate coupled cluster with singles
and doubles (NEO-CC2) method, as well as its scaled-opposite-spin (SOS)
versions. The NEO-SOS$'$-CC2 method, which scales the electron-proton
correlation energy as well as the opposite-spin and same-spin components of the
electron-electron correlation energy, achieves nearly the same accuracy as the
NEO-CCSD(eep) method for the properties studied. Because of its low
computational cost, this method will enable a wide range of chemical and
photochemical applications for large molecular systems. This work sets the
stage for a wide range of developments and applications within the NEO
framework.",2206.13616v1
2022-07-08,Electron transport in quantum channels with spin-orbit interaction: Effects of the sign of the Rashba coupling and applications to nanowires,"We investigate the effects of the sign of the Rashba spin-orbit coupling
(RSOC) on electron transmission through a single-channel Nanowire (NW) in the
quantum coherent regime. We show that, while for a finite length NW with
homogeneous RSOC contacted to two electrodes the sign of its RSOC does not
affect electron transport, the situation can be quite different in the presence
of an inhomogeneous RSOC and a magnetic field applied along the NW axis. By
analyzing transport across an interface between two regions of different RSOC
we find that, if the two regions have equal RSOC signs, the transmission within
the magnetic gap energy range is almost perfect, regardless of the ratio of the
spin-orbit energies to the Zeeman energy. In contrast, when the two regions
have opposite RSOC signs and are Rashba-dominated, the transmission gets
suppressed. Furthermore, we discuss the implementation on a realistic NW setup
where two RSOC regions are realized with suitably coupled gates separated by a
finite distance. We find that the low-temperature NW conductance exhibits a
crossover from a short distance behavior that strongly depends on the relative
RSOC sign of the two regions to a large distance oscillatory behavior that is
independent of such relative sign. We are thus able to identify the conditions
where the NW conductance mainly depends on the sign of the RSOC and the ones
where only the RSOC magnitude matters.",2207.03773v2
2023-08-16,Ab-initio Insights on the Fermiology of $d^1$ Transition metals in Honeycomb lattice : Hierarchy of hopping pathways and spin-orbit coupling,"Motivated by the intriguing suggestion of realizing SU(8) Dirac semi-metal
with $J=3/2$ electrons on a honeycomb lattice, we provide a systematic study of
the interplay of various hopping pathways and atomic spin-orbit coupling for
the low energy electrons in candidate d$^1$ transition metal halides MX$_3$
(M=Ti, Zr, Hf; X=F, Cl, Br). By combining first principle calculations and
minimal hopping Hamiltonian, we uncover the role of dominant direct metal-metal
hopping on top of indirect metal-halide-metal hopping. This sets up a hierarchy
of hopping pathways that centrally modify the SU(8) picture for the above
materials. These hopping interactions, along with the spin-orbit coupling, lead
to a plethora of exactly compensated metals instead of the SU(8) Dirac
semi-metal. Remarkably the same can be understood as descendants of a
topological insulator obtained by gapping out the SU(8) Dirac semi-metallic
phase. The resultant compensated metals have varied Fermi surface topology and
are separated by Lifshitz phase transitions. We discuss the implications of the
proximate Lifshitz transition, which may be accessed via strain, in the context
of the relevant materials.",2308.08526v1
2023-08-28,"Surface Hopping, Electron Translation Factors, Electron Rotation Factors, Momentum Conservation, and Size Consistency","For a system without spin-orbit coupling, the (i) nuclear plus electronic
linear momentum and (ii) nuclear plus orbital electronic angular momentum are
good quantum numbers. Thus, when a molecular system undergoes a nonadiabatic
transition, there should be no change in the total linear or angular momentum.
Now, the standard surface hopping algorithm ignores the electronic momentum and
indirectly equates the momentum of the nuclear degrees of freedom to the total
momentum. However, even with this simplification, the algorithm still does not
conserve either the nuclear linear or the nuclear angular momenta. Here, we
show that one way to address these failures is to dress the derivative
couplings (i.e. the hopping directions) in two ways: (i) we disallow changes in
the nuclear linear momentum by working in a translating basis (which is well
known and leads to electron translation factors [ETFs]); and (ii) we disallow
changes in the nuclear angular momentum by working in a basis that rotates
around the center of mass (which is not well-known and leads to a novel,
rotationally removable component of the derivative coupling that we will call
electron rotation factors [ERFs] below, cf. Eq. 96). The present findings
should be helpful in the short term as far as interpreting surface hopping
calculations for singlet systems (without spin) and then developing new surface
hopping algorithm in the long term for systems where one cannot ignore the
electronic orbital and/or spin angular momentum.",2308.14621v1
2020-07-08,Strong spin-orbit interaction and $g$-factor renormalization of hole spins in Ge/Si nanowire quantum dots,"The spin-orbit interaction lies at the heart of quantum computation with spin
qubits, research on topologically non-trivial states, and various applications
in spintronics. Hole spins in Ge/Si core/shell nanowires experience a
spin-orbit interaction that has been predicted to be both strong and
electrically tunable, making them a particularly promising platform for
research in these fields. We experimentally determine the strength of
spin-orbit interaction of hole spins confined to a double quantum dot in a
Ge/Si nanowire by measuring spin-mixing transitions inside a regime of
spin-blockaded transport. We find a remarkably short spin-orbit length of
$\sim$65 nm, comparable to the quantum dot length and the interdot distance. We
additionally observe a large orbital effect of the applied magnetic field on
the hole states, resulting in a large magnetic field dependence of the
spin-mixing transition energies. Strikingly, together with these orbital
effects, the strong spin-orbit interaction causes a significant enhancement of
the $g$-factor with magnetic field.The large spin-orbit interaction strength
demonstrated is consistent with the predicted direct Rashba spin-orbit
interaction in this material system and is expected to enable ultrafast Rabi
oscillations of spin qubits and efficient qubit-qubit interactions, as well as
provide a platform suitable for studying Majorana zero modes.",2007.04308v1
2022-04-04,Inverse Orbital Torque via Spin-Orbital Entangled States,"While current-induced torque by orbital current has been experimentally found
in various structures, evidence for its reciprocity has been missing so far.
Here, we report experimental evidence of strong inverse orbital torque in
YIG/Pt/CuOx (YIG = Y3Fe5O12) mediated by spin-orbital entangled electronic
states in Pt. By injecting spin current from YIG to Pt by the spin pumping via
ferromagnetic resonance and by the spin Seebeck effect, we find a pronounced
inverse spin Hall effect-like signal. While a part of the signal is explained
as due to the inverse spin-orbital Hall effect in Pt, we also find substantial
increase of the signal in YIG/Pt/CuOx structures compared to the signal in
YIG/Pt. We attribute this to the inverse orbital Rashba-Edelstein effect at
Pt/CuOx interface mediated by the spin-orbital entangled states in Pt. Our work
paves the way toward understanding of spin-orbital entangled physics in
nonequilibrium and provides a way for electrical detection of the orbital
current in orbitronic device applications.",2204.01825v2
2009-07-23,Spin Currents in Semiconductor Nanostructures: A Nonequilibrium Green-Function Approach,"This chapter of ""The Oxford Handbook of Nanoscience and Technology: Frontiers
and Advances"" reviews nonequilibrium Green function (NEGF) approach to modeling
spin current generation, transport, and detection in semiconductor
nanostructures containing different types of spin-orbit (SO) couplings. Its
tutorial style--with examples drawn from the field of the spin Hall effects
(SHEs) and with treatment of the Rashba, Dresselhaus and extrinsic SO
couplings--offers practical recipes to compute total spin and charge currents
flowing out of the device, as well as the nonequilibrium local spin densities
and spin fluxes within the multiterminal nanostructure. These quantities, which
are obtained from the knowledge of spin-resolved NEGFs that can describe both
ballistic and diffusive transport regimes while handling phase-coherent effects
or dephasing mechanisms relevant at room temperature, can be employed to
understand recent experiments on all-electrical detection of mesoscopic and
quantum SHE in complicated low-dimensional nanostructures, as well as to model
a multitude of ""second generation"" spintronic devices exploiting coherent spin
dynamics. The chapter also provides extensive coverage of relevant technical
and computational details, such as: (i) the construction of retarded and lesser
Green functions for SO-coupled nanostructures attached to many electrodes; (ii)
computation of self-energies introduced by different types of electrodes
attached to the central region; and (iii) accelerated algorithms for NEGF
evaluation that make possible spin transport modeling in devices of the size
comparable to the spin precession length (typically few hundreds of nanometers)
that sets the scale where mesoscopic SHE effect in ballistic SO-coupled
nanostructures is expected to reach its optimal magnitude.",0907.4122v1
2011-07-23,Dephasing and Hyperfine Interaction in Carbon Nanotubes Double Quantum Dots: The Clean Limit,"We consider theoretically ${}^{13}$C-hyperfine interaction induced dephasing
in carbon nanotubes double quantum dots with curvature induced spin-orbit
coupling. For two electrons initially occupying a single dot, we calculate the
average return probability after separation into the two dots, which have
random nuclear-spin configurations. We focus on the long time saturation value
of the return probability, $P_\infty$. Because of the valley degree of freedom,
the analysis is more complex than in, for example, GaAs quantum dots, which
have two distinct $P_\infty$ values depending on the magnetic field. Here the
prepared state and the measured state is non-unique because two electrons in
the same dot are allowed in six different states. Moreover, for one electron in
each dot sixteen states exist and therefore are available for being mixed by
the hyperfine field. The return probability experiment is found to be strongly
dependent on the prepared state, on the external magnetic field---both Zeeman
and orbital effects - and on the spin-orbit splitting. The lowest saturation
value, being $P_\infty$=1/3, occurs at zero magnetic field for nanotubes with
spin-orbit coupling and the initial state being the groundstate, this situation
is equivalent to double dots without the valley degree of freedom. In total, we
report nine dynamically different situations that give $P_\infty$=1/3, 3/8,
2/5, 1/2 and for valley anti-symmetric prepared states in an axial magnetic
field, $P_\infty$=1. When the groundstate is prepared the ratio between the
spin-orbit splitting and the Zeeman energy due to a perpendicular magnetic
field can tune the effective hyperfine field continuously from being three
dimensional to two dimensional giving saturation values from $P_\infty$=1/3 to
3/8.",1107.4710v1
2018-08-29,Hundness versus Mottness in a three-band Hubbard-Hund model: On the origin of strong correlations in Hund metals,"Hund metals are multi-orbital systems with moderate Coulomb interaction, $U$,
and sizeable Hund's rule coupling, $J<U$, that aligns the spins in different
orbitals. They show strong correlation effects, like very low Fermi-liquid
coherence scales and intriguing incoherent transport regimes, resulting in bad
metallic behavior. But to what extent are these strong correlations governed by
Mottness, i.e. the blocking of charge fluctuations close to a Mott insulator
transition (MIT) induced by $U$, or by Hundness, a new route towards strong
correlations induced by $J$? To answer this question, we study the full phase
diagram of a degenerate three-band Hubbard-Hund model on a Bethe lattice at
zero temperature using single-site DMFT and the numerical renormalization group
as efficient real-frequency multi-band impurity solver. Hund metal behavior
occurs in this minimal model for a filling close to $n_d=2$, moderate $U$ and
sizeable $J$, the ""Hund-metal regime"", with strong correlations manifest by a
low quasiparticle weight, $Z$. We show that ""spin-orbital separation"" (SOS) is
a generic $J$-induced feature in the whole metallic regime of the phase diagram
for $1<n_d<3$ and sizeable $J$: orbital screening occurs at much higher
energies than spin screening, below which Fermi-liquid behavior sets in. The
low $Z$ can then be explained in terms of the $J$-reduced Fermi-liquid scale.
We further show that, in the Hund-metal regime, far from any MIT, Hundness --
the localization of large spins -- is the key player to induce strong
correlations. There, physical properties are governed by a broad incoherent
energy regime of SOS with intriguing Hund metal physics: large, almost
unscreened spins are coupled to screened orbital degrees of freedom.",1808.09936v3
2021-09-28,Impact of Spin-Orbit Coupling on Quantum Transport in Magnetic Tunnel Junction with an anti-ferromagnetic Capping Layer,"Using first-principles calculations, we explore the role of an
anti-ferromagnetic heavy-metal, L1$_0$-IrMn, as a capping layer in a
perpendicular magnetic tunnel junction (\emph{p}-MTJ). A comparative study is
conducted by employing conventional non-magnetic heavy-metals (Ta, W or Mo)
capping layers along with an anti-ferromagnetic IrMn in a symmetric-MTJ
X/FeCo/MgO/FeCo/X, where X=Ta, W, Mo or IrMn. Firstly, the calculations without
including spin-orbit coupling (SOC) are presented where the highest TMR is
achieved in IrMn-IrMn MTJ compared to that of Ta-Ta, W-W and Mo-Mo MTJs. The
origin of this large TMR is attributed to, both, the large spin-polarization
due to reduced lattice-mismatch and the non-identical signatures of both the
anti-parallel conduction-channels caused by the anti-ferromagnetic ordering of
IrMn that reflects the spins at IrMn/FeCo interface. Moreover, when SOC is
switched-on, the increase of TMR is observed in all the MTJs with a
particularly giant enhancement in IrMn-IrMn MTJ. This SOC-induced increase in
TMR is ascribed to the mixed contribution of $\Delta_1$ and $\Delta_5$ states
and the additional increase in the band levels of the out-of-plane orbitals,
\emph{p}$_z$, \emph{d}$_{z}^2$ and \emph{d}$_{xz}$ due to the lifting of
degeneracy. Furthermore, it was also observed that the lattice-mismatch-induced
strain might create an orbital reconstruction within the capping layer,
probably, due to the crystallographic deformation and, in turn, in the adjacent
FeCo-electrode. This microscopic mechanism also plays an additional decisive
role in enhancing the TMR. Finally, our results indicate that IrMn can offer
giant TMR in future spin-orbit toque (SOT) based MRAM devices with a
straightforward design strategy.",2109.13740v2
2013-11-13,Quantum criticality in an asymmetric three-leg spin tube: A strong rung-coupling perspective,"We study quantum phase transitions in the asymmetric variation of the
three-leg Heisenberg tube for half-odd-integer spin, with a modulation of one
of the rung exchange couplings $J'_\perp$ while the other two are kept constant
$J_\perp$. We focus on the strong rung-coupling regime $J_\perp \gg
J_\parallel$, where $J_\parallel$ is the leg coupling, and analyze the
effective spin-orbital model with a transverse crystal field in detail.
Applying the Abelian bosonization to the effective model, we find that the
system is in the dimer phase for the general half-odd-integer-spin cases
without the rung modulation; the phase transition between the dimer and
Tomonaga-Luttinger-liquid phases induced by the rung modulation is of the
SU(2)-symmetric Berezinskii-Kosterlitz-Thouless type. Moreover, we perform a
level spectroscopy analysis for the effective model for spin-1/2 using exact
diagonalization, to determine the precise transition point $| J'_\perp -
J_\perp| /J_\parallel \sim 0.283$ in the strong rung-coupling limit. The
presence of the dimer phase in a small but finite region is also confirmed by a
density-matrix renormalization group calculation on the original spin-tube
model.",1311.3041v2
2017-06-17,Electron-phonon coupling in the spin-split valence band of single layer WS$_2$,"The absence of inversion symmetry leads to a strong spin-orbit splitting of
the upper valence band of semiconducting single layer transition metal
dichalchogenides such as MoS$_2$ or WS$_2$. This permits a direct comparison of
the electron-phonon coupling strength in states that only differ by their spin.
Here, the electron-phonon coupling in the valence band maximum of single-layer
WS$_2$ is studied by first principles calculations and angle-resolved
photoemission. The coupling strength is found to be drastically different for
the two spin-split branches, with calculated values of $\lambda_K=$0.0021 and
0.40 for the upper and lower spin-split valence band of the free-standing
layer, respectively. This difference is somewhat reduced when including
scattering processes involving the Au(111) substrate present in the experiment
and the experimental results confirm the strongly branch-dependent coupling
strength.",1706.05484v1
2009-05-19,Dynamical spin-spin correlation functions in the Kondo model out of equilibrium,"We calculate the dynamical spin-spin correlation functions of a Kondo dot
coupled to two noninteracting leads held at different chemical potentials. To
this end we generalize a recently developed real-time renormalization group
method in frequency space (RTRG-FS) to allow the calculation of dynamical
correlation functions of arbitrary dot operators in systems describing spin
and/or orbital fluctuations. The resulting two-loop RG equations are
analytically solved in the weak-coupling regime. This implies that the method
can be applied provided either the voltage $V$ through the dot or the external
magnetic field $h_0$ are sufficiently large, $\max\{V,h_0\}\gg T_K$, where the
Kondo temperature $T_K$ is the scale where the system enters the
strong-coupling regime. Explicitly, we calculate the longitudinal and
transverse spin-spin correlation and response functions as well as the
resulting fluctuation-dissipation ratios. The correlation functions in
real-frequency space can be calculated in Matsubara space without the need of
any analytical continuation. We obtain analytic results for the line-shape, the
small- and large-frequency limits and several other features like the height
and width of the peak in the transverse susceptibility at
$\Omega\approx\tilde{h}$, where $\tilde{h}$ denotes the reduced magnetic field.
Furthermore, we discuss how the developed method can be generalized to
calculate dynamical correlation functions of other operators involving
reservoir degrees of freedom as well.",0905.3095v2
2020-01-23,Bulk quantum Hall effect of spin-valley-coupled Dirac fermions in a polar antiferromagnet BaMnSb$_2$,"Unconventional features of relativistic Dirac/Weyl quasi-particles in
topological materials are most evidently manifested in the 2D quantum Hall
effect (QHE), whose variety is further enriched by their spin and/or valley
polarization. Although its extension to three dimensions has been long-sought
and inspired theoretical proposals, material candidates have been lacking. Here
we have discovered valley-contrasting spin-polarized Dirac fermions in a
multilayer form in bulk antiferromagnet BaMnSb$_2$, where the out-of-plane
Zeeman-type spin splitting is induced by the in-plane inversion symmetry
breaking and spin-orbit coupling (SOC) in the distorted Sb square net.
Furthermore, we have observed well-defined quantized Hall plateaus together
with vanishing interlayer conductivity at low temperatures as a hallmark of the
half-integer QHE in a bulk form. The Hall conductance of each layer is found to
be nearly quantized to $2(N+1/2)e^2/h$ with $N$ being the Landau index, which
is consistent with two spin-polarized Dirac valleys protected by the strong
spin-valley coupling.",2001.08683v1
2018-06-18,The family of topological Hall effects for electrons in skyrmion crystals,"Hall effects of electrons can be produced by an external magnetic field, spin
orbit-coupling or a topologically non-trivial spin texture. The topological
Hall effect (THE) - caused by the latter - is commonly observed in magnetic
skyrmion crystals. Here, we show analogies of the THE to the conventional Hall
effect (HE), the anomalous Hall effect (AHE), and the spin Hall effect (SHE).
In the limit of strong coupling between conduction electron spins and the local
magnetic texture the THE can be described by means of a fictitious, 'emergent'
magnetic field. In this sense the THE can be mapped onto the HE caused by an
external magnetic field. Due to complete alignment of electron spin and
magnetic texture, the transverse charge conductivity is linked to a transverse
spin conductivity. They are disconnected for weak coupling of electron spin and
magnetic texture; the THE is then related to the AHE. The topological
equivalent to the SHE can be found in antiferromagnetic skyrmion crystals. We
substantiate our claims by calculations of the edge states for a finite sample.
These states reveal in which situation the topological analogue to a quantized
HE, quantized AHE, and quantized SHE can be found.",1806.06958v1
2018-07-30,Observation of Quantum Interference and Coherent Control in a Photochemical Reaction,"Coherent control of reactants remains a longstanding challenge in quantum
chemistry. In particular, we have studied laser-induced molecular formation
(photoassociation) in a Raman-dressed spin-orbit-coupled 87Rb Bose-Einstein
condensate, whose spin quantum state is a superposition of multiple bare spin
components. In contrast to the notably different photoassociation-induced
fractional atom losses observed for the bare spin components of a statistical
mixture, a superposition state with a comparable spin composition displays the
same fractional loss on every spin component. We interpret this as the
superposition state itself undergoing photoassociation. For superposition
states induced by a large Raman coupling and zero Raman detuning, we observe a
nearly complete suppression of the photoassociation rate. This suppression is
consistent with a model based upon quantum destructive interference between two
photoassociation pathways for colliding atoms with different spin combinations.
This model also explains the measured dependence of the photoassociation rate
on the Raman detuning at a moderate Raman coupling. Our work thus suggests that
preparing atoms in quantum superpositions may represent a powerful new
technique to coherently control photochemical reactions.",1807.11608v3
2021-11-01,Magnon-phonon coupling from a crossing symmetric screened interaction,"The magnon-phonon coupling has received growing attention in recent years due
to its central role in spin caloritronics and the emerging field of acoustic
spintronics. At resonance, this magnetoelastic interaction drives the formation
of magnon polarons, which underpin exotic phenomena such as magnonic heat
currents and phononic spin, but has with a few recent exceptions only been
investigated using mesoscopic spin-lattice models. Motivated to integrate the
magnon-phonon coupling into first-principle many-body electronic structure
theory, we set up to derive the non-relativistic exchange-contribution, which
is more subtle than the spin-orbit contribution, using Schwinger's method of
functional derivatives. To avoid having to solve the famous Hedin-Baym
equations self-consistently, the phonons are treated as a perturbation to the
electronic structure. A formalism is developed around the idea of imposing
crossing symmetry on the interaction, in order to treat charge and spin on
equal footing. By an iterative scheme, we find that the spin-flip component of
the ${\mathit collective}$ four-point interaction, $\mathcal{V}$, which is used
to calculate the magnon spectrum, contains a first-order ""screened T matrix""
part and an arguably more important second-order part, which in the limit of
local spins describes the same processes of phonon emission and absorption as
obtained from phenomenological magnetoelastic models. Here, the ""order"" refers
to the ${\mathit screened}$ ${\mathit collective}$ four-point interaction,
$\mathcal{W}$ - the crossing-symmetric analog of Hedin's $W$.
Proof-of-principle model calculations are performed at varying temperatures for
the isotropic magnon spectrum in three dimensions in the presence of a flat
optical phonon branch.",2111.00908v1
2010-11-15,Orbital fluctuations and orbital order below the Jahn-Teller transition in Sr3Cr2O8,"We report on the magnetic and phononic excitation spectrum of Sr3Cr2O8
determined by THz and infrared (IR) spectroscopy, and electron spin resonance
(ESR) measurements across the Jahn-Teller transition, which is detected by
specific-heat measurements to occur at T_{JT} = 285 K. We identify the
singlet-triplet excitations in the dimerized ground state and estimate the
exchange couplings in the system. Moreover, ESR absorptions were observed up to
T* = 120 K with a linewidth proportional to exp{-Delta/k_{B}T} and Delta/k_{B}
= 388 K indicating a phonon-mediated spin relaxation via the excited orbital
state of the Cr $e$ doublet in the orbitally ordered state. In contrast to the
expected drastic change of the IR active phonons upon entering the low-symmetry
Jahn-Teller distorted phase below T_{JT}, we find an extended regime
T*<T<T_{JT} where the IR active phonons change only gradually with decreasing
temperature. This regime is associated with strong fluctuations in the orbital
and lattice degrees of freedom in agreement with the loss of the ESR signal
above T*. Using the measured magnetic and phononic excitation spectrum we model
the orbital contribution to the specific heat and find the persistence of
strong fluctuations far below T_{JT}.",1011.3314v3
2019-03-12,Atomic-Scale Magnetic Toroidal Dipole under Odd-Parity Hybridization,"Magnetic toroidal dipole (MTD) is one of a fundamental constituent to induce
magneto-electric effects in the absence of both spatial inversion and
time-reversal symmetries. We report on a microscopic investigation of the
atomic-scale MTD in solids by taking into account the orbital degree of freedom
with a different parity. We construct an effective two-orbital $d$-$f$
tight-binding model on a polar tetragonal system for describing the
atomic-scale MTD, which are obtained by incorporating the atomic spin-orbit
coupling and odd-parity hybridization. The effective model exhibits two types
of the MTDs: in-plane $x, y$ components activated through spontaneous
ferromagnetic ordering or external magnetic field and an out-of-plane $z$
component by a spontaneous odd-parity hybridization without spin moments. We
show that the intra-orbital (inter-orbital) Coulomb interaction in
multi-orbital systems plays an important role in stabilizing the in-plane
(out-of-plane) MTD orderings. We also examine the magneto-electric effect under
each MTD ordering by calculating a linear response tensor. We show that the
odd-parity hybridization enhances the magneto-electric effect for the in-plane
MTDs, while it suppresses that for the out-of-plane MTD.",1903.04708v1
2021-08-10,The orbital effect on the anomalous magnetism and evolution in La$_x$Y$_{1-x}$VO$_3$($0\le x \le 0.2$) single crystals,"The orbital effect on the anomalous magnetism and evolution of low La-doping
single crystals, La$_x$Y$_{1-x}$VO$_{3}$ (x = 0, 0.1, and 0.2), has been
investigated by applying the X-ray diffraction, specific heat, magnetization
and Raman scattering techniques. The larger nearest-neighbor (NN) exchange
interaction along c-axis stabilizes the fluctuant G-type orbital ordering
(G-OO) which favors the exotic C-type antiferromagnetic order (C-AF). It is
found that the NN exchange interaction in ab plane is anisotropy relating to
the in plane magnetic anisotropy, which becomes smaller in high La-doped
sample. Most interestingly, with increasing the La$^{3+}$ content the orbital
fluctuation and hybridization are decreased which stabilizes the C-OO phase and
destabilizes the G-OO phase. Meanwhile, the diamagnetism in the exotic C-AF
phase becomes weak and the possible mechanism relates to the change of the
competition between the single-ion magnetic anisotropy and the
Dzyaloshinsky-Moriya (DM) interaction with increasing x. Finally, the strong
spin-orbital coupling has been observed at temperature just above T$_N$ in
La$_{0.2}$Y$_{0.8}$VO$_{3}$ and a short range spin-orbital correlation is
suggested.",2108.04648v1
2022-06-10,"J = 0 nonmagnetic insulating state in K$_2$Os$X_6$ (X = F, Cl and Br)","In $4d/5d$ transition-metal systems, many interesting physical properties
arise from the interplay of bandwidth, electronic correlations, and spin-orbit
interactions. Here, using {\it ab initio} density functional theory, we
systematically study the double-perovskite-like system K$_2$Os$X_6$ (X = F, Cl,
and Br) with a $5d^4$ electronic configuration. Our main result is that the $J
= 0$ nonmagnetic insulating state develops in this system, induced by strong
spin-orbital coupling. Specifically, the well-separated Os$X_6$ octahedra lead
to the cubic crystal-field limit and result in dramatically decreasing hoppings
in nearest neighbor Os-Os sites. In this case, the three degenerate $t_{2g}$
orbitals are reconstructed into two ``effective'' $j_{\rm eff}$ ($j_{\rm eff} =
1/2$ and $j_{\rm eff} = 3/2$ states) states separated by the strong SOC,
opening a gap with four electrons occupying the $j_{\rm eff} = 3/2$ orbitals.
Furthermore, the hybridization between the Os $5d$ orbitals and the $X$ ($X$ =
F, Cl, and Br) $p$ orbitals increases from F to Br, leading the electrons in
K$_2$OsF$_6$ to be more localized than in K$_2$OsCl$_6$ and K$_2$OsBr$_6$,
resulting in a smaller bandwidth for K$_2$OsF$_6$ than in the Cl- or Br- cases.
Our results provide guidance to experimentalists and theorists working on this
interesting family of osmium halides.",2206.05223v2
2006-03-27,Coupling Between the Spin and Gravitational Field and the Equation of Motion of the Spin,"In general relativity, the equation of motion of the spin is given by the
equation of parallel transport, which is a result of the space-time geometry.
Any result of the space-time geometry can not be directly applied to gauge
theory of gravity. In gauge theory of gravity, based on the viewpoint of the
coupling between the spin and gravitational field, an equation of motion of the
spin is deduced. In the post Newtonian approximation, it is proved that this
equation gives out the same result as that of the equation of parallel
transport. So, in the post Newtonian approximation, gauge theory of gravity
gives out the same prediction on the precession of orbiting gyroscope as that
of general relativity.",0603104v1
2003-12-18,Frustrated quantum-spin system on a triangle coupled with $e_g$ lattice vibrations - Correspondence to Longuet-Higgins et al.'s Jahn-Teller model -,"We investigate the quantum three spin model $({\bf S_1},{\bf S_2},{\bf S_3})$
of spin$=1/2$ on a triangle, in which spins are coupled with
lattice-vibrational modes through the exchange interaction depending on
distances between spin sites. The present model corresponds to the dynamic
Jahn-Teller system $E_g\otimes e_g$ proposed by Longuet-Higgins {\it et al.},
Proc.R.Soc.A.{\bf 244},1(1958). This correspondence is revealed by using the
transformation to Nakamura-Bishop's bases proposed in Phys.Rev.Lett.{\bf
54},861(1985). Furthermore, we elucidate the relationship between the behavior
of a chiral order parameter ${\hat \chi}={\bf S_1\cdot(S_2\times S_3)}$ and
that of the electronic orbital angular momentum ${\hat \ell_z}$ in $E_g\otimes
e_g$ vibronic model: The regular oscillatory behavior of the expectation value
$<{\hat \ell_z}>$ for vibronic structures with increasing energy can also be
found in that of $<{\hat \chi}>$. The increase of the additional
anharmonicity(chaoticity) is found to yield a rapidly decaying irregular
oscillation of $<{\hat \chi}>$.",0312039v1
2007-09-10,Towards a dephasing diode: asymmetric and geometric dephasing,"We study the effect of a noisy environment on spin and charge transport in
ballistic quantum wires with spin-orbit coupling (Rashba coupling). We find
that the wire then acts as a ``dephasing diode'', inducing very different
dephasing of the spins of right and left movers. We also show how Berry phase
(geometric phase) in a curved wire can induce such asymmetric dephasing, in
addition to purely geometric dephasing. We propose ways to measure these
effects through spin detectors, spin-echo techniques, and Aharanov-Bohm
interferometry.",0709.1381v2
2009-05-29,Spin-spiral states in undoped manganites,"The experimental observation of multiferroic behavior in perovskite
manganites with a spiral spin structure demands to clarify the origin of these
magnetic states and their relation to ferroelectricity. We show that
spin-spiral phases with diagonal wavevector and also the E-type phase exist for
intermediate values of the Hund's rule and the Jahn-Teller coupling in the
orbitally ordered and insulating state of the standard two-band model
Hamiltonian for manganites. Our results support the spin-current mechanism for
ferroelectricity and present an alternative view to earlier conclusions where
frustrating superexchange couplings were crucial to obtain spin-spiral states.",0905.4811v2
2013-06-15,Circuit QED with Hole-Spin Qubits in Ge/Si Nanowire Quantum Dots,"We propose a setup for universal and electrically controlled quantum
information processing with hole spins in Ge/Si core/shell nanowire quantum
dots (NW QDs). Single-qubit gates can be driven through electric-dipole-induced
spin resonance, with spin-flip times shorter than 100 ps. Long-distance
qubit-qubit coupling can be mediated by the cavity electric field of a
superconducting transmission line resonator, where we show that operation times
below 20 ns seem feasible for the entangling square-root-of-iSWAP gate. The
absence of Dresselhaus spin-orbit interaction (SOI) and the presence of an
unusually strong Rashba-type SOI enable precise control over the transverse
qubit coupling via an externally applied, perpendicular electric field. The
latter serves as an on-off switch for quantum gates and also provides control
over the g factor, so single- and two-qubit gates can be operated
independently. Remarkably, we find that idle qubits are insensitive to charge
noise and phonons, and we discuss strategies for enhancing noise-limited gate
fidelities.",1306.3596v2
2014-02-05,First-Principles Study of the Honeycomb-Lattice Iridates Na2IrO3 in the Presence of Strong Spin-Orbit Interaction and Electron Correlations,"An effective low-energy Hamiltonian of itinerant electrons for iridium oxide
Na2IrO3 is derived by an ab initio downfolding scheme. The model is then
reduced to an effective spin model on a honeycomb lattice by the strong
coupling expansion. Here we show that the ab initio model contains spin-spin
anisotropic exchange terms in addition to the extensively studied Kitaev and
Heisenberg exchange interactions, and allows to describe the experimentally
observed zigzag magnetic order, interpreted as the state stabilized by the
antiferromagnetic coupling of the ferromagnetic chains. We clarify possible
routes to realize quantum spin liquids from existing Na2IrO3.",1402.1030v2
2014-07-16,Tunnel Magnetoresistance scan of a pristine three-dimensional topological insulator,"Though the Fermi surface of surface states of a 3D topological insulator (TI)
has zero magnetization, an arbitrary segment of the full Fermi surface has a
unique magnetic moment consistent with the type of spin-momentum locking in
hand. We propose a three-terminal set up, which directly couples to the
magnetization of a chosen segment of a Fermi surface hence leading to a finite
tunnel magnetoresistance (TMR) response of the nonmagnetic TI surface states,
when coupled to spin polarized STM probe. This multiterminal TMR not only
provides a unique signature of spin-momentum locking for a pristine TI but also
provides a direct measure of momentum resolved out of plane polarization of
hexagonally warped Fermi surfaces relevant for $Bi_2Te_3$, which could be as
comprehensive as spin-resolved ARPES. Implication of this unconventional TMR is
also discussed in the broader context of 2D spin-orbit (SO) materials.",1407.4407v2
2014-08-02,Crossover from Room-temperature Double-channel Ballistic Transport to Single-channel Ballistic Transport in Zigzag Graphene Nanoribbons,"Very recently, it was demonstrated explicitly that a zigzag graphene
nanoribbon (GNR) exhibits a crossover of conductance from G0 to G0/2 with
increasing the length (G0 = 2e2/h is the quantum of conductance) even at
room-temperature [Baringhaus, et al. Nature 506, 349 (2014)]. Such a result is
puzzling as none of previous theories seem to match the experimental
observations. Here, we propose a model to explain the crossover from
double-channel to single-channel ballistic transport in zigzag GNR. The sp3
distortion of carbon atoms at the GNR edges induces a large spin-orbit coupling
on the edges atoms, which enhances spin-flip scattering of edge states of the
zigzag GNR. With sufficient spin-flip scattering, the wave-function of edge
states becomes a superposition of the spin-up and spin-down components. Then
the coupling of the two edges becomes important. This removes the edge degree
of freedom in the zigzag GNR and results in the evolution of the conductance
from G0 to G0/2 with increasing the length.",1408.0327v3
2015-05-01,Local Spectroscopic Characterization of Spin and Layer Polarization in WSe$_2$,"We report scanning tunneling microscopy (STM) and spectroscopy (STS)
measurements of monolayer and bilayer WSe$_2$. We measure a band gap of 2.21
$\pm$ 0.08 eV in monolayer WSe$_2$, which is much larger than the energy of the
photoluminescence peak indicating a large excitonic binding energy. We
additionally observe significant electronic scattering arising from
atomic-scale defects. Using Fourier transform STS (FT-STS), we map the energy
versus momentum dispersion relations for monolayer and bilayer WSe$_2$.
Further, by tracking allowed and forbidden scattering channels as a function of
energy we infer the spin texture of both the conduction and valence bands. We
observe a large spin-splitting of the valence band due to strong spin-orbit
coupling, and additionally observe spin-valley-layer coupling in the conduction
band of bilayer WSe$_2$.",1505.00245v2
2015-07-07,Solutions of Mathisson-Papapetrou equations for highly relativistic spinning particles,"Different types of essentially nongeodesic motions of highly relativistic
spinning particles in Schwarzschild's and Kerr's background which follows from
the Mathisson-Papapetrou (MP) equations are considered. It is shown that
dependently on the correlation of signs of the spin and the particle's orbital
velocity the spin-gravity coupling acts as a significant repulsive or
attractive force. Numerical estimates for electrons, protons, and neutrinos in
the gravitational field of black holes are presented. The correspondence
between the general relativistic Dirac equation and MP equations is discussed.
It is stressed that for the highly relativistic motions the adequate
supplementary condition for the MP equations is the Mathisson-Pirani condition.
In the following it is important to study the possible role of the highly
relativistic spin-gravity coupling in astrophysics, cosmology, and high energy
physics.",1507.01696v1
2015-09-15,Dynamical current-induced ferromagnetic and antiferromagnetic resonances,"We demonstrate that ferromagnetic and antiferromagnetic excitations can be
triggered by the dynamical spin accumulations induced by the bulk and surface
contributions of the spin Hall effect. Due to the spin-orbit interaction, a
time-dependent spin density is generated by an oscillatory electric field
applied parallel to the atomic planes of Fe/W(110) multilayers. For symmetric
trilayers of Fe/W/Fe in which the Fe layers are ferromagnetically coupled, we
demonstrate that only the collective out-of-phase precession mode is excited,
while the uniform (in-phase) mode remains silent. When they are
antiferromagnetically coupled, the oscillatory electric field sets the Fe
magnetizations into elliptical precession motions with opposite angular
velocities. The manipulation of different collective spin-wave dynamical modes
through the engineering of the multilayers and their thicknesses may be used to
develop ultrafast spintronics devices. Our work provides a general framework
that probes the realistic responses of materials in the time or frequency
domain.",1509.04599v2
2014-06-26,High-Energy Damping by Particle-Hole Excitations in the Spin-Wave Spectrum of Iron-Based Superconductors,"Using a degenerate double-exchange model, we investigate the spin excitation
spectra of iron pnictides. The model consists of local spin moments on each Fe
site, as well as itinerant electrons from the degenerate $d_{xz}$ and $d_{yz}$
orbitals. The local moments interact with each other through antiferromagnetic
$J_{1}$-$J_{2}$ Heisenberg interactions, and they couple to the itinerant
electrons through a ferromagnetic Hund coupling. We employ the fermionic spinon
representation for the local moments and perform a generalized random-phase
approximation calculation on both spinons and itinerant electrons. We find that
in the $\left(\pi,0\right)$ magnetically-ordered state, the spin-wave
excitation at $\left(\pi,\pi\right)$ is pushed to a higher energy due to the
presence of itinerant electrons, which is consistent with a previous study
using the Holstein-Primakoff transformation. In the paramagnetic state, the
particle-hole continuum keeps the collective spin excitation near
$\left(\pi,\pi\right)$ at a higher energy even without any $C_{4}$ symmetry
breaking. The implications for recent high temperature neutron scattering
measurements will be discussed.",1406.6737v3
2016-08-07,An electrically driven spin qubit based on valley mixing,"The electrical control of single spin qubits based on semiconductor quantum
dots is of great interest for scalable quantum computing since electric fields
provide an alternative mechanism for qubit control compared with magnetic
fields and can also be easier to produce. Here we outline the mechanism for a
drastic enhancement in the electrically-driven spin rotation frequency for
silicon quantum dot qubits in the presence of a step at a hetero-interface. The
enhancement is due to the strong coupling between the ground and excited states
which occurs when the electron wave-function overcomes the potential barrier
induced by the interface step. We theoretically calculate single qubit gate
times of 170ns for a quantum dot confined at a silicon/silicon-dioxide
interface. The engineering of such steps could be used to achieve fast
electrical rotation and entanglement of spin qubits despite the weak spin-orbit
coupling in silicon.",1608.02189v2
2017-12-09,Photon-induced tunability of the thermospin current in a Rashba ring,"The goal of this work is to show how the thermospin polarization current in a
quantum ring changes in the presence of Rashba spin-orbit coupling and a
quantized single photon mode of a cavity the ring is placed in. Employing the
reduced density operator and a general master equation formalism, we find that
both the Rashba interaction and the photon field can significantly modulate the
spin polarization and the thermospin polarization current. Tuning the Rashba
coupling constant, degenerate energy levels are formed corresponding to the
Aharonov-Casher destructive phase interference in the quantum ring system. Our
analysis indicates that the maximum spin polarization can be observed at the
points of degenerate energy levels due to spin accumulation in the system
without the photon field. The thermospin current is thus suppressed. In the
presence of the cavity, the photon field leads to an additional kinetic
momentum of the electron. As a result the spin polarization can be enhanced by
the photon field.",1712.03386v1
2018-09-07,Spin-Conserving Resonant Tunneling in Twist-Controlled WSe2-hBN-WSe2 Heterostructures,"We investigate interlayer tunneling in heterostructures consisting of two
tungsten diselenide (WSe2) monolayers with controlled rotational alignment, and
separated by hexagonal boron nitride. In samples where the two WSe2 monolayers
are rotationally aligned we observe resonant tunneling, manifested by a large
conductance and negative differential resistance in the vicinity of zero
interlayer bias, which stem from energy- and momentum-conserving tunneling.
Because the spin-orbit coupling leads to coupled spin-valley degrees of
freedom, the twist between the two WSe2 monolayers allows us to probe the
conservation of spin-valley degree of freedom in tunneling. In heterostructures
where the two WSe2 monolayers have a 180{\deg} relative twist, such that the
Brillouin zone of one layer is aligned with the time-reversed Brillouin zone of
the opposite layer, the resonant tunneling between the layers is suppressed.
These findings provide evidence that in addition to momentum, the spin-valley
degree of freedom is also conserved in vertical transport.",1809.02639v1
2018-09-17,Chiral and helical $p$-wave superconductivity in doped bilayer BiH,"We investigate the superconductivity (SC) driven by correlation effects in
electron-doped bilayer BiH near a type-II van Hove singularity (vHS). By
functional renormalization group, we find triplet $p$-wave pairing prevails in
the interaction parameter space, except for spin density wave (SDW) closer to
the vHS or when the interaction is too strong. Because of the large atomic
spin-orbital coupling (SOC), the $p$-wave pairing occurs between equal-spin
electrons, and is chiral and two-fold degenerate. The chiral state supports
in-gap edge states, even though the low energy bands in the SC state are
topologically trivial. The absence of mirror symmetry allows Rashba SOC that
couples unequal spins, but we find its effect is of very high order, and can
only drive the chiral $p$-wave into helical $p$-wave deep in the SC state.
Interestingly, there is a six-fold degeneracy in the helical states, reflected
by the relative phase angle $\theta=n\pi/3$ (for integer $n$) between the spin
components of the helical pairing function. The phase angle is shown to be
stable in the vortex state.",1809.06103v1
2019-07-07,Spin-valley system in a gated MoS$_2$-monolayer quantum dot,"The aim of presented research is to design a nanodevice based on a
gate-defined quantum dot within a MoS$_2$ monolayer in which we confine a
single electron. By applying control voltages to the device gates we modulate
the confinement potential and force intervalley transitions. The present Rashba
spin-orbit coupling additionally allows for spin operations. Moreover, both
effects enable the spin-valley SWAP. The device structure is modeled
realistically, taking into account feasible dot-forming potential and electric
field that controls the Rasha coupling. Therefore, by performing reliable
numerical simulations, we show how by electrically controlling the state of the
electron in the device, we can obtain single- and two-qubit (thus universal)
gates in a spin-valley two-qubit system. Through simulations we investigate
possibility of implementation of two qubits \textit{locally}, based on single
electron, with an intriguing feature that two-qubit gates are easier to realize
than single ones.",1907.03299v2
2019-04-18,Phase coherent transport in bilayer and trilayer MoS2,"Bilayer MoS2 is a centrosymmetric semiconductor with degenerate spin states
in the six valleys at the corners of the Brillouin zone. It has been proposed
that breaking of this inversion symmetry by an out-of-plane electric field
breaks this degeneracy, allowing for spin and valley lifetimes to be
manipulated electrically in bilayer MoS2 with an electric field. In this work,
we report phase-coherent transport properties of double-gated mono-, bi-, and
tri-layer MoS2. We observe a similar crossover from weak localization to weak
anti-localization, from which we extract the spin relaxation time as a function
of both electric field and temperature. We find that the spin relaxation time
is inversely proportional to momentum relaxation time, indicating that
D'yakonov-Perel mechanism is dominant in all devices despite its
centrosymmetry. Further, we found no evidence of electric-field induced changes
in spin-orbit coupling strength. This suggests that the interlayer coupling is
sufficiently weak and that electron-doped dichalcogenide multilayers behave
electrically as decoupled monolayers.",1904.08597v1
2020-05-06,Phase Shift in Skyrmion Crystals,"The skyrmion crystal is a periodic array of a swirling topological spin
texture. Since it is regarded as an interference pattern by multiple helical
spin density waves, the texture changes with the relative phases among the
constituent waves. Although the phase degree of freedom is relevant to not only
magnetism but also transport properties, its effect has not been elucidated
thus far. We here theoretically show that a phase shift can occur in the
skyrmion crystals to stabilize tetra-axial vortex crystals with staggered
scalar spin chirality. This leads to spontaneous breaking of the lattice
symmetry, which results in nonreciprocal transport phenomena even without the
relativistic spin-orbit coupling. We show that such a phase shift is driven by
long-range chirality interactions or thermal fluctuations in spin-charge
coupled systems.",2005.03168v1
2021-04-28,Magnetically induced polarization in centrosymmetric bonds,"We reveal the microscopic origin of electric polarization $\vec{P}$ induced
by noncollinear magnetic order. We show that in Mott insulators, such $\vec{P}$
is given by all possible combinations of position operators $\hat{\vec{r}}_{ij}
= (\vec{r}_{ij}^{\, 0},\vec{\boldsymbol{r}}_{ij}^{\phantom{0}})$ and transfer
integrals $\hat{t}_{ij} = (t_{ij}^{0},\boldsymbol{t}_{ij}^{\phantom{0}})$ in
the bonds, where $\vec{r}_{ij}^{\, 0}$ and $t_{ij}^{0}$ are spin-independent
contributions in the basis of Kramers doublet states, while
$\vec{\boldsymbol{r}}_{ij}^{\phantom{0}}$ and
$\boldsymbol{t}_{ij}^{\phantom{0}}$ stem solely from the spin-orbit
interaction. Among them, the combination $t_{ij}^{0}
\vec{\boldsymbol{r}}_{ij}^{\phantom{0}}$, which couples to the spin current,
remains finite in the centrosymmetric bonds, thus yielding finite $\vec{P}$ in
the case of noncollinear arrangement of spins. The form of the magnetoelectric
coupling, which is controlled by $\vec{\boldsymbol{r}}_{ij}^{\phantom{0}}$,
appears to be rich and is not limited to the phenomenological law $\vec{P} \sim
\boldsymbol{\epsilon}_{ij} \times [\boldsymbol{e}_{i} \times
\boldsymbol{e}_{j}]$ with $\boldsymbol{\epsilon}_{ij}$ being the bond vector
connecting the spins $\boldsymbol{e}_{i}$ and $\boldsymbol{e}_{j}$. Using
density-functional theory, we illustrate how the proposed mechanism work in the
spiral magnets CuCl$_2$, CuBr$_2$, CuO, and $\alpha$-Li$_2$IrO$_3$, providing
consistent explanation to available experimental data.",2104.13711v2
2016-03-13,The vicinity of hyper-honeycomb $β$-Li2IrO3 to a three-dimensional Kitaev spin liquid state,"Due to the combination of a substantial spin-orbit coupling and correlation
effects, iridium oxides hold a prominent place in the search for novel quantum
states of matter, including, e.g., Kitaev spin liquids and topological Weyl
states. We establish the promise of the very recently synthesized
hyper-honeycomb iridate $\beta$-Li2IrO3 in this regard. A detailed theoretical
analysis reveals the presence of large ferromagnetic first-neighbor Kitaev
interactions, while a second-neighbor antiferromagnetic Heisenberg exchange
drives the ground state from ferro to zigzag order via a three-dimensional
Kitaev spin liquid and an incommensurate phase. Experiment puts the system in
the latter regime but the Kitaev spin liquid is very close and reachable by a
slight modification of the ratio between the second- and first-neighbor
couplings, for instance via strain.",1603.04003v1
2016-10-21,Unconventional superconductivity from magnetism in transition metal dichalcogenide,"We investigate proximity-induced superconductivity in monolayers of
transition metal dichalcogenides (TMDs) in the presence of an externally
generated exchange field. A variety of superconducting order parameters is
found to emerge from the interplay of magnetism and superconductivity, covering
the entire spectrum of possibilities to be symmetric or antisymmetric with
respect to the valley and spin degrees of freedom, as well as even or odd in
frequency. More specifically, when a conventional \emph{s}-wave superconductor
with singlet Copper pairs is tunnel-coupled to the TMD layer, both spin-singlet
and triplet pairings between electrons from the same and opposite valleys arise
due to the combined effects of intrinsic spin-orbit coupling and a
magnetic-substrate-induced exchange field. As a key finding, we reveal the
existence of an exotic even-frequency triplet pairing between equal-spin
electrons from different valleys, which arises whenever the spin orientations
in the two valleys are noncollinear. All types of superconducting order turn
out to be highly tunable via straightforward manipulation of the external
exchange field.",1610.06730v2
2019-06-18,Indirect Chiral Magnetic Exchange through Dzyaloshinskii-Moriya--Enhanced RKKY Interactions in Manganese Oxide Chains on Ir(100),"Ruderman-Kittel-Kasuya-Yosida interaction even if their wave functions lack
direct overlap. Theory predicts that spin-orbit scattering leads to a
Dzyaloshinskii-Moriya type enhancement of this indirect exchange interaction,
giving rise to chiral exchange terms. Here we present a combined spin-polarized
scanning tunneling microscopy, angle-resolved photoemission, and density
functional theory study of MnO$_2$ chains on Ir(100). Whereas we find
antiferromagnetic Mn--Mn coupling along the chain, the inter-chain coupling
across the non-magnetic Ir substrate turns out to be chiral with a
$120^{\circ}$ rotation between adjacent MnO$_2$ chains. Calculations reveal
that the Dzyaloshinskii-Moriya interaction results in spin spirals with a
periodicity in agreement with experiment. Our findings confirm the existence of
indirect chiral magnetic exchange, potentially giving rise to exotic phenomena,
such as chiral spin-liquid states in spin ice systems or the emergence of new
quasiparticles.",1906.07703v1
2019-06-27,Signatures of quantum mechanical Zeeman effect in classical transport due to topological properties of two-dimensional spin-3/2 holes,"The Zeeman interaction is a quantum mechanical effect that underpins
spin-based quantum devices such as spin qubits. Typically, identification of
the Zeeman interaction needs a large out-of-plane magnetic field coupled with
ultralow temperatures, which limits the practicality of spin-based devices.
However, in two-dimensional (2D) semiconductor holes, the strong spin-orbit
interaction causes the Zeeman interaction to couple the spin, the magnetic
field, and the momentum, and has terms with different winding numbers. In this
work, we demonstrate a physical mechanism by which the Zeeman terms can be
detected in classical transport. The effect we predict is very strong, and
tunable by means of both the density and the in-plane magnetic field. It is a
direct signature of the topological properties of the 2D hole system, and a
manifestation in classical transport of an effect stemming from relativistic
quantum mechanics. We discuss experimental observation and implications for
quantum technologies.",1906.11439v2
2020-09-02,Giant inverse Faraday effect in Dirac semimetals,"We have studied helicity dependent photocurrent (HDP) in Bi-based Dirac
semimetal thin films. HDP increases with film thickness before it saturates,
changes its sign when the majority carrier type is changed from electrons to
holes and takes a sharp peak when the Fermi level lies near the charge
neutrality point. These results suggest that irradiation of circularly
polarized light to Dirac semimetals induces an effective magnetic field that
aligns the carrier spin along the light spin angular momentum and generates a
spin current along the film normal. The effective magnetic field is estimated
to be orders of magnitude larger than that caused by the inverse Faraday effect
(IFE) in typical transition metals. We consider the small effective mass and
the large $g$-factor, characteristics of Dirac semimetals with strong spin
orbit coupling, are responsible for the giant IFE, opening pathways to develop
systems with strong light-spin coupling.",2009.01388v1
2022-05-05,Anomalous zero-field splitting for hole spin qubits in Si and Ge quantum dots,"An anomalous energy splitting of spin triplet states at zero magnetic field
has recently been measured in germanium quantum dots. This zero-field splitting
could crucially alter the coupling between tunnel-coupled quantum dots, the
basic building blocks of state-of-the-art spin-based quantum processors, with
profound implications for semiconducting quantum computers. We develop an
analytical model linking the zero-field splitting to spin-orbit interactions
that are cubic in momentum. Such interactions naturally emerge in hole
nanostructures, where they can also be tuned by external electric fields, and
we find them to be particularly large in silicon and germanium, resulting in a
significant zero-field splitting in the $\mu$eV range. We confirm our
analytical theory by numerical simulations of different quantum dots, also
including other possible sources of zero-field splitting. Our findings are
applicable to a broad range of current architectures encoding spin qubits and
provide a deeper understanding of these materials, paving the way towards the
next generation of semiconducting quantum processors.",2205.02582v1
2022-07-06,Continuous transition between Ising magnetic order and a chiral spin liquid,"The competition between fractionalized spin-liquid states and magnetically
ordered phases is an important paradigm in frustrated magnetism. Spin-orbit
coupled Mott insulators with Ising-like magnetic anisotropies, such as Kitaev
materials, are a particularly rich playground to explore this competition. In
this work, we use effective field theory methods to show that a direct quantum
phase transition can occur in two-dimensional (2D) Ising spin systems between a
topologically ordered chiral spin liquid and a phase with magnetic long-range
order. Such a transition can be protected by lattice symmetries and is
described by a theory of massless Majorana fields coupled to non-Abelian
$SO(N)$ gauge fields with a Chern-Simons term. We further show that Euclidean
Majorana zero modes bound to $\mathbb{Z}_2$ monopole-instantons in the emergent
non-Abelian gauge field are key to understanding spontaneous symmetry breaking
in the ordered phase.",2207.02701v3
2023-07-04,Probing general relativistic spin-orbit coupling with gravitational waves from hierarchical triple systems,"Wave packets propagating in inhomogeneous media experience a coupling between
internal and external degrees of freedom and, as a consequence, follow
spin-dependent trajectories. These are known as spin Hall effects, which are
well known in optics and condensed matter physics. Similarly, the gravitational
spin Hall effect is expected to affect the propagation of gravitational waves
on curved spacetimes. In this general-relativistic setup, the curvature of
spacetime acts as impurities in a semiconductor or inhomogeneities in an
optical medium, leading to a frequency- and polarization-dependent propagation
of wave packets. In this letter, we study this effect for strong-field lensed
gravitational waves generated in hierarchical triple black hole systems in
which a stellar-mass binary merges near a more massive black hole. We calculate
how the gravitational spin Hall effect modifies the gravitational waveforms and
show its potential for experimental observation. If detected, these effects
will bear profound implications for astrophysics and tests of general
relativity.",2307.01903v1
2007-08-15,Spin relaxation in $n$-type GaAs quantum wells with transient spin grating,"By solving the kinetic spin Bloch equations, we study the time evolution of
the transient spin grating, whose spin polarization varies periodically in real
space, confined in (001) GaAs quantum wells. With this study we can investigate
the properties of both the spin transport and the spin relaxation at the same
time. The Fourier component of the spin signal decays double exponentially with
two decay rates $1/\tau_+$ and $1/\tau_-$. In high temperature regime, the
average of these two rates varies with the grating wave-vector $q$
quadratically, i.e., $(1/\tau_++1/\tau_-)/2=D_sq^2+1/\tilde{\tau}_s$, with
$D_s$ and $\tilde{\tau}_s$ representing the spin diffusion coefficient and the
average of the out-of-plane and the in-plane spin relaxation times
respectively. $\tau_{\pm}$ calculated from our theory are in good agreement
with the experimental data by Weber {\em et al.} [Phys. Rev. Lett. {\bf 98},
076604 (2007)]. By comparing $D_s$ with and without the electron-electron
Coulomb scattering, we calculate the contribution of Coulomb drag to the spin
diffusion coefficient. With the transient spin grating result, we further
reveal the relations among different characteristic parameters such as spin
diffusion coefficient $D_s$, spin relaxation time $\tau_s$, and spin injection
length $L_s$. We show that in the presence of the Dresselhaus and/or Rashba
spin-orbit coupling, the widely used relation $L_s=\sqrt{D_s\tau_s}$ is
generally inaccurate and can even be very wrong in some special cases. We
present an accurate way to extract the steady-state transport characteristic
parameters from the transient spin grating signals.",0708.1975v4
2020-07-07,Proposed ordering of textured spin singlets in a bulk infinite layer nickelate,"The infinite-layer structure nickelate Ba$_2$NiO$_2$(AgSe)$_2$ (BNOAS) with
$d^8$ Ni ions and a peculiar susceptibility $\chi(T)$ is studied with
correlated density functional methods. The overriding feature of the
calculations is violation of Hund's rule coupled with complete but
unconventional spin-orbital polarization, leading to an unexpected low spin
$^1B_1$, ""off-diagonal singlet"" (ODS) textured by an internal orbital structure
of compensating $d_{x^2-y^2}^{\uparrow}$ and $d_{z^2}^{\downarrow}$ spins. This
unconventional configuration has lower energy than conventional high-spin or
low-spin alternatives. An electronic transition is obtained at a critical Ni-O
separation $d_c^{Ni-O}=$2.03 \AA, above which Ni becomes magnetic in square
planar NiO$_2$ compounds. We propose scenarios for the signature of magnetic
reconstruction in $\chi(T)$ at $T_{m}$=130 K without any Curie-Weiss background
(no moment) that invoke ordering of Ni $d^8$ moieties that are largely this
generalized Kondo singlet. The underlying physics of this system is modeled by
a Kondo sieve model (2D Kondo necklace) of a ""Kondo"" $d_{z^2}$ spin on each
site, coupled to a $d_{x^2-y^2}$ spin that is itself strongly coupled to
neighboring like-spins within the layer. The observed magnetic order places
BNOAS below the quantum critical point of the Kondo sieve model, providing a
realization of the previously unreported long-range ordered near-singlet weak
antiferromagnetic phase. We propose electron doping experiments that would
drive the system toward a $d^{9-\delta}$ configuration and possible
superconductivity with similarity to the recently reported Ba$_2$CuO$_{3.2}$
that superconducts at 73 K.",2007.03185v3
2022-12-15,Non-trivial band topology and orbital-selective electronic nematicity in a new titanium-based kagome superconductor,"Electronic nematicity that spontaneously breaks rotational symmetry has been
shown as a generic phenomenon in correlated quantum systems including
high-temperature superconductors and the AV3Sb5 (A = K, Rb, Cs) family with a
kagome network. Identifying the driving force has been a central challenge for
understanding nematicity. In iron-based superconductors, the problem is
complicated because the spin, orbital and lattice degrees of freedom are
intimately coupled. In vanadium-based kagome superconductors AV3Sb5, the
electronic nematicity exhibits an intriguing entanglement with the charge
density wave order (CDW), making understanding its origin difficult. Recently,
a new family of titanium-based kagome superconductors ATi3Bi5 has been
synthesized. In sharp contrast to its vanadium-based counterpart, the
electronic nematicity occurs in the absence of CDW. ATi3Bi5 provides a new
window to explore the mechanism of electronic nematicity and its interplay with
the orbital degree of freedom. Here, we combine polarization-dependent
angle-resolved photoemission spectroscopy with density functional theory to
directly reveal the band topology and orbital characters of the multi-orbital
RbTi3Bi5. The promising coexistence of flat bands, type-II Dirac nodal line and
nontrivial Z2 topological states is identified in RbTi3Bi5. Remarkably, our
study clearly unveils the orbital character change along the G-M and G-K
directions, implying a strong intrinsic inter-orbital coupling in the Ti-based
kagome metals, reminiscent of iron-based superconductors. Furthermore,
doping-dependent measurements directly uncover the orbital-selective features
in the kagome bands, which can be well explained by the d-p hybridization. The
suggested d-p hybridization, in collaboration with the inter-orbital coupling,
could account for the electronic nematicity in ATi3Bi5.",2212.07958v1
2001-12-19,Influence of orbital pair breaking on paramagnetically limited states in clean superconductors,"Paramagnetic pair breaking is believed to be of increasing importance in many
layered superconducting materials such as cuprates and organic compounds.
Recently, strong evidence for a phase transition to the
Fulde-Ferrell-Larkin-Ovchinnikov(FFLO) state has been obtained for the first
time. We present a new theory of competing spin and orbital pair breaking in
clean superconducting films or layers. As a general result, we find that the
influence of orbital pair breaking on the paramagnetically limited phase
boundary is rather strong, and its neglect seldom justified. This is
particularly true for the FFLO state which can be destroyed by a very small
orbital contribution. We discuss the situation in YBa_2Cu_3O_7 which has two
coupled conducting Cu-O layers per unit cell. As a consequence, an intrinsic
orbital pair breaking component might exist even for applied field exactly
parallel to the layers.",0112353v1
2012-08-28,Orbital-selective Mott Phase in Multiorbital Models for Alkaline Iron Selenides K(1-x)Fe(2-y)Se2,"We study a multiorbital model for the alkaline iron selenides
K(1-x)Fe(2-y)Se2 using a slave-spin method. With or without ordered vacancies,
we identify a metal-to-Mott-insulator transition at the commensurate filling of
six 3d electrons per iron ion. For Hund's couplings beyond a threshold value,
this occurs via an intermediate orbital-selective Mott phase, in which the 3d
xy orbital is Mott localized while the other 3d orbitals remain itinerant. This
phase is still stabilized over a range of carrier dopings. Our results lead to
an overall phase diagram for the alkaline iron selenides, which provides a
unified framework to understand the interplay between the strength of vacancy
order and carrier doping. In this phase diagram, the orbital-selective Mott
phase provides a natural link between the superconducting K(1-x)Fe(2-y)Se2 and
its Mott-insulating parent compound.",1208.5547v1
2015-07-09,Dirac fermions in Fe ultra-thin film,"We show the existence of massive Dirac fermions in electronic band structures
of a few Fe atomic layers with perpendicular magnetization. Based on a tight
binding model fitted to ab-initio band structure, we observe four distinct
massive Dirac fermions near the Fermi level, which result from atomic
spin-orbit coupling of Fe and a band inversion between Fe $4s$-$3d_{x^2-y^2}$
hybrid orbital band and $3d_{xy}$ orbital band. These lead to a valence band
with finite Chern integer (+2) and chiral edge modes near the Fermi level. When
the chemical potential is set inside the Dirac gap by carrier doping, the Hall
conductivity exhibits a plateau-like structure with quantized value
$2\frac{e^2}{h}$, and orbital magnetization shows a prominent increase, latter
of which is mostly due to chiral orbital motion of electrons along the edge
modes. We discuss the stability of the Dirac fermions in Fe(001) monolayer on
MgO(001) substrate and Fe(001) bilayer case.",1507.02382v2
2015-11-03,Converting normal insulators into topological insulators via tuning orbital levels,"Tuning the spin-orbit coupling strength via foreign element doping and/or
modifying bonding strength via strain engineering are the major routes to
convert normal insulators to topological insulators. We here propose an
alternative strategy to realize topological phase transition by tuning the
orbital level. Following this strategy, our first-principles calculations
demonstrate that a topological phase transition in some cubic perovskite-type
compounds CsGeBr$_3$ and CsSnBr$_3$ could be facilitated by carbon
substitutional doping. Such unique topological phase transition predominantly
results from the lower orbital energy of the carbon dopant, which can pull down
the conduction bands and even induce band inversion. Beyond conventional
approaches, our finding of tuning the orbital level may greatly expand the
range of topologically nontrivial materials.",1511.00832v1
2019-07-22,Electrically Tunable Superconductivity Through Surface Orbital Polarization,"We investigate the physical mechanisms for achieving an electrical control of
conventional spin-singlet superconductivity in thin films by focusing on the
role of surface orbital polarization. Assuming a multi-orbital description of
the metallic state, due to screening effects the electric field acts by
modifying the strength of the surface potential and, in turn, yields
non-trivial orbital-Rashba couplings. The resulting orbital polarization at the
surface and in its close proximity is shown to have a dramatic impact on
superconductivity. We demonstrate that, by varying the strength of the electric
field, the superconducting phase can be either suppressed, i.e. turned into
normal metal, or undergo a $0-\pi$ transition with the $\pi$ phase being marked
by non-trivial sign change of the superconducting order parameter between
different bands. These findings unveil a rich scenario to design
heterostructures with superconducting orbitronics effects.",1907.09227v3
2019-09-06,Possible 'symmetry-imposed' near-nodal two-dimensional p-wave pairing in Sr$_2$RuO$_4$,"One key feature of the multi-orbital superconducting Sr$_2$RuO$_4$ is the
presence of nodal or near-nodal quasiparticle excitations revealed in a wide
variety of experiments. Typically, a nodal gap structure in a two-dimensional
model would be inconsistent with the chiral or helical p-wave interpretations.
However, we demonstrate that true gap nodes may emerge along certain
high-symmetry directions on the quasi-one-dimensional Fermi surfaces, if the
multi-orbital chiral or helical p-wave pairings acquire peculiar forms wherein
the $d_{xz}$ and $d_{yz}$ orbitals develop $k_y$- and $k_x$-like pairings,
respectively. Spin-orbit coupling $\eta$ induces a near-nodal gap of order
$\eta^2/W^2 \Delta_0$, where $\Delta_0$ is the gap amplitude and $W$ roughly
the bandwidth. Provided the aforementioned pairing is predominant, the
near-nodal gap structure is robust upon the inclusion of other multi-orbital
pairings that share the same symmetries. In light of the recent experimental
progresses, our proposal suggests that two-dimensional p-wave pairings may
still be viable candidate ground states for Sr$_2$RuO$_4$. A near-nodal helical
p-wave order, for example, would also be consistent with the substantial drop
in the NMR Knight shift under an in-plane magnetic field.",1909.03141v2
2012-05-02,Na2IrO3 as a molecular orbital crystal,"Contrary to previous studies that classify Na2IrO3 as a realization of the
Heisenberg-Kitaev model with dominant spin-orbit coupling, we show that this
system represents a highly unusual case in which the electronic structure is
dominated by the formation of quasi-molecular orbitals (QMOs), with substantial
quenching of the orbital moments. The QMOs consist of six atomic orbitals on an
Ir hexagon, but each Ir atom belongs to three different QMOs. The concept of
such QMOs in solids invokes very different physics compared to the models
considered previously. Employing density functional theory calculations and
model considerations we find that both the insulating behavior and the
experimentally observed zigzag antiferromagnetism in Na2IrO3 naturally follow
from the QMO model.",1205.0434v3
2019-06-12,Orbital Selectivity and Magnetic Ordering in Fe intercalated Dirac Semimetal Bi$_2$Se$_3$,"In this paper we investigate the intercalation effects of Iron (Fe) in the
van der Waals gap of Bi$_2$Se$_3$ on the magnetic and transport properties
using first-principles band structure estimations combined using dynamical
mean-field theory. Inclusion of electronic correlations and spin-orbit coupling
effects are found to result in the emergence of ferromagnetic properties in an
intercalated Bi$_2$Se$_3$. Further the Dirac cone in the band structure of
Bismuth Selenide is modified via Fe intercalation at moderate densities.
Accompanied by novel structural effects, the onset of an orbital selective
metal insulator transition in the Fe 3$d$ orbitals brings about a magnetic
phase transition in the Fe intercalated Bi$_2$Se$_3$. Further we have explored
the dependency of the inter-orbital electron-electron correlations on the
magnetic ordering and the effects of intercalation in establishing new physical
properties.",1906.05249v2
2023-10-27,Theory of $d + id$ Second-Order Topological Superconductors,"Topological superconductors are a class of unconventional superconducting
materials featuring sub-gap zero-energy Majorana bound modes that hold promise
as a building block for topological quantum computing. In this work, we study
the realization of second-order topology that defines anomalous gapless
boundary modes in a two-orbital superconductor with spin-orbital couplings. We
reveal a time-reversal symmetry-breaking second-order topological
superconducting phase with $d+id$-wave orbital-dependent paring without the
need for the external magnetic field. Remarkably, this orbital-active $d$-wave
paring gives rise to anomalous zero-energy Majorana corner modes, which is in
contrast to conventional chiral $d$-wave pairing, accommodating one-dimensional
Majorana edge modes. Our work not only reveals a unique mechanism of
time-reversal symmetry breaking second-order topological superconductors but
also bridges the gap between second-order topology and orbital-dependent
pairings.",2310.17992v1
2012-07-26,Effect of pressure on the electronic and magnetic properties of CdV$_2$O$_4$: Density functional theory studies,"We investigate the effect of pressure on the electronic and magnetic states
of CdV$_2$O$_4$ by using ab initio electronic structure calculations. The
Coulomb correlation and spin-orbit coupling play important role in deciding the
structural, electronic and magnetic properties of the compound. The total
magnetic moment of V ion is found to be $\sim$1.3 $\mu_B$ and making an angle
of $\sim$9.5 degree with the z-axis. In the tetragonal phase, the ground state
is the orbital ordered state where V $d_{xz}$ and $d_{yz}$ obtitals are mainly
occupied at the neighbouring sites. This work predicts the electronic phase
transition from orbital-ordered-insulator to orbital-ordered-metal to
orbital-disordered-metal with increasing pressure. The pressure induced
broadening of lower and upper Hubbard bands gives rise to metal-insulator
transition above 35 GPa. The simple mean-field theory used in the present work
is able to describe the pressure dependent variation of the antiferromagnetic
transition temperature suggesting the applicability of the method in the study
of the magnetic behaviour of similar geometrically frustrated systems.",1207.6168v1
2012-12-07,Monte Carlo study of an unconventional superconducting phase in Ir-oxide J_{eff}=1/2 Mott insulators induced by carrier doping,"Based on a microscopic theoretical study, we show that novel
superconductivity is induced by carrier doping in layered perovskite Ir oxides
where a strong spin-orbit coupling causes an effective total angular momentum
J_{eff}=1/2 Mott insulator. Using a variational Monte Carlo method, we find an
unconventional superconducting state in the ground state phase diagram of a
t_{2g} three-orbital Hubbard model on the square lattice. This superconducting
state is characterized by a d_{x^2-y^2}-wave ""pseudospin singlet"" formed by the
J_{eff}=1/2 Kramers doublet, which thus contains inter-orbital as well as both
singlet and triplet components of t_{2g} electrons. The superconducting state
is found stable only by electron doping, but not by hole doping, for the case
of carrier doped Sr_2IrO_4. We also study an effective single-orbital Hubbard
model to discuss the similarities to high-T_c cuprate superconductors and the
multi-orbital effects.",1212.1546v1
2013-07-14,Weyl semimetals and superconductors designed in an orbital selective superlattice,"We propose two complementary design principles for engineering
three-dimensional (3D) Weyl semimetals and superconductors in a layer-by-layer
setup which includes even and odd parity orbitals in alternating layers -
dubbed orbital selective superlattice. Such structure breaks mirror symmetry
along the superlattice growth axis which, with the help of either a basal plane
spin-orbit coupling or a spinless p+ip superconductivity, stabilizes a 3D Dirac
node. To explore this idea, we develop a 3D generalization of Haldane model and
a Bogoliubov-de-Gennes (BdG) Hamiltonian for the two cases, respectively, and
show that a tunable single or multiple Weyl nodes with linear dispersion in all
spatial directions can be engineered desirably in a widespread parameter space.
We also demonstrate that a single helical Weyl band can be created at the
$\Gamma$-point at the Fermi level in the superconducting case via gapping out
either of the orbital state by violating its particle-hole symmetry but not any
other symmetries. Finally, implications of our results for the realization of
anomalous Hall effect and Majorana bound state are discussed.",1307.3697v2
2012-01-17,Theory of orbital magnetization in disordered systems,"We present a general formula of the orbital magnetization of disordered
systems based on the Keldysh Green's function theory in the gauge-covariant
Wigner space. In our approach, the gauge invariance of physical quantities is
ensured from the very beginning, and the vertex corrections are easily
included. Our formula applies not only for insulators but also for metallic
systems where the quasiparicle behavior is usually strongly modified by the
disorder scattering. In the absence of disorders, our formula recovers the
previous results obtained from the semiclassical theory and the perturbation
theory. As an application, we calculate the orbital magnetization of a weakly
disordered two-dimensional electron gas with Rashba spin-orbit coupling. We
find that for the short range disorder scattering, its major effect is to the
shifting of the distribution of orbital magnetization corresponding to the
quasiparticle energy renormalization.",1201.3446v1
2017-10-23,Chiral orbital magnetism of $p$-orbital bosons in optical lattices,"Chiral magnetism is a fascinating quantum phenomena that has been found in
low-dimensional magnetic materials. It is not only interesting for
understanding the concept of chirality, but also important for potential
applications in spintronics. Past studies show that chiral magnets require both
lack of the inversion symmetry and spin-orbit coupling to induce the
Dzyaloshinskii-Moriya (DM) interaction. Here we report that the combination of
inversion symmetry breaking and quantum degeneracy of orbital degrees of
freedom will provide a new paradigm to achieve the chiral orbital magnetism. By
means of the density matrix renormalization group (DMRG) calculation, we
demonstrate that the chiral orbital magnetism can be found when considering
bosonic atoms loaded in the $p$-band of an optical lattice in the Mott regime.
The high tunability of our scheme is also illustrated through simply
manipulating the inversion symmetry of the system for the cold atom
experimental conditions.",1710.08145v1
2020-11-17,Dichotomy Between Orbital and Magnetic Nematic Instabilities in BaFe2S3,"Nematic orders emerge nearly universally in iron-based superconductors, but
elucidating their origins is challenging because of intimate couplings between
orbital and magnetic fluctuations. The iron-based ladder material BaFe2S3,
which superconducts under pressure, exhibits antiferromagnetic order below TN ~
117K and a weak resistivity anomaly at T* ~ 180K, whose nature remains elusive.
Here we report angle-resolved magnetoresistance (MR) and elastoresistance (ER)
measurements in BaFe2S3, which reveal distinct changes at T*. We find that MR
anisotropy and ER nematic response are both suppressed near T*, implying that
an orbital order promoting isotropic electronic states is stabilized at T*.
Such an isotropic state below T* competes with the antiferromagnetic order,
which is evidenced by the nonmonotonic temperature dependence of nematic
fluctuations. In contrast to the cooperative nematic orders in spin and orbital
channels in iron pnictides, the present competing orders can provide a new
platform to identify the separate roles of orbital and magnetic fluctuations.",2011.08600v1
2021-03-16,Unconventional Pairing from Local Orbital Fluctuations in Strongly Correlated A$_3$C$_{60}$,"The pairing mechanism in A$_3$C$_{60}$ is investigated by studying the
properties of a three-orbital Hubbard model with antiferromagnetic Hund
coupling in the normal and superconducting phase. Local orbital fluctuations
are shown to be substantially enhanced in the superconducting state, with a
fluctuation energy scale that matches the low-energy peak in the spectral
weight of the order parameter. Our results demonstrate that local orbital
fluctuations provide the pairing glue in strongly correlated fulleride
superconductors and support the spin/orbital freezing theory of unconventional
superconductivity. They are also consistent with the experimentally observed
universal relation between the gap energy and local susceptibility in a broad
range of unconventional superconductors.",2103.08925v1
2022-01-24,Low-energy physics for an iron phthalocyanine molecule on Au(111),"The system of an iron phthalocyanine molecule on the Au(111) surface, has
been studied recently due to its peculiar properties. In particular, several
surprising results of scanning tunneling spectroscopy changing the position of
the molecule and applying magnetic field can be explained by the {\it
non-Landau} Fermi liquid state of a 2-channel spin-1 Kondo model with
anisotropy. The localized orbitals near the Fermi level are three, one of
symmetry $z^2$ and two (nearly) degenerate $\pi$ orbitals of symmetry $xz$ and
$yz$. Previous studies using the numerical renormalization group neglected one
of these orbitals to render the problem tractable. Here we investigate, using a
slave-boson mean-field approximation, if the splitting $S$ between $\pi$
orbitals caused by spin-orbit coupling (SOC) justifies this approximation. We
obtain an abrupt transition from a 3-band regime to a 2-band one at a value of
$S$ which is about 1/3 of the atomic SOC for Fe, justifying the 2-band model
for the system.",2201.10010v2
2018-03-11,Pressure-driven collapse of the relativistic electronic ground state in a honeycomb iridate,"The electronic ground state in many iridate materials is described by a
complex wave-function in which spin and orbital angular momenta are entangled
due to relativistic spin-orbit coupling (SOC). Such a localized electronic
state carries an effective total angular momentum of $J_{eff}=1/2$. In
materials with an edge-sharing octahedral crystal structure, such as the
honeycomb iridates Li2IrO3 and Na2IrO3, these $J_{eff}=1/2$ moments are
expected to be coupled through a special bond-dependent magnetic interaction,
which is a necessary condition for the realization of a Kitaev quantum spin
liquid. However, this relativistic electron picture is challenged by an
alternate description, in which itinerant electrons are confined to a
benzene-like hexagon, keeping the system insulating despite the delocalized
nature of the electrons. In this quasi-molecular orbital (QMO) picture, the
honeycomb iridates are an unlikely choice for a Kitaev spin liquid. Here we
show that the honeycomb iridate Li2IrO3 is best described by a $J_{eff}=1/2$
state at ambient pressure, but crosses over into a QMO state under the
application of small (~ 0.1 GPa) hydrostatic pressure. This result illustrates
that the physics of iridates is extremely rich due to a delicate balance
between electronic bandwidth, spin-orbit coupling, crystal field, and electron
correlation.",1803.04056v1
2023-10-27,"Dirac surface states, multiorbital dimerization and superconductivity in Nb- and Ta-based A15 compounds","Using first-principle calculations, we investigate the electronic,
topological and superconducting properties of Nb$_3$X (X = Ge, Sn, Sb) and
Ta$_3$Y (Y = As, Sb, Bi) A15 compounds. We demonstrate that these compounds
host Dirac surface states which are related to a nontrivial Z$_2$ topological
value. The spin-orbit coupling (SOC) splits the eightfold degenerate R point
close to the Fermi level enhancing the amplitude of the spin Hall conductance.
Indeed, despite the moderate spin-orbit of the Nb-compounds, a large spin Hall
effect is also obtained in Nb$_3$Ge and Nb$_3$Sn compounds. We show that the
Coulomb interaction opens the gap at the R point thus making more evident the
occurrence of Dirac surface states. We then investigate the superconducting
properties by determining the strength of the electron-phonon BCS coupling. The
evolution of the critical temperature is tracked down to the 2D limit
indicating a reduction of the transition temperature which mainly arises from
the suppression of the density of states at the Fermi level. Finally, we
propose a minimal tight-binding model based on three coupled
Su-Schrieffer-Heeger chains with t$_{2g}$ Ta- and Nb-orbitals reproducing the
spin-orbit splittings at the R point among the $\pi$-bond bands in this class
of compounds. We separate the kinetic parameters in $\pi$ and $\delta$-bonds,
in intradimer and interdimer hoppings and discuss their relevance for the
topological electronic structure. We point out that Nb$_3$Ge might represent a
Z$_2$ topological metal with the highest superconducting temperature ever
recorded.",2310.18245v2
2002-07-26,Coulomb couplings in positively charged fullerene,"We compute, based on density-functional electronic-structure calculations,
the Coulomb couplings in the h_u highest occupied orbital of molecular C60. We
obtain a multiplet-averaged Hubbard U ~ 3 eV, and four Hund-rule-like
intra-molecular multiplet-splitting terms, each of the order of few hundreds of
meVs. According to these couplings, all C60^n+ ions should possess a high-spin
ground state if kept in their rigid, undistorted form. Even after molecular
distortions are allowed, however, the Coulomb terms still appear to be somewhat
stronger than the previously calculated Jahn-Teller couplings, the latter
favoring low-spin states. Thus for example in C60^2+, unlike C60^2-, the
balance between Hund rule and Jahn Teller yields, even if marginally, a
high-spin ground state. That seems surprising in view of reports of
superconductivity in field-doped C60^n+ systems.",0207635v3
2011-05-31,"Role of Hund's coupling in stabilization of the (0,pi) ordered SDW state within the minimal two-band model for iron pnictides","Spin wave excitations and stability of the (0,pi) ordered SDW state are
investigated within the minimal two-band model for iron pnictides including a
Hund's coupling term. The SDW state is shown to be stable in two distinct
doping regimes --- finite hole doping in the lower SDW band for small second
neighbour hoppings, and small electron doping in the upper SDW band for
comparable first and second neighbour hoppings. In both cases, Hund's coupling
strongly stabilizes the SDW state due to generation of additional ferromagnetic
spin couplings involving the inter-orbital part of the particle-hole
propagator. Spin wave energies for the two-band model are very similar to the
one-band t-t' Hubbard model results obtained earlier, and are in agreement with
inelastic neutron scattering studies of iron pnictides.",1105.6191v1
2018-04-03,Adjustable current-induced magnetization switching utilizing interlayer exchange coupling,"Electrical current-induced deterministic magnetization switching in a
magnetic multilayer structure without external magnetic field is realized by
utilizing interlayer exchange coupling. Two ferromagnetic Co layers, with
in-plane and out-of-plane anisotropy respectively, are separated by a spacer Ta
layer, which plays a dual role of inducing antiferromagnetic interlayer
coupling, and contributing to the current-induced effective magnetic field
through the spin Hall effect. The current-induced magnetization switching
behavior can be tuned by pre-magnetizing the in-plane Co layer. The
antiferromagnetic exchange coupling field increases with decreasing thickness
of the Ta layer, reaching 630+-5 Oe for a Ta thickness of 1.5nm. The magnitude
of the current-induced perpendicular effective magnetic field from spin-orbit
torque is 9.2 Oe/(107Acm-2). The large spin Hall angle of Ta, opposite in sign
to that of Pt, results in a low critical current density of 9*10^6A/cm^2. This
approach is promising for the electrical switching of magnetic memory elements
without external magnetic field.",1804.00798v1
2019-12-19,Magnetic Topological Kagome Systems,"The recently discovered material Co$_3$Sn$_2$S$_2$ shows an impressive
behavior of the quantum anomalous Hall (QAH) conductivity driven by the
interplay between ferromagnetism in the $z$ direction and antiferromagnetism in
the $xy$ plane. Motivated by these facts, first we build and study a spin-1/2
model to describe the magnetism of Co-atoms on the Kagome planes. Then, we
include conduction electrons which are coupled to the spins-1/2 through a
strong Hund's coupling. The spin-orbit coupling results in topological
low-energy bands. For 2/3 on-site occupancy, we find a topological transition
from a QAH ferromagnetic insulating phase with Chern number one to a quantum
spin Hall (QSH) antiferromagnetic phase. The QAH phase is metallic when
slightly changing the on-site occupancy. To account for temperature effects, we
include fluctuations in the direction of the Hund's coupling. We show how the
Hall conductivity can now smoothly evolve when spins develop a $120^o$
antiferromagnetism in the $xy$ plane and can synchronize with the ferromagnetic
fraction.",1912.09214v2
2020-08-19,Magnetic competition in topological kagome magnets,"Magnetic competition in topological kagome magnets is studied by
incorporating the spin-orbit coupling, the anisotropic Hund coupling and spin
exchange into the kagome lattice. Using the Bogoliubov variational principle we
find the stable phases at zero and finite temperatures. At zero temperature and
in the strong Ising-Hund coupling regime, a magnetic tunability from the
out-of-plane ferromagnetism (FM) to the in-plane antiferromagnetism (AFM) is
achieved by a universal property of the critical in-plane Hund coupling. At
two-thirds filling the phase transition from the out-of-plane FM to the
in-plane AFM is accompanied by a topological transition from quantum anomalous
Hall (QAH) to quantum anomalous spin Hall (QASH) effect. Nearby half filling a
large anomalous Hall conductance is observed at the magnetic phase transition.
At finite temperature the out-of-plane FM is stable until a crossing
temperature, above which the in-plane AFM is stable, but the out-of-plane FM
magnetization is still finite. This suggests a coexistence of these magnetic
phases in a finite temperature range.",2008.08260v1
2024-01-19,Photodriven germanium hole qubit,"Hole qubits in germanium quantum dots are promising candidates for coherent
control and manipulation of the spin degree of freedom through electric dipole
spin resonance. We theoretically study the time dynamics of a single heavy-hole
qubit in a laser-driven planar germanium quantum dot confined laterally by a
harmonic potential in presence of linear and cubic Rashba spin-orbit couplings
and an out-of-plane magnetic field. We obtain an approximate analytical formula
of the Rabi frequency using a Schrieffer-Wolff transformation and establish a
connection of our model with the ESDR results obtained for this system. For
stronger beams, we employ different methods such as unitary transformation and
Floquet theory to study the time evolution numerically. We observe that high
radiation intensity is not suitable for the qubit rotation due to the presence
of high frequency noise superimposed on the Rabi oscillations. We display the
Floquet spectrum and highlight the quasienergy levels responsible for the Rabi
oscillations in the Floquet picture. We study the interplay of both the types
of Rashba couplings and show that the Rabi oscillations, which are brought
about by the linear Rashba coupling, vanish for typical values of the cubic
Rashba coupling in this system.",2401.10570v1
2020-03-17,Hole-phonon interactions in quantum dots: Effects of phonon confinement and encapsulation materials on spin-orbit qubits,"Spin-phonon interactions are one of the mechanisms limiting the lifetime of
spin qubits made in semiconductor quantum dots. At variance with other
mechanisms such as charge noise, phonons are intrinsic to the device and can
hardly be mitigated. They set, therefore fundamental limits to the relaxation
time of the qubits. Here we introduce a general framework for the calculation
of the spin (and charge) transition rates induced by bulk (3D) and strongly
confined 1D or 2D phonons. We discuss the particular case of hole spin-orbit
qubits described by the 6 bands kp model. We next apply this theory to a hole
qubit in a silicon-on-insulator device. We show that spin relaxation in this
device is dominated by a band mixing term that couples the holes to transverse
acoustic phonons through the valence band deformation potential d, and optimize
the bias point and magnetic field orientation to maximize the number of Rabi
oscillations Q that can be achieved within on relaxation time T1. Despite the
strong spin-orbit coupling in the valence band, the phonon-limited Q can reach
a few tens of thousands. We next explore the effects of phonon confinement in
1D and 2D structures, and the impact of the encapsulation materials on the
relaxation rates. We show that the spin lifetimes can depend on the structure
of the device over micrometer-long length scales and that they improve when the
materials around the qubit get harder. Phonon engineering in semiconductor
qubits may therefore become relevant once the extrinsic sources of relaxation
have been reduced.",2003.07592v2
2015-06-16,Next-to-next-to-leading order gravitational spin-orbit coupling via the effective field theory for spinning objects in the post-Newtonian scheme,"We implement the effective field theory for gravitating spinning objects in
the post-Newtonian scheme at the next-to-next-to-leading order level to derive
the gravitational spin-orbit interaction potential at the third and a half
post-Newtonian order for rapidly rotating compact objects. From the
next-to-next-to-leading order interaction potential, which we obtain here in a
Lagrangian form for the first time, we derive straightforwardly the
corresponding Hamiltonian. The spin-orbit sector constitutes the most elaborate
spin dependent sector at each order, and accordingly we encounter a
proliferation of the relevant Feynman diagrams, and a significant increase of
the computational complexity. We present the evaluation of the interaction
potential, going over contributing Feynman diagrams. The computation is carried
out in terms of the nonrelativistic gravitational fields, together with the
various gauge choices included in the effective field theory for gravitating
spinning objects, which optimize the calculation. In addition, we automatize
the effective field theory computations, and carry out the automated
computations in parallel. Such automated effective field theory computations
would be most useful to obtain higher order post-Newtonian corrections. We
compare our Hamiltonian to the ADM Hamiltonian, and arrive at a complete
agreement between the ADM and effective field theory results. We provide
complete gauge invariant relations among the binding energy, angular momentum,
and orbital frequency of an inspiralling binary with generic compact spinning
components to third and a half post-Newtonian order. The derivation presented
here is essential to obtain further higher order post-Newtonian corrections,
and to reach the accuracy level required for the successful detection of
gravitational radiation.",1506.05056v4
2012-06-22,Tight Binding Model of Mn12 Single Molecule Magnets: Electronic and Magnetic Structure and Transport Properties,"We describe and analyze a tight-binding model of single molecule magnets
(SMMs) that captures both the spin and spatial aspects of the SMM electronic
structure. The model generalizes extended Huckel theory to include the effects
of spin polarization and spin-orbit coupling. For neutral and negatively
charged Mn12 SMMs with acetate or benzoate ligands the model yields the total
SMM spin, the spins of the individual Mn ions, the magnetic easy axis
orientation, the size of the magnetic anisotropy barrier and the size of the
HOMO-LUMO gap consistent with experiment. For neutral molecules the predicted
spins and spatial locations of the HOMO are consistent with the results of
density functional calculations. For the total spin and location of the LUMO
density functional theory-based calculations yield varied results while the
present model yield results consistent with experiments on negatively charged
molecules. For Mn12 SMMs with thiolate- and methylsulphide-terminated benzoate
ligands (Mn12-Ph-Th) we find the HOMO to be located on the magnetic core of the
molecule, but (unlike for the Mn12 SMMs that have previously been studied
theoretically), we predict the LUMO and near LUMO orbitals of Mn12-Ph-Th to be
located on ligands. Therefore we predict that for these Mn12 SMMs resonant and
off-resonant coherent transport via near-LUMO orbitals, not subject to Coulomb
blockade, should occur. We propose that this effect can be used to identify
specific experimentally realized SMM transistors in which the easy axis and
magnetic moment are approximately parallel to the direction of the current
flow. We also predict effective spin filtering by these SMMs to occur at low
bias whether the transport is mediated by the HOMO that is on the magnetic core
of the SMM or by near LUMO orbitals located on the nominally non-magnetic
ligands.",1206.5314v1
2023-11-28,Engineering a Spin-Orbit Bandgap in Graphene-Tellurium Heterostructures,"Intensive research has focused on harnessing the potential of graphene for
electronic, optoelectronic, and spintronic devices by generating a bandgap at
the Dirac point and enhancing the spin-orbit interaction in the graphene layer.
Proximity to heavy p elements is a promising approach; however, their
interaction in graphene heterostructures has not been as intensively studied as
that of ferromagnetic, noble, or heavy d metals, neither as interlayers nor as
substrates. In this study, the effective intercalation of Te atoms in a
graphene on Ir(111) heterostructure is achieved. Combining techniques such as
low energy electron diffraction and scanning tunneling microscopy, the
structural evolution of the system as a function of the Te coverage is
elucidated, uncovering up to two distinct phases. The presented angle-resolved
photoemission spectroscopy analysis reveals the emergence of a bandgap of about
240 meV in the Dirac cone at room temperature, which preserves its
characteristic linear dispersion. Furthermore, a pronounced n-doping effect
induced by Te in the heterostructure is also observed, and remarkably the
possibility of tuning the Dirac point energy towards the Fermi level by
reducing the Te coverage while maintaining the open bandgap is demonstrated.
Spin-resolved measurements unveil a non-planar chiral spin texture with
significant splitting values for both in-plane and out-of-plane spin
components. These experimental findings are consistent with the development of
a quantum spin Hall phase, where a Te-enhanced intrinsic spin orbit coupling in
graphene surpasses the Rashba one and promotes the opening of the spin-orbit
bandgap.",2311.16792v1
2023-12-01,The maximum mass of a black hole which can tidally disrupt a star: measuring black hole spins with tidal disruption events,"The tidal acceleration experienced by an object at the event horizon of a
black hole decreases as one over the square of the black hole's mass. As such
there is a maximum mass at which a black hole can tidally disrupt an object
outside of its event horizon and potentially produce observable emission. This
maximum mass is known as the ``Hills mass'', and in full general relativity is
a function of both the black hole's spin $a_\bullet$ and the inclination angle
of the incoming object's orbit with respect to the black hole's spin axis
$\psi$. In this paper we demonstrate that the Hills mass can be represented by
a simple analytical function of $a_\bullet$ and $\psi$, the first general
solution of this problem. This general solution is found by utilising the
symmetries of a class of critical Kerr metric orbits known as the innermost
bound spherical orbits. Interestingly, at fixed black hole spin the maximum
Hills mass can lie at incoming orbital inclinations outside of the black hole's
equatorial plane $\psi \neq \pi/2$. When compared to previous results in the
literature this effect can lead to an increase in the maximum Hills mass (at
fixed spin) by as much as a factor of $\sqrt{11/5} \simeq 1.48$ for a maximally
rotating black hole. We then demonstrate how Bayesian inference, coupled with
an estimate of the mass of a black hole in a tidal disruption event, can be
used to place conservative constraints on that black hole's spin. We provide a
publicly available code tidalspin which computes these spin distributions.",2312.00557v2
2011-05-18,Importance of including small body spin effects in the modelling of extreme and intermediate mass-ratio inspirals,"We explore the ability of future low-frequency gravitational wave detectors
to measure the spin of stellar mass and intermediate mass black holes that
inspiral onto super-massive Kerr black holes (SMBHs). We develop a kludge
waveform model based on the equations of motion derived by Saijo et al. [Phys
Rev D 58, 064005, 1998] for spinning BH binaries, augmented with spin-orbit and
spin-spin couplings taken from perturbative and post-Newtonian (PN)
calculations, and the associated conservative self-force corrections, derived
by comparison to PN results. We model the inspiral phase using accurate fluxes
which include perturbative corrections for the spin of the inspiralling body,
spin-spin couplings and higher-order fits to solutions of the Teukolsky
equation. We present results of Monte Carlo simulations of parameter estimation
errors and of the model errors that arise when we omit conservative corrections
from the waveform template. For a source 5000+10^6 solar mass observed with an
SNR of 1000, LISA will be able to determine the two masses to within a
fractional error of ~0.001, measure the SMBH spin magnitude, q, and the spin
magnitude of the inspiralling BH to 0.0001, 10%, respectively, and determine
the location of the source in the sky and the SMBH spin orientation to within
0.0001 steradians. For a 10+10^6 solar mass system observed with SNR of 30,
LISA will not be able to determine the spin magnitude of the inspiralling BH,
although the measurement of the other waveform parameters is not significantly
degraded by the presence of spin. The model errors which arise from ignoring
conservative corrections become significant for mass-ratios above 0.0001, but
including these corrections up to 2PN order may be sufficient to reduce these
systematic errors to an acceptable level.",1105.3567v3
2023-04-21,Emergence of Rashba spin valley state in two-dimensional strained bismuth oxychalcogenides Bi$_{2}$O$_{2}$Se,"The experimental evidence of the ultra-high electron mobility and strong
spin-orbit coupling in the two-dimensional (2D) layered bismuth-based
oxyselenide, Bi$_{2}$O$_{2}$Se, makes it a potential material for spintronic
devices. However, its spin-related properties have not been extensively studied
due to the centrosymmetric nature of its crystal structure. By using
first-principles density-functional theory calculation, this study reports the
emergence of Rashba-spin-valley states in Bi$_{2}$O$_{2}$Se monolayer (ML).
Breaking the crystal inversion symmetry of Bi$_{2}$O$_{2}$Se ML using an
external electric field enables the Rashba-spin-valley formation, causing the
appearance of the Rashba-type splitting around the $\Gamma$ valley and
spin-valley coupling at the $D$ valleys located near the middle of $\Gamma-M$
line. In addition to the typical Rashba-type spin textures around the $\Gamma$
valley, the study also observed in-plane unidirectional spin textures around
the $D$ valleys, which is a rare phenomenon in 2D materials. The observed
Rashba-spin-valley states are driven by the lowering point group symmetry of
the crystal from $D_{4h}$ to $C_{4v}$ enforced by the electric field, as
clarified through $\vec{k}\cdot\vec{p}$ model derived from symmetry analysis.
More importantly, tuning the Rashba and spin-valley states by using biaxial
strain offers a promising route to regulate the spin textures and spin
splitting preventing the electron from back-scattering in spin transport.
Finally, we proposed a more realistic system, namely, Bi$_{2}$O$_{2}$Se
ML/SrTiO$_{3}$ (001) heterointerface that supports the strong
Rashba-spin-valley states and highlighting the potential of the
Bi$_{2}$O$_{2}$Se ML for future spintronics and valleytronics-based devices.",2304.10746v2
1995-02-06,Superconducting Instability in a 1D lattice of Berry Phase Molecules,"We study the 1D model of conduction electrons interacting with local vibronic
modes. States in the conduction band are two-fold degenerate both in orbital
index and spin. It is shown that such 1D system has a strong tendency to
superconductivity. The superconducting pairing originates from coupling of two
charge density waves; the scaling dimension of the order parameter is close to
1/4.",9502023v1
2002-07-05,Gap nodes in the superconducting phase of the itinerant ferromagnet $UGe_2$,"For the UGe$_2$ ferromagnetic superconductor the forms of the order parameter
admitted by the crystal symmetry within the strong spin-orbit coupling scheme
are written down. For each of the two possible phases existence of gap nodes
required by symmetry is discussed and the nodes are found. Some consequences of
presence of the nodes, which may be useful for experimental identification of
the phases are discussed as well.",0207152v1
2005-10-21,De Haas-van Alphen effect in metals without inversion center,"We show how the de Haas-van Alphen effect can be used to directly measure the
magnitude of spin-orbit coupling in non-centrosymmetric metals, such as CePt3Si
and LaPt3Si.",0510587v1
2008-04-22,Pressure-temperature phase diagram of ferromagnetic superconductors,"The symmetry approach to the description of the (P,T) phase diagram of
ferromagnet superconductors with triplet pairing is developed. Taking into
account the recent experimental observations made on UCoGe it is considered the
case of a crystal with orthorhombic structure and strong spin-orbital coupling.
It is shown that formation of ferromagnet superconducting state from a
superconducting state is inevitably accompanied by the first order type
transition.",0804.3546v1
2008-11-13,Spin-orbit coupling in ballistic carbon nanotubes,This paper has been withdrawn.,0811.2171v3
2012-08-14,Antiferromagnetic Exchange Interaction between Electrons on Degenerate LUMOs in Benzene Dianion,"We discuss the ground state of Benzene dianion (Bz$^{2-}$) on the basis of
the numerical diagonalization method of an effective model of $\pi$ orbitals.
It is found that the ground state can be the spin singlet state, and the
exchange coupling between LUMOs can be antiferromagnetic.",1208.2817v1
2016-02-18,Gapped triplet $p$-wave superconductivity in strong spin-orbit-coupled semiconductor quantum wells in proximity to $s$-wave superconductor,"We show that the {\it gapped} triplet superconductivity, i.e., a triplet
superconductor with triplet order parameter, can be realized in strong
spin-orbit-coupled quantum wells in proximity to $s$-wave superconductor. It is
revealed that with the singlet order parameter induced from the superconducting
proximity effect, in quantum wells, not only can the triplet pairings arise due
to the spin-orbit coupling, but also the triplet order parameter can be induced
due to the repulsive effective electron-electron interaction, including the
electron-electron Coulomb and electron-phonon interactions. This is a natural
extension of the work of de Gennes, in which the repulsive-interaction-induced
singlet order parameter arises in the normal metal in proximity to $s$-wave
superconductor [Rev. Mod. Phys. {\bf 36}, 225 (1964)]. Specifically, we derive
the effective Bogoliubov-de Gennes equation, in which the self-energies due to
the effective electron-electron interactions contribute to the singlet and
triplet order parameters. It is further shown that for the singlet order
parameter, it is efficiently suppressed due to this self-energy
renormalization; whereas for the triplet order parameter, it is the $p$-wave
($p_x\pm ip_y$) one with the ${\bf d}$-vector parallel to the effective
magnetic field due to the spin-orbit coupling. Finally, we perform the
numerical calculation in InSb (100) quantum wells. Specifically, we reveal that
the Coulomb interaction is much more important than the electron-phonon
interaction at low temperature. Moreover, it shows that with proper electron
density, the minimum of the renormalized singlet and the maximum of the induced
triplet order parameters are comparable, and hence can be experimentally
distinguished.",1602.05797v2
2011-11-02,Dispersion and wavefunction symmetry in cold atoms experiencing artificial gauge fields,"We analyze the single particle quantum mechanics of an atom whose dispersion
is modified by spin orbit coupling to Raman lasers. We calculate how the novel
dispersion leads to unusual single particle physics. We focus on the symmetry
of the ground state wavefunction in different potentials.",1111.0578v1
2012-01-26,Topological superfluid in one-dimensional spin-orbit coupled atomic Fermi gases,"ARC Centre of Excellence for Quantum-Atom Optics, Centre for Atom Optics and
Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122,
Australia",1201.5663v1
2020-01-01,Ernest Henley and the shape of baryons,"Calculations of pion-baryon couplings, baryon quadrupole and octupole
moments, baryon spin and orbital angular momentum done in collaboration with
Ernest Henley are reviewed. A common theme of this work is the shape of
baryons. Also, a personal account of my work with Ernest Henley during the
period 1999-2013 is given.",2001.00203v1
2019-08-29,Non-Abelian geometric potentials and spin-orbit coupling for periodically driven systems,"We demonstrate the emergence of the non-Abelian geometric potentials and thus
the three-dimensional (3D) spin-orbit coupling (SOC) for ultracold atoms
without using the laser beams. This is achieved by subjecting an atom to a
periodic perturbation which is the product of a position-dependent Hermitian
operator $\hat{V}\left(\mathbf{r}\right)$ and a fast oscillating periodic
function $f\left(\omega t\right)$ with a zero average. To have a significant
spin-orbit coupling (SOC), we analyze a situation where the characteristic
energy of the periodic driving is not necessarily small compared to the driving
energy $\hbar\omega$. Applying a unitary transformation to eliminate the
original periodic perturbation, we arrive at a non-Abelian (non-commuting)
vector potential term describing the 3D SOC. The general formalism is
illustrated by analyzing the motion of an atom in a spatially inhomogeneous
magnetic field oscillating in time. A cylindrically symmetric magnetic field
provides the SOC involving the coupling between the spin $\mathbf{F}$ and all
three components of the orbital angular momentum (OAM) $\mathbf{L}$. In
particular, the spherically symmetric monopole-type synthetic magnetic field
$\mathbf{B}\propto\mathbf{r}$ generates the 3D SOC of the $\mathbf{L}\cdot
\mathbf{F}$ form, which resembles the fine-structure interaction of hydrodgen
atom. However, the strength of the SOC here goes as $1/r^{2}$ for larger
distances, instead of $1/r^3$ as in atomic fine structure. Such a longer-ranged
SOC significantly affects not only the lower states of the trapped atom, but
also the higher ones. Furthermore, by properly tailoring the external trapping
potential, the ground state of the system can occur at finite OAM, while the
ground state of hydrogen atom has zero OAM.",1908.11275v3
2016-10-29,Nodal lines and nodal loops in non-symmorphic odd-parity superconductors,"We discuss the nodal structure of odd-parity superconductors in the presence
of non-symmorphic crystal symmetries, both with and without spin-orbit
coupling, and with and without time reversal symmetry. We comment on the
relation of our work to previous work in the literature, and also the
implications for unconventional superconductors such as UPt$_3$.",1610.09510v2
2021-03-15,Linear magnetoconductivity in magnetic metals,"We theoretically describe a mechanism of low-field linear magnetoconductivity
in helical magnetic metals. Two ingredients for the mechanism in
three-dimensional metals are identified to be the spin-orbit coupling and
momentum-dependent ferromagnetic exchange interaction. We propose and study a
number of minimal theoretical models which have linear magnetoconductivity, and
discuss their implications for recent experiments.",2103.08503v2
2021-08-11,Symmetry-enforced topological band crossings in orthorhombic crystals: Classification and materials discovery,"We identify all symmetry-enforced band crossings in nonmagnetic orthorhombic
crystals with and without spin-orbit coupling and discuss their topological
properties. We find that orthorhombic crystals can host a large number of
different band degeneracies, including movable Weyl and Dirac points with
hourglass dispersions, fourfold double Weyl points, Weyl and Dirac nodal lines,
almost movable nodal lines, nodal chains, and topological nodal planes.
Interestingly, spin-orbit coupled materials in the space groups 18, 36, 44, 45,
and 46 can have band pairs with only two Weyl points in the entire Brillouin
zone. This results in a simpler connectivity of the Fermi arcs and more
pronounced topological responses than in materials with four or more Weyl
points. In addition, we show that the symmetries of the space groups 56, 61,
and 62 enforce nontrivial weak $\mathbb{Z}_2$ topology in materials with strong
spin-orbit coupling, leading to helical surface states. With these
classification results in hand, we perform extensive database searches for
orthorhombic materials crystallizing in the relevant space groups. We find that
Sr$_2$Bi$_3$ and Ir$_2$Si have bands crossing the Fermi energy with a
symmetry-enforced nontrivial $\mathbb{Z}_2$ invariant, CuIrB possesses nodal
chains near the Fermi energy, Pd$_7$Se$_4$ and Ag$_2$Se exhibit fourfold double
Weyl points, the latter one even in the absence of spin-orbit coupling, whereas
the fourfold degeneracies in AuTlSb are made up from intersecting nodal lines.
For each of these examples we compute the ab-initio band structures, discuss
their topologies, and for some cases also calculate the surface states.",2108.05375v1
2021-09-17,Symmetries of the Schroedinger-Pauli equations for charged particles and quasirelativistic Schroedinger equations,"Lie symmetries of the Schroedinger-Pauli equations for charged particles and
quasirelativistic Schroedinger equations are classified. In particular a new
superintegrable system with spin-orbit coupling is discovered.",2109.08528v2
2023-11-18,Edelstein effect and supercurrent diode effect,"We self-consistently calculate the supercurrent diode effect from microscopic
models of quasi one- and two-dimensional clean superconductors with spin-orbit
coupling under external Zeeman fields, and show that the Edelstein effect is
responsible for the supercurrent diode effect. In turn, the supercurrent diode
effect may serve as a direct measurement of the Edelstein effect as its
application.",2311.11087v1
2024-02-05,Topological metal and high-order Dirac point in cubic Rashba model,"We investigate the properties of the two-dimensional model with Rashba-type
spin-orbit coupling cubic in electron momentum. In the normal phase, edge
states emerge on open boundaries. In the superconducting phase, edge states
could evolve into gapped fermionic edge states. Applications to realistic
materials of interface superconductors are also discussed.",2402.03005v1
2000-01-18,Spin-orbit interaction in Hartree-Fock calculations,"The contribution of the spin-orbit interaction in Hartree-Fock calculations
for closed shell nuclei is studied. We obtain explicit expressions for the
finite range spin-orbit force. New terms with respect to the traditional
spin-orbit expressions are found. The importance of the finite-range is
analyzed. Results obtained with spin-orbit terms taken from realistic
interactions are presented. The effect of the spin-orbit isospin dependent
terms is evaluated.",0001031v1
2021-02-15,"Post-Keplerian obliquity variations and the habitability of rocky planets orbiting fast spinning, oblate late M dwarfs","A couple of dozen Earth-like planets orbiting M dwarfs have been discovered
so far. Some of them have attracted interest because of their potential
long-term habitability; such a possibility is currently vigorously debated in
the literature. I show that post-Keplerian (pK) orbit precessions may impact
the habitability of a fictitious telluric planet orbiting an oblate late-type M
dwarf of spectral class M9V with $M_\star=0.08\,M_\odot$ at
$a=0.02\,\mathrm{au}$, corresponding to an orbital period $P_\mathrm{b}\simeq
4\,\mathrm{d}$, inducing long-term variations of the planetary obliquity
$\varepsilon$ which, under certain circumstances, may not be deemed as
negligible from the point of view of life's sustainability. I resume the
analytical orbit-averaged equations of the pK precessions, both classical and
general relativistic, of the unit vectors
$\boldsymbol{\hat{S}},\,\boldsymbol{\hat{h}}$ of both the planet's spin and
orbital angular momenta $\boldsymbol S,\,\boldsymbol{L}$ entering
$\varepsilon$, and numerically integrate them by producing time series of the
pK changes $\Delta\varepsilon(t)$ of the obliquity. For rapidly rotating M
dwarfs with rotational periods of the order of $P_\star \simeq
0.1-1\,\mathrm{d}$, the planet's obliquity $\varepsilon$ can undergo classical
pK large variations $\Delta\varepsilon(t)$ up to tens of degrees over
timescales $\Delta t \simeq 20-200\,\mathrm{kyr}$, depending on the mutual
orientations of the star's spin ${\boldsymbol J}_\star$, of $\boldsymbol S$,
and of $\boldsymbol L$. Instead, $\Delta\varepsilon(t)$ are $\lesssim
1-1.5^\circ$ for the planet b of the Teegarden's Star. In certain
circumstances, the M dwarf's oblateness $J_2^\star$ should be considered as one
of the key dynamical features to be taken into account in compiling budgets of
the long-term habitability of rocky planets around fast spinning late M dwarfs.
(Abridged)",2102.07815v2
2017-06-07,Star-planet interactions. IV. Possibility of detecting the orbit-shrinking of a planet around a red giant,"The surface rotations of some red giants are so fast that they must have been
spun up by tidal interaction with a close companion, either another star, a
brown dwarf, or a planet. We focus here on the case of red giants that are spun
up by tidal interaction with a planet. When the distance between the planet and
the star decreases, the spin period of the star decreases, the orbital period
of the planet decreases, and the reflex motion of the star increases. We study
the change rate of these three quantities when the circular orbit of a planet
of 15 M$_{J}$ that initially orbits a 2 M$_\odot$ star at 1 au shrinks under
the action of tidal forces during the red giant phase. We use stellar evolution
models coupled with computations of the orbital evolution of the planet, which
allows us to follow the exchanges of angular momentum between the star and the
orbit in a consistent way. We obtain that the reflex motion of the red giant
star increases by more than 1 m s$^{-1}$ per year in the last $\sim$40 years
before the planet engulfment. During this phase, the reflex motion of the star
is between 660 and 710 m s$^{-1}$. The spin period of the star increases by
more than about 10 minutes per year in the last 3000 y before engulfment.
During this period, the spin period of the star is shorter than 0.7 year.
During this same period, the variation in orbital period, which is shorter than
0.18 year, is on the same order of magnitude. Changes in reflex-motion and spin
velocities are very small and thus most likely out of reach of being observed.
The most promising way of detecting this effect is through observations of
transiting planets, that is, through{\it } changes of the beginning or end of
the transit. A space mission like PLATO might be of great interest for
detecting planets that are on the verge of being engulfed by red giants.",1706.02234v1
2004-10-15,Suppression of spin-orbit effects in 1D system,"We report the absence of spin effects such as spin-galvanic effect, spin
polarization and spin current under static electric field and
inter-spin-subband absorption in 1D system with spin-orbit interaction of
arbitrary form. It was also shown that the accounting for the direct
interaction of electron spin with magnetic field violates this statement.",0410393v1
1993-03-03,Van Hove Excitons and High-T$_c$ Superconductivity: VIIIC Dynamic Jahn-Teller Effects vs Spin-Orbit Coupling in the LTO Phase of La$_{2-x}$Sr$_x$CuO$_4$,"The possible role of the van Hove singularity (vHs) in stabilizing the
low-temperature orthorhombic (LTO) phase transition in
La$_{2-x}$\-Sr$_x$\-CuO$_ 4$ (LSCO) is discussed. It is found that the vHs can
drive a structural distortion in two different ways, either due to spin-orbit
coupling or to dynamic Jahn-Teller (JT) effects. This paper discusses the
latter effect in some detail. It is shown that a model Hamiltonian introduced
earlier to describe the coupled electron -- octahedral tilt motions (`cageons')
has a series of phase transitions, from a high-temperature disordered JT phase
(similar to the high-temperature tetragonal phase of LSCO) to an intermediate
temperature dynamic JT phase, of average orthorhombic symmetry (the LTO phase)
to a low temperature static JT phase (the low temperature tetragonal phase).
For some parameter values, the static JT phase is absent.",9303020v1
2006-01-04,Prospect for room temperature tunneling anisotropic magnetoresistance effect: density of states anisotropies in CoPt systems,"Tunneling anisotropic magnetoresistance (TAMR) effect, discovered recently in
(Ga,Mn)As ferromagnetic semiconductors, arises from spin-orbit coupling and
reflects the dependence of the tunneling density of states in a ferromagnetic
layer on orientation of the magnetic moment. Based on ab initio relativistic
calculations of the anisotropy in the density of states we predict sizable TAMR
effects in room-temperature metallic ferromagnets. This opens prospect for new
spintronic devices with a simpler geometry as these do not require
antiferromagnetically coupled contacts on either side of the tunnel junction.
We focus on several model systems ranging from simple hcp-Co to more complex
ferromagnetic structures with enhanced spin-orbit coupling, namely bulk and
thin film L1$_0$-CoPt ordered alloys and a monatomic-Co chain at a Pt surface
step edge. Reliability of the predicted density of states anisotropies is
confirmed by comparing quantitatively our ab initio results for the
magnetocrystalline anisotropies in these systems with experimental data.",0601071v1
2008-06-23,Low energy excitations in CoO studied by temperature dependent x-ray absorption spectroscopy,"We have measured the intricate temperature dependence of the Co L2,3 x-ray
absorption spectra (2p-3d excitations) of CoO. To allow for accurate total
electron yield measurements, the material has been grown in thin film form on a
metallic substrate in order to avoid charging problems usually encountered
during electron spectroscopic studies on bulk CoO samples. The changes in
spectra due to temperature are in good agreement with detailed ligand-field
calculations indicating that these changes are mostly due to thermal population
of closely lying excited states, originating from degenerate t2g levels lifted
by the spin-orbit coupling. Magnetic coupling in the ordered phase, modeled as
a mean-field exchange field, mixes in excited states inducing a tetragonal
charge density. The spin-orbit coupling induced splitting of the low energy
states results in a non-trivial temperature dependence for the magnetic
susceptibility.",0806.3736v1
2011-03-06,"The Influence of Magnetic Anisotropy on the Kondo Effect and Spin-Polarized Transport through Magnetic Molecules, Adatoms and Quantum Dots","Transport properties in the Kondo regime of a nanosystem displaying uniaxial
magnetic anisotropy (such as a magnetic molecule, magnetic adatom or quantum
dot coupled to a localized magnetic moment) are analyzed theoretically. In
particular, the influence of spin-polarized transport through a local orbital
of the system and exchange coupling of conduction electrons to the system's
magnetic core on the Kondo effect is discussed. The numerical renormalization
group method is applied to calculate the spectral functions and linear
conductance in the case of the parallel and antiparallel configurations of the
electrodes' magnetic moments. It is shown that both the magnetic anisotropy as
well as the exchange coupling between electrons tunneling through the
conducting orbital and magnetic core play an important role in formation of the
Kondo resonance, leading generally to its suppression. Specific transport
properties of such a system appear also as a nontrivial behavior of tunnel
magnetoresistance. It is also shown that the Kondo effect can be restored by an
external magnetic field in both the parallel and antiparallel magnetic
configurations.",1103.1128v2
2011-06-14,Majorana Zero Modes in 1D Quantum Wires Without Long-Ranged Superconducting Order,"We show that long-ranged superconducting order is not necessary to guarantee
the existence of Majorana fermion zero modes at the ends of a quantum wire. We
formulate a concrete model which applies, for instance, to a semiconducting
quantum wire with strong spin-orbit coupling and Zeeman splitting coupled to a
wire with algebraically-decaying superconducting fluctuations. We solve this
model by bosonization and show that it supports Majorana fermion zero modes. We
argue that a large class of models will also show the same phenomenon. We
discuss the implications for experiments on spin-orbit coupled nanowires coated
with superconducting film and for LaAlO3/SrTiO3 interfaces.",1106.2598v3
2012-06-27,"Evaluation of the importance of spin-orbit couplings in the nonadiabatic quantum dynamics with quantum fidelity and with its efficient ""on-the-fly"" ab initio semiclassical approximation","We propose to measure the importance of spin-orbit couplings (SOCs) in the
nonadiabatic molecular quantum dynamics rigorously with quantum fidelity. To
make the criterion practical, quantum fidelity is estimated efficiently with
the multiple-surface dephasing representation (MSDR). The MSDR is a
semiclassical method that includes nuclear quantum effects through interference
of mixed quantum-classical trajectories without the need for the Hessian of
potential energy surfaces. Two variants of the MSDR are studied, in which the
nuclei are propagated either with the fewest-switches surface hopping or with
the locally mean field dynamics. The fidelity criterion and MSDR are first
tested on one-dimensional model systems amenable to numerically exact quantum
dynamics. Then, the MSDR is combined with ""on-the-fly"" computed electronic
structure to measure the importance of SOCs and nonadiabatic couplings (NACs)
in the photoisomerization dynamics of CH2NH2+ considering 20 electronic states
and in the collision of F + H2 considering six electronic states.",1206.6299v1
2012-07-09,Theory of magnetism and metal-insulator transition in layered perovskite iridates,"We investigate the metal-insulator transition in the layered Ruddelsden
Popper series of strontium iridates Srn+1IrnO3n+1. Tight-binding models of t2g
orbitals for n = 1, 2, and infinity are constructed, and changes in band
dispersion due to dimensionality and spin-orbit coupling are presented.
Identifying the states near the Fermi level to be predominantly Jeff = 1/2, we
use an effective Hubbard model to study the effect of correlations. Transitions
from a metallic state to various magnetically ordered states at different
critical interactions are obtained. A canted antiferromagnetic insulator is
found for Sr2IrO4, a c-axis collinear antiferromagnetic insulator for Sr3Ir2O7,
and non-coplanar canted antiferromagnetic insulator via magnetic metal for
SrIrO3. We derive the strong-coupling spin-model and compare the magnetic
ordering patterns obtained in the weak and strong coupling limits. We find that
they are identical, indicating that magnetic ordering is not sufficient to
justify Mott physics in this series of iridates.",1207.2183v3
2012-08-24,Stability of Excited Dressed States with Spin-Orbit Coupling,"We study the decay behaviors of ultracold atoms in metastable states with
spin-orbit coupling (SOC), and demonstrate that there are two SOC-induced decay
mechanisms. One arises from the trapping potential and the other is due to
interatomic collision. We present general schemes for calculating decay rates
from these two mechanisms, and illustrate how the decay rates can be controlled
by experimental parameters.We experimentally measure the decay rates over a
broad parameter region, and the results agree well with theoretical
calculations. This work provides an insight for both quantum simulation
involving metastable dressed states and studies on few-body problems with SO
coupling.",1208.4941v2
2013-01-03,Emergence of Topological and Strongly Correlated Ground States in trapped Rashba Spin-Orbit Coupled Bose Gases,"We theoretically study an interacting few-body system of Rashba spin-orbit
coupled two-component Bose gases confined in a harmonic trapping potential. We
solve the interacting Hamiltonian at large Rashba coupling strengths using
Exact Diagonalization scheme, and obtain the ground state phase diagram for a
range of interatomic interactions and particle numbers. At small particle
numbers, we observe that the bosons condense to an array of topological states
with n+1/2 quantum angular momentum vortex configurations, where n = 0, 1, 2,
3... At large particle numbers, we observe two distinct regimes: at weaker
interaction strengths, we obtain ground states with topological and symmetry
properties that are consistent with mean-field theory computations; at stronger
interaction strengths, we report the emergence of strongly correlated ground
states.",1301.0800v1
2013-07-20,Phase diagrams of voltage-gated oxide interfaces with strong Rashba coupling,"We propose a model for the two-dimensional electron gas formed at the
interface of oxide heterostructures that includes a Rashba spin-orbit coupling
proportional to an electric field oriented perpendicularly to the interface.
Taking into account the electron density dependence of this electric field
confining the electron gas at the interface, we report the occurrence of a
phase separation instability (signaled by a negative compressibility) for
realistic values of the spin-orbit coupling and of the electronic
band-structure parameters at zero temperature. We extend the analysis to finite
temperatures and in the presence of an in-plane magnetic field, thereby
obtaining two phase diagrams which exhibit a phase separation dome. By varying
the gating potential the phase separation dome may shrink and vanish at zero
temperature into a quantum critical point where the charge fluctuates
dynamically. Similarly the phase separation may be spoiled by a planar magnetic
field even at zero temperature leading to a line of quantum critical points.",1307.5427v3
2013-11-08,Novel magnetic state in $d^4$ Mott insulators,"We show that the interplay of strong Hubbard interaction $U$ and spin-orbit
coupling $\lambda$ in systems with $d^4$ electronic configuration leads to
several unusual magnetic phases. Most notably, we find that competition between
superexchange and spin-orbit coupling leads to a phase transition from a
non-magnetic state predicted by atomic physics to a novel magnetic state in the
large $U$ limit. We show that the local moment changes dramatically across this
phase transition, challenging the conventional wisdom that local moments are
robust against small perturbations in a Mott insulator. The Hund's coupling
plays an important role in determining the nature of the magnetism. We identify
candidate materials and present predictions for Resonant X-ray Scattering (RXS)
signatures of the unusual magnetism in $d^4$ Mott insulators.",1311.2823v2
2013-11-14,Fidelity susceptibility and topological phase transition of a two dimensional spin-orbit coupled Fermi superfluid,"We investigate the fidelity susceptibility (FS) of a two-dimensional
spin-orbit coupled (SOC) Fermi superfluid and the topological phase transition
driven by a Zeeman field in the perspective of its ground-state wave-function.
Without Zeeman coupling, FS shows new features characterizing the BCS-BEC
crossover induced by SOC. In the presence of a Zeeman field, the topological
phase transition is explored using both FS and the topological invariant. In
particular, we obtain the analytical result of the topological invariant which
explicitly demonstrates that the topological phase transition corresponds to a
sudden change of the ground state wave-function. Consequently, FS diverges at
the phase transition point with its critical behavior being: $\chi \propto
ln|h-h_{c}|$ . Based on this observation, we conclude that the topological
phase transition can be detected by measuring the momentum distribution in cold
atoms experiment.",1311.3349v2
2015-02-25,Tunable spin-orbit coupling synthesized with a modulating gradient magnetic field,"We report the observation of tunable spin-orbit coupling (SOC) for ultracold
$^{87}$Rb atoms in hyperfine spin-1 states. Different from most earlier
experiments where atomic SOC of pseudo-spin-1/2 are synthesized with Raman
coupling lasers, the scheme we demonstrate employs a gradient magnetic field
(GMF) with ground state atoms and is immune to atomic spontaneous emission. The
effect of the SOC is confirmed through the studies of: 1) the collective dipole
oscillation of an atomic condensate in a harmonic trap after the synthesized
SOC is abruptly turned on; and 2) the minimum energy state at a finite
adiabatically adjusted momentum when the SOC strength is slowly ramped up. The
coherence properties of the spinor condensates remain very good after
interacting with modulating GMFs, which prompts the enthusiastic claim that our
work provides a new repertoire for synthesized gauge fields aimed at quantum
simulation studies with cold atoms.",1502.07091v2
2015-04-20,Raman scattering as a probe of nematic correlations,"We use the symmetry constrained low energy effective Hamiltonian of iron
based superconductors to study the Raman scattering in the normal state of
underdoped iron-based superconductors. The incoming and scattered Raman photons
couple directly to orbital fluctuations and indirectly to the spin
fluctuations. We computed both couplings within the same low energy model. The
symmetry constrained Hamiltonian yields the coupling between the orbital and
spin fluctuations of only the same symmetry type. Attraction in B2g symmetry
channel was assumed for the system to develop the subleading instability
towards the discrete in-plane rotational symmetry breaking, referred to as
Ising nematic transition. We find that upon approaching this instability, the
Raman spectral function develops a quasi-elastic peak as a function of energy
transferred by photons to the crystal. We attribute this low-energy B2g
scattering to the critical slow-down associated with the build up of nematic
correlations.",1504.05054v2
2016-06-21,Interplay between spin-orbit coupling and crystal-field effect in topological insulators,"Band inversion, one of the key signatures of time-reversal invariant
topological insulators (TIs), arises mostly due to the spin-orbit (SO)
coupling. Here, based on ab initio density-functional calculations, we report a
theoretical investigation of the SO-driven band inversion in isostructural
bismuth and antimony chalcogenide TIs from the viewpoint of its interplay with
the crystal-field effect. We calculate the SO-induced energy shift of states in
the top valence and bottom conduction manifolds and reproduce this behavior
using a simple one-atom model adjusted to incorporate the crystal-field effect.
The crystal-field splitting is shown to compete with the SO coupling, that is,
stronger crystal-field splitting leads to weaker SO band shift. We further show
how both these effects can be controlled by changing the chemical composition,
whereas the crystal-field splitting can be tuned by means of uniaxial strain.
These results provide a practical guidance to the rational design of novel TIs
as well as to controlling the properties of existing materials.",1606.06761v1
2016-09-07,Entanglement-symmetry control in a quantum-dot Cooper-pair splitter,"The control of nonlocal entanglement in solid state systems is a crucial
ingredient of quantum technologies. We investigate a Cooper-pair splitter based
on a double quantum dot realised in a semiconducting nanowire. In the presence
of interdot tunnelling the system provides a simple mechanism to develop
spatial entanglement even in absence of nonlocal coupling with the
superconducting lead. We discuss the possibility to control the symmetry
(singlet or triplet) of spatially separated, entangled electron pairs taking
advantage of the spin-orbit coupling of the nanowire. We also demonstrate that
the spin-orbit coupling does not impact over the entanglement purity of the
nonlocal state generated in the double quantum dot system.",1609.01902v2
2016-09-26,One- and two-dimensional solitons in PT-symmetric systems emulating the spin-orbit coupling,"We introduce a two-dimensional (2D) system, which can be implemented in
dual-core planar optical couplers with the Kerr nonlinearity in its cores,
making it possible to blend effects of the PT symmetry, represented by the
balanced linear gain and loss in the two cores, and spin-orbit coupling (SOC),
emulated by a spatially biased coupling between the cores. Families of 1D and
2D solitons and their stability boundaries are identified. In the 1D setting,
the addition of the SOC terms leads, at first, to shrinkage of the stability
area for PT-symmetric solitons, which is followed by its rapid expansion. 2D
solitons have their stability region too, in spite of the simultaneous action
of two major destabilizing factors, viz., the collapse driven by the Kerr
nonlinearity, and a trend towards spontaneous breakup of the gain-loss balance.
In the limit of the SOC terms dominating over the intrinsic diffraction, the 1D
system gives rise to a new model for gap solitons, which admits exact
analytical solutions.",1609.07988v1
2020-07-16,Spontaneous generation of vortices by a nonuniform Zeeman field in a two-dimensional Rashba coupled superconductor,"The interplay of the electron exchange interaction and spin-orbit coupling
results in spontaneous supercurrents near magnetic insulator islands, which are
placed on the top of a two-dimensional (2D) superconductor, and whose
magnetization is parallel to 2D electron gas. It is shown that in contrast to
the well studied situation, where such an effect involves only topologically
trivial spatial variations of the superconducting order parameter, one should
take into account supercurrent vortices. The latter are spontaneously generated
around the island's boundary of an arbitrary shape and result in screening of
the Zeeman field. This problem has been considered for electrons subject to a
strong Rashba spin-orbit coupling, including Dirac systems as well. In the
latter case vortices can carry Majorana zero modes.",2007.08276v2
2020-07-16,Thermal noise effects on the magnetization switching of a ferromagnetic anomalous Josephson junction,"We discuss the effects of thermal noise on the magnetic response of a lateral
ferromagnetic Josephson junction with spin-orbit coupling and out-of-plane
magnetization. The direction of the magnetic moment in the ferromagnetic layer
can be inverted by using controlled current pulses. This phenomenon is due to
the magnetoelectric effect that couples the flowing charge current and the
magnetization of the ferromagnet. We investigate the magnetization reversal
effect versus intrinsic parameters of the ferromagnet, such as the Gilbert
damping and strength of the spin-orbit coupling. We estimate the magnetization
reversing time and find the optimal values of the parameters for fast
switching. With the aim of increasing the operation temperature we study the
effects induced by thermal fluctuations on the averaged stationary
magnetization, and find the conditions that make the system more robust against
noise.",2007.08414v3
2020-07-27,Josephson oscillations of chirality and identity in two-dimensional solitons in spin-orbit-coupled condensates,"We investigate dynamics of two-dimensional chiral solitons of semi-vortex
(SV) and mixed-mode (MM) types in spin-orbit-coupled Bose-Einstein condensates
with the Manakov nonlinearity, loaded in a dual-core (double-layer) trap. The
system supports two novel manifestations of Josephson phenomenology: one in the
form of persistent oscillations between SVs or MMs with opposite chiralities in
the two cores, and another one demonstrating robust periodic switching
(identity oscillations) between SV in one core and MM in the other, provided
that the strength of the inter-core coupling exceeds a threshold value. Below
the threshold, the system creates composite states, which are asymmetric with
respect to the two cores, or suffer the collapse. Robustness of the chirality
and identity oscillations against deviations from the Manakov nonlinearity is
investigated too. These dynamical regimes are possible only in the nonlinear
system. In the linear one, exact stationary and dynamical solutions for SVs and
MMs of the Bessel type are found. They sustain Josephson self-oscillations in
different modes, with no interconversion between them.",2007.13359v1
2017-01-09,Spin-orbit coupled interferometry with ring-trapped Bose--Einstein condensates,"We propose a method of atom-interferometry using a spinor Bose-Einstein
condensate (BEC) with a time-varying magnetic field acting as a coherent
beam-splitter. Our protocol creates long-lived superpositional counterflow
states, which are of fundamental interest and can be made sensitive to both the
Sagnac effect and magnetic fields on the sub-micro-G scale. We split a
ring-trapped condensate, initially in the $m_f=0$ hyperfine state, into
superpositions of internal $m_f=\pm1$ states and condensate superflow, which
are spin-orbit coupled. After interrogation, relative phase accumulation can be
inferred from a population transfer to the $m_f=\pm1$ states. The counterflow
generation protocol is adiabatically deterministic and does not rely on
coupling to additional optical fields or mechanical stirring techniques. Our
protocol can maximise the classical Fisher information for any rotation,
magnetic field, or interrigation time, and so has the maximum sensitivity
available to uncorrelated particles. Precision can increase with the
interrogation time, and so is limited only by the lifetime of the condensate.",1701.02154v2
2017-01-30,Landau's criterion for an anisotropic Bose-Einstein condensate,"In this work, we discuss the Landau's criterion for anisotropic
superfluidity. To this end, we consider a point-like impurity moving in a
uniform Bose-Einstein condensate with either interparticle dipole-dipole
interaction or Raman induced spin-orbit coupling. In both cases, we find that
the Landau critical velocity $v_{\rm c}$ is generally smaller than the sound
velocity in the moving direction. Beyond $v_{\rm c}$, the energy dissipation
rate is explicitly calculated via a perturbation approach. In the plane-wave
phase of a spin-orbit coupled Bose gas, the dissipationless motion is
suppressed by the Raman coupling even in the direction orthogonal to the recoil
momentum. Our predictions can be tested in the experiments with ultracold
atoms.",1701.08686v2
2018-05-08,Phonon-induced Majorana Qubit Relaxation in Tunnel-Coupled Two-Island Topological Superconductors,"A Majorana-based qubit can form within the fermion parity subspace of a
two-island topological superconductor setup consisting of four Majorana zero
modes. We study the relaxation time of this Majorana qubit induced by the
intrinsic Majorana-phonon interaction in combination with single electron
tunneling between the two islands. The theory is developed for both the
spinless p-wave Kitaev chain model and the spin-orbit-coupled semiconductor
nanowire with induced superconductivity and Zeeman splitting. We systematically
discuss the dependence of the relaxation rate on Majorana charge distribution
(varying with the chemical potential, magnetic field, superconducting paring,
spin-orbit coupling and island length) as well as on phonon wavelength and the
length of the tunnel barrier. Importantly, the accompanied phonon energy can be
tuned by the voltage bias over the tunnel barrier, leading to relatively easy
manipulation and suppression of the relaxation rate.",1805.03213v2
2018-05-09,Scattering of solitons in binary Bose-Einstein condensates with spin-orbit and Rabi couplings,"In this paper we study the scattering of solitons in a binary Bose-Einstein
Condensate (BEC) including SO- and Rabi-couplings. To this end, we derive a
reduced ODE model in view to provide a variational description of the
collisional dynamics. Also, we assume negative intra- and inter-component
interaction strengths, such that one obtains localized solutions even in
absence of external potentials. By performing extensive numerical simulations
of this model we observe that, for specific conditions, the final propagation
velocity of the scattered solitons could be highly sensitive to small changes
in the initial conditions, being a possible signature of chaos. Additionally,
there are infinitely many intervals of regularity emerging from the obtained
chaotic-like regions and forming a fractal-like structure of
reflection/transmission windows. Finally, we investigate how the value of the
spin-orbit coupling strength changes the critical velocities, which are
minimum/maximum values for the occurrence of solitons bound-states, as well as
the fractal-like structure.",1805.03340v1
2014-05-12,Exciton Condensates in Double Quantum Wells: A Laboratory for nontrivial topologies and unconventional superconductivity,"It is shown that exciton condensates exhibit an incredible richness in the
role that fundamental symmetries play whether manifest or broken. We
investigate the appearance of the singlet and the triplet excitonic condensates
under spin-orbit coupling (SOC) and consider realistic couplings to the
radiation field as manipulated by the fundamental symmetries related to spin,
time, orbital and particle degrees of freedom. The role of the strong SOC in
inducing a ground state with coexisting singlet and triplet components is
shown. It is also shown that the ground state of an excitonic condensate, in
the realistic senario of spontaneous coupling to the radiation field, is
dominated by a dark component transparent to photoluminescence.",1405.2829v1
2016-05-07,Superfluid Density of a Spin-orbit Coupled Bose Gas,"We discuss the superfluid properties of a Bose-Einstein condensed gas with
spin-orbit coupling, recently realized in experiments. We find a finite normal
fluid density $\rho_n$ at zero temperature which turns out to be a function of
the Raman coupling. In particular, the entire fluid becomes normal at the
transition point from the zero momentum to the plane wave phase, even though
the condensate fraction remains finite. We emphasize the crucial role played by
the gapped branch of the elementary excitations and discuss its contributions
to various sum rules. Finally, we prove that an independent definition of
superfluid density $\rho_s$, using the phase twist method, satisfies the
equality $\rho_n+\rho_s=\rho$, the total density, despite the breaking of
Galilean invariance.",1605.02136v1
2016-05-08,Dirac-Kondo semimetals and topological Kondo insulators in the dilute carrier limit,"Heavy fermion systems contain not only strong electron correlations, which
promote a rich set of quantum phases, but also a large spin-orbit coupling,
which tends to endow the electronic states a topological character. Kondo
insulators are understood in terms of a lattice of local moments coupled to
conduction electrons in a half-filled band, i.e., with a dense population of
about one electron per unit cell. Here, we propose that a new class of Kondo
insulator arises when the conduction-electron band is nearly empty ( or,
equivalently, full ) . We demonstrated the effect through a honeycomb Anderson
lattice model. In the empty carrier limit, spin-orbit coupling produces a gap
in the hybridized heavy fermion band, thereby generating a topological Kondo
insulator. This state can be understood in terms of a nearby phase in the
overall phase diagram, a Dirac-Kondo semimetal whose quasiparticle excitations
exhibit a non-trivial Berry phase. Our results point to the dilute carrier
limit of the heavy-fermion systems as a new setting to study strongly
correlated insulating and topological states.",1605.02380v1
2016-08-01,Double quantum dot Cooper-pair splitter at finite couplings,"We consider the sub-gap physics of a hybrid double-quantum dot Cooper-pair
splitter with large single-level spacings, in the presence of tunnelling
between the dots and finite Coulomb intra- and inter-dot Coulomb repulsion. In
the limit of a large superconducting gap, we treat the coupling of the dots to
the superconductor exactly. We employ a generalized master-equation method
which easily yields currents, noise and cross-correlators. In particular, for
finite inter- and intra-dot Coulomb interaction, we investigate how the
transport properties are determined by the interplay between local and nonlocal
tunneling processes between the superconductor and the dots. We examine the
effect of inter-dot tunneling on the particle-hole symmetry of the currents
with and without spin-orbit interaction. We show that spin-orbit interaction in
combination with finite Coulomb energy opens the possibility to control the
nonlocal entanglement and its symmetry (singlet/triplet). We demonstrate that
the generation of nonlocal entanglement can be achieved even without any direct
nonlocal coupling to the superconducting lead.",1608.00504v1
2017-12-23,Band resolved imaging of photocurrent in a topological insulator,"We study the microscopic origins of photocurrent generation in the
topological insulator Bi$_2$Se$_3$ via time- and angle-resolved photoemission
spectroscopy. We image the unoccupied band structure as it evolves following a
circularly polarized optical excitation and observe an asymmetric electron
population in momentum space, which is the spectroscopic signature of a
photocurrent. By analyzing the rise times of the population we identify which
occupied and unoccupied electronic states are coupled by the optical
excitation. We conclude that photocurrents can only be excited via resonant
optical transitions coupling to spin-orbital textured states. Our work provides
a microscopic understanding of how to control photocurrents in systems with
spin-orbit coupling and broken inversion symmetry.",1712.08694v2
2018-01-16,From Nodal Ring Topological Superfluids to Spiral Majorana Modes in Cold Atomic Systems,"In this work, we consider a 3D cubic optical lattice composed of coupled 1D
wires with 1D spin-orbit coupling. When the s-wave pairing is induced through
Feshbach resonance, the system becomes a topological superfluid with ring
nodes, which are the ring nodal degeneracies in the bulk, and supports a large
number of surface Majorana zero energy modes. The large number of surface
Majorana modes remain at zero energy even in the presence of disorder due to
the protection from a chiral symmetry. When the chiral symmetry is broken, the
system becomes a Weyl topological superfluid with Majorana arcs. With 3D
spin-orbit coupling, the Weyl superfluid becomes a novel gapless phase with
spiral Majorana modes on the surface. The spatial resolved radio frequency
spectroscopy is suggested to detect this novel nodal ring topological
superfluid phase.",1801.05182v1
2020-02-13,Low-loss two-dimensional plasmon modes in antimonene,"The effects of spin-orbit (SOC) and electron-phonon coupling on the
collective excitation of doped monolayer Sb$_2$ are investigated using density
functional and many-body perturbation theories. The spin-orbit coupling is
exclusively important for the monolayer Sb$_2$ and it leads to the
reconstruction of the electronic band structure. In particular, plasmon modes
of monolayer Sb$_2$ are quite sensitive to the SOC and are characterized by
very low damping rates owing to small electron-phonon scatterings. Our results
show plasmons in antimonene are significantly less damped compared to monolayer
graphene when plasmon energies are $\hbar \omega> 0.2$ eV due to smaller
plasmon-phonon coupling in the former material.",2002.05302v1
2020-04-05,Phase diagrams of tunable spin-orbit coupled Bose-Einstein condensates,"We analytically calculate phase boundaries of tunable spin-orbit coupled BECs
with effective two-body interactions by using variational method. Phase
diagrams for periodically driving $^{87}\rm{Rb}$ and $^{23}\rm{Na}$ systems are
presented, respectively, which display several characteristic features contrast
with those of undriven systems. In the $^{87}\rm{Rb}$ BECs, the critical
density $n_{c}$ (density at quantum tricritical point) can be dramatically
reduced in some parameter regions, thus the prospect of observing this
intriguing quantum tricritical point is greatly enlarged. Moreover, a series of
quantum tricritical points emerge quasi-periodically with increasing the Raman
coupling strength for fixed $^{87}\rm{Rb}$ density. In the $^{23}\rm{Na}$ BECs,
two hyperfine states of $^{23}\rm{Na}$ atoms can be miscible due to driving
under proper parameters. As a result, $^{23}\rm{Na}$ systems can stay in the
stripe phase with small Raman frequency at typical density. This expands the
region of stripe phase in the phase diagram. In addition, there is no quantum
tricritical point in such $^{23}\rm{Na}$ system , which is different from
$^{87}\rm{Rb}$ system.",2004.02063v1
2018-06-01,Effect of distance on photoluminescence quenching and proximity-induced spin-orbit coupling in graphene-WSe2 heterostructures,"Spin-orbit coupling (SOC) in graphene can be greatly enhanced by proximity
coupling it to transition metal dichalcogenides (TMDs) such as WSe2. We find
that the strength of the acquired SOC in graphene depends on the stacking order
of the heterostructures when using hexagonal boron nitride (h-BN) as the
capping layer, i.e., SiO2/graphene/WSe2/h-BN exhibiting stronger SOC than
SiO2/WSe2/graphene/h-BN. We utilize photoluminescence (PL) as an indicator to
characterize the interaction between graphene and monolayer WSe2 grown by
chemical vapor deposition. We observe much stronger PL quenching in the
SiO2/graphene/WSe2/h-BN stack than in the SiO2/WSe2/graphene/h-BN stack, and
correspondingly a much larger weak antilocalization (WAL) effect or stronger
induced SOC in the former than in the latter. We attribute these two effects to
the interlayer distance between graphene and WSe2, which depends on whether
graphene is in immediate contact with h-BN. Our observations and hypothesis are
further supported by first-principles calculations which reveal a clear
difference in the interlayer distance between graphene and WSe2 in these two
stacks.",1806.00501v1
2019-11-17,Ideal Weyl semimetal with 3D spin-orbit coupled ultracold quantum gas,"There is an immense effort in search for various types of Weyl semimetals, of
which the most fundamental phase consists of the minimal number of i.e. two
Weyl points, but is hard to engineer in solids. Here we demonstrate how such
fundamental Weyl semimetal can be realized in a maneuverable optical Raman
lattice, with which the three-dimensional (3D) spin-orbit (SO) coupling is
synthesised for ultracold atoms. In addition, a new novel Weyl phase with
coexisting Weyl nodal points and nodal ring is also predicted here, and is
shown to be protected by nontrivial linking numbers. We further propose
feasible techniques to precisely resolve 3D Weyl band topology through 2D
equilibrium and dynamical measurements. This work leads to the first
realization of the most fundamental Weyl semimetal band and the 3D SO coupling
for ultracold quantum gases, which are respectively the significant issues in
the condensed matter and ultracold atom physics.",1911.07169v2
2020-05-29,Bound states of spin-orbit coupled cold atoms in a Dirac delta-function potential,"Dirac delta-function potential is widely studied in quantum mechanics because
it usually can be exactly solved and at the same time is useful in modeling
various physical systems. Here we study a system of delta-potential trapped
spinorbit coupled cold atoms. The spin-orbit coupled atomic matter wave has two
kinds of evanescent modes, one of which has pure imaginary wavevector and is an
ordinary evanescent wave; while the other with a complex number wave vector is
recognized as oscillating evanescent wave. We identified the eigenenergy
spectra and the existence of bound states in this system. The bound states can
be constructed analytically using the two kinds of evanescent modes and we
found that they exhibit typical features of stripe phase, separated phase or
zero-momentum phase. In addition to that, the properties of semi-bound states
are also discussed, which is a localized wave packet on a plane wave
background.",2005.14604v1
2020-08-27,Pseudospin-lattice coupling and electric control of the square-lattice iridate Sr2IrO4,"$\rm Sr_2IrO_4$ is an archetypal spin-orbit-coupled Mott insulator and has
been extensively studied in part because of a wide range of predicted novel
states. Limited experimental characterization of these states thus far brings
to light the extraordinary susceptibility of the physical properties to the
lattice, particularly, the Ir-O-Ir bond angle. Here, we report a newly observed
microscopic rotation of the IrO$_6$ octahedra below 50~K measured by single
crystal neutron diffraction. This sharp lattice anomaly provides keys to
understanding the anomalous low-temperature physics and a direct confirmation
of a crucial role that the Ir-O-Ir bond angle plays in determining the ground
state. Indeed, as also demonstrated in this study, applied electric current
readily weakens the antiferromagnetic order via the straightening of the
Ir-O-Ir bond angle, highlighting that even slight change in the local structure
can disproportionately affect the physical properties in the spin-orbit-coupled
system.",2008.12355v1
2021-04-15,Magnetotransport of Functional Oxide Heterostructures Affected by Spin-Orbit Coupling: A Tale of Two-Dimensional Systems,"Oxide heterostructures allow for detailed studies of 2D electronic transport
phenomena. Herein, different facets of magnetotransport in selected
spin-orbit-coupled systems are analyzed and characterized by their single-band
and multiband behavior, respectively. Experimentally, temperature- and magnetic
field-dependent measurements in the single-band system BaPbO$_3$/SrTiO$_3$
reveal strong interplay of weak antilocalization (WAL) and electron-electron
interaction (EEI). Within a scheme which treats both, WAL and EEI, on an equal
footing a strong contribution of EEI at low temperatures is found which
suggests the emergence of a strongly correlated ground state. Furthermore, now
considering multiband effects as they appear, e.g., in the model system
LaAlO$_3$/SrTiO$_3$, theoretical investigations predict a huge impact of
filling on the topological Hall effect in systems with intermingled bands.
Already weak band coupling produces striking deviations from the well-known
Hall conductivity that are explainable in a fully quantum mechanical treatment
which builds upon the hybridization of intersecting Hofstadter bands.",2104.07270v2
2017-07-06,Ground state properties of a two dimensional Fermi superfluid with an anisotropic spin-orbit coupling,"We performed a theoretical investigation on the ground state properties of a
two dimensional ultra-cold Fermi superfluid with an anisotropic spin-orbit
coupling (SOC). In the absence of Zeeman field, the system evolves from weak
coupling BCS regime to strongly interacting BEC regime (BCS-BEC crossover) with
increasing either the two-particle interaction strength or SOC parameters. We
focused on the behaviors of pairing parameter and density of states (DOS) when
increasing the anisotropic parameter of the SOC. Surprisingly, we discovered
that the gap parameter decreases with increasing the anisotropic parameters,
but the DOS at the Fermi surface shows non-monotonic behavior as a function of
the anisotropic parameter. In the presence of the Zeeman field, we discussed a
particular type of topological phase transition by obtaining the analytical
result of the topological invariant and directly related this quantum phase
transition with a sudden change of the ground state wave-function. Effects of
higher partial wave pairing terms on this topological phase transition were
briefly discussed.",1707.01607v1
2017-07-13,Spin-orbit coupling and nonlinear modes of the polariton condensate in a harmonic trap,"We consider a model of the exciton-polariton condensate based on a system of
two Gross-Pitaevskii equations coupled by the second-order differential
operator, which represents the spin-orbit coupling (SOC) in the system. Also
included are the linear gain, effective diffusion, nonlinear loss, and the
standard harmonic-oscillator trapping potential, as well as the Zeeman
splitting. By means of combined analytical and numerical methods, we identify
stable two-dimensional modes supported by the nonlinear system. In the absence
of the Zeeman splitting, these are mixed modes, which combine zero and nonzero
vorticities in each of the two spinor components, and vortex-antivortex
complexes. We have also found a range of parameters where the mixed-mode and
vortex-antivortex states coexist and are simultaneously stable. Sufficiently
strong Zeeman splitting creates stable semi-vortex states, with vorticities 0
in one component and 2 in the other.",1707.04107v1
2017-11-21,Novel spin-orbit coupling driven emergent states in iridate-based heterostructures,"Recent years have seen many examples of how the strong spin-orbit coupling
(SOC) present in iridates can stabilize new emergent states that are difficult
or impossible to realize in more conventional materials. In this review we
outline a representative set of studies detailing how heterostructures based on
Ruddlesden-Popper (RP) and perovskite iridates can be used to access yet more
novel physics. Beginning with a short synopsis of iridate thin film growth, the
effects of the heterostructure morphology on the RP iridates including Sr2IrO4
and SrIrO3 are discussed. Example studies explore the effects of epitaxial
strain, laser-excitation to access transient states, topological
semimetallicity in SrIrO3, 2D magnetism in artificial RP iridates, and
interfacial magnetic coupling between iridate and neighboring layers. Taken
together, these works show the fantastic potential for controlled engineering
of novel quantum phenomena in iridate heterostructures.",1711.07609v1
2018-10-02,Topological phases of non-symmorphic crystals : Shastry-Sutherland lattice at integer filling,"Motivated by intertwined crystal symmetries and topological phases, we study
the possible realization of topological insulator in nonsymmorphic crystals at
integer fillings. In particular, we consider spin orbit coupled electronic
systems of two-dimensional crystal Shastry-Sutherland lattice at integer
filling where the gapless line degeneracy is protected by glide reflection
symmetry. Based on a simple tight-binding model, we investigate how the
topological insulating phase is stabilized by breaking nonsymmorphic symmetries
but in the presence of time reversal symmetry and inversion symmetry. In
addition, we also discuss the regime where Dirac semimetal is stabilized,
having non trivial $Z_2$ invariants even without spin orbit coupling (SOC). Our
study can be extended to more general cases where all lattice symmetries are
broken and we also discuss possible application to topological Kondo insulators
in nonsymmorphic crystals where crystal symmetries can be spontaneously broken
as a function of Kondo coupling.",1810.01451v1
2020-06-16,Stabilization of one-dimensional Townes solitons by spin-orbit coupling in a dual-core system,"It was recently demonstrated that two-dimensional Townes solitons (TSs) in
two-component systems with cubic self-focusing, which are normally made
unstable by the critical collapse, can be stabilized by linear spin-orbit
coupling (SOC), in Bose-Einstein condensates and optics alike. We demonstrate
that one-dimensional TSs, realized as optical spatial solitons in a planar
dual-core waveguide with dominant quintic self-focusing, may be stabilized by
SOC-like terms emulated by obliquity of the coupling between cores of the
waveguide. Thus, SOC offers a universal mechanism for the stabilization of the
TSs. A combination of systematic numerical considerations and analytical
approximations identifies a vast stability area for skew-symmetric solitons in
the system's main (semi-infinite) and annex (finite) bandgaps. Tilted
(""moving"") solitons are unstable, spontaneously evolving into robust breathers.
For broad solitons, diffraction, represented by second derivatives in the
system, may be neglected, leading to a simplified model with a finite bandgap.
It is populated by skew-antisymmetric gap solitons, which are nearly stable
close to the gap's bottom.",2006.09555v1
2021-02-12,Atom-dimer and dimer-dimer scatterings in a spin-orbit coupled Fermi gas,"Using the diagrammatic approach, here we study how spin-orbit coupling (SOC)
affects the fermion-dimer and dimer-dimer scattering lengths in the Born
approximation, and benchmark their accuracy with the higher-order
approximations. We consider both isotropic and Rashba couplings in three
dimensions, and show that the Born approximation gives accurate results in the
$1/(m \alpha a_s) \ll -1$ limit, where $m$ is the mass of the fermions,
$\alpha$ is the strength of the SOC, and $a_s$ is the $s$-wave scattering
length between fermions. This is because the higher-loop contributions form a
perturbative series in the $1/(m \alpha a_s) < 0$ region that is controlled by
the smallness of the residue $Z$ of the dimer propagator. In sharp contrast,
since $Z$ grows with the square-root of the binding energy of the dimer in the
$1/(m \alpha a_s) > 0$ region, all of the higher-loop contributions are of
similar order.",2102.06730v1
2021-03-24,Femtosecond Intersystem Crossing in the DNA Nucleobase Cytosine,"Ab initio molecular dynamics including non-adiabatic and spin-orbit couplings
on equal footing is used to unravel the deactivation of cytosine after UV light
absorption. Intersystem crossing (ISC) is found to compete directly with
internal conversion in tens of femtoseconds, thus making cytosine the organic
compound with the fastest triplet population calculated so far. It is found
that close degeneracy between singlet and triplet states can more than
compensate for very small spin-orbit couplings, leading to efficient ISC. The
femtosecond nature of the intersystem crossing process highlights its
importance in photochemistry and challenges the conventional view that large
singlet-triplet couplings are required for an efficient population flow into
triplet states. These findings are important to understand DNA photostability
and the photochemistry and dynamics of organic molecules in general.",2103.13070v1
2021-06-10,Spin-Orbit Coupled Exciton-Polariton Condensates in Lead Halide Perovskites,"Spin-orbit coupling (SOC) is responsible for a range of spintronic and
topological processes in condensed matter. Here we show photonic analogs of
SOCs in exciton-polaritons and their condensates in microcavities composed of
birefringent lead halide perovskite single crystals. The presence of
crystalline anisotropy coupled with splitting in the optical cavity of the
transverse electric (TE) and transverse magnetic (TM) modes gives rise to a
non-Abelian gauge field, which can be described by the Rashba-Dresselhaus
Hamiltonian near the degenerate points of the two polarization modes. With
increasing density, the exciton polaritons with pseudospin textures undergo
phase transitions to competing condensates with orthogonal polarizations.
Unlike their pure photonic counterparts, these exciton polaritons and
condensates inherit nonlinearity from their excitonic components and may serve
as quantum simulators of many-body SOC processes.",2106.06034v2
2022-01-16,Solitons in $\mathcal{PT}$-symmetric systems with spin-orbit coupling and critical nonlinearity,"We construct families of one-dimensional (1D) stable solitons in
two-component $\mathcal{PT}$-symmetric systems with spin-orbit coupling (SOC)
and quintic nonlinearity, which plays the critical role in 1D setups. The
system models light propagation in a dual-core waveguide with skewed coupling
between the cores. Stability regions for the solitons are identified in the
system's parameter space. They include the main semi-infinite gap, and an
additional finite $\textit{annex gap}$. Stability boundaries are identified by
means of simulations of the perturbed evolution, which agree with results
produced by the linear-stability analysis for small perturbations. Distinct
evolution scenarios are identified for unstable solitons. Generally, they
suffer blowup or decay, while weakly unstable solitons transform into
breathers. Due to a regularizing effect of SOC, stationary solitons are also
found beyond the exceptional point, at which the $\mathcal{PT}$ symmetry breaks
down, but they are unstable. Interactions between adjacent solitons are
explored too, featuring rebound or merger followed by blowup. Slowly moving
(tilted) solitons develop weak oscillations, while fast ones are completely
unstable. Also considered is the reduced diffractionless system, which creates
only unstable solitons.",2201.06139v1
2022-02-11,Pseudopotentials for Two-dimentional Ultracold Scattering in the Presence of Synthetic Spin-orbit-coupling,"We derive a pseudopotential in two dimensions (2D) with the presence of a 2D
Rashba spin-orbit-coupling (SOC), following the same spirit of frame
transformation in {[}Phys. Rev. A 95, 020702(R) (2017){]}. The frame
transformation correctly describes the non-trivial phase accumulation and
partial wave couplings due to the presence of SOC and gives rise to a different
pseudopotential than the free-space one, even when the length scale of SOC is
significantly larger than the two-body potential range. As an application, we
apply our pseudopotential with the Lippmann-Schwinger equation to obtain an
analytical scattering matrix. To demonstrate the validity, we compare our
results with a numerical scattering calculation of finite-range potential and
show perfect agreement over a wide range of scattering energy and SOC strength.
Our results also indicate that the differences between our pseudopotential and
the original free-space pseudopotential are essential to reproduce scattering
observables correctly.",2202.05431v1
2022-03-07,Texture-induced spin-orbit coupling and Skyrmion-electron bound states in a Néel antiferromagnet,"We derive effective-mass electron Hamiltonian for a N\'eel antiferromagnet in
the presence of a smooth texture of the staggered magnetization. For certain
locations of electron band extrema, the texture produces a peculiar and
anomalously strong spin-orbit coupling of the scale $\hbar v / L$, with $v$ the
Fermi velocity and $L$ the characteristic length scale of the texture. For a
Skyrmion texture, this coupling generates electron bound states, whose energy
scale is given by the gap $\Delta$ in the electron spectrum. With dopant
carriers, such bound states turn the Skyrmion into a charged particle, that can
be manipulated by electric field.",2203.03569v3
2022-03-15,Imaginary spin-orbital coupling in parity-time symmetric systems with momentum-dependent gain and loss,"Spin-orbital coupling (SOC) and parity-time ($\mathcal{PT}$) symmetry both
have attracted paramount research interest in condensed matter physics, cold
atom physics, optics and acoustics to develop spintronics, quantum computation,
precise sensors and novel functionalities. Natural SOC is an intrinsic
relativistic effect. However, there is an increasing interest in synthesized
SOC nowadays. Here, we show that in a $\mathcal{PT}$-symmetric spin-1/2 system,
the momentum-dependent balanced gain and loss can synthesize a new type of SOC,
which we call imaginary SOC. The imaginary SOC can substantially change the
energy spectrum of the system. Firstly, we show that it can generate a pure
real energy spectrum with a double-valleys structure. Therefore, it has the
ability to generate supersolid stripe states. Especially, the imaginary SOC
stripe state can have a high contrast of one. Moreover, the imaginary SOC can
also generate a spectrum with tunable complex energy band, in which the waves
are either amplifying or decaying. Thus, the imaginary SOC would also find
applications in the engineering of $\mathcal{PT}$-symmetry-based coherent wave
amplifiers/absorbers. Potential experimental realizations of imaginary SOC are
proposed in cold atomic gases and systems of coupled waveguides constituted of
nonlocal gain and loss.",2203.07764v1
2022-06-01,One- and two-dimensional solitons in spin-orbit-coupled Bose-Einstein condensates with fractional kinetic energy,"We address effects of spin-orbit coupling (SOC), phenomenologically added to
a two-component Bose-Einstein condensate composed of particles moving by Levy
flights, in one- and two-dimensional (1D and 2D) settings. The corresponding
system of coupled Gross-Pitaevskii equations includes fractional kinetic-energy
operators, characterized by the Levy index, \alpha < 2 (the normal kinetic
energy corresponds to \alpha = 2). The SOC terms, with strength \lambda,
produce strong effects in the 2D case: they create families of stable solitons
of the semi-vortex (SV) and mixed-mode (MM) types in the interval of 1 < \alpha
< 2, where the supercritical collapse does not admit the existence of stable
solitons in the absence of the SOC. At \lambda --> 0, amplitudes of these
solitons vanish as (\lambda)^{1/(\alpha - 1)}.",2206.00404v1
2022-06-02,Control of dimer chain topology by Rashba-Dresselhaus spin-orbit coupling,"We study theoretically a dimer chain in the presence of Rashba-Dresselhaus
spin-orbit coupling (RDSOC) with equal strength. We show that the RDSOC can be
described as a synthetic gauge field that controls not only the magnitude but
also the sign of tunneling coefficients between sites. This allows to emulate
not only a Su-Schrieffer-Heeger chain which is commonly implemented in various
platforms, but also, all energy spectra of the transverse field Ising model
with both ferromagnetic and antiferromagnetic coupling. We simulate a realistic
implementation of these effective Hamiltonians based on liquid crystal
microcavities. In that case, the RDSOC can be switched on and off by an applied
voltage, which controls the band topology, the existence and characteristics of
topological edge states, or the nature of the ground state. This setting is
promising for topological photonics applications and from a quantum simulation
perspective.",2206.01060v1
2022-07-12,Origin of subgap states in normal-insulator-superconductor van der Waals heterostructures,"Superconductivity in van der Waals materials, such as NbSe$_{2}$ and
TaS$_{2}$, is fundamentally novel due to the effects of dimensionality, crystal
symmetries, and strong spin-orbit coupling. In this work we perform tunnel
spectroscopy on NbSe$_{2}$ by utilizing MoS$_{2}$ or hexagonal Boron Nitride
(hBN) as a tunnel barrier. We observe subgap excitations and probe their origin
by studying various heterostructure designs. We show that the edge of
NbSe$_{2}$ hosts many defect states, which strongly couple to the
superconductor and form Andreev bound states. Furthermore, by isolating the
NbSe$_{2}$ edge we show that the subgap states are ubiquitous in MoS$_{2}$
tunnel barriers, but absent in hBN tunnel barriers, suggesting defects in
MoS$_{2}$ as their origin. Their magnetic nature reveals a singlet or a doublet
type ground state and based on nearly vanishing g-factors or avoided-crossing
of subgap excitations we highlight the role of strong spin-orbit coupling.",2207.05741v1
2022-11-09,Anisotropic Rashba coupling to polar modes in KTaO3,"Motivated by the discovery of superconductivity in KTaO3-based
heterostructures, we study a pairing mechanism based on spin-orbit assisted
coupling between the conduction electrons and the ferroelectric modes present
in the material. We use ab initio frozen-phonon computations to show a
linear-in-momentum Rashba-like coupling with a strong angular dependence in
momentum for the lower j=3/2 manifold, deviating from the conventional
isotropic Rashba model. This implies the Rashba-like interaction with the polar
modes has substantial L=3 cubic harmonic corrections, which we quantify for
each electronic band. The strong anisotropy of the Rashba interaction is
captured by a microscopic toy model for the t2g electrons. We find its origin
to be the angular dependence in electronic momentum imposed by the kinetic term
on the degenerate j=3/2 manifold. A comparison between the toy model and ab
initio results indicate that additional symmetry allowed terms beyond
odd-parity spin-conserving inter-orbital hopping processes are needed to
describe the Rashba-like polar interaction between the electrons and the soft
ferroelectric mode.",2211.05056v2
2023-01-18,Chirality Dependent Photon Transport and Helical Superradiance,"Chirality, or handedness, is a geometrical property denoting a lack of mirror
symmetry. Chirality is ubiquitous in nature and is associated with the
non-reciprocal interactions observed in complex systems ranging from
biomolecules to topological materials. Here, we demonstrate that chiral
arrangements of dipole-coupled atoms or molecules can facilitate the
unidirectional transport of helical photonic excitations without breaking
time-reversal symmetry. We show that such helicity dependent transport stems
from an emergent spin-orbit coupling induced by the chiral geometry, which
results in nontrivial topological properties. We also examine the effects of
collective dissipation and find that many-body coherences lead to helicity
dependent photon emission: an effect we call helical superradiance. Our results
demonstrate an intimate connection between chirality, topology, and photon
helicity that may contribute to molecular photodynamics in nature and could be
probed with near-term quantum simulators.",2301.07231v4
2023-02-01,Superconductivity from repulsive interactions in Bernal-stacked bilayer graphene,"A striking series of experiments have observed superconductivity in
Bernal-stacked bilayer graphene (BBG) when the energy bands are flattened by
applying an electrical displacement field. Intriguingly, superconductivity
manifests only at non-zero magnetic fields, or when spin-orbit coupling is
induced in BBG by coupling to a substrate. We present detailed functional
renormalization group and random-phase approximation calculations that provide
a unified explanation for the superconducting mechanism in both cases. Both
calculations yield a purely electronic $p$-wave instability of the
Kohn-Luttinger (KL) type. The latter can be enhanced either by magnetic fields
or Ising spin-orbit coupling, naturally explaining the behaviour seen in
experiments.",2302.00682v2
2023-06-29,Wannier solitons in spin-orbit-coupled Bose-Einstein condensates in optical lattices with a flat-band,"We investigate families of soliton solutions in a spin-orbit coupled
Bose-Einstein condensate embedded in an optical lattice, which bifurcate from
the nearly flat lowest band. Unlike the conventional gap solitons the obtained
solutions have the shape well approximated by a Wannier function (or a few
Wannier functions) of the underlying linear Hamiltonian with amplitudes varying
along the family and with nearly constant widths. The Wannier solitons (WSs)
sharing all symmetries of the system Hamiltonian are found to be stable. Such
solutions allow for the construction of Wannier breathers, that can be viewed
as nonlinearly coupled one-hump solitons. The breathers are well described by a
few-mode model and manifest stable behavior either in an oscillatory regime
with balanced average populations or in a self-trapping regime characterized by
unbalanced atomic populations of the local potential minima (similarly to the
conventional boson Josephson junction), with the frequencies controlled by the
inter-atomic interactions.",2306.16813v1
2023-10-01,High-temperature magneto-inter-chirality oscillations in 2D systems with strong spin-orbit coupling,"Conventional magneto-oscillations of conductivity in three dimensions are
washed out as the temperature exceeds the spacing between the Landau levels.
This is due to smearing of the Fermi distribution. In two dimensions, in the
presence of two or more size-quantization sub-bands, there is an additional
type of magneto-oscillations, usually referred to as magneto-inter-sub-band
oscillations, which do not decay exponentially with temperature. The period of
these oscillations is determined by the condition that the energy separation
between the sub-bands contains an integer number of Landau levels. Under this
condition, which does not contain the Fermi distribution, the inter-sub-band
scattering rate is maximal. Here we show that, with only one sub-band,
high-temperature oscillations are still possible. They develop when the
electron spectrum is split due to the spin-orbit coupling. For these additional
oscillations, the coupling enters both, the period and the decay rate.",2310.00774v1
2023-11-20,The impact of Rashba spin-orbit coupling in charge-ordered systems,"We study the impact of the Rashba spin-orbit coupling (RSOC) on the stability
of charge-density wave (CDW) in systems with large electron-phonon coupling
(EPC). Here, the EPC is considered in the framework of the Holstein model at
the half-filled square lattice. We start obtaining the phase diagram of the
Rashba-Holstein model using the Hartree-Fock mean-field theory, and identifying
the boundaries of the CDW and Rashba metal phases. As our main result, we
notice that the RSOC disfavors the CDW phase, driving the system to a
correlated Rashba metal. Proceeding, we employ a cluster perturbation theory
(CPT) approach to investigate the phase diagram beyond the Hartree-Fock
approximation. The quantum correlations captured by CPT indicate that the RSOC
is even more detrimental to CDW than previously anticipated. That is, the
Rashba metal region is observed to be expanded in comparison to the mean-field
case. Additionally, we investigate pairing correlations, and the results
further strengthen the identification of critical points.",2311.11984v1
2024-02-29,"Topological flat bands, valley polarization, and interband superconductivity in magic-angle twisted bilayer graphene with proximitized spin-orbit couplings","We study theoretically the magic-angle twisted bilayer graphene with
proximity-induced Ising and Rashba spin-orbit couplings on the top layer. We
demonstrate topological flat bands and identify three distinct topological
phases. Using a weak coupling analysis, we find that (partial) valley
polarization prevails for a wide range of doping, suppressing the usual
superconductivity with a pairing between time-reversal partners. Remarkably, we
uncover that observable unconventional intervalley interband phonon-mediated
superconductivity (with the highest $T_c\approx 1.2$K) can coexist with strong
valley imbalance due to the approximate Fermi surface nesting between two flat
bands not related by time-reversal symmetry, and the dominant pairing is an
intersublattice Ising pairing, corresponding to a mixture of $p$- and
$d$-waves. In contrast, the intrasublattice Ising phonon-mediated
superconductivity with $s$- and $f$-wave mixing emerges in the absence of
valley imbalance. Our work reveals a novel route of realizing unconventional
superconductivity, and potentially explains the superconductivity phenomenology
in existing experiments.",2402.19478v1
2020-01-15,Utilizing Essential Symmetry Breaking in Auxiliary-Field Quantum Monte Carlo: Application to the Spin Gaps of the C$_{36}$ Fullerene and an Iron Porphyrin Model Complex,"We present three distinct examples where phaseless auxiliary-field Quantum
Monte Carlo (ph-AFQMC) can be reliably performed with a single-determinant
trial wavefunction with essential symmetry breaking. We first utilized
essential time-reversal symmetry breaking with ph-AFQMC to compute the
triplet-singlet energy gap in the TS12 set. We found statistically better
performance of ph-AFQMC with complex-restricted orbitals than with
spin-unrestricted orbitals. We then showed the utilization of essential spin
symmetry breaking when computing the single-triplet gap of a known
biradicaloid, C$_{36}$. ph-AFQMC with spin-unrestricted Hartree-Fock
(ph-AFQMC+UHF) fails catastrophically even with spin-projection and predicts no
biradicaloid character. With approximate Brueckner orbitals obtained from
regularized orbital-optimized second-order M{\o}ller-Plesset perturbation
theory ($\kappa$-OOMP2), ph-AFQMC quantitatively captures strong biradicaloid
character of C$_{36}$. Lastly, we applied ph-AFQMC to the computation of the
quintet-triplet gap in a model iron porphyrin complex where brute-force methods
with a small active space fail to capture the triplet ground state. We show
unambiguously that neither triplet nor quintet is strongly correlated using
UHF, $\kappa$-OOMP2, and coupled-cluster with singles and doubles (CCSD)
performed on UHF and $\kappa$-OOMP2 orbitals. There is no essential symmetry
breaking in this problem. By virtue of this, we were able to perform
UHF+ph-AFQMC reliably with a cc-pVTZ basis set and predicted a triplet ground
state for this model geometry. The largest ph-AFQMC in this work correlated 186
electrons in 956 orbitals. Our work highlights the utility, scalability, and
accuracy of ph-AFQMC with a single determinant trial wavefunction with
essential symmetry breaking for systems mainly dominated by dynamical
correlation with little static correlation.",2001.05109v2
1997-12-04,Is the magnetic field necessary for the Aharonov-Bohm effect in mesoscopics?,"A new class of topological mesoscopic phenomena in absence of external
magnetic field (meso-nucleo-spinics)is predicted, which is based on combined
action of the nonequilibrium nuclear spin population and charge carriers
spin-orbit interaction . As an example, we show that Aharonov-Bohm like
oscillations of the persistent current in GaAs/AlGaAs based mesoscopic rings
may exist, in the absence of the external magnetic field, provided that a
topologically nontrivial strongly nonequilibrium nuclear spin population is
created. This phenomenon is due to the breaking, via the spin-orbit coupling,
of the clock wise - anti clock wise symmetry of the charge carriers momentum,
which results in the oscillatory in time persistent current.",9712057v1
2006-07-08,Spin-orbit interaction in symmetric wells with two subbands,"We investigate the spin-orbit (s-o) interaction in two-dimensional electron
gases (2DEGs) in quantum wells with two subbands. From the $8\times 8$ Kane
model, we derive a new inter-subband-induced s-o term which resembles the
functional form of the Rashba s-o -- but is non-zero even in \emph{symmetric}
structures. This follows from the distinct parity of the confined states
(even/odd) which obliterates the need for asymmetric potentials. We
self-consistently calculate the new s-o coupling strength for realistic wells
and find it comparable to the usual Rashba constant. Our new s-o term gives
rise to a non-zero ballistic spin-Hall conductivity, which changes sign as a
function of the Fermi energy ($\epsilon_F$), and can induce an unusual
\emph{zitterbewegung} with cycloidal trajectories \textit{without} magnetic
fields.",0607218v2
2004-01-26,Numerical Models of Spin-Orbital Coupling in Neutron Star Binaries,"We present a new numerical scheme for solving the initial value problem for
quasiequilibrium binary neutron stars allowing for arbitrary spins. We
construct sequences of circular-orbit binaries of varying separation, keeping
the rest mass and circulation constant along each sequence. The spin angular
frequency of the stars is shown to vary along the sequence, a result that can
be derived analytically in the PPN limit. This spin effect, in addition to
leaving an imprint on the gravitational waveform emitted during binary
inspiral, is measurable in the electromagnetic signal if one of the stars is a
pulsar visible from Earth.",0401104v1
2008-09-30,Quantum pumping and rectification effects in Aharonov-Bohm-Casher ring-dot systems,"We study the time-dependent transport of charge and spin through a
ring-shaped region sequentially coupled to a weakly interacting quantum dot in
the presence of an Aharonov-Bohm flux and spin-orbit interaction. The
time-dependent modulation of the spin-orbit interaction, or of the
corresponding Aharonov-Casher flux, together with the modulation of the
dot-level induces an electrically pumped spin current even in absence of a
charge current. The results beyond the adiabatic regime show that an additional
rectification current proportional to \cos(\phi), being \phi the relative phase
between the time varying parameters, is generated. We discuss the relevance of
such term in connection with recent experiments on out-of-equilibrium quantum
dots.",0809.5246v1
2009-04-06,Multipole decomposition of LDA+$U$ energy and its application to actinides compounds,"A general reformulation of the exchange energy of $5f$-shell is applied in
the analysis of the magnetic structure of various actinides compounds in the
framework of LDA+U method. The calculations are performed in an efficient
scheme with essentially only one free parameter, the screening length. The
results are analysed in terms of different polarisation channels, due to
different multipoles. Generally it is found that the spin-orbital polarisation
is dominating. This can be viewed as a strong enhancement of the spin-orbit
coupling in these systems. This leads to a drastic decrease in spin
polarisation, in accordance with experiments. The calculations are able to
correctly differentiate magnetic and non-magnetic Pu system. Finally, in all
magnetic systems a new multipolar order is observed, whose polarisation energy
is often larger in magnitude than that of spin polarisation.",0904.0742v5
2010-02-24,Effects of impurities in noncentrosymmetric superconductors,"Effects of disorder on superconducting properties of noncentrosymmetric
compounds are discussed. Elastic impurity scattering, even for scalar
impurities, leads to a strongly anisotropic mixing of the electron states in
the bands split by the spin-orbit coupling. We focus on the calculation of the
critical temperature, the upper critical field, and the spin susceptibility. It
is shown that the impurity effects on the critical temperature are similar to
those in multi-band centrosymmetric superconductors, in particular, Anderson's
theorem holds for isotropic singlet pairing. In contrast, scalar impurities
affect the spin susceptibility in the same way as spin-orbit impurities do in
centrosymmetric superconductors. Another peculiar feature is that in the
absence of inversion symmetry scalar disorder can mix singlet and triplet
pairing channels. This leads to significant deviations of the upper critical
field from the predictions of the Werthamer-Helfand-Hohenberg theory in the
conventional centrosymmetric case.",1002.4639v1
2010-11-11,Semiconductor quantum ring as a solid-state spin qubit,"The implementation of a spin qubit in a quantum ring occupied by one or a few
electrons is proposed. Quantum bit involves the Zeeman sublevels of the highest
occupied orbital. Such a qubit can be initialized, addressed, manipulated, read
out and coherently coupled to other quantum rings. An extensive discussion of
relaxation and decoherence is presented. By analogy with quantum dots, the spin
relaxation times due to spin-orbit interaction for experimentally accessible
quantum ring architectures are calculated. The conditions are formulated under
which qubits build on quantum rings can have long relaxation times of the order
of seconds. Rapidly improving nanofabrication technology have made such ring
devices experimentally feasible and thus promising for quantum state
engineering.",1011.2540v1
2010-11-26,Spin-orbit interaction and asymmetry effects on Kondo ridges at finite magnetic field,"We study electron transport through a serial double quantum dot with Rashba
spin-orbit interaction (SOI) and Zeeman field of amplitude B in presence of
local Coulomb repulsion. The linear conductance as a function of a gate voltage
Vg equally shifting the levels on both dots shows two B=0 Kondo ridges which
are robust against SOI as time-reversal symmetry is preserved. Resulting from
the crossing of a spin-up and a spin-down level at vanishing SOI two additional
Kondo plateaus appear at finite B. They are not protected by symmetry and
rapidly vanish if the SOI is turned on. Left-right asymmetric level-lead
couplings and detuned on-site energies lead to a simultaneous breaking of
left-right and bonding-anti-bonding state symmetry. In this case the finite-B
Kondo ridges in the Vg-B plane are bent with respect to the Vg-axis. For the
Kondo ridge to develop different level renormalizations must be compensated by
adjusting B.",1011.5916v2
2012-02-09,Interlayer magnetic frustration driven quantum spin disorder in honeycomb compound In$_{3}$Cu$_{2}$VO$_{9}$,"We present electronic and magnetic properties of a honeycomb compound
In$_{3}$Cu$_{2}$VO$_{9}$ in this paper. We find that the parent phase is a
charge transfer insulator with an energy gap of about 1.5 eV. Singly occupied
d$_{3z^{2}-r^{2}}$ electrons of copper ions contribute an $S$ = 1/2 spin, while
vanadium ions show nonmagnetism. Oxygen 2$p$ orbitals hybridizing with a small
fraction of Cu 3$d$ orbitals dominate the density of states near $E_{F}$. The
planar nearest-neighbor, next-nearest-neighbor and interplane superexchange
couplings of Cu spins are $J_{1}$ $\approx$ 16.2 meV, $J_{2}$ $\approx$ 0.3 meV
and $J_{z}$ $\approx$ 1.2 meV, suggesting a low-dimensional antiferromagnet
\cite{Sondhi10}. We propose that the magnetic frustration along the c-axis
leads to a quantum spin disorder in In$_{3}$Cu$_{2}$VO$_{9}$, in accordance
with the recent experiments. {abstract}",1202.1861v3
2012-07-03,Approximate relativistic bound state solutions of the Tietz-Hua rotating oscillator for any -state,"Approximate analytic solutions of the Dirac equation with Tietz-Hua (TH)
potential are obtained for arbitrary spin-orbit quantum number using the
Pekeris approximation scheme to deal with the spin-orbit coupling terms In the
presence of exact spin and pseudo-spin (pspin) symmetric limitation, the bound
state energy eigenvalues and associated two-component wave functions of the
Dirac particle moving in the field of attractive and repulsive TH potential are
obtained using the parametric generalization of the Nikiforov-Uvarov (NU)
method. The cases of the Morse potential, the generalized Morse potential and
non-relativistic limits are studied.",1207.0675v1
2012-07-25,Full magnetoelectric response of Cr2O3 from first principles,"The linear magnetoelectric response of Cr2O3 at zero temperature is
calculated from first principles by tracking the change in magnetization under
a macroscopic electric field. Both the spin and the orbital contributions to
the induced magnetization are computed, and in each case the response is
decomposed into lattice and electronic parts. We find that the transverse
response is dominated by the spin-lattice and spin-electronic contributions,
whose calculated values are consistent with static and optical magnetoelectric
measurements. In the case of the longitudinal response, orbital contributions
dominate over spin contributions, but the net calculated longitudinal response
remains much smaller than the experimentally measured one at low temperatures.
We also discuss the absolute sign of the magnetoelectric coupling in the two
time-reversed magnetic domains of Cr2O3.",1207.5873v2
2012-10-10,Rashba spin-orbit interaction in graphene armchair nanoribbons,"We study graphene nanoribbons (GNRs) with armchair edges in the presence of
Rashba spin-orbit interaction (RSOI). We impose the boundary conditions on the
tight binding Hamiltonians for bulk graphene with RSOI by means of a sine
transform and study in detail the influence of RSOI on the spectra and the spin
polarization. We show that the spin polarization perpendicular to the GNR
changes sign when reversing the momentum along the GNR if the bands are coupled
by strong RSOI. Furthermore, we derive a linearized approximation to the RSOI
Hamiltonian and find that only the neighboring modes of an energy band have to
be taken into account in order to achieve a good approximation for the same
band. Due to their experimental availability and various proposals for
engineering appropriate RSOI, GNRs with armchair edges are a promising
candidate for possible spintronics applications.",1210.2865v3
2013-03-21,"Co monolayers and adatoms on Pd(100), Pd(111) and Pd(110): Anisotropy of magnetic properties","We investigate to what extent the magnetic properties of deposited
nanostructures can be influenced by selecting as a support different surfaces
of the same substrate material. Fully relativistic ab initio calculations were
performed for Co monolayers and adatoms on Pd(100), Pd(111), and Pd(110)
surfaces. Changing the crystallographic orientation of the surface has a
moderate effect on the spin magnetic moment and on the number of holes in the d
band, a larger effect on the orbital magnetic moment but sometimes a dramatic
effect on the magnetocrystalline anisotropy energy (MAE) and on the magnetic
dipole term T_alpha. The dependence of T_alpha on the magnetization direction
alpha can lead to a strong apparent anisotropy of the spin magnetic moment as
deduced from the X-ray magnetic circular dichroism (XMCD) sum rules. For
systems in which the spin-orbit coupling is not very strong, the T_alpha term
can be understood as arising from the differences between components of the
spin magnetic moment associated with different magnetic quantum numbers m.",1303.5262v1
2013-04-11,Probing the Rashba effect via the induced magnetization around a Kondo impurity,"When a single magnetic adatom is deposited on a surface of a metal, it
affects the charge and spin texture of the electron gas surrounding it. The
screening of the local moment by conduction electrons gives rise to the Kondo
effect. Here we investigate the effect of the Rashba spin orbit coupling on the
local magnetization density of states (LMDOS) around a Cobalt impurity on a
Au(111) surface in a magnetic field. We show that the in-plane component of the
LMDOS is exclusively associated with the Rashba spin orbit interaction. This
observation can be experimentally exploited to confirm the presence of the
Rashba effect on surfaces, such as Au(111), by performing spin-polarized STM
measurements around the Kondo impurity.",1304.3293v1
2013-07-30,Theory of quasiparticle scattering interference on the surface of topological superconductors,"Topological superconductors, such as noncentrosymmetric superconductors with
strong spin-orbit coupling, exhibit protected zero-energy surface states, which
possess an intricate helical spin structure. We show that this nontrival spin
character of the surface states can be tested experimentally from the absence
of certain backscattering processes in Fourier-transform scanning tunneling
measurements. A detailed theoretical analysis is given of the quasiparticle
scattering interference on the surface of both nodal and fully gapped
topological superconductors with different crystal point-group symmetries. We
determine the universal features in the interference patterns resulting from
magnetic and nonmagnetic scattering processes of the surface quasiparticles. It
is shown that Fourier-transform scanning tunneling spectroscopy allows us to
uniquely distinguish among different types of topological surface states, such
as zero-energy flat bands, arc surface states, and helical Majorana modes,
which in turn provides valuable information on the spin and orbital pairing
symmetry of the bulk superconducting state.",1307.7873v2
2013-10-04,Influence of Dielectric Environment on Role of Spin-Orbit Interaction for Image Potentials,"We present a formalism for calculating the image potential for a
two-dimensional electron gas (2DEG) with Rashba spin-orbit interaction (SOI) as
well as for a 2D topological insulator (TI). The formalism is further
generalized for including the Coulomb coupled multiple layers. Roles of broken
inversion symmetry near the surface and the dielectric environment are
investigated by using a surface-response function. The insignificant role of
SOI in 2DEG is dramatically enhanced in TI by selecting a small relative
permittivity $\epsilon_b$ for the dielectric environment. Manipulating
$\epsilon_b$ is proven to provide an efficient way to drive electrons with
opposite spins into two different integral quantum Hall states. The prediction
made in this paper is expected to be experimentally observable for a 2DTI
system, such as Bi$_2$Se$_3$, with a helical spin behavior and a dominant
linear Rashba SOI-like term in the energy dispersion.",1310.1332v1
2014-02-18,Two-dimensional time-reversal-invariant topological superconductivity in a doped quantum spin Hall insulator,"Time-reversal-invariant topological superconductors have a full paring gap in
the bulk and gapless Majorana states at the edge or on the surface. Here, we
theoretically propose topological superconductivity in a doped quantum spin
Hall insulator. We study the pairing symmetry of doped Sn$X$ film within a
two-orbital model, and show that it realizes a topological superconductor when
the intraorbital attractive interaction is stronger than the interorbital
interaction, which is generic for a doped quantum spin Hall insulator with
strong spin-orbit coupling. Edge channels are studied in a tight-binding model
numerically. Finally, we discuss the possible topological superconductivity in
Sn$X$ film by comparing to $3d$ superconductivity in bulk Sn.",1402.4433v3
2015-06-17,Orthogonal Cherenkov sound in spin-orbit coupled systems,"Conventionally the Cherenkov sound is governed by {\it orbital} degrees of
freedom and is excited by {\it supersonic} particles. Additionally, it usually
has a {\it forward} nature with a conic geometry known as the Cherenkov cone
whose axis is oriented {\it along} the {\it supersonic} particle motion. Here
we predict Cherenkov sound of a unique nature entirely resulting from the
electronic {\it spin} degree of freedom and demonstrate a fundamentally
distinct Cherenkov effect originating from essentially {\it subsonic} electrons
in two-dimensional gases with both Bychkov-Rashba and Dresselhaus spin-orbit
interactions. Specifically, we show that the axis of the conventional {\it
forward} Cherenkov cone gets a nontrivial {\it quarter-turn} and at the same
time the sound distribution strongly localizes around this rotated axis being
now {\it orthogonal} to the {\it subsonic} particle motion. Apart from its
fundamentally appealing nature, the orthogonal Cherenkov sound could have
applications in planar semiconductor technology combining spin and acoustic
phenomena to develop, {\it e.g.}, acoustic amplifiers or sound sources with a
flexible spin dependent orientation of the sound propagation.",1506.05358v1
2018-11-15,Boltzmann transport from density matrix theory: interband and intraband coherences,"To account for the anomalous/spin Hall conductivities and spin-orbit torque
in the zeroth order of electron scattering time in strongly spin-orbit coupled
systems, the Boltzmann transport theory in the case of weak disorder-potentials
has been augmented by adding some interband coherence effects by hand. In this
work these interband coherence terms are derived systematically from analyzing
the equation of motion of the single-particle density matrix in the Bloch
representation. Interband elements of the out-of-equilibrium density matrix are
related to only one part of interband-coherence responses. Disorder-induced
off-diagonal elements of the equilibrium density matrix are shown to be vital
in producing the coordinate-shift anomalous driving term in the modified
Boltzmann equation. Moreover, intraband coherence is inherent in the Boltzmann
equation, whose contribution to anomalous/spin Hall conductivities is
parametrically the same as the interband coherence.",1811.06204v1
2020-07-04,Impurities in 3D quadratic band-touching Luttinger semimetals : Friedel and RKKY oscillations,"We investigate the response of 3D Luttinger semimetals to localized charge
and spin impurities as a function of doping. The strong spin-orbit coupling of
these materials strongly influences the Friedel oscillations and RKKY
interactions. This can be seen at short distances with an $1/r^4$ divergence of
the responses, and anisotropic behavior. Certain of the spin-orbital signatures
are robust to temperature, even if the charge and spin oscillations are smeared
out, and give an unusual diamagnetic Pauli susceptibility. We compare our
results to the experimental literature on the bismuth-based half-Heuslers such
as YPtBi and on the pyrochlore iridate Pr$_2$Ir$_2$O$_7$.",2007.02046v2
2016-11-23,Symmetry enforced line nodes in unconventional superconductors,"We classify line nodes in superconductors with strong spin-orbit interactions
and time-reversal symmetry, where the latter may include non-primitive
translations in the magnetic Brillouin zone to account for coexistence with
antiferromagnetic order. We find four possible combinations of irreducible
representations of the order parameter on high symmetry planes, two of which
allow for line nodes in pseudo-spin triplet pairs and two that exclude
conventional fully gapped pseudo-spin singlet pairs. We show that the former
can only be realized in the presence of band-sticking degeneracies, and verify
their topological stability using arguments based on Clifford algebra
extensions. Our classification exhausts all possible symmetry protected line
nodes in the presence of spin-orbit coupling and a (generalized) time-reversal
symmetry. Implications for existing non-symmorphic and antiferromagnetic
superconductors are discussed.",1611.07590v3
2011-11-09,Low-density molecular gas of tightly-bound Rashba-Dresselhaus fermions,"We study interacting Rashba-Dresselhaus fermions in two spatial dimensions.
First, we present a new exact solution to the two-particle pairing problem of
spin-orbit-coupled fermions for arbitrary Rashba and Dresselhaus spin-orbit
interactions. An exact molecular wave function and the Green function are
explicitly derived along with the binding energy and the spectrum of the
molecular state. In the second part, we consider a thermal Boltzmann gas of
fermionic molecules and compute the time-of-flight velocity and spin
distributions for a single fermion in the gas. We show that the pairing
signatures can be observed already in the first-moment expectation values, such
as time-of-flight density and spin profiles.",1111.2340v2
2014-06-06,Relativistic Particle and Relativistic Fluids: Magnetic Moment and Spin-Orbit Interactions,"We consider relativistic charged particle dynamics and relativistic
magnetohydrodynamics using symplectic structures and actions given in terms of
co-adjoint orbits of the Poincar\'e group. The particle case is meant to
clarify some points such as how minimal coupling (as defined in text) leads to
a gyromagnetic ratio of $2$, and to set the stage for fluid dynamics. The
general group-theoretic framework is further explained and is then used to set
up Abelian magnetohydrodynamics including spin effects. An interesting new
physical effect is precession of spin density induced by gradients in pressure
and energy density. The Euler equation (the dynamics of the velocity field) is
also modified by gradients of the spin density.",1406.1551v1
2018-01-23,The dominancy of damping like torque for the current induced magnetization switching in Pt/Co/W multilayers,"Two classes of spin-orbit coupling (SOC) mechanisms have been considered as
candidate sources for the spin orbit torque (SOT): the spin Hall Effect (SHE)
in heavy metals with strong SOC and the Rashba effect arising from broken
inversion symmetry at material surfaces and interfaces. In this work, we have
investigated the SOT in perpendicularly magnetized Pt/Co/W films, which is
compared with the results in Pt/Co/AlOx films. Theoretically, in the case of
the asymmetric structure of trilayers with opposite sign of spin Hall angle,
both damping like torque and field like torque due to the SHE and the Rashba
effect will be enhanced. Using the harmonic measurements, we have characterized
the effective fields corresponding to the damping like torque and the field
like torque, but we have found the dominancy of damping like torque in the
Pt/Co/W films. It is much different from the results in the Pt/Co/AlOx films,
in which both the damping like torque and the field like torque are strong.",1801.07408v1
2018-01-30,Strain engineering of the silicon-vacancy center in diamond,"We control the electronic structure of the silicon-vacancy (SiV) color-center
in diamond by changing its static strain environment with a
nano-electro-mechanical system. This allows deterministic and local tuning of
SiV optical and spin transition frequencies over a wide range, an essential
step towards multi-qubit networks. In the process, we infer the strain
Hamiltonian of the SiV revealing large strain susceptibilities of order 1
PHz/strain for the electronic orbital states. We identify regimes where the
spin-orbit interaction results in a large strain suseptibility of order 100
THz/strain for spin transitions, and propose an experiment where the SiV spin
is strongly coupled to a nanomechanical resonator.",1801.09833v2
2018-09-07,Gravitational self-force corrections to gyroscope precession along circular orbits in the Kerr spacetime,"We generalize to Kerr spacetime previous gravitational self-force results on
gyroscope precession along circular orbits in the Schwarzschild spacetime. In
particular we present high order post- Newtonian expansions for the gauge
invariant precession function along circular geodesics valid for arbitrary Kerr
spin parameter and show agreement between these results and those derived from
the full post-Newtonian conservative dynamics. Finally we present strong field
numerical data for a range of the Kerr spin parameter, showing agreement with
the GSF-PN results, and the expected lightring divergent behaviour. These
results provide useful testing benchmarks for self- force calculations in Kerr
spacetime, and provide an avenue for translating self-force data into the
spin-spin coupling in effective-one-body models.",1809.02516v1
2019-07-25,Circular polarization reversal of half-vortex cores in polariton condensates,"Vortices are topological objects carrying quantized orbital angular momentum
and have been widely studied in many physical systems for their applicability
in information storage and processing. In systems with spin degree of freedom
the elementary excitations are so called half-vortices, carrying a quantum
rotation only in one of the two spin components. We study the spontaneous
formation and stability of localized such half-vortices in semiconductor
microcavity polariton condensates, non-resonantly excited by a linearly
polarized ring-shaped pump. The TE-TM splitting of optical modes in the
microcavity system leads to an effective spin-orbit coupling, resulting in
solutions with discrete rotational symmetry. The cross-interaction between
different spin components provides an efficient method to realize all-optical
half-vortex core switching inverting its circular polarization state. This
switching can be directly measured in the polarization resolved intensity in
the vortex core region and it can also be applied to higher order half-vortex
states.",1907.10974v2
2020-01-25,Spin and charge fluctuations in the two-band Hubbard model,"A model of CuO$_2$ planes of cuprate perovskites, containing $d_{x^2-y^2}$
copper orbitals and symmetric combinations of oxygen $p_\sigma$ orbitals, is
investigated using the strong coupling diagram technique. This approach allows
one to take into account the interactions of carriers with spin and charge
fluctuations of all ranges. Derived equations for Green's function are
self-consistently solved for the set of parameters corresponding to hole- and
electron-doped cuprates. It is shown that the mentioned interactions lead to
the appearance of spin polarons -- bound states of carriers with spin
excitations, which show themselves as sharp peaks of the density of states and
spectral functions at the Fermi level. Hole and electron doping are strongly
asymmetric. This, in particular, manifests itself in the antiferromagnetic
response for the electron-doped case and in an incommensurate magnetic ordering
for hole doping. In the latter case, the incommensurability parameter grows
with doping. The double occupancy shows that the electron-doped system retains
strong correlations up to the concentration 0.23, while for hole doping the
correlations decay rapidly. These results are in agreement with experimental
observations in cuprates.",2001.09270v1
2020-12-14,Tunable Electronic Properties and Large Rashba Splittings Found in Few-Layer Bi$_2$Se$_3$/PtSe$_2$ Van der Waals Heterostructures,"We use first-principles calculations to show that van der Waals (vdW)
heterostructures consisting of few-layer Bi$_2$Se$_3$ and PtSe$_2$ exhibit
electronic and spintronics properties that can be tuned by varying the
constituent layers. Type-II band alignment with layer-tunable band gaps and
type-III band alignment with spin-splittings have been found. Most noticeably,
we reveal the coexistence of Rashba-type spin-splittings (with large
$\alpha_{\rm R}$ parameters) in both the conduction and valence band stemming
from few-layer Bi$_2$Se$_3$ and PtSe$_2$, respectively, which has been
confirmed by spin-texture plots. We discuss the role of inversion symmetry
breaking, changes in orbital hybridization and spin-orbit coupling in altering
electronic dispersion near the Fermi level. Since low-temperature growth
mechanisms are available for both materials, we believe that few-layer
Bi$_2$Se$_3$/PtSe$_2$ vdW heterostructures are feasible to realize
experimentally, offering great potential for electronic and spintronics
applications.",2012.07445v1
2012-05-20,Dimensionality Driven Spin-Flop Transition in Layered Iridates,"Using resonant x-ray diffraction, we observe an easy c-axis collinear
antiferromagnetic structure for the bilayer Sr$_3$Ir$_2$O$_7$, a significant
contrast to the single layer Sr$_2$IrO$_4$ with in-plane canted moments. Based
on a microscopic model Hamiltonian, we show that the observed spin-flop
transition as a function of number of IrO$_2$ layers is due to strong
competition among intra- and inter-layer bond-directional pseudo-dipolar
interactions of the spin-orbit entangled $J_{eff}$=1/2 moments. With this we
unravel the origin of anisotropic exchange interactions in a Mott insulator in
the strong spin-orbit coupling regime, which holds the key to the various types
of unconventional magnetism proposed in 5$d$ transition metal oxides.",1205.4381v1
2018-06-26,Spin and valley manipulation in single and double electrostatic silicene quantum dots,"We study single and double quantum dots defined electrostatically within
silicene. The spin-valley structure of the confined single- and two-electron
system is determined and the effects of the intervalley scattering induced by
the crystal edge and the Coulomb interaction are quantified. The states in a
double quantum system are discussed in the context of the spatial symmetry of
the single- and two-electron extended orbitals. We determine the charge, spin
and valley transitions times induced by alternate electric fields of the
microwave frequency. The valley transition times can be controlled by several
orders of magnitude by the confinement potential. Also, the spin transition
rates can be enhanced by orders of magnitude by the coupling of the bonding and
antibonding orbitals mediated by the Rashba interaction.",1806.10012v1
2018-08-29,"Spin-orbit-stable type-II nodal line band crossing in n-doped monolayer MoX2 (X=S,Se,Te)","1H-phase monolayer transition-metal dichalcogenides have spin-split
electronic band structures near the K(K') point due to strong spin-orbit
coupling and intrinsic inversion symmetry breaking. In case of the monolayer
MoX2 (X=S, Se, Te), the spin-split conduction bands cross near the K(K') point.
We show that the band crossing occurs not only along the high symmetry
directions, but also along arbitrary directions due to a mirror reflection
symmetry of the monolayer. As a result, n-doped monolayer MoX2 is a
two-dimensional type-II nodal-line material.",1808.09585v2
2019-01-30,Excited states of molecules in strong uniform and non-uniform magnetic fields,"This paper reports an implementation of Hartree-Fock linear response with
complex orbitals for computing electronic spectra of molecules in a strong
external magnetic fields. The implementation is completely general, allowing
for spin-restricted, spin-unrestricted, and general two-component reference
states. The method is applied to small molecules placed in strong uniform and
non-uniform magnetic fields of astrochemical importance at the Random Phase
Approximation level of theory. For uniform fields, where comparison is
possible, the spectra are found to be qualitatively similar to those recently
obtained with equation of motion coupled cluster theory. We also study the
behaviour of spin-forbidden excitations with progressive loss of spin symmetry
induced by non-uniform magnetic fields. Finally, the equivalence of length and
velocity gauges for oscillator strengths when using complex orbitals is
investigated and found to hold numerically.",1901.11086v1
2019-02-14,Breakdown of the Hebel-Slichter effect in superconducting graphene due to the emergence of Yu-Shiba-Rusinov states at magnetic resonant scatterers,"Employing analytical methods and quantum transport simulations we investigate
the relaxation of quasiparticle spins in graphene proximitized by an $s$-wave
superconductor in the presence of resonant magnetic and spin-orbit active
impurities. Off resonance, the relaxation increases with decreasing temperature
when electrons scatter off magnetic impurities---the Hebel-Slichter
effect---and decreases when impurities have spin-orbit coupling. This distinct
temperature~dependence (not present in the normal state) uniquely discriminates
between the two scattering mechanisms. However, we show that the Hebel-Slichter
picture breaks down at resonances. The emergence of Yu-Shiba-Rusinov bound
states within the superconducting gap redistributes the spectral weight away
from magnetic resonances. The result is opposite to the Hebel-Slichter
expectation: the spin relaxation decreases with decreasing temperature. Our
findings hold for generic $s$-wave superconductors with resonant magnetic
impurities, but also, as we show, for resonant magnetic Josephson junctions.",1902.05474v2
2019-12-27,Nuclear spin relaxation rate near the disorder-driven quantum critical point in Weyl fermion systems,"Disorder such as impurities and dislocations in Weyl semimetals (SMs) drives
a quantum critical point (QCP) where the density of states at the Weyl point
gains a non-zero value. Near the QCP, the asymptotic low energy singularities
of physical quantities are controlled by the critical exponents $\nu$ and $z$.
The nuclear spin-lattice relaxation rate, which originates from the hyperfine
coupling between a nuclear spin and long-range orbital currents in Weyl fermion
systems, shows intriguing critical behavior. Based on the self-consistent Born
approximation for impurities, we study the nuclear spin-lattice relaxation rate
$1/T_1$ due to the orbital currents in disordered Weyl SMs. We find that
$(T_1T)^{-1}\sim E^{2/z}$ at the QCP where $E$ is the maximum of temperature
$T$ and chemical potential $\mu(T)$ relative to the Weyl point. This scaling
behavior of $(T_1T)^{-1}$ is also confirmed by the self-consistent $T$-matrix
approximation, where a remarkable temperature dependence of $\mu(T)$ could play
an important role. We hope these results of $(T_1T)^{-1}$ will serve as an
impetus for exploration of the disorder-driven quantum criticality in Weyl
materials.",1912.11996v1
2020-10-10,Paramagnetic effects of j-electron superconductivity and application to UTe2,"The putative spin-triplet superconductor UTe2 has an Ising-like magnetic
anisotropy, indicating the Cooper pair spins parallel to the easy-axis.
However, the upper critical field for the hard-axis direction is much larger
than that for the easy-axis, implying the strong suppression of the Pauli
depairing effect even for the hard-axis direction. This observation is
consistent with the recent NMR measurements which show the tiny decrease of the
Knight shift below the transition temperature Tc for hard-axis magnetic fields.
We clarify that these behaviors are naturally understood as a result of
multi-orbital f -electron bands with total angular momentum j=5/2. Taking into
account spin-orbit couplings for an orthorhombic structure, we demonstrate that
for hard-axis magnetic fields, the decrease of the spin susceptibility below Tc
and the Pauli depairing effect are strongly suppressed.",2010.05112v3
2016-12-20,Spintronics in half-passivated graphene,"In this thesis, I propose a practical way to stabilize half passivated
graphene (graphone). I show that the dipole moments induced by a
hexagonal-boron nitride (h-BN) substrate on graphene stabilize the hydrogen
atoms on one sublattice of the graphene layer and suppress the migration of the
adsorbed hydrogen atoms. I also present the substrate effect of h-BN that
reduces distortion induced by fluorination of graphene and stabilizes
half-passivated graphene in a single sublattice. Then using spin-polarized
density functional calculations I investigate magnetic properties of graphone.
I show the system has different magnetic order which can be described by either
super-exchange or double exchange mechanisms depending on the type the of add
atom. The hybridization of graphene changes from $sp^2$- to $sp^3$- type
hybridization due to the buckling induced by passivation. The change in
hybridization together with add-atom orbitals induces a fairly large spin orbit
coupling (SOC). Based upon first principle spin-polarized density of states
calculations, I show that the graphone obtained in different graphene/h-BN
heterostructures exhibits a half metallic state. I propose to use this exotic
material for spin valve systems and other spintronics devices.",1612.06846v1
2017-07-18,Large Magnetic Anisotropy of an Iron-Porphyrin Complex on Metal Substrate,"Single magnetic atoms or molecules with large single-ion magnetic anisotropy
are highly desired for future applications in high-density data storage and
quantum computation. Here we have synthesized an Fe-porphyrin complex on
Au(111) substrate in a controlled way, and revealed large magnetic anisotropy
energy of more than 15 meV by low-temperature scanning tunneling microscopy and
spectroscopy. Two magnetic states with opposite spin directions are
discriminated by inelastic electron tunneling spectroscopy in varied magnetic
field, and are found to have long spin lifetimes. First-principle calculations
reveal that the weak ligand filed in this complex keeps the Fe atom in a
high-spin state and preserves its large orbital angular momentum, which gives
rise to an easy-axis perpendicular to the molecular plane and large magnetic
anisotropy energy by spin-orbit coupling.",1707.05434v1
2019-04-30,Ferromagnetism and Spin-Valley liquid states in Moiré Correlated Insulators,"Motivated by the recent observation of evidences of ferromagnetism in
correlated insulating states in systems with Moir\'{e} superlattices, we study
a two-orbital quantum antiferromagnetic model on the triangular lattice, where
the two orbitals physically correspond to the two valleys of the original
graphene sheet. For simplicity this model has a SU(2)$^s$$\otimes$SU(2)$^v$
symmetry, where the two SU(2) symmetries correspond to the rotation within the
spin and valley space respectively. Through analytical argument, Schwinger
boson analysis and also DMRG simulation, we find that even though all the
couplings in the Hamiltonian are antiferromagnetic, there is still a region in
the phase diagram with fully polarized ferromagnetic order. We argue that a
Zeeman field can drive a metal-insulator transition in our picture, as was
observed experimentally. We also construct spin liquids and topological ordered
phases at various limits of this model. Then after doping this model with extra
charge carriers, the system most likely becomes spin-triplet/valley-singlet
$d+id$ topological superconductor as was predicted previously.",1905.00033v2
2019-05-29,Antiferromagnetic Kitaev Interactions in Polar Spin-Orbit Mott Insulators,"A bond-directional anisotropic exchange interaction, called the Kitaev
interaction, is a promising route to realize quantum spin liquids. The Kitaev
interactions were found in Mott insulators with the strong spin-orbit coupling,
in the presence of quantum interference between indirect electron transfers.
Here we theoretically propose a different scenario by introducing a polar
structural asymmetry that unbalances the quantum interference. We show that the
imbalance activates additional exchange processes and gives rise to a dominant
antiferromagnetic Kitaev interaction, in stark contrast to the conventional
ferromagnetic ones. We demonstrate by ab initio calculations that polar Ru
trihalides with multiple anions, $\alpha$-RuH$_{3/2}X_{3/2}$ ($X$=Cl and Br),
exhibit the antiferromagnetic Kitaev interaction whose magnitude is several
times larger compared to existing candidates. Our proposal opens the way for
materializing the Kitaev spin liquids in unexplored parameter regions.",1905.12139v1
2021-02-18,Inhomogeneous Knight shift in vortex cores of superconducting FeSe,"We report $^{77}$Se NMR data in the normal and superconducting states of a
single crystal of FeSe for several different field orientations. The Knight
shift is suppressed in the superconducting state for in-plane fields, but does
not vanish at zero temperature. For fields oriented out of the plane, little or
no reduction is observed below $T_c$. These results reflect spin-singlet
pairing emerging from a nematic state with large orbital susceptibility and
spin-orbit coupling. The spectra and spin-relaxation rate data reveal
electronic inhomogeneity that is enhanced in the superconducting state,
possibly arising from enhanced density of states in the vortex cores. Despite
the spin polarization of these states, there is no evidence for
antiferromagnetic fluctuations.",2102.09090v1
2021-06-30,Design and realization of topological Dirac fermions on a triangular lattice,"Large-gap quantum spin Hall insulators are promising materials for
room-temperature applications based on Dirac fermions. Key to engineer the
topologically non-trivial band ordering and sizable band gaps is strong
spin-orbit interaction. Following Kane and Mele's original suggestion, one
approach is to synthesize monolayers of heavy atoms with honeycomb coordination
accommodated on templates with hexagonal symmetry. Yet, in the majority of
cases, this recipe leads to triangular lattices, typically hosting metals or
trivial insulators. Here, we conceive and realize ""indenene"", a triangular
monolayer of indium on SiC exhibiting non-trivial valley physics driven by
local spin-orbit coupling, which prevails over inversion-symmetry breaking
terms. By means of tunneling microscopy of the 2D bulk we identify the quantum
spin Hall phase of this triangular lattice and unveil how a hidden honeycomb
connectivity emerges from interference patterns in Bloch $p_x \pm ip_y$-derived
wave functions.",2106.16025v1
2021-07-14,Magnetic order and its interplay with structure phase transition in van der Waals ferromagnet VI$_3$,"Van der Waals magnet VI$_3$ demonstrates intriguing magnetic properties that
render it great for use in various applications. However, its microscopic
magnetic structure has not been determined yet. Here, we report neutron
diffraction and susceptibility measurements in VI$_3$ that revealed a
ferromagnetic order with the moment direction tilted from the $c$-axis by
~36{\deg} at 4 K. A spin reorientation accompanied by a structure distortion
within the honeycomb plane is observed at a temperature of ~27 K, before the
magnetic order completely disappears at $T_C$ = 50 K. The refined magnetic
moment of ~1.3 $\mu_B$ at 4 K is considerably lower than the fully ordered spin
moment of 2 $\mu_B$/ V$^{3+}$, suggesting the presence of a considerable
orbital moment antiparallel to the spin moment and strong spin-orbit coupling
in VI$_3$. This results in strong magnetoelastic interactions that make the
magnetic properties of VI$_3$ easily tunable via strain and pressure.",2107.06443v1
2021-09-12,Spin-polarized zero-bias peak from a single magnetic impurity at an s-wave superconductor: first-principles study,"Magnetic impurities at surfaces of superconductors can induce bound states
referred to as Yu-Shiba-Rusinov (YSR) states within superconducting gaps.
Understanding of YSR states with spin-orbit coupling (SOC) plays a pivotal role
in studies of Majorana zero modes. Spin polarization of a zero-bias peak (ZBP)
is used to determine its topological nature. Here we investigate the YSR states
of single magnetic impurities at the surface of Pb using the fully relativistic
first-principles simulations including band structure of Pb and five 3$d$
orbitals of the impurity in the superconducting state. We show that for single
Fe and Co impurities, strong SOC can induce a ZBP with rotation of the impurity
magnetic moment and that the ZBP has large spin polarization in contrast to
effective model studies. Conditions for a ZBP from a single magnetic impurity
are discussed. Our results are relevant to longer atomic chains considering
their canting and noncollinear magnetism.",2109.05511v1
2021-11-11,Edge states in proximitized graphene ribbons and flakes in a perpendicular magnetic field: emergence of lone pseudohelical pairs and pure spin-current states,"We investigate the formation of edge states in graphene ribbons and flakes
with proximity induced valley-Zeeman and Rashba spin-orbit couplings in the
presence of a perpendicular magnetic field $B$. Two types of edges states
appear in the spin-orbit gap at the Fermi level at zero field: strongly
localized pseudohelical (intervalley) states and weakly localized intravalley
states. We show that if the magnetic field is stronger than a crossover field
$B_c$, which is a few mT for realistic systems such as graphene/WSe$_2$, only
the pseudohelical edge states remain in zigzag graphene ribbons; the
intravalley states disappear. The crossover is directly related to the closing
and reopening of the bulk gap formed between nonzero Landau levels. Remarkably,
in finite flakes the pseudohelical states undergo perfect reflection at the
armchair edges if $B > B_c$, forming standing waves at the zigzag edges. These
standing waves comprise two counterpropagating pseudohelical states, so while
they carry no charge current, they do carry (pure) spin current.",2111.06369v1
2022-03-23,Nonlinear optical Hall effect of few-layered NbSe2,"NbSe$_2$ is one of metallic two-dimensional (2D) transition-metal
dichalcogenide (TMDC) materials. Because of broken crystal inversion symmetry,
large spin splitting is induced by Ising-type spin-orbit coupling in
odd-number-layered NbSe$_2$, but absent for even-number-layered NbSe$_2$ with
the inversion symmetry. In this paper, we numerically calculate nonlinear
optical charge and spin Hall conductivities of few-layered NbSe$_2$ based on an
effective tight-binding model which includes $d_{z^2}$, $d_{x^2-y^2}$ and
$d_{xy}$ orbitals of Nb atom. We show that the nonlinear optical Hall
conductivity for second harmonic generation (SHG) process has nonvanishing
value in odd-number-layered NbSe$_2$. Also, we provide nonlinear optical
selection rule in few-layered NbSe$_2$ and their polarization dependences. In
further, for even-number-layered case, the nonlinear optical Hall currents can
be generated by applying electric fields which break inversion symmetry. We
also discuss that the nonlinear optical Hall effect is expected to occur in
TMDC materials in general. Thus, our results will serve to design potential
opt-spintronics devices based on 2D materials to generate the spin Hall current
by SHG.",2203.12767v1
2022-05-22,Rashba spin-orbit interaction induced modulation of magnetic anisotropy,"In past few decades, Rashba spin-orbit coupling (SOC) has been successfully
employed for the emergence of exotic phenomena at the quantum oxide interfaces.
In these systems, the combined effect of charge transfer, broken symmetries and
SOC yields intriguing interfacial magnetism and transport properties. Here, we
provide an insight to control and tune interfacial phenomena in CaMnO3/CaIrO3
based 3d-5d oxide heterostructures by the charge transfer driven Rashba SOC.
Anomalous Hall effect in these canted antiferromagnetic heterostructures
originates from the intrinsic contribution associated with the topology of the
electronic band structure and it is mostly confined to the interface. Rashba
SOC reconstructs the Berry curvature and enhances the anomalous Hall
conductivity by two orders of magnitude. From the anisotropy magnetoresistance
measurements we demonstrate that Rashba SOC is instrumental in tailoring
magnetic anisotropy where magnetization easy-axis rotates from the out-of-plane
direction to the in-plane direction. The ability to tune Rashba SOC and
resulting competing magnetic anisotropy provides a route to manipulate
electronic band structure for the origin of non-trivial spin texture useful for
spin-orbitronics applications.",2205.10859v1
2022-06-21,Field-induced Kitaev multipolar liquid in spin-orbit coupled $d^{2}$ honeycomb Mott insulators,"The Kitaev model, characterized by bond-dependent Ising spin interactions
among spin-orbit entangled dipole moments in Mott insulators, offered a new
approach to quantum spin liquids. Motivated by another type of bond-dependent
interaction among quadrupole moments in $5d^2$ Mott insulators, we provide a
microscopic route to uncover the Kitaev multipolar liquid, featuring
fractionalized excitations out of non-Kramers doublets carrying multipole
moments. The key ingredient is the magnetic field that allows for
bond-anisotropic quadrupole-octupole interactions via mixing with the excited
triplet states. The conditions to realize signatures of this phase in real
materials are also discussed.",2206.10647v2
2022-08-03,Chiral Stoner magnetism in Dirac bands,"We argue that Stoner magnetism in bands endowed with Berry curvature is
profoundly influenced by the chiral interaction between Berry's orbital
magnetization and spin chirality density. The key effect is that carriers
moving in the presence of a spin texture see it as a source of a
pseudo-magnetic field coupled to their orbital motion through a chiral
Aharonov-Bohm effect. This interaction favors chiral spin textures such as
skyrmions -- the topologically protected objects with particle-like properties,
stabilized in the ground state. The chiral interaction softens the threshold
for Stoner instability, rendering chiral spin-ordered phases readily accessible
under realistic conditions. We illustrate this effect for a graphene multilayer
model, with magnetization and pseudo-magnetic fields taking different values in
different valleys, yet the results are applicable to generic Stoner magnets.",2208.02051v2
2022-10-06,Superconductivity from electronic interactions and spin-orbit enhancement in bilayer and trilayer graphene,"We discuss a Kohn-Luttinger-like mechanism for superconductivity in Bernal
bilayer graphene and rhombohedral trilayer graphene. Working within the
continuum model description, we find that the screened long-range Coulomb
interaction alone gives rise to superconductivity with critical temperatures
that agree with experiments. We observe that the order parameter changes sign
between valleys, which implies that both materials are valley-singlet,
spin-triplet superconductors. Adding Ising spin-orbit coupling leads to a
significant enhancement in the critical temperature, also in line with
experiment, and the superconducting order parameter shows locking between the
spin and valley degrees of freedom.",2210.02915v3
2023-02-23,Ultrafast laser-induced spin-lattice dynamics in the van der Waals antiferromagnet CoPS3,"CoPS3 stands out in the family of the van der Waals antiferromagnets XPS3
(X=Mn, Ni, Fe, Co) due to the unquenched orbital momentum of the magnetic Co2+
ions which is known to facilitate the coupling of spins to both electromagnetic
waves and lattice vibrations. Here, using a time-resolved magneto-optical
pump-probe technique we experimentally study the ultrafast laser-induced
dynamics of mutually correlated spins and lattice. It is shown that a
femtosecond laser pulse acts as an ultrafast heater and thus results in the
melting of the antiferromagnetic order. At the same time, the resonant pumping
of the 4T1g - 4T2g electronic transition in Co2+ ions effectively changes their
orbital momentum, giving rise to a mechanical force that moves the ions in the
direction parallel to the orientation of their spins, thus generating a
coherent Bg phonon mode at the frequency of about 4.7 THz.",2302.12104v1
2023-03-06,Spin excitation of Co atoms at monatomic Cu chains,"The zero-bias anomaly in conductance spectra of single Co atoms on Cu(111)
observed at $\approx$ 4 K, which has been interpreted as being due to a Kondo
resonance, is strongly modified when the Co atoms are attached to monatomic Cu
chains. Scanning tunneling spectra measured at 340 mK in magnetic fields
exhibit all characteristics of spin-flip excitations. Their dependence on the
magnetic field reveals a magnetic anisotropy and suggests a non-collinear spin
state. This indicates that spin-orbit coupling (SOC), which has so far been
neglected in theoretical studies of Co/Cu(111), has to be taken into account.
According to our density functional theory and multi-orbital quantum Monte
Carlo calculations SOC suppresses the Kondo effect for all studied geometries.",2303.03317v1
2023-09-27,Investigation of magnetic properties of $4f$-adatoms on graphene,"Rare-earth (RE) atoms on top of 2D materials represent an interesting
platform with the prospect of tailoring the magnetic anisotropy for practical
applications. Here, we investigate the ground state and magnetic properties of
selected $4f$-atoms deposited on a graphene substrate in the framework of the
DFT+$U$ approach. The inherent strong spin-orbit interaction in conjunction
with crystal field effects acting on the localized $4f$-shells results in a
substantial magnetic anisotropy energy (tens of meVs), whose angular dependence
is dictated by the $C_{6v}$ symmetry of the graphene substrate. We obtain the
crystal field parameters and investigate spin-flip events via quantum tunneling
of magnetization in the view of achieving a protected quantum-spin behavior.
Remarkably, the large spin and orbital moments of the open $4f$-shells (Dy, Ho
and Tm) generate a strong magneto-elastic coupling which provides more
flexibility to control the magnetic state via the application of external
strain.",2309.15513v1
2023-11-09,Spectroscopy and Annihilation Decay Widths of Charmonium and Bottomonium Excitations,"We study the charmonium ($c\bar{c}$) and bottomonium ($b\bar{b}$) spectra,
using Cornell potential with additional constant potential term in a
non-relativistic framework, with spin-dependent corrections corresponding to
the spin-spin, spin-orbit, and tensor interactions added perturbatively. We
predict the masses of low-lying and excited states of charmonium and
bottomonium up to $n=6$ and $L=2$. We analyze the radial and orbital Regge
trajectories of both the systems and investigate their departure from
linearity. Further, we estimate the wave function at the origin and,
consequently, predict the decay widths of charmonium and bottomonium states
annihilating to leptons and photons. Also, we investigate the effect of scale
dependence of the wave function at the origin and the strong coupling constant
on the predictions of annihilation decay widths. We compare our predictions of
heavy quarkonium spectra and decay widths with experimental results and other
theoretical models.",2311.05274v2
1998-10-21,Ferromagnetic ground state of an orbital degenerate electronic model for transition-metal oxides: exact solution and physical mechanism,"We present an exact ground state solution of a one-dimensional electronic
model for transition-metal oxides in the strong coupling limit. The model
contains doubly degenerated orbit for itinerant electrons and the Hund coupling
between the itinerant electrons and localized spins. The ground state is proven
to be a full ferromagnet for any density of electrons. Our model provides a
rigorous example for metallic ferromagnetism in narrow band systems. The
physical mechanism for ferromagnetism and its relevance to high-dimensional
systems, like R$_{1-x}$X$_x$MnO$_3$, are discussed. Due to the orbital
degeneracy of itinerant electrons, the superexchange coupling can be
ferromagnetic rather than antiferromagnetic in the one-band case.",9810268v1
2010-07-19,An analytical approach for calculating transfer integrals in superexchange coupled dimers,"An analytical expression for the transfer integral HAB between the localized
magnetic orbitals in superexchange-coupled dimers as a function of the type of
atoms and geometry of the molecule has been derived by explicitly including
orbital interactions. It is shown that HAB plays the key role for the magnetic
coupling constant J in understanding magneto-structural correlations. The
reliability and capability of this approach is confirmed by comparison with
numerical electronic structure calculations in the local spin-density
approximation on singly and doubly bridged Cu(II)-dimers with fluorine ligands.
All results can be calculated and understood within the analytical formalism
representing, therefore, a powerful tool for understanding the
magneto-structural correlations and also for constructing magnetic orbitals
analytically.",1007.3107v3
2019-09-13,Anomalous ferromagnetism and magneto-optical Kerr effect in semiconducting double perovskite Ba2NiOsO6 and its (111) (Ba2NiOsO6)/(BaTiO3)10 superlattice,"We carry out a first-principles investigation on magnetism, electronic
structure, magneto-optical effects and topological property of newly grown
cubic double perovskite Ba2NiOsO6 and its (111) (Ba2NiOsO6)/(BaTiO3)10
superlattice, based on the density functional theory with the generalized
gradient approximation (GGA) plus onsite Couloumb interactions. Interestingly,
we find that both structures are rare ferromagnetic (FM) semiconductors with
estimated Curie temperatures of ~150 and 70 K, respectively. The calculated
near-neighbor exchange coupling parameters reveal that the ferromagnetism is
driven by exotic FM coupling between Ni and Os atoms, which is due to the FM
superexchange interaction caused by the abnormally strong hybridization between
the half-filled Nieg and unoccupied Os eg orbitals. The strong spin-orbit
coupling (SOC) on the Os atom is found to not only open the semiconducting gap
but also produce a large antiparallel orbital magnetic moment on the Os atom,
thus reducing the total magnetization from 4.0 uB/f.u.,",1909.05996v1
2018-12-04,Quantum interference in transport through almost symmetric double quantum dots,"We theoretically investigate transport signatures of quantum interference in
highly symmetric double quantum dots in a parallel geometry and demonstrate
that extremely weak symmetry-breaking effects can have a dramatic influence on
the current. Our calculations are based on a master equation where quantum
interference enters as non-diagonal elements of the density matrix of the
double quantum dots. We also show that many results have a physically intuitive
meaning when recasting our equations as Bloch-like equations for a pseudo spin
associated with the dot occupation. In the perfectly symmetric configuration
with equal tunnel couplings and orbital energies of both dots, there is no
unique stationary state density matrix. Interestingly, however, adding
arbitrarily small symmetry-breaking terms to the tunnel couplings or orbital
energies stabilizes a stationary state either with or without quantum
interference, depending on the competition between these two perturbations. The
different solutions can correspond to very different current levels. Therefore,
if the orbital energies and/or tunnel couplings are controlled by, e.g.,
electrostatic gating, the double quantum dot can act as an exceptionally
sensitive electric switch.",1812.01138v2
2020-10-16,Hyperfine Couplings as a Probe of Orbital Anisotropy in Heavy Fermion Materials,"The transferred hyperfine interaction between nuclear and electron spins in
an heavy fermion material depends on the hybridization between the $f$-electron
orbitals and those surrounding a distant nucleus. In CeMIn$_5$ (M=Rh, Ir, Co),
both the hyperfine coupling to the two indium sites as well as the crystalline
electric field at the Ce are strongly dependent on the transition metal. We
measure a series of CeRh$_{1-x}$Ir$_x$In$_5$ crystals and find that the
hyperfine coupling reflects the orbital anisotropy of the ground state Ce 4$f$
wavefunction. These findings provide direct proof that the localized to
itinerant transition is dominated by hybridization out of the Ce-In plane in
this system.",2010.08636v1
1995-08-21,A Microscopic Model of Non-Reciprocal Optical Effects in Cr_2 O_3,"This manuscript deals with the question ""How does light couple to an
antiferromagnetic order parameter""? For that we develop a microscopic model
that explains the non-reciprocal optical effects in centrosymmetric Cr_2 O_3.
It is shown that light can couple {\em directly} to the antiferromagnetic order
parameter. This coupling is mediated by the spin-orbit interaction and involves
an interplay between the breaking of inversion symmetry due to the
antiferromagnetic order parameter and the trigonal field contribution to the
ligand field at the Cr^{3+} ion.",9508082v1
2003-04-11,Coupled plasmon-phonon modes in a two-dimensional electron gas in the presence of Rashba effect,"Elementary electronic excitation is studied theoretically for a 2DEG in the
presence of spin orbit (SO) interaction induced by Rashba effect. In such a
system, coupled plasmon-phonon excitation can be achieved via intra- and
inter-SO electronic transitions. As a result, six branches of the coupled
plasmon-phonon oscillations can be observed. The interesting features of these
excitation modes are analyzed.",0304257v1
2002-11-12,Effect of tensor couplings in a relativistic Hartree approach for finite nuclei,"The relativistic Hartree approach describing the bound states of both
nucleons and anti-nucleons in finite nuclei has been extended to include tensor
couplings for the $\omega$- and $\rho$-meson. After readjusting the parameters
of the model to the properties of spherical nuclei, the effect of
tensor-coupling terms rises the spin-orbit force by a factor of 2, while a
large effective nucleon mass $m^{*}/M_{N} \approx 0.8$ sustains. The overall
nucleon spectra of shell-model states are improved evidently. The predicted
anti-nucleon spectra in the vacuum are deepened about 20 -- 30 MeV.",0211034v1
2013-03-19,Tunnel conductance spectroscopy via harmonic generation in a hybrid capacitor device,"We address the measurement of density of states within and beyond the
superconducting gap in tunnel-coupled finite-size nanostructures using a
capacitive method. Third-harmonic generation is used to yield the full
differential conductance spectrum without destruction of the low dimensionality
otherwise induced by intimate ohmic coupling to an electrode. The method is
particularly relevant to attempts to discern the presence of the fragile
Majorana quasiparticle at the end of spin-orbit-coupled nanowires in
appropriate magnetic field conditions by their signature mid-gap density of
states.",1303.4719v4
2014-08-17,Detecting a quantum critical point in topological SN junctions,"A spin-orbit coupled quantum wire, with one end proximate to an s-wave
superconductor, can become a topological superconductor, with a Majorana mode
localized at each end of the superconducting region. It was recently shown that
coupling one end of such a topological superconductor to $two$ normal channels
of interacting electrons leads to a novel type of frustration and a quantum
critical point when both channels couple with equal strength. We propose an
experimental method to access this critical point in a $single$ quantum wire
and show its resilience to disorder.",1408.3804v3
2015-06-03,Double-expansion impurity solver for multiorbital models with dynamically screened U and J,"We present a continuous-time Monte Carlo impurity solver for multiorbital
impurity models which combines a strong-coupling hybridization expansion and a
weak-coupling expansion in the Hund's coupling parameter J. This
double-expansion approach allows to treat the dominant density-density
interactions U within the efficient segment representation. We test the
approach for a two-orbital model with static interactions, and then explain how
the double-expansion allows to simulate models with frequency dependent
U(\omega) and J(\omega). The method is used to investigate spin state
transitions in a toy model for fullerides, with repulsive bare J but attractive
screened J.",1506.01173v1
2015-11-05,From Coupled Rashba Electron and Hole Gas Layers to 3D Topological Insulators,"We introduce a system of stacked two-dimensional electron and hole gas layers
with Rashba spin orbit interaction and show that the tunnel coupling between
the layers induces a strong three- dimensional (3D) topological insulator
phase. At each of the two-dimensional bulk boundaries we find the spectrum
consisting of a single anistropic Dirac cone, which we show by analytical and
numerical calculations. Our setup has a unit-cell consisting of four tunnel
coupled Rashba layers and presents a synthetic strong 3D topological insulator
and is distinguished by its rather high experimental feasibility.",1511.01742v1
2016-02-19,Nonlinear waves in coherently coupled Bose-Einstein condensates,"We consider a quasi-one-dimensional two-component Bose-Einstein condensate
subject to a coherent coupling between its components, such as realized in
spin-orbit coupled condensates. We study how nonlinearity modifies the dynamics
of the elementary excitations. The spectrum has two branches which are affected
in different ways. The upper branch experiences a modulational instability
which is stabilized by a long wave-short wave resonance with the lower branch.
The lower branch is stable. In the limit of weak nonlinearity and small
dispersion it is described by a Korteweg-de Vries equation or by the Gardner
equation, depending on the value of the parameters of the system.",1602.06141v1
2011-11-07,Description of single-Lambda hypernuclei with relativistic point coupling model,"We extend the relativistic point coupling model to single-$\Lambda$
hypernuclei. For this purpose, we add $N$-$\Lambda$ effective contact couplings
to the model Lagrangian, and determine the parameters by fitting to the
experimental data for $\Lambda$ binding energies. Our model well reproduces the
data over a wide range of mass region although some of our interactions yield
the reverse ordering of the spin-orbit partners from that of nucleons for heavy
hypernuclei. The consistency of the interaction with the quark model
predictions is also discussed.",1111.1488v1
2018-01-09,Magneto-electric effect in doped magnetic ferroelectrics,"We propose a model of magneto-electric effect in doped magnetic
ferroelectrics. This magneto-electric effect does not involve the spin-orbit
coupling and is based purely on the Coulomb interaction. We calculate magnetic
phase diagram of doped magnetic ferroelectrics. We show that magneto-electric
coupling is pronounced only for ferroelectrics with low dielectric constant. We
find that magneto-electric coupling leads to modification of magnetization
temperature dependence in the vicinity of ferroelectric phase transition. A
peak of magnetization appears. We find that magnetization of doped magnetic
ferroelectrics strongly depends on applied electric field.",1801.03114v1
2021-08-10,The correlation function of a two-dimensional electron gas with anharmonic potential and Rashba coupling,"In this paper, we study a two-dimensional gas of electrons with Rashba
spin-orbit coupling with anharmonic potential. The splitting of the Hamiltonian
in two parts can be recovering the Jaynes-Cummings model, which describes a
system with two states. The dynamics of the rising Pauli operator and the
creation operators are studied. Finally, we examined the behavior of the
correlation function of emission and absorption photons for the strong and weak
coupling.",2108.04574v1
2004-02-13,Probing spin and orbital Kondo effects with a mesoscopic interferometer,"We investigate theoretically the transport properties of a closed
Aharonov-Bohm interferometer containing two quantum dots in the strong coupling
regime. We find two distinct physical scenarios depending on the strength of
the interdot Coulomb interaction. When the interdot Coulomb interaction is
negligible only spin fluctuations are important and each dot develops a Kondo
resonance at the Fermi level independently of the applied magnetic flux. The
transport is characterized by the interference of these two independent Kondo
resonances. On the contrary, for large interdot interaction, only one electron
can be accommodated onto the double dot system. In this situation, not only the
spin can fluctuate but also the orbital degree of freedom (the pseudo-spin). As
a result, we find different ground states depending on the value of the applied
flux. When $\phi=\pi$ (mod $2\pi$) ($\phi=2\pi\Phi/\Phi_0$, where $\Phi$ is
applied flux, and $\Phi_0=h/e$ the flux quantum) the electronic transport can
take place via simultaneous correlations in the spin and pseudo-spin sectors,
leading to the highly symmetric SU(4) Kondo state. Nevertheless, we find
situations with $\phi>0$ (mod $2\pi$) where the pseudo-spin quantum number is
not conserved during tunneling events, giving rise to the common SU(2) Kondo
state with an enhanced Kondo temperature. We investigate the crossover between
both ground states and discuss possible experimental signatures of this physics
as a function of the applied magnetic flux.",0402361v2
2002-06-25,Initial-State Interactions and Single-Spin Asymmetries in Drell-Yan Processes,"We show that the initial-state interactions from gluon exchange between the
incoming quark and the target spectator system lead to leading-twist
single-spin asymmetries in the Drell-Yan process. The QCD initial-state
interactions produce a $T-$odd spin-correlation between the target spin and the
virtual photon production plane which is not power-law suppressed in the
Drell-Yan scaling limit. The origin of the single-spin asymmetry in $\pi
p^\uparrow \to \ell^+ \ell^- X$ is a phase difference between two amplitudes
coupling the proton target with $J^z_p = \pm {1\over 2}$ to the same
final-state, the same amplitudes which are necessary to produce a nonzero
proton anomalous magnetic moment. The calculation requires the overlap of
target light-front wavefunctions differing by one unit of orbital angular
momentum projection $L_z;$ thus the SSA in the Drell-Yan reaction provides a
direct measure of orbital angular momentum in the QCD bound state. The
single-spin asymmetry predicted for the Drell-Yan process $\pi p^\uparrow \to
\ell^+ \ell^- X$ is similar to the single-spin asymmetries in deep inelastic
semi-inclusive leptoproduction $\ell p^\uparrow \to \ell' \pi X$ which arises
from the final-state rescattering of the outgoing quark.",0206259v1
2008-08-15,Wigner crystal physics in quantum wires,"The physics of interacting quantum wires has attracted a lot of attention
recently. When the density of electrons in the wire is very low, the strong
repulsion between electrons leads to the formation of a Wigner crystal. We
review the rich spin and orbital properties of the Wigner crystal, both in the
one-dimensional and quasi-one-dimensional regime. In the one-dimensional Wigner
crystal the electron spins form an antiferromagnetic Heisenberg chain with
exponentially small exchange coupling. In the presence of leads the resulting
inhomogeneity of the electron density causes a violation of spin-charge
separation. As a consequence the spin degrees of freedom affect the conductance
of the wire. Upon increasing the electron density, the Wigner crystal starts
deviating from the strictly one-dimensional geometry, forming a zigzag
structure instead. Spin interactions in this regime are dominated by ring
exchanges, and the phase diagram of the resulting zigzag spin chain has a
number of unpolarized phases as well as regions of complete and partial spin
polarization. Finally we address the orbital properties in the vicinity of the
transition from a one-dimensional to a quasi-one-dimensional state. Due to the
locking between chains in the zigzag Wigner crystal, only one gapless mode
exists. Manifestations of Wigner crystal physics at weak interactions are
explored by studying the fate of the additional gapped low-energy mode as a
function of interaction strength.",0808.2076v2
2011-05-04,Quantum Spin Hall Effect in Graphene Nanoribbons: Effect of Edge Geometry,"There has been tremendous recent progress in realizing topological insulator
initiated by the proposal of Kane and Mele for the graphene system. They have
suggested that the odd $Z_2$ index for the graphene manifests the spin filtered
edge states for the graphene nanoribbons, which lead to the quantum spin Hall
effect(QSHE). Here we investigate the role of the spin-orbit interaction both
for the zigzag and armchair nanoribbons with special care in the edge geometry.
For the pristine zigzag nanoribbons, we have shown that one of the $\sigma$
edge bands located near E=0 lifts up the energy of the spin filtered chiral
edge states at the zone boundary by warping the $\pi$-edge bands, and hence the
QSHE does not occur. Upon increasing the carrier density above a certain
critical value, the spin filtered edge states are formed leading to the QSHE.
We suggest that the hydrogen passivation on the edge can recover the original
feature of the QSHE. For the armchair nanoribbon, the QSHE is shown to be
stable. We have also derived the real space effective hamiltonian, which
demonstrates that the on-site energy and the effective spin orbit coupling
strength are strongly enhanced near the ribbon edges. We have shown that the
steep rise of the confinement potential thus obtained is responsible for the
warping of the $\pi$-edge bands.",1105.0733v1
2011-06-27,"Meissner effect, Spin Meissner effect and charge expulsion in superconductors","The Meissner effect and the Spin Meissner effect are the spontaneous
generation of charge and spin current respectively near the surface of a metal
making a transition to the superconducting state. The Meissner effect is well
known but, I argue, not explained by the conventional theory, the Spin Meissner
effect has yet to be detected. I propose that both effects take place in all
superconductors, the first one in the presence of an applied magnetostatic
field, the second one even in the absence of applied external fields. Both
effects can be understood under the assumption that electrons expand their
orbits and thereby lower their quantum kinetic energy in the transition to
superconductivity. Associated with this process, the metal expels negative
charge from the interior to the surface and an electric field is generated in
the interior. The resulting charge current can be understood as arising from
the magnetic Lorentz force on radially outgoing electrons, and the resulting
spin current can be understood as arising from a spin Hall effect originating
in the Rashba-like coupling of the electron magnetic moment to the internal
electric field. The associated electrodynamics is qualitatively different from
London electrodynamics, yet can be described by a small modification of the
conventional London equations. The stability of the superconducting state and
its macroscopic phase coherence hinge on the fact that the orbital angular
momentum of the carriers of the spin current is found to be exactly $\hbar/2$,
indicating a topological origin. The simplicity and universality of our theory
argue for its validity, and the occurrence of superconductivity in many classes
of materials can be understood within our theory.",1106.5311v1
2013-05-06,Liquid-like correlations in single crystalline Y2Mo2O7: an unconventional spin glass,"The spin glass behavior of Y2Mo2O7 has puzzled physicists for nearly three
decades. Free of bulk disorder within the resolution of powder diffraction
methods, it is thought that this material is a rare realization of a spin glass
resulting from weak disorder such as bond disorder or local lattice
distortions. Here, we report on the single crystal growth of Y2Mo2O7. Using
neutron scattering, we present unique isotropic magnetic diffuse scattering
arising beneath the spin glass transition despite having a well-ordered
structure at the bulk level. Despite our attempts to model the diffuse
scattering using a computationally exhaustive search of a class of simple spin
Hamiltonians, we were unable to replicate the experimentally observed
energy-integrated (diffuse) neutron scattering. A T^2-temperature dependence in
the heat capacity and density functional theory calculations hint at
significant frozen degeneracy in both the spin and orbital degrees of freedom
resulting from spin-orbital coupling (Kugel-Khomskii type) and random
fluctuations in the Mo environment at the local level.",1305.1274v2
2014-10-14,Current-induced spin polarization at the surface of metallic films: a theorem and an ab initio calculation,"The broken inversion symmetry at the surface of a metallic film (or, more
generally, at the interface between a metallic film and a different metallic or
insulating material) greatly amplifies the influence of the spin-orbit
interaction on the surface properties. The best known manifestation of this
effect is the momentum-dependent splitting of the surface state energies
(Rashba effect). Here we show that the same interaction also generates a
spin-polarization of the bulk states when an electric current is driven through
the bulk of the film. For a semi-infinite jellium model, which is
representative of metals with a closed Fermi surface, we prove as a theorem
that, regardless of the shape of the confinement potential, the induced surface
spin density at each surface is given by ${\bf S} =-\gamma \hbar {\bf \hat
z}\times {\bf j}$, where ${\bf j}$ is the particle current density in the bulk,
${\bf \hat z}$ the unit vector normal to the surface, and
$\gamma=\frac{\hbar}{4mc^2}$ contains only fundamental constants. For a general
metallic solid $\gamma$ becomes a material-specific parameter that controls the
strength of the interfacial spin-orbit coupling. Our theorem, combined with an
{\it ab initio} calculation of the spin polarization of the current-carrying
film, enables a determination of $\gamma$, which should be useful in modeling
the spin-dependent scattering of quasiparticles at the interface.",1410.3693v1
2014-12-02,Spin-Orbit Proximity Effect in Graphene,"The development of a spintronics device relies on efficient generation of
spin polarized currents and their electric field controlled manipulation. While
observation of exceptionally long spin relaxation lengths make graphene an
intriguing material for spintronics studies, modulation of spin currents by
gate field is almost impossible due to negligibly small intrinsic spin orbit
coupling (SOC) of graphene. In this work, we create an artificial interface
between monolayer graphene and few-layers semiconducting tungsten disulfide
(WS2). We show that in such devices graphene acquires a SOC as high as 17meV,
three orders of magnitude higher than its intrinsic value, without modifying
any of the structural properties of the graphene. Such proximity SOC leads to
the spin Hall effect even at room temperature and opens the doors for spin
FETs. We show that intrinsic defects in WS2 play an important role in this
proximity effect and that graphene can act as a probe to detect defects in
semiconducting surfaces.",1412.0920v1
2016-04-11,Quantum Diagrammatic Theory of the Extrinsic Spin Hall Effect in Graphene,"We present a rigorous microscopic theory of the extrinsic spin Hall effect in
disordered graphene based on a nonperturbative quantum diagrammatic treatment
incorporating skew scattering and anomalous---impurity
concentration-independent---quantum corrections on equal footing. The leading
skew scattering contribution to the spin Hall conductivity is shown to
quantitatively agree with Boltzmann transport theory over a wide range of
parameters. Our self-consistent approach---where all topologically equivalent
noncrossing diagrams are resummed---unveils that the skewness generated by
spin--orbit-active impurities deeply influences the anomalous component of the
spin Hall conductivity, even in the weak scattering regime. This seemingly
counterintuitive result is explained by the rich sublattice structure of
scattering potentials in graphene, for which traditional Gaussian disorder
approximations fail to capture the intricate correlations between skew
scattering and side jumps generated through diffusion. Finally, we assess the
role of quantum interference corrections by evaluating an important subclass of
crossing diagrams recently considered in the context of the anomalous Hall
effect, the $X$ and $\Psi$ diagrams [Ado et al., EPL 111, 37004 (2015)]. We
show that $\Psi$ diagrams---encoding quantum coherent skew scattering---display
a strong Fermi energy dependence, dominating the anomalous spin Hall component
away from the Dirac point. Our findings have direct implications for nonlocal
transport experiments in spin--orbit-coupled graphene systems.",1604.03111v1
2020-07-13,Molecule Oxygen Induced Ferromagnetism and Half-metallicity in α-BaNaO4: A First Principles Study,"Molecule oxygen resembles 3d and 4f metals in exhibiting long-range spin
ordering and electron strong correlated behaviors in compounds. The
ferromagnetic spin ordering and half-metallicity, however, are quite elusive
and have not been well acknowl-edged. In this article, we address this issue to
study how spins will interact each other if the oxygen dimers are arranged in a
dif-ferent way from that in the known super- and per-oxides by first principles
calculations. Based on the results of structure search, thermodynamic study and
lattice dynamics, we show that tetragonal {\alpha}-BaNaO4 is a stable
half-metal with a Curie temperature at 120 K, a first example in this class of
compounds. Like 3d and 4f metals, the O2 dimer carries a local magnetic moment
0.5 {\mu}B due to the unpaired electrons in its {\pi}* orbitals. This compound
can be regarded as forming from the O2 dimer layers stacking in a head to head
way. Different from that in AO2 (A=K, Rb, Cs), the spins are both
ferromagnetically coupled within and between the layers. Spin polarization
occurs in {\pi}* orbitals with spin-up electrons fully occupying the valence
band and spin-down electrons partially the conduction band, forming the
semiconducting and metallic channels, respectively. Our results highlight the
im-portance of geometric arrangement of O2 dimers in inducing ferromagnetism
and other novel properties in O2 dimer containing compounds.",2007.06433v1
2020-02-26,Local spin polarizations in relativistic heavy ion collisions,"Based on a generalized side-jump formalism for massless chiral fermions,
which naturally takes into account the spin-orbit coupling in the scattering of
two chiral fermions and the chiral vortical effect in a rotating chiral fermion
matter, we have developed a covariant and total angular momentum conserved
chiral transport model to study both the global and local polarizations of this
matter. For a system of massless quarks of random spin orientations and finite
vorticity in a box, we have demonstrated that the model can exactly conserve
the total angular momentum of the system and dynamically generate the quark
spin polarization expected from a thermally equilibrated quark matter. Using
this model to study the spin polarization in relativistic heavy-ion collision,
we have found that the local quark spin polarizations depend strongly on the
reference frame where they are evaluated as a result of the nontrivial axial
charge distribution caused by the chiral vortical effect. We have further shown
that because of the anomalous orbital or side-jump contribution to the quark
spin polarization, the local quark polarizations calculated in the medium rest
frame are qualitatively consistent with the local polarizations of Lambda
hyperons measured in experiments.",2002.11752v1
2018-03-02,Neutron spin resonance in the 112-type iron-based superconductor,"We use inelastic neutron scattering to study the low-energy spin excitations
of 112-type iron pnictide Ca$_{0.82}$La$_{0.18}$Fe$_{0.96}$Ni$_{0.04}$As$_{2}$
with bulk superconductivity below $T_c=22$ K. A two-dimensional spin resonance
mode is found around $E=$ 11 meV, where the resonance energy is almost
temperature independent and linearly scales with $T_c$ along with other
iron-based superconductors. Polarized neutron analysis reveals the resonance is
nearly isotropic in spin space without any $L$ modulations. Due to the unique
monoclinic structure with additional zigzag arsenic chains, the As $4p$
orbitals contribute to a three-dimensional hole pocket around $\Gamma$ point
and an extra electron pocket at $X$ point. Our results suggest that the energy
and momentum distribution of spin resonance does not directly response to the
$k_z$ dependence of fermiology, and the spin resonance intrinsically is a
spin-1 mode from singlet-triplet excitations of the Cooper pairs in the case of
weak spin-orbital coupling.",1803.00779v2
2018-08-15,Chirality and intrinsic dissipation of spin modes in two-dimensional electron liquids,"We review recent theoretical and experimental developments concerning
collective spin excitations in two-dimensional electron liquid (2DEL) systems,
with particular emphasis on the interplay between many-body and spin-orbit
effects, as well as the intrinsic dissipation due to the spin-Coulomb drag.
Historically, the experimental realization of 2DELs in silicon inversion layers
in the 60s and 70s created unprecedented opportunities to probe subtle quantum
effects, culminating in the discovery of the quantum Hall effect. In the
following years, high quality 2DELs were obtained in doped quantum wells made
in typical semiconductors like GaAs or CdTe. These systems became important
test beds for quantum many-body effects due to Coulomb interaction, spin
dynamics, spin-orbit coupling, effects of applied magnetic fields, as well as
dissipation mechanisms. Here we focus on the recent results involving chiral
effects and intrinsic dissipation of collective spin modes: these are not only
of fundamental interest but also important towards demonstrating new concepts
in spintronics. Moreover, new realizations of 2DELs are emerging beyond
traditional semiconductors, for instance in multilayer graphene, oxide
interfaces, dichalcogenide monolayers, and many more. The concepts discussed in
this review will be relevant also for these emerging systems.",1808.05266v2
2020-05-09,Valley and spin polarized broken symmetry states of interacting electrons in gated MoS$_2$ quantum dots,"Understanding strongly interacting electrons enables the design of materials,
nanostructures and devices. Developing this understanding relies on the ability
to tune and control electron-electron interactions by, e.g., confining
electrons to atomically thin layers of 2D crystals with reduced screening. The
interplay of strong interactions on a hexagonal lattice with two nonequivalent
valleys, topological moments, and the Ising-like spin-orbit interaction gives
rise to a variety of phases of matter corresponding to valley and spin
polarized broken symmetry states. In this work we describe a highly tunable
strongly interacting system of electrons laterally confined to monolayer
transition metal dichalcogenide MoS$_2$ by metalic gates. We predict the
existence of valley and spin polarized broken symmetry states tunable by the
parabolic confining potential using exact diagonalization techniques for up to
$N=6$ electrons. We find that the ground state is formed by one of two phases,
either both spin and valley polarized or valley unpolarised but spin
intervalley antiferromagnetic, which compete as a function of electronic shell
spacing. This finding can be traced back to the combined effect of Ising-like
spin-orbit coupling and weak intervalley exchange interaction. These results
provide an explanation for interaction-driven symmetry-breaking effects in
valley systems and highlight the important role of electron-electron
interactions for designing valleytronic devices.",2005.04467v1
2021-06-23,Electrical control of the hole spin qubit in Si and Ge nanowire quantum dots,"Strong, direct Rashba spin-orbit coupling in Si, Ge, and the Ge/Si core/shell
nanowire quantum dot (QD) allows for all electrical manipulation of the hole
spin qubit. Motivated by this fact, we analyze different fabrication-dependent
properties of nanowires, such as orientation, cross section, and the presence
of strain, with the goal being to find the material and geometry that enables
the fastest qubit manipulation, whose speed can be identified using the Rabi
frequency. We show that QD in nanowires with a circular cross section (cNWs)
enables much weaker driving of the hole spin qubit than QDs embedded in square
profile nanowires (sNWs). Assuming the orientation of the Si nanowire that
maximizes the spin-orbit effects, our calculations predict that the Rabi
frequencies of the hole spin qubits inside Ge and Si sNW QD have comparable
strengths for weak electric fields. The global maximum of the Rabi frequency is
found in Si sNW QD for strong electric fields, putting this setup ahead of
others in creating the hole spin qubit. Finally, we demonstrate that strain in
the Si/Ge core/shell nanowire QD decreases the Rabi frequency. In cNW QD, this
effect is weak; in sNW QD, it is possible to optimize the impact of strain with
the appropriate tuning of the electric field strength.",2106.12551v2
2021-06-29,Spin Hall effect in a spin-1 chiral semimetal,"Spin-1 chiral semimetal is a new state of quantum matter hosting
unconventional chiral fermions that extend beyond the common Dirac and Weyl
fermions. B20-type CoSi is a prototypal material that accommodates such an
exotic quasiparticle. To date, the spin transport properties in the spin-1
chiral semimetals, have not been explored yet. In this work, we fabricated
B20-CoSi thin films on sapphire c-plane substrates by magnetron sputtering and
studied the spin Hall effect (SHE) by combining experiments and
first-principles calculations. The SHE of CoSi using CoSi/CoFeB/MgO
heterostructures was investigated via spin Hall magnetoresistance and harmonic
Hall measurements. First-principles calculations yield an intrinsic spin Hall
conductivity (SHC) at the Fermi level that is consistent with the experiments
and reveal its unique Fermi-energy dependence. Unlike the Dirac and Weyl
fermion-mediated Hall conductivities that exhibit a peak-like structure
centering around the topological node, SHC of B20-CoSi is odd and crosses zero
at the node with two antisymmetric local extrema of opposite sign situated
below and above in energy. Hybridization between Co d-Si p orbitals and
spin-orbit coupling are essential for the SHC, despite the small (~1%) weight
of Si p-orbital near the Fermi level. This work expands the horizon of
topological spintronics and highlights the importance of Fermi-level tuning in
order to fully exploit the topology of spin-1 chiral fermions for spin current
generation.",2106.15107v1
2021-07-08,"Magnetism, symmetry and spin transport in van der Waals layered systems","The discovery of an ever increasing family of atomic layered magnetic
materials, together with the already established vast catalogue of strong
spin-orbit coupling (SOC) and topological systems, calls for some guiding
principles to tailor and optimize novel spin transport and optical properties
at their interfaces. Here we focus on the latest developments in both fields
that have brought them closer together and make them ripe for future fruitful
synergy. After outlining fundamentals on van der Waals (vdW) magnetism and SOC
effects, we discuss how their coexistence, manipulation and competition could
ultimately establish new ways to engineer robust spin textures and drive the
generation and dynamics of spin current and magnetization switching in 2D
materials-based vdW heterostructures. Grounding our analysis on existing
experimental results and theoretical considerations, we draw a prospective
analysis about how intertwined magnetism and spin-orbit torque (SOT) phenomena
combine at interfaces with well-defined symmetries, and how this dictates the
nature and figures-of-merit of SOT and angular momentum transfer. This will
serve as a guiding role in designing future non-volatile memory devices that
utilize the unique properties of 2D materials with the spin degree of freedom.",2107.03763v2
2022-08-15,Nonperturbative approach to interfacial spin-orbit torques induced by Rashba effect,"Current-induced spin-orbit torque (SOT) in normal metal/ferromagnet (NM/FM)
bilayers bears great promise for technological applications, but the
microscopic origin of purely interfacial SOTs in ultra-thin systems is not yet
fully understood. Here, we show that a linear response theory with a
nonperturbative treatment of spin-dependent interactions and impurity
scattering potential predicts damping-like SOTs that are strictly absent in
perturbative approaches. The technique is applied to a two-dimensional
Rashba-coupled ferromagnet (the paradigmatic model of a NM/FM interface), where
higher-order scattering processes encoding skew scattering from nonmagnetic
impurities allow for current-induced spin polarization with nonzero components
along all spatial directions. This is in stark contrast to previous results of
perturbative methods (neglecting skew scattering), which predict a coplanar
spin-polarization locked perpendicular to the charge current as a result of
conventional Rashba-Edelstein effect. Furthermore, the angular dependence of
ensuing SOTs and their dependence upon the scattering potential strength is
analysed numerically. Simple analytic expressions for the
spin-density--charge-current response function, and related SOT efficiencies,
are obtained in the weak scattering limit. We find that the extrinsic
damping-like torques driven by impurity scattering reaches efficiencies of up
to 7% of the field-like (Rashba-Edelstein) torque. Our microscopic theory shows
that bulk phenomena, such as the spin Hall effect, are not a necessity in the
generation of the damping-like SOTs of the type observed in experiments on
ultra-thin systems.",2208.07296v1
2024-03-25,Stellar Spin Down in Post-Mass Transfer Binary Systems,"Motivated by measurements of the rotation speed of accretor stars in
post-mass-transfer (post-MT) systems, we investigate how magnetic braking
affects the spin-down of individual stars during binary evolution with the
\texttt{MESAbinary} module. Unlike the conventional assumption of tidal
synchronization coupled with magnetic braking in binaries, we first calculate
whether tides are strong enough to synchronize the orbit. Subsequently, this
influences the spin-down of stars and the orbital separation. In this study, we
apply four magnetic braking prescriptions to reduce the spin angular momentum
of the two stars throughout the entire binary evolution simulation. Our
findings reveal that despite magnetic braking causing continuous spin-down of
the accretor, when the donor begins to transfer material onto the accretor, the
accretor can rapidly spin up to its critical rotation rate. After MT, magnetic
braking becomes more important in affecting the angular momentum evolution of
the stars. Post-MT accretor stars thus serve as a valuable testbed for
observing how the magnetic braking prescriptions operate in spinning down stars
from their critical rotation, including the saturation regimes of the magnetic
braking. The rotation rate of the accretor star, combined with its mass, could
provide age information since the cessation of MT. By comparing the models
against observation, the magnetic braking prescription by Garraffo et al.
(2018b) is found to better align with the rotation data of post-MT accretors.",2403.17279v1
2017-06-19,"Proximity effects in bilayer graphene on monolayer WSe$_2$: Field-effect spin-valley locking, spin-orbit valve, and spin transistor","Proximity orbital and spin-orbit effects of bilayer graphene on monolayer
WSe$_2$ are investigated from first-principles. We find that the built-in
electric field induces an orbital band gap of about 10 meV in bilayer graphene.
Remarkably, the proximity spin-orbit splitting for holes is two orders of
magnitude---the spin-orbit splitting of the valence band at K is about 2
meV---more than for electrons. Effectively, holes experience spin-valley
locking due to the strong proximity of the lower graphene layer to WSe$_2$.
However, applying an external transverse electric field of some 1 V/nm,
countering the built-in field of the heterostructure, completely reverses this
effect and allows, instead for holes, electrons to be spin-valley locked with 2
meV spin-orbit splitting. Such a behavior constitutes a highly efficient
field-effect spin-orbit valve, making bilayer graphene on WSe$_2$ a potential
platform for a field-effect spin transistor.",1706.06149v1
2007-08-04,The Spin Density Matrix I: General Theory and Exact Master Equations,"We consider a scenario where interacting electrons confined in quantum dots
(QDs) are either too close to be resolved, or we do not wish to apply
measurements that resolve them. Then the physical observable is an electron
spin only (one cannot unambiguously ascribe a spin to a QD) and the system
state is fully described by the spin-density matrix. Accounting for the spatial
degrees of freedom, we examine to what extent a Hamiltonian description of the
spin-only degrees of freedom is valid. We show that as long as there is no
coupling between singlet and triplet states this is indeed the case, but when
there is such a coupling there are open systems effects, i.e., the dynamics is
non-unitary even without interaction with a true bath. Our primary focus is an
investigation of non-unitary effects, based on exact master equations we derive
for the spin-density matrix in the Lindblad and time-convolutionless (TCL)
forms, and the implications for quantum computation. In particular, we
demonstrate that the Heisenberg interaction does not affect the unitary part
(apart from a Lamb shift) but does affect the non-unitary contributions to time
evolution of the spin-density matrix. In a sequel paper we present a detailed
analysis of an example system of two quantum dots, including spin-orbit
effects.",0708.0644v1
2015-05-06,Bipolar polaron pair recombination in P3HT/PCBM solar cells,"The unique properties of organic semiconductors make them versatile base
materials for many applications ranging from light emitting diodes to
transistors. The low spin-orbit coupling typical for carbon-based materials and
the resulting long spin lifetimes give rise to a large influence of the
electron spin on charge transport which can be exploited in spintronic devices
or to improve solar cell efficiencies. Magnetic resonance techniques are
particularly helpful to elucidate the microscopic structure of paramagnetic
states in semiconductors as well as the transport processes they are involved
in. However, in organic devices the nature of the dominant spin-dependent
processes is still subject to considerable debate. Using multi-frequency pulsed
electrically detected magnetic resonance (pEDMR), we show that the
spin-dependent response of P3HT/PCBM solar cells at low temperatures is
governed by bipolar polaron pair recombination involving the positive and
negative polarons in P3HT and PCBM, respectively, thus excluding a unipolar
bipolaron formation as the main contribution to the spin-dependent charge
transfer in this temperature regime. Moreover the polaron-polaron coupling
strength and the recombination times of polaron pairs with parallel and
antiparallel spins are determined. Our results demonstrate that the pEDMR pulse
sequences recently developed for inorganic semiconductor devices can very
successfully be transferred to the study of spin and charge transport in
organic semiconductors, in particular when the different polarons can be
distinguished spectrally.",1505.01411v1
2015-09-17,A magnetic Impurity in a Weyl semimetal,"We utilize the variational method to study the Kondo screening of a
spin-$1/2$ magnetic impurity in a three-dimensional (3D) Weyl semimetal with
two Weyl nodes along the $k_z$-axis. The model reduces to a 3D Dirac semimetal
when the separation of the two Weyl nodes vanishes. When the chemical potential
lies at the nodal point, $\mu=0$, the impurity spin is screened only if the
coupling between the impurity and the conduction electron exceeds a critical
value. For finite but small $\mu$, the impurity spin is weakly bound due to the
low density of state, which is proportional to $\mu^2$, contrary to that in a
2D Dirac metal such as graphene and 2D helical metal where the density of
states is proportional to $|\mu|$. The spin-spin correlation function
$J_{uv}(\mathbf{r})$ between the spin $v$-component of the magnetic impurity at
the origin and the spin $u$-component of a conduction electron at spatial point
$\mathbf{r}$, is found to be strongly anisotropic due to the spin-orbit
coupling, and it decays in the power-law. The main difference of the Kondo
screening in 3D Weyl semimetals and in Dirac semimetals is in the spin $x$-
($y$-) component of the correlation function in the spatial direction of the
$z$-axis.",1509.05180v2
2020-07-16,Direct measurement of electron intervalley relaxation in a Si/SiGe quantum dot,"The presence of non-degenerate valley states in silicon can drastically
affect electron dynamics in silicon-based heterostructures, leading to electron
spin relaxation and spin-valley coupling. In the context of solid-state spin
qubits, it is important to understand the interplay between spin and valley
degrees of freedom to avoid or alleviate these decoherence mechanisms. Here we
report the observation of relaxation from the excited valley state to the
ground state in a Si/SiGe quantum dot, at zero magnetic field. Valley state
read-out is aided by a valley-dependent tunneling effect, which we attribute to
valley-orbit coupling. We find a long intervalley relaxation time of 12.0 $\pm$
0.3 ms, a value that is unmodified when a magnetic field is applied.
Furthermore, we compare our findings with the spin relaxation time and find
that the spin-valley ""hot spot"" relaxation is roughly four times slower than
intervalley relaxation, consistent with established theoretical predictions.
The precision of this technique, adapted from electron spin read-out via
energy-dependent tunneling, is an improvement over indirect valley relaxation
measurements and could be a useful probe of valley physics in spin and valley
qubit implementations.",2007.08680v1
2017-12-17,Harnessing the giant out-of-plane Rashba effect and the nanoscale persistent spin helix via ferroelectricity in SnTe thin films,"A non-vanishing electric field inside a non-centrosymmetric bulk crystal
transforms into a momentum- dependent magnetic field, namely, a spin-orbit
field (SOF). SOFs are of great use in spintronics because they enable spin
manipulation via the electric field. At the same time, however, spintronic
applications are severely limited by the SOF, as electrons traversing the SOF
easily lose their spin information. Here, we propose that in-plane
ferroelectricity in (001)-oriented SnTe thin films harness the Janus-faced SOF
in a reconcilable way to enable electrical spin controllability and suppress
spin dephasing. The in-plane ferroelectricity produces a unidirectional
out-of-plane Rashba SOF that can host a long-lived helical spin mode known as a
persistent spin helix (PSH). Through direct coupling between the inversion
asymmetry and the SOF, the ferroelectric switching reverses the out-of-plane
Rashba SOF, giving rise to a maximally field-tunable PSH. Furthermore, the
giant out- of-plane Rashba SOF seen in the SnTe thin films is linked to the
nano-sized PSH, potentially reducing spintronic device sizes to the nanoscale.
We combine the two ferroelectric-coupled degrees of freedom, longitudinal
charge and transverse PSH, to design intersectional electro-spintronic
transistors governed by non-volatile ferroelectric switching within nanoscale
lateral and atomic-thick vertical dimensions.",1712.06112v3
2019-07-31,Spin-spiral formalism based on the multiple scattering Green's function technique with applications to ultrathin magnetic films and multilayers,"Based on the Korringa-Kohn-Rostoker Green's function technique we present a
computational scheme for calculating the electronic structure of layered
systems with homogeneous spin-spiral magnetic state. From the self-consistent
non-relativistic calculations the total energy of the spin-spiral states is
determined as a function of the wave vector, while a relativistic extension of
the formalism in first order of the spin-orbit coupling gives an access to the
effect of the Dzyaloshinskii-Moriya interactions. We demonstrate that the newly
developed method properly describes the magnetic ground state of a Mn monolayer
on W(001) and that of a Co monolayer on Pt(111). The obtained spin-spiral
energies are mapped to a classical spin model, the parameters of which are
compared to those calculated directly from the relativistic torque method. In
case of the Co/Pt(111) system we find that the isotropic interaction between
the Co atoms is reduced and the Dzyaloshinskii-Moriya interaction is increased
when capped by a Ru layer. In addition, we perform spin-spiral calculations on
Ir/Fe/Co/Pt and Ir/Co/Fe/Pt multilayer systems and find a spin-spiral ground
state with very long wavelength due to the frustrated isotropic couplings
between the Fe atoms, whereas the Dzyaloshinskii-Moriya interaction strongly
depends on the sequence of the Fe and Co layers.",1907.13328v1
2022-12-30,Selection rules for ultrafast laser excitation and detection of spin correlations dynamics in a cubic antiferromagnet,"Exchange interactions determine the correlations between microscopic spins in
magnetic materials. Probing the dynamics of these spin correlations on
ultrashort length and time scales is, however rather challenging, since it
requires simultaneously high spatial and high temporal resolution. Recent
experimental demonstrations of laser-driven two-magnon modes - zone-edge
excitations in antiferromagnets governed by exchange coupling - posed questions
about the microscopic nature of the observed spin dynamics, the mechanism
underlying its excitation, and their macroscopic manifestation enabling
detection. Here, on the basis of a simple microscopic model, we derive the
selection rules for cubic systems that describe the polarization of pump and
probe pulses required to excite and detect dynamics of nearest-neighbor spin
correlations, and can be employed to isolate such dynamics from other magnetic
excitations and magneto-optical effects. We show that laser-driven spin
correlations contribute to optical anisotropy of the antiferromagnet even in
the absence of spin-orbit coupling. In addition, we highlight the role of
subleading anisotropy in the spin system and demonstrate that the dynamics of
the antiferromagnetic order parameter occurs only in next-to-leading order,
determined by the smallness of the magnetic anisotropy as compared to the
isotropic exchange interactions in the system. We expect that our results will
stimulate and support further studies of magnetic correlations on the shortest
length and time scale.",2212.14698v2
2011-10-17,Quantum oscillations in the linear chain of coupled orbits: the organic metal with two cation layers theta-(ET)(4)CoBr(4)(C(6)H(4)Cl(2)),"Analytical formulae for de Haas-van Alphen (dHvA) oscillations in linear
chain of coupled two-dimensional (2D) orbits (Pippard's model) are derived
systematically taking into account the chemical potential oscillations in
magnetic field. Although corrective terms are observed, basic (alpha) and
magnetic breakdown-induced (beta and 2beta - alpha) orbits can be accounted for
by the Lifshits-Kosevich (LK) and Falicov-Stachowiak semiclassical models in
the explored field and temperature ranges. In contrast, the 'forbidden orbit'
beta - alpha amplitude is described by a non-LK equation involving a product of
two classical orbit amplitudes. Furthermore, strongly non-monotonic field and
temperature dependence may be observed for the second harmonics of basic
frequencies such as 2alpha and the magnetic breakdown orbit beta + alpha,
depending on the value of the spin damping factors. These features are in
agreement with the dHvA oscillation spectra of the strongly 2D organic metal
theta- theta-(ET)(4)CoBr(4)(C(6)H(4)Cl(2)).",1110.3696v3
2014-08-26,ESR evidence for partial melting of the orbital order in LaMnO$_3$ below the Jahn-Teller transition,"We report on high-temperature electron spin resonance studies of a detwinned
LaMnO$_3$ single crystal across the Jahn-Teller transition at $T_{\rm JT}$ =
750 K. The anisotropy of the linewidth and g-factor reflects the local
Jahn-Teller distortions in the orbitally ordered phase. A clear jump in the
linewidth accompanies the Jahn-Teller transition at $T_{\rm JT}$ = 750 K
confirming that the transition is of first order. Already at $T^*$ = 550 K a
significant decrease of the reduced linewidth is observed. This temperature
scale is discussed with respect to the interaction of the $e_g$-electrons of
the Mn$^{3+}$-ions and the elastic field of the cooperative distortions. Our
results support a partial melting of the orbital order along the
antiferromagnetically coupled $b$-axis at $T^*$. The remaining two-dimensional
orbital ordering within the ferromagnetically coupled $ac$-plane finally
disappears together with the cooperative distortion at $T_{\rm JT}$. Moreover
in our discussion we show that elastic strain field interactions can explain
the melting of the orbital order and, thus, has to be taken into account to
explain the orbital ordering in LaMnO$_3$.",1408.6160v1
2018-08-30,Correlations and electronic order in a two-orbital honeycomb lattice model for twisted bilayer graphene,"The recent observation of superconductivity in proximity to an insulating
phase in twisted bilayer graphene (TBG) at small `magic' twist angles has been
linked to the existence of nearly-flat bands, which make TBG a fresh playground
to investigate the interplay between correlations and superconductivity. The
low-energy narrow bands were shown to be well-described by an effective
tight-binding model on the honeycomb lattice (the dual of the triangular
Moir\'e superlattice) with a local orbital degree of freedom. In this paper, we
perform a strong-coupling analysis of the proposed $\left(p_{x},\,p_{y}\right)$
two-orbital extended Hubbard model on the honeycomb lattice. By decomposing the
interacting terms in the particle-particle and particle-hole channels, we
classify the different possible superconducting, magnetic, and charge
instabilities of the system. In the pairing case, we pay particular attention
to the two-component ($d$-wave) pairing channels, which admit vestigial phases
with nematic or chiral orders, and study their phenomenology. Furthermore, we
explore the strong-regime by obtaining a simplified spin-orbital exchange model
which may describe a putative Mott-like insulating state at quarter-filling.
Our mean-field solution reveals a rich intertwinement between ferro- and
antiferro-magnetic orders with different types of nematic and magnetic orbital
orders. Overall, our work provides a solid framework for further investigations
of the phase diagram of the two-orbital extended Hubbard model in both strong-
and weak-coupling regimes.",1808.10416v3
2021-09-28,Charge Singlets and Orbital-Selective Charge Density Wave Transitions,"The possibility of ""orbitally selective Mott transitions"" within a multiband
Hubbard model, in which one orbital with large on-site electron-electron
repulsion $U_1$ is insulating and another orbital, to which it is hybridized,
with small $U_{-1}$, is metallic, is a problem of long-standing debate and
investigation. In this paper we study an analogous phenomenon, the co-existence
of metallic and insulating bands in a system of orbitals with different
electron-phonon coupling (EPC). To this end, we examine two variants of the
bilayer Holstein model: a uniform bilayer and a ""Holstein-Metal interface""
where the electron-phonon coupling, $\lambda$, is zero in the ""metallic"" layer.
In the uniform bilayer Holstein model, charge density wave (CDW) order
dominates at small interlayer hybridization $t_3$, but decreases and eventually
vanishes as $t_3$ grows, providing a charge analog of singlet (spin liquid)
physics. In the interface case, we show that CDW order penetrates into the
metal layer and forms long-range CDW order at intermediate ratio of inter- to
intra-layer hopping strengths, $1.4 \lesssim t_3/t \lesssim 3.4$. This is
consistent with the occurrence of an ""orbitally selective CDW"" regime at weak
$t_3$ in which the layer with $\lambda_{1} \neq 0$ exhibits long-range charge
order, but the ""metallic layer"" with $\lambda_{-1}=0$, to which it is
hybridized, does not.",2109.13482v2
2009-02-26,On the tidal evolution of Hot Jupiters on inclined orbits,"Tidal friction is thought to be important in determining the long-term
spin-orbit evolution of short-period extrasolar planetary systems. Using a
simple model of the orbit-averaged effects of tidal friction, we study the
evolution of close-in planets on inclined orbits, due to tides. We analyse the
effects of the inclusion of stellar magnetic braking by performing a
phase-plane analysis of a simplified system of equations, including the braking
torque. The inclusion of magnetic braking is found to be important, and its
neglect can result in a very different system history. We then present the
results of numerical integrations of the tidal evolution equations, where we
find that it is essential to consider coupled evolution of the orbital and
rotational elements, including dissipation in both the star and planet, to
accurately model the evolution. The main result of our integrations is that for
typical Hot Jupiters, tidal friction aligns the stellar spin with the orbit on
a similar time as it causes the orbit to decay. This means that if a planet is
observed to be aligned, then it probably formed coplanar. This reinforces the
importance of Rossiter-McLaughlin effect observations in determining the degree
of spin-orbit alignment in transiting systems. We apply these results to the
XO-3 system, and constrain the tidal quality factors Q' in both the star and
planet in this system. Using a model in which inertial waves are excited by
tidal forcing in the outer convective envelope and dissipated by turbulent
viscosity, we calculate Q' for a range of F-star models, and find it to vary
considerably within this class of stars. This means that assuming a single Q'
applies to all stars is probably incorrect. We propose an explanation for the
survival of WASP-12 b & OGLE-TR-56 b, in terms of weak dissipation in the star.",0902.4563v1
2022-03-02,"Machine-learned model Hamiltonian and strength of spin-orbit interaction in strained Mg2X (X = Si, Ge, Sn, Pb)","Machine-learned multi-orbital tight-binding (MMTB) Hamiltonian models have
been developed to describe the electronic characteristics of intermetallic
compounds $\rm Mg_2Si, Mg_2Ge, Mg_2Sn$, and $\rm Mg_2Pb$ subject to strain. The
MMTB models incorporate spin-orbital mediated interactions and they are
calibrated to the electronic band structures calculated via density functional
theory (DFT) by a massively parallelized multi-dimensional Monte-Carlo search
algorithm. The results show that a machine-learned five-band tight-binding
model reproduces the key aspects of the valence band structures in the entire
Brillouin zone. The five-band model reveals that compressive strain localizes
the contribution of the $3s$ orbital of $\rm Mg$ to the conduction bands and
the outer shell $p$ orbitals of $\rm X~(X=Si,Ge,Sn,Pb)$ to the valence bands.
In contrast, tensile strain has a reversed effect as it weakens the
contribution of the $3s$ orbital of $\rm Mg$ and the outer shell $p$ orbitals
of $\rm X$ to the conduction bands and valence bands, respectively. The $\pi$
bonding in the $\rm Mg_2X$ compounds is negligible compared to the $\sigma$
bonding components, which follow the hierarchy
$|\sigma_{sp}|>|\sigma_{pp}|>|\sigma_{ss}|$, and the largest variation against
strain belongs to $\sigma_{pp}$. The five-band model allows for estimating the
strength of spin-orbit coupling (SOC) in $\rm Mg_2X$ and obtaining its
dependence on the atomic number of $\rm X$ and strain. Further, the band
structure calculations demonstrate a significant band gap tuning and band
splitting due to strain. A compressive strain of $-10\%$ can open a band gap at
the $\Gamma$ point in metallic $\rm Mg_2Pb$, whereas a tensile strain of
$+10\%$ closes the semiconducting band gap of $\rm Mg_2Si$. A tensile strain of
$+5\%$ removes the three-fold degeneracy of valence bands at the $\Gamma$ point
in semiconducting $\rm Mg_2Ge$.",2203.01353v3
2020-10-21,Orbit topology analysed from $π$ phase shift of magnetic quantum oscillations in three-dimensional Dirac semimetal,"With the emergence of Dirac fermion physics in the field of condensed matter,
magnetic quantum oscillations (MQOs) have been used to discern the topology of
orbits in Dirac materials. However, many previous researchers have relied on
the single-orbit Lifshiftz-Kosevich formula, which overlooks the significant
effect of degenerate orbits on MQOs. Since the single-orbit LK formula is valid
for massless Dirac semimetals with small cyclotron masses, it is imperative to
generalize the method applicable to a wide range of Dirac semimetals, whether
massless or massive. This report demonstrates how spin-degenerate orbits affect
the phases in MQOs of three-dimensional massive Dirac semimetal, NbSb$_2$. With
varying the direction of the magnetic field, an abrupt $\pi$ phase shift is
observed due to the interference between the spin-degenerate orbits. We
investigate the effect of cyclotron mass on the $\pi$ phase shift and verify
its close relation to the phase from the Zeeman coupling. We find that the
$\pi$ phase shift occurs when the cyclotron mass is 1/2 of the electron mass,
indicating the effective spin gyromagnetic ratio is $g_s$ = 2. Our approach is
not only useful for analysing MQOs of massless Dirac semimetals with a small
cyclotron mass, but also can be used for MQOs in massive Dirac materials with
degenerate orbits, especially in topological materials with a sufficiently
large cyclotron mass. Furthermore, this method provides a useful way to
estimate the precise $g_s$ value of the material.",2010.10826v3
2004-08-17,Two-photon spin injection in semiconductors,"A comparison is made between the degree of spin polarization of electrons
excited by one- and two-photon absorption of circularly polarized light in bulk
zincblende semiconductors. Time- and polarization-resolved experiments in
(001)-oriented GaAs reveal an initial degree of spin polarization of 49% for
both one- and two-photon spin injection at wavelengths of 775 and 1550 nm, in
agreement with theory. The macroscopic symmetry and microscopic theory for
two-photon spin injection are reviewed, and the latter is generalized to
account for spin-splitting of the bands. The degree of spin polarization of
one- and two-photon optical orientation need not be equal, as shown by
calculations of spectra for GaAs, InP, GaSb, InSb, and ZnSe using a 14x14 k.p
Hamiltonian including remote band effects. By including the higher conduction
bands in the calculation, cubic anisotropy and the role of allowed-allowed
transitions can be investigated. The allowed-allowed transitions do not
conserve angular momentum and can cause a high degree of spin polarization
close to the band edge; a value of 78% is calculated in GaSb, but by varying
the material parameters it could be as high as 100%. The selection rules for
spin injection from allowed-allowed transitions are presented, and interband
spin-orbit coupling is found to play an important role.",0408386v1
2007-01-04,Rashba interferometers: Spin-dependent single and two-electron interference,"Quantum transport in semiconductor nanostructures can be described
theoretically in terms of the propagation and scattering of electron
probability waves. Within this approach, elements of a phase-coherent electric
circuit play a role similar to quantum-optical devices that can be
characterised by scattering matrices. Electronic analogues of well-know optical
interferometers have been fabricated and used to study special features of
charge carriers in solids. We present results from our theoretical
investigation into the interplay between spin precession and quantum
interference in an electronic Mach-Zehnder interferometer with spin-orbit
coupling of the Rashba type. Intriguing spin-dependent transport effects occur,
which can be the basis for novel spintronic devices such as a magnet-less
spin-controlled field-effect transistor and a variety of single-qubit gates.
Their functionality arises entirely from spin-dependent interference of each
single input electron with itself. We have also studied two-electron
interference effects for the spin-dependent Mach-Zehnder interferometer,
obtaining analytical expressions for its two-fermion-state scattering matrix.
Using this result, we consider ways to generate two-electron output states for
which the Rashba spin-subband quantum number and the output-arm index are
entangled. Combining spin-dependent interference in our proposed Mach-Zehnder
interferometer with a projective charge measurement at the output enables
entanglement generation. As our particular scheme involves tuneable spin
precession, electric-field control of entanglement production can be achieved.",0701065v3
2014-09-14,All-optical formation of coherent dark states of silicon-vacancy spins in diamond,"Spin impurities in diamond can be versatile tools for a wide range of
solid-state-based quantum technologies, but finding spin impurities which offer
sufficient quality in both photonic and spin properties remains a challenge for
this pursuit. The silicon-vacancy center has recently attracted a lot of
interest due to its spin-accessible optical transitions and the quality of its
optical spectrum. Complementing these properties, spin coherence is essential
for the suitability of this center as a spin-photon quantum interface. Here, we
report all-optical generation of coherent superpositions of spin states in the
ground state of a negatively charged silicon-vacancy center using coherent
population trapping. Our measurements reveal a characteristic spin coherence
time, T2*, exceeding 250 nanoseconds at 4 K. We further investigate the role of
phonon-mediated coupling between orbital states as a source of irreversible
decoherence. Our results indicate the feasibility of all-optical coherent
control of silicon-vacancy spins using ultrafast laser pulses.",1409.4069v1
2015-09-05,Antiferromagnetic nuclear spin helix and topological superconductivity in $^{13}$C nanotubes,"We investigate the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction arising
from the hyperfine coupling between localized nuclear spins and conduction
electrons in interacting $^{13}$C carbon nanotubes. Using the Luttinger liquid
formalism, we show that the RKKY interaction is sublattice dependent,
consistent with the spin susceptibility calculation in noninteracting carbon
nanotubes, and it leads to an antiferromagnetic nuclear spin helix in
finite-size systems. The transition temperature reaches up to tens of mK, due
to a strong boost by a positive feedback through the Overhauser field from
ordered nuclear spins. Similar to GaAs nanowires, the formation of the helical
nuclear spin order gaps out half of the conduction electrons, and is therefore
observable as a reduction of conductance by a factor of 2 in a transport
experiment. The nuclear spin helix leads to a density wave combining spin and
charge degrees of freedom in the electron subsystem, resulting in synthetic
spin-orbit interaction, which induces non-trivial topological phases. As a
result, topological superconductivity with Majorana fermion bound states can be
realized in the system in the presence of proximity-induced superconductivity
without the need of fine tuning the chemical potential. We present the phase
diagram as a function of system parameters, including the pairing gaps, the gap
due to the nuclear spin helix, and the Zeeman field perpendicular to the
helical plane.",1509.01685v2
2020-07-07,Spin shuttling in a silicon double quantum dot,"The transport of quantum information between different nodes of a quantum
device is among the challenging functionalities of a quantum processor. In the
context of spin qubits, this requirement can be met by coherent electron spin
shuttling between semiconductor quantum dots. Here we theoretically study a
minimal version of spin shuttling between two quantum dots. To this end, we
analyze the dynamics of an electron during a detuning sweep in a silicon double
quantum dot (DQD) occupied by one electron. Possibilities and limitations of
spin transport are investigated. Spin-orbit interaction and the Zeeman effect
in an inhomogeneous magnetic field play an important role for spin shuttling
and are included in our model. Interactions that couple the position, spin and
valley degrees of freedom open a number of avoided crossings in the spectrum
allowing for diabatic transitions and interfering paths. The outcomes of single
and repeated spin shuttling protocols are explored by means of numerical
simulations and an approximate analytical model based on the solution of the
Landau--Zener problem. We find that a spin infidelity as low as $1-F_s\lesssim
0.002$ with a relatively fast level velocity of $\alpha = 600\, {\mu}$eV/ns is
feasible for optimal choices of parameters or by making use of constructive
interference.",2007.03598v1
2011-11-22,Multivalley spin relaxation in $n$-type bulk GaAs in the presence of high electric fields,"Multivalley spin relaxation in $n$-type bulk GaAs in the presence of high
electric field is investigated from the microscopic kinetic spin Bloch equation
approach with the $\Gamma$ and $L$ valleys included. We show that the spin
relaxation time decreases monotonically with the electric field, which differs
from the two-dimensional case and is recognized due to to the cubic form of the
Dresselhauss spin-orbit coupling of the $\Gamma$ valley in bulk. In addition to
the direct modulation of the spin relaxation time, the electric field also
strongly influences the density and temperature dependences of the spin
relaxation. In contrast to the monotonic decrease with increasing lattice
temperature in the field-free condition, the spin relaxation time is shown to
decrease more slowly under the influence of the electric field and even to
increase monotonically in the case with small electron density and high
electric field. We even predict a peak in weakly doped samples under moderate
electric field due to the anomalous lattice-temperature dependence of the
hot-electron temperature. As for the $L$ valleys, we show that instead of
playing the role of a ""drain"" of the total spin polarization as in quantum well
systems, in bulk they serve as a ""momentum damping area"", which prevents
electrons from drifting to higher momentum states. This tends to suppress the
inhomogeneous broadening and hence leads to an increase of the spin relaxation
time.",1111.5353v1
2020-12-29,Observation of spin-momentum-layer locking in centrosymmetric BiOI,"Spin polarization effects in nonmagnetic materials are generally believed as
an outcome of spin-orbit coupling provided that the global inversion symmetry
is lacking, also known as 'spin-momentum locking'. The recently discovered
hidden spin polarization indicates that specific atomic site asymmetry could
also induce measurable spin polarization, leading to a paradigm shift to
centrosymmetric crystals for potential spintronic applications. Here, combining
spin- and angle-resolved photoemission spectroscopy and theoretical
calculations, we report distinct spin-layer locking phenomena surrounding
different high-symmetry momenta in a centrosymmetric, layered material BiOI.
The measured spin is highly polarized along the Brillouin zone boundary, while
is almost vanishing around the zone center due to its nonsymmorphic crystal
structure. Our work not only demonstrates the existence of hidden spin
polarization, but also uncovers the microscopic mechanism of the way spin,
momentum and layer locking to each other, shedding lights on the design metrics
for future spintronic devices.",2012.14807v1
2019-08-21,Tunable room-temperature spin galvanic and spin Hall effects in van der Waals heterostructures,"Spin-orbit coupling stands as a powerful tool to interconvert charge and spin
currents and to manipulate the magnetization of magnetic materials through the
spin torque phenomena. However, despite the diversity of existing bulk
materials and the recent advent of interfacial and low-dimensional effects,
control of the interconvertion at room-temperature remains elusive. Here, we
unequivocally demonstrate strongly enhanced room-temperature spin-to-charge
(StC) conversion in graphene driven by the proximity of a semiconducting
transition metal dichalcogenide(WS2). By performing spin precession experiments
in properly designed Hall bars, we separate the contributions of the spin Hall
and the spin galvanic effects. Remarkably, their corresponding conversion
effiencies can be tailored by electrostatic gating in magnitude and sign,
peaking nearby the charge neutrality point with a magnitude that is comparable
to the largest efficiencies reported to date. Such an unprecedented
electric-field tunability provides a new building block for spin generation
free from magnetic materials and for ultra-compact magnetic memory
technologies.",1908.07868v1
2019-08-25,All-electrical creation and control of giant spin-galvanic effect in 1T-MoTe2/graphene heterostructures at room temperature,"The ability to engineer new states of matter and to control their electronic
and spintronic properties by electric fields is at the heart of the modern
information technology and driving force behind recent advances in van der
Waals (vdW) heterostructures of two-dimensional materials. Here, we exploit a
proximity-induced Rashba-Edelstein (REE) effect in vdW heterostructures of Weyl
semimetal candidate MoTe2 and CVD graphene, where an unprecedented
gate-controlled switching of spin-galvanic effect emerges due to an efficient
spin-to-charge conversion at room temperature. The magnitude of the measured
spin-galvanic signal is found to be an order of magnitude larger than the other
systems, giving rise to a giant REE. The magnitude and the sign of the
spin-galvanic signal are shown to be strongly modulated by gate electric field
near the charge neutrality point, which can be understood considering the spin
textures of the Rashba spin-orbit coupling-induced spin-splitting in conduction
and valence bands of the heterostructure. These findings open opportunities for
utilization of gate-controlled switching of spin-galvanic effects in spintronic
memory and logic technologies and possibilities for realization of new states
of matter with novel spin textures in vdW heterostructures with gate-tunable
functionalities.",1908.09367v2
2019-06-11,"Intrinsic persistent spin helix in two-dimensional group-IV monochalcogenide MX (M : Sn, Ge; X: S, Se, Te) monolayer","Energy-saving spintronics are believed to be implementable on the systems
hosting persistent spin helix (PSH) since they support an extraordinarily long
spin lifetime of carriers. However, achieving the PSH requires a unidirectional
spin configuration in the momentum space, which is practically non-trivial due
to the stringent conditions for fine-tuning the Rashba and Dresselhaus
spin-orbit couplings. Here, we predict that the PSH can be intrinsically
achieved on a two-dimensional (2D) group-IV monochalcogenide M X monolayer, a
new class of the noncentrosymmetric 2D materials having in-plane
ferroelctricity. Due to the C2v point group symmetry in the MX monolayer, a
unidirectional spin configuration is preserved in the out-of-plane direction
and thus maintains the PSH that is similar to the [110] Dresselhaus model in
the [110]-oriented quantum well. Our first-principle calculations on various MX
(M : Sn, Ge; X: S, Se, Te) monolayers confirmed that such typical spin
configuration is observed, in particular, at near the valence band maximum
where a sizable spin splitting and a substantially small wavelength of the spin
polarization are achieved. Importantly, we observe reversible out-of-plane spin
orientation under opposite in-plane ferroelectric polarization, indicating that
an electrically controllable PSH for spintronic applications is plausible.",1906.04337v2
2021-01-05,Symmetry and Control of Spin-Scattering Processes in Two-Dimensional Transition Metal Dichalcogenides,"Transition metal dichalcogenides (TMDs) combine interesting optical and
spintronic properties in an atomically-thin material, where the light
polarization can be used to control the spin and valley degrees-of-freedom for
the development of novel opto-spintronic devices. These promising properties
emerge due to their large spin-orbit coupling in combination with their crystal
symmetries. Here, we provide simple symmetry arguments in a group-theory
approach to unveil the symmetry-allowed spin scattering mechanisms, and
indicate how one can use these concepts towards an external control of the spin
lifetime. We perform this analysis for both monolayer (inversion asymmetric)
and bilayer (inversion symmetric) crystals, indicating the different mechanisms
that play a role in these systems. We show that, in monolayer TMDs, electrons
and holes transform fundamentally differently -- leading to distinct
spin-scattering processes. We find that one of the electronic states in the
conduction band is partially protected by time-reversal symmetry, indicating a
longer spin lifetime for that state. In bilayer and bulk TMDs, a hidden
spin-polarization can exist within each layer despite the presence of global
inversion symmetry. We show that this feature enables control of the interlayer
spin-flipping scattering processes via an out-of-plane electric field,
providing a mechanism for electrical control of the spin lifetime.",2101.01565v3
2023-07-30,Stationary equilibrium torus supported by Weyssenhoff ideal spin fluid in Schwarzschild spacetime -- I: Case of constant specific angular momentum distribution,"We consider a non-self-gravitating geometrically thick torus described by
Weyssenhoff ideal spin fluid in a black hole spacetime. The Weyssenhof spin
fluid shares the same symmetries of the background geometry, i,e. stationarity
and axisymmetry and further describes circular orbital motion in the black hole
spacetime. We further assume that assume the alignment of the spin is
perpendicular to the equatorial plane. Under this setup, we determine the
integrability conditions of the general relativistic momentum conservation
equation of Weyssenhoff ideal spin fluid using the Frenkel spin supplementary
condition. In the light of the integrability conditions, we then present
stationary equilibrium solutions of the spin fluid torus with constant specific
angular momentum distributions around the Schwarzschild black hole by
numerically solving the general relativistic momentum conservation equation.
Our study reveals that both the iso-pressure and iso-density surfaces of torus
get significantly modified in comparison to the ideal fluid torus without a
spin fluid, owing to the spin tensor and its coupling to the curvature of the
Schwarzschild black hole. In fact, the size of the torus is also found to be
enhanced (diminished) depending on positive (negative) magnitude of spin
parameter $s_0$. We finally estimate the magnitude of $s_0$ by assuming the
torus to be composed of spin-1/2 particles.",2307.16292v1
2024-01-25,Room temperature nonlocal detection of charge-spin interconversion in a topological insulator,"Topological insulators (TIs) are emerging materials for next-generation
low-power nanoelectronic and spintronic device applications. TIs possess
non-trivial spin-momentum locking features in the topological surface states in
addition to the spin-Hall effect (SHE), and Rashba states due to high
spin-orbit coupling (SOC) properties. These phenomena are vital for observing
the charge-spin conversion (CSC) processes for spin-based memory, logic and
quantum technologies. Although CSC has been observed in TIs by potentiometric
measurements, reliable nonlocal detection has so far been limited to cryogenic
temperatures up to T = 15 K. Here, we report nonlocal detection of CSC and its
inverse effect in the TI compound Bi1.5Sb0.5Te1.7Se1.3 at room temperature
using a van der Waals heterostructure with a graphene spin-valve device. The
lateral nonlocal device design with graphene allows observation of both
spin-switch and Hanle spin precession signals for generation, injection and
detection of spin currents by the TI. Detailed bias- and gate-dependent
measurements in different geometries prove the robustness of the CSC effects in
the TI. These findings demonstrate the possibility of using topological
materials to make all-electrical room-temperature spintronic devices.",2401.14262v1
2008-06-28,Spin-dependent scattering in a silicon transistor,"The scattering of conduction electrons off neutral donors depends sensitively
on the relative orientation of their spin states. We present a theory of
spin-dependent scattering in the two dimensional electron gas (2DEG) of field
effect transistors. Our theory shows that the scattering mechanism is dominated
by virtual transitions to negatively ionized donor levels. This effect
translates into a source-drain current that always gets reduced when donor
spins are at resonance with a strong microwave field. We propose a model for
donor impurities interacting with conduction electrons in a silicon transistor,
and compare our explicit numerical calculations to electrically detected
magnetic resonance (EDMR) experiments. Remarkably, we show that EDMR is optimal
for donors placed into a sweet spot located at a narrow depth window quite far
from the 2DEG interface. This allows significant optimization of spin signal
intensity for the minimal number of donors placed into the sweet spot, enabling
the development of single spin readout devices. Our theory reveals an
interesting dependence on conduction electron spin polarization p_c. As p_c
increases upon spin injection, the EDMR amplitude first increases as p_{c}^{2},
and then saturates when a polarization threshold p_T is reached. These results
show that it is possible to use EDMR as an in-situ probe of carrier spin
polarization in silicon and other materials with weak spin-orbit coupling.",0806.4638v3
2021-09-15,Electronic Impurity Scattering Induced Spin Accumulation in Metallic Thin Films,"In order to explore the spin accumulation, evaluating the spin galvanic and
spin Hall effect, we utilize the semi-classical Boltzmann equation based on
input from the relativistic Korringa-Kohn-Rostoker Green's function method,
within the density functional theory. We calculate the spin accumulation
including multiple contributions, especially skew-scattering (scattering-in
term) and compare this to three different approximations, which include the
isotropic and anisotropic relaxation time approximation. For heavy metals, with
strong intrinsic spin-orbit coupling, we find that almost all the effects are
captured within the anisotropic relaxation time approximation. On the other
hand, in light metals the contributions from the vertex corrections
(scattering-in term) are comparable to the induced effect in anisotropic
relaxation time approximation. We put a particular focus on the influence of
the atomic character of the substitutional impurities on the spin accumulation
as well as the dependence on the impurity position. As impurities will break
space inversion symmetry of the thin film, this will give rise to both
symmetric and antisymmetric contributions to the spin accumulation. In general,
we find the impurities at the surface generate the largest efficiency of
charge-to-spin conversion in case of the spin accumulation. Comparing our
results to existing experimental findings for Pt we find a good agreement.",2109.07271v2
2021-10-11,Topological phonons in an inhomogeneously strained silicon-4: Large spin dependent thermoelectric response and thermal spin transfer torque due to topological electronic magnetism of phonons,"The superposition of flexoelectronic doping and topological phonons give rise
to topological electronic magnetism of phonon in an inhomogeneously strained Si
in the bilayer structure with metal. In case of ferromagnetic metal and Si
bilayer structure, the flexoelectronic doping will also give rise to larger
spin current, which will lead to large spin to charge conversion due to
topological electronic magnetism of phonon. By applying a temperature
difference to ferromagnetic metal/Si bilayer structure under an applied strain
gradient, a large thermoelectric response can be generated. In this
experimental study, we report a large spin dependent thermoelectric response at
Ni80Fe20/Si bilayer structure. The spin dependent response is found to be an
order of magnitude larger than that in Pt thin films and similar to topological
insulators surface states in spite of negligible intrinsic spin-orbit coupling
of Si. This large response is attributed to the flexoelectronic doping and
topological electronic magnetism of phonons, which was uncovered using
topological Nernst effect measurement. This alternative and novel approach of
using inhomogeneous strain engineering to address both spin current density and
spin to charge conversion can open a new window to the realization of
spintronics and spin-caloritronics devices using metal and doped-semiconductor
layered materials.",2110.04939v1
2022-07-06,Calculating the spin memory loss at Cu$|$metal interfaces from first principles,"The role played by interfaces in metallic multilayers is not only to change
the momenta of incident electrons; their symmetry lowering also results in an
enhancement of the effects of spin-orbit coupling, in particular the flipping
of the spins of conduction electrons. This leads to a significant reduction of
a spin current through a metallic interface that is quantitatively
characterized by a dimensionless parameter $\delta$ called the spin memory loss
(SML) parameter, the interface counterpart of the spin-flip diffusion length
for bulk metals. In this paper we use first-principles scattering calculations
that include temperature-induced lattice and spin disorder to systematically
study three parameters that govern spin transport through metallic interfaces
of Cu with Pt, Pd, Py (permalloy) and Co: the interface resistance, spin
polarization and the SML. The value of $\delta$ for a Cu$|$Pt interface is
found to be comparable to what we recently reported for a Au$|$Pt interface
[Gupta {\it et al.}, Phys. Rev. Lett. 124, 087702 (2020)]. For Cu$|$Py and
Cu$|$Co interfaces, $\delta$ decreases monotonically with increasing
temperature to become negligibly small at room temperature. The calculated
results are in good agreement with currently available experimental values in
the literature. Inserting a Cu layer between Pt and the Py or Co layers
slightly increases the total spin current dissipation at these ""compound""
interfaces.",2207.02395v1
2023-05-25,Photogalvanic effect induced charge and spin photocurrent in group-V monolayer systems,"Photogalvanic effect (PGE) occurs in materials with non-centrosymmetric
structures when irradiated by linearly or circularly polarized light. Here,
using non-equilibrium Green's function combined with density functional theory
(NEGF-DFT), we investigated the linear photogalvanic effect (LPGE) in
monolayers of group-V elements (As, Sb, and Bi) by first-principles
calculations. First, by designing a two-probe structure based on the group-V
elements, we found a giant anisotropy photoresponse of As between the armchair
and zigzag directions. Then, we analyzed Sb and Bi's charge and spin
photocurrent characteristics when considering the spin-orbit coupling (SOC)
effect. It is found that when the polarization direction of linearly polarized
light is parallel or perpendicular to the transport direction ($\theta$ = $0^
\circ$ or $90^ \circ$), the spin up and spin down photoresponse in the armchair
direction has the same magnitude and direction, leading to the generation of
net charge current. However, in the zigzag direction, the spin up and spin down
photoresponse have the same magnitude with opposite directions, leading to the
generation of pure spin current. Furthermore, it is understood by analyzing the
bulk spin photovoltaic (BSPV) coefficient from the symmetry point of view.
Finally, we found that the net charge current generated in the armchair
direction and the pure spin current generated in the zigzag direction can be
further tuned with the increase of the material's buckling height $|h|$. Our
results highlight that these group-V monolayers are promising candidates for
novel functional materials, which will provide a broad prospect for the
realization of ultrathin ferroelectric devices in optoelectronics due to their
spontaneous polarization characteristics and high Curie temperature.",2305.16032v1
2023-12-12,Photonic spin Hall effect in Haldane materials,"The photonic spin Hall effect of light beams reflected from the surfaces of
various two-dimensional hexagonal crystalline structures, considering their
associated time-reversal $\mathcal{T}$ and inversion $\mathcal{I}$ symmetries,
is investigated. Employing the Haldane model with tunable parameters as a
generic model, we examine the longitudinal and transverse spin-separations of
the reflected beam in both topological non-trivial and trivial systems. The
study reveals that the sign switching of the PSHE in these materials is
attributed to the non-trivial and trivial topology. By manipulating the
interplay between spin-orbit coupling and external electric fields, we
demonstrate topological phase transitions in buckled Xene monolayer materials
through the photonic spin Hall effect. Different behaviors of the photonic spin
Hall effect are observed in various topological phases within these materials.
Additionally, we explore the reflected spin and valley-polarized spatial shifts
in monolayer transition metal dichalcogenides. The photonic spin Hall effect in
buckled Xene monolayer materials and transition metal dichalcogenides is highly
influenced by the spin and valley degrees of freedom of charge carriers,
offering a promising avenue to explore spintronics and valleytronics in these
hexagonal materials. We propose that the photonic spin Hall effect in Haldane
materials can serve as a metrological tool for optical parameter
characterization and as a promising method for determining Chern numbers and
topological phase transitions through direct optical weak measurement
techniques.",2312.07013v1
2006-09-13,Room Temperature Reversible Spin Hall Effect,"Reversible spin Hall effect comprising the ""direct"" and ""inverse"" spin Hall
effects was successfully detected at room temperature. This experimental
demonstration proves the fundamental relations called Onsager reciprocal
relations between spin and charge currents. A platinum wire with a strong
spin-orbit interaction is used not only as a spin current absorber but also as
a spin current source in the present lateral structure specially designed for
clear detection of both charge and spin accumulations via the spin-orbit
interaction. The obtained spin Hall conductivity is much larger than the
reported value of Aluminum wire because of the larger spin-orbit interaction.",0609304v1
2010-04-05,Kondo effect in spin-orbit mesoscopic interferometers,"We consider a flux-threaded Aharonov-Bohm ring with an embedded quantum dot
coupled to two normal leads. The local Rashba spin-orbit interaction acting on
the dot electrons leads to a spin-dependent phase factor in addition to the
Aharonov-Bohm phase caused by the external flux. Using the numerical
renormalization group method, we find a splitting of the Kondo resonance at the
Fermi level which can be compensated by an external magnetic field. To fully
understand the nature of this compensation effect, we perform a scaling
analysis and derive an expression for the effective magnetic field. The
analysis is based on a tight-binding model which leads to an effective Anderson
model with a spin-dependent density of states for the transformed lead states.
We find that the effective field originates from the combined effect of Rashba
interaction and magnetic flux and that it contains important corrections due to
electron-electron interactions. We show that the compensating field is an
oscillatory function of both the spin-orbit and the Aharonov-Bohm phases.
Moreover, the effective field never vanishes due to the particle-hole symmetry
breaking independently of the gate voltage.",1004.0670v2
2010-11-08,"Manipulation of the Land$\acute{\text{e}}$ g-factor in InAs quantum dots through the application of anisotropic gate potentials: Exact diagonalization, numerical and perturbation methods","We study the variation in the Land$\acute{\text{e}}$ g-factor of electron
spins induced by both anisotropic gate potentials and magnetic fields in InAs
quantum dots for possible implementation towards solid state quantum computing.
In this paper, we present analytical expressions and numerical simulations of
the variation in the Land$\acute{\text{e}}$ g-factor for both isotropic and
anisotropic quantum dots. Using both analytical techniques and numerical
simulations, we show that the Rashba spin-orbit coupling has a major
contribution in the variation of the g-factor with electric fields before the
regime, where level crossing or anticrossing occurs. In particular, the
electric field tunability is shown to cover a wide range of g-factor through
strong Rashba spin-orbit interaction. Another major result of this paper is
that the anisotropic gate potential gives quenching effect in the orbital
angular momentum that reduces the variation in the E-field and B-field
tunability of the g-factor if the area of the symmetric and asymmetric quantum
dots is held constant. We identify level crossings and anticrossings of the
electron states in the variation of the Land$\acute{\text{e}}$ g-factor. We
model the wavefunctions of electron spins and estimate the size of the
anticrossing for the spin states $|0,-1,+1/2>$ and $|0,0,-1/2>$ corresponding
to a quantum dot that has been recently studied experimentally (Phys. Rev.
Lett. \textbf{104}, 246801 (2010)).",1011.1921v2
2015-11-25,Spin-texture induced by oxygen vacancies in Strontium perovskites (001) surfaces: A theoretical comparison between SrTiO3 and SrHfO3,"The electronic structure of SrTiO3 and SrHfO3 (001) surfaces with oxygen
vacancies is studied by means of first-principles calculations. We reveal how
oxygen vacancies within the first atomic layer of the SrTiO3 surface (i) induce
a large antiferrodistortive motion of the oxygen octahedra at the surface, (ii)
drive localized magnetic moments on the Ti-3d orbitals close to the vacancies
and (iii) form a two-dimensional electron gas localized within the first
layers. The analysis of the spin-texture of this system exhibits a splitting of
the energy bands according to the Zeeman interaction, lowering of the Ti-3dxy
level in comparison with dxz and dyz and also an in-plane precession of the
spins. No Rashba-like splitting for the ground state neither for ab-initio
molecular dynamics trajectory at 400K is recognized as suggested recently by A.
F. Santander-Syro et al. [1]. Instead, a sizeable Rashba-like splitting is
observed when the Ti atom is replaced by a heavier Hf atom with a much larger
spin-orbit interaction. However, we observe the disappearance of the magnetism
and the surface two dimensional electron gas when full structural optimization
of the SrHfO3 surface is performed. Our results uncover the sensitive interplay
of spin-orbit coupling, atomic relaxations and magnetism when tuning these
Sr-based perovskites.",1511.08079v1
2017-03-10,Room-temperature perpendicular magnetization switching through giant spin-orbit torque from sputtered BixSe(1-x) topological insulator material,"The spin-orbit torque (SOT) arising from materials with large spin-orbit
coupling promises a path for ultra-low power and fast magnetic-based storage
and computational devices. We investigated the SOT from magnetron-sputtered
BixSe(1-x) thin films in BixSe(1-x)/CoFeB heterostructures by using a dc planar
Hall method. Remarkably, the spin Hall angle (SHA) was found to be as large as
18.83, which is the largest ever reported at room temperature (RT). Moreover,
switching of a perpendicular CoFeB multilayer using SOT from the BixSe(1-x) has
been observed with the lowest-ever switching current density reported in a
bilayer system: 2.3 * 105 A/cm2 at RT. The giant SHA, smooth surface, ease of
growth of the films on silicon substrate, successful growth and switching of a
perpendicular CoFeB multilayer on BixSe(1-x) film opens a path for use of
BixSe(1-x) topological insulator (TI) material as a spin-current generator in
SOT-based memory and logic devices.",1703.03822v1
2013-08-08,Imprints of spin-orbit density wave in the hidden order state of URu2Si2,"The mysterious second order quantum phase transition, commonly attributed to
the `hidden-order' (HO) state, in heavy-fermion metal URu2Si2 exhibits a number
of paradoxical electronic and magnetic properties which cannot be associated
with any conventional order parameter. We characterize and reconcile these
exotic properties of the HO state based on a spin-orbit density wave order
(SODW), constructed on the basis of a realistic density-functional theory (DFT)
band structure. We quantify the nature of the gapped electronic and magnetic
excitation spectrum, in agreement with measurements, while the magnetic moment
is calculated to be zero owing to the spin-orbit coupling induced time-reversal
invariance. Furthermore, a new collective mode in the spin-1 excitation
spectrum is predicted to localize at zero momentum transfer in the HO state
which can be visualized, for example, by electron spin resonance (ESR) at zero
magnetic field or polarized inelastic neutron scattering measurements. The
results demonstrate that the concomitant broken and invariant symmetries
protected SODW order not only provides insights into numerous nontrivial
hidden-order phenomena, but also offers a parallel laboratory to the formation
of a topologically protected quantum state beyond the quantum spin-Hall state
and Weyl semimetals.",1308.1992v2
2016-11-10,Andreev spectrum with high spin-orbit interactions: revealing spin splitting and topologically protected crossings,"We investigate numerically the Andreev spectrum of a multichannel mesoscopic
quantum wire (N) with high spin-orbit interaction coupled to superconducting
electrodes (S), contrasting topological and non topological behaviors.
  In the non topological case, modeled by a square lattice with Rashba
interactions, we find that as soon as the normal quantum wires can host several
conduction channels, the spin degeneracy of Andreev levels is lifted by a phase
difference between the S reservoirs which breaks time reversal symmetry in zero
Zeeman field. The Andreev states remain degenerate at phases multiple of $\pi$
for which time reversal symmetry is preserved, giving rise to level crossings
which are not lifted by disorder. In contrast with the dc Josephson current,
the finite frequency admittance (susceptibility) is very sensitive to these
level crossings and the lifting of their degeneracy by a small Zeeman field.
More interesting is the case of the hexagonal lattice with next nearest
neighbor spin-orbit interactions which exhibit 1D topological helical edge
states \cite{Kane2005}. The finite frequency admittance carries then a very
specific signature at low temperature of a protected Andreev level crossing at
$\pi$ and zero energy in the form of a sharp peak split by a Zeeman field.",1611.03526v1
2018-05-21,Spin-orbit-driven electron pairing in two dimensions,"We show that the spin-orbit interaction (SOI) arising due to the in-plane
electric field of the Coulomb repulsion between electrons in a two-dimensional
quantum well produces an attractive component in the pair interaction
Hamiltonian that depends on the spins and momenta of electrons. If the Rashba
SOI constant of the material is high enough the attractive component overcomes
the Coulomb repulsion and the centrifugal barrier, which leads to the formation
of the two-electron bound states. There are two distinct types of two-electron
bound states. The relative bound states are formed by the electrons orbiting
around their common barycenter. They have the triplet spin structure and are
independent of the center-of-mass momentum. In contrast, the convective bound
states are formed because of the center-of-mass motion, which couples the
electrons with opposite spins. The binding energy in the meV range is
attainable for realistic conditions.",1805.08216v7
2017-05-17,Landau quantization in buckled monolayer GaAs,"Magneto-electronic properties of buckled monolayer GaAs is studied by the
developed generalized tight-binding model, considering the buckled structure,
multi-orbital chemical bondings, spin-orbit coupling, electric field, and
magnetic field simultaneously. Three group of spin-polarized Landau levels
(LLs) near the Fermi level are induced by the magnetic quantization, whose
initial energies, LL degeneracy, energy spacings, magnetic-field-dependence,
and spin polarization are investigated. The Landau state probabilities
describing the oscillation patterns, localization centers, and node
regularities of the dominated/minor orbitals are analyzed, and their
energy-dependent variations are discussed. The given density of states directly
reflects the main features of the LL energy spectra in the structure, height,
number, and frequency of the spin-polarized LL peaks. The electric field causes
the monotonous/nonmonotonous LL energy dispersions, LL crossing, gap
modulation, phase transition and spin splitting enhancement. The complex gap
modulations and phase transitions based on the competition between magnetic and
electric fields are explored in detail by the phase diagram. The
field-controlled gap modulations and phase transitions are helpful in designing
the top-gated and phase-change electronic devices. These predicted
magneto-electronic properties could be verified by scanning tunneling
spectroscopy measurements.",1705.06016v1
2019-04-08,Effect of orbital eccentricity on the dynamics of precessing compact binaries,"We study precession dynamics of generic binary black holes in eccentric
orbits using an effective potential based formalism derived in [M. Kesden et
al., PRL {\bf 114}, 081103 (2015)]. This effective potential is used to
classify binary black holes into three mutually exclusive spin morphologies.
During the inspiral phase, binaries make transitions from one morphology to
others. We evolve a population of binary black holes from an initial separation
of $1000\mathbf{M}$ to a final separation of $10\mathbf{M}$ using
post-Newtonian accurate evolution equations. We find that, given suitable
initial conditions, a binary's eccentricity can follow one of three distinct
evolutionary patterns: (i) eccentricity monotonically increasing until final
separation, (ii) eccentricity rising after decaying to a minimum value, and
(iii) eccentricity monotonically decreasing throughout the inspiral. The
monotonic growth or growth after reaching a certain minimum of eccentricity is
due to the effect of 2PN spin-spin coupling. Further, we investigate the
morphology transitions in eccentric binaries and find that the probability of
such binaries transiting from one to other is similar to those in circular
orbits, implying that eccentricity plays a sub-dominant role in spin morphology
evolution of a precessing binary black hole. We, hence, argue that the
morphological classification of spin precession dynamics is a robust tool to
constrain the formation channels of binaries with arbitrary eccentricity as
well.",1904.03985v2
2022-10-06,Tunable superconductivity and Möbius Fermi surfaces in an inversion-symmetric twisted van der Waals heterostructure,"We study theoretically a moir\'e superlattice geometry consisting of
mirror-symmetric twisted trilayer graphene surrounded by identical transition
metal dichalcogenide layers. We show that this setup allows to switch on/off
and control the spin-orbit splitting of the Fermi surfaces via application of a
perpendicular displacement field $D_0$, and explore two manifestations of this
control: first, we compute the evolution of superconducting pairing with $D_0$;
this features a complex admixture of singlet and triplet pairing and, depending
on the pairing state in the parent trilayer system, phase transitions between
competing superconducting phases. Second, we reveal that, with application of
$D_0$, the spin-orbit-induced spin textures exhibit vortices which lead to
""M\""obius fermi surfaces'' in the interior of the Brillouin zone: diabatic
electron trajectories, which are predicted to dominate quantum oscillation
experiments, require encircling the $\Gamma$ point twice, making their M\""obius
nature directly observable. We further show that the superconducting order
parameter inherits the unconventional, M\""obius spin textures. Our findings
suggest that this system provides a promising experimental avenue for studying
systematically the impact of spin-orbit coupling on the multitude of
topological and correlated phases in near-magic-angle twisted trilayer
graphene.",2210.03125v1
2023-08-29,Relativistic and Spin-Orbit Dynamics at Non-Relativistic Intensities in Strong-Field Ionization,"Spin-orbit dynamics and relativistic corrections to the kinetic energy in
strong-field dynamics, have long been ignored for near- and mid-IR fields with
intensities $10^{13}$--$10^{14}$ W/cm$^2$, as the final photoelectron energies
are considered too low for these effects to play a role. However, using a
precise and flexible path-integral formalism, we include all correction terms
from the fine-structure, Breit-Pauli Hamiltonian. This enables a treatment of
spin, through coherent spin-states, which is the first model to use this
approach in strong-field physics. We are able to show that the most
energetically rescattered wavepackets, undergo huge momentum transfer and
briefly reach relativistic velocities, which warrants relativistic kinetic
energy corrections. We probe these effects and show that they yield notable
differences for a $1600$ nm wavelength laser field on the dynamics and the
photoelectron spectra. Furthermore, we find that the dynamical spin-orbit
coupling is strongly overestimated if relativistic corrections to kinetic
energy are not considered. Finally, we derive a new condition that demonstrates
that relativistic effects begin to play a role at intensities orders of
magnitude lower than expected. Our findings may have important implication for
imaging processes such as laser-induced electron diffraction, which includes
high-energy photoelectron recollisions.",2308.15374v1
1999-06-08,Toward a Theory of Orbiton Dispersion in LaMnO_3,"At 750K, LaMnO_3 has a cooperative Jahn-Teller (JT) distortion, with Mn atoms
in distorted oxygen octahedra. This lifts the degeneracy of the singly-occupied
$e_g$ orbitals of the Mn$^{3+}$ ions, which then become orbitally ordered. We
use a minimal model to describe the ordered phase at T=0. The on-site Coulomb
repulsion $U$ is set to infinity. There are two electronic orbitals and three
oxygen vibrational coordinates per unit cell. In addition to spin excitations
and phonons, the model has electronic excitations consisting of mis-orienting
orbitals on Mn ions. Neglecting coupling to the oxygen displacements, the gap
to such excitations is $2\Delta=16g^2/K$ where $g$ is the electron-phonon
coupling and $K$ is the oxygen spring constant. When static oxygen
displacements are coupled, this excitation becomes a self-trapped exciton with
energy $\Delta$, half the JT gap. Adding dynamic oxygen displacements in
one-phonon approximation introduces dispersion to both the (previously
Einstein-like) phonons and the orbital excitons (``orbitons''). One of the
phonon branches has zero frequency at $\vec{k}=(0,0,\pi)$. This is the
Goldstone mode of the JT broken symmetry.",9906118v1
2007-10-16,Global quark polarization in non-central $A+A$ collisions,"Partons produced in the early stage of non-central heavy-ion collisions can
develop a longitudinal fluid shear because of unequal local number densities of
participant target and projectile nucleons. Under such fluid shear, local
parton pairs with non-vanishing impact parameter have finite local relative
orbital angular momentum along the direction opposite to the reaction plane.
Such finite relative orbital angular momentum among locally interacting quark
pairs can lead to global quark polarization along the same direction due to
spin-orbital coupling. Local longitudinal fluid shear is estimated within both
Landau fireball and Bjorken scaling model of initial parton production. Quark
polarization through quark-quark scatterings with the exchange of a thermal
gluon is calculated beyond small-angle scattering approximation in a
quark-gluon plasma. The polarization is shown to have a non-monotonic
dependence on the local relative orbital angular momentum dictated by the
interplay between electric and magnetic interaction. It peaks at a value of
relative orbital angular momentum which scales with the magnetic mass of the
exchanged gluons. With the estimated small longitudinal fluid shear in
semi-peripheral $Au+Au$ collisions at the RHIC energy, the final quark
polarization is found to be small $|P_q|<0.04$ in the weak coupling limit.
Possible behavior of the quark polarization in the strong coupling limit and
implications on the experimental detection of such global quark polarization at
RHIC and LHC are also discussed.",0710.2943v1
2001-11-28,Exchange coupling in CaMnO$_3$ and LaMnO$_3$: configuration interaction and the coupling mechanism,"The equilibrium structure and exchange constants of CaMnO$_3$ and LaMnO$_3$
have been investigated using total energy unrestricted Hartree-Fock (UHF) and
localised orbital configuration interaction (CI) calculations on the bulk
compounds and Mn$_2$O$_{11}^{14-}$ and Mn$_2$O$_{11}^{16-}$ clusters. The
predicted structure and exchange constants for CaMnO$_3$ are in reasonable
agreement with estimates based on its N\'eel temperature. A series of
calculations on LaMnO$_3$ in the cubic perovskite structure shows that a
Hamiltonian with independent orbital ordering and exchange terms accounts for
the total energies of cubic LaMnO$_3$ with various spin and orbital orderings.
Computed exchange constants depend on orbital ordering. UHF calculations tend
to underestimate exchange constants in LaMnO$_3$, but have the correct sign
when compared with values obtained by neutron scattering; exchange constants
obtained from CI calculations are in good agreement with neutron scattering
data provided the Madelung potential of the cluster is appropriate. Cluster CI
calculations reveal a strong dependence of exchange constants on Mn d e$_g$
orbital populations in both compounds. CI wave functions are analysed in order
to determine which exchange processes are important in exchange coupling in
CaMnO$_3$ and LaMnO$_3$.",0111536v1
2013-10-28,Metal-insulator transition and superconductivity in the two-orbital Hubbard-Holstein model for iron-based superconductors,"We investigate a two-orbital model for iron-based superconductors to
elucidate the effect of interplay between electron correlation and Jahn-Teller
electron-phonon coupling by using the dynamical mean-field theory combined with
the exact diagonalization method. When the intra- and inter-orbital Coulomb
interactions, $U$ and $U'$, increase with $U=U'$, both the local spin and
orbital susceptibilities, $\chi_{s}$ and $\chi_{o}$, increase with
$\chi_{s}=\chi_{o}$ in the absence of the Hund's rule coupling $J$ and the
electron-phonon coupling $g$. In the presence of $J$ and $g$, there are
distinct two regimes: for $J \stackrel{>}{_\sim} 2g^2/\omega_0$ with the phonon
frequency $\omega_0$, $\chi_{s}$ is enhanced relative to $\chi_{o}$ and shows a
divergence at $J=J_c$ above which the system becomes Mott insulator, while for
$J \stackrel{<}{_\sim} 2g^2/\omega_0$, $\chi_{o}$ is enhanced relative to
$\chi_{s}$ and shows a divergence at $g=g_c$ above which the system becomes
bipolaronic insulator. In the former regime, the superconductivity is mediated
by antiferromagnetic fluctuations enhanced due to Fermi-surface nesting and is
found to be largely dependent on carrier doping. On the other hand, in the
latter regime, the superconductivity is mediated by ferro-orbital fluctuations
and is observed for wide doping region including heavily doped case without the
Fermi-surface nesting.",1310.7327v3
2010-01-22,Josephson effect through a multilevel dot near a singlet-triplet transition,"We investigate the Josephson effect through a two-level quantum dot with an
exchange coupling between two dot electrons. We compute the superconducting
phase relationship and construct the phase diagram in the superconducting
gap--exchange coupling plane in the regime of the singlet-triplet transition
driven by the exchange coupling. In our study two configurations for the
dot-lead coupling are considered: one where effectively only one channel
couples to the dot, and the other where the two dot orbitals have opposite
parities. Perturbative analysis in the weak-coupling limit reveals that the
system experiences transitions from 0 to $\pi$ (negative critical current)
behavior, depending on the parity of the orbitals and the spin correlation
between dot electrons. The strong coupling regime is tackled with the numerical
renormalization group method, which first characterizes the Kondo correlations
due to the dot-lead coupling and the exchange coupling in the absence of
superconductivity. In the presence of superconductivity, many-body correlations
such as two-stage Kondo effect compete with the superconductivity and the
comparison between the gap and the relevant Kondo temperature scales allows to
predict a rich variety of phase diagrams for the ground state of the system and
for the Josephson current. Numerical calculations predicts that our system can
exhibit Kondo-driven 0-$\pi$-0 or $\pi$-0-$\pi$ double transitions and, more
interestingly, that if proper conditions are met a Kondo-assisted
$\pi$-junction can arise, which is contrary to a common belief that the Kondo
effect opens a resonant level and makes the 0-junction. Our predictions could
be probed experimentally for a buckminster fullerene sandwiched between two
superconductors.",1001.3914v1
2001-09-10,Magnetic-field Manipulation of Chemical Bonding in Artificial Molecules,"The effect of orbital magnetism on the chemical bonding of lateral,
two-dimensional artificial molecules is studied in the case of a 2e double
quantum dot (artificial molecular hydrogen). It is found that a perpendicular
magnetic field reduces the coupling (tunneling) between the individual dots
and, for sufficiently high values, it leads to complete dissociation of the
artificial molecule. The method used is building on Lowdin's work on Projection
Operators in Quantum Chemistry; it is a spin-and-space unrestricted
Hartree-Fock method in conjunction with the companion step of the restoration
of spin and space symmetries via Projection Techniques (when such symmetries
are broken). This method is able to describe the full range of couplings in
two-dimensional double quantum dots, from the strong-coupling regime exhibiting
delocalized molecular orbitals to the weak-coupling and dissociation regimes
associated with a Generalized Valence Bond combination of atomic-type orbitals
localized on the individual dots.",0109167v1
2016-06-20,Anisotropic electron-phonon coupling in the spinel oxide superconductor,"Among hundreds of spinel oxides, LiTi2O4 (LTO) is the only one that exhibits
superconductivity (Tc ~13 K). Although the general electron-phonon coupling is
still the main mechanism for electron pairing in LTO, unconventional behaviors
such as the anomalous magnetoresistance, anisotropic orbital/spin
susceptibilities, etc. reveal that both the spin and the orbital interactions
should also be considered for understanding the superconductivity. Here, we
investigate tunneling spectra of [111]-, [110]- and [001]-oriented high quality
LTO thin films. Several bosonic modes in tunneling spectra are observed in the
[111]- and [110]-oriented films but not in [001]-oriented ones, and these modes
still exist at T = 2Tc and beyond the upper critical field, which are confirmed
as stemming from electron-phonon interaction by DFT calculations. These modes
only appear in special surface orientations, indicating that the
electron-phonon coupling in LTO system is highly anisotropic and may be
enhanced by orbital-related state. The anisotropic electron-phonon coupling
should be taken seriously in understanding the nature of LTO superconductivity.",1606.06109v3
2019-11-28,Hund-Heisenberg model in superconducting infinite-layer nickelates,"We theoretically investigate the unconventional superconductivity in the
newly discovered infinite-layer nickelates Nd$_{1-x}$Sr$_{x}$NiO$_{2}$ based on
a two-band model. By analyzing the transport experiments, we propose that the
doped holes dominantly enter the Ni $d_{xy}$ or/and $d_{3z^{2}-r^{2}}$ orbitals
as charged carriers, and form a conducting band. Via the onsite Hund coupling,
the doped holes are coupled to the Ni localized holes in the $d_{x^{2}-y^{2}}$
orbital band. We demonstrate that this two-band model could be further reduced
to a Hund-Heisenberg model. Using the reduced model, we show the non-Fermi
liquid state above the critical $T_{c}$ could stem from the carriers coupled to
the spin fluctuations of the localized holes. In the superconducting phase, the
short-range spin fluctuations mediate the carriers into Cooper pairs and
establish $d_{x^{2}-y^{2}}$-wave superconductivity. We further predict that the
doped holes ferromagnetically coupled with the local magnetic moments remain
itinerant even at very low temperature, and thus the pseudogap hardly emerges
in nickelates. Our work provides a new superconductivity mechanism for strongly
correlated multi-orbital systems and paves a distinct way to exploring new
superconductors in transition or rare-earth metal oxides.",1911.12731v3
2021-03-24,Boosting proximity spin orbit coupling in graphene/WSe$_2$ heterostructures via hydrostatic pressure,"Van der Waals heterostructures composed of multiple few layer crystals allow
the engineering of novel materials with predefined properties. As an example,
coupling graphene weakly to materials with large spin orbit coupling (SOC)
allows to engineer a sizeable SOC in graphene via proximity effects. The
strength of the proximity effect depends on the overlap of the atomic orbitals,
therefore, changing the interlayer distance via hydrostatic pressure can be
utilized to enhance the interlayer coupling between the layers. In this work,
we report measurements on a graphene/WSe$_2$ heterostructure exposed to
increasing hydrostatic pressure. A clear transition from weak localization to
weak anti-localization is visible as the pressure increases, demonstrating the
increase of induced SOC in graphene.",2103.13325v1
2022-01-18,Magnetic correlation between two local spins in a quantum spin Hall insulator,"Two spins located at the edge of a quantum spin Hall insulator may interact
with each other via indirect spin-exchange interaction mediated by the helical
edge states, namely the RKKY interaction, which can be measured by the magnetic
correlation between the two spins. By means of the newly developed natural
orbitals renormalization group (NORG) method, we investigated the magnetic
correlation between two Kondo impurities interacting with the helical edge
states, based on the Kane-Mele model defined in a finite zigzag graphene
nanoribbon with spin-orbital coupling (SOC). We find that the SOC effect breaks
the symmetry in spatial distribution of the magnetic correlation, leading to
anisotropy in the RKKY interaction. Specifically, the total correlation is
always ferromagnetic (FM) when the two impurities are located at the same
sublattice, while it is always antiferromagnetic (AFM) when at the different
sublattices. Meanwhile, the behavior of the in-plane correlation is consistent
with that of the total correlation. However, the out-of-plane correlation can
be tuned from FM to AFM by manipulating either the Kondo coupling or the
interimpurity distance. Furthermore, the magnetic correlation is tunable by the
SOC, especially that the out-of-plane correlation can be adjusted from FM to
AFM by increasing the strength of SOC. Dynamic properties of the system,
represented by the spin-staggered excitation spectrum and the spin-staggered
susceptibility at the two impurity sites, are finally explored. It is shown
that the spin-staggered susceptibility is larger when the two impurities are
located at the different sublattices than at the same sublattice, which is
consistent with the behavior of the out-of-plane correlation. On the other
hand, our study further demonstrates that the NORG is an effective numerical
method for studying the quantum impurity systems.",2201.06790v1
2022-02-07,Quantum spin liquids of Rydberg excitations in a honeycomb lattice induced by density-dependent Peierls phases,"We show that the nonlinear transport of bosonic excitations in a
two-dimensional honeycomb lattice of spin-orbit coupled Rydberg atoms gives
rise to disordered quantum phases which are candidates for quantum spin
liquids. As recently demonstrated in [Lienhard et al. Phys. Rev. X, 10, 021031
(2020)] the spin-orbit coupling breaks time-reversal and chiral symmetries and
leads to a tunable density-dependent complex hopping of the hard-core bosons or
equivalently to complex XY spin interactions. Using exact diagonalization (ED)
we numerically investigate the phase diagram resulting from the competition
between density-dependent and direct transport terms. In mean-field
approximation there is a phase transition from a quasi-condensate to a
120{\deg} phase when the amplitude of the complex hopping exceeds that of the
direct one. In the full model a new phase with a finite spin gap emerges close
to the mean-field critical point as a result of quantum fluctuations induced by
the density-dependence of the complex hopping. We show that this phase is a
genuine disordered one, has a non-vanishing spin chirality and is characterized
by a non-trivial many-body Chern number. ED simulations of small lattices with
up to 28 lattice sites point to a non-degenerate ground state and thus to a
bosonic integer-quantum Hall (BIQH) phase, protected by U(1) symmetry. The
Chern number of C = 1, which is robust to disorder, is however different from
the even Chern numbers found in BIQH phases. For very strong, nonlinear
hoppings of opposite sign we find another disordered regime with vanishing spin
gap. This phase also has a large spin chirality and could be a gapless
spin-liquid but lies outside the parameter regime accessible in the Rydberg
system.",2202.03860v4
2023-10-27,"Twist- and gate-tunable proximity spin-orbit coupling, spin relaxation anisotropy, and charge-to-spin conversion in heterostructures of graphene and transition-metal dichalcogenides","We present a DFT-based investigation of the twist-angle dependent proximity
spin-orbit coupling (SOC) in graphene/TMDC structures. We find that for
Mo-based TMDCs the proximity valley-Zeeman SOC exhibits a maximum at around
15--20{\deg}, and vanishes at 30{\deg}, while for W-based TMDCs we find an
almost linear decrease of proximity valley-Zeeman SOC when twisting from
0{\deg} to 30{\deg}. The induced Rashba SOC is rather insensitive to twisting,
while acquiring a nonzero Rashba phase angle, $\varphi \in [-20;40]${\deg}, for
twist angles different from 0{\deg} and 30{\deg}. This finding contradicts
earlier tight-binding predictions that the Rashba angle can be 90{\deg} in the
studied systems. In addition, we study the influence of several tunability
knobs on the proximity SOC for selected twist angles. By applying a transverse
electric field in the limits of $\pm 2$ V/nm, mainly the Rashba SOC can be
tuned by about 50\%. The interlayer distance provides a giant tunability, since
the proximity SOC can be increased by a factor of 2--3, when reducing the
distance by about 10\%. Encapsulating graphene between two TMDCs, both twist
angles are important to control the interference of the individual proximity
SOCs, allowing to precisely tailor the valley-Zeeman SOC in graphene, while the
Rashba SOC becomes suppressed. Finally, based on our effective Hamiltonians
with fitted parameters, we calculate experimentally measurable quantities such
as spin lifetime anisotropy and charge-to-spin conversion efficiencies. The
spin lifetime anisotropy can become giant, up to $10^4$, in encapsulated
structures. The charge-to-spin conversion, which is due to spin-Hall and
Rashba-Edelstein effects, can lead to twist-tunable non-equilibrium
spin-density polarizations that are perpendicular and parallel to the applied
charge current.",2310.17907v1
2011-09-19,Dynamics of nuclear single-particle structure in covariant theory of particle-vibration coupling: from light to superheavy nuclei,"The impact of particle-vibration coupling and polarization effects due to
deformation and time-odd mean fields on single-particle spectra is studied
systematically in doubly magic nuclei from low mass $^{56}$Ni up to superheavy
ones. Particle-vibration coupling is treated fully self-consistently within the
framework of relativistic particle-vibration coupling model. Polarization
effects due to deformation and time-odd mean field induced by odd particle are
computed within covariant density functional theory. It has been found that
among these contributions the coupling to vibrations makes a major impact on
the single-particle structure. The impact of particle-vibration coupling and
polarization effects on calculated single-particle spectra, the size of the
shell gaps, the spin-orbit splittings and the energy splittings in pseudospin
doublets is discussed in detail; these physical observables are compared with
experiment. Particle-vibration coupling has to be taken into account when model
calculations are compared with experiment since this coupling is responsible
for observed fragmentation of experimental levels; experimental spectroscopic
factors are reasonably well described in model calculations.",1109.3969v1
2007-09-19,Spin-Orbit Correlations and Single-Spin Asymmetries,"Several examples for the role of orbital angular momentum and spin-orbit
correlations in hadron structure are discussed.",0709.2966v3
2020-02-18,Anisotropic RKKY interactions mediated by $j=3/2$ quasiparticles in half-Heusler topological semimetal,"We theoretically explore the RKKY interaction mediated by spin-3/2
quasiparticles in half-Heusler topological semimetals in quasi-two-dimensional
geometries. We find that while the Kohn-Luttinger terms gives rise to
generalized Heisenberg coupling of the form ${\cal H}_{\rm RKKY} \propto
{\sigma}_{1,i} {\cal I}_{ij} {\sigma}_{2,j}$ with a symmetric matrix ${\cal
I}_{ij}$, addition of small antisymmetric linear spin-orbit coupling term leads
to Dzyaloshinskii-Moriya (DM) coupling with an antisymmetric matrix ${\cal
I}'_{ij}$. We demonstrate that besides the oscillatory dependence on the
distance, all coupling strengths strongly depend on the relative orientation of
the two impurities with respect to the lattice. This yields a strongly
anisotropic behavior for ${\cal I}_{ij}$ such that by only rotating one
impurity around another at a constant distance, we can see further oscillations
of the RKKY couplings. This unprecedented effect is unique to our system which
combines spin-orbit coupling with strongly anisotropic Fermi surfaces. We
further find that all of the RKKY terms have two common features: a tetragonal
warping in their map of spatial variations, and a complex beating pattern.
Intriguingly, all these features survive in all dopings and we see them in both
electron- and hole-doped cases. In addition, due to the lower dimensionality
combined with the effects of different spin-orbit couplings, we see that only
one symmetric off-diagonal term, ${\cal I}_{xy}$ and two DM components ${\cal
I}'_{xz}$ and ${\cal I}'_{yz}$ are nonvanishing, while the remaining three
off-diagonal components are identically zero. This manifests another drastic
difference of RKKY interaction in half-Heusler topological semimetals compared
to the electronic systems with spin-1/2 effective description.",2002.07736v1
2007-06-17,Spin-orbital entanglement near quantum phase transitions,"Spin-orbital entanglement in the ground state of a one-dimensional
SU(2)$\otimes$SU(2) spin-orbital model is analyzed using exact diagonalization
of finite chains. For $S=1/2$ spins and $T=1/2$ pseudospins one finds that the
quantum entanglement is similar at the SU(4) symmetry point and in the
spin-orbital valence bond state. We also show that quantum transitions in
spin-orbital models turn out to be continuous under certain circumstances, in
constrast to the discontinuous transitions in spin models with SU(2) symmetry.",0706.2477v1
2010-09-10,Effect of Electron-Electron Interactions on Rashba-like and Spin-Split Systems,"The role of electron-electron interactions is analyzed for Rashba-like and
spin-split systems within a tight-binding single-band Hubbard model with
on-site and all nearest-neighbor matrix elements of the Coulomb interaction. By
Rashba-like systems we refer to the Dresselhaus and Rashba spin-orbit coupled
phases; spin-split systems have spin-up and spin-down Fermi surfaces shifted
relative to each other. Both systems break parity but preserve time-reversal
symmetry. They belong to a class of symmetry-breaking ground states that
satisfy: (i) electron crystal momentum is a good quantum number (ii) these
states have no net magnetic moment and (iii) their distribution of `polarized
spin' in momentum space breaks the lattice symmetry. In this class, the
relevant Coulomb matrix elements are found to be nearest-neighbor exchange $J$,
pair-hopping $J'$ and nearest-neighbor repulsion $V$. These ground states lower
their energy most effectively through $J$, hence we name them Class $J$ states.
The competing effects of $V-J'$ on the direct and exchange energies determine
the relative stability of Class $J$ states. We show that the spin-split and
Rashba-like phases are the most favored ground states within Class $J$ because
they have the minimum anisotropy in `polarized spin'. On a square lattice we
find that the spin-split phase is always favored for near-empty bands; above a
critical filling, we predict a transition from the paramagnetic to the
Rashba-like phase at $ J_{c1}$ and a second transition to the spin-split state
at $J_{c2}>J_{c1}$. An energetic comparison with ferromagnetism highlights the
importance of the role of $V$ in the stability of Class $J$ states. We discuss
the relevance of our results to (i) the $\alpha$ and $\beta$ phases proposed by
Wu and Zhang in the Fermi Liquid formalism and (ii) experimental observations
of spin-orbit splitting in \emph{Au}(111) surface states.",1009.2121v1
2023-05-15,Extreme mass-ratio inspiral of a spinning body into a Kerr black hole I: Evolution along generic trajectories,"The study of spinning bodies moving in curved spacetime has relevance to
binary black hole systems with large mass ratios, as well as being of formal
interest. At zeroth order in a binary's mass ratio, the smaller body moves on a
geodesic of the larger body's spacetime. Post-geodesic corrections describing
forces driving the small body's worldline away from geodesics must be
incorporated to model the system accurately. An important post-geodesic effect
is the gravitational self-force, which describes the small body's interaction
with its own spacetime curvature. This effect includes the backreaction due to
gravitational-wave emission that leads to the inspiral of the small body into
the black hole. When a spinning body orbits a black hole, its spin couples to
spacetime curvature. This introduces another post-geodesic correction known as
the spin-curvature force. An osculating geodesic integrator that includes both
the backreaction due to gravitational waves and spin-curvature forces can be
used to generate a spinning-body inspiral. In this paper, we use an osculating
geodesic integrator to combine the leading backreaction of gravitational waves
with the spin-curvature force. Our analysis only includes the leading
orbit-averaged dissipative backreaction, and examines the spin-curvature force
to leading order in the small body's spin. This is sufficient to build generic
inspirals of spinning bodies, and serves as a foundation for further work
examining how to include secondary spin in large-mass-ratio waveform models.",2305.08919v2
2001-03-02,Orbital effect of Cooper pairs on Kondo effect in unconventional superconductors,"A new type of Kondo effect peculiar to unconventional superconductors is
studied theoretically by using the Wilson's numerical renormalization group
method. In this case, an angular momentum of a Cooper pair plays an important
role in the Kondo effect. It produces multichannel exchange couplings with a
local spin. Here we focus on a $p_x +i p_y$-wave state which is a full gap
system. The calculated impurity susceptibility shows that the local spin is
almost quenched by the Kondo effect in the strong coupling region ($T_{\rm
K}/\Delta \to \infty$), while the ground state is always a spin doublet over
all the $T_{\rm K}/\Delta$ region. Here $T_{\rm K}$ and $\Delta$ are the Kondo
temperature and the superconducting energy gap, respectively. This is different
from the s-wave pairing case where the Kondo singlet is realized for large
$T_{\rm K}/\Delta$ values. The strong coupling analysis shows that the $p_x +i
p_y$-wave Cooper pair is connected to the Kondo singlet via the orbital
dynamics of the paired electrons, generating the spin of the ground state. This
type of Kondo effect reflects the symmetry of the conduction electron system.",0103053v2
2010-02-04,Quantized Anomalous Hall Effect in Magnetic Topological Insulators,"The Hall effect, the anomalous Hall effect and the spin Hall effect are
fundamental transport processes in solids arising from the Lorentz force and
the spin-orbit coupling respectively. The quantum versions of the Hall effect
and the spin Hall effect have been discovered in recent years. However, the
quantized anomalous Hall (QAH) effect has not yet been realized experimentally.
In a QAH insulator, spontaneous magnetic moments and spin-orbit coupling
combine to give rise to a topologically non-trivial electronic structure,
leading to the quantized Hall effect without any external magnetic field. In
this work, based on state-of-art first principles calculations, we predict that
the tetradymite semiconductors Bi$_2$Te$_3$, Bi$_2$Se$_3$, and Sb$_2$Te$_3$
form magnetically ordered insulators when doped with transition metal elements
(Cr or Fe), in sharp contrast to conventional dilute magnetic semiconductor
where free carriers are necessary to mediate the magnetic coupling. Magnetic
order in two-dimensional thin films gives rise to a topological electronic
structure characterized by a finite Chern number, with quantized Hall
conductance $e^{2}/h$. Experimental realization of the long sought-after QAH
insulator state could enable robust dissipationless charge transport at room
temperature.",1002.0946v1
2011-10-26,Dynamically generating arbitrary spin-orbit couplings for neutral atoms,"Spin-orbit coupling (SOC) can give rise to interesting physics, from spin
Hall to topological insulators, normally in condensed matter systems. Recently,
this topical area has extended into atomic quantum gases in searching for
artificial/synthetic gauge potentials. The prospects of tunable interaction and
quantum state control promote neutral atoms as nature's quantum emulators for
SOC. Y.-J. Lin {\it et al.} recently demonstrated a special form of the SOC
$k_x\sigma_y$: which they interpret as an equal superposition of Rashba and
Dresselhaus couplings, in bose condensed atoms [Nature (London) \textbf{471},
83 (2011)]. This work reports an idea capable of implementing arbitrary forms
of SOC by switching between two pairs of Raman laser pulses like that used by
Lin {\it et al.}. While one pair affects $k_x\sigma_y$ for some time, a second
pair creates $k_y\sigma_y$ over other times with Raman pulses from different
directions and a subsequent spin rotation into $\pm k_y\sigma_x$. With
sufficient many pulses, the effective actions from different durations are
small and accumulate in the same exponent despite that $k_x\sigma_y$ and $\pm
k_y\sigma_x$ do not commute. Our scheme involves no added complication, and can
be demonstrated within current experiments. It applies equally to bosonic or
fermionic atoms.",1110.5705v2
2018-11-22,Common nonlinear features and spin-orbit coupling effects in the Zeeman splitting of novel wurtzite materials,"The response of semiconductor materials to external magnetic fields is a
reliable approach to probe intrinsic electronic and spin-dependent properties.
In this study, we investigate the common Zeeman splitting features of novel
wurtzite materials, namely InP, InAs, and GaAs. We present values for the
effective g-factors of different energy bands and show that spin-orbit coupling
effects, responsible for the spin splittings, also have noticeable
contributions to the g-factors. Within the Landau level picture, we show that
the nonlinear Zeeman splitting recently explained in magneto photoluminescence
experiments for InP nanowires by Tedeschi et al. [Phys. Rev. B 99, 161204
(2019)] are also present in InAs, GaAs and even in the conventional GaN. Such
nonlinear features stem from the peculiar coupling of the A and B valence
bands, as a consequence of the interplay between the wurtzite crystal symmetry
and the breaking of time-reversal symmetry by the external magnetic field.
Moreover, we develop an analytical model to describe the experimental nonlinear
Zeeman splitting and apply it to InP and GaAs data. Extrapolating our fitted
results, we found that the Zeeman splitting of InP reaches a maximum value,
which is a prediction that could be probed at higher magnetic fields.",1811.09288v2
2020-07-12,Anisotropic Kondo screening induced by spin-orbit coupling in quantum wires,"Using the numerical renormalization group (NRG) method we study a magnetic
impurity coupled to a quantum wire with Rashba and Dresselhaus spin-orbit
coupling (SOC) in an external magnetic field. We consider the low-filling
regime with the Fermi energy close to the bottom of the band and report the
results for local static and dynamic properties in the Kondo regime. In the
absence of the field, local impurity properties remain isotropic in spin space
despite the SOC-induced magnetic anisotropy of the conduction band. In the
presence of the field, clear fingerprints of anisotropy are revealed through
the strong field-direction dependence of the impurity spin polarization and
spectra, in particular of the Kondo peak height. The detailed behavior depends
on the relative magnitudes of the impurity and band $g$-factors. For the case
of impurity $g$-factor somewhat lower than the band $g$-factor, the maximal
Kondo peak suppression is found for field oriented along the effective SOC
field axis, while for a field perpendicular to this direction we observe a
compensation effect (``revival of the Kondo peak''): the SOC counteracts the
Kondo peak splitting effects of the local Zeeman field. We demonstrate that the
SOC-induced anisotropy, measurable by tunneling spectroscopy techniques, can
help to determine the ratio of Rashba and Dresselhaus SOC strengths in the
wire.",2007.06044v1
2020-07-13,Spin-orbit coupled depairing of a dipolar biexciton superfluid,"We consider quantum phase transitions in a system of bright dipolar excitons
which can form bound pairs (dipolar biexcitons). We assume a narrow resonance
in the interaction of excitons with opposite spins. At sufficiently large
density a resonant exciton superfluid transforms into a superfluid of
biexcitons. The transition may be either of the first or the second kind. The
average relative momenta of excitons in the pairs being beyond the light cone,
the transition should be accompanied by reduction of the photoluminescence
intensity. Effective magnetic fields due to the long-range exchange splitting
of non-radiative exciton states induce broadening of the biexciton resonance.
The fields shift the position of the gap in the elementary excitation spectrum
to a circle of degenerate minima in the k-space. Closing the new gap defines a
second order phase transition into a mixture of counter-propagating plane-wave
excitonic condensates polarized linearly in the direction perpendicular to
their wavevectors. In the resonance energy vs density phase diagram the novel
phase intervenes between the dark biexciton and radiative exciton superfluids.
We conclude that formation of a BCS-like biexciton condensate induces
correlated alignment of the effective magnetic fields and excitonic spins. We
outline important differences of the emergent mechanism from the phenomenon of
spin-orbit (SO) coupled Bose-Einstein condensation. We expect existence of
analogous mechanisms in SO-coupled fermionic superfluids and superconductors.",2007.06474v2
2018-05-15,Thermal Hall effect and topological edge states in a square lattice antiferromagnet,"We show that the two dimensional spatial inversion-symmetry (SIS) broken
square lattice antiferromagnet with easy-plane spin anisotropy exhibits a
thermal Hall effect and the edge modes characterized by the Z 2 topological
invariant. These topological properties require a nonzero Berry curvature, and
its origin is ascribed to the Dzyaloshinskii-Moriya (DM) interactions or the
noncoplanar magnetic ordering generating a U(1) gauge field that couples to the
kinetic motion of magnons. Although this picture is established in ferromagnets
on the kagome and pyrochlore lattices, it does not apply to our square lattice
model since such gauge field cancels out in an edge shared geometry. Instead,
our case has an analogy with the anomalous Hall effect of Rashba electronic
system where the spin orbit coupling generates an SU(2) gauge field. The two
species of magnons defined on antiferromagnetic sublattices can be regarded as
the pseudo-spin degrees of freedom of magnons. The DM interactions that emerge
due to the SIS breaking serve as a pseudo-spin orbit coupling of magnons and
generate a Berry curvature, when the direction of the magnetic moments is
properly controlled by the magnetic field. The thermal Hall conductivity of our
antiferromagnet shows rapid growth in temperature T beyond the power-law,
reflecting the almost gapless low energy branch of the antiferromagnet, which
distinctively differs from the T^7/2 -dependence in the pyrochlore
ferromagnets. The present system serves as a standard model for the
noncentrosymmetric crystals Ba2MnGe2O7 and Ba2CoGe2O7.",1805.05872v3
2020-01-16,Tailoring magnetic order via atomically stacking 3d/5d electrons,"The ability to tune magnetic orders, such as magnetic anisotropy and
topological spin texture, is desired in order to achieve high-performance
spintronic devices. A recent strategy has been to employ interfacial
engineering techniques, such as the introduction of spin-correlated interfacial
coupling, to tailor magnetic orders and achieve novel magnetic properties. We
chose a unique polar-nonpolar LaMnO3/SrIrO3 superlattice because Mn (3d)/Ir
(5d) oxides exhibit rich magnetic behaviors and strong spin-orbit coupling
through the entanglement of their 3d and 5d electrons. Through magnetization
and magnetotransport measurements, we found that the magnetic order is
interface-dominated as the superlattice period is decreased. We were able to
then effectively modify the magnetization, tilt of the ferromagnetic easy axis,
and symmetry transition of the anisotropic magnetoresistance of the
LaMnO3/SrIrO3 superlattice by introducing additional Mn (3d) and Ir (5d)
interfaces. Further investigations using in-depth first-principles calculations
and numerical simulations revealed that these magnetic behaviors could be
understood by the 3d/5d electron correlation and Rashba spin-orbit coupling.
The results reported here demonstrate a new route to synchronously engineer
magnetic properties through the atomic stacking of different electrons,
contributing to future applications.",2001.05821v2
2021-06-30,Origin of Nonlinear Damping due to Mode Coupling in Auto-Oscillatory Modes Strongly Driven by Spin-Orbit Torque,"We investigate the physical origin of nonlinear damping due to mode coupling
between several auto-oscillatory modes driven by spin-orbit torque in
constricted Py/Pt heterostructures by examining the dependence of
auto-oscillation on temperature and applied field orientation. We observe a
transition in the nonlinear damping of the auto-oscillation modes extracted
from the total oscillation power as a function of drive current, which
coincides with the onset of power redistribution amongst several modes and the
crossover from linewidth narrowing to linewidth broadening in all individual
modes. This indicates the activation of another relaxation process by nonlinear
magnon-magnon scattering within the modes. We also find that both nonlinear
damping and threshold current in the mode-interaction damping regime at high
drive current after transition are temperature independent, suggesting that the
mode coupling occurs dominantly through a non-thermal magnon scattering process
via a dipole or exchange interaction rather than thermally excited
magnon-mediated scattering. This finding presents a promising pathway to
overcome the current limitations of efficiently controlling the interaction
between two highly nonlinear magnetic oscillators to prevent mode crosstalk or
inter-mode energy transfer and deepens understanding of complex nonlinear spin
dynamics in multimode spin wave systems.",2107.00150v2
2021-12-09,Polarization-dependent magnetic properties of periodically driven $α$-RuCl$_{3}$,"We study magnetic properties of a periodically driven Mott insulator with
strong spin-orbit coupling and show some properties characteristic of linearly
polarized light. We consider a $t_{2g}$-orbital Hubbard model driven by
circularly or linearly polarized light with strong spin-orbit coupling and
derive its effective Hamiltonian in the strong-interaction limit for a
high-frequency case. We show that linearly polarized light can change not only
the magnitudes and signs of the exchange interactions, but also their bond
anisotropy even without the bond-anisotropic hopping integrals. Because of this
property, the honeycomb-network spin system could be transformed into weakly
coupled zigzag or step spin chains for the light field polarized along the $b$-
or $a$-axis, respectively. Then, analyzing how the light fields affect several
magnetic states in a mean-field approximation, we show that linearly polarized
light can change the relative stability of the competing magnetic states,
whereas such a change is absent for circularly polarized light. We also analyze
the effects of both the bond anisotropy of nearest-neighbor hopping integrals
and a third-neighbor hopping integral on the magnetic states and show that the
results obtained in a simple model, in which the bond-averaged nearest-neighbor
hopping integrals are considered, remain qualitatively unchanged except for the
stability of zigzag states in the non-driven case and the degeneracy lifting of
the zigzag or stripy states.",2112.04690v1
2022-04-06,Leading superconducting instabilities in three-dimensional models for Sr2RuO4,"The superconductor Sr2RuO4 has been the subject of enormous interest over
more than two decades, but until now the form of its order parameter has not
been determined. Since groundbreaking NMR experiments revealed that the pairs
are of dominant spin-singlet character, attention has focused on time-reversal
symmetry breaking linear combinations of $s$-, $d$- and $g$-wave
one-dimensional (1D) irreducible representations. However, a state of the form
$d_{xz}+id_{yz}$ has also been proposed. We present a systematic study of the
stability of various superconducting candidate states, assuming that pairing is
driven by the fluctuation exchange mechanism, including a realistic
three-dimensional Fermi surface, full treatment of both local and non-local
spin-orbit couplings, and a wide range of interaction parameters $U,J,U',J'$.
The leading superconducting instabilities are found to exhibit nodal
even-parity $A_{1g} (s')$ or $B_{1g} (d_{x^2-y^2})$ symmetries, similar to the
findings in two-dimensional models without longer-range Coulomb interaction
which tends to favor $d_{xy}$ over $d_{x^2-y^2}$. Within the so-called Hund's
coupling mean-field pairing scenario, the $E_g (d_{xz}/d_{yz})$ solution can be
stabilized for large $J$ and specific forms of the spin-orbit coupling, but for
all cases studied here the eigenvalues of other superconducting solutions are
significantly larger when the full fluctuation exchange vertex is included in
the pairing kernel. Additionally, we compute the spin susceptibility in
relevant superconducting candidate phases and compare to recent neutron
scattering and NMR Knight shift measurements.",2204.02880v1
2023-10-26,Multiband $k \cdot p$ theory for hexagonal germanium,"The direct bandgap found in hexagonal germanium and some of its alloys with
silicon allows for an optically active material within the group-IV
semiconductor family with various potential technological applications.
However, there remain some unanswered questions regarding several aspects of
the band structiure, including the strength of the electric dipole transitions
at the center of the Brillouin zone. Using the $\mathbf{k\cdot p}$ method near
the $\Gamma$ point, including 10 bands, and taking spin-orbit coupling into
account, we obtain a self-consistent model that produces the correct band
curvatures, with previously unknown inverse effective mass parameters, to
describe 2H-Ge via fitting to {\it ab initio} data and to calculate effective
masses for electrons and holes. To understand the weak dipole coupling between
the lowest conduction band and the top valance band, we start from a spinless
12-band model and show that when adding spin-orbit coupling, the lowest
conduction band hybridizes with a higher-lying conduction band, which cannot be
explained by the spinful 10-band model. With the help of L\""owdin's
partitioning, we derive the effective low-energy Hamiltonian for the conduction
bands for the possible spin dynamics and nanostructure studies and in a similar
manner, we give the best fit parameters for the valance-band-only model that
can be used in the transport studies. Finally, using the self-consistent
10-band model, we include the effects of a magnetic field and predict the
electron and hole g-factor of the conduction and valance bands.",2310.17366v1
2023-12-01,Large enhancement of spin-orbit torques under a MHz modulation due to phonon-magnon coupling,"The discovery of spin-orbit torques (SOTs) generated through the spin Hall or
Rashba effects provides an alternative write approach for magnetic
random-access memory (MRAM), igniting the development of spin-orbitronics in
recent years. Quantitative characterization of SOTs highly relies on the
SOT-driven ferromagnetic resonance (ST-FMR), where a modulated microwave
current is used to generate ac SOTs and the modulation-frequency is usually
less than 100 kHz (the limit of conventional lock-in amplifiers). Here we have
investigated the SOT of typical SOT material/ferromagnet bilayers in an
extended modulation-frequency range, up to MHz, by developing the ST-FMR
measurement. Remarkably, we found that the measured SOTs are enhanced about
three times in the MHz range, which cannot be explained according to present
SOT theory. We attribute the enhancement of SOT to additional magnon
excitations due to phonon-magnon coupling, which is also reflected in the
slight changes of resonant field and linewidth in the acquired ST-FMR spectra,
corresponding to the modifications of effective magnetization and damping
constant, respectively. Our results indicate that the write current of SOT-MRAM
may be reduced with the assistant of phonon-magnon coupling.",2401.02967v1
2007-10-31,Localization problem of the quasiperiodic system with the spin orbit interaction,"We study one dimensional quasiperiodic system obtained from the tight-binding
model on the square lattice in a uniform magnetic field with the spin orbit
interaction. The phase diagram with respect to the Harper coupling and the
Rashba coupling are proposed from a number of numerical studies including a
multifractal analysis. There are four phases, I, II, III, and IV in this order
from weak to strong Harper coupling. In the weak coupling phase I all the wave
functions are extended, in the intermediate coupling phases II and III mobility
edges exist, and accordingly both localized and extended wave functions exist,
and in the strong Harper coupling phase IV all the wave functions are
localized. Phase I and Phase IV are related by the duality, and phases II and
III are related by the duality, as well. A localized wave function is related
to an extended wave function by the duality, and vice versa. The boundary
between phases II and III is the self-dual line on which all the wave functions
are critical. In the present model the duality does not lead to pure spectra in
contrast to the case of Harper equation.",0710.5816v2
2019-07-17,Symmetry breaking of a matter-wave soliton in a double-well potential formed by spatially confined spin-orbit coupling,"We consider the symmetry breaking of a matter-wave soliton formed by spinor
Bose-Einstein condensates (BECs) illuminated by a two-spot laser beam. This
laser beam introduces spin-orbit (SO) coupling in the BECs such that the SO
coupling produces an effect similar to a linear doublewell potential (DWP). It
is well known that symmetry breaking in a DWP is an important effect and has
been discussed in many kinds of systems. However, it has not yet been discussed
in a DWP formed by SO coupling. The objective of this work is to study the
symmetry breaking of spinor BECs trapped by a DWP formed by SO coupling. We
find that two kinds of symmetry breaking, displacement symmetry breaking and
bimodal symmetry breaking, can be obtained in this model. The influence of the
symmetry transition is systematically discussed by controlling the interaction
strength of the BECs and the distance between the center of the two spots.
Moreover, because SO coupling violates Galilean invariance, the influence of
symmetry breaking in the moving system is also addressed in this paper.",1907.07416v1
2020-01-13,Improved effective equation for the Rashba spin-orbit coupling in semiconductor nanowires,"Semiconductor Rashba nanowires are quasi-one dimensional systems that have
large spin-orbit (SO) coupling arising from a broken inversion symmetry due to
an external electric field. There exist parametrized multiband models that can
describe accurately this effect. However, simplified single band models are
highly desirable to study geometries of recent experimental interest, since
they may allow to incorporate the effects of the low dimensionality and the
nanowire electrostatic environment at a reduced computational cost. Commonly
used conduction band approximations, valid for bulk materials, greatly
underestimate the SO coupling in Zinc-blende crystal structures and
overestimate it for Wurtzite ones when applied to finite cross-section wires,
where confinement effects turn out to play an important role. We demonstrate
here that an effective equation for the linear Rashba SO coupling of the
semiconductor conduction band can reproduce the behavior of more sophisticated
eight-band k$\cdot$p model calculations. This is achieved by adjusting a single
effective parameter that depends on the nanowire crystal structure and its
chemical composition. We further compare our results to the Rashba coupling
extracted from magnetoconductance measurements in several experiments on InAs
and InSb nanowires, finding excellent agreement. This approach may be relevant
in systems where Rashba coupling is known to play a major role, such as in
spintronic devices or Majorana nanowires.",2001.04375v3
2018-06-04,Electric field tunable superconductor-semiconductor coupling in Majorana nanowires,"We study the effect of external electric fields on
superconductor-semiconductor coupling by measuring the electron transport in
InSb semiconductor nanowires coupled to an epitaxially grown Al superconductor.
We find that the gate voltage induced electric fields can greatly modify the
coupling strength, which has consequences for the proximity induced
superconducting gap, effective g-factor, and spin-orbit coupling, which all
play a key role in understanding Majorana physics. We further show that level
repulsion due to spin-orbit coupling in a finite size system can lead to
seemingly stable zero bias conductance peaks, which mimic the behavior of
Majorana zero modes. Our results improve the understanding of realistic
Majorana nanowire systems.",1806.00988v1
2021-06-28,Creating tunable and coupled Rashba-type quantum dots atom-by-atom,"Artificial lattices created by assembling atoms on a surface with scanning
tunneling microscopy present a platform to create matter with tailored
electronic, magnetic and topological properties. However, such artificial
lattices studies to date have focused exclusively on surfaces with weak
spin-orbit coupling. Here, we created artificial and coupled quantum dots by
fabricating quantum corrals from iron atoms on the prototypical Rashba surface
alloy, BiCu2, using low-temperature scanning tunneling microscopy. We
quantified the quantum confinement of such quantum dots with various diameter
and related this to the spatially dependent density of states, using scanning
tunneling spectroscopy. We found that the density of states shows complex
distributions beyond the typical isotropic patterns seen in radially symmetric
structures on (111) noble metal surfaces. We related these to the
energy-dependent interplay of the confinement potential with the hexagonal
warping and multiple intra- and interband scattering vectors, which we
simulated with a particle-in-a-box model that considers the Rashba-type band
structure of BiCu2. Based on these results, we studied the effect of coupling
two quantum dots and exploited the resultant anisotropic coupling derived from
the symmetry of the various scattering channels. The large anisotropy and
spin-orbit coupling provided by the BiCu2 platform are two key ingredients
toward creation of correlated artificial lattices with non-trivial topology.",2106.14561v1
2022-10-11,Generalized Rashba Electron-Phonon Coupling and Superconductivity in Strontium Titanate,"SrTiO3 is known for its proximity to a ferroelectric phase and for showing an
'optimal' doping for superconductivity with a characteristic dome-like
behaviour resembling systems close to a quantum critical point. Several
mechanisms have been proposed to link these phenomena, but the abundance of
undetermined parameters prevents a definite assessment. Here, we use ab initio
computations supplemented with a microscopic model to study the linear coupling
between conduction electrons and the ferroelectric soft transverse modes
allowed in the presence of spin-orbit coupling. We find a robust Rashba-like
coupling, which can become surprisingly strong for particular forms of the
polar eigenvector. We characterize this sensitivity for general eigenvectors
and, for the particular form deduced by hyper-Raman scattering experiments, we
find a BCS pairing coupling constant of the right order of magnitude to support
superconductivity. The ab initio computations enable us to go beyond the
linear-in-momentum conventional Rashba-like interaction and naturally explain
the dome behaviour including a characteristic asymmetry. The dome is attributed
to a momentum dependent quenching of the angular momentum due to a competition
between spin-orbit and hopping energies. The optimum density for having maximum
Tc results in rather good agreement with experiments without free parameters.
These results make the generalized Rashba dynamic coupling to the ferroelectric
soft mode a compelling pairing mechanism to understand bulk superconductivity
in doped SrTiO3.",2210.05753v2
2023-10-10,Rashba-Dresselhaus spin-orbit coupling and polarization-coupled luminescence in an organic single crystal microcavity,"Spin-orbit coupling (SOC) of light plays a fundamental photophysics that is
important for various fields such as materials science, optics, and quantum
technology, contributing to the elucidation of new physical phenomena and the
development of innovative applications. In this study, we investigate the
impact of SOC in a microcavity system using the highly oriented molecular
crystal. The unique molecular alignment of our crystal creates substantial
optical anisotropy, enabling the observation of significant SOC effects within
a microcavity form. Through angle-resolved photoluminescence measurements and
theoretical calculations, the presence of Rashba-Dresselhaus (RD) SOC in the
lower branch of polariton modes is revealed. We have observed for the first
time polarization-coupled emission from polariton modes due to the RD-SOC
effect in a microcavity with a medium having both strong light-matter coupling
and strong optical anisotropy. Theoretical investigations further elucidate the
intricate interplay between the RD-SOC effect and anisotropic light-matter
coupling, leading to the emergence of both circularly and diagonally polarized
mode splittings. This study not only advances our understanding of optical SOC
in microcavities but also highlights the potential of highly oriented molecular
crystals in manipulating SOC effects without external electric or magnetic
fields. These findings offer greatly promising platforms for developing
topological photonics and quantum technologies.",2310.06465v1
2019-09-26,"Perdeuteration of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (d-MEHPPV): control of microscopic charge-carrier spin-spin coupling and of magnetic-field effects in optoelectronic devices","Control of the effective local hyperfine fields in a conjugated polymer,
poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEHPPV), by
isotopic engineering is reported. These fields, evident as a
frequency-independent line broadening mechanism in electrically detected
magnetic resonance spectroscopy (EDMR), originate from the unresolved hyperfine
coupling between the electronic spin of charge carrier pairs and the nuclear
spins of surrounding hydrogen isotopes. The room temperature study of effects
caused by complete deuteration of this polymer through magnetoresistance,
magnetoelectroluminescence, coherent pulsed and multi-frequency EDMR, as well
as inverse spin-Hall effect measurements, confirm the weak hyperfine broadening
of charge carrier magnetic resonance lines. As a consequence, we can resolve
coherent charge-carrier spin-beating, allowing for direct measurements of the
magnitude of electronic spin-spin interactions. In addition, the weak hyperfine
coupling allows us to resolve substantial spin-orbit coupling effects in EDMR
spectra, even at low magnetic field strengths. These results illustrate the
dramatic influence of hyperfine fields on the spin physics of organic
light-emitting diode (OLED) materials at room temperature, and point to routes
to reaching exotic ultra-strong resonant-drive regimes needed for the study of
light-matter interactions.",1909.12213v1
2018-02-25,Interplay of spin-dependent delocalization and magnetic anisotropy in the ground and excited states of [Gd$_2$@C$_{78}$]$^{-1}$ and [Gd$_2$@C$_{80}$]$^{-1}$,"The magnetic properties and electronic structure of the ground and excited
states of two recently characterized endohedral metallo-fullerenes,
[Gd$_2$@C$_{78}$]$^{-}$ (1) and [Gd$_2$@C$_{80}$]$^{-}$ (2), have been studied
by theoretical methods. The systems can be considered as [Gd$_2$]$^{5+}$ dimers
encapsulated in a fullerene cage with the fifteen unpaired electrons
ferromagnetically coupled into an $S=15/2$ high-spin configuration in the
ground state. The microscopic mechanisms governing the Gd--Gd interactions
leading to the ferromagnetic ground state are examined by a combination of
density functional and ab initio calculations and the full energy spectrum of
the ground and lowest excited states is constructed by means of ab initio model
Hamiltonians. The ground state is characterized by strong electron
delocalization bordering on a $\sigma$ type one-electron covalent bond and
minor zero-field splitting (ZFS) which is successfully described as a second
order spin-orbit coupling effect. We have shown that the observed ferromagnetic
interaction originates from Hund's rule coupling and not from the conventional
double exchange mechanism. The calculated ZFS parameters of 1 and 2 in their
optimized geometries are in qualitative agreement with experimental EPR
results. The higher excited states display less electron delocalization but at
the same time they possess unquenched first-order angular momentum. This leads
to strong spin-orbit coupling and highly anisotropic energy spectrum. The
analysis of the excited states presented here constitutes the first detailed
study of the effects of spin-dependent delocalization in the presence of first
order orbital angular momentum and the obtained results can be applied to other
mixed valence lanthanide systems.",1802.09068v1
2017-07-12,Superconductivity in three-dimensional spin-orbit coupled semimetals,"Motivated by the experimental detection of superconductivity in the
low-carrier density half-Heusler compound YPtBi, we study the pairing
instabilities of three-dimensional strongly spin-orbit coupled semimetals with
a quadratic band touching point. In these semimetals the electronic structure
at the Fermi energy is described by spin j=3/2 quasiparticles, which are
fundamentally different from those in ordinary metals with spin j=1/2. We
develop a general approach to analyzing pairing instabilities in j=3/2
materials by decomposing the pair scattering interaction into irreducible
channels, projecting them to the Fermi surface and deriving the corresponding
Eliashberg theory. Applying our method to a generic density-density interaction
in YPtBi we establish the following results: (i) The pairing strength in each
channel uniquely encodes the j=3/2 nature of the Fermi surface band
structure--a manifestation of the fundamental difference with ordinary metals.
In particular, this implies that Anderson's theorem, which addresses the effect
of spin-orbit coupling and disorder on pairing states of spin-1/2 electrons,
cannot be applied in this case. (ii) The leading pairing instabilities are
different for electron and hole doping. This implies that superconductivity
depends on carrier type. (iii) In the case of hole doping--relevant to YPtBi,
we find two odd-parity channels in close competition with s-wave pairing. One
of these two channels is a multicomponent pairing channel, allowing for the
possibility of time-reversal symmetry breaking. (iv) In the case of Coulomb
interactions mediated by the long-ranged electric polarization of optical
phonon modes, a significant coupling strength is generated in spite of the
extremely low density of carriers. Furthermore, non-linear response and Fermi
liquid corrections can favor non-s-wave pairing and potentially account for the
experimentally-observed Tc.",1707.03831v2
2020-07-01,One-dimensional spin-orbit coupled Dirac system with extended $s$-wave superconductivity: Majorana modes and Josephson effects,"Motivated by the spin-momentum locking of electrons at the boundaries of
topological insulators, we study a one-dimensional system of spin-orbit coupled
massless Dirac electrons with $s$-wave superconducting pairing. As a result of
the spin-orbit coupling, our model has only two kinds of linearly dispersing
modes, which we take to be right-moving spin-up and left-moving spin-down. Both
lattice and continuum models are studied. In the lattice model, we find that a
single Majorana zero energy mode appears at each end of a finite system
provided that the $s$-wave pairing has an extended form, with the
nearest-neighbor pairing being larger than the on-site pairing. We confirm this
both numerically and analytically by calculating the winding number. Next we
study a lattice version of a model with both Schr\""odinger and Dirac-like terms
and find that the model hosts a topological transition between topologically
trivial and non-trivial phases depending on the relative strength of the
Schr\""odinger and Dirac terms. We then study a continuum system consisting of
two $s$-wave superconductors with different phases of the pairing. Remarkably,
we find that the system has a {\it single} Andreev bound state which is
localized at the junction. When the pairing phase difference crosses a multiple
of $2 \pi$, an Andreev bound state touches the top of the superconducting gap
and disappears, and a different state appears from the bottom of the gap. We
also study the AC Josephson effect in such a junction with a voltage bias that
has both a constant $V_0$ and a term which oscillates with a frequency
$\omega$. We find that, in contrast to standard Josephson junctions, Shapiro
plateaus appear when the Josephson frequency $\omega_J= 2eV_0/\hbar$ is a
rational fraction of $\omega$. We discuss experiments which can realize such
junctions.",2007.00357v2
2023-07-20,Observation of long-range ferromagnetism via anomalous supercurrents in a spin-orbit coupled superconductor,"Conventional superconductors naturally disfavor ferromagnetism because the
supercurrent-carrying electrons are paired into anti-parallel spin singlets. In
superconductors with strong Rashba spin-orbit coupling, impurity magnetic
moments induce supercurrents through the spin-galvanic effect. As a result,
long-range ferromagnetic interaction among the impurity moments may be mediated
through such anomalous supercurrents in a similar fashion as in itinerant
ferromagnets. Fe(Se,Te) is such a superconductor with topological surface
bands, previously shown to exhibit quantum anomalous vortices around impurity
spins. Here, we take advantage of the flux sensitivity of scanning
superconducting quantum interference devices to investigate superconducting
Fe(Se,Te) in the regime where supercurrents around impurities overlap. We find
homogeneous remanent flux patterns after applying a supercurrent through the
sample. The patterns are consistent with anomalous edge and bulk supercurrents
generated by in-plane magnetization, which occur above a current threshold and
follow hysteresis loops reminiscent of those of a ferromagnet. Similar
long-range magnetic orders can be generated by Meissner current under a small
out-of-plane magnetic field. The magnetization weakens with increasing
temperature and disappears after thermal cycling to above superconducting
critical temperature; further suggesting superconductivity is central to
establishing and maintaining the magnetic order. These observations demonstrate
surface anomalous supercurrents as a mediator for ferromagnetism in a
spin-orbit coupled superconductor, which may potentially be utilized for
low-power cryogenic memory.",2307.10722v2
2004-06-08,Spin injection and detection by resonant tunneling structure,"A theory of spin-dependent electron transmission through resonant tunneling
diode (RTD) grown of non-centrosymmetrical semiconductor compounds has been
presented. It has been shown that RTD can be employed for injection and
detection of spin-polarized carriers: (i) electric current flow in the
interface plane leads to spin polarization of the transmitted carriers, (ii)
transmission of the spin-polarized carriers through the RTD is accompanied by
generation of an in-plane electric current. The microscopic origin of the
effects is the spin-orbit coupling-induced splitting of the resonant level.",0406191v1
2004-12-07,Spin Hall effect in a Doped Mott Insulator,"The existence of conserved spin Hall currents is shown in a strongly
correlated system without involving spin-orbit coupling. The spin Hall
conductivity is determined by intrinsic bulk properties, which remains finite
even when the charge resistivity diverges in strong magnetic fields at zero
temperature. The state in the latter limit corresponds to a spin Hall
insulator. Such a system is a doped Mott insulator described by the phase
string theory, and spin Hall effect is predicted to coexist with the Nernst
effect to characterize the intrinsic properties of the low-temperature
pseudogap phase. Possible applications in spintronics are also mentioned.",0412146v2
2004-12-22,Can Non-Equilibrium Spin Hall Accumulation be Induced in Ballistic Nanostructures?,"We demonstrate that flow of longitudinal unpolarized current through a
ballistic two-dimensional electron gas with Rashba spin-orbit coupling will
induce nonequilibrium spin accumulation which has opposite sign for the two
lateral edges and it is, therefore, the principal observable signature of the
spin Hall effect in two-probe semiconductor nanostructures. The magnitude of
its out-of-plane component is gradually diminished by static disorder, while it
can be enhanced by an in-plane transverse magnetic field. Moreover, our
prediction of the longitudinal component of the spin Hall accumulation, which
is insensitive to the reversal of the bias voltage, offers a smoking gun to
differentiate experimentally between the extrinsic, intrinsic, and mesoscopic
spin Hall mechanisms.",0412595v3
2005-03-15,Disorder effects on the spin-Hall current in a diffusive Rashba two-dimensional heavy-hole system,"We investigate the spin-Hall effect in a two-dimensional heavy-hole system
with Rashba spin-orbit coupling using a nonequilibrium Green's function
approach. Both the short- and long-range disorder scatterings are considered in
the self-consistent Born approximation. We find that, in the case of long-range
collisions, the disorder-mediated process leads to an enhancement of the
spin-Hall current at high heavy-hole density, whereas for short-range
scatterings it gives a vanishing contribution. This result suggests that the
recently observed spin-Hall effect in experiment is a result of the sum of the
intrinsic and disorder-mediated contributions. We have also calculated the
temperature dependence of spin-Hall conductivity, which reveals a decrease with
increasing the temperature.",0503352v4
2006-02-10,Spin Hall Conductance of the Two Dimensional Hole Gas in a Perpendicular Magnetic Field,"The charge and spin Hall conductance of the two-dimensional hole gas within
the Luttinger model with and without inversion symmetry breaking terms in a
perpendicular magnetic field are studied, and two key phenomena are predicted.
The sign of the spin Hall conductance is modulated periodically by the external
magnetic field, which means a possible application in the future. Furthermore,
a resonant spin Hall conductance in the two-dimensional hole gas with a certain
hole density at a typical magnetic field is indicated, which implies a likely
way to firmly establish the intrinsic spin Hall effect. The charge Hall
conductance is unaffected by the spin-orbit coupling.",0602258v3
2006-11-30,Quantized spin Hall effect in Helium three-A and other p-wave paired Fermi systems,"In this paper we propose the quantized spin Hall effect (SHE) in the vortex
state of a rotating p-wave paired Fermi system in an inhomogeneous magnetic
field and in a weak periodic potential. It is the three dimensional extension
of the spin Hall effect for a 3He-A superfluid film studied in Ref. [1]. It may
also be considered as a generalization of the 3D quantized charge Hall effect
of Bloch electrons in Ref. [2] to the spin transport. The A-phase of 3He or,
more generally, the p-wave paired phase of a cold Fermi atomic gas, under
suitable conditions should be a good candidate to observe the SHE, because the
system has a conserved spin current (with no spin-orbit couplings).",0612005v4
2007-01-05,Spin Hall utilizing U(1) and SU(2) gauge fields,"We propose a two-dimensional electron gas (2DEG) system in which an external
magnetic (B) field with a small chirality is applied to provide a topological
U(1) U(1) gauge field that separates conduction electrons of opposite spins in
the transverse direction. Additionally, the vertical electric (E) field in the
2DEG, together with spin-orbit coupling, produces a SU(2) gauge field which
reinforces / opposes the effect of the topological gauge. The system thus
provides a tunable spin Hall effect, where an applied gate voltage on the 2DEG
can be used to modulate the transverse spin current. As this method leads to
the enhancement or cancellation of intrinsic spin Hall, it naturally
distinguishes the extrinsic from the intrinsic effect.",0701111v3
2007-02-06,Spin Triplet Superconducting State due to Broken Inversion Symmetry in Li_2Pt_3B,"We report ^{11}B and ^{195}Pt NMR measurements in non-centrosymmetric
superconductor Li_2Pt_3B. We find that the spin susceptibility measured by the
Knight shift remains unchanged across the superconducting transition
temperature T_c. With decreasing temperature (T) below T_c, the spin-lattice
relaxation rate 1/T_1 decreases with no coherence peak and is in proportion to
T^3. These results indicate that the Cooper pair is in the spin-triplet state
and that there exist line nodes in the superconducting gap function. They are
in sharp contrast with those in the isostructural Li_2Pd_3B which is a
spin-singlet, s-wave superconductor, and are ascribed to the enhanced
spin-orbit coupling due to the lack of spatial inversion symmetry. Our finding
points to a new paradigm where exotic superconductivity arises in the absence
of strong electron-electron correlations.",0702130v1
2007-07-19,Graphene based spin field effect transistor,"A spin field effect transistor (FET) is proposed by utilizing a graphene
nanoribbon as the channel. Similar to the conventional spin FETs, the device
involves ferromagnetic metals as a source and drain; they, in turn, are
connected to the graphene channel. Due to the negligible spin-orbital coupling
in the carbon based materials, the bias can accomplishes spin manipulation by
means of electrical control of electron exchange interaction with a
ferromagnetic dielectric attached to the nanoribbon between source and drain.
The numerical estimations show the feasibility of graphene-based spin FET if a
bias varies exchange interaction on the amount around 5 meV. It was shown that
the device stability to the thermal dispersion can provide the armchair
nanoribbons of specific width that keeps the Dirac point in electron dispersion
law.",0707.2966v1
2007-10-21,Geometric phases in semiconductor spin qubits: Manipulations and decoherence,"We describe the effect of geometric phases induced by either classical or
quantum electric fields acting on single electron spins in quantum dots in the
presence of spin-orbit coupling. On one hand, applied electric fields can be
used to control the geometric phases, which allows performing quantum coherent
spin manipulations without using high-frequency magnetic fields. On the other
hand, fluctuating fields induce random geometric phases that lead to spin
relaxation and dephasing, thus limiting the use of such spins as qubits. We
estimate the decay rates due to piezoelectric phonons and conduction electrons
in the circuit, both representing dominant electric noise sources with
characteristically differing power spectra.",0710.3931v2
2008-08-21,Theory of Electron Spin Relaxation in ZnO,"Doped ZnO is a promising material for spintronics applications. For such
applications, it is important to understand the spin dynamics and particularly
the spin coherence of this II-VI semiconductor. The spin lifetime $\tau_{s}$
has been measured by optical orientation experiments, and it shows a surprising
non-monotonic behavior with temperature. We explain this behavior by invoking
spin exchange between localized and extended states. Interestingly, the effects
of spin-orbit coupling are by no means negligible, in spite of the relatively
small valence band splitting. This is due to the wurtzite crystal structure of
ZnO. Detailed analysis allows us to characterize the impurity binding energies
and densities, showing that optical orientation experiments can be used as a
characterization tool for semiconductor samples.",0808.2913v3
2011-09-28,Spin Transport Properties of Fractal and Non-Fractal Thinfilm,"Spatial behavior of spin transport in a Sierpinski gasket fractal is studied
from two dimensions to quasi-one dimension subject to the Rashba spin-orbital
coupling. With two normal metal leads represented by self-energy matrix,
discretizing the derived continuous Hamiltonian to a tight-binding version,
Landauer-Keldysh formalism for nonequilibrium transport can be applied. It was
observed that the spin Hall effect presents in the distribution of spin density
critically depends on the fractal structure and the shape of the thinfilm. The
local spin density and transmission are numerically tested by the present
quantum transport calculation for the fractal and non-fractal thinfilm varying
from two-dimensional square-lattice into quasi-one dimensional fractal shape
(Sierpinski triangles).",1109.6120v1
2012-02-29,Spin-transfer torque and spin-polarization in topological-insulator/ferromagnet vertical heterostructures,"We predict an unconventional spin-transfer torque (STT) acting on the
magnetization of a free ferromagnetic (F) layer within N/TI/F vertical
heterostructures which originates from strong spin-orbit coupling (SOC) on the
surface of a three-dimensional topological insulator (TI), as well as from
charge current becoming spin-polarized in the direction of transport as it
flows from the normal metal (N) across the bulk of the TI slab. Unlike
conventional STT in symmetric F'/I/F magnetic tunnel junctions, where only the
in-plane STT component is non-zero in the linear response, both the in-plane
and perpendicular torque are sizable in N/TI/F junctions while not requiring
fixed F' layer as spin-polarizer which is advantageous for spintronic
applications. Using the nonequilibrium Born-Oppenheimer treatment of
interaction between fast conduction electrons and slow magnetization, we derive
a general Keldysh Green function-based STT formula which makes it possible to
analyze torque in the presence of SOC either in the bulk or at the interface of
the free F layer.",1202.6602v1
2012-11-01,Spin-polarized Majorana Bound States inside a Vortex Core in Topological Superconductors,"We reveal that Majorana bound states inside the vortex core in an odd-parity
topological superconductivity classified as ""pseudo-scalar"" type in the gap
function are distinctly spin-polarized by solving the massive Dirac
Bogoliubov-de Gennes (BdG) equation considering the spin-orbit coupling. This
result is universal for ""Dirac superconductivity"" whose rotational degree of
freedom is characterized by the total angular momentum J = S + L and in marked
contrast to the spin-degeneracy of the core bound states as the consequence of
the conventional BdG equation. The spin-polarized vortex core can be easily
detected by spin-sensitive probes such as the neutron scattering and other
measurements well above the first critical magnetic field H_{c1}.",1211.0125v2
2012-11-02,Dynamic Spin Injection into Chemical Vapor Deposited Graphene,"We demonstrate dynamic spin injection into chemical vapor deposition (CVD)
grown graphene by spin pumping from permalloy (Py) layers. Ferromagnetic
resonance measurements at room temperature reveal a strong enhancement of the
Gilbert damping at the Py/graphene interface, exceeding that observed in even
Py/platinum interfaces. Similar results are also shown on Co/graphene layers.
This enhancement in the Gilbert damping is understood as the consequence of
spin pumping at the interface driven by magnetization dynamics. Our
observations suggest a strong enhancement of spin-orbit coupling in CVD
graphene, in agreement with earlier spin valve measurements.",1211.0492v1
2013-02-05,Spin-valley lifetimes in a silicon quantum dot with tunable valley splitting,"Although silicon is a promising material for quantum computation, the
degeneracy of the conduction band minima (valleys) must be lifted with a
splitting sufficient to ensure formation of well-defined and long-lived spin
qubits. Here we demonstrate that valley separation can be accurately tuned via
electrostatic gate control in a metal-oxide-semiconductor quantum dot,
providing splittings spanning 0.3 - 0.8 meV. The splitting varies linearly with
applied electric field, with a ratio in agreement with atomistic tight-binding
predictions. We demonstrate single-shot spin readout and measure the spin
relaxation for different valley configurations and dot occupancies, finding
one-electron lifetimes exceeding 2 seconds. Spin relaxation occurs via phonon
emission due to spin-orbit coupling between the valley states, a process not
previously anticipated for silicon quantum dots. An analytical theory describes
the magnetic field dependence of the relaxation rate, including the presence of
a dramatic rate enhancement (or hot-spot) when Zeeman and valley splittings
coincide.",1302.0983v2
2013-03-01,Spontaneous and resonant lifting of the spin blockade in nanowire quantum dots,"A complete numerical description of the charge and spin dynamics of a
two-electron system confined in narrow nanowire quantum dots under oscillating
electric field is presented in the context of recent electric dipole spin
resonance experiments. We find that the spin-orbit coupling results in lifting
the spin blockade by phonon mediated relaxation provided that the initially
occupied state is close in energy to the ground state. This leads to
suppression of the blockade from the triplet state with spins polarized
parallel to the external magnetic field B. At higher B, after singlet-triplet
ground-state transition a new channel for lifting the Pauli blockade opens
which results in an appearance of additional resonance lines. The calculated
signatures of this transition are consistent with recent experimental results
[S. M. Frolov et al., Phys. Rev. Lett. 109, 236805 (2012)].",1303.0211v2
2013-05-16,Interplay between edge and bulk states in silicene nanoribbon,"We investigate the interplay between the edge and bulk states, induced by the
Rashba spin-orbit coupling, in a zigzag silicene nanoribbon in the presence of
an external electric field. The interplay can be divided into two kinds, one is
the interplay between the edge and bulk states with opposite velocities, and
the other is that with the same velocity direction. The former can open small
direct spin-dependent subgaps. A spin-polarized current can be generated in the
nanoribbon as the Fermi energy is in the subgaps. While the later can give rise
to the spin precession in the nanoribbon. Therefore, the zigzag silicene
nanoribbon can be used as an efficient spin filter and spin modulation device.",1305.3684v1
2014-08-20,Effects of interaction on field-induced resonances in confined Fermi liquid,"We consider the two-dimensional electron gas confined laterally to a narrow
channel by a harmonic potential. As the Zeeman splitting matches the
intersubband separation the nonlocal spin polarization develops a minimum as
reported by Frolov et al. [Nature (London) 458, 868 (2009)]. This phenomenon
termed Ballistic Spin Resonance is due to the degeneracy between the nearest
oppositely polarized subbands that is lifted by spin-orbit coupling. We showed
that the resonance survives the weak and short-range interaction. The latter
detunes it and as a result shifts the Zeeman splitting at which the minimum in
spin polarization occurs. Here this shift is attributed to the absence of Kohn
theorem for the spin sloshing collective mode. We characterized the shift due
to weak interaction qualitatively by analyzing the spin sloshing mode within
the Fermi liquid phenomenology.",1408.4707v2
2015-05-31,Thermoelectric response of spin polarization in Rashba spintronic systems,"Motivated by recent discovery of strongly spin-orbit coupled two-dimensional
(2D) electron gas near the surface of Rashba semiconductors BiTeX (X=Cl, Br,
I), we calculate thermoelectric responses of spin polarization in 2D Rashba
model using an exact solution of the linearized Boltzmann equation for elastic
scattering. When the Fermi energy $E_{F}$ lies below the band crossing point we
find a non-Edelstein electric-field induced spin polarization which is linear
in $E_{F}$. We show that the Mott-like relation between spin polarizations
induced by the temperature gradient and electric field breaks down
significantly when $E_{F}$ lies in the vicinity of the band crossing point. As
the temperature tends to zero, the temperature-gradient induced spin
polarization vanishes. These results differ from previous ones obtained by
relaxation time approximations.",1506.00203v2
2015-06-26,Spin-dependent coherent transport in a double quantum dot system,"We study spin-resolved resonant tunneling in a system of two quantum dots
sandwiched between doped quantum wells. In the coherent (Dicke) regime, i.e.,
when quantum dot separation is smaller than the Fermi wavelength in a
two-dimensional electron gas in quantum wells, application of an in-plane
magnetic field leads to a pronounced spin-resolved structure of the conductance
peak lineshape even for very small Zeeman splitting of the quantum dots'
resonant levels. In the presence of electron-gas spin-orbit coupling, this
spin-resolved structure gets washed out due to Fermi surface deformation in the
momentum space. We also show that Aharonov-Bohm flux penetrating the area
enclosed by electron tunneling pathways completely destroys conductance spin
structure.",1506.08214v2
2016-04-05,Effective spin dephasing mechanism in confined two-dimensional topological insulators,"A Kramers pair of helical edge states in quantum spin Hall effect (QSHE) is
robust against normal dephasing but not robust to spin dephasing. In our work,
we provide an effective spin dephasing mechanism in the puddles of
two-dimensional (2D) QSHE, which is simulated as quantum dots modeled by 2D
massive Dirac Hamiltonian. We demonstrate that the spin dephasing effect can
originate from the combination of the Rashba spin-orbit coupling and
electron-phonon interaction, which gives rise to inelastic backscattering in
edge states within the topological insulator quantum dots, although the
time-reversal symmetry is preserved throughout. Finally, we discuss the
tunneling between extended helical edge states and local edge states in the QSH
quantum dots, which leads to backscattering in the extended edge states. These
results can explain the more robust edge transport in InAs/GaSb QSH systems.",1604.01194v1
2016-06-23,Rashba-Dresselhaus spin-splitting in the bulk ferroelectric oxide BiAlO$_3$,"It has been recently suggested that the coexistence of ferroelectricity and
Rashba-like spin-splitting effects due to spin-orbit coupling in a single
material may allow for a non-volatile electric control of spin degrees of
freedom. In the present work, we compared the structural and ferroelectric
properties of tetragonal and rhombohedral phases of ferroelectric BiAlO$_3$ by
means of density-functional calculations. In both phases, we carefully
investigated Rashba and Dresselhaus effects, giving rise to spin-splitting in
their bulk electronic structure, particularly near the conduction band minimum,
supplementing our first-principles results with an effective $ k\cdot p$ model
analysis. The full reversal of the spin texture with ferroelectric polarization
switching was also predicted. BiAlO$_3$ can therefore be considered as the
first known oxide to exhibit a coexistence of ferroelectricity and
Rashba-Dresselhaus effects.",1606.07400v2
2017-02-03,Spin qubit manipulation of acceptor bound states in group IV quantum wells,"The large spin-orbit coupling in the valence band of group IV semiconductors
provides an electric field knob for spin-qubit manipulation. This fact can be
exploited with acceptor based qubits. Spin manipulation of holes bound to
acceptors in engineered SiGe quantum wells depends very strongly on the
electric field applied and on the heterostructure parameters. The g-factor is
enhanced by the Ge content and can be tuned by shifting the hole wave-function
between the heterostructure constituent layers. The lack of inversion symmetry
induced both by the quantum well and the electric fields together with the
g-factor tunability allows the possibility of different qubit manipulation
methods such as electron spin resonance, electric dipole spin resonance and
g-tensor modulation resonance. Rabi frequencies up to hundreds of MHz can be
achieved with heavy-hole qubits, and of the order of GHz with light-hole
qubits.",1702.00960v1
2017-02-23,Nematic order on the surface of a three-dimensional topological insulator,"We study the spontaneous breaking of rotational symmetry in the helical
surface state of three-dimensional topological insulators due to strong
electron-electron interactions, focusing on time-reversal invariant nematic
order. Owing to the strongly spin-orbit coupled nature of the surface state,
the nematic order parameter is linear in the electron momentum and necessarily
involves the electron spin, in contrast with spin-degenerate nematic Fermi
liquids. For a chemical potential at the Dirac point (zero doping), we find a
first-order phase transition at zero temperature between isotropic and nematic
Dirac semimetals. This extends to a thermal phase transition that changes from
first to second order at a finite-temperature tricritical point. At finite
doping, we find a transition between isotropic and nematic helical Fermi
liquids that is second order even at zero temperature. Focusing on finite
doping, we discuss various observable consequences of nematic order, such as
anisotropies in transport and the spin susceptibility, the partial breakdown of
spin-momentum locking, collective modes and induced spin fluctuations, and
non-Fermi liquid behavior at the quantum critical point and in the nematic
phase.",1702.07364v2
2017-08-02,The Formation of Rapidly Rotating Black Holes in High Mass X-ray Binaries,"High mass X-ray binaries (HMXRBs) like Cygnus X-1, host some of the most
rapidly spinning black holes (BHs) known to date, reaching spin parameters $a
\gtrsim 0.84$. However, there are several effects that can severely limit the
maximum BH spin parameter that could be obtained from direct collapse, such as
tidal synchronization, magnetic core-envelope coupling and mass loss. Here we
propose an alternative scenario where the BH is produced by a {\it failed}
supernova (SN) explosion that is unable to unbind the stellar progenitor. A
large amount of fallback material ensues, whose interaction with the secondary
naturally increases its overall angular momentum content, and therefore, the
spin of the BH when accreted. Through SPH hydrodynamic simulations, we studied
the unsuccessful explosion of a $8M_{\odot }$ pre-SN star in a close binary
with a $12M_{\odot}$ companion with an orbital period of $\approx1.2$ days,
finding that it is possible to obtain a BH with a high spin parameter
$a\gtrsim0.8$ even when the expected spin parameter from direct collapse is $a
\lesssim 0.3$. This scenario also naturally explains the atmospheric metal
pollution observed in HMXRB stellar companions.",1708.00570v1
2018-11-04,Spin polarization through Intersystem Crossing in the silicon vacancy of silicon carbide,"Silicon carbide (SiC)-based defects are promising for quantum communications,
quantum information processing, and for the next generation of quantum sensors,
as they feature long coherence times, frequencies near the telecom, and optical
and microwave transitions. For such applications, the efficient initialization
of the spin state is necessary. We develop a theoretical description of the
spin polarization process by using the intersystem crossing of the silicon
vacancy defect, which is enabled by a combination of optical driving,
spin-orbit coupling, and interaction with vibrational modes. By using distinct
optical drives, we analyze two spin polarization channels. Interestingly, we
find that different spin projections of the ground state manifold can be
polarized. This work helps to understand initialization and readout of the
silicon vacancy and explains some existing experiments with the silicon vacancy
center in SiC.",1811.01398v1
2020-07-07,Heisenberg-Kitaev model in a magnetic field: $1/S$ expansion,"The exact solution of Kitaev's spin-$1/2$ honeycomb spin-liquid model has
sparked an intense search for Mott insulators hosting bond-dependent Kitaev
interactions, of which $\mathrm{Na}_{2}\mathrm{IrO}_{3}$ and
$\alpha-\mathrm{RuCl}_{3}$ are prime examples. Subsequently, it has been
proposed that also spin-$1$ and spin-$3/2$ analogs of Kitaev interactions may
occur in materials with strong spin-orbit coupling. As a minimal model to
describe these Kitaev materials, we study the Heisenberg-Kitaev Hamiltonian in
a consistent $1/S$ expansion, with $S$ being the spin size. We present a
comprehensive study of this model in the presence of an external magnetic field
applied along two different directions, [001] and [111], for which an intricate
classical phase diagram has been reported. In both settings, we employ
spin-wave theory in a number of ordered phases to compute phase boundaries at
the next-to-leading order in $1/S$ and show that quantum corrections
substantially modify the classical phase diagram. More broadly, our work
presents a consistent route to investigate the leading quantum corrections in
spin models that break spin-rotational symmetry.",2007.03717v2
2014-03-26,Proposal for an ac spin current source,"We propose an ac current source that can be tuned from a pure charge to a
pure spin current source. The device consists of two mesoscopic capacitors
attached to a two-dimensional strip of a topological insulator. The change from
charge to spin current is controlled by an offset in the top gate potentials
that drive the capacitors. In addition to this setup, which anticipates the
experimental realisation of quantum point contacts in topological insulators,
we propose an analogous source in the quantum Hall regime which only relies on
presently available building blocks. To this end, we calculate the band
structure of a topological insulator in a magnetic field. The intrinsic
spin-orbit coupling, together with a split gate, allows for an analogous
source, where charge and spin current can be manipulated. The realisation of
the device as well as the detection of the ac spin current are within reach of
present experimental technology.",1403.6674v2
2017-01-03,Momentum-Space Spin Texture in a Topological Superconductor,"A conventional superconductor with spin-orbit coupling turns into a
topological superconductor beyond a critical strength of the Zeeman energy. The
spin-expectation values $\mathbf{S}(\mathbf{k})$ in momentum space trace this
transition via a characteristic change in the topological character of the spin
texture within the Brillouin zone. At the transition the skyrmion counting
number switches from 0 to 1/2 identifying the topological superconductor via
its meron-like spin texture. The change in the skyrmion counting number is
crucially controlled by singular points of the map
$\mathbf{S}(\mathbf{k})/|\mathbf{S}(\mathbf{k})|$ from the Brillouin zone, i.e.
a torus, to the unit sphere. The complexity of this spin-map is discussed at
zero temperature as well as for the extension to finite temperatures.",1701.00788v1
2017-04-28,Significant Dzyaloshinskii-Moriya Interaction at Graphene-Ferromagnet Interfaces due to Rashba-effect,"The possibility of utilizing the rich spin-dependent properties of graphene
has attracted great attention in pursuit of spintronics advances. The promise
of high-speed and low-energy consumption devices motivates a search for layered
structures that stabilize chiral spin textures such as topologically protected
skyrmions. Here we demonstrate that chiral spin textures are induced at
graphene/ferromagnetic metal interfaces. This is unexpected because graphene is
a weak spin-orbit coupling material and is generally not expected to induce
sufficient Dzyaloshinskii-Moriya interaction to affect magnetic chirality. We
demonstrate that graphene induces a new type of Dzyaloshinskii-Moriya
interaction due to a Rashba effect. First-principles calculations and
experiments using spin-polarized electron microscopy show that this
graphene-induced Dzyaloshinskii-Moriya interaction can have similar magnitude
as at interfaces with heavy metals. This work paves a new path towards
two-dimensional material based spin orbitronics.",1704.09023v1
2011-11-07,Effects of scattering area shape on spin conductance in a four-terminal spin-Hall setup,"We study spin conductance in a ballistic and quasi-ballistic two dimensional
electron system with Rasbha spin-orbit coupling. The system has a four-terminal
geometry with round corners at the connection to the leads. It is found that by
going from sharp corners to more round corners in the ballistic system the
energy depended spin conductance goes from being relatively flat to a curve
showing a series of minima and maxima. It is also found that when changing the
size of the terminal area by modifying the roundness of the terminal corners
the maxima and minima in the transverse spin conductance are shifted in energy.
This shift is due increased (decreased) energy for smaller (larger) terminal
area. These results were also found to be reasonably stable in quasi-ballistic
systems.",1111.1529v1
2012-04-24,Spin Configuration and Scattering Rates on the Heavily Electron-doped Surface of Topological Insulator Bi$_2$Se$_3$,"Heavily electron-doped surfaces of Bi$_2$Se$_3$ have been studied by spin and
angle resolved photoemission spectroscopy. Upon doping, electrons occupy a
series of {\bf k}-split pairs of states above the topological surface state.
The {\bf k}-splitting originates from the large spin-orbit coupling and results
in a Rashba-type behavior, unequivocally demonstrated here via the spin
analysis. The spin helicities of the lowest laying Rashba doublet and the
adjacent topological surface state alternate in a left-right-left sequence.
This spin configuration sets constraints to inter-band scattering channels
opened by electron doping. A detailed analysis of the scattering rates suggests
that intra-band scattering dominates with the largest effect coming from
warping of the Fermi surface.",1204.5263v1
2012-04-24,Non-Abelian spin singlet states of two-component Bose gases in artificial gauge fields,"We study strongly correlated phases of a pseudo-spin-1/2 Bose gas in an
artificial gauge field using the exact diagonalization method. The atoms are
confined in two dimensions and interact via a two-body contact potential. In
Abelian gauge fields, pseudo-spin singlets are favored by pseudo-spin
independent interactions. We find a series of incompressible phases at fillings
\nu=2k/3. By comparison with the non-Abelian spin singlet (NASS) states,
constructed as zero-energy eigenstates of a (k+1)-body contact interaction, we
classify the non-trivial topology of the states. An additional spin-orbit
coupling is shown to switch between NASS-like states and spin-polarized phases
from the Read-Rezayi series.",1204.5423v2
2012-04-26,Approximate Spin and Pseudospin Solutions of the Dirac equation with Rosen-Morse Potential including a Coulomb Tensor Interaction,"By applying the Pekeris-type approximation to deal with the (pseudo or)
centrifugal term, the spin and pseudospin symmetry solutions of the Dirac
equation for the Rosen-Morse potential including a Coulomb-like tensor
potential with arbitrary spin-orbit coupling quantum number $\kappa$ are
obtained by standard method. It has been shown from the numerical results that
the degeneracies between spin and pseudospin state doublets are removed by the
tensor interaction. Special case of this potential, that is, the spin and
pseudospin solutions of the Dirac equation with the modified P\""{o}schl-Teller
potential including a tensor interaction is also considered. The results
obtained in this case show that the tensor interaction removes the degeneracies
between the members of doublets states in spin and pseudospin symmetries.",1204.5898v1
2015-12-23,Giant room temperature interface spin Hall and inverse spin Hall effects,"The spin Hall angle (SHA) is a measure of the efficiency with which a
transverse spin current is generated from a charge current by the spin-orbit
coupling and disorder in the spin Hall effect (SHE). In a study of the SHE for
a Pt$|$Py (Py=Ni$_{80}$Fe$_{20}$) bilayer using a first-principles scattering
approach, we find a SHA that increases monotonically with temperature and is
proportional to the resistivity for bulk Pt. By decomposing the room
temperature SHE and inverse SHE currents into bulk and interface terms, we
discover a giant interface SHA that dominates the total inverse SHE current
with potentially major consequences for applications.",1512.07418v2
2016-05-16,Manifestation of extrinsic spin Hall effect in superconducting structures: Non-dissipative magnetoelectric effects,"We present a comprehensive quasiclassical approach for studying transport
properties of superconducting diffusive hybrid structures in the presence of
extrinsic spin-orbit coupling. We derive a generalized Usadel equation and
boundary conditions that in the normal state reduce to the drift-diffusion
theory governing the spin-Hall effect in inversion symmetric materials. These
equations predict the non-dissipative spin-galvanic effect, that is the
generation of supercurrents by a spin-splitting field, and its inverse -- the
creation of magnetic moment by a supercurrent. These effects can be seen as
counterparts of the spin-Hall, anomalous Hall and their inverse effects in the
superconducting state. Our theory opens numerous possibilities for using
superconducting structures in magnetoelectronics.",1605.04689v2
2016-08-08,Biaxial-stress-driven full spin polarization in ferromagnetic hexagonal chromium telluride,"It is important to spintronics to achieve fully-spin-polarized magnetic
materials that are stable and can be easily fabricated. Here, through
systematical density-functional-theory investigations, we achieve high and even
full spin polarization for carriers in the ground-state phase of CrTe by
applying tensile biaxial stress. The resulting strain is tensile in the xy
plane and compressive in the z axis. With the in-plane tensile strain
increasing, the ferromagnetic order is stable against antiferromagnetic
fluctuations, and a half-metallic ferromagnetism is achieved at an in-plane
strain of 4.8%. With the spin-orbit coupling taken into account, the spin
polarization is equivalent to 97% at the electronic phase transition point, and
then becomes 100.0% at the in-plane strain of 6.0%. These make us believe that
the full-spin-polarized ferromagnetism in this stable and easily-realizable
hexagonal phase could be realized soon, and applied in spintronics.",1608.02405v3
2017-12-18,Frustrated superfluids in a non-Abelian flux,"We study possible superfluid states of the Rashba spin-orbit coupled (SOC)
spinor bosons with the spin anisotropic interaction $ \lambda $ hopping in a
square lattice. The frustrations from the non-abelian flux due to the SOC leads
to novel spin-bond correlated superfluids. By using a recently developed
systematic ""order from quantum disorder"" analysis, we not only determine the
true quantum ground state, but also evaluate the mass gap in the spin sector at
$ \lambda < 1 $, especially compute the the excitation spectrum of the
Goldstone mode in the spin sector at $ \lambda=1 $ which would be quadratic
without the analysis. The analysis also leads to different critical exponents
on the two sides of the 2nd order transition driven by a roton touchdown at $
\lambda=1 $. The intimate analogy at $ \lambda=1 $ with the charge neutral
Goldstone mode in the pseudo-spin sector in the Bilayer quantum Hall systems at
the total filling factor $ \nu_T=1 $ are stressed. The experimental
implications and detections of these novel phenomena in cold atoms loaded on a
optical lattice are presented.",1712.06545v1
2018-01-31,Proposal for detecting nodal-line semimetal surface-states with resonant spin-flipped reflection,"Topological nodal-line semimetals are predicted to exhibit unique
drumhead-like surface states (DSS). Yet, a direct detection of such states
remains a challenge. Here, we propose spin-resolved transport in a junction
between a normal metal and a spin-orbit coupled nodal-line semimetal as the
mechanism for their detection. Specifically, we find that in such a device, the
DSS induce resonant spin-flipped reflection. This effect can be probed by both
vertical spin transport and lateral charge transport between anti-parallel
magnetic terminals. In the tunneling limit of the junction, both spin and
charge conductances exhibit a resonant peak around zero energy, providing a
unique evidence of the DSS. This signature is robust to both dispersive DSS and
interface disorder. Based on numerical calculations, we show that the scheme
can be implemented in the topological semimetal HgCr$_2$Se$_4$.",1801.10337v3
2019-09-10,Kitaev Magnetism and Fractionalized Excitations in Double Perovskite Sm2ZnIrO6,"The quest for Kitaev spin liquids in particular three dimensional solids is
long sought goal in condensed matter physics, as these states may give rise to
exotic new types of quasi-particle excitations carrying fractional quantum
numbers namely Majorana Fermionic excitations. Here we report the experimental
signature of this characteristic feature of the Kitaev spin liquid via Raman
measurements. Sm2ZnIrO6 is a strongly spin orbit coupled Mott insulator, where
Jeff = 1/2 controls the physics, which provide striking evidence for this
characteristic feature of the Kitaev spin liquid. As the temperature is
lowered, we find that the spin excitations form a continuum in contrast to the
conventional sharp modes expected in ordered antiferromagnets. Our observation
of a broad magnetic continuum and anomalous renormalization of the phonon
self-energy parameters evidence the existence of Majorana fermions from spin
fractionalization in double perovskites structure as theoretically conjectured
in a Kitaev-Heisenberg geometrically frustrated double perovskite systems.",1909.04322v2
2020-02-19,Effective Hamiltonian model for helically constrained quantum systems within adiabatic perturbation theory: application to the Chirality-Induced Spin Selectivity (CISS) Effect,"The chirality-induced spin selectivity (CISS) effect has been confirmed
experimentally for a large class of organic molecules. Adequately modeling the
effect remains a challenging task, with both phenomenological models and
first-principle simulations yielding inconclusive results. Building upon a
previously presented model by K. Michaeli and R. Naaman (J. Phys. Chem C 123,
17043 (2019)) we systematically investigate an effective 1-dimensional model
derived as the limit of a 3-dimensional quantum system with strong confinement
and including spin-orbit coupling. Having a simple analytic structure, such
models can be considered a minimal setup for the description of spin-dependent
effects. We use adiabatic perturbation theory to provide a mathematically sound
approximation procedure applicable to a large class of spin-dependent continuum
models. We take advantage of the models simplicity by analyzing its structure
to gain a better understanding how the occurrence and magnitude of spin
polarization effects relate to the model's parameters and geometry.",2002.08052v1
2017-05-08,$θ_0$ thermal Josephson junction,"We predict the thermal counterpart of the anomalous Josephson effect in
superconductor/ferromagnet/superconductor junctions with non-coplanar magnetic
texture. The heat current through the junction is shown to have the
phase-sensitive interference component proportional to $\cos(\theta -
\theta_0)$, where $\theta$ is the Josephson phase difference and $\theta_0$ is
the texture-dependent phase shift. In the generic tri-layer magnetic structure
with the spin-filtering tunnel barrier $\theta_0$ is determined by the spin
chirality of magnetic configuration and can be considered as the direct
manifestation of the energy transport with participation of spin-triplet Cooper
pairs. In case of the ideal spin filter the phase shift is shown to be robust
against spin relaxation caused by the spin-orbital scattering. Possible
applications of the coupling between heat flow and magnetic precession are
discussed.",1705.02835v2
2019-02-22,Coexistent spin-triplet superconducting and ferromagnetic phases induced by the Hund's rule coupling and electronic correlations II: Effect of applied magnetic field,"Recently proposed local-correlation-driven pairing mechanism, describing
ferromagnetic phases (FM1 and FM2) coexisting with spin-triplet
superconductivity (SC) within a single orbitally degenerate Anderson lattice
model, is extended to the situation with applied Zeeman field. The model
provides and rationalizes in a semiquantitative manner the principal features
of the phase diagram observed for $\mathrm{UGe_2}$ in the field absence [cf.
Phys. Rev. B $\mathbf{97}$, 224519 (2018)]. As spin-dependent effects play a
crucial role for both the ferromagnetic and SC states, the role of the Zeeman
field is to single out different stable spin-triplet SC phases. This analysis
should thus be helpful in testing the proposed real-space pairing mechanism,
which may be regarded as complementary to spin-fluctuation theory suitable for
$\mathrm{^3He}$. Specifically, we demonstrate that the presence of the two
distinct phases, FM1 and FM2, and associated field-driven metamagnetic
transition between them, induce respective metasuperconducting phase
transformation. At the end, we discuss briefly how the spin fluctuations might
be incorporated as a next step into the considered here renormalized
quasiparticle picture.",1902.08444v2
2019-04-30,Electric-field control and noise protection of the flopping-mode spin qubit,"We propose and analyze a novel ""flopping-mode"" mechanism for electric dipole
spin resonance based on the delocalization of a single electron across a double
quantum dot confinement potential. Delocalization of the charge maximizes the
electronic dipole moment compared to the conventional single dot spin resonance
configuration. We present a theoretical investigation of the flopping-mode spin
qubit properties through the crossover from the double to the single dot
configuration by calculating effective spin Rabi frequencies and single-qubit
gate fidelities. The flopping-mode regime optimizes the artificial spin-orbit
effect generated by an external micromagnet and draws on the existence of an
externally controllable sweet spot, where the coupling of the qubit to charge
noise is highly suppressed. We further analyze the sweet spot behavior in the
presence of a longitudinal magnetic field gradient, which gives rise to a
second order sweet spot with reduced sensitivity to charge fluctuations.",1904.13117v2
2019-12-31,Identification of Spin-Triplet Superconductivity through a Helical-Chiral Phase Transition in Sr$_2$RuO$_4$ Thin-Films,"Despite much effort for over the two decades, the paring symmetry of a
Sr$_2$RuO$_4$ superconductor has been still unclear. In this Rapid
Communication, motivated by the recent rapid progress in fabrication techniques
for Sr$_2$RuO$_4$ thin-films, we propose a promising strategy for identifying
the spin-triplet superconductivity in the thin-film geometry by employing an
antisymmetric spin-orbit coupling potential and a Zeeman potential due to an
external magnetic field. We demonstrate that a spin-triplet superconducting
thin-film undergoes a phase transition from a helical state to a chiral state
by increasing the applied magnetic field. This phase transition is accompanied
by a drastic change in the property of surface Andreev bound states. As a
consequence, the helical-chiral phase transition, which is unique to the
spin-triplet superconductors, can be detected through a sudden change in a
tunneling conductance spectrum of a normal-metal/superconductor junction.
Importantly, our proposal is constructed by combining fundamental and rigid
concepts regarding physics of spin-triplet superconductivity.",1912.13250v1
2020-05-12,Thermoelectricity carried by proximity-induced odd-frequency pairing in ferromagnet/superconductor junctions,"We explore the role of proximity-induced odd-frequency pairing in the
thermoelectricity of a ferromagnet when coupled to a conventional $s$-wave
spin-singlet superconductor through a spin-active interface. By varying both
the polarization and its direction in the ferromagnet and the interfacial
spin-orbit interaction strength, we analyze the behavior of all
proximity-induced pair amplitudes in the ferromagnet and their contributions to
the thermoelectric coefficients. Based on our results for the Seebeck
coefficient, we predict that odd-frequency spin-triplet Cooper pairs are much
efficient than the conventional spin-singlet even-frequency pairs in enhancing
thermoelectricity of the junction, especially mixed-spin triplet pairing is
favorable. Our results on the thermoelectric figure of merit show that
ferromagnet/superconductor junctions are very good thermoelectric systems when
superconductivity is dominated by odd-frequency pairing.",2005.05950v2
2019-06-05,Noncollinear Antiferromagnetic Order and Effect of Spin-Orbit Coupling in Spin-1 Honeycomb Lattice,"Motivated by the recently synthesized insulating nickelate Ni$_2$Mo$_3$O$_8$,
which has been reported to have an unusual non-collinear magnetic order of
Ni$^{2+}$ $S=1$ moments with a nontrivial angle between adjacent spins, we
construct an effective spin-1 model on the honeycomb lattice, with the exchange
parameters determined with the help of first principles electronic structure
calculations. The resulting bilinear-biquadratic model, supplemented with the
realistic crystal-field induced anisotropy, favors the collinear N\'eel state.
We find that the crucial key to explaining the observed noncollinear spin
structure is the inclusion of the Dzyaloshinskii--Moriya (DM) interaction
between the neighboring spins. By performing the variational mean-field and
linear spin-wave theory (LSWT) calculations, we determine that a realistic
value of the DM interaction $D\approx 2.78$ meV is sufficient to quantitatively
explain the observed angle between the neighboring spins. We furthermore
compute the spectrum of magnetic excitations within the LSWT and random-phase
approximation (RPA) which should be compared to future inelastic neutron
measurements.",1906.02215v3
2020-09-06,Spin photogalvanic effect in two-dimensional collinear antiferromagnets,"Spin photogalvanic effect (SPGE) is an efficient method to generate a spin
current by photoexcitation in a contactless and ultra-fast way. In
two-dimensional (2D) collinear antiferromagnetic (AFM) materials that preserve
the combined time-reversal (T) and inversion (I) symmetry (i.e., TI symmetry),
we find that the photogalvanic currents in two magnetic sublattices carry
different kinds of spins and propagate in opposite direction if the spin-orbit
coupling is negligible, resulting in a pure spin current without net charge
current. Based on the first-principles calculations, we show that two
experimentally synthesized 2D collinear AFM materials, monolayer MnPS$_3$ and
bilayer CrCl$_3$, host the required symmetry and support sizable SPGE. The
predicted SPGE in 2D collinear AFM materials makes them promising platforms for
nano spintronics devices.",2009.02748v1
2020-09-25,Spin-selective resonant tunneling induced by Rashba spin-orbit interaction in semiconductor nanowire,"We consider a single electron confined within a quantum wire in a system of
two electrostatically-induced QDs defined by nearby gates. The time-varying
electric field, of single GHz frequency, perpendicular to the quantum wire, is
used to induce the Rashba coupling and enable spin-dependent resonant tunneling
of the electron between two adjacent potential wells with fidelity over 99.5%.
This effect can be used for the high fidelity all-electrical electron-spin
initialization or readout in the spin-based quantum computer. In contrast to
other spin initialization methods, our technique can be performed adiabatically
without increase in the energy of the electron. Our simulations are supported
by a realistic self-consistent time-dependent Poisson-Schroedinger
calculations.",2009.12439v2
2021-03-01,Charge Redistribution and Spin Polarization Driven by Correlation Induced Electron Exchange in Chiral Molecules,"Chiral induced spin selectivity is a phenomenon that has been attributed to
chirality, spin-orbit interactions, and non-equilibrium conditions, while the
role of electron exchange and correlations have been investigated only
marginally until very recently. However, as recent experiments show that chiral
molecules acquire a finite spin-polarization merely by being in contact with a
metallic surface, these results suggest that electron correlations play a more
crucial role for the emergence of the phenomenon than previously thought. Here,
it is demonstrated that molecular vibrations give rise to molecular charge
redistribution and accompanied spin-polarization when coupling a chiral
molecule to a non-magnetic metal. It is, moreover, shown that enantiomer
separation, due to spin-polarization intimately related to the chirality, can
be understood in terms of the proposed model.",2103.00840v1
2021-09-30,Magneto-optical Kerr spectra of gold induced by spin accumulation,"We report the magneto optic Kerr effect (MOKE) angle of Au magnetically
excited by spin accumulation. We perform time resolved polar MOKE measurements
on Au/Co heterostructures. In our experiment, the ultrafast optical excitation
of the Co drives spin accumulation into an adjacent Au layer. The spin
accumulation, together with spin-orbit coupling, leads to non-zero terms in the
off-diagonal conductivity tensor of Au, which we measure by recording the
polarization and ellipticity of light reflected from the Au surface for photon
energies between 1.3 and 3.1 eV. At energies near the interband transition
threshold of Au, the Kerr rotation per A/m exceeds 1 urad. Typical values for
Kerr rotation per moment in transition ferromagnetic metals like Ni are < 10
nrad per A/m, while predicted values for heavy metals like Pt or W are < 13
nrad per A/m. The exceptional sensitivity of the optical properties of Au to
spin magnetic moments make Au to be an exceptionally sensitive optical
magnetometer, with potential applications in the development of optospintronic
technologies.",2109.14954v3
2021-10-19,Ising and XY paramagnons in two-dimensional 2H-NbSe$_2$,"Paramagnons are the collective modes that govern the spin response of nearly
magnetic conductors. In some cases they mediate electron pairing leading to
superconductivity. This scenario may occur in 2H-NbSe$_2$ monolayers, that
feature spin-valley coupling on account of spin-orbit interactions and their
lack of inversion symmetry. Here we explore spin anisotropy of paramagnons both
for non-centrosymmetric Kane-Mele-Hubbard models for 2H-NbSe$_2$ monolayers
described with a DFT-derived tight-binding model. In the infinite wavelength
limit we find spatially uniform paramagnons with energies around $1$~meV that
feature a colossal off-plane uniaxial magnetic anisotropy, with quenched
transversal spin response. At finite wave vectors, longitudinal and transverse
channels reverse roles: XY fluctuations dominate within a significant portion
of the Brillouin zone. Our results show that 2H-NbSe$_2$ is close to a
Coulomb-driven in-plane (XY) spin density wave instability.",2110.09809v2
2021-10-25,Superconducting triplet rim currents in a spin-textured ferromagnetic disk,"Since the discovery of the long-range superconducting proximity effect, the
interaction between spin-triplet Cooper pairs and magnetic structures such as
domain walls and vortices has been the subject of intense theoretical
discussions, while the relevant experiments remain scarce. We have developed
nanostructured Josephson junctions with highly controllable spin texture, based
on a disk-shaped Nb/Co bilayer. Here, the vortex magnetization of Co and the
Cooper pairs of Nb conspire to induce long-range triplet (LRT)
superconductivity in the ferromagnet. Surprisingly, the LRT correlations emerge
in highly localized (sub-80 nm) channels at the rim of the ferromagnet, despite
its trivial band structure. We show that these robust rim currents arise from
the magnetization texture acting as an effective spin-orbit coupling, which
results in spin accumulation at the bilayer-vacuum boundary. Lastly, we
demonstrate that by altering the spin texture of a single ferromagnet, both $0$
and $\pi$-channels can be realized in the same device.",2110.13035v2
2022-03-03,Symmetry-protected Dirac nodal lines and large spin Hall effect in $\mathbf{V_6Sb_4}$ with kagome bilayer,"Recently, a family of nonmagnetic kagome metals \textit{A}$\mathrm{V_3Sb_5}$
(\textit{A}=K, Rb, and Cs) has attracted significant attention for realizing
the intertwining of quantum order and nontrivial topology. However, these
compounds have been identified to host complex band structures. Therefore, it
is desirable to design and synthesize novel kagome materials with a simple band
topology and good transport properties. In this study, using first-principles
calculations, we present the electronic properties and the intrinsic spin Hall
effect of V$_6$Sb$_4$, the latest experimentally synthesized vanadium-based
compounds with a kagome bilayer. In the absence of spin-orbital coupling (SOC),
this compound is a Dirac nodal line semimetal with symmetry-protected nodal
rings near the Fermi level. Within the SOC, the spin-rotation symmetry breaks
the gaps of the nodal rings with a small band gap. Furthermore, based on the
Wannier tight-binding approach and the Kubo formula, we propose a large spin
Hall effect in V$_6$Sb$_4$, which intrinsically originates from the spin Berry
curvature. Our work further expands nonmagnetic kagome compounds for
applications in spintronics accompanied by exotic quantum order.",2203.01558v1
2022-05-18,Twist Angle Controlled Collinear Edelstein Effect in van der Waals Heterostructures,"The generation of spatially homogeneous spin polarization by application of
electric current is a fundamental manifestation of symmetry-breaking
spin--orbit coupling (SOC) in solid-state systems, which underpins a wide range
of spintronic applications. Here, we show theoretically that twisted van der
Waals heterostructures with proximity-induced SOC are candidates par excellence
to realize exotic spin-charge transport phenomena due to their highly tunable
momentum-space spin textures. Specifically, we predict that graphene/group-VI
dichalcogenide bilayers support room temperature spin--current responses that
can be manipulated via twist-angle control. For critical twist angles, the
non-equilibrium spin density is pinned parallel to the applied current. This
effect is robust against twist-angle disorder, with graphene/$\text{WSe}_{2}$
possessing a critical angle (purely collinear response) of $\theta_{c} \simeq
14^{\circ}$. A simple electrical detection scheme to isolate the collinear
Edelstein effect is proposed.",2205.08804v2
2022-06-07,Quantized spin pumping in topological ferromagnetic-superconducting nanowires,"Semiconducting nanowires with strong spin-orbit coupling in the presence of
induced superconductivity and ferromagnetism can support Majorana zero modes.
We study the pumping due to the precession of the magnetization in
single-subband nanowires and show that spin pumping is robustly quantized when
the hybrid nanowire is in the topologically nontrivial phase, whereas charge
pumping is not quantized. Moreover, there exists one-to-one correspondence
between the quantized conductance, entropy change and spin pumping in long
topologically nontrivial nanowires but these observables are uncorrelated in
the case of accidental zero-energy Andreev bound states in the trivial phase.
Thus, we conclude that observation of correlated and quantized peaks in the
conductance, entropy change and spin pumping would provide strong evidence of
Majorana zero modes, and we elaborate how topological Majorana zero modes can
be distinguished from quasi-Majorana modes potentially created by a smooth
tunnel barrier at the lead-nanowire interface. Finally, we discuss peculiar
interference effects affecting the spin pumping in short nanowires at very low
energies.",2206.03527v2
2022-06-20,Emergence of Rashba splitting and spin-valley properties in Janus MoGeSiP2As2 and WGeSiP2As2 monolayers,"First-principles calculations are performed to study the structural stability
and spintronics properties of Janus MoGeSiP2As2 and WGeSiP2As2 monolayers. The
high cohesive energies and the stable phonon modes confirm that both these
structures are experimentally accessible. In contrast to pristine MoSi2P4, the
Janus monolayers demonstrate reduced direct bandgaps and large spin-split
states at K/-K. In addition, their spin textures exposed that breaking the
mirror symmetry brings Rashba-type spin splitting in the systems which can be
increased by using higher atomic spin-orbit coupling. The large valley spin
splitting together with the Rashba splitting in these Janus monolayer
structures can make a remarkable contribution to semiconductor valleytronics
and spintronics.",2206.09737v1
2022-08-17,$\mathbb{Z}_{2}$ Spin Hopf Insulator: Helical Hinge States and Returning Thouless Pump,"We introduce a time-reversal-symmetric analog of the Hopf insulator that we
call a spin Hopf insulator. The spin Hopf insulator harbors nontrivial
Kane-Mele $\Z_2$ invariants on its surfaces, and is the first example of a
nonmagnetic delicate topological insulator with spin-orbit coupling. We show
that the Kane-Mele $\Z_2$ topology on the surface is generically unstable, but
can be stabilized by the addition of a composition of the particle hole and
spatial inversion symmetry. Such a symmetry not only protects the surface
$\Z_2$ invariant, but also protects gapless helical hinge states on the spin
Hopf insulator. Furthermore, we show that in the presence of four-fold
rotational symmetry, the spin Hopf insulator exhibits a returning Thouless
pump, as well as surface states on sharp boundary terminations.",2208.08455v4
2022-09-02,Accidental persistent spin textures in the proustite mineral family,"Persistent spin textures (PSTs) in momentum space have the potential to
enable spintronic devices which are currently limited by low spin lifetimes in
nonmagnetic spin-orbit coupled materials. We perform a first-principles study
on the proustite mineral family, Ag$_3$BQ$_3$} (B=As,\,Sb; Q=S,\,Se), and show
these chalcogenides exhibit a non-symmetry protected PST, which we refer to as
symmetry-assisted PSTs. Chemical substitution can be used to tune the PST
quality and properties, e.g., spin lifetime, and we find that a Rashba
anisotropy criterion correlates with the PST area and spin lifetime for two of
the three proustites examined. Last, we show that a first-order effective SOC
Hamiltonian, often used in two-dimensional systems, is insufficient to describe
the PST state in all proustites, suggesting that higher order models are
necessary to fully describe PSTs in bulk three-dimensional materials.",2209.01109v1
2022-09-23,Ballistic transport and spin dependent anomalous quantum tunnelling in Rashba-Zeeman and bilayer graphene hybrid structures,"In this work, we have studied the spin-dependent ballistic transport and
anomalous quantum tunnelling in Bilayer Graphene (BLG) hybrid connected to two
Rashba-Zeeman (RZ) leads under an external electric biasing. We investigated
the transmission and conductance for the proposed system using scattering
matrix formalism and Landauer - Buttiker formula considering a double
delta-like barrier under a set of experimentally viable parameters. We found
that the transmission characteristics are notably different for up and down
spin incoming electrons depending upon the strength of magnetization. Moreover,
the transmission of up and down spin electrons is found to be magnetization
orientation dependent. The maximum tunnelling and conductance can be achieved
by tuning biasing energy and magnetization strength and choosing a material
with suitable Rashba Spin-Orbit Coupling (RSOC). This astonishing property of
our system can be utilized in fabricating devices like spin filters. We found
the Fano factor of our system is 0.4 under strong magnetization conditions
while it reduces to 0.3 under low magnetization conditions. Moreover, we also
noticed that the transmission and conductance significantly depend on the
Rashba - Zeeman effect. So, considering a suitable RZ material, the tunnelling
of the electrons can be tuned and controlled.",2209.11573v1
2022-09-28,Spin and Valley Hall effects induced by asymmetric interparticle scattering,"We develop the theory of the spin and valley Hall effects in two-dimensional
systems caused by asymmetric -- skew -- scattering of the quasiparticles. The
collision integral is derived in the third order in the particle-particle
interaction with account for the spin-orbit coupling both for bosons and
fermions. It is shown that the scattering asymmetry appears only in the
processes where the interaction between the particles in the initial and
intermediate state is present. We show that for degenerate electrons or
nondegenerate particles the spin and valley currents induced by interparticle
collisions are suppressed with their steady-state values being proportional to
the squared temperature or density, respectively. Our results imply non-Fermi
liquid properties of electrons in the presence of electron-electron skew
scattering. Strong deviations from conventional picture of interparticle
scattering are also demonstrated for the skew scattering of two-dimensional
degenerate bosons, e.g. excitons or exciton polaritons: The spin or valley
current of degenerate bosons contains the enhancement factor exponentially
growing with increase in the particle density.",2209.14173v1
2022-10-25,Recent advances in hole-spin qubits,"In recent years, hole-spin qubits based on semiconductor quantum dots have
advanced at a rapid pace. We first review the main potential advantages of
these hole-spin qubits with respect to their electron-spin counterparts, and
give a general theoretical framework describing them. The basic features of
spin-orbit coupling and hyperfine interaction in the valence band are
discussed, together with consequences on coherence and spin manipulation. In
the second part of the article we provide a survey of experimental
realizations, which spans a relatively broad spectrum of devices based on GaAs,
Si, or Si/Ge heterostructures. We conclude with a brief outlook.",2210.13725v2
2023-05-16,Spin scattering and Hall effects in monolayer Fe3GeTe2,"We theoretically show that the carrier transport in monolayer Fe3GeTe2
experiences a transition between anomalous Hall effect and spin Hall effect
when the spin polarization of disorders switches between out-of-plane and
in-plane. These Hall effects are allowed when the magnetization is polarized
in-plane, breaking the C3 rotation symmetry. The transition originates from the
selection rule of spin scattering, the strong spin-orbit coupling, and the van
Hove singularities near the Fermi surface. The scattering selection rule
tolerates the sign change of the disorder spin, which provides a convenient
method to detect the switching of antiferromagnetic insulators regardless of
the interfacial roughness in a heterostructure. This provides a convenient
platform for the study of 2D spintronics through various van-der-Waals
heterostructures.",2305.09743v1
2023-07-26,Electromagnon excitations in high temperature superconducting states,"In this article, we discover a fundamental excitation called electromagnon in
the cuprate superconducting states. Doped holes render local inversion
asymmetry which produces hidden Rashba spin-orbit coupling in copper-oxide
plane. Rashba effect leads to Dzyaloshinskii-Moriya (DM) interaction between
neighboring spins, which establishes a general spin Hamitonian combined with
Heisenberg exchange interaction. The physical origin of spin fluctuations has
been revealed from Rashba-induced DM term. Electromagnon excitations are found
to result from spin fluctuations manifested as spin spiral states by hopping of
doped holes in high temperature superconducting states. The frequency of
electromagnon excitations, peak position of dielectric constant spectrum,
decreases linearly with decrease of exchange interaction in various families of
superconductors. Comparisons with superconductivity-induced B1g Raman peaks
show good agreement and thus possibly provide the experimental evidences for
electromagnon excitations in cuprates.",2307.14533v2
2023-08-10,Protocols to measure the non-Abelian Berry phase by pumping a spin qubit through a quantum-dot loop,"A quantum system constrained to a degenerate energy eigenspace can undergo a
nontrival time evolution upon adiabatic driving, described by a non-Abelian
Berry phase. This type of dynamics may provide logical gates in quantum
computing that are robust against timing errors. A strong candidate to realize
such holonomic quantum gates is an electron or hole spin qubit trapped in a
spin-orbit-coupled semiconductor, whose twofold Kramers degeneracy is protected
by time-reversal symmetry. Here, we propose and quantitatively analyze
protocols to measure the non-Abelian Berry phase by pumping a spin qubit
through a loop of quantum dots. One of these protocols allows to characterize
the local internal Zeeman field directions in the dots of the loop. We expect a
near-term realisation of these protocols, as all key elements have been already
demonstrated in spin-qubit experiments. These experiments would be important to
assess the potential of holonomic quantum gates for spin-based quantum
information processing.",2308.05455v1
2023-10-25,Photo-induced electronic and spin topological phase transitions in monolayer bismuth,"Ultrathin bismuth exhibits rich physics including strong spin-orbit coupling,
ferroelectricity, nontrivial topology, and light-induced structural dynamics.
We use \textit{ab initio} calculations to show that light can induce structural
transitions to four transient phases in bismuth monolayers. These light-induced
phases exhibit nontrivial topological character, which we illustrate using the
recently introduced concept of spin bands and spin-resolved Wilson loops.
Specifically, we find that the topology changes via the closing of the electron
and spin band gaps during photo-induced structural phase transitions, leading
to distinct edge states. Our study provides strategies to tailor electronic and
spin topology via ultrafast control of photo-excited carriers and associated
structural dynamics.",2310.16886v2
2004-08-02,Electric generation of spin in crystals with reduced symmetry,"We propose a simple way of evaluating the bulk spin generation of an
arbitrary crystal with a known band structure in the strong spin-orbit coupling
limit. We show that, in the presence of an electric field, there exists an
intrinsic torque term which gives rise to a nonzero spin generation rate. Using
methods similar to those of recent experiments which measure spin polarization
in semiconductors, this spin generation rate should be experimentally
observable. The wide applicability of this effect is emphasized by explicit
consideration of a range of examples: bulk wurtzite and strained zincblende
(n-GaAs) lattices, as well as quantum well heterojunction systems.",0408020v2
2009-09-04,Quantum Imaging of Topologically Unpaired Spin-Polarized Dirac Fermions,"The motion of a relativistic particle is linked to its spin by the Dirac
equation. Remarkably, electrons in two-dimensional materials can mimic such
Dirac particles but must always appear in pairs of opposite spin chirality.
Using topological ideas of chiral boundary electrons wrapping a
three-dimensional crystal with tuned spin-orbit coupling, we show that elusive
unpaired Dirac fermions exist on the surface of a topological insulator parent
matrix, pure antimony. Using scanning tunneling microscopy and angle-resolved
photoemission spectroscopy we image coherent quantum interference between these
particles, map their helical spin texture, and ultimately observe a transition
to a single Dirac fermion distinguished by backscattering suppression via Berry
phase interference. The robust dynamics of these unique spin-polarized carriers
envisage future applications in spintronics and topological quantum
computation.",0909.0921v2
2010-01-10,Normal-State Hourglass Dispersion of the Spin Excitations in FeSe$_{x}$Te$_{1-x}$,"We use cold neutron spectroscopy to study the low-energy spin excitations of
superconducting (SC) FeSe$_{0.4}$Te$_{0.6}$ and essentially non-superconducting
(NSC) FeSe$_{0.45}$Te$_{0.55}$. In contrast to BaFe$_{2-x}$(Co,Ni)$_{x}$As$_2$,
where the low-energy spin excitations are commensurate both in the SC and
normal state, the normal-state spin excitations in SC FeSe$_{0.4}$Te$_{0.6}$
are incommensurate and show an hourglass dispersion near the resonance energy.
Since similar hourglass dispersion is also found in the NSC
FeSe$_{0.45}$Te$_{0.55}$, we argue that the observed incommensurate spin
excitations in FeSe$_{1-x}$Te$_{x}$ are not directly associated with
superconductivity. Instead, the results can be understood within a picture of
Fermi surface nesting assuming extremely low Fermi velocities and spin-orbital
coupling.",1001.1505v2
2010-03-02,Prediction of extremely long electron spin lifetimes at room temperature in wurtzite semiconductor quantum wells,"Many proposed spintronics devices require mobile electrons at room
temperature with long spin lifetimes. One route to achieving this is to use
quantum wells with tunable spin-orbit (SO) parameters. Research has focused on
zinc-blende materials such as GaAs which do not have long spin lifetimes at
room temperature. We show that wurtzite (w) materials, which possess smaller SO
coupling due to being low-Z, are better suited for spintronics applications.
This leads to predictions of spin lifetimes in w-AlN exceeding 2 ms at helium
temperatures and, relevant to spintronic devices, spin lifetimes up to 0.5 $\mu
s$ at room temperature.",1003.0494v2
2011-05-18,Spintronic devices from bilayer graphene in contact to ferromagnetic insulators,"Graphene-based materials show promise for spintronic applications due to
their potentially large spin coherence length. On the other hand, because of
their small intrinsic spin-orbit interaction, an external magnetic source is
desirable in order to perform spin manipulation. Because of the flat nature of
graphene, the proximity interaction with a ferromagnetic insulator (FI) surface
seems a natural way to introduce magnetic properties into graphene. Exploiting
the peculiar electronic properties of bilayer graphene coupled with FIs, we
show that it is possible to devise very efficient gate-tunable spin-rotators
and spin-filters in a parameter regime of experimental feasibility. We also
analyze the composition of the two spintronic building blocks in a
spin-field-effect transistor.",1105.3609v2
2011-09-26,Spin and Majorana polarization in topological superconducting wires,"We study a one-dimensional wire with strong Rashba and Dresselhaus spin-orbit
coupling (SOC), which supports Majorana fermions when subject to a Zeeman
magnetic field and in proximity of a superconductor. Using both analytical and
numerical techniques we calculate the electronic spin texture of the Majorana
end states. We find that the spin polarization of these states depends on the
relative magnitude of the Rashba and Dresselhaus SOC components. Moreover, we
define and calculate a local ""Majorana polarization"" and ""Majorana density"" and
argue that they can be used as order parameters to characterize the topological
transition between the trivial system and the system exhibiting Majorana bound
modes. We find that the local ""Majorana polarization"" is correlated to the
transverse spin polarization, and we propose to test the presence of Majorana
fermions in a 1D system by a spin-polarized density of states measurement.",1109.5697v2
2014-07-29,Controllable Schottky Barriers between MoS2 and Permalloy,"MoS2 is a layered two-dimensional material with strong spin-orbit coupling
and long spin lifetime, which is promising for electronic and spintronic
applications. However, because of its large band gap and small electron
affinity, a considerable Schottky barrier exists between MoS2 and contact
metal, hindering the further study of spin transport and spin injection in
MoS2. Although substantial progress has been made in improving device
performance, the existence of metal-semiconductor Schottky barrier has not yet
been fully understood. Here, we investigate permalloy (Py) contacts to both
multilayer and monolayer MoS2. Ohmic contact is developed between multilayer
MoS2 and Py electrodes with a negative Schottky barrier, which yields a high
field-effect mobility exceeding 55 cm2V-1s-1 at low temperature. Further, by
applying back gate voltage and inserting different thickness of Al2O3 layer
between the metal and monolayer MoS2, we have achieved a good tunability of the
Schottky barrier height (down to zero). These results are important in
improving the performance of MoS2 transistor devices; and it may pave the way
to realize spin transport and spin injection in MoS2.",1407.7652v2
2014-10-27,Magnetoresistance in multilayer fullerene spin valves: a first-principles study,"Carbon-based molecular semiconductors are explored for application in
spintronics because their small spin-orbit coupling promises long spin life
times. We calculate the electronic transport from first principles through spin
valves comprising bi- and tri-layers of the fullerene molecules C60 and C70,
sandwiched between two Fe electrodes. The spin polarization of the current, and
the magnetoresistance depend sensitively on the interactions at the interfaces
between the molecules and the metal surfaces. They are much less affected by
the thickness of the molecular layers. A high current polarization (CP > 90%)
and magnetoresistance (MR > 100%) at small bias can be attained using C70
layers. In contrast, the current polarization and the magnetoresistance at
small bias are vanishingly small for C60 layers. Exploiting a generalized
Julli`ere model we can trace the differences in spin-dependent transport
between C60 and C70 layers to differences between the molecule-metal interface
states. These states also allow one to interpret the current polarization and
the magnetoresistance as a function of the applied bias voltage.",1410.7344v1
2015-02-12,Unusual spin dynamics in topological insulators,"The dynamic spin susceptibility (DSS) has a ubiquitous Lorentzian form in
conventional materials with weak spin orbit coupling, whose spectral width
characterizes the spin relaxation rate. We show that DSS has an unusual
non-Lorentzian form in topological insulators, which are characterized by
strong SOC. At zero temperature, the high frequency part of DSS is universal
and increases in certain directions as $\omega^{d-1}$ with $d=2$ and 3 for
surface states and Weyl semimetals, respectively, while for helical edge
states, the interactions renormalize the exponent as $d=2K-1$ with $K$ the
Luttinger-liquid parameter. As a result, spin relaxation rate cannot be deduced
from the DSS in contrast to the case of usual metals, which follows from the
strongly entangled spin and charge degrees of freedom in these systems. These
parallel with the optical conductivity of neutral graphene.",1502.03680v1
2015-04-16,Thermoelectric and thermospin transport in a ballistic junction of graphene,"We consider theoretically a wide graphene ribbon, that on both ends is
attached to electronic reservoirs which generally have different temperatures.
The graphene ribbon is assumed to be deposited on a substrate, that leads to a
spin-orbit coupling of Rashba type. We calculate the thermally induced charge
current in the ballistic transport regime as well as the thermoelectric voltage
(Seebeck effect). Apart from this, we also consider thermally induced spin
current and spin polarization of the graphene ribbon. The spin currents are
shown to have generally two components; one parallel to the temperature
gradient and the other one perpendicular to this gradient. The latter
corresponds to the spin current due to the spin Nernst effect. Additionally, we
also consider the heat current between the reservoirs due to transfer of
electrons.",1504.04265v1
2015-05-22,Symmetry induced hole-spin mixing in quantum dot molecules,"We investigate theoretically the spin purity of single holes confined in
vertically coupled GaAs/AlGaAs quantum dots (QDs) under longitudinal magnetic
fields. A unique behavior is observed for triangular QDs, by which the spin is
largely pure when the hole is in one of the dots, but it becomes strongly mixed
when an electric field is used to drive it into molecular resonance. The spin
admixture is due to the valence band spin-orbit interaction, which is greatly
enhanced in C3h symmetry environments. The strong yet reversible electrical
control of hole spin suggests that molecules with C3-symmetry QDs, like those
obtained with [111] growth, can outperform the usual C2-symmetry QDs obtained
with [001] growth for the development of scalable qubit architectures.",1505.06009v2
2015-10-21,Ising Superconductivity and Majorana Fermions in Transition Metal Dichalcogenides,"In monolayer transition metal dichalcogenides (TMDs), electrons in opposite
$K$ valleys are subject to opposite effective Zeeman fields, which are referred
to as Ising spin-orbit coupling (SOC) fields. The Ising SOC, originated from
in-plane mirror symmetry breaking pins the electron spins in out-of-plane
directions, and results in the newly discovered Ising superconducting states
with strongly enhanced upper critical fields. In this work, we show that the
Ising SOC generates equal-spin triplet Cooper pairs with spin polarization in
the in-plane directions. Importantly, the spin-triplet Cooper pairs can induce
superconducting pairings in a half-metal wire placed on top of the TMD and
result in a topological superconductor with Majorana end states. Direct ways to
detect equal-spin triplet Cooper pairs and the differences between Ising
superconductors and Rashba superconductors are discussed.",1510.06289v4
2016-01-25,"Fermi surfaces, spin-mixing parameter, and colossal anisotropy of spin relaxation in transition metals from ab initio theory","The Fermi-surfaces and Elliott-Yafet spin-mixing parameter (EYP) of several
elemental metals are studied by \emph{ab initio} calculations. We focus first
on the anisotropy of the EYP as a function of the direction of the
spin-quantization axis [Phys.~Rev.~Lett.\ \textbf{109}, 236603 (2012)]. We
analyze in detail the origin of the gigantic anisotropy in $5d$ hcp metals as
compared to $5d$ cubic metals by band-structure calculations and discuss the
stability of our results against an applied magnetic field. We further present
calculations of light (4$d$ and 3$d$) hcp crystals, where we find a huge
increase of the EYP anisotropy, reaching colossal values as large as $6000\%$
in hcp Ti. We attribute these findings to the reduced strength of spin-orbit
coupling, which promotes the anisotropic spin-flip hot loops at the Fermi
surface.
  In order to conduct these investigations, we developed an adapted
tetrahedron-based method for the precise calculation of Fermi surfaces of
complicated shape and accurate Fermi-surface integrals within the
full-potential relativistic Korringa-Kohn-Rostoker Green-function method.",1601.06605v1
2016-06-07,Photo-modulation of the spin Hall conductivity of mono-layer transition metal dichalcogenides,"We report on a possible optical tuning of the spin Hall conductivity in
mono-layer transition metal dichalcogenides. Light beams of frequencies much
higher than the energy scale of the system (the \textit{off-resonant}
condition) does not excite electrons but rearranges the band structure. The
rearrangement is quantitatively established using the Floquet formalism. For
such a system of mono-layer transition metal dichalcogenides, the spin Hall
conductivity (calculated with the Kubo expression in presence of disorder)
exhibits a drop at higher frequencies and lower intensities. Finally, we
compare the spin Hall conductivity of the higher spin-orbit coupled WSe$_{2} $
to MoS$_{2} $; the spin Hall conductivity of WSe$_{2}$ was found to be larger.",1606.02089v1
2016-09-29,Rattleback: a model of how geometric singularity induces dynamic chirality,"The rattleback is a boat-shaped top with an asymmetric preference in spin.
Its dynamics can be described by nonlinearly coupled pitching, rolling, and
spinning modes. The chirality, designed into the body as a skewed mass
distribution, manifests itself in the quicker transition of $+$spin
$\rightarrow$ pitch $\rightarrow$ $-$spin than that of $-$spin $\rightarrow$
roll $\rightarrow$ $+$spin. The curious guiding idea of this work is that we
can formulate the dynamics as if a symmetric body were moving in a chiral
space. By elucidating the duality of matter and space in the Hamiltonian
formalism, we attribute asymmetry to space. The rattleback is shown to live in
the space dictated by the Bianchi type ${\rm VI}_{h < -1}$ (belonging to class
B) algebra; this particular algebra is used here for the first time in a
mechanical example. The class B algebra has a singularity that separates the
space (Poisson manifold) into mirror-asymmetric subspaces, breaking the
time-reversal symmetry of nearby orbits.",1609.09223v2
2017-03-30,Study of spin pumping in Co thin film vis-a-vis seed and capping layer using ferromagnetic resonance spectroscopy,"We investigated the dependence of the seed [Ta/Pt, Ta/Au] and capping [Pt/Ta,
Au/Ta] layers on spin pumping effect in the ferromagnetic 3 nm thick Co thin
film using ferromagnetic resonance spectroscopy. The data is fitted with Kittel
equation to evaluate damping constant and g-factor. A strong dependence of seed
and capping layers on spin pumping has been discussed. The value of damping
constant {alpha} is found to be relatively large i.e. 0.0326 for the
Ta{3}/Pt{3}/Co{3}/Pt{3}/Ta{3} {nm} multi-layer structure, while it is 0.0104
for Ta{3}/Co{3}/Ta{3} {nm}. Increase in {alpha} is observed due to Pt layer
that works as a good sink for spins due to high spin orbit coupling. In
addition, we measured the effective spin conductance = 2.0e18 m-2 for the
trilayer structure Pt{3}/Co{3}/Pt{3} {nm} as a result of the enhancement in
{alpha} relative to its bulk value. We observed that the evaluated g-factor
decreases as effective demagnetizing magnetic field increases in all the
studied samples. The azimuthal dependence of magnetic resonance field and line
width showed relatively high anisotropy in the trilayer Ta{3}/Co{3}/Ta{3} {nm}
structure.",1703.10630v1
2013-08-14,Hubbard Model on the Pyrochlore Lattice: a 3D Quantum Spin Liquid,"We demonstrate that the insulating one-band Hubbard model on the pyrochlore
lattice contains, for realistic parameters, an extended quantum spin-liquid
phase. This is a three-dimensional spin liquid formed from a highly degenerate
manifold of dimer-based states, which is a subset of the classical dimer
coverings obeying the ice rules. It possesses spinon excitations, which are
both massive and deconfined, and on doping it exhibits spin-charge separation.
We discuss the realization of this state in effective S = 1/2 pyrochlore
materials with and without spin-orbit coupling.",1308.3186v3
2014-03-16,Subband anticrossing and the spin Hall effect in quantum wires,"We report on numerical simulations of the intrinsic spin Hall effect in
semiconductor quantum wires as a function of the Rashba spin-orbit coupling
strength, the electron density, and the width of the wire. We find that the
strength of the spin Hall effect does not depend monotonically on these
parameters, but instead exhibits a local maximum. This behavior is explained by
considering the dispersion relation of the electrons in the wire, which is
characterized by the anticrossing of adjacent subbands. These results lead to a
simple estimate of the optimal wire width for spin Hall transport experiments,
and simulations indicate that this optimal width is independent of disorder.
The anticrossing of adjacent subbands is related to a quantum phase transition
in momentum space, and is accompanied by an enhancement of the Berry curvature
and subsequently in the magnitude of the spin Hall effect.",1403.3940v1
2016-11-28,Nuclear scissors modes and hidden angular momenta,"The coupled dynamics of low lying modes and various giant resonances are
studied with the help of the Wigner Function Moments method generalized to take
into account spin degrees of freedom and pair correlations simultaneously. The
method is based on Time Dependent Hartree-Fock-Bogoliubov equations. The model
of the harmonic oscillator including spin-orbit potential plus
quadrupole-quadrupole and spin-spin interactions is considered. New low lying
spin dependent modes are analyzed. Special attention is paid to the scissors
modes. A new source of nuclear magnetism, connected with counter-rotation of
spins up and down around the symmetry axis (hidden angular momenta), is
discovered. Its inclusion into the theory allows one to improve substantially
the agreement with experimental data in the description of energies and
transition probabilities of scissors modes.",1611.09037v1
2017-06-06,Spinon magnetic resonance of quantum spin liquids,"We describe electron spin resonance in a quantum spin liquid with significant
spin-orbit coupling. We find that the resonance directly probes spinon
continuum which makes it an efficient and informative probe of exotic
excitations of the spin liquid. Specifically, we consider spinon resonance of
three different spinon mean-field Hamiltonians, obtained with the help of
projective symmetry group analysis, which model a putative quantum spin liquid
state of the triangular rare-earth antiferromagnet YbMgGaO4. The band of
absorption is found to be very broad and exhibit strong van Hove singularities
of single spinon spectrum as well as pronounced polarization dependence.",1706.01597v2
2017-10-18,Selective equal spin Andreev reflection at vortex core center in magnetic semiconductor-superconductor heterostructure,"Sau, Lutchyn, Tewari and Das Sarma (SLTD) proposed a heterostructure
consisting of a semiconducting thin film sandwiched between an s-wave
superconductor and a magnetic insulator and showed possible Majorana zero mode.
Here we study spin polarization of the vortex core states and spin selective
Andreev reflection at the vortex center of the SLTD model. In the topological
phase, the differential conductance at the vortex center contributed from the
Andreev reflection, is spin selective and has a quantized value
$(dI/dV)^{topo}_A =2e^2/h$ at zero bias. In the topological trivial phase,
$(dI/dV)^{trivial}_A$ at the lowest quasiparticle energy of the vortex core is
spin selective due to the spin-orbit coupling (SOC). Unlike in the topological
phase, $(dI/dV)^{trivial}_A$ is suppressed in the Giaever limit and vanishes
exactly at zero bias due to the quantum destruction interference.",1710.06625v1
2018-01-31,Spin susceptibility of three-dimensional Dirac semimetals,"We theoretically study the spin susceptibility of Dirac semimetals using the
linear response theory. The spin susceptibility is decomposed into an intraband
contribution and an interband contribution. We obtain analytical expressions
for the intraband and interband contributions of massless Dirac fermions. The
spin susceptibility is independent of the Fermi energy while it depends on the
cutoff energy, which is introduced to regularize the integration. We find that
the cutoff energy is appropriately determined by comparing the results for the
Wilson-Dirac lattice model, which approximates the massless Dirac Hamiltonian
around the Dirac point. We also calculate the spin susceptibility of massive
Dirac fermions for the model of topological insulators. We discuss the effect
of the band inversion and the strength of spin-orbit coupling.",1801.10397v2
2018-01-31,Kramers' revenge,"The combination of space inversion and time reversal symmetries result in
doubly-degenerate Bloch states with opposite spin. Many lattices with these
symmetries can be constructed by combining a noncentrosymmetric potential
(lacking this degeneracy) with its inverted copy. Using simple models, we
unravel the evolution of local spin-splitting during this process of inversion
symmetry restoration, in the presence of spin-orbit interaction and sublattice
coupling. Importantly, through an analysis of quantum mechanical commutativity,
we examine the difficulty of identifying states that are simultaneously
spatially segregated and spin polarized. We also explain how experimental
probes (such as angle-resolved photoemission spectroscopy, or ARPES) of `hidden
spin polarization' in layered materials are susceptible to unrelated spin
splitting intrinsically induced by broken inversion symmetry at the surface.",1801.10581v2
2020-01-15,Evolution of valence-specific spin states and local distortions in La$_{2-x}$Sr$_x$CoO$_4$,"We present X-ray spectroscopic evidence for the evolution of valence-specific
spin states and tetragonal distortions in single-layer cobaltates. Measurements
of Co $L_3$-edge resonant inelastic X-ray scattering reveal the $t_{2g}$
electronic structure of Co for hole-doped La$_{2-x}$Sr$_x$CoO$_4$ ($x$ = 0.5,
0.7 and 0.8). As the Sr-doping $x$ increases, the tetragonal splitting of the
$t_{2g}$ states of high-spin Co$^{2+}$ decreases, whereas that of low-spin
Co$^{3+}$ increases and the fraction of high-spin Co$^{3+}$ increases. The
results enable us to clarify the origin of the change of magnetic anisotropy
and in-plane resistivity in a mixed-valence cobaltate caused by the interplay
of spin-orbit coupling and tetragonal distortion.",2001.05194v3
2017-09-29,Photo-induced spin and valley-dependent Seebeck effect in the low-buckled Dirac materials,"Employing the Landauer-Buttiker formula we investigate the spin and valley
dependence of Seebeck effect in low-buckled Dirac materials (LBDMs), whose band
structure are modulated by local application of a gate voltage and off-resonant
circularly polarized light. We calculate the charge, spin and valley Seebeck
coefficients of an irradiated LBDM as functions of electronic doping, light
intensity and the amount of the electric field in the linear regime. Our
calculation reveal that all Seebeck coefficients always shows an odd features
with respect to the chemical potential. Moreover, we show that, due to the
strong spin-orbit coupling in the LBDMs, the induced thermovoltage in the
irradiated LBDMs is spin polarized, and can also become valley polarized if the
gate voltage is applied too. It is also found that the valley (spin)
polarization of the induced thermovoltage could be inverted by reversing the
circular polarization of light or reversing the direction the electric field
(only by reversing the circular polarization of light).",1709.10357v1
2019-02-14,Coupled dynamics of long-range and internal spin cluster order in Cu$_{2}$OSeO$_{3}$,"Cu$_4$ triplet clusters form the relevant spin entity for the formation of
long-range magnetic order in the cluster magnet Cu$_2$OSeO$_3$. Using
time-resolved Raman spectroscopy, we probed photoinduced spin and lattice
dynamics in this Mott insulator. Multiple ps-decade spin-lattice relaxation
dynamics is observed, evidencing a separation of the order parameter dynamics
into disordering of long-range and internal spin cluster order. Our study
exemplifies the double order parameter dynamics of generalized molecular
crystals of charge, spin, and orbital nature.",1902.05329v1
2018-10-22,Controlled engineering of spin polarized transport properties in a zigzag graphene nanojunction,"We investigate a novel way to manipulate the spin polarized transmission in a
two terminal zigzag graphene nanoribbon in presence of Rashba spin-orbit (SO)
interaction with circular shaped cavity engraved into it. A usual technique to
control the spin polarized transport behaviour of a nanoribbon can be achieved
by tuning the strength of the SO coupling, while we show that an efficient
engineering of the spin polarized transport properties can also be done via
cavities of different radii engraved in the nanoribbon. Simplicity of the
technique in creating such cavities in the experiments renders an additional
handle to explore transport properties as a function of the location of the
cavity in the nanoribbon. Further, a systematic assessment of the interplay of
the Rashba interaction and the dimensions of the nanoribbon is presented. These
results should provide useful input to the spintronic behaviour of such
devices. In addition to the spin polarization, we have also included an
interesting discussion on the charge transmission properties of the nanoribbon,
where, in absence of any SO interaction a metal-insulator transition induced by
the presence of a cavity is observed.",1810.09088v1
2020-06-16,Gate tunability of highly efficient spin-to-charge conversion by spin Hall effect in graphene proximitized with WSe$_2$,"The proximity effect opens ways to transfer properties from one material into
another and is especially important in two-dimensional materials. In van der
Waals heterostructures, transition metal dichalcogenides (TMD) can be used to
enhance the spin-orbit coupling of graphene leading to the prediction of gate
controllable spin-to-charge conversion (SCC). Here, we report for the first
time and quantify the SHE in graphene proximitized with WSe$_2$ up to room
temperature. Unlike in other graphene/TMD devices, the sole SCC mechanism is
the spin Hall effect and no Rashba-Edelstein effect is observed. Importantly,
we are able to control the SCC by applying a gate voltage. The SCC shows a high
efficiency, measured with an unprecedented SCC length larger than 20 nm. These
results show the capability of two-dimensional materials to advance towards the
implementation of novel spin-based devices and future applications.",2006.09227v1
2021-09-27,Spin Texture as Polarization Fingerprint of Halide Perovskites,"Halide perovskites are perceived to be the promising class of materials for
optoelectronics, spinorbitronics and topological electronics due to presence of
strong spin-orbit coupling and polarized field. Here, we develop a Hamiltonian
using quasi-degenerate perturbation theory to describe polarized field driven
band structures and unique topological phases such as Dirac semimetallic rings
for the universal class of Halide perovskites including both inorganic and
hybrid members. The spin textures obtained through this theoretical model
captures minute effects of polarization and hence can be used as a modern tool
to determine the polarized field directions which have significant influence on
spinorbitronics. The analysis brings out the concepts of hybrid spin textures
intermixing the effects of valence and conduction bands under topological
quantum phase transitions, and spin texture binaries where alignment of the
spins are reversed between domains in the momentum space with sharp boundaries.
The results are validated through density functional calculations.",2109.13195v2
2021-10-22,"Magnetic order, disorder, and excitations under pressure in the Mott insulator Sr$_2$IrO$_4$","Protected by the interplay of on-site Coulomb interactions and spin-orbit
coupling, Sr$_2$IrO$_4$ at high pressure is a rare example of a Mott insulator
with a paramagnetic ground state. Here, using optical Raman scattering, we
measure both the phonon and magnon evolution in Sr$_2$IrO$_4$ under pressure,
and identify three different magnetically-ordered phases, culminating in a
spin-disordered state beyond 18 GPa. A strong first-order structural phase
transition drives the magnetic evolution at $\sim$10 GPa with reduced
structural anisotropy in the IrO$_6$ cages, leading to increasingly isotropic
exchange interactions between the Heisenberg spins and a spin-flip transition
to $c$-axis-aligned antiferromagnetic order. In the disordered phase of
Heisenberg $J_\mathrm{eff}=1/2$ pseudospins, the spin excitations are
quasi-elastic and continuous to 10 meV, potentially hosting a gapless quantum
spin liquid in Sr$_2$IrO$_4$.",2110.11588v1
2021-12-14,"Electrical detection of the spin-flop and room-temperature magnetic ordering in van der Waals CrPS$_{4}$/(Pt, Pd) heterostructures","We study magneto-transport in heterostructures composed of the van der Waals
antiferromagnet CrPS$_{4}$ and the heavy metals Pt and Pd. The transverse
resistance (R$_{xy}$) signal reveals the spin-flop transition of CrPS$_{4}$ and
a strongly enhanced magnetic ordering temperature (>300 K), which might
originate from a strong spin-orbit coupling at the interface. While
CrPS$_{4}$/Pt devices allow for easy detection of the spin-flop transition,
CrPS$_{4}$/Pd devices show a more substantial enhancement in magnetic ordering
temperature and exhibit a topological Hall effect signal, possibly related to
chiral spin structures at the interface. The longitudinal magnetoresistance
(R$_{xx}$) results from a combination of spin-Hall magnetoresistance and the
negative magnetoresistance that can be explained by a field-induced change of
the electronic band structure of CrPS$_{4}$.",2112.07306v1
2022-05-31,Spin field-effect transistors based on massless birefringent Dirac fermions in polar Dirac semimetals,"The Datta-Das-type spin field-effect transistor, using a two-dimensional
electron gas in a semiconductor heterostructure as a channel, plays a key role
in spintronics. Here, we theoretically present a type of spin field-effect
transistor based on massless birefringent Dirac fermions in polar Dirac
semimetals. The manipulation of spin arises from the existence of the strong
spin-orbit coupling, polar space groups, and Dirac cones in a single phase. The
oscillatory channel conductance can be controlled by the sign of gate voltage
in addition to its magnitude due to the gapless band structures of polar Dirac
semimetals. Such spin field-effect transistor provides guidance for the further
design of spintronic devices.",2205.15847v1
2022-08-08,Spin Hall conductivity of interacting two-dimensional electron systems,"We consider a two-dimensional electron system subjected to a short-ranged
nonmagnetic disorder potential, Coulomb interactions, and Rashba spin-orbit
coupling. The path-integral approach incorporated within the Keldysh formalism
is used to derive the kinetic equation for the semiclassical Green's function
and applied to compute the spin current within the linear response theory. We
discuss the frequency dependence of the spin Hall conductivity and further
elucidate the role of electron interactions at finite temperatures for both the
ballistic and diffusive regimes of transport. We argue that interaction
corrections to the spin Hall effect stem from the quantum interference
processes whose magnitude is estimated in terms of parameters of the considered
model.",2208.03888v2
2022-09-20,Calculating interface transport parameters at finite temperatures: Nonmagnetic interfaces,"First-principles scattering calculations are used to investigate spin
transport through interfaces between diffusive nonmagnetic metals where the
symmetry lowering leads to an enhancement of the effect of spin-orbit coupling
(SOC) and to a discontinuity of the spin currents passing through the
interfaces. From the conductance and local spin currents calculated for
nonmagnetic bilayers, we extract values of the room temperature interface
resistance $R_{\rm I}$, of the spin memory loss parameter $\delta$ and of the
interface spin Hall angle $\Theta_{\rm I}$ for nonmagnetic Au$|$Pt and Au$|$Pd
interfaces using a frozen thermal disorder scheme to model finite temperatures.
Substantial values of all three parameters are found with important
consequences for experiments involving nonmagnetic spacer and capping layers.
The temperature dependence of the interface parameters is determined for
Au$|$Pt.",2209.09885v1
2023-03-06,Phase driving hole spin qubits,"The spin-orbit interaction in spin qubits enables spin-flip transitions,
resulting in Rabi oscillations when an external microwave field is resonant
with the qubit frequency. Here, we introduce an alternative driving mechanism
of hole spin qubits, where a far-detuned oscillating field couples to the qubit
phase. Phase driving at radio frequencies, orders of magnitude slower than the
microwave qubit frequency, induces highly non-trivial spin dynamics, violating
the Rabi resonance condition. By using a qubit integrated in a silicon fin
field-effect transistor (Si FinFET), we demonstrate a controllable suppression
of resonant Rabi oscillations, and their revivals at tunable sidebands. These
sidebands enable alternative qubit control schemes using global fields and
local far-detuned pulses, facilitating the design of dense large-scale qubit
architectures with local qubit addressability. Phase driving also decouples
Rabi oscillations from noise, an effect due to a gapped Floquet spectrum and
can enable Floquet engineering high-fidelity gates in future quantum
processors.",2303.03350v1
2023-06-05,Critical Phenomena Study of 3D Heisenberg Magnet,"Recent discovery of several van der waals magnetic material and moire magnet
introduce to us an extremely challenging and revolutionary era of 2D magnetism
and correlated phenomena for low dimensional material.More often the simplest
spin models which is based on inter-atomic exchange and spin-orbit
coupling(SOC) potentially able to capture and explain the critical phenomena of
extremely complicated correlated magnetic material.In this work we have
attempted to simulate 3D Heisenberg magnet using classical Monte Carlo
simulation.Our goal is to establish a new and simplest spin simulation
technique which can help us to understand those van der waals magnet from its
microscopic length scale.Here we have been proposing a completely new
methodology of classical Monte Carlo simulation of Heisenberg spin which is
based on single spin flipping Metropolis algorithm.Our state of art simulation
technique potentially able to study the phase transition of isotropic XY(O(2))
and XYZ(O(3))spin model very efficiently.With this simulation technique we
overcome the barrier of critical slowing down during the phase transition in a
effective way and able to predict the transition temperature($T_c$) very
accurately.",2306.02566v1
2023-08-04,Anisotropy of the spin Hall effect in a Dirac ferromagnet,"We study the intrinsic spin Hall effect of a Dirac Hamiltonian system with
ferromagnetic exchange coupling, a minimal model combining relativistic
spin-orbit interaction and ferromagnetism. The energy bands of the Dirac
Hamiltonian are split after introducing a Stoner-type ferromagnetic ordering
which breaks the spherical symmetry of pristine Dirac model. The totally
antisymmetric spin Hall conductivity (SHC) tensor becomes axially anisotropic
along the direction of external electric field. Interestingly, the anisotropy
does not vanish in the asymptotic limit of zero magnetization. We show that the
ferromagnetic ordering breaks the spin degeneracy of the eigenfunctions and
modifies the selection rules of the interband transitions for the intrinsic
spin Hall effect. The difference in the selection rule between the pristine and
the ferromagnetic Dirac phases causes the anisotropy of the SHC, resulting in a
discontinuity of the SHC as the magnetization, directed orthogonal to the
electric field, is reduced to zero in the ferromagnetic Dirac phase and enters
the pristine Dirac phase.",2308.02336v1
2023-08-27,How to produce spin-splitting in antiferromagnetic materials,"Antiferromagnetic (AFM) materials have potential advantages for spintronics
due to their robustness, ultrafast dynamics, and magnetotransport effects.
However, the missing spontaneous polarization and magnetization hinders the
efficient utilization of electronic spin in these AFM materials. Here, we
propose a simple way to produce spin-splitting in AFM materials by making the
magnetic atoms with opposite spin polarization locating in the different
environment (surrounding atomic arrangement), which does not necessarily
require the presence of spin-orbital coupling (SOC). We confirm our proposal by
four different types of two-dimensional (2D) AFM materials within the
first-principles calculations. Our works provide a intuitional design principle
to find or produce spin-splitting in AFM materials.",2308.14097v1
2023-09-21,Superfluidity of Total Angular Momentum,"Spontaneous symmetry breaking of a U(1) symmetry leads to superfluidity of a
corresponding conserved charge. We generalize the superfluidity to systems with
U(1) symmetries acting on both matter fields and two-dimensional spatial
coordinates. Such systems can be effectively realized in easy-plane
ferromagnetic systems with spin-orbit coupling where the conserved charge is a
total angular momentum. We clarify that under a steady injection of spin
angular momentum, the superfluid of the total angular momentum shows spacetime
oscillations of the spin density and geometry-dependent spin hydrodynamics. We
also demonstrate that the steady spin injection destabilizes the superfluid of
total angular momentum, causing a dissipation effect in its spin hydrodynamic
properties. Our study broadens the comprehension of superfluidity and sheds new
light on the interplay between symmetries and phases of matter.",2309.12068v2
2023-10-17,Altermagnetic Schottky Contact,"Altermagnet is an emerging antiferromagnetic material subclass that exhibits
spin-splitting in momentum space without net global magnetization and
spin-orbit-coupling effect. In this work, we develop a model of thermal charge
injection across an altermagnet/semiconductor (AM/S) Schottky contact. We
obtain analytical expressions describing the spin-dependent thermionic current
injection across the AM/S contact under any arbitrary interface orientation
angles. Interestingly, the spin-contrasting Fermi surface of an altermagnetic
electrode enables spin-polarized current to be injected into a nonmagnetic
semiconductor even though the system has net-zero magnetization. Our findings
thus reveal an altermagntic mechanism to achieve spin injection without
involving ferromagnetic ordering. The AM/S Schottky contact proposed here shall
provide a potential altermagnetic building block of spintronic devices that are
resilient against stray magnetic field perturbation and inherently compatible
with ultracompact integration.",2310.11289v1
2024-01-15,Theoretical Design of Mono-Elemental Ferroelectricity with Tunable Spin Textures in Bilayer Tellurium,"2D Ferroelectricity with switchable electric polarization has drawn
widespread attention in condensed matter physics due to its crucial
applications in non-volatile memory and ferroelectric spin devices. Despite
recent progress in 2D ferroelectric, achieving the mono-elemental
ferroelectricity still remains a great challenge because most nonmetallic
mono-elemental materials are stabilized in nonpolar crystal structures. In this
work, we theoretically designed mono-elemental ferroelectricity with tunable
and significant spin textures in bilayer tellurium (BL-Te). Comprehensive
quantitative polarization calculations demonstrate that asymmetric stacking in
BL-Te can generate out-of-plane (OOP) polarization with a magnitude of 0.78
pC/m. This polarization stems from distinguishing interlayer and intra-layer
contributions. Moreover, these stacked BL-Te, characterized by significant
spin-orbit coupling, serve as an ideal platform for investigating both
conventional spin polarization and layer-dependent/hidden spin polarization
through ferroelectric reversion. Our work not only broaden the category of 2D
mono-elemental ferroelectric but also offer a new platform for multifunctional
nanodevices.",2401.07752v1
2005-03-16,"Disorder, spin-orbit, and interaction effects in dilute ${\rm Ga}_{1-x}{\rm Mn}_x{\rm As}$","We derive an effective Hamiltonian for ${\rm Ga}_{1-x}{\rm Mn}_x {\rm As}$ in
the dilute limit, where ${\rm Ga}_{1-x}{\rm Mn}_x {\rm As}$ can be described in
terms of spin $F=3/2$ polarons hopping between the {\rm Mn} sites and coupled
to the local {\rm Mn} spins. We determine the parameters of our model from
microscopic calculations using both a variational method and an exact
diagonalization within the so-called spherical approximation. Our approach
treats the extremely large Coulomb interaction in a non-perturbative way, and
captures the effects of strong spin-orbit coupling and Mn positional disorder.
We study the effective Hamiltonian in a mean field and variational calculation,
including the effects of interactions between the holes at both zero and finite
temperature. We study the resulting magnetic properties, such as the
magnetization and spin disorder manifest in the generically non-collinear
magnetic state. We find a well formed impurity band fairly well separated from
the valence band up to $x_{\rm active} \lesssim 0.015$ for which finite size
scaling studies of the participation ratios indicate a localization transition,
even in the presence of strong on-site interactions, where $x_{\rm
active}<x_{\rm nom}$ is the fraction of magnetically active Mn. We study the
localization transition as a function of hole concentration, Mn positional
disorder, and interaction strength between the holes.",0503382v1
2006-05-18,Transport properties for a Luttinger liquid wire with Rashba spin-orbit coupling and Zeeman splitting,"We study the transport properties for a Luttinger-liquid (LL) quantum wire in
the presence of both Rashba spin-orbit coupling (SOC) and a weak external
in-plane magnetic field. The bosonized Hamiltonian of the system with an
externally applied longitudinal electric field is established. And then the
equations of motion for the bosonic phase fields are solved in the Fourier
space, with which the both charge and spin conductivities for the system are
calculated analytically based on the linear response theory. Generally, the ac
conductivity is an oscillation function of the strengths of electron-electron
interaction, Rashba SOC and magnetic field, as well as the driving frequency
and the measurement position in the wire. Through analysis with some examples
it is demonstrated that the modification on the conductivity due to
electron-electron interactions is more remarkable than that due to SOC, while
the effects of SOC and Zeeman splitting on the conductivity are very similar.
The spin-polarized conductivities for the system in the absence of Zeeman
effect or SOC are also discussed, respectively. The ratio of the spin-polarized
conductivities $\sigma_\uparrow/\sigma_\downarrow$ is dependent of the
electron-electron interactions for the system without SOC, while it is
independent of the electron-electron interactions for the system without Zeeman
splitting.",0605450v2
2008-09-04,Aharonov-Casher and spin Hall effects in two-dimensional mesoscopic ring structures with strong spin-orbit interaction,"We study the quantum interference effects induced by the Aharonov-Casher
phase in asymmetrically confined two-dimensional electron and heavy-hole ring
structures systems taking into account the electrically tunable spin-orbit (SO)
interaction. We have calculated the non-adiabatic transport properties of
charges (heavy-holes and electrons) in two-probe thin ring structures and
compare how the form of the SO coupling of the carries affects it. We show that
both the SO splitting of the bands and the carrier density can be used to
modulate the conductance through the ring. We show that the dependence on
carrier density is due to the backscattering from the leads which shows
pronounce resonances when the Fermi energy is close to the eigenenergy of the
ring. We also calculate the spin Hall conductivity and longitudinal
conductivity in four-probe rings as a function of the carrier density and SO
interaction, demonstrating that for heavy-hole carriers both conductivities are
larger than for electrons. Finally, we investigate the transport properties of
mesoscopic rings with spatially inhomogeneous SO coupling. We show that devices
with inhomogeneous SO interaction exhibit an electrically controlled
spin-flipping mechanism.",0809.0880v1
2010-06-01,Double Quantum Dots in Carbon Nanotubes,"We study the two-electron eigenspectrum of a carbon-nanotube double quantum
dot with spin-orbit coupling. Exact calculation are combined with a simple
model to provide an intuitive and accurate description of single-particle and
interaction effects. For symmetric dots and weak magnetic fields, the
two-electron ground state is antisymmetric in the spin-valley degree of freedom
and is not a pure spin-singlet state. When double occupation of one dot is
favored by increasing the detuning between the dots, the Coulomb interaction
causes strong correlation effects realized by higher orbital-level mixing.
Changes in the double-dot configuration affect the relative strength of the
electron-electron interactions and can lead to different ground state
transitions. In particular, they can favor a ferromagnetic ground state both in
spin and valley degrees of freedom. The strong suppression of the energy gap
can cause the disappearance of the Pauli blockade in transport experiments and
thereby can also limit the stability of spin-qubits in quantum information
proposals. Our analysis is generalized to an array of coupled dots which is
expected to exhibit rich many-body behavior.",1006.0209v2
2014-07-25,Low temperature magnetic properties of NpNi$_5$,"We present the result of an extended experimental characterization of the
hexagonal intermetallic Haucke compound NpNi$_{5}$. By combining macroscopic
and shell-specific techniques, we determine the 5$f$-shell occupation number
$n_f$ close to 4 for the Np ions, together with orbital and spin components of
the ordered moment in the ferromagnetic phase below T$_C$ = 16 K ($\mu_{S}$ =
-1.88~$\mu_{B}$ and $\mu_{L}$ = 3.91~$\mu_{B}$). The apparent coexistence of
ordered and disordered phases observed in the M\""{o}ssbauer spectra is
explained in terms of slow relaxation between the components of a quasi-triplet
ground state. The ratio between the expectation value of the magnetic dipole
operator and the spin magnetic moment ($3\langle T_{z}\rangle/ \langle
S_{z}\rangle$ = +1.43) is positive and large, suggesting a localized character
of the 5$f$ electrons. The angular part of the spin-orbit coupling
($\langle\vec{\ell}\cdot\vec{s}\rangle$ = -5.55) is close to the value of -6.25
calculated for trivalent Np ions in intermediate coupling approximation. The
results are discussed against the prediction of first-principle electronic
structure calculations based on the spin-polarized local spin density
approximation plus Hubbard interaction, and of a mean field model taking into
account crystal field and exchange interactions.",1407.6825v1
2014-09-24,Functional renormalization and mean-field approach to multiband systems with spin-orbit coupling: Application to the Rashba model with attractive interaction,"The functional renormalization group (RG) in combination with Fermi surface
patching is a well-established method for studying Fermi liquid instabilities
of correlated electron systems. In this article, we further develop this method
and combine it with mean-field theory to approach multiband systems with
spin-orbit coupling, and we apply this to a tight-binding Rashba model with an
attractive, local interaction. The spin dependence of the interaction vertex is
fully implemented in a RG flow without SU(2) symmetry, and its momentum
dependence is approximated in a refined projection scheme. In particular, we
discuss the necessity of including in the RG flow contributions from both bands
of the model, even if they are not intersected by the Fermi level. As the
leading instability of the Rashba model, we find a superconducting phase with a
singlet-type interaction between electrons with opposite momenta. While the gap
function has a singlet spin structure, the order parameter indicates an
unconventional superconducting phase, with the ratio between singlet and
triplet amplitudes being plus or minus one on the Fermi lines of the upper or
lower band, respectively. We expect our combined functional RG and mean-field
approach to be useful for an unbiased theoretical description of the
low-temperature properties of spin-based materials.",1409.7087v4
2015-01-17,Superfluidity of Bose-Einstein condensates in ultracold atomic gases,"Liquid helium 4 had been the only bosonic superfluid available in experiments
for a long time. This situation was changed in 1995, when a new superfluid was
born with the realization of the Bose-Einstein condensation in ultracold atomic
gases. The liquid helium 4 is strongly interacting and has no spin; there is
almost no way to change its parameters, such as interaction strength and
density. The new superfluid, Bose-Einstein condensate (BEC), offers various
aspects of advantages over liquid helium. On the one hand, BEC is weakly
interacting and has spin degrees of freedom. On the other hand, it is
convenient to tune almost all the parameters of a BEC, for example, the kinetic
energy by spin-orbit coupling, the density by the external potential, and the
interaction by Feshbach resonance. Great efforts have been devoted to studying
these new aspects of superfluidity, and the results have greatly enriched our
understanding of superfluidity. Here we review these developments by focusing
on the stability and critical velocity of various superfluids. The BEC systems
considered include a uniform superfluid in free space, a superfluid with its
density periodically modulated, a superfluid with artificially engineered
spin-orbit coupling, and a superfluid of pure spin current. Due to the weak
interaction, these BEC systems can be well described by the mean field
Gross-Pitaevskii theory and their superfluidity, in particular critical
velocities, can be examined with Landau's theory of superfluid. Experimental
proposals to observe these new aspects of superfluidity are discussed.",1501.04153v1
2015-05-15,Filling constraints for spin-orbit coupled insulators in symmorphic and non-symmorphic crystals,"We determine conditions on the filling of electrons in a crystalline lattice
to obtain the equivalent of a band insulator -- a gapped insulator with neither
symmetry breaking nor fractionalized excitations. We allow for strong
interactions, which precludes a free particle description. Previous approaches
that extend the Lieb-Schultz-Mattis argument invoked spin conservation in an
essential way, and cannot be applied to the physically interesting case of
spin-orbit coupled systems. Here we introduce two approaches, the first an
entanglement based scheme, while the second studies the system on an
appropriate flat `Bieberbach' manifold to obtain the filling conditions for all
230 space groups. These approaches only assume time reversal rather than spin
rotation invariance. The results depend crucially on whether the crystal
symmetry is symmorphic. Our results clarify when one may infer the existence of
an exotic ground state based on the absence of order, and we point out
applications to experimentally realized materials. Extensions to new situations
involving purely spin models are also mentioned.",1505.04193v4
2017-08-09,Dynamics of interacting fermions under spin-orbit coupling in an optical lattice clock,"Quantum statistics and symmetrization dictate that identical fermions do not
interact via s-wave collisions. However, in the presence of spin-orbit coupling
(SOC), fermions prepared in identical internal states with distinct momenta
become distinguishable. The resulting strongly interacting system can exhibit
exotic topological and pairing behaviors, many of which are yet to be observed
in condensed matter systems. Ultracold atomic gases offer a promising pathway
for simulating these rich phenomena. Two recent experiments reported the
observation of single atom SOC in optical lattice clocks (OLCs) based on
alkaline-earth atoms. In these works encoding the effective spin degree of
freedom in the long-lived electronic clock states significantly reduced the
detrimental effects of spontaneous emission and heating that have thus far
hindered the study of interacting SOC with alkali atoms. Beyond first studies
of interacting SOC with alkali atoms in a bulk gas and with two particles in a
lattice, here we enter a new regime of many-body interacting SOC in an OLC.
Using clock spectroscopy, we observe the precession of the collective
magnetization and the emergence of spin locking effects arising from an
interplay between p-wave and SOC-induced exchange interactions. The many-body
dynamics are well captured by a collective XXZ spin model, which describes a
broad class of condensed matter systems ranging from superconductors to quantum
magnets. Furthermore, our work will aid in the design of next-generation OLCs
by offering a route for avoiding the observed large density shifts caused by
SOC-induced exchange interactions.",1708.02704v2
2017-01-29,Spin-triplet $f$-wave symmetry in superconducting monolayer $MoS_2$,"The proximity-induced spin-triplet $f$-wave symmetry pairing in a monolayer
molybdenum disulfide-superconductor hybrid features an interesting
electron-hole excitations and also effective superconducting subgap, giving
rise to a distinct Andreev resonance state. Owing to the complicated Fermi
surface and momentum dependency of $f$-wave pair potential, monolayer $MoS_2$
with strong spin-orbit coupling can be considered an intriguing structure to
reveal the superconducting state. Actually, this can be possible by calculating
the peculiar spin-valley polarized transport of quasiparticles in a related
normal metal/superconductor junction. We theoretically study the formation of
effective gap at the interface and resulting normalized conductance on top of a
$MoS_2$ under induction of $f$-wave order parameter, using
Bloder-Tinkham-Klapwijk formalism. The superconducting excitations shows that
the gap is renormalized by a \textit{bias limitation} coefficient including
dynamical band parameters of monolayer $MoS_2$, especially, ones related to the
Schrodinger-type momentum of Hamiltonian. The effective gap is more sensitive
to the n-doping regime of superconductor region. The signature of spin-orbit
coupling, topological and asymmetry mass-related terms in the resulting subgap
conductance and, in particular, maximum conductance is presented. In the
absence of topological term, the effective gap reaches to its maximum value.
The unconventional nature of superconducting order leads to the appearance of
zero-bias conductance. In addition, the maximum value of conductance can be
controlled by tuning the doping level of normal and superconductor regions.",1701.08352v1
2020-12-02,Layer- and Gate-tunable Spin-Orbit Coupling in a High Mobility Few-Layer Semiconductor,"Spin-orbit coupling (SOC) is a relativistic effect, where an electron moving
in an electric field experiences an effective magnetic field in its rest frame.
In crystals without inversion symmetry, it lifts the spin degeneracy and leads
to many magnetic, spintronic and topological phenomena and applications. In
bulk materials, SOC strength is a constant that cannot be modified. Here we
demonstrate SOC and intrinsic spin-splitting in atomically thin InSe, which can
be modified over an unprecedentedly large range. From quantum oscillations, we
establish that the SOC parameter \alpha is thickness-dependent; it can be
continuously modulated over a wide range by an out-of-plane electric field,
achieving intrinsic spin splitting tunable between 0 and 20 meV. Surprisingly,
\alpha could be enhanced by an order of magnitude in some devices, suggesting
that SOC can be further manipulated. Our work highlights the extraordinary
tunability of SOC in 2D materials, which can be harnessed for in operando
spintronic and topological devices and applications.",2012.00937v1
2020-12-18,Fortuitous partners of antiferromagnetic and Mott states in spin-orbit-coupled Sr2IrO4: A study of Sr2Ir1-xMxO4 (M=Fe or Co),"Sr2IrO4 is an archetypal spin-orbit-coupled Mott insulator with an
antiferromagnetic state below 240 K. Here we report results of our study on
single crystals of Sr2Ir1-xFexO4 (0<x<0.32) and Sr2Ir1-xCoxO4 (0<x<0.22). Fe
doping retains the antiferromagnetic state but simultaneously precipitates an
emergent metallic state whereas Co doping causes a rapid collapse of both the
antiferromagnetic and Mott states, giving rise to a confined metallic state
featuring a pronounced linearity of the basal-plane resistivity up to 700 K.
The results indicate tetravalent Fe4+(3d4) ions in the intermediate spin state
with S=1 and Co4+(3d5) ions in the high spin state with S=5/2 substituting for
Ir4+(5d5) ions in Sr2IrO4, respectively. The effective magnetic moment closely
tracks the N\'eel temperature as doping increases, suggesting that the spin
state of the dopant predominately determines the magnetic properties in doped
Sr2IrO4. Furthermore, all relevant properties including charge-carrier density
(e.g., 1028/m3), Sommerfeld coefficient (e.g., 19 mJ/mole K2) and Wilson ratio
(e.g., 2.6), consistently demonstrates a metallic state that is both robust and
highly correlated in the two systems, arising from the percolation of bound
states and the weakening of structural distortions. This study strongly
suggests that the antiferromagnetic and Mott states merely coexist in a
fortuitous manner in Sr2IrO4.",2012.09989v1
2020-08-03,Symmetry-resolved two-magnon excitations in a strong spin-orbit-coupled bilayer antiferromagnet,"We used a combination of polarized Raman spectroscopy and spin wave
calculations to study magnetic excitations in the strong spin-orbit-coupled
(SOC) bilayer perovskite antiferromagnet $Sr_3Ir_2O_7$. We observed two broad
Raman features at ~ 800 $cm^{-1}$ and ~ 1400 $cm^{-1}$ arising from magnetic
excitations. Unconventionally, the ~ 800 $cm^{-1}$ feature is fully symmetric
($A_{1g}$) with respect to the underlying tetragonal ($D_{4h}$) crystal lattice
which, together with its broad line shape, definitively rules out the
possibility of a single magnon excitation as its origin. In contrast, the ~
1400 $cm^{-1}$ feature shows up in both the $A_{1g}$ and $B_{2g}$ channels.
From spin wave and two-magnon scattering cross-section calculations of a
tetragonal bilayer antiferromagnet, we identified the ~ 800 $cm^{-1}$ (~ 1400
$cm^{-1}$) feature as two-magnon excitations with pairs of magnons from the
zone-center $\Gamma$ point (zone-boundary van Hove singularity X point). We
further found that this zone-center two-magnon scattering is unique to bilayer
perovskite magnets which host an optical branch in addition to the acoustic
branch, as compared to their single layer counterparts. This zone-center
two-magnon mode is distinct in symmetry from the time-reversal symmetry broken
spin wave gap and phase mode proposed to explain the ~ 92 meV (742 $cm^{-1}$)
gap in RIXS magnetic excitation spectra of $Sr_3Ir_2O_7$.",2008.01052v1
2021-04-05,Transverse Rashba Effect and Unconventional Magnetocrystalline Anisotropy in Double-Gd-adsorbed Zigzag Graphene Nanoribbon,"The transverse Rashba effect is proposed and investigated by the
first-principle calculations based on density functional theory in a
quasi-one-dimensional antiferromagnet with a strong perpendicular
magnetocrystalline anisotropy, which is materialized by the Gd-adsorbed
graphene nanoribbon with a centric symmetry. The Rashba effect in this system
is associated with the local dipole field transverse to and in the plane of the
nanoribbon. That dipole field is induced by the off-center adsorption of the Gd
adatom above the hex-carbon ring near the nanoribbon edges. The transverse
Rashba effect at the two Gd adatoms enhances each other in the
antiferromagnetic (AFM) ground state and cancels each other in the
ferromagnetic (FM) meta-stable state, because of the centrosymmetric atomic
structure. The transverse Rashba parameter is 1.51 eV A. This system shows a
strong perpendicular magnetocrystalline anisotropy (MCA), which is 1.4 meV per
Gd atom in the AFM state or 2.2 meV per Gd atom in the FM state. The origin of
the perpendicular MCA is analyzed in k-space by filtering out the contribution
of the transverse Rashba effect from the band structures perturbed by the
spin-orbit coupling interactions. The first-order perturbation of the orbit and
spin angular momentum coupling is the major source of the MCA, which is
associated with the one-dimensionality of the system. The transverse Rashba
effect and the strong perpendicular magnetization hosted simultaneously by the
proposed AFM Gd-adsorbed graphene nanoribbon lock the up- (or down-) spin
quantization direction to the forward (or backward) movement. This finding
offers a magnetic approach to a high coherency spin propagation in
one-dimensionality, and open a new door to manipulating spin transportation in
graphene-based spintronics.",2104.01922v1
2019-05-27,Proximity Effect in Superconducting Heterostructures with Strong Spin-Orbit Coupling and Spin Splitting,"It has been shown that singlet Cooper pairs can be converted into triplet
ones and diffuse into a ferromagnet over a long distance in a phenomenon known
as the long-range proximity effect (LRPE). This happens in materials with
inhomogeneous magnetism or spin-orbit coupling (SOC). Most of the previous
studies focus on the cases with small SOC and exchange field. However, the
physics was not clear when SOC and exchange field strength are both much
greater than the disorder strength. In this work, we consider a two dimensional
system with a large Rashba-type SOC and exchange field in the case where only
one band is partially occupied. We develop a generalized quasiclassical theory
by projecting the Green function onto the partially occupied band (POB). We
find that when the SOC energy scale is comparable with the exchange field,
there is no LRPE. The reason is that the nonmagnetic impurities together with
the large SOC and exchange field can effectively generate spin-flip scattering,
which suppresses the proximity effect. We also show that when increasing either
SOC or exchange field, the decay length of superconducting correlations can be
significantly increased due to an approximately restored time reversal symmetry
or spin rotation symmetry around the $z$ (out-of-plane) axis.",1905.11135v1
2019-05-29,Electrically driven optical interferometry with spins in silicon carbide,"Interfacing solid-state defect electron spins to other quantum systems is an
ongoing challenge. The ground-state spin's weak coupling to its environment
bestows excellent coherence properties, but also limits desired drive fields.
The excited-state orbitals of these electrons, however, can exhibit stronger
coupling to phononic and electric fields. Here, we demonstrate electrically
driven coherent quantum interference in the optical transition of single,
basally oriented divacancies in commercially available 4H silicon carbide. By
applying microwave frequency electric fields, we coherently drive the
divacancy's excited-state orbitals and induce Landau-Zener-Stuckelberg
interference fringes in the resonant optical absorption spectrum. Additionally,
we find remarkably coherent optical and spin subsystems enabled by the basal
divacancy's symmetry. These properties establish divacancies as strong
candidates for quantum communication and hybrid system applications, where
simultaneous control over optical and spin degrees of freedom is paramount.",1905.12780v1
2020-03-05,N$^3$LO gravitational spin-orbit coupling at order $G^4$,"In this paper we derive for the first time the N$^3$LO gravitational
spin-orbit coupling at order $G^4$ in the post-Newtonian (PN) approximation
within the effective field theory (EFT) of gravitating spinning objects. This
represents the first computation in a spinning sector involving three-loop
integration. We provide a comprehensive account of the topologies in the
worldline picture for the computation at order $G^4$. Our computation makes use
of the publicly-available \texttt{EFTofPNG} code, which is extended using
loop-integration techniques from particle amplitudes. We provide the results
for each of the Feynman diagrams in this sector. The three-loop graphs in the
worldline picture give rise to new features in the spinning sector, including
divergent terms and logarithms from dimensional regularization, as well as
transcendental numbers, all of which survive in the final result of the
topologies at this order. This result enters at the 4.5PN order for
maximally-rotating compact objects, and together with previous work in this
line, paves the way for the completion of this PN accuracy.",2003.02827v3
2021-02-04,Self-duality of One-dimensional Quasicrystals with Spin-Orbit Interaction,"Non-interacting spinless electrons in one-dimensional quasicrystals,
described by the Aubry-Andr\'{e}-Harper (AAH) Hamiltonian with nearest
neighbour hopping, undergoes metal to insulator transition (MIT) at a critical
strength of the quasi-periodic potential. This transition is related to the
self-duality of the AAH Hamiltonian. Interestingly, at the critical point,
which is also known as the self-dual point, all the single particle wave
functions are multifractal or non-ergodic in nature, while they are ergodic and
delocalized (localized) below (above) the critical point. In this work, we have
studied the one dimensional quasi-periodic AAH Hamiltonian in the presence of
spin-orbit (SO) coupling of Rashba type, which introduces an additional spin
conserving complex hopping and a spin-flip hopping. We have found that,
although the self-dual nature of AAH Hamiltonian remains unaltered, the
self-dual point gets affected significantly. Moreover, the effect of the
complex and spin-flip hoppings are identical in nature. We have extended the
idea of Kohn's localization tensor calculations for quasi-particles and
detected the critical point very accurately. These calculations are followed by
detailed multifractal analysis along with the computation of inverse
participation ratio and von Neumann entropy, which clearly demonstrate that the
quasi-particle eigenstates are indeed multifractal and non-ergodic at the
critical point. Finally, we mapped out the phase diagram in the parameter space
of quasi-periodic potential and SO coupling strength.",2102.02387v2
2021-03-03,Spinorial formulation of the GW-BSE equations and spin properties of excitons in 2D Transition Metal Dichalcogenides,"In many paradigmatic materials, like Transition Metal Dichalcogenides, the
role played by the spin degrees of freedom is as important as the one played by
the electron-electron interaction. Thus an accurate treatment of the two
effects and of their interaction is necessary for an accurate and predictive
study of the optical and electronic properties of these materials. Despite the
GW-BSE approach correctly accounts for electronic correlations the spin-orbit
coupling effect is often neglected or treated perturbatively. Recently
spinorial formulations of GW-BSE have become available in different flavours in
material-science codes. Still an accurate validation and comparison of
different approaches is missing. In this work we go through the derivation of
non collinear GW-BSE approach. The scheme is applied to transition metal
dichalcogenides comparing perturbative and full spinorial approach. Our
calculations reveal that dark-bright exciton splittings are generally improved
when the spin orbit coupling is included non perturbatively. The
exchange-driven intravalley mixing between the A and B exciton is found to be
extremely important in the case of MoSe$_2$. We finally define the excitonic
spin and use it to sharply analyze the spinorial properties of Transition Metal
Dichalcogenides excitonic states.",2103.02266v1
2021-07-23,Coexistence of topological and nontopological Fermi-superfluid phases,"The two-dimensional spin-imbalanced Fermi gas subject to s-wave pairing and
spin-orbit coupling is considered a promising platform for realizing a
topological chiral-p-wave superfluid. In the BCS limit of s-wave pairing, i.e.,
when Cooper pairs are only weakly bound, the system enters the topological
phase via a second-order transition driven by increasing the Zeeman
spin-splitting energy. Stronger attractive two-particle interactions cause the
system to undergo the BCS-BEC crossover, in the course of which the topological
transition becomes first-order. As a result, topological and nontopological
superfluids coexist in spatially separated domains in an extended region of
phase space spanned by the strength of s-wave interactions and the Zeeman
energy. Here we investigate this phase-coexistence region theoretically using a
zero-temperature mean-field approach. Exact numerical results are presented to
illustrate basic physical characteristics of the coexisting phases and to
validate an approximate analytical description derived for weak spin-orbit
coupling. Besides extending our current understanding of spin-imbalanced
superfluid Fermi systems, the present approach also provides a platform for
future studies of unconventional Majorana excitations that, according to
topology, should be present at the internal interface between coexisting
topological and nontopological superfluid parts of the system.",2107.10973v3
2022-07-05,Unidirectional Magnetoresistance in Antiferromagnet/Heavy-metal bilayers,"The interplay between electronic transport and antiferromagnetic order has
attracted a surge of interest as recent studies have shown that a moderate
change in the spin orientation of a collinear antiferromagnet may have a
significant effect on the electronic band structure. Among numerous electrical
probes to read out such magnetic order, unidirectional magnetoresistance (UMR),
where the resistance changes under the reversal of the current direction, can
provide rich insights into the transport properties of spin-orbit coupled
systems. However, UMR has never been observed in antiferromagnets before, given
the absence of intrinsic spin-dependent scattering. Here, we report a UMR in
the antiferromagnetic phase of a FeRh$|$Pt bilayer, which undergoes a sign
change and then increases strongly with an increasing external magnetic field,
in contrast to UMRs in ferromagnetic and nonmagnetic systems. We show that
Rashba spin-orbit coupling alone cannot explain the sizable UMR in the
antiferromagnetic bilayer and that field-induced spin canting distorts the
Fermi contours to greatly enhance the UMR by two orders of magnitude. Our
results can motivate the growing field of antiferromagnetic spintronics, and
suggest a route to the development of tunable antiferromagnet-based spintronics
devices.",2207.02293v1
2022-08-21,Phase diagram of the square lattice Hubbard model with Rashba-type antisymmetric spin-orbit coupling,"We clarify the ground state phase diagram of the half-filled square-lattice
Hubbard model with Rashba spin-orbit coupling (SOC) characterized by the
spin-split energy bands due to broken inversion symmetry. Although the Rashba
metals and insulating magnets have been studied well, the intermediate
interaction strength of the system remained elusive due to the lack of
appropriate theoretical tools to unbiasedly describe the large-scale magnetic
structures. We complementarily apply four different methods; sine square
deformed mean-field theory, random phase approximation, Luttinger-Tisza method,
and density matrix embedding theory, and succeed in capturing the
incommensurate spin density-wave (SDW) phases with very long spatial periods
which were previously overlooked. The transition to the SDW phases from the
metallic phase is driven by an unprecedented instability that nests the two
parts of the Fermi surface carrying opposite spins. For large SOC, the spiral,
stipe, and vortex phases are obtained, when the four Dirac points exist near
the Fermi level and their whole linear dispersions nest by a wavelength $\pi$,
opening a band gap. These two types of transition provide Fermiology that
distinguishes the antisymmetric SOC systems, generating a variety of magnetic
phases that start from the relatively weak correlation regime and continue to
the strongly interacting limit.",2208.09902v2
2023-04-12,Reentrant proximity-induced superconductivity for GeTe semimetal,"We experimentally investigate charge transport in In-GeTe and In-GeTe-In
proximity devices, which are formed as junctions between superconducting indium
leads and thick single crystal flakes of $\alpha$-GeTe topological semimetal.
We observe nonmonotonic effects of the applied external magnetic field,
including reentrant superconductivity in In-GeTe-In Josephson junctions:
supercurrent reappears at some finite magnetic field. For a single In-GeTe
Andreev junction, the superconducting gap is partially suppressed in zero
magnetic field, while the gap is increased nearly to the bulk value for some
finite field before its full suppression. We discuss possible reasons for the
results obtained, taking into account spin polarization of Fermi arc surface
states in topological semimetal $\alpha$-GeTe with a strong spin-orbit
coupling. In particular, the zero-field surface state spin polarization
partially suppresses the superconductivity, while it is recovered due to the
modified spin-split surface state configuration in finite fields. As an
alternative possible scenario, the transition into the
Fulde-Ferrell-Larkin-Ovchinnikov state is discussed. However, the role of
strong spin-orbit coupling in forming the nonmonotonic behavior has not been
analyzed for heterostructures in the Fulde-Ferrell-Larkin-Ovchinnikov state,
which is crucial for junctions involving GeTe topological semimetal.",2304.05971v2
2024-02-02,Symmetry breaking and spin-orbit coupling for individual vacancy-induced in-gap states in MoS2 monolayers,"Spins confined to point defects in atomically-thin semiconductors constitute
well-defined atomic-scale quantum systems that are being explored as single
photon emitters and spin qubits. Here, we investigate the in-gap electronic
structure of individual sulphur vacancies in molybdenum disulphide (MoS2)
monolayers using resonant tunneling scanning probe spectroscopy in the Coulomb
blockade regime. Spectroscopic mapping of defect wavefunctions reveals an
interplay of local symmetry breaking by a charge-state dependent Jahn-Teller
lattice distortion that, when combined with strong (~100 meV) spin-orbit
coupling, leads to a locking of an unpaired spin-1/2 magnetic moment to the
lattice at low temperature, susceptible to lattice strain. Our results provide
new insights into spin and electronic structure of vacancy induced in-gap
states towards their application as electrically and optically addressable
quantum systems.",2402.01193v2
2011-07-07,Reduced effective spin-orbital degeneracy and spin-orbital ordering in paramagnetic transition metal oxides: Sr2IrO4 vs. Sr2RhO4,"We discuss the notions of spin-orbital polarization and ordering in
paramagnetic materials, and address their consequences in transition metal
oxides. Extending the combined density functional and dynamical mean field
theory scheme to the case of materials with large spin-orbit interactions, we
investigate the electronic excitations of the paramagnetic phases of Sr2IrO4
and Sr2RhO4. We show that the interplay of spin-orbit interactions, structural
distortions and Coulomb interactions suppresses spin-orbital fluctuations. As a
result, the room temperature phase of Sr2IrO4 is a paramagnetic spin-orbitally
ordered Mott insulator. In Sr2RhO4, the effective spin-orbital degeneracy is
reduced, but the material remains metallic, due to both, smaller spin-orbit and
smaller Coulomb interactions. We find excellent agreement of our ab-initio
calculations for Sr2RhO4 with angle-resolved photoemission, and make
predictions for spectra of the paramagnetic phase of Sr2IrO4.",1107.1371v1
2021-05-20,Spin-orbital-momentum locking under odd-parity magnetic quadrupole ordering,"Odd-parity magnetic and magnetic toroidal multipoles in the absence of both
spatial-inversion and time-reversal symmetries are sources of multiferroic and
nonreciprocal optical phenomena. We investigate electronic states caused by an
emergent odd-parity magnetic quadrupole (MQ) as a representative example of
magnetic odd-parity multipoles. It is shown that spontaneous ordering of the MQ
leads to an antisymmetric spin-orbital polarization in momentum space, which
corresponds to a spin-orbital momentum locking at each wave vector. By symmetry
argument, we show that the orbital or sublattice degree of freedom is
indispensable to give rise to the spin-orbital momentum locking. We demonstrate
how the electronic band structures are modulated by the MQ ordering in the
three-orbital system, in which the MQ is activated by the spin-dependent
hybridization between the orbitals with different spatial parities. The
spin-orbital momentum locking is related with the microscopic origin of
cross-correlated phenomena, e.g., the magnetic-field-induced symmetric and
antisymmetric spin polarization in the band structure, the current-induced
distortion, and the magnetoelectric effect. We also discuss similar
spin-orbital momentum locking in antiferromagnet where the MQ degree of freedom
is activated through the antiferromagnetic spin structure in a sublattice
system.",2105.09444v1
2022-07-25,Spin-orbit torques from topological insulator surface states: Effect of extrinsic spin-orbit scattering on an out-of-plane magnetization,"The origins of the spin-orbit torque (SOT) at ferromagnet/topological
insulator (FM/TI) interfaces are incompletely understood. Theory has
overwhelmingly focussed on the Edelstein effect due to the surface states in
the presence of a scalar scattering potential. We investigate here the
contribution to the SOT due to extrinsic spin-orbit scattering of the surface
states, focusing on the case of an out-of-plane magnetization. We show that
spin-orbit scattering brings about a sizable renormalization of the field-like
SOT, which exceeds 20$\%$ at larger strengths of the extrinsic spin-orbit
parameter. The resulting SOT exhibits a maximum as a function of the Fermi
energy, magnetization, and extrinsic spin-orbit strength. The field-like SOT
decreases with increasing disorder strength while the damping-like SOT is
independent of the impurity density. With experimental observation in mind we
also determine the role of extrinsic spin-orbit scattering on the anomalous
Hall effect. Our results suggest extrinsic spin-orbit scattering is a
significant contributor to the surface SOT stemming from the Edelstein effect
when the magnetization is out of the plane.",2207.12440v1
2004-11-27,Estimating spinning binary parameters and testing alternative theories of gravity with LISA,"We investigate the effect of spin-orbit and spin-spin couplings on the
estimation of parameters for inspiralling compact binaries of massive black
holes, and for neutron stars inspiralling into intermediate-mass black holes,
using hypothetical data from the proposed Laser Interferometer Space Antenna
(LISA). We work both in Einstein's theory and in alternative theories of
gravity of the scalar-tensor and massive-graviton types. We restrict the
analysis to non-precessing spinning binaries, i.e. to cases where the spins are
aligned normal to the orbital plane. We find that the accuracy with which
intrinsic binary parameters such as chirp mass and reduced mass can be
estimated within general relativity is degraded by between one and two orders
of magnitude. We find that the bound on the coupling parameter omega_BD of
scalar-tensor gravity is significantly reduced by the presence of spin
couplings, while the reduction in the graviton-mass bound is milder. Using fast
Monte-Carlo simulations of 10^4 binaries, we show that inclusion of spin terms
in massive black-hole binaries has little effect on the angular resolution or
on distance determination accuracy. For stellar mass inspirals into
intermediate-mass black holes, the angular resolution and the distance are
determined only poorly, in all cases considered. We also show that, if LISA's
low-frequency noise sensitivity can be extrapolated from 10^-4 Hz to as low as
10^-5 Hz, the accuracy of determining both extrinsic parameters (distance, sky
location) and intrinsic parameters (chirp mass, reduced mass) of massive
binaries may be greatly improved.",0411129v2
2021-09-30,Spin pumping from antiferromagnetic insulator spin-orbit-proximitized by adjacent heavy metal: A first-principles Floquet-nonequilibrium Green's function study,"Motivated by recent experiments [P. Vaidya {\em et al.}, Science {\bf 368},
160 (2020)] on spin pumping from sub-THz radiation-driven uniaxial
antiferromagnetic insulator (AFI) MnF$_2$ into heavy metal (HM) Pt hosting
strong spin-orbit (SO) coupling, we compute and compare pumped spin currents in
Cu/MnF$_2$/Cu and Pt/MnF$_2$/Cu heterostructures. Recent theories of spin
pumping by AFI have relied on simplistic Hamiltonians (such as tight-binding)
and the scattering approach to quantum transport yielding the so-called
interfacial spin mixing conductance (SMC), but the concept of SMC ceases to be
applicable when SO coupling is present directly at the interface. In contrast,
we use more general first-principles quantum transport approach which combines
noncollinear density functional theory with Floquet-nonequilibrium Green's
functions in order to take into account: {\em SO-proximitized AFI} as a new
type of quantum material, different from isolated AFI and brought about by AFI
hybridization with adjacent HM layer; SO coupling at interfaces; and evanescent
wavefunctions penetrating from Pt or Cu into AFI layer to make its interfacial
region {\em conducting} rather than insulating as in the original AFI. The DC
component of pumped spin current $I_\mathrm{DC}^{S_z}$ vs. precession cone
angle $\theta_{\vb*{l}}$ of the N\'eel vector $\vb*{l}$ of AFI {\em does not}
follow putative $I^{S_z}_\mathrm{DC} \propto \sin^2 \theta_{\vb*{l}}$, except
for very small angles $\theta_{\vb*{l}} \lesssim 10^\circ$ for which we can
define an {\em effective} SMC from the prefactor and find that it doubles from
MnF$_2$/Cu to MnF$_2$/Pt interface. In addition, the angular dependence
$I^{S_z}_\mathrm{DC}(\theta_{\vb*{l}})$ differs for opposite directions of
precession of the N\'{e}el vector, leading to twice as large SMC for the
right-handed than for the left-handed chirality of the precession mode.",2109.15249v2
2014-02-16,Tidal Dissipation and Obliquity Evolution in Hot Jupiter Systems,"Two formation scenarios have been proposed to explain the tight orbits of hot
Jupiters. They could be formed in orbits with a small inclination (with respect
to the stellar spin) via disk migration, or in more highly inclined orbits via
high-eccentricity migration, where gravitational interactions with a companion
and tidal dissipation are at play. Here we target hot Jupiter systems where the
misalignment $\lambda$ has been inferred observationally and we investigate
whether their properties are consistent with high-eccentricity migration.
Specifically, we study whether stellar tides can be responsible for the
observed distribution of $\lambda$ and orbital separations. Improving on
previous studies, we use detailed models for each star, thus accounting for how
convection (and tidal dissipation) depends on stellar properties. In line with
observations suggesting that hotter stars have higher $\lambda$, we find that
$\lambda$ increases as the amount of stellar surface convection decreases. This
trend supports the hypothesis that tides are the mechanism shaping the observed
distribution of $\lambda$. Furthermore, we study the past orbital evolution of
five representative systems, chosen to cover a variety of temperatures and
misalignments. We consider various initial orbital configurations and integrate
the equations describing the coupled evolution of the orbital separation,
stellar spin, and misalignment. We account for stellar tides and wind mass
loss, stellar evolution, and magnetic braking. We show that the current
properties of these five representative systems can be explained naturally,
given our current understanding of tidal dissipation and with physically
motivated assumptions for the effects driving the orbital evolution.",1402.3857v2
2021-08-26,Coherent strong-coupling of terahertz magnons and phonons in a Van der Waals antiferromagnetic insulator,"Emergent cooperative motions of individual degrees of freedom, i.e.
collective excitations, govern the low-energy response of system ground states
under external stimulations and play essential roles for understanding
many-body phenomena in low-dimensional materials. The hybridization of distinct
collective modes provides a route towards coherent manipulation of coupled
degrees of freedom and quantum phases. In magnets, strong coupling between
collective spin and lattice excitations, i.e., magnons and phonons, can lead to
coherent quasi-particle magnon polarons. Here, we report the direct observation
of a series of terahertz magnon polarons in a layered zigzag antiferromagnet
FePS3 via far-infrared (FIR) transmission measurements. The characteristic
avoided-crossing behavior is clearly seen as the magnon-phonon detuning is
continuously changed via Zeeman shift of the magnon mode. The coupling strength
g is giant, achieving 120 GHz (0.5 meV), the largest value reported so far.
Such a strong coupling leads to a large ratio of g to the resonance frequency
(g/{\omega}) of 4.5%, and a value of 29 in cooperativity
(g^2/{\gamma}_{ph}{\gamma}_{mag}). Experimental results are well reproduced by
first-principle calculations, where the strong coupling is identified to arise
from phonon-modulated anisotropic magnetic interactions due to spin-orbit
coupling. These findings establish FePS3 as an ideal testbed for exploring
hybridization-induced topological magnonics in two dimensions and the coherent
control of spin and lattice degrees of freedom in the terahertz regime.",2108.11619v1
2019-08-13,Chaotic rotation and evolution of asteroids and small planets in high-eccentricity orbits around white dwarfs,"Observed planetary debris in white dwarf atmospheres predominately originate
from the destruction of small bodies on highly eccentric ($>0.99$) orbits.
Despite their importance, these minor planets have coupled physical and orbital
evolution which has remained largely unexplored. Here, we present a novel
approach for estimating the influence of fast chaotic rotation on the orbital
evolution of high-eccentricity triaxial asteroids, and formally characterize
the propagation of their angular rotation velocities and orbital elements as
random time processes. By employing the impulse approximation, we demonstrate
that the violent gravitational interactions during periastron passages transfer
energy between the orbit and asteroid's rotation. If the distribution of spin
impulses were symmetric around zero, then the net result would be a secular
decrease of the semimajor axis and a further increase of the eccentricity. We
find evidence, however, that the chaotic rotation may be self-regulated in such
a manner that these effects are reduced or nullified. We discover that
asteroids on highly eccentric orbits can break themselves apart --- in a type
of YORP-less rotational fission --- without actually entering the Roche radius,
with potentially significant consequences for the distribution of debris and
energy requirements for gravitational scattering in metal-polluted white dwarf
planetary systems. This mechanism provides a steady stream of material
impacting a white dwarf without rapidly depleting the number of small bodies in
the stellar system.",1908.04612v1
2018-10-18,First-principles quantum transport simulation of CuPc on Au(111) and Ag(111),"We investigate equilibrium and transport properties of a copper
phthalocyanine (CuPc) molecule adsorbed on Au(111) and Ag(111) surfaces. The
CuPc molecule has essentially three localized orbitals close to the Fermi
energy resulting in strong local Coulomb repulsion not accounted for properly
in density functional calculations. Hence, they require a proper many-body
treatment within, e.g., the Anderson impurity model (AIM). The occupancy of
these orbitals varies with the substrate on which CuPc is adsorbed. Starting
from density functional theory calculations, we determine the parameters for
the AIM embedded in a noninteracting environment that describes the residual
orbitals of the entire system. While correlation effects in CuPc on Au(111) are
already properly described by a single orbital AIM, for CuPc on Ag(111) the
three orbital AIM problem can be simplified into a two orbital problem coupled
to the localized spin of the third orbital. This results in a Kondo effect with
a mixed character, displaying a symmetry between SU(2) and SU(4). The computed
Kondo temperature is in good agreement with experimental values. To solve the
impurity problem we use the recently developed fork tensor product state
solver. To obtain transport properties, a scanning tunneling microscope (STM)
tip is added to the CuPc molecule absorbed on the surface. We find that the
transmission depends on the detailed position of the STM tip above the CuPc
molecule in good agreement with differential conductance measurements.",1810.07963v2
2007-07-19,Quantum transport in noncentrosymmetric superconductors and thermodynamics of ferromagnetic superconductors,"We consider a general Hamiltonian describing coexistence of itinerant
ferromagnetism, spin-orbit coupling and mixed spin-singlet/triplet
superconducting pairing in the context of mean-field theory. The Hamiltonian is
diagonalized and exact eigenvalues are obtained, thus allowing us to write down
the coupled gap equations for the different order parameters. Our results may
then be applied to any model describing coexistence of any combination of these
three phenomena. As a specific application of our results, we consider
tunneling between a normal metal and a noncentrosymmetric superconductor with
mixed singlet and triplet gaps. The conductance spectrum reveals information
about these gaps in addition to how the influence of spin-orbit coupling is
manifested. We also consider the coexistence of itinerant ferromagnetism and
triplet superconductivity as a model for recently discovered ferromagnetic
superconductors. The coupled gap equations are solved self-consistently, and we
study the conditions necessary to obtain the coexistent regime of
ferromagnetism and superconductivity. Analytical expressions are presented for
the order parameters, and we provide an analysis of the free energy to identify
the preferred system state. Moreover, we make specific predictions concerning
the heat capacity for a ferromagnetic superconductor. In particular, we report
a nonuniversal relative jump in the specific heat, depending on the
magnetization of the system, at the uppermost superconducting phase transition.
[Shortened abstract due to arXiv submission.]",0707.2875v2
2018-05-25,Solitons and Josephson-type oscillations in Bose-Einstein condensates with spin-orbit coupling and time-varying Raman frequency,"The existence and dynamics of solitons in quasi-one-dimensional Bose-Einstein
condensates (BEC) with spin-orbit coupling (SOC) and attractive two-body
interactions are described for two coupled atomic pseudo-spin components with
slowly and rapidly varying time-dependent Raman frequency. By varying the Raman
frequency linearly in time, it was shown that ordinary nonlinear
Schr\""odinger-type bright solitons can be converted to striped bright solitons
and vice versa. The internal Josephson oscillations between atom-number of the
coupled soliton components, and the corresponding center-of-mass motion, are
studied for different parameter configurations. In this case, a mechanism to
control the soliton parameters is proposed by considering parametric
resonances, which can emerge when using time-varying Raman frequencies. Full
numerical simulations confirm variational analysis predictions when applied to
the region where regular solitons are expected. In the limit of high
frequencies, the system is described by a time-averaged Gross-Pitaevskii
formalism with renormalized nonlinear and SOC parameters and modified
phase-dependent nonlinearities. By comparing full-numerical simulations with
averaged results, we have also studied the lower limits for the frequency of
Raman oscillations in order to obtain stable soliton solutions.",1805.10357v1
2012-01-10,"Microscopic theory for a ferromagnetic-nanowire/superconductor heterostructure: Transport, fluctuations and topological superconductivity","Motivated by the recent experiment of Wang et al. [Nature Physics 6, 389
(2010)], who observed a highly unusual transport behavior of ferromagnetic
Cobalt nanowires proximity-coupled to superconducting electrodes, we study
proximity effect and temperature-dependent transport in such a mesoscopic
hybrid structure. It is assumed that the asymmetry in the tunneling barrier
gives rise to the Rashba spin-orbit-coupling in the barrier that enables
induced p-wave superconductivity in the ferromagnet to exist. We first develop
a microscopic theory of Andreev scattering at the spin-orbit-coupled interface,
derive a set of self-consistent boundary conditions, and find an expression for
the p-wave minigap in terms of the microscopic parameters of the contact.
Second, we study temperature-dependence of the resistance near the
superconducting transition and find that it should generally feature a
fluctuation-induced peak. The upturn in resistance is related to the
suppression of the single-particle density of states due to the formation of
fluctuating pairs, whose tunneling is suppressed. In conclusion, we discuss
this and related setups involving ferromagnetic nanowires in the context of
one-dimensional topological superconductors. It is argued that to realize
unpaired end Majorana modes, one does not necessarily need a half-metallic
state, but a partial spin polarization may suffice. Finally, we propose yet
another related class of material systems -- ferromagnetic semiconductor wires
coupled to ferromagnetic superconductors -- where direct realization of
Kitaev-Majorana model should be especially straightforward.",1201.2180v2
2018-06-10,Properties of the electronic fluid of superconducting cuprates from $^{63}$Cu NMR shift and relaxation,"Nuclear magnetic resonance (NMR) provides local, bulk information about the
electronic properties of materials, and it has been influential for theory of
high-temperature superconducting cuprates. Importantly, NMR found early that
nuclear relaxation is much faster than what one expects from coupling to
fermionic excitations above the critical temperature for superconductivity
($T_{\rm c}$), i.e. what one estimates from the Knight shift with the Korringa
law. As a consequence, special electronic spin fluctuations have been invoked.
Here, based on literature relaxation data it is shown that the electronic
excitations, to which the nuclei couple with a material and doping dependent
anisotropy, are rather ubiquitous and Fermi liquid-like. A suppressed NMR spin
shift rather than an enhanced relaxation leads to the failure of the Korringa
law for most materials. Shift and relaxation below $T_{\rm c}$ support the view
of suppressed shifts, as well. A simple model of two coupled electronic spin
components, one with $3d(x^2-y^2)$ orbital symmetry and the other with an
isotropic $s$-like interaction can explain the data. The coupling between the
two components is found to be negative, and it must be related to the pseudogap
behavior of the cuprates. We can also explain the negative shift conundrum and
the long-standing orbital shift discrepancy for NMR in the cuprates.",1806.03644v4
2017-11-15,Geometric effects resulting from square and circular confinements for a particle constrained to a space curve,"Investigating the geometric effects resulting from the detailed behaviors of
the confining potential, we consider square and circular confinements to
constrain a particle to a space curve. We find a torsion-induced geometric
potential and a curvature-induced geometric momentum just in the square case,
while a geometric gauge potential solely in the circular case. In the presence
of electromagnetic field, a geometrically induced magnetic moment couples with
magnetic field as an induced Zeeman coupling only for the circular confinement,
also. As spin-orbit interaction is considered, we find some additional terms
for the spin-orbit coupling, which are induced not only by torsion, but also
curvature. Moreover, in the circular case, the spin also couples with an
intrinsic angular momentum, which describes the azimuthal motions mapped on the
space curve. As an important conclusion for the thin-layer quantization
approach, some substantial geometric effects result from the confinement
boundaries. Finally, these results are proved on a helical wire.",1711.05453v4
2021-06-04,Resonant optical topological Hall conductivity from skyrmions,"We study the high frequency Hall conductivity in a two-dimensional (2D) model
of conduction electrons coupled to a background magnetic skyrmion texture via
an effective Hund's coupling term. For an ordered skyrmion crystal, a Kubo
formula calculation using the basis of skyrmion crystal Chern bands reveals a
resonant Hall response at a frequency set by the Hund's coupling:
$\hbar\omega_{\text{res}} \approx J_H$. A complementary real-space Kubo formula
calculation for an isolated skyrmion in a box reveals a similar resonant Hall
response. A linear relation between the area under the Hall resonant curve and
the skyrmion density is discovered numerically and is further elucidated using
a gradient expansion which is valid for smooth textures and a local
approximation based on a spin-trimer calculation. We point out the issue of
distinguishing this skyrmion contribution from a similar feature arising from
spin-orbit interactions, as demonstrated in a model for Rashba spin-orbit
coupled electrons in a collinear ferromagnet, which is analogous to the
difficulty of unambiguously separating the d.c. topological Hall effect from
the anomalous Hall effect. The resonant feature in the high frequency
topological Hall effect is proposed to provide a potentially useful local
optical signature of skyrmions via probes such as scanning magneto-optical Kerr
microscopy.",2106.02641v2
2009-12-18,Diffusive versus local spin currents in dynamic spin pumping systems,"Using microscopic theory, we investigate the properties of a spin current
driven by magnetization dynamics. In the limit of smooth magnetization texture,
the dominant spin current induced by the spin pumping effect is shown to be the
diffusive spin current, i.e., the one arising from only a diffusion associated
with spin accumulation. That is to say, there is no effective field that
locally drives the spin current. We also investigate the conversion mechanism
of the pumped spin current into a charge current by spin-orbit interactions,
specifically the inverse spin Hall effect. We show that the spin-charge
conversion does not always occur and that it depends strongly on the type of
spin-orbit interaction. In a Rashba spin-orbit system, the local part of the
charge current is proportional to the spin relaxation torque, and the local
spin current, which does not arise from the spin accumulation, does not play
any role in the conversion. In contrast, the diffusive spin current contributes
to the diffusive charge current. Alternatively, for spin-orbit interactions
arising from random impurities, the local charge current is proportional to the
local spin current that constitutes only a small fraction of the total spin
current. Clearly, the dominant spin current (diffusive spin current) is not
converted into a charge current. Therefore, the nature of the spin current is
fundamentally different depending on its origin and thus the spin transport and
the spin-charge conversion behavior need to be discussed together along with
spin current generation.",0912.3607v2
2001-12-31,Kondo effect and anti-ferromagnetic correlation in transport through tunneling-coupled double quantum dots,"We propose to study the transport through tunneling-coupled double quantum
dots (DQDs) connected in series to leads, using the finite-$U$ slave-boson mean
field approach developed initially by Kotliar and Ruckenstein [Phys. Rev. Lett.
{\bf 57}, 1362 (1986)]. This approach treats the dot-lead coupling and the
inter-dot tunnelling $t$ nonperturbatively at arbitrary Coulomb correlation
$U$, thus allows the anti-ferromagnetic exchange coupling parameter $J=4t^2/U$
to appear naturally. We find that, with increasing the inter-dot hopping, the
DQDs manifest three distinct physical scenarios: the Kondo singlet state of
each dot with its adjacent lead, the spin singlet state consisting of local
spins on each dot and the doubly occupied bonding orbital of the coupled dots.
The three states exhibit remarkably distinct behavior in transmission spectrum,
linear and differential conductance and their magnetic-field dependence.
Theoretical predictions agree with numerical renormalization group and Lanczos
calculations, and some of them have been observed in recent experiments.",0112500v2
2013-06-19,Spin-Orbit Coupling Induced Coherent Production of Feshbach Molecules in a Degenerate Fermi Gas,"In this work we demonstrate a dynamic process in which SO coupling can
coherently produce s-wave Feshbach molecules from a fully polarized Fermi gas,
and can induce a coherent oscillation between Feshbach molecules and spin
polarized gas. For comparison, we also show that such phenomena are absent if
the inter-component coupling is momentum-independent. This demonstrates
experimentally that SO coupling does provide finite matrix element between a
singlet state and a triplet state, and therefore, implies the bound pairs of a
system with SO coupling have triplet p-wave component, which can become
topological superfluid by further cooling these pairs to condensation and
confining them to lower dimension.",1306.4568v2
2023-10-29,Coupling conduction-band valleys in modulated SiGe heterostructures via shear strain,"Engineering conduction-band valley couplings is a key challenge for Si-based
spin qubits. Recent work has shown that the most reliable method for enhancing
valley couplings entails adding Ge concentration oscillations to the quantum
well. However, ultrashort oscillation periods are difficult to grow, while long
oscillation periods do not provide useful improvements. Here, we show that the
main benefits of short-wavelength oscillations can be achieved in
long-wavelength structures through a second-order coupling process involving
Brillouin-zone folding, induced by shear strain. Moreover, we find that the
same long-wavelength period also boosts spin-orbit coupling. We finally show
that such strain can be achieved through common fabrication techniques, making
this an exceptionally promising system for scalable quantum computing.",2310.18879v2
2001-06-22,Quantum phase transitions in models of coupled magnetic impurities,"We discuss models of interacting magnetic impurities coupled to a metallic
host. If twice the sum of the impurity spins is larger than the total number of
host screening channels, the system shows one or more quantum phase transitions
where the ground-state spin changes as a function of the inter-impurity
couplings. The simplest example is realized by two spin-1/2 Kondo impurities
coupled to a single orbital of the host; this model exhibits a singlet-doublet
transition. We investigate the phase diagram and crossover behavior of this
model and present Numerical Renormalization Group results together with general
arguments showing that the quantum phase transition is either of first order or
of the Kosterlitz-Thouless type, depending on the symmetry of the Kondo
couplings. Connections to other models and possible applications are discussed.",0106458v2
2013-10-15,Magneto-Electric Effect in Three-dimensional Coupled Zigzag Chains,"Stimulated by recent studies of quantum phases with broken local inversion
symmetry, we study the magnetoelectric effect in locally noncentrosymmetric
metals. We consider three-dimensional (3D) coupled zigzag chains and
demonstrate that the antiferromagnetic moment is induced by the electric
current through a staggered antisymmetric spin-orbit coupling. This
current-induced magnetism is much larger than that in globally
noncentrosymmetric metals. We provide an intuitive understanding of the
current-induced antiferromagnetic moment by showing the inverse magnetoelectric
effect, that is, the ferroic p-wave charge nematic order accompanied by the
asymmetric band structure in the antiferromagnetic state. We also examine
conduction electrons coupled to localized spins via Kondo exchange coupling and
demonstrate a significant enhancement of the magnetoelectric effect. A possible
experimental observation of the magnetoelectric effect in metals is discussed,
with focus on LnM_2Al_10 compounds, such as NdRu_Al_10 and TbRu_2Al_10.",1310.3920v2
2015-05-06,Effects of large induced superconducting gap on semiconductor Majorana nanowires,"With the recent achievement of extremely high-quality epitaxial interfaces
between InAs nanowires and superconducting Al shells with strong
superconductor-semiconductor tunnel coupling, a new regime of proximity-induced
superconductivity in semiconductors can be explored where the induced gap may
be similar in value to the bulk Al gap (large gap) with negligible subgap
conductance (hard gap). We propose several experimentally relevant consequences
of this large-gap strong-coupling regime for tunneling experiments, and we
comment on the prospects of this regime for topological superconductivity. In
particular, we show that the advantages of having a strong spin-orbit coupling
and a large spin g-factor in the semiconductor nanowire may both be compromised
in this strongly coupled limit, and somewhat weaker interface tunneling may be
necessary for achieving optimal proximity superconductivity in the
semiconductor nanowire. We derive a minimal, generic theory for the
strong-coupling hard-gap regime obtaining good qualitative agreement with the
experiment and pointing out future directions for further progress toward
Majorana nanowires in hybrid semiconductor-superconductor structures.",1505.01482v2
2002-08-15,Low temperature electronic properties of Sr_2RuO_4 II: Superconductivity,"The body centered tetragonal structure of Sr_2RuO_4 gives rise to umklapp
scattering enhanced inter-plane pair correlations in the d_{yz} and d_{zx}
orbitals. Based on symmetry arguments, Hund's rule coupling, and a bosonized
description of the in-plane electron correlations the superconducting order
parameter is found to be a orbital-singlet spin-triplet with two spatial
components. The spatial anisotropy is 7%. The different components of the order
parameter give rise to two-dimensional gapless fluctuations. The phase
transition is of third order. The temperature dependence of the pair density,
specific heat, NQR, Knight shift, and susceptibility are in agreement with
experimental results.",0208307v1
2003-03-12,Origin of the Orbital Ordering in LaMnO$_3$,"We use the temperature of the structural phase transition to determine the
Jahn-Teller (JT) coupling constant in the model derived for LaMnO$_3$ which
includes both the superexchange between S=2 spins and the JT effect. We also
investigate the dependence of the exchange constants on the value of the
on-site Coulomb element $U$, and on the orbital ordering.",0303232v1
2003-03-25,Orbital entanglement and violation of Bell inequalities in mesoscopic conductors,"We propose a spin-independent scheme to generate and detect two-particle
entanglement in a mesoscopic normal-superconductor system. A superconductor,
weakly coupled to the normal conductor, generates an orbitally entangled state
by injecting pairs of electrons into different leads of the normal conductor.
The entanglement is detected via violation of a Bell inequality, formulated in
terms of zero-frequency current cross-correlators. It is shown that the Bell
inequality can be violated for arbitrary strong dephasing in the normal
conductor.",0303531v1
2003-04-22,Lattice and superexchange effects in doped CMR manganites,"We report on the influence of the lattice degrees of freedom on charge,
orbital and spin correlations in colossal magnetoresistance (CMR) manganites.
For the weakly doped compounds we demonstrate that the electron-phonon coupling
promotes the trapping of charge carriers, the disappearance of the orbital
polaron pattern and the breakdown of ferromagnetism at the CMR transition. The
role of different superexchange interactions is explored.",0304491v1
2005-06-23,Comment on a Phys. Rev. Lett. paper: 94 (2005) 146402: Orbital symmetry and Electron Correlation in NaxCoO2,"We argue that the electronic structure considered in a Phys. Rev. Lett. paper
94 (2005) 146402 of the Co3+ ion in the CoO6 octahedron of NaxCoO2 is
completely wrong. The presented Fig. 1 is redrawn here as Fig. 1. For
physically adequate electronic structure it is necessary to take into account
strong intra-atomic electron correlations and spin-orbit coupling. For Co3+
ions there are 15 low lying many-electron states within 0.1 eV as can be
obtained in the many-electron CEF approach.",0506615v1
2005-09-09,Correlated hybridization in transition metal complexes,"We apply local orbital basis density functional theory (using SIESTA) coupled
with a mapping to the Anderson impurity model to estimate the Coulomb assisted
or correlated hybridization between transition metal d-orbitals and ligand
sp-orbitals for a number of molecular complexes. We find remarkably high values
which can have several physical implications including: (i) renormalization of
effective single band or multiband Hubbard model parameters for the cuprates
and, potentially, elemental iron, and (ii) spin polarizing molecular
transistors.",0509259v4
2005-11-16,Electronic structure and crystal-field states in V2O3*,"We have calculated the electronic structure of V2O3 associated with the V3+
ions taking into account strong on-site electron correlations and the
spin-orbit coupling. Closely lying 9 states of the subterm 3T1g are a physical
reason for exotic phenomena of V2O3. Electronic structure and magnetism of V3+
ions in the octahedral surroundings are strongly susceptible to lattice
distortions and magnetic interactions. Our approach accounts both for the
insulating ground state, magnetism, including its orbital contribution, as well
as thermodynamical properties.",0511395v1
2005-11-25,"Comment on a Phys. Rev. Lett. paper: ""All-Electron Self-Consistent GW Approximation: Application to Si, MnO, and NiO"". Magnetic moment of NiO","We claim that any approach neglecting the spin-orbit coupling and the orbital
magnetism is not physically adequate for 3d oxides, including NiO, and that in
reaching ""excellent agreement"" in a Phys. Rev. Lett. 93, 126406 (2004) paper
too small experimental value of 1.9 muB has been taken for the Ni magnetic
moment despite publication of a new experimental value of 2.2 muB, at 300 K
yielding 2.6 muB at T = 0 K, already in a year of 1998.",0511624v1
2006-07-05,Hybridization expansion impurity solver: General formulation and application to Kondo lattice and two-orbital models,"A recently developed continuous time solver based on an expansion in
hybridization about an exactly solved local limit is reformulated in a manner
appropriate for general classes of quantum impurity models including spin
exchange and pair hopping terms. The utility of the approach is demonstrated
via applications to the dynamical mean field theory of the Kondo lattice and
two-orbital models. The algorithm can handle low temperatures and strong
couplings without encountering a sign problem.",0607136v2
2007-09-14,Phase diagram of hole doped two-leg Cu-O ladders,"In the weak coupling limit, we establish the phase diagram of a two-leg
ladder with a unit cell containing both Cu and O atoms, as a function of
doping. We use bosonization and design a specific RG procedure to handle the
additional degrees of freedom. Significant differences are found with the
single orbital case; for purely repulsive interactions, a completely massless
quantum critical region is obtained at intermediate carrier concentrations
(well inside the bands) where the ground state consists of an incommensurate
pattern of orbital currents plus a spin density wave (SDW) structure.",0709.2303v1
2011-09-06,Topological insulators from complex orbital order in transition-metal oxides heterostructures,"Topological band insulators which are dynamically generated by
electron-electron interactions have been the- oretically proposed in two and
three dimensional lattice models. We present evidence that the two-dimensional
version can be stabilized in digital (111) heterostructures of transition-metal
oxides as a result of purely local interactions. The topological phases are
accompanied by spontaneous ordering of complex orbitals and we discuss their
stability with respect to the Hund's rule coupling, Jahn-Teller interaction and
inversion symmetry breaking terms. As main competitors we identify spin-nematic
and magnetic phases.",1109.1297v2
2014-02-07,Exotic magnetic order in the orbital-selective Mott regime of multiorbital systems,"The orbital-selective Mott phase (OSMP) of multiorbital Hubbard models has
been extensively analyzed before using static and dynamical mean-field
approximations. In parallel, the properties of Block states
(antiferromagnetically coupled ferromagnetic spin clusters) in Fe-based
superconductors have also been much discussed. The present effort uses
numerically exact techniques in one-dimensional systems to report the
observation of Block states within the OSMP regime, connecting two seemingly
independent areas of research, and providing analogies with the physics of
Double-Exchange models.",1402.1689v1
2015-07-01,A tight-binding model for MoS$_2$ monolayers,"We propose an accurate tight-binding parametrization for the band structure
of MoS$_2$ monolayers near the main energy gap. We introduce a generic and
straightforward derivation for the band energies equations that could be
employed for other monolayer dichalcogenides. A parametrization that includes
spin-orbit coupling is also provided. The proposed set of model parameters
reproduce both the correct orbital compositions and location of valence and
conductance band in comparison with ab initio calculations. The model gives a
suitable starting point for realistic large-scale atomistic electronic
transport calculations.",1507.00356v1
2015-10-22,Molecular Anisotropic Magnetoresistance,"Using density functional theory calculations, we demonstrate that the effect
of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude
with respect to conventional bulk ferromagnets in junctions containing
molecules sandwiched between ferromagnetic leads. We study ballistic transport
in metal-benzene complexes contacted by $3d$ transition-metal wires. We show
that the gigantic AMR can arise from spin-orbit coupling effects in the leads,
drastically enhanced by orbital-symmetry filtering properties of the molecules.
We further discuss how this molecular anisotropic magnetoresistance (MAMR) can
be tuned by proper choice of materials and their electronic properties.",1510.06632v1
2016-04-04,Approximation schemes for the study of multi-band Gutzwiller wave functions,"The minimum of the Gutzwiller energy functional depends on the number of
parameters considered in the variational state. For a three-orbital Hubbard
model we find that the frequently used diagonal Ansatz is very accurate in
high-symmetry situations. For lower symmetry, induced by a crystal-field
splitting or the spin-orbit coupling, the discrepancies in energy between the
most general and a diagonal Gutzwiller Ansatz can be quite significant. We
discuss approximate schemes that may be employed in multi-band cases where a
minimization of the general Gutzwiller energy functional is too demanding
numerically.",1604.00819v1
2014-06-09,Tidal dissipation in stars and giant planets,"Astrophysical fluid bodies that orbit close to one another induce tidal
distortions and flows that are subject to dissipative processes. The spin and
orbital motions undergo a coupled evolution over astronomical timescales, which
is relevant for many types of binary star, short-period extrasolar planetary
systems and the satellites of the giant planets in the solar system. I review
the principal mechanisms that have been discussed for tidal dissipation in
stars and giant planets in both linear and nonlinear regimes. I also compare
the expectations based on theoretical models with recent observational
findings.",1406.2207v1
2018-08-28,Theory of chiral $p$-wave superconductivity with near-nodes for Sr$_2$RuO$_4$,"We use functional renormalization group method to study a three-orbital model
for superconducting Sr$_2$RuO$_4$. Although the pairing symmetry is found to be
chiral $p$-wave, the atomic spin-orbit coupling induces near-nodes for
quasiparticle excitations. Our theory explains a major experimental puzzle
between $d$-wave-like feature observed in thermal experiments and the chiral
$p$-wave triplet pairing revealed in nuclear-magnetic-resonance and Kerr
effect.",1808.09210v2
2019-01-19,Calculating the Band Structure of 3C-SiC Using sp3d5s*+$Δ$ Model,"We report on a semi-empirical tight binding model for 3C-SiC including the
effect of sp3d5s* orbitals and spin-orbital coupling. In this work, we
illustrate in detail the method to develop such a model for semiconductors with
zincblende structure, based on Slater-Koster integrals, and we explain the
optimization method used to fit the experimental results with such a model.
This method shows high accuracy for the evaluation of 3C-SiC band diagram both
in terms of the experimental energy levels at high symmetry points and the
effective masses.",1901.06600v1
2017-11-17,Renormalization of the Majorana bound state decay length in a perpendicular magnetic field,"Orbital effects of a magnetic field in a proximitized semiconductor nanowire
are studied in the context of the spatial extent of Majorana bound states. We
develop analytical model that explains the impact of concurring effects of
paramagnetic coupling of the nanowire bands via the kinetic energy operator and
spin-orbit interaction on the Majorana modes. We find, that the perpendicular
field, so far considered as to be detrimental to the Majorana fermion
formation, is in fact helpful in establishing the topological zero-energy-modes
in a finite system due to significant decrease in the Majorana decay length.",1711.06643v3
2021-10-18,Self-consistent Analysis of Doping Effect for Magnetic Ordering in Stacked-Kagome Weyl System,"We theoretically study the carrier doping effect for magnetism in a
stacked-kagome system $\rm{{Co}_3{Sn}_2{S}_2}$ based on an effective model and
the Hartree-Fock method. We show the electron filling and temperature
dependences of the magnetic order parameter. The perpendicular ferromagnetic
ordering is suppressed by hole doping, wheres undoped $\rm{{Co}_3{Sn}_2{S}_2}$
shows magnetic Weyl semimetal state. Additionally, in the electron-doped
regime, we find a non-collinear antiferromagnetic ordering. Especially, in the
non-collinear antiferromagnetic state, by considering a certain spin-orbit
coupling, the finite orbital magnetization and the anomalous Hall conductivity
are obtained.",2110.09459v1
2022-04-24,Engineering Majorana corner modes from two-dimensional hexagonal crystals,"Second order topological insulator can be engineered from two-dimensional
materials with strong spin-orbit coupling and in-plane Zeeman field. In
proximity to superconductor, topological superconducting phase could be induced
in the two-dimensional materials, which host Majorana corner modes at the
intersection between two zigzag edges. Two types of tight binding models in
hexagonal lattice, which include $p_{z}$ or $p_{x,y}$ orbit(s) in each lattice
site, are applied to engineer two-dimensional materials in topological
superconducting phase. In both models, the condition that induces the second
order topological superconductor requires nonuniform value of either in-plane
Zeeman fields or superconductor pairing parameters in two sublattices. The
finite size effect of the second model is weaker than that of the first model.",2204.11178v1
2023-10-08,Role of Centrosymmetry in the Photophysics of Molecular Aggregates,"To understand the photophysics of molecular aggregates, exciton model of J-
and H-aggregate has been extensively utilized. However, it lacks consideration
of crystal symmetry. Although discrete molecules may lack symmetry, their
aggregates can exhibit a high degree of symmetry. Herein, we utilized group
theory to study the optical properties of centrosymmetric molecular aggregates,
showing that their optical selection rules (transition dipole moment and
spin-orbit coupling) are determined by the symmetry of singlet and triplet
excited states and the intermolecular orbital overlap. Symmetry-forbidden
electronic transitions are closely related to ultralong organic
phosphorescence. Our model's scope is broad, as over 50% of organic crystals
belong to centrosymmetric space groups according to Cambridge Structural
Database.",2310.05100v1
2023-12-21,Finite Temperature Minimal Entangled Typical Thermal States Impurity Solver,"We present a minimally entangled typical thermal state (METTS) quantum
impurity solver for general multi-orbital systems at finite temperatures. We
introduce an improved estimator for the single-particle Green's function that
strongly reduces the large fluctuations at long imaginary time and low
temperature, which were a severe limitation of the original algorithm. In
combination with the fork tensor product states ansatz, we obtain a dynamical
mean field theory (DMFT) quantum impurity solver, which we benchmark for single
and three-band models down to low temperatures, including the effect of
spin-orbit coupling in a realistic DMFT computation for the Hund's metal
Sr$_2$RuO$_4$ down to low temperatures.",2312.13668v2
2014-02-28,Single-shot readout and relaxation of singlet/triplet states in exchange-coupled $^{31}$P electron spins in silicon,"We present the experimental observation of a large exchange coupling $J
\approx 300$ $\mu$eV between two $^{31}$P electron spin qubits in silicon. The
singlet and triplet states of the coupled spins are monitored in real time by a
Single-Electron Transistor, which detects ionization from tunnel-rate-dependent
processes in the coupled spin system, yielding single-shot readout fidelities
above 95%. The triplet to singlet relaxation time $T_1 \approx 4$ ms at zero
magnetic field agrees with the theoretical prediction for $J$-coupled $^{31}$P
dimers in silicon. The time evolution of the 2-electron state populations gives
further insight into the valley-orbit eigenstates of the donor dimer, valley
selection rules and relaxation rates, and the role of hyperfine interactions.
These results pave the way to the realization of 2-qubit quantum logic gates
with spins in silicon, and highlight the necessity to adopt gating schemes
compatible with weak $J$-coupling strengths.",1402.7148v3
2016-12-09,Bridging single- and multireference domains for electron correlation: spin-extended coupled electron pair approximation,"We propose a size-consistent generalization of the recently developed
spin-extended configuration interaction with singles and doubles (ECISD), where
a CI wave function is explicitly spin-projected. The size-consistent effect is
effectively incorporated by treating quadruples within the formulation of
coupled electron pair approximation. As in coupled-cluster theory, quadruple
excitations are approximated by a disconnected product of double excitations.
Despite its conceptual similarity to the standard single- and multireference
analogues, such a generalization requires careful derivation, as the
spin-projected CI space is non-orthogonal and overcomplete. Although our
methods generally yield better results than ECISD, size-consistency is only
approximately retained because the action of a symmetry-projection operator is
size-inconsistent. In this work, we focus on simple models where
exclusion-principle-violating terms, which eliminate undesired contributions to
the correlation effects, are either completely neglected or averaged. These
models possess an orbital-invariant energy functional that is to be minimized
by diagonalizing an energy-shifted effective Hamiltonian within the singles and
doubles manifold. This allows for a straightforward generalization of the ECISD
analytical gradients needed to determine molecular properties and geometric
optimization. Given the multireference nature of the spin-projected
Hartree--Fock method, the proposed approaches are expected to handle static
correlation, unlike single-reference analogues. We critically assess the
performance of our methods using dissociation curves of molecules,
singlet-triplet splitting gaps, hyperfine coupling constants, and the chromium
dimer. The size-consistency and size-extensivity of the methods are also
discussed.",1612.02945v2
2022-11-23,"Electronic structure, magnetic properties, spin orientation, and doping effect in Mn$_3$Si$_2$Te$_6$","The layered material Mn$_3$Si$_2$Te$_6$, with alternating stacking honeycomb
and triangular layers, is attracting considerable attention due to its rich
physical properties. Here, using density functional theory and classical Monte
Carlo (MC) methods, we systematically study this system. Near the Fermi level,
the states are mainly contributed by Te $5p$ orbitals hybridized with Mn $3d$
orbitals, resembling a charge transfer system. Furthermore, the spin
orientations of the ferrimagnetic (FiM) ground state display different
conductive behaviors when along the $ab$ plane or out-of-plane directions:
insulating vs. metallic states. The energy difference between the FiM [110]
insulating and FiM [001] metallic phases is very small($ \sim 0.71$ meV/Mn).
Changing the angle $\theta$ of spin orientation from in-plane to out-of-plane
directions, the band gaps of this system are gradually reduced, leading to an
insulator-metal transition, resulting in an enhanced electrical conductivity,
related to the colossal angular magnetoresistance (MR) effect. In addition, we
also constructed the magnetic phase diagram using the classical $XY$ spin model
studied with the MC method. Three magnetic phases were obtained including
antiferromagnetic order, noncollinear spin patterns, and FiM order. Moreover,
we also investigated the Se- and Ge- doping into the Mn$_3$Si$_2$Te$_6$ system:
the FiM state has the lowest energy among the magnetic candidates for both Se-
or Ge- doped cases. The magnetic anisotropy energy (MAE) decreases in the
Se-doped case because the Mn orbital moment is reduced as the doping $x$
increases. Due to the small spin-orbital coupling effect of Se, the
insulator-metal transition caused by the spin orientation disappears in the
Se-doped case, resulting in an insulating phase in the FiM [001] phase. This
causes a reduced colossal angular MR.",2211.13321v2
2014-08-29,Strong-coupling limit of depleted Kondo- and Anderson-lattice models,"Fourth-order strong-coupling degenerate perturbation theory is used to derive
an effective low-energy Hamiltonian for the Kondo-lattice model with a depleted
system of localized spins. In the strong-J limit, completely local Kondo
singlets are formed at the spinful sites which bind a fraction of conduction
electrons. The low-energy theory describes the scattering of the excess
conduction electrons at the Kondo singlets as well as their effective
interactions generated by virtual excitations of the singlets. Besides the
Hubbard term, already discussed by Nozieres, we find a ferromagnetic Heisenberg
interaction, an antiferromagnetic isospin interaction, a correlated hopping
and, in more than one dimensions, three- and four-site interactions. The
interaction term can be cast into highly symmetric and formally simple
spin-only form using the spin of the bonding orbital symmetrically centered
around the Kondo singlet. This spin is non-local. We show that, depending on
the geometry of the depleted lattice, spatial overlap of the non-local spins
around different Kondo singlets may cause ferromagnetic order. This is
sustained by a rigorous argument, applicable to the half-filled model, by a
variational analysis of the stability of the fully polarized Fermi sea of
excess conduction electrons as well as by exact diagonalization of the
effective model. A similar fourth-order perturbative analysis is performed for
the depleted Anderson lattice in the limit of strong hybridization. Even in a
parameter regime where the Schrieffer-Wolff transformation does not apply, this
yields the same effective theory albeit with a different coupling constant.",1408.7018v2
2017-03-01,Quantum-disordered state of magnetic and electric dipoles in a hydrogen-bonded Mott system,"Strongly enhanced quantum fluctuations often lead to a rich variety of
quantum-disordered states. A representative case is liquid helium, in which
zero-point vibrations of the helium atoms prevent its solidification at low
temperatures. A similar behaviour is found for the internal degrees of freedom
in electrons. Among the most prominent is a quantum spin liquid (QSL), in which
localized spins are highly correlated but fluctuate even at absolute zero.
Recently, a coupling of spins with other degrees of freedom has been proposed
as an innovative approach to generate even more fascinating QSLs such as
orbital--spin liquids. However, such ideas are limited to the internal degrees
of freedom in electrons. Here, we demonstrate that a coupling of localized
spins with the zero-point motion of hydrogen atoms (proton fluctuations) in a
hydrogen-bonded organic Mott insulator provides a new class of QSLs. We find
that a divergent dielectric behaviour towards a hydrogen-bond order is
suppressed by the quantum proton fluctuations, resulting in a quantum
paraelectric (QPE) state. Furthermore, our thermal-transport measurements
reveal that a QSL state with gapless spin excitations rapidly emerges upon
entering the QPE state. These findings indicate that the quantum proton
fluctuations give rise to a novel QSL --- a quantum-disordered state of
magnetic and electric dipoles --- through the coupling between the electron and
proton degrees of freedom.",1703.00324v1
2016-08-27,Impact of g-factors and valleys on spin qubits in a silicon double quantum dot,"We define single electron spin qubits in a silicon MOS double quantum dot
system. By mapping the qubit resonance frequency as a function of gate-induced
electric field, the spectrum reveals an anticrossing that is consistent with an
inter-valley spin-orbit coupling. We fit the data from which we extract an
inter-valley coupling strength of 43 MHz. In addition, we observe a narrow
resonance near the primary qubit resonance when we operate the device in the
(1,1) charge configuration. The experimental data is consistent with a
simulation involving two weakly exchanged-coupled spins with a g-factor
difference of 1 MHz, of the same order as the Rabi frequency. We conclude that
the narrow resonance is the result of driven transitions between the T- and T+
triplet states, using an ESR signal of frequency located halfway between the
resonance frequencies of the two individual spins. The findings presented here
offer an alternative method of implementing two-qubit gates, of relevance to
the operation of larger scale spin qubit systems.",1608.07748v2
2019-09-25,Quantum information processing with closely-spaced diamond color centers in strain and magnetic fields,"Electron and nuclear spins of diamond nitrogen-vacancy (NV) centers are good
candidates for quantum information processing as they have long coherence time
and can be initialized and read out optically. However, creating a large number
of coherently coupled and individually addressable NV centers for quantum
computing has been a big challenge. Here we propose methods to use high-density
diamond NV centers coupled by spin-spin interaction with an average separation
on the order of 10 nm for quantum computing. We propose to use a strain
gradient to encode the position information of each NV center in the energy
level of its excited electron orbital state, which causes a shift of its
optical transition frequency. With such strain encoding, more than 100
closely-packed NV centers below optical diffraction limit can be read out
individually by resonant optical excitation. A magnetic gradient will be used
to shift the electron spin resonant (ESR) frequencies of NV centers. Therefore,
the spin state of each NV center can be individually manipulated and different
NV centers can be selectively coupled. A universal set of quantum operations
for two-qubit and three-qubit system is introduced by careful design of
external drives. Moreover, entangled states with multiple qubits can be created
by this protocol, which is a major step towards quantum information processing
with solid-state spins.",1909.11775v1
2022-10-02,"Metal-organic kagome systems as candidates to study spin liquids, spin ice or the quantum anomalous Hall effect","We present the results of first-principle calculations using the Vienna
Ab-initio Simulation Package (VASP) for a new class of organometallics labeled
TM3C6O6 (TM =Sc, Ti, V, Cr, Fe, Co, Ni and Cu) in the form of planar,
two-dimensional, periodic free-standing layers. These materials, which can be
produced by on-surface coordination on metallic surfaces, have a kagome lattice
of TM ions. Calculating the structural properties, we show that all considered
materials have local magnetic moments in the ground state, but four of them
(with Fe, Co, Ni and Cu) show spin-crossover behavior by changing the lattice
constant, which could be valuable for possible epitaxy routes on various
substrates. Surprisingly, we find a very large richness of electronic and
magnetic properties, qualifying these materials as highly promising
metal-organic topological quantum materials. We find semi-conductors with
nearest-neighbor ferromagnetic (FM) or antiferromagnetic (AFM) couplings for V,
and Sc and Cr, respectively, being of potential interest to study spin ice or
spin liquids on the 2D kagome lattice. Other TM ion systems combine AFM
couplings with metallic behavior (Ti, Fe and Ni) or are ferromagnetic kagome
metals like Cu3C6O6 with symmetry protected Weyl crossings at the Fermi
surface. For the latter compound, the spin orbit coupling is shown to be
responsible for small gaps which should allow the observation of the quantum
anomalous Hall effect (QAHE).",2210.00435v2
2021-09-25,"Anomalies in the electronic structure of a 5$d$ transition metal oxide, IrO$_2$","Ir-based materials have drawn much attention due to the observation of
insulating phase believed to be driven by spin-orbit coupling while Ir 5$d$
states are expected to be weakly correlated due to their large orbital
extensions. IrO$_2$, a simple binary material, shows metallic ground state
which seems to deviate from the behavior of most other Ir-based materials and
varied predictions in these material class. We studied the electronic structure
of IrO$_2$ at different temperatures employing high resolution photoemission
spectroscopy with photon energies spanning from ultraviolet to hard $x$-ray
range. Experimental spectra exhibit a signature of enhancement of Ir-O
covalency in the bulk compared to the surface electronic structure. The
branching ratio of the spin-orbit split Ir core level peaks is found to be
larger than its atomic values and it enhances further in the bulk electronic
structure. Such deviation from the atomic description of the core level
spectroscopy manifests the enhancement of the orbital moment due to the solid
state effects. The valence band spectra could be captured well within the
density functional theory. The photon energy dependence of the features in the
valence band spectra and their comparison with the calculated results show
dominant Ir 5$d$ character of the features near the Fermi level; O 2$p$ peaks
appear at higher binding energies. Interestingly, the O 2$p$ contributions of
the feature at the Fermi level is significant and it enhances at low
temperatures. This reveals an orbital selective enhancement of the covalency
with cooling which is an evidence against purely spin-orbit coupling based
scenario proposed for these systems.",2109.12330v1
2011-05-30,Bodily tides near spin-orbit resonances,"Spin-orbit coupling can be described in two approaches. The method known as
""the MacDonald torque"" is often combined with an assumption that the quality
factor Q is frequency-independent. This makes the method inconsistent, because
the MacDonald theory tacitly fixes the rheology by making Q scale as the
inverse tidal frequency.
  Spin-orbit coupling can be treated also in an approach called ""the Darwin
torque"". While this theory is general enough to accommodate an arbitrary
frequency-dependence of Q, this advantage has not yet been exploited in the
literature, where Q is assumed constant or is set to scale as inverse tidal
frequency, the latter assertion making the Darwin torque equivalent to a
corrected version of the MacDonald torque.
  However neither a constant nor an inverse-frequency Q reflect the properties
of realistic mantles and crusts, because the actual frequency-dependence is
more complex. Hence the necessity to enrich the theory of spin-orbit
interaction with the right frequency-dependence. We accomplish this programme
for the Darwin-torque-based model near resonances. We derive the
frequency-dependence of the tidal torque from the first principles, i.e., from
the expression for the mantle's compliance in the time domain. We also explain
that the tidal torque includes not only the secular part, but also an
oscillating part.
  We demonstrate that the lmpq term of the Darwin-Kaula expansion for the tidal
torque smoothly goes through zero, when the secondary traverses the lmpq
resonance (e.g., the principal tidal torque smoothly goes through nil as the
secondary crosses the synchronous orbit).
  We also offer a possible explanation for the unexpected frequency-dependence
of the tidal dissipation rate in the Moon, discovered by LLR.",1105.6086v9
2020-02-13,"Multipolar magnetism in d-orbital systems: Crystal field levels, octupolar order, and orbital loop currents","Quantum magnets with spin $J=2$, which arise in spin-orbit coupled Mott
insulators, can potentially display multipolar orders. We carry out an exact
diagonalization study of a simple octahedral crystal field Hamiltonian for two
electrons, incorporating spin-orbit coupling (SOC) and interactions, finding
that either explicitly including the $e_g$ orbitals, or going beyond the
rotationally invariant Coulomb interaction within the $t_{2g}$ sector, causes a
degeneracy breaking of the $J\!=\!2$ level degeneracy. This can lead to a
low-lying non-Kramers doublet carrying quadrupolar and octupolar moments and an
excited triplet which supports magnetic dipole moments, bolstering our previous
phenomenological proposal for the stabilization of ferro-octupolar order in
heavy transition metal oxides. We show that the spontaneous time-reversal
symmetry breaking due to ferro-octupolar ordering within the non-Kramers
doublet leads to electronic orbital loop currents. The resulting internal
magnetic fields can potentially explain the small fields inferred from
muon-spin relaxation ($\mu$SR) experiments on cubic $5d^2$ osmate double
perovskites Ba$_2$ZnOsO$_6$, Ba$_2$CaOsO$_6$, and Ba$_2$MgOsO$_6$, which were
previously attributed to weak dipolar magnetism. We make further predictions
for oxygen NMR experiments on these materials. We also study the reversed level
scheme, where the $J\!=\!2$ multiplet splits into a low-lying magnetic triplet
and excited non-Kramers doublet, presenting single-ion results for the magnetic
susceptibility in this case, and pointing out its possible relevance for the
rhenate Ba$_2$YReO$_6$. Our work highlights the intimate connection between the
physics of heavy transition metal oxides and that of $f$-electron based heavy
fermion compounds.",2002.05737v2
2023-06-27,Chemical bond analysis for the entire periodic table: Energy Decomposition and Natural Orbitals for Chemical Valence in the Four-Component Relativistic Framework,"Chemical bonding is a ubiquitous concept in chemistry and it provides a
common basis for experimental and theoretical chemists to explain and predict
the structure, stability and reactivity of chemical species. Among others, the
Energy Decomposition Analysis (EDA, also known as the Extended Transition State
method) in combination with Natural Orbitals for Chemical Valence (EDA-NOCV) is
a very powerful tool for the analysis of the chemical bonds based on a charge
and energy decomposition scheme within a common theoretical framework. While
the approach has been applied in a variety of chemical contexts, the current
implementations of the EDA-NOCV scheme include relativistic effects only at
scalar level, so simply neglecting the spin-orbit coupling effects and de facto
limiting its applicability. In this work, we extend the EDA-NOCV method to the
relativistic four-component Dirac-Kohn-Sham theory that variationally accounts
for spin-orbit coupling. Its correctness and numerical stability have been
demonstrated in the case of simple molecular systems, where the relativistic
effects play a negligible role, by comparison with the implementation available
in the ADF modelling suite (using the non-relativistic Hamiltonian and the
scalar ZORA approximation). As an illustrative example we analyse the
metal-ethylene coordination bond in the group 6-element series
(CO)$_5$TM-C$_2$H$_4$, with TM =Cr, Mo, W, Sg, where relativistic effects are
likely to play an increasingly important role as one moves down the group. The
method provides a clear measure (also in combination with the CD analysis) of
the donation and back-donation components in coordination bonds, even when
relativistic effects, including spin-orbit coupling, are crucial for
understanding the chemical bond involving heavy and superheavy atoms.",2306.15386v1
2023-09-20,"Orbit-Spin Coupling, the Solar Dynamo, and the Planetary Theory of Sunspots","Orbit spin coupling is proposed as an alternative to planetary tidal models
for the excitation of solar variability as a function of time. Momentum sourced
from the orbital angular momenta of solar system bodies is deposited within the
circulating fluid envelopes of the Sun and planets in this hypothesis. A
reversing torque acts about an axis lying within the Sun's equatorial plane.
The torque gives rise to tangential differential accelerations of solar
materials as a function of longitude, latitude, depth, and time. The
accelerations pulse in amplitude, and change sign, on timescales corresponding
to the periods, beats, and harmonics of inner and outer planet orbital motions.
In contrast to planetary tidal models, no special amplification mechanism may
be required, as estimated peak accelerations are about 2 orders of magnitude
larger than the largest tidal accelerations. Organized mass motions driven by
the torque may be incorporated in dynamo simulations through the flow velocity
term of the MHD induction equation. The spatiotemporal variability of flow
velocities may then influence the variability with time of solar magnetic
activity. We provide torque values at 1 day timesteps for the years 1660 to
2220. We discuss the time variability of the torque in juxtaposition with SIDC
monthly sunspot numbers from 1750 to present. We investigate Hale cycle
synchronization, and the variability with time of the total solar irradiance,
with reference to outer and inner planet contributions respectively. We propose
a 3 component model for understanding and simulating the solar magnetic cycle,
which includes processes internal to the Sun, external forcing, due to orbit
spin coupling, and a time-delay, or system memory, component. This model
supplies a physical explanation for the observed variability with time of
Schwabe cycle periods and Hale cycle periods from 1712 to present.",2309.13076v1
2009-04-08,First observation of spin-helical Dirac fermions and topological phases in undoped and doped Bi2Te3 demonstrated by spin-ARPES spectroscopy,"Electron systems that possess light-like dispersion relations or the conical
Dirac spectrum, such as graphene and bismuth, have recently been shown to
harbor unusual collective states in high magnetic fields. Such states are
possible because their light-like electrons come in spin pairs that are
chiral,which means that their direction of propagation is tied to a quantity
called pseudospin that describes their location in the crystal lattice. An
emerging direction in quantum materials research is the manipulation of atomic
spin-orbit coupling to simulate the effect of a spin dependent magnetic
field,in attempt to realize novel spin phases of matter. This effect has been
proposed to realize systems consisting of unpaired Dirac cones that are
helical, meaning their direction of propagation is tied to the electron spin
itself, which are forbidden to exist in graphene or bismuth. The experimental
existence of topological order can not be determined without spin-resolved
measurements. Here we report a spin-and angle-resolved photoemission study of
the hexagonal surface of the Bi2Te3 and Bi{2-x}MnxTe3 series, which is found to
exhibit a single helical Dirac cone that is fully spin-polarized. Our
observations of a gap in the bulk spin-degenerate band and a spin-resolved
surface Dirac node close to the chemical potential show that the low energy
dynamics of Bi2Te3 is dominated by the unpaired spin-helical Dirac modes. Our
spin-texture measurements prove the existence of a rare topological phase in
this materials class for the first time, and suggest its suitability for novel
2D Dirac spin device applications beyond the chiral variety or traditional
graphene.",0904.1260v1
2006-09-08,Nonlocal spin Hall effect and spin-orbit interaction in nonmagnetic metals,"Spin Hall effect in a nonlocal spin-injection device is theoretically
studied. Using a nonlocal spin-injection technique, a pure spin current is
created in a nonmagnetic metal (N). The spin current flowing in N is deflected
by spin-orbit scattering to induce the Hall current in the transverse direction
and accumulate charge at the edges of N, yielding the spin-current induced Hall
effect. We propose a method for extracting information for spin-orbit
scattering in nonmagnetic metals.",0609192v1
2016-12-02,Stability of topological properties of bismuth (111) bilayer,"We investigate electronic and transport properties of bismuth (111) bilayer
in the context of stability of its topological properties against different
perturbations. The effects of spin-orbit coupling variations, geometry
relaxation and an interaction with a substrate are considered. Transport
properties are studied in the presence of Anderson disorder. Band structure
calculations are performed within multi-orbital tight-binding model and density
functional theory methods. A band inversion process in bismuth (111) infinite
bilayer and an evolution of edge states dispersion in ribbons as a function of
spin-orbit coupling strength are analyzed. A significant change of orbital
composition of the conduction and valence bands during a topological phase
transition is observed. A topological phase is shown to be robust when the
effect of geometry relaxation is taken into account. An interaction with a
substrate has similar effect to an external perpendicular electric field. The
robust quantized conductance is observed when the Fermi energy lies within the
bulk energy gap, where only two counter-propagating edge states are present.
For energies where the Fermi level crosses more in-gap states, a scattering is
possible between channels lying close in $k-$space. When the energy of edge
states overlaps with bulk states, no topological protection is observed.",1612.00647v2
2020-09-28,Electric field induced topological phase transition and large enhancements of spin-orbit coupling and Curie temperature in two-dimensional ferromagnetic semiconductors,"Tuning topological and magnetic properties of materials by applying an
electric field is widely used in spintronics. In this work, we find a
topological phase transition from topologically trivial to nontrivial states at
an external electric field of about 0.1 V/A in MnBi$_2$Te$_4$ monolayer that is
a topologically trivial ferromagnetic semiconductor. It is shown that when
electric field increases from 0 to 0.15 V/A, the magnetic anisotropy energy
(MAE) increases from about 0.1 to 6.3 meV, and the Curie temperature Tc
increases from 13 to about 61 K. The increased MAE mainly comes from the
enhanced spin-orbit coupling due to the applied electric field. The enhanced Tc
can be understood from the enhanced $p$-$d$ hybridization and decreased energy
difference between $p$ orbitals of Te atoms and $d$ orbitals of Mn atoms.
Moreover, we propose two novel Janus materials MnBi$_2$Se$_2$Te$_2$ and
MnBi$_2$S$_2$Te$_2$ monolayers with different internal electric polarizations,
which can realize quantum anomalous Hall effect (QAHE) with Chern numbers $C$=1
and $C$=2, respectively. Our study not only exposes the electric field induced
exotic properties of MnBi2Te4 monolayer, but also proposes novel materials to
realize QAHE in ferromagnetic Janus semiconductors with electric polarization.",2009.13328v2
2022-09-14,Moiré Engineering and Topological Flat Bands in Twisted Orbital-Active Bilayers,"Topological flat bands at the Fermi level offer a promising platform to study
a variety of intriguing correlated phase of matter. Here we present band
engineering in the twisted orbital-active bilayers with spin-orbit coupling.
The symmetry constraints on the interlayer coupling that determines the
effective potential for low-energy physics of moir\'e electrons are
exhaustively derived for two-dimensional point groups. We find the line graph
or biparticle sublattice of moir\'e pattern emerge with a minimal $C_3$
symmetry, which exhibit isolated electronic flat bands with nontrivial
topology. The band flatness is insensitive to the twist angle since they come
from the interference effect. Armed with this guiding principle, we predict
that twisted bilayers of 2H-PbS$_2$ and CdS realize the salient physics to
engineer two-dimensional topological quantum phases. At small twist angles,
PbS$_2$ heterostructures give rise to an emergent moir\'e Kagom\'e lattice,
while CdS heterostructures lead to an emergent moir\'e honeycomb lattice, and
both of them host moir\'e quantum spin Hall insulators with almost flat
topological bands. We further study superconductivity of these two systems with
local attractive interactions. The superfluid weight and
Berezinskii-Kosterlitz-Thouless temperature are determined by multiband
processes and quantum geometry of the band in the flat-band limit when the
pairing potential exceeds the band width. Our results demonstrate twisted
bilayers with multi-orbitals as a promising tunable platform to realize
correlated topological phases.",2209.06524v1
2023-04-07,Tight-binding model with sublattice-asymmetric spin-orbit coupling for square-net nodal line Dirac semimetals,"We study a 4-orbital tight-binding (TB) model for ZrSiS from the square
sublattice generated by the Si atoms. After studying three other alternatives,
we endow such model with a new effective spin-orbit coupling (SOC) consistent
with {\em ab initio} dispersions around the Fermi energy ($E_F$) in four
systematic steps: (1) We calculate the electronic dispersion of bulk ZrSiS
using an implementation of density-functional theory (DFT) based on numeric
atomic orbitals [{\em J. Phys.: Condens. Matter} {\bf 14}, 2745 (2002)] in
which on-site and off-site SOC can be told apart. As a result, we determine
that local SOC-induced band gaps around $E_F$ are predominantly created by the
on-site contribution. (2) Gradually reducing the atomic basis set size, we then
create an electronic band structure with 16 orbitals per unit cell (u.c.) which
retains the qualitative features of the dispersion around $E_F$, including
SOC-induced band gaps. (3) Zr is the heaviest element on this compound and it
has a non-negligible contribution to the electronic dispersion around $E_F$; we
show that it provides the strongest contribution to the SOC-induced band gap.
(4) Using L\""{o}wdin partitioning approach, we project the effect of SOC onto
the 4-orbital Hamiltonian. This way, we facilitate an effective SOC interaction
that was explicitly informed by {\em ab initio} input.",2304.03438v3
2015-06-27,Theory of the nonlinear Rashba-Edelstein effect,"It is well known that a current driven through a two-dimensional electron gas
with Rashba spin-orbit coupling induces a spin polarization in the
perpendicular direction (Edelstein effect). This phenomenon has been
extensively studied in the linear response regime, i.e., when the average drift
velocity of the electrons is a small fraction of the Fermi velocity. Here we
investigate the phenomenon in the nonlinear regime, meaning that the average
drift velocity is comparable to, or exceeds the Fermi velocity. This regime is
realized when the electric field is very large, or when electron-impurity
scattering is very weak. The quantum kinetic equation for the density matrix of
noninteracting electrons is exactly and analytically solvable, reducing to a
problem of spin dynamics for ""unpaired"" electrons near the Fermi surface. The
crucial parameter is $\gamma=eEL_s/E_F$, where $E$ is the electric field, $e$
is the absolute value of the electron charge, $E_F$ is the Fermi energy, and
$L_s = \hbar/(2m\alpha)$ is the spin-precession length in the Rashba spin-orbit
field with coupling strength $\alpha$. If $\gamma\ll1$ the evolution of the
spin is adiabatic, resulting in a spin polarization that grows monotonically in
time and eventually saturates at the maximum value $n(\alpha/v_F)$, where $n$
is the electron density and $v_F$ is the Fermi velocity. If $\gamma \gg 1$ the
evolution of the spin becomes strongly non-adiabatic and the spin polarization
is progressively reduced, and eventually suppressed for $\gamma\to \infty$. We
also predict an inverse nonlinear Edelstein effect, in which an electric
current is driven by a magnetic field that grows linearly in time. The
""conductivities"" for the direct and the inverse effect satisfy generalized
Onsager reciprocity relations, which reduce to the standard ones in the linear
response regime.",1506.08330v1
2012-01-06,Antiferromagnetic order and domains in Sr3Ir2O7 probed by x-ray resonant scattering,"This article reports a detailed x-ray resonant scattering study of the
bilayer iridate compound, Sr3Ir2O7, at the Ir L2 and L3 edges. Resonant
scattering at the Ir L3 edge has been used to determine that Sr3Ir2O7 is a
long-range ordered antiferromagnet below TN 230K with an ordering wavevector,
q=(1/2,1/2,0). The energy resonance at the L3 edge was found to be a factor of
~30 times larger than that at the L2. This remarkable effect has been seen in
the single layer compound Sr2IrO4 and has been linked to the observation of a
Jeff=1/2 spin-orbit insulator. Our result shows that despite the modified
electronic structure of the bilayer compound, caused by the larger bandwidth,
the effect of strong spin-orbit coupling on the resonant magnetic scattering
persists. Using the programme SARAh, we have determined that the magnetic order
consists of two domains with propagation vectors k1=(1/2,1/2,0) and
k2=(1/2,-1/2,0), respectively. A raster measurement of a focussed x-ray beam
across the surface of the sample yielded images of domains of the order of 100
microns size, with odd and even L components, respectively. Fully relativistic,
monoelectronic calculations (FDMNES), using the Green's function technique for
a muffin-tin potential have been employed to calculate the relative intensities
of the L2,3 edge resonances, comparing the effects of including spin-orbit
coupling and the Hubbard, U, term. A large L3 to L2 edge intensity ratio (~5)
was found for calculations including spin-orbit coupling. Adding the Hubbard,
U, term resulted in changes to the intensity ratio <5%.",1201.1452v1
2012-09-22,Transport across an Anderson quantum dot in the intermediate coupling regime,"We describe linear and nonlinear transport across a single impurity Anderson
model quantum dot with intermediate coupling to the leads, i.e., with tunnel
coupling of the order of the thermal energy k_B T. The coupling is large enough
that sequential tunneling processes alone do not suffice to properly describe
the transport characteristics. Upon applying a density matrix approach, the
current is expressed in terms of rates obtained by considering a very small
class of diagrams which dress the sequential tunneling processes by charge
fluctuations. We call this the ""dressed second order"" (DSO) approximation. One
major achievement of the DSO is that, still in the Coulomb blockade regime, it
can describe the crossover from thermally broadened to tunneling broadened
conductance peaks. When the temperature is decreased even further, the DSO
captures ""Kondesque"" behaviours of the Anderson quantum dot qualitatively: We
find a zero bias anomaly of the differential conductance versus applied bias,
an enhancement of the conductance with decreasing temperature as well as the
onset of universality of the shape of the conductance as function of the
temperature. We can address the case of a spin-degenerate level split
energetically by a magnetic field and show that, if we assume in addition
different capacitive couplings of the two spin-levels to the leads, one of the
resonance peaks is vanishing. In case spin-dependent chemical potentials are
introduced and only one of the four is varied, the DSO yields in principle only
one resonance. This seems to be in agreement with experiments with pseudo-spin.
Furthermore, we get qualitative agreement with experimental data showing a
cross-over from the Kondo to the empty orbital regime.",1209.4995v2
2016-01-25,Duo: a general program for calculating spectra of diatomic molecules,"Duo is a general, user-friendly program for computing rotational,
rovibrational and rovibronic spectra of diatomic molecules. Duo solves the
Schr\""{o}dinger equation for the motion of the nuclei not only for the simple
case of uncoupled, isolated electronic states (typical for the ground state of
closed-shell diatomics) but also for the general case of an arbitrary number
and type of couplings between electronic states (typical for open-shell
diatomics and excited states). Possible couplings include spin-orbit, angular
momenta, spin-rotational and spin-spin. Corrections due to non-adiabatic
effects can be accounted for by introducing the relevant couplings using
so-called Born-Oppenheimer breakdown curves.
  Duo requires user-specified potential energy curves and, if relevant, dipole
moment, coupling and correction curves. From these it computes energy levels,
line positions and line intensities. Several analytic forms plus interpolation
and extrapolation options are available for representation of the curves. Duo
can refine potential energy and coupling curves to best reproduce reference
data such as experimental energy levels or line positions. Duo is provided as a
Fortran 2003 program and has been tested under a variety of operating systems.",1601.06531v2
2018-02-22,Magnetic properties of metal-organic coordination networks based on 3d transition metal atoms,"The magnetic anisotropy and exchange coupling between spins localized at the
positions of 3d transition metal atoms forming two-dimensional metal-organic
coordination networks (MOCNs) grown on the Au(111) metal surface are studied.
In particular, we consider MOCNs made of Ni or Mn metal centers linked by TCNQ
(7,7,8,8-tetracyanoquinodimethane) organic ligands, which form rectangular
networks with 1:1 stoichiometry. Based on the analysis of X-ray magnetic
circular dichroism (XMCD) data taken at T= 2.5 K, we find that Ni atoms in the
Ni-TCNQ MOCNs are coupled ferromagnetically and do not show any significant
magnetic anisotropy, while Mn atoms in the Mn-TCNQ MOCNs are coupled
antiferromagnetically and do show a weak magnetic anisotropy with
in-planemagnetization. We explain these observations using both
amodelHamiltonian based on mean-fieldWeiss theory and density functional theory
calculations that include spin-orbit coupling. Our main conclusion is that the
antiferromagnetic coupling between Mn spins and the in-plane magnetization of
the Mn spins can be explained neglecting effects due to the presence of the
Au(111) surface, while for Ni-TCNQ the metal surface plays a role in
determining the absence of magnetic anisotropy in the system.",1802.08243v1
1999-04-22,Orbital order out of spin disorder: How to measure the orbital gap,"The interplay between spin and orbital degrees of freedom in the Mott-Hubbard
insulator is studied by considering an orbitally degenerate superexchange
model. We argue that orbital order and the orbital excitation gap in this model
are generated through the order-from-disorder mechanism known previously from
frustrated spin models. We propose that the orbital gap should show up
indirectly in the dynamical spin structure factor; it can therefore be measured
using the conventional inelastic neutron scattering method.",9904318v1
2004-02-13,Electrical current noise of a beam splitter as a test of spin-entanglement,"We investigate the spin entanglement in the superconductor-quantum dot system
proposed by Recher, Sukhorukov and Loss, coupling it to an electronic
beam-splitter. The superconductor-quantum dot entangler and the beam-splitter
are treated within a unified framework and the entanglement is detected via
current correlations. The state emitted by the entangler is found to be a
linear superposition of non-local spin-singlets at different energies, a
spin-entangled two-particle wavepacket. Colliding the two electrons in the
beam-splitter, the singlet spin-state gives rise to a bunching behavior,
detectable via the current correlators. The amount of bunching depends on the
relative positions of the single particle levels in the quantum dots and the
scattering amplitudes of the beam-splitter. The singlet spin entanglement,
insensitive to orbital dephasing but suppressed by spin dephasing, is
conveniently quantified via the Fano factors. It is found that the
entanglement-dependent contribution to the Fano factor is of the same magnitude
as the non-entangled, making an experimental detection feasible. A detailed
comparison between the current correlations of the non-local spin-singlet state
and other states, possibly emitted by the entangler, is performed. This
provides conditions for an unambiguous identification of the non-local singlet
spin entanglement.",0402368v2
2006-06-14,Time Reversal Polarization and a Z_2 Adiabatic Spin Pump,"We introduce and analyze a class of one dimensional insulating Hamiltonians
which, when adiabatically varied in an appropriate closed cycle, define a
""$Z_2$ pump"". For an isolated system a single closed cycle of the pump changes
the expectation value of the spin at each end even when spin orbit interactions
violate the conservation of spin. A second cycle, however returns the system to
its original state. When coupled to leads, we show that the $Z_2$ pump
functions as a spin pump in a sense which we define, and transmits a finite,
though non quantized spin in each cycle. We show that the $Z_2$ pump is
characterized by a $Z_2$ topological invariant that is analogous to the Chern
invariant that characterizes a topological charge pump. The $Z_2$ pump is
closely related to the quantum spin Hall effect, which is characterized by a
related $Z_2$ invariant. This work presents an alternative formulation which
clarifies both the physical and mathematical meaning of that invariant. A
crucial role is played by time reversal symmetry, and we introduce the concept
of the time reversal polarization, which characterizes time reversal invariant
Hamiltonians and signals the presence or absence of Kramers degenerate end
states. For non interacting electrons we derive a formula for the time reversal
polarization which is analogous to the Berry's phase formulation of the charge
polarization. For interacting electrons, we show that abelian bosonization
provides a simple formulation of the time reversal polarization. We discuss
implications for the quantum spin Hall effect, and argue in particular that the
$Z_2$ classification of the quantum spin Hall effect is valid in the presence
of electron electron interactions.",0606336v1
2006-08-18,Spin diffusion/transport in $n$-type GaAs quantum wells,"The spin diffusion/transport in $n$-type (001) GaAs quantum well at high
temperatures ($\ge120$ K) is studied by setting up and numerically solving the
kinetic spin Bloch equations together with the Poisson equation
self-consistently. All the scattering, especially the electron-electron Coulomb
scattering, is explicitly included and solved in the theory. This enables us to
study the system far away from the equilibrium, such as the hot-electron effect
induced by the external electric field parallel to the quantum well. We find
that the spin polarization/coherence oscillates along the transport direction
even when there is no external magnetic field. We show that when the scattering
is strong enough, electron spins with different momentums oscillate in the same
phase which leads to equal transversal spin injection length and ensemble
transversal injection length. It is also shown that the intrinsic scattering is
already strong enough for such a phenomena. The oscillation period is almost
independent on the external electric field which is in agreement with the
latest experiment in bulk system at very low temperature [Europhys. Lett. {\bf
75}, 597 (2006)]. The spin relaxation/dephasing along the diffusion/transport
can be well understood by the inhomogeneous broadening, which is caused by the
momentum-dependent diffusion and the spin-orbit coupling, and the scattering.
The scattering, temperature, quantum well width and external magnetic/electric
field dependence of the spin diffusion is studied in detail.",0608413v2
2005-08-16,Transition from inspiral to plunge in precessing binaries of spinning black holes,"We investigate the non-adiabatic dynamics of spinning black hole binaries by
using an analytical Hamiltonian completed with a radiation-reaction force,
containing spin couplings, which matches the known rates of energy and angular
momentum losses on quasi-circular orbits. We consider both a straightforward
post-Newtonian-expanded Hamiltonian (including spin-dependent terms), and a
version of the resummed post-Newtonian Hamiltonian defined by the Effective
One-Body approach. We focus on the influence of spin terms onto the dynamics
and waveforms. We evaluate the energy and angular momentum released during the
final stage of inspiral and plunge. For an equal-mass binary the energy
released between 40Hz and the frequency beyond which our analytical treatment
becomes unreliable is found to be, when using the more reliable Effective
One-Body dynamics: 0.6% M for anti-aligned maximally spinning black holes, 5% M
for aligned maximally spinning black hole, and 1.8% M for non-spinning
configurations. In confirmation of previous results, we find that, for all
binaries considered, the dimensionless rotation parameter J/E^2 is always
smaller than unity at the end of the inspiral, so that a Kerr black hole can
form right after the inspiral phase. By matching a quasi-normal mode ringdown
to the last reliable stages of the plunge, we construct complete waveforms
approximately describing the gravitational wave signal emitted by the entire
process of coalescence of precessing binaries of spinning black holes.",0508067v1
2008-05-20,ADM canonical formalism for gravitating spinning objects,"In general relativity, systems of spinning classical particles are
implemented into the canonical formalism of Arnowitt, Deser, and Misner [1].
The implementation is made with the aid of a symmetric stress-energy tensor and
not a 4-dimensional covariant action functional. The formalism is valid to
terms linear in the single spin variables and up to and including the
next-to-leading order approximation in the gravitational spin-interaction part.
The field-source terms for the spinning particles occurring in the Hamiltonian
are obtained from their expressions in Minkowski space with canonical variables
through 3-dimensional covariant generalizations as well as from a suitable
shift of projections of the curved spacetime stress-energy tensor originally
given within covariant spin supplementary conditions. The applied coordinate
conditions are the generalized isotropic ones introduced by Arnowitt, Deser,
and Misner. As applications, the Hamiltonian of two spinning compact bodies
with next-to-leading order gravitational spin-orbit coupling, recently obtained
by Damour, Jaranowski, and Schaefer [2], is rederived and the derivation of the
next-to-leading order gravitational spin(1)-spin(2) Hamiltonian, shown for the
first time in [3], is presented.",0805.3136v2
2010-04-05,Electron spin relaxation in graphene from a microscopic approach: Role of electron-electron interaction,"Electron spin relaxation in graphene on a substrate is investigated from the
fully microscopic kinetic spin Bloch equation approach. All the relevant
scatterings, such as the electron-impurity, electron--acoustic-phonon,
electron--optical-phonon, electron--remote-interfacial-phonon, as well as
electron-electron Coulomb scatterings, are explicitly included. Our study
concentrates on clean intrinsic graphene, where the spin-orbit coupling from
the adatoms can be neglected. We discuss the effect of the electron-electron
Coulomb interaction on spin relaxation under various conditions. It is shown
that the electron-electron Coulomb scattering plays an important role in spin
relaxation at high temperature. We also find a significant increase of the spin
relaxation time for high spin polarization even at room temperature, which is
due to the Coulomb Hartree-Fock contribution-induced effective longitudinal
magnetic field. It is also discovered that the spin relaxation time increases
with the in-plane electric field due to the hot-electron effect, which is
different from the non-monotonic behavior in semiconductors. Moreover, we show
that the electron-electron Coulomb scattering in graphene is not strong enough
to establish the steady-state hot-electron distribution in the literature and
an alternative approximate one is proposed based on our computation.",1004.0638v2
2010-09-15,Mesoscopic spin Hall effect along a potential step in graphene,"We consider a straight one-dimensional potential step created across a
graphene flake. Charge and spin transport through such a potential step are
studied in the presence of both intrinsic and extrinsic (Rashba) spin-orbit
coupling (SOC). At normal incidence electrons are completely reflected when the
Rashba interaction (with strength $\lambda_R$) is dominant whereas they are
perfectly transmitted if the two types of SOC are exactly balanced. At normal
incidence, the transmission probability of the step is thus controlled
continuously from 0 to 1 by tuning the ratio of the two types of SOC. Besides
the transport of charge in the direction normal to the barrier, we show the
existence of a spin transport along the barrier. The magnitude of the spin Hall
current is determined by a subtle interplay between the height of the potential
step and the position of Fermi energy. It is demonstrated that contributions
from inter-band matrix elements and evanescent modes are dominant in spin
transport. Moreover, in the case of vanishing extrinsic SOC ($\lambda_R =0$),
each channel carries a conserved spin current, in contrast to the general case
of a finite $\lambda_R$, in which only integrated spin current is a conserved
quantity. Finally, we provide a quasi-classical picture of the charge and spin
transport by imaging flow lines over the entire sample and Veselago lensing
(negative refraction) in the case of a $p-n$ junction.",1009.2842v1
2010-12-06,Electric manipulation of electron spin relaxation induced by confined phonons in nanowire-based double quantum dots,"We investigate theoretically the electron spin relaxation in single-electron
nanowire-based semiconductor double quantum dots induced by confined phonons
and find that the electron spin relaxation rate can be efficiently manipulated
by external electric fields in such system. An anti-crossing, due to the
coaction of the electric field, the magnetic field and the spin-orbit coupling,
exists between the lowest two excited states. Both energies and spins of the
electron states can be efficiently tuned by the electric field around the
anti-crossing point. Multiple sharp peaks exist in the electric-field
dependence of the spin relaxation rate induced by the confined phonons, which
can be ascribed to the large density of states of the confined phonons at the
van Hove singularities. This feature suggests that the nanowire-based double
quantum dots can be used as electric tunable on-and-off spin switches, which
are more sensitive and flexible than the ones based on quantum-well based
double quantum dots. The temperature dependence of the spin relaxation rate at
the anti-crossing point are calculated and a smooth peak, indicating the
importance of the contribution of the off-diagonal elements of the density
matrix to the spin relaxation, is observed.",1012.1074v1
2013-01-16,Self-induced inverse spin Hall effect in permalloy at room temperature,"Inverse spin Hall effect (ISHE) allows the conversion of pure spin current
into charge current in nonmagnetic materials (NM) due to spin-orbit interaction
(SOI). In ferromagnetic materials (FM), SOI is known to contribute to anomalous
Hall effect (AHE), anisotropic magnetoresistance (AMR), and other
spin-dependent transport phenomena. However, SOI in FM has been ignored in ISHE
studies in spintronic devices, and the possibility of ""self-induced ISHE"" in FM
has never been explored until now. In this paper, we demonstrate the
experimental verification of ISHE in FM. We found that the spin-pumping-induced
spin current in permalloy (Py) film generates a transverse electromotive force
(EMF) in the film itself, which results from the coupling of spin current and
SOI in Py. The control experiments ruled out spin rectification effect and
anomalous Nernst effect as the origin of the EMF.",1301.3580v5
2014-11-18,Spin transfer torques generated by the anomalous Hall effect and anisotropic magnetoresistance,"Spin-orbit coupling in ferromagnets gives rise to the anomalous Hall effect
and the anisotropic magnetoresistance, both of which can be used to create
spin-transfer torques in a similar manner as the spin Hall effect. In this
paper we show how these effects can be used to reliably switch perpendicularly
magnetized layers and to move domain walls. A drift-diffusion treatment of the
anomalous Hall effect and the anisotropic magnetoresistance describes the spin
currents that flow in directions perpendicular to the electric field. In
systems with two ferromagnetic layers separated by a spacer layer, an in-plane
electric field cause spin currents to be injected from one layer into the
other, creating spin transfer torques. Unlike the related spin Hall effect in
non-magnetic materials, the anomalous Hall effect and the anisotropic
magnetoresistance allow control of the orientation of the injected spins, and
hence torques, by changing the direction of the magnetization in the injecting
layer. The torques on one layer show a rich angular dependence as a function of
the orientation of the magnetization in the other layer. The control of the
torques afforded by changing the orientation of the magnetization in a fixed
layer makes it possible to reliably switch a perpendicularly magnetized free
layer. Our calculated critical current densities for a representative
CoFe/Cu/FePt structure show that the switching can be efficient for appropriate
material choices. Similarly, control of the magnetization direction can drive
domain wall motion, as shown for NiFe/Cu/NiFe structures.",1411.4863v1
2015-03-23,Strong mechanical driving of a single electron spin,"Quantum devices for sensing and computing applications require coherent
quantum systems which can be manipulated in a fast and robust way. Such quantum
control is typically achieved using external electric or magnetic fields which
drive the system's orbital or spin degrees of freedom. However, most of these
approaches require complex and unwieldy antenna or gate structures, and with
few exceptions are limited to the regime of weak driving. Here, we present a
novel approach to strongly and coherently drive a single electron spin in the
solid state using internal strain fields in an integrated quantum device.
Specifically, we study individual Nitrogen-Vacancy (NV) spins embedded in
diamond mechanical oscillators and exploit the intrinsic strain coupling
between spin and oscillator to strongly drive the spins. As hallmarks of the
strong driving regime, we directly observe the energy spectrum of the emerging
phonon-dressed states and employ our strong, continuous driving for enhancement
of the NV spin coherence time. Our results constitute a first step towards
strain-driven, integrated quantum devices and open new perspectives to
investigate unexplored regimes of strongly driven multi-level systems and to
study exotic spin dynamics in hybrid spin-oscillator devices.",1503.06793v1
2015-04-03,Out-of-Plane Spin-Orientation Dependent Magnetotransport Properties in the Anisotropic Helimagnet Cr$_{1/3}$NbS$_2$,"Understanding the role of spin-orbit coupling (SOC) has been crucial to
controlling magnetic anisotropy in magnetic multilayer films. It has been shown
that electronic structure can be altered via interface SOC by varying the
superlattice structure, resulting in spontaneous magnetization perpendicular or
parallel to the plane. In lieu of magnetic thin films, we study the similarly
anisotropic helimagnet Cr$_{1/3}$NbS$_2$, where the spin polarization
direction, controlled by the applied magnetic field, can modify the electronic
structure. As a result, the direction of spin polarization can modulate the
density of states, and in turn affect the in-plane electrical conductivity. In
Cr$_{1/3}$NbS$_2$, we found an enhancement of in-plane conductivity when the
spin polarization is out-of-plane, as compared to in-plane spin polarization.
This is consistent with the increase of density of states near the Fermi energy
at the same spin configuration, found from first principles calculations. We
also observe unusual field dependence of the Hall signal in the same
temperature range. This is unlikely to originate from the non-collinear spin
texture, but rather further indicates strong dependence of electronic structure
on spin orientation relative to the plane.",1504.00916v1
2014-03-25,Kondo screening of spin-charge separated fluxons by a helical liquid,"The insertion of a magnetic $\pi$ flux into a quantum spin Hall insulator
creates four localized, spin-charge separated states: the charge and spin
fluxons with either charge $Q=\pm1$ or spin $S_z=\pm1/2$, respectively. In the
presence of repulsive Coulomb interactions, the charged states are gapped out
and a local moment is formed. We consider the Kane-Mele-Hubbard model on a
ribbon with zigzag edges to construct an impurity model where the spin fluxon
is screened by the helical edge liquid. In the noninteracting model, the
hybridization between fluxon and edge states is dominated by the extent of the
latter. It becomes larger with increasing spin-orbit coupling $\lambda$ but
only has nonzero values for even distances between the $\pi$ flux and the edge.
For the interacting system, we use the continuous-time quantum Monte Carlo
method, which we have extended by global susceptibility measurements to
reproduce the characteristic Curie law of the spin fluxon. However, due to the
finite extent of the fluxons, the local moment is formed at rather low
energies. The screening of the spin fluxon leads to deviations from the Curie
law that follow the universal behavior obtained from a data collapse.
Additionally, the Kondo resonance arises in the local spectral function between
the two low-lying Hubbard peaks.",1403.6372v2
2013-09-23,Zinc Oxide - From Dilute Magnetic Doping to Spin Transport,"During the past years there has been renewed interest in the wide-bandgap
II-VI semiconductor ZnO, triggered by promising prospects for spintronic
applications. First, ferromagnetism was predicted for dilute magnetic doping.
In comprehensive investigation of ZnO:Co thin films based on the combined
measurement of macroscopic and microscopic properties, we find no evidence for
carrier-mediated itinerant ferromagnetism. Phase-pure, crystallographically
excellent ZnO:Co is uniformly paramagnetic. Superparamagnetism arises when
phase separation or defect formation occurs, due to nanometer-sized metallic
precipitates. Other compounds like ZnO:(Li,Ni) and ZnO:Cu do not exhibit
indication of ferromagnetism.
  Second, its small spin-orbit coupling and correspondingly large spin
coherence length makes ZnO suitable for transporting or manipulating spins in
spintronic devices. From optical pump/optical probe experiments, we find a spin
dephasing time of the order of 15 ns at low temperatures which we attribute to
electrons bound to Al donors. In all-electrical magnetotransport measurements,
we successfully create and detect a spin-polarized ensemble of electrons and
transport this spin information across several nanometers. We derive a spin
lifetime of 2.6 ns for these itinerant spins at low temperatures, corresponding
well to results from an electrical pump/optical probe experiment.",1309.5857v1
2017-12-14,Interaction Approach to Anomalous Spin Texture in Warped Topological Insulators,"Interactions between the surface and the bulk in a strong topological
insulator (TI) cause a finite lifetime of the topological surface states (TSS)
as shown by the recent experiments. On the other hand, interactions also induce
unitary processes, which, in the presence of anisotropy and the spin-orbit
coupling (SOC), can induce non-trivial effects on the spin texture. Recently,
such effects were observed experimentally in the $Bi_2X_3$ family, raising the
question that the hexagonal warping (HW) may be linked with new spin-related
anomalies. The most remarkable among which is the 6-fold periodic canting of
the in-plane spin vector. Here, we show that, this anomaly is the result of a
{\it triple cooperation between the interactions, the SOC and the HW}. To
demonstrate it, we formulate the spin-off-diagonal self energy. A unitary phase
with an even symmetry develops in the latter and modulates the spin-1/2 vortex
when the Fermi surface is anisotropic. When the anisotropy is provided by the
HW, a 6-fold in-plane spin-canting is observed. Our theory suggests that the
spin-canting anomaly in $Bi_2X_3$ is a strong evidence of the interactions.
High precision analysis of the spin-texture is a promising support for further
understanding of the interactions in TIs.",1712.05140v3
2019-07-30,Universal spin diffusion length in polycrystalline graphene,"Graphene grown by chemical vapor deposition (CVD) is the most promising
material for industrial-scale applications based on graphene monolayers. It
also holds promise for spintronics; despite being polycrystalline, spin
transport in CVD graphene has been measured over lengths up to 30 $\mu$m, which
is on par with the best measurements made in single-crystal graphene. These
results suggest that grain boundaries (GBs) in CVD graphene, while impeding
charge transport, may have little effect on spin transport. However, to date
very little is known about the true impact of disordered networks of GBs on
spin relaxation. Here, by using first-principles simulations, we derive an
effective tight-binding model of graphene GBs in the presence of spin-orbit
coupling (SOC), which we then use to evaluate spin transport in realistic
morphologies of polycrystalline graphene. The spin diffusion length is found to
be independent of the grain size, and is determined only by the strength of the
substrate-induced SOC. This result is consistent with the D'yakonov-Perel'
mechanism of spin relaxation in the diffusive regime, but we find that it also
holds in the presence of quantum interference. These results clarify the role
played by GBs and demonstrate that the average grain size does not dictate the
upper limit for spin transport in CVD-grown graphene, a result of fundamental
importance for optimizing large-scale graphene-based spintronic devices.",1907.12761v2
2020-01-11,Materials design of Kitaev spin liquids beyond the Jackeli-Khaliullin mechanism,"The Kitaev spin liquid provides a rare example of well-established quantum
spin liquids in more than one dimension. It is obtained as the exact ground
state of the Kitaev spin model with bond-dependent anisotropic interactions.
The peculiar interactions can be yielded by the synergy of spin-orbit coupling
and electron correlations for specific electron configuration and lattice
geometry, which is known as the Jackeli-Khaliullin mechanism. Based on this
mechanism, there has been a fierce race for the materialization of the Kitaev
spin liquid over the last decade, but the candidates have been still limited
mostly to $4d$- and $5d$-electron compounds including cations with the low-spin
$d^5$ electron configuration, such as Ir$^{4+}$ and Ru$^{3+}$. Here we discuss
recent efforts to extend the material perspective beyond the Jackeli-Khaliullin
mechanism, by carefully reexamining the two requisites, formation of the
$j_{\rm eff}=1/2$ doublet and quantum interference between the exchange
processes, for not only $d$- but also $f$-electron systems. We present three
examples: the systems including Co$^{2+}$ and Ni$^{3+}$ with the high-spin
$d^7$ electron configuration, Pr$^{4+}$ with the $f^1$-electron configuration,
and polar asymmetry in the lattice structure. In particular, the latter two are
intriguing since they may realize the antiferromagnetic Kitaev interactions, in
contrast to the ferromagnetic ones in the existing candidates. This partial
overview would stimulate further material exploration of the Kitaev spin
liquids and its topological properties due to fractional excitations.",2001.03731v2
2012-05-11,Optical effects of spin currents in semiconductors,"A spin current has novel linear and second-order nonlinear optical effects
due to its symmetry properties. With the symmetry analysis and the eight-band
microscopic calculation we have systematically investigated the interaction
between a spin current and a polarized light beam (or the ""photon spin
current"") in direct-gap semiconductors. This interaction is rooted in the
intrinsic spin-orbit coupling in valence bands and does not rely on the Rashba
or Dresselhaus effect. The light-spin current interaction results in an optical
birefringence effect of the spin current. The symmetry analysis indicates that
in a semiconductor with inversion symmetry, the linear birefringence effect
vanishes and only the circular birefringence effect exists. The circular
birefringence effect is similar to the Faraday rotation in magneto-optics but
involves no net magnetization nor breaking the time-reversal symmetry.
Moreover, a spin current can induce the second-order nonlinear optical
processes due to the inversion-symmetry breaking. These findings form a basis
of measuring a pure spin current where and when it flows with the standard
optical spectroscopy, which may provide a toolbox to explore a wealth of
physics connecting the spintronics and photonics.",1205.2592v1
2018-03-07,Magnetoresistance in Hybrid Pt/CoFe2O4 Bilayers Controlled by Competing Spin Accumulation and Interfacial Chemical Reconstruction,"Pure spin currents hold promises for an energy-friendlier spintronics. They
can be generated by a flow of charge along a non-magnetic metal having a large
spin-orbit coupling. It produces a spin accumulation at its surfaces,
controllable by the magnetization of an adjacent ferromagnetic layer.
Paramagnetic metals typically used are close to a ferromagnetic instability and
thus magnetic proximity effects can contribute to the observed
angular-dependent magnetoresistance (ADMR). As interface phenomena govern the
spin conductance across the metal/ferromagnetic-insulator heterostructures,
unraveling these distinct contributions is pivotal to full understanding of
spin current conductance. We report here x-ray absorption and magnetic circular
dichroism (XMCD) at Pt-M and (Co,Fe)-L absorption edges and atomically-resolved
energy loss electron spectroscopy (EELS) data of Pt/CoFe2O4 bilayers where
CoFe2O4 layers have been capped by Pt grown at different temperatures. It turns
out that the ADMR differs dramatically, being either dominated by spin Hall
magnetoresistance (SMR) associated to spin Hall effect or anisotropic
magnetoresistance (AMR). The XMCD and EELS data indicate that the Pt layer
grown at room temperature does not display any magnetic moment, whereas when
grown at higher temperature it is magnetic due to interfacial Pt-(Co,Fe)
alloying. These results allow disentangling spin accumulation from interfacial
chemical reconstructions and for tailoring the angular dependent
magnetoresistance.",1803.02611v1
2018-06-25,Spin relaxation due to the D'yakonov-Perel' mechanism in 2D semiconductors with an elliptic band structure,"D'yakonov-Perel' (DP) mechanism describes the dynamics of non-equilibrium
spin distribution in a two-dimensional (2D) system in the presence of Rashba
spin-orbit coupling. In this paper, we study the anisotropy of spin relaxation
via the DP mechanism for a 2D semiconductor with an elliptic band structure.
Within the effective-mass approximation, the low-energy band structure is
described using anisotropic in-plane effective mass of free carriers. Spin
relaxation time of free carriers is calculated theoretically using the time
evolution equation of the density matrix of a polarized spin ensemble in the
strong momentum scattering regime. Results are obtained for scattering
potential due to both Coulomb interaction and neutral defects in the sample. We
show that the ratio of spin relaxation time in the y- and x-direction within
the 2D plane displays a power-law dependence on the effective mass ratio, while
the exponent captures the details of the scattering potential. The model is
applied to study electron spin relaxation in monolayer black phosphorus, which
is known to exhibit significant band structure ellipticity. The model can also
predict spin relaxation anisotropy in mechanically strained 2D materials in
which elliptic band structure emerges as a consequence of the modification of
the lattice constants.",1806.09488v3
2019-02-10,Unconventional anomalous Hall effect in 3d/5d multilayers mediated by the nonlocal spin-conductivity,"We evidenced unconventionnal Anomalous Hall Effects (AHE) in 3d/5d
(Co0.2nm/Ni0.6nm)N multilayers grown on a thin Pt layer or thin Au:W alloy. The
inversion observed on AHE originates from the opposite sign of the spin-orbit
coupling of Pt compared to Ni. Via advanced simulations methods for the
description of the spin-current profiles based on the spin-dependent Boltzmann
formalism, we extracted the spin Hall angle (SHA) of Pt and (Co/Ni) as well as
the relevant transport parameters. The extracted SHA for Pt, +20%, is opposite
to the one of (Co/Ni), giving rise to an effective AHE inversion for thin
(Co/Ni) multilayers (N < 17). The spin Hall angle in Pt is found to be larger
than the one previously measured in combined spin-pumping inverse spin-Hall
effect experiments in a geometry of current perpendicular to plane. Whereas
magnetic proximity effects cannot explain the effect, spin-current leakage and
anisotropic electron scattering at Pt/(Co,Ni) interfaces fit the experiments.",1902.03564v2
2020-08-29,Unveiling the polarity of the spin-to-charge current conversion in $Bi_2Se_3$,"We report an investigation of the spin- to charge-current conversion in
sputter-deposited films of topological insulator $Bi_2Se_{3}$ onto single
crystalline layers of YIG $(Y_{3}Fe_{5}O_{12})$ and polycrystalline films of
Permalloy $(Py = Ni_{81}Fe_{19})$. Pure spin current was injected into the
$Bi_{2}Se_{3}$ layer by means of the spin pumping process in which the spin
precession is obtained by exciting the ferromagnetic resonance of the
ferromagnetic film. The spin-current to charge-current conversion, occurring at
the $Bi_{2}Se_{3}/$ferromagnet interface, was attribute to the inverse
Rashba-Edelstein effect (IREE). By analyzing the data as a function of the
$Bi_{2}Se_{3}$ thickness we calculated the IREE length used to characterize the
efficiency of the conversion process and found that 1.2 pm
$\leq|{\lambda}_{IREE}|\leq$ 2.2 pm. These results support the fact that the
surface states of $Bi_{2}Se_{3}$ have a dominant role in the spin-charge
conversion process, and the mechanism based on the spin diffusion process plays
a secondary role. We also discovered that the spin- to charge-current mechanism
in $Bi_{2}Se_{3}$ has the same polarity as the one in Ta, which is the opposite
to the one in Pt. The combination of the magnetic properties of YIG and Py,
with strong spin-orbit coupling and dissipationless surface states
topologically protected of $Bi_{2}Se_{3}$ might lead to spintronic devices with
fast and efficient spin-charge conversion.",2008.12900v1
2020-10-16,Complete polarization of electronic spins in OLEDs,"At low temperatures and high magnetic fields, electron and hole spins in an
organic light-emitting diode (OLED) become polarized so that recombination
preferentially forms molecular triplet excited-state species. For low device
currents, magnetoelectroluminescence (MEL) perfectly follows Boltzmann
activation, implying a virtually complete polarization outcome. As the current
increases, the MEL effect is reduced because spin polarization is suppressed by
the reduction in carrier residence time within the device. Under these
conditions, an additional field-dependent process affecting the spin-dependent
recombination emerges, which appears to relate to the build-up of triplet
excitons and the interaction with free charge carriers. Suppression of the EL
at high fields on its own does not, strictly, prove electronic spin
polarization. We therefore probe changes in the spin statistics of
recombination directly in a dual singlettriplet emitting OLED, which shows a
concomitant rise in phosphorescence intensity as fluorescence is suppressed.
Finite spin-orbit coupling in these materials gives rise to a microscopic
distribution in effective g factors of electrons and holes, $\Delta g$, i.e. a
distribution in Larmor frequencies, leading to singlet-triplet mixing within
the electronhole pair as a function of applied field. This $\Delta g$ effect in
the pair further suppresses singlet-exciton formation in addition to thermal
spin polarization of the individual carriers. Since the $\Delta g$ process
involves weakly bound carrier pairs rather than free electrons and holes, in
contrast to thermal spin polarization, the effect does not depend significantly
on current or temperature.",2010.08313v1
2017-11-02,Theory of Large Intrinsic Spin Hall Effect in Iridate Semimetals,"We theoretically investigate the mechanism to generate large intrinsic spin
Hall effect in iridates or more broadly in 5d transition metal oxides with
strong spin-orbit coupling. We demonstrate such a possibility by taking the
example of orthorhombic perovskite iridate with nonsymmorphic lattice symmetry,
SrIrO$_3$, which is a three-dimensional semimetal with nodal line spectrum. It
is shown that large intrinsic spin Hall effect arises in this system via the
spin-Berry curvature originating from the nearly degenerate electronic spectra
surrounding the nodal line. This effect exists even when the nodal line is
gently gapped out, due to the persistent nearly degenerate electronic
structure, suggesting a distinct robustness. The magnitude of the spin Hall
conductivity is shown to be comparable to the best known example such as doped
topological insulators and the biggest in any transition metal oxides. To gain
further insight, we compute the intrinsic spin Hall conductivity in both of the
bulk and thin film systems. We find that the geometric confinement in thin
films leads to significant modifications of the electronic states, leading to
even bigger spin Hall conductivity in certain cases. We compare our findings
with the recent experimental report on the discovery of large spin Hall effect
in SrIrO$_3$ thin films.",1711.00861v1
2018-10-09,Coherent spin dynamics of electrons and holes in CsPbBr$_3$ perovskite crystals,"The lead halide perovskites demonstrate huge potential for optoelectronic
applications, high energy radiation detectors, light emitting devices and solar
energy harvesting. Those materials exhibit strong spin-orbit coupling enabling
efficient optical orientation of carrier spins in perovskite-based devices with
performance controlled by a magnetic field. Perovskites are promising for
spintronics due to substantial bulk and structure inversion asymmetry, however,
their spin properties are not studied in detail. Here we show that elaborated
time-resolved spectroscopy involving strong magnetic fields can be successfully
used for perovskites. We perform a comprehensive study of high-quality
CsPbBr$_3$ crystals by measuring the exciton and charge carrier $g$-factors,
spin relaxation times and hyperfine interaction of carrier and nuclear spins by
means of coherent spin dynamics. Owing to their ""inverted"" band structure,
perovskites represent appealing model systems for semiconductor spintronics
exploiting the valence band hole spins, while in conventional semiconductors
the conduction band electrons are considered for spin functionality.",1810.04081v1
2019-05-01,Competing orders in pyrochlore magnets from a $\mathbb{Z}_2$ spin liquid perspective,"The pyrochlore materials have long been predicted to harbor a quantum spin
liquid, an intrinsic long-range-entangled state supporting fractionalized
excitations. Existing pyrochlore experiments, on the other hand, have
discovered several weakly ordered states and a tendency of close competition
amongst them. Motivated by these facts, we give a complete classification of
spin-orbit-coupled $\mathbb{Z}_2$ spin-liquid states on the pyrochlore lattice
by using the projective symmetry group (PSG) approach for bosonic spinons. For
each spin liquid, we construct a mean-field Hamiltonian that can be used to
describe phase transitions out of the spin liquid via spinon condensation.
Studying these phase transitions, we establish phase diagrams for our
mean-field Hamiltonians that link magnetic orders to specific spin liquids. In
general, we find that seemingly unrelated magnetic orders are intertwined with
each other and that the conventional spin orders seen in the experiments are
accompanied by more exotic hidden orders. Our critical theories are categorized
into $z=1$ and $z=2$ types, based on their spinon dispersion and Hamiltonian
diagonalizability, and are shown to give distinct signatures in the heat
capacity and the spin structure factor. This study provides a clear map of
pyrochlore phases for future experiments and variational Monte Carlo studies in
pyrochlore materials.",1905.00460v2
2021-06-01,Quantum control of the tin-vacancy spin qubit in diamond,"Group-IV color centers in diamond are a promising light-matter interface for
quantum networking devices. The negatively charged tin-vacancy center (SnV) is
particularly interesting, as its large spin-orbit coupling offers strong
protection against phonon dephasing and robust cyclicity of its optical
transitions towards spin-photon entanglement schemes. Here, we demonstrate
multi-axis coherent control of the SnV spin qubit via an all-optical stimulated
Raman drive between the ground and excited states. We use coherent population
trapping and optically driven electronic spin resonance to confirm coherent
access to the qubit at 1.7 K, and obtain spin Rabi oscillations at a rate of
$\Omega/2\pi$=3.6(1) MHz. All-optical Ramsey interferometry reveals a spin
dephasing time of $T_2^*$=1.3(3)$\mu$s and two-pulse dynamical decoupling
already extends the spin coherence time to $T_2$=0.33(14) ms. Combined with
transform-limited photons and integration into photonic nanostructures, our
results make the SnV a competitive spin-photon building block for quantum
networks.",2106.00723v1
2021-06-08,Observation of the out-of-plane polarized spin current from CVD grown WTe2,"Weyl semimetal Td-phase WTe2 possesses the spin-resolved band structure with
strong spin-orbit coupling, holding promises as a useful spin source material.
The noncentrosymmetric crystalline structure of Td-WTe2 endows the generation
of the out-of-plane polarized spin, which is of great interest in magnetic
memory applications. Previously, WTe2 was explored in spin devices based on
mechanically exfoliated single crystal flakes with a size of micrometers. For
practical spintronics applications, it is highly desirable to implement
wafer-scale thin films. In this work, we utilize centimeter-scale chemical
vapor deposition (CVD)-grown Td-WTe2 thin films and study the spin current
generation by the spin torque ferromagnetic resonance technique. We find the
in-plane and out-of-plane spin conductivities of 7.36 x 10^3 (h/2e) (ohm-m)^-1
and 1.76 x 10^3 (h/2e) (ohm-m)^-1, respectively, in CVD-growth 5 nm-WTe2. We
further demonstrate the current-induced magnetization switching in WTe2/NiFe at
room temperature in the domain wall motion regime, which may invigorate
potential spintronic device innovations based on Weyl semimetals.",2106.04154v1
2021-10-25,Spin relaxation in a single-electron graphene quantum dot,"The relaxation time of a single-electron spin is an important parameter for
solid-state spin qubits, as it directly limits the lifetime of the encoded
information. Thanks to the low spin-orbit interaction and low hyperfine
coupling, graphene and bilayer graphene (BLG) have long been considered
promising platforms for spin qubits. Only recently, it has become possible to
control single-electrons in BLG quantum dots (QDs) and to understand their
spin-valley texture, while the relaxation dynamics have remained mostly
unexplored. Here, we report spin relaxation times ($T_1$) of single-electron
states in BLG QDs. Using pulsed-gate spectroscopy, we extract relaxation times
exceeding 200 $\mu$s at a magnetic field of 1.9 T. The $T_1$ values show a
strong dependence on the spin splitting, promising even longer $T_1$ at lower
magnetic fields, where our measurements are limited by the signal-to-noise
ratio. The relaxation times are more than two orders of magnitude larger than
those previously reported for carbon-based QDs, suggesting that graphene is a
potentially promising host material for scalable spin qubits.",2110.13051v3
2021-11-18,Spin transport at finite temperatures: A first-principles study for ferromagnetic$|$nonmagnetic interfaces,"Symmetry lowering at an interface leads to an enhancement of the effect of
spin-orbit coupling and to a discontinuity of spin currents passing through the
interface. This discontinuity is characterized by a ""spin-memory loss"" (SML)
parameter $\delta$ that has only been determined directly at low temperatures.
Although $\delta$ is believed to be significant in experiments involving
interfaces between ferromagnetic and nonmagnetic metals, especially heavy
metals like Pt, it is more often than not neglected to avoid introducing too
many unknown interface parameters in addition to often poorly known bulk
parameters like the spin-flip diffusion length $l_{\rm sf}$. In this work, we
calculate $\delta$ along with the interface resistance $AR_{\rm I}$ and the
spin-asymmetry parameter $\gamma$ as a function of temperature for Co$|$Pt and
Py$|$Pt interfaces where Py is the ferromagnetic Ni$_{80}$Fe$_{20}$ alloy,
permalloy. We use first-principles scattering theory to calculate the
conductance as well as local charge and spin currents, modeling
temperature-induced disorder with frozen thermal lattice and, for ferromagnetic
materials, spin disorder within the adiabatic approximation. The bulk and
interface parameters are extracted from the spin currents using a Valet-Fert
model generalized to include SML.",2111.09731v1
2022-04-13,Non-local spin entanglement in a fermionic chain,"An effective two-spin density matrix (TSDM) for a pair of spin-$1/2$ degree
of freedom, residing at a distance of $R$ in a spinful Fermi sea, can be
obtained from the two-electron density matrix following the framework
prescribed in Phys. Rev. A 69, 054305 (2004). We note that the single spin
density matrix (SSDM) obtained from this TSDM for generic spin-degenerate
systems of free fermions is always pinned to the maximally mixed state $i.e.$
$(1/2) \ \mathbb{I}$, independent of the distance $R$ while the TSDM confirms
to the form for the set of maximally entangled mixed state (the so called
""X-state"") at finite $R$. The X-state reduces to a pure state (a singlet) in
the $R\rightarrow 0$ limit while it saturates to an X-state with largest
allowed value of von-Neumann entropy of $2 \ln2$ as $R \rightarrow \infty$
independent of the value of chemical potential. However, once an external
magnetic field is applied to lift the spin-degeneracy, we find that the
von-Neumann entropy of SSDM becomes a function of the distance $R$ between the
two spins. We also show that the von-Neumann entropy of TSDM in the
$R\rightarrow \infty$ limit becomes a function of the chemical potential and it
saturate to $2 \ln2$ only when the band in completely filled unlike the
spin-degenerate case. Finally we extend our study to include spin-orbit
coupling and show that it does effect these asymptotic results. Our findings
are in sharp contrast with previous works which were based on continuum models
owing to physics which stem from the lattice model.",2204.06579v1
2022-07-15,Spin-split collinear antiferromagnets: a large-scale ab-initio study,"It was recently discovered that, depending on their symmetries, collinear
antiferromagnets can actually break the spin degeneracy in momentum space, even
in the absence of spin-orbit coupling. Such systems, recently dubbed
altermagnets, are signalled by the emergence of a spin-momentum texture set
mainly by the crystal and magnetic structure, relativistic effects playing a
secondary role. Here we consider all collinear $q$=0 antiferromagnetic
compounds in the MAGNDATA database allowing for spin-split bands. Based on
density-functional calculations for the experimentally reported crystal and
magnetic structures, we study more than sixty compounds and introduce numerical
measures for the average momentum-space spin splitting. We highlight some
compounds that are of particular interest, either due to a relatively large
spin splitting, such as CoF$_2$ and FeSO$_4$F, or because of their low-energy
electronic structure. The latter include LiFe$_2$F$_6$, which hosts nearly flat
spin-split bands next to the Fermi energy, as well as RuO$_2$, CrNb$_4$S$_8$,
and CrSb, which are spin-split antiferromagnetic metals.",2207.07592v2
2022-11-01,Spin-polarization anisotropy included by mechanical bending in tungsten diselenide nanoribbons and tunable excitonic states,"A WSe$_2$ monolayer shows many interesting properties due to its spin-orbit
coupling induced spin splitting in bands around the Fermi level and the
spin-valley configuration. The orientation of the spin polarization in the
relevant bands is crucial for the nature of exciton states and the optical
valley selectivity. In this work, we studied the WSe$_2$ nanoribbons under
different mechanical bending curvatures and electron/hole doping with density
functional theory and their optical absorption and excitonic states with
many-body perturbation GW and BSE (Bethe-Salpeter equation) methods. We found
that the WSe$_2$ nanoribbons can exhibit an enhanced SOC effect and a spatially
varying spin polarization in bands around the Fermi level under bending. The
spin-polarization can show an anisotropy (or asymmetry) in those nearly
degenerate bands, leading to a controllable magnetism via bending and
electron/hole doping to the nanoribbons, suggesting a potential application in
compact and controllable magnetic nanodevices and spintronics. The optical
absorption spectrum of the nanoribbon presents a large tunability with bending
within the near infrared region of about 0.4 to 1.5 eV, showing an enhanced
absorption at a large bending condition. The exciton states generally show
mixed or various spin configuration in the electron and hole pairs that are
controlled by bending, potentially useful for applications in spin-based
quantum information processes.",2211.00258v1
2022-12-08,"Spin Relaxation, Diffusion and Edelstein Effect in Chiral Metal Surface","We study electron spin transport at spin-splitting surface of
chiral-crystalline-structured metals and Edelstein effect at the interface, by
using the Boltzmann transport equation beyond the relaxation time
approximation. We first define spin relaxation time and spin diffusion length
for two-dimensional systems with anisotropic spin--orbit coupling through the
spectrum of the integral kernel in the collision integral. We then explicitly
take account of the interface between the chiral metal and a nonmagnetic metal
with finite thickness. For this composite system, we derive analytical
expressions for efficiency of the charge current--spin current interconversion
as well as other coefficients found in the Edelstein effect. We also develop
the Onsager's reciprocity in the Edelstein effect along with experiments so
that it relates local input and output, which are respectively defined in the
regions separated by the interface. We finally provide a transfer matrix
corresponding to the Edelstein effect through the interface, with which we can
easily represent the Onsager's reciprocity as well as the charge--spin
conversion efficiencies we have obtained. We confirm the validity of the
Boltzmann transport equation in the present system starting from the Keldysh
formalism in the supplemental material. Our formulation also applies to the
Rashba model and other spin-splitting systems.",2212.04202v2
2023-03-07,Tunability of Andreev levels in a spin-active Ising Superconductor/Half Metal Josephson junction,"We study the Andreev levels, supercurrent and tunnelling conductance in a
clean Ising superconductor (ISC)/half metal (HM)/Ising superconductor (ISC)
Josephson junction with spin-active interfaces using Bogoliubov-de Gennes
equations. We theoretically demonstrate the effect of spin mixing, spin
flipping processes and spin-orbit coupling (SOC) of the ISC on Andreev Bound
States (ABS) spectra, current phase relation (CPR) and tunnelling conductance
in transparent and opaque barrier limit. We witness an additional splitting of
the Andreev levels due to SOC of the ISC and $0 - \pi$ transition for different
barrier magnetic moments. Also, different $\phi$ - junctions can be achieved by
tuning the strength of the barrier magnetic moment and spin mismatch angle.
Moreover, a possible $0 - \pi$ transition can also be achieved for SOC stronger
than the chemical potential of the ISC using suitable control parameters. The
interplay of spin mixing and spin flipping processes with SOC can also host
Majorana modes in the proposed system. The tunnelling conductance is found to
be dependent on the spin mismatch angle. Also, a finite sub-gap conductance is
observed, which indicates different probabilities of Andreev reflected
electrons and holes in the presence of SOC. Furthermore, anomalous Andreev
levels are observed for different HM length scales signifying its role in the
tunability of the $\phi$ - phase Josephson junction.",2303.03784v1
2023-07-12,Spintronics in 2D graphene-based van der Waals heterostructures,"Spintronics has become a broad and important research field that intersects
with magnetism, nano-electronics, and materials science. Its overarching aim is
to provide a fundamental understanding of spin-dependent phenomena in
solid-state systems that can enable a new generation of spin-based logic
devices. Over the past decade, graphene and related 2D van der Waals crystals
have taken center stage in expanding the scope and potential of spintronic
materials. Their distinctive electronic properties and atomically thin nature
have opened new opportunities to probe and manipulate internal electronic
degrees of freedom. Purely electrical control over conduction-electron spins
can be attained in graphene-transition metal dichalcogenide heterostructures,
due to proximity effects combined with graphene's high electronic mobility.
Specifically, graphene experiences a proximity-induced spin-orbit coupling that
enables efficient spin-charge interconversion processes; the two most
well-known and at the forefront of current research are the spin Hall and
inverse spin galvanic effects, wherein an electrical current yields a spin
current and non-equilibrium spin polarization, respectively. This article
provides an overview of the basic principles, theory, and experimental methods
underpinning the nascent field of 2D material-based spintronics.",2307.06273v1
2023-07-26,Giant spin-charge conversion in ultrathin films of the MnPtSb half-Heusler compound,"Half-metallic half-Heusler compounds with strong spin-orbit-coupling and
broken inversion symmetry in their crystal structure are promising materials
for generating and absorbing spin-currents, thus enabling the electric
manipulation of magnetization in energy-efficient spintronic devices. In this
work, we report the spin-to-charge conversion in sputtered ultrathin films of
the half-Heusler compound MnPtSb with thickness (t) in the range from 1 to 6
nm. A combination of X-ray and transmission electron microscopy measurements
evidence the epitaxial nature of these ultrathin non-centrosymmetric MnPtSb
films, with a clear (111)-orientation obtained on top of (0001) single-crystal
sapphire substrates. The study of the thickness (t)-dependent magnetization
dynamics of the MnPtSb(t)/Co(5nm)/Au(5nm) heterostructure revealed that the
MnPtSb compound can be used as an efficient spin current generator, even at
film thicknesses as low as 1 nm. By making use of spin pumping FMR, we measure
a remarkable t-dependent spin-charge conversion in the MnPtSb layers, which
clearly demonstrate the interfacial origin of the conversion. When interpreted
as arising from the inverse Edelstein effect (IEE), the spin-charge conversion
efficiency extracted at room temperature for the thinnest MnPtSb layer reaches
{\lambda}IEE~3 nm, representing an extremely high spin-charge conversion
efficiency at room temperature. The still never explored ultrathin regime of
the MnPtSb films studied in this work and the discover of their outstanding
functionality are two ingredients which demonstrate the potentiality of such
materials for future applications in spintronics.",2307.14516v1
2023-10-09,Mapping of Spin-Wave Transport in Thulium Iron Garnet Thin Films Using Diamond Quantum Microscopy,"Spin waves, collective dynamic magnetic excitations, offer crucial insights
into magnetic material properties. Rare-earth iron garnets offer an ideal
spin-wave (SW) platform with long propagation length, short wavelength,
gigahertz frequency, and applicability to magnon spintronic platforms. Of
particular interest, thulium iron garnet (TmIG) has attracted a huge interest
recently due to its successful growth down to a few nanometers, observed
topological Hall effect and spin orbit torque-induced switching effects.
However, there is no direct spatial measurement of its SW properties. This work
uses diamond nitrogen vacancy (NV) magnetometry in combination with SW
electrical transmission spectroscopy to study SW transport properties in TmIG
thin films. NV magnetometry allows probing spin waves at the sub-micrometer
scale, seen by the amplification of the local microwave magnetic field due to
the coupling of NV spin qubits with the stray magnetic field produced by the
microwave-excited spin waves. By monitoring the NV spin resonances, the SW
properties in TmIG thin films are measured as function of the applied magnetic
field, including their amplitude, decay length (~ 50 um), and wavelength (0.8 -
2 um). These results pave the way for studying spin qubit-magnon interactions
in rare-earth magnetic insulators, relevant to quantum magnonics applications.",2310.06188v4
2024-03-01,Microwave Control of the Tin-Vacancy Spin Qubit in Diamond with a Superconducting Waveguide,"Group-IV color centers in diamond are promising candidates for quantum
networks due to their dominant zero-phonon line and symmetry-protected optical
transitions that connect to coherent spin levels. The negatively charged
tin-vacancy (SnV) center possesses long electron spin lifetimes due to its
large spin-orbit splitting. However, the magnetic dipole transitions required
for microwave spin control are suppressed, and strain is necessary to enable
these transitions. Recent work has shown spin control of strained emitters
using microwave lines that suffer from Ohmic losses, restricting coherence
through heating. We utilize a superconducting coplanar waveguide to measure SnV
centers subjected to strain, observing substantial improvement. A detailed
analysis of the SnV center electron spin Hamiltonian based on the
angle-dependent splitting of the ground and excited states is performed. We
demonstrate coherent spin manipulation and obtain a Hahn echo coherence time of
up to $T_2 = 430\,\mu$s. With dynamical decoupling, we can prolong coherence to
$T_2 = 10\,$ms, about six-fold improved compared to earlier works. We also
observe a nearby coupling $^{13}\mathrm{C}$ spin which may serve as a quantum
memory. This substantiates the potential of SnV centers in diamond and
demonstrates the benefit of superconducting microwave structures.",2403.00521v1
2013-05-14,How to construct the proper gauge-invariant density matrix in steady-state nonequilibrium: Applications to spin-transfer and spin-orbit torques,"Experiments observing spin density and spin currents (responsible for, e.g.,
spin-transfer torque) in spintronic devices measure only the nonequilibrium
contributions to these quantities, typically driven by injecting unpolarized
charge current or by applying external time-dependent fields. On the other
hand, theoretical approaches to calculate them operate with both the
nonequilibrium (carried by electrons around the Fermi surface) and the
equilibrium (carried by the Fermi sea electrons) contributions. Thus, an
unambiguous procedure should remove the equilibrium contributions, thereby
rendering the nonequilibrium ones which are measurable and satisfy the
gauge-invariant condition according to which expectation values of physical
quantities should not change when electric potential everywhere is shifted by a
constant amount. Using the framework of nonequilibrium Green functions, we
delineate such procedure which yields the proper gauge-invariant nonequilibrium
density matrix in the linear-response and elastic transport regime for
current-carrying steady state of an open quantum system connected to two
macroscopic reservoirs. Its usage is illustrated by computing: (i) conventional
spin-transfer torque (STT) in asymmetric F/I/F magnetic tunnel junctions
(MTJs); (ii) unconventional STT in asymmetric N/I/F semi-MTJs with the strong
Rashba spin-orbit coupling (SOC) at the I/F interface and injected current
perpendicular to that plane; and (iii) current-driven spin density within a
clean ferromagnetic Rashba spin-split two-dimensional electron gas (2DEG) which
generates SO torque in laterally patterned N/F/I heterostructures when such
2DEG is located at the N/F interface and injected charge current flows parallel
to the plane.",1305.3180v2
2005-07-04,Tight-Binding model for semiconductor nanostructures,"An empirical $s_cp^3_a$ tight-binding (TB) model is applied to the
investigation of electronic states in semiconductor quantum dots. A basis set
of three $p$-orbitals at the anions and one $s$-orbital at the cations is
chosen. Matrix elements up to the second nearest neighbors and the spin-orbit
coupling are included in our TB-model. The parametrization is chosen so that
the effective masses, the spin-orbit-splitting and the gap energy of the bulk
CdSe and ZnSe are reproduced. Within this reduced $s_cp_a^3$ TB-basis the
valence (p-) bands are excellently reproduced and the conduction (s-) band is
well reproduced close to the $\Gamma$-point, i.e. near to the band gap. In
terms of this model much larger systems can be described than within a (more
realistic) $sp^3s^*$-basis. The quantum dot is modelled by using the (bulk)
TB-parameters for the particular material at those sites occupied by atoms of
this material. Within this TB-model we study pyramidal-shaped CdSe quantum dots
embedded in a ZnSe matrix and free spherical CdSe quantum dots (nanocrystals).
Strain-effects are included by using an appropriate model strain field. Within
the TB-model, the strain-effects can be artifically switched off to investigate
the infuence of strain on the bound electronic states and, in particular, their
spatial orientation. The theoretical results for spherical nanocrystals are
compared with data from tunneling spectroscopy and optical experiments.
Furthermore the influence of the spin-orbit coupling is investigated.",0507052v1
2011-01-27,Global analysis of data on the spin-orbit coupled $A^{1}Σ_{u}^{+}$ and $b^{3}Π_{u}$ states of Cs2,"We present experimentally derived potential curves and spin-orbit interaction
functions for the strongly perturbed $A^{1}\Sigma_{u}^{+}$ and $b^{3}\Pi_{u}$
states of the cesium dimer. The results are based on data from several sources.
Laser-induced fluorescence Fourier transform spectroscopy (LIF FTS) was used
some time ago in the Laboratoire Aim\'{e} Cotton primarily to study the $X
^{1}\Sigma_{g}^{+}$ state. More recent work at Tsinghua University provides
information from moderate resolution spectroscopy on the lowest levels of the
$b^{3}\Pi_{0u}^{\pm}$ states as well as additional high resolution data. From
Innsbruck University, we have precision data obtained with cold Cs$_{2}$
molecules. Recent data from Temple University was obtained using the
optical-optical double resonance polarization spectroscopy technique, and
finally, a group at the University of Latvia has added additional LIF FTS data.
In the Hamiltonian matrix, we have used analytic potentials (the Expanded Morse
Oscillator form) with both finite-difference (FD) coupled-channels and discrete
variable representation (DVR) calculations of the term values. Fitted diagonal
and off-diagonal spin-orbit functions are obtained and compared with {\it ab
initio} results from Temple and Moscow State universities.",1101.5412v1
2011-11-30,Semimetal and Topological Insulator in Perovskite Iridates,"The two-dimensional layered perovskite Sr2IrO4 was proposed to be a
spin-orbit Mott insulator, where the effect of Hubbard interaction is amplified
on a narrow J_{eff} = 1/2 band due to strong spin-orbit coupling. On the other
hand, the three-dimensional orthorhombic perovskite (Pbnm) SrIrO3 remains
metallic. To understand the physical origin of the metallic state and possible
transitions to insulating phases, we construct a tight-binding model for
SrIrO3. The band structure possesses a line node made of J_{eff} = 1/2 bands
below the Fermi level. As a consequence, instability towards magnetic ordering
is suppressed and the system remains metallic. This line node, originating from
the underlying crystal structure, turns into a pair of three-dimensional nodal
points on the introduction of a staggered potential or spin-orbit coupling
strength between alternating layers. Increasing this potential beyond a
critical strength induces a transition to a strong topological insulator,
followed by another transition to a normal band insulator. We propose that
materials constructed with alternating Ir- and Rh-oxide layers along the (001)
direction, such as Sr2IrRhO6, are candidates for a strong topological
insulator.",1112.0015v2
2012-06-25,Interplay between spin-orbit coupling and Hubbard interaction in SrIrO3 and related Pbnm perovskites,"There has been a rapidly growing interest on the interplay between spin-orbit
coupling (SOC) and Hubbard interaction U in correlated materials. A current
consensus is that the stronger the SOC, the smaller is the critical interaction
Uc required for a spin-orbit Mott insulator, because the atomic SOC splits a
band into different total angular momentum bands narrowing the effective
bandwidth. It was further claimed that at large enough SOC, the stronger the
SOC, the weaker the Uc because in general the effective SOC is enhanced with
increasing electron-electron interaction strength. Contrary to this
expectation, we find that, in orthorhombic perovskite oxides (Pbnm), the
stronger the SOC, the bigger the Uc. This is originated from a line of Dirac
node in Jeff=1/2 bands near the Fermi level inherited from a combination of the
lattice structure and a large SOC. Due to this protected line of nodes, there
are small hole and electron pockets in SrIrO3, and such a small density of
states makes Hubbard interaction less efficient in building a magnetic
insulator. The full phase diagram in U vs. SOC is obtained, where non-magnetic
semimetal, magnetic metal, and magnetic insulator are found. Magnetic ordering
patterns beyond Uc are also presented. We further discuss implications of our
finding in relation to other perovskites such as SrRhO3 and SrRuO3.",1206.5836v2
2013-12-17,Dynamical resonance locking in tidally interacting binary systems,"We examine the dynamics of resonance locking in detached, tidally interacting
binary systems. In a resonance lock, a given stellar or planetary mode is
trapped in a highly resonant state for an extended period of time, during which
the spin and orbital frequencies vary in concert to maintain the resonance.
This phenomenon is qualitatively similar to resonance capture in planetary
dynamics. We show that resonance locks can accelerate the course of tidal
evolution in eccentric systems and also efficiently couple spin and orbital
evolution in circular binaries. Previous analyses of resonance locking have not
treated the mode amplitude as a fully dynamical variable, but rather assumed
the adiabatic (i.e. Lorentzian) approximation valid only in the limit of
relatively strong mode damping. We relax this approximation, analytically
derive conditions under which the fixed point associated with resonance locking
is stable, and further check these analytic results using numerical
integrations of the coupled mode, spin, and orbital evolution equations. These
show that resonance locking can sometimes take the form of complex limit cycles
or even chaotic trajectories. We provide simple analytic formulae that define
the binary and mode parameter regimes in which resonance locks of some kind
occur (stable, limit cycle, or chaotic). We briefly discuss the astrophysical
implications of our results for white dwarf and neutron star binaries as well
as eccentric stellar binaries.",1312.4966v2
2014-12-17,Giant negative magnetoresistance driven by spin-orbit coupling at the LAO/STO interface,"The LAO/STO interface hosts a two-dimensional electron system that is
unusually sensitive to the application of an in-plane magnetic field.
Low-temperature experiments have revealed a giant negative magnetoresistance
(dropping by 70\%), attributed to a magnetic-field induced transition between
interacting phases of conduction electrons with Kondo-screened magnetic
impurities. Here we report on experiments over a broad temperature range,
showing the persistence of the magnetoresistance up to the 20~K range ---
indicative of a single-particle mechanism. Motivated by a striking
correspondence between the temperature and carrier density dependence of our
magnetoresistance measurements we propose an alternative explanation. Working
in the framework of semiclassical Boltzmann transport theory we demonstrate
that the combination of spin-orbit coupling and scattering from finite-range
impurities can explain the observed magnitude of the negative
magnetoresistance, as well as the temperature and electron density dependence.",1412.5614v2
2016-04-20,Spin-orbital coupling effect on power factor in semiconducting transition-metal dichalcogenide monolayers,"The electronic structures and thermoelectric properties of semiconducting
transition-metal dichalcogenide monolayers $\mathrm{MX_2}$ (M=Zr, Hf, Mo, W and
Pt; X=S, Se and Te) are investigated by combining first-principles and
Boltzmann transport theory, including spin-orbital coupling (SOC). It is found
that the gap decrease increases from S to Te in each cation group, when the SOC
is opened. The spin-orbital splitting has the same trend with gap reducing.
Calculated results show that SOC has noteworthy detrimental effect on p-type
power factor, while has a negligible influence in n-type doping except W cation
group, which can be understood by considering the effects of SOC on the valence
and conduction bands. For $\mathrm{WX_2}$ (X=S, Se and Te), the SOC leads to
observably enhanced power factor in n-type doping, which can be explained by
SOC-induced band degeneracy, namely bands converge. Among all cation groups, Pt
cation group shows the highest Seebeck coefficient, which leads to best power
factor, if we assume scattering time is fixed. Calculated results show that
$\mathrm{MS_2}$ (M=Zr, Hf, Mo, W and Pt) have best p-type power factor for all
cation groups, and that $\mathrm{MSe_2}$ (M=Zr and Hf), $\mathrm{WS_2}$ and
$\mathrm{MTe_2}$ (M=Mo and Pt) have more wonderful n-type power factor in
respective cation group. Therefore, these results may be useful for further
theoretical prediction or experimental search of excellent thermoelectric
materials from semiconducting transition-metal dichalcogenide monolayers.",1604.05934v1
2016-06-09,Giant spin-orbit splitting of point defect states in monolayer WS$_2$,"The spin-orbit coupling (SOC) effect has been known to be profound in
monolayer pristine transition metal dichalcogenides (TMDs). Here we show that
point defects, which are omnipresent in the TMD membranes, exhibit even
stronger SOC effects and change the physics of the host materials drastically.
In this Article we chose the representative monolayer WS\sub{2} slabs from the
TMD family together with seven typical types of point defects including
monovacancies, interstitials, and antisites. We calculated the formation
energies of these defects, and studied the effect of spin-orbit coupling (SOC)
on the corresponding defect states. We found that the S monovacancy (V\sub{S} )
and S interstitial (adatom) have the lowest formation energies. In the case of
V\sub{S} and both of the W\sub{S and W\sub{S2} antisites, the defect states
exhibit giant splitting up to 296 meV when SOC is considered. Depending on the
relative position of the defect state with respect to the conduction band
minimum (CBM), the hybrid functional HSE will either increase the splitting by
up to 60 meV (far from CBM), or decrease the splitting by up to 57 meV (close
to CBM). Furthermore, we found that both the W\sub{S} and W\sub{S2} antisites
possess a magnetic moment of 2 $\mu_{B}$ localized at the antisite W atom and
the neighboring W atoms. All these findings provide new insights in the defect
behavior under SOC point to new possibilities for spintronics applications for
TMDs.",1606.02906v1
2016-09-30,Three-dimensional higher-spin Dirac and Weyl dispersions in the strongly isotropic $K_4$ crystal,"We analyze the electronic structure in the three-dimensional (3D) crystal
formed by the $sp^2$ hybridized orbitals ($K_4$ crystal), by the tight-binding
approach based on the first-principles calculation. We discover that the bulk
Dirac-cone dispersions are realized in the $K_4$ crystal. In contrast to the
graphene, the energy dispersions of the Dirac cones are isotropic in 3D and the
pseudospin $S=1$ Dirac cones emerge at the $\Gamma$ and $H$ points of the bcc
Brillouin zone, where three bands become degenerate and merge at a single point
belonging to the $T_2$ irreducible representation. In addition, the usual
$S=1/2$ Dirac cones emerge at the $P$ point. By focusing the hoppings between
the nearest-neighbor sites, we show an analytic form of the tight-binding
Hamiltonian with a $4\times 4 $ matrix, and we give an explicit derivation of
the $S=1$ and $S=1/2$ Dirac-cone dispersions. We also analyze the effect of the
spin-orbit coupling to examine how the degeneracies at Dirac points are lifted.
At the $S=1$ Dirac points, the spin-orbit coupling lifts the energy level with
sixfold degeneracy into two energy levels with two-dimensional $\bar E_2$ and
four-dimensional $\bar F$ representations. Remarkably, all the dispersions near
the $\bar F$ point show the linear dependence in the momentum with different
velocities. We derive the effective Hamiltonian near the $\bar F$ point and
find that the band contact point is described by the $S=3/2$ Weyl point.",1609.09762v2
2018-01-07,High-pressure insulator-to-metal transition in Sr$_3$Ir$_2$O$_7$ studied by x-ray absorption spectroscopy,"High-pressure x-ray absorption spectroscopy was performed at the Ir $L_3$ and
$L_2$ absorption edges of Sr$_3$Ir$_2$O$_7$. The branching ratio of white line
intensities continuously decreases with pressure, reflecting a reduction in the
angular part of the expectation value of the spin-orbit coupling operator,
$\left\langle {\bf L} \cdot {\bf S} \right\rangle$. Up to the high-pressure
structural transition at 53 GPa, this behavior can be explained within a
single-ion model, where pressure increases the strength of the cubic crystal
field, which suppresses the spin-orbit induced hybridization of $J_{\text{eff}}
= 3/2$ and $e_g$ levels. We observe a further reduction of the branching ratio
above the structural transition, which cannot be explained within a single-ion
model of spin-orbit coupling and cubic crystal fields. This change in
$\left\langle {\bf L} \cdot {\bf S} \right\rangle$ in the high-pressure,
metallic phase of Sr$_3$Ir$_2$O$_7$ could arise from non-cubic crystal fields
or a bandwidth-driven hybridization of $J_{\text{eff}}=1/2,\,3/2$ states, and
suggests that the electronic ground state significantly deviates from the
$J_{\text{eff}}=1/2$ limit.",1801.02234v1
2019-03-06,Spin and orbital ordering in TlMnO3: Neutron diffraction study,"Crystal and magnetic structures of the high-pressure stabilized perovskite
phase of TlMnO3 have been studied by neutron powder diffraction. The crystal
structure involves two types of primary structural distortions:
a+b-b-octahedral tilting and antiferrodistortive type of orbital ordering,
whose common action reduces the symmetry down to triclinic P -1. The orbital
pattern and the way it is combined with the octahedral tilting are different
from the family of LnMnO3 (Ln = lanthanide or Y) manganites who share with
TlMnO3 the same tilting scheme. The experimentally determined magnetic
structure with the k = (1/2,0,1/2) propagation vector and P_S-1 symmetry
implies anisotropic exchange interactions with a ferromagnetic coupling within
the (1,0,-1) planes and an antiferromagnetic one between them (A type). The
spins in the primary magnetic mode were found to be confined close to the
(1,0,-1) plane, which underlines the predominant role of the single ion
anisotropy with the local easy axes of Mn3+ following the Jahn-Teller
distortions of the octahedra. In spite of the same octahedral tilting scheme in
the perovskite structures of both LnMnO3 and TlMnO3 manganites, a coupling of
the secondary ferromagnetic component to the primary A-type spin configuration
through antisymmetric exchange interaction is allowed in the former and
forbidden in the latter cases.",1903.02347v1
2020-08-04,Strong-field physics in three-dimensional topological insulators,"We investigate theoretically the strong-field regime of light-matter
interactions in the topological-insulator class of quantum materials. In
particular, we focus on the process of non-perturbative high-order harmonic
generation from the paradigmatic three-dimensional topological insulator
bismuth selenide (Bi$_2$Se$_3$) subjected to intense mid-infrared laser fields.
We analyze the contributions from the spin-orbit-coupled bulk states and the
topological surface bands separately and reveal a major difference in how their
harmonic yields depend on the ellipticity of the laser field. Bulk harmonics
show a monotonous decrease in their yield as the ellipticity increases, in a
manner reminiscent of high harmonic generation in gaseous media. However, the
surface contribution exhibits a highly non-trivial dependence, culminating with
a maximum for circularly polarized fields. We attribute the observed anomalous
behaviour to: (i) the enhanced amplitude and the circular pattern of the
interband dipole and the Berry connections in the vicinity of the Dirac point;
and (ii) the influence of the higher-order, ""hexagonal warping"" terms in the
Hamiltonian, which are responsible for the hexagonal deformation of the energy
surface at higher momenta. The latter are associated directly with
spin-orbit-coupling parameters. Our results thus establish the sensitivity of
strong-field driven high harmonic emission to the topology of the band
structure as well as to the manifestations of spin-orbit interaction.",2008.01265v1
2020-11-16,"Interplay of electron correlations, spin-orbit couplings, and structural effects for Cu centers in the quasi-two-dimensional magnet InCu$_{2/3}$V$_{1/3}$O$_3$","Less common ligand coordination of transition-metal centers is often
associated with peculiar valence-shell electron configurations and outstanding
physical properties. One example is the Fe$^+$ ion with linear coordination,
actively investigated in the research area of single-molecule magnetism. Here
we address the nature of 3$d^9$ states for Cu$^{2+}$ ions sitting in the center
of trigonal bipyramidal ligand cages in the quasi-two-dimensional honeycomb
compound InCu$_{2/3}$V$_{1/3}$O$_3$, whose unusual magnetic properties were
intensively studied in the recent past. In particular, we discuss the interplay
of structural effects, electron correlations, and spin-orbit couplings in this
material. A relevant computational finding is a different sequence of the Cu
($xz$, $yz$) and ($xy$, $x^2\!-\!y^2$) levels as compared to existing
electronic-structure models, which has implications for the interpretation of
various excitation spectra. Spin-orbit interactions, both first- and
second-order, turn out to be stronger than previously assumed, suggesting that
rather rich single-ion magnetic properties can be in principle achieved also
for the 3$d^9$ configuration by properly adjusting the sequence of
crystal-field states for such less usual ligand coordination.",2011.08246v1
2016-12-07,Dielectric properties of graphene on transition metal dichalcogenide substrate,"The tunability of the dielectric properties induced by the substrate driven
interactions (SDI) and the exchange field (M) due to the ferro-magnetic
impurities in graphene monolayer on transition metal dichalcogenide (TMDC)
(viz., XY2 , X = Mo, W; Y = S, Se) around K and K prime points is reported
here. The cavalcade of interactions involve sub-lattice-resolved, strongly
enhanced intrinsic spin-orbit couplings(SOC), the extrinsic Rashba spin-orbit
coupling (RSOC), and the orbital gap related to the transfer of the electronic
charge from graphene to XY2. The RSOC allows for external tuning of the band
gap in graphene and connects the nearest neighbors with spin-flip. We obtain
the usual gapped bands with an effective, RSOC-dependent Zeeman field due to
the interplay of SDI. Using these bands we obtain the closed analytical
expression of the dielectric function in the finite doping case. The zero of
the dielectric function corresponds to the collective mode. Upon including the
full dispersion of graphene on TMDC, we find that there is in fact only one
collective mode and it corresponds to charge plasmons. The dispersion of the
latter yields the q^2/3 behavior and not the well known q^1/2 behavior. We also
find that the plasmon frequency could be changed by the tuning of the chemical
potential.",1612.02359v2
2020-06-21,"Crystal Structure, Magnetism, and Electronic Properties of New Rare-Earth-Free Ferromagnetic MnPt5As","The design and synthesis of targeted functional materials have been a
long-term goal for material scientists. Although a universal design strategy is
difficult to generate for all types of materials, however, it is still helpful
for a typical family of materials to have such design rules. Herein, we
incorporated several significant chemical and physical factors regarding
magnetism, such as structure type, atom distance, spin-orbit coupling, and
successfully synthesized a new rare-earth-free ferromagnet, MnPt5As, for the
first time. MnPt5As can be prepared by using high-temperature pellet methods.
According to X-ray diffraction results, MnPt5As crystallizes in a tetragonal
unit cell with the space group P4/mmm (Pearson symbol tP7). Magnetic
measurements on MnPt5As confirm ferromagnetism in this phase with a Curie
temperature of ~301 K and a saturated moment of 3.5 uB per formula. Evaluation
by applying the Stoner Criterion also indicates that MnPt5As is susceptible to
ferromagnetism. Electronic structure calculations using the WIEN2k program with
local spin density approximation imply that the spontaneous magnetization of
this phase arises primarily from the hybridization of d orbitals on both Mn and
Pt atoms. The theoretical assessments are consistent with the experimental
results. Moreover, the spin-orbit coupling effects heavily influence on
magnetic moments in MnPt5As. MnPt5As is the first high-performance magnetic
material in this structure type. The discovery of MnPt5As offers a platform to
study the interplay between magnetism and structure.",2006.11897v1
2020-09-10,Fractionalized fermionic quantum criticality in spin-orbital Mott insulators,"We study transitions between topological phases featuring emergent
fractionalized excitations in two-dimensional models for Mott insulators with
spin and orbital degrees of freedom. The models realize fermionic quantum
critical points in fractionalized Gross-Neveu$^\ast$ universality classes in
(2+1) dimensions. They are characterized by the same set of critical exponents
as their ordinary Gross-Neveu counterparts, but feature a different energy
spectrum, reflecting the nontrivial topology of the adjacent phases. We
exemplify this in a square-lattice model, for which an exact mapping to a
$t$-$V$ model of spinless fermions allows us to make use of large-scale
numerical results, as well as in a honeycomb-lattice model, for which we employ
$\epsilon$-expansion and large-$N$ methods to estimate the critical behavior.
Our results are potentially relevant for Mott insulators with $d^1$ electronic
configurations and strong spin-orbit coupling, or for twisted bilayer
structures of Kitaev materials.",2009.05051v3
2021-09-08,Relativistic first principles theory of Yu--Shiba--Rusinov states applied to an Mn adatom and Mn dimers on Nb(110),"We present a fully relativistic first principles based theoretical approach
for the calculation of the spectral properties of magnetic impurities on the
surface of a superconducting substrate, providing a material specific framework
for the investigation of the Yu--Shiba--Rusinov (YSR) states. By using a
suitable orbital decomposition of the local densities of states we discuss in
great details the formation of the YSR states for an Mn adatom and for two
kinds of Mn dimers placed on the Nb(110) surface and compare our results to
recent experimental findings. In case of the adatom we find that the spin-orbit
coupling slightly shifts some of the YSR peaks and also the local
spin-polarization on the Nb atoms have marginal effects to the their positions.
Moreover, by scaling the exchange field on the Mn site we could explain the
lack of the $d_{x^2-y^2}$-like YSR state in the spectrum. While our results for
a close packed ferromagnetic dimer are in satisfactory agreement with the
experimentally observed splitting of the YSR states, in case of an
antiferromagnetic dimer we find that the spin-orbit coupling is not
sufficiently large to explain the splitting of the YSR states seen in the
experiment. Changing the relative orientation of the magnetic moments in this
dimer induces splitting of the YSR states and also shifts their energy, leading
even to the formation of a zero bias peak in case of the deepest YSR state.",2109.03499v1
2022-04-16,Unique electronic state in ferromagnetic semiconductor FeCl$_{2}$ monolayer,"Two-dimensional (2D) van der Waals (vdW) magnetic materials could be an ideal
platform for ultracompact spintronic applications. Among them, FeCl$_{2}$
monolayer in the triangular lattice is subject to a strong debate. Thus, we
critically examine its spin-orbital state, electronic structure, and magnetic
properties, using a set of delicate first-principles calculations, crystal
field level analyses, and Monte Carlo simulations. Our work reveals that
FeCl$_{2}$ monolayer is a ferromagnetic (FM) semiconductor in which the
electron correlation of the narrow Fe $3d$ bands determines the band gap of
about 1.2 eV. Note that only when the spin-orbit coupling (SOC) is properly
handled, the unique $d$$^{5\uparrow}$$l$$^\downarrow_{z+}$ electronic ground
state is achieved. Then, both the orbital and spin contributions (0.59
$\mu_{\rm B}$ plus 3.56 $\mu_{\rm B}$) to the total magnetic moment well
account for, for the first time, the experimental perpendicular moment of 4.3
$\mu_{\rm B}$/Fe. Moreover, we find that a compressive strain further
stabilizes the $d$$^{5\uparrow}$$l$$^\downarrow_{z+}$ ground state, and that
the enhanced magnetic anisotropy and exchange coupling would boost the Curie
temperature ($T_{\rm C}$) from 25 K for the pristine FeCl$_{2}$ monolayer to
69-102 K under 3$\%$-5$\%$ compressive strain. Therefore, FeCl$_{2}$ monolayer
is indeed an appealing 2D FM semiconductor.",2204.07755v2
2023-06-11,"Strain and spin orbit coupling effects on electronic and optical properties of 2D CX/graphene (X = S, Se, Te) vdW heterostructure for solar energy harvesting","Vertically stacked two-dimensional (2D) graphene-based van der Waals (vdW)
heterostructures have emerged as the technological materials for electronic and
optoelectronic device applications. In this regard, for the first time, we
systematically predicted the electronic and optical properties of CX/G (X = S,
Se and Te; G = graphene) heterostructures under biaxial strain and spin orbit
coupling (SOC) by first-principles calculations. Strain is induced by applying
mechanical stress to the heterostructures, while SOC arises due to the
interaction between the electron spin and its orbital motion. The electronic
property calculations reveal that all three heterostructures exhibit indirect
semiconducting nature with a narrow bandgap of 0.47-0.62 eV and remain indirect
under compressive and tensile strains. Strong band splitting of 78.4 meV has
been observed in the conduction band edge of CTe/G heterostructure in the
presence of SOC due to the lack of an inversion center attributed to the large
hole effective mass. Under compressive strain, the p-type of Schottky contact
of CX/G heterostructures is converted into p-type Ohmic contact because of
nearly negligible Schottky barrier height. Further, the optical property
assessment reveals red and blue shifts in the absorption peak of CX/G
heterostructures with regard to tensile and compressive strains, respectively.
Despite this, the CTe/G heterostructure achieves a remarkable high {\eta} of
24.53% in the strain-free case whereas, it reaches to 28.31% with 4%
compressive strain, demonstrating the potential for solar energy conversion
device applications. Our findings suggest that CX/G heterostructures could be
promising candidates for high-performance optoelectronic devices.",2306.06690v1
2023-10-27,Emergent spin-glass state in the doped Hund's metal CsFe2As2,"Hund's metal is one kind of correlated metal, in which the electronic
correlation is strongly influenced by the Hund's interaction. At high
temperatures, while the charge and orbital degrees of freedom are quenched, the
spin degrees of freedom can persist in terms of frozen moments. As temperature
decreases, a coherent electronic state with characteristic orbital
differentiation always emerges at low temperatures through an
incoherent-to-coherent crossover, which has been widely observed in iron-based
superconductors (e.g., iron selenides and AFe2As2 (A = K, Rb, Cs)).
Consequently, the above frozen moments are ""screened"" by coupling to orbital
degrees of freedom, leading to an emergent Fermi-liquid state. In contrast, the
coupling among frozen moments should impede the formation of the Fermi-liquid
state by competitive magnetic ordering, which is still unexplored in Hund's
metal. Here, in the iron-based Hund's metal CsFe2As2, we adopt a chemical
substitution at iron sites by Cr/Co atoms to explore the competitive magnetic
ordering. By a comprehensive study of resistivity, magnetic susceptibility,
specific heat and nuclear magnetic resonance, we demonstrate that the
Fermi-liquid state is destroyed in Cr-doped CsFe2As2 by a spinfreezing
transition below T_g ~ 22 K. Meanwhile, the evolution of charge degrees of
freedom measured by angle-resolved photoemission spectroscopy also supports the
competition between the Fermi-liquid state and spin-glass state.",2310.17858v1
2010-08-04,Sympathetic cooling of the Ba$^+$ ion by collisions with ultracold Rb atoms: theoretical prospects,"State-of-the-art {\em ab initio} techniques have been applied to compute the
potential energy curves of the (BaRb)$^+$ molecular ion in the Born-Oppenheimer
approximation. The long-range coefficients describing the electrostatic,
induction, and dispersion interactions at large interatomic distances are also
reported. The electric transition dipole moments governing the X$^1\Sigma \to
^1\Sigma, ^1\Pi$ have been obtained as the first residue of the polarization
propagator computed with the linear response coupled-cluster method restricted
to single and double excitations. Nonadiabatic radial and angular coupling
matrix elements, as well as the spin-orbit coupling matrix elements have been
evaluated using the multireference configuration interaction method restricted
to single and double excitations with a large active space. With these
couplings, the spin-orbit coupled (relativistic) potential energy curves for
the 0$^+$ and 1 states relevant for the running experiments have been obtained.
Finally, relativistic transition moments and nonadiabatic coupling matrix
elements were obtained from the nonrelativistic results and spin-orbit
eigenvectors. The electronic structure input has been employed in the single
channel scattering calculations of the collisional cross sections between the
Ba$^+$ ion and Rb atom. Both nonrelativistic and relativistic potentials were
used in these calculations. Our results show that the inelastic cross section
corresponding to the charge transfer from the Rb atom to the Ba$^+$ ion is much
smaller than the elastic one over a wide range of energies up to 1 mK. This
suggests that sympathetic cooling of the Ba$^+$ ion by collisions with
ultracold Rb atoms should be possible.",1008.0840v2
2007-07-20,Diamagnetism of doped two-leg ladders and probing the nature of their commensurate phases,"We study the magnetic orbital effect of a doped two-leg ladder in the
presence of a magnetic field component perpendicular to the ladder plane.
Combining both low-energy approach (bosonization) and numerical simulations
(density-matrix renormalization group) on the strong coupling limit (t-J
model), a rich phase diagram is established as a function of hole doping and
magnetic flux. Above a critical flux, the spin gap is destroyed and a Luttinger
liquid phase is stabilized. Above a second critical flux, a reentrance of the
spin gap at high magnetic flux is found. Interestingly, the phase transitions
are associated with a change of sign of the orbital susceptibility. Focusing on
the small magnetic field regime, the spin-gapped superconducting phase is
robust but immediately acquires algebraic transverse (i.e. along rungs) current
correlations which are commensurate with the 4k_F density correlations. In
addition, we have computed the zero-field orbital susceptibility for a large
range of doping and interactions ratio J/t : we found strong anomalies at low
J/t only in the vicinity of the commensurate fillings corresponding to delta =
1/4 and 1/2. Furthermore, the behavior of the orbital susceptibility reveals
that the nature of these insulating phases is different: while for delta = 1/4
a 4k_F charge density wave is confirmed, the delta = 1/2 phase is shown to be a
bond order wave.",0707.3017v3
2010-07-12,Magnetic order in orbital models of the iron pnictides,"We examine the appearance of the experimentally-observed stripe
spin-density-wave magnetic order in five different orbital models of the iron
pnictide parent compounds. A restricted mean-field ansatz is used to determine
the magnetic phase diagram of each model. Using the random phase approximation,
we then check this phase diagram by evaluating the static spin susceptibility
in the paramagnetic state close to the mean-field phase boundaries. The momenta
for which the susceptibility is peaked indicate in an unbiased way the actual
ordering vector of the nearby mean-field state. The dominant orbitally resolved
contributions to the spin susceptibility are also examined to determine the
origin of the magnetic instability. We find that the observed stripe magnetic
order is possible in four of the models, but it is extremely sensitive to the
degree of the nesting between the electron and hole Fermi pockets. In the more
realistic five-orbital models, this order competes with a strong-coupling
incommensurate state which appears to be controlled by details of the
electronic structure below the Fermi energy. We conclude by discussing the
implications of our work for the origin of the magnetic order in the pnictides.",1007.1949v2
2017-08-04,Direct experimental observation of the molecular Jeff=3/2 ground state in the lacunar spinel GaTa4Se8,"Strong spin-orbit coupling lifts the degeneracy of t2g orbitals in 5d
transition-metal systems, leaving a Kramers doublet and quartet with effective
angular momentum of Jeff = 1/2 and 3/2, respectively. These spin-orbit
entangled states can host exotic quantum phases such as topological Mott state,
unconventional superconductivity, and quantum spin liquid. The lacunar spinel
GaTa4Se8 was theoretically predicted to form the molecular Jeff = 3/2 ground
state. Experimental verification of its existence is an important first step to
exploring the consequences of the Jeff = 3/2 state. Here, we report direct
experimental evidence of the Jeff = 3/2 state in GaTa4Se8 by means of
excitation spectra of resonant inelastic x-rays scattering at the Ta L3 and L2
edges. We found that the excitations involving the Jeff = 1/2 molecular orbital
were suppressed only at the Ta L2 edge, manifesting the realization of the
molecular Jeff = 3/2 ground state in GaTa4Se8.",1708.01416v2
2017-04-28,Confinement-driven electronic and topological phases in corundum-derived $3d$-oxide honeycomb lattices,"Using density functional theory calculations including an on-site Coulomb
term, we explore electronic and possibly topologically nontrivial phases in
$3d$ transition metal oxide honeycomb layers confined in the corundum structure
($\alpha$-Al$_2$O$_3$) along the [0001] direction. In most cases the ground
state is a trivial antiferromagnetic Mott insulator, often with distinct
orbital or spin states compared to the bulk phases. With imposed symmetry of
the two sublattices the ferromagnetic phases of Ti, Mn, Co and Ni exhibit a
characteristic set of four bands, two relatively flat and two with a Dirac
crossing at K, associated with the single electron occupation of $e_{g}'$ (Ti)
or $e_{g}$ (Mn, Co, Ni) orbitals. Our results indicate that the Dirac point can
be tuned to the Fermi level using strain. Applying spin-orbit coupling (SOC)
leads to a substantial anomalous Hall conductivity with values up to 0.94
$e^2/h$. Moreover, at $a_{Al_2O_3}$=4.81\AA\ we identify a particularly strong
effect of SOC with out-of-plane easy axis for
($Ti_2$O$_3$)$_1$/(Al$_2$O$_3$)$_5$(0001) which stabilizes dynamically the
system. Due to the unusually high orbital moment of -0.88$\mu_{\rm B}$ that
nearly compensates the spin moment of 1.01$\mu_{\rm B}$, this system emerges as
a candidate for the realization of the topological Haldane model of spinless
fermions. Parallels to the perovskite analogs
(La$X$O$_3$)$_2$/(LaAlO$_3$)$_4$(111) are discussed.",1704.08981v2
2014-05-07,On the tidal origin of hot Jupiter stellar obliquity trends,"It is debated whether the two hot Jupiter populations --- those on orbits
misaligned from their host star's spin axis and those well-aligned --- result
from two migration channels or from two tidal realignment regimes. Here I
demonstrate that equilibrium tides raised by a planet on its star can account
for three observed spin-orbit alignment trends: the aligned orbits of hot
Jupiters orbiting cool stars, the planetary mass cut-off for retrograde
planets, and the stratification by planet mass of cool host stars' rotation
frequencies. The first trend can be caused by strong versus weak magnetic
braking (the Kraft break), rather than realignment of the star's convective
envelope versus the entire star. The second trend can result from a small
effective stellar moment of inertia participating in the tidal realignment in
hot stars, enabling massive retrograde planets to partially realign to become
prograde. The third trend is attributable to higher mass planets more
effectively counteracting braking to spin up their stars. Both hot and cool
star require a small effective stellar moment of inertia participating in the
tidal realignment, e.g., an outer layer weakly coupled to the interior. I
demonstrate via Monte Carlo that this model can match the observed trends and
distributions of sky-projected misalignments and stellar rotation frequencies.
I discuss implications for inferring hot Jupiter migration mechanisms from
obliquities, emphasizing that even hot stars do not constitute a pristine
sample.",1405.1735v2
2017-05-19,Pressure-tuning of bond-directional exchange interactions and magnetic frustration in hyperhoneycomb iridate $β$-$\mathrm{Li_2IrO_3}$,"We explore the response of Ir $5d$ orbitals to pressure in
$\beta$-$\mathrm{Li_2IrO_3}$, a hyperhoneycomb iridate in proximity to a Kitaev
quantum spin liquid (QSL) ground state. X-ray absorption spectroscopy reveals a
reconstruction of the electronic ground state below 2 GPa, the same pressure
range where x-ray magnetic circular dichroism shows an apparent collapse of
magnetic order. The electronic reconstruction, which manifests a reduction in
the effective spin-orbit (SO) interaction in $5d$ orbitals, pushes
$\beta$-$\mathrm{Li_2IrO_3}$ further away from the pure $J_{\rm eff}=1/2$
limit. Although lattice symmetry is preserved across the electronic transition,
x-ray diffraction shows a highly anisotropic compression of the hyperhoneycomb
lattice which affects the balance of bond-directional Ir-Ir exchange
interactions driven by spin-orbit coupling at Ir sites. An enhancement of
symmetric anisotropic exchange over Kitaev and Heisenberg exchange interactions
seen in theoretical calculations that use precisely this anisotropic Ir-Ir bond
compression provides one possible route to realization of a QSL state in this
hyperhoneycomb iridate at high pressures.",1705.07059v3
2020-05-06,Nonlinear dynamical tides in white dwarf binaries,"Compact white dwarf (WD) binaries are important sources for space-based
gravitational-wave (GW) observatories, and an increasing number of them are
being identified by surveys like ZTF. We study the effects of nonlinear
dynamical tides in such binaries. We focus on the global three-mode parametric
instability and show that it has a much lower threshold energy than the local
wave-breaking condition studied previously. By integrating networks of coupled
modes, we calculate the tidal dissipation rate as a function of orbital period.
We construct phenomenological models that match these numerical results and use
them to evaluate the spin and luminosity evolution of a WD binary. While in
linear theory the WD's spin frequency can lock to the orbital frequency, we
find that such a lock cannot be maintained when nonlinear effects are taken
into account. Instead, as the orbit decays, the spin and orbit go in and out of
synchronization. Each time they go out of synchronization, there is a brief but
significant dip in the tidal heating rate. While most WDs in compact binaries
should have luminosities that are similar to previous traveling-wave estimates,
a few percent should be about ten times dimmer because they reside in heating
rate dips. This offers a potential explanation for the low luminosity of the CO
WD in J0651. Lastly, we consider the impact of tides on the GW signal and show
that LISA and TianGO can constrain the WD's moment of inertia to better than 1%
for deci-Hz systems.",2005.03058v1
2021-03-19,"Differentiating Hund from Mott physics in a three-band Hubbard-Hund model: Temperature dependence of spectral, transport, and thermodynamic properties","We study the interplay between Mott physics, driven by Coulomb repulsion U,
and Hund physics, driven by Hund's coupling J, for a minimal model for Hund
metals, the orbital-symmetric three-band Hubbard-Hund model (3HHM) for a
lattice filling of 1/3. Hund-correlated metals are characterized by
spin-orbital separation (SOS), a Hund's-rule-induced two-stage Kondo-type
screening process, in which spin screening occurs at much lower energy scales
than orbital screening. By contrast, in Mott-correlated metals, lying close to
the phase boundary of a metal-insulator transition, the SOS window becomes
negligibly small and the Hubbard bands are well separated. Using dynamical
mean-field theory and the numerical renormalization group as real-frequency
impurity solver, we identify numerous fingerprints distinguishing Hundness from
Mottness in the temperature dependence of various physical quantities. These
include ARPES-type spectra, the local self-energy, static local orbital and
spin susceptibilities, resistivity, thermopower, and lattice and impurity
entropies. Our detailed description of the behavior of these quantities within
the context of a simple model Hamiltonian will be helpful for distinguishing
Hundness from Mottness in experimental and theoretical studies of real
materials.",2103.11045v3
2021-12-06,Role of Spin-Orbit Coupling in High-order Harmonic Generation Revealed by Super-Cycle Rydberg Trajectories,"High-harmonic generation is typically thought of as a sub-laser-cycle
process, with the electron's excursion in the continuum lasting a fraction of
the optical cycle. However, it was recently suggested that long-lived Rydberg
states can play a particularly important role in atoms driven by the
combination of the counter-rotating circularly polarized fundamental light
field and its second harmonic. Here we report direct experimental evidence of
long and stable Rydberg trajectories contributing to high-harmonic generation.
We confirm their effect on the harmonic emission via Time-Dependent
Schr{\""o}dinger Equation simulations and track their dynamics inside the laser
pulse using the spin-orbit evolution in the ionic core, utilizing the
spin-orbit Larmor clock. Our observations contrast sharply with the general
view that long-lived Rydberg orbits should generate negligible contribution to
the macroscopic far-field high harmonic response of the medium. Indeed, we show
how and why radiation from such states can lead to well collimated macroscopic
signal in the far field.",2112.02981v3
2021-12-26,Quark spin-orbit correlations in the proton,"Generalized transverse momentum-dependent parton distributions (GTMDs)
provide a comprehensive framework for imaging the internal structure of the
proton. In particular, by encoding the simultaneous distribution of quark
transverse positions and momenta, they allow one to directly access
longitudinal quark orbital angular momentum, and, moreover, to correlate it
with the quark helicity. The relevant GTMD is evaluated through a lattice
calculation of a proton matrix element of a quark bilocal operator (the
separation in which is Fourier conjugate to the quark momentum) featuring a
momentum transfer (which is Fourier conjugate to the quark position), as well
as the Dirac structure appropriate for capturing the quark helicity. The
weighting by quark transverse position requires a derivative with respect to
momentum transfer, which is obtained in unbiased fashion using a direct
derivative method. The lattice calculation is performed directly at the
physical pion mass, using domain wall fermions to mitigate operator mixing
effects. Both the Jaffe-Manohar as well as the Ji quark spin-orbit correlations
are extracted, yielding evidence for a strong quark spin-orbit coupling in the
proton.",2112.13464v1
2017-09-01,Scaling of the Rashba spin-orbit torque in magnetic domain walls,"Spin-orbit torque in magnetic domain walls was investigated by solving the
Pauli-Schr\""{o}dinger equation for the itinerant electrons. The Rashba
interaction considered is derived from the violation of inversion symmetry at
interfaces between ferromagnets and heavy metals. In equilibrium, the Rashba
spin-orbit interaction gives rise to a torque corresponding to the
Dzyaloshinskii-Moriya interaction. When there is a current flowing, the
spin-orbit torque experienced by the itinerant electrons in short domain walls
has both field-like and damping-like components. However, when the domain wall
width is increased, the damping-like component, which is the counterpart of the
non-adiabatic spin transfer torque, decreases rapidly at the domain wall
center. In contrast to the non-adiabatic spin transfer torque, the damping-like
spin-orbit torque does not approach to zero far away from the domain wall
center, even in the adiabatic limit. The scattering of spin-up and spin-down
wave functions, which is caused by the Rashba spin-orbit interaction and the
spatial variation of magnetization profile in the domain wall, gives rise to
the finite damping-like spin-orbit torque.",1709.00187v3
2024-01-17,Torque-dependent orbital modulation of X-ray pulsar Cen X-3,"Cen X-3 shows alternate spin-up/spin-down episodes lasting for tens of days.
We study the orbital profiles and spectra of Cen X-3 during these
spin-up/spin-down intervals, using long-term data monitored by Fermi/GBM,
Swift/BAT and MAXI/GSC. In spin-up intervals, its orbital profile in 2-10 keV
is symmetrically peaked around orbital phase 0.42, while in spin-down intervals
of similar fluxes and similar magnitudes of spin change rate, its profile
reaches a peak around orbital phase 0.22 and then declines gradually. Such a
distinct orbital difference between spin-up and spin-down states of similar
flux is hard to explain in the standard disk model and indicates that its
torque reversals are related to processes on the orbital scale. The durations
of continuous spin-up/spin-down trend (tens of days) also point to a
superorbital variation. One possible scenario is the irradiation-driven warping
disk instability, which may produce a flipped inner disk for tens of days.",2401.09197v1
2018-12-11,Out-of-time-ordered correlators of the Hubbard model: SYK strange metal in the spin freezing crossover region,"The Sachdev-Ye-Kitaev (SYK) model describes a strange metal that shows
peculiar non-Fermi liquid properties without quasiparticles. It exhibits a
maximally chaotic behavior characterized by out-of-time-ordered correlators
(OTOCs), and is expected to be a holographic dual to black holes. Recently, a
striking similarity between the SYK model and the Hund-coupling induced
spin-freezing crossover in multi-orbital Hubbard models has been pointed out.
To further explore this connection, we study OTOCs for fermionic Hubbard
models, which are prototypical models for strongly correlated electrons in
solids. We introduce an imaginary-time four-point correlation function with an
appropriate time ordering, which by means of the spectral representation and
the out-of-time-order fluctuation-dissipation theorem can be analytically
continued to real-time OTOCs. Based on this approach, we numerically evaluate
real-time OTOCs for Hubbard models in the thermodynamic limit, using the
dynamical mean-field theory in combination with a numerically exact
continuous-time Monte Carlo impurity solver. The results for the single-orbital
model show that a certain spin-related OTOC captures local moment formation in
the vicinity of the metal-insulator transition, while the self-energy does not
show SYK-like non-Fermi liquid behavior. On the other hand, for the two- and
three-orbital models with nonzero Hund coupling we find that the OTOC exhibits
a rapid damping at short times and an approximate power-law decay at longer
times in the spin-freezing crossover regime characterized by fluctuating local
moments and a non-Fermi liquid self-energy $\Sigma(\omega) \sim \sqrt{\omega}$.
These results are in a good agreement with the behavior of the SYK model,
providing firm evidence for the close relation between the spin-freezing
crossover physics of multi-orbital Hubbard models and the SYK strange metal.",1812.04217v2
2010-10-13,Electric-field control of spin waves at room temperature in multiferroic BiFeO3,"To face the challenges lying beyond current CMOS-based technology, new
paradigms for information processing are required. Magnonics proposes to use
spin waves to carry and process information, in analogy with photonics that
relies on light waves, with several advantageous features such as potential
operation in the THz range and excellent coupling to spintronics. Several
magnonic analog and digital logic devices have been proposed, and some
demonstrated. Just as for spintronics, a key issue for magnonics is the large
power required to control/write information (conventionally achieved through
magnetic fields applied by strip lines, or by spin transfer from large
spin-polarized currents). Here we show that in BiFeO3, a room-temperature
magnetoelectric material, the spin wave frequency (>600 GHz) can be tuned
electrically by over 30%, in a non-volatile way and with virtually no power
dissipation. Theoretical calculations indicate that this effect originates from
a linear magnetoelectric effect related to spin-orbit coupling induced by the
applied electric field. We argue that these properties make BiFeO3 a promising
medium for spin wave generation, conversion and control in future magnonics
architectures.",1010.2678v1
2019-12-16,Electrically controlled emission from triplet charged excitons in atomically thin heterostructures,"Excitons are composite bosons that can feature spin singlet and triplet
states. In usual semiconductors, without an additional spin-flip mechanism,
triplet excitons are extremely inefficient optical emitters. Large spin-orbit
coupling in transition metal dichalcogenides (TMDs) couples circularly
polarized light to excitons with selective valley and spin. Here, we
demonstrate electrically controlled brightening of spin-triplet interlayer
excitons in a MoSe$_2$/WSe$_2$ TMD van der Waals (vdW) heterostructure. The
atomic registry of vdW layers in TMD heterostructures provides a quasi-angular
momentum to interlayer excitons, enabling emission from otherwise dark
spin-triplet excitons. Employing magnetic field, we show that photons emitted
by triplet and singlet excitons in the same valley have opposite chirality. We
also measure effective exciton g-factors, presenting direct and quantitative
evidence of triplet interlayer excitons. We further demonstrate gate tuning of
the relative photoluminescence intensity between singlet and triplet charged
excitons. Electrically controlled emission between singlet and triplet excitons
enables a route for optoelectronic devices that can configure excitonic chiral,
spin, and valley quantum states.",1912.07678v1
2021-03-31,Resistively detected NMR as a probe of the topological nature of conducting edge/surface states,"Electron spins in edge or surface modes of topological insulators (TIs) with
strong spin-orbit coupling cannot be directly manipulated with microwaves due
to the locking of electron spin to its momentum. We show by contrast that a
resistively detected nuclear magnetic resonance (RDNMR) based technique can be
used to probe the helical nature of surface conducting states. In such
experiments, one applies a radio frequency (RF) field to reorient nuclear spins
that then couple to electronic spins by the hyperfine interaction. The spin of
the boundary electrons can thereby be modulated, resulting in changes in
conductance at nuclear resonance frequencies. Here, we demonstrate that the
conductivity is sensitive to the direction of the applied magnetic field with
respect to the helicity of the electrons. This dependence of the RDNMR signal
on angle probes the nature of the conductive edge or surface states. In the
case of 3D TI in the quantum Hall regime, we establish that the dominant
mechanism responsible for the conductance change in a RDNMR experiment is based
on the Overhauser field effect. Our findings indicate that the same physics
underlying the use of RDNMR to probe TI states also enables us to use RF
control of nuclear spins to coherently manipulate topologically protected
states which could be useful for a new generation of devices.",2104.00146v2
2019-05-10,Functional renormalization group for frustrated magnets with nondiagonal spin interactions,"In the field of quantum magnetism, the advent of numerous spin-orbit assisted
Mott insulating compounds, such as the family of Kitaev materials, has led to a
growing interest in studying general spin models with non-diagonal interactions
that do not retain the SU(2) invariance of the underlying spin degrees of
freedom. However, the exchange frustration arising from these non-diagonal and
often bond-directional interactions for two- and three-dimensional lattice
geometries poses a serious challenge for numerical many-body simulation
techniques. In this paper, we present an extended formulation of the
pseudo-fermion functional renormalization group that is capable of capturing
the physics of frustrated quantum magnets with generic (diagonal and
off-diagonal) two-spin interaction terms. Based on a careful symmetry analysis
of the underlying flow equations, we reveal that the computational complexity
grows only moderately, as compared to models with only diagonal interaction
terms. We apply the formalism to a kagome antiferromagnet which is augmented by
general in-plane and out-of-plane Dzyaloshinskii-Moriya (DM) interactions, as
argued to be present in the spin liquid candidate material herbertsmithite. We
calculate the complete ground state phase diagram in the strength of in-plane
and out-of-plane DM couplings, and discuss the extended stability of the spin
liquid of the unperturbed kagome antiferromagnet in the presence of these
couplings.",1905.04190v2
2021-10-19,Non-reciprocal Pauli Spin Blockade in a Silicon Double Quantum Dot,"Spin qubits in gate-defined silicon quantum dots are receiving increased
attention thanks to their potential for large-scale quantum computing. Readout
of such spin qubits is done most accurately and scalably via Pauli spin
blockade (PSB), however various mechanisms may lift PSB and complicate readout.
In this work, we present an experimental observation of a new, highly prevalent
PSB-lifting mechanism in a silicon double quantum dot due to incoherent
tunneling between different spin manifolds. Through dispersively-detected
magnetospectroscopy of the double quantum dot in 16 charge configurations, we
find the mechanism to be energy-level selective and non-reciprocal for
neighbouring charge configurations. Additionally, using input-output theory we
report a large coupling of different electron spin manifolds of 7.90 $\mu$eV,
the largest reported to date, indicating an enhanced spin-orbit coupling which
may enable all-electrical qubit control.",2110.09842v2
2023-03-09,Electrical manipulation of a single electron spin in CMOS with micromagnet and spin-valley coupling,"For semiconductor spin qubits, complementary-metal-oxide-semiconductor (CMOS)
technology is the ideal candidate for reliable and scalable fabrication. Making
the direct leap from academic fabrication to qubits fabricated fully by
industrial CMOS standards is difficult without intermediate solutions. With a
flexible back-end-of-line (BEOL) new functionalities such as micromagnets or
superconducting circuits can be added in a post-CMOS process to study the
physics of these devices or achieve proof of concepts. Once the process is
established it can be incorporated in the foundry-compatible process flow.
Here, we study a single electron spin qubit in a CMOS device with a micromagnet
integrated in the flexible BEOL. We exploit the synthetic spin orbit coupling
(SOC) to control the qubit via electric field and we investigate the
spin-valley physics in the presence of SOC where we show an enhancement of the
Rabi frequency at the spin-valley hotspot. Finally, we probe the high frequency
noise in the system using dynamical decoupling pulse sequences and demonstrate
that charge noise dominates the qubit decoherence in this range.",2303.04960v1
2023-08-11,Design of Sn-doped cadmium chalcogenide based monolayers for valleytronics properties,"Valleytronics, that uses the valley index or valley pseudospin to encode
information, has emerged as an interesting field of research in two-dimensional
(2D) systems with promising device applications. Spin-orbit coupling (SOC) and
inversion symmetry breaking leads to spin-splitting of bands near the energy
extrema (valleys). In order to find a new 2D material useful for valleytronics,
we have designed hexagonal planar monolayers of cadmium chalcogenides (CdX, X =
S, Se, Te) from the (111) surface of bulk CdX zinc blende structure. Band
structure study reveals valence band local maxima at symmetry point K and its
time reversal conjugate point K$\textquotesingle$. Application of SOC initiates
spin-splitting in the valleys that lifts the energy degeneracy and shows strong
valley-spin coupling character. We have substituted two Cd atoms in the planar
monolayers by Sn atoms which increases the spin-splitting significantly. The
structural, dynamic, mechanical and thermal stability of all the monolayers has
been confirmed. Values of formation energies indicate that it may be feasible
to synthesize the Sn-doped CdSe and CdTe monolayers using bottom-up approach.
Zeeman-type spin-splitting is observed in the valley region and Rashba
spin-splitting is observed at the $\Gamma$ point for Sn-doped CdSe and CdTe
monolayers. Berry curvature values are more in all the Sn-doped monolayers than
the pristine monolayers. These newly designed monolayers are thus found to be
suitable for valleytronics applications. Sn-doped monolayers show band
inversion deep in the valence and conduction bands between Sn~$s$ and $p$ and
X~$p$ states but lack topological properties.",2308.06011v1
2023-09-04,Impact of electrostatic crosstalk on spin qubits in dense CMOS quantum dot arrays,"Quantum processors based on integrated nanoscale silicon spin qubits are a
promising platform for highly scalable quantum computation. Current CMOS spin
qubit processors consist of dense gate arrays to define the quantum dots,
making them susceptible to crosstalk from capacitive coupling between a dot and
its neighbouring gates. Small but sizeable spin-orbit interactions can transfer
this electrostatic crosstalk to the spin g-factors, creating a dependence of
the Larmor frequency on the electric field created by gate electrodes
positioned even tens of nanometers apart. By studying the Stark shift from tens
of spin qubits measured in nine different CMOS devices, we developed a
theoretical frawework that explains how electric fields couple to the spin of
the electrons in increasingly complex arrays, including those electric
fluctuations that limit qubit dephasing times $T_2^*$. The results will aid in
the design of robust strategies to scale CMOS quantum technology.",2309.01849v1
2017-05-03,"Interacting chains of orbital polarons in ""Colossal"" magnetoresistive La1-xSrxMnO3 revealed by spin and lattice dynamics","The origin of the effect of colossal magneto-resistance (CMR) remains still
unexplained. In this work we revisit the spin dynamics of the pseudo-cubic
La1-xSrxMnO3 along the Mn-O-Mn bond direction at four x doping values (x < 0.5)
and various temperatures and report a new lattice dynamics study at x0=0.2,
representative of the optimal doping for CMR. We propose an interpretation of
the spin dynamics in terms of orbital polarons. This picture is supported by
the observation of a discrete magnetic energy spectrum Enmag (q) characteristic
of the internal excitations of ""orbital polarons"" defined by Mn3+ neighbors
surrounding a Mn4+ center with a hole. Because of its hopping, the hole mixes
up dynamically all the possible orbital configurations of its surrounding Mn3+
sites with degenerate energies. The Enmag values indicate a lift of orbital
degeneracy by phonon excitations. The number n varies with the spatial
dimension D of the polaron and the q-range determines its size. At x=0.125 and
x=0.3 the spectrum reveals 2D polarons coupled by exchange and 3D ""free""
polarons respectively, with sizes l=1.67a < 2a in all bond directions. At
x0=0.2, the spin and the lattice dynamics provide evidence for chains of
orbital polarons of size l=2a with a periodic distribution over ~ 3a and an
interaction energy ~ 3 meV. At T < Tc the charges propagate together with the
longitudinal acoustic phonons along the chains enhancing their ferromagnetic
character. The phase separation between metallic and ferromagnetic chains in a
non-metallic matrix may be crucial for CMR.",1705.01476v3
2010-03-09,Self force on a scalar charge in Kerr spacetime: circular equatorial orbits,"We present a calculation of the scalar field self-force (SSF) acting on a
scalar-charge particle in a strong-field orbit around a Kerr black hole. Our
calculation specializes to circular and equatorial geodesic orbits. The
analysis is an implementation of the standard mode-sum regularization scheme:
We first calculate the multipole modes of the scalar-field perturbation using
numerical integration in the frequency domain, and then apply a certain
regularization procedure to each of the modes. The dissipative piece of the SSF
is found to be consistent with the flux of energy and angular momentum carried
by the scalar waves through the event horizon and out to infinity. The
conservative (radial) component of the SSF is found to be attractive (inward
pointing) for $r_0>r_{\rm c}(a)$ and repulsive (outward pointing) for
$r_0<r_{\rm c}(a)$, where $a$ is the Kerr spin parameter, $r_0$ is the
Boyer-Lindquist orbital radius, and $r_{\rm c}$ is a critical $a$-dependent
radius at which the conservative SSF vanishes. When the motion is retrograde
the conservative SSF is repulsive for all $r_0$ (as in the Schwarzschild case).
The dominant conservative effect of the SSF in Schwarzschild spacetime is known
to be of 3rd post-Newtonian (PN) order (with a logarithmic running). Our
numerical results suggest that the leading-order PN correction due to the black
hole's spin arises from spin-orbit coupling at 3PN, which dominates the overall
SSF effect at large $r_0$. In PN language, the change-of-sign of the radial SSF
is attributed to an interplay between the spin-orbit term ($\propto
-ar_0^{-4.5}$) and the ""Schwarzschild"" term ($\propto r_0^{-5}\log r_0$).",1003.1860v3
2009-08-18,"""Spin"" and ""Orbital"" Flows in a Circularly Polarized Paraxial Beam: Orbital Rotation without Orbital Angular Momentum","In light beams with circular or elliptic polarization, the transverse energy
flow consists of the ""spin"" and ""orbital"" parts. Both of them can induce the
orbital motion of microparticles suspended within the field of a light beam,
and this should be taken into account in experiments on the spin-to-orbital
angular momentum conversion. The character of the spin, orbital and total
transverse energy flows in circular Laguerre-Gaussian beams is studied
analytically; graphical representations of the flows in the beam cross section
(flow maps) are calculated and analyzed. The spin circulatory flow can be
directed oppositely to the orbital one and/or to the polarization handedness.
As a result, the total transverse energy circulation of a beam with homogeneous
circular polarization can be of different handedness in different regions of
the beam cross section, which are separated by the contours of zero transverse
energy flow. Regarding the particle position within the beam cross section, it
can perform orbital, spinning or combined spinning-orbital motion with variable
parameters. Possible applications to optical driving of microparticles are
discussed.",0908.2526v1
2016-01-08,Detecting the orbital character of the spin fluctuation in the Iron-based superconductors with the resonant inelastic X-ray scattering spectroscopy,"The orbital distribution of the spin fluctuation in the iron-based
superconductors(IBSs) is the key information needed to understand the
magnetism, superconductivity and electronic nematicity in these multi-orbital
systems. In this work, we propose that the resonant inelastic X-ray
scattering(RIXS) technique can be used to probe selectively the spin
fluctuation on different Fe $3d$ orbitals. In particular, the spin fluctuation
on the three $t_{2g}$ orbitals, namely, the $3d_{xz}$, $3d_{yz}$ and the
$3d_{xy}$ orbital, can be selectively probed in the $\sigma\rightarrow\pi'$
scattering geometry by aligning the direction of the outgoing photon in the
$y$, $x$ and $z$ direction. Such orbital-resolved information on the spin
fluctuation is invaluable for the study of the orbital-selective physics in the
IBSs and can greatly advance our understanding on the relation between orbital
ordering and spin nematicity in the IBSs and the orbital-selective pairing
mechanism in these multi-orbital systems.",1601.01809v3
2021-09-29,Magnetic interlayer coupling between ferromagnetic SrRuO$_3$ layers through a SrIrO$_3$ spacer,"A key element to tailor the properties of magnetic multilayers is the
coupling between the individual magnetic layers. In case of skyrmion hosting
multilayers, coupling of skyrmions across the magnetic layers is highly
desirable. Here the magnetic interlayer coupling was studied in epitaxial
all-oxide heterostructures of ferromagnetic perovskite SrRuO$_3$ layers
separated by spacers of the strong spin-orbit coupling oxide SrIrO$_3$. This
combination of oxide layers is being discussed as a potential candidate system
to host N\'{e}el skyrmions. First order reversal curve (FORC) measurements were
performed in order to distinguish between magnetic switching processes of the
individual layers and to disentangle the signal of soft magnetic impurities
from the samples$'$ signal. Additionally, FORC investigations enabled to
determine whether the coupling between the magnetic layers is ferromagnetic or
antiferromagnetic. The observed interlayer coupling strength was weak for all
the heterostructures, with SrIrO$_3$ spacers between 2 monolayers and 12
monolayers thick.",2109.14292v2
2003-05-19,Physics and Initial Data for Multiple Black Hole Spacetimes,"An orbiting black hole binary will generate strong gravitational radiation
signatures, making these binaries important candidates for detection in
gravitational wave observatories. The gravitational radiation is characterized
by the orbital parameters, including the frequency and separation at the
inner-most stable circular orbit (ISCO). One approach to estimating these
parameters relies on a sequence of initial data slices that attempt to capture
the physics of the inspiral. Using calculations of the binding energy, several
authors have estimated the ISCO parameters using initial data constructed with
various algorithms. In this paper we examine this problem using conformally
Kerr-Schild initial data. We present convergence results for our initial data
solutions, and give data from numerical solutions of the constraint equations
representing a range of physical configurations. In a first attempt to
understand the physical content of the initial data, we find that the Newtonian
binding energy is contained in the superposed Kerr-Schild background before the
constraints are solved. We examine some deficiencies with the initial data
approach to orbiting binaries, especially touching on the effects of prior
motion and spin-orbital coupling of the angular momenta. Making rough estimates
of these effects, we find that they are not insignificant compared to the
binding energy, leaving some doubt of the utility of using initial data to
predict ISCO parameters. In computations of specific initial-data
configurations we find spin-specific effects that are consistent with
analytical estimates.",0305071v1
2016-02-21,Orbital-selective Mott phases of a one-dimensional three-orbital Hubbard model studied using computational techniques,"A recently introduced one-dimensional three-orbital Hubbard model displays
orbital-selective Mott phases with exotic spin arrangements such as spin block
states [J. Rinc\'on {\em et al.}, Phys. Rev. Lett. \textbf{112}, 106405
(2014)]. In this publication we show that the Constrained-Path Quantum Monte
Carlo (CPQMC) technique can accurately reproduce the phase diagram of this
multiorbital one-dimensional model, paving the way to future CPQMC studies in
systems with more challenging geometries, such as ladders and planes. The
success of this approach relies on using the Hartree-Fock technique to prepare
the trial states needed in CPQMC. We also study a simplified version of the
model where the pair-hopping term is neglected and the Hund coupling is
restricted to its Ising component. The corresponding phase diagrams are shown
to be only mildly affected by the absence of these technically
difficult-to-implement terms. This is confirmed by additional Density Matrix
Renormalization Group and Determinant Quantum Monte Carlo calculations carried
out for the same simplified model, with the latter displaying only mild Fermion
sign problems. We conclude that these methods are able to capture
quantitatively the rich physics of the several orbital-selective Mott phases
(OSMP) displayed by this model, thus enabling computational studies of the OSMP
regime in higher dimensions, beyond static or dynamic mean field
approximations.",1602.06478v2
2017-10-20,"Reliability and applicability of magnetic force linear response theory: Numerical parameters, predictability, and orbital resolution","We investigated the reliability and applicability of so-called magnetic force
linear response method to calculate spin-spin interaction strengths from
first-principles. We examined the dependence on the numerical parameters
including the number of basis orbitals and their cutoff radii within
non-orthogonal LCPAO (linear combination of pseudo-atomic orbitals) formalism.
It is shown that the parameter dependence and the ambiguity caused by these
choices are small enough in comparison to the other computation approach and
experiments. Further, we tried to pursue the possible extension of this
technique to a wider range of applications. We showed that magnetic force
theorem can provide the reasonable estimation especially for the case of
strongly localized moments even when the ground state configuration is unknown
or the total energy value is not accessible. The formalism is extended to carry
the orbital resolution from which the matrix form of the magnetic coupling
constant is calculated. From the applications to Fe-based superconductors
including LaFeAsO, NaFeAs, BaFe$_2$As$_2$ and FeTe, the distinctive
characteristics of orbital-resolved interactions are clearly noticed in between
single-stripe pnictides and double-stripe chalcogenides.",1710.07533v1
2022-02-28,Strongly anisotropic electronic and magnetic structures in oxide dichlorides RuOCl$_2$ and OsOCl$_2$,"Here, using density functional theory and density matrix renormalization
group methods, we investigate the electronic and magnetic properties of
RuOCl$_2$ and OsOCl$_2$ with $d^4$ electronic configurations. Different from a
previous study using VOI$_2$ with $d^1$ configuration, these systems with
$4d^4$ or $5d^4$ do not exhibit a ferroelectric instability along the $a$-axis.
Due to the fully-occupied $d_{xy}$ orbital in RuOCl$_2$ and OsOCl$_2$, the
Peierls instability distortion disappears along the $b$-axis, leading to an
undistorted I${\rm mmm}$ phase (No. 71). Furthermore, we observe strongly
anisotropic electronic and magnetic structures along the $a$-axis. The large
crystal-field splitting energy (between $d_{xz/yz}$ and $d_{xy}$ orbitals) and
large hopping between nearest-neighbor Ru and Os atoms suppresses the
spin-orbital effect in $M$OCl$_2$ ($M$ = Ru or Os) with electronic density $n =
4$, resulting in a spin-1 system instead of a $J = 0$ singlet ground state.
Moreover, we find staggered antiferromagnetic order with $\pi$ wavevector along
the $M$-O chain direction ($a$-axis) while the magnetic coupling along the
$b$-axis is weak. Based on Wannier functions from first-principles
calculations, we calculated the relevant hopping amplitudes and crystal-field
splitting energies of the $t_{2g}$ orbitals for the Os atoms to construct a
multi-orbital Hubbard model for the $M$-O chains. Staggered AFM with
$\uparrow$-$\downarrow$-$\uparrow$-$\downarrow$ spin structure dominates in our
DMRG calculations, in agreement with DFT calculations.",2203.00060v2
2024-01-10,Observation of correlation induced metal to half-metal phase transition and large orbital moment in $\mathrm{Sr_2CoO_4}$,"We present a detailed mean-field study to address the fundamental discrepancy
in the ground state magnetization of $\mathrm{Sr_{2}CoO_{4}}$ (SCO). In
contrast to the ferromagnetic metallic ground state obtained from density
functional theory (DFT), DFT+$U$ gives three ferromagnetic solutions converging
to integer moment values (1, 2 \& 3 $\mu_B$/f.u) over a range of $U$.
Interestingly, two of the solutions are found to exhibit half-metallicity with
correspondingly $S$=1/2 and S=3/2 spin states. The half-metallic ferromagnetic
state with $S$=3/2 is found to be the ground state solution for SCO. Co atoms
show a large deviation from the formal +4 oxidation state indicating the
presence of strong covalency effects. Our results suggest a plausible metal to
half-metal phase transition around $U$($J$)=4.4(1.16) eV. The Fermi surface
study shows gradual collapse in states leading to half-metallicity suggesting
\textit{\textbf{k}}-dependence of effective $U$ around the critical region.
Surprisingly, in the presence of spin-orbit coupling (SOC), unexpectedly large
orbital moment ($L_{z}$=0.6) is noted in SCO putting it among the class of 3$d$
based transition metal compounds exhibiting pronounced orbital magnetization.
The calculations give large magnetocrystalline anisotropy energy (MAE) of
$\sim$48 meV. Large values of orbital magnetic moment contribution and MAE, in
the presence of strong correlation effects, provide a better interpretation of
experimental magnetization observed in SCO.",2401.05149v1
2019-07-02,"ARPES study of orbital characters, symmetry breakings and pseudogaps in doped and pure Sr2IrO4","Sr2IrO4 is characterized by a large spin-orbit coupling, which gives rise to
bands with strongly entangled spin and orbital characters, called J=1/2 and
J=3/2. We use light-polarization dependent ARPES to study directly the orbital
character of these bands and fully map out their dispersion. We observe bands
in very good agreement with our cluster dynamical mean-field theory
calculations. We show that the J=1/2 band, the closest to the Fermi level Ef,
is dominated by dxz character along kx and dyz along ky. This is actually in
agreement with an isotropic J=1/2 character on average, but this large orbital
dependence in k-space was mostly overlooked before. It gives rise to strong
modulations of the ARPES intensity that we explain and carefully take into
account to compare dispersions in equivalent directions of the Brillouin zone.
Although the latter dispersions look different at first, suggesting possible
symmetry breakings, they are found essentially similar, once corrected for
these intensity variations. In particular, the pseudogap-like features close to
the $X$ point appearing in the nearly metallic 15% Rh-doped Sr2IrO4 strongly
depend on experimental conditions. We reveal that there is nevertheless an
energy scale of 30meV below which spectral weight is suppressed, independent of
the experimental conditions, which gives a reliable basis to analyze this
behavior. We suggest it is caused by disorder.",1907.01247v1
2021-10-06,Epitaxial Growth of Ultraflat Bismuthene with Large Topological Band Inversion Enabled by Substrate-Orbital-Filtering Effect,"Quantum spin Hall (QSH) systems hold promises of low-power-consuming
spintronic devices, yet their practical applications are extremely impeded by
the small energy gaps. Fabricating QSH materials with large gaps, especially
under the guidance of design principles, is essential for both scientific
research and practical applications. Here, we demonstrate that large on-site
atomic spin-orbit coupling can be directly exploited via the intriguing
substrate-orbital-filtering effect to generate large-gap QSH systems and
experimentally realized on the epitaxially synthesized ultraflat bismuthene on
Ag(111). Theoretical calculations reveal that the underlying substrate
selectively filters Bi pz orbitals away from the Fermi level, leading pxy
orbitals with nonzero magnetic quantum numbers, resulting in large topological
gap of ~1 eV at the K point. The corresponding topological edge states are
identified through scanning tunneling spectroscopy combined with density
functional theory calculations. Our findings provide general strategies to
design large-gap QSH systems and further explore their topology-related
physics.",2110.02461v2
2022-02-11,DFT+$U$ within the framework of linear combination of numerical atomic orbitals,"We present a formulation and implementation of the DFT+\textit{U} method
within the framework of linear combination of numerical atomic orbitals (NAO).
Our implementation not only enables single-point total energy and
electronic-structure calculations but also provides access to atomic forces and
stresses, hence allowing for full structure relaxations of periodic systems.
Furthermore, our implementation allows one to deal with non-collinear spin
texture, with the spin-orbit coupling (SOC) effect treated self-consistently.
The key aspect behind our implementation is a suitable definition of the
correlated subspace when multiple atomic orbitals with the same angular
momentum are used, and this is addressed via the ""Mulliken charge projector""
constructed in terms of the first (most localized) atomic orbital within the
$d/f$ angular momentum channel. The important Hubbard $U$ and Hund $J$
parameters can be estimated from a screened Coulomb potential of the Yukawa
type, with the screening parameter either chosen semi-empirically or determined
from the Thomas-Fermi screening model. Benchmark calculations are performed for
four late transition metal monoxide bulk systems, i.e., MnO, FeO, CoO, and NiO,
and for the 5$d$-electron compounds IrO$_2$. For the former type of systems, we
check the performance of our DFT+$U$ implementation for calculating band gaps,
magnetic moments, electronic band structures, as well as forces and stresses;
for the latter, the efficacy of our DFT+$U$+SOC implementation is assessed.
Systematic comparisons with available experimental results, and especially with
the results from other implementation schemes are carried out, which
demonstrate the validity of our NAO-based DFT+$U$ formalism and implementation.",2202.05409v1
2008-12-16,Evidence for reversible control of magnetization in a ferromagnetic material via spin-orbit magnetic field,"Conventional computer electronics creates a dichotomy between how information
is processed and how it is stored. Silicon chips process information by
controlling the flow of charge through a network of logic gates. This
information is then stored, most commonly, by encoding it in the orientation of
magnetic domains of a computer hard disk. The key obstacle to a more intimate
integration of magnetic materials into devices and circuit processing
information is a lack of efficient means to control their magnetization. This
is usually achieved with an external magnetic field or by the injection of
spin-polarized currents. The latter can be significantly enhanced in materials
whose ferromagnetic properties are mediated by charge carriers. Among these
materials, conductors lacking spatial inversion symmetry couple charge currents
to spin by intrinsic spin-orbit (SO) interactions, inducing nonequilibrium spin
polarization tunable by local electric fields. Here we show that magnetization
of a ferromagnet can be reversibly manipulated by the SO-induced polarization
of carrier spins generated by unpolarized currents. Specifically, we
demonstrate domain rotation and hysteretic switching of magnetization between
two orthogonal easy axes in a model ferromagnetic semiconductor.",0812.3160v2
2009-03-13,Unified Description of the Intrinsic Spin-Hall Effects,"The intrinsic spin-Hall effects (SHE) in $p$-doped semiconductors [S.
Murakami et al., Science 301, 1348 (2003)] and two-dimensional electron gases
with Rashba spin-orbit coupling [J. Sinova et al., Phys. Rev. Lett. 92, 126603
(2004)] have been the subject of many theoretical studies, but their driving
mechanisms have yet to be described in a unified manner. The former effect
arises from the adiabatic topological curvature of momentum space, from which
holes acquire a spin-dependent anomalous velocity. The SHE in the Rashba
system, on the other hand, results from the momentum-dependent spin dynamics in
the presence of an external electric field. The two effects clearly appear to
originate from distinct mechanisms. Our motivation for this article is to
address this apparent disparity and, in particular, to seek a unifying
description of the effects. In this endeavor, we consider the explicit
time-dependence of SHE systems starting with a general spin-orbit model. We
find that by performing a gauge transformation of the general model with
respect to time, a well-defined gauge field appears in time space which has the
physical significance of an effective magnetic field. This magnetic field is
shown to precisely account for the SHE in the Rashba system in the adiabatic
limit. Remarkably, by carefully analyzing the equation of motion of the general
model, this field component is also found to be the origin of the anomalous
velocity due to the momentum space curvature. Our study therefore unifies the
two seemingly disparate intrinsic SHEs under a common adiabatic framework.",0903.2305v2
2014-07-18,"Production, storage and release of spin currents in quantum circuits","Quantum rings connected to ballistic circuits couple strongly to external
magnetic fields if the connection is not symmetric. By analytical theory and
computer simulation I show that properly connected rings can be used to pump
currents in the wires giving raise to a number of interesting new phenomena.
One can pump spin polarized currents into the wires by using rotating magnetic
fields or letting the ring rotate around the wire. This method works without
any need for the spin-orbit interaction, and without stringent requirements
about the conduction band filling. On the other hand, another method works at
half filling using a time-dependent magnetic field in the plane of the (fixed)
ring. This can be used to pump a pure spin current, excited by the the
spin-orbit interaction in the ring. One can use magnetizable bodies as storage
units to concentrate and save the magnetization in much the same way as
capacitors store electric charge. The polarization obtained in this way can
then be used on command to produce spin currents in a wire. These currents show
interesting oscillations while the storage units exchange their polarizations
and the intensity and amplitude of the oscillations can controlled by tuning
the conductance of the wire used to connect the units.",1407.4983v2
2017-03-10,Superexchange theory of electronic polarization driven by relativistic spin-orbit interaction at the half-filling,"By applying Berry-phase theory for the effective half-filled Hubbard model,
we derive an analytical expression for the electronic polarization driven by
the relativistic spin-orbit (SO) coupling. The model itself is constructed in
the Wannier basis, using the input from the first-principles electronic
structure calculations in the local-density approximation, and then treated in
the spirit of the superexchange theory. The obtained polarization has the
following form: ${\bf P}_{ij} = \boldsymbol{\epsilon}_{ji} \boldsymbol{\cal
P}_{ij} \cdot [\boldsymbol{e}_i \times \boldsymbol{e}_j]$, where
$\boldsymbol{\epsilon}_{ji}$ is the direction of the bond $\langle ij \rangle$,
$\boldsymbol{e}_i$ and $\boldsymbol{e}_j$ are the directions of spins in this
bond, and $\boldsymbol{\cal P}_{ij}$ is the pseudovector containing all the
information about the crystallographic symmetry of the considered system. The
expression describes the ferroelectric activity in various magnets with
noncollinear but otherwise nonpolar magnetic structures, which would yield no
polarization without SO interaction, including the magnetoelectric (ME) effect,
caused by the ferromagnetic canting of spins in the external magnetic field,
and spin-spiral multiferroics. The abilities of this theory are demonstrated
for the the analysis of linear ME effect in Cr$_2$O$_3$ and BiFeO$_3$ and
properties multiferroic MnWO$_4$ and $\beta$-MnO$_2$. In all considered
examples, the theory perfectly describes the symmetry properties of the induced
polarization. However, in some cases, the values of this polarization are
underestimated, suggesting that other effects, besides the spin and electronic
ones, can also play an important role.",1703.03556v1
2018-02-27,Spin-polaron ladder spectrum of the spin-orbit-induced Mott insulator Sr$_2$IrO$_{4}$ probed by scanning tunneling spectroscopy,"The motion of doped electrons or holes in an antiferromagnetic lattice with
strong on-site Coulomb interactions touches one of the most fundamental open
problems in contemporary condensed matter physics. The doped charge may
strongly couple to elementary spin excitations resulting in a dressed
quasiparticle which is subject to confinement. This 'spin-polaron' possesses
internal degrees of freedom with a characteristic 'ladder' excitation spectrum.
Despite its fundamental importance for understanding high-temperature
superconductivity, clear experimental spectroscopic signatures of these
internal degrees of freedom are scarce. Here we present scanning tunneling
spectroscopy results of the spin-orbit-induced Mott insulator Sr$_2$IrO$_{4}$.
Our spectroscopy data reveal distinct shoulder-like features for occupied and
unoccupied states beyond a measured Mott gap of $\Delta\approx620$~meV. Using
the self-consistent Born approximation we assign the anomalies in the
unoccupied states to the spin-polaronic ladder spectrum with excellent
quantitative agreement and estimate the Coulomb repulsion $U$ = 2.05 ...2.28 eV
in this material. These results confirm the strongly correlated electronic
structure of this compound and underpin the previously conjectured paradigm of
emergent unconventional superconductivity in doped Sr$_2$IrO$_{4}$.",1802.10028v3
2018-01-12,First-order symmetry-adapted perturbation theory for multiplet splittings,"We present a symmetry-adapted perturbation theory (SAPT) for the interaction
of two high-spin open-shell molecules (described by their restricted open-shell
Hartree-Fock determinants) resulting in low-spin states of the complex. The
previously available SAPT formalisms, except for some system-specific studies
for few-electron complexes, were restricted to the high-spin state of the
interacting system. Thus, the new approach provides, for the first time, a
SAPT-based estimate of the splittings between different spin states of the
complex. We have derived and implemented the lowest-order SAPT term responsible
for these splittings, that is, the first-order exchange energy. We show that
within the so-called S2 approximation commonly used in SAPT (neglecting effects
that vanish as fourth or higher powers of intermolecular overlap integrals),
the first-order exchange energies for all multiplets are linear combinations of
two matrix elements: a diagonal exchange term that determines the spin-averaged
effect and a {\em spin-flip term} responsible for the splittings between the
states. The numerical factors in this linear combination are determined solely
by the Clebsch-Gordan coefficients: accordingly, the S2 approximation implies a
Heisenberg Hamiltonian picture with a single coupling strength parameter
determining all the splittings. The new approach is cast into both
molecular-orbital and atomic-orbital expressions: the latter enable an
efficient density-fitted implementation. We test the newly developed formalism
on several open-shell complexes ranging from diatomic systems (Li+H, Mn+Mn,...)
to the phenalenyl dimer.",1801.04078v1
2020-02-12,Hyperfine and quadrupole interactions for Dy isotopes in DyPc$_2$ molecules,"Nuclear spin levels play an important role in understanding magnetization
dynamics and implementation and control of quantum bits in lanthanide-based
single-molecule magnets. We investigate the hyperfine and nuclear quadrupole
interactions for $^{161}$Dy and $^{163}$Dy nucleus in anionic DyPc$_2$
(Pc=phthalocyanine) single-molecule magnets, using multiconfigurational
ab-initio methods (beyond density-functional theory) including spin-orbit
interaction. The two isotopes of Dy are chosen because the others have zero
nuclear spin. Both isotopes have the nuclear spin $I=5/2$, although the
magnitude and sign of the nuclear magnetic moment differ from each other. The
large energy gap between the electronic ground and first-excited Kramers
doublets, allows us to map the microscopic hyperfine and quadrupole interaction
Hamiltonian onto an effective Hamiltonian with an electronic pseudo-spin
$S_{\rm eff}=1/2$ that corresponds to the ground Kramers doublet. Our ab-initio
calculations show that the coupling between the nuclear spin and electronic
orbital angular momentum contributes the most to the hyperfine interaction and
that both the hyperfine and nuclear quadrupole interactions for $^{161}$Dy and
$^{163}$Dy nucleus are much smaller than those for $^{159}$Tb nucleus in
TbPc$_2$ single-molecule magnets. The calculated separations of the
electronic-nuclear levels are comparable to experimental data reported for
$^{163}$DyPc$_2$. We demonstrate that hyperfine interaction for Dy Kramers ion
leads to tunnel splitting (or quantum tunneling of magnetization) at zero
field. This effect does not occur for TbPc$_2$ single-molecule magnets. The
magnetic field values of the avoided level crossings for $^{161}$DyPc$_2$ and
$^{163}$DyPc$_2$ are found to be noticeably different, which can be observed
from experiment.",2002.05134v1
2018-03-08,Persistent spin texture enforced by symmetry,"Persistent spin texture (PST) is the property of some materials to maintain a
uniform spin configuration in the momentum space. This property has been
predicted to support an extraordinarily long spin lifetime of carriers
promising for spintronics applications. The PST is known to emerge when the
strengths of two dominant spin-orbit couplings, the Rashba and linear
Dresselhaus, are equal. This condition, however, is not trivial to achieve and
requires tuning the Rashba and Dresselhaus parameters, as has been demonstrated
with semiconductor quantum-well structures. Here we predict that there exist a
class of non-centrosymmetric bulk materials where the PST is enforced by the
non-symmorphic space group symmetry of the crystal. Around certain high
symmetry points in the Brillouin zone, the sublattice degrees of freedom impose
a constraint on the effective spin-orbit field, which remains independent of
the momentum orientation and thus maintains the PST. We illustrate this
behavior using density-functional theory calculations for a handful of
promising candidates accessible experimentally. Among them is the ferroelectric
oxide BiInO3-a wide band gap semiconductor which sustains a PST around the
conduction band minimum. Our results broaden the range of materials, which can
be employed in spintronics.",1803.02964v2
2018-08-22,Spin-orbit Interactions for Singlet-Triplet Qubits in Silicon,"Spin-orbit coupling is relatively weak for electrons in bulk silicon, but
enhanced interactions are reported in nanostructures such as the quantum dots
used for spin qubits. These interactions have been attributed to various
dissimilar interface effects, including disorder or broken crystal symmetries.
In this Letter, we use a double-quantum-dot qubit to probe these interactions
by comparing the spins of separated singlet-triplet electron pairs. We observe
both intravalley and intervalley mechanisms, each dominant for [110] and [100]
magnetic field orientations, respectively, that are consistent with a broken
crystal symmetry model. We also observe a third spin-flip mechanism caused by
tunneling between the quantum dots. This improved understanding is important
for qubit uniformity, spin control and decoherence, and two-qubit gates.",1808.07378v2
2019-02-27,Symmetry-assisted protection and compensation of hidden spin polarization in centrosymmetric systems,"It is recently noted that in certain centrosymmetric compounds, spin-orbit
interaction couples each local sector that lacks inversion symmetry and thus
leads to visible spin polarization effects in the real space, dubbed as 'hidden
spin polarization (HSP)'. However, observable spin polarization of a given
local sector suffers interference by its inversion partner, impeding material
realization and potential applications of HSP. Starting from a single-orbital
tight-binding model, we propose a nontrivial way to protect strong
sector-projected spin texture through minimizing the interaction between
inversion partners by nonsymmorphic symmetry. The HSP effect is generally
compensated by inversion partners near the {\Gamma} point but immune from
interaction around the boundary of the Brillouin zone. We further summarize 17
layer groups that support such symmetry-assisted HSP and identify by
first-principle calculations hundreds of quasi-2D materials from the existing
databases, among which a group of rare-earth compounds LnOI (Ln = Pr, Nd, Ho,
Tm and Lu) serves as great candidates showing strong Rashba- and
Dresselhaus-type HSP. Our finding also provides an ideal platform to control
HSP for emergent physical effects, such as opening a hybridization gap by
tensile strain to realize the time-reversal-invariant topological
superconductivity.",1902.10277v1
2019-03-19,Kitaev quantum spin liquid - concept and materialization,"A decade ago, Alexei Kitaev proposed an exactly solvable $S$ = 1/2 model on a
two-dimensional honeycomb lattice, where the spins fractionalize into Majorana
fermions and form a topological quantum spin liquid (QSL) in the ground state.
It was soon recognized that a family of complex iridium oxides, as well as
ruthenium chloride, with honeycomb structure are magnetic insulators and
accommodate essential ingredients of the Kitaev model, due to the interplay of
electron correlation and spin-orbit coupling. This initiated a race to
materialize the Kitaev QSL and to capture the signature of Majorana fermions.
In this review, we provide a wide perspective of this rapidly growing field,
including theory, materials and experiment. We first summarize the theoretical
background of the Kitaev QSL ground state and its materialization using
spin-orbital-entangled $J_{\rm eff}$ = 1/2 moments. This is followed by an
overview of candidate materials and their magnetic properties, including
Na$_2$IrO$_3$, $\alpha$, $\beta$, $\gamma$-Li$_2$IrO$_3$,$\alpha$-RuCl$_3$ and
H$_3$LiIr$_2$O$_6$. Finally, we review the latest exciting progress in the
search for the Kitaev QSL. In particular, H$_3$LiIr$_2$O$_6$ and
$\alpha$-RuCl$_3$ in applied magnetic field show signatures of the QSL state,
and $\alpha$-RuCl$_3$ has unusual magnetic excitations and thermal transport
properties that are consistent with spin fractionalization.",1903.08081v1
2020-05-07,Effect of interfacial oxidation layer in spin pumping experiments on Ni$_{80}$Fe$_{20}$/SrIrO$_3$ heterostructures,"SrIrO$_3$ with its large spin-orbit coupling and low charge conductivity has
emerged as a potential candidate for efficient spin-orbit torque magnetization
control in spintronic devices. We here report on the influence of an
interfacial oxide layer on spin pumping experiments in Ni$_{80}$Fe$_{20}$
(NiFe)/SrIrO$_3$ bilayer heterostructures. To investigate this scenario we have
carried out broadband ferromagnetic resonance (BBFMR) measurements, which
indicate the presence of an interfacial antiferromagnetic oxide layer. We
performed in-plane BBFMR experiments at cryogenic temperatures, which allowed
us to simultaneously study dynamic spin pumping properties (Gilbert damping)
and static magnetic properties (such as the effective magnetization and
magnetic anisotropy). The results for NiFe/SrIrO$_3$ bilayer thin films were
analyzed and compared to those from a NiFe/NbN/SrIrO$_3$ trilayer reference
sample, where a spin-transparent, ultra-thin NbN layer was inserted to prevent
oxidation of NiFe. At low temperatures, we observe substantial differences in
the magnetization dynamics parameters of these samples, which can be explained
by an antiferromagnetic interfacial layer in the NiFe/SrIrO$_3$ bilayers.",2005.03727v1
2020-10-17,Time-Energy Uncertainty Limit for spin-related wavepacket evolution,"In this report we study the quantum transport of charge carriers for low
dimensional systems with spin-orbit coupling by means of Heisenberg's
inequalities. To develop our analysis, an accurate \emph{gendanken} experiment
was carefully put together, mainly based on the spin-field effect transistor
phenomenology and taking into account several wide accepted approaches on
quantum mechanical limited determinism. While verifying the applicability of
time-energy uncertainty relation (TEUR) during electronic wavepacket's
evolution through a semiconductor quantum wire, some qualitative information
related the dynamic behavior of the system is found. The problem is also
approached in the framework of the stationary phase method to guarantee robust
coherence for wavepacket's evolution, which lately implies certain restrictions
on the incident energy values for the envisioned cases. Tailoring different
input parameters such as: incoming particles spin polarization, barrier
thickness and Rashba's spin-orbit interaction (R-SOI) strength, we have
observed appealing effects while the packet evolves through a quasi-1D
heterostructure. Hopefully some of them could be of help in spintronics device
designing. We have obtained most of the numerical simulation results, within
the so-called conservation zone. However, for certain barrier thicknesses, some
values drop into the forbidden area regarding the clear theoretical limit
imposed by the TEUR. As an expected bonus throughout our theoretical validation
of the TEUR, spin splitting due to finite values of R-SOI was nicely noticed.",2010.08803v3
2017-07-16,First Principles Study of the Giant Magnetic Anisotropy Energy in Bulk Na4IrO4,"In 5d transition metal oxides, novel properties arise from the interplay of
electron correlations and spin--orbit interactions. Na4IrO4, where 5d
transition-metal Ir atom occupies the center of the square-planar coordination
environment, is synthesized. Based on density functional theory, we calculate
its electronic and magnetic properties. Our numerical results show that the
Ir-5d bands are quite narrow, and the bands around the Fermi level are mainly
contributed by d_{xy},d_{yz} and d_{zx} orbitals. The magnetic easy-axis is
perpendicular to the IrO4 plane, and the magnetic anisotropy energy (MAE) of
Na4IrO4 is found to be very giant. We estimate the magnetic parameters by
mapping the calculated total energy for different spin configurations onto a
spin model. The next nearest neighbor exchange interaction J2 is much larger
than other intersite exchange interactions and results in the magnetic ground
state configuration. Our study clearly demonstrates that the huge MAE comes
from the single-ion anisotropy rather than the anisotropic interatomic spin
exchange. This compound has a large spin gap but very narrow spin-wave
dispersion, due to the large single-ion anisotropy and relatively small
exchange couplings. Noticing this remarkable magnetic feature originated from
its highly isolated IrO4 moiety, we also explore the possiblity to further
enhance the MAE.",1707.04865v1
2017-07-28,Helical edge states in silicene and germanene nanorings in perpendicular magnetic field,"Due to nonzero intrinsic spin-orbit interaction in buckled honeycomb crystal
structures, silicene and germanene exhibit interesting topological properties,
and are therefore candidates for the realization of the quantum spin Hall
effect. We employ the Kane-Mele model to investigate the electron states in
hexagonal silicene and germanene nanorings having either zigzag or armchair
edges in the presence of a perpendicular magnetic field. We present results for
the energy spectra as function of magnetic field, the electron density of the
spin-up and spin-down states in the ring plane, and the calculation of the
probability current density. The quantum spin Hall phase is found at the edges
between the nontrivial topological phase in silicene and germanene and vacuum.
We demonstrate that the helical edge states in zigzag silicene and germanene
nanorings can be qualitatively well understood by means of classical magnetic
moments. However, this is not the case for comparable-sized armchair nanorings,
where the eigenfunctions spread throughout the ring. Finally, we note that the
energy spectra of silicene and germanene nanorings are similar and that the
differences between the two are mainly related to the difference in magnitude
of the spin-orbit coupling.",1707.09179v2
2022-01-21,Electrical and thermal transport in a twisted heterostructure of transition metal dichalcogenide and CrI$_3$ connected to a superconductor,"The broad tunability of the proximity exchange effect between
transition-metal dichalcogenides (TMDCs) and chromium iodide (CrI$_3$)
heterostructures offers intriguing possibilities for the use of TMDCs in
two-dimensional magnetoelectrics. In this work, the influence of the twist
angle and the gate electric field on the electric and thermal transport in a
TMDC/CrI$_3$ junction is investigated using the Dirac -Bogoliubov-de Gennes
equation. We show that significant amounts can be controlled by spin-splitting
of band structures due to spin-orbit interaction, and that the
exchange-splitting of bands arises from the proximity effect. The property of
the Andreev reflection (AR) process is highly dependent on the spin valley
polarized states due to spin-orbit coupling. Remarkably, perfect spin valley
polarized AR is possible over a wide bias range by using a gate voltage to tune
the local Fermi energy and varying the type of charge doping. The proposed
structure with $p$-type doping is found to have larger spin valley polarized
Andreev conductance and high thermal conductance. We further show that,
depending on the TMDC material and chemical potential of the TMDC/CrI$_3$
layer, twisting can lead to suppression or a significant increase in Andreev
conductance as well as enhancement of thermal conductance for chemical
potentials smaller than that of the superconducting regime.",2201.08573v2
2022-04-08,Manipulating the transverse spin angular momentum and Belinfante momentum of spin-polarized light by a tilted stratified medium in optical tweezers,"In the recent past, optical tweezers incorporating a stratified medium have
been exploited to generate complex translational and rotational dynamics in
mesoscopic particles due to the coupling between the spin and orbital angular
momentum of the light, generated as a consequence of the tight focusing of
light by a high numerical aperture objective lens into the stratified medium.
Here, we consider an optical tweezers system with a tilted stratified medium
(direction of stratification at an angle with the axis of the incident beam),
and show that for input circularly polarized Gaussian beams, the resulting
spin-orbit interaction deeply influences the generation of transverse spin
angular momentum (TSAM) and Belinfante momentum of light, and allows additional
control on their magnitude. Importantly, the TSAM generated in our system
consists of both the orthogonal components, which is in sharp contrast to the
case of evanescent waves and surface plasmons, where only one of the TSAM
components are generated. The broken symmetry due to the tilt ensures that,
depending upon the helicity of the input beam, the magnitude of the mutually
orthogonal components of the TSAM depend entirely on the tilt angle. This may
prove to be an effective handle in exotic spin-controlled manipulation of
particles in experiments.",2204.04316v2
2022-12-22,"Explicit derivation of the chiral and (generic) helical edge states for the Kane-Mele model: Closed expressions for the wave function, dispersion relation, and spin rotation","While one of the most important and intriguing features of the topological
insulators is the presence of edge states, the closed-form expressions for the
edge states of some famous topological models are still lacking. Here, we focus
on the Kane-Mele model with and without Rashba spin-orbit coupling as a
well-known model to describe a two-dimensional version of the $\mathbb{Z}_2$
topological insulator to study the properties of its edge states analytically.
By considering the tight-binding model on a honeycomb lattice with zigzag
boundaries and introducing a perturbative approach, we derive explicit
expressions for the wave functions, energy dispersion relations, and the spin
rotations of the (generic) helical edge states. To this end, we first map the
edge states of the ribbon geometry into an effective two-leg ladder model with
momentum-dependent energy parameters. Then, we split the Hamiltonian of the
system into an unperturbed part and a perturbation. The unperturbed part has a
flat-band energy spectrum and can be solved exactly which allows us to consider
the remaining part of the Hamiltonian perturbatively. The resulting energy
dispersion relation within the first-order perturbation, surprisingly, is in
excellent agreement with the numerical spectra over a very wide range of
wavenumbers. Our perturbative framework also allows deriving an explicit form
for the rotation of the spins of the momentum edge states in the absence of
axial spin symmetry due to the Rashba spin-orbit interaction.",2212.11520v1
2022-12-29,Every-other-layer Dipolar Excitons in a Spin-Valley locked Superlattice,"Monolayer semiconducting transition metal dichalcogenides possess broken
inversion symmetry and strong spin-orbit coupling, which leads to unique
spin-valley locking effect. In 2H stacked pristine multilayers, the spin-valley
locking yields an electronic superlattice structure, where alternating layers
correspond to barrier and quantum well respectively, conditioned on the
spin-valley indices. Here, we show that the spin-valley locked superlattice
hosts a new kind of dipolar excitons with the electron and hole constituents
separated in an every-other-layer configuration, i.e., either in two even or
two odd layers. Such excitons become optically bright via hybridization with
intralayer excitons, displaying multiple anti-crossing patterns in optical
reflection spectrum as the dipolar exciton is tuned through the intralayer
resonance by electric field. The reflectance spectra also reveal an excited
state orbital of the every-other-layer exciton, pointing to a sizable binding
energy in the same order of magnitude as the intralayer exciton. As layer
thickness increases, the dipolar exciton can form one-dimensional Bose-Hubbard
chain displaying a layer number dependent fine-structures in the reflectance
spectra. Our work reveals a distinct valleytronic superlattice with highly
tunable dipolar excitons for exploring light-matter interactions.",2212.14140v1
2023-01-12,Spin-orbital order and excitons in magnetoresistive HoBi,"The magnetism of the rock-salt $fcc$ rare-earth monopnictide HoBi, a
candidate topological material with extreme magnetoresistance, is investigated.
From the Ho$^{3+}$ non-Kramers $J$=8 spin-orbital multiplet, the cubic crystal
electric field yields six nearly degenerate low-energy levels. These constitute
an anisotropic magnetic moment with a Jahn-Teller-like coupling to the lattice.
In the cubic phase for $T>T_N~=~5.72(1)~K$, the paramagnetic neutron scattering
is centered at $\mathbf{k}=(\frac{1}{2}\frac{1}{2}\frac{1}{2})$ and was fit to
dominant antiferromagnetic interactions between Ho spins separated by $\{100\}$
and ferromagnetic interactions between spins displaced by
$\{\frac{1}{2}\frac{1}{2}0\}$. For $T<T_N$, a type-II AFM long-range order with
$\mathbf{k}=(\frac{1}{2}\frac{1}{2}\frac{1}{2})$ develops along with a
tetragonal lattice distortion. While neutron diffraction from a multi-domain
sample cannot unambiguously determine the spin orientation within a domain, the
bulk magnetization, structural distortion, and our measurements of the magnetic
excitations all show the easy axis coincides with the tetragonal axis. The
weakly dispersive excitons for $T<T_N$ can be accounted for by a spin
Hamiltonian that includes the crystal electric field and exchange interactions
within the Random Phase Approximation.",2301.05141v1
2023-07-21,Magnetic Proximity induced efficient charge-to-spin conversion in large area PtSe$_{2}$/Ni$_{80}$Fe$_{20}$ heterostructures,"As a topological Dirac semimetal with controllable spin-orbit coupling and
conductivity, PtSe$_2$, a transition-metal dichalcogenide, is a promising
material for several applications from optoelectric to sensors. However, its
potential for spintronics applications is yet to be explored. In this work, we
demonstrate that PtSe$_{2}$/Ni$_{80}$Fe$_{20}$ heterostructure can generate a
large damping-like current-induced spin-orbit torques (SOT), despite the
absence of spin-splitting in bulk PtSe$_{2}$. The efficiency of charge-to-spin
conversion is found to be $(-0.1 \pm 0.02)$~nm$^{-1}$ in
PtSe$_{2}$/Ni$_{80}$Fe$_{20}$, which is three times that of the control sample,
Ni$_{80}$Fe$_{20}$/Pt. Our band structure calculations show that the SOT due to
the PtSe$_2$ arises from an unexpectedly large spin splitting in the
interfacial region of PtSe$_2$ introduced by the proximity magnetic field of
the Ni$_{80}$Fe$_{20}$ layer. Our results open up the possibilities of using
large-area PtSe$_{2}$ for energy-efficient nanoscale devices by utilizing the
proximity-induced SOT.",2307.11524v1
2000-04-24,Magnetic Phase Transition of the Perovskite-type Ti Oxides,"Properties and mechanism of the magnetic phase transition of the
perovskite-type Ti oxides, which is driven by the Ti-O-Ti bond angle
distortion, are studied theoretically by using the effective spin and
pseudo-spin Hamiltonian with strong Coulomb repulsion. It is shown that the
A-type antiferromagnetic(AFM(A)) to ferromagnetic(FM) phase transition occurs
as the Ti-O-Ti bond angle is decreased. Through this phase transition, the
orbital state is hardly changed so that the spin-exchange coupling along the
c-axis changes nearly continuously from positive to negative and takes
approximately zero at the phase boundary. The resultant strong
two-dimensionality in the spin coupling causes a rapid suppression of the
critical temperature as is observed experimentally.",0004389v1
2004-07-28,Tunneling Anisotropic Magnetoresistance: A spin-valve like tunnel magnetoresistance using a single magnetic layer,"We introduce a new class of spintronics devices in which a spin-valve like
effect results from strong spin-orbit coupling in a single ferromagnetic layer
rather than from injection and detection of a spin-polarized current by two
coupled ferromagnets. The effect is observed in a
normal-metal/insulator/ferromagnetic-semiconductor tunneling device. This
behavior is caused by the interplay of the anisotropic density of states in
(Ga,Mn)As with respect to the magnetization direction, and the two-step
magnetization reversal process in this material.",0407735v1
2007-05-04,Two Qubit Entanglement in $XYZ$ Magnetic Chain with DM Antisymmetric Anisotropic Exchange Interaction,"In the present paper we study two qubit entanglement in the most general
$XYZ$ Heisenberg magnetic chain with (non)homogeneous magnetic fields and the
DM anisotropic antisymmetric exchange interaction, arising from the spin-orbit
coupling . The model includes all known results as particular cases, for both
antiferromagnetic and ferromagnetic $XX, XY, XXX, XXZ, XYZ$ chains. The
concurrence of two qubit thermal entanglement and its dependence on anisotropic
parameters, external magnetic field and temperature are studied in details. We
found that in all cases, inclusion of the DM interaction, which is responsible
for weak ferromagnetism in mainly antiferromagnetic crystals and spin
arrangement in low symmetry magnets, creates (when it does not exist) or
strengthens (when it exists) entanglement in $XYZ$ spin chain. This implies
existence of a relation between arrangement of spins and entanglement, in which
the DM coupling plays an essential role. It suggests also that anisotropic
antisymmetric exchange interaction could be an efficient control parameter of
entanglement in the general $XYZ$ case.",0705.0679v1
2009-05-07,Fractional vortex lattice structures in spin triplet superconductors,"Motivated by recent interest in spin triplet superconductors, we investigate
the vortex lattice structures for this class of unconventional superconductors.
We discuss how the order parameter symmetry can give rise to U(1)$\times$U(1)
symmetry in same sense as in spinor condensates, making half-quantum vortices
(HQV) topologically stable. We then calculate the vortex lattice structure of
HQV's, with particular attention on the roles of the crystalline lattice, the
Zeeman coupling, and Meissner screening, all absent in spinor condensates.
Finally, we consider how spin-orbit coupling leads to a breakdown of the
U(1)$\times$U(1) symmetry in free energy and whether the HQV lattice survives
this symmetry breaking. As examples, we examine simpler spin-triplet models
proposed in the context of NaxCoO2$\cdot$yH2O and Bechgaard salts, as well as
the better known and more complex model for Sr2RuO4.",0905.1132v2
2010-02-24,Spin interference and Fano effect in electron transport through a mesoscopic ring side-coupled with a quantum dot,"We investigate the electron transport through a mesoscopic ring side-coupled
with a quantum dot(QD) in the presence of Rashba spin-orbit(SO) interaction. It
is shown that both the Fano resonance and the spin interference effects play
important roles in the electron transport properties. As the QD level is around
the Fermi energy, the total conductance shows typical Fano resonance line
shape. By applying an electrical gate voltage to the QD, the total transmission
through the system can be strongly modulated. By threading the mesoscopic ring
with a magnetic flux, the time-reversal symmetry of the system is broken, and a
spin polarized current can be obtained even though the incident current is
unpolarized.",1002.4455v1
2010-07-02,"Unconventional superconductivity in weakly correlated, non-centrosymmetric $\rm{Mo_3Al_2C}$","Electrical resistivity, specific heat and NMR measurements classify
non-centrosymmetric $\rm Mo_3Al_2C$ ($\beta$-Mn type, space group $P4_132$) as
a strong-coupled superconductor with $T_c = 9$~K deviating notably from
BCS-like behaviour. The absence of a Hebbel-Slichter peak, a power law
behaviour of the spin-lattice relaxation rate (from $^{27}$Al NMR), a $T^3$
temperature dependence of the specific heat and a pressure enhanced $T_c$
suggest unconventional superconductivity with a nodal structure of the
superconducting gap. Relativistic DFT calculations reveal a splitting of
degenerate electronic bands due to the asymmetric spin-orbit coupling,
favouring a mix of spin-singlet and spin triplet components in the
superconducting condensate, in absence of strong correlations among electrons.",1007.0420v1
2012-12-07,Nanomechanical read-out of a single spin,"The spin of a single electron in a suspended carbon nanotube can be read out
by using its coupling to the nano-mechanical motion of the nanotube. To show
this, we consider a single electron confined within a quantum dot formed by the
suspended carbon nanotube. The spin- orbit interaction induces a coupling
between the spin and one of the bending modes of the suspended part of the
nanotube. We calculate the response of the system to pulsed external driving of
the mechanical motion using a Jaynes-Cummings model. To account for resonator
damping, we solve a quantum master equation, with parameters comparable to
those used in recent experiments, and show how information of the spin state of
the system can be acquired by measuring its mechanical motion. The latter can
be detected by observing the current through a nearby charge detector.",1212.1569v1
2013-01-24,Topological phase in a two-dimensional metallic heavy-fermion system,"We report on a topological insulating state in a heavy-fermion system away
from half-filling, which is hidden within a ferromagnetic metallic phase. In
this phase, the cooperation of the RKKY interaction and the Kondo effect,
together with the spin-orbit coupling, induces a spin-selective gap, bringing
about topologically non-trivial properties. This topological phase is robust
against a change in the chemical potential in a much wider range than the gap
size. We analyze these remarkable properties by using dynamical mean field
theory and the numerical renormalization group. Its topological properties
support a gapless chiral edge mode, which exhibits a non-Tomonaga-Luttinger
liquid behavior due to the coupling with bulk ferromagnetic spin fluctuations.
We also propose that the effects of the spin fluctuations on the edge mode can
be detected via the NMR relaxation time measurement.",1301.5688v2
2013-02-28,Spin-flip phonon-mediated charge relaxation in double quantum dots,"We theoretically study the $(1,1)$ triplet to $(0,2)$ singlet relaxation rate
in a lateral gate-defined double quantum dot tuned to the regime of Pauli spin
blockade. We present a detailed derivation of the effective phonon density of
states for this specific charge transition, keeping track of the contribution
from piezoelectric as well as deformation potential electron-phonon coupling.
We further investigate two different spin-mixing mechanisms which can couple
the triplet and singlet states: a magnetic field gradient over the double dot
(relevant at low external magnetic field) and spin-orbit interaction (relevant
at high field), and we also indicate how the two processes could interfere at
intermediate magnetic field. Finally, we show how to combine all results and
evaluate the relaxation rate for realistic system parameters.",1302.7169v1
2013-10-22,Thermal conductivity of anisotropic spin - 1/2 two leg ladder:Green's function approach,"We study the thermal transport of a spin-1/2 two leg antiferromagnetic ladder
in the direction of legs. The possible effect of spin-orbit coupling and
crystalline electric field are investigated in terms of anisotropies in the
Heisenberg interactions on both leg and rung couplings. The original spin
ladder is mapped to a bosonic model via a bond-operator transformation where an
infinite hard-core repulsion is imposed to constrain one boson occupation per
site. The Green's function approach is applied to obtain the energy spectrum of
quasi-particle excitations responsible for thermal transport. The thermal
conductivity is found to be monotonically decreasing with temperature due to
increased scattering among triplet excitations at higher temperatures. A tiny
dependence of thermal transport on the anisotropy in the leg direction at low
temperatures is observed in contrast to the strong one on the anisotropy along
the rung direction, due to the direct effect of the triplet density. Our
results reach asymptotically the ballistic regime of the spin - 1/2 Heisenberg
chain and compare favorably well with exact diagonalization data.",1310.5943v1
2014-04-07,Spin and impurity effects on flux-periodic oscillations in core-shell nanowires,"We study the quantum mechanical states of electrons situated on a cylindrical
surface of finite axial length to model a semiconductor core-shell nanowire. We
calculate the conductance in the presence of a longitudinal magnetic field by
weakly coupling the cylinder to semi-infinite leads. Spin effects are accounted
for through Zeeman coupling and Rashba spin-orbit interaction (SOI). Emphasis
is on manifestations of flux-periodic (FP) oscillations and we show how factors
such as impurities, contact geometry and spin affect them. Oscillations survive
and remain periodic in the presence of impurities, noncircular contacts and
SOI, while Zeeman splitting results in aperiodicity, beating patterns and
additional background fluctuations. Our results are in qualitative agreement
with recent magnetotransport experiments performed on GaAs/InAs core-shell
nanowires. Lastly, we propose methods of data analysis for detecting the
presence of Rashba SOI in core-shell systems and for estimating the electron
g-factor in the shell.",1404.1798v2
2019-09-01,Magnetic field-dependent low-energy magnon dynamics in $α$-RuCl3,"Revealing the spin excitations of complex quantum magnets is key to
developing a minimal model that explains the underlying magnetic correlations
in the ground state. We investigate the low-energy magnons in $\alpha$-RuCl$_3$
by combining time-domain terahertz spectroscopy under an external magnetic
field and model Hamiltonian calculations. We observe two absorption peaks
around 2.0 and 2.4 meV, which we attribute to zone-center spin waves. Using
linear spin-wave theory with only nearest-neighbor terms of the exchange
couplings, we calculate the antiferromagnetic resonance frequencies and reveal
their dependence on an external field applied parallel to the nearest-neighbor
Ru-Ru bonds. We find that the magnon behavior in an applied magnetic field can
be understood only by including an off-diagonal $\Gamma$ exchange term to the
minimal Heisenberg-Kitaev model. Such an anisotropic exchange interaction that
manifests itself as a result of strong spin-orbit coupling can naturally
account for the observed mixing of the modes at higher fields strengths.",1909.00462v1
2020-02-14,All-electrical spectroscopy of topological phases in semiconductor-superconductor heterostructures,"Semiconductors in the proximity of superconductors have been proposed to
support phases hosting Majorana bound states. When the systems undergo a
topological phase transition towards the Majorana phase, the spectral gap
closes, then reopens, and the quasiparticle band spin polarization is inverted.
We focus on two paradigmatic semiconductor-superconductor heterostructures and
propose an all-electrical spectroscopic probe sensitive to the spin inversion
at the topological transition. Our proposal relies on the indirect coupling of
a time-dependent electric field to the electronic spin due to the strong Rashba
spin-orbit coupling in the semiconductor. We analyze within linear response
theory the dynamical correlation functions and demonstrate that some components
of the susceptibility can be used to detect the nontrivial topological phases.",2002.06092v2
2020-04-17,Superconductivity induced by fluctuations of momentum-based multipoles,"Recent studies of unconventional superconductivity have focused on charge or
spin fluctuation, instead of electron-phonon coupling, as an origin of
attractive interaction between electrons. On the other hand, a multipole order,
which represents electrons' degrees of freedom in strongly correlated and
spin-orbit-coupled systems, has recently been attracting much attention.
Stimulated by this background, we investigate multipole-fluctuation-mediated
superconductivity, which proposes a new pairing mechanism of unconventional
superconductivity. Indeed, previous works have shown spin-triplet
superconductivity induced by fluctuations of odd-parity electric multipole
orders in isotropic systems. In this study, we establish a general formulation
of the multipole-fluctuation-mediated superconductivity for all multipole
symmetries, in both isotropic and crystalline systems. As a result, we reveal
various anisotropic pairings induced by odd-parity and/or higher-order
multipole fluctuations, which are beyond the ordinary charge or spin
fluctuations. Topological superconductivity due to the mechanism is also
discussed. Based on the obtained results, we discuss unconventional
superconductivity in doped SrTiO$_3$, PrTi$_2$Al$_{20}$, Li$_2$(Pd, Pt)$_3$B,
and magnetic multipole metals.",2004.08086v3
2017-09-13,Negative-mass instability of the spin and motion of an atomic gas driven by optical cavity backaction,"We realize a spin-orbit interaction between the collective spin precession
and center-of-mass motion of a trapped ultracold atomic gas, mediated by spin-
and position-dependent dispersive coupling to a driven optical cavity. The
collective spin, precessing near its highest-energy state in an applied
magnetic field, can be approximated as a negative-mass harmonic oscillator.
When the Larmor precession and mechanical motion are nearly resonant, cavity
mediated coupling leads to a negative-mass instability, driving exponential
growth of a correlated mode of the hybrid system. We observe this growth
imprinted on modulations of the cavity field and estimate the full covariance
of the resulting two-mode state by observing its transient decay during
subsequent free evolution.",1709.04531v2
2019-02-19,"Spinning extensions of $D(2,1;α)$ superconformal mechanics","As is known, any realization of SU(2) in the phase space of a dynamical
system can be generalized to accommodate the exceptional supergroup
$D(2,1;\alpha)$, which is the most general $\mathcal{N}{=}\,4$ supersymmetric
extension of the conformal group in one spatial dimension. We construct novel
spinning extensions of $D(2,1;\alpha)$ superconformal mechanics by adjusting
the SU(2) generators associated with the relativistic spinning particle coupled
to a spherically symmetric Einstein-Maxwell background. The angular sector of
the full superconformal system corresponds to the orbital motion of a particle
coupled to a symmetric Euler top, which represents the spin degrees of freedom.
This particle moves either on the two-sphere, optionally in the external field
of a Dirac monopole, or in the SU(2) group manifold. Each case is proven to be
superintegrable, and explicit solutions are given.",1902.06851v1
2019-03-01,Anomalous Knight shift and low-energy spin dynamics in the nematic state of FeSe$_{\rm 1-x}$S$_{\rm x}$,"The interplay between the nematic order and magnetism in FeSe is not yet well
understood. There is a controversy concerning the relationship between orbital
and spin degrees of freedom in FeSe and their relevance for superconductivity.
Here we investigate the effect of S substitution on the nematic transition
temperature ($T_{\rm n}$) and the low-energy spin fluctuations (SF) in FeSe
single crystals. We show that the low-energy SF emerge below the nematic
transition. The difference between the onset temperature for the critical SF
($T_{\rm SF}$) and $T_{\rm n}$ is small for FeSe but significantly increases
with S substitution. Below $T_{\rm SF}$ the Korringa relation is violated and
the effective muon hyperfine coupling constant changes a sign. Our results
exclude a direct coupling of the low-energy SF to the electronic nematic order
indicating a presence of multiple spin degrees of freedom in FeSe$_{\rm
1-x}$S$_{\rm x}$.",1903.00530v1
2019-08-14,Magnetic hedgehog lattices in noncentrosymmetric metals,"The magnetic hedgehog lattice (HL) is a noncoplanar magnetic texture with a
periodic array of magnetic monopoles and anti-monopoles. Despite
phenomenological and numerical studies thus far, there remain open issues on
the microscopic origin, especially with respect to the recent experimental
findings of two different types of HLs even at zero magnetic field. Here, we
study the stability of the HLs for an effective spin model with long-range
interactions arising from itinerant nature of electrons. By variational
calculations and simulated annealing, we find that the HLs are stabilized in
the ground state at zero magnetic field by the synergetic effect of the
anti-symmetric exchange interactions generated by the spin-orbit coupling and
the multiple-spin interactions generated by the spin-charge coupling. We also
clarify the phase diagram in the magnetic fields, which includes topological
phase transitions with pair annihilation of the monopoles and anti-monopoles
depending on the field directions.",1908.05044v2
2019-12-25,Approaching the quantum critical point in a highly-correlated all-in-all-out antiferromagnet,"Continuous quantum phase transitions involving all-in-all-out (AIAO)
antiferromagnetic order in strongly spin-orbit-coupled 5d compounds could give
rise to various exotic electronic phases and strongly-coupled quantum critical
phenomena. Here we experimentally trace the AIAO spin order in Sm2Ir2O7 using
direct resonant x-ray magnetic diffraction techniques under high pressure. The
magnetic order is suppressed at a critical pressure Pc=6.30 GPa, while the
lattice symmetry remains in the cubic Fd-3m space group across the quantum
critical point. Comparing pressure tuning and the chemical series R2Ir2O7
reveals that the suppression of the AIAO order and the approach to the
spin-disordered state is characterized by contrasting evolutions of both the
pyrochlore lattice constant a and the trigonal distortion x. The former affects
the 5d bandwidth, the latter the Ising anisotropy, and as such we posit that
the opposite effects of pressure and chemical tuning lead to spin fluctuations
with different Ising and Heisenberg character in the quantum critical region.
Finally, the observed low-pressure scale of the AIAO quantum phase transition
in Sm2Ir2O7 identifies a circumscribed region of P-T space for investigating
the putative magnetic Weyl-semimetal state.",1912.11640v1
2020-09-29,Quantum phase transitions in the spin-1 Kitaev-Heisenberg chain,"Recently, it has been proposed that higher-spin analogues of the Kitaev
interactions $K>0$ may also occur in a number of materials with strong Hund's
and spin-orbit coupling. In this work, we use Lanczos diagonalization and
density matrix renormalization group methods to investigate numerically the
$S=1$ Kitaev-Heisenberg model. The ground-state phase diagram and quantum phase
transitions are investigated by employing local and nonlocal spin correlations.
We identified two ordered phases at negative Heisenberg coupling $J<0$:
a~ferromagnetic phase with $\langle S_i^zS_{i+1}^z\rangle>0$ and an
intermediate left-left-right-right phase with $\langle
S_i^xS_{i+1}^x\rangle\neq 0$. A~quantum spin liquid is stable near the Kitaev
limit, while a topological Haldane phase is found for $J>0$.",2009.14159v1
2021-03-07,Phonon Hall Viscosity in Magnetic Insulators,"The Phonon Hall Viscosity is the leading term evincing time-reversal symmetry
breaking in the low energy description of lattice phonons. It may generate
phonon Berry curvature, and can be observed experimentally through the acoustic
Faraday effect and thermal Hall transport. We present a systematic procedure to
obtain the phonon Hall viscosity induced by phonon-magnon interactions in
magnetic insulators under an external magnetic field. We obtain a general
symmetry criterion that leads to non-zero Faraday rotation and Hall
conductivity, and clarify the interplay between lattice symmetry,
spin-orbit-coupling, external magnetic field and magnetic ordering. The
symmetry analysis is verified through a microscopic calculation. By
constructing the general symmetry-allowed effective action that describes the
spin dynamics and spin-lattice coupling, and then integrating out the spin
fluctuations, the leading order time-reversal breaking term in the phonon
effective action, i.e. the phonon Hall viscosity, can be obtained. The analysis
of the square lattice antiferromagnet for a cuprate Mott insulator,
Sr$_2$CuO$_2$Cl$_2$, is presented explicitly, and the procedure described here
can be readily generalized to other magnetic insulators.",2103.04223v1
2021-07-07,Meron-antimeron crystals in noncentrosymmetric itinerant magnets on a triangular lattice,"Multiple-$Q$ magnetic states often induce nontrivial topological spin
textures, such as a skyrmion and a hedgehog. We theoretically investigate yet
another multiple-$Q$ state with topological defects, a meron-antimeron crystal
(MAX), represented by a periodic array of the meron and antimeron with a
half-integer skyrmion number. Performing simulated annealing for an effective
spin model of noncentrosymmetric itinerant magnets on a triangular lattice, we
show that rectangular-shaped and triangular-shaped MAXs are stabilized by the
interplay between the biquadratic interaction arising from the spin-charge
coupling and the Dzyaloshinskii-Moriya interaction arising from the spin-orbit
coupling. We also discuss the effect of a magnetic field on the triangular MAX,
where highly anisotropic responses against a field direction are found. In
particular, we show that the triangular MAX turns into the skyrmion crystal for
the fields along the $y$ and $z$ directions, while it is replaced by another
chiral state for the field along the $x$ direction. These results would inspire
further experimental investigation of the MAXs in itinerant magnets.",2107.03501v1
2021-10-25,Engineering crystal structure and spin-phonon coupling in Ba1-xSrxMnO3,"The interplay between different degrees of freedom such as charge, spin,
orbital, and lattice has received a great deal of interest due to its potential
to engineer materials properties and their functionalities for device
applications. In this work, we have explored the crystallographic phase diagram
of Ba1-xSrxMnO3 and studied the correlation between two degrees of freedom,
namely phonons and spins using magnetization and inelastic light scattering
measurements. The system undergoes a series of crystallographic phase
transitions 2H -> 9R -> 4H as a function of doping (Sr) as observed by X-ray
diffraction measurements. Investigation of their temperature-dependent
magnetization reveals a para- to antiferro-magnetic transition for all the
compositions. An Eg phonon in the 9R phase and an E1g phonon in the 4H phase
involving Mn or O-vibrations, show anomalous temperature-dependence in the
antiferromagnetic phase arising due to spin-phonon coupling.",2110.12821v1
2021-12-23,Curvature control of the superconducting proximity effect in diffusive ferromagnetic nanowires,"Coupling a conventional s-wave superconductor to a ferromagnet allows, via
the proximity effect, to generate superconducting triplet correlations. This
feature can be employed to achieve a superconducting triplet spin-valve effect
in superconductor-ferromagnet (SF) hybrid structures, for example by switching
the magnetizations of the ferromagnets between parallel and antiparallel
configurations in F1SF2 and SF1F2 trilayers, or in SF bilayers with both Rashba
and Dresselhaus SOC. It was recently reported that geometric curvature can
control the generation of long ranged triplets. We use this property to show
that the superconducting critical temperature of an SF hybrid nanowire can be
tuned by varying the curvature of the ferromagnetic side alone, with no need of
another ferromagnet or SOC. We show that the variation of the critical
temperature as a function of the curvature can be exploited to obtain a robust,
curvature-controlled, superconducting triplet spin-valve effect. Furthermore,
we perform an analysis with the inclusion of spin-orbit coupling and explain
how it modifies the spin-valve effect both quantitatively and qualitatively.",2112.12797v1
2022-01-31,A method for the variational calculation of hyperfine-resolved rovibronic spectra of diatomic molecules,"An algorithm for the calculation of hyperfine structure and spectra of
diatomic molecules based on the variational nuclear motion is presented.
Hyperfine coupling terms considered are Fermi-contact, nuclear spin-electron
spin dipole-dipole, nuclear spin-orbit, nuclear spin-rotation and nuclear
electric quadrupole interactions. Initial hyperfine-unresolved wavefunctions
are obtained for given set of potential energy curves and associated couplings
by variation solution of the nuclear-motion Schr\""odinger equation. Fully
hyperfine-resolved parity-conserved rovibronic Hamiltonian matrices for a given
final angular momentum, $\bm{F}$, are constructed and then diagonalized to give
hyperfine-resolved energies and wavefunctions.Electric transition dipole moment
curves can then be used to generate a hyperfine-resolved line list by applying
rigorous selection rules.The algorithm is implemented in \textsc{Duo}, which is
a general program for calculating spectra of diatomic molecules. This approach
is tested for NO and MgH,and the results are compared to experiment and shown
to be consistent with those given the well-used effective Hamiltonian code
PGOPHER.",2201.13104v1
2022-08-22,Ultrafast Spin Dynamics and Photoinduced Insulator-to-Metal Transition in $α$-$RuCl_3$,"Laser-induced ultrafast demagnetization is a phenomenon of utmost interest
and attracts significant attention because it enables potential applications in
ultrafast optoelectronics and spintronics. As a spin-orbit coupling assisted
magnetic insulator, $\alpha$-$RuCl_3$ provides an attractive platform to
explore the physics of electronic correlations and related unconventional
magnetism. Using time-dependent density functional theory, we explore the
ultrafast laser-induced dynamics of the electronic and magnetic structures in
$\alpha$-$RuCl_3$. Our study unveils that laser pulses can introduce ultrafast
demagnetizations in $\alpha$-$RuCl_3$, accompanied by an out-of-equilibrium
insulator-to-metal transition in a few tens of femtoseconds. The spin response
significantly depends on the laser wavelength and polarization on account of
the electron correlations, band renormalizations and charge redistributions.
These findings provide physical insights into the coupling between the
electronic and magnetic degrees of freedom in $\alpha$-$RuCl_3$ and shed light
on suppressing the long-range magnetic orders and reaching a proximate spin
liquid phase for two-dimensional magnets on an ultrafast timescale.",2208.10222v1
2006-08-03,Persistent spin helix in Rashba-Dresselhaus two-dimensional electron systems,"A persistent spin helix (PSH) in spin-orbit-coupled two-dimensional electron
systems was recently predicted to exist in two cases: [001] quantum wells (QWs)
with equal coupling strengths of the Rashba and the Dresselhaus interactions
(RD), and Dresselhaus-only [110] QWs. Here we present supporting results and
further investigations, using our previous results [Phys. Rev. B 72, 153305
(2005)]. Refined PSH patterns for both RD [001] and Dresselhaus [110] QWs are
shown, such that the feature of the helix is clearly seen. We also discuss the
time dependence of spin to reexamine the origin of the predicted persistence of
the PSH. For the RD [001] case, we further take into account the random Rashba
effect, which is much more realistic than the constant Rashba model. The
distorted PSH pattern thus obtained suggests that such a PSH may be more
observable in the Dresselhaus [110] QWs, if the dopants cannot be regularly
enough distributed.",0608077v2
2007-12-29,Four-Step Evolution of Spin-Hall Conductance: Tight-Binding Electrons with Rashba Coupling in a Magnetic Field,"An intriguing magneto-transport property is demonstrated by tight-binding
lattice electrons with Rashba spin-orbit coupling (SOC) in a magnetic field.
With the flux strength $\phi={2\pi/N}$ ($N$ is an integer) and the Zeeman
splitting fixed, when increasing the Rashba SOC $\lambda$, the spin-Hall and
charge-Hall conductances (SHC and CHC) undergo four-step evolutions: the SHC
shows size-dependent resonances and jumps at three critical $\lambda_{c}$'s,
and changes its sign at $\lambda_{c1}$ and $\lambda_{c3}$; while the CHC
exhibits three quantum jumps by $-Ne^2/h$, $+2Ne^2/h$ and $-Ne^2/h$. Such
four-step evolutions are also reflected in topological characters and spin
polarizations of edge states of a cylindrical system, and are robust against
weak disorder.",0801.0035v1
2009-09-23,Decoherence of spin qubits due to a nearby charge fluctuator in gate-defined double dots,"The effects of a nearby two-level charge fluctuator on a double-dot two-spin
qubit are studied theoretically. Assuming no direct tunneling between the
charge fluctuator and the qubit quantum dots, the Coulomb couplings between the
qubit orbital states and the fluctuator are calculated within the Hund-Mulliken
framework to quadrupole-quadrupole order in a multipole expansion. We identify
and quantify the coupling term that entangles the qubit to the fluctuator and
analyze qubit decoherence effects that result from the decay of the fluctuator
to its reservoir. Our results show that the charge environment can severely
impact the performance of spin qubits, and indicate working points at which
this decoherence channel is minimized. Our analysis also suggests that an
ancillary double-dot can provide a convenient point for single-qubit operations
and idle position, adding flexibility in the quantum control of the two-spin
qubit.",0909.4116v1
2010-03-04,Generic nodeless Larkin Ovchinnikov states due to singlet-triplet mixing,"Larkin-Ovchinnikov (LO) states typically have a singlet-gap that vanishes
along real-space lines. These real-space nodes lead to Andreev midgap states
which can serve as a signature of LO pairing. We show that at these nodes, an
odd-parity, spin-triplet component is always induced, leading to a nodeless LO
phase. We find the two-dimensional weak coupling, clean limit s-wave phase
diagram when this spin-triplet part is included. The triplet component is large
and increases the stability of the FFLO phase. We also show that the
spin-triplet contribution pushes the midgap states away from zero energy.
Finally, we show how our results can be explained phenomenologically though
Lifshitz invariants. These invariants provide a simple approach to understand
the role of unconventional pairing states, spin-orbit coupling, and
inhomogeneous mixed singlet-triplet states that are not due to a FFLO
instability. We discuss our results in the context of organic superconductors.",1003.1152v1
2010-07-27,Magnetic Response in Quantized Spin Hall Phase of Correlated Electrons,"We investigate the magnetic response in the quantized spin Hall (SH) phase of
layered-honeycomb lattice system with intrinsic spin-orbit coupling lambda_SO
and on-site Hubbard U. The response is characterized by a parameter g= 4 U a^2
d / 3, where a and d are the lattice constant and interlayer distance,
respectively. When g< (sigma_{xy}^{s2} mu)^{-1}, where sigma_{xy}^{s} is the
quantized spin Hall conductivity and mu is the magnetic permeability, the
magnetic field inside the sample oscillates spatially. The oscillation vanishes
in the non-interacting limit U -> 0. When g > (sigma_{xy}^{s2} mu)^{-1}, the
system shows perfect diamagnetism, i.e., the Meissner effect occurs. We find
that superlattice structure with large lattice constant is favorable to see
these phenomena. We also point out that, as a result of Zeeman coupling, the
topologically-protected helical edge states shows weak diamagnetism which is
independent of the parameter g.",1007.4671v3
2012-10-04,Relativistic new Yukawa-like potential and tensor coupling,"We approximately solve the Dirac equation for a new suggested generalized
inversely quadratic Yukawa (GIQY) potential including a Coulomb-like tensor
interaction with arbitrary spin-orbit coupling quantum number In the framework
of the spin and pseudospin (p-spin) symmetry, we obtain the energy eigenvalue
equation and the corresponding eigenfunctions, in closed form, by using the
parametric Nikiforov-Uvarov (NU) method. The numerical results show that the
Coulomb-like tensor interaction, removes degeneracies between spin and p-spin
state doublets. The Dirac solutions in the presence of exact spin symmetry are
reduced to Schr\""odinger solutions for Yukawa and inversely quadratic Yukawa
potentials.",1210.1406v1
2014-12-13,On the Role of a Torsion-like Field in a Scenario for the Spin Hall Effect,"Starting from an action that describes a Dirac fermion, we propose and
analyze a model based on a low-relativistic Pauli equation coupled to a
torsion-like term to study Spin Hall Effect (SHE). We point out a very
particular connection between the modified Pauli equation and the (SHE), where
what we refer to torsion as field playing an important r\^ole in the spin-orbit
coupling process. In this scenario, we present a proposal of a spin-type
current, considering the tiny contributions of torsion in connection with
geometrical properties of the material.",1412.4272v2
2017-02-16,Anomalous Nonlocal Resistance and Spin-charge Conversion Mechanisms in Two-Dimensional Metals,"We uncover two anomalous features in the nonlocal transport behavior of
two-dimensional metallic materials with spin-orbit coupling. Firstly, the
nonlocal resistance can have negative values and oscillate with distance, even
in the absence of a magnetic field. Secondly, the oscillations of the nonlocal
resistance under an applied in-plane magnetic field (Hanle effect) can be
asymmetric under field reversal. Both features are produced by direct
magnetoelectric coupling, which is possible in materials with broken inversion
symmetry but was not included in previous spin diffusion theories of nonlocal
transport. These effects can be used to identify the relative contributions of
different spin-charge conversion mechanisms. They should be observable in
adatom-functionalized graphene, and may provide the reason for discrepancies in
recent nonlocal transport experiments on graphene.",1702.04955v3
2019-07-09,"Large, tunable valley splitting and single-spin relaxation mechanisms in a Si/Si$_x$Ge$_{1-x}$ quantum dot","Valley splitting is a key figure of silicon-based spin qubits. Quantum dots
in Si/SiGe heterostructures reportedly suffer from a relatively low valley
splitting, limiting the operation temperature and the scalability of such qubit
devices. Here, we demonstrate a robust and large valley splitting exceeding 200
$\mu$eV in a gate-defined single quantum dot, hosted in molecular-beam
epitaxy-grown $^{28}$Si/SiGe. The valley splitting is monotonically and
reproducibly tunable up to 15 % by gate voltages, originating from a 6 nm
lateral displacement of the quantum dot. We observe static spin relaxation
times $T_1>1$ s at low magnetic fields in our device containing an integrated
nanomagnet. At higher magnetic fields, $T_1$ is limited by the valley hotspot
and by phonon noise coupling to intrinsic and artificial spin-orbit coupling,
including phonon bottlenecking.",1907.04146v2
2019-10-01,Nickelate superconductors $--$ Multiorbital nature and spin freezing,"Superconductivity with a remarkably high $T_c$ has recently been found in
Sr-doped NdNiO$_2$ thin films. While this system bears strong similarities to
the cuprates, some differences, such as a weaker antiferromagnetic exchange
coupling and possible high-spin moments on the doped Ni sites have been pointed
out. Here, we investigate the effect of Hund coupling and crystal field
splitting in a simple model system and argue that a multiorbital description of
nickelate superconductors is warranted, especially in the strongly hole-doped
regime. We then look at this system from the viewpoint of the spin-freezing
theory of unconventional superconductivity, which provides a unified
understanding of unconventional superconductivity in a broad range of
compounds. Sr$_{0.2}$Nd$_{0.8}$NiO$_2$ falls into a parameter regime influenced
by two spin-freezing crossovers, one related to the emergent multi-orbital
nature in the strongly doped regime and the other related to the single-band
character and square lattice geometry in the weakly doped regime.",1910.00473v1
2020-03-13,The remarkable accuracy of an $O(N^6)$ perturbative correction to opposite-spin CCSD: are triples necessary for chemical accuracy in coupled cluster?,"The focus of this work is OS-CCSD-SPT(2), which is a second-order similarity
transformed perturbation theory correction to opposite spin coupled cluster
singles doubles, where in the latter the same-spin amplitudes are removed and
the opposite-spin ones are solved self consistently. We demonstrate that, for
non-multireference molecules, OS-CCSD-SPT(2) produces relative energies that
rival the accuracy of higher-order methods like CCSD(T). For example, using
PBE0 orbitals in the reference, OS-CCSD-SPT(2) exhibits a mean absolute
deviation (MAD) of 0.66 kcal/mol with respect to CCSD(2) benchmark values for
the non-multireference subset of W4-08 atomization energies (c.f. a MAD > 6
kcal/mol for CCSD). OS-CCSD-SPT(2) is free of empirical parameters, has an
instrinsic scaling of $O(N^6)$, and makes no use of triples. It is also
naturally amenable to higher order corrections: the associated third-order
correction, OS-CCSD-SPT(3), which does involve connected triples and
quadruples, exhibits a MAD of 0.44 kcal/mol for the same benchmark.",2003.06088v1
2021-07-06,Constructive Quantum Interference in a Photo-Chemical Reaction of $^{87}$Rb Bose Einstein Condensate,"Interferences emerge when multiple pathways coexist together leading towards
the same result. A Recent study by Blasing and coworkers [PRL 121(7):073202]
showed that in a photo-association reaction of Raman dressed spin orbit coupled
$^{87}$Rb Bose Einstein Condensate when the reactant spin state is prepared in
a coherent superposition of multiple bare spin states it leads to a destructive
interference between reaction pathways. Here we report a theoretical study for
a reaction scheme which leads to constructive quantum interference. This is
achieved by changing the reactive scattering channel in the reaction. As the
origin of coherent control comes from the spin part of the wavefunction it is
sufficient to use radio frequency coupling to achieve the superposition state.
Our results show that interferences can be used as a resource for the coherent
control of photo-chemical reactions. The approach is general and can be
employed to study a wide spectra of chemical reactions in the ultracold regime.",2107.05441v1
2022-01-28,Electron spin spectroscopy of single TEMPO dimers coupled via interfering tunneling currents,"We report the detection of electron spin resonance (ESR) in individual dimers
of the stable free radical 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO). ESR
is measured by the current fluctuations in a scanning tunnelling microscope
(ESR-STM method). The multi-peak power spectra, distinct from macroscopic data,
are assigned to dimers having exchange and Dzyaloshinskii-Moriya interactions
in presence of spin-orbit coupling. These interactions are generated in our
model by interfering electronic tunneling pathways from tip to sample via the
dimer's two molecules. This is the first demonstration that tunneling via two
spins is a valid mechanism of the ESR-STM method.",2201.12154v1
2023-04-01,Magnetic proximity effect at the interface of two-dimensional materials and magnetic oxide insulators,"Two-dimensional (2D) materials provide a platform for developing novel
spintronic devices and circuits for low-power electronics. In particular,
inducing magnetism and injecting spins in graphene have promised the emerging
field of graphene spintronics. This review focuses on the magnetic proximity
effect at the interface of 2D materials and magnetic oxide insulators. We
highlight the unique spin-related phenomena arising from magnetic exchange
interaction and spin-orbital coupling in 2D materials coupled with magnetic
oxides. We also describe the fabrication of multifunctional hybrid devices
based on spin transport. We conclude with a perspective of the field and
highlight challenges for the design and fabrication of 2D spintronic devices
and their potential applications in information storage and logic devices.",2304.00356v1
2024-04-01,"Harnessing Interlayer Magnetic Coupling for Efficient, Field-Free Current-Induced Magnetization Switching in a Magnetic Insulator","Owing to the unique features of low Gilbert damping, long spin-diffusion
lengths and zero Ohmic losses, magnetic insulators are promising candidate
materials for next-generation spintronic applications. However, due to the
localized magnetic moments and the complex metal-oxide interface between
magnetic insulators and heavy metals, spin-functional Dzyaloshinskii-Moriya
interactions or spin Hall and Edelstein effects are weak, which diminishes the
performance of these typical building blocks for spintronic devices. Here, we
exploit the exchange coupling between metallic and insulating magnets for
efficient electrical manipulation of heavy metal/magnetic insulator
heterostructures. By inserting a thin Co layer, we enhance the spin-orbit
torque efficiency by more than 20 times, which significantly reduces the
switching current density. Moreover, we demonstrate field-free current-induced
magnetization switching caused by a symmetry-breaking non-collinear magnetic
texture. Our work launches magnetic insulators as an alternative platform for
low-power spintronic devices.",2404.00845v1
2018-12-28,Strong-coupling formula for momentum-dependent susceptibilities in dynamical mean-field theory,"Computing momentum-dependent susceptibilities in the dynamical mean-field
theory (DMFT) requires solving the Bethe-Salpeter equation, which demands large
computational cost. Exploiting the strong-coupling feature of local
fluctuations, we derive a simplified formula that can be solved at a
considerably lower cost. The validity and the physical meaning of the formula
are confirmed by deriving the effective intersite interactions in the
strong-coupling limit, such as the kinetic exchange and RKKY interactions.
Furthermore, numerical calculations for single-orbital and multiorbital models
demonstrate surprisingly wider applicability including weak-coupling region.
Based on this formula, we propose three levels of practical approximations that
can be chosen depending on complexity of problems. Simpler evaluations of spin
and orbital susceptibilities in multiorbital systems thus become possible
within DMFT.",1812.10918v2
2023-06-25,A first-principles investigation of the origin of superconductivity in TlBi$_2$,"The intermetallic compound TlBi$_2$ crystallizes in the MgB$_2$ structure and
becomes superconducting below 6.2 K. Considering that both Tl and Bi have heavy
atomic masses, it is puzzling why TlBi$_2$ is a conventional phonon-mediated
superconductor. We have performed comprehensive first-principles calculations
of the electronic structures, the phonon dispersions and the electron-phonon
couplings for TlBi$_2$. The $6p$ orbitals of bismuth dominate over the states
near the Fermi level, forming strong intra-layer $p_{x/y}$ and inter-layer
$p_z$ $\sigma$ bonds which is known to have strong electron-phonon coupling. In
addition, the large spin-orbit coupling interaction in TlBi$_2$ increases its
electron-phonon coupling constant significantly. As a result, TlBi$_2$, with a
logarithmic phonon frequency average one tenth that of MgB$_2$, is a
phonon-mediated superconductor.",2306.14365v1
2003-10-09,Quantum Phase Transitions in the One-Dimensional S=1 Spin-Orbital Model: Implications for Cubic Vanadates,"We investigate ground-state properties and quantum phase transitions in the
one-dimensional S=1 spin-orbital model relevant to cubic vanadates. Using the
density matrix renormalization group, we compute the ground-state energy, the
magnetization and the correlation functions for different values of the Hund's
coupling $J_H$ and the external magnetic field. It is found that the
magnetization jumps at a certain critical field, which is a hallmark of the
field-induced first-order phase transition. The phase transition driven by
$J_H$ is also of first order. We also consider how the lattice-induced
ferro-type interaction between orbitals modifies the phase diagram, and discuss
the results in a context of the first-order phase transition observed in
YVO$_3$ at 77K.",0310223v1
2003-12-05,"TiOCl, an orbital-ordered system?","We present first principles density functional calculations and downfolding
studies of the electronic and magnetic properties of the layered quantum spin
system
  TiOCl. We discuss explicitely the nature of the exchange pathes and attempt
to clarify the concept of orbital ordering in this material. An analysis of the
electronic structure of slightly distorted structures according to the phononic
modes allowed in this material suggests that this system is subject to large
orbital fluctuations driven by the electron-phonon coupling. Based on these
results, we propose a microscopic explanation of the behavior of TiOCl near the
phase transition to a spin-gapped system.",0312156v2
2004-04-21,"Magnetic and orbital ordering of RuO2 planes in RuSr2(Eu,Gd)Cu2O8","We start from an effective Hamiltonian for Ru ions in a square lattice, which
includes the on-site interactions between t_2g orbitals derived from Coulomb
repulsion, and a tetragonal crystal-field splitting. Using perturbation theory
in the hopping terms, we derive effective Hamiltonians to describe the RuO2
planes of RuSr2(Eu,Gd)Cu2O8. For undoped planes (formal valence Ru{+5}),
depending on the parameters we find three possible orderings of spin and
orbitals, and construct a phase diagram. This allows to put constraints on the
parameters based on experimental data. When electron doping consistent with the
hole doping of the superconducting RuO2 planes is included, we obtain (for
reasonable parameters) a double-exchange model with infinite antiferromagnetic
coupling between itinerant electrons and localized spins. This model is
equivalent to one used before [H. Aliaga and A. A. Aligia, Physica B 320, 34
(2002)] which consistently explains the seemingly contradictory magnetic
properties of RuSr2(Eu,Gd)Cu2O8.",0404506v1
2004-07-20,The magnetic structure of the Jahn-Teller System LaTiO3,"We investigate the effect of the experimentally observed Jahn-Teller
distortion of the oxygen octahedra in LaTiO3 on the magnetic exchange. We
present a localized model for the effective hopping between nearest-neighbor Ti
ions and the intra-site Coulomb interactions, based on a non-degenerate orbital
ground state due to the static crystal field. The latter corresponds to an
orbital order which recently has been confirmed experimentally. Using
perturbation theory we calculate, in addition to the Heisenberg coupling,
antisymmetric and symmetric anisotropy terms of the superexchange spin
Hamiltonian which are caused by the spin-orbit interaction. Employing our
superexchange Hamiltonian, we deduce the magnetic order at low temperatures
which is found to be in good agreement with experiment.",0407524v2
2005-02-04,Effective Interaction between the inter-penetrating Kagome lattices in Na_xCoO_2,"A multi-orbital model for a CoO_2-layer in Na_xCoO_2 is derived. In this
model the kinetic energy for the degenerate t_2g-orbitals is given by indirect
hopping over oxygen, leading naturally to the concept of four inter-penetrating
Kagome lattices. Local Coulomb interaction couples the four lattices and an
effective Hamiltonian for the interaction in the top band can be written in
terms of fermionic operators with four different flavors. Focusing on charge
and spin density instabilities, a big variety of possible metallic states with
spontaneously broken symmetry are found. These states lead to different charge,
orbital, spin and angular momentum ordering patterns. The strong superstructure
formation at x=0.5 is also discussed within this model.",0502116v1
2006-02-13,Giant Anisotropic Magneto-Resistance in ferromagnetic atomic contacts,"Magneto-resistance is a physical effect of great fundamental and industrial
interest since it is the basis for the magnetic field sensors used in computer
read-heads and Magnetic Random Access Memories. As device dimensions are
reduced, some important physical length scales for magnetism and electrical
transport will soon be attained. Ultimately, there is a strong need to know if
the physical phenomena responsible for magneto-resistance still hold at the
atomic scale. Here, we show that the anisotropy of magneto-resistance is
greatly enhanced in atomic size constrictions. We explain this physical effect
by a change in the electronic density of states in the junction when the
magnetization is rotated, as supported by our ab-initio calculations. This
stems from the ""spin-orbit coupling"" mechanism linking the shape of the
orbitals with the spin direction. This sensitively affects the conductance of
atomic contacts which is determined by the overlap of the valence orbitals.",0602298v1
2007-10-16,Interaction and thermodynamics of spinons in the XX chain,"The mapping between the fermion and spinon compositions of eigenstates in the
one-dimensional spin-1/2 XX model on a lattice with N sites is used to describe
the spinon interaction from two different perspectives: (i) For finite N the
energy of all eigenstates is expressed as a function of spinon momenta and
spinon spins, which, in turn, are solutions of a set of Bethe ansatz equations.
The latter are the basis of an exact thermodynamic analysis in the spinon
representation of the XX model. (ii) For N -> infinity the energy per site of
spinon configurations involving any number of spinon orbitals is expressed as a
function of reduced variables representing momentum, filling, and magnetization
of each orbital. The spins of spinons in a single orbital are found to be
coupled in a manner well described by an Ising-like equivalent-neighbor
interaction, switching from ferromagnetic to antiferromagnetic as the filling
exceeds a critical level. Comparisons are made with results for the
Haldane-Shastry model.",0710.3097v1
2008-09-03,Interaction of a CO molecule with a Pt monoatomic chain: the top geometry,"Recent experiments showed that the conductance of Pt nanocontacts and
nanowires is measurably reduced by adsorption of CO. We present DFT
calculations of the electronic structure and ballistic conductance of a Pt
monoatomic chain and a CO molecule adsorbed in an on-top position. We find that
the main electronic molecule-chain interaction occurs via the $5\sigma$ and
$2\pi^{\star}$ orbitals of the molecule, involved in a donation/back-donation
process similar to that of CO on transition-metal surfaces. The ideal ballistic
conductance of the monoatomic chain undergoes a moderate reduction by about 1.0
G_0 (from 4 G_0 to 3.1 G_0) upon adsorption of CO. By repeating all
calculations with and without spin-orbit coupling, no substantial spin-orbit
induced change emerges either in the chain-molecule interaction mechanism or in
the conductance.",0809.0630v1
2008-10-10,Orbital-limiting and modulation induced by missing parity in non-centrosymmetric superconductors,"We examine the depairing field $H_{c2}(T)$ of non-centrosymmetric
superconductors with a spin-orbit coupling larger than the Zeeman energy at
$H_{c2}(0)$ by taking account of the mixing of spin-singlet and triplet pairing
states due to the missing parity. When the singlet and triplet pairing
components are mixed with an equal weight in a cubic non-centrosymmetric
system, the paramagnetic depairing effect is significantly suppressed so that
$H_{c2}(T)$ approaches its orbital-limited value. A similar event also occurs
in a quasi two-dimensional Rashba non-centrosymmetric system. The present
results are relevant to the $H$-$T$ phase diagrams of CePt$_3$Si and the
families of Li$_2$Pd$_{3-x}$Pt$_x$B.",0810.1820v2
2010-03-22,Magnetic excitations of spin and orbital moments in cobalt oxide,"Magnetic and phonon excitations in the antiferromagnet CoO with an unquenched
orbital angular momentum are studied by neutron scattering. Results of energy
scans in several Brillouin zones in the (HHL) plane for energy transfers up to
16 THz are presented. The measurements were performed in the antiferromagnetic
ordered state at 6 K (well below TN~290 K) as well as in the paramagnetic state
at 450 K. Several magnetic excitation modes are identified from the dependence
of their intensity on wavevector and temperature. Within a Hund's rule model
the excitations correspond to fluctuations of coupled orbital and spin degrees
of freedom whose bandwidth is controlled by interionic superexchange. The
different <111> ordering domains give rise to several magnetic peaks at each
wavevector transfer.",1003.4166v1
2011-07-28,Two-Spinon and Orbital Excitations of the Spin-Peierls System TiOCl,"We combine high-resolution resonant inelastic x-ray scattering with cluster
calculations utilizing a recently derived effective magnetic scattering
operator to analyze the polarization, excitation energy, and momentum dependent
excitation spectrum of the low-dimensional quantum magnet TiOCl in the range
expected for orbital and magnetic excitations (0 - 2.5 eV). Ti 3d orbital
excitations yield complete information on the temperature-dependent
crystal-field splitting. In the spin-Peierls phase we observe a dispersive
two-spinon excitation and estimate the inter- and intra-dimer magnetic exchange
coupling from a comparison to cluster calculations.",1107.5800v2
2013-07-23,S-wave Superconductivity due to Orbital and Spin fluctuations in Fe-pnictides: Self-Consistent Vertex Correction with Self-Energy (SC-VCΣ) Analysis,"To understand the amazing variety of the superconducting states of Fe-based
superconductors, we analyze the multiorbital Hubbard models for LaFeAsO and
LiFeAs going beyond the random-phase approximation (RPA), by calculating the
vertex correction (VC) and self-energy correction. Due to the spin+orbital mode
coupling described by the VC, both orbital and spin fluctuations mutually
develop, consistently with the experimental phase diagram with the orbital and
magnetic orders. Due to both fluctuations, the s-wave gap function with
sign-reversal ($s_{\pm}$-wave), without sign-reversal ($s_{++}$-wave), and
nodal s-wave states are obtained, compatible with the experimental wide variety
of the gap structure. Thus, the present theory provides a microscopic
explanation of the normal and superconducting phase diagram based on the
realistic Hubbard model.",1307.6119v2
2013-12-01,"Electronic structure, cohesive properties and magnetism of SrRuO$_3$; a theoretical investigation","We have performed an extensive test of the ability of density functional
theory within several approximations for the exchange-correlation functional,
local density approximation+Hubbard $U$ and local density approximation +
dynamic mean field theory to describe magnetic and electronic properties of
SrRuO$_3$. We focus on the ferromagnetic phase, illustrating differences
between the orthorhombic low temperature structure vs the cubic high
temperature structure. We assess how magnetism, spectral function, and cohesive
properties are affected by methodology, on-site Hubbard $U$ and double counting
corrections. Further, we compare the impact of the impurity solver on the
quasiparticle weight $Z$, which is in turn compared to experimental results.
The spectral functions resulting from the different treatments are also
compared to experimental data. The impact of spin-orbit coupling is also
studied, allowing us to determine the orbital moments. In the orthorhombic
phase the orbital moments are found to be tilted with respect to the spin
moments, emphasising the importance of taking into account the distortion of
the oxygen octahedra.",1312.0270v2
2015-05-05,"Suppression of magnetism in Ba5AlIr2O11: interplay of Hund's coupling, molecular orbitals and spin-orbit interaction","The electronic and magnetic properties of Ba$_5$AlIr$_2$O$_{11}$ containing
Ir-Ir dimers are investigated using the GGA and GGA+SOC calculations. We found
that strong suppression of the magnetic moment in this compound recently found
in [J. Terzic {\it et al.}, Phys. Rev. B {\bf 91}, 235147 (2015)] is not due to
charge-ordering, but is related to the joint effect of the spin-orbit
interaction and strong covalency, resulting in the formation of metal-metal
bonds. They conspire and act against the intra-atomic Hund's rule exchange
interaction to reduce total magnetic moment of the dimer. We argue that the
same mechanism could be relevant for other $4d$ and $5d$ dimerized transition
metal compounds.",1505.00877v2
2015-06-12,"A Study of Shell Model Neutron States in $^{207,209}Pb$ Using the Generalized Woods-Saxon plus Spin-Orbit Potential","The experimental binding energies of single-particle and single-hole neutron
states belonging to neutron shells that extend from N = 126 to 184 and 82 to
126 respectively, have been reproduced by solving the Schr\""{o}dinger equation
with a potential that has two components: the generalized Woods-Saxon (GWS)
potential and the spin-orbit (SO) coupling term. The GWS potential contains the
traditional WS potential plus a term (SU) whose intensity reaches a maximum in
the nuclear surface. Our results indicate the existence of a explicit
relationship between the strength of the SU potential and the orbital angular
momentum quantum number $\ell$ of the state. This dependence has been used to
make reasonable predictions for the excitation energy centroids of states
located inside and outside the neutron shells investigated. Comparisons are
made with results reported in previous investigations.",1506.04055v2
2015-09-11,Two-magnon Raman scattering and pseudospin-lattice interactions in Sr2IrO4 and Sr3Ir2O7,"We have used Raman scattering to investigate the magnetic excitations and
lattice dynamics in the prototypical spin-orbit Mott insulators Sr2IrO4 and
Sr3Ir2O7. Both compounds exhibit pronounced two-magnon Raman scattering
features with different energies, lineshapes, and temperature dependencies,
which in part reflect the different influence of long-range frustrating
exchange interactions. Additionally, we find strong Fano asymmetries in the
lineshapes of low-energy phonon modes in both compounds, which disappear upon
cooling below the antiferromagnetic ordering temperatures. These unusual phonon
anomalies indicate that the spin-orbit coupling in Mott-insulating iridates is
not sufficiently strong to quench the orbital dynamics in the paramagnetic
state.",1509.03396v1
2016-08-14,Composite electronic orders induced by orbital Kondo effect,"In a large number of rare-earth and actinide systems, Kondo effect tends to
suppress magnetic order by making the spin singlet between localized and
conduction electron spins. In the presence of orbital degrees of freedom,
however, there emerge exotic electronic orders induced by Kondo effect. The
orbital Kondo effect can collectively make diagonal and off-diagonal
(superconducting) orders. With the particle-hole symmetry in conduction bands,
these orders are all degenerate, forming a macroscopic SO(5) multiplet. This
paper discusses recent theoretical development on these electronic orders which
are relevant to Pr$^{3+}$ and U$^{4+}$ systems with even number of $f$
electrons per site. In the superconducting order, each conduction-electron pair
is coupled with local degrees of freedom, forming a composite entity with a
staggered spatial pattern. The quasi-particle spectrum is best interpreted as
virtual hybridization with resonant states at the Fermi level. Possible order
parameter for URu$_2$Si$_2$ in the hidden order state is discussed in the
context of composite orders. Briefly discussed are related issues such as
homogeneous odd-frequency pairing and SO(5) theory for high-temperature
superconductors.",1608.04076v1
2017-10-11,Effects of finite coverage on global polarization observables in heavy ion collisions,"In non-central relativistic heavy ion collisions, the created matter
possesses a large initial orbital angular momentum. Particles produced in the
collisions could be polarized globally in the direction of the orbital angular
momentum due to spin-orbit coupling. Recently, the STAR experiment has
presented polarization signals for $\Lambda$ hyperons and possible spin
alignment signals for $\phi$ mesons. Here we discuss the effects of finite
coverage on these observables. The results from a multi-phase transport and a
toy model both indicate that a pseudorapidity coverage narrower than $|\eta|<
\sim 1$ will generate a larger value for the extracted $\phi$-meson $\rho_{00}$
parameter; thus a finite coverage can lead to an artificial deviation of
$\rho_{00}$ from 1/3. We also show that a finite $\eta$ and $p_T$ coverage
affect the extracted $p_H$ parameter for $\Lambda$ hyperons when the real $p_H$
value is non-zero. Therefore proper corrections are necessary to reliably
quantify the global polarization with experimental observables.",1710.03895v2
2017-10-27,Enhanced Magneto-optical Kerr Effect at Fe/Insulator Interfaces,"Using density functional theory calculations, we have found an enhanced
magneto-optical Kerr effect in Fe/insulator interfaces. The results of our
study indicate that interfacial Fe atoms in the Fe films have a low-dimensional
nature, which causes the following two effects: (i) The diagonal component
$\sigma_{xx}$ of the optical conductivity decreases dramatically because the
hopping integral for electrons between Fe atoms is suppressed by the low
dimensionality. (ii) The off-diagonal component $\sigma_{xy}$ of the optical
conductivity does not change at low photon energies, but it is enhanced at
photon energies around 2 eV, where we obtain enhanced orbital magnetic moments
and spin-orbit correlations for the interfacial Fe atoms. A large Kerr angle
develops in proportion to the ratio $\sigma_{xy}/\sigma_{xx}$. Our findings
indicate an efficient way to enhance the effect of spin-orbit coupling at
metal/insulator interfaces without using heavy elements.",1710.09986v1
2018-03-01,"Charge density functional plus $U$ theory of LaMnO$_3$: Phase diagram, electronic structure, and magnetic interaction","We perform charge density functional theory plus $U$ calculation of
LaMnO$_3$. While all the previous calculations were based on spin density
functionals, our result and analysis show that the use of spin-unpolarized
charge-only density is crucial to correctly describe the phase diagram,
electronic structure and magnetic property. Using magnetic force linear
response calculation, a long-standing issue is clarified regarding the second
neighbor out-of-plane interaction strength. We also estimate the
orbital-resolved magnetic couplings. Remarkably, the inter-orbital
$e_g$-$t_{2g}$ interaction is quite significant due to the Jahn-Teller
distortion and orbital ordering.",1803.00213v1
2018-08-28,Lateral Interfaces of Transition Metal Dichalcogenides: A Stable Tunable One-Dimensional Physics Platform,"We study in-plane lateral heterostructures of commensurate transition-metal
dichalcogenides, such as MoS$_{2}$-WS$_{2}$ and MoSe$_{2}$-WSe$_{2}$, and find
interfacial and edge states that are highly localized to these regions of the
heterostructure. These are one-dimensional (1D) in nature, lying within the
bandgap of the bulk structure and exhibiting complex orbital and spin
structure. We describe such heteroribbons with a three-orbital tight-binding
model that uses first principles and experimental parameters as input, allowing
us to model realistic systems. Analytical modeling for the 1D interfacial bands
results in long-range hoppings due to the hybridization along the interface,
with strong spin-orbit couplings. We further explore the
Ruderman-Kittel-Kasuya-Yosida indirect interaction between magnetic impurities
located at the interface. The unusual features of the interface states result
in effective long-range exchange non-collinear interactions between impurities.
These results suggest that transition-metal dichalcogenide interfaces could
serve as stable, tunable 1D platform with unique properties for possible use in
exploring Majorana fermions, plasma excitations and spintronics applications.",1808.09402v2
2019-04-05,Multi-dimensional entanglement transport through single-mode fibre,"The global quantum network requires the distribution of entangled states over
long distances, with significant advances already demonstrated using entangled
polarisation states, reaching approximately 1200 km in free space and 100 km in
optical fibre. Packing more information into each photon requires Hilbert
spaces with higher dimensionality, for example, that of spatial modes of light.
However spatial mode entanglement transport requires custom multimode fibre and
is limited by decoherence induced mode coupling. Here we transport
multi-dimensional entangled states down conventional single-mode fibre (SMF).
We achieve this by entangling the spin-orbit degrees of freedom of a bi-photon
pair, passing the polarisation (spin) photon down the SMF while accessing
multi-dimensional orbital angular momentum (orbital) subspaces with the other.
We show high fidelity hybrid entanglement preservation down 250 m of SMF across
multiple 2x2 dimensions, demonstrating quantum key distribution protocols,
quantum state tomographies and quantum erasers. This work offers an alternative
approach to spatial mode entanglement transport that facilitates deployment in
legacy networks across conventional fibre.",1904.03114v1
2020-05-07,Detecting quadrupole: a hidden source of magnetic anisotropy for Manganese alloys,"Mn-based alloys exhibit unique properties in the spintronics materials
possessing perpendicular magnetic anisotropy (PMA) beyond the Fe and Co-based
alloys. It is desired to figure out the quantum physics of PMA inherent to
Mn-based alloys, which have never been reported. Here, the origin of PMA in
ferrimagnetic Mn$_{3-{\delta}}$Ga ordered alloys is investigated to resolve
antiparallel-coupled Mn sites using x-ray magnetic circular and linear
dichroism (XMCD/XMLD) and a first-principles calculation. We found that the
contribution of orbital magnetic moments in PMA is small from XMCD and that the
finite quadrupole-like orbital distortion through spin-flipped electron hopping
is dominant from XMLD and theoretical calculations. These findings suggest that
the spin-flipped orbital quadrupole formations originate from the PMA in
Mn$_{3-{\delta}}$Ga and bring the paradigm shift in the researches of PMA
materials using x-ray magnetic spectroscopies.",2005.03249v1
2021-04-23,Evidence of topological Shiba bands in artificial spin chains on superconductors,"A major challenge in developing topological superconductors for implementing
topological quantum computing is their characterization and control. It has
been proposed that a p-wave gapped topological superconductor can be fabricated
with single-atom precision by assembling chains of magnetic atoms on s-wave
superconductors with spin-orbit coupling. Here, we analyze the Bogoliubov
quasiparticle interference in atom-by-atom constructed Mn chains on Nb(110) and
for the first time reveal the formation of multi-orbital Shiba bands using
momentum resolved measurements. We find evidence that one band features a
topologically non-trivial p-wave gap as inferred from its shape and
particle-hole asymmetric intensity. Our work is an important step towards a
distinct experimental determination of topological phases in multi-orbital
systems by bulk electron band structure properties only.",2104.11497v2
2019-06-08,Possible emergence of a skyrmion phase in ferroelectric GaMo$_4$S$_8$,"Polar lacunar spinels, such as GaV$_4$S$_8$ and GaV$_4$Se$_8$, were proposed
to host skyrmion phases under magnetic field. In this work, we put forward, as
a candidate for N\'eel-type skyrmion lattice, the isostructural GaMo$_4$S$_8$,
here systematically studied via both first-principles calculations and Monte
Carlo simulations of model Hamiltonian. Electric polarization, driven by
Jahn-Teller distortion, is predicted to arise in GaMo$_4$S$_8$, showing a
comparable size but an opposite sign with respect to that evaluated in V-based
counterparts and explained in terms of different electron counting arguments
and resulting distortions. Interestingly, a larger spin-orbit coupling of 4d
orbitals with respect to 3d orbitals in vanadium-spinels leads to stronger
Dzyaloshinskii-Moriya interactions, which are beneficial to stabilize a
cycloidal spin texture, as well as smaller-sized skyrmions (radius<10 nm).
Furthermore, the possibly large exchange anisotropy of GaMo4S8 may lead to a
ferroelectric-ferromagnetic ground state, as an alternative to the
ferroelectric-skyrmionic one, calling for further experimental verification.",1906.03399v1
2022-02-09,Gate tunable anomalous Hall effect at (111) LaAlO$_3$/SrTiO$_3$ interface,"We present the theoretical prediction of a gate tunable anomalous Hall effect
(AHE) in an oxide interface as a hallmark of spin-orbit coupling. The observed
AHE at low-temperatures in the presence of an external magnetic field emerges
from a complex structure of the Berry curvature of the electrons on the Fermi
surface and strongly depends on the orbital character of the occupied bands. A
detailed picture of the results comes from a multiband low-energy model with a
generalized Rashba interaction that supports characteristic out-of-plane spin
and orbital textures. We discuss strategies for optimizing the intrinsic AHE in
(111) SrTiO$_3$ heterostructure interfaces.",2202.04664v1
2022-07-05,Strong bulk Dzyaloshinskii-Moriya interaction in composition-uniform centrosymmetric magnetic single layers,"Dzyaloshinskii-Moriya interaction (DMI) is the key ingredient of chiral
spintronic phenomena and the emerging technologies based on such phenomena. A
nonzero DMI usually occurs at magnetic interfaces or within non-centrosymmetric
single crystals. Here, we report the observation of a strong unexpected DMI
within a centrosymmetric polycrystalline ferromagnet that has neither a crystal
inversion symmetry breaking nor a composition gradient. This DMI is a bulk
effect, increases with the thickness of the magnetic layer, and is insensitive
to the symmetry of the interfaces or the neighboring materials. We observe a
total DMI strength that is a factor of >2 greater than the highest interfacial
DMI in the literature. This DMI most likely arises from the strong spin-orbit
coupling, strong orbital hybridization, and a ""hidden"" long-range asymmetry in
the material. Our discovery of the strong unconventional bulk DMI in
centrosymmetric, composition-uniform magnetic single layers provide fundamental
building blocks for the emerging field of spintronics and will stimulate the
exploitation of unconventional spin-orbit phenomena in a wide range of
materials.",2207.01766v1
2022-08-17,Photoinduced Pseudospin Polarization in a Three-Orbital Hubbard Model,"In a Hubbard model for the Kitaev spin-liquid candidate material
$\alpha$-RuCl$_3$ with three $t_{2g}$ orbitals per Ru site, we calculate
photoinduced dynamics based on the exact diagonalization method and interpret
them with the help of a high-frequency expansion in quantum Floquet theory. The
high-frequency expansion shows two types of effective magnetic fields during
the application of a circularly polarized light field. One of them originates
from spin-orbit coupling and is within the honeycomb lattice. The other is of
purely kinetic origin and perpendicular to the lattice. The former fields are
antiparallel at the two sites within a unit cell and rotate in accordance with
the momentum distribution of holes that follow the light field. When the light
field is weak, pseudospin dynamics are governed by the former fields; thus, the
average of the pseudospins almost vanishes. The latter fields are parallel at
the two sites within a unit cell and produce nonzero perpendicular components
of the pseudospins when the light field is strong. Numerically obtained
perpendicular components are consistent with the latter fields when the
frequency of the light field is well below the Mott gap. The relevance to the
inverse Faraday effect recently observed in $\alpha$-RuCl$_3$ is discussed.",2208.08531v1
2022-11-07,When Plasmonic Colloids Meet Optical Vortices -- A Brief Review,"Structured light has emerged as an important tool to interrogate and
manipulate matter at micron and sub-micron scale. One form of structured light
is an optical vortex beam. The helical wavefront of these vortices carry
orbital angular momentum which can be transferred to a Brownian colloid. When
the colloid is made of metallic nanostructures, such as silver and gold,
resonant optical effects play a vital role, and the interaction leads to
complex dynamics and assembly. This brief review aims to discuss some recent
work on trapping plasmonic colloids with optical vortices and their lattices.
The role of optical scattering and absorption has important implications on the
underlying forces and torques, which is specifically enunciated. The effect of
spin and orbital angular momentum in an optical vortex can lead to spin-orbit
coupling dynamics, and these effects are highlighted with examples from the
literature. In addition to assembly and dynamics, enhanced Brownian motion of
plasmonic colloids under the influence of a vortex-lattice is discussed. The
pedagogical aspects to understand the interaction between optical vortex and
plasmonic colloids is emphasized.",2211.03547v1
2023-04-12,Janus monolayer TaNF: a new ferrovalley material with large valley splitting and tunable magnetic properties,"Materials with large intrinsic valley splitting and high Curie temperature
are a huge advantage for studying valleytronics and practical applications. In
this work, using first-principles calculations, a new Janus TaNF monolayer is
predicted to exhibit excellent piezoelectric properties and intrinsic valley
splitting, resulting from the spontaneous spin polarization, the spatial
inversion symmetry breaking and strong spin-orbit coupling (SOC). TaNF is also
a potential two-dimensional (2D) magnetic material due to its high Curie
temperature and huge magnetic anisotropy energy. The effective control of the
band gap of TaNF can be achieved by biaxial strain, which can transform TaNF
monolayer from semiconductor to semi-metal. The magnitude of valley splitting
at the CBM can be effectively tuned by biaxial strain due to the changes of
orbital composition at the valleys. The magnetic anisotropy energy (MAE) can be
manipulated by changing the energy and occupation (unoccupation) states of d
orbital compositions through biaxial strain. In addition, Curie temperature
reaches 373 K under only -3% biaxial strain, indicating that Janus TaNF
monolayer can be used at high temperatures for spintronic and valleytronic
devices.",2304.05670v1
2012-08-08,"Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals","The chain-polymer Cu(II) breathing crystals C21H19CuF12N4O6 were studied
using the x-ray diffraction and ab initio band structure calculations. We show
that the crystal structure modification at T=146 K, associated with the spin
crossover transition, induces the changes of the orbital order in half of the
Cu sites. This in turn results in the switch of the magnetic interaction sign
in accordance with the Goodenough-Kanamori-Andersen theory of the coupling
between the orbital and spin degrees of freedom.",1208.1624v2
2013-01-17,The planetary spin and rotation period: A modern approach,"Using a new approach, we have obtained a formula for calculating the rotation
period and radius of planets. In the ordinary gravitomagnetism the
gravitational spin ($S$) orbit ($L$) coupling, $\vec{L}\cdot\vec{S}\propto
L^2$, while our model predicts that $\vec{L}\cdot\vec{S}\propto
\frac{m}{M}\,L^2$, where $M$ and $m$ are the central and orbiting masses,
respectively.
  Hence, planets during their evolution exchange $L$ and $S$ until they reach a
final stability at which $MS\propto mL$, or $S\propto \frac{m^2}{v}$, where $v$
is the orbital velocity of the planet.
  Rotational properties of our planetary system and exoplanets are in agreement
with our predictions.
  The radius ($R$) and rotational period ($D$) of tidally locked planet at a
distance $a$ from its star, are related by, $D^2\propto
\sqrt{\frac{M}{m^3}}\,\,R^3$ and that $R\propto \sqrt{\frac{m}{M}}\,\, a$.$a$
from its star, are related by, $D^2\propto \sqrt{\frac{M}{m^3}} R^3$ and that
$R\propto \sqrt{\frac{m}{M}} a$.",1301.4720v2
2013-06-26,Observation of the SU(4) Kondo state in a double quantum dot,"Central to condensed matter physics are quantum impurity models, which
describe how a local degree of freedom interacts with a continuum.
Surprisingly, these models are often universal in that they can quantitatively
describe many outwardly unrelated physical systems. Here we develop a double
quantum dot-based experimental realization of the SU(4) Kondo model, which
describes the maximally symmetric screening of a local four-fold degeneracy. As
demonstrated through transport measurements and detailed numerical
renormalization group calculations, our device affords exquisite control over
orbital and spin physics. Because the two quantum dots are coupled only
capacitively, we can achieve orbital state- or ""pseudospin""-resolved bias
spectroscopy, providing intimate access to the interplay of spin and orbital
Kondo effects. This cannot be achieved in the few other systems realizing the
SU(4) Kondo state.",1306.6326v1
2014-04-03,Three-Leaf Quantum Interference Clovers in a Trigonal Single-Molecule Magnet,"The control of spin-orbit coupling (SOC) at the microscopic level has become
a major research quest within the magnetism and spintronics communities.
Altering the interaction between the spin and orbital degrees of freedom can
fundamentally alter the electronic structure of a system, including electronic
band inversion, and lead to new states of matter such as topological
insulators. Whether based on high SOC lanthanides or transition metal ions,
where the crystal field often quenches the orbital angular momentum,
single-molecule magnets are an excellent playground for the study of the more
fundamental aspects of this interaction and its intrinsic symmetries. This is
the case of the molecular magnet reported in this article, where the trigonal
symmetry imposed by the spatial arrangement of three constituent manganese ions
and the corresponding orientations of their SOC anisotropy tensors result in a
fascinating three-fold angular modulation of the quantum tunneling of the
magnetization (QTM) rates never before observed, as well as in trigonal quantum
interference patterns that mimic the form of a three-leaf clover.",1404.1114v1
2015-02-08,Artificial Gauge Field and Quantum Spin Hall States in a Conventional Two-dimensional Electron Gas,"Based on the Born-Oppemheimer approximation, we divide total electron
Hamiltonian in a spinorbit coupled system into slow orbital motion and fast
interband transition process. We find that the fast motion induces a gauge
field on slow orbital motion, perpendicular to electron momentum, inducing a
topological phase. From this general designing principle, we present a theory
for generating artificial gauge field and topological phase in a conventional
two-dimensional electron gas embedded in parabolically graded
GaAs/In$_{x}$Ga$_{1-x}$As/GaAs quantum wells with antidot lattices. By tuning
the etching depth and period of antidot lattices, the band folding caused by
superimposed potential leads to formation of minibands and band inversions
between the neighboring subbands. The intersubband spin-orbit interaction opens
considerably large nontrivial minigaps and leads to many pairs of helical edge
states in these gaps.",1502.02656v2
2015-05-09,Spin-orbit-free Weyl-loop and Weyl-point semimetals in a stable three-dimensional carbon allotrope,"Topological band theory has revolutionized our understanding of electronic
structure of materials, in particular, a novel state - Weyl semimetal - has
been predicted for systems with strong spin-orbit coupling (SOC). Here, a new
class of Weyl semimetals, solely made of light elements with negligible SOC, is
proposed. Our first-principles calculations show that conjugated p orbital
interactions in a three-dimensional pure carbon network, termed interpenetrated
graphene network, is sufficient to produce the same Weyl physics. This carbon
allotrope has an exceptionally good structural stability. Its Fermi surface
consists of two symmetry-protected Weyl loops with linear dispersion along
perpendicular directions. Upon the breaking of inversion symmetry, each Weyl
loop is reduced to a pair of Weyl points. The surface band of the network is
nearly flat with a very large density of states at the Fermi level. It is
reduced to Fermi arcs upon the symmetry breaking, as expected.",1505.02284v1
2017-04-17,Electronically highly cubic conditions for Ru in alpha-RuCl3,"We studied the local Ru 4d electronic structure of alpha-RuCl3 by means of
polarization dependent x-ray absorption spectroscopy at the Ru-L2,3 edges. We
observed a vanishingly small linear dichroism indicating that electronically
the Ru 4d local symmetry is highly cubic. Using full multiplet cluster
calculations we were able to reproduce the spectra excellently and to extract
that the trigonal splitting of the t2g orbitals is -12 $\pm10$ meV, i.e.
negligible as compared to the Ru 4d spin-orbit coupling constant. Consistent
with our magnetic circular dichroism measurements, we found that the ratio of
the orbital and spin moments is 2.0, the value expected for a Jeff = 1/2 ground
state. We have thus shown that as far as the Ru 4d local properties are
concerned, alpha-RuCl3 is an ideal candidate for the realization of Kitaev
physics.",1704.05100v1
2019-09-09,Electrical Control of Large Rashba Effect in Oxide Heterostructures,"Large Rashba effect efficiently tuned by an external electric field is highly
desired for spintronic devices. Using first-principles calculations, we
demonstrate that large Rashba splitting is locked at conduction band minimum in
ferroelectric Bi(Sc/Y/La/Al/Ga/In)O3/PbTiO3 heterostructures where the position
of Fermi level is precisely controlled via its stoichiometry. Fully reversible
Rashba spin texture and drastic change of Rashba splitting strength with
ferroelectric polarization switching are realized in the symmetric and
asymmetric heterostructures, respectively. By artificially tuning the local
ferroelectric displacement and the orbital hybridization, the synergetic effect
of local potential gradient and orbital overlap on the dramatic change of
splitting strength is confirmed. These results improve the feasibility of
utilizing Rashba spin-orbit coupling in spintronic devices.",1909.03727v1
2019-03-18,Type-II Ising Pairing in Few-Layer Stanene,"Spin-orbit coupling has proven indispensable in realizing topological
materials and more recently Ising pairing in two-dimensional superconductors.
This pairing mechanism relies on inversion symmetry breaking and sustains
anomalously large in-plane polarizing magnetic fields whose upper limit is
expected to diverge at low temperatures, although experimental demonstration of
this has remained elusive due to the required fields. In this work, the
recently discovered superconductor few-layer stanene, i.e. epitaxially strained
$\alpha$-Sn, is shown to exhibit a new type of Ising pairing between carriers
residing in bands with different orbital indices near the $\Gamma$-point. The
bands are split as a result of spin-orbit locking without the participation of
inversion symmetry breaking. The in-plane upper critical field is strongly
enhanced at ultra-low temperature and reveals the sought for upturn.",1903.07627v1
2017-11-16,Extended orbital modeling of spin qubits in double quantum dots,"Orbital modeling of two electron spins confined in a double quantum dot is
revisited. We develop an extended Hund Mulliken approach that includes excited
orbitals, allowing for a triplet configuration with both electrons residing in
a single dot. This model improves the reliability and applicability of the
standard Hund Mulliken approximation, while remaining largely analytical, thus
it enables us to identify the mechanisms behind the exchange coupling dynamics
that we find. In particular, our calculations are in close agreement with
exchange values that were recently measured at a high interdot bias regime,
where the double occupancy triplet configuration is energetically accessible,
demonstrating reduced sensitivity to bias fluctuations, while maintaining the
large exchange needed for fast gating.",1711.06292v2
2020-06-17,Tunable spin and orbital polarization in SrTiO3-based heterostructures,"We formulate the effective Hamiltonian of Rashba spin-orbit coupling (RSOC)
in $\mathrm{LaAlO_3/SrTiO_3}$ (LAO/STO) heterostructures. We derive analytical
expressions of properties, e.g., Rashba parameter, effective mass, band edge
energy and orbital occupancy, as functions of material and tunable
heterostructure parameters. While linear RSOC is dominant around the
$\Gamma$-point, cubic RSOC becomes significant at the higher-energy
anti-crossing region. We find that linear RSOC stems from the structural
inversion asymmetry (SIA), while the cubic term is induced by both SIA and bulk
asymmetry. Furthermore, the SOC strength shows a striking dependence on the
tunable heterostructure parameters such as STO thickness and the interfacial
electric field which is ascribed to the quantum confinement effect near the
LAO/STO interface. The calculated values of the linear and cubic RSOC are in
agreement with previous experimental results.",2006.09617v1
2021-07-02,Three-dimensional Stacking of Canted Antiferromagnetism and Pseudospin Current in Undoped Sr$_2$IrO$_4$: Symmetry Analysis and Microscopic Model Realization,"Recent optical second-harmonic generation experiments observed unexpected
broken spatial symmetries in the undoped spin-orbit Mott insulator
Sr$_2$IrO$_4$, leading to intensive debates on the nature of its ground state.
We propose that it is a canted antiferromagnetism with a hidden order of
circulating staggered pseudospin current. Symmetry analysis shows that a proper
$c$-axis stacking of the canted antiferromagnetism and the pseudospin current
lead to a magnetoelectric coexistence state that breaks the two-fold rotation,
inversion, and time-reversal symmetries, consistent with experimental
observations. We construct a three-dimensional Hubbard model with spin-orbit
coupling for the five localized 5$d$ Wannier orbitals centered at Ir sites, and
demonstrate the microscopic realization of the desired coexistence state in a
wide range of band parameters via a combination of self-consistent Hartree-Fock
and variational calculations.",2107.00876v1
2021-10-27,Manipulation of Jeff=3/2 states by tuning the tetragonal distortion,"The spin-orbit entangled quantum states in 4d/5d compounds, e.g., the
Jeff=1/2 and Jeff=3/2 states, have attracted great interests for their unique
physical roles in unconventional superconductivity and topological states.
Here, the key role of tetragonal distortion is clarified, which determines the
ground states of 4d1/5d1 systems to be the Jeff=3/2 one (e.g. K2NbCl6) or S=1/2
one (e.g. Rb2NbCl6). By tuning the tetragonal distortion via epitaxial strain,
the occupation weights of dxy/dyz/dxz orbitals can be subtly modulated,
competing with the spin-orbit coupling. Consequently, quantum phase transitions
between S=1/2 state and Jeff=3/2 state, as well as between different Jeff=3/2
states, can be achieved, resulting in significant changes of local magnetic
moments. Our prediction points out a reliable route to engineer new
functionality of Jeff states in these quantum materials.",2110.14252v1
2024-01-20,Inferring binary parameters with dual-line gravitational wave detection from tight inspiraling double neutron stars,"Neutron star (NS) binaries can be potentially intriguing gravitational wave
(GW) sources, with both high- and low-frequency radiations from the possibly
aspherical individual stars and the binary orbit, respectively. The successful
detection of such a dual-line source could provide fresh insights into binary
geometry and NS physics. In the absence of electromagnetic observations, we
develop a strategy for inferring the spin-orbit misalignment angle using the
tight dual-line double NS system under the spin-orbit coupling. Based on the
four-year joint detection of a typical dual-line system with LISA and Cosmic
Explorer, we find that the misalignment angle and the NS moment of inertia can
be measured with sub-percentage and 5% accuracy, respectively.",2401.11241v1
2020-03-04,Excitation of f-modes during mergers of spinning binary neutron star,"Tidal effects have important imprints on gravitational waves (GWs) emitted
during the final stage of the coalescence of binaries that involve neutron
stars (NSs). Dynamical tides can be significant when NS oscillations become
resonant with orbital motion; understanding this process is important for
accurately modeling GW emission from these binaries, and for extracting NS
information from GW data. In this paper, we carry out a systematic study on the
tidal excitation of fundamental modes of spinning NSs in coalescencing
binaries, focusing on the case when the NS spin is anti-aligned with the
orbital angular momentum-where the tidal resonance is most likely to take
place. We first expand NS oscillations into stellar eigen-modes, and then
obtain a Hamiltonian that governs the tidally coupled orbit-mode evolution. We
next find a new approximation that can lead to analytic expressions of tidal
excitations to a high accuracy, and are valid in all regimes of the binary
evolution: adiabatic, resonant, and post-resonance. Using the method of
osculating orbits, we obtain semi-analytic approximations to the orbital
evolution and GW emission; their agreements with numerical results give us
confidence in on our understanding of the system's dynamics. In particular, we
recover both the averaged post-resonance evolution, which differs from the
pre-resonance point-particle orbit by shifts in orbital energy and angular
momentum, as well as instantaneous perturbations driven by the tidal motion.
Finally, we use the Fisher matrix technique to study the effect of dynamical
tides on parameter estimation. We find that the dynamical tides may potentially
provide an additional channel to study the physics of NSs. The method presented
in this paper is generic and not restricted to f mode; it can also be applied
to other types of tide.",2003.02373v2
2000-06-21,Gravitational Effects of Rotating Bodies,"We study two type effects of gravitational field on mechanical gyroscopes
(i.e. rotating extended bodies). The first depends on special relativity and
equivalence principle. The second is related to the coupling (i.e. a new force)
between the spins of mechanical gyroscopes, which would violate the equivalent
principle. In order to give a theoretical prediction to the second we suggest a
spin-spin coupling model for two mechanical gyroscopes. An upper limit on the
coupling strength is then determined by using the observed perihelion
precession of the planet's orbits in solar system. We also give predictions
violating the equivalence principle for free-fall gyroscopes .",0006075v2
2016-06-26,Hyperfine coupling constants from internally contracted multireference perturbation theory,"We present an accurate method for calculating hyperfine coupling constants
(HFCCs) based on the complete active space second-order perturbation theory
(CASPT2) with full internal contraction. The HFCCs are computed as a
first-order property using the relaxed CASPT2 spin-density matrix that takes
into account orbital and configurational relaxation due to dynamical electron
correlation. The first-order unrelaxed spin-density matrix is calculated from
one- and two-body spin-free counterparts that are readily available in the
CASPT2 nuclear gradient program [M. K. MacLeod and T. Shiozaki, J. Chem. Phys.
142, 051103 (2015)], whereas the second-order part is computed directly using
the newly extended automatic code generator. The relaxation contribution is
then calculated from the so-called Z-vectors that are available in the CASPT2
nuclear gradient program. Numerical results are presented for the CN and AlO
radicals, for which the CASPT2 values are comparable (or, even superior in some
cases) to the ones computed by the coupled-cluster and density matrix
renormalization group methods. The HFCCs for the hexaaqua complexes with VII,
CrIII, and MnII are also presented to demonstrate the accuracy and efficiency
of our code.",1606.08032v2
2020-12-18,A natural heavy-hole flopping mode qubit in germanium,"Flopping mode qubits in double quantum dots (DQDs) allow for coherent
spin-photon hybridization and fast qubit gates when coupled to either an
alternating external or a quantized cavity electric field. To achieve this,
however, electronic systems rely on synthetic spin-orbit interaction (SOI) by
means of a magnetic field gradient as a coupling mechanism. Here we
theoretically show that this challenging experimental setup can be avoided in
heavy-hole (HH) systems in germanium (Ge) by utilizing the sizeable cubic
Rashba SOI. We argue that the resulting natural flopping mode qubit possesses
highly tunable spin coupling strengths that allow for one- and two-qubit gate
times in the nanosecond range when the system is designed to function in an
optimal operation mode which we quantify.",2012.10214v1
2020-10-02,Synthetic chiral magnets promoted by the Dzyaloshinskii-Moriya interaction,"The ability to engineer the interactions in assemblies of nanoscale magnets
is central to the development of artificial spin systems and spintronic
technologies. Following the emergence of the Dzyaloshinskii-Moriya interaction
(DMI) in thin film magnetism, new routes have been opened to couple the
nanomagnets via strong chiral interactions, which is complementary to the
established dipolar and exchange coupling mechanisms. In this Perspective, we
review recent progress in the engineering of synthetic magnets coupled by the
interlayer and intralayer DMI. We show how multilayer chiral magnetic
structures and two-dimensional synthetic antiferromagnets, skyrmions, and
artificial spin systems can be realized by simultaneous control of the DMI and
magnetic anisotropy. In addition, we show that, with the combination of DMI and
current-induced spin-orbit torques, field-free switching of synthetic magnetic
elements is obtained as well as all-electric domain wall logic circuits.",2010.01077v1
2021-05-19,Long-living excited states of a 2D diamagnetic exciton,"Hydrogenic excited states of a 2D exciton are degenerate. In the presence of
a weak magnetic field, the $S$-states with a zero momentum of the center of
mass get coupled to the $P$-states with finite momentum of the center of mass.
This field-induced coupling leads to a strong modification of the dispersion
branches of the exciton spectrum. Namely, the lower branch acquires a shape of
a ""mexican hat"" with a minimum at a finite momentum. At certain magnetic field,
exciton branches exhibit a linear crossing, similarly to the spectrum of a 2D
electron in the presence of spin-orbit coupling. While spin is not involved,
degenerate $S$ and $P$ states play the role of the spin projections. Lifting of
degeneracy due to diamagnetic shifts and deviation of electron-hole attraction
from purely Coulomb suppresses the linear crossing.",2105.08914v1
2021-09-30,Interaction of magnons with plasmons in a system of antiferromagnetic insulators coupled to a superconductor microwave cavity through the interfacial exchange interaction,"A superconductor can interact with magnets through the magnetic field which
is induced by the supercurrent. However, this interaction is rather weak and
requires relatively large magnets to reach a sizable hybridization of microwave
electromagnetic modes with magnons. The size of the device can be drastically
reduced by means of the large interfacial exchange interaction between spins in
a magnet and a superconductor. In the spin-orbit coupled superconductor this
interaction can be transmitted to the s-wave condensate through a mixing of
triplet and singlet Cooper pairs. In this paper we theoretically consider thin
antiferromagnetic films, which make a spin compensated contact to a
superconducting wire, which forms a cavity for Mooij-Sch\""{o}n plasma waves.
The effective Lagrangian is derived where the interaction of these waves with
magnons is taken into account. Frequencies of hybrid magnon-plasmon modes are
calculated. A system of two micromagnets placed far apart are also considered
and their mutual coupling through the cavity mode is calculated.",2109.14973v1
2005-09-14,Magnetic ordering in trigonal chain compounds,"We present electronic structure calculations for the one-dimensional magnetic
chain compounds Ca_3CoRhO_6 and Ca_3FeRhO_6. The calculations are based on
density functional theory and the local density approximation. We use the
augmented spherical wave (ASW) method. The observed alternation of low- and
high-spin states along the Co-Rh and Fe-Rh chains is related to differences in
the oxygen coordination of the transition metal sites. Due to strong
hybridization the O 2p states are polarized, giving rise to extended localized
magnetic moments centered at the high-spin sites. Strong metal-metal overlap
along the chains leads to a substantial contribution of the low-spin Rh
4d_{3z^2-r^2} orbitals to the exchange coupling of the extended moments.
Interestingly, this mechanism holds for both compounds, even though the
coupling is ferromagnetic for the cobalt and antiferromagnetic for the iron
compound. However, our results allow to understand the different types of
coupling from the filling dependence of the electronic properties.",0509374v1
2009-01-29,Electric field tunable exchange interaction in InAs/GaAs coupled quantum dots,"Spin manipulation in coupled quantum dots is of interest for quantum
information applications. Control of the exchange interaction between electrons
and holes via an applied electric field may provide a promising technique for
such spin control. Polarization dependent photoluminescence (PL) spectra were
used to investigate the spin dependent interactions in coupled quantum dot
systems and by varying an electric field, the ground state hole energy levels
are brought into resonance, resulting in the formation of molecular orbitals
observed as anticrossings between the direct and indirect transitions in the
spectra. The indirect and direct transitions of the neutral exciton demonstrate
high and low circular polarization memory respectively due to variation in the
exchange interaction. The ratio between the polarization values as a function
of electric field, and the barrier height was measured. These results indicate
a possible method of tuning between indirect and direct configurations to
control the degree of exchange interaction.",0901.4751v1
2010-01-25,Approximate bound state solutions of Dirac equation with Hulthén potential including Coulomb-like tensor potential,"We solve the Dirac equation approximately for the attractive scalar $S(r)$
and repulsive vector $V(r)$ Hulth\'{e}n potentials including a Coulomb-like
tensor potential with arbitrary spin-orbit coupling quantum number $\kappa .$
In the framework of the spin and pseudospin symmetric concept, we obtain the
analytic energy spectrum and the corresponding two-component upper- and
lower-spinors of the two Dirac particles by means of the Nikiforov-Uvarov
method in closed form. The limit of zero tensor coupling and the
non-relativistic solution are obtained. The energy spectrum for various levels
is presented for several $\kappa $ values under the condition of exact spin
symmetry in the presence or absence of tensor coupling.",1001.4327v2
2010-11-01,Multi-stability in an optomechanical system with two-component Bose-Einstein condensate,"We investigate a system consisting of a two-component Bose-Einstein
condensate interacting dispersively with a Fabry-Perot optical cavity where the
two components of the condensate are resonantly coupled to each other by
another classical field. The key feature of this system is that the atomic
motional degrees of freedom and the internal pseudo-spin degrees of freedom are
coupled to the cavity field simultaneously, hence an effective spin-orbital
coupling within the condensate is induced by the cavity. The interplay among
the atomic center- of-mass motion, the atomic collective spin and the cavity
field leads to a strong nonlinearity, resulting in multi- stable behavior in
both matter wave and light wave at the few-photon level.",1011.0394v2
2012-10-18,Magnetic excitation spectra in pyrochlore iridates,"Metal-insulator transitions in pyrochlore iridates (A2Ir2O7) are believed to
occur due to subtle interplay of spin-orbit coupling, geometric frustration,
and electron interactions. In particular, the nature of magnetic ordering of
iridium ions in the insulating phase is crucial for understanding of several
exotic phases recently proposed for these materials. We study the spectrum of
magnetic excitations in the intermediate-coupling regime for the so-called
all-in/all-out magnetic state in pyrochlore iridates with non-magnetic A-site
ions (A=Eu,Y), which is found to be preferred in previous theoretical studies.
We find that the effect of charge fluctuations on the spin-waves in this regime
leads to strong departure from the lowest-order spin-wave calculations based on
models obtained in strong-coupling calculations. We discuss the characteristic
features of the magnetic excitation spectrum that can lead to conclusive
identification of the magnetic order in future resonant inelastic x-ray (or
neutron) scattering experiments. Knowledge of the nature of magnetic order and
its low-energy features may also provide useful information on the accompanying
metal-insulator transition.",1210.5242v2
2014-02-04,Rashba coupling induced spin susceptibility and magnetic phase transition of conduction electrons in monolayer graphene,"Using the Kubo formalism, the magnetic properties of the system in the linear
regime have been investigated. Mainly the effect of non-magnetic substrate on
the spin susceptibility is calculated. Results show that the Rashba coupling
interaction has a central role in the magnetic response function of the system
and it is really remarkable since this type of spin orbit coupling can be
effectively controlled by an external gate voltage. Most importantly it was
shown that, in the presence of the Rashba interaction a magnetic phase
transition could be observed. This magnetic phase corresponds to a magnetic
order of conduction electrons that takes place at some especial frequency of
external magnetic field.",1402.0646v2
2015-11-10,Triplet FFLO Superconductivity in the doped Kitaev-Heisenberg Honeycomb Model,"We provide analytical and numerical evidence of a spin-triplet FFLO
superconductivity in the itinerant Kitaev-Heisenberg model (anti-ferromagnetic
Kitaev coupling and ferromagnetic Heisenberg coupling) on the honeycomb lattice
around quarter filling. The strong spin-orbit coupling in our model leads to
the emergence of 6 inversion symmetry centers for the Fermi surface at non zero
momenta in the first Brillouin zone. We show how the Cooper pairs condense into
these non-trivial momenta, causing the spatial modulation of the
superconducting order parameter. Applying a Ginzburg-Landau expansion analysis,
we find that the superconductivity has three separated degenerate ground states
with three different spin-triplet pairings. This picture is also supported by
exact diagonalizations on finite clusters.",1511.03289v1
2013-09-19,Exact spectral function for hole-magnon coupling in the ferromagnetic CuO$_3$-like chain,"We present the exact spectral function for a single oxygen hole with spin
opposite to ferromagnetic order within a one-dimensional CuO$_{3}$-like spin
chain. We find that local Kondo-like exchange interaction generates five
different states in the strong coupling regime. It stabilizes a spin polaron
which is a bound state of a moving charge dressed by magnon excitations, with
essentially the same dispersion as predicted by mean field theory. We then
examine in detail the evolution of the spectral function for increasing
strength of the hole-magnon interaction. We also demonstrate that the $s$ and
$p$ symmetry of orbital states in the conduction band are essentially
equivalent to each other and find that the simplified models do not suffice to
reproduce subtle aspects of hole-magnon coupling in the charge-transfer model.",1309.5054v1
2018-01-22,Optical fingerprint of non-covalently functionalized transition metal dichalcogenides,"Atomically thin transition metal dichalcogenides (TMDs) hold promising
potential for applications in optoelectronics. Due to their direct band gap and
the extraordinarily strong Coulomb interaction, TMDs exhibit efficient
light-matter coupling and tightly bound excitons. Moreover, large spin orbit
coupling in combination with circular dichroism allows for spin and valley
selective optical excitation. As atomically thin materials, they are very
sensitive to changes in the surrounding environment. This motivates a
functionalization approach, where external molecules are adsorbed to the
materials surface to tailor its optical properties. Here, we apply the density
matrix theory to investigate the potential of non-covalently functionalized
TMDs. Considering exemplary spiropyran molecules with a strong dipole moment,
we predict spectral redshifts and the appearance of an additional side peak in
the absorption spectrum of functionalized TMDs. We show that the molecular
characteristics, e.g. coverage, orientation and dipole moment, crucially
influence the optical properties of TMDs, leaving a unique optical fingerprint
in the absorption spectrum. Furthermore, we find that the molecular dipole
moments open a channel for coherent intervalley coupling between the
high-symmetry K and K' points which may open new possibilities for
spin-valleytronics application.",1801.07039v1
2021-06-26,Anomalous Andreev interferometer: Study of an anomalous Josephson junction coupled to a normal wire,"Josephson junctions (JJs), where both time-reversal and inversion symmetry
are broken, exhibit a phase shift $\phi_0$ in their current-phase relation.
This allows for an anomalous supercurrent to flow in the junction even in the
absence of a phase bias between the superconductors. We show that a finite
phase shift also manifests in the so-called Andreev interferometers - a device
that consists of a mesoscopic conductor coupled to the $\phi_0$-junction. Due
to the proximity effect, the resistance of this conductor is phase-sensitive -
it oscillates by varying the phase of the JJ. As a result, the quasiparticle
current $I_{\mathrm{qp}}$ flowing through the conductor has an anomalous
component, which exists only at finite $\phi_0$. Thus, the Andreev
interferometry could be used to probe the $\phi_0$ effect. We consider two
realizations of the $\phi_0$-junction and calculate $I_{\mathrm{qp}}$ in the
interferometer: a superconducting structure with spin-orbit coupling and a
system of spin-split superconductors with spin-polarized tunneling barriers.",2106.14021v2
2021-10-26,Spin-phonon coupling in Sr and Ti incorporated 9R-BaMnO3,"Materials having strong coupling between different degrees of freedom such as
spin, lattice, orbital, and charge are of immense interest due to their
potential device applications. Here, we have stabilized the 9R phase of BaMnO3,
by Sr (Ti) doping in the Ba (Mn) site using solid-state route at ambient
pressure, which otherwise requires high-pressure conditions to syntheize.
Crsyatl structure, phonon spectra, and their evolution with temperature are
investigated using x-ray diffraction and Raman spectroscopic techniques.
Temperature-dependent magnetization data reveal an antiferromagnetic transition
at around (TN =) 262 K and 200 K for Ba0.9Sr0.1MnO3 and BaMn0.9Ti0.1O3,
respectively. No structural phase transition or lattice instabilities are
observed in the measured temperature range (80 - 400 K) for both the compounds.
We have observed anomalous behaviour of four different phonon modes involving
Mn or O-vibrations at low temperatures which have been attributed to
spin-phonon coupling.",2110.13737v1
2021-10-25,Phonon Anomaly In 9R-Ba0.9Sr0.1MnO3,"Materials which possess coupling between different degrees of freedom such as
charge, spin, orbital and lattice are of tremendous interest due to their
potential for device applications. It has been recently realized that some of
manganite perovskite oxides show structural and ferroelectric instabilities
which may be tuned by imposing internal or external strain. Among manganite
perovskites, AMnO3 (A = Ca, Sr and Ba) are reported to be good candidates to
show spin-phonon coupling driven multiferroicity. Here, we have probed the
correlation between vibrational and magnetic properties in the 9R-type
hexagonal Ba0.9Sr0.1MnO3 (BSM10). Nine Raman active modes are observed which
are characteristic phonon modes for 9R phase. The frequency ({omega}) of an Eg
(344 cm-1) mode which is related to Mn vibrations shows anomaly with
temperature (T) manifested as a change in slope of {omega} vs T at 260 K. The
temperature-dependent magnetization of BSM10 suggests a possible
antiferromagnetic ordering at ~ 260 K. We, therefore, attribute the phonon
anomaly to spin-phonon coupling arising due to the magnetic ordering.",2110.13808v1
2021-11-07,Unraveling complex magnetism in two-dimensional FeS$_2$,"Atomically thin two dimensional magnets have given rise to emergent phenomena
due to magnetic exchange and spin-orbit coupling showing a great promise for
realizing ultrathin device structures. In this paper, we critically examine the
magnetic properties of 2D FeS$_2$, which has been recently claimed to exhibit
room temperature ferromagnetism in the (111) orientation. Our ab initio study
based on collinear density functional theory has revealed the ground state as
an antiferromagnetic one with an ordering temperature of around 100K along with
a signature of spin-phonon coupling, which may trigger a ferromagnetic coupling
via strain. Moreover, our calculations based on spin-spirals indicate the
possibility of non-collinear magnetic structures, which is also supported by
Monte Carlo simulations based on ab initio magnetic exchange parameters. This
opens up an excellent possibility to manipulate magnetic structures by the
application of directional strain.",2111.04128v1
2024-03-21,Shadows and Properties of Spin-Induced Scalarized Black Holes with and without a Ricci Coupling,"In this work, we explore the properties and shadows of spin-induced
scalarized black holes, as well as investigate how a Ricci coupling influences
them. Our findings reveal significant deviations from the Kerr metric in terms
of the location and geodesic frequencies of the innermost stable circular orbit
and light ring, with the former exhibiting more pronounced disparities. The
shadows of scalarized black holes exhibit relatively minor deviations when
compared to those of Kerr black holes with the same mass and spin. Overall, the
presence of a Ricci coupling is observed to mitigate deviations from the Kerr
metric.",2403.14596v1
2007-04-03,Evolution of the Carter constant for inspirals into a black hole: effect of the black hole quadrupole,"We analyze the effect of gravitational radiation reaction on generic orbits
around a body with an axisymmetric mass quadrupole moment Q to linear order in
Q, to the leading post-Newtonian order, and to linear order in the mass ratio.
This system admits three constants of the motion in absence of radiation
reaction: energy, angular momentum, and a third constant analogous to the
Carter constant. We compute instantaneous and time-averaged rates of change of
these three constants. For a point particle orbiting a black hole, Ryan has
computed the leading order evolution of the orbit's Carter constant, which is
linear in the spin. Our result, when combined with an interaction quadratic in
the spin (the coupling of the black hole's spin to its own radiation reaction
field), gives the next to leading order evolution. The effect of the
quadrupole, like that of the linear spin term, is to circularize eccentric
orbits and to drive the orbital plane towards antialignment with the symmetry
axis. In addition we consider a system of two point masses where one body has a
single mass multipole or current multipole. To linear order in the mass ratio,
to linear order in the multipole, and to the leading post-Newtonian order, we
show that there does not exist an analog of the Carter constant for such a
system (except for the cases of spin and mass quadrupole). With mild additional
assumptions, this result falsifies the conjecture that all vacuum, axisymmetric
spacetimes posess a third constant of geodesic motion.",0704.0389v8
2017-11-14,Strong spin-orbit coupling and magnetism in (111) (La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35})$/SrTiO$_3$,"Strong correlations, multiple lattice degrees of freedom, and the ease of
doping make complex oxides a source of great research interest. Complex oxide
heterointerfaces break inversion symmetry and can host a two dimensional
carrier gas, which can display a variety of coexisting and competing phenomena.
In the case of heterointerfaces based on SrTiO$_3$, many of these phenomena can
be effectively tuned by using an electric gate, due to the large dielectric
constant of SrTiO$_3$. Most studies so far have focused on (001) oriented
heterostructures; however, (111) oriented heterostructures have recently gained
attention due to the possibility of finding exotic physics in these systems due
their hexagonal surface crystal symmetry. In this work, we use
magnetoresistance to study the evolution of spin-orbit interaction and
magnetism in a new system, (111) oriented
(La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)/SrTiO$_3$. At more positive
values of the gate voltage, which correspond to high carrier densities, we find
that transport is multiband, and dominated by high mobility carriers with a
tendency towards weak localization. At more negative gate voltages, the carrier
density is reduced, the high mobility bands are depopulated, and weak
antilocalization effects begin to dominate, indicating that spin-orbit
interaction becomes stronger. At millikelvin temperatures, and gate voltages
corresponding to the strong spin-orbit regime, we observe hysteresis in
magnetoresistance, indicative of ferromagnetism in the system. Our results
suggest that in the (111)
(La$_{0.3}$Sr$_{0.7}$)(Al$_{0.65}$Ta$_{0.35}$)/SrTiO$_3$ system, low mobility
carriers which experience strong spin-orbit interactions participate in
creating magnetic order in the system.",1711.05322v2
2021-07-09,Failure to achieve the $J_{eff}$~=~0 state even in nearly isolated Ir$^{5+}$ in Sr$_3$NaIrO$_6$: are iridates enough for realizing true $j$-$j$ coupling?,"Spin-orbit coupling (SOC) often gives rise to interesting electronic and
magnetic phases in an otherwise ordinary pool of paramagnetic heavy metal
oxides. In presence of strong SOC, assumed to be working in $j$-$j$ coupling
regime, 5$d^4$ iridates are generally speculated to possess a nonmagnetic
$J_{eff}$~=~0 singlet ground state, which invariably gets masked due to
different solid-state effects (e.g. hopping). Here, we try to probe the
trueness of the atomic SOC-based proposal in an apparently 1-dimensional
system, Sr$_3$NaIrO$_6$, possessing a 2$H$ hexagonal structure with well
separated Ir$^{5+}$ (5$d^4$) ions. But all the detailed experimental as well as
theoretical characterizations reveal that the ground state of Sr$_3$NaIrO$_6$
is not nonmagnetic, rather accommodating a significantly high effective
magnetic moment on Ir$^{5+}$ ion. However our combined dc susceptibility
($\chi$), ${}^{23}$Na nuclear magnetic resonance (NMR),
muon-spin-relaxation/rotation ($\mu$SR) and heat capacity ($C_p$) measurements
clearly refute any sign of spin-freezing or ordered magnetism among the
Ir$^{5+}$ moments due to geometrical exchange frustration, while in-depth
zero-field (ZF) and longitudinal field (LF) $\mu$SR investigations strongly
point towards inhomogeneous quantum spin-orbital liquid (QSOL)-like ground
state. In addition, the linear temperature dependence of both the NMR
spin-lattice relaxation rate and the magnetic heat capacity at low temperatures
suggest low-lying gapless spin excitations in the QSOL phase of this material.
Finally, we conclude that the effective SOC realised in $d^4$ iridates are
unlikely to offer a ground state which will be consistent with a purely atomic
$j$-$j$ coupling description.",2107.04431v1
2011-12-01,Measuring nonadiabaticity of molecular quantum dynamics with quantum fidelity and with its efficient semiclassical approximation,"We propose to measure nonadiabaticity of molecular quantum dynamics
rigorously with the quantum fidelity between the Born-Oppenheimer and fully
nonadiabatic dynamics. It is shown that this measure of nonadiabaticity applies
in situations where other criteria, such as the energy gap criterion or the
extent of population transfer, fail. We further propose to estimate this
quantum fidelity efficiently with a generalization of the dephasing
representation to multiple surfaces. Two variants of the multiple-surface
dephasing representation (MSDR) are introduced, in which the nuclei are
propagated either with the fewest-switches surface hopping (FSSH) or with the
locally mean field dynamics (LMFD). The LMFD can be interpreted as the
Ehrenfest dynamics of an ensemble of nuclear trajectories, and has been used
previously in the nonadiabatic semiclassical initial value representation. In
addition to propagating an ensemble of classical trajectories, the MSDR
requires evaluating nonadiabatic couplings and solving the Schr\""{o}dinger (or
more generally, the quantum Liouville-von Neumann) equation for a single
discrete degree of freedom. The MSDR can be also used to measure the importance
of other terms present in the molecular Hamiltonian, such as diabatic
couplings, spin-orbit couplings, or couplings to external fields, and to
evaluate the accuracy of quantum dynamics with an approximate nonadiabatic
Hamiltonian. The method is tested on three model problems introduced by Tully,
on a two-surface model of dissociation of NaI, and a three-surface model
including spin-orbit interactions. An example is presented that demonstrates
the importance of often-neglected second-order nonadiabatic couplings.",1112.0258v1
2023-09-21,Ferromagnetic quantum critical point in a locally noncentrosymmetric and nonsymmorphic Kondo metal,"Quantum critical points (QCPs), zero-temperature phase transitions, are
windows to fundamental quantum-mechanical phenomena associated with universal
behaviour and can provide parallels to the physics of black holes. Magnetic
QCPs have been extensively investigated in the vicinity of antiferromagnetic
order. However, QCPs are rare in metallic ferromagnets due to the coupling of
the order parameter to electronic soft modes [1,2]. Recently, antisymmetric
spin-orbit coupling in noncentrosymmetric systems was suggested to protect
ferromagnetic QCPs [3]. Nonetheless, multiple centrosymmetric materials host FM
QCPs, suggesting a more general mechanism behind their protection. In this
context, CeSi$_{2-\delta}$, a dense Kondo lattice crystallising in a
centrosymmetric structure, exhibits ferromagnetic order when Si is replaced
with Ag. We report that the Ag-substitution controls the strength of the Kondo
coupling, leading to a transition between paramagnetic and ferromagnetic Kondo
phases. Remarkably, a ferromagnetic QCP accompanied by concurrent strange-metal
behaviour emerges. Herein, we suggest that, despite the centrosymmetric
structure, spin-orbit coupling arising from the local noncentrosymmetric
structure, in combination with nonsymmorphic symmetry, can protect
ferromagnetic QCPs. Our findings present a unique example of Kondo
coupling-driven ferromagnetic QCP through chemical doping and offer a general
guideline for discovering new ferromagnetic QCPs.",2309.12497v1
2020-01-14,Anisotropic superconductivity mediated by ferroelectric fluctuations in cubic systems with spin-orbit coupling,"Motivated by the experimental observation that superconductivity in bulk
doped SrTiO$_{3}$ is enhanced as a putative ferroelectric quantum critical
point (FE-QCP) is approached, we study the pairing instability of a cubic
system in which electrons exchange low-energy ferroelectric fluctuations.
Instead of the gradient coupling to the lattice distortion associated with
ferroelectricity, we consider a direct coupling between the electrons and the
bosonic ferroelectric field that appears in the presence of spin-orbit
coupling. Working in the weak-coupling regime, we find that the pairing
interaction is dominated by the soft transverse optical (TO) mode, resulting in
a $T_{c}$ enhancement upon approaching the FE-QCP. Focusing on even-parity
states, we find that although the $s$-wave state always wins, states with
higher Cooper-pair angular momentum become close competitors as the TO mode
softens. We show that the cubic anisotropy of the FE fluctuations mixes the
$s$-wave and $g$-wave states, resulting in a characteristic anisotropy of the
gap function. The gap anisotropy behaves non-monotonically as the FE-QCP is
approached: upon decreasing the TO mode frequency, the gap anisotropy first
changes sign and then increases in magnitude. We discuss the possible
applications of our results to the superconducting state of SrTiO$_{3}$.",2001.04919v1
2022-01-01,"Kondo effect in a non-Hermitian, $\mathcal{PT}$-symmetric Anderson model with Rashba spin-orbit coupling","The non-interacting and non-Hermitian, parity-time ($\mathcal{PT}$)-symmetric
Anderson model exhibits an exceptional point (EP) at a non-Hermitian coupling
$g=1$, which remains unrenormalized in the presence of interactions (Lourenco
et al, arXiv:1806.03116), where the EP was shown to coincide with the quantum
critical point (QCP) for Kondo destruction. In this work, we consider a quantum
dot hybridizing with metallic leads having Rashba spin-orbit coupling
($\lambda$). We show that for a non-Hermitian hybridization, $\lambda$ can
renormalize the exceptional point even in the non-interacting case, stabilizing
$\mathcal{PT}$-symmetry beyond $g=1$. Through exact diagonalization of a
zero-bandwidth, three-site model, we show that the quantum critical point and
the exceptional point bifurcate, with the critical point for Kondo destruction
at $g_c=1$, and the exceptional coupling being $g_{\scriptscriptstyle{EP}} > 1$
for all $U\neq 0$ and $\lambda\geq 0; \lambda\neq U/2$. On the line
$\lambda=U/2$, the critical point and the EP again coincide at
$g_c=g_{\scriptscriptstyle{EP}}=1$. The full model with finite bandwidth leads
is investigated through the slave-boson approach, using which we show that, in
the strong coupling regime, $\lambda$ and interactions co-operate in strongly
reducing the critical point associated with Kondo destruction, below the
$\lambda=0$ value.",2201.00175v3
2012-12-19,Emergent Nesting of the Fermi Surface from Local-Moment Description of Iron-Pnictide High-Tc Superconductors,"We uncover the low-energy spectrum of a t-J model for electrons on a square
lattice of spin-1 iron atoms with 3dxz and 3dyz orbital character by applying
Schwinger-boson-slave-fermion mean-field theory and by exact diagonalization of
one hole roaming over a 4 x 4 x 2 lattice. Hopping matrix elements are set to
produce hole bands centered at zero two-dimensional (2D) momentum in the
free-electron limit. Holes can propagate coherently in the t-J model below a
threshold Hund coupling when long-range antiferromagnetic order across the d+ =
3d(x+iy)z and d- = 3d(x-iy)z orbitals is established by magnetic frustration
that is off-diagonal in the orbital indices. This leads to two hole-pocket
Fermi surfaces centered at zero 2D momentum. Proximity to a commensurate
spin-density wave (cSDW) that exists above the threshold Hund coupling results
in emergent Fermi surface pockets about cSDW momenta at a quantum critical
point (QCP). This motivates the introduction of a new Gutzwiller wavefunction
for a cSDW metal state. Study of the spin-fluctuation spectrum at cSDW momenta
indicates that the dispersion of the nested band of one-particle states that
emerges is electron-type. Increasing Hund coupling past the QCP can push the
hole-pocket Fermi surfaces centered at zero 2D momentum below the Fermi energy
level, in agreement with recent determinations of the electronic structure of
mono-layer iron-selenide superconductors.",1212.4619v3
2019-11-01,Ground-state phase diagram and excitation spectrum of a Bose-Einstein condensate with spin-orbital-angular-momentum coupling,"We investigate the ground-state phase diagram and excitation spectrum of an
interacting spinor Bose-Einstein condensate with spin-orbital-angular-momentum
(SOAM) coupling realized in recent experiments by introducing atomic Raman
transition with a pair of copropagating Laguerre-Gaussian laser beams that
carry different orbital angular momenta (OAM) [Chen et al., Phys. Rev. Lett.
121, 113204 (2018) and Zhang et al., Phys. Rev. Lett. 122, 110402 (2019)].
Because of the ground-state degeneracy of the single-particle Hamiltonian at
vanishing detuning, several angular-stripe phases, which are superposition of
states with different angular quantum numbers, appear in the phase diagram.
However, these phases normally exist at small detuning, which makes them hard
to be probed in experiments. We show that for a large OAM difference of the
laser beams, an asymmetric kind of angular-stripe phase can exist even at large
detuning. The excitation spectra in different phases exhibit distinct features:
In the angular-stripe phase there exist two gapless bands corresponding to the
broken U(1) and rotational symmetries, while in the half-skyrmion phase the
gapless band exhibits a roton-like structure. Our predictions of the
angular-stripe phases and the low-energy excitations can be examined in
recently realized BECs with SOAM coupling.",1911.00255v3
2016-12-15,Covalency and vibronic couplings make a nonmagnetic j=3/2 ion magnetic,"For 4$d^1$ and 5$d^1$ spin-orbit-coupled electron configurations, the notion
of nonmagnetic j=3/2 quartet ground state discussed in classical textbooks is
at odds with the observed variety of magnetic properties. Here we throw fresh
light on the electronic structure of 4$d^1$ and 5$d^1$ ions in molybdenum- and
osmium-based double-perovskite systems and reveal different kinds of on-site
many-body physics in the two families of compounds: while the sizable magnetic
moments and $g$ factors measured experimentally are due to both metal
$d$-ligand $p$ hybridization and dynamic Jahn-Teller interactions for 4$d$
electrons, it is essentially $d$-$p$ covalency for the 5$d^1$ configuration.
These results highlight the subtle interplay of spin-orbit interactions,
covalency and electron-lattice couplings as the major factor in deciding the
nature of the magnetic ground states of 4$d$ and 5$d$ quantum materials. Cation
charge imbalance in the double-perovskite structure is further shown to allow a
fine tuning of the gap between the $t_{2g}$ and $e_g$ levels, an effect of much
potential in the context of orbital engineering in oxide electronics.",1612.05158v1
2020-01-09,Bismuth iron garnet: ab initio study of electronic properties,"Bismuth iron garnet (BIG), i.e. Bi3Fe5O12, is a strong ferrimagnet that also
possess outstanding magneto-optical properties such as the largest known
Faraday rotation. These properties are related with the distribution of
magnetic moments on octahedral and tetrahedral sites, the presence of spin gaps
in the density of state and a strong spin-orbit coupling. In this work,
first-principles ab initio calculations are performed to study the structural,
electronic and magnetic properties of BIG using Density Functional Theory with
Hubbard+U (DFT+U) correction including spin-orbit coupling and HSE06 hybrid
functional. We found that the presence of spin gaps in the electronic structure
results from the interplay between exchange and correlation effects and the
crystal field strengths for tetrahedral and octahedral iron sublattices. The
DFT+U treatment tends to close the spin-gaps for larger U due to
over-localization effects, notably in the octahedral site. On the other hand,
the hybrid functional confirms the occurrences of three spin gaps in the iron
states of the conduction band as expected from optical measurements. A strong
exchange splitting at the top of the valence bands associated with a lone-pair
type mixture of O p and Bi s,p states is also obtained. Similar exchange
splitting was not previously observed for other iron based garnets, such as for
yttrium iron garnet. It follows that hole doping, as obtained by Ca
substitution at Bi sites, results in a full spin polarized density at the Fermi
energy. This work helps to shed more light on the theoretical comprehension of
the properties of BIG and opens the route towards the use of advanced Many Body
calculations to predict the magneto-optical coupling effects in BIG in a direct
comparison with the experimental measurements.",2001.02910v1
2019-02-20,Optical valley Hall effect for highly valley-coherent exciton-polaritons in an atomically thin semiconductor,"Spin-orbit coupling is a fundamental mechanism that connects the spin of a
charge carrier with its momentum. Likewise, in the optical domain, a synthetic
spin-orbit coupling is accessible, for instance, by engineering optical
anisotropies in photonic materials. Both, akin, yield the possibility to create
devices directly harnessing spin- and polarization as information carriers.
Atomically thin layers of transition metal dichalcogenides provide a new
material platform which promises intrinsic spin-valley Hall features both for
free carriers, two-particle excitations (excitons), as well as for photons. In
such materials, the spin of an exciton is closely linked to the high-symmetry
point in reciprocal space it emerges from. Here, we demonstrate, that spin, and
hence valley selective propagation is accessible in an atomically thin layer of
MoSe2, which is strongly coupled to a microcavity photon mode. We engineer a
wire-like device, where we can clearly trace the flow, and the helicity of
exciton-polaritons expanding along a channel. By exciting a coherent
superposition of K and K- tagged polaritons, we observe valley selective
expansion of the polariton cloud without neither any applied external magnetic
fields nor coherent Rayleigh scattering. Unlike the valley Hall effect for TMDC
excitons, the observed optical valley Hall effect (OVHE) strikingly occurs on a
macroscopic scale, and clearly reveals the potential for applications in
spin-valley locked photonic devices.",1902.07620v1
2022-03-31,First-principles theory of intrinsic spin and orbital Hall and Nernst effects in metallic monoatomic crystals,"The generation of spin and orbital currents is of crucial importance in the
field of spin-orbitronics. In this work, using relativistic density functional
theory and the Kubo linear-response formalism, we systematically investigate
the spin Hall and orbital Hall effects for 40 monoatomic metals. The spin Hall
conductivity (SHC) and orbital Hall conductivity (OHC) are computed as a
function of the electrochemical potential and the influence of the spin-orbit
interaction strength is also investigated. Our calculations predict a rather
small OHC in $sp$ metals, but a much larger OHC in $d$-band metals, with
maximum values [$\sim 8000\,(\hbar/e)\Omega^{-1}{\rm cm}^{-1}$] near the middle
of the $d$ series. Using the Mott formula, we evaluate the thermal counterparts
of the spin and orbital Hall effects, the spin Nernst effect (SNE) and the
orbital Nernst effect (ONE). We find that the as-yet unobserved ONE is
significantly larger ($\sim 10 \times$) than the SNE and has maximum values for
group 10 elements (Ni, Pd, and Pt). Our work provides a broad overview of
electrically- and thermally-induced spin and orbital transport in monoatomic
metals.",2203.17037v1
2023-03-29,Asymptotic gravitational-wave fluxes from a spinning test body on generic orbits around a Kerr black hole,"This work provides gravitational wave energy and angular momentum asymptotic
fluxes from a spinning body moving on generic orbits in a Kerr spacetime up to
linear in spin approximation. To achieve this, we have developed a new
frequency domain Teukolsky equation solver that calculates asymptotic
amplitudes from generic orbits of spinning bodies with their spin aligned with
the total orbital angular momentum. However, the energy and angular momentum
fluxes from these orbits in the linear in spin approximation are appropriate
for adiabatic models of extreme mass ratio inspirals even for spins non-aligned
to the orbital angular momentum. To check the newly obtained fluxes, they were
compared with already known frequency domain results for equatorial orbits and
with results from a time domain Teukolsky equation solver called Teukode for
off-equatorial orbits. The spinning body framework of our work is based on the
Mathisson-Papapetrou-Dixon equations under the Tulczyjew-Dixon spin
supplementary condition.",2303.16798v1
2017-09-03,Optical properties of van der Waals heterostructure of uniaxially strained graphene on TMD,"The spin and valley polarizations and plasmonics in Van der Waals
heterostructures of strained graphene monolayer on 2D transition metal
dichalcogenide (GrTMD) substrate are reported in this communication. The
substrate induced interactions (SII) involve sub-lattice-resolved, and enhanced
intrinsic spin-orbit couplings, the extrinsic Rashba spin-orbit coupling
(RSOC), and the orbital gap related to the transfer of the electronic charge
from graphene to the substrate. Furthermore, magnetic impurity atoms are
deposited to the graphene surface and the corresponding exchange field is
included in the band dispersion. A Rashba coupling dependent pseudo Zeeman term
arising due to the interplay of SIIs was found to be responsible for the spin
degeneracy lifting and the spin polarization. The latter turns out to be
electrostatic doping and the exchange field tunable and inversely proportional
to the square root of the carrier concentration. The strain field, on the other
hand, brings about the valley polarization. The intra-band plasmon dispersion
for the finite doping and the long wavelength limit has also been obtained. The
dispersion involves the q2/3 behavior and not the well known q1/2 behavior. The
uniform, uniaxial strain does not bring about any change in this behavior.
However, the plasmon dispersion gets steeper for the wavevector perpendicular
to the direction of strain and is flattened for wave vectors along the
direction of the strain with the term responsible for the flattening
proportional to the strain field. The stronger confinement capability of GrTMD
Plasmon compared to that of standalone, doped graphene is an important outcome
of the present work. One finds that whereas the intra-band absorbance of GrTMD
is decreasing function of the frequency at a given strain field, it is an
increasing function of the strain field at a given frequency.",1709.00667v1
2018-10-22,Tuning a binary ferromagnet into a multi-state synapse with spin-orbit torque induced plasticity,"Inspired by ion-dominated synaptic plasticity in human brain, artificial
synapses for neuromorphic computing adopt charge-related quantities as their
weights. Despite the existing charge derived synaptic emulations, schemes of
controlling electron spins in ferromagnetic devices have also attracted
considerable interest due to their advantages of low energy consumption,
unlimited endurance, and favorable CMOS compatibility. However, a generally
applicable method of tuning a binary ferromagnet into a multi-state memory with
pure spin-dominated synaptic plasticity in the absence of an external magnetic
field is still missing. Here, we show how synaptic plasticity of a
perpendicular ferromagnetic FM1 layer can be obtained when it is
interlayer-exchange-coupled by another in-plane ferromagnetic FM2 layer, where
a magnetic-field-free current-driven multi-state magnetization switching of FM1
in the Pt/FM1/Ta/FM2 structure is induced by spin-orbit torque. We use current
pulses to set the perpendicular magnetization state which acts as the synapse
weight, and demonstrate spintronic implementation of the excitatory/inhibitory
postsynaptic potentials and spike timing-dependent plasticity. This
functionality is made possible by the action of the in-plane interlayer
exchange coupling field which leads to broadened, multi-state magnetic reversal
characteristics. Numerical simulations, combined with investigations of a
reference sample with a single perpendicular magnetized Pt/FM1/Ta structure,
reveal that the broadening is due to the in-plane field component tuning the
efficiency of the spin-orbit-torque to drive domain walls across a landscape of
varying pinning potentials. The conventionally binary FM1 inside our
Pt/FM1/Ta/FM2 structure with inherent in-plane coupling field is therefore
tuned into a multi-state perpendicular ferromagnet and represents a synaptic
emulator for neuromorphic computing.",1810.09064v1
2006-05-27,Higher-order spin effects in the dynamics of compact binaries II. Radiation field,"Motivated by the search for gravitational waves emitted by binary black
holes, we investigate the gravitational radiation field of point particles with
spins within the framework of the multipolar-post-Newtonian wave generation
formalism. We compute: (i) the spin-orbit (SO) coupling effects in the binary's
mass and current quadrupole moments one post-Newtonian (1PN) order beyond the
dominant effect, (ii) the SO contributions in the gravitational-wave energy
flux and (iii) the secular evolution of the binary's orbital phase up to 2.5PN
order. Crucial ingredients for obtaining the 2.5PN contribution in the orbital
phase are the binary's energy and the spin precession equations, derived in
paper I of this series. These results provide more accurate gravitational-wave
templates to be used in the data analysis of rapidly rotating Kerr-type
black-hole binaries with the ground-based detectors LIGO, Virgo, GEO 600 and
TAMA300, and the space-based detector LISA.",0605140v4
2011-03-04,Chiral orbital-angular-momentum in the surface states of Bi2Se3,"Locking of the spin of a quasi-particle to its momentum in split bands of on
the surfaces of metals and topological insulators (TIs) is understood in terms
of Rashba effect where a free electron in the surface states feels an effective
magnetic field. On the other hand, the orbital part of the angular momentum
(OAM) is usually neglected. We performed angle resolved photoemission
experiments with circularly polarized lights and first principles density
functional calculation with spin-orbit coupling on a TI, Bi2Se3, to study the
local OAM of the surface states. We show from the results that OAM in the
surface states of Bi2Se3 is significant and locked to the electron momentum in
opposite direction to the spin, forming chiral OAM states. Our finding opens a
new possibility to have strong light-induced spin-polarized current in the
surface states.",1103.0805v2
2015-06-18,The absence of intraband scattering in a consistent theory of Gilbert damping in metallic ferromagnets,"Damping of magnetization dynamics in a ferromagnetic metal is usually
characterized by the Gilbert parameter alpha. Recent calculations of this
quantity, using a formula due to Kambersky, find that it is infinite for a
perfect crystal owing to an intraband scattering term which is of third order
in the spin-orbit parameter xi This surprising result conflicts with recent
work by Costa and Muniz who study damping numerically by direct calculation of
the dynamical transverse spin susceptibility in the presence of spin-orbit
coupling. We resolve this inconsistency by following the Costa-Muniz approach
for a slightly simplified model where it is possible to calculate alpha
analytically. We show that to second order in the spin-orbit parameter xi one
retrieves the Kambersky result for alpha, but to higher order one does not
obtain any divergent intraband terms. The present work goes beyond that of
Costa and Muniz by pointing out the necessity of including the effect of
long-range Coulomb interaction in calculating damping for large xi. A direct
derivation of the Kambersky formula is given which shows clearly the
restriction of its validity to second order in xi so that no intraband
scattering terms appear. This restriction has an important effect on the
damping over a substantial range of impurity content and temperature. The
experimental situation is discussed.",1506.05622v2
2016-06-07,"Fermi level position, Coulomb gap, and Dresselhaus splitting in (Ga,Mn)As","Carrier-induced nature of ferromagnetism in a ferromagnetic semiconductor,
(Ga,Mn)As, offers a great opportunity to observe novel spin-related phenomena
as well as to demonstrate new functionalities of spintronic devices. Here, we
report on low-temperature angle-resolved photoemission studies of the valence
band in this model compound. By a direct determination of the distance of the
split-off band to the Fermi energy EF, we conclude that EF is located within
the heavy/light hole band. However, the bands are strongly perturbed by
disorder and disorder-induced carrier correlations that lead to the Coulomb gap
at EF, which we resolve experimentally in a series of samples, and show that
its depth and width enlarge when the Curie temperature decreases. Furthermore,
we have detected surprising linear magnetic dichroism in photoemission spectra
of the split-off band. By a quantitative theoretical analysis we demonstrate
that it arises from the Dresselhaus-type spin-orbit term in zinc-blende
crystals. The spectroscopic access to the magnitude of such asymmetric part of
spin-orbit coupling is worthwhile, as they account for spin-orbit torque in
spintronic devices of ferromagnets without inversion symmetry.",1606.02047v1
2017-03-29,Driving force of the orbital-relevant electronic nematicity in Fe-based superconductors,"The electronic nematic responses in Fe-based superconductors have been
observed ubiquitously in various experimental probes. One novel nematic
character is the d-wave {\it bond} orbital-relevant nematic charge order which
was firstly proposed by symmetry analysis and then conformed by angle-resolved
photoemission spectroscopy. In this paper, we present a mechanism that the
driving force of the orbital-relevant nematic charge order is the reduction of
the large Hubbard energy in the particle-hole charge channel by virtual hopping
processes. This is one scenario from strong-coupling consideration. The same
virtual hopping processes can lead to a super-exchange interaction for the spin
magnetic order in the particle-hole spin channel and a pairing interaction for
the superconducting order in the particle-particle channel. Thus the electronic
nematic order, the spin magnetic order and the pairing superconducting order
are intrinsically entangled and they can all stem from the same microscopic
virtual hopping processes in reduction of the Hubbard energy. The electronic
nematicity, the spin magnetism and the pairing superconductivity in
unconventional superconductors are proposed to be unified within this
mechanism.",1703.09841v3
2017-06-19,Investigation of the Dzyaloshinskii-Moriya interaction and room temperature skyrmions in W/CoFeB/MgO thin films and microwires,"Recent studies have shown that material structures, which lack structural
inversion symmetry and have high spin-orbit coupling can exhibit chiral
magnetic textures and skyrmions which could be a key component for next
generation storage devices. The Dzyaloshinskii-Moriya Interaction (DMI) that
stabilizes skyrmions is an anti-symmetric exchange interaction favoring
non-collinear orientation of neighboring spins. It has been shown that material
systems with high DMI can lead to very efficient domain wall and skyrmion
motion by spin-orbit torques. To engineer such devices, it is important to
quantify the DMI for a given material system. Here we extract the DMI at the
Heavy Metal (HM) /Ferromagnet (FM) interface using two complementary
measurement schemes namely asymmetric domain wall motion and the magnetic
stripe annihilation. By using the two different measurement schemes, we find
for W(5 nm)/Co20Fe60B20(0.6 nm)/MgO(2 nm) the DMI to be 0.68 +/- 0.05 mJ/m2 and
0.73 +/- 0.5 mJ/m2, respectively. Furthermore, we show that this DMI stabilizes
skyrmions at room temperature and that there is a strong dependence of the DMI
on the relative composition of the CoFeB alloy. Finally we optimize the layers
and the interfaces using different growth conditions and demonstrate that a
higher deposition rate leads to a more uniform film with reduced pinning and
skyrmions that can be manipulated by Spin-Orbit Torques.",1706.05987v1
2017-06-26,The $SU(4)-SU(2)$ crossover and spin filter properties of a double quantum dot nanosystem,"The $SU(4)-SU(2)$ crossover, driven by an external magnetic field $h$, is
analyzed in a capacitively-coupled double-quantum-dot device connected to
independent leads. As one continuously charges the dots from empty to
quarter-filled, by varying the gate potential $V_g$, the crossover starts when
the magnitude of the spin polarization of the double quantum dot, as measured
by $\langle n_{\uparrow}\rangle -\langle n_{\downarrow}\rangle$, becomes
finite. Although the external magnetic field breaks the $SU(4)$ symmetry of the
Hamiltonian, the ground state preserves it in a region of $V_g$, where $\langle
n_{\uparrow}\rangle -\langle n_{\downarrow}\rangle =0$. Once the spin
polarization becomes finite, it initially increases slowly until a sudden
change occurs, in which $\langle n_{\downarrow}\rangle$ (polarization direction
opposite to the magnetic field) reaches a maximum and then decreases to
negligible values abruptly, at which point an orbital $SU(2)$ ground state is
fully established. This crossover from one Kondo state, with emergent $SU(4)$
symmetry, where spin and orbital degrees of freedom all play a role, to
another, with $SU(2)$ symmetry, where only orbital degrees of freedom
participate, is triggered by a competition between $g\mu_Bh$, the energy gain
by the Zeeman-split polarized state and the Kondo temperature $T_K^{SU(4)}$,
the gain provided by the $SU(4)$ unpolarized Kondo-singlet state.",1706.08618v1
2020-01-30,Localized spin-orbit polaron in magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$,"The kagome lattice Co$_3$Sn$_2$S$_2$ exhibits the quintessential topological
phenomena of a magnetic Weyl semimetal such as the chiral anomaly and Fermi-arc
surface states. Probing its magnetic properties is crucial for understanding
this correlated topological state. Here, using spin-polarized scanning
tunneling microscopy/spectroscopy (STM/S), we report the discovery of localized
spin-orbit polarons (SOPs) with three-fold rotation symmetry nucleated around
single-S vacancies in Co$_3$Sn$_2$S$_2$. The SOPs carry a spin-polarized
magnetic moment and a large orbital magnetization of a topological origin
associated with the Berry phase and the persistent circulating current.
Appreciable magneto-elastic coupling of the SOP is detected by atomic force
microscope and STM. Our findings suggest that the SOPs can enhance magnetism
and stability of the magnetic Weyl nodes for more robust
time-reversal-symmetry-breaking topological phenomena. Controlled engineering
of the SOPs may pave the way toward practical applications in functional
quantum devices.",2001.11295v2
2020-02-20,Giant anisotropic magnetoresistance through a tilted molecular $π$-orbital,"Anisotropic magnetoresistance (AMR), originating from spin-orbit coupling
(SOC), is the sensitivity of the electrical resistance in magnetic systems to
the direction of spin magnetization. Although this phenomenon has been
experimentally reported for several nanoscale junctions, a clear understanding
of the physical mechanism behind it is still elusive. Here we discuss a novel
concept based on orbital symmetry considerations to attain a significant AMR of
up to 95\% for a broad class of $\pi$-type molecular spin-valves. It is
illustrated at the benzene-dithiolate molecule connected between two monoatomic
nickel electrodes. We find that SOC opens, via spin-flip events at the
ferromagnet-molecule interface, a new conduction channel, which is fully
blocked by symmetry without SOC. Importantly, the interplay between main and
new transport channels turns out to depend strongly on the magnetization
direction in the nickel electrodes due to the tilting of molecular orbital.
Moreover, due to multi-band quantum interference, appearing at the band edge of
nickel electrodes, a transmission drop is observed just above the Fermi energy.
Altogether, these effects lead to a significant AMR around the Fermi level,
which even changes a sign. Our theoretical understanding, corroborated in terms
of \textit{ab initio} calculations and simplified analytical models, reveals
the general principles for an efficient realization of AMR in molecule-based
spintronic devices.",2002.08678v2
2020-12-09,Disentangling the role of bond lengths and orbital symmetries in controlling $T_c$ in YBa$_2$Cu$_3$O$_7$,"Optimally doped YBCO (YBa$_{2}$Cu$_{3}$O$_{7}$) has a high critical
temperature, at 92 K. It is largely believed that Cooper pairs form in YBCO and
other cuprates because of spin fluctuations, the issue and the detailed
mechanism is far from settled. In the present work, we employ a
state-of-the-art \emph{ab initio} ability to compute both the low and high
energy spin fluctuations in optimally doped YBCO. We benchmark our results
against recent inelastic neutron scattering and resonant inelastic X-ray
scattering measurements. Further, we use strain as an external parameter to
modulate the spin fluctuations and superconductivity. We disentangle the roles
of Barium-apical Oxygen hybridization, the interlayer coupling and orbital
symmetries by applying an idealized strain, and also a strain with a fully
relaxed structure. We show that shortening the distance between Cu layers is
conducive for enhanced Fermi surface nesting, that increases spin fluctuations
and drives up $T_{c}$. However, when the structure is fully relaxed electrons
flow to the d$_{z^2}$ orbital as a consequence of a shortened Ba-O bond which
is detrimental for superconductivity",2012.04897v1
2019-12-21,Stacking-configuration-enriched essential properties in bilayer silicenes,"The geometric, electronic and magnetic properties of silicene-related systems
present the diversified phenomena through the first-principles calculations.
The critical factors, the group-IV monoelements, buckled/planar structures,
stacking configurations, layer numbers, and van der Waals interactions of
bilayer composites are taken into account simultaneously. The developed
theoretical framework is responsible for the concise physical and chemical
pictures. The delicate evaluations and analyses are conducted on the optimal
lattices, the atom- $\&$ spin-dominated energy bands, the atom-, orbital- $\&$
spin-projected vanHove singularities, and the magnetic moments. Most
importantly, they achieve the decisive mechanisms, the buckled/planar honeycomb
lattices, the multi-/single-orbital hybridizations, and the
significant/negligible spin-orbital couplings. Furthermore, we investigate the
stacking-configuration-induced dramatic transformations of the essential
properties by the relative shift in bilayer graphene and silicene. The lattice
constant, interlayer distance, the buckle height, and the total energy
essentially depend on the magnitude and direction of the relative shift: AA
$\rightarrow$ AB $\rightarrow$ AA$^{\prime}$ $\rightarrow$ AA. Apparently,
sliding bilayer systems are quite different between silicene and graphene in
terms of electronic properties, strongly depending on the buckled/planar
honeycomb lattices, the multi-/single-orbital hybridizations, the
dominant/observable interlayer hopping integrals, and the
significant/negligible spin interactions. The predicted results can account for
the up-to-date experimental measurements.",1912.10257v1
2021-07-06,Relativistic aspects of orbital and magnetic anisotropies in the chemical bonding and structure of lanthanide molecules,"The electronic structure of magnetic lanthanide atoms is fascinating from a
fundamental perspective. They have electrons in a submerged open 4f shell lying
beneath a filled 6s shell with strong relativistic correlations leading to a
large magnetic moment and large electronic orbital angular momentum. This large
angular momentum leads to strong anisotropies, i. e. orientation dependencies,
in their mutual interactions. The long-ranged molecular anisotropies are
crucial for proposals to use ultracold lanthanide atoms in spin-based quantum
computers, the realization of exotic states in correlated matter, and the
simulation of orbitronics found in magnetic technologies. Short-ranged
interactions and bond formation among these atomic species have thus far not
been well characterized. Efficient relativistic computations are required.
Here, for the first time we theoretically determine the electronic and
ro-vibrational states of heavy homonuclear lanthanide Er2 and Tm2 molecules by
applying state-of-the-art relativistic methods. In spite of the complexity of
their internal structure, we were able to obtain reliable spin-orbit and
correlation-induced splittings between the 91 Er2 and 36 Tm2 electronic
potentials dissociating to two ground-state atoms. A tensor analysis allows us
to expand the potentials between the atoms in terms of a sum of seven spin-spin
tensor operators simplifying future research. The strengths of the tensor
operators as functions of atom separation are presented and relationships among
the strengths, derived from the dispersive long-range interactions, are
explained. Finally, low-lying spectroscopically relevant ro-vibrational energy
levels are computed with coupled-channels calculations and analyzed.",2107.02676v1
2022-03-27,Giant bulk spin-orbit torque and efficient electrical switching in single ferrimagnetic FeTb layers with strong perpendicular magnetic anisotropy,"Efficient manipulation of antiferromagnetically coupled materials that are
integration-friendly and have strong perpendicular magnetic anisotropy (PMA) is
of great interest for low-power, fast, dense magnetic storage and computing.
Here, we report a distinct, giant bulk damping-like spin-orbit torque in
strong-PMA ferrimagnetic Fe100-xTbx single layers that are integration-friendly
(composition-uniform, amorphous, sputter-deposited). For sufficiently-thick
layers, this bulk torque is constant in the efficiency per unit layer
thickness, {\xi}_DL^j/t, with a record-high value of 0.036nm-1, and the
dampinglike torque efficiency {\xi}_DL^j achieves very large values for thick
layers, up to 300% for 90 nm layers. This giant bulk torque by itself switches
tens of nm thick Fe100-xTbx layers that have very strong PMA and high
coercivity at current densities as low as a few MA/cm2. Surprisingly, for a
given layer thickness, {\xi}_DL^j shows strong composition dependence and
becomes negative for composition where the total angular momentum is oriented
parallel to the magnetization rather than antiparallel. Our findings of giant
bulk spin torque efficiency and intriguing torque-compensation correlation will
stimulate study of such unique spin-orbit phenomena in a variety of
ferrimagnetic hosts. This work paves a promising avenue for developing
ultralow-power, fast, dense ferrimagnetic storage and computing devices.",2203.14193v1
2006-10-24,Non-dissipative tidal synchronization in accreting binary white dwarf systems,"We study a non-dissipative hydrodynamical mechanism that can stabilize the
spin of the accretor in an ultra-compact double white dwarf binary. This novel
synchronization mechanism relies on a nonlinear wave interaction spinning down
the background star. The essential physics of the synchronization mechanism is
summarized as follows. As the compact binary coalesces due to gravitational
wave emission, the largest star eventually fills its Roche lobe and accretion
starts. The accretor then spins up due to infalling material and eventually
reaches a spin frequency where a normal mode of the star is resonantly driven
by the gravitational tidal field of the companion. If the resonating mode
satisfies a set of specific criteria, which we elucidate in this paper, it
exchanges angular momentum with the background star at a rate such that the
spin of the accretor locks at this resonant frequency, even though accretion is
ongoing. Some of the accreted angular momentum that would otherwise spin up the
accretor is fed back into the orbit through this resonant tidal interaction.
  Two modes capable of stabilizing the accretor's spin are the l=4,m=2 and
l=5,m=3 CFS unstable hybrid r-modes, which stabilize the spin of the accretor
at frequency 2.6 and 1.5 times the binary's orbital frequency respectively.
Since the stabilization mechanism relies on continuously driving a mode at
resonance, its lifetime is limited since eventually the mode amplitude
saturates due to non-linear mode-mode coupling. Rough estimates of the lifetime
of the effect lie from a few orbits to millions of years.",0610692v2
2014-02-05,Spin Transfer Torque Generated by the Topological Insulator Bi_2Se_3,"Magnetic devices are a leading contender for implementing memory and logic
technologies that are nonvolatile, that can scale to high density and high
speed, and that do not suffer wear-out. However, widespread applications of
magnetic memory and logic devices will require the development of efficient
mechanisms for reorienting their magnetization using the least possible current
and power. There has been considerable recent progress in this effort, in
particular discoveries that spin-orbit interactions in heavy metal/ferromagnet
bilayers can yield strong current-driven torques on the magnetic layer, via the
spin Hall effect in the heavy metal or the Rashba-Edelstein effect in the
ferromagnet. As part of the search for materials to provide even more efficient
spin-orbit-induced torques, some proposals have suggested topological
insulators (TIs), which possess a surface state in which the effects of
spin-orbit coupling are maximal in the sense that an electron's spin
orientation is locked relative to its propagation direction. Here we report
experiments showing that charge current flowing in-plane in a thin film of the
TI Bi_2Se_3 at room temperature can indeed apply a strong spin-transfer torque
to an adjacent ferromagnetic permalloy (Py = Ni81Fe19) thin film, with a
direction consistent with that expected from the topological surface state. We
find that the strength of the torque per unit charge current density in the
Bi_2Se_3 is greater than for any other spin-torque source material measured to
date, even for non-ideal TI films wherein the surface states coexist with bulk
conduction. Our data suggest that TIs have potential to enable very efficient
electrical manipulation of magnetic materials at room temperature for memory
and logic applications.",1402.1124v1
2016-05-30,On the Coupling of Photon Spin to Electron Orbital Angular Momentum,"Partially gold coated 90 degree glass wedges and a semi - infinite slit in a
thin film of gold ending in a conducting nano-junction serve as samples to
investigate the transfer of photon spin to electron orbital angular momentum.
These structures were specifically designed as samples where an incident beam
of light is retroreflected. Since in the process of retroreflection the turning
sense of a circularly polarized beam of light does not change and the direction
of propagation is inverted, the photon spin is inverted. Due to conservation of
angular momentum a transfer of photon spin to electron orbital angular momentum
of conduction electrons occurs. In the structures a circular movement of
electrons is blocked and therefore the transfered spin can be detected as a
photovoltage due to an electromotive force which is induced by the transfer of
angular momentum. Depending on the polarization of the incident beam, a maximum
photovoltage of about 0,2 micro V was measured for both structures. The results
are interpreted in terms of a classical electrodynamic model of the
monochromatic linearly polarized photon as a propagating solitary
electromagnetic wave of finite energy hf which carries an angular momentum
h/2pi which is elaborated elsewhere where h is Plancks constant and f the
frequency of light. The relative values of the measured photovoltages for
different polarizations can well be explained by the electrodynamic model of a
photon and an associated spin angular momentum. The absolute values of the
measured photovoltages are also consistent with the interpretation. The
observed effects are closely related to the lateral Fedorov Imbert shift of
focused beams in optics and the optical spin Hall effect and to other non
linear optical effects such as the inverse faraday effect for which a new
interpretation is given here in terms of the electrodynamic model of the photon
and its spin.",1609.05218v1
2020-02-06,Spin-orbit torque switching of perpendicular magnetization in ferromagnetic trilayers,"In ferromagnetic trilayers, a spin-orbit-induced spin current can have a spin
polarization of which direction is deviated from that for the spin Hall effect.
Recently, magnetization switching in ferromagnetic trilayers has been proposed
and confirmed by the experiments. In this work, we theoretically and
numerically investigate the switching current required for perpendicular
magnetization switching in ferromagnetic trilayers. We confirm that the tilted
spin polarization enables field-free deterministic switching at a lower current
than conventional spin-orbit torque or spin-transfer torque switching, offering
a possibility for high-density and low-power spin-orbit torque devices.
Moreover, we provide analytical expressions of the switching current for an
arbitrary spin polarization direction, which will be useful to design
spin-orbit torque devices and to interpret spin-orbit torque switching
experiments.",2002.02132v1
2020-01-26,Lanthanide-radical magnetic coupling in [LnPc$_2$]$^0$: Competing exchange mechanisms captured via ab initio multi-reference calculations,"We present a computational investigation of the intramolecular exchange
coupling in [LnPc$_2$]$^0$ (Ln = Tb, Dy, Ho, and Er) between the Ln$^{3+}$ 4f
electrons and the spin-1/2 radical on the phthalocyanine ligands. A series of
ab initio multi-configurational/multi-reference Complete/Restricted Active
Space Self-Consistent-Field calculations (CASSCF/RASSCF), including
non-perturbative spin--orbit coupling, were performed on [LnPc$_2$]$^0$ and on
the smaller model compound [LnPz$_2$]$^0$. We find that the exchange coupling
mechanisms are restricted by symmetry, but also dependent on the spin
polarization effect triggered by the Pc$_2$ ligands $\pi$--$\pi^*$ excitations.
The calculated exchange splittings are small, amounting to at most a few
cm$^{-1}$, in disagreement with previous literature reports of strong
antiferromagnetic coupling, but in good agreement with recent EPR experiments
on [TbPc$_2$]$^0$. Furthermore, the coupling strength is found to decrease from
[TbPc$_2$]$^0$ to [ErPc$_2$]$^0$, with decreasing number of unpaired electron
spins in the lanthanide ground (Hund's rule) Russell--Saunders term.",2001.09420v1
2016-12-22,Bismuth iron garnet Bi3Fe5O12: a room temperature magnetoelectric material,"The possibility to control the magnetic properties of a material with an
electric field at room temperature is highly desirable for modern applications.
Moreover, a coupling between magnetic and electric orders within a single
material presenting a wide range of exceptional physical properties, such as
bismuth iron garnet (BIG), may lead to great advances in the field of
spintronic applications. In particular, the combination of the magnetoelectric
(ME) coupling with the low damping of spin waves in BIG can allow the control
and manipulation of spin waves by an electric field in magnonic devices. Here
we report the unambiguous observation of linear magnetoelectric coupling above
300 K in BIG using ferromagnetic resonance technique with electric field
modulation. The measured coupling value is comparable with that observed for
prototypal magnetoelectric Cr2O3. On the basis of our experimental results, the
strength of this linear ME coupling is directly linked to the presence of
bismuth ions inducing strong spin orbit coupling and to the appearance of local
magnetic inhomogeneities related to the magnetic domain structure. The
unprecedented combination of magnetic, optical and magnetoelectrical properties
in BIG is expected to trigger significant interest for technological
applications as well as for theoretical studies.",1612.07531v3
2021-01-29,Probing the Spatial Variation of the Inter-Valley Tunnel Coupling in a Silicon Triple Quantum Dot,"Electrons confined in silicon quantum dots exhibit orbital, spin, and valley
degrees of freedom. The valley degree of freedom originates from the bulk
bandstructure of silicon, which has six degenerate electronic minima. The
degeneracy can be lifted in silicon quantum wells due to strain and electronic
confinement, but the ""valley splitting"" of the two lowest lying valleys is
known to be sensitive to atomic-scale disorder. Large valley splittings are
desirable to have a well-defined spin qubit. In addition, an understanding of
the inter-valley tunnel coupling that couples different valleys in adjacent
quantum dots is extremely important, as the resulting gaps in the energy level
diagram may affect the fidelity of charge and spin transfer protocols in
silicon quantum dot arrays. Here we use microwave spectroscopy to probe spatial
variations in the valley splitting, and the intra- and inter-valley tunnel
couplings ($t_{ij}$ and $t'_{ij}$) that couple dots $i$ and $j$ in a triple
quantum dot (TQD). We uncover large spatial variations in the ratio of
inter-valley to intra-valley tunnel couplings $t_{12}'/t_{12}=0.90$ and
$t_{23}'/t_{23}=0.56$. By tuning the interdot tunnel barrier we also show that
$t'_{ij}$ scales linearly with $t_{ij}$, as expected from theory. The results
indicate strong interactions between different valley states on neighboring
dots, which we attribute to local inhomogeneities in the silicon quantum well.",2101.12594v1
2022-05-20,Quantum dot molecule devices with optical control of charge status and electronic control of coupling,"Tunnel-coupled pairs of optically active quantum dots - quantum dot molecules
(QDMs) - offer the possibility to combine excellent optical properties such as
strong light-matter coupling with two-spin singlet-triplet ($S-T_0$) qubits
having extended coherence times. The $S-T_0$ basis formed using two spins is
inherently protected against electric and magnetic field noise. However, since
a single gate voltage is typically used to stabilize the charge occupancy of
the dots and control the inter-dot orbital couplings, operation of the $S-T_0$
qubits under optimal conditions remains challenging. Here, we present an
electric field tunable QDM that can be optically charged with one (1h) or two
holes (2h) on demand. We perform a four-phase optical and electric field
control sequence that facilitates the sequential preparation of the 2h charge
state and subsequently allows flexible control of the inter-dot coupling.
Charges are loaded via optical pumping and electron tunnel ionization. We
achieve one- and two-hole charging efficiencies of 93.5 $\pm$ 0.8 % and 80.5
$\pm$ 1.3 %, respectively. Combining efficient charge state preparation and
precise setting of inter-dot coupling allows control of few-spin qubits, as
would be required for on-demand generation of two-dimensional photonic cluster
states or quantum transduction between microwaves and photons.",2205.10001v1
2023-03-10,Coherent detection of hidden spin-lattice coupling in a van der Waals antiferromagnet,"Strong interactions between different degrees of freedom lead to exotic
phases of matter with complex order parameters and emergent collective
excitations. Conventional techniques, such as scattering and transport, probe
the amplitudes of these excitations, but they are typically insensitive to
phase. Therefore, novel methods with phase sensitivity are required to
understand ground states with phase modulations and interactions that couple to
the phase of collective modes. Here, by performing phase-resolved coherent
phonon spectroscopy (CPS), we reveal a hidden spin-lattice coupling in a vdW
antiferromagnet FePS$_{3}$ that eluded other phase-insensitive conventional
probes, such as Raman and X-ray scattering. With comparative analysis and
analytical calculations, we directly show that the magnetic order in FePS$_{3}$
selectively couples to the trigonal distortions through partially filled
t$_{2g}$ orbitals. This magnetoelastic coupling is linear in magnetic order and
lattice parameters, rendering these distortions inaccessible to inelastic
scattering techniques. Our results not only capture the elusive spin-lattice
coupling in FePS$_3$, but also establish phase-resolved CPS as a tool to
investigate hidden interactions.",2303.05963v1
2004-10-14,The distribution and cosmic evolution of massive black hole spins,"We study the expected distribution of massive black hole (MBH) spins and its
evolution with cosmic time in the context of hierarchical galaxy formation
theories. Our model uses Monte Carlo realizations of the merger hierarchy in a
LCDM cosmology, coupled to semi-analytical recipes, to follow the merger
history of dark matter halos, the dynamics of the MBHs they host, and their
growth via gas accretion and binary coalescences. The coalescence of comparable
mass holes increases the spin of MBHs, while the capture of smaller companions
in randomly-oriented orbits acts to spin holes down. We find that, given the
distribution of MBH binary mass ratios in hierarchical models, binary
coalescences alone do not lead to a systematic spin-up or spin-down of MBHs
with time: the spin distribution retains memory of its initial conditions. By
contrast, because of the Bardeen-Petterson effect, gas accretion via a thin
disk tends to spin holes up even if the direction of the spin axis changes
randomly in time. In our models, accretion dominates over black hole captures
and efficiently spins holes up. The spin distribution is heavily skewed towards
fast-rotating Kerr holes, is already in place at early epochs, and does not
change much below redshift 5. If accretion is via a thin disk, about 70% of all
MBHs are maximally rotating and have radiative efficiencies approaching 30%
(assuming a ""standard'' spin-efficiency conversion). Even in the conservative
case where accretion is via a geometrically thick disk, about 80% of all MBHs
have spin parameters a/m > 0.8 and accretion efficiencies > 12%. Rapidly
spinning holes with high radiative efficiencies may satisfy constraints based
on comparing the local MBH mass density with the mass density inferred from
luminous quasars (Soltan's argument).",0410342v1
2019-11-20,"Tunable large spin Hall and spin Nernst effects in Dirac semimetals ZrXY (X=Si, Ge; Y=S, Se, Te)","The ZrSiS-type compounds are Dirac semimetals and have been attracting
considerable interest in recent years due to their topological electronic
properties and possible applications. In particular, gapped Dirac nodes can
possess large spin Berry curvatures and thus give rise to large spin Hall
effect (SHE) and spin Nernst effect (SNE), which may be used to generate pure
spin current for spintronics and spin caloritronics without applied magnetic
field or magnetic material. In this paper we study both SHE and SNE in ZrXY (X
= Si, Ge; Y = S, Se, Te) based on \textit{ab initio} relativistic band
structure calculations. Our theoretical calculations reveal that some of these
compounds exhibit large intrinsic spin Hall conductivity (SHC) and spin Nernst
conductivity (SNC). The calculated SHC of ZrSiTe is as large as -755
($\hbar$/e)(S/cm). Since the electric conductivity of these Dirac semimetals
are much smaller than that of platinum which has the largest intrinsic SHC of
$\sim$2200 ($\hbar$/e)(S/cm), this indicates that they will have a larger spin
Hall angle than that of platinum. Remarkably, we find that both the magnitude
and sign of the SHE and SNE in these compounds can be significantly tuned by
changing either the electric field direction or spin current direction and may
also be optimized by slightly varying the Fermi level via chemical doping.
Analysis of the calculated band- and $k$-resolved spin Berry curvatures show
that the large SHE and SNE as well as their remarkable tunabilities originate
from the presence of many slightly spin-orbit coupling-gapped Dirac nodal lines
near the Fermi level in these Dirac semimetals. Our findings suggest that the
ZrSiS-type compounds are promising candidates for spintronic and spin
caloritronic devices, and will certainly stimulate further experiments on these
Dirac semimetals.",1911.08902v1
2021-05-19,Optical manipulation of Rashba-split 2-Dimensional Electron Gas,"In spintronic devices, the two main approaches to actively control the
electrons' spin degree of freedom involve either static magnetic or electric
fields. An alternative avenue relies on the application of optical fields to
generate spin currents, which promises to bolster spin-device performance
allowing for significantly faster and more efficient spin logic. To date,
research has mainly focused on the optical injection of spin currents through
the photogalvanic effect, and little is known about the direct optical control
of the intrinsic spin splitting. Here, to explore the all-optical manipulation
of a material's spin properties, we consider the Rashba effect at a
semiconductor interface. The Rashba effect has long been a staple in the field
of spintronics owing to its superior tunability, which allows the observation
of fully spin-dependent phenomena, such as the spin-Hall effect, spin-charge
conversion, and spin-torque in semiconductor devices. In this work, by means of
time and angle-resolved photoemission spectroscopy (TR-ARPES), we demonstrate
that an ultrafast optical excitation can be used to manipulate the
Rashba-induced spin splitting of a two-dimensional electron gas (2DEG)
engineered at the surface of the topological insulator Bi$_{2}$Se$_{3}$. We
establish that light-induced photovoltage and charge carrier redistribution --
which in concert modulate the spin-orbit coupling strength on a sub-picosecond
timescale -- can offer an unprecedented platform for achieving all
optically-driven THz spin logic devices.",2105.09320v2
1994-03-03,An Orbitally Degenerate Spin Fluctuation Model for Heavy Fermion Superconductivity,"In this paper, a generalization of standard spin fluctuation theory is
considered by replacing the simple Hubbard interaction by the screened
Hartree-Fock interaction for f electrons. This model is then used in both an LS
and a JJ coupling scheme to construct the particle-particle scattering vertex
in an on-site approximation. This vertex is shown to lead to an instability for
a superconducting pair state which obeys Hunds rules, with L=5, S=1, and J=4.
The degeneracy of this state is broken by anisotropy of the quasiparticle
wavefunctions. Detailed calculations are presented for the case of $UPt_3$.",9403018v1
1999-08-03,Semiclassical mechanics of a non-integrable spin cluster,"We study detailed classical-quantum correspondence for a cluster system of
three spins with single-axis anisotropic exchange coupling. With autoregressive
spectral estimation, we find oscillating terms in the quantum density of states
caused by classical periodic orbits: in the slowly varying part of the density
of states we see signs of nontrivial topology changes happening to the energy
surface as the energy is varied. Also, we can explain the hierarchy of quantum
energy levels near the ferromagnetic and antiferromagnetic states with EKB
quantization to explain large structures and tunneling to explain small
structures.",9908055v1
1999-11-10,The energy-level statistics in the core of a vortex in a p-wave superconductor,"In the presence of strong disorder, the statistics of quasiparticle levels in
the core of a vortex in a two-dimensional p-wave superconductor belongs to the
universality class B corresponding to the ensemble of orthogonal matrices in
odd dimensions. This novel universality class appears as a consequence of the
O(2) spin symmetry of p-wave pairing. It is preserved in the presence of random
disorder, of electromagnetic vector potential, and of an admixture of the
pairing of opposite chirality in the vortex core, but may be destroyed by
spin-orbit coupling and by Zeeman splitting.",9911147v2
2000-01-19,Ground and Metastable States in $γ$-Ce from Correlated Band Theory,"Multiple energy minima of the LDA+U energy functional are obtained for
$\gamma$-Ce when it is implemented in a full potential, rotationally invariant
scheme including spin-orbit coupling, and different starting local
configurations are chosen. The lowest energy solution leads to a fully spin
polarized 4f state and the lattice constant of $\gamma$-Ce. The higher energy
local minima (additional self-consistent solutions) are shown to be strongly
indicative of crystal electric field and multiplet excitations.",0001255v1
2000-02-09,Fluctuating spin g-tensor in small metal grains,"In the presence of spin-orbit scattering, the splitting of an energy level in
a generic small metal grain due to the Zeeman coupling to a magnetic field B
depends on the direction of B, as a result of mesoscopic fluctuations. The
anisotropy is described by the eigenvalues g_j^2 (j=1,2,3) of a tensor G,
corresponding to the (squares of) g-factors along three principal axes. We
consider the statistical distribution of G and find that the anisotropy is
enhanced by eigenvalue repulsion between the g_j.",0002139v1
2000-05-28,Highly anisotropic g-factor of two-dimensional hole systems,"Coupling the spin degree of freedom to the anisotropic orbital motion of
two-dimensional (2D) hole systems gives rise to a highly anisotropic Zeeman
splitting with respect to different orientations of an in-plane magnetic field
B relative to the crystal axes. This mechanism has no analogue in the bulk band
structure. We obtain good, qualitative agreement between theory and
experimental data, taken in GaAs 2D hole systems grown on (113) substrates,
showing the anisotropic depopulation of the upper spin subband as a function of
in-plane B.",0005488v1
2002-10-08,Coulomb Correlations and Magnetic Anisotropy in ordered $L1_0$ CoPt and FePt alloys,"We present results of the magneto-crystalline anisotropy energy (MAE)
calculations for chemically ordered $L1_0$ CoPt and FePt alloys taking into
account the effects of strong electronic correlations and spin-orbit coupling.
The local spin density + Hubbard U approximation (LSDA+U) is shown to provide a
consistent picture of the magnetic ground state properties when intra-atomic
Coulomb correlations are included for both 3$d$ and 5$d$ elements. Our results
demonstrate significant and complex contribution of correlation effects to
large MAE of these material.",0210157v2
2003-02-20,Prediction of a surface magnetic moment in alpha-uranium,"Recently, there has been an increased interest in first-principles
calculations of the actinides as well as in finding the new materials which
display surface magnetism. We predict the existence of a magnetic moment on the
uranium (001) surface by performing density functional calculations for a slab
geometry in the generalized gradient and local spin density approximations with
included spin orbit coupling. The ferromagnetic phase is energetically favored
for all geometries. The calculated total magnetic moment, $0.65{\mu_{B}}$, is
stable on films of different thickness and it should be observable
experimentally.",0302423v1
2003-06-13,Rashba precession in quantum wires,"The length over which electron spins reverse direction due to the Rashba
effect when injected with an initial polarization along the axes of a quantum
wire is investigated theoretically. A soft wall confinement of the wire
renormalizes the spin-orbit parameter (and the effective mass) stronger than
hard walls. Electron-electron interactions enhance the Rashba precession while
evidence is found that the coupling between transport channels may suppress it.",0306359v1
2003-11-03,"Comment on ""Low-dimensional spin S=1/2 system at the quantum critical limit: Na2V3O7""","We contest the interpretation by Gavilano et al. (Phys.Rev.Lett. 90 (2003)
167202) of violation of the Curie law behavior of the paramagnetic
susceptibility at low temperatures by means of the quenching of the V4+-ion
moment. These results can be understood as caused by well-known conventional
phenomena like crystal-field interactions but with taking into account the
intra-atomic spin-orbit coupling for the V4+ ion.",0311033v1
2003-11-28,g-factor engineering and control in self-assembled quantum dots,"The knowledge of electron and hole g-factors, their control and engineering
are key for the usage of the spin degree of freedom for information processing
in solid state systems. The electronic g-factor will be materials dependent,
the effect being larger for materials with large spin-orbit coupling. Since
electrons can be individually trapped into quantum dots in a controllable
manner, they may represent a good platform for the implementation of quantum
information processing devices. Here we use self-assembled quantum dots of InAs
embedded in GaAs for the g-factor control and engineering.",0311644v1
2004-06-22,Are Th doped Y2C3 and La2C3 two-band superconductors?,"The superconducting sesquicarbides R2C3 have noncentrosymmetric point group
symmetry Td. Spin-orbit coupling lifts the spin degeneracy of electronic bands
in the most of the Brillouin zone. Nevertheless, due to high symmetry, there
are a few directions along which the Fermi surfaces must touch. This leads to
the two-band effects in the superconducting state.",0406527v2
2005-11-18,Charge ordering in quasi-one-dimensional systems with frustrating interactions,"Motivated by the co-existing charge and spin order found in strongly
correlated ladder systems, we study an effective pseudospin model on a coupled
two-leg ladder. A bosonisation analysis yields a rich phase diagram showing
Wigner/Peierls charge order and Neel/dimer spin order. In a broad parameter
regime, the orbital antiferromagnetic phase is found to be stable. An
intermediate gapless phase of finite width is found to lie in between two
charge-ordered gapped phases. Our work is potentially relevant for a unified
description of a class of strongly correlated, quarter-filled ladder systems.",0511458v1
2005-12-11,Interplay between Zeeman interaction and spin-orbit coupling in a two-dimensional semiconductor system,"We analyse the interplay between Dresselhaus, Bychkov-Rashba, and Zeeman
interactions in a two-dimensional semiconductor quantum system under the action
of a magnetic field. When a vertical magnetic field is considered, we predict
that the interplay results in an effective cyclotron frequency that depends on
a spin-dependent contribution. For in-plane magnetic fields, we found that the
interplay induces an anisotropic effective gyromagnetic factor that depends on
the orientation of the applied field as well as on the orientation of the
electron momentum.",0512231v1
2006-08-01,Ferroelectricity in the Magnetic E-Phase of Orthorhombic Perovskites,"We show that the symmetry of the spin zigzag chain E phase of the
orthorhombic perovskite manganites and nickelates allows for the existence of a
finite ferroelectric polarization. The proposed microscopic mechanism is
independent of spin-orbit coupling. We predict that the polarization induced by
the E-type magnetic order can potentially be enhanced by up to two orders of
magnitude with respect to that in the spiral magnetic phases of TbMnO3 and
similar multiferroic compounds.",0608025v2
1998-01-05,Flow equations in the light-front perturbation theory,"The method of flow equations is applied to QED in the light-front dynamics.
To second order in the coupling the particle number conserving part of the
effective QED Hamiltonian has two terms of different structure. The first term
gives the Coulomb interaction and the correct spin splittings of positronium;
the contribution of the second term to mass spectrum depends on the explicit
form of unitary transformation and may influence the spin-orbit.",9801018v3
1998-10-30,T-Duality and Spinning Solutions in 2 + 1 Gravity,"Starting with the 2+1 Einstein--Maxwell--Dilaton system with a cosmological
constant and assuming two commuting Killing symmetries we derive the
corresponding $1+0 \sigma$--model. It is shown that, for general values of the
coupling parameters, the $T$--duality group is $SL(2,R)$, which coincides with
the group of linear coordinate transformations along the Killing orbits. This
duality, along with a suitable parameter choice, is applied to obtain some new
spinning solutions in the alternative gravity theories: Einstein--Maxwell,
Brans--Dicke and Einstein--Maxwell--Dilaton.",9810245v1
2006-04-01,Galilei invariant theories. I. Constructions of indecomposable finite-dimensional representations of the homogeneous Galilei group: directly and via contractions,"All indecomposable finite-dimensional representations of the homogeneous
Galilei group which when restricted to the rotation subgroup are decomposed to
spin 0, 1/2 and 1 representations are constructed and classified. These
representations are also obtained via contractions of the corresponding
representations of the Lorentz group. Finally the obtained representations are
used to derive a general Pauli anomalous interaction term and Darwin and
spin-orbit couplings of a Galilean particle interacting with an external
electric field.",0604002v1
2003-03-20,Dressed Qubits,"Inherent gate errors can arise in quantum computation when the actual system
Hamiltonian or Hilbert space deviates from the desired one. Two important
examples we address are spin-coupled quantum dots in the presence of spin-orbit
perturbations to the Heisenberg exchange interaction, and off-resonant
transitions of a qubit embedded in a multilevel Hilbert space. We propose a
``dressed qubit'' transformation for dealing with such inherent errors. Unlike
quantum error correction, the dressed qubits method does not require additional
operations or encoding redundancy, is insenstitive to error magnitude, and
imposes no new experimental constraints.",0303129v3
2004-02-23,Holonomic Quantum Computing Based on the Stark Effect,"We propose a spin manipulation technique based entirely on electric fields
applied to acceptor states in $p$-type semiconductors with spin-orbit coupling.
While interesting in its own right, the technique can also be used to implement
fault-resilient holonomic quantum computing. We explicitly compute adiabatic
transformation matrix (holonomy) of the degenerate states and comment on the
feasibility of the scheme as an experimental technique.",0402165v1
2006-05-11,On the Generator of Lorentz Boost,"Traditionally, the theory related to the spatial angular momentum has been
studied completely, while the investigation in the generator of Lorentz boost
is inadequate. In this paper we show that the generator of Lorentz boost has a
nontrivial physical significance, it endows a charged system with an electric
moment, and has an important significance for the electrical manipulations of
electron spin in spintronics. An alternative treatment and interpretation for
the traditional Darwin term and spin-orbit coupling are given.",0605101v4
2007-04-23,Ferroelectricity driven by the non-centrosymmetric magnetic ordering in multiferroic TbMn_2O_5: a first-principles study,"The ground state structural, electronic and magnetic properties of
multiferroic TbMn$_2$O$_5$ are investigated via first-principles calculations.
We show that the ferroelectricity in TbMn$_2$O$_5$ is driven by the
non-centrosymmetric magnetic ordering, without invoking the spin-orbit coupling
and non-collinear spins. The {\it intrinsic} electric polarization in this
compound is calculated to be 1187 $nC\cdot$ cm$^{-2}$, an order of magnitude
larger than previously thought.",0704.2908v2
2007-09-05,Effects of interactions in transport through Aharonov-Bohm-Casher interferometers,"We study the conductance through a ring described by the Hubbard model (such
as an array of quantum dots), threaded by a magnetic flux and subject to Rashba
spin-orbit coupling (SOC). We develop a formalism that is able to describe the
interference effects as well as the Kondo effect when the number of electrons
in the ring is odd. In the Kondo regime, the SOC reduces the conductance from
the unitary limit, and in combination with the magnetic flux, the device acts
as a spin polarizer.",0709.0643v1
2008-05-18,The Aharonov-Bohm-Casher ring-dot as a flux-tunable resonant tunneling diode,"A mesoscopic ring subject to the Rashba spin-orbit interaction and
sequentially coupled to an interacting quantum dot, in the presence of
Aharonov-Bohm flux, is proposed as a flux tunable tunneling diode. The analysis
of the conductance by means of the nonequilibrium Green's function technique,
shows an intrinsic bistability at varying the Aharonov-Bohm flux when 2U > \pi
\Gamma, U being the charging energy on the dot and \Gamma the effective
resonance width. The bistability properties are discussed in connection with
spin-switch effects and logical storage device applications.",0805.2715v1
2009-02-18,"Structural, Magnetic, and Electronic Properties of the Monometallofullerene Gd@C_82 : Theory","The structural, electronic, and magnetic properties of Gd@C_82 endohedral
metallofullerene have been studied by employing on-site correlation corrected,
scalar-relativistic and full-relativistic density functional theory within the
local density and generalized gradient approximations. The experimentally
observed reduction of the magnetic moment of Gd@C_82 with respect to that of a
free Gd^+3 ion can be explained by a tiny hybridization between unoccupied
Gd-4f states and carbon-pi states, resulting in a generic antiferromagnetic
coupling of the Gd-4f spin with the remaining unpaired spin in the hybridized
molecular orbital.",0902.3218v1
2010-01-11,Nonlocal effects on magnetism in the diluted magnetic semiconductor Ga_{1-x}Mn_{x}As,"The magnetic properties of the diluted magnetic semiconductor
Ga_{1-x}Mn_{x}As are studied within the dynamical cluster approximation. We use
the k-dot-p Hamiltonian to describe the electronic structure of GaAs with
spin-orbit coupling and strain effects. We show that nonlocal effects are
essential for explaining the experimentally observed transition temperature and
saturation magnetization. We also demonstrate that the cluster anisotropy is
very strong and induces rotational frustration and a cube-edge direction
magnetic anisotropy at low temperature. With this, we explain the
temperature-driven spin reorientation in this system.",1001.1716v1
2010-03-05,Helical liquids and Majorana bound states in quantum wires,"We show that the combination of spin-orbit coupling with a Zeeman field or
strong interactions may lead to the formation of a helical liquid in
single-channel quantum wires. In a helical liquid, electrons with opposite
velocities have opposite spin precession. We argue that zero-energy Majorana
bound states are formed in various situations when the wire is situated in
proximity to a conventional s-wave superconductor. This occurs when the
external magnetic field, the superconducting gap, or, in particular, the
chemical potential vary along the wire. We discuss experimental consequences of
the formation of the helical liquid and the Majorana bound states.",1003.1145v2
2011-04-29,Meissner effect in the layered Kane-Mele model with Hubbard interaction,"We investigate the magnetic response in the quantum spin Hall phase of the
layered Kane-Mele model with Hubbard interaction, and argue a condition to
obtain the Meissner effect. The effect of Rashba spin orbit coupling is also
discussed.",1104.5555v1
2012-02-22,A description of odd mass W-isotopes in the Interacting 2 Boson-Fermion Model,"The negative and positive parity low-spin states of the even-odd Tungsten
isotopes, 183,185,187W are studied in the frame work of the Interacting
Boson-Fermion Approximation (IBFA) model. The fermion that is coupled to the
system of bosons is taken to be in the negative parity 2f_7|2, 2f_5\2, 3p_3\2,
3p_1\2 and in the positive parity 1i_13\2 single-particle orbits. The
calculated energies of low-spin energy levels of the odd isotopes are found to
agree well with the experimental data. Also B(E2) values and spectroscopic
factors for single-neutron transfer are calculated and found to be in good
agreement with experimental data.",1202.4987v1
2012-06-20,Magnetoelectric nature of skyrmions in a chiral magnetic insulator Cu2OSeO3,"Dielectric properties were investigated under various magnitudes and
directions of magnetic field (H) for a chiral magnetic insulator Cu2OSeO3. We
found that the skyrmion crystal induces electric polarization (P) along either
in-plane or out-of-plane direction of the spin vortices depending on the
applied H-direction. The observed H-dependence of P in ferrimagnetic,
helimagnetic, and skyrmion crystal state can be consistently described by the
d-p hybridization model, highlighting an important role of relativistic
spin-orbit interaction in the magnetoelectric coupling in Cu2OSeO3. Our
analysis suggests that each skyrmion particle can locally carry electric dipole
or quadrupole, which implies that the dynamics of skyrmions are controllable by
the external electric field.",1206.4404v1
2012-08-13,Helical States in Curved Bilayer Graphene,"We study spin effects of quantum wires formed in bilayer graphene by
electrostatic confinement. With a proper choice of the confinement direction,
we show that in the presence of magnetic field, spin-orbit interaction induced
by curvature, and intervalley scattering, bound states emerge that are helical.
The localization length of these helical states can be modulated by the gate
voltage which enables the control of the tunnel coupling between two parallel
wires. Allowing for proximity effect via an s-wave superconductor, we show that
the helical modes give rise to Majorana fermions in bilayer graphene.",1208.2601v1
2013-02-04,Rashba split surface states in BiTeBr,"Within density functional theory, we study bulk band structure and surface
states of BiTeBr. We consider both ordered and disordered phases which differ
in atomic order in the Te-Br sublattice. On the basis of relativistic ab-initio
calculations, we show that the ordered BiTeBr is energetically preferable as
compared with the disordered one. We demonstrate that both Te- and
Br-terminated surfaces of the ordered BiTeBr hold surface states with a giant
spin-orbit splitting. The Te-terminated surface-state spin splitting has the
Rashba-type behavior with the coupling parameter \alpha_R ~ 2 eV\AA.",1302.0704v1
2013-03-14,Intrinsic Bistability In Quantum Point Contacts with in-plane Side Gates,"We study the onset of intrinsic bistability and accompanying hysteresis in a
single quantum point contact (QPC) with in-plane side gates in the presence of
lateral spin-orbit coupling. The hysteresis in the conductance versus common
gate voltage applied to the two side gates exists only if the narrow portion of
the QPC is long enough. The hysteresis is absent if the effects of
electron-electron interaction are neglected but increases with the strength of
the electron-electron interaction. The hysteresis appears in the region of
conductance anomalies, i.e., less than 2e2/h, and is due to multistable spin
textures in these regions.",1303.3429v1
2013-04-26,Ferroelectricity from iron valence ordering in rare earth ferrites?,"The possibility of multiferroicity arising from charge ordering in LuFe2O4
and structurally related rare earth ferrites is reviewed. Recent experimental
work on macroscopic indications of ferroelectricity and microscopic
determination of coupled spin and charge order indicates that this scenario
does not hold. Understanding the origin of the experimentally observed charge
and spin order will require further theoretical work. Other aspects of recent
research in these materials, such as geometrical frustration effects, possible
electric-field-induced transitions, or orbital order are also briefly treated.",1304.7255v1
2013-12-26,Prediction of a quantum anomalous Hall state in Co decorated silicene,"Based on first-principles calculations, we demonstrate that Co decorated
silicene can host a quantum anomalous Hall state. The exchange field induced by
the Co atoms combined with the strong spin orbit coupling of the silicene opens
a nontrivial band gap at the K-point. As compared to other transition metals,
Co decorated silicene is unique in this respect, since usually hybridization
and spin-polarization induced in the silicene suppress a quantum anomalous Hall
state.",1312.7127v2
2014-08-20,Vortex Core Structure in Multilayered Rashba Superconductors,"We numerically study the electronic structure of a single vortex in two
dimensional superconducting bilayer systems within the range of the mean-field
theory. The lack of local inversion symmetry in the system is taken into
account through the layer dependent Rashba spin-orbit coupling. The spatial
profiles of the pair potential and the local quasiparticle density of states
are calculated in the clean spin-singlet superconductor on the basis of the
quasiclassical theory. In particular, we discuss the characteristic core
structure in the pair-density wave state, which is spatially modulated exotic
superconducting phase in a high magnetic field.",1408.4550v1
2015-02-05,DFT calculations of magnetic anisotropy energy for GeMnTe ferromagnetic semiconductor,"Density functional theory (DFT) calculations of the energy of magnetic
anisotropy for diluted ferromagnetic semiconductor GeMnTe were performed using
using OpenMX package with fully relativistic pseudopotentials. The influence of
hole concentration and magnetic ion neighborhood on magnetic anisotropy energy
is presented. Analysis of microscopic mechanism of magnetic anisotropy is
provided, in particular the role of spin-orbit coupling, spin polarization and
spatial changes of electron density are discussed. The calculations are in
accordance with the experimental observation of perpendicular magnetic
anisotropy in rhombohedral GeMnTe (111) thin layers.",1502.01715v3
2016-02-02,Majorana bound states in magnetic skyrmions,"Magnetic skyrmions are highly mobile nanoscale topological spin textures. We
show, both analytically and numerically, that a magnetic skyrmion of an even
azimuthal winding number placed in proximity to an s-wave superconductor hosts
a zero-energy Majorana bound state in its core, when the exchange coupling
between the itinerant electrons and the skyrmion is strong. This Majorana bound
state is stabilized by the presence of a spin-orbit interaction. We propose the
use of a superconducting tri-junction to realize non-Abelian statistics of such
Majorana bound states.",1602.00968v3
2017-02-23,Azimuthal asymmetries in SIDIS di-hadron muoproduction off longitudinally polarized protons at COMPASS,"In this review a first comprehensive study of azimuthal asymmetries in
semi-inclusive deep inelastic muoproduction of hadron pairs off longitudinally
polarized protons at COMPASS is presented. The study is based on data taken in
2007 and 2011, obtained by impinging a high-energetic $\mu^+$ beam of $160$
GeV/$\it{c}$, respectively $200$ GeV/$\it{c}$, momentum on a solid ammonia
target. The discussion is focused on both leading and subleading longitudinal
target-spin-dependent asymmetries arising in the di-hadron SIDIS cross section,
addressing the role of spin-orbit couplings and quark-gluon correlations in the
framework of collinear or transverse momentum dependent factorization.",1702.07317v1
2011-11-04,Rashba diamond in an Aharonov-Casher ring,"Spin interference due to Rashba spin-orbit interaction (SOI) in a ballistic
two-dimensional electron gas (2DEG) ring conductor submitted to a bias voltage
is investigated theoretically. We calculate the scattering matrices and
differential conductance with lead-ring junction coupling as an adjustable
parameter. Due to the interference of electronic waves traversing the ring, the
differential conductance modulated by both bias voltage and SOI exhibits a
diamond-shaped pattern, thus termed as \ti{Rashba diamond}. This feature offers
a supplementary degree of freedom to manipulate phase interference.",1111.1244v1
2011-11-21,Hexagonal pnictide SrPtAs: superconductivity with locally broken inversion symmetry,"Unlike other pnictides, SrPtAs has a hexagonal structure, containing layers
with As-Pt atoms that form a honeycomb lattice. These layers lack inversion
symmetry which allows for a spin-orbit coupling that we show has a dramatic
effect on superconductivity in this material. In particular, for conventional
s-wave superconductivity in SrPtAs, both the spin susceptibility and the
paramagnetic limiting field are enhanced significantly with respect to that
usually expected for s-wave superconductors. SrPtAs provides a prime example of
a superconductor with locally broken inversion symmetry.",1111.5058v1
2012-01-06,Anisotropic magneto-resistance in a GaMnAs-based single impurity tunnel diode: a tight binding approach,"Using an advanced tight-binding approach, we estimate the anisotropy of the
tunnel transmission associated with the rotation of the 5/2 spin of a single Mn
atom forming an acceptor state in GaAs and located near an AlGaAs tunnel
barrier. Significant anisotropies in both in-plane and out-of-plane geometries
are found, resulting from the combination of the large spin-orbit coupling
associated with the p-d exchange interaction, cubic anisotropy of heavy-hole
dispersion and the low C2v symmetry of the chemical bonds.",1201.1439v1
2018-01-10,Zeeman-Induced Gapless Superconductivity with Partial Fermi Surface,"We show that an in-plane magnetic field can drive two-dimensional
spin-orbit-coupled systems under superconducting proximity effect into a
gapless phase where parts of the normal state Fermi surface are gapped, and the
ungapped parts are reconstructed into a small Fermi surface of Bogoliubov
quasiparticles at zero energy. Charge distribution, spin texture, and density
of states of such ""partial Fermi surface"" are discussed. Material platforms for
its physical realization are proposed.",1801.03522v3
2019-02-13,Curvature stabilized skyrmions with angular momentum,"We examine skyrmionic field configurations on a spherical ferromagnet with
large normal anisotropy. Exploiting variational concepts of angular momentum we
find a new family of localized solutions to the Landau-Lifshitz equation that
are topologically distinct from the ground state and not equivariant.
Significantly, we observe an emergent spin-orbit coupling on the level of
magnetization dynamics in a simple system without individual rotational
invariance in spin and coordinate space.",1902.04881v2
2019-03-21,Non-Abelian Majorana fermions in topological $s$-wave Fermi superfluids,"By solving the Bogoliubov--De Gennes equations analytically, we derive the
fermionic zero-modes satisfying the Majorana property that exist in vortices of
a two-dimensional $s$-wave Fermi superfluid with spin-orbit coupling and Zeeman
spin-splitting. The Majorana zero-mode becomes normalisable and exponentially
localised to the vicinity of the vortex core when the superfluid is
topologically non-trivial. We calculate the energy splitting due to Majorana
hybridisation and identify that the $s$-wave Majorana vortices obey non-Abelian
statistics.",1903.09131v3
2020-08-16,Magnon dispersion in bilayers of two-dimensional ferromagnets,"We determine magnon spectra of an atomic bilayer magnet with ferromagnetic
intra- and both ferro- and anti- ferromagnetic interlayer coupling. Analytic
expressions for the full magnon band of the latter case reveal that both
exchange interactions govern the fundamental magnon gap. The inter and
intralayer magnetic ordering are not independent: the intralayer ferromagnetism
stabilizes antiferromagnetic inter-layer order. The topology of these
exchange-anisotropy spin models without spin-orbit interaction turns out to be
trivial.",2008.06875v2
2017-07-05,Multiband Electronic Structure of Magnetic Quantum Dots: Numerical Studies,"Semiconductor quantum dots (QDs) doped with magnetic impurities have been a
focus of continuous research for a couple of decades. A significant effort has
been devoted to studies of magnetic polarons (MP) in these nanostructures.
These collective states arise through exchange interaction between a carrier
confined in a QD and localized spins of the magnetic impurities (typically:
Mn). We discuss our theoretical description of various MP properties in
self-assembled QDs. We present a self-consistent, temperature-dependent
approach to MPs formed by a valence band hole. We use the Luttinger-Kohn k.p
Hamiltonian to account for the important effects of spin-orbit interaction.",1707.01565v1
2017-07-27,Ultrafast nanoscale magnetic switching via intense picosecond electron bunches,"The magnetic field associated with a picosecond intense electron pulse is
shown to switch locally the magnetization of extended films and nanostructures
and to ignite locally spin waves excitations. Also, topologically protected
magnetic textures such as skyrmions can be imprinted swiftly in a sample with a
residual Dzyaloshinskii-Moriya spin-orbital coupling. Characteristics of the
created excitations such as the topological charge or the width of the magnon
spectrum can be steered via the duration and the strength of the electron
pulses. The study points to a possible way for a spatiotemporally controlled
generation of magnetic and skyrmionic excitations.",1707.08838v1
2021-01-22,Optical polarization skyrmionic fields in free space,"We construct optical beams in free space with robust skyrmionic structures in
their polarization fields, both in the electric spin vector for near-circular
fields and in the polarization direction for near-linear fields, and for both
Bloch (spiral) and N\'eel (hedgehog) textures. These structures are made
possible by the spin-orbit coupling of tightly-focused nonparaxial optics as
applied to higher-order Full-Poincar\'e beams, as well as by standing-wave
configurations comprising forwards- and backwards-propagating waves. Our
constructions show near-uniform circular and linear polarizations, providing a
high degree of topological protection in the absence of nonlinear interactions.",2101.09254v2
2022-02-21,Bilinear magnetoresistance in topological insulators: role of magnetic disorder,"Bilinear magnetoresistance is a nonlinear transport phenomenon that scales
linearly with the electric and magnetic fields, and appears in nonmagnetic
systems with strong spin-orbit coupling, such as topological insulators (TIs).
Using the semiclassical Boltzmann theory and generalized relaxation time
approximation, we consider in detail the bilinear magnetoresistance in an
effective model describing surface states of three-dimensional topological
insulators. We show that the presence of magnetic impurities remarkably
modifies the BMR signal. In general, scattering on magnetic impurities reduces
magnitude of BMR. Apart from this, an additional modulation of the angular
dependence of BMR appears when the spin-dependent component of the impurity
potential dominates the scalar one.",2202.10077v1
2022-07-12,Stability of Skyrmion Crystal Phase in Centrosymmetric Distorted Triangular-Lattice Antiferromagnets,"The stability of a magnetic skyrmion crystal in a centrosymmetric
orthorhombic lattice system is numerically investigated. By performing the
simulated annealing for an effective spin model with the momentum-resolved
interaction on a uniaxially distorted triangular lattice, we find that the
skyrmion crystal is robustly realized when dominant interaction channels
consist of the double-$Q$ structure in momentum space. Moreover, we show that
an anti-type skyrmion crystal with the opposite skyrmion number is obtained by
tuning the sign of the bond-dependent anisotropic exchange interaction that
originates from the relativistic spin-orbit coupling.",2207.05862v1
2022-09-20,Possible origin of the interface field in spintronic experiments,"The effective field at the interface between ferromagnetic and metal layers
is often observed in spintronic experiments. It is common to ascribe it to
specific exchange interactions caused by spin-orbit coupling, namely, Rashba
field, Dzyaloshinskiy-Moriya interaction, spin currents, etc. Alternative view
involves the global magnetic field (Oersted field) generated by current both
inside and outside the conductor. It is shown here that the inhomogeneous stray
field surrounding ferromagnetic layers can produce significant contribution
into the observed interface field. This mechanism should be taken into account
for better understanding the current-induced phenomena in magnetic multilayers.",2209.09738v1
2022-12-27,Tuning quantum paramagnetism and d-wave superconductivity in single-layer iron chalcogenides by chemical pressure,"By substituting S into single-layer FeSe/SrTiO3, chemical pressure is applied
to tune its paramagnetic state that is modeled as an incoherent superposition
of spin-spiral states. The resulting electronic bands resemble an ordered
checkerboard antiferromagnetic structure, consistent with angle-resolved
photoemission spectroscopy measurements. Scanning tunneling spectroscopy
reveals a gap evolving from U-shaped for FeSe to V-shaped for FeS with
decreasing size, attributed to a d-wave superconducting state for which nodes
emerge once the gap size is smaller than the effective spin-orbit coupling.",2212.13603v2
2023-03-24,Total Angular Momentum Conservation in Ab Initio Born-Oppenheimer Molecular Dynamics,"We prove both analytically and numerically that the total angular momentum of
a molecular system undergoing adiabatic Born-Oppenheimer dynamics is conserved
only when pseudo-magnetic Berry forces are taken into account. This finding
sheds light on the nature of Berry forces for molecular systems with spin-orbit
coupling and highlights how ab initio Born-Oppenheimer molecular dynamics
simulations can successfully capture the entanglement of spin and nuclear
degrees of freedom as modulated by electronic interactions.",2303.13787v1
2023-11-22,The layered RuBr$_3$-RuI$_3$ honeycomb system,"The layered RuBr3-RuI3 honeycomb system was synthesized at high-pressures.
The crystal structures are centrosymmetric (space group R-3), and based on
honeycomb layers of Ru$^{3+}$ (S=1/2). Their basic physical properties are
surveyed. The solid solution switches from insulating to metallic in the range
of concentrations between RuBr$_{0.75}$I$_{2.25}$ and RuBr$_{0.50}$I$_{2.50}$.
A preliminary structure/property phase diagram is presented. Our results
suggest that this solid solution may provide insight into the influence of
disorder on spin-orbit-coupled quantum spin liquids.",2311.13645v1
2024-02-11,Discrete Time Crystal Phase of Higher Dimensional Integrable Models,"This paper investigates the possibility of generating Floquet-time crystals
in higher dimensions ($d\geq 2$) through the time-periodic driving of
integrable free-fermionic models. The realization leads to rigid time-crystal
phases that are ideally resistant to thermalization and decoherence. By
utilizing spin-orbit coupling, we are able to realize a robust time-crystal
phase that can be detected using novel techniques. Moreover, we discuss the
significance of studying the highly persistent subharmonic responses and their
implementation in a Kitaev spin liquid, which contributes to our understanding
of time translational symmetry breaking and its practical implications.",2402.07279v1
2016-07-04,Low-energy microscopic models for iron-based superconductors: a review,"The development of sensible microscopic models is essential to elucidate the
normal-state and superconducting properties of the iron-based superconductors.
Because these materials are mostly metallic, a good starting point is an
effective low-energy model that captures the electronic states near the Fermi
level and their interactions. However, in contrast to cuprates, iron-based
high-$T_{c}$ compounds are multi-orbital systems with Hubbard and Hund
interactions, resulting in a rather involved 10-orbital lattice model. Here we
review different minimal models that have been proposed to unveil the universal
features of these systems. We first review minimal models defined solely in the
orbital basis, which focus on a particular subspace of orbitals, or solely in
the band basis, which rely only on the geometry of the Fermi surface. The
former, while providing important qualitative insight into the role of the
orbital degrees of freedom, do not distinguish between high-energy and
low-energy sectors and, for this reason, generally do not go beyond mean-field.
The latter allow one to go beyond mean-field and investigate the interplay
between superconducting and magnetic orders as well as Ising-nematic order.
However, they cannot capture orbital-dependent features like spontaneous
orbital order. We then review recent proposals for a minimal model that
operates in the band basis but fully incorporates the orbital composition and
symmetries of the low-energy excitations. We discuss the results of the
renormalization group study of such a model, particularly of the interplay
between superconductivity, magnetism, and spontaneous orbital order, and
compare theoretical predictions with experiments on iron pnictides and
chalcogenides. We also discuss the impact of the glide-plane symmetry on the
low-energy models, highlighting the key role played by the spin-orbit coupling.",1607.00865v2
1996-05-22,Theory of Magnetocrystalline Anisotropy Energy for Wires and Corrals of Fe adatoms: A Non-Perturbative Theory,"The magnetocrystalline anisotropy energy $E_{anis}$ for free-standing chains
(quantum wires) and rings (quantum corrals) of Fe-adatoms $N=$(2...48) is
determined using an electronic tight-binding theory. Treating spin-orbit
coupling non-perturbatively, we analyze the relationship between the electronic
structure of the Fe $d$-electrons and $E_{anis}(n_{d})$, for both the chain and
ring conformations. We find that $E_{anis}(N)$ is larger for wires than for
rings or infinite monolayers. Generally $E_{anis}(n_{d})$ decreases in chains
upon increasing $N$, while for rings $E_{anis}(n_{d})$ is essentially
independent of $N$. For increasing $N$, $E_{anis}(n_{d})$ in corrals approaches
the results for freestanding monolayers. Small rings exhibit clear odd-even
oscillations of $E_{anis}(N)$. Within our theoretical framework we are able to
explain the experimentally observed oscillations of $E_{anis}(n_{d})$ during
film growth with a period of one monolayer. Finally, a generalization of Hund's
third rule on spin-orbit coupling to itinerant ferromagnets is proposed.",9605137v1
1998-04-14,Spin-Landau Orbit Coupling in Units of the Flux Quantum Observed from Zeeman Splitting of a Quantum Wire Array,"In Zeeman spectra of a GaAs-AlGaAs quantum wire array with superlattice
period lp, the zero-field shift is found to increase in steps of (2 pi hbar/
e)lp^{-2} at the cyclotron radius Rc ~lp, lp/2, and lp/3. This shift, caused by
spin-Landau orbit coupling and quantized in units of the flux quantum 2 pi hbar
/e,is a manifestation of the gauge invariance, and the first observation of the
flux quantization in a non-superconducting material.The quantum interference
associated with the phase difference in the quantum barrier scattering is also
reported.",9804135v1
1999-01-28,Nonlinear Magneto-Optics of freestanding Fe monolayers from first principles,"The nonlinear magneto-optical Kerr-effect (NOLIMOKE) is determined for
freestanding Fe monolayers with several in-plane structures from first
principles. Based on the theory of nonlinear magneto-optics by H\""ubner and
Bennemann [Phys. Rev. B, {\bf 40}, 5973 (1989)] we calculate the nonlinear
susceptibilities of the monolayers using the ab initio FLAPW-method WIEN95 with
the additional implementation of spin-orbit coupling and the calculation of the
dipole transition matrix elements appropriate for freestanding monolayers. We
present results for the spectral dependence of the nonlinear susceptibility
tensor elements and the resulting intensities and Kerr angles. Special
emphasize is put on the effects of structural changes such as the variation of
the lattice constant and different surface orientations. The influence of
spin-orbit coupling on the tensor elements for different magnetization
directions is presented as well as the azimuthal dependence of the intensities
generated by several low index surfaces, showing the pronounced sensitivity of
second harmonic generation to lateral structural changes as well as magnetic
properties even in the monolayer range.",9901329v1
2000-03-03,Nonadiabatic noncyclic geometric phase and ensemble average spectrum of conductance in disordered mesoscopic rings with spin-orbit coupling,"We generalize Yang's theory from the U(1) gauge field to the non-Abelian
$U(1)\times SU(2)_{spin}$ gauge field. Based on this generalization and taking
into account the geometric Pancharatnam phase as well as an effective
Aharonov-Bohm (AB) phase in nonadiabatic noncyclic transport, we calculate the
ensemble average Fourier spectrum of the conductance in disordered mesoscopic
rings connected to two leads. Our theory can explain the experimental results
reported by Morpurgo {\sl et al.} [Phys. Rev. Lett. {\bf 80}, 1050 (1998)]
satisfactorily. In particular, we clarify that the experimentally observed
splitting, as well as some structure on the sides of the main peak in the
ensemble average Fourier spectrum, stem from the nonadiabatic noncyclic
Pancharatnam phase and the effective AB phase, both being dependent on
spin-orbit coupling.",0003039v2
2002-11-26,The 3d-electron states in LaMnO3*,"Three fundamentally different electronic structures for 3d electron states in
LaMnO3, discussed in the current literature, have been presented. We are in
favour of the localized electron atomic-like crystal-field approach that yields
the discrete energy spectrum, in the scale of 1 meV, associated with the
atomic-like states of the Mn3+ ions in contrary to the continuous energy
spectrum yielded by band theories. In our atomic-like approach the d electrons
form the highly-correlated electron system 3d4 described by two Hund's rules
quantum numbers S=2 and L=2. We take into account the spin-orbit coupling,
Jahn-Teller distortion and formation of the magnetic state. The resulting
electronic structure is completely different from that presented in the current
literature. The superiority of our model relies in the fact that it explains
consistently properties of LaMnO3, the insulating and magnetic ground state and
thermodynamics, using well-established physical concepts.
  Keywords: 3d magnetism, Hund's rules, spin-orbit coupling, crystal field,
LaMnO3 PACS: No: 71.70.Ej : 75.10.Dg : 73.30.-m",0211595v1
2002-11-28,The 3d-electron states in FeBr2,"The fundamental controversy about the electronic structure for 3d-electron
states in FeBr2 is discussed. We advocate for the localized electron
atomic-like many-electron crystal-field approach that yields the discrete
energy spectrum, in the scale of 1 meV, associated with the atomic-like states
of the Fe2+ ions in contrary to the (semi-)continuous energy spectrum yielded
by band theories. In our approach the six d electrons of the Fe2+ ion form the
highly-correlated atomic-like electron system 3d6 described by two Hund's rules
quantum numbers S=2 and L=2 with taking into account the spin-orbit coupling.
The superiority of our model relies in the fact that it explains consistently
properties of FeBr2, the insulating and the magnetic ground state as well as
thermodynamics and Raman low-energy spectra, using well-established physical
concepts.
  Keywords: 3d magnetism, Hund's rules, spin-orbit coupling, crystal field,
FeBr2 PACS: No: 75.50.Ee : 71.15.Mb",0211657v1
2004-03-01,Spin-orbit-induced correlations of the local density of states in two-dimensional electron gas,"We study the local density of states (LDOS) of two-dimensional electrons in
the presence of spin-orbit (SO) coupling. Although SO coupling has no effect on
the average density of states, it manifests itself in the correlations of the
LDOS. Namely, the correlation function acquires two satellites centered at
energy difference equal to the SO splitting, $2\omega_{SO}$, of the electron
Fermi surface. For a smooth disorder the satellites are well separated from the
main peak. Weak Zeeman splitting $\omega_{Z} \ll \omega_{SO}$ in a parallel
magnetic field causes an anomaly in the shape of the satellites. We consider
the effect of SO-induced satellites in the LDOS correlations on the shape of
the correlation function of resonant-tunneling conductances at different
source-drain biases, which can be measured experimentally. This shape is
strongly sensitive to the relation between $\omega_{SO}$ and $\omega_{Z}$.",0403057v1
2004-04-16,Magnetic properties of superconductors with strong spin-orbit coupling,"We study the response of a superconductor with a strong spin-orbit coupling
on an external magnetic field. The Ginzburg-Landau free energy functional is
derived microscopically for a general crystal structure, both with and without
an inversion center, and for an arbitrary symmetry of the superconducting order
parameter. As a by-product, we obtain the general expressions for the intrinsic
magnetic moment of the Cooper pairs. It is shown that the Ginzburg-Landau
gradient energy in a superconductor lacking inversion symmetry has unusual
structure. The general formalism is illustrated using as an example CePt$_3$Si,
which is the first known heavy-fermion superconductor without an inversion
center.",0404407v3
2004-11-19,Tuning of the Gap in a Laughlin-Bychkov-Rashba Incompressible Liquid,"We report on our investigation of the influence of Bychkov-Rashba spin-orbit
interaction (SOI) on the incompressible Laughlin state. We find that
experimentally obtainable values of the spin-orbit coupling strength can induce
as much as a 25% increase in the quasiparticle-quasihole gap Eg at low magnetic
fields in InAs, thereby increasing the stability of the liquid state. The
SOI-modulated enhancement of Eg is also significant for filling factors 1/5 and
1/7, where the FQH state is usually weak. This raises the intriguing
possibility of tuning, via the SO coupling strength, the liquid to solid
transition to much lower densities.",0411524v1
2005-10-11,Bound states in a 2D short range potential induced by spin-orbit interaction,"We have discovered an unexpected and surprising fact: a 2D axially symmetric
short-range potential contains {\it infinite} number of the levels of negative
energy {\it if one takes into account the spin-orbit (SO) interaction.} For a
shallow well ($m_eU_0R^2/\hbar^2 \ll 1$, where $m_e$ is the effective mass,
$U_0$ and $R$ are the depth and the radius of the well, correspondingly) and
weak SO coupling ($|\alpha|m_eR/\hbar \ll 1$, $\alpha$ is the SO coupling
constant) exactly one two-fold degenerate bound state exists for each value of
the half-integer moment $j=m+1/2$, and the corresponding binding energy $E_m$
extremely rapidly decreases with increasing $m$.",0510271v2
2005-12-22,Localized versus itinerant magnetic moments in Na0.72CoO2,"Based on experimental 59Co-NMR data in the temperature range between 0.1 and
300 K, we address the problem of the character of the Co 3d-electron based
magnetism in Na0.7CoO2. Temperature dependent 59Co-NMR spectra reveal different
Co environments below 300 K and their differentiation increases with decreasing
temperature. We show that the 23Na- and 59Co-NMR data may consistently be
interpreted by assuming that below room temperature the Co 3d-electrons are
itinerant. Their magnetic interaction appears to favor an antiferromagnetic
coupling, and we identify a substantial orbital contribution corb to the
d-electron susceptibility. At low temperatures corb seems to acquire some
temperature dependence, suggesting an increasing influence of spin-orbit
coupling. The temperature dependence of the spin-lattice relaxation rate
T1-1(T) confirms significant variations in the dynamics of this electronic
subsystem between 200 and 300K, as previously suggested. Below 200 K, Na0.7CoO2
may be viewed as a weak antiferromagnet with TN below 1 K but this scenario
still leaves a number of open questions.",0512561v1
2006-01-22,Borderline magnetism in Sr4Ru3O10: Impact of dilute La and Ca doping on itinerant ferromagnetism and metamagnetism,"An investigation of La and Ca doped Sr4Ru3O10, featuring a coexistence of
interlayer ferromagnetism and intralayer metamagnetism, is presented. La doping
readily changes magnetism between ferromagnetism and metamagnetism by tuning
the density of states. It also results in different Curie temperatures for the
c-axis and the basal plane, highlighting a rare spin-orbit coupling with the
crystal field states. In contrast, Ca doping enhances the c-axis ferromagnetism
and the magnetic anisotropy. La doping also induces a dimensional crossover in
the interlayer transport whereas Ca doping exhibits a tunneling
magnetoresistance and an extraordinary T3/2-dependence of the resisitivity. The
drastic changes caused by the dilute doping demonstrate a rare borderline
magnetism that is delicately linked to the interplay of the density of states
and spin-orbit coupling.",0601498v1
2006-09-25,Ion beam induced modification of exchange interaction and spin-orbit coupling in the Co$_2$FeSi Heusler compound,"A Co$_2$FeSi (CFS) film with L2$_1$ structure was irradiated with different
fluences of 30 keV Ga$^+$ ions. Structural modifications were subsequently
studied using the longitudinal (LMOKE) and quadratic (QMOKE) magneto-optical
Kerr effect. Both the coercivity and the LMOKE amplitude were found to show a
similar behavior upon irradiation: they are nearly constant up to ion fluences
of $\approx6\times10^{15}$ ion/cm$^2$, while they decrease with further
increasing fluences and finally vanish at a fluence of $\approx9\times10^{16}$
ion/cm$^2$, when the sample becomes paramagnetic. However, contrary to this
behavior, the QMOKE signal nearly vanishes even for the smallest applied
fluence of $3\times10^{14}$ ion/cm$^2$. We attribute this reduction of the
QMOKE signal to an irradiation-induced degeneration of second or higher order
spin-orbit coupling, which already happens at small fluences of 30 keV Ga$^+$
ions. On the other hand, the reduction of coercivity and LMOKE signal with high
ion fluences is probably caused by a reduction of the exchange interaction
within the film material.",0609633v2
2007-03-10,Imaging transverse electron focusing in semiconducting heterostructures with spin-orbit coupling,"Transverse electron focusing in two-dimensional electron gases (2DEGs) with
strong spin-orbit coupling is revisited. The transverse focusing is related to
the transmission between two contacts at the edge of a 2DEG when a
perpendicular magnetic field is applied. Scanning probe microscopy imaging
techniques can be used to study the electron flow in these systems. Using
numerical techniques we simulate the images that could be obtained in such
experiments. We show that hybrid edge states can be imaged and that the
outgoing flux can be polarized if the microscope tip probe is placed in
specific positions.",0703267v2
1999-01-22,Non-perturbative membrane spin-orbit couplings in M/IIA theory,"Membrane source-probe dynamics is investigated in the framework of the finite
N-sector DLCQ M theory compactified on a transverse two-torus for an arbitrary
size of the longitudinal dimension. The non-perturbative two fermion terms in
the effective action of the matrix theory, the (2+1)-dimensional supersymmetric
Yang-Mills theory, that are related to the four derivative F^4 terms by the
supersymmetry transformation are obtained, including the one-loop term and full
instanton corrections. On the supergravity side, we compute the classical probe
action up to two fermion terms based on the classical supermembrane formulation
in an arbitrary curved background geometry produced by source membranes
satisfying the BPS condition; two fermion terms correspond to the spin-orbit
couplings for membranes. We find precise agreement between two approaches when
the background space-time is chosen to be that of the DLCQ M theory, which is
asymptotically locally Anti-de Sitter.",9901105v3
1997-08-08,Antisymmetry and channel coupling contributions to the absorption for p + alpha/d + 3He,"To understand recently established empirical p + alpha potentials, RGM
calculations followed by inversion are made to study contributions of the d +
3He reaction channels and deuteron distortion effects to the p + alpha
potential. An equivalent study of the d + 3He potential is also presented. The
contributions of exchange non-locality to the absorption are simulated by
including an phenomenological imaginary potential in the RGM. These effects
alone strongly influence the shape of the imaginary potentials for both p +
alpha and d + 3He. The potentials local-equivalent to the fully
antisymmetrised-coupled channels calculations have a significant
parity-dependence in both real and imaginary components, which for p + alpha is
qualitatively similar to that found empirically. The effects on the potentials
of the further inclusion of deuteron distortion are also presented. The
inclusion of a spin-orbit term in the RGM, adds additional terms to the
phase-equivalent potential, most notably the comparatively large imaginary
spin-orbit term found empirically.",9708013v1
2007-07-10,Extra Current and Integer Quantum Hall Conductance in the Spin-Orbit Coupling System,"We study the extra term of particle current in a 2D k-cubic Rashba spin-orbit
coupling system and the integer quantization of the Hall conductance in this
system. We provide a correct formula of charge current in this system and the
careful consideration of extra currents provides a stronger theoretical basis
for the theory of the quantum Hall effect which has not been considered before.
The non-trivial extra contribution to the particle current density and local
conductivity, which originates from the cubic dependence on the momentum
operator in the Hamiltonian, will have no effect on the integer quantization of
the Hall conductance. The extension of Noether's theorem for the 2D k-cubic
Rashba system is also addressed. The two methods reach to exactly the same
results.",0707.1472v2
2007-08-23,Using Josephson junctions to determine the pairing state of superconductors without crystal inversion symmetry,"Theoretical studies of a planar tunnel junction between two superconductors
with antisymmetric spin-orbit coupling are presented. The half-space Green's
function for such a superconductor is determined. This is then used to derive
expressions for the dissipative current and the Josephson current of the
junction. Numerical results are presented in the case of the Rashba spin-orbit
coupling, relevant to the much studied compound CePt$_3$Si. Current-voltage
diagrams, differential conductance and the critical Josephson current are
presented for different crystallographic orientations and different weights of
singlet and triplet components of the pairing state. The main conclusion is
that Josephson junctions with different crystallographic orientations may
provide a direct connection between unconventional pairing in superconductors
of this kind and the absence of inversion symmetry in the crystal.",0708.3169v3
2008-12-09,Jahn-Teller induced Berry phase in spin-orbit coupled Bose-Einstein condensates,"We demonstrate that Berry phases may greatly affect the dynamics of
spin-orbit coupled Bose-Einstein condensates. The effective model Hamiltonian
under consideration is shown to be equivalent to the Exe Jahn-Teller model
first introduced in molecular physics. The corresponding conical intersection
is identified and the Berry phase acquired for a wave packet encircling the
intersection studied. It is found that this phase manifests itself in the
density profile of the condensate, making it a directly measurable quantity via
time-of-flight detection. Moreover, the non-Abelian gauge structure of the
system is addressed and we verify how it affects the dynamics.",0812.1725v2
2009-07-01,Electronic structure of ferromagnetic semiconductor Ga1-xMnxAs probed by sub-gap magneto-optical spectroscopy,"We employ Faraday and Kerr effect spectroscopy in the infrared range to
investigate the electronic structure of Ga1-xMnxAs near the Fermi energy. The
band structure of this archetypical dilute-moment ferromagnetic semiconductor
has been a matter of controversy, fueled partly by previous measurements of the
unpolarized infrared absorption and their phenomenological impurity-band
interpretation. The infrared magneto-optical effects we study arise directly
from the spin-splitting of the carrier bands and their chiral asymmetry due to
spin-orbit coupling. Unlike the unpolarized absorption, they are intimately
related to ferromagnetism and their interpretation is much more microscopically
constrained in terms of the orbital character of the relevant band states. We
show that the conventional theory of the disordered valence band with dominant
As p-orbital character and coupled by kinetic-exchange to Mn local moments
accounts semi-quantitatively for the overall characteristics of the measured
infrared magneto-optical spectra.",0907.0207v1
2009-07-02,Control of Josephson current by Aharonov-Casher Phase in a Rashba Ring,"We study the interference effect induced by the Aharonov-Casher phase on the
Josephson current through a semiconducting ring attached to superconducting
leads. Using a 1D model that incorporates spin-orbit coupling in the
semiconducting ring, we calculate the Andreev levels analytically and
numerically, and predict oscillations of the Josephson current due to the AC
phase. This result is valid from the point contact limit to the long channel
length limit, as defined by the ratio of the junction length and the BCS
healing length. We show in the long channel length limit that the impurity
scattering has no effect on the oscillation of the Josephson current, in
contrast to the case of conductivity oscillations in a spin-orbit coupled ring
system attached to normal leads where impurity scattering reduces the amplitude
of oscillations. Our results suggest a new scheme to measure the AC phase with,
in principle, higher sensitivity. In addition, this effect allows for control
of the Josephson current through the gate voltage tuned AC phase.",0907.0272v1
2009-08-25,Chiral confinement in quasirelativistic Bose-Einstein condensates,"In the presence of a laser-induced spin-orbit coupling an interacting ultra
cold spinor Bose-Einstein condensate may acquire a quasi-relativistic character
described by a non-linear Dirac-like equation. We show that as a result of the
spin-orbit coupling and the non-linearity the condensate may become
self-trapped, resembling the so-called chiral confinement, previously studied
in the context of the massive Thirring model. We first consider 1D geometries
where the self-confined condensates present an intriguing sinusoidal dependence
on the inter-particle interactions. We further show that multi-dimensional
chiral-confinement is also possible under appropriate feasible laser
arrangements, and discuss the properties of 2D and 3D condensates, which differ
significantly from the 1D case.",0908.3631v1
2009-10-26,A theorem for the existence of Majorana fermion modes in spin-orbit-coupled semiconductors,"We prove an index theorem for the existence of Majorana zero modes in a
semiconducting thin film with a sizable spin-orbit coupling when it is adjacent
to an s-wave superconductor. The theorem, which is analogous to the
Jackiw-Rebbi index theorem for the zero modes in mass domain walls in
one-dimensional Dirac theory, applies to vortices with odd flux quantum in a
semiconducting film in which s-wave superconductivity and a Zeeman splitting
are induced by proximity effect. The momentum-space construction of the
zero-mode solution presented here is complementary to the approximate
real-space solution of the Bogoliubov-de Gennes equations at a vortex core [J.
D. Sau et al., arXiv:0907.2239], proving the existence of non-degenerate
zero-energy Majorana excitations and the resultant non-Abelian topological
order in the semiconductor heterostructure. With increasing magnitude of the
proximity-induced pairing potential, the non-Abelian superconducting state
makes a topological quantum phase transition to an ordinary s-wave
superconducting state which no topological order.",0910.4763v1
2009-11-24,"The electronic structure of epitaxially stabilized 5d perovskite Ca_{1-x}Sr_xIrO_3 (x = 0, 0.5, and 1) thin films: the role of strong spin-orbit coupling","We have investigated the electronic structure of meta-stable perovskite
Ca1-xSrxIrO3 (x = 0, 0.5, and 1) thin films using transport measurements,
optical spectroscopy, and first-principles calculations. We artificially
fabricated the perovskite phase of Ca1-xSrxIrO3, which has a hexagonal or post
perovskite crystal structure in bulk form, by growing epitaxial thin films on
perovskite GdScO3 substrates using epi-stabilization technique. The transport
properties of the perovskite Ca1-xSrxIrO3 films systematically changed from
nearly insulating (or semi-metallic) for x = 0 to bad metallic for x = 1. Due
to the extended wavefunctions, 5d electrons are usually delocalized. However,
the strong spin-orbit coupling in Ca1-xSrxIrO3 results in the formation of
effective total angular momentum Jeff = 1/2 and 3/2 states, which puts
Ca1-xSrxIrO3 in the vicinity of a metal-insulator phase boundary. As a result,
the electrical properties of the Ca1-xSrxIrO3 films are found to be sensitive
to x and strain.",0911.4542v1
2010-04-27,Probing non-Abelian statistics with Majorana fermion interferometry in spin-orbit-coupled semiconductors,"The list of quantum mechanical systems with non-Abelian statistics has
recently been expanded by including generic spin-orbit-coupled semiconductors
e.g., InAs) in proximity to a s-wave superconductor. Demonstration of the
anyonic statistics using Majorana fermion interferometry in this system is a
necessary first step towards topological quantum computation (TQC). However,
since all isolated chiral edges that can be created in the semiconductor are
charge neutral, it is not clear if electrically controlled interferometry is
possible in this system. Here we show that when two isolated chiral Majorana
edges are brought into close contact, the resultant interface supports charge
current, enabling electrically controlled Majorana fermion interferometry in
the semiconductor structure. Such interferometry experiments on the
semiconductor are analogous to similar interferometry experiments on the
$\nu=5/2$ fractional quantum Hall systems and on the surface of a 3D strong
topological insulator, illustrating the usefulness of the 2D semiconductor
heterostructure as a suitable TQC platform. In particular, we proposed Majorana
interferometers may be the most direct method for establishing non-Abelian
braiding statistics in topological superconductors.",1004.4702v2
2010-07-16,"Strain control of magnetic anisotropy in (Ga,Mn)As microbars","We present an experimental and theoretical study of magnetocrystalline
anisotropies in arrays of bars patterned lithographically into (Ga,Mn)As
epilayers grown under compressive lattice strain. Structural properties of the
(Ga,Mn)As microbars are investigated by high-resolution X-ray diffraction
measurements. The experimental data, showing strong strain relaxation effects,
are in good agreement with finite element simulations. SQUID magnetization
measurements are performed to study the control of magnetic anisotropy in
(Ga,Mn)As by the lithographically induced strain relaxation of the microbars.
Microscopic theoretical modeling of the anisotropy is performed based on the
mean-field kinetic-exchange model of the ferromagnetic spin-orbit coupled band
structure of (Ga,Mn)As. Based on the overall agreement between experimental
data and theoretical modeling we conclude that the micropatterning induced
anisotropies are of the magnetocrystalline, spin-orbit coupling origin.",1007.2766v1
2010-11-29,Majorana End-States in Multi-band Microstructures with Rashba Spin-Orbit Coupling,"A recent work [1] demonstrated, for an ideal spinless p+ip superconductor,
that Majorana end-states can be realized outside the strict one-dimensional
limit, so long as: 1) the sample width does not greatly exceed the
superconducting coherence length and 2) an odd number of transverse sub-bands
are occupied. Here we extend this analysis to the case of an effective p+ip
superconductor engineered from Rashba spin-orbit coupled surface with induced
magnetization and superconductivity, and find a number of new features.
Specifically, we find that finite size quantization allows Majorana end-states
even when the chemical potential is outside of the induced Zeeman gap where the
bulk material would not be topological. This is relevant to proposals utilizing
semiconducting quantum wires, however, we also find that the bulk energy gap is
substantially reduced if the induced magnetization is too large. We next
consider a slightly different geometry, and show that Majorana end-states can
be created at the ends of ferromagnetic domains. Finally, we consider the case
of meandering edges and find, surprisingly, that the existence of well-defined
transverse sub-bands is not necessary for the formation of robust Majorana
end-states.",1011.6371v1
2010-12-28,Probing non-Abelian statistics of Majorana fermions in ultracold atomic superfluid,"We propose an experiment to directly probe the non-Abelian statistics of
Majorana fermions by braiding them in an s-wave superfluid of ultracold atoms.
We show different orders of braiding operations give orthogonal output states
that can be distinguished through Raman spectroscopy. Realization of Majorana
bound states in an s-wave superfluid requires strong spin-orbital coupling and
a controllable Zeeman field in the perpendicular direction. We present a simple
laser configuration to generate the artificial spin-orbital coupling and the
required Zeeman field in the dark state subspace.",1012.5761v2
2011-01-11,Quantum Anomalous Hall Effect in Single-layer and Bilayer Graphene,"The quantum anomalous Hall effect can occur in single and few layer graphene
systems that have both exchange fields and spin-orbit coupling. In this paper,
we present a study of the quantum anomalous Hall effect in single-layer and
gated bilayer graphene systems with Rashba spin-orbit coupling. We compute
Berry curvatures at each valley point and find that for single-layer graphene
the Hall conductivity is quantized at $\sigma_{xy} = 2e^2/h$, with each valley
contributing a unit conductance and a corresponding chiral edge state. In
bilayer graphene, we find that the quantized anomalous Hall conductivity is
twice that of the single-layer case when the gate voltage $U$ is smaller than
the exchange field $M$, and zero otherwise. Although the Chern number vanishes
when $U > M$, the system still exhibits a quantized valley Hall effect, with
the edge states in opposite valleys propagating in opposite directions. The
possibility of tuning between different topological states with an external
gate voltage suggests possible graphene-based spintronics applications.",1101.2042v2
2011-03-16,Spatial correlations in chaotic nanoscale systems with spin-orbit coupling,"We investigate the statistical properties of wave functions in chaotic
nanostructures with spin-orbit coupling (SOC), focussing in particular on
spatial correlations of eigenfunctions. Numerical results from a microscopic
model are compared with results from random matrix theory in the crossover from
the gaussian orthogonal to the gaussian symplectic ensembles (with increasing
SOC); one- and two-point distribution functions were computed to understand the
properties of eigenfunctions in this crossover. It is found that correlations
of wave function amplitudes are suppressed with SOC; nevertheless,
eigenfunction correlations play a more important role in the two-point
distribution function(s), compared to the case with vanishing SOC. Experimental
consequences of our results are discussed.",1103.3265v1
2011-05-09,BCS-BEC Crossover and Topological Phase Transition in 3D Spin-Orbit Coupled Degenerate Fermi Gases,"We investigate the BCS-BEC crossover in three dimensional degenerate Fermi
gases in the presence of spin-orbit coupling (SOC) and Zeeman field. We show
that the superfluid order parameter destroyed by a large Zeeman field can be
restored by the SOC. With increasing strengths of the Zeeman field, there is a
series of topological quantum phase transitions from a non-topological
superfluid state with fully gapped fermionic spectrum to a topological
superfluid state with four topologically protected Fermi points (i.e., nodes in
the quasiparticle excitation gap) and then to a second topological superfluid
state with only two topologically protected Fermi points. The quasiparticle
excitations near the Fermi points realize the long-sought low-temperature
analog of Weyl fermions of particle physics. We show that the topological phase
transitions can be probed using the experimentally realized momentum resolved
photoemission spectroscopy.",1105.1796v3
2011-05-23,Low-lying energy spectrum of the cerium dimer,"The electronic structure of Ce2 is studied in a valence bond model with two
4f electrons localized at two cerium sites. It is shown that the low-lying
energy spectrum of the simplest cerium chemical bond is determined by
peculiarities of the occupied 4f states. The model allows for an analytical
solution which is discussed along with the numerical analysis. The energy
spectrum is a result of the interplay between the 4f valence bond exchange, the
4f Coulomb repulsion and the spin-orbit coupling. The calculated ground state
is the even \Omega=\Lambda=\Sigma=0 level, the lowest excitations situated at
30 K are the odd \Omega=\Lambda=\Sigma=0 state and the $^{3} 6_5$ doublet
(\Omega=\pm5,\, \Lambda=\pm6,\, \Sigma=\mp1). The calculated magnetic
susceptibility displays different behavior at high and low temperatures. In the
absence of the spin-orbit coupling the ground state is the ${}^3 \Sigma_g^-$
triplet. The results are compared with other many-electron calculations and
experimental data.",1105.4415v2
2011-05-31,Spin and orbital angular momentum of the tensor gauge field,"Following the recent studies of the trickiness in spin and orbital angular
momentum of the vector gauge fields, we perform here a parallel analysis for
the tensor gauge field, which has certain relation to gravitation. Similarly to
the vector case, we find a nice feature that after removing all gauge degrees
of freedom the angular momentum of the tensor gauge field vanishes for a
stationary system. This angular momentum also shows a one-parameter invariance
over the infinitely many ways of complete gauge fixing for the tensor field.
The tensor gauge coupling, however, does exhibit a critical difference from the
vector gauge coupling that it may induce intrinsic interaction terms into the
spatial translation and rotation generators, leaving none of the ten Poincar\'e
generators interaction-free.",1105.6300v1
2011-06-02,Stability of spin-orbit coupled Fermi gases with population imbalance,"We use the self-consistent mean-field theory to analyze the effects of
Rashba-type spin-orbit coupling (SOC) on the ground-state phase diagram of
population-imbalanced Fermi gases throughout the BCS-BEC evolution. We find
that the SOC and population imbalance are counteracting, and that this
competition tends to stabilize the uniform superfluid phase against the phase
separation. However, we also show that the SOC stabilizes (destabilizes) the
uniform superfluid phase against the normal phase for low (high) population
imbalances. In addition, we find topological quantum phase transitions
associated with the appearance of momentum space regions with zero
quasiparticle energies, and study their signatures in the momentum
distribution.",1106.0473v2
2011-06-13,Universal phase structure of dilute Bose gases with Rashba spin-orbit coupling,"A Bose gas subject to a light-induced Rashba spin-orbit coupling possesses a
dispersion minimum on a circle in momentum space; we show that kinematic
constraints due to this dispersion cause interactions to renormalize to
universal, angle-dependent values that govern the phase structure in the
dilute-gas limit. We find that, regardless of microscopic interactions, (a) the
ground state involves condensation at two opposite momenta, and is, in finite
systems, a fragmented condensate; and (b) there is a nonzero-temperature
instability toward the condensation of pairs of bosons. We discuss how our
results can be reconciled with the qualitatively different mean-field phase
diagram, which is appropriate for dense gases.",1106.2552v3
2011-07-15,Renormalization of interactions of ultracold atoms in simulated Rashba gauge fields,"Interactions of ultracold atoms with Rashba spin-orbit coupling, currently
being studied with simulated (artificial) gauge fields, have nontrivial
ultraviolet and infrared behavior. Examining the ultraviolet structure of the
Bethe-Salpeter equation, we show that the linear ultraviolet divergence in the
bare interaction can be renormalized as usual in terms of low-energy scattering
lengths, and that for both bosons and fermions ultraviolet logarithmic
divergences are absent. Calculating the leading order effective interaction
with full dependence on the spin-orbit coupling strength and the center-of-mass
momentum of the colliding pair, we elucidate the relation between mean-field
interactions and physical three-dimensional scattering lengths. As a
consequence of infrared logarithmic divergences in the two-particle propagator,
the effective interaction vanishes as the center-of-mass momentum approaches
zero.",1107.3162v2
2011-07-20,Weak localization of bulk channels in topological insulator thin film,"Weak antilocalization (WAL) is expected whenever strong spin-orbit coupling
or scattering comes into play. Spin-orbit coupling in the bulk states of a
topological insulator is very strong, enough to result in the topological phase
transition. However, the recently observed WAL in topological insulators seems
to have an ambiguous origin from the bulk states. Starting from the effective
model for three-dimensional topological insulators, we find that the lowest
two-dimensional (2D) bulk subbands of a topological insulator thin film can be
described by the modified massive Dirac model. We derive the
magnetoconductivity formula for both the 2D bulk subbands and surface bands.
Because with Relatively large gap, the 2D bulk subbands may lie in the regimes
where the unitary behavior or even weak localization (WL) is also expected,
instead of always WAL. As a result, the bulk states may contribute small
magnetoconductivity or even compensate the WAL from the surface states.
Inflection in magnetoconductivity curves may appear when the bulk WL channels
outnumber the surface WAL channels, providing a signature of the weak
localization from the bulk states.",1107.3959v2
2011-08-04,Electronic Liquid Crystalline Phases in a Spin-Orbit Coupled Two-Dimensional Electron Gas,"We argue that the ground state of a two-dimensional electron gas with Rashba
spin-orbit coupling realizes one of several possible liquid crystalline or
Wigner crystalline phases in the low-density limit, even for short-range
repulsive electron-electron interactions (which decay with distance with a
power larger than 2). Depending on specifics of the interactions, preferred
ground-states include an anisotropic Wigner crystal with an increasingly
anisotropic unit cell as the density decreases, a striped or electron smectic
phase, and a ferromagnetic phase which strongly breaks the lattice point-group
symmetry, i.e. exhibits nematic order. Melting of the anisotropic Wigner
crystal or the smectic phase by thermal or quantum fluctuations can gives rise
to a non-magnetic nematic phase which preserves time-reversal symmetry.",1108.1222v3
2011-08-22,Quantum phases of atomic Fermi gases with anisotropic spin-orbit coupling,"We consider a general anisotropic spin-orbit coupling (SOC) and analyze the
phase diagrams of both balanced and imbalanced Fermi gases for the entire
BCS--Bose-Einstein condensate (BEC) evolution. In the first part, we use the
self-consistent mean-field theory at zero temperature, and show that the
topological structure of the ground-state phase diagrams is quite robust
against the effects of anisotropy. In the second part, we go beyond the
mean-field description, and investigate the effects of Gaussian fluctuations
near the critical temperature. This allows us to derive the time-dependent
Ginzburg-Landau theory, from which we extract the effective mass of the Cooper
pairs and their critical condensation temperature in the molecular BEC limit.",1108.4263v2
2011-09-22,Order by Disorder in Spin-Orbit Coupled Bose-Einstein Condensates,"Motivated by recent experiments, we investigate the system of
isotropically-interacting bosons with Rashba spin-orbit coupling. At the
non-interacting level, there is a macroscopic ground-state degeneracy due to
the many ways bosons can occupy the Rashba spectrum. Interactions treated at
the mean-field level restrict the possible ground-state configurations, but
there remains an accidental degeneracy not corresponding to any symmetry of the
Hamiltonian, indicating the importance of fluctuations. By finding analytical
expressions for the collective excitations in the long-wavelength limit and
through numerical solution of the full Bogoliubov- de Gennes equations, we show
that the system condenses into a single momentum state of the Rashba spectrum
via the mechanism of order by disorder. We show that in 3D the quantum
depletion for this system is small, while the thermal depletion has an infrared
logarithmic divergence, which is removed for finite-size systems. In 2D, on the
other hand, thermal fluctuations destabilize the system.",1109.4945v3
2011-10-17,Opposite effect of spin-orbit coupling on condensation and superfluidity,"We investigated effects of a Rashba-type spin-orbit coupling (SOC) on the
condensed density and superfluid density tensor of a two-component Fermi gas in
the BCS-BEC crossover at zero temperature. In anisotropic three dimensions
(3D), we found that SOC has an opposite effect on condensation (enhanced) and
superfluidity (suppressed in the SOC direction) and this effect becomes most
pronounced for very weak interactions and the SOC strength being larger than a
characteristic value. Furthermore, as functions of SOC strength, the condensed
density changes monotonously for all interaction parameters while the
superfluid density has a minimum when the interaction parameter is below a
critical value. We also discussed the isotropic two dimensional (2D) case where
analytical expressions for the gap and number equations were obtained and the
same phenomena was found as that of the 3D case.",1110.3565v2
2011-10-26,Tuning the Tricritical Point with Spin-orbit Coupling in Polarized Fermionic Condensates,"We investigate a two-component atomic Fermi gas with population imbalance in
the presence of Rashba-type spin-orbit coupling (SOC). As a competition between
SOC and population imbalance, the finite-temperature phase diagram reveals a
large varieties of new features, including the expanding of the superfluid
state regime and the shrinking of both the phase separation and the normal
regimes. For sufficiently strong SOC, the phase separation region disappears,
giving way to the superfluid state. We find that the tricritical point moves
toward regime of low temperature, high magnetic field, and high polarization as
the SOC increases.",1110.5818v2
2011-12-19,Effects of the Spin-Orbit Coupling and the Superconductivity in simple-cubic alpha-Polonium,"We have investigated the mechanism of stabilizing the simple-cubic (SC)
structure in polonium (alpha- Po), based on the phonon dispersion calculations
using the first-principles all-electron band method. We have demonstrated that
the stable SC structure results from the suppression of the Peierls instability
due to the strong spin-orbit coupling (SOC) in alpha-Po. Further, we have
explored the possible superconductivity in alpha-Po, and predicted that it
becomes a superconductor with Tc ~ 4 K. The transverse soft phonon mode at q ~
2/3 R, which is greatly influenced by the SOC, plays an important role both in
the structural stability and the superconductivity in alpha-Po. We have
discussed effects of the SOC and the volume variation on the phonon dispersions
and superconducting properties of alpha-Po.",1112.4224v2
2011-12-27,2D and 3D topological insulators with isotropic and parity-breaking Landau levels,"We investigate topological insulating states in both two and three dimensions
with the harmonic potential and strong spin-orbit couplings breaking the
inversion symmetry. Landau-level like quantizations appear with the full 2D and
3D rotational symmetry and time-reversal symmetry. Inside each band, states are
labeled by their angular momenta over which energy dispersions are strongly
suppressed by spin-orbit coupling to nearly flat. The radial quantization
generates energy gaps between neighboring bands at the order of the harmonic
frequency. Helical edge or surface states appear on open boundaries
characterized by the Z2 index. These Hamiltonians can be viewed from the
dimensional reduction of the high dimensional quantum Hall states in 3D and 4D
flat spaces. These states can be realized with ultra-cold fermions inside
harmonic traps with the synthetic gauge fields.",1112.5907v3
2012-03-03,Interatomic collisions in two-dimensional and quasi-two-dimensional confinements with spin-orbit coupling,"We investigate the low-energy scattering and bound states of two
two-component fermionic atoms in pure two-dimensional (2D) and quasi-2D
confinements with Rashba spin-orbit coupling (SOC). We find that the SOC
qualitatively changes the behavior of the 2D scattering amplitude in the
low-energy limit. For quasi-2D systems we obtain the analytic expression for
the effective-2D scattering amplitude and the algebraic equations for the
two-atom bound state energy. Based on these results, we further derive the
effective 2D interaction potential between two ultracold atoms in the quasi-2D
confinement with Rashba SOC. These results are crucial for the control of the
2D effective physics in quasi-2D geometry via the confinement intensity and the
atomic three-dimensional scattering length.",1203.0623v3
2012-03-13,Quantum anomalous Hall effect on star lattice with spin-orbit coupling and exchange field,"We study the star lattice with Rashba spin-orbit coupling and exchange field
and find that there exists the quantum anomalous Hall effect in this system and
there are five energy gaps at Dirac points and quadratic band crossing points.
We calculate the Berry curvature distribution and obtain the Hall conductivity
(Chern number $\nu$) quantized as integers, and find that $\nu=-1,2,1,1,2$,
respectively, when the Fermi level lies in these five gaps. Our model can be
view as a general quantum anomalous Hall system and, in limit cases, can give
what the honeycomb lattice and kagome lattice gave. We also find there exists a
nearly flat band with $\nu=1$ which may provide an opportunity to realize the
fractional quantum anomalous Hall effect. Finally, the chiral edge states on a
zigzag star lattice are given numerically to confirm the topological property
of this system.",1203.2855v2
2012-03-27,Topological thermoelectric effects in spin-orbit coupled electron and hole doped semiconductors,"We compute the intrinsic contributions to the Berry-phase mediated anomalous
Hall and Nernst effects in electron- and hole-doped semiconductors in the
presence of an in-plane magnetic field as well as Rashba and Dresselhaus spin
orbit couplings. For both systems we find that the regime of chemical potential
which supports the topological superconducting state in the presence of
superconducting proximity effect can be characterized by plateaus in the
topological Hall and Nernst coefficients flanked by well-defined peaks marking
the emergence of the topological regime. The plateaus arise from a clear
momentum space separation between the region where the Berry curvature is
peaked (at the `near-band-degeneracy' points) and the region where the single
(or odd number of) Fermi surface lies in the Brillouin zone. The plateau for
the Nernst coefficient is at vanishing magnitudes surrounded by two peaks of
opposite signs as a function of the chemical potential. These results could be
useful for experimentally deducing the chemical potential regime suitable for
realizing topological states in the presence of proximity effect.",1203.6109v1
2012-03-28,Stability of ultracold atomic Bose condensates with Rashba spin-orbit coupling against quantum and thermal fluctuations,"We study the stability of Bose condensates with Rashba-Dresselhaus spin-orbit
coupling in three dimensions against quantum and thermal fluctuations. The
ground state depletion of the plane-wave condensate due to quantum fluctuations
is, as we show, finite, and therefore the condensate is stable. We also
calculate the corresponding shift of the ground state energy. Although the
system cannot condense in the absence of interparticle interactions, we show by
estimating the number of excited particles that interactions stabilize the
condensate even at non-zero temperature. Unlike in the usual Bose gas, the
normal phase is not kinematically forbidden at any temperature; calculating the
free energy of the normal phase at finite temperature, and comparing with the
free energy of the condensed state, we infer that generally the system is
condensed at zero temperature, and undergoes a transition to normal at non-zero
temperature.",1203.6367v2
2012-06-26,Enhancement of condensate depletion due to spin-orbit coupling,"We show that spin-orbit coupling (SOC) significantly enhances the depletion
of a homogeneous Bose-Einstein condensate in three dimensions. With decreasing
anisotropy of the SOC, both the quantum and thermal depletion increase. In
particular, different types of SOC give rise to qualitatively different
dependences of the condensate depletion on microscopic variables including the
scattering length, the strength of the SOC, and the temperature, which can be
directly observed once these types of SOC are realized in experiments.
Moreover, we point out that thermal depletion in three dimensions becomes
logarithmically divergent at any given finite temperature when both the SOC and
the interaction approach the isotropic limit.",1206.5918v3
2012-07-12,Near-zero-energy end states in topologically trivial spin-orbit coupled superconducting nanowires with a smooth confinement,"A one-dimensional spin-orbit coupled nanowire with proximity-induced pairing
from a nearby s-wave superconductor may be in a topological nontrivial state,
in which it has a zero energy Majorana bound state at each end. We find that
the topological trivial phase may have fermionic end states with an
exponentially small energy, if the confinement potential at the wire's ends is
smooth. The possible existence of such near-zero energy levels implies that the
mere observation of a zero-bias peak in the tunneling conductance is not an
exclusive signature of a topological superconducting phase even in the ideal
clean single channel limit.",1207.3067v1
2012-08-01,Odd-Parity Pairing and Topological Superconductivity in a Strongly Spin-Orbit Coupled Semiconductor,"The existence of topological superconductors preserving time-reversal
symmetry was recently predicted, and they are expected to provide a solid-state
realization of itinerant massless Majorana fermions and a route to topological
quantum computation. Their first concrete example, CuxBi2Se3, was discovered
last year, but the search for new materials has so far been hindered by the
lack of guiding principle. Here, we report point-contact spectroscopy
experiments showing that the low-carrier-density superconductor
Sn_{1-x}In_{x}Te is accompanied with surface Andreev bound states which, with
the help of theoretical analysis, give evidence for odd-parity pairing and
topological superconductivity. The present and previous finding of topological
superconductivity in Sn_{1-x}In_{x}Te and CuxBi2Se3 demonstrates that
odd-parity pairing favored by strong spin-orbit coupling is a common underlying
mechanism for materializing topological superconductivity.",1208.0059v2
2012-08-15,Synthetic Spin-Orbit Coupling in Two-level Cold Atoms,"Synthetic spin-orbit coupling (SOC) in controlled quantum systems such as
cold atoms or trapped ions has been of great interest. Here we show, both
theoretically and computationally, a simplest realization of SOC using
two-level cold atoms interacting with only one laser beam. The underlying
mechanism is based upon the non-adiabatic nature of laser-atom interaction,
with the Rabi frequency and atom's kinetic energy being comparable to each
other. We use the Zitterbewegung (ZB) oscillation to further illustrate the
effects of the synthesized SOC on the quantum dynamics of the two-level cold
atoms. We expect our proposal to be of experimental interest in quantum
simulation of SOC-related physics.",1208.3005v1
2012-08-27,Majorana fermions in one-dimensional spin-orbit coupled Fermi gases,"We theoretically study trapped one-dimensional Fermi gases in the presence of
spin-orbit coupling induced by Raman lasers. The gas changes from a
conventional (non-topological) superfluid to a topological superfluid as one
increases the intensity of the Raman lasers above a critical chemical-potential
dependent value. Solving the Bogoliubov-de Gennes equations self-consistently,
we calculate the density of states in real and momentum space at finite
temperatures. We study Majorana fermions (MFs) which appear at the boundaries
between topologically trivial and topologically non-trivial regions. We
linearize the trap near the location of a MF, finding an analytic expression
for the localized MF wavefunction and the gap between the MF state and other
edge states.",1208.5450v4
2012-09-05,Majorana fermions in s-wave noncentrosymmetric superconductor with Rashba and Dresselhaus (110) spin-orbit couplings,"The asymmetric spin-orbit (SO) interactions play a crucial role in realizing
topological phases in noncentrosymmetric superconductor (NCS).We investigate
the edge states and the vortex core states in s-wave NCS with Rashba and
Dresselhaus (110) SO couplings by both numerical and analytical methods. In
particular, we demonstrate that there exists a novel semimetal phase
characterized by the flat Andreev bound states in the phase diagram of the
s-wave Dresselhaus NCS which supports the emergence of Majorana fermion (MF).
The flat dispersion implies a peak in the density of states which has a clear
experimental signature in the tunneling conductance measurements and the MFs
proposed here should be experimentally detectable.",1209.0930v2
2012-09-13,Ground State Properties of Spin-Orbit Coupled Bose Gases for Arbitrary Interactions,"We develop a field integral formalism to study spin-orbit-coupled (SOC) Bose
gases with arbitrary interspecies interaction. We identify various features
arising from the interplay of SOC and interspecies interaction, including a
roton minimum in the excitation spectrum and dual effects of SOC on
ground-state energies depending on interspecies interactions.
Counterintuitively, we find that at low interspecies interaction the SOC
stabilizes the system by suppressing the quantum depletion. We show that the
static structure factor is immune to the SOC in the phase space where
time-reversal symmetry is preserved. Furthermore, we present an alternate way
of studying phase fluctuations of the system.",1209.2897v2
2012-10-18,Zitterbewegung effect in spin-orbit coupled spin-1 ultracold atoms,"The Zitterbewegung effect in spin-orbit coupled spin-1 cold atoms is
investigated in the presence of the Zeeman field and a harmonic trap. It is
shown that the Zeeman field and the harmonic trap have significant effect on
the Zitterbewegung oscillatory behaviors. The external Zeeman field could
suppress or enhance the Zitterbewegung amplitude and change the frequencies of
oscillation. A much slowly damping Zitterbewegung oscillation can be achieved
by adjusting both the linear and quadratic Zeeman field. Multi-frequency
Zitterbewegung oscillation can be induced by the applied Zeeman field. In the
presence of the harmonic trap, the subpackets corresponding to different
eigenenergies would always keep coherent, resulting in the persistent
Zitterbewegung oscillations. The Zitterbewegung oscillation would display very
complicated and irregular oscillation characteristics due to the coexistence of
different frequencies of the Zitterbewegung oscillation. Numerical results show
that, the Zitterbewegung effect is robust even in the presence of interaction
between atoms.",1210.5030v2
2012-10-23,g-Tensor Control in Bent Carbon Nanotube Quantum Dots,"We demonstrate gate control of the electronic g-tensor in single and double
quantum dots formed along a bend in a carbon nanotube. From the dependence of
the single-dot excitation spectrum on magnetic field magnitude and direction,
we extract spin-orbit coupling, valley coupling, spin and orbital magnetic
moments. Gate control of the g-tensor is measured using the splitting of the
Kondo peak in conductance as a sensitive probe of Zeeman energy. In the double
quantum dot regime, the magnetic field dependence of the position of
cotunneling lines in the two dimensional charge stability diagram is used to
infer the positions of the two dots along the nanotube.",1210.6402v2
2012-11-02,Majorana Kramers Doublets in $d_{x^2-y^2}$-wave Superconductors with Rashba Spin-Orbit Coupling,"In this work, we show that a quasi-one-dimensional $d_{x^2-y^2}$-wave
superconductor with Rashba spin-orbit coupling is a DIII class, time-reversal
invariant, topological superconductor (TS) which supports a Majorana Kramers
Doublet (MKD) at each end of the TS. A MKD is a pair of Majorana end states
(MESs) protected by time-reversal symmetry (TRS). An external magnetic field
breaks TRS and drives the system from DIII to D class in which case a single
MES appears at each end of the TS. We show that a MKD induces resonant Andreev
reflection with zero bias conductance peak of $4e^2/h$. Experimental
realizations of the proposed model are discussed.",1211.0338v2
2012-11-08,Flow enhanced pairing and other novel effects in Fermi gases in synthetic gauge fields,"Recent experiments on fermions in synthetic gauge fields result in systems
with a spin-orbit coupling along one spatial axis, a detuning field, and a
Zeeman field. We show theoretically that the presence of all three results in
interesting and unusual phenomena in such systems in the presence of a contact
singlet attraction between the fermions (described by a scattering length). For
two particles, bound states appear over certain range of the centre of mass
momenta when a critical positive scattering length is attained, with the
deepest bound state appearing at a nonzero centre of mass momentum. For the
centre of mass momenta without a bound state, the gauge field induces a
resonance like feature in the scattering continuum resulting in a large
scattering phase shift. For many particles, we demonstrate that the system, in
a parameter range, shows flow enhanced pairing, i.e., a more robust superfluid
at finite centre of mass momentum. Yet another regime of parameters offers the
opportunity to study strongly interacting normal states of spin-orbit coupled
fermionic systems utilizing the resonance like feature induced by the synthetic
gauge field.",1211.1831v1
2012-11-16,Topological superfluid phases of an atomic Fermi gas with in- and out-of-plane Zeeman fields and equal Rashba-Dresselhaus spin-orbit coupling,"We analyze the effects of in- and out-of-plane Zeeman fields on the BCS-BEC
evolution of a Fermi gas with equal Rashba-Dresselhaus (ERD) spin-orbit
coupling (SOC). We show that the ground state of the system involves novel
gapless superfluid phases that can be distinguished with respect to the
topology of the momentum-space regions with zero excitation energy. For the
BCS-like uniform superfluid phases with zero center-of-mass momentum, the zeros
may correspond to one or two doubly-degenerate spheres, two or four spheres,
two or four concave spheroids, or one or two doubly-degenerate circles,
depending on the combination of Zeeman fields and SOC. Such changes in the
topology signal a quantum phase transition between distinct superfluid phases,
and leave their signatures on some thermodynamic quantities. We also analyze
the possibility of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like nonuniform
superfluid phases with finite center-of-mass momentum and obtain an even richer
phase diagram.",1211.4020v3
2012-11-25,Unconventional superfluid in a two-dimensional Fermi gas with anisotropic spin-orbit coupling and Zeeman fields,"We study the phase diagram of a two-dimensional ultracold Fermi gas with the
synthetic spin-orbit coupling (SOC) that has recently been realized at NIST.
Due to the coexistence of anisotropic SOC and effective Zeeman fields in the
NIST scheme, the system shows rich structure of phase separation involving
exotic gapless superfluid and Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing
states with different center-of-mass momentum. In particular, we characterize
the stability region of FFLO states and demonstrate their unique features under
SOC. We then show that the effective transverse Zeeman field in the NIST scheme
can qualitatively change the landscape of the thermodynamic potential which
leads to intriguing effects such as the disappearance of pairing instability,
the competition between different FFLO states, and the stabilization of a fully
gapped FFLO state. These interesting features may be probed for example by
measuring the in-situ density profiles or by the momentum-resolved
radio-frequency spectroscopy.",1211.5780v3
2012-12-05,Non-Fermi liquid and topological states with strong spin-orbit coupling,"We argue that a class of strongly spin-orbit coupled materials, including
some pyrochlore iridates and the inverted band gap semiconductor HgTe, may be
described by a minimal model consisting of the Luttinger Hamiltonian
supplemented by Coulomb interactions, a problem studied by Abrikosov and
collaborators. It contains two-fold degenerate conduction and valence bands
touching quadratically at the zone center. Using modern renormalization group
methods, we update and extend Abrikosov's classic work and show that
interactions induce a quantum critical non-Fermi liquid phase, stable provided
time-reversal and cubic symmetries are maintained. We determine the universal
power-law exponents describing various observables in this ""Luttinger Abrikosov
Beneslavskii"" state, which include conductivity, specific heat,non-linear
susceptibility and magnetic Gruneisen number. Furthermore, we determine the
phase diagram in the presence of cubic and/or time-reversal symmetry breaking
perturbations, which includes topological insulator and Weyl semi-metal phases.
Many of these phases possess an extraordinarily large anomalous Hall effect,
with the Hall conductivity scaling sub-linearly with magnetization.",1212.1168v1
2012-12-12,Electron correlation and spin-orbit coupling effects in US3 and USe3,"A systematic density functional theory (DFT)+U study is conducted to
investigate the electron correlation and spin-orbit coupling (SOC) effects in
US3 and USe3. Our calculations reveal that inclusion of the U term is essential
to get energy band gaps for them, indicating the strong correlation effects for
uranium 5f electrons. Taking consideration of the SOC effect results in small
reduction on the electronic band gaps of US3 and USe3, but largely changes the
energy band shapes around the Fermi energy. As a result, US3 has a direct band
gap while USe3 has an indirect one. Our calculations predict that both US3 and
USe3 are antiferromagnetic insulators, in agreement with corresponding
experimental results. Based on our DFT+U calculations, we systematically
present the ground-state electronic, mechanical, and Raman properties for US3
and USe3.",1212.2682v1
2013-01-08,Tuning thermoelectric power factor by crystal-field and spin-orbit couplings in Kondo lattice materials,"We study thermoelectric transport at low temperatures in correlated Kondo
insulators, motivated by the recent observation of a high thermoelectric figure
of merit(ZT) in $FeSb_2$ at $T \sim 10 K$. Even at room temperature,
correlations have the potential to lead to high ZT, as in $YbAl_3$, one of the
most widely used thermoelectric metals. At low temperature correlation effects
are especially worthy of study because fixed band structures are unlikely to
give rise to the very small energy gaps $E_g \sim 5 kT$ necessary for a weakly
correlated material to function efficiently at low temperature. We explore the
possibility of improving the thermoelectric properties of correlated Kondo
insulators through tuning of crystal field and spin-orbit coupling and present
a framework to design more efficient low-temperature thermoelectrics based on
our results.",1301.1441v1
2013-01-18,Manipulating Majorana fermions in one-dimensional spin-orbit coupled atomic Fermi gases,"Majorana fermions are promising candidates for storing and processing
information in topological quantum computation. The ability to control such
individual information carriers in trapped ultracold atomic Fermi gases is a
novel theme in quantum information science. However, fermionic atoms are
neutral and thus are difficult to manipulate. Here, we theoretically
investigate the control of emergent Majorana fermions in one-dimensional
spin-orbit coupled atomic Fermi gases. We discuss (i) how to move Majorana
fermions by increasing or decreasing an effective Zeeman field, which acts like
a solid state control voltage gate; and (ii) how to create a pair of Majorana
fermions by adding a magnetic impurity potential. We discuss the experimental
realization of our control scheme in an ultracold Fermi gas of $^{40}$K atoms.",1301.4303v1
2013-01-20,Impurity probe of topological superfluid in one-dimensional spin-orbit coupled atomic Fermi gases,"We investigate theoretically non-magnetic impurity scattering in a
one-dimensional atomic topological superfluid in harmonic traps, by solving
self-consistently the microscopic Bogoliubov-de Gennes equation. In sharp
contrast to topologically trivial Bardeen-Cooper-Schrieffer \textit{s}-wave
superfluid, topological superfluid can host a mid-gap state that is bound to
localized non-magnetic impurity. For strong impurity scattering, the bound
state becomes universal, with nearly zero energy and a wave-function that
closely follows the symmetry of that of Majorana fermions. We propose that the
observation of such a universal bound state could be a useful evidence for
characterizing the topolgoical nature of topological superfluids. Our
prediction is applicable to an ultracold resonantly-interacting Fermi gas of
$^{40}$K atoms with spin-orbit coupling confined in a two-dimensional optical
lattice.",1301.4619v1
2013-01-29,Phase Diagram of a Spin-Orbit Coupled Fermi Gases in a Bilayer Optical Lattice,"We investigate the stability of helical superfluid phase in a spin-orbit
coupled Fermi gas loaded in a bilayer optical lattice. The phase diagram of the
system is constructed in the mean field framework. We investigate the
topological properties of the superfluid phases by a nontrivial application of
the Fermi surface topological invariant to our time-reversal invariant system
with degeneracies on the Fermi surface. We find that there is a first-order
phase boundary in the phase diagram of half filling case and the superfluid
phases are all topological trivial. The superfluid phase is topological
nontrivial when the filling fraction deviates from the half filling. In the
topological nontrivial superfluid phase, a full pairing gap exists in the bulk
and gapless helical Majorana edge states exist at the boundary.",1301.6871v1
2013-03-14,Aharonov-Bohm conductance of a disordered single-channel quantum ring,"We study the effect of weak disorder on tunneling conductance of a
single-channel quantum ring threaded by magnetic flux. We assume that
temperature is higher than the level spacing in the ring and smaller than the
Fermi energy. In the absence of disorder, the conductance shows sharp dips
(antiresonances) as a function of magnetic flux. We discuss different types of
disorder and find that the short-range disorder broadens antiresonances, while
the long-range one leads to arising of additional resonant dips. We demonstrate
that the resonant dips have essentially non-Lorentzian shape. The results are
generalized to account for the spin-orbit interaction which leads to splitting
of the disorder-broadened resonant dips, and consequently to coexisting of two
types of oscillations (both having the form of sharp dips): Aharonov-Bohm
oscillations with magnetic flux and Aharonov-Casher oscillations with the
strength of the spin-orbit coupling. We also discuss the effect of the Zeeman
coupling.",1303.3486v1
2013-03-18,Non-Abelian Gauge Fields in Photonic Cavities and Photonic Superfluids,"We show that the interplay between the structure anisotropy and the energy
splitting between the TE and TM modes of a microcavity leads to the appearance
of a gauge field for a propagating polariton condensate. This field is analog
with a spin-orbit coupling and the field texture can be tuned by rotating the
sample and ranges continuously from a Rashba to a monopolar field. In the
linear regime, the monopolar field leads to a remarkable focusing effect. In
the interacting regime, the effective spin-orbit coupling induces a breakdown
of superfluidity. The spatially homogeneous flows become unstable and
dynamically evolve into textured ground states such as stripes and domain
walls.",1303.4286v4
2013-04-03,Vortex states and Majorana fermions in spin-orbit coupled semiconductor-superconductor hybrid structures,"We study the energy spectrum of a vortex core in a two-dimensional
semiconductor with Rashba spin-orbit interaction and proximity-coupled to a
conventional superconductor and a ferromagnetic insulator. We perform
self-consistent calculations using the microscopic tight-binding Bogoliubov-de
Gennes method on a lattice and confirm the existence of Majorana fermions in
the non-trivial topological phase. We also find two different topologically
trivial bulk superconducting phases, only differing in the type of vortex core
structure they support and separated by a zero-energy excitation. Furthermore,
we find an asymmetry in the energy spectrum with respect to both Zeeman
splitting and vortex rotation direction and explain its physical origin.",1304.0981v2
2013-04-05,Magnetic monopoles and synthetic spin-orbit coupling in Rydberg macrodimers,"We show that sizeable Abelian and non-Abelian gauge fields arise in the
relative motion of two dipole-dipole interacting Rydberg atoms. Our system
exhibits two magnetic monopoles for adiabatic motion in one internal two-atom
state. These monopoles occur at a characteristic distance between the atoms
that is of the order of one micron. The deflection of the relative motion due
to the Lorentz force gives rise to a clear signature of the effective magnetic
field. In addition, we consider non-adiabatic transitions between two
near-degenerate internal states and show that the associated gauge fields are
non-Abelian. We present quantum mechanical calculations of this synthetic
spin-orbit coupling and show that it realizes a velocity-dependent
beamsplitter.",1304.1597v2
2013-04-05,Matter-wave dark solitons and their excitation spectra in spin-orbit coupled Bose-Einstein condensates,"We present three types of dark solitons in quasi-one-dimensional spin-orbit
coupled repulsive Bose-Einstein condensates. Among these families, two are
always stable, while the third one is only stable sufficiently close to the
linear regime. The solitons' excitation spectra reveal the potential existence
of a second anomalous mode. While the first such mode describes the soliton
oscillatory motion in a parabolic trap, the second, when present, reflects the
double well structure of the underlying single-particle spectrum. This novel
mode results in moving density stripes in the vicinity of the soliton core, or
in an out-of-phase oscillation of the constituent components, with little
effect on the nearly stationary striped total density of the composite soliton.",1304.1742v2
2013-05-03,Supercurrent and dynamical instability of spin-orbit-coupled ultracold Bose gases,"We investigate the stability of supercurrents in a Bose-Einstein condensate
with one-dimensional spin-orbit and Raman couplings. The consequence of the
lack of Galilean invariance is explicitly discussed. We show that in the
plane-wave phase, characterized by a uniform density, the supercurrent state
can become dynamically unstable, the instability being associated with the
occurrence of a complex sound velocity, in a region where the effective mass is
negative. We also discuss the emergence of energetic instability in these
supercurrent states. We argue that both the dynamical and the energetic
instabilities in these systems can be generated experimentally through
excitation of the collective dipole oscillation.",1305.0645v2
2013-05-08,Tuning the electronic properties of J_eff=1/2 correlated semimetal in epitaxial perovskite SrIrO3,"We investigated the electronic properties of epitaxially stabilized
perovskite SrIrO3 and demonstrated the effective strain-control on its
electronic structure. Comprehensive transport measurements showed that the
strong spin-orbit coupling renders a novel semimetallic phase for the J_eff=1/2
electrons rather than an ordinary correlated metal, elucidating the nontrivial
mechanism underlying the dimensionality-controlled metal-insulator transition
in iridates. The electron-hole symmetry of this correlated semimetal was found
to exhibit drastic variation when subject to bi-axial strain. Under compressive
strain, substantial electron-hole asymmetry is observed in contrast to the
tensile side, where the electron and hole effective masses are comparable,
illustrating the susceptivity of the J_eff=1/2 to structural distortion.
Tensile strain also shrinks the Fermi surface, indicative of an increasing
degree of correlation which is consistent with optical measurements. These
results pave a pathway to investigate and manipulate the electronic states in
spin-orbit-coupled correlated oxides, and lay the foundation for constructing
5d transition metal heterostructures.",1305.1732v1
2013-05-08,Magnetic Exchange Coupling and Anisotropy of 3d Transition-Metal Nanowire on the Surface of Graphyne Sheet,"Using density functional theory plus Hubbard-U (DFT+U) approach, we find that
quasi one-dementation(1D) 3d transition metal(TM) zigzag nanowire can be
constructed by TM adsorbed on the surface of graphyne sheet. The results show
that the TM exchange coupling of the zigzag nanowire mediated by sp hybridized
carbon atoms gives rise to long range ferromagnetic order except for Cr with
anti-ferromagnetic order. The magnetic exchange interaction of TM chains
follows like-Zener's p_z-d exchange mechanism: the coexistence of out-of plane
p_z-d and in-plane p_x-y-d exchange. Finally, by including spin-orbit
interactions within spin-DFT, we calculate the magnetic anisotropy energy of
the TM chain on graphyne. We find that the Fe and Co chains show considerable
magnetic anisotropy energy (MAE) and orbital magnetic moment. The easy axis of
V, Cr, Mn and Fe chains is perpendicular to the surface, whereas the easy axis
of Co lies in the surface. Moreover, only V chain shows relatively larger
in-plane anisotropy. Our results open a new route to realize the applications
of graphyne in spintronics.",1305.1791v2
2013-05-16,"Anomalous Josephson current, incipient time-reversal symmetry breaking, and Majorana bound states in interacting multi-level dots","We study the combined effects of spin-orbit interaction, magnetic field, and
Coulomb charging on the Josephson current-phase relation, I(\varphi), for a
multi-level quantum dot tunnel-contacted by two conventional s-wave
superconductors with phase difference \varphi. A general model is formulated
and analyzed in the cotunneling regime (weak tunnel coupling) and in the deep
subgap limit, fully taking into account interaction effects. We determine the
conditions for observing a finite anomalous supercurrent I_a=I(\varphi=0). For
a two-level dot with spin-orbit coupling and arbitrarily weak Zeeman field B,
we find the onset behavior I_a\propto {\rm sgn}(B) in the presence of
interactions, suggesting the incipient spontaneous breakdown of time-reversal
symmetry. We also provide conditions for realizing spatially separated (but
topologically unprotected) Majorana bound states in this system, which have a
clear signature in the 2\pi-periodic current-phase relation.",1305.3816v2
2013-05-21,Complex-Stripe Phases Induced by Staggered Rashba Spin-Orbit Coupling,"We study superconducting phases in a quasi-two-dimensional multilayer system
without local inversion symmetry. Broken local inversion symmetry induces
layer-dependent Rashba-type spin-orbit couplings. We find that a complex-stripe
phase, which is the intermediate phase between the Fulde-Ferrell (FF) phase and
Larkin-Ovchinnikov (LO) phase, is realized in the magnetic field applied
parallel to the layers. A crossover from the FF phase to the LO phase appears
by tuning temperature and magnetic field. We show the local density of states
that characterizes the complex-stripe phase. As a possible realization of the
complex-stripe phase, we discuss the artificial superlattices of CeCoIn_5.",1305.4748v2
2013-05-28,Probing Majorana Flat Bands in Nodal $d_{x^2-y^2}$-wave Superconductors with Rashba Spin-Orbit Coupling,"We show that Majorana fermions associated with Majorana flat bands emerge as
zero energy modes on the [110] edge of single layer or multilayer nodal
superconductors with $d_{x^2-y^2}$-wave pairing and Rashba spin-orbit coupling.
Moreover, as long as the global inversion symmetry of the single layer or
multilayer superconductor is broken, and in the presence of an in-plane
magnetic field parallel to the [110] edge, the Majorana fermions together with
usual fermionic Andreev bound states induce a triple-peak structure in
tunnelling spectroscopy experiments. Importantly, we show that the zero bias
conductance peak is induced by Majorana fermions. Therefore, tunnelling
spectroscopy can be used to probe Majorana fermions in nodal $d_{x^2-y^2}$-wave
superconductors.",1305.6446v1
2013-05-29,Helical edge states induced by lateral spin-orbit coupling,"The presence of edges locally breaks the inversion symmetry of
heterostructures and gives rise to lateral (edge) spin-orbit coupling (SOC),
which, under some conditions, can lead to the formation of helical edge states.
If the edge SOC is strong enough, the helical edge states can penetrate the
band-gap and be energetically isolated from the bulk-like states. As a result
backward scattering is suppressed, dissipationless helical edge channels
protected against time-inversion symmetric perturbations emerge, and the system
behaves as a 2D topological insulator (TI). However, unlike in previous works
on TIs, the mechanism proposed here for the creation of protected helical edge
states relies on the strong edge SOC rather than on band inversion.",1305.6953v2
2013-06-27,Rashbon condensation in a Bose gas with Rashba spin-orbit coupling,"We show that in a two-component Bose gas with Rashba spin-orbit coupling
(SOC) two atoms can form bound states (Rashbons) with any intra-species
scattering length. At zero center-of-mass momentum there are two degenerate
Rashbons due to time-reversal symmetry, but the degeneracy is lifted at finite
in-plane momentum with two different effective masses. A stable Rashbon
condensation can be created in a dilute system with weakly attractive
intra-species and repulsive inter-species interactions. The critical
temperature of Rashbon condensation is about six times smaller than the BEC
transition temperature of an ideal Bose gas. Due Rashba SOC, excitations in the
Rashbon condensation phase are anisotropic in momentum space.",1306.6440v3
2013-12-04,"Comment on ""Quantum Quasicrystals of Spin-Orbit-Coupled Dipolar Bosons""","In a recent Letter, Gopalakrishnan, Martin, and Demler [Phys. Rev. Lett. 111
(2013) 185304] show that quasi-two-dimensional dipolar Bose gases, subject to a
Rashba spin-orbit coupling, exhibit a variety of spatially ordered, or
crystalline, ground states, including a pentagonal quasicrystal. Indeed, as the
authors say, realizing quasicrystalline condensates would provide new ways to
explore the physics of quasicrystals, and in particular to study the quantum
dynamics of their unique collective phason modes. Yet, the authors conclude
that ""there are typically additional phasons in quantum-mechanical
quasicrystals, when compared with their classical equivalents."" In this Comment
I review the notion of phason modes in quasicrystals, and explain why their
number does not depend on whether they are classical or quantum.",1312.1388v1
2013-12-08,Theoretical prediction of the importance of the 3B2 state in the dynamics of sulfur dioxide,"While, the sulfur dioxide molecule has been extensively studied over the last
decades, its photoexcitation dynamics is still unclear, due to its complexity,
combining conical intersections and spin-orbit coupling between a manifold of
states. We present for the first time a comprehensive ab initio study of the
intersystem crossing of the molecule in the low energy domain, based on a
wave-packet propagation on the manifold of the lowest singlet and triplet
states. Furthermore, spin-orbit couplings are evaluated on a geometry-dependent
grid, and diabatized along with the different conical intersections. Our
results show for the first time the primordial role of the triplet $^3$B$_2$
state which has not been discussed before, giving new insights into the
dynamics of the intersystem crossing in $SO_2$.",1312.2275v1
2013-12-20,Spin-orbit coupling and weak antilocalization in thermoelectric material $β$-K$_{2}$Bi$_{8}$Se$_{13}$,"We have studied the effect of spin-orbital coupling (SOC) on electronic
transport properties of the thermoelectric material
$\beta$-K$_{2}$Bi$_{8}$Se$_{13}$ via magnetoresistance (MR) measurements. We
found that the strong SOC in this material results in weak antilocalization
(WAL) effect, which can be well described by the three-dimensional weak
localization model. The phase coherence length extracted from theoretical
fitting exhibits a power-law temperature dependence with an exponent around
2.1, indicating that the electron phase dephasing is governed by electron -
transverse phonon interactions. Like in topological insulators, the WAL effect
in $\beta$-K$_{2}$Bi$_{8}$Se$_{13}$ can be quenched by magnetic impurities (Mn)
but is robust against non-magnetic impurities (Te). Although our
magnetotransport studies do not provide any evidences for topological surface
states, our analyses suggest that SOC plays an important role in determining
thermoelectric properties of $\beta$-K$_{2}$Bi$_{8}$Se$_{13}$.",1312.6091v1
2013-12-23,Josephson Effect and Triplet--Singlet Ratio of Non--centrosymmetric Superconductors,"We calculate the Andreev bound states and the corresponding Josephson current
for an asymmetric 2-dimensional Josephson junction by solving
Bogoliubov-de-Gennes equations. The junction consists of a non-centrosymmetric
superconductor (NCS) separated by a tunneling barrier with a variable height to
a conventional s-wave superconductor. In addition to the antisymmetric
spin-orbit coupling in the NCS on the one side, this asymmetric junction gives
rise to a Rashba spin-orbit coupling at the interface. We explore the rich
parameter space and recover various limiting cases such as s-wave/p-wave
junction and the asymmetric s-wave junctions. In addition, we report a
transition from a 0-junction to a pi/2-junction with increasing triplet-singlet
pairing ratio of the NCS, which serves as a novel mechanism to determine the
unknown ratio in a variety of NCS's.",1312.6548v1
2013-12-24,Non-analytic behavior of the Casimir force across a Lifshitz transition in a spin-orbit coupled material,"We propose the Casimir effect as a general method to observe Lifshitz
transitions in electron systems. The concept is demonstrated with a planar
spin-orbit coupled semiconductor in a magnetic field. We calculate the Casimir
force between two such semiconductors and between the semiconductor and a metal
as a function of the Zeeman splitting in the semiconductor. The Zeeman field
causes a Fermi pocket in the semiconductor to form or collapse by tuning the
system through a topological Lifshitz transition. We find that the Casimir
force experiences a kink at the transition point and noticeably different
behaviors on either side of the transition. The simplest experimental
realization of the proposed effect would involve a metal-coated sphere
suspended from a micro-cantilever above a thin layer of InSb (or another
semiconductor with large $g$-factor). Numerical estimates are provided and
indicate that the effect is well within experimental reach.",1312.6754v1
2014-01-18,Axionic Antiferromagnetic Insulator Phase in a Correlated and Spin-Orbit Coupled System,"We study theoretically a three-dimensional correlated and spin-orbit coupled
system, the half-filled extended Fu-Kane-Mele-Hubbard model on a diamond
lattice, focusing on the topological magnetoelectric response of the
antiferromagnetic insulator phase. In the antiferromagnetic insulator phase,
the Dirac-like low-energy effective Hamiltonian is obtained. Then the theta
term, which results in the magnetoelectric response, is derived as a
consequence of the chiral anomaly. The realization of the dynamical axion field
in our model is discussed. The relation with a symmetry broken phase induced by
interactions in lattice quantum chromodynamics is also discussed.",1401.4523v3
2014-02-20,Fully Gapped s-wave-like Superconducting State and Electronic Structures in the Ir0.95Pd0.05Te2 Single Crystals with Strong Spin-orbital Coupling,"Due to the large spin-orbital coupling in the layered 5d-transition metal
chalcogenides compound, the occurrence of superconductivity in Ir2-xPdxTe2
offers a good chance to search for possible topological superconducting states
in this system. We did comprehensive studies on the superconducting properties
and electronic structures of single crystalline Ir0.95Pd0.05Te2 samples. The
superconducting gap size, critical fields and coherence length along different
directions were experimentally determined. Macroscopic bulk measurements and
microscopic low temperature scanning tunneling spectroscopy results suggest
that Ir0.95Pd0.05Te2 possesses a BCS-like s-wave state. No sign of zero bias
conductance peak were found in the vortex core at 0.4K.",1402.4858v1
2014-07-11,Thermodynamic Properties of Rashba Spin-Orbit-Coupled Fermi Gas,"We investigate the thermodynamic properties of a superfluid Fermi gas subject
to Rashba spin-orbit coupling and effective Zeeman field. We adopt a T-matrix
scheme that takes beyond-mean-field effects, which are important for strongly
interacting systems, into account. We focus on the calculation of two important
quantities: the superfluid transition temperature and the isothermal
compressibility. Our calculation shows very distinct influences of the
out-of-plane and the in-plane Zeeman fields on the Fermi gas. We also confirm
that the in-plane Zeeman field induces a Fulde-Ferrell superfluid below the
critical temperature and an exotic finite-momentum pseudo-gap phase above the
critical temperature.",1407.3203v3
2014-07-13,Berezinskii-Kosterlitz-Thouless Phase Transition in 2D Spin-Orbit Coupled Fulde-Ferrell Superfluids,"The experimental observation of traditional Zeeman-field induced
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superfluids has been hindered by
various challenges, in particular, the requirement of low dimensional systems.
In 2D, finite temperature phase fluctuations lead to extremely small
Berezinskii-Kosterlitz-Thouless (BKT) transition temperature for FFLO
superfluids, raising serious concerns regarding their experimental
observability. Recently, it was shown that FFLO superfluids can be realized
using a Rashba spin-orbit coupled Fermi gas subject to Zeeman fields, which may
also support topological excitations such as Majorana fermions in 2D. Here we
address the finite temperature BKT transition issue in this system, which may
exhibit gapped, gapless, topological, and gapless topological FF phases. We
find a large BKT transition temperature due to large effective superfluid
densities, making it possible to observe 2D FF superfluids at finite
temperature. In addition, we show that gapless FF superfluids can be stable due
to their positive superfluid densities. These findings pave the way for the
experimental observation of 2D gapped and gapless FF superfluids and their
associated topological excitations at finite temperature.",1407.3483v3
2014-07-28,Majorana fermions in ferromagnetic chains on the surface of bulk spin-orbit coupled $s$-wave superconductors,"Majorana fermion (MF) excitations in solid state system have non-Abelian
statistics which is essential for topological quantum computation. Previous
proposals to realize MF, however, generally requires fine-tuning of parameters.
Here we explore a platform which avoids the fine-tuning problem, namely a
ferromagnetic chain deposited on the surface of a spin-orbit coupled $s$-wave
superconductor. We show that it generically supports zero-energy topological MF
excitations near the two ends of the chain with minimal fine-tuning. Depending
on the strength of the ferromagnetic moment in the chain, the number of MFs at
each end, $n$, can be either one or two, and should be revealed by a robust
zero-bias peak (ZBP) of height $2ne^2/h$ in scanning tunneling microscopy (STM)
measurements which would show strong (weak) signals at the ends (middle) of the
chain. The role of an approximate chiral symmetry which gives an integer
topological invariant to the system is discussed.",1407.7519v2
2014-09-03,Thermal Phase Transitions of Strongly Correlated Bosons with Spin-Orbit Coupling,"Experiments on ultracold atomic gases have begun to explore lattice effects
and thermal fluctuations for two-component bosons with spin-orbit coupling
(SOC). Motivated by this, we study a $tJ$ model of strongly correlated lattice
bosons, with equal Rashba-Dresselhaus SOC and a uniform magnetic field. At zero
temperature, a Gutzwiller ansatz is shown to capture lattice variants of stripe
superfluid (SF) ground states. We formulate a finite temperature generalization
of the Gutzwiller approach and show that thermal fluctuations in the doped Mott
insulator drive a two-step melting of the stripe SF, revealing a wide
intermediate regime of a normal fluid with stripe order.",1409.1216v3
2014-09-12,Toroidal order in a partially disordered state on a layered triangular lattice: implication to UNi4B,"A partial disorder on a layered triangular lattice is theoretically
investigated from a viewpoint of toroidal ordering and magnetoelectric effects.
We consider an extended periodic Anderson model including a site-dependent
antisymmetric spin-orbit coupling between conduction and localized electrons.
We show that, by the mean-field approximation, the model exhibits a coplanar
vortex-lattice-type magnetic order as observed in a hexagonal uranium compound
UNi4B, in the parameter region with intermediate hybridization and electron
correlation. This peculiar state accommodates a toroidal order, which leads to
the linear magnetoelectric effect. We discuss the implications of our results
to UNi4B, focusing on the possible source of the site-dependent antisymmetric
spin-orbit coupling.",1409.3657v1
2014-09-24,Interaction-induced quantum anomalous Hall phase in (111) bilayer of LaCoO$_3$,"In the present paper, the Gutzwiller density functional theory (LDA+G) has
been applied to study a bilayer system of LaCoO$_3$ grown along the $(111)$
direction on SrTiO$_3$. The LDA calculations show that there are two nearly
flat bands located at the top and bottom of $e_{g}$ bands of Co atoms with the
Fermi level crossing the lower one, which is almost half-filled. After
including both the spin-orbit coupling and the Coulomb interaction in the LDA+G
method, we find that the interplay between spin-orbit coupling and Coulomb
interaction stabilizes a very robust ferromagnetic insulator phase with
non-zero Chern number, which indicates the possibility to realize quantum
anomalous Hall effect in this system.",1409.6797v2
2014-10-14,Majorana Bound States in Proximity Junctions of Superconducting Nanowires with Dresselhaus Spin-orbit Coupling,"We theoretically study transport properties of nanowires with the Dresselhaus
[110] spin-orbit coupling under the in-plane Zeeman potential and the
proximity-induced s-wave pair potential. In the topologically nontrivial phase,
the nanowire hosts the Majorana fermions at its edges and the number of the
Majorana bound states is equal to the number propagating channels (Nc). When we
attach a normal metal to the superconductor, such Majorana bound states
penetrate into the dirty normal segment and form the Nc resonant transmission
channels there. We show that chiral symmetry of the electronic states protects
the Majorana bound states at the zero energy even in the presence of
impurities. As a result, we find that the zero-bias conductance of
normal-nanowire/superconducting-nanowire junctions is quantized at 2e2Nc/h
independent of the random potentials.",1410.3626v1
2014-10-16,Goos-Hänchen shifts in spin-orbit-coupled cold atoms,"We consider a matter wave packet of cold atom gas impinging upon a step
potential created by the optical light field. In the presence of spin-orbit
(SO) coupling, the atomic eigenstates contain two types of evanescent states,
one of which is the ordinary evanescent state with pure imaginary wave vector
while the other possesses complex wave vector and is recognized as oscillating
evanescent state. We show that the presence and interplay of these two types of
evanescent states can give rise to two different mechanisms for total internal
reflection (TIR), and thus lead to unusual Goos-H\""anchen (GH) effect. As a
result, not only large positive but also large negative GH shift can be
observed in the reflected atomic beam. The dependence of the GH shift on the
incident angle, energy and height of the step potential is studied numerically.",1410.4283v2
2014-10-20,Probing the Flat Band of Optically-Trapped Spin-Orbital Coupled Bose Gases Using Bragg Spectroscopy,"Motivated by the recent efforts in creating the flat band in ultracold atomic
systems, we investigate how to probe the flat band in an optically-trapped
spin-orbital coupled Bose-Einstein condensate using Bragg spectroscopy. We have
found that the excitation spectrum and the dynamic structure factor of the
condensate alter dramatically, when the band structure exhibits various level
of flatness. In particular, when the band exhibits perfect flatness around the
band minima corresponding to a near infinite effective mass, a quadratic
dispersion emerges in the low-energy excitation spectrum; in sharp contrast,
for the opposite case when an ordinary band is present, the familiar linear
dispersion arises. Such linear-to-quadratic crossover in the energy spectrum
presents a striking manifestation of the transition of an ordinary band into a
flat band, thereby allows the direct probe of the flat band by using Bragg
spectroscopy.",1410.5142v3
2014-11-26,Structured Weyl Points in Spin-Orbit Coupled Fermionic Superfluids,"We demonstrate that a Weyl point, widely examined in 3D Weyl semimetals and
superfluids, can develop a pair of non-degenerate gapless spheres. Such a
bouquet of two spheres is characterized by three distinct topological
invariants of manifolds with full energy gaps, i.e., the Chern number of a 0D
point inside one developed sphere, the winding number of a 1D loop around the
original Weyl point, and the Chern number of a 2D surface enclosing the whole
bouquet. We show that such structured Weyl points can be realized in the
superfluid quasiparticle spectrum of a 3D degenerate Fermi gas subject to
spin-orbit couplings and Zeeman fields, which supports Fulde-Ferrell
superfluids as the ground state.",1411.7316v4
2015-01-19,Electronic correlations in Hund metals,"To clarify the nature of correlations in Hund metals and its relationship
with Mott physics we analyze the electronic correlations in multiorbital
systems as a function of intraorbital interaction U, Hund's coupling JH and
electronic filling n. We show that the main process behind the enhancement of
correlations in Hund metals is the suppression of the double-occupancy of a
given orbital, as it also happens in the Mott-insulator at half-filling.
However, contrary to what happens in Mott correlated states the reduction of
the quasiparticle weight Z with JH can happen on spite of increasing charge
fluctuations. Therefore, in Hund metals the quasiparticle weight and the mass
enhancement are not good measurements of the charge localization. Using simple
energetic arguments we explain why the spin polarization induced by Hund's
coupling produces orbital decoupling. We also discuss how the behavior at
moderate interactions, with correlations controlled by the atomic spin
polarization, changes at large $U$ and $J_H$ due to the proximity to a Mott
insulating state.",1501.04607v2
2015-02-03,Spin-orbit coupled j=1/2 iridium moments on the geometrically frustrated fcc lattice,"Motivated by experiments on the double perovskites La2ZnIrO6 and La2MgIrO6,
we study the magnetism of spin-orbit coupled j=1/2 iridium moments on the
three-dimensional, geometrically frustrated, face-centered cubic lattice. The
symmetry-allowed nearest-neighbor interaction includes Heisenberg, Kitaev, and
symmetric off-diagonal exchange. A Luttinger-Tisza analysis shows a rich
variety of orders, including collinear A-type antiferromagnetism, stripe order
with moments along the [111]-direction, and incommensurate non-coplanar
spirals, and we use Monte Carlo simulations to determine their magnetic
ordering temperatures. We argue that existing thermodynamic data on these
iridates underscores the presence of a dominant Kitaev exchange, and also
suggest a resolution to the puzzle of why La2ZnIrO6 exhibits `weak'
ferromagnetism, but La2MgIrO6 does not.",1502.01031v4
2015-02-12,A new material for probing spin-orbit coupling in Iridates,"We report the structure and magnetic properties of a new iridate compound,
SrxLa11-xIr4O24, where the d-electron count of Ir and therefore its number of
unpaired electrons can be tuned continuously from 5d5 Ir4+ to 5d4 Ir5+, i.e.
from SrLa10Ir4O24 to Sr5La6Ir4O24. The IrO6 octahedra in SrxLa11-xIr4O24 are
isolated from each other and from other transition elements, minimizing band
effects, and the doping is on the framework sites, not the Ir sites, minimizing
the effects of disorder. Measurements of the temperature dependent magnetic
susceptibility are employed to determine the evolution of the Ir magnetic
moment on progressing from 5d5 Ir4+ to 5d4 Ir5+, and are clearly best described
by a transition from a J=1/2 to a J=0 Ir magnetic state; that is, the evolution
of the magnetic susceptibility shows the dominance of spin-orbit coupling in
determining the magnetic properties of a material with highly isolated IrO6
octahedra.",1502.03833v2
2015-02-19,Positive and negative mass solitons in spin-orbit coupled Bose-Einstein condensates,"We present a unified description of different types of matter-wave solitons
that can emerge in quasi one-dimensional spin-orbit coupled (SOC) Bose-Einstein
condensates (BECs). This description relies on the reduction of the original
two-component Gross-Pitaevskii SOC-BEC model to a single nonlinear
Schr\""{o}dinger equation, via a multiscale expansion method. This way, we find
approximate bright and dark soliton solutions, for attractive and repulsive
interatomic interactions respectively, for different regimes of the SOC
interactions. Beyond this, our approach also reveals ""negative mass"" regimes,
where corresponding ""negative mass"" bright or dark solitons can exist for
repulsive or attractive interactions, respectively. Such a unique opportunity
stems from the structure of the excitation spectrum of the SOC-BEC. Numerical
results are found to be in excellent agreement with our analytical predictions.",1502.05574v1
2015-03-23,Conductance spectroscopy of topological superconductor wire junctions,"We study the zero-temperature transport properties of one-dimensional
normal-superconductor (NS) junctions with topological superconductors across
their topological transitions. Working within the Blonder-Tinkham-Klapwijk
(BTK) formalism generalized for topological NS junctions, we analytically
calculate the differential conductance for tunneling into two models of a
topological superconductor: a spinless intrinsic $p$-wave superconductor and a
spin-orbit-coupled $s$-wave superconductor in a Zeeman field. In both cases we
verify that the zero-bias conductance is robustly quantized at $2e^2/h$ in the
topological regime, while it takes nonuniversal values in the non-topological
phase. The conductance spectra in the topological state develops a peak at zero
bias for certain parameter regimes, with the peak width controlled by the
strength of spin-orbit coupling and barrier transparency.",1503.06801v3
2015-04-08,Unidirectional sub-diffraction waveguiding based on optical spin-orbit coupling in subwavelength plasmonic waveguides,"Subwavelength plasmonic waveguides show the unique ability of strongly
localizing (down to the nanoscale) and guiding light. These structures are
intrinsically two-way optical communication channels, providing two opposite
light propagation directions. As a consequence, when light is coupled to these
planar integrated devices directly from the top (or bottom) surface using
strongly focused beams, it is equally shared into the two opposite propagation
directions. Here, we show that symmetry can be broken by using incident
circularly polarized light, on the basis of a spin-orbital angular momentum
transfer directly within waveguide bends. We predict that up to 94 \% of the
incoupled light is directed into a single propagation channel of a gap plasmon
waveguide. Unidirectional propagation of strongly localized optical energy, far
beyond the diffraction limit, becomes switchable by polarization, with no need
of intermediate nano-antennas/scatterers as light directors. This study may
open new perspectives in a large panel of scientific domains, such as
nanophotonic circuitry, routing and sorting, optical nanosensing, nano-optical
trapping and manipulation.",1504.02038v3
2015-04-18,Asymmetric Landau bands due to spin-orbit coupling,"We show that the Landau bands obtained in a two-dimensional lateral
semiconductor superlattice with spin-orbit coupling (SOC) of the
Rashba/Dresselhaus type, linear in the electron momentum, placed in a tilted
magnetic field, do not follow the symmetry of the spatial modulation. Moreover,
this phenomenology is found to depend on the relative tilt of magnetic field
and on the SOC type: a) when only Rashba SOC exists and the magnetic field is
tilted in the direction of the superlattice b) Dresselhaus SOC exists and the
magnetic field is tilted in the direction perpendicular to the superlattice.
Consequently, measurable properties of the modulated system become anisotropic
in a tilted magnetic field when the field is conically rotated around the $z$
axis, at a fixed polar angle, as we demonstrate by calculating the resistivity
and the magnetization.",1504.04699v2
2015-05-18,Quasiclassical analysis of vortex lattice states in Rashba noncentrosymmetric superconductors,"Vortex lattice states occurring in noncentrosymmetric superconductors with
the spin-orbit coupling of Rashba type under a magnetic field parallel to the
symmetry plane are examined by assuming the $s$-wave pairing case and in an
approach combining the quasiclassical theory with the Landau level expansion of
the superconducting order parameter. The resulting field-temperature phase
diagrams include not only a discontinuous transition but a continuous crossover
between different vortex lattice structures, and, further, a critical end point
of a structural transition line is found in an intermediate field and at a low
temperature in the present approach. It is pointed out that the strange field
dependence of the vortex lattice structure is a consequence of that of an
anisotropy stemming from the Rashba spin-orbit coupling, and that the critical
end point is related to the helical phase modulation peculiar to these
materials in the ideal Pauli-limited case. Further, calculation results on the
local density of states detectable in STM experiments are also presented.",1505.04559v2
2015-05-21,Topological superconductivity in a multichannel Yu-Shiba-Rusinov chain,"Chains of magnetic atoms placed on the surface of an s-wave superconductor
with large spin-orbit coupling provide a promising platform for the realization
of topological superconducting states characterized by the presence of Majorana
zero-energy modes. In this work we study the properties of the one-dimensional
chain of Yu-Shiba-Rusinov states induced by magnetic impurities using a
realistic model for the magnetic atoms that include the presence of multiple
scattering channels. These channels are mixed by the spin-orbit coupling and,
via the hybridization of the Yu-Shiba-Rusinov states at different sites of the
chain, result in a multi-band structure for the chain. We obtain the
topological phase diagram for such band structure. We identify the parameter
regimes for which the different bands lead to a topological phase and show that
the inclusion of higher bands can greatly enlarge the phase space for the
realization of topological states.",1505.05862v2
2015-05-22,Vector solitons in a spin-orbit coupled spin-$2$ Bose-Einstein condensate,"Five-component minimum-energy bound states and mobile vector solitons of a
spin-orbit-coupled quasi-one-dimensional hyperfine-spin-2 Bose-Einstein
condensate are studied using the numerical solution and variational
approximation of a mean-field model. Two distinct types of solutions with
single-peak and multi-peak density distribution of the components are
identified in different domains of interaction parameters. From an analysis of
Galilean invariance and time-reversal symmetry of the Hamiltonian, we establish
that vector solitons with multi-peak density distribution preserve
time-reversal symmetry, but cannot propagate maintaining the shape of
individual components. However, those with single-peak density distribution
violate time-reversal symmetry of the Hamiltonian, but can propagate with a
constant velocity maintaining the shape of individual components.",1505.06190v2
2015-06-10,Topological nodal line semimetals with and without spin-orbital coupling,"We theoretically study three-dimensional topological semimetals (TSMs) with
nodal lines protected by crystalline symmetries. Compared with TSMs with point
nodes, e.g., Weyl semimetals and Dirac semimetals, where the conduction and the
valence bands touch at discrete points, in these new TSMs the two bands cross
at closed lines in the Brillouin zone. We propose two new classes of symmetry
protected nodal lines in the absence and in the presence of spin-orbital
coupling (SOC), respectively. In the former, we discuss nodal lines that are
protected by the combination of inversion symmetry and time-reversal symmetry;
yet unlike any previously studied nodal lines in the same symmetry class, each
nodal line has a $Z_2$ monopole charge and can only be created (annihilated) in
pairs. In the second class, with SOC, we show that a nonsymmorphic symmetry
(screw axis) protects a four-band crossing nodal line in systems having both
inversion and time-reversal symmetries.",1506.03449v3
2015-06-22,Edge states and topological insulating phases generated by curving a nanowire with Rashba spin-orbit coupling,"We prove that curvature effects in low-dimensional nanomaterials can promote
the generation of topological states of matter by considering the paradigmatic
example of quantum wires with Rashba spin-orbit coupling, which are
periodically corrugated at the nanometer scale. The effect of the periodic
curvature generally results in the appearance of insulating phases with a
corresponding novel butterfly spectrum characterized by the formation of fine
measure complex regions of forbidden energies. When the Fermi energy lies in
the gaps, the system displays localized end states protected by topology. We
further show that for certain corrugation periods the system possesses
topologically non-trivial insulating phases at half-filling. Our results
suggest that the local curvature and the topology of the electronic states are
inextricably intertwined in geometrically deformed nanomaterials.",1506.06676v1
2015-07-06,Spin-orbit coupled ultracold gases in optical lattices: High-band physics and insufficiency of tight-binding models,"We study the interplay effect of spin-orbit coupling(SOC) and optical lattice
to the single-particle physics and superfluid-insulator transition in ultracold
Fermi gases. We consider the type of SOC that has been realized in cold atoms
experiments via two-photon Raman processes. Our analyses are based on the
knowledge of full single-particle spectrum in lattices, without relying on any
tightbinding approximation.We evaluate existing tight-binding models and point
out their limitations in predicting the correct single-particle physics due to
the missed high-band contributions. Moreover, we show that the Raman field
(creating SOC) can induce band-gap closing in a two-dimensional optical
lattice, leading to the intriguing phenomenon of superfluidity-reentrance for
interacting fermions at integer filling. We present the superfluid-insulator
phase diagram in a wide parameter regime of chemical potentials and Raman
fields. All these results are far beyond any tight-binding model can predict,
and can be directly probed in current cold atoms experiments.",1507.01341v4
2015-09-14,Stable Solitons in Three Dimensional Free Space: Self-Trapped Bose-Einstein Condensates with Spin-Orbit Coupling,"By means of variational methods and systematic numerical analysis, we
demonstrate the existence of stable solitons in three-dimensional (3D) free
space, in the context of binary atomic condensates combining contact
self-attraction and spin-orbit coupling, which can be engineered by available
experimental techniques. Depending on the relative strength of the intra- and
inter-component attraction, the stable solitons feature a semi-vortex or
mixed-mode structure. In spite of the fact that the local cubic self-attraction
gives rise to the supercritical collapse in 3D, the solitons are stable against
random perturbations, motion, and collisions.",1509.04087v2
2015-10-07,Cavity optomagnonics with spin-orbit coupled photons,"We experimentally implement a system of cavity optomagnonics, where a sphere
of ferromagnetic material supports whispering gallery modes (WGMs) for photons
and the magnetostatic mode for magnons. We observe pronounced nonreciprocity
and asymmetry in the sideband signals generated by the magnon-induced Brillouin
scattering of light. The spin-orbit coupled nature of the WGM photons, their
geometric birefringence and the time-reversal symmetry breaking in the magnon
dynamics impose the angular-momentum selection rules in the scattering process
and account for the observed phenomena. The unique features of the system may
find interesting applications at the crossroad between quantum optics and
spintronics.",1510.01837v4
2015-10-15,Symmetry-protected topological phase in a one-dimensional correlated bosonic model with a synthetic spin-orbit coupling,"By performing large-scale density-matrix renormalization group simulations,
we investigate a one-dimensional correlated bosonic lattice model with a
synthetic spin-orbit coupling realized in recent experiments. In the insulating
regime, this model exhibits a symmetry-protected topological phase. This
symmetry-protected topological phase is stabilized by time-reversal symmetry
and it is identified as a Haldane phase. We confirm our conclusions further by
analyzing the entanglement spectrum. In addition, we find four conventional
phases: a Mott insulating phase with no long range order, a ferromagnetic
superfluid phase, a ferromagnetic insulating phase and a density-wave phase.",1510.04554v2
2015-10-22,The energy level crossing behavior and quantum Fisher information in a quantum well with spin-orbit coupling,"We study the energy level crossing behavior in two-dimensional quantum well
with the Rashba and Dresselhaus spin-orbit couplings (SOCs). By mapping the SOC
Hamiltonian onto an anisotropic Rabi model, we obtain the approximate ground
state and its quantum Fisher information (QFI) via performing a unitary
transformation. We find that the energy level crossing can occur in the quantum
well system within the available parameters rather than in cavity and circuit
quantum eletrodynamics systems. Futhermore, the influence of two kinds of SOCs
on the QFI is investigated and an intuitive explanation from the viewpoint of
the stationary perturbation theory is given.",1510.06491v1
2015-10-22,Quantum capacitance in monolayers of silicene and related buckled materials,"Silicene and related buckled materials are distinct from both the
conventional two dimensional electron gas and the famous graphene due to strong
spin orbit coupling and the buckled structure. These materials have potential
to overcome limitations encountered for graphene, in particular the zero band
gap and weak spin orbit coupling. We present a theoretical realization of
quantum capacitance which has advantages over the scattering problems of
traditional transport measurements. We derive and discuss quantum capacitance
as a function of the Fermi energy and temperature taking into account
electron-hole puddles through a Gaussian broadening distribution. Our predicted
results are very exciting and pave the way for future spintronic and
valleytronic devices.",1510.06614v1
2016-01-06,Valley detection using a graphene gradual pn junction with spin-orbit coupling: an analytical conductance calculation,"Graphene pn junction is the brick to build up variety of graphene
nano-structures. The analytical formula of the conductance of graphene gradual
pn junctions in the whole bipolar region has been absent up to now. In this
paper, we analytically calculated that pn conductance with the spin-orbit
coupling and stagger potential taken into account. Our analytical expression
indicates that the energy gap causes the conductance to drop a constant value
with respect to that without gap in a certain parameter region, and manifests
that the curve of the conductance versus the stagger potential consists of two
Gaussian peaks -- one valley contributes one peak. The latter feature allows
one to detect the valley polarization without using double-interface resonant
devices.",1601.01275v1
2016-01-15,Topological Superfluidity of Spin-Orbit Coupled Bilayer Fermi Gases,"Topological superfluid, new quantum matter that possesses gapless exotic
excitations known as Majorana fermions, has attracted extensive attention
recently. These excitations, which can encode topological qubits, could be
crucial ingredients for fault-tolerant quantum computation. However, creating
and manipulating multiple Majorana fermions remain an ongoing challenge.
Loading a topologically protected system in multi-layer structures would be a
natural and simple way to achieve this goal. Here we investigate the system of
bilayer Fermi gases with spin-orbit coupling and show that the topological
condition is significantly influenced by the inter-layer tunneling, yielding
two novel topological phases, which support more Majorana Fermions. We
demonstrate the existence of such novel topological phases and associated
multiple Majorana fermions using bilayer Fermi gases trapped inside a harmonic
potential. This research pave a new way for generating multiple Majorana
fermions and would be a significant step towards topological quantum
computation.",1601.03914v1
2016-02-07,"Electronic structures of transition metal dipnictides $XPn_2$ ($X$=Ta, Nb; $Pn$=P, As, Sb)","The electronic structures and topological properties of transition metal
dipnictides $XPn_2$ ($X$=Ta, Nb; $Pn$=P, As, Sb) have been systematically
studied using first-principles calculations. In addition to small bulk Fermi
surfaces, the band anticrossing features near the Fermi level can be identified
from band structures without spin-orbit coupling, leading to nodal lines in all
these compounds. Inclusion of spin-orbit coupling gaps out these nodal lines
leaving only a pair of disentangled electron/hole bands crossing the Fermi
level. Therefore, the low energy physics can be in general captured by the
corresponding two band model with several isolated small Fermi pockets.
Detailed analysis of the Fermi surfaces suggests that the arsenides and
NbSb$_2$ are nearly compensated semimetals while the phosphorides and TaSb$_2$
are not. Based on the calculated band parities, the electron and hole bands are
found to be weakly topological non-trivial giving rise to surface states. As an
example, we presented the surface-direction-dependent band structure of the
surfaces states in TaSb$_2$.",1602.02344v2
2016-02-22,Giant Optical Polarization Rotation Induced by Spin-Orbit Coupling in Polarons,"We have uncovered a giant gyrotropic magneto-optical response for doped
ferromagnetic manganite La2/3Ca1/3MnO3 around the near room-temperature
paramagnetic-to-ferromagnetic transition. At odds with current wisdom, where
this response is usually assumed to be fundamentally fixed by the electronic
band structure, we point to the presence of small polarons as the driving force
for this unexpected phenomenon. We explain the observed properties by the
intricate interplay of mobility, Jahn-Teller effect and spin-orbit coupling of
small polarons. As magnetic polarons are ubiquitously inherent to many strongly
correlated systems, our results provide an original, general pathway towards
the generation of gigantic gyrotropic responses that can be harnessed for
nonreciprocal devices that exploit the polarization of light.",1602.06875v1
2016-06-03,Superconductivity in FeSe thin films driven by the interplay between nematic fluctuations and spin-orbit coupling,"The origin of the high-temperature superconducting state observed in FeSe
thin films, whose phase diagram displays no sign of magnetic order, remains a
hotly debated topic. Here we investigate whether fluctuations arising due to
the proximity to a nematic phase, which is observed in the phase diagram of
this material, can promote superconductivity. We find that nematic fluctuations
alone promote a highly degenerate pairing state, in which both $s$-wave and
$d$-wave symmetries are equally favored, and $T_{c}$ is consequently
suppressed. However, the presence of a sizable spin-orbit coupling or inversion
symmetry-breaking at the film interface lifts this harmful degeneracy and
selects the $s$-wave state, in agreement with recent experimental proposals.
The resulting gap function displays a weak anisotropy, which agrees with
experiments in monolayer FeSe and intercalated Li$_{1-x}$(OH)$_{x}$FeSe.",1606.01170v2
2016-06-27,Superfluidity in the absence of kinetics in spin-orbit-coupled optical lattices,"At low temperatures bosons typically condense to minimize their
single-particle kinetic energy while interactions stabilize superfluidity.
Optical lattices with artificial spin-orbit coupling challenge this paradigm
because here kinetic energy can be quenched in an extreme regime where the
single-particle band flattens. To probe the fate of superfluidity in the
absence of kinetics we construct and numerically solve interaction-only
tight-binding models in flat bands. We find that novel superfluid states arise
entirely from interactions operating in quenched kinetic energy bands, thus
revealing a distinct and unexpected condensation mechanism. Our results have
important implications for the identification of quantum condensed phases of
ultracold bosons beyond conventional paradigms.",1606.08439v2
2016-06-30,Stability of Emergent Kinetics in Optical Lattices with Artificial Spin-Orbit Coupling,"Artificial spin-orbit coupling in optical lattices can be engineered to tune
band structure into extreme regimes where the single-particle band flattens
leaving only inter-particle interactions to define many-body states of matter.
Lin et al. [Phys. Rev. Lett 112, 110404 (2014)] showed that under such
conditions interactions lead to a Wigner crystal of fermionic atoms under
approximate conditions: no bandwidth or band mixing. The excitations were shown
to possess emergent kinetics with fractionalized charge derived entirely from
interactions. In this work we use numerical exact diagonalization to study a
more realistic model with non-zero bandwidth and band mixing. We map out the
stability phase diagram of the Wigner crystal. We find that emergent properties
of the Wigner crystal excitations remain stable for realistic experimental
parameters. Our results validate the approximations made by Lin et al. and
define parameter regimes where strong interaction effects generate emergent
kinetics in optical lattices.",1607.00001v2
2016-07-15,Tunable spin-orbit coupling and symmetry-protected edge states in graphene/WS$_2$,"We demonstrate clear weak anti-localization (WAL) effect arising from induced
Rashba spin-orbit coupling (SOC) in WS$_2$-covered single-layer and bilayer
graphene devices. Contrary to the uncovered region of a shared single-layer
graphene flake, WAL in WS$_2$-covered graphene occurs over a wide range of
carrier densities on both electron and hole sides. At high carrier densities,
we estimate the Rashba SOC relaxation rate to be $\sim 0.2 \rm{ps}^{-1}$ and
show that it can be tuned by transverse electric fields. In addition to the
Rashba SOC, we also predict the existence of a `valley-Zeeman' SOC from
first-principles calculations. The interplay between these two SOC's can open a
non-topological but interesting gap in graphene; in particular, zigzag
boundaries host four sub-gap edge states protected by time-reversal and
crystalline symmetries. The graphene/WS$_2$ system provides a possible platform
for these novel edge states.",1607.04647v1
2016-07-24,Harmonic trap resonance enhanced synthetic atomic spin-orbit coupling,"Spin-orbit coupling (SOC) plays an essential role in many exotic and
interesting phenomena in condensed matter physics. In neutral-atom-based
quantum simulations, synthetic SOC constitutes a key enabling element. The
strength of SOC realized so far is limited by various reasons or constraints.
This work reports tunable SOC synthesized with a gradient magnetic field (GMF)
for atoms in a harmonic trap. Nearly ten-fold enhancement is observed when the
GMF is modulated near the harmonic-trap resonance in comparison with free-space
atoms. A theory is developed that well explains the experimental results. Our
work offers a clear physical insight into and analytical understanding of how
to tune the strength of atomic SOC synthesized with GMF using harmonic trap
resonance.",1607.07005v1
2016-07-27,Isothermal anisotropic magnetoresistance in antiferromagnetic metallic IrMn,"Antiferromagnetic spintronics is an emerging field; antiferromagnets can
improve the functionalities of ferromagnets with higher response times, and
having the information shielded against external magnetic field. Moreover, a
large list of aniferromagnetic semiconductors and metals with N\'eel
temperatures above room temperature exists. In the present manuscript, we
persevere in the quest for the limits of how large can anisotropic
magnetoresistance be in antiferromagnetic materials with very large spin-orbit
coupling. We selected IrMn as a prime example of first-class moment (Mn) and
spin-orbit (Ir) combination. Isothermal magnetotransport measurements in an
antiferromagnetic-metal(IrMn)/ferromagnetic-insulator thin film bilayer have
been performed. The metal/insulator structure with magnetic coupling between
both layers allows the measurement of the modulation of the transport
properties exclusively in the antiferromagnetic layer. Anisotropic
magnetoresistance as large as 0.15 % has been found, which is much larger than
that for a bare IrMn layer. Interestingly, it has been observed that
anisotropic magnetoresistance is strongly influenced by the field cooling
conditions, signaling the dependence of the found response on the formation of
domains at the magnetic ordering temperature.",1607.07999v1
2016-09-07,Emerging magnetism and anomalous Hall effect in iridate-manganite heterostructures,"Strong Coulomb repulsion and spin-orbit coupling are known to give rise to
exotic physical phenomena in transition metal oxides. Initial attempts to
investigate systems where both of these fundamental interactions are comparably
strong, such as 3d and 5d complex oxide superlattices, have revealed properties
that only slightly differ from the bulk ones of the constituent materials.
Here, we observe that the interfacial coupling between the 3d antiferromagnetic
insulator SrMnO3 and the 5d paramagnetic metal SrIrO3 is enormously strong,
yielding an anomalous Hall response as the result of charge transfer driven
interfacial ferromagnetism. These findings show that low dimensional spin-orbit
entangled 3d-5d interfaces provide an avenue to uncover technologically
relevant physical phenomena unattainable in bulk materials.",1609.01973v1
2016-09-30,Nonlinear localized flatband modes with spin-orbit coupling,"We report the coexistence and properties of stable compact localized states
(CLSs) and discrete solitons (DSs) for nonlinear spinor waves on a flatband
network with spin-orbit coupling (SOC). The system can be implemented by means
of a binary Bose-Einstein condensate loaded in the corresponding optical
lattice. In the linear limit, the SOC opens a minigap between flat and
dispersive bands in the system's bandgap structure, and preserves the existence
of CLSs at the flatband frequency, simultaneously lowering their symmetry.
Adding onsite cubic nonlinearity, the CLSs persist and remain available in an
exact analytical form, with frequencies which are smoothly tuned into the
minigap. Inside of the minigap, the CLS and DS families are stable in narrow
areas adjacent to the FB. Deep inside the semi-infinite gap, both the CLSs and
DSs are stable too.",1609.09640v1
2017-02-08,"Quantum oscillation studies of topological semimetal candidate ZrGeM (M=S, Se, Te)","The WHM - type materials (W=Zr/Hf/La, H=Si/Ge/Sn/Sb, M=O/S/Se/Te) have been
predicted to be a large pool of topological materials. These materials allow
for fine tuning of spin-orbit coupling, lattice constant and structural
dimensionality for various combinations of W, H and M elements, thus providing
an excellent platform to study how these parameters' tuning affect topological
semimetal state. In this work, we report the high field quantum oscillation
studies on ZrGeM (M=S, Se, and Te). We have found the first experimental
evidence for their theoretically-predicted topological semimetal states. From
the angular dependence of quantum oscillation frequency, we have also studied
the Fermi surface topologies of these materials. Moreover, we have compared
Dirac electron behavior between the ZrGeM and ZrSiM systems, which reveals deep
insights to the tuning of Dirac state by spin-orbit coupling and lattice
constants in the WHM systems.",1702.02292v2
2017-08-15,"Emergence of Topological Nodal Lines and Type II Weyl Nodes in Strong Spin--Orbit Coupling System InNbX2(X=S,Se)","Using first--principles density functional calculations, we systematically
investigate electronic structures and topological properties of InNbX2 (X=S,
Se). In the absence of spin--orbit coupling (SOC), both compounds show nodal
lines protected by mirror symmetry. Including SOC, the Dirac rings in InNbS2
split into two Weyl rings. This unique property is distinguished from other
dicovered nodal line materials which normally requires the absence of SOC. On
the other hand, SOC breaks the nodal lines in InNbSe2 and the compound becomes
a type II Weyl semimetal with 12 Weyl points in the Brillouin Zone. Using a
supercell slab calculation we study the dispersion of Fermi arcs surface states
in InNbSe2, we also utilize a coherent potential approximation to probe their
tolernace to the surface disorder effects. The quasi two--dimensionality and
the absence of toxic elements makes these two compounds an ideal experimental
platform for investigating novel properties of topological semimetals.",1708.04556v1
2018-02-01,Retrieving the Size of Deep-subwavelength Objects via Tunable Optical Spin-Orbit Coupling,"We propose a scheme to retrieve the size parameters of a nano-particle on a
glass substrate at a scale much smaller than the wavelength. This is achieved
by illuminating the particle using two plane waves to create rich and
non-trivial local polarization distributions, and observing the far-field
scattering pattern into the substrate. A simple dipole model which exploits
tunneling effect of evanescent field into regions beyond the critical angle, as
well as directional scattering due to spin-orbit coupling is developed, to
relate the particle's shape, size and position to the far-field scattering with
remarkable sensitivity. Our method brings about a far-field super-resolution
imaging scheme based on the interaction of vectorial light with nanoparticles.",1802.00268v1
2018-02-26,Transport Properties of Near Surface InAs Two-dimensional Heterostructures,"Two-dimensional electron systems (2DESs) confined to the surface of
narrowband semiconductors have attracted great interest since they can easily
integrate with superconductivity (or ferromagnetism) enabling new possibilities
in hybrid device architectures and study of exotic states in proximity of
superconductors. In this work, we study indium arsenide heterostructures where
combination of clean interface with superconductivity, high mobility and
spin-orbit coupling can be achieved. The weak antilocalization measurements
indicate presence of strong spin-orbit coupling at high densities. We study the
magnetotransport as a function of top barrier and density and report clear
observation of integer quantum Hall states. We report improved electron
mobility reaching up to 44,000 cm$^{2}$/Vs in undoped heterstructures and well
developed integer quantum Hall states starting as low as 2.5~T.",1802.09569v3
2018-04-04,Magnetic properties of isolated Re ion and Re-Re complex in ZnO studied by GGA +U approach,"Magnetic properties of Re substituting for the divalent Zn ions and impurity
pairs in wurtzite and zinc blende ZnO are analyzed by employing the Generalized
Gradient Approximation with the +U corrections. The +U term applied to d(Zn),
p(O), and d(Re) orbitals stabilizes spin polarization of Re. Re impurity
introduces a defect level located in the band gap, and Re2+ generates the local
spin 5/2 in both wurtzite and zinc blende structures. Magnetic coupling of
Re-Re pairs as a function of distance between the defects, their relative
orientation, and the charge state was calculated. All magnetic coupling between
impurities is antiferromagnetic and due to an intermediate O atom via strong
d(Re)-p(O) hybridization between Re and O states. The defect states and
magnetic moments come from d(Re) with a contribution of p(O) orbitals of the O
nearest neighbors of Re. The results show that the Re-doped wurtzite ZnO may be
a new type of magneto-optical materials with a great promise.",1804.01332v1
2018-04-16,Gauge-potential-induced rotation of spin-orbit-coupled Bose-Einstein condensates,"We demonstrate that a spin-orbit-coupled Bose-Einstein condensate can be
effectively rotated by adding a real magnetic field to inputting gauge angular
momentum, which is distinctly different from the traditional ways of rotation
by stirring or Raman laser dressing to inputting canonical angular momentum.
The gauge angular momentum is accompanied by the spontaneous generation of
equal and opposite canonical angular momentum in the ground states, and it
leads to the nucleation of quantized vortices. We explain this by indicating
that the effective rotation with the vortex nucleation results from the
effective magnetic flux induced by the gauge potential, which is essentially
different from the previous scheme of creating vortices by synthetic magnetic
fields. In the weakly interacting regime, symmetrically placed domains
separated by vortex lines as well as half-integer giant vortices are
discovered. With relatively strong interatomic interaction, we predict a
structure of coaxially arranged annular vortex arrays, which is in stark
contrast to the familiar Abrikosov vortex lattice. The developed way of
rotation may be extended to a more general gauge system.",1804.05700v3
2018-11-14,Majorana lattices from the quantized Hall limit of a proximitized spin-orbit coupled electron gas,"Motivated by recent experiments demonstrating intricate quantum Hall physics
on the surface of elemental bismuth, we consider proximity coupling an $s$-wave
superconductor to a two-dimensional electron gas with strong Rashba spin-orbit
interactions in the presence of a strong perpendicular magnetic field. We focus
on the high-field limit so that the superconductivity can be treated as a
perturbation to the low-lying Landau levels. In the clean case, wherein the
superconducting order parameter takes the form of an Abrikosov vortex lattice,
we show that a lattice of hybridized Majorana modes emerges near the plateau
transition of the lowest Landau level. However, unless
magnetic-symmetry-violating perturbations are present, the system always has an
even number of chiral Majorana edge modes and thus is strictly speaking Abelian
in nature, in agreement with previous work on related setups. Interestingly,
however, a weak topological superconducting phase can very naturally be
stabilized near the plateau transition for the square vortex lattice. The
relevance of our findings to potential near-term experiments on proximitized
materials such as bismuth will be discussed.",1811.05990v1
2020-07-01,Emulation of Astrocyte Induced Neural Phase Synchrony in Spin-Orbit Torque Oscillator Neurons,"Astrocytes play a central role in inducing concerted phase synchronized
neural-wave patterns inside the brain. In this article, we demonstrate that
injected radio-frequency signal in underlying heavy metal layer of spin-orbit
torque oscillator neurons mimic the neuron phase synchronization effect
realized by glial cells. Potential application of such phase coupling effects
is illustrated in the context of a temporal ""binding problem"". We also present
the design of a coupled neuron-synapse-astrocyte network enabled by compact
neuromimetic devices by combining the concepts of local spike-timing dependent
plasticity and astrocyte induced neural phase synchrony.",2007.00776v6
2020-07-10,Exotic Vortex States with Discrete Rotational Symmetry in Atomic Fermi Gases with Spin-Orbital-Angular-Momentum Coupling,"We investigate the superfluidity of a two-component Fermi gas with
spin-orbital-angular-momentum coupling (SOAMC). Due to the intricate interplay
of SOAMC, two-photon detuning and atom-atom interaction, a family of vortex
ground states emerge in a broad parameter regime of the phase diagram, in
contrast to the usual case where an external rotation or magnetic field is
generally required. More strikingly, an unprecedented vortex state, which
breaks the continuous rotational symmetry to a discrete one spontaneously, is
predicted to occur. The underlying physics are elucidated and verified by
numerical simulations. The unique density distributions of the predicted vortex
states enable a direct observation in experiment.",2007.05560v1
2020-07-14,Non-linear transport without spin-orbit coupling or warping in two-dimensional Dirac semimetals,"It has recently been realized that the first-order moment of the Berry
curvature, namely the Berry curvature dipole (BCD) can give rise to non-linear
current in a wide variety of time-reversal invariant and non-centrosymmetric
materials. While the BCD in two-dimensional Dirac systems is known to be finite
only in the presence of either substantial spin-orbit coupling where low-energy
Dirac quasiparticles form tilted cones or higher order warping of the Fermi
surface, we argue that the low-energy Dirac quasiparticles arising from the
merging of a pair of Dirac points without any tilt or warping of the Fermi
surface can lead to a non-zero BCD. Remarkably, in such systems, the BCD is
found to be independent of Dirac velocity as opposed to the Dirac dispersion
with a tilt or warping effects. We further show that the proposed systems can
naturally host helicity-dependent photocurrent due to their linear
momentum-dependent Berry curvatures. Finally, we discuss an important byproduct
of this work, i.e., nonlinear anomalous Nernst effect as a second-order thermal
response.",2007.07274v2
2013-08-09,Majorana Fermions on Zigzag Edge of Monolayer Transition Metal Dichalcogenides,"Majorana fermions, quantum particles with non-Abelian exchange statistics,
are not only of fundamental importance, but also building blocks for
fault-tolerant quantum computation. Although certain experimental breakthroughs
for observing Majorana fermions have been made recently, their conclusive
dection is still challenging due to the lack of proper material properties of
the underlined experimental systems. Here we propose a new platform for
Majorana fermions based on edge states of certain non-topological
two-dimensional semiconductors with strong spin-orbit coupling, such as
monolayer group-VI transition metal dichalcogenides (TMD). Using
first-principles calculations and tight-binding modeling, we show that zigzag
edges of monolayer TMD can host well isolated single edge band with strong
spin-orbit coupling energy. Combining with proximity induced s-wave
superconductivity and in-plane magnetic fields, the zigzag edge supports robust
topological Majorana bound states at the edge ends, although the
two-dimensional bulk itself is non-topological. Our findings points to a
controllable and integrable platform for searching and manipulating Majorana
fermions.",1308.2032v1
2014-03-02,Shaping topological properties of the band structures in a shaken optical lattice,"To realize band structures with non-trivial topological properties in an
optical lattice is an exciting topic in current studies on ultra cold atoms.
Here we point out that this lofty goal can be achieved by using a simple scheme
of shaking an optical lattice, which is directly applicable in current
experiments. The photon-assistant band hybridization leads to the production of
an effective spin-orbit coupling, in which the band index represents the
pseudospin. When this spin-orbit coupling has finite strengths along multiple
directions, non-trivial topological structures emerge in the Brillouin zone,
such as topological defects with a winding number 1 or 2 in a shaken square
lattice. The shaken lattice also allows one to study the transition between two
band structures with distinct topological properties.",1403.0210v2
2014-03-05,Superfluid Breakdown and Multiple Roton Gaps in Spin-Orbit Coupled Bose-Einstein Condensates on an Optical Lattice,"We investigate the superfluid phases of a Rashba spin-orbit coupled
Bose-Einstein condensate residing on a two dimensional square optical lattice
in the presence of an effective Zeeman field $\Omega$. At a critical value
$\Omega=\Omega_c$, the single-particle spectrum $ E_k $ changes from having a
set of four degenerate minima to a single minimum at $k=0$, corresponding to
condensation at finite or zero momentum, respectively. We describe this quantum
phase transition and the symmetry breaking of the condensate phases. We use the
Bogoliubov theory to treat the superfluid phases and determine the phase
diagram, the excitation spectrum and the sound velocity of the phonon
excitations. A novel dynamically unstable superfluid regime occurring when
$\Omega$ is close to $\Omega_c$ is analytically identified and the behavior of
the condensate quantum depletion is discussed. Moreover, we show that there are
two types of roton excitations occurring in the $\Omega<\Omega_c$ regime and
obtain explicit values for the corresponding energy gaps.",1403.1267v2
2014-03-18,Tunneling-assisted Spin-orbit Coupling in Bilayer Bose-Einstein Condensates,"Motivated by a goal of realizing spin-orbit coupling (SOC) beyond
one-dimension (1D), we propose and analyze a method to generate an effective 2D
SOC in bilayer BECs with laser-assisted inter-layer tunneling. We show that an
interplay between the inter-layer tunneling, SOC and intra-layer atomic
interaction can give rise to diverse ground state configurations. In
particular, the system undergoes a transition to a new type of stripe phase
which spontaneously breaks the time-reversal symmetry. Different from the
ordinary Rashba-type SOC, a fractionalized skyrmion lattice emerges
spontaneously in the bilayer system without external traps. Furthermore, we
predict the occurrence of a tetracritical point in the phase diagram of the
bilayer BECs, where four different phases merge together. The origin of the
emerging different phases is elucidated.",1403.4338v2
2016-11-23,"Electron interactions, spin-orbit coupling, intersite correlations in pyrochlore iridates","We perform combined density functional and dynamical mean-field calculations
to study the pyrochlore iridates Lu$_2$Ir$_2$O$_7$, Y$_2$Ir$_2$O$_7$ and
Eu$_2$Ir$_2$O$_7$. Both single-site and cluster dynamical mean-field
calculations are performed and spin-orbit coupling is included. Paramagnetic
metallic phases, antiferromagnetic metallic phases with tilted Weyl cones and
antiferromagnetic insulating phases are found. The magnetic phases display
all-in/all-out magnetic ordering, consistent with previous studies. Unusually
for electronically three dimensional materials, the single-site dynamical
mean-field approximation fails to reproduce qualitative material trends,
predicting in particular that the paramagnetic phase properties of
Y$_2$Ir$_2$O$_7$ and Eu$_2$Ir$_2$O$_7$ are almost identical, although in
experiments the Y compound has a much higher resistance than the Eu compound.
This qualitative failure is attributed to the importance of intersite magnetic
correlations in the physics of these materials.",1611.07997v2
2017-01-14,Multichannel Molecular State and Rectified Short-range Boundary Condition for Spin-orbit Coupled Ultracold Fermions Near p-wave Resonances,"We study the interplay of spin-orbit coupling (SOC) and strong p-wave
interaction to the scattering property of spin-1/2 ultracold Fermi gases. Based
on a two-channel square-well potential generating p-wave resonance, we show
that the presence of an isotropic SOC, even for its length much longer than the
potential range, can greatly modify the p-wave short-range boundary
condition(BC). As a result, the conventional p-wave BC cannot predict the
induced molecules near p-wave resonance, which can be fully destroyed to vanish
due to strong interference between s- and p-wave channels. By analyzing the
intrinsic reasons for the breakdown of conventional BC, we propose a new p-wave
BC that can excellently reproduce the exact molecule solutions and also equally
apply for a wide class of single-particle potentials besides SOC. This work
reveals the significant effect of SOC to both the short- and long-range
properties of fermions near p-wave resonance, paving the way for future
exploring interesting few- and many-body physics in such system.",1701.03857v2
2017-01-17,Disorder robustness and protection of Majorana bound states in ferromagnetic chains on conventional superconductors,"Majorana bound states (MBS) are well-established in the clean limit in chains
of ferromagnetically aligned impurities deposited on conventional
superconductors with finite spin-orbit coupling. Here we show that these MBS
are very robust against disorder. By performing self-consistent calculations we
find that the MBS are protected as long as the surrounding superconductor show
no large signs of inhomogeneity. We find that longer chains offer more
stability against disorder for the MBS, albeit the minigap decreases, as do
increasing strengths of spin-orbit coupling and superconductivity.",1701.04670v2
2018-05-10,Interplay of Floquet Lifshitz transitions and topological transitions in bilayer Dirac materials,"We show how transitions between different Lifshitz phases in bilayer Dirac
materials with and without spin-orbit coupling can be studied by driving the
system. The periodic driving is induced by a laser and the resultant phase
diagram is studied in the high frequency limit using the Brillouin-Wigner
perturbation approach to leading order. The examples of such materials include
bilayer graphene and spin-orbit coupled materials such as bilayer silicene. The
phase diagrams of the effective static models are analyzed to understand the
interplay of topological phase transitions, with changes in the Chern number
and topological Lifshitz transitions, with the ensuing changes in the Fermi
surface. Both the topological transitions and the Lifshitz transitions are
tuned by the amplitude of the drive.",1805.04125v1
2011-11-08,Probing Majorana fermions in spin-orbit coupled atomic Fermi gases,"We examine theoretically the visualization of Majorana fermions in a
two-dimensional trapped ultracold atomic Fermi gas with spin-orbit coupling. By
increasing an external Zeeman field, the trapped gas transits from
non-topological to topological superfluid, via a mixed phase in which both
types of superfluids coexist. We show that the zero-energy Majorana fermion,
supported by the topological superfluid and localized at the vortex core, is
clearly visible through (i) the core density and (ii) the local density of
states, which are readily measurable in experiment. We present a realistic
estimate on experimental parameters for ultracold $^{40}$K atoms.",1111.1798v2
2011-11-28,Noncollinear magnetism and spin-orbit coupling in 5d pyrochlore oxide Cd2Os2O7,"We investigated the electronic and magnetic properties of the pyrochlore
oxide Cd$_2$Os$_2$O$_7$ using the density-functional theory plus on-site
repulsion ($U$) method, and depict the ground-state phase diagram with respect
to $U$. We conclude that the all-in/all-out non-collinear magnetic order is
stable in a wide range of $U$. We also show that the easy-axis anisotropy
arising from the spin-orbit (SO) coupling plays a significant role in
stabilizing the all-in/all-out magnetic order. A \textit{pseudo gap} was
observed near the transition between the antiferromagnetic metallic and
insulating phases. Finally, we discuss possible origins of the peculiar
low-temperature($T$) properties observed in experiments.",1111.6347v2
2011-11-28,Topological invariants for spin-orbit coupled superconductor nanowires,"We show that a spin-orbit coupled semiconductor nanowire with Zeeman
splitting and s-wave superconductivity is in symmetry class BDI (not D as is
commonly thought) of the topological classification of band Hamiltonians. The
class BDI allows for an integer Z topological invariant equal to the number of
Majorana fermion (MF) modes at each end of the quantum wire protected by the
chirality symmetry (reality of the Hamiltonian). Thus it is possible for this
system (and all other d=1 models related to it by symmetry) to have an
arbitrary integer number, not just 0 or 1 as is commonly assumed, of MFs
localized at each end of the wire. The integer counting the number of MFs at
each end reduces to 0 or 1, and the class BDI reduces to D, in the presence of
terms in the Hamiltonian that break the chirality symmetry.",1111.6592v2
2012-01-10,Topological Superconductivity and Majorana Fermions in Metallic Surface-States,"Heavy metals, such as Au, Ag, and Pb, often have sharp surface states that
are split by strong Rashba spin-orbit coupling. The strong spin-orbit coupling
and two-dimensional nature of these surface states make them ideal platforms
for realizing topological superconductivity and Majorana fermions. In this
paper, we further develop a proposal to realize Majorana fermions at the ends
of quasi-one-dimensional metallic wires. We show how superconductivity can be
induced on the metallic surface states by a combination of proximity effect,
disorder, and interactions. Applying a magnetic field along the wire can drive
the wire into a topologically non-trivial state with Majorana end-states.
Unlike the case of a perpendicular field, where the chemical potential must be
fined tuned near the Rashba-band crossing, the parallel field allows one to
realize Majoranas for arbitrarily large chemical potential. We then show that,
despite the presence of a large carrier density from the bulk metal, it is
still possible to effectively control the chemical potential of the surface
states by gating. The simplest version of our proposal, which involves only an
Au(111) film deposited on a conventional superconductor, should be readily
realizable.",1201.2176v1
2012-04-29,Molecule and polaron in a highly polarized two-dimensional Fermi gas with spin-orbit coupling,"We show that spin-orbit coupling (SOC) gives rise to pairing instability in a
highly polarized two-dimensional Fermi gas for arbitrary interaction strength.
The pairing instability can lead to a Fulde-Ferrell-Larkin-Ovchinnikov-like
molecular state, which undergoes a first-order transition into a pairing state
with zero center-of-mass momentum as the parameters are tuned. These pairing
states are metastable against a polaron state dressed by particle-hole
fluctuations for small SOC. At large SOC, a polaron-molecule transition exists,
which suggests a phase transition between the topological superfluid state and
the normal state for a highly polarized Fermi gas in the thermodynamic limit.
As polarization in a Fermi gas with SOC is induced by the effective Zeeman
field, we also discuss the influences of the effective Zeeman field on the
ground state of the system. Our findings may be tested directly in future
experiments.",1204.6476v4
2012-04-30,Striped states in weakly trapped ultracold Bose gases with Rashba spin-orbit coupling,"The striped state of ultracold bosons with Rashba spin-orbit coupling in a
homogeneous infinite system has, as we show, a constant particle flow, which in
a finite-size system would accumulate particles at the boundaries; it is thus
not a physical steady state of the system. We propose, as a variational ansatz,
a condensate wave function for a weakly trapped system which behaves similarly
to the striped state near the center, but does not have particle flow at the
boundaries. This state has a line of unquantized coreless vortices. We show, by
minimizing the total energy, that our modified striped state has lower energy
than the conventional striped state and it is thus a physically appropriate
starting point to analyze striped states in finite systems.",1204.6534v3
2013-09-03,The plasma oscillations in a two-dimensional electron-hole liquid under influence Rashba spin-orbit coupling,"The plasma oscillations of the two-dimensional electron-hole system in the
presence of a Rashba spin-orbit coupling are studied. Only the intra-Landau
level excitations are taken into account when the electrons and holes are
situated on their lowest Landau levels, the filling factor $v^{2}$ being less
than 1. The ground state of the two-dimensional electron-hole system is
supposed to be the electron-hole liquid. The dispersion relations for the
optical and acoustical plasmon modes were obtained. The acoustical plasmon
branch has a linear dispersion law in the range of small wave vectors and
monotonically increases with saturation at higher values of wave vectors. The
optical plasmon branch has a quadratic dependence in the range of long
wavelength and a monotonic increasing with saturation as in the case of
acoustical branch.",1309.0716v1
2013-09-11,Majorana bound states in two-channel time-reversal-symmetric nanowire systems,"We consider time-reversal-symmetric two-channel semiconducting quantum wires
proximity coupled to an s-wave superconductor. We analyze the requirements for
a nontrivial topological phase and find that necessary conditions are 1) the
determinant of the pairing matrix in channel space must be negative, 2)
inversion symmetry must be broken, and 3) the two channels must have different
spin-orbit couplings. The first condition can be implemented in semiconducting
nanowire systems where interactions suppress intra-channel pairing, while the
inversion symmetry can be broken by tuning the chemical potentials of the
channels. For the case of collinear spin-orbit directions, we find a general
expression for the topological invariant by block diagonalization into two
blocks with chiral symmetry only. By projection to the low-energy sector, we
solve for the zero modes explicitly and study the details of the gap closing,
which in the general case happens at finite momenta.",1309.2808v3
2014-06-22,"Landau quantization, Rashba spin-orbit coupling and Zeeman splitting of two-dimensional heavy holes","The origin of the g-factor of the two-dimensional (2D) electrons and holes
moving in the periodic crystal lattice potential with the perpendicular
magnetic and electric fields is discussed. The Pauli equation describing the
Landau quantization accompanied by the Rashba spin-orbit coupling (RSOC) and
Zeeman splitting (ZS) for 2D heavy holes with nonparabolic dispersion law is
solved exactly. The solutions have the form of the pairs of the Landau
quantization levels due to the spinor-type wave functions. The energy levels
depend on amplitudes of the magnetic and electric fields, on the g-factor
{g-h}, and on the parameter of nonparabolicity C. The dependences of two energy
levels in any pair on the Zeeman parameter {Z_h}={g_h}{m_h}/4{m_0}, where {m_h}
is the hole effective mass, are nonmonotonous and without intersections. The
smallest distance between them at C=0 takes place at the value {Z_h}=n/2, where
n is the order of the chirality terms determined by the RSOC and is the same
for any quantum number of the Landau quantization.",1406.5697v2
2014-06-25,Magnetic structure of GdBiPt: A candidate antiferromagnetic topological insulator,"A topological insulator is a state of matter which does not break any
symmetry and is characterized by topological invariants, the integer
expectation values of non-local operators. Antiferromagnetism on the other hand
is a broken symmetry state in which the translation symmetry is reduced and
time reversal symmetry is broken. Can these two phenomena coexist in the same
material? A proposal by Mong {\it et al.}\cite{Mong2010} asserts that the
answer is yes. Moreover, it is theoretically possible that the onset of
antiferromagnetism enables the non-trivial topology since it may create
spin-orbit coupling effects which are absent in the non-magnetic phase. The
current work examines a real system, half-Heusler GdBiPt, as a candidate for
topological anti ferromagnetism. We find that the magnetic moments of the
gadolinium atoms form ferromagnetic sheets which are stacked
antiferromagnetically along the body diagonal. This magnetic structure may
induce spin orbit coupling on band electrons as they hop perpendicular to the
ferromagnetic sheets.",1406.6663v1
2014-06-25,Tilting of the magnetic field in Majorana nanowires: critical angle and zero-energy differential conductance,"Semiconductor nanowires with strong spin-orbit coupling and proximity-induced
s-wave superconductivity in an external magnetic field have been the most
promising settings for approaches towards experimental evidence of topological
Majorana zero-modes. We investigate the effect of tilting the magnetic field
relative to the spin-orbit coupling direction in a simple continuum model and
provide an analytical derivation of the critical angle, at which the
topological states disappear. We also obtain the differential conductance
characteristic of a junction with a normal wire for different tilting angles
and propose the qualitative change of the dependence of the zero-energy
differential conductance on the tunnel barrier strength at the critical angle
as a new criterion for establishing the topological nature of the observed
signal.",1406.6695v2
2014-06-27,Equivalence of Rashba-Hubbard and Hubbard chains,"We review the fact that U(1) gauge symmetry enables the mapping of
one-dimensional Hubbard chains with Rashba-type spin orbit coupling to
renormalized Hubbard Hamiltonians. The existence of the mapping has important
consequences for the interpretation of ARPES experiments on one-dimensional
chains subject to Rashba spin orbit coupling and can be exploited to check for
the applicability of the mapping. We show numerical applications of the mapping
and consider the implications for bosonization as well as for the
Heisenberg-limit of the Hubbard model. In addition we point out the
consequences for various generalized Hubbard models.",1406.7293v2
2015-12-13,Phase transitions and elementary excitations in spin-1 Bose gases with Raman-induced spin-orbit coupling,"We study the ground state phase diagram and the quantum phase transitions in
spin-1 Bose gases with Raman induced spin-orbit coupling. In addition to the
Bose-Einstein condensates with uniform density, three types of stripe
condensation phases that simultaneously break the U(1) symmetry and the
translation symmetry are identified. The transitions between these phases are
investigated, and the occurrences of the various tricritical points are
predicted. The excitation spectra in the plane-wave phase and the zero-momentum
phase show rich roton-maxon structures, and their instabilities indicate the
tendency to develop the crystalline order. We propose the atomic gas of
$^{23}$Na could be a candidate for observing the stripe condensate with high
contrast fringes.",1512.04091v2
2015-12-23,Exotic superfluid of trapped Fermi gases with spin-orbit coupling in dimensional crossover,"We have studied the exotic superfluid phases of degenerated Fermi gases with
spin-orbit coupling in a mixed dimensional system, where the motion of atoms
are free in the x-direction and the tunneling between nearest tubes in the
y-direction is permitted. Using the mean-field method, we obtain the phase
diagrams of the system during the dimensional crossover between quasi one
dimension to quasi two dimension. We find the existence of the topological
state and Majorana edge mode in the weak tunneling case, and a rich phase
diagram including two kinds of nodal superfluid phase and gapped superfluid
phase in the opposite case. Our results show that topological pairing is
favoured in quasi one dimension while nodal pairing state is favoured in quasi
two dimension.",1512.07406v2
2016-05-06,Optical-lattice-assisted magnetic phase transition in a spin-orbit-coupled Bose-Einstein condensate,"We investigate the effect of a periodic potential generated by a
one-dimensional optical lattice on the magnetic properties of an $S=1/2$
spin-orbit-coupled Bose gas. By increasing the lattice strength one can achieve
a magnetic phase transition between a polarized and an unpolarized Bloch wave
phase, characterized by a significant enhancement of the contrast of the
density fringes. If the wave vector of the periodic potential is chosen close
to the roton momentum, the transition could take place at very small lattice
intensities, revealing the strong enhancement of the response of the system to
a weak density perturbation. By solving the Gross-Pitaevskii equation in the
presence of a three-dimensional trapping potential, we shed light on the
possibility of observing the magnetic phase transition in currently available
experimental conditions.",1605.02108v2
2016-05-13,Two-Carrier Transport Induced Hall Anomaly and Large Tunable Magnetoresistance in Dirac Semimetal Cd3As2 Nanoplates,"Cd3As2 is a model material of Dirac semimetal with a linear dispersion
relation along all three directions in the momentum space. The unique band
structure of Cd3As2 makes it with both Dirac and topological properties. It can
be driven into a Weyl semimetal by the symmetry breaking or a topological
insulator by enhancing the spin-orbit coupling. Here we report the temperature
and gate voltage dependent magnetotransport properties of Cd3As2 nanoplates
with Fermi level near the Dirac point. The Hall anomaly demonstrates the
two-carrier transport accompanied by a transition from n-type to p-type
conduction with decreasing temperature. The carrier-type transition is
explained by considering the temperature dependent spin-orbit coupling. The
magnetoresistance exhibits a large non-saturating value up to 2000% at high
temperatures, which is ascribed to the electron-hole compensation in the
system. Our results are valuable for understanding the experimental
observations related to the two-carrier transport in Dirac/Weyl semimetals,
such as Na3Bi, ZrTe5, TaAs, NbAs, and HfTe5.",1605.04062v1
2016-05-16,Topological edge states in single layers of honeycomb materials with strong spin-orbit coupling,"We study possible edge states in single layers of honeycomb materials such as
$\alpha$-RuCl$_3$ and A$_2$IrO$_3$ (A=Li, Na) with strong spin-orbit coupling
(SOC). These two dimensional systems exhibit linearly dispersing
one-dimensional (1D) edge states when their 1D boundary forms a zig-zag shape.
Using an effective tight-binding model based on first principles band structure
calculations including Hubbard U and SOC, we find degenerate edge states at the
zone center and zone boundary. The roles of chiral symmetry and time-reversal
symmetry are presented. The implications to experimental signatures and the
effects of disorder are also discussed.",1605.04916v1
2016-05-26,Fermionic boundary modes in two-dimensional noncentrosymmetric superconductors,"We calculate the spectrum of the Andreev boundary modes in a two-dimensional
superconductor formed at an interface between two different non-superconducting
materials, e.g. insulating oxides. Inversion symmetry is absent in this system,
and both the electron band structure and the superconducting pairing are
strongly affected by the spin-orbit coupling of the Rashba type. We consider
isotropic s-wave pairing states, both with and without time-reversal symmetry
breaking, as well as various d-wave states. In all cases, there exist subgap
Andreev boundary states, whose properties, in particular, the number and
location of the zero-energy modes, qualitatively depend on the gap symmetry and
the spin-orbit coupling strength.",1605.08394v4
2016-08-01,Growth and engineering of perovskite SrIrO3 thin films,"5d transition-metal-based oxides display emergent phenomena due to the
competition between the relevant energy scales of the correlation, bandwidth,
and most importantly, the strong spin-orbit coupling (SOC). Starting from the
prediction of novel oxide topological insulators in bilayer ABO3 (B = 5d
elements) thin-film grown along the (111) direction, 5d-based perovskites (Pv)
form a new paradigm in the thin-film community. Here, we reviewed the
scientific accomplishments in Pv-SrIrO3 thin films, a popular candidate for
observing non-trivial topological phenomena. Although the predicted topological
phenomena are unknown, the Pv-SrIrO3 thin film shows many emergent properties
due to the delicate interplay between its various degrees of freedom. These
observations provide new physical insight and encourage further research on the
design of new 5d-based heterostructures or superlattices for the observation of
the hidden topological quantum phenomena in strong spin-orbit coupled oxides.",1608.00482v2
2016-08-12,Dynamic response functions and helical gaps in interacting Rashba nanowires with and without magnetic fields,"A partially gapped spectrum due to the application of a magnetic field is one
of the main probes of Rashba spin-orbit coupling in nanowires. Such a ""helical
gap"" manifests itself in the linear conductance, as well as in dynamic response
functions such as the spectral function, the structure factor, or the
tunnelling density of states. In this paper, we investigate theoretically the
signature of the helical gap in these observables with a particular focus on
the interplay between Rashba spin-orbit coupling and electron-electron
interactions. We show that in a quasi-one-dimensional wire, interactions can
open a helical gap even without magnetic field. We calculate the dynamic
response functions using bosonization, a renormalization group analysis, and
the exact form factors of the emerging sine-Gordon model. For special
interaction strengths, we verify our results by refermionization. We show how
the two types of helical gaps, caused by magnetic fields or interactions, can
be distinguished in experiments.",1608.03756v3
2017-06-01,Spin-orbit coupling and transport of strongly correlated two-dimensional systems,"Measuring the magnetoresistance (MR) of ultraclean {\it GaAs} two-dimensional
holes in a large $r_s$ range of 20-50, two striking behaviors in relation to
the spin-orbit coupling (SOC) emerge in response to strong electron-electron
interaction. First, in exact correspondence to the zero-field
metal-to-insulator transition (MIT), the sign of the MR switches from being
positive in the metallic regime to being negative in the insulating regime when
the carrier density crosses the critical density $p_c$ of MIT ($r_s\sim 39$).
Second, as the SOC-driven correction $\Delta\rho$ to the MR decreases with
reducing carrier density (or the in-plane wave vector), it exhibits an upturn
in the close proximity just above $p_c$ where $r_s$ is beyond 30, indicating a
substantially enhanced SOC effect. This peculiar behavior echoes with a trend
of delocalization long suspected for the SOC-interaction interplay. Meanwhile,
for $p<p_c$ or $r_s>40$, in contrast to the common belief that a magnet field
enhances Wigner crystallization, the negative MR is likely linked to enhanced
interaction.",1706.00297v1
2017-06-29,Dimensionality-driven metal-insulator-transition in spin-orbit coupled SrIrO$_3$,"Upon reduction of the film thickness we observe a metal-insulator transition
in epitaxially stabilized, spin-orbit coupled SrIrO$_3$ ultrathin films. By
comparison of the experimental electronic dispersions with density functional
theory at various levels of complexity we identify the leading microscopic
mechanisms, i.e., a dimensionality-induced re-adjustment of octahedral
rotations, magnetism, and electronic correlations. The astonishing resemblance
of the band structure in the two-dimensional limit to that of bulk
Sr$_2$IrO$_4$ opens new avenues to unconventional superconductivity by ""clean""
electron doping through electric field gating.",1706.09694v1
2017-10-10,One dimensional phase transition problem modelling striped spin orbit coupled Bose-Einstein condensates,"We study the behaviour of a Modica-Mortola phase transition type problem with
a non-homogeneous Neumann boundary condition. According to the parameters of
the problem, this leads to the existence of either one component occupying most
of the condensate with an outer boundary layer containing the other component,
or to many interfaces, on a periodic pattern. This is related to the striped
behaviour of a two component Bose-Einstein condensate with spin orbit coupling
in one dimension. We prove that minimizers of the full Gross-Pitaevskii energy
in 1D converge, in the Thomas-Fermi limit of strong intra-component
interaction, to those of the simplified Modica-Mortola problem we have studied
in the first part.",1710.03644v1
2017-10-24,Truncated unity functional renormalization group for multiband systems with spin-orbit coupling,"Although the functional renormalization group (fRG) is by now a
well-established method for investigating correlated electron systems, it is
still undergoing significant technical and conceptual improvements. In
particular, the motivation to optimally exploit the parallelism of modern
computing platforms has recently led to the development of the
""truncated-unity"" functional renormalization group (TU-fRG). Here, we review
this fRG variant, and we provide its extension to multiband systems with
spin-orbit coupling. Furthermore, we discuss some aspects of the implementation
and outline opportunities and challenges ahead for predicting the ground-state
ordering and emergent energy scales for a wide class of quantum materials.",1710.08830v2
2017-10-27,Topological superconductivity in the extended Kitaev-Heisenberg model,"We study superconducting pairing in the doped Kitaev-Heisenberg model by
taking into account the recently proposed symmetric off-diagonal exchange
$\Gamma$. By performing a mean-field analysis, we classify all possible
superconducting phases in terms of symmetry, explicitly taking into account
effects of spin-orbit coupling. Solving the resulting gap equations
self-consistently, we map out a phase diagram that involves several
topologically nontrivial states. For $\Gamma<0$, we find a competition between
a time-reversal symmetry breaking chiral phase with Chern number $\pm1$ and a
time-reversal symmetric nematic phase that breaks the rotational symmetry of
the lattice. On the other hand, for $\Gamma \geq 0$ we find a time-reversal
symmetric phase that preserves all the lattice symmetries, thus yielding
clearly distinguishable experimental signatures for all superconducting phases.
Both of the time-reversal symmetric phases display a transition to a
$\mathbb{Z}_2$ non-trivial phase at high doping levels. Finally, we also
include a symmetry-allowed spin-orbit coupling kinetic energy and show that it
destroys a tentative symmetry protected topological order at lower doping
levels. However, it can be used to tune the time-reversal symmetric phases into
a $\mathbb{Z}_2$ non-trivial phase even at lower doping.",1710.10014v1
2017-12-05,"Competition between spin-orbit coupling, magnetism, and dimerization in the honeycomb iridates: $α$-Li$_{2}$IrO$_{3}$ under pressure","Single-crystal x-ray diffraction studies with synchrotron radiation on the
honeycomb iridate $\alpha$-Li$_{2}$IrO$_{3}$ reveal a pressure-induced
structural phase transition with symmetry lowering from monoclinic to triclinic
at a critical pressure of $P_{c}$ = 3.8 GPa. According to the evolution of the
lattice parameters with pressure, the transition mainly affects the $ab$ plane
and thereby the Ir hexagon network, leading to the formation of Ir--Ir dimers.
These observations are independently predicted and corroborated by our
\textit{ab initio} density functional theory calculations where we find that
the appearance of Ir--Ir dimers at finite pressure is a consequence of a subtle
interplay between magnetism, correlation, spin-orbit coupling, and covalent
bonding. Our results further suggest that at $P_{c}$ the system undergoes a
magnetic collapse. Finally we provide a general picture of competing
interactions for the honeycomb lattices $A_{2}$$M$O$_{3}$ with $A$= Li, Na and
$M$ = Ir, Ru.",1712.01669v1
2017-12-08,Odd-frequency pairing and Kerr effect in the heavy-fermion superconductor UPt$_3$,"We study the emergence of odd-frequency superconducting pairing in UPt$_3$.
Starting from a tight-binding model accounting for the nonsymmorphic crystal
symmetry of UPt$_3$ and assuming an order parameter in the $E_{2u}$
representation, we demonstrate that odd-frequency pairing arises very
generally, as soon as inter-sublattice hopping or spin-orbit coupling is
present. We also show that in the low temperature superconducting $B$ phase,
the presence of a chiral order parameter together with spin-orbit coupling,
leads to additional odd-frequency pair amplitudes not present in the $A$ or $C$
phases. Furthermore, we show that a finite Kerr rotation in the $B$ phase is
only present if odd-$\omega$ pairing also exists.",1712.03021v2
2017-12-19,Emergent magnetic degeneracy in iron pnictides due to the interplay between spin-orbit coupling and quantum fluctuations,"Recent experiments in iron pnictide superconductors reveal that, as the
putative magnetic quantum critical point is approached, different types of
magnetic order coexist over a narrow region of the phase diagram. Although
these magnetic configurations share the same wave-vectors, they break distinct
symmetries of the lattice. Importantly, the highest superconducting transition
temperature takes place close to this proliferation of near-degenerate magnetic
states. In this paper, we employ a renormalization group calculation to show
that such a behavior naturally arises due to the effects of spin-orbit coupling
on the quantum magnetic fluctuations. Formally, the enhanced magnetic
degeneracy near the quantum critical point is manifested as a stable Gaussian
fixed point with a large basin of attraction. Implications of our findings to
the superconductivity of the iron pnictides are also discussed.",1712.07188v4
2017-12-23,Interfacial exchange coupling induced chiral symmetry-breaking of Spin-Orbit effects,"We demonstrate that the interfacial exchange coupling in
ferromagnetic/antiferromagnetic (FM/AFM) systems induces symmetry-breaking of
the Spin-Orbit (SO) effects. This has been done by studying the field and angle
dependencies of anisotropic magnetoresistance and vectorialresolved
magnetization hysteresis loops, measured simultaneously and reproduced with
numerical simulations. We show how the induced unidirectional magnetic
anisotropy at the FM/AFM interface results in strong asymmetric transport
behaviors, which are chiral around the magnetization hard-axis direction.
Similar asymmetric features are anticipated in other SO-driven phenomena.",1712.08766v1
2018-01-30,Tuning Rashba spin-orbit coupling in homogeneous semiconductor nanowires,"We use $\vec{k}\cdot\vec{p}$ theory to estimate the Rashba spin-orbit
coupling (SOC) in large semiconductor nanowires. We specifically investigate
GaAs- and InSb-based devices with different gate configurations to control
symmetry and localization of the electron charge density. We explore
gate-controlled SOC for wires of different size and doping, and we show that in
high carrier density SOC has a non-linear electric field susceptibility, due to
large reshaping of the quantum states. We analyze recent experiments with InSb
nanowires in light of our calculations. Good agreement is found with SOC
coefficients reported in Phys. Rev.B 91, 201413(R) (2015), but not with the
much larger values reported in Nat Commun., 8, 478 (2017). We discuss possible
origins of this discrepancy.",1801.09905v1
2018-09-24,Crystalline topological Dirac semimetal phase in rutile structure $β'$-PtO$_2$,"Based on first-principles calculations and symmetry analysis, we propose that
a transition metal rutile oxide, in particular $\beta'$-PtO$_2$, can host a
three-dimensional topological Dirac semimetal phase. We find that
$\beta'$-PtO$_2$ possesses a linked nodal rings structure when spin-orbit
coupling is neglected. Incorporating spin-orbit coupling gaps the nodal rings,
while preserving a single pair of three-dimensional Dirac points protected by a
screw rotation symmetry. This Dirac point is created by a band inversion of two
$d$ bands, which is a realization of a DSM phase in correlated electron
systems. Moreover, a mirror plane in the momentum space carries a nontrivial
mirror Chern number $n_M = -2$, which distinguishes $\beta'$-PtO$_2$ from the
Dirac semimetals known so far, such as Na$_3$Bi and Cd$_3$As$_2$. If we apply a
perturbation that breaks the rotation symmetry and preserves the mirror
symmetry, the Dirac points are gapped and the system becomes a topological
crystalline insulator.",1809.08963v2
2018-09-25,Band structure and carrier effective masses of boron arsenide: effects of quasiparticle and spin-orbit coupling corrections,"We determine the fundamental electronic and optical properties of the
high-thermal-conductivity III-V semiconductor boron arsenide (BAs) using
density functional and many body perturbation theory including quasiparticle
and spin-orbit coupling corrections. We find that the fundamental band gap is
indirect with a value of 2.049 eV, while the minimum direct gap has a value of
4.135 eV. We calculate the carrier effective masses and report smaller values
for the holes than the electrons, indicating higher hole mobility and easier
p-type doping. The small difference between the static and high frequency
dielectric constants indicates that BAs is only weakly ionic. We also observe
that the imaginary part of the dielectric function exhibits a strong absorption
peak, which corresponds to parallel bands in the band structure. Our estimated
exciton binding energy of 43 meV indicates that excitons are relatively stable
against thermal dissociation at room temperature. Our work provides theoretical
insights on the fundamental electronic properties of BAs to guide experimental
characterization and device applications.",1809.09549v2
2019-07-17,Generating superconducting vortices via spin-orbit coupling,"Spin-orbit coupling (SOC) is known to play an important role in
superconductor/ferromagnet heterostructures. Here we demonstrate that SOC
results in the spontaneous generation of vortices in an \textit{s}-wave
superconductor placed below a ferromagnetic metal with intrinsic or interfacial
SOC. By using the generalized London and Ginzburg-Landau theories, we calculate
the supercurrent amplitude in various types of S/F heterostructures at and
below the superconducting critical temperature. In particular, we show that
even in the limit of weak SOC, vortex-antivortex pairs are stabilized and that
an attractive interaction between vortices and SOC act to pin vortices along
the S/F interface. We discuss key experiments to investigate these phenomena,
which would provide a platform to the creation of Abrikosov vortex memory.",1907.07510v1
2019-07-19,Unconventional topology with a Rashba spin-orbit coupled quantum gas,"Topological order can be found in a wide range of physical systems, from
crystalline solids, photonic meta-materials and even atmospheric waves to
optomechanic, acoustic and atomic systems. Topological systems are a robust
foundation for creating quantized channels for transporting electrical current,
light, and atmospheric disturbances. These topological effects are quantified
in terms of integer-valued invariants, such as the Chern number, applicable to
the quantum Hall effect, or the $\mathbb{Z}_2$ invariant suitable for
topological insulators. Here we engineered Rashba spin-orbit coupling for a
cold atomic gas giving non-trivial topology, without the underlying crystalline
structure that conventionally yields integer Chern numbers. We validated our
procedure by spectroscopically measuring the full dispersion relation, that
contained only a single Dirac point. We measured the quantum geometry
underlying the dispersion relation and obtained the topological index using
matter-wave interferometry. In contrast to crystalline materials, where
topological indices take on integer values, our continuum system reveals an
unconventional half-integer Chern number, potentially implying new forms of
topological transport.",1907.08637v1
2019-09-05,Imaginary-time matrix product state impurity solver in a real material calculation: Spin-orbit coupling in Sr$_2$RuO$_4$,"Using an imaginary-time matrix-product state (MPS) based quantum impurity
solver we perform a realistic dynamical mean-field theory (DMFT) calculation
combined with density functional theory (DFT) for Sr$_2$RuO$_4$. We take the
full Hubbard-Kanamori interactions and spin-orbit coupling (SOC) into account.
The MPS impurity solver works at essentially zero temperature in the presence
of SOC, a regime of parameters currently inaccessible to continuous-time
quantum Monte Carlo (CTQMC) methods, due to a severe sign problem. We show that
earlier results obtained at high temperature, namely that the diagonal
self-energies are nearly unaffected by SOC and that interactions lead to an
effective enhancement of the SOC, hold even at low temperature. We observe that
realism makes the numerical solution of the impurity model with MPS much more
demanding in comparison to earlier works on Bethe lattice models, requiring
several algorithmic improvements.",1909.02503v2
2019-09-09,Weak anti-localization in spin-orbit coupled lattice systems,"The quantum correction to electrical conductivity is studied on the basis of
two-dimensional Wolff Hamiltonian, which is an effective model for a spin-orbit
coupled (SOC) lattice system. It is shown that weak anti-localization (WAL)
arises in SOC lattices, although its mechanism and properties are different
from the conventional WAL in normal metals with SOC impurities. The interband
SOC effect induces the contribution from the interband singlet Cooperon, which
plays a crucial role for WAL in the SOC lattice. It is also shown that there is
a crossover from WAL to weak localization in SOC lattices when the Fermi energy
or band gap changes. The implications of the present results to Bi-Sb alloys
and PbTe under pressure are discussed.",1909.03757v1
2019-10-17,Piezoelectricity and Topological Quantum Phase Transitions in Two-Dimensional Spin-Orbit Coupled Crystals with Time-Reversal Symmetry,"Finding new physical responses that signal topological quantum phase
transitions is of both theoretical and experimental importance. Here, we
demonstrate that the piezoelectric response can change discontinuously across a
topological quantum phase transition in two-dimensional time-reversal invariant
systems with spin-orbit coupling, thus serving as a direct probe of the
transition. We study all gap closing cases for all 7 plane groups that allow
non-vanishing piezoelectricity and find that any gap closing with 1 fine-tuning
parameter between two gapped states changes either the $Z_2$ invariant or the
locally stable valley Chern number. The jump of the piezoelectric response is
found to exist for all these transitions, and we propose the HgTe/CdTe quantum
well and BaMnSb$_2$ as two potential experimental platforms. Our work provides
a general theoretical framework to classify topological quantum phase
transitions and reveals their ubiquitous relation to the piezoelectric
response.",1910.08050v3
2019-10-22,Berry Curvature Dipole in Strained Graphene: a Fermi Surface Warping Effect,"It has been recently established that optoelectronic and non-linear transport
experiments can give direct access to the dipole moment of the Berry curvature
in non-magnetic and non-centrosymmetric materials. Thus far, non-vanishing
Berry curvature dipoles have been shown to exist in materials with substantial
spin-orbit coupling where low-energy Dirac quasiparticles form tilted cones.
Here, we prove that this topological effect does emerge in two-dimensional
Dirac materials even in the complete absence of spin-orbit coupling. In these
systems, it is the warping of the Fermi surface that triggers sizeable Berry
dipoles. We show indeed that uniaxially strained monolayer and bilayer
graphene, with substrate-induced and gate-induced band gaps respectively, are
characterized by Berry curvature dipoles comparable in strength to those
observed in monolayer and bilayer transition metal dichalcogenides.",1910.09872v1
2019-10-30,Phononic Helical Nodal Lines with $\mathcal{PT}$ Protection in MoB$_{2}$,"While condensed matter systems host both Fermionic and Bosonic
quasi-particles, reliably predicting and empirically verifying topological
states is only mature for Fermionic electronic structures, leaving topological
Bosonic excitations sporadically explored. This is unfortunate, as Bosonic
systems such a phonons offer the opportunity to assess spinless band structures
where nodal lines can be realized without invoking special additional symetries
to protect against spin-orbit coupling. Here we combine first-principles
calculations and meV-resolution inelastic x-ray scattering to demonstrate the
first realization of parity-time reversal ($\mathcal{PT}$) symmetry protected
helical nodal lines in the phonon spectrum of MoB$_{2}$. This structure is
unique to phononic systems as the spin-orbit coupling present in electronic
systems tends to lift the degeneracy away from high-symmetry locations. Our
study establishes a protocol to accurately identify topological Bosonic
excitations, opening a new route to explore exotic topological states in
crystalline materials.",1910.13637v1
2020-01-08,Bardeen-Cooper-Schrieffer--type pairing in a spin-$\frac{1}{2}$ Bose gas with spin-orbit coupling,"We apply the functional path-integral approach to analyze how the presence of
a spin-orbit coupling (SOC) affects the basic properties of a BCS-type paired
state in a two-component Bose gas. In addition to a mean-field theory that is
based on the saddle-point approximation for the inter-component pairing, we
derive a Ginzburg-Landau theory by including the Gaussian fluctuations on top,
and use them to reveal the crucial roles played by the momentum-space structure
of an arbitrary SOC field in the stability of the paired state at finite
temperatures. For this purpose, we calculate the critical transition
temperature for the formation of paired bosons, and that of the gapless
quasiparticle excitations for a broad range of interaction and SOC strengths.
In support of our results for the many-body problem, we also benchmark our
numerical calculations against the analytically-tractable limits, and provide a
full account of the two-body limit including its non-vanishing binding energy
for arbitrarily weak interactions and the anisotropic effective mass tensor.",2001.02584v1
2020-01-28,"Realization of a density-dependent Peierls phase in a synthetic, spin-orbit coupled Rydberg system","We experimentally realize a Peierls phase in the hopping amplitude of
excitations carried by Rydberg atoms, and observe the resulting characteristic
chiral motion in a minimal setup of three sites. Our demonstration relies on
the intrinsic spin-orbit coupling of the dipolar exchange interaction combined
with time-reversal symmetry breaking by a homogeneous external magnetic field.
Remarkably, the phase of the hopping amplitude between two sites strongly
depends on the occupancy of the third site, thus leading to a correlated
hopping associated to a density-dependent Peierls phase. We experimentally
observe this density-dependent hopping and show that the excitations behave as
anyonic particles with a non-trivial phase under exchange. Finally, we confirm
the dependence of the Peierls phase on the geometrical arrangement of the
Rydberg atoms.",2001.10357v1
2020-02-04,Signatures of bosonic excitations in high-harmonic spectra of Mott insulators,"The high harmonic spectrum of the Mott insulating Hubbard model has recently
been shown to exhibit plateau structures with cutoff energies determined by
$n$th nearest neighbor doublon-holon recombination processes. The spectrum thus
allows to extract the on-site repulsion $U$. Here, we consider generalizations
of the single-band Hubbard model and discuss the signatures of bosonic
excitations in high harmonic spectra. Specifically, we study an
electron-plasmon model which captures the essential aspects of the dynamically
screened Coulomb interaction in solids and a multi-orbital Hubbard model with
Hund coupling which allows to analyze the effect of local spin excitations. For
the electron-plasmon model, we show that the high harmonic spectrum can reveal
information about the screened and bare onsite interaction, the boson
frequency, as well as the relation between boson coupling strength and boson
frequency. In the multi-orbital case, string states formed by local spin
excitations result in an increase of the radiation intensity and cutoff energy
associated with higher order recombination processes.",2002.01327v1
2020-12-29,Topological turbulence in spin-orbit-coupled driven-dissipative quantum fluids of light generates high angular momentum states,"We demonstrate the formation of a high angular momentum turbulent state in an
exciton-polariton quantum fluid with TE-TM Spin-Orbit Coupling (SOC). The
transfer of particles from quasi-resonantly cw pumped \spl component to \sm
component is accompanied with the generation of a turbulent gas of quantum
vortices by inhomogeneities. We show that this system is unstable with respect
to the formation of bogolons at a finite wave vector, controlled by the laser
detuning. In a finite-size cavity, the domains with this wave vector form a
ring-like structure along the border of a cavity, with a gas of mostly
same-sign vortices in the center. The total angular momentum is imposed by the
sign of TE-TM SOC, the wave vector of instability, and the cavity size. This
effect can be detected experimentally via local dispersion measurements or by
interference. The proposed configuration thus allows simultaneous experimental
studies of quantum turbulence and high-angular momentum states in
continuously-pumped exciton-polariton condensates.",2012.14814v1
2012-05-03,Electronic structure and magnetic properties of NaOsO$_{3}$,"A comprehensive investigation of the electronic and magnetic properties of
NaOsO3 has been made using the first principle calculations, in order to
understand the importance of Coulomb interaction, spin-orbit coupling and
magnetic order in its temperature-induced and magnetic-related metal-insulator
transition. It is found that its electronic structure near the Fermi energy is
dominated by strongly hybridized Os 5d and O 2p states. Despite of the large
strength of spin-orbit coupling, it has only small effect on the electronic and
magnetic properties of NaOsO3. On the other hand, the on-site Coulomb repulsion
affects the band structure significantly, but, a reasonable U alone cannot open
a band gap. Its magnetism is itinerant, and the magnetic configuration plays an
important role in determining the electronic structure. Its ground state is of
a G-type antiferromagnet, and it is the combined effect of U and magnetic
configuration that results in the insulating behavior of NaOsO3.",1205.0740v1
2017-05-03,Theory of Ultra Low Tc Superconductivity in Bismuth: Tip of an Iceberg ?,"Superconductivity with an ultra low Tc $\sim$ 0.5 mK was discovered recently
in bismuth, a semimetal. To develop a model and scenario for Bi we begin with a
cubic reference lattice, close to A7 (dimerized cubic) structure of Bi. Three
valence electrons hop among 6p$_x$, 6p$_y$ and 6p$_z$ orbitals and form
\textit{quasi one dimensional chains at half filling}. An interesting interplay
follows: i) Mott localization tendency in the chains, ii) metallization by
interchain hopping and iii) lattice dimerization by electron-phonon coupling.
In our proposal, a potential high Tc superconductivity from RVB mechanism is
lost in the game. However some superconducting fluctuations survive. Tiny fermi
pockets seen in Bi are viewed as remnant \textit{evanescent Bogoliubov quasi
particles} in an anomalous normal state. Multi band character admits
possibility of PT violating \textit{chiral singlet superconductivity}. Bi has a
strong spin orbit coupling; Kramers theorem protects our proposal for the bulk
by replacing real spin by Kramer pair. Control of chain dimerization might
resurrect high Tc superconductivity in Bi, Sb and As.",1705.01506v1
2017-05-24,Evolution of Band Topology by Competing Band Overlap and Spin-Orbit Coupling: Twin Dirac Cones in Ba$_3$SnO as a Prototype,"We theoretically demonstrate how competition between band inversion and
spin-orbit coupling (SOC) results in nontrivial evolution of band topology,
taking antiperovskite Ba$_3$SnO as a prototype material. A key observation is
that when the band inversion dominates over SOC, there appear ""twin"" Dirac
cones in the band structure. Due to the twin Dirac cones, the band shows highly
peculiar structure in which the upper cone of one of the twin continuously
transforms to the lower cone of the other. Interestingly, the relative size of
the band inversion and SOC is controlled in this series of antiperovskite
A$_3$EO by substitution of A (Ca, Sr, Ba) and/or E (Sn, Pb) atoms. Analysis of
an effective model shows that the emergence of twin Dirac cones is general,
which makes our argument a promising starting point for finding a singular band
structure induced by the competing band inversion and SOC.",1705.08934v1
2018-03-12,Rashba induced Kondo screening of a magnetic impurity in two-dimensional superconductor,"We study the Kondo screening of a magnetic impurity in a two-dimensional
superconductor with Rashba spin-orbit coupling (SOC). It is found that the
Rashba interaction generates a novel Kondo screening channel, in which the
local moment is screened by the exchange coupling with conduction electrons in
different spin and orbital states. The Kondo temperature associated with this
process is determined by the interplay between the Rashba SOC and
superconducting energy gap. As a result, the quantum phase transition between
the magnetic doublet and Kondo singlet ground states is significantly affected
by increasing Rashba SOC in such a system. This result uncovers that the Rashba
SOC plays an instructive role and provides a novel screening channel for the
Kondo effect, which is expected to be observed in future experiments.",1803.04080v1
2018-03-12,Type-I and type-II Nodal Lines Coexistence in the Antiferromagnetic monolayer CrAs$_{2}$,"Topological nodal line semimetals, hosting one-dimensional Fermi lines with
symmetry protection, has become a hot topic in topological quantum matter. Due
to the breaking of time reversal symmetry in magnetic system, nodal lines
require protection by additional symmetries. Here, we report the discovery of
antiferromagnetic type-I and type-II nodal lines coexist in the monolayer
CrAs$_{2}$ based on a systematic first-principles calculation. Remarkably, the
type-I nodal line in CrAs$_{2}$ form a concentric loop centered around the
$\Gamma$ point is filling-enforced by nonsymmorphic analogue symmetry and
robust against spin-orbital coupling. The type-II nodal lines, a kind of open
nodal lines appear around the Fermi level, are protected by the mirror symmetry
in the absence of spin-orbital coupling. The antiferromagnetic monolayer
CrAs$_{2}$ proposed here may provide a platform for the correlation between
magnetism and exotic topological phases.",1803.04133v2
2018-03-12,Universal dynamics of zero-momentum to plane-wave transition in spin-orbit coupled Bose-Einstein condensates,"We investigate the universal spatiotemporal dynamics in spin-orbit coupled
Bose-Einstein condensates which are driven from the zero-momentum phase to the
plane-wave phase. The excitation spectrum reveals that, at the critical point,
the Landau critical velocity vanishes and the correlation length diverges.
Therefore, according to the Kibble-Zurek mechanism, spatial domains will
spontaneously appear in such a quench through the critical point. By simulating
the real-time dynamics, we numerically extract the static correlation length
critical exponent v and the dynamic critical exponent z from the scalings of
the temporal bifurcation delay and the spatial domain number. The numerical
scalings consist well with the analytical ones obtained by analyzing the
excitation spectrum.",1803.04768v1
2018-03-20,Spin-orbit-coupled ferroelectric superconductivity,"Motivated by recent studies on ferroelectric-like order coexisting with
metallicity, we investigate ferroelectric (FE) superconductivity in which a
FE-like structural phase transition occurs in the superconducting state. We
consider a two-dimensional s-wave superconductor with Rashba-type antisymmetric
spin-orbit coupling (ASOC). Assuming linear relationship between polar lattice
displacement and strength of the ASOC, we treat the Rashba-type ASOC as a
molecular field of FE-like order. It is shown that the FE-like order is induced
by the magnetic field when the system is superconducting. Furthermore, we
clarify the FE superconductivity in a low carrier density regime, which was
recently discovered in doped SrTiO$_3$. It is demonstrated that the FE
superconducting state can be stable in this regime in the absence of the
magnetic field. Our results open a way to control the electric polarization by
superconductivity, that is, superconducting multiferroics.",1803.07279v3
2018-03-20,Topological phase transition with nanoscale inhomogeneity in (Bi$_{1-x}$In$_{x}$)$_{2}$Se$_{3}$,"Topological insulators are a class of band insulators with non-trivial
topology, a result of band inversion due to the strong spin-orbit coupling. The
transition between topological and normal insulator can be realized by tuning
the spin-orbit coupling strength, and has been observed experimentally.
However, the impact of chemical disorders on the topological phase transition
was not addressed in previous studies. Herein, we report a systematic scanning
tunneling microscopy/spectroscopy and first-principles study of the topological
phase transition in single crystals of In doped Bi$_2$Se$_3$. Surprisingly, no
band gap closure was observed across the transition. Furthermore, our
spectroscopic-imaging results reveal that In defects are extremely effective
""suppressors"" of the band inversion, which leads to microscopic phase
separation of topological-insulator-like and normal-insulator-like nano regions
across the ""transition"". The observed topological electronic inhomogeneity
demonstrates the significant impact of chemical disorders in topological
materials, shedding new light on the fundamental understanding of topological
phase transition.",1803.07481v1
2018-03-22,On the Emergence of Topologically Protected Boundary States in Topological/Normal Insulator Heterostructures,"We have performed a systematic investigation of the formation of
topologically protected boundary states (TPBS) in topological/normal insulators
(TI/NI) heterostructures. Using a recently developed scheme to construct {\it
ab-initio} tight-binding Hamiltonian matrices from density functional theory
(DFT) calculations, we studied systems of realistic size with high accuracy and
control over the relevant parameters such as TI and NI band alignment, NI gap
and spin-orbit coupling strength. Our findings point to the existence of an NI
critical thickness for the emergence of TPBS and to the importance of the band
alignment between the TI and NI for the appearance of the TPBS. We chose
Bi$_{2}$Se$_{3}$ as a prototypical case where the topological/normal insulator
behavior is modeled by regions with/without spin-orbit coupling. Finally, we
validate our approach comparing our model with fully relativistic DFT
calculations for TI/NI heterostructures of Bi$_{2}$Se$_{3}$/Sb$_{2}$Se$_{3}$.",1803.08587v1
2018-06-06,Negative magnetoresistance suppressed through topological phase transition in (Cd1-xZnx)3As2 films,"The newly discovered topological Dirac semimetals host the possibilities of
various topological phase transitions through the control of spin-orbit
coupling as well as symmetries and dimensionalities. Here, we report a
magnetotransport study of high-mobility (Cd1-xZnx)3As2 films, where the
topological Dirac semimetal phase can be turned into a trivial insulator via
chemical substitution. By high-field measurements with a Hall-bar geometry,
magnetoresistance components ascribed to the chiral charge pumping have been
distinguished from other extrinsic effects. The negative magnetoresistance
exhibits a clear suppression upon Zn doping, reflecting decreasing Berry
curvature of the band structure as the topological phase transition is induced
by reducing the spin-orbit coupling.",1806.02302v1
2018-07-05,Role of Hydrogen in the spin-orbital-entangled quantum liquid candidate H$_3$LiIr$_2$O$_6$,"Motivated by recent reports of H$_3$LiIr$_2$O$_6$ as a spin-orbital-entangled
quantum liquid, we investigate via a combination of density functional theory
and non-perturbative exact diagonalization the microscopic nature of its
magnetic interactions. We find that while the interlayer O-H-O bond geometry
strongly affects the local magnetic couplings, these bonds are likely to remain
symmetrical due to large zero-point fluctuations of the H positions. In this
case, the estimated magnetic model lies close to the classical tricritical
point between ferromagnetic, zigzag and incommensurate spiral orders, what may
contribute to the lack of magnetic ordering. However, we also find that
substitution of H by D (deuterium) as well as disorder-induced inhomogeneities
destabilize the O-H/D-O bonds modifying strongly the local magnetic couplings.
These results suggest that the magnetic response in H$_3$LiIr$_2$O$_6$ is
likely sensitive to both the stoichiometry and microstructure of the samples
and emphasize the importance of a careful treatment of hydrogen for similar
systems.",1807.02124v2
2018-07-06,Parity-mixing superconducting phase in the Rashba-Hubbard model and its topological properties from dynamical mean field theory,"We investigate parity-mixing superconductivity in the two-dimensional Hubbard
model with Rashba spin-orbit coupling, using Cellular Dynamical Mean-Field
Theory (CDMFT). A superconducting state with mixed singlet $d$-wave and triplet
$p$-wave character is found in a wide range of doping. The singlet component
decreases with the amplitude of the Rashba spin-orbit coupling, whereas the
triplet component increases, but both disappear at about 20\% doping. The
effect of a Zeeman field is also investigated; it tends to suppress both types
of superconductivity, but induces nontrivial topological properties: the
computed bulk Chern number is nonzero in the mixed superconductivity phase, at
least in the underdoped region. A strong suppression of the excitation gap
occurs slightly after optimal doping; this might be the sign of a topological
transition within the superconducting dome.",1807.02489v1
2018-07-10,Hall and Faraday effects in interacting multi-band systems with arbitrary band topology and spin-orbit coupling,"A formula for the Hall response of interacting multi-band systems with
arbitrary band topology and spin-orbit coupling is derived. The formula is
valid at finite frequency, which is relevant for Faraday rotation, and it takes
into account all particle-hole vertex corrections. The formula includes both
three-leg (triangular) and four-leg (rectangular) diagrams. The latter diagrams
are absent in the single band case. We show that the rectangular diagrams are
necessary to recover the semiclassical formula for the Hall effect from the
Kubo formula in the DC limit. They also give the linear response of the
anomalous Hall effect to an external magnetic field, an effect which goes
beyond the semiclassical theory. Three- and four-particle scatterings are
neglected.",1807.03852v2
2018-07-16,Odd-parity multipole fluctuation and unconventional superconductivity in locally noncentrosymmetric crystal,"A microscopic calculation and symmetry argument reveal superconductivity in
the vicinity of parity-violating magnetic order. An augmented cluster magnetic
multipole order in a crystal lacking local space inversion parity may break
global inversion symmetry, and then, it is classified into an odd-parity
multipole order. We investigate unconventional superconductivity induced by an
odd-parity magnetic multipole fluctuation in a two-dimensional two-sublattice
Hubbard model motivated by Sr$_2$IrO$_4$. We find that even-parity
superconductivity is more significantly suppressed by a spin-orbit coupling
than that in a globally noncentrosymmetric system. Consequently, two odd-parity
superconducting states are stabilized by magnetic multipole fluctuations in a
large spin-orbit coupling region. Both of them are identified as $Z_2$
topological superconducting states. The obtained gap function of
inter-sublattice pairing shows a gapped/nodal structure protected by
nonsymmorphic symmetry. Our finding implies a new family of odd-parity
topological superconductors. Candidate materials are discussed.",1807.05707v3
2018-08-21,"Quantum anomalous vortex and Majorana zero mode in iron-based superconductor Fe(Te,Se)","In topological insulators doped with magnetic ions, spin-orbit coupling and
ferromagnetism give rise to the quantum anomalous Hall effect. Here we show
that in s-wave superconductors with strong spin-orbit coupling, magnetic
impurity ions can generate topological vortices in the absence of external
magnetic fields. Such vortices, dubbed quantum anomalous vortices, support
robust Majorana zero-energy modes when superconductivity is induced in the
topological surface states. We demonstrate that the zero-energy bound states
observed in Fe(Te,Se) superconductors are possible realizations of the Majorana
zero modes in quantum anomalous vortices produced by the interstitial magnetic
Fe. The quantum anomalous vortex matter not only advances fundamental
understandings of topological defect excitations of Cooper pairing, but also
provides new and advantageous platforms for manipulating Majorana zero modes in
quantum computing.",1808.07072v4
2018-12-05,Effect of photonic spin-orbit coupling on the topological edge modes of a Su-Schrieffer-Heeger chain,"We study the effect of photonic spin-orbit coupling (SOC) in micropillar
lattices on the topological edge states of a one-dimensional chain with a
zigzag geometry, corresponding to the Su-Schrieffer-Heeger model equipped with
an additional internal degree of freedom. The system combines the strong
hopping anisotropy of the $p$-type pillar modes with the large TE-TM splitting
in Bragg microcavities. By resolving the photoluminescence emission in energy
and polarization we probe the effects of the resulting SOC on the spatial and
spectral properties of the edge modes. We find that the edge modes feature a
fine structure of states that penetrate by different amounts into the bulk of
the chain, depending on the strength of the SOC terms present, thereby opening
a route to manipulation of the topological states in the system.",1812.02034v1
2018-12-14,Isospin-phonon coupling and Fano-interference in spin-orbit Mott insulator Sr2IrO4,"The isospin-phonon coupling in Sr2IrO4 is investigated by temperature
dependent phonon Raman scattering. Anomalous behavior in the frequency of all
studied optical phonons is observed below the magnetic transition temperature
TN ~240 K. The strongest effect is detected for the A1g mode at 272 cm-1
associated with the modulation of the Ir-O-Ir bond angle. Additionally, the A1g
mode at 560 cm-1 shows a Fano asymmetric lineshape sensitive to TN, supporting
the existence of low-energy (~70 meV) electronic excitations that are
renormalized by the magnetic order. These results reveal new aspects of the
interaction between the crystal lattice and electronic degrees of freedom in
this spin-orbit entangled Mott insulator.",1812.06006v2
2018-12-18,Cluster State Generation with Spin-Orbit Coupled Fermionic Atoms in Optical Lattices,"Measurement-based quantum computation, an alternative paradigm for quantum
information processing, uses simple measurements on qubits prepared in cluster
states, a class of multiparty entangled states with useful properties. Here we
propose and analyze a scheme that takes advantage of the interplay between
spin-orbit coupling and superexchange interactions, in the presence of a
coherent drive, to deterministically generate macroscopic arrays of cluster
states in fermionic alkaline earth atoms trapped in three dimensional (3D)
optical lattices. The scheme dynamically generates cluster states without the
need of engineered transport, and is robust in the presence of holes, a typical
imperfection in cold atom Mott insulators. The protocol is of particular
relevance for the new generation of 3D optical lattice clocks with coherence
times $>10$ s, two orders of magnitude larger than the cluster state generation
time. We propose the use of collective measurements and time-reversal of the
Hamiltonian to benchmark the underlying Ising model dynamics and the generated
many-body correlations.",1812.07686v2
2018-12-20,Thermopower generation and thermoelectric cooling in a Kane-Mele normal-insulator-superconductor nano-junction,"We have studied thermoelectric effect of a Kane-Mele
normal-insulator-superconductor (KMNIS) junction at ultra-low temperatures
using a modified version of the well-known Blonder-Tinkham-Klapwijk (BTK)
theory. Since both the (electronic) charge and thermal current due to the
carriers are sensitive to the strengths of the spin-orbit coupling (SOC)
present in the Kane-Mele model, a tunability of this junction device with
regard to its thermoelectric properties can be experimentally achieved by
certain techniques that are used to manipulate the values of the spin-orbit
couplings. We have computed the Seebeck coefficient, the Figure of Merit, the
thermoelectric cooling, the coefficient of performance of the KMNIS junction as
a self-cooling device and investigated the role of the Rashba SOC (RSOC) and
intrinsic SOC (ISOC) parameters therein. Our results on the thermoelectric
cooling indicate practical realizability and usefulness for efficient cooling
detectors, sensors, and quantum devices and hence could be crucial to
experimental success of the thermoelectric applications of such junction
devices. Further we have briefly touched upon the condition that distinguishes
transmission through a topological insulator from an ordinary one.",1812.08381v1
2019-01-04,Weak ferromagnetic insulator with huge coercivity in monoclinic double perovskite La2CuIrO6,"Insulating ferromagnets with high TC are required for many new magnetic
devices. More complexity arises when strongly correlated 3d ions coexist with
strongly spin-orbit coupled 5d ones in a double perovskite. Here, we perform
the structural, magnetic, and density functional theory study of such double
perovskite La2CuIrO6. A new P21/n polymorph is found according to the
comprehensive analysis of x-ray, Raman scattering and phonon spectrum. The
magnetization reveals a weak ferromagnetic (FM) transition at TC = 62 K and
short range FM order in higher temperature range. A huge coercivity is found as
high as HC~11.96 kOe at 10K, which in combination with the negative trapped
field results in the magnetization reversal in the zero field cooling
measurement. The first principle calculations confirm the observed FM state and
suggest La2CuIrO6 of this polymorph is a Mott insulating ferromagnet assisted
by the spin-orbit coupling.",1901.01106v4
2019-01-04,The gate-tunable strong and fragile topology of multilayer-graphene on a transition metal dichalcogenide,"We analyze the phase diagram of multilayer-graphene sandwiched between
identical transition metal dichalcogenides. Recently realized in all
van-der-Wall heterostructures, these sandwiches induce sizable (1-15 meV) spin
orbit coupling in the graphene, offering a way to engineer topological
band-structures in a pristine and gate-tunable platform. We find a rich phase
diagram that depends on the number of layers $N$ and the gate-tunable
perpendicular electric field. For $N > 1$ and odd, the system is a strong 2D
topological insulator with a gap equal to the strength of proximity-induced
Ising spin-orbit coupling, which reverts to a trivial phase at moderate
electric fields. For $N$-even, the low energy bands exhibit a recently proposed
form of ""fragile"" crystalline topology, as well as electric-field tuned
symmetry-protected phase transitions between distinct atomic insulators. Hence
AB-stacked bilayer and ABC-stacked trilayer graphene are predicted to provide
controllable experimental realizations of fragile and strong topology.",1901.01294v2
2019-01-09,Angular Stripe Phase in Spin-Orbital-Angular-Momentum Coupled Bose Condensates,"We propose that novel superfluid with supersolid-like properties - angular
stripe phase - can be realized in a pancake-like spin-1/2 Bose gas with
spin-orbital-angular-momentum coupling. We predict a rich ground-state phase
diagram, including the vortex-antivortex pair phase, half-skyrmion phase, and
two different angular stripe phases. The stripe phases feature modulated
angular density-density correlation with sizable contrast and can occupy a
relatively large parameter space. The low-lying collective excitations, such as
the dipole and breathing modes, show distinct behaviors in different phases.
The existence of the novel stripe phase is also clearly indicated in the
energetic and dynamic instabilities of collective modes near phase transitions.
Our predictions of the angular stripe phase could be readily examined in
current cold-atom experiments with $^{87}$Rb and $^{41}$K.",1901.02595v3
2019-01-18,Four-wave mixing in spin-orbit coupled Bose-Einstein condensates,"We describe possibilities of spontaneous, degenerate four-wave mixing (FWM)
processes in spin-orbit coupled Bose-Einstein condensates. Phase matching
conditions (i.e., energy and momentum conservation laws) in such systems allow
one to identify four different configurations characterized by involvement of
distinct spinor states in which such a process can take place. We derived these
conditions from first principles and then illustrated dynamics with direct
numerical simulations. We found, among others, the unique configuration, where
both probe waves have smaller group velocity than pump wave and proved
numerically that it can be observed experimentally under proper choice of the
parameters. We also reported the case when two different FWM processes can
occur simultaneously. The described resonant interactions of matter waves is
expected to play important role in the experiments of BEC with artificial gauge
fields. Beams created by FWM processes are important source of correlated
particles and can be used the experiments testing quantum properties of atomic
ensembles.",1901.06173v3
2019-01-30,Electronic structure of full-shell InAs/Al hybrid semiconductor-superconductor nanowires: Spin-orbit coupling and topological phase space,"We study the electronic structure of full-shell superconductor-semiconductor
nanowires, which have recently been proposed for creating Majorana zero modes,
using an eight-band $\vec{k} \cdot \vec{p}$ model within a fully
self-consistent Schr\""{o}dinger-Poisson scheme. We find that the spin-orbit
coupling induced by the intrinsic radial electric field is generically weak for
sub-bands with their minimum near the Fermi energy. Furthermore, we show that
the chemical potential windows consistent with the emergence of a topological
phase are small and sparse and can only be reached by fine tunning the diameter
of the wire. These findings suggest that the parameter space consistent with
the realization of a topological phase in full-shell InAs/Al nanowires is, at
best, very narrow.",1901.11005v1
2019-03-13,Nonlinear management of topological solitons in a spin-orbit-coupled system,"We consider possibilities to control dynamics of solitons of two types,
maintained by the combination of cubic attraction and spin-orbit coupling (SOC)
in a two-component system, namely, semi-dipoles (SDs) and mixed modes (MMs), by
making the relative strength of the cross-attraction, gamma, a function of time
periodically oscillating around the critical value, gamma = 1, which is an
SD/MM stability boundary in the static system. The structure of SDs is
represented by the combination of a fundamental soliton in one component and
localized dipole mode in the other, while MMs combine fundamental and dipole
terms in each component. Systematic numerical analysis reveals a finite
bistability region for the SDs and MMs around gamma = 1, which does not exist
in the absence of the periodic temporal modulation (""management""), as well as
emergence of specific instability troughs and stability tongues for the
solitons of both types, which may be explained as manifestations of resonances
between the time-periodic modulation and intrinsic modes of the solitons. The
system can be implemented in Bose-Einstein condensates, and emulated in
nonlinear optical waveguides.",1903.05279v1
2019-04-07,Anomalous ground state properties of SmB6 -- a density functional theoretical study,"We studied the electronic structure of SmB6 employing density functional
theory (DFT) using different exchange potentials, spin-orbit coupling (SOC) and
electron correlation (U = correlation strength). All the calculations carried
out in this study converge to metallic ground state indicating bulk metallicity
in SmB6, which is in line with the low temperature anomalies observed in this
system. We show that while spin-orbit coupling and electron correlation is
important to capture the ground state properties, generalized gradient
approximation provides the best description of the Sm 4f multiplets observed in
angle-resolved photoemission spectroscopy (ARPES) data. The Fermi surface plots
exhibit electron and hole pockets having dominant Sm 4f character; the
observation of these Fermi surfaces is consistent with the recent quantum
oscillation measurements. In addition to primarily Sm 4f contributions observed
at the Fermi level, we discover significantly large contribution from B 2p
states compared to weak Sm 5d contributions. This suggests important role of B
2p - Sm 4f hybridization in the exotic physics of this system.",1904.03594v2
2019-04-15,Magnetic response of Sr$_2$RuO$_4$: quasi-local spin fluctuations due to Hund's coupling,"We study the magnetic susceptibility in the normal state of Sr$_2$RuO$_4$
using dynamical mean-field theory including dynamical vertex corrections.
Besides the well known incommensurate response, our calculations yield
quasi-local spin fluctuations which are broad in momentum and centered around
the $\Gamma$ point, in agreement with recent inelastic neutron scattering
experiments [P. Steffens, et al., Phys. Rev. Lett. 122, 047004 (2019)]. We show
that these quasi-local fluctuations are controlled by the Hund's coupling and
account for the dominant contribution to the momentum-integrated response.
While all orbitals contribute equally to the incommensurate response, the
enhanced $\Gamma$ point response originates from the planar xy orbital.",1904.07324v1
2019-08-09,Magnetic phase transitions of insulating spin-orbit coupled Bose atoms in one-dimensional optical lattices,"We consider the insulating spin-orbit coupled Bose atoms confined within
one-dimensional optical lattices and explore their ground-state magnetic phase
transitions. Under strong interactions, the charge degrees of atoms are frozen
and the system can be described by an anisotropic XXZ Heisenberg chain with
Dzyaloshinskii-Moriya interaction and transverse field. We apply the matrix
product state method to obtain low-energy states and analyze the lowest energy
gaps and the ground-state magnetization and correlations. We find when the
transverse field is absent, the ground state is a gapped ferromagnetic phase
with long-range correlation in the z direction if the interspin s-wave
interacting strength is stronger than that of the intraspin one, otherwise it
is a gapless Luttinger liquid (LL) phase with algebraic decaying correlation.
When the transverse field is turned on, the gapless LL phase is broken, there
emerges a long-range correlated phase with ferromagnetic, antiferromagnetic or
spiral order, which depends on the DM interaction strength. We believe our
study provides a complete understanding of the interplay between SOC and
quantum magnetism of spinor atoms in optical lattices.",1908.03300v1
2019-08-26,Vectorial nonlinear optics: type-II second-harmonic generation driven by spin-orbit coupled fields,"Vectorial nonlinear optics refers to the investigation of optical processes
whose nonlinear polarization (NP) undergoes spin-orbit coupling (SOC)
interactions where, in general, the driving light field or the new field
generated by the interaction containing the SOC property. To contribute to
fundamental knowledge in this domain, we examine the type-II second harmonic
generation (SHG) induced by vectorial laser modes. First, we provide a general
theory to analyze the vectorial SHG process. Second, by using two typical
vector modes as examples, we show how the SOC of the pump field dictates
nonlinear interaction. Finally, we corroborate our theoretical predictions
through experiments to confirm the crucial role of the SOC in nonlinear
interactions. These results enhance our fundamental understanding of
SOC-mediated nonlinear optics and lay the foundation for further fundamental
studies as well as possible applications.",1908.09437v2
2019-11-09,Interaction-Range Effects and Universality in the BCS-BEC Crossover of Spin-Orbit Coupled Fermi Gases,"We explore the evolution of a ultracold quantum gas of interacting fermions
crossing from a Bardeen-Cooper-Schrieffer (BCS) superfluidity to a
Bose-Einstein condensation (BEC) of molecular bosons in the presence of a
tunable-range interaction among the fermions and of an artificial magnetic
field, which can be used to simulate a pseudo-spin-orbit coupling (SOC) and to
produce topological states. We find that the crossover is affected by a
competition between the finite range of the interaction and the SOC and that
the threshold $\lambda_B$ for the topological transition is affected by the
interactions only in the small pair size, BEC-like, regime. Below $\lambda_B$,
we find persistence of universal behavior in the critical temperature, chemical
potential, and condensate fraction, provided that the pair correlation length
is used as a driving parameter. Above threshold, universality is lost in the
regime of large pair sizes. Here, the limiting ground state departs from a
weakly-interacting BCS-like, so that a different description is required. Our
results can be relevant in view of current experiments with cold atoms in
optical cavities, where tunable-range effective atomic interactions can be
engineered.",1911.03657v1
2019-12-12,Multidimensional hybrid Bose-Einstein condensates stabilized by lower-dimensional spin-orbit coupling,"We show that attractive spinor Bose-Einstein condensates under the action of
spin-orbit coupling (SOC) and Zeeman splitting form self-sustained stable two-
and three-dimensional (2D and 3D) states in free space, even when SOC acts in a
lower-dimensional form. We find that two-dimensional states are stabilized by
one-dimensional (1D) SOC in a broad range of chemical potentials, for atom
numbers (or norm of the spinor wavefunction) exceeding a threshold value, which
strongly depends on the SOC strength and vanishes at a critical point. The
zero-threshold point is a boundary between single-peaked and striped states,
realizing hybrids combining 2D and 1D structural features. In a vicinity of
such point, an asymptotic equation describing the bifurcation of the solitons
from the linear spectrum is derived and investigated analytically. We show that
striped 3D solitary states are as well stabilized by 2D SOC, albeit in a
limited range of chemical potentials and norms.",1912.05880v1
2020-05-09,Quest for New Quantum States via Field-Editing Technology,"We report new quantum states in spin-orbit-coupled single crystals that are
synthesized using a game-changing technology that ""field-edits"" crystal
structures (borrowing from the phrase ""genome editing"") via application of
magnetic field during crystal growth. This study is intended to fundamentally
address a major challenge facing the research community today: A great deal of
theoretical work predicting exotic states for strongly spin-orbit-coupled,
correlated materials has thus far met very limited experimental confirmation.
These conspicuous discrepancies are due chiefly to the extreme sensitivity of
these materials to structural distortions. The results presented here
demonstrate that the ""field-edited"" materials not only are much less distorted
but also exhibit novel phenomena absent in their ""non-edited"" counterparts. The
field-edited materials include an array of 4d and 5d transition metal oxides,
and three representative materials presented here are Ba4Ir3O10, Ca2RuO4, and
Sr2IrO4. This study provides an entirely new paradigm for discovery of new
quantum states and materials otherwise unavailable.",2005.04327v3
2020-10-21,Three-dimensional non-Abelian generalizations of the Hofstadter model: spin-orbit-coupled butterfly trios,"We theoretically introduce and study a three-dimensional Hofstadter model
with linearly varying non-Abelian gauge potentials along all three dimensions.
The model can be interpreted as spin-orbit coupling among a trio of Hofstadter
butterfly pairs since each Cartesian surface ($xy$, $yz$, or $zx$) of the model
reduces to a two-dimensional non-Abelian Hofstadter problem. By evaluating the
commutativity among arbitrary loop operators around all axes, we derive its
genuine (necessary and sufficient) non-Abelian condition, namely, at least two
out of the three hopping phases should be neither 0 nor $\pi$. Under different
choices of gauge fields in either the Abelian or the non-Abelian regime, both
weak and strong topological insulating phases are identified in the model.",2010.11308v2
2021-04-23,Rotation of optically bound particle assembly due to scattering induced spin-orbit coupling of light,"The optical binding of many particles has great potential to achieve the
wide-area formation of a ""crystal"" of small materials. Unlike conventional
optical binding, where the whole assembly of targeted particles is irradiated
with light, if one can indirectly manipulate remote particles using a single
trapped particle through optical binding, the degrees of freedom to create
ordered structures will be greatly enhanced. In this Letter, we theoretically
investigate the dynamics of the assembly of gold nanoparticles that is
manipulated using a single particle trapped by a focused laser. As a result, we
demonstrate that the spin--orbit coupling and angular momentum generation of
light via scattering induce the assembly and rotational motion of particles
through indirect optical force. This result opens the possibility of creating
ordered structures with a wide area and manipulating them, controlling local
properties using scanning laser beams.",2104.11387v1
2015-08-17,"Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films: interplay between correlation, disorder, and spin-orbit coupling","We investigate the effects of compressive strain on the electrical
resistivity of 5d iridium based perovskite SrIrO3 by depositing epitaxial films
of thickness 35 nm on various substrates such as GdScO3 (110), DyScO3 (110),
and SrTiO3 (001). Surprisingly, we find anomalous transport behaviors in the
tempeature dependent resistivity, where the temperature exponent evolves
continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain.
Furthermore, magnetoresistance always remains positive irrespective of
resistivity upturns at low temperatures. These observations imply that the
delicate interplay between correlation and disorder in the presence of strong
spin-orbit coupling is responsible for the emergence of the non-Fermi liquid
behaviors in 5d perovskite SrIrO3 thin films. We offer a theoretical framework
for the interpretation of the experimental results.",1508.03944v1
2015-08-27,Spin-orbit-coupled Bose-Einstein-condensed atoms confined in annular potentials,"A spin-orbit-coupled Bose-Einstein-condensed cloud of atoms confined in an
annular trapping potential shows a variety of phases that we investigate in the
present study. Starting with the non-interacting problem, the homogeneous phase
that is present in an untrapped system is replaced by a sinusoidal density
variation in the limit of a very narrow annulus. In the case of an untrapped
system there is another phase with a striped-like density distribution, and its
counterpart is also found in the limit of a very narrow annulus. As the width
of the annulus increases, this picture persists qualitatively. Depending on the
relative strength between the inter- and the intra-components, interactions
either favor the striped phase, or suppress it, in which case either a
homogeneous, or a sinusoidal-like phase appears. Interactions also give rise to
novel solutions with a nonzero circulation.",1508.06761v2
2016-03-17,J$_{eff}$ description of the honeycomb Mott insulator $α$-RuCl$_3$,"Novel ground states might be realized in honeycomb lattices with strong
spin-orbit coupling. Here we study the electronic structure of
${\alpha}$-RuCl$_3$, in which the Ru ions are in a d5 configuration and form a
honeycomb lattice, by angle-resolved photoemission, x-ray photoemission and
electron energy loss spectroscopy supported by density functional theory and
multiplet calculations. We find that ${\alpha}$-RuCl$_3$ is a Mott insulator
with significant spin-orbit coupling, whose low energy electronic structure is
naturally mapped onto Jeff states. This makes ${\alpha}$-RuCl$_3$ a promising
candidate for the realization of Kitaev physics. Relevant electronic parameters
such as the Hubbard energy U, the crystal field splitting 10Dq and the charge
transfer energy are evaluated. Furthermore, we observe significant Cl
photodesorption with time, which must be taken into account when interpreting
photoemission and other surface sensitive experiments.",1603.05507v1
2016-03-29,Yu-Shiba-Rusinov states and topological superconductivity in Ising paired superconductors,"An unusual form of superconductivity, called Ising superconductivity, has
recently been uncovered in mono- and few-layered transition metal
dichalcogenides. This 2D superconducting state is characterized by the
so-called Ising spin-orbit coupling (SOC), which produces strong oppositely
oriented effective Zeeman fields perpendicular to the 2D layer in opposite
momentum space valleys. We examine the Yu-Shiba-Rusinov (YSR) bound states
localized at magnetic impurities in Ising superconductors and show that the
unusual SOC manifests itself in unusually strong anisotropy in magnetic field
response of zero bias conductance peaks observable in STM experiments on
impurity sites. For a chain of magnetic impurities with moments parallel to the
plane of Ising superconductors we show that the low energy YSR band can host
topological superconductivity and Majorana fermions as a direct manifestation
of Ising spin-orbit coupling induced topological effects.",1603.08909v2
2016-03-31,Superconductivity in magnetic multipole states,"Stimulated by recent studies of superconductivity and magnetism with local
and global broken inversion symmetry, we investigate the superconductivity in
magnetic multipole states in locally noncentrosymmetric metals. We consider a
one-dimensional zigzag chain with sublattice-dependent antisymmetric spin-orbit
coupling and suppose three magnetic multipole orders: monopole order, dipole
order, and quadrupole order. It is demonstrated that the
Bardeen-Cooper-Schrieffer state, the pair-density wave (PDW) state, and the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state are stabilized by these multipole
orders, respectively. We show that the PDW state is a topological
superconducting state specified by the nontrivial $\mathbb{Z}_2$ number and
winding number. The origin of the FFLO state without macroscopic magnetic
moment is attributed to the asymmetric band structure induced by the magnetic
quadrupole order and spin-orbit coupling.",1603.09440v3
2016-10-26,Observation of the supersolid stripe phase in spin-orbit coupled Bose-Einstein condensates,"Supersolidity is an intriguing concept. It combines the property of
superfluid flow with the long-range spatial periodicity of solids, two
properties which are often mutually exclusive. The original discussion of
quantum crystals and supersolidity focuses on solid Helium-4 where it was
predicted that vacancies could form dilute weakly interacting Bose-Einstein
condensates. In this system, direct observation of supersolidity has been
elusive. The concept of supersolidity was then generalized to include other
superfluid systems which break the translational symmetry of space. One of such
systems is a Bose-Einstein condensate with spin-orbit coupling which has a
supersolid stripe phase. Despite several recent studies of this system, the
stripe phase has not been observed. Here we report the direct observation of
the predicted density modulation of the stripe phase using Bragg reflection.
Our work establishes a system with unique symmetry breaking properties. Of
future interest is further spatial symmetry breaking through the introduction
of vortices, solitons, impurities or disorder.",1610.08194v2
2016-10-29,Spin-orbit-coupled Bose-Einstein condensates held under toroidal trap,"We study a quasispin-$1/2$ Bose-Einstein condensate with synthetically
generated spin-orbit coupling in a toroidal trap, and show that the system has
a rich variety of ground and metastable states. As the central hole region
increases, i.e., the potential changes from harmonic-like to ring-like, the
condensate exhibits a variety of structures, such as triangular stripes,
flower-petal patterns, and counter-circling states. We also show that the
rotating systems have exotic vortex configurations. In the limit of a quasi-one
dimensional ring, the quantum many-body ground state is obtained, which is
found to be the fragmented condensate.",1610.09458v1
2016-10-31,A critical point in Sr2-xIrO4 and less distorted IrO6 octahedra induced by deep Sr-vacancies,"For the Sr2-xIrO4 system, recent work pointed out the abnormal electronic and
magnetic properties around the critical point. Here, to understand Sr-vacancy
effect on spin-orbit coupled Mott insulator Sr2IrO4, the electronic structure
and local structure distortion for Sr2-xIrO4 system have been investigated by
x-ray absorption spectroscopy (XAS). By comparing the intensity of white-line
features at the IrL2,3-edge x-ray absorption near-edge spectroscopy (XANES), we
observe a sudden rise of the branching ratio in the vicinity of the critical
point.Further analysis on theIrL3 -edge extended x-ray absorption fine
structure (EXAFS) and calculated data demonstrated that the abrupt enhancement
of the branching ratio is intimately related to the less distorted IrO6
octahedra induced by deep Sr-vacancies, which in turn alters the relatively
strength of the spin-orbit coupling (SOC) and crystal electric field (CEF)that
would dictate the abnormal behavior of electronic and magnetic structure near
the critical point.",1610.09817v1
2016-12-02,Comment on Influence of induced interactions on superfluid properties of quasi-two-dimensional dilute Fermi gases with spin-orbit coupling,"In an article in 2013, Caldas et al. [Phys. Rev. A 88, 023615 (2013)] derived
analytical expressions of the induced interaction within the scheme of Gorkov
and Melik-Barkhudrov in quasi-two-dimensional Fermi gases with Rashba
spin-orbit coupling (SOC). They claimed that the induced interaction is exactly
the same as the one for the case without SOC when the SOC is weak, and in the
region of strong SOC, it starts from a reduced value and then recovers the
value for the zero SOC in the limit of large SOC. We point out that their
calculations contain the critical errors and inconsistencies that significantly
affect the basis of these claims.",1612.00600v1
2016-12-06,Laser-induced topological superconductivity in cuprate thin films,"We propose a possible way to realize topological superconductivity with
application of laser light to superconducting cuprate thin films. Applying
Floquet theory to a model of $d$-wave superconductors with Rashba spin-orbit
coupling, we derive an effective model and discuss its topological nature.
Interplay of the Rashba spin-orbit coupling and the laser light effect induces
the synthetic magnetic fields, thus making the system gapped. Then the system
acquires the topologically non-trivial nature which is characterized by Chern
numbers. The effective magnetic fields do not create the vortices in
superconductors, and thus the proposed scheme provides a promising way to
dynamically realize a topological superconductor in cuprates. We also discuss
an experimental way to detect the signature.",1612.01596v1
2016-12-14,Successive spatial symmetry breaking under high pressure in the spin-orbit-coupled metal Cd2Re2O7,"The 5d-transition metal pyrochlore oxide Cd2Re2O7, which was recently
suggested to be a prototype of the spin-orbit-coupled metal [Phys. Rev. Lett.
115, 026401 (2015)], exhibits an inversion-symmetry breaking (ISB) transition
at 200 K and a subsequent superconductivity below 1 K at ambient pressure. We
study the crystal structure at high pressures up to 5 GPa by means of
synchrotron X-ray powder diffraction. A rich structural phase diagram is
obtained, which contains at least seven phases and is almost consistent with
the electronic phase diagram determined by previous resistivity measurements.
Interestingly, the ISB transition vanishes at ~4 GPa, where the enhancement of
the upper critical field was observed in resistivity. Moreover, it is shown
that the point groups at 8 K, probably kept in the superconducting phases,
sequentially transform into piezoelectric, ferroelectric, and centrosymmetric
structures on the application of pressure.",1612.04577v2
2019-05-17,Symmetry-protected metallic and topological phases in penta-materials,"We analyze the symmetry and topological features of a family of materials
closely related to penta-graphene, derived from it by adsorption or
substitution of different atoms. Our description is based on a novel approach,
called topological quantum chemistry, that allows to characterize the topology
of the electronic bands, based on the mapping between real and reciprocal
space.
  In particular, by adsorption of alkaline (Li or Na) atoms we obtain a nodal
line metal at room temperature, with a continuum of Dirac points around the
perimeter of the Brillouin zone. This behavior is also observed in some
substitutional derivatives of penta-graphene, such as penta-PC$_2$.
  Breaking of time-reversal symmetry can be achieved by the use of magnetic
atoms; we study penta-MnC$_2$, which also presents spin-orbit coupling and
reveals a topological insulator phase.
  We find that for this family of materials, symmetry is the source of
protection for metallic and nontrivial topological phases that can be
associated to the presence of fractional band filling, spin-orbit coupling and
time-reversal symmetry breaking.",1905.07381v1
2019-05-29,Gate Controlled Anomalous Phase Shift in Al/InAs Josephson Junctions,"In a standard Josephson junction the current is zero when the phase
difference between the superconducting leads is zero. This condition is
protected by parity and time-reversal symmetries. However, the combined
presence of spin-orbit coupling and magnetic field breaks these symmetries and
can lead to a finite supercurrent even when the phase difference is zero. This
is the so called anomalous Josephson effect -- the hallmark effect of
superconducting spintronics --and can be characterized by the corresponding
anomalous phase shift ($\phi_0$). We report the observation of a tunable
anomalous Josephson effect in InAs/Al Josephson junctions measured via a
superconducting quantum interference device (SQUID). By gate controlling the
density of InAs we are able to tune the spin-orbit coupling of the Josephson
junction by more than one order of magnitude. This gives us the ability to tune
$\phi_0$, and opens several new opportunities for superconducting spintronics,
and new possibilities for realizing and characterizing topological
superconductivity.",1905.12670v1
2020-03-03,Topological superconductivity in carbon nanotubes with a small magnetic flux,"We show that a one-dimensional topological superconductor can be realized in
carbon nanotubes, using a relatively small magnetic field. Our analysis relies
on the intrinsic curvature-enhanced spin-orbit coupling of the nanotubes, as
well as on the orbital effect of a magnetic flux threaded through the nanotube.
Tuning experimental parameters, we show that a half-metallic state may be
induced in the nanotube. Coupling the system to an Ising superconductor, with
an appreciable spin-triplet component, can then drive the nanotube into a
topological superconducting phase. The proposed scheme is investigated by means
of real-space tight-binding simulations, accompanied by an effective continuum
low-energy theory, which allows us to gain some insight on the roles of
different terms in the Hamiltonian. We calculate the topological phase diagram
and ascertain the existence of localized Majorana zero modes near the edges.
Moreover, we find that in the absence of a magnetic field, a regime exists
where sufficiently strong interactions drive the system into a
time-reversal-invariant topological superconducting phase.",2003.01730v1
2020-03-26,Chiral Domain Wall Injector Driven by Spin-orbit Torques,"Memory and logic devices that encode information in magnetic domains rely on
the controlled injection of domain walls to reach their full potential. In this
work, we exploit the chiral coupling induced by the Dzyaloshinskii-Moriya
interaction between in-plane and out-of-plane magnetized regions of a
Pt/Co/AlO\textsubscript{x} trilayer in combination with current-driven
spin-orbit torques to control the injection of domain walls into magnetic
conduits. We demonstrate that the current-induced domain nucleation is strongly
inhibited for magnetic configurations stabilized by the chiral coupling and
promoted for those that have the opposite chirality. These configurations allow
for efficient domain wall injection using current densities of the order of
$4\times$\SI{e11}{A m^{-2}}, which are lower than those used in other injection
schemes. Furthermore, by setting the orientation of the in-plane magnetization
using an external field, we demonstrate the use of a chiral domain wall
injector to create a controlled sequence of alternating domains in a racetrack
structure driven by a steady stream of unipolar current pulses.",2003.11805v1
2020-06-03,Topological Nodal Line Electrides: Realization of Ideal Nodal Line State Nearly Immune from Spin-Orbit Coupling,"Nodal line semimetals (NLSs) have attracted broad interest in current
research. In most of existing NLSs, the intrinsic properties of nodal lines are
greatly destroyed because nodal lines usually suffer sizable gaps induced by
non-negligible spin-orbit coupling (SOC). In this work,we propose the
topological nodal line electrides (TNLEs), which achieve electronic structures
of nodal lines and electrides simultaneously, provide new insight on designing
excellent NLSs nearly immune from SOC. Since the states near the Fermi level
are most contributed by nonnucleus-bounded interstitial electrons, nodal lines
in TNLEs manifest extremely small SOCinduced gap even possessing heavy
elements. Especially, we propose the family of A2B (A = Ca, Sr, Ba; B= As, Sb,
Bi) materials are realistic TNLEs with negligible SOC-induced gaps, which can
play as excellent platforms to study the intrinsic properties of TNLEs",2006.02019v1
2020-06-12,Majorana corner pairs in a two-dimensional $s$-wave cold atomic superfluid,"We propose a method to prepare Majorana pairs at the corners of imprinted
defects on a two-dimensional cold atom optical lattice with $s$-wave superfluid
pairing. Different from previous proposals that manipulate the effective Dirac
masses, our scheme relies on the sign flip of the spin-orbit coupling at the
corners, which can be tuned in experiments by adjusting the angle of incident
Raman lasers. The Majorana corner pairs are found to be located at the
interface between two regimes with opposite spin orbit coupling strengths in an
anticlockwise direction and are robust against certain symmetry-persevered
perturbations. Our work provides a new way for implementing and manipulating
Majorana pairs with existing cold-atom techniques.",2006.06905v1
2020-09-26,"First-Principles Prediction of Graphene-Like XBi (X=Si, Ge, Sn) Nanosheets","Research progress on single-layer group III monochalcogenides have been
increasing rapidly owing to their interesting physics. Herein, we predict the
dynamically stable single-layer forms of XBi (X=Ge, Si, or Sn) by using density
functional theory calculations. Phonon band dispersion calculations and
ab-initio molecular dynamics simulations reveal the dynamical and thermal
stability of predicted nanosheets. Raman spectra calculations indicate the
existence of 5 Raman active phonon modes 3 of which are prominent and can be
observed in a possible Raman measurement. Electronic band structures of the XBi
single-layers investigated with and without spin-orbit coupling effects (SOC).
Our results show that XBi single-layers show semiconducting property with the
narrow band gap values without SOC. However only the single-layer SiBi is an
indirect band gap semiconductor while GeBi and SnBi exhibit metallic behaviors
by adding spin-orbit coupling effects. In addition, the calculated
linear-elastic parameters indicate the soft nature of predicted monolayers.
Moreover, our predictions for the thermoelectric properties of single-layer XBi
reveal that SiBi is a good thermoelectric material with increasing temperature.
Overall, it is proposed that single-layer XBi structures can be alternative,
stable 2D single-layers with their varying electronic and thermoelectric
properties.",2009.12561v1
2021-01-21,Unusual $H$-$T$ phase diagram of CeRh$_2$As$_2$ -- the role of staggered non-centrosymmetricity,"Superconductivity in a crystalline lattice without inversion is subject to
complex spin-orbit-coupling effects, which can lead to mixed-parity pairing and
an unusual magnetic response. In this study, the properties of a layered
superconductor with alternating Rashba spin-orbit coupling in the stacking of
layers, hence (globally) possessing a center of inversion, is analyzed in an
applied magnetic field, using a generalized Ginzburg-Landau model. The
superconducting order parameter consists of an even- and an odd-parity pairing
component which exchange their roles as dominant pairing channel upon
increasing the magnetic field. This leads to an unusual kink feature in the
upper critical field and a first-order phase transition within the mixed phase.
We investigate various signatures of this internal phase transition. The
physics we discuss here could explain the recently found $H$--$T$ phase diagram
of the heavy Fermion superconductor CeRh$_2$As$_2$.",2101.08821v2
2021-03-03,Strained BiFeO$_{3}$ perovskite structure for enhanced photovoltaic effect,"BiFeO$_{3}$ is multiferroic material with space group Pbnm exhibits coupling
of both magnetic and electric orders under strain force. To analyze band gap
Tauc plot extrapolation method is used $\&$ remarkably smaller than some
reported literature values for space group R3c structure. The dielectric
function $\varepsilon(\omega)$ demonstrated that light energy upon transition
through BiFeO$_{3}$ has shown a decline inconsistent pattern with index of
refraction variation in range of 13 to 8, 8 to 5, 5 to 3, $\&$ 3 to 1 as per
photon energy. Moreover, non crossing degenerate energy level and hybridized
spin-orbit interaction lead to linear dispersion relation which is typical
photonic nature with zero DM interaction. Thus, BiFeO$_{3}$ could exhibit
photonic property under strain force. Generally strained structure had enhanced
photovoltaic effect with smaller optical band gap because of
$Dzyaloshinskii$-$Moriya(DM)$ and spin-orbit coupling interactions.",2103.02194v1
2021-03-04,Origin of the different electronic structure of Rh- and Ru-doped Sr2IrO4,"One way to induce insulator to metal transitions in the spin-orbit Mott
insulator Sr2IrO4 is to substitute iridium with transition metals (Ru, Rh).
However, this creates intriguing inhomogeneous metallic states, which cannot be
described by a simple doping effect. We detail the electronic structure of the
Ru-doped case with angle-resolved photoemission and show that, contrary to Rh,
it cannot be connected to the undoped case by a rigid shift. We further
identify bands below $E_F$ coexisting with the metallic ones that we assign to
non-bonding Ir sites. We rationalize the differences between Rh and Ru by a
different hybridization with oxygen, which mediates the coupling to Ir and
sensitively affects the effective doping. We argue that the spin-orbit coupling
does not control neither the charge transfer nor the transition threshold.",2103.03056v1
2021-03-15,Direct observation of the spin-orbit coupling effect in Magnetic Weyl semimetal Co3Sn2S2,"The spin-orbit coupling (SOC) lifts the band degeneracy that plays a vital
role in the search for different topological states, such as topological
insulators (TIs) and topological semimetals (TSMs). In TSMs, the SOC can
partially gap a degenerate nodal line, leading to the formation of Dirac/Weyl
semimetals (DSMs/WSMs). However, such SOC-induced gap structure along the nodal
line in TSMs has not yet been systematically investigated experimentally. Here,
we report a direct observation of such gap structure in a magnetic WSM Co3Sn2S2
using high resolution angle-resolved photoemission spectroscopy. Our results
not only reveal the existence and importance of the strong SOC effect in the
formation of the WSM phase in Co3Sn2S2, but also provide insights for the
understanding of its exotic physical properties.",2103.08113v1
2021-05-06,Effective Landé factors for an electrostatically defined quantum point contact in silicene,"The transconductance and effective Land\'{e} $g^*$ factors for a quantum
point contact defined in silicene by the electric field of a split gate is
investigated. The strong spin-orbit coupling in buckled silicene reduces the
$g^*$ factor for in-plane magnetic field from the nominal value 2 to around 1.2
for the first- to 0.45 for the third conduction subband. However, for
perpendicular magnetic field we observe an enhancement of $g^*$ factors for the
first subband to 5.8 in nanoribbon with zigzag and to 2.5 with armchair edge.
The main contribution to the Zeeman splitting comes from the intrinsic
spin-orbit coupling defined by the Kane-Mele form of interaction.",2105.02843v2
2021-05-08,From Majorana fermions to topological quantum computation in semiconductor/superconductor heterostructures,"We present a pedagogical review of topological superconductivity and its
consequences in spin-orbit coupled semiconductor/superconductor
heterostructures. We start by reviewing the historical origins of the notions
of Dirac and Majorana fermions in particle physics and discuss how lower
dimensional versions of these emerge in one dimensional superconductors.
Ultimately, we focus on Majorana zero-modes, which emerge at defects in the
Majorana equation. We then review the definition of the topological invariant,
and how it allows the prediction of such Majorana modes from the bulk
bandstructure of realistic superconductors, which do not have Lorentz
invariance. Finally, we end with a discussion of protocols for how to detect
such Majorana modes and use them for topological quantum computation.",2105.03769v1
2021-05-18,Planar chirality and optical spin-orbit coupling for chiral Fabry-Perot cavities,"We design, in a most simple way, Fabry-Perot cavities with longitudinal
chiral modes by sandwiching between two smooth metallic silver mirrors a layer
of polystyrene made planar chiral by torsional shear stress. We demonstrate
that the helicity-preserving features of our cavities stem from a spin-orbit
coupling mechanism seeded inside the cavities by the specific chiroptical
features of planar chirality. Planar chirality gives rise to an extrinsic
source of three-dimensional chirality under oblique illumination that endows
the cavities with enantiomorphic signatures measured experimentally and
simulated with excellent agreement. The simplicity of our scheme is
particularly promising in the context of chiral cavity QED and polaritonic
asymmetric chemistry.",2105.08605v1
2021-05-26,Antiferromagnetic magnons and local anisotropy: dynamical mean-field study,"We present a dynamical mean-field study of antiferromagnetic magnons in one-,
two- and three-orbital Hubbard model of square and bcc cubic lattice at
intermediate coupling strength. Weinvestigate the effect of anisotropy
introduced by an external magnetic field or single-ion anisotropy.For the
latter we tune continuously between the easy-axis and easy-plane models. We
also analyzea model with spin-orbit coupling in cubic site-symmetry setting.
The ordered states as well as themagnetic excitations are sensitive to even a
small breaking ofSU(2)symmetry of the model andfollow the expectations of
spin-wave theory as well as general symmetry considerations.",2105.12468v2
2021-06-28,Penrose process for a charged black hole in a uniform magnetic field,"Spinning black holes create electromagnetic storms when immersed in ambient
magnetic fields, illuminating the otherwise epically dark terrain. In an
electromagnetic extension of the Penrose process, tremendous energy can be
extracted, boosting the energy of radiating particles far more efficiently than
the mechanical Penrose process. We locate the regions from which energy can be
mined and demonstrate explicitly that they are no longer restricted to the
ergosphere. We also show that there can be toroidal regions that trap negative
energy particles in orbit around the black hole. We find that the effective
charge coupling between the black hole and the super-radiant particles
decreases as energy is extracted, much like the spin of a black hole decreases
in the mechanical analogue. While the effective coupling decreases, the actual
charge of the black hole increases in magnitude reaching the
energetically-favored Wald value, at which point energy extraction is impeded.
We demonstrate the array of orbits for products from the electromagnetic
Penrose process.",2106.15010v3
2021-07-04,Dynamics of kicked spin-orbit-coupled Bose-Einstein condensates,"We investigate the dynamics of kicked pseudo-spin-1/2 Bose-Einstein
condensates (BECs) with spin-orbit coupling (SOC) in a tightly confined
toroidal trap. The system exhibits different dynamical behaviors depending on
the competition among SOC, kick strength, kick period and interatomic
interaction. For weak kick strength, with the increase of SOC the density
profiles of two components evolve from overlapped symmetric distributions into
staggered antisymmetric distributions, and the evolution of energy experiences
a transition from quasiperiodic motion to modulated quantum beating. For large
kick strength, when the SOC strength increases, the overlapped symmetric
density distributions become staggered irregular patterns, and the energy
evolution undergoes a transition from quasiperiodic motion to dynamical
localization. Furthermore, in the case of weak SOC, the increase of kick period
leads to a transition of the system from quantum beating to Rabi oscillation,
while for the case of strong SOC the system demonstrates complex quasiperiodic
motion.",2107.01565v1
2021-07-27,Photovoltaic transistor of atoms due to spin-orbit coupling in three optical traps,"In this paper, spin-orbit coupling induced photovoltaic effect of cold atoms
has been studied in a three-trap system which is an two-dimensional extension
of a two-trap system reported previously. It is proposed here that atom
coherent length is one of the important influence to the resistance of this
photovoltaic battery. Current properties of the system for different
geometrical structures of the trapping potentials are discussed. Numerical
results show extension in the number of traps could cause current increase
directly. Quantum master equation at finite temperature is used to treat this
opened system. This work may give a theoretical basis for further development
of the photovoltaic effect of neutral atoms.",2107.12882v1
2021-08-06,Fulde-Ferrel-Larkin-Ovchinnikov phase in one dimensional Fermi gas with attractive interactions and transverse spin-orbit coupling,"We examine the existence and characteristics of the exotic
Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) phase in a one-dimensional Fermi gas
with attractive Hubbard interactions, in the presence of spin-orbit coupling
(SOC) and Zeeman field. We show that a robust FFLO phase can be created in the
presence of attractive on-site interactions and Zeeman field, and that the
addition of SOC suppresses the FFLO order and enhances the pair formation. In
absence of SOC, the system shows four phases: Bardeen-Cooper-Schrieffer (BCS),
FFLO, multi- mode pairing and fully polarized phases by tuning the Zeeman field
h, and the quantum transition between these phases is discontinuous with
respect to h. In the presence of SOC, the transition from the BCS to FFLO phase
becomes continuous. We present a complete phase diagram of this model both in
the presence and in the absence of SOC at quarter electron filling and also
explore the effect of SOC on the FFLO phase.",2108.03314v1
2021-08-12,Less is more: Vacancy-engineered nodal-line semimetals,"A nodal-line semimetal phase which is enforced by the symmetries of the
material is interesting from fundamental and application standpoints. We
demonstrate that such a phase of matter can be engineered by a simple method:
Introducing vacancies in certain configurations in common symmorphic materials
leads to nonsymmorphic polymorphs with symmetry-enforced nodal lines which are
immune to symmetry-preserving perturbations, such as spin-orbit coupling.
Furthermore, the spectrum acquires also accidental nodal lines with enhanced
robustness to perturbations. These phenomena are explained on the basis of a
symmetry analysis of a minimal effective two-dimensional model which captures
the relevant symmetries of the proposed structures, and verified by
first-principles calculations of vacancy-engineered borophene polymorphs, both
with vanishing and with strong Rashba spin-orbit coupling. Our findings offer
an alternative path to using complicated nonsymmorphic compounds to design
robust nodal-line semimetals; one can instead remove atoms from a simple
symmorphic monoatomic material.",2108.05502v1
2021-09-07,Phase diagram of a model for topological superconducting wires,"We calculate the phase diagram of a model for topological superconducting
wires with local s-wave pairing, spin-orbit coupling $\vec{\lambda}$ and
magnetic field $\vec{B}$ with arbitrary orientations. This model is a
generalized lattice version of the one proposed by Lutchyn $\textit{et al.}$
[Phys. Rev. Lett. $\textbf{105}$ 077001 (2010)] and Oreg $\textit{et al.}$
[Phys. Rev. Lett. $\textbf{105}$ 177002 (2010)], who considered $\vec{\lambda}$
perpendicular to $\vec{B}$. The model has a topological gapped phase with
Majorana zero modes localized at the ends of the wires. We determine
analytically the boundary of this phase. When the directions of the spin-orbit
coupling and magnetic field are not perpendicular, in addition to the
topological phase and the gapped non topological phase, a gapless
superconducting phase appears.",2109.03190v2
2021-09-08,Emergent inductance by dynamical Aharonov-Casher phases,"We propose a mechanism of inductance operation originating from a dynamical
Aharonov-Casher (AC) phase of an electron in ferromagnets. By taking into
account spin-orbit coupling effects, we extend the theory of emergent
inductance, which has recently been discovered in spiral magnets, to arbitrary
magnetic textures. The inductance of dynamical AC phase origin universally
arises in the coexistence of magnetism and a spin-orbit coupling, even with
spatially-uniform magnetization, allowing its stable operation in wide ranges
of temperature and frequency. Revisiting the widely studied systems, such as
ferromagnets with spatial inversion asymmetry, with the new perspective offered
by our work will lead to opening a new paradigm in the study of AC phase
physics and the spintronics-based power management in ultra-wideband frequency
range.",2109.03558v1
2021-10-04,Quantum-geometric perspective on spin-orbit-coupled Bose superfluids,"We employ the Bogoliubov approximation to study how the quantum geometry of
the helicity states affects the superfluid properties of a spin-orbit-coupled
Bose gas in continuum. In particular we derive the low-energy Bogoliubov
spectrum for a plane-wave condensate in the lower helicity band and show that
the geometric contributions to the sound velocity are distinguished by their
linear dependences on the interaction strength, i.e., they are in sharp
contrast to the conventional contribution which has a square-root dependence.
We also discuss the roton instability of the plane-wave condensate against the
stripe phase and determine their phase transition boundary. In addition we
derive the superfluid density tensor by imposing a phase-twist on the
condensate order parameter and study the relative importance of its
contribution from the interband processes that is related to the quantum
geometry.",2110.01385v2
2021-11-06,Phase transition in the 5d1 double perovskite Ba2CaReO6 induced by high magnetic field,"Magnetic properties of an antiferromagnetic double perovskite oxide
Ba2CaReO6, where Re6+ (5d1) ions with large spin-orbit coupling are arranged on
the face-centered-cubic lattice, are investigated using pulsed high magnetic
field up to 66 T. Magnetization and magnetostriction measurements have revealed
a magnetic field induced phase transition at around 50 T. The phase transition
accompanies a jump of magnetization and longitudinal magnetostriction of
approximately 2 10^(-4) with the change of power law behavior, indicating
sizable coupling between the electronic degrees of freedom and the lattice. The
high field phase exhibits a magnetic moment approximately 0.2 {\mu}B, which is
close to the values observed in 5d1 double perovskite oxides with non-collinear
magnetic structure. We argue that Ba2CaReO6 is an antiferromagnet that sits
close to the phase boundary between the collinear and non-collinear phases,
providing the target material for investigating the interplay between
spin-orbital entangled electrons and magnetic field.",2111.03807v1
2021-12-13,Induction of Large Magnetic Anisotropy Energy and Formation of Multiple Dirac States in SrIrO$_3$ Films: Role of correlation and spin-orbit coupling,"The 5$d$ transition metal oxides, in particular iridates, host novel
electronic and magnetic phases due to the interplay between onsite Coulomb
repulsion ($U$) and spin-orbit coupling (SOC). The reduced dimensionality
brings another degree of freedom to increase the functionality of these
systems. By taking the example of ultrathin films of SrIrO$_3$,theoretically,
we demonstrate that confinement led localization can introduce large magnetic
anisotropy energy (MAE) in the range 2-7 meV/Ir which is one to two orders
higher than that of the traditional MAE compounds formed out of transition
metals and their multilayers. Furthermore, in the weak correlation limit,
tailored terminations can yield multiple Dirac states across a large energy
window of 2 eV around the Fermi energy which is a rare phenomena in correlated
oxides and upon experimental realization it will give rise to unique transport
properties with excitation and doping.",2112.06813v2
2021-12-23,Dragging spin-orbit-coupled solitons by a moving optical lattice,"It is known that the interplay of the spin-orbit-coupling (SOC) and
mean-field self-attraction creates stable two-dimensional (2D) solitons (ground
states) in spinor Bose-Einstein condensates. However, SOC destroys the system's
Galilean invariance, therefore moving solitons exist only in a narrow interval
of velocities, outside of which the solitons suffer delocalization. We
demonstrate that the application of a relatively weak moving optical lattice
(OL), with the 2D or quasi-1D structure, makes it possible to greatly expand
the velocity interval for stable motion of the solitons. The stability domain
in the system's parameter space is identified by means of numerical methods. In
particular, the quasi-1D OL produces a stronger stabilizing effect than its
full 2D counterpart. Some features of the domain are explained analytically.",2112.12429v1
2022-01-19,Supercurrent-Induced Weyl Superconductivity,"We show that Weyl superconductivity can be induced by finite supercurrent in
noncentrosymmetric spin-orbit-coupled superconductors with line nodes. We
introduce a three-dimensional tight-binding model of a tetragonal
superconductor in a $D+p$-wave pairing state with a finite center-of-mass
momentum, and elucidate that a line-nodal to point-nodal spectral transition
occurs by applying an infinitesimal supercurrent. We also clarify that the
higher-order effect in spin-orbit coupling is particularly important for this
phenomenon. The point nodes are protected by topologically nontrivial Weyl
charges, and therefore gapless arc states appear on the surface of the
superconductor. Furthermore, both the positions and the Weyl charges of the
point nodes depend on the direction of the current. In addition, a quantized
Berry phase defined on high-symmetry planes characterizes the Weyl nodes when
the in-plane supercurrent is considered. Our proposition paves a new way for
controlling the superconducting gap structures by using an external field.",2201.07397v3
2022-01-19,Self-ordered supersolid phase beyond Dicke superradiance in a ring cavity,"The supersolid phase characterized by the superfluid and long-range spatial
periodicity of crystalline order is central to many branches of science ranging
from condensed matter physics to ultracold atomic physics. Here we study a
self-ordered checkerboard supersolid phase originating from dynamical
spin-orbit coupling for a transversely pumped atomic Bose-Einstein condensate
trapped in a ring cavity, corresponding to a superradiant anti-Tavis-Cummings
phase transition. In particular, an undamped gapless Goldstone mode is observed
in contrast to the experimentally realized lattice supersolid with a gapped
roton mode for Dicke superradiance. This zero energy mode reveals the rigidity
of the self-ordered superradiant phase, which spontaneously breaks a continuous
translational symmetry. Our work will highlight the significant opportunities
for exploring long-lived supersolid matter by utilizing dynamical spin-orbit
coupling in controllable optical cavities.",2201.07664v2
2022-01-21,Fine structure of the stripe phase in ring-shaped Bose-Einstein condensates with spin-orbital-angular-momentum coupling,"We report on a theoretical study of a ring-shaped Bose-Einstein condensate
with Raman-induced spin-orbital-angular-momentum coupling. We analyze the
structure of the ground-state of the system depending different physical
parameters and reveal a peculiar fine structure within the stripe phase on the
phase diagram. We demonstrate the existence of the predicted stripe sub-phases
within a wide range of physical parameters, their traceability through physical
observables, and compare the results with several commonly used variational
approximations. We also show that predicted sub-phases of the stripe phase can
be observed within experimentally realizable conditions.",2201.08728v1
2022-01-27,Topological flat bands in a kagomé lattice multiorbital system,"Flat bands and dispersive Dirac bands are known to coexist in the electronic
bands in a two-dimensional kagome lattice. Including the relativistic
spin-orbit coupling, such systems often exhibit nontrivial band topology,
allowing for gapless edge modes between flat bands at several locations in the
band structure, and dispersive bands or at the Dirac band crossing. Here, we
theoretically demonstrate that a multiorbital system on a kagome lattice is a
versatile platform to explore the interplay between nontrivial band topology
and electronic interaction. Specifically, here we report that the multiorbital
kagome model with the atomic spin-orbit coupling naturally supports topological
bands characterized by nonzero Chern numbers $\cal C$, including a flat band
with $|{\cal C}| =1$. When such a flat band is $1/3$ filled, the non-local
repulsive interactions induce a fractional Chern insulating state. We also
discuss the possible realization of our findings in real kagome materials.",2201.11530v2
2022-01-29,Angular topological superfluid and topological vortex in an ultracold Fermi gas,"We show that pairing in an ultracold Fermi gas under
spin-orbital-angular-momentum coupling (SOAMC) can acquire topological
characters encoded in the quantized angular degrees of freedom. The resulting
topological superfluid is the angular analog of its counterpart in a
one-dimensional Fermi gas with spin-orbit coupling, but characterized by a Zak
phase defined in the angular-momentum space. Upon tuning the SOAMC parameters,
a topological phase transition occurs, which is accompanied by the closing of
the quasiparticle excitation gap. Remarkably, a topological vortex state can
also be stabilized by deforming the Fermi surface, which is topologically
non-trivial in both the coordinate and angular-momentum space, offering
interesting potentials for applications in quantum information and quantum
control. We discuss how the topological phase transition and the exotic vortex
state can be detected experimentally.",2201.12486v2
2022-02-14,Magnetic orderings from spin-orbit coupled electrons on kagome lattice,"We investigate magnetic orderings on kagome lattice numerically from the
tight-binding Hamiltonian of electrons, governed by the filling factor and
spin-orbit coupling (SOC) of electrons. We find that even a simple kagome
lattice model can host both ferromagnetic and noncollinear antiferromagnetic
orderings depending on the electron filling, reflecting gap structures in the
Dirac and flat bands characteristic to the kagome lattice. Kane--Mele- or
Rashba-type SOC tends to stabilize noncollinear orderings, such as magnetic
spirals and 120-degree antiferromagnetic orderings, due to the effective
Dzyaloshinskii--Moriya interaction from SOC. The obtained phase structure helps
qualitative understanding of magnetic orderings in various kagome-layered
materials with Weyl or Dirac electrons.",2202.06665v1
2022-02-23,Chiral Superconductivity in UTe$_2$ via Emergent $C_4$ Symmetry and Spin Orbit Coupling,"A lot of attention has been drawn to superconductivity in UTe$_2$, with
suggestions of time-reversal symmetry breaking triplet chiral superconducting
order parameter. The chirality of the order parameter has been attributed to an
accidental near degeneracy of two superconducting components belonging to 1D
irreps $B_{2u}$ and $B_{3u}$ of the relevant $D_{2h}$ point group, and it has
been argued that the chiral $B_{2u}+iB_{3u}$ combination is selected by
ferromagnetic fluctuations. In this work we present a possible explanation of
the near-degeneracy as a result of an accidental $C_4$ symmetry of the band
structure, with the superconducting order parameter belonging the 2D $E_u$
irrep of $D_{4h}$ that uniquely descends to the sought after $B_{2u}+iB_{3u}$
combination. We show that the $C_4$ symmetry is emergent at the level of the
interactions using a renormalization group calculation and argue that the
chiral combination of the order parameter is favored when spin-orbit coupling
is added to the model.",2202.11732v1
2022-02-28,Topological band structure via twisted photons in a degenerate cavity,"Synthetic dimensions based on particles' internal degrees of freedom, such as
frequency, spatial modes and arrival time, have attracted significant
attention. They offer ideal large-scale lattices to simulate nontrivial
topological phenomena. Exploring more synthetic dimensions is one of the paths
toward higher dimensional physics. In this work, we design and experimentally
control the coupling among synthetic dimensions consisting of the intrinsic
photonic orbital angular momentum and spin angular momentum degrees of freedom
in a degenerate optical resonant cavity, which generates a periodically driven
spin-orbital coupling system. We directly characterize the system's properties,
including the density of states, energy band structures and topological
windings, through the transmission intensity measurements. Our work
demonstrates a novel mechanism for exploring the spatial modes of twisted
photons as the synthetic dimension, which paves the way to design rich
topological physics in a highly compact platform.",2202.13516v1
2022-03-12,Crystal-field effects competing with spin-orbit interactions in NaCeO$_2$,"Ce compounds feature a remarkable diversity of electronic properties, which
motivated extensive investigations over the last decades. Inelastic neutron
scattering represents an important tool for understanding their underlying
electronic structures but in certain cases a straightforward interpretation of
the measured spectra is hampered by the presence of strong vibronic couplings.
The latter may give rise to extra spectral features, which complicates the
mapping of experimental data onto standard multiplet diagrams. To benchmark the
performance of embedded-cluster quantum chemical computational schemes for the
case of $4f$ systems, we here address the Ce 4$f^1$ multiplet structure of
NaCeO$_2$, an antiferromagnet with $D_{2d}$ magnetic-site symmetry for which
neutron scattering measurements indicate only weak vibronic effects. Very good
agreement with the experimental results is found in the computations, which
validates our computational approach and confirms NaCeO$_2$ as a 4$f$ magnet in
the intermediate coupling regime with equally strong 4$f$-shell spin-orbit and
crystal-field interactions.",2203.06394v2
2022-03-25,Intrinsic emergence of Majorana modes in Luttinger j=3/2 systems,"We analyze theoretically two different setups for s-wave superconductivity
(SC) proximitized $j=3/2$ particles in Luttinger materials that are able to
host Majorana bound states (MBSs). First, we consider a one-dimensional SC wire
with intrinsic bulk inversion asymmetry (BIA). In contrast to wires, modeled by
a quadratic dispersion with Rashba spin-orbit coupling, there are two
topological phase transitions in our systems at finite magnetic fields. Second,
we analyze a two-dimensional Josephson junction on the Luttinger model finding
a topological region even in the absence of BIA and Rashba spin-orbit
couplings. This originates from the hybridization of the light and heavy hole
bands of the $j=3/2$ states in combination with the SC pairing. As a
consequence, both systems can be driven into a topological phase hosting MBSs.
Hence, we predict that MBSs form in any SC proximitized Josephson junction on
2D Luttinger materials by the application of magnetic field alone. This opens a
new avenue for the search of topological SC.",2203.13646v2
2022-04-04,Hubbard model on the kagome lattice with time-reversal invariant flux and spin-orbit coupling,"We study the Hubbard model with time-reversal invariant flux and spin-orbit
coupling and position-dependent onsite energies on the kagome lattice, using
numerical and analytical methods. In particular, we perform calculations using
real space dynamical mean-field theory (R-DMFT). To study the topological
properties of the system, we use the topological Hamiltonian approach. We
obtain a rich phase diagram: for weak and intermediate interactions, depending
on the model parameters, the system is in the band insulator, topological
insulator, or metallic phase, while for strong interactions the system is in
the Mott insulator phase. We also investigate the magnetic phases that occur in
this system. For this purpose, in addition to R-DMFT, we also use two
analytical methods: perturbation theory for large interactions and onsite
energies, and stochastic mean-field theory.",2204.01350v2
2022-04-07,Spontaneous time-reversal symmetry breaking in twisted double bilayer graphene,"Twisted double bilayer graphene (tDBG) comprises two Bernal-stacked bilayer
graphene sheets with a twist between them. Gate voltages applied to top and
back gates of a tDBG device tune both the flatness and topology of the
electronic bands, enabling an unusual level of experimental control. Broken
spin/valley symmetry metallic states have been observed in tDBG devices with
twist angles $\sim $ 1.2-1.3$^\circ$, but the topologies and order parameters
of these states have remained unclear. We report the observation of an
anomalous Hall effect in the correlated metal state of tDBG, with hysteresis
loops spanning 100s of mT in out-of-plane magnetic field ($B_{\perp}$) that
demonstrate spontaneously broken time-reversal symmetry. The $B_{\perp}$
hysteresis persists for in-plane fields up to several Tesla, suggesting valley
(orbital) ferromagnetism. At the same time, the resistivity is strongly
affected by even mT-scale values of in-plane magnetic field, pointing to
spin-valley coupling or to a direct orbital coupling between in-plane field and
the valley degree of freedom.",2204.03442v1
2022-05-20,Effect of substrate spin-orbit coupling on the topological gap size of Shiba chains,"Realizing Majorana bound states in chains of magnetic impurities on $s$-wave
superconducting substrates relies on a fine tuning of the energy and
hybridization of the single magnetic impurity bound states and of the
spin-orbit coupling (SOC). While recent experiments investigate the influence
of the former two parameters, the effect of SOC remained experimentally largely
unexplored. Here, we present a scanning tunneling spectroscopy study of
close-packed Mn chains along the [001]-direction on Ta(110) which has almost
identical atomic and surface electronic structure compared to the previously
studied Nb(110) system, but a three times larger SOC. The dominant Shiba band
has a very similar dispersion, but its minigap, taken relative to $\varDelta$,
is increased by a factor of 1.9 with respect to the Nb case, which can be
ascribed to the stronger SOC.",2205.10062v2
2022-05-23,Conductance matrix symmetries of multiterminal semiconductor-superconductor devices,"Nonlocal tunneling spectroscopy of multiterminal semiconductor-superconductor
hybrid devices is a powerful tool to investigate the Andreev bound states below
the parent superconducting gap. We examine how to exploit both microscopic and
geometrical symmetries of the system to extract information on the normal and
Andreev transmission probabilities from the multiterminal electric or
thermoelectric differential conductance matrix under the assumption of an
electrostatic potential landscape independent of the bias voltages, as well as
the absence of leakage currents. These assumptions lead to several symmetry
relations on the conductance matrix. Next, by considering a numerical model of
a proximitized semiconductor wire with spin-orbit coupling and two normal
contacts at its ends, we show how such symmetries can be used to identify the
direction and relative strength of Rashba versus Dresselhaus spin-orbit
coupling. Finally, we study how a voltage-bias-dependent electrostatic
potential as well as quasiparticle leakage break the derived symmetry relations
and investigate characteristic signatures of these two contributions.",2205.11193v3
2022-06-07,Localization of ultracold atoms in incommensurate spin-orbit-coupling and Zeeman lattices,"We consider a particle governed by a one-dimensional Hamiltonian in which
artificial periodic spin-orbit coupling and Zeeman lattice have incommensurate
periods. Using best rational approximations to such quasiperiodic Hamiltonian,
the problem is reduced to description of spinor states in a superlattice. In
the absence of a constant Zeeman splitting, the system acquires an additional
symmetry, which hinders the localization. However, if the lattices are deep
enough, then localized states can appear even for Zeeman field with zero or
small mean value. Spatial distribution of localized modes is nearly uniform and
is directly related to the topological properties of the effective
superlattice: center-of-mass coordinates of modes are determined by Zak phases
computed from the superlattice band structure. The best rational approximations
feature the `memory' effect: each rational approximation holds the information
about the energies and spatial distribution of the modes obtained under
preceding, less accurate approximations. Dispersion of low-energy initial
wavepackets is characterized by the law $\propto t^\beta$ with $\beta$ varying
between $1/2$ at the initial stage and $1$ at longer, but still finite-time,
evolution. The dynamics of initial wavepackets, exciting mainly localized
modes, manifests quantum revivals.",2206.03412v1
2022-06-15,Polarization dependent photoemission as a probe of the magnetic ground state in the layered ferromagnet VI3,"Layered ferromagnets are thrilling materials from both a fundamental and
technological point of view. VI3 is an interesting example, with a complex
magnetism that differentiates it from the first reported Cr based layered
ferromagnets. Here, we show in an indirect way through Angle Resolved
Photoemission Spectroscopy (ARPES) experiments, the importance of spin-orbit
coupling setting the electronic properties of this material. Our light
polarized photoemission measurements point to a ground state with a half-filled
e'_+- doublet, where a gap opening is triggered by spin-orbit coupling enhanced
by electronic correlations.",2206.07233v1
2022-07-01,Superexchange and spin-orbit coupling in monolayer and bilayer chromium trihalides,"We build a microscopic model to study the intra- and inter-layer
superexchange due to electrons hopping in chromium trihalides
($\mathrm{CrX}_3$, X= Cl, Br, and I). In evaluating the superexchange, we
identify the relevant intermediate excitations in the hopping. In our study, we
find that the intermediate hole-pairs excitations in the $p$-orbitals on X ion
play a crucial role in mediating various types of exchange interactions. In
particular, the inter-layer antiferromagnetic exchange may be realized by the
hole-pair-mediated superexchange. Interestingly, we also find that these
virtual hopping processes compete with each other leading to weak intra-layer
ferromagnetic exchange. In addition, we also study the spin-orbit coupling
effects on the superexchange and investigate the Dzyaloshinskii-Moriya
interaction. Finally, we extract the microscopic model parameters from density
functional theory for analyzing the exchange interactions in a monolayer
$\mathrm{CrI}_3$.",2207.00365v2
2022-07-04,Recipe for higher-order topology on the triangular lattice,"We present a recipe for an electronic 2D higher order topological insulator
(HOTI) on the triangular lattice that can be realized in a large family of
materials. The essential ingredient is mirror symmetry breaking, which allows
for a finite quadrupole moment and trivial $\mathbb{Z}_2$ index. The
competition between spin-orbit coupling and the symmetry breaking terms gives
rise to four topologically distinct phases; the HOTI phase appears when
symmetry breaking dominates, including in the absence of spin-orbit coupling.
We identify triangular monolayer adsorbate systems on the (111) surface of
zincblende/diamond type substrates as ideal material platforms and predict the
HOTI phase for $X=$(Al,B,Ga) on SiC.",2207.01359v1
2022-07-06,A comparison between the one- and two-step spin-orbit coupling approaches based on the ab initio Density Matrix Renormalization Group,"The efficient and reliable treatment of both spin-orbit coupling (SOC) and
electron correlation is essential for understanding f-element chemistry. We
analyze two approaches to the problem, the one-step approach where both effects
are treated simultaneously, and the two-step state interaction approach. We
report an implementation of the ab initio density matrix renormalization group
(DMRG) with a one-step treatment of the SOC effect which can be compared to
prior two-step treatments on an equal footing. Using a dysprosium octahedral
complex and bridged dimer as benchmark systems, we identify characteristics of
problems where the one-step approach is beneficial for obtaining the low-energy
spectrum.",2207.02435v2
2022-07-12,Spinless Mirror Chern Insulator from Projective Symmetry Algebra,"It was commonly believed that a mirror Chern insulator (MCI) must require
spin-orbital coupling, since time-reversal symmetry for spinless systems
contradicts with the mirror Chern number. So MCI cannot be realized in spinless
systems which include the large field of topological artificial crystals. Here,
we disprove this common belief. The first point to clarify is that the
fundamental constraint is not from spin-orbital coupling but the symmetry
algebra of time reversal and mirror operations. Then, our theory is based on
the conceptual transformation that the symmetry algebras will be projectively
modified under gauge fields. Particularly, we show that the symmetry algebra of
mirror reflection and time-reversal required for MCI can be achieved
projectively in spinless systems with lattice $\mathbb{Z}_2$ gauge fields,
i.e., by allowing real hopping amplitudes to take $\pm$ signs. Moreover, we
propose the basic structure, the twisted $\pi$-flux blocks, to fulfill the
projective symmetry algebra, and develop a general approach to construct
spinless MCIs based on these building blocks. Two concrete spinless MCI models
are presented, which can be readily realized in artificial systems such as
acoustic crystals.",2207.05654v1
2022-08-09,Single crystal synthesis and low-lying electronic structure of V$_3$S$_4$,"We report successful growth of millimeter-sized high quality single crystals
of V$_3$S$_4$, a candidate topological semimetal belonging to a low-symmetry
space group and consisting of only low atomic number elements. Using density
functional theory calculations and angle-resolved photoemission spectroscopy,
we show that the nonmagnetic phase of monoclinic V$_3$S$_4$ hosts type-II
Dirac-like quasiparticles which opens a sizable gap due to spin orbit coupling,
as well as theoretical multiple nodal lines that are eliminated also by spin
orbit coupling. These results suggest that relativistic effects give rise to
profound modifications of the topological properties even in compounds with
low-weight elements.",2208.04586v2
2022-08-22,Electronic structure and physical properties of EuAuAs single crystal,"High-quality single crystals of EuAuAs were studied by means of powder x-ray
diffraction, magnetization, magnetic susceptibility, heat capacity, electrical
resistivity and magnetoresistance measurements. The compound crystallizes with
a hexagonal structure of the ZrSiBe type (space group $P6_3/mmc$). It orders
antiferromagnetically below 6 K due to the magnetic moments of divalent Eu
ions. The electrical resistivity exhibits metallic behavior down to 40 K,
followed by a sharp increase at low temperatures. The magnetotransport
isotherms show a distinct metamagnetic-like transition in concert with the
magnetization data. The antiferromagnetic ground state in \mbox{EuAuAs} was
corroborated in the \textit{ab initio} electronic band structure calculations.
Most remarkably, the calculations revealed the presence of nodal line without
spin-orbit coupling and Dirac point with inclusion of spin-orbit coupling. The
\textit{Z}$_2$ invariants under the effective time reversal and inversion
symmetries make this system nontrivial topological material. Our findings,
combined with experimental analysis, makes EuAuAs a plausible candidate for an
antiferromagnetic topological nodal-line semimetal.",2208.10405v1
2022-09-04,Theory of intermolecular exchange in coupled spin-1/2 nanographenes,"Open-shell nanographenes can be covalently bonded and still preserve their
local moments, forming interacting spins lattices. In the case of benzenoid
nanographenes, the Ovchinnikov-Lieb rules anticipate the spin of the ground
state of the superstructure, and thereby the sign of the intermolecular
exchange. Here we address the underlying microscopic mechanisms for
intermolecular exchange in this type of system. We find that, in general, three
different mechanisms contribute. First, Hund's ferromagnetic exchange that
promotes ferromagnetic interactions of electrons in overlapping orbitals.
Second, superexchange driven by intermolecular hybridization, identical to
Anderson kinetic exchange, which is a decreasing function of the Hubbard-$U$
energy scale, and is always antiferromagnetic. Third, a Coulomb-driven
superexchange, that increases as a function of $U$, and involves virtual
excitation of excited molecular orbitals that are extended over the entire
structure. We find that Coulomb-driven superexchange can be either ferro or
antiferromagnetic, accounting for Ovchinnikov-Lieb rules. We compute these
exchange energies for the case of coupled $S=1/2$ phenalenyl triangulenes,
using multi-configurational methods both with Hubbard and extended Hubbard
models, thereby addressing the influence of long-range Coulomb interactions on
the exchange interactions.",2209.01577v2
2022-09-05,Honeycomb lattice iridate on the verge of Mott-collapse,"A new honeycomb lattice iridate (La,Na)IrO$_3$ ($\approx$ LaNaIr$_2$O$_6$) is
successfully synthesized from the spin-orbit coupled Mott insulator
Na$_2$IrO$_3$ by replacing the interlayer Na$^+$ ions with La$^{3+}$ ions.
(La,Na)IrO$_3$ shows a finite Sommerfeld term in heat capacity and a $-\ln T$
dependence of resistivity, indicating a realization of a metallic state driven
by a Mott collapse. Furthermore, crystal structure analysis reveals the
formation of Ir zig-zag chains with metal-metal bonding, increasing kinetic
energy resulting in the Mott collapse. This observation would be due to a Mott
collapse induced in a $J_{\mathrm{eff}} = 1/2$ spin-orbit coupling Mott
insulator with an Ir honeycomb lattice by topochemical control of the ionic
configuration.",2209.01861v1
2022-11-30,"Phase diagram, band structure and density of states in two-dimensional attractive Fermi-Hubbard model with Rashba spin-orbit coupling","Based on the two-dimensional (2D) attractive Fermi-Hubbard model with Rashba
spin-orbit coupling (SOC), the SOC strength and Zeeman field dependences of the
phase diagram are investigated by calculating the pairing gap
self-consistently. The results reveal that the phase transition from the BCS
superfluid to the topological superfluid happens under proper Zeeman field
strength and SOC strength. In particular, in contrast to the BCS superfluid
decreasing monotonically as the SOC strength increasing, the topological
superfluid region shows a dome with the SOC strength increasing. An optimal
region in the phase diagram to find the topological superfluid can be found,
which is important to realize the topological superfluid in optical lattice
experimentally. Then we obtain the change of both band structure and density of
states (DOS) during the topological phase transition, and explain the four
peaks of DOS in the topological superfluid by the topology change of the
low-energy branch of quasiparticle energy spectra. Moreover, the topological
superfluid can be suppressed by the doping concentration.",2211.16974v1
2022-12-05,The supercurrent diode effect and nonreciprocal paraconductivity due to the chiral structure of nanotubes,"The research interest in the supercurrent diode effect (SDE) has been
growing. It has been found in various kinds of systems, in a large part of
which it may be understood by combining spin-orbit coupling and Zeeman field.
Here, we show that there exists another mechanism of generating SDE in chiral
nanotubes that trap magnetic fluxes, without spin-orbit coupling or Zeeman
field. We further show that the same generalized Ginzburg-Landau theory leads
to nonreciprocal paraconductivity (NPC) near the transition temperature. The
main features of both the SDE and the NPC are revealed by their parameter
dependence. Our study suggests a new kind of platforms to explore nonreciprocal
properties of superconducting materials. It also provides a theoretical link
between the SDE and the NPC, which were often studied separately.",2212.02183v1
2022-12-10,Tunable energy-level inversion in spin-orbit-coupled Bose-Einstein condensates,"A method to realize controllable inversion of energy levels in a
one-dimensional spin-orbit (SO)-coupled two-component Bose-Einstein condensate
under the action of a gradient magnetic field and harmonic-oscillator (HO)
trapping potential is proposed. The linear version of the system is solved
exactly. By adjusting the SO coupling strength and magnetic-field gradient, the
energy-level inversion makes it possible to transform any excited state into
the ground state. The full nonlinear system is solved numerically, and it is
found that the results are consistent with the linear prediction in the case of
the repulsive inter-component interaction. On the other hand, the
inter-component attraction gives rise to states of superposition and edge
types. Similar results are also reported for the system with the HO trap
replaced by the box potential. These results suggest a possibility to realize
any excited state and observe it in the experiment.",2212.05205v1
2022-12-13,Tuning the parity of superconductivity in CeRh2As2 via pressure,"In the recently discovered heavy fermion superconductor CeRh2As2, a magnetic
field induced phase transition has been observed inside the superconducting
state, which is proposed to be a transition from an even to an odd-parity
superconducting state. The odd-parity superconducting state and its large upper
critical field has been explained by local inversion symmetry breaking and
consequent Rashba spin-orbit coupling. Here we report the experimental tuning
of the parity of superconductivity in CeRh2As2 via applied pressure.
Superconductivity is enhanced by pressure after its initial suppression,
forming a second dome. However, the odd-parity state only exists in the first
dome and the second dome is dominated by the even-parity state. This parity
switch of superconductivity under pressure is consistent with the competition
between Rashba spin-orbit coupling and interlayer hopping in determining the
parity of superconductivity in systems with local inversion symmetry breaking.
Our results provide insightful guidance on how to look for new odd-parity
superconductors.",2212.06930v1
2022-12-20,Bessel Vortices in Spin-Orbit Coupled Spin-1 Bose-Einstein Condensates,"We investigate the stationary vortex solutions in two-dimensional (2D) Rashba
spin-orbit (SO) coupled spin-1 Bose-Einstein condensate (BEC). By introducing
the generalized momentum operator, the linear version of the system can be
solved exactly and its solutions are a set of the Bessel vortices. Based on the
linear version solutions, the stationary vortex solutions of the full nonlinear
system are constructed and determined entirely by the variational
approximation. The results show that the variational results are in good
agreement with the numerical ones. By means of the variational results, the
vortex ground state phase-transition between the stationary vortex solutions,
stability, and the unit Bloch vector textures are discussed in detail. The
results have the potential to be realized in experiment.",2212.10145v1
2022-12-25,Stationary solitons in F=1 spin-orbit coupled Bose-Einstein condensates,"We consider solitary wave excitations above the ground state of $F=1$
spin-orbit coupled Bose-Einstein condensates (SOBECs). The low energy
properties of SOBECs in any of the three branches of the single particle
dispersion relation can be described by suitable scalar nonlinear Schr\""odinger
(NLS) equations which we obtain using multiple-scale expansions. This enables
us to examine a variety of different configurations, such as dark solitary
waves associated with higher energy branches, as well as dark and bright
structures in the lowest branch. The lowest branch can also exhibit a
``superstripe'' phase that supports solitary waves. In all cases, we provide
explicit expressions for the NLS coefficients, and confirm their validity with
full numerical simulations of the SOBEC system including a harmonic confining
potential.",2212.12966v2
2023-01-21,Discovery of a magnetic Dirac system with large intrinsic non-linear Hall effect,"Magnetic materials exhibiting topological Dirac fermions are attracting
significant attention for their promising technological potential in
spintronics. In these systems, the combined effect of the spin-orbit coupling
and magnetic order enables the realization of novel topological phases with
exotic transport properties, including the anomalous Hall effect and
magneto-chiral phenomena. Herein, we report experimental signature of
topological Dirac antiferromagnetism in TaCoTe2 via angle-resolved
photoelectron spectroscopy (ARPES) and first-principles density functional
theory (DFT) calculations. In particular, we find the existence of spin-orbit
coupling-induced gaps at the Fermi level, consistent with the manifestation of
a large intrinsic non-linear Hall conductivity. Remarkably, we find that the
latter is extremely sensitive to the orientation of the N\'eel vector,
suggesting TaCoTe2 a suitable candidate for the realization of non-volatile
spintronic devices with an unprecedented level of intrinsic tunability.",2301.08927v1
2023-01-30,Measuring Electron Correlation. The Impact of Symmetry and Orbital Transformations,"In this perspective, the various measures of electron correlation used in
wavefunction theory, density functional theory and quantum information theory
are briefly reviewed. We then focus on a more traditional metric based on
dominant weights in the full configuration solution and discuss its behaviour
with respect to the choice of the $N$-electron and the one-electron basis. The
impact of symmetry is discussed and we emphasize that the distinction between
determinants, configuration state functions and configurations as reference
functions is useful because the latter incorporate spin-coupling into the
reference and should thus reduce the complexity of the wavefunction expansion.
The corresponding notions of single determinant, single spin-coupling and
single configuration wavefunctions are discussed and the effect of orbital
rotations on the multireference character is reviewed by analysing a simple
model system. In molecular systems, the extent of correlation effects should be
limited by finite system size and in most cases the appropriate choices of
one-electron and $N$-electron bases should be able to incorporate these into a
low-complexity reference function, often a single configurational one.",2301.12807v2
2023-02-08,Superconducting diode effect in quasi-one-dimensional systems,"The recent observations of the superconducting diode effect pose the
challenge to fully understand the necessary ingredients for non-reciprocal
phenomena in superconductors. In this theoretical work, we focus on the
non-reciprocity of the critical current in a quasi-one-dimensional
superconductor. We define the critical current as the value of the supercurrent
at which the quasiparticle excitation gap closes (depairing). Once the critical
current is exceeded, the quasiparticles can exchange energy with the
superconducting condensate, giving rise to dissipation. Our minimal model can
be microscopically derived as a low-energy limit of a Rashba spin-orbit coupled
superconductor in a Zeeman field. Within the proposed model, we explore the
nature of the non-reciprocal effects of the critical current both analytically
and numerically. Our results quantify how system parameters such as spin-orbit
coupling and quantum confinement affect the strength of the superconducting
diode effect. Our theory provides a complementary description to
Ginzburg-Landau theories of the effect.",2302.04277v1
2023-02-10,Cross-polarization extinction enhancement and spin-orbit coupling of light for quantum-dot cavity-QED spectroscopy,"Resonant laser spectroscopy is essential for the characterization, operation,
and manipulation of single quantum systems such as semiconductor quantum dots.
The separation of the weak resonance fluorescence from the excitation laser is
key for high-quality single- and entangled photon sources. This is often
achieved by cross-polarization laser extinction, which is limited by the
quality of the optical elements. Recently, it was discovered that
Fresnel-reflection birefringence in combination with single-mode filtering
counteracting spin-orbit coupling effects enables a three-order of magnitude
improvement of polarization extinction [PRX 11, 021007 (2021)]. Here, we first
investigate multiple reflections and analyze beam reshaping, and observe that
the single-reflection extinction enhancement is optimal. We then demonstrate
this method for cross-polarization extinction enhancement for a resonantly
excited semiconductor quantum dot in a birefringent optical micro cavity, and
observe a 10x improvement of single-photon contrast.",2302.05359v1
2023-02-11,Controllable quantum scars induced by spin-orbit couplings in quantum dots,"The spin-orbit couplings (SOCs) which are the relativistic corrections
originated from the Dirac equation, offer nonlinearity in the classical limit
and are capable of driving the chaotic dynamics. In a nanoscale quantum dot
confined by a two dimensional parabolic potential with the SOCs, various
quantum scar states emerge quasi-periodically in the eigenstates of the system,
when the ratio of the confinement energies in the two directions are nearly
commensurable. The scars, displaying both the quantum interference and the
classical trajectory on the electron density, induced by the relativistic
effects, indicate the bridge between the classical and quantum behaviors of the
system. When the strengths of the Rashba and Dresselhauss SOCs are identical,
the chaos in the classical limit is eliminated as the classical Hamilton's
equations being linear and all the quantum scar states disappear consequently.
The quantum scars induced by SOCs are found to be robust against small
perturbations of the systematic parameters. As the Rashba SOC been controlled
precisely by an external gate, the quantum scar here is fully controllable and
detectable.",2302.05739v2
2023-03-30,Antiferromagnetically ordered Dirac semimetal in Hubbard model with spin-orbit coupling,"We examine the possible existence of Dirac semimetal with magnetic order in a
two-dimensional system with a nonsymmorphic symmetry by using the Hartree-Fock
mean-field theory within the Hubbard model. We locate the region in the
second-neighbor spin-orbit coupling vs Hubbard interaction phase diagram, where
such a state is stabilized. The edge states for the ribbons along two
orthogonal directions concerning the orientation of in-plane magnetic moments
are obtained. Finally, the effect of the in-plane magnetic field, which results
in the stabilization of the Weyl semimetallic state, and the nature of the edge
states corresponding to the Weyl semimetallic state for ribbon geometries are
also explored.",2303.17101v3
2023-03-31,Superconducting topological Dirac semimetals: $P6/m$-Si$_6$ and $P6/m$-NaSi$_6$,"We theoretically propose that hexagonal silicon-based crystals, $P6/m$-Si$_6$
and $P6/m$-NaSi$_6$, are topological Dirac semimetals with superconducting
critical temperatures of 12 K and 13 K, respectively, at ambient pressure. Band
inversion occurs with the Fu-Kane topological invariant $\mathbb{Z}_2=1$, even
in the absence of spin-orbit coupling. The Dirac nodes protected by $C_6$
crystal rotational symmetry remain gapless with spin-orbit coupling. Using
first-principles calculations, we find pressure-induced topological phase
transitions for $P6/m$-Si$_6$ and $P6/m$-NaSi$_6$ with critical external
pressures of 11.5 GPa and 14.9 GPa, respectively. Above the critical pressures,
the Dirac bands are gapped with $\mathbb{Z}_2=0$, while the superconducting
states and the crystal symmetries are retained.Our results may shed light into
a search for silicon-based topological materials with superconductivity.",2303.17953v1
2023-04-27,Enhanced Critical Field of Superconductivity at an Oxide Interface,"The nature of superconductivity and its interplay with strong spin-orbit
coupling at the KTaO3(111) interfaces remains a subject of debate. To address
this problem, we grew epitaxial LaMnO3/KTaO3(111) heterostructures. We show
that superconductivity is robust against the in-plane magnetic field, with the
critical field of superconductivity reaching 25 T in optimally doped
heterostructures. The superconducting order parameter is highly sensitive to
carrier density. We argue that spin-orbit coupling drives the formation of
anomalous quasiparticles with vanishing magnetic moment, providing the
condensate significant immunity against magnetic fields beyond the Pauli
paramagnetic limit. These results offer design opportunities for
superconductors with extreme resilience against magnetic field.",2304.14426v1
2023-06-08,Topological Superconducting States and Quasiparticle Transport on Kagome Lattice,"The pairing symmetry of superconducting states is a critical topic in the
realm of topological superconductivity. However, the pairing symmetry of the
$A\mathrm{V_3Sb_5}$ family, wherein $A=\mathrm{K,Rb,Cs}$, remains
indeterminate. To address this issue, we formulate an effective model on the
kagome lattice to describe topological superconducting states featuring chiral
charge density wave. Through this model, we explore the topological phase
diagrams and thermal Hall conductivity under various parameters, with and
without spin-orbit coupling. Our analysis reveals that the disparities in
thermal Hall conductivity curves between different pairing symmetries are
safeguarded by the topology resulting from the interplay of spin-orbital
coupling and superconducting states. Remarkably, this theoretical prediction
can potentially enable the differentiation of various superconducting pairing
symmetries in materials via experimental measurements of thermal Hall
conductivity curves.",2306.05034v2
2023-06-16,Magnetochiral anisotropy-induced nonlinear Hall effect in spin-orbit coupled Rashba conductors,"We theoretically predict the existence of a non-zero magnetochiral
anisotropy-induced nonlinear Hall effect or a second harmonic Hall voltage
transverse to an applied current in spin-orbit coupled Rashba conductors in the
presence of an in-plane magnetic field B. This is distinct from the Berry
curvature dipole (BCD)-induced nonlinear Hall effect in systems with
non-trivial bandstructure because the former requires broken time-reversal
symmetry while the BCD-induced effect is non-zero even in time-reversal
symmetric systems. This result is independent of the existence of other types
of interactions, such as hexagonal warping or cubic Dresselhaus interactions.
We find that for E||B, the magnitude of the nonlinear Hall current flowing in a
direction perpendicular to the applied electric field is exactly 1/3 of the
magnitude of the non-linear rectification current responsible for
magnetoresistance parallel to the applied electric field obtained in the E\perp
B configuration.",2306.09993v2
2023-07-14,Aharonov-Bohm caging in spin-orbit coupled exciton-polariton lattices,"We study the Aharonov-Bohm (AB) caging effect in rhombic exciton-polariton
lattices, with the Rashba-Dresselhaus spin-orbit coupling (RDSOC) in acting a
synthetic gauge field. The effective magnetic flux through each plaquette is
controlled by the orientation of the RDSOC and geometry of the rhombic lattice.
The results show that the interplay of lattice geometry and the RDSOC will
dramatically influence the energy band structure, furthermore, determining the
transportation properties of exciton-polariton condensates. Non-Hermitian
effects, which arise from the polariton intrinsic loss mechanism, on the AB
caging is also discussed in detail. Meanwhile, the effect of disorder on the
dynamics of AB caging is investigated, and we find that the disorder will lead
to the inverse Anderson localization. We propose that using the AB caging
effect allows to trap and steer the propagation of polaritons in a given
parameter regime. Considering the specific example of a photonic liquid crystal
microcavity to achieve our theoretical predictions, the AB caging could be
switched on and off by applying an external voltage.",2307.07230v1
2023-07-20,Superconductivity Induced Ferromagnetism In The Presence of Spin-Orbit Coupling,"We investigate the behavior of magnetic impurities placed on the surface of
superconductor thin films with spin-orbit coupling. Our study reveals
long-range interactions between the impurities, which decay according to a
power law, mediated by the supercurrents. Importantly, these interactions
possess a ferromagnetic component when considering the influence of the
electromagnetic field, leading to the parallel alignment of the magnetic
moments in the case of two impurities. In a Bravais lattice of magnetic
impurities, superconductivity facilitates the establishment of ferromagnetic
order within specific parameter ranges. These findings challenge the
conventional understanding that ferromagnetism and superconductivity are
mutually exclusive phenomena. Our theoretical framework provides a plausible
explanation for the recently observed remanent flux in iron-based
superconductors, particularly Fe(Se,Te).",2307.10723v3
2023-07-31,Spectrum and quench-induced dynamics of spin-orbit coupled quantum droplets,"We investigate the ground state and dynamics of one-dimensional spin-orbit
coupled (SOC) quantum droplets within the extended Gross-Pitaevskii approach.
As the SOC wavenumber increases, stripe droplet patterns emerge, with a
flat-top background, for larger particle numbers. The surface energy decays
following a power-law with respect to the interactions. At small SOC
wavenumbers, a transition from Gaussian to flat-top droplets occurs for either
a larger number of atoms or reduced intercomponent attraction. The excitation
spectrum shows that droplets for relatively small SOC wavenumbers are stable,
otherwise stripe droplets feature instabilities as a function of the particle
number or the interactions. We also witness rich droplet dynamical features
using velocity imprinting and abrupt changes in the intercomponent interaction
or the SOC parameters. Characteristic responses include breathing oscillations,
expansion, symmetric and asymmetric droplet fragmentation, admixtures of single
and stripe droplet branches, and erratic spatial distributions suggesting the
triggering of relevant instabilities. Our results reveal the controlled
dynamical generation and stability properties of stripe droplets that should be
detectable in current cold-atom experiments.",2307.16742v2
2023-08-02,Over-Barrier Photoelectron Emission with Rashba Spin-Orbit Coupling,"We develop a theoretical model to calculate the quantum efficiency (QE) of
photoelectron emission from materials with Rashba spin-orbit coupling (RSOC)
effect. In the low temperature limit, an analytical scaling between QE and the
RSOC strength is obtained as QE $\propto (\hbar\omega-W)^2+2E_R(\hbar \omega-W)
-E_R^2/3$, where $\hbar\omega$, $W$ and $E_R$ are the incident photon energy,
work function and the RSOC parameter respectively. Intriguingly, the RSOC
effect substantially improves the QE for strong RSOC materials. For example,
the QE of Bi$_2$Se$_3$ and Bi/Si(111) increases, by 149\% and 122\%,
respectively due to the presence of strong RSOC. By fitting to the
photoelectron emission characteristics, the analytical scaling law can be
employed to extract the RSOC strength, thus offering a useful tool to
characterize the RSOC effect in materials. Importantly, when the traditional
Fowler-Dubridge model is used, the extracted results may substantially deviate
from the actual values by $\sim90\%$, thus highlighting the importance of
employing our model to analyse the photoelectron emission especially for
materials with strong RSOC. These findings provide a theoretical foundation for
the design of photoemitters using Rashba spintronic materials.",2308.00952v1
2023-09-12,Kubo formula for dc conductivity: generalization to systems with spin-orbit coupling,"We revise the Kubo formula for the electric dc conductivity in the presence
of spin-orbit coupling (SOC). We discover that each velocity operator that
enters this formula differs from $\partial H/\partial \boldsymbol p$, where $H$
is the Hamiltonian and $\boldsymbol p$ is the canonical momentum. Moreover, we
find an additional contribution to the Hall dc conductivity from noncommuting
coordinates that is missing in the conventional Kubo-Streda formula. This
contribution originates from the ""electron-positron"" matrix elements of the
velocity and position operators. We argue that the widely used Rashba model
does in fact provide a finite anomalous Hall dc conductivity in the metallic
regime (in the noncrossing approximation) if SOC-corrections to the velocity
and position operators are properly taken into account. While we focus on the
response of the charge current to the electric field, linear response theories
of other SOC-related effects should be modified similarly.",2309.06416v5
2023-10-10,Skyrmions and magnetic bubbles in spin-orbit coupled metallic magnets,"Motivated by the observation of Skyrmion-like magnetic textures in 2D
itinerant ferromagnets Fe$_n$GeTe$_2$ ($n \geq3$), we develop a microscopic
model combining itinerant magnetism and spin-orbit coupling on a triangular
lattice. The ground state of the model in the absence of magnetic field
consists of filamentary magnetic domain walls revealing a striking similarity
with our magnetic force microscopy experiments on Fe$_3$GeTe$_2$. In the
presence of magnetic field, these filaments were found to break into large size
magnetic bubbles in our experiments. We identify uniaxial magnetic anisotropy
as an important parameter in the model that interpolates between magnetic
Skyrmions and ferromagnetic bubbles. Consequently, our work uncovers new
topological magnetic textures that merge properties of Skyrmions and
ferromagnetic bubbles.",2310.06521v1
2023-10-12,Three-dimensional solitons in Rydberg-Dressed cold atomic gases with spin-orbit coupling,"We present numerical results for three-dimensional (3D) solitons with
symmetries of the semi-vortex (SV) and mixed-mode (MM) types, which can be
created in spinor Bose-Einstein condensates of Rydberg atoms under the action
of the spin-orbit coupling (SOC). By means of systematic numerical
computations, we demonstrate that the interplay of SOC and long-range
spherically symmetric Rydberg interactions stabilize the 3D solitons, improving
their resistance to collapse. We find how the stability range depends on the
strengths of the SOC and Rydberg interactions and the soft-core atomic radius.",2310.07961v1
2023-10-18,Quadratic nodal point in a two-dimensional noncollinear antiferromagnet,"Quadratic nodal point (QNP) in two dimensions has so far been reported only
in nonmagnetic materials and in the absence of spin-orbit coupling. Here, by
first-principles calculations and symmetry analysis, we predict stable QNP near
Fermi level in a two-dimensional kagome metal-organic framework material,
Cr$_3$(HAB)$_2$, which features noncollinear antiferromagnetic ordering and
sizable spin-orbit coupling. Effective kp and lattice models are constructed to
capture such magnetic QNPs. Besides QNP, we find Cr$_3$(HAB)$_2$ also hosts six
magnetic linear nodal points protected by mirror as well as $C_{2z}T$ symmetry.
Properties associated to these nodal points, such as topological edge states
and quantized optical absorbance, are discussed.",2310.11810v1
2023-10-24,Physics of excitons in layered BiI$_{3}$. Effects of dimensionality and crystal anisotropy,"We carry out a detailed theoretical study of the electronic and optical
properties of bulk and monolayer bismuth triiodide (BiI$_{3}$), a layered metal
halide, using the ab initio GW+BSE scheme with a full spinorial formulation. We
discuss in detail the effects due to the change of dimensionality and the role
of spin-orbit coupling. Moreover, we compute the exciton dispersion by solving
the BSE at finite momentum, also analysing transverse (TE) and longitudinal
(LE) excitons, and the L-T splitting at $\bf{q}\approx\Gamma$. The results
provide a reference for future experimental measurements. In addition, the
interplay between spin-orbit coupling and large binding energy, together with
the role of quantum confinement, confirm that BiI$_{3}$ is an interesting
material for opto-electronic applications and show that it is a good candidate
for the study of exciton dynamics.",2310.16024v1
2023-11-29,Non-reciprocal electron transport in finite-size superconductor/ferromagnet bilayers with strong spin-orbit coupling,"We show that spin-orbit coupling at the interface between a superconducting
film of the finite lateral size and the underlying ferromagnetic insulator with
in-plane exchange field gives rise to a series of non-reciprocal effects
provided the superconducting pairing is enhanced near the boundaries of the
superconductor due to, e.g., variation of the film thickness or of the
interlayer electron transparency. Specifically, the critical temperature and
the critical depairing current are shown to depend on the relative orientation
between the exchange field in the ferromagnet and the superconducting film
boundaries. The discovered anisotropy of the superconducting properties is
promising for the design of diode-type elements in superconducting spintronics.",2311.17534v2
2024-01-20,Emergent bright excitons with Rashba spin-orbit coupling in atomic monolayers,"Optical properties in van der Waals heterostructures based on monolayer
transition-metal dichalcogenides (TMDs), are often dominated by excitonic
transitions. While intrinsic spin-orbit coupling (SOC) and an isotropic band
structure are typically studied in TMDs, in their heterostructures Rashba SOC
and trigonal warping (TW), resulting in bands with threefold anisotropy, are
also present. By considering a low-energy effective Hamiltonian and
Bethe-Salpeter equation, we study the effect of Rashba SOC and TW on the band
structure and absorption spectra. Rashba SOC is predicted to lead to emergent
excitons, which are identified as an admixture between 1s and 2p symmetries. In
contrast, for experimentally relevant values, TW has only a negligible effect
on the absorption spectrum. These findings could guide experimental
demonstrations of emergent bright excitons and further studies of the proximity
effects in van der Waals heterostructure.",2401.11079v2
2024-01-24,Layer-Dependent Quantum Anomalous Hall Effect in Rhombohedral Graphene,"The quantum anomalous Hall (QAH) effect, first proposed by the Haldane model,
has become a paradigmatic example of application of band topology to condensed
matter physics. The recent experimental discoveries of high Chern number QAH
effect in pentalayer and tetralayer rhombohedral graphene highlights the
intriguing interplay between strong interactions and spin-orbit coupling (SOC).
Here we propose a minimal interacting model for spin-orbit coupled rhombohedral
graphene and use the Hartree-Fock analysis to explore the phase diagram at
charge neutrality. We find that with Ising SOC on one outmost graphene layer,
the in-plane layer-antiferromagnetic order is the insulating ground state
without displacement field. Upon increasing the gate displacement field, we
find that the QAH state with Chern number being equal to the layer number
emerges between layer-antiferromagentic state and layer-polarized state, which
is consistent with experimental observations. We further study phase diagram
for different thickness and find pentalayer is optimal for the QAH effect.
Finally, we predict that QAH state is enlarged by engineering opposite Ising
SOC on the opposite outmost layers of rhombohedral graphene.",2401.13413v1
2024-01-30,A universal pairing gap measurement proposal by dynamical excitations in 2D doped attractive Fermi-Hubbard model with spin-orbit coupling,"By calculating dynamical structure factor of two-dimensional doped attractive
Fermi-Hubbard model with Rashba spin-orbit coupling, we not only investigate
collective modes and single-particle excitations of the system during the phase
transition between Bardeen-Cooper-Schrieffer superfluid and topological
superfluid, but also propose a universal method to measure pairing gap
measurement in an optical lattice system. Our numerical results show that the
area of the molecular excitation peak at the transferred momentum ${\bf
q}=\left[\pi,\pi\right]$ is proportional to the square of the pairing gap in
the system with Rashba SOC. In particular, this method is very sensitive to the
pairing gap. This goes on verifying that this method is universal to measure
the pairing gap in a doped optical lattice with Rashba SOC. These theoretical
results are important for experimentally measuring the pairing gap and studying
the topological superfluid in an optical lattice.",2401.17488v1
2024-01-31,Topological superconductivity in a magnetic-texture coupled Josephson junction,"Topological superconductors are appealing building blocks for robust and
reliable quantum information processing. Most platforms for engineering
topological superconductivity rely on a combination of superconductors,
materials with intrinsic strong spin-orbit coupling, and external magnetic
fields, detrimental for superconductivity. We propose a setup where a
conventional Josephson junction is linked via a magnetic-textured barrier.
Antiferromagnetic and ferromagnetic insulators with periodically arranged
domains are compatible with our proposal which does not require intrinsic
spin-orbit or external magnetic fields. We find that the topological phase
depends on the magnitude and period of the barrier magnetization. The
superconducting phase controls the topological transition, which could be
detected as a sharp suppression of the supercurrent across the junction.",2401.17670v1
2024-03-04,Complete Interband Transitions for Non-Hermitian Spin-Orbit-Coupled Cold-Atom Systems,"Recently, synthetic spin-orbit coupling has been introduced into cold-atom
systems for more flexible control of the Hamiltonian, which was further made
time-varying through two-photon detuning to achieve dynamic control of the
cold-atom state. While an intraband transition can be adiabatically obtained, a
complete interband transition, rather than a superposition of different bands,
obtained through fast sweeping is usually guaranteed by having the positions of
the initial and final states be far away from any band gap in the quasimomentum
space. Here, by introducing an additional non-Hermitian parameter through an
atom-loss contrast together with two-photon detuning as two controllable
external parameters, both intraband and complete interband transitions can be
achieved independent of the positions of the initial and final states. In
addition, a point-source diagram approach in the 2D external parameter space is
developed to visualize and predict the locations of any nonadiabatic
transitions. This control protocol can have potential applications in quantum
state control and quantum simulations using cold-atom systems.",2403.01821v1
2024-03-08,Multipolar magnetism in $5d^2$ vacancy-ordered halide double perovskites,"Vacancy-ordered halide double perovskites hosting 4d/5d transition metals
have emerged as a distinct platform for investigating unconventional magnetism
arising out of the interplay of strong atomic spin-orbit coupling (SOC) and
Coulomb interactions. Focusing on the $d^2$ system Cs$_2$WCl$_6$, our ab initio
electronic structure calculation reveals very narrow electronic bands,
fulfilling the necessary condition to realize exotic orders. Using this input,
we solve the many-body spin-orbit coupled single-site problem by exact
diagonalization and show that the multiplet structure of Cs$_2$WCl$_6$ hosts
ground non-Kramers doublets on W, with vanishing dipole moment and a small gap
to an excited magnetic triplet. Our work provides the rationale for the
observed strong deviation from the classic Kotani behaviour in Cs$_2$WCl$_6$
for the measured temperature dependence of the magnetic moment. The non-Kramers
doublets on W exhibit non-zero quadrupolar and octupolar moments, and our
calculated two-site exchange supports the dominance of inter-site octupolar
exchange over quadrupolar interactions. We predict ferro-octupolar order with a
transition temperature $T_c \sim 5$K which may get somewhat suppressed by
quantum fluctuations and disorder; this could be tested in future
low-temperature experiments.",2403.05633v1
2024-03-22,Crossover from relativistic to non-relativistic net magnetization for MnTe altermagnet candidate,"We experimentally study magnetization reversal curves for MnTe single
crystals, which is the altermagnetic candidate. Above 85~K temperature, we
confirm the antiferromagnetic behavior of magnetization $M$, which is known for
$\alpha$--MnTe. Below 85~K, we observe anomalous low-field magnetization
behavior, which is accompanied by the sophisticated $M(\alpha)$ angle
dependence with beating pattern as the interplay between $M(\alpha)$ maxima and
minima: in low fields, $M(\alpha)$ shows ferromagnetic-like 180$^\circ$
periodicity, while at high magnetic fields, the periodicity is changed to the
90$^\circ$ one. This angle dependence is the most striking result of our
experiment, while it can not be expected for standard magnetic systems. In
contrast, in altermagnets, symmetry allows ferromagnetic behavior only due to
the spin-orbit coupling. Thus, we claim that our experiment shows the effect of
weak spin-orbit coupling in MnTe, with crossover from relativistic to
non-relativistic net magnetization, and, therefore, we experimentally confirm
altermagnetism in MnTe.",2403.15348v1
2024-03-25,Layer-selective spin-orbit coupling and strong correlation in bilayer graphene,"Spin-orbit coupling (SOC) and electron-electron interaction can mutually
influence each other and give rise to a plethora of intriguing phenomena in
condensed matter systems. In pristine bilayer graphene, which has weak SOC,
intrinsic Lifshitz transitions and concomitant van-Hove singularities lead to
the emergence of many-body correlated phases. Layer-selective SOC can be
proximity induced by adding a layer of tungsten diselenide (WSe2) on its one
side. By applying an electric displacement field, the system can be tuned
across a spectrum wherein electronic correlation, SOC, or a combination of both
dominates. Our investigations reveal an intricate phase diagram of
proximity-induced SOC-selective bilayer graphene. Not only does this phase
diagram include those correlated phases reminiscent of SOC-free doped bilayer
graphene, but it also hosts unique SOC-induced states allowing a compelling
measurement of valley g-factor and a seemingly impossible correlated insulator
at charge neutrality, thereby showcasing the remarkable tunability of the
interplay between interaction and SOC in WSe2 enriched bilayer graphene.",2403.17140v1
2024-04-04,Light-element and purely charge-based topological materials,"We examine a class of Hamiltonians characterized by interatomic, interorbital
even-odd parity hybridization as a model for a family of topological insulators
without the need for spin-orbit coupling. Non-trivial properties of these
materials are exemplified by studying the topologically-protected edge states
of s-p hybridized alkali and alkaline earth atoms in one and two-dimensional
lattices. In 1D the topological features are analogous to the canonical
Su-Schrieffer-Heeger model but, remarkably, occur in the absence of
dimerization. Alkaline earth chains, with Be standing out due to its gap size
and near particle-hole symmetry, are of particular experimental interest since
their Fermi energy without doping lies directly at the level of topological
edge stats. Similar physics is demonstrated to occur in a 2D honeycomb lattice
system of s-p bonded atoms, where dispersive edge states emerge. Lighter
elements are predicted using this model to host topological states in contrast
to spin-orbit coupling-induced band inversion favoring heaving atoms.",2404.03832v1
2001-04-12,Ferromagnetism in the one-dimensional Hubbard model with orbital degeneracy: From low to high electron density,"We studied ferromagnetism in the one-dimensional Hubbard model with doubly
degenerate atomic orbitals by means of the density-matrix renormalization-group
method and obtained the ground-state phase diagrams. It was found that
ferromagnetism is stable from low to high (0< n < 1.75) electron density when
the interactions are sufficiently strong. Quasi-long-range order of triplet
superconductivity coexists with the ferromagnetic order for a strong Hund
coupling region, where the inter-orbital interaction U'-J is attractive. At
quarter-filling (n=1), the insulating ferromagnetic state appears accompanying
orbital quasi-long-range order. For low densities (n<1), ferromagnetism occurs
owing to the ferromagnetic exchange interaction caused by virtual hoppings of
electrons, the same as in the quarter-filled system. This comes from separation
of the charge and spin-orbital degrees of freedom in the strong coupling limit.
This ferromagnetism is fragile against variation of band structure. For high
densities (n>1), the phase diagram of the ferromagnetic phase is similar to
that obtained in infinite dimensions. In this case, the double exchange
mechanism is operative to stabilize the ferromagnetic order and this long-range
order is robust against variation of the band-dispersion. A partially polarized
state appears in the density region 1.68<n<1.75 and phase separation occurs for
n just below the half-filling (n=2).",0104223v2
2005-05-31,Tidal coupling of a Schwarzschild black hole and circularly orbiting moon,"We describe the possibility of using LISA's gravitational-wave observations
to study, with high precision, the response of a massive central body to the
tidal gravitational pull of an orbiting, compact, small-mass object. Motivated
by this application, we use first-order perturbation theory to study tidal
coupling for an idealized case: a massive Schwarzschild black hole, tidally
perturbed by a much less massive moon in a distant, circular orbit. We
investigate the details of how the tidal deformation of the hole gives rise to
an induced quadrupole moment in the hole's external gravitational field at
large radii. In the limit that the moon is static, we find, in Schwarzschild
coordinates and Regge-Wheeler gauge, the surprising result that there is no
induced quadrupole moment. We show that this conclusion is gauge dependent and
that the static, induced quadrupole moment for a black hole is inherently
ambiguous. For the orbiting moon and the central Schwarzschild hole, we find
(in agreement with a recent result of Poisson) a time-varying induced
quadrupole moment that is proportional to the time derivative of the moon's
tidal field. As a partial analog of a result derived long ago by Hartle for a
spinning hole and a stationary distant companion, we show that the orbiting
moon's tidal field induces a tidal bulge on the hole's horizon, and that the
rate of change of the horizon shape leads the perturbing tidal field at the
horizon by a small angle.",0505156v3
2021-09-27,Octupolar order and Ising quantum criticality tuned by strain and dimensionality: Application to $d$-orbital Mott insulators,"Recent experiments have discovered multipolar orders in a variety of
$d$-orbital Mott insulators. Motivated by uncovering the exchange interactions
which underlie octupolar order proposed in the osmate double perovskites, we
study a two-site model using exact diagonalization on a five-orbital
Hamiltonian, incorporating spin-orbit coupling (SOC) and interactions, and
including both intra-orbital and inter-orbital hopping. Using an exact
Schrieffer-Wolff transformation, we then extract an effective pseudospin
Hamiltonian for the non-Kramers doublets, uncovering dominant ferrooctupolar
coupling driven by the interplay of two distinct intra-orbital hopping terms.
Using classical Monte Carlo simulations on the face-centered cubic lattice, we
obtain a ferrooctupolar transition temperature which is in good agreement with
experiments on the osmate double perovskites. We also explore the impact of
uniaxial strain and dimensional tuning via ultrathin films, which are shown to
induce a transverse field on the Ising octupolar order. This suppresses $T_c$
and potentially allows one to access octupolar Ising quantum critical points.
We discuss possible implications of our results for a broader class of
materials which may host such non-Kramers doublet ions.",2109.13266v3
2022-09-21,Dynamics of photo-induced ferromagnetism in oxides with orbital degeneracy,"By using intense coherent electromagnetic radiation, it may be possible to
manipulate the properties of quantum materials very quickly, or even induce new
and potentially useful phases that are absent in equilibrium. For instance,
ultrafast control of magnetic dynamics is crucial for a number of proposed
spintronic devices and can also shed light on the possible dynamics of
correlated phases out of equilibrium. Inspired by recent experiments on
spin-orbital ferromagnet YTiO$_3$ we consider the nonequilibrium dynamics of
Heisenberg ferromagnetic insulator with low-lying orbital excitations. We model
the dynamics of the magnon excitations in this system following an optical
pulse which resonantly excites infrared-active phonon modes. As the phonons
ring down they can dynamically couple the orbitals with the low-lying magnons,
leading to a dramatically modified effective bath for the magnons. We show this
transient coupling can lead to a dynamical acceleration of the magnetization
dynamics, which is otherwise bottlenecked by small anisotropy. Exploring the
parameter space more we find that the magnon dynamics can also even completely
reverse, leading to a negative relaxation rate when the pump is blue-detuned
with respect to the orbital bath resonance. We therefore show that by using
specially targeted optical pulses, one can exert a much greater degree of
control over the magnetization dynamics, allowing one to optically steer
magnetic order in this system. We conclude by discussing interesting parallels
between the magnetization dynamics we find here and recent experiments on
photo-induced superconductivity, where it is similarly observed that depending
on the initial pump frequency, an apparent metastable superconducting phase
emerges.",2209.10567v1
2001-10-01,Orbital variability of the PSR J2051-0827 Binary System,"We have carried out high-precision timing measurements of the binary
millisecond pulsar PSR J2051$-$0827 with the Effelsberg 100-m radio telescope
of the Max-Planck-Institut f\""ur Radioastronomie and with the Lovell 76-m radio
telescope at Jodrell Bank. The 6.5-yrs radio timing measurements have revealed
a significant secular variation of the projected semi-major axis of the pulsar
at a rate of $\dot x\equiv d(a_{\rm 1} \sin i)/dt = (-0.23\pm 0.03)\times
10^{-12}$, which is probably caused by the Newtonian spin-orbit coupling in
this binary system leading to a precession of the orbital plane. The required
misalignment of the spin and orbital angular momenta of the companion are
evidence for an asymmetric supernova explosion. We have also confirmed that the
orbital period is currently decreasing at a rate of $\dot P_{\rm b}=(-15.5 \pm
0.8)\times 10^{-12}$s s$^{-1}$ and have measured second and third orbital
period derivatives $d^2P_{\rm b}/dt^2=(+2.1 \pm 0.3)\times 10^{-20} {\rm
s^{-1}}$ and $d^3P_{\rm b}/dt^3 =(3.6 \pm 0.6)\times 10^{-28} {\rm s^{-2}}$,
which indicate a quasi-cyclic orbital period variation similar to those found
in another eclipsing pulsar system, PSR B1957+20. The observed variation of the
orbital parameters constrains the maximal value of the companion radius to
$R_{\rm c max} \sim 0.06 R_{\odot}$ and implies that the companion is
underfilling its Roche lobe by 50 %. The derived variation in the quadrupole
moment of the companion is probably caused by tidal dissipation similar to the
mechanism proposed for PSR B1957+20. We conclude that the companion is at least
partially non-degenerate, convective and magnetically active.",0110023v2
2005-01-05,Post-Newtonian accurate parametric solution to the dynamics of spinning compact binaries in eccentric orbits: The leading order spin-orbit interaction,"We derive Keplerian-type parametrization for the solution of post-Newtonian
(PN) accurate conservative dynamics of spinning compact binaries moving in
eccentric orbits. The PN accurate dynamics that we consider consists of the
third post-Newtonian accurate conservative orbital dynamics influenced by the
leading order spin effects, namely the leading order spin-orbit interactions.
The orbital elements of the representation are explicitly given in terms of the
conserved orbital energy, angular momentum and a quantity that characterizes
the leading order spin-orbit interactions in Arnowitt, Deser, and Misner-type
coordinates. Our parametric solution is applicable in the following two
distinct cases: (i) the binary consists of equal mass compact objects, having
two arbitrary spins, and (ii) the binary consists of compact objects of
arbitrary mass, where only one of them is spinning with an arbitrary spin. As
an application of our parametrization, we present gravitational wave
polarizations, whose amplitudes are restricted to the leading quadrupolar
order, suitable to describe gravitational radiation from spinning compact
binaries moving in eccentric orbits. The present parametrization will be
required to construct `ready to use' reference templates for gravitational
waves from spinning compact binaries in inspiralling eccentric orbits. Our
parametric solution for the post-Newtonian accurate conservative dynamics of
spinning compact binaries clearly indicates, for the cases considered, the
absence of chaos in these systems. Finally, we note that our parametrization
provides the first step in deriving a fully second post-Newtonian accurate
`timing formula', that may be useful for the radio observations of relativistic
binary pulsars like J0737-3039.",0501011v1
2021-06-26,"Electronic and magnetic properties of iridium ilmenites $A$IrO$_3$ ($A=$ Mg, Zn, and Mn)","We theoretically investigate the electronic band structures and magnetic
properties of ilmenites with edge-sharing IrO$_6$ honeycomb layers, $A$IrO$_3$
with $A=$ Mg, Zn, and Mn, in comparison with a collinear antiferromagnet
MnTiO$_3$. The compounds with $A=$ Mg and Zn were recently reported in
Y.~Haraguchi {\it et al.}, Phys. Rev. Materials {\bf 2}, 054411 (2018), while
MnIrO$_3$ has not been synthesized yet but the honeycomb stacking structure was
elaborated in a superlattice with MnTiO$_3$ in K.~Miura {\it et al.}, Commun.
Mater. {\bf 1}, 55 (2020). We find that, in contrast to MnTiO$_3$, where an
energy gap opens in the Ti $3d$ bands by antiferromagnetic ordering of the
high-spin $S=5/2$ moments, MgIrO$_3$ and ZnIrO$_3$ have a gap in the Ir $5d$
bands under the influence of both spin-orbit coupling and electron correlation.
Their electronic structures are similar to those in the spin-orbit coupled Mott
insulators with the $j_{\rm eff}=1/2$ pseudospin degree of freedom, as found in
monoclinic $A_2$IrO$_3$ with $A=$ Na and Li which have been studied as
candidates for the Kitaev spin liquid. Indeed, we find that the effective
exchange interactions between the $j_{\rm eff}=1/2$ pseudospins are dominated
by the Kitaev-type bond-dependent interaction and the symmetric off-diagonal
interactions. On the other hand, for MnIrO$_3$, we show that the local lattice
structure is largely deformed, and both Mn $3d$ and Ir $5d$ bands appear near
the Fermi level in a complicated manner, which makes the electronic and
magnetic properties qualitatively different from MgIrO$_3$ and ZnIrO$_3$. Our
results indicate that the IrO$_6$ honeycomb network in the ilmenites $A$IrO$_3$
with $A=$ Mg and Zn would offer a good platform for exotic magnetism by the
spin-orbital entangled moments like the Kitaev spin liquid.",2106.14105v1
2008-11-17,"Dirac fermion quantization on graphene edges: Isospin-orbit coupling, zero modes and spontaneous valley polarization","The paper addresses boundary electronic properties of graphene with a complex
edge structure of the armchair/zigzag/armchair type. It is shown that the
finite zigzag region supports edge bound states with discrete equidistant
spectrum obtained from the Green's function of the continuum Dirac equation.
The energy levels exhibit the coupling between the valley degree of freedom and
the orbital quantum number, analogous to a spin-orbit interaction. The
characteristic feature of the spectrum is the presence of a zero mode, the
bound state of vanishing energy. It resides only in one of the graphene
valleys, breaking spontaneously Kramers' symmetry of the edge states. This
implies the spontaneous valley polarization characterized by the valley isospin
$\pm 1/2$. The polarization is manifested by a zero-magnetic field anomaly in
the local tunneling density of states, and is directly related to the local
electric Hall conductivity.",0811.2698v2
2009-05-18,Ferro-Orbital Order and Strong Magnetic Anisotropy in the Parent Compounds of Iron-Pnictide Superconductors,"The puzzling nature of magnetic and lattice phase transitions of iron
pnictides is investigated via a first-principles Wannier function analysis of
representative parent compound LaOFeAs. A rare ferro-orbital ordering is found
to give rise to the recently observed highly anisotropic magnetic coupling, and
drive the phase transitions--without resorting to widely employed frustration
or nesting picture. The revealed necessity of the additional orbital physics
leads to a correlated electronic structure fundamentally distinct from that of
the cuprates. In particular, the strong coupling to the magnons advocates
active roles of light orbitons in spin dynamics and electron pairing in iron
pnictides.",0905.2957v2
2010-02-01,Orbital magnetoelectric coupling in band insulators,"Magnetoelectric responses are a fundamental characteristic of materials that
break time-reversal and inversion symmetries (notably multiferroics) and,
remarkably, of ""topological insulators"" in which those symmetries are unbroken.
Previous work has shown how to compute spin and lattice contributions to the
magnetoelectric tensor. Here we solve the problem of orbital contributions by
computing the frozen-lattice electronic polarization induced by a magnetic
field. One part of this response (the ""Chern-Simons term"") can appear even in
time-reversal-symmetric materials and has been previously shown to be quantized
in topological insulators. In general materials there are additional orbital
contributions to all parts of the magnetoelectric tensor; these vanish in
topological insulators by symmetry and also vanish in several simplified models
without time-reversal and inversion those magnetoelectric couplings were
studied before. We give two derivations of the response formula, one based on a
uniform magnetic field and one based on extrapolation of a long-wavelength
magnetic field, and discuss some of the consequences of this formula.",1002.0290v2
2011-08-30,Study of the magnetic state of K$_{0.8}$Fe$_{1.6}$Se$_2$ using the five-orbital Hubbard model in the Hartree-Fock approximation,"Motivated by the recent discovery of Fe-based superconductors close to an
antiferromagnetic insulator in the experimental phase diagram, here the
five-orbital Hubbard model (without lattice distortions) is studied using the
real-space Hartree-Fock approximation, employing a 10x10 Fe cluster with Fe
vacancies in a $\sqrt{5}x\sqrt{5}$ pattern. Varying the Hubbard and Hund
couplings, and at electronic density $n$=6.0, the phase diagram contains an
insulating state with the same spin pattern as observed experimentally,
involving 2x2 ferromagnetic plaquettes coupled with one another
antiferromagnetically. The presence of local ferromagnetic tendencies is in
qualitative agreement with Lanczos results for the three-orbital model also
reported here. The magnetic moment ~ 3$\mu_B$/Fe is in good agreement with
experiments. Several other phases are also stabilized in the phase diagram, in
agreement with recent calculations using phenomenological models.",1108.5807v2
2013-01-30,Orbital-selective Mott transitions in a doped two-band Hubbard model with crystal field splitting,"We investigate the effects of crystal field splitting in a doped two-band
Hubbard model with different bandwidths within dynamical mean-field theory
(DMFT), using a quantum Monte Carlo impurity solver. In addition to an
orbital-selective Mott phase (OSMP) of the narrow band, which is adiabatically
connected with the well-studied OSMP in the half-filled case without crystal
field splitting, we find, for sufficiently strong interaction and a suitable
crystal field, also an OSMP of the wide band. We establish the phase diagram
(in the absence of magnetic or orbital order) at moderate doping as a function
of interaction strength and crystal field splitting and show that also the
wide-band OSMP is associated with non-Fermi-liquid behavior in the case of
Ising type Hund rule couplings. Our numerical results are supplemented by
analytical strong-coupling studies of spin order and spectral functions at
integer filling.",1301.7252v2
2013-12-10,Amplification of Angular Rotations Using Weak Measurements,"We present a weak measurement protocol that permits a sensitive estimation of
angular rotations based on the concept of weak-value amplification. The shift
in the state of a pointer, in both angular position and the conjugate orbital
angular momentum bases, is used to estimate angular rotations. This is done by
an amplification of both the real and imaginary parts of the weak-value of a
polarization operator that has been coupled to the pointer, which is a spatial
mode, via a spin-orbit coupling. Our experiment demonstrates the first
realization of weak-value amplification in the azimuthal degree of freedom. We
have achieved effective amplification factors as large as 100, providing a
sensitivity that is on par with more complicated methods that employ quantum
states of light or extremely large values of orbital angular momentum.",1312.2981v3
2018-05-14,Charge-transfer insulation in twisted bilayer graphene,"We studied the real space structure of states in twisted bilayer graphene at
the `magic angle' $\theta = 1.08^\circ$. The flat bands close to charge
neutrality are composed of a mix of `ring' and `center' orbitals around the AA
stacking region. An effective model with localized orbitals is constructed,
which necessarily includes more than just the four flat bands. Long-range
Coulomb interaction causes a charge-transfer at half-filling of the flat bands
from the `center' to the `ring' orbitals. Consequently, the Mott phase is a
featureless spin-singlet paramagnet. We estimate the effective Heisenberg
coupling that favors the singlet coupling to be $J = 3.3$ K, consistent with
experimental values. The superconducting state depends on the nature of the
dopants: hole-doping yields $p+ip$-wave whereas electron-doping yields
$d+id$-wave pairing symmetry.",1805.05294v2
2017-10-17,Coupling effect of topological states and Chern insulators in two-dimensional triangular lattices,"We investigate topological states of two-dimensional (2D) triangular lattices
with multi-orbitals. Tight-binding model calculations of a 2D triangular
lattice based on $\emph{p}_{x}$ and \emph{p}_{y} orbitals exhibit very
interesting doubly degenerate energy points at different positions ($\Gamma$
and K/K$^{\prime}$) in momentum space, with quadratic non-Dirac and linear
Dirac band dispersions, respectively. Counterintuitively, the system shows a
global topologically trivial rather than nontrivial state with consideration of
spin-orbit coupling due to the ""destructive interference effect"" between the
topological states at the $\Gamma$ and K/K$^{\prime}$ points. The topologically
nontrivial state can emerge by introducing another set of triangular lattices
to the system (bitriangular lattices) due to the breakdown of the interference
effect. With first-principles calculations, we predict an intrinsic Chern
insulating behavior (quantum anomalous Hall effect) in a family of 2D
triangular lattice metal-organic framework of Co(C$_{21}$N$_{3}$H$_{15}$)
(TPyB-Co) from this scheme. Our results provide a different path and
theoretical guidance for the search for and design of new 2D topological
quantum materials.",1710.06453v2
2019-09-26,Particle motion around generic black holes coupled to non-linear electrodynamics,"We study spherically symmetric magnetically charged generic black hole
solutions of general relativity coupled to non-linear electrodynamics (NED).
For characteristic values of the generic spacetime parameters we give the
position of horizons in dependence on the charge parameter, demonstrating
separation of the black hole and no-horizon solutions, and possibility of
existence of solutions containing three horizons. We show that null, weak and
strong energy conditions are violated when the outer horizon is approaching the
center. We study effective potentials for photons and massive test particles
and location of circular photon orbits (CPO) and innermost stable circular
orbit (ISCO). We show that the unstable photon orbit can become stable, leading
to the possibility of photon capture which affects on silhouette of the central
object. The position of ISCO approaches the horizon with increasing charge
parameter q and the energy at ISCO decreases with increasing charge parameter.
We investigate this phenomenon and summarize for a variety of the generic
spacetime parameters the upper estimate on the spin parameter of the Kerr black
which can be mimicked by the generic charged black hole solutions.",1909.12026v1
2020-02-05,Multiferroic behavior confined by symmetry in EuTiO3 films,"We have elucidated the spin, lattice, charge and orbital coupling mechanism
underlying the multiferroic character in tensile strained EuTiO3 films.
Symmetry determined by oxygen octahedral tilting shapes the hybridization
between the Eu 4f and Ti 3d orbitals and this inhibits predicted Ti
displacement proper ferroelectricity. Instead, phonon softening emerges at low
temperatures within the pseudo-cube (110) plane, orthogonal to the anticipated
ferroelectric polarization symmetry. Additionally, the magnetic anisotropy is
determined by orbital distortion through hybridization between the Ti 3d and
typically isotropic Eu2+ 4f. This unique scenario demonstrates the critical
role symmetry plays in the coupling of order parameters defining multiferroic
behaviour.",2002.01996v1
2020-12-02,"Strongly coupled charge, orbital and spin order in TbTe$_{3}$","We report a ground state with strongly coupled magnetic and charge density
wave orders mediated via orbital ordering in the layered compound \tbt. In
addition to the commensurate antiferromagnetic (AFM) and charge density wave
(CDW) orders, new magnetic peaks are observed whose propagation vector equals
the sum of the AFM and CDW propagation vectors, revealing an intricate and
highly entwined relationship. This is especially interesting given that the
magnetic and charge orders lie in different layers of the crystal structure
where the highly localized magnetic moments of the Tb$^{3+}$ ions are netted in
the Tb-Te stacks, while the charge order is formed by the conduction electrons
of the adjacent Te-Te layers. Our results, based on neutron diffraction and
resonant x-ray scattering reveal that the charge and magnetic subsystems
mutually influence each other via the orbital ordering of Tb$^{3+}$ ions.",2012.01217v1
2012-05-01,Topological orbital ladders,"We unveil a topological phase of interacting fermions on a two-leg ladder of
unequal parity orbitals, derived from the experimentally realized double-well
lattices by dimension reduction. $Z_2$ topological invariant originates simply
from the staggered phases of $sp$-orbital quantum tunneling, requiring none of
the previously known mechanisms such as spin-orbit coupling or artificial gauge
field. Another unique feature is that upon crossing over to two dimensions with
coupled ladders, the edge modes from each ladder form a parity-protected flat
band at zero energy, opening the route to strongly correlated states controlled
by interactions. Experimental signatures are found in density correlations and
phase transitions to trivial band and Mott insulators.",1205.0254v2
2022-02-14,Counter-intuitive Ferroelectric Property And Non-negligible Orbital Magnetic Moment In Cr/Cu Based Perovskite Metal-Organic Frameworks,"Metal-organic frameworks (MOFs) possess a hybrid nature, combining the
inorganic properties from the metal ions and the organic properties from the
molecular linkers. Stroppa, \textit{et al.}, showed that the perovskite-type
MOF [C(NH$_2$)$_3$]M[(HCOO)$_3$] (M = Cr, Cu) exhibits the magneto-electric
coupled multiferroicity [Angew. Chem. Int. Ed. 50, 5847 (2011) and Adv. Mater.
25, 2284 (2013)]. Moreover, their ferroelectricity arises from the hybrid
improper mechanism, which also explains the magneto-electric coupling. In this
work, we further examine the electric and magnetic properties of
[C(NH$_2$)$_3$]M[(HCOO)$_3$]. We find that the hybrid mode composed of
non-polar modes induces purely electronic polarization even without the polar
mode. The polar mode compensates for the purely electronic polarization. It
leads to a counter-intuitive argument that the inversion of the polar mode
rather enhances the polarization. We provide microscopic origin and macroscopic
analysis for this polarization property. In addition, we find that the orbital
magnetic moment is comparable to the spin contribution in the Cu-based MOF.
Finally, we establish the model for the orbital magnetic moment based on the
perturbation theory.",2202.06537v1
2023-01-09,Resonating holes vs molecular spin-orbit coupled states in group-5 lacunar spinels,"The valence electronic structure of magnetic centers is one of the factors
that determines the characteristics of a magnet. It may refer to orbital
degeneracy, as for $j_\text{eff}=1/2$ Kitaev magnets, or near-degeneracy, e.g.
involving the third and fourth shells in cuprate superconductors. Here we
explore the inner structure of magnetic moments in group-5 lacunar spinels,
fascinating materials featuring multisite magnetic units in the form of
tetrahedral tetramers. Our quantum chemical analysis reveals a very colorful
landscape, much richer than the single-electron, single-configuration
description applied so far to all group-5 Ga$M_4X_8$ chalcogenides, and
clarifies the basic multiorbital correlations on $M_4$ tetrahedral clusters:
while for V strong correlations yield a wave-function that can be well
described in terms of four V$^{4+}$V$^{3+}$V$^{3+}$V$^{3+}$ resonant valence
structures, for Nb and Ta a picture of dressed molecular-orbital-like
$j_\text{eff}=3/2$ entities is more appropriate. These internal degrees of
freedom likely shape vibronic couplings, phase transitions, and
magneto-electric properties in each of these systems.",2301.03392v3
2023-01-13,The quark orbital angular momentum of ground state octet baryons,"Here we study the quark orbital angular momentum of the ground octet baryons
employing an extended chiral constituent quark model, within which the baryon
wave functions are taken to be superposition of the traditional $qqq$ and the
$qqqq\bar{q}$ higher Fock components. Coupling between the two configurations
is estimated using the $^3P_{0}$ quark-antiquark creation mechanism, and the
corresponding coupling strength is determined by fitting the sea flavor
asymmetry of the nucleon. The obtained numerical results show that the quark
angular momentum of the nucleon, $\Sigma$, $\Lambda$ and $\Xi$ hyperons are in
the range $0.10$-$0.30$. In addition, the quark angular momentum of all the
hyperons are a little bit smaller than that of the nucleon. And the octet
baryons spin fractions taken by the intrinsic quark orbital angular momentum
could be up to $60\%$ in present model.",2301.05634v1
2023-10-04,Photonic molecule approach to multi-orbital topology,"The concepts of topology provide a powerful tool to tailor the propagation
and localization of light. While electromagnetic waves have only two
polarization states, engineered degeneracies of photonic modes provide novel
opportunities resembling orbital or spin degrees of freedom in condensed
matter. Here, we tailor such degeneracies for the array of femtosecond laser
written waveguides in the optical range exploiting the idea of photonic
molecules -- clusters of strongly coupled waveguides. In our experiments, we
observe the emergence of topological modes caused by the inter-orbital coupling
and track multiple topological transitions in the system with the change of the
lattice spacings and excitation wavelength. This strategy opens an avenue in
designing novel types of photonic topological phases and states.",2310.03160v1
2001-04-25,Photoemission spectra of LaMnO3 controlled by orbital excitations,"We investigate the spectral function of a hole moving in the orbital-ordered
ferromagnetic planes of LaMnO$_3$, and show that it depends critically on the
type of orbital ordering. While the hole does not couple to the spin
excitations, it interacts strongly with the excitations of $e_g$ orbitals
(orbitons), leading to new type of quasiparticles with a dispersion on the
orbiton energy scale and with strongly enhanced mass and reduced weight.
Therefore we predict a large redistribution of spectral weight with respect to
the bands found in local density approximation (LDA) or in LDA+U.",0104496v1
2001-12-22,Orbital Ordering in Paramagnetic LaMnO3 and KCuF3,"{\it Ab-initio} studies of the stability of orbital ordering, its coupling to
magnetic structure and its possible origins (electron-phonon and/or
electron-electron interactions) are reported for two perovskite systems,
LaMnO$_3$ and KCuF$_3$. We present a new Average Spin State (ASS) calculational
scheme that allowed us to treat a paramagnetic state. Using this scheme, we
succesfully described the experimental magnetic/orbital phase diagram of both
LaMnO$_3$ and KCuF$_3$ in crystal structures when the Jahn-Teller distortions
are neglected. Hence, we conclude that the orbital ordering in both compounds
is purely electronic in origin.",0112423v2
2003-09-13,A New Scenario on the Metal-Insulator Transition in VO2,"The metal-insulator transition in VO2 was investigated using the three-band
Hubbard model, in which the degeneracy of the 3d orbitals, the on-site Coulomb
and exchange interactions, and the effects of lattice distortion were
considered. A new scenario on the phase transition is proposed, where the
increase in energy level separation among the t_2g orbitals caused by the
lattice distortion triggers an abrupt change in the electronic configuration in
doubly occupied sites from an S=1 Hund's coupling state to a spin S=0 state
with much larger energy, and this strongly suppresses the charge fluctuation.
Although the material is expected to be a Mott-Hubbard insulator in the
insulating phase, the metal-to-insulator transition is not caused by an
increase in relative strength of the Coulomb interaction against the electron
hopping as in the usual Mott transition, but by the level splitting among the
t_2g orbitals against the on-site exchange interaction. The metal-insulator
transition in Ti2O3 can also be explained by the same scenario. Such a large
change in the 3d orbital occupation at the phase transition can be detected by
linear dichroic V 2p x-ray absorption measurements.",0309331v1
2006-09-29,Orbital-selective Mott transitions in two-band Hubbard models,"The anisotropic two-orbital Hubbard model is investigated at low temperatures
using high-precision quantum Monte Carlo (QMC) simulations within dynamical
mean-field theory (DMFT). We demonstrate that two distinct orbital-selective
Mott transitions (OSMTs) occur for a bandwidth ratio of 2 even without
spin-flip contributions to the Hund exchange, and we quantify numerical errors
in earlier QMC data which had obscured the second transition. The limit of
small inter-orbital coupling is introduced via a new generalized Hamiltonian
and studied using QMC and Potthoff's self-energy functional method, yielding
insight into the nature of the OSMTs and the non-Fermi-liquid OSM phase and
opening the possibility for a new quantum-critical point.",0609758v1
2007-09-26,Metal-insulator transition in half-filling two-orbital Hubbard model on triangular lattice,"We have investigated the half-filling two-orbital Hubbard model on a
triangular lattice by means of the dynamical mean-field theory (DMFT). The
densities of states and optical conductivity clearly show the occurence of
metal-insulating transition (MIT) at U$_{c}$, U$_{c}$=18.2, 16.8, 6.12 and 5.85
for J=0, 0.01U, U/4 and U/3, respectively. The distinct continuities of double
occupation of electrons, local square moments and local susceptibility of the
charge, the spin and the orbital at J > 0 suggest that the MIT is the
first-order; however at J=0, the MIT is the second-order in the half-filling
two-orbital Hubbard model on triangular lattices. We attribute the first-order
nature of the MIT to the low symmetry of the systems with finite Hund's
coupling J.",0709.4108v2
2010-11-25,First-principles investigation of the very large Perpendicular Magnetic Anisotropy at Fe|MgO Interfaces,"The perpendicular magnetic anisotropy (PMA) arising at the interface between
ferromagnetic transition metals and metallic oxides are investigated via
first-principles calculations. In this work very large values of PMA up to 3
erg/cm$^2$ at Fe$|$MgO interfaces are reported in agreement with recent
experiments. The origin of PMA is attributed to overlap between O-$p_z$ and
transition metal $d_{z^2}$ orbitals hybridized with $d_{xz(yz)}$ orbitals with
stronger spin-orbit coupling induced splitting around the Fermi level for
perpendicular magnetization orientation. Furthemore, it is shown that the PMA
value weakens in case of over- or underoxidation when oxygen $p_z$ and
transition metal $d_{z^2}$ orbitals overlap is strongly affected by disorder,
in agreement with experimental observations in magnetic tunnel junctions.",1011.5667v1
2012-12-18,Magnetoelasticity in ACr2O4 spinel oxides,"Dynamical properties of the lattice structure was studied by optical
spectroscopy in ACr2O4 chromium spinel oxide magnetic semiconductors over a
broad temperature region of T=10-335K. The systematic change of the A-site ions
(A=Mn, Fe, Co, Ni and Cu) showed that the occupancy of 3d orbitals on the
A-site, has strong impact on the lattice dynamics. For compounds with orbital
degeneracy (FeCr2O4, NiCr2O4 and CuCr2O4), clear splitting of infrared-active
phonon modes and/or activation of silent vibrational modes have been observed
upon the Jahn-Teller transition and at the onset of the subsequent long-range
magnetic order. Although MnCr2O4 and CoCr2O4 show multiferroic and
magnetoelectric character, no considerable magnetoelasticity was found in
spinel compounds without orbital degeneracy as they closely preserve the
high-temperature cubic spinel structure even in their magnetic ground state.
Besides lattice vibrations, intra-atomic 3d-3d transitions of the A$^{2+}$ ions
were also investigated to determine the crystal field and Racah parameters and
the strength of the spin-orbit coupling.",1212.4301v1
2013-05-14,Effect of electron-phonon interactions on orbital fluctuations in iron-based superconductors,"To investigate the possibility whether electron-phonon coupling can enhance
orbital fluctuations in iron-based superconductors, we develop an ab initio
method to construct the effective low-energy models including the
phonon-related terms. With the derived effective electron-phonon interactions
and phonon frequencies, we estimate the static part (\omega=0) of the
phonon-mediated effective on-site intra- or inter-orbital electron-electron
attractions as ~ -0.4 eV and exchange or pair-hopping terms as ~ -0.02 eV. We
analyze the model with the derived interactions together with the electronic
repulsions within the random phase approximation. We find that the enhancement
of the orbital fluctuations due to the electron-phonon interactions is small,
making the spin fluctuations dominant. As a result, the superconducting state
with the sign reversal in gap functions ($s_\pm$-wave) is realized.",1305.2995v2
2014-07-16,Density matrix approach to the orbital ordering in the spinel vanadates: A case study,"In this work we apply the density matrices approach to orbital ordering (OO)
in order to study the OO of the spinel vanadates AV$_{2}$O$_{4}$ (A $\equiv$
Zn, Cd and Mg), which is normally believed to be responsible for the structural
transition from cubic to tetragonal phase observed in these compounds. The
density matrices of vanadium atoms are obtained by using {\it state-of-the-art}
full-potential linearized augmented plane wave method based GGA+U calculations.
In the absence of spin-orbit coupling, the present study shows the existence of
anti-ferro OO in the global (local octahedral) coordinate system where $d_{xz}$
and $d_{yz}$ ($d_{xz}$+$d_{yz}$ and $d_{xz}$-$d_{yz}$) orbitals are mainly
occupied at the neighboring V sites for all the compounds.",1407.4217v2
2014-11-06,Towards Mott design by $δ$-doping of strongly correlated titanates,"Doping the distorted-perovskite Mott insulators LaTiO$_3$ and GdTiO$_3$ with
a single SrO layer along the [001] direction gives rise to a rich correlated
electronic structure. A realistic superlattice study by means of the charge
self-consistent combination of density functional theory with dynamical
mean-field theory reveals layer- and temperature-dependent multi-orbital
metal-insulator transitions. An orbital-selective metallic layer at the
interface dissolves via an orbital-polarized doped-Mott state into an
orbital-ordered insulating regime beyond the two conducting TiO$_2$ layers. We
find large differences in the scattering behavior within the latter. Breaking
the spin symmetry in $\delta$-doped GdTiO$_3$ results in blocks of
ferromagnetic itinerant and ferromagnetic Mott-insulating layers which are
coupled antiferromagnetically.",1411.1637v3
2015-03-13,Magnetic interactions in iron superconductors: A review,"High temperature superconductivity in iron pnictides and chalcogenides
emerges when a magnetic phase is suppressed. The multi-orbital character and
the strength of correlations underlie this complex phenomenology, involving
magnetic softness and anisotropies, with Hund's coupling playing an important
role. We review here the different theoretical approaches used to describe the
magnetic interactions in these systems. We show that taking into account the
orbital degree of freedom allows us to unify in a single phase diagram the main
mechanisms proposed to explain the (\pi,0) order in iron pnictides: the
nesting-driven, the exchange between localized spins, and the Hund induced
magnetic state with orbital differentiation. Comparison of theoretical
estimates and experimental results helps locate the Fe superconductors in the
phase diagram. In addition, orbital physics is crucial to address the magnetic
softness, the doping dependent properties, and the anisotropies.",1503.04223v2
2015-06-14,Orbital two-channel Kondo effect in epitaxial ferromagnetic L10-MnAl films,"We report the first experimental realization of orbital two-channel Kondo
(2CK) effect from two-level systems (TLSs) in epitaxial L10-MnAl films with
giant perpendicular magnetic anisotropy. The resistivity exhibits a
low-temperature (T) upturn with a clear transition from a lnT-dependence to
T1/2-dependence and deviation from it in three distinct T regimes, which are
independent of applied magnetic fields. The magnitudes of Kondo temperature and
energy splitting of the TLSs are greatly enhanced in comparison to those in
other systems exhibiting orbital 2CK, suggesting strong coupling between the
tunneling centers with conduction electrons via resonant scattering. These
results point to a considerable robustness of the orbital 2CK effect even in
the presence of ferromagnetic ordering and significant spin polarization of the
conduction electrons.",1506.04360v2
2016-06-30,Slave Boson Theory of Orbital Differentiation with Crystal Field Effects: Application to UO$_2$,"We derive an exact operatorial reformulation of the rotational invariant
slave boson method and we apply it to describe the orbital differentiation in
strongly correlated electron systems starting from first principles. The
approach enables us to treat strong electron correlations, spin-orbit coupling
and crystal field splittings on the same footing by exploiting the gauge
invariance of the mean-field equations. We apply our theory to the archetypical
nuclear fuel UO$_2$, and show that the ground state of this system displays a
pronounced orbital differention within the $5f$ manifold, with Mott localized
$\Gamma_8$ and extended $\Gamma_7$ electrons.",1606.09614v3
2016-09-09,A nonorthogonal state-interaction approach for matrix product state wave functions,"We present a state-interaction approach for matrix product state (MPS) wave
functions in a nonorthogonal molecular orbital basis. Our approach allows us to
calculate for example transition and spin-orbit coupling matrix elements
between arbitrary electronic states provided that they share the same
one-electron basis functions and active orbital space, respectively. The key
element is the transformation of the MPS wave functions of different states
from a nonorthogonal to a biorthonormal molecular orbital basis representation
exploiting a sequence of non-unitary transformations following a proposal by
Malmqvist (Int. J. Quantum Chem. 30, 479 (1986)). This is well-known for
traditional wave-function parametrizations but has not yet been exploited for
MPS wave functions.",1609.02684v1
2017-02-16,Effect of laser induced orbital momentum on magnetization switching,"The observed magnetization switching by circularly polarized ultrafast laser
pulses has been attributed to the inverse Faraday effect in which the induced
non-equilibrium orbital momentum serves as an effective magnetic filed via
spin-orbit coupling for magnetization rotation and switching. We critically
examine this scenario by explicitly calculating the magnitude of the induced
orbital momentum for generic itinerant band. We show that the calculated
induced angular momentum is not large enough for reversing the magnetization in
one laser pulse with the order of 100 femtosecond duration. Instead, we propose
that each laser pulse is capable to expand a reverse domain a few nano-meters
and it takes multiple pulses to complete the magnetization reversal process via
domain wall motion.",1702.04823v3
2020-07-16,Increasing the number of topological nodal lines in semimetals via uniaxial pressure,"The application of pressure has been demonstrated to induce intriguing phase
transitions in topological nodal-line semimetals. In this work we analyze how
uniaxial pressure affects the topological character of BaSn2 , a Dirac
nodal-line semimetal in the absence of spin-orbit coupling. Using calculations
based on the density functional theory and a model tight-binding Hamiltonian,
we find the emergence of a second nodal line for pressures higher than 4 GPa.
We examine the topological features of both phases demonstrating that a
nontrivial character is present in both of them. Thus, providing evidence of a
topological-to-topological phase transition in which the number of topological
nodal lines increases. The orbital overlap increase between Ba dxz and dyz
orbitals and Sn pz orbitals and the preservation of crystal symmetries are
found to be responsible for the advent of this transition. Furthermore, we pave
the way to experimentally test this kind of transition by obtaining a
topological relation between the zero-energy modes that arise in each phase
when a magnetic field is applied.",2007.08502v2
2009-12-11,Superconductivity in a Two-Orbital Hubbard Model with Electron and Hole Fermi Pockets: Application in Iron Oxypnictide Superconductors,"We investigate the electronic states of a one-dimensional two-orbital Hubbard
model with band splitting by the exact diagonalization method. The Luttinger
liquid parameter $K_{\rho}$ is calculated to obtain superconducting (SC) phase
diagram as a function of on-site interactions: the intra- and inter-orbital
Coulomb $U$ and $U'$, the Hund coupling $J$, and the pair transfer $J'$. In
this model, electron and hole Fermi pockets are produced when the Fermi level
crosses both the upper and lower orbital bands. We find that the system shows
two types of SC phases, the SC \Roman{u'-large} for $U>U'$ and the SC
\Roman{u-large} for $U<U'$, in the wide parameter region including both weak
and strong correlation regimes. Pairing correlation functions indicate that the
most dominant pairing for the SC \Roman{u'-large} (SC \Roman{u-large}) is the
intersite (on-site) intraorbital spin-singlet with (without) sign reversal of
the order parameters between two Fermi pockets. The result of the SC
\Roman{u'-large} is consistent with the sign-reversing s-wave pairing that has
recently been proposed for iron oxypnictide superconductors.",0912.2173v1
2016-05-19,SU(2)-SU(4) Kondo Crossover and Emergent Electric Polarization in a Triangular Triple Quantum Dot,"We study an orbitally degenerate Kondo effect in a triangular triple quantum
dot (TTQD), where the three dots are connected vertically with a single
metallic lead through electron tunneling. Both spin and orbital degrees of
freedom play an important role in the SU(4) Kondo effect. This is demonstrated
by an equilateral TTQD Kondo system at half-filling, by Wilson's numerical
renormalization group method. We show how an emergent electric polarization of
the TTQD is associated with a crossover from SU(4) to SU(2) symmetry in the
low-temperature state. A marked sign reversal of the electric polarization is
generated by the fine-tuning of Kondo coupling with degenerate orbitals, which
can be utilized to reveal orbital dynamics in the SU(4) Kondo effect.",1605.05803v1
2016-05-27,Atomic defect states in monolayers of MoS$_2$ and WS$_2$,"The influence of atomic vacancy defects at different concentrations on
electronic properties of MoS$_2$ and WS$_2$ monolayers is studied by means of
Slater-Koster tight-binding model with non-orthogonal $sp^3d^5$ orbitals and
including the spin-orbit coupling. The presence of vacancy defects induces
localized states in the bandgap of pristine MoS$_2$ and WS$_2$, which have
potential to modify the electronic structure of the systems, depending on the
type and concentration of the defects. It is shown that although the
contribution of metal (Mo or W) $d$ orbitals is dominant in the formation of
midgap states, the sulphur $p$ and $d$ orbitals have also considerable
contribution in the localized states, when metal defects are introduced. Our
results suggest that Mo and W defects can turn the monolayers into p-type
semiconductors, while the sulphur defects make the system a n-type
semiconductor, in agreement with ab initio results and experimental
observations.",1605.08756v1
2020-01-22,Constraining the origin of the planetary debris surrounding ZTF J0139+5245 through rotational fission of a triaxial asteroid,"White dwarfs containing orbiting planetesimals or their debris represent
crucial benchmarks by which theoretical investigations of post-main-sequence
planetary systems may be calibrated. The photometric transit signatures of
likely planetary debris in the ZTF J0139+5245 white dwarf system has an orbital
period of about 110 days. An asteroid which breaks up to produce this debris
may spin itself to destruction through repeated close encounters with the star
without entering its Roche radius and without influence from the white dwarf's
luminosity. Here, we place coupled constraints on the orbital pericentre ($q$)
and the ratio ($\beta$) of the middle to longest semiaxes of a triaxial
asteroid which disrupts outside of this white dwarf's Roche radius ($r_{\rm
Roche}$) soon after attaining its 110-day orbit. We find that disruption within
tens of years is likely when $\beta \lesssim 0.6$ and $q\approx 1.0-2.0r_{\rm
Roche}$, and when $\beta \lesssim 0.2$ out to $q\approx 2.5r_{\rm Roche}$.
Analysing the longer-timescale disruption of triaxial asteroids around ZTF
J0139+5245 is desirable but may require either an analytical approach relying
on ergodic theory or novel numerical techniques.",2001.08223v1
2020-02-23,Local polarization in oxygen-deficient LaMnO$_3$ induced by charge localization in the Jahn-Teller distorted structure,"The functional properties of transition metal perovskite oxides are known to
result from a complex interplay of magnetism, polarization, strain, and
stoichiometry. Here, we show that for materials with a cooperative Jahn-Teller
distortion, such as LaMnO$_3$ (LMO), the orbital order can also couple to the
defect chemistry and induce novel material properties. At low temperatures, LMO
exhibits a strong Jahn-Teller distortion that splits the $e_g$ orbitals of the
high-spin Mn$^{3+}$ ions and leads to alternating long, short, and intermediate
Mn--O bonds. Our DFT+$U$ calculations show that, as a result of this orbital
order, the charge localization in LMO upon oxygen vacancy formation differs
from other manganites, like SrMnO$_3$, where the two extra electrons reduce the
two Mn sites adjacent to the vacancy. In LMO, relaxations around the defect
depend on which type of Mn--O bond is broken, affecting the $d$-orbital
energies and leading to asymmetric and hence polar excess-electron localization
with respect to the vacancy. Moreover, we show that the Mn--O bond lengths,
orbital order and consequently the charge localization and polarity are tunable
via strain.",2002.09921v1
2020-04-21,Merging Compact Binaries Near a Rotating Supermassive Black Hole: Eccentricity Excitation due to Apsidal Precession Resonance,"We study the dynamics of merging compact binaries near a rotating
supermassive black hole (SMBH) in a hierarchical triple configuration. We
include various general relativistic effects that couple the inner orbit, the
outer orbit and the spin of the SMBH. During the orbital decay due to
gravitational radiation, the inner binary can encounter an ""apsidal precession
resonance"" and experience eccentricity excitation. This resonance occurs when
the apsidal precession rate of the inner binary matches that of the outer
binary, with the precessions driven by both Newtonian interactions and various
post-Newtonian effects. The eccentricity excitation requires the outer orbit to
have a finite eccentricity, and is most effective for triples with small mutual
inclinations, in contrast to the well-studied Lidov-Kozai effect. The resonance
and the associated eccentricity growth may occur while the binary emits
gravitational waves in the low-frequency band, and may be detectable by future
space-based gravitational wave detectors.",2004.10205v3
2017-09-06,Evolution of the magnetic and structural properties of Fe$_{1-x}$Co$_x$V$_2$O$_4$,"The magnetic and structural properties of single crystal
Fe$_{1-x}$Co$_x$V$_2$O$_{4}$ samples have been investigated by performing
specific heat, susceptibility, neutron diffraction, and X-ray diffraction
measurements. As the orbital-active Fe$^{2+}$ ions with larger ionic size are
gradually substituted by the orbital-inactive Co$^{2+}$ ions with smaller ionic
size, the system approaches the itinerant electron limit with decreasing V-V
distance. Then, various factors such as the Jahn-Teller distortion and the
spin-orbital coupling of the Fe$^{2+}$ ions on the A sites and the orbital
ordering and electronic itinerancy of the V$^{3+}$ ions on the B sites compete
with each other to produce a complex magnetic and structural phase diagram.
This phase diagram is compared to those of Fe$_{1-x}$Mn$_x$V$_2$O$_{4}$ and
Mn$_{1-x}$Co$_x$V$_2$O$_{4}$ to emphasize several distinct features.",1709.01842v1
2018-03-19,New superexchange paths due to breathing-enhanced hopping in corner-sharing cuprates,"We present ab initio calculations of the superexchange antiferromagnetic spin
coupling $J$ for two cuprates, Sr$_2$CuO$_3$ and La$_2$CuO$_4$. Good agreement
with experimental estimates is obtained. We find that $J$ increases
substantially as the distance between Cu and apical O is increased. There is an
important synergetic effect of the Coulomb interaction, expanding the Cu $3d$
orbital when an electron hops into this orbital, and the O-Cu hopping, being
increased by this orbital expansion (breathing). This is a new ingredient in
superexchange models. In a model with a fixed basis, breathing effects can be
described as a mixing of $3d$ and $4d$ orbitals or as a single $3d \to 4d$
excitation.",1803.07026v1
2018-03-21,Isolated highly localized bands in $\mathrm{YbI_2}$ monolayer caused by $4f$ orbitals,"The novel electronic structures can induce unique physical properties in
two-dimensional (2D) materials. In this work, we report isolated highly
localized bands in $\mathrm{YbI_2}$ monolayer by the first-principle
calculations within generalized gradient approximation (GGA) plus spin-orbit
coupling (SOC). It is found that $\mathrm{YbI_2}$ monolayer is an indirect-gap
semiconductor using both GGA and GGA+SOC. The calculations reveal that Yb-$4f$
orbitals constitute isolated highly localized bands below the Fermi level at
the absence of SOC, and the bands are split into the $j = 7/2$ and $j = 5/2$
states with SOC. The isolated highly localized bands can lead to very large
Seebeck coefficient and very low electrical conductivity in p-type doping by
producing very large effective mass of the carrier. It is proved that isolated
highly localized bands have very strong stability again strain, which is very
important for practical application. When the onsite Coulomb interaction is
added to the Yb-$4f$ orbitals, isolated highly localized bands persist, and
only their relative positions in the gap change. These findings open a new
window to search for novel electronic structures in 2D materials.",1803.07982v1
2018-08-08,Heavy quasiparticle bands in the underscreened quasiquartet Kondo lattice,"We study the quasiparticle spectrum in an underscreened Kondo-lattice (KL)
model that involves a single spin degenerate conduction band and two
crystalline-electric-field (CEF) split Kramers doublets coupled by both
orbital-diagonal and non-diagonal exchange interactions. We find the three
quasiparticle bands of the model using a constrained fermionic mean field
approach. While two bands are similar to the one-orbital model a new genuinely
heavy band inside the main hybridization gap appears in the quasiquartet model.
Its dispersion is due to effective hybridization with conduction states but the
bandwidth is controled by the size of the CEF splitting. Furthermore several
new indirect and direct hybridztion gaps may be identified. By solving the
selfconsistency equation we calculate the CEF- splitting and exchange
dependence of effective Kondo low energy scale, hybridization gaps and band
widths. We also derive the quasiparticle spectral densities and their partial
orbital contributions. We suggest that the two-orbital KL model can exhibit
mixed CEF/Kondo excitonic magnetism.",1808.02699v2
2018-08-21,Majorana fermions in finite-size strips in the presence of orbital effects: what is the Majorana polarization telling us?,"We study numerically the formation of Majorana bound states in a finite-size
quasi-one-dimensional square-lattice strip with Rashba spin-orbit coupling, in
the presence of a proximity-induced superconducting pairing and a magnetic
field perpendicular to the strip. We take into account both the Zeeman and
orbital effects of the field. First, using the Majorana polarization, we
demonstrate that such a system can host more than one pair of Majorana
quasiparticles. We construct the corresponding topological phase diagram and we
conclude that the topological regions are extended in the presence of orbital
effects, however the gap protecting the topological states is reduced.",1808.07058v1
2019-02-14,Hall coefficient signals orbital differentiation in the Hund's metal Sr$_2$RuO$_4$,"The Hall coefficient $R_H$ of Sr$_2$RuO$_4$ exhibits a non-monotonic
temperature dependence with two sign reversals. We show that this puzzling
behavior is the signature of two crossovers which are key to the physics of
this material. The increase of $R_H$ and the first sign change upon cooling are
associated with a crossover into a regime of coherent quasiparticles with
strong orbital differentiation of the inelastic scattering rates. The eventual
decrease and the second sign change at lower temperature is driven by the
crossover from inelastic to impurity-dominated scattering. This qualitative
picture is supported by quantitative calculations of $R_H(T)$ using Boltzmann
transport theory in combination with dynamical mean-field theory, taking into
account the effect of spin-orbit coupling. Our insights shed new light on the
temperature dependence of the Hall coefficient in materials with strong orbital
differentiation, as observed in Hund's metals.",1902.05503v2
2019-05-24,Group-theoretic classification of superconducting states of Strontium Ruthenate,"The possible superconducting states of strontium ruthenate (Sr$_2$RuO$_4$)
are organized into irreducible representations of the point group $D_{4h}$,
with a special emphasis on nodes occurring within the superconducting gap. Our
analysis covers the cases with and without spin-orbit coupling and takes into
account the possibility of inter-orbital pairing within a three-band,
tight-binding description of Sr$_2$RuO$_4$. No dynamical treatment if
performed: we are confining ourselves to a group-theoretical analysis. The case
of uniaxial deformations, under which the point group symmetry is reduced to
$D_{2h}$, is also covered. It turns out that nodal lines, in particular
equatorial nodal lines, occur in most representations. We also highlight some
results specific to multiorbital superconductivity. Among other things, we find
that odd inter-orbital pairing allows to combine singlet and triplet
superconductivity whithin the same irreducible representation, that pure
inter-orbital superconductivity leads to nodal surfaces and that the notion of
nodes imposed by symmetry is not clearly defined.",1905.10467v1
2020-06-25,Ferroelectricity-induced multiorbital odd-frequency superconductivity in SrTiO$_3$,"We demonstrate that SrTiO$_3$ can be a platform for observing the bulk
odd-frequency superconducting state owing to the multiorbital/multiband nature.
We consider a three-orbital tight-binding model for SrTiO$_3$ in the vicinity
of a ferroelectric critical point. Assuming an intraorbital spin-singlet
$s$-wave superconducting order parameter, it is shown that the odd-frequency
pair correlations are generated due to the intrinsic LS coupling which leads to
the local orbital mixing. Furthermore, we show the existence of additional
odd-frequency pair correlations in the ferroelectric phase, which is induced by
an odd-parity orbital hybridization term proportional to the ferroelectric
order parameter. We also perform a group theoretical classification of the
odd-frequency pair amplitudes based on the fermionic and space group symmetries
of the system. The classification table enables us to predict dominant
components of the odd-frequency pair correlations based on the symmetry of the
normal state Hamiltonian that we take into account. Furthermore, we show that
experimental signatures of the odd-parity orbital hybridization, which is an
essential ingredient for the ferroelectricity-induced odd-frequency pair
correlations, can be observed in the spectral functions and density of states.",2006.14181v1
2021-02-05,"A Colossal Electroresistance response, accompanied by metal-insulator transition, in a mixed-valent vanadate","Colossal electroresistance (CER) in manganites, i.e., a large change in
electrical resistance under the influence of either an applied electric field
or an applied electric current, has often been described as complimentary to
the colossal magnetoresistance (CMR) effect. Mixed valent vanadates with active
t2g and empty eg orbitals, unlike manganites, have not naturally been discussed
in this context, as double exchange based CMR is not realizable in them.
However, presence of coupled spin and orbital degrees of freedom,
metal-insulator transition (MIT) accompanied by orbital order-disorder
transition, etc., anyway make the vanadates an exciting group of materials.
Here we probe a Fe-doped hollandite lead vanadate PbFe1.75V4.25O11 (PFVO),
which exhibits a clear MIT as a function of temperature. Most importantly, a
giant fall in the resistivity, indicative of a CER, as well as a systematic
shift in the MIT towards higher temperature are observed as a function of
applied electric current. Detailed structural, magnetic, thermodynamic and
transport studies point towards a complex interplay between orbital
order/disorder effect, MIT and double exchange in this system.",2102.03128v1
2021-06-11,Orbital-selective Mott phase and non-Fermi liquid in FePS$_3$,"The layered metal phosphorous trisulfide FePS$_3$ is reported to be a Mott
insulator at ambient conditions and to undergo structural and insulator-metal
phase transitions under pressure. However, the character of the resulting
metallic states has not been understood clearly so far. Here, we theoretically
study the phase transitions of FePS$_3$ using first-principles methods based on
density functional theory and embedded dynamical mean field theory. We find
that the Mott transition in FePS$_3$ can be orbital-selective, with $t_{2g}$
states undergoing a correlation-induced insulator-to-metal transition while
$e_g$ states remain gapped. We show that this orbital-selective Mott phase,
which occurs only when non-hydrostatic pressure is used, is a bad metal (or
non-Fermi liquid) with large fluctuating moments due to Hund's coupling.
Further application of pressure increases the crystal-field splitting and
converts the system to a conventional Fermi liquid with low-spin configurations
dominant. Our results show that FePS$_3$ is a novel example of a system that
realizes an orbital-selective Mott phase, allowing tuning between correlated
and uncorrelated metallic properties in an accessible pressure range ($\leq$ 18
GPa).",2106.06204v1
2021-07-14,Description of molecular nanomagnets by the multi-orbital Hubbard model with correlated hopping,"We present a microscopic description of molecular magnets by the
multi-orbital Hubbard model, which includes the correlated hopping term, i.e.
the dependence of electron hopping amplitude between orbitals on the degree of
their occupancy. In the limit of large Coulomb on-site interaction, we derived
the spin Hamiltonian using the perturbation theory. The magnetic coupling
constant between two ions we determined in two different ways: a)from the
expression obtained in the perturbation calculus and b)from the analysis of
distances between the lowest levels of the energy spectrum obtained by the
diagonalization of the multi-orbital Hubbard model. The procedure we use can be
applied to various nanomagnets, but the final calculations we performed for the
molecular ring $Cr_8$. We showed that the correlated hopping can reduce the
antiferromagnetic exchange between ions, what is essential for a proper
description of $Cr_8$.",2107.06576v1
2023-12-14,Nonlinear optical responses in multi-orbital topological superconductors,"We theoretically study first and second-order optical responses in a
transition metal dichalcogenide monolayer with distinct trivial, nodal, and
time-reversal invariant topological superconducting (TRITOPS) phases. We show
that the second-order DC response, also known as the photogalvanic response,
contains signatures for differentiating these phases while the first-order
optical response does not. We find that the high-frequency photogalvanic
response is insensitive to the phase of the system, while the low-frequency
response exhibits features distinguishing the three phases. At zero doping,
corresponding to an electron filling in which the Fermi level lies at nodal
points, there are opposite sign zero-frequency divergences in the response when
approaching the nodal phase boundaries from the trivial and the TRITOPS phases.
In the trivial phase, both the high-frequency and low-frequency response of the
system are negative, but in the TRITOPS phase, the low-frequency response
becomes positive while the high-frequency response remains negative.
Furthermore, since phase transitions are controlled by the Rashba spin-orbit
coupling and the ratio of intra-orbital and inter-orbital paring amplitudes,
our results not only help distinguish the phases but can also provide an
estimate of the pairing amplitudes based on the photogalvanic response of the
system.",2312.08638v1
2023-09-10,Non-zero Integral Spin of Acoustic Vortices and Spin-orbit Interaction in Longitudinal Acoustics,"Spin and orbital angular momenta (AM) are of fundamental interest in wave
physics. Acoustic wave, as a typical longitudinal wave, has been well studied
in terms of orbital AM, but still considered unable to carry non-zero integral
spin AM or spin-orbital interaction in homogeneous media due to its spin-0
nature. Here we give the first self-consistent analytical calculations of spin,
orbital and total AM of guided vortices under different boundary conditions,
revealing that vortex field can carry non-zero integral spin AM. We also
introduce for acoustic waves the canonical-Minkowski and kinetic-Abraham AM,
which has aroused long-lasting debate in optics, and prove that only the former
is conserved with the corresponding symmetries. Furthermore, we present the
theoretical and experimental observation of the spin-orbit interaction of
vortices in longitudinal acoustics, which is thought beyond attainable in
longitudinal waves in the absence of spin degree of freedom. Our work provides
a solid platform for future studies of the spin and orbital AM of guided
acoustic waves and may open up a new dimension for acoustic vortex-based
applications such as underwater communications and object manipulations.",2309.04989v1
1997-07-29,Spin-Orbit-Induced Magnetic Anisotropy for Impurities in Metallic Samples II. Finite Size Dependence in the Kondo Resistivity,"The electrical resistivity including the Kondo resistivity increase at low
temperature is calculated for thin films of dilute magnetic alloys. Assuming
that in the non-magnetic host the spin-orbit interaction is strong like in Au
and Cu, the magnetic impurities have a surface anisotropy calculated in part I.
That anisotropy hinders the motion of the spin. Including that anisotropy the
effective electron-impurity coupling is calculated by using the second order
renormalization group equations. The amplitude of the Kondo resistivity
contribution is reduced as the position of the impurity approaches the surface
but the increase occurs approximately at the bulk Kondo temperature. Different
proximity effects observed by Giordano are also explained qualitatively where
the films of magnetic alloys are covered by pure second films with different
mean free path. The theory explains the experimental results in those cases
where a considerable amount of impurities is at the surface inside the
ballistic region.",9707299v1
1999-02-16,Phenomenology of the superconducting state in Sr2RuO4,"The symmetry of the superconducting phase of Sr2RuO4 is identified as the
odd-parity pairing state d(k)=\hat{z}(k_x \pm i k_y) based on recent
experiments. The experimental evidence for the so-called orbital dependent
superconductivity leads to a single-band description of superconductivity based
on spin fluctuation mechanism. It is shown that the state \hat{z}(k_x \pm i
k_y) can be stabilized by the spin fluctuation feedback mechanism analogous to
the A-phase in 3He and by spin-orbit coupling effects.",9902214v1
1999-07-20,Local Time-Reversal Symmetry Breaking in d_(x2-y2) Superconductors,"We show that an isolated impurity in a spin singlet d_{x2-y2} superconductor
generates a d_{xy} order parameter with locally broken time-reversal symmetry.
The origin of this effect is a coupling between the d_{x2-y2} and the d_{xy}
order parameter induced by spin-orbit scattering off the impurity. The
signature of locally broken time-reversal symmetry is an induced orbital charge
current near the impurity, which generates a localized magnetic field in the
vicinity of the impurity. We present a microscopic theory for the impurity
induced d_{xy} component, discuss its spatial structure as well as the pattern
of induced current and local magnetic field near the localized impurity spin.",9907300v1
2000-08-02,Origin of Magnetoresistance Anomalies in Antiferromagnetic YBa_{2}Cu_{3}O_{6+x},"Specific d-wave angular dependence of the in-plane magnetoresistence in
antiferromagnetic tetragonal YBa_{2}Cu_{3}O_{6+x} (x~0.3) on orientation of the
external magnetic field in (a,b) plane is assigned to the effective hole
transport through low lying excited purely oxygen doublet O2pe_u state, not the
ground b_{1g}(d_{x^2-y^2}) state. External magnetic field determines the
orientation of the strong exchange field for the spin-triplet
b_{1g}e_u:{}^{3}E_u state of the hole CuO_4 center and due to the spin-orbital
coupling results in either orbital polarization of the E_u doublet giving rise
to the spatial anisotropy of the hole transport. Experimental data allow to
estimate parameter of the effective spin Hamiltonian.",0008035v3
2000-08-22,Elementary excitations in one-dimensional spin-orbital models: neutral and charged solitons and their bound states,"We study, both numerically and variationally, the interplay between different
types of elementary excitations in the model of a spin chain with anisotropic
spin-orbit coupling, in the vicinity of the ""dimer line"" with an exactly known
dimerized ground state. Our variational treatment is found to be in a
qualitative agreement with the exact diagonalization results. Soliton pairs are
shown to be the lowest excitations only in a very narrow region of the phase
diagram near the dimer line, and the phase transitions are always governed by
magnon-type excitations which can be viewed as soliton-antisoliton bound
states. It is shown that when the anisotropy exceeds certain critical value, a
new phase boundary appears. In the doped model on the dimer line, the exact
elementary charge excitation is shown to be a hole bound to a soliton. Bound
states of those ""charged solitons"" are studied; exact solutions for N-hole
bound states are presented.",0008321v1
2003-04-09,Field-induced magnetic anisotropy in La0.7Sr0.3CoO3,"Magnetic anisotropy has been measured for the ferromagnetic La0.7Sr0.3CoO3
perovskite from an analysis of the high-field part of the magnetization vs.
field curves, i.e., the magnetic saturation regime. These measurements give a
magnetic anistropy one order of magnitude higher than that of reference
manganites. Surprisingly, the values of the magnetic anisotropy calculated in
this way do not coincide with those estimated from measurements of coercive
fields which are one order of magnitude smaller. It is proposed that the reason
of this anomalous behaviour is a transition of the trivalent Co ions under the
external magnetic field from a low-spin to an intermediate-spin state. Such a
transition converts the Co3+ ions into Jahn-Teller ions having an only
partially quenched orbital angular momentum, which enhances the intra-atomic
spin-orbit coupling and magnetic anisotropy.",0304211v1
2004-06-18,A test of the spin-orbit sum rule for actinides using an ab-initio calculation,"The expectation value of the angular part of the spin-orbit-coupling (SOC)
operator $<l\cdot s>$ and the branching ratio for the $N_{4,5}$
X-ray-absorption spectroscopy in $\delta$-Pu, $\alpha$-U and
face-centered-cubic (fcc) Th are calculated within the framework of the
density-functional theory in combination with the local-spin-density
approximation (LSDA), the generalized-gradient approximation (GGA) and the
LDA+$U$ method. The SOC contribution is calculated in terms of the first- and
the second- variational schemes. A strong variation in the magnitudes of the
calculated $<l\cdot s>$ operator along the actinide series is found. The
results show that the SOC sum rule for $\delta$-Pu and $\alpha$-U is reasonably
valid, whereas there is a sign mismatch for the case of fcc Th. The calculated
branching ratios for the case without SOC in the valence shell strongly deviate
from the statistical value.",0406433v1
2004-08-27,"Confined spin waves reveal an assembly of nanosize domains in ferromagnetic La(1-x)CaxMnO3 (x=0.17,0.2)","We report a study of spin-waves in ferromagnetic La$_{1-x}$Ca$_{x}$MnO$_3$,
at concentrations x=0.17 and x=0.2 very close to the metallic transition
(x=0.225). Below T$_C$, in the quasi-metallic state (T=150K), nearly
q-independent energy levels are observed. They are characteristic of standing
spin waves confined into finite-size ferromagnetic domains, defined in {\bf a,
b) plane for x=0.17 and in all q-directions for x=0.2. They allow an estimation
of the domain size, a few lattice spacings, and of the magnetic coupling
constants inside the domains. These constants, anisotropic, are typical of an
orbital-ordered state, allowing to characterize the domains as ""hole-poor"". The
precursor state of the CMR metallic phase appears, therefore, as an assembly of
small orbital-ordered domains.",0408611v2
2005-01-10,Band structure and magnetotransport of a two-dimensional electron gas in the presence of spin-orbit interaction,"The band structure and magnetotransport of a two-dimensional electron gas
(2DEG), in the presence of the Rashba (RSOI) and Dresselhaus (DSOI) terms of
the spin-orbit interaction and of a perpendicular magnetic field, is
investigated. Exact and approximate analytical expressions for the band
structure are obtained and used to calculate the density of states (DOS) and
the longitudinal magnetoresitivity assuming a Gaussian type of level
broadening. The interplay between the Zeeman coupling and the two terms of the
SOI is discussed. If the strengths $\alpha$ and $ \beta$, of the RSOI and DSOI,
respectively, are equal and the $g$ factor vanishes, the two spin states are
degenerate and a shifted Landau-level structure appears. With the increase of
the difference $\alpha- \beta$, a novel beating pattern of the DOS and of the
Shubnikov-de Haas (SdH) oscillations appears distinctly different from that
occurring when one of these strengths vanishes.",0501214v1
2005-05-10,Electronically smectic-like phase in a nearly half-doped manganite,"We use neutron scattering to study the spin and charge/orbital ordering
(CO-OO) in the nearly half-doped perovskite manganite
$Pr_{0.55}(Ca_{0.8}Sr_{0.2})_{0.45}MnO_3$ (PCSMO). On cooling from room
temperature, PCSMO first enters into a CO-OO state below $T_{CO}$ and then
becomes a CE-type long-range ordered antiferromagnet below $T_N$. At
temperatures above $T_N$ but below $T_{CO}$ ($T_N<T<T_{CO}$), the spins in
PCSMO form highly anisotropic smectic liquid-crystal-like texture with
ferromagnetic (FM) quasi-long-range ordered one-dimensional zigzag chains
weakly coupled antiferromagnetically. Such a magnetic smectic-like phase
results directly from the spin-orbit interaction and demonstrates the presence
of textured `electronic soft' phases in doped Mott insulators.",0505255v2
2006-07-31,Colossal magnetostriction and negative thermal expansion in the frustrated antiferromagnet ZnCr2Se4,"A detailed investigation of ZnCr2Se4 is presented which is dominated by
strong ferromagnetic exchange but orders antiferromagnetically at T_N = 21 K.
Specific heat C and thermal expansion Delta L/L exhibit sharp first-order
anomalies at the antiferromagnetic transition. T_N is strongly reduced and
shifted to lower temperatures by external magnetic fields and finally is fully
suppressed suggesting a field induced quantum critical behavior close to 60
kOe. Delta L/L(T) is unusually large and exhibits negative thermal expansion
below 75 K down to T_N indicating strong frustration of the lattice.
Magnetostriction Delta L/L(H) reveals colossal values (0.5x10^{-3}) comparable
to giant magnetostriction materials. Electron-spin resonance, however, shows
negligible spin-orbital coupling excluding orbitally induced Jahn-Teller
distortions. The obtained results point to a spin-driven origin of the
structural instability at T_N explained in terms of competing ferromagnetic and
antiferromagnetic exchange interactions yielding strong bond frustration.",0607811v1
2006-09-27,Optimized Effective Potential Method in Current-Spin Density Functional Theory,"Current-spin density functional theory (CSDFT) provides a framework to
describe interacting many-electron systems in a magnetic field which couples to
both spin- and orbital-degrees of freedom. Unlike in usual (spin-) density
functional theory, approximations to the exchange-correlation energy based on
the model of the uniform electron gas face problems in practical applications.
In this work, explicitly orbital-dependent functionals are used and a
generalization of the Optimized Effective Potential (OEP) method to the CSDFT
framework is presented. A simplifying approximation to the resulting integral
equations for the exchange-correlation potentials is suggested. A detailed
analysis of these equations is carried out for the case of open-shell atoms and
numerical results are given using the exact-exchange energy functional. For
zero external magnetic field, a small systematic lowering of the total energy
for current-carrying states is observed due to the inclusion of the current in
the Kohn-Sham scheme. For states without current, CSDFT results coincide with
those of spin density functional theory.",0609696v1
2007-11-23,Gap structure in noncentrosymmetric superconductors,"Gap structure in noncentrosymmetric superconductors with spin-orbit band
splitting is studied using a microscopic model of pairing mediated by phonons
and/or spin fluctuations. The general form of pairing interaction in the band
representation is derived, which includes both the intraband and interband
pairing terms. In the case of isotropic interaction (in particular, for a
BCS-contact interaction), the interband pairing terms vanish identically at any
magnitude of the band splitting. The effects of pairing interaction anisotropy
are analyzed in detail for a metal of cubic symmetry with strong spin-orbit
coupling. It is shown that if phonons are dominant then the gaps in two bands
are isotropic, nodeless, and have in general different amplitudes. Applications
to the Li_2(Pd_{1-x},Pt_x)_3B family of noncentrosymmetric superconductors are
discussed.",0711.3681v3
2008-12-31,Structural distortion and frustrated magnetic interactions in the layered copper oxychloride [CuCl]LaNb(2)O(7),"We present a computational study of the layered copper oxychloride
[CuCl]LaNb(2)O(7) that has been recently proposed as a spin-1/2 frustrated
square lattice compound. Our results evidence an orbitally degenerate ground
state for the reported tetragonal crystal structure and reveal a
Jahn-Teller-type structural distortion. This distortion heavily changes the
local environment of copper -- CuO(2)Cl(2) plaquettes are formed instead of
CuO(2)Cl(4) octahedra -- and restores the single-orbital scenario typical for
copper oxides and oxyhalides. The calculated distortion is consistent with the
available diffraction data and the experimental results on the electric field
gradients for the Cu and Cl sites. The band structure suggests a complex
three-dimensional spin model with the interactions up to the fourth neighbors.
Despite the layered structure of (CuCl)LaNb(2)O(7), the spin system has
pronounced one-dimensional features. Yet, sizable interchain interactions lead
to the strong frustration and likely cause the spin-gap behavior. Computational
estimates of individual exchange couplings are in qualitative agreement with
the experimental data.",0901.0154v2
2009-10-22,Metal-insulator transition through a semi-Dirac point in oxide nanostructures: VO$_2$ (001) layers confined within TiO$_2$,"Multilayer (TiO$_2$)$_m$/(VO$_2$)$_n$ nanostructures ($d^1$ - $d^0$
interfaces with no polar discontinuity) show a metal-insulator transition with
respect to the VO$_2$ layer thickness in first principles calculations. For $n$
$\geq$ 5 layers, the system becomes metallic, while being insulating for $n$ =
1 and 2. The metal-insulator transition occurs through a semi-Dirac point phase
for $n$ = 3 and 4, in which the Fermi surface is point-like and the electrons
behave as massless along the zone diagonal in k-space and as massive fermions
along the perpendicular direction. We provide an analysis of the evolution of
the electronic structure through this unprecedented insulator-to-metal
transition, and identify it as resulting from quantum confinement producing a
non-intuitive orbital ordering on the V $d^1$ ions, rather than being a
specific oxide interface effect. Spin-orbit coupling does not destroy the
semi-Dirac point for the calculated ground state, where the spins are aligned
along the rutile c-axis, but it does open a substantial gap if the spins lie in
the basal plane.",0910.4411v1
2010-10-18,Gate-controlled weak antilocalization effect in inversion layer on p-type HgCdTe,"We discover weak antilocalization effect of two-dimensional electron gas with
one electric subband occupied in the inversion layer on p-type HgCdTe crystal.
By fitting the model of Iordanskii, Lyanda-Geller and Pikus to data at varies
temperatures and gate voltages, we extract phase coherence and spin-orbit
scattering times as functions of temperature and carrier density. We find that
Elliot-Yafet mechanism and Nyquist mechanism are the dominating spin
decoherence and dephasing mechanisms, respectively. We also find that the
Rashba parameter is relatively large and the dependence of Rashba parameter
upon carrier density is not monotonic and an optimal carrier density exists for
the maximization of spin-orbit coupling.",1010.3464v1
2011-02-08,Multi-orbital Non-Crossing Approximation from maximally localized Wannier functions: the Kondo signature of copper phthalocyanine on Ag (100),"We have developed a multi-orbital approach to compute the electronic
structure of a quantum impurity using the non-crossing approximation. The
calculation starts with a mean-field evaluation of the system's electronic
structure using a standard quantum chemistry code. Here we use density
functional theory (DFT). We transformed the one-electron structure into an
impurity Hamiltonian by using maximally localized Wannier functions (MLWF).
Hence, we have developed a method to study the Kondo effect in systems based on
an initial one-electron calculation. We have applied our methodology to a
copper phthalocyanine molecule chemisorbed on Ag (100), and we have described
its spectral function for three different cases where the molecule presents a
single spin or two spins with ferro- and anti-ferromagnetic exchange couplings.
We find that the use of broken-symmetry mean-field theories such as Kohn-Sham
DFT cannot deal with the complexity of the spin of open-shell molecules on
metal surfaces and extra modeling is needed.",1102.1667v2
2011-06-02,Microscopic Study of Electronic and Magnetic Properties for Ir Oxide,"The exact diagonalization and the variational cluster approximation (VCA) are
used to study the nature of a novel Mott insulator induced by a strong
spin-orbit coupling for a two-dimensional three-band Hubbard model consisting
of the $t_{2g}$ manifold of $5d$ orbitals. To characterize the ground state, we
introduce a local Kramer's doublet which can represent a state with effective
angular momentum $J_{\rm eff}=|{\bm S}-{\bm L}|=1/2$ as well as spin $S=1/2$.
Our systematic study of the pseudo-spin structure factor defined by the
Kramer's doublet shows that the $J_{\rm eff}=1/2$ Mott insulator is smoothly
connected to the $S=1/2$ Mott insulator. Using the Kramer's doublet as a
variational state for the VCA, we examine the one-particle excitations for the
Mott insulating phase. These results are compared with recent experiments on
Sr$_2$IrO$_4$.",1106.0413v1
2011-06-13,Lattice-Driven Magnetoresistivity and Metal-Insulator Transition in Single-Layered Iridates,"Sr2IrO4 exhibits a novel insulating state driven by spin-orbit interactions.
We report two novel phenomena, namely a large magnetoresistivity in Sr2IrO4
that is extremely sensitive to the orientation of magnetic field but exhibits
no apparent correlation with the magnetization, and a robust metallic state
that is induced by dilute electron (La3+) or hole (K+) doping for Sr2+ ions in
Sr2IrO4. Our structural, transport and magnetic data reveal that a strong
spin-orbit interaction alters the balance between the competing energies so
profoundly that (1) the spin degree of freedom alone is no longer a dominant
force; (2) underlying transport properties delicately hinge on the Ir-O-Ir bond
angle via a strong magnetoelastic coupling; and (3) a highly insulating state
in Sr2IrO4 is proximate to a metallic state, and the transition is governed by
lattice distortions. This work suggests that a novel class of lattice-driven
electronic materials can be developed for applications.",1106.2381v1
2012-07-06,Energy spectrum reconstruction at the edge of a two-dimensional electron system with strong spin-orbit coupling,"We experimentally demonstrate the simultaneous reconstruction of the bulk and
the edge energy spectra caused by strong spin-orbit interaction, at the two
lowest filling factors $\nu=1$ and $\nu=2$ for $In_xGa_{1-x}As$ two-dimensional
electron system with $x = 0.75$. The observed reconstruction is of different
character at these filling factors: it is characterized by zeroing of the
energy gap at the levels crossing point at $\nu=2$, while the reconstruction at
$\nu=1$ goes through the coexistence of two $\nu=1$ quantum Hall phases with
different spin projections. An analysis indicates a strong influence of
many-body interaction on the reconstruction at $\nu=1$.",1207.1627v1
2012-08-06,Change of an insulator's topological properties by a Hubbard interaction,"We introduce two dimensional fermionic band models with two orbitals per
lattice site, or one spinful orbital, and which have a non-zero topological
Chern number that can be changed by varying the ratio of hopping parameters. A
topologically non-trivial insulator is then realized if there is one fermion
per site. When interactions in the framework of the Hubbard model are
introduced, the effective hopping parameters are renormalized and the system's
topological number can change at a certain interaction strength, $U=\bar U$,
smaller than that for the Mott transition. Two different situations may then
occur: either the anomalous Hall conductivity $\sigma_{xy}$ changes abruptly at
$\bar U$, as the system undergoes a transition from one topologically
non-trivial insulator to another, or the transition is through an anomalous
Hall metal, and $\sigma_{xy}$ changes smoothly between two different quantized
values as $U$ grows. Restoring time-reversal symmetry by adding spin to
spinless models, the half-filled system becomes a $\mathbb{Z}_2$ topological
insulator. The topological number $\nu$ then changes at a critical coupling
$\bar U$ and the quantized spin Hall response changes abruptly.",1208.1289v2
2012-09-20,Rashba Spin Orbit Interaction and Birefringent Electron Optics in Graphene,"Electron optics exploits the analogies between rays in geometrical optics and
electron trajectories, leading to interesting insights and potential
applications. Graphene, with its two-dimensionality and photon-like behavior of
its charge carriers, is the perfect candidate for the exploitation of electron
optics. We show that a circular gate-controlled region in the presence of
Rashba spin-orbit interaction in graphene may indeed behave as a Veselago
electronic lens but with two different indices of refraction. We demonstrate
that this birefringence results in complex caustics patterns for a circular
gate, selective focusing of different spins, and the possible direct
measurement of the Rashba coupling strength in scanning probe experiments.",1209.4415v2
2013-07-09,Topological and edge state properties of a three-band model for Sr2RuO4,"Modeling the spin-triplet superconductor Sr2RuO4 through a three-orbital
tight-binding model we investigate topological properties and edge states
assuming chiral p-wave pairing. In concordance with experiments the three Fermi
surfaces consist of two electron-like and one hole-like one corresponding to
the alpha-, beta- and gamma-band on the level of a two-dimensional system. The
quasi-particle spectra and other physical quantities of the superconducting
phase are calculated by means of a self-consistent Bogoliubov-de Gennes
approach for a ribbon shaped system. While a full quasiparticle excitation gap
is realized in the bulk system, at the edges gapless states appear some of
which have linear and others nearly flat dispersion around zero energy. This
study shows the interplay between spin-orbit coupling induced spin currents,
chiral edge currents and correlation driven surface magnetism. The topological
nature of the chiral p-wave state manifests itself in the gamma-band
characterized by an integer Chern number. As the gamma-band is close to a
Lifshitz transition in Sr2RuO4, changing the sign of the Chern number, the
topological nature may be rather fragile.",1307.2382v2
2013-12-04,Rashba Spin-Orbit Anisotropy and the Electric Field Control of Magnetism,"The control of the magnetism of ultra-thin ferromagnetic layers using an
electric field rather than a current, if large enough, would lead to many
technologically important applications. To date, while it is usually assumed
the changes in the magnetic anisotropy, leading to such a control, arises from
surface charge doping of the magnetic layer, a number of key experiments cannot
be understood within such a scenario. Much studied is the fact that, for
non-magnetic metals or semi-conductors, a large surface electric field gives
rise to a Rashba spin-orbit coupling which leads to a spin-splitting of the
conduction electrons. For a magnet, this splitting is modified by the exchange
field resulting in a large magnetic anisotropy energy via the
Dzyaloshinskii-Moriya mechanism. This different, yet traditional, path to an
electrically induced anisotropy energy can explain the electric field,
thickness, and material dependence reported in many experiments.",1312.1021v1
2014-02-10,Magnetic edge anisotropy in graphene-like honeycomb crystals,"The independent predictions of edge ferromagnetism and the Quantum Spin Hall
phase in graphene have inspired the quest of other two dimensional honeycomb
systems, such as silicene, germanene, stanene, iridiates, and organometallic
lattices, as well as artificial superlattices, all of them with electronic
properties analogous to those of graphene, but much larger spin orbit coupling.
Here we study the interplay of ferromagnetic order and spin orbit interactions
at the zigzag edges of these graphene-like systems. We find an in-plane
magnetic anisotropy that opens a gap in the otherwise conducting edge channels,
that should result in large changes of electronic properties upon rotation of
the magnetization.",1402.2235v2
2014-07-15,Strong competition between orbital-ordering and itinerancy in a frustrated spinel vanadate,"The crossover from localized- to itinerant-electron behavior is associated
with many intriguing phenomena in condensed-matter physics. In this paper, we
investigate the crossover from localized to itinerant regimes in the spinel
system Mn$_{1-x}$Co$_x$V$_2$O$_4$. At low Co doping, orbital order (OO) of the
localized electrons on the V3+ ions suppresses magnetic frustration by
triggering a tetragonal distortion. With Co doping, electronic itinerancy melts
the OO and suppresses the structural phase transition while the reduced
spin-lattice coupling produces magnetic frustration. Neutron scattering
measurements and first-principles-guided spin models reveal that the
non-collinear state at high Co doping is produced by weakened local anisotropy
and enhanced Co-V spin interactions.",1407.4143v2
2014-07-28,Topological states of non-Dirac electrons on triangular lattice,"We demonstrate the possibility of topological states for non-Dirac electrons.
Specifically it is shown that, because of the $C_{\rm 3}$ crystal symmetry and
time reversal symmetry, $p_x$ and $p_y$ orbits accommodated on triangular
lattice exhibit a quadratic band touching at $\Gamma$ point at the Fermi level.
When the atomic spin-orbit coupling (SOC) is taken into account, a gap is
opened resulting in a quantum spin Hall effect state. As revealed explicitly by
a $k\cdot p$ model, the topology is associated with a meron structure in the
pseudo spin texture with vorticity two, a mechanism different from honeycomb
lattice and the band inversion. One possible realization of this scheme is the
1/3 coverage by Bi atom adapted on the Si[111] surface. First-principle
calculations are carried out, and a global gap of $\sim 0.15$eV is observed.
With the Si substrate taking part in realizing the nontrivial topology, the
present template is expected to make the integration of topological states into
existing electronics and photonics technologies promising.",1407.7320v1
2015-04-21,Anisotropic interactions opposing magnetocrystalline anisotropy in Sr$_3$NiIrO$_6$,"We report our investigation of the electronic and magnetic excitations of
Sr$_3$NiIrO$_6$ by resonant inelastic x-ray scattering at the Ir L$_3$ edge.
The intra-$t_{2g}$ electronic transitions are analyzed using an atomic model,
including spin-orbit coupling and trigonal distortion of the IrO$_6$
octahedron, confronted to {\it ab initio} quantum chemistry calculations. The
Ir spin-orbital entanglement is quantified and its implication on the magnetic
properties, in particular in inducing highly anisotropic magnetic interactions,
is highlighted. These are included in the spin-wave model proposed to account
for the dispersionless magnetic excitation that we observe at 90 meV. By
counterbalancing the strong Ni$^{2+}$ easy-plane anisotropy that manifests
itself at high temperature, the anisotropy of the interactions finally leads to
the remarkable easy-axis magnetism reported in this material at low
temperature.",1504.05420v2
2015-04-29,Dirac Semimetals in Two Dimensions,"Graphene is famous for being a host of 2D Dirac fermions. However, spin-orbit
coupling introduces a small gap, so that graphene is formally a quantum spin
hall insulator. Here we present symmetry-protected 2D Dirac semimetals, which
feature Dirac cones at high-symmetry points that are \emph{not} gapped by
spin-orbit interactions, and exhibit behavior distinct from both graphene and
3D Dirac semimetals. Using a two-site tight-binding model, we construct
representatives of three possible distinct Dirac semimetal phases, and show
that single symmetry-protected Dirac points are impossible in two dimensions.
An essential role is played by the presence of non-symmorphic space group
symmetries. We argue that these symmetries tune the system to the boundary
between a 2D topological and trivial insulator. By breaking the symmetries we
are able to access trivial and topological insulators as well as Weyl semimetal
phases.",1504.07977v2
2015-10-30,Identifying the Stern-Gerlach force of classical electron dynamics,"Different classical theories are commonly applied in various branches of
physics to describe the relativistic dynamics of electrons by coupled equations
for the orbital motion and spin precession. Exemplarily, we benchmark the
Frenkel model and the classical Foldy-Wouthuysen model with spin-dependent
forces (Stern-Gerlach forces) to the quantum dynamics as predicted by the Dirac
equation. Both classical theories can lead to different or even contradicting
predictions how the Stern-Gerlach forces modify the electron's orbital motion,
when the electron moves in strong electromagnetic field configurations of
emerging high-intensity laser facilities. In this way, one may evaluate the
validity and identify the limits of these classical theories via a comparison
with possible experiments to provide a proper description of spin-induced
dynamics. Our results indicate that the Foldy-Wouhuysen model is qualitatively
in better agreement with the Dirac theory than the widely used Frenkel model.",1510.09145v2
2016-01-07,Topological Protection from Random Rashba Spin-Orbit Backscattering: Ballistic Transport in a Helical Luttinger Liquid,"The combination of Rashba spin-orbit coupling and potential disorder induces
a random current operator for the edge states of a 2D topological insulator. We
prove that charge transport through such an edge is ballistic at any
temperature, with or without Luttinger liquid interactions. The solution
exploits a mapping to a spin 1/2 in a time-dependent field that preserves the
projection along one randomly undulating component (integrable dynamics). Our
result is exact and rules out random Rashba backscattering as a source of
temperature-dependent transport, absent integrability-breaking terms.",1601.01684v2
2016-01-22,Optimal geometry of lateral GaAs and Si/SiGe quantum dots for electrical control of spin qubits,"We investigate the effects of the orientation of the magnetic field and the
orientation of a quantum dot, with respect to crystallographic coordinates, on
the quality of an electrically controlled qubit realized in a gated
semiconductor quantum dot. We find that, due to the anisotropy of the
spin-orbit interactions, varying the two orientations it is possible to tune
the qubit in the sense of optimizing the ratio of its couplings to phonons and
to a control electric field. We find conditions under which such optimal setup
can be reached by solely reorienting the magnetic field, and when a specific
positioning of the dot is required. We also find that the knowledge of the
relative sign of the spin-orbit interactions strengths allows to choose a
robust optimal dot geometry, with the dot main axis along [110], or
[1$\overline{1}$0], where the qubit can be always optimized by reorienting the
magnetic field.",1601.05881v2
2017-02-23,Spin-Orbit Coupling of Conduction Electrons in Magnetization Switching,"Strong magnetic field pulses associated with a relativistic electron bunch
can imprint switching patterns in magnetic thin films that have uniaxial
in-plane anisotropy. In experiments with Fe and FeCo alloy films the pattern
shape reveals an additional torque acting on magnetization during the short (in
the 100fs time scale) magnetic field pulse. The magnitude of the torque is as
high as 15% of the torque from the magnetic field. The torque symmetry is that
of a uniaxial anisotropy along the direction of the eddy current screening the
magnetic field. Spin-orbit interaction acting on the conduction electrons can
produce such a torque with the required symmetry and magnitude. The same
interaction causes the anomalous Hall current to be spin-polarized, exerting a
back reaction on magnetization direction. Such a mechanism may be at work in
all-optical laser switching of magnetic materials.",1702.07153v1
2018-11-04,Current cross-correlation in the Anderson impurity model with exchange interaction,"We study spin-entanglement of the quasiparticles of the local Fermi liquid
excited in nonlinear current through a quantum dot described by the Anderson
impurity model with two degenerate orbitals coupled to each other via an
exchange interaction. Applying the renormalized perturbation theory, we obtain
the precise form of the cumulant generating function and cross-correlations for
the currents with spin angled to arbitrary directions, up to third order in the
applied bias voltage. It is found that the exchange interaction gives rise to
spin-angle dependency in the cross-correlation between the currents through the
two different orbitals, and also brings an intrinsic cross-correlation of
currents with three different angular momenta.",1811.01451v2
2018-11-09,Optical orientation with linearly polarized light in transition metal dichalcogenides,"We study the optical properties of semiconducting transition metal
dichalcogenide monolayers under the influence of strong out-of-plane magnetic
fields, using the effective massive Dirac model. We pay attention to the role
of spin-orbit coupling effects, doping level and electron-electron
interactions, treated at the Hartree-Fock level. We find that optically-induced
valley and spin imbalance, commonly attained with circularly polarized light,
can also be obtained with linearly polarized light in the doped regime.
Additionally, we explore an exchange-driven mechanism to enhance the spin-orbit
splitting of the conduction band, in n-doped systems, controlling both the
carrier density and the intensity of the applied magnetic field.",1811.04003v2
2020-07-16,Complete Multipole Basis Set for Single-Centered Electron Systems,"A whole series of expressions for four species of multipoles (electric,
magnetic, magnetic toroidal, and electric toroidal) is provided as a complete
basis set to describe arbitrary single-centered spinful electron systems. A
compact formula to calculate matrix elements of these multipoles is also
derived. A visualization method of an electronic state characterized in terms
of multipoles is proposed. The complete basis set is useful to narrow down a
candidate order parameter of electron systems in phase transition, to describe
a property of cross-correlated phenomena, to analyze spectra of x-ray
scattering in magnetically ordered state, and so on. We demonstrate a usage of
the complete basis set by taking monopole and toroidal dipole orderings, and
the mutual relationship among three distinct magnetic dipoles (orbital, spin
angular momenta and anisotropic dipole) in a spin-orbit coupled system as prime
examples.",2007.08039v2
2013-08-13,Strain effects on the spin-orbit induced band structure splittings in monolayer MoS2 and graphene,"The strain effects on the spin-orbit induced splitting of the valence band
maximum and conduction band minimum in monolayer MoS2 and the gap in graphene
are calculated using first-principles calculations. The dependence of these
splittings on the various symmetry types of strain is described by means of an
effective Hamiltonian based on the method of invariants and the parameters in
the model are extracted by fitting to the theory. These splittings are related
to acoustic phonon deformation potentials, or electron-phonon coupling matrix
elements which enter the spin-dependent scattering theory of conduction in
these materials.",1308.2733v1
2017-01-26,Mechanism for nematic superconductivity in FeSe,"Despite its seemingly simple composition and structure, the pairing mechanism
of FeSe remains an open problem due to several striking phenomena. Among them
are nematic order without magnetic order, nodeless gap and unusual inelastic
neutron spectra with a broad continuum, and gap anisotropy consistent with
orbital selection of unknown origin. Here we propose a microscopic description
of a nematic quantum spin liquid that reproduces key features of neutron
spectra. We then study how the spin fluctuations of the local moments lead to
pairing within a spin-fermion model. We find the resulting superconducting
order parameter to be nodeless $s\pm d$-wave within each domain. Further we
show that orbital dependent Hund's coupling can readily capture observed gap
anisotropy. Our prediction calls for inelastic neutron scattering in a
detwinned sample.",1701.07813v2
2018-05-04,Rotational-tidal phasing of the binary neutron star waveform,"Tidal forces cause inspiralling binary neutron stars to deform, leaving a
measurable imprint on the gravitational waves they emit. The induced stellar
multipoles are an added source of gravitational radiation and modify the
orbital dynamics, producing a slight acceleration of the coalescence which
manifests as a phase shift in the waveform relative to point-particles. The
dominant piece of this tidal phase comes from the mass quadrupoles, which
contribute at fifth post-Newtonian order (5PN). Current quadrupoles and mass
octupoles contribute at higher orders. For spinning neutron stars, additional
multipole moments are induced by nonlinear couplings between spin and tides. We
calculate these rotational-tidal deformations assuming the stars are rotating
slowly and the tides are weak and quasi-stationary. The stellar multipole
moments are read off from an asymptotically flat metric that encodes the
difference between their tidal response and a black hole's. The multipoles are
subsequently inserted into post-Newtonian formulas for the orbit and the
gravitational radiation. We find that, at leading order, the rotational-tidal
deformations make a 6.5PN contribution to the tidal phase. Their effect on the
waveform is thus larger than that of the mass octupoles, and nearly as large as
that of the current quadrupoles, in systems with non-negligible spin.",1805.01882v1
2018-05-10,Spin freezing and the Sachdev-Ye model,"Spin-freezing is the origin of bad-metal physics and non-Fermi liquid
(non-FL) properties in a broad range of correlated compounds. In a
multi-orbital lattice system with Hund coupling, doping of the half-filled Mott
insulator results in a highly incoherent metal with frozen magnetic moments.
These moments fluctuate and collapse in a crossover region that is
characterized by unusual non-Fermi liquid properties such as a self-energy
whose imaginary part varies $\propto \sqrt{\omega}$ over a wide energy range.
At low enough temperature, the local moment fluctuations induce electron
pairing and this mechanism may be the unifying principle of unconventional
superconductivity. While this physics has been discovered in numerical studies
of multi-orbital Hubbard systems, it exhibits a striking similarity to the
analytically solvable Sachdev-Ye (SY) model, and its recent fermionic
extensions. Here, we clarify the relation between spin-freezing and SY physics,
and thus shed light on fundamental properties of Hund metals.",1805.04102v2
2013-09-05,Kondo effect and spin quenching in high-spin molecules on metal substrates,"Using a state-of-the art combination of density functional theory and
impurity solver techniques we present a complete and parameter-free picture of
the Kondo effect in the high-spin ($S=3/2$) coordination complex known as
Manganese Phthalocyanine adsorbed on the Pb(111) surface. We calculate the
correlated electronic structure and corresponding tunnel spectrum and find an
asymmetric Kondo resonance, as recently observed in experiments. Contrary to
previous claims, the Kondo resonance stems from only one of three possible
Kondo channels with origin in the Mn 3d-orbitals, its peculiar asymmetric shape
arising from the modulation of the hybridization due to strong coupling to the
organic ligand. The spectral signature of the second Kondo channel is strongly
suppressed as the screening occurs via the formation of a many-body singlet
with the organic part of the molecule. Finally, a spin-1/2 in the 3d-shell
remains completely unscreened due to the lack of hybridization of the
corresponding orbital with the substrate, hence leading to a spin-3/2
underscreened Kondo effect.",1309.1324v1
2016-05-31,Band Structure and Topological Properties of Graphene in a Superlattice Spin Exchange Field,"We analyze the energy spectrum of graphene in the presence of spin-orbit
coupling and a unidirectionally periodic Zeeman field, focusing on the
stability and location of Dirac points it may support. It is found that the
Dirac points at the $K$ and $K'$ points are generically moved to other
locations in the Brillouin zone, but that they remain present when the Zeeman
field $\vec{\Delta}(x)$ integrates to zero within a unit cell. A large variety
of locations for the Dirac points is shown to be possible: when $\vec\Delta
\parallel \hat{z}$ they are shifted from their original locations along the
direction perpendicular to the superlattice axis, while realizations of
$\vec\Delta(x)$ that rotate periodically move the Dirac points to locations
that can reflect the orbit of the rotating electron spin as it moves through a
unit cell. When a uniform Zeeman field is applied in addition to a periodic
$\vec\Delta \parallel \hat{z}$ integrating to zero, the system can be brought
into a metallic, Dirac semimetal, or insulating state, depending on the
direction of the uniform field. The latter is shown to be an anomalous quantum
Hall insulator.",1605.09485v1
2018-01-29,Hall effect driven by non-collinear magnetic polarons in diluted magnetic semiconductors,"In this letter we develop the theory of Hall effect driven by non-collinear
magnetic textures (topological Hall effect - THE) in diluted magnetic
semiconductors (DMS). We show that a carrier spin-orbit interaction induces a
chiral magnetic ordering inside a bound magnetic polaron (BMP). The inner
structure of non-collinear BMP is controlled by the type of spin-orbit
coupling, allowing to create skyrmion- (Rashba) or antiskyrmion-like
(Dresselhaus) configurations. The asymmetric scattering of itinerant carriers
on polarons leads to the Hall signal which exists in weak external magnetic
fields and low temperatures. We point out that DMS-based systems allow one to
investigate experimentally the dependence of THE both on a carrier spin
polarization and on a non-collinear magnetic texture shape.",1801.09459v1
2018-09-04,"Computational study of heavy group IV elements (Ge, Sn, Pb) triangular lattice atomic layers on SiC(0001) surface","Group IV heavy elements atomic layers are expected to show an interesting
physical properties due to their large spin-orbit coupling (SOC). Using density
functional theory (DFT) calculations with/without SOC we investigate the
variation of group IV heavy elements overlayers, namely dense triangular
lattice atomic layers (TLAL) on the surface of SiC(0001) semiconductor. The
possibility of such layers formation and their properties have not been
addressed before. Here we show, that these layers may indeed be stable and,
owing to peculiar bonding configuration, exhibit robust Dirac-like energy bands
originating from $p_x+p_y$ orbitals and localized mostly within the layer, and
$p_z$ band localized outside the layer and interacting with SiC substrate. We
found that a $T_1$ adsorption site is most favorable for such TLAL structure
and this results in an unusual SOC-induced spin polarization of the states
around $\bar{K}$ points of Brillouin zone, namely the coexistence of Rashba-
and Zeeman-like spin polarization of different states. We explain this
phenomena in terms of symmetry of partial electronic density rather than
symmetry of atomic structure.",1809.00829v1
2019-09-19,Microscopic theory of in-plane critical field in two-dimensional Ising superconducting systems,"We study the in-plane critical magnetic field of two-dimensional Ising
superconducting systems, and propose the microscopic theory for these systems
with or without inversion symmetry. Protected by certain specific spin-orbit
interaction which polarizes the electron spin to the out-of-plane direction,
the in-plane critical fields largely surpass the Pauli limit and show
remarkable upturn in the zero temperature limit. The impurity scattering and
Rashba spin-orbit coupling, treated on equal-footing in the microscopic
framework, both weaken the critical field but in qualitatively different
manners. The microscopic theory is consistent with recent experimental results
in stanene and Pb superconducting ultra-thin films.",1909.08819v1
2017-05-06,Model of ultrafast demagnetization driven by spin-orbit coupling in a photoexcited antiferromagnetic insulator Cr2O3,"We theoretically study the dynamic time evolution following laser pulse
pumping in an antiferromagnetic insulator Cr$_{2}$O$_{3}$. From the
photoexcited high-spin quartet states to the long-lived low-spin doublet
states, the ultrafast demagnetization processes are investigated by solving the
dissipative Schr\""odinger equation. We find that the demagnetization times are
of the order of hundreds of femtosecond, in good agreement with recent
experiments. The switching times could be strongly reduced by properly tuning
the energy gaps between the multiplet energy levels of Cr$^{3+}$. Furthermore,
the relaxation times also depend on the hybridization of atomic orbitals in the
first photoexcited state. Our results suggest that the selective manipulation
of electronic structure by engineering stress-strain or chemical substitution
allows effective control of the magnetic state switching in photoexcited
insulating transition-metal oxides.",1705.02439v2
2018-03-02,Interference in spin-orbit coupled transverse magnetic focusing; emergent phase due to in-plane magnetic fields,"Spin-orbit (SO) interactions in two dimensional systems split the Fermi
surface, and allow for the spatial separation of spin-states via transverse
magnetic focusing (TMF). In this work, we consider the case of combined Rashba
and Zeeman interactions, which leads to a Fermi surface without cylindrical
symmetry. While the classical trajectories are effectively unchanged, we
predict an additional contribution to the phase, linear in the applied in-plane
magnetic field. We show that this term is unique to TMF, and vanishes for
magnetic (Shubnikov de Haas) oscillations. Finally we propose some experimental
signatures of this phase.",1803.00714v1
2018-08-08,Gate-tunable infrared plasmons in electron-doped single-layer antimony,"We report on a theoretical study of collective electronic excitations in
single-layer antimony crystals (antimonene), a novel two-dimensional
semiconductor with strong spin-orbit coupling. Based on a tight-binding model,
we consider electron-doped antimonene and demonstrate that the combination of
spin-orbit effects with external bias gives rise to peculiar plasmon
excitations in the mid-infrared spectral range. These excitations are
characterized by low losses and negative dispersion at frequencies effectively
tunable by doping and bias voltage. The observed behavior is attributed to the
spin-splitting of the conduction band, which induces interband resonances,
affecting the collective excitations. Our findings open up the possibility to
develop plasmonic and optoelectronic devices with high tunability, operating in
a technologically relevant spectral range.",1808.02619v2
2018-08-16,Angular momentum-dependent topological transport and its experimental realization using a transmission line network,"Novel classical wave phenomenon analogs of the quantum spin Hall effect are
mostly based on the construction of pseudo-spins. Here we show that the
non-trivial topology of a system can also be realized using orbital angular
momentum through angular-momentum-orbital coupling. The idea is illustrated
with a tight-binding model and experimentally demonstrated with a transmission
line network. We show experimentally that even a very small network cluster
exhibits one-way topological edge states, and their properties can be described
in terms of local Chern numbers. Our work provides a new mechanism to realize
counterparts of the quantum spin Hall effect in classical waves and may offer
insights for other systems.",1808.05413v1
2019-08-21,Skyrme Functional with Tensor Terms from ab initio Calculations: Results for the Spin-Orbit Splittings,"A new Skyrme functional including tensor terms is presented. The tensor terms
have been determined by fitting the results of relativistic
Brueckner-Hartree-Fock (RBHF) studies on neutron-proton drops. Unlike all
previous studies, where the tensor terms were usually determined by fitting to
experimental data of single-particle levels, the pseudodata calculated by RBHF
does not contain beyond mean-field effect such as the particle-vibration
coupling and, therefore, can provide information on the tensor term without
ambiguities. The obtained new functional, named SAMi-T, can describe well
ground-state properties such as binding energies, radii, spin-orbit splittings
and, at the same time, the excited state properties such as those of the Giant
Monopole Resonance (GMR), Giant Dipole Resonance (GDR), Gamow-Teller Resonance
(GTR), and Spin-Dipole Resonance (SDR).",1908.08090v1
2019-12-16,Thermalization of photoexcited carriers in two-dimensional transition metal dichalcogenides and internal quantum efficiency of van der Waals heterostructures,"Van der Waals semiconductor heterostructures could be a platform to harness
hot photoexcited carriers in the next generation of optoelectronic and
photovoltaic devices. The internal quantum efficiency of hot-carrier devices is
determined by the relation between photocarrier extraction and thermalization
rates. Using \textit{ab-initio} methods we show that the photocarrier
thermalization time in single-layer transition metal dichalcogenides strongly
depends on the peculiarities of the phonon spectrum and the electronic
spin-orbit coupling. In detail, the lifted spin degeneracy in the valence band
suppresses the hole scattering on acoustic phonons, slowing down the
thermalization of holes by one order of magnitude as compared to electrons.
Moreover, the hole thermalization time behaves differently in MoS$_2$ and
WSe$_2$ because spin-orbit interactions differ in these seemingly similar
materials. We predict that the internal quantum efficiency of a tunneling van
der Waals semiconductor heterostructure depends qualitatively on whether
MoS$_2$ or WSe$_2$ is used.",1912.07480v1
2020-10-01,"Anisotropic spin distribution and perpendicular magnetic anisotropy in the layered ferromagnetic semiconductor (Ba,K)(Zn,Mn)$_{2}$As$_{2}$","Perpendicular magnetic anisotropy of the new ferromagnetic semiconductor
(Ba,K)(Zn,Mn)$_{2}$As$_{2}$ is studied by angle-dependent x-ray magnetic
circular dichroism measurements. The large magnetic anisotropy with the
anisotropy field of 0.85 T is deduced by fitting the Stoner-Wohlfarth model to
the magnetic-field-angle dependence of the projected magnetic moment.
Transverse XMCD spectra highlights the anisotropic distribution of Mn 3$d$
electrons, where the $d_{xz}$ and $d_{yz}$ orbitals are less populated than the
$d_{xy}$ state because of the $D_{2d}$ splitting arising from the elongated
MnAs$_{4}$ tetrahedra. It is suggested that the magnetic anisotropy originates
from the degeneracy lifting of $p$-$d_{xz}$, $d_{yz}$ hybridized states at the
Fermi level and resulting energy gain due to spin-orbit coupling when spins are
aligned along the $z$ direction.",2010.00158v1
2020-11-27,Ultrafast spin dynamics in inhomogeneous systems: a density-matrix approach applied to Co/Cu interfaces,"Ultrafast spin dynamics on femto- to picosecond timescales is simulated
within a density-operator approach for a Co/Cu bilayer. The electronic
structure is represented in a tight-binding form; during the evolution of the
density operator, optical excitation by a femtosecond laser pulse, coupling to
a bosonic bath as well as dephasing are taken into account. Our simulations
corroborate the importance of interfaces for ultrafast transport phenomena and
demagnetisation processes. Moreover, we establish a reflow from Cu $d$ orbitals
across the interface into Co $d$ orbitals, which shows up prominently in the
mean occupation numbers. On top of this, this refilling manifests itself as a
minority-spin current proceeding several layers into the Cu region. The present
study suggests that the approach captures essential ultrafast phenomena and
provides insight into microscopic processes.",2011.13763v1
2021-04-21,Possible two-component spin-singlet pairings in Sr2RuO4,"Recent experiments suggest a multi-component pairing function in Sr2RuO4,
which appears to be inconsistent with the absence of an apparent cusp in the
transition temperature (Tc) as a function of the uniaxial strain. We show,
however, that the theoretical cusp in Tc for a multi-component pairing can be
easily smeared out by the spatial inhomogeneity of strain, and the experimental
data can be reproduced qualitatively by a percolation model. This shed new
light on multi-component pairings. We then perform a thorough group-theoretical
classification of the pairing functions, taking the spin-orbit coupling into
account. We list all 13 types of two-component spin-singlet pairing functions,
with 8 of them belonging to the Eg representation. In particular, we find two
types of intra-orbital pairings in the Eg representation ($k_xk_z$, $k_yk_z$)
are favorable in view of most existing experiments.",2104.10560v1
2016-12-28,Symmetry-protected topological states for interacting fermions in alkaline-earth-like atoms,"We discuss the quantum simulation of symmetry-protected topological (SPT)
states for interacting fermions in quasi-one-dimensional gases of
alkaline-earth-like atoms such as $^{173}$Yb. Taking advantage of the
separation of orbital and nuclear-spin degrees of freedom in these atoms, we
consider Raman-assisted spin-orbit couplings in the clock states, which,
together with the spin-exchange interactions in the clock-state manifolds, give
rise to SPT states for interacting fermions. We numerically investigate the
phase diagram of the system, and study the phase transitions between the SPT
phase and the symmetry-breaking phases. The interaction-driven topological
phase transition can be probed by measuring local density distribution of the
topological edge modes.",1612.08880v3
2017-07-23,Majorana surface modes of nodal topological pairings in spin-$\frac{3}{2}$ semi-metals,"Multi-component electronic systems can appear in solid state systems with
active orbital band structures. They exhibit richer structures of topological
superconductivity beyond the conventional scenarios of spin singlet and triplet
pairings in spin-$\frac{1}{2}$ systems. Examples include the half-Heusler
compounds RPtBi series (R for a rare earth element), whose electronic
structures are described by the effective Luttinger-Kohn model with
spin-$\frac{3}{2}$ fermions exhibiting strong spin-orbit coupling and band
conversion. Recent experiments provide evidence to unconventional
superconductivity in the YPtBi material with nodal spin-septet pairing. We
systematically study topological pairing structures in spin-$\frac{3}{2}$
systems with cubic group symmetries and calculate surface Majorana spectra,
which exhibit both the zero energy flat band and the cubic dispersion. The
signatures of these surface states in the quasi-particle interference patterns
are studied, which can be tested in future tunneling experiments.",1707.07261v3
2018-10-20,Realization of anisotropic compass model on the diamond lattice of Cu$^{2+}$ in CuAl$_2$O$_4$,"Spin-orbit (SO) Mott insulators are regarded as a new paradigm of magnetic
materials, whose properties are largely influenced by SO coupling and featured
by highly anisotropic bond-dependent exchange interactions between the
spin-orbital entangled Kramers doublets, as typically manifested in $5d$
iridates. Here, we propose that a very similar situation can be realized in
cuprates when the Cu$^{2+}$ ions reside in a tetrahedral environment, like in
spinel compounds. Using first-principles electronic structure calculations, we
construct a realistic model for the diamond lattice of the Cu$^{2+}$ ions in
CuAl$_2$O$_4$ and show that the magnetic properties of this compound are
largely controlled by anisotropic compass-type exchange interactions that
dramatically modify the magnetic ground state by lifting the spiral spin-liquid
degeneracy and stabilizing a commensurate single-$\boldsymbol{q}$ spiral.",1810.08818v2
2019-05-17,Spin-valley density wave in moiré materials,"We introduce and study a minimum two-orbital Hubbard model on a triangular
lattice, which captures the key features of both the trilayer ABC-stacked
graphene-boron nitride heterostructure and twisted transition metal
dichalcogenides in a broad parameter range. Our model comprises first- and
second-nearest neighbor hoppings with valley-contrasting flux that accounts for
trigonal warping in the band structure. For the strong-coupling regime with one
electron per site, we derive a spin-orbital exchange Hamiltonian and find the
semiclassical ground state to be a spin-valley density wave. We show that a
relatively small second-neighbor exchange interaction is sufficient to
stabilize the ordered state against quantum fluctuations. Effects of spin- and
valley Zeeman fields as well as thermal fluctuations are also examined.",1905.07401v1
2019-06-04,Theory of the giant thermal Hall effect in the high temperature superconductors,"Recent transport measurement finds giant negative thermal Hall signal in the
pseudo-gap phase of the high temperature superconductors\cite{Taillefer}. Such
a signal is found to increase in magnitude with decreasing doping and to reach
its maximum in the half-filled antiferromagnetic ordered parent compounds. It
is still elusive what is the implication of such a phenomena for the mechanism
of the pseudo-gap phase. The observation of such a signal may also challenge
our well established understanding of the parent compounds as perfect
Heisenberg antiferromagnets. Here we show that such a giant thermal Hall effect
can be naturally understood as the orbital magnetic response of a quantum
Heisenberg antiferromagnet with sizable multi-spin exchange coupling. We also
argue that the observation of the giant thermal Hall effect in the pseudo-gap
phase imply that the origin of the pseudo-gap in the high temperature
superconductors is closely related to the antiferromagnetic correlation between
local spins.",1906.01712v2
2020-03-10,Dzyaloshinskii-Moriya interaction in absence of spin-orbit coupling,"In contrast to conventional assumptions, we show that the
Dzyaloshinskii-Moriya interaction can be of non-relativistic origin, in
particular in materials with a non-collinear magnetic configuration, where
non-relativistic contributions can dominate over spin-orbit effects. The weak
antiferromagnetic phase of Mn$_{3}$Sn is used to illustrate these findings.
Using electronic structure theory as a conceptual platform, all relevant
exchange interactions are derived for a general, non-collinear magnetic state.
It is demonstrated that non-collinearity influences all three types of exchange
interaction and that physically distinct mechanisms, which connect to electron-
and spin-density and currents, may be used as a general way to analyze and
understand magnetic interactions of the solid state.",2003.04680v2
2020-06-25,Plumbene on a magnetic substrate: a combined STM and DFT study,"As heavy analog of graphene, plumbene is a two-dimensional material with
strong spin-orbit coupling effects. Using scanning tunneling microscopy (STM),
we observe that Pb forms a flat honeycomb lattice on an Fe monolayer on
Ir(111). In contrast, without the Fe layer, a c(2x4) structure of Pb on Ir(111)
is found. We use density functional theory (DFT) calculations to rationalize
these findings and analyze the impact of the hybridization on the plumbene band
structure. In the unoccupied states the splitting of the Dirac cone by
spin-orbit interaction is clearly observed while in the occupied states of the
freestanding plumbene we find a band inversion that leads to the formation of a
topologically non-trivial gap. Exchange splitting as mediated by the strong
hybridization with the Fe layer drives a quantum spin Hall to quantum anomalous
Hall state transition.",2006.14516v1
2021-01-29,"Magnetism-driven unconventional effects in Ising superconductors: role of proximity, tunneling, and nematicity","Hybrid Ising superconductor-ferromagnetic insulator heterostructures provide
a unique opportunity to explore the interplay between proximity-induced
magnetism, spin-orbit coupling and superconductivity. Here we use a combination
of first-principles calculations of NbSe$_{2}$/CrBr$_{3}$ heterostructures and
an analytical theory of Ising superconductivity to analyze the existing
experiments and provide a complete explanation of highly nontrivial and largely
counterintuitive effects: an increase in the magnitude of the superconducting
gap accompanied by the broadening of the tunneling peaks; hysteretic behavior
of the tunneling conductance that sets in $\approx 2$ K below $T_c$; and
nematic symmetry breaking in the superconducting state. The microscopic reason
in all three cases appears to be the interplay between the proximity-induced
exchange splitting and intrinsic defects. Finally, we predict additional
interesting effects that at the moment cannot be addressed experimentally:
spin-filtering when tunneling across CrBr$_{3}$ and tunneling ``hot spots'' in
momentum space that are anticorrelated with regions where the spin-orbit
splitting is maximum.",2101.12674v3
2021-07-05,Unified Treatment of Magnons and Excitons in Monolayer CrI$_3$ from Many-Body Perturbation Theory,"We present first principles calculations of the two-particle excitation
spectrum of CrI$_3$ using many-body perturbation theory including spin-orbit
coupling. Specifically, we solve the Bethe-Salpeter equation, which is
equivalent to summing up all ladder diagrams with static screening and it is
shown that excitons as well as magnons can be extracted seamlessly from the
calculations. The resulting optical absorption spectrum as well as the magnon
dispersion agree very well with recent measurements and we extract the
amplitude for optical excitation of magnons resulting from spin-orbit
interactions. Importantly, the results do not rely on any assumptions on the
microscopic magnetic interactions such as Dzyaloshinskii-Moriya (DM), Kitaev or
biquadratic interactions and we obtain a model independent estimate of the gap
between acoustic and optical magnons of 0.3 meV. In addition, we resolve the
magnon wavefunction in terms of band transitions and show that the magnon
carries a spin that is significantly smaller than $\hbar$. This highlights the
importance of terms that do not commute with $S^z$ in any Heisenberg model
description.",2107.02284v1
2021-08-09,Realization of 0 - $π$ states in SFIS Josephson junctions. The role of spin-orbit interaction and lattice impurities,"Josephson devices with ferromagnetic barriers have been widely studied. Much
less is known when the ferromagnetic layer is insulating. In this manuscript we
investigate the transport properties of superconductor-ferromagnetic
insulator-superconductor (SFIS) junctions with particular attention to the
temperature behavior of the critical current, that may be used as a fingerprint
of the junction. We investigate the specific role of impurities as well as of
possible spin mixing mechanisms, due to the spin orbit coupling. Transition
between the 0 and the $\pi$ phases can be properly tuned, thus achieving stable
$\pi$ junctions over the whole temperature range, that may be possibly employed
in superconducting quantum circuits.",2108.04292v2
2021-09-07,"Aspects of topological superconductivity in 2D systems: noncollinear magnetism, skyrmions, and higher-order topology","The review is aimed at highlighting the aspects of topological
superconductivity in the absence of spin-orbit interaction in two-dimensional
systems with long-range non-collinear spin ordering or magnetic skyrmions.
Another purpose is to give a brief introduction to the new concept of
topological superconductivity, i.e. higher-order topology in two-dimensional
systems including spin-orbit coupled structures. The formation of Majorana
modes due to magnetic textures is discussed. The role of effective triplet
pairings and odd fermion parity of the ground state wave function in different
systems is emphasized. We describe the peculiarities of the magnetic skyrmions,
leading to the formation of the Majorana modes and defects on which the modes
are localized. The problem of braiding in the two-dimensional systems,
especially in higher-order topological superconductors, is considered.",2109.03169v2
2021-10-29,Spinons and damped phonons in spin-1/2 quantum-liquid Ba$_{4}$Ir${}_3$O${}_{10}$ observed by Raman scattering,"In spin-1/2 Mott insulators, non-magnetic quantum liquid phases are often
argued to arise when the system shows no magnetic ordering, but identifying
positive signatures of these phases or related spinon quasiparticles can be
elusive. Here we use Raman scattering to provide three signatures for spinons
in a possible spin-orbit quantum liquid material Ba${}_4$Ir${}_3$O${}_{10}$:
(1) A broad hump, which we show can arise from Luttinger Liquid spinons in
Raman with parallel photon polarizations normal to 1D chains; (2) Strong phonon
damping from phonon-spin coupling via the spin-orbit interaction; and (3) the
absence of (1) and (2) in the magnetically ordered phase that is produced when
2% of Ba is substituted by Sr
((Ba${}_{0.98}$Sr${}_{0.02}$)${}_4$Ir${}_3$O${}_{10}$). The phonon damping via
itinerant spinons seen in this quantum-liquid insulator suggests a new
mechanism for enhancing thermoelectricity in strongly correlated conductors,
through a neutral quantum liquid that need not affect electronic transport.",2110.15916v1
2022-05-24,Compact Molecular Simulation on Quantum Computers via Combinatorial Mapping and Variational State Preparation,"Compact representations of fermionic Hamiltonians are necessary to perform
calculations on quantum computers that lack error-correction. A fermionic
system is typically defined within a subspace of fixed particle number and spin
while unnecessary states are projected out of the Hilbert space. We provide a
bijective mapping using combinatoric ranking to bijectively map fermion basis
states to qubit basis states and express operators in the standard spin
representation. We then evaluate compact mapping using the Variational Quantum
Eigensolver (VQE) with the unitary coupled cluster singles and doubles
excitations (UCCSD) ansatz in the compact representation. Compactness is
beneficial when the orbital filling is well away from half, and we show at 30
spin orbital $H_{2}$ calculation with only 8 qubits. We find that the gate
depth needed to prepare the compact wavefunction is not much greater than the
full configuration space in practice. A notable observation regards the number
of calls to the optimizer needed for the compact simulation compared to the
full simulation. We find that the compact representation converges faster than
the full representation using the ADAM optimizer in all cases. Our analysis
demonstrates the effect of compact mapping in practice.",2205.11742v1
2022-06-08,Spin triplet superconducting pairing in doped MoS$_2$,"Searching for triplet superconductivity has been pursued intensively in a
broad field of material science and quantum information for decades.
Nevertheless, these novel states remain rare. Within a simplified effective
three-orbital model, we reveal a spin triplet pairing in doped MoS$_2$ by
employing both the finite temperature determinant quantum Monte Carlo approach
and the ground state constrained-phase quantum Monte Carlo method. In a wide
filling region of $\avg{n}=0.60-0.80$ around charge neutrality $\avg{n}=2/3$,
the $f$-wave pairing dominates over other symmetries. The pairing
susceptibility strongly increases as the on-site Coulomb interaction increases,
and it is insensitive to spin-orbit coupling.",2206.03850v2
2022-08-11,Magneto-anisotropic weak antilocalization in near-surface quantum wells,"We investigate the effects of an in-plane magnetic field on the weak
antilocalization signature of near-surface quantum wells lacking bulk and
inversion symmetry. The measured magnetoconductivity exhibits a strong
anisotropy with respect to the direction of the in-plane magnetic field. The
two-fold symmetry of the observed magneto-anisotropy originates from the
competition between Rashba and Dresselhaus spin-orbit couplings. The high
sensitivity of the weak antilocalization to the spin texture produced by the
combined Zeeman and spin-orbit fields results in very large anisotropy ratios,
reaching 100%. Using a semiclassical universal model in quantitative agreement
with the experimental data, we uniquely determine the values of the Dresselhaus
and Rashba parameters as well as the effective in-plane g-factor of the
electrons. Understanding these parameters provides new prospects for novel
applications ranging from spintronics to topological quantum computing.",2208.06050v3
2022-10-13,Correlated insulating states in carbon nanotubes controlled by magnetic field,"We investigate competing insulating phases in nearly metallic zigzag carbon
nanotubes, under conditions where an applied magnetic flux approximately closes
the single particle gap in one valley. Recent experiments have shown that an
energy gap persists throughout magnetic field sweeps where the single-particle
picture predicts that the gap should close and reopen. Using a bosonic
low-energy effective theory to describe the interplay between electron-electron
interactions, spin-orbit coupling, and magnetic field, we obtain a phase
diagram consisting of several competing insulating phases that can form in the
vicinity of the single-particle gap closing point. We characterize these phases
in terms of spin-resolved charge polarization densities, each of which can
independently take one of two possible values consistent with the mirror
symmetry of the system, or can take an intermediate value through a spontaneous
mirror symmetry breaking transition. In the mirror symmetry breaking phase,
adiabatic changes of the orbital magnetic flux drive charge and spin currents
along the nanotube. We discuss the relevance of these results to recent and
future experiments.",2210.07254v1
2023-01-04,Magnetization dynamics with time-dependent spin-density functional theory: significance of exchange-correlation torques,"In spin-density-functional theory (SDFT) for noncollinear magnetic materials,
the Kohn-Sham system features exchange-correlation (xc) scalar potentials and
magnetic fields. The significance of the xc magnetic fields is not very well
explored; in particular, they can give rise to local torques on the
magnetization, which are absent in standard local and semilocal approximations.
Exact benchmark solutions for a five-site extended Hubbard lattice at half
filling and in the presence of spin-orbit coupling are compared with SDFT
results obtained using orbital-dependent exchange-only approximations. The
magnetization dynamics following short-pulse excitations is found to be
reasonably well described in the exchange-only approximation for weak to
moderate interactions. For stronger interactions and near transitions between
magnetically ordered and frustrated phases, exchange and correlation torques
tend to compensate each other and must both be accounted for.",2301.01509v1
2023-09-08,Microscopic analysis of dipole electric and magnetic strengths in $^{156}$Gd,"The dipole electric ($E1$) and magnetic ($M1$) strengths in strongly deformed
$^{156}$Gd are investigated within a fully self-consistent Quasiparticle Random
Phase Approximation (QRPA) with Skyrme forces SVbas, SLy6 and SG2. We inspect,
on the same theoretical footing, low-lying dipole states and the isovector
giant dipole resonance in $E1$ channel and the orbital scissors resonance as
well as the spin-flip giant resonance (SFGR) in $M1$ channel. Besides, $E1$
toroidal mode and low-energy spin-flip $M1$ excitations are considered. The
deformation splitting and dipole-octupole coupling of electric excitations are
analyzed. The origin of SFGR gross structure, impact of the residual
interaction and interference of orbital and spin contributions to SFGR are
discussed. The effect of the central exchange $\textbf{J}^2$-term from the
Skyrme functional is demonstrated. The calculations show a satisfactory
agreement with available experimental data, except for the recent NRF
measurements of M. Tamkas et al for $M1$ strength at 4-6 MeV, where, in
contradiction with our calculations and previous $(p,p')$ data, almost no $M1$
strength was observed.",2309.04294v2
2023-11-15,Strongly pinned skyrmionic bubbles and higher-order nonlinear Hall resistances at the interface of Pt/FeSi bilayer,"Engineering of magnetic heterostructures for spintronic applications has
entered a new phase, driven by the recent discoveries of topological materials
and exfoliated van der Waals materials. Their low-dimensional properties can be
dramatically modulated in designer heterostructures via proximity effects from
adjacent materials, thus enabling the realization of diverse quantum states and
functionalities. Here we investigate spin-orbit coupling (SOC) proximity
effects of Pt on the recently discovered quasi-two-dimensional ferromagnetic
state at FeSi surface. Skyrmionic bubbles (SkBs) are formed as a result of the
enhanced interfacial Dzyloshinskii-Moriya interaction. The strong pinning
effects on the SkBs are evidenced from the significant dispersion in size and
shape of the SkBs and are further identified as a greatly enhanced threshold
current density required for depinning of the SkBs. The robust integrity of the
SkB assembly leads to the emergence of higher-order nonlinear Hall effects in
the high current density regime, which originate from nontrivial Hall effects
due to the noncollinearity of the spin texture, as well as from the
current-induced magnetization dynamics via the augmented spin-orbit torque.",2311.08730v1
2024-04-09,Probing Berry phase effect in topological surface states,"We have observed the Berry phase effect associated with interband coherence
in topological surface states (TSSs) using two-color high-harmonic
spectroscopy. This Berry phase accumulates along the evolution path of strong
field-driven election-hole quasiparticles in electronic bands with strong
spin-orbit coupling. By introducing a secondary weak field, we perturb the
evolution of Dirac fermions in TSSs and thus provide access to the Berry phase.
We observe a significant shift in the oscillation phase of the even-order
harmonics from the spectral interferogram. We reveal that such a modulation
feature is linked to the geometric phase acquired in the nonperturbative
dynamics of TSSs. Furthermore, we show that the overwhelming Berry phase effect
can significantly deform the quantum paths of electron-hole pairs, thus
enhancing the ability to harness electron spin using lightwaves in quantum
materials with strong spin-orbit interactions.",2404.06086v1
2017-12-19,Magnetic phase diagram of the iron pnictides in the presence of spin-orbit coupling: Frustration between $C_2$ and $C_4$ magnetic phases,"We investigate the impact of spin anisotropic interactions, promoted by
spin-orbit coupling, on the magnetic phase diagram of the iron-based
superconductors. Three distinct magnetic phases with Bragg peaks at $(\pi,0)$
and $(0,\pi)$ are possible in these systems: one $C_2$ (i.e. orthorhombic)
symmetric stripe magnetic phase and two $C_4$ (i.e. tetragonal) symmetric
magnetic phases. While the spin anisotropic interactions allow the magnetic
moments to point in any direction in the $C_2$ phase, they restrict the
possible moment orientations in the $C_4$ phases. As a result, an interesting
scenario arises in which the spin anisotropic interactions favor a $C_2$ phase,
but the other spin isotropic interactions favor a $C_4$ phase. We study this
frustration via both mean-field and renormalization-group approaches. We find
that, to lift this frustration, a rich magnetic landscape emerges well below
the magnetic transition temperature, with novel $C_2$, $C_4$, and mixed
$C_2$-$C_4$ phases. Near the putative magnetic quantum critical point, spin
anisotropies promote a stable Gaussian fixed point in the renormalization-group
flow, which is absent in the spin isotropic case, and is associated with a
near-degeneracy between $C_2$ and $C_4$ phases. We argue that this frustration
is the reason why most $C_4$ phases in the iron pnictides only appear inside
the $C_2$ phase, and discuss additional manifestations of this frustration in
the phase diagrams of these materials.",1712.07192v4
2018-03-28,"Electronic structure of the Co(0001)/MoS2 interface, and its possible use for electrical spin injection in a single MoS2 layer","The ability to perform efficient electrical spin injection from ferromagnetic
metals into two-dimensional semiconductor crystals based on transition metal
dichalcogenide monolayers is a prerequisite for spintronic and valleytronic
devices using these materials. Here, the hcp Co(0001)/MoS2 interface electronic
structure is investigated by first-principles calculations based on the density
functional theory. In the lowest energy configuration of the hybrid system
after optimization of the atomic coordinates, we show that interface sulfur
atoms are covalently bound to one, two or three cobalt atoms. A decrease of the
Co atom spin magnetic moment is observed at the interface, together with a
small magnetization of S atoms. Mo atoms also hold small magnetic moments which
can take positive as well as negative values. The charge transfers due to
covalent bonding between S and Co atoms at the interface have been calculated
for majority and minority spin electrons and the connections between these
interface charge transfers and the induced magnetic properties of the MoS2
layer are discussed. Band structure and density of states of the hybrid system
are calculated for minority and majority spin electrons, taking into account
spin-orbit coupling. We demonstrate that MoS2 bound to the Co contact becomes
metallic due to hybridization between Co d and S p orbitals. For this metallic
phase of MoS2, a spin polarization at the Fermi level of 16 % in absolute value
is calculated, that could allow spin injection into the semiconducting MoS2
monolayer channel. Finally, the symmetry of the majority and minority spin
electron wave functions at the Fermi level in the Co-bound metallic phase of
MoS2 and the orientation of the border between the metallic and semiconducting
phases of MoS2 are investigated, and their impact on spin injection into the
MoS2 channel is discussed.",1803.10612v1
2000-05-15,Dynamics of multiply charged ions in intense laser fields,"We numerically investigate the dynamics of multiply charged hydrogenic ions
in near-optical linearly polarized laser fields with intensities of order 10^16
to 10^17 W/cm^2. Depending on the charge state Z of the ion the relation of
strength between laser field and ionic core changes. We find around Z=12
typical multiphoton dynamics and for Z=3 tunneling behaviour, however with
clear relativistic signatures. In first order in v/c the magnetic field
component of the laser field induces a Z-dependent drift in the laser
propagation direction and a substantial Z-dependent angular momentum with
repect to the ionic core. While spin oscillations occur already in first order
in v/c as described by the Pauli equation, spin induced forces via spin orbit
coupling only appear in the parameter regime where (v/c)^2 corrections are
significant. In this regime for Z=12 ions we show strong splittings of resonant
spectral lines due to spin-orbit coupling and substantial corrections to the
conventional Stark shift due to the relativistic mass shift while those to the
Darwin term are shown to be small. For smaller charges or higher laser
intensities, parts of the electronic wavepacket may tunnel through the
potential barrier of the ionic core, and when recombining are shown to give
rise to keV harmonics in the radiation spectrum. Some parts of the wavepacket
do not recombine after ionisation and we find very energetic electrons in the
weakly relativistic regime of above threshold ionization.",0005053v1
2008-11-04,"Perspectives in spintronics: magnetic resonant tunneling, spin-orbit coupling, and GaMnAs","Spintronics has attracted wide attention by promising novel functionalities
derived from both the electron charge and spin. While branching into new areas
and creating new themes over the past years, the principal goals remain the
spin and magnetic control of the electrical properties, essentially the I-V
characteristics, and vice versa. There are great challenges ahead to meet these
goals. One challenge is to find niche applications for ferromagnetic
semiconductors, such as GaMnAs. Another is to develop further the science of
hybrid ferromagnetic metal/semiconductor heterostructures, as alternatives to
all-semiconductor room temperature spintronics. Here we present our
representative recent efiorts to address such challenges. We show how to make a
digital magnetoresistor by combining two magnetic resonant diodes, or how
introducing ferromagnetic semiconductors as active regions in resonant
tunneling diodes leads to novel efiects of digital magnetoresistance and of
magnetoelectric current oscillations. We also discuss the phenomenon of
tunneling anisotropic magnetoresistance in Fe/GaAs junctions by introducing the
concept of the spin-orbit coupling field, as an analog of such fields in
all-semiconductor junctions. Finally, we look at fundamental electronic and
optical properties of GaMnAs by employing reasonable tight-binding models to
study disorder efiects.",0811.0500v1
2012-03-13,Electronic and magnetic properties of molecule-metal interfaces: transition metal phthalocyanines adsorbed on Ag(100),"We present a systematic investigation of molecule-metal interactions for
transition-metal phthalocyanines (TMPc, with TM = Fe, Co, Ni, Cu) adsorbed on
Ag(100). Scanning tunneling spectroscopy and density functional theory provide
insight into the charge transfer and hybridization mechanisms of TMPc as a
function of increasing occupancy of the 3d metal states. We show that all four
TMPc receive approximately one electron from the substrate. Charge transfer
occurs from the substrate to the molecules, inducing a charge reorganization in
FePc and CoPc, while adding one electron to ligand \pi-orbitals in NiPc and
CuPc. This has opposite consequences on the molecular magnetic moment: in FePc
and CoPc the interaction with the substrate tends to reduce the TM spin,
whereas in NiPc and CuPc an additional spin is induced on the aromatic Pc
ligand, leaving the TM spin unperturbed. In CuPc, the presence of both TM and
ligand spins leads to a triplet ground state arising from intramolecular
exchange coupling between d and \pi electrons. In FePc and CoPc the magnetic
moment of C and N atoms is antiparallel to that of the TM. The different
character and symmetry of the frontier orbitals in the TMPc series leads to
varying degrees of hybridization and correlation effects, ranging from the
mixed-valence (FePc, CoPc) to the Kondo regime (NiPc, CuPc). Coherent coupling
between Kondo and inelastic excitations induces finite-bias Kondo resonances
involving vibrational transitions in both NiPc and CuPc and triplet-singlet
transitions in CuPc.",1203.2747v1
2012-12-21,Correlated Topological Phases and Exotic Magnetism with Ultracold Fermions,"Motivated by the recent progress in engineering artificial non-Abelian gauge
fields for ultracold fermions in optical lattices, we investigate the
time-reversal-invariant Hofstadter-Hubbard model. We include an additional
staggered lattice potential and an artificial Rashba--type spin-orbit coupling
term available in experiment. Without interactions, the system can be either a
(semi)-metal, a normal or a topological insulator, and we present the
non-Abelian generalization of the Hofstadter butterfly. Using a combination of
real-space dynamical mean-field theory (RDMFT), analytical arguments, and
Monte-Carlo simulations we study the effect of strong on-site interactions. We
determine the interacting phase diagram, and discuss a scenario of an
interaction-induced transition from normal to topological insulator. At
half-filling and large interactions, the system is described by a quantum spin
Hamiltonian, which exhibits exotic magnetic order due to the interplay of
Rashba--type spin-orbit coupling and the artificial time-reversal-invariant
magnetic field term. We determine the magnetic phase diagram: both for the
itinerant model using RDMFT and for the corresponding spin model in the
classical limit using Monte-Carlo simulations.",1212.5607v2
2013-07-29,Two-orbital physics of high spin fermionic alkaline earth atoms confined in a one-dimensional chain,"We study the effect of the coupling between the electronic ground state of
high spin alkaline-earth fermionic atoms and their metastable optically excited
state, when the system is confined in a one-dimensional chain, and show that
the system provides a possible realization of a finite momentum pairing
(Fulde-Ferrell-Larkin-Ovchinnikov-like) state without spin- or bare mass
imbalance. We determine the $\beta$-functions of the renormalization group
trajectories for general spin and analyze the structure of the possible gapped
and gapless states in the hydrodynamic limit. Due to the SU(N) symmetry in the
spin space, complete mode separation can not be observed even in the fully
gapless 2N-component Luttinger liquid state. Contrary, 4 velocities
characterize the system. We solve the renormalization group equations for
spin-9/2 strontium-87 isotope and analyze in detail its phase diagram. The
fully gapless Luttinger liquid state does not stabilize in the two-orbital
system of the $^{87}$Sr atoms, instead, different gapped non-Gaussian fixed
points are identified either with dominant density or superconducting
fluctuations. The superconducting states are stable in a nontrivial shaped
region in the parameter space as a consequence of the coupling between the two
electronic states.",1307.7558v2
2014-08-13,Topological Floquet states on a Möbius band irradiated by circularly polarised light,"Topological states of matter in equilibrium, as well as out of equilibrium,
have been thoroughly investigated during the last years in condensed-matter and
cold-atom systems. However, the geometric topology of the studied samples is
usually trivial, such as a ribbon or a cylinder. In this paper, we consider a
graphene M\""obius band irradiated with circularly polarised light.
Interestingly, due to the non-orientability of the M\""obius band, a homogeneous
quantum Hall effect cannot exist in this system, but the quantum spin Hall
effect can. To avoid this restriction, the irradiation is applied in a
longitudinal-domain-wall configuration. In this way, the periodic
time-dependent driving term tends to generate the quantum anomalous Hall
effect. On the other hand, due to the bent geometry of the M\""obius band, we
expect a strong spin-orbit coupling, which may lead to quantum spin Hall-like
topological states. Here, we investigate the competition between these two
phenomena upon varying the amplitude and the frequency of the light, for a
fixed value of the spin-orbit coupling strength. The topological properties are
analysed by identifying the edge states in the Floquet spectrum at intermediate
frequencies, when there are resonances between the light frequency and the
energy difference between the conduction and valence bands of the graphene
system.",1408.3087v1
2016-04-18,Numerical study of the giant nonlocal resistance in spin-orbital coupled graphene,"Recent experiments find the signal of giant nonlocal resistance $R_{NL}$ in
H-shaped graphene samples due to the spin/valley Hall effect. Interestingly,
when the Fermi energy deviates from the Dirac point, $R_{NL}$ decreases to zero
much more rapidly compared with the local resistance $R_L$, and the well-known
relation of $R_{NL}\propto R_L^3$ is not satisfied. In this work, based on the
non-equilibrium Green's function method, we explain such transport phenomena in
the H-shaped graphene with Rashba spin-orbit coupling. When the Fermi energy is
near the Dirac point, the nonlocal resistance is considerably large and is much
sharper than the local one. Moreover, the relationship between the Rashba
effect and the fast decay of $R_{NL}$ compared with $R_L$ is further
investigated. We find that the Rashba effect does not contribute not only to
the fast decay but also to the peak of $R_{NL}$ itself. Actually, it is the
extremely small density of states near the Dirac point that leads to the large
peak of $R_{NL}$, while the fast decay results from the quasi-ballistic
mechanism. Finally, we revise the classic formula $R_{NL}\propto R_L^3$ by
replacing $R_{NL}$ with $R_{Hall}$, which represents the nonlocal resistance
merely caused by the spin Hall effect, and the relation holds well.",1604.04993v2
2016-09-01,Microwave spectroscopy of spinful Andreev bound states in ballistic semiconductor Josephson junctions,"The superconducting proximity effect in semiconductor nanowires has recently
enabled the study of new superconducting architectures, such as gate-tunable
superconducting qubits and multiterminal Josephson junctions. As opposed to
their metallic counterparts, the electron density in semiconductor nanosystems
is tunable by external electrostatic gates providing a highly scalable and
in-situ variation of the device properties. In addition, semiconductors with
large $g$-factor and spin-orbit coupling have been shown to give rise to exotic
phenomena in superconductivity, such as $\varphi_0$ Josephson junctions and the
emergence of Majorana bound states. Here, we report microwave spectroscopy
measurements that directly reveal the presence of Andreev bound states (ABS) in
ballistic semiconductor channels. We show that the measured ABS spectra are the
result of transport channels with gate-tunable, high transmission probabilities
up to $0.9$, which is required for gate-tunable Andreev qubits and beneficial
for braiding schemes of Majorana states. For the first time, we detect
excitations of a spin-split pair of ABS and observe symmetry-broken ABS, a
direct consequence of the spin-orbit coupling in the semiconductor.",1609.00333v2
2016-09-19,Superconductivity and spin-orbit coupling in non-centrosymmetric materials: a review,"In non-centrosymmetric superconductors, where the crystal structure lacks a
centre of inversion, parity is no longer a good quantum number and an
electronic antisymmetric spin-orbit coupling (ASOC) is allowed to exist by
symmetry. If this ASOC is sufficiently large, it has profound consequences on
the superconducting state. For example, it generally leads to a superconducting
pairing state which is a mixture of spin-singlet and spin-triplet components.
The possibility of such novel pairing states, as well as the potential for
observing a variety of unusual behaviours, led to intensive theoretical and
experimental investigations. Here we review the experimental and theoretical
results for superconducting systems lacking inversion symmetry. Firstly we give
a conceptual overview of the key theoretical results. We then review the
experimental properties of both strongly and weakly correlated bulk materials,
as well as two dimensional systems. Here the focus is on evaluating the effect
of ASOC on the superconducting properties and the extent to which there is
evidence for singlet-triplet mixing. This is followed by a more detailed
overview of theoretical aspects of non-centrosymmetric superconductivity. This
includes the effects of the ASOC on the pairing symmetry and the
superconducting magnetic response, magneto-electric effects, superconducting
finite momentum pairing states, and the potential of non-centrosymmetric
superconductors to display topological superconductivity.",1609.05953v1
2017-08-08,Gate tunable spin-orbit coupling and weak antilocalization effect in an epitaxial La$_{2/3}$Sr$_{1/3}$MnO$_3$ thin film,"Epitaxial La$_{2/3}$Sr$_{1/3}$MnO$_3$ (LSMO) films have been grown on
SrTiO$_3$ (001) substrates via pulsed laser deposition. In a 22-nm thick LSMO
film with a low residual resistivity of $\rho_0$ = 59 $\mu \Omega$ cm, we found
a zero-field dip in the magnetoresistance (MR) below 10 K, manifesting the weak
antilocalization (WAL) effect due to strong spin-orbit coupling (SOC). We have
analyzed the MR data by including the D'yakonov-Perel' spin-relaxation
mechanism in the WAL theory. We explain that the delocalized spin-down electron
subband states play a crucial role for facilitating marked SOC in clean LSMO.
Moreover, we find that the SOC strength and gate voltage tunability is similar
to that in the 2DEG at LaAlO$_3$/SrTiO$_3$ interface, indicating the presence
of an internal electric field near the LSMO/SrTiO$_3$ interface. In a control
measurement on a 5-nm thick high resistivity ($\rho_0$ = 280 $\mu \Omega$ cm)
LSMO film, we observe only a small zero-field peak in MR from weak localization
effect, indicating negligible SOC.",1708.02338v1
2017-08-15,Transport properties of Co in Cu(100) from first principles,"The electronic transport properties of a point-contact system formed by a
single Co atom adsorbed on Cu (100) and contacted by a copper tip is evaluated
in the presence of intra-atomic Coulomb interactions and spin-orbit coupling.
The calculations are performed using equilibrium Green's functions evaluated
within density functional theory completed with a Hubbard $U$ term and
spin-orbit interaction, as implemented in the Gollum package. We show that the
contribution to the transmission between electrodes of spin-flip components is
negative and scaling as $\lambda^2/\Gamma^2$ where $\lambda$ is the SOC and
$\Gamma$ the Co atom-electrode coupling. Hence, due to this unfavorable ratio,
SOC effects in transport in this system are small. However, we show that the
spin-flip transmission component can increase by two orders of magnitude
depending on the value of the Hubbard $U$ term. These effects are particularly
important in the contact regime because of the prevalence of $d$-electron
transport, while in the tunneling regime, transport is controlled by the
$sp$-electron transmission and results are less dependent on the values of $U$
and SOC. Using our electronic structure and the elastic transmission
calculations, we discuss the effect of $U$ and SOC on the well-known Kondo
effect of this system.",1708.04472v1
2012-01-02,Microscopic theory of quantum anomalous Hall effect in graphene,"We present a microscopic theory to give a physical picture of the formation
of quantum anomalous Hall (QAH) effect in graphene due to a joint effect of
Rashba spin-orbit coupling $\lambda_R$ and exchange field $M$. Based on a
continuum model at valley $K$ or $K'$, we show that there exist two distinct
physical origins of QAH effect at two different limits. For $M/\lambda_R\gg1$,
the quantization of Hall conductance in the absence of Landau-level
quantization can be regarded as a summation of the topological charges carried
by Skyrmions from real spin textures and Merons from \emph{AB} sublattice
pseudo-spin textures; while for $\lambda_R/M\gg1$, the four-band low-energy
model Hamiltonian is reduced to a two-band extended Haldane's model, giving
rise to a nonzero Chern number $\mathcal{C}=1$ at either $K$ or $K'$. In the
presence of staggered \emph{AB} sublattice potential $U$, a topological phase
transition occurs at $U=M$ from a QAH phase to a quantum valley-Hall phase. We
further find that the band gap responses at $K$ and $K'$ are different when
$\lambda_R$, $M$, and $U$ are simultaneously considered. We also show that the
QAH phase is robust against weak intrinsic spin-orbit coupling $\lambda_{SO}$,
and it transitions a trivial phase when
$\lambda_{SO}>(\sqrt{M^2+\lambda^2_R}+M)/2$. Moreover, we use a tight-binding
model to reproduce the ab-initio method obtained band structures through doping
magnetic atoms on $3\times3$ and $4\times4$ supercells of graphene, and explain
the physical mechanisms of opening a nontrivial bulk gap to realize the QAH
effect in different supercells of graphene.",1201.0543v1
2019-10-08,Correlated fluctuations in spin orbit torque-coupled perpendicular nanomagnets,"Low barrier nanomagnets have attracted a lot of research interest for their
use as sources of high quality true random number generation. More recently,
low barrier nanomagnets with tunable output have been shown to be a natural
hardware platform for unconventional computing paradigms such as probabilistic
spin logic. Efficient generation and tunability of high quality random bits is
critical for these novel applications. However, current spintronic random
number generators are based on superparamagnetic tunnel junctions (SMTJs) with
tunability obtained through spin transfer torque (STT), which unavoidably leads
to challenges in designing concatenated networks using these two terminal
devices. The more recent development of utilizing spin orbit torque (SOT)
allows for a three terminal device design, but can only tune in-plane
magnetization freely, which is not very energy efficient due to the needs of
overcoming a large demagnetization field. In this work, we experimentally
demonstrate for the first time, a stochastic device with perpendicular magnetic
anisotropy (PMA) that is completely tunable by SOT without the aid of any
external magnetic field. Our measurements lead us to hypothesize that a tilted
anisotropy might be responsible for the observed tunability. We carry out
stochastic Landau-Lifshitz-Gilbert (sLLG) simulations to confirm our
experimental observation. Finally, we build an electrically coupled network of
two such stochastic nanomagnet based devices and demonstrate that finite
correlation or anti-correlation can be established between their output
fluctuations by a weak interconnection, despite having a large difference in
their natural fluctuation time scale. Simulations based on a newly developed
dynamical model for autonomous circuits composed of low barrier nanomagnets
show close agreement with the experimental results.",1910.03184v1
2020-01-19,Controlling Dzyaloshinskii-Moriya interactions in the skyrmion host candidates FePd$_{1-x}$Pt$_x$Mo$_3$N,"Ferromagnets crystallizing in structures described by chiral cubic space
groups, including compounds with the B20 or $\beta$-Mn structures, are known to
host long-period chiral spin textures such as skyrmion lattices. These spin
textures are stabilized by a competition between ferromagnetic exchange and
antisymmetric Dyzaloshinskii-Moriya (DM) exchange, which is enhanced by the
spin-orbit coupling associated with high-atomic-number elements. For real-world
application, it is desirable to find materials that can host compact skyrmion
lattices at readily accessible temperatures. Here, we report on the crystal
chemistry and magnetic phase diagrams of a family of compounds with the filled
$\beta$-Mn structure, FePd$_{1-x}$Pt$_x$Mo$_3$N with $T_C$ ranging from 175 K
to 240 K. DC and AC magnetization measurements reveal magnetic phase diagrams
consistent with the formation of a skyrmion pocket just below $T_C$. The
magnitudes of ferromagnetic and DM exchanges are determined from the phase
diagrams, demonstrating that the introduction of increasing amounts of Pt can
be used to increase spin-orbit coupling in order to control the expected
skyrmion lattice parameter between 140 nm and 65 nm while simultaneously
increasing $T_C$.",2001.06783v1
2018-06-29,Proximity-induced topological transition and strain-induced charge transfer in graphene/MoS2 bilayer heterostructures,"Graphene/MoS2 heterostructures are formed by combining the nanosheets of
graphene and monolayer MoS2. The electronic features of both constituent
monolayers are rather well-preserved in the resultant heterostructure due to
the weak van der Waals interaction between the layers. However, the proximity
of MoS2 induces strong spin orbit coupling effect of strength ~1 meV in
graphene, which is nearly three orders of magnitude larger than the intrinsic
spin orbit coupling of pristine graphene. This opens a bandgap in graphene and
further causes anticrossings of the spin-nondegenerate bands near the Dirac
point. Lattice incommensurate graphene/MoS2 heterostructure exhibits
interesting moire' patterns which have been observed in experiments. The
electronic bandstructure of heterostructure is very sensitive to biaxial strain
and interlayer twist. Although the Dirac cone of graphene remains intact and no
charge-transfer between graphene and MoS2 layers occurs at ambient conditions,
a strain-induced charge-transfer can be realized in graphene/MoS2
heterostructure. Application of a gate voltage reveals the occurrence of a
topological phase transition in graphene/MoS2 heterostructure. In this chapter,
we discuss the crystal structure, interlayer effects, electronic structure,
spin states, and effects due to strain and substrate proximity on the
electronic properties of graphene/MoS2 heterostructure. We further present an
overview of the distinct topological quantum phases of graphene/MoS2
heterostructure and review the recent advancements in this field.",1806.11469v1
2020-10-26,Topological defects in rotating spin-orbit-coupled dipolar spin-1 Bose-Einstein condensates,"We consider the topological defects and spin structures of spin-1
Bose-Einstein condensates (BECs) with spin-orbit coupling (SOC) and
dipole-dipole interaction (DDI) in a rotating harmonic plus quartic trap. The
combined effects of SOC, DDI and rotation on the ground-state phases of the
system are analyzed. Our results show that for fixed rotation frequency
structural phase transitions can be achieved by adjusting the magnitudes of the
SOC and DDI. A ground-state phase diagram is given as a function of the SOC and
DDI strengths. It is shown that the system exhibits rich quantum phases
including vortex string phase with isolated density peaks (DPs), triangular
(square) vortex lattice phase with DPs, checkerboard phase, and stripe phase
with hidden vortices and antivortices. For given SOC and DDI strengths, the
system can display pentagonal vortex lattice with DPs, vortex necklace with
DPs, and exotic topological structure composed of multi-layer visible vortex
necklaces, a hidden giant vortex and hidden vortex necklaces, depending on the
rotation frequency. In addition, the system sustains fascinating novel spin
textures and skyrmion excitations, such as an antiskyrmion pair,
antiskyrmion-half-antiskyrmion (antiskyrmion-antimeron) cluster,
skyrmion-antiskyrmion lattice, skyrmion-antiskyrmion cluster,
skyrmion-antiskyrmion-meron-antimeron lattice, double-layer half-antiskyrmion
necklaces, and composite giant-antiskyrmion-antimeron necklaces.",2010.13576v1
2020-11-05,Strong in-plane magnetic field induced reemergent superconductivity in the van der Waals heterointerface of NbSe2 and CrCl3,"A magnetic field is generally considered to be incompatible with
superconductivity as it tends to spin-polarize electrons and breaks apart the
opposite-spin singlet superconducting Cooper pairs. Here, an experimental
phenomenon is observed that an intriguing reemergent superconductivity evolves
from a conventional superconductivity undergoing a hump-like intermediate phase
with a finite electric resistance in the van der Waals heterointerface of
layered NbSe2 and CrCl3 flakes. This phenomenon merely occurred when the
applied magnetic field is parallel to the sample plane and perpendicular to the
electric current direction as compared to the reference sample of a NbSe2 thin
flake. The strong anisotropy of the reemergent superconducting phase is pointed
to the nature of the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state driven by
the strong interfacial spin-orbit coupling between NbSe2 and CrCl3 layers. The
theoretical picture of FFLO state nodes induced by Josephson vortices
collectively pinning is presented for well understanding the experimental
observation of the reemergent superconductivity. This finding sheds light on an
opportunity to search for the exotic FFLO state in the van der Waals
heterostructures with strong interfacial spin-orbit coupling.",2011.02643v1
2015-08-02,"Absence of Perfect Conductance Quantization of Helical-edge Transport in Graphene under a Strong, Tilted Magnetic Field","In a recent experiment, Young et al. [Nature {\bf 505}, 528 (2014)] observed
a metal to insulator transition as well as transport through helical edge
states in monolayer graphene under a strong, tilted magnetic field. Under such
conditions, the bulk is a magnetic insulator which can exhibit metallic
conduction through helical edges. It was found that two-terminal conductance of
the helical channels deviates from the expected quantized value at
low-temperatures ($=e^2/h$ per edge, at zero temperature). Motivated by this
observation, we study the effect of disorder on the conduction through the edge
channels. We show that, unlike the situation in semiconducting quantum wells, a
disorder Rashba spin-orbit coupling does not lead to backscattering, at least
to leading order. Instead we find the lack of perfect anti-alignment of the
electron spins in the helical channels to be the most likely source for
backscattering arising from scalar (i.e. spin-independent) impurities. The
intrinsic spin-orbit coupling and other time-reversal symmetry breaking and/or
sublattice-parity breaking potentials also lead to (sub-leading) corrections to
the channel conductance.",1508.00220v2
2015-08-30,Drumhead Surface States and Topological Nodal-Line Fermions in TlTaSe2,"A topological nodal-line semimetal is a new condensed matter state with
one-dimensional bulk nodal lines and two-dimensional drumhead surface bands.
Based on first-principles calculations and our effective k . p model, we
propose the existence of topological nodal-line fermions in the ternary
transition- metal chalcogenide TlTaSe2. The noncentrosymmetric structure and
strong spin-orbit coupling give rise to spinful nodal-line bulk states which
are protected by a mirror reflection symmetry of this compound. This is
remarkably distinguished from other proposed nodal-line semimetals such as
Cu3NPb(Zn) in which nodal lines exist only in the limit of vanishing spin-orbit
coupling. We show that the drumhead surface states in TlTaSe2, which are
associated with the topological nodal lines, exhibit an unconventional chiral
spin texture and an exotic Lifshitz transition as a consequence of the linkage
among multiple drumhead surface-state pockets.",1508.07521v1
2016-12-19,Coherent Electron Zitterbewegung,"Zitterbewegung is a striking consequence of relativistic quantum mechanics
which predicts that free Dirac electrons exhibit a rapid trembling motion even
in the absence of external forces. The trembling motion of an electron results
from the interference between the positive and the negative-energy solutions of
the Dirac equation, separated by one MeV, leading to oscillations at extremely
high frequencies which are out of reach experimentally. Recently, it was shown
theoretically that electrons in III-V semiconductors are governed by similar
equations in the presence of spin-orbit coupling. The small energy splittings
up to meV result in Zitterbewegung at much smaller frequencies which should be
experimentally accessible as an AC current. Here, we demonstrate the
Zitterbewegung of electrons in a solid. We show that coherent electron
Zitterbewegung can be triggered by initializing an ensemble of electrons in the
same spin states in strained n-InGaAs and is probed as an AC current at GHz
frequencies. Its amplitude is shown to increase linearly with both the
spin-orbit coupling strength and the Larmor frequency of the external magnetic
field. The latter dependence is the hallmark of the dynamical generation
mechanism of the oscillatory motion of the Zitterbewegung. Our results
demonstrate that relativistic quantum mechanics can be studied in a rather
simple solid state system at moderate temperatures. Furthermore, the large
amplitude of the AC current at high precession frequencies enables ultra-fast
spin sensitive electric read-out in solids.",1612.06190v1
2018-10-15,"Effect of Rashba spin-orbit coupling, magnetization and mixing of gap parameter on tunnelling conductance in F$|$NCSC junction of an F$|$S$|$F spin valve","In this paper, we study the quantum transport at the
Ferromagnet$|$Noncentrosymmetric Superconductor (F$|$NCSC) interface of an
F$|$S$|$F spin valve. In this context, we investigate the tunneling conductance
and its dependence on Rashba Spin-Orbit Coupling (RSOC) considering different
barrier strength and a significant Fermi Wave-vector Mismatch (FWM) at the
ferromagnetic and superconducting regions. The study is carried out for
different magnetization orientations and its strength. We developed Bogoliubov
de Gennes (BdG) Hamiltonian introducing RSOC and exchange interaction for such
an hybrid structure. To study charge conductance we use an extended Blonder -
Tinkham - Klapwijk (BTK) approach along with scattering matrix formalism to
calculate the scattering coefficients. Our results strongly suggest that the
tunneling conductance is strongly dependent on RSOC, magnetization strength,
its orientation and the FWM. The work has also been done for different
singlet-triplet mixing of the gap parameter. We have observed that with the
rise of singlet-triplet mixing ratio the conductance decreases. It is also
observed that a transparent barrier with moderate RSOC and having moderate
magnetization strength with arbitrary orientation is highly suitable for
maximum conductance.",1810.06261v1
2019-05-12,Knight Shift and Leading Superconducting Instability From Spin Fluctuations in Sr2RuO4,"Recent nuclear magnetic resonance studies [A. Pustogow {\it et al.},
arXiv:1904.00047] have challenged the prevalent chiral triplet pairing scenario
proposed for Sr$_2$RuO$_4$. To provide guidance from microscopic theory as to
which other pair states might be compatible with the new data, we perform a
detailed theoretical study of spin-fluctuation mediated pairing for this
compound. We map out the phase diagram as a function of spin-orbit coupling,
interaction parameters, and band-structure properties over physically
reasonable ranges, comparing when possible with photoemission and inelastic
neutron scattering data information. We find that even-parity pseudospin
singlet solutions dominate large regions of the phase diagram, but in certain
regimes spin-orbit coupling favors a near-nodal odd-parity triplet
superconducting state, which is either helical or chiral depending on the
proximity of the $\gamma$ band to the van Hove points. A surprising
near-degeneracy of the nodal $s^\prime$- and $d_{x^2-y^2}$-wave solutions leads
to the possibility of a near-nodal time-reversal symmetry broken
$s^\prime+id_{x^2-y^2}$ pair state. Predictions for the temperature dependence
of the Knight shift for fields in and out of plane are presented for all
states.",1905.04782v1
2022-12-05,Topological superconductivity driven by correlations and linear defects in multiband superconductors,"There have been several proposals for platforms sustaining topological
superconductivity in high temperature superconductors, in order to make use of
the larger superconducting gap and the expected robustness of Majorana zero
modes towards perturbations. In particular, the iron-based materials offer
relatively large $T_c$ and nodeless energy gaps. In addition, atomically flat
surfaces enable the engineering of defect structures and the subsequent
measurement of spectroscopic properties to reveal topological aspects. From a
theory perspective, a materials-specific description is challenging due to the
correlated nature of the materials and complications arising from the multiband
nature of the electronic structure. Here we include both aspects in realistic
interacting models, and find that the correlations themselves can lead to local
magnetic order close to linear potential scattering defects at the surface of
the superconductor. Using a self-consistent Bogoliubov-de Gennes framework in a
real-space setup using a prototype electronic structure, we allow for arbitrary
magnetic orders and show how a topological superconducting state emerges. The
calculation of the topological invariant and the topological gap allows us to
map out the phase diagram for the case of a linear chain of potential
scatterers. While intrinsic spin-orbit coupling is not needed to enter the
topological state in presence of spin-spiral states, it enlarges the
topological phase. We discuss the interplay of a triplet component of the
superconducting order parameter and the spin spiral leading effectively to
extended spin orbit coupling terms, and connect our results to experimental
efforts on the Fe(Se,Te) system.",2212.02394v1
2023-01-15,Metastable supersolid in spin-orbit coupled Bose-Einstein condensates,"Supersolid is a special state of matter with both superfluid properties and
spontaneous modulation of particle density. In this paper, we focus on the
supersolid stripe phase realized in a spin-orbit coupled Bose-Einstein
condensate and explore the properties of a class of metastable supersolids. In
particular, we study a one-dimensional supersolid whose characteristic wave
number $k$ (magnitude of wave vector) deviates from $k_{m}$, i.e., the one at
ground state. In other words, the period of density modulation is shorter or
longer than the one at ground state. We find that this class of supersolids can
still be stable if their wave numbers fall in the range $k_{c1}<k<k_{c2}$, with
two thresholds $k_{c1}$ and $k_{c2}$. Stripes with $k$ outside this range
suffer from dynamical instability with complex Bogoliubov excitation spectrum
at long wavelength. Experimentally, these stripes with $k$ away from $k_m$ are
accessible by exciting the longitudinal spin dipole mode, resulting in temporal
oscillation of stripe period as well as $k$. Within the mean-field
Gross-Pitaevskii theory, we numerically confirm that for a large enough
amplitude of spin dipole oscillation, the stripe states become unstable through
breaking periodicity, in qualitative agreement with the existence of thresholds
of $k$ for stable stripes. Our work extends the concept of supersolid and
uncovers a new class of metastable supersolids to explore.",2301.06094v1
2023-03-02,Ballistic transport spectroscopy of spin-orbit-coupled bands in monolayer graphene on WSe$_2$,"Van der Waals interactions with transition metal dichalcogenides was shown to
induce strong spin-orbit coupling (SOC) in graphene, offering great promises to
combine large experimental flexibility of graphene with unique tuning
capabilities of the SOC that can rotate spin by moving electrons or vice versa.
Here, we probe SOC-driven band splitting and electron dynamics in graphene on
WSe$_2$ by measuring ballistic transverse magnetic focusing. We found a clear
splitting in the first focusing peak whose evolution in charge density and
magnetic field is well reproduced by calculations using SOC strength of ~13 meV
and no splitting in the second peak that indicates stronger Rashba SOC. A
possible suppression of electron-electron scatterings was also found in
temperature dependence measurement. Further, we found that Shubnikov-de Haas
oscillations exhibit SOC strength of ~3.4 meV, suggesting that it probes
different electron dynamics, calling for new theory. Our study demonstrates an
interesting possibility to exploit ballistic electron motion pronounced in
graphene for emerging spin-orbitronics.",2303.01018v2
2023-08-31,Nature of the mixed-parity pairing of attractive fermions with spin-orbit coupling in optical lattice,"The admixture of spin-singlet and spin-triplet pairing states in
superconductors can be typically induced by breaking spatial inversion
symmetry. Employing the {\it numerically exact} auxiliary-field Quantum Monte
Carlo method, we study such mixed-parity pairing phenomena of attractive
fermions with Rashba spin-orbit coupling (SOC) in two-dimensional optical
lattice at finite temperature. We systematically demystify the evolution of the
essential pairing structure in both singlet and triplet channels versus the
temperature, fermion filling, SOC and interaction strengths, via computing the
condensate fraction and pair wave function. Our numerical results reveal that
the singlet channel dominates in the fermion pairing and the triplet pairing
has relatively small contribution to the superfluidity for physically relevant
parameters. In contrast to the singlet channel mainly consisted of the on-site
Cooper pairs, the triplet pairing has plentiful patterns in real space with the
largest contributions from several nearest neighbors. As the SOC strengh
increases, the pairing correlation is firstly enhanced and then suppressed for
triplet pairing while it's simply weakened in singlet channel. We have also
obtained the Berezinskii-Kosterlitz-Thouless transition temperatures through
the finite-size analysis of condensate fraction. Our results can serve as
quantitative guide for future optical lattice experiments as well as accurate
benchmarks for theories and other numerical methods.",2308.16657v2
2023-10-17,Low-energy electronic interactions in ferrimagnetic Sr2CrReO6 thin films,"We reveal in this study the fundamental low-energy landscape in the
ferrimagnetic Sr2CrReO6 double perovskite and describe the underlying
mechanisms responsible for the three low-energy excitations below 1.4 eV. Based
on resonant inelastic x-ray scattering and magnetic dynamics calculations, and
experiments collected from both Sr2CrReO6 powders and epitaxially strained thin
films, we reveal a strong competition between spin-orbit coupling, Hund's
coupling, and the strain-induced tetragonal crystal field. We also demonstrate
that a spin-flip process is at the origin of the lowest excitation at 200 meV,
and we bring insights into the predicted presence of orbital ordering in this
material. We study the nature of the magnons through a combination of ab initio
and spin-wave theory calculations, and show that two nondegenerate magnon bands
exist and are dominated either by rhenium or chromium spins. The rhenium band
is found to be flat at about 200 meV ($\pm$25 meV) through X-L-W-U
high-symmetry points and is dispersive toward $\Gamma$",2310.11585v1
2024-02-07,Nodal fermions in a strongly spin-orbit coupled frustrated pyrochlore superconductor,"The pyrochlore lattice, a three-dimensional network of corner-sharing
tetrahedra, is a promising material playground for correlated topological
phases arising from the interplay between spin-orbit coupling (SOC) and
electron-electron interactions. Due to its geometrically frustrated lattice
structure, exotic correlated states on the pyrochlore lattice have been
extensively studied using various spin Hamiltonians in the localized limit. On
the other hand, the topological properties of the electronic structure in the
pyrochlore lattice have rarely been explored, due to the scarcity of pyrochlore
materials in the itinerant paramagnetic limit. Here, we explore the topological
electronic band structure of pyrochlore superconductor RbBi$_{2}$ using
angle-resolved photoemission spectroscopy. Thanks to the strong SOC of the Bi
pyrochlore network, we experimentally confirm the existence of
three-dimensional (3D) massless Dirac fermions enforced by nonsymmorphic
symmetry, as well as a 3D quadratic band crossing protected by cubic
crystalline symmetry. Furthermore, we identify an additional 3D linear Dirac
dispersion associated with band inversion protected by threefold rotation
symmetry. These observations reveal the rich non-trivial band topology of
itinerant pyrochlore lattice systems in the strong SOC regime. Through
manipulation of electron correlations and SOC of the frustrated pyrochlore
lattices, this material platform is a natural host for exotic phases of matter,
including the fractionalized quantum spin Hall effect in the topological Mott
insulator phase, as well as axion electrodynamics in the axion insulator phase.",2402.04509v1
2024-02-20,Magnetotransport Signatures of the Radial Rashba Spin-Orbit Coupling in Proximitized Graphene,"Graphene-based van der Waals heterostructures take advantage of tailoring
spin-orbit coupling (SOC) in the graphene layer by proximity effect. At
long-wavelength -- saddled by the electronic states near the Dirac points --
the proximitized features can be effectively modelled by the Hamiltonian
involving novel SOC terms and allow for an admixture of the tangential and
radial spin textures -- by the so-called Rashba angle $\theta_{\text{R}}$.
Taking such effective models we perform realistic large-scale magneto-transport
calculations -- transverse magnetic focusing and Dyakonov-Perel spin relaxation
-- and show that there are unique qualitative and quantitative features
allowing for an unbiased experimental disentanglement of the conventional
Rashba SOC from its novel radial counterpart, called here the radial Rashba
SOC. Along with that, we propose a scheme for a direct estimation of the Rashba
angle by exploring the magneto-response symmetries when swapping an in-plane
magnetic field. To complete the story, we analyze the magneto-transport
signatures in the presence of an emergent Dresselhaus SOC and also provide some
generic ramifications about possible scenarios of the radial superconducting
diode effect.",2402.13424v1
2003-06-20,Pure spin currents and associated electrical voltage,"We present a generalize Landauer-B\""uttiker transport theory for
multi-terminal spin transport in presence of spin-orbit interaction. It is
pointed out that the presence of spin-orbit interaction results in {\it
equilibrium spin currents}, since in presence of spin-orbit interaction spin is
not a conserved quantitative. Further we illustrate the theory by applying it
to a three terminal Y-shaped conductor. It is shown that when one of the
terminal is a potential probe, there exist {\it nonequilibrium pure spin
currents} without a n accompanying charge current. It is shown that this pure
spin currents causes a voltage drop which can be measured if the potential
probe is ferromagnetic.",0306526v1
2008-01-16,Charge and Spin Currents Generated by Dynamical Spins,"We demonstrate theoretically that a charge current and a spin current are
generated by spin dynamics in the presence of spin-orbit interaction in the
perturbative regime. We consider a general spin-orbit interaction including the
spatially inhomogeneous case. Spin current due to spin damping is identified as
one origin of generated charge current, but other contributions exist, such as
the one due to an induced conservative field and the one arising from the
inhomogeneity of spin-orbit interaction.",0801.2466v2
2015-04-25,Ab initio spin-flip conductance of hydrogenated graphene nanoribbons: Spin-orbit interaction and scattering with local impurity spins,"We calculate the spin-dependent zero-bias conductance $G_{\sigma\sigma'}$ in
armchair graphene nanoribbons with hydrogen adsorbates employing a DFT-based ab
initio transport formalism including spin-orbit interaction. We find that the
spin-flip conductance $G_{\sigma\bar{\sigma}}$ can reach the same order of
magnitude as the spin-conserving one, $G_{\sigma\sigma}$, due to
exchange-mediated spin scattering. In contrast, the genuine spin-orbit
interaction appears to play a secondary role, only.",1504.06720v1
2019-04-10,Enhancement of spin transparency by interfacial alloying,"We report that atomic-layer alloying (intermixing) at a Pt/Co interface can
increase, by approximately 30%, rather than degrade the interfacial spin
transparency, and thereby strengthen the efficiency of the dampinglike
spin-orbit torque arising from the spin Hall effect in the Pt. At the same
time, this interfacial alloying substantially reduces fieldlike spin-orbit
torque. Insertion of an ultrathin magnetic alloy layer at
heavy-metal/ferromagnet interfaces represents an effective approach for
improving interfacial spin transparency that may enhance not only spin-orbit
torques but also the spin detection efficiency in inverse spin Hall
experiments.",1904.05455v1
2014-04-01,Magnetic states of the five-orbital Hubbard model for one-dimensional iron-based superconductors,"The magnetic phase diagrams of models for quasi one-dimensional compounds
belonging to the iron-based superconductors family are presented. The
five-orbital Hubbard model and the real-space Hartree-Fock approximation are
employed, supplemented by density functional theory to obtain the hopping
amplitudes. Phase diagrams are constructed varying the Hubbard $U$ and Hund $J$
couplings and at zero temperature. The study is carried out at electronic
density (electrons per iron) $n = 5.0$, which is of relevance for the already
known material TlFeSe$_2$, and also at $n = 6.0$, where representative
compounds still need to be synthesized. At $n = 5.0$ there is a clear dominance
of staggered spin order along the chain direction. At $n = 6.0$ and the
realistic Hund coupling $J/U = 0.25$, the phase diagram is far richer including
a variety of ``block'' states involving ferromagnetic clusters that are
antiferromagnetically coupled, in qualitative agreement with recent Density
Matrix Renormalization Group calculations for the three-orbital Hubbard model
in a different context. These block states arise from the competition between
ferromagnetic order (induced by double exchange, and prevailing at large $J/U$)
and antiferromagnetic order (dominating at small $J/U$). The density of states
and orbital compositions of the many phases are also provided.",1404.0069v1
2019-09-02,Doublon-holon excitations split by Hund's rule coupling within the orbital-selective Mott phase,"Multiorbital interactions have the capacity to produce an interesting kind of
doublon-holon bound state that consists of a single-hole state in one band and
a doubly-occupied state in another band. Interband doublon-holon pair
excitations in the two-orbital Hubbard model are studied by using dynamical
mean-field theory with the Lanczos method as the impurity solver. We find that
the interband bound states may provide several in-gap quasiparticle peaks in
the density of states of the narrow band in the orbital-selective Mott phase
with a small Hund's rule coupling ($J$). There exists a corresponding energy
relation between the in-gap states of the narrow band and the peaks in the
excitation spectrum of the doublon for the wide band. We also find that the
spin flip and pair-hopping Hund interactions can divide one quasiparticle peak
into two peaks, where the splitting energy increases linearly with increasing
$J$. Strong Hund's rule coupling can move the interband doublon-holon pair
excitations outside the Mott gap and restrict the bound states by suppressing
the orbital selectivity of the doubly-occupied and single-hole states.",1909.00605v1
2006-05-15,Orbital Order Instability and Orbital Excitations in Degenerate Itinerant Electron Systems,"We present the theory of orbital ordering in orbital-degenerate itinerant
electron systems. After proposing the criterion of instability for orbital
ordering or orbital density wave ordering, we find that the orbital and the
spin-orbital collective excitation spectra in ferro-orbital ordered phase
exhibit finite gaps. The anomalous electronic energy spectra manifested in the
angle-resolved photoemission spectroscopy (ARPES) and the orbital occupation in
the resonant X-ray scattering (RXS) intensities are also presented for the
orbital-ordered phase.",0605379v1
1999-06-25,Sound and Heat Absorption by a 2D Electron Gas in an Odd-Integer Quantized-Hall Regime,"The absorption of bulk acoustic phonons in a two-dimensional (2D) GaAs/AlGaAs
heterostructure is studied (in the clean limit) where the 2D electron-gas
(2DEG), being in an odd-integer quantum-Hall state, is in fact a spin
dielectric. Of the two channels of phonon absorption associated with excitation
of spin waves, one, which is due to the spin-orbit (SO) coupling of electrons,
involves a change of the spin state of the system and the other does not. We
show that the phonon-absorption rate corresponding to the former channel (in
the paper designated as the second absorption channel) is finite at zero
temperature ($T$), whereas that corresponding to the latter (designated as the
first channel) vanishes for $T\to 0$. The long-wavelength limit, being the
special case of the first absorption channel, corresponds to sound (bulk and
surface) attenuation by the 2DEG. At the same time, the ballistic phonon
propagation and heat absorption are determined by both channels. The 2DEG
overheat and the attendant spin-state change are found under the conditions of
permanent nonequilibrium phonon pumping.",9906396v3
2000-10-27,Ground state spin and Coulomb blockade peak motion in chaotic quantum dots,"We investigate experimentally and theoretically the behavior of Coulomb
blockade (CB) peaks in a magnetic field that couples principally to the
ground-state spin (rather than the orbital moment) of a chaotic quantum dot. In
the first part, we discuss numerically observed features in the magnetic field
dependence of CB peak and spacings that unambiguously identify changes in spin
S of each ground state for successive numbers of electrons on the dot, N. We
next evaluate the probability that the ground state of the dot has a particular
spin S, as a function of the exchange strength, J, and external magnetic field,
B. In the second part, we describe recent experiments on gate-defined GaAs
quantum dots in which Coulomb peak motion and spacing are measured as a
function of in-plane magnetic field, allowing changes in spin between N and N+1
electron ground states to be inferred.",0010441v1
2002-07-08,Static and Dynamical Dzyaloshinsky-Moriya interactions in gapped spin systems,"Anisotropic spin-spin interactions of Dzyaloshinsky and Moriya symmetry are
generally considered weak, as they depend on the spin-orbit couplings. In spin
systems with gapped ground states they can, however, have rather strong
effects. We will discuss recent results related to the results of neutron
scattering and ESR for $\rm SrCu_2(BO_3)_2$. Inclusion of the
Dzyaloshinsky-Moriya interactions can explain much of the dynamics of the
systems discussed, in particular the splitting and dispersion of the triplet
modes. Some effects remain to be explained, however. Symmetries of the crystal
lead to the prediction of zero intensity for transitions, for example between
the ground state and the triplets observed in ESR.
  We present recent calculations of the effects of anisotropic terms generated
dynamically, ie linearly in the phonon coordinates. We discuss how this leads
to a novel mechanism to explain the ESR intensities. For polarized neutron
scattering experiments, we can calculate the mixing of nuclear and magnetic
scattering amplitudes by such a term and how such mixing should be observed.",0207191v1
2002-07-16,Probing entanglement via Rashba-induced shot noise oscillations,"We have recently calculated shot noise for entangled and spin-polarized
electrons in novel beam-splitter geometries with a local Rashba s-o interaction
in the incoming leads. This interaction allows for a gate-controlled rotation
of the incoming electron spins. Here we present an alternate simpler route to
the shot noise calculation in the above work and focus on only electron pairs.
Shot noise for these shows continuous bunching and antibunching behaviors. In
addition, entangled and unentangled triplets yield distinctive shot noise
oscillations. Besides allowing for a direct way to identify triplet and singlet
states, these oscillations can be used to extract s-o coupling constants
through noise measurements. Incoming leads with spin-orbit interband mixing
give rise an additional modulation of the current noise. This extra rotation
allows the design of a spin transistor with enhanced spin control.",0207392v1
2002-10-25,Anisotropic and incommensurate spin fluctuations in hcp iron and some other nearly magnetic metals,"We present an ab initio theoretical formalism for the static paramagnetic
spin susceptibility of metals at finite temperatures. Since relativistic
effects, e.g. spin-orbit coupling, are included, we can identify the anisotropy
or easy axes of the spin fluctuations. Our calculations find hcp-iron to be
unstable to in ab-plane, incommensurate anti-ferromagnetic (AFM) modes (linked
to nested Fermi surface) below T_N =69K for the lowest pressures under which it
is stable. T_N swiftly drops to zero as the pressure is increased. The
calculated susceptibility of yttrium is consistent with the helical,
incommensurate AFM order found in many rare-earth-dilute yttrium alloys.
Lastly, in line with experimental data, we find the easy axes of the
incommensurate AFM and ferromagnetic spin fluctuations of the normal state of
the triplet superconductor Sr2RuO4 to be perpendicular and parallel with the
crystal c-axis resepctively.",0210581v1
2002-11-25,Spin Current Generation and Detection in the Presence of AC Gate,"We predict that in a narrow gap III-V semiconductor quantum well or a wire an
observable spin current can be generated with a time dependent gate to modify
the Rashba spin-orbit coupling constant. Methods to rectify the so generated AC
current are discussed. An all-electric method of spin current detection is
suggested, which measures the voltage on the gate in the vicinity of a 2D
electron gas carrying a time dependent spin current. Both the generation and
detection do not involve any optical or magnetic mediators.",0211559v2
2002-11-26,Non-ballistic spin field-effect transistor,"We propose a spin field-effect transistor based on spin-orbit (s-o) coupling
of both the Rashba and the Dresselhaus types. Differently from earlier
proposals, spin transport through our device is tolerant against
spin-independent scattering processes. Hence the requirement of strictly
ballistic transport can be relaxed. This follows from a unique interplay
between the Dresselhaus and the (gate-controlled) Rashba interactions; these
can be tuned to have equal strengths thus yielding k-independent eigenspinors
even in two dimensions. We discuss implementations with two-dimensional devices
and quantum wires. In the latter, our setup presents strictly parabolic
dispersions which avoids complications arising from anticrossings of different
bands.",0211603v2
2003-04-24,Shot noise of spin polarized electrons,"The shot noise of spin polarized electrons is shown to be generically
dependent upon spin-flip processes. Such a situation represents perhaps the
simplest instance where the two-particle character of current fluctuations out
of equilibrium is explicit, leading to trinomial statistics of charge transfer
in a single channel model. We calculate the effect of spin-orbit coupling,
magnetic impurities, and precession in an external magnetic field on the noise
in the experimentally relevant cases of diffusive wires and lateral
semiconductor dots, finding dramatic enhancements of the Fano factor. The
possibility of using the shot noise to measure the spin-relaxation time in an
open mesoscopic system is raised.",0304544v2
2003-12-17,Goldstone-Mode Relaxation in a Quantized Hall Ferromagnet in the Presence of Smooth Random Potential,"We discuss the spin relaxation of a strongly correlated two-dimensional (2D)
electron gas (2DEG) in the quantized Hall regime when the filling factor is
close to an odd-integer. As the initial state we consider a coherent deviation
of the spin system from the ${\bf B}$ direction and investigate a break-down of
this Goldstone-mode state due to the spin-orbit (SO) coupling and smooth
disorder. The spin relaxation (SR) process is considered in terms of
annihilation transitions in the system of spin excitons (magnons).",0312427v5
2004-11-28,The effect of in-plane magnetic field on the spin Hall effect in Rashba-Dresselhaus system,"In a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit
couplings, there are two spin-split energy surfaces connected with a degenerate
point. Both the energy surfaces and the topology of the Fermi surfaces can be
varied by an in-plane magnetic field. We find that, if the chemical potential
falls between the bottom of the upper band and the degenerate point, then
simply by changing the direction of the magnetic field, the magnitude of the
spin Hall conductivity can be varied by about 100 percent. Once the chemical
potential is above the degenerate point, the spin Hall conductivity becomes the
constant $e/8\pi$, independent of the magnitude and direction of the magnetic
field. In addition, we find that the in-plane magnetic field exerts no
influence on the charge Hall conductivity.",0411697v1
2005-05-13,Spin-state transition in LaCoO3: direct neutron spectroscopic evidence of excited magnetic states,"A gradual spin-state transition occurs in LaCoO3 around T~80-120 K, whose
detailed nature remains controversial. We studied this transition by means of
inelastic neutron scattering (INS), and found that with increasing temperature
an excitation at ~0.6 meV appears, whose intensity increases with temperature,
following the bulk magnetization. Within a model including crystal field
interaction and spin-orbit coupling we interpret this excitation as originating
from a transition between thermally excited states located about 120 K above
the ground state. We further discuss the nature of the magnetic excited state
in terms of intermediate-spin (IS, S=1) vs. high-spin (HS, S=2) states. Since
the g-factor obtained from the field dependence of the INS is g~3, the second
interpretation looks more plausible.",0505344v2
2005-12-02,Spin-Hall effect: Back to the Beginning on a Higher Level,"The phenomena of the spin-Hall effect, initially proposed over three decades
ago in the context of asymmetric Mott skew scattering, was revived recently by
the proposal of a possible intrinsic spin-Hall effect originating from a
strongly spin-orbit coupled band structure. This new proposal has generated an
extensive debate and controversy over the past two years. The purpose of this
workshop, held at the Asian Pacific Center for Theoretical Physics, was to
bring together many of the leading groups in this field to resolve such issues
and identify future challenges. We offer this short summary to clarify the now
settled issues on some of the more controversial aspects of the debate and help
refocus the research efforts in new and important avenues.",0512054v1
2006-01-17,Electron Correlations and the Minority-Spin Band Gap in Half-Metallic Heusler Alloys,"Electron-electron correlations affect the band gap of half-metallic
ferromagnets by introducing non-quasiparticle states just above the Fermi
level. In contrast to the spin-orbit coupling, a large asymmetric
non-quasiparticle spectral weight is present in the minority-spin channel,
leading to a peculiar finite-temperature spin depolarization effects. Using
recently developed first-principle dynamical mean field theory, we investigate
these effects for the half-metallic ferrimagnetic Heusler compound FeMnSb. We
discuss depolarization effects in terms of strength of local Coulomb
interaction $U$ and temperature in FeMnSb. We propose Ni$_{1-x}$Fe$_{x}$MnSb
alloys as a perspective materials to be used in spin-valve structures and for
experimental search of non-quasiparticle states in half-metallic materials.",0601376v1
2006-03-07,Spin-Hall effect in a [110] quantum well,"A self-consistent treatment of the spin-Hall effect requires consideration of
the spin-orbit coupling and electron-impurity scattering on equal footing. This
is done here for the experimentally relevant case of a [110] GaAs quantum well
[Sih {\it et al.}, Nature Physics 1, 31 (2005)]. Working within the framework
of the exact linear response formalism we calculate the spin-Hall conductivity
including the Dresselhaus linear and cubic terms in the band structure, as well
as the electron-impurity scattering and electron-electron interaction to all
orders. We show that the spin-Hall conductivity naturally separates into two
contributions, skew-scattering and side-jump, and we propose an experiment to
distinguish between them.",0603144v3
2006-06-23,Dynamical spin chirality and spin anisotropy in gapped S=1/2 quantum systems,"We have studied the spin anisotropy in spin-singlet ground state compounds
and the magnetic chirality, as measured by inelastic polarized neutron
scattering techniques, in the chain-sublattice of Sr14Cu24O41. In-plane and out
of plane magnetic fluctuations are measured to be anisotropic and further
discussed in the light of the current hypothesis of spin-orbit coupling. We
show that under appropriate conditions of magnetic field and neutron
polarization, the \textit{trivial} magnetic chirality selects only one of the
Zeeman splitted triplet states for scattering and erases the other one that
posses opposite helicity. Our analysis pertains to previous studies on
dynamical magnetic chirality and chiral critical exponents, where the ground
state is chiral itself, the so-called \textit{non-trivial} dynamical magnetic
chirality. As it turns out, both \textit{trivial} and \textit{non-trivial}
dynamical magnetic chirality have identical selection rules for inelastic
polarized neutron scattering experiments and it is not at all evident that they
can be distinguished in a paramagnetic compound.",0606598v1
2006-10-12,Fermi liquid instabilities in the spin channel,"We study the Fermi surface instabilities of the Pomeranchuk type in the spin
triplet channel with high orbital partial waves ($F_{l}^a ~(l>0)$). The ordered
phases are classified into two classes, dubbed the $\alpha$ and $\beta$-phases
by analogy to the superfluid $^3$He-A and B-phases. The Fermi surfaces in the
$\alpha$-phases exhibit spontaneous anisotropic distortions, while those in the
$\beta$-phases remain circular or spherical with topologically non-trivial spin
configurations in momentum space. In the $\alpha$-phase, the Goldstone modes in
the density channel exhibit anisotropic overdamping. The Goldstone modes in the
spin channel have nearly isotropic underdamped dispersion relation at small
propagating wavevectors. Due to the coupling to the Goldstone modes, the spin
wave spectrum develops resonance peaks in both the $\alpha$ and $\beta$-phases,
which can be detected in inelastic neutron scattering experiments. In the
p-wave channel $\beta$-phase, a chiral ground state inhomogeneity is
spontaneously generated due to a Lifshitz-like instability in the originally
nonchiral systems. Possible experiments to detect these phases are discussed.",0610326v2
2006-12-12,Electric-Field-Induced Resonant Spin Polarization in a Two-Dimensional Electron Gas,"Electric response of spin polarization in two-dimensional electron gas with
structural inversion asymmetry subjected to a magnetic field was studied by
means of the linear and non-linear theory and numerical simulation with the
disorder effect. It was found by Kubo linear reponse theory that an electric
resonant response of spin polarization occurs when the Fermi surface is located
near the crossing of two Landau levels, which is induced from the competition
between the spin-orbit coupling and Zeeman splitting. The scaling behavior was
investigated with a simplified two-level model by non-linear method, and the
resonant peak value is reciprocally proportional to the electric field at low
temperatures and to temperature for finite electric fields. Finally numerical
simulation illustrated that impurity potential opens an enegy gap near the
resonant point and suppresses the effect gradually with the increasing strength
of disorder. This resonant effect may provide an efficient way to control spin
polarization by an external electric field.",0612277v2
2007-02-10,Spin-dependent Rotating Wigner Molecules in Quantum dots,"The spin-dependent trial wave functions with rotational symmetry are
introduced to describe rotating Wigner molecular states with spin degree of
freedom in four- and five-electron quantum dots under magnetic fields. The
functions are constructed with unrestricted Hartree-Fock orbits and projection
technique in long-range interaction limit. They highly overlap with the
exact-diagonalized ones and give the accurate energies in strong fields. The
zero points, i.e. vortices of the functions have straightforward relations to
the angular momenta of the states. The functions with different total spins
automatically satisfy the angular momentum transition rules with the increase
of magnetic fields and explicitly show magnetic couplings and characteristic
oscillations with respect to the angular momenta. Based on the functions, it is
demonstrated that the entanglement entropies of electrons depend on the
z-component of total spin and rise with the increase of angular momenta.",0702256v2
2000-10-04,Gravitational field and equations of motion of spinning compact binaries to 2.5 post-Newtonian order,"We derive spin-orbit coupling effects on the gravitational field and
equations of motion of compact binaries in the 2.5 post-Newtonian approximation
to general relativity, one PN order beyond where spin effects first appear. Our
method is based on that of Blanchet, Faye, and Ponsot, who use a post-Newtonian
metric valid for general (continuous) fluids and represent pointlike compact
objects with a delta-function stress-energy tensor, regularizing divergent
terms by taking the Hadamard finite part. To obtain post-Newtonian spin
effects, we use a different delta-function stress-energy tensor introduced by
Bailey and Israel. In a future paper we will use the 2.5PN equations of motion
for spinning bodies to derive the gravitational-wave luminosity and phase
evolution of binary inspirals, which will be useful in constructing matched
filters for signal analysis. The gravitational field derived here may help in
posing initial data for numerical evolutions of binary black hole mergers.",0010014v1
2005-12-21,Noncommutative geometry induced by spin effects,"In this paper we study the nonlocal effects of noncommutative spacetime on
simple physical systems. Our main point is the assumption that the
noncommutative effects are consequences of a background field which generates a
local spin structure. So, we reformulate some simple electrostatic models in
the presence of a spin-deformation contribution to the geometry of the motion,
and we obtain an interesting correlation amongst the deformed area vector, the
3D noncommutative effects and the usual spin vector given in quantum mechanics
framework. Remarkably we can observe that a spin-orbit coupling term comes to
light on the spatial sector of a potential wrote in terms of noncommutative
coordinates what indicates that bound states are particular cases in this
procedure. Concerning to confined or bounded particles in this noncommutative
domain we verify that the kinetic energy is modified by a deformation factor.
Finally, we discuss about perspectives.",0512266v1
2007-04-25,"Charge and spin stripe in La$_{2-x}$Sr$_{x}$NiO$_{4}$ (x=1/3,1/2)","Electronic structure of stripe ordered La$_{2-x}$Sr$_{x}$NiO$_{4}$ is
investigated. The system with x=1/3 is insulator, in LSDA+U calculations, and
shows charge and spin stripe, consistent with the experimental results. Highly
correlated system of x=1/2 is studied by using exact diagonalization of
multi-orbital many body Hamiltonian derived from LDA calculations and including
on-site and inter-site Coulomb interactions. The fluctuation of the residual
spin on Ni$^{3+}$ (hole) site couples with the charge fluctuation between
Ni$^{3+}$ and Ni$^{2+}$ states and this correlation lowers the total energy.
The resultant ground state is insulator with charge and spin stripe of the
energy gap 0.9eV, consistent with observed one. The on-site Coulomb interaction
stabilizes integral valency of each Ni ion (Ni$^{3+}$ and Ni$^{2+}$), but does
not induce the charge order. Two quantities, inter-site Coulomb interaction and
anisotropy of hopping integrals, play an important role to form the charge and
spin stripe order in a system of x=1/2.",0704.3323v2
2007-07-24,Intrinsic spin-Hall accumulation in honeycomb lattices: Band structure effects,"Local spin and charge densities on a two-dimensional honeycomb lattice are
calculated by the Landauer-Keldysh formalism (LKF). Through the empirical
tight-binding method, we show how the realistic band structure can be brought
into the LKF. Taking the Bi(111) surface, on which strong surface states and
Rashba spin-orbit coupling are present [Phys. Rev. Lett. 93, 046403 (2004)], as
a numeric example, we show typical intrinsic spin-Hall accumulation (ISHA)
patterns thereon. The Fermi-energy-dependence of the spin and charge transport
in two-terminal nanostructure samples is subsequently analyzed. By changing
E_{F}, we show that the ISHA pattern is nearly isotropic (free-electron-like)
only when E_{F} is close to the band bottom, and is sensitive/insensitive to
E_{F} for the low/high bias regime with such E_{F}. With E_{F} far from the
band bottom, band structure effects thus enter the ISHA patterns and the
transport direction becomes significant.",0707.3626v3
2007-08-07,Direct measurement of a pure spin current by a polarized light beam,"The photon helicity may be mapped to a spin-1/2, whereby we put forward an
intrinsic interaction between a polarized light beam as a ``photon spin
current'' and a pure spin current in a semiconductor, which arises from the
spin-orbit coupling in valence bands as a pure relativity effect without
involving the Rashba or the Dresselhaus effect due to inversion asymmetries.
The interaction leads to circular optical birefringence, which is similar to
the Faraday rotation in magneto-optics but nevertheless involve no net
magnetization. The birefringence effect provide a direct, non-demolition
measurement of pure spin currents.",0708.0881v4
2008-02-08,Tunneling conductance of a metal-semiconductor heterostructure with Rashba effect,"We theoretically studied the in-plane tunneling spectroscopy of the hybrid
structure composed of a metal and a semiconductor with Rashba spin-orbit
coupling. We found that the energy spacing between two distinct features in the
conductance spectrum can be used to measure the Rashba energy of the
semiconductor. We also considered the effect that varying the probability of
spin-conserving and spin-flip scattering at the interface has on the overall
conductance. Surprisingly, an increase in interface scattering probability can
actually result in increased conductance under certain conditions.
Particularly, in the tunneling regime, an increase in spin-flip scattering
probability enhances the conductance. It is also found that the interfacial
scattering greatly affects the spin polarization of the conductance in metal,
but hardly affects that in the semiconductor.",0802.1097v2
2008-03-05,A Fractionalized Quantum Spin Hall Effect,"Effects of electron correlations on a two dimensional quantum spin Hall (QSH)
system are studied. We examine possible phases of a generalized Hubbard model
on a bilayer honeycomb lattice with a spin-orbit coupling and short range
electron-electron repulsions at half filling, based on the slave rotor
mean-field theory. Besides the conventional QSH phase and a broken-symmetry
insulating phase, we find a new phase, a fractionalized quantum spin Hall
phase, where the QSH effect arises for fractionalized spinons which carry only
spin but not charge. Experimental manifestations of the exotic phase and
effects of fluctuations beyond the saddle point approximation are also
discussed.",0803.0756v3
2008-04-18,Molecular spin resonance in the geometrically frustrated MgCr2O4 magnet by inelastic neutron scattering,"We measured two magnetic modes with finite and discrete energies in an
antiferromagnetic ordered phase of a geometrically frustrated magnet MgCr2O4 by
single-crystal inelastic neutron scattering, and clarified the spatial spin
correlations of the two levels: one is an antiferromagnetic hexamer and the
other is an antiferromagnetic heptamer. Since these correlation types are
emblematic of quasielastic scattering with geometric frustration, our results
indicate instantaneous suppression of lattice distortion in an ordered phase by
spin-lattice coupling, probably also supported by orbital and charge. The
common features in the two levels, intermolecular independence and discreteness
of energy, suggest that the spin molecules are interpreted as quasiparticles
(elementary excitations with energy quantum) of highly frustrated spins, in
analogy with the Fermi liquid approximation.",0804.2993v1
2008-06-26,Unscreened Coulomb interactions and quantum spin Hall phase in neutral zigzag graphene ribbons,"A study of the effect of unscreened Coulomb interactions on the quantum spin
Hall (QSH) phase of finite-width neutral zigzag graphene ribbons is presented.
By solving a tight-binding Hamiltonian that includes the intrinsic spin-orbit
interaction (I-SO), exact expressions for band-structures and edge-states
wavefunctions are obtained. These analytic results, supported by tight-binding
calculations, show that chiral spin-filtered edge states are composed of
localized and damped oscillatory wavefunctions, reminiscent of the ones
obtained in armchair ribbons. The addition of long-range Coulomb interactions
opens a gap in the charge sector with a gapless spin sector. In contrast to
armchair terminations, the charge-gap vanishes exponentially with the ribbon
width and its amplitude and decay-length are strongly dependent on the I-SO
coupling. Comparison with reported ab-initio calculations are presented.",0806.4235v2
2009-03-13,Perfect spin filtering device through a Mach Zehnder interferometer in GaAs/AlGaAs electron gas,"Spin filtering through quantum spin interference is addressed exactly, in two
dimensions, in a medium that has both Rashba and Dresselhaus spin-orbit
couplings and an applied external magnetic field. The problem is addressed from
the fully non-Abelian Gauge formulation. We propose an experimentally feasible
electronic Mach Zehnder Interferometer and solve for the perfect spin filtering
conditions. We find two broad solutions, one where filtering is achieved in the
original incoming basis, that is purely a non-Abelian solution, and the other
where one needs a tilted axis to observe the polarized output spinor. The
latter solution is well approximated by an Abelianized approximation. Both
solutions apply for arbitrary incoming polarization, and are only limited by
the randomness of the incoming spinor state.",0903.2468v2
2009-03-23,Possible origin of the 0.5 plateau in the ballistic conductance of quantum point contacts,"A non-equilibrium Green function formalism (NEGF) is used to study the
conductance of a side-gated quantum point contact (QPC) in the presence of
lateral spin-orbit coupling (LSOC). A small difference of bias voltage between
the two side gates (SGs) leads to an inversion asymmetry in the LSOC between
the opposite edges of the channel. In single electron modeling of transport,
this triggers a spontaneous but insignificant spin polarization in the QPC.
However, the spin polarization of the QPC is enhanced substantially when the
effect of electron-electron interaction is included. The spin polarization is
strong enough to result in the occurrence of a conductance plateau at 0.5G0 (G0
= 2e2/h) in the absence of any external magnetic field. In our simulations of a
model QPC device, the 0.5 plateau is found to be quite robust and survives up
to a temperature of 40K. The spontaneous spin polarization and the resulting
magnetization of the QPC can be reversed by flipping the polarity of the source
to drain bias or the potential difference between the two SGs. These numerical
simulations are in good agreement with recent experimental results for
side-gated QPCs made from the low band gap semiconductor InAs.",0903.3915v2
2009-04-01,All-electric-spin control in interference single electron transistors,"Single particle interference lies at the heart of quantum mechanics. The
archetypal double-slit experiment has been repeated with electrons in vacuum up
to the more massive $C_{60}$ molecules. Mesoscopic rings threaded by a magnetic
flux provide the solid-state analogous. Intra-molecular interference has been
recently discussed in molecular junctions. Here we propose to exploit
interference to achieve all-electrical control of a single electron spin in
quantum dots, a highly desirable property for spintronics and spin-qubit
applications. The device consists of an interference single electron transistor
(ISET), where destructive interference between orbitally degenerate electronic
states produces current blocking at specific bias voltages. We show that in the
presence of parallel polarized ferromagnetic leads the interplay between
interference and the exchange coupling on the system generates an effective
energy renormalization yielding different blocking biases for majority and
minority spins. Hence, by tuning the bias voltage full control over the spin of
the trapped electron is achieved.",0904.0167v1
2009-07-17,Spin-order driven Fermi surface revealed by quantum oscillations in an underdoped high Tc superconductor,"We use quantum oscillation measurements to distinguish between spin and
orbital components of the lowest energy quasiparticle excitations in
YBa2Cu3O6.54, each of which couple differently to a magnetic field. Our
measurements reveal the phase of the observed quantum oscillations to remain
uninverted over a wide angular range, indicating that the twofold spin
degeneracy of the Landau levels is virtually unaltered by the magnetic field.
The inferred suppression of the spin degrees of freedom indicates a spin
density-wave is responsible for creation of the small Fermi surface pockets in
underdoped YBa2Cu3O6+x - further suggesting that excitations of this phase are
important contributors to the unconventional superconducting pairing mechanism.",0907.2958v1
2010-04-04,Spin selective transport through Aharonov-Bohm and Aharonov-Casher triple quantum dot systems,"We calculate the conductance through a system of three quantum dots under two
different sets of conditions that lead to spin filtering effects under an
applied magnetic field. In one of them, a spin is localized in one quantum dot,
as proposed by Delgado et al. [Phys. Rev. Lett. 101, 226810 (2008)]. In the
other one, all dots are equivalent by symmetry and the system is subject to a
Rashba spin-orbit coupling. We solve the problem using a simple effective
Hamiltonian for the low-energy subspace, improving the accuracy of previous
results. We obtain that correlation effects related to the Kondo physics play a
minor role for parameters estimated previously and high enough magnetic field.
Both systems lead to a magnetic field tunable ""spin valve"".",1004.0538v2
2010-04-07,"Comments on ""Spin-dependent tunneling through a symmetric semiconductor barrier: The Dresselhaus effect""","In a recent paper [Phys. Rev. B 72, 153314 (2005)], the $k^{3}$-Dresselhaus
term in the contacts and the full form of the current operator are considered
for spin-dependent tunneling through a symmetric barrier. The authors found
that the full form of the current operator has a much larger influence on the
spin polarization than it was initially thought. In this Comment we will show
that their treatment of the other problem, the $k^{3}$-Dresselhaus term in the
contacts, is incorrect. Their proposed solution in the contacts simply does not
obey the Schr\""{o}dinger equation. In this context we also comment on the
definition and the suitability of spin polarization in contacts with spin-orbit
coupling.",1004.1019v1
2010-08-30,Relativistic spin-precession in binary pulsars,"After the first prediction to expect geodetic precession in binary pulsars in
1974, made immediately after the discovery of a pulsar with a companion, the
effects of relativistic spin precession have now been detected in all binary
systems where the magnitude of the precession rate is expected to be
sufficiently high. Moreover, the first quantitative test leads to the only
available constraints for spin-orbit coupling of a strongly self-gravitating
body for general relativity (GR) and alternative theories of gravity. The
current results are consistent with the predictions of GR, proving the
effacement principle of spinning bodies. Beyond tests of theories of gravity,
relativistic spin precession has also become a useful tool to perform beam
tomography of the pulsar emission beam, allowing to infer the unknown beam
structure, and to probe the physics of the core collapse of massive stars.",1008.5032v1
2010-09-16,The rise of spin-flip transitions in the anomalous Hall effect of FePt alloy,"We carry out first-principles calculations which demonstrate the importance
of spin-flip transitions for the intrinsic anomalous Hall conductivity of
ordered FePt alloys. We show the such transitions get enhanced by large
spin-orbit coupling of Pt atoms, becoming negligible when Pt is replaced by
lighter isoelectronic Pd. We find that spin-flip transitions in FePt originate
not only from conventional band anticrossings at the Fermi level, but also from
transitions between well-separated pairs of bands with similar dispersions. We
also predict a strong anisotropy in the anomalous Hall conductivity of FePt,
which comes from spin-flip transitions entirely, and investigate the influence
of disorder on it.",1009.3184v1
2011-02-22,Nodeless energy gaps of single-crystalline Ba0.68K0.32Fe2As2 as seen via 75As NMR,"We report $^{75}$As nuclear magnetic resonance studies on a very clean
hole-doped single-crystal Ba$_{0.68}$K$_{0.32}$Fe$_{2}$As$_{2}$ ($T_{\rm
{c}}=38.5$ K). The spin-lattice relaxation rate $1/T_{1}$ shows an exponential
decrease below $T \simeq 0.45 T_{\rm c}$ down to $T \simeq 0.11 T_{\rm c}$,
which indicates a fully opened energy gap. From the ratio $(T_{1})_{c} /
(T_{1})_{a}$, where $a$ and $c$ denote the crystal directions, we find that the
antiferromagnetic spin fluctuation is anisotropic in the spin space above
$T_{\rm c}$. The anisotropy decreases below $T_{\rm c}$ and disappears at $T
\rightarrow 0$. We argue that the anisotropy stems from spin-orbit coupling
whose effect vanishes when spin-singlet electron pairs form with a nodeless
gap.",1102.4417v2
2011-04-17,Topological surface state under graphene for two-dimensional spintronics in air,"Spin currents which allow for a dissipationless transport of information can
be generated by electric fields in semiconductor heterostructures in the
presence of a Rashba-type spin-orbit coupling. The largest Rashba effects occur
for electronic surface states of metals but these cannot exist but under
ultrahigh vacuum conditions. Here, we reveal a giant Rashba effect ({\alpha}_R
~ 1.5E-10 eVm) on a surface state of Ir(111). We demonstrate that its spin
splitting and spin polarization remain unaffected when Ir is covered with
graphene. The graphene protection is, in turn, sufficient for the spin-split
surface state to survive in ambient atmosphere. We discuss this result along
with evidences for a topological protection of the surface state.",1104.3308v1
2011-06-08,Quantum Magnetism with Polar Alkali Dimers,"We show that dipolar interactions between ultracold polar alkali dimers in
optical lattices can be used to realize a highly tunable generalization of the
t-J model, which we refer to as the t-J-V-W model. The model features
long-range spin-spin interactions J_z and J_perp of XXZ type, long-range
density-density interaction V, and long-range density-spin interaction W, all
of which can be controlled in both magnitude and sign independently of each
other and of the tunneling t. The ""spin"" is encoded in the rotational degree of
freedom of the molecules, while the interactions are controlled by applied
static electric and continuous-wave microwave fields. Furthermore, we show that
nuclear spins of the molecules can be used to implement an additional (orbital)
degree of freedom that is coupled to the original rotational degree of freedom
in a tunable way. The presented system is expected to exhibit exotic physics
and to provide insights into strongly correlated phenomena in condensed matter
systems. Realistic experimental imperfections are discussed.",1106.1655v1
2012-02-01,Fractionalized topological insulators from frustrated spin models in three dimensions,"We present a theory of three dimensional fractionalized topological
insulators in the form of U(1) spin liquids with gapped fermionic spinons in
the bulk and topologically protected gapless spinon surface states. Starting
from a spin-1/2 model on a pyrochlore lattice, with frustrated
antiferromagnetic and ferromagnetic exchange interactions, we show that
decomposition of the latter interactions, within slave-fermion representation
of the spins, can naturally give rise to an emergent spin-orbit coupling for
the spinons. This stabilizes a fractionalized topological insulators which also
have bulk bond spin-nematic order. Finally, we describe the low energy
properties of these states.",1202.0291v3
2012-02-26,Topologically non-trivial superfluid phases and Majorana fermions from Kohn-Luttinger effect,"Spin-triplet p-wave superfluids of single-species (or spin-polarized)
fermionic atoms is a topological superfluid. In 2D such a superfluid supports
zero-energy topological Majorana fermion excitations in order parameter defects
such as vortices and sample edges. In 3D these superfluids support
topologically protected Dirac points in the bulk spectrum and flat surface
Majorana arcs. Despite the promise, creating a spin-triplet p-wave
single-species fermionic superfluid either from direct p-wave Feshbach
resonance or indirectly from the recently proposed artificial spin-orbit and
Zeeman couplings can be technologically challenging. Here we show that such
topological superfluids can be far more simply created by using the
Kohn-Luttinger effect applied to two species of spin-polarized fermions with a
density imbalance. We discuss how the topological Majorana excitations of the
resulting superfluids can be identified using recently-developed experimental
techniques.",1202.5784v1
2012-06-07,Magneto-Josephson effects in junctions with Majorana bound states,"We investigate 1D quantum systems that support Majorana bound states at
interfaces between topologically distinct regions. In particular, we show that
there exists a duality between particle-hole and spin degrees of freedom in
certain spin-orbit-coupled 1D platforms such as topological insulator edges.
This duality results in a spin analogue of previously explored `fractional
Josephson effects'---that is, the spin current flowing across a magnetic
junction exhibits 4\pi-periodicity in the relative magnetic field angle across
the junction. Furthermore, the interplay between the particle-hole and spin
degrees of freedom results in unconventional magneto-Josephson effects, such
that the Josephson current is a function of the magnetic field orientation with
periodicity 4\pi.",1206.1581v1
2012-07-13,Spin and Pseudospin symmetries in the Dirac equation with central Coulomb potentials,"We analyze in detail the analytical solutions of the Dirac equation with
scalar S and vector V Coulomb radial potentials near the limit of spin and
pseudospin symmetries, i.e., when those potentials have the same magnitude and
either the same sign or opposite signs, respectively. By performing an
expansion of the relevant coefficients we also assess the perturbative nature
of both symmetries and their relations the (pseudo)spin-orbit coupling. The
former analysis is made for both positive and negative energy solutions and we
reproduce the relations between spin and pseudospin symmetries found before for
nuclear mean-field potentials. We discuss the node structure of the radial
functions and the quantum numbers of the solutions when there is spin or
pseudospin symmetry, which we find to be similar to the well-known solutions of
hydrogenic atoms.",1207.3324v1
2013-03-06,Li$_2$RhO$_3$: A spin-glassy relativistic Mott insulator,"Motivated by the rich interplay among electronic correlation, spin-orbit
coupling (SOC), crystal-field splitting, and geometric frustrations in the
honeycomb-like lattice, we systematically investigated the electronic and
magnetic properties of Li$_2$RhO$_3$. The material is semiconducting with a
narrow band gap of $\Delta\sim$78 meV, and its temperature dependence of
resistivity conforms to 3D variable range hopping mechanism. No long-range
magnetic ordering was found down to 0.5 K, due to the geometric frustrations.
Instead, single atomic spin-glass behavior below the spin-freezing temperature
($\sim$6 K) was observed and its spin dynamics obeys the universal critical
slowing down scaling law. First principle calculations suggested it to be a
relativistic Mott insulator mediated by both electronic correlation and SOC.
With moderate strength of electronic correlation and SOC, our results shed new
light to the research of Heisenberg-Kitaev model in realistic materials.",1303.1235v2
2013-06-07,Negative Magnetoresistance and Spin Filtering of Spin-Coupled Diiron-Oxo Clusters,"Spin dependent transport has been investigated for an {\it open shell
singlet} diiron-oxo cluster. Currents and magnetoresistances have been studied,
as a function of spin state, within the non-equilibrium Green's function
approach. The applied bias can be used for tuning the sign of the observed
magnetoresistance. A colossal magnetoresistance ratio has been determined, on
the order of to 6000$%$, for hydrogen anchoring. Applied biases lower than 0.3
V, in conjunction with sulfur anchoring, induce a negative magnetoresistance
due to lowering of the anchor-scatterer tunneling barrier. In addition, the
diiron-oxo cluster displays nearly perfect spin filtering for parallel
alignment of the iron magnetic moments due to energetic proximity, relative to
the Fermi level, of its highest occupied molecular orbitals.",1306.1588v2
2013-06-19,AC/DC Spin and Valley Hall Effects in Silicene and Germanene,"The intrinsic spin and valley Hall conductivities of silicene, germanene and
other similar two dimensional crystals are explored theoretically. Particular
attention is given to the effects of the intrinsic spin-orbit coupling,
electron doping and the type of insulating phase of the system (i.e., a
topological insulator or a band insulator) which can be tuned by a
perpendicular electric field. At finite frequency, the transverse edge to which
carriers of particular spin and valley label flow can be controlled such that
an accumulation of a particular combination of spin and valley index can be
obtained. The direction of flow is found to be dependent on the type of
insulating phase. The magnitude of the Hall conductivity response is enhanced
from the DC values at certain incident photon frequencies associated with the
onset of interband transitions. Analytic results are presented for both the DC
and finite frequency results.",1306.4591v1
2013-10-07,"Spin-dependent phenomena and device concepts explored in (Ga,Mn)As","Over the past two decades, the research of (Ga,Mn)As has led to a deeper
understanding of relativistic spin-dependent phenomena in magnetic systems. It
has also led to discoveries of new effects and demonstrations of unprecedented
functionalities of experimental spintronic devices with general applicability
to a wide range of materials. In this article we review the basic material
properties that make (Ga,Mn)As a favorable test-bed system for spintronics
research and discuss contributions of (Ga,Mn)As studies in the general context
of the spin-dependent phenomena and device concepts. Special focus is on the
spin-orbit coupling induced effects and the reviewed topics include the
interaction of spin with electrical current, light, and heat.",1310.1944v2
2013-10-29,Ferromagnetic Order Analysis of Fe- and FeO-modified Graphene-nano-ribbon,"Graphene-nano-ribbon (GNR) is very attractive for ultra-high density
spintronics devices. For checking a capability of self-induced ferromagnetic
order, Fe- and FeO-modified GNR were analyzed based on the density functional
theory. Model unit cells were [C32H2Fe2] and [C32H2Fe2O2]. Calculated results
show the most stable spin state to be Sz=8/2 in [C32H2Fe2], whereas Sz=6/2 in
[C32H2Fe2O2]. Magnetic moment M of Fe in [C32H2Fe2] was 3.65{\mu}B, which could
be explained based on the Hund-rule considering donated charge to carbon to be
M*=3.67{\mu}B . There is a capability of ferromagnetic Fe spin array through an
interaction with carbon {\pi}-conjugated spin system. There shows a long-range
super-exchange order in [C32H2Fe2O2]. Optimized atomic configuration gave the
typical 90 degree super-exchange coupling between Fe-3d and O-2p orbit.
Magnetic moment of Fe by DFT was 2.58{\mu}B, whereas super-exchange model
considering donated charge to oxygen gave an estimated magnetic moment to be
2.60{\mu}B. Sign of magnetic moment of Fe and O are all up-spin each other. We
could expect ferromagnetic long-range-order. Band structure was analyzed in
FeO-modified case, which suggested half-metal like behavior. We can expect
several spintronics applications as like a spin filter.",1310.7740v1
2013-11-05,Interplay of exciton condensation and quantum spin Hall effect in InAs/GaSb bilayers,"We study the phase diagram of the inverted InAs/GaSb bilayer quantum wells.
For small tunneling amplitude between the layers, we find that the system is
prone to formation of an s-wave exciton condensate phase, where the
spin-structure of the order parameter is uniquely determined by the small
spin-orbit coupling arising from the bulk inversion asymmetry. The phase is
topologically trivial and does not support edge transport. On the contrary, for
large tunneling amplitude, we obtain a topologically non-trivial quantum spin
Hall insulator phase with a p-wave exciton order parameter, which enhances the
hybridization gap. These topologically distinct insulators are separated by an
insulating phase with spontaneously broken time-reversal symmetry. Close to the
phase transition between the quantum spin Hall and time-reversal broken phases,
the edge transport shows quantized conductance in small samples, whereas in
long samples the mean free path associated with the backscattering at the edge
is temperature independent, in agreement with recent experiments.",1311.1111v2
2014-01-17,Nonreciprocal spin-wave channeling along textures driven by the Dzyaloshinskii-Moriya interaction,"Ultrathin metallic ferromagnets on substrates with strong spin-orbit coupling
can exhibit induced chiral interactions of the Dzyaloshinskii-Moriya (DM) form.
For systems with perpendicular anisotropy, the presence of DM interactions has
important consequences for current-driven domain-wall motion and underpins
possible spintronic applications involving skyrmions. We show theoretically how
spin textures driven by the DM interaction allow nonreciprocal channeling of
spin waves, leading to measurable features in magnetic wires, dots, and domain
walls. Our results provide methods for detecting induced DM interactions in
metallic multilayers and controlling spin wave propagation in ultrathin
nanostructures.",1401.4439v3
2014-06-30,Spin-dependent polaron formation dynamics in Eu$_{0.75}$Y$_{0.25}$MnO$_3$ probed by femtosecond pump-probe spectroscopy,"We present a femtosecond optical pump-probe study of the multiferroic
manganite Eu$_{0.75}$Y$_{0.25}$MnO$_3$. The optical response of the material at
pump energies of 1.55 and 3.1 eV is dominated by the $d$-$d$ and $p$-$d$
transitions of the Mn$^{3+}$ ions. The relaxation of photoexcited electrons
includes the relaxation of the Jahn-Teller distortion and polaron trapping at
Mn$^{2+}$ and Mn$^{4+}$ sites. Ultrafast switching of superexchange
interactions due to modulated $e_g$ orbital occupancy creates a localized spin
excitation, which then decays on a time scale of tens of picoseconds at low
temperatures. The localized spin state decay appears as a tremendous increase
in the amplitude of the photoinduced reflectance, due to the strong coupling of
optical transitions to the spin-spin correlations in the crystalline $a$-$b$
plane.",1407.0073v1
2014-07-03,Geometric Photonic Spin Hall Effect with Metapolarization,"We develop a geometric photonic spin Hall effect (PSHE) which manifests as
spin-dependent shift in momentum space. It originates from an effective
space-variant Pancharatnam-Berry (PB) phase created by artificially engineering
the polarization distribution of the incident light. Unlikely the previously
reported PSHE involving the light-matter interaction, the resulting
spin-dependent splitting in the geometric PSHE is purely geometrically depend
upon the polarization distribution of light which can be tailored by assembling
its circular polarization basis with suitably magnitude and phase. This
metapolarization idea enables us to manipulate the geometric PSHE by suitably
tailoring the polarization geometry of light. Our scheme provides great
flexibility in the design of various polarization geometry and
polarization-dependent application, and can be extrapolated to other physical
system, such as electron beam or atom beam, with the similar spin-orbit
coupling underlying.",1407.0805v1
2014-07-15,Transverse Spin and Classical Gluon Fields: Combining Two Perspectives on Hadronic Structure,"In recent decades, the spin and transverse momentum of quarks and gluons were
found to play integral roles in the structure of the nucleon. Simultaneously,
the onset of gluon saturation in hadrons and nuclei at high energies was
predicted to result in a new state of matter dominated by classical gluon
fields. Understanding both of these contributions to hadronic structure is
essential for current and future collider phenomenology. In this Dissertation,
we study the combined effects of transverse spin and gluon saturation using the
Glauber-Gribov-Mueller / McLerran-Venugopalan model of a heavy nucleus in the
quasi-classical approximation. We investigate the use of a
transversely-polarized projectile as a probe of the saturated gluon fields in
the nucleus, finding that the transverse spin asymmetry of produced particles
couples to the component of the gluon fields which is antisymmetric under both
time reversal and charge conjugation. We also analyze the effects of saturation
on the transverse spin asymmetry (Sivers function) of quarks within the wave
function of the nucleus, finding that gluon saturation preferentially generates
the asymmetry through the orbital angular momentum of the nucleons, together
with nuclear shadowing.",1407.4047v1
2014-09-04,Electron with arbitrary pseudo spins in multilayer graphene,"Using the low-energy effective Hamiltonian of the ABC-stacked multilayer
graphene, pseudo spin coupling to real orbital angular momentum of electron in
multilayer graphene is investigated. We show that electron wave function in
N-layer graphene mimics behavior of particle with spin of N/2. It is said that
for N greater than 1 the low-energy effective Hamiltonian for ABC-stacked
graphene is no longer used to describe pseudo spin 1/2-particle wave function.
The wave function of electron in multilayer graphene may behave like fermionic
(or bosonic) particle when N is odd (or even). This work proposes a theory of
graphene as a host material of electron with arbitrary pseudo spins, tunable by
changing number of graphene layers.",1409.1426v3
2014-09-19,Many-Body Spin Echo,"We predict a universal echo phenomenon present in the time evolution of
many-body states of interacting quantum systems described by Fermi-Hubbard
models. It consists of the coherent revival of transition probabilities echoing
a sudden flip of the spins that, contrary to its single-particle (Hahn)
version, is not dephased by interactions or spin-orbit coupling. The many-body
spin echo signal has a universal shape independent of the interaction strength,
and an amplitude and sign depending only on combinatorial relations between the
number of particles and the number of applied spin flips. Our analytical
predictions, based on semiclassical interfering amplitudes in Fock space
associated with chaotic mean-field solutions, are tested against extensive
numerical simulations confirming that the coherent origin of the echo lies in
the existence of anti-unitary symmetries.",1409.5684v3
2014-09-28,Universal Ratio of Intrinsic Resistivities of Spin Helix in B20 (Fe-Co)Si Magnets,"The B20 magnets with the Dzyaloshinskii-Moriya (D-M) interaction exhibit spin
helix and Skyrmion spin textures unattainable in traditional Heisenberg
ferromagnets. We have determined the intrinsic resistivity of the spin helix,
which is a macroscopic Bloch domain wall, in B20 (Fe-Co)Si magnets. We found a
universal resistance ratio of gamma = 1.35 with current parallel and
perpendicular to the helix, independent of composition and temperature. This
gamma value is much smaller than 3, the well-known minimum value for domain
wall resistivity in traditional ferromagnets, due to the significant spin-orbit
coupling in the B20 magnets.",1409.7869v1
2014-10-20,Gravitational spin Hamiltonians from the S matrix,"We utilize generalized unitarity and recursion relations combined with
effective field theory(EFT) techniques to compute spin dependent interaction
terms for inspiralling binary systems in the post newtonian(PN) approximation.
Using these methods offers great computational advantage over traditional
techniques involving feynman diagrams, especially at higher orders in the PN
expansion. As a specific example, we reproduce the spin-orbit interaction up to
2.5 PN order as also the leading order $S^2$(3PN) hamiltonian for an arbitrary
massive object. We also obtain the unknown $S^3$(3.5PN) spin hamiltonian for an
arbitrary massive object in terms of its low frequency linear response to
gravitational perturbations, which was till now known only for a black hole.
Furthermore, we derive the missing $S^4$ Hamiltonian at leading order(4PN) for
an arbitrary massive object and establish that a minimal coupling of a massive
elementary particle to gravity leads to a black hole structure. Finally, the
Kerr metric is obtained as a series in $G_N$ by comparing the action of a test
particle in the vicinity of a spinning black hole to the derived potential.",1410.5348v2
2014-11-07,Effect of cosmic string on spin dynamics,"In the present paper, we have investigated the role of cosmic string on spin
current and Hall electric field. Due to the background cosmic string, the
modified electric field of the system generates renormalized spin orbit
coupling, which induces a modified non-Abelian gauge field. The defect causes a
change in the AB and AC phases appearing due to the modified electromagnetic
field. In addition, for a time varying electric field we perform explicit
analytic calculations to derive the exact form of spin electric field and spin
current, which is defect parameter dependent and of oscillating type.
Furthermore, in an asymmetric crystal within the Drude model approach we
investigate the dependence of the cosmic string parameters on cosmic string
induced Hall electric field.",1411.1818v1
2015-01-22,Relativistic dynamical spin excitations of magnetic adatoms,"We present a first-principles theory of dynamical spin excitations in the
presence of spin-orbit coupling. The broken global spin rotational invariance
leads to a new sum rule. We explore the competition between the magnetic
anisotropy energy and the external magnetic field, as well as the role of
electron-hole excitations, through calculations for 3$d$-metal adatoms on the
Cu(111) surface. The spin excitation resonance energy and lifetime display
non-trivial behavior, establishing the strong impact of relativistic effects.
We legitimate the use of the Landau-Lifshitz-Gilbert equation down to the
atomic limit, but with parameters that differ from a stationary theory.",1501.05509v1
2015-02-24,Unidirectional spin Hall magnetoresistance in ferromagnet/normal metal bilayers,"Magnetoresistive effects are usually invariant upon inversion of the
magnetization direction. In noncentrosymmetric conductors, however, nonlinear
resistive terms can give rise to a current dependence that is quadratic in the
applied voltage and linear in the magnetization. Here we demonstrate that such
conditions are realized in simple bilayer metal films where the spin-orbit
interaction and spin-dependent scattering couple the current-induced spin
accumulation to the electrical conductivity. We show that the longitudinal
resistance of Ta|Co and Pt|Co bilayers changes when reversing the polarity of
the current or the sign of the magnetization. This unidirectional
magnetoresistance scales linearly with current density and has opposite sign in
Ta and Pt, which we associate with the modification of the interface scattering
potential induced by the spin Hall effect in these materials. Our results
suggest a route to control the resistance and detect magnetization switching in
spintronic devices using a two-terminal geometry, which applies also to
heterostructures including topological insulators.",1502.06898v2
2015-06-15,Charge and spin edge currents in two-dimensional Floquet topological superconductors,"A time periodic driving on a topologically trivial system induces edge modes
and topological properties. In this work we consider triplet and singlet
superconductors subject to periodic variations of the chemical potential,
spin-orbit coupling and magnetization, in both topologically trivial and
nontrivial phases, and study their influence on the charge and spin currents
that propagate along the edges of the two-dimensional system, for moderate to
large driving frequencies. Currents associated with the edge modes are induced
in the trivial phases and enhanced in the topological phases. In some cases
there is a sign reversal of the currents as a consequence of the periodic
driving. The edge states associated with the finite quasi-energy states at the
edge of the Floquet zone are in general robust, while the stability of the zero
quasi-energy states depends on the parameters. Also, the spin polarization of
the Floquet spectrum quasi-energies is strong as for the unperturbed
topological phases. It is found that in some cases the unperturbed edge states
are immersed in a continuum of states due to the perturbation, particularly if
the driving frequency is not large enough. However, their contribution to the
edge currents and spin polarization is still significant.",1506.04678v1
2015-06-17,Partial-wave and helicity operators for the scattering of two hadrons in lattice QCD,"Partial-wave operators for lattice QCD are developed in order to facilitate
the identification of the spins of two-hadron scattering states corresponding
to zero total momentum. Taking the periodic boundary conditions for lattice
states into account, orthogonal sets of partial-wave operators for orbital
angular momentum are identified. When combined with the intrinsic spins of the
hadrons, orthogonal sets of parent operators for total angular momentum $J$ and
projection $M$ are obtained. The parent operators are subduced to irreducible
representations of the octahedral group in order to obtain descendant operators
for use in lattice calculations. The descendant operators retain orthogonality
with respect to $J$. The spin of a state can be identified by the spin of
parent operators that dominate creation of the state. For nonzero total
momentum, operators are developed for a range of helicities and they are
subduced to irreducible representations corresponding to the different
directions of total momentum. Sets of operators that include a sufficient range
of helicities allow identification of spin $J$ when a state couples to
operators with helicities less than or equal to $J$, but not to operators with
higher helicities.",1506.05492v1
2015-07-21,Interaction Vertex for Classical Spinning Particles,"We consider a model of the classical spinning particle in which the coadjoint
orbits of the Poincare group are parametrized by two pairs of canonically
conjugate four vectors, one representing the standard position and momentum
variables and the other which encodes the spinning degrees of freedom. This
""Dual Phase Space Model"" is shown to be a consistent theory of both massive and
massless particles and allows for coupling to background fields such as
electromagnetism. The on-shell action is derived and shown to be a sum of two
terms, one associated with motion in spacetime and the other with motion in
""spin space."" Interactions between spinning particles are studied and a
necessary and sufficient condition for consistency of a three-point vertex is
established.",1507.05826v1
2015-11-26,Strong magnetic frustration and anti-site disorder causing spin-glass behavior in honeycomb Li2RhO3,"With large spin-orbit coupling, the $t_{2g}^5$ electron configuration in
$d$-metal oxides is prone to highly anisotropic exchange interactions and
exotic magnetic properties. In $5d^5$ iridates, given the existing variety of
crystal structures, the magnetic anisotropy can be tuned from antisymmetric to
symmetric Kitaev-type, with interaction strengths that outsize the isotropic
terms. By many-body electronic-structure calculations we here address the
nature of the magnetic exchange and the intriguing spin-glass behavior of
Li$_2$RhO$_3$, a $4d^5$ honeycomb oxide. For pristine crystals without Rh-Li
site inversion, we predict a dimerized ground state as in the isostructural
$5d^5$ iridate Li$_2$IrO$_3$, with triplet spin dimers effectively placed on a
frustrated triangular lattice. With Rh-Li anti-site disorder, we explain the
observed spin-glass phase as a superposition of different, nearly degenerate
symmetry-broken configurations.",1511.08333v1
2016-04-13,Charge and spin diffusion on the metallic side of the metal-insulator transition: a self-consistent approach,"We develop a self-consistent theory describing the spin and spatial electron
diffusion in the impurity band of doped semiconductors under the effect of a
weak spin-orbit coupling. The resulting low-temperature spin-relaxation time
and diffusion coefficient are calculated within different schemes of the
self-consistent framework. The simplest of these schemes qualitatively
reproduces previous phenomenological developments, while more elaborate
calculations provide corrections that approach the values obtained in numerical
simulations. The results are universal for zinc-blende semiconductors with
electron conductance in the impurity band, and thus they are able to account
for the measured spin-relaxation times of materials with very different
physical parameters. From a general point of view, our theory opens a new
perspective for describing the hopping dynamics in random quantum networks.",1604.03917v2
2016-07-22,Quantum spin Hall insulators in centrosymmetric thin films composed from topologically trivial BiTeI trilayers,"The quantum spin Hall insulators predicted ten years ago and now
experimentally observed are instrumental for a breakthrough in nanoelectronics
due to non-dissipative spin-polarized electron transport through their edges.
For this transport to persist at normal conditions, the insulators should
possess a sufficiently large band gap in a stable topological phase. Here, we
theoretically show that quantum spin Hall insulators can be realized in
ultra-thin films constructed from a trivial band insulator with strong
spin-orbit coupling. The thinnest film with an inverted gap large enough for
practical applications is a centrosymmetric sextuple layer built out of two
inversely stacked non-centrosymmetric BiTeI trilayers. This nontrivial sextuple
layer turns out to be the structure element of an artificially designed strong
three-dimensional topological insulator Bi$_2$Te$_2$I$_2$. We reveal general
principles of how a topological insulator can be composed from the structure
elements of the BiTeX family (X=I, Br, Cl), which opens new perspectives
towards engineering of topological phases.",1607.06612v2
2016-09-07,Spin-electric Berry phase shift in triangular molecular magnets,"We propose a Berry phase effect on the chiral degrees of freedom of a
triangular magnetic molecule. The phase is induced by adiabatically varying an
external electric field in the plane of the molecule via a spin-electric
coupling mechanism present in these frustrated magnetic molecules. The Berry
phase effect depends on spin-orbit interaction splitting and on the electric
dipole moment. By varying the amplitude of the applied electric field, the
Berry phase difference between the two spin states can take any arbitrary value
between zero and $\pi$, which can be measured as a phase shift between the two
chiral states by using spin-echo techniques. Our result can be used to realize
an electric field induced geometric phase-shift gate acting on a chiral qubit
encoded in the ground state manifold of the triangular magnetic molecule.",1609.02055v3
2016-09-25,Quantum Spin Hall Effect in Twisted Bilayer Graphene,"Motivated by a recent experiment (Sanchez-Yamagishi et.al, arXiv:1602.06815)
reporting evidence of helical spin-polarized edge states in layer-biased
twisted bilayer graphene under a magnetic flux, we study the possibility of
stabilising a Quantum Spin Hall (QSH) phase in such a system, without Zeeman or
spin-orbit couplings, and with a QSH gap induced instead by electronic
interactions. We analyse how magnetic flux, electric field, interlayer rotation
angle, and interactions (treated at a mean field level) combine to produce a
pseudo-QSH with broken time-reversal symmetry, and spin-polarized helical edge
states. The effect is a consequence of a robust interaction-induced
ferrimagnetic ordering of the Quantum Hall ground state under an interlayer
bias, provided the two rotated layers are effectively decoupled at low
energies. We discuss in detail the electronic structure, and the constraints on
system parameters, such as the angle, interactions and magnetic flux, required
to reach the pseudo-QSH phase. We find, in particular, that purely local
electronic interactions are not sufficient to account for the experimental
observations, which demand at least nearest-neighbour interactions to be
included.",1609.07734v1
2018-01-31,Exotic Superconductivity with Enhanced Energy Scales in Three Band Crossing Materials,"Three band crossings can arise in three dimensional quantum materials with
certain space group symmetries. The low energy Hamiltonian supports spin
$\textit{one}$ fermions and a flat band. We study the pairing problem in this
setting. We write down a minimal BCS Hamiltonian and decompose it into
spin-orbit coupled irreducible pairing channels. We then solve the resulting
gap equations in channels with zero total angular momentum. We find that in the
spin singlet channel (and also in an unusual `spin quintet' channel),
superconductivity is enormously enhanced, with a possibility for the critical
temperature to be $\textit{linear}$ in interaction strength. Meanwhile, in the
spin triplet channel, the superconductivity exhibits features of conventional
BCS theory due to the absence of flat band pairing. Three band crossings thus
represent an exciting new platform for realizing exotic superconducting states
with enhanced energy scales. We also discuss the effects of doping, nonzero
temperature, and of retaining additional terms in the $\mathbf{k} \cdot
\mathbf{p}$ expansion of the Hamiltonian.",1802.00013v2
2018-11-01,Spin-valley-controlled photonic topological insulator,"The discovery of photonic topological insulators (PTIs) has opened the door
to fundamentally new topological states of light.Current
time-reversal-invariant PTIs emulate either the quantum spin Hall (QSH) effect
or the quantum valley Hall (QVH) effect in condensed-matter systems, in order
to achieve topological transport of photons whose propagation is predetermined
by either 'photonic pseudospin' (abbreviated as 'spin') or valley. Here we
demonstrate a new class of PTIs, whose topological phase is not determined
solely by spin or valley, but is controlled by the competition between their
induced gauge fields. Such a competition is enabled by tuning the strengths of
spin-orbit coupling (SOC) and inversion-symmetry breaking in a single PTI. An
unprecedented topological transition between QSH and QVH phases that is hard to
achieve in condensed-matter systems is demonstrated. Our study merges the
emerging fields of spintronics and valleytronics in the same photonic platform,
and offers novel PTIs with reconfigurable topological phases.",1811.00393v1
2018-11-30,Subsecond nuclear spin dynamics in $n$-GaAs,"We use time-resolved detection of the Hanle effect and polarized
photoluminescence with dark intervals to investigate the buildup and decay of
the spin polarization of nuclei interacting with donor-bound electrons in
$n$-doped GaAs. Strong hyperfine coupling defines the millisecond timescale of
the spin dynamics of these nuclei, as distinct from the nuclei far from
impurity centers, characterized by a thousand times longer spin-relaxation
time. The dynamics of spin polarization and relaxation attributed to the nuclei
inside the donor orbit is observed on the time scale from 200 to 425 ms.",1811.12885v2
2020-07-28,Electron correlation effects on exchange interactions and spin excitations in 2D van der Waals materials,"Despite serious effort, the nature of the magnetic interactions and the role
of electron-correlation effects in magnetic two-dimensional (2D) van der Waals
materials remain elusive. Using CrI$_3$ as a model system, we show that the
calculated electronic structure including nonlocal electron correlations yields
spin excitations consistent with inelastic neutron scattering measurements.
Remarkably, this approach identifies an unreported correlation-enhanced
interlayer super-superexchange, which rotates the magnon Dirac lines off, and
introduces a gap along, the high-symmetry $\Gamma$-$K$-$M$ path. This discovery
provides a different perspective on the gap opening mechanism observed in
CrI$_3$, which was previously associated with spin-orbit coupling through the
Dzyaloshinskii-Moriya interaction or Kitaev interaction. Our observation
elucidates the critical role of electron correlations on the spin ordering and
spin dynamics in magnetic van der Waals materials and demonstrates the
necessity of explicit treatment of electron correlations in the broad family of
2D magnetic materials.",2007.14518v2
2014-03-26,Strongly frustrated triangular spin lattice emerging from triplet dimer formation in honeycomb Li2IrO3,"In quantum magnetism spin dimers are typically associated with spin-singlet
states. To date, $triplet$ $dimerization$ has not been observed in any 3D or
quasi-2D material. With this in mind we here discuss the electronic structure
of the spin-orbit driven $5d^5$ Mott insulator Li$_2$IrO$_3$, a
honeycomb-lattice system with two crystallographically inequivalent Ir-Ir
bonds. From $ab$ $initio$ many-body calculations we find that, while both
Heisenberg and Kitaev couplings are present, the magnetic interactions are
dominated by a strong isotropic ferromagnetic exchange on only one set of
bonds. This causes the formation of triplet spin dimers effectively placed on a
strongly frustrated triangular lattice. The triplet dimers remain protected in
a large region of the phase diagram, suggesting that Li$_2$IrO$_3$ has a
long-range incommensurate magnetic ground state that is pushed by the Kitaev
exchange interactions beyond a standard planar helix configuration.",1403.6698v2
2017-04-03,Tuning Pairing Amplitude and Spin-Triplet Texture by Curving Superconducting Nanostructures,"We investigate the nature of the superconducting state in curved
nanostructures with Rashba spin-orbit coupling (RSOC). In bent nanostructures
with inhomogeneous curvature we find a local enhancement or suppression of the
superconducting order parameter, with the effect that can be tailored by tuning
either the RSOC strength or the carrier density. Apart from the local
superconducting spin-singlet amplitude control, the geometric curvature
generates non-trivial textures of the spin-triplet pairs through a spatial
variation of the d-vector. By employing the representative case of an
elliptically deformed quantum ring, we demonstrate that the amplitude of the
d-vector strongly depends on the strength of the local curvature and it
generally exhibits a three-dimensional profile whose winding is tied to that of
the single electron spin in the normal state. Our findings unveil novel paths
to manipulate the quantum structure of the superconducting state in RSOC
nanostructures through their geometry.",1704.00578v1
2018-05-02,"Symmetry, spin-texture, and tunable quantum geometry in a WTe$_2$ monolayer","The spin orientation of electronic wavefunctions in crystals is an internal
degree of freedom, typically insensitive to electrical knobs. We argue from a
general symmetry analysis and a $\vec k \cdot \vec p$ perspective, that
monolayer 1T'-WTe$_2$ possesses a gate-activated canted spin texture that
produces an electrically tunable bulk band quantum geometry. In particular, we
find that due to its out-of-plane asymmetry, an applied out-of-plane electric
field breaks inversion symmetry to induce both in-plane and out-of-plane
electric dipoles. These in-turn generate spin-orbit coupling to lift the spin
degeneracy and enable a bulk band Berry curvature and magnetic moment
distribution to develop. Further, due to its low symmetry, Berry curvature and
magnetic moment in 1T'-WTe$_2$ possess a dipolar distribution in momentum
space, and can lead to unconventional effects such as a current induced
magnetization and quantum non-linear anomalous Hall effect. These render
1T'-WTe$_2$ a rich two-dimensional platform for all-electrical control over
quantum geometric effects.",1805.00939v2
2011-11-04,Diffusive spin dynamics in ferromagnetic thin films with a Rashba interaction,"In a ferromagnetic metal layer, the coupled charge and spin diffusion
equations are obtained in the presence of both Rashba spin-orbit interaction
and magnetism. The mis-alignment between the magnetization and the
non-equilibrium spin density induced by the Rashba field gives rise to Rashba
spin torque acting on the ferromagnetic order parameter. In a general form, we
find that the Rashba torque consists of both in-plane and out-of-plane
components, ie $\bm{T}=T_{\bot}\hat{\bm{y}}\times{\hat{\bm
m}}+T_{\parallel}{\hat{\bm m}}\times({\hat{\bm y}}\times{\hat{\bm m}})$.
Numerical simulations on a two dimensional nano-wire discuss the impact of
diffusion on the Rashba torque, which reveals a large enhancement to the ratio
$T_{\parallel}/T_{\bot}$ for thin wires. Our theory provides an explanation to
the mechanism that drives the magnetization switching in a single ferromagnet
as observed in the recent experiments.",1111.1216v2
2012-04-20,Spin Polarization in a AlGaAs/GaAs Quantum Point Contact with in-plane side gates,"We report the observation of an anomalous conductance plateau near G = 0.5 G0
(G0 = 2e2/h) in asymmetrically biased AlGaAs/GaAs quantum point contacts
(QPCs), with in-plane side gates in the presence of lateral spin-orbit
coupling. This is a signature of spin polarization in the narrow portion of the
QPC. The appearance and evolution of the conductance anomaly has been studied
at T=4.2K as a function of the potential asymmetry between the side gates. The
observation of spontaneous spin polarization in a side-gated GaAs QPC could
eventually lead to the realization of an all-electric spin-valve at tens of
degrees Kelvin.",1204.4729v1
2014-06-02,"Berry Phase, Lorentz Covariance, and Anomalous Velocity for Dirac and Weyl Particles","We consider the relation between spin and the Berry-phase contribution to the
anomalous velocity of massive and massless Dirac particles. We extend the Berry
connection that depends only on the spatial components of the particle momentum
to one that depends on the the space and time components in a covariant manner.
We show that this covariant Berry connection captures the Thomas-precession
part of the Bargmann-Michel-Telegdi spin evolution, and contrast it with the
traditional (unitary, but not naturally covariant) Berry connection that
describes spin-orbit coupling. We then consider how the covariant connection
enters the classical relativistic dynamics of spinning particles due to
Mathisson, Papapetrou and Dixon. We discuss the problems that arise with
Lorentz covariance in the massless case, and trace them mathematically to a
failure of the Wigner-translation part of the massless-particle little group to
be an exact gauge symmetry in the presence of interactions, and physically to
the fact that the measured position of a massless spinning particle is
necessarily observer dependent.",1406.0354v2
2016-05-11,Anisotropy of spin coherence in high mobility quantum wells with arbitrary magnetic fields,"We present a theoretical study of the anisotropy of the spin relaxation and
decoherence in typical quantum wells with an arbitrary magnetic field. In such
systems, the orientation of the magnetic field relative to the main
crystallographic directions is crucial, owing to the lack of spin-rotation
symmetry. For typical high mobility samples, relaxation anisotropies in the
motional narrowing limit owing to the interplay of Rashba and Dresselhaus spin
orbit coupling are calculated. We also include the effect of the
cubic-in-momentum terms. Although commonly ignored in literature, the latter
were experimentally evidenced by the observation of strong anisotropy in spin
decoherence measurements by different experimental groups and has long remained
unexplained.",1605.03399v2
2016-08-21,Topological transitions and fractional charges induced by strain and magnetic field in carbon nanotubes,"We show that carbon nanotubes (CNT) can be driven through a topological phase
transition using either strain or a magnetic field. This can naturally lead to
Jackiw-Rebbi soliton states carrying fractionalized charges, similar to those
found in a domain wall in the Su-Schrieffer-Heeger model, in a setup with a
spatially inhomogeneous strain and an axial field. Two types of fractionalized
states can be formed at the interface between regions with different strain: a
spin-charge separated state with integer charge and spin zero (or zero charge
and spin $\pm \hbar/2$), and a state with charge $\pm e/2$ and spin $\pm
\hbar/4$. The latter state requires spin-orbit coupling in the CNT. We show
that in our setup, the precise quantization of the fractionalized interface
charges is a consequence of the symmetry of the CNT under a combination of a
spatial rotation by $\pi$ and time reversal. Finally, we comment on the effects
of many-body interaction on this phenomena.",1608.05976v3
2017-06-07,Density-controlled quantum Hall ferromagnetic transition in a two-dimensional hole system,"Quantum Hall ferromagnetic transitions are typically achieved by increasing
the Zeeman energy through in-situ sample rotation, while transitions in systems
with pseudo-spin indices can be induced by gate control. We report here a
gate-controlled quantum Hall ferromagnetic transition between two real spin
states in a conventional two-dimensional system without any in-plane magnetic
field. We show that the ratio of the Zeeman splitting to the cyclotron gap in a
Ge two-dimensional hole system increases with decreasing density owing to
inter-carrier interactions. Below a critical density of $\sim2.4\times 10^{10}$
cm$^{-2}$, this ratio grows greater than $1$, resulting in a ferromagnetic
ground state at filling factor $\nu=2$. At the critical density, a resistance
peak due to the formation of microscopic domains of opposite spin orientations
is observed. Such gate-controlled spin-polarizations in the quantum Hall regime
opens the door to realizing Majorana modes using two-dimensional systems in
conventional, low-spin-orbit-coupling semiconductors.",1706.02044v1
2017-06-09,Non-equilibrium quantum transport and analytical conductance formula in spin-textured diffusive superconducting heterostructures,"We study non-equilibrium quantum transport of spin, heat, and charge in
diffusive heterostructures including both superconductors and materials with
spin-dependent fields, such as textured ferromagnets and spin-orbit coupled
materials. Using the quasiclassical theory of superconductivity, we derive a
general analytical formula for the zero-temperature charge conductance valid in
the non-linear regime. The analytical results are in excellent agreement with
previous numerical calculations at small but finite temperatures. We predict a
strong deviation between the conductance spectra and local density of states in
certain junctions, which is important to correctly identify spectroscopic
fingerprints of unconventional superconductivity.",1706.03069v2
2017-06-13,Generalized quasiclassical theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets,"We present the generalized quasiclassical theory of the long-range
superconducting proximity effect in heterostructures with strong ferromagnets,
where the exchange splitting is of the order of Fermi energy. In the
ferromagnet the propagation of spin-triplet Cooper pairs residing on the
spin-split Fermi surfaces is shown to be governed by the spin-dependent Abelian
gauge field which results either from the spin-orbital coupling or from the
magnetic texture. The additional gauge field enters into the quasiclassical
equations in superposition with the usual electromagnetic vector potential and
results in the generation of spontaneous superconducting currents and phase
shifts in various geometries which provide the sources of long-range
spin-triplet correlations. We derive the Usadel equations and boundary
conditions for the strong ferromagnet and consider several generic examples of
the Josephson systems supporting spontaneous currents.",1706.04239v2
2017-06-19,Chiral Spin Mode on the Surface of a Topological Insulator,"Using polarization-resolved resonant Raman spectroscopy, we explore
collective spin excitations of the chiral surface states in a three dimensional
topological insulator, Bi$_2$Se$_3$. We observe a sharp peak at 150 meV in the
pseudovector $A_2$ symmetry channel of the Raman spectra. By comparing the data
with calculations, we identify this peak as the transverse collective spin mode
of surface Dirac fermions. This mode, unlike a Dirac plasmon or a surface
plasmon in the charge sector of excitations, is analogous to a spin wave in a
partially polarized Fermi liquid, with spin-orbit coupling playing the role of
an effective magnetic field.",1706.05776v3
2017-10-16,Band splitting in bilayer stanene electronic structure scrutinized via first principle DFT calculations,"The recent work on stanene as quantum spin Hall insulators made us
investigate bilayer stanene using first principle calculations. With an aim of
improving and developing new properties, via modulating the stacking order (and
angle) of the bilayers. This stacking of layers has been proven technique for
modulating the properties of monolayer materials. Here we design multiple
bilayer systems, with different stacking angles and AA and AB configurations.
Rather observing an improvement in bandgap due to spin-orbit coupling (SOC), we
witness a splitting of the band due to SOC, a characteristic behavior of
stacked MoS2 sheets. This splitting of the bands gives rise to different,
independent and distinct spin-up and spin-down channels, manifesting a valley
dependent spin polarization. Also, as a contrast to stacked MoS2 system we
notice in our system the stacking angle and order, does effect electronic
states.",1710.05701v2
2017-10-20,Robust non-Abelian spin liquid and possible intermediate phase in antiferromagnetic Kitaev model with magnetic field,"We investigate the non-Abelian topological chiral spin liquid phase in the
two-dimensional (2D) Kitaev honeycomb model subject to a magnetic field. By
combining density matrix renormalization group (DMRG) and exact diagonalization
(ED) we study the energy spectra, entanglement, topological degeneracy, and
expectation values of Wilson loop operators, allowing for robust
characterization. While the ferromagnetic (FM) Kitaev spin liquid is already
destroyed by a weak magnetic field with Zeeman energy $H_*^\text{FM} \approx
0.02$, the antiferromagnetic (AFM) spin liquid remains robust up to a magnetic
field that is an order of magnitude larger, $H_*^\text{AFM} \approx 0.2$.
Interestingly, for larger fields $H_*^\text{AFM} < H < H_{**}^\text{AFM}$, an
intermediate gapless phase is observed, before a second transition to the
high-field partially-polarized paramagnet. We attribute this rich phase
diagram, and the remarkable stability of the chiral topological phase in the
AFM Kitaev model, to the interplay of strong spin-orbit coupling and
frustration enhanced by the magnetic field. Our findings suggest relevance to
recent experiments on RuCl$_3$ under magnetic fields.",1710.07595v3
2017-12-20,Electrical spin manipulation in graphene nanostructures,"We propose a mechanism to drive singlet-triplet spin transitions
electrically, in a wide class of graphene nanostructures that present pairs of
in-gap zero modes, localized at opposite sublattices. Examples are rectangular
nanographenes with short zigzag edges, armchair ribbon heterojunctions with
topological in-gap states and graphene islands with sp$^3$ functionalization.
The interplay between the hybridization of zero modes and Coulomb repulsion
leads to symmetric exchange interaction that favors a singlet ground state.
Application of an off-plane electric field to the graphene nanostructure
generates an additional Rashba spin-orbit coupling, which results in
antisymmetric exchange interaction that mixes $S=0$ and $S=1$ manifolds. We
show that modulation in time of either the off-plane electric field or the
applied magnetic field permits to perform electrically driven spin resonance in
a system with very long spin relaxation times.",1712.07282v1
2019-09-25,Extension of the standard Heisenberg Hamiltonian to multispin exchange interactions,"An extension of the Heisenberg Hamiltonian is discussed, that allows to go
beyond the standard bilinear spin Hamiltonian taking into account various
contributions due to multispin interactions having both chiral and non-chiral
character. The parameters of the extended Hamiltonian are calculated from first
principles within the framework of the multiple scattering Green function
formalism giving access to an explicit representation of these parameters in
real space. The discussions are focused on the chiral interactions, i.e.\
biquadratic and three-spin Dzyaloshinskii-Moriya like vector interactions
$\vec{\cal{D}}_{ijij}$ (BDMI) and $\vec{\cal{D}}_{ijkj}$ (TDMI), respectively,
as well as the three-spin chiral interaction (TCI) $J_{ijk}$. Although all
parameters are driven by spin-orbit coupling (SOC), some differences in their
properties are demonstrated by calculations for real materials. In particular
it is shown that the three-spin chiral interactions $J_{ijk}$ may be topology
as well as SOC induced, while the TDMI is associated only with the SOC. As the
magnitude of the chiral interactions can be quite sizable, they can lead to a
stabilization of a noncollinear magnetic texture in some materials that is
absent when these interactions are neglected.",1909.11361v2
2020-01-30,Disorder Dependence of Interface Spin Memory Loss,"The discontinuity of a spin-current through an interface caused by spin-orbit
coupling is characterized by the spin memory loss (SML) parameter {\delta}. We
use first-principles scattering theory and a recently developed local current
scheme to study the SML for Au|Pt, Au|Pd, Py|Pt and Co|Pt interfaces. We find a
minimal temperature dependence for nonmagnetic interfaces and a strong
dependence for interfaces involving ferromagnets that we attribute to the spin
disorder. The SML is larger for Co|Pt than for Py|Pt because the interface is
more abrupt. Lattice mismatch and interface alloying strongly enhance the SML
that is larger for a Au|Pt than for a Au|Pd interface. The effect of the
proximity induced magnetization of Pt is negligible.",2001.11520v1
2020-02-12,Meron-Like Topological Spin Defects in Monolayer CrCl3,"Noncollinear spin textures in low-dimensional magnetic systems have been
studied for decades because of their extraordinary properties and promising
applications derived from the chirality and topological nature. However,
material realizations of topological spin states are still limited. Employing
first-principles and Monte Carlo simulations, we propose that monolayer
chromium trichloride (CrCl3) can be a promising candidate for observing the
vortex/antivortex type of topological defects, so-called merons. The numbers of
vortices and antivortices are found to be the same, maintaining an overall
integer topological unit. By perturbing with external magnetic fields, we show
the robustness of these meron pairs and reveal a rich phase space to tune the
hybridization between the ferromagnetic order and meron-like defects. The
signatures of topological excitations under external magnetic field also
provide crucial information for experimental justifications. Our study predicts
that two-dimensional magnets with weak spin-orbit coupling can be a promising
family for realizing meron-like spin textures.",2002.05208v2
2020-02-23,An analytic model of chiral-induced spin selectivity,"Organic materials are known to feature long spin-diffusion times, originating
in a generally small spin-orbit coupling observed in these systems. From that
perspective, chiral molecules acting as efficient spin selectors pose a puzzle,
that attracted a lot of attention during the recent years. Here we revisit the
physical origins of chiral-induced spin selectivity (CISS), and propose a
simple analytic minimal model to describe it. The model treats a chiral
molecule as an anisotropic wire with molecular dipole moments aligned
arbitrarily with respect to the wire's axes, and is therefore quite general.
Importantly, it shows that helical structure of the molecule is not necessary
to observe CISS and other chiral non-helical molecules can also be considered
as a potential candidates for CISS effect. We also show that the suggested
simple model captures the main characteristics of CISS observed in experiment,
without the need for additional constraints employed in the previous studies.
The results pave the way for understanding other related physical phenomena
where CISS effect plays an essential role.",2002.09938v2
2020-04-02,Reversible edge spin currents in antiferromagnetically proximitized dichalcogenides,"We explore proximity effects on transition metal dichalcogenide ribbons
deposited on antiferromagnetic (AFM) insulating substrates. We model these
hybrid heterostructures using a tight-binding model that incorporates exchange
and Rashba fields induced by proximity to the AFM material. The robust edge
states that disperse in the midgap of the dichalcogenide are strongly affected
by induced exchange fields that reflect different AFM ordering in the
substrate. This results in enhanced spin-orbit coupling effects and complex
spin projection content for states on zigzag ribbon edges. Gated systems that
shift the Fermi level in the midgap range are also shown to exhibit spin
polarized currents on these edges. Antiparallel exchange fields along the edge
results in spin currents that can reverse polarization with the applied field.
The added functionality of these hybrid structures can provide spintronic
devices and versatile platforms to further exploit proximity effects in diverse
material systems.",2004.01064v1
2020-12-09,Spin-lattice model for cubic crystals,"We present a methodology based on the N\'{e}el model to build a classical
spin-lattice Hamiltonian for cubic crystals capable of describing magnetic
properties induced by the spin-orbit coupling like magnetocrystalline
anisotropy and anisotropic magnetostriction, as well as exchange
magnetostriction. Taking advantage of the analytical solutions of the N\'{e}el
model, we derive theoretical expressions for the parameterization of the
exchange integrals and N\'{e}el dipole and quadrupole terms that link them to
the magnetic properties of the material. This approach allows to build accurate
spin-lattice models with the desire magnetoelastic properties. We also explore
a possible way to model the volume dependence of magnetic moment based on the
Landau energy. This new feature can allow to consider the effects of
hydrostatic pressure on the saturation magnetization. We apply this method to
develop a spin-lattice model for BCC Fe and FCC Ni, and we show that it
accurately reproduces the experimental elastic tensor, magnetocrystalline
anisotropy under pressure, anisotropic magnetostrictive coefficients, volume
magnetostriction and saturation magnetization under pressure at
zero-temperature. This work could constitute a step towards large-scale
modeling of magnetoelastic phenomena.",2012.05076v3
2012-05-16,In-gap impurity states as the hallmark of the Quantum Spin Hall phase,"We study the different response to an impurity of the two topologically
different phases shown by a two dimensional insulator with time reversal
symmetry, namely, the Quantum Spin Hall and the normal phase. We consider the
case of graphene as a toy model that features the two phases driven,
respectively, by intrinsic spin-orbit coupling and inversion symmetry breaking.
We find that strictly normalizable in-gap impurity states only occur in the
Quantum Spin Hall phase and carry dissipationless current whose quirality is
determined by the spin and pseudospin of the residing electron. Our results
imply that topological order can be unveiled by local probes of defect states.",1205.3737v1
2017-05-02,Strongly interaction-enhanced valley magnetic response in monolayer WSe2,"Coulomb interaction between electrons lies at the heart of magnetism in
solids. In contrast to conventional two-dimensional (2D) systems, electrons in
monolayer transition metal dichalcogenides (TMDs) possess coupled spin and
valley degrees of freedom by the spin-orbit interaction. The electrons are also
strongly interacting even in the high-density regime because of the weak
dielectric screening in two dimensions and a large band mass. The combination
of these properties presents a unique platform for exploring spin and valley
magnetism in 2D electron liquids. Here we report an observation by
magneto-photoluminescence spectroscopy of a nonlinear valley Zeeman effect,
correlated with an over fourfold enhancement in the exciton g-factor in
monolayer WSe2. The effect occurs when the Fermi level crosses the spin-split
upper conduction band, corresponding to a change of the spin-valley degeneracy
from 2 to 4. The enhancement increases, shows no sign of saturation as the
sample temperature decreases. Our result suggests the possibility of rich
many-body ground states in monolayer TMDs with multiple internal degrees of
freedom.",1705.01078v1
2017-05-09,"Anomalous, spin, and valley Hall effects in graphene deposited on ferromagnetic substrates","Spin, anomalous, and valley Hall effects in graphene-based hybrid structures
are studied theoretically within the Green function formalism and linear
response theory. Two different types of hybrid systems are considered in
detail: (i) graphene/boron nitride/cobalt(nickel), and (ii) graphene/YIG. The
main interest is focused on the proximity-induced exchange interaction between
graphene and magnetic substrate and on the proximity-enhanced spin-orbit
coupling. The proximity effects are shown to have a significant influence on
the electronic and spin transport properties of graphene. To find the spin,
anomalous and valley Hall conductivities we employ certain effective
Hamiltonians which have been proposed recently for the hybrid systems under
considerations. Both anomalous and valley Hall conductivities have universal
values when the Fermi level is inside the energy gap in the electronic
spectrum.",1705.03220v1
2019-01-31,Direct Observation of Unusual Interfacial Dzyaloshinskii-Moriya Interaction in Graphene/NiFe/Ta Heterostructure,"Graphene/ferromagnet interface promises a plethora of new science and
technology. The interfacial Dzyaloshinskii Moriya interaction (iDMI) is
essential for stabilizing chiral spin textures, which are important for future
spintronic devices. Here, we report direct observation of iDMI in
graphene/Ni80Fe20/Ta heterostructure from non-reciprocity in spin-wave
dispersion using Brillouin light scattering (BLS) technique. Linear scaling of
iDMI with the inverse of Ni80Fe20 thicknesses suggests primarily interfacial
origin of iDMI. Both iDMI and spin-mixing conductance increase with the
increase in defect density of graphene obtained by varying argon pressure
during sputter deposition of Ni80Fe20. This suggests that the observed iDMI
originates from defect-induced extrinsic spin-orbit coupling at the interface.
The direct observation of iDMI at graphene/ferromagnet interface without
perpendicular magnetic anisotropy opens new route in designing thin film
heterostructures based on 2-D materials for controlling chiral spin structure
such as skyrmions and bubbles, and magnetic domain-wall-based storage and
memory devices.",1901.11287v1
2019-02-20,Kitaev-like honeycomb magnets: Global phase behavior and emergent effective models,"Compounds of transition metal ions with strong spin-orbit coupling recently
attracted attention due to the possibility to host frustrated bond-dependent
anisotropic magnetic interactions. In general, such interactions lead to
complex phase diagrams that may include exotic phases, e.g. the Kitaev spin
liquid. Here we report on our comprehensive analysis of the global phase
diagram of the extended Kitaev-Heisenberg model relevant to honeycomb lattice
compounds Na2IrO3 and alpha-RuCl3. We have utilized recently developed method
based on spin coherent states that enabled us to resolve arbitrary spin
patterns in the cluster ground states obtained by exact diagonalization. Global
trends in the phase diagram are understood in combination with the analytical
mappings of the Hamiltonian that uncover peculiar links to known models -
Heisenberg, Ising, Kitaev, or compass models on the honeycomb lattice - or
reveal entire manifolds of exact fluctuation-free ground states. Finally, our
study can serve as a methodological example that can be applied to other spin
models with complex bond-dependent non-Heisenberg interactions.",1902.07451v1
2019-02-22,Spin-dependent directional emission from an asymmetry optical waveguide with an embedded quantum dot ensemble,"In this study, we examine a photonic wire waveguide embedded with an ensemble
of quantum dots that directionally emits into the waveguide depending on the
spin state of the ensemble. This is accomplished through the aid of the
spin-orbit interaction of light. The waveguide has a two-step stair-like cross
section and embeds quantum dots (QDs) only in the upper step, such that the
circular polarization of emission from the spin-polarized QDs controls the
direction of the radiation. We numerically verify that more than 70% of the
radiation from the ensemble emitter is toward a specific direction in the
waveguide. We also examine a microdisk resonator with a stair-like edge, that
supports selective coupling of the QD ensemble radiation into a whispering
galley mode rotating unidirectionally. Our study provides a foundation for
spin-dependent optoelectronic devices.",1902.08385v1
2019-03-26,Fully spin-polarized nodal loop semimetals in alkaline-metal monochalcogenide monolayers,"Topological semimetals in ferromagnetic materials have attracted enormous
attention due to the potential applications in spintronics. Using the
first-principles density functional theory together with an effective lattice
model, here we present a new family of topological semimetals with a fully
spin-polarized nodal loop in alkaline-metal monochalcogenide $MX$ ($M$ = Li,
Na, K, Rb, Cs; $X$ = S, Se, Te) monolayers. The half-metallic ferromagnetism
can be established in $MX$ monolayers, in which one nodal loop formed by two
crossing bands with the same spin components is found at the Fermi energy. This
nodal loop half-metal survives even when considering the spin-orbit coupling
owing to the symmetry protection provided by the $\mathcal{M}_{z}$ mirror
plane. The quantum anomalous Hall state and Weyl-like semimetal in this system
can be also achieved by rotating the spin from the out-of-plane to the in-plane
direction. The $MX$ monolayers hosting rich topological phases thus offer an
excellent materials platform for realizing the advanced spintronics concepts.",1903.11025v1
2019-11-21,Comprehensive Control of Metamagnetic Transition of Antiferromagnetic Mott Insulator Sr2IrO4 by in-situ Anisotropic Strain,"Metamagnetism in antiferromagnets exhibits distinct critical behaviors and
dynamics when invoking spin reversal and rotation. Here we show a 0.05%
anisotropic strain suffices to in-situ modulate the metamagnetic critical field
of the Mott insulator Sr2IrO4 by over 50%, enabling electrical switching of the
transition. Resonant x-ray scattering and model simulation reveal that the
transition is completely tuned from the spin-flop to spin-flip type as the
strain introduces C4-symmetry-breaking magnetic anisotropy. Simultaneous
transport study indicates the metamagnetic responses are reflected in the large
elasto- and magnetoconductance, highlighting the active charge degree of
freedom in the spin-orbit-coupled Mott state and its potential for
spin-electronics.",1911.09504v2
2020-08-26,The Electrical and Spin Properties of Monolayer and Bilayer Janus HfSSe under Vertical Electrical Field,"In this paper, the electrical and spin properties of mono- and bilayer HfSSe
in the presence of a vertical electric field are studied. The density
functional theory is used to investigate their properties. Fifteen different
stacking orders of bilayer HfSSe are considered. The mono- and bilayer
demonstrate an indirect bandgap, whereas the bandgap of bilayer can be
effectively controlled by electric field. While the bandgap of bilayer closes
at large electric fields and a semiconductor to metal transition occurs, the
effect of a normal electric field on the bandgap of the monolayer HfSSe is
quite weak. Spin-orbit coupling causes band splitting in the valence band and
Rashba spin splitting in the conduction band of both mono- and bilayer
structures. The band splitting in the valence band of the bilayer is smaller
than a monolayer, however, the vertical electric field increases the band
splitting in bilayer one. The stacking configurations without mirror symmetry
exhibit Rashba spin splitting which is enhanced with the electric field.",2008.11361v1
2020-10-27,Spin-dependent Tunneling Barriers in CoPc/VSe2 from Many-Body Interactions,"Mixed-dimensional magnetic heterostructures are intriguing, newly available
platforms to explore quantum physics and its applications. Using
state-of-the-art many-body perturbation theory, we predict the energy level
alignment for a self-assembled monolayer of cobalt phthalocyanine (CoPc)
molecules on magnetic VSe 2 monolayers. The predicted projected density of
states on CoPc agrees with experimental scanning tunneling spectra. Consistent
with experiment, we predict a shoulder in the unoccupied region of the spectra
that is absent from mean-field calculations. Unlike the nearly spin-degenerate
gas phase frontier molecular orbitals, the tunneling barriers at the interface
are spin-dependent, a finding of interest for quantum information and
spintronics applications. Both the experimentally observed shoulder and the
predicted spin-dependent tunneling barriers originate from many-body
interactions in the interface-hybridized states. Our results showcase the
intricate many-body physics that governs the properties of these
mixed-dimensional magnetic heterostructures, and suggests the possibility of
manipulating the spin-dependent tunneling barriers through modifications of
interface coupling.",2010.14012v1
2020-11-14,Photogalvanic Effect in Silicene,"Silicene has introduced itself as an outstanding novel material, which seeks
its meritorious place among common spintronic devices like Cu and Ag. In this
work, photogalvanic effect in silicene is studied within the semi-classical
approach and beyond Dirac point approximation. Normal electric field plays the
role of effective pseudo-magnetic field which breaks the inversion symmetry and
splits the conduction and valence bands. The interplay between this external
field and intrinsic spin-orbit coupling provides spin-valley locking in
silicene. Spin-valley locking in silicene makes this material superior to its
carbon counterpart, graphene. Since the absorption of the polarized photons is
not equivalent at both of the valleys, spin-valley locking leads to a
spin-polarized photocurrent injection.",2011.07250v2
2021-04-06,Topological Green function of interacting systems,"We construct a Green function, which can identify the topological nature of
interacting systems. It is equivalent to the single-particle Green function of
effective non-interacting particles, the Bloch Hamiltonian of which is given by
the inverse of the full Green function of the original interacting particles at
zero frequency. The topological nature of the interacting insulators is
originated from the coincidence of the poles and the zeros of the diagonal
elements of the constructed Green function. The cross of the zeros in the
momentum space closely relates to the topological nature of insulators. As a
demonstration, using the zero's cross, we identify the topological phases of
magnetic insulators, where both the ionic potential and the spin exchange
between conduction electrons and magnetic moments are present together with the
spin-orbital coupling. The topological phase identification is consistent with
the topological invariant of the magnetic insulators. We also found an
antiferromagnetic state with topologically breaking of the spin symmetry, where
electrons with one spin orientation are in topological insulating state, while
electrons with the opposite spin orientation are in topologically trivial one.",2104.02344v2
2021-04-07,Switchable Rashba Anisotropy in Two-dimensional Hybrid Organic-Inorganic Perovskite by Hybrid Improper Ferroelectricity,"Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) are
introducing new directions in the 2D materials landscape. The coexistence of
ferroelectricity and spin-orbit interactions play a key role in their
optoelectronic properties. We perform a detailed study on a recently
synthesized ferroelectric 2D-HOIP, (AMP)PbI$_4$ (AMP =
4-aminomethyl-piperidinium). The calculated polarization and Rashba parameter
are in excellent agreement with experimental values. We report a striking new
effect, i.e., an extraordinarily large Rashba anisotropy that is tunable by
ferroelectric polarization: as polarization is reversed, not only the spin
texture chirality is inverted, but also the major and minor axes of the Rashba
anisotropy ellipse in k-space are interchanged - a pseudo rotation. A $k \cdot
p$ model Hamiltonian and symmetry-mode analysis reveal a quadrilinear coupling
between the cation-rotation modes responsible for the Rashba ellipse
pseudo-rotation, the framework rotation, and the polarization. These findings
may provide new avenues for spin-optoelectronic devices such as spin valves or
spin FETs.",2104.02970v1
2021-04-09,Non-thermal breaking of magnetic order via photo-generated spin defects,"In Mott insulators the evolution of antiferromagnetic order to
superconducting or charge-density-wave-like states upon chemical doping
underpins the control of quantum phases. Photo-doping can induce similar
transitions on the ultrafast timescale, however the response of the spin system
has remained elusive. Here, we use 4D-ultrafast optical spectroscopy to extract
quantitative magnetic dynamics in the spin-orbit coupled Mott insulator
Sr3Ir2O7. We demonstrate that light can non-thermally melt long-range spin
order. At low fluences magnetic order recovers within 1 ps despite
demagnetization of roughly 50%. However, high fluences induce a crossover to a
long-lived demagnetized state without increasing the lattice temperature. We
show that the generation of photo-induced spin defects enables a mechanism that
stabilizes the demagnetized state which could help expose new transient phases.",2104.04294v2
2016-03-10,Killing Auger recombination in nanostructures by carrier spin polarization,"In semiconductor nanostructures nonradiative Auger recombination is enhanced
by the presence of boundaries which relax the momentum conservation and thereby
removes the threshold reduction for these processes. We propose a method to
strongly reduce the Auger recombination rate by injecting spin-polarized
carriers. Our method is illustrated on the example of a quantum well in which
the spin-orbit coupling of conduction band is negligible as compared to valence
band and thus holes can be considered as spin-unpolarized. The suppression
factor of the Auger recombination is determined by the two-dimensional
character of the system, given by the ratio of the Fermi energy of electrons
and the separation of the electron levels quantized in the growth direction.
Our predictions can be tested experimentally and we discuss their implications
for semiconductor lasers relying on injection of spin-polarized electrons.",1603.03410v1
2016-12-16,Ultrafast demagnetization in bulk vs thin films: an ab-initio study,"We report on {\it ab-initio} simulations of the quantum dynamics of
electronic charge and spin when subjected to intense laser pulses. By
performing separate calculations for a Ni thin film and bulk Ni, we conclude
that surface effects have a dramatic influence on amplifying the laser induced
demagnetization. We show that the reason for this amplification is due to
increased spin-currents on the surface of the thin film. This enhancement is a
direct consequence of the broken symmetry originating from the surface
formation. We find that the underlying physics of demagnetization, during the
early femtoseconds, for both bulk and thin film is dominated by spin-flips
induced by spin-orbit coupling. After the first $\sim 40$ fs this changes in
that the dominant cause of demagnetization is the flow of spin-currents, which
leads to stronger demagnetization in the film compared to that of the bulk.",1612.05663v2
2017-07-11,Putative spin liquid in the triangle-based iridate Ba$_3$IrTi$_2$O$_9$,"We report on thermodynamic, magnetization, and muon spin relaxation
measurements of the strong spin-orbit coupled iridate Ba$_3$IrTi$_2$O$_9$,
which constitutes a new frustration motif made up a mixture of edge- and
corner-sharing triangles. In spite of strong antiferromagnetic exchange
interaction of the order of 100~K, we find no hint for long-range magnetic
order down to 23 mK. The magnetic specific heat data unveil the $T$-linear and
-squared dependences at low temperatures below 1~K. At the respective
temperatures, the zero-field muon spin relaxation features a persistent spin
dynamics, indicative of unconventional low-energy excitations. A comparison to
the $4d$ isostructural compound Ba$_3$RuTi$_2$O$_9$ suggests that a concerted
interplay of compass-like magnetic interactions and frustrated geometry
promotes a dynamically fluctuating state in a triangle-based iridate.",1707.03140v1
2019-06-27,Spin-polarized electronic surface states of Re(0001): an ab-initio investigation,"We study the electronic structure of the Re(0001) surface by means of
ab-initio techniques based on the Fully Relativistic (FR) Density Functional
Theory (DFT) and the Projector Augmented-Wave (PAW) method. We identify the
main surface states and resonances and study in detail their energy dispersion
along the main symmetry lines of the SBZ. Moreover, we discuss the effect of
spin-orbit coupling on the energy splittings and the spin-polarization of the
main surface states and resonances. Whenever possible, we compare the results
with previously studied heavy metals surfaces. We find empty resonances,
located below a gap similar to the L-gap of the (111) fcc surfaces, that have a
downward dispersion and cross the Fermi level, similarly to the recently
studied Os(0001) surface. Their spin polarization at the Fermi level is similar
to that predicted by the Rashba model, but the usual level crossing at
$\bar{\Gamma}$ is not found with our slab thickness. Moreover, for selected
states, we follow the spin polarization along the high symmetry lines,
discussing its behavior with respect to ${\bf k}_{\parallel}$, the wave-vector
parallel to the surface.",1906.12196v1
2020-03-06,Competing long-range interactions and spin vector chirality in spin-chains,"Studies of competing orders in 1D magnetic chains have attracted considerable
attention in recent years, as the presence of long-range Heisenberg
interactions is found to allow interesting quantum phase transitions. We
investigate here the role of spin-orbit effects by considering spin-1/2 chains
in the presence of both collinear and non-collinear long-range interactions. By
employing exact diagonalization and density matrix renormalization group
calculations we investigate the rich phase diagram of this system. We find
transitions from collinear to transverse magnetic correlated order as the
strength of the non-collinear coupling increases, accompanied by a jump in the
vector spin chirality order parameter of the system. This shows that tuning
long-range interactions allows control of the onset of sizable vector spin
chirality in a system, which may be used to transmit information down the
chain. We investigate the characteristic structure of the distinct phases and
explore their possible physical implementation in different materials systems.",2003.03322v1
2020-06-03,Nonthermal excitonic condensation near a spin-state transition,"We consider a two-orbital Hubbard model with Hund coupling and crystal-field
splitting and show that in the vicinity of the high-spin/low-spin transition,
crystal-field quenches can induce an excitonic condensation at initial
temperatures above the highest ordering temperature in equilibrium. This
condensation is the effect of an increase in the spin entropy and an associated
cooling of the effective electronic temperature. We identify a dynamical phase
transition and show that such quenches can result in long-lived nonthermal
excitonic condensates which have no analogue in the equilibrium phase diagram.
The results are interpreted by means of an effective pseudo-spin model.",2006.02096v2
2020-06-23,Doping-induced quantum spin Hall insulator to superconductor transition,"A unique property of a dynamically generated quantum spin Hall state are
Goldstone modes that correspond to the long-wavelength fluctuations of the
spin-orbit coupling order parameter whose topological Skyrmion excitations
carry charge 2$e$. Within the model considered here, upon varying the chemical
potential, we observe two transitions: An s-wave superconducting order
parameter develops at a critical chemical potential $\mu_{c1}$, corresponding
to the excitation gap of pairs of fermions, and at $\mu_{c2}$ the SO(3) order
parameter of the quantum spin Hall state vanishes. Using negative-sign-free,
large-scale quantum Monte Carlo simulations, we show that $\mu_{c1}=\mu_{c2}$
within our accuracy -- we can resolve dopings away from half filling down to
$\delta = 0.0017$. The length scale associated with the fluctuations of the
quantum spin Hall order parameter grows down to our lowest doping, suggesting
either a continuous or a weakly first-order transition. Contrary to mean-field
expectations, the doping versus chemical potential curve is not linear,
indicating a dynamical critical exponent $z > 2$ if the transition is
continuous.",2006.13239v2
2021-02-02,Spontaneous magnetization in unitary superconductors with time reversal symmetry breaking,"We report the study of spontaneous magnetization (i.e., spin-polarization)
for time-reversal symmetry (TRS)-breaking superconductors with unitary pairing
potentials, in the absence of external magnetic fields or Zeeman fields.
Spin-singlet ($\Delta_s$) and spin-triplet ($\Delta_t$) pairings can coexist in
superconductors whose crystal structure lacks inversion symmetry. The TRS can
be spontaneously broken once a relative phase of $\pm\pi/2$ is developed,
forming a TRS-breaking unitary pairing state ($\Delta_s\pm i\Delta_t$). We
demonstrate that such unitary pairing could give rise to spontaneous
spin-polarization with the help of spin-orbit coupling. Our result provides an
alternative explanation to the TRS breaking, beyond the current understanding
of such phenomena in the noncentrosymmetric superconductors. The experimental
results of Zr$_3$Ir and CaPtAs are also discussed in the view of our theory.",2102.01267v5
2021-02-22,"Interplay between multipolar spin interactions, Jahn-Teller effect and electronic correlation in a $J_{eff}=\frac{3}{2}$ insulator","In this work we study the complex entanglement between spin interactions,
electron correlation and Janh-Teller structural instabilities in the 5d$^1$
$J_{eff}=\frac{3}{2}$ spin-orbit coupled double perovskite $\rm Ba_2NaOsO_6$
using first principles approaches. By combining non-collinear magnetic
calculations with multipolar pseudospin Hamiltonian analysis and many-body
techniques we elucidate the origin of the observed quadrupolar canted
antifferomagnetic. We show that the non-collinear magnetic order originates
from Jahn-Teller distortions due to the cooperation of Heisenberg exchange,
quadrupolar spin-spin terms and both dipolar and multipolar
Dzyaloshinskii-Moriya interactions. We find a strong competition between
ferromagnetic and antiferromagnetic canted and collinear quadrupolar magnetic
phases: the transition from one magnetic order to another can be controlled by
the strength of the electronic correlation ($U$) and by the degree of
Jahn-Teller distortions.",2102.10839v1
2021-07-07,Spin-orbit pumping,"We study theoretically the effect of a rotating electric field on a diffusive
nanowire and find an effect that is analogous to spin pumping, which refers to
the generation of spin through a rotating magnetic field. The electron spin
couples to the electric field because the particle motion induces an effective
magnetic field in its rest frame. In a diffusive system the velocity of the
particle, and therefore also its effective magnetic field, rapidly and randomly
changes direction. Nevertheless, we demonstrate analytically and via a physical
argument why the combination of the two effects described above produces a
finite magnetization along the axis of rotation. This manifests as a measurable
spin-voltage in the range of tens of microvolts.",2107.03392v2
2021-07-08,Emergence of Unconventional Interfacial Magnetic Phenomenon in Topological Insulator-Based Magnetic Heterostructures,"In a topological insulator (TI)/magnetic insulator (MI) hetero-structure,
large spin-orbit coupling of the TI and inversion symmetry breaking at the
interface could foster non-planar spin textures such as skyrmions at the
interface. This is observed as topological Hall effect in a conventional Hall
set-up. While this effect has been observed at the interface of TI/MI, where MI
beholds perpendicular magnetic anisotropy, non-trivial spin-textures that
develop in interfacial MI with in-plane magnetic anisotropy is under-reported.
In this work, we study Bi$_2$Te$_3$/EuS hetero-structure using planar Hall
effect (PHE). We observe planar topological Hall and spontaneous planar Hall
features that are characteristic of non-trivial in-plane spin textures at the
interface. We find that the latter is minimum when the current and magnetic
field directions are aligned parallel, and maximum when they are aligned
perpendicularly within the sample plane, which maybe attributed to the
underlying planar anisotropy of the spin-texture. These results demonstrate the
importance of PHE for sensitive detection and characterization of non-trivial
magnetic phase that has evaded exploration in the TI/MI interface.",2107.03596v2
2021-08-17,Spin-polarized Majorana zero-modes in double zigzag honeycomb nanoribbons,"We study the emergence of Majorana zero modes (MZMs) at the ends of a finite
double zigzag honeycomb nanoribbon (zHNR). We show that a double zHNR geometry
can host spin-polarized MZMs at its ends. We considered a minimal model
composed by first nearest neighbor hopping, Rashba spin-orbit coupling (RSOC),
p-wave superconducting pairing, and an applied external magnetic field (EMF).
The energy spectrum regions with either spin up or down MZMs belong to distinct
topological phase transitions characterized by their corresponding winding
numbers and can be accessed by tunning the chemical potential of the
nanoribbons. Hybrid systems constituted by zHNRs deposited on conventional
s-wave superconductors are potential candidates for experimentally realizing
the proposal. The spin's discrimination of MZMs suggests a possible route for
performing topological-conventional qubit operations using Majorana
spintronics.",2108.07785v1
2021-08-18,The temperature-dependent chiral-induced spin selectivity effect: Experiments and theory,"The theoretical explanation for the chiral-induced spin selectivity effect,
in which electrons' passage through a chiral system depends on their spin and
the handedness of the system, remains vague. Although most experimental work
was performed at room temperature, most of the proposed theories did not
include vibrations. Here, we present temperature-dependent experiments and a
theoretical model that captures all observations and provides spin polarization
values that are consistent with the experimental results. The model includes
vibrational contribution to the spin orbit coupling. It shows the importance of
dissipation and the relation between the effect and the optical activity.",2108.08037v1
2021-08-19,"IrCrMnZ (Z=Al, Ga, Si, Ge) Heusler alloys as electrode materials for MgO-based magnetic tunneling junctions: A first-principles study","We study IrCrMnZ (Z=Al, Ga, Si, Ge) systems using first-principles
calculations from the perspective of their application as the electrode
materials of MgO-based MTJs. These materials have highly spin-polarized
conduction electrons with partially occupied $\Delta_1$ band, which is
important for coherent tunneling in parallel magnetization configuration. The
Curie temperatures of IrCrMnAl and IrCrMnGa are very high (above 1300 K) as
predicted from mean-field-approximation. The stability of ordered phase against
various antisite disorders has been investigated. We discuss here the effect of
""spin-orbit-coupling"" on the electronic structure around Fermi level. Further,
we investigate the electronic structure of IrCrMnZ/MgO heterojunction along
(001) direction. IrCrMnAl/MgO and IrCrMnGa/MgO maintain half-metallicity even
at the MgO interface, with no interfacial states at/around Fermi level in the
minority-spin channel. Large majority-spin conductance of IrCrMnAl/MgO/IrCrMnAl
and IrCrMnGa/MgO/IrCrMnGa is reported from the calculation of ballistic
spin-transport property for parallel magnetization configuration. We propose
IrCrMnAl/MgO/IrCrMnAl and IrCrMnGa/MgO/IrCrMnGa as promising MTJs with a weaker
temperature dependence of tunneling magnetoresistance ratio, owing to their
very high Curie temperatures.",2108.08501v1
2021-09-16,Magnetoelectric polarizability and optical activity: spin and frequency dependence,"We extend a microscopic theory of polarization and magnetization to include
the spin degree of freedom of the electrons, introducing a general spin orbit
coupling and Zeeman interaction term in the Hamiltonian. At finite frequencies
and including spin, the magnetoelectric polarizability tensor is replaced by
two separate tensors, one that relates the polarization \textbf{P} to the
magnetic field \textbf{B} and a separate tensor that relates the magnetization
\textbf{M} to the electric field \textbf{E}. When combined with other relevant
response tensors a third rank tensor that relates the induced current density
to gradients in the electric field can be introduced; it is gauge invariant, in
a form suitable for numerical calculations, and describes optical activity --
including spin effects -- even in materials that may lack time reversal
symmetry.",2109.07997v3
2021-10-04,Transmission of a single electron through a Berry's ring,"A theoretical model of transmission and reflection of an electron with spin
is proposed for a mesoscopic ring with rotating localized magnetic moment. This
model may be realized in a pair of domain walls connecting two ferromagnetic
domains with opposite magnetization. If the localized magnetic moment and the
traveling spin is ferromagnetically coupled and if the localized moment rotates
with opposite chirality in the double-path, our system is formulated in the
model of an emergent spin-orbit interaction in a ring. The scattering problem
for the transmission spectrum of the traveling spin is solved both in a single
path and a double path model. In the double path, the quantum-path interference
changes dramatically the transmission spectrum due to the effect of the Berry's
phase. Specifically, the spin-flip transmission and reflection are both
strictly forbidden.",2110.01472v2
2021-10-11,Antiferromagnetic spin fluctuations and superconductivity in NbRh$_2$B$_2$ and TaRh$_2$B$_2$ with a chiral crystal structure,"We report the $^{11}$B nuclear magnetic resonance (NMR) measurements on
non-centrosymmetric superconductors NbRh$_2$B$_2$ (superconducting transition
temperature $T_c$ = 7.8 K) and TaRh$_2$B$_2$ ($T_c$ = 5.9 K) with a chiral
crystal structure. The nuclear spin-lattice relaxation rate $1/T_1$ shows no
coherence peak below $T_{\rm c}$, which suggests unconventional nature of the
superconductivity. In the normal state, $1/T_1T$ increases with decreasing
temperature $T$ at low temperatures below $T$ = 200 K for TaRh$_2$B$_2$ and $T$
= 15 K for NbRh$_2$B$_2$, while the Knight shift remains constant. These
results suggest the presence of antiferromagnetic spin fluctuations in both
compounds. The stronger spin fluctuations in TaRh$_2$B$_2$ compared to
NbRh$_2$B$_2$ is discussed in the context of spin-orbit coupling.",2110.04958v2
2021-11-01,Sr$_3$LiIrO$_6$: a potential quantum spin liquid candidate in the one dimensional $d^4$ iridate family,"Spin-orbit coupling (SOC) offers a large variety of novel and extraordinary
magnetic and electronic properties in otherwise `ordinary pool' of heavy ion
oxides. Here we present a detailed study on an apparently isolated hexagonal
2$H$ spin-chain $d^4$ iridate Sr$_3$LiIrO$_6$ (SLIO) with geometric
frustration. Our structural studies clearly reveal perfect Li-Ir chemical order
in this compound. Our combined experimental and {\it ab-initio} electronic
structure investigations establish a magnetic ground state with finite
Ir$^{5+}$ magnetic moments in this compound, contrary to the anticipated
nonmagnetic $J$=0 state. Furthermore, the dc magnetic susceptibility ($\chi$),
heat capacity ($C_p$) and spin-polarized density functional theory (DFT)
studies unravel that despite having noticeable antiferromagnetic correlation
among the Ir$^{5+}$ local moments, this SLIO system evades any kind of magnetic
ordering down to at least 2 K due to geometrical frustration, arising from the
comparable interchain Ir-O-O-Ir superexchange interaction strengths, hence
promoting SLIO as a potential quantum spin liquid candidate.",2111.00925v1
2022-05-20,Microscopic analysis of spin-momentum locking on a geometric phase metasurface,"We revisit spin-orbit coupling in a plasmonic Berry metasurface comprised of
rotated nanoapertures, which is known to imprint a robust far-field
polarization response. We present a scattering formalism that shows how that
spin-momentum locking emerges from the geometry of the unit cell without
requiring global rotation symmetries. We find and confirm with Mueller
polarimetry measurements that spin-momentum locking is an approximate symmetry.
The symmetry breakdown is ascribed to the elliptical projection of circularly
polarized light into the planar surface. This breakdown is maximal when surface
waves are excited, and a new set of spin-momentum locking rules is presented
for this case.",2205.10245v2
2022-06-01,Transient spin injection efficiencies at ferromagnet/metal interfaces,"Spin injection across interfaces driven by ultrashort optical pulses on
femtosecond timescales constitutes a new way to design spintronics
applications. Targeted utilization of this phenomenon requires knowledge of the
efficiency of non-equilibrium spin injection. From a quantitative comparison of
ab-initio time-dependent density functional theory and interface-sensitive,
time-resolved non-linear optical experiment, we determine the spin injection
efficiencies (SIE) across ferromagnetic/metal interfaces and discuss their
microscopic origin, i.e. the influence of spin-orbit coupling and the interface
electronic structure. Moreover, we find that the SIE can be optimized through
laser pulse and materials parameters, namely the fluence, pulse duration, and
substrate material.",2206.00498v1
2022-09-21,Cross effects in spin hydrodynamics: A revisit Entropy analysis and statistical operator,"We revisit the construction of first-order spin hydrodynamics and find that
the constitution relations receive the corrections from the cross effects
resulting from spin-orbit coupling. Starting from a routine entropy analysis,
we show how to identify cross effects and new cross transport coefficients from
the second law of thermodynamics. Interestingly, the conventional transport
coefficient heat conductivity $\kappa$ is bounded from below by the product of
cross transport coefficients, which means the threshold of heat conduction is
changed. With recourse to Zubarev's non-equilibrium statistical operator, we
reproduce the construction of first-order spin hydrodynamics and identification
of cross effects in a more rigorous way. By seeking the dispersion relations of
normal modes, we find that these cross effects suppress the attenuation of
sound modes and heat mode appearing in conventional hydrodynamics and also have
impacts on the damping of non-hydrodynamic spin modes.",2209.10979v2
2022-09-23,Time-reversal symmetry adaptation in relativistic density matrix renormalization group algorithm,"In the nonrelativistic Schr\""{o}dinger equation, the total spin $S$ and spin
projection $M$ are good quantum numbers. In contrast, spin symmetry is lost in
the presence of spin-dependent interactions such as spin-orbit couplings in
relativistic Hamiltonians. Previous implementations of relativistic density
matrix renormalization group algorithm (R-DMRG) only employing particle number
symmetry are much more expensive than nonrelativistic DMRG. Besides, artificial
breaking of Kramers degeneracy can happen in the treatment of systems with odd
number of electrons. To overcome these issues, we introduce time-reversal
symmetry adaptation for R-DMRG. Since the time-reversal operator is
antiunitary, this cannot be simply achieved in the usual way. We define a
time-reversal symmetry-adapted renormalized basis and present strategies to
maintain the structure of basis functions during the sweep optimization. With
time-reversal symmetry adaptation, only half of the renormalized operators are
needed and the computational costs of Hamiltonian-wavefunction multiplication
and renormalization are reduced by half. The present construction of
time-reversal symmetry-adapted basis also directly applies to other tensor
network states without loops.",2209.11380v1
2022-09-26,Real-space Obstruction in Quantum Spin Hall Insulators,"The recently introduced classification of two-dimensional insulators in terms
of topological crystalline invariants has been applied so far to ""obstructed""
atomic insulators characterized by a mismatch between the centers of the
electronic Wannier functions and the ionic positions. We extend this notion to
quantum spin Hall insulators in which the ground state cannot be described in
terms of time-reversal symmetric localized Wannier functions. A system
equivalent to graphene in all its relevant electronic and topological
properties except for a real-space obstruction is identified and studied via
symmetry analysis as well as with density functional theory. The low-energy
model comprises a local spin-orbit coupling and a non-local symmetry breaking
potential, which turn out to be the essential ingredients for an obstructed
quantum spin Hall insulator. An experimental fingerprint of the obstruction is
then measured in a large-gap triangular quantum spin Hall material.",2209.12915v1
2022-10-06,Magnetic excitations in the helical Rashba superconductor,"We investigate the magnetic excitation spectrum in the helical state of a
noncentrosymmetric superconductor with inversion symmetry breaking and strong
Rashba spin-orbit coupling. For this purpose, we derive the general expressions
of the dynamical spin response functions under the presence of strong Rashba
splitting of conduction bands, superconducting gap, and external field which
lead to stabilization of Cooper pairs with finite overall momentum in a helical
state. The latter is characterized by momentum space regions of paired and
unpaired states with different quasiparticle dispersions. The magnetic response
is determined by i) excitations within and between both paired and unpaired
regions ii) anomalous coherence factors and iii) additional spin matrix
elements due to helical Rashba spin texture of bands. We show that as a
consequence typical correlated real space and spin space anisotropies appear in
the dynamical susceptibility which would be observable as a characteristic
fingerprint for a helical superconducting state in inelastic neutron scattering
investigations.",2210.03059v1
2022-10-17,Spin Hall angle in single-layer graphene,"We investigate the spin Hall effect in a single-layer graphene device with
disorder and interface-induced spin-orbit coupling. Our graphene device is
connected to four semi-infinite leads that are embedded in a
{Landauer-B\""uttiker} setup for quantum transport. We show that the spin Hall
angle of graphene devices exhibits mesoscopic fluctuations that are similar to
metal devices. Furthermore, the product between the {maximum spin Hall angle
deviation} and dimensionless longitudinal conductivity follows a universal
relationship $\Theta_{sH} \times \sigma = 0.18$. Finally, we compare the
universal relation with recent experimental data and numerically exact
real-space simulations from the tight-binding model.",2210.09393v1
2022-12-08,Semiclassical analysis of Dirac fields on curved spacetime,"We present a semiclassical analysis for Dirac fields on an arbitrary
spacetime background and in the presence of a fixed electromagnetic field. Our
approach is based on a Wentzel-Kramers-Brillouin approximation, and the results
are analyzed at leading and next-to-leading order in the small expansion
parameter $\hbar$. Taking into account the spin-orbit coupling between the
internal and external degrees of freedom of wave packets, we derive effective
ray equations with spin-dependent terms. These equations describe the
gravitational spin Hall effect of localized Dirac wave packets. We treat both
massive and massless Dirac fields and show how a covariantly defined Berry
connection and the associated Berry curvature govern the semiclassical
dynamics. The gravitational spin Hall equations are shown to be particular
cases of the Mathisson-Papapetrou equations for spinning objects.",2212.04414v2
2023-01-08,Switchable Giant Bulk Photocurrents and Photo-spin-currents in Monolayer PT-symmetric Anti-ferromagnet MnPSe3,"Converting light into steady currents and spin-currents in two-dimensional
(2D) platform is essential for future energy harvesting and spintronics. We
show that the giant and modulable bulk photovoltaic effects (BPVEs) can be
achieved in air-stable 2D antiferromagnet (AFM) monolayer MnPSe3, with
nonlinear photoconductance > 4000 nm$\cdot\mu$A/V2 and photo-spin-conductance >
2000 (nm$\cdot\mu$A/V2 $\hbar$/2e) in the visible spectrum. The propagation and
the spin-polarizations of photocurrents can be switched via simply rotating the
N$\'e$el vector. We unveil that the PT-symmetry, mirror symmetries, and
spin-orbital-couplings are the keys for the observed sizable and controllable
2D BPVEs. All the results provide insights into the BPVEs of 2D AFM, and
suggest that the layered MnPSe3 is an outstanding 2D platform for energy device
and photo-spintronics.",2301.02985v1
2023-03-24,Andreev reflection in altermagnets,"Recent works have predicted materials featuring bands with a large
spin-splitting distinct from ferromagnetic and relativistically spin-orbit
coupled systems. Materials displaying this property are known as altermagnets
and feature a spin-polarized band structure reminiscent of a $d$-wave
superconducting order parameter. We here consider the contact between an
altermagnet and a superconductor and determine how the altermagnetism affects
the fundamental process of Andreev reflection. We show that the resulting
charge conductance depends strongly on the interfacial orientation of the
altermagnet relative to the superconductor, displaying features similar to
normal metals or ferromagnets. The zero-bias conductance peak present at the
interface in the $d$-wave case are robust toward the presence of an
altermagnetic interaction. Moreover, the spin conductance strongly depends on
the orientation of the altermagnet relative the interface. These results show
how the anisotropic altermagnetic state can be probed by conductance
spectroscopy and how it offers voltage control over charge and spin currents
that are modulated due to superconductivity.",2303.14236v3
2023-05-18,Assembling Kitaev honeycomb spin liquids from arrays of 1D symmetry protected topological phases,"The Kitaev honeycomb model, which is exactly solvable by virtue of an
extensive number of conserved quantities, supports a gapless quantum spin
liquid phase as well as gapped descendants relevant for fault-tolerant quantum
computation. We show that the anomalous edge modes of 1D cluster-state-like
symmetry protected topological (SPT) phases provide natural building blocks for
a variant of the Kitaev model that enjoys only a subextensive number of
conserved quantities. The symmetry of our variant allows a single additional
nearest-neighbor perturbation, corresponding to an anisotropic version of the
$\Gamma$ term studied in the context of Kitaev materials. We determine the
phase diagram of the model using exact diagonalization. Additionally, we use
DMRG to show that the underlying 1D SPT building blocks can emerge from a
ladder Hamiltonian exhibiting only two-spin interactions supplemented by a
Zeeman field. Our approach may inform a new pathway toward realizing Kitaev
honeycomb spin liquids in spin-orbit-coupled Mott insulators.",2305.11221v1
2023-09-25,The influence of antiferromagnetic spin cantings on the magnetic helix pitch in cubic helimagnets,"In cubic helimagnets MnSi and Cu2OSeO3 with their nearly isotropic magnetic
properties, the magnetic structure undergoes helical deformation, which is
almost completely determined by the helicoid wavenumber k = D / J, where
magnetization field stiffness J is associated with isotropic spin exchange, and
D is a pseudoscalar value characterizing the antisymmetric
Dzyaloshinskii-Moriya (DM) interaction. While the wavenumber can be measured
directly in a diffraction experiment, the values of J and D can be calculated
from the constants of pair spin interactions, which enter as parameters into
the Heisenberg energy. However, the available analytical expression for D,
which is of the first order in the spin-orbit coupling (SOC), has significant
problems with accuracy. Here we show that hardly observable distortions of the
magnetic structure, namely the antiferromagnetic spin cantings, can
significantly change the constant D in the next approximation in SOC, thus
affecting the wavenumber of magnetic helicoids. The obtained analytical
expressions agree with the results of numerical simulation of magnetic helices
in Cu2OSeO3 to within a few percent.",2309.14480v1
2023-12-01,Incommensurate Spiral Spin Order in CaMn$_2$Bi$_2$ observed via High Pressure Neutron Diffraction,"High pressure neutron diffraction is employed to investigate the magnetic
behavior of CaMn$_2$Bi$_2$ in extreme conditions. In contrast to
antiferromagnetic ordering on Mn atoms reported at ambient pressure, our
results reveal that at high pressure, incommensurate spiral spin order emerges
due to the interplay between magnetism on the Mn atoms and strong spin-orbit
coupling on the Bi atoms: sinusoidal spin order is observed at pressures as
high as 7.4 GPa. Competing antiferromagnetic order is observed at different
temperatures in the partially frustrated lattice. This research provides a
unique toolbox for conducting experimental magnetic and spin dynamics studies
on magnetic quantum materials via high pressure neutron diffraction.",2312.00397v1
2024-01-16,Spin Waves in Ferrimagnets near the Angular Magnetization Compensation Temperature: A Micromagnetic Study,"Spin wave propagation along a ferrimagnetic strip with out-of-plane
magnetization is studied by means of micromagnetic simulations. The
ferrimagnetic material is considered as formed by two antiferromagnetically
coupled sublattices. Two critical temperatures can be defined for such systems:
that of magnetization compensation and that of angular momentum compensation,
both different due to distinct Land\'e factors for each sub-lattice. Spin waves
in the strip are excited by a spin current injected at one of its edges. The
obtained dispersion diagrams show exchange-dominated forward volume spin waves.
For a given excitation frequency, N\'eel vector describes highly eccentric
orbits, the eccentricity depending on temperature, whose semi-major axis are
oriented differently at distinct locations on the FiM strip.",2401.08235v1
2006-07-25,The Structure of Hydrated Electron. Part 1. Magnetic Resonance of Internally Trapping Water Anions: A Density Functional Theory Study,"Density functional theory (DFT) is used to rationalize magnetic parameters of
hydrated electron trapped in alkaline glasses as observed using Electron
Paramagnetic Resonance (EPR) and Electron Spin Echo Envelope Modulation (ESEEM)
spectroscopies. To this end, model water cluster anions (n=4-8 and n=20,24)
that localize the electron internally are examined. It is shown that EPR
parameters of such water anions (such as hyperfine coupling tensors of H/D
nuclei in the water molecules) are defined mainly by the cavity size and the
coordination number of the electron; the water molecules in the second
solvation shell play a relatively minor role. An idealized model of hydrated
electron (that is usually attributed to L. Kevan) in which six hydroxyl groups
arranged in an octahedral pattern point towards the common center is shown to
provide the closest match to the experimental parameters, such as isotropic and
anisotropic hyperfine coupling constants for the protons (estimated from
ESEEM), the second moment of the EPR spectra, and the radius of gyration. The
salient feature of these DFT models is the significant transfer (10-20%) of
spin density into the frontal O 2p orbitals of water molecules. Spin bond
polarization involving these oxygen orbitals accounts for small, negative
hyperfine coupling constants for protons in hydroxyl groups that form the
electron-trapping cavity. In Part 2, these results are generalized for more
realistic geometries of core anions obtained using a dynamic one-electron mixed
qunatum/classical molecular dynamics model.",0607228v1
2012-10-29,Interaction proximity effect at the interface between a superconductor and a topological insulator quantum well,"A material whose electrons are correlated can affect electron dynamics across
the interface with another material. Such a ""proximity effect"" can have several
manifestations, from order parameter leakage to generated effective
interactions. The resulting combination of induced electron correlations and
their intrinsic dynamics at the surface of the affected material can give rise
to qualitatively new quantum states. For example, the leaking of a
superconducting order parameter into certain Rashba spin-orbit-coupled
materials has been recently identified as a path to creating ""topological
superconductors"" that can host Majorana particles of use in quantum computing.
Here we analyze the other aspects of the superconducting proximity effect. The
proximity-induced interactions are a promising path to incompressible quantum
liquids with non-Abelian fractional quasiparticles in topological insulator
quantum wells, which could also find applications in topological quantum
computing. We discuss the operational and design principles of a
heterostructure device that could realize such states. We apply
field-theoretical methods to characterize the properties of induced
interactions via the electron-phonon coupling and Cooper pair tunneling across
the interface. We argue that bound-state Cooper pairs can be stabilized by the
interaction proximity effect inside a topological insulator quantum well at
experimentally observable energy scales. The condensation of spinful triplet
pairs, enabled by the Rashba spin-orbit coupling and tunable by gate voltage,
would lead to novel superconducting states and fractional topological
insulators.",1210.7821v2
2015-05-19,Stanene: Atomically Thick Free-standing Layer of 2D Hexagonal Tin,"Two dimensional (2D) layered materials have recently gained renewed interest
due to their exotic electronic properties along with high specific surface
area. The prospects of exploiting these properties in sensing, catalysis,
energy storage, protective coatings and electrochromism have witnessed a
paradigm shift towards the exploration of these sophisticated 2D materials. The
exemplary performance of graphene (1) which is among the first of these
elemental 2D materials have initiated a runaway effect in the pursuit of
studying alternative 2D materials. Even though graphene has tunable exotic
electronic properties (2), the spin-orbit (SO) coupling is weak (3) limiting
its applications as spin filters, topological insulators etc. Topological
insulators by their very nature force the electrons to travel on the surface at
very high speeds thereby finding useful applications in electronic and photonic
devices. Exploration of group IV elements using first principles calculations
have revealed that the SO coupling increases as the atomic weight of the basis
atoms in the honeycomb lattice (4). Tin is one of the heaviest elements in this
series having strong spin-orbit coupling making it a promising applicant for
room temperature topological insulator. Thus there is an urgent need to
discover novel 2D materials in the post graphene age to overcome its
deficiencies. We have synthesized and investigated the optical transitions in
2D material referred to as few-layer stanene (FLS). These are analogous to
few-layer graphene and can be visualized by replacing carbon atoms by tin on a
graphene lattice. We have been able to synthesize from mono to few atomic
layers of free standing stanene and characterize them optically using UV-Vis
absorption, Raman and photoluminescence spectroscopy. First principles
calculations have been performed to interpret experimental results.",1505.05062v1
2020-12-24,Energy scales in 4f1 delafossite magnets: crystal-field splittings larger than the strength of spin-orbit coupling in KCeO2,"Ytterbium-based delafossites with effective S=1/2 moments are investigated
intensively as candidates for quantum spin-liquid ground states. While the
synthesis of related cerium compounds has also been reported,many important
details concerning their crystal, electronic, and magnetic structures are
unclear. Here we analyze the S=1/2 system KCeO2, combining complementary
theoretical methods. The lattice geometry was optimized and the band structure
investigated using density functional theory extended to the level of a GGA+U
calculation in order to reproduce the correct insulating behavior. The Ce 4f1
states were then analyzed in more detail with the help of ab initio
wave-function-based computations. Unusually large effective crystal-field
splittings of up to 320 meV are predicted, which puts KCeO2 in the strong field
coupling regime. Our results reveal a subtle interplay between ligand-cage
electrostatics and the trigonal field generated by the extended crystalline
surroundings, relevant in the context of recent studies on tuning the nature of
the ground-state wave function in 4f triangular-lattice and pyrochlore
compounds. It also makes KCeO2 an interesting model system in relation to the
effect of large crystal-field splittings on the anisotropy of intersite
exchange in spin-orbit coupled quantum magnets.",2012.13174v1
2018-07-04,"Spin-orbit coupling driven insulating state in hexagonal iridates Sr3MIrO6 (M = Sr, Na and Li)","The spin-orbit coupling (SOC) interactions, electron correlation effects and
Hund coupling cooperate and compete with each other, leading to novel
properties, quantum phase and non-trivial topological electronic behavior in
iridium oxides. Because of the well separated IrO6 octahedra approaching cubic
crystal-field limit, the hexagonal iridates Sr3MIrO6 (M = Sr, Na and Li) serves
as a canonical model system to investigate the underlying physical properties
that arises from the novel Jeff state. Based on density functional theory
calculations complemented by Green's function methods, we systematically
explore the critical role of SOC on the electronic structure and magnetic
properties of Sr3MIrO6. The crystal-field splitting combined with correlation
effects are insufficient to account for the insulating nature, but the SOC
interactions is the intrinsic source to trigger the insulating ground states in
these hexagonal iridates. The decreasing geometry connectivity of IrO6
octahedra gives rise to the increasing of effective electronic correlations and
SOC interactions, tuning the hexagonal iridates from low-spin Jeff = 1/2 states
with large local magnetic moments for the Ir4+ (5d5) ions in Sr4IrO6 to
nonmagnetic singlet Jeff = 0 states without magnetic moments for the Ir5+ (5d4)
ions in Sr3NaIrO6 and Sr3LiIrO6. The theoretical calculated results are in good
agreement with available experimental data, and explain the magnetic properties
of Sr3MIrO6 well.",1807.01807v1
2020-11-17,Competing energy scales in topological superconducting heterostructures,"Artificially engineered topological superconductivity has emerged as a viable
route to create Majorana modes, exotic quasiparticles which have raised great
expectations for storing and manipulating information in topological quantum
computational schemes. The essential ingredients for their realization are spin
non-degenerate metallic states proximitized to an s-wave superconductor. In
this context, proximity-induced superconductivity in materials with a sizable
spin-orbit coupling has been heavily investigated in recent years. Although
there is convincing evidence that superconductivity may indeed be induced, it
has been difficult to elucidate its topological nature. In this work, we
systematically engineer an artificial topological superconductor by
progressively introducing superconductivity (Nb) into metals with strong
spin-orbital coupling (Pt) and 3D topological surface states (Bi2Te3). Through
a longitudinal study of the character of superconducting vortices within s-wave
superconducting Nb and proximity-coupled Nb/Pt and Nb/Bi2Te3, we detect the
emergence of a zero-bias peak that is directly linked to the presence of
topological surface states. Supported by a detailed theoretical model, our
results are rationalized in terms of competing energy trends which are found to
impose an upper limit to the size of the minigap separating Majorana and
trivial modes, its size being ultimately linked to fundamental materials
properties.",2011.08812v1
2017-07-26,High-buckled R3 stanene with topologically nontrivial energy gap,"Stanene has been predicted to be a two-dimensional topological insulator
(2DTI). Its low-buckled atomic geometry and the enhanced spin-orbit coupling
are expected to cause a prominent quantum spin hall (QSH) effect. However, most
of the experimentally grown stanene to date displays a metallic state without a
real gap, possibly due to the chemical coupling with the substrate and the
stress applied by the substrate. Here,we demonstrate an efficient way of tuning
the atomic buckling in stanene to open a topologically nontrivial energy gap.
Via tuning the growth kinetics, we obtain not only the low-buckled 1x1 stanene
but also an unexpected high-buckled R3xR3 stanene on the Bi(111) substrate.
Scanning tunneling microscopy (STM) study combined with density functional
theory (DFT) calculation confirms that the R3xR3 stanene is a distorted 1x1
structure with a high-buckled Sn in every three 1x1 unit cells. The
high-buckled R3xR3 stanene favors a large band inversion at the {\Gamma} point,
and the spin orbital coupling open a topologically nontrivial energy gap. The
existence of edge states as verified in both STM measurement and DFT
calculation further confirms the topology of the R3xR3 stanene. This study
provides an alternate way to tune the topology of monolayer 2DTI materials.",1707.08657v1
2018-04-30,Networks of Coadjoint Orbits: from Geometric to Statistical Mechanics,"A class of network models with symmetry group $G$ that evolve as a
Lie-Poisson system is derived from the framework of geometric mechanics, which
generalises the classical Heisenberg model studied in statistical mechanics. We
considered two ways of coupling the spins: one via the momentum and the other
via the position and studied in details the equilibrium solutions and their
corresponding nonlinear stability properties using the energy-Casimir method.
We then took the example $G=SO(3)$ and saw that the momentum-coupled system
reduces to the classical Heisenberg model with massive spins and the
position-coupled case reduces to a new system that has a broken symmetry group
$SO(3)/SO(2)$ similar to the heavy top. In the latter system, we numerically
observed an interesting synchronisation-like phenomenon for a certain class of
initial conditions. Adding a type of noise and dissipation that preserves the
coadjoint orbit of the network model, we found that the invariant measure is
given by the Gibbs measure, from which the notion of temperature is defined. We
then observed a surprising `triple-humped' phase transition in the heavy
top-like lattice model, where the spins switched from one equilibrium position
to another before losing magnetisation as we increased the temperature. This
work is only a first step towards connecting geometric mechanics with
statistical mechanics and several interesting problems are open for further
investigation.",1804.11139v1
2015-12-13,Hermitian spin-orbit Hamiltonians on a surface in orthogonal curvilinear coordinates: a new practical approach,"The Hermitian Hamiltonian of a spin one-half particle with spin-orbit
coupling (SOC) confined to a surface that is embedded in a three-dimensional
space spanned by a general Orthogonal Curvilinear Coordinate (OCC) is
constructed. A gauge field formalism, where the SOC is expressed as a
non-Abelian $SU(2)$ gauge field is used. A new practical approach, based on the
physical argument that upon confining the particle to the surface by a
potential, then it is the physical Hermitian momentum operator transverse to
the surface, rather than just the derivative with respect to the transverse
coordinate that should be dropped from the Hamiltonian.Doing so, it is shown
that the Hermitian Hamiltonian for SOC is obtained with the geometric potential
and the geometric kinetic energy terms emerging naturally. The geometric
potential is shown to represent a coupling between the transverse component of
the gauge field and the mean curvature of the surface that replaces the
coupling between the transverse momentum and the gauge field. The most general
Hermitian Hamiltonian with linear SOC on a general surface embedded in any 3D
OCC system is reported. Explicit plug-and-play formulae for this Hamiltonian on
the surfaces of a cylinder, a sphere and a torus are given. The formalism is
applied to the Rashba SOC in three dimensions (3D RSOC) and the explicit
expressions for the surface Hamiltonians on these three geometries are worked
out.",1512.08719v1
2017-10-18,Models of spin-orbit coupled oligomers,"We address the stability and dynamics of eigenmodes in linearly-shaped
strings (dimers, trimers, tetramers, and pentamers) built of droplets of a
binary Bose-Einstein condensate (BEC). The binary BEC is composed of atoms in
two pseudo-spin states with attractive interactions, dressed by properly
arranged laser fields, which induce the (pseudo-) spin-orbit (SO) coupling. We
demonstrate that the SO-coupling terms help to create eigenmodes of particular
types in the strings. Dimer, trimer, and pentamer eigenmodes of the linear
system, which correspond to the zero eigenvalue (EV, alias chemical potential)
extend into the nonlinear ones, keeping an exact analytical form, while
tetramers do not admit such a continuation, because the respective spectrum
does not contain a zero EV. Stability areas of these modes shrink with the
increasing nonlinearity. Besides these modes, other types of nonlinear states,
which are produced by the continuation of their linear counterparts
corresponding to some nonzero EVs, are found in a numerical form (including
ones for the tetramer system). They are stable in nearly entire existence
regions in trimer and pentamer systems, but only in a very small area for the
tetramers. Similar results are also obtained, but not displayed in detail, for
hexa- and septamers.",1710.06802v1
2020-02-27,Controlling in-gap end states by linking nonmagnetic atoms and artificially-constructed spin chains on superconductors,"Chains of magnetic atoms with either strong spin-orbit coupling or spiral
magnetic order which are proximity-coupled to superconducting substrates can
host topologically non-trivial Majorana bound states. The experimental
signature of these states consists of spectral weight at the Fermi energy and
spatially localized near the ends of the chain. However, topologically trivial
Yu-Shiba-Rusinov in-gap states localized near the ends of the chain can lead to
similar spectra. Here, we explore a protocol to disentangle these contributions
by artificially augmenting a candidate Majorana spin chain with
orbitally-compatible nonmagnetic atoms. Combining scanning tunneling
spectroscopy with ab-initio and tight-binding calculations, we realize a sharp
spatial transition between the proximity-coupled spiral magnetic order and the
non-magnetic superconducting wire termination, with persistent zero-energy
spectral weight localized at either end of the magnetic spiral. Our findings
open a new path towards the control of the spatial position of in-gap end
states, trivial or Majorana, via different chain terminations, and the
realization of designer Majorana chain networks for demonstrating topological
quantum computation.",2002.12294v2
2019-12-16,Stable multi-peak vector solitons in spin-orbit coupled spin-1 polar condensates,"We demonstrate the formation of multi-peak three-component stationary stripe
vector solitons in a quasi-one-dimensional spin-orbit-coupled hyper-fine spin
$F = 1$ polar Bose-Einstein condensate. The present investigation is carried
out through a numerical solution by imaginary-time propagation and an analytic
variational approximation of the underlying mean-field Gross-Pitaevskii
equation. Simple analytic results for energy and component densities were found
to be in excellent agreement with the numerical results for solitons with more
than 100 pronounced maxima and minima. The vector solitons are one of the two
types: dark-bright-dark or bright-dark-bright. In the former a maximum density
in component $ F_z = 0 $ at the center is accompanied by a zero in components
$F_z = \pm 1$. The opposite happens in the latter case. The vector solitons are
demonstrated to be mobile and dynamically stable. The collision between two
such vector solitons is found to be quasi elastic at large velocities with the
conservation of total density of each vector soliton. However, at very small
velocity, the collision is inelastic with a destruction of the initial vector
solitons. It is possible to observe and study the predicted SO-coupled vector
solitons in a laboratory.",1912.07675v1
2016-12-15,Heisenberg and Dzyaloshinskii-Moriya interactions controlled by molecular packing in tri-nuclear organometallic clusters,"Motivated by recent synthetic and theoretical progress we consider magnetism
in crystals of multi-nuclear organometallic complexes. We calculate the
Heisenberg symmetric exchange and the Dzyaloshinskii-Moriya antisymmetric
exchange. We show how, in the absence of spin-orbit coupling, the interplay of
electronic correlations and quantum interference leads to a quasi-one
dimensional effective spin model in a typical tri-nuclear complex,
Mo$_3$S$_7$(dmit)$_3$, despite its underlying three dimensional band structure.
We show that both intra- and inter-molecular spin-orbit coupling can cause an
effective Dzyaloshinskii-Moriya interaction. Furthermore, we show that, even
for an isolated pair of molecules the relative orientation of the molecules
controls the nature of the Dzyaloshinskii-Moriya coupling. We show that
interference effects also play a crucial role in determining the
Dzyaloshinskii-Moriya interaction. Thus, we argue, that multi-nuclear
organometallic complexes represent an ideal platform to investigate the effects
of Dzyaloshinskii-Moriya interactions on quantum magnets.",1612.04926v3
2022-02-23,Secular Spin-orbit Resonances of Black Hole Binaries in AGN Disks,"The spin-orbit misalignment of stellar-mass black hole (sBH) binaries provide
important constraints on the formation channels of merging sBHs. Here, we study
the role of secular spin-orbit resonance in the evolution of a sBH binary
component around a supermassive BH (SMBH) in an AGN disk. We consider the sBH's
spin-precession due to the $J_2$ moment introduced by a circum-sBH disk within
the warping/breaking radius of the disk. We find that the sBH's spin-orbit
misalignment (obliquity) can be excited via spin-orbit resonance between the
sBH binary's orbital nodal precession and the sBH spin-precession driven by a
massive circum-sBH disk. Using an $\alpha$-disk model with
Bondi-Hoyle-Lyttleton accretion, the resonances typically occur for sBH
binaries with semi-major axis of $1$AU, and at a distance of $\sim 1000$AU
around a $10^7$\msun SMBH. The spin-orbit resonances can lead to high sBH
obliquities, and a broad distribution of sBH binary spin-spin misalignments.
However, we note that the Bondi-Hoyle-Lyttleton accretion is much higher than
that of Eddington accretion, which typically results in spin precession being
too low to trigger spin-orbit resonances. Thus, the secular spin-orbit
resonances can be quite rare for sBHs in AGN disks.",2202.11739v2
1996-10-15,Interlayer exchange coupling in Fe/Cr multilayers,"We investigate the origin of the long period oscillation of the interlayer
exchange coupling in Fe/Cr trilayer systems. Within the stationary phase
approximation the periods of the oscillations are associated with extremal
vectors of the Fermi sphere of Cr. Using a realistic tight-binding model with
spin-orbit interaction we calculate the coupling strength for each extremal
vector based on the spin-asymmetry of the reflection amplitude for a
propagating state impinging from the Cr to Fe layer. We find that for (001) and
(110) growth direction the biggest coupling strength comes from the extremal
vector centered at the ellipsoid N of the Fermi surface of Cr.",9610121v1
2006-10-19,Dzyaloshinsky-Moriya antisymmetric exchange coupling in cuprates: Oxygen effects,"We revisit a problem of Dzyaloshinsky-Moriya antisymmetric exchange coupling
for a single bond in cuprates specifying the local spin-orbital contributions
to Dzyaloshinsky vector focusing on the oxygen term. The Dzyaloshinsky vector
and respective weak ferromagnetic moment is shown to be a superposition of
comparable and, sometimes, competing local Cu and O contributions. The
intermediate oxygen $^{17}$O Knight shift is shown to be an effective tool to
inspect the effects of Dzyaloshinsky-Moriya coupling in an external magnetic
field. We predict the effect of $strong$ oxygen weak antiferromagnetism in
edge-shared CuO$_2$ chains due to uncompensated oxygen Dzyaloshinsky vectors.
Finally, we revisit the effects of symmetric spin anisotropy, in particular,
those directly induced by Dzyaloshinsky-Moriya coupling.",0610537v1
2012-06-26,Temperature dependence of electronic transport through molecular magnets in the Kondo regime,"The effects of finite temperature in transport through nanoscopic systems
exhibiting uniaxial magnetic anisotropy D, such as molecular magnets, adatoms,
or quantum dots side-coupled to a large spin are analyzed in the Kondo regime.
The linear-response conductance is calculated by means of the full
density-matrix numerical renormalization group method as a function of
temperature T, magnetic anisotropy D, and exchange coupling J between the
molecule's core spin and the orbital level. It is shown that such system
displays a two-stage Kondo effect as a function of temperature and a quantum
phase transition as a function of the exchange coupling J. Moreover, additional
peaks are found in the linear conductance for temperatures of the order of
T\sim|J| and T\simD. It is also shown that the conductance variation with T
remarkably depends on the sign of the exchange coupling J.",1206.6069v2
2012-10-01,Magnetic impurities in graphane with dehydrogenated channels,"We have investigated the electronic and magnetic response of a single Fe atom
and a pair of interacting Fe atoms placed in patterned dehydrogenated channels
in graphane within the framework of density functional theory. We have
considered two channels: ""armchair"" and ""zigzag"" channels. Fully relaxed
calculations have been carried out for three different channel widths. Our
calculations reveal that the response to the magnetic impurities is very
different for these two channels. We have also shown that one can stabilize
magnetic impurities (Fe in the present case) along the channels of bare carbon
atoms, giving rise to a magnetic insulator or a spin gapless semiconductor. Our
calculations with spin-orbit coupling shows a large in-plane magnetic
anisotropy energy for the case of the armchair channel. The magnetic exchange
coupling between two Fe atoms placed in the semiconducting channel with an
armchair edge is very weakly ferromagnetic whereas a fairly strong
ferromagnetic coupling is observed for reasonable separations between Fe atoms
in the zigzag-edged metallic channel with the coupling mediated by the bare
carbon atoms. The possibility of realizing an ultrathin device with interesting
magnetic properties is discussed.",1210.0465v2
2012-01-19,Emergence of Chiral Magnetism in Spinor Bose-Einstein Condensate with Rashba Coupling,"Hydrodynamic theory of the spinor BEC condensate with Rashba spin-orbit
coupling is presented. A close mathematical analogy of the Rashba-BEC model to
the recently developed theory of chiral magnetism is found. Hydrodynamic
equations for mass density, superfluid velocity, and the local magnetization
are derived. The mass current is shown to contain an extra term proportional to
the magnetization direction, as a result of the Rashba coupling. Elementary
excitations around the two known ground states of the Rashba-BEC Hamiltonian,
the plane-wave and the stripe states, are worked out in the hydrodynamic
framework, highlighting the cross-coupling of spin and superflow velocity
excitations due to the Rashba term.",1201.3958v2
2014-06-12,Ferrimagnetism in the double perovskite Ca2FeOsO6: a density functional study,"Using density functional calculations, we find that the newly synthesized
Ca$_2$FeOsO$_6$ has the high-spin Fe$^{3+}$ ($3d^5$)-Os$^{5+}$ ($5d^3$) state.
The octahedral Os$^{5+}$ ion has a large intrinsic exchange splitting, and its
$t_{2g\uparrow}^3$ configuration makes the spin-orbit coupling ineffective.
Moreover, there is a strong antiferromagnetic (AF) coupling between the
neighboring Fe$^{3+}$ ($S$ = 5/2) and Os$^{5+}$ ($S$ = -3/2), but the AF
couplings within both the fcc Fe$^{3+}$ and Os$^{5+}$ sublattices are one order
of magnitude weaker. Therefore, a magnetic frustration is suppressed and a
stable ferrimagnetic (FiM) ground state appears. This FiM order is due to the
virtual hopping of the $t_{2g}$ electrons from Os$^{5+}$ ($t_{2g\downarrow}^3$)
to Fe$^{3+}$ ($t_{2g\uparrow}^3e_{g\uparrow}^2$). However, if the experimental
bended Fe$^{3+}$-O$^{2-}$-Os$^{5+}$ exchange path gets straight, the $e_g$
hopping from Fe$^{3+}$ ($t_{2g\uparrow}^3e_{g\uparrow}^2$) to Os$^{5+}$
($t_{2g\uparrow}^3$) would be facilitated and then a ferromagnetic (FM)
coupling would occur.",1406.3101v1
2016-12-04,Massless Dirac-like fermions under external fields: a nonminimal coupling approach,"We investigate the unusual properties of quasirelativistic massless fermions
under a magnetic or electric field by means of nonminimal couplings. Within
this approach, the spin-orbit coupling (SOC) effects are properly generated in
the energy spectrum of the quasiparticles. By including a magnetic field, $B$,
we show that the spin splitting of Landau Levels (LL) obeys a $\sqrt{B}$ linear
dependence with SOC, typical of relativistic particles. Moreover, our
calculated spectrum of LLs resembles the behavior of the three-dimensional (3D)
massless Kane fermions. Using a nonminimal coupling with an external electric
field, we demonstrate that a Rashba-like SOC naturally appears into the
relativistic equations and apply to the case of two-dimensional (2D) massless
Dirac fermions. Still considering our proposed approach, the Hall conductivity
is also computed for the 2D case under transverse electric field both at zero
and finite temperatures for a general chemical potential. The results feature a
typical quantization of the Hall conductivity at low temperatures, when the
absolute value of the gap opened by the electric field is larger than the
considered chemical potential.",1612.01148v1
2023-03-09,Ultrafast Phonon-Diffuse Scattering as a Tool for Observing Chiral Phonons in Monolayer Hexagonal Lattices,"At the 2D limit, hexagonal systems such as monolayer transition metal
dichalcogenides (TMDs) and graphene exhibit unique coupled spin and
momentum-valley physics (valley pseudospin) owing to broken spatial inversion
symmetry and strong spin-orbit coupling. Circularly polarized light provides
the means for pseudospin-selective excitation of excitons (or electrons and
holes) and can yield momentum-valley polarized populations of carriers that are
the subject of proposed valleytronic applications. The chirality of these
excited carriers have important consequences for the available
relaxation/scattering pathways, which must conserve (pseudo)angular momentum as
well as energy. One available relaxation channel that satisfies these
constraints is coupling to chiral phonons. Here we show that chiral
carrier-phonon coupling following valley-polarized photoexcitation is expected
to leads to a strongly valley-polarized chiral phonon distribution that is
directly measurable using ultrafast phonon-diffuse scattering techniques. Using
ab-initio calculations we show how the dynamic phonon occupations and valley
anisotropy determined by nonequilibrium observations can provide a new window
on the physical processes that drive carrier valley-depolarization in monolayer
TMDs.",2303.05562v1
2012-09-07,Quadrupole Susceptibility of Gd-Based Filled Skutterudite Compounds,"It is shown that quadrupole susceptibility can be detected in Gd compounds
contrary to our textbook knowledge that Gd$^{3+}$ ion induces pure spin moment
due to the Hund's rules in an $LS$ coupling scheme. The ground-state multiplet
of Gd$^{3+}$ is always characterized by $J$=7/2, where $J$ denotes total
angular momentum, but in a $j$-$j$ coupling scheme, one $f$ electron in $j$=7/2
octet carries quadrupole moment, while other six electrons fully occupy $j$=5/2
sextet, where $j$ denotes one-electron total angular momentum. For realistic
values of Coulomb interaction and spin-orbit coupling, the ground-state
wavefunction is found to contain significant amount of the $j$-$j$ coupling
component. From the evaluation of quadrupole susceptibility in a simple
mean-field approximation, we point out a possibility to detect the softening of
elastic constant in Gd-based filled skutterudites.",1209.1469v1
2015-06-12,Spin-momentum coupled Bose-Einstein condensates with lattice band pseudospins,"The quantum emulation of spin-momentum coupling (SMC), a crucial ingredient
for the emergence of topological phases, is currently drawing considerable
interest. In previous quantum gas experiments, typically two atomic hyperfine
states were chosen as pseudospins. Here, we report the observation of a new
kind of SMC achieved by loading a Bose-Einstein condensate (BEC) into
periodically driven optical lattices. The s- and p-bands of a static lattice,
which act as pseudospins, are coupled through an additional moving lattice
which induces a momentum dependent coupling between the two pseudospins,
resulting in s-p hybrid Floquet-Bloch bands. We investigate the band structures
by measuring the quasimomentum of the BEC for different velocities and
strengths of the moving lattice and compare our measurements to theoretical
predictions. The realization of SMC with lattice bands as pseudospins paves the
way for engineering novel quantum matter using hybrid orbital bands.",1506.03887v1
2015-11-05,Rashba realization: Raman with RF,"We theoretically explore a Rashba spin-orbit coupling scheme which operates
entirely in the absolute ground state manifold of an alkali atom, thereby
minimizing all inelastic processes. An energy gap between ground eigenstates of
the proposed coupling can be continuously opened or closed by modifying laser
polarizations. Our technique uses far-detuned ""Raman"" laser coupling to create
the Rashba potential, which has the benefit of low spontaneous emission rates.
At these detunings, the Raman matrix elements that link $m_F$ magnetic sublevel
quantum numbers separated by two are also suppressed. These matrix elements are
necessary to produce the Rashba Hamiltonian within a single total angular
momentum $f$ manifold. However, the far-detuned Raman couplings can link the
three XYZ states familiar to quantum chemistry, which possess the necessary
connectivity to realize the Rashba potential. We show that these XYZ states are
essentially the hyperfine spin eigenstates of $^{87}\text{Rb}$ dressed by a
strong radio-frequency magnetic field.",1511.01588v2
2022-01-27,Resonant thermal Hall effect of phonons coupled to dynamical defects,"We present computations of the thermal Hall coefficient of phonons scattering
off a defect with multiple energy levels. Using a microscopic formulation based
on the Kubo formula, we find that the leading contribution perturbative in the
phonon-defect coupling is proportional to the phonon lifetime, and has a
`side-jump' interpretation. Consequently, the thermal Hall angle is independent
of the phonon lifetime. The contribution to the thermal Hall coefficient is at
resonance when the phonon energy equals a defect level spacing. Our results are
obtained for three different defect models, which apply to different correlated
electron materials. For the pseudogap regime of the cuprates, we propose a
model of phonons coupled to an impurity quantum spin in the presence of
quasi-static magnetic order with an isotropic Zeeman coupling to the applied
field, and without spin-orbit interaction.",2201.11681v6
2023-01-03,Anomalous circular phonon dichroism in transition metal dichalcogenides,"A magnetic field can generally induce circular phonon dichroism based on the
formation of Landau levels of electrons. Here, we study the
magnetization-induced circular phonon dichroism in transition metal
dichalcogenides, without forming Landau levels. We find that, instead of the
conventional deformation potential coupling, pseudogauge-type electron-phonon
coupling plays an essential role in the emergence of the phenomenon. As a
concrete example, a large dichroism signal is obtained in monolayer MoTe2 on a
EuO substrate, even without considering Rashba spin-orbit coupling. Due to the
two-dimensional spin-valley-coupled band structure, MoTe2 shows a reciprocal
and nonreciprocal absorption of circularly polarized acoustic phonons upon
reversing the direction of phonon propagation and magnetization, respectively.
By varying the gate voltage, a tunable circular phonon dichroism can be
realized, which paves a way toward different physics and applications of
two-dimensional acoustoelectronics.",2301.00917v1
2005-12-14,Electronic spin precession and interferometry from spin-orbital entanglement in a double quantum dot,"A double quantum dot inserted in parallel between two metallic leads allows
to entangle the electron spin with the orbital (dot index) degree of freedom.
An Aharonov-Bohm orbital phase can then be transferred to the spinor
wavefunction, providing a geometrical control of the spin precession around a
fixed magnetic field. A fully coherent behaviour is obtained in a mixed
orbital/spin Kondo regime. Evidence for the spin precession can be obtained,
either using spin-polarized metallic leads or by placing the double dot in one
branch of a metallic loop.",0512324v3
2012-03-20,"Rovibrational dynamics of the strontium molecule in the A^1Σ_u^+, c^3Π_u, and a^3Σ_u^+ manifold from state-of-the-art ab initio calculations","State-of-the-art ab initio techniques have been applied to compute the
potential energy curves for the electronic states in the A^1\Sigma_u^+,
c^3\Pi_u, and a^3\Sigma_u^+ manifold of the strontium dimer, the spin-orbit and
nonadiabatic coupling matrix elements between the states in the manifold, and
the electric transition dipole moment from the ground X^1\Sigma_g^+ to the
nonrelativistic and relativistic states in the A+c+a manifold. The potential
energy curves and transition moments were obtained with the linear response
(equation of motion) coupled cluster method limited to single, double, and
linear triple excitations for the potentials and limited to single and double
excitations for the transition moments. The spin-orbit and nonadiabatic
coupling matrix elements were computed with the multireference configuration
interaction method limited to single and double excitations. Our results for
the nonrelativistic and relativistic (spin-orbit coupled) potentials deviate
substantially from recent ab initio calculations. The potential energy curve
for the spectroscopically active (1)0_u^+ state is in quantitative agreement
with the empirical potential fitted to high-resolution Fourier transform
spectra [A. Stein, H. Knoeckel, and E. Tiemann, Eur. Phys. J. D 64, 227
(2011)]. The computed ab initio points were fitted to physically sound
analytical expressions, and used in converged coupled channel calculations of
the rovibrational energy levels in the A+c+a manifold and line strengths for
the A^1\Sigma_u^+ <-- X^1\Sigma_g^+ transitions. Positions and lifetimes of
quasi-bound Feshbach resonances lying above the ^1S + ^3P_1 dissociation limit
were also obtained. Our results reproduce (semi)quantitatively the experimental
data observed thus far. Predictions for on-going and future experiments are
also reported.",1203.4524v2
2015-07-13,Ambipolar spin-spin coupling in p$^+$-GaAs,"A novel spin-spin coupling mechanism that occurs during the transport of
spin-polarized minority electrons in semiconductors is described. Unlike the
Coulomb spin drag, this coupling arises from the ambipolar electric field which
is created by the differential movement of the photoelectrons and the
photoholes. Like the Coulomb spin drag, it is a pure spin coupling that does
not affect charge diffusion. Experimentally, the coupling is studied in $p^+$
GaAs using polarized microluminescence. The coupling manifests itself as an
excitation power dependent reduction in the spin polarization at the excitation
spot \textit{without} any change of the spatially averaged spin polarization.",1507.03347v1
2012-12-26,Anomalous spin precession and spin Hall effect in semiconductor quantum wells,"Spin-orbit (SO) interactions give a spin-dependent correction r_so to the
position operator, referred to as the anomalous position operator. We study the
contributions of r_so to the spin-Hall effect (SHE) in quasi two-dimensional
(2D) semiconductor quantum wells with strong band structure SO interactions
that cause spin precession. The skew scattering and side-jump scattering terms
in the SHE vanish, but we identify two additional terms in the SHE, due to
r_so, which have not been considered in the literature so far. One term
reflects the modification of the spin precession due to the action of the
external electric field (the field drives the current in the quantum well),
which produces, via r_so, an effective magnetic field perpendicular to the
plane of the quantum well. The other term reflects a similar modification of
the spin precession due to the action of the electric field created by random
impurities, and appears in a careful formulation of the Born approximation. We
refer to these two effects collectively as anomalous spin precession and we
note that they contribute to the SHE to the first order in the SO coupling
constant even though they formally appear to be of second order. In electron
systems with weak momentum scattering, the contribution of the anomalous spin
precession due to the external electric field equals 1/2 the usual side-jump
SHE, while the additional impurity-dependent contribution depends on the form
of the band structure SO coupling. For band structure SO linear in wave vector
the two additional contributions cancel. For band structure SO cubic in wave
vector only the contribution due to external electric field is present, and can
be detected through its density dependence. In 2D hole systems both anomalous
spin precession contributions vanish identically.",1212.6262v2
2013-02-13,Relativistic mergers of compact binaries in clusters: The fingerprint of the spin,"Dense stellar systems such as globular clusters and dense nuclear clusters
are the breeding ground of sources of gravitational waves for the advanced
detectors LIGO and Virgo. These systems deserve a close study to estimate rates
and parameter distribution. This is not an easy task, since the evolution of a
dense stellar cluster involves the integration of $N$ bodies with high
resolution in time and space and including hard binaries and their encounters
and, in the case of gravitational waves (GWs), one needs to take into account
important relativistic corrections. In this work we present the first
implementation of the effect of spin in mergers in a direct-summation code,
NBODY6. We employ non-spinning post-Newtonian corrections to the Newtonian
accelerations up to 3.5 post-Newtonian (PN) order as well as the spin-orbit
coupling up to next-to-lowest order and the lowest order spin-spin coupling. We
integrate spin precession and add a consistent treatment of mergers. We analyse
the implementation by running a set of two-body experiments and then we run a
set of 500 simulations of a relativistic stellar cluster. In spite of the large
number of mergers in our tests, the application of the algorithm is robust. We
find in particular the formation of a runaway star whose spin decays with the
mass it wins, independently of the initial value of the spins of the stars.
More remarkably, the subset of compact objects that do not undergo many
mergers, and hence represent a more realistic system, has a correlation between
the final absolute spin and the initial choice for the initial distribution,
which could provide us with information about the evolution of spins in dense
clusters once the first detections have started.",1302.3135v2
2017-02-16,Stretchable persistent spin helices in GaAs quantum wells,"The Rashba and Dresselhaus spin-orbit (SO) interactions in 2D electron gases
act as effective magnetic fields with momentum-dependent directions, which
cause spin decay as the spins undergo arbitrary precessions about these
randomly-oriented SO fields due to momentum scattering. Theoretically and
experimentally, it has been established that by fine-tuning the Rashba $\alpha$
and Dresselhaus $\beta$ couplings to equal $\it{fixed}$ strengths
$\alpha=\beta$, the total SO field becomes unidirectional thus rendering the
electron spins immune to dephasing due to momentum scattering. A robust
persistent spin helix (PSH) has already been experimentally realized at this
singular point $\alpha=\beta$. Here we employ the suppression of weak
antilocalization as a sensitive detector for matched SO fields together with a
technique that allows for independent electrical control over the SO couplings
via top gate voltage $V_T$ and back gate voltage $V_B$. We demonstrate for the
first time the gate control of $\beta$ and the $\it{continuous\,locking}$ of
the SO fields at $\alpha=\beta$, i.e., we are able to vary both $\alpha$ and
$\beta$ controllably and continuously with $V_T$ and $V_B$, while keeping them
locked at equal strengths. This makes possible a new concept: ""stretchable
PSHs"", i.e., helical spin patterns with continuously variable pitches $P$ over
a wide parameter range. The extracted spin-diffusion lengths and decay times as
a function of $\alpha/\beta$ show a significant enhancement near
$\alpha/\beta=1$. Since within the continuous-locking regime quantum transport
is diffusive (2D) for charge while ballistic (1D) for spin and thus amenable to
coherent spin control, stretchable PSHs could provide the platform for the much
heralded long-distance communication $\sim 8 - 25$ $\mu$m between solid-state
spin qubits.",1702.05190v2
2018-10-24,Long spin coherence length and bulk-like spin-orbit torque in ferrimagnetic multilayers,"Ferromagnetic spintronics has been a main focus as it offers non-volatile
memory and logic applications through current-induced spin-transfer torques.
Enabling wider applications of such magnetic devices requires a lower switching
current for a smaller cell while keeping the thermal stability of magnetic
cells for non-volatility. As the cell size reduces, however, it becomes
extremely difficult to meet this requirement with ferromagnets because
spin-transfer torque for ferromagnets is a surface torque due to rapid spin
dephasing, leading to the 1/ferromagnet-thickness dependence of the spin-torque
efficiency. Requirement of a larger switching current for a thicker and thus
more thermally stable ferromagnetic cell is the fundamental obstacle for
high-density non-volatile applications with ferromagnets. Theories predicted
that antiferromagnets have a long spin coherence length due to the staggered
spin order on an atomic scale, thereby resolving the above fundamental
limitation. Despite several spin-torque experiments on antiferromagnets and
ferrimagnetic alloys, this prediction has remained unexplored. Here we report a
long spin coherence length and associated bulk-like-torque characteristic in an
antiferromagnetically coupled ferrimagnetic multilayer. We find that a
transverse spin current can pass through > 10 nm-thick ferrimagnetic Co/Tb
multilayers whereas it is entirely absorbed by 1 nm-thick ferromagnetic Co/Ni
multilayer. We also find that the switching efficiency of Co/Tb multilayers
partially reflects a bulk-like-torque characteristic as it increases with the
ferrimagnet-thickness up to 8 nm and then decreases, in clear contrast to
1/thickness-dependence of Co/Ni multilayers. Our results on
antiferromagnetically coupled systems will invigorate researches towards
energy-efficient spintronic technologies.",1810.10404v1
2011-09-04,Isotope sensitive measurement of the hole-nuclear spin interaction in quantum dots,"Decoherence caused by nuclear field fluctuations is a fundamental obstacle to
the realization of quantum information processing using single electron spins.
Alternative proposals have been made to use spin qubits based on valence band
holes having weaker hyperfine coupling. However, it was demonstrated recently
both theoretically and experimentally that the hole hyperfine interaction is
not negligible, although a consistent picture of the mechanism controlling the
magnitude of the hole-nuclear coupling is still lacking. Here we address this
problem by performing isotope selective measurement of the valence band
hyperfine coupling in InGaAs/GaAs, InP/GaInP and GaAs/AlGaAs quantum dots.
Contrary to existing models we find that the hole hyperfine constant along the
growth direction of the structure (normalized by the electron hyperfine
constant) has opposite signs for different isotopes and ranges from -15% to
+15%. We attribute such changes in hole hyperfine constants to the competing
positive contributions of p-symmetry atomic orbitals and the negative
contributions of d-orbitals. Furthermore, we find that the d-symmetry
contribution leads to a new mechanism for hole-nuclear spin flips which may
play an important role in hole spin decoherence. In addition the measured
hyperfine constants enable a fundamentally new approach for verification of the
computed Bloch wavefunctions in the vicinity of nuclei in semiconductor
nanostructures.",1109.0733v3
2018-09-09,Rare-earth chalcogenides: A large family of triangular lattice spin liquid candidate,"Frustrated quantum magnets are expected to host many exotic quantum spin
states like quantum spin liquid (QSL), and have attracted numerous interest in
modern condensed matter physics. The discovery of the triangular lattice spin
liquid candidate YbMgGaO$_4$ stimulated an increasing attention on the
rare-earth-based frustrated magnets with strong spin-orbit coupling. Here we
report the synthesis and characterization of a large family of rare-earth
chalcogenides AReCh$_2$ (A = alkali or monovalent ions, Re = rare earth, Ch =
O, S, Se). The family compounds share the same structure (R$\bar{3}$m) as
YbMgGaO$_4$, and antiferromagnetically coupled rare-earth ions form perfect
triangular layers that are well separated along the $c$-axis. Specific heat and
magnetic susceptibility measurements on NaYbO$_2$, NaYbS$_2$ and NaYbSe$_2$
single crystals and polycrystals, reveal no structural or magnetic transition
down to 50mK. The family, having the simplest structure and chemical formula
among the known QSL candidates, removes the issue on possible exchange
disorders in YbMgGaO$_4$. More excitingly, the rich diversity of the family
members allows tunable charge gaps, variable exchange coupling, and many other
advantages. This makes the family an ideal platform for fundamental research of
QSLs and its promising applications.",1809.03025v2
2018-06-15,Field-free Magnetization Switching by Utilizing the Spin Hall Effect and Interlayer Exchange Coupling of Iridium,"Magnetization switching by spin-orbit torque (SOT) via spin Hall effect
represents as a competitive alternative to that by spin-transfer torque (STT)
used for magnetoresistive random access memory (MRAM), as it does not require
high-density current to go through the tunnel junction. For perpendicular MRAM,
however, SOT driven switching of the free layer requires an external in-plane
field, which poses limitation for viability in practical applications. Here we
demonstrate field-free magnetization switching of a perpendicular magnet by
utilizing an Iridium (Ir) layer. The Ir layer not only provides SOTs via spin
Hall effect, but also induce interlayer exchange coupling with an in-plane
magnetic layer that eliminates the need for the external field. Such dual
functions of the Ir layer allows future build-up of magnetoresistive stacks for
memory and logic applications. Experimental observations show that the SOT
driven field-free magnetization reversal is characterized as domain nucleation
and expansion. Micromagnetic modeling is carried out to provide in-depth
understanding of the perpendicular magnetization reversal process in the
presence of an in-plane exchange coupling field.",1806.05961v4
2021-04-06,Renormalization of spin excitations and Kondo effect in open shell nanographenes,"We study spin excitations and Kondo effect in open-shell nanographenes,
motivated by recent scanning tunneling inelastic spectroscopy experiments.
Specifically, we consider three systems, the triangulene, the extended
triangulene with rocket shape, both with an $S=1$ ground state, and a
triangulene dimer with $S=0$ on account of intermolecular exchange. We focus on
the consequences of hybridization of the nanographene zero-modes with a
conducting substrate on the $dI/dV$ lineshapes associated with spin
excitations. The partially filled nanographene zero-modes coupled to the
conduction electrons in the substrate constitute multi-orbital Anderson
impurity models that we solve in the one-crossing approximation which treats
the coupling to the substrate to infinite order. We find that the coupling to
the substrate leads to (i) renormalization of the spin flip excitation energies
of the bare molecule, (ii) broadening of the spectral features and (iii) the
emergence of zero bias Kondo peaks for the $S=1$ ground states. The calculated
substrate induced shift of the spin excitation energies is found to be
significantly larger than their broadening, which implies that this effect has
to be considered when comparing experimental results and theory.",2104.02503v2
2022-03-04,Exchange interactions and spin dynamics in the layered honeycomb ferromagnet CrI$_3$,"We derive the microscopic spin Hamiltonian for rhombohedral CrI$_3$ using
extensive first-principles density functional theory (DFT) calculations which
incorporate spin-orbit coupling and Hubbard U. Our calculations indicate a
dominant nearest-neighbor ferromagnetic Heisenberg exchange with weaker
further-neighbor Heisenberg terms. In addition, we find a Dzyaloshinskii-Moriya
interaction which primarily drives a topological gap in the spin-wave spectrum
at the Dirac point, and uncover a non-negligible antiferromagnetic Kitaev
coupling between the S=3/2 Cr moments. The out-of-plane magnetic moment is
stabilized by weak symmetric bond-dependent terms and a local single-ion
anisotropy. Using linear spin wave theory, we find that our exchange parameters
are in reasonably good agreement with inelastic neutron scattering (INS)
experiments. Employing classical Monte Carlo simulations, we study the magnetic
phase transition temperature $T_c$ and its evolution with an applied in-plane
magnetic field. We further demonstrate how future high-resolution INS
experiments on the magnon dispersion of single crystals in an in-plane magnetic
field may be used to quantitatively extract the strength of the
antiferromagnetic Kitaev exchange coupling.",2203.02567v1
2022-12-14,Identifying Pauli blockade regimes in bilayer graphene double quantum dots,"Recent experimental observations of current blockades in 2-D material
quantum-dot platforms have opened new avenues for spin and valley-qubit
processing. Motivated by experimental results, we construct a model capturing
the delicate interplay of Coulomb interactions, inter-dot tunneling, Zeeman
splittings, and intrinsic spin-orbit coupling in a double quantum dot structure
to simulate the Pauli blockades. Analyzing the relevant Fock-subspaces of the
generalized Hamiltonian, coupled with the density matrix master equation
technique for transport across the setup, we identify the generic class of
blockade mechanisms. Most importantly, and contrary to what is widely
recognized, we show that conducting and blocking states responsible for the
Pauli-blockades are a result of the coupled effect of all degrees of freedom
and cannot be explained using the spin or the valley pseudo-spin only. We then
numerically predict the regimes where Pauli blockades might occur, and, to this
end, we verify our model against actual experimental data and propose that our
model can be used to generate data sets for different values of parameters with
the ultimate goal of training on a machine learning algorithm. Our work
provides an enabling platform for a predictable theory-aided experimental
realization of single-shot readout of the spin and valley states on DQDs based
on 2D-material platforms.",2212.07208v1
2023-10-18,Large Rashba splittings in bulk and monolayer of BiAs,"Two-dimensional materials with Rashba split bands near the Fermi level are
key to developing upcoming next-generation spintronics. They enable generating,
detecting, and manipulating spin currents without an external magnetic field.
Here, we propose BiAs as a novel layered semiconductor with large Rashba
splitting in bulk and monolayer forms. Using first-principles calculations, we
determined the lowest energy structure of BiAs and its basic electronic
properties. Bulk BiAs has a layered crystal structure with two atoms in a
rhombohedral primitive cell, similar to the parent Bi and As elemental phases.
It is a semiconductor with a narrow and indirect band gap. The spin-orbit
coupling leads to Rashba-Dresselhaus spin splitting and characteristic spin
texture around the L-point in the Brillouin zone of the hexagonal conventional
unit cell, with Rashba energy and Rashba coupling constant for valence
(conduction) band of $E_R$= 137 meV (93 meV) and $\alpha_R$= 6.05 eV\AA~(4.6
eV{\AA}). In monolayer form (i.e., composed of a BiAs bilayer), BiAs has a much
larger and direct band gap at $\Gamma$, with a circular spin texture
characteristic of a pure Rashba effect. The Rashba energy $E_R$= 18 meV and
Rashba coupling constant $\alpha_R$= 1.67 eV{\AA} of monolayer BiAs are quite
large compared to other known 2D materials, and these values are shown to
increase under tensile biaxial strain.",2310.12094v1
2002-03-22,Roles of Electron Correlations in the Spin-Triplet Superconductivity of Sr2RuO4,"We discuss a microscopic mechanism of the spin-tiplet superconductivity in
the quasi-two-dimensional ruthenium oxide Sr2RuO4 on the basis of
two-dimensional three-band Hubbard model. We solve the linearized Eliashberg
equation by taking into account the full momentum-frequency dependence of the
order parameter for the spin-triplet and the spin-singlet states, and estimate
the transition temperature as a function of the Coulomb integrals. The
effective pairing interaction is expanded perturbatively with respect to the
Coulomb interaction at the Ru sites up to the third order. As a result, we show
that the spin-triplet p-wave state is more stable than the spin-singlet d-wave
state for moderately strong Coulomb interaction. Our results suggest that one
of the three bands, $\gamma$, plays a dominant role in the superconducting
transition, and the pairing on the other two bands($\alpha$ and $\beta$) is
induced passively through the inter-orbit couplings. The most significant
momentum dependence for the p-wave pairing originates from the vertex
correction terms, while the incommensurate antiferromagnetic spin fluctuations,
which are observed in inelastic neutron scattering experiments, are expected to
disturb the p-wave pairing by enhancing the d-wave pairing. Therefore we can
regard the spin-triplet superconductivity in Sr2RuO4 as one of the natural
results of the electron correlations, and cannot consider as a result of some
strong magnetic fluctuations. We will also mention the normal Fermi liquid
properties of Sr2RuO4.",0203453v2
2005-02-03,Charge-induced maximal spin states of a polynuclear transition-metal complex,"We theoretically investigate the ground state spin of a polynuclear
transition-metal complex as a function of the number of added electrons taking
into account strong electron correlations. Our phenomenological model of the
so-called [$2\times2$]-grid molecule incorporates the relevant electronic
degrees of freedom on the four transition-metal centers (either Fe$^{2+}$ or
Co$^{2+}$) and the four organic bridging ligands. Extra electrons preferably
occupy redox orbitals on the ligands. Magnetic interactions between these
ligands are mediated by transition-metal ions {\em and vice versa}. Using both
perturbation theory and exact diagonalization we find that for certain charge
states the maximally attainable total spin (either $S_{\mathsf{tot}}=3/2$ or
$S_{\mathsf{tot}}=7/2$) may actually be achieved. Due to the Nagaoka mechanism,
all unpaired electron spins couple to a total maximal spin, including unpaired
electron spins on the metal-ions in the case of Co$^{2+}$. The parameters are
chosen to be consistent with cyclovoltammetry experiments in which up to twelve
redox states have been observed. The above effect may also be realized in other
complexes with an appropriate connectivity between the redox sites. The maximal
spin states of such a charge-switchable molecular magnet may be experimentally
observed as spin-blockade effects on the electron tunneling in a three-terminal
transport setup.",0502093v1
2008-02-04,Thermospin Hall effect generated by thermal influence and thermoelectric effect,"In this paper, we present the theoretical predication of a thermospin Hall
effect, in which a transverse spin current can be generated in semiconductors
in the presence of spin-orbit coupling by a frequency-dependent longitudinal
temperature gradient. Because of the thermoelectric effect, there is no net
charge current but there is a heat flow from the hot side to the cold side. We
perform the theoretical calculation of dynamical thermospin Hall conductivity
in a two-dimensional Rashba spintronic system. It has been shown that the
direct interband optical transition dominates the ordering and manipulation of
spin in the generation of a transverse intrinsic spin current. In view of the
role of the thermoelectric effect, the contributions to the thermospin Hall
effect are classified as that originating from a direct contribution of thermal
electronic diffusion and that from the compensatory electron flow in balance
with the thermal diffusion. For a finite system, the analysis yields evidence
that the spin accumulation around the edges of a plate determines the
magnetization. In equilibrium, a field created by a magnetization gradient
emerges in the direction perpendicular to the temperature gradient. The
experimental observation of the thermospin Hall effect is proposed by measuring
the longitudinal temperature difference with the injection of a transverse spin
current and by analyzing the Hall angle. In addition, in order to achieve pure
spin accumulation in the spin Hall effect, an extension of the thermospin Hall
effect for exciting electron-hole pairs in semiconductors is proposed.",0802.0348v1
2011-11-30,Probing Relativistic Astrophysics Around SMBHs: The Suzaku AGN Spin Survey,"In addition to providing vital clues as to the formation and evolution of
black holes, the spin of black holes may be an important energy source in the
Universe. Over the past couple of years, tremendous progress has been made in
the realm of observational measurements of spin. In particular, detailed
characterization and modeling of X-ray spectral features emitted from the inner
regions of black hole accretion disks have allowed us to probe the location of
the innermost stable circular orbit and hence the spin. In this contribution, I
will describe the Suzaku AGN Spin Survey, an on-going Cycle 4--6 Suzaku Key
Project that aims to probe five nearby AGN with sufficient depth that strong
gravity effects and spin can be robustly assessed. Of the three objects for
which we currently have our deep datasets, we can constrain spin in two
(NGC3783, a>0.9; Fairall 9, $a=0.45\pm 0.15$) whereas complexities with the
warm absorber prevent us from reporting results for NGC3516. We conclude with a
brief discussion of spin-dependent selection biases in flux-limited surveys.",1112.0036v1
2014-08-25,Equivalence of ADM Hamiltonian and Effective Field Theory approaches at next-to-next-to-leading order spin1-spin2 coupling of binary inspirals,"The next-to-next-to-leading order spin1-spin2 potential for an inspiralling
binary, that is essential for accuracy to fourth post-Newtonian order, if both
components in the binary are spinning rapidly, has been recently derived
independently via the ADM Hamiltonian and the Effective Field Theory
approaches, using different gauges and variables. Here we show the complete
physical equivalence of the two results, thereby we first prove the equivalence
of the ADM Hamiltonian and the Effective Field Theory approaches at
next-to-next-to-leading order with the inclusion of spins. The main difficulty
in the spinning sectors, which also prescribes the manner in which the
comparison of the two results is tackled here, is the existence of redundant
unphysical spin degrees of freedom, associated with the spin gauge choice of a
point within the extended spinning object for its representative worldline.
After gauge fixing and eliminating the unphysical degrees of freedom of the
spin and its conjugate at the level of the action, we arrive at curved
spacetime generalizations of the Newton-Wigner variables in closed form, which
can also be used to obtain further Hamiltonians, based on an Effective Field
Theory formulation and computation. Finally, we make use of our validated
result to provide gauge invariant relations among the binding energy, angular
momentum, and orbital frequency of an inspiralling binary with generic compact
spinning components to fourth post-Newtonian order, including all known sectors
up to date.",1408.5762v2
2017-08-24,Hierarchy of exchange interactions in the triangular-lattice spin-liquid YbMgGaO$_{4}$,"The spin-1/2 triangular lattice antiferromagnet YbMgGaO$_{4}$ has attracted
recent attention as a quantum spin-liquid candidate with the possible presence
of off-diagonal anisotropic exchange interactions induced by spin-orbit
coupling. Whether a quantum spin-liquid is stabilized or not depends on the
interplay of various exchange interactions with chemical disorder that is
inherent to the layered structure of the compound. We combine time-domain
terahertz spectroscopy and inelastic neutron scattering measurements in the
field polarized state of YbMgGaO$_{4}$ to obtain better microscopic insights on
its exchange interactions. Terahertz spectroscopy in this fashion functions as
high-field electron spin resonance and probes the spin-wave excitations at the
Brillouin zone center, ideally complementing neutron scattering. A global
spin-wave fit to all our spectroscopic data at fields over 4T, informed by the
analysis of the terahertz spectroscopy linewidths, yields stringent constraints
on $g$-factors and exchange interactions. Our results paint YbMgGaO$_{4}$ as an
easy-plane XXZ antiferromagnet with the combined and necessary presence of
sub-leading next-nearest neighbor and weak anisotropic off-diagonal
nearest-neighbor interactions. Moreover, the obtained $g$-factors are
substantially different from previous reports. This works establishes the
hierarchy of exchange interactions in YbMgGaO$_{4}$ from high-field data alone
and thus strongly constrains possible mechanisms responsible for the observed
spin-liquid phenomenology.",1708.07503v3
2018-02-18,Magnetoanisotropic spin-triplet Andreev reflection in ferromagnet-Ising superconductor junctions,"We theoretically study the electronic transport through a ferromagnet-Ising
superconductor junction. A tight-binding Hamiltonian describing the Ising
superconductor is presented. Then by combing the non-equilibrium Green's
function method, the expressions of Andreev reflection coefficient and
conductance are obtained. A strong magnetoanisotropic spin-triplet Andreev
reflection is shown, and the magnetoanisotropic period is $\pi$ instead of
$2\pi$ as in the conventional magnetoanisotropic system. We demonstrate a
significant increase of the spin-triplet Andreev reflection for the single-band
Ising superconductor. Furthermore, the dependence of the Andreev reflection on
the incident energy and incident angle are also investigated. A complete
Andreev reflection can occur when the incident energy is equal to the
superconductor gap, regardless of the Fermi energy (spin polarization) of the
ferromagnet. For the suitable oblique incidence, the spin-triplet Andreev
reflection can be strongly enhanced. In addition, the conductance
spectroscopies of both zero bias and finite bias are studied, and the influence
of gate voltage, exchange energy, and spin-orbit coupling on the conductance
spectroscopy are discussed in detail. The conductance reveals a strong
magnetoanisotropy with period $\pi$ as the Andreev reflection coefficient. When
the magnetization direction is parallel to the junction plane, a large
conductance peak always emerges at the superconductor gap. This work offers a
comprehensive and systematic study of the spin-triplet Andreev reflection, and
has underlying application of $\pi$-periodic spin valve in spintronics.",1802.06414v1
2020-07-25,Fully spin-polarized nodal chain state in half metal LiV$_2$O$_4$,"Nodal-chain fermions, as novel topological states of matter, have been hotly
discussed in non-magnetic materials. Here, by using first-principles
calculations and symmetry analysis, we propose the realization of fully
spin-polarized nodal chain in the half-metal state of LiV$_2$O$_4$ compound.
The material naturally shows a ferromagnetic ground state, and takes on a
half-metal band structure with only the bands from the spin-up channel present
near the Fermi level. The spin-up bands cross with each other, which form two
types of nodal loops. These nodal loops arise from band inversion and are under
the protection of the glide mirror symmetries. Remarkably, we find the nodal
loops conjunct with each other and form chain-like nodal structure.
Correspondingly, the w-shaped surface states are also fully spin-polarized. The
fully spin-polarized nodal chain identified here has not been proposed in
realistic materials before. An effective model is constructed to describe the
nature of nodal chain. The effects of the electron correlation, the lattice
strains, and the spin-orbit coupling are discussed. The fully spin-polarized
bulk nodal-chain and the associated nontrivial surface states for a half-metal
may open novel applications in spintronics.",2007.12842v1
2019-07-18,Topological theory of Lieb-Schultz-Mattis theorems in quantum spin systems,"The Lieb-Schultz-Mattis (LSM) theorem states that a spin system with
translation and spin rotation symmetry and half-integer spin per unit cell does
not admit a gapped symmetric ground state lacking fractionalized excitations.
That is, the ground state must be gapless, spontaneously break a symmetry, or
be a gapped spin liquid. Thus, such systems are natural spin-liquid candidates
if no ordering is found. In this work, we give a much more general criterion
that determines when an LSM-type theorem holds in a spin system. For example,
we consider quantum magnets with arbitrary space group symmetry and/or
spin-orbit coupling. Our criterion is intimately connected to recent work on
the general classification of topological phases with spatial symmetries and
also allows for the computation of an ""anomaly"" associated with the existence
of an LSM theorem. Moreover, our framework is also general enough to encompass
recent works on ""SPT-LSM"" theorems where the system admits a gapped symmetric
ground state without fractionalized excitations, but such a ground state must
still be non-trivial in the sense of symmetry-protected topological (SPT)
phases.",1907.08204v3
2019-10-28,Rashba-like spin splitting along three momentum directions in trigonal layered PtBi2,"Spin-orbit coupling (SOC) has gained much attention for its rich physical
phenomena and highly promising applications in spintronic devices. The
Rashba-type SOC in systems with inversion symmetry breaking is particularly
attractive for spintronics applications since it allows for flexible
manipulation of spin current by external electric fields. Here, we report the
discovery of a giant anisotropic Rashba-like spin splitting along three
momentum directions (3D Rashba-like spin splitting) with a helical spin
polarization around the M points in the Brillouin zone of trigonal layered
PtBi2. Due to its inversion asymmetry and reduced symmetry at the M point,
Rashba-type as well as Dresselhaus-type SOC cooperatively yield a 3D spin
splitting with alpha~ 4.36 eVA in PtBi2. The experimental realization of 3D
Rashba-like spin splitting not only has fundamental interests but also paves
the way to the future exploration of a new class of material with unprecedented
functionalities for spintronics applications.",1910.12671v1
2020-01-16,Characterizing spin-one Kitaev quantum spin liquids,"Material realizations of the bond-dependent Kitaev interactions with $S$=1/2
local moments have vitalized the research in quantum spin liquids. Recently, it
has been proposed that higher-spin analogues of the Kitaev interactions may
also occur in a number of materials with strong spin-orbit coupling. In
contrast to the celebrated $S$=1/2 Kitaev model on the honeycomb lattice, the
higher-spin Kitaev models are not exactly solvable. Hence, the existence of
quantum spin liquids in these systems remains an outstanding question. In this
work, we use the density matrix renormalization group (DMRG) methods to
numerically investigate the $S$=1 Kitaev model with both ferromagnetic (FM) and
antiferromagnetic (AFM) interactions. Using results on a cylindrical geometry
with various circumferences, we conclude that the ground state of the $S$=1
Kitaev model is a quantum spin liquid with a $\mathbb{Z}_2$ gauge structure. We
also put a bound on the excitation gap, which turns out to be quite small. The
magnetic field responses for the FM and AFM models are similar to those of the
$S$=1/2 counterparts. In particular, in the AFM $S$=1 model, a gapless quantum
liquid state emerges in an intermediate window of magnetic field strength,
before the system enters a trivial polarized state.",2001.06000v2
2019-01-17,Interface-driven unusual anomalous Hall effect in MnxGa/Pt bilayers: No correlation with chiral spin structures,"The effects of spin-orbit coupling and symmetry breaking at the interface
between a ferromagnet and heavy metal are particularly important for spin-based
information storage and computation. Recent discoveries suggest they can create
chiral spin structures (e.g. skyrmions), which have often been identified
through the appearance of the bump/dip features of Hall signals, the so-called
topological Hall effect (THE). In this work, however, we have present an
unusual anomalous Hall effect (UAHE) in MnxGa/Pt bilayers and demonstrated that
the features extremely similar to THE can be generated without involving any
chiral spin structures. The low temperature magnetic force microscopy has been
used to explore the magnetic field-dependent behavior of spin structures, and
the UAHE as a function of magnetic field does not peak near the maximal density
of magnetic bubbles. The results unambiguously evidence that the UAHE in
MnxGa/Pt bilayers shows no correlation with chiral spin structures but is
driven by the modified interfacial properties. The bump/dip features of Hall
signals cannot be taken as an unambiguous signature for the emergence of chiral
spin structures, and a wealth of underlying and interesting physics need
explored.",1901.05646v3
2019-02-26,Tunneling-related electron spin relaxation in self-assembled quantum-dot molecules,"We study theoretically spin relaxation during phonon-assisted tunneling of a
single electron in self-assembled InAs/GaAs quantum-dot molecules formed by
vertically stacked dots. We find that the spin-flip tunneling rate may be as
high as 1% of the spin-conserving one. By studying the dependence of spin
relaxation rate on external fields, we show that the process is active at a
considerable rate even without the magnetic field, and scales with the latter
differently than the relaxation in a Zeeman doublet. Utilizing a multiband
$\boldsymbol{k}\cdot\boldsymbol{p}$ theory, we selectively investigate the
impact of various spin-mixing terms in the electron energy and carrier-phonon
interaction Hamiltonians. As a result, we identify the main contribution to
come from the Dresselhaus spin-orbit interaction, which is responsible for the
zero-field effect. At magnetic fields above $\sim$ 15 T, this is surpassed by
other contributions due to the structural shear strain. We also study the
impact of the sample morphology and determine that the misalignment of the dots
may enhance relaxation rate by over an order of magnitude. Finally, via virtual
tunneling at nonzero temperature, the process in question also affects
stationary electrons in tunnel-coupled structures and provides a Zeeman-doublet
spin relaxation channel even without the magnetic field.",1902.10112v2
2019-08-19,Tunable Giant Rashba-type Spin Splitting in PtSe$_2$/MoSe$_2$ Heterostructure,"We report a giant Rashba-type spin splitting in two-dimensional
heterostructure PtSe$_2$/MoSe$_2$ with first-principles calculations. We obtain
a large value of spin splitting energy 110 meV at the momentum offset
$k_0$=0.23 \AA$^{-1}$ around $\mathrm{\Gamma}$ point, arising from the emerging
strong interfacial spin-orbital coupling induced by the hybridization between
PtSe$_2$ and MoSe$_2$. Moreover, we find that the band dispersion close to
valence band maximum around $\Gamma$ point can be well approximated by the
generalized Rashba Hamiltonian $H(k_{||})=-\frac{\hbar^2 k_{||}^2}{2m}+c
k_{||}+\alpha_R \vec{\sigma}\cdot(\vec{k}_{||} \times \vec{z})$. It is found
that the generalized Rashba constant $\eta_R=c+\alpha_R$ in PtSe$_2$/MoSe$_2$
is as large as 1.3 eV$\cdot\text{\AA}$, and importantly $\eta_R$ can be
effectively tuned by biaxial strain and external out-of-plane electrical field,
presenting a potential application for the spin field-effect transistor. In
addition, with the spin-valley physics at $\mathrm{K}/\mathrm{K}'$ points in
monolayer MoSe$_2$, we propose a promising model for spin field-effect
transistor with opto-valleytronic spin injection based on PtSe$_2$/MoSe$_2$
heterostructure.",1908.06689v3
2020-10-13,"Large band splitting with tunable spin polarization in two-dimensional ferroelectric GaXY (X= Se, Te; Y= Cl, Br, I) family","It has been generally accepted that the spin-orbit coupling effect in
noncentrosymmetric materials leads to the band splitting and non-trivial spin
polarization in the momentum space. However, in some cases, zero net spin
polarization in the split bands may occurs, dubbed as the band splitting with
vanishing spin polarization (BSVSP) effect, protected by non-pseudo-polar point
group symmetry of the wave vector in the first Brillouin zone [Liu et. al.,
Nat. Commun. \textbf{10}, 5144 (2019)]. In this paper, by using
first-principles calculations, we show that the BSVSP effect emerges in
two-dimensional (2D) nonsymmorphic Ga$XY$ ($X$= Se, Te; $Y$= Cl, Br, I) family,
a new class of 2D materials having in-plane ferroelectricity. Taking the GaTeCl
monolayer as a representative example, we observe the BSVSP effect in the split
bands along the $X-M$ line located in the proximity of the conduction band
minimum. By using $\vec{k}\cdot\vec{p}$ Hamiltonian derived based on the
symmetry analysis, we clarify that such effect is originated from the
cancellation of the local spin polarization, enforced by non-pseudo-polar
$C_{2v}$ point group symmetry of the wave vector along the $X-M$ line.
Importantly, we find that the spin polarization can be effectively induced by
applying an external out-of-plane electric field, indicating that an
electrically tunable spin polarization for spintronic applications is
plausible.",2010.06191v2
2018-10-04,Ultrafast Spin-To-Charge Conversion at the Surface of Topological Insulator Thin Films,"Strong spin-orbit coupling, resulting in the formation of
spin-momentum-locked surface states, endows topological insulators with
superior spin-to-charge conversion characteristics, though the dynamics that
govern it have remained elusive. Here, we present an all-optical method that
enables unprecedented tracking of the ultrafast dynamics of spin-to-charge
conversion in a prototypical topological insulator Bi$_2$Se$_3$/ferromagnetic
Co heterostructure, down to the sub-picosecond timescale. Compared to pure
Bi$_2$Se$_3$ or Co, we observe a giant terahertz emission in the
heterostructure than originates from spin-to-charge conversion, in which the
topological surface states play a crucial role. We identify a 0.12-picosecond
timescale that sets a technological speed limit of spin-to-charge conversion
processes in topological insulators. In addition, we show that the
spin-to-charge conversion efficiency is temperature independent in Bi$_2$Se$_3$
as expected from the nature of the surface states, paving the way for designing
next-generation high-speed opto-spintronic devices based on topological
insulators at room temperature.",1810.02253v1
2021-03-13,Room-temperature ferroelectric switching of spin-to-charge conversion in GeTe,"Since its birth in the 1990s, semiconductor spintronics has suffered from
poor compatibility with ferromagnets as sources of spin. While the broken
inversion symmetry of some semiconductors may alternatively allow for
spin-charge interconversion, its control by electric fields is volatile.
Ferroelectric Rashba semiconductors stand as appealing materials unifying
semiconductivity, large spin-orbit coupling, and non-volatility endowed by
ferroelectricity. However, their potential for spintronics has been little
explored. Here, we demonstrate the non-volatile, ferroelectric control of
spin-to-charge conversion at room temperature in epitaxial GeTe films. We show
that ferroelectric switching by electrical gating is possible in GeTe despite
its high carrier density. We reveal a spin-to-charge conversion as effective as
in Pt, but whose sign is controlled by the orientation of the ferroelectric
polarization. The comparison between theoretical and experimental data suggests
that spin Hall effect plays a major role for switchable conversion. These
results open a route towards devices combining spin-based logic and memory
integrated into a silicon-compatible material.",2103.07646v1
2021-08-20,Tilted spin current generated by the collinear antiferromagnet RuO2,"We report measurements demonstrating that when the Neel vector of the
collinear antiferromagnet RuO2 is appropriately canted relative to the sample
plane, the antiferromagnet generates a substantial out of plane damping-like
torque. The measurements are in good accord with predictions that when an
electric field, E is applied to the spin split band structure of RuO2 it can
cause a strong transverse spin current even in the absence of spin-orbit
coupling. This produces characteristic changes in all three components of the E
induced torque vector as a function of the angle of E relative to the crystal
axes, corresponding to a spin current with a well defined tilted spin
orientation s approximately (but not exactly) parallel to the Neel vector,
flowing perpendicular to both E and S. This angular dependence is the signature
of an antiferromagnetic spin Hall effect with symmetries that are distinct from
other mechanisms of spin-current generation reported in antiferromagnetic or
ferromagnetic materials.",2108.09150v1
2021-12-20,Spin current transport in hybrid Pt / multifunctional magnetoelectric Ga0.6Fe1.4O3 bilayers,"The low power manipulation of magnetization is currently a highly
sought-after objective in spintronics. Non ferromagnetic large spin-orbit
coupling heavy metal (NM) / ferromagnet (FM) heterostructures offer interesting
elements of response to this issue, by granting the manipulation of the FM
magnetization by the NM spin Hall effect (SHE) generated spin current.
Additional functionalities, such as the electric field control of the spin
current generation, can be offered using multifunctional ferromagnets. We have
studied the spin current transfer processes between Pt and the multifunctional
magnetoelectric Ga0.6Fe1.4O3 (GFO). In particular, via angular dependent
magnetotransport measurements, we were able to differentiate between magnetic
proximity effect (MPE)-induced anisotropic magnetoresistance (AMR) and spin
Hall magnetoresistance (SMR). Our analysis shows that SMR is the dominant
phenomenon at all temperatures and is the only one to be considered near room
temperature, with a magnitude comparable to those observed in Pd/YIG or Pt/YIG
heterostructures. These results indicate that magnetoelectric GFO thin films
show promises for achieving an electric-field control of the spin current
generation in NM/FM oxide-based heterostructures.",2112.10406v1
2022-08-09,Exploiting anisotropic Rashba effects on real-time photocurrents and spin polarization for transient symmetry breaking,"We theoretically investigate the real-time transient responses of a
two-dimensional (2D) electron gas with anisotropic Rashba spin-orbit coupling
(SOC) to laser pulses. Through explicitly monitoring the time-dependent
photocurrents and spin polarization under different linear polarizations of the
laser pulse, we find that the transient breaking of the mirror symmetry in
combination with the anisotropy of the Rashba SOC results in significant
distinction between the charge-mediated and the spin-mediated contributions to
the photocurrents. Such distinction is obtained by analyzing the dependence of
the symmetry-breaking induced (transverse) components of the photocurrents on
the linear polarization angle of the laser pulse. This suggests a possibility
of inferring spin-mediated processes in photocurrents without the use of
circularly polarized lights. Moreover, the interplay between transient symmetry
breaking and the anisotropy of the Rashba SOC also leads to transiently nonzero
spin polarization components that are otherwise zero in the steady-state limit
and the linear response regime. Especially, the out-of-plane spin polarization
component can be induced or turned off by controlling the relative orientation
of the linear polarization with respect to the symmetry axis of the 2D
electronic system, without involving material-intrinsic magnetization effects.
Our findings demonstrate the efficacy of a particular coordination between the
polarization of the ultrafast laser pulses and the spatial symmetry of the
electronic materials in directing the real-time charge and the spin responses
that are fundamental to the development of ultrafast spintronics in solid
states.",2208.04805v1
2022-08-29,Spin Current Density Functional Theory of the Quantum Spin-Hall Phase,"The spin current density functional theory (SCDFT) is the generalization of
the standard DFT to treat a fermionic system embedded in the effective external
field produced by the spin-orbit coupling interaction. Even in the absence of a
spin polarization, the SCDFT requires the electron-electron potential to depend
on the spin currents $\mathbf{J}^x$, $\mathbf{J}^y$ and $\mathbf{J}^z$, which
only recently was made possible for practical relativistic quantum-mechanical
simulations [Phys. Rev. B {\bf 102}, 235118 (2020)]. Here, we apply the SCDFT
to the quantum spin-Hall phase and show how it improves (even qualitatively)
the description of its electronic structure relative to the DFT. We study the
Bi (001) 2D bilayer and its band insulator to topological insulator phase
transition (via $s+p_z \leftrightarrow p_x +ip_y$ band inversion) as a function
of mechanical strain. We show that the explicit account of spin currents in the
electron-electron potential of the SCDFT is key to the appearance of a Dirac
cone at the $\Gamma$ point in the valence band structure at the onset of the
topological phase transition. Finally, the valence band structure of this
system is rationalized using a simple first-order $\mathbf{k} \cdot \mathbf{p}$
quasi-degenerate perturbation theory model.",2208.13878v1
2022-10-03,Spin canting and lattice symmetry in La$_2$CuO$_4$,"While the dominant magnetic interaction in La$_2$CuO$_4$ is superexchange
between nearest-neighbor Cu moments, the pinning of the spin direction depends
on weak anisotropic effects associated with spin-orbit coupling. The symmetry
of the octahedral tilt pattern allows an out-of-plane canting of the Cu spins,
which is compensated by an opposite canting in nearest-neighbor layers. A
strong magnetic field applied perpendicular to the planes can alter the spin
canting pattern to induce a weak ferromagnetic phase. In light of recent
evidence that the lattice symmetry is lower than originally assumed, we take a
new look at the nature of the field-induced spin-rotation transition. Comparing
low-temperature neutron diffraction intensities for several magnetic Bragg
peaks measured in fields of 0 and 14 T, we find that a better fit is provided
by a model in which spins rotate within both neighboring planes but by
different amounts, resulting in a noncollinear configuration. This model allows
a more consistent relationship between lattice symmetry and spin orientation at
all Cu sites.",2210.01156v3
2023-03-11,Power efficient ReLU design for neuromorphic computing using spin Hall effect,"We demonstrate a magnetic tunnel junction injected with spin Hall current to
exhibit linear rotation of magnetization of the free-ferromagnet using only the
spin current. Using the linear resistance change of the MTJ, we devise a
circuit for the rectified linear activation (ReLU) function of the artificial
neuron. We explore the role of different spin Hall effect (SHE) heavy metal
layers on the power consumption of the ReLU circuit. We benchmark the power
consumption of the ReLU circuit with different SHE layers by defining a new
parameter called the spin Hall power factor. It combines the spin Hall angle,
resistivity, and thickness of the heavy metal layer, which translates to the
power consumption of the different SHE layers during spin-orbit
switching/rotation of the free FM. We employ a hybrid spintronics-CMOS
simulation framework that couples Keldysh non-equilibrium Green's function
formalism with Landau-Lifshitz-Gilbert-Slonzewski equations and the HSPICE
circuit simulator to account for diverse physics of spin-transport and the CMOS
elements in our proposed ReLU design. We also demonstrate the robustness of the
proposed ReLU circuit against thermal noise and non-trivial power-error
trade-off that enables the use of an unstable free-ferromagnet for
energy-efficient design. Using the proposed circuit, we evaluate the
performance of the convolutional neural network for MNIST datasets and
demonstrate comparable classification accuracies to the ideal ReLU with an
energy consumption of 75 $pJ$ per sample.",2303.06463v1
2023-03-28,Generation of third-harmonic spin oscillation from strong spin precession induced by terahertz magnetic near fields,"The ability to drive a spin system to state far from the equilibrium is
indispensable for investigating spin structures of antiferromagnets and their
functional nonlinearities for spintronics. While optical methods have been
considered for spin excitation, terahertz (THz) pulses appear to be a more
convenient means of direct spin excitation without requiring coupling between
spins and orbitals or phonons. However, room-temperature responses are usually
limited to small deviations from the equilibrium state because of the
relatively weak THz magnetic fields in common approaches. Here, we studied the
magnetization dynamics in a HoFeO3 crystal at room temperature. A custom-made
spiral-shaped microstructure was used to locally generate a strong multicycle
THz magnetic near field perpendicular to the crystal surface; the maximum
magnetic field amplitude of about 2 T was achieved. The observed time-resolved
change in the Faraday ellipticity clearly showed second- and third-order
harmonics of the magnetization oscillation and an asymmetric oscillation
behaviour. Not only the ferromagnetic vector M but also the antiferromagnetic
vector L plays an important role in the nonlinear dynamics of spin systems far
from equilibrium.",2303.16016v1
2023-05-01,Hydrogenic Spin-Valley states of the Bromine donor in 2H-MoTe$_2$,"In semiconductors, the identification of doping atomic elements allowing to
encode a qubit within spin states is of intense interest for quantum
technologies. In transition metal dichalcogenides semiconductors, the strong
spin-orbit coupling produces locked spin-valley states with expected long
coherence time. Here we study the substitutional Bromine Br\textsubscript{Te}
dopant in 2H-MoTe$_2$. Electron spin resonance measurements show that this
dopant carries a spin with long-lived nanoseconds coherence time. Using
scanning tunneling spectroscopy, we find that the hydrogenic wavefunctions
associated with the dopant levels have characteristics spatial modulations that
result from their hybridization to the \textbf{Q}-valleys of the conduction
band. From a Fourier analysis of the conductance maps, we find that the
amplitude and phase of the Fourier components change with energy according to
the different irreducible representations of the impurity-site point-group
symmetry. These results demonstrate that a dopant can inherit the locked
spin-valley properties of the semiconductor and so exhibit long spin-coherence
time.",2305.00719v1
2023-05-25,Optically controlling the competition between spin flips and intersite spin transfer in a Heusler half-metal on sub-100 fs timescales,"The direct manipulation of spins via light may provide a path toward
ultrafast energy-efficient devices. However, distinguishing the microscopic
processes that can occur during ultrafast laser excitation in magnetic alloys
is challenging. Here, we study the Heusler compound Co2MnGa, a material that
exhibits very strong light-induced spin transfers across the entire M-edge. By
combining the element-specificity of extreme ultraviolet high harmonic probes
with time-dependent density functional theory, we disentangle the competition
between three ultrafast light-induced processes that occur in Co2MnGa:
same-site Co-Co spin transfer, intersite Co-Mn spin transfer, and ultrafast
spin-flips mediated by spin-orbit coupling. By measuring the dynamic magnetic
asymmetry across the entire M-edges of the two magnetic sublattices involved,
we uncover the relative dominance of these processes at different probe energy
regions and times during the laser pulse. Our combined approach enables a
comprehensive microscopic interpretation of laser-induced magnetization
dynamics on timescales shorter than 100 fs.",2305.16455v2
2023-06-12,Unraveling the connection between high-order magnetic interactions and local-to-global spin Hamiltonian in non-collinear magnetic dimers,"A spin Hamiltonian, which characterizes interatomic interactions between spin
moments, is highly valuable in predicting and comprehending the magnetic
properties of materials. A deeper understanding of the microscopic origin of
magnetic interactions can open new pathways toward realizing nanometer-scale
systems for future spintronic devices. Here, we explore a method for explicitly
calculating interatomic exchange interactions in non-collinear configurations
of magnetic materials considering only a bilinear spin Hamiltonian in a local
scenario. Based on density-functional theory (DFT) calculations of dimers
adsorbed on metallic surfaces, and with a focus on the Dzyaloshinskii-Moriya
interaction (DMI) which is essential for stabilizing chiral non-collinear
magnetic states, we discuss the interpretation of the DMI when decomposed into
microscopic electron and spin densities and currents. We clarify the distinct
origins of spin currents induced in the system and their connection to the DMI.
In addition, we reveal how non-collinearity affects the usual DMI, which is
solely induced by spin-orbit coupling, and DMI-like interactions brought about
by non-collinearity. We explain how the dependence of the DMI on the magnetic
configuration establishes a connection between high-order magnetic
interactions, enabling the transition from a local to a global spin
Hamiltonian.",2306.07222v2
2023-07-24,Spintronic Quantum Phase Transition in a $Graphene/Pb_{0.24}Sn_{0.76}Te$ Heterostructure with Giant Rashba Spin-Orbit Coupling,"Mechanical stacking of two dissimilar materials often has surprising
consequences for heterostructure behavior. In particular, a two-dimensional
electron gas (2DEG) is formed in the heterostructure of the topological
crystalline insulator Pb0.24Sn0.76Te and graphene due to contact of a polar
with a nonpolar surface and the resulting changes in electronic structure
needed to avoid polar catastrophe. We study the spintronic properties of this
heterostructure with non-local spin valve devices. We observe spin-momentum
locking at lower temperatures that transitions to regular spin channel
transport only at ~40 K. Hanle spin precession measurements show a spin
relaxation time as high as 2.18 ns. Density functional theory calculations
confirm that the spin-momentum locking is due to a giant Rashba effect in the
material and that the phase transition is a Lifshitz transition. The
theoretically predicted Lifshitz transition is further evident in the phase
transition-like behavior in the Land\'e g-factor and spin relaxation time.",2307.13113v1
2023-10-31,Rashba spin splitting based on trilayer graphene systems,"We establish a general Rashba Hamiltonian for trilayer graphene (TLG) by
introducing an extrinsic layer-dependent Rashba spin-orbit coupling (SOC)
arising from the off-plane inversion symmetry breaking. Our results indicate
that the band spin splitting depends strongly on the layer-distribution and
sign of Rashba SOC as well as the ABA or ABC stacking order of TLG. We find
that spin splitting is significantly enhanced as the number of layers of the
Rashba SOC with the same sign and magnitude increases. For the
spatially-separated two Rashba SOCs of the same magnitude but the opposite
sign, no spin splitting arises in ABC-TLG due to the preservation of inversion
symmetry that ensures the complete cancellation of contributions from the
opposite layers, whereas nonzero spin splitting is observed for ABA-TLG due to
its own lack of inversion symmetry. We further illustrate that gate voltage is
effective to modulate the spin-polarized states near the band edges. Moreover,
we use density functional theory calculations to verify the Rashba splitting
effect in the example of TLG interfaced by Au layer(s), which induce
simultaneously the effective terms of Rashba SOC and gate voltage. Our results
demonstrate the significance of layer and symmetry in manipulating spin and can
be extended to multilayer graphene or other van der Waals interface systems.",2310.20136v1
2023-12-12,Quantum Anomalous Hall and Spin Hall Effects in Magnetic Graphene,"A promising approach to attain long-distance coherent spin propagation is
accessing quantum Hall topological spin-polarized edge states in graphene.
Achieving this without large external magnetic fields necessitates engineering
graphene band structure, obtainable through proximity to 2D magnetic materials.
In this work, we detect spin-polarized helical edge transport in graphene at
zero external magnetic field, allowed by the out-of-plane magnetic proximity of
CrPS$_4$ that spin-splits the zeroth Landau level. This zero-field detection of
the quantum anomalous spin Hall state is enabled by large induced spin-orbit
and exchange couplings in the graphene that also lead to the detection of an
enhanced Berry curvature, shifting the Landau levels, and result in an
unconventional sequence of quantum Hall plateaus. Remarkably, we observe that
the quantum anomalous Hall transport in the magnetized graphene persists up to
room temperature. The detection of spin-polarized helical edge states at zero
magnetic field and the robustness of the quantum anomalous Hall transport up to
room temperature open the route for practical applications of magnetic graphene
in quantum information processing and spintronic circuitries.",2312.07515v1
2023-12-16,Topological phase transitions and thermal Hall effect in a noncollinear spin texture,"The noncollinear spin textures provide promising avenues to stabilize exotic
magnetic phases and excitations. They have attracted vast attention owning to
their nontrivial band topology in the past decades. Distinct from the
conventional route of involving the Dzyaloshinskii-Moriya interaction in a
honeycomb magnet, the interplay of bond-dependent Kitaev and $\Gamma$
interactions, originating from the spin-orbit coupling and octahedra crystal
field in real materials, has demonstrated to be another source to generate
noncollinear spin textures with multiple spins in a magnetic unit cell.
Notably, earlier works have revealed a triple-meron crystal (TmX) consisting of
eighteen spins in the frustrated Kitaev-$\Gamma$ model. Aligning with previous
efforts, here we attempt to identity that the TmX hosts several peculiar
features with the help of the linear spin-wave theory. To begin with, the
symmetric anisotropic exchanges are beneficial for the existence of
nonreciprocal magnons, which are stabilized by an external magnetic field.
Further, within the regime of TmX, successive topological phase transitions
occur, accompanied by the changes of Chern number in value and thermal Hall
conductivity in sign. In addition, topological nature of magnons is also
verified by the onset of chiral edge modes in a nanoribbon geometry. Our
findings pave the way to study topological phenomena of noncollinear spin
textures in potential Kitaev materials.",2312.10473v1
2022-11-07,Quantum-classical approach to spin and charge pumping and the ensuing radiation in THz spintronics: Example of ultrafast-light-driven Weyl antiferromagnet Mn$_3$Sn,"The interaction of fs light pulses with magnetic materials has been intensely
studied for more than two decades in order to understand ultrafast
demagnetization in single magnetic layers or THz emission from their bilayers
with nonmagnetic spin-orbit (SO) materials. Here we develop a multiscale
quantum-classical formalism -- where conduction electrons are described by
quantum master equation of the Lindblad type; classical dynamics of local
magnetization is described by the Landau-Lifshitz-Gilbert (LLG) equation; and
incoming light is described by classical vector potential while outgoing
electromagnetic radiation is computed using Jefimenko equations for retarded
electric and magnetic fields -- and apply it a bilayer of antiferromagnetic
Weyl semimetal Mn$_3$Sn with noncollinear local magnetization in contact with
SO-coupled nonmagnetic material. Our QME+LLG+Jefimenko scheme makes it possible
to understand how fs light pulse generates directly spin and charge pumping and
electromagnetic radiation by the latter, including both odd and even high
harmonics (of the pulse center frequency) up to order $n \le 7$. The directly
pumped spin current then exert spin torque on local magnetization whose
dynamics, in turn, pumps additional spin and charge currents radiating in the
THz range. By switching on and off LLG dynamics and SO couplings, we unravel
which microscopic mechanism contribute the most to emitted THz radiation --
charge pumping by local magnetization of Mn$_3$Sn in the presence of its
intrinsic SO coupling is far more important than standardly assumed (for other
types of magnetic layers) spin pumping and subsequent spin-to-charge conversion
within the neighboring nonmagnetic SO-coupled material.",2211.03645v3
2008-09-08,Jahn-Teller Inactivity and Magnetic Frustration in GeCo$_2$O$_4$ Probed by Ultrasound Velocity Measurements,"Ultrasound velocity measurements of cubic spinel GeCo$_2$O$_4$ in single
crystal were performed for the investigation of shear and compression moduli.
The shear moduli in the paramagnetic state reveal an absence of Jahn-Teller
activity despite the presence of orbital degeneracy in the Co$^{2+}$ ions. Such
a Jahn-Teller inactivity indicates that the intersite orbital-orbital
interaction is much stronger than the Jahn-Teller coupling. The compression
moduli in the paramagnetic state near the N$\acute{e}$el temperature $T_N$
reveal that the most relevant exchange path for the antiferromagnetic
transition lies in the [111] direction. This exchange-path anisotropy is
consistent with the antiferromagnetic structure with the wave vector $q
\parallel$ [111], suggesting the presence of bond frustration due to
competition among a direct ferromagnetic and several distant-neighbors
antiferromagnetic interactions. In the JT-inactive condition, the bond
frustration can be induced by geometrical orbital frustration of
$t_{2g}$-$t_{2g}$ interaction between the Co$^{2+}$ ions which can be realized
in the pyrochlore lattice of the high spin Co$^{2+}$ with $t_{2g}$-orbital
degeneracy. In GeCo$_2$O$_4$, the tetragonal elongation below $T_N$ releases
the orbital frustration by quenching the orbital degeneracy.",0809.1263v1
2014-12-01,Novel electronic behavior driving NdNiO3 metal-insulator transition,"We present evidence that the metal-insulator transition (MIT) in a tensile
strained NdNiO3 (NNO) film is facilitated by a redistribution of electronic
density and neither requires Ni charge disproportionation nor symmetry change
[1, 2]. Given epitaxial tensile strain in thin NNO films induces preferential
occupancy of the $e_g$ $d_{x^2-y^2}$ orbital ($s_{3z^2-r^2}$) we propose the
larger transfer integral of this orbital state with the O 2p mediates a
redistribution of electronic density from the Ni atom. A decrease in Ni
$d_{x^2-y^2}$ orbital occupation is directly observed by resonant inelastic
x-ray scattering below the MIT temperature. Furthermore, an increase in Nd
charge occupancy is measured by x-ray absorption at the Nd L3 edge. Both
spin-orbit coupling and crystal field effects combine to break the degeneracy
of the Nd 5d states shifting the energy of the Nd $e_g$ $d_{x^2-y^2}$ orbital
towards the Fermi level allowing the A site to become an active acceptor during
the MI transition. This work identifies the relocation of electrons from the Ni
3d to the Nd 5d orbitals across the MIT. We propose the insulating gap opens
between the Ni 3d and O 2p resulting from Ni 3d electron localization mediated
by charge loss. The transition seems neither purely Mott-Hubbard nor simple
charge transfer.",1412.0676v3
2016-01-15,Multiband $d-p$ model and self-doping in the electronic structure of Ba$_2$IrO$_4$,"We introduce and investigate the multiband $d-p$ model describing a IrO$_4$
layer (such as realized in Ba$_2$IrO$_4$) where all $34$ orbitals per unit cell
are partly occupied, i.e., $t_{2g}$ and $e_g$ orbitals at iridium and $2p$
orbitals at oxygen ions. The model takes into account anisotropic
iridium-oxygen $d-p$ and oxygen-oxygen $p-p$ hopping processes, crystal-field
splittings, spin-orbit coupling, and the on-site Coulomb interactions, both at
iridium and at oxygen ions. We show that the predictions based on assumed
idealized ionic configuration (with $n_0=5+4\times 6=29$ electrons per IrO$_4$
unit) do not explain well the independent \textit{ab initio} data and the
experimental data for Ba$_2$IrO$_4$. Instead we find that the total electron
density in the $d-p$ states is smaller, $n=29-x<n_0$ ($x>0$). When we fix
$x=1$, the predictions for the $d-p$ model become more realistic and weakly
insulating antiferromagnetic ground state with the moments lying within IrO$_2$
planes along (110) direction is found, in agreement with experiment and
\textit{ab initio} data. We also show that: (i) holes delocalize over the
oxygen orbitals and the electron density at iridium ions is enhanced, hence
(ii) their $e_g$ orbitals are occupied by more than one electron and have to be
included in the multiband $d-p$ model describing iridates.",1601.03985v1
2020-08-12,Tidal Dissipation Impact on the Eccentric Onset of Common Envelope Phases in Massive Binary Star Systems,"Tidal dissipation due to turbulent viscosity in the convective regions of
giant stars plays an important role in shaping the orbits of pre-common
envelope systems. Such systems are possible sources of transients and close
compact binary systems that will eventually merge and produce detectable
gravitational wave signals. Most previous studies of the onset of common
envelope episodes have focused on circular orbits and synchronously rotating
donor stars under the assumption that tidal dissipation can quickly spin up the
primary and circularize the orbit before the binary reaches Roche-lobe overflow
(RLO). We test this assumption by coupling numerical models of the post main
sequence stellar evolution of massive-stars with the model for tidal
dissipation in convective envelopes developed in Vick & Lai (2020) $-$ a tidal
model that is accurate even for highly eccentric orbits with small pericentre
distances. We find that, in many cases, tidal dissipation does not circularize
the orbit before RLO. For a $10~M_\odot$ ($15~M_\odot$) primary star
interacting with a $1.4~M_\odot$ companion, systems with pericentre distances
within 3 AU (6 AU) when the primary leaves the main sequence will retain the
initial orbital eccentricity when the primary grows to the Roche radius. Even
in systems that tidally circularize before RLO, the donor star may be rotating
subsynchronously at the onset of mass transfer. Our results demonstrate that
some possible precursors to double neutron star systems are likely eccentric at
the Roche radius. The effects of pre-common envelope eccentricity on the
resulting compact binary merit further study.",2008.05476v2
2015-08-07,Correlation-enhanced odd-parity inter-orbital singlet pairing in the iron-pnictide superconductor LiFeAs,"The rich variety of iron-based superconductors and their complex electronic
structure lead to a wide range of possibilities for gap symmetry and pairing
components. Here we solve in the 2-Fe Brillouin zone the full
frequency-dependent linearized Eliashberg equations for LiFeAs with
spin-fluctuation mediated pairing interactions. The magnetic excitations are
calculated with the random phase approximation on a correlated electronic
structure obtained with density functional theory and dynamical mean field
theory. Correlations induce long-lived local moments with orbital-dependent
dynamics. The interaction between electrons through Hund's coupling promotes
inter-orbital magnetic susceptibility. As a consequence, the leading pairing
channel, conventional $s^{+-}$, acquires sizeable inter-orbital
$d_{xy}-d_{xz(yz)}$ singlet pairing with odd parity under glide-plane symmetry.
These components reduce the superconducting gap magnitude induced by the
intra-orbital components of the gap function at the electron pockets
intersection where the Fe-d $t_{2g}$ orbitals strongly mix. This in turn makes
the results consistent with available experiments on the angular dependence of
the gaps observed on the different Fermi surfaces.",1508.01789v4
2023-07-31,The Perturbed Full Two-Body Problem: Application to Post-DART Didymos,"With the successful impact of the NASA DART spacecraft in the
Didymos-Dimorphos binary asteroid system, we provide an initial analysis of the
post-impact perturbed binary asteroid dynamics. To compare our simulation
results with observations, we introduce a set of ""observable elements""
calculated using only the physical separation of the binary asteroid, rather
than traditional Keplerian elements. Using numerical methods that treat the
fully spin-orbit-coupled dynamics, we estimate the system's mass and the
impact-induced changes in orbital velocity, semimajor axis, and eccentricity.
We find that the changes to the mutual orbit depend strongly on the separation
distance between Didymos and Dimorphos at the time of impact. If Dimorphos
enters a tumbling state after the impact, this may be observable through
changes in the system's eccentricity and orbit period. We also find that any
DART-induced reshaping of Dimorphos would generally reduce the required change
in orbital velocity to achieve the measured post-impact orbit period and will
be assessed by the ESA Hera mission in 2027.",2307.16777v1
2023-09-05,"On the origin of circular dichroism in angular resolved photoemission from graphene, graphite, and WSe$_2$ family of materials","Circular dichroism in angle-resolved photoemission (CD-ARPES) is one of the
promising techniques for obtaining experimental insight into topological
properties of novel materials, in particular to the orbital angular momentum
(OAM) in dispersive bands, which might be related, albeit certainly in a
non-trivial way, to the momentum resolved Berry curvature of the bands.
Therefore, it is important to understand how non-vanishing CD-ARPES signal
arises in graphene, a material where Dirac bands are made from C $|2p_z\rangle$
orbitals that carry zero OAM, spin-orbit-coupling (SOC) can be neglected, and
Berry curvature effectively vanishes. Dubs et al., Phys. Rev. B 32, 8389 (1985)
have demonstrated non-vanishing cricular dichroism in angular distribution
(CDAD) from an oriented $p_z$ orbital, and this process can be responsible for
the experimentally observed CD-ARPES in graphene. In this paper, we derive the
CD-ARPES from $p_z$ orbitals by elementary means, using only simple algebraic
formulas and tabulated numerical values, and show that it leads to significant
CD-ARPES signal over the entire vacuum ultraviolet and soft x-ray energy range,
with an exception of the photon energy region near $h\nu \approx 40$ eV. We
also demonstrate that another process, emerging from the finite electron
inelastic mean free path, also leads to CD-ARPES of the potentially similar
order of magnitude, as previously discussed by Moser, J. Electron Spectrosc.
Relat. Phenom. 214, 29 (2017). We present calculated CDAD maps for selected
orbitals and briefly discuss the consequences of the findings for CD-ARPES,
focusing on graphene, graphite and WSe$_2$.",2309.02187v1
2012-07-30,"Aligned Spins: Orbital Elements, Decaying Orbits, and Last Stable Circular Orbit to high post-Newtonian Orders","In this article the quasi-Keplerian parameterisation for the case that spins
and orbital angular momentum in a compact binary system are aligned or
anti-aligned with the orbital angular momentum vector is extended to 3PN
point-mass, next-to-next-to-leading order spin-orbit, next-to-next-to-leading
order spin(1)-spin(2), and next-to-leading order spin-squared dynamics in the
conservative regime. In a further step, we use the expressions for the
radiative multipole moments with spin to leading order linear and quadratic in
both spins to compute radiation losses of the orbital binding energy and
angular momentum. Orbital averaged expressions for the decay of energy and
eccentricity are provided. An expression for the last stable circular orbit is
given in terms of the angular velocity type variable $x$.",1207.6961v2
2012-07-12,Fingerprints of spin-orbital entanglement in transition metal oxides,"The concept of spin-orbital entanglement on superexchange bonds in transition
metal oxides is introduced and explained on several examples. It is shown that
spin-orbital entanglement in superexchange models destabilizes the long-range
(spin and orbital) order and may lead either to a disordered spin-liquid state
or to novel phases at low temperature which arise from strongly frustrated
interactions. Such novel ground states cannot be described within the
conventionally used mean field theory which separates spin and orbital degrees
of freedom. Even in cases where the ground states are disentangled,
spin-orbital entanglement occurs in excited states and may become crucial for a
correct description of physical properties at finite temperature. As an
important example of this behaviour we present spin-orbital entanglement in the
$R$VO$_3$ perovskites, with $R$=La,Pr,...,Yb,Lu, where such finite temperature
properties of these compounds can be understood only using entangled states:
($i$) thermal evolution of the optical spectral weights, ($ii$) the dependence
of transition temperatures for the onset of orbital and magnetic order on the
ionic radius in the phase diagram of the $R$VO$_3$ perovskites, and ($iii$)
dimerization observed in the magnon spectra for the $C$-type antiferromagnetic
phase of YVO$_3$. Finally, it is shown that joint spin-orbital excitations in
an ordered phase with coexisting antiferromagnetic and alternating orbital
order introduces topological constraints for the hole propagation and will thus
radically modify transport properties in doped Mott insulators where hole
motion implies simultaneous spin and orbital excitations.",1207.3010v1
2017-01-20,Probing dark excitons in atomically thin semiconductors via near-field coupling to surface plasmon polaritons,"Transition metal dichalcogenide (TMD) monolayers are direct bandgap
semiconductors that feature tightly bound excitons, strong spin-orbit coupling,
and spin-valley degrees of freedom. Depending on the spin configuration of the
electron-hole pairs, intra-valley excitons of TMD monolayers can be either
optically bright or dark. Dark excitons involve nominally spin-forbidden
optical transitions with zero in-plane transition dipole moment, making their
detection with conventional far-field optical techniques challenging. Here, we
introduce a new method for probing the optical properties of two-dimensional
(2D) materials via near-field coupling to surface plasmon polaritons (SPPs),
which selectively enhances optical transitions with dipole moments normal to
the 2D plane. We utilize this method to directly detect dark excitons in
monolayer TMDs. When a WSe2 monolayer is placed on top of a single-crystal
silver film, its emission into near-field-coupled SPPs displays new spectral
features whose energies and dipole orientations are consistent with dark
neutral and charged excitons. The SPP-based near-field spectroscopy
significantly enhances experimental capabilities for probing and manipulating
exciton dynamics of atomically thin materials.",1701.05938v1
2019-02-13,Metamagnetism stabilized giant magnetoelectric coupling in ferroelectric \textit{x}BaTiO${_3}$-(1-\textit{x})BiCoO${_3}$ solid solution,"In order to establish the correlation between the magnetoelectric coupling
and magnetic instability, we have studied the structural, magnetic, and
ferroelectric properties of \textit{x}BaTiO${_3}$-(1-\textit{x})BiCoO${_3}$ as
a function of BaTiO$_3$ concentration ($x$) and volume.The $G-$type
antiferromagnetic ordering is found to be energetically favorable for $x<$ 0.45
and higher concentrations stabilize with nonmagnetic states. We observe
metamagnetic spin state transitions associated with paraelectric to
ferrolectric transitions as a function of volume and $x$ using synchrotron
diffraction and computational studies, indicating a strong magnetoelectric
coupling. Specifically for $x=$ 0.33 composition, a pressure induced high spin
(HS) to low spin (LS) transition occurs when the volume is compressed below
5\%. Our orbital$-$projected density of states show a HS state for Co$^{3+}$ in
the ferroelectric ground state for $x<$ 0.45 and the corresponding paraelectric
phase is stable in the nonmagnetic state due to the stabilization of LS state
as evident from our fixed$-$spin$-$moment calculations and magnetic
measurements. High values of spontaneous ferroelectric polarizations are
predicted for lower $x$ values which inversely vary with $x$ because of the
reduction of tetragonality ($c/a$) with increase in $x$. Moreover, we find that
the HS$-$LS transition point and magnetoelectric coupling strength can be
varied by $x$.",1902.05013v1
2006-08-04,Kondo Effects in Carbon Nanotubes: From SU(4) to SU(2) symmetry,"We study the Kondo effect in a single-electron transistor device realized in
a single-wall carbon nanotube. The K-K' double orbital degeneracy of a
nanotube, which originates from the peculiar two-dimensional band structure of
graphene, plays the role of a pseudo-spin. Screening of this pseudo-spin,
together with the real spin, can result in an SU(4) Kondo effect at low
temperatures. For such an exotic Kondo effect to arise, it is crucial that this
orbital quantum number is conserved during tunneling. Experimentally, this
conservation is not obvious and some mixing in the orbital channel may occur.
Here we investigate in detail the role of mixing and asymmetry in the tunneling
coupling and analyze how different Kondo effects, from the SU(4) symmetry to a
two-level SU(2) symmetry, emerge depending on the mixing and/or asymmetry. We
use four different theoretical approaches to address both the linear and
non-linear conductance for different values of the external magnetic field. Our
results point out clearly the experimental conditions to observe exclusively
SU(4) Kondo physics. Although we focus on nanotube quantum dots, our results
also apply to vertical quantum dots. We also mention that a finite amount of
orbital mixing corresponds, in the pseudospin language, to having non-collinear
leads with respect to the orbital ''magnetization'' axis which defines the two
pseudospin orientations in the nanotube quantum dot. In this sense, some of our
results are also relevant to the problem of a Kondo quantum dot coupled to
non-collinear ferromagnetic leads.",0608110v3
2019-03-18,Orbital-selective bad metals due to Hund's rule and orbital anisotropy: a finite-temperature slave-spin treatment of the two-band Hubbard model,"We study the finite-temperature properties of the half-filled two-band
Hubbard model in the presence of Hund's rule coupling and orbital anisotropy.
We use the mean-field treatment of the $Z_2$ slave-spin theory with a
finite-temperature extension of the zero-temperature gauge variable previously
developed by Hassan and de' Medici
http://dx.doi.org/10.1103/PhysRevB.81.035106}{Phys. Rev. B {\bf 81}, 035106
(2010)}]. We consider the instability of the Fermi liquid phases and how it is
enhanced by the Hund's rule. We identify paramagnetic solutions that have zero
quasi-particle weight with bad metallic phases, and the first-order transition
temperature between it and the Fermi liquid phase as a coherence temperature
that signals the crossover to the bad metallic state. When orbital anisotropy
is present, we found an intermediate transition to an orbital-selective bad
metal (OSBM), where the narrow band becomes a bad metal while the wide band
remains a renormalised Fermi liquid. The temperatures $T_\textrm{coh}$ and
$T_\textrm{OSBM}$ at which the system transitions to the bad metal phases can
be orders of magnitude less than the Fermi temperature associated with the
non-interacting band. The parameter dependence of the temperature at which the
OSBM is destroyed can be understood in terms of a ferromagnetic Kondo-Hubbard
lattice model. In general, Hund's rule coupling enhances the bad metallic
phases, reduce interorbital charge fluctuations and increase spin fluctuations.
The qualitative difference found in the ground state whether the Hund's rule is
present or not, related to the degeneracy of the low energy manifold, is also
maintained for finite temperatures.",1903.07237v3
2023-03-08,Spin-orbital mechanisms for negative thermal expansion in Ca2RuO$_4$,"The phenomenon of negative thermal expansion (NTE) deals with the increase of
the lattice parameters and the volume of the unit cell when the material is
thermally cooled. The NTE is typically associated with thermal phonons and
anomalous spin-lattice coupling at low temperatures. However, the underlying
mechanisms in the presence of strong electron correlations in multi-orbital
systems are not yet fully established. Here, we investigate the role of Coulomb
interaction in the presence of lattice distortions in setting out the NTE
effect, by focusing on the physical case of layered Ca$_2$RuO$_4$ with $d^4$
configuration at each Ru ion site. We employ the Slater-Koster parametrization
to describe the electron-lattice coupling through the dependence of the $d-p$
hybridization on the Ru-O-Ru bond angle. The evaluation of the minimum of the
free energy at finite temperature by fully solving the multi-orbital many-body
problem on finite size cluster allows us to identify the regime for which the
system is prone to exhibit NTE effects. The analysis shows that the nature of
the spin-orbital correlations is relevant to drive the reduction of the bond
angle by cooling, and in turn the tendency toward a NTE. This is confirmed by
the fact that a changeover of the electronic and orbital configuration from
$d^4$ to $d^3$ by transition metal substitution is shown to favor the
occurrence of NTE in Ca$_2$RuO$_4$. This finding is in agreement with the
experimental observations of a NTE effect which is significantly dependent on
the transition metal substitution in the Ca$_2$RuO$_4$ compound.",2303.04951v1
2005-07-07,Conservation of spin current,"The conventional definition of spin-current, namely spin density multiplied
by the group velocity, is not a conserved quantity due to possible spin
rotations caused by spin-orbit (SO) interaction. However, in a model with
spin-spin interactions, rotation of a spin causes a dynamic response of
surrounding spins that opposes the rotation. Such a many-body effect restores
the spin-current conservation. Here we prove that the non-conservation problem
of spin-current can be resolved if a self-consistent spin-spin interaction is
included in the analysis. We further derive a spin-conductance formula which
partitions spin-current into different leads of a multi-lead conductor.",0507159v2
2014-05-06,Spin-orbit-induced circulating currents in a semiconductor nanostructure,"Circulating orbital currents produced by the spin-orbit interaction for a
single electron spin in a quantum dot are explicitly evaluated at zero magnetic
field, along with their effect on the total magnetic moment (spin and orbital)
of the electron spin. The currents are dominated by coherent superpositions of
the conduction and valence envelope functions of the electronic state, are
smoothly varying within the quantum dot, and are peaked roughly halfway between
the dot center and edge. Thus the spatial structure of the spin contribution to
the magnetic moment (which is peaked at the dot center) differs greatly from
the spatial structure of the orbital contribution. Even when the spin and
orbital magnetic moments cancel (for $g=0$) the spin can interact strongly with
local magnetic fields, e.g. from other spins, which has implications for spin
lifetimes and spin manipulation.",1405.1151v1
2018-03-16,Intrinsic spin-orbit torque in an antiferromagnet with a weakly noncollinear spin configuration,"An antiferromagnet is a promising material for spin-orbit torque generation.
Earlier studies of the spin-orbit torque in an antiferromagnet are limited to
collinear spin configurations. We calculate the spin-orbit torque in an
antiferromagnet whose spin ordering is weakly noncollinear. Such
noncollinearity may be induced spontaneously during the magnetization dynamics
even when the equilibrium spin configuration is perfectly collinear. It is
shown that deviation from perfect collinearity can modify properties of the
spin-orbit torque since noncollinearity generates extra Berry phase
contributions to the spin-orbit torque, which are forbidden for collinear spin
configurations. In sufficiently clean antiferromagnets, this modification can
be significant. We estimate this effect to be of relevance for fast
antiferromagnetic domain wall motion.",1803.06428v2
1995-07-24,Double Degeneracy and Jahn-Teller Effects in CMR Perovskites,"Jahn-Teller (JT) electron-phonon coupling effects in the colossal
magnetoresistance perovskite compounds $La_{1-x}A_xMnO_3$ are investigated.
Electron-electron correlations between two degenerate Mn $e_g$ orbitals are
studied in the Gutzwiller approximation. The static JT distortion and
antiadiabatic polaron effects are studied in a modified Lang-Firsov
approximation. We find that (i) the electron or hole character of the charge
carrier depends on the static JT distortion, and (ii) due to the two-component
nature of the JT coupling, fluctuations in the JT distortion direction
contribute to the charge transport in similar fashion as the local spins.",9507097v1
1996-02-29,Theory of Non-Reciprocal Optical Effects in Antiferromagnets: The Case Cr_2O_3,"A microscopic model of non-reciprocal optical effects in antiferromagnets is
developed by considering the case of Cr_2O_3 where such effects have been
observed. These effects are due to a direct coupling between light and the
antiferromagnetic order parameter. This coupling is mediated by the spin-orbit
interaction and involves an interplay between the breaking of inversion
symmetry due to the antiferromagnetic order parameter and the trigonal field
contribution to the ligand field at the magnetic ion. We evaluate the matrix
elements relevant for the non-reciprocal second harmonic generation and
gyrotropic birefringence.",9602159v2
1999-07-13,Theory of the pi state in 3He Josephson junctions,"The flow of superfluid 3He-B through a 65 x 65 array of nanometer size
apertures has been measured recently by Backhaus et al. They find in the
current--phase relation a new branch, so-called pi state. We study two limiting
cases which show that the pi state arises from coupling of the phase degree of
freedom to the spin-orbit rotation. The pi state exists in a single large
aperture, but is difficult to observe because of hysteresis. A better
correspondence with experiments is obtained by assuming a thin wall, where the
Josephson coupling between the two sides arises from a dense array of
pin-holes.",9907181v1
2001-09-06,Lattice-Spin Mechanism in Colossal Magnetoresistant Manganites,"We present a single-orbital double-exchange model, coupled with cooperative
phonons (the so called breathing-modes of the oxygen octahedra in manganites).
The model is studied with Monte Carlo simulations. For a finite range of doping
and coupling constants, a first-order Metal-Insulator phase transition is
found, that coincides with the Paramagnetic-Ferromagnetic phase transition. The
insulating state is due to the self-trapping of every carrier within an oxygen
octahedron distortion.",0109127v2
2002-07-12,Electronic Ferroelectricity in the Falicov-Kimball Model,"I show that a spontaneous electric polarization is developed in the solution
of the Falicov-Kimball model (FKM) by mapping the strong coupling limit of the
model into an $xxz$ spin 1/2 model with a magnetic field. In this way, I can
determine the phase diagram of the strongly interacting model that shows a
transition to a mixed valence regime containing two phases: orbital ordering
and Bose-Einstein condensation of excitons with a built in electric
polarization. The results are extended to the intermeditate and weak coupling
regimes.",0207331v2
2003-04-24,On Superconducting Double Transition in PrOs_4_Sb_12,"Superconducting double transition in PrOs_4_Sb_12 is investigated by
analyzing the anisotropy of the upper critical field H_c2 in the ab-plane, and
the possible pairing state is discussed. When mixing due to gradient coupling
is active, the twofold-symmetric component is necessarily induced in the
fourfold symmetric phase, leading to the twofold oscillation of H_c2, contrary
to the experimental result. To avoid the mixing effect, the weak spin-orbit
coupling triplet pairing state is considered as a likely pairing function,
where time-reversal symmetry is broken.",0304538v1
2003-09-16,Superconducting states in the tetrahedral compound PrOs4Sb12,"We find possible superconducting states for tetrahedral (Th) symmetry
crystals with strong spin-orbit coupling using Landau theory. Additional
symmetry breaking within the superconducting state is considered. We discuss
nodes of the gap functions for the different states, secondary superconducting
order parameters and coupling to the elastic strain. By comparing our results
to experiments, we find that superconductivity in PrOs4Sb12 is best described
by the three-dimensional representations of point group Th.",0309382v2
2004-04-21,Theory of Coupled Multipole Moments Probed by X-ray Scattering in CeB$_6$,"A minimal model for multipole orders in CeB$_6$ shows that degeneracy of the
quadrupole order parameters and strong spin-orbit coupling lead to peculiar
temperature and magnetic-field dependences of the X-ray reflection intensity at
superlattice Bragg points. Furthermore, the intensity depends sensitively on
the surface direction. These theoretical results explain naturally recent X-ray
experiments in phases II and III of CeB$_6$. It is predicted that under weak
magnetic field perpendicular to the (111) surface, the reflection intensity
should change non-monotonically as a function of temperature.",0404498v1
2005-01-19,Effective quantum dimer model for trimerized kagome antiferromagnet,"An effective spin-orbit Hamiltonian is derived for a spin-1/2 trimerized
kagome antiferromagnet in the second-order of perturbation theory in the ratio
of two coupling constants. Low-energy singlet states of the obtained model are
mapped to a quantum dimer model on a triangular lattice. The quantum dimer
model is dominated by dimer resonances on a few shortest loops of the
triangular lattice. Characteristic energy scale for the dimer model constitutes
only a small fraction of the weaker exchange coupling constant.",0501460v1
2006-08-17,Fano-Rashba effect in a quantum wire,"We predict the occurrence of Fano lineshapes in a semiconductor quantum wire
with local spin-orbit (Rashba) coupling. We show that the Rashba interaction
acts in a strictly one dimensional channel as an attractive impurity, leading
to the formation of purely bound states. In a quasi-one dimensional system
these bound states couple to the conduction ones through the Rashba
intersubband mixing, giving rise to pronounced dips in the linear conductance
plateaus. We give exact numerical results and propose an approximate model
capturing the main ingredients of the effect.",0608392v2
2006-08-22,The magnetic orders induced ferroelectricity,"We studied the ferroelectricity of magnetic oxides in which its emergence
coincides with the onset of a second incommensurate magnetic order. We solved
for the wave function of e_{g} electrons in the presence of magnetic orders.
The coupling between the magnetic and electric orders is provided by the
spin-orbit interaction. It was found that the net electric dipole moment of the
system came from the bond between the transition metal and oxygen atoms. The
anisotropy of d-orbitals also played an important role. Finally, the form of
the coupling leads us to the conclusion that it is an improper
ferroelectricity.",0608470v1
2003-10-30,Gravitomagnetic effect and spin-torsion coupling,"We study the gravitomagnetic effect in the context of absolute parallelism
with the use of a modified geodesic equation via a free parameter b. We
calculate the time difference in two atomic clocks orbiting the Earth in
opposite directions and find a small correction due to the coupling between the
torsion of the spacetime and the internal structure of atomic clocks measured
by the free parameter.",0310131v1
1996-08-13,A new effective Lagrangian for nuclear matter,"The relativistic mean field model, the Zim\'anyi - Moszkowski (ZM) Lagrangian
describes nuclear matter and stable finite nuclei even in the non-relativistic
limit. It fails, however, to predict the correct non-relativistic spin-orbit
(SO) coupling. In this paper we improve on this matter by an additional tensor
coupling analogous to the anomalous gyromagnetic ratio. It can be adjusted to
describe the SO-term without changing the mean field solution of the
ZM-Lagrangian for nuclear matter.",9608021v1
1998-09-11,On the relativistic L-S coupling,"The fact that the Dirac equation is linear in the space and time derivatives
leads to the coupling of spin and orbital angular momenta that is of a pure
relativistic nature. We illustrate this fact by computing the solutions of the
Dirac equation in an infinite spherical well, which allows to go from the
relativistic to the non-relativistic limit by just varying the radius of the
well.",9809015v1
2007-06-14,Physical properties of the noncentrosymmetric superconductor Mg_10Ir_19B_16,"Specific heat, electrical resistivity, and magnetic susceptibility
measurements on a high quality sample of Mg10Ir19B16 provide a self-consistent
determination of its superconducting properties. They indicate that Mg10Ir19B16
is a type-II superconductor (Tc=4.45K, k(0)=20), with an electron-phonon
coupling constant l_ep=0.66. An analysis of the T-dependent specific heat shows
that superconducting properties are dominated by an s-wave gap (D=0.7 meV).
Point contact tunneling data provide evidence for multiple superconducting
gaps, as expected from strong asymmetric spin-orbit coupling.",0706.2177v2
2008-04-29,Angular Momentum Coupling and Rabi Frequencies for Simple Atomic Transitions,"The Rabi frequency (coupling strength) of an electric-dipole transition is an
important experimental parameter in laser-cooling and other atomic physics
experiments. Though the relationship between Rabi frequency and atomic
wavefunctions and/or atomic lifetimes is discussed in many references, there is
a need for a concise, self-contained, accessible introduction to such
calculations suitable for use by the typical student of laser cooling
(experimental or theoretical). In this paper, I outline calculations of the
Rabi frequencies for atoms with sub-structure due to orbital, spin and nuclear
angular momentum. I emphasize the physical meaning of the calculations.",0804.4528v1
2008-06-25,A Neutron diffraction study of multiferroics RMn2O5,"The magnetic properties of RMn2O5 multiferrroics as obtained by unpolarized
and polarized neutron diffraction experiments are reviewed. We discuss the
qualitative features of the magnetic phase diagram both in zero magnetic field
and in field and analyze the commensurate magnetic structure and its coupling
to an applied electric field. The origin of ferrolectricity is discussed based
on calculations of the ferroelectric polarization predicted by different
microscopic coupling mechanisms (exchange striction and cycloidal spin-orbit
models). A minimal model containing a small set of parameters is also presented
in order to understand the propagation of the magnetic structure along the
c-direction.",0806.4128v1
2010-01-27,Semi-Holographic Fermi Liquids,"We show that the universal physics of recent holographic non-Fermi liquid
models is captured by a semi-holographic description, in which a dynamical
boundary field is coupled to a strongly coupled conformal sector having a
gravity dual. This allows various generalizations, such as a dynamical exponent
and lattice and impurity effects. We examine possible relevant deformations,
including multi-trace terms and spin-orbit effects. We discuss the matching
onto the UV theory of the earlier work, and an alternate description in which
the boundary field is integrated out.",1001.5049v2
2010-03-05,Giant magneto-elastic coupling in a metallic helical metamagnet,"Using high resolution neutron diffraction and capacitance dilatometry we show
that the thermal evolution of the helimagnetic state in CoMnSi is accompanied
by a change in inter-atomic distances of up to 2%, the largest ever found in a
metallic magnet. Our results and the picture of competing exchange and strongly
anisotropic thermal expansion that we use to understand them sheds light on a
new mechanism for large magnetoelastic effects that does not require large
spin-orbit coupling.",1003.1206v3
2011-01-14,Non-Spinning Black Holes in Alternative Theories of Gravity,"We study two large classes of alternative theories, modifying the action
through algebraic, quadratic curvature invariants coupled to scalar fields. We
find one class that admits solutions that solve the vacuum Einstein equations
and another that does not. In the latter, we find a deformation to the
Schwarzschild metric that solves the modified field equations in the small
coupling approximation. We calculate the event horizon shift, the innermost
stable circular orbit shift, and corrections to gravitational waves, mapping
them to the parametrized post-Einsteinian framework.",1101.2921v2
2012-08-31,Coupled Ferromagnetic and Nematic Ordering of Fermions in an Optical Flux Lattice,"Ultracold atoms in Raman-dressed optical lattices allow for effective
momentum-dependent interactions among single-species fermions originating from
short-range s-wave interactions. These dressed-state interactions combined with
very flat bands encountered in the recently introduced optical flux lattices
push the Stoner instability towards weaker repulsive interactions, making it
accessible with current experiments. As a consequence of the coupling between
spin and orbital degrees of freedom, the magnetic phase features Ising nematic
order.",1208.6540v3
2013-01-30,Fractional Helical Liquids and Non-Abelian Anyons in Quantum Wires,"We study one dimensional wires with spin-orbit coupling. We show that in the
presence of Zeeman field and strong electron-electron interaction a clean wire
may form fractional helical liquid states with phenomenology similar to
fractional quantum Hall liquids. Most notably, the wire's two terminal
conductance is predicted to show fractional quantized conductance plateaus at
low electron density. When the system is proximity-coupled to a superconductor,
fractional Majorana bound states may be stabilized. We discuss how disorder
destabilizes these fractional phases. Possible experimental realizations of
similar states in double wire systems are discussed.",1301.7335v1
2013-05-18,Excitonic Collapse in Semiconducting Transition Metal Dichalcogenides,"Semiconducting transition metal dichalcogenides (STMDC) are two-dimensional
(2D) crystals characterized by electron volt size band gaps, spin-orbit
coupling (SOC), and d-orbital character of its valence and conduction bands. We
show that these materials carry unique exciton quasiparticles (electron-hole
bound states) with energy within the gap but which can ``collapse'' in the
strong coupling regime by merging into the band structure continuum. The
exciton collapse seems to be a generic effect in these 2D crystals.",1305.4278v2
2013-11-15,Route to observing topological edge modes in ultracold fermions,"We show how to exploit the rich hyperfine structure of fermionic alkali atoms
to produce a quasi-1D topological superfluid while avoiding excessive heating
from off-resonant scattering. We model interacting fermions where four
hyperfine states are coupled by a variety of optical and microwave fields. We
calculate the local density of states in a trap, finding regimes with zero
energy topological edge modes. Heating rates in this system are significantly
suppressed compared to simple Raman-induced spin-orbit coupling approaches.",1311.3892v2
2014-11-06,Double path interference and magnetic oscillations in Cooper pair transport through a single nanowire,"We show that the critical current of the Josephson junction consisting of
superconducting electrodes coupled through a nanowire with two conductive
channels can reveal the multi-periodic magnetic oscillations. The
multi-periodicity originates from the quantum mechanical interference between
the channels affected by both the strong spin-orbit coupling and Zeeman
interaction. This minimal two-channel model is shown to explain the complicated
interference phenomena observed recently in Josephson transport through Bi
nanowires.",1411.1626v1
2014-12-03,Proximity-induced ferromagnetism in graphene revealed by anomalous Hall effect,"We demonstrate the anomalous Hall effect (AHE) in single-layer graphene
exchange-coupled to an atomically flat yttrium iron garnet (YIG) ferromagnetic
thin film. The anomalous Hall conductance has magnitude of ~0.09(2e2/h) at low
temperatures and is measurable up to ~ 300 K. Our observations indicate not
only proximity-induced ferromagnetism in graphene/YIG with large exchange
interaction, but also enhanced spin-orbit coupling which is believed to be
inherently weak in ideal graphene. The proximity-induced ferromagnetic order in
graphene can lead to novel transport phenomena such as the quantized AHE which
are potentially useful for spintronics.",1412.1521v1
2015-01-09,Enhancing triplet superconductivity by the proximity to a singlet superconductor in oxide heterostructures,"We show how in principle a coherent coupling between two superconductors of
opposite parity can be realized in a three-layer oxide heterostructure. Due to
strong intraionic spin-orbit coupling in the middle layer, singlet Cooper pairs
are converted into triplet ones and vice versa. This results in a large
enhancement of the triplet superconductivity, persisting well above the native
triplet critical temperature.",1501.02077v2
2015-03-10,Characterization of the Heavy Metal Pyrochlore Lattice Superconductor CaIr2,"We report the electronic properties of the cubic laves phase superconductor
CaIr2 (Tc = 5.8 K), in which the Ir atoms have a Pyrochlore lattice. The
estimated superconducting parameters obtained from magnetization and specific
heat measurements indicate that CaIr2 is a weakly coupled BCS superconductor.
Electronic band structure calculations show that the Ir d-states are dominant
at the Fermi level, creating a complex Fermi surface that is impacted
substantially by spin orbit coupling.",1503.02744v1
2015-09-14,Crystallization of fractional charges in a strongly interacting quasi-helical quantum dot,"The ground-state electron density of a one-dimensional spin-orbit coupled
quantum dot with a Zeeman term and strong electron interaction is studied at
the fractional helical liquid points. We show that at fractional filling
factors $\nu=(2n+1)^{-1}$ (with $n$ a non-negative integer) the density
oscillates with $N_{0}/\nu$ peak. For $n\geq 1$ a number of peaks larger than
the number of electrons $N_{0}$ suggests that a crystal of fractional
quasi-particles with charge $\nu e$ (with $e$ the electron charge) occurs. The
reported effect is amenable of verification via transport measurements in
charged AFM-coupled dot.",1509.03965v1
2017-01-11,Theory of Quantum Oscillations of Magnetization in Kondo Insulators,"The Kondo lattice model of spin-1/2 local moments coupled to the conduction
electrons at half-filling is studied for its orbital response to magnetic field
on bipartite lattices. Through an effective charge dynamics, in a canonical
representation of electrons that appropriately describes the Kondo insulating
ground state, the magnetization is found to show de Haas-van Alphen
oscillations from intermediate to weak Kondo coupling. These oscillations are
ascribed to Lifshitz-like inversion of a dispersion of the gapped
quasiparticles, whose chemical potential surface is measured by the oscillation
frequency. Such oscillations are also predicted to occur in spin-density wave
insulators.",1701.02825v2
2017-05-28,Mechanisms of localization in isotope-substituted dynamical Jahn-Teller systems,"The mechanisms of localization of Jahn-Teller deformations and vibronic
wavefunctions in isotope substituted dynamical Jahn-Teller systems are
elucidated. It is found that the localization in the trough is of potential
type in the case of strong vibronic coupling, while it becomes of kinetic type
in the case of intermediate and weak coupling. It is shown that the vibronic
levels in the linear $E\otimes e$-problem remain double degenerate upon
arbitrary isotope substitution on the reasons similar to time reversal symmetry
in which the role of spin is played by orbital pseudospin.",1705.09959v1
2021-04-01,Ultrafast dynamics with the exact factorization,"The exact factorization of the time-dependent electron-nuclear wavefunction
has been employed successfully in the field of quantum molecular dynamics
simulations for interpreting and simulating light-induced ultrafast processes.
In this work, we summarize the major developments leading to the formulation of
a trajectory-based approach, derived from the exact factorization equations,
capable of dealing with nonadiabatic electronic processes, and including
spin-orbit coupling and the non-perturbative effect of an external
time-dependent field. This trajectory-based quantum-classical approach has been
dubbed coupled-trajectory mixed quantum-classical (CT-MQC) algorithm, whose
performance is tested here to study the photo-dissociation dynamics of IBr.",2104.00738v1
2019-05-23,Devil's staircase structures in $\varphi_{0}$ junction,"The superconductor-ferromagnet-superconductor $\varphi_{0}$ junction provides
a direct coupling between Josephson phase and magnetic moment of ferromagnetic
barrier. We demonstrate an appearance of additional fractional subharmonic
steps in the IV-characteristics of $\varphi_{0}$ junction under external
electromagnetic radiation due to spin-orbit coupling. An origin of subharmonic
steps is related to the locking of magnetic moment precession to the Josephson
oscillations. We prove that the positions of those steps follow a continued
fraction algorithm.",1905.09672v1
2021-02-25,Stability of highly-twisted Skyrmions from contact topology,"We describe a topological protection mechanism for highly-twisted
two-dimensional Skyrmions in systems with Dyloshinskii-Moriya (DM) coupling,
where non-zero DM energy density (dubbed ""twisting energy density"") acts as a
kind of band gap in real space, yielding an N invariant for highly twisted
Skyrmions. We prove our result through the application of contact topology by
extending our system along a fictitious third dimension, and further establish
the structural stability of highly-twisted Skyrmions under arbitrary
chirality-preserving distortions. Our results apply for all two-dimensional
systems hosting Skyrmion excitations including spin-orbit coupled systems
exhibiting quantum Hall ferromagnetism.",2102.13126v1
2021-05-13,Electron correlation effects in superconducting nanowires in and out of equilibrium,"One-dimensional nanowires with strong spin-orbit coupling and
proximity-induced superconductivity are predicted to exhibit topological
superconductivity with condensed-matter analogues to Majorana fermions. Here,
the nonequilibrium Green's function approach with the generalized Kadanoff-Baym
ansatz is employed to study the electron-correlation effects and their role in
the topological superconducting phase in and out of equilibrium.
Electron-correlation effects are found to affect the transient signatures
regarding the zero-energy Majorana states, when the superconducting nanowire is
subjected to external perturbations such as magnetic-field quenching,
laser-pulse excitation, and coupling to biased normal-metal leads.",2105.06193v1
2022-03-27,Quantized and half-quantized Anomalous Hall effect induced by in-plane magnetic field,"In this paper we propose that, quantized and nearly half-quantized intrinsic
anomalous Hall effect can be induced by in-plane external magnetic field
through the Zeeman coupling in non-magnetic 2D systems with sizeable
spin-orbital coupling but without two-fold rotational symmetry. An analytical
result is derived for 2D electron gas model with $C_{3v}$ symmetry. Based on
the $\boldsymbol{k\cdot p}$ Hamiltonian derived from first principle
calculations, we find that quantized and nearly half-quantized conductance can
be observed in $\mathrm{Sb_2Te_3}$ thin film in the clean limit with strong
in-plane magnetic field $B>20\ \mathrm{T}$ and low temperature $T<100\
\mathrm{mK}$.",2203.14301v1
2024-01-09,Co-doping Er plus V or Er plus Nb into CaWO4,"Er3+ plus V5+, and Er3+ plus Nb5+ co-doped CaWO4, formulas Ca1-xErxW1-xMxO4,
were synthesized in air by a conventional solid-state method. A color change
from white to pink was observed in the final products. An equal fraction of
dopants was employed to obtain charge neutrality, and the limits of the
solubility for our conditions are lower than x=0.15. The magnetic
susceptibility data shows that that the magnetic coupling becomes increasingly
antiferromagnetic with increasing Er3+content. The Curie-Weiss fit and
isothermal magnetization imply that different degrees of spin-orbit coupling
appear to be present in the two doping systems. No transitions were observed in
the heat capacity data above 0.4 K.",2401.04790v1
2015-10-11,Spin Hall and spin Nernst effects in a two-dimensional electron gas with Rashba spin-orbit interaction: temperature dependence,"Using the Matsubara Green function formalism we calculate the temperature
dependence of spin Hall and spin Nernst conductivities of a two-dimensional
electron gas with Rashba spin-orbit interaction in the linear response regime.
In the case of spin Nernst effect we also include the contribution from
spin-resolved orbital magnetization, which assures correct behavior of the spin
Nernst conductivity in the zero-temperature limit. Analytical formulas for the
spin Hall and spin Nernst conductivities are derived in some specific
situations. Using the Ioffe-Regel localization criterion, we have also
estimated the range of parameters where the calculated results for the spin
Hall and spin Nernst conductivities are applicable. Analytical results show
that the vertex correction totally suppresses the spin Hall conductivity at
arbitrary temperature. The spin Nernst conductivity, in turn, vanishes at $T=0$
when the orbital contribution is taken into account, but generally is nonzero
at finite temperatures.",1510.03080v2
2018-08-21,Recent advances in spin-orbit torques: Moving towards device applications,"The ability of spintronic devices to utilize an electric current for
manipulating the magnetization has resulted in large-scale developments, such
as, magnetic random access memories and boosted the spintronic research area.
In this regard, over the last decade, magnetization manipulation using
spin-orbit torque has been devoted a lot of research attention as it shows a
great promise for future ultrafast and power efficient magnetic memories. In
this review, we summarize the latest advancements in spin-orbit torque research
and highlight some of the technical challenges for practical spin-orbit torque
devices. We will first introduce the basic concepts and highlight the latest
material choices for spin-orbit torque devices. Then, we will summarize the
important advancements in the study of magnetization switching dynamics using
spin-orbit torque, which are important from scientific as well as technological
aspect. The final major section focuses on the concept of external assist field
free spin-orbit torque switching which is a requirement for practical
spin-orbit torque devices.",1808.06829v1
2022-11-13,Long-range spin-orbital order in the spin-orbital SU(2)$\times$SU(2)$\times$U(1) model,"By using the tensor-network state algorithm, we study a spin-orbital model
with SU(2)$\times$SU(2)$\times$U(1) symmetry on the triangular lattice. This
model was proposed to describe some triangular $d^1$ materials and was argued
to host a spin-orbital liquid ground state. In our work the trial wavefunction
of its ground state is approximated by an infinite projected entangled simplex
state and optimized by the imaginary-time evolution. Contrary to the previous
conjecture, we find that the two SU(2) symmetries are broken, resulting in a
stripe spin-orbital order with the same magnitude $m=0.085(10)$. This value is
about half of that in the spin-1/2 triangular Heisenberg antiferromagnet. Our
result demonstrates that although the long-sought spin-orbital liquid is absent
in this model the spin-orbital order is significantly reduced due to the
enhanced quantum fluctuation. This suggests that high-symmetry spin-orbital
models are promising in searching for exotic states of matter in
condensed-matter physics.",2211.06852v1
2004-12-23,Quasiperiodic spin-orbit motion and spin tunes in storage rings,"We present an in-depth analysis of the concept of spin precession frequency
for integrable orbital motion in storage rings. Spin motion on the periodic
closed orbit of a storage ring can be analyzed in terms of the Floquet theorem
for equations of motion with periodic parameters and a spin precession
frequency emerges in a Floquet exponent as an additional frequency of the
system. To define a spin precession frequency on nonperiodic synchro-betatron
orbits we exploit the important concept of quasiperiodicity. This allows a
generalization of the Floquet theorem so that a spin precession frequency can
be defined in this case too. This frequency appears in a Floquet-like exponent
as an additional frequency in the system in analogy with the case of motion on
the closed orbit. These circumstances lead naturally to the definition of the
uniform precession rate and a definition of spin tune. A spin tune is a uniform
precession rate obtained when certain conditions are fulfilled. Having defined
spin tune we define spin-orbit resonance on synchro--betatron orbits and
examine its consequences. We give conditions for the existence of uniform
precession rates and spin tunes (e.g. where small divisors are controlled by
applying a Diophantine condition) and illustrate the various aspects of our
description with several examples. The formalism also suggests the use of
spectral analysis to ``measure'' spin tune during computer simulations of spin
motion on synchro-betatron orbits.",0412157v1
2020-08-19,Prediction of low-Z collinear and noncollinear antiferromagnetic compounds having momentum-dependent spin splitting even without spin-orbit coupling,"Recent study (Yuan et. al., Phys. Rev. B 102, 014422 (2020)) revealed a
SOC-independent spin splitting and spin polarization effect induced by
antiferromagnetic ordering which do not necessarily require breaking of
inversion symmetry or the presence of SOC, hence can exist even in
centrosymmetric, low-Z light element compounds, considerably broadening the
material base for spin polarization. In the present work we develop the
magnetic symmetry conditions enabling such effect, dividing the 1651 magnetic
space groups into 7 different spin splitting prototypes (SST-1 to SST-7). We
use the 'Inverse Design' approach of first formulating the target property
(here, spin splitting in low-Z compounds not restricted to low symmetry
structures), then derive the enabling physical design principles to search
realizable compounds that satisfy these a priori design principles. This
process uncovers 422 magnetic space groups (160 centrosymmetric and 262
non-centrosymmetric) that could hold AFM-induced, SOC-independent spin
splitting and spin polarization. We then search for stable compounds following
such enabling symmetries. We investigate the electronic and spin structures of
some selected prototype compounds by density functional theory (DFT) and find
spin textures that are different than the traditional Rashba-Dresselhaus
patterns. We provide the DFT results for all antiferromagnetic spin splitting
prototypes (SST-1 to SST-4) and concentrate on revealing of the AFM-induced
spin splitting prototype (SST-4). The symmetry design principles along with
their transformation into an Inverse Design material search approach and DFT
verification could open the way to their experimental examination.M). The
symmetry design principles along with their transformation into an Inverse
Design material search approach and DFT verification could open the way to
their experimental examination.",2008.08532v1
2011-03-11,Spin-orbital resonating valence bond liquid on a triangular lattice: Evidence from finite-cluster diagonalization,"We investigate the ground state of the $d^1$ spin-orbital model for triply
degenerate $t_{2g}$ orbitals on a triangular lattice which unifies intrinsic
frustration of spin and orbital interactions with geometrical frustration.
Using full or Lanczos exact diagonalization of finite clusters we establish
that the ground state of the spin-orbital model which interpolates between the
superexchange and direct exchange interactions on the bonds is characterized by
valence-bond correlations. In the absence of Hund's exchange the model
describes a competition between various possible valence-bond states. By
considering the clusters with open boundary conditions we demonstrate that
orbital interactions are always frustrated, but this frustration is removed by
pronounced spin singlet correlations which coexist with supporting them dimer
orbital correlations. Such local configurations contribute to the disordered
ground states found for the clusters with periodic boundary conditions which
interpolate between a highly resonating, dimer-based, entangled spin-orbital
liquid phase, and a valence-bond state with completely static spin-singlet
states. We argue that these states are also realized for the infinite lattice
and anticipate that pronounced transitions between different regimes found for
particular geometries will turn out to smooth crossovers in the properties of
the spin-orbital liquid in the thermodynamic limit. Finally, we provide
evidence that the resonating spin-orbital liquid phase involves entangled
states on the bonds. In such a phase classical considerations based on the
mean-field theory cannot be used, spin exchange interactions do not determine
spin bond correlations, and quantum fluctuations play a crucial role in the
ground states and magnetic transitions.",1103.2319v1
2014-11-03,Strain dependence of antiferromagnetic interface coupling in La0.7Sr0.3MnO3/SrRuO3 superlattices,"We have investigated the magnetic response of La0.7Sr0.3MnO3/SrRuO3
superlattices to biaxial in-plane strain applied in-situ. Superlattices grown
on piezoelectric substrates of 0.72PbMg1/3Nb2/3O3-0.28PbTiO3(001) (PMN-PT) show
strong antiferromagnetic coupling of the two ferromagnetic components. The
coupling field of mu0HAF = 2.8 T is found to decrease by deltaHAF/delta epsilon
~ -520 mT %-1 under reversible biaxial strain mu0HAF at 80 K in a
[La0.7Sr0.3MnO3(22)/SrRuO3(55)]15 superlattice. This reveals a significant
strain effect on interfacial coupling. The applied in-plane compression
enhances the ferromagnetic order in the manganite layers which are under
as-grown tensile strain. It is thus difficult to disentangle the contributions
from strain-dependent antiferromagnetic Mn-O-Ru interface coupling and Mn-O-Mn
ferromagnetic double exchange near the interface, since the enhanced magnetic
order of Mn spins leads to a larger net coupling of SrRuO3 layers at the
interface. Strain-dependent orbital occupation in a single-ion picture cannot
explain the sign of the observed strain dependence, whereas the enhanced Mn
order at the interface is qualitatively in line with it.",1411.0411v2
2016-06-24,Two-dimensional electron gas in the regime of strong light-matter coupling: Dynamical conductivity and all-optical measurements of Rashba and Dresselhaus coupling,"A nonperturbative interaction of an electronic system with a laser field can
substantially modify its physical properties. In particular, in two-dimensional
(2D) materials with a lack of inversion symmetry, the achievement of a regime
of strong light-matter coupling allows direct optical tuning of the strength of
the Rashba spin-orbit interaction (SOI). Capitalizing on these results, we
build a theory of the dynamical conductivity of a 2D electron gas with both
Rashba and Dresselhaus SOIs coupled to an off-resonant high-frequency
electromagnetic wave. We argue that strong light-matter coupling modifies
qualitatively the dispersion of the electrons and can be used as a powerful
tool to probe and manipulate the coupling strengths and adjust the frequency
range where optical conductivity is essentially nonzero.",1606.07663v2
2020-05-27,Rydberg spectrum of a single trapped Ca$^+$ ion: A Floquet analysis,"We compute the Rydberg spectrum of a single Ca$^+$ ion in a Paul trap by
incorporating various internal and external coupling terms of the ion to the
trap in the Hamiltonian. The coupling terms include spin-orbit coupling in
Ca$^+$, charge (electron and ionic core) coupling to the radio frequency and
static fields, ion-electron coupling in the Paul trap, and ion center-of-mass
coupling. The electronic Rydberg states are precisely described by a
one-electron model potential for e$^-$+Ca$^{2+}$, and accurate eigenenergies,
quantum defect parameters, and static and tensor polarizabilities for a number
of excited Rydberg states are obtained. The time-periodic rf Hamiltonian is
expanded in the Floquet basis, and the trapping-field-broadened Rydberg lines
are compared with recent observations of Ca$^+(23P)$ and Ca$^+(52F)$ Rydberg
lines.",2005.13659v1
2016-03-11,Proximity effect and Majorana bound states in clean semiconductor nanowires coupled to disordered superconductors,"We study a semiconductor wire with strong spin-orbit coupling, which is
proximity-coupled to a superconductor with chemical potential disorder. When
tunneling at the semiconductor- superconductor interface is very weak, it is
known that disorder in the superconductor does not affect the induced
superconductivity nor, therefore, the effective topological superconductivity
that emerges above a critical magnetic field. We demonstrate nonperturbatively
how this result breaks down with stronger proximity coupling by obtaining the
low-energy (i.e., subgap) excitation spectrum through direct numerical
diagonalization of an appropriate BdG hamiltonian. With strong proximity
coupling, we find that disorder in the parent superconductor suppresses the
(non- topological) induced gap at zero magnetic field by disordering the
induced pair potential. In the topological superconducting phase at large
magnetic field, strong proximity coupling reduces the localization length of
Majorana bound states, such that the induced disorder eliminates the
topological gap while bulk Majorana zero modes emerge, even for short wires.",1603.03780v1
2023-03-28,Analysis of ultrafast magnetization switching dynamics in exchange-coupled ferromagnet-ferrimagnet heterostructures,"Magnetization switching in ferromagnets has so far been limited to the
current-induced spin-orbit-torque effects. Recent observation of
helicity-independent all-optical magnetization switching in exchange-coupled
ferromagnet ferrimagnet heterostructures expanded the range and applicability
of such ultrafast heat-driven magnetization switching. Here we report the
element-resolved switching dynamics of such an exchange-coupled system, using a
modified microscopic three-temperature model. We have studied the effect of i)
the Curie temperature of the ferromagnet, ii) ferrimagnet composition, iii) the
long-range RKKY exchange-coupling strength, and iv) the absorbed optical energy
on the element-specific time-resolved magnetization dynamics. The phase-space
of magnetization illustrates how the RKKY coupling strength and the absorbed
optical energy influence the switching time. Our analysis demonstrates that the
threshold switching energy depends on the composition of the ferrimagnet and
the switching time depends on the Curie temperature of the ferromagnet as well
as RKKY coupling strength. This simulation anticipates new insights into
developing faster and more energy-efficient spintronics devices.",2303.16294v1
2016-09-02,Semiclassical theory of anisotropic transport at LaAlO3/SrTiO3 interfaces under in-plane magnetic field,"The unconventional magnetotransport at the interface between transition-metal
oxides $LaAlO_3$ (LAO) and $SrTiO_3$ (STO) is frequently related to mobile
electrons interacting with localized magnetic moments. However nature and
properties of magnetism at this interface are not well understood so far. In
this paper, we focus on transport effects driven by spin-orbit coupling and
intentionally neglect possible strong correlations. The electrical resistivity
tensor is calculated as a function of the magnitude and orientation of an
external magnetic field parallel to the interface. The semiclassical Boltzmann
equation is solved numerically for the two-dimensional system of spin-orbit
coupled electrons accelerated by an electric field and scattered by
spatially-correlated impurities. At temperatures of a few Kelvin and densities
such that the chemical potential crosses the second pair of spin-orbit split
bands, we find a strongly anisotropic modulation of the (negative)
magnetoresistance above 10 T, characterized by multiple maxima and minima away
from the crystalline axes. Along with the drop of the magnetoresistance, an
abrupt enhancement of the transverse resistivity occurs. The angular modulation
of the latter considerably deviates from a (low-field) sinusoidal dependence to
a (high-field) step-like behaviour. These peculiar features are the
consequences of the anisotropy of both (intra-band and inter-band )
scattering-amplitudes in the Brillouin zone when the relevant energy scales in
the system - chemical potential, spin-orbit interaction and Zeeman energy - are
all comparable to each other. The theory provides good qualitative agreement
with experimental data in the literature.",1609.00663v3
2019-03-01,Spin-orbit-controlled metal-insulator transition in Sr$_2$IrO$_4$,"In the context of correlated insulators, where electron-electron interactions
(U) drive the localization of charge carriers, the metal-insulator transition
(MIT) is described as either bandwidth (BC) or filling (FC) controlled.
Motivated by the challenge of the insulating phase in Sr$_2$IrO$_4$, a new
class of correlated insulators has been proposed, in which spin-orbit coupling
(SOC) is believed to renormalize the bandwidth of the half-filled
$j_{\mathrm{eff}} = 1/2$ doublet, allowing a modest U to induce a
charge-localized phase. Although this framework has been tacitly assumed, a
thorough characterization of the ground state has been elusive. Furthermore,
direct evidence for the role of SOC in stabilizing the insulating state has not
been established, since previous attempts at revealing the role of SOC have
been hindered by concurrently occurring changes to the filling. We overcome
this challenge by employing multiple substituents that introduce well defined
changes to the signatures of SOC and carrier concentration in the electronic
structure, as well as a new methodology that allows us to monitor SOC directly.
Specifically, we study Sr$_2$Ir$_{1-x}$T$_x$O$_4$ (T = Ru, Rh) by
angle-resolved photoemission spectroscopy (ARPES), combined with ab-initio and
supercell tight-binding calculations. This allows us to distinguish
relativistic and filling effects, thereby establishing conclusively the central
role of SOC in stabilizing the insulating state of Sr$_2$IrO$_4$. Most
importantly, we estimate the critical value for spin-orbit coupling in this
system to be $\lambda_c = 0.42 \pm 0.01$ eV, and provide the first
demonstration of a spin-orbit-controlled MIT.",1903.00484v2
2000-09-28,"Andreev-Tunneling, Coulomb Blockade, and Resonant Transport of Non-Local Spin-Entangled Electrons","We propose and analyze a spin-entangler for electrons based on an s-wave
superconductor coupled to two quantum dots each of which is tunnel-coupled to
normal Fermi leads. We show that in the presence of a voltage bias and in the
Coulomb blockade regime two correlated electrons provided by the Andreev
process can coherently tunnel from the superconductor via different dots into
different leads. The spin-singlet coming from the Cooper pair remains preserved
in this process, and the setup provides a source of mobile and nonlocal
spin-entangled electrons. The transport current is calculated and shown to be
dominated by a two-particle Breit-Wigner resonance which allows the injection
of two spin-entangled electrons into different leads at exactly the same
orbital energy, which is a crucial requirement for the detection of spin
entanglement via noise measurements. The coherent tunneling of both electrons
into the same lead is suppressed by the on-site Coulomb repulsion and/or the
superconducting gap, while the tunneling into different leads is suppressed
through the initial separation of the tunneling electrons. In the regime of
interest the particle-hole excitations of the leads are shown to be negligible.
The Aharonov-Bohm oscillations in the current are shown to contain single- and
two-electron periods with amplitudes that both vanish with increasing Coulomb
repulsion albeit differently fast.",0009452v2
2014-07-22,Theoretical elucidation of possibility of Majorana modes in a two dimensional Dirac system,"Here we present the theoretical clarification of possibility of eight
Majorana-like modes (quasi-particles which are self-conjugate) close to the
experimentally inaccessible Dirac points of a two-dimensional monolayer Dirac
system. The valley-mixing and the spin-degeneracy lifting are the main
requirements. These are possible by wedging in the requisite ingredients in the
description, viz. the atomically sharp scatterers and the strong spin-orbit
coupling (SOC). The latter can possibly be achieved in graphene folding a
sheet; the higher curvature of deformations correspond to stronger values of
the coupling. In silicene, the buckled structure of the system generates a
staggered sub-lattice potential between silicon atoms at A sites and B sites
for an applied electric field perpendicular to its plane. The stronger SOC in
silicene has its origin also in the buckled structure of the system. Tuning of
electric field, allows for rich behavior varying from a topological insulator
to a normal insulator with a valley spin-polarized metal (VSPM) at a critical
value in between. The VSPM stage is characterized by the valley-spin locking,
i.e. the opposite spin polarization at different valleys. We shall see that in
this phase, if the inter-valley scattering process and the real spin-flip
process in moderation are allowed to take place, we have the right condition
for capturing Majoranas in the proximity of a s-wave superconductor.",1407.5938v1
2015-02-26,"Strong Interplay between Stripe Spin Fluctuations, Nematicity and Superconductivity in FeSe","Elucidating the microscopic origin of nematic order in iron-based
superconducting materials is important because the interactions that drive
nematic order may also mediate the Cooper pairing. Nematic order breaks
fourfold rotational symmetry in the iron plane, which is believed to be driven
by either orbital or spin degrees of freedom. However, as the nematic phase
often develops at a temperature just above or coincides with a stripe magnetic
phase transition, experimentally determining the dominant driving force of
nematic order is difficult. Here, we use neutron scattering to study
structurally the simplest iron-based superconductor FeSe, which displays a
nematic (orthorhombic) phase transition at $T_s=90$ K, but does not order
antiferromagnetically. Our data reveal substantial stripe spin fluctuations,
which are coupled with orthorhombicity and are enhanced abruptly on cooling to
below $T_s$. Moreover, a sharp spin resonance develops in the superconducting
state, whose energy (~4 meV) is consistent with an electron boson coupling mode
revealed by scanning tunneling spectroscopy, thereby suggesting a spin
fluctuation-mediated sign-changing pairing symmetry. By normalizing the dynamic
susceptibility into absolute units, we show that the magnetic spectral weight
in FeSe is comparable to that of the iron arsenides. Our findings support
recent theoretical proposals that both nematicity and superconductivity are
driven by spin fluctuations.",1502.07544v1
2016-09-01,Topical Review: Spins and mechanics in diamond,"There has been rapidly growing interest in hybrid quantum devices involving a
solid-state spin and a macroscopic mechanical oscillator. Such hybrid devices
create exciting opportunities to mediate interactions between disparate qubits
and to explore the quantum regime of macroscopic mechanical objects. In
particular, a system consisting of the nitrogen-vacancy defect center in
diamond coupled to a high quality factor mechanical oscillator is an appealing
candidate for such a hybrid quantum device, as it utilizes the highly coherent
and versatile spin properties of the defect center. In this paper, we will
review recent experimental progress on diamond-based hybrid quantum devices in
which the spin and orbital dynamics of single defects are driven by the motion
of a mechanical oscillator. In addition, we discuss prospective applications
for this device, including long range, phonon-mediated spin-spin interactions,
and phonon cooling in the quantum regime. We conclude the review by evaluating
the experimental limitations of current devices and identifying alternative
device architectures that may reach the strong coupling regime.",1609.00418v2
2016-08-16,Revealing frustrated local moment model for pressurized hyperhoneycomb iridate: paving a way toward quantum spin liquid,"There have been tremendous experimental and theoretical efforts toward
discovery of quantum spin liquid phase in honeycomb-based-lattice materials
with strong spin-orbit coupling. Here the bond-dependent Kitaev interaction
between local moments provides strong magnetic frustration and if it is the
only interaction present in the system, it will lead to an exactly solvable
quantum spin liquid ground state. In all of these materials, however, the
ground state is in a magnetically ordered phase due to additional interactions
between local moments. Recently, it has been reported that the magnetic order
in hyperhoneycomb material, $\beta$-Li$_2$IrO$_3$, is suppressed upon applying
hydrostatic pressure and the resulting state becomes a quantum paramagnet or
possibly a quantum spin liquid. Using ab-initio computations and strong
coupling expansion, we investigate the lattice structure and resulting local
moment model in pressurized $\beta$-Li$_2$IrO$_3$. Remarkably, the dominant
interaction under high pressure is not the Kitaev interaction nor further
neighbor interactions, but a different kind of bond-dependent interaction. This
leads to strong magnetic frustration and may provide a platform for discovery
of a new kind of quantum spin liquid ground state.",1608.04741v2
2020-08-13,Magnetization Dynamics of Nanoscale Magnetic Materials: A Perspective,"Nanomagnets form the building blocks for a gamut of miniaturized
energy-efficient devices including data storage, memory, wave-based computing,
sensors and biomedical devices. They also offer a span of exotic phenomena and
stern challenges. The progress in the magnetization dynamics of single
nanomagnets and one- and two-dimensional arrays of nanostructures in the form
of dots, antidots, nanoparticles, binary and bicomponent structures and
patterned multilayers have been presented. Progress in unconventional and new
structures like artificial spin ice and three-dimensional nanomagnets and spin
textures like domain walls, vortex and skyrmions have been presented.
Furthermore, a huge variety of new topics in the magnetization dynamics of
magnetic nanostructures are rapidly emerging. An overview of the steadily
evolving topics like spatio-temporal imaging of fast dynamics of
nanostructures, dynamics of spin textures, artificial spin ice have been
discussed. In addition, dynamics of contemporary and newly transpired magnetic
architectures such as nanomagnet arrays with complex basis and symmetry,
magnonic quasicrystals, fractals, defect structures, novel three-dimensional
structures have been introduced. Effects of various spin-orbit coupling and
ensuing spin textures as well as quantum hybrid systems comprising of
magnon-photon, magnon-phonon and magnon-magnon coupling, antiferromagnetic
nanostructures are rapidly growing and are expected to dominate this research
field in the coming years. Finally, associated topics like nutation dynamics
and nanomagnet antenna are briefly discussed. Despite showing a great progress,
only a small fraction of nanomagnetism and its ancillary topics have been
explored so far and huge efforts are envisaged in this evergrowing research
area in the generations to come.",2008.05819v1
2020-10-19,Geometrical Hall effect and momentum-space Berry curvature from spin-reversed band pairs,"When nanometric, noncoplanar spin textures with scalar spin chirality (SSC)
are coupled to itinerant electrons, they endow the quasiparticle wavefunctions
with a gauge field, termed Berry curvature, in a way that bears analogy to
relativistic spin-orbit coupling (SOC). The resulting deflection of moving
charge carriers is termed geometrical (or topological) Hall effect. Previous
experimental studies modeled this signal as a real-space motion of wavepackets
under the influence of a quantum-mechanical phase. In contrast, we here compare
the modification of Bloch waves themselves, and of their energy dispersion, due
to SOC and SSC. Using the canted pyrochlore ferromagnet Nd$_2$Mo$_2$O$_7$ as a
model compound, our transport experiments and first-principle calculations show
that SOC impartially mixes electronic bands with equal or opposite spin, while
SSC is much more effective for opposite spin band pairs.",2010.09537v4
2019-05-23,Efficient variational approach to dynamics of a spatially extended bosonic Kondo model,"We develop an efficient variational approach to studying dynamics of a
localized quantum spin coupled to a bath of mobile spinful bosons. We use
parity symmetry to decouple the impurity spin from the environment via a
canonical transformation and reduce the problem to a model of the interacting
bosonic bath. We describe coherent time evolution of the latter using bosonic
Gaussian states as a variational ansatz. We provide full analytical expressions
for equations describing variational time evolution that can be applied to
study in- and out-of-equilibrium phenomena in a wide class of quantum impurity
problems. In the accompanying paper [Y. Ashida {\it et al.}, Phys. Rev. Lett.
123, 183001 (2019)], we present a concrete application of this general
formalism to the analysis of the Rydberg Central Spin Model, in which the
spin-1/2 Rydberg impurity undergoes spin-changing collisions in a dense cloud
of two-component ultracold bosons. To illustrate new features arising from
orbital motion of the bath atoms, we compare our results to the Monte Carlo
study of the model with spatially localized bosons in the bath, in which random
positions of the atoms give rise to random couplings of the standard central
spin model.",1905.09615v5
2022-08-23,Microwave spectroscopy of interacting Andreev spins,"Andreev bound states are fermionic states localized in weak links between
superconductors which can be occupied with spinful quasiparticles. Microwave
experiments using superconducting circuits with InAs/Al nanowire Josephson
junctions have recently enabled probing and coherent manipulation of Andreev
states but have remained limited to zero or small fields. Here we use a
flux-tunable superconducting circuit in external magnetic fields up to 1T to
perform spectroscopy of spin-polarized Andreev states up to ~250 mT, beyond
which the spectrum becomes gapless. We identify singlet and triplet states of
two quasiparticles occupying different Andreev states through their dispersion
in magnetic field. These states are split by exchange interaction and couple
via spin-orbit coupling, analogously to two-electron states in quantum dots. We
also show that the magnetic field allows to drive a direct spin-flip transition
of a single quasiparticle trapped in the junction. Finally, we measure a gate-
and field-dependent anomalous phase shift of the Andreev spectrum, of magnitude
up to approximately $0.7\pi$. Our observations demonstrate new ways to
manipulate Andreev states in a magnetic field and reveal spin-polarized triplet
states that carry supercurrent.",2208.11198v1
2022-11-21,General time-reversal equivariant neural network potential for magnetic materials,"This study introduces time-reversal E(3)-equivariant neural network and
SpinGNN++ framework for constructing a comprehensive interatomic potential for
magnetic systems, encompassing spin-orbit coupling and noncollinear magnetic
moments. SpinGNN++ integrates multitask spin equivariant neural network with
explicit spin-lattice terms, including Heisenberg, Dzyaloshinskii-Moriya,
Kitaev, single-ion anisotropy, and biquadratic interactions, and employs
time-reversal equivariant neural network to learn high-order spin-lattice
interactions using time-reversal E(3)-equivariant convolutions. To validate
SpinGNN++, a complex magnetic model dataset is introduced as a benchmark and
employed to demonstrate its capabilities. SpinGNN++ provides accurate
descriptions of the complex spin-lattice coupling in monolayer CrI$_3$ and
CrTe$_2$, achieving sub-meV errors. Importantly, it facilitates large-scale
parallel spin-lattice dynamics, thereby enabling the exploration of associated
properties, including the magnetic ground state and phase transition.
Remarkably, SpinGNN++ identifies a new ferrimagnetic state as the ground
magnetic state for monolayer CrTe2, thereby enriching its phase diagram and
providing deeper insights into the distinct magnetic signals observed in
various experiments.",2211.11403v3
2024-03-31,Charge and spin current pumping by ultrafast demagnetization dynamics,"The surprising discovery of ultrafast demagnetization -- where electric field
of femtosecond laser pulse couples to electrons of a ferromagnetic (FM) layer
causing its magnetization vector {\em to shrink while not rotating}, is also
assumed to be accompanied by generation of spin current in the direction
orthogonal to electric field. However, understanding of the microscopic origin
of such spin current and how efficiently it can be converted into charge
current, as the putative source of THz radiation, is lacking despite nearly
three decades of intense studies. Here we connect the standard pumping
phenomena driven by microwave precession of magnetization vector replacing
periodic time-dependence of magnetization precession with nonperiodic
time-dependence of demagnetization, as obtained from experiments on
ultrafast-light-driven Ni layer. Applying time-dependent nonequilibrium Green's
functions, able to evolve such setup with arbitrary time dependence, reveals
how demagnetization dynamics pumps both charge and spin currents in directions
both parallel and orthogonal to electric field of laser pulse, even in the
absence of spin-orbit coupling and thereby induced spin-to-charge conversion
mechanisms. Although pumped currents follow $dM_z/dt$ in some setups, this
becomes obscured when NM layers are disconnected and pumped currents start to
reflect from FM boundaries (as is the case of experimental setups). Finally, we
use the Jefimenko equations to compute electromagnetic radiation by charge
current pumped in disconnected setup during demagnetization, or later during
its slow recovery, unraveling that radiated electric field only in the former
time interval exhibits features in 0.1--30 THz frequency range probed
experimentally or explored for applications of spintronic THz emitters.",2404.00779v1
2013-12-29,The spin-orbit resonances of the Solar system: A mathematical treatment matching physical data,"In the mathematical framework of a restricted, slightly dissipative
spin-orbit model, we prove the existence of periodic orbits for astronomical
parameter values corresponding to all satellites of the Solar system observed
in exact spin-orbit resonance.",1312.7544v1
2021-10-27,The Rossiter-McLaughlin effect Revolutions: An ultra-short period planet and a warm mini-Neptune on perpendicular orbits,"Comparisons of the alignment of exoplanets with a common host star can be
used to distinguish among concurrent evolution scenarios. However, multi-planet
systems usually host mini-Neptunes and super-Earths, whose size make orbital
architecture measurements challenging. We introduce the Rossiter-McLaughlin
effect Revolutions technique, which can access spin-orbit angles of small
planets by exploiting the full information contained in spectral transit time
series. We validated the technique on published HARPS-N data of the
mini-Neptune HD3167c, refining its high sky-projected spin-orbit angle
(-108.9+5.4-5.5 deg), and we applied it to new ESPRESSO observations of the
super-Earth HD3167b, revealing an aligned orbit (-6.6+6.6-7.9 deg).
Surprisingly different variations in the contrast of the stellar lines occulted
by the planets can be reconciled with a latitudinal dependence of the stellar
line shape. In this scenario, a joint fit to both datasets constrains the
inclination of the star (111.6+3.1-3.3 deg) and the 3D spin-orbit angles of
HD3167b (29.5+7.2-9.4 deg) and HD3167c (107.7+5.1-4.9 deg). The projected
spin-orbit angles do not depend on the model for the line contrast variations,
and so, with a mutual inclination of 102.3+7.4-8.0 deg, we conclude that the
two planets are on perpendicular orbits. This could be explained by HD3167b
being strongly coupled to the star and retaining its primordial alignment,
whereas HD3167c would have been brought to a nearly polar orbit via secular
gravitational interactions with an outer companion. Follow-up observations and
dynamical evolution simulations are required to search for this companion and
explore this scenario. HD3167b is the smallest exoplanet with a confirmed
spectroscopic Rossiter-McLaughlin signal. Our new technique opens the way to
determining the orbital architectures of the super-Earth and Earth-sized planet
populations.",2110.14214v1
2001-07-23,"Electronic structure study of double perovskites $A_{2}$FeReO$_{6}$ (A=Ba,Sr,Ca) and Sr$_{2}M$MoO$_{6}$ (M=Cr,Mn,Fe,Co) by LSDA and LSDA+U","We have implemented a systematic LSDA and LSDA+U study of the double
perovskites $A_{2}$FeReO$_{6}$ (A=Ba,Sr,Ca) and Sr$_{2}$$M$MoO$_{6}$
(M=Cr,Mn,Fe,Co) for understanding of their intriguing electronic and magnetic
properties. The results suggest a ferrimagnetic (FiM) and half-metallic (HM)
state of $A_{2}$FeReO$_{6}$ (A=Ba,Sr) due to a pdd-$\pi$ coupling between the
down-spin Re$^{5+}$/Fe$^{3+}$ $t_{2g}$ orbitals via the intermediate O
$2p_{\pi}$ ones, also a very similar FiM and HM state of Sr$_{2}$FeMoO$_{6}$.
In contrast, a decreasing Fe $t_{2g}$ component at Fermi level ($E_{F}$) in the
distorted Ca$_{2}$FeReO$_{6}$ partly accounts for its nonmetallic behavior,
while a finite $pdd$-$\sigma$ coupling between the down-spin
Re$^{5+}$/Fe$^{3+}$ $e_{g}$ orbitals being present at $E_{F}$ serves to
stabilize its FiM state. For Sr$_{2}$CrMoO$_{6}$ compared with
Sr$_{2}$FeMoO$_{6}$, the coupling between the down-spin Mo$^{5+}$/Cr$^{3+}$
$t_{2g}$ orbitals decreases as a noticeable shift up of the Cr$^{3+}$ 3d
levels, which is likely responsible for the decreasing $T_{C}$ value and weak
conductivity. Moreover, the calculated level distributions indicate a
Mn$^{2+}$(Co$^{2+}$)/Mo$^{6+}$ ionic state in Sr$_{2}$MnMoO$_{6}$
(Sr$_{2}$CoMoO$_{6}$), in terms of which their antiferromagnetic insulating
ground state can be interpreted. While orbital population analyses show that
owing to strong intrinsic pd covalence effects, Sr$_{2}M$MoO$_{6}$
(M=Cr,Mn,Fe,Co) have nearly the same valence state combinations, as accounts
for the similar M-independent spectral features observed in them.",0107462v1
2020-09-25,Strain-engineering of the charge and spin-orbital interactions in Sr2IrO4,"In the high spin-orbit coupled Sr2IrO4, the high sensitivity of the ground
state to the details of the local lattice structure shows a large potential for
the manipulation of the functional properties by inducing local lattice
distortions. We use epitaxial strain to modify the Ir-O bond geometry in
Sr2IrO4 and perform momentum-dependent Resonant Inelastic X-ray Scattering
(RIXS) at the metal and at the ligand sites to unveil the response of the low
energy elementary excitations. We observe that the pseudospin-wave dispersion
for tensile-strained Sr2IrO4 films displays large softening along the [h,0]
direction, while along the [h,h] direction it shows hardening. This evolution
reveals a renormalization of the magnetic interactions caused by a
strain-driven crossover from anisotropic to isotropic interactions between the
magnetic moments. Moreover, we detect dispersive electron-hole pair excitations
which shift to lower (higher) energies upon compressive (tensile) strain,
manifesting a reduction (increase) in the size of the charge gap. This behavior
shows an intimate coupling between charge excitations and lattice distortions
in Sr2IrO4, originating from the modified hopping elements between the t2g
orbitals. Our work highlights the central role played by the lattice degrees of
freedom in determining both the pseudospin and charge excitations of Sr2IrO4
and provides valuable information towards the control of the ground state of
complex oxides in the presence of high spin-orbit coupling.",2009.12262v1
2023-09-17,Relativistic Douglas-Kroll-Hess Calculations of Hyperfine Interactions within First Principles Multireference Methods,"Relativistic magnetic hyperfine interaction Hamiltonian based on the
Douglas-Kroll-Hess (DKH) theory up to the second order is implemented within
the ab initio multireference methods including spin-orbit coupling in the
Molcas/OpenMolcas package. This implementation is applied to calculate
relativistic hyperfine coupling (HFC) parameters for atomic systems and
diatomic radicals with valence s or d orbitals by systematically varying active
space size in the restricted active space self-consistent field (RASSCF)
formalism with restricted active space state interaction (RASSI) for spin-orbit
coupling. The DKH relativistic treatment of the hyperfine interaction reduces
the Fermi contact contribution to the HFC due to the presence of kinetic
factors that regularize the singularity of the Dirac delta function in the
nonrelativitic Fermi contact operator. This effect is more prominent for
heavier nuclei. As the active space size increases, the relativistic correction
of the Fermi contact contribution converges well to the experimental data for
light and moderately heavy nuclei. The relativistic correction, however, does
not significantly affect the spin-dipole contribution to the hyperfine
interaction. In addition to the atomic and molecular systems, the
implementation is applied to calculate the relativistic HFC parameters for
large trivalent and divalent Tb-based single-molecule magnets (SMMs) such as
Tb(III)Pc$_2$ and Tb(II)(Cp$^\text{iPr5}$)$_2$ without ligand truncation using
well-converged basis sets. In particular, for the divalent SMM which has an
unpaired valence 6s/5d hybrid orbital, the relativistic treatment of HFC is
crucial for a proper description of the Fermi contact contribution. Even with
the relativistic hyperfine Hamiltonian, the divalent SMM is shown to exhibit
strong tunability of HFC via an external electric field (i.e., strong hyperfine
Stark effect).",2309.09349v1
2012-04-26,"Linear bands, zero-momentum Weyl semimetal, and topological transition in skutterudite-structure pnictides","It was reported earlier [Phys. Rev. Lett. 106, 056401 (2011)] that the
skutterudite structure compound CoSb$_3$ displays a unique band structure with
a topological transition versus a symmetry-preserving sublattice (Sb)
displacement very near the structural ground state. The transition is through a
massless Dirac-Weyl semimetal, point Fermi surface phase which is unique in
that (1) it appears in a three dimensional crystal, (2) the band critical point
occurs at $k$=0, and (3) linear bands are degenerate with conventional
(massive) bands at the critical point (before inclusion of spin-orbit
coupling). Further interest arises because the critical point separates a
conventional (trivial) phase from a topological phase. In the native cubic
structure this is a zero-gap topological semimetal; we show how spin-orbit
coupling and uniaxial strain converts the system to a topological insulator
(TI). We also analyze the origin of the linear band in this class of materials,
which is the characteristic that makes them potentially useful in
thermoelectric applications or possibly as transparent conductors. We
characterize the formal charge as Co$^{+}$ $d^8$, consistent with the gap, with
its $\bar{3}$ site symmetry, and with its lack of moment. The Sb states are
characterized as $p_x$ (separately, $p_y$) $\sigma$-bonded $Sb_4$ ring states
occupied and the corresponding antibonding states empty. The remaining
(locally) $p_z$ orbitals form molecular orbitals with definite parity centered
on the empty $2a$ site in the skutterudite structure. Eight such orbitals must
be occupied; the one giving the linear band is an odd orbital singlet $A_{2u}$
at the zone center. We observe that the provocative linearity of the band
within the gap is a consequence of the aforementioned near-degeneracy, which is
also responsible for the small band gap.",1204.5905v1
2024-03-27,Analytical computation of bifurcation of orbits near collinear libration point in the restricted three-body problem,"A unified analytical solution is presented for constructing the phase space
near collinear libration points in the Circular Restricted Three-body Problem
(CRTBP), encompassing Lissajous orbits and quasihalo orbits, their invariant
manifolds, as well as transit and non-transit orbits. Traditional methods could
only derive separate analytical solutions for the invariant manifolds of
Lissajous orbits and halo orbits, falling short for the invariant manifolds of
quasihalo orbits. By introducing a coupling coefficient {\eta} and a
bifurcation equation, a unified series solution for these orbits is
systematically developed using a coupling-induced bifurcation mechanism and
Lindstedt-Poincar\'e method. Analyzing the third-order bifurcation equation
reveals bifurcation conditions for halo orbits, quasihalo orbits, and their
invariant manifolds. Furthermore, new families of periodic orbits similar to
halo orbits are discovered, and non-periodic/quasi-periodic orbits, such as
transit orbits and non-transit orbits, are found to undergo bifurcations. When
{\eta} = 0, the series solution describes Lissajous orbits and their invariant
manifolds, transit, and non-transit orbits. As {\eta} varies from zero to
non-zero values, the solution seamlessly transitions to describe quasihalo
orbits and their invariant manifolds, as well as newly bifurcated transit and
non-transit orbits. This unified analytical framework provides a more
comprehensive understanding of the complex phase space structures near
collinear libration points in the CRTBP.",2403.18237v1
1993-09-13,Persistent Currents in Mesoscopic Hubbard Rings with Spin-Orbit Interaction,"The effect of spin-orbit interaction on persistent currents in mesoscopic
Hubbard rings threaded by an Aharonov-Bohm flux is investigated putting stress
on the orbital magnetism. The non-perturbative treatment of the spin-orbit
interaction developed by Meir {\em et al.} is combined with the Bethe ansatz
solution to deal with this problem exactly. We find that the interplay of
spin-orbit interaction and electron-electron interaction plays a crucial role,
bringing about some new effects on the orbital magnetism.",9309012v1
1997-10-08,Spin and orbital excitation spectrum in the Kugel-Khomskii model,"We discuss spin and orbital ordering in the twofold orbital degenerate
superexchange model in three dimensions relevant to perovskite transition metal
oxides. We focus on the particular point on the classical phase diagram where
orbital degeneracy is lifted by quantum effects exclusively. Dispersion and
damping of the spin and orbital excitations are calculated at this point taking
into account their mutual interaction. Interaction corrections to the
mean-field order parameters are found to be small. We conclude that
quasi-one-dimensional Neel spin order accompanied by the uniform
d_{3z^2-r^2}-type orbital ordering is stable against quantum fluctuations.",9710070v1
1999-08-31,Linear spin and orbital wave theory for undoped manganites,"We present a linear spin and orbital wave theory to account for the spin and
orbital orderings observed experimentally in undoped manganite. It is found
that the anisotropy of the magnetic structure is closely related to the orbital
ordering, and the Jahn-Teller effect stabilizes the orbital ordering. The phase
diagram and the low energy excitation spectra for both spin and orbital
orderings are obtained. The calculated critical temperatures can be
quantitatively comparable to the experimental data.",9908464v1
2004-10-01,Suppression of Spin Frustration due to Orbital Selection,"In order to clarify a crucial role of orbital degree of freedom in
geometrically frustrated systems, we investigate both ground- and excited-state
properties of the e_g-orbital degenerate Hubbard model on two kinds of
lattices, ladder and zigzag chain, by using numerical techniques. In the
ladder, spin correlation extends on the whole system, while the zigzag chain is
decoupled to a double chain and spin excitation is confined in one side of the
double chain due to the selection of a specific orbital. We envision a kind of
self-organization phenomenon that the geometrically frustrated multi-orbital
system is spontaneously reduced to a one-orbital model to suppress the spin
frustration.",0410023v1
2011-10-24,Spin-orbital Kondo effect in a parallel double quantum dot,"Transport properties of the two-orbital Kondo effect involving both spin and
orbital (pseudospin) degrees of freedom were examined in a parallel double
quantum dot with a sufficient interdot Coulomb interaction and negligibly small
interdot tunneling. The Kondo effect was observed at the interdot Coulomb
blockade region with degeneracies of both spin and orbital degrees of freedom.
When the orbital degeneracy is lifted by applying a finite detuning, the Kondo
resonance exhibits a triple-peak structure, indicating that both spin and
orbital contributions are involved.",1110.5130v1
2017-06-07,Topological Phases emerging from Spin-Orbital Physics,"We study the evolution of spin-orbital correlations in an inhomogeneous
quantum system with an impurity replacing a doublon by a holon orbital degree
of freedom. Spin-orbital entanglement is large when spin correlations are
antiferromagnetic, while for a ferromagnetic host we obtain a pure orbital
description. In this regime the orbital model can be mapped on spinless
fermions and we uncover topological phases with zero energy modes at the edge
or at the domain between magnetically inequivalent regions.",1706.02140v1
2023-02-13,Perturbation Theory Treatment of Spin-Orbit Coupling. III: Coupled Perturbed Method for Solids,"A previously proposed non-canonical coupled-perturbed Kohn-Sham density
functional theory (KS-DFT)/Hartree-Fock (HF) treatment for spin-orbit coupling
is here generalized to infinite periodic systems. The scalar-relativistic
periodic KS-DFT/HF solution, obtained with a relativistic effective core
potential, is taken as the zeroth-order approximation. Explicit expressions are
given for the total energy through 3rd-order, which satisfy the 2N + 1 rule
(i.e. requiring only the 1st-order perturbed wave function for determining the
energy through 3rd-order). Expressions for additional 2nd-order corrections to
the perturbed wave function (as well as related one-electron properties) are
worked out at the uncoupled-perturbed level of theory. The approach is
implemented in the \textsc{Crystal} program and validated with calculations of
the total energy, electronic band structure, and density variables of
spin-current DFT on the tungsten dichalcogenide hexagonal bilayer series (i.e.
WSe$_2$, WTe$_2$, WPo$_2$, WLv$_2$), including 6p and 7p elements as a stress
test. The computed properties through second- or third-order match well with
those from reference two-component self-consistent field (2c-SCF) calculations.
For total energies, $E^{(3)}$ was found to consistently improve the agreement
against the 2c-SCF reference values. For electronic band structures, visible
differences w.r.t. 2c-SCF remained through second-order in only the single-most
difficult case of WLv$_2$. As for density variables of spin-current DFT, the
perturbed electron density, being vanishing in first-order, is the most
challenging for the perturbation theory approach. The visible differences in
the electron densities are, however, largest close to the core region of atoms
and smaller in the valence region. Perturbed spin-current densities, on the
other hand, are well reproduced in all tested cases.",2302.06143v1
2021-03-11,"Intertwined charge, spin, and pairing orders in doped iron ladders","Motivated by recent experimental progress on iron-based ladder compounds, we
study the doped two-orbital Hubbard model for the two-leg ladder BaFe$_2$S$_3$.
The model is constructed by using {\it ab initio} hopping parameters and the
ground state properties are investigated using the density matrix
renormalization group method. We show that the $(\pi,0)$ magnetic ordering at
half-filling, with ferromagnetic rungs and antiferromagnetic legs, becomes
incommensurate upon hole doping. Moreover, depending on the strength of the
Hubbard $U$ coupling, other magnetic patterns, such as $(0,\pi)$, are also
stabilized. We found that the binding energy for two holes becomes negative for
intermediate Hubbard interaction strength, indicating hole pairing. Due to the
crystal-field split among orbitals, the holes primarily reside in one orbital,
with the other one remaining half-filled. This resembles orbital selective Mott
states. The formation of tight hole pairs continues with increasing hole
density, as long as the magnetic order remains antiferromagnetic in one
direction. The study of pair-pair correlations indicates the dominance of the
intra-orbital spin-singlet channel, as opposed to other pairing channels.
Although in a range of hole doping pairing correlations decay slowly, our
results can also be interpreted as corresponding to a charge-density-wave made
of pairs, a precursor of eventual superconductivity after interladder couplings
are included. Such scenario of intertwined orders has been extensively
discussed before in the cuprates, and our results suggest a similar physics
could exist in ladder iron-based superconductors. Finally, we also show that a
robust Hund's coupling is needed for pairing to occur.",2103.06407v2
2021-10-13,"A Combined First Principles Study of the Structural, Magnetic, and Phonon Properties of Monolayer CrI$_{3}$","The first magnetic 2D material discovered, monolayer (ML) CrI$_3$, is
particularly fascinating due to its ground state ferromagnetism. Yet, because
monolayer materials are difficult to probe experimentally, much remains
unresolved about ML CrI$_{3}$'s structural, electronic, and magnetic
properties. Here, we leverage Density Functional Theory (DFT) and high-accuracy
Diffusion Monte Carlo (DMC) simulations to predict lattice parameters, magnetic
moments, and spin-phonon and spin-lattice coupling of ML CrI$_{3}$. We exploit
a recently developed surrogate Hessian DMC line search technique to determine
CrI$_{3}$'s monolayer geometry with DMC accuracy, yielding lattice parameters
in good agreement with recently-published STM measurements - an accomplishment
given the $\sim 10$% variability in previous DFT-derived estimates depending
upon the functional. Strikingly, we find previous DFT predictions of ML
CrI$_3$'s magnetic spin moments are correct on average across a unit cell, but
miss critical local spatial fluctuations in the spin density revealed by more
accurate DMC. DMC predicts magnetic moments in ML CrI$_3$ are 3.62 $\mu_B$ per
chromium and -0.145 $\mu_B$ per iodine; both larger than previous DFT
predictions. The large disparate moments together with the large spin-orbit
coupling of CrI$_3$'s I-$\textit{p}$ orbital suggests a ligand
superexchange-dominated magnetic anisotropy in ML CrI$_3$, corroborating recent
observations of magnons in its 2D limit. We also find ML CrI$_3$ exhibits a
substantial spin-phonon coupling of $\sim$3.32 cm$^{-1}$. Our work thus
establishes many of ML CrI$_{3}$'s key properties, while also continuing to
demonstrate the pivotal role DMC can assume in the study of magnetic and other
2D materials.",2110.06731v1
2022-02-27,A topological realization of spin polarization through vortex formation in collisions of Bose-Einstein condensates,"The global spin polarization of hadrons in heavy ion collisions has been
measured in STAR (the Solenoidal Tracker At Relativistic heavy ion collider)
experiments, which opens up a new window in the study of the hottest, least
viscous and most vortical fluid that has ever been produced in the laboratory.
We present a different approach to spin polarization from conventional ones: a
topological realization of spin polarization through quantum vortex formation
in collisions of Bose-Einstein condensates (BEC). This approach is based on the
observation that the vortex is a topological excitation in a superfluid in
presence of local orbital angular momentum and is an analogue of spin degrees
of freedom. The formation processes of vortices and vortex-antivortex pairs are
investigated by solving the Gross-Pitaevskii Equation with a large-scale
parallel algorithm on Graphics Processing Unit (GPU) to very high precision. In
a rotating environment, the primary vortex with winding number one is stable
against perturbation, which has a minimal energy and fixed orbital angular
momentum (OAM), but the vortices with larger winding numbers are unstable and
will decay into primary vortices through a redistribution of the energy and
vorticity. The injection of OAM can also be realized in non-central collisions
of self-interacting condensates, part of the OAM of the initial state will
induce the formation of vortices through concentration of energy and vorticity
density around topological defects. Different from a hydrodynamical
description, the interference of the wave function plays an important role in
the transport of energy and vorticity, reflecting the quantum nature of the
vortex formation process. The study of the vortex formation may shed light on
the nature of particle spin and spin-orbit couplings in strong interaction
matter produced in heavy-ion collisions.",2202.13300v3
2006-12-19,Fingerprints of Spin-Orbital Physics in Crystalline O$_2$,"The alkali hyperoxide KO$_2$ is a molecular analog of strongly-correlated
systems, comprising of orbitally degenerate magnetic O$_2^-$ ions. Using
first-principles electronic structure calculations, we set up an effective
spin-orbital model for the low-energy \textit{molecular} orbitals and argue
that many anomalous properties of KO$_2$ replicate the status of its orbital
system in various temperature regimes.",0612475v1
2016-07-06,Introduction of spin-orbit interaction into graphene with hydrogenation,"Introduction of spin-orbit interaction (SOI) into graphene with weak
hydrogenation ($\sim$0.1\%) by dissociation of hydrogen silsesquioxane resist
has been confirmed through the appearance of inverse spin Hall effect. The spin
current was produced by spin injection from permalloy electrodes excluding
non-spin relating experimental artifact.",1607.01558v1
2003-12-18,"Searching for Gravitational Waves from the Inspiral of Precessing Binary Systems: Astrophysical Expectations and Detection Efficiency of ""Spiky'' Templates","Relativistic spin-orbit and spin-spin couplings has been shown to modify the
gravitational waveforms expected from inspiraling binaries with a black hole
and a neutron star. As a result inspiral signals may be missed due to
significant losses in signal-to-noise ratio, if precession effects are ignored
in gravitational-wave searches. We examine the sensitivity of the anticipated
loss of signal-to-noise ratio on two factors: the accuracy of the precessing
waveforms adopted as the true signals and the expected distributions of
spin-orbit tilt angles, given the current understanding of their physical
origin. We find that the results obtained using signals generated by
approximate techniques are in good agreement with the ones obtained by
integrating the 2PN equations. This shows that a complete account of all
high-order post-Newtonian effects is usually not necessary for the
determination of detection efficiencies. Based on our current astrophysical
expectations, large tilt angles are not favored and as a result the decrease in
detection rate varies rather slowly with respect to the black hole spin
magnitude and is within 20--30% of the maximum possible values.",0312084v2
2009-09-26,Time-reversal-protected single-Dirac-cone topological-insulator states in Bi2Te3 and Sb2Te3: Topologically Spin-polarized Dirac fermions with pi Berry's Phase,"We show that the strongly spin-orbit coupled materials Bi2Te3 and Sb2Te3
(first non-Bi topological insulator) and their derivatives belong to the Z2
(Time-Reversal-Protected, elastic backscattering suppressed)
topological-insulator class. Using a combination of first-principles
theoretical calculations and photoemission spectroscopy, we directly show that
Bi2Te3 is a large spin-orbit-induced indirect bulk band gap (about 150 meV)
semiconductor whose surface is characterized by a single topological spin-Dirac
cone. The electronic structure of self-doped Sb2Te3 exhibits similar Z2
topological properties. We demonstrate that the dynamics of surface spin-only
Dirac fermions can be controlled through systematic Mn doping, making these
materials classes potentially suitable for exploring novel topological physics.
We emphasize (theoretically and experimentally) that the Dirac node is well
within the bulk-gap and not degenerate with the bulk valence band.",0909.4804v1
2010-07-29,Spectral analysis for the iron-based superconductors: Anisotropic spin fluctuations and fully gapped s^{\pm}-wave superconductivity,"Spin fluctuations are considered to be one of the candidates that drive a
sign-reversed s^{\pm} superconducting state in the iron pnictides. In the
magnetic scenario, whether the spin fluctuation spectrum exhibits certain
unique fine structures is an interesting aspect for theoretical study in order
to understand experimental observations. We investigate the detailed momentum
dependence of the short-range spin fluctuations using a 2-orbital model in the
self-consistent fluctuation exchange approximation and find that a common
feature of those fluctuations that are capable of inducing a fully gapped
s^{\pm} state is the momentum anisotropy with lengthened span along the
direction transverse to the antiferromagnetic momentum transfer. Performing a
qualitative analysis based on the orbital character and the deviation from
perfect nesting of the electronic structure for the 2-orbital and a more
complete 5-orbital model, we gain the insight that this type of anisotropic
spin fluctuations favor superconductivity due to their enhancement of
intra-orbital, but inter-band, pair scattering processes. The momentum
anisotropy leads to elliptically shaped magnetic responses which have been
observed in inelastic neutron scattering measurements. Meanwhile, our detailed
study on the magnetic and the electronic spectrum shows that the dispersion of
the magnetic resonance mode in the nearly isotropic s^{\pm} superconducting
state exhibits anisotropic propagating behavior in an upward pattern and the
coupling of the resonance mode to fermions leads to a dip feature in the
spectral function.",1007.5321v3
2012-10-16,Possible spin-orbit driven spin-liquid ground state in the double perovskite phase of Ba3YIr2O9,"We report the structural transformation of hexagonal Ba3YIr2O9 to a cubic
double perovskite form (stable in ambient conditions) under an applied pressure
of 8GPa at 1273K. While the ambient pressure (AP) synthesized sample undergoes
long-range magnetic ordering at 4K, the high pressure(HP) synthesized sample
does not order down to 2K as evidenced from our susceptibility, heat capacity
and nuclear magnetic resonance (NMR) measurements. Further, for the HP sample,
our heat capacity data have the form gamma*T+beta*T3 in the temperature (T)
range of 2-10K with the Sommerfeld coefficient gamma=10mJ/mol-Ir K2. The 89Y
NMR shift has no T-dependence in the range of 4-120K and its spin-lattice
relaxation rate varies linearly with T in the range of 8-45K (above which it is
T-independent). Resistance measurements of both the samples confirm that they
are semiconducting. Our data provide evidence for the formation of a 5d based,
gapless, quantum spin-liquid (QSL) in the cubic (HP) phase of Ba3YIr2O9. In
this picture, the T term in the heat capacity and the linear variation of 89Y
1/T1 arises from excitations out of a spinon Fermi surface. Our findings lend
credence to the theoretical suggestion [G. Chen, R. Pereira, and L. Balents,
Phys. Rev. B 82, 174440 (2010)] that strong spin-orbit coupling can enhance
quantum fluctuations and lead to a QSL state in the double perovskite lattice.",1210.4355v3
2015-03-27,Nonequilibrium spin texture within a thin layer below the surface of current-carrying topological insulator Bi$_2$Se$_3$: A first-principles quantum transport study,"We predict that unpolarized charge current injected into a ballistic thin
film of prototypical topological insulator (TI) Bi$_2$Se$_3$ will generate a
{\it noncollinear spin texture} $\mathbf{S}(\mathbf{r})$ on its surface.
Furthermore, the nonequilibrium spin texture will extend into $\simeq 2$ nm
thick layer below the TI surfaces due to penetration of evanescent
wavefunctions from the metallic surfaces into the bulk of TI. Averaging
$\mathbf{S}(\mathbf{r})$ over few \AA{} along the longitudinal direction
defined by the current flow reveals large component pointing in the transverse
direction. In addition, we find an order of magnitude smaller out-of-plane
component when the direction of injected current with respect to Bi and Se
atoms probes the largest hexagonal warping of the Dirac-cone dispersion on TI
surface. Our analysis is based on an extension of the nonequilibrium Green
functions combined with density functional theory (NEGF+DFT) to situations
involving noncollinear spins and spin-orbit coupling. We also demonstrate how
DFT calculations with properly optimized local orbital basis set can precisely
match putatively more accurate calculations with plane-wave basis set for the
supercell of Bi$_2$Se$_3$.",1503.08046v2
2015-06-08,Aspects of Neutrino Oscillation in Alternative Gravity Theories,"Neutrino spin and flavour oscillation in curved spacetime have been studied
for the most general static spherically symmetric configuration. Using the
symmetry properties we have derived spin oscillation frequency for neutrino
moving along a geodesic or in a circular orbit. Starting from the expression of
neutrino spin oscillation frequency we have shown that even in this general
context, in high energy limit the spin oscillation frequency for neutrino
moving along circular orbit vanishes. This finally lends itself to non-zero
probability of neutrino helicity flip. While for neutrino flavour oscillation
we have derived general results for oscillation phase, which subsequently have
been applied to different gravity theories. These include dilaton field coupled
to Maxwell field tensor, generalization of Schwarzschild solution by
introduction of quadratic curvature terms of all possible form to the
Einstein-Hilbert action and finally regular black hole solutions. In all these
cases using the solar neutrino oscillation data we can put bounds on the
parameters of these gravity theories. While for spin oscillation probability,
we have considered two cases, Gauss-Bonnet term added to the Einstein-Hilbert
action and the f(R) gravity theory. In both these cases we could impose bounds
on the parameters which are consistent with previous considerations.
Implications are also discussed.",1506.02647v2
2017-02-27,Current Induced Damping of Nanosized Quantum Moments in the Presence of Spin-Orbit Interaction,"Motivated by the need to understand current-induced magnetization dynamics at
the nanoscale, we have developed a formalism, within the framework of Keldysh
Green function approach, to study the current-induced dynamics of a
ferromagnetic (FM) nanoisland overlayer on a spin-orbit-coupling (SOC) Rashba
plane. In contrast to the commonly employed classical micromagnetic LLG
simulations the magnetic moments of the FM are treated {\it quantum
mechanically}. We obtain the density matrix of the whole system consisting of
conduction electrons entangled with the local magnetic moments and calculate
the effective damping rate of the FM. We investigate two opposite limiting
regimes of FM dynamics: (1) The precessional regime where the magnetic
anisotropy energy (MAE) and precessional frequency are smaller than the
exchange interactions, and (2) The local spin-flip regime where the MAE and
precessional frequency are comparable to the exchange interactions. In the
former case, we show that due to the finite size of the FM domain, the
\textquotedblleft Gilbert damping\textquotedblright does not diverge in the
ballistic electron transport regime, in sharp contrast to Kambersky's breathing
Fermi surface theory for damping in metallic FMs. In the latter case, we show
that above a critical bias the excited conduction electrons can switch the
local spin moments resulting in demagnetization and reversal of the
magnetization. Furthermore, our calculations show that the bias-induced
antidamping efficiency in the local spin-flip regime is much higher than that
in the rotational excitation regime.",1702.08408v2
2016-11-15,Quantum Spin-quantum Anomalous Hall Effect with Tunable Edge States in Sb Monolayer-based Heterostructures,"A novel topological insulator with tunable edge states, called quantum
spin-quantum anomalous Hall (QSQAH) insulator, is predicted in a
heterostructure of a hydrogenated Sb (SbH) monolayer on a LaFeO3 substrate by
using ab initio methods. The substrate induces a drastic staggered exchange
field in the SbH film, which plays an important role to generate the QSQAH
effect. A topologically nontrivial band gap (up to 35 meV) is opened by Rashba
spin-orbit coupling, which can be enlarged by strain and electric field. To
understand the underlying physical mechanism of the QSQAH effect, a
tight-binding model based on px and py orbitals is constructed. With the model,
the exotic behaviors of the edge states in the heterostructure are
investigated. Dissipationless chiral charge edge states related to one valley
are found to emerge along the both sides of the sample, while low-dissipation
spin edge states related to the other valley flow only along one side of the
sample. These edge states can be tuned flexibly by polarization-sensitive
photoluminescence controls and/or chemical edge modifications. Such flexible
manipulations of the charge, spin, and valley degrees of freedom provide a
promising route towards applications in electronics, spintronics, and
valleytronics.",1611.04715v2
2018-05-24,Role of oxygen vacancy in the spin-state change and magnetic ordering in SrCoO$_{3-δ}$,"We present the first-principles investigation of the structural, electronic,
and magnetic properties of SrCoO$_{3-\delta}$ ($\delta=0, 0.25, 0.5$) to
understand the multivalent nature of Co ions in SrCoO$_{3-\delta}$ along the
line of topotactic transition between perovskite SrCoO$_{3}$ and brownmillerite
SrCoO$_{2.5}$. From the on-site Coulomb interaction $U$-dependent ground state
of stoichiometric SrCoO$_{3}$, we show the proximity of its metallic
ferromagnetic ground state to other antiferromagnetic states. The structural
and magnetic properties of SrCoO$_{3-\delta}$ depending on their oxygen-content
provide an interesting insight into the relationship between the Co-Co
distances and the magnetic couplings so that the spin-state transition of Co
spins can understood by the change of $pd$-hybridization depending on the Co-Co
distances. The \emph{strong} suppression of the $dp\sigma$-hybridization
between Co $d$ and O $p$ orbitals in brownmillerite SrCoO$_{2.5}$ brings on the
high-spin state of Co$^{3+}$ $d^{6}$ and is responsible for the
antiferromagnetically ordered insulating ground state. The increase of
effective Co-Co distances driven by the presence of oxygen vacancies in
SrCoO$_{3-\delta}$ is consistent with the reduction of the effective
$pd$-hybridization between Co $d$ and O $p$ orbitals. We conclude that the
configuration of neighboring Co spins is shown to be crucial to their local
electronic structure near the metal-to-insulator transition along the line of
the topotactic transition in SrCoO$_{3-\delta}$. Incidentally, we also find
that the \textit{I2mb} symmetry of SrCoO$_{2.5}$ is energetically stable and
exhibits ferroelectricity via the ordering of CoO$_{4}$ tetrahedra, where this
polar lattice can be stabilized by the presence of a large activation barrier.",1805.09524v1
2012-01-22,Spin Hall effect in a Kagome lattice driven by Rashba spin-orbit interaction,"Using four-terminal Landauer-B\""{u}ttiker formalism and Green's function
technique, in this present paper, we calculate numerically spin Hall
conductance (SHC) and longitudinal conductance of a finite size kagome lattice
with Rashba spin-orbit (SO) interaction both in presence and absence of
external magnetic flux in clean limit. In the absence of magnetic flux, we
observe that depending on the Fermi surface topology of the system SHC changes
its sign at different values of Fermi energy, along with the band center.
Unlike the infinite system (where SHC is a universal constant $\pm \frac{e}{8
\pi}$), here SHC depends on the external parameters like SO coupling strength,
Fermi energy, etc. We show that in the presence of any arbitrary magnetic flux,
periodicity of the system is lost and the features of SHC tends to get reduced
because of elastic scattering. But again at some typical values of flux
($\phi=1/2, 1/4, 3/4..., etc.) the system retains its periodicity depending on
its size and the features of spin Hall effect (SHE) reappears. Our predicted
results may be useful in providing a deeper insight into the experimental
realization of SHE in such geometries.",1201.4563v4
2012-04-02,Floquet spin states in graphene under ac driven spin-orbit interaction,"We study the role of periodically driven time-dependent Rashba spin-orbit
coupling (RSOC) on a monolayer graphene sample. After recasting the originally
$4\times 4$ system of dynamical equations as two time-reversal related
two-level problems, the quasi-energy spectrum and the related dynamics are
investigated via various techniques and approximations. In the static case the
system is a gapped at the Dirac point. The rotating wave approximation (RWA)
applied to the driven system unphysically preserves this feature, while the
Magnus-Floquet approach as well as a numerically exact evaluation of the
Floquet equation show that this gap is dynamically closed. In addition, a
sizable oscillating pattern of the out-of-plane spin polarization is found in
the driven case for states which completely unpolarized in the static limit.
Evaluation of the autocorrelation function shows that the original uniform
interference pattern corresponding to time-independent RSOC gets distorted. The
resulting structure can be qualitatively explained as a consequence of the
transitions induced by the ac driving among the static eigenstates, i.e., these
transitions modulate the relative phases that add up to give the quantum
revivals of the autocorrelation function. Contrary to the static case, in the
driven scenario, quantum revivals (suppresions) are correlated to spin up
(down) phases.",1204.0404v2
2017-10-06,Optimal control of universal quantum gates in a double quantum dot,"We theoretically investigate electron spin operations driven by applied
electric fields in a semiconductor double quantum dot (DQD). Our model
describes a DQD formed in semiconductor nanowire with longitudinal potential
modulated by local gating. The eigenstates for two electron occupation,
including spin-orbit interaction, are calculated and then used to construct a
model for the charge transport cycle in the DQD taking into account the spatial
dependence and spin mixing of states. The dynamics of the system is simulated
aiming at implementing protocols for qubit operations, that is, controlled
transitions between the singlet and triplet states. In order to obtain fast
spin manipulation, the dynamics is carried out taking advantage of the
anticrossings of energy levels introduced by the spin-orbit and interdot
couplings. The theory of optimal quantum control is invoked to find the
specific electric-field driving that performs qubit logical operations. We
demonstrate that it is possible to perform within high efficiency a universal
set of quantum gates $\{$CNOT, H$\otimes$I, I$\otimes$H, T$\otimes$I, and
T$\otimes$I$\}$, where H is the Hadamard gate, T is the $\pi/8$ gate, and I is
the identity, even in the presence of a fast charge transport cycle and charge
noise effects.",1710.02499v1
2020-12-21,Spin-orbit-assisted electron pairing in 1D waveguides,"Understanding and controlling the transport properties of interacting
fermions is a key forefront in quantum physics across a variety of experimental
platforms. Motivated by recent experiments in 1D electron channels written on
the $\mathrm{LaAlO_3}$/$\mathrm{SrTiO_3}$ interface, we analyse how the
presence of different forms of spin-orbit coupling (SOC) can enhance electron
pairing in 1D waveguides. We first show how the intrinsic Rashba SOC felt by
electrons at interfaces such as $\mathrm{LaAlO_3}$/$\mathrm{SrTiO_3}$ can be
reduced when they are confined in 1D. Then, we discuss how SOC can be
engineered, and show using a mean-field Hartree-Fock-Bogoliubov model that SOC
can generate and enhance spin-singlet and triplet electron pairing. Our results
are consistent with two recent sets of experiments [Briggeman et al.,
arXiv:1912.07164; Sci. Adv. 6, eaba6337 (2020)] that are believed to engineer
the forms of SOC investigated in this work, which suggests that metal-oxide
heterostructures constitute attractive platforms to control the collective spin
of electron bound states. However, our findings could also be applied to other
experimental platforms involving spinful fermions with attractive interactions,
such as cold atoms.",2012.11425v1
2019-12-04,Thermodynamic Evidence of Proximity to a Kitaev Spin-Liquid in Ag$_{3}$LiIr$_{2}$O$_{6}$,"Kitaev magnets are materials with bond-dependent Ising interactions between
localized spins on a honeycomb lattice. Such interactions could lead to a
quantum spin-liquid (QSL) ground state at zero temperature. Recent theoretical
studies suggest two potential signatures of a QSL at finite temperatures,
namely a scaling behavior of thermodynamic quantities in the presence of
quenched disorder, and a two-step release of the magnetic entropy. Here, we
present both signatures in Ag$_{3}$LiIr$_{2}$O$_{6}$ which is synthesized from
$\alpha$-Li$_{2}$IrO$_{3}$ by replacing the inter-layer Li atoms with Ag atoms.
In addition, the DC susceptibility data confirm absence of a long-range order,
and the AC susceptibility data rule out a spin-glass transition. These
observations suggest a closer proximity to the QSL in Ag$_{3}$LiIr$_{2}$O$_{6}$
compared to its parent compound $\alpha$-Li$_{2}$IrO$_{3}$ that orders at 15 K.
We discuss an enhanced spin-orbit coupling due to a mixing between silver d and
oxygen p orbitals as a potential underlying mechanism.",1912.02118v1
2015-08-12,Strong interface-induced spin-orbit coupling in graphene on WS2,"Interfacial interactions allow the electronic properties of graphene to be
modified, as recently demonstrated by the appearance of satellite Dirac cones
in the band structure of graphene on hexagonal boron nitride (hBN) substrates.
Ongoing research strives to explore interfacial interactions in a broader class
of materials in order to engineer targeted electronic properties. Here we show
that at an interface with a tungsten disulfide (WS2) substrate, the strength of
the spin-orbit interaction (SOI) in graphene is very strongly enhanced. The
induced SOI leads to a pronounced low-temperature weak anti-localization (WAL)
effect, from which we determine the spin-relaxation time. We find that
spin-relaxation time in graphene is two-to-three orders of magnitude smaller on
WS2 than on SiO2 or hBN, and that it is comparable to the intervalley
scattering time. To interpret our findings we have performed first-principle
electronic structure calculations, which both confirm that carriers in
graphene-on-WS2 experience a strong SOI and allow us to extract a
spin-dependent low-energy effective Hamiltonian. Our analysis further shows
that the use of WS2 substrates opens a possible new route to access topological
states of matter in graphene-based systems.",1508.02912v1
2019-06-04,Tuning spin filtering by anchoring groups in benzene derivative molecular junctions,"One of the important issues of molecular spintronics is the control and
manipulation of charge transport and, in particular, its spin polarization
through single-molecule junctions. Using $ab$ $initio$ calculations, we explore
spin-polarized electron transport across single benzene derivatives attached
with six different anchoring groups (S, CH$_3$S, COOH, CNH$_2$NH, NC and
NO$_2$) to Ni(111) electrodes. We find that molecule-electrode coupling,
conductance and spin polarization (SP) of electric current can be modified
significantly by anchoring groups. In particular, a high spin polarization (SP
$>$ 80%) and a giant magnetoresistance (MR $>$ 140%) can be achieved for NO$_2$
terminations and, more interestingly, SP can be further enhanced (up to 90%) by
a small voltage. The S and CH$_3$S systems, on the contrary, exhibit rather low
SP while intermediate values are found for COOH and CNH$_2$NH groups. The
results are analyzed in detail and explained by orbital symmetry arguments,
hybridization and spatial localization of frontier molecular orbitals. We hope
that our comparative and systematic studies will provide valuable quantitative
information for future experimental measurements on that kind of systems and
will be useful for designing high-performance spintronics devices.",1906.01429v3
2019-06-24,"Weak ferromagnetism in hexagonal Mn3Z (Z=Sn, Ge, Ga) alloys","We present combined spin model and first principles electronic structure
calculations to study the weak ferromagnetism in bulk Mn$_3$Z (Z=Sn, Ge, Ga)
compounds. The spin model parameters were determined from a spin-cluster
expansion technique based on the relativistic disordered local moment formalism
implemented in the screened Korringa--Kohn--Rostoker method. We describe the
magnetic ground state of the system within a three-sublattice model and
investigate the formation of the weak ferromagnetic states in terms of the
relevant model parameters. First, we give a group-theoretical argument how the
point-group symmetry of the lattice leads to the formation of weak
ferromagnetic states. Then we study the ground states of the classical spin
model and derive analytical expressions for the weak ferromagnetic distortions
by recovering the main results of the group-theoretical analysis. As a third
approach we obtain the weak ferromagnetic ground states from self-consistent
density functional calculations and compare our results with previous first
principles calculations and with available experimental data. In particular, we
demonstrate that the orbital moments follow a decomposition predicted by group
theory. For a deeper understanding of the formation of weak ferromagnetism we
selectively trace the effect of the spin-orbit coupling at the Mn and Z sites.
In addition, for the case of Mn$_3$Ga, we gain information on the role of the
induced moment of Ga from constrained local density functional calculations.",1906.10062v1
2021-12-06,First principles theory for the magnetic and charge instabilities in AV$_3$Sb$_5$ systems,"Vanadium-based materials AV$_3$Sb$_5$ (A=K, Rb, Cs) with layered kagome
lattice structures have drawn great attention recently due to the discoveries
of topologically nontrivial band structures, charge density wave states, giant
anomalous Hall effect, as well as unusual superconducting phase at low
temperatures. In this work, we theoretically study the magnetic and charge
instabilities for this class of materials based on first principles
calculations. We develop a method to calculate the generalized susceptibility
tensor defined in the sublattice-orbital-spin space, with the effects of
Coulomb interactions treated by generalized random phase approximation (RPA).
The RPA susceptibility calculations indicate that there are three leading
ferromagnetic instability modes at $\Gamma$ point, which are further verified
by unrestricted self-consistent Hartree-Fock calculations including both the
on-site and inter-site Coulomb interactions. The inclusion of inter-site
interactions tend to suppress the spin ferromagnetism due to charge transfer
from the V to Sb sites, leading to weak spin magnetic moments $\sim
0.1\mu_{\textrm{B}}$ per V atom with small intrinsic anomalous Hall
conductivity. Current loops can be generated in such weak spin ferromagnetic
states as a result of spin-orbit coupling effects. The electronic structures in
the ferromagnetic states are significantly reconstructed which have nearly
compensated electron and hole carriers from two bands. On the other hand, we do
not find any diverging instability mode at $M$ point driven by
electron-electron Coulomb interactions. First principles phonon calculations
indicate that there are unstable phonon modes which tend to drive the system
into an inverse star-of-David structure. Our results indicate that there may be
separate phase transitions in the magnetic and charge channels in the system.",2112.02808v1
2022-03-22,Quantum sensing and imaging of spin-orbit-torque-driven spin dynamics in noncollinear antiferromagnet Mn3Sn,"Novel noncollinear antiferromagnets with spontaneous time-reversal symmetry
breaking, nontrivial band topology, and unconventional transport properties
have received immense research interest over the past decade due to their rich
physics and enormous promise in technological applications. One of the central
focuses in this emerging field is exploring the relationship between the
microscopic magnetic structure and exotic material properties. Here, the
nanoscale imaging of both spin-orbit-torque-induced deterministic magnetic
switching and chiral spin rotation in noncollinear antiferromagnet Mn3Sn films
using nitrogen-vacancy (NV) centers is reported. Direct evidence of the
off-resonance dipole-dipole coupling between the spin dynamics in Mn3Sn and
proximate NV centers is also demonstrated with NV relaxometry measurements.
These results demonstrate the unique capabilities of NV centers in accessing
the local information of the magnetic order and dynamics in these emergent
quantum materials and suggest new opportunities for investigating the interplay
between topology and magnetism in a broad range of topological magnets.",2203.11465v1
2022-09-14,From the gates of the abyss: Frequency- and polarization-dependent lensing of gravitational waves in strong gravitational fields,"The propagation of gravitational waves can be described in terms of null
geodesics by using the geometrical optics approximation. However, at large but
finite frequencies the propagation is affected by the spin-orbit coupling
corrections to geometrical optics, known as the gravitational spin Hall effect.
Consequently, gravitational waves follow slightly different frequency- and
polarization-dependent trajectories, leading to dispersive and birefringent
phenomena. We study the potential for detecting the gravitational spin Hall
effect in hierarchical triple black hole systems, consisting of an emitting
binary orbiting a more massive body acting as a gravitational lens. We
calculate the difference in time of arrival with respect to the geodesic
propagation and find that it follows a simple power-law dependence on frequency
with a fixed exponent. We calculate the gravitational spin Hall-corrected
waveform and its mismatch with respect to the original waveform. The waveform
carries a measurable imprint of the strong gravitational field if the source,
lens, and observer are sufficiently aligned, or for generic observers if the
source is close enough to the lens. We present constraints on dispersive time
delays from GWTC-3, translated from limits on Lorentz invariance violation.
Finally, we address the sensitivity of current and future ground detectors to
dispersive lensing. Our results demonstrate that the gravitational spin Hall
effect can be detected, providing a novel probe of general relativity and the
environments of compact binary systems.",2209.06459v2
2023-03-05,Circular Dichroism of Crystals from First Principles,"Chiral crystals show promise for spintronic technologies on account of their
high spin selectivity, which has led to significant recent interest in
quantitative characterization and first-principles prediction of their
spin-optoelectronics properties. Here, we outline a computational framework for
efficient ab-initio calculations of circular dichroism (CD) in crystalline
materials. We leverage direct calculations of orbital angular momentum and
quadrupole matrix element calculations in density-functional theory (DFT) and
Wannier interpolation to calculate CD in complex materials, removing the need
for band convergence and accelerating Brillouin-zone convergence compared to
prior approaches. We find strong agreement with measured CD signals in
molecules and crystals ranging in complexity from small bulk unit cells to 2D
hybrid perovskites, and show the importance of the quadrupole contribution to
the anisotropic CD in crystals. Spin-orbit coupling affects the CD of crystals
with heavier atoms, as expected, but this is primarily due to changes in the
electronic energies, rather than due to direct contributions from the spin
matrix elements. We showcase the capability to predict CD for complex
structures on a 2D hybrid perovskite, finding strong orientation dependence and
identifying the eigen-directions of the unit cell with the strongest CD. We
additionally decompose CD into separate contributions from inorganic, organic,
and mixed organic-inorganic transitions, finding the chiral molecules to
dominate the CD, with the inorganic lattice contributing at higher frequencies
in specific directions. This unprecedented level of detail in CD predictions in
crystals will facilitate experimental development of complex chiral crystals
for spin selectivity.",2303.02764v2
2024-03-28,Tuning intrinsic anomalous Hall effect from large to zero in two ferromagnetic states of SmMn2Ge2,"The intrinsic anomalous Hall conductivity (AHC) in a ferromagnetic metal is
completely determined by its band structure. Since the spin orientation
direction is an important band structure tuning parameter, it is highly
desirable to study the anomalous Hall effect in a system with multiple spin
reorientation transitions. We study a layered tetragonal room temperature
ferromagnet SmMn2Ge2, which gives us the opportunity to measure
magneto-transport properties where the long c-axis and the short a-axis can
both be magnetically easy axes depending on the temperature range we choose. We
show a moderately large fully intrinsic AHC up to room temperature when the
crystal is magnetized along the c-axis. Interestingly, the AHC can be tuned to
completely extrinsic with extremely large values when the crystal is magnetized
along the a-axis, regardless of whether the a-axis is magnetically easy or hard
axis. First principles calculations show that nodal line states originate from
Mn-d orbitals just below the Fermi energy (EF) in the electronic band structure
when the spins are oriented along the c-axis. Intrinsic AHC originates from the
Berry curvature effect of the gapped nodal lines in the presence of spin-orbit
coupling. AHC almost disappears when the spins are aligned along the a-axis
because the nodal line states shift above EF and become unoccupied states.
Since the AHC can be changed from fully extrinsic to intrinsic even at 300 K,
SmMn2Ge2 becomes a potential candidate for room temperature spintronics
applications.",2403.19581v2
2017-07-31,Color superfluidity of neutral ultra-cold fermions in the presence of color-flip and color-orbit fields,"We describe how color superfluidity is modified in the presence of color-flip
and color-orbit fields in the context of ultra-cold atoms, and discuss
connections between this problem and that of color superconductivity in quantum
chromodynamics. We consider s-wave contact interactions between different
colors, and we identify superfluid phases, with five being nodal and one being
fully gapped. When our system is described in a mixed color basis, the
superfluid order parameter tensor is characterized by six independent
components with explicit momentum dependence induced by color-orbit coupling.
The nodal superfluid phases are topological in nature, and the low temperature
phase diagram of color-flip field versus interaction parameter exhibits a
pentacritical point, where all five nodal color superfluid phases converge.
These results are in sharp contrast to the case of zero color-flip and
color-orbit fields, where the system has perfect U(3) symmetry and possess a
superfluid phase that is characterized by fully gapped quasiparticle
excitations with a single complex order parameter with no momentum dependence
and by inert unpaired fermions representing a non-superfluid component.
Furthermore, we analyse the order parameter tensor in a total pseudo-spin
basis, investigate its momentum dependence in the singlet, triplet and quintet
sectors, and compare the results with the simpler case of spin-1/2 fermions in
the presence of spin-flip and spin-orbit fields. Finally, we analyse in detail
spectroscopic properties of color superfluids in the presence of color-flip and
color-orbit fields, such as the quasiparticle excitation spectrum, momentum
distribution, and density of states to help characterize all the encountered
topological quantum phases, which can be realized in fermionic isotopes of
Lithium, Potassium and Ytterbium atoms with three internal states trapped.",1707.09923v2
2022-12-19,Timing analysis of the 2022 outburst of the accreting millisecond X-ray pulsar SAX J1808.4$-$3658: hints of an orbital shrinking,"We present a pulse timing analysis of NICER observations of the accreting
millisecond X-ray pulsar SAX J1808.4$-$3658 during the outburst that started on
2022 August 19. Similar to previous outbursts, after decaying from a peak
luminosity of $\simeq 1\times10^{36} \, \mathrm{erg \, s^{-1}}$ in about a
week, the pulsar entered in a $\sim 1$ month-long reflaring stage. Comparison
of the average pulsar spin frequency during the outburst with those previously
measured confirmed the long-term spin derivative of
$\dot{\nu}_{\textrm{SD}}=-(1.15\pm0.06)\times 10^{-15} \, \mathrm{Hz\,s^{-1}}$,
compatible with the spin-down torque of a $\approx 10^{26} \, \mathrm{G \,
cm^3}$ rotating magnetic dipole. For the first time in the last twenty years,
the orbital phase evolution shows evidence for a decrease of the orbital
period. The long-term behaviour of the orbit is dominated by a $\sim 11 \,
\mathrm{s}$ modulation of the orbital phase epoch consistent with a $\sim 21 \,
\mathrm{yr}$ period. We discuss the observed evolution in terms of a coupling
between the orbit and variations in the mass quadrupole of the companion star.",2212.09778v2
2017-06-20,On the timing properties of SAX J1808.4-3658 during its 2015 outburst,"We present a timing analysis of the 2015 outburst of the accreting
millisecond X-ray pulsar SAX J1808.4-3658, using non-simultaneous XMM-Newton
and NuStar observations. We estimate the pulsar spin frequency and update the
system orbital solution. Combining the average spin frequency from the previous
observed, we confirm the long-term spin down at an average rate
$\dot{\nu}_{\text{SD}}=1.5(2)\times 10^{-15}$ Hz s$^{-1}$. We also discuss
possible corrections to the spin down rate accounting for mass accretion onto
the compact object when the system is X-ray active. Finally, combining the
updated ephemerides with those of the previous outbursts, we find a long-term
orbital evolution compatible with a binary expansion at a mean rate
$\dot{P}_{orb}=3.6(4)\times 10^{-12}$ s s$^{-1}$, in agreement with previously
reported values. This fast evolution is incompatible with an evolution driven
by angular momentum losses caused by gravitational radiation under the
hypothesis of conservative mass transfer. We discuss the observed orbital
expansion in terms of non-conservative mass transfer and gravitational
quadrupole coupling mechanism. We find that the latter can explain, under
certain conditions, small fluctuations (of the order of few seconds) of the
orbital period around a global parabolic trend. At the same time, a
non-conservative mass transfer is required to explain the observed fast orbital
evolution, which likely reflects ejection of a large fraction of mass from the
inner Lagrangian point caused by the irradiation of the donor by the
magneto-dipole rotator during quiescence (radio-ejection model). This strong
outflow may power tidal dissipation in the companion star and be responsible of
the gravitational quadrupole change oscillations.",1706.06554v1
2019-07-08,Single and bilayer graphene on the topological insulator Bi$_2$Se$_3$: Electronic and spin-orbit properties from first principles,"We present a detailed study of the electronic and spin-orbit properties of
single and bilayer graphene in proximity to the topological insulator
Bi$_2$Se$_3$. Our approach is based on first-principles calculations, combined
with symmetry derived model Hamiltonians that capture the low-energy band
properties. We consider single and bilayer graphene on 1--3 quintuple layers of
Bi$_2$Se$_3$ and extract orbital and proximity induced spin-orbit coupling
(SOC) parameters. We find that graphene gets significantly hole doped (350
meV), but the linear dispersion is preserved. The proximity induced SOC
parameters are about 1 meV in magnitude, and are of valley-Zeeman type. The
induced SOC depends weakly on the number of quintuple layers of Bi$_2$Se$_3$.
We also study the effect of a transverse electric field, that is applied across
heterostructures of single and bilayer graphene above 1 quintuple layer of
Bi$_2$Se$_3$. Our results show that band offsets, as well as proximity induced
SOC parameters can be tuned by the field. Most interesting is the case of
bilayer graphene, in which the band gap, originating from the intrinsic dipole
of the heterostructure, can be closed and reopened again, with inverted band
character. The switching of the strong proximity SOC from the conduction to the
valence band realizes a spin-orbit valve. Additonally, we find a giant increase
of the proximity induced SOC of about 200%, when we decrease the interlayer
distance between graphene and Bi$_2$Se$_3$ by only 10%. Finally, for a
different substrate material Bi$_2$Te$_2$Se, band offsets are significantly
different, with the graphene Dirac point located at the Fermi level, while the
induced SOC strength stays similar in magnitude compared to the Bi$_2$Se$_3$
substrate.",1907.03494v2
2020-07-25,Accessing new magnetic regimes by tuning the ligand spin-orbit coupling in van der Waals magnets,"Van der Waals (VdW) materials have opened new directions in the study of low
dimensional magnetism. A largely unexplored arena is the intrinsic tuning of
VdW magnets toward new ground-states. The chromium trihalides provided the
first such example with a change of inter-layer magnetic coupling emerging upon
exfoliation. Here, we take a different approach to engineer new ground-states,
not by exfoliation, but by tuning the spin-orbit coupling (SOC) of the
non-magnetic ligand atoms (Cl,Br,I). We synthesize a three-halide series,
CrCl$_{3-x-y}$Br$_{x}$I$_{y}$, and map their magnetic properties as a function
of Cl, Br, and I content. The resulting triangular phase diagrams unveil a
frustrated regime near CrCl$_{3}$. First-principles calculations confirm that
the frustration is driven by a competition between the chromium and halide
SOCs. Furthermore, we reveal a field-induced change of inter-layer coupling in
the bulk of CrCl$_{3-x-y}$Br$_{x}$I$_{y}$ crystals at the same field as in the
exfoliation experiments.",2007.12818v1
2017-06-27,"Dirac, Rashba and Weyl type spin-orbit couplings: toward experimental realization in ultracold atoms","We propose a hierarchy set of minimal optical Raman lattice schemes toward
the experimental realization of spin-orbit (SO) couplings of various types for
ultracold atoms, including two-dimensional (2D) Dirac type of $C_4$ symmetry,
2D Rashba and 3D Weyl types. These schemes are well accessible with current
cold-atom technology, and in particular, a long-lived Bose-Einstein
condensation of the 2D Dirac SO coupling has been experimentally proved. The
generation of 2D Rashba and 3D Weyl types has an exquisite request that two
sources of laser beams have distinct frequencies of factor-two difference.
Surprisingly, we find that $^{133}$Cs atoms provide an ideal candidate for the
realization. A common and essential feature is the absence of any fine-tuning
and phase-locking in the realization, and the resulted SO coupled ultracold
atoms have a long lifetime. These schemes essentially improve over the current
experimental accessibility and controllability, and open new experimental
platforms to study high-dimensional SO physics and novel topological phases
with ultracold atoms.",1706.08961v2
2016-12-10,Vortex-bright solitons in a spin-orbit coupled spin-$1$ condensate,"We study the vortex-bright solitons in a quasi-two-dimensional
spin-orbit-coupled (SO-coupled) hyperfine spin-1 three-component Bose-Einstein
condensate (BEC) using variational method and numerical solution of a
mean-field model. The ground state of these vortex-bright solitons is radially
symmetric for weak ferromagnetic and polar interactions. For a sufficiently
strong ferromagnetic interaction, we observe the emergence of an asymmetric
vortex-bright soliton as the ground state. We also numerically investigate
stable moving solitons and binary collision between them. The present
mean-field model is not Galilean invariant, and we use a Galilean-transformed
model for generating the moving solitons. At low velocities, the head-on
collision between two {\em in-phase} solitons results either in collapse or
fusion of the soliton pair. On the other hand, in head-on collision, the two
{\em out-of-phase} solitons strongly repel each other and trace back their
trajectories before the actual collision. At low velocities, in a collision
with an impact parameter, the {\em out-of-phase} solitons get deflected from
their original trajectory like two rigid classical disks. These {\em
out-of-phase solitons} behave like classical disks, and their collision
dynamics is governed by classical laws of motion. However, at large velocities
two SO-coupled spinor solitons, irrespective of phase difference, can pass
through each other in a head-on collision like two quantum solitons.",1612.03264v1
2022-03-24,Supercurrent-enabled Andreev reflection in a chiral quantum Hall edge state,"A chiral quantum Hall (QH) edge state placed in proximity to an s-wave
superconductor experiences induced superconducting correlations. Recent
experiments have observed the effect of proximity-coupling in QH edge states
through signatures of the mediating process of Andreev reflection. We present
the microscopic theory behind this effect by modeling the system with a
many-body Hamiltonian, consisting of an s-wave superconductor, subject to
spin-orbit coupling and a magnetic field, which is coupled by electron
tunneling to a QH edge state. By integrating out the superconductor we obtain
an effective pairing Hamiltonian in the QH edge state. We clarify the
qualitative appearance of nonlocal superconducting correlations in a chiral
edge state and analytically predict the suppression of electron-hole conversion
at low energies (Pauli blocking) and negative resistance as experimental
signatures of Andreev reflection in this setup. In particular, we show how two
surface phenomena of the superconductor, namely Rashba spin-orbit coupling and
a supercurrent due to the Meissner effect, are essential for the Andreev
reflection. Our work provides a promising pathway to the realization of
Majorana zero-modes and their parafermionic generalizations.",2203.13384v3
2022-11-10,Spontaneous symmetry breaking of dual-layer solitons in spin-orbit-coupled Bose-Einstein condensates,"It is known that stable 2D solitons of the semi-vortex (SV) and mixed-mode
(MM) types are maintained by the interplay of the cubic attractive nonlinearity
and spin-orbit coupling (SOC) in binary Bose-Einstein condensates. We introduce
a double-layer system, in which two binary condensates, stabilized by the SOC,
are linearly coupled by tunneling. By means of the numerical methods, it is
found that symmetric two-layer solitons undergo the
spontaneous-symmetry-breaking (SSB) bifurcation of the subcritical type. The
bifurcation produces families of asymmetric 2D solitons, which exist up to the
value of the total norm equal to the norm of the Townes solitons, above which
the collapse occurs. This situation terminates at a critical value of the
inter-layer coupling, beyond which the SSB bifurcation is absent, as the
collapse sets in earlier. Symmetric 2D solitons that are destabilized by the
SSB demonstrate dynamical symmetry breaking, in combination with intrinsic
oscillations of the solitons, or transition to the collapse, if the soliton's
norm is sufficiently large. Asymmetric MMs produced by the SSB instability
start spontaneous drift, in addition to the intrinsic vibrations. Consideration
of moving 2D solitons is a nontrivial problem because SOC breaks the Galilean
invariance. It is found that the system supports moving MMs up to a critical
value of the velocity, beyond which they undergo delocalization.",2211.05841v1
2023-05-03,Transport features of a topological superconducting nanowire with a quantum dot: conductance and noise,"We study two-terminal configurations in junctions between a topological
superconducting wire with spin-orbit coupling and magnetic field, and an
ordinary conductor with an embedded quantum dot. One of the signatures of the
Majorana zero modes in the topological phase is a quantization of the zero-bias
conductance at $G(V=0)=2e^2/h$. However, the finite size of the wires and the
presence of the quantum dot in the junction generate more complicated features
which lead to deviations from this simple picture. Here, we analyze the
behavior of the conductance at zero and finite bias, $G(V)$, as a function of a
gate voltage applied at the quantum dot in the case of a finite-length wire. We
analyze the effect of the angle between the magnetic field and the orientation
associated to the spin-orbit coupling. We provide a detailed description of the
spectral features of the quantum wire weakly and also strongly coupled to the
quantum dot and describe the conditions to have zero-energy states in these two
regimes for both the topological and non-topological phases. We also analyze
the concomitant behavior of the noise. We identify qualitative features that
are useful to distinguish between the topological and non-topological phases.
We show that in a strongly coupled quantum dot the simultaneous hybridization
with the topological modes and the supragap states of the wire mask the
signatures of the Majorana bound states in both the conductance and the Fano
factor.",2305.02040v2
2010-06-30,Pseudospin Conserving Shell Model Interactions,"Pseudospin symmetry is approximately conserved in nuclei. Normally shell
model interactions are written in terms of spin an orbital angular momentum
operators, not in terms of pseudospin and pseudo-orbital angular momentum
operators. We determine the shell model interactions which conserve pseudospin
symmetry and pseudo-orbital angular momentum symmetry and write them in terms
of spin and orbital angular momentum operators including the tensor
interaction. We show that, although the tensor interaction by itself does not
conserve pseudo-orbital angular momentum, certain combinations of the tensor
interaction with the two body angular momentum squared interaction and the two
body spin orbit interaction do conserve pseudo-orbital angular momentum.",1006.5954v1
2017-04-10,Tunable mode coupling in nano-contact spin torque oscillators,"Recent experiments on spin torque oscillators have revealed interactions
between multiple magnetodynamic modes, including mode-coexistence,
mode-hopping, and temperature-driven cross-over between modes. Initial
multimode theory has indicated that a linear coupling between several dominant
modes, arising from the interaction of the subdynamic system with a magnon
bath, plays an essential role in the generation of various multimode behaviors,
such as mode hopping and mode coexistence. In this work, we derive a set of
rate equations to describe the dynamics of coupled magnetodynamic modes in a
nano-contact spin torque oscillator. Expressions for both linear and nonlinear
coupling terms are obtained, which allow us to analyze the dependence of the
coupled dynamic behaviors of modes on external experimental conditions as well
as intrinsic magnetic properties. For a minimal two-mode system, we further map
the energy and phase difference of the two modes onto a two-dimensional phase
space, and demonstrate in the phase portraits, how the manifolds of periodic
orbits and fixed points vary with external magnetic field as well as with
temperature.",1704.03076v2
2019-06-14,Engineering electron-phonon coupling of quantum defects to a semi-confocal acoustic resonator,"Diamond-based microelectromechanical systems (MEMS) enable direct coupling
between the quantum states of nitrogen-vacancy (NV) centers and the phonon
modes of a mechanical resonator. One example, diamond high-overtone bulk
acoustic resonators (HBARs), feature an integrated piezoelectric transducer and
support high-quality factor resonance modes into the GHz frequency range. The
acoustic modes allow mechanical manipulation of deeply embedded NV centers with
long spin and orbital coherence times. Unfortunately, the spin-phonon coupling
rate is limited by the large resonator size, $>100~\mu$m, and thus
strongly-coupled NV electron-phonon interactions remain out of reach in current
diamond BAR devices. Here, we report the design and fabrication of a
semi-confocal HBAR (SCHBAR) device on diamond (silicon carbide) with $f\cdot
Q>10^{12}$($>10^{13}$). The semi-confocal geometry confines the phonon mode
laterally below 10~$\mu$m. This drastic reduction in modal volume enhances
defect center electron-phonon coupling. For the native NV centers inside the
diamond device, we demonstrate mechanically driven spin transitions and show a
high strain-driving efficiency with a Rabi frequency of
$(2\pi)2.19(14)$~MHz/V$_{p}$, which is comparable to a typical microwave
antenna at the same microwave power.",1906.06309v1
2021-07-26,Symbiotic solitons in a quasi-one- and quasi-two-dimensional spin-1 condensates,"We study the formation of spin-1 symbiotic spinor solitons in a quasi-one-
(quasi-1D) and quasi-two-dimensional (quasi-2D) hyper-fine spin $F=1$
ferromagnetic Bose-Einstein condensate (BEC). The symbiotic solitons
necessarily have a repulsive intraspecies interaction and are bound due to an
attractive interspecies interaction. Due to a collapse instability in higher
dimensions, an additional spin-orbit coupling is necessary to stabilize a
quasi-2D symbiotic spinor soliton. Although a quasi-1D symbiotic soliton has a
simple Gaussian-type density distribution, novel spatial periodic structure in
density is found in quasi-2D symbiotic SO-coupled spinor solitons. For a weak
SO coupling, the quasi-2D solitons are of the $(-1, 0, +1)$ or $(+1, 0, -1)$
type with intrinsic vorticity and multi-ring structure, for Rashba or
Dresselhaus SO coupling, respectively, where the numbers in the parentheses are
angular momenta projections in spin components $F_z = +1, 0, -1$, respectively.
For a strong SO coupling, stripe and superlattice solitons, respectively, with
a stripe and square-lattice modulation in density, are found in addition to the
multi-ring solitons. The stationary states were obtained by imaginary-time
propagation of a mean-field model; dynamical stability of the solitons was
established by real-time propagation over a long period of time. The
possibility of the creation of such a soliton by removing the trap of a
confined spin-1 BEC in a laboratory is also demonstrated.",2107.12194v2
2021-12-21,CrSbSe3: a pseudo one-dimensional ferromagnetic semiconductor,"Low-dimensional magnetic materials have attracted much attention due to their
novel properties and high potential for spintronic applications. In this work,
we study the electronic structure and magnetic properties of the pseudo
one-dimensional compound CrSbSe$_3$, using density functional calculations,
superexchange model analyses, and Monte Carlo simulations. We find that
CrSbSe$_3$ is a ferromagnetic (FM) semiconductor with a band gap of about 0.65
eV. The FM couplings within each zig-zag spin chain are due to the Cr-Se-Cr
superexchange with the near-90$^\circ$ bonds, and the inter-chain FM couplings
are one order of magnitude weaker. By inclusion of the spin-orbit coupling
(SOC) effects, our calculations reproduce the experimental observation of the
easy magnetization $a$ axis and the hard $b$ axis (the spin-chain direction),
with the calculated moderate magnetic anisotropy of 0.19 meV/Cr. Moreover, we
identify the nearly equal contributions from the single ion anisotropy of Cr,
and from the exchange anisotropy due to the strong SOC of the heavy elements Sb
and Se and their couplings with Cr. Using the parameters of the magnetic
coupling and anisotropy from the above calculations, our Monte Carlo
simulations yield the Curie temperature $T_{\rm{C}}$ of 108 K.",2112.10937v1
2022-09-16,Valley-Spin Hall Effect-based Nonvolatile Memory with Exchange-Coupling-Enabled Electrical Isolation of Read and Write Paths,"Valley-spin hall (VSH) effect in monolayer WSe2 has been shown to exhibit
highly beneficial features for nonvolatile memory (NVM) design. Key advantages
of VSH-based magnetic random-access memory (VSH-MRAM) over spin orbit torque
(SOT)-MRAM include access transistor-less compact bit-cell and low power
switching of perpendicular magnetic anisotropy (PMA) magnets. Nevertheless,
large device resistance in the read path (RS) due to low mobility of WSe2 and
Schottky contacts deteriorates sense margin, offsetting the benefits of
VSH-MRAM. To address this limitation, we propose another flavor of VSH-based
MRAM that (while inheriting most of the benefits of VSH-MRAM) achieves lower RS
in the read path by electrically isolating the read and write terminals. This
is enabled by coupling VSH with electrically-isolated but magnetically-coupled
PMA magnets via interlayer exchange-coupling. Designing the proposed devices
using object oriented micro magnetic framework (OOMMF) simulation, we ensure
the robustness of the exchange-coupled PMA system under process variations. To
maintain a compact memory footprint, we share the read access transistor across
multiple bit-cells. Compared to the existing VSH-MRAMs, our design achieves
39%-42% and 36%-46% reduction in read time and energy, respectively, along with
1.1X-1.3X larger sense margin at a comparable area. This comes at the cost of
1.7X and 2.0X increase in write time and energy, respectively. Thus, the
proposed design is suitable for applications in which reads are more dominant
than writes.",2209.08188v1
2010-06-29,Topological Berry phase and semiclassical quantization of cyclotron orbits for two dimensional electrons in coupled band models,"The semiclassical quantization of cyclotron orbits for two-dimensional Bloch
electrons in a coupled two band model with a particle-hole symmetric spectrum
is considered. As concrete examples, we study graphene (both mono and bilayer)
and boron nitride. The main focus is on wave effects -- such as Berry phase and
Maslov index -- occurring at order $\hbar$ in the semiclassical quantization
and producing non-trivial shifts in the resulting Landau levels. Specifically,
we show that the index shift appearing in the Landau levels is related to a
topological part of the Berry phase -- which is basically a winding number of
the direction of the pseudo-spin 1/2 associated to the coupled bands --
acquired by an electron during a cyclotron orbit and not to the complete Berry
phase, as commonly stated. As a consequence, the Landau levels of a coupled
band insulator are shifted as compared to a usual band insulator. We also study
in detail the Berry curvature in the whole Brillouin zone on a specific example
(boron nitride) and show that its computation requires care in defining the
""k-dependent Hamiltonian"" H(k), where k is the Bloch wavevector.",1006.5632v2
2019-08-01,Giant magnetoelectric coupling in multiferroic PbTi$_{1-x}$V$_x$O$_{3}$ from density functional calculations,"The giant magnetoelectric coupling is a very rare phenomenon which has gained
a lot of attention for the past few decades because of fundamental interest as
well as practical applications. Here, we have successfully achieved the giant
magnetoelectric coupling in PbTi1-xVxO3 (x= 0-1) with the help of a series of
generalized-gradient-corrected (GGA), GGA including on-site coulomb repulsion
(U) corrected spin polarized calculations based on accurate density functional
theory. Our total energy calculations show that PbTi1-xVxO3 stabilizes in
C-type antiferromagnetic ground state for x>0.123. With the substitution of V
into PbTiO3, the tetragonal distortion is highly enhanced accompanied by a
linear increase in polarization. In addition, our band structure analysis shows
that for lower x values, the tendency to form 2Dmagnetism of PbTi1-xVxO3
decreases. A non-magnetic metallic ground state is observed for the
paraelectric phase for V concentration (x) = 1 competing with a volume change
of 10% showing a large magnetovolume effect. Our orbital projected DOS as well
as orbital ordering analysis suggest that the orbital ordering plays a major
role in the magnetic to non-magnetic transition when going from ferroelectric
to paraelectric phase. The calculated magnetic anisotropic energy shows that
the direction [110] is the easy axis of magnetization for x= 1 composition. The
present study adds a new series of compounds to the magnetoelectric family with
rarely existing giant coupling between electric and magnetic order parameters.
These results show that such kind of materials can be used for novel practical
applications where one can change the magnetic properties drastically (magnetic
to non-magnetic as shown here) with external electric fieldand vice-versa.",1908.00238v1
2019-08-02,Isoelectronic tuning of heavy fermion systems: Proposal to synthesize Ce3Sb4Pd3,"The study of (quantum) phase transitions in heavy-fermion compounds relies on
a detailed understanding of the microscopic control parameters that induce
them. While the influence of external pressure is rather straight forward,
atomic substitutions are more involved. Nonetheless, replacing an elemental
constituent of a compound with an isovalent atom is---effects of disorder
aside---often viewed as merely affecting the lattice constant. Based on this
picture of chemical pressure, the unit-cell volume is identified as an
empirical proxy for the Kondo coupling. Here instead, we propose an ""orbital
scenario"" in which the coupling in complex systems can be tuned by
isoelectronic substitutions with little or no effect onto cohesive properties.
Starting with the Kondo insulator Ce$_3$Bi$_4$Pt$_3$, we consider---within
band-theory---isoelectronic substitutions of the pnictogen (Bi$\rightarrow$Sb)
and/or the precious metal (Pt$\rightarrow$Pd). We show for the isovolume series
Ce$_3$Bi$_4$(Pt$_{1-x}$Pd$_x$)$_3$ that the Kondo coupling is in fact
substantially modified by the different radial extent of the $5d$ (Pt) and $4d$
(Pd) orbitals, while spin-orbit coupling mediated changes are minute. Combining
experimental Kondo temperatures with simulated hybridization functions, we also
predict effective masses $m^*$, finding excellent agreement with many-body
results for Ce$_3$Bi$_4$Pt$_3$. Our analysis motivates studying the so-far
unknown Kondo insulator Ce$_3$Sb$_4$Pd$_3$, for which we predict
$m^*/m_{band}=\mathcal{O}(10)$.",1908.00840v1
1999-09-02,Orbital Polarization and Fluctuation in Manganese Oxides,"In a form which include the mother compound, we studied the extended
Hubbard-type model with the orbital degeneracy for any doping concentration.
Meanfield phase diagram and the spin wave excitation in RPA are calculated. It
turned out that a large orbital polarization is essential to reproduce the
magnetic phases depending on the doping concentration. Base on this result, we
discuss the spin canting, the spin wave dispersion, and spin wave stiffness
from the standing point of the large orbital polarization. We also discuss the
orbital fluctuation which turned out to be important in the ferromagnetic
metallic region where the CMR is observed. Spin wave softening near the zone
boundary is also discussed in this context.",9909023v1
2004-02-02,Suppression of Spin-Orbit Scattering in Strong-Disordered Gold Nanojunctions,"We discovered that spin-orbit scattering in strong-disordered gold
nanojunctions is strongly suppressed relative to that in weak-disordered gold
thin films. This property is unusual because in weak-disordered films,
spin-orbit scattering increases with disorder. Granularity and freezing of
spin-orbit scattering inside the grains explains the suppression of spin-orbit
scattering. We propose a generalized Elliot-Yafet relation that applies to
strong-disordered granular regime.",0402054v2
2005-06-10,Spin-charge-orbital ordering on triangle-based lattices,"We investigate the ground-state property of an e_g-orbital Hubbard model at
quarter filling on a zigzag chain by exploiting the density matrix
renormalization group method. When two orbitals are degenerate, the zigzag
chain is decoupled to a doble-chain spin system to suppress the spin
frustration due to the spatial anisotropy of the occupied orbital. On the other
hand, when the level splitting is increased and the orbital anisotropy
disappears, a characteristic change in the spin incommnsurability is observed
due to the revival of the spin frustration.",0506242v1
1998-01-17,Quark Orbital Motion in the Nucleon,"An unified scheme for describing both spin and orbital motion in
symmetry-breaking chiral quark model is suggested. The analytic results of the
spin and orbital angular momenta carried by different quark flavors in the
nucleon are given. The quark spin reduction due to spin-flip in the chiral
splitting processes is compensated by the increase of the orbital angular
momentum carried by the quarks and antiquarks. The sum of both spin and orbital
angular momenta in the nucleon is 1/2, if the gluons and other degrees of
freedom are neglected. The same conclusion holds for other octet and decuplet
baryons. Possible modification and application are briefly discussed.",9801332v2
2008-04-07,Paired Orbitals for Different Spins equations,"Eigenvalue-type equations for Lowdin-Amos-Hall spin-paired (corresponding)
orbitals are developed to provide an alternative to the standard spin-polarized
Hartree-Fock or Kohn-Sham equations. Obtained equations are non-canonical
unrestricted Hartree-Fock-type equations in which non-canonical orbitals are
fixed to be biorthogonal spin-paired orbitals. To derive paired orbitals for
different spins (PODS) equations there has been applied Adams-Gilbert
localizing operator approach. PODS equations are especially useful for
treatment of the broken-symmetry solutions for antiferromagnetic materials.",0804.0967v1
2012-06-14,Spin-Orbital Liquid on a Triangular Lattice,"Using Lanczos exact diagonalization of finite clusters we demonstrate that
the spin-orbital $d^1$ model for triply degenerate $t_{2g}$ orbitals on a
triangular lattice provides an example of a spin-orbital liquid ground state.
We also show that the spin-orbital liquid involves entangled valence bond
states which violate the Goodenough-Kanamori rules, and modify effective spin
exchange constants.",1206.3216v1
2009-11-30,Chaotic orbits for spinning particles in Schwarzschild spacetime,"We consider the orbits of particles with spin in the Schwarzschild spacetime.
Using the Papapetrou-Dixon equations of motion for spinning particles, we solve
for the orbits and focus on those that exhibit chaos using both Poincar\'e maps
and Lyapunov exponents. In particular, we develop a method for comparing the
Lyapunov exponents of chaotic orbits. We find chaotic orbits for smaller spin
values than previously thought and with spins that could be realized
astrophysically.",0912.0031v2
2006-12-13,Spin Flips and Precession in Black-Hole-Binary Mergers,"We use the `moving puncture' approach to perform fully non-linear evolutions
of spinning quasi-circular black-hole binaries with individual spins not
aligned with the orbital angular momentum. We evolve configurations with the
individual spins (parallel and equal in magnitude) pointing in the orbital
plane and 45-degrees above the orbital plane. We introduce a technique to
measure the spin direction and track the precession of the spin during the
merger, as well as measure the spin flip in the remnant horizon. The former
configuration completes 1.75 orbits before merging, with the spin precessing by
98-degrees and the final remnant horizon spin flipped by ~72-degrees with
respect to the component spins. The latter configuration completes 2.25 orbits,
with the spins precessing by 151-degrees and the final remnant horizon spin
flipped ~34-degrees with respect to the component spins. These simulations show
for the first time how the spins are reoriented during the final stage of
binary black hole mergers verifying the hypothesis of the spin-flip phenomenon.
We also compute the track of the holes before merger and observe a precession
of the orbital plane with frequency similar to the orbital frequency and
amplitude increasing with time.",0612076v4
2023-06-30,Comparing spin supplementary conditions for particle motion around traversable wormholes,"The Mathisson-Papapetrou-Dixon (MPD) equations describe the motion of
spinning test particles. It is well-known that these equations, which couple
the Riemann curvature tensor with the antisymmetric spin tensor S, together
with the normalization condition for the four-velocity, is a system of eleven
equations relating fourteen unknowns. To ``close'' the system, it is necessary
to introduce a constraint of the form V_\mu S^{\mu \nu} = 0, usually known as
the spin supplementary condition (SSC), where V_\mu is a future-oriented
reference vector satisfying the normalization condition V_\alpha V^\alpha = -1.
There are several SSCs in the literature. In particular, the Tulzcyjew-Dixon,
Mathisson-Pirani, and Ohashi-Kyrian-Semer\'ak are the most used by the
community. From the physical point of view, choosing a different SSC (a
different reference vector $V^\mu$) is equivalent to fixing the centroid of the
test particle. In this manuscript, we compare different SSCs for spinning test
particles moving around a Morris-Thorne traversable wormhole. To do so, we
first obtain the orbital frequency and expand it up to third-order in the
particle's spin; as expected, the zero-order coincides with the Keplerian
frequency, the same in all SSCs; nevertheless, we found that differences appear
in the second order of the expansion, similar to the Schwarzschild and Kerr
black holes. We also compare the behavior of the innermost stable circular
orbit (ISCO). Since each SSC is associated with a different centroid of the
test particle, we analyze (separately) the radial and spin corrections for each
SSC. We found that the radial corrections improve the convergence, especially
between Tulzcyjew-Dixon and Mathisson-Pirani SSCs. In the case of
Ohashi-Kyrian-Semer\'ak, we found that the spin corrections remove the
divergence for the ISCO and extend its existence for higher values of the
particle's spin.",2306.17394v1
2013-01-31,Defect states and excitations in a Mott insulator with orbital degrees of freedom: Mott-Hubbard gap versus optical and transport gaps in doped systems,"We address the role played by charged defects in doped Mott insulators with
active orbital degrees of freedom. It is observed that defects feature a rather
complex and rich physics, which is well captured by a degenerate Hubbard model
extended by terms that describe crystal-field splittings and orbital-lattice
coupling, as well as by terms generated by defects such as the Coulomb
potential terms that act both on doped holes and on electrons within occupied
orbitals at undoped sites. We show that the multiplet structure of the excited
states generated in such systems by strong electron interactions is well
described within the unrestricted Hartree-Fock approximation, once the symmetry
breaking caused by the onset of magnetic and orbital order is taken into
account. Furthermore, we uncover new spectral features that arise within the
Mott-Hubbard gap and in the multiplet spectrum at high energies due to the
presence of defect states and strong correlations. These features reflect the
action on electrons/holes of the generalized defect potential that affects
charge and orbital degrees of freedom, and indirectly also spin ones. The
present study elucidates the mechanism behind the Coulomb gap appearing in the
band of defect states and investigates the dependence on the electron-electron
interactions and the screening by the orbital polarization field. As an
illustrative example of our general approach, we present explicit calculations
for the model describing three t_2g orbital flavors in the perovskite vanadates
doped by divalent Sr or Ca ions, such as in La_(1-x)Sr_xVO_3 and
Y_(1-x)Ca_xVO_3 systems. We analyze the orbital densities at vanadium ions in
the vicinity of defects, and the excited defect states which determine the
optical and transport gaps in doped systems.",1302.0020v2
2012-12-31,Fulde-Ferrell-Larkin-Ovchinnikov Phases in Two-dimensional Spin-Orbit Coupled Degenerate Fermi Gases,"The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, a superconducting state
with non-zero total momentum Cooper pairs in a strong magnetic field, was
predicted more than 50 years ago and now becomes an important concept in many
branches of physics. However, no unambiguous experimental evidences for the
existence of FFLO phases have been observed yet. Recently, spin-imbalanced
ultracold degenerate Fermi gases have emerged as a new powerful platform for
the observation of FFLO phases due to their high experimental controllability
and the lack of disorder. However, in three dimensional degenerate Fermi gases
where the FFLO phases can be described within the simple mean field theory, the
parameter region for the FFLO phases is too small to be observed in
experiments. Recently, we showed that the Rashba type spin-orbit coupling and
in-plane Zeeman field in three dimensional degenerate Fermi gases provide a
more efficient way to create the FFLO phase because (1) the parameter region
for the FFLO phase is greatly enlarged in the phase diagram and (2) the FFLO
phase is stabilized due to the enhanced energy difference between FFLO phase
and conventional Bardeen-Cooper-Schrieffer (BCS) phase. In this work we
investigate the FFLO phase in two dimensional spin-orbit coupled degenerate
Fermi gases using the mean field theory, with special concerns on the physical
origin of the FFLO state. The basic properties of the FFLO phase are discussed
and the phase diagram is obtained at zero temperature. The symmetry of
different quantum phases is examined, which provide important basis for the
experimental observation of FFLO phases using the time-of-flight imaging.",1212.6826v2
2018-10-31,Novel Strongly Spin-Orbit Coupled Quantum Dimer Magnet: Yb$_2$Si$_2$O$_7$,"The quantum dimer magnet (QDM) is the canonical example of quantum magnetism.
The QDM state consists of entangled nearest-neighbor spin dimers and often
exhibits a field-induced triplon Bose-Einstein condensate (BEC) phase. We
report on a new QDM in the strongly spin-orbit coupled, distorted
honeycomb-lattice material Yb$_2$Si$_2$O$_7$. Our single crystal neutron
scattering, specific heat, and ultrasound velocity measurements reveal a gapped
singlet ground state at zero field with sharp, dispersive excitations. We find
a field-induced magnetically ordered phase reminiscent of a BEC phase, with
exceptionally low critical fields of $H_{c1} \sim 0.4$ T and $H_{c2} \sim 1.4$
T. Using inelastic neutron scattering in an applied magnetic field we observe a
Goldstone mode (gapless to within $\delta E$ = 0.037 meV) that persists
throughout the entire field-induced magnetically ordered phase, suggestive of
the spontaneous breaking of U(1) symmetry expected for a triplon BEC. However,
in contrast to other well-known cases of this phase, the high-field
($\mu$$_0$$H\geq1.2$T) part of the phase diagram in Yb$_2$Si$_2$O$_7$ is
interrupted by an unusual regime signaled by a change in the field dependence
of the ultrasound velocity and magnetization, as well as the disappearance of a
sharp anomaly in the specific heat. These measurements raise the question of
how anisotropy in strongly spin-orbit coupled materials modifies the field
induced phases of QDMs.",1810.13096v2
2022-05-06,Strong Effects of Interlayer Interaction on Valence-Band Splitting in Transition Metal Dichalcogenides,"Understanding the origin of valence band maxima (VBM) splitting in transition
metal dichalcogenides (TMDs) is important because it governs the unique spin
and valley physics in monolayer and multilayer TMDs. In this work, we present
our systematic study of VBM splitting ($\Delta$) in atomically thin MoS$_2$ and
WS$_2$ by employing photocurrent spectroscopy as we change the temperature and
the layer numbers. We found that VBM splitting in monolayer MoS$_2$ and WS$_2$
depends strongly on temperature, which contradicts the theory that spin-orbit
coupling solely determines the VBM splitting in monolayer TMDs. We also found
that the rate of change of VBM splitting with respect to temperature
($m=\frac{\partial\Delta}{\partial T}$) is the highest for monolayer (-0.14
meV/K for MoS$_2$) and the rate decreases as the layer number increases ($m ~
0$ meV/K for 5 layers MoS$_2$). We performed density functional theory (DFT)
and the GW with Bethe-Salpeter Equation (GW-BSE) calculations to determine the
electronic band structure and optical absorption for a bilayer MoS$_2$ with
different interlayer separations. Our simulations agree with the experimental
observations and demonstrate that the temperature dependence of VBM splitting
in atomically thin monolayer and multilayer TMDs originates from the changes in
the interlayer coupling strength between the neighboring layers. By studying
two different types of TMDs and many different layer thicknesses, we also
demonstrate that VBM splitting also depends on the layer numbers and type of
transition metals. Our study will help understand the role spin-orbit coupling
and interlayer interaction play in determining the VBM splitting in quantum
materials and develop next-generation devices based on spin-orbit interactions.",2205.03449v2
2023-04-14,Emergent SU(8) Dirac semimetal and novel proximate phases of spin-orbit coupled fermions on a honeycomb lattice,"Emergent Dirac fermions provide the starting point to understanding the
plethora of novel condensed matter phases. The nature of the associated phases
and phase transitions crucially depends on both the emergent symmetries as well
as the implementation of the microscopic ones on the low-energy Dirac fermions.
Here, we show that $j=3/2$ electrons in spin-orbit coupled materials on
honeycomb lattice can give rise to SU(8) symmetric Dirac semimetals with
symmetry implementation very different from that of graphene. This non-trivial
embedding of the microscopic symmetries in the low energy is reflected in the
nature of phases proximate to the Dirac semimetal. Such phases can arise from
finite short-range electron-electron interactions. In particular, we identify
24 such phases - divided into three classes - and their low energy properties
obtained by condensing particle-number conserving fermion bilinears that break
very different microscopic symmetries and/or are topologically protected by
symmetries. The latter includes interesting generalisations of quantum
spin-Hall phases. Remarkably some of the resultant phases still support a
sub-set of gapless fermions - protected by a sub-group of SU(8) - resulting in
interesting density wave semimetals. Near the phase transitions to such density
wave semimetals, the surviving gapless fermions strongly interact with the
bosonic order parameter field and give rise to novel quantum critical points.
Our study is applicable to a wide class of $d^1$ and $d^3$ transition metals
with strong spin-orbit coupling and predicts that such materials can harbour a
very rich interplay of symmetries and competing interactions in the
intermediate correlation regime.",2304.07223v2
2023-10-23,Complete zero-energy flat bands of surface states in fully gapped chiral noncentrosymmetric superconductors,"Noncentrosymmetric superconductors can support flat bands of zero-energy
surface states in part of their surface Brillouin zone. This requires that they
obey time-reversal symmetry and have a sufficiently strong
triplet-to-singlet-pairing ratio to exhibit nodal lines in the bulk. These
bands are protected by a winding number that relies on chiral symmetry, which
is realized as the product of time-reversal and particle-hole symmetry. We
reveal a way to stabilize a flat band in the entire surface Brillouin zone,
while the bulk dispersion is fully gapped. This idea could lead to a robust
platform for quantum computation and represents an alternative route to
strongly correlated flat bands in two dimensions, besides twisted bilayer
graphene. The necessary ingredient is an additional spin-rotation symmetry that
forces the direction of the spin-orbit-coupling vector not to depend on the
momentum component normal to the surface. We define a winding number that leads
to flat zero-energy surface bands due to bulk-boundary correspondence. We
discuss under which conditions this winding number is nonzero in the entire
surface Brillouin zone and verify the occurrence of zero-energy surface states
by exact numerical diagonalization of the Bogoliubov-de Gennes Hamiltonian for
a slab. In addition, we consider how a weak breaking of the additional symmetry
affects the surface band, employing first-order perturbation theory and a
quasiclassical approximation. We find that the surface states and the bulk gap
persist for weak breaking of the additional symmetry but that the band does not
remain perfectly flat. The broadening of the band strongly depends on the
deviation of the spin-orbit-coupling vector from its unperturbed direction as
well as on the spin-orbit-coupling strength and the triplet-pairing amplitude.",2310.14800v2
2006-01-17,Fingerprints of spin-orbital physics in cubic Mott insulators: Magnetic exchange interactions and optical spectral weights,"The temperature dependence and anisotropy of optical spectral weights
associated with different multiplet transitions is determined by the spin and
orbital correlations. To provide a systematic basis to exploit this close
relationship between magnetism and optical spectra, we present and analyze the
spin-orbital superexchange models for a series of representative
orbital-degenerate transition metal oxides with different multiplet structure.
For each case we derive the magnetic exchange constants, which determine the
spin wave dispersions, as well as the partial optical sum rules. The magnetic
and optical properties of early transition metal oxides with degenerate
$t_{2g}$ orbitals (titanates and vanadates with perovskite structure) are shown
to depend only on two parameters, viz. the superexchange energy $J$ and the
ratio $\eta$ of Hund's exchange to the intraorbital Coulomb interaction, and on
the actual orbital state. In $e_g$ systems important corrections follow from
charge transfer excitations, and we show that KCuF$_3$ can be classified as a
charge transfer insulator, while LaMnO$_3$ is a Mott insulator with moderate
charge transfer contributions. In some cases orbital fluctuations are quenched
and decoupling of spin and orbital degrees of freedom with static orbital order
gives satisfactory results for the optical weights. On the example of cubic
vanadates we describe a case where the full quantum spin-orbital physics must
be considered. Thus information on optical excitations, their energies,
temperature dependence and anisotropy, combined with the results of magnetic
neutron scattering experiments, provides an important consistency test of the
spin-orbital models, and indicates whether orbital and/or spin fluctuations are
important in a given compound.",0601381v1
2018-09-10,Lattice distortion in the spin-orbital entangled state in RVO3 perovskites,"We report a thorough study of Y$_{0.7}$La$_{0.3}$VO$_3$ single crystals by
measuring magnetic properties, specific heat, thermal conductivity, x-ray and
neutron diffraction with the motivation of revealing the lattice response to
the spin-orbital entanglement in \textit{R}VO$_3$. Upon cooling from room
temperature, the orbitally disordered paramagnetic state changes around
T*$\sim$220\,K to spin-orbital entangled state which is then followed by a
transition at T$_N$=116\,K to C-type orbital ordered (OO) and G-type
antiferromagnetic ordered (AF) ground state. In the temperature interval
T$_N<T<T^*$, the VO$_{6/2}$ octahedra have two comparable in-plane V-O bonds
which are longer than the out-of-plane V-O1 bond. This local structural
distortion supports the spin-orbital entanglement of partially filled and
degenerate yz/zx orbitals. However, this distortion is incompatible with the
steric octahedral site distortion intrinsic to orthorhombic perovskites. Their
competition induces a second order transition from the spin-orbital entangled
state to C-OO/G-AF ground state where the long range OO suppresses the
spin-orbital entanglement. Our analysis suggests that the spin-orbital
entangled state and G-OO are comparable in energy and compete with each other.
Rare earth site disorder favors the spin-orbital entanglement rather than a
cooperative Jahn-Teller distortion. The results also indicate for LaVO$_3$ a
C-OO/G-AF state in T$_t$\,$\leq$\,T\,$\leq$T$_N$ and an orbital flipping
transition at T$_t$.",1809.03360v1
2005-04-03,Microscopic Approach to Magnetism and Superconductivity of $f$-Electron Systems with Filled Skutterudite Structure,"In order to gain a deep insight into $f$-electron properties of filled
skutterudite compounds from a microscopic viewpoint, we investigate the
multiorbital Anderson model including Coulomb interactions, spin-orbit
coupling, and crystalline electric field effect. For each case of
$n$=1$\sim$13, where $n$ is the number of $f$ electrons per rare-earth ion, the
model is analyzed by using the numerical renormalization group (NRG) method to
evaluate magnetic susceptibility and entropy of $f$ electron. In order to make
further step to construct a simplified model which can be treated even in a
periodic system, we also analyze the Anderson model constructed based on the
$j$-$j$ coupling scheme by using the NRG method. Then, we construct an orbital
degenerate Hubbard model based on the $j$-$j$ coupling scheme to investigate
the mechanism of superconductivity of filled skutterudites. In the 2-site
model, we carefully evaluate the superconducting pair susceptibility for the
case of $n$=2 and find that the susceptibility for off-site Cooper pair is
clearly enhanced only in a transition region in which the singlet and triplet
ground states are interchanged.",0504052v1
2006-06-22,Quantum phases of correlated electrons in artificial molecules under magnetic fields,"We investigate the stability of few-electron quantum phases in vertically
coupled quantum dots under a magnetic field of arbitrary strength and
direction. The orbital and spin stability diagrams of realistic devices
containing up to five electrons, from strong to weak inter-dot coupling, is
determined. Correlation effects and realistic sample geometries are fully taken
into account within the Full Configuration Interaction method. In general, the
magnetic field drives the system into a strongly correlated regime by
modulating the single-particle gaps. In coupled quantum dots different
components of the field, either parallel or perpendicular to the tunneling
direction, affect single-dot orbitals and tunneling energy, respectively.
Therefore, the stability of the quantum phases is related to different
correlation mechanisms, depending on the field direction. Comparison of exact
diagonalization results with simple models allows to identify the specific role
of correlations.",0606582v1
2008-10-23,Quantum Optomechanics with Single Atom,"The recently increasing explorations for cavity optomechanical coupling
assisted by a single atom or an atomic ensemble have opened an experimentally
accessible fashion to interface quantum optics and nano (micro) -mechanical
systems. In this paper, we study in details such composite quantum dynamics of
photon, phonon and atoms, specified by the triple coupling, which only exists
in this triple hybrid system: The cavity QED system with a movable end mirror.
We exactly diagonalize the Hamiltonian of the triple hybrid system under the
parametric resonance condition. We find that, with the rotating-wave
approximation, the hybrid system is modeled by a generalized spin-orbit
coupling where the orbital angular momentum operator is defined through a
Jordan-Schwinger realization with two bosonic modes, corresponding to the
mirror oscillation and the single mode photon of the cavity. In the
quasi-classical limit of very large angular momentum, this system will behave
like a standard cavity-QED system described by the Jaynes-Cummings model as the
angular momentum operators are transformed to bosonic operators of a single
mode. We test this observation with an experimentally accessible system with
the atom in the cavity with a moving mirror.",0810.4206v1
2010-04-13,Coupled frustrated quantum spin-1/2 chains with orbital order in volborthite Cu3V2O7(OH)2(H2O)2,"We present a microscopic magnetic model for the spin-liquid candidate
volborthite Cu3V2O7(OH)2(H2O)2. The essentials of this DFT-based model are (i)
the orbital ordering of Cu(1) 3d 3z2-r2 and Cu(2) 3d 3x2-y2, (ii) three
relevant couplings J_ic, J_1 and J_2, (iii) the ferromagnetic nature of J_1 and
(iv) frustration governed by the next-nearest-neighbor exchange interaction
J_2. Our model implies magnetism of frustrated coupled chains in contrast to
the previously proposed anisotropic kagome model. Exact diagonalization studies
reveal agreement with experiments.",1004.2185v2
2010-06-16,Intervalley coupling for interface-bound electrons in silicon: An effective mass study,"Orbital degeneracy of the electronic conduction band edge in silicon is a
potential roadblock to the storage and manipulation of quantum information
involving the electronic spin degree of freedom in this host material. This
difficulty may be mitigated near an interface between Si and a barrier
material, where intervalley scattering may couple states in the conduction
ground state, leading to nondegenerate orbital ground and first excited states.
The level splitting is experimentally found to have a strong sample dependence,
varying by orders of magnitude for different interfaces and samples. The basic
physical mechanisms leading to such coupling in different systems are
addressed. We expand our recent study based on an effective mass approach,
incorporating the full plane-wave expansions of the Bloch functions at the
conduction band minima. Physical insights emerge naturally from a simple
Si/barrier model. In particular, we present a clear comparison between ours and
different approximations and formalisms adopted in the literature and establish
the applicability of these approximations in different physical scenarios.",1006.3338v2
2015-02-26,Orbital Kondo effect in fractional quantum Hall systems,"We study transport properties of a charge qubit coupling two chiral Luttinger
liquids, realized by two antidots placed between the edges of an integer
$\nu=1$ or fractional $\nu=1/3$ quantum Hall bar. We show that in the limit of
a large capacitive coupling between the antidots, their quasiparticle occupancy
behaves as a pseudo-spin corresponding to an orbital Kondo impurity coupled to
a chiral Luttinger liquid, while the inter antidot tunnelling acts as an
impurity magnetic field. The latter tends to destabilize the Kondo fixed point
for the $\nu=1/3$ fractional Hall state, producing an effective inter-edge
tunnelling. We relate the inter-edge conductance to the susceptibility of the
Kondo impurity and calculate it analytically in various limits for both $\nu=1$
and $\nu=1/3$.",1502.07430v1
2018-04-24,Pseudocontact shifts and paramagnetic susceptibility in semiempirical and quantum chemistry theories,"Pseudocontact shifts are traditionally described as a function of the
anisotropy of the paramagnetic susceptibility tensor, according to the
semiempirical theory mainly developed by Kurland and McGarvey (R.J. Kurland and
B.R. McGarvey, J. Magn. Reson. 2, 286 (1970)). The paramagnetic susceptibility
tensor is required to be symmetric. Applying point-dipole approximation to the
quantum chemistry theory of hyperfine shift, pseudocontact shifts are found to
scale with a non-symmetric tensor that differs by a factor g/ge from the
paramagnetic susceptibility tensor derived within the semiempirical framework.
We analyze the foundations of the Kurland-McGarvey pseudocontact shift
expression and recall that it is inherently based on the Russell-Saunders (LS)
coupling approximation for the spin-orbit coupling. We show that the difference
between the semiempirical and quantum chemistry pseudocontact shift expressions
arises directly from the different treatment of the orbital contribution to the
hyperfine coupling.",1804.09055v2
2009-12-14,Local breaking of the spin-orbit interaction: the microscopic origin of exchange bias in Co/FeMn,"Modern magnetic thin film devices owe their success in large part to effects
emerging from interlayer coupling and exchange interaction at interfaces. A
prominent example is exchange bias (EB), a magnetic coupling phenomenon found
in ferromagnet (F)/antiferromagnet (AF) systems. Uncompensated pinned moments
in the AF couple to the F via the interface causing an additional
unidirectional anisotropy. As a result, the hysteresis of the F is shifted. The
existence of such pinned moments is nowadays accepted although their physical
nature and origin is still unknown. Here we present a thorough spectroscopic
investigation based on X-ray magnetic circular dichroism which does for the
first time provide direct information about the physics of pinned magnetic
moments. Our data clearly shows that the orbital magnetic moment, which is
usually widely quenched in transition metal systems, is the driving force
behind exchange bias in Co/FeMn.",0912.2353v1
2020-10-21,Symmetry breaking and phase transitions in Bose-Einstein condensates with spin-orbital-angular-momentum coupling,"Theoretical study is presented for a spinor Bose-Einstein condensate, whose
two components are coupled by copropagating Raman beams with different orbital
angular momenta. The investigation is focused on the behavior of the ground
state of this condensate, depending on the atom-light coupling strength. By
analyzing the ground state, we have identified a number of quantum phases,
which reflect the symmetries of the effective Hamiltonian and are characterized
by the specific structure of the wave function. In addition to the well-known
stripe, polarized and zero-momentum phases, our results show that the system
can support phases, whose wave function contains a complex vortex molecule.
Such molecule plays an important role in the continuous phase transitions of
the system. The predicted behavior of vortex-molecule phases can be examined in
cold-atom experiments using currently existing techniques.",2010.10965v1
2017-07-12,Effective Interactions in a Graphene Layer Induced by the Proximity to a Ferromagnet,"The proximity-induced couplings in graphene due to the vicinity of a
ferromagnetic insulator are analyzed. We combine general symmetry principles
and simple tight-binding descriptions to consider different orientations of the
magnetization. We find that, in addition to a simple exchange field, a number
of other terms arise. Some of these terms act as magnetic orbital couplings,
and others are proximity-induced spin-orbit interactions. The couplings are of
similar order of magnitude, and depend on the orientation of the magnetization.
A variety of phases, and anomalous Hall effect regimes, are possible.",1707.03868v1
2020-03-13,Broken symmetry $G_0W_0$ approach for the evaluation of exchange coupling constants,"The applicability of a broken symmetry version of the $G_0W_0$ approximation
to the calculation of isotropic exchange coupling constants has been studied.
Using a simple H--He--H model system the results show a significant and
consistent improvement of the results over both broken symmetry Hartree--Fock
and broken symmetry density functional theory. In the case of more realistic
bimetallic Cu(II) complexes, inclusion of the $G_0W_0$ correction does not lead
to obvious improvement in the results. The discrepancies are explained by
improved description of the interactions within the magnetic orbital space upon
inclusion of the $G_0W_0$ corrections but deterioration of the description of
charge- and spin-polarization effects outside the magnetic orbital space.
Overall the results show that computational methods based on the $GW$ method
have a potential to improve computational estimates of exchange coupling
constants.",2003.06334v1
2022-10-17,Microscopic study of orbital textures,"Many interesting spin and orbital transport phenomena originate from orbital
textures, referring to $\vec{k}$-dependent orbital states. Most of previous
works are based on symmetry analysis to model the orbital texture and analyze
its consequences. However the microscopic origins of orbital texture and its
strength are largely unexplored. In this work, we derive the orbital texture
Hamiltonians from microscopic tight-binding models for various situations. To
form an orbital texture, $\vec{k}$-dependent hybridization of orbital states
are necessary. We reveal two microscopic mechanisms for the hybridization: (i)
lattice structure effect and (ii) mediation by other orbital states. By
considering the orbital hybridization, we not only reproduce the orbital
Hamiltonian obtained by the symmetry analysis but also reveal previously
unreported orbital textures like orbital Dresselhaus texture and anisotropic
orbital texture. The orbital Hamiltonians obtained here would be useful for
analyzing the orbital physics and designing the materials suitable for
spin-orbitronic applications. We show that our theory also provides useful
microscopic insight into physical phenomena such as the orbital Rashba effect
and the orbital Hall effect. Our formalism is so generalizable that one can
apply it to obtain effective orbital Hamiltonians for arbitrary orbitals in the
presence of periodic lattice structures.",2210.08876v1
2021-06-21,Resonant Measurement of Non-Reorientable Spin-Orbit Torque from a Ferromagnetic Source Layer Accounting for Dynamic Spin Pumping,"Using a multilayer structure containing (cobalt detector layer)/(copper
spacer)/(Permalloy source layer), we show experimentally how the
non-reorientable spin-orbit torque generated by the Permalloy source layer (the
component of spin-orbit torque that does not change when the Permalloy
magnetization is rotated) can be measured using spin-torque ferromagnetic
resonance (ST-FMR) with lineshape analysis. We find that dynamic spin pumping
between the magnetic layers exerts torques on the magnetic layers as large or
larger than the spin-orbit torques, so that if dynamic spin pumping is
neglected the result would be a large overestimate of the spin-orbit torque.
Nevertheless, the two effects can be separated by performing ST-FMR as a
function of frequency. We measure a non-reorientable spin torque ratio
$\xi_{\text{Py}} = 0.04 \pm 0.01$ for spin current flow from Permalloy through
an 8 nm Cu spacer to the Co, and a strength of dynamic spin pumping that is
consistent with previous measurements by conventional ferromagnetic resonance.",2106.11127v1
2015-06-09,Theory of the spin-galvanic effect and the anomalous phase-shift $\varphi_{0}$ in superconductors and Josephson junctions with intrinsic spin-orbit coupling,"Due to the spin-orbit coupling (SOC) an electric current flowing in a normal
metal or semiconductor can induce a bulk magnetic moment. This effect is known
as the Edelstein (EE) or magneto-electric effect. Similarly, in a bulk
superconductor a phase gradient may create a finite spin density. The inverse
effect, also known as the spin-galvanic effect, corresponds to the creation of
a supercurrent by an equilibrium spin polarization. Here, by exploiting the
analogy between a linear-in-momentum SOC and a background SU(2) gauge field, we
develop a quasiclassical transport theory to deal with magneto-electric effects
in superconducting structures. For bulk superconductors this approach allows us
to easily reproduce and generalize a number of previously known results. For
Josephson junctions we establish a direct connection between the inverse EE and
the appearance of an anomalous phase-shift $\varphi_{0}$ in the current-phase
relation. In particular we show that $\varphi_{0}$ is proportional to the
equilibrium spin-current in the weak link. We also argue that our results are
valid generically, beyond the particular case of linear-in-momentum SOC. The
magneto-electric effects discussed in this study may find applications in the
emerging field of coherent spintronics with superconductors.",1506.02977v3
2016-06-06,Origin and magnitude of 'designer' spin-orbit interaction in graphene on semiconducting transition metal dichalcogenides,"We use a combination of experimental techniques to demonstrate a general
occurrence of spin-orbit interaction (SOI) in graphene on transition metal
dichalcogenide (TMD) substrates. Our measurements indicate that SOI is
ultra-strong and extremely robust, despite it being merely
interfacially-induced, with neither graphene nor the TMD substrates changing
their structure. This is found to be the case irrespective of the TMD material
used, of the transport regime, of the carrier type in the graphene band, and of
the thickness of the graphene multilayer. Specifically, we perform weak
antilocalization measurements as the simplest and most general diagnostic of
SOI, and show that the spin relaxation time is very short in all cases
regardless of the elastic scattering time. Such a short spin-relaxation time
strongly suggests that the SOI originates from a modification of graphene band
structure. We confirmed this expectation by measuring a gate-dependent beating,
and a corresponding frequency splitting, in the low-field Shubnikov-de Haas
magneto-resistance oscillations in high quality bilayer graphene on WSe$_2$.
These measurements provide an unambiguous diagnostic of a SOI-induced splitting
in the electronic band structure, and their analysis allows us to determine the
SOI coupling constants for the Rashba term and the so-called spin-valley
coupling term, i.e., the terms that were recently predicted theoretically for
interface-induced SOI in graphene. The magnitude of the SOI splitting is found
to be on the order of 10 meV, more than 100 times greater than the SOI
intrinsic to graphene. Both the band character of the interfacially induced
SOI, as well as its robustness and large magnitude make graphene-on-TMD a
promising system to realize and explore a variety of spin-dependent transport
phenomena, such as, in particular, spin-Hall and valley-Hall topological
insulating states.",1606.01789v1
2018-04-19,Phenomenological Three-Orbital Spin-Fermion Model for Cuprates,"A spin-fermion model that captures the charge-transfer properties of Cu-based
high critical temperature superconductors is introduced and studied via Monte
Carlo simulations. The strong Coulomb repulsion among $d$-electrons in the Cu
orbitals is phenomenologically replaced by an exchange coupling between the
spins of the itinerant electrons and localized spins at the Cu sites, formally
similar to double-exchange models for manganites. This interaction induces a
charge-transfer insulator gap in the undoped case (five electrons per unit
cell). Adding a small antiferromagnetic Heisenberg coupling between localized
spins reinforces the global tendency towards antiferromagnetic order. To
perform numerical calculations the localized spins are considered classical, as
in previous related efforts. In this first study, undoped and doped $8\times 8$
clusters are analyzed in a wide range of temperatures. The numerical results
reproduce experimental features in the one-particle spectral function and the
density-of-states such as $(i)$ the formation of a Zhang-Rice-like band with a
dispersion of order $\sim 0.5$ eV and with rotational symmetry about wavevector
$(\pi/2,\pi/2)$ at the top of the band, and $(ii)$ the opening of a pseudogap
at the chemical potential upon doping. We also observed incipient tendencies
towards spin incommensurability. This simple model offers a formalism
intermediate between standard mean-field approximations, that fail at finite
temperatures in regimes with short-range order, and sophisticated many-body
techniques such as Quantum Monte Carlo, that suffer sign problems.",1804.07191v1
2018-05-18,Hamiltonian formulation of general relativity and post-Newtonian dynamics of compact binaries,"Hamiltonian formalisms provide powerful tools for the computation of
approximate analytic solutions of the Einstein field equations. The
post-Newtonian computations of the explicit analytic dynamics and motion of
compact binaries are discussed within the most often applied
Arnowitt-Deser-Misner formalism. The obtention of autonomous Hamiltonians is
achieved by the transition to Routhians. Order reduction of higher derivative
Hamiltonians results in standard Hamiltonians. Tetrad representation of general
relativity is introduced for the tackling of compact binaries with spinning
components. Configurations are treated where the absolute values of the spin
vectors can be considered constant. Compact objects are modeled by use of Dirac
delta functions and their derivatives. Consistency is achieved through
transition to d-dimensional space and application of dimensional
regularization. At the fourth post-Newtonian level, tail contributions to the
binding energy show up. The conservative spin-dependent dynamics finds explicit
presentation in Hamiltonian form through next-to-next-to-leading-order
spin-orbit and spin1-spin2 couplings and to leading-order in the cubic and
quartic in spin interactions. The radiation reaction dynamics is presented
explicitly through the third-and-half post-Newtonian order for spinless
objects, and, for spinning bodies, to leading-order in the spin-orbit and
spin1-spin2 couplings. The most important historical issues get pointed out.",1805.07240v4
2021-12-29,High-harmonic generation in spin and charge current pumping at ferromagnetic or antiferromagnetic resonance in the presence of spin-orbit coupling,"One of the cornerstone effects in spintronics is spin pumping by dynamical
magnetization that is steadily precessing (around, e.g., the $z$-axis) with
frequency $\omega_0$, due to absorption of low-power microwaves of frequency
$\omega_0$ under the resonance conditions and in the absence of any applied
bias voltage. The two-decades-old ""standard model"" of this effect, based on the
scattering theory of adiabatic quantum pumping, predicts that component
$I^{S_z}$ of spin current vector $\big( I^{S_x}(t),I^{S_y}(t),I^{S_z} \big)
\propto \omega_0$ is time-independent while $I^{S_x}(t)$ and $I^{S_y}(t)$
oscillate harmonically in time with a single frequency $\omega_0$; whereas
pumped charge current is zero $I \equiv 0$ in the same adiabatic $\propto
\omega_0$ limit. Here we employ more general than ""standard model"" approaches,
time-dependent nonequilibrium Green's function (NEGF) and Floquet-NEGF, to
predict unforeseen features of spin pumping -- precessing localized magnetic
moments within ferromagnetic metal (FM) or antiferromagnetic metal (AFM), whose
conduction electrons are exposed to spin-orbit coupling (SOC) of either
intrinsic or proximity origin, will pump both spin $I^{S_\alpha}(t)$ and charge
$I(t)$ currents. All four of these functions harmonically oscillate in time at
both even an odd integer multiples $N\omega_0$ of the driving frequency
$\omega_0$. The cutoff order of such high-harmonics increases with SOC
strength, reaching $N_\mathrm{max} \simeq 11$ in the chosen-for-demonstration
one-dimensional FM or AFM models. Higher cutoff $N_\mathrm{max} \simeq 25$ can
be achieved in realistic two-dimensional (2D) FM models defined on the
honeycomb lattice, where we provide prescription on how to realize them using
2D magnets and their heterostructures.",2112.14685v3
2023-02-08,Tunable correlation effects of magnetic impurities by the cubic Rashba spin-orbit couplings,"We theoretically study the influence of the $k$-cubic Rashba spin-orbit
coupling (SOC) on the correlation effects of magnetic impurities by combining
the variational method and the Hirsch-Fye quantum Monte Carlo (HFQMC)
simulations. Markedly different from the normal $k$-linear Rashba SOC, even a
small cubic Rashba term can greatly alter the band structure and induce a Van
Hove singularity in a wide range of energy, thus the single impurity local
moment becomes largely tunable. The cubic Rashba SOC adopted in this work
breaks the rotational symmetry, but the host material is still invariant under
the operations $\mathcal{R}^z(\pi)$, $\mathcal{IR}^z(\pi/2)$,
$\mathcal{M}_{xz}$, $\mathcal{M}_{yz}$, where $\mathcal{R}^z(\theta)$ is the
rotation of angle $\theta$ about the $z$-axis, $\mathcal{I}$ is the inversion
operator and $\mathcal{M}_{xz}$ ($\mathcal{M}_{yz}$) is the mirror reflection
about the $x$-$z$ ($y$-$z$) principal plane. Saliently, various components of
spin-spin correlation between the single magnetic impurity and the conduction
electrons show three- or six-fold rotational symmetry. This unique feature is
due to the triple winding of the spins with a $2\pi$ rotation of $\mathbf{k}$,
which is a hallmark of the cubic Rashba effect and can possibly be an
identifier to distinguish the cubic Rashba SOC from the normal $k$-linear
Rashba term in experiments. Although the cubic Rashba term drastically alters
the electronic properties of the host, we find that the spatial decay rate of
the spin-spin correlation function remains essentially unchanged. Moreover, the
carrier-mediated Ruderman-Kittel-Kasuya-Yosida interactions between two
magnetic impurities show twisted features, the ferromagnetic diagonal terms
dominate when two magnetic impurities are very close, but the off-diagonal
terms become important at long distances.",2302.03993v2
2024-03-23,Bilinear magnetoresistance in 2DEG with isotropic cubic Rashba spin-orbit interaction,"Bilinear magnetoresistance has been studied theoretically in 2D systems with
isotropic cubic form of Rashba spin-orbit interaction. We have derived the
effective spin-orbital field due to current-induced spin polarization and
discussed its contribution to the unidirectional system response. The analysed
model can be applied to the semiconductor quantum wells as well as 2DEG at the
surfaces and interfaces of perovskite oxides.",2403.15817v1
2022-01-05,Equatorial orbits of spinning test particle in rotating boson star,"In this paper, we study the circular orbit of the spinning test particle in
the background of a rotating boson star. Using the pole-dipole approximation
and neglecting the back-reaction of the spinning test particle on the
spacetime, the equation of motion of the spinning test particle is described by
the Mathisson-Papapetrou-Dixon equation. We solve this equation under the
Tulczyjew spin-supplementary condition and obtain the four-momentum and
four-velocity of the spinning test particle. Quite different from the spinless
particle, the effective potential of the spinning particle with zero orbital
angular momentum goes to infinite at the center of the rotating boson star.
This will lead to the fact that the spinning particle can not pass through the
center of the boson star. However, when the spin angular momentum and orbital
angular momentum satisfy $2\bar{s}+\bar{l}=0$, the effective potential is not
divergent anymore and the spinning particle can pass through the center of the
rotating boson star. {We still investigate how the spin affects the structure
of the circular orbits and we find that the spin will induce the larger or
smaller regions of no circular orbits, unstable circular orbits, and stable
circular orbits.} Moreover, the radius and energy of the circular orbit will be
decreased or increased by the particle spin. These results will have an
important application in testing the gravitational waves in the boson star
background.",2201.01498v3
2022-01-31,Tuning spin-orbit torques across the phase transition in VO$_2$/NiFe heterostructure,"The emergence of spin-orbit torques as a promising approach to
energy-efficient magnetic switching has generated large interest in material
systems with easily and fully tunable spin-orbit torques. Here, current-induced
spin-orbit torques in VO$_2$/NiFe heterostructures were investigated using
spin-torque ferromagnetic resonance, where the VO$_2$ layer undergoes a
prominent insulator-metal transition. A roughly two-fold increase in the
Gilbert damping parameter, $\alpha$, with temperature was attributed to the
change in the VO$_2$/NiFe interface spin absorption across the VO$_2$ phase
transition. More remarkably, a large modulation ($\pm$100%) and a sign change
of the current-induced spin-orbit torque across the VO$_2$ phase transition
suggest two competing spin-orbit torque generating mechanisms. The bulk spin
Hall effect in metallic VO$_2$, corroborated by our first-principles
calculation of spin Hall conductivity, $\sigma_{SH} \approx 10^4
\frac{\hbar}{e} \Omega^{-1} m^{-1}$, is verified as the main source of the
spin-orbit torque in the metallic phase. The self-induced/anomalous torque in
NiFe, of the opposite sign and a similar magnitude to the bulk spin Hall effect
in metallic VO$_2$, could be the other competing mechanism that dominates as
temperature decreases. For applications, the strong tunability of the torque
strength and direction opens a new route to tailor spin-orbit torques of
materials which undergo phase transitions for new device functionalities.",2201.12984v1
2010-03-13,Single-shot readout of an electron spin in silicon,"The size of silicon transistors used in microelectronic devices is shrinking
to the level where quantum effects become important. While this presents a
significant challenge for the further scaling of microprocessors, it provides
the potential for radical innovations in the form of spin-based quantum
computers and spintronic devices. An electron spin in Si can represent a
well-isolated quantum bit with long coherence times because of the weak
spin-orbit coupling and the possibility to eliminate nuclear spins from the
bulk crystal. However, the control of single electrons in Si has proved
challenging, and has so far hindered the observation and manipulation of a
single spin. Here we report the first demonstration of single-shot,
time-resolved readout of an electron spin in Si. This has been performed in a
device consisting of implanted phosphorus donors coupled to a
metal-oxide-semiconductor single-electron transistor - compatible with current
microelectronic technology. We observed a spin lifetime approaching 1 second at
magnetic fields below 2 T, and achieved spin readout fidelity better than 90%.
High-fidelity single-shot spin readout in Si opens the path to the development
of a new generation of quantum computing and spintronic devices, built using
the most important material in the semiconductor industry.",1003.2679v3
2015-09-07,Tidal Love numbers of a slowly spinning neutron star,"By extending our recent framework to describe the tidal deformations of a
spinning compact object, we compute for the first time the tidal Love numbers
of a spinning neutron star to linear order in the angular momentum. The spin of
the object introduces couplings between electric and magnetic distortions and
new classes of spin-induced (""rotational"") tidal Love numbers emerge. We focus
on stationary tidal fields, which induce axisymmetric perturbations. We present
the perturbation equations for both electric-led and magnetic-led rotational
Love numbers for generic multipoles and explicitly solve them for various
tabulated equations of state and for a tidal field with an electric (even
parity) and magnetic (odd parity) component with $\ell=2,3,4$. For a binary
system close to the merger, various components of the tidal field become
relevant. In this case we find that an octupolar magnetic tidal field can
significantly modify the mass quadrupole moment of a neutron star. Preliminary
estimates, assuming a spin parameter $\chi\approx0.05$, show modifications
$\gtrsim10\%$ relative to the static case, at an orbital distance of five
stellar radii. Furthermore, the rotational Love numbers as functions of the
moment of inertia are much more sensitive to the equation of state than in the
static case, where approximate universal relations at the percent level exist.
For a neutron-star binary approaching the merger, we estimate that the
approximate universality of the induced mass quadrupole moment deteriorates
from $1\%$ in the static case to roughly $6\%$ when $\chi\approx0.05$. Our
results suggest that spin-tidal couplings can introduce important corrections
to the gravitational waveforms of spinning neutron-star binaries approaching
the merger.",1509.02171v3
2022-05-05,Parity Violation in Spin-Precessing Binaries: Gravitational Waves from the Inspiral of Black Holes in Dynamical Chern-Simons Gravity,"Spin precession in compact binaries is intricately tuned to the multipole
structure of the underlying bodies. For black holes, violations of the no-hair
theorems induced by modifications to general relativity correct the precession
dynamics, which in turn imprints onto the amplitude and phase modulations of
the gravitational waves emitted by the binary. Recently, the spin precession
equations were derived up to second order in spin for dynamical Chern-Simons
gravity, a parity violating modified theory of gravity. We here solve these
equations and construct, for the first time, analytic expressions for the time-
and frequency-domain gravitational waves emitted in the quasi-circular inspiral
of spin-precessing black hole binaries in a modified theory of gravity using
the post-Newtonian approximation. Working within the small coupling
approximation and using multiple scale analysis, we show that the corrections
to the nutation phase enter at relative 1PN order, and the corrections to the
precession angle and Thomas phase enter at relative 0PN order. Making use of
the stationary phase approximation and shifted uniform asymptotics, we find
that the Fourier phase of the waveform is characterized by three modifications,
two due to the back-reaction of the precession dynamics onto the spin-orbit and
spin-spin couplings that enter at 1.5PN and 2PN orders, and a 2PN modification
due to the emission of dipole radiation. We also find that back-reaction of the
precession dynamics forces the dCS corrections to the Fourier amplitude to
enter at 0PN order, as opposed to 2PN order, as expected for spin-aligned
binaries. Our work lays the first foundational stones to build an
inspiral-merger-ringdown phenomenological model for spin-precessing binaries in
a modified theory of gravity.",2205.02675v2
2000-03-10,Light-Cone Representation of the Spin and Orbital Angular Momentum of Relativistic Composite Systems,"The matrix elements of local operators such as the electromagnetic current,
the energy momentum tensor, angular momentum, and the moments of structure
functions have exact representations in terms of light-cone Fock state
wavefunctions of bound states such as hadrons. We illustrate all of these
properties by giving explicit light-cone wavefunctions for the two-particle
Fock state of the electron in QED, thus connecting the Schwinger anomalous
magnetic moment to the spin and orbital momentum carried by its Fock state
constituents. We also compute the QED one-loop radiative corrections for the
form factors for the graviton coupling to the electron and photon. Although the
underlying model is derived from elementary QED perturbative couplings, it in
fact can be used to simulate much more general bound state systems by applying
spectral integration over the constituent masses while preserving all of the
Lorentz properties, giving explicit realization of the spin sum rules and other
local matrix elements. The role of orbital angular momentum in understanding
the ""spin crisis"" problem for relativistic systems is clarified. We also prove
that the anomalous gravitomagnetic moment B(0) vanishes for any composite
system. This property is shown to follow directly from the Lorentz boost
properties of the light-cone Fock representation and holds separately for each
Fock state component. We show how the QED perturbative structure can be used to
model bound state systems while preserving all Lorentz properties. We thus
obtain a theoretical laboratory to test the consistency of formulae which have
been proposed to probe the spin structure of hadrons.",0003082v3
2021-04-23,Roadmap of spin-orbit torques,"Spin-orbit torque (SOT) is an emerging technology that enables the efficient
manipulation of spintronic devices. The initial processes of interest in SOTs
involved electric fields, spin-orbit coupling, conduction electron spins and
magnetization. More recently interest has grown to include a variety of other
processes that include phonons, magnons, or heat. Over the past decade, many
materials have been explored to achieve a larger SOT efficiency. Recently,
holistic design to maximize the performance of SOT devices has extended
material research from a nonmagnetic layer to a magnetic layer. The rapid
development of SOT has spurred a variety of SOT-based applications. In this
Roadmap paper, we first review the theories of SOTs by introducing the various
mechanisms thought to generate or control SOTs, such as the spin Hall effect,
the Rashba-Edelstein effect, the orbital Hall effect, thermal gradients,
magnons, and strain effects. Then, we discuss the materials that enable these
effects, including metals, metallic alloys, topological insulators,
two-dimensional materials, and complex oxides. We also discuss the important
roles in SOT devices of different types of magnetic layers. Afterward, we
discuss device applications utilizing SOTs. We discuss and compare
three-terminal and two-terminal SOT-magnetoresistive random-access memories
(MRAMs); we mention various schemes to eliminate the need for an external
field. We provide technological application considerations for SOT-MRAM and
give perspectives on SOT-based neuromorphic devices and circuits. In addition
to SOT-MRAM, we present SOT-based spintronic terahertz generators,
nano-oscillators, and domain wall and skyrmion racetrack memories. This paper
aims to achieve a comprehensive review of SOT theory, materials, and
applications, guiding future SOT development in both the academic and
industrial sectors.",2104.11459v2
2022-06-02,"Fully relativistic $GW$/Bethe-Salpeter calculations in BerkeleyGW: implementation, symmetries, benchmarking, and performance","Computing the $GW$ quasiparticle bandstructure and Bethe-Salpeter Equation
(BSE) absorption spectra for materials with spin-orbit coupling has commonly
been done by treating $GW$ corrections and spin-orbit coupling as separate
perturbations to density-functional theory. However, accurate treatment of
materials with strong spin-orbit coupling often requires a fully relativistic
approach using spinor wavefunctions in the Kohn-Sham equation and $GW$/BSE.
Such calculations have only recently become available, in particular for the
BSE. We have implemented this approach in the plane-wave pseudopotential
$GW$/BSE code BerkeleyGW, which is highly parallelized and widely used in the
electronic-structure community. We present reference results for quasiparticle
bandstructures and optical absorption spectra of solids with different
strengths of spin-orbit coupling, including Si, Ge, GaAs, GaSb, CdSe, Au, and
Bi$_2$Se$_3$. The calculated quasiparticle band gaps of these systems are found
to agree with experiment to within a few tens of meV. The absorption spectrum
of GaSb calculated with the fully-relativistic $GW$-BSE captures the large
spin-orbit splitting of peaks in the spectrum. For Bi$_2$Se$_3$, we find a
drastic change in the low-energy bandstructure compared to that of DFT, with
the fully-relativistic treatment of the $GW$ approximation correctly capturing
the parabolic nature of the valence and conduction bands after including
off-diagonal self-energy matrix elements. We present the detailed methodology,
approach to spatial symmetries for spinors, comparison against other codes, and
performance compared to spinless $GW$/BSE calculations and perturbative
approaches to SOC. This work aims to spur further development of spinor
$GW$/BSE methodology in excited-state research software.",2206.00808v1
2005-10-31,Intrinsic spin current for an arbitrary Hamiltonian and scattering potential,"We have described electron spin dynamics in the presence of the spin-orbit
interaction and disorder using the spin-density matrix method. Exact solution
is obtained for an arbitrary 2D spin-orbit Hamiltonian and arbitrary smoothness
of the disorder potential. Spin current depends explicitely on the disorder
properties, namely the smoothness of the disorder potential, even in the
ballistic limit when broadening by scattering is much smaller than the
spin-orbit related splitting of the energy spectrum. In this sense universal
intrinsic spin current does not exist.",0510815v2
2008-05-08,Spin current diode based on an electron waveguide with spin-orbit interaction,"We propose a spin current diode which can work even in a small applied bias
condition (the linear-response regime). The prototypal device consists of a
hornlike electron waveguide with Rashba spin-orbit interaction, which is
connected to two leads with different widths. It is demonstrated that when
electrons are incident from the narrow lead, the generated spin conductance
fluctuates around a constant value in a wide range of incident energy. When the
transport direction is reversed, the spin conductance is suppressed strongly.
Such a remarkable difference arises from spin-flipped transitions caused by the
spin-orbit interaction.",0805.1106v1
2014-01-23,Tidal evolution of the spin-orbit angle in exoplanetary systems,"The angle between the stellar spin and the planetary orbit axes (spin-orbit
angle) is supposed to carry valuable information on the initial condition of
the planet formation and the subsequent migration history. Indeed current
observations of the Rossiter- McLaughlin effect have revealed a wide range of
spin-orbit misalignments for transiting exoplanets. We examine in detail the
tidal evolution of a simple system comprising a Sun-like star and a hot Jupiter
adopting the equilibrium tide and the inertial wave dissipation effects
simultaneously. We find that the combined tidal model works as a very efficient
realignment mechanism; it predicts three distinct states of the spin-orbit
angle (i.e., parallel, polar, and anti-parallel orbits) for a while, but the
latter two states eventually approach the parallel spin-orbit configuration.
The intermediate spin-orbit angles as measured in recent observations are
difficult to be achieved. Therefore the current model cannot reproduce the
observed broad distribution of the spin-orbit angles, at least in its simple
form. This indicates that the observed diversity of the spin-orbit angles may
emerge from more complicated interactions with outer planets and/or may be the
consequence of the primordial misalignment between the proto-planetary disk and
the stellar spin, which requires future detailed studies.",1401.5876v1
2014-04-22,Conservation of the spin and orbital angular momenta in electromagnetism,"We review and re-examine the description and separation of the spin and
orbital angular momenta (AM) of an electromagnetic field in free space. While
the spin and orbital AM of light are not separately-meaningful physical
quantities in orthodox quantum mechanics or classical field theory, these
quantities are routinely measured and used for applications in optics. A
meaningful quantum description of the spin and orbital AM of light was recently
provided by several authors, which describes separately conserved and
measurable integral values of these quantities. However, the electromagnetic
field theory still lacks corresponding locally-conserved spin and orbital AM
currents. In this paper, we construct these missing spin and orbital AM
densities and fluxes that satisfy the proper continuity equations. We show that
these are physically measurable and conserved quantities. These are, however,
not Lorentz-covariant, so only make sense in the single laboratory reference
frame of the measurement probe. The fluxes we derive improve the canonical
(non-conserved) spin and orbital AM fluxes, and include a `spin-orbit' term
that describes the spin-orbit interaction effects observed in nonparaxial
optical fields. We also consider both standard and dual-symmetric versions of
the electromagnetic field theory. Applying the general theory to nonparaxial
optical vortex beams validates our results and allows us to discriminate
between earlier approaches to the problem. Our treatment yields the complete
and consistent description of the spin and orbital AM of free Maxwell fields in
both quantum-mechanical and field-theory approaches.",1404.5486v3
2016-09-02,Spin-resolved orbital magnetization in Rashba two-dimensional electron gas,"We calculate orbital spin-dependent magnetization in a two-dimensional
electron gas with spin-orbit interaction of Rashba type. Such an orbital
magnetization is admitted by the time-reversal symmetry of the system, and
gives rise to spin currents when the system is not in thermal equilibrium. The
theoretical approach is based on the linear response theory and the Matsubara
Green's function formalism. To account for the spin-resolved orbital
magnetization a spin-dependent vector potential has been introduced. The spin
currents which appear in thermal nonequilibrium due to the spin-resolved
orbital magnetization play an important role in the spin Nernst effect, and
have to be included in order to correctly describe the low-temperature spin
Nernst conductivity.",1609.00470v1
2018-03-19,Enhanced spin-orbit torque via interface engineering in Pt/CoFeB/MgO heterostructures,"Spin-orbit torque facilitates efficient magnetization switching via an
in-plane current in perpendicularly magnetized heavy metal/ferromagnet
heterostructures. The efficiency of spin-orbit-torque-induced switching is
determined by the charge-to-spin conversion arising from either bulk or
interfacial spin-orbit interactions, or both. Here, we demonstrate that the
spin-orbit torque and the resultant switching efficiency in Pt/CoFeB systems
are significantly enhanced by an interfacial modification involving Ti
insertion between the Pt and CoFeB layers. Spin pumping and X-ray magnetic
circular dichroism experiments reveal that this enhancement is due to an
additional interface-generated spin current of the nonmagnetic interface and/or
improved spin transparency achieved by suppressing the proximity-induced moment
in the Pt layer. Our results demonstrate that interface engineering affords an
effective approach to improve spin-orbit torque and thereby magnetization
switching efficiency.",1803.06961v1
2014-04-28,Self-consistent linear response for the spin-orbit interaction related properties,"In many cases, the relativistic spin-orbit (SO) interaction is regarded to be
small and can be treated using perturbation theory. The major obstacle on this
route comes from the fact that the SO interaction can also polarize the
electron system and produce additional contributions to the perturbation
theory, arising from the electron-electron interactions. In electronic
structure calculations, it may even lead to necessity to abandon the
perturbation theory and return to the self-consistently solution of
Kohn-Sham-like equations with the effective potential $\hat{v}$, incorporating
the effects of the electron-electron interactions and the SO coupling, even
though the latter is small. In this work, we present the theory of
self-consistent linear response (SCLR), which allows us to get rid of numerical
self-consistency and formulate it analytically in the first order of the SO
coupling. This strategy is applied to the Hartree-Fock solution of the
effective Hubbard model, derived from electronic structure calculations in the
Wannier basis. By using $\hat{v}$, obtained from SCLR, one can successfully
reproduce results of ordinary calculations for the orbital magnetization and
other properties in the first order of the SO coupling. Particularly, SCLR
appears to be extremely useful for calculations of antisymmetric
Dzyaloshinskii-Moriya (DM) interactions based on the magnetic force theorem.
Furthermore, due to the powerful 2n+1 theorem, the SCLR theory allows us to
calculate the magnetic anisotropy energy up to the third order of the SO
coupling. The fruitfulness of this approach is illustrated on a number of
example, including the spin canting in YTiO$_3$ and LaMnO$_3$, formation of
spiral magnetic order in BiFeO$_3$, and the magnetic inversion symmetry
breaking in BiMnO$_3$, which gives rise to both ferroelectric activity and DM
interactions, responsible for the ferromagnetism.",1404.6872v1
2014-12-08,Non-local effect of a varying in space Zeeman field on the supercurrent and helix state in a spin-orbit-coupled s-wave superconductor,"A weak parallel Zeeman field combined with the spin-orbit coupling can induce
the supercurrent in an s-wave two-dimensional superconductor. At the same time,
the thermodynamically equilibrium state of such a system is characterized by
the helix phase where the order parameter varies in space as
$\exp(i\mathbf{Qr})$. In this state the electric current that is induced by the
Zeeman interaction is exactly counterbalanced by the current produced by the
gradient of the order-parameter. We studied the interplay of the helix state
and magnetoelectric current in the case of a varying in space Zeeman field, as
it might be realized in hybrid heterostructures with magnetic and
superconducting layers. The theoretical analysis was based on Usadel equations
for Green functions in a dirty superconductor. It is shown that even a weak
inhomogeneity produces a strong long-range effect on the magnetoelectric
current and the order-parameter phase. Consequently, depending on the
macroscopic shape of such an inhomogeneity, either the helix state with the
zero supercurrent, or a locally uniform state with the finite supercurrent are
realized. A mixture of these two extreme situations is also possible. It is
also shown that the current can be induced at a large distance from a
ferromagnetic island embedded into a superconductor. Quantum effects associated
with the magnetoelectric effect are briefly discussed for multiply connected
systems. The theory proposes a new point of view on interplay of the
magnetoelectric effect and helix phase in spin-orbit coupled superconductors.
It also suggests an interesting method allowing to couple superconducting and
magnetic circuits.",1412.2527v5
2017-06-21,Two-dimensional solitons and quantum droplets supported by competing self- and cross-interactions in spin-orbit-coupled condensates,"We study two-dimensional (2D) matter-wave solitons in spinor Bose-Einstein
condensates (BECs) under the action of the spin-orbit coupling (SOC) and
opposite signs of the self- and cross-interactions. Stable 2D two-component
solitons of the mixed-mode (MM) type are found if the cross-interaction between
the components is attractive, while the self-interaction is repulsive in each
component. Stable solitons of the semi-vortex type are formed in the opposite
case, under the action of competing self-attraction and cross-repulsion. The
solitons exist with the total norm taking values below a collapse threshold.
Further, in the case of the repulsive self-interaction and inter-component
attraction, stable 2D self-trapped modes, which may be considered as quantum
droplets (QDs), are created if the beyond-mean-field Lee-Huang-Yang (LHY) terms
are added to the self-repulsion in the underlying system of coupled
Gross-Pitaevskii equations. Stable QDs of the MM type, of a large size with an
anisotropic density profile, exist with arbitrarily large values of the norm,
as the LHY terms eliminate the collapse. The effect of the SOC term on
characteristics of the QDs is systematically studied. We also address the
existence and stability of QDs in the case of SOC with mixed Rashba and
Dresselhaus terms, which makes the density profile of the QD more isotropic.
Thus, QDs in the spin-orbit-coupled binary BEC are for the first time studied
in the present work.",1706.06725v3
2021-07-02,Interplay between singlet and triplet pairings in multi-band two-dimensional oxide superconductors,"We theoretically study the superconducting properties of multi-band
two-dimensional transition metal oxide superconductors by analyzing not only
the role played by conventional singlet pairings, but also by the triplet order
parameters, favored by the spin-orbit couplings present in these ma- terials.
In particular, we focus on the two-dimensional electron gas at the (001)
interface between LaAlO3 and SrTiO3 band insulators where the low electron
densities and the sizeable spin-orbit couplings affect the superconducting
features. Our theoretical study is based on an extended su- perconducting
mean-field analysis of the typical multi-band tight-binding Hamiltonian, as
well as on a parallel analysis of the effective electronic bands in the
low-momentum limit, including static on-site and inter-site intra-band
attractive potentials under applied magnetic fields. The presence of triplet
pairings is able to strongly reduce the singlet order parameters which, as a
result, are no longer a monotonic function of the charge density. The interplay
between the singlet and the triplet pairings affects the dispersion of
quasi-particle excitations in the Brillouin zone and also induces anisotropy in
the superconducting behavior under the action of an in-plane and of an out-
of-plane magnetic fields. Finally, non-trivial topological superconducting
states become stable as a function of the charge density, as well as of the
magnitude and of the orientation of the magnetic field. In addition to the
chiral, time-reversal breaking, topological superconducting phase, favored by
the linear Rashba couplings and by the on-site attractive potentials in the
presence of an out- of-plane magnetic field, we find that a time-reversal
invariant topological helical superconducting phase is promoted by not-linear
spin-orbit couplings and by the inter-site attractive interactions in the
absence of magnetic field.",2107.01100v2
2014-09-11,Anisotropic magnetoresistance in antiferromagnetic Sr2IrO4,"We report point-contact measurements of anisotropic magnetoresistance (AMR)
in a single crystal of antiferromagnetic (AFM) Mott insulator Sr2IrO4. The
point-contact technique is used here as a local probe of magnetotransport
properties on the nanoscale. The measurements at liquid nitrogen temperature
revealed negative magnetoresistances (MRs) (up to 28%) for modest magnetic
fields (250 mT) applied within the IrO2 a-b plane and electric currents flowing
perpendicular to the plane. The angular dependence of MR shows a crossover from
four-fold to two-fold symmetry in response to an increasing magnetic field with
angular variations in resistance from 1-14%. We tentatively attribute the
four-fold symmetry to the crystalline component of AMR and the field-induced
transition to the effects of applied field on the canting of AFM-coupled
moments in Sr2IrO4. The observed AMR is very large compared to the crystalline
AMRs in 3d transition metal alloys/oxides (0.1-0.5%) and can be associated with
the large spin-orbit interactions in this 5d oxide while the transition
provides evidence of correlations between electronic transport, magnetic order
and orbital states. The finding of this work opens an entirely new avenue to
not only gain a new insight into physics associated with spin-orbit coupling
but also better harness the power of spintronics in a more technically
favorable fashion.",1409.3491v2
2015-10-09,Enhanced and Tunable Spin-Orbit Coupling in Tetragonally Strained Fe-Co-B Films,"We have synthesized 20 nm thick films of tetragonally strained interstitial
Fe-Co-B alloys epitaxially grown on Au55Cu45 buffer layer. The strained axis is
perpendicular to the film plane and the corresponding lattice constant c is
enlarged with respect to the in-plane lattice parameter a. By adding the
interstitial boron with different concentrations 0, 4, and 10 at.% we were able
to stabilize the tetragonal strain in 20 nm Fe-Co films with different c/a
ratios of 1.013, 1.034 and 1.02, respectively. Using ferromagnetic resonance
(FMR) and x-ray magnetic circular dichroism (XMCD) we found that the orbital
magnetic moment increases with increasing the c/a ratio, pointing towards the
enhancement of spin-orbit coupling (SOC) at larger strain. Our results show
that careful doping of ferromagnetic films allows to control the SOC by
stabilizing anisotropic strain states. These findings are applicable in
material design for spintronics applications. We also discuss the influence of
B doping on the Fe-Co film microstructure, its magnetic properties and magnetic
relaxation.",1510.02624v1
2020-02-04,Topological flat bands in frustrated kagome lattice CoSn,"Electronic flat bands in momentum space, arising from strong localization of
electrons in real space, are an ideal stage to realize strong correlation
phenomena. In certain lattices with built-in geometrical frustration,
electronic confinement and flat bands can naturally arise from the destructive
interference of electronic hopping pathways. Such lattice-borne flat bands are
often endowed with nontrivial topology if combined with spin-orbit coupling,
while their experimental realization in condensed matter system has been
elusive so far. Here, we report the direct observation of topological flat
bands in the vicinity of the Fermi level in frustrated kagome system CoSn,
using angle-resolved photoemission spectroscopy and band structure
calculations. The flat band manifests itself as a dispersionless electronic
excitation along the G-M high symmetry direction, with an order of magnitude
lower bandwidth (below 150 meV) compared to the Dirac bands originating from
the same orbitals. The frustration-driven nature of the flat band is directly
confirmed by the real-space chiral d-orbital texture of the corresponding
effective Wannier wave functions. Spin-orbit coupling opens a large gap of 80
meV at the quadratic band touching point between the Dirac and flat bands,
endowing a nonzero Z2 topological invariant to the flat band in the
two-dimensional Brillouin zone. Our observation of lattice-driven topological
flat band opens a promising route to engineer novel emergent phases of matter
at the crossroad between strong correlation physics and electronic topology.",2002.01452v1
2019-08-20,Wavelength-scale errors in optical localization due to spin-orbit coupling of light,"The precise determination of the position of point-like emitters and
scatterers using far-field optical imaging techniques is of utmost importance
for a wide range of applications in medicine, biology, astronomy, and physics.
Although the optical wavelength sets a fundamental limit to the image
resolution of unknown objects, the position of an individual emitter can in
principle be estimated from the image with arbitrary precision. This is used,
e.g., in stars' position determination and in optical super-resolution
microscopy. Furthermore, precise position determination is an experimental
prerequisite for the manipulation and measurement of individual quantum
systems, such as atoms, ions, and solid state-based quantum emitters. Here we
demonstrate that spin-orbit coupling of light in the emission of elliptically
polarized emitters can lead to systematic, wavelength-scale errors in the
estimate of the emitter's position. Imaging a single trapped atom as well as a
single sub-wavelength-diameter gold nanoparticle, we demonstrate a shift
between the emitters' measured and actual positions which is comparable to the
optical wavelength. Remarkably, for certain settings, the expected shift can
become arbitrarily large. Beyond their relevance for optical imaging
techniques, our findings apply to the localization of objects using any type of
wave that carries orbital angular momentum relative to the emitter's position
with a component orthogonal to the direction of observation.",1908.07268v1
2019-12-18,The Phenomenon of Shape Evolution due to Solar Driven Outgassing for Analogues of Small Kuiper Belt Objects,"One of the key findings of the Rosetta's mission to the Jupiter family comet
67P/Churyumov-Gerasimenko was its peculiar bilobed shape along with the
apparent north/south dichotomy in large scale morphology. This has re-ignited
scientific discussions on the topic of origin, evolution and age of the
nucleus. In this work we set up a general numerical investigation on the role
of solar driven activity on the overall shape change. Our goal is to isolate
and study the influence of key parameters for solar driven mass loss, and
hopefully obtain a classification of the final shapes. We consider five general
classes of three-dimensional (3D) objects for various initial conditions of
spin-axis and orbital parameters, propagating them on different orbits
accounting for solar driven CO ice sublimation. A detailed study of the
coupling between sublimation curve and orbital parameters (for CO and H$_{2}$O
ices) is also provided. The idealizations used in this study are aimed to
remove the ad-hoc assumptions on activity source distribution, composition,
and/or chemical inhomogeneities as applied in similar studies focusing on
explaining a particular feature or observation. Our numerical experiments show
that under no condition a homogeneous nucleus with solar driven outgassing can
produce concave morphology on a convex shape. On the other hand, preexisting
concavities can hardly be smoothed/removed for the assumed activity. In
summary, the coupling between solar distance, eccentricity, spin-axis and its
orientation, as well as effects on shadowing and self-heating do combine to
induce morphology changes that might not be deducible without numerical
simulations.",1912.08617v1
2020-10-24,Dynamics of test particles around regular black holes in modified gravity,"In the work, we have presented detailed analyses of the event horizon and
curvature properties of spacetime around a regular black hole in modified
gravity so-called regular MOG black hole. The motion of neutral, electrically
charged and magnetized particles with magnetic dipole moment, in the close
environment of the regular MOG black hole immersed in an external
asymptotically uniform magnetic field has been also explored. Through the study
on the motion of the neutral test particle, we have obtained that the positive
(negative) values of the MOG parameter mimic the spin of a rotating Kerr black
hole giving the same values for innermost stable pro-grade (retrograde) orbits
of the particles in the range of the spin parameter $a/M \in(-0.4125, \
0.6946)$. The efficiency of energy release from the accretion disk by the
Novikov-Thorne model has been calculated and shown that the efficiency is
linearly proportional to the increase of the MOG parameter $\alpha$, and
exceeds up to 15 \% at the critical limiting value of the MOG parameter
$\alpha_{\rm cr}$. The study of the charged particles dynamics has shown that
innermost stable circular orbits (ISCOs) of the particle increases with the
increase of the MOG parameter, while the increase of cyclotron frequency being
responsible to the magnetic interaction causes the decrease of the latter.
Moreover, the dynamics of magnetic dipoles has shown that the increase of the
MOG and the magnetic coupling parameters lead to an increase of the inner
radius and the width of the accretion disk consisting of magnetized particles.
Finally, we have focused on showing the range of values of the magnetic
coupling parameter causing the orbits to be stable.",2010.12863v1
2021-09-13,Magnetic anisotropy of the van der Waals ferromagnet Cr$_2$Ge$_2$Te$_6$ studied by angular-dependent XMCD,"The van der Waals ferromagnet Cr$_2$Ge$_2$Te$_6$ (CGT) has a two-dimensional
crystal structure where each layer is stacked through van der Waals force. We
have investigated the nature of the ferromagnetism and the weak perpendicular
magnetic anisotropy (PMA) of CGT by means of X-ray absorption spectroscopy and
X-ray magnetic circular dichroism (XMCD) studies of CGT single crystals. The
XMCD spectra at the Cr $L_{2,3}$ edge for different magnetic field directions
were analyzed on the basis of the cluster-model multiplet calculation. The Cr
valence is confirmed to be 3+ and the orbital magnetic moment is found to be
nearly quenched, as expected for the high-spin $t_{2g}$$^3$ configuration of
the Cr$^{3+}$ ion. A large ($\sim 0.2$ eV) trigonal crystal-field splitting of
the $t_{2g}$ level caused by the distortion of the CrTe$_6$ octahedron has been
revealed, while the single-ion anisotropy (SIA) of the Cr atom is found to have
a sign {\it opposite} to the observed PMA and too weak compared to the reported
anisotropy energy. The present result suggests that anisotropic exchange
coupling between the Cr atoms through the ligand Te $5p$ orbitals having strong
spin-orbit coupling has to be invoked to explain the weak PMA of CGT, as in the
case of the strong PMA of CrI$_3$.",2109.05715v1
2022-03-09,"The interplay between structural, magnetic and electronic states in the pyrochlore iridate Eu2Ir2O7","We address the concomitant metal-insulator transition (MIT) and
antiferromagnetic ordering in the novel pyrochlore iridate Eu2Ir2O7 by
combining x-ray absorption spectroscopy, x-ray and neutron diffractions and
density functional theory (DFT) based calculations. The temperature dependent
powder x-ray diffraction clearly rules out any change in the lattice symmetry
below the MIT, nevertheless a clear anomaly in the Ir-O-Ir bond angle and Ir-O
bond length is evident at the onset of MIT. From the x-ray absorption near edge
structure (XANES) spectroscopic study of Ir-L3 and L2 edges, the effective
spin-orbit coupling is found to be intermediate, at least quite far from the
strong atomic spin-orbit coupling limit. Powder neutron diffraction measurement
is in line with an all-in-all-out magnetic structure of the Ir-tetrahedra in
this compound, which is quite common among rare-earth pyrochlore iridates. The
sharp change in the Ir-O-Ir bond angle around the MIT possibly arises from the
exchange striction mechanism, which favors an enhanced electron correlation via
weakening of Ir-Ir orbital overlap and an insulating phase below TMI . The
theoretical calculations indicate an insulating state for shorter bond angle
validating the experimental observation. Our DFT calculations show a
possibility of intriguing topological phase below a critical value of the Ir-O
distance, which is shorter than the experimentally observed bond length.
Therefore, a topological state may be realized in bulk Eu2Ir2O7 sample if the
Ir-O bond length can be reduced by the application of sufficient external
pressure.",2203.04939v1
2022-03-24,Ab Initio Study of K${_3}$Cu${_3}$P${_2}$ Material for Photovoltaic Applications,"Search for efficient materials for application in the fields of
optoelectronics and photovoltaics are active areas of research across the
world. The potential of compounds such as K${_3}$Cu${_3}$P${_2}$ is not yet
fully realized. Therefore, we perform the ab initio studies based on density
functional theory to investigate the structural, electronic, elastic, and
optical properties of K${_3}$Cu${_3}$P${_2}$. Ground state properties were
computed in three different scenarios, i.e: with spin-orbit coupling (SOC),
without spin-orbit coupling, and with Hubbard U parameter. Direct electronic
bandgaps of 1.338 eV, 1.323 eV and 1.673 eV were obtained for
K${_3}$Cu${_3}$P${_2}$ without SOC, K${_3}$Cu${_3}$P${_2}$ with SOC and
K${_3}$Cu${_3}$P${_2}$ with Hubbard U respectively. In all the cases, Cu-d
orbitals were dominant at the top of the valence band. The effect of SOC on the
K${_3}$Cu${_3}$P${_2}$ computed lattice constant and bandgap was insignificant.
The mechanical stability test indicated that K${_3}$Cu${_3}$P${_2}$ is
mechanically stable at zero pressure. The optical band gap was found to
increase by 0.635 eV when Hubbard U was taken into consideration. Generally,
the inclusion of the Hubbard U parameter in density functional theory improves
the predictions of the bandgap and optical properties.",2203.13230v1
2022-05-18,Gadolinium halide monolayers: a fertile family of two-dimensional 4f magnets,"Two-dimensional (2D) magnets have great potentials for applications in
next-generation information devices. Since the recent experimental discovery of
intrinsic 2D magnetism in monolayer CrI$_3$ and few-layer Cr$_2$Ge$_2$Te$_6$,
intensive studies have been stimulated in pursuing more 2D magnets and
revealing their intriguing physical properties. In comparison to the magnetism
based on $3d$ electrons, $4f$ electrons can provide larger magnetic moments and
stronger spin-orbit coupling, but have been much less studied in the 2D forms.
Only in very recent years, some exciting results have been obtained in this
area. In this mini-review, we will introduce some recent progress in 2D Gd
halides from a theoretical aspect. It is noteworthy that $4f$ and $5d$ orbitals
of Gd both play key roles in these materials. For Gd$X_2$ ($X$=I, Br, Cl and F)
monolayers and related Janus monolayers, robust ferromagnetism with large
exchanges comes from the $4f^7$+$5d^1$ hybridization of Gd$^{2+}$. The
spatially expanded $5d$ electrons act as a bridge to couple localized $4f$
spins. For Gd$X_3$ monolayers, the intercalation of metal atoms can dope
electrons into Gd's $5d$ orbitals, which leads to numerous intriguing physical
properties, such as ferroelasticity, ferromagnetism, and anisotropic
conductance. In brief, Gd halides establish an effective strategy to take
advantage of $f$-electron magnetism in 2D materials.",2205.08666v1
2022-12-01,"An insight into the properties of ATiO3 (A=Ti,Sr) materials for photovoltaic applications","One of the most active research areas in the world is the search for
effective materials for use in the fields of optoelectronics and photovoltaics.
The potential of materials like ATiO3 (A=Ti,Sr) is yet largely untapped. Ab
initio studies based on density functional theory (DFT) have been used to
comprehensively explore the structural, electronic, elastic, and optical
properties of Ti2O3 and SrTiO3. In this study, the ground state properties were
computed with spin-orbit coupling (SOC), without spin-orbit coupling, and with
the inclusion of Hubbard U parameter. The electronic bandgaps of Ti2O3 have
been found to be 0.059 eV without SOC, 0.131 eV with SOC, and 1.665 eV with
Hubbard U. Electronic bandgaps of 1.612 eV, 1.761 eV, and 2.769 eV have been
obtained for SrTiO3, respectively, without SOC, with SOC, and with Hubbard U.
In every single case, it has been found that Ti-4d orbitals predominate close
to the top of the valence band. The bandgap and estimated lattice constants for
ATiO3 (A=Ti,Sr) were not significantly affected by SOC. The mechanical
stability test showed that ATiO3 (A=Ti,Sr) is mechanically stable at zero
pressure. The optical band gap has been seen to increase when Hubbard U is
taken into account. In general, the Hubbard U parameter enhances bandgap and
optical property predictions. Ti2O3 and SrTiO3 are good UV-Vis absorbers and
appropriate for photovoltaic applications owing to the optical absorption
coefficient curves being found to cover the ultraviolet to visible (UV-Vis)
ranges.",2212.00635v1
2023-05-22,Existence of nodal-arc and its evolution into Weyl-nodes in the presence of spin-orbit coupling in TaAs & TaP,"In this work, we report the existence of nodal-arc, which acts as the
building block of all the nodal-rings in TaAs & TaP. This nodal-arc is found to
be capable of generating all the nodal-rings in these materials upon the
application of space-group symmetry operations including time-reversal
symmetry. The arcs are obtained to be dispersive with the energy spread of
$\sim$109 ($\sim$204) meV in TaAs (TaP). Also, the orbitals leading to
bands-inversion and thus the formation of nodal-arcs are found to be Ta-5d &
As-4p (P-3p) in TaAs (TaP). The area of nodal-rings is found to be highly
sensitive to the change in hybridization-strength, where the increase in
hybridization-strength leads to the decrease in the area of nodal-rings. In the
presence of spin-orbit coupling (SOC), all the points on these arcs get
gaped-up and two pairs of Weyl-nodes are found to evolve from them. Out of the
two pair, one is found to be situated close to the joining point of the two
arcs forming a ring. This causes the evolution of each nodal-ring into three
pairs of Weyl-nodes. The coordinates of these Weyl-nodes are found to be robust
to the increase in SOC-strength from $\sim$ 0.7-3.5 eV. All the results are
obtained at the first-principle level. This work provides a clear picture of
the existence of nodal-arc due to accidental degeneracy and its evolution into
Weyl-nodes under the effect of SOC.",2305.15432v2
2023-11-15,Proximity-induced gapless superconductivity in two-dimensional Rashba semiconductor in magnetic field,"Two-dimensional semiconductor-superconductor heterostructures form the
foundation of numerous nanoscale physical systems. However, measuring the
properties of such heterostructures, and characterizing the semiconductor
in-situ is challenging. A recent experimental study [arXiv:2107.03695] was able
to probe the semiconductor within the heterostructure using microwave
measurements of the superfluid density. This work revealed a rapid depletion of
superfluid density in semiconductor, caused by the in-plane magnetic field
which in presence of spin-orbit coupling creates so-called Bogoliubov Fermi
surfaces. The experimental work used a simplified theoretical model that
neglected the presence of non-magnetic disorder in the semiconductor, hence
describing the data only qualitatively. Motivated by experiments, we introduce
a theoretical model describing a disordered semiconductor with strong
spin-orbit coupling that is proximitized by a superconductor. Our model
provides specific predictions for the density of states and superfluid density.
Presence of disorder leads to the emergence of a gapless superconducting phase,
that may be viewed as a manifestation of Bogoliubov Fermi surface. When applied
to real experimental data, our model showcases excellent quantitative
agreement, enabling the extraction of material parameters such as mean free
path and mobility, and estimating $g$-tensor after taking into account the
orbital contribution of magnetic field. Our model can be used to probe in-situ
parameters of other superconductor-semiconductor heterostructures and can be
further extended to give access to transport properties.",2311.09347v2
2011-02-10,Strain effects on ferroelectric polarization and magnetism in orthorhombic HoMnO3,"Aiming at increasing the ferroelectric polarization in AFM-E ortho-\hmo, we
investigate the in-plane strain effects on both the magnetic configuration and
the polarization by means of density functional theory calculations and model
Hamiltonian approaches. Our results show that the net polarization is largely
enhanced under compressive strain, due to an increase of the electronic
contribution to the polarization, whereas the ionic contribution is found to
decrease. We identify the electron-lattice coupling, due to Jahn-Teller (JT)
distortions, and its response to strain to be responsible for the observed
behavior. The JT-induced orbital ordering of occupied Mn-e$_g^1$ electrons in
alternating $3x^2-r^2/3y^2-r^2$ orbital states at equilibrium changes to a
mixture with $x^2-z^2/y^2-z^2$ states under in-plane compressive strain. The
asymmetric hopping of e$_g$ electrons between Mn ions along zig-zag spin chains
(typical of the AFM-E spin configuration) is therefore enhanced under strain,
explaining the large value of the polarization. We reproduce the change in the
orbital ordering pattern in a degenerate double-exchange model supplemented
with electron-phonon interaction. In this picture, the orbital ordering change
is related to a change of the Berry phase of the e$_g$ electrons, which in turn
causes an increase of the polarization, whose origin is purely electronic.",1102.2168v1
2015-07-29,H$_4$: A Challenging System For Natural Orbital Functional Approximations,"The correct description of nondynamic correlation by electronic structure
methods not belonging to the multireference family is a challenging issue. The
transition of $D_{2h}$ to $D_{4h}$ symmetry in H$_4$ molecule is among the most
simple archetypal examples to illustrate the consequences of missing nondynamic
correlation effects. The resurge of interest in density matrix functional
methods has brought several new methods including the family of Piris Natural
Orbital Functionals (PNOF). In this work we compare PNOF5 and PNOF6, which
include nondynamic electron correlation effects to some extent, with other
standard ab initio methods in the H$_4$ $D_{4h}/D_{2h}$ potential energy
surface. Thus far, the wrongful behavior of single-reference methods at the
$D_{2h}-D_{4h}$ transition of H$_4$ has been attributed to wrong account of
nondynamic correlation effects, whereas in geminal-based approaches it has been
assigned to a wrong coupling of spins and the localized nature of the orbitals.
We will show that actually $\textit{interpair}$ nondynamic correlation is the
key to a cusp-free qualitatively correct description of H$_4$ PES. By
introducing $\textit{interpair}$ nondynamic correlation, PNOF6 is shown to
avoid cusps and provide the correct smooth PES features at distances close to
equilibrium, total and local spin properties along with the correct electron
delocalization, as reflected by natural orbitals and multicenter delocalization
indices.",1507.08244v2
2018-02-18,Orbitally limited pair-density wave phase of multilayer superconductors,"We investigate the magnetic field dependence of an ideal superconducting
vortex lattice in the parity-mixed pair-density wave phase of multilayer
superconductors within a circular cell Ginzburg-Landau approach. In multilayer
systems, due to local inversion symmetry breaking, a Rashba spin-orbit coupling
is induced at the outer layers. This combined with a perpendicular paramagnetic
(Pauli) limiting magnetic field stabilizes a staggered layer dependent
pair-density wave phase in the superconducting singlet channel. The high-field
pair-density wave phase is separated from the low-field BCS phase by a
first-order phase transition. The motivating guiding question in this paper is:
what is the minimal necessary Maki parameter $\alpha_M$ for the appearance of
the pair-density wave phase of a superconducting trilayer system? To address
this problem we generalize the circular cell method for the regular flux-line
lattice of a type-II superconductor to include paramagnetic depairing effects.
Then, we apply the model to the trilayer system, where each of the layers are
characterized by Ginzburg-Landau parameter $\kappa_0$, and a Maki parameter
$\alpha_M$. We find that when the spin-orbit Rashba interaction compares to the
superconducting condensation energy, the orbitally limited pair-density wave
phase stabilizes for Maki parameters $\alpha_M> 10$.",1802.06365v1
2015-12-03,Orbitally induced hierarchy of exchange interactions in zigzag antiferromagnetic state of honeycomb silver delafossite Ag3Co2SbO6,"We report the revised crystal structure, static and dynamic magnetic
properties of quasi-two dimensional honeycomb-lattice silver delafossite
Ag3Co2SbO6. The magnetic susceptibility and specific heat data are consistent
with the onset of antiferromagnetic long range order at low temperatures with
N\'eel temperature TN ~ 21.2 K. In addition, the magnetization curves revealed
a field-induced (spin-flop type) transition below TN in moderate magnetic
fields. The GGA+U calculations show the importance of the orbital degrees of
freedom, which maintain a hierarchy of exchange interaction in the system. The
strongest antiferromagnetic exchange coupling was found in the shortest Co-Co
pairs and is due to direct and superexchange interactions between the
half-filled xz+yz orbitals pointing directly to each other. The other four out
of six nearest neighbor exchanges within the cobalt hexagon are suppressed,
since for these bonds active half-filled orbitals turned out to be parallel and
do not overlap. The electron spin resonance (ESR) spectra reveal a Gaussian
shape line attributed to Co2+ ion in octahedral coordination with average
effective g-factor g=2.3+/-0.1 at room temperature and shows strong divergence
of ESR parameters below 120 K, which imply an extended region of short-range
correlations. Based on the results of magnetic and thermodynamic studies in
applied fields, we propose the magnetic phase diagram for the new
honeycomb-lattice delafossite.",1512.01016v1
2015-12-10,Two-site fluctuations and multipolar superexchange interactions in strongly correlated systems,"An approach is proposed for evaluating dipolar and multipolar inter-site
interactions in strongly correlated materials. This approach is based on the
single-site dynamical mean-field theory (DMFT) in conjunction with the atomic
approximation for the local self-energy. Starting from the local moment
paramagnetic state described by DMFT we derive inter-site interactions by
considering the response of the DMFT grand potential to small fluctuations of
atomic configurations on two neighboring sites. The present method is validated
by applying it to one-band and two-band e$_g$ Hubbard models on the
simple-cubic 3$d$ lattice. It is also applied to study the spin-orbital order
in the parent cubic structure of ternary chromium fluoride KCrF$_3$. We obtain
the onset of a G-type antiferro-orbital order at a significantly lower
temperature compared to that in real distorted KCrF$_3$. In contrast, its
layered A-type antiferromagnetic order and N\'eel temperature are rather well
reproduced. The calculated full Kugel-Khomskii Hamiltonian contains
spin-orbital coupling terms inducing a misalignment in the antiferro-orbital
order upon the onset of antiferromagnetism.",1512.03394v3
2020-06-21,Chemical Bonding Governs Complex Magnetism in MnPt5P,"Subtle changes in chemical bonds may result in dramatic revolutions in
magnetic properties in solid state materials. MnPt5P, a new derivative of the
rare-earth-free ferromagnetic MnPt5As, was discovered and is presented in this
work. MnPt5P was synthesized and its crystal structure and chemical composition
were characterized by X-ray diffraction as well as energy-dispersive X-ray
spectroscopy. Accordingly, MnPt5P crystallizes in the layered tetragonal
structure with the space group P4/mmm (No. 123), in which the face-shared
Mn@Pt12 polyhedral layers are separated by P layers. In contrast to the
ferromagnetism observed in MnPt5As, the magnetic properties measurements on
MnPt5P show antiferromagnetic ordering occurs at ~188 K with a strong magnetic
anisotropy in and out of the ab-plane. Moreover, a spin-flop transition appears
when a high magnetic field is applied. An A-type antiferromagnetic structure
was obtained from the analysis of powder neutron diffraction (PND) patterns
collected at 150 K and 9 K. Calculated electronic structures imply that
hybridization of Mn-3d and Pt-5d orbitals are critical for both the structural
stability and observed magnetic properties. Semi-empirical molecular orbitals
calculations on both MnPt5P and MnPt5As indicate that the lack of 4p character
on the P atoms at the highest occupied molecular orbital (HOMO) in MnPt5P may
cause the different magnetic behavior in MnPt5P compared to MnPt5As. The
discovery of MnPt5P, along with our previously reported MnPt5As, parametrizes
the end points of a tunable system to study the chemical bonding which tunes
the magnetic ordering from ferromagnetism to antiferromagnetism with strong
spin-orbit coupling (SOC) effect.",2006.11903v1
2021-06-29,Breakup of the Synchronous State of Binary Asteroid Systems,"This paper continues the authors' previous work and presents a coplanar
averaged ellipsoid-ellipsoid model of synchronous binary asteroid system (BAS)
plus thermal and tidal effects. Using this model, we analyze the breakup
mechanism of the synchronous BAS. Different from the classical spin-orbit
coupling model which neglects the rotational motion's influence on the orbital
motion, our model considers simultaneously the orbital motion and the
rotational motions. Our findings are following. (1) Stable region of the
secondary's synchronous state is mainly up to the secondary's shape. The
primary's shape has little influence on it. (2) The stable region shrinks
continuously with the increasing value of the secondary's shape parameter
$a_B/b_B$. Beyond the value of $a_B/b_B=\sqrt{2}$, the planar stable region for
the secondary's synchronous rotation is small but not zero. (3) Considering the
BYORP torque, our model shows agreement with the 1-degree of freedom adiabatic
invariance theory in the outwards migration process, but an obvious difference
in the inwards migration process. In particular, our studies show that the
so-called 'long-term' stable equilibrium between the BYORP torque and the tidal
torque is never a real equilibrium state, although the binary asteroid system
can be captured in this state for quite a long time. (4) In case that the
primary's angular velocity gradually reduces due to the YORP effect, the
secondary's synchronous state may be broken when the primary's rotational
motion crosses some major spin-orbit resonances.",2106.15039v1
2024-01-09,Jahn-Teller driven quadrupolar ordering and spin-orbital dimer formation in GaNb$_{4}$Se$_{8}$,"The lacunar spinel GaNb$_4$Se$_8$ is a tetrahedral cluster Mott insulator
where spin-orbit coupling on molecular orbitals and Jahn-Teller energy scales
are competitive. GaNb$_4$Se$_8$ undergoes a structural and anti-polar ordering
transition at T$_Q$ = 50 K that corresponds to a quadrupolar ordering of
molecular orbitals on Nb$_4$ clusters. A second transition occurs at T$_M$ = 29
K, where local distortions on the Nb$_4$ clusters rearrange. We present a
single crystal x-ray diffraction investigation these phase transitions and
solve the crystal structure in the intermediate T$_M$ < T < T$_Q$ and low T <
T$_M$ temperature phases. The intermediate phase is a primitive cubic P2$_1$3
structure with a staggered arrangement of Nb4 cluster distortions. A symmetry
mode analysis reveals that the transition at TQ is continuous and described by
a single Jahn-Teller active amplitude mode. In the low temperature phase, the
symmetry of Nb$_4$ clusters is further reduced and the unit cell doubles into
an orthorhombic P2$_1$2$_1$2$_1$ space group. Nb$_4$ clusters rearrange through
this transition to form a staggered arrangement of intercluster dimers,
suggesting a valence bond solid magnetic state.",2401.04671v1
2024-04-02,"Black Hole-Disk Interactions in Magnetically Arrested Active Galactic Nuclei: General Relativistic Magnetohydrodynamic Simulations Using A Time-Dependent, Binary Metric","Perturber objects interacting with supermassive black hole accretion disks
are often invoked to explain observed quasi-periodic behavior in active
galactic nuclei (AGN). We present global, 3D general relativistic
magnetohydrodynamic (GRMHD) simulations of black holes on inclined orbits
colliding with magnetically arrested thick AGN disks using a binary black hole
spacetime with mass ratio $0.1$. We do this by implementing an approximate
time-dependent binary black hole metric into the GRMHD code Athena++. The
secondary enhances the unbound mass outflow rate 2-4 times above that provided
by the disk in quasi-periodic outbursts, eventually merging into a more
continuous outflow at larger distances. We present a simple analytic model that
qualitatively agrees well with this result and can be used to extrapolate to
unexplored regions of parameter space. We show self-consistently for the first
time that spin-orbit coupling between the primary black hole spin and the
binary orbital angular momentum causes the accretion disk and jet directions to
precess significantly (by 60$^\circ$-80$^\circ$) on long time-scales (e.g.,
$\sim$ 20 times the binary orbital period). Because this effect may be the only
way for thick AGN disks to consistently precess, it could provide strong
evidence of a secondary black hole companion if observed in such a system.
Besides this new phenomenology, the time-average properties of the disk and
accretion rates onto the primary are only marginally altered by the presence of
the secondary, consistent with our estimate for a perturbed thick disk. This
situation might drastically change in cooled thin disks.",2404.02193v1
2005-11-29,Transformation of spin information into large electrical signals via carbon nanotubes,"Spin electronics (spintronics) exploits the magnetic nature of the electron,
and is commercially exploited in the spin valves of disc-drive read heads.
There is currently widespread interest in using industrially relevant
semiconductors in new types of spintronic devices based on the manipulation of
spins injected into a semiconducting channel between a spin-polarized source
and drain. However, the transformation of spin information into large
electrical signals is limited by spin relaxation such that the magnetoresistive
signals are below 1%. We overcome this long standing problem in spintronics by
demonstrating large magnetoresistance effects of 61% at 5 K in devices where
the non-magnetic channel is a multiwall carbon nanotube that spans a 1.5 micron
gap between epitaxial electrodes of the highly spin polarized manganite
La0.7Sr0.3MnO3. This improvement arises because the spin lifetime in nanotubes
is long due the small spin-orbit coupling of carbon, because the high nanotube
Fermi velocity permits the carrier dwell time to not significantly exceed this
spin lifetime, because the manganite remains highly spin polarized up to the
manganite-nanotube interface, and because the interfacial barrier is of an
appropriate height. We support these latter statements regarding the interface
using density functional theory calculations. The success of our experiments
with such chemically and geometrically different materials should inspire
adventure in materials selection for some future spintronics",0511697v2
2011-08-01,Electron spin relaxation in graphene with random Rashba field: Comparison of D'yakonov-Perel' and Elliott-Yafet--like mechanisms,"Aiming to understand the main spin relaxation mechanism in graphene, we
investigate the spin relaxation with random Rashba field induced by both
adatoms and substrate, by means of the kinetic spin Bloch equation approach.
The charged adatoms on one hand enhance the Rashba spin-orbit coupling locally
and on the other hand serve as Coulomb potential scatterers. Both effects
contribute to spin relaxation limited by the D'yakonov-Perel' mechanism. In
addition, the random Rashba field also causes spin relaxation by spin-flip
scattering, manifesting itself as an Elliott-Yafet--like mechanism. Both
mechanisms are sensitive to the correlation length of the random Rashba field,
which may be affected by the environmental parameters such as electron density
and temperature. By fitting and comparing the experiments from the Groningen
group [J\'ozsa {\it et al.}, Phys. Rev. B {\bf 80}, 241403(R) (2009)] and
Riverside group [Pi {\it et al.}, Phys. Rev. Lett. {\bf 104}, 187201 (2010);
Han and Kawakami, {\it ibid.} {\bf 107}, 047207 (2011)] which show either
D'yakonov-Perel'-- (with the spin relaxation rate being inversely proportional
to the momentum scattering rate) or Elliott-Yafet--like (with the spin
relaxation rate being proportional to the momentum scattering rate) properties,
we suggest that the D'yakonov-Perel' mechanism dominates the spin relaxation in
graphene. The latest experimental finding of a nonmonotonic dependence of spin
relaxation time on diffusion coefficient by Jo {\it et al.} [Phys. Rev. B {\bf
84}, 075453 (2011)] is also well reproduced by our model.",1108.0283v3
2013-02-20,Photoelectron spin-flipping and texture manipulation in a topological insulator,"Recently discovered materials called three-dimensional topological insulators
constitute examples of symmetry protected topological states in the absence of
applied magnetic fields and cryogenic temperatures. A hallmark characteristic
of these non-magnetic bulk insulators is the protected metallic electronic
states confined to the material's surfaces. Electrons in these surface states
are spin polarized with their spins governed by their direction of travel
(linear momentum), resulting in a helical spin texture in momentum space. Spin-
and angle-resolved photoemission spectroscopy (spin-ARPES) has been the only
tool capable of directly observing this central feature with simultaneous
energy, momentum, and spin sensitivity. By using an innovative photoelectron
spectrometer with a high-flux laser-based light source, we discovered another
surprising property of these surface electrons which behave like Dirac
fermions. We found that the spin polarization of the resulting photoelectrons
can be fully manipulated in all three dimensions through selection of the light
polarization. These surprising effects are due to the spin-dependent
interaction of the helical Dirac fermions with light, which originates from the
strong spin-orbit coupling in the material. Our results illustrate unusual
scenarios in which the spin polarization of photoelectrons is completely
different from the spin state of electrons in the originating initial states.
The results also provide the basis for a novel source of highly spin-polarized
electrons with tunable polarization in three dimensions.",1302.5094v1
2016-07-12,Quantum Spin Liquid States,"This article is an introductory review of the physics of quantum spin liquid
(QSL) states. Quantum magnetism is a rapidly evolving field, and recent
developments reveal that the ground states and low-energy physics of frustrated
spin systems may develop many exotic behaviors once we leave the regime of
semi-classical approaches. The purpose of this article is to introduce these
developments. The article begins by explaining how semi-classical approaches
fail once quantum mechanics become important and then describes the alternative
approaches for addressing the problem. We discuss mainly spin $1/2$ systems,
and we spend most of our time in this article on one particular set of
plausible spin liquid states in which spins are represented by fermions. These
states are spin-singlet states and may be viewed as an extension of Fermi
liquid states to Mott insulators, and they are usually classified in the
category of so-called $SU(2)$, $U(1)$ or $Z_2$ spin liquid states. We review
the basic theory regarding these states and the extensions of these states to
include the effect of spin-orbit coupling and to higher spin ($S>1/2$) systems.
Two other important approaches with strong influences on the understanding of
spin liquid states are also introduced: (i) matrix product states and projected
entangled pair states and (ii) the Kitaev honeycomb model. Experimental
progress concerning spin liquid states in realistic materials, including
anisotropic triangular lattice systems ($\kappa$-(ET)$_{2}$Cu$_{2}$(CN)$_{3}$
and EtMe$_{3}$Sb[(Pd(dmit)$_{2}$]$_{2}$), kagome lattice systems
(ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$) and hyperkagome lattice systems
(Na$_{4}$Ir$_{3}$O$_{8}$), is reviewed and compared against the corresponding
theories.",1607.03228v3
2021-08-14,"Relativistic Mechanics Theory for Electrons that Exhibits Spin, Zitterbewegung, Superposition and Produces Dirac's Wave Equation","A neo-classical relativistic mechanics theory is presented where the spin of
an electron is a natural part of its space-time path as a point particle. The
fourth-order equation of motion corresponds to the same Lagrangian function in
proper time as in special relativity except for an additional spin energy term.
The total motion can be decomposed into a sum of a local spin motion about a
point and a global motion of this point, called the spin center. The global
motion is sub-luminal and obeys Newton's second law in proper time, the time
for a clock fixed at the spin center, while the total motion occurs at the
speed of light c, consistent with the eigenvalues of Dirac's velocity operators
having magnitude c. The local spin motion corresponds to Schr\""odinger's
zitterbewegung and is a perpetual motion, which for a free electron has a
circular path in the spin-center frame. In an electro-magnetic field, this spin
motion generates magnetic and electric dipole energies through the Lorentz
force on the electron's point charge. The corresponding electric dipole energy
is consistent with the spin-orbit coupling term in the corrected Pauli
non-relativistic Hamiltonian but the magnetic dipole energy is one half of that
in Dirac's theory. By defining a spin tensor as the angular momentum of the
electron's total motion about its spin center, the fundamental equations of
motion can be re-written in an identical form to those of the Barut-Zanghi
electron theory. These equations of motion can then be expressed using
operators applied to a state function of proper time satisfying a
Dirac-Schr\""odinger spinor equation. The operators produce dynamic variables
without any probability implications. For the free electron, the state function
satisfies Dirac's relativistic wave equation when the Lorentz transformation is
applied to express proper time in terms of an observer's space-time
coordinates.",2108.07267v3
2022-10-15,Parallel spin-momentum locking in a chiral topological semimetal,"Spin-momentum locking in solids describes a directional relationship between
the electron's spin angular momentum and its linear momentum over the entire
Fermi surface. While orthogonal spin-momentum locking, such as Rashba
spin-orbit coupling, has been studied for decades and inspired a vast number of
applications, its natural counterpart, the purely parallel spin-momentum
locking, has remained elusive in experiments. Recently, chiral topological
semimetals that host single- and multifold band crossings have been predicted
to realize such parallel locking. Here, we use spin- and angle-resolved
photoelectron spectroscopy to probe spin-momentum locking of a multifold
fermion in the chiral topological semimetal PtGa via the spin-texture of its
topological Fermi-arc surface states. We find that the electron spin of the
Fermi-arcs points orthogonal to their Fermi surface contour for momenta close
to the projection of the bulk multifold fermion, which is consistent with
parallel spin-momentum locking of the latter. We anticipate that our discovery
of parallel spin-momentum locking of multifold fermions will lead to the
integration of chiral topological semimetals in novel spintronic devices, and
the search for spin-dependent superconducting and magnetic instabilities in
these materials.",2210.08221v1
2024-04-05,Direct Electrical Detection of Spin Chemical Potential Due to Spin Hall Effect in $β$-Tungsten and Platinum Using a Pair of Ferromagnetic and Normal Metal Voltage probes,"The phenomenon of Spin Hall Effect (SHE) generates a pure spin current
transverse to an applied current in materials with strong spin-orbit coupling,
although not detectable through conventional electrical measurement. An
intuitive Hall effect like measurement configuration is implemented to directly
measure pure spin chemical potential of the accumulated spins at the edges of
heavy metal (HM) channels that generates large SHE. A pair of transverse
linearly aligned voltage probes in placed in ohmic contact with the top surface
of HM , one being a ferromagnetic metal (FM) with non-zero spin polarization
and other is the reference metal (RM) with zero polarization of carriers. This
combination of FM/RM electrodes is shown to induce an additional voltage
proportional to a spin accumulation potential, which is anti symmetric with
respect to opposite orientations of FM controlled by a 2D vector magnet. Proof
of concept of the measurement scheme is verified by comparing the signs of
voltages for HM channels of Tungsten (W) and Platinum (Pt) which are known to
generate opposite spin accumulation under similar conditions of applied
current. The same devices are also able to detect the reciprocal effect,
inverse spin Hall effect (ISHE) by swapping the current and voltage leads and
the results are consistent with reciprocity principle. Further, exploiting a
characteristic feature of W thin film deposition, a series of devices were
fabricated with W resistivity varying over a wide range of 10 - 750 $\mu
\Omega$-cm and the calculated spin Hall resistivity exhibits a pronounced power
law dependence on resistivity. Our measurement scheme combined with almost two
decades of HM resistivity variation provides the ideal platform required to
test the underlying microscopic mechanism responsible for SHE/ISHE.",2404.03934v1
2021-01-13,Spin-Induced Orbital Frustration in a Hexagonal Optical Lattice,"Complex lattices provide a versatile ground for fascinating quantum many-body
physics. Here, we propose an exotic mechanics for generating orbital
frustration in hexagonal lattices. We study two-component (pseudospin-$1/2$)
Bose gases in $p$-orbital bands of two-dimensional hexagonal lattices, and find
that the system exhibits previously untouched orbital frustration as a result
of the interplay of spin and orbital degrees of freedom, in contrast to normal
Ising-type orbital ordering of spinless $p$-orbital band bosons in
two-dimensional hexagonal lattices. Based on the classification by symmetry
analysis, we find the interplay of orbital frustration and strong interaction
leads to exotic Mott and superfluid phases with spin-orbital intertwined
orders, in spite of the complete absence of spin-orbital interaction in the
Hamiltonian. Our study implies many-body correlations in a multi-orbital
setting could induce rich spin-orbital intertwined physics in complex lattice
structures.",2101.05367v2
2000-11-02,"First principles study of the origin and nature of ferromagnetism in (Ga,Mn)As","The properties of diluted Ga$_{1-x}$Mn$_x$As are calculated for a wide range
of Mn concentrations within the local spin density approximation of density
functional theory. M\""ulliken population analyses and orbital-resolved
densities of states show that the configuration of Mn in GaAs is compatible
with either 3d$^5$ or 3d$^6$, however the occupation is not integer due to the
large $p$-$d$ hybridization between the Mn $d$ states and the valence band of
GaAs. The spin splitting of the conduction band of GaAs has a mean field-like
linear variation with the Mn concentration and indicates ferromagnetic coupling
with the Mn ions. In contrast the valence band is antiferromagnetically coupled
with the Mn impurities and the spin splitting is not linearly dependent on the
Mn concentration. This suggests that the mean field approximation breaks down
in the case of Mn-doped GaAs and corrections due to multiple scattering must be
considered. We calculate these corrections within a simple free electron model
and find good agreement with our {\it ab initio} results if a large exchange
constant ($N\beta=-4.5$eV) is assumed.",0011050v1
2002-04-11,Role of spin-orbit coupling in the far infrared absorption of lateral semiconductor dots,"We investigate the relevance of the spin-orit coupling to the far-infrared
absorption of two-dimensional semiconductor dots. Varying the strength of the
Dresselhaus term, a mechanism feasible in experiment by changing the dot width,
distinctive splittings of the Kohn peak as well as additional low energy modes
are predicted in a non-interacting model. Each mode has a spatial distribution
of charge, perpendicular and in-plane spin densities that correlate in a
peculiar way with the frequency and polarization of the external field. We
study the robustness of these features against electron-electron interactions
as well as the appearance of interaction-induced additional characteristics.",0204256v1
2002-12-03,Effective Hamiltonian for Ga_{1-x}Mn_xAs in the Dilute Limit,"We derive an effective Hamiltonian for ${\rm Ga}_{1-x}{\rm Mn}_x {\rm As}$ in
the dilute limit, where ${\rm Ga}_{1-x}{\rm Mn}_x {\rm As}$ can be described in
terms of spin $F=3/2$ polarons hopping between the {\rm Mn} sites and coupled
to the local {\rm Mn} spins. We determine the parameters of our model from
microscopic calculations. Our approach treats the large Coulomb interaction in
a non-perturbative way, captures the effects of spin-orbit coupling and
disorder, and is appropriate for other p-doped magnetic semiconductors. Our
model applies to uncompensated {\rm Mn} concentrations up to $x \sim 0.03$.",0212074v2
2005-02-24,Spin-related magnetoresistance of n-type ZnO:Al and Zn_{1-x}Mn_{x}O:Al thin films,"Effects of spin-orbit coupling and s-d exchange interaction are probed by
magnetoresistance measurements carried out down to 50 mK on ZnO and
Zn_{1-x}Mn_{x}O with x = 3 and 7%. The films were obtained by laser ablation
and doped with Al to electron concentration ~10^{20} cm^{-3}. A quantitative
description of the data for ZnO:Al in terms of weak-localization theory makes
it possible to determine the coupling constant \lambda_{so} = (4.4 +-
0.4)*10^{-11} eVcm of the kp hamiltonian for the wurzite structure, H_{so} =
\lambda_{so}*c(s x k). A complex and large magnetoresistance of
Zn_{1-x}Mn_{x}O:Al is interpreted in terms of the influence of the s-d
spin-splitting and magnetic polaron formation on the disorder-modified
electron-electron interactions. It is suggested that the proposed model
explains the origin of magnetoresistance observed recently in many magnetic
oxide systems.",0502574v1
2005-06-20,Asymmetric exchange between electron spins in coupled semiconductor quantum dots,"We obtain a microscopic description of the interaction between electron spins
in bulk semiconductors and in pairs of semiconductor quantum dots. Treating the
k.p band mixing and the Coulomb interaction on the same footing, we obtain in
the third order an asymmetric contribution to the exchange interaction arising
from the coupling between the spin of one electron and the relative orbital
motion of the other. This contribution does not depend on the inversion
asymmetry of the crystal. We find that it is ~0.001 of the isotropic exchange,
which is of interest in quantum information. Detailed evaluations are given for
several quantum dot systems.",0506510v2
2007-03-26,Magnetodielectric coupling in Mn3O4,"We have investigated the dielectric anomalies associated with spin ordering
transitions in the tetragonal spinel Mn$_3$O$_4$, using thermodynamic,
magnetic, and dielectric measurements. We find that two of the three magnetic
ordering transitions in Mn$_3$O$_4$ lead to decreases in the temperature
dependent dielectric constant at zero applied field. Applying a magnetic field
to the polycrystalline sample leaves these two dielectric anomalies practically
unchanged, but leads to an increase in the dielectric constant at the
intermediate spin-ordering transition. We discuss possible origins for this
magnetodielectric behavior in terms of spin-phonon coupling. Band structure
calculations suggest that in its ferrimagnetic state, Mn$_3$O$_4$ corresponds
to a semiconductor with no orbital degeneracy due to strong Jahn-Teller
distortion.",0703685v1
2009-01-30,Prediction of large linear-in-k spin splitting for holes in the 2D GaAs/AlAs system,"The spin-orbit interaction generally leads to spin splitting (SS) of electron
and hole energy states in solids, a splitting that is characterized by a
scaling with the wavevector $\bf k$. Whereas for {\it 3D bulk zincblende}
solids the electron (heavy hole) SS exhibits a cubic (linear) scaling with $k$,
in {\it 2D quantum-wells} the electron (heavy hole) SS is currently believed to
have a mostly linear (cubic) scaling. Such expectations are based on using a
small 3D envelope function basis set to describe 2D physics. By treating
instead the 2D system explicitly in a multi-band many-body approach we discover
a large linear scaling of hole states in 2D. This scaling emerges from hole
bands coupling that would be unsuspected by the standard model that judges
coupling by energy proximity. This discovery of a linear Dresselhaus k-scaling
for holes in 2D implies a different understanding of hole-physics in
low-dimensions.",0901.4943v2
2009-08-31,Global nuclear structure effects of tensor interaction,"A direct fit of the isoscalar spin-orbit (SO) and both isoscalar and
isovector tensor coupling constants to the f5/2-f7/2 SO splittings in 40Ca,
56Ni, and 48Ca nuclei requires a drastic reduction of the isoscalar SO strength
and strong attractive tensor coupling constants. The aim of this work is to
address further consequences of these strong attractive tensor and weak SO
fields on binding energies, nuclear deformability, and high-spin states. In
particular, we show that contribution to the nuclear binding energy due to the
tensor field shows generic magic structure with tensorial magic numbers at
N(Z)=14, 32, 56, or 90 corresponding to the maximum spin-asymmetries in 1d5/2,
1f7/2-2p3/2, 1g9/2-2d5/2 and 1h11/2-2f7/2 single-particle configurations and
that these numbers are smeared out by pairing correlations and deformation
effects. We also examine the consequences of strong attractive tensor fields
and weak SO interaction on nuclear stability at the drip lines, in particular
close to the tensorial doubly magic nuclei and discuss the possibility of an
entirely new tensor-force driven deformation effect.",0908.4486v2
2009-10-28,Effect of Tensor Correlations on Single-particle and Collective States,"We study the effect of tensor correlations on single-particle and collective
states within Skyrme Hartree-Fock and RPA model. Firstly, We study the role of
tensor interactions in Skyrme effective interaction on the spin-orbit
splittings of N=82 isotones and Z=50 isotope.
  The isospin dependence of the shell structure is well described as the
results of the tensor interactions without destroying good properties of the
binding energy and the rms charge radii of the heavy nuclei. Secondly, We
performed self-consistent HF+RPA calculations for charge exchange 1$^+$ states
in $^{90}$Zr and $^{208}$Pb to elucidate the role of tensor interactions on
spin dependent excitations. It is pointed out that Gamow-Teller(GT) states can
couple strongly with the spin-quadrupole (SQ) 1$^+$ states in the high energy
region above E$_x$=30 MeV due to the tensor interactions. As the result of this
coupling, more than 10% of the GT strength is shifted to the energy region
above 30 MeV, and the main GT peak is moved 2 MeV downward.",0910.5277v1
2010-02-04,Magnetic excitations in ferro-pnictide materials controlled by a quantum critical point into hidden order,"The two-orbital J1-J2 model that describes a square lattice of frustrated
spin-1 iron atoms is analyzed within the linear spin-wave approximation and by
exact diagonalization over a 4x4 cluster. A quantum critical point (QCP) is
identified that separates hidden magnetic order at weak Hund's rule coupling
from a commensurate spins density wave (cSDW) at strong Hund's rule coupling.
Although the moment for cSDW order is small at the QCP, the critical linear
spin-wave spectrum shows strong low-energy excitations centered at the
wavenumbers that correspond to cSDW order. These disperse anisotropically. A
fit to the magnetic excitation spectrum of ferro-pnictide materials obtained
recently by inelastic neutron scattering measurements notably accounts for the
absence of softening at the wavenumber that corresponds to Neel order.",1002.0891v3
2011-06-30,Superconductivity near Pomeranchuk instabilities in the spin channel,"We study the competition between a Pomeranchuk instability in the spin
channel with angular momentum $\ell=1$ and an attractive interaction, favoring
Cooper-pair formation. We found that the superconducting gap strongly
suppresses the phase space for the Pomeranchuk instability. We computed a
mean-field phase diagram displaying a first order transition between two
superconductor phases with different symmetries: p-wave (with spontaneously
generated spin-orbit interaction) and s-wave for greater values of the coupling
constant. Moreover, we have looked for a possible modulated superconducting
phase. We have found that this phase appears only as a meta-stable state in the
strong coupling regime.",1106.6311v3
2011-08-18,Gravitomagnetism and spinor quantum mechanics,"We give a systematic treatment of a spin 1/2 particle in a combined
electromagnetic field and a weak gravitational field that is produced by a
slowly moving matter source. This paper continues previous work on a spin zero
particle, but it is largely self-contained and may serve as an introduction to
spinors in a Riemann space. The analysis is based on the Dirac equation
expressed in generally covariant form and coupled minimally to the
electromagnetic field. The restriction to a slowly moving matter source, such
as the earth, allows us to describe the gravitational field by a
gravitoelectric (Newtonian) potential and a gravitomagnetic (frame-dragging)
vector potential, the existence of which has recently been experimentally
verified. Our main interest is the coupling of the orbital and spin angular
momenta of the particle to the gravitomagnetic field. Specifically we calculate
the gravitational gyromagnetic ratio as gsubg=1 ; this is to be compared with
the electromagnetic gyromagnetic ratio of gsube=2 for a Dirac electron.",1108.3859v1
2012-09-05,Optical measurement and modeling of interactions between two hole or two electron spins in coupled InAs quantum dots,"Two electron spins in quantum dots coupled through coherent tunneling are
generally acknowledged to approximately obey Heisenberg isotropic exchange.
This has not been established for two holes. Here we measure the spectra of two
holes and of two electrons in two vertically stacked self-assembled InAs
quantum dots using optical spectroscopy as a function of electric and magnetic
fields. We find that the exchange is approximately isotropic for both systems,
but that significant asymmetric contributions, arising from spin-orbit and
Zeeman interactions combined with spatial asymmetries, are required to explain
large anticrossings and fine-structure energy splittings in the spectra.
Asymmetric contributions to the isotropic Hamiltonian for electrons are of the
order of a few percent while those for holes are an order of magnitude larger.",1209.0920v2
2012-10-17,Odd parity bottom-flavored baryon resonances,"The LHCb Collaboration has recently observed two narrow baryon resonances
with beauty. Their masses and decay modes look consistent with the quark model
orbitally excited states Lambda_b(5912) and Lambda*_b(5920), with quantum
numbers J^P=1/2^- and 3/2^-, respectively. We predict the existence of these
states within a unitarized meson-baryon coupled-channel dynamical model, which
implements heavy-quark spin symmetry. Masses, quantum numbers and couplings of
these resonances to the different meson-baryon channels are obtained. We find
that the resonances Lambda^0_b(5912) and Lambda^0_b(5920) are heavy-quark spin
symmetry partners, which naturally explains their approximate mass degeneracy.
Corresponding bottom-strange baryon resonances are predicted at Xi_b(6035.4)
(J^P=1/2^-) and Xi_b(6043.3) (J^P=3/2^-). The two Lambda_b and two Xi_b
resonances complete a multiplet of SU(3)-flavor times heavy-quark spin
symmetry.",1210.4755v3
2012-11-08,Giant atomic displacement induced by built-in strain in metastable Mn$_3$O$_4$,"We present x-ray, neutron scattering and heat capacity data that reveal a
coupled first-order magnetic and structural phase transition of the metastable
mixed-valence post-spinel compound Mn$_3$O$_4$ at 210 K. Powder neutron
diffraction measurements reveal a magnetic structure in which Mn$^{3+}$ spins
align antiferromagnetically along the edge-sharing \emph{a}-axis, with a
magnetic propagation vector k = [1/2, 0, 0]. In contrast, the Mn$^{2+}$ spins,
which are geometrically frustrated, do not order until a much lower
temperature. Although the Mn$^{2+}$ spins do not directly participate in the
magnetic phase transition at 210 K, structural refinements reveal a large
atomic shift at this phase transition, corresponding to a physical motion of
approximately 0.25 {\AA} even though the crystal symmetry remains unchanged.
This ""giant"" response is due to the coupled effect of built-in strain in the
metastable post-spinel structure with the orbital realignment of the Mn$^{3+}$
ion.",1211.1667v1
2012-12-06,Indirect exchange interaction between magnetic adatoms in a monolayer MoS2,"We study the Ruderman-Kittle-Kasuya-Yosida (RKKY) interaction in a monolayer
MoS$_2$. We show that the rotation of the itinerant electron spin due to the
spin-orbit coupling causes a twisted interaction between two magnetic adatoms
which consists of different RKKY coupling terms, the Heisenberg,
Dzyaloshinsky-Moriya and Ising interactions. We find that the interaction terms
are very sensitive to the Fermi energy values and change dramatically from
doped to undoped systems. A finite doping causes that all parts of the
interaction oscillate with the distance of two magnetic impurities, $R$ and the
interaction behaves like $R^{-2}$ for the long distance between two localized
spins. We explore a beating pattern of oscillations of the RKKY interaction
which occurs for the doped system.",1212.1318v2
2013-05-06,Spin fluctuations and pairing symmetry in A$_{x}$Fe$_{2-y}$Se$_{2}$: dual effect of the itinerant and the localized nature of electrons,"We investigate the spin fluctuations and the pairing symmetry in
A$_{x}$Fe$_{2-y}$Se$_{2}$ by the fluctuation exchange approximation. Besides
the on-site interactions, the next-nearest-neighbor antiferromagnetic coupling
$J_{2}$ is also included. We find that both the itinerant and the localized
natures of electrons are important to describe the recent experimental results
of the spin fluctuations and the pairing symmetry. In particular, a small
$J_{2}$ coupling can change the pairing gap from the d-wave symmetry to the
s-wave symmetry. We have also studied the real-space structures of the gap
functions for different orbits in order to gain more insight on the nature of
the pairing mechanism.",1305.1090v1
2013-07-12,The electron-phonon interaction from fundamental local gauge symmetries in solids,"The elastic properties of solids are described in close analogy with General
Relativity, by locally gauging the translational group of space-time. Electron
interactions with the crystal lattice are thus generated by enforcing full
gauge invariance, with the introduction of a gauge field. Elementary
excitations are associated with the local gauge, contrasting to the usual
interpretation as being Goldstone bosons emerging from global symmetry
breaking. In the linear limit of the theory, the gauge field displays elastic
waves, that we identify with acoustic phonons, when the field is quantized.
Coupling with the electronic part of the system yields the standard
electron-phonon interaction. If spin-orbit effects are included, unusual
couplings emerge between the strain field and the electronic spin current,
leading to novel physics that may be relevant for spintronic applications.",1307.3571v1
2014-09-29,Zero-field and time-reserval-symmetry-broken topological phase transitions in graphene,"We propose a quantum electronic device based on strained graphene nanoribbon.
Mechanical strain, internal exchange field and spin-orbit couplings (SOCs) have
been exploited as principle parameters to tune physical properties of the
device. We predict a remarkable zero-field topological quantum phase transition
between the time-reversal-symmetry broken quantum spin hall (QSH) and quantum
anomalous hall (QAH) states, which was previously thought to take place only in
the presence of finite magnetic field. We illustrate as intrinsic SOC is tuned,
how two different helicity edge states located in the opposite edges of the
nanoribbon exchange their locations. Our results indicates that pseudomagnetic
field induced by the strain could be coupled to the spin degrees of freedom
through the SOC responsible for the stability of QSH state. The controllability
of this zero-field phase transition with strength and direction of the strain
is also demonstrated. Our prediction offers a tempting prospect of strain,
electric and magnetic manipulation of the QSH effect.",1409.8247v2
2014-10-31,Thermal conductivity across the metal-insulator transition in single crystalline hyperkagome Na$_{3+x}$Ir$_3$O$_8$,"The hyperkagome antiferromagnet Na$_{4}$Ir$_3$O$_8$ represents the first
genuine candidate for the realisation of a three-dimensional quantum
spin-liquid. It can also be doped towards a metallic state, thus offering a
rare opportunity to explore the nature of the metal-insulator transition in
correlated, frustrated magnets. Here we report thermodynamic and transport
measurements in both metallic and weakly insulating single crystals down to 150
mK. While in the metallic sample the phonon thermal conductivity
($\kappa^{ph}$) is almost in the boundary scattering regime, in the insulating
sample we find a large reduction $\kappa^{ph}$ over a very wide temperature
range. This result can be ascribed to the scattering of phonons off nanoscale
disorder or off the gapless magnetic excitations that are seen in the
low-temperature specific heat. This works highlights the peculiarity of the
metal-insulator transition in Na$_{3+x}$Ir$_3$O$_8$ and demonstrates the
importance of the coupling between lattice and spin degrees of freedom in the
presence of strong spin-orbit coupling.",1410.8792v1
2015-02-27,Backscattering in helical edge states from a magnetic impurity and Rashba disorder,"Transport by helical edge states of a quantum spin Hall insulator is
experimentally characterized by a weakly temperature-dependent mean free path
of a few microns and by reproducible conductance oscillations, challenging
proposed theoretical explanations. We consider a model where edge electrons
experience spatially random Rashba spin-orbit coupling and couple to a magnetic
impurity with spin S >= 1/2. In a finite bias steady state, we find for S > 1/2
an impurity induced resistance with a temperature dependence in agreement with
experiments. Since backscattering is elastic, interference between different
scatterers possibly explains conductance fluctuations.",1502.07927v2
2015-06-17,Rarita-Schwinger-Weyl semimetal in Jeff=3/2 electron systems,"We propose a relativistic Jeff=3/2 semimetal with 4d1 or 5d1 electrons on a
cubic lattice when the strong spin-orbital coupling takes over the Hunds'
coupling. A relativistic spinor with spin 3/2 is historically called
Rarita-Schwinger spinor. In the massless case, the right- and left-handed
chiral degrees of freedom of the Rarita-Schwinger spinors are independent. In
the lattice model that we propose, the right- and left- handed gapless points
in Brillouin zone are separated. We call this linearly dispersed semimetal
Rarita-Schwinger-Weyl semimetal, similar to Weyl semimetal for spin 1/2
systems. There is a network of gapless Fermi arcs in the surface Brillouin zone
if n1+n2+n3 is even for the normal vector (n1,n2,n3) of the surface while the
surface is insulator if n1+n2+n3 is odd.",1506.05359v1
2015-06-25,Two Dimensional Ising Superconductivity in Gated MoS$_{2}$,"The Zeeman effect, which is usually considered to be detrimental to
superconductivity, can surprisingly protect the superconducting states created
by gating a layered transition metal dichalcogenide. This effective Zeeman
field, which is originated from intrinsic spin orbit coupling induced by
breaking in-plane inversion symmetry, can reach nearly a hundred Tesla in
magnitude. It strongly pins the spin orientation of the electrons to the
out-of-plane directions and protects the superconductivity from being destroyed
by an in-plane external magnetic field. In magnetotransport experiments of
ionic-gate MoS$_{2}$ transistors, where gating prepares individual
superconducting state with different carrier doping, we indeed observe a spin-
protected superconductivity by measuring an in-plane critical field
$\textit{B}$$_{c2}$ far beyond the Pauli paramagnetic limit. The
gating-enhanced $\textit{B}$$_{c2}$ is more than an order of magnitude larger
compared to the bulk superconducting phases where the effective Zeeman field is
weakened by interlayer coupling. Our study gives the first experimental
evidence of an Ising superconductor, in which spins of the pairing electrons
are strongly pinned by an effective Zeeman field.",1506.07620v2
2015-11-25,"Antiferromagnetism, $f$-wave and chiral $p$-wave superconductivity in a Kagome lattice with possible application to $sd^2$-graphenes","We investigate the electronic instabilities in a Kagome lattice with Rashba
spin-orbital coupling by the unbiased singular-mode functional renormalization
group. At the parent $1/3$-filling, the normal state is a quantum spin Hall
system. Since the bottom of the conduction band is near the van Hove
singularity, the electron-doped system is highly susceptible to competing
orders upon electron interactions. The topological nature of the parent system
enriches the complexity and novelty of such orders. We find $120^o$-type
intra-unitcell antiferromagnetic order, $f$-wave superconductivity and chiral
$p$-wave superconductivity with increasing electron doping above the van Hove
point. In both types of superconducting phases, there is a mixture of
comparable spin singlet and triplet components because of the Rashba coupling.
The chiral $p$-wave superconducting state is characterized by a Chern number
$Z=1$, supporting a branch of Weyl fermion states on each edge. The model bares
close relevance to the so-called $sd^2$-graphenes proposed recently.",1511.08001v1
2016-02-19,Critical Temperature Enhancement of Topological Superconductors: A Dynamical Mean Field Study,"We show that a critical temperature Tc for spin-singlet two-dimensional
superconductivity is enhanced by a cooperation between the Zeeman magnetic
field and the Rashba spin-orbit coupling, where a superconductivity becomes
topologically non-trivial below Tc. The dynamical mean field theory (DMFT) with
the segment-based hybridization-expansion continuous-time quantum Monte Carlo
impurity solver (ct-HYB) is used for accurately evaluating a critical
temperature, without any Fermion sign problem. A strong-coupling approach shows
that spin-flip driven local pair hopping leads to part of this enhancement,
especially effects of the magnetic field. We propose physical settings suitable
for verifying the present calculations, one-atom-layer system on Si(111) and
ionic-liquid based electric double-layer transistors (EDLTs).",1602.06087v2
2016-09-14,Rashba-Edelstein Magnetoresistance in Metallic Heterostructure,"We report the observation of magnetoresistance originating from Rashba
spin-orbit coupling (SOC) in a metallic heterostructure: the Rashba-Edelstein
(RE) magnetoresistance. We show that the simultaneous action of the direct and
inverse RE effects in a Bi/Ag/CoFeB trilayer couples current-induced spin
accumulation to the electric resistance. The electric resistance changes with
the magnetic-field angle, reminiscent of the spin Hall magnetoresistance,
despite the fact that bulk SOC is not responsible for the magnetoresistance. We
further found that, even when the magnetization is saturated, the resistance
increases with increasing the magnetic-field strength, which is attributed to
the Hanle magnetoresistance in this system.",1609.04122v1
2017-03-08,Observation of topological Bloch-state defects and their merging transition,"Topological defects in Bloch bands, such as Dirac points in graphene, and
their resulting Berry phases play an important role for the electronic dynamics
in solid state crystals. Such defects can arise in systems with a two-atomic
basis due to the momentum-dependent coupling of the two sublattice states,
which gives rise to a pseudo-spin texture. The topological defects appear as
vortices in the azimuthal phase of this pseudo-spin texture. Here, we
demonstrate a complete measurement of the azimuthal phase in a hexagonal
optical lattice employing a versatile method based on time-of-flight imaging
after off-resonant lattice modulation. Furthermore we map out the merging
transition of the two Dirac points induced by beam imbalance. Our work paves
the way to accessing geometric properties in optical lattices also with
spin-orbit coupling and interactions.",1703.02813v2
2017-08-12,Localized magnetic moments with tunable spin exchange in a gas of ultracold fermions,"We report on the experimental realization of a state-dependent lattice for a
two-orbital fermionic quantum gas with strong interorbital spin exchange. In
our state-dependent lattice, the ground and metastable excited electronic
states of $^{173}$Yb take the roles of itinerant and localized magnetic
moments, respectively. Repulsive on-site interactions in conjunction with the
tunnel mobility lead to spin exchange between mobile and localized particles,
modeling the coupling term in the well-known Kondo Hamiltonian. In addition, we
find that this exchange process can be tuned resonantly by varying the on-site
confinement. We attribute this to a resonant coupling to center-of-mass excited
bound states of one interorbital scattering channel.",1708.03810v2
2014-03-23,Non-collinear Andreev reflections in semiconductor nanowires,"We show that noncollinear Andreev reflections can be induced at interfaces of
semiconductor nanowires with spin-orbit coupling, Zeeman splitting and
proximity-induced superconductivity. In a noncollinear local Andreev
reflection, the spin polarizations of the injected and the retro-reflected
carriers are typically at an angle which is tunable via system parameters.
While in a nonlocal transport, this noncollinearity enables us to identify and
block, at different voltage configurations, the noncollinear cross Andreev
reflection and the direct charge transfer processes. We demonstrate that the
intriguing noncollinearity originates from the spin-dependent coupling between
carriers in the lead and the lowest discrete states in the wire, which, for a
topological superconducting nanowire, are related to the overlap-induced
hybridization of Majorana edge states in a finite system. These interesting
phenomena can be observed in semiconductor nanowires of experimentally relevant
lengths, and are potentially useful for spintronics.",1403.5756v3
2008-07-18,Optical properties of ZnCr2Se4 - Spin-phonon coupling and electronic d-d-like excitations,"We studied the optical properties of antiferromagnetic ZnCr2Se4 by infrared
spectroscopy up to 28,000 cm-1 and for temperatures from 5 to 295 K. At the
magnetic phase transition at 21 K, one of the four phonon modes reveals a clear
splitting of 3 cm-1 as a result of spin-phonon coupling, the other three
optical eigenmodes only show shifts of the eigenfrequencies. The
antiferromagnetic ordering and the concomitant splitting of the phonon mode can
be suppressed in a magnetic field of 7 T. At higher energies we observed a
broad excitation band which is dominated by a two-peak-structure at about
18,000 cm-1 and 22,000 cm-1, respectively. These energies are in good agreement
with the expected spin-allowed crystal-field transition of the Cr3+ ions. The
unexpected strength of these forbidden onsite d-d transitions is attributed to
a considerable hybridization of the selenium p with the chromium d orbitals.",0807.2935v2
2009-12-08,Proposal for manipulating and detecting spin and orbital states of trapped electrons on helium using cavity quantum electrodynamics,"We propose to couple an on-chip high finesse superconducting cavity to the
lateral-motion and spin state of a single electron trapped on the surface of
superfluid helium. We estimate the motional coherence times to exceed 15
microseconds, while energy will be coherently exchanged with the cavity photons
in less than 10 nanoseconds for charge states and faster than 1 microsecond for
spin states, making the system attractive for quantum information processing
and cavity quantum electrodynamics experiments. Strong interaction with cavity
photons will provide the means for both nondestructive readout and coupling of
distant electrons.",0912.1406v3
2014-06-23,Kane-Mele-Hubbard model on the $π$-flux honeycomb lattice,"We consider the Kane-Mele-Hubbard model with a magnetic $\pi$ flux threading
each honeycomb plaquette. The resulting model has remarkably rich physical
properties. In each spin sector, the noninteracting band structure is
characterized by a total Chern number $C=\pm 2$. Fine-tuning of the intrinsic
spin-orbit coupling $\lambda$ leads to a quadratic band crossing point
associated with a topological phase transition. At this point, quantum Monte
Carlo simulations reveal a magnetically ordered phase which extends to weak
coupling. Although the spinful model has two Kramers doublets at each edge and
is explicitly shown to be a $Z_{2}$ trivial insulator, the helical edge states
are protected at the single-particle level by translation symmetry. Drawing on
the bosonized low-energy Hamiltonian, we predict a correlation-induced gap as a
result of umklapp scattering for half-filled bands. For strong interactions,
this prediction is confirmed by quantum Monte Carlo simulations.",1406.6077v2
2017-06-04,Directing nanoscale optical flows by coupling photon spin to plasmon extrinsic angular momentum,"As any physical object, light undergoing a circular trajectory features a
constant extrinsic angular momentum. Within strong curvatures, this angular
momentum can match the spin momentum of a photon, thus providing the
opportunity of a strong spin-orbit interaction. Using this effect, we
demonstrate tunable symmetry breaking in the coupling of light in a curved
nanoscale plasmonic waveguide. The helicity of the impinging optical wave
controls the power distribution between the two counter-propagating guided
modes, including unidirectional waveguiding. We found that up to 95 % of the
incoupled light can be directed into one of the two propagation directions of
the waveguide. This approach offers appealing new prospects for the development
of advanced, deeply subwavelength optical functionalities.",1706.01125v2
2017-10-31,Generation and control of noncollinear magnetism by supercurrent,"When superconductivity couples with noncollinear spin textures, rich physics
arises; for instance, singlet Cooper pairs can be converted to triplet pairs,
and topological superconductors can be realized. For their applications, the
controllability of noncollinear magnetism is a crucial issue. Here, we propose
that a supercurrent can induce and control noncollinear magnetic orders in a
correlated metal on top of a singlet superconductor. We show that the magnetic
instability in the correlated metal is enhanced by the proximity effect of
supercurrents, which leads to phase transitions from a paramagnetic state to
noncollinear magnetic phases with helical or vortexlike spin textures.
Furthermore, these magnetic orders can be switched by the direction of the
supercurrent. We also discuss the effect of the Rashba spin-orbit coupling and
the experimental realization.",1710.11349v2
2017-12-15,Molecular Tuning of the Magnetic Response in Organic Semiconductors,"The tunability of high-mobility organic semi-conductors (OSCs) holds great
promise for molecular spintronics. In this study, we show this extreme
variability - and therefore potential tunability - of the molecular
gyromagnetic coupling (""g-"") tensor with respect to the geometric and
electronic structure in a much studied class of OSCs. Composed of a structural
theme of phenyl- and chalcogenophene (group XVI element containing,
five-membered) rings and alkyl functional groups, this class forms the basis of
several intensely studied high-mobility polymers and molecular OSCs. We show
how in this class the g-tensor shifts, $\Delta g$, are determined by the
effective molecular spin-orbit coupling (SOC), defined by the overlap of the
atomic spin-density and the heavy atoms in the polymers. We explain the
dramatic variations in SOC with molecular geometry, chemical composition,
functionalization, and charge life-time using a first-principles theoretical
model based on atomic spin populations. Our approach gives a guide to tuning
the magnetic response of these OSCs by chemical synthesis.",1712.05620v1
2017-12-21,Spin-triplet paired phases inside ferromagnet induced by Hund's rule coupling and electronic correlations: Application to $\mathrm{UGe}_2$,"We discuss a mechanism of real-space spin-triplet pairing, alternative to
that due to quantum paramagnon excitations, and demonstrate its applicability
to $\mathrm{UGe_2}$. Both the Hund's rule ferromagnetic exchange and
inter-electronic correlations contribute to the same extent to the equal-spin
pairing, particularly in the regime in which the weak-coupling solution does
not provide any. The theoretical results, obtained within the
orbitally-degenerate Anderson lattice model, match excellently the observed
phase diagram for $\mathrm{UGe_2}$ with the coexistent ferromagnetic (FM1) and
superconducting ($A_1$-type) phase. Additionally, weak $A_2$- and $A$-type
paired phases appear in very narrow regions near the metamaganetic (FM2
$\rightarrow$ FM1) and FM1 $\rightarrow$ paramagnetic first-order
phase-transition borders, respectively. The values of magnetic moments in the
FM2 and FM1 states are also reproduced correctly in a semiquantitative manner.
The Hund's metal regime is also singled out as appearing near FM1-FM2 boundary.",1712.08028v2
2019-09-16,Quantum anomalous Hall effect in two dimensional Janus Mn2Cl3Br3 with large magnetic anisotropy energy,"The quantum anomalous Hall (QAH) effect have been experimentally observed in
magnetically-doped topological insulators. However, the QAH effect only at
extremely low temperatures due to the weak magnetic coupling, small band gap
and low carrier mobility. Here, based on first-principles density functional
theory, we predict that the Janus Mn2Cl3Br3 is high Curie temperature
ferromagnet that host the QAH phase. Furthermore, we find that it is a Dirac
half-metal characterized by a Dirac cone in one spin channel with carrier
mobilities comparable to freestanding germanene and an large band gap in other
spin channel. Simultaneously, when the spin-orbital coupling interaction is
considered, the Janus Mn2Cl3Br3 exhibit lager magnetic anisotropic energy of
11.89 meV/cell and a nontrivial band gap. More interestingly, both the Chern
number sign and the chiral edge current are tuned by changing the direction of
magnetization. Our finding would suggest the possibility of not only realized
the QAH effect but also designed the flow direction of the edge current.",1909.07812v2
2018-06-25,Stripe order and magnetic anisotropy in the $S=1$ antiferromagnet BaMoP$_2$O$_8$,"Magnetic behavior of BaMoP$_2$O$_8$ with the spatially anisotropic triangular
arrangement of the $S=1$ Mo$^{4+}$ ions is explored using thermodynamic
measurements, neutron diffraction, and density-functional band-structure
calculations. A broad maximum in the magnetic susceptibility around 46\,K is
followed by the stripe antiferromagnetic order with the propagation vector
${\mathbf k}=(\frac{1}{2},\frac{1}{2},\frac{1}{2})$ formed below $T_N\simeq 21$
K. This stripe phase is triggered by a pronounced one-dimensionality of the
spin lattice, where one of the in-plane couplings, $J_2\simeq 4.6$ meV, is much
stronger than its $J_1\simeq 0.4$ meV counterpart, and stabilized by the weak
easy-axis anisotropy. The ordered moment of 1.42(9) $\mu_B$ at 1.5 K is
significantly lower than the spin-only moment of 2 $\mu_B$ due to a combined
effect of quantum fluctuations and spin-orbit coupling.",1806.09314v2
2018-12-28,Enhanced fermion pairing and superfluidity by an imaginary magnetic field,"We show that an imaginary magnetic field(IMF), which can be generated in
non-Hermitian systems with spin-dependent dissipations, can greatly enhance the
s-wave pairing and superfluidity of spin-1/2 fermions, in distinct contrast to
the effect of a real magnetic field. The enhancement can be attributed to the
increased coupling constant in low-energy space and the reduced spin gap in
forming singlet pairs. We have demonstrated this effect in a number of
different fermion systems with and without spin-orbit coupling, using both the
two-body exact solution and many-body mean-field theory. Our results suggest an
alternative route towards strong fermion superfluid with high superfluid
transition temperature.",1812.11008v2
2019-01-22,Magnetic stripe soliton and localized stripe wave in spin-1 Bose-Einstein condensates,"The recent experimental realization of spin-orbit coupling for ultracold
atomic gases opens a new avenue for engineering solitons with internal spatial
structures through tuning atomic band dispersions. However, the types of the
resulting stripe solitons in a spin-1/2 Bose-Einstein condensate (BEC) have
been limited to dark-dark or bright-bright with the same density profiles for
different spins. Here we propose that general types of stripe solitons,
including magnetic stripe (e.g., dark-bright) and localized stripe waves
(neither bright nor dark), could be realized in a spin-1 BEC with widely
tunable band dispersions through modulating the coupling between three spin
states and the linear momentum of atoms. \ Surprisingly, a moving magnetic
stripe soliton can possess both negative and positive effective masses at
different velocities, leading to a zero mass soliton at certain velocity. Our
work showcases the great potential of realizing novel types of solitons through
band dispersion engineering, which may provide a new approach for exploring
soliton physics in many physical branches.",1901.07631v2
2016-03-15,Colossal Magnetocapacitance Effect and Multiferroism of Polycrystalline La0.2Pb0.7Fe12O19,"The mutual control of the electric and magnetic properties of a multiferroic
solid is of fundamental and great technological importance. We report here on
the colossal magnetoelectric coupling effect of polycrystalline
La0.2Pb0.7Fe12O19. A large classic ferroelectric hysteresis loop with full
saturation and a strong magnetic hysteresis loop were observed simultaneously
in polycrystalline La0.2Pb0.7Fe12O19 due to the coexistence of an off-centered
FeO6 octahedron in its unit cell and electron spins in the partially filled 3d
orbits of the Fe3+ ions. The coupling voltage and capacity demonstrate giant
oscillations, along with magnetic field; the maximum magnetocapacitance ratio
exceeds 1.9E5 at 80 Hz. The substitution of La ions with Pb ions progressively
stabilized the conical spin structure, which gave rise to the spin-current
induced capacity oscillations upon magnetic field.",1603.04508v1
2016-12-22,Excitonic magnetism in $d^6$ perovskites,"We use the LDA+U method to study the possibility of exciton condensation in
perovskites of transition metals with $d^6$ electronic configuration such as
LaCoO$_3$. For realistic interaction parameters we find several distinct
solutions exhibiting spin-triplet exciton condensate, which gives rise to a
local spin density distribution while the ordered moments are vanishingly
small. Rhombohedral distortion from the ideal cubic structure suppresses the
ordered state, contrary to the spin-orbit coupling which enhances the excitonic
condensation energy. We explain the trends observed in the numerical
simulations with the help of a simplified strong-coupling model. Our results
indicate that LaCoO$_3$ is close to the excitonic instability and suggest ways
to make it order.",1612.07576v2
2020-06-10,Strongly parity-mixed superconductivity in Rashba-Hubbard model,"Heterostructures containing strongly correlated electron systems provide a
platform to clarify interplay of electron correlation and Rashba spin-orbit
coupling in unconventional superconductors. Motivated by recent fabrication of
artificially-engineered heavy fermion superlattices and high-temperature
cuprate superconductors, we conduct a thorough study on superconductivity in
Rashba-Hubbard model. In contrast to previous weak coupling approaches, we
employ fluctuation-exchange approximation to describe quantum critical magnetic
fluctuations and resulting superconductivity. As a result, robust Fermi
surfaces against magnetic fluctuations, incommensurate spin fluctuations, and a
strongly parity-mixed superconducting phase are demonstrated in a wide range of
electron filling from type-II van Hove singularity to half-filling. We also
clarify impacts of type-II van Hove singularity on magnetic fluctuations and
superconductivity. Whereas the $d_{x^2-y^2}$-wave pairing always dominant,
subdominant spin-triplet pairing with either $p$-wave or $f$-wave symmetry
shows a comparable magnitude, especially near the type-II van Hove singularity.
Our results resolve unsettled issues on strongly correlated Rashba systems and
uncover candidate systems of nonreciprocal transport and topological
superconductivity.",2006.05952v1
2021-05-26,Symmetry invariants and classes of quasi-particles in magnetically ordered systems having weak spin-orbit coupling,"Symmetry invariants of a group specify the classes of quasiparticles, namely
the classes of projective irreducible \emph{co-representations} (irReps) in
systems having that symmetry. More symmetry invariants exist in discrete point
groups than the full rotation group $\mathrm{O(3)}$, leading to new
quasiparticles restricted to lattices that have not any counterpart in vacuum.
We focus on the fermionic quasiparticle excitations under ``spin-space group''
symmetries, applicable to materials where long-range magnetic structure and
itinerant electrons coexist. We provide a list of 218 classes of new
quasiparticles with symmetry group $P\times Z_2^T$ (with $P$ a crystallographic
point group) that can \emph{only} be realized in the spin-space groups, and
then prove a theorem that each of these new types of quasiparticles has unique
physical properties in terms of the dispersion and the coupling to external
probe fields.",2105.12738v4
2022-08-29,Determining Kitaev interaction in spin-$S$ honeycomb Mott insulators,"The Kitaev interaction in a honeycomb lattice with higher-spin $S$ has been
one of the central attractions, as it may offer quantum spin liquids. A
microscopic theory showed that when the Hund's coupling at the transition metal
generates $S> \frac{1}{2}$, the spin-orbit coupling at the heavy ligands
provides a route to the Kitaev interaction. However, there have been debates
over its strength compared to other symmetry-allowed interactions.
Investigating the symmetry of the Hamiltonian for general $S$, we show the
magnon energies at two momentum points related by a broken mirror symmetry
reflect the Kitaev interaction when a magnetic field is in the mirror plane.
Applying the symmetry analysis to CrI$_3$ with $S=\frac{3}{2}$ together with
the available angle-dependent ferromagnetic resonance data, we estimate the
Kitaev interaction out of the full Hamiltonian and find that it is
sub-dominant. Our theory can be tested by inelastic neutron scattering on
candidate materials under the proposed magnetic field direction, which will
advance the search for general $S$ Kitaev materials.",2208.13807v2
2022-11-03,Magnetism in Two-Dimensional Ilmenenes: Intrinsic Order and Strong Anisotropy,"Iron ilmenene is a new two-dimensional material that has recently been
exfoliated from the naturally-occurring iron titanate found in ilmenite ore, a
material that is abundant on earth surface. In this work, we theoretically
investigate the structural, electronic and magnetic properties of 2D
transition-metal-based ilmenene-like titanates. The study of magnetic order
reveals that these ilmenenes usually present intrinsic antiferromagnetic
coupling between the 3d magnetic metals decorating both sides of the Ti-O
layer. Furthermore, the ilmenenes based on late 3d brass metals, such as
CuTiO$_3$ and ZnTiO$_3$, become ferromagnetic and spin compensated,
respectively. Our calculations including spin-orbit coupling reveal that the
magnetic ilmenenes have large magnetocrystalline anisotropy energies when the
3d shell departs from being either filled or half-filled, with their spin
orientation being out-of-plane for elements below half-filling of 3d states and
in-plane above. These interesting magnetic properties of ilmenenes make them
useful for future spintronic applications because they could be synthesized as
already realized in the iron case.",2211.01732v1
2024-02-27,Expansion dynamics of Bose-Einstein condensates in a synthetic magnetic field,"We investigate the expansion dynamics of spin-orbit-coupled Bose-Einstein
condensates subjected to a synthetic magnetic field, after their release from
an external harmonic trap. Our findings reveal that the condensate experiences
a spin-dependent rotation and separation due to the rigid-like rotational
velocity field, which leads to a spin density deflection. The deflection angle
reaches a peak at a time that is inversely related to the frequency of the
harmonic trap. When the detuning gradient is below a critical value for vortex
nucleation, our analytical results derived from a spinor hydrodynamic theory
align closely with numerical results using the coupled Gross-Pitaevskii
equations. Beyond this critical value, we also numerically simulated the
expansion dynamics of the condensates containing vortices with negative
circulation. Our findings highlight the pivotal role of the rigid-like
rotational velocity field on the dynamics of the condensate and may stimulate
further experimental investigations into the rich superfluid dynamics induced
by synthetic magnetic fields.",2402.17691v1
2024-02-28,Cotunneling effects in the geometric statistics of a nonequilibrium spintronic junction,"In the nonequilibrium steadystate of electronic transport across a
spin-resolved quantronic junction, we investigate the role of cotunneling on
the emergent statistics under phase-different adiabatic modulation of the
reservoirs' chemical potentials. By explicitly identifying the sequential and
inelastic cotunneling rates, we numerically evaluate the geometric or
Pancharatnam-Berry contributions to the spin exchange flux. We identify the
relevant conditions wherein the sequential and cotunneling processes compete
and selectively influence the total geometric flux upshot. The Fock space
coherences are found to suppress the cotunneling effects when the system
reservoir couplings are comparable. The cotunneling contribution to the total
geometric flux can be made comparable to the sequential contribution by
creating a rightsided asymmetry in the system-reservoir coupling strength.
Using a recently proposed geometric thermodynamic uncertainty relationship, we
numerically estimate the total rate of minimal entropy production. The
geometric flux and the minimum entropy are found to be nonlinear as a function
of the interaction energy of the junction's spin orbitals.",2402.18283v1
2006-10-19,Gap-mediated magnetization of a pseudo-one-dimensional system with a spin-orbit interaction,"We argue that a pseudo-one-dimensional electron gas is magnetized when a
voltage bias is applied with the Fermi level tuned to be in the energy gap
generated by a spin-orbit interaction. The magnetization is an indication of
spin-carrying currents due to the spin-orbit interaction. The origin of the
magnetization, however, is essentially different from the ""spin accumulation""
in two-dimensional systems with spin-orbit interactions.",0610531v1
2007-10-29,Electron-electron and spin-orbit interactions in armchair graphene ribbons,"The effects of intrinsic spin-orbit and Coulomb interactions on low-energy
properties of finite width graphene armchair ribbons are studied by means of a
Dirac Hamiltonian. It is shown that metallic states subsist in the presence of
intrinsic spin-orbit interactions as spin-filtered edge states, in contrast
with the insulating behavior predicted for graphene planes. A charge-gap opens
due to Coulomb interactions in neutral ribbons, that vanishes as $\Delta\sim
1/W $, with a gapless spin sector. Weak intrinsic spin-orbit interactions do
not change the insulating behavior. Explicit expressions for the
width-dependent gap and various correlation functions are presented.",0710.5405v1
2014-03-27,Spin-orbit effects in armchair carbon nanotubes: analytical results,"Energy spectra and transport properties of armchair nanotubes with curvature
induced spin-orbit interaction are investigated thoroughly. The spin-orbit
interaction consists of two terms: the first one preserves the spin symmetry in
rotating frame, while the second one breaks it. It is found that the both terms
are equally important: i)at scattering on the potential step which mimics a
long-range potential in the nanotubes; ii)at transport via nanotube quantum
dots. It is shown that an armchair nanotube with the first spin-orbit term
works as an ideal spin-filter, while the second term produces a parasitic
inductance.",1403.7070v1
2010-07-20,Quantum criticality of vanadium chains with strong relativistic spin-orbit interaction,"We study quantum phase transitions induced by the on-site spin-orbit
interaction lambda(L.S) in a toy model of vanadium chains. In the lambda->0
limit, the decoupled spin and orbital sectors are described by a Haldane and an
Ising chain, respectively. The gapped ground state is composed of a
ferro-orbital order and a spin liquid with finite correlation lengths. In the
opposite limit, strong spin-orbital entanglement results in a simultaneous spin
and orbital-moment ordering, which can be viewed as an orbital liquid. Using a
combination of analytical arguments and density-matrix renormalization group
calculation, we show that an intermediate phase, where the ferro-orbital state
is accompanied by a spin Neel order, is bounded on both sides by Ising
transition lines. Implications for vanadium compounds CaV2O4 and ZnV2O4 are
also discussed.",1007.3472v3
2022-04-27,Hidden interplay of current-induced spin and orbital torques in bulk Fe$_3$GeTe$_2$,"Low crystal symmetry of magnetic van der Waals materials naturally promotes
spin-orbital complexity unachievable in common magnetic materials used for
spin-orbit torque switching. Here, using first-principles methods, we
demonstrate that an interplay of spin and orbital degrees of freedom has a
profound impact on spin-orbit torques in a prototype van der Waals ferromagnet:
Fe$_3$GeTe$_2$ (FGT). While we show that bulk FGT hosts strong ""hidden""
current-induced torques harvested by each of its layers, we uncover that their
origin alternates between the conventional spin flux torque and the so-called
orbital torque as the magnetization direction is varied. A drastic difference
in the behavior of the two types of torques results in a non-trivial evolution
of switching properties with doping. Our findings promote the design of
non-equilibrium orbital properties as the guiding mechanism for crafting the
properties of spin-orbit torques in layered van der Waals materials.",2204.13052v3
2004-01-29,Correlated two-pion exchange and large-N(C) behavior of nuclear forces,"The effect of correlated scalar-isoscalar two-pion exchange (CrTPE) modes is
considered in connection with central and spin-orbit parts of the NN force. The
two-pion correlation function is coupled directly to the scalar form factor of
the nucleon which we calculate in the large-N(C) limit where the nucleon can be
described as a soliton of an effective chiral theory. The results for the
central NN force show a strong repulsive core at short internucleon distances
supplemented by a moderate attraction beyond 1 fm. The long-range tail of the
central NN potential is driven by the the pion-nucleon sigma term and
consistent with the effective $\sigma$ meson exchange. The spin-orbit part of
the NN potential is repulsive. The large-N(C) scaling behavior of the
scalar-isoscalar NN interaction is addressed. We show that the spin-orbit part
is O(1/N^2(C)) in strength relative to the central force resulting in the ratio
$\simeq 1/9$ suggested by the 1/N(C) expansion for N(C)=3. The latter is in
agreement with our numerical analysis and with the Kaplan-Manohar large-N(C)
power counting. Unitarization of the $\pi \pi$ scattering amplitude plays here
an important role and improves the tree level results. Analytical
representations of the CrTPE NN potential in terms of elementary functions are
derived and their chiral content is discussed.",0401061v3
2008-02-06,Tight-binding electronic spectra on graphs with spherical topology. II. The effect of spin-orbit interaction,"This is the second of two papers devoted to tight-binding electronic spectra
on graphs with the topology of the sphere. We investigate the problem of an
electron subject to a spin-orbit interaction generated by the radial electric
field of a static point charge sitting at the center of the sphere. The
tight-binding Hamiltonian considered is a discretization on polyhedral graphs
of the familiar form ${\bm L}\cdot{\bm S}$ of the spin-orbit Hamiltonian. It
involves SU(2) hopping matrices of the form $\exp({\rm i}\mu{\bm
n}\cdot{\bm\sigma})$ living on the oriented links of the graph. For a given
structure, the dimensionless coupling constant $\mu$ is the only parameter of
the model. An analysis of the energy spectrum is carried out for the five
Platonic solids (tetrahedron, cube, octahedron, dodecahedron and icosahedron)
and the C$_{60}$ fullerene. Except for the latter, the $\mu$-dependence of all
the energy levels is obtained analytically in closed form. Rather unexpectedly,
the spectra are symmetric under the exchange $\mu\leftrightarrow\Theta-\mu$,
where $\Theta$ is the common arc length of the links. For the symmetric point
$\mu=\Theta/2$, the problem can be exactly mapped onto a tight-binding model in
the presence of the magnetic field generated by a Dirac monopole, studied
recently. The dependence of the total energy at half filling on $\mu$ is
investigated in all examples.",0802.0795v2
2013-11-04,Carrier localization and electronic phase separation in a doped spin-orbit driven Mott phase in Sr3(Ir1-xRux)2O7,"Interest in many strongly spin-orbit coupled 5d-transition metal oxide
insulators stems from mapping their electronic structures to a J=1/2 Mott
phase. One of the hopes is to establish their Mott parent states and explore
these systems' potential of realizing novel electronic states upon carrier
doping. However, once doped, little is understood regarding the role of their
reduced Coulomb interaction U relative to their strongly correlated 3d-electron
cousins. Here we show that, upon hole-doping a candidate J=1/2 Mott insulator,
carriers remain localized within a nanoscale phase separated ground state. A
percolative metal-insulator transition occurs with interplay between localized
and itinerant regions, stabilizing an antiferromagnetic metallic phase beyond
the critical region. Our results demonstrate a surprising parallel between
doped 5d- and 3d-electron Mott systems and suggest either through the near
degeneracy of nearby electronic phases or direct carrier localization that U is
essential to the carrier response of this doped spin-orbit Mott insulator.",1311.0783v2
2014-11-01,Quantum Čerenkov Radiation: Spectral Cutoffs and the Role of Spin and Orbital Angular Momentum,"We show that the well-known \v{C}erenkov Effect contains new phenomena
arising from the quantum nature of charged particles. The \v{C}erenkov
transition amplitudes allow coupling between the charged particle and the
emitted photon through their orbital angular momentum (OAM) and spin, by
scattering into preferred angles and polarizations. Importantly, the spectral
response reveals a discontinuity immediately below a frequency cutoff that can
occur in the optical region. Specifically, with proper shaping of electron
beams (ebeams), we predict that the traditional \v{C}erenkov radiation angle
splits into two distinctive cones of photonic shockwaves. One of the shockwaves
can move along a backward cone, otherwise considered impossible for
\v{C}erenkov radiation in ordinary matter. Our findings are observable for
ebeams with realistic parameters, offering new applications including novel
quantum optics sources, and open a new realm for \v{C}erenkov detectors
involving the spin and orbital angular momentum of charged particles.",1411.0083v2
2015-06-08,Demonstration of Optimal Control of Laser Induced Spin-Orbit Mediated Ultrafast Demagnetization,"Laser induced ultrafast demagnetization is the process whereby the magnetic
moment of a ferromagnetic material is seen to drop significantly on a timescale
of $10-100$s of femtoseconds due to the application of a strong laser pulse. If
this phenomenon can be harnessed for future technology, it offers the
possibility for devices operating at speeds several orders of magnitude faster
than at present. A key component to successful transfer of such a process to
technology is the controllability of the process, i.e. that it can be tuned in
order to overcome the practical and physical limitations imposed on the system.
In this paper, we demonstrate that the spin-orbit mediated form of ultrafast
demagnetization recently investigated [arXiv:1406.6607] by ab-initio
time-dependent density functional theory (TDDFT) can be controlled. To do so we
use quantum optimal control theory (OCT) to couple our TDDDT simulations to the
optimization machinery of OCT. We show that a laser pulse can be found which
maximizes the loss of moment within a given time interval while subject to
several practical and physical constraints. Furthermore we also include a
constraint on the fluence of the laser pulses and find the optimal pulse that
combines significant demagnetization with a desire for less powerful pulses.
These calculations demonstrate optimal control is possible for spin-orbit
mediated ultrafast demagnetization and lay the foundation for future
optimizations/simulations which can incorporate even more constraints.",1506.02332v1
2016-04-26,A pedagogic review on designing model topological insulators,"Following the centuries old concept of the quantization of flux through a
Gaussian curvature (Euler characteristic) and its successive dispersal into
various condensed matter properties such as quantum Hall effect, and
topological invariants, we can establish a simple and fairly universal
understanding of various modern topological insulators (TIs). Formation of a
periodic lattice (which is a non-trivial Gaussian curvature) of 'cyclotron
orbits' with applied magnetic field, or 'chiral orbits' with fictitious
'momentum space magnetic field' (Berry curvature) guarantees its flux
quantization, and thus integer quantum Hall (IQH), and quantum spin-Hall (QSH)
insulators, respectively, occur. The bulk-boundary correspondence associated
with all classes of TIs dictates that some sort of pumping or polarization of a
'quantity' at the boundary must be associated with the flux quantization or
topological invariant in the bulk. Unlike charge or spin polarizations at the
edge for IQH and QSH states, the time-reversal (TR) invariant Z2 TIs pump a
mathematical quantity called 'TR polarization' to the surface. This requires
that the valence electron's wavefunction (say, {\psi}_{\uparrow} (k)) switches
to its TR conjugate ({\psi}_{\downarrow}^* (-k)) odd number of times in half of
the Brillouin zone. These two universal features can be considered as 'targets'
to design and predict various TIs. For example, we demonstrate that when two
adjacent atomic chains or layers are assembled with opposite spin-orbit
coupling (SOC), serving as the TR partner to each other, the system naturally
becomes a Z2 TI. This review delivers a holistic overview on various concepts,
computational schemes, and engineering principles of TIs.",1604.07546v1
2018-01-31,SU(4)-symmetric spin-orbital liquids on the hyperhoneycomb lattice,"We study the effective spin-orbital model that describes the magnetism of
4$d^1$ or 5$d^1$ Mott insulators in ideal tricoordinated lattices. In the limit
of vanishing Hund's coupling, the model has an emergent SU(4) symmetry which is
made explicit by means of a Klein transformation on pseudospin degrees of
freedom. Taking the hyperhoneycomb lattice as an example, we employ parton
constructions with fermionic representations of the pseudospin operators to
investigate possible quantum spin-orbital liquid states. We then use
variational Monte Carlo (VMC) methods to compute the energies of the projected
wave functions. Our numerical results show that the lowest-energy quantum
liquid corresponds to a zero-flux state with a Fermi surface of four-color
fermionic partons. In spite of the Fermi surface, we demonstrate that this
state is stable against tetramerization. A combination of linear flavor wave
theory and VMC applied to the complete microscopic model also shows that this
liquid state is stable against the formation of collinear long-range order.",1802.00044v3
2017-04-21,Time- and spatially-resolved magnetization dynamics driven by spin-orbit torques,"Current-induced spin-orbit torques (SOTs) represent one of the most effective
ways to manipulate the magnetization in spintronic devices. The orthogonal
torque-magnetization geometry, the strong damping, and the large domain wall
velocities inherent to materials with strong spin-orbit coupling make SOTs
especially appealing for fast switching applications in nonvolatile memory and
logic units. So far, however, the timescale and evolution of the magnetization
during the switching process have remained undetected. Here, we report the
direct observation of SOT-driven magnetization dynamics in Pt/Co/AlO$_x$ dots
during current pulse injection. Time-resolved x-ray images with 25 nm spatial
and 100 ps temporal resolution reveal that switching is achieved within the
duration of a sub-ns current pulse by the fast nucleation of an inverted domain
at the edge of the dot and propagation of a tilted domain wall across the dot.
The nucleation point is deterministic and alternates between the four dot
quadrants depending on the sign of the magnetization, current, and external
field. Our measurements reveal how the magnetic symmetry is broken by the
concerted action of both damping-like and field-like SOT and show that
reproducible switching events can be obtained for over $10^{12}$ reversal
cycles.",1704.06402v1
2014-05-04,Magnetic braking of Ap/Bp stars: an alternative formation mechanism of compact intermediate-mass binary pulsars,"It is difficult for the intermediate-mass X-ray binaries (IMXBs) evolutionary
channel to form intermediate-mass binary pulsars (IMBPs) with a short orbital
period (less than 3 d) via stable mass transfer. The main reason is that the
magnetic braking mechanisms are generally thought not to work for donor stars
with a mass of greater than 1.5 $\rm M_{\odot}$ in the canonical model.
However, some intermediate-mass stars have anomalously strong magnetic fields
(about 100 -- 10000 G), i. e. so-called Ap or Bp stars. With the coupling
between the magnetic field and the irradiation-driven wind from the surface of
Ap/Bp stars, a plausible magnetic braking mechanism should be expected. In this
work, we attempt to investigate if IMXBs with Ap/Bp stars can produce IMBPs
with a short orbital period (less than 3 d) by such an anomalous magnetic
braking mechanism. Using a stellar evolution code, we have simulated the
evolution of a large number of IMXBs consisting of a NS and an Ap/Bp star. For
the spin evolution of the NS, we consider the accretion torque, the propeller
torque, and the spin-down torque caused by the interaction between the magnetic
field and the accretion disc. The calculated results show that, employing
anomalous magnetic braking of Ap/Bp stars, IMXBs can evolve into compact IMBPs
with short orbital periods of less than 3 d. However, there exists significant
discrepancy between the spin periods of IMBPs in our simulated results and
those observed.",1405.0691v1
2018-03-20,Interaction-driven spin-orbit effects and Chern insulating phases in corundum-based $4d$ and $5d$ oxide honeycomb lattices,"Using density functional theory calculations with a Hubbard $U$, we explore
topologically nontrivial phases in $X_2$O$_3$ honeycomb layers with $X=$ $4d$
and $5d$ cation inserted in the band insulator $\alpha$-Al$_2$O$_3$ along the
[0001]-direction. Several promising candidates for quantum anomalous Hall
insulators (QAHI) are identified. In particular, for $X$=Tc and Pt spin-orbit
coupling (SOC) opens a gap of 54 and 59 meV, respectively, leading to Chern
insulators (CI) with $C$=--2 and --1. The nature of different Chern numbers is
related to the corresponding spin textures. The Chern insulating phase is
sensitive to the Coulomb repulsion strength: $X$=Tc undergoes a transition from
a CI to a trivial metallic state beyond a critical strength of $U_c$ =2.5 eV. A
comparison between the isoelectronic metastable FM phases of $X$=Pd and Pt
emphasizes the intricate balance between electronic correlations and SOC: while
the former is a trivial insulator, the latter is a Chern insulator. In
addition, $X$=Os turns out to be a FM Mott insulator with an unpaired electron
in the $t_{2g}$ manifold where SOC induces an unusually high orbital moment of
0.34 $\mu_{\rm B}$ along the $z$-axis. Parallels to the $3d$ honeycomb corundum
cases are discussed.",1803.07392v2
2018-07-25,A new paradigm for the quantum spin Hall effect at high temperatures,"The quantum spin Hall effect (QSHE) has formed the seed for contemporary
research on topological quantum states of matter. Since its discovery in
HgTe/CdTe quantum wells and AlGaAs/GaAs heterostructures, all such systems have
so far been suffering from extremely low operating temperatures, rendering any
technological application out of reach. We formulate a theoretical paradigm to
accomplish the high temperature QSHE in monolayer-substrate heterostructures.
Specifically, we explicate our proposal for hexagonal compounds formed by
monolayers of heavy group-V elements (As, Sb, Bi) on a SiC substrate. We show
how orbital filtering due to substrate hybridization, a tailored multi-orbital
density of states at low energies, and large spin-orbit coupling can conspire
to yield QSH states with bulk gaps of several hundreds of meV. Combined with
the successful realization of Bi/SiC (0001), with a measured bulk gap of 800
meV reported previously [Reis et al., 10.1126/science.aai8142 (2017)], our
paradigm elevates the QSHE from an intricate quantum phenomenon at low
temperatures to a scalable effect amenable to device design and engineering.",1807.09552v1
2020-05-06,The Dirac oscillator: an alternative basis for nuclear structure calculations,"Background: The isotropic harmonic oscillator supplemented by a strong
spin-orbit interaction has been the cornerstone of nuclear structure since its
inception more than seven decades ago. In this paper we introduce---or rather
re-introduced---the ""Dirac Oscillator"", a fully relativistic basis that has all
the desired attributes of the ordinary harmonic oscillator while naturally
incorporating a strong spin-orbit coupling.
  Purpose: To assess---to our knowledge for the first time---the power and
flexibility of the Dirac Oscillator basis in the solution of nuclear structure
problems within the framework of covariant density functional theory.
  Methods: Self-consistent calculations of binding energies and ground-state
densities for a selected set of doubly-magic magic are performed using the
Dirac-oscillator basis and are then compared against results obtained with the
often-used Runge-Kutta method.
  Results: Results obtained using the Dirac oscillator basis reproduced with
high accuracy those derived using the Runge-Kutta method and suggest a clear
path for a generalization to systems with axial symmetry.
  Conclusions: Although the three-dimensional harmonic oscillator with
spin-orbit corrections has been the staple of the nuclear shell model since the
beginning, the Dirac oscillator is practically unknown among the nuclear
physics community. In this paper we illustrate the power and flexibility of the
Dirac oscillator and suggest extensions to the study of systems without
spherical symmetry as required in constrained calculations of nuclear
excitations.",2005.03134v1
2021-04-28,Fragile topological insulators protected by rotation symmetry without spin-orbit coupling,"We present a series of models of three-dimensional rotation-symmetric fragile
topological insulators in class AI (time-reversal symmetric and spin-orbit-free
systems), which have gapless surface states protected by time-reversal ($T$)
and $n$-fold rotation ($C_n$) symmetries ($n=2,4,6$). Our models are
generalizations of Fu's model of a spinless topological crystalline insulator,
in which orbital degrees of freedom play the role of pseudo-spins. We consider
minimal surface Hamiltonian with $C_n$ symmetry in class AI and discuss
possible symmetry-protected gapless surface states, i.e., a quadratic band
touching and multiple Dirac cones with linear dispersion. We characterize
topological structure of bulk wave functions in terms of two kinds of
topological invariants obtained from Wilson loops: $\mathbb{Z}_2$ invariants
protected by $C_n$ ($n=4,6$) and time-reversal symmetries, and
$C_2T$-symmetry-protected $\mathbb{Z}$ invariants (the Euler class) when the
number of occupied bands is two. Accordingly, our models realize two kinds of
fragile topological insulators. One is a fragile $\mathbb{Z}$ topological
insulator whose only nontrivial topological index is the Euler class that
specifies the number of surface Dirac cones. The other is a fragile
$\mathbb{Z}_2$ topological insulator having gapless surface states with either
a quadratic band touching or four (six) Dirac cones, which are protected by
time-reversal and $C_4$ ($C_6$) symmetries. Finally, we discuss the instability
of gapless surface states against the addition of $s$-orbital bands and
demonstrate that surface states are gapped out through hybridization with
surface-localized $s$-orbital bands.",2104.13631v2
2016-10-17,"Structural, magnetic, electric, dielectric, and thermodynamic properties of multiferroic GeV4S8","The lacunar spinel GeV4S8 undergoes orbital and ferroelectric ordering at the
Jahn-Teller transition around 30 K and exhibits antiferromagnetic order below
about 14 K. In addition to this orbitally driven ferroelectricity, lacunar
spinels are an interesting material class, as the vanadium ions form V4
clusters representing stable molecular entities with a common electron
distribution and a well-defined level scheme of molecular states resulting in a
unique spin state per V4 molecule. Here we report detailed x-ray, magnetic
susceptibility, electrical resistivity, heat capacity, thermal expansion, and
dielectric results to characterize the structural, electric, dielectric,
magnetic, and thermodynamic properties of this interesting material, which also
exhibits strong electronic correlations. From the magnetic susceptibility, we
determine a negative Curie-Weiss temperature, indicative for antiferromagnetic
exchange and a paramagnetic moment close to a spin S = 1 of the V4 molecular
clusters. The low-temperature heat capacity provides experimental evidence for
gapped magnon excitations. From the entropy release, we conclude about strong
correlations between magnetic order and lattice distortions. In addition, the
observed anomalies at the phase transitions also indicate strong coupling
between structural and electronic degrees of freedom. Utilizing dielectric
spectroscopy, we find the onset of significant dispersion effects at the polar
Jahn-Teller transition. The dispersion becomes fully suppressed again with the
onset of spin order. In addition, the temperature dependencies of dielectric
constant and specific heat possibly indicate a sequential appearance of orbital
and polar order.",1610.05244v1
2016-10-19,Structural evolution and electronic properties of (Sr1-xCax)2-yIrO4+z spin-orbit assisted insulators,"The effect of isoelectronic substitution within single crystals of
(Sr1-xCax)2-yIrO4+z is explored. The nominal n=1 Ruddlesden-Popper phase with
y=0, z=0 remains stable from x=0 until x=0.11, where the antiferromagnet
spin-orbit Mott insulating state persists. An increase in the saturated moment
is observed with increasing Ca-substitution, suggesting a modified coupling of
the in-plane moments relative to the in-plane rotation of IrO6 octahedra.
Beyond x=0.11, the x=1/4, y=0, z=1/2 structural phase Sr3CaIr2O9, consisting of
a three-dimensional network of corner sharing octahedra, begins to intermix and
eventually nucleates phase pure crystals at higher starting Ca-content. An
insulating, nonmagnetic ground state is observed in this phase attributable to
the J=0 state and is consistent with a recent powder study. At higher
Ca-concentrations beyond x = 0.75, crystals begin to stabilize in the y=1/3,
z=0 quasi one-dimensional Ca5Ir3O12 structure. The low temperature transport in
this chain-based structure is well described via variable range hopping, and an
antiferromagnetic ordering transition appears below T$_N=9$ K. Our data provide
a detailed mapping of the electronic and structural properties accessible as
the structural framework of the canonical spin orbit Mott insulator Sr2IrO4 is
destabilized via isovalent chemical substitution.",1610.06055v1
2020-09-11,Electronic nematic states tuned by isoelectronic substitution in bulk FeSe1-xSx,"Isoelectronic substitution is an ideal tuning parameter to alter electronic
states and correlations in iron-based superconductors. As this substitution
takes place outside the conducting Fe planes, the electronic behaviour is less
affected by the impurity scattering experimentally and relevant key electronic
parameters can be accessed. In this short review, I present the experimental
progress made in understanding the electronic behaviour of the nematic
electronic superconductors, FeSe1-xSx. A direct signature of the nematic
electronic state is in-plane anisotropic distortion of the Fermi surface
triggered by orbital ordering effects and electronic interactions that result
in multi-band shifts detected by ARPES. Upon sulphur substitution, the
electronic correlations and the Fermi velocities decrease in the tetragonal
phase. Quantum oscillations are observed for the whole series in ultra-high
magnetic fields and show a complex spectra due to the presence of many small
orbits. Effective masses associated to the largest orbit display non-divergent
behaviour at the nematic end point (x~0.175(5)), as opposed to critical
spin-fluctuations in other iron pnictides. Magnetotransport behaviour has a
strong deviation from the Fermi liquid behaviour and linear T resistivity is
detected at low temperatures inside the nematic phase, where scattering from
low energy spin-fluctuations are likely to be present. The superconductivity is
not enhanced in FeSe1-xSx and there are no divergent electronic correlations at
the nematic end point. These manifestations indicate a strong coupling with the
lattice in FeSe1-xSx and a pairing mechanism likely promoted by spin
fluctuations.",2009.05523v1
2022-01-15,Robust Dirac lines against Ge vacancy and possible spin-orbit Dirac points in nonsymmorphic HfGe0.92Te,"Looking for new materials with Dirac points has been a fascinating subject of
research. Here we report the growth, crystal structure, and band structure of
HfGe0.92Te single crystals, featuring three different types of Dirac points.
HfGe0.92Te crystalizes in a nonsymmorphic tetragonal space group P4/nmm (No.
129), having square Ge-atom plane with vacancies about 8%. Despite the
vacancies on Ge site, the Dirac nodal line composed of conventional Dirac
points vulnerable to spin-orbit coupling (SOC) is observed using angle-resolved
photoemission spectroscopy, accompanied with the robust Dirac line protected by
the nonsymmorphic symmetry against both SOC and vacancies. Specially,
spin-orbit Dirac points (SDPs) originated from the surface formed under SOC are
hinted to exist according to our experiments and calculations.
Quasi-two-dimensional (quasi-2D) characters are observed and further confirmed
by angular-resolved magnetoresistance. HfGe0.92Te is a good candidate to
explore exotic topological phases or topological properties with three
different types of Dirac points and a promising candidate to realize 2D SDPs.",2201.05833v1
2022-06-09,Exchange interactions in $d^{5}$ Kitaev materials: From Na$_2$IrO$_3$ to $α$-RuCl$_3$,"We present an analytical study of the exchange interactions between
pseudospin one-half $d^{5}$ ions in honeycomb lattices with edge-shared
octahedra. Various exchange channels involving Hubbard U, charge-transfer
excitations, and cyclic exchange are considered. Hoppings within $t_{2g}$
orbitals as well as between $t_{2g}$ and $e_g$ orbitals are included. Special
attention is paid to the trigonal crystal field $\Delta$ effects on the
exchange parameters. The obtained exchange Hamiltonian is dominated by
ferromagnetic Kitaev interaction K within a wide range of $\Delta$. It is found
that a parameter region close to the charge-transfer insulator regime and with
a small $\Delta$ is most promising to realize the Kitaev spin liquid phase. Two
representative honeycomb materials Na$_2$IrO$_3$ and $\alpha$-RuCl$_3$ are
discussed based on our theory. We have found that both materials share dominant
ferromagnetic K and positive non-diagonal $\Gamma$ values. However, their
Heisenberg J terms have opposite signs: AFM J>0 in Na$_2$IrO$_3$ and FM J<0 in
$\alpha$-RuCl$_3$. This brings different magnetic fluctuations and results in
their different magnetization behaviors and spin excitation spectra. Proximity
to FM state due to the large FM J is emphasized in $\alpha$-RuCl$_3$. The
differences between the exchange couplings of these two materials originate
from the opposite $\Delta$ values, indicating that the crystal field can serve
as an efficient control parameter to tune the magnetic properties of $d^{5}$
spin-orbit Mott insulators.",2206.04326v1
2022-09-18,Control of chiral orbital currents in a colossal magnetoresistance material,"Colossal magnetoresistance (CMR) is an extraordinary enhancement of the
electric conductivity in the presence of a magnetic field. It is conventionally
associated with a field-induced spin polarization, which drastically reduces
spin scattering and thus electric resistance. However, ferrimagnetic Mn3Si2Te6
is an intriguing exception to this rule: it exhibits a 7-order-of-magnitude
reduction in ab-plane resistivity with a 13-Tesla anisotropy field which occur
only when a magnetic polarization is avoided [1]. Here we report an exotic
quantum state that is driven by ab-plane chiral orbital currents (COC) flowing
along edges of MnTe6 octahedra. The c-axis orbital moments of ab-plane COC
couple to the ferrimagnetic Mn spins to drastically increase the ab-plane
conductivity (CMR) when an external magnetic field is aligned along the
magnetic hard c-axis. Both the COC state and its CMR are extraordinarily
susceptible to small DC currents exceeding a critical threshold, and a hallmark
of this COC state is an exotic time-dependent, bistable switching mimicking a
first-order melting transition. The control of the COC-enabled CMR and bistable
switching offers a fundamentally new paradigm for quantum technologies.",2209.08672v1
2022-11-21,Two-dimensional hourglass Weyl nodal loop in monolayer Pb(ClO$_{2}$)$_{2}$ and Sr(ClO$_{2}$)$_{2}$,"The hourglass fermions in solid-state materials have been attracting
significant interest recently. However, realistic two-dimensional (2D)
materials with hourglass-shaped band structures are still very scarce. Here,
through the first-principles calculations, we identify the monolayer
Pb(ClO$_{2}$)$_{2}$ and Sr(ClO$_{2}$)$_{2}$ materials as the new realistic
materials platform to realize 2D hourglass Weyl nodal loop. We show that these
monolayer materials possess an hourglass Weyl nodal loop circling around the
$\Gamma$ point and Weyl nodal line on the Brillouin zone (BZ) boundary in the
absence of spin-orbit coupling (SOC). Through the symmetry analysis, we
demonstrate that the hourglass Weyl nodal loop and Weyl nodal line are
protected by the nonsymmorphic symmetries, and are robust under the biaxial
strains. When we include the SOC, a tiny gap will be opened in the hourglass
nodal loop and nodal line, and the nodal line can be transformed into the
spin-orbit Dirac points. Our results provide a new realistic material platform
for studying the intriguing physics associated with the 2D hourglass Weyl nodal
loop and spin-orbit Dirac points.",2211.11269v1
2023-05-01,Atomically-precise engineering of spin-orbit polarons in a kagome magnetic Weyl semimetal,"Atomically-precise engineering of defects in topological quantum materials,
which is essential for constructing new artificial quantum materials with
exotic properties and appealing for practical quantum applications, remains
challenging due to the hindrances in modifying complex lattice with atomic
precision. Here, we report the atomically-precise engineering of the
vacancy-localized spin-orbital polarons (SOP) in a kagome magnetic Weyl
semimetal Co3Sn2S2, using scanning tunneling microscope. We achieve the
step-by-step repairing of the selected vacancies, which results in the
formation of artificial sulfur vacancy with elaborate geometry. We find that
that the bound states localized around the vacancies experience a
symmetry-dependent energy shift towards Fermi level with increasing vacancy
size. Strikingly, as vacancy size increases, the localized magnetic moments of
SOPs are tunable and ultimately extended to the negative magnetic moments
resulting from spin-orbit coupling in the kagome flat band. These findings
establish a new platform for engineering atomic quantum states in topological
quantum materials, offering potential for kagome-lattice-based spintronics and
quantum technologies.",2305.00824v2
2005-05-21,Spin unrestricted linear scaling electronic structure theory and its application to magnetic carbon doped BN nanotubes,"We present an extension of density matrix based linear scaling electronic
structure theory to incorporate spin degrees of freedom. When the spin
multiplicity of the system can be predetermined, the generalization of the
existing linear scaling methods to spin unrestricted cases is straightforward.
However, without calculations it is hard to determine the spin multiplicity of
some complex systems, such as, many magnetic nanostuctures, some inorganic or
bioinorganic molecules. Here we give a general prescription to obtain the
spin-unrestricted ground state of open shell systems. Our methods are
implemented into the linear scaling trace-correcting density matrix
purification algorithm. The numerical atomic orbital basis, rather than the
commonly adopted Gaussian basis functions is used. The test systems include O2
molecule, and magnetic carbon doped BN(5,5) and BN(7,6) nanotubes. Using the
newly developed method, we find the magnetic moments in carbon doped BN
nanotubes couple antiferromagnetically with each other. Our results suggest
that the linear scaling spin-unrestricted trace-correcting purification method
is very powerful to treat large magnetic systems.",0505528v2
2002-03-01,Baryon resonances and strong QCD,"Light-baryon resonances (with u,d, and s quarks in the SU(3) classification)
fall on Regge trajectories. When their squared masses are plotted against the
intrinsic orbital angular momenta {\rm L}, $\Delta^*$'s with even and odd
parity can be described by the same Regge trajectory. For a given {\rm L},
nucleon resonances with spin {\rm S}=3/2 are approximately degenerate in mass
with $\Delta$ resonances. To which total angular momentum {\rm L} and {\rm S}
couple has no significant impact on the baryon mass. Nucleons with spin 1/2 are
shifted in mass; the shift is - in units of squared masses - proportional to
the component in the wave function which is antisymmetric in spin and flavor.
Based on these observations, a new baryon mass formula is proposed which
reproduces nearly all known baryon masses. It is shown that the masses are
compatible with a quark-diquark picture while the richness of the
experimentally known states require three particles to participate in the
dynamics. This conflict is resolved by proposing that quarks polarize the QCD
condensates and are surrounded by a polarization cloud shielding the color. A
new interpretation of constituent quarks as colored quark clusters emerges;
their interaction is responsible for the mass spectrum. Fast flavor exchange
between the colored quark clusters exhausts the dynamical richness of the
three-particle dynamics. The colored-quark-cluster model provides a mechanism
in which the linear confinement potential can be traced to the increase of the
volume in which the condensates are polarized. The quark-spin magnetic moment
induces currents in the polarized condensates which absorb the quark-spin
angular momentum: the proton spin is not carried by quark spins. The model
provides a new picture of hybrids and glueballs.",0203002v1
2009-09-13,"Quantum Transport in Ladder-Type Networks: Role of nonlinearity, topology and spin","We investigate quantum transport of electrons, phase solitons, etc. through
mesoscopic networks of zero-dimensional quantum dots. Straight and circular
ladders are chosen as networks with each coupled with three semi-infinite leads
(with one incoming and the other two outgoing). Two transmission probabilities
(TPs) as a function of the incident energy $\epsilon$ show a transition from
anti-phase aperiodic to degenerate periodic spectra at the critical energy
$\epsilon_c$ which is determined by a bifurcation point of the bulk energy
dispersions. TPs of the circular ladder depend only on the parity of the
winding number. Introduction of a single missing bond (MB) or missing step
doubles the period of the periodic spectra at $\epsilon>\epsilon_c$ . Shift of
the MB by lattice constant results in a striking switching effect at
$\epsilon<\epsilon_c$. In the presence of the electric-field induced spin-orbit
interaction (SOI), an obvious spin filtering occurs against the
spin-unpolarized injection. Against the spin-polarized injection, on the other
hand, the spin transport shows spin-flip (magnetization reversal) oscillations
with respect to SOI. We also show a role of soliton in the context of its
transport through the ladder networks.",0909.2401v1
2011-04-05,Magnetic domain wall motion in a nanowire: depinning and creep,"The domain wall motion in a magnetic nanowire is examined theoretically in
the regime where the domain wall driving force is weak and its competition
against disorders is assisted by thermal agitations. Two types of driving
forces are considered; magnetic field and current. While the field induces the
domain wall motion through the Zeeman energy, the current induces the domain
wall motion by generating the spin transfer torque, of which effects in this
regime remain controversial. The spin transfer torque has two mutually
orthogonal vector components, the adiabatic spin transfer torque and the
nonadiabatic spin transfer torque. We investigate separate effects of the two
components on the domain wall depinning rate in one-dimensional systems and on
the domain wall creep velocity in two-dimensional systems, both below the
Walker breakdown threshold. In addition to the leading order contribution
coming from the field and/or the nonadiabatic spin transfer torque, we find
that the adiabatic spin transfer torque generates corrections, which can be of
relevance for an unambiguous analysis of experimental results. For instance, it
is demonstrated that the neglect of the corrections in experimental analysis
may lead to incorrect evaluation of the nonadiabaticity parameter. Effects of
the Rashba spin-orbit coupling on the domain wall motion are also analyzed.",1104.0744v2
2016-01-29,Giant edge spin accumulation in a symmetric quantum well with two subbands,"We have studied the edge spin accumulation in a high mobility two-dimensional
electron gas formed in a symmetric well with two subbands. This study is
strongly motivated by the recent experiment of Hernandez et al. [Phys. Rev. B
{\bf 88}, 161305(R) (2013)] who demonstrated the spin accumulation near the
edges of a bilayer symmetric GaAs structure in contrast to no effect in a
single-layer configuration. The intrinsic mechanism of the spin-orbit
interaction we consider arises from the coupling between two subband states of
opposite parities. We obtain a parametrically large magnitude of the edge spin
density for the two-subband sample as compared to the usual single-subband
structure. We show that the presence of a gap in the system, i.e., the energy
separation $\Delta$ between the two subband bottoms, changes drastically the
picture of the edge spin accumulation. Thus one can easily proceed from the
regime of weak spin accumulation to the regime of strong one by varying the
Fermi energy (electron density) and/or $\Delta$. We estimate that by changing
the gap $\Delta$ from zero up to $1\div 2$ K, the magnitude of the effect
changes by three orders of magnitude. This opens up the possibility for the
design of new spintronic devices.",1602.00026v2
2020-07-16,Theory of the Inverse Faraday Effect due to the Rashba Spin-Oribt Interactions: Roles of Band Dispersions and Fermi Surfaces,"We theoretically study the inverse Faraday effect, i.e., the optical
induction of spin polarization with circularly polarized light, by particularly
focusing on effects of band dispersions and Fermi surfaces in crystal systems
with the spin-orbit interaction (SOI). By numerically solving the
time-dependent Schr\""odinger equation of a tight-binding model with the
Rashba-type SOI, we reproduce the light-induced spin polarization proportional
to $E_0^2/\omega^3$ where $E_0$ and $\omega$ are the electric-field amplitude
and the angular frequency of light, respectively. This optical spin induction
is attributed to dynamical magnetoelectric coupling between the light electric
field and the electron spins mediated by the SOI. We elucidate that the
magnitude and sign of the induced spin polarization sensitively depend on the
electron filling. To understand these results, we construct an analytical
theory based on the Floquet theorem. The theory successfully explains the
dependencies on $E_0$ and $\omega$ and ascribes the electron-filling dependence
to a momentum-dependent effective magnetic field governed by the Fermi-surface
geometry. Several candidate materials and experimental conditions relevant to
our theory and model parameters are also discussed. Our findings will enable us
to engineer the magneto-optical responses of matters via tuning the material
parameters.",2007.08072v1
2020-07-16,Large spin to charge conversion in topological superconductor \b{eta}-PdBi2 at room temperature,"\b{eta}-PdBi2 has attracted much attention for its prospective ability to
possess simultaneously topological surface and superconducting states due to
its unprecedented spin-orbit interaction (SOC). Whereas most works have focused
solely on investigating its topological surface states, the coupling between
spin and charge degrees of freedom in this class of quantum material remains
unexplored. Here we first report a study of spin-to-charge conversion in a
\b{eta}-PdBi2 ultrathin film grown by molecular beam epitaxy, utilizing a spin
pumping technique to perform inverse spin Hall effect measurements. We find
that the room temperature spin Hall angle of Fe/\b{eta}-PdBi2,
{\theta}_SH=0.037. This value is one order of magnitude larger than that of
reported conventional superconductors, and is comparable to that of the best
SOC metals and topological insulators. Our results provide an avenue for
developing superconductor-based spintronic applications.",2007.08693v1
2016-05-19,Longitudinal spin-relaxation of donor-bound electrons in direct bandgap semiconductors,"We measure the donor-bound electron longitudinal spin-relaxation time ($T_1$)
as a function of magnetic field ($B$) in three high-purity direct-bandgap
semiconductors: GaAs, InP, and CdTe, observing a maximum $T_1$ of
$1.4~\text{ms}$, $0.4~\text{ms}$ and $1.2~\text{ms}$, respectively. In GaAs and
InP at low magnetic field, up to $\sim2~\text{T}$, the spin-relaxation
mechanism is strongly density and temperature dependent and is attributed to
the random precession of the electron spin in hyperfine fields caused by the
lattice nuclear spins. In all three semiconductors at high magnetic field, we
observe a power-law dependence ${T_1 \propto B^{-\nu}}$ with ${3\lesssim \nu
\lesssim 4}$. Our theory predicts that the direct spin-phonon interaction is
important in all three materials in this regime in contrast to quantum dot
structures. In addition, the ""admixture"" mechanism caused by Dresselhaus
spin-orbit coupling combined with single-phonon processes has a comparable
contribution in GaAs. We find excellent agreement between high-field theory and
experiment for GaAs and CdTe with no free parameters, however a significant
discrepancy exists for InP.",1605.05978v1
2018-03-01,Classical and quantum spin dynamics of the honeycomb $Γ$ model,"Quantum to classical crossover is a fundamental question in dynamics of
quantum many-body systems. In frustrated magnets, for example, it is highly
non-trivial to describe the crossover from the classical spin liquid with a
macroscopically-degenerate ground-state manifold, to the quantum spin liquid
phase with fractionalized excitations. This is an important issue as we often
encounter the demand for a sharp distinction between the classical and quantum
spin liquid behaviors in real materials. Here we take the example of the
classical spin liquid in a frustrated magnet with novel bond-dependent
interactions to investigate the classical dynamics, and critically compare it
with quantum dynamics in the same system. In particular, we focus on signatures
in the dynamical spin structure factor. Combining Landau-Lifshitz dynamics
simulations and the analytical Martin-Siggia-Rose (MSR) approach, we show that
the low energy spectra are described by relaxational dynamics and highly
constrained by the zero mode structure of the underlying degenerate classical
manifold. Further, the higher energy spectra can be explained by precessional
dynamics. Surprisingly, many of these features can also be seen in the
dynamical structure factor in the quantum model studied by finite-temperature
exact diagonalization. We discuss the implications of these results, and their
connection to recent experiments on frustrated magnets with strong spin-orbit
coupling.",1803.00601v2
2018-06-20,Current-induced modulation of interfacial Dzyaloshinskii-Moriya interaction,"The Dzyaloshinskii-Moriya (DM) interaction is an antisymmetric exchange
interaction that is responsible for the emergence of chiral magnetism. The
origin of the DM interaction, however, remains to be identified albeit the
large number of studies reported on related effects. It has been recently
suggested that the DM interaction is equivalent to an equilibrium spin current
density originating from spin-orbit coupling, an effect referred to as the spin
Doppler effect. The model predicts that the DM interaction can be controlled by
spin current injected externally. Here we show that the DM exchange constant
($D$) in W/CoFeB based heterostructures can be modulated with external current
passed along the film plane. At higher current, $D$ decreases with increasing
current, which we infer is partly due to the adiabatic spin transfer torque. At
lower current, $D$ increases linearly with current regardless of the polarity
of current flow. The rate of increase in $D$ with the current density agrees
with that predicted by the model based on the spin Doppler effect. These
results imply that the DM interaction at the HM/FM interface partly originates
from an equilibrium interface spin (polarized) current which can be modulated
externally.",1806.07746v2
2018-07-17,"Field-induced intermediate phase in $α$-RuCl$_3$: Non-coplanar order, phase diagram, and proximate spin liquid","Frustrated magnets with strong spin-orbit coupling promise to host
topological states of matter, with fractionalized excitations and emergent
gauge fields. Kitaev's proposal for a honeycomb-lattice Majorana spin liquid
has triggered an intense search for experimental realizations, with
bond-dependent Ising interaction being the essential building block. A prime
candidate is $\alpha$-RuCl$_3$ whose phase diagram in a magnetic field is,
however, not understood to date. Here we present conclusive experimental
evidence for a novel field-induced ordered phase in $\alpha$-RuCl$_3$,
sandwiched between the zigzag and quantum disordered phases at low and high
fields, respectively. We provide a detailed theoretical study of the relevant
effective spin model which we show to display a field-induced intermediate
phase as well. We fully characterize the intermediate phase within this model,
including its complex spin structure, and pinpoint the parameters relevant to
$\alpha$-RuCl$_3$ based on the experimentally observed critical fields. Most
importantly, our study connects the physics of $\alpha$-RuCl$_3$ to that of the
Kitaev-$\Gamma$ model, which displays a quantum spin liquid phase in zero
field, and hence reveals the spin liquid whose signatures have been detected in
a variety of dynamical probes of $\alpha$-RuCl$_3$.",1807.06192v2
2020-03-06,Emergence of an upper bound to the electric field controlled Rashba spin splitting in InAs nanowires,"The experimental assessment of the strength ($\alpha_R$) of the Rashba
spin-orbit coupling is rather indirect and involves the measurement of the spin
relaxation length from magnetotransport, together with a model of weak
antilocalization. The analysis of the spin relaxation length in nanowires,
however, clouds the experimental assessment of the $\alpha_R$ and leads to the
prevailing belief that it can be tuned freely with electric field--a central
tenant of spintronics. Here, we report direct theory of $\alpha_R$ leading to
atomistic calculations of the spin band structure of InAs nanowires upon
application of electric field-- a direct method that does not require a theory
of spin relaxation. Surprisingly, we find an {\it upper bound} to the electric
field tunable Rashba spin splitting and the ensuing $\alpha_R$; for InAs
nanowires, $\alpha_R$ is pinned at about 170 meV{\AA} irrespective of the
applied field strength. We find that this pinning is due to the quantum
confined stark effect, that reduces continuously the nanowire band gap with
applied electric field, leading eventually to band gap closure and a
considerable increase in the density of free carriers. This results in turn in
a strong screening that prevents the applied electric field inside the nanowire
from increasing further beyond around 200 kV/cm for InAs nanowires. Therefore,
further increase in the gate voltage will not increase $\alpha_R$. This finding
clarifies the physical trends to be expected in nanowire Rashba SOC and the
roles played by the nano size and electric field.",2003.02984v1
2021-03-03,Optical spin conductivity in ultracold quantum gases,"We show that the optical spin conductivity being a small AC response of a
bulk spin current and elusive in condensed matter systems can be measured in
ultracold atoms. We demonstrate that this conductivity contains rich
information on quantum states by analyzing experimentally achievable systems
such as a spin-1/2 superfluid Fermi gas, a spin-1 Bose-Einstein condensate, and
a Tomonaga-Luttinger liquid. The obtained conductivity spectra being absent in
the Drude conductivity reflect quasiparticle excitations and non-Fermi liquid
properties. Accessible physical quantities include the superfluid gap and the
contact for the superfluid Fermi gas, gapped and gapless spin excitations as
well as quantum depletion for the Bose-Einstein condensate, and the spin part
of the Tomonaga-Luttinger liquid parameter elusive in cold-atom experiments.
Unlike its mass transport counterpart, the spin conductivity serves as a probe
applicable to clean atomic gases without disorder and lattice potentials. Our
formalism can be generalized to various systems such as spin-orbit coupled and
nonequilibrium systems.",2103.02418v4
2021-03-12,Atomic-layer Rashba-type superconductor protected by dynamic spin-momentum locking,"Spin-momentum locking is essential to the spin-split Fermi surfaces of
inversion-symmetry broken materials, which are caused by either Rashba-type or
Zeeman-type spin-orbit coupling (SOC). While the effect of Zeeman-type SOC on
superconductivity has experimentally been shown recently, that of Rashba-type
SOC remains elusive. Here we report on convincing evidence for the critical
role of the spin-momentum locking on crystalline atomic-layer superconductors
on surfaces, for which the presence of the Rashba-type SOC is demonstrated.
In-situ electron transport measurements reveal that in-plane upper critical
magnetic field is anomalously enhanced, reaching approximately three times the
Pauli limit at $T = 0$. Our quantitative analysis clarifies that dynamic
spin-momentum locking, a mechanism where spin is forced to flip at every
elastic electron scattering, suppresses the Cooper pair-breaking parameter by
orders of magnitude and thereby protects superconductivity. The present result
provides a new insight into how superconductivity can survive the detrimental
effects of strong magnetic fields and exchange interactions.",2103.07143v1
2021-05-06,Spin-valley locked instabilities in moire transition metal dichalcogenides with conventional and higher-order Van Hove singularities,"Recent experiments have observed correlated insulating and possible
superconducting phases in twisted homobilayer transition metal dichalcogenides
(TMDs). Besides the spin-valley locked moire bands due to the intrinsic Ising
spin-orbit coupling, homobilayer moire TMDs also possess either logarithmic or
power-law divergent Van Hove singularities (VHS) near the Fermi surface,
controllable by an external displacement field. The former and the latter are
dubbed conventional and higher-order VHS, respectively. Here, we perform a
perturbative renormalization group (RG) analysis to unbiasedly study the
dominant instabilities in homobilayer TMDs for both the conventional and
higher-order VHS cases. We find that the spin-valley locking largely alters the
RG flows and leads to instabilities unexpected in the corresponding
extensively-studied graphene-based moire systems, such as spin- and
valley-polarized ferromagnetism and topological superconductivity with mixed
parity. In particular, for the case with two higher-order VHS, we find a
spin-valley-locking-driven metallic state with no symmetry breaking in the TMDs
despite the diverging bare susceptibility. Our results show how the spin-valley
locking significantly affects the RG analysis and demonstrate that moire TMDs
are suitable platforms to realize various interaction-induced spin-valley
locked phases, highlighting physics fundamentally different from the
well-studied graphene-based moire systems.",2105.02415v2
2021-06-20,"Reversible giant out-of-plane Rashba effect in two-dimensional Ga$XY$ ($X$= Se, Te; $Y$= Cl, Br, I) compounds for persistent spin helix","The coexistence of ferroelectricity and spin-orbit coupling (SOC) in
noncentrosymmetric systems may allow for a nonvolatile control of spin degrees
of freedom by switching the ferroelectric polarization through the well-known
ferroelectric Rashba effect (FRE). Although the FER has been widely observed
for bulk ferroelectric systems, its existence in two-dimensional (2D)
ferroelectric systems is still very rarely discovered. Based on
first-principles calculations, supplemented with $\vec{k}\cdot\vec{p}$
analysis, we report the emergence of the FRE in the Ga$XY$ ($X$= Se, Te; $Y$=
Cl, Br, I) monolayer compounds, a new class of 2D materials having in-plane
ferroelectricity. Due to the large in-plane ferroelectric polarization, a giant
out-of-plane Rashba effect is observed in the topmost valence band, producing
unidirectional out-of-plane spin textures in the momentum space. Importantly,
such out-of-plane spin textures, which can host a long-lived helical spin mode
known as a persistent spin helix, can be fully reversed by switching the
direction of the in-plane ferroelectric polarization. Thus, our findings can
open avenues for interplay between the unidirectional out-of-plane Rashba
effect and the in-plane ferroelectricity in 2D materials, which is useful for
efficient and non-volatile spintronic devices.",2106.10596v1
2021-06-29,Berry curvature-induced local spin polarisation in gated graphene/WTe$_2$ heterostructures,"Full experimental control of local spin-charge interconversion is of primary
interest for spintronics. Heterostructures combining graphene with a strongly
spin-orbit coupled two-dimensional (2D) material enable such functionality by
design. Electric spin valve experiments have provided so far global information
on such devices, while leaving the local interplay between symmetry breaking,
charge flow across the heterointerface and aspects of topology unexplored.
Here, we utilize magneto-optical Kerr microscopy to resolve the gate-tunable,
local current-induced spin polarisation in graphene/WTe$_2$ van der Waals (vdW)
heterostructures. It turns out that even for a nominal in-plane transport,
substantial out-of-plane spin accumulation is induced by a corresponding
out-of-plane current flow. We develop a theoretical model which explains the
gate- and bias-dependent onset and spatial distribution of the massive Kerr
signal on the basis of interlayer tunnelling, along with the reduced point
group symmetry and inherent Berry curvature of the heterostructure. Our
findings unravel the potential of 2D heterostructure engineering for harnessing
topological phenomena for spintronics, and constitute an important further step
toward electrical spin control on the nanoscale.",2106.15509v1
2021-10-21,Angular harmonic Hall voltage and magnetoresistance measurements of Pt/FeCoB and Pt-Ti/FeCoB bilayers for spin Hall conductivity determination,"Materials with significant spin-orbit coupling enable efficient
spin-to-charge interconversion, which can be utilized in novel spin electronic
devices. A number of elements, mainly heavy-metals (HM) have been identified to
produce a sizable spin current ($j_\mathrm{s}$), while supplied with a charge
current ($j$), detected mainly in the neighbouring ferromagnetic (FM) layer.
Apart from the spin Hall angle $\theta_\mathrm{SH}$ = $j_\mathrm{s}$/$j$, spin
Hall conductivity ($\sigma_\mathrm{SH}$) is an important parameter, which takes
also the resistivity of the material into account. In this work, we present a
measurement protocol of the HM/FM bilayers, which enables for a precise
$\sigma_\mathrm{SH}$ determination. Static transport measurements, including
resistivity and magnetization measurements are accompanied by the angular
harmonic Hall voltage analysis in a dedicated low-noise rotating probe station.
Dynamic characterization includes effective magnetization and magnetization
damping measurement, which enable HM/FM interface absorption calculation. We
validate the measurement protocol in Pt and Pt-Ti underlayers in contact with
FeCoB and present the $\sigma_\mathrm{SH}$ of up to 3.3$\times$10$^5$ S/m,
which exceeds the values typically measured in other HM, such as W or Ta.",2110.11483v1
2021-12-22,Vanishing of the quantum spin Hall phase in a semi-Dirac Kane Mele model,"We study the vanishing of the topological properties of a quantum spin Hall
insulator induced by a deformation of the band structure that interpolates
between the Dirac and the semi-Dirac limits of a tight-binding model on a
honeycomb lattice. The above scenario is mimicked in a simple model, where
there exists a differential hopping along one of the three neighbours (say,
$t_1$) compared to the other two (say, $t$). For $t_1 = t$, the properties of
the quantum spin Hall phase is described by the familiar Kane Mele model, while
$t<t_1<2t$ denotes a situation in which the spin resolved bands are
continuously deformed. $t_1 = 2t$ represents a special case which is called as
the semi-Dirac limit. Here, the spectral gaps between the conduction and the
valence bands vanish. A closer inspection of the properties of such a deformed
system yields insights on a topological phase transition occurring at the
semi-Dirac limit, which continues to behave as a band insulator for $t_1>2t$.
We demonstrate the evolution of the topological phase in presence of the Rashba
and intrinsic spin-orbit couplings via computing the electronic band structure,
edge modes in a nanoribbon and the $\mathbb{Z}_2$ invariant. The latter aids in
arriving at the phase diagram which conclusively shows vanishing of the
topological phase in the semi-Dirac limit. Further we demonstrate in gradual
narrowing down of the plateau in the spin Hall conductivity, which along with a
phase diagram provide robust support on the vanishing of the $\mathbb{Z}_2$
invariant and hence the quantum spin Hall phase.",2112.11737v1
2022-06-14,Probing of large interfacial contribution to spin orbit coupling in CoFeB/Ta heterostructure by ultrafast THz emission spectroscopy,"Ultrafast THz radiation generation from ferromagnetic/nonmagnetic bilayer
heterostructure-based spintronic emitters generally exploits the conversion
from spin- to charge-current within the nonmagnetic layer and its interface
with the ferromagnetic layer. Various possible sub-contributions to the
underlying mechanism of inverse spin Hall effect for the THz emission from such
structures, need to be exploited for not only investigating the intricacies at
the fundamental level in the material properties themselves but also for
improving their performance for broadband and high-power THz emission. Here, we
report ultrafast THz emission from CoFeB/Ta bilayer at varying sample
temperatures in a large range to unravel the role of intrinsic and extrinsic
spin to charge conversion processes. In addition to an enhancement in the THz
emission, its temperature dependence shows a THz signal polarity reversal if
the CoFeB/Ta sample is annealed at an elevated temperature. We extract the
behaviour of the spin Hall resistivity, determine the intrinsic spin Hall
conductivity contribution in it and compare those with the standard Fe/Pt
system. Our results clearly demonstrate a giant interfacial contribution to the
overall spin Hall angle arising from the modified interface in the annealed
CoFeB/Ta, where a sign reversal in the corresponding spin Hall angle is
manifested from the THz amplitude variation with the temperature.",2206.06718v2
2022-06-20,First-principles calculation of the parameters used by atomistic magnetic simulations,"While the ground state of magnetic materials is in general well described on
the basis of spin density functional theory (SDFT), the theoretical description
of finite-temperature and non-equilibrium properties require an extension
beyond the standard SDFT. Time-dependent SDFT (TD-SDFT), which give for example
access to dynamical properties are computationally very demanding and can
currently be hardly applied to complex solids. Here we focus on the alternative
approach based on the combination of a parameterized phenomenological spin
Hamiltonian and SDFT-based electronic structure calculations, giving access to
the dynamical and finite-temperature properties for example via spin-dynamics
simulations using the Landau-Lifshitz-Gilbert (LLG) equation or Monte Carlo
simulations. We present an overview on the various methods to calculate the
parameters of the various phenomenological Hamiltonians with an emphasis on the
KKR Green function method as one of the most flexible band structure methods
giving access to practically all relevant parameters. Concerning these, it is
crucial to account for the spin-orbit coupling (SOC) by performing relativistic
SDFT-based calculations as it plays a key role for magnetic anisotropy and
chiral exchange interactions represented by the DMI parameters in the spin
Hamiltonian. This concerns also the Gilbert damping parameters characterizing
magnetization dissipation in the LLG equation, chiral multispin interaction
parameters of the extended Heisenberg Hamiltonian, as well as spin-lattice
interaction parameters describing the interplay of spin and lattice dynamics
processes, for which an efficient computational scheme has been developed
recently by the present authors.",2206.09969v1
2022-11-07,Optically controlled single-valley exciton doublet states with tunable internal spin structures and spin magnetization generation,"Manipulating quantum states through light-matter interactions has been
actively pursued in two-dimensional (2D) materials research. Significant
progress has been made towards the optical control of the valley degrees of
freedom in semiconducting monolayer transition-metal dichalcogenides (TMD),
based on doubly degenerate excitons from their two distinct valleys in
reciprocal space. Here, we introduce a novel kind of optically controllable
doubly degenerate exciton states that come from a single valley, dubbed as
single-valley exciton doublet (SVXD) states. They are unique in that their
constituent holes originate from the same valence band, making possible the
direct optical control of the spin structure of the excited constituent
electrons. Combining ab initio GW plus Bethe-Salpeter equation (GW-BSE)
calculations and a newly developed theoretical analysis method, we demonstrate
such novel SVXD in substrate-supported monolayer bismuthene -- which has been
successfully grown using molecular beam epitaxy. In each of the two distinct
valleys in the Brillouin zone, strong spin-orbit coupling and $C_{3v}$ symmetry
lead to a pair of degenerate 1s exciton states (the SVXD states) with opposite
spin configurations. Any coherent linear combinations of the SVXD in a single
valley can be excited by light with a specific polarization, enabling full
manipulation of their internal spin configurations. In particular, a
controllable net spin magnetization can be generated through light excitation.
Our findings open new routes to control quantum degrees of freedom, paving the
way for applications in spintronics and quantum information science.",2211.03334v2
2022-11-10,Triplet Cooper pair splitting in a two-dimensional electron gas,"Cooper pairs occupy the ground state of typical s-wave superconductors and
are composed of maximally entangled electrons with opposite spin. In order to
study the spin and entanglement properties of these electrons, one must
separate them spatially via a process known as Cooper pair splitting (CPS).
Here we provide the first demonstration of CPS in a semiconductor
two-dimensional electron gas (2DEG). By coupling two quantum dots to a
superconductor-semiconductor hybrid region we achieve efficient Cooper pair
splitting, and clearly distinguish it from other local and non-local processes.
In the presence of a magnetic field, the dots are operated as spin-filters to
obtain information about the spin of the electrons forming the Cooper pair. Not
only do we demonstrate the splitting of Cooper pairs into opposite-spin
electrons (i.e. singlet pairing), but also into equal-spin electrons, thus
achieving a triplet pairing between the quantum dots. Notably, the
exceptionally strong spin-orbit interaction in our 2DEGs, results in comparable
amplitudes of singlet and triplet pairing. The demonstration of singlet and
triplet CPS in 2DEGs opens the possibility to study on-chip entanglement and
topological superconductivity in the form of artificial Kitaev chains.",2211.05763v1
2023-03-01,"Universal mechanism of Ising superconductivity in twisted bilayer, trilayer and quadrilayer graphene","We show that the superconducivity in twisted graphene multilayers originates
from a common feature, which is the strong valley symmetry breaking
characteristic of these moir\'e systems at the magic angle. This leads to a
breakdown of the rotational symmetry of the flat moir\'e bands down to $C_3$,
and to ground states in which the time-reversal symmetry is broken for a given
spin projection. However, this symmetry can be recovered upon exchange of
spin-up and spin-down electrons, as we illustrate by means of a self-consistent
microscopic Hartree-Fock resolution where the states for the two spin
projections acquire opposite sign of the valley polarization. There is then a
spin-valley locking by which the Fermi lines for the two spin projections are
different and related by inversion symmetry. This effect represents a large
renormalization of the bare spin-orbit coupling of the graphene multilayers,
lending protection to the superconductivity against in-plane magnetic fields.
In the twisted bilayer as well as in trilayer and quadrilayer graphene, the
pairing glue is shown to be given by the nesting between parallel segments of
the Fermi lines which arise from the breakdown of symmetry down to $C_3$. This
leads to a strong Kohn-Luttinger pairing instability, which is relevant until
the Fermi line recovers gradually a more isotropic shape towards the bottom of
the second valence band, explaining why the superconductivity fades away beyond
three-hole doping of the moir\'e unit cell.",2303.00583v1
2023-05-22,Ultralong 100 ns Spin Relaxation Time in Graphite at Room Temperature,"Graphite has been intensively studied, yet its electron spins dynamics
remains an unresolved problem even 70 years after the first experiments. The
central quantities, the longitudinal ($T_1$) and transverse ($T_2$) relaxation
times were postulated to be equal, mirroring standard metals, but $T_1$ has
never been measured for graphite. Here, based on a detailed band structure
calculation including spin-orbit coupling, we predict an unexpected behavior of
the relaxation times. We find, based on saturation ESR measurements, that $T_1$
is markedly different from $T_2$. Spins injected with perpendicular
polarization with respect to the graphene plane have an extraordinarily long
lifetime of $100$ ns at room temperature. This is ten times more than in the
best graphene samples. The spin diffusion length across graphite planes is thus
expected to be ultralong, on the scale of $\sim 70~\mu$m, suggesting that thin
films of graphite -- or multilayer AB graphene stacks -- can be excellent
platforms for spintronics applications compatible with 2D van der Waals
technologies. Finally, we provide a qualitative account of the observed spin
relaxation based on the anisotropic spin admixture of the Bloch states in
graphite obtained from density functional theory calculations.",2305.15433v1
2023-07-06,Spin-Polarized Majorana Zero Modes in Proximitized Superconducting Penta-Silicene Nanoribbons,"We theoretically investigate the possibility of obtaining Majorana zero modes
(MZMs) in penta-silicene nanoribbons (p-SiNRs) with induced \textit{p}-wave
superconductivity. The model explicitly considers an external magnetic field
perpendicularly applied to the nanoribbon plane, as well as an extrinsic Rashba
spin-orbit coupling (RSOC), in addition to the first nearest neighbor hopping
term and \textit{p}-wave superconducting pairing. By analyzing the dispersion
relation profiles, we observe the successive closing and reopening of the
induced superconducting gap with a single spin component, indicating a
spin-polarized topological phase transition (TPT). Correspondingly, the plots
of the energy spectrum versus the chemical potential reveal the existence of
zero-energy states with a preferential spin orientation characterized by
nonoverlapping wave functions localized at opposite ends of the superconducting
p-SiNRs. These findings strongly suggest the emergence of topologically
protected, spin-polarized MZMs at the ends of the p-SiNRs with induced
\textit{p}-wave superconducting pairing, which can be realized by proximitizing
the nanoribbon with an \textit{s}-wave superconductor, such as lead. The
proposal paves the way for silicene-based Majorana devices hosting multiple
MZMs with a well-defined spin orientation, with possible applications in
fault-tolerant quantum computing platforms and Majorana spintronics.",2307.03185v1
2023-07-19,Spin Space Groups: Full Classification and Applications,"In this work, we exhaust all the spin-space symmetries, which fully
characterize collinear, non-collinear, commensurate, and incommensurate spiral
magnetism, and investigate enriched features of electronic bands that respect
these symmetries. We achieve this by systematically classifying the so-called
spin space groups (SSGs) - joint symmetry groups of spatial and spin operations
that leave the magnetic structure unchanged. Generally speaking, they are
accurate (approximate) symmetries in systems where spin-orbit coupling (SOC) is
negligible (finite but weaker than the interested energy scale); but we also
show that specific SSGs could remain valid even in the presence of a strong
SOC. By representing the SSGs as O($N$) representations, we - for the first
time - obtain the complete classifications of 1421, 9542, and 56512 distinct
SSGs for collinear ($N=1$), coplanar ($N=2$), and non-coplanar ($N=3$)
magnetism, respectively. SSG not only fully characterizes the symmetry of spin
d.o.f., but also gives rise to exotic electronic states, which, in general,
form projective representations of magnetic space groups (MSGs). Surprisingly,
electronic bands in SSGs exhibit features never seen in MSGs, such as
nonsymmorphic SSG Brillouin zone (BZ), where SSG operations behave as glide or
screw when act on momentum and unconventional spin-momentum locking, which is
completely determined by SSG, independent of Hamiltonian details. To apply our
theory, we identify the SSG for each of the 1604 published magnetic structures
in the MAGNDATA database on the Bilbao Crystallographic Server. Material
examples exhibiting aforementioned novel features are discussed with emphasis.
We also investigate new types of SSG-protected topological electronic states
that are unprecedented in MSGs.",2307.10364v2
2023-12-12,Dzyaloshinskii-Moriya interaction inducing weak ferromagnetism in centrosymmetric altermagnets and weak ferrimagnetism in noncentrosymmetric altermagnets,"The Dzyaloshinskii-Moriya interaction (DMI) has explained successfully the
weak ferromagnetism in some centrosymmetric antiferromagnets. However, in the
last years, it was generally claimed that the DMI is not effective in
centrosymmetric systems. We reconciled these views by separating the
conventional antiferromagnets and altermagnets. Altermagnets represent
collinear antiferromagnetic compounds with spin-up and spin-down sublattices
connected only by mirror and roto-translational symmetries. Consequently, the
system shows even-parity wave spin order in the k-space lifting the Kramer's
degeneracy in the non-relativistic band structure. We emphasize that the DMI
can create weak ferromagnetism in centrosymmetric altermagnets while it is not
effective in centrosymmetric conventional antiferromagnets. Additionally, DMI
can create weak ferromagnetism or weak ferrimagnetism in noncentrosymmetric
altermagnets. Once the spin-orbit coupling is included in an altermagnetic
system without time-reversal symmetry, the components of spin moments of the
two sublattices along the Neel vector are antiparallel but the other two spin
components orthogonal to the N\'eel vector can be either parallel or
antiparallel for centrosymetric systems. For noncentrosymmetric systems, we can
have different bands showing parallel or antiparallel spin components resulting
in weak ferrimagnetism. We can divide the altermagnetic compounds into classes
based on the weak ferromagnetism or weak ferrimagnetism properties. The weak
ferromagnetism and weak ferrimagnetism induced by DMI is a property exclusively
of the altermagnets, not present in either ferromagnets or conventional
antiferromagnets so we propose that altermagnets should be classified based on
this property.",2312.07678v2
2023-12-13,Antiparallel spin polarization and spin current induced by thermal current and locally-broken inversion symmetry in a double-quantum-well structure,"Generating a nonequilibrium spin polarization with a driving force has been
first realized by the electric current in a system with broken inversion
symmetry and extended to that induced by the thermal current and that appearing
in an inversion-symmetric system with locally-broken inversion symmetry. This
paper theoretically explores the spin polarization generated by the thermal
current and the locally-broken inversion symmetry in a symmetric
double-quantum-well structure (DQWS). This thermally-induced spin polarization
(TISP) appears in the antiparallel configuration with the TISP of two wells in
opposite directions. The calculation using the Boltzmann equation in the
relaxation-time approximation under the condition of zero charge current shows
that the local TISP exhibits the maximum at a finite Rashba spin-orbit
interaction when the electron density is fixed. This is because the local TISP
in the DQWS is enhanced at the chemical potential near the bottom of the
first-excited subband. This enhancement also occurs in a single quantum well
with globally-broken inversion symmetry. Another finding is that the maximum of
the local TISP appears at a nonzero interwell coupling. The spin current by the
diffusion of the local TISP into an adjacent electrode is also calculated.",2312.07944v1
2024-03-27,Rashba spin splitting-induced topological Hall effect in a Dirac semimetal-ferromagnetic semiconductor heterostructure,"We use a concerted theory-experiment effort to investigate the formation of
chiral real space spin texture when the archetypal Dirac semimetal Cd$_3$As$_2$
is interfaced with In$_{1-x}$Mn$_x$As, a ferromagnetic semiconductor with
perpendicular magnetic anisotropy. Our calculations reveal a nonzero
off-diagonal spin susceptibility in the Cd$_3$As$_2$ layer due to the Rashba
spin-orbit coupling from broken inversion symmetry. This implies the presence
of a Dzyaloshinskii-Moriya interaction between local moments in the
In$_{1-x}$Mn$_x$As layer, mediated by Dirac electrons in the vicinal
Cd$_3$As$_2$ layer, potentially creating the conditions for a real space chiral
spin texture. Using electrical magnetoresistance measurements at low
temperature, we observe an emergent excess contribution to the transverse
magneto-resistance whose behavior is consistent with a topological Hall effect
arising from the formation of an interfacial chiral spin texture. This excess
Hall voltage varies with gate voltage, indicating a promising
electrostatically-tunable platform for understanding the interplay between the
helical momentum space states of a Dirac semimetal and chiral real space spin
textures in a ferromagnet.",2403.18485v1
2015-06-26,Modeling and Simulation of Spin Transfer Torque Generated at Topological Insulator/Ferromagnetic Heterostructure,"Topological Insulator (TI) has recently emerged as an attractive candidate
for possible application to spintronic circuits because of its strong spin
orbit coupling. TIs are unique materials that have an insulating bulk but
conducting surface states due to band inversion and these surface states are
protected by time reversal symmetry. In this paper, we propose a physics-based
spin dynamics simulation framework for TI/Ferromagnet (TI/FM) bilayer
heterostructures that is able to capture the electronic band structure of a TI
while calculating the electron and spin transport properties. Our model differs
from TI/FM models proposed in the literature in that it is able to account for
the 3D band structure of TIs and the effect of exchange coupling and external
magnetic field on the band structure. Our proposed approach uses 2D surface
Hamiltonian for TIs that includes all necessary features for spin transport
calculations so as to properly model the characteristics of a TI/FM
heterostructure. Using this Hamiltonian and appropriate parameters, we show
that the effect of quantum confinement and exchange coupling are successfully
captured in the calculated surface band structure compared with the quantum
well band diagram of a 3D TI, and matches well with experimental data reported
in the literature. We then show how this calibrated Hamiltonian is used with
the self-consistent non equilibrium Green's functions (NEGF) formalism to
determine the charge and spin transport in TI/FM bilayer heterostructures. Our
calculations agree well with experimental data and capture the unique features
of a TI/FM heterostructure such as high spin Hall angle, high spin conductivity
etc. Finally, we show how the results obtained from NEGF calculations may be
incorporated into the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) formulation to
simulate the magnetization dynamics of an FM layer sitting on top of a TI.",1506.07932v2
2006-02-22,Spin-Hall effect in semiconductor heterostructures with cubic Rashba spin-orbit interaction,"We study the spin-Hall effect in systems with weak cubic Rashba spin-orbit
interaction. To this end we derive particle and spin diffusion equations and
explicit expressions for the spin-current tensor in the diffusive regime. We
discuss the impact of electric fields on the Green's functions and the
diffusion equations and establish a relationship between the spin-current
tensor and the spin diffusion equations for the model under scrutiny. We use
our results to calculate the edge spin-accumulation in a spin-Hall experiment
and show that there is also a new Hall-like contribution to the electric
current in such systems.",0602517v1
2018-05-04,"Metal-insulator transitions, superconductivity, and magnetism in the two-band Hubbard model","We explore the ground-state properties of the two-band Hubbard model with
degenerate electronic bands, parametrized by nearest-neighbor hopping $t$,
intra- and inter-orbital on-site Coulomb repulsions $U$ and $U^\prime$, and
Hund coupling $J$, focusing on the case with $J>0$. Using Jastrow-Slater wave
functions, we consider both states with and without magnetic/orbital order.
Electron pairing can also be included in the wave function, in order to detect
the occurrence of superconductivity for generic electron densities $n$. When no
magnetic/orbital order is considered, the Mott transition is continuous for
$n=1$ (quarter filling); instead, at $n=2$ (half filling), it is first order
for small values of $J/U$, while it turns out to be continuous when the ratio
$J/U$ is increased. A significant triplet pairing is present in a broad region
around $n=2$. By contrast, singlet superconductivity (with $d$-wave symmetry)
is detected only for small values of the Hund coupling and very close to half
filling. When including magnetic and orbital order, the Mott insulator acquires
antiferromagnetic order for $n=2$; instead, for $n=1$ the insulator has
ferromagnetic and antiferro-orbital orders. In the latter case, a metallic
phase is present for small values of $U/t$ and the metal-insulator transition
becomes first order. In the region with $1<n<2$, we observe that ferromagnetism
(with no orbital order) is particularly robust for large values of the Coulomb
repulsion and that triplet superconductivity is strongly suppressed by the
presence of antiferromagnetism. The case with $J=0$, which has an enlarged
SU(4) symmetry due to the interplay between spin and orbital degrees of
freedom, is also analyzed.",1805.01856v2
2014-07-08,Exotic Spin Order due to Orbital Fluctuations,"We investigate the phase diagrams of the spin-orbital $d^9$ Kugel-Khomskii
model for increasing system dimensionality: from the square lattice monolayer,
via the bilayer to the cubic lattice. In each case we find strong competition
between different types of spin and orbital order, with entangled spin-orbital
phases at the crossover from antiferromagnetic to ferromagnetic correlations in
the intermediate regime of Hund's exchange. These phases have various types of
exotic spin order and are stabilized by effective interactions of longer range
which follow from enhanced spin-orbital fluctuations. We find that orbital
order is in general more robust and spin order melts first under increasing
temperature, as observed in several experiments for spin-orbital systems.",1407.2142v1
2015-04-10,Proton and neutron correlations in $^{10}$B,"We investigate positive-parity states of $^{10}$B with the calculation of
antisymmetrized molecular dynamics focusing on $pn$ pair correlations. We
discuss effects of the spin-orbit interaction on energy spectra and $pn$
correlations of the $J^\pi T=1^+_10$, $=3^+_10$, and $0^+_11$ states. The
$1^+_10$ state has almost no energy gain of the spin-orbit interaction, whereas
the $3^+_10$ state gains the spin-orbit interaction energy largely to come down
to the ground state. We interpret a part of the two-body spin-orbit interaction
in the adopted effective interactions as a contribution of the genuine $NNN$
force, and find it to be essential for the level ordering of the $3^+_10$ and
$1^+_10$ states in $^{10}$B. We also apply a $2\alpha+pn$ model to discuss
effects of the spin-orbit interaction on $T=0$ and $T=1$ $pn$ pairs around the
2$\alpha$ core. In the spin-aligned $J^\pi T=3^+0$ state, the spin-orbit
interaction affects the $(ST)=(10)$ pair attractively and keeps the pair close
to the core, whereas, in the $1^+0$ state, it gives a minor effect to the
$(ST)=(10)$ pair. In the $0^+1$ state, the $(ST)=(01)$ pair is somewhat
dissociated by the spin-orbit interaction.",1504.02594v1
2008-07-10,Self-Spin-Controlled Rotation of Spatial States of a Dirac Electron in a Cylindrical Potential via Spin-Orbit Interaction,"Solution of the Dirac equation predicts that when an electron with non-zero
orbital angular momentum propagates in a cylindrically symmetric potential, its
spin and orbital degrees of freedom interact, causing the electron's phase
velocity to depend on whether its spin and orbital angular momenta vectors are
oriented parallel or anti-parallel with respect to each other. This spin-orbit
splitting of the electronic dispersion curves can result in a rotation of the
electron's spatial state in a manner controlled by the electron's own spin
z-component value. These effects persist at non-relativistic velocities. To
clarify the physical origin of this effect, we compare solutions of the Dirac
equation to perturbative predictions of the Schrodinger-Pauli equation with a
spin-orbit term, using the standard Foldy-Wouthuysen Hamiltonian. This clearly
shows that the origin of the effect is the familiar relativistic spin-orbit
interaction.",0807.1566v2
2002-09-13,"Reply to a Comment by J. Bolte, R. Glaser and S. Keppeler on: Semiclassical theory of spin-orbit interactions using spin coherent states","We reply to a Comment on our recently proposed semiclassical theory for
systems with spin-orbit interactions.",0209028v1
2003-07-17,Optical Generation and Quantitative Characterizations of Electron-hole Entanglement,"Using a method of characterizing entanglement in the framework of quantum
field theory, we investigate the optical generation and quantitative
characterizations of quantum entanglement in an electron-hole system, in
presence of spin-orbit coupling, and especially make a theoretical analysis of
a recent experimental result. Basically, such entanglement should be considered
as between occupation numbers of single particle basis states, and is
essentially generated by coupling between different single particle basis
states in the second quantized Hamiltonian. Interaction with two resonant light
modes of different circular polarizations generically leads to a superposition
of ground state and two heavy-hole excitonic states. When and only when the
state is a superposition of only the two excitonic eigenstates, the
entanglement reduces to that between two distinguishable particles, each with
two degrees of freedom, namely, band index, as characterized by angular
momentum, and orbit, as characterized by position or momentum. The band-index
state, obtained by tracing over the orbital degree of freedom, is found to be a
pure state, hence the band-index and orbital degrees of freedom are separated
in this state. We propose some basic ideas on spatially separating the electron
and the hole, so that the entanglement of band-indices, or angular momenta, is
between spatially separated electron and hole.",0307437v2
2011-02-15,Tidal Evolution of Close-in Extrasolar Planets: High Stellar Q from New Theoretical Models,"In recent years it has been shown that the tidal coupling between extrasolar
planets and their stars could be an important mechanism leading to orbital
evolution. Both the tides the planet raises on the star and vice versa are
important and dissipation efficiencies ranging over four orders of magnitude
are being used. In addition, the discovery of extrasolar planets extremely
close to their stars has made it clear that the estimates of the tidal quality
factor, Q, of the stars based on Jupiter and its satellite system and on main
sequence binary star observations are too low, resulting in lifetimes for the
closest planets orders of magnitude smaller than their age. We argue that those
estimates of the tidal dissipation efficiency are not applicable for stars with
spin periods much longer than the extrasolar planets' orbital period. We
address the problem by applying our own values for the dissipation efficiency
of tides, based on our numerical simulations of externally perturbed volumes of
stellar-like convection. The range of dissipation we find for main-sequence
stars corresponds to stellar $Q_*$ of $10^8$ to $3{\times}10^9$. The derived
orbit lifetimes are comparable to, or much longer than the ages of the observed
extrasolar planetary systems. The predicted orbital decay transit timing
variations due to the tidal coupling are below the rate of ms/yr for currently
known systems, but within reach of an extended Kepler mission provided such
objects are found in its field.",1102.3187v1
2023-03-06,Theory for charge density wave and orbital-flux state in antiferromagnetic kagome metal FeGe,"In this work, we theoretically study the charge order and orbital magnetic
properties of a new type of antiferromagnetic kagome metal FeGe. Based on first
principles density functional theory (DFT) calculations, we have studied the
electronic structures, Fermi-surface quantum fluctuations, as well as phonon
properties of the antiferromagnetic kagome metal FeGe. We find that charge
density wave emerges in such a system due to a subtle cooperation between
electron-electron ($e$-$e$) interactions and electron-phonon couplings, which
gives rise to an unusual scenario of interaction-triggered phonon
instabilities, and eventually yields a charge density wave (CDW) state. We
further show that, in the CDW phase, the ground-state current density
distribution exhibits an intriguing star-of-David pattern, leading to flux
density modulation. The orbital fluxes (or current loops) in this system
emerges as a result of the subtle interplay between magnetism, lattice
geometries, charge order, and spin-orbit coupling (SOC), which can be described
by a simple, yet universal, tight-binding theory including a Kane-Mele type SOC
term and a magnetic exchange interaction. We further study the origin of the
peculiar step-edge states in FeGe, which shed light on the topological
properties and correlation effects in this new type of kagome antiferromagnetic
material.",2303.02824v1
2023-07-11,Charge Transfer and Zhang-Rice Singlet Bands in the Nickelate Superconductor $\mathrm{La_3Ni_2O_7}$ under Pressure,"Recently, a bulk nickelate superconductor $\mathrm{La_3Ni_2O_7}$ is
discovered at pressures with a remarkable high transition temperature $T_c \sim
80K$. Here, we study a Hubbard model with tight-binding parameters derived from
\textit{ab initio} calculations of $\mathrm{La_3Ni_2O_7}$, by employing large
scale determinant quantum Monte Carlo and cellular dynamical mean-field theory.
Our result suggests that the superexchange couplings in this system are
comparable to that of cuprates. The system is a charge transfer insulator as
hole concentration becomes four per site at large Hubbard $U$. Upon hole
doping, two low-energy spin-singlet bands emerge in the system exhibiting
distinct correlation properties: while the one composed of the out-of-plane
Ni-$d_{3z^2-r^2}$ and O-$p_z$ orbitals demonstrates strong antiferromagnetic
correlations and narrow effective bandwidth, the in-plane singlet band
consisting of the Ni-$d_{x^2-y^2}$ and O-$p_x / p_y$ orbitals is in general
more itinerant. Over a broad range of hole doping, the doped holes occupy
primarily the $d_{x^2-y^2}$ and $p_x / p_y$ orbitals, whereas the
$d_{3z^2-r^2}$ and $p_z$ orbitals retain underdoped. We propose an effective $
t-J$ model to capture the relevant physics and discuss the implications of our
result for comprehending the $\mathrm{La_3Ni_2O_7}$ superconductivity.",2307.05662v2
2010-05-28,Spinning compact binary inspiral II: Conservative angular dynamics,"We establish the evolution equations of the set of independent variables
characterizing the 2PN rigorous conservative dynamics of a spinning compact
binary, with the inclusion of the leading order spin-orbit, spin-spin and mass
quadrupole - mass monopole effects, for generic (noncircular, nonspherical)
orbits. More specifically, we give a closed system of first order ordinary
differential equations for the orbital elements of the osculating ellipse and
for the angles characterizing the spin orientations with respect to the
osculating orbit. We also prove that (i) the relative angle of the spins stays
constant for equal mass black holes, irrespective of their orientation, and
(ii) the special configuration of equal mass black holes with equal, but
antialigned spins, both laying in the plane of motion (leading to the largest
recoil found in numerical simulations) is preserved at 2PN level of accuracy,
with leading order spin-orbit, spin-spin and mass quadrupolar contributions
included.",1005.5330v2
2020-03-17,Experimental evidence of spin-orbit torque from metallic interfaces,"Spin currents can modify the magnetic state of ferromagnetic ultrathin films
through spin-orbit torque. They may be generated by means of spin-orbit
interaction by either bulk or interfacial phenomena. Electrical transport
measurements reveal a six-fold increase of the spin-orbit torque accompanied by
a drastic reduction of the spin Hall magnetoresistance upon the introduction of
a Cu interlayer in a Pt/Cu/Co/Pt structure with perpendicular magnetic
anisotropy. We analyze the dependence of the spin Hall magnetoresistance with
the thickness of the interlayer in the frame of a drift diffusion model that
provides information on the expected spin currents and spin accumulations in
the system. The results demonstrate that the major responsible of both effects
is spin memory loss at the interface. The enhancement of the spin-orbit torque
when introducing an interlayer opens the possibility to design more effient
spintronic devices based on materials that are cheap and abundant such as
copper.",2003.07677v1
2019-09-04,Spin--lattice coupling and the emergence of the trimerized phase in the $S=1$ Kagome antiferromagnet Na$_2$Ti$_3$Cl$_8$,"Spin-1 antiferromagnets are abundant in nature, but few theories or results
exist to understand their general properties and behavior, particularly in
situations when geometric frustration is present. Here we study the $S=1$
Kagome compound Na$_2$Ti$_3$Cl$_8$ using a combination of Density Functional
Theory, Exact Diagonalization, and Density Matrix Renormalization Group methods
to achieve a first principles supported explanation of exotic magnetic phases
in this compound. We find that the effective magnetic Hamiltonian includes
essential non-Heisenberg terms that do not stem from spin-orbit coupling, and
both trimerized and spin-nematic magnetic phases are relevant. The
experimentally observed structural transition to a breathing Kagome phase is
driven by spin--lattice coupling, which favors the trimerized magnetic phase
against the quadrupolar one. We thus show that lattice effects can be necessary
to understand the magnetism in frustrated magnetic compounds, and surmise that
Na$_2$Ti$_3$Cl$_8$ is a compound which cannot be understood from only
electronic or only lattice Hamiltonians, very much like VO$_2$.",1909.02020v1
2012-05-11,Nonequilibrium quantum dynamics of the magnetic Anderson model,"We study the non-equilibrium dynamics of a spinful single-orbital quantum dot
with an incorporated quantum mechanical spin-1/2 magnetic impurity. Due to the
spin degeneracy, double occupancy is allowed, and Coulomb interaction together
with the exchange coupling of the magnetic impurity influence the dynamics. By
extending the iterative summation of real-time path integrals (ISPI) to this
coupled system, we monitor the time-dependent non-equilibrium current and the
impurity spin polarization to determine features of the time-dependent
non-equilibrium dynamics. We particulary focus on the deep quantum regime,
where all time and energy scales are of the same order of magnitude and no
small parameter is available. We observe a significant influence of the
non-equilibrium decay of the impurity spin polarization both in the presence
and in the absence of Coulomb interaction. The exponential relaxation is faster
for larger bias voltages, electron-impurity interactions and temperatures. We
show that the exact relaxation rate deviates from the corresponding
perturbative result. In addition, we study in detail the impurity's back action
on the charge current and find a reduction of the stationary current for
increasing coupling to the impurity. Moreover, our approach allows us to
systematically distinguish mean-field Coulomb and impurity effects from the
influence of quantum fluctuations and flip-flop scattering, respectively. In
fact, we find a local maximum of the current for a finite Coulomb interaction
due to the presence of the impurity.",1205.2462v2
2018-08-21,Single and Double Hole Quantum Dots in Strained Ge/SiGe Quantum Wells,"Even as today's most prominent spin-based qubit technologies are maturing in
terms of capability and sophistication, there is growing interest in exploring
alternate material platforms that may provide advantages, such as enhanced
qubit control, longer coherence times, and improved extensibility. Recent
advances in heterostructure material growth have opened new possibilities for
employing hole spins in semiconductors for qubit applications. Undoped,
strained Ge/SiGe quantum wells are promising candidate hosts for hole
spin-based qubits due to their low disorder, large intrinsic spin-orbit
coupling strength, and absence of valley states. Here, we use a simple
one-layer gated device structure to demonstrate both a single quantum dot as
well as coupling between two adjacent quantum dots. The hole effective mass in
these undoped structures, $m$* ~ 0.08 $m$$_0$, is significantly lower than for
electrons in Si/SiGe, pointing to the possibility of enhanced tunnel couplings
in quantum dots and favorable qubit-qubit interactions in an
industry-compatible semiconductor platform.",1808.07077v2
2021-03-04,Canted antiferromagnetic order and spin dynamics in the honeycomb-lattice Tb2Ir3Ga9,"Single crystal neutron diffraction, inelastic neutron scattering, bulk
magnetization measurements, and first-principles calculations are used to
investigate the magnetic properties of the honeycomb lattice $\rm
Tb_2Ir_3Ga_9$. While the $R\ln2$ magnetic contribution to the low-temperature
entropy indicates a $\rm J_{eff}=1/2$ moment for the lowest-energy
crystal-field doublet, the Tb$^{3+}$ ions form a canted antiferromagnetic
structure below 12.5 K. Due to the Dzyalloshinskii-Moriya interactions, the Tb
moments in the $ab$ plane are slightly canted towards $b$ by $6^\circ$ with a
canted moment of 1.22 $\mu_{\rm B} $ per formula unit. A minimal $xxz$ spin
Hamiltonian is used to simultaneously fit the spin-wave frequencies along the
high symmetry directions and the field dependence of the magnetization along
the three crystallographic axes. Long-range magnetic interactions for both
in-plane and out-of-plane couplings up to the second nearest neighbors are
needed to account for the observed static and dynamic properties. The $z$
component of the exchange interactions between Tb moments are larger than the
$x$ and $y$ components. This compound also exhibits bond-dependent exchange
with negligible nearest exchange coupling between moments parallel and
perpendicular to the 4$f$ orbitals. Despite the $J_{{\rm eff}}=1/2$ moments,
the spin Hamiltonian is denominated by a large in-plane anisotropy $K_z \sim
-1$ meV. DFT calculations confirm the antiferromagnetic ground state and the
substantial inter-plane coupling at larger Tb-Tb distances.",2103.03157v1
2003-09-11,The transition to classical chaos in a coupled quantum system through continuous measurement,"Continuous observation of a quantum system yields a measurement record that
faithfully reproduces the classically predicted trajectory provided that the
measurement is sufficiently strong to localize the state in phase space but
weak enough that quantum backaction noise is negligible. We investigate the
conditions under which classical dynamics emerges, via continuous position
measurement, for a particle moving in a harmonic well with its position coupled
to internal spin. As a consequence of this coupling we find that classical
dynamics emerges only when the position and spin actions are both large
compared to $\hbar$. These conditions are quantified by placing bounds on the
size of the covariance matrix which describes the delocalized quantum coherence
over extended regions of phase space. From this result it follows that a mixed
quantum-classical regime (where one subsystem can be treated classically and
the other not) does not exist for a continuously observed spin 1/2 particle.
When the conditions for classicallity are satisfied (in the large-spin limit),
the quantum trajectories reproduce both the classical periodic orbits as well
as the classically chaotic phase space regions. As a quantitative test of this
convergence we compute the largest Lyapunov exponent directly from the measured
quantum trajectories and show that it agrees with the classical value.",0309093v1
2021-10-07,Spatial aspects of spin polarization of structurally split surface states in thin films with magnetic exchange and spin-orbit interaction,"A theoretical study is presented of the effect of an in-plane magnetic
exchange field on the band structure of centrosymmetric films of noble metals
and topological insulators. Based on an ab initio relativistic
$\mathbf{k}\cdot\mathbf{p}$ theory, a minimal effective model is developed that
describes two coupled copies of a Rashba or Dirac electronic system residing at
the opposite surfaces of the film. The coupling leads to a structural gap at
$\bar{\Gamma}$ and causes an exotic redistribution of the spin density in the
film when the exchange field is introduced. We apply the model to a
nineteen-layer Au(111) film and to a five-quintuple-layer Sb$_2$Te$_3$ film. We
demonstrate that at each film surface the exchange field induces spectrum
distortions similar to those known for Rashba or Dirac surface states with an
important difference due to the coupling: At some energies, one branch of the
state loses its counterpart with the oppositely directed group velocity. This
suggests that a large-angle electron scattering between the film surfaces
through the interior of the film is dominant or even the only possible for such
energies. The spin-density redistribution accompanying the loss of the
counterpart favors this scattering channel.",2110.03583v2
2023-09-18,Incorporation of random alloy GaBi$_{x}$As$_{1-x}$ barriers in InAs quantum dot molecules: alloy strain and orbital effects towards enhanced tunneling,"Self-assembled InAs quantum dots (QDs), which have long hole-spin coherence
times and are amenable to optical control schemes, have long been explored as
building blocks for qubit architectures. One such design consists of vertically
stacking two QDs to create a quantum dot molecule (QDM). The two dots can be
resonantly tuned to form ""molecule-like"" coupled hole states from the
hybridization of hole states otherwise localized in each respective dot.
Furthermore, spin-mixing of the hybridized states in dots offset along their
stacking direction enables qubit rotation to be driven optically, allowing for
an all-optical qubit control scheme. Increasing the magnitude of this spin
mixing is important for optical quantum control protocols. To enhance the
tunnel coupling and spin-mixing across the dots, we introduce Bi in the GaAs
inter-dot barrier. Previously, we showed how to model InAs/GaBiAs in an
atomistic tight-binding formalism, and how the dot energy levels are affected
by the alloy. In this paper, we discuss the lowering of the tunnel barrier,
which results in a three fold increase of hole tunnel coupling strength in the
presence of a 7% alloy. Additionally, we show how an asymmetric strain between
the two dots caused by the alloy shifts the resonance. Finally, we discuss
device geometries for which the introduction of Bi is most advantageous.",2309.10115v4
2023-11-28,Deriving quantum spin model for a zigzag-chain ytterbium magnet with anisotropic exchange interactions,"We derive a quantum spin Hamiltonian of the spin-1/2 zigzag chain realized in
a rare earth ytterbium-based magnetic insulator, YbCuS2. This material
undergoes a transition at 0.95K to an incommensurate magnetic phase with small
moments, which does not conform to the nonmagnetic singlet ground state of the
spin-1/2 Heisenberg model. We take account of octahedral crystal field effect,
atomic spin-orbit coupling, and strong Coulomb interactions on Yb ions, and
perform a four-order perturbation theory to evaluate the superexchange coupling
constants. A small but finite anisotropic exchange coupling called
{\Gamma}-term appears similarly to the case reported previously in other
triangular-based magnets. By varying several material parameters, we figure out
two important factors to enhance {\Gamma}-term. One is the splitting of excited
f-states with two holes, which efficiently selects the perturbation terms
associated with the lowest excited state having large total angular momentum,
and accordingly with high spatial anisotropy. The other is the tilting of
octahedra or distortion of S-Yb-S bond angle, which break the symmetry of the
Slater-Koster overlap. These effects are systematically analyzed by the
exchange anisotropy in units of pairs of octahedra within the local spin frame,
which significantly reduces the complexity of directly referring to the
Hamiltonian discussed in the global axis.",2311.16669v1
2024-01-11,Suppressed Kondo screening in two-dimensional altermagnets,"We have studied the Kondo effect of a spin-1/2 impurity coupled to a
two-dimensional altermagnet host material. To attain the low-temperature
many-body Kondo physics of the system, we have performed a numerical
renormalization group calculations that allows us to access the spectral
properties of the system at zero temperature. The impurity spectral function
and the Kondo temperature were calculated for different set of parameters,
including Rashba spin-orbit coupling (RSOC) and an external magnetic field.
Interestingly, in the RSOC and altermagnetic fields, the hybridization function
is spin independent, despite the characteristic broken time-reversal symmetry
of the altermagnet. This is because the alternating sign of the spin splitting
of the bands in the momentum space renders equal contributions for both spin
components of the hybridization function. Our results demonstrate that,
although the hybridization function is time-reversal symmetric, the Kondo
temperature is substantially suppressed by the altermagnet coupling. Moreover,
we have investigated the effect of an external magnetic field applied in the
altermagnet along different directions. Interestingly, we observe an important
restraining of the Kondo peak which depends strongly on the direction of the
field. This anisotropic effect is, however, masked if strong Zeeman splitting
takes place at the impurity, as it shatters the Kondo-singlet state.",2401.06065v2
2011-03-03,Impurity effects on semiconductor quantum bits in coupled quantum dots,"We theoretically consider the effects of having unintentional charged
impurities in laterally coupled two-dimensional double (GaAs) quantum dot
systems, where each dot contains one or two electrons and a single charged
impurity in the presence of an external magnetic field. Using molecular orbital
and configuration interaction method, we calculate the effect of the impurity
on the 2-electron energy spectrum of each individual dot as well as on the
spectrum of the coupled-double-dot 2-electron system. We find that the
singlet-triplet exchange splitting between the two lowest energy states, both
for the individual dots and the coupled dot system, depends sensitively on the
location of the impurity and its coupling strength (i.e. the effective charge).
A strong electron-impurity coupling breaks down equality of the two
doubly-occupied singlets in the left and the right dot leading to a mixing
between different spin singlets. As a result, the maximally entangled qubit
states are no longer fully obtained in zero magnetic field case. Moreover, a
repulsive impurity results in a triplet-singlet transition as the impurity
effective charge increases or/and the impurity position changes. We comment on
the impurity effect in spin qubit operations in the double dot system based on
our numerical results.",1103.0767v2
2022-01-17,Chiral multiple-q and skyrmion phases induced by Rashba-Hund interactions in the kagome lattice,"Engineering non trivial topological phases in materials, specially
skyrmion-like arrangements, has been of great interest in the last decade due
to its potential technological applications. In this work, we study a model of
electrons coupled to a magnetic texture in the kagome lattice interacting with
magnetic moments via Rashba spin orbit coupling in the large Hund interaction
limit. We obtain the effective spin Hamiltonian and study the emergent low
temperature phases under an external magnetic field using large scale Monte
Carlo simulations. We show that strong geometric frustration, characteristic of
the kagome lattice, and the competition between the effective exchange,
antisymmetric and anisotropic couplings, gives rise to a large variety of
non-trivial topological phases. On the one hand, for antiferromagnetic exchange
coupling a pseudo-antiferromagnetic skyrmion crystal is stabilized for a broad
range of parameters. As the exchange coupling gets smaller, chiral single-q and
double-q phases emerge. On the other hand, in the ferromagnetic case, even
though the competition of the different interactions produce a series of exotic
textures, a remarkable parallel may be drawn with the pure ferromagnetic model
with antisymmetric interactions. Finally, for the special case where the
exchange coupling is completely suppressed, we show that, coming from a higher
temperature cooperative paramagnet, an ""umbrella-like"" plaquette order with
semiextensive degeneracy is induced by the external magnetic field.",2201.06668v2
2007-03-18,Equilibrium spin currents in the Rashba medium,"We analyze equilibrium spin currents in a 2D electron gas with Rashba
spin-orbit interaction (Rashba medium). In a uniform Rashba medium these
currents are constant, and their ability to really transport spin is not
evident. But even weak inhomogeneity of the Rashba medium allows to reveal that
equilibrium spin currents can transport spin from areas where spin is produced
to areas where spin is absorbed.",0703468v1
2009-09-17,Edge spin accumulation: spin Hall effect without bulk spin current,"Spin accumulation in a 2D electron gas with Rashba spin-orbit interaction
subject to an electric field can take place without bulk spin currents (edge
spin Hall effect). This is demonstrated for the collisional regime using the
non-equilibrium distribution function determined from the standard Boltzmann
equation. Spin accumulation originates from interference of incident and
reflected electron waves at the sample boundary.",0909.3156v1
2000-08-15,Electronic Structure and Fermiology of Sr$_3$Ru$_2$O$_7$,"The electronic structure of layered Sr$_{3}$Ru$_{2}$O$_{7}$ in its
orthorhombic structure is investigated using density functional calculations.
The band structure near the Fermi energy, consists of Ru $% t_{2g}$ states
hybridized with O $p$ orbitals. The $yz$ and $xz$ bands, which are largely
responsible for the nesting related antiferromagnetic spin fluctuations in
Sr$_{2}$RuO$_{4}$ split pairwise into even and odd combinations due to the
interlayer coupling reducing the strength of the nesting. The $xy$ bands show
much less interplanar coupling as expected, and also less $c$-axis dispersion,
so that the barrel like sections are largely intact compared to the single
layer material. The zone folding due to orthorhombicity yields small
cylindrical lens shaped Fermi surfaces centered at the midpoints of the former
tetragonal $\Gamma -X$ lines. Fixed spin moment calculations indicate that
tetragonal Sr$_{3}$Ru$_{2}$O$_{7}$ is borderline ferromagnetic but that
orthorhombicity favors magnetism via a substantial magnetoelastic coupling.
These results are related to experimental observations particularly in regard
to magnetic properties.",0008220v1
2004-11-24,Electronic States and Magnetism of Mn Impurities and Dimers in Narrow-Gap and Wide-Gap III-V Semiconductors,"Electronic states and magnetic properties of single $Mn$ impurity and dimer
doped in narrow-gap and wide-gap $III$-$V$ semiconductors have been studied
systematically. It has been found that in the ground state for single $Mn$
impurity, $Mn$-$As(N)$ complex is antiferromagnetic (AFM) coupling when $p$-$d$
hybridization $V_{pd}$ is large and both the hole level $E_{v}$ and the
impurity level $E_{d}$ are close to the midgap; or very weak ferromagnetic (FM)
when $V_{pd}$ is small and both $E_{v}$ and $E_d$ are deep in the valence band.
In $Mn$ dimer situation, the $Mn$ spins are AFM coupling for half-filled or
full-filled $p$ orbits; on the contrast, the Mn spins are double-exchange-like
FM coupling for any $p$-orbits away from half-filling. We propose the strong
{\it p-d} hybridized double exchange mechanism is responsible for the FM order
in diluted $III$-$V$ semiconductors.",0411598v1
2006-01-25,Anomalous Hall Effect due to the spin chirality in the Kagomé lattice,"We consider a model for a two dimensional electron gas moving on a kagom\'{e}
lattice and locally coupled to a chiral magnetic texture. We show that the
transverse conductivity $\sigma\_{xy}$ does not vanish even if spin-orbit
coupling is not present and it may exhibit unusual behavior. Model parameters
are the chirality, the number of conduction electrons and the amplitude of the
local coupling. Upon varying these parameters, a topological transition
characterized by change of the band Chern numbers occur. As a consequence,
$\sigma\_{xy}$ can be quantized, proportional to the chirality or have a non
monotonic behavior upon varying these parameters.",0601583v1
2006-02-23,Dynamical magneto-electric coupling in helical magnets,"Collective mode dynamics of the helical magnets coupled to electric
polarization via spin-orbit interaction is studied theoretically. The soft
modes associated with the ferroelectricity are not the transverse optical
phonons, as expected from the Lyddane-Sachs-Teller relation, but are the spin
waves hybridized with the electric polarization. This leads to the Drude-like
dielectric function $\epsilon(\omega)$ in the limit of zero magnetic
anisotropy. There are two more low-lying modes; phason of the spiral and
rotation of helical plane along the polarization axis. The roles of these soft
modes in the neutron scattering and antiferromagnetic resonance are revealed,
and a novel experiment to detect the dynamical magneto-electric coupling is
proposed.",0602547v1
2002-10-10,Covariant L-S Scheme for the effective N*NM couplings,"For excited nucleon states $N^*$ of arbitrary spin coupling to nucleon (N)
and meson (M), we propose a Lorentz covariant orbital-spin (L-S) scheme for the
effective $N^*NM$ couplings. To be used for the partial wave analysis of
various $N^*$ production and decay processes, it combines merits of two
conventional schemes, {\sl i.e.}, covariant effective Lagrangian approach and
multipole analysis with amplitudes expanded according to angular momentum L. As
examples, explicit formulae are given for $N^*\to N\pi$, $N^*\to N\omega$ and
$\psi\to N^*\bar N$ processes which are under current experimental studies.",0210164v1
2010-03-24,Ultrafast Electron Dynamics Theory of Photo-excited Ruthenium Complexes,"An explanation is provided for the ultrafast photo-excited electron dynamics
in low-spin Ruthenium (II) organic complexes. The experimentally-observed
singlet to triplet decay in the metal-to-ligand charge-transfer (MLCT) states
contradicts the expectation that the system should oscillate between the
singlet and triplet states in the presence of a large spin-orbit coupling and
the absence of a significance change in metal-ligand bond length. This dilemma
is solved with a novel quantum decay mechanism that causes a singlet to triplet
decay in about 300 femtoseconds. The decay is mediated by the triplet
metal-centered state ($^3$MC) state even though there is no direct coupling
between the $^1$MLCT and $^3$MC states. The coupling between the $^3$MLCT and
$^3$MC via excited phonon states leads to vibrational cooling that allows the
local system to dissipate the excess energy. In the relaxed state, the
population of the $^3$MC state is low and the metal-ligand bond length is
almost unchanged with respect to the initial photoexcited state, in agreement
with experiment.",1003.4752v1
2010-10-03,Entanglement Transfer via XXZ Heisenberg chain with DM Interaction,"The role of spin-orbit interaction, arises from the Dzyaloshinski-Moriya
anisotropic antisymmetric interaction, on the entanglement transfer via an
antiferromagnetic XXZ Heisenberg chain is investigated. From symmetrical point
of view, the XXZ Hamiltonian with Dzyaloshinski-Moriya interaction can be
replaced by a modified XXZ Hamiltonian which is defined by a new exchange
coupling constant and rotated Pauli operators. The modified coupling constant
and the angle of rotations are depend on the strength of Dzyaloshinski-Moriya
interaction. In this paper we study the dynamical behavior of the entanglement
propagation through a system which is consist of a pair of maximally entangled
spins coupled to one end of the chain. The calculations are performed for the
ground state and the thermal state of the chain, separately. In both cases the
presence of this anisotropic interaction make our channel more efficient, such
that the speed of transmission and the amount of the entanglement are improved
as this interaction is switched on. We show that for large values of the
strength of this interaction a large family of XXZ chains becomes efficient
quantum channels, for whole values of an isotropy parameter in the region $-2
\leq \Delta \leq 2$.",1010.0387v1
2013-03-01,Magnetic field dependence of Raman coupling in Alkali atoms,"We calculate the magnetic field dependence of Rabi rates for two-photon
optical Raman processes in alkali atoms. Due to a decoupling of the nuclear and
electronic spins, these rates fall with increasing field. At the typical
magnetic fields of alkali atom Feshbach resonances (B\sim 200G-1200G), the
Raman rates have the same order of magnitude as their zero field values,
suggesting one can combine Raman-induced gauge fields/spin-orbital coupling
with strong Feshbach-induced interactions. The exception is $^6$Li, where there
is a factor of 7 suppression in the Raman coupling, compared to its already
small zero-field value.",1303.0061v2
2014-02-05,Diabolical points in multi-scatterer optomechanical systems,"Diabolical points, which originate from parameter-dependent accidental
degeneracies of a system's energy levels, have played a fundamental role in the
discovery of the Berry phase as well as in photonics (conical refraction), in
chemical dynamics, and more recently in novel materials such as graphene, whose
electronic band structure possess Dirac points. Here we discuss diabolical
points in an optomechanical system formed by multiple scatterers in an optical
cavity with periodic boundary conditions. Such configuration is close to
experimental setups using micro-toroidal rings with indentations or near-field
scatterers. We find that the optomechanical coupling is no longer an analytic
function near the diabolical point and demonstrate the topological phase
arising through the mechanical motion. Similar to a Fabry-Perot resonator, the
optomechanical coupling can grow with the number of scatterers. We also
introduce a minimal quantum model of a diabolical point, which establishes a
connection to the motion of an arbitrary-spin particle in a 2D parabolic
quantum dot with spin-orbit coupling.",1402.0926v2
2014-07-14,Applications of the tensor pomeron model to exclusive central diffractive meson production,"We discuss exclusive central diffractive production of scalar ($f_{0}(980)$,
$f_{0}(1370)$, $f_{0}(1500)$), pseudoscalar ($\eta$, $\eta'(958)$), and vector
($\rho^{0}$) mesons in proton-proton collisions. We show that high-energy
central production of mesons could provide crucial information on the spin
structure of the soft pomeron. The amplitudes are formulated in terms of
effective vertices respecting standard rules of Quantum Field Theory and
propagators for the exchanged pomeron and reggeons. For the scalar and
pseudoscalar meson production, in most cases, two lowest orbital angular
momentum - spin couplings are necessary to describe WA102 experimental
differential distributions. Different pomeron-pomeron-meson tensorial
(vectorial) coupling structures are possible in general. For the $\rho^{0}$
production the photon-tensor pomeron/reggeon exchanges are considered and the
coupling parameters are fixed from the H1 and ZEUS experimental data of the
$\gamma p \to \rho^{0} p$ reaction. We present first predictions of this
mechanism for the $pp \to pp (\rho^{0} \to \pi^{+} \pi^{-})$ reaction being
studied at COMPASS, RHIC, Tevatron, and LHC. We analyse influence of the
experimental cuts on integrated cross section and various differential
distributions for produced mesons.",1407.3649v1
2015-06-01,Lattice correlation of Hubbard excitons in a Mott insulator Sr2IrO4 and reconstruction of their hopping dynamics via time-dependent coherence analysis of the Bragg diffraction,"In correlated oxides the coupling of quasiparticles to other degrees of
freedom such as spin and lattice plays critical roles in the emergence of
symmetry-breaking quantum ordered states such as high temperature
superconductivity. We report a strong lattice coupling of photon induced
Hubbard excitonic quasiparticles in spin-orbital coupling Mott insulator
Sr2IrO4. Combining time-resolved optical spectroscopy techniques, we further
reconstructed spatiotemporal map of the diffusion of quasiparticles via
time-dependent coherence analysis of the x-ray Bragg diffraction peak. Due to
the unique electronic configuration of the exciton, the strong lattice
correlation is unexpected but extends the similarity between Sr2IrO4 and
cuprates under highly non-equilibrium conditions. The coherence analysis method
we developed may have important implications for characterizing the structure
and carrier dynamics in a wider group of oxide heterostructures.",1506.00630v1
2015-06-10,Quantum Anomalous Hall Effect of Magnetic Topological Insulator Thin Films by Phase Boundary Engineering,"We generalize the topological phase diagram of magnetic topological insulator
(TI) thin films in an extended parameter space comprising out-of-plane (OP) and
in-plane (IP) exchange fields in the presence of structural inversion asymmetry
(SIA) while taking a generic orbital-dependent spin coupling allowed for TIs
into consideration. The results show that an IP field substantially deforms
phase boundaries and generically induces the quantum anomalous Hall (QAH)
effect. For symmetric spin coupling, extremely weak OP and IP exchange fields
create the QAH state by tuning SIA with a gate bias. For antisymmetric
coupling, the QAH phase is absent without a strong enough IP field. These
findings demonstrate that in the thin-film regime, engineering the phase
boundary is a key process to efficiently realize and manipulate the QAH effect
for nondissipative electronic applications.",1506.03191v3
2017-04-05,Spin-Frustrated Pyrochlore Chains in the Volcanic Mineral Kamchatkite (KCu3OCl(SO4)2),"Search of new frustrated magnetic systems is of a significant importance for
physics studying the condensed matter. The platform for geometric frustration
of magnetic systems can be provided by copper oxocentric tetrahedra (OCu4)
forming the base of crystalline structures of copper minerals from Tolbachik
volcanos in Kamchatka. The present work was devoted to a new frustrated
antiferromagnetic - kamchatkite (KCu3OCl(SO4)2). The calculation of the sign
and strength of magnetic couplings in KCu3OCl(SO4)2 has been performed on the
basis of structural data by the phenomenological crystal chemistry method with
taking into account corrections on the Jahn-Teller orbital degeneracy of Cu2.
It has been established that kamchatkite (KCu3OCl(SO4)2) contains AFM
spin-frustrated chains of the pyrochlore type composed of cone-sharing Cu4
tetrahedra. Strong AFM intrachain and interchain couplings compete with each
other. Frustration of magnetic couplings in tetrahedral chains is combined with
the presence of electric polarization.",1704.01324v3
2017-10-18,Cluster-glass phase in pyrochlore XY antiferromagnets with quenched disorder,"We study the impact of quenched disorder (random exchange couplings or site
dilution) on easy-plane pyrochlore antiferromagnets. In the clean system,
order-by-disorder selects a magnetically ordered state from a classically
degenerate manifold. In the presence of randomness, however, different orders
can be chosen locally depending on details of the disorder configuration. Using
a combination of analytical considerations and classical Monte-Carlo
simulations, we argue that any long-range-ordered magnetic state is destroyed
beyond a critical level of randomness where the system breaks into magnetic
domains due to random exchange anisotropies, becoming, therefore, a glass of
spin clusters, in accordance with the available experimental data. These random
anisotropies originate from off-diagonal exchange couplings in the microscopic
Hamiltonian, establishing their relevance to other magnets with strong
spin-orbit coupling.",1710.06658v2
2020-01-30,Fluctuation-driven superconductivity in Sr$_2$RuO$_4$ from weak repulsive interactions,"We provide results for the leading superconducting instabilities for a model
pertaining to Sr$_2$RuO$_4$ obtained within spin-fluctuation mediated
superconductivity in the very weak-coupling limit. The theory incorporates
spin-orbit coupling (SOC) effects both in the band structure and in the pairing
kernel in the form of associated magnetic anisotropies. The leading
superconducting phase is found to be $d_{x^2-y^2}$ and a nodal $s$-wave state.
However, the odd-parity helical solution can become leading either for small
SOC and Hund's coupling $J$ in the weak $U$-limit, or in the opposite limit
with large SOC and $J$ at larger values of the Hubbard-$U$. The odd-parity
chiral solution is never found to be leading. Finally we discuss the form of
the resulting superconducting spectral gaps in the different explored parameter
regimes.",2001.11265v1
2017-04-29,"Observation, Evidence and Origin of Room Temperature Magnetodielectric Effect in Mn doped LaGaO3","We report an observation of room temperature magnetodielectric (RTMD) effect
in Mn doped LaGaO3. Results of frequency dependent magnetoresistance (FDMR)
measurements discards the possibility of any magnetoresistive contribution in
the observed MD effect. The intrinsic nature of MD coupling has been
validated/evidenced by means of magnetic field dependent Raman spectroscopy and
explained in terms of modified volume strain governed by magnetic field induced
rerotation of spin coupled Mn-orbitals. Ultimately, present RTMD effect is
attributed to magneto-compression/magnetostriction associated with spin-phonon
coupling as evidenced in the form of magnetic field induced hardening of
symmetric stretching (SS) MnO6 octahedral Raman modes. Presently studied Mn
doped LaGaO3 can be a candidate for magnetodielectric applications.",1705.00184v1
2019-08-30,"Ising superconductors: Interplay of magnetic field, triplet channels, and disorder","We study the superconducting instability in disordered non-centrosymmetric
monolayers with intrinsic Ising spin-orbit coupling (SOC) subjected to an
in-plane Zeeman magnetic field. The pairing interaction contains the channels
allowed by crystal symmetry, such that in general, the pairing state is a
mixture of singlet and triplet Cooper pairs. The joint action of SOC and Zeeman
field selects a specific in-plane $\mathbf{d}$-vector triplet component to
couple with the singlets, which gains robustness against disorder through the
coupling. The out-of-plane $\mathbf{d}$-vector component, that in the clean
case is immune to both the Zeeman field and SOC is obliterated by a very small
impurity scattering rate. We formulate the quasi-classical theory of Ising
superconductors and solve the linearized Eilenberger equations to obtain the
pair-breaking equations that determine the Zeeman field -- temperature
dependence of the continuous superconducting transition. Our discussion
emphasizes how the Zeeman field, SOC and disorder affect the different
superconducting order parameters, and we show how the spin-fields inevitably
induce odd-frequency pairing correlations.",1908.11662v2
2016-03-24,Composite Topological Excitations in Ferromagnet-Superconductor Heterostructures,"We investigate the formation of a new type of composite topological
excitation -- the skyrmion-vortex pair (SVP) -- in hybrid systems consisting of
coupled ferromagnetic and superconducting layers. Spin-orbit interaction in the
superconductor mediates a magnetoelectric coupling between the vortex and the
skyrmion, with a sign (attractive or repulsive) that depends on the topological
indices of the constituents. We determine the conditions under which a bound
SVP is formed, and characterize the range and depth of the effective binding
potential through analytical estimates and numerical simulations. Furthermore,
we develop a semiclassical description of the coupled skyrmion-vortex dynamics
and discuss how SVPs can be controlled by applied spin currents.",1603.07550v2
2016-03-30,Implementation of Chiral Quantum Optics with Rydberg and Trapped-ion Setups,"We propose two setups for realizing a chiral quantum network, where two-level
systems representing the nodes interact via directional emission into discrete
waveguides, as introduced in T. Ramos et al. [Phys. Rev. A 93, 062104 (2016)].
The first implementation realizes a spin waveguide via Rydberg states in a
chain of atoms, whereas the second one realizes a phonon waveguide via the
localized vibrations of a string of trapped ions. For both architectures, we
show that strong chirality can be obtained by a proper design of synthetic
gauge fields in the couplings from the nodes to the waveguide. In the Rydberg
case, this is achieved via intrinsic spin-orbit coupling in the dipole-dipole
interactions, while for the trapped ions it is obtained by engineered sideband
transitions. We take long-range couplings into account that appear naturally in
these implementations, discuss useful experimental parameters, and analyze
potential error sources. Finally, we describe effects that can be observed in
these implementations within state-of-the-art technology, such as the
driven-dissipative formation of entangled dimer states.",1603.09097v2
2016-10-26,Spontaneous structural distortion of metallic Shastry-Sutherland system DyB4 by quadrupole-spin-lattice coupling,"DyB4 has a two-dimensional Shastry-Sutherland (Sh-S) lattice with strong
Ising character of the Dy ions. Despite the intrinsic frustrations,
surprisingly, it undergoes two successive transitions: a magnetic ordering at
TN = 20K, and a quadrupole ordering at TQ=12.5 K. From high-resolution neutron
and synchrotron X-ray powder diffraction studies, we have obtained full
structural information on this material in all phases, and demonstrate that
structural modifications occurring at quadrupolar transition lead to the
lifting of frustrations inherent in the Sh-S model. Our study thus provides a
complete experimental picture of how the intrinsic frustration of the Sh-S
lattice can be lifted by the coupling to quadrupole moments. We show that two
other factors, i.e. strong spin-orbit coupling and long-range RKKY interaction
in metallic DyB4, play an important role in this behavior.",1610.08215v1
2018-10-06,Origin of topologically trivial states and topological phase transitions in low-buckled plumbene,"Combining tight-binding (TB) models with first-principles calculations, we
investigate electronic and topological properties of plumbene. Different from
the other two-dimensional (2D) topologically nontrivial insulators in group IVA
(from graphene to stanene), low-buckled plumbene is a topologically trivial
insulator. The plumbene without spin-orbit coupling exhibits simultaneously two
kinds of degeneracies, i.e., quadratic non-Dirac and linear Dirac band
dispersions around the \Gamma and K/K' points, respectively. Our TB model
calculations show that it is the coupling between the two topological states
around the \Gamma and K/K' points that triggers the global topologically
trivial property of plumbene. Quantum anomalous Hall effects with Chern numbers
of 2 or -2 can be, however, achieved after an exchange field is introduced.
When the plumbene is functionalized with ethynyl (PbC2H), quantum spin Hall
effects appear due to the breaking of the coupling effect of the local
topological states.",1810.02934v1
2021-12-22,Topological magnon modes on honeycomb lattice with coupling textures,"Topological magnon modes are expected to be useful for novel applications
such as robust information propagation, since they are immune to backscattering
and robust against disorder. Although there are several of theoretical
proposals for topological magnon modes and growing experimental efforts for
realizing them by now, it is still desirable to add complementary insights on
this important phenomenon. Here, we propose a new scheme to achieve topological
magnon where only nearest-neighbour exchange couplings on honeycomb lattice are
necessary. In both ferromagnets and antiferromagnets, tuning exchange couplings
between and inside hexagonal unit cells induces a topological state accompanied
by a band inversion between p-orbital and d-orbital like magnon modes.
Topological magnon modes appear at the interface between a topological domain
and a trivial domain with magnon currents, which counterpropagate depending on
pseudospins originated from orbital angular momenta of magnon modes. This
mimics the spin-momentum locking phenomenon in the quantum spin Hall effect.",2112.11652v1
2021-12-28,Two-dimensional Paired Topological Superfluids of Rydberg Fermi Gases,"We systematically investigate the topological properties of spin polarized
Rydberg-dressed fermionic atoms loaded in a bilayer optical lattice. Through
tuning the Rydberg coupling strength and the inter-layer tunneling amplitude,
we identify different types of topological superfluid states generated from the
inter-layer pairing and relative gauge phase modulation of the couples 2D
$p$-wave superfluids. These phases includes gapped/gapless with/without time
reversal symmetry. One of the most interesting states is a gapless paired
topological superfluid with both the time-reversal symmetry and particle-hole
symmetry. This state is equivalent to a topological Kondo lattice model with
the spin-orbit coupling, an in-plane magnetic field, and an additional
particle-hole symmetry. The flexibility of experimental manipulation in such
Rydberg-dressed ferminoic systems therefore becomes a promising system for
realizing interesting topological superfluids.",2112.14027v1
2022-03-12,Thermal entanglement and quantum coherence of a single electron in a double quantum dot with Rashba Interaction,"In this work, we study the thermal quantum coherence and fidelity in a
semiconductor double quantum dot. The device consists of a single electron in a
double quantum dot with Rashba spin-orbit coupling in the presence of an
external magnetic field. In our scenario, the thermal entanglement of the
single electron is driven by the charge and spin qubits, the latter controlled
by Rashba coupling. Analytical expressions are obtained for thermal concurrence
and correlated coherence using the density matrix formalism. The main goal of
this work is to provide a good understanding of the effects of temperature and
several parameters in quantum coherence. In addition, our findings show that we
can use the Rashba coupling to tune in the thermal entanglement, quantum
coherence, as well as, the thermal fidelity behavior of the system. Moreover,
we focus on the role played by thermal entanglement and correlated coherence
responsible for quantum correlations. We observe that the correlated coherence
is more robust than the thermal entanglement in all cases, so quantum
algorithms based only on correlated coherence may be stronger than those based
on entanglement.",2203.06301v2
2022-04-07,Topological multiferroic order in twisted transition metal dichalcogenide bilayers,"Layered van der Waals materials have risen as powerful platforms to
artificially engineer correlated states of matter. Here we show the emergence
of a multiferroic order in a twisted dichalcogenide bilayer superlattice at
quarter-filling. We show that the competition between Coulomb interactions
leads to the simultaneous emergence of ferrimagnetic and ferroelectric orders.
We derive the magnetoelectric coupling for this system, which leads to a direct
strong coupling between the charge and spin orders. We show that, due to
intrinsic spin-orbit coupling effects, the electronic structure shows a
non-zero Chern number, thus displaying a topological multiferroic order. We
show that this topological state gives rise to interface modes at the different
magnetic and ferroelectric domains of the multiferroic. We demonstrate that
these topological modes can be tuned with external electric fields as well as
triggered by supermoire effects generated by a substrate. Our results put
forward twisted van der Waals materials as a potential platform to explore
multiferroic symmetry breaking orders and, ultimately, controllable topological
excitations in magnetoelectric domains.",2204.03360v2
2022-04-27,Accurate core excitation and ionization energies from a state-specific coupled-cluster singles and doubles approach,"We investigate the use of orbital-optimized references in conjunction with
single-reference coupled-cluster theory with single and double substitutions
(CCSD) for the study of core excitations and ionizations of 18 small organic
molecules, without any use of response theory or equation-of-motion formalisms.
Three schemes are employed to successfully address the convergence difficulties
associated with the coupled-cluster equations, and the spin contamination
resulting from the use of a spin symmetry-broken reference, in the case of
excitations. In order to gauge the inherent potential of the methods studied,
an effort is made to provide reasonable basis set limit estimates for the
transition energies. Overall, we find that the two best-performing schemes
studied here for Delta-CCSD are capable of predicting excitation and ionization
energies with errors comparable to experimental accuracies. The proposed
Delta-CCSD schemes seem to fare better than the widely used equation-of-motion
CCSD (EOM-CCSD) with core-valence separation protocol, with statistical errors
being reduced by more than a factor of two when compared to FC-CVS-EOM-CCSD.",2204.13056v2
2023-06-30,Achiral dipoles on a ferromagnet can affect its magnetization direction,"We demonstrate the possibility of a coupling between the magnetization
direction of a ferromagnet and the tilting angle of adsorbed achiral molecules.
To illustrate the mechanism of the coupling, we analyze a minimal Stoner model
that includes Rashba spin-orbit coupling due to the electric field on the
surface of the ferromagnet. The proposed mechanism allows us to study magnetic
anisotropy of the system with an extended Stoner-Wohlfarth model, and argue
that adsorbed achiral molecules can change magnetocrystalline anisotropy of the
substrate. Our research's aim is to motivate further experimental studies of
the current-free chirality induced spin selectivity effect involving both
enantiomers.",2306.17592v2
2023-08-15,Controlling Majorana hybridization in magnetic chain-superconductor systems,"We propose controlling the hybridization between Majorana zero modes at the
ends of magnetic adatom chains on superconductors by an additional magnetic
adatom deposited close by. By tuning the additional adatom's magnetization,
position, and coupling to the superconductor, we can couple and decouple the
Majorana modes as well as control the ground state parity. The scheme is
independent of microscopic details in ferromagnetic and helical magnetic chains
on superconductors with and without spin-orbit coupling, which we show by
studying their full microscopic models and their common low-energy description.
Our results show that scanning tunneling microscopy and electron spin resonance
techniques are promising tools for controlling the Majorana hybridization in
magnetic adatoms-superconductor setups, providing a basis for Majorana parity
measurements, fusion, and braiding techniques.",2308.07961v2
2023-10-06,Spin-Mediated Direct Photon Scattering by Plasmons in BiTeI,"We use polarization resolved Raman spectroscopy to demonstrate that for a 3D
giant Rashba system the bulk plasmon collective mode can directly couple to the
Raman response even in the long wavelength $\mathbf q \rightarrow 0$ limit.
Although conventional theory predicts the plasmon spectral weight to be
suppressed as the square of its quasi-momentum and thus negligibly weak in the
Raman spectra, we observe a sharp in-gap plasmon mode in the Raman spectrum of
BiTeI below the Rashba continuum. This coupling, in a polar system with
spin-orbit coupling, occurs without assistance from phonons when the incoming
photon excitation is resonant with Rashba-split intermediate states. We discuss
the distinctive features of BiTeI's giant Rashba system band structure that
enable the direct observation of plasmon in Raman scattering.",2310.04394v2
2023-10-12,Effective potential engineering by emergent anisotropy in a tunable open-access microcavity,"Photonic spin-orbit (SO) coupling is an important physical mechanism leading
to numerous interesting phenomena in the systems of microcavity photons and
exciton-polaritons. We report the effect of SO coupling in a tunable
open-access microcavity embedded with anisotropic active media. The SO coupling
associated with the TE-TM splitting results in an emergent anisotropy, which
further leads to fine energy splittings allowing clear observation of the full
set of eigenstates, in sharp contrast with the isotropic situation which leads
to the isotropic eigenstates of spin vortices. We show that the photonic
potential can be engineered by playing with the relation between the emergent
anisotropy and the cavity ellipticity. All the experimental results are well
reproduced by the degenerate perturbation theory. Our results constitute a
significant extension to the research field of microcavity spinoptronics, with
potential applications in polarization control and optical property measurement
of photonic devices and materials.",2310.08024v1
2024-03-25,Rotational Doppler Effect and Spin-Rotation Coupling,"The Rotational Doppler Effect (RDE) involves both the orbital angular
momentum of electromagnetic radiation as well as its helicity. The RDE
phenomena associated with photon helicity go beyond the standard theory of
relativity. The purpose of this paper is to elucidate the theoretical basis of
the helicity-dependent RDE in terms of the general phenomenon of spin-rotation
coupling. The physical implications of this coupling are briefly pointed out
and the nonlocal theory of rotating observers is described. For an observer
rotating uniformly about the direction of incidence of a plane wave of definite
helicity, the nonlocally measured amplitude of the wave is larger (smaller) if
the observer rotates in the same (opposite) sense as the electromagnetic field.
The implications of the nonlocal helicity dependence of the measured amplitude
of the radiation are briefly discussed.",2403.17151v1
2012-08-30,Spin Evolution of Supermassive Black Holes and Galactic Nuclei,"The spin angular momentum S of a supermassive black hole (SBH) precesses due
to torques from orbiting stars, and the stellar orbits precess due to dragging
of inertial frames by the spinning hole. We solve the coupled post-Newtonian
equations describing the joint evolution of S and the stellar angular momenta
Lj, j = 1...N in spherical, rotating nuclear star clusters. In the absence of
gravitational interactions between the stars, two evolutionary modes are found:
(1) nearly uniform precession of S about the total angular momentum vector of
the system; (2) damped precession, leading, in less than one precessional
period, to alignment of S with the angular momentum of the rotating cluster.
Beyond a certain distance from the SBH, the time scale for angular momentum
changes due to gravitational encounters between the stars is shorter than
spin-orbit precession times. We present a model, based on the
Ornstein-Uhlenbeck equation, for the stochastic evolution of star clusters due
to gravitational encounters and use it to evaluate the evolution of S in nuclei
where changes in the Lj are due to frame dragging close to the SBH and to
encounters farther out. Long-term evolution in this case is well described as
uniform precession of the SBH about the cluster's rotational axis, with an
increasingly important stochastic contribution when SBH masses are small. Spin
precessional periods are predicted to be strongly dependent on nuclear
properties, but typical values are 10-100 Myr for low-mass SBHs in dense
nuclei, 100 Myr - 10 Gyr for intermediate mass SBHs, and > 10 Gyr for the most
massive SBHs. We compare the evolution of SBH spins in stellar nuclei to the
case of torquing by an inclined, gaseous accretion disk.",1208.6274v1
2022-01-18,On-demand electrical control of spin qubits,"Once called a ""classically non-describable two-valuedness"" by Pauli , the
electron spin is a natural resource for long-lived quantum information since it
is mostly impervious to electric fluctuations and can be replicated in large
arrays using silicon quantum dots, which offer high-fidelity control.
Paradoxically, one of the most convenient control strategies is the integration
of nanoscale magnets to artificially enhance the coupling between spins and
electric field, which in turn hampers the spin's noise immunity and adds
architectural complexity. Here we demonstrate a technique that enables a
\emph{switchable} interaction between spins and orbital motion of electrons in
silicon quantum dots, without the presence of a micromagnet. The naturally weak
effects of the relativistic spin-orbit interaction in silicon are enhanced by
more than three orders of magnitude by controlling the energy quantisation of
electrons in the nanostructure, enhancing the orbital motion. Fast electrical
control is demonstrated in multiple devices and electronic configurations,
highlighting the utility of the technique. Using the electrical drive we
achieve coherence time $T_{2,{\rm Hahn}}\approx50 \mu$s, fast single-qubit
gates with ${T_{\pi/2}=3}$ ns and gate fidelities of 99.93 % probed by
randomised benchmarking. The higher gate speeds and better compatibility with
CMOS manufacturing enabled by on-demand electric control improve the prospects
for realising scalable silicon quantum processors.",2201.06679v2
2007-12-10,Quantum well states in Fe/Nb(001) multilayers: First principles study,"We present a first-principles study to understand the phenomena of interlayer
exchange coupling in Fe/Nb multilayers using the linearized-muffin-tin-orbitals
method within the generalized gradient approximation. We find that the exchange
coupling oscillates with both short and long periodicities, which have been
examined in terms of the Ruderman-Kittel-Kasuya-Yosida (RKKY) model as well as
the quantum well (QW) model. We have investigated the behavior of the exchange
coupling by artificially varying moments of Fe atoms in ferromagnetic layers.
For a small moment of Fe, the coupling shows bilinearity in the magnetic
moments, implying its RKKY character. However, at higher moments close to that
of bulk Fe, the saturation of long-period oscillations is in accordance with
the QW model. Quantum well dispersions around the Fermi level demonstrate that
the majority-spin bands contribute largely to the formation of quantum well
states, which we analyze quantitatively by making use of the phase accumulation
model. Our analysis indicates that the quantum well model gives a better
description of the oscillatory behavior of the exchange coupling in Fe/Nb
multilayers.",0712.1432v1
2010-07-08,Neutron and ARPES Constraints on the Couplings of the Multiorbital Hubbard Model for the Pnictides,"The results of neutron scattering and angle-resolved photoemission
experiments for the Fe-pnictide parent compounds, and their metallic nature,
are shown to impose severe constraints on the range of values that can be
considered ""realistic"" for the intraorbital Hubbard repulsion U and Hund
coupling J in multiorbital Hubbard models treated in the mean-field
approximation. Phase diagrams for three- and five-orbital models are here
provided, and the physically realistic regime of couplings is highlighted, to
guide future theoretical work into the proper region of parameters of Hubbard
models. In addition, using the random phase approximation, the pairing
tendencies in these realistic coupling regions are investigated. It is shown
that the dominant spin-singlet pairing channels in these coupling regimes
correspond to nodal superconductivity, with strong competition between several
states that belong to different irreducible representations. This is compatible
with experimental bulk measurements that have reported the existence of nodes
in several Fe-pnictide compounds.",1007.1436v3
2013-04-24,Graphene-mediated exchange coupling between cobaltocene and magnetic substrates,"Using first-principles calculations we demonstrate sizable exchange coupling
between a magnetic molecule and a magnetic substrate via a graphene layer. As a
model system we consider cobaltocene (CoCp$_2$) adsorbed on graphene deposited
on Ni(111). We find that the magnetic coupling between the molecule and the
substrate is antiferromagnetic and varies considerably depending on the
molecule structure, the adsorption geometry, and the stacking of graphene on
Ni(111). We show how this coupling can be tuned by intercalating a magnetic
monolayer, e.g. Fe or Co, between graphene and Ni(111). We identify the leading
mechanism responsible for the coupling to be the spatial and energy matching of
the frontier orbitals of CoCp$_2$ and graphene close to the Fermi level, and we
demonstrate the role of graphene as an electronic decoupling layer, yet
allowing spin communication between molecule and substrate.",1304.6665v1
2014-09-05,Long-range magnetic interaction and frustration in double perovskite Sr$_{2}$NiIrO$_{6}$,"Sr$_{2}$NiIrO$_{6}$ would be a ferromagnetic (FM) insulator in terms of the
common superexchange mechanism between the first nearest neighboring (1NN)
magnetic ions Ni$^{2+}$ ($t_{2g}^{6}e_{g}^{2}$) and Ir$^{6+}$ ($t_{2g}^{3}$).
However, the observed antiferromagnetic (AF) order questions this viewpoint. In
this work, we present first-principles calculations and find that while the 1NN
Ni$^{2+}$-Ir$^{6+}$ exchange is indeed FM, the 2NN and 3NN couplings in the fcc
Ir (and Ni) sublattice are AF. Moreover, the 2NN AF Ir-Ir coupling turns out to
be even stronger than the 1NN FM Ni-Ir coupling, thus giving rise to a magnetic
frustration. Sr$_{2}$NiIrO$_{6}$ hence becomes a distorted low-temperature
antiferromagnet. Naturally, a very similar magnetic property in
Sr$_{2}$ZnIrO$_{6}$ can be explained by the frustrated AF coupling in the fcc
Ir$^{6+}$ sublattice. This work highlights the long-range magnetic interaction
of the delocalized $5d$ electrons, and also addresses why the spin-orbit
coupling is ineffective here.",1409.1688v1
2016-04-12,"EPW: Electron-phonon coupling, transport and superconducting properties using maximally localized Wannier functions","The EPW (Electron-Phonon coupling using Wannier functions) software is a
Fortran90 code that uses density-functional perturbation theory and maximally
localized Wannier functions for computing electron-phonon couplings and related
properties in solids accurately and efficiently. The EPW v4 program can be used
to compute electron and phonon self-energies, linewidths, electron-phonon
scattering rates, electron-phonon coupling strengths, transport spectral
functions, electronic velocities, resistivity, anisotropic superconducting gaps
and spectral functions within the Migdal-Eliashberg theory. The code now
supports spin-orbit coupling, time-reversal symmetry in non-centrosymmetric
crystals, polar materials, and $\mathbf{k}$ and $\mathbf{q}$-point
parallelization. Considerable effort was dedicated to optimization and
parallelization, achieving almost a ten times speedup with respect to previous
releases. A computer test farm was implemented to ensure stability and
portability of the code on the most popular compilers and architectures. Since
April 2016, version 4 of the EPW code is fully integrated in and distributed
with the Quantum ESPRESSO package, and can be downloaded through QE-forge at
http://qe-forge.org/gf/project/q-e.",1604.03525v2
2010-05-17,Electronic structure and magnetic state of transuranium metals under pressure,"Electronic structure of bcc Np, fcc Pu, Am, and Cm pure metals under pressure
has been investigated employing the LDA+U method with spin-orbit coupling
(LDA+U+SO). Magnetic state of the actinide ions was analyzed in both LS and jj
coupling schemes to reveal the applicability of corresponding coupling bases.
It was demonstrated that whereas Pu and Am are well described within the jj
coupling scheme, Np and Cm can be described appropriately neither in {m-sigma},
nor in {jmj} basis, due to intermediate coupling scheme realizing in these
metals that requires some finer treatment. The LDA+U+SO results for the
considered transuranium metals reveal bands broadening and gradual 5f electron
delocalization under pressure.",1005.2851v1
2014-06-30,Nanophotonic control of circular dipole emission: toward a scalable solid-state to flying-qubits interface,"Controlling photon emission by single quantum emitters with nanostructures is
crucial for scalable on-chip quantum information processing. Nowadays
nanoresonators can affect the lifetime of emitters and ultimately induce strong
coupling between the emitters and the light field, while nanoantennas can
control the directionality of the emission. Expanding this control to the
manipulation of the emission of orbital angular momentum-changing transitions
would enable coupling between long-lived solid-state qubits and flying qubits.
As these transitions are associated with circular rather than linear dipoles,
such control requires detailed knowledge of the spatially dependent interaction
of a complex dipole with highly structured optical eigenstates containing local
helicity. Using a classical analogue, we experimentally map the coupling of
circular dipoles to photonic modes in a model structure, a photonic crystal
waveguide. We show that depending on the local helicity the dipoles can be made
to couple to modes either propagating to the left or to the right. The maps are
in excellent agreement with calculations. Our measurements, therefore,
demonstrate the coupling of spin to photonic pathway with near-unity (0.8 $\pm$
0.1) efficiency.",1406.7741v2
2016-03-31,Dirac Hamiltonian and Reissner-Nordstrom Metric: Coulomb Interaction in Curved Space-Time,"We investigate the spin-1/2 relativistic quantum dynamics in the curved
space-time generated by a central massive charged object (black hole). This
necessitates a study of the coupling of a Dirac particle to the
Reissner-Nordstrom space-time geometry and the simultaneous covariant coupling
to the central electrostatic field. The relativistic Dirac Hamiltonian for the
Reissner-Nordstrom geometry is derived. A Foldy-Wouthuysen transformation
reveals the presence of gravitational, and electro-gravitational spin-orbit
coupling terms which generalize the Fokker precession terms found for the
Dirac-Schwarzschild Hamiltonian, and other electro-gravitational correction
terms to the potential proportional to alpha^n G, where alpha is the
fine-structure constant, and G is the gravitational coupling constant. The
particle-antiparticle symmetry found for the Dirac-Schwarzschild geometry (and
for other geometries which do not include electromagnetic interactions) is
shown to be explicitly broken due to the electrostatic coupling. The resulting
spectrum of radially symmetric, electrostatically bound systems (with
gravitational corrections) is evaluated for example cases.",1603.09668v1
2022-03-02,Strong and tunable magnetoelectric coupling in 2D trilayer heterostructures,"The quest for electric-field control of nanoscale magnetic states such as
skyrmions, which would impact the field of spintronics, has led to a
challenging search for multiferroic materials or structures with strong
magnetoelectric coupling and efficient electric-field control. Here we report a
theoretical prediction that such phenomena can be realized in two-dimensional
(2D) bilayer FE/PMM and trilayer FE/PMM/FE heterostructures (two-terminal and
three-terminal devices), where FE is a 2D ferroelectric and PMM is a polar
magnetic metal with strong spin-orbit coupling. Such a PMM has strong
Dzyaloshinskii-Moriya interactions (DMI) that can generate skyrmions, while the
FE can generate strong magnetoelectric coupling through
polarization-polarization interactions. In trilayer heterostructures, contact
to the metallic PMM layer enables multiple polarization configurations for
electric-field control of skyrmions. We report density-functional-theory
calculations for particular material choices that demonstrate the effectiveness
of these arrangements, with the key driver being the polarization-polarization
interactions between the PMM and FE layers. The present findings provide a
method to achieve strong magnetoelectric coupling in the 2D limit and a new
perspective for the design of related spintronics.",2203.00884v2
2022-06-30,Uncertainty quantification of transition operators in the empirical shell model,"While empirical shell model calculations have successfully described
low-lying nuclear data for decades, only recently has significant effort been
made to quantify the uncertainty in such calculations. Here we quantify the
statistical error in effective parameters for transition operators in empirical
calculations in the $sd$ ($1s_{1/2}$-$0d_{3/2}$-$0d_{5/2}$) valence space,
specifically the quenching of Gamow-Teller transitions, effective charges for
electric quadrupole (E2) transitions, and the effective orbital and spin
couplings for magnetic dipole (M1) transitions. We find the quenching factor
for Gamow-Teller transitions relative to free-space values is tightly
constrained and that the isoscalar coupling of E2 is much more tightly
constrained than the isovector coupling. For effective M1 couplings, we found
isovector components more constrained than isoscalar, but that to get any
sensible result we had to fix one of four couplings. This detailed
quantification of uncertainties, while highly empirical, nonetheless is an
important step towards interpretation of experiments.",2206.14956v2
2008-09-18,Isospin phases of vertically coupled double quantum rings under the influence of perpendicular magnetic fields,"Vertically coupled double quantum rings submitted to a perpendicular magnetic
field $B$ are addressed within the local spin-density functional theory. We
describe the structure of quantum ring molecules containing up to 40 electrons
considering different inter-ring distances and intensities of the applied
magnetic field. When the rings are quantum mechanically strongly coupled, only
bonding states are occupied and the addition spectrum of the artificial
molecules resembles that of a single quantum ring, with some small differences
appearing as an effect of the magnetic field. Despite the latter has the
tendency to flatten the spectra, in the strong coupling limit some clear peaks
are still found even when $B\neq 0$ that can be interpretated from the
single-particle energy levels analogously as at zero applied field, namely in
terms of closed-shell and Hund's-rule configurations. Increasing the inter-ring
distance, the occupation of the first antibonding orbitals washes out such
structures and the addition spectra become flatter and irregular. In the weak
coupling regime, numerous isospin oscillations are found as a function of $B$.",0809.3103v1
2016-07-31,The twofold diabatization of the KRb $(1\sim 2)^1Π$ complex in the framework of \emph{ab initio} and deperturbation approaches,"We performed a diabatization of the mutually perturbed $1^1\Pi$ and $2^1\Pi$
states of KRb based on both electronic structure calculation and direct
coupled-channel deperturbation analysis of experimental energies. The potential
energy curves (PECs) of the diabatic states and their scalar coupling were
constructed from the \textit{ab initio} adiabatic PECs by analytically
integrating the radial $\langle \psi_1^{ad}|\partial /\partial
R|\psi_2^{ad}\rangle$ matrix element obtained by a finite-difference method.
The diabatic potentials and electronic coupling function were refined by the
least squares fitting of the rovibronic termvalues of the $1^1\Pi\sim 2^1\Pi$
complex. The empirical PECs combined with the coupling function as well as the
diabatized spin-orbit coupling and transition dipole matrix elements are useful
for further deperturbation treatment of both singlet and triplet states
manifold.",1608.00225v1
2017-12-11,Critical phenomena at the complex tensor ordering phase transition,"We investigate the critical properties of the phase transition towards
complex tensor order that has been proposed to occur in spin-orbit coupled
superconductors. For this purpose we formulate the bosonic field theory for
fluctuations of the complex irreducible second-rank tensor order parameter
close to the transition. We then determine the scale dependence of the
couplings of the theory by means of the perturbative Renormalization Group
(RG). For the isotropic system we generically detect a fluctuation-induced
first-order phase transition. The initial values for the running couplings are
determined by the underlying microscopic model for the tensorial order. As an
example we study three-dimensional Luttinger semimetals with electrons at a
quadratic band touching point. Whereas the strong-coupling transition of the
model receives substantial fluctuation corrections, the weak-coupling
transition at low temperatures is rendered only weakly first-order due to the
presence of a fixed point in the vicinity of the RG trajectory. If the number
of fluctuating complex components of the order parameter is reduced by cubic
anisotropy, the theory maps onto the field theory for frustrated magnetism.",1712.03981v2
2018-03-30,Interstate Vibronic Coupling Constants Between Electronic Excited States for Complex Molecules,"In the construction of diabatic vibronic Hamiltonians for quantum dynamics in
the excited-state manifold of molecules, the coupling constants are often
extracted solely from information on the excited-state energies. Here, a new
protocol is applied to get access to the interstate vibronic coupling constants
at the time-dependent density functional theory level through the overlap
integrals between excited-state adiabatic auxiliary wavefunctions. We discuss
the advantages of such method and its potential for future applications to
address complex systems, in particular those where multiple electronic states
are energetically closely lying and interact. As examples, we apply the
protocol to the study of prototype rhenium carbonyl complexes
[Re(CO)$_3$(N,N)(L)]$^{n+}$ for which non-adiabatic quantum dynamics within the
linear vibronic coupling model and including spin-orbit coupling have been
reported recently.",1803.11360v1
2018-06-09,Effective Long-Range Pairing and Hopping in Topological Nanowires Weakly Coupled to $ s $-Wave Superconductors,"In this Letter, we first formulate an effective theory, which generally
captures long-range proximity effects of a surface system weakly coupled to an
s-wave superconductor. The long-range proximity effects include both the
emergent long-range pairing and hopping interactions in the surface system. We
then model the Rashba spin-orbit-coupled nanowire in proximity with an s-wave
superconductor by taking into account the emergent nonlocal effects in the
weak-coupling limit. In this limit the induced superconducting pair potential
is found much smaller than that of the host superconductor, which is in good
agreement with recent experiments. Compared with the previously considered
strong coupling limit with local proximity effects, the long-range interactions
can significantly modify the topological phase diagram, and considerably lower
the threshold magnetic field for the emergence of Majorana zero modes.",1806.03399v1
2018-07-25,Tuning of non-paraxial effects of the Laguerre-Gaussian beam interacting with the two-component Bose-Einstein condensates,"We present the theory of microscopic interaction of the spin-orbit coupled
focused Laguerre-Gaussian (LG) beam with the two-component Bose-Einstein
condensate (BEC), composed of two hyperfine states of $^{87}$Rb in a harmonic
trap. We have shown that Raman Rabi frequency distributions over the
inter-component coupling identify phase separation coupling strength. A
significant enhancement of side-band transitions due to non-paraxial nature of
vortex beam is observed for particular values of inter-component coupling
around 1.25 and 0.64 in unit of 5.5nm for $10^5$ and $10^6$ number of atoms,
respectively. The uncertainty in the estimation of these coupling strengths is
improved with the focusing angles of the beam. We discuss an experimental
scheme to verify this non-paraxial effect on ultra-cold atoms.",1807.09733v2
2022-12-22,Reducing the frequency of the Higgs mode in a helical superconductor coupled to an LC-circuit,"We show that the amplitude, or Higgs mode of a superconductor with strong
spin-orbit coupling and an exchange field, couples linearly to the
electromagnetic field. Furthermore, by coupling such a superconductor to an LC
resonator, we demonstrate that the Higgs resonance becomes a regular mode at
frequencies smaller than the quasiparticle energy threshold $2\Delta$. We
finally propose and discuss a possible experiment based on microwave
spectroscopy for an unequivocal detection of the Higgs mode. Our approach may
allow visualizing Higgs modes also in more complicated multiband
superconductors with a coupling between the charge and other electronic degrees
of freedom.",2212.11615v1
2023-02-19,Anharmonic electron-phonon coupling in ultrasoft and locally disordered perovskites,"Anharmonicity and local disorder (polymorphism) are ubiquitous in perovskite
physics, inducing various phenomena observed in scattering and spectroscopy
experiments. Several of these phenomena still lack interpretation from
first-principles since, hitherto, no approach is available to account for
anharmonicity and disorder in electron-phonon couplings. Here, relying on the
special displacement method, we develop a unified treatment of both and
demonstrate that electron-phonon coupling is strongly influenced when we employ
polymorphous perovskite networks. We uncover that polymorphism in halide
perovskites leads to vibrational dynamics far from the ideal noninteracting
phonon picture and drives the gradual change in their band gap around phase
transition temperatures. We also clarify that combined band gap corrections
arising from disorder, spin-orbit coupling, exchange-correlation functionals of
high accuracy, and electron-phonon coupling are all essential. Our findings
agree with experiments, suggesting that polymorphism is the key to address
pending questions on perovskites' technological applications.",2302.09625v2
2005-07-06,The free precession and libration of Mercury,"An analysis based on the direct torque equations including tidal dissipation
and a viscous core-mantle coupling is used to determine the damping time scales
of O(10^5) years for free precession of the spin about the Cassini state and
free libration in longitude for Mercury. The core-mantle coupling dominates the
damping over the tides by one to two orders of magnitude for the plausible
parameters chosen. The short damping times compared with the age of the solar
system means we must find recent or on-going excitation mechanisms if such free
motions are found by the current radar experiments or the future measurement by
the MESSENGER and BepiColombo spacecraft that will orbit Mercury. We also show
that the average precession rate is increased by about 30% over that obtained
from the traditional precession constant because of a spin-orbit resonance
induced contribution by the C_{22} term in the expansion of the gravitational
field. The C_{22} contribution also causes the path of the spin during the
precession to be slightly elliptical with a variation in the precession rate
that is a maximum when the obliquity is a minimum. An observable free
precession will compromise the determination of obliquity of the Cassini state
and hence of C/MR^2 for Mercury, but a detected free libration will not
compromise the determination of the forced libration amplitude and thus the
verification of a liquid core",0507117v1
2009-09-10,Transverse force generated by an electric field and transverse charge imbalance in spin-orbit coupled systems,"We use linear response theory to study the transverse force generated by an
external electric field and hence possible charge Hall effect in spin-orbit
coupled systems. In addition to the Lorentz force that is parallel to the
electric field, we find that the transverse force perpendicular to the applied
electric field may not vanish in a system with an anisotropic energy
dispersion. Surprisingly, in contrast to the previous results, the transverse
force generated by the electric field does not depend on the spin current, but
in general, it is related to the second derivative of energy dispersion only.
Furthermore, we find that the transverse force does not vanish in the
Rashba-Dresselhaus system. Therefore, the non-vanishing transverse force acts
as a driving force and results in charge imbalance at the edges of the sample.
The estimated ratio of the Hall voltage to the longitudinal voltage is $\sim
10^{-3}$. The disorder effect is also considered in the study of the
Rashba-Dresselhaus system. We find that the transverse force vanishes in the
presence of impurities in this system because the vertex correction and the
anomalous velocity of the electron accidently cancel each other.",0909.1979v1
2011-08-15,Low-energy effective Hamiltonian involving spin-orbit coupling in Silicene and Two-Dimensional Germanium and Tin,"Starting from the symmetry aspects and tight-binding method in combination
with first-principles calculation, we systematically derive the low-energy
effective Hamiltonian involving spin-orbit coupling (SOC) for silicene, which
is very general because this Hamiltonian applies to not only the silicene
itself but also the low-buckled counterparts of graphene for other group IVA
elements Ge and Sn, as well as graphene when the structure returns to the
planar geometry. The effective Hamitonian is the analogue to the first graphene
quantum spin Hall effect (QSHE) Hamiltonian. Similar to graphene model, the
effective SOC in low-buckled geometry opens a gap at Dirac points and
establishes QSHE. The effective SOC actually contains first order in the atomic
intrinsic SOC strength $\xi_{0}$, while such leading order contribution of SOC
vanishes in planar structure. Therefore, silicene as well as low-buckled
counterparts of graphene for other group IVA elements Ge and Sn has much larger
gap opened by effective SOC at Dirac points than graphene due to low-buckled
geometry and larger atomic intrinsic SOC strength. Further, the more buckled is
the structure, the greater is the gap. Therefore, QSHE can be observed in
low-buckled Si, Ge, and Sn systems in an experimentally accessible temperature
regime. In addition, the Rashba SOC in silicene is intrinsic due to its own
low-buckled geometry, which vanishes at Dirac point $K$, while has nonzero
value with $\vec{k}$ deviation from the $K$ point. Therefore, the QSHE in
silicene is robust against to the intrinsic Rashba SOC.",1108.2933v1
2012-09-26,Significance of dressed molecules in a quasi-two-dimensional polarized Fermi gas,"We investigate the properties of a spin-orbit coupled quasi-two-dimensional
Fermi gas with tunable s-wave interaction between the two spin species. By
analyzing the two-body bound state, we find that the population of the excited
states in the tightly-confined axial direction can be significant when the
two-body binding energy becomes comparable or exceeds the axial confinement.
Since the Rashba spin-orbit coupling that we study here tends to enhance the
two-body binding energy, this effect can become prominent at unitarity or even
on the BCS side of the Feshbach resonance. To study the impact of these excited
modes along the third dimension, we adopt an effective two-dimensional
Hamiltonian in the form of a two-channel model, where the dressed molecules in
the closed channel consist of the conventional Feshbach molecules as well as
the excited states occupation in the axial direction. With properly
renormalized interactions between atoms and dressed molecules, we find that
both the density distribution and the phase structure in the trap can be
significantly modified near a wide Feshbach resonance. In particular, the
stability region of the topological superfluid phase is increased. Our findings
are helpful for the experimental search for the topological superfluid phase in
ultra-cold Fermi gases, and have interesting implications for
quasi-low-dimensional polarized Fermi gases in general.",1209.5935v2
2013-03-19,Anisotropic magnetoresistance in antiferromagnetic semiconductor Sr2IrO4 epitaxial heterostructure,"Lord Kelvin with his discovery of the anisotropic magnetoresistance (AMR)
phenomenon in Ni and Fe was 70 years ahead of the formulation of relativistic
quantum mechanics the effect stems from, and almost one and a half century
ahead of spintronics whose first commercial applications relied on the AMR.
Despite the long history and importance in magnetic sensing and memory
technologies, the microscopic understanding of the AMR has struggled to go far
beyond the basic notion of a relativistic magnetotransport phenomenon arising
from combined effects on diffusing carriers of spin-orbit coupling and broken
symmetry of a metallic ferromagnet. Our work demonstrates that even this
seemingly generic notion of the AMR phenomenon needs revisiting as we observe
the ohmic AMR effect in a nano-scale film of an antiferromagnetic (AFM)
semiconductor Sr2IrO4 (SIO). Our work opens the recently proposed path for
integrating semiconducting and spintronic technologies in AFMs. SIO is a
particularly favorable material for exploring this path since its
semiconducting nature is entangled with the AFM order and strong spin-orbit
coupling. For the observation of the low-field Ohmic AMR in SIO we prepared an
epitaxial heterostructure comprising a nano-scale SIO film on top of an
epilayer of a FM metal La2/3Sr1/3MnO3 (LSMO). This allows the magnetic field
control of the orientation of AFM spins in SIO via the exchange spring effect
at the FM-AFM interface.",1303.4704v1
2013-03-24,Various probes of Dirac matter: from graphene to topological insulators,"Graphene, the atomic-thin layer of carbon atoms, was first isolated on an
insulating substrate in 2004 by two groups in Manchester University [1, 2] and
Columbia [3]. Those milestone experiments established the Dirac nature of the
charge carriers in graphene. The same year, C.L. Kane and E.G. Mele predicted
that intrinsic spin-orbit coupling in graphene, if strong enough, would lead to
a novel state of electronic matter called the Quantum Spin Hall (QSH) state [4,
5]. The QSH state is characterized by conducting gapless edge states
circulating around an insulating bulk. Those edge states are protected from
moderate disorder and interactions by a new topological invariant of the Z_2
nature. While the strength of spin-orbit coupling is too weak in graphene, it
was soon predicted [6] and verified by transport experiments [7, 8] that the
QSH state is realized in HgTe/CdTe quantum wells. In this manuscript, I will
summarize some selected aspects of this huge field of research focused on Dirac
matter including graphene and topological insulators. By Dirac matter, we have
in mind various systems whose excitations obey a relativistic Dirac-like
equation instead of the non relativistic Schrodinger equation. This report is
mainly focused on the 2D topological insulators using graphene as a guideline.
In chapter 1, the semimetallic character of graphene is derived and the
symmetry protection of the Dirac points is discussed while chapters 2 and 3 are
devoted to Chern insulators and QSH insulators respectively.",1303.5902v1
2014-02-25,Quasiuniversal properties of neutron star mergers,"Binary neutron star mergers are studied using nonlinear 3+1 numerical
relativity simulations and the analytical effective-one-body (EOB) model. The
EOB model predicts quasiuniversal relations between the mass-rescaled
gravitational wave frequency and the binding energy at the moment of merger,
and certain dimensionless binary tidal coupling constants depending on the
stars Love numbers, compactnesses and the binary mass ratio. These relations
are quasiuniversal in the sense that, for a given value of the tidal coupling
constant, they depend significantly neither on the equation of state nor on the
mass ratio, though they do depend on stars spins. The spin dependence is
approximately linear for small spins aligned with the orbital angular momentum.
The quasiuniversality is a property of the conservative dynamics; nontrivial
relations emerge as the binary interaction becomes tidally dominated. This
analytical prediction is qualitatively consistent with new, multi-orbit
numerical relativity results for the relevant case of equal-mass irrotational
binaries. Universal relations are thus expected to characterize neutron star
mergers dynamics. In the context of gravitational wave astronomy, these
universal relations may be used to constrain the neutron star equation of state
using waveforms that model the merger accurately.",1402.6244v2
2014-08-28,Effect of Zn doping on the Magneto-Caloric effect and Critical Constants of Mott Insulator MnV2O4,"X-ray absorption near edge spectra (XANES) and magnetization of Zn doped
MnV2O4 have been measured and from the magnetic measurement the critical
exponents and magnetocaloric effect have been estimated. The XANES study
indicates that Zn doping does not change the valence states in Mn and V. It has
been shown that the obtained values of critical exponents \b{eta}, {\gamma} and
{\delta} do not belong to universal class and the values are in between the 3D
Heisenberg model and the mean field interaction model. The magnetization data
follow the scaling equation and collapse into two branches indicating that the
calculated critical exponents and critical temperature are unambiguous and
intrinsic to the system. All the samples show large magneto-caloric effect. The
second peak in magneto-caloric curve of Mn0.95Zn0.05V2O4 is due to the strong
coupling between orbital and spin degrees of freedom. But 10% Zn doping reduces
the residual spins on the V-V pairs resulting the decrease of coupling between
orbital and spin degrees of freedom.",1408.6679v1
2014-10-07,Real-time dynamics induced by quenches across the quantum critical points in gapless Fermi systems with a magnetic impurity,"The energy-dependent scattering of fermions from a localized orbital at an
energy-dependent rate $\Gamma(\epsilon)\propto |\epsilon|^r$ gives rise to
quantum critical points (QCPs) in the pseudogap single-impurity Anderson model
separating a local moment phase with an unscreened spin moment from a
strong-coupling phase which slightly deviates from the screened phase of
standard Kondo problem. Using the time-dependent numerical renormalization
group (TD-NRG) approach we show that local dynamic properties always
equilibrate towards a steady-state value even for quenches across the QCP but
with systematic deviations from the thermal equilibrium depending on the
distance to the critical coupling. Local non-equilibrium properties are
presented for interaction quenches and hybridization quenches. We augment our
numerical data by an analytical calculation that becomes exact at short times
and find excellent agreement between the numerics and the analytical theory.
For interaction quenches within the screened phase we find a universal function
for the time-dependent local double occupancy. We trace back the discrepancy
between our results and the data obtained by a time-dependent Gutzwiller
variational approach to restrictions of the wave-function ansatz in the
Gutzwiller theory: while the NRG ground states properly account for the
formation of an extended spin moment which decouples from the system in the
unscreened phase, the Gutzwiller ansatz only allows the formation of the spin
moment on the local impurity orbital.",1410.1770v2
2014-10-22,SNS junctions in nanowires with spin-orbit coupling: role of confinement and helicity on the sub-gap spectrum,"We study normal transport and the sub-gap spectrum of
superconductor-normal-superconductor (SNS) junctions made of semiconducting
nanowires with strong Rashba spin-orbit coupling. We focus, in particular, on
the role of confinement effects in long ballistic junctions. In the normal
regime, scattering at the two contacts gives rise to two distinct features in
conductance, Fabry-Perot resonances and Fano dips. The latter arise in the
presence of a strong Zeeman field $B$ that removes a spin sector in the leads
(\emph{helical} leads), but not in the central region. Conversely, a helical
central region between non-helical leads exhibits helical gaps of half-quantum
conductance, with superimposed helical Fabry-Perot oscillations. These normal
features translate into distinct subgap states when the leads become
superconducting. In particular, Fabry-Perot resonances within the helical gap
become parity-protected zero-energy states (parity crossings), well below the
critical field $B_c$ at which the superconducting leads become topological. As
a function of Zeeman field or Fermi energy, these zero-modes oscillate around
zero energy, forming characteristic loops, which evolve continuously into
Majorana bound states as $B$ exceeds $B_c$. The relation with the physics of
parity crossings of Yu-Shiba-Rusinov bound states is discussed.",1410.6074v2
2015-09-18,Multiple Unpinned Dirac Points in Group-Va Single-layers with Phosphorene Structure,"Emergent Dirac fermion states underlie many intriguing properties of
graphene, and the search for them constitute one strong motivation to explore
two-dimensional (2D) allotropes of other elements. Phosphorene, the ultrathin
layers of black phosphorous, has been a subject of intense investigations
recently, and it was found that other group-Va elements could also form 2D
layers with similar puckered lattice structure. Here, by a close examination of
their electronic band structure evolution, we discover two types of Dirac
fermion states emerging in the low-energy spectrum. One pair of (type-I) Dirac
points is sitting on high-symmetry lines, while two pairs of (type-II) Dirac
points are located at generic $k$-points, with different anisotropic
dispersions determined by the reduced symmetries at their locations. Such
fully-unpinned (type-II) 2D Dirac points are discovered for the first time. In
the absence of spin-orbit coupling, we find that each Dirac node is protected
by the sublattice symmetry from gap opening, which is in turn ensured by any
one of three point group symmetries. The spin-orbit coupling generally gaps the
Dirac nodes, and for the type-I case, this drives the system into a quantum
spin Hall insulator phase. We suggest possible ways to realize the unpinned
Dirac points in strained phosphorene.",1509.05629v2
2016-06-10,"Spin-orbit coupling control of anisotropy, ground state and frustration in 5d2 Sr2MgOsO6","The influence of spin-orbit coupling (SOC) on the physical properties of the
5d2 system Sr2MgOsO6 is probed via a combination of magnetometry, specific heat
measurements, elastic and inelastic neutron scattering, and density functional
theory calculations. Although a significant degree of frustration is expected,
we find that Sr2MgOsO6 orders in a type I antiferromagnetic structure at the
remarkably high temperature of 108 K. The measurements presented allow for the
first accurate quantification of the size of the magnetic moment in a 5d2
system of 0.60(2) muB - a significantly reduced moment from the expected value
for such a system. Furthermore, significant anisotropy is identified via a spin
excitation gap, and we confirm by first principles calculations that SOC not
only provides the magnetocrystalline anisotropy, but also plays a crucial role
in determining both the ground state magnetic order and the size of the local
moment in this compound. Through comparison to Sr2ScOsO6, it is demonstrated
that SOC-induced anisotropy has the ability to relieve frustration in 5d2
systems relative to their 5d3 counterparts, providing an explanation of the
high TN found in Sr2MgOsO6.",1606.03231v1
2016-06-14,Spin-orbit coupling effects on the stability of two competing structures in Pb/Si(111) and Pb/Ge(111),"Using first-principles density-functional theory (DFT) calculations, we
investigate the 4/3-monolayer structure of Pb on the Si(111) or Ge(111) surface
within the two competing structural models termed the H$_3$ and T$_4$
structures. We find that the spin-orbit coupling (SOC) influences the relative
stability of the two structures in both the Pb/Si(111) and Pb/Ge(111) systems:
i.e., our DFT calculation without including the SOC predicts that the T$_4$
structure is energetically favored over the H$_3$ structure by ${\Delta}E$ = 25
meV for Pb/Si(111) and 22 meV for Pb/Ge(111), but the inclusion of SOC reverses
their relative stability as ${\Delta}E$ = $-$12 and $-$7 meV, respectively. Our
analysis shows that the SOC-induced switching of the ground state is attributed
to a more asymmetric surface charge distribution in the H$_3$ structure, which
gives rise to a relatively larger Rashba spin splitting of surface states as
well as a relatively larger pseudo-gap opening compared to the T$_4$ structure.
By the nudged elastic band calculation, we obtain a sizable energy barrier from
the H$_3$ to the T$_4$ structure as ${\sim}$0.59 and ${\sim}$0.27 eV for
Pb/Si(111) and Pb/Ge(111), respectively. It is thus likely that the two
energetically competing structures can coexist at low temperatures.",1606.04208v1
2018-04-10,Asymmetric and symmetric exchange in a generalized 2D Rashba ferromagnet,"Dzyaloshinskii-Moriya interaction (DMI) is investigated in a 2D ferromagnet
(FM) with spin-orbit interaction of Rashba type at finite temperatures. The FM
is described in the continuum limit by an effective $s$-$d$ model with
arbitrary dependence of spin-orbit coupling (SOC) and kinetic energy of
itinerant electrons on the absolute value of momentum. In the limit of weak
SOC, we derive a general expression for the DMI constant $D$ from a microscopic
analysis of the electronic grand potential. We compare $D$ with the exchange
stiffness $A$ and show that, to the leading order in small SOC strength
$\alpha_{\text{R}}$, the conventional relation $D=(4
m\alpha_{\text{R}}/\hbar)A$, in general, does not hold beyond the
Bychkov-Rashba model. Moreover, in this model, both $A$ and $D$ vanish at zero
temperature in the metal regime (i.e., when two spin sub-bands are partly
occupied). For nonparabolic bands or nonlinear Rashba coupling, these
coefficients are finite and acquire a nontrivial dependence on the chemical
potential that demonstrates the possibility to control the size and chirality
of magnetic textures by adjusting a gate voltage.",1804.03739v3
2017-01-04,Controlling plasmon modes and damping in buckled two-dimensional material open systems,"Full ranges of both hybrid plasmon-mode dispersions and their damping are
studied systematically by our recently developed mean-field theory in open
systems involving a conducting substrate and a two-dimensional (2D) material
with a buckled honeycomb lattice, such as silicene, germanene, and a group
\rom{4} dichalcogenide as well. In this hybrid system, the single plasmon mode
for a free-standing 2D layer is split into one acoustic-like and one
optical-like mode, leading to a dramatic change in the damping of plasmon
modes. In comparison with gapped graphene, critical features associated with
plasmon modes and damping in silicene and molybdenum disulfide are found with
various spin-orbit and lattice asymmetry energy bandgaps, doping types and
levels, and coupling strengths between 2D materials and the conducting
substrate. The obtained damping dependence on both spin and valley degrees of
freedom is expected to facilitate measuring the open-system dielectric property
and the spin-orbit coupling strength of individual 2D materials. The unique
linear dispersion of the acoustic-like plasmon mode introduces additional
damping from the intraband particle-hole modes which is absent for a
free-standing 2D material layer, and the use of molybdenum disulfide with a
large bandgap simultaneously suppresses the strong damping from the interband
particle-hole modes.",1701.01084v1
2018-05-04,Selective measurements of intertwined multipolar orders: non-Kramers doublets on a triangular lattice,"Motivated by the rapid experimental progress on the spin-orbit-coupled Mott
insulators, we propose and study a generic spin model that describes the
interaction between the non-Kramers doublets on a triangular lattice and is
relevant for triangular lattice rare-earth magnets. We predict that the system
supports both pure quadrupolar orders and intertwined multipolar orders in the
phase diagram. Besides the multipolar orders, we explore the magnetic
excitations to reveal the dynamic properties of the systems. Due to the
peculiar properties of the non-Kramers doublets and the selective coupling to
the magnetic field, we further study the magnetization process of the system in
the magnetic field. We point out the selective measurements of the static and
dynamic properties of the intertwined multipolarness in the neutron scattering,
NMR and $\mu$SR probes and predict the experimental consequences. The relevance
to the existing materials such as TmMgGaO$_{4}$, Pr-based and Tb-based magnets,
and many ternary chalcogenides is discussed. Our results illustrate the rich
physics and the promising direction in the interplay between strong
spin-orbit-entangled multipole moments and the geometrical frustration.",1805.01865v3
2018-05-31,Creating solitons by means of spin-orbit coupling,"This mini-review collects theoretical results predicting the creation of
matter-wave solitons by the pseudo-spinor system of Gross-Pitaevskii equations
(GPEs) with the self-attractive cubic nonlinearity and linear
first-order-derivative terms accounting for the spin-orbit coupling (SOC). In
one dimension (1D), the so predicted bright solitons are similar to their
well-known counterparts supported by the GPE in the absence of SOC. Completely
novel results were recently obtained for 2D and 3D systems: SOC suppresses the
collapse instability of the multidimensional GPE, creating fully stable 2D
ground-state solitons and metastable 3D ones of two types: semi-vortices (SVs),
with vorticities m = 1 in one spin component and m = 0 in the other, and mixed
modes (MMs), with m = 0 and m = (+/-)1 present in both components. With the
Galilean invariance broken by SOC, moving solitons exist up to a certain
critical velocity, suffering delocalization above it. The newest result
predicts stable 2D ""quantum droplets"" of the MM type in the presence of the
Lee-Huang-Yang corrections to the GPE system, induced by quantum fluctuations
around the mean-field states, in the case when the inter-component attraction
dominates over the self-repulsion in each component.",1805.12359v1
2019-09-03,"Intrinsic topological superconductivity with exactly flat surface bands in the quasi-one-dimensional A$_2$Cr$_3$As$_3$ (A=Na, K, Rb, Cs) superconductors","A spin-U(1)-symmetry protected momentum-dependent integer-$Z$-valued
topological invariant is proposed to time-reversal-invariant (TRI)
superconductivity (SC) whose nonzero value will lead to exactly flat surface
band(s). The theory is applied to the weakly spin-orbit coupled quasi-1D
A$_2$Cr$_3$As$_3$ (A=Na, K, Rb, Cs) superconductors family with highest $T_c$
up to 8.6 K with $p_z$-wave pairing in the $S_z=0$ channel. It's found that up
to the leading atomic spin-orbit-coupling (SOC), the whole (001) surface
Brillouin zone is covered with exactly-flat surface bands, with some regime
hosting three flat bands and the remaining part hosting two. Such exactly-flat
surface bands will lead to very sharp zero-bias conductance peak in the
scanning tunneling microscopic spectrum. When a tiny subleading spin-flipping
SOC is considered, the surface bands will only be slightly split. The
application of this theory can be generalized to other unconventional
superconductors with weak SOC, particularly to those with mirror-reflection
symmetry.",1909.00943v3
2019-09-06,Octupolar order in d-orbital Mott insulators,"Motivated by experimental and theoretical interest in realizing multipolar
orders in $d$-orbital materials, we discuss the quantum magnetism of $J\!=\!2$
ions which can be realized in spin-orbit coupled oxides with $5d^2$ transition
metal ions. Based on the crystal field environment, we argue for a splitting of
the $J\!=\!2$ multiplet, leading to a low lying non-Kramers doublet which hosts
quadrupolar and octupolar moments. We discuss a microscopic mechanism whereby
the combined perturbative effects of orbital repulsion and antiferromagnetic
Heisenberg spin interactions leads to ferro-octupolar coupling between
neighboring sites, and stabilizes ferro-octupolar order for a face-centered
cubic lattice. This same mechanism is also shown to disfavor quadrupolar
ordering. We show that studying crystal field levels via Raman scattering in a
magnetic field provides a probe of octupolar order. We study spin dynamics in
the ferro-octupolar state using a slave-boson approach, uncovering a gapped and
dispersive magnetic exciton. For sufficiently strong magnetic exchange, the
dispersive exciton can condense, leading to conventional type-I
antiferromagnetic (AFM) order which can preempt octupolar order. Our proposal
for ferrooctupolar order, with specific results in the context of a model
Hamiltonian, provides a comprehensive understanding of thermodynamics, $\mu$SR,
X-ray diffraction, and inelastic neutron scattering measurements on a range of
cubic $5d^2$ double perovskite materials including Ba$_2$ZnOsO$_6$,
Ba$_2$CaOsO$_6$, and Ba$_2$MgOsO$_6$. Our proposal for exciton condensation
leading to type-I AFM order may be relevant to materials such as
Sr$_2$MgOsO$_6$.",1909.03089v3
2019-09-24,Quantum Hall Effect Measurement of Spin-Orbit Coupling Strengths in Ultraclean Bilayer Graphene/WSe2 Heterostructures,"We study proximity-induced spin-orbit coupling (SOC) in bilayer
graphene/few-layer WSe2 heterostructure devices. Contact mode atomic force
microscopy (AFM) cleaning yields ultra-clean interfaces and high-mobility
devices. In a perpendicular magnetic field, we measure the quantum Hall effect
to determine the Landau level structure in the presence of out-of-plane Ising
and in-plane Rashba SOC. A distinct Landau level crossing pattern emerges when
tuning the charge density and displacement field independently with dual gates,
originating from a layer-selective SOC proximity effect. Analyzing the Landau
level crossings and measured inter-Landau level energy gaps yields the
proximity induced SOC energy scale. The Ising SOC is ~ 2.2 meV, 100 times
higher than the intrinsic SOC in graphene, while its sign is consistent with
theories predicting a dependence of SOC on interlayer twist angle. The Rashba
SOC is ~15 meV. Finally, we infer the magnetic field dependence of the
inter-Landau level Coulomb interactions. These ultraclean bilayer graphene/WSe2
heterostructures provide a high mobility system with the potential to realize
novel topological electronic states and manipulate spins in nanostructures.",1909.10931v1
2019-10-24,DFT study of itinerant ferromagnetism in $p$-doped monolayers of MoS$_2$,"We use density functional theory to explore the possibility of making the
semiconducting transition-metal dichalcogenide MoS$_2$ ferromagnetic by
introducing holes into the narrow Mo $d$ band that forms the top of the valence
band. In the single impurity limit, the repulsive Coulomb potential of an
acceptor atom and intervalley scattering lead to a twofold orbitally degenerate
effective-mass like $e'$ state being formed from Mo $d_{x^2-y^2}$ and $d_{xy}$
states, bound to the K and K$'$ valence band maxima. It also leads to a singly
degenerate $a'_1$ state with Mo $d_{3z^2-r^2}$ character bound to the slightly
lower lying valence band maximum at $\Gamma$. Within the accuracy of our
calculations, these $e'$ and $a'_1$ states are degenerate for MoS$_2$ and
accommodate the hole that polarizes fully in the local spin density
approximation in the impurity limit. With spin-orbit coupling included, we find
a single ion magnetic anisotropy of $\sim 5\,$meV favouring out-of-plane
orientation of the magnetic moment. Pairs of such hole states introduced by V,
Nb or Ta doping are found to couple ferromagnetically unless the dopant atoms
are too close in which case the magnetic moments are quenched by the formation
of spin singlets. Combining these exchange interactions with Monte Carlo
calculations allows us to estimate ordering temperatures as a function of the
dopant concentration $x$. For $x \sim 9\%$, Curie temperatures as high as 100K
for Nb and Ta and in excess of 160K for V doping are predicted. Factors
limiting the ordering temperature are identified and suggestions made to
circumvent these limitations.",1910.10992v1
2020-01-30,Self-controlled growth of highly uniform Ge/Si hut wires for scalable qubit devices,"Semiconductor nanowires have been playing a crucial role in the development
of nanoscale devices for the realization of spin qubits, Majorana fermions,
single photon emitters, nanoprocessors, etc. The monolithic growth of
site-controlled nanowires is a prerequisite towards the next generation of
devices that will require addressability and scalability. Here, combining
top-down nanofabrication and bottom-up self-assembly, we report on the growth
of Ge wires on pre-patterned Si (001) substrates with controllable position,
distance, length and structure. This is achieved by a novel growth process
which uses a SiGe strain-relaxation template and can be generalized to other
material combinations. Transport measurements show an electrically tunable
spin-orbit coupling, with a spin-orbit length similar to that of III-V
materials. Also, capacitive coupling between closely spaced wires is observed,
which underlines their potential as a host for implementing two qubit gates.
The reported results open a path towards scalable qubit devices with Si
compatibility.",2001.11305v2
2020-04-09,Anomalous Hall effect in $κ$-type organic antiferromagnets,"We theoretically propose a mechanism for the anomalous Hall effect (AHE) in
an antiferrromagnetic (AFM) state of $\kappa$-type organic conductors. We
incorporate the spin-orbit coupling in the effective Hubbard model on the
$\kappa$-type lattice structure taking into account the orientation of the
molecules and their arrangement with dimerization. Treating this model by means
of the Hartree-Fock approximation and the linear response theory, we find that
an intrinsic contribution to the Hall conductivity becomes nonzero in the
electron-doped AFM metallic phase with a small canted ferromagnetic moment. We
show that, contrary to the conventional wisdom, the spin canting is irrelevant
to the Hall response; the nonzero Hall conductivity originates from the
collinear component of the AFM order in the presence of the spin-orbit
coupling. These features are well explained analytically in the limit of strong
dimerization on the anisotropic triangular lattice. Furthermore, we present an
intuitive picture for the present AHE by considering the real-space
configuration of emergent magnetic fluxes. We also find that the Hall response
appears even in the undoped AFM insulating phase at nonzero frequency as the
magneto-optical Kerr effect, which is enhanced around the charge transfer
excitations. We discuss possible detections of the AHE in ET based compounds.",2004.04578v1
2018-03-23,Observation of hedgehog skyrmions in sub-100 nm soft magnetic nanodots,"Magnetic skyrmions are nanometric spin textures of outstanding potential for
spintronic applications due to unique features governed by their non-trivial
topology. It is well known that skyrmions of definite chirality are stabilized
by the Dzyaloshinskii-Moriya exchange interaction (DMI) in bulk
non-centrosimmetric materials or ultrathin films with strong spin-orbit
coupling in the interface. In this work, we report on the detection of magnetic
hedgehog-skyrmions at room temperature in confined systems with neither DMI nor
perpendicular magnetic anisotropy. We show that soft magnetic (permalloy)
nanodots are able to host non- chiral hedgehog skyrmions that can be further
stabilized by the magnetic field arising from the Magnetic Force Microscopy
probe. Analytical calculations and micromagnetic simulations confirmed the
existence of metastable N\'eel skyrmions in permalloy nanodots even without
external stimuli in a certain size range. Our work implies the existence of a
new degree of freedom to create and manipulate skyrmions in soft nanodots. The
stabilization of skyrmions in soft magnetic materials opens a possibility to
study the skymion magnetization dynamics otherwise limited due to the large
damping constant coming from the high spin-orbit coupling in materials with
high magnetic anisotropy.",1803.08768v1
2019-04-09,Thermoelectric and optical probes for a Fermi surface topology change in noncentrosymmetric metals,"Noncentrosymmetric metals such as Li$_2$(Pd$_{1-x}$Pt$_x$)$_3$B have
different Fermi surface topology below and above the band touching point where
spin-degeneracy is not lifted by the spin-orbit coupling. We investigate
thermoelectric and optical response as probes for this Fermi surface topology
change. We show that the chemical potential displays a dimensional crossover
from a three-dimensional to one-dimensional characteristics as the descending
Fermi energy crosses the band touching point. This dimensional crossover is due
to the existence of different Fermi surface topology above and below the band
touching point. We obtain an exact expression of relaxation time due to
short-range scatterer by solving Boltzmann transport equations
self-consistently. The thermoelctric power and figure of merit are
significantly enhanced as the Fermi energy goes below the band touching point
owing to the underlying one-dimensional-like nature of noncentrosymmteric bulk
metals. The value of thermoelectric figure of merit goes beyond two as the
Fermi energy approaches to the van Hove singularity for lower spin-orbit
coupling. Similarly, the studies of the zero-frequency and finite-frequency
optical conductivities in the zero-momentum limit reflect the nature of
topological change of the Fermi surface. The Hall coefficient and optical
absorption width exhibit distinct signatures in response to the changes in
Fermi surface topology.",1904.04656v2
2019-12-05,Steering magnonic dynamics and permeability at exceptional points in a parity-time symmetric waveguide,"Tuning the low-energy magnetic dynamics is a key element in designing novel
magnetic metamaterials, spintronic devices and magnonic logic circuits. This
study uncovers a new, highly effective way of controlling the magnetic
permeability via shaping the magnonic properties in coupled magnetic waveguides
separated by current carrying spacer with strong spin-orbit coupling. The
spin-orbit torques exerted on the waveguides leads to an externally tunable
enhancement of magnetic damping in one waveguide and a decreased damping in the
other, constituting so a magnetic parity-time (PT) symmetric system with
emergent magnetic properties at the verge of the exceptional point where
magnetic gains/losses are balanced. In addition to controlling the magnetic
permeability, phenomena inherent to PT-symmetric systems are identified,
including the control on magnon power oscillations, nonreciprocal magnon
propagation, magnon trapping and enhancement as well as the increased
sensitivity to magnetic perturbation and abrupt spin reversal. These
predictions are demonstrated analytically and confirmed by full numerical
simulations under experimentally feasible conditions. The position of the
exceptional points and the strength of the spontaneous PT symmetry breaking can
be tuned by external electric and/or magnetic fields. The roles of the
intrinsic magnetic damping, and the possibility of an electric control via
Dzyaloshinskii-Moriya interaction are exposed and utilized for mode dispersion
shaping and magnon amplification and trapping. The results point to a new route
to designing optomagnonic waveguides, traps, sensors, and circuits.",1912.02500v1
2020-08-14,Spontaneous Valley Spirals in Magnetically Encapsulated Twisted Bilayer Graphene,"Van der Waals heterostructures provide a rich platform for emergent physics
due to their tunable hybridization of electronic orbital- and spin-degrees of
freedom. Here, we show that a heterostructure formed by twisted bilayer
graphene sandwiched between ferromagnetic insulators develops flat bands
stemming from the interplay between twist, exchange proximity and spin-orbit
coupling. We demonstrate that in this flat-band regime, the spin degree of
freedom is hybridized, giving rise to an effective triangular superlattice with
valley as a degenerate pseudospin degree of freedom. Incorporating electronic
interactions at half-filling leads to a spontaneous valley-mixed state, i.e., a
correlated state in the valley sector with geometric frustration of the valley
spinor. We show that an electric interlayer bias generates an artificial
valley-orbit coupling in the effective model, controlling both the valley
anisotropy and the microscopic details of the correlated state, with both
phenomena understood in terms of a valley-Heisenberg model with easy-plane
anisotropic exchange. Our results put forward twisted graphene encapsulated
between magnetic van der Waals heterostructures as platforms to explore purely
valley-correlated states in graphene.",2008.06441v1
2020-10-19,Novel $J_{\rm{eff}}$=3/2 Metallic Phase and Unconventional Superconductivity in GaTa$_4$Se$_8$,"By means of density functional theory plus dynamical mean-field theory
(DFT+DMFT) calculations and resonant inelastic x-ray scattering (RIXS)
experiments, we investigate the high-pressure phases of the spin-orbit-coupled
$J_{\rm{eff}}=3/2$ insulator GaTa$_4$Se$_8$. Its metallic phase, derived from
the Mott state by applying pressure, is found to carry $J_{\rm{eff}}=3/2$
moments. The characteristic excitation peak in the RIXS spectrum maintains its
destructive quantum interference of $J_{\rm{eff}}$ at the Ta $L_2$-edge up to
10.4 GPa. Our exact diagonalization based DFT+DMFT calculations including
spin-orbit coupling also reveal that the $J_{\rm{eff}}=3/2$ character can be
clearly identified under high pressure. These results establish the intriguing
nature of the correlated metallic magnetic phase, which represents the first
confirmed example of $J_{\rm{eff}}$=3/2 moments residing in a metal. They also
indicate that the pressure-induced superconductivity is likely unconventional
and influenced by these $J_{\rm{eff}}=3/2$ moments. Based on a self-energy
analysis, we furthermore propose the possibility of doping-induced
superconductivity related to a spin-freezing crossover.",2010.09234v1
2017-07-08,RKKY interaction in three-dimensional electron gases with linear spin-orbit coupling,"We theoretically study the impacts of linear spin-orbit coupling (SOC) on the
Ruderman-Kittel-Kasuya-Yosida interaction between magnetic impurities in two
kinds of three-dimensional noncentrosymmetric systems. It has been found that
linear SOCs lead to the Dzyaloshinskii-Moriya interaction and the Ising
interaction, in addition to the conventional Heisenberg interaction. These
interactions possess distinct range functions from three dimensional electron
gases and Dirac/Weyl semimetals. In the weak SOC limit, the Heisenberg
interaction dominates over the other two interactions in a moderately large
region of parameters. Sufficiently strong Rashba SOC makes the
Dzyaloshinskii-Moriya interaction or the Ising interaction dominate over the
Heisenberg interaction in some regions. The change in topology of the Fermi
surface leads to some quantitative changes in periods of oscillations of range
functions. The anisotropy of Ruderman-Kittel-Kasuya-Yosida interaction in
bismuth tellurohalides family BiTe$X$ ($X$ = Br, Cl, and I) originates from
both the specific form of Rashba SOC and the anisotropic effective mass. Our
work provides some insights into understanding observed spin textures and the
application of these materials in spintronics.",1707.02381v3
2018-10-19,Dynamic tomography of the spin-orbit coupling in nonlinear optics,"Spin-orbit coupled (SOC) light fields with spatially inhomogeneous
polarization have attracted increasing research interest within the optical
community. In particular, owing to their spin-dependent phase and spatial
structures, many nonlinear optical phenomena which we have been familiar with
up to now are being re-examined, hence a revival of research in nonlinear
optics. To fully investigate this topic, knowledge on how the topological
structure of the light field evolves is necessary, but, as yet, there are few
studies that address the structural evolution of the light field. Here, for the
first time, we present a universal approach for theoretical tomographic
treatment of the structural evolution of SOC light in nonlinear optics
processes. Based on a Gedanken vector second harmonic generation, a
fine-grained slice of evolving SOC light in a nonlinear interaction and the
following diffraction propagation are studied theoretically and verified
experimentally, and which at the same time reveal several interesting
phenomena. The approach provides a useful tool for enhancing our capability to
obtain a more nuanced understanding of vector nonlinear optics, and sets a
foundation for further broad-based studies in nonlinear systems.",1810.08358v2
2018-10-30,Charged fermion in $(1+2)$-dimensional wormhole with axial magnetic field,"We investigate the effects of magnetic field on a charged fermion in a
$(1+2)$-dimensional wormhole. Applying external magnetic field along the axis
direction of the wormhole, the Dirac equation is set up and analytically solved
in two scenarios, constant magnetic flux and constant magnetic field through
the throat of the wormhole. For the constant magnetic flux scenario, the system
can be solved analytically and exact solutions are found. For the constant
magnetic field scenario, with the short wormhole approximation, the quantized
energies and eigenstates are obtained. The system exhibits both the spin-orbit
coupling and the Landau quantization for the stationary states in both
scenarios. The intrinsic curvature of the surface induces the spin-orbit and
spin-magnetic Landau couplings that generate imaginary energy. Imaginary energy
can be interpreted as the energy dissipation and instability of the states.
Generically, the states of charged fermion in wormhole are quasinormal
modes~(QNMs) that could be unstable for positive imaginary frequencies and
decaying for negative imaginary ones. For the constant flux scenario, the
fermions in the wormhole can behave like bosons and have arbitrary statistics
depending on the flux. We also discuss the implications of our results in the
graphene wormhole system.",1810.12668v2
2019-05-26,Two-body bound state of ultracold Fermi atoms with two-dimensional spin-orbit coupling,"In a recent experiment, a two-dimensional spin-orbit coupling (SOC) was
realized for fermions in the continuum [Nat. Phys. 12, 540 (2016)], which
represents an important step forward in the study of synthetic gauge field
using cold atoms. In the experiment, it was shown that a Raman-induced
two-dimensional SOC exists in the dressed-state basis close to a Dirac point of
the single-particle spectrum. By contrast, the short-range inter-atomic
interactions of the system are typically expressed in the hyperfine-spin basis.
The interplay between synthetic SOC and interactions can potentially lead to
interesting few- and many-body phenomena but has so far eluded theoretical
attention. Here we study in detail properties of two-body bound states of such
a system. We find that, due to the competition between SOC and interaction, the
stability region of the two-body bound state is in general reduced.
Particularly, the threshold of the lowest two-body bound state is shifted to a
positive, SOC-dependent scattering length. Furthermore, the center-of-mass
momentum of the lowest two-body bound state becomes nonzero, suggesting the
emergence of Fulde-Ferrell pairing states in a many-body setting. Our results
reveal the critical difference between the experimentally realized
two-dimensional SOC and the more symmetric Rashba or Dresselhaus SOCs in an
interacting system, and paves the way for future characterizations of
topological superfluid states in the experimentally relevant systems.",1905.10735v1
2019-06-27,A three-dimensional superconformal quantum mechanics with $sl(2|1)$ dynamical symmetry,"We construct a three-dimensional superconformal quantum mechanics (and its
associated de Alfaro-Fubini-Furlan deformed oscillator) possessing an $sl(2|1)$
dynamical symmetry. At a coupling parameter $\beta\neq 0$ the Hamiltonian
contains a $\frac{1}{r^2}$ potential and a spin-orbit (hence, a first-order
differential operator) interacting term. At $\beta=0$ four copies of undeformed
three-dimensional oscillators are recovered. The Hamiltonian gets diagonalized
in each sector of total $j$ and orbital $l$ angular momentum (the spin of the
system is $\frac{1}{2}$). The Hilbert space of the deformed oscillator is given
by a direct sum of $sl(2|1)$ lowest weight representations. The selection of
the admissible Hilbert spaces at given values of the coupling constant $\beta$
is discussed. The spectrum of the model is computed. The vacuum energy (as a
function of $\beta$) consists of a recursive zigzag pattern. The degeneracy of
the energy eigenvalues grows linearly up to $E\sim \beta$ (in proper units) and
quadratically for $E>\beta$. The orthonormal energy eigenstates are expressed
in terms of the associated Laguerre polynomials and the spin spherical
harmonics. The dimensional reduction of the model to $d=2$ produces two copies
(for $\beta$ and $-\beta$, respectively) of the two-dimensional $sl(2|1)$
deformed oscillator. The dimensional reduction to $d=1$ produces the
one-dimensional $D(2,1;\alpha)$ deformed oscillator, with $\alpha$ determined
by $\beta$.",1906.11705v2
2020-06-03,Topological Hall Effect and Skyrmion-like Bubbles at a Charge-transfer Interface,"Exploring exotic interface magnetism due to charge transfer and strong
spin-orbit coupling has profound application in future development of
spintronic memory. Here, the emergence, tuning and interpretation of hump-shape
Hall Effect from a CaMnO3/CaIrO3/CaMnO3 trilayer structure are studied in
detail. The hump signal can be recognized as Topological Hall Effect suggesting
the presence of Skyrmion-like magnetic bubbles; but the debated alternative
interpretation where the signal being an artefact between two cancelling
Anomalous Hall Effect loops is also discussed. Firstly, by tilting the magnetic
field direction, the evolution of Hall signal suggests transformation of the
bubbles topology into a more trivial kind. Secondly, by varying the thickness
of CaMnO3, the optimal thicknesses for the hump signal emergence are found,
suggesting a tuning of charge transfer fraction. Using high-resolution
transmission electron microscopy, a stacking fault is also identified, which
distinguishes the top and bottom CaMnO3/CaIrO3 interfaces in terms of charge
transfer fraction and possible interfacial Dzyaloshinskii-Moriya Interaction.
Finally, a spin-transfer torque experiment revealed a low threshold current
density of ~10^9 A/m^2 for initiating the motion of bubbles. This discovery
opens a possible route for integrating Skyrmions with antiferromagnetic
spintronics.",2006.02004v1
2021-02-12,Spin-orbit driven ferromagnetism at half moiré filling in magic-angle twisted bilayer graphene,"Strong electron correlation and spin-orbit coupling (SOC) provide two
non-trivial threads to condensed matter physics. When these two strands of
physics come together, a plethora of quantum phenomena with novel topological
order have been predicted to emerge in the correlated SOC regime. In this work,
we examine the combined influence of electron correlation and SOC on a
2-dimensional (2D) electronic system at the atomic interface between
magic-angle twisted bilayer graphene (tBLG) and a tungsten diselenide (\WSe)
crystal. In such a structure, strong electron correlation within the moir\'e
flatband stabilizes correlated insulating states at both quarter and
half-filling, whereas SOC transforms these Mott-like insulators into
ferromagnets, evidenced by robust anomalous Hall effect with hysteretic
switching behavior. The coupling between spin and valley degrees of freedom is
unambiguously demonstrated as the magnetic order is shown to be tunable with an
in-plane magnetic field, or a perpendicular electric field. In addition, we
examine the influence of SOC on the isospin order and stability of
superconductivity. Our findings establish an efficient experimental knob to
engineer topological properties of moir\'e bands in twisted bilayer graphene
and related systems.",2102.06566v2
2021-08-31,Self-generated quantum gauge fields in arrays of Rydberg atoms,"As shown in recent experiments [V. Lienhard et al., Phys. Rev. X 10, 021031
(2020)], spin-orbit coupling in systems of Rydberg atoms can give rise to
density-dependent Peierls Phases in second-order hoppings of Rydberg spin
excitations and nearest-neighbor (NN) repulsion. We here study theoretically a
one-dimensional zig-zag ladder system of such spin-orbit coupled Rydberg atoms
at half filling. The second-order hopping is shown to be associated with an
effective gauge field, which in mean-field approximation is static and
homogeneous. Beyond the mean-field level the gauge potential attains a
transverse quantum component whose amplitude is dynamical and linked to density
modulations. We here study the effects of this to the possible ground-state
phases of the system. In a phase where strong repulsion leads to a density
wave, we find that as a consequence of the induced quantum gauge field a
regular pattern of current vortices is formed. However also in the absence of
density-density interactions the quantum gauge field attains a non-vanishing
amplitude. Above a certain critical strength of the second-order hopping the
energy gain due to gauge-field induced transport overcomes the energy cost from
the associated build-up of density modulations leading to a spontaneous
generation of the quantum gauge field.",2108.13896v1
2022-02-16,Spectroscopic characterization of singlet-triplet doorway states of aluminum monofluoride,"Aluminum monofluoride (AlF) possesses highly favorable properties for laser
cooling, both via the A$^1\Pi$ and a$^3\Pi$ states. Determining efficient
pathways between the singlet and the triplet manifold of electronic states will
be advantageous for future experiments at ultralow temperatures. The lowest
rotational levels of the A$^1\Pi, v=6$ and b$^3\Sigma^+, v=5$ states of AlF are
nearly iso-energetic and interact via spin-orbit coupling. These levels thus
have a strongly mixed spin-character and provide a singlet-triplet doorway. We
here present a hyperfine resolved spectroscopic study of the A$^1\Pi, v=6$ //
b$^3\Sigma^+, v=5$ perturbed system in a jet-cooled, pulsed molecular beam.
From a fit to the observed energies of the hyperfine levels, the fine and
hyperfine structure parameters of the coupled states, their relative energies
as well as the spin-orbit interaction parameter are determined. The standard
deviation of the fit is about 15 MHz. We experimentally determine the radiative
lifetimes of selected hyperfine levels by time-delayed ionization, Lamb dip
spectroscopy and accurate measurements of the transition lineshapes. The
measured lifetimes range between 2 ns and 200 ns, determined by the degree of
singlet-triplet mixing for each level.",2202.07920v1
2022-09-20,Evidence for non-unitary triplet-pairing superconductivity in noncentrosymmetric TaRuSi and comparison with isostructural TaReSi,"We have studied the superconducting properties of the isostructural ternary
noncentrosymmetric superconductors TaXSi (X = Re, Ru) with the help of muon
spin rotation/relaxation ($\mu$SR) and density functional theory calculations.
Our transverse-field $\mu$SR measurements indicate isotropic s-wave
superconductivity in TaReSi and multi-gap superconductivity in TaRuSi.
Zero-field $\mu$SR measurements, highly sensitive to very small magnetic
fields, and no evidence for spontaneous fields in the superconducting state of
TaReSi, whereas we observe small spontaneous fields that onset with
superconductivity indicating broken time-reversal symmetry (TRS)
superconductivity in TaRuSi. Using density functional theory calculations, we
find that spin-orbit coupling is relatively weak in TaRuSi and strong in
TaReSi. Using symmetry analysis, we attribute the broken time-reversal symmetry
(TRS) in TaRuSi to a non-unitary triplet pairing state. Such a state is not
allowed in the presence of strong spin-orbit coupling: our finding of no
evidence for broken TRS in TaReSi is consistent with this expectation.",2209.09852v2
2023-01-04,Coexistence of bulk-nodal and surface-nodeless Cooper pairings in a superconducting Dirac semimetal,"The interplay of nontrivial topology and superconductivity in condensed
matter physics gives rise to exotic phenomena. However, materials are extremely
rare where it is possible to explore the full details of the superconducting
pairing. Here, we investigate the momentum dependence of the superconducting
gap distribution in a novel Dirac material PdTe. Using high resolution, low
temperature photoemission spectroscopy, we establish it as a spin-orbit coupled
Dirac semimetal with the topological Fermi arc crossing the Fermi level on the
(010) surface. This spin-textured surface state exhibits a fully gapped
superconducting Cooper pairing structure below Tc~4.5K. Moreover, we find a
node in the bulk near the Brillouin zone boundary, away from the topological
Fermi arc.These observations not only demonstrate the band resolved electronic
correlation between topological Fermi arc states and the way it induces Cooper
pairing in PdTe, but also provide a rare case where surface and bulk states
host a coexistence of nodeless and nodal gap structures enforced by spin-orbit
coupling.",2301.01402v1
2023-03-15,Ultrafast Opto-magnetic Effects in the Extreme Ultraviolet Spectral Range,"Coherent light-matter interactions mediated by opto-magnetic phenomena like
the inverse Faraday effect (IFE) are expected to provide a non-thermal pathway
for ultrafast manipulation of magnetism on timescales as short as the
excitation pulse itself. As the IFE scales with the spin-orbit coupling
strength of the involved electronic states, photo-exciting the strongly
spin-orbit coupled core-level electrons in magnetic materials appears as an
appealing method to transiently generate large opto-magnetic moments. Here, we
investigate this scenario in a ferrimagnetic GdFeCo alloy by using intense and
circularly polarized pulses of extreme ultraviolet radiation. Our results
reveal ultrafast and strong helicity-dependent magnetic effects which are in
line with the characteristic fingerprints of an IFE, corroborated by ab initio
opto-magnetic IFE theory and atomistic spin dynamics simulations.",2303.08564v1
2023-04-06,Protection of Ising spin-orbit coupling in bulk misfit superconductors,"Low-dimensional materials have remarkable properties that are distinct from
their bulk counterparts. A paradigmatic example is Ising superconductivity that
occurs in monolayer materials such as NbSe2 which show a strong violation of
the Pauli limit. In monolayers, this occurs due to a combination of broken
inversion symmetry and spin-orbit coupling that locks the spins of the
electrons out-of-plane. Bulk NbSe2 is centrosymmetric and is therefore not an
Ising superconductor. We show that bulk misfit compound superconductors,
(LaSe)1.14(NbSe2) and (LaSe)1.14(NbSe2)2, comprised of monolayers and bilayers
of NbSe2, exhibit unexpected Ising protection with a Pauli-limit violation
comparable to monolayer NbSe2, despite formally having inversion symmetry. We
study these misfit compounds using complementary experimental methods in
combination with first-principles calculations. We propose theoretical
mechanisms of how the Ising protection can survive in bulk materials. We show
how some of these mechanisms operate in these bulk compounds due to a concerted
effect of charge-transfer, defects, reduction of interlayer hopping, and
stacking. This highlights how Ising superconductivity can, unexpectedly, arise
in bulk materials, and possibly enable the design of bulk superconductors that
are resilient to magnetic fields.",2304.03074v1
2023-05-20,$\mathbb{Z}_n$ symmetry broken supersolid in spin-orbit-coupled Bose-Einstein condensates,"Supersolid is an exotic state of matter characterized by both superfluid
properties and periodic particle density modulation, due to spontaneous
breaking of U(1) gauge symmetry and spatial translation symmetry, respectively.
For conventional supersolids,continuous translation symmetry breaking is
accompanied by one gapless Goldstone mode in the excitation spectra. An
interesting question naturally arises: what is the consequence of breaking
discrete translation symmetry for supersolids? In this work, we propose the
concept of $\mathbb{Z}_n$ supersolid resulting from spontaneous breaking of a
discrete $\mathbb{Z}_n$ symmetry, or equivalently, a discrete translation
symmetry. This $\mathbb{Z}_n$ supersolid is realized in the stripe phase of
spin-orbit-coupled Bose-Einstein condensate under an external periodic
potential with period $1/n$ of intrinsic stripe period. For $n\geq2$, there are
$n$ degenerate ground states with spontaneously broken lattice translation
symmetry. The low-energy excitations of $\mathbb{Z}_n$ supersolid include a
pseudo-Goldstone mode, whose excitation gap at long wavelength limit is found
to decrease fast with $n$. We further numerically show that, when confined in a
harmonic trap, a spin-dependent perturbation can result in the transition
between degenerate ground states of $\mathbb{Z}_n$ supersolid. With the integer
$n$ tunable using the experimental technique of generating subwavelength
optical lattice, the $\mathbb{Z}_n$ supersolid proposed here offers a cold atom
platform to simulate physics related with generic $\mathbb{Z}_n$ symmetry
breaking, which is interesting not only in the field of cold atoms, but also in
particle physics and cosmology.",2305.12069v1
2023-07-25,"Tuning the magnetic properties in MPS3 (M = Mn, Fe, and Ni) by proximity-induced Dzyaloshinskii Moriya interactions","Tailoring the quantum many-body interactions in layered materials through
appropriate heterostructure engineering can result in emergent properties that
are absent in the constituent materials thus promising potential future
applications. In this article, we have demonstrated controlling the otherwise
robust magnetic properties of transition metal phosphorus trisulphides
(Mn/Fe/NiPS3) in their heterostructures with Weyl semimetallic MoTe2 which can
be attributed to the Dzyaloshinskii Moriya (DM) interactions at the interface
of the two different layered materials. While the DM interaction is known to
scale with the strength of the spin-orbit coupling (SOC), we also demonstrate
here that the effect of DM interaction strongly varies with the spin
orientation/dimensionality of the magnetic layer and the low-energy electronic
density of state of the spin-orbit coupled layer. The observations are further
supported by a series of experiments on heterostructures with a variety of
substrates/underlayers hosting variable SOC and electronic density of states.",2307.13400v1
2023-10-05,Unconventional superconductivity in Sc$_2$Ir$_{4-x}$Si$_x$ by spin-orbit coupling driven flat band,"The kagome lattice is very attractive as it can host many novel quantum
states, such as the charge density wave, superconductivity, quantum spin
liquid, etc. Meanwhile, iridates often exhibit a strong spin-orbit coupling
(SOC) effect due to the large atomic mass of 5$d$ elements, which has important
implications for both the energy bands and the pairing symmetry of
superconductors. For the Laves phase superconductor Sc$_2$Ir$_4$ with a kagome
lattice, by doping Si to the Ir sites, we observed a nonmonotonic and two-dome
like doping dependence of the superconducting transition temperature $T_{\rm
c}$, which is typically found in many unconventional superconducting systems.
Interestingly, for some samples, especially Sc$_2$Ir$_{3.5}$Si$_{0.5}$ with the
optimal $T_{\rm c}$, after the suppression of superconductivity, the
normal-state resistivity exhibits a semiconducting behavior; meanwhile, the
specific heat coefficient shows an upturn which follows the relation
$C/T\propto{\rm ln}(T_0/T)$ at low temperatures. Around the optimal doping, the
resistance measurements exhibit strong superconducting fluctuations. And the
superconductivity related specific heat can be fitted by the model of a
$d$-wave gap after subtracting the normal-state background. These strongly
suggest unconventional superconductivity and correlation effect in the samples,
which is mainly induced by a flat band near the Fermi level when considering
the SOC, as supported by the first-principles calculations. Our results reveal
a new unconventional superconducting system Sc$_2$Ir$_{4-x}$Si$_x$ with strong
correlation effects induced by the flat band in the kagome system with strong
SOC.",2310.03609v1
2023-11-28,Spin-Orbital Coupling in All-Inorganic Metal-Halide Perovskites: the Hidden Force that Matters,"Highlighted with improved long-term thermal and environmental stability,
all-inorganic metal halide perovskites exhibit tunable physical properties,
cost-effective synthesis, and satisfactory optoelectronic performance,
attracting increasing research interests worldwide. However, a less explored
feature of these materials is their strong spin-orbit coupling (SOC), which is
the hidden force influencing not only band structure but also properties
including magnetoresistance, spin lifetime and singlet-triplet splitting. This
review provides an overview of the fundamental aspects and the latest progress
of the SOC and debate regarding Rashba effects in all-inorganic metal halide
perovskites, providing critical insights into the physical phenomena and
potential applications. Meanwhile, crystal structures and photophysics of
all-inorganic perovskite are discussed in the context of SOC, along with the
related experimental and characterization techniques. Furthermore, a recent
understanding of the band topology in the all-inorganic halide perovskites is
introduced to push the boundary even further for the novel applications of
all-inorganic halide perovskites. Finally, an outlook is given on the potential
directions of breakthroughs via leveraging the SOC in halide perovskites.",2311.16695v1
2024-01-18,Stable semivortex gap solitons in a spin-orbit-coupled Fermi gas,"We demonstrate the existence of semivortex (SV) solitons, with vorticities
$0$ and $1$ in the two components, in a two-dimensional (2D) fermionic spinor
system under the action of the Rashba-type spin-orbit coupling in the
combination with the Zeeman splitting (ZS). In the ``heavy-atom"" approximation,
which was previously elaborated for the bosonic system, the usual kinetic
energy is neglected, which gives rise to a linear spectrum with a bandgap. The
model includes the effective Pauli self-repulsion with power $7/3$, as produced
by the density-functional theory of Fermi superfluids. In the general case, the
inter-component contact repulsion is included too. We construct a family of gap
solitons of the SV type populating the spectral bandgap. A stability region is
identified for the SV solitons, by means of systematic simulations, in the
parameter plane of the cross-repulsion strength and chemical potential. The
stability region agrees with the prediction of the anti-Vakhitov-Kolokolov
criterion, which is a relevant necessary stability condition for systems with
self-repulsive nonlinearities. We also test the stability of the SV solitons
against a sudden change of the ZS strength, which initiates robust oscillations
in the spin state of the soliton due to transfer of particles between the
system's components.",2401.10406v1
2024-02-05,Intrinsic nonlinear Hall effect in two-dimensional honeycomb topological antiferromagnets,"Two-dimensional systems with honeycomb lattice are known to be a paradigmatic
platform to explore the various types of Hall effects, owing to that the
interplay of lattice geometry, spin-orbit coupling and magnetism can give rise
to very rich features in the quantum geometry of wave functions. In this work,
we consider honeycomb topological antiferromagets that are effectively
described by a $\mathcal{PT}$-symmetric antiferromagnetic Kane-Mele model, and
explore the evolution of its nonlinear Hall response with respect to the change
of lattice anisotropy, chemical potential, and the direction of the N\'{e}el
vector. Due to the $\mathcal{PT}$-symmetry, the leading-order Hall effect of
quantum geometric origin is the intrinsic nonlinear Hall effect, which is a
second-order effect of electric fields and is independent of the scattering
time. We investigate the behavior of the intrinsic nonlinear Hall conductivity
tensor across topological phase transitions driven by antiferromagnetic
exchange field and lattice anisotropy and find that its components do not
change sign, which is different from the extrinsic nonlinear Hall effect. In
the weakly doped regime, we find that the intrinsic nonlinear Hall effect is
valley-polarized. By varying the chemical potential, we find that the nonlinear
Hall conductivity tensors exhibit kinks when the Fermi surface undergoes
Lifshitz transitions. Furthermore, we find that the existence of spin-orbit
coupling to lift the spin-rotation symmetry is decisive for the use of
intrinsic nonlinear Hall effect to detect the direction of the N\'{e}el vector.
Our work shows that the two-dimensional honeycomb topological antiferromagnets
are an ideal class of material systems with rich properties for the study of
intrinsic nonlinear Hall effect.",2402.02685v1
2024-03-18,Tailoring topological band properties of twisted double bilayer graphene: effects due to spin-orbit coupling,"Our theoretical study unfolds the topological phase transitions (within bands
of the Moir\'e super-lattice) in small angle twisted double bilayer graphene
(tDBLG) under the influence of external gate voltage and intrinsic spin-orbit
coupling (SOC) for both AB-AB and AB-BA stacking configurations. Utilizing a
low-energy continuum model, we investigate the band structure and perform a
comprehensive topological characterization of the system by analysing the
direct band gap closing as well as various Chern numbers. In the absence of
SOC, the tDBLG exhibits characteristics of a valley Hall insulator. However, in
the presence of SOC, we observe a transition to a quantum spin Hall insulator
state and band topology emerges in the parameter spaces of non-topological
regime without SOC. Furthermore, we conduct a comparative analysis between
untwisted double bilayer graphene and tDBLG to assess the impact of twisting on
the system's properties. Our findings reveal the construction of topological
phase diagrams that showcase distinct phases arising from changes in the twist
angle compared to the untwisted case. These phase diagrams provide valuable
insights into the diverse topological phases achievable in tDBLG with SOC. Our
findings contribute to the understanding of the interplay between small twist
angle, SOC, and external electric field on the topological band properties of
twisted multilayer graphene systems.",2403.11660v1
1992-12-09,Theory of Anisotropic Superexchange in Insulating Cuprates,"Spin-orbit corrections to superexchange are calculated using the method of
Moriya [T.\ Moriya, {\it Phys.\ Rev.}~{\bf 120} 91, (1960)] for two of the
insulating parent compounds of the cuprate superconductors: (1)
La$_{2-x}$Nd$_x$CuO$_4$ where the CuO$_6$ octahedra forming each Cu-O layer are
tilted in staggered fashion about an axis which depends on $x$ and temperature;
and (2) YBa$_2$Cu$_3$O$_{6+x}$ ($x \alt 0.4$) where the Cu-O layers form
CuO$_2$-Y-CuO$_2$ bilayers in which the in-plane O$^{2-}$ ions are displaced
uniformly towards the Y$^{3+}$ layer. For (1) a simple formula is derived for
the weak ferromagnetic moment in each Cu-O layer as a function of the tilting
axis and magnitude. For (2) it is shown that the anisotropic corrections to
superexchange are different from what has previously been assumed. For the
correct spin Hamiltonian a classical N\'eel state in which the Cu spins are
lying in the plane is unstable in a single Cu-O layer, but when a bilayer is
considered there is a critical value of the interlayer exchange coupling which
stabilizes this state. For both cases (1) and (2) spin-wave spectra are
calculated and shown to compare favorably with experiment.",9212015v1
2001-12-20,Mechanism of unconventional superconductivity induced by skyrmion excitations in two-dimensional strongly-correlated electron systems,"We propose a mechanism of unconventional superconductivity in two-dimensional
strongly-correlated electron systems. We consider a two-dimensional Kondo
lattice system or double-exchange system with spin-orbit coupling arising from
buckling of the plane. We show that a Chern-Simons term is induced for a gauge
field describing the phase fluctuations of the localized spins. Through the
induced Chern-Simons term, carriers behave like skyrmion excitations that lead
to a destruction mechanism of magnetic long-range order by carrier doping.
After magnetic long-range order is destroyed by carrier doping, the
Chern-Simons term plays a dominant role and the attractive interaction between
skyrmions leads to unconventional superconductivity. For the case of the
ferromagnetic interaction between the localized spins, the symmetry of the
Cooper pair is p-wave ($p_x \pm ip_y$). For the case of the antiferromagnetic
interaction between the localized spins, the symmetry of the Cooper pair is
d-wave ($d_{x^2-y^2}$). Applications to various systems are discussed, in
particular to the high-$T_c$ cuprates.",0112374v1
2003-03-29,Superconductivity in Sr$_2$RuO$_4$ Mediated by Coulomb Scattering,"We investigate the superconductivity in Sr$_2$RuO$_4$ on the basis of the
three-dimensional three-band Hubbard model. We propose a model with Coulomb
interactions among the electrons on the nearest-neighbor Ru sites. In our model
the intersite Coulomb repulsion and exchange coupling can work as the effective
interaction for the spin-triplet paring. This effective interaction is enhanced
by the band hybridization, which is mediated by the interlayer transfers. We
investigate the possibility of this mechanism in the ground state and find that
the orbital dependent spin-triplet superconductivity is more stable than the
spin-singlet one for realistic parameters. This spin-triplet superconducting
state has horizontal line nodes on the Fermi surface.",0303620v1
2004-08-09,"Role of Disorder in Mn:GaAs, Cr:GaAs, and Cr:GaN","We present calculations of magnetic exchange interactions and critical
temperature T_c in Mn:GaAs, Cr:GaAs and Cr:GaN. The local spin density
approximation is combined with a linear-response technique to map the magnetic
energy onto a Heisenberg hamiltonion, but no significant further approximations
are made. Special quasi-random structures in large unit cells are used to
accurately model the disorder. T_c is computed using both a spin-dynamics
approach and the cluster variation method developed for the classical
Heisenberg model.
  We show the following: (i) configurational disorder results in large
dispersions in the pairwise exchange interactions; (ii) the disorder strongly
reduces T_c; (iii) clustering in the magnetic atoms, whose tendency is
predicted from total-energy considerations, further reduces T_c. Additionally
the exchange interactions J(R) are found to decay exponentially with distance
R^3 on average; and the mean-field approximation is found to be a very poor
predictor of T_c, particularly when J(R) decays rapidly. Finally the effect of
spin-orbit coupling on T_c is considered. With all these factors taken into
account, T_c is reasonably predicted by the local spin-density approximation in
MnGaAs without the need to invoke compensation by donor impurities.",0408185v1
2005-05-04,Superconductors without an inversion center of symmetry: The s-wave state,"In materials without an inversion center of symmetry the spin degeneracy of
the conducting band is lifted by an antisymmetric spin orbit coupling (ASOC).
Under such circumstances, spin and parity cannot be separately used to classify
the Cooper pairing states. Consequently, the superconducting order parameter is
generally a mixture of spin singlet and triplet pairing states. In this paper
we investigate the structure of the order parameter and its response to
disorder for the most symmetric pairing state ($A_1$). Using the example of the
heavy Fermion superconductor CePt$_3$Si, we determine characteristic properties
of the superconducting instability as a function of (non-magnetic) impurity
concentrations. Moreover, we explore the possibility of the presence of
accidental line nodes in the quasiparticle gap. Such nodes would be essential
to explain recent low-temperature data of thermodynamic quantities such as the
NMR-$T_1^{-1}$, London penetration depth, and heat conductance.",0505108v2
2006-03-23,Extrinsic Entwined with Intrinsic Spin Hall Effect in Disordered Mesoscopic Bars,"We show that pure spin Hall current, flowing out of a four-terminal
phase-coherent two-dimensional electron gas (2DEG) within inversion asymmetric
semiconductor heterostructure, contains contributions from both the extrinsic
mechanisms (spin-orbit dependent scattering off impurities) and the intrinsic
ones (due to the Rashba coupling). While the extrinsic contribution vanishes in
the weakly and strongly disordered limits, and the intrinsic one dominates in
the quasiballistic limit, in the crossover transport regime the spin Hall
conductance, exhibiting sample-to-sample large fluctuations and sign change, is
not simply reducible to either of the two mechanisms, which can be relevant for
interpretation of experiments on dirty 2DEGs [V. Sih et al., Nature Phys. 1, 31
(2005)].",0603595v1
2006-06-19,"Giant current-driven domain wall mobility in (Ga,Mn)As","We study theoretically hole current-driven domain wall dynamics in (Ga,Mn)As.
We show that the spin-orbit coupling causes significant hole reflection at the
domain wall, even in the adiabatic limit when the wall is much thicker than the
Fermi wavelength, resulting in spin accumulation and mistracking between
current-carrying spins and the domain wall magnetization. This increases the
out-of-plane non-adiabatic spin transfer torque and consequently the
current-driven domain wall mobility by three to four orders of magnitude.
Trends and magnitude of the calculated domain wall current mobilities agree
with experimental findings.",0606498v3
2006-07-14,Zeeman splitting in ballistic hole quantum wires,"We have studied the Zeeman splitting in ballistic hole quantum wires formed
in a (311)A quantum well by surface gate confinement. Transport measurements
clearly show lifting of the spin degeneracy and crossings of the subbands when
an in-plane magnetic field B is applied parallel to the wire. When B is
oriented perpendicular to the wire, no spin-splitting is discernible up to B =
8.8 T. The observed large Zeeman splitting anisotropy in our hole quantum wires
demonstrates the importance of quantum-confinement for spin-splitting in
nanostructures with strong spin-orbit coupling.",0607355v1
2006-10-02,g-Factor Tuning and Manipulation of Spins by an Electric Current,"We investigate the Zeeman splitting of two-dimensional electrons in an
asymmetric silicon quantum well, by electron-spin-resonance (ESR) experiments.
Applying a small dc current we observe a shift in the resonance field due to
the additional current-induced Bychkov-Rashba (BR) type of spin-orbit (SO)
field. This finding demonstrates SO coupling in the most straightforward way:
in the presence of a transverse electric field the drift velocity of the
carriers imposes an effective SO magnetic field. This effect allows selective
tuning of the g-factor by an applied dc current. In addition, we show that an
ac current may be used to induce spin resonance very efficiently.",0610046v1
2007-02-08,Two-dimensional spin-filtered chiral network model for the Z_2 quantum spin-Hall effect,"The effects of static disorder on the Z_2 quantum spin-Hall effect for
non-interacting electrons propagating in two-dimensional space is studied
numerically. A two-dimensional time-reversal symmetric network model is
constructed to account for the effects of static disorder on the propagation of
non-interacting electrons subjected to spin-orbit couplings. This network model
is different from past network models belonging to the symplectic symmetry
class in that the propagating modes along the links of the network can be
arranged into an odd number of Kramers doublet. It is found that (1) a
two-dimensional metallic phase of finite extent is embedded in a Z_2 insulating
phase in parameter space and (2) the quantum phase transitions between the
metallic and Z_2 insulating phases belong to the conventional symplectic
universality class in two space dimensions.",0702199v2
2002-02-24,Universal Quantum Logic from Zeeman and Anisotropic Exchange Interactions,"Some of the most promising proposals for scalable solid-state quantum
computing, e.g., those using electron spins in quantum dots or donor electron
or nuclear spins in Si, rely on a two-qubit quantum gate that is ideally
generated by an isotropic exchange interaction. However, an anisotropic
perturbation arising from spin-orbit coupling is inevitably present. Previous
studies focused on removing the anisotropy. Here we introduce a new universal
set of quantum logic gates that takes advantage of the anisotropic
perturbation. The price is a constant but modest factor in additional pulses.
The gain is a scheme that is compatible with the naturally available
interactions in spin-based solid-state quantum computers.",0202135v2
2007-05-14,Broken spin-Hall accumulation symmetry by magnetic field and coexisted Rashba and Dresselhaus interactions,"The spin-Hall effect in the two-dimensional electron gas (2DEG) generates
symmetric out-of-plane spin Sz accumulation about the current axis in the
absence of external magnetic field. Here we employ the real space
Landauer-Keldysh formalism [B. K. Nikolic et al., Phys. Rev. Lett. 95, 046601
(2005); Phys. Rev. B 73, 075303 (2006)] by considering a four-terminal setup to
investigate the circumstances in which this symmetry is broken. For the absence
of Dresselhaus interaction, starting from the applied out-of-plane B
corresponding to Zeeman splitting energy 0 - 0.5 times the Rashba hopping
energy tR, the breaking process is clearly seen. The influence of the Rashba
interaction on the magnetization of the 2DEG is studied herein. For coexisted
Rashba tR and Dresselhaus tD spin-orbit couplings in the absence of B,
interchanging tR and tD reverses the entire accumulation pattern.",0705.1884v1
2007-11-03,Magnetic Properties in Non-centrosymmetric Superconductors with and without Antiferromagnetic Order,"The paramagnetic properties in non-centrosymmetric superconductors with and
without antiferromagnetic (AFM) order are investigated with focus on the heavy
Fermion superconductors, CePt_3Si, CeRhSi_3 and CeIrSi_3. First, we investigate
the spin susceptibility in the linear response regime and elucidate the role of
AFM order. The spin susceptibility at T=0 is independent of the pairing
symmetry and increases in the AFM state. Second, the non-linear response to the
magnetic field are investigated on the basis of an effective model for CePt_3Si
which may be also applicable to CeRhSi_3 and CeIrSi_3. The role of
antisymmetric spin-orbit coupling (ASOC), helical superconductivity,
anisotropic Fermi surfaces and AFM order are examined in the dominantly s-, p-
and d-wave states. We emphasize the qualitatively important role of the mixing
of superconducting (SC) order parameters in the p-wave state which enhances the
spin susceptibility and suppresses paramagnetic depairing effect in a
significant way. Therefore, the dominantly p-wave superconductivity admixed
with the s-wave order parameter is consistent with the paramagnetic properties
of CePt_3Si at ambient pressure. We propose some experiments which can
elucidate the novel pairing states in CePt_3Si as well as CeRhSi_3 and
CeIrSi_3.",0711.0440v1
2008-01-25,Ab initio study of spin-dependent transport in carbon nanotubes with iron and vanadium adatoms,"We present an ab initio study of spin dependent transport in armchair carbon
nanotubes with transition metal adsorbates, iron or vanadium. We neglect the
effect of tube curvature and model the nanotube by graphene with periodic
boundary conditions. A density functional theory based nonequilibrium Green's
function method is used to compute the electronic structure and zero-bias
conductance. The presence of the adsorbate causes a strong scattering of
electrons of one spin type only. The scattering is shown to be due to coupling
of the two armchair band states to the metal 3d orbitals with matching symmetry
causing Fano resonances appearing as dips in the transmission function. The
spin type (majority/minority) being scattered depends on the adsorbate and is
explained in terms of d-state filling. The results are qualitatively reproduced
using a simple tight-binding model, which is then used to investigate the
dependence of the transmission on the nanotube width. We find a decrease in the
width of the transmission dip as the tube-size increases.",0801.3997v1
2008-03-19,Spin-Orbit Coupling and Ion Displacements in Multiferroic TbMnO3,"The electronic and magnetic properties of TbMnO3 leading to its ferroelectric
(FE) polarization were investigated on the basis of relativistic density
functional theory (DFT) calculations. In agreement with experiment, we show
that the spin-spiral plane of TbMnO3 can be either the bc- or ab-plane, but not
the ac-plane. As for the mechanism of FE polarization, our work reveals that
the ""pure electronic"" model by Katsura, Nagaosa and Balatsky (KNB) is
inadequate in predicting the absolute direction of FE polarization. For the
ab-plane spin-spiral state of TbMnO3, the direction of FE polarization
predicted by the KNB model is opposite to that predicted by DFT calculations.
In determining the magnitude and the absolute direction of FE polarization in
spin-spiral states, it is found crucial to consider the displacements of the
ions from their ecntrosymmetric positions.",0803.2741v4
2008-12-31,A new mechanism of electric dipole spin resonance: hyperfine coupling in quantum dots,"A recently discovered mechanism of electric dipole spin resonance, mediated
by the hyperfine interaction, is investigated experimentally and theoretically.
The effect is studied using a spin-selective transition in a GaAs double
quantum dot. The resonant frequency is sensitive to the instantaneous hyperfine
effective field, revealing a nuclear polarization created by driving the
resonance. A device incorporating a micromagnet exhibits a magnetic field
difference between dots, allowing electrons in either dot to be addressed
selectively. An unexplained additional signal at half the resonant frequency is
presented.",0901.0124v1
2009-08-13,Predicted band structures of III-V semiconductors in wurtzite phase,"While non-nitride III-V semiconductors typically have a zincblende structure,
they may also form wurtzite crystals under pressure or when grown as
nanowhiskers. This makes electronic structure calculation difficult since the
band structures of wurtzite III-V semiconductors are poorly characterized. We
have calculated the electronic band structure for nine III-V semiconductors in
the wurtzite phase using transferable empirical pseudopotentials including
spin-orbit coupling. We find that all the materials have direct gaps. Our
results differ significantly from earlier {\it ab initio} calculations, and
where experimental results are available (InP, InAs and GaAs) our calculated
band gaps are in good agreement. We tabulate energies, effective masses, and
linear and cubic Dresselhaus zero-field spin-splitting coefficients for the
zone-center states. The large zero-field spin-splitting coefficients we find
may lead to new functionalities for designing devices that manipulate spin
degrees of freedom.",0908.1984v1
2010-08-20,Charge-induced spin polarization in non-magnetic organic molecule Alq$_{3}$,"Electrical injection in organic semiconductors is a key prerequisite for the
realization of organic spintronics. Using density-functional theory
calculations we report the effect of electron transfer into the organic
molecule Alq$_3$. Our first-principles simulations show that electron injection
spontaneously spin-polarizes non-magnetic Alq$_3$ with a magnetic moment
linearly increasing with induced charge. An asymmetry of the Al--N bond lengths
leads to an asymmetric distribution of injected charge over the molecule. The
spin-polarization arises from a filling of dominantly the nitrogen $p_z$
orbitals in the molecule's LUMO together with ferromagnetic coupling of the
spins on the quinoline rings.",1008.3525v2
2011-03-05,"Low-moment magnetism in the double perovskites Ba2MOsO6 (M=Li,Na)","The magnetic ground states of the isostructural double perovskites
Ba$_2$NaOsO$_6$ and Ba$_2$LiOsO$_6$ are investigated with muon-spin rotation.
In Ba$_2$NaOsO$_6$ long-range magnetic order is detected via the onset of a
spontaneous muon-spin precession signal below $T_{\mathrm{c}}=7.2\pm
0.2\;\mathrm{K}$, while in Ba$_2$LiOsO$_6$ a static but spatially-disordered
internal field is found below 8 K. A novel probabilistic argument is used to
show from the observed precession frequencies that the magnetic ground state in
Ba$_2$NaOsO$_6$ is most likely to be low-moment ($\approx 0.2$\,$\mu_{\rm B}$)
ferromagnetism and not canted antiferromagnetism. Ba$_2$LiOsO$_6$ is
antiferromagnetic and we find a spin-flop transition at 5.5\,T. A reduced
osmium moment is common to both compounds, probably arising from a combination
of spin-orbit coupling and frustration.",1103.1039v2
2011-03-23,Time-reversal-symmetry-broken quantum spin Hall effect,"Quantum spin Hall (QSH) state of matter is usually considered to be protected
by time-reversal (TR) symmetry. We investigate the fate of the QSH effect in
the presence of the Rashba spin-orbit coupling and an exchange field, which
break both inversion and TR symmetries. It is found that the QSH state
characterized by nonzero spin Chern numbers $C_{\pm}=\pm 1$ persists when the
TR symmetry is broken. A topological phase transition from the TR
symmetry-broken QSH phase to a quantum anomalous Hall phase occurs at a
critical exchange field, where the bulk band gap just closes. It is also shown
that the transition from the TR symmetry-broken QSH phase to an ordinary
insulator state can not happen without closing the band gap.",1103.4473v2
2011-06-30,Doping the Kane-Mele-Hubbard model: A Slave-Boson Approach,"We study the Kane-Mele-Hubbard model both at half-filling and away from
half-filling using a slave-boson mean-field approach at zero temperature. We
obtain a phase diagram at half-filling and discuss its connection to recent
results from quantum Monte Carlo, slave-rotor, and $Z_2$ mean-field studies. In
particular, we find a small window in parameter space where a spin liquid phase
with gapped spin and charge excitations reside. Upon doping, we show the spin
liquid state becomes a superconducting state by explicitly calculating the
singlet pairing order parameters. Interestingly, we find an ""optimal"" doping
for such superconductivity. Our work reveals some of the phenomenology
associated with doping an interacting system with strong spin-orbit coupling.",1107.0007v2
2011-08-30,Electrically tunable quantum anomalous Hall effect in 5d transition-metal adatoms on graphene,"The combination of the unique properties of graphene with spin polarization
and magnetism for the design of new spintronic concepts and devices has been
hampered by the small Coulomb interaction and the tiny spin-orbit coupling of
carbon in pristine graphene. Such device concepts would take advantage of the
control of the spin degree of freedom utilizing the widely available electric
fields in electronics or of topological transport mechanisms such as the
conjectured quantum anomalous Hall effect. Here we show, using first-principles
methods, that 5d transition-metal (TM) adatoms deposited on graphene display
remarkable magnetic properties. All considered TM adatoms possess significant
spin moments with colossal magnetocrystalline anisotropy energies as large as
50 meV per TM atom. We reveal that the magneto-electric response of deposited
TM atoms is extremely strong and in some cases offers even the possibility to
switch the spontaneous magnetization direction by a moderate external electric
field. We predict that an electrically tunable quantum anomalous Hall effect
can be observed in this type of hybrid materials.",1108.5915v1
2011-10-31,One-sign order parameter in iron based superconductor,"The onset of superconductivity at the transition temperature is marked by the
onset of order, which is characterized by an energy gap. Most models of the
iron-based superconductors find a sign-changing (s\pm) order parameter [1-6],
with the physical implication that pairing is driven by spin fluctuations.
Recent work, however, has indicated that LiFeAs has a simple isotropic order
parameter [7-9] and spin fluctuations are not necessary [7,10], contrary to the
models [1-6]. The strength of the spin fluctuations has been controversial
[11,12], meaning that the mechanism of superconductivity cannot as yet be
determined. Here we report the momentum dependence of the superconducting
energy gap, where we find an anisotropy that rules out coupling through spin
fluctuations and the sign change. The results instead suggest that orbital
fluctuations assisted by phonons [13,14] are the best explanation for
superconductivity.",1110.6922v2
2012-02-15,Current-induced motion of a transverse magnetic domain wall in the presence of spin Hall effect,"We theoretically study the current-induced dynamics of a transverse magnetic
domain wall in bi-layer nanowires consisting of a ferromagnet on top of a
nonmagnet having strong spin-orbit coupling. Domain wall dynamics is
characterized by two threshold current densities, $J_{th}^{WB}$ and
$J_{th}^{REV}$, where $J_{th}^{WB}$ is a threshold for the chirality switching
of the domain wall and $J_{th}^{REV}$ is another threshold for the reversed
domain wall motion caused by spin Hall effect. Domain walls with a certain
chirality may move opposite to the electron-flow direction with high speed in
the current range $J_{th}^{REV} < J < J_{th}^{WB}$ for the system designed to
satisfy the conditions $J_{th}^{WB} > J_{th}^{REV}$ and \alpha > \beta, where
\alpha is the Gilbert damping constant and \beta is the nonadiabaticity of spin
torque. Micromagnetic simulations confirm the validity of analytical results.",1202.3450v1
2012-03-22,Enhanced anisotropic spin fluctuations below tetragonal-to-orthorhombic transition in LaFeAs(O_{1-x}F_x) probed by ^{75}As and ^{139}La NMR,"$^{75}$As and $^{139}$La NMR results of LaFeAs(O$_{1-x}$F$_x$) ($x$=0, 0.025,
and 0.04) were reported. Upon F-doping, the tetragonal-to-orthorhombic
structural phase transition temperature $T_S$, antiferromagnetic transition
temperature $T_N$ and internal magnetic field $\mu_0H_{\rm int}$ are gradually
reduced for $x<0.04$. However, at $x=0.04$, $T_N$ is abruptly suppressed to be
30 K along with a tiny $\mu_0H_{\rm int}$, which is distinct from the
continuous disappearance of the ordered phases in the Ba122 systems of
Ba(Fe,Co)$_2$As$_2$ and BaFe$_2$(As,P)$_2$. The anisotropy of the spin-lattice
relaxation rate $T_1^{-1}$, $(T_1)^{-1}_{H\parallel ab}/(T_1)^{-1}_{H\parallel
c}$, in the paramagnetic phase of $x = 0$ and 0.025 is constant ($\sim 1.5$),
but increases abruptly below $T_S$ due to the enhancement of
$(T_1)^{-1}_{H\parallel ab}$ by the slowing down of magnetic fluctuations. This
indicates that the tetragonal-to-orthorhombic structural distortion enhances
the anisotropy in the spin space via magnetoelastic coupling and/or spin-orbit
interaction.",1203.4937v1
2012-07-12,Electrical control of the Kondo effect in a helical edge liquid,"Magnetic impurities affect the transport properties of the helical edge
states of quantum spin Hall insulators by causing single-electron
backscattering. We study such a system in the presence of a Rashba spin-orbit
interaction induced by an external electric field, showing that this can be
used to control the Kondo temperature, as well as the correction to the
conductance due to the impurity. Surprisingly, for a strongly anisotropic
electron-impurity spin exchange, Kondo screening may get obstructed by the
presence of a non-collinear spin interaction mediated by the Rashba coupling.
This challenges the expectation that the Kondo effect is stable against
time-reversal invariant perturbations.",1207.3028v3
2012-07-27,Topological phase transitions driven by next-nearest-neighbor hopping in two-dimensional lattices,"For two-dimensional lattices in a tight-binding description, the intrinsic
spin-orbit coupling, acting as a complex next-nearest-neighbor hopping, opens
gaps that exhibit the quantum spin Hall effect. In this paper, we study the
effect of a real next-nearest-neighbor hopping term on the band structure of
several Dirac systems. In our model, the spin is conserved, which allows us to
analyze the spin Chern numbers. We show that in the Lieb, kagome, and T_3
lattices, variation of the amplitude of the real next-nearest-neighbor hopping
term drives interesting topological phase transitions. These transitions may be
experimentally realized in optical lattices under shaking, when the ratio
between the nearest- and next-nearest-neighbor hopping parameters can be tuned
to any possible value. Finally, we show that in the honeycomb lattice,
next-nearest-neighbor hopping only drives topological phase transitions in the
presence of a magnetic field, leading to the conjecture that these transitions
can only occur in multigap systems.",1207.6545v3
2012-11-01,Self-consistent spin-fluctuation spectrum and correlated electronic structure of actinides,"We present an overview of various theoretical methods with detailed emphasis
on an intermediate Coulomb-U coupling model. This model is based on
material-specific ab-initio band structure from which correlation effects are
computed via self-consistent GW-based self-energy corrections arising from
spin-fluctuations. We apply this approach to four isostructural intermetallic
actinides PuCoIn5, PuCoGa5, PuRhGa5 belonging to the Pu-115 family, and UCoGa5,
a member of the U-115 family. The 115 families share the property of spin-orbit
split density of states enabling substantial spin fluctuations around 0.5 eV,
whose feedback effect on the electronic structure create mass renormalization
and electronic `hot spots`, i.e., regions of large spectral weight. A detailed
comparison is provided for the angle-resolved and angle-integrated
photoemission spectra and de Haas-van Alphen experimental data as available.
The results suggest that this class of actinides is adequately described by the
intermediate Coulomb interaction regime, where both itinerant and incoherent
features coexist in the electronic structure.",1211.0240v1
2013-01-06,Spin Susceptibility in Non-centrosymmetric Superconductors with Topological Transition of Fermi Surfaces,"The non-centrosymmetric superconductors Li2Pd3B and Li2Pt3B show different
superconducting properties despite having the same crystal symmetry. Motivated
by experimental results, we investigate the spin susceptibility of
non-centrosymmetric superconductors accompanied by the topological transition
of Fermi surfaces due to antisymmetric spin-orbit coupling, which is indicated
by the first-principles band structure calculation for Li2Pt3B. We study three
types of topological transition, namely, (A) the disappearance of the Fermi
surface, (B) crossing the Dirac point, and (C) crossing the saddle point
van-Hove singularity. The spin susceptibility in the superconducting state is
increased by the topological transitions (A) and (C), while it is decreased by
(B). We discuss the unusual magnetic properties observed in Li2Pt3B on the
basis of these results.",1301.0976v2
2013-01-15,Mechanisms for Sub-Gap Optical Conductivity in Herbertsmithite,"Recent terahertz conductivity measurements observed low-power-law frequency
dependence of optical conduction within the Mott gap of the Kagome lattice
spin-liquid candidate Herbertsmithite. We investigate mechanisms for this
observed sub-gap conductivity for two possible scenarios in which the
ground-state is described by: 1) a U(1) Dirac spin-liquid with emergent
fermionic spinons or 2) a nearly critical Z2 spin-liquid in the vicinity of a
continuous quantum phase transition to magnetic order. We identify new
mechanisms for optical-absorption via magneto-elastic effects and spin- orbit
coupling. In addition, for the Dirac spin-liquid scenario, we establish an
explicit microscopic origin for previously proposed absorption mechanisms based
on slave-particle effective field theory descriptions.",1301.3495v2
2013-01-17,Electrically Tunable Topological State in [111] Perovskite Materials with Antiferromagnetic Exchange Field,"A topological state with simultaneous nonzero Chern number and spin Chern
number is possible for electrons on honeycomb lattice based on band engineering
by staggered electric potential and antiferromagnetic exchange field in
presence of intrinsic spin-orbit coupling. With first principles calculation we
confirm that the scheme can be realized by material modification in perovskite
G-type antiferromagnetic insulators grown along [111] direction, where d
electrons hop on a single buckled honeycomb lattice. This material is ideal for
spintronics applications, since it provides a spin-polarized quantized edge
current, robust to both nonmagnetic and magnetic defects, with the spin
polarization tunable by inverting electric field.",1301.4113v1
2013-03-09,The fundamental differences between Quantum Spin Hall edge-states at zig-zag and armchair terminations of honeycomb and ruby nets,"Combining an analytical and numerical approach we investigate the dispersion
of the topologically protected spin-filtered edge-states of the Quantum Spin
Hall state on honeycomb and ruby nets with zigzag (ZZ) and armchair (AC) edges.
We show that the Fermi velocity of the helical edge-states on ZZ edges
increases linearly with the strength of the spin-orbit coupling (SOC) whereas
for AC edges the Fermi velocity is independent of the SOC. Also the decay
length of edge states into the bulk is dramatically different for AC and ZZ
edges, displaying an inverse functional dependence on the SOC.",1303.2252v1
2013-03-27,Observation of the geometric spin Hall effect of light,"The spin Hall effect of light (SHEL) is the photonic analogue of spin Hall
effects occurring for charge carriers in solid-state systems. Typical examples
of this intriguing phenomenon occur when a light beam refracts at an air-glass
interface, or when it is projected onto an oblique plane, the latter effect
being known as geometric SHEL. It amounts to a polarization-dependent
displacement perpendicular to the plane of incidence. Here, we experimentally
demonstrate the geometric SHEL for a light beam transmitted across an oblique
polarizer. We find that the spatial intensity distribution of the transmitted
beam depends on the incident state of polarization and its centroid undergoes a
positional displacement exceeding one wavelength. This novel phenomenon is
virtually independent from the material properties of the polarizer and, thus,
reveals universal features of spin-orbit coupling.",1303.6974v4
2013-06-27,Finding the Rashba-type spin-splitting from interband scattering in quasiparticle interference maps,"We have studied the BiCu$_2$/Cu(111) surface alloy using low-temperature
scanning tunneling microscopy and spectroscopy. We observed standing waves
caused by scattering off defects and step edges. Different from previous
studies on similar Rashba-type surfaces, we identified multiple scattering
vectors that originate from various intraband as well as interband scattering
processes. A detailed energy-dependent analysis of the standing-wave patterns
enables a quantitative determination of band dispersions, including the Rashba
splitting. The results are in good agreement with ARPES data and demonstrate
the usefulness of this strategy to determine the band structure of Rashba
systems. The lack of other possible scattering channels will be discussed in
terms of spin conservation and hybridization effects. The results open new
possibilities to study spin-dependent scattering on complex spin-orbit coupled
surfaces.",1306.6662v1
2014-08-06,"Half metallic ferromagnetism in tri-layered perovskites Sr$_4$T$_{3}$O$_{10}$ (T=Co, Rh)","First-principles density functional theory (DFT) is used to investigate the
electronic and magnetic properties of Sr$_4$Rh$_3$O$_{10}$, a member of the
Ruddlesden-Popper series. Based on the DFT calculations taking into account the
co-operative effect of Coulomb interaction ($U$) and spin-orbit couplings
(SOC), Sr$_4$Rh$_3$O$_{10}$ is found to be a half metallic ferromagnet (HMF)
with total angular moment $\mu_{\rm {tot}}$=12$\mu_B$ per unit cell. The
material has almost 100$\%$ spin-polarization at the Fermi level despite of
sizable SOC. Replacement of Rh atom by the isovalent Co atom is considered.
Upon full-replacement of Co, a low-spin to intermediate spin transition happens
resulting in a HMF state with the total angular moment three-time larger (i.e.
$\mu_{\rm {tot}}$=36$\mu_B$ per unit cell), compared to Sr$_4$Rh$_3$O$_{10}$.
We propose Sr$_4$Rh$_3$O$_{10}$ and Sr$_4$Co$_3$O$_{10}$ as candidates of half
metals.",1408.1216v1
2014-08-08,Half Metal Transition Driven by Doping Effects in Osmium Double Perovskite,"Using the first-principles density functional approach, we investigate
Ca$_2$FeOsO$_6$, a material of double perovskite structure synthesized
recently. According to the calculations, Ca$_2$FeOsO$_6$ is a ferrimagnetic
Mott-insulator influenced by the cooperative effect of spin-orbit coupling
(SOC) and Coulomb interactions of Fe-3$d$ and Os-5$d$ electrons, as well as the
crystal field. When Fe is replaced with Ni, the system exhibits half metallic
(HM) states desirable for spintronic applications. In
[Ca$_2$Fe$_{1-x}$Ni$_x$OsO$_6$]$_2$, HM ferrimagnetism is observed with
$\mu_{\rm tot}=2\mu_{\rm B}$ per unit cell for doping rate $x=0.5$, whereas HM
antiferromagnetism (HMAFM) with nearly zero spin magnetization in the unit cell
for $x=1$, respectively. It is emphasized that half metallicity is retained
even with SOC effect due to the large exchange-splitting between spin-up and
spin-down bands close to the Fermi level.",1408.1771v1
2014-10-01,Transverse anisotropy effects on spin-resolved transport through large-spin molecules,"The transport properties of a large-spin molecule strongly coupled to
ferromagnetic leads in the presence of transverse magnetic anisotropy are
studied theoretically. The relevant spectral functions, linear-response
conductance and the tunnel magnetoresistance are calculated by means of the
numerical renormalization group method. We study the dependence of transport
characteristics on orbital level position, uniaxial and transverse
anisotropies, external magnetic field and temperature. It is shown that while
uniaxial magnetic anisotropy leads to the suppression of the Kondo effect,
finite transverse anisotropy can restore the Kondo resonance. The effect of
Kondo peak restoration strongly depends on the magnetic configuration of the
device and leads to nontrivial behavior of the tunnel magnetoresistance. We
show that the temperature dependence of the conductance at points where the
restoration of the Kondo effect occurs is universal and shows a scaling typical
for usual spin-one-half Kondo effect.",1410.0315v1
2015-01-23,Giant gap in the magnon excitations of the quasi-1D chain compound Sr3NiIrO6,"Inelastic neutron scattering on the spin-chain compound Sr$_3$NiIrO$_6$
reveals gapped quasi-1D magnetic excitations. The observed one-magnon band
between 29.5 and 39 meV consists of two dispersive modes. The spin wave
spectrum could be well fitted with an antiferromagnetic anisotropic exchange
model and single ion anisotropy on the Ni site. The extracted dominant
anisotropic antiferromagnetic intra-chain exchange interaction between Ir and
Ni ions are $J_z=19.5$ meV and $J_{xy}=12.1$ meV. These values justify previous
electronic structure calculations, showing the importance of Ir spin orbit
coupling on the electron correlations. The magnetic excitations survive up to
200 K well above the magnetic ordering temperature of $T_N \sim 70$ K, also
indicating a quasi-1D nature of the magnetic interactions in Sr$_3$NiIrO$_6$.
Our results not only support the idea of the existence of a new temperature
scale well above $T_N$, but also emphasize the need to consider new exchange
paths complicated by the SOC, resulting in additional characteristic
temperatures in such spin-chain systems.",1501.05735v1
2015-06-16,Weyl nodes in periodic structures of superconductors and spin active materials,"Motivated by recent progress in epitaxial growth of proximity structures of
s-wave superconductors (S) and spin-active materials (M), we show that the
periodic structure of S and M can behave effectively as a superconductor with
pairs of point nodes, near which the low energy excitations are Weyl fermions.
A simple toy model, where M is described by a Kronig-Penney potential with both
spin-orbit coupling and exchange field, is proposed and solved to obtain the
phase diagram of the nodal structure, the spin texture of the Weyl fermions, as
well as the zero energy surface states in the form of open Fermi lines (""Fermi
arcs""). Going beyond the simple model, a lattice model with alternating layers
of S and magnetic $Z_2$ topological insulators (M) is solved. The calculated
spectrum confirms previous prediction of Weyl nodes based on tunneling
Hamiltonian of Dirac electrons. Our results provide further evidence that
periodic structures of S and M are well suited for engineering gapless
topological superconductors.",1506.05166v2
2015-07-12,Indirect Spin Exchange Interaction in Substituted Copper Phthalocyanine Crystalline Thin Films,"The origins of indirect spin exchange in crystalline thin films of Copper
Octabutoxy Phthalocyanine (Cu-OBPc) are investigated using Magnetic Circular
Dichroism (MCD) spectroscopy. These studies are made possible by a solution
deposition technique which produces highly ordered films with macroscopic grain
sizes suitable for optical studies. For temperatures lower than 2 K, the
contribution of a specific state in the valence band manifold originating from
the hybridized lone pair in nitrogen orbitals of the Phthalocyanine ring, bears
the Brillouin-like signature of an exchange interaction with the localized
$\textit{d}$-shell Cu spins. A comprehensive MCD spectral analysis coupled with
a molecular field model of a $\sigma\pi-d$ exchange analogous to
$\textit{sp-d}$ interactions in Diluted Magnetic Semiconductors (DMS) renders
an enhanced Zeeman splitting and a modified $\textit{g}$-factor of -4 for the
electrons that mediate the interaction. These studies define an experimental
tool for identifying electronic states involved in spin-dependent exchange
interactions in organic materials.",1507.03249v1
2015-09-30,Electron spin rotations induced by oscillating Rashba interaction in a quantum wire,"A novel method and nanodevice are introduced that allows to rotate the single
electron spin confined in a gated electrostatic InSb nanowire quantum dot.
Proposed method does not require application of any (oscillating or static)
external magnetic fields. Our proposal instead employs spatial and time
modulation of confining potential induced by electric gates, which, in turn
leads to oscillating Rashba type spin-orbit coupling. Moving electron back and
forth in such a variable Rashba field allows for realization of spin rotations
around two different axes separately without using an external magnetic field.
The results are supported by realistic three-dimensional time dependent
Poisson-Schr\""{o}dinger calculations for systems and material parameters
corresponding to experimentally accessible structures.",1509.09145v2
2016-04-16,"Spin-orbit excitation energies, anisotropic exchange, and magnetic phases of honeycomb RuCl3","Using quantum chemistry calculations we shed fresh light on the electronic
structure and magnetic properties of RuCl3, a proposed realization of the
honeycomb Kitaev spin model. It is found that the nearest-neighbor Kitaev
exchange K is weaker than in 5d5 Ir oxides but still larger than other
effective spin couplings. The electronic-structure computations also indicate a
ferromagnetic K in the halide, which is supported by a detailed analysis of the
field-dependent magnetization. From exact-diagonalization calculations for
extended Kitaev-Heisenberg Hamiltonians we additionally find that a transition
from zigzag order to a spin-liquid ground state can be induced in RuCl3 with
external magnetic field.",1604.04755v1
2016-07-15,"Honeycomb-lattice Heisenberg-Kitaev model in a magnetic field: Spin canting, metamagnetism, and vortex crystals","The Heisenberg-Kitaev model is a paradigmatic model to describe the magnetism
in honeycomb-lattice Mott insulators with strong spin-orbit coupling, such as
A$_2$IrO$_3$ (A = Na, Li) and $\alpha$-RuCl$_3$. Here we study in detail the
physics of the Heisenberg-Kitaev model in an external magnetic field. Using a
combination of Monte-Carlo simulations and spin-wave theory we map out the
classical phase diagram for different directions of the magnetic field. Broken
SU(2) spin symmetry renders the magnetization process rather complex, with
sequences of phases and metamagnetic transitions. In particular, we find
various large-unit-cell and multi-Q phases including a vortex-crystal phase for
a field in the [111] direction. We also discuss quantum corrections in the
high-field phase.",1607.04640v2
2016-07-23,Magneto-optical transport properties of monolayer WSe2,"The recent experimental realization of a high quality WSe$% _{2} $ leads to
the possibility of magneto-optical measurements and the manipulation of the
spin and valley degrees of freedom. We study the influence of the very strong
spin-orbit coupling and of the anisotropic lifting of the valley pseudospin
degeneracy on its magnetotransport properties. The energy spectrum of WSe$_{2}
$ is derived and discussed in the presence of a perpendicular magnetic field
$B$. Correspondingly we evaluate the magneto-optical Hall conductivity and the
optical longitudinal conductivity as functions of the frequency, magnetic
field, and Fermi energy. They are strongly influenced by the field $B$ and the
strong spin splitting. The former exhibits valley polarization and the latter
beatings of oscillations. The magneto-optical responses can be tuned in two
different regimes: the mictrowave-to-terahertz regime and the visible-frequency
one. The absorption peaks involving the $n=0$ LL appear in between these two
regimes and show a magnetic control of the spin and valley splittings. We also
evaluate the power absorption spectrum.",1607.06917v1
2016-09-28,Odd-parity superconductivity near inversion breaking quantum critical point in one dimension,"We study how an inversion-breaking quantum critical point affects the ground
state of a one-dimensional electronic liquid with repulsive interaction and
spin-orbit coupling. We find that regardless of the interaction strength, the
critical fluctuations always lead to a gap in the electronic spin-sector. The
origin of the gap is a two-particle backscattering process, which becomes
relevant due to renormalization of the Luttinger parameter near the critical
point. The resulting spin-gapped state is a one-dimensional version of spin
triplet superconductivity. Interestingly, in the case of a ferromagnetic
critical point the Luttinger parameter is renormalized in the opposite manner,
such that the system remains non-superconducting.",1609.09084v3
2017-02-08,Measuring Majorana non-locality and spin structure with a quantum dot,"Robust zero bias transport anomalies in semiconducting nanowires with
proximity-induced superconductivity have been convincingly demonstrated in
various experiments. While these are compatible with the existence of Majorana
zero modes at the ends of the nanowire, a direct proof of their non-locality
and topological protection is now needed. Here we show that a quantum dot at
the end of the nanowire may be used as a powerful spectroscopic tool to
quantify the degree of Majorana non-locality through a local transport
measurement. Moreover, the spin polarization of dot sub-gap states at
singlet-doublet transitions in the Coulomb blockade regime allows the dot to
directly probe the spin structure of the Majorana wave function, and indirectly
measure the spin-orbit coupling of the nanowire.",1702.02525v3
2017-03-07,Magnetic-field orientation dependence of transport properties of topologically superconducting wire,"We present the study of transport properties of a superconducting wire with
strong Rashba spin-orbit coupling for different orientations of an external
magnetic field. Using the nonequilibrium Green's functions in the tight-binding
approach the crucial impact of the relative alignment of lead magnetization and
the Majorana bound state (MBS) spin polarization on the low-bias conductance
and shot noise is presented. Depending on this factor the transport regime can
effectively vary from symmetric to extremely asymmetric. In the last situation
the current-symmetry breaking, the suppression of the MBS-assisted conductance
and specific Fano factor behavior lead to current-switch effect. The
persistence of these features under the presence of diagonal disorder and
phenomenologically modeled g-factor anisotropy is demonstrated. In the case of
paramagnetic leads the MBS spin polarization gives rise to the spin-filtering
effect depending on the magnetic-field orientation.",1703.02320v3
2017-08-11,Dimensional reduction by pressure in the magnetic framework material CuF$_{2}$(D$_{2}$O)$_{2}$pyz: from spin-wave to spinon excitations,"Metal organic magnets have enormous potential to host a variety of electronic
and magnetic phases that originate from a strong interplay between the spin,
orbital and lattice degrees of freedom. We control this interplay in the
quantum magnet CuF$_2$(D$_2$O)$_2$pyz by using high pressure to drive the
system through a structural and magnetic phase transition. Using neutron
scattering, we show that the low pressure state, which hosts a two-dimensional
square lattice with spin-wave excitations and a dominant exchange coupling of
0.89 meV, transforms at high pressure into a one-dimensional spin-chain
hallmarked by a spinon continuum and a reduced exchange interaction of 0.43
meV. This direct microscopic observation of a magnetic dimensional crossover as
a function of pressure opens up new possibilities for studying the evolution of
fractionalised excitations in low dimensional quantum magnets and eventually
pressure-controlled metal--insulator transitions.",1708.03586v1
2017-08-27,Electronic and spin dynamics in the insulating iron pnictide NaFe$_{0.5}$Cu$_{0.5}$As,"NaFe$_{0.5}$Cu$_{0.5}$As represents a rare exception in the metallic iron
pnictide family, in which a small insulating gap is opened. Based on
first-principles study, we provide a comprehensive theoretical characterization
of this insulating compound. The Fe$^{3+} $spin degree of freedom is quantified
as a quasi-1D $S=\frac{5}{2}$ Heisenberg model. The itinerant As hole state is
downfolded to a $p_{xy}$-orbital hopping model on a square lattice. A unique
orbital-dependent Hund's coupling between the spin and the hole is revealed.
Several important material properties are analyzed, including (a) factors
affecting the small $p-d$ charge-transfer gap; (b) role of the extra interchain
Fe; and (c) the quasi-1D spin excitation in the Fe chains. The experimental
manifestations of these properties are discussed.",1708.08065v1
2018-02-02,Can the quantum spin Hall state of silicene be preserved on substrate,"The substrate-induced topological phase transition of silience is a
formidable obstacle for developing silicene-based materials and devices for
compatibility with current electronics by using its topologically protected
dissipationless edge states. First-principles calculations indicate that the
substrate will result in a phase transition from topological nontrivial phase
to trivial phase of silicene, although its Dirac cone is still obvious. The
substrate effect (equivalent to an electric field) annihilates its spin-orbit
coupling effect, the reason why its quantum spin Hall effect (QSHE) of silicene
has not been experimentally observed. Unfortunately, external electric field
seems impossible to recover the QSHE due to the screen effect of substrate. We
here first propose a viable strategy (constructing inverse symmetrical sandwich
structure (protective layer/silicene/substrate)) to preserve quantum spin Hall
(QSH) state of silicene, which is demonstrated by using two representatives
(CeO2(111)/silicene/CeO2(111) and CaF2(111)/silicene/CaF2(111)) through the
calculated edge states and Z2 invariant. This work takes a critical step
towards fundamental physics and realistic applications of silicene-based
nanoelectronic devices.",1802.00591v1
2020-07-02,Wave-particle duality of electrons with spin-momentum locking,"We investigate the effects of spin-momentum locking on the interference and
diffraction patterns due to a double- or single-slit in an electronic
\emph{Gedankenexperiment}. We show that the inclusion of the
spin-degree-of-freedom, when coupled to the motion direction of the carrier --
a typical situation that occurs in systems with spin-orbit interaction -- leads
to a modification of the interference and diffraction patterns that depend on
the geometrical parameters of the system.",2007.01021v3
2020-07-03,Emergence of Intra-Particle Entanglement and Time-Varying Violation of Bell's Inequality in Dirac Matter,"We demonstrate the emergence and dynamics of intra-particle entanglement in
massless Dirac fermions. This entanglement, generated by spin-orbit coupling,
arises between the spin and sublattice pseudospin of electrons in graphene. The
entanglement is a complex dynamic quantity but is generally large, independent
of the initial state. Its time dependence implies a dynamical violation of a
Bell inequality, while its magnitude indicates that large intra-particle
entanglement is a general feature of graphene on a substrate. These features
are also expected to impact entanglement between pairs of particles, and may be
detectable in experiments that combine Cooper pair splitting with nonlocal
measurements of spin-spin correlation in mesoscopic devices based on Dirac
materials.",2007.01584v2
2020-07-03,Dynamic spin-triplet order induced by alternating electric fields in superconductor-ferromagnet-superconductor Josephson junctions,"Dynamic states offer extended possibilities to control the properties of
quantum matter. Recent efforts are focused on studying the ordered states which
appear exclusively under the time-dependent drives. Here we demonstrate a class
of systems which feature dynamic spin-triplet superconducting order stimulated
by the alternating electric field. The effect is based on the interplay of
ferromagnetism, interfacial spin-orbital coupling (SOC) and the condensate
motion driven by the field, which converts hidden static p-wave order, produced
by the joint action of the ferromagnetism and the SOC, into dynamical s-wave
equal-spin triplet correlations. We demonstrate that the critical current of
Josephson junctions hosting these states is proportional to the electromagnetic
power, supplied either by the external irradiation or by the ac current source.
Based on these unusual properties we propose the scheme of a Josephson
transistor which can be switched by the ac voltage and demonstrates an
even-numbered sequence of Shapiro steps. Combining the photo-active Josephson
junctions with recently discovered Josephson phase batteries we find
photo-magnetic SQUID devices which can generate spontaneous magnetic fields
while being exposed to irradiation.",2007.01805v2
2013-07-31,Relativistic symmetries in trigonometric Poschl-Teller potential plus tensor interaction,"The Dirac equation is solved to obtain its approximate bound states for a
spin-1/2 particle in the presence of trigonometric Poschl-Teller (tPT)
potential including a Coulomb-like tensor interaction with arbitrary spin-orbit
quantum number $\kappa$ using an approximation scheme to substitute the
centrifugal terms k(k+1)/r^2. In view of spin and pseudo-spin (p-spin)
symmetries, the relativistic energy eigenvalues and the corresponding
two-component wave functions of a particle moving in the field of attractive
and repulsive tPT potentials are obtained using the asymptotic iteration method
(AIM). We present numerical results in the absence and presence of tensor
coupling $A$ and for various values of spin and p-spin constants and quantum
numbers n and k. The non-relativistic limit is also obtained.",1308.0008v1
2013-08-15,Magnetic order in pyrochlore iridate Nd$_2$Ir$_2$O$_7$ probed by muon spin relaxation,"Muon-spin relaxation results on the pyrochlore iridate Nd$_2$Ir$_2$O$_7$ are
reported. Spontaneous coherent muon-spin precession below the metal-insulator
transition (MIT) temperature of about 33 K is observed, indicating the
appearance of a long-ranged magnetic ordering of Ir$^{4+}$ moments. With
further decrease in temperature, the internal field at the muon site increases
again below about 9 K. The second increase of internal field suggests the
ordering of Nd$^{3+}$ moments, which is consistent with a previous neutron
experiment. Our results suggest that the MIT and magnetic ordering of Ir$^{4+}$
moments have a close relationship and that the large spin-orbit coupling of Ir
5\textit{d} electrons plays a key role for both MIT and the mechanism of the
magnetic ordering in pyrochlore iridates in the insulting ground state.",1308.3283v1
2017-01-13,Proximity induced spin-valley polarization in silicene/germanene on F-doped WS$_2$,"Silicene and germanene are key materials for the field of valleytronics.
However, interaction with the substrate, which is necessary to support the
electronically active medium, becomes a major obstacle. In the present work, we
propose a substrate (F-doped WS$_2$) that avoids detrimental effects and at the
same time induces the required valley polarization, so that no further steps
are needed for this purpose. The behavior is explained by proximity effects on
silicene/germanene, as demonstrated by first-principles calculations. Broken
inversion symmetry due to the presence of WS$_2$ opens a substantial band gap
in silicene/germanene. F doping of WS$_2$ results in spin polarization, which,
in conjunction with proximity-enhanced spin orbit coupling, creates sizable
spin-valley polarization.",1701.03667v1
2017-01-26,Antiferromagnetic textures and dynamics on the surface of a heavy metal,"We investigate the formation and dynamics of spin textures in
antiferromagnetic insulators adjacent to a heavy-metal substrate with strong
spin-orbit interactions. Exchange coupling to conduction electrons engenders an
effective anisotropy, Dzyaloshinskii-Moriya interactions, and a magnetoelectric
effect for the N\'{e}el order, which can conspire to produce nontrivial
antiferromagnetic textures. Current-driven spin transfer enabled by the heavy
metal, furthermore, triggers ultrafast (THz) oscillations of the N\'{e}el order
for dc currents exceeding a critical threshold, opening up the possibility of
Terahertz spin-torque self-oscillators. For a commonly invoked
antidamping-torque geometry, however, the instability current scales with the
energy gap of the antiferromagnetic insulator and, therefore, may be
challenging to reach experimentally. We propose an alternative generic geometry
for inducing ultrafast autonomous antiferromagnetic dynamics.",1701.07863v2
2017-01-29,Signatures of interaction-induced helical gaps in nanowire quantum point contacts,"Spin-momentum locking in a semiconductor device with strong spin-orbit
coupling (SOC) is a fundamental goal of nanoscale spintronics and an important
prerequisite for the formation of Majorana bound states. Such a helical state
is predicted in one-dimensional (1D) nanowires subject to strong Rashba SOC and
spin-mixing, its hallmark being a characteristic reentrant behaviour in the
conductance. Here, we report the first direct experimental observations of the
reentrant conductance feature, which reveals the formation of a helical liquid,
in the lowest 1D subband of an InAs nanowire. Surprisingly, the feature is very
prominent also in the absence of magnetic fields. This behaviour suggests that
exchange interaction exhibits substantial impact on transport in our device. We
attribute the opening of the pseudogap to spin-flipping two-particle
backscattering. The all-electric origin of the ideal helical transport bears
momentous implications for topological quantum computing.",1701.08439v1
2017-01-31,Dirac nodal lines and induced spin Hall effect in metallic rutile oxides,"We have found Dirac nodal lines (DNLs) in the band structures of metallic
rutile oxides IrO$_2$, OsO$_2$, and RuO$_2$ and revealed a large spin Hall
conductivity contributed by these nodal lines, which explains a strong spin
Hall effect (SHE) of IrO$_2$ discovered recently. Two types of DNLs exist. The
first type forms DNL networks that extend in the whole Brillouin zone and
appears only in the absence of spin-orbit coupling (SOC), which induces surface
states on the boundary. Because of SOC-induced band anti-crossing, a large
intrinsic SHE can be realized in these compounds. The second type appears at
the Brillouin zone edges and is stable against SOC because of the protection of
nonsymmorphic symmetry. Besides reporting new DNL materials, our work reveals
the general relationship between DNLs and the SHE, indicating a way to apply
Dirac nodal materials for spintronics.",1701.09089v1
2018-05-10,Current-Modulated Magnetoplasmonic Devices,"We model the operation and readout sensitivity of two current-modulated
magnetoplasmonic devices which exploit spin Hall effect-like behavior as a
function of their device and material parameters. In both devices, current
pulses are applied to an electrically-isolated stack, containing an active
layer (either a metal with large spin orbit coupling or a topological
insulator) embedded within a plasmonic metal (Au). The first device, composed
of a ferromagnet and the active layer, illustrates a plasmonic readout scheme
for detecting magnetic reorientation driven by current-induced spin transfer
torques. The plasmonic readout of these current-modulated non-volatile states
may facilitate the development of plasmon-based memory or logic devices. The
second device, containing only the active layer, explores the magnetoplasmonic
readout conditions required to directly measure the spin accumulation in these
materials. The estimated thickness-dependent sensitivity agrees with recent
experimental magneto-optical Kerr effect observations.",1805.03926v1
2009-12-23,Current-induced torques in continuous antiferromagnetic textures,"We study the influence of an electric current on a continuous non-collinear
antiferromagnetic texture. Despite the lack of a net magnetic moment we find
that the exchange interaction between conduction electrons and local
magnetization generally results in current-induced torques that are similar in
phenomenology to spin transfer torques in ferromagnets. We present the
generalization of the non-linear sigma model equation of motion for the
N\'{e}\`{e}l vector that includes these current-induced torques, and briefly
discuss the resulting current-induced antiferromagnetic domain wall motion and
spin-wave Doppler shift. We give an interpretation of our results using a
unifying picture of current-induced torques in ferromagnets and
antiferromagnets in which they are viewed as due to the current-induced spin
polarization resulting from an effective spin-orbit coupling.",0912.4519v1
2011-11-16,Interaction correction to the conductivity of two-dimensional electron gas in In$_x$Ga$_{1-x}$As/InP quantum well structure with strong spin-orbit coupling,"The electron-electron interaction quantum correction to the conductivity of
the gated single quantum well InP/In$_{0.53}$Ga$_{0.47}$As heterostructures is
investigated experimentally. The analysis of the temperature and magnetic field
dependences of the conductivity tensor allows us to obtain reliably the
diffusion part of the interaction correction for different values of spin
relaxation rate, $1/\tau_s$. The surprising result is that the spin relaxation
processes do not suppress the interaction correction in the triplet channel
and, thus, do not enhance the correction in magnitude contrary to theoretical
expectations even in the case of relatively fast spin relaxation,
$1/T\tau_s\simeq (20-25)\gg 1$.",1111.3767v1
2011-11-16,Quantum phase transitions in the Kane-Mele-Hubbard model,"We study the two-dimensional Kane-Mele-Hubbard model at half filling by means
of quantum Monte Carlo simulations. We present a refined phase boundary for the
quantum spin liquid. The topological insulator at finite Hubbard interaction
strength is adiabatically connected to the groundstate of the Kane-Mele model.
In the presence of spin-orbit coupling, magnetic order at large Hubbard U is
restricted to the transverse direction. The transition from the topological
band insulator to the antiferromagnetic Mott insulator is in the universality
class of the three-dimensional XY model. The numerical data suggest that the
spin liquid to topological insulator and spin liquid to Mott insulator
transitions are both continuous.",1111.3949v2
2014-05-19,Quantum Spin Hall Effect in Strip of Stripes Model,"We consider quantum spin Hall effect in an anisotropic strip of stripes and
address both integer and fractional filling factors. The first model is based
on a gradient of spin-orbit interaction in the direction perpendicular to the
stripes. The second model is based on two weakly coupled strips with reversed
dispersion relations. We demonstrate that these systems host helical modes,
modes in which opposite spins propagate in opposite directions. In the integer
regime, the modes carry an elementary electron charge whereas in the fractional
regime they carry fractional charges, and their excitations possess anyonic
braiding statistics. These simple quasi-one-dimensional models can serve as a
platform for understanding effects arising due to electron-electron
correlations in topological insulators.",1405.4793v1
2014-06-17,Renormalization of electron self-energies via their interaction with spin excitations: A first-principles investigation,"Access to magnetic excitation spectra of single atoms deposited on surfaces
is nowadays possible by means of low-temperature inelastic scanning tunneling
spectroscopy. We present a first-principles method for the calculation of
inelastic tunneling spectra utilizing the Korringa-Kohn-Rostoker Green function
method combined with time-dependent density functional theory and many-body
perturbation theory. The key quantity is the electron self-energy describing
the coupling of the electrons to the spin excitation within the adsorbate. By
investigating Cr, Mn, Fe and Co adatoms on a Cu(111) substrate, we
spin-characterize the spectra and demonstrate that their shapes are altered by
the magnetization of the adatoms, of the tip and the orbital decay into vacuum.
Our method also predicts spectral features more complex than the steps obtained
by simpler models for the adsorbate (e.g., localized spin models).",1406.4195v1
2017-06-27,"Intrinsic 2D ferromagnetism, quantum anomalous Hall conductivity, and fully-spin-polarized edge states of FeBr3 monolayer","It is of great interest to explore intrinsic two-dimensional ferromagnetism
and seek better two-dimensional quantum anomalous Hall insulator materials.
Here, we show that the FeBr$_3$ monolayer is an intrinsic two-dimensional
ferromagnetic material whose Curie temperature is 140 K thanks to its strong
spin exchange interaction and giant uniaxial magnetic anisotropy. Our phonon
spectra and mechanical analysis indicate that the FeBr$_3$ monolayer is
dynamically and mechanically stable. Our electronic structure calculation shows
that there is one Dirac cone at K point in the Brillouin zone and the
spin-orbit coupling opens a semiconductor gap of 33.5 meV. Further
tight-binding analysis reveals that the Chern number is equivalent to 1 and
there is a quantum anomalous Hall conductivity $\sigma _{xy} = e^2/h$, and the
chiral edge states are fully spin-polarized when an edge is created.
Furthermore, it is shown that the main results are not affected by electron
correlation effects and biaxial strain. Therefore, this FeBr$_3$ monolayer as
2D material would be useful for spintronic applications.",1706.08943v2
2017-12-11,Prediction of a large-gap and switchable Kane-Mele quantum spin Hall insulator,"Fundamental research and technological applications of topological insulators
are hindered by the rarity of materials exhibiting a robust topologically
non-trivial phase, especially in two dimensions. Here, by means of extensive
first-principles calculations, we propose a novel quantum spin Hall insulator
with a sizeable band gap of $\sim$0.5 eV that is a monolayer of Jacutingaite, a
naturally occurring layered mineral first discovered in 2008 in Brazil and
recently synthesised. This system realises the paradigmatic Kane-Mele model for
quantum spin Hall insulators in a potentially exfoliable two-dimensional
monolayer, with helical edge states that are robust and that can be manipulated
exploiting a unique strong interplay between spin-orbit coupling,
crystal-symmetry breaking and dielectric response.",1712.03873v2
2017-12-28,Helical liquid in carbon nanotubes wrapped with DNA molecules,"The measured electric resistance of carbon nanotubes wrapped with DNA
molecules depends strongly on the spin of the injected electrons. Motivated by
these experiments, we study the effect of helix-shaped potentials on the
electronic spectrum of carbon nanotubes. We find that in combination with the
curvature-induced spin-orbit coupling inherent to nanotubes, such a
perturbation opens helicity-dependent gaps. Within these partial gaps,
left-moving electrons carry a fixed spin-projection that is reversed for
right-moving electrons, and the probability of electrons to transfer through
the nanotube correlates with their helicity. We explain the origin of this
effect and show that it can alternatively be induced by twisting the nanotube.
Our findings suggest that carbon nanotubes hold great potential for
implementing spin filters and may form an ideal platform to study the physical
properties of one-dimensional helical liquids.",1712.09950v1
2018-01-09,Unidirectional spin density wave state in metallic (Sr1-xLax)2IrO4,"Materials that exhibit both strong spin orbit coupling and electron
correlation effects are predicted to host numerous new electronic states. One
prominent example is the Jeff =1/2 Mott state in Sr2IrO4, where introducing
carriers is predicted to manifest high temperature superconductivity analogous
to the S=1/2 Mott state of La2CuO4. While bulk superconductivity currently
remains elusive, anomalous quasi-particle behaviors paralleling those in the
cuprates such as pseudogap formation and the formation of a d-wave gap are
observed upon electron-doping Sr2IrO4. Here we establish a magnetic parallel
between electron-doped Sr2IrO4 and hole-doped La2CuO4 by unveiling a spin
density wave state in electron-doped Sr2IrO4. Our magnetic resonant x-ray
scattering data reveal the presence of an incommensurate magnetic state
reminiscent of the diagonal spin density wave state observed in the monolayer
cuprate (La1-xSrx)2CuO4. This link supports the conjecture that the quenched
Mott phases in electron-doped Sr2IrO4 and hole-doped La2CuO4 support common
competing electronic phases.",1801.03076v1
2018-01-14,Rashba-driven anomalous Nernst conductivity of lead chalcogenide films,"The presence of a finite Berry curvature $\left(\Omega\left(k\right)\right)$
leads to anomalous thermal effects. In this letter, we compute the coefficients
for the anomalous Nernst effect $\left(ANE\right) $ and its spin analogue, the
spin Nernst effect $\left(SNE\right)$ in lead chalcogenide (\textit{PbX};
\textit{X} = S, Se, Te) films. The narrow gapped \textit{PbX} films with a
large spin-orbit coupling (\textit{soc}) offer a significant Rashba interaction
that gives rise to $ \Omega\left(k\right) $ and the attendant anomalous thermal
behaviour. In presence of a temperature gradient, the $ ANE $ and $ SNE $
establish a thermal and spin current and are characterized by their respective
coefficients which acquire higher values for a stronger Rashba interaction. We
further show that an extrinsic \textit{soc} generated by an in-plane electric
field offers a gate-like mechanism to control (and turn-off) the anomalous
thermal currents. Finally, we conclude by deriving the efficiency of an $ ANE
$-driven low-temperature Carnot heat engine and demonstrate that it can be
gainfully optimized in systems with a robust intrinsic \textit{soc} resulting
in low carrier effective masses.",1801.04516v2
2018-09-03,Generating high-order optical and spin harmonics from ferromagnetic monolayers,"High-order harmonic generation (HHG) in solids has entered a new phase of
intensive research, with envisioned band-structure mapping on an ultrashort
time scale. This partly benefits from a flurry of new HHG materials discovered,
but so far has missed an important group. HHG in magnetic materials should have
profound impact on future magnetic storage technology advances. Here we
introduce and demonstrate HHG in ferromagnetic monolayers. We find that HHG
carries spin information and sensitively depends on the relativistic spin-orbit
coupling; and if they are dispersed into the crystal momentum ${\bf k}$ space,
harmonics originating from real transitions can be ${\bf k}$-resolved and carry
the band structure information. Geometrically, the HHG signal is sensitive to
spatial orientations of monolayers. Different from the optical counterpart, the
spin HHG, though probably weak, only appears at even orders, a consequence of
SU(2) symmetry. Our findings open an unexplored frontier -- magneto-high-order
harmonic generation.",1809.00613v1
2018-09-14,Visualizing entanglement in atoms and molecules,"In this work we show how constructing Wigner functions of heterogeneous
quantum systems leads to new capability in the visualization of quantum states
of atoms and molecules. This method allows us to display quantum correlations
(entanglement) between spin and spatial degrees of freedom (spin-orbit
coupling) and between spin degrees of freedom, as well as more complex
combinations of spin and spatial entanglement for the first time. This is
important as there is growing recognition that such properties affect the
physical characteristics, and chemistry, of atoms and molecules. Our
visualizations are sufficiently accessible that, with some preparation, those
with a non-technical background can gain an appreciation of subtle quantum
properties of atomic and other systems. By providing new insights and modelling
capability, our phase-space representation will be of great utility in
understanding aspects of atomic physics and chemistry not available with
current techniques.",1809.05431v3
2018-09-28,Helical Topological Edge States in a Quadrupole Phase,"Topological electric quadrupole is a recently proposed concept that extends
the theory of electric polarization of crystals to higher orders. Such a
quadrupole phase supports topological states localized on both edges and
corners. In this work, we show that in a quadrupole phase of honeycomb lattice,
topological helical edge states and pseudo-spin-polarized corner states appear
by making use of a pseudo-spin degree of freedom related to point group
symmetry. Furthermore, we argue that a general condition for emergence of
helical edge states in a (pseudo-)spinful quadrupole phase is mirror or
time-reversal symmetry. Our results offers a way of generating topological
helical edge states without spin-orbital couplings.",1809.10824v2
2019-09-19,Colloquium: Spintronics in graphene and other two-dimensional materials,"After the first unequivocal demonstration of spin transport in graphene
(Tombros et al., 2007), surprisingly at room temperature, it was quickly
realized that this novel material was relevant for both fundamental spintronics
and future applications. Over the decade since, exciting results have made the
field of graphene spintronics blossom, and a second generation of studies has
extended to new two-dimensional (2D) compounds. This Colloquium reviews recent
theoretical and experimental advances on electronic spin transport in graphene
and related 2D materials, focusing on emergent phenomena in van der Waals
heterostructures and the new perspectives provided by them. These phenomena
include proximity-enabled spin-orbit effects, the coupling of electronic spin
to light, electrical tunability, and 2D magnetism.",1909.09188v2
2019-09-30,Spin-dependent refraction at the interface of lateral heterostructures of 2$H$-type transition-metal dichalcogenide monolayers,"We study the refraction effect of electronic wave in hole-doped lateral
heterojunctions of metallic and semiconducting transition-metal dichalcogenide
monolayers. This effect is theoretically investigated in 2$H$-type
MoSe$_2$-NbS$_2$ and WSe$_2$-NbS$_2$ junctions by combining the
first-principles calculation and the lattice Green's function method. We show
that the electronic waves change the direction of motion at the interface and
collimate the velocity along two different directions depending on the spin. We
find that the transmission probability increases with the charge density and
that the direction of refracted electron beams is close to $\pm30^\circ$ with
respect to the perpendicular axis to the interface. The metallic
transition-metal dichalcogenide is essential for the refraction effect because
of the strong trigonal-warping effect, the large Fermi surface, and the
Zeeman-type spin-orbit coupling. The refraction effect enables to generate the
spin-polarized electronic current by using a simple fabrication of
transition-metal dichalcogenide monolayers.",1909.13401v1
2019-10-25,Twisted magnon as a magnetic tweezer,"Wave fields with spiral phase dislocations carrying orbital angular momentum
(OAM) have been realized in many branches of physics, such as for photons,
sound waves, electron beams, and neutrons. However, the OAM states of magnons
(spin waves)$-$the building block of modern magnetism$-$and particularly their
implications have yet to be addressed. Here, we theoretically investigate the
twisted spin-wave generation and propagation in magnetic nanocylinders. The OAM
nature of magnons is uncovered by showing that the spin-wave eigenmode is also
the eigenstate of the OAM operator in the confined geometry. Inspired by
optical tweezers, we predict an exotic ""magnetic tweezer"" effect by showing
skyrmion gyrations under twisted magnons in exchange coupled
nanocylinder$|$nanodisk heterostructure, as a practical demonstration of
magnonic OAM to manipulate topological spin defects. Our study paves the way
for the emerging magnetic manipulations by harnessing the OAM degree of freedom
of magnons.",1910.11528v2
2019-10-30,Synthesizing the Quantum Spin Hall Phase for Ultracold Atoms in Bichromatic Chiral Optical Ladders,"Realizing the topological bands of helical states poses a challenge in
studying ultracold atomic gases. Motivated by the recent experimental success
in realizing chiral optical ladders, here we present a scheme for synthesizing
topological quantum matter, especially the quantum spin Hall phase, in the
chiral optical ladders. More precisely, we first establish the synthetic
pseudo-spin-orbit coupling and Zeeman splitting in the chiral ladders. We
analyze the band structure of the ladders exposed to the bichromatic optical
potentials and report the existence of quantum spin Hall phase. We further
identify a rich phase diagram of the bichromatic chiral ladders, illustrating
that our proposal features a large space of system parameters exhibiting a
variety of quantum phase transitions. Our scheme can be readily implemented in
the existing experimental systems and hence provides a new method to engineer
the sophisticated topological bands for cold atomic gases.",1910.13663v1
2020-02-12,Volkov-Pankratov states in topological superconductors,"We study the in-gap states that appear at the boundaries of both 1D and 2D
topological superconductors. While the massless Majorana quasiparticles are
guaranteed to arise by the bulk-edge correspondence, we find that they could be
accompanied by massive Volkov-Pankratov (VP) states which are present only when
the interface is sufficiently smooth. These predictions can be tested in an
s-wave superconductor with Rashba spin-orbit coupling placed on top of a
magnetic domain wall. We calculate the spin-resolved local density of states of
the VP states about the band inversion generated by a magnetic domain wall and
find that they are oppositely spin-polarized on either side of the topological
phase boundary. We also demonstrate that the spatial position, energy-level
spacing, and spin polarization of the VP states can be modified by the
introduction of in-plane electric fields.",2002.05236v1
2020-04-02,Spin-Dependent Charge-Carrier Recombination Processes in Tris(8-Hydroxyquinolinato) Aluminum,"We have studied the nature and dynamics of spin-dependent charge carrier
recombination in Tris(8-hydroxyquinolinato) aluminum (Alq$_3$) films in light
emitting diodes at room temperature using continuous wave and pulsed
electrically detected magnetic resonance (EDMR) spectroscopy. We found that the
EDMR signal is dominated by an electron-hole recombination process, and
another, weaker EDMR signal whose fundamental nature was investigated. From the
pulsed EDMR measurements we obtained a carrier spin relaxation time, $T_2 =
45\pm 25$ ns which is much shorter than $T_2$ in conjugated polymers, but
relatively long for a molecule containing elements with high atomic number.
Using multi-frequency continuous wave EDMR spectroscopy, we obtained the local
hyperfine field distributions for electrons and holes, as well as their
respective spin-orbit coupling induced g-factor and g-strain values.",2004.00765v1
2018-03-09,Experimental determination of exchange constants in antiferromagnetic Mn$_2$Au,"Mn$_2$Au is an important antiferromagnetic (AF) material for spintronics
applications. Due to its very high N\'eel temperature of about 1500 K, some of
the basic properties are difficult to explore, such as the AF susceptibility
and the exchange constants. Experimental determination of these properties is
further complicated in thin films by unavoidable presence of uncompensated and
quasiloose spins on antisites and at interfaces. Using x-ray magnetic circular
dichroism (XMCD), we have measured the spin and orbital contribution to the
susceptibility in the direction perpendicular to the in-plane magnetic moments
of a Mn$_2$Au(001) film and in fields up to 8 T. By performing these
measurements at a low temperature of 7 K and at room temperature, we were able
to separate the loose spin contribution from the susceptibility of AF coupled
spins. The value of the AF exchange constant obtained with this method for a 10
nm thick Mn$_2$Au(001) film equals to (24 $\pm$ 5) meV.",1803.03524v1
2018-03-12,"Kramers degeneracy and relaxation in vanadium, niobium and tantalum clusters","In this work we use magnetic deflection of V, Nb, and Ta atomic clusters to
measure their magnetic moments. While only a few of the clusters show weak
magnetism, all odd-numbered clusters deflect due to the presence of a single
unpaired electron. Surprisingly, for majority of V and Nb clusters an
atomic-like behavior is found, which is a direct indication of the absence of
spin-lattice interaction. This is in agreement with Kramers degeneracy theorem
for systems with a half-integer spin. This purely quantum phenomenon is
surprisingly observed for large systems of more than 20 atoms, and also
indicates various quantum relaxation processes, via Raman two-phonon and Orbach
high-spin mechanisms. In heavier, Ta clusters, the relaxation is always
present, probably due to larger masses and thus lower phonon energies, as well
as increased spin-orbit coupling.",1803.04320v1
2018-08-08,High throughput screening for spin-gapless semiconductors in quaternary Heusler compounds,"Based on high throughput density functional theory calculations, we performed
systematic screening for spin-gapless semiconductors (SGSs) in quaternary
Heusler alloys XX 0 YZ (X, X 0 , and Y are transition metal elements without
Tc, and Z is one of B, Al, Ga, In, Si, Ge, Sn, Pb, P, As, Sb, and Bi).
Following the empirical rule, we focused on compounds with 21, 26, or 28
valence electrons, resulting in 12, 000 possible chemical compositions. After
systematically evaluating the thermodynamic, mechanical, and dynamical
stabilities, we successfully identified 70 stable SGSs, confirmed by explicit
electronic structure calculations with proper magnetic ground states. It is
demonstrated that all four types of SGSs can be realized, defined based on the
spin characters of the bands around the Fermi energy, and the type-II SGSs show
promising transport properties for spintronic applications. The effect of
spin-orbit coupling is investigated, resulting in large anisotropic
magnetoresistance and anomalous Nernst effects.",1808.02684v1
2018-08-09,Switchable and tunable Rashba-type spin splitting in covalent perovskite oxides,"In transition metal perovskites (ABO3) most physical properties are tunable
by structural parameters such as the rotation of the BO6 octahedra. Examples
include the N\'eel temperature of orthoferrites, the conductivity of
mixed-valence manganites, or the band gap of rare-earth scandates. Since oxides
often host large internal electric dipoles and can accommodate heavy elements,
they also emerge as prime candidates to display Rashba spin-orbit coupling,
through which charge and spin currents may be efficiently interconverted.
However, despite a few experimental reports in SrTiO3-based interface systems,
the Rashba interaction has been little studied in these materials, and its
interplay with structural distortions remain unknown. In this Letter, we
identify a bismuth-based perovskite with a giant, electrically-switchable
Rashba interaction whose amplitude can be controlled by both the ferroelectric
polarization and the breathing mode of oxygen octahedra. This particular
structural parameter arises from the strongly covalent nature of the Bi-O
bonds, reminiscent of the situation in perovskite nickelates. Our results not
only provide novel strategies to craft agile spin-charge converters but also
highlight the relevance of covalence as a powerful handle to design emerging
properties in complex oxides.",1808.03123v1
2019-01-03,Novel Chern insulators with half-metallic edge states,"The central target of spintronics research is to achieve flexible control of
highly efficient and spin-polarized electronic currents. Based on
first-principles calculations and k-p models, we demonstrate that Cu2S/MnSe
heterostructures are a novel type of Chern insulators with half-metallic chiral
edge states and a very high Fermi velocity (0.87 * 10^6 m/s). The full
spin-polarization of the edge states is found to be robust against the tuning
of the chemical potential. Unlike the mechanisms reported previously, this
heterostructure has quadratic bands with a normal band order, that is, the
p/d-like band is below the s-like band. Charge transfer between the Cu2S moiety
and the substrate results in variation in the occupied bands, which together
with spin-orbit coupling, triggers the appearance of the topological state in
the system. These results imply that numerous ordinary semiconductors with
normal band order may convert into Chern insulators with half-metallic chiral
edge states through this mechanism, providing a strategy to find a rich variety
of materials for dissipationless, 100% spin-polarized and high-speed spintronic
devices.",1901.00629v1
2019-03-18,Tunnel magnetoresistance of a supramolecular spin valve,"We theoretically study the transport properties of a supramolecular spin
valve, consisting of a carbon nanotube with two attached magnetic molecules,
weakly coupled to metallic contacts. The emphasis is put on analyzing the
change of the system's transport properties with the application of an external
magnetic field, which aligns the spins of the molecules. It is shown that
magnetoresistive properties of the considered molecular junction, which are
associated with changing the state of the molecules from superparamagnetic to
the ferromagnetic one, strongly depend on the applied bias voltage and the
position of the nanotube's orbital levels, which can be tuned by a gate
voltage. A strong dependence on the transport regime is also found in the case
of the spin polarization of the current flowing through the system. The
mechanisms leading to those effects are explained by invoking appropriate
molecular states responsible for transport. The analysis is done with aid of
the real-time diagrammatic technique up to the second order of expansion with
respect to tunneling processes.",1903.07326v1
2019-03-20,Two-dimensional Weyl Half Semimetal and Tunable Quantum Anomalous Hall Effect in Monolayer PtCl$_{3}$,"We propose a new topological quantum state of matter---the two-dimensional
(2D) Weyl half semimetal (WHS), which features 2D Weyl points at Fermi level
belonging to a single spin channel, such that the low-energy electrons are
described by fully spin-polarized 2D Weyl fermions. We predict its realization
in the ground state of monolayer PtCl$_3$. We show that the material is a half
metal with an in-plane magnetization, and its Fermi surface consists of a pair
of fully spin-polarized Weyl points protected by a mirror symmetry, which are
robust against spin-orbit coupling. Remarkably, we show that the WHS state is a
critical state at the topological phase transition between two quantum
anomalous Hall insulator phases with opposite Chern numbers, such that a
switching between quantum anomalous Hall states can be readily achieved by
rotating the magnetization direction. Our findings demonstrate that WHS offers
new opportunity to control the chiral edge channels, which will be useful for
designing new topological electronic devices.",1903.08373v1
2019-04-02,Direct evidence for efficient ultrafast charge separation in epitaxial WS$_2$/graphene heterostructure,"We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) to
investigate ultrafast charge transfer in an epitaxial heterostructure made of
monolayer WS$_2$ and graphene. This heterostructure combines the benefits of a
direct gap semiconductor with strong spin-orbit coupling and strong
light-matter interaction with those of a semimetal hosting massless carriers
with extremely high mobility and long spin lifetimes. We find that, after
photoexcitation at resonance to the A-exciton in WS$_2$, the photoexcited holes
rapidly transfer into the graphene layer while the photoexcited electrons
remain in the WS$_2$ layer. The resulting charge transfer state is found to
have a lifetime of $\sim1$\,ps. We attribute our findings to differences in
scattering phase space caused by the relative alignment of WS$_2$ and graphene
bands as revealed by high resolution ARPES. In combination with spin-selective
excitation using circularly polarized light the investigated WS$_2$/graphene
heterostructure might provide a new platform for efficient optical spin
injection into graphene.",1904.01379v1
2019-08-20,Quasi-two-dimensional Fermi surfaces and unitary spin-triplet pairing in the heavy fermion superconductor UTe$_2$,"We report first-principles and strongly-correlated calculations of the
newly-discovered heavy fermion superconductor UTe$_2$. Our analyses reveal
three key aspects of its magnetic, electronic, and superconducting properties,
that include: (1) a two-leg ladder-type structure with strong magnetic
frustrations, which might explain the absence of long-range orders and the
observed magnetic and transport anisotropy; (2) quasi-two-dimensional Fermi
surfaces composed of two separate electron and hole cylinders with similar
nesting properties as in UGe$_2$, which may potentially promote magnetic
fluctuations and help to enhance the spin-triplet pairing; (3) a unitary
spin-triplet pairing state of strong spin-orbit coupling at zero field, with
point nodes presumably on the heavier hole Fermi surface along the
$k_x$-direction, in contrast to the previous belief of non-unitary pairing. Our
proposed scenario is in excellent agreement with latest thermal conductivity
measurement and provides a basis for understanding the peculiar magnetic and
superconducting properties of UTe$_2$.",1908.07396v1
2019-12-20,All-Electrical Control of an Electron Spin/Valley Quantum Bit in SOI CMOS Technology,"We fabricated Quantum Dot (QD) devices using a standard SOI CMOS process
flow, and demonstrated that the spin of confined electrons could be controlled
via a local electrical-field excitation, owing to inter-valley spin-orbit
coupling. We discuss that modulating the confinement geometry via an additional
electrode may enable switching a quantum bit (qubit) between an
electrically-addressable valley configuration and a protected spin
configuration. This proposed scheme bears relevance to improve the trade-off
between fast operations and slow decoherence for quantum computing on a Si
qubit platform. Finally, we evoke the impact of process-induced variability on
the operating bias range.",1912.11403v1
2020-05-15,Off-axis dipole forces in optical tweezers by an optical analog of the {Magnus} effect,"It is shown that a circular dipole can deflect the focused laser beam that
induces it, and will experience a corresponding transverse force. Quantitative
expressions are derived for Gaussian and angular tophat beams, while the
effects vanish in the plane-wave limit. The phenomena are analogous to the
Magnus effect pushing a spinning ball onto a curved trajectory. The optical
case originates in the coupling of spin and orbital angular momentum of the
dipole and the light. In optical tweezers the force causes off-axis
displacement of the trapping position of an atom by a spin-dependent amount up
to $\lambda/2\pi$, set by the direction of a magnetic field. This suggests
direct methods to demonstrate and explore these effects, for instance to induce
spin-dependent motion.",2005.07790v3
2020-11-06,Picosecond Switching of Optomagnetic Tunnel Junctions,"Perpendicular magnetic tunnel junctions are one of the building blocks for
spintronic memories, which allow fast nonvolatile data access, offering
substantial potentials to revolutionize the mainstream computing architecture.
However, conventional switching mechanisms of such devices are fundamentally
hindered by spin polarized currents4, either spin transfer torque or spin orbit
torque with spin precession time limitation and excessive power dissipation.
These physical constraints significantly stimulate the advancement of modern
spintronics. Here, we report an optomagnetic tunnel junction using a
spintronic-photonic combination. This composite device incorporates an
all-optically switchable Co/Gd bilayer coupled to a CoFeB/MgO-based
perpendicular magnetic tunnel junction by the Ruderman-Kittel-Kasuya-Yosida
interaction. A picosecond all-optical operation of the optomagnetic tunnel
junction is explicitly confirmed by time-resolved measurements. Moreover, the
device shows a considerable tunnel magnetoresistance and thermal stability.
This proof-of-concept device represents an essential step towards ultrafast
spintronic memories with THz data access, as well as ultralow power
consumption.",2011.03612v1
2016-03-29,Optomechanical measurement of photon spin angular momentum and optical torque in integrated photonic devices,"Photons carry linear momentum, and spin angular momentum when circularly or
elliptically polarized. During light-matter interaction, transfer of linear
momentum leads to optical forces, while angular momentum transfer induces
optical torque. Optical forces including radiation pressure and gradient forces
have long been utilized in optical tweezers and laser cooling. In nanophotonic
devices optical forces can be significantly enhanced, leading to unprecedented
optomechanical effects in both classical and quantum regimes. In contrast, to
date, the angular momentum of light and the optical torque effect remain
unexplored in integrated photonics. Here, we demonstrate the measurement of the
spin angular momentum of photons propagating in a birefringent waveguide and
the use of optical torque to actuate rotational motion of an optomechanical
device. We show that the sign and magnitude of the optical torque are
determined by the photon polarization states that are synthesized on the chip.
Our study reveals the mechanical effect of photon's polarization degree of
freedom and demonstrates its control in integrated photonic devices. Exploiting
optical torque and optomechanical interaction with photon angular momentum can
lead to torsional cavity optomechanics and optomechanical photon spin-orbit
coupling, as well as applications such as optomechanical gyroscope and
torsional magnetometry.",1603.08950v1
2016-10-03,NiCl3 Monolayer: Dirac Spin-Gapless Semiconductor and Chern Insulator,"The great obstacle for practical applications of the quantum anomalous Hall
(QAH) effect is the lack of suitable QAH materials (Chern insulators) with
large non-trivial band gap, room-temperature magnetic order and high carrier
mobility. The Nickle chloride (NiCl3) monolayer characteristics are
investigated herein using first-principles calculations. It is reported that
NiCl3 monolayers constitute a new class of Dirac materials with Dirac
spin-gapless semiconducting and high-temperature ferromagnetism (~400K). Taking
into account the spin-orbit coupling, the NiCl3 monolayer becomes an intrinsic
insulator with a large non-trivial band gap of ~24 meV, corresponding to an
operating temperature as high as ~280K at which the quantum anomalous Hall
effect could be observed. The calculated large non-trivial gap, high Curie
temperature and single-spin Dirac states reported herein for the NiCl3
monolayer lead us to propose that this material give a great promise for
potential realization of a near-room temperature QAH effect and potential
applications in spintronics. Last but not least the calculated Fermi velocities
of Dirac fermion of about 4x105 m/s indicate very high mobility in NiCl3
monolayers.",1610.00407v1
2019-05-14,Anapole Correlations in Sr2IrO4 Defy the jeff = 1/2 Model,"Zel'dovich (spin) anapole correlations in Sr2IrO4 unveiled by magnetic
neutron diffraction contravene the spin-orbit coupled ground state used by the
jeff = 1/2 (pseudo-spin) model. Specifically, spin and space know inextricable
knots which bind each to the other in the iridate. The diffraction property
studied in the Letter is enforced by strict requirements from quantum mechanics
and magnetic symmetry. It has not been exploited in the past, whereas neutron
diffraction by anapole moments is established. Entanglement of the electronic
degrees of freedom is captured by binary correlations of the anapole and
position operators, and hallmarked in the diffraction amplitude by axial atomic
multipoles with an even rank.",1905.05535v2
2019-06-24,On the Exciton Fine-Structure of Transition-Metal Dichalcogenides Mono-Layers,"In order to discuss the exciton fine-structure of transition-metal
dichalcogenides mono-layers, excitons are first defined in the subspace of
electron- and hole states, including the lowest conduction band (LCB) and the
uppermost valence band (UVB). Both bands are spin degenerate at the
Gamma-point. All other states are neglected. The resulting exciton states are
analyzed in the framework of an invariant expansion of a model Hamiltonian: The
spin-orbit coupling in the conduction- and valence band is simulated by
introducing a fictive magnetic field, giving rise to a splitting of the
electron- and hole states outside the $\Gamma$-point. Then the electron-hole
exchange-interaction is introduced into the exciton Hamiltonian. It is due to
the fact that electron and hole are indistinguishable particles in the exciton
problem. In D3h crystal symmetry this electron-hole exchange-interaction has
two different contributions: While a first term accounts for an energy
re-normalization of all exciton states, a second term does not influence the
optical active (spin-singlet) states but affects only the optical inactive
(spin-triplet) states, which become mixed in-between the different exciton
series.",1906.09790v1
2021-01-24,Magnetic gradient free two axis control of a valley spin qubit in SiGe,"Spins in SiGe quantum dots are promising candidates for quantum bits but are
also challenging due to the valley degeneracy which could potentially cause
spin decoherence and weak spin-orbital coupling. In this work we demonstrate
that valley states can serve as an asset that enables two-axis control of a
singlet-triplet qubit formed in a double quantum dot without the application of
a magnetic field gradient. We measure the valley spectrum in each dot using
magnetic field spectroscopy of Zeeman split triplet states. The interdot
transition between ground states requires an electron to flip between valleys,
which in turn provides a g-factor difference $\Delta g$ between two dots. This
$\Delta g$ serves as an effective magnetic field gradient and allows for qubit
rotations with a rate that increases linearly with an external magnetic field.
We measured several interdot transitions and found that this valley introduced
$\Delta g$ is universal and electrically tunable. This could potentially
simplify scaling up quantum information processing in the SiGe platform by
removing the requirement for magnetic field gradients which are difficult to
engineer.",2101.09786v1
2021-01-25,Antiferromagnetic State in $κ$-type Molecular Conductors: Spin Splitting and Mott Gap,"We numerically investigate the dynamical properties of $\kappa$-type
molecular conductors in their antiferromagnetic Mott insulating state. By
treating the extended Hubbard model on the two-dimensional $\kappa$-type
lattice within the Lanzcos exact diagonalization method, we calculate the
one-particle spectral function $A(\boldsymbol{k}, \omega)$ and the optical
absorption spectra taking advantage of twisted boundary conditions. We find
spin splitting in $A(\boldsymbol{k}, \omega)$ predicted by a previous
Hartree-Fock study [M. Naka et al., Nat. Commun. 10, 4305 (2019)]; namely,
their up- and down-spin components become different in the general
$\boldsymbol{k}$-points of the Brillouin zone, even without the spin-orbit
coupling. Furthermore, we demonstrate the variation in the optical properties
near the Mott gap by the presence or absence of the antiferromagnetic order,
tuned by a small staggered magnetic field.",2101.09883v2
2021-02-03,Spin-flip pair-density functional theory: A practical approach to treat static and dynamical correlations in large molecules,"We present a practical approach to treat static and dynamical correlation
accurately in large multi-configurational systems. The static correlation is
accounted for using the spin-flip approach which is well known for capturing
static correlation accurately at low-computational expense. Unlike previous
approaches to add dynamical correlation to spin-flip models which use
perturbation theory or coupled-cluster theory, we explore the ability to use
the on-top pair-density functional theory approaches recently developed by
Gagliardi and co-workers (JCTC, 10, 3669, 2014). External relaxations are
carried out in the spin-flip calculations though a restricted active space
framework for which a truncation scheme for the orbitals used in the external
excitation is presented. The performance of the approach is demonstrated by
computing energy gaps between ground and excited states for diradicals,
triradicals and linear polyacene chains ranging from naphthalene to dodecacene.
Accurate results are obtained using the new approach for these challenging
open-shell molecular systems.",2102.02325v1
2021-05-31,Field-Direction Sensitive Skyrmion Crystals in Cubic Chiral Systems: Implication to $4f$-Electron Compound EuPtSi,"We theoretically study the stability of magnetic skyrmion crystals (SkXs) in
chiral cubic antiferromagnets with the EuPtSi hosting unconventional nanometric
SkXs in mind. By performing numerical simulations for a minimal effective spin
model with the long-range Dzyaloshinskii-Moriya interaction and the
multiple-spin interaction arising from itinerant nature of electrons, we
clarify two key ingredients for the emergence of the SkXs in EuPtSi: One is the
low-symmetric ordering vectors that lead to the field-direction sensitive SkXs
in an external magnetic field, while the other is the synergy between
spin-charge and spin-orbit couplings in itinerant magnets that results in the
nanometric SkXs. The present study will not only provide the microscopic
mechanism of the SkXs in EuPtSi but also guide for a search of further
materials hosting short-period SkXs.",2106.00113v1
2021-07-13,Exploration of trivial and non-trivial electronic phases and of collinear and non-collinear magnetic phases in low-spin d$^5$ perovskites,"The $4d$ and $5d$ transition metal oxides have become important members of
the emerging quantum materials family due to competition between onsite Coulomb
repulsion ($U$) and spin-orbit coupling (SOC). Specifically, the systems with
$d^5$ electronic configuration in an octahedral environment are found to be
capable of posessing invariant semimetallic state and perturbations can lead to
diverse magnetic phases. In this work, by formulating a multi-band Hubbard
model and performing SOC tunable DFT+$U$ calculations on a prototype SrIrO$_3$
and extending the analysis to other iso-structural and isovalent compounds, we
present eight possible electronic and magnetic configurations in the $U$-SOC
phase diagram that can be observed in the family of low-spin $d^5$ perovskites.
They include the protected Dirac semimetal state, metal and insulator regimes,
collinear and noncollinear spin ordering. The latter is explained through
connecting hopping interactions to the rotation and tilting of the octahedra as
observed in GdFeO$_3$. Presence of several soft phase boundaries makes the
family of $d^5$ perovskites an ideal platform to study electronic and magnetic
phase transitions under external stimuli.",2107.06016v2
2021-07-23,Carrier-induced ferromagnetism in 2D magnetically-doped semiconductor structures,"We show theoretically that the magnetic ions, randomly distributed in a
two-dimensional (2D) semiconductor system, can generate a ferromagnetic
long-range order via the RKKY interaction. The main physical reason is the
discrete (rather than continuous) symmetry of the 2D Ising model of the
spin-spin interaction mediated by the spin-orbit coupling of 2D free carriers,
which precludes the validity of the Mermin-Wagner theorem. Further, the
analysis clearly illustrates the crucial role of the molecular field
fluctuations as opposed to the mean field. The developed theoretical model
describes the desired magnetization and phase-transition temperature $T_c$ in
terms of a single parameter; namely, the chemical potential $\mu$. Our results
highlight a path way to reach the highest possible $T_c$ in a given material as
well as an opportunity to control the magnetic properties externally (e.g., via
a gate bias). Numerical estimations show that magnetic impurities such as
Mn$^{2+}$ with spins $S=5/2$ can realize ferromagnetism with $T_c$ close to
room temperature.",2107.11377v1
2021-08-12,Polarized neutron scattering studies of magnetic excitations in iron-selenide superconductor (Li$_{0.8}$Fe$_{0.2}$)ODFeSe ($T_c$ = 41 K),"We report polarized neutron scattering measurements of the low energy spin
fluctuations of the iron-selenide superconductor Li$_{0.8}$Fe$_{0.2}$ODFeSe
below and above its superconducting transition temperature $T_c=41$ K. Our
experiments confirmed that the resonance mode near 21 meV is magnetic.
Moreover, the spin excitations are essentially isotropic in spin space at
5$\leq E\leq$ 29 meV in the superconducting and normal states. Our results
suggest that the resonance mode in iron-based superconductors becomes isotropic
when the influence of spin-orbit coupling and magnetic/nematic order is
minimized, similar to those observed in cuprate superconductors.",2108.05832v1
2021-09-02,Enhanced magnon spin current using the bosonic Klein paradox,"Efficient manipulation of magnons for information processing is a central
topic in spintronics and magnonics. An outstanding challenge for long-distance
spin transport with minimal dissipation is to overcome the relaxation of
magnons and to amplify the spin current they carry. Here, we propose to amplify
magnon currents based on the realization of the bosonic Klein paradox in
magnetic nanostructures. This paradox involves the magnon's antiparticle, the
antimagnon, of which the existence is usually precluded by magnetic
instabilities as it is an excitation at negative energy. We show that, by
appropriately tuning the effective dissipation through spin-orbit torques, both
magnons and antimagnons are dynamically stabilized. As a result, we find that
the reflection coefficient of incident magnons at an interface between two
coupled magnets can become larger than one, thereby amplifying the reflected
magnon current. Our findings can lead to magnon amplifier devices for
spintronic applications. Furthermore, our findings yield a solid-state platform
to study the relativistic behavior of bosonic particles, which is an
outstanding challenge with fundamental particles.",2109.00865v3
2021-09-07,Topologically protected one-dimensional electronic states in group IV two-dimensional Dirac materials,"In this report we give a brief introduction on the occurrence of
topologically protected one-dimensional electronic states in group IV
two-dimensional graphene-like materials. We discuss the effect of spin-orbit
coupling on the electronic band structure and show that these materials are
potential candidates to exhibit the quantum spin Hall effect. The quantum spin
Hall effect is characterized by a gapped interior and metallic
counter-propagating spin-polarized topologically protected edges states. We
also elaborate on the electric-field induced formation of a hexagonal network
of one-dimensional topologically protected electronic states in small-angle
twisted bilayer graphene.",2109.03071v3
2021-10-19,"Nematic, chiral and topological superconductivity in transition metal dichalcogenides","We introduce and study a realistic model for superconductivity in twisted
bilayer WSe$_{2}$, where electron pairing arises from spin-valley fluctuations
in the weak-coupling regime. Our model comprises both the full continuum model
moir\'{e} bandstructure and a short-ranged repulsive interaction that accounts
for the Coulomb interaction projected onto the localized Wannier orbitals. By
calculating the spin-valley susceptibility, we identify a Fermi surface nesting
feature near half-filling of the top-most moir\'{e} band, which induces
significantly enhanced spin-valley fluctuations. We then analyze the dominant
Kohn-Luttinger pairing instabilities due to these spin-valley fluctuations and
show that the leading instability can induce nematic, chiral and topological
superconductivity. As our findings are asymptotically exact for small
interaction strengths, they provide a viable starting point for future studies
of superconductivity in twisted transition metal dichalcogenide bilayers.",2110.10172v1
2021-10-20,Nonlinear response induced by Ferromagnetism in a Noncentrosymmetric Kondo Lattice system,"Recently, nonlinear responses have been actively studied in both experiments
and theory. Particularly interesting are inversion-symmetry broken systems,
where an even-order nonlinear electrical conductivity can be nonzero, resulting
in nonreciprocity. Second-order nonlinear conductivities attract much attention
because of their sensitivity to detect inversion-symmetry breaking in materials
and their functionalities. However, while the nonlinear response has been
actively studied in noninteracting systems for a long time, the nonlinear
response in strongly correlated materials is still poorly understood. This
paper analyzes the nonlinear conductivity in a correlated noncentrosymmetric
system, namely a Kondo lattice system with Rashba type spin-orbit coupling. We
mainly focus on the ferromagnetic phase, in which the second-order nonlinear
conductivity becomes finite. Remarkably, we find that the second-order
conductivity becomes only finite perpendicular to the ferromagnetic
magnetization and has a strong spin dependence; due to a gap at the Fermi
energy for one spin direction, the linear and nonlinear conductivity is only
finite for the ungapped spin direction. Finally, we analyze sign changes in the
nonlinear conductivity, which can be explained by a combination of correlation
effects and the energetic shift due to the occurring ferromagnetism.",2110.10496v1
2021-11-14,Superconductivity in noncentrosymmetric NbReSi investigated by muon spin rotation and relaxation,"Noncentrosymmetric materials are promising paradigm to explore unconventional
superconductivity. In particular, several Re containing noncentrosymmetric
materials have attracted considerable attention due to a superconducting state
with a broken time reversal symmetry. A comprehensive study on the
superconducting ground state of NbReSi was investigated using magnetization,
resistivity, and muon spin rotation/relaxation measurements. Zero field muon
spectroscopy results showed the absence of any spontaneous magnetic field below
the superconducting transition temperature, T$ _{c} $ = 6.29 K, indicating the
preserved time-reversal symmetry. Transverse field muon spin rotation
measurements confirms a s-wave nature of the sample with $\Delta(0)/k_{B}T_{c}
$ = 1.726. This study urges further investigation on more noncentrosymmetric
materials to elucidate the selective appearance of unconventional nature and
unveil its dependence on antisymmetric spin-orbit coupling strength.",2111.07247v1
2021-11-29,Element selective ultrafast magnetization dynamics of hybrid Stoner-Heisenberg magnets,"Stoner and Heisenberg excitations in magnetic materials are inherently
different. The former involves an effective reduction of the exchange
splitting, whereas the latter comprises excitation of spin-waves. In this work,
we test the impact of these two excitations in the hybrid Stoner-Heisenberg
system FePd. We present a microscopic picture of ultrafast demagnetization
dynamics in this alloy, which represents both components of strong local
exchange splitting in Fe, and induced polarization in Pd. We identify
spin-orbit coupling and optical inter-site spin transfer as the two dominant
factors for demagnetization at ultrashort timescales. By tuning the external
laser pulse, the extrinsic inter-site spin transfer can be manipulated for site
selective demagnetization on femtosecond time scales providing the fastest way
for optical and selective control of the magnetization dynamics in alloys.
Remarkably, the drastic difference in origin of the magnetic moment of the Fe
and Pd species is not deciding the initial magnetization dynamics in this
alloy.",2111.14607v1
2021-12-20,Bad topological semimetals in layered honeycomb compounds,"The Mott transition in honeycomb compounds with significant spin-orbit
coupling is explored. At finite temperatures we identify a novel semimetallic
phase located between a topological insulator and a topological Mott insulator.
This semimetal is characterized by having no charge gap, no quasiparticles and
gapped spin excitations with non-trivial topological properties. While charge
conduction is incoherent involving mean-free paths violating the
Mott-Ioffe-Regel limit, spin excitations can be transported ballistically along
the edges giving rise to a quantized spin conductance. Such bad topological
semimetal could be searched for close to the Mott transition in certain twisted
bilayers of transition metal dicalchogenides.",2112.10455v2
2022-02-21,Lorentz-covariant kinetic theory for massive spin-1/2 particles,"We construct a matrix-valued spin-dependent distribution function (MVSD) for
massive spin-1/2 fermions and study its properties under Lorentz
transformations. Such transformations result in a Wigner rotation in spin space
and in a nontrivial matrix-valued shift in space-time, which corresponds to the
side jump in the massless case. We express the vector and axial-vector
components of the Wigner function in terms of the MVSD and show that they
transform in a Lorentz-covariant manner. We then construct a manifestly
Lorentz-covariant Boltzmann equation which contains a nonlocal collision term
encoding spin-orbit coupling. Finally, we obtain the spin-dependent
distribution function in local equilibrium by demanding detailed balance.",2202.10160v2
2022-04-07,Superconductivity in multiorbital systems with repulsive interactions: Hund's pairing vs. spin-fluctuation pairing,"Hund's pairing refers to Cooper pairing generated by onsite interactions that
become attractive due to large Hund's exchange $J$. This is possible in
multiorbital systems even when all local bare interactions are repulsive, since
attraction in specific channels are given by certain linear combinations of
interaction parameters. On the other hand, pairing processes such as the
exchange of spin fluctuations, are also present. We compare these two
mechanisms on an equal footing using electronic bands appropriate for different
classes of multiorbital systems over a wide range of interaction parameters. We
find that for systems without clear nesting features, the superconducting state
generated by the Hund's mechanism agrees well with that from the full
fluctuation exchange vertex when Hund's exchange and spin-orbit coupling are
sufficiently large. On the other hand, for systems characterized by a peaked
finite-momentum particle-hole susceptibility, spin-fluctuation pairing
generally dominates over Hund's pairing. We conclude that Hund's pairing states
are unlikely to be realized in systems like Sr$_2$RuO$_4$ and generic
iron-based superconductors.",2204.03496v2
2022-04-15,Spin Conductivity Based on Magnetic Toroidal Quadrupole Hidden in Antiferromagnets,"We report our theoretical results on spin conductivity in antiferromagnets by
focusing on the role of the magnetic toroidal quadrupole (MTQ) in electron
systems. The MTQ is characterized as a time-reversal-odd rank-2 polar tensor
degree of freedom in electrons, which is distinct from conventional rank-1
magnetic and magnetic toroidal dipoles. Based on a microscopic $sd$ model
analysis for a tetragonal system under both collinear and noncollinear
antiferromagnetic orderings, we clarify that the MTQ becomes a source of an
extrinsic spin conductivity even with neither a uniform magnetization nor
spin-orbit coupling. We also list all the magnetic point groups to accommodate
the MTQs as a primary order parameter as well as the candidate
antiferromagnetic materials.",2204.07326v1
2022-06-13,Recent advances of defect-induced spin and valley polarized states in graphene,"Electrons in graphene have fourfold spin and valley degeneracies owing to the
unique bipartite honeycomb lattice and an extremely weak spin-orbit coupling,
which can support a series of broken symmetry states. Atomic-scale defects in
graphene are expected to lift these degenerate degrees of freedom at the
nanoscale, and hence, lead to rich quantum states, highlighting promising
directions for spintronics and valleytronics. In this article, we mainly review
the recent scanning tunneling microscopy (STM) advances on the spin and/or
valley polarized states induced by an individual atomic-scale defect in
graphene, including a single-carbon vacancy, a nitrogen-atom dopant, and a
hydrogen-atom chemisorption. Lastly, we give a perspective in this field.",2206.05936v1
2022-06-15,Giant Rashba electrical control of magnetism in band models,"It is of considerable technological importance to achieve an electrical
control of magnetism of sufficient magnitude. To overcome the in-plane shape
anisotropy, needed is the electrical control of a perpendicular magnetic
anisotropy (PMA). It is known, within a free electron model, the Rashba
spin-orbit coupling provides such a control. Surprisingly, this same Rashba PMA
is enhanced by two to three orders of magnitude when a periodic potential is
added. Usually spin Berry phase physics reflects time dependent magnetic
fields. Here it is shown, within a time independent model, such physics arises
because the Rashba effective magnetic field has texture within the unit cell.
Predicted are electrical controllable band-structure gaps, linear in the
applied electric field $E$, that can result in a truly giant linear PMA. Also
possible is a Peierls mechanism, in which the magnetisation tilts from the
vertical, shifting these gaps to the Fermi level. As a consequence there are
low dissipation electric field driven dynamics, an alternative to the more
dissipative spin torque transfer (STT) effect. The theory requires the
introduction of an intrinsic spin Berry connection $\vec A_s$, an effective
vector potential, and is incompatible with current density functional theories
(DFT).",2206.07399v1
2022-07-08,Two-dimensional anisotropic Dirac materials PtN4C2 and Pt2N8C6 with quantum spin and valley Hall effects,"We propose two novel two-dimensional topological Dirac materials, planar
PtN4C2 and Pt2N8C6, which exhibit graphene-like electronic structures with
linearly dispersive Dirac-cone states exactly at the Fermi level. Moreover, the
Dirac cone is anisotropic, resulting in anisotropic Fermi velocities and making
it possible to realize orientation-dependent quantum devices. Using the
first-principles electronic structure calculations, we have systemically
studied the structural, electronic, and topological properties. We find that
spin-orbit coupling opens a sizable topological band gap so that the materials
can be classified as quantum spin Hall insulators as well as quantum valley
Hall insulators. Helical edge states that reside in the insulating band gap
connecting the bulk conduction and valence bands are observed. Our work not
only expands the Dirac cone material family, but also provides a new avenue to
searching for more two-dimensional topological quantum spin and valley Hall
insulators.",2207.03703v1
2022-08-09,Modelling of planar germanium hole qubits in electric and magnetic fields,"Hole-based spin qubits in strained planar germanium quantum wells have
received considerable attention due to their favourable properties and
remarkable experimental progress. The sizeable spin-orbit interaction in this
structure allows for efficient electric qubit operations. However, it also
couples the qubit to electrical noise. In this work we perform simulations of a
heterostructure hosting these hole spin qubits. We solve the effective mass
equations for a realistic heterostructure, provide a set of analytical basis
wave functions, and compute the effective g-factor of the heavy-hole
ground-state. Our investigations reveal a strong impact of highly excited light
hole states located outside the quantum well on the g-factor. Consequently,
contrary to recent predictions, we find that sweet spots in out-of-plane
magnetic fields are shifted to impractically large electric fields. However,
for magnetic fields close to in-plane alignment, sweet spots at low electric
fields are recovered. This work will be helpful in understanding and improving
coherence of germanium hole spin qubits.",2208.04795v1
2023-02-16,Nodeless superconductivity in the noncentrosymmetric ThIrSi compound,"The ThIrSi superconductor, with $T_c = 6.5$ K, is expected to show unusual
features in view of its noncentrosymmetric structure and the presence of heavy
elements featuring a sizable spin-orbit coupling. Here, we report a
comprehensive study of its electronic properties by means of local-probe
techniques: muon-spin rotation and relaxation ({\textmu}SR) and nuclear
magnetic resonance (NMR). Both the superfluid density $\rho_\mathrm{sc}(T)$
(determined via transverse-field {\textmu}SR) and the spin-lattice relaxation
rate $T_1^{-1}(T)$ (determined via NMR) suggest a nodeless superconductivity.
Furthermore, the absence of spontaneous magnetic fields below $T_c$, as evinced
from zero-field {\textmu}SR measurements, indicates a preserved time-reversal
symmetry in the superconducting state of ThIrSi. Temperature-dependent upper
critical fields as well as field-dependent superconducting muon-spin
relaxations suggest the presence of multiple superconducting gaps in ThIrSi.",2302.08075v1
2023-03-21,Controllable spin splitting in 2D Ferroelectric few-layer ${$γ}$-GeSe,"${\gamma}$-GeSe is a new type of layered bulk material that was recently
successfully synthesized. By means of density functional theory
first-principles calculations, we systematically studied the physical
properties of two-dimensional (2D) few-layer ${\gamma}$-GeSe. It is found that
few-layer ${\gamma}$-GeSe are semiconductors with band gaps decreasing with
increasing layer number; and 2D ${\gamma}$-GeSe with layer number $n \geq 2$
are ferroelectric with rather low transition barriers, consistent with the
sliding ferroelectric mechanism. Particularly, spin-orbit coupling induced spin
splitting is observed at the top of the valence band, which can be switched by
the ferroelectric reversal; furthermore, their negative piezoelectricity also
enables the regulation of spin splitting by strain. Finally, excellent optical
absorption was also revealed. These intriguing properties make 2D few-layer
${\gamma}$-GeSe promising in spintronic and optoelectric applications.",2303.11667v2
2023-03-24,Symmetry manipulation of nonlinear optical effect for metallic TMDC,"Nonlinear optical (NLO) effect plays a crucial role to engineer optical
angular frequency and symmetry of electronic system. Metallic transition-metal
dichalcogenide (TMDC) is one of two-dimensional (2D) materials, which has no
inversion symmetry for odd-number-layer. In particular, odd-number-layered
NbSe$_2$ has spin splitting owing to Ising-type spin-orbit coupling. In this
paper, we numerically calculate the NLO charge and spin conductivities of
NbSe$_2$ based on an effective tight-binding model for several different
optical effects, i.e., symmetry manipulation by bi-circular light (BCL) and
bulk photovoltaic effect (shift and injection current). Under irradiation of
BCL which can control the symmetry of electronic system, the current can be
generated even in even-number-layered NbSe$_2$. Also, we find that shift
current can be generated for odd-number-layered NbSe$_2$, which is robust
against electronic scattering, i.e., topological current. The direction of
generated shift current can be switched by altering polarization of light. Our
results will serve to design opt-spintronics devices based on 2D materials to
manipulate the charge and spin current and their directions by controlling the
polarization of incident light which recasts the symmetry of electronic system.",2303.13768v1
2023-05-18,Observation and enhancement of room temperature bilinear magnetoelectric resistance in sputtered topological semimetal Pt3Sn,"Topological semimetal materials have become a research hotspot due to their
intrinsic strong spin-orbit coupling which leads to large charge-to-spin
conversion efficiency and novel transport behaviors. In this work, we have
observed a bilinear magnetoelectric resistance (BMER) of up to 0.1 nm2A-1Oe-1
in a singlelayer of sputtered semimetal Pt3Sn at room temperature. Different
from previous observations, the value of BMER in sputtered Pt3Sn does not
change out-of-plane due to the polycrystalline nature of Pt3Sn. The observation
of BMER provides strong evidence of the existence of spin-momentum locking in
the sputtered polycrystalline Pt3Sn. By adding an adjacent CoFeB magnetic
layer, the BMER value of this bilayer system is doubled compared to the single
Pt3Sn layer. This work broadens the material system in BMER study, which paves
the way for the characterization of topological states and applications for
spin memory and logic devices.",2305.10720v2
2023-05-25,Crystallization dynamics of magnetic skyrmions in a frustrated itinerant magnet,"We investigate the phase ordering kinetics of skyrmion lattice (SkL) in a
metallic magnet. The SkL can be viewed as a superposition of magnetic stripes
whose periods are determined by the quasi-nesting wave vectors of the
underlying Fermi surface. An effective magnetic Hamiltonian that describes the
electron-mediated spin-spin interaction is obtained for a two-dimensional s-d
model with the Rashba spin-orbit coupling. Large-scale Landau-Lifshitz-Gilbert
dynamics simulations based on the effective spin Hamiltonian reveal a two-stage
phase ordering of the SkL phase after a thermal quench. The initial fast
crystallization of skyrmions is followed by a slow relaxation dominated by the
annihilation dynamics of dislocations, which are topological defects of the
constituent magnetic stripe orders. The late-stage phase ordering also exhibits
a dynamical scaling symmetry. We further show that the annihilation of
dislocations follows a power-law time dependence with a logarithmic correction
that depends on magnetic fields. Implications of our results for SkL phases in
magnetic materials are also discussed.",2305.16182v1
2023-06-15,First-Principles Study of Large Gyrotropy in MnBi for Infrared Thermal Photonics,"Nonreciprocal gyrotropic materials have attracted significant interest
recently in material physics, nanophotonics, and topological physics. Most of
the well-known nonreciprocal materials, however, only show nonreciprocity under
a strong external magnetic field and within a small segment of the
electromagnetic spectrum. Here, through first-principles density functional
theory calculations, we show that due to strong spin-orbit coupling
manganese-bismuth (MnBi) exhibits nonreciprocity without any external magnetic
field and a large gyrotropy in a broadband long-wavelength infrared regime
(LWIR). Further, we design a multi-layer structure based on MnBi to obtain a
maximum degree of spin-polarized thermal emission at 7 $\mu$m. The connection
established here between large gyrotropy and the spin-polarized thermal
emission points to a potential use of MnBi to develop spin-controlled thermal
photonics platforms.",2306.09233v1
2023-06-29,$γ$-ray Angular Distributions in Single Nucleon Transfer Reactions with Exotic Strontium Isotopes,"$\gamma$-ray angular distributions help assign spin and parity to excited
energy levels in nuclei. The spectroscopy of $^{94,96}$Sr studied through the
single neutron transfer reactions with $^{95}$Sr beam in inverse kinematics
[$^{95}$Sr(d,p)$^{96}$Sr; $^{95}$Sr(d,t)$^{94}$Sr] revealed a rich nuclear
structure with many excited states. While the spin-parities were assigned to
low lying states through techniques like particle angular distributions and
angular momentum transfer, those for higher lying states were ambiguous. The
goal of this project is to develop the Gamma-ray angular distributions and
correlations techniques to assign spin-parity to these states. In this work,
the $\gamma$-ray angular distributions for 815 keV transition from the first
excited state to ground state $(2^{+} \rightarrow 0^{+})$ in $^{96}$Sr are
measured. The alignment of this state is calculated from these measurements and
compared to the theoretically calculated alignment for this state which is
determined by coupling the spins of reactants and the orbital angular momentum
transfered. The values agree within experimental limits justifying the
technique. It is then applied to some other transitions and important results
are discussed. Angular correlations cannot be performed with this data since
statistics turn out to be limiting factor at the crystal level.",2306.17048v1
2023-07-23,Ru doping induced spin frustration and enhancement of the room-temperature anomalous Hall effect in La2/3Sr1/3MnO3 films,"In transition-metal-oxide heterostructures, the anomalous Hall effect (AHE)
is a powerful tool for detecting the magnetic state and revealing intriguing
interfacial magnetic orderings. However, achieving a larger AHE at room
temperature in oxide heterostructures is still challenging due to the dilemma
of mutually strong spin-orbit coupling and magnetic exchange interactions.
Here, we exploit the Ru doping-enhanced AHE in LSMRO epitaxial films. As the
B-site Ru doping level increases up to 20 percent, the anomalous Hall
resistivity at room temperature can be enhanced from nOhmcm to uOhmcm scale. Ru
doping leads to strong competition between ferromagnetic double-exchange
interaction and antiferromagnetic super-exchange interaction. The resultant
spin frustration and spin-glass state facilitate a strong skew-scattering
process, thus significantly enhancing the extrinsic AHE. Our findings could
pave a feasible approach for boosting the controllability and reliability of
oxide-based spintronic devices.",2307.12253v1
2023-07-24,Enhanced Magnetism and Phase Transitions in Ultrathin Quantum Spin Liquid Na2IrO3 Flakes,"The quest for quantum spin liquids has garnered significant attention due to
their rich physics and disruptive prospects in quantum communication and
computation. Spin-orbit coupling, electron correlation, and structural
distortion play critical roles in the candidate materials that eventually order
antiferromagnetically at low temperatures. We introduce quantum electron
confinement to the existing complexity and explore the interplay between
Heisenberg and Kitaev interactions in ultrathin \ce{Na2IrO3} layers using
first-principles calculations. The zigzag antiferromagnetic state in the
monolayer is reinforced and pushed further away from the Kitaev spin liquid
state due to the increased strength of Heisenberg and off-diagonal exchange
interactions. In contrast, the carrier-doped flakes undergo a Mott
insulator-to-metal transition accompanied by an antiferromagnetic to
ferromagnetic transition. These findings present exciting prospects for
comprehending magnetism in a novel two-dimensional framework of non-van der
Waals correlated oxide flakes.",2307.12554v1
2023-08-07,Frustration relief and reorientation transition in the kagome-like dolerophanite Cu$_2$OSO$_4$,"We present a theoretical study of dolerophanite Cu$_2$OSO$_4$, a layered
kagome-like spin-$\frac{1}{2}$ magnetic insulator that can be described either
as a system of chains coupled through dimers or as a kagome lattice where every
third spin is replaced by a ferromagnetic spin dimer. Building on insights from
ab initio calculations, classical numerical minimizations, and semiclassical
expansions, we arrive at a minimal microscopic description that accounts for
the experimental data reported so far, including the nature of the magnetic
order, the reported spin length, and the observed anisotropy. The latter arises
by a peculiar competition between the antisymmetric (Dzyaloshinskii-Moriya) and
the symmetric part of the exchange anisotropy, which gives rise to a two-step
re-orientation process involving two successive continuous phase transitions.
Our work uncovers mechanisms stabilizing canted ferrimagnetic order in kagome
systems, and highlights strong magnetic anisotropy in the presence if
dissimilar magnetic orbitals on crystallographically nonequivalent Cu sites. We
also show how these anisotropy terms affect the spin-wave spectrum and how they
can be tracked experimentally.",2308.03599v2
2023-09-02,Electron Spin Polarization as a Predictor of Chiroptical Activity in Helical Molecules,"Chiral structures, breaking spatial inversion symmetry, exhibit non-zero
chiroptical activity (COA) due to the interaction between their electric and
magnetic responses under external electromagnetic fields, an effect that is
otherwise absent in achiral systems. Non-magnetic chiral structures also
exhibit Chiral Induced Spin Selectivity (CISS), where spin-polarization (SP)
emerges without external magnetic influence. We have obtained a COA-SP
connection for a model system of an electron constrained to a helix including
spin-orbit coupling (SOC), and in the presence of an external electromagnetic
field. Despite its simplicity, this model captures the relevant physics
required to address the problem. In particular, our results reveal that the
norm of the SP vector can be used as a predictor of COA. In addition to SOC and
the breaking of space inversion, a non-vanishing SP requires the breaking of
time-reversal symmetry (TRS), as demanded by Onsager's reciprocity. Beyond the
relationship between SP and COA, we obtain the novel result that TRS breaking
is also necessary to yield a non-vanishing contribution of the SOC to the COA.",2309.00919v1
2024-03-15,Half-metallic transport and spin-polarized tunneling through the van der Waals ferromagnet Fe${_4}$GeTe$_{2}$,"The recent emergence of van der Waals (vdW) ferromagnets has opened new
opportunities for designing spintronic devices. We theoretically investigate
the coherent spin-dependent transport properties of the vdW ferromagnet
Fe$_4$GeTe$_2$, by using density functional theory combined with the
non-equilibrium Green's functions method. We find that the conductance in the
direction perpendicular to the layers is half-metallic, namely it is entirely
spin-polarized, as a result of the material's electronic structure. This
characteristic persists from bulk to single layer, even under significant bias
voltages, and it is little affected by spin-orbit coupling and electron
correlation. Motivated by this observation, we then investigate the tunnel
magnetoresistance (TMR) effect in an magnetic tunnel junction, which comprises
two Fe$_4$GeTe$_2$ layers separated by the vdW gap acting as insulating
barrier. We predict a TMR ratio of almost 500\%, which can be further boosted
by increasing the number of Fe$_4$GeTe$_2$ layers in the junction.",2403.10195v1
2017-03-06,Transport in superconductor--normal metal--superconductor tunneling structures: Spinful p-wave and spin-orbit-coupled topological wires,"We theoretically study transport properties of voltage-biased one-dimensional
superconductor--normal metal--superconductor tunnel junctions with arbitrary
junction transparency where the superconductors can have trivial or nontrivial
topology. Motivated by recent experimental efforts on Majorana properties of
superconductor-semiconductor hybrid systems, we consider two explicit models
for topological superconductors: (i) spinful p-wave, and (ii) spin-split
spin-orbit-coupled s-wave. We provide a comprehensive analysis of the
zero-temperature dc current $I$ and differential conductance $dI/dV$ of
voltage-biased junctions with or without Majorana zero modes (MZMs). The
presence of an MZM necessarily gives rise to two tunneling conductance peaks at
voltages $eV = \pm \Delta_{\mathrm{lead}}$, i.e., the voltage at which the
superconducting gap edge of the lead aligns with the MZM. We find that the MZM
conductance peak probed by a superconducting lead $without$ a BCS singularity
has a non-universal value which decreases with decreasing junction
transparency. This is in contrast to the MZM tunneling conductance measured by
a superconducting lead $with$ a BCS singularity, where the conductance peak in
the tunneling limit takes the quantized value $G_M = (4-\pi)2e^2/h$ independent
of the junction transparency. We also discuss the ""subharmonic gap structure"",
a consequence of multiple Andreev reflections, in the presence and absence of
MZMs. Finally, we show that for finite-energy Andreev bound states (ABSs), the
conductance peaks shift away from the gap bias voltage $eV = \pm
\Delta_{\mathrm{lead}}$ to a larger value set by the ABSs energy. Our work
should have important implications for the extensive current experimental
efforts toward creating topological superconductivity and MZMs in semiconductor
nanowires proximity coupled to ordinary s-wave superconductors.",1703.02047v2
2017-10-01,Slater Insulator in Iridate Perovskites with Strong Spin-Orbit Coupling,"The perovskite SrIrO3 is an exotic narrow-band metal owing to a confluence of
the strengths of the spin-orbit coupling (SOC) and the electron-electron
correlations. It has been proposed that topological and magnetic insulating
phases can be achieved by tuning the SOC, Hubbard interactions, and/or lattice
symmetry. Here, we report that the substitution of nonmagnetic, isovalent Sn4+
for Ir4+ in the SrIr1-xSnxO3 perovskites synthesized under high pressure leads
to a metal-insulator transition to an antiferromagnetic (AF) phase at TN > 225
K. The continuous change of the cell volume as detected by x-ray diffraction
and the lamda-shape transition of the specific heat on cooling through TN
demonstrate that the metal-insulator transition is of second-order. Neutron
powder diffraction results indicate that the Sn substitution enlarges an
octahedral-site distortion that reduces the SOC relative to the spin-spin
exchange interaction and results in the type-G AF spin ordering below TN.
Measurement of high-temperature magnetic susceptibility shows the evolution of
magnetic coupling in the paramagnetic phase typical of weak itinerant-electron
magnetism in the Sn-substituted samples. A reduced structural symmetry in the
magnetically ordered phase leads to an electron gap opening at the Brillouin
zone boundary below TN in the same way as proposed by Slater.",1710.00304v2
2012-10-10,Bodily tides near the 1:1 spin-orbit resonance. Correction to Goldreich's dynamical model,"Spin-orbit coupling is often described in the ""MacDonald torque"" approach
which has become the textbook standard. Within this method, a concise
expression for the additional tidal potential, derived by MacDonald (1964; Rev.
Geophys. 2, 467), is combined with an assumption that the Q factor is
frequency-independent (i.e., that the geometric lag angle is constant in time).
This makes the approach unphysical because MacDonald's derivation of the said
formula was implicitly based on keeping the time lag frequency-independent,
which is equivalent to setting Q to scale as the inverse tidal frequency. The
contradiction requires the MacDonald treatment of both non-resonant and
resonant rotation to be rewritten.
  The non-resonant case was reconsidered by Efroimsky & Williams (2009; CMDA
104, 257), in application to spin modes distant from the major
commensurabilities. We continue this work by introducing the necessary
alterations into the MacDonald-torque-based model of falling into a 1:1
resonance. (For the original version of the model, see Goldreich 1966; AJ 71,
1.)
  We also study the effect of the triaxiality on both circulating and librating
rotation near the synchronous state. Circulating rotation may evolve toward the
libration region or toward a spin rate larger than synchronous
(pseudosynchronous spin). Which behaviour depends on the eccentricity, the
triaxiality of the primary, and the mass ratio of the secondary and primary
bodies. The spin evolution will always stall for the oblate case. For
small-amplitude librations, expressions are derived for the libration
frequency, damping rate, and average orientation.
  However, the stability of pseudosynchronous spin hinges upon the dissipation
model. Makarov and Efroimsky (2012; arXiv:1209.1616) have found that a more
realistic dissipation model than the corrected MacDonald torque makes
pseudosynchronous spin unstable.",1210.2923v3
2019-12-29,Giant momentum-dependent spin splitting in centrosymmetric low Z antiferromagnets,"The energy vs. crystal momentum E(k) diagram for a solid (band structure)
constitutes the road map for navigating its optical, magnetic, and transport
properties. By selecting crystals with specific atom types, composition and
symmetries, one could design a target band structure and thus desired
properties. A particularly attractive outcome would be to design energy bands
that are split into spin components with a momentum-dependent splitting, as
envisioned by Pekar and Rashba [Zh. Eksperim. i Teor. Fiz. 47 (1964)], enabling
spintronic application. The current paper provides ""design principles"" for
wavevector dependent spin splitting (SS) of energy bands that parallels the
traditional Dresselhaus and Rashba spin-orbit coupling (SOC) - induce
splitting, but originates from a fundamentally different source --
antiferromagnetism. We identify a few generic AFM prototypes with distinct SS
patterns using magnetic symmetry design principles. These tools allow also the
identification of specific AFM compounds with SS belonging to different
prototypes. A specific compound -- centrosymmetric tetragonal MnF2 -- is used
via density functional band structure calculations to quantitatively illustrate
one type of AFM SS. Unlike the traditional SOC-induced effects restricted to
non-centrosymmetric crystals, we show that antiferromagnetic-induced spin
splitting broadens the playing field to include even centrosymmetric compounds,
and gives SS comparable in magnitude to the best known ('giant') SOC effects,
even without SOC, and consequently does not rely on the often-unstable high
atomic number elements required for high SOC. We envision that use of the
current design principles to identify an optimal antiferromagnet with
spin-split energy bands would be beneficial for efficient spin-charge
conversion and spin orbit torque applications without the burden of requiring
compounds containing heavy elements.",1912.12689v3
2018-10-30,On the Origin of Black Hole Spin in High-mass X-Ray Binaries,"Black hole (BH) spins in low-mass X-ray binaries (LMXBs) cover a range of
values that can be explained by accretion after BH birth. In contrast, the
three BH spin measurements in high-mass X-ray binaries (HMXBs) show only values
near the maximum and likely have a different origin connected to the BH stellar
progenitor. We explore here two possible scenarios to explain the high spins of
BHs in HMXBs: formation in binaries that undergo mass transfer (MT) during the
main sequence (MS; Case-A MT), and very close binaries undergoing chemically
homogeneous evolution (CHE). We find that both scenarios are able to produce
high-spin BHs if internal angular momentum (AM) transport in the progenitor
star after its MS evolution is not too strong (i.e., weak coupling between the
stellar core and its envelope). If instead efficient AM transport is assumed,
we find that the resulting BH spins are always too low with respect to
observations. The Case-A MT model provides a good fit for the BH spins, the
masses of the two components, and the final orbital periods for two of the
three BHs in HMXBs with measured spins. For one of them, the mass predicted for
the BH companion is significantly lower than observed, but this depends
strongly on the assumed efficiency of mass transfer. The CHE models predict
orbital periods that are too large for all three cases considered here. We
expect the Case-A MT to be much more frequent at the metallicities involved, so
we conclude that the Case-A MT scenario is preferred. Finally, we predict that
the stellar companions of HMXBs formed through the Case-A MT have enhanced
nitrogen surface abundances, which can be tested by future observations.",1810.13016v3
2013-01-17,"63,65Cu Nuclear Resonance Study of the Coupled Spin Dimers and Chains Compound Cu2Fe2Ge4O13","Nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) of Cu
have been measured in a coupled spin dimers and chains compound Cu2Fe2Ge4O13.
Cu NQR has also been measured in an isostructural material Cu2Sc2Ge4O13
including only spin dimers. Comparison of the temperature dependence of the
63Cu nuclear spin-lattice relaxation rate between the two compounds reveals
that the Fe chains in Cu2Fe2Ge4O13 do not change a spin gap energy of the Cu
dimers from that in Cu2Sc2Ge4O13, contributing additionally to the relaxation
rate at the Cu site. A modestly large internal field of 3.39 T was observed at
the Cu site in the antiferromagnetic state of Cu2Fe2Ge4O13 at 4.2 K, which is
partly because of quantum reduction of the ordered moment of a Cu atom. The
internal field and the ordered moment of Cu are noncollinear due to large
anisotropy of the hyperfine interaction at the Cu site. A model analysis of the
internal field based on the fourfold planar coordination of Cu suggests that a
3d hole of the Cu2+ ion is mainly in the d(x2-y2) orbital state.",1301.3974v2
2014-07-03,Hyperfine coupling and spin polarization in the bulk of the topological insulator Bi$_2$Se$_3$,"Nuclear magnetic resonance (NMR) and transport measurements have been
performed at high magnetic fields and low temperatures in a series of $n$-type
Bi$_{2}$Se$_{3}$ crystals. In low density samples, a complete spin polarization
of the electronic system is achieved, as observed from the saturation of the
isotropic component of the $^{209}$Bi NMR shift above a certain magnetic field.
The corresponding spin splitting, defined in the phenomenological approach of a
3D electron gas with a large (spin-orbit-induced) effective $g$-factor, scales
as expected with the Fermi energy independently determined by simultaneous
transport measurements. Both the effective electronic $g$-factor and the
""contact"" hyperfine coupling constant are precisely determined. The magnitude
of this latter reveals a non negligible $s$-character of the electronic wave
function at the bottom of the conduction band. Our results show that the bulk
electronic spin polarization can be directly probed via NMR and pave the way
for future NMR investigations of the electronic states in Bi-based topological
insulators.",1407.1040v2
2015-11-24,Dynamical magnetoelectric phenomena of multiferroic skyrmions,"Magnetic skyrmions, vortex-like swirling spin textures characterized by a
quantized topological invariant, realized in chiral-lattice magnets are
currently attracting intense research interest. In particular, their dynamics
under external fields is an issue of vital importance both for fundamental
science and for technical application. Whereas observations of magnetic
skyrmions had been limited to metallic magnets so far, their realization was
discovered also in a chiral-lattice insulating magnet Cu2OSeO3 in 2012.
Skyrmions in the insulator turned out to exhibit multiferroic nature with
spin-induced ferroelectricity. Strong magnetoelectric coupling between
noncollinear skyrmion spins and electric polarizations mediated by relativistic
spin-orbit interaction enables us to drive motion and oscillation of magnetic
skyrmions by application of electric fields instead of injection of electric
currents. Insulating materials also provide an environment suitable for
detection of pure spin dynamics through spectroscopic measurements owing to
absence of appreciable charge excitations. In this article, we review recent
theoretical and experimental studies on multiferroic properties and dynamical
magnetoelectric phenomena of magnetic skyrmions in insulators. We argue that
multiferroic skyrmions show unique coupled oscillation modes of magnetizations
and polarizations, so-called electromagnon excitations, which are both
magnetically and electrically active, and interference between the electric and
magnetic activation processes leads to peculiar magnetoelectric effects in a
microwave frequency regime.",1511.07761v1
2016-02-19,Helical currents in metallic Rashba strips,"We study the texture of helical currents in metallic planar strips in the
presence of Rashba spin-orbit coupling (RSOC) on the lattice at zero
temperature. In the noninteracting case, and in the absence of external
electromagnetic sources, we determine by exact numerical diagonalization of the
single-particle Hamiltonian, the distribution across the strip section of these
Rashba helical currents (RHC) as well as their sign oscillation, as a function
of the RSOC strength, strip width, electron filling, and strip boundary
conditions. Then, we study the effects of charge currents introduced into the
system by an Aharonov-Bohm flux for the case of rings or by a voltage bias in
the case of open strips. The former setup is studied by variational Monte
Carlo, and the later, by the time-dependent density-matrix-renormalization
group technique. Particularly for strips formed by two, three and four coupled
chains, we show how these RHC vary in the presence of such induced charge
current, and how their differences between spin-up and spin-down electron
currents on each chain, help to explain the distribution across the strip of
charge currents, both of the spin conserving and the spin flipping types. We
also predict the appearance of polarized charge currents on each chain.
Finally, we show that these Rashba helical currents and their derived features
remain in the presence of an on-site Hubbard repulsion as long as the system
remains metallic, at quarter filling, and even at half-filling where a
Mott-Hubbard metal-insulator transition occurs for large Hubbard repulsion.",1602.06193v2
2018-05-26,Distinct spin-lattice and spin-phonon interactions in monolayer magnetic CrI$_3$,"We apply the density-functional theory to study various phases (including
non-magnetic (NM), anti-ferromagnetic (AFM), and ferromagnetic (FM)) in
monolayer magnetic chromium triiodide (CrI$_3$), a recently fabricated 2D
magnetic material. It is found that: (1) the introduction of magnetism in
monolayer CrI$_3$ gives rise to metal-to-semiconductor transition; (2) the
electronic band topologies as well as the nature of direct and indirect band
gaps in either AFM or FM phases exhibit delicate dependence on the magnetic
ordering and spin-orbit coupling; and (3)the phonon modes involving Cr atoms
are particularly sensitive to the magnetic ordering, highlighting distinct
spin-lattice and spin-phonon coupling in this magnet. First-principles
simulations of the Raman spectra demonstrate that both frequencies and
intensities of the Raman peaks strongly depend on the magnetic ordering. The
polarization dependent $A_{1g}$ modes at 77 cm$^{-1}$ and 130 cm$^{-1}$ along
with the $E_g$ mode at about 50 cm$^{-1}$ in the FM phase may offer a useful
fingerprint to characterize this material. Our results not only provide a
detailed guiding map for experimental characterization of CrI$_3$, but also
reveal how the evolution of magnetism can be tracked by its lattice dynamics
and Raman response.",1805.10479v2
2018-05-27,Simulation of inelastic spin flip excitations and Kondo effect in STM spectroscopy of magnetic molecules on metal substrates,"Single-ion magnetic anisotropy in molecular magnets leads to spin flip
excitations that can be measured by inelastic scanning tunneling microscope
(STM) spectroscopy. Here I present a semi ab initio scheme to compute the
spectral features associated with inelastic spin flip excitations and Kondo
effect of single molecular magnets. To this end density functional theory
calculations of the molecule on the substrate are combined with more
sophisticated many-body techniques for solving the Anderson impurity problem of
the spin-carrying orbitals of the magnetic molecule coupled to the rest of the
system, containing a phenomenological magnetic anisotropy term. For calculating
the STM spectra an exact expression for the dI/dV in the ideal STM limit, when
the coupling to the STM tip becomes negligibly small, is derived. In this limit
the dI/dV is simply related to the spectral function of the molecule-substrate
system. For the case of an Fe porphyrin molecule on the Au(111) substrate, the
calculated STM spectra are in good agreement with recently measured STM
spectra, showing the typical step features at finite bias associated with spin
flip excitation of a spin-1 quantum magnet. For the case of Kondo effect in Mn
porphyrin on Au(111), the agreement with the experimental spectra is not as
good due to the neglect of quantum interference in the tunneling.",1805.10624v1
2020-10-26,Pressure-induced phase transition in the $J_1$-$J_2$ square lattice antiferromagnet RbMoOPO$_4$Cl,"We report results of magnetization and $^{31}$P NMR measurements under high
pressure up to 6.4~GPa on RbMoOPO$_4$Cl, which is a frustrated square-lattice
antiferromagnet with competing nearest-neighbor and next-nearest-neighbor
interactions. Anomalies in the pressure dependences of the NMR shift and the
transferred hyperfine coupling constants indicate a structural phase transition
at 2.6~GPa, which is likely to break mirror symmetry and triggers significant
change of the exchange interactions. In fact, the NMR spectra in magnetically
ordered states reveal a change from the columnar antiferromagnetic (CAF) order
below 3.3~GPa to the N\'{e}el antiferromagnetic (NAF) order above 3.9~GPa. The
spin lattice relaxation rate $1/T_1$ also indicates a change of dominant
magnetic fluctuations from CAF-type to NAF-type with pressure. Although the NMR
spectra in the intermediate pressure region between 3.3 and 3.9 GPa show
coexistence of the CAF and NAF phases, a certain component of $1/T_1$ shows
paramagnetic behavior with persistent spin fluctuations, leaving possibility
for a quantum disordered phase. The easy-plane anisotropy of spin fluctuations
with unusual nonmonotonic temperature dependence at ambient pressure gets
reversed to the Ising anisotropy at high pressures. This unexpected anisotropic
behavior for a spin 1/2 system may be ascribed to the strong spin-orbit
coupling of Mo-4$d$ electrons.",2010.13538v2
2016-03-16,"First-principles study of the magnetic ground state in kagome francisites Cu3Bi(SeO3)2O2X (X=Cl, Br)","We explore magnetic behavior of kagome francisites Cu3Bi(SeO3)2O2X (X = Cl
and Br) using first-principles calculations. To this end, we propose an
approach based on the Hubbard model in the Wannier functions basis constructed
on the level of local-density approximation (LDA). The ground-state spin
configuration is determined by a Hartree-Fock solution of the Hubbard model
both in zero magnetic field and in applied magnetic fields. Additionally,
parameters of an effective spin Hamiltonian are obtained by taking into account
the hybridization effects and spin-orbit coupling. We show that only the former
approach, the Hartree-Fock solution of the Hubbard model, allows for a complete
description of the anisotropic magnetization process. While our calculations
confirm that the canted zero-field ground state arises from a competition
between ferromagnetic nearest-neighbor and antiferromagnetic
next-nearest-neighbor couplings in the kagome planes, weaker anisotropic terms
are crucial for fixing spin directions and for the overall magnetization
process. We thus show that the Hartree-Fock solution of an electronic
Hamiltonian is a viable alternative to the analysis of effective spin
Hamiltonians when a magnetic ground state and effects of external field are
considered.",1603.05192v1
2017-07-22,Electronic and magnetic properties of the monolayer RuCl$_3$: A first-principles and Monte Carlo study,"Recent experiments revealed that monolayer $\alpha$-RuCl$_3$ can be obtain by
chemical exfoliation method and exfoliation or restacking of nanosheets can
manipulate the magnetic properties of the materials. In this present paper, the
electronic and magnetic properties of $\alpha$-RuCl$_3$ monolayer are
investigated by combining first-principles calculations and Monte Carlo
simulations. From first-principles calculations, we found that the spin
configuration FM corresponds to the ground state for $\alpha$-RuCl$_3$,
however, the other excited zigzag oriented spin configuration has energy of 5
meV/atom higher than the ground state. Energy band gap has been obtained as $3$
meV using PBE functionals. When spin-orbit coupling effect is taken into
account, corresponding energy gap is determined to be as $57$ meV. We also
investigate the effect of Hubbard U energy terms on the electronic band
structure of $\alpha$-RuCl$_3$ monolayer and revealed band gap increases
approximately linear with increasing U value. Moreover, spin-spin coupling
terms ($J_1$, $J_2$, $J_3$) have been obtained using first principles
calculations. By benefiting from these terms, Monte Carlo simulations with
single site update Metropolis algorithm have been implemented to elucidate
magnetic properties of the considered system. Thermal variations of
magnetization, susceptibility and also specific heat curves indicate that
monolayer $\alpha$-RuCl$_3$ exhibits a phase transition between ordered and
disordered phases at the Curie temperature $14.21$ K. We believe that this
study can be utilized to improve two-dimensional magnet materials.",1707.07198v2
2021-03-23,Rare-earth chalcohalides: A family of van der Waals layered Kitaev spin liquid candidates,"Kitaev spin liquid (KSL) system has attracted tremendous attention in past
years because of its fundamental significance in condensed matter physics and
promising applications in fault-tolerant topological quantum computation.
Material realization of such a system remains a major challenge in the field
due to the unusual configuration of anisotropic spin interactions, though great
effort has been made before. Here we reveal that rare-earth chalcohalides REChX
(RE=rare earth, Ch=O, S, Se, Te, X=F, Cl, Br, I) can serve as a family of KSL
candidates. Most family members have the typical SmSI-type structure with a
high symmetry of R-3m and rare-earth magnetic ions form an undistorted
honeycomb lattice. The strong spin-orbit coupling of 4f electrons intrinsically
offers anisotropic spin interactions as required by Kitaev model. We have grown
the crystals of YbOCl and synthesized the polycrystals of SmSI, ErOF, HoOF and
DyOF, and made careful structural characterizations. We carry out magnetic and
heat capacity measurements down to 1.8 K and find no obvious magnetic
transition in all the samples but DyOF. The van der Waals interlayer coupling
highlights the true two-dimensionality of the family which is vital for the
exact realization of Abelian/non-Abelian anyons, and the graphene-like feature
will be a prominent advantage for developing miniaturized devices. The family
is expected to act as an inspiring material platform for the exploration of KSL
physics.",2103.12309v2
2021-09-02,Supercurrent-induced long-range triplet correlations and controllable Josephson effect in superconductor/ferromagnet hybrids with extrinsic SOC,"We predict that long-range triplet correlations (LRTC) in
superconductor/ferromagnet (S/F) hybrids with extrinsic impurity spin-orbit
coupling (SOC) can be generated and manipulated by supercurrent flowing in the
superconducting leads along the S/F interfaces. The LRTC appear via two basic
mechanisms. The essence of the first one is the generation of triplets by the
superconducting spin Hall effect. These pairs are long-range in the ferromagnet
under the appropriate mutual orientation of the condensate momentum and the
ferromagnet magnetization. The second mechanism is based on the singlet-triplet
conversion at the S/F interface followed by the rotation of the spin of the
obtained short-range opposite-spin pairs via the spin current swapping
mechanism. The structure of the supercurrent-induced LRTC is studied both for
S/F bilayers and S/F/S Josephson junctions. We demonstrate that in S/F/S
junctions, where the Josephson coupling is realized via the
supercurrent-induced LRTC, the ground state phase can be switched between $0$
and $\pi$ in a controllable manner. The switching is performed by reversing the
supercurrent in one of superconducting leads, thus realizing a new physical
principle of the $0-\pi$ shifter.",2109.00966v2
2021-12-29,Twisted nodal wires and three-dimensional quantum spin Hall effect in distorted square-net compounds,"Recently, square-net materials have attracted lots of attention for the Dirac
semimetal phase with negligible spin-orbit coupling (SOC) gap, e.g.
ZrSiS/LaSbTe and CaMnSb$_2$. In this paper, we demonstrate that the Jahn-Teller
effect enlarges the nontrivial SOC gap in the distorted structure, e.g. LaAsS
and SrZnSb$_2$. Its distorted $X$ square-net layer ($X=$ P, As, Sb, Bi)
resembles a quantum spin Hall (QSH) insulator. Since these QSH layers are
simply stacked in the $\hat{x}$ direction and weakly coupled, three-dimensional
QSH effect can be expected in these distorted materials, such as insulating
compounds CeAs$_{1+x}$Se$_{1-y}$ and EuCdSb$_2$. Our detailed calculations show
that it hosts two twisted nodal wires without SOC [each consists of two
noncontractible time-reversal symmetry- and inversion symmetry-protected nodal
lines touching at a fourfold degenerate point], while with SOC it becomes a
topological crystalline insulator with symmetry indicators $(000; 2)$ and
mirror Chern numbers $(0, 0)$. The nontrivial band topology is characterized by
a generalized spin Chern number $C_{s+}=2$ when there is a gap between two sets
of $\hat{s}_{x}$ eigenvalues. The nontrivial topology of these materials can be
well reproduced by our tight-binding model and the calculated spin Hall
conductivity is quantized to $\sigma^{x}_{yz} =
(\frac{\hbar}{e})\frac{G_xe^2}{\pi h}$ with $G_x$ a reciprocal lattice vector.",2112.14467v3
2022-06-03,Anisotropic Laser-Pulse-Induced Magnetization Dynamics in van der Waals Magnet Fe$_3$GeTe$_2$,"Femtosecond laser-pulse excitation provides an energy efficient and fast way
to control magnetization at the nanoscale, providing great potential for
ultrafast next-generation data manipulation and nonvolatile storage devices.
Ferromagnetic van der Waals materials have garnered much attention over the
past few years due to their low dimensionality, excellent magnetic properties,
and large response to external stimuli. Nonetheless, their behaviour upon fs
laser-pulse excitation remains largely unexplored. Here, we investigate the
ultrafast magnetization dynamics of a thin flake of Fe$_3$GeTe$_2$ (FGT) and
extract its intrinsic magnetic properties using a microscopic framework. We
find that our data is well described by our modelling, with FGT undergoing a
slow two-step demagnetization, and we experimentally extract the
spin-relaxation timescale as a function of temperature, magnetic field and
excitation fluence. Our observations indicate a large spin-flip probability in
agreement with a theoretically expected large spin-orbit coupling, as well as a
weak interlayer exchange coupling. The spin-flip probability is found to
increase when the magnetization is pulled away from its quantization axis,
opening doors to an external control over the spins in this material. Our
results provide a deeper understanding of the dynamics van der Waals materials
upon fs laser-pulse excitation, paving the way towards two-dimensional
materials-based ultrafast spintronics.",2206.01452v1
2023-09-05,Tunable Magnetism and Valleys in VSiZ$_3$ monolayers,"Two-dimensional magnetism and valleys have recently emerged as two
significant research areas, with intriguing properties and practical uses in
advanced information technology. Considering the importance of these two areas
and their couplings, controllable creations of both the magnetism and valley
polarization are highly sought after. Based on first-principles calculations,
we propose a new class of two-dimensional monolayers with a chemical formula of
MAZ$_3$, which is viewed as a 2H-MZ$_2$ trilayer passivated by the A-Z bilayer
on its one side. Taking VSiN$_3$ as an example, the MAZ$_3$ monolayers are
found to exhibit tunable magnetism and valleys. For the intrinsic VSiN$_3$
monolayer, it is a non-magnetic semiconductor, with multiple degenerate valleys
and trigonal warping near $K_\pm$ points in the band structure. Besides, the
bands have spin splittings owing to the spin-orbit coupling. Under a moderate
carrier doping, the monolayer becomes a Stoner ferromagnet, which enhances the
spin splittings of the valence band and generates valley splittings. Moreover,
the Berry curvature is valley contrasting, leading to distinct valley-spin
related anomalous Hall currents as the doping concentration increases. Our work
opens up new way to modulate the spin splittings and valley splittings via
electric means, and provides opportunities for exploring advanced spintronic
and valleytronic devices.",2309.01873v1
2012-08-08,Spin-charge conversion in multiterminal Aharonov-Casher ring coupled to precessing ferromagnets: A charge conserving Floquet-nonequilibrium Green function approach,"We derive a non-perturbative solution to the Floquet-nonequilibrium Green
function (Floquet-NEGF) describing open quantum systems periodically driven by
an external field of arbitrary strength of frequency. By adopting the
reduced-zone scheme, we obtain expressions rendering conserved charge currents
for any given maximum number of photons, distinguishable from other existed
Floquet-NEGF-based expressions where, less feasible, infinite number of photons
needed to be taken into account to ensure the conservation. To justify our
derived formalism and to investigate spin-charge conversions by spin-orbit
coupling (SOC), we consider the spin-driven setups as reciprocal to the
electric-driven setups in S. Souma et. al., Phys. Rev. B 70, 195346 (2004) and
Phys. Rev. Lett. 94, 106602 (2005). In our setups, pure spin currents are
driven by the magnetization dynamics of a precessing ferromagnetic (FM) island
and then are pumped into the adjacent two- or four-terminal mesoscopic
Aharonov-Casher (AC) ring of Rashba SOC where spin-charge conversions take
place. Our spin-driven results show reciprocal features that excellently agree
with the findings in the electric-driven setups mentioned above. We propose two
types of symmetry operations, under which the AC ring Hamiltonian is invariant,
to argue the relations of the pumped/converted currents in the leads within the
same or between different pumping configurations. The symmetry arguments are
independent of the ring width and the number of open channels in the leads,
terminals, and precessing FM islands, In particular, net pure in-plane spin
currents and pure spin currents can be generated in the leads for certain
setups of two terminals and two precessing FM islands with the current
magnitude and polarization direction tunable by the pumping configuration, gate
voltage covering the two-terminal AC ring in between the FM islands.",1208.2275v1
2015-03-17,Surface versus bulk contributions to the giant Rashba splitting in the ferroelectric α-GeTe(111) semiconductor,"In systems with broken inversion symmetry spin-orbit coupling (SOC) yields a
Rashba-type spin splitting of electronic states, manifested in a k-dependent
splitting of the bands. While most research had previously focused on 2D
electron systems, recently a three-dimensional (3D) form of such Rashba-effect
was found in a series of bismuth tellurohalides. Whereas these materials
exhibit a very large spin-splitting, they lack an important property concerning
functionalization, namely the possibility to switch or tune the spin texture.
This limitation can be overcome in a new class of functional materials
displaying Rashba-splitting coupled to ferroelectricity: the ferroelectric
Rashba semiconductors (FERS). Using spin- and angle-resolved photoemission
spectroscopy (SARPES) we show that GeTe(111) forms a prime member of this
class, displaying a complex spin-texture for the Rashba-split surface and bulk
bands arising from the intrinsic inversion symmetry breaking caused by the
ferroelectric polarization of the bulk (FE). Apart from pure surface and bulk
states we find surface-bulk resonant states (SBR) whose wavefunctions entangle
the spinors from the bulk and surface contributions. At the Fermi level their
hybridization results in unconventional spin topologies with cochiral
helicities and concomitant gap opening. The GeTe(111) surface and SBR states
make the semiconductor surface conducting. At the same time our SARPES data
confirm that GeTe is a narrow-gap semiconductor, suggesting that GeTe(111)
electronic states are endowed with spin properties that are theoretically
challenging to anticipate. As the helicity of the spins in Rashba bands is
connected to the direction of the FE polarization, this work paves the way to
all-electric non-volatile control of spin-transport properties in
semiconductors.",1503.05004v1
2013-09-25,Spin-Seebeck effect on the surface of topological insulator due to nonequilibrium spin-polarization parallel to the direction of thermally driven electronic transport,"We study the transverse spin-Seebeck effect (SSE) on the surface of a
three-dimensional topological insulator (TI) thin film, such as Bi$_2$Se$_3$,
which is sandwiched between two normal metal leads. The temperature bias
$\Delta T$ applied between the leads generates surface charge current which
becomes spin-polarized due to strong spin-orbit coupling on the TI surface,
with polarization vector acquiring a component $P_x \simeq 60%$ {\em parallel
to the direction of transport}. When the third nonmagnetic voltage probe is
attached to the portion of the TI surface across its width $L_y$, pure spin
current will be injected into the probe where the inverse spin Hall effect
(ISHE) converts it into a voltage signal
\mbox{$|V_\mathrm{ISHE}|^\mathrm{max}/\Delta T \simeq 2.5$ $\mu$V/K} (assuming
the SH angle of Pt voltage probe and $L_y=1$ mm). The existence of predicted
nonequilibrium spin-polarization parallel to the direction of electronic
transport and the corresponding electron-driven SSE crucially relies on
orienting quintuple layers (QLs) of Bi$_2$Se$_3$ {\em orthogonal} to the TI
surface and {\em tilted} by $45^\circ$ with respect to the direction of
transport. Our analysis is based on the Landauer-B\""{u}ttiker-type formula for
spin currents in the leads of a multi-terminal quantum-coherent junction, which
is constructed using nonequilibrium Green function formalism within which we
show how to take into account arbitrary orientation of QLs via the self-energy
describing coupling between semi-infinite normal metal leads and TI.",1309.6447v3
2019-12-09,Ultrafast Microscopy of a Plasmonic Spin Skyrmion,"We present an ultrafast microscopy imaging experiment and a general
analytical description of a new quasiparticle composed of plasmonic
Skyrmion-like spin texture at the core of a surface plasmon polariton (SPP)
vortex. The illumination of a circular coupling structure milled in an Ag film
by circularly polarized light (CPL) couples its spin angular momentum (SAM)
into orbital angular momentum (OAM) of SPPs launching them to form a plasmonic
vortex. The coupling of the cycloidal motion of the SPP polarization at the 2D
interface, with their orbital swirl at the vortex core causes the plasmonic
field to generate 3D SAM pseudovectors, whose topological texture has integer
Skyrmion number and is homotopic to a twisted magnetic Skyrmion quasiparticle
with the boundary defined by an optical L-line singularity contour. An
analytical description finds that the dielectric discontinuity at the Ag/vacuum
interface supports on each side entwined twisted Skyrmion pairs that are
characterized by stable topological textures with opposite Skyrmion numbers.
The SAM texture of the Skyrmion pair within the primary vortex ring corresponds
to a monopole-hedgehog type SAM texture, with a SAM singularity at the vortex
core. Interferometric time-resolved two-photon photoemission electron
microscopy (ITR-2P-PEEM) imaging of the nanofemto spatiotemporal evolution of
the SPP fields and simulation by an analytical model, establish the twisted
topological plasmonic SAM Skyrmion quasiparticle at the vortex core. The SAM
textures can probe and simulate topological responses in trivial and
topological materials that can be coupled in the near-field of the SPP vortex.
The theory anticipates different field structures and the accompanying
topological spin textures that construct single Skyrmion and meron-like
quasiparticles as well as their arrays.",1912.03826v1
2012-12-21,Next-to-next-to-leading order spin-orbit effects in the near-zone metric and precession equations of compact binaries,"We extend our previous work devoted to the computation of the
next-to-next-to-leading order spin-orbit correction (corresponding to 3.5PN
order) in the equations of motion of spinning compact binaries, by: (i)
Deriving the corresponding spin-orbit terms in the evolution equations for the
spins, the conserved integrals of the motion and the metric regularized at the
location of the particles (obtaining also the metric all-over the near zone but
with some lower precision); (ii) Performing the orbital reduction of the
precession equations, near-zone metric and conserved integrals to the center-
of-mass frame and then further assuming quasi-circular orbits (neglecting
gravitational radiation reaction). The results are systematically expressed in
terms of the spin variables with conserved Euclidean norm instead of the
original antisymmetric spin tensors of the pole-dipole formalism. This work
paves the way to the future computation of the next-to-next-to-leading order
spin-orbit terms in the gravitational-wave phasing of spinning compact
binaries.",1212.5520v2
2014-11-17,Spin-orbital exchange of strongly interacting fermions on the $p$-band of a two-dimensional optical lattice,"Mott insulators with both spin and orbital degeneracy are pertinent to a
large number of transition metal oxides. The intertwined spin and orbital
fluctuations can lead to rather exotic phases such as quantum spin-orbital
liquids. Here we consider two-component (spin 1/2) fermionic atoms with strong
repulsive interactions on the $p$-band of the optical square lattice. We derive
the spin-orbital exchange for quarter filling of the $p$-band when the density
fluctuations are suppressed, and show it frustrates the development of long
range spin order. Exact diagonalization indicates a spin-disordered ground
state with ferro-orbital order. The system dynamically decouples into
individual Heisenberg spin chains, each realizing a Luttinger liquid accessible
at higher temperatures compared to atoms confined to the $s$-band.",1411.4496v2
2021-02-24,Realization of exciton-mediated optical spin-orbit interaction in organic microcrystalline resonators,"The ability to control the spin-orbit interaction of light in optical
microresonators is of fundamental importance for future photonics. Organic
microcrystals, due to their giant optical anisotropy, play a crucial role in
spin-optics and topological photonics. Here we realize controllable and
wavelength-dependent Rashba-Dresselhaus spin-orbit interaction, attributed to
the anisotropic excitonic response in an optical microcavity filled with an
organic microcrystalline. We also investigate the transition of the spin-orbit
interaction from dominant photonic type caused by the splitting of the
transverse-electric and transverse-magnetic modes to spin-orbit interaction of
the Rashba-Dresselhaus type. The interplay of the two allows us to engineer the
spin-orbit interaction of light in organic microcavities, which besides its
fundamental interest promises applications in spin-controlled on-chip
integrated nanophotonic elements, towards exploiting non-magnetic and low-cost
spin-photonic devices.",2102.12200v1
2017-11-16,Effect of lattice distortion on U magnetic moments in $\mathrm{U_{4}Ru_{7}Ge_{6}}$ studied by polarized neutron diffraction,"Small spontaneous lattice distortion of a cubic ferromagnet at temperatures
below $T_{\mathrm{C}}$ is expected, but usually a neglected phenomenon. This
study is focused on such effect on the example of $\mathrm{U_{4}Ru_{7}Ge_{6}}$.
We propose the lattice distortion from the cubic space group to a lower
symmetry as a result of our DFT calculations. The strong spin-orbit coupling on
the U site plays the most essential role, that should lower the symmetry of the
system and give rise to the two different U sites (U1 and U2). We bring
convincing experimental evidence for this splitting resulting from our
polarized neutron diffraction experiment. Proper treatment of the flipping
ratios collected in the ordered state and in the paramagnetic state reveals
dramatically different magnetic moments on the U1 and U2 sites. We have reached
good agreement of the results from the MAXENT method and from direct fitting of
the data. The ratio of the orbital and spin component on the U2 site is lower
than for the free $\mathrm{U^{3+}}$ or $\mathrm{U^{4+}}$ ion and points to a
strong hybridization between the U $5f$ and Ru $4d$ wave functions. The same
ratio on the U1 site is unexpectedly low. This would mean that its orbital
component is almost quenched. We have observed the absence of a magnetic moment
on the Ru1 site, but a rather large induced moment on the Ru2 site. Very
similar results were obtained also in the paramagnetic state in the regime
induced by the magnetic field. It points to the intimate coupling of the
magnetic ordering and structural distortion as it is possible to split the U
site in to two different polarizing paramagnetic U moments above
$T_{\mathrm{C}}$ by a strong magnetic field. We propose that the difference
between the magnetic moment on the U sites is caused by the change of local
point symmetry of the sites that is tightly bound to the role of the strong
spin-orbit interaction.",1711.06113v2
2010-10-05,The barycentric motion of exoplanet host stars: tests of solar spin-orbit coupling,"Empirical evidence suggests a tantalising but unproven link between various
indicators of solar activity and the barycentric motion of the Sun. The latter
is exemplified by transitions between regular and more disordered motion
modulated by the motions of the giant planets, and rare periods of retrograde
motion with negative orbital angular momentum. An examination of the
barycentric motion of exoplanet host stars, and their stellar activity cycles,
has the potential of proving or disproving the Sun's motion as an underlying
factor in the complex patterns of short- and long-term solar variability
indices, by establishing whether such correlations exist in other planetary
systems. A variety of complex patterns of barycentric motions of exoplanet host
stars is demonstrated, depending on the number, masses and orbits of the
planets. Each of the behavioural types proposed to correlate with solar
activity are also evident in exoplanet host stars: repetitive patterns
influenced by massive multiple planets, epochs of rapid change in orbital
angular momentum, and intervals of negative orbital angular momentum. The study
provides the basis for independent investigations of the widely-studied but
unproven suggestion that the Sun's motion is somehow linked to various
indicators of solar activity. We show that, because of the nature of their
barycentric motions, the host stars HD168443 and HD74156 offer particularly
powerful tests of this hypothesis.",1010.0966v1
2011-02-28,Evidence for gravitational quadrupole moment variations in the companion of PSR J2051-0827,"We have conducted radio timing observations of the eclipsing millisecond
binary pulsar J2051-0827 with the European Pulsar Timing Array network of
telescopes and the Parkes radio telescope, spanning over 13 years. The
increased data span allows significant measurements of the orbital
eccentricity, e = (6.2 {\pm} 1.3) {\times} 10^{-5} and composite proper motion,
{\mu}_t = 7.3 {\pm} 0.4 mas/yr. Our timing observations have revealed secular
variations of the projected semi-major axis of the pulsar orbit which are much
more extreme than those previously published; and of the orbital period of the
system. Investigation of the physical mechanisms producing such variations
confirm that the variations of the semi-major axis are most probably caused by
classical spin-orbit coupling in the binary system, while the variations in
orbital period are most likely caused by tidal dissipation leading to changes
in the gravitational quadrupole moment of the companion.",1102.5646v1
2012-07-02,Tidal effects around higher-dimensional black holes,"In four-dimensional spacetime, moons around black holes generate
low-amplitude tides, and the energy extracted from the hole's rotation is
always smaller than the gravitational radiation lost to infinity. Thus, moons
orbiting a black hole inspiral and eventually merge. However, it has been
conjectured that in higher-dimensional spacetimes orbiting bodies generate much
stronger tides, which backreact by tidally accelerating the body outwards. This
effect, analogous to the tidal acceleration experienced by the Earth-Moon
system, would determine the evolution of the binary. Here, we put this
conjecture to the test, by studying matter coupled to a massless scalar field
in orbit around a singly-spinning rotating black hole in higher dimensions. We
show that in dimensions larger than five the energy extracted from the black
hole through superradiance is larger than the energy carried out to infinity.
Our numerical results are in excellent agreement with analytic approximations
and lend strong support to the conjecture that tidal acceleration is the rule,
rather than the exception, in higher dimensions. Superradiance dominates the
energy budget and moons ""outspiral""; for some particular orbital frequency, the
energy extracted at the horizon equals the energy emitted to infinity and
""floating orbits"" generically occur. We give an interpretation of this
phenomenon in terms of the membrane paradigm and of tidal acceleration due to
energy dissipation across the horizon.",1207.0504v2
2012-08-04,"Coupled evolutions of the stellar obliquity, orbital distance, and planet's radius due to the Ohmic dissipation induced in a diamagnetic hot Jupiter around a magnetic T Tauri star","We revisit the calculation of the Ohmic dissipation in a hot Jupiter
presented in Laine et al. (2008) by considering more realistic interior
structures, stellar obliquity, and the resulting orbital evolution. In this
simplified approach, the young hot Jupiter of one Jupiter mass is modelled as a
diamagnetic sphere with a finite resistivity, orbiting across tilted stellar
magnetic dipole fields in vacuum. Since the induced Ohmic dissipation occurs
mostly near the planet's surface, we find that the dissipation is unable to
significantly expand the young hot Jupiter. Nevertheless, the planet inside a
small co-rotation orbital radius can undergo orbital decay by the dissipation
torque and finally overfill its Roche lobe during the T Tauri star phase. The
stellar obliquity can evolve significantly if the magnetic dipole is
parallel/anti-parallel to the stellar spin. Our results are validated by the
general torque-dissipation relation in the presence of the stellar obliquity.
We also run the fiducial model in Laine et al. (2008) and find that the
planet's radius is sustained at a nearly constant value by the Ohmic heating,
rather than being thermally expanded to the Roche radius as suggested by the
authors.",1208.0933v2
2014-12-19,Fragment Model Study of Molecular Multi-Orbital System $X$[Pd(dmit)$_2$]$_2$,"Electronic properties of quasi-two-dimensional molecular conductors
$X$[Pd(dmit)$_2$]$_2$ are studied theoretically. We construct an effective
model based on the fragment molecular orbital scheme developed recently, which
can describe the multi-orbital degree of freedom in this system. The
tight-binding parameters for a series of $\beta'$-type compounds with different
cations $X$ are evaluated by fitting to first-principles band calculations. We
find that the transfer integrals within the dimers of Pd(dmit)$_2$ molecules,
along the intramolecular and intermolecular bonds including the diagonal ones,
are the same order, leading to hybridization between different molecular
orbitals. This results in charge disproportionation within each molecule, as
seen in our previous ab initio study [T. Tsumuraya et al, J. Phys. Soc. Jpn.
82, 033709 (2013)], and also to a revised picture of an effective dimer model.
Furthermore, we discuss broken-symmetry insulating states triggered by
interaction effects, which show characteristic features owing to the
multi-orbital nature. The on-site Coulomb interaction induces antiferromagnetic
states with intramolecular antiparallel spin pattern, while electron-lattice
couplings stabilize non-magnetic charge-lattice ordered states where two kinds
of dimers with different charge occupation arrange periodically. These states
showing different spatial patterns compete with each other as well as with the
paramagnetic metallic state.",1412.6369v2
2015-04-26,Charge transfer model for the electronic structure of layered ruthenates,"Motivated by the earlier experimental results and \textit{ab initio} studies
on the electronic structure of layered ruthenates (Sr$_2$RuO$_4$ and
Ca$_2$RuO$_4$) we introduce and investigate the multiband $d-p$ charge transfer
model describing a single RuO$_4$ layer, similar to the charge transfer model
for a single CuO$_2$ plane including apical oxygen orbitals in high $T_c$
cuprates. The present model takes into account nearest-neighbor anisotropic
ruthenium-oxygen $d-p$ and oxygen-oxygen $p-p$ hopping elements, crystal-field
splittings and spin-orbit coupling. The intraorbital Coulomb repulsion and
Hund's exchange are defined not only at ruthenium but also at oxygen ions. Our
results demonstrate that the RuO$_4$ layer cannot be regarded to be a pure
ruthenium $t_{2g}$ system. We examine a different scenario in which ruthenium
$e_g$ orbitals are partly occupied and highlight the significance of oxygen
orbitals. We point out that the predictions of an idealized model based on
ionic configuration (with $n_0=4+4\times 6=28$ electrons per RuO$_4$ unit) do
not agree with the experimental facts for Sr$_2$RuO$_4$ which support our
finding that the electron number in the $d-p$ states is significantly smaller.
In fact, we find the electron occupation of $d$ and $p$ orbitals for a single
RuO$_4$ unit $n=28-x$, being smaller by at least 1--1.5 electrons from that in
the ionic model and corresponding to self-doping with $x\simeq 1.5$.",1504.06850v1
2015-06-29,\textit{Ab-initio} Tight-Binding Hamiltonian for Transition Metal Dichalcogenides,"We present an accurate \textit{ab-initio} tight-binding hamiltonian for the
transition-metal dichalcogenides, MoS$_2$, MoSe$_2$, WS$_2$, WSe$_2$, with a
minimal basis (the \textit{d} orbitals for the metal atoms and \textit{p}
orbitals for the chalcogen atoms) based on a transformation of the Kohn-Sham
density function theory (DFT) hamiltonian to a basis of maximally localized
Wannier functions (MLWF). The truncated tight-binding hamiltonian (TBH), with
only on-site, first and partial second neighbor interactions, including
spin-orbit coupling, provides a simple physical picture and the symmetry of the
main band-structure features. Interlayer interactions between adjacent layers
are modeled by transferable hopping terms between the chalcogen \textit{p}
orbitals. The full-range tight-binding hamiltonian (FTBH) can be reduced to
hybrid-orbital k $\cdot$ p effective hamiltonians near the band extrema that
captures important low-energy excitations. These \textit{ab-initio}
hamiltonians can serve as the starting point for applications to interacting
many-body physics including optical transitions and Berry curvature of bands,
of which we give some examples.",1506.08860v3
2016-08-19,Milankovitch Cycles of Terrestrial Planets in Binary Star Systems,"The habitability of planets in binary star systems depends not only on the
radiation environment created by the two stars, but also on the perturbations
to planetary orbits and rotation produced by the gravitational field of the
binary and neighbouring planets. Habitable planets in binaries may therefore
experience significant perturbations in orbit and spin. The direct effects of
orbital resonances and secular evolution on the climate of binary planets
remain largely unconsidered.
  We present latitudinal energy balance modelling of exoplanet climates with
direct coupling to an N Body integrator and an obliquity evolution model. This
allows us to simultaneously investigate the thermal and dynamical evolution of
planets orbiting binary stars, and discover gravito-climatic oscillations on
dynamical and secular timescales.
  We investigate the Kepler-47 and Alpha Centauri systems as archetypes of P
and S type binary systems respectively. In the first case, Earthlike planets
would experience rapid Milankovitch cycles (of order 1000 years) in
eccentricity, obliquity and precession, inducing temperature oscillations of
similar periods (modulated by other planets in the system). These secular
temperature variations have amplitudes similar to those induced on the much
shorter timescale of the binary period.
  In the Alpha Centauri system, the influence of the secondary produces
eccentricity variations on 15,000 year timescales. This produces climate
oscillations of similar strength to the variation on the orbital timescale of
the binary. Phase drifts between eccentricity and obliquity oscillations
creates further cycles that are of order 100,000 years in duration, which are
further modulated by neighbouring planets.",1608.05592v2
2019-09-10,Electronic structures and topological properties in nickelates $Ln_{n+1}$Ni$_n$O$_{2n+2}$,"After the significant discovery of the hole-doped nickelate compound
Nd$_{0.8}$Sr$_{0.2}$NiO$_2$, an analysis of the electronic structure, orbital
components, Fermi surfaces and band topology could be helpful to understand the
mechanism of its superconductivity. Based on the first-principles calculations,
we find that Ni $3d_{x^2-y^2}$ states contribute the largest Fermi surface.
$Ln~5d_{3z^2-r^2}$ states form an electron pocket at $\Gamma$, while $5d_{xy}$
states form a relatively bigger electron pocket at A. These Fermi surfaces and
symmetry characteristics can be reproduced by our two-band model, which
consists of two elementary band representations: $B_{1g}@1a~\oplus~A_{1g}@1b$.
We find that there is a band inversion near A, giving rise to a pair of Dirac
points along A--M below the Fermi level once including spin-orbit coupling.
Furthermore, we have performed the LDA+Gutzwiller calculations to treat the
strong correlation effect of Ni 3d orbitals. In particular, the bandwidth of
$3d_{x^2-y^2}$ has been renormalized largely. After the renormalization of the
correlated bands, the Ni $3d_{xy}$ states and the Dirac points become very
close to the Fermi level. Thus, a hole pocket at A could be introduced by hole
doping, which may be related to the observed sign change of Hall coefficient.
By introducing an additional Ni $3d_{xy}$ orbital, the hole-pocket band and the
band inversion can be captured in our modified model. Besides, the nontrivial
band topology in the ferromagnetic two-layer compound La$_3$Ni$_2$O$_6$ is
discussed and the band inversion is associated with Ni $3d_{x^2-y^2}$ and La
$5d_{xy}$ orbitals.",1909.04657v2
2019-03-04,Obliquity-Driven Sculpting of Exoplanetary Systems,"NASA's Kepler mission revealed that $\sim 30\%$ of Solar-type stars harbor
planets with sizes between that of Earth and Neptune on nearly circular and
co-planar orbits with periods less than 100 days. Such short-period compact
systems are rarely found with planet pairs in mean-motion resonances (MMRs) --
configurations in which the planetary orbital periods exhibit a simple integer
ratio -- but there is a significant overabundance of planet pairs lying just
wide of the first-order resonances. Previous work suggests that tides raised on
the planets by the host star may be responsible for forcing systems into these
configurations by draining orbital energy to heat. Such tides, however, are
insufficient unless there exists a substantial and as-yet unidentified source
of extra dissipation. Here we show that this cryptic heat source may be linked
to ""obliquity tides"" generated when a large axial tilt (obliquity) is
maintained by secular resonance-driven spin-orbit coupling. We present evidence
that typical compact, nearly-coplanar systems frequently experience this
mechanism, and we highlight additional features in the planetary orbital period
and radius distributions that may be its signatures. Extrasolar planets that
maintain large obliquities will exhibit infrared light curve features that are
detectable with forthcoming space missions. The observed period ratio
distribution can be explained if typical tidal quality factors for super-Earths
and sub-Neptunes are similar to those of Uranus and Neptune.",1903.01386v1
2022-05-13,Isotropic orbital magnetic moments in magnetically anisotropic SrRuO3 films,"Epitaxially strained SrRuO3 films have been a model system for understanding
the magnetic anisotropy in metallic oxides. In this paper, we investigate the
anisotropy of the Ru 4d and O 2p electronic structure and magnetic properties
using high-quality epitaxially strained (compressive and tensile) SrRuO3 films
grown by machine-learning-assisted molecular beam epitaxy. The element-specific
magnetic properties and the hybridization between the Ru 4d and O 2p orbitals
were characterized by Ru M2,3-edge and O K-edge soft X-ray absorption
spectroscopy and X-ray magnetic circular dichroism measurements. The
magnetization curves for the Ru 4d and O 2p magnetic moments are identical,
irrespective of the strain type, indicating the strong magnetic coupling
between the Ru and O ions. The electronic structure and the orbital magnetic
moment relative to the spin magnetic moment are isotropic despite the
perpendicular and in-plane magnetic anisotropy in the compressive-strained and
tensile-strained SrRuO3 films; i.e., the orbital magnetic moments have a
negligibly small contribution to the magnetic anisotropy. This result
contradicts Bruno model, where magnetic anisotropy arises from the difference
in the orbital magnetic moment between the perpendicular and in-plane
directions. Contributions of strain-induced electric quadrupole moments to the
magnetic anisotropy are discussed, too.",2205.06563v1
2023-08-04,S-wave pairing in a two-orbital t-J model on triangular lattice: possible application to Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O,"Recently room temperature superconductor was claimed in
Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O (also known as LK-99) with $x\in (0.9,1.1)$.
Density functional theory (DFT) calculations suggest that the conduction
electrons are from the doped Cu atoms with valence close to $d^{9}$. Motivated
by this picture, we build a two-orbital Hubbard model on a triangular lattice
formed by the $d_{xz}$ and $d_{yz}$ orbitals with total hole density (summed
over spin and orbital) $n=1-p$. When $p=0$, the system is in a Mott insulator
within this model. When $p>0$, we derive a $t-J$ model and perform a
self-consistent slave boson mean field calculation. Interestingly we find a
s-wave pairing in contrast to the one-orbital t-J model which favors $d+id$
pairing. S wave pairing should be more robust to disorder and may lead to high
Tc superconductor with sufficiently large values of $t$ and $J$. However, the
DFT calculations predict a very small value of $t$ and then the $T_c$ is
expected to be small. If LK99 is really a high Tc superconductor, ingredients
beyond the current model are needed. We conjecture that the doped Cu atoms may
distort the original lattice and form local clusters with smaller Cu -Cu
distance and thus larger values of $t$ and $J$. Within these clusters, we may
locally apply our t-J model calculation and expect high Tc s-wave
superconductor. Then the superconducting islands couple together, which may
eventually become a global superconductor, an insulator or even an anomalous
metal depending on sample details.",2308.02469v1
2015-01-06,Spin excitations used to probe the nature of the exchange coupling in the magnetically ordered ground state of Pr$_{0.5}$Ca$_{0.5}$MnO$_{3}$,"We have used time-of-flight inelastic neutron scattering to measure the spin
wave spectrum of the canonical half-doped manganite
Pr$_{0.5}$Ca$_{0.5}$MnO$_{3}$, in its magnetic and orbitally ordered phase. The
data, which cover multiple Brillouin zones and the entire energy range of the
excitations, are compared with several different models that are all consistent
with the CE-type magnetic order, but arise through different exchange coupling
schemes. The Goodenough model, i.e. an ordered state comprising strong nearest
neighbor ferromagnetic interactions along zig-zag chains with antiferromagnetic
inter-chain coupling, provides the best description of the data, provided that
further neighbor interactions along the chains are included. We are able to
rule out a coupling scheme involving formation of strongly bound ferromagnetic
dimers, i.e. Zener polarons, on the basis of gross features of the observed
spin wave spectrum. A model with weaker dimerization reproduces the observed
dispersion but can be ruled out on the basis of discrepancies between the
calculated and observed structure factors at certain positions in reciprocal
space. Adding further neighbor interactions results in almost no dimerization,
i.e. recovery of the Goodenough model. These results are consistent with
theoretical analysis of the degenerate double exchange model for half-doping,
and provide a recipe for how to interpret future measurements away from
half-doping, where degenerate double exchange models predict more complex
ground states.",1501.01148v2
2013-08-24,Spin-chain magnetism and uniform Dzyaloshinsky-Moriya anisotropy in BaV$_3$O$_8$,"We report on the microscopic magnetic model of a spin-1/2 magnet
BaV$_3$O$_8$. In contrast to earlier phenomenological analysis, our
density-functional band-structure calculations combined with quantum
Monte-Carlo simulations establish a relatively simple and non-frustrated model
of weakly coupled spin chains with the intrachain coupling of $J\sim$ 38 K and
the Neel temperature of $T_N\sim$ 6 K, both in excellent agreement with the
experiment. The intrachain coupling between the spin-1/2 V$^{+4}$ ions takes
place via two contiguous V$^{+5}$O$_4$ tetrahedra forming an extended
superexchange pathway with the V$^{+4}$--V$^{+4}$ distance of 7.44 A.
Surprisingly, this pathway is preferred over shorter V$^{+4}$--V$^{+4}$
connections, owing to peculiarities in the interacting orbitals of the magnetic
V$^{+4}$ ions and V$^{+5}$ ions that are non-magnetic, but feature low-lying
$3d$ states contributing to the superexchange process. We also note that the
crystal structure of BaV$_3$O$_8$ supports the long-sought uniform arrangement
of Dzyaloshinsky-Moriya (DM) couplings on a spin-1/2 chain. While our
calculations yield only a weak DM anisotropy in BaV$_3$O$_8$, the crystal
structure of this compound provides a suitable framework for the search of spin
chains with the uniform DM anisotropy in other compounds of the vanadate
family.",1308.5305v2
2019-12-27,Flat bands and nontrivial topological properties in an extended Lieb lattice,"We report the appearance of multiple numbers of completely flat band states
in an extended Lieb lattice model in two dimensions with five atomic sites per
unit cell. We also show that this edge-centered square lattice can host
intriguing topologically nontrivial phases when intrinsic spin-orbit (ISO)
coupling is introduced in the microscopic description of the corresponding
tight-binding Hamiltonian of the system. This ISO coupling strength acts like a
complex next-nearest-neighbor hopping term for this model and can be, in
principle, tuned in a real-life experimental setup. In the presence of this ISO
coupling, the band spectrum of the system gets gapped out, leading to nonzero
integer values of the spin Chern number for different bands, indicating the
nontrivial topological properties of the system. Furthermore, we show that for
certain values of the ISO coupling, nearly flat bands with nonzero Chern
numbers emerge in this lattice model. This opens up the possibility of
realizing interesting fractional quantum spin Hall physics in this model when
interaction is taken into account. This study might be very useful in an
analogous optical lattice experimental setup. A possible application of our
results can also be anticipated in the field of photonics using single-mode
photonic waveguide networks.",1912.12308v1
2016-09-28,All-optical spin switching: A new frontier in femtomagnetism -- A short review and a simple theory,"Using an ultrafast laser pulse to manipulate the spin degree of freedom has
broad technological appeal. It allows one to control the spin dynamics on a
femtosecond time scale. The discipline, commonly called femtomagnetism, started
with the pioneering experiment by Beaurepaire and coworkers in 1996, who showed
subpicosecond demagnetization occurs in magnetic Ni thin films. This finding
has motivated extensive research worldwide. All-optical helicity-dependent spin
switching (AOS) represents a new frontier in femtomagnetism, where a single
ultrafast laser pulse can permanently switch spin without any assistance from a
magnetic field. This review summarizes some of the crucial aspects of this new
discipline: key experimental findings, leading mechanisms, controversial
issues, and possible future directions. The emphasis is on our latest
investigation. We first develop the all-optical spin switching rule that
determines how the switchability depends on the light helicity. This rule
allows one to understand microscopically how the spin is reversed and why the
circularly polarized light appears more powerful than the linearly polarized
light. Then we invoke our latest spin-orbit coupled harmonic oscillator model
to simulate single spin reversal. We consider both cw excitation and pulsed
laser excitation. The results are in a good agreement with the experimental
result. We then extend the code to include the exchange interaction among
different spin sites. We show where the ""inverse Faraday field"" comes from and
how the laser affects the spin reversal nonlinearly. Our hope is that this
review will motivate new experimental and theoretical investigations and
discussions.",1609.09139v2
2023-04-11,Collinear Rashba-Edelstein effect in non-magnetic chiral materials,"Efficient generation and manipulation of spin signals in a given material
without invoking external magnetism remain one of the challenges in
spintronics. The spin Hall effect (SHE) and Rashba-Edelstein effect (REE) are
well-known mechanisms to electrically generate spin accumulation in materials
with strong spin-orbit coupling (SOC), but the exact role of the strength and
type of SOC, especially in crystals with low symmetry, has yet to be explained.
In this study, we investigate REE in two different families of non-magnetic
chiral materials, elemental semiconductors (Te and Se) and semimetallic
disilicides (TaSi$_2$ and NbSi$_2$), using an approach based on density
functional theory (DFT). By analyzing spin textures across the full Brillouin
zones and comparing them with REE magnitudes calculated as a function of
chemical potential, we link specific features in the electronic structure with
the efficiency of the induced spin accumulation. Our findings show that
magnitudes of REE can be increased by: (i) the presence of purely radial
(Weyl-type) spin texture manifesting as the parallel spin-momentum locking,
(ii) high spin polarization of bands along one specific crystallographic
direction, (iii) low band velocities. By comparing materials possessing the
same crystal structures, but different strengths of SOC, we conclude that
larger SOC may indirectly contribute to the enhancement of REE. It yields
greater spin-splitting of bands along specific crystallographic directions,
which prevents canceling the contributions from the oppositely spin-polarized
bands over wider energy regions and helps maintain larger REE magnitudes. We
believe that these results will be useful for designing spintronics devices and
may aid further computational studies searching for efficient REE in materials
with different symmetries and SOC strengths.",2304.05287v1
2012-03-18,Hole spin relaxation in $p$-type (111) GaAs quantum wells,"Hole spin relaxation in $p$-type (111) GaAs quantum wells is investigated in
the case with only the lowest hole subband, which is heavy-hole like in (111)
GaAs/AlAs and light-hole like in (111) GaAs/InP quantum wells, being relevant.
The subband L\""{o}wdin perturbation method is applied to obtain the effective
Hamiltonian including the Dresselhaus and Rashba spin-orbit couplings. Under a
proper gate voltage, the total in-plane effective magnetic field in (111)
GaAs/AlAs quantum wells can be strongly suppressed in the whole momentum space,
while the one in (111) GaAs/InP quantum wells can be suppressed only on a
special momentum circle. The hole spin relaxation due to the D'yakonov-Perel'
and Elliott-Yafet mechanisms is calculated by means of the fully microscopic
kinetic spin Bloch equation approach with all the relevant scatterings
explicitly included. For (111) GaAs/AlAs quantum wells, extremely long
heavy-hole spin relaxation time (upto hundreds of nanoseconds) is predicted. In
addition, we predict a pronounced peak in the gate-voltage dependence of the
heavy-hole spin relaxation time due to the D'yakonov-Perel' mechanism. This
peak origins from the suppression of the unique inhomogeneous broadening in
(111) GaAs/AlAs quantum wells. Moreover, the Elliott-Yafet mechanism influences
the spin relaxation only around the peak area due to the small spin mixing
between the heavy and light holes in quantum wells with small well width. We
also show the anisotropy of the spin relaxation. In (111) GaAs/InP quantum
wells, a mild peak, similar to the case for electrons in (111) GaAs quantum
wells, is also predicted in the gate-voltage dependence of the light-hole spin
relaxation time. The contribution of the Elliott-Yafet mechanism is always
negligible in this case.",1203.3931v1
2016-07-12,Theory for Spin Selective Andreev Reflection in Vortex Core of Topological Superconductor: Majorana Zero Modes on Spherical Surface and Application to Spin Polarized Scanning Tunneling Microscope Probe,"Majorana zero modes (MZMs) have been predicted to exist in the topological
insulator (TI)/superconductor (SC) heterostructure. Recent spin polarized
scanning tunneling microscope (STM) experiment$^{1}$ has observed
spin-polarization dependence of the zero bias differential tunneling
conductance at the center of vortex core, which may be attributed to the spin
selective Andreev reflection, a novel property of the MZMs theoretically
predicted in 1-dimensional nanowire$^{2}$. Here we consider a helical electron
system described by a Rashba spin orbit coupling Hamiltonian on a spherical
surface with a s-wave superconducting pairing due to proximity effect. We
examine in-gap excitations of a pair of vortices with one at the north pole and
the other at the south pole. While the MZM is not a spin eigenstate, the spin
wavefunction of the MZM at the center of the vortex core, r = 0, is parallel to
the magnetic field, and the local Andreev reflection of the MZM is spin
selective, namely occurs only when the STM tip has the spin polarization
parallel to the magnetic field, similar to the case in 1-dimensional nanowire2.
The total local differential tunneling conductance consists of the normal term
proportional to the local density of states and an additional term arising from
the Andreev reflection. We also discuss the finite size effect, for which the
MZM at the north pole is hybridized with the MZM at the south pole. We apply
our theory to examine the recently reported spin-polarized STM experiments and
show good agreement with the experiments.",1607.03449v1
2020-07-30,"Tunable spin Hall and spin Nernst effects in Dirac line-node semimetals XCuYAs (X=Zr, Hf; Y=Si, Ge)","The quaternary arsenide compounds XCuYAs (X=Zr, Hf; Y= Si, Ge) belong to the
vast family of the 1111-type quaternary compounds, which possess outstanding
physical properties ranging from $p$-type transparent semiconductors to
high-temperature Fe-based superconductors. In this paper, we study the
electronic structure topology, spin Hall effect (SHE) and spin Nernst effect
(SNE) in these compounds based on density functional theory calculations. First
we find that the four considered compounds are Dirac semimetals with the
nonsymmorphic symmetry-protected Dirac line nodes along the Brillouin zone
boundary $A$-$M$ and $X$-$R$ and low density of states (DOS) near the Fermi
level ($E_F$). Second, the intrinsic SHE and SNE in some of these considered
compounds are found to be large. In particular, the calculated spin Hall
conductivity (SHC) of HfCuGeAs is as large as -514 ($\hbar$/e)(S/cm). The spin
Nernst conductivity (SNC) of HfCuGeAs at room temperature is also large, being
-0.73 ($\hbar$/e)(A/m-K). Moreover, both the magnitude and sign of the SHC and
SNC in these compounds can be manipulated by varying either the applied
electric field direction or spin current direction. The SHE and SNE in these
compounds can also be enhanced by tuning the Fermi level via chemical doping or
electric gating. Finally, a detailed analysis of the band-decomposed and
$k$-resolved spin Berry curvatures reveals that these large SHC and SNC as well
as their notable tunabilities originate largely from the presence of a large
number of spin-orbit coupling-gapped Dirac points near the Fermi level as well
as the gapless Dirac line-nodes, which give rise to large spin Berry
curvatures. Our findings thus suggest that the four XCuYAs compounds not only
provide a valuable platform for exploring the interplay between SHE, SNE and
band topology but also have promising applications in spintronics and spin
caloritronics.",2007.15303v1
2017-07-13,Transmission Line Model for Materials with Spin-Momentum Locking,"We provide a transmission line representation for channels exhibiting
spin-momentum locking (SML) which can be used for both time-dependent and
steady-state transport analysis on a wide variety of materials with spin-orbit
coupling such as topological insulators, heavy metals, oxide interfaces, and
narrow bandgap semiconductors. This model is based on a time-dependent
four-component diffusion equation obtained from the Boltzmann transport
equation assuming linear response and elastic scattering in the channel. We
classify all electronic states in the channel into four groups ($U^+$, $D^+$,
$U^-$, and $D^-$) depending on the spin index (up ($U$), down ($D$)) and the
sign of the $x$-component of the group velocity ($+,-$) and assign an average
electrochemical potential to each of the four groups to obtain the
four-component diffusion equation. For normal metal channels, the model
decouples into the well-known transmission line model for charge and a
time-dependent version of Valet-Fert equation for spin. We first show that in
the steady-state limit our model leads to simple expressions for charge-spin
interconversion in SML channels in good agreement with existing experimental
data on diverse materials. We then use the full time-dependent model to study
spin-charge separation in the presence of SML, a subject that has been
controversial in the past. Our model shows that the charge and spin signals
travel with two distinct velocities resulting in well-known spin-charge
separation which is expected to persist even in the presence of SML. However,
our model predicts that the lower velocity signal is purely spin while the
higher velocity signal is largely charge with an additional spin component
which has not been noted before. Finally, we note that our model can be used
within standard circuit simulators like SPICE to obtain numerical results for
complex geometries.",1707.04051v3
2022-02-18,Rashba-induced spin texture and spin-layer-locking effects in the antiferromagnetic CrI3 bilayer,"The antiferromagnetic (AFM) CrI$_3$ bilayer is a particularly interesting
representative of van der Waals 2D semiconductors, which are currently being
studied for their magnetism and for their potential in spintronics. Using ab
initio density-functional theory calculations, we investigate the spin texture
in momentum space of the states of the (doubly degenerate) highest valence band
of the AFM CrI$_3$ bilayer with Cr-spin moments perpendicular to the layers. We
find the existence, in the main central part of the Brillouin zone, of a Rashba
in-plane spin texture of opposite signs on the two layers, resulting from the
intrinsic local electric fields acting on each layer. To study the layer
segregation of the wavefunctions, we apply a small electric field that splits
the degenerate states according to their layer occupancy. We find that the
wavefunctions of the highest valence band are layer-segregated, belonging to
only one of the two layers with opposite in-plane spin textures, and the
segregation occurs over nearly the whole Brillouin zone. The corresponding
layer locking of the in-plane-canted spin is related to the separation in
energy of the highest AFM band from the rest of the valence bands. We explain
how the band interactions destroy the layer locking at the $K$, $K'$, and
$\Gamma$ points. Furthermore, we compare the layer locking of the
in-plane-canted spin in our AFM bilayer system with the hidden spin
polarization in centrosymmetric nonmagnetic materials, pointing out the
differences in segregation mechanisms and their consequences for the layer
locking. We note that a similar Rashba effect with layer locking of
in-plane-canted spin could occur in other van der Waals AFM bilayers with
strong spin-orbit coupling and an isolated energy band.",2202.09431v2
2023-03-08,Observation of plaid-like spin splitting in a noncoplanar antiferromagnet,"Spatial, momentum and energy separation of electronic spins in condensed
matter systems guides the development of novel devices where spin-polarized
current is generated and manipulated. Recent attention on a set of previously
overlooked symmetry operations in magnetic materials leads to the emergence of
a new type of spin splitting, enabling giant and momentum-dependent spin
polarization of energy bands on selected antiferromagnets. Despite the
ever-growing theoretical predictions, the direct spectroscopic proof of such
spin splitting is still lacking. Here, we provide solid spectroscopic and
computational evidence for the existence of such materials. In the noncoplanar
antiferromagnet MnTe$_2$, the in-plane components of spin are found to be
antisymmetric about the high-symmetry planes of the Brillouin zone, comprising
a plaid-like spin texture in the antiferromagnetic (AFM) ground state. Such an
unconventional spin pattern, further found to diminish at the high-temperature
paramagnetic state, stems from the intrinsic AFM order instead of spin-orbit
coupling (SOC). Our finding demonstrates a new type of quadratic spin texture
induced by time-reversal breaking, placing AFM spintronics on a firm basis and
paving the way for studying exotic quantum phenomena in related materials.",2303.04549v3
2023-06-22,"Gilbert damping in metallic ferromagnets from Schwinger-Keldysh field theory: Intrinsically nonlocal and nonuniform, and made anisotropic by spin-orbit coupling","Understanding the origin of damping mechanisms in magnetization dynamics of
metallic ferromagnets is a fundamental problem for nonequilibrium many-body
physics of systems where quantum conduction electrons interact with localized
spins assumed to be governed by the classical Landau-Lifshitz-Gilbert (LLG)
equation. It is also of critical importance for applications, as damping
affects energy consumption and speed of spintronic and magnonic devices. Since
the 1970s, a variety of linear-response and scattering theory approaches have
been developed to produce widely used formulas for computation of
spatially-independent Gilbert scalar parameter as the magnitude of the Gilbert
damping term in the LLG equation. The largely unexploited for this purpose
Schwinger-Keldysh field theory (SKFT) offers additional possibilities, such as
to rigorously derive an extended LLG equation by integrating quantum electrons
out. Here we derive such equation whose Gilbert damping for metallic
ferromagnets is nonlocal, i.e., dependent on all localized spins at a given
time, and nonuniform, even if all localized spins are collinear and spin-orbit
coupling (SOC) is absent. This is in sharp contrast to standard lore, where
nonlocal damping is considered to emerge only if localized spins are
noncollinear; for such situations, direct comparison on the example of magnetic
domain wall shows that SKFT-derived nonlocal damping is an order of magnitude
larger than the previously considered one. Switching on SOC makes such nonlocal
damping anisotropic, in contrast to standard lore where SOC is usually
necessary to obtain nonzero Gilbert damping scalar parameter. Our analytical
formulas, with their nonlocality being more prominent in low spatial
dimensions, are fully corroborated by numerically exact quantum-classical
simulations.",2306.13013v4
2023-09-23,Origin of spin-driven ferroelectricity and effect of external pressure on the complex magnetism of 6H-perovskite Ba3HoRu2O9,"The compound Ba3HoRu2O9 magnetically orders at 50 K (TN1) followed by another
complex magnetic ordering at 10 K (TN2). The 2nd magnetic phase transition was
characterized by the co-existence of two competing magnetic ground states
associated with two different magnetic wave vectors (K1=1/2 0 0 and K2=1/4 1/4
0). We have investigated the compound through time-of-flight neutron
diffraction, ac susceptibility, complex dielectric spectroscopy, and
magnetization under external pressure. We demonstrate that the non-colinear
structure involving two different magnetic ions, Ru(4d) and Ho(4f), breaks the
spatial inversion symmetry via inverse Dzyaloshinskii-Moriya (D-M) interaction
through strong4d-4f magnetic correlation, which shifts the oxygen atoms and
results in non-zero polarization. Such an observation of inverse D-M
interaction from two different magnetic spins ions which caused
ferroelectricity is rarely observed. The stronger spin-orbit coupling of
4d-orbital might play a major role in creating D-M interaction of non-collinear
spins. We have systematically studied the spin and dipolar dynamics, which
exhibit intriguing behavior with shorter coherence lengths of 2nd magnetic
phase associated with the K2-wave vector. The results manifest the development
of magnetoelectric domains instead of true long-range ordering which justifies
the experimentally obtained low value of ferroelectric polarization. Further,
we have investigated the effect of external pressure on this complex magnetism.
The result reveals an enhancement of ordering temperature by the application of
external pressure (1.6K/GPa). The external pressure might favor stabilizing the
ground state associated with 2nd magnetic phase. Our study shows an
unconventional mechanism of spin-driven ferroelectricity involving inverse D-M
interaction between Ru(4d) and Ho(4f) magnetic ions due to strong 4d-4f
cross-coupling.",2309.13465v3
2014-08-07,Spin relaxation in a Si quantum dot due to spin-valley mixing,"We study the relaxation of an electron spin qubit in a Si quantum dot due to
electrical noise. In particular, we clarify how the presence of conduction-band
valleys influences spin relaxation. In single-valley semiconductor quantum
dots, spin relaxation is through the mixing of spin and envelope orbital states
via spin-orbit interaction. In Si, the relaxation could also be through the
mixing of spin and valley states. We find that the additional spin relaxation
channel, via spin-valley mixing and electrical noise, is indeed important for
an electron spin in a Si quantum dot. By considering both spin-valley and
intravalley spin-orbit mixings and Johnson noise in a Si device, we find that
the spin relaxation rate peaks at the hot spot, where the Zeeman splitting
matches the valley splitting. Furthermore, because of a weaker field
dependence, the spin relaxation rate due to Johnson noise could dominate over
phonon noise at low magnetic fields, which fits well with recent experiments.",1408.1666v2
2018-04-16,Phase diagram description of the CaCu$_3$Fe$_4$O$_{12}$ double perovskite,"CaCu$_3$Fe$_4$O$_{12}$ exhibits a temperature-induced transition from a
ferrimagnetic-insulating phase, in which Fe appears charge disproportionated,
as Fe$^{3+}$ and Fe$^{5+}$, to a paramagnetic-metallic phase at temperatures
above 210 K, with Fe$^{4+}$ present. To describe it, we propose a microscopic
effective model with two interpenetrating sublattices of Fe$^{(4-\delta)+}$ and
Fe$^{(4+\delta)+}$, respectively, being $\delta$ the Fe-charge
disproportionation. We include all $3d$-Fe orbitals: $t_{2g}$ localized
orbitals, with spin 3/2 and magnetically coupled, plus two degenerate itinerant
$e_g$ orbitals with local and nearest-neighbor (NN) electron correlations, and
hopping between NN $e_g$ orbitals of the same symmetry. Allub and Alascio
previously proposed a model to describe the phase transition in
LaCu$_3$Fe$_4$O$_{12}$ from a paramagnetic-metal to an
antiferromagnetic-insulator, induced by temperature or pressure, involving
charge transfer between Fe and Cu ions, in contrast to Fe-charge
disproportionation. With the model proposed for CaCu$_3$Fe$_4$O$_{12}$,
modified to account for this difference between the two compounds, the density
of states of the itinerant Fe orbitals was obtained, using Green's functions
methods. The phase diagram for CaCu$_3$Fe$_4$O$_{12}$ was calculated, including
phases exhibiting Fe-charge disproportionation, where the two eg orbitals in
each site are symmetrically occupied, as well as novel phases exhibiting local
orbital selectivity/asymmetric occupation of $e_g$ orbitals. Both kinds of
phases may exhibit paramagnetism and ferromagnetism. We determined the model
parameters which best describe the phase transition observed in
CaCu$_3$Fe$_4$O$_{12}$, and found other phases at different parameter ranges,
which might be relevant for other compounds of the ACu$_3$Fe$_4$O$_{12}$
family, which present both types of transitions.",1804.05726v1
2013-10-18,Extreme orbital evolution from hierarchical secular coupling of two giant planets,"Observations of exoplanets over the last two decades have revealed a new
class of Jupiter-size planets with orbital periods of a few days, the so-called
""hot Jupiters"". Recent measurements using the Rossiter-McLaughlin effect have
shown that many (~ 50%) of these planets are misaligned; furthermore, some (~
15%) are even retrograde with respect to the stellar spin axis. Motivated by
these observations, we explore the possibility of forming retrograde orbits in
hierarchical triple configurations consisting of a star-planet inner pair with
another giant planet, or brown dwarf, in a much wider orbit. Recently Naoz et
al. (2011) showed that in such a system, the inner planet's orbit can flip back
and forth from prograde to retrograde, and can also reach extremely high
eccentricities. Here we map a significant part of the parameter space of
dynamical outcomes for these systems. We derive strong constraints on the
orbital configurations for the outer perturber that could lead to the formation
of hot Jupiters with misaligned or retrograde orbits. We focus only on the
secular evolution, neglecting other dynamical effects such as mean-motion
resonances, as well as all dissipative forces. For example, with an inner
Jupiter-like planet initially on a nearly circular orbit at 5 AU, we show that
a misaligned hot Jupiter is likely to be formed in the presence of a more
massive planetary companion (> 2 MJ) within 140 AU of the inner system, with
mutual inclination 50 degrees and eccentricity above 0.25. This is in striking
contrast to the test-particle approximation, where an almost perpendicular
configuration can still cause large eccentricity excitations, but flips of an
inner Jupiter-like planet are much less likely to occur. The constraints we
derive can be used to guide future observations, and, in particular, searches
for more distant companions in systems containing a hot Jupiter.",1310.5048v2
2019-05-08,Updated orbital ephemeris of the ADC source X 1822-371: a stable orbital expansion over 40 years,"The source X 1822-371 is an eclipsing compact binary system with a period
close to 5.57 hr and an orbital period derivative $\dot{P}_{\rm orb}$ of
1.51(7)$\times 10^{-10}$ s s$^{-1}$. The very large value of $\dot{P}_{\rm
orb}$ is compatible with a super-Eddington mass transfer rate from the
companion star, as suggested by X-ray and optical data. The XMM-Newton
observation taken in 2017 allows us to update the orbital ephemeris and verify
whether the orbital period derivative has been stable over the last 40 yr. We
added to the X-ray eclipse arrival times from 1977 to 2008 two new values
obtained from the RXTE and XMM-Newton observations performed in 2011 and 2017,
respectively. We estimated the number of orbital cycles and the delays of our
eclipse arrival times spanning 40 yr using as reference time the eclipse
arrival time obtained from the Rossi-XTE observation taken in 1996. Fitting the
delays with a quadratic model, we found an orbital period $P_{\rm
orb}=5.57062957(20)$ hr and a $\dot{P}_{\rm orb}$ value of $1.475(54) \times
10^{-10}$ s s$^{-1}$. The addition of a cubic term to the model does not
significantly improve the quality of the fit. We also determined a spin-period
value of $P_{\rm spin}=0.5915669(4)$ s and its first derivative $\dot{P}_{\rm
spin}= -2.595(11) \times 10^{-12}$ s s$^{-1}$. The obtained results confirm the
scenario of a super-Eddington mass transfer rate; we also exclude a
gravitational coupling between the orbit and the change in the oblateness of
the companion star triggered by the nuclear luminosity of the companion star.",1905.03149v1
2023-12-28,Chaotic Capture of a Retrograde Moon by Venus and the Reversal of Its Spin,"(Abridged) Planets are surrounded by fractal surfaces (traditionally called
Hill spheres), separating the inner zones of long-term stable orbital motion of
their satellites from the outer space where the gravitational pull from the Sun
takes over. Through this surface, external minor bodies in trajectories loosely
co-orbital to a planet can be stochastically captured by the planet without any
assistance from external perturbative forces, and can become moons chaotically
orbiting the planet for extended periods of time. Using state-of-the-art
orbital integrators, we simulate such capture events for Venus, resulting in
long-term attachment phases by reversing the forward integration of a moon
initially attached to the planet and escaping it after an extended period of
time. Although the probability of a long-term chaotic capture from a single
encounter is generally low, the high density of co-orbital bodies in the
primordial protoplanetary disk makes this outcome possible, if not probable.
The early Venus was surrounded by a dusty gaseous disk of its own, which,
coupled with the tidal dissipation of the kinetic energy in the moon and the
planet, could shrink the initial orbit and stabilize the captured body within
the Hill surface. The tidal torque from the moon, for which we use the
historical name Neith, gradually brakes the prograde rotation of Venus, and
then reverses it, while the orbit continues to decay. Neith eventually reaches
the Roche radius and disintegrates, probably depositing most of its material on
Venus' surface. Our calculations show that surface density values of about 0.06
kg m$^{-2}$ for the debris disk may be sufficient to stabilize the initial
chaotic orbit of Neith and to bring it down within several radii of Venus,
where tidal dissipation becomes more efficient.",2312.17049v1
2001-09-07,Coulomb blockade of strongly coupled quantum dots studied via bosonization of a channel with a finite barrier,"A pair of quantum dots, coupled through a point contact, can exhibit Coulomb
blockade effects that reflect an oscillatory term in the dots' total energy
whose value depends on whether the total number of electrons on the dots is
even or odd. The effective energy associated with this even-odd alternation is
reduced, relative to the bare Coulomb blockade energy for uncoupled dots, by a
factor (1-f) that decreases as the interdot coupling is increased. When the
transmission coefficient for interdot electronic motion is independent of
energy and the same for all channels within the point contact (which are
assumed uncoupled), the factor (1-f) takes on a universal value determined
solely by the number of channels and the dimensionless conductance g of each
individual channel.
  This paper studies corrections to the universal value of (1-f) that result
when the transmission coefficent varies over energy scales of the size of the
bare Coulomb blockade energy. We consider a model in which the point contact is
described by a single orbital channel containing a parabolic barrier potential,
and we calculate the leading correction to (1-f) for one-channel (spin-split)
and two-channel (spin-degenerate) point contacts in the limit where the single
orbital channel is almost completely open. By generalizing a previously used
bosonization technique, we find that, for a given value of the dimensionless
conductance g, the value of (1-f) is increased relative to its value for a
zero-thickness barrier, but the absolute value of the increase is small in the
region where our calculations apply.",0109135v1
2011-04-15,Formation of ultracold SrYb molecules in an optical lattice by photoassociation spectroscopy: theoretical prospects,"State-of-the-art {\em ab initio} techniques have been applied to compute the
potential energy curves for the SrYb molecule in the Born-Oppenheimer
approximation for the ground state and first fifteen excited singlet and
triplet states within the coupled-cluster framework. The leading long-range
coefficients describing the dispersion interactions at large interatomic
distances are also reported. The electric transition dipole moments have been
obtained as the first residue of the polarization propagator computed with the
linear response coupled-cluster method restricted to single and double
excitations. Spin-orbit coupling matrix elements have been evaluated using the
multireference configuration interaction method restricted to single and double
excitations with a large active space. The electronic structure data was
employed to investigate the possibility of forming deeply bound ultracold SrYb
molecules in an optical lattice in a photoassociation experiment using
continuous-wave lasers. Photoassociation near the intercombination line
transition of atomic strontium into the vibrational levels of the strongly
spin-orbit mixed $b^3\Sigma^+$, $a^3\Pi$, $A^1\Pi$, and $C^1\Pi$ states with
subsequent efficient stabilization into the $v^{\prime\prime}=1$ vibrational
level of the electronic ground state is proposed. Ground state SrYb molecules
can be accumulated by making use of collisional decay from $v^{\prime\prime}=1$
to $v^{\prime\prime}=0$. Alternatively, photoassociation and stabilization to
$v^{\prime\prime}=0$ can proceed via stimulated Raman adiabatic passage
provided that the trapping frequency of the optical lattice is large enough and
phase coherence between the pulses can be maintained over at least tens of
microseconds.",1104.3015v1
2012-09-23,Seeing Majorana fermions in time-of-flight images of spinless fermions coupled by s-wave pairing,"The Chern number, nu, as a topological invariant that identifies the winding
of the ground state in the particle-hole space, is a definitive theoretical
signature that determines whether a given superconducting system can support
Majorana zero modes. Here we show that such a winding can be faithfully
identified for any superconducting system (p-wave or s-wave with spin-orbit
coupling) through a set of time-of-flight measurements, making it a diagnostic
tool also in actual cold atom experiments. As an application, we specialize the
measurement scheme for a chiral topological model of spinless fermions. The
proposed model only requires the experimentally accessible s-wave pairing and
staggered tunnelling that mimics spin-orbit coupling. By adiabatically
connecting this model to Kitaev's honeycomb lattice model, we show that it
gives rise to nu = \pm 1 phases, where vortices bind Majorana fermions, and
nu=\pm 2 phases that emerge as the unique collective state of such vortices.
Hence, the preparation of these phases and the detection of their Chern numbers
provide an unambiguous signature for the presence of Majorana modes. Finally,
we demonstrate that our detection procedure is resilient against most
inaccuracies in experimental control parameters as well as finite temperature.",1209.5115v2
2013-05-01,Classification of engineered topological superconductors,"I perform a complete classification of 2d, quasi-1d and 1d topological
superconductors which originate from the suitable combination of inhomogeneous
Rashba spin-orbit coupling, magnetism and superconductivity. My analysis
reveals alternative types of topological superconducting platforms for which
Majorana fermions are accessible. Specifically, I observe that for quasi-1d
systems with Rashba spin-orbit coupling and time-reversal violating
superconductivity, as for instance due to a finite Josephson current flow,
Majorana fermions can emerge even in the absence of magnetism. Furthermore, for
the classification I also consider situations where additional ""hidden""
symmetries emerge, with a significant impact on the topological properties of
the system. The latter, generally originate from a combination of space group
and complex conjugation operations that separately do not leave the Hamiltonian
invariant. Finally, I suggest alternative directions in topological quantum
computing for systems with additional unitary symmetries.",1305.0131v3
2013-07-30,Unconventional superconductivity in a two-dimensional repulsive gas of fermions with spin-orbit coupling,"We investigate the superconducting instability of a two-dimensional repulsive
fermion gas with Rashba spin-orbit coupling $\al_R$. Using renormalization
group approach, we find the superconducting transition temperature as a
function of the dimensionless ratio $\Theta={1}{2}m\al_R^2/E_F$ where $E_F=0$
when the smaller Fermi surface shrinks to a (Dirac) point. The general trend is
that superconductivity is enhanced as $\Theta$ increases, but in an
intermediate regime $\Theta\sim0.1$, a dome-like behavior appears. At a very
small value of $\Theta$, the angular momentum channel $j_z$ in which
superconductivity occurs is quite high. With increasing $\Theta$, $j_z$
decreases with a step of 2 down to $j_z=6$, after which we find the sequence
$j_z=6, 4, 6, 2$, the last value of which continues to
$\Theta\rightarrow\infty$. In an extended range of $\Theta$, the
superconducting gap predominantly resides on the large Fermi surface, while
Josephson coupling induces a much smaller gap on the small Fermi surface. Below
the superconducting transition temperature, we apply mean field theory to
derive the self-consistent equations and find the condensation energies. The
state with the lowest condensation energy is an unconventional superconducting
state which breaks time reversal symmetry, and in which singlet and triplet
pairings are mixed. In general, these states are topologically nontrivial, and
the Chern number of the state with total angular momentum $j_z$ is $C=2j_z$.",1307.7953v1
2013-10-24,Finite-field calculation of the polarizabilities and hyperpolarizabilities of Al$^{+}$,"In this study, accurate static dipole polarizability and hyperpolarizability
are calculated for Al$^+$ ground state 3s$^{2}$ $^{1}$S$_{0}$ and excited state
$3s3p$ $^{3}$P$_{J}$ with $J$=0, 1, 2. The finite-field computations use
energies obtained with the relativistic configuration interaction approach and
the relativistic coupled-cluster approach. Excellent agreement with previously
recommended values is found for the dipole polarizability of Al$^{+}$ ground
state 3s$^{2}$ $^{1}$S$_{0}$ and excited state $3s3p$ $^{3}$P$_{0}$ as well as
the hyperpolarizability of the ground state 3s$^{2}$ $^{1}$S$_{0}$. The
recommended values of the dipole polarizability of the Al$^{+}$ $3s3p$
$^{3}$P$_{1}$ and $^{3}$P$_{2}$ and the hyperpolarizability of Al$^{+}$ $3s3p$
$^{3}$P$_{0}$, $^{3}$P$_{1}$, and $^{3}$P$_{2}$ are also given. The impacts of
the relativity and spin-orbit coupling are elucidated by analyzing the angular
momentum dependence of the dipole polarizability and the hyperpolarizability
and comparing the fully and scalar relativistic calculated data. It is shown
that the impact of the relativity and spin-orbit coupling are small for the
dipole polarizability but become significant for the hyperpolarizability.
Finally, the black-body radiation shifts contributed by the dipole
polarizability and hyperpolarizability respectively are evaluated for
transitions of Al$^{+}$ 3s$^{2}$ $^{1}$S$_{0}$ to $3s3p$ $^{3}$P$_{J}$ with
$J$=0, 1, 2.",1310.6456v3
2015-06-16,Majorana Zero Modes in Graphene,"A clear demonstration of topological superconductivity (TS) and Majorana zero
modes remains one of the major pending goal in the field of topological
materials. One common strategy to generate TS is through the coupling of an
s-wave superconductor to a helical half-metallic system. Numerous proposals for
the latter have been put forward in the literature, most of them based on
semiconductors or topological insulators with strong spin-orbit coupling. Here
we demonstrate an alternative approach for the creation of TS in
graphene/superconductor junctions without the need of spin-orbit coupling. Our
prediction stems from the helicity of graphene's zero Landau level edge states
in the presence of interactions, and on the possibility, experimentally
demonstrated, to tune their magnetic properties with in-plane magnetic fields.
We show how canted antiferromagnetic ordering in the graphene bulk close to
neutrality induces TS along the junction, and gives rise to isolated,
topologically protected Majorana bound states at either end. We also discuss
possible strategies to detect their presence in graphene Josephson junctions
through Fraunhofer pattern anomalies and Andreev spectroscopy. The latter in
particular exhibits strong unambiguous signatures of the presence of the
Majorana states in the form of universal zero bias anomalies. Remarkable
progress has recently been reported in the fabrication of the proposed type of
junctions, which offers a promising outlook for Majorana physics in graphene
systems.",1506.04961v3
2015-11-19,A Tight Binding Approach to Strain and Curvature in Monolayer Transition-Metal Dichalcogenides,"We present a model of the electronic properties of monolayer transition-metal
dichalcogenides based on a tight binding approach which includes the effects of
strain and curvature of the crystal lattice. Mechanical deformations of the
lattice offer a powerful route for tuning the electronic structure of the
transition-metal dichalcogenides, as changes to bond lengths lead directly to
corrections in the electronic Hamiltonian while curvature of the crystal
lattice mixes the orbital structure of the electronic Bloch bands. We first
present an effective low energy Hamiltonian describing the electronic
properties near the K point in the Brillouin zone, then present the corrections
to this Hamiltonian due to arbitrary mechanical deformations and curvature in a
way which treats both effects on an equal footing. This analysis finds that
local area variations of the lattice allow for tuning of the band gap and
effective masses, while the application of uniaxial strain decreases the
magnitude of the direct band gap at the K point. Additionally, strain induced
bond length modifications create a fictitious gauge field with a coupling
strength that is smaller than that seen in related materials like graphene. We
also find that curvature of the lattice leads to the appearance of both an
effective in-plane magnetic field which couples to spin degrees of freedom and
a Rashba-like spin-orbit coupling due to broken mirror inversion symmetry.",1511.06254v2
2016-06-19,Giant Rashba Splitting in CH3NH3PbBr3 Organic-Inorganic Perovskite,"As they combine decent mobilities with extremely long carrier lifetimes,
organic-inorganic perovskites have opened a whole new field in
opto\-electronics. Measurements of their underlying electronic structure,
however, are still lacking. Using angle-resolved photoelectron spectroscopy, we
measure the valence band dispersion of single-crystal CH$_3$NH$_3$PbBr$_3$. The
dispersion of the highest energy band is extracted applying a modified leading
edge method, which accounts for the particular density of states of
organic-inorganic perovskites. The surface Brillouin zone is consistent with
bulk-terminated surfaces both in the low-temperature orthorhombic and the
high-temperature cubic phase. In the low-temperature phase, we find a
ring-shaped valence band maximum with a radius of 0.043 {\AA}$^{-1}$, centered
around a 0.16 eV deep local minimum in the dispersion of the valence band at
the high-symmetry point. Intense circular dichroism is observed. This
dispersion is the result of strong spin-orbit coupling. Spin-orbit coupling is
also present in the room-temperature phase. The coupling strength is one of the
largest reported so far.",1606.05867v3
2014-03-18,The XYZ chain with Dzyaloshinsky-Moriya interactions: from spin-orbit-coupled lattice bosons to interacting Kitaev chains,"Using the density-matrix renormalization-group algorithm (DMRG) and a
finite-size scaling analysis, we study the properties of the one-dimensional
completely-anisotropic spin-1/2 XYZ model with Dzyaloshinsky-Moriya (DM)
interactions. The model shows a rich phase diagram: depending on the value of
the coupling constants, the system can display different kinds of ferromagnetic
order and Luttinger-liquid behavior. Transitions from ferromagnetic to
Luttinger-liquid phases are first order. We thoroughly discuss the transition
between different ferromagnetic phases, which, in the absence of DM
interactions, belongs to the XX universality class. We provide evidence that
the DM exchange term turns out to split this critical line into two separated
Ising-like transitions and that in between a disordered phase may appear. Our
study sheds light on the general problem of strongly-interacting
spin-orbit-coupled bosonic gases trapped in an optical lattice and can be used
to characterize the topological properties of superconducting nanowires in the
presence of an imposed supercurrent and of interactions.",1403.4568v3
2013-09-01,Topological Uniform Superfluid and FFLO Phases in 3D to 1D crossover of spin-orbit coupled Fermi gases,"We consider the quasi-one dimensional system realized by an array of weakly
coupled parallel one-dimensional ""tubes"" in a two-dimensional lattice which
permits free motion of atoms in an axial direction in the presence of a Zeeman
field, Rashba type spin orbit coupling (SOC), and an s-wave attractive
interaction, while the radial motion is tightly confined. We solve the
zero-temperature (T=0) Bogoliubov-de Gennes (BdG) equations for the quasi-1D
Fermi gas with the dispersion modified by tunneling between the tubes, and show
that the T=0 phase diagram hosts the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)
phase with non-zero center of mass momentum Cooper pairs for small values of
the SOC while for larger values of the SOC and high Zeeman fields the uniform
superfluid phase with zero center of mass momentum Cooper pairs has an
instability towards the topological uniform superfluid phase with Majorana
fermions at the tube ends. Also, we show that tuning the two-dimensional
optical lattice strength in this model allows one to explore the crossover
behaviors of the phases during the transition between the 3D and the 1D system
and in general the FFLO (for small SOC) and the topological uniform superfluid
phase (for large SOC) are favored as the system becomes more one-dimensional.
We also find evidence of the existence of a Zeeman tuned topological quantum
phase transition (TQPT) within the FFLO phase itself and for large values of
the Zeeman field and small SOC the TQPT gives rise to a topologically distinct
FFLO phase.",1309.0258v1
2015-12-09,Two-dimensional solitons in dipolar Bose-Einstein condensates with spin-orbit coupling,"We report families of two-dimensional (2D) composite solitons in spinor
dipolar Bose-Einstein condensates, with two localized components linearly mixed
by the spin-orbit coupling (SOC), and the intrinsic nonlinearity represented by
the dipole-dipole interaction (DDI) between atomic magnetic moments polarized
in-plane by an external magnetic field. Recently, stable solitons were
predicted in the form of \textit{semi-vortices} (composites built of coupled
fundamental and vortical components) in the 2D system combining the SOC and
contact attractive interactions. Replacing the latter by the anisotropic
long-range DDI, we demonstrate that, for a fixed norm of the soliton, the
system supports a \emph{continuous family} of stable spatially asymmetric
vortex solitons (AVSs), parameterized by an offset of the pivot of the vortical
component relative to its fundamental counterpart. The offset is limited by a
certain maximum value, while the energy of the AVS practically does not depend
on the offset. At small values of the norm, the vortex solitons are subject to
a weak oscillatory instability. In the present system, with the Galilean
invariance broken by the SOC, the composite solitons are set in motion by a
kick whose strength exceeds a certain depinning value. The kicked solitons
feature a negative effective mass, drifting along a spiral trajectory opposite
to the direction of the kick. A critical angular velocity, up to which the
semi-vortices may follow rotation of the polarizing magnetic field, is found
too.",1512.02856v2
2016-08-25,Interplay between Rashba spin-orbit coupling and adiabatic rotation in a two-dimensional Fermi gas,"We explore the trap profiles of a two-dimensional atomic Fermi gas in the
presence of a Rashba spin-orbit coupling and under an adiabatic rotation. We
first consider a non-interacting gas and show that the competition between the
effects of Rashba coupling on the local density of single-particle states and
the Coriolis effects caused by rotation gives rise to a characteristic
ring-shaped density profile that survives at experimentally-accessible
temperatures. Furthermore, Rashba splitting of the Landau levels takes the
density profiles on a ziggurat shape in the rapid-rotation limit. We then
consider an interacting gas under the BCS mean-field approximation for local
pairing, and study the pair-breaking mechanism that is induced by the Coriolis
effects on superfluidity, where we calculate the critical rotation frequencies
both for the onset of pair breaking and for the complete destruction of
superfluidity in the system. In particular, by comparing the results of
fully-quantum-mechanical Bogoliubov-de Gennes approach with those of
semi-classical local-density approximation, we construct extensive phase
diagrams for a wide-range of parameter regimes in the trap where the
aforementioned competition may, e.g., favor an outer normal edge that is
completely phase separated from the central superfluid core by vacuum.",1608.07110v2
2017-12-27,Two- and one-dimensional gap solitons in spin-orbit-coupled systems with Zeeman splitting,"We elaborate a mechanism for the formation of stable solitons of the
semi-vortex type (with vorticities 0 and 1 in their two components), populating
a finite bandgap in the spectrum of the spin-orbit-coupled binary Bose-Einstein
condensate with the Zeeman splitting, in the two-dimensional free space, under
conditions which make the kinetic-energy terms in the respective coupled
Gross-Pitaevskii equations negligible. Unlike a recent work which used
long-range dipole-dipole interactions to construct stable gap solitons in a
similar setting, we here demonstrate that stable solitons are supported by
generic local interactions of both attractive and repulsive signs, provided
that the relative strength of the cross/self interaction in the two-component
system does not exceed a critical value ~ 0.77. A boundary between stable and
unstable fundamental 2D gap solitons is precisely predicted by the
Vakhitov-Kolokolov criterion, while all excited states of the 2D solitons, with
vorticities (m, 1 + m) in the two components, m = 1, 2, ..., are unstable. The
analysis of the one-dimensional (1D) reduction of the system produces an exact
analytical solution for the family of gap solitons which populate the entire
bandgap, the family being fully stable. Motion of the 1D solitons in the
trapping potential is considered too, showing that their effective mass is
positive or negative if the cubic nonlinearity is attractive or repulsive,
respectively.",1712.09519v1
2018-09-21,Inhibition of tunnelling and edge state control in polariton topological insulators,"We address the inhibition of tunnelling in polariton condensates confined in
a potential landscape created by a honeycomb array of microcavity pillars in
the presence of spin-orbit coupling and Zeeman splitting in the external
magnetic field. The coupling rate between the microcavity pillars can be
strongly impacted even by weak out-of-phase temporal modulations of the depths
of the corresponding potential wells. When such a modulation is implemented in
truncated honeycomb arrays that realize a polariton topological insulator,
which supports unidirectional edge states in the presence of spin-orbit
coupling and Zeeman splitting, it allows controlling the velocity of the
states. The origin of the phenomenon is the dynamical modulation with a proper
frequency, which notably changes the dispersion of the system and the group
velocity of edge states. We show that such a control is possible for modulation
frequencies close to resonances for inhibition of tunnelling in a two-well
configuration. Edge states considerably slow down, and even stop completely,
when the modulation frequency approaches a resonant value, while above such
frequency splitting of the edge states into wavepackets moving with different
velocities occurs.",1809.08105v1
2019-10-16,Electronic Band Structure and Superconducting Properties of SnAs,"We report comprehensive study of physical properties of the binary
superconductor compound SnAs. The electronic band structure of SnAs was
investigated using both angle-resolved photoemission spectroscopy (ARPES) in a
wide binding energy range and density functional theory (DFT) within
generalized gradient approximation (GGA). The DFT/GGA calculations were done
including spin-orbit coupling for both bulk and (111) slab crystal structures.
Comparison of the DFT/GGA band dispersions with ARPES data shows that (111)
slab much better describes ARPES data than just bulk bands. Superconducting
properties of SnAs were studied experimentally by specific heat, magnetic
susceptibility, magnetotransport measurements and Andreev reflection
spectroscopy. Temperature dependences of the superconducting gap and of the
specific heat were found to be well consistent with those expected for the
single band BCS superconductors with an isotropic s-wave order parameter.
Despite spin-orbit coupling is present in SnAs, our data shows no signatures of
a potential unconventional superconductivity, and the characteristic BCS ratio
$2\Delta/T_c = 3.48 - 3.73$ is very close to the BCS value in the weak coupling
limit.",1910.07426v1
2020-04-06,Realization of ideal Weyl semimetal band in ultracold quantum gas with 3D Spin-Orbit coupling,"The Weyl semimetals [1-6] are three-dimensional (3D) gapless topological
phases with Weyl cones in the bulk band, and host massless quasiparticles known
as Weyl fermions which were theorized by Hermann Weyl in the last twenties [7].
The lattice theory constrains that Weyl cones must come in pairs, with the
minimal number of cones being two. The semimetal with only two Weyl cones is an
ideal Weyl semimetal (IWSM) which is the optimal platform to explore broad Weyl
physics but hard to engineer in solids. Here, we report the experimental
realization of the IWSM band by synthesising for the first time a 3D spin-orbit
(SO) coupling for ultracold atoms. Engineering a 3D configuration-tunable
optical Raman lattice [8], we realize the Weyl type SO coupling for ultracold
quantum gas, with which the IWSM band is achieved with controllability. The
topological Weyl points are clearly measured via the virtual slicing imaging
technique [8, 9] in equilibrium, and further resolved in the quench dynamics,
revealing the key information of the realized IWSM bands. The realization of
the IWSM band opens an avenue to investigate various exotic phenomena based on
the optimal Weyl semimetal platforms.",2004.02413v1
2020-12-10,BaOsO$_3$: A Hund's metal in the presence of strong spin-orbit coupling,"We investigate the 5d transition metal oxide BaOsO$_3$ within a combination
of density functional theory (DFT) and dynamical mean-field theory (DMFT),
using a matrix-product-state impurity solver. BaOsO$_3$ has 4 electrons in the
t$_{2g}$ shell akin to ruthenates but stronger spin-orbit coupling (SOC) and is
thus expected to reveal an interplay of Hund's metal behavior with SOC. We
explore the paramagnetic phase diagram as a function of SOC and Hubbard
interaction strengths, identifying metallic, band (van-Vleck) insulating and
Mott insulating regions. At the physical values of the two couplings we find
that BaOsO$_3$ is still situated inside the metallic region and has a moderate
quasiparticle renormalization $m^*/m \approx 2$; consistent with specific heat
measurements. SOC plays an important role in suppressing electronic
correlations (found in the vanishing SOC case) through the splitting of a
van-Hove singularity (vHs) close to the Fermi energy, but is insufficient to
push the material into an insulating van-Vleck regime. In spite of the strong
effect of SOC, BaOsO$_3$ can be best pictured as a moderately correlated Hund's
metal.",2012.05597v2
2019-03-03,Full proximity treatment of topological superconductors in Josephson-junction architectures,"Experiments on planar Josephson junction architectures have recently been
shown to provide an alternative way of creating topological superconductors
hosting accessible Majorana modes. These zero-energy modes can be found at the
ends of a one-dimensional channel in the junction of a two-dimensional electron
gas (2DEG) proximitized by two spatially separated superconductors. The
channel, which is below the break between the superconductors, is not in direct
contact with the superconducting leads, so that proximity coupling is expected
to be weaker and less well-controlled than in the simple nanowire configuration
widely discussed in the literature. This provides a strong incentive for this
paper which investigates the nature of proximitization in these Josephson
architectures. At a microscopic level we demonstrate how and when it can lead
to topological phases. We do so by going beyond simple tunneling models through
solving self-consistently the Bogoliubov-de Gennes equations of a
heterostructure multicomponent system involving two spatially separated
$s$-wave superconductors in contact with a normal Rashba spin-orbit-coupled
2DEG. Importantly, within our self-consistent theory we present ways of
maximizing the proximity-induced superconducting gap by studying the effect of
the Rashba spin-orbit coupling, chemical potential mismatch between the
superconductor and 2DEG, and sample geometry on the gap. Finally, we note (as
in experiment) a Fulde-Ferrell-Larkin-Ovchinnikov phase is also found to appear
in the 2DEG channel, albeit under circumstances which are not ideal for
topological superconducting phase.",1903.00844v2
2020-08-07,Explicitly correlated coupled cluster method for accurate treatment of open-shell molecules with hundreds of atoms,"We present a near-linear scaling formulation of the explicitly-correlated
coupled-cluster singles and doubles with perturbative triples method
(CCSD(T)$_{\overline{\text{F12}}}$) for high-spin states of open-shell species.
The approach is based on the conventional open-shell CCSD formalism [M. Saitow
et al., J. Chem. Phys. 146, 164105 (2017)] utilizing the domain local
pair-natural orbitals (DLPNO) framework. The use of spin-independent set of
pair-natural orbitals ensures exact agreement with the closed-shell formalism
reported previously, with only marginally impact on the cost (e.g. the
open-shell formalism is only 1.5 times slower than the closed-shell counterpart
for the $\text{C}_\text{160}\text{H}_{\text{322}}$ n-alkane, with the measured
size complexity of $\approx1.2$). Evaluation of coupled-cluster energies near
the complete-basis-set (CBS) limit for open-shell systems with more than 550
atoms and 5000 basis functions is feasible on a single multi-core computer in
less than 3 days. The aug-cc-pVTZ DLPNO-CCSD(T)$_{\overline{\text{F12}}}$
contribution to the heat of formation for the 50 largest molecules among the
348 core combustion species benchmark set [J. Klippenstein et al., J. Phys.
Chem. A 121, 6580 (2017)] had root-mean-square deviation (RMSD) from the
extrapolated CBS CCSD(T) reference values of 0.3 kcal/mol. For a more
challenging set of 50 reactions involving small closed- and open-shell
molecules [G. Knizia et al., J. Chem. Phys. 130, 054104 (2009)] the
aug-cc-pVQ(+d)Z DLPNO-CCSD(T)$_{\overline{\text{F12}}}$ yielded a RMSD of
$\sim$0.4 kcal/mol with respect to the CBS CCSD(T) estimate.",2008.03237v1
2021-04-02,Quantum Criticality in a Layered Iridate,"Iridates provide a fertile ground to investigate correlated electrons in the
presence of strong spin-orbit coupling. Bringing these systems to the proximity
of a metal-insulator quantum phase transition is a challenge that must be met
to access quantum critical fluctuations with charge and spin-orbital degrees of
freedom. Here, electrical transport and Raman scattering measurements provide
evidence that a metal-insulator quantum critical point is effectively reached
in 5 % Co-doped Sr$_2$IrO$_4$ with high structural quality. The dc-electrical
conductivity shows a linear temperature dependence that is successfully
captured by a model involving a Co acceptor level at the Fermi energy that
becomes gradually populated at finite temperatures, creating
thermally-activated holes in the $J_{\text {eff}}=1/2$ lower Hubbard band. The
so-formed quantum critical fluctuations are exceptionally heavy and the
resulting electronic continuum couples with an optical phonon at all
temperatures. The magnetic order and pseudospin-phonon coupling are preserved
under the Co doping. This work brings quantum phase transitions, iridates and
heavy-fermion physics to the same arena.",2104.01098v1
2016-12-12,Kondo Insulator to Semimetal Transformation Tuned by Spin-Orbit Coupling,"Recent theoretical studies of topologically nontrivial electronic states in
Kondo insulators have pointed to the importance of spin-orbit coupling (SOC)
for stabilizing these states. However, systematic experimental studies that
tune the SOC parameter $\lambda_{\rm{SOC}}$ in Kondo insulators remain elusive.
The main reason is that variations of (chemical) pressure or doping strongly
influence the Kondo coupling $J_{\text{K}}$ and the chemical potential $\mu$ --
both essential parameters determining the ground state of the material -- and
thus possible $\lambda_{\rm{SOC}}$ tuning effects have remained unnoticed. Here
we present the successful growth of the substitution series
Ce$_3$Bi$_4$(Pt$_{1-x}$Pd$_x$)$_3$ ($0 \le x \le 1$) of the archetypal
(noncentrosymmetric) Kondo insulator Ce$_3$Bi$_4$Pt$_3$. The Pt-Pd substitution
is isostructural, isoelectronic, and isosize, and therefore likely to leave
$J_{\text{K}}$ and $\mu$ essentially unchanged. By contrast, the large mass
difference between the $5d$ element Pt and the $4d$ element Pd leads to a large
difference in $\lambda_{\rm{SOC}}$, which thus is the dominating tuning
parameter in the series. Surprisingly, with increasing $x$ (decreasing
$\lambda_{\rm{SOC}}$), we observe a Kondo insulator to semimetal transition,
demonstrating an unprecedented drastic influence of the SOC. The fully
substituted end compound Ce$_3$Bi$_4$Pd$_3$ shows thermodynamic signatures of a
recently predicted Weyl-Kondo semimetal.",1612.03972v3
2017-11-23,Majorana edge state in a number-conserving Fermi gas with tunable p-wave interaction,"The remarkable properties and potential applications of Majorana fermions
have led to considerable efforts in recent years to realize topological matters
that host these excitations. For a number-conserving system, there have been a
few proposals, using either coupled-chain models or multi-component system with
spin-orbit coupling, to create number fluctuation of fermion pairs in achieving
Majorana fermion. In this work, we show that Majorana edge states can occur in
a spinless Fermi gas in 1D lattices with tunable $p$-wave interaction. This is
facilitated by the conversion between a pair of (open-channel) fermions and a
(close-channel) boson, thereby allowing the number fluctuation of fermion pairs
in a single chain. This scheme requires neither spin-orbit coupling nor
multi-chain setup and can be implemented easily. Using the
density-matrix-renormalization-group method, we have identified the Majorana
phase in a wide range of parameter regime as well as its associated phase
transitions. The topological nature of the Majorana phase manifests itself in a
strong edge-edge correlation in an open chain that is robust against disorder,
as well as in a non-trivial winding number in the bulk generated by using
twisted boundary condition. It is also shown that the Majorana phase in this
system can be stable against atom losses due to few-body collisions on the same
site, and can be easily identified from the fermion momentum distribution.
These results pave the way for probing the intriguing Majorana physics in a
simple and stable cold atoms system.",1711.08765v2
2020-03-14,Topological phase transition in layered magnetic compound MnSb2Te4: Spin-orbit coupling and interlayer coupling dependeces,"Based on the first-principles calculations and theoretical analysis, we
investigate the electronic structures, topological phase transition (TPT) and
topological properties of layered magnetic compound MnSb2Te4. It has the
similar crystal and magnetic structure as the magnetic topological insulator
MnBi2Te4. We find that when the spin-orbit coupling (SOC) is considered, the
band structure of MnSb2Te4 in antiferromagnetic (AFM) state has no band
inversion at {\Gamma}. This is due to the SOC strength of Sb is less than that
of Bi. The band inversion can be realized by increasing the SOC of Sb by 0.3
times, which drives MnSb2Te4 from a trivial AFM insulator to an AFM topological
insulator (TI) or axion insulator. Uniaxial compressive strain along the layer
stacking direction is another way to control the band inversion. The interlayer
distance shorten by 5% is needed to drive the similar TPT. For the
ferromagnetic (FM) MnSb2Te4 with experimental crystal structure, it is a normal
FM insulator. The band inversion can happen when SOC is enhanced by 0.1 times
or the interlayer distance is decreased by more than 1%. Thus, FM MnSb2Te4 can
be tuned to be the simplest type-I Weyl semimetal with only one pair of Weyl
nodes on the three-fold rotational axis. These two Weyl nodes are projected
onto (1-10) surface with one Fermi arc connecting them.",2003.06553v1
2021-05-21,InSbAs two-dimensional electron gases as a platform for topological superconductivity,"Topological superconductivity can be engineered in semiconductors with strong
spin-orbit interaction coupled to a superconductor. Experimental advances in
this field have often been triggered by the development of new hybrid material
systems. Among these, two-dimensional electron gases (2DEGs) are of particular
interest due to their inherent design flexibility and scalability. Here we
discuss results on a 2D platform based on a ternary 2DEG (InSbAs) coupled to
in-situ grown Aluminum. The spin-orbit coupling in these 2DEGs can be tuned
with the As concentration, reaching values up to 400 meV$\unicode{xC5}$, thus
exceeding typical values measured in its binary constituents. In addition to a
large Land\'e g-factor $\sim$ 55 (comparable to InSb), we show that the clean
superconductor-semiconductor interface leads to a hard induced superconducting
gap. Using this new platform we demonstrate the basic operation of
phase-controllable Josephson junctions, superconducting islands and quasi-1D
systems, prototypical device geometries used to study Majorana zero modes.",2105.10437v2
2021-07-16,An upper and lower bound to the orientation-dependent linear Rashba spin-orbit coupling of two-dimensional hole gases in semiconductor quantum wells,"Our recent study [Phys. Rev. B 103, 085309 (2021)] verified the existence of
$\bf{k}$-linear Rashba spin-orbit coupling (SOC) of two-dimensional hole gases
in quantum wells (QWs) which originates from a combination of
heavy-hole-light-hole (HH-LH) mixing and direct dipolar coupling to the
external electric field. However, the Rashba SOC dependence on QW orientations
remains unclear. Here, we explore this dependence on QW orientations and
uncover an upper and lower bound to the orientation-dependent $\bf{k}$-linear
Rashba SOC along the [110]- and [111]- crystalline directions by performing
atomistic pseudopotential calculations associated with theoretical analysis.
The intrinsic HH-LH mixing at the Brillouin zone center, maximal in
[110]-oriented quantum wells and minimal in [111]- and [001]-oriented QWs,
plays an essential role. Remarkably, we find that only $\bf{k}$-cubic Rashba
SOC exists in [111]-oriented QWs. These findings help understand the physical
mechanism of the Rashba SOC dependence on QW orientations and provide a
strategic prediction for experiments to realize the large Rashba SOC.",2107.07681v2
2022-05-06,Magnetic frustration in the cubic double perovskite Ba2NiIrO6,"Hybrid transition metal oxides continue to attract attention due to their
multiple degrees of freedom ($e.g.$, lattice, charge, spin, and orbital) and
versatile properties. Here we investigate the magnetic and electronic
properties of the newly synthesized double perovskite Ba$_2$NiIrO$_6$, using
crystal field theory, superexchange model analysis, density functional
calculations, and parallel tempering Monte Carlo (PTMC) simulations. Our
results indicate that Ba$_2$NiIrO$_6$ has the Ni$^{2+}$
($t_{2g}^{6}e_{g}^{2}$)-Ir$^{6+}$ ($t_{2g}^{3}$) charge states. The first
nearest-neighboring (1NN) Ni$^{2+}$-Ir$^{6+}$ ions prefer a ferromagnetic (FM)
coupling as expected from the Goodenough-Kanamori-Anderson rules, which
contradicts the experimental antiferromagnetic (AF) order in Ba$_2$NiIrO$_6$.
We find that the strong 2NN AF couplings are frustrated in the fcc sublattices,
and they play a major role in determining the observed AF ground state. We also
prove that the $J_{\rm eff}$ = 3/2 and $J_{\rm eff}$ = 1/2 states induced by
spin-orbit coupling, which would be manifested in low-dimensional (e.g.,
layered) iridates, are however not the case for cubic Ba$_2$NiIrO$_6$. Our PTMC
simulations show that when the long-range (2NN and 3NN) AF interactions are
included, an AF transition with $T_{\rm N}$ = 66 K would be obtained and it is
well comparable with the experimental 51 K. Meanwhile, we propose a possible
2$\times$2$\times$2 noncollinear AF structure for Ba$_2$NiIrO$_6$.",2205.03049v1
2023-06-06,Possible $S_\pm$-wave superconductivity in La$_3$Ni$_2$O$_7$,"Recently, the bulk nickelate La$_3$Ni$_2$O$_7$ is reported to show signature
of high-temperature superconductivity under high pressure above $14$GPa [H. Sun
et al., Nature 621, 493 (2023)]. We analyze the pairing mechanism and pairing
symmetry in a bilayer Hubbard model with two orbitals in the $E_g$ multiplet.
In the weak to moderate interaction regime, our functional renormalization
group (FRG) calculations yield $S_\pm$-wave Cooper pairing triggered by leading
spin fluctuations. The gap function changes sign across the Fermi pockets, and
in real space the pairing is dominated by intra-unitcell intra-orbital
components with antiphase between the onsite ones. In the strong coupling
limit, we develop a low-energy effective theory in terms of atomic one- and
two-electron states in the $E_g$ multiplet. The variational treatment of the
effective theory produces results consistent with the FRG ones, suggesting the
robustness of such a pairing function. The driving force for superconductivity
in the strong coupling limit can be attributed to the local pair-hopping term
and the spin-exchange on vertical bonds. We also discuss a possible scenario
for the weak insulating behavior under low pressures in terms of the tendency
toward the formation of charge order in the strong coupling limit.",2306.03706v3
2024-02-15,Doping induced multiferroicity and quantum anomalous Hall effect in $α$-In$_2$Se$_3$ thin films,"In flat-band materials, the strong Coulomb interaction between electrons can
lead to exotic physical phenomena. Recently, $\alpha$-In$_2$Se$_3$ thin films
were found to possess ferroelectricity and flat bands. In this work, using
first-principles calculations, we find that for the monolayer, there is a Weyl
point at $\Gamma$ in the flat band, where the inclusion of the spin-orbit
coupling opens a gap. Shifting the Fermi level into the spin-orbit gap gives
rise to nontrivial band topology, which is preserved for the bilayer regardless
of the interlayer polarization couplings. We further calculate the Chern number
and edge states for both the monolayer and bilayer, for which the results
suggest that they become quantum anomalous Hall insulators under appropriate
dopings. Moreover, we find that the doping-induced magnetism for In$_2$Se$_3$
bilayer is strongly dependent on the interlayer polarization coupling.
Therefore, doping the flat bands in In$_2$Se$_3$ bilayer can also yield
multiferroicity, where the magnetism is electrically tunable as the system
transforms between different polarization states. Our study thus reveals that
multiferroicity and nontrivial band topology can be unified into one material
for designing multifunctional electronic devices.",2402.09770v1
2019-08-05,"Preparing single SiV$^{-}$ center in nanodiamonds for external, optical coupling with access to all degrees of freedom","Optical coupling enables intermediate- and long-range interactions between
distant quantum emitters. Such interaction may be the basic element in
bottom-up approaches of coupled spin systems or for integrated quantum
photonics and quantum plasmonics. Here, we prepare nanodiamonds carrying
single, negatively-charged silicon-vacancy centers for evanescent optical
coupling with access to all degrees of freedom by means of atomic force
nanomanipulation. The color centers feature excellent optical properties,
comparable to silicon-vacancy centers in bulk diamond, resulting in a
resolvable fine structure splitting, a linewidth close to the Fourier-Transform
limit under resonant excitation and a good polarization contrast. We determine
the orbital relaxation time $T_{1}$ of the orbitally split ground states and
show that all optical properties are conserved during translational
nanomanipulation. Furthermore, we demonstrate the rotation of the nanodiamonds.
In contrast to the translational operation, the rotation leads to a change in
polarization contrast. We utilize the change in polarization contrast before
and after nanomanipulation to determine the rotation angle. Finally, we
evaluate the likelihood for indistinguishable, single photon emission of
silicon-vacancy centers located in different nanodiamonds. Our work enables
ideal evanescent, optical coupling of distant nanodiamonds containing
silicon-vacancy centers with applications in the realization of quantum
networks, quantum repeaters or complex quantum systems.",1908.01591v2
2016-10-10,Hallmarks of Hund's coupling in the Mott insulator Ca$_2$RuO$_4$,"A paradigmatic case of multi-band Mott physics including spin-orbit and
Hund's coupling is realised in Ca$_2$RuO$_4$. Progress in understanding the
nature of this Mott insulating phase has been impeded by the lack of knowledge
about the low-energy electronic structure. Here we provide -- using
angle-resolved photoemission electron spectroscopy -- the band structure of the
paramagnetic insulating phase of Ca$_2$RuO$_4$ and show how it features several
distinct energy scales. Comparison to a simple analysis of atomic multiplets
provides a quantitative estimate of the Hund's coupling $J=0.4$ eV.
Furthermore, the experimental spectra are in good agreement with electronic
structure calculations performed with Dynamical Mean-Field Theory. The crystal
field stabilisation of the d$_{xy}$ orbital due to $c$-axis contraction is
shown to be important in explaining the nature of the insulating state. It is
thus a combination of multiband physics, Coulomb interaction and Hund's
coupling that generates the Mott insulating state of Ca$_2$RuO$_4$. These
results underscore the importance of Hund's coupling in the ruthenates and
related multiband materials.",1610.02854v1
2023-04-26,Critical Cavity-Magnon Polariton Mediated Strong Long-Distance Spin-Spin Coupling,"Strong long-distance spin-spin coupling is desperately demanded for
solid-state quantum information processing, but it is still challenged. Here,
we propose a hybrid quantum system, consisting of a coplanar waveguide (CPW)
resonator weakly coupled to a single nitrogen-vacancy spin in diamond and a
yttrium-iron-garnet (YIG) nanosphere holding Kerr magnons, to realize strong
long-distance spin-spin coupling. With a strong driving field on magnons, the
Kerr effect can squeeze magnons, and thus exponentially enhance the coupling
between the CPW resonator and the squeezed magnons, which produces two
cavity-magnon polaritons, i.e., the high-frequency polariton (HP) and
low-frequency polariton (LP). When the enhanced cavity-magnon coupling
approaches to the critical value, the spin is fully decoupled from the HP,
while the coupling between the spin and the LP is significantly improved. In
the dispersive regime, a strong spin-spin coupling is achieved with accessible
parameters, and the coupling distance can be up to $\sim$cm. Our proposal
provides a promising way to manipulate remote solid spins and perform quantum
information processing in weakly coupled hybrid systems.",2304.13553v2
2016-02-08,"Gap opening and large spin-orbit splitting in MX2 (M=Mo,W X=S,Se,Te) from the interplay between crystal field and hybridizations: insights from ab-initio theory","By means of first-principles density functional calculations, we study the
maximally localized Wannier functions for the 2D transition metal
dichalcogenides MX2 (M=Mo,W X=S,Se,Te). We found a M^+4-like ionic charge and a
single occupied d-band. The center of the d-like maximally localized Wannier
function associated with this band is distributed among three M sites. Part of
the energy gap is opened by the crystal field splitting induced by the
X^-2-like atoms. We extract the hopping parameters for the Wannier functions
and provide a perspective on tight-binding model. From the analysis of the
tight binding model, we have found an inversion of the band character between
the Gamma and the K points of the Brillouin zone due to the M-M hybridization.
The consequence of this inversion is the closure of the gap. The M-X
hybridization is the only one that tends to open the gap at every k-point, the
change in the M-X and M-M hybridization is the main responsible for the
difference in the gap between the different dichalcogenide materials. The
inversion of the bands gives rise to different spin-orbit splitting at Gamma
and K point in the valence band. The different character of the gap at Gamma
and K point offers the chance to manipulate the semiconductive properties of
these compounds. For a bilayer system, the hybridizations between the out of
plane orbitals and the hybridizations between the in plane orbitals split the
valence band respectively at the Gamma and K point. The splitting in the
valence band is opened also without spin-orbit coupling and comes from the M-M
and X-X hybridization between the two monolayers.",1602.02625v1
2008-03-17,Anisotropic spin transport in two-terminal mesoscopic rings: the Rashba and Dresselhaus spin-orbit interactions,"We investigate theoretically the spin transport in two-terminal mesoscopic
rings in the presence of both the Rashba spin-orbit interaction (RSOI) and the
Dresselhaus spin-orbit interaction (DSOI). We find that the interplay between
the RSOI and DSOI breaks the original cylindric symmetry of mesoscopic ring and
consequently leads to the anisotropic spin transport, i.e., the conductance is
sensitive to the positions of the incoming and outgoing leads. The anisotropic
spin transport can survive even in the presence of disorder caused by impurity
elastic scattering in a realistic system.",0803.2408v1
2010-09-28,Spin-orbit anisotropy measured using ballistic spin resonance,"Spin relaxation can be greatly enhanced in narrow channels of two-dimensional
electron gas due to ballistic spin resonance, which is mediated by spin-orbit
interaction for trajectories that bounce rapidly between channel walls. The
channel orientation determines which momenta affect the relaxation process, so
comparing relaxation for two orientations provides a direct determination of
spin-orbit anisotropy. Electrical measurements of pure spin currents are shown
to reveal an order of magnitude stronger relaxation for channels fabricated
along the [110] crystal axis in a GaAs electron gas compared to [-110]
channels, believed to result from interference between structural and bulk
inversion asymmetries.",1009.5702v1
2013-10-02,Spin snake states with spin-orbit and Zeeman interactions in an inhomogeneous magnetic field,"We study the spin edge states, induced by the combined effect of
Bychkov-Rashba spin-orbit, Zeeman interactions and inhomogeneous magnetic
field, exposed perpendicularly to two-dimensional electron systems. We
calculate analytically the spectrum of the spin edge states (the spin snakes
orbits) in systems where the magnetic field exhibits a discontinuous jump in
the transverse direction and changes its sign at the magnetic interface. The
obtained magnetic spin edge states in a 2DES exhibit several interesting
properties: in particular, electrons reverse their propagation direction at
finite values of their momentum.",1310.0571v1
2013-11-13,Spin current source based on a quantum point contact with local spin-orbit interaction,"Proposal for construction of a source of spin-polarized current based on
quantum point contact with local spin-orbit interaction is presented. We show
that spin-orbit interaction present within the narrowing acts like a spin
filter. The spin polarization of the current is discussed as a function of the
Fermi energy and the width of the quantum point contact.",1311.3065v1
2003-06-06,Maximized Orbital and Spin Kondo effects in a single-electron transistor,"We investigate the charge fluctuations of a single-electron box (metallic
grain) coupled to a lead via a smaller quantum dot in the Kondo regime. The
most interesting aspect of this problem resides in the interplay between spin
Kondo physics stemming from the screening of the spin of the small dot and
orbital Kondo physics emerging when charging states of the grain with (charge)
Q=0 and Q=e are almost degenerate. Combining Wilson's numerical
renormalization-group method with perturbative scaling approaches we push
forward our previous work [K. Le Hur and P. Simon, Phys. Rev. B 67, 201308R
(2003)]. We emphasize that for symmetric and slightly asymmetric barriers, the
strong entanglement of charge and spin flip events in this setup inevitably
results in a non trivial stable SU(4) Kondo fixed point near the degeneracy
points of the grain. By analogy with a small dot sandwiched between two leads,
the ground state is Fermi-liquid like which considerably smears out the Coulomb
staircase behavior and hampers the Matveev logarithmic singularity to arise.
Most notably, the associated Kondo temperature $T_K^{SU(4)}$ might be raised
compared to that in the conductance experiments through a small quantum dot
$(\sim 1K)$ which makes the observation of our predictions a priori accessible.
We discuss the robustness of the SU(4) correlated state against the inclusion
of an external magnetic field, a deviation from the degeneracy points,
particle-hole symmetry in the small dot, asymmetric tunnel junctions and
comment on the different crossovers.",0306186v1
2003-07-22,Hidden Symmetries and their Consequences in $t_{2g}$ Cubic Perovskites,"The five-band Hubbard model for a $d$ band with one electron per site is a
model which has very interesting properties when the relevant ions are located
at sites with high (e. g. cubic) symmetry. In that case, if the crystal field
splitting is large one may consider excitations confined to the lowest
threefold degenerate $t_{2g}$ orbital states. When the electron hopping matrix
element ($t$) is much smaller than the on-site Coulomb interaction energy
($U$), the Hubbard model can be mapped onto the well-known effective
Hamiltonian (at order $t^{2}/U$) derived by Kugel and Khomskii (KK). Recently
we have shown that the KK Hamiltonian does not support long range spin order at
any nonzero temperature due to several novel hidden symmetries that it
possesses. Here we extend our theory to show that these symmetries also apply
to the underlying three-band Hubbard model. Using these symmetries we develop a
rigorous Mermin-Wagner construction, which shows that the three-band Hubbard
model does not support spontaneous long-range spin order at any nonzero
temperature and at any order in $t/U$ -- despite the three-dimensional lattice
structure. Introduction of spin-orbit coupling does allow spin ordering, but
even then the excitation spectrum is gapless due to a subtle continuous
symmetry. Finally we showed that these hidden symmetries dramatically simplify
the numerical exact diagonalization studies of finite clusters.",0307515v1
2008-02-22,Study of Short-distance Spin and Charge Correlations and Local Density-of-States in the CMR regime of the One-Orbital Model for Manganites,"The metal-insulator transition, and the associated magnetic transition, in
the colossal magnetoresistance (CMR) regime of the one-orbital model for
manganites is here studied using Monte Carlo (MC) techniques. Both cooperative
oxygen lattice distortions and a finite superexchange coupling among the
$t_{\rm 2g}$ spins are included in our investigations. Charge and spin
correlations are studied. In the CMR regime, a strong competition between the
ferromagnetic metallic and antiferromagnetic charge-ordered insulating states
is observed. This competition is shown to be important to understand the
resistivity peak that appears near the critical temperature. Moreover, it is
argued that the system is dynamically inhomogeneous, with short-range charge
and spin correlations that slowly evolve with MC time, producing the glassy
characteristics of the CMR state. The local density-of-states (LDOS) is also
investigated, and a pseudogap (PG) is found to exist in the CMR temperature
range. The width of the PG in the LDOS is calculated and directly compared with
recent scanning-tunneling-spectroscopy (STS) experimental results. The
agreement between our calculation and the experiment suggests that the
depletion of the conductance at low bias observed experimentally is a
reflection on the existence of a PG in the LDOS spectra, as opposed to a hard
gap. The apparent homogeneity observed via STS techniques could be caused by
the slow time characteristics of this probe. Faster experimental methods should
unveil a rather inhomogeneous state in the CMR regime, as already observed in
neutron scattering experiments.",0802.3382v1
2013-02-07,Interaction-driven transition between topological states in a Kondo insulator,"Heavy fermion materials naturally combine strong spin-orbit interactions and
electronic correlations. When there is precisely one conduction electron per
impurity spin, the coherent heavy fermion state is insulating. This Kondo
insulating state has recently been argued to belong to the class of quantum
spin Hall states. Motivated by this conjecture and a very recent experimental
realization of this state, we investigate a model for Kondo insulators with
spin-orbit coupling. Using DMFT, we observe an interaction-driven transition
between two distinct topological states, indicated by a closing of the bulk gap
and a simultaneous change of the Z2 topological invariant. At large interaction
strength we find a topological heavy fermion state, characterized by strongly
renormalized heavy bulk bands, hosting a pair of zero-energy edge modes. The
model allows a detailed understanding of the temperature dependence of the
single particle spectral function and in particular the energy scales at which
one observes the appearance of edge states within the bulk gap.",1302.1874v3
2013-06-13,From antiferromagnetic order to magnetic textures in the two dimensional Fermi Hubbard model with synthetic spin orbit interaction,"We study the interacting Fermi-Hubbard model in two spatial dimensions with
synthetic gauge coupling of the spin orbit Rashba type, at half-filling. Using
real space mean field theory, we numerically determine the phase as a function
of the interaction strength for different values of the gauge field parameters.
For a fixed value of the gauge field, we observe that when the strength of the
repulsive interaction is increased, the system enters into an antiferromagnetic
phase, then undergoes a first order phase transition to an non collinear
magnetic phase. Depending on the gauge field parameter, this phase further
evolves to the one predicted from the effective Heisenberg model obtained in
the limit of large interaction strength. We explain the presence of the
antiferromagnetic phase at small interaction from the computation of the
spin-spin susceptibility which displays a divergence at low temperatures for
the antiferromagnetic ordering. We discuss, how the divergence is related to
the nature of the underlying Fermi surfaces. Finally, the fact that the first
order phase transitions for different gauge field parameters occur at unrelated
critical interaction strengths arises from a Hofstadter-like situation, i.e.
for different magnetic phases, the mean-field Hamiltonians have different
translational symmetries.",1306.3124v2
2014-09-12,The dynamics of a doped hole in cuprates is not controlled by spin fluctuations,"Twenty seven years after the discovery of high-temperature superconductivity
\cite{BedMu}, consensus on its theoretical explanation is still absent. To a
good extent, this is due to the difficulty of studying strongly correlated
systems near half-filling, needed to understand the behaviour of one or few
holes doped into a CuO$_2$ layer. To simplify this task it is customary to
replace three-band models \cite{Emery} describing the doping holes as entering
the O $2p$ orbitals of these charge-transfer insulators \cite{ZSA} with much
simpler one-band Hubbard or $tJ$ models \cite{rev1,rev2}. Here we challenge
this approach, showing that not only is the dynamics of a doped hole easier to
understand in models that explicitly include the O orbitals, but also that our
solution contradicts the long-held belief that the quantum spin fluctuations of
the antiferromagnetic (AFM) background play a key role in determining this
dynamics. Indeed, we show that the correct, experimentally observed dispersion
is generically obtained for a hole moving on the O sublattice, and coupled to a
N\'eel lattice of spins without spin fluctuations. This marks a significant
conceptual change in our understanding of the relevant phenomenology and opens
the way to studying few-holes dynamics without finite-size effect issues
\cite{BayoB}, to understand the actual strength of the ""magnetic glue"".",1409.3647v1
2015-06-03,Antidamping spin-orbit torque driven by spin-flip reflection mechanism on the surface of a topological insulator: A time-dependent nonequilibrium Green function approach,"Motivated by recent experiments observing spin-orbit torque (SOT) acting on
the magnetization $\vec{m}$ of a ferromagnetic (F) overlayer on the surface of
a three-dimensional topological insulator (TI), we investigate the origin of
the SOT and the magnetization dynamics in such systems. We predict that lateral
F/TI bilayers of finite length, sandwiched between two normal metal leads, will
generate a large antidamping-like SOT per very low charge current injected
parallel to the interface. The large values of antidamping-like SOT are {\it
spatially localized} around the transverse edges of the F overlayer. Our
analysis is based on adiabatic expansion (to first order in $\partial
\vec{m}/\partial t$) of time-dependent nonequilibrium Green functions (NEGFs),
describing electrons pushed out of equilibrium both by the applied bias voltage
and by the slow variation of a classical degree of freedom [such as
$\vec{m}(t)$]. From it we extract formulas for spin torque and charge pumping,
which show that they are reciprocal effects to each other, as well as Gilbert
damping in the presence of SO coupling. The NEGF-based formula for SOT
naturally splits into four components, determined by their behavior (even or
odd) under the time and bias voltage reversal. Their complex angular dependence
is delineated and employed within Landau-Lifshitz-Gilbert simulations of
magnetization dynamics in order to demonstrate capability of the predicted SOT
to efficiently switch $\vec{m}$ of a perpendicularly magnetized F overlayer.",1506.01303v3
2016-06-11,"Conetronics in 2D Metal-Organic Frameworks: Double Dirac Cones, Magnetic Half Dirac Cones and Quantum Anomalous Hall Effect","Based on recently synthesized Ni3C12S12 class 2D metal-organic frameworks, we
predict electronic properties of M3C12S12 and M3C12O12, where M is Zn, Cd, Hg,
Be, or Mg with no M orbital contributions to bands near Fermi level. For
M3C12S12, their band structures exhibit double Dirac cones with different Fermi
velocities that are n and p type, respectively, which are switchable by
few-percent strain. The crossing of two cones are symmetry-protected to be
non-hybridizing, leading to two independent channels in 2D node-line semimetals
at the same k-point akin to spin-channels in spintronics, rendering conetronics
device possible. The node line rings right at their crossing, which are both
electron and hole pockets at the Fermi level, can give rise to
magnetoresistance that will not saturate when the magnetic field is infinitely
large, due to perfect n-p compensation. For M3C12O12, together with conjugated
metal-tricatecholate polymers M3(HHTP)2, the spin-polarized slow Dirac cone
center is pinned precisely at the Fermi level, making the systems conducting in
only one spin or cone channel. Quantum anomalous Hall effect can arise in MOFs
with non-negligible spin-orbit coupling like Cu3C12O12. Compounds of M3C12S12
and M3C12O12 with different M, can be used to build spintronic and
cone-selecting heterostructure devices, tunable by strain or electrostatic
gating.",1606.04094v1
2018-02-20,Asymmetric skyrmion Hall effect in systems with a hybrid Dzyaloshinskii-Moriya interaction,"We examine the current-induced dynamics of a skyrmion that is subject to both
structural and bulk inversion asymmetry. There arises a hybrid type of
Dzyaloshinskii-Moriya interaction (DMI) which is in the form of a mixture of
interfacial and bulk DMIs. Examples include crystals with symmetry classes
C$_n$ as well as magnetic multilayers composed of a ferromagnet with a
noncentrosymmetric crystal and a nonmagnet with strong spin-orbit coupling. As
a striking result, we find that, in systems with a hybrid DMI, the
spin-orbit-torque-induced skyrmion Hall angle is asymmetric for the two
different skyrmion polarities ($\pm 1$ given by out-of-plane core
magnetization), even allowing one of them to be tuned to zero. We propose
several experimental ways to achieve the necessary straight skyrmion motion
(with zero Hall angle) for racetrack memories, even without antiferromagnetic
interactions or any interaction with another magnet. Our results can be
understood within a simple picture by using a global spin rotation which maps
the hybrid DMI model to an effective model containing purely interfacial DMI.
The formalism directly reveals the effective spin torque and effective current
that result in qualitatively different dynamics. Our work provides a way to
utilize symmetry breaking to eliminate detrimental phenomena as hybrid DMI
eliminates the skyrmion Hall angle.",1802.07327v2
2018-03-31,Understanding current-driven dynamics of magnetic Néel walls in heavy metal/ferromagnetic metal/oxide trilayers,"We consider analytically current-driven dynamics of magnetic N\'{e}el walls
in heavy metal/ferromagnetic metal/oxide trilayers where strong spin-orbit
coupling and interfacial Dzyaloshinskii-Moriya interaction (i-DMI) coexist. We
show that field-like spin-orbit torque (FL-SOT) with effective field along
$\mathbf{n}\times\hat{\mathbf{J}}$ ($\mathbf{n}$ being the interface normal and
$\hat{\mathbf{J}}$ being the charge current direction) and i-DMI induced torque
can both lead to Walker breakdown suppression meanwhile leaving the wall
mobility (velocity versus current density) unchanged. However, i-DMI itself can
not induce the ""universal absence of Walker breakdown"" (UAWB) while FL-SOT
exceeding a certain threshold can. Finitely-enlarged Walker limits before UAWB
are theoretically calculated and well explain existing data. In addition,
change in wall mobility and even its sign-inversion can be understood only if
the anti-damping-like (ADL) SOT is appended. For N\'{e}el walls in
ferromagnetic-metal layer with both perpendicular and in-plane anisotropies, we
have calculated the respective modifications of wall mobility under the
coexistence of spin-transfer torque, SOTs and i-DMI. Analytics shows that in
trilayers with perpendicular anisotropy strong enough spin Hall angle and
appropriate sign of i-DMI parameter can lead to sign-inversion in wall mobility
even under small enough current density, while in those with in-plane
anisotropy this only occurs for current density in a specific range.",1804.00127v4
2010-05-11,Spin susceptibility of interacting two-dimensional electrons in the presence of spin-orbit coupling,"A long-range interaction via virtual particle-hole pairs between Fermi-liquid
quasiparticles leads to a nonanalytic behavior of the spin susceptibility
$\chi$ as a function of the temperature ($T$), magnetic field ($\mathbf{B}$),
and wavenumber. In this paper, we study the effect of the Rashba spin-orbit
interaction (SOI) on the nonanalytic behavior of $\chi$ for a two-dimensional
electron liquid. Although the SOI breaks the SU(2) symmetry, it does not
eliminate nonanalyticity but rather makes it anisotropic: while the linear
scaling of $\chi_{zz}$ with $T$ and $|\mathbf{B}|$ saturates at the energy
scale set by the SOI, that of $\chi_{xx}$ ($=\chi_{yy}$) continues through this
energy scale, until renormalization of the electron-electron interaction in the
Cooper channel becomes important. We show that the Renormalization Group flow
in the Cooper channel has a non-trivial fixed point, and study the consequences
of this fixed point for the nonanalytic behavior of $\chi$. An immediate
consequence of SOI-induced anisotropy in the nonanalytic behavior of $\chi$ is
a possible instability of a second-order ferromagnetic quantum phase transition
with respect to a first-order transition to an XY ferromagnetic state.",1005.1913v2
2017-04-26,Paths to collapse for isolated skyrmions in few-monolayer ferromagnetic films,"Magnetic skyrmions are topological spin configurations in materials with
chiral Dzyaloshinskii-Moriya interaction (DMI), that are potentially useful for
storing or processing information. To date, DMI has been found in few bulk
materials, but can also be induced in atomically thin magnetic films in contact
with surfaces with large spin-orbit interactions. Recent experiments have
reported that isolated magnetic skyrmions can be stabilized even near room
temperature in few-atom thick magnetic layers sandwiched between materials that
provide asymmetric spin-orbit coupling. Here we present the minimum-energy path
analysis of three distinct mechanisms for the skyrmion collapse, based on ab
initio input and the performed atomic-spin simulations. We focus on the
stability of a skyrmion in three atomic layers of Co, either epitaxial on the
Pt(111) surface, or within a hybrid multilayer where DMI nontrivially varies
per monolayer due to competition between different symmetry-breaking from two
sides of the Co film. In laterally finite systems, their constrained geometry
causes poor thermal stability of the skyrmion toward collapse at the boundary,
which we show to be resolved by designing the high-DMI structure within an
extended film with lower or no DMI.",1704.08025v1
2014-05-06,Locally tunable disorder and entanglement in the one-dimensional plaquette orbital model,"We introduce a one-dimensional plaquette orbital model with a topology of a
ladder and alternating interactions between $x$ and $z$ pseudospin components
along both the ladder legs and on the rungs. We show that it is equivalent to
an effective spin model in a magnetic field, with spin dimers that replace
plaquettes and are coupled along the chain by three-spin interactions. Using
perturbative treatment and mean field approaches with dimer correlations we
study the ground state spin configuration and its defects in the lowest excited
states. By the exact diagonalization approach we find that the quantum effects
in the model are purely short-range and we get estimated values of the ground
state energy and the gap in the thermodynamic limit from the system sizes up to
$L=12$ dimers. Finally, we study a class of excited states with classical-like
defects accumulated in the central region of the chain to find that in this
region the quantum entanglement measured by the mutual information of
neighboring dimers is locally increased and coincides with disorder and
frustration. Such islands of entanglement in otherwise rather classical system
may be of interest in the context of quantum computing devices.",1405.1401v1
2018-01-29,Magnetism of a Co monolayer on Pt(111) capped by overlayers of $5d$ elements: a spin-model study,"Using first-principles calculations, we study the magnetic properties of a Co
monolayer on a Pt(111) surface with a capping monolayer of selected $5d$
elements (Re, Os, Ir, Pt and Au). First we determine the tensorial exchange
interactions and magnetic anisotropies characterizing the Co monolayer for all
considered systems. We find a close relationship between the magnetic moment of
the Co atoms and the nearest-neighbor isotropic exchange interaction, which is
attributed to the electronic hybridization between the Co and the capping
layers, in spirit of the Stoner picture of ferromagnetism. The
Dzyaloshinskii-Moriya interaction is decreased for all overlayers compared to
the uncapped Co/Pt(111) system, while even the sign of the
Dzyaloshinskii-Moriya interaction changes in case of the Ir overlayer. We
conclude that the variation of the Dzyaloshinskii-Moriya interaction is well
correlated with the change of the magnetic anisotropy energy and of the orbital
moment anisotropy. The unique influence of the Ir overlayer on the
Dzyaloshinskii-Moriya interaction is traced by scaling the strength of the
spin--orbit coupling of the Ir atoms in Ir/Co/Pt(111) and by changing the Ir
concentration in the Au$_{1-x}$Ir$_{x}$/Co/Pt(111) system. Our spin dynamics
simulations indicate that the magnetic ground state of Re/Co/Pt(111) thin film
is a spin spiral with a tilted normal vector, while the other systems are
ferromagnetic.",1801.09426v1
2019-09-24,Two-band superconductivity with unconventional pairing symmetry in HfV$_2$Ga$_4$,"In this letter, we have examined the superconducting ground state of the
HfV$_2$Ga$_4$ compound using resistivity, magnetization, zero-field (ZF) and
transverse-field (TF) muon-spin relaxation and rotation ($\mu$SR) measurements.
Resistivity and magnetization unveil the onset of bulk superconductivity with
$T_{\bf c}\sim$ 3.9~K, while TF-$\mu$SR measurements show that the temperature
dependence of the superfluid density is well described by a nodal two-gap
$s$+$d$-wave order parameter model. In addition, ZF muon relaxation rate
increases with decreasing temperature below 4.6 K, indicating the presence of
weak spin fluctuations. These observations suggest an unconventional multiband
nature of the superconductivity possibly arising from the distinct $d$-bands of
V and Hf ions with spin fluctuations playing an important role. To better
understand these findings, we carry out first-principles electronic-structure
calculations, further highlighting that the Fermi surface consists of multiple
disconnected sheets with very different orbital weights and spin-orbit
coupling, bridging the way for a nodal multiband superconductivity scenario. In
this vein, therefore, HfV$_2$Ga$_4$-family stands out as an open avenue to
novel unexplored unconventional superconducting compounds, such as
ScV$_2$Ga$_4$ and ZrV$_2$Ga$_4$, and other many rare earths based materials.",1909.10712v1
2019-10-29,Common Envelope Wind Tunnel: The Effects of Binary Mass Ratio and Implications for the Accretion-Driven Growth of LIGO Binary Black Holes,"We present three-dimensional local hydrodynamic simulations of flows around
objects embedded within stellar envelopes using a ""wind tunnel"" formalism. Our
simulations model the common envelope dynamical inspiral phase in binary star
systems in terms of dimensionless flow characteristics. We present suites of
simulations that study the effects of varying the binary mass ratio, stellar
structure, equation of state, relative Mach number of the object's motion
through the gas, and density gradients across the gravitational focusing scale.
For each model, we measure coefficients of accretion and drag experienced by
the embedded object. These coefficients regulate the coupled evolution of the
object's masses and orbital tightening during the dynamical inspiral phase of
the common envelope. We extrapolate our simulation results to accreting black
holes with masses comparable to that of the population of LIGO black holes. We
demonstrate that the mass and spin accrued by these black holes per unit
orbital tightening are directly related to the ratio of accretion to drag
coefficients. We thus infer that the mass and dimensionless spin of initially
non-rotating black holes change by of order $1\%$ and 0.05, respectively, in a
typical example scenario. Our prediction that the masses and spins of black
holes remain largely unmodified by a common envelope phase aids in the
interpretation of the properties of the growing observed population of merging
binary black holes. Even if these black holes passed through a common envelope
phase during their assembly, features of mass and spin imparted by previous
evolutionary epochs should be preserved.",1910.13333v1
2019-01-11,Quantitative imaging of hybrid chiral spin textures in magnetic multilayer systems by Lorentz microscopy,"Chiral magnetic textures in ultrathin perpendicularly magnetised multilayer
film stacks with an interfacial Dzyaloshinskii-Moriya interaction have been the
focus of much research recently. The chirality associated with the broken
inversion symmetry at the interface between an ultrathin ferromagnetic layer
and a heavy metal with large spin-orbit coupling supports homochiral N\'eel
domain walls and hedgehog (N\'eel) skyrmions. Under spin-orbit torques these
N\'eel type magnetic structures are predicted, and have been measured, to move
at high velocities. However recent studies have indicated that some
multilayered systems may possess a more complex hybrid domain wall
configuration, due to the competition between interfacial DMI and interlayer
dipolar fields. These twisted textures are expected to have thickness dependent
N\'eel and Bloch contributions to the domain or skyrmion walls. In this work,
we use the methods of Lorentz microscopy to measure quantitatively for the
first time experimentally both; i) the contributions of the N\'eel and Bloch
contributions and ii) their spatial spin variation at high resolution. These
are compared with modelled and simulated structures which are in excellent
agreement with our experimental results. Our quantitative analysis provides
powerful direct evidence of the Bloch wall component which exists in these
hybrid walls and will be significant when exploiting such phenomena in
spintronic applications.",1901.03652v1
2019-11-26,Interplay between superconductivity and spin-dependent fields in nanowire-based systems,"The interplay between superconductivity, spin-orbit coupling, and Zeeman or
exchange field, is studied theoretically in two different setups: a single wire
in which all these fields coexist, and a double wire system in which
superconducting pairing and the spin-dependent fields are spatially separated.
We first explore a magnetoelectric effect, namely the appearance of anomalous
charge supercurrents. We determine the conditions under which such currents are
allowed by symmetry and express them in terms of the SU(2) electric and
magnetic fields. In leading order in the strength of the fields we find that in
the single wire setup such currents may appear only when the Zeeman field has
both, a longitudinal and transverse component with respect to the spin-orbit
field. In contrast, in the two wire setup a parallel component to the SOC can
generate the anomalous current, which is allowed by symmetry. We confirm these
findings by calculating explicitly the current in both setups together with the
self-consistent superconducting order parameter. The latter shows in the
ground-state a spatial modulation of the phase that leads to currents that
compensate the anomalous current, such that in both cases the ground state
corresponds to a total zero-current state. However, in the two wire setup this
zero-current state consists of two finite currents flowing in each of the wires
in opposite direction.",1911.11741v3
2017-07-13,Role of Square Planar Coordination in the Magnetic Properties of Na4IrO4,"Iridates supply fertile grounds for unconventional phenomena and exotic
electronic phases. With respect to well-studied octahedrally-coordinated
iridates, we pay our attention to a rather unexplored iridate, Na4IrO4, showing
an unusual square-planar coordination. The latter is key to rationalize the
electronic structure and magnetic property of Na4IrO4, which is here explored
by first-principles density functional theory and Monte Carlo simulations. Due
to the uncommon square-planar crystal field, Ir 5d states adopt
intermediate-spin state with double occupation of dz2 orbital, leading to a
sizable local spin moment, at variance with many other iridates. The
square-planar crystal field splitting is also crucial in opening a robust
insulating gap in Na4IrO4, irrespective of the specific magnetic ordering or
treatment of electronic correlations. Spin-orbit coupling plays a minor role in
shaping the electronic structure, but leads to a strong magnetocrystalline
anisotropy. The easy axis perpendicular to the IrO4 plaquette, well explained
using perturbation theory, is again closely related to the square-planar
coordination. Finally, the large single-ion anisotropy suppresses the spin
frustration and stabilizes a collinear antiferromagnetic long-range magnetic
ordering, as confirmed by Monte Carlo simulations predicting a quite low N\'eel
temperature, expected from almost isolated IrO4 square-planar units as
crystalline building blocks.",1707.04052v1
2021-02-01,Pure Gauge Spin-Orbit Couplings,"Planar systems with a general linear spin-orbit interaction (SOI) that can be
cast in the form of a non-Abelian pure gauge field are investigated using the
language of non-Abelian gauge field theory. A special class of these fields
that, though a $2\times2$ matrix, are Abelian are seen to emerge and their
general form is given. It is shown that the unitary transformation that gauges
away these fields induces at the same time a rotation on the wavefunction about
a fixed axis but with a space-dependent angle, both of which being
characteristics of the SOI involved.The experimentally important case of
equal-strength Rashba and Dresselhaus SOI (R+D SOI) is shown to fall within
this special class of Abelian gauge fields, and the phenomenon of Persistent
Spin Helix (PSH) that emerges in the presence of this latter SOI in a plane is
shown to fit naturally within the general formalism developed. The general
formalism is also extended to the case of a particle confined to a ring. It is
shown that the Hamiltonian on a ring in the presence of equal-strength R+D SOI
is unitarily equivalent to that of a particle subject to only a
spin-independent but $\theta$-dependent potential with the unitary
transformation relating the two being again the space-dependent rotation
operator characteristic of R+D SOI.",2102.00907v1
2021-05-01,Anisotropy and Current Control of Magnetization in SrRuO$_3$ SrTiO$_3$ Heterostructures for Spin-Memristors,"Spintronics-based nonvolatile components in neuromorphic circuits offer the
possibility of realizing novel functionalities at low power. Current-controlled
electrical switching of magnetization is actively researched in this context.
Complex oxide heterostructures with perpendicular magnetic anisotropy (PMA),
consisting of SrRuO$_3$ (SRO) grown on SrTiO$_3$ (STO) are strong material
contenders. Utilizing the crystal orientation, magnetic anisotropy in such
simple heterostructures can be tuned to either exhibit a perfect or slightly
tilted PMA. Here, we investigate current-induced magnetization modulation in
such tailored ferromagnetic layers with a material with strong spin-orbit
coupling (Pt), exploiting the spin Hall effect. We find significant differences
in the magnetic anisotropy between the SRO/STO heterostructures, as manifested
in the first and second harmonic magnetoresistance measurements.
Current-induced magnetization switching can be realized with spin-orbit
torques, but for systems with perfect PMA this switching is probabilistic as a
result of the high symmetry. Slight tilting of the PMA can break this symmetry
and allow the realization of deterministic switching. Control over the magnetic
anisotropy of our heterostructures therefore provides control over the manner
of switching. Based on our findings, we propose a three-terminal spintronic
memristor, with a magnetic tunnel junction design, that shows several resistive
states controlled by electric charge. Non-volatile states can be written
through SOT by applying an in-plane current, and read out as a tunnel current
by applying a small out-of-plane current. Depending on the anisotropy of the
SRO layer, the writing mechanism is either deterministic or probabilistic
allowing for different functionalities to emerge. We envisage that the
probabilistic MTJs could be used as synapses while the deterministic devices
can emulate neurons",2105.00269v1
2021-08-03,Dynamic transformation between a skyrmion string and a bimeron string in a layered frustrated system,"Frustrated topological spin textures have unique properties that may enable
novel spintronic applications, such as helicity-based information storage and
computing. Here, we report the statics and current-induced dynamics of
two-dimensional (2D) pancake skyrmions in a stack of weakly coupled frustrated
magnetic monolayers, which form a three-dimensional (3D) skyrmion string. The
Bloch-type skyrmion string is energetically more stable than its N\'eel-type
counterpart. It can be driven into translational motion by the dampinglike
spin-orbit torque and shows the damping-dependent skyrmion Hall effect. Most
notably, the skyrmion string can be transformed to a dynamically stable bimeron
string by the dampinglike spin-orbit torque. The current-induced bimeron string
rotates stably with respect to its center, which can spontaneously transform
back to a skyrmion string when the current is switched off. Our results reveal
unusual physical properties of 3D frustrated spin textures, and may open up
different possibilities for spintronic applications based on skyrmion and
bimeron strings.",2108.01365v2
2023-01-18,Toward arbitrary spin-orbit flat optics via structured geometric phase gratings,"Reciprocal spin-orbit coupling (SOC) via geometric phase with flat optics
provides a promising platform for shaping and controlling paraxial structured
light. Current devices, from the pioneering q-plates to the recent J-plates,
provide only spin-dependent wavefront modulation without amplitude control.
However, achieving control over all the spatial dimensions of paraxial SOC
states requires spin-dependent control of corresponding complex amplitude,
which remains challenging for flat optics. Here, to address this issue, we
present a new type of flat-optics elements termed structured geometric phase
gratings that is capable of conjugated complex-amplitude control for orthogonal
input circular polarizations. By using a microstructured liquid crystal
photoalignment technique, we engineered a series of flat-optics elements and
experimentally showed their excellent precision in arbitrary SOC control. This
principle unlocks the full-field control of paraxial structured light via flat
optics, providing a promising way to develop an information exchange and
processing units for general photonic SOC states, as well as extra-/intracavity
mode convertors for high-precision laser beam shaping.",2301.07408v1
2023-06-11,Magnetic properties of a cavity-embedded square lattice of quantum dots or antidots,"We apply quantum electrodynamical density functional theory to obtain the
electronic density, the spin polarization, as well as the orbital and the spin
magnetization of square periodic arrays of quantum dots or antidots subjected
to the influence of a far-infrared cavity photon field. A gradient-based
exchange-correlation functional adapted to a two-dimensional electron gas in a
transverse homogeneous magnetic field is used in the theoretical framework and
calculations. The obtained results predict a non-trivial effect of the cavity
field on the electron distribution in the unit cell of the superlattice, as
well as on the orbital and the spin magnetization. The number of electrons per
unit cell of the superlattice is shown to play a crucial role in the
modification of the magnetization via the electron-photon coupling. The
calculations show that cavity photons strengthen the diamagnetic effect in the
quantum dots structure, while they weaken the paramagnetic effect in an antidot
structure. As the number of electrons per unit cell of the lattice increases
the electron-photon interaction reduces the exchange forces that would
otherwise promote strong spin splitting for both the dot and the antidot array.",2306.06765v1
2023-07-19,Linear-in-momentum spin orbit interactions in planar Ge/GeSi heterostructures and spin qubits,"We investigate the existence of linear-in-momentum spin-orbit interactions in
the valence band of Ge/GeSi heterostructures using an atomistic tight-binding
method. We show that symmetry breaking at the Ge/GeSi interfaces gives rise to
a linear Dresselhaus-type interaction for heavy-holes. This interaction results
from the heavy-hole/light-hole mixings induced by the interfaces and can be
captured by a suitable correction to the minimal Luttinger-Kohn, four bands
$\vec{k}\cdot\vec{p}$ Hamiltonian. It is dependent on the steepness of the
Ge/GeSi interfaces, and is suppressed if interdiffusion is strong enough.
Besides the Dresselhaus interaction, the Ge/GeSi interfaces also make a
contribution to the in-plane gyromagnetic $g$-factors of the holes. The
tight-binding calculations also highlight the existence of a small linear
Rashba interaction resulting from the couplings between the
heavy-hole/light-hole manifold and the conduction band enabled by the low
structural symmetry of Ge/GeSi heterostructures. These interactions can be
leveraged to drive the hole spin. The linear Dresselhaus interaction may, in
particular, dominate the physics of the devices for out-of-plane magnetic
fields. When the magnetic field lies in-plane, it is, however, usually far less
efficient than the $g$-tensor modulation mechanisms arising from the motion of
the dot in non-separable, inhomogeneous electric fields and strains.",2307.10007v2
2023-08-03,Flavor-wave theory with quasiparticle damping at finite temperatures: Application to chiral edge modes in the Kitaev model,"We propose a theoretical framework to investigate elementary excitations at
finite temperatures within a localized electron model that describes the
interactions between multiple degrees of freedom, such as quantum spin models
and Kugel-Khomskii models. Thus far, their excitation structures have been
mainly examined using the linear flavor-wave theory, an SU($N$) generalization
of the linear spin-wave theory. These techniques introduce noninteracting
bosonic quasiparticles as elementary excitations from the ground state, thereby
elucidating numerous physical phenomena, including excitation spectra and
transport properties characterized by topologically nontrivial band structures.
Nevertheless, the interactions between quasiparticles cannot be ignored in
systems exemplified by $S=1/2$ quantum spin models, where strong quantum
fluctuations are present. Recent studies have investigated the effects of
quasiparticle damping at zero temperature in such models. In our study,
extending this approach to the flavor-wave theory for general localized
electron models, we construct a comprehensive method to calculate excitation
spectra with the quasiparticle damping at finite temperatures. We apply our
method to the Kitaev model under magnetic fields, a typical example of models
with topologically nontrivial magnon bands. Our calculations reveal that chiral
edge modes undergo significant damping in weak magnetic fields, amplifying the
damping rate by the temperature increase. This effect is caused by collisions
with thermally excited quasiparticles. Since our approach starts from a general
Hamiltonian, it will be widely applicable to other localized systems, such as
spin-orbital coupled systems derived from multi-orbital Hubbard models in the
strong correlation limit.",2308.01711v1
2023-11-13,Origin of reduced dynamical friction by dark matter halos with net prograde rotation,"We provide an explanation for the reduced dynamical friction on galactic bars
in spinning dark matter halos. Earlier work based on linear theory predicted an
increase in dynamical friction when dark halos have a net forward rotation,
because prograde orbits couple to bars with greater strength than retrograde
orbits. Subsequent numerical studies, however, found the opposite trend:
dynamical friction weakens with increasing spin of the halo. We revisit this
problem and demonstrate that linear theory in fact correctly predicts a reduced
torque in forward-rotating halos. We show that shifting the halo mass from
retrograde to prograde phase space generates a positive gradient in the
distribution function near the origin of the z-angular momentum (Lz=0), which
results in a resonant transfer of Lz to the bar, making the net dynamical
friction weaker. While this effect is subdominant for the major resonances,
including the corotation resonance, it leads to a significant positive torque
on the bar for the series of direct radial resonances, as these resonances are
strongest at Lz=0. The overall dynamical friction from spinning halos is shown
to decrease with the halo's spin, in agreement with the secular behavior of
N-body simulations. We validate our linear calculation by computing the
nonlinear torque from individual resonances using the angle-averaged
Hamiltonian.",2311.07640v2
2023-11-20,Interplay between moment-dependent and field-driven unidirectional magnetoresistance in CoFeB/InSb/CdTe heterostructures,"Magnetoresistance effects are crucial for understanding the charge/spin
transport as well as propelling the advancement of spintronic applications.
Here we report the coexistence of magnetic moment-dependent (MD) and magnetic
field-driven (FD) unidirectional magnetoresistance (UMR) effects in
CoFeB/InSb/CdTe heterostructures. The strong spin-orbital coupling of InSb and
the matched impedance at the CoFeB/InSb interface warrant a distinct MD-UMR
effect at room temperature, while the interaction between the in-plane magnetic
field and the Rashba effect at the InSb/CdTe interface induces the marked
FD-UMR signal that dominates the high-field region. Moreover, owning to the
different spin transport mechanisms, these two types of nonreciprocal charge
transport show opposite polarities with respect to the magnetic field
direction, which further enable an effective phase modulation of the
angular-dependent magnetoresistance. Besides, the demonstrations of both the
tunable UMR response and two-terminal spin-orbit torque-driven magnetization
switching validate our CoFeB/InSb/CdTe system as a suitable integrated building
block for multifunctional spintronic device design.",2311.11843v1
2020-06-18,Electron correlation effects in the exchange coupling at the Fe/CoO/Ag(001) ferro-/antiferro-magnetic interface,"Angle resolved-Auger-photoelectron coincidence spectroscopy (AR-APECS) has
been exploited to investigate the role that electron correlation plays in the
exchange-coupling at the ferromagnetic/antiferromagnetic interface of a Fe/CoO
bilayer growth on Ag(001). The effective correlation energy U$_{\textrm{eff}}$,
usually employed to assess the energy distribution of core-valence-valence
Auger spectra, has been experimentally determined for each possible combination
of the orbital (e$_g$ or t$_{2g}$) and the spin (majority or minority) of the
two valence electrons involved in the Auger decay. Coulomb and exchange
interactions have been identified and compared with the result obtained on the
Fe/Ag system. The presented analysis reveals in the Fe/CoO interface an
enhancement of the Coulomb interaction for the e$_g$ orbital and of the
exchange interaction for the t$_{2g}$ orbital with respect to the Fe/Ag case
that can be associated to the stronger electron confinement and to the exchange
coupling between the two layers, respectively.",2006.10854v2
2016-06-27,Hidden-charm pentaquarks as a meson-baryon molecule with coupled channels for $\bar{D}^{(\ast)}Λ_{\rm c}$ and $\bar{D}^{(\ast)}Σ^{(\ast)}_{\rm c}$,"The recent observation of two hidden-charm pentaquark states by LHCb
collaborations prompted us to investigate the exotic states close to the
$\bar{D}\Lambda_{\rm c}$, $\bar{D}^{\ast}\Lambda_{\rm c}$, $\bar{D}\Sigma_{\rm
c}$, $\bar{D}\Sigma^{\ast}_{\rm c}$, $\bar{D}^{\ast}\Sigma_{\rm c}$ and
$\bar{D}^{\ast}\Sigma^{\ast}_{\rm c}$ thresholds. We therefore studied the
hadronic molecules that form the coupled-channel system of
$\bar{D}^{(\ast)}\Lambda_{\rm c}$ and
  $\bar{D}^{(\ast)}\Sigma^{(\ast)}_{\rm c}$. As the heavy quark spin symmetry
manifests the mass degenerations of $\bar{D}$ and $\bar{D}^\ast$ mesons, and of
$\Sigma_{\rm c}$ and $\Sigma^\ast_{\rm c}$ baryons, the coupled channels of
$\bar{D}^{(\ast)}\Sigma^{(\ast)}_{\rm c}$ are important in these molecules. In
addition, we consider the coupling to the $\bar{D}^{(\ast)}\Lambda_{\rm c}$
channel whose thresholds are near the $\bar{D}^{(\ast)}\Sigma^{(\ast)}_{\rm c}$
thresholds, and the coupling to the state with nonzero orbital angular momentum
mixed by the tensor force. This full coupled channel analysis of
$\bar{D}^{(\ast)}\Lambda_{\rm c}-\bar{D}^{(\ast)}\Sigma^{(\ast)}_{\rm c}$ with
larger orbital angular momentum has never been performed before. By solving the
coupled-channel Schr\""odinger equations with the one meson exchange potentials
that respected to the heavy quark spin and chiral symmetries, we studied the
hidden-charm hadronic molecules with $I(J^P)=1/2(3/2^\pm)$ and $1/2(5/2^\pm)$.
We conclude that the $J^P$ assignment of the observed pentaquarks is $3/2^+$
for $P^+_{\rm c}(4380)$ and $5/2^-$ for $P^+_{\rm c}(4450)$, which is agreement
with the results of the LHCb analysis. In addition, we give predictions for
other $J^P=3/2^\pm$ states at 4136.0, 4307.9 and 4348.7 MeV in $J^P=3/2^-$, and
4206.7 MeV in $J^P=3/2^+$, which can be further investigated by means of
experiment.",1606.08330v2
1997-12-26,Innermost Stable Circular Orbit of a Spinning Particle in Kerr Spacetime,"We study stability of a circular orbit of a spinning test particle in a Kerr
spacetime. We find that some of the circular orbits become unstable in the
direction perpendicular to the equatorial plane, although the orbits are still
stable in the radial direction. Then for the large spin case ($S < \sim O(1)),
the innermost stable circular orbit (ISCO) appears before the minimum of the
effective potential in the equatorial plane disappears. This changes the radius
of ISCO and then the frequency of the last circular orbit.",9712095v1
2013-10-30,Ground state of S=1 zigzag spin-orbital chain,"We investigate ground-state properties of a $t_{\rm 2g}$-orbital Hubbard
model on a zigzag chain relevant for CaV$_{2}$O$_{4}$, by exploiting numerical
techniques such as Lanczos diagonalization and density-matrix renormalization
group. Assuming a V$^{3+}$ ion, a local spin $S$=$1$ state is formed by two
electrons in the $t_{\rm 2g}$ orbitals. That is, the system is a Haldane system
with active $t_{\rm 2g}$-orbital degrees of freedom. We observe orbital-state
transitions, yielding a distinct spin system under the orbital-ordered
background. We also discuss the orbital structure induced by open edges,
originating in the spatial anisotropy of the $t_{\rm 2g}$ orbitals.",1310.8018v1
2002-04-01,Spin Fluctuation Induced Superconductivity Controlled by Orbital Fluctuation,"A microscopic Hamiltonian reflecting the correct symmetry of $f$-orbitals is
proposed to discuss superconductivity in heavy fermion systems. In the
orbitally degenerate region in which not only spin fluctuations but also
orbital fluctuations develop considerably, cancellation between spin and
orbital fluctuations destabilizes $d_{x^{2}-y^{2}}$-wave superconductivity.
Entering the non-degenerate region by increasing the crystalline electric
field, $d_{x^{2}-y^{2}}$-wave superconductivity mediated by antiferromagnetic
spin fluctuations emerges out of the suppression of orbital fluctuations. We
argue that the present scenario can be applied to recently discovered
superconductors CeTIn$_{5}$ (T=Ir, Rh, and Co).",0204023v2
2007-03-05,Orbital correlations in monolayer manganites - From spin t-J model to orbital t-J model,"On the example of monolayer manganites we show that the theoretical ideas
developed long ago along the derivation of the spin t-J model from the Hubbard
model are nowadays very helpful in strongly correlated oxides with partly
filled degenerate orbitals. We analyze a realistic orbital t-J model for e_g
electrons in La_{1-x}Sr_{1+x}MnO_4 monolayer manganites, and discuss the
evolution of spin and orbital correlations under increasing doping by
performing exact diagonalization of finite clusters, with electronic kinetic
energy determined self-consistently at finite temperature by classical Monte
Carlo for t_2g spins. Several experimental results are reproduced.",0703127v1
2013-08-05,Pseudospin symmetry in supersymmetric quantum mechanics: II. Spin-orbit effects,"Following a previous paper [Haozhao Liang \textit{et al.}, Phys. Rev. C
\textbf{87}, 014334 (2013)], we discuss the spin-orbit effects on the
pseudospin symmetry (PSS) within the framework of supersymmetric quantum
mechanics. By using the perturbation theory, we demonstrate that the
perturbative nature of PSS maintains when a substantial spin-orbit potential is
included. With the explicit PSS-breaking potential, the spin-orbit effects on
the pseudospin-orbit splittings are investigated in a quantitative way.",1308.1143v1
1994-11-19,Order $\hbar$ Corrections to the Classical Dynamics of a Particle with Intrinsic Spin Moving in a Constant Magnetic Field,"$O(\hbar)$ effects that modify the classical orbit of a charged particle are
described for the case of a classical spin-1/2 particle moving in a constant
magnetic field, using a manifestly covariant formalism reported previously. It
is found that the coupling between the momentum and spin gives rise to a shift
in the cyclotron frequency, which is explicitly calculated. In addition the
orbit is found to exhibit $O(\hbar)$ oscillations along the axis of the uniform
static magnetic field whenever the gyromagnetic ratio $g$ of the particle is
not 2. This oscillation is found to occur at a frequency $\propto$ $\frac{g}{2}
- 1$, and is an observable source of electric dipole radiation.",9411002v1
1998-05-11,Superflow-Stabilized Nonlinear NMR in Rotating 3He-B,"Nonlinear spin precession has been observed in 3He-B in large counterflow of
the normal and superfluid fractions. The new precessing state is stabilized at
high rf excitation level and displays frequency-locked precession over a large
range of frequency shifts, with the magnetization at its equilibrium value.
Comparison to analytical and numerical calculation indicates that in this state
the orbital angular momentum L of the Cooper pairs is oriented transverse to
the external magnetic field in a ``non-Leggett'' configuration with broken
spin-orbit coupling. The resonance shift depends on the tipping angle theta of
the magnetization as omega - omega_L = (Omega_B^2 / 2 omega_L)(cos(theta) -
1/5). The phase diagram of the precessing modes with arbitrary orientation of L
is constructed.",9805119v2
2002-06-03,Quantum in-plane magnetoresistance in 2D electron systems,"We review various aspects of magnetoresistance in (quasi-)twodimensional
systems subject to an in-plane magnetic field. Concentrating on single-particle
effects, three mechanisms leading to magnetoresistance are discussed: the
orbital effect of the magnetic field -- due to inter-subband mixing -- and the
sensitivity of this effect to the geometrical symmetry of the system, the
interplay between spin-orbit coupling and Zeeman splitting, and the influence
of the field on spin scattering at magnetic impurities.",0206024v1
2004-07-29,Anisotropy in Ferromagnetic Nanoparticles: Level-to-Level Fluctuations of a Collective Effect,"We calculate the mesoscopic fluctuations of the magnetic anisotropy of
ferromagnetic nanoparticles. A microscopic spin-orbit Hamiltonian considered as
a perturbation of the much stronger exchange interaction first yields an
explicit expression for the anisotropy tensor. Then, assuming a simple random
matrix model for the spin-orbit coupling allows us to describe the fluctuation
of such a tensor. In the case of uniaxial anisotropy, we calculate the
distribution of the anisotropy constant for a given number of electrons, and
its variation upon increasing this number by one. The magnitude of the latter
is sufficient to account for the experimental data.",0407771v2
2005-04-08,On the crystal field in the modern solid-state theory,"We point out the high physical correctness of the use and the concept of the
crystal-field approach, even if is used to metallic magnetic materials of
transition-metal 3d/4f/5f compounds. We discuss the place of the crystal-field
theory in modern solid-state physics and we point out the necessity to consider
the crystal-field approach with the spin-orbit coupling and strong electron
correlations, as a contrast to the single-electron version of the crystal field
customarily used for 3d electrons. We have extended the strongly-correlated
crystal-field theory to a Quantum Atomistic Solid-State Theory (QUASST) to
account for the translational symmetry and inter-site spin-dependent
interactions indispensable for formation of magnetically-ordered state. We have
correlated macroscopic magnetic and electronic properties with the atomic-scale
electronic structure for ErNi5, UPd2Al3, FeBr2, LaCoO3 and LaMnO3. In QUASST we
have made unification of 3d and rare-earth compounds in description of the
low-energy electronic structures and magnetism of open 3d-/4f-/5f-shell
electrons. QUASST offers consistent description of zero-temperature properties
and thermodynamic properties of 4f-/5f-/3d-atom containing compounds. Our
studies indicate that it is the highest time to unquench the orbital magnetism
in 3d oxides.",0504199v1
2005-08-16,Charge order and spin-singlet pairs formation in Ti4O7,"Charge ordering in the low-temperature triclinic structure of titanium oxide
(Ti4O7) is investigated using the local density approximation (LDA)+U method.
Although the total 3d charge separation is rather small, an orbital order
parameter defined as the difference between t2g occupancies of Ti$^{3+}$ and
Ti$^{4+}$ cations is large and gives direct evidence for charge ordering. Ti 4s
and 4p states make a large contribution to the static ""screening"" of the total
3d charge difference. This effective charge screening leads to complete loss of
the disproportionation between the charges at 3+ and 4+ Ti sites. The occupied
t2g states of Ti$^{3+}$ cations are predominantly of $d_{xy}$ character and
form a spin-singlet molecular orbital via strong direct antiferromagnetic
exchange coupling between neighboring Ti(1) and Ti(3) sites, whereas the role
of superexchange is found to be negligible.",0508378v1
2006-06-30,Room-temperature delayed giant magnetodielectric effects observed in Bi4Fe2TiO12 film,"This letter reports our experimental results on magnetic-field-induced
aftereffects in solution derived Bi4Fe2TiO12 film, in which e' decreases as
much as 600 times after treated in a 5T magnetic field as that of the pristine
one. The phenomena are explained by an unusual spin-orbital coupling in film,
where strong magnetic field provides drive force for spin polarized electrons
of electrode to enter film, so as to form a ferromagnetic orbital state,
increase the relaxation time of defect dipoles and then produce giant
magnetodielectric effects. This process is reversible just by applying a
opposite 0.5T magnetic field. Our findings have potential applications on
magnetic fabrication of nanopatterns somehow to evade nanohazard, as well as on
integraged phononic or photonic crystals on chip.",0606791v2
2006-07-07,"Partial localization of correlated electrons: spin dependent masses, saturated ferromagnetism, and effective s-d model","We determine the localization threshold in a partially filled and orbitally
degenerate model of correlated electrons. Particular emphasis is put on a
non-integer band filling, when the system decomposes into the localized and the
itinerant subsystems; this situation is described by an effective s-d model. A
simultaneous transition to the ferromagnetic state is discussed as driven by
the Hund's rule coupling. Dependence of the quasiparticle mass on the spin
direction appears naturally in the ferromagnetic phase and is attributed to the
electron correlation effects, as is also a metamagnetic transition in an
applied field. Although the main results have been obtained within the saddle
point slave-boson approach, their qualitative features are discussed in general
terms, i.e. as a transition from quantum-mechanical indistinguishability of
particles to the two-component situation. A comparison with the situation for
the orbitally nondegenerate band is also briefly mentioned.",0607188v1
2006-09-09,Ground-state Competition of Two-Component Bosons in Optical Lattice near a Feshbach Resonance,"We investigate the ground state properties of an equal mixture of two species
of bosons in its Mott-insulator phase at a filling factor two per site. We
identify one type of spin triplet-singlet transition through the competition of
ground state. When the on-site interaction is weak ($U<U_c$) the two particles
prefer to stay in the lowest band and with weak tunnelling between neighboring
sites the system is mapped into an effective spin-1 ferromagnetic exchange
Hamiltonian. When the interaction is tuned by a Feshbach resonance to be large
enough ($U>U_c$), higher band will be populated. Due to the orbital coupling
term $S^+S^-$ in the Hamiltonian, the two atoms in different orbits on a site
would form an on-site singlet. For a non-SU(2)-symmetric model, easy-axis or
easy-plane ferromagnetic spin exchange models may be realized corresponding to
phase separation or counter-flow superfluidity, respectively.",0609219v3
2002-08-16,Effect of Earth's rotation on the trajectories of free-fall bodies in Equivalence Principle Experiment,"Owing to Earth's rotation a free-fall body would move in an elliptical orbit
rather than along a straight line forward to the center of the Earth. In this
paper on the basis of the theory for spin-spin coupling between macroscopic
rotating bodies we study violation of the equivalence principle from
long-distance free-fall experiments by means of a rotating ball and a
non-rotating sell. For the free-fall time of 40 seconds, the difference between
the orbits of the two free-fall bodies is of the order of 10^{-9}cm which could
be detected by a SQUID magnetometer owing to such a magnetometer can be used to
measure displacements as small as 10^{-13} centimeters.",0208041v1
1997-04-18,Generalization of the Bound State Model,"In the bound state approach the heavy baryons are constructed by binding,
with any orbital angular momentum, the heavy meson multiplet to the nucleon
considered as a soliton in an effective meson theory. We point out that this
picture misses an entire family of states, labeled by a different angular
momentum quantum number, which are expected to exist according to the geometry
of the three-body constituent quark model (for N_C=3). To solve this problem we
propose that the bound state model be generalized to include orbitally excited
heavy mesons bound to the nucleon. In this approach the missing angular
momentum is ``locked-up'' in the excited heavy mesons. In the simplest
dynamical realization of the picture we give conditions on a set of coupling
constants for the binding of the missing heavy baryons of arbitrary spin. The
simplifications made include working in the large M limit, neglecting nucleon
recoil corrections, neglecting mass differences among different heavy spin
multiplets and also neglecting the effects of light vector mesons.",9704358v1
2002-02-13,Semiclassical trace formulae for systems with spin-orbit interactions: successes and limitations of present approaches,"We discuss the semiclassical approaches for describing systems with
spin-orbit interactions by Littlejohn and Flynn (1991, 1992), Frisk and Guhr
(1993), and by Bolte and Keppeler (1998, 1999). We use these methods to derive
trace formulae for several two- and three-dimensional model systems, and
exhibit their successes and limitations. We discuss, in particular, also the
mode conversion problem that arises in the strong-coupling limit.",0202028v3
2000-06-05,Successive approximations for charged particle motion,"Single particle dynamics in electron microscopes, ion or electron
lithographic instruments, particle accelerators, and particle spectrographs is
described by weakly nonlinear ordinary differential equations. Therefore, the
linear part of the equation of motion is usually solved and the nonlinear
effects are then found in successive order by iteration methods. A Hamiltonian
nature of these equations can lead to simplified computations of particle
transport through an optical device when a suitable computational method is
used. Many ingenious microscopic and lithographic devices were found by H. Rose
and his group due to the simple structure of the eikonal method. In the area of
accelerator physics the eikonal method has never become popular. Here I will
therefore generalize the eikonal method and derive it from a Hamiltonian quite
familiar to the accelerator physics community. With the event of high energy
polarized electron beams and plans for high energy proton beams, nonlinear
effects in spin motion have become important in high energy accelerators. I
will introduce a successive approximation for the nonlinear effects in the
coupled spin and orbit motion of charged particles which resembles some of the
simplifications resulting from the eikonal method for the pure orbit motion.",0006008v1
2007-08-03,Strong spin-orbit induced Gilbert damping and g-shift in iron-platinum nanoparticles,"The shape of ferromagnetic resonance spectra of highly dispersed, chemically
disordered Fe_{0.2}Pt_{0.8} nanospheres is perfectly described by the solution
of the Landau-Lifshitz-Gilbert (LLG) equation excluding effects by crystalline
anisotropy and superparamagnetic fluctuations. Upon decreasing temperature, the
LLG damping $\alpha(T)$ and a negative g-shift, g(T)-g_0, increase proportional
to the particle magnetic moments determined from the Langevin analysis of the
magnetization isotherms. These novel features are explained by the scattering
of the $q \to 0$ magnon from an electron-hole (e/h) pair mediated by the
spin-orbit coupling, while the sd-exchange can be ruled out. The large
saturation values, $\alpha(0)=0.76$ and $g(0)/g_0-1=-0.37$, indicate the
dominance of an overdamped 1 meV e/h-pair which seems to originate from the
discrete levels of the itinerant electrons in the d_p=3 nm nanoparticles.",0708.0463v1
2008-05-21,Upper critical field in noncentrosymmetric superconductors,"We calculate the upper critical field in superconductors without inversion
symmetry at arbitrary temperatures, in the presence of scalar impurities. Both
orbital and spin (paramagnetic) mechanisms of pair breaking are considered. The
superconducting phase transition at nonzero field occurs into a helical vortex
state, in which the order parameter is modulated along the applied field (in a
cubic crystal). The helical state is stable with respect to disorder. However,
if the difference between the densities of states in the electron bands split
by spin-orbit coupling is neglected, then the order parameter modulation is
present only at low temperatures, and only if the system is sufficiently clean
and paramagnetically limited. This state resembles the
Larkin-Ovchinnikov-Fulde-Ferrell state in centrosymmetric superconductors.",0805.3338v2
2008-12-31,"Accurate calculations of the dissociation energy, equilibrium distance and spectroscopic constants for the Yb dimer","The dissociation energy, equilibrium distance, and spectroscopic constants
for the $^1\Sigma_g^+$ ground state of the Yb$_2$ molecule are calculated. The
relativistic effects are introduced through generalized relativistic effective
core potentials with very high precision. The scalar relativistic coupled
cluster method particularly well suited for closed-shell van-der-Waals systems
is used for the correlation treatment. Extensive generalized correlation basis
sets were constructed and employed. The relatively small corrections for
high-order cluster amplitudes and spin-orbit interactions are taken into
account using smaller basis sets and the spin-orbit density functional theory.",0901.0077v6
2010-09-27,"Remote Preparation of Single-Photon ""Hybrid"" Entangled and Vector-Polarization States","Quantum teleportation faces increasingly demanding requirements for
transmitting large or even entangled systems. However, knowledge of the state
to be transmitted eases its reconstruction, resulting in a protocol known as
remote state preparation. A number of experimental demonstrations to date have
been restricted to single-qubit systems. We report the remote preparation of
two-qubit ""hybrid"" entangled states, including a family of vector-polarization
beams. Our single-photon states are encoded in the photon spin and orbital
angular momentum. We reconstruct the states by spin-orbit state tomography and
transverse polarization tomography. The high fidelities achieved for the
vector-polarization states opens the door to optimal coupling of down-converted
photons to other physical systems, such as an atom, as required for scalable
quantum networks, or plasmons in photonic nanostructures.",1009.5412v1
2011-02-07,Competing Pairing Symmetries in a Generalized Two-Orbital Model for the Pnictides,"We introduce and study an extended ""t-U-J"" two-orbital model for the
pnictides that includes Heisenberg terms deduced from the strong coupling
expansion. Including these J terms explicitly allows us to enhance the strength
of the (pi, 0)-(0, pi) spin order which favors the presence of tightly bound
pairing states even in the small clusters that are here exactly diagonalized.
The A1g and B2g pairing symmetries are found to compete in the realistic
spin-ordered and metallic regime. The dynamical pairing susceptibility
additionally unveils low-lying B1g states, suggesting that small changes in
parameters may render any of the three channels stable.",1102.1445v2
2011-03-19,Charge Stripes in the Two-Orbital Hubbard Model for Pnictides,"The two-orbital Hubbard model for the pnictides is studied numerically using
the real-space Hartree-Fock approximation on finite clusters. Upon electron
doping, states with a nonuniform distribution of charge are stabilized. The
observed patterns correspond to charge stripes oriented perpendicular to the
direction of the spin stripes of the undoped magnetic ground state. While these
charge striped states are robust when the undoped state has a Hubbard gap,
their existence when the intermediate-coupling magnetic metallic state of
pnictides is doped was also observed for particular model parameters. Results
for hole doping and implications for recent experiments that reported
electronic nematic states and spin incommensurability are also briefly
discussed.",1103.3743v1
2011-09-05,Superconductivity in the topological semimetal YPtBi,"The noncentrosymmetric Half Heusler compound YPtBi exhibits superconductivity
below a critical temperature T_c = 0.77 K with a zero-temperature upper
critical field H_c2(0) = 1.5 T. Magnetoresistance and Hall measurements support
theoretical predictions that this material is a topologically nontrivial
semimetal having a surprisingly low positive charge carrier density of 2 x
10^18 cm^-3. Unconventional linear magnetoresistance and beating in
Shubnikov-de Haas oscillations point to spin-orbit split Fermi surfaces. The
sensitivity of magnetoresistance to surface roughness suggests a possible
contribution from surface states. The combination of noncentrosymmetry and
strong spin-orbit coupling in YPtBi presents a promising platform for the
investigation of topological superconductivity.",1109.0979v2
2012-03-20,Formation of deeply bound ultracold Sr_2 molecules by photoassociation near the ^1S + ^3P_1 intercombination line,"We predict feasibility of the photoassociative formation of Sr_2 molecules in
arbitrary vibrational levels of the electronic ground state based on
state-of-the-art ab initio calculations. Key is the strong spin-orbit
interaction between the c^3\Pi_u, A^1\Sigma_u^+ and B^1\Sigma_u^+ states. It
creates not only an effective dipole moment allowing free-to-bound transitions
near the ^1S + ^3P_1 intercombination line but also facilitates bound-to-bound
transitions via resonantly coupled excited state rovibrational levels to deeply
bound rovibrational levels of the ground X^1\Sigma_g^+ potential, with v"" as
low as v""=6. The spin-orbit interaction is responsible for both optical
pathways. Therefore, those excited state levels that have the largest
bound-to-bound transition moments to deeply bound ground state levels also
exhibit a sufficient photoassociation probability, comparable to that of the
lowest weakly bound excited state level previously observed by Zelevinsky et
al. [Phys. Rev. Lett. 96, 203201 (2006)]. Our study paves the way for an
efficient photoassociative production of Sr_2 molecules in ground state levels
suitable for experiments testing the electron-to-proton mass ratio.",1203.4552v1
2012-03-26,Magneto-transport in mesoscopic rings and cylinders: Effects of electron-electron interaction and spin-orbit coupling,"We undertake an in-depth analysis of the magneto-transport properties in
mesoscopic single-channel rings and multi-channel cylinders within a
tight-binding formalism. The main focus of this review is to illustrate how the
long standing anomalies between the calculated and measured current amplitudes
carried by a small conducting ring upon the application of a magnetic flux
$\phi$ can be removed. We discuss two different cases. First, we examine the
combined effect of second-neighbor hopping integral and Hubbard correlation on
the enhancement of persistent current in presence of disorder. A significant
change in current amplitude is observed compared to the traditional
nearest-neighbor hopping model and the current amplitude becomes quite
comparable to experimental realizations. In the other case we verify that in
presence of spin-orbit interaction a considerable enhancement of persistent
current amplitude takes place, and the current amplitude in a disordered ring
becomes almost comparable to that of an ordered one. In addition to these, we
also present the detailed band structures and some other related issues to get
a complete picture of the phenomena at the microscopic level.",1203.5779v1
2012-08-21,Optimized production of ultracold ground-state molecules: Stabilization employing potentials with ion-pair character and strong spin-orbit coupling,"We discuss the production of ultracold molecules in their electronic ground
state by photoassociation employing electronically excited states with ion-pair
character and strong spin-orbit interaction. A short photoassociation laser
pulse drives a non-resonant three-photon transition for alkali atoms colliding
in their lowest triplet state. The excited state wave packet is transferred to
the ground electronic state by a second laser pulse, driving a resonant
two-photon transition. After analyzing the transition matrix elements governing
the stabilization step, we discuss the efficiency of population transfer using
transform-limited and linearly chirped laser pulses. Finally, we employ optimal
control theory to find the most efficient stabilization pathways. We find that
the stabilization efficiency can be increased by one and two orders of
magnitude for linearly chirped and optimally shaped laser pulses, respectively.",1208.4331v2
2013-03-05,Gate defined wires in HgTe quantum wells: from Majorana fermions to spintronics,"We introduce a promising new platform for Majorana zero-modes and various
spintronics applications based on gate-defined wires in HgTe quantum wells. Due
to the Dirac-like band structure for HgTe the physics of such systems differs
markedly from that of conventional quantum wires. Most strikingly, we show that
the subband parameters for gate-defined HgTe wires exhibit exquisite
tunability: modest gate voltage variation allows one to modulate the Rashba
spin-orbit energies from zero up to ~30K, and the effective g-factors from zero
up to giant values exceeding 600. The large achievable spin-orbit coupling and
g-factors together allow one to access Majorana modes in this setting at
exceptionally low magnetic fields while maintaining robustness against
disorder. As an additional benefit, gate-defined wires (in HgTe or other
settings) should greatly facilitate the fabrication of networks for refined
transport experiments used to detect Majoranas, as well as the realization of
non-Abelian statistics and quantum information devices.",1303.1207v1
2013-03-08,"Anisotropic Current-Controlled Magnetization Reversal in the Ferromagnetic Semiconductor (Ga,Mn)As","Electrical current manipulation of magnetization switching through
spin-orbital coupling in ferromagnetic semiconductor (Ga,Mn)As Hall bar devices
has been investigated. The efficiency of the current-controlled magnetization
switching is found to be sensitive to the orientation of the current with
respect to the crystalline axes. The dependence of the spin-orbit effective
magnetic field on the direction and magnitude of the current is determined from
the shifts in the magnetization switching angle. We find that the strain
induced effective magnetic field is about three times as large as the Rashba
induced magnetic field in our GaMnAs devices.",1303.1907v1
2013-12-06,An all electron topological insulator in InAs double wells,"We show that electrons in ordinary III-V semiconductor double wells with an
in-plane modulating periodic potential and inter well spin-orbit interaction
are tunable Topological Insulators (TIs). Here the essential TI ingredients,
namely, band inversion and the opening of an overall bulk gap in the spectrum
arise, respectively, from (i) the combined effect of the double well even-odd
state splitting $\Delta_{SAS}$ together with the superlattice potential and
(ii) the interband Rashba spin-orbit coupling $\eta$. We corroborate our exact
diagonalization results by an analytical nearly-free electron description that
allows us to derive an effective Bernevig-Hughes-Zhang (BHZ) model.
Interestingly, the gate-tunable $\Delta_{SAS}$ drives a topological phase
transition featuring a discontinuous Chern number at $\Delta_{SAS}\sim 5.4$
meV. Finally, we explicitly verify the bulk-edge correspondence by considering
a strip configuration and determining not only the bulk bands in the
non-topological and topological phases but also the edge states and their
Dirac-like spectrum in the topological phase. The edge electronic densities
exhibit peculiar spatial oscillations as they decay away into the bulk. For
concreteness, we present our results for InAs-based wells with realistic
parameters.",1312.2034v2
2013-12-23,Broken SU(4) symmetry in a Kondo-correlated carbon nanotube,"Understanding the interplay between many-body phenomena and non-equilibrium
in systems with entangled spin and orbital degrees of freedom is a central
objective in nano-electronics. We demonstrate that the combination of Coulomb
interaction, spin-orbit coupling and valley mixing results in a particular
selection of the inelastic virtual processes contributing to the Kondo
resonance in carbon nanotubes at low temperatures. This effect is dictated by
conjugation properties of the underlying carbon nanotube spectrum at zero and
finite magnetic field. Our measurements on a clean carbon nanotube are
complemented by calculations based on a new approach to the non-equilibrium
Kondo problem which well reproduces the rich experimental observations in Kondo
transport.",1312.6586v4
2014-07-04,Spin-orbit spillage as a measure of band inversion in insulators,"We propose a straightforward and effective approach for quantifying the band
inversion induced by spin-orbit coupling in band insulators. In this approach
we define a quantity as a function of wavevector in the Brillouin zone
measuring the spillage between the occupied states of a system with and without
SOC. Plots of the spillage throughout the BZ provide a ready indication of the
number and location of band inversions driven by SOC. To illustrate the method,
we apply this approach to the 2D Kane-Mele model, a 2D Bi bilayer with applied
Zeeman field, and to first-principles calculations of some 3D materials
including both trivial and \Z2\ topological insulators. We argue that the
distribution of spillage in the BZ is closely related to the topological
indices in these systems. Our approach provides a fresh perspective for
understanding topological character in band theory, and should be helpful in
searching for new materials with non-trivial band topology.",1407.1244v2
2014-07-16,Tunability of the Fractional Quantum Hall States in Buckled Dirac Materials,"We report on the fractional quantum Hall states of germanene and silicene
where one expects a strong spin-orbit interaction. This interaction causes an
enhancement of the electron-electron interaction strength in one of the Landau
levels corresponding to the valence band of the system. This enhancement
manifests itself as an increase of the fractional quantum Hall effect gaps
compared to that in graphene and is due to the spin-orbit induced coupling of
the Landau levels of the conduction and valence bands, which modifies the
corresponding wave functions and the interaction within a single level. Due to
the buckled structure, a perpendicular electric field lifts the valley
degeneracy and strongly modifies the interaction effects within a single Landau
level: in one valley the perpendicular electric field enhances the interaction
strength in the conduction band Landau level, while in another valley, the
electric field strongly suppresses the interaction effects.",1407.4441v1
2014-08-12,Interplay of spin-orbit and entropic effects in Cerium,"We perform first-principle calculations of elemental cerium and compute its
pressure-temperature phase diagram, finding good quantitative agreement with
the experiments. Our calculations indicate that, while a signature of the
volume-collapse transition appears in the free energy already at low
temperatures, at larger temperatures this signature is enhanced because of the
entropic effects, and originates an actual thermodynamical instability.
Furthermore, we find that the catalyst determining this feature is --- in all
temperature regimes --- a pressure-induced effective reduction of the $f$-level
degeneracy due to the spin-orbit coupling. Our analysis suggests also that the
lattice vibrations might be crucial in order to capture the behavior of the
pressure-temperature transition line at large temperatures.",1408.2815v1
2014-08-29,Electric Octupole Order in Bilayer Ruthenate Sr$_3$Ru$_2$O$_7$,"Although the odd-parity multipole order barely occurs in crystals with high
symmetry, it can be formed in locally noncentrosymmetric crystals. We
illustrate the odd-parity electric octupole order generated in a bilayer
structure. When the local electric quadrupole is alternatively stacked between
layers, it is regarded as an electric octupole order from the viewpoint of
symmetry. We show that the $p_y s_x + p_x s_y$ spin nematic order is induced by
the spin-orbit coupling in the electric octupole state, and it results from the
spontaneous inversion symmetry breaking leading to the $D_{2d}$ point group
symmetry. We investigate the possible realization of the electric octupole
order in the bilayer ruthenate Sr$_3$Ru$_2$O$_7$, assuming a local electric
quadrupole arising from the Pomeranchuk instability and/or the orbital order.
Effects of the lattice distortion and magnetic field are also clarified, and
the nature of the ""electronic nematic state"" of Sr$_3$Ru$_2$O$_7$ is discussed.
It is proposed that the asymmetric band structure is a signature of the
electric octupole order in Sr$_3$Ru$_2$O$_7$. The odd-parity multipole order in
other strongly correlated electron systems is discussed.",1408.6936v2
2014-09-23,Negative Tunneling Magneto-Resistance in Quantum Wires with Strong Spin-Orbit Coupling,"We consider a two-dimensional magnetic tunnel junction of the
FM/I/QW(FM+SO)/I/N structure, where FM, I and QW(FM+SO) stand for a
ferromagnet, an insulator and a quantum wire (QW) with both magnetic ordering
and Rashba spin-orbit (SOC), respectively. The tunneling magneto-resistance
(TMR) exhibits strong anisotropy and switches sign as the polarization
direction varies relative to the QW axis, due to interplay among the
one-dimensionality, the magnetic ordering, and the strong SOC of the QW. The
results may provide a possible explanation for the sign-switching anisotropic
TMR recently observed in the LaAlO$_3$/SrTiO$_3$ interface.",1409.6374v2
2014-11-12,Spin-Orbit-Free Topological Insulators,"In this lecture for the Nobel symposium, we review previous research on a
class of translational-invariant insulators without spin-orbit coupling. These
may be realized in intrinsically spinless systems such as photonic crystals and
ultra-cold atoms. Some of these insulators have no time-reversal symmetry as
well, i.e., the relevant symmetries are purely crystalline. Nevertheless,
topological phases exist which are distinguished by their robust surface modes.
To describe these phases, we introduce the notions of (a) a halved-mirror
chirality: an integer invariant which characterizes half-mirror planes in the
3D Brillouin zone, and (b) a bent Chern number: the traditional
Thouless-Kohmoto-Nightingale-Nijs invariant generalized to bent 2D manifolds.
Like other well-known topological phases, their band topology is unveiled by
the crystalline analog of Berry phases, i.e., parallel transport across certain
non-contractible loops in the Brillouin zone. We also identify certain
topological phases without any robust surface modes - they are uniquely
distinguished by parallel transport along bent loops, whose shapes are
determined by the symmetry group. Finally, we describe the Weyl semimetallic
phase that intermediates two distinct, gapped phases.",1411.3338v1
2014-12-03,Electronic structure of quasi-one-dimensional superconductor K$_2$Cr$_3$As$_3$ from first-principles calculations,"The electronic structure of quasi-one-dimensional superconductor
K$_2$Cr$_3$As$_3$ is studied through systematic first-principles calculations.
The ground state of K$_2$Cr$_3$As$_3$ is paramagnetic but very close to a
ferromagnetic instability. Close to the Fermi level, the Cr-3d$_{z^2}$,
d$_{xy}$, and d$_{x^2-y^2}$ orbitals dominate the electronic states, and three
bands cross $E_F$ to form one 3D Fermi surface sheet and two quasi-1D sheets.
The electron DOS at $E_F$ is less than 1/3 of the experimental value,
indicating an intermediate electron renormalization factor around $E_F$.
Despite of the relatively small atomic numbers, the antisymmetric spin-orbit
coupling splitting is sizable ($\approx$ 60 meV) on the 3D Fermi surface sheet
as well as on one of the quasi-1D sheets. Finally, the imaginary part of bare
electron susceptibility shows large peaks at $\Gamma$, suggesting the existence
of large ferromagnetic spin fluctuation in the compound.",1412.1309v2
2014-12-12,Doping-dependent bandwidth renormalization and spin-orbit coupling in (Sr$_{1-x}$La$_x$)$_2$RhO$_4$,"We investigate the electronic structure of (Sr$_{1-x}$La$_x$)$_2$RhO$_4$
using a combination of the density functional and dynamical mean-field
theories. Unlike the earlier local density approximation plus Hubbard $U$
(LDA+U) studies, we find no sizable enhancement of the spin-orbit splitting due
to electronic correlations and show that such an enhancement is a spurious
effect of the static mean-field approximation of the LDA+U method. The electron
doping suppresses the importance of electronic correlations, which is reflected
in quasi-particle bandwidth increasing with $x$. (Sr$_{1-x}$La$_x$)$_2$RhO$_4$
can be classified as weakly correlated metal, which becomes an itinerant
in-plane ferromagnet (but possibly A-type antiferromagnet) due to Stoner
instability around $x=0.2$.",1412.4766v2
2015-04-15,Triangular lattice exciton model,"We present a minimalistic equilateral triangular lattice model, from which we
derive electron and exciton band structures for semiconducting transition-metal
dichalcogenides. With explicit consideration of the exchange interaction, this
model is appropriate across the spectrum from Wannier to Frenkel excitons. The
single-particle contributions are obtained from a nearest-neighbor
tight-binding model parameterized using the effective mass and spin-orbit
coupling. The solutions to the characteristic equation, computed in direct
space, are in qualitative agreement with first-principles calculations and
highlight the inadequacy of the two-dimensional hydrogen model to describe the
lowest-energy exciton bands. The model confirms the lack of subshell degeneracy
and shows that the A-B exciton split depends on the electrostatic environment
as well as the spin-orbit interaction.",1504.04040v1
2015-07-21,Induced p-wave superconductivity without spin-orbit interactions,"The study of Majorana fermions is of great importance for the implementation
of a quantum computer. These modes are topologically protected and very stable.
It is now well known that a p-wave superconducting wire can sustain, in its
topological non-trivial phase, Majorana quasi-particles at its ends. Since this
type of superconductor is not found in nature, many methods have been devised
to implement it. Most of them rely on the spin-orbit interaction. In this paper
we study the superconducting properties of a two-band system in the presence of
antisymmetric hybridization. We consider inter-band attractive interactions and
also an attractive interaction in one of the bands. We show that
superconducting fluctuations with p-wave character are induced in the
non-interacting band due to the combined effects of inter-band coupling and
hybridization. In the case of a wire, this type of induced superconductivity
gives rise to four Majorana modes at its ends. The long range correlation
between the different charge states of these modes offers new possibilities for
the implementation of protected q-bits.",1507.05906v1
2015-07-22,Spin-Orbit Physics Giving Rise to Novel Phases in Correlated Systems: Iridates and Related Materials,"Recently, the effects of spin-orbit coupling (SOC) in correlated materials
have become one of the most actively studied subjects in condensed matter
physics, as correlations and SOC together can lead to the discovery of new
phases. Among candidate materials, iridium oxides (iridates) have been an
excellent playground to uncover such novel phenomena. In this review, we
discuss recent progress in iridates and related materials, focusing on the
basic concepts, relevant microscopic Hamiltonians, and unusual properties of
iridates in perovskite- and honeycomb-based structures. Perspectives on SOC and
correlation physics beyond iridates are also discussed.",1507.06323v1
2015-10-01,"Line-Node Dirac Semimetal and Topological Insulating Phase in Noncentrosymmetric Pnictides CaAgX (X = P, As)","Two noncentrosymmetric ternary pnictides, CaAgP and CaAgAs, are reported as
topological line-node semimetals protected solely by mirror-reflection
symmetry. The band gap vanishes on a circle in momentum space, and surface
states emerge within the circle. Extending this study to spin-orbit coupled
systems reveals that, compared with CaAgP, a substantial band gap is induced in
CaAgAs by large spin-orbit interaction. The resulting states are a topological
insulator, in which the Z2 topological invariant is given by 1; 000. To clarify
the Z2 topological invariants for time-reversal-invariant systems without
spatial-inversion symmetry, we introduce an alternative way to calculate the
invariants characterizing a line node and topological insulator for
mirror-reflection-invariant systems.",1510.00202v3
2016-01-09,Pressure enhanced thermoelectric properties in Mg2Sn,"Pressure dependence of electronic structures and thermoelectric properties of
$\mathrm{Mg_2Sn}$ are investigated by using a modified Becke and Johnson (mBJ)
exchange potential, including spin-orbit coupling (SOC). The corresponding
value of spin-orbit splitting at $\Gamma$ point is 0.47 eV, which is in good
agreement with the experimental value 0.48 eV. With the pressure increasing,
the energy band gap first increases, and then decreases. In certain doping
range, the power factor for n-type has the same trend with energy band gap,
when the pressure increases. Calculated results show that the pressure can lead
to significantly enhanced power factor in n-type doping below the critical
pressure, and the corresponding lattice thermal conductivity near the critical
pressure shows the relatively small value. These results make us believe that
thermoelectric properties of $\mathrm{Mg_2Sn}$ can be improved in n-type doping
by pressure.",1601.02079v1
2016-04-13,Terahertz Spin-Orbital Excitations in the paramagnetic state of multiferroic Sr$_2$FeSi$_2$O$_7$,"We studied the novel multiferroic material Sr$_2$FeSi$_2$O$_7$, and found 3
absorption modes above the magnetic ordering transition temperature using
time-domain terahertz spectroscopy. These absorption modes can be explained as
the optical transitions between the spin-orbit coupling and crystal field split
3d$^6$ Fe$^{2+}$ ground state term in this material. Consideration of the
compressed tetrahedral environment of the Fe$^{2+}$ site is crucial to
understand the excitations. We point out, however, discrepancies between the
single-site atomic picture and the experimental results.",1604.03771v2
2016-04-18,Superconductivity in doped Dirac semimetals,"We theoretically study intrinsic superconductivity in doped Dirac semimetals.
Dirac semimetals host bulk Dirac points, which are formed by doubly degenerate
bands, so the Hamiltonian is described by a $4 \times 4$ matrix and six types
of $k$-independent pair potentials are allowed by the Fermi-Dirac statistics.
We show that the unique spin-orbit coupling leads to characteristic
superconducting gap structures and $d$ vectors on the Fermi surface and the
electron-electron interaction between intra and interorbitals gives a novel
phase diagram of superconductivity. It is found that when the inter-orbital
attraction is dominant, an unconventional superconducting state with point
nodes appears. To verify the experimental signature of possible superconducting
states, we calculate the temperature dependence of bulk physical properties
such as electronic specific heat and spin susceptibility and surface state. In
the unconventional superconducting phase, either dispersive or flat Andreev
bound states appear between point nodes, which leads to double peaks or single
peak in the surface density of states, respectively. As a result, possible
superconducting states can be distinguished by combining bulk and surface
measurements.",1604.05081v2
2016-07-14,Presence of Exotic Electronic Surface States in LaBi and LaSb,"Extremely high magnetoresistance (XMR) in the lanthanum monopnictides La$X$
($X$ = Sb, Bi) has recently attracted interest in these compounds as candidate
topological materials. However, their perfect electron-hole compensation
provides an alternative explanation, so the possible role of topological
surface states requires verification through direct observation. Our
angle-resolved photoemission spectroscopy (ARPES) data reveal multiple
Dirac-like surface states near the Fermi level in both materials. Intriguingly,
we have observed circular dichroism in both surface and near-surface bulk
bands. Thus the spin-orbit coupling-induced orbital and spin angular momentum
textures may provide a mechanism to forbid backscattering in zero field,
suggesting that surface and near-surface bulk bands may contribute strongly to
XMR in La$X$. The extremely simple rock salt structure of these materials and
the ease with which high-quality crystals can be prepared suggests that they
may be an ideal platform for further investigation of topological matter.",1607.04178v2
2016-09-29,Modulational instability and solitary waves in polariton topological insulators,"Optical microcavities supporting exciton-polariton quasi-particles offer one
of the most powerful platforms for investigation of rapidly developing area of
topological photonics in general, and of photonic topological insulators in
particular. Energy bands of the microcavity polariton graphene are readily
controlled by magnetic field and influenced by the spin-orbit coupling effects,
a combination leading to formation of linear unidirectional edge states in
polariton topological insulators as predicted very recently. In this work we
depart from the linear limit of non-interacting polaritons and predict
instabilities of the nonlinear topological edge states resulting in formation
of the localized topological quasi-solitons, which are exceptionally robust and
immune to backscattering wavepackets propagating along the graphene lattice
edge. Our results provide a background for experimental studies of nonlinear
polariton topological insulators and can influence other subareas of photonics
and condensed matter physics, where nonlinearities and spin-orbit effects are
often important and utilized for applications.",1609.09533v1
2017-08-07,"Chiral damping, chiral gyromagnetism and current-induced torques in textured one-dimensional Rashba ferromagnets","We investigate Gilbert damping, spectroscopic gyromagnetic ratio and
current-induced torques in the one-dimensional Rashba model with an additional
noncollinear magnetic exchange field. We find that the Gilbert damping differs
between left-handed and right-handed N\'eel-type magnetic domain walls due to
the combination of spatial inversion asymmetry and spin-orbit interaction
(SOI), consistent with recent experimental observations of chiral damping.
Additionally, we find that also the spectroscopic $g$ factor differs between
left-handed and right-handed N\'eel-type domain walls, which we call chiral
gyromagnetism. We also investigate the gyromagnetic ratio in the Rashba model
with collinear magnetization, where we find that scattering corrections to the
$g$ factor vanish for zero SOI, become important for finite spin-orbit
coupling, and tend to stabilize the gyromagnetic ratio close to its
nonrelativistic value.",1708.02008v2
2018-02-27,Spin-orbit and anisotropic strain effects on the electronic correlations of Sr$_2$RuO$_4$,"We present an implementation of the rotationally invariant slave boson
technique as an impurity solver for density functional theory plus dynamical
mean field theory (DFT+DMFT). Our approach provides explicit relations between
quantities in the local correlated subspace treated with DMFT and the Bloch
basis used to solve the DFT equations. In particular, we present an expression
for the mass enhancement of the quasiparticle states in reciprocal space. We
apply the method to the study of the electronic correlations in Sr$_2$RuO$_4$
under anisotropic strain. We find that the spin-orbit coupling plays a crucial
role in the mass enhancement differentiation between the quasi-one-dimensional
$\alpha$ and $\beta$ bands, and on its momentum dependence over the Fermi
surface. The mass enhancement, however, is only weakly affected by either
uniaxial or biaxial strain, even across the Lifshitz transition induced by the
strain.",1802.10150v1
2018-04-17,Ultrasensitive multi-mode ESR probed ferromagnetic two-level system of $Mn^{4+}$ impurity ion in the insulated $MnO_6$ complex of $SrLaAlO_4$ at $20~mK$,"Ultrasnsitive multi-mode electron spin resonance spectroscopy in the
$SrLaAlO_4$ dielectric resonator at $20~mK$ reveals ferromagnetic states of
$Mn^{4+}$ impurity ion. The formation of ferromagnetic states in the $MnO_6$
complex implies to oxygen deficiency of this multi-valence $Mn^{4+}$ ion.
Experiment results supports that an intricate electronic hybridization in
$MnO_6$ structural instability is related to Pseudo Jahn-Teller effect.
Measured dipolar hyperfine structure parameter of nucleus is
$P_{\scriptscriptstyle\parallel} =-3.7\times 10^{-4}~cm^{-1}$. Mean inverse
third power of the electron distance is $\langle r_q^{-3}\rangle=3.325~a.u.$
assuming nuclear electric quadruple moment $Q=+0.33(1)~barn$. In such a state,
giant g-factor is observed due to magneto (ferromagnetic) impedance taking in
to account a two-level system on the adiabatic-potential-energy-surface. The
spins exhibited parity is opposite in the interaction of
highest-occupied-molecular-orbital and lowest-unoccupied-molecular-orbital
coupling.",1804.06320v1
2018-04-26,Resonant reflection of interacting electrons from an impurity in a quantum wire: interplay of Zeeman and spin-orbit effects,"A single-channel quantum wire with two well-separated Zeeman subbands and in
the presence of a weak spin-orbit coupling is considered. An impurity level
which is split off the upper subband is degenerate with the continuum of the
lower subband. We show that, when the Fermi level lies in the vicinity of the
impurity level, the transport is completely blocked. This is the manifestation
of the effect of resonant reflection and can be viewed as resonant tunneling
between left-moving and right-moving electrons via the impurity level. We
incorporate electron-electron interactions and study their effect on the shape
of the resonant-reflection profile. This profile becomes a two-peak structure,
where one peak is caused by resonant reflection itself, while the origin of the
other peak is reflection from the Friedel oscillations of the electron density
surrounding the impurity.",1804.10283v1
2020-07-11,Ferromagnetic Weyl Fermions in Two-Dimensional Layered Electride Gd$_2$C,"Recently, two-dimensional layered electrides have emerged as a new class of
materials which possess anionic electron layers in the interstitial spaces
between cationic layers. Here, based on first-principles calculations, we
discover a time-reversal-symmetry-breaking Weyl semimetal phase in a unique
two-dimensional layered ferromagnetic (FM) electride Gd$_2$C. It is revealed
that the crystal field mixes the interstitial electron states and Gd 5$d$
orbitals near the Fermi energy to form band inversions. Meanwhile, the FM order
induces two spinful Weyl nodal lines (WNLs), which are converted into multiple
pairs of Weyl nodes through spin-orbit coupling. Further, we not only identify
Fermi-arc surface states connecting the Weyl nodes but also predict a large
intrinsic anomalous Hall conductivity due to the Berry curvature produced by
the gapped WNLs. Our findings demonstrate the existence of Weyl fermions in the
room-temperature FM electride Gd$_2$C, therefore offering a new platform to
investigate the intriguing interplay between electride materials and magnetic
Weyl physics.",2007.05695v1
2020-07-14,Unveiling Giant Hidden Rashba Effects in Two-Dimensional Si$_2$Bi$_2$,"Recently, it has been known that the hidden Rashba (R-2) effect in
two-dimensional materials gives rise to a novel physical phenomenon called
spin-layer locking (SLL). However, not only has its underlying fundamental
mechanism been unclear, but also there are only a few materials exhibiting weak
SLL. Here, through the first-principles density functional theory and model
Hamiltonian calculation, we reveal that the R-2 SLL can be determined by the
competition between the sublayer-sublayer interaction and the spin-orbit
coupling (SOC), which is related to the Rashba strength. In addition, the
orbital angular momentum distribution is another crucial point to realize the
strong R-2 SLL. We propose that a novel 2D material Si$_2$Bi$_2$ possesses an
ideal condition for the strong R-2 SLL, whose Rashba strength is evaluated to
be 2.16 eV{\AA}, which is the greatest value ever observed in 2D R-2 materials
to the best of our knowledge. Furthermore, we reveal that the interlayer
interaction in a bilayer structure ensures R-2 states spatially farther apart,
implying a potential application in spintronics.",2007.06742v2
2018-05-09,Nature of the Magnetic Interactions in Sr$_3$NiIrO$_6$,"Iridates abound with interesting magnetic behaviours because of their strong
spin-orbit coupling. Sr$_3$NiIrO$_6$ brings together the spin-orbital
entanglement of the Ir$^{4+}$ ion with a 3$d$ Ni cation and a one-dimensional
crystal structure. It has a ferrimagnetic ground state with a 55 T coercive
field. We perform a theoretical study of the magnetic interactions in this
compound, and elucidate the role of anisotropic symmetric exchange as the
source of its strong magnetic anisotropy. Our first-principles calculations
reproduce the magnon spectra of this compound and predict a signature in the
cross sections that can differentiate the anisotropic exchange from single-ion
anisotopy.",1805.03733v2
2018-05-18,Band crossings in honeycomb-layered transition metal compounds,"Two-dimensional electron dispersions with peculiar band crossings provide a
platform for realizing topological phases of matter. Here we theoretically show
that the $e_g$-orbital manifold of honeycomb-layered transition metal compounds
accommodates a plethora of peculiar band crossings, such as multiple Dirac
point nodes, quadratic band crossings, and line nodes. From the tight-binding
analysis, we find that the band topology is systematically changed by the
orbital dependent transfer integrals on the honeycomb network of edge-sharing
octahedra, which can be modulated by distortions of the octahedra as well as
chemical substitutions. The band crossings are gapped out by the spin-orbit
coupling, which brings about a variety of topological phases distinguished by
the spin Chern numbers. The results provide a comprehensive understanding of
the previous studies on various honeycomb compounds. We also propose another
candidate materials by ab initio calculations.",1805.07068v2
2018-05-21,Proximitized Materials,"Advances in scaling down heterostructures and having an improved interface
quality together with atomically-thin two-dimensional materials suggest a novel
approach to systematically design materials. A given material can be
transformed through proximity effects whereby it acquires properties of its
neighbors, for example, becoming superconducting, magnetic, topologically
nontrivial, or with an enhanced spin-orbit coupling. Such proximity effects not
only complement the conventional methods of designing materials by doping or
functionalization, but can also overcome their various limitations. In
proximitized materials it is possible to realize properties that are not
present in any constituent region of the considered heterostructure. While the
focus is on magnetic and spin-orbit proximity effects with their applications
in spintronics, the outlined principles provide also a broader framework for
employing other proximity effects to tailor materials and realize novel
phenomena.",1805.07942v1
2013-09-20,Jeff=1/2 Mott spin-orbit insulating state close to the cubic limit in Ca4IrO6,"The Jeff=1/2 state is manifested in systems with large cubic crystal field
splitting and spin-orbit coupling that are comparable to the on-site Coulomb
interaction, U. 5d transition metal oxides host parameters in this regime and
strong evidence for this state in Sr2IrO4, and additional iridates, has been
presented. All the candidates, however, deviate from the cubic crystal field
required to provide an unmixed canonical Jeff=1/2 state, impacting the
development of a robust model of this novel insulating and magnetic state. We
present results that not only show Ca4IrO6 hosts the state, but furthermore
uniquely resides close to the ideal case required for an unmixed Jeff=1/2
state.",1309.5411v1
2014-05-07,Many-body and spin-orbit effects on direct-indirect band gap transition of strained monolayer MoS$_2$ and WS$_2$,"Monolayer transition metal dichalcogenides are promising materials for
photoelectronic devices. Among them, molybdenum disulphide (MoS$_2$) and
tungsten disulphide (WS$_2$) are some of the best candidates due to their
favorable band gap values and band edge alignments. Here we consider various
perturbative corrections to the DFT electronic structure, e.g. GW, spin-orbit
coupling, as well as many-body excitonic and trionic effects, and calculate
accurate band gaps as a function of homogeneous strain in these materials. We
show that all of these corrections are of comparable magnitudes and need to be
included in order to obtain an accurate electronic structure. We calculate the
strain at which the direct-to-indirect gap transition occurs. After considering
all contributions, the direct to indirect gap transition strain is found to be
at 2.7% in MoS$_2$ and 3.9% in WS$_2$. These values are generally higher than
the previously reported theoretical values.",1405.1699v2
2014-06-17,Magnetic field resistant quantum interferences in bismuth nanowires based Josephson junctions,"We investigate proximity induced superconductivity in micrometer-long bismuth
nanowires con- nected to superconducting electrodes with a high critical field.
At low temperature we measure a supercurrent that persists in magnetic fields
as high as the critical field of the electrodes (above 11 T). The critical
current is also strongly modulated by the magnetic field. In certain samples we
find regular, rapid SQUID-like periodic oscillations occurring up to high
fields. Other samples ex- hibit less periodic but full modulations of the
critical current on Tesla field scales, with field-caused extinctions of the
supercurrent. These findings indicate the existence of low dimensionally, phase
coherent, interfering conducting regions through the samples, with a subtle
interplay between orbital and spin contributions. We relate these surprising
results to the electronic properties of the surface states of bismuth, strong
Rashba spin-orbit coupling, large effective g factors, and their effect on the
induced superconducting correlations.",1406.4280v1
2015-12-18,Substrate-tuning of correlated spin-orbit oxides,"We have systematically investigated substrate-strain effects on the
electronic structures of two representative Sr-iridates, a correlated-insulator
Sr$_2$IrO$_4$ and a metal SrIrO$_3$. Optical conductivities obtained by the
\emph{ab initio} electronic structure calculations reveal that the tensile
strain shifts the optical peak positions to higher energy side with altered
intensities, suggesting the enhancement of the electronic correlation and
spin-orbit coupling (SOC) strength in Sr-iridates. The response of the
electronic structure upon tensile strain is found to be highly correlated with
the direction of magnetic moment, the octahedral connectivity, and the SOC
strength, which cooperatively determine the robustness of $J_{eff}$=1/2 ground
states. Optical responses are analyzed also with microscopic model calculation
and compared with corresponding experiments. In the case of SrIrO$_3$, the
evolution of the electronic structure near the Fermi level shows high
tunability of hole bands, as suggested by previous experiments.",1512.05932v1
2015-12-23,Semimetal with both Rarita-Schwinger-Weyl and Weyl excitations,"A relativistic spinor with spin 3/2 is historically called Rarita-Schwinger
spinor. The right- and left-handed chiral degrees of freedom for the massless
Rarita-Schwinger spinor are independent and are thought of as the left- and
right-Weyl fermion with helicity \pm3/2. We study three orbital spin-1/2 Weyl
semimetals in the strong spin-orbital coupling limit with time reversal
symmetry breaking. We find that in this limit the systems can be a J_{eff}=1/2
Weyl semimetal or a J_{eff}=3/2 semimetal, depending on the Fermi level
position. The latter near Weyl points includes both degrees of freedom of
Rarita-Schwinger-Weyl and Weyl's. A non-local potential separates the Weyl and
Rarita-Schwinger-Weyl degrees of freedom and a relativistic
Rarita-Schwinger-Weyl semimetal emerges. This recipe can be generalized to
mulit-Weyl semimetal and Weyl fermions with pairing interaction and obtain high
monopole charges.
  Similarly, a spatial inversion breaking Raita-Schwinger-Weyl semimetal may
also emerge.",1512.07460v1
2016-08-11,Collective magnetic excitations of $C_{4}$ symmetric magnetic states in iron-based superconductors,"We study the collective magnetic excitations of the recently discovered
$C_{4}$ symmetric spin-density wave states of iron-based superconductors with
particular emphasis on their orbital character based on an itinerant
multiorbital approach. This is important since the $C_{4}$ symmetric
spin-density wave states exist only at moderate interaction strengths where
damping effects from a coupling to the continuum of particle-hole excitations
strongly modifies the shape of the excitation spectra compared to predictions
based on a local moment picture. We uncover a distinct orbital polarization
inherent to magnetic excitations in $C_{4}$ symmetric states, which provide a
route to identify the different commensurate magnetic states appearing in the
continuously updated phase diagram of the iron-pnictide family.",1608.03493v1
2016-08-25,Hidden multipolar orders of dipole-octupole doublets on a triangular lattice,"Motivated by the recent development in strong spin-orbit-coupled materials,
we consider the dipole-octupole doublets on the triangular lattice. We propose
the most general interaction between these unusual local moments. Due to the
spin-orbit entanglement and the special form of its wavefunction, the
dipole-octupole doublet has a rather peculiar property under the lattice
symmetry operation. As a result, the interaction is highly anisotropic in the
pseudospin space, but remarkably, is uniform spatially. We analyze the ground
state properties of this generic model and emphasize the hidden multipolar
orders that emerge from the dipolar and octupolar interactions. We clarify the
quantum mutual modulations between the dipolar and octupolar orders. We predict
the experimental consequences of the multipolar orders and propose the
rare-earth triangular materials as candidate systems for these unusual
properties.",1608.07008v1
2017-06-22,Spin-flip doublets of $^9$Be spectrum within a cluster model,"The structure of the $^9$Be low-lying spectrum is studied within the cluster
model $\alpha+\alpha+n$. In the model the total orbital momentum is fixed for
each energy level. Thus each level is determined as a member of the spin-flip
doublet corresponding to the total orbital momentum ($L^\pi=0^+, 2^+,4^+, 1^-,
2^-,3^-, 4^-$) of the system. The Ali-Bodmer potential (model E) is applied for
the $\alpha\alpha$ interaction. We employ a local $\alpha n$ potential which
was constructed to reproduce the $\alpha-n$ scattering data. The Pauli blocking
is simulated by the repulsive core of the $s$-wave components of these
potentials. Configuration space Faddeev equations are used to calculate the
energy of the bound state ($E_{cal.}$=-1.493 MeV v.s. $E_{exp.}$=-1.5735 MeV)
and resonances. A variant of the method of analytical continuation in the
coupling constant is applied to calculate the energies of low-lying levels.
Available $^9$Be spectral data are satisfactorily reproduced by the proposed
model.",1706.07481v1
2017-12-05,Self-trapping under the two-dimensional spin-orbit-coupling and spatially growing repulsive nonlinearity,"We elaborate a method for the creation of two- and one-dimensional (2D and
1D) self-trapped modes in binary spin-orbit (SO)-coupled Bose-Einstein
condensates (BECs) with the contact repulsive interaction, whose local strength
grows fast enough from the center to periphery. In particular, an exact
semi-vortex (SV) solution is found for the anti-Gaussian radial-modulation
profile. The exact modes are included in the numerically produced family of SV
solitons. Other families, in the form of mixed modes(MMs), as well as excited
state of SVs and MMs, are produced too. While the excited states are unstable
in all previously studied models, they are partially stable in the present one.
In the 1D version of the system, exact solutions for the counterpart of the
SVs, namely, \textit{semi-dipole} solitons, are found too. Families of
semi-dipoles, as well as the 1D version of MMs, are produced numerically.",1712.01430v2
2018-09-21,Electronic correlations and competing orders in multiorbital dimers: a cluster DMFT study,"We investigate the violation of the first Hund's rule in 4$d$ and 5$d$
transition metal oxides that form solids of dimers. Bonding states within these
dimers reduce the magnetization of such materials. We parametrize the dimer
formation with realistic hopping parameters and find not only regimes, where
the system behaves as a Fermi liquid or as a Peierls insulator, but also
strongly correlated regions due to Hund's coupling and its competition with the
dimer formation. The electronic structure is investigated using the cluster
dynamical mean-field theory for a dimer in the two-plane Bethe lattice with two
orbitals per site and $3/8$-filling, that is three electrons per dimer. It
reveals dimer-antiferromagnetic order of a high-spin (double exchange) state
and a low-spin (molecular orbital) state. At the crossover region we observe
the suppression of long-range magnetic order, fluctuation enhancement and
renormalization of electron masses. At certain interaction strengths the system
becomes an incoherent antiferromagnetic metal with well defined local moments.",1809.07989v1
2019-09-08,Evolution of the magnetic and polaronic order of $\rm{Pr_{1/2}Ca_{1/2}MnO_3}$ following an ultrashort light pulse,"The dynamics of electrons, spins and phonons induced by optical femtosecond
pulses has been simulated for the polaronic crystal
$\rm{Pr_{1/2}Ca_{1/2}MnO_3}$. The model used for the simulation has been
derived from first-principles calculations. The simulations reproduce the
experimentally observed melting of charge/orbital order with increasing
fluence. The loss of charge order in the high-fluence regime induces a
transition to a ferromagnetic metal. At low fluence, the dynamics is
deterministic and coherent phonons are created by the repopulation of
electronic orbitals, which are strongly coupled to the phonon degrees of
freedom. In contrast to the low-fluence regime, the magnetic transitions
occurring at higher fluence can be attributed to a quasi-thermal transition of
a cold-plasma-like state with hot electrons and cold phonons and spins. The
findings can be rationalized in a more complete picture of the electronic
structure that goes beyond the simple ionic picture of charge order.",1909.03412v4
2019-10-15,Time-Reversal Invariant Topological Superconductivity in Planar Josephson Bijunction,"We consider a Josephson bijunction consisting of a thin $SIS$ $\pi$-Josephson
junction sandwiched between two-dimensional semiconducting layers with strong
Rashba spin-orbit interaction. Each of these layers forms an $SNS$ junction due
to proximity-induced superconductivity. The $SIS$ junction is assumed to be
thin enough such that the two Rashba layers are tunnel-coupled. We show that,
by tuning external gates, this system can be controllably brought into a
time-reversal invariant topological superconducting phase with a Kramers pair
of Majorana bound states being localized at the end of the normal region for a
large parameter phase space. In particular, in the strong spin-orbit
interaction limit, the topological phase can be accessed already in the regime
of small tunneling amplitudes.",1910.06921v1
2020-01-03,Self focusing Hybrid Skyrmions in spatially varying canted ferromagnetic systems,"Magnetic skyrmions are quasiparticle configurations in a magnetic film that
can act as information carrying bits for ultrasmall, all-electronic nonvolatile
memory. The skyrmions can be nucleated and driven by spin-orbit torque from a
current driven in a heavy metal underlayer. Along its gyrotropic path, a Magnus
force can cause a skyrmion to be annihilated at the boundaries. By combining
interfacial and bulk Dzyaloshinskii-Moriya interactions (DMIs), for instance by
using a B20 material on top of a heavy metal layer with high spin-orbit
coupling, it is possible to engineer a hybrid skyrmion that will travel
parallel to the racetrack with zero Magnus force. We show that by using a
spatially varying interfacial DMI, a hybrid skyrmion will automatically
self-focus onto such a track as its domain angle evolves along the path.
Furthermore, using a gate driven voltage controlled magnetic anisotropy, we can
control the trajectory of the hybrid skyrmion and its eventual convergence path
and lane selection in a racetrack geometry.",2001.00729v3
2020-01-12,Excitonic effect on two-photon absorption of two-dimensional semiconductors: Theory and applications to MoS2 and WS2 monolayers,"Based on the Bethe-Salpeter equation eigenstates, we present a
first-principles many-body formalism for calculating the two-photon absorption
(TPA) coefficient of semiconductors. We apply this formalism to calculate the
TPA spectra of MoS2 and WS2 monolayers. The all-electron full-potential
linearised augmented-plane wave based functions are used for solving the
Bethe-Salpeter equation. The calculated spectra are in good agreement with the
available experimental ones for WS2 monolayer. The calculated TPA spectra
exhibit significant excitonic effects when compared to those based on the
independent particle approximation. The physical origin of TPA excitonic
transitions of MoS2 and WS2 monolayers are revealed by tracing the
sum-over-states process. We show that the spin-orbit coupling effect leads to
characteristic double peaks with an interval of half spin-orbit splitting
energy. These double peaks mainly originate from the transitions at the
vicinity of K point.",2001.03907v1
2020-02-12,Effective dynamics for a spin-1/2 particle constrained to a space curve in an electric and magnetic field,"We consider the dynamics of a spin-1/2 particle constrained to move in an
arbitrary space curve with an external electric and magnetic field applied.
With the aid of gauge theory, we successfully decouple the tangential and
normal dynamics and derive the effective Hamiltonian. A new type of quantum
potential called SU(2) Zeeman interaction appears, which is induced by the
electric field and couples spin and intrinsic orbital angular momentum. Based
on the Hamiltonian, we discuss the spin precession for zero intrinsic orbital
angular momentum case and the energy splitting caused by the SU(2) Zeeman
interaction for a helix as examples, showing the combined effect of geometry
and external field. The new interaction may bring new approaches to manipulate
quantum states in spintronics.",2002.04891v1
2020-04-19,"Nonsymmorphic nodal-line metals in the two-dimensional rare earth monochalcogenides MX (M = Sc, Y; X = S, Se, Te)","We predict a new family of two-dimensional (2D) rare earth monochalcogenide
materials MX (M = Sc, Y; X = S, Se, Te). Based on first-principles
calculations, we confirm their stability and systematically investigate their
mechanical properties. We find that these materials are metallic and
interestingly, they possess nodal lines in the low-energy band structure
surrounding the whole Brillouin zone, protected by nonsymmorphic crystal
symmetries in the absence of spin-orbit coupling (SOC). SOC opens small energy
gaps at the nodal line, except for two high-symmetry points, at which fourfold
degenerate 2D spin-orbit Dirac points are obtained. We show that these
topological band features are robust under uniaxial and biaxial strains, but
can be lifted by the shear strain. We also investigate the optical
conductivities of these materials, and show that the transformation of the band
structure under strain can be inferred from the optical absorption spectrum.
Our work reveals a new family of 2D topological metal materials with
interesting mechanical and electronic properties, which will facilitate the
study of nonsymmorphic symmetry enabled nodal features in 2D.",2004.08737v1
2020-12-22,Perovskite oxide heterojunction for Rashba-Dresselhaus assisted antiferromagnetic spintronics,"A major impediment towards realizing technologies based on the emerging
principles of antiferromagnetic spintronics is the shortage of suitable
materials. In this paper, we propose a design of polar|nonpolar
heterostructures of perovskite oxides, where a single unit cell of SrIrO3 is
sandwiched between a thin film of LaAlO3 and a substrate of SrTiO3. Our
calculations within the framework of density-functional theory + Hubbard U +
spin-orbit coupling reveal a two-dimensional conducting layer with electron and
hole pockets at the interface, exhibiting a strong anisotropic
Rashba-Dresselhaus effect along with noncollinear antiferromagnetism,
indicating the possibility of realizing a spin-orbit torque. An insightful
physical model for the anisotropic Rashba-Dresselhaus effect nicely interprets
our results, providing an estimate for the Rashba-Dresselhaus coefficients and
illustrating pseudospin orientation.We also observe a proximity-induced
prominent Rashba-like effect for Ti 3d empty bands. Our results suggest that
the heterostructure may possess the essential ingredients for antiferromagnetic
spintronics, deserving experimental verification.",2012.11868v1
2017-05-26,Zeeman and spin-orbit effects in the Andreev spectra of nanowire junctions,"We study the energy spectrum and the electromagnetic response of Andreev
bound states in short Josephson junctions made of semiconducting nanowires. We
focus on the joint effect of Zeeman and spin-orbit coupling on the Andreev
level spectra. Our model incorporates the penetration of the magnetic field in
the proximitized wires, which substantially modifies the spectra. We pay
special attention to the occurrence of fermion parity switches at increasing
values of the field and to the magnetic field dependence of the absorption
strength of microwave-induced transitions. Our calculations can be used to
extract quantitative information from microwave and tunneling spectroscopy
experiments, such as the recently reported measurements in Van Woerkom et al.,
arXiv:1609.00333.",1705.09671v2
2017-09-27,Sequential localization of a complex electron fluid,"Complex and correlated quantum systems with promise for new functionality
often involve entwined electronic degrees of freedom. In such materials, highly
unusual properties emerge and could be the result of electron localization.
Here, a cubic heavy fermion metal governed by spins and orbitals is chosen as a
model system for this physics. Its properties are found to originate from
surprisingly simple low-energy behavior, with two distinct localization
transitions driven by a single degree of freedom at a time. This result is
unexpected, but we are able to understand it by advancing the notion of
sequential destruction of an SU(4) spin-orbital-coupled Kondo entanglement. Our
results implicate electron localization as a unified framework for strongly
correlated materials and suggest ways to exploit multiple degrees of freedom
for quantum engineering.",1709.09376v3
2018-03-14,Dynamic polarizabilities and magic wavelengths of Sr$^+$ for focused vortex light,"A theory of dynamic polarizability for trapping relevant states of Sr$^+$ is
presented here when the ions interact with a focused optical vortex. The
coupling between the orbital and spin angular momentum of the optical vortex
varies with focusing angle of the beam and is studied in the calculation of the
magic wavelengths for $5s_{{1}/{2}}\rightarrow 4d_{{3}/{2}, {5}/{2}}$
transitions of Sr$^+$. The initial state of our interest here is $5s_{{1}/{2}}$
with $m_J = -1/2$ of which is different possible trapping state compare to our
recent work on Sr$^+$ [Phys. Rev. A \textbf{97}, 022511 (2018)]. We find
variation in magic wavelengths and the corresponding polarizabilities with
different combinations of orbital and spin angular momentum of the vortex beam.
The variation is very significant when the wavelengths of the beam are in the
infrared region of electromagnetic spectrum. The calculated magic wavelengths
will help the experimentalists to trap the ion for performing the high
precision spectroscopic measurements.",1803.05153v2
2018-06-13,Magnetic tilting and emergent Majorana spin connection in topological superconductors,"Due to the charge neutral and localized nature of surface Majorana modes,
detection schemes usually rely on local spectroscopy or interference through
the Josephson effect. Here, we theoretically study the magnetic response of a
two-dimensional cone of Majorana fermions localized at the surface of class
DIII Topological Superconductors. For a field parallel to the surface the
Zeeman term vanishes and the orbital term induces a Doppler shift of the
Andreev levels resulting in a tilting of the surface Majorana cone. For fields
larger than a critical threshold field $H^*$ the system undergoes a transition
from type I to type II Dirac-Majorana cone. In a spherical geometry the surface
curvature leads to the emergence of the Majorana spin connection in the tilting
term via an interplay between orbital and Zeeman, that generates a finite
non-trivial coupling between negative and positive energy states. Majorana
modes are thus expected to show a finite response to the applied field, that
acquires a universal character in finite geometries and opens the way to
detection of Majorana modes via time-dependent magnetic fields.",1806.05969v2
2018-06-25,Ferromagnetism above 1000 K in highly cation-ordered double-perovskite insulator Sr3OsO6,"Magnetic insulators have been intensively studied for over 100 years, and
they, in particular ferrites, are considered to be the cradle of magnetic
exchange interactions in solids. Their wide range of applications include
microwave devices and permanent magnets . They are also suitable for spintronic
devices owing to their high resistivity, low magnetic damping, and
spin-dependent tunneling probabilities. The Curie temperature is the crucial
factor determining the temperature range in which any ferri/ferromagnetic
system remains stable. However, the record Curie temperature has stood for over
eight decades in insulators and oxides (943 K for spinel ferrite LiFe5O8). Here
we show that a highly B-site ordered double-perovskite, Sr2(SrOs)O6 (Sr3OsO6),
surpasses this long standing Curie temperature record by more than 100 K. We
revealed this B-site ordering by atomic-resolution scanning transmission
electron microscopy. The density functional theory (DFT) calculations suggest
that the large spin-orbit coupling (SOC) of Os6+ 5d2 orbitals drives the system
toward a Jeff = 3/2 ferromagnetic (FM) insulating state. Moreover, the Sr3OsO6
is the first epitaxially grown osmate, which means it is highly compatible with
device fabrication processes and thus promising for spintronic applications.",1806.09308v1
2019-08-15,The nature of the two-peak structure in NiO valence band photoemission,"In spite of extensive studies on NiO and their accomplishments, the rich
physics still raises unsolved physical problems. In particular, the nature of
the two-peak structure in the valence band photoemission spectra is still
controversial. By using \textit{ab initio} LQSGW+DMFT, the two-peak structure
is shown to be driven by the concerted effect of antiferromagnetic ordering and
intersite electron hopping. Magnetic ordering in the Ni-$e_{g}$ orbitals splits
majority- and minority-spin Ni-$t_{2g}$ levels due to local Hund's coupling.
Strong hybridization between O-$p$ and Ni-$e_g$, a signature of the Zhang-Rice
bound state formation, boosts oxygen-mediated intersite Ni-$e_g$ orbital
hopping, resulting in the enhancement of majority-spin Ni $t_{2g}$-$e_{g}$
splitting. Interestingly, these two splittings of distinct physical origins
match and give rise to the observed two-peak structure in NiO. Our new
understanding should be useful in designing advanced devices based on the NiO
for the hole transport.",1908.05643v1
2019-08-22,Sensing the spin of an individual Ce adatom,"The magnetic moment of rare earth elements originates from electrons in the
partially filled 4f orbitals. Accessing this moment electrically by scanning
tunneling spectroscopy is hampered by shielding of outer-lying orbitals. Here
we show that we can detect the magnetic moment of an individual Ce atom
adsorbed on a Cu2N ultrathin film on Cu(100) by using a sensor tip that has its
apex functionalized with a Kondo screened spin system. We calibrate the sensor
tip by deliberately coupling it to a well characterized Fe atom. Subsequently,
we use the splitting of the tip's Kondo resonance when approaching a
spectroscopically dark Ce atom to sense its magnetic moment.",1908.08267v2
2019-11-04,Photovoltaic effect generated by spin-orbit interactions,"An AC electric field applied to a junction comprising two spin-orbit coupled
weak links connecting a quantum dot to two electronic terminals is proposed to
induce a DC current and to generate a voltage drop over the junction if it is a
part of an open circuit. This photovoltaic effect requires a junction in which
mirror reflection-symmetry is broken. Its origin lies in the different fashion
inelastic processes modify the reflection of electrons from the junction back
into the two terminals, which leads to uncompensated DC transport. The effect
can be detected by measuring the voltage drop that is built up due to that DC
current. This voltage is an even function of the frequency of the AC electric
field and is {\em not} related to quantum pumping.",1911.01168v3
2019-11-29,Multiorbital singlet pairing and $d+d$ superconductivity,"Recent experiments in multiband Fe-based and heavy-fermion superconductors
have challenged the long-held dichotomy between simple $s$- and $d$-wave
spin-singlet pairing states. Here, we advance several time-reversal-invariant
irreducible pairings that go beyond the standard singlet functions through a
matrix structure in the band/orbital space, and elucidate their naturalness in
multiband systems. We consider the $s\tau_{3}$ multiorbital superconducting
state for Fe-chalcogenide superconductors. This state, corresponding to a $d+d$
intra- and inter-band pairing, is shown to contrast with the more familiar $d
+\text{i}d$ state in a way analogous to how the B- triplet pairing phase of
\enhe superfluid differs from its A- phase counterpart. In addition, we
construct an analogue of the $s\tau_{3}$ pairing for the heavy-fermion
superconductor CeCu$_{2}$Si$_{2}$, using degrees-of-freedom that incorporate
spin-orbit coupling. Our results lead to the proposition that $d$-wave
superconductors in correlated multiband systems will generically have a
fully-gapped Fermi surface when they are examined at sufficiently low energies.",1911.13274v3
2019-12-20,Theory of Four-Wave Mixing of Cylindrical Vector Beams in Optical Fibers,"Cylindrical vector (CV) beams are a set of transverse spatial modes that
exhibit a cylindrically symmetric intensity profile and a variable polarization
about the beam axis. They are composed of a non-separable superposition of
orbital and spin angular momentum. Critically, CV beams are also the eigenmodes
of optical fiber and, as such, are of wide-spread practical importance in
photonics and have the potential to increase communications bandwidth through
spatial multiplexing. Here, we derive the coupled amplitude equations that
describe the four-wave mixing (FWM) of CV beams in optical fibers. These
equations allow us to determine the selection rules that govern the
interconversion of CV modes in FWM processes. With these selection rules, we
show that FWM conserves the total angular momentum, the sum of orbital and spin
angular momentum, in the conversion of two input photons to two output photons.
When applied to spontaneous four-wave mixing, the selection rules show that
photon pairs can be generated in CV modes directly and can be entangled in
those modes. Such quantum states of light in CV modes could benefit
technologies such as quantum key distribution with satellites.",1912.10109v1
2020-11-23,Spin-orbit-enhanced magnetic surface second-harmonic generation in Sr$_2$IrO$_4$,"An anomalous optical second-harmonic generation (SHG) signal was previously
reported in Sr$_2$IrO$_4$ and attributed to a hidden odd-parity bulk magnetic
state. Here we investigate the origin of this SHG signal using a combination of
bulk magnetic susceptibility, magnetic-field-dependent SHG rotational
anisotropy, and overlapping wide-field SHG imaging and atomic force microscopy
measurements. We find that the anomalous SHG signal exhibits a two-fold
rotational symmetry as a function of in-plane magnetic field orientation that
is associated with a crystallographic distortion. We also show a change in SHG
signal across step edges that tracks the bulk antiferromagnetic stacking
pattern. While we do not rule out the existence of hidden order in
Sr$_2$IrO$_4$, our results altogether show that the anomalous SHG signal in
parent Sr$_2$IrO$_4$ originates instead from a surface-magnetization-induced
electric-dipole process that is enhanced by strong spin-orbit coupling.",2011.11662v1
2021-04-05,Possible quadrupole order in tetragonal Ba2CdReO6 and chemical trend in the ground states of 5d1 double perovskites,"The synthesis and physical properties of the double perovskite (DP) compound
Ba2CdReO6 with the 5d1 electronic configuration are reported. Three successive
phases originating from a spin-orbit-entangled Jeff = 3/2 state, confirmed by
the reduced effective magnetic moment of 0.72 {\mu}B, were observed upon
cooling. X-ray diffraction measurements revealed a structural transition from a
high-temperature cubic structure to a low-temperature tetragonal structure at
Ts = 170 K, below which the Jeff = 3/2 state was preserved. Magnetization, heat
capacity, and thermal expansion measurements showed two more electronic
transitions to a possible quadrupole ordered state at Tq = 25 K, and an
antiferromagnetic order of dipoles accompanied by a ferromagnetic moment of ~
0.2 {\mu}B at Tm = 12 K. These properties were compared with those of the
sister compounds Ba2BReO6 (B = Mg, Zn, and Ca) and the chemical trend is
discussed in terms of the mean-field theory for spin-orbit-coupled 5d electrons
[G. Chen et al., Phys. Rev. B 82, 174440 (2010)]. The DP compound Ba2BReO6
provides a unique opportunity for a systematic investigation on symmetry
breaking in the presence of multipolar degrees of freedom.",2104.01833v1
2015-08-23,Asymmetric Magnon Excitation by Spontaneous Toroidal Ordering,"Effects of spontaneous toroidal ordering on magnetic excitation are
theoretically investigated for a localized spin model that includes a staggered
Dzyaloshinsky-Moriya interaction and anisotropic exchange interactions, which
arise from the antisymmetric spin-orbit coupling and the multi-orbital
correlation effect. We show that the model exhibits a Neel-type
antiferromagnetic order, which simultaneously accompanies a ferroic toroidal
order. We find that the occurrence of toroidal order modulates the magnon
dispersion in an asymmetric way with respect to the wave number: a toroidal
dipole order on the zigzag chain leads to a band-bottom shift, while a toroidal
octupole order on the honeycomb lattice gives rise to a valley splitting. These
asymmetric magnon excitations could be a source of unusual magnetic responses,
such as nonreciprocal magnon transport. A variety of modulations are discussed
while changing the lattice and magnetic symmetries. Implications of candidate
materials for asymmetric magnon excitations are presented.",1508.05627v2
2016-03-29,Energy-momentum mapping of d-derived Au(111) states in a thin film,"The quantum well states of a film can be used to sample the electronic
structure of the parent bulk material and determine its band parameters. We
highlight the benefits of two-dimensional film band mapping, with respect to
complex bulk analysis, in an angle-resolved photoemission spectroscopy study of
the 5d states of Au(111). Discrete 5d-derived quantum well states of various
orbital characters form in Au(111) films and span the width of the
corresponding bulk bands. For sufficiently thick films, the dispersion of these
states samples the bulk band edges, as confirmed by first-principles
calculations, thus providing the positions of the critical points of bulk Au in
agreement with previously determined values. In turn, this analysis identifies
several d-like surface states and resonances with large spin-splittings that
originate from the strong spin-orbit coupling of the Au 5d atomic levels.",1603.08879v1
2016-10-01,Spin-orbit-induced resonances and threshold anomalies in a reduced dimension Fermi gas,"We calculate the reflection and transmission probabilities in a
one-dimensional Fermi gas with an equal mixing of the Rashba and Dresselhaus
spin-orbit coupling (RD-SOC) produced by an external Raman laser field. These
probabilities are computed over multiple relevant energy ranges within the
pseudo-potential approximation. Strong scattering resonances are found whenever
the incident energy approaches either a scattering threshold or a quasi-bound
state attached to one of the energetically closed higher dispersion branches. A
striking difference is demonstrated between two very different regimes set by
the Raman laser intensity, namely between scattering for the single- minimum
dispersion versus the double-minimum dispersion at the lowest threshold. The
presence of RD-SOC together with the Raman field fundamentally changes the
scattering behavior and enables the realization of very different
one-dimensional theoretical models in a single experimental setup when combined
with a confinement-induced resonance.",1610.00190v2
2016-10-07,Symmetries and hybridization in the indirect interaction between magnetic moments in MoS$_{2}$ nanoflakes,"We study the Ruderman-Kittel-Kasuya-Yosida interaction between magnetic
impurities embedded in $p$-doped transition metal dichalcogenide triangular
flakes. The role of underlying symmetries is exposed by analyzing the
interaction as a function of impurity separation along zigzag and armchair
trajectories, in specific parts of the sample. The large spin-orbit coupling in
these materials produces strongly anisotropic interactions, including a
Dzyaloshinskii-Moriya component that can be sizable and tunable. We consider
impurities hybridized to different orbitals of the host transition-metal and
identify specific characteristics for onsite and hollow site adsorption. In the
onsite case, the different components of the interaction have similar
magnitude, while for the hollow site, the Ising component dominates. We also
study the dependence of the interaction with the level of hole doping, which
supplies a further degree of tunability. Our results could provide ways of
controlling helical long range spin order in magnetic impurity arrays embedded
in these materials.",1610.02142v2
2016-10-17,Tunable bandgap and spin-orbit coupling by composition control of MoS$_{2}$ and MoO$_{x}$ (X=2 and 3) compounds,"We report on composition controlled MoS$_{2}$ and MoO$_{x}$ (x=2 and 3)
compounds electrodeposited on Flourine dopped Tin Oxide (FTO) substrate. It was
observed that the relative content has systematic electrical and optical
changes for different thicknesses of layers ranging from $\approx$20 to 540 nm.
Optical and electrical bandgaps reveals a tuneable behavior by controlling the
relative content of compounds as well as a sharp transition from p to n-type of
semiconductivity. Moreover, spin-orbit interaction of Mo 3d doublet enhances by
reduction of MoO$_{3}$ content in thicker films. Our results convey path-way of
applying such compounds in optoelectronics and nanoelectronics devices.",1610.05110v1
2016-12-12,General technique for analytical derivatives of post-projected Hartree-Fock,"In electronic structure theory, the availability of analytical derivative is
one of the desired features for a method to be useful in practical
applications, as it allows for geometry optimization as well as computation of
molecular properties. With the recent advances in the development of
symmetry-projected Hartree-Fock (PHF) methods, we here aim at further
extensions by devising the analytic gradients of post-PHF approaches with a
special focus on spin-extended (spin-projected) configuration interaction with
single and double substitutions (ECISD). Just like standard single-reference
methods, the mean-field PHF part does not require the corresponding
coupled-perturbed equation to be solved, while the correlation energy term
needs the orbital relaxation effect to be accounted for, unless the underlying
molecular orbitals are variationally optimized in the presence of the
correlation energy. We present a general strategy for post-PHF analytical
gradients, which closely parallels that for single-reference methods, yet
addressing the major difference between them. The similarity between ECISD and
multi-reference CI not only in the energy but also in the optimized geometry is
clearly demonstrated by the numerical examples of ozone and cyclobutadiene.",1612.03521v2
2017-07-26,Long-range effect of a Zeeman field on the electric current through the helical metal-superconductor interface in Andreev interferometer,"It is shown that the spin-orbit and Zeeman interactions result in phase
shifts of Andreev-reflected holes in disordered topological insulator, or
normal Rashba spin-orbit-coupled wires, which are in a contact with an s-wave
superconductor. Due to interference of the holes reflected through different
paths in Andreev interferometer the electric current through the contact varies
depending on the strength and direction of the Zeeman field. It also depends on
mutual orientations of Zeeman fields in different shoulders of the
interferometer. Such a nonlocal effect is a result of the long-range coherency
caused by the superconducting proximity effect. This current has been
calculated within the semiclassical theory for Green functions of a dirty
system.",1707.08335v2
2018-10-05,Chirality-controlled spontaneous currents in spin-orbit coupled superconducting rings,"At a superconductor interface with a ferromagnetic insulator (FI), the FI
acts to induce a local exchange field within the S layer, which in the presence
of spin-orbit interaction promotes a phase modulated superconducting state.
Here we demonstrate that within a thin superconducting loop that is partially
proximitized by a FI, spontaneous currents form with a
magnetization-orientation-dependent chirality with sizable shifts in
Little-Parks oscillations. Furthermore, the critical temperature of the loop is
also magnetization-orientation-dependent and conversely, the superconducting
transition itself may influence the magnetization direction. More generally,
the superconducting region above the FI may serve as a phase battery and so
offer a new device concept for superconducting spintronics.",1810.02696v1
2019-05-22,The fine structure of the neutral nitrogen-vacancy center in diamond,"The nitrogen-vacancy (NV) center in diamond is a widely-utilized system due
to its useful quantum properties. Almost all research focuses on the negative
charge state (NV$^-$) and comparatively little is understood about the neutral
charge state (NV$^0$). This is surprising as the charge state often fluctuates
between NV$^0$, and NV$^-$, during measurements. There are potentially under
utilized technical applications that could take advantage of NV$^0$, either by
improving the performance of NV$^-$, or utilizing NV$^0$, directly. However,
the fine-structure of NV$^0$, has not been observed. Here, we rectify this lack
of knowledge by performing magnetic circular dichroism (MCD) measurements that
quantitatively determine the fine-structure of NV$^0$. The observed behavior is
accurately described by spin-Hamiltonians in the ground and excited states with
the ground state yielding a spin-orbit coupling of $\lambda = 2.24 \pm 0.05$
GHz and a orbital $g-$factor of $0.0186 \pm 0.0005$. The reasons why this
fine-structure has not been previously measured are discussed and
strain-broadening is concluded to be the likely reason",1905.09037v1
2019-06-18,"Evidence for bulk nodal loops and universality of Dirac-node arc surface states in ZrGeXc (Xc = S, Se, Te)","We have performed angle-resolved photoemission spectroscopy (ARPES) on
layered ternary compounds ZrGeXc (Xc = S, Se, and Te) with square Ge lattices.
ARPES measurements with bulk-sensitive soft-x-ray photons revealed a
quasi-two-dimensional bulk-band structure with the bulk nodal loops protected
by glide mirror symmetry of the crystal lattice. Moreover, high-resolution
ARPES measurements near the Fermi level with vacuum-ultraviolet photons
combined with first-principles band-structure calculations elucidated a
Dirac-node-arc surface state traversing a tiny spin-orbit gap associated with
the nodal loops. We found that this surface state commonly exists in ZrGeXc
despite the difference in the shape of nodal loops. The present results suggest
that the spin-orbit coupling and the multiple nodal loops cooperatively play a
key role in creating the exotic Dirac-node-arc surface states in this class of
topological line-node semimetals.",1906.07406v1
2019-06-25,Tunneling spectroscopy of localized states of $\mathrm{WS}_2$ barriers in vertical van der Waals heterostructures,"In transition metal dichalcogenides, defects have been found to play an
important role, affecting doping, spin-valley relaxation dynamics, and
assisting in proximity effects of spin-orbit coupling. Here, we study localized
states in $\mathrm{WS}_2$ and how they affect tunneling through van der Waals
heterostructures of h-BN/graphene/$\mathrm{WS}_2$/metal. The obtained
conductance maps as a function of bias and gate voltage reveal single-electron
transistor behavior (Coulomb blockade) with a rich set of transport features
including excited states and negative differential resistance regimes. Applying
a perpendicular magnetic field, we observe a shift in the energies of the
quantum levels and information about the orbital magnetic moment of the
localized states is extracted.",1906.10389v1
2020-03-11,Signatures of Hundness in Kagome Metals,"By means of the density functional theory in combination with the dynamical
mean-field theory, we tried to examine the electronic structure of hexagonal
FeGe, in which the Fe atoms form a quasi-2D layered Kagome lattice. We predict
that it is a representative Kagome metal characterized by orbital selective
Dirac fermions and extremely flat bands. Furthermore, Fe's 3$d$ electrons are
strongly correlated. They exhibit quite apparent signatures of electronic
correlation induced by Hund's rule coupling, such as sizable differentiation in
band renormalization, non-Fermi-liquid behavior, spin-freezing state, and
spin-orbital separation. Thus, FeGe can be regarded as an ideal platform to
study the interplay of Kagome physics and Hundness. 5",2003.05301v1
2020-03-27,Perspective: Strongly correlated and topological states in [111] grown transition metal oxide thin films and heterostructures,"We highlight recent advances in the theory, materials fabrication, and
experimental characterization of strongly correlated and topological states in
[111] oriented transition metal oxide thin films and heterostructures, which
are notoriously difficult to realize compared to their [001] oriented
counterparts. We focus on two classes of complex oxides, with the chemical
formula ABO3 and A2B2O7, where the B sites are occupied by an open-shell
transition metal ion with a local moment, and the A sites are typically a rare
earth. The [111] oriented quasi-two-dimensional lattices derived from these
parent compound lattices can exhibit peculiar geometries and symmetries,
namely, a buckled honeycomb lattice, as well as kagome and triangular lattices.
These lattice motifs form the basis for emergent strongly correlated and
topological states expressed in exotic magnetism, various forms of orbital
ordering, topological insulators, topological semimetals, quantum anomalous
Hall insulators, and quantum spin liquids. For transition metal ions with high
atomic number, spin-orbit coupling plays a significant role and may give rise
to additional topological features in the electronic band structure and in the
spectrum of magnetic excitations. We conclude the Perspective by articulating
open challenges and opportunities in this actively developing field.",2003.12211v1
2020-09-23,Kondo effects in small bandgap carbon nanotube quantum dots,"We study magnetoconductance of the small bandgap carbon nanotube quantum dots
in the presence of spin-orbit coupling in the strong correlations regime. The
finite-U mean field slave boson approach is used to study many-body effects.
Different degeneracies are restored in magnetic field and Kondo effects of
different symmetries arise including SU(3) effects of different types. Full
spin-orbital degeneracy might be recovered for zero field and correspondingly
SU(4) Kondo effect sets in. We point out on the possibility of the occurrence
of electron-hole Kondo effects in slanting magnetic fields, which we predict
will occur in the available magnetic fields for orientation of fields close to
perpendicular. When the field approaches transverse orientation a crossover
from SU(2) or SU(3) symmetry into SU(4) is observed.",2009.11052v1
2021-02-11,Phase transitions in superconductor/ferromagnet bilayer driven by spontaneous supercurrents,"We investigate superconducting phase transition in
superconductor(S)/ferromagnet(F) bilayer with Rasba spin-orbit interaction at
S/F interface. This spin-orbit coupling produces spontaneous supercurrents
flowing inside the atomic-thickness region near the interface, which are
compensated by the screening Meissner currents [S. Mironov and A. Buzdin, Phys.
Rev. Lett \textbf{118}, 077001 (2017)]. In the case of thin superconducting
film the emergence of the spontaneous surface currents causes the increase of
the superconducting critical temperature and we calculate the actual value of
the critical temperature shift. We also show that in the case of type-I
superconducting film this phase transition can be of the first order. In the
external magnetic field the critical temperature depends on the relative
orientation of the external magnetic field and the exchange field in the
ferromagnet. Also we predict the in-plane anisotropy of the critical current
which may open an alternative way for the experimental observation of the
spontaneous supercurrents generated by the SOC.",2102.05885v1
2021-07-01,Impact of the valley orbit coupling on exchange gate for spin qubits in silicon quantum dots,"The presence of degenerate conduction band valleys and how they are mixed by
interfaces play critical roles in determining electron interaction and spectrum
in a silicon nanostructure. Here we investigate how the valley phases affect
the exchange interaction in a symmetric two-electron silicon double quantum
dot. Through a configuration interaction calculation, we find that exchange
splitting is suppressed at a finite value of valley phase difference between
the two dots, and reaches its minimum value ({\sim} 0) when the phase
difference is {\pi}. Such a suppression can be explained using the Hubbard
model, through the valley-phase-dependent dressing by the doubly occupied
states on the ground singlet and triplet states. The contributions of the
higher orbital states also play a vital role in determining the value of the
exchange energy in general, which is a crucial parameter for applications such
as exchange gates for spin qubits.",2107.00732v1
2021-07-05,Identifying intrinsic and extrinsic mechanisms of anisotropic magnetoresistance with terahertz probes,"Identifying the intrinsic and extrinsic origins of magneto-transport in
spin-orbit coupled systems has long been a central theme in condensed matter
physics. However, it has been elusive owing to the lack of an appropriate
experimental tool. In this work, using terahertz time-domain spectroscopy, we
unambiguously disentangle the intrinsic and extrinsic contributions to the
anisotropic magnetoresistance (AMR) of a permalloy film. We find that the
scattering-independent intrinsic contribution to AMR is sizable and is as large
as the scattering-dependent extrinsic contribution to AMR. Moreover, the
portion of intrinsic contribution to total AMR increases with increasing
temperature due to the reduction of extrinsic contribution. Further
investigation reveals that the reduction of extrinsic contribution is caused by
the phonon/magnon-induced negative AMR. Our result will stimulate further
researches on other spin-orbit-interaction-induced phenomena for which
identifying the intrinsic and extrinsic contributions is important.",2107.01770v1
2021-08-26,Fully linear band crossings at high symmetry points in layers: classification and role of spin-orbit coupling and time reversal,"All of 320 layer groups, distributed into 80 clusters - single/double
ordinary/gray groups - are used to complete systematization of linear (in all
directions) band crossings and corresponding effective Hamiltonians in
high-symmetry Brillouin zone points of layered materials, refining and
expanding in literature existing data. Two- and four-dimensional effective
Hamiltonians are determined by the allowed (half)integer (co)representations of
the same dimension in the crossing point and one- or two-dimensional generic
allowed representations. The resulting dispersion types (having isotropic or
anisotropic form) are: single cone (with double degenerate crossing point and
non-degenerate branches, or 4-fold degenerate crossing point with double
degenerate conical branches), poppy-flower (4-fold degenerate crossing point
with two pairs of non-degenerate mutually rotated conical branches), and a
fortune teller (with nodal lines). Transition to double group, enabling to
include spin-orbit interaction, results in various scenarios at high symmetry
points: gap closing, gap opening, cone preserving, cone splitting etc.
Analogously, analyzing ordinary to gray group transitions, the role of time
reversal symmetry is clarified.",2108.11733v1
2021-09-08,Spiraling light: from donut modes to a Magnus effect analogy,"The insight that optical vortex beams carry orbital angular momentum (OAM),
which emerged in Leiden about 30 years ago, has since led to an ever expanding
range of applications and follow-up studies. This paper starts with a short
personal account of how these concepts arose. This is followed by a description
of some recent ideas where the coupling of transverse orbital and spin angular
momentum (SAM) in tightly focused laser beams produces interesting new effects.
The deflection of a focused light beam by an atom in the focus is reminiscent
of the Magnus effect known from aerodynamics. Momentum conservation dictates an
accompanying light force on the atom, transverse to the optical axis. As a
consequence, an atom held in an optical tweezer will be trapped at a small
distance of up to $\lambda/2\pi$ away from the optical axis, which depends on
the spin state of the atom and the magnetic field direction. This opens up new
avenues to control the state of motion of atoms in optical tweezers as well as
potential applications in quantum gates and interferometry.",2109.03937v2
2021-09-20,Giant anomalous Nernst signal in the antiferromagnet YbMnBi2,"Searching for a high anomalous Nernst effect (ANE) is crucial for
thermoelectric energy conversion applications because the associated unique
transverse geometry facilitates module fabrication. Topological ferromagnets
with large Berry curvatures show high ANEs; however, they face drawbacks such
as strong magnetic disturbances and low mobility due to high magnetization.
Herein, we demonstrate that YbMnBi2, a canted antiferromagnet, has a large ANE
conductivity of ~10 Am-1K-1 that surpasses the common high values (i.e. 3-5
Am-1K-1) observed so far in ferromagnets. The canted spin structure of Mn
guarantees a nonzero Berry curvature but generates only a weak magnetization
three orders of magnitude lower than that of general ferromagnets. The heavy Bi
with a large spin-orbit coupling enables a high ANE and low thermal
conductivity, whereas its highly dispersive px/y orbitals ensure low
resistivity. The high anomalous transverse thermoelectric performance and
extremely small magnetization makes YbMnBi2 an excellent candidate for
transverse thermoelectrics.",2109.09382v1
2021-12-13,Flat Magic Window,"Magic windows (or mirrors) consist of optical devices with a surface
deformation or thickness distribution devised in such a way to form a desired
image. The associated image intensity distribution has been shown to be related
to the Laplacian of the height of the surface relief. We experimentally realize
such devices with flat optics employing optical spin-to-orbital angular
momentum coupling, which represent a new paradigm for light manipulation. The
desired pattern and experimental specifications for designing the flat optics
was implemented with a re-configurable spatial light modulator which acted as
the magic mirror. The flat plate, optical spin-to-orbital angular momentum
coupler, is then fabricated by spatially structuring nematic liquid crystals.
The plate is used to demonstrate the concept of a polarization-switchable magic
window, where, depending on the input circular polarization handedness, one can
display either the desired image or the image resulting from the negative of
the window's phase.",2112.07053v1
2022-01-25,"Topological $p_z$-wave nodal-line superconductivity with flat surface bands in the AH$_{x}$Cr${_3}$As${_3}$ (A=Na, K, Rb, Cs) superconductors","We study the pairing symmetry and the topological properties of the
hydrogen-doped ACr$_3$As$_3$ superconductors. Based on our first-principle band
structure with spin-orbit-coupling (SOC), we construct tight binding model
including the on-site SOC terms, equipped with the multi-orbital Hubbard
interactions. Then using the random-phase-approximation (RPA) approach, we
calculate the pairing phase diagram of this model. Our RPA results yield the
triplet pz-wave pairing in the
($\left(\uparrow\downarrow+\downarrow\uparrow\right)$) spin channel to be the
leading pairing symmetry all over the experiment relevant hydrogen-doping
regimes. This pairing state belongs to the spin-U(1)-symmetry protected
time-reversal-invariant topological nodal-line superconductivity. Determined by
the momentum-dependent topological invariant Z (kx; ky), the whole (001)
surface Brillouin zone is covered with topological flat bands with different
regimes covered with different numbers of flat surface bands, which can be
detected by the scanning tunneling microscope experiments.",2201.10089v1
2022-06-08,SmI3: 4f5 honeycomb magnet with spin-orbital entangled Γ7 Kramers doublet,"We report magnetic properties of a 4f-honeycomb iodide SmI3 made up of
edge-shared network of SmI6 octahedra. High temperature magnetic susceptibility
indicates {\Gamma}7 Kramers doublet ground state of Sm3+ (4f5) ions stabilized
by the spin-orbit coupling and octahedral crystal electric field, which
interact with Sm-I-Sm bond angle nearly 90 degree. Magnetization measurements
down to 0.1 K detected antiferromagnetic correlations and an anomaly in the
magnetization curve before saturation without a sign of long-range order.
Relevance between SmI3 and the antiferromagnetic Kitaev material proposed in
the 4f-electron system is discussed.",2206.03628v1
2022-07-06,Study of excited electronic states of the $^{39}$KCs molecule correlated with the K($4^2$S)+Cs($5^2$D) asymptote: experiment and theory,"Using the polarisation labelling spectroscopy, we performed the detailed
analysis of the level structure of excited electronic states of the $^{39}$KCs
molecule in the excitation energy interval between 17500~cm$^{-1}$ and
18600~cm$^{-1}$ above the $v=0$ level of the $X^1\Sigma^+$ ground state. We
prove that the observed states are strongly coupled by spin-orbit interaction
above 18200~cm$^{-1}$, as manifested by numerous perturbations in the recorded
spectra. The spectra are interpreted with the guidance of accurate electronic
structure calculations on KCs, including potential energy curves, transition
electric dipole moments, and representation of the spin-orbit interaction with
a quasi-diabatic effective Hamiltonian approach. The agreement between theory
and experiment is found remarkable, clearly discriminating among the available
theoretical data. This study confirms the accuracy of the polarisation
labelling spectroscopy to analyse highly-excited electronic molecular states
which present a dense level structure.",2207.02484v1
2022-07-12,Twistronics of Janus transition metal dichalcogenide bilayers,"Twisted multilayers of two-dimensional (2D) materials are an increasingly
important platform for investigating quantum phases of matter, and in
particular, strongly correlated electrons. The moir\'e pattern introduced by
the relative twist between layers creates effective potentials of
long-wavelength, leading to electron localization. However, in contrast to the
abundance of 2D materials, few twisted heterostructures have been studied until
now. Here we develop a first-principle continuum theory to study the electronic
bands introduced by moire patterns of twisted Janus transition metal
dichalcogenides (TMD) homo- and hetero-bilayers. The model includes lattice
relaxation, stacking-dependent effective mass, and Rashba spin-orbit coupling.
We then perform a high-throughput generation and characterization of
DFT-extracted continuum models for more than a hundred possible combinations of
materials and stackings. Our model predicts that the moir\'e physics and
emergent symmetries depend on chemical composition, vertical layer orientation,
and twist angle, so that the minibands wavefunctions can form triangular,
honeycomb, and Kagome networks. Rashba spin-orbit effects, peculiar of these
systems, can dominate the moir\'e bandwidth at small angles. Our work enables
the detailed investigation of Janus twisted heterostructures, allowing the
discovery and control of novel electronic phenomena.",2207.05788v2
2022-07-15,Band splitting induced Berry flux and intrinsic anomalous Hall conductivity in NiCoMnGa quaternary Heusler compound,"The anomalous transport properties of Heusler compounds become a hotspot of
research in recent years due to their unique band structure and possible
application in spintronics. In this paper, we report the anomalous Hall effect
in polycrystalline NiCoMnGa quaternary Heusler compound by experimental means
and theoretical calculations. The experimental anomalous Hall conductivity
(AHC) was found at about 256 S/cm at 10K with an intrinsic contribution of ~
121 S/cm. The analysis of Hall data reveals the presence of both extrinsic and
intrinsic contributions in AHE. Our theoretical calculations show that a pair
of spin-orbit coupled band formed by the band splitting due to spin-orbit
interaction (SOI) at the Fermi level produces a finite Berry flux in the system
that provides the intrinsic AHC about 100 S/cm, which is in good agreement with
the experiment.",2207.07313v1
2022-11-14,A computational method to estimate spin-orbital interaction strength in solid state systems,"Spin-orbit coupling (SOC) drives interesting and non-trivial phenomena in
solid state physics, ranging from topological to magnetic to transport
properties. Thorough study of such phenomena often require effective models
where SOC term is explicitly included. However, estimation of SOC strength for
such models mostly depend on the spectroscopy experiments which can only
provide a rough estimate. In this work, we provide a simple yet effective
computational approach to estimate the on-site SOC strength using a combination
of the $ab$ $initio$ and tight-binding calculations. We demonstrate the wider
applicability and high sensitivity of our method considering materials with
varying SOC strengths and the number of SOC active ions. The estimated SOC
strengths agree well with the proposed values in literature lending support to
our methodology. This simplistic approach can readily be applied to a wide
range of materials.",2211.07256v1
2023-07-12,Giant non-volatile electric field control of proximity induced magnetism in the spin-orbit semimetal SrIrO3,"With its potential for drastically reduced operation power of information
processing devices, electric field control of magnetism has generated huge
research interest. Recently, novel perspectives offered by the inherently large
spin-orbit coupling of 5d transition metals have emerged. Here, we demonstrate
non-volatile electrical control of the proximity induced magnetism in SrIrO3
based back-gated heterostructures. We report up to a 700 % variation of the
anomalous Hall conductivity {\sigma}_AHE and Hall angle {\theta}_AHE as
function of the applied gate voltage Vg. In contrast, the Curie temperature TC
= 100K and magnetic anisotropy of the system remain essentially unaffected by
Vg indicating a robust ferromagnetic state in SrIrO3 which strongly hints to
gating-induced changes of the anomalous Berry curvature. The electric-field
induced ferroelectric-like state of SrTiO3 enables non-volatile switching
behavior of {\sigma}_AHE and {\theta}_AHE below 60 K. The large tunability of
this system, opens new avenues towards efficient electric-field manipulation of
magnetism.",2307.06064v2
2023-07-27,Topological superconductivity with large Chern numbers in a ferromagnetic metal-superconductor heterostructure,"The ferromagnetic metal-superconductor heterostructure with interface Rashba
spin-orbit hopping is a promising candidate for topological superconductivity.
We study the interplay between the interface Rashba hopping and the intrinsic
Dresselhaus spin-orbit coupling in this heterostructure, and demonstrate rich
topological phases with five distinct Chern numbers. In particular, we find a
topological state with a Chern number as large as four in the parameter space
of the heterostructure. We calculate the Berry curvatures that construct the
Chern numbers, and show that these Berry curvatures induce anomalous thermal
Hall transport of the superconducting quasiparticles. We reveal chiral edge
states in the topological phases, as well as helical edge states in the trivial
phase, and show that the wave functions of these edge states mostly concentrate
on the ferrometal layer of the heterostructure.",2307.14838v2
2023-09-16,Anisotropy of Antiferromagnetic Domains in a Spin-orbit Mott Insulator,"The temperature-dependent behavior of magnetic domains plays an essential
role in the magnetic properties of materials, leading to widespread
applications. However, experimental methods to access the three-dimensional
(3D) magnetic domain structures are very limited, especially for
antiferromagnets. Over the past decades, the spin-orbit Mott insulator iridate
$Sr_2IrO_4$ has attracted particular attention because of its interesting
magnetic structure and analogy to superconducting cuprates. Here, we apply
resonant x-ray magnetic Bragg coherent diffraction imaging to track the
real-space 3D evolution of antiferromagnetic ordering inside a $Sr_2IrO_4$
single crystal as a function of temperature, finding that the antiferromagnetic
domain shows anisotropic changes. The anisotropy of the domain shape reveals
the underlying anisotropy of the antiferromagnetic coupling strength within
$Sr_2IrO_4$. These results demonstrate the high potential significance of 3D
domain imaging in magnetism research.",2309.09091v1
2023-09-27,Enhancing the Josephson diode effect with Majorana bound states,"We consider phase-biased Josephson junctions with spin-orbit coupling under
external magnetic fields and study the emergence of the Josephson diode effect
in the presence of Majorana bound states. We show that junctions having middle
regions with Zeeman fields along the spin-orbit axis develop a low-energy
Andreev spectrum that is asymmetric with respect to the superconducting phase
difference $\phi=\pi$, which is strongly influenced by Majorana bound states in
the topological phase. This asymmetric Andreev spectrum gives rise to anomalous
current-phase curves and critical currents that are different for positive and
negative supercurrents, thus signaling the emergence of the Josephson diode
effect. While this effect exists even in the trivial phase, it gets enhanced in
the topological phase due to the spatial nonlocality of Majorana bound states.
Our work thus establishes the utilization of topological superconductivity for
enhancing the functionalities of Josephson diodes.",2309.15567v2
2023-10-23,The role of spin-orbit interaction in low thermal conductivity of Mg$_3$Bi$_2$,"Three-dimensional layered Mg$_3$Bi$_2$ has emerged as thermoelectric material
due to its high cooling performance at ambient temperature, which benefits from
its low lattice thermal conductivity and semimetal character. However, the
semimetal character of Mg$_3$Bi$_2$ is sensitive to spin-orbit coupling (SOC).
Thus, the underlying origin of low lattice thermal conductivity needs to be
clarified in the presence of the SOC. In this work, the first-principles
calculations within the two-channel model are employed to investigate the
effects of the SOC on the phonon-phonon scattering on the phonon transport of
Mg$_3$Bi$_2$. Our results show that the SOC strongly reduces the lattice
thermal conductivity (up to $\sim 35$ %). This reduction originates from the
influence of the SOC on the transverse acoustic modes involving interlayer
shearing, leading to weak interlayer bonding and enhancement anharmonicity
around 50 cm$^{-1}$. Our results clarify the mechanism of low thermal
conductivity in Mg$_3$Bi$_2$ and support the design of Mg$_3$Bi$_2$-based
materials for thermoelectric applications.",2310.14639v1
2023-11-16,Enhanced opposite Imbert-Fedorov shifts of vortex beams for precise sensing of temperature and thickness,"Imbert-Fedorov (IF) shift, which refers to a tiny transverse splitting
induced by spin-orbit interaction at a reflection/refraction interface, is
sensitive to the refractive index of a medium and momentum state of incident
light. Most of studies have focused on the shift for an incident light beam
with a spin angular momentum (SAM) i.e., circular polarization. Compared to
SAM, orbital angular momentum (OAM) has infinite dimensions in theory as a new
degree of freedom of light and plays an important role in light-matter
coupling. We demonstrate experimentally that the relative IF shifts of vortex
beams with large opposite OAMs are highly enhanced in resonant structures when
light refracts through a double-prism structure (DPS), in which the thickness
and temperature of the air gap are precisely sensed via the observed relative
IF shifts. The thickness and temperature sensitivities increase as the absolute
value of opposite OAMs increases. Our results offer a technological and
practical platform for applications in sensing of thickness and temperature,
ingredients of environment gas, spatial displacement, chemical substances and
deformation structure.",2311.09673v1
2023-12-27,Universal orbital and magnetic structures in infinite-layer nickelates,"We conducted a comparative study of the rare-earth infinite-layer nickelates
films, RNiO2 (R = La, Pr, and Nd) using resonant inelastic X-ray scattering
(RIXS). We found that the gross features of the orbital configurations are
essentially the same, with minor variations in the detailed hybridization. For
low-energy excitations, we unambiguously confirm the presence of damped
magnetic excitations in all three compounds. By fitting to a linear spin-wave
theory, comparable spin exchange coupling strengths and damping coefficients
are extracted, indicating a universal magnetic structure in the infinite-layer
nickelates. Interestingly, while signatures of a charge order are observed in
LaNiO2 in the quasi-elastic region of the RIXS spectrum, it is absent in NdNiO2
and PrNiO2. This prompts further investigation into the universality and the
origins of charge order within the infinite-layer inickelates.",2312.16444v1
2024-01-04,Emergent transverse-field Ising model in $\boldsymbol{d}^\mathbf{4}$ spin-orbit Mott insulators,"Mott-insulating transition metal oxides containing $t_{2g}^4$ ions with
strong spin-orbit coupling were recently demonstrated to display unusual
magnetism due to a dynamical mixing of the low-energy multiplet states via
exchange processes. Here we derive exchange interactions in the situation where
a tetragonal or trigonal crystal field selects a single relevant excited state
on top of the singlet ionic ground state, producing an effective
spin-$\frac12$. We show that these moments universally obey antiferromagnetic
transverse-field Ising model (TFIM) with an intrinsic transverse field
generated by the splitting of the two ionic singlets. Using Ru$^{4+}$ as a
example ion, we provide quantitative estimates of the exchange and illustrate
the emergent TFIM physics based on phase diagrams and excitation spectra
obtained for several 2D lattices - square, honeycomb, as well as for the
frustrated triangular lattice.",2401.02532v1
2024-02-01,Gate-tunable Josephson diode effect in Rashba spin-orbit coupled quantum dot junctions,"We theoretically explore Josephson diode effect (JDE) in
superconductor/quantum dot (QD)/superconductor junctions in the presence of a
magnetic field and Rashba spin-orbit interaction (RSOI). We calculate the
Josephson current in our QD junction using Keldysh non-equilibrium Green's
function technique. We show that RSOI can induce JDE in our junction without
any magnetic field. However, the rectification coefficient (RC) of our QD based
Josephson diode (JD) is amplified when both are present. Interestingly, the
sign and magnitude of the RC are highly controllable by the magnetic field and
RSOI. For realistic RSOI strength in the presence of magnetic field and
chirality, the RC can be tuned to be as high as $70\%$ by an external gate
potential, indicating a giant JDE in our QD junction. Our proposed QD based JD
may serve as a potential superconducting device component.",2402.00817v1
2024-03-04,Spectroscopic investigations on trivalent ruthenium ions in ruthenium perovskite oxide thin films,"The $d^5$ electron configurations under the crystal field, spin-orbit
coupling, and Coulomb interaction give rise to a plethora of profound ground
states. Ruthenium perovskite oxides exhibit a number of unconventional
properties yet the Ru$^{4+}$ state ($4d^4$) is usually stable in these
materials. In this regard, Ru$^{3+}$ ions in perovskite materials are expected
to be a mesmerising playground of $4d^5$ electron configurations. Here, we
report measurements of x-ray photoemission spectroscopy on recently synthesized
perovskite ruthenium oxide thin films, LaRuO$_3$ and NdRuO$_3$, whose valence
state of the ruthenium ions is trivalent. We discuss correlation and spin-orbit
effects from the valence-band spectra, in particular an additional peak
structure around 3-5 eV, reminiscent of the so-called 3 eV peak observed in
Sr$_2$RuO$_4$. Moreover, we find that the core-level spectra of these materials
are quantitatively different from those in other ruthenates which possess
Ru$^{4+}$ ions, e.g., SrRuO$_3$. We therefore argue that the core level spectra
of LaRuO$_3$ and NdRuO$_3$ are peculiar to the Ru$^{3+}$ states.",2403.01853v1
2024-03-14,Kitaev physics in the two-dimensional magnet NiPSe$_3$,"The Kitaev interaction, found in candidate materials such as
$\alpha$-RuCl$_3$, occurs through the metal ($M$)-ligand ($X$)-metal ($M$)
paths of the edge-sharing octahedra because the large spin-orbit coupling (SOC)
on the metal atoms activates directional spin interactions. Here, we show that
even in $3d$ transition-metal compounds, where the SOC of the metal atom is
negligible, heavy ligands can induce bond-dependent Kitaev interactions. In
this work, we take as an example the $3d$ transition-metal chalcogenophosphate
NiPSe$_3$ and show that the key is found in the presence of a sizable SOC on
the Se $p$ orbital, one which mediates the super-exchange between the
nearest-neighbor Ni sites. Our study provides a pathway for engineering
enhanced Kitaev interactions through the interplay of SOC strength, lattice
distortions, and chemical substitutions.",2403.09831v1
2024-04-01,Electrical-controllable antiferromagnet-based tunnel junction,"Electrical-controllable antiferromagnet tunnel junction is a key goal in
spintronics, holding immense promise for ultra-dense and ultra-stable
antiferromagnetic memory with high processing speed for modern information
technology. Here, we have advanced towards this goal by achieving an
electrical-controllable antiferromagnet-based tunnel junction of
Pt/Co/Pt/Co/IrMn/MgO/Pt. The exchange coupling between antiferromagnetic IrMn
and Co/Pt perpendicular magnetic multilayers results in the formation of
interfacial exchange bias and exchange spring in IrMn. Encoding information
states 0 and 1 is realized through the exchange spring in IrMn, which can be
electrically written by spin-orbit torque switching with high cyclability and
electrically read by antiferromagnetic tunneling anisotropic magnetoresistance.
Combining spin-orbit torque switching of both exchange spring andexchange bias,
16 Boolean logic operation is successfully demonstrated. With both memory and
logic functionalities integrated into our electrical-controllable
antiferromagnetic-based tunnel junction, we chart the course toward
high-performance antiferromagnetic logic-in-memory.",2404.01144v1
2000-07-28,Orbital and spin Kondo effects in a double quantum dot,"Motivated by recent experiments, in which the Kondo effect has been observed
for the first time in a double quantum-dot structure, we study electron
transport through a system consisting of two ultrasmall, capacitively-coupled
dots with large level spacing and charging energy. Due to strong interdot
Coulomb correlations, the Kondo effect has two possible sources, the spin and
orbital degeneracies, and it is maximized when both occur simultaneously. The
large number of tunable parameters allows a range of manipulations of the Kondo
physics -- in particular, the Kondo effect in each dot is sensitive to changes
in the state of the other dot. For a thorough account of the system dynamics,
the linear and nonlinear conductance is calculated in perturbative and
non-perturbative approaches. In addition, the temperature dependence of the
resonant peak heights is evaluated in the framework of a renormalization group
analysis.",0007469v1
2003-06-20,Manganites at Quarter Filling: Role of Jahn-Teller Interactions,"We have analyzed different correlation functions in a realistic spin-orbital
model for half-doped manganites. Using a finite-temperature diagonalization
technique the CE phase was found in the charge-ordered phase in the case of
small antiferromagnetic interactions between $t_{2g}$ electrons. It is shown
that a key ingredient responsible for stabilization of the CE-type spin and
orbital-ordered state is the cooperative Jahn-Teller (JT) interaction between
next-nearest Mn$^{+3}$ neighbors mediated by the breathing mode distortion of
Mn$^{+4}$ octahedra and displacements of Mn$^{+4}$ ions. The topological phase
factor in the Mn-Mn hopping leading to gap formation in one-dimensional models
for the CE phase as well as the nearest neighbor JT coupling are not able to
produce the zigzag chains typical for the CE phase in our model.",0306532v2
2004-10-29,Level structure and spin-orbit effects in semiconductor nanorod dots,"We investigate theoretically how the spin-orbit Dresselhaus and Rashba
effects influence the electronic structure of quasi-one-dimensional
semiconductor quantum dots, similar to those that can be formed inside
semiconductor nanorods. We calculate electronic energy levels, eigen-functions,
and effective g-factors for coupled, double dots made out of different
materials, especially GaAs and InSb. We show that by choosing the form of the
lateral confinement, the contributions of the Dresselhaus and Rashba terms can
be tuned and suppressed, and we consider several possible cases of interest. We
also study how, by varying the parameters of the double-well confinement in the
longitudinal direction, the effective g-factor can be controlled to a large
extent.",0411003v1
2001-08-14,GRECP/5e-MRD-CI calculation of the electronic structure of PbH,"The correlation calculation of the electronic structure of PbH is carried out
with the Generalized Relativistic Effective Core Potential (GRECP) and
MultiReference single- and Double-excitation Configuration Interaction (MRD-CI)
methods. The 22-electron GRECP for Pb is used and the outer core 5s, 5p and 5d
pseudospinors are frozen using the level-shift technique, so only five external
electrons of PbH are correlated. A new configuration selection scheme with
respect to the relativistic multireference states is employed in the framework
of the MRD-CI method. The [6,4,3,2] correlation spin-orbit basis set is
optimized in the coupled cluster calculations on the Pb atom using a recently
proposed procedure, in which functions in the spin-orbital basis set are
generated from calculations of different ionic states of the Pb atom and those
functions are considered optimal which provide the stationary point for some
energy functional. Spectroscopic constants for the two lowest-lying electronic
states of PbH ($^2\Pi_{1/2}, ^2\Pi_{3/2}$) are found to be in good agreement
with the experimental data.",0108021v1
2008-08-12,Anisotropy and Magnetism in the LSDA+U Method,"Consequences of anisotropy (variation of orbital occupation) and magnetism,
and their coupling, are analyzed for LSDA+U functionals, both the commonly used
ones as well as less commonly applied functionals. After reviewing and
extending some earlier observations for an isotropic interaction, the
anisotropies are examined more fully and related to use with the local density
(LDA) or local spin density (LSDA) approximations. The total energies of all
possible integer configurations of an open $f$ shell are presented for three
functionals, where some differences are found to be dramatic. Differences in
how the commonly used ""around mean field"" (AMF) and ""fully localized limit""
(FLL) functionals perform are traced to such differences. The LSDA+U
interaction term, applied self-consistently, usually enhances spin magnetic
moments and orbital polarization, and the double-counting terms of both
functionals provide an opposing, moderating tendency (""suppressing the magnetic
moment""). The AMF double counting term gives magnetic states a significantly
larger energy penalty than does the FLL counterpart.",0808.1706v3
2008-11-13,Heavy baryon spectroscopy in the QCD string model,"QCD string model formulated in the framework of the Field Correlator Method
(FCM) in QCD is employed to calculate the masses of $\Sigma_c$, $\Xi_c$ and
recently observed at Tevatron $\Sigma_b$, $\Xi_b$ baryons and their orbital
excitations.
  The auxiliary field formalism allows one to write a simple local form of the
effective Hamiltonian for the three quark system, which comprises both
confinement and relativistic effects, and contains only universal parameters:
the string tension $\sigma$, the strong coupling constant $\alpha_s$, and the
bare (current) quark masses $m_i$. We calculate the hyperfine splitting with
account of the both perturbative and non--perturbative spin-spin forces between
quarks in a baryon. For the orbital excitations we estimate the string
correction for the confinement potential - the leading correction to the
contribution of the proper inertia of the rotating string. This correction
lowers the masses of the P-states by 50 MeV. We find our numerical results to
be in good agreement with experimental data.",0811.2184v1
2009-05-18,Analog of the spin-orbit induced anomalous Hall effect with quantized radiation,"We demonstrate how the term describing interaction between a single two-level
atom and two cavity field modes may attain a Rashba form. As an outcome, cavity
QED provides a testbed for studies of phenomena reminiscent of the spin-orbit
induced anomalous Hall effect. The effective magnetic field, deriving from the
non-Abelian gauge potentials rendered by the Rashba coupling, induces a
transverse force acting on the phase space distributions. Thereby, the phase
space distributions build up a transverse motion manifesting itself in spiral
trajectories, rather than circular ones obtained for a zero magnetic field as
one would acquire for the corresponding Abelian gauge potentials. Utilizing
realistic experimental parameters, the phenomenon is numerically verified,
ascertain that it should be realizable with current techniques.",0905.2829v2
2009-06-19,Liquids in multi-orbital SU(N) Magnets with Ultracold Alkaline Earth Atoms,"In this work we study one family of liquid states of k-orbital SU(N) spin
systems, focusing on the case of k = 2 which can be realized by ultracold
alkaline earth atoms trapped in optical lattices, with N as large as 10. Five
different algebraic liquid states with selectively coupled charge, spin and
orbital quantum fluctuations are considered. The algebraic liquid states can be
stabilized with large enough N, and the scaling dimension of physical order
parameters is calculated using a systematic 1/N expansion. The phase
transitions between these liquid states are also studied, and all the algebraic
liquid states discussed in this work can be obtained from one ""mother"" state
with SU(2) x U(1) gauge symmetry.",0906.3727v3
2011-04-13,Two component Bose-Hubbard model with higher angular momentum states,"We study a Bose-Hubbard Hamiltonian of ultracold two component gas of spinor
Chromium atoms. Dipolar interactions of magnetic moments while tuned resonantly
by ultralow magnetic field can lead to spin flipping. Due to approximate axial
symmetry of individual lattice site, total angular momentum is conserved.
Therefore, all changes of the spin are accompanied by the appearance of the
angular orbital momentum. This way excited Wannier states with non vanishing
angular orbital momentum can be created. Resonant dipolar coupling of the two
component Bose gas introduces additional degree of control of the system, and
leads to a variety of different stable phases. The phase diagram for small
number of particles is discussed.",1104.2512v3
2011-07-09,Spin-orbit induced mixed-parity pairing in Sr$_2$RuO$_4$: a quantum many-body calculation,"The unusual superconducting state in Sr$_2$RuO$_4$ has long been viewed as
being analogous to a superfluid state in liquid $^3$He. Nevertheless,
calculations based on this odd-parity state are presently unable to completely
reconcile the properties of Sr$_2$RuO$_4$. Using a self-consistent quantum
many-body scheme that employs realistic parameters, we are able to model
several signature properties of the normal and superconducting states of
Sr$_2$RuO$_4$. We find that the dominant component of the model superconducting
state is of even parity and closely related to superconducting state for the
high-$T_c$ cuprates although a smaller odd-parity component is induced by
spin-orbit coupling. This mixed pairing state gives a more complete
representation of the complex phenomena measured in Sr$_2$RuO$_4$.",1107.1757v1
2013-04-01,Realization of 2D Spin-orbit Interaction and Exotic Topological Orders in Cold Atoms,"Majorana zero bound mode exists in the vortex core of a chiral $p+ip$
superconductor or superfluid, which can be driven from an s-wave pairing state
by two-dimensional (2D) spin-orbit (SO) coupling. We propose here a novel
scheme based on realistic cold atom platforms to generate 2D SO interactions in
a blue-detuned square optical lattice, and predict both the quantum anomalous
Hall effect and chiral topological superfluid phase in the experimentally
accessible parameter regimes. This work opens a new direction with experimental
feasibility to observe non-Abelian topological orders in cold atom systems.",1304.0291v3
2013-04-23,Aharonov-Casher effect in quantum ring ensembles,"We study the transport of electrons through a single-mode quantum ring with
electric field induced Rashba spin-orbit interaction that is subjected to an
in-plane magnetic field and weakly coupled to electron reservoirs. Modelling a
ring array by ensemble averaging over a Gaussian distribution of energy level
positions, we predict slow conductance oscillations as a function of the Rashba
interaction and electron density due to spin-orbit interaction-induced beating
of the spacings between the levels crossed by the Fermi energy. Our results
agree with experiments by Nitta c.s., thereby providing an interpretation that
differs from the ordinary Aharonov-Casher effect in a single ring.",1304.6195v1
2013-05-17,Proximity-induced unconventional superconductivity in topological insulators,"We study and classify the proximity-induced superconducting pairing in a
topological insulator (TI)-superconductor (SC) hybrid structure for SCs with
different symmetries. The Dirac surface state gives a coupling between
spin-singlet and spin-triplet pairing amplitudes as well as pairing that is odd
in frequency for p-wave SCs. We also find that all SCs induce pairing that is
odd in both frequency and orbital (band) index, with oddness in frequency and
orbital index being completely interchangeable. The different induced pairing
amplitudes significantly modifies the density of states in the TI surface
layer.",1305.4142v2
2013-10-09,Emergent topological and half semimetallic Dirac Fermions at oxide interfaces,"It is highly desirable to combine recent advances in the topological quantum
phases with technologically relevant materials. Chromium dioxide (CrO2) is a
half-metallic material, widely used in high-end data storage applications.
Using first principles calculations, we show via interfacial orbital design
that a novel class of half semi-metallic Dirac electronic phase emerges at the
interface CrO2 with TiO2 in both thin film and superlattice configurations,
with four spin-polarized Dirac points in momentum-space (k-space) band
structure. When the spin and orbital degrees of freedom are allowed to couple,
the CrO2/TiO2 superlattice becomes a Chern insulator without external fields or
additional doping. With topological gaps equivalent to 43 Kelvin and a Chern
number 2, the ensuing quantization of Hall conductance to 2e^2/h will enable
potential development of these highly industrialized oxides for applications in
topologically high fidelity data storage and energy-efficient electronic and
spintronic devices.",1310.2471v1
2014-01-13,Antilocalization of Coulomb Blockade in a Ge-Si Nanowire,"The distribution of Coulomb blockade peak heights as a function of magnetic
field is investigated experimentally in a Ge-Si nanowire quantum dot. Strong
spin-orbit coupling in this hole-gas system leads to antilocalization of
Coulomb blockade peaks, consistent with theory. In particular, the peak height
distribution has its maximum away from zero at zero magnetic field, with an
average that decreases with increasing field. Magnetoconductance in the
open-wire regime places a bound on the spin-orbit length ($l_{so}$ < 20 nm),
consistent with values extracted in the Coulomb blockade regime ($l_{so}$ < 25
nm).",1401.2948v1
2014-01-15,Effects of isovector scalar $δ$-meson on hypernuclei,"We analyze the effects of $\delta-$ meson on hypernuclei within the
frame-work of relativistic mean field theory. The $\delta-$ meson is included
into the Lagrangian for hypernuclei. The extra nucleon-meson coupling
($g_\delta$) affects the every piece of physical observables, like binding
energy, radii and single particle energy of hypernuclei. The lambda mean field
potential is investigated which is consistent with other predictions. Flipping
of single particle energy levels are observed with the strength of $g_\delta$
in the considered hypernuclei as well as normal nuclei. The spin-orbit
potentials are observed for considered hypernuclei and the effect of $g_\delta$
on spin-orbit potentials is also analyzed. The calculated single-$\Lambda$
binding energies ($B_\Lambda$) are quite agreeable with the experimental data.",1401.3608v1
2014-02-11,Engineering relativistic effects in ferroelectric SnTe,"Spin-orbit coupling is increasingly seen as a rich source of novel phenomena,
as shown by the recent excitement around topological insulators and Rashba
effects. We here show that the addition of ferroelectric degrees of freedom to
a semiconductor featuring topologically-non-trivial properties, such as SnTe,
merges the intriguing field of spin-orbit-driven physics with non-volatile
functionalities appealing for spintronics. By using a variety of modelling
techniques, we show that a strikingly rich sequence of phases can be induced in
SnTe, when going from a room-temperature cubic phase to a low-temperature
ferroelectric structure, ranging from a topological crystalline insulator to a
time-reversal-invariant $Z_2$ topological insulator to a ""ferroelectric Rashba
semiconductor"", exhibiting a huge electrically-controllable Rashba effect in
the bulk band structure.",1402.2574v2
2014-09-30,Majorana Fermions in Ge/Si Hole Nanowires,"We consider Ge/Si core/shell nanowires with hole states coupled to an
$s$-wave superconductor in the presence of electric and magnetic fields. We
employ a microscopic model that takes into account material-specific details of
the band structure such as strong and electrically tunable Rashba-type
spin-orbit interaction and $g$ factor anisotropy for the holes. In addition,
the proximity-induced superconductivity Hamiltonian is derived starting from a
microscopic model. In the topological phase, the nanowires host Majorana
fermions with localization lengths that depend strongly on both the magnetic
and electric fields. We identify the optimal regime in terms of the directions
and magnitudes of the fields in which the Majorana fermions are the most
localized at the nanowire ends. In short nanowires, the Majorana fermions
hybridize and form a subgap fermion whose energy is split away from zero and
oscillates as a function of the applied fields. The period of these
oscillations could be used to measure the dependence of the spin-orbit
interaction on the applied electric field and the $g$ factor anisotropy.",1409.8645v2
2015-02-25,Edge states in graphene-like systems,"The edges of graphene and graphene like systems can host localized states
with evanescent wave function with properties radically different from those of
the Dirac electrons in bulk. This happens in a variety of situations, that are
reviewed here. First, zigzag edges host a set of localized non dispersive state
at the Dirac energy. At half filling, it is expected that these states are
prone to ferromagnetic instability, causing a very interesting type of edge
ferromagnetism. Second, graphene under the influence of external perturbations
can host a variety of topological insulating phases, including the conventional
Quantum Hall effect, the Quantum Anomalous Hall (QAH) and the Quantum Spin Hall
phase, in all of which phases conduction can only take place through
topologically protected edge states. Here we provide an unified vision of the
properties of all these edge states, examined under the light of the same one
orbital tight-binding model. We consider the combined action of interactions,
spin orbit coupling and magnetic field, which produces a wealth of different
physical phenomena. We briefly address what has been actually observed
experimentally.",1502.07112v2
2015-03-23,Giant magnetothermal conductivity and magnetostriction effect in charge ordered Nd$_{0.8}$Na$_{0.2}$MnO$_{3}$ compound,"We present results on resistivity ($\rho$), magnetization ($M$), thermal
conductivity ($\kappa$), magnetostriction ($\frac{\Delta L}{L(0)}$) and
specific heat ($C_{p}$) of charge-orbital ordered antiferromagnetic
Nd$_{0.8}$Na$_{0.2}$MnO$_{3}$ compound. Magnetic field-induced
antiferromagnetic/charge-orbital ordered insulating to ferromagnetic metallic
transition leads to giant magnetothermal conductivity and magnetostriction
effect. The low-temperature irreversibility behavior in $\rho$, $M$, $\kappa$
and $\frac{\Delta L}{L(0)}$ due to field cycling together with striking
similarity among the field and temperature dependence of these parameters
manifest the presence of strong and complex spin-charge-lattice coupling in
this compound. The giant magnetothermal conductivity is attributed mainly to
the suppression of phonon scattering due to the destabilization of spin
fluctuations and static/dynamic Jahn-Teller distortion by the application of
magnetic field.",1503.06552v2
2015-07-13,Spin-orbit interaction driven collective electron-hole excitations in a noncentrosymmetric nodal loop Weyl semimetal,"NbP is one member of a new class of nodal loop semimetals characterized by
the cooperative effects of spin-orbit coupling (SOC) and a lack of inversion
center. Here transport and spectroscopic properties of NbP are evaluated using
density functional theory methods. SOC together with the lack of inversion
symmetry splits degeneracies, giving rise to ""Russian doll nested"" Fermi
surfaces containing 4*10$^{-4}$ electron (hole) carriers/f.u. Due to the modest
SOC strength in Nb, the Fermi surfaces map out the Weyl nodal loops. Calculated
structure around T$^*$~100 K in transport properties reproduces well the
observed transport behavior only when SOC is included, attesting to the
precision of the (delicate) calculations and the stoichiometry of the samples.
Low energy collective electron-hole excitations (plasmons) in the 20-60 meV
range result from the nodal loop splitting.",1507.03637v4
2015-11-30,Spin-orbit driven magnetic insulating state with ${J}_{\mathrm{eff}}\mathbf{=}1/2$ character in a 4d oxide,"The unusual magnetic and electronic ground states of 5d iridates has been
shown to be driven by intrinsically enhanced spin-orbit coupling (SOC). The
influence of appreciable but reduced SOC in creating the manifested magnetic
insulating states in 4d oxides is less clear, with one hurdle being the
existence of such compounds. Here we present experimental and theoretical
results on Sr$_4$RhO$_6$ that reveal SOC dominated behavior. Neutron
measurements show the octahedra are both spatially separated and locally ideal,
making the electronic ground state susceptible to alterations by SOC. Magnetic
ordering is observed with a similar structure to an analogous
${J}_{\mathrm{eff}}\mathbf{=}1/2$ Mott iridate. We consider the underlying role
of SOC in this rhodate with density functional theory and x-ray absorption
spectroscopy and find a magnetic insulating ground state with
${J}_{\mathrm{eff}}\mathbf{=}1/2$ character.",1511.09431v1
2016-06-18,Potential thermoelectric material $\mathrm{Cs_2[PdCl_4]I_2}$: a first-principles study,"The electronic structures and thermoelectric properties of
$\mathrm{Cs_2[PdCl_4]I_2}$ are investigated by the first-principles
calculations and semiclassical Boltzmann transport theory. Both electron and
phonon transport are considered to attain the figure of merit $ZT$. A modified
Becke and Johnson (mBJ) exchange potential, including spin-orbit coupling
(SOC), is employed to investigate electronic part of
$\mathrm{Cs_2[PdCl_4]I_2}$. It is found that SOC has obvious effect on valence
bands, producing huge spin-orbital splitting, which leads to remarkable
detrimental effect on p-type power factor. However, SOC has a negligible
influence on conduction bands, so the n-type power factor hardly change. The
temperature dependence of lattice thermal conductivity by assuming an inverse
temperature dependence is attained from reported ultralow lattice thermal
conductivity of 0.31 $\mathrm{W m^{-1} K^{-1}}$ at room temperature.
Calculating scattering time $\tau$ is challenging, but a hypothetical $\tau$
can be adopted to estimate thermoelectric conversion efficiency. The maximal
figure of merit $ZT$ is up to about 0.70 and 0.60 with scattering time
$\tau$=$10^{-14}$ s and $\tau$=$10^{-15}$ s, respectively. These results make
us believe that $\mathrm{Cs_2[PdCl_4]I_2}$ may be a potential thermoelectric
material.",1606.05727v1
2016-06-22,Numerics for the spin orbit equation of Makarov with constant eccentricity,"We present an algorithm for the rapid numerical integration of a
time-periodic ODE with a small dissipation term that is $C^1$ in the velocity.
Such an ODE arises as a model of spin-orbit coupling in a star/planet system,
and the motivation for devising a fast algorithm for its solution comes from
the desire to estimate probability of capture in various solutions, via Monte
Carlo simulation: the integration times are very long, since we are interested
in phenomena occurring on times similar to the formation time of the planets.
The proposed algorithm is based on the High-order Euler Method (HEM) which was
described in~\cite{hem}, and it requires computer algebra to set up the code
for its implementation. The pay-off is an overall increase in speed by a factor
of about $7.5$ compared to standard numerical methods. Means for accelerating
the purely numerical computation are also discussed",1606.06946v1
2016-09-09,Electronic structure and magnetism of samarium and neodymium adatoms on free-standing graphene,"The electronic structure of selected rare-earth atoms adsorbed on a
free-standing graphene was investigated using methods beyond the conventional
density functional theory (DFT+U, DFT+HIA and DFT+ED). The influence of the
electron correlations and the spin-orbit coupling on the magnetic properties
has been examined. The DFT+U method predicts both atoms to carry local magnetic
moments (spin and orbital) contrary to a nonmagnetic $f^6$ ($J=0$) ground-state
configuration of Sm in the gas phase. Application of DFT${}+{}$Hubbard-I (HIA)
and DFT${}+{}$exact diagonalization (ED) methods cures this problem, and yields
a nonmagnetic ground state with six $f$ electrons and $J=0$ for the Sm adatom.
Our calculations show that Nd adatom remains magnetic, with four localized $f$
electrons and $J=4.0$. These conclusions could be verified by STM and XAS
experiments.",1609.02725v1
2018-02-10,Tipping the magnetic instability in paramagnetic Sr$_3$Ru$_2$O$_7$ by Fe impurities,"We report the magnetic and electronic properties of the bilayer ruthenate
Sr$_3$Ru$_2$O$_7$ upon Fe substitution for Ru. We find that
Sr$_3$(Ru$_{1-x}$Fe$_x$)$_2$O$_7$ shows a spin-glass-like phase below 4 K for
$x$ = 0.01 and commensurate E-type antiferromagnetically ordered insulating
ground state characterized by the propagation vector $q_c$ = (0.25 0.25 0) for
$x$ $\geq$ 0.03, respectively, in contrast to the paramagnetic metallic state
in the parent compound with strong spin fluctuations occurring at wave vectors
$q$ = (0.09 0 0) and (0.25 0 0). The observed antiferromagnetic ordering is
quasi-two-dimensional with very short correlation length along the $c$ axis, a
feature similar to the Mn-doped Sr$_3$Ru$_2$O$_7$. Our results suggest that
this ordered ground state is associated with the intrinsic magnetic instability
in the pristine compound, which can be readily tipped by the local magnetic
coupling between the 3$d$ orbitals of the magnetic dopants and Ru 4$d$
orbitals.",1802.03633v1
2017-04-19,Anisotropic features in the electronic structure of the two-dimensional transition metal trichalcogenide TiS$_3$: electron doping and plasmons,"Analysis of the band structure of TiS$_3$ single-layers suggests the
possibility of changing their physical behaviour by injecting electron
carriers. The anisotropy of the valence and conduction bands is explained in
terms of their complex orbital composition. The nature of the Fermi surface and
Lindhard response function for different doping concentrations is studied by
means of first-principles DFT calculations. It is suggested that for electron
doping levels $x$ (number of electrons per unit cell) $\sim$ 0.18-0.30$e^-$ the
system could exhibit incommensurate charge or spin modulations which, however,
would keep the metallic state whereas systems doped with smaller $x$ would be
2D metals without any electronic instability. The effect of spin-orbit coupling
in the band dispersion is analysed. The DFT effective masses are used to study
the plasmon spectrum from an effective low energy model. We find that this
material supports highly anisotropic plasmons, with opposite anisotropy for the
electron and hole bands.",1704.05824v1
2015-12-16,Observation of spin-orbit insulator-like behavior in LaOBiS$_{2-x}$F$_x$ (0.05 $\leq$ $x$ $\leq$ 0.2),"We report the effects of electron doping on the crystal structure and
electrical resistivity of LaOBiS$_{2-x}$F$_x$ (0.05 $\leq$ $x$ $\leq$ 0.2). The
$ab$ plane is found to be relatively insensitive to the amount of F, whereas
the $c$ axis shrinks continuously with increasing $x$, suggesting that the
doped F atoms substitute selectively into the apical sites in the BiS$_2$
layer. At $x$ = 0.10, as the temperature is decreased from room temperature,
the electrical resistivity is temperature-independent from room temperature to
285 K, increases linearly with decreasing temperature from 285 K to 205 K and
then shows obvious insulating behavior below 205 K, which may be due to strong
spin-orbit coupling. LaOBiS$_{1.9}$F$_{0.1}$ shows the significantly weak and
temperature-independent diamagnetism without any evident anomalies caused by a
phase transition.",1512.05070v1
2019-10-09,Superconductivity from Coulomb repulsion in three-dimensional quadratic band touching Luttinger semimetals,"We study superconductivity driven by screened Coulomb repulsion in
three-dimensional Luttinger semimetals with a quadratic band touching and
strong spin-orbit coupling. In these semimetals, the Cooper pairs are formed by
spin-3/2 fermions with non-trivial wavefunctions. We numerically solve the
linear Eliashberg equation to obtain the critical temperature of a singlet
s-wave gap function as a function of doping, with account of spin-orbit and
self-energy corrections. In order to understand the underlying mechanism of
superconductivity, we compute the sensitivity of the critical temperature to
changes in the dielectric function $\epsilon(i\Omega_n,q)$. We relate our
results to the plasmon and Kohn-Luttinger mechanisms. Finally, we discuss the
validity of our approach and compare our results to the litterature. We find
good agreement with some bismuth-based half-Heuslers, such as YPtBi, and
speculate on superconductivity in the iridate Pr2Ir2O7.",1910.04189v2
2018-03-13,Gamow-Teller transitions and neutron-proton-pair transfer reactions,"We propose a schematic model of nucleons moving in spin--orbit partner
levels, $j=l\pm{\sfrac12}$, to explain Gamow--Teller and two-nucleon transfer
data in $N=Z$ nuclei above $^{40}$Ca. Use of the $LS$ coupling scheme provides
a more transparent approach to interpret the structure and reaction data.We
apply the model to the analysis of charge-exchange,
$^{42}$Ca($^3$He,t)$^{42}$Sc, and np-transfer, $^{40}$Ca($^3$He,p)$^{42}$Sc,
reactions data to define the elementary modes of excitation in terms of both
isovector and isoscalar pairs, whose properties can be determined by adjusting
the parameters of the model (spin--orbit splitting, isovector pairing strength
and quadrupole matrix element) to the available data. The overall agreement
with experiment suggests that the approach captures the main physics
ingredients and provides the basis for a boson approximation that can be
extended to heavier nuclei. Our analysis also reveals that the SU(4)-symmetry
limit is not realized in $^{42}$Sc.",1803.04704v1
2018-03-20,Conductance of fractional Luttinger liquids at finite temperatures,"We study the electrical conductance in single-mode quantum wires with Rashba
spin-orbit interaction subjected to externally applied magnetic fields in the
regime in which the ratio of spin-orbit momentum to the Fermi momentum is close
to an odd integer, so that a combined effect of multi-electron interaction and
applied magnetic field leads to a partial gap in the spectrum. We study how
this partial gap manifests itself in the temperature dependence of the
fractional conductance of the quantum wire. We use two complementing techniques
based on bosonization: refermionization of the model at a particular value of
the interaction parameter and a semiclassical approach within a dilute soliton
gas approximation of the functional integral. We show how the low-temperature
fractional conductance can be affected by the finite length of the wire, by the
properties of the contacts, and by a shift of the chemical potential, which
takes the system away from the resonance condition. We also predict an internal
resistivity caused by a dissipative coupling between gapped and gapless modes.",1803.07359v1
2018-08-15,Collective excitations in two-component one-dimensional massless Dirac plasma,"We study spectra of long wavelength plasma oscillations in a system of two
energy splitted one-dimensional (1D) massless Dirac fermion subbands coupled by
spin-orbit interaction. Such a system may be formed by edge subbands in
semiconducting transition metal dichalcogenide monolayers. Intrasubband
transitions of massless Dirac fermions give rise to optical and acoustic
gapless branches of intrasubband 1D plasmons. We reveal that the optical branch
is of quantum character with group velocity being inverse proportional to
square root of the Planck constant, whereas the acoustic branch is classical
one with group velocity proportional to geometric mean of the edge subband
velocities. Spin-orbit interaction, allowing intersubband transitions in the
system, results in emergence of two branches of intersubband 1D plasmons: upper
and lower ones. The upper and lower branches are gapped at small wave vectors
and evolve with positive and negative group velocities, respectively, from
energy splitting of the edge subbands at Fermi-level. The both intersubband
branches adjoin intersubband single particle excitation continuum from above,
while in case of the edge subbands with unequal velocities the lower one
experiences Landau damping at small wave vectors. In addition, the lower
branch, attaining zero frequency at a non-zero wave vector, alters its group
velocity from negative to positive one.",1808.05180v1
2020-08-19,Spin-Orbit and Strain Induced Modification in Electrical Properties of Monolayer InSb,"In this work, the electrical properties of monolayer InSb in the presence of
biaxial strain using density functional theory are investigated. Here, we first
explore the band structure of InSb with and without spin-orbit coupling (SOC)
consideration. The electron and hole effective mass modify with SOC
consideration. The electron and hole effective masses lowered two and ten
times, respectively. The location of valleys in conduction and valence band for
various strains are explored, and the corresponding effective masses are
reported. A lower effective mass is obtained for both electron and hole with
applying tensile strain, whereas, the bandgap closes for large tensile strain.
A numeric fitting has applied to effective mass versus strain, and an equation
for every curve is reported. Finally, the work function of this material for
different strains is obtained.",2008.08266v1
2020-10-12,Lattice Collective Modes from a Continuum Model of Magic-Angle Twisted Bilayer Graphene,"We show that the insulating states of magic-angle twisted bilayer graphene
support a series of collective modes corresponding to local particle-hole
excitations on triangular lattice sites. Our theory is based on a continuum
model of the magic angle flat bands. When the system is insulating at moir\'e
band filling $\nu=-3$, our calculations show that the ground state supports
seven low-energy modes that lie well below the charge gap throughout the
moir\'e Brillouin zone, one of which couples strongly to THz photons. The
low-energy collective modes are faithfully described by a model with a local
$SU(8)$ degree of freedom in each moir\'e unit cell that we identify as the
direct product of spin, valley, and an orbital pseudospin. Apart from spin and
valley-wave modes, the collective mode spectrum includes a low-energy
intra-flavor exciton mode associated with transitions between flat valence and
conduction band orbitals.",2010.05946v2
2016-03-30,Effective p-wave interaction and topological superfluids in s-wave quantum gases,"P-wave interaction in cold atoms may give rise to exotic topological
superfluids. However, the realization of p-wave interaction in cold atom system
is experimentally challenging. Here we propose a simple scheme to synthesize
effective $p$-wave interaction in conventional $s$-wave interacting quantum
gases. The key idea is to load atoms into spin-dependent optical lattice
potential. Using two concrete examples involving spin-1/2 fermions, we show how
the original system can be mapped into a model describing spinless fermions
with nearest neighbor p-wave interaction, whose ground state can be a
topological superfluid that supports Majorana fermions under proper conditions.
Our proposal has the advantage that it does not require spin-orbit coupling or
loading atoms onto higher orbitals, which is the key in earlier proposals to
synthesize effective $p$-wave interaction in $s$-wave quantum gases, and may
provide a completely new route for realizing $p$-wave topological superfluids.",1603.09011v1
2017-07-27,"Analysis of the behavior of singlet pairs in inorganic crystal XOCl(X=Ti,Bi)","This article explore the behavior of singlet pairs in Inorganic crystals and
take the Ti-Ti and Bi-Bi dimer for example, including the transition in
critical temperture by directly or indirectly. Through the analysis, It is
proposed that with the decrease of temperature, the strength of spin-orbit
coupling (SOC) increases and the phase difference also increases. In the
one-dimensional spin 1/2 chain system of TiOCl and BiOCl crystals, the
possibility of reversible parameter modulation is proposed by the calculation
of the first principle analyzing the process and analysis of the structural
phase transition process. It's shown that the different sturcture transition is
relate to the difference of the dimer structure and the fluctuation of orbital
order through the comparative study of TiOCl and BiOCl.",1707.09033v1
2017-11-21,3D Topological Kondo Insulators,"Topological Kondo insulators (TKIs) are new type of symmetry-protected
topological insulators, which develop through the interplay of strong
correlations and spin-orbit interactions. In these materials, the bulk is a
perfect band insulator due to Kondo screening of localized moments via
conduction electrons. Furthermore, strong spin-orbit coupling (SOC) and crystal
field effect (CFE) of the localized moments result in a nonlocal odd-parity,
time-reversal invariant hybridization between the local-moments and conduction
bands, which creates a ground-state with nontrivial topology and gapless
surface excitations (Physical Review Letters 104 (2010) 106408). In the present
work, we develop a self-consistent theory to study topological Kondo insulators
at the mean-field level. To achieve this, we apply slave-boson mean-field
theory for a system with and without periodic boundary conditions, in order to
study the system at bulk and slab geometry configuration. This enables us to
observe a clear signature of protected edge states through band structure and
calculation of spectral functions.",1711.07976v1
2017-11-27,Electrical Control of Structural and Physical Properties via Strong Spin-Orbit Interactions in Sr2IrO4,"Electrical control of structural and physical properties is a long-sought,
but elusive goal of contemporary science and technology. We demonstrate that a
combination of strong spin-orbit interactions (SOI) and a canted
antiferromagnetic (AFM) Mott state is sufficient to attain that goal. The AFM
insulator Sr2IrO4 provides a model system in which strong SOI lock canted Ir
magnetic moments to IrO6-octahedra, causing them to rigidly rotate together. A
novel coupling between an applied electrical current and the canting angle
reduces the N\'eel temperature and drives a large, non-linear lattice expansion
that closely tracks the magnetization, increases the electron mobility, and
precipitates a unique resistive switching effect. Our observations open new
avenues for understanding fundamental physics driven by strong SOI in condensed
matter, and provide a new paradigm for functional materials and devices.",1711.10021v1
2017-11-30,Magnetic anisotropy by Rashba spin-orbit coupling in antiferromagnetic thin films,"Magnetic anisotropy in an antiferromagnet (AFM) with inversion symmetry
breaking (ISB) is investigated. The magnetic anisotropy energy (MAE) resulting
from the Rashba spin-orbit and s-d type exchange interactions is determined for
two different models of AFMs. The global ISB model, representing the effect of
a surface, an interface, or a gating electric field, results in an easy-plane
magnetic anisotropy. In contrast, for a local ISB model, i.e., for a
noncentrosymmetric AFM, perpendicular magnetic anisotropy (PMA) arises. Both
results differ from the ferromagnetic case, in which the result for PMA depends
on the band structure and dimensionality. These MAE contributions play a key
role in determining the direction of the Neel order parameter in
antiferromagnetic nanostructures, and reflect the possibility of
electrical-field control of the Neel vector.",1711.11184v2
2018-10-06,Sr$_3$Ir$_2$O$_7$F$_2$: Topochemical conversion of a relativistic Mott state into a spin-orbit driven band insulator,"The topochemical transformation of single crystals of Sr$_3$Ir$_2$O$_7$ into
Sr$_3$Ir$_2$O$_7$F$_2$ is reported via fluorine insertion. Characterization of
the newly formed Sr$_3$Ir$_2$O$_7$F$_2$ phase shows a nearly complete oxidation
of Ir$^{4+}$ cations into Ir$^{5+}$ that in turn drives the system from an
antiferromagnetic Mott insulator with a half-filled J$_{eff}=1/2$ band into a
nonmagnetic $J=0$ band insulator. First principles calculations reveal a
remarkably flat insertion energy that locally drives the fluorination process
to completion. Band structure calculations support the formation of a band
insulator whose charge gap relies on the strong spin-orbit coupling inherent to
the Ir metal ions of this compound.",1810.02942v1
2018-10-11,Coulomb pairing of electrons in thin films with strong spin-orbit interaction,"In low-dimensional structures with strong Rashba spin-orbit interaction
(SOI), the Coulomb fields between moving electrons produce a SOI component of
the pair interaction that competes with the potential Coulomb repulsion. If the
Rashba SOI constant of the material is sufficiently high, the total
electron-electron interaction becomes attractive, which leads to the formation
of the two-electron bound states. We show that because of the dielectric
screening in a thin film the binding energy is significantly higher as compared
to the case of the bulk screening.",1810.05144v2
2018-10-30,Novel topological insulators from crystalline symmetries,"We discuss recent advances in the study of topological insulators protected
by spatial symmetries by reviewing three representative, theoretical examples.
In three dimensions, these states of matter are generally characterized by the
presence of gapless boundary states at surfaces that respect the protecting
spatial symmetry. We discuss the appearance of these topological states both in
crystals with negligible spin-orbit coupling and a fourfold rotational
symmetry, as well as in mirror-symmetric crystals with sizable spin-orbit
interaction characterized by the so-called mirror Chern number. Finally, we
also discuss similar topological crystalline states in one-dimensional
insulators, such as nanowires or atomic chains, with mirror symmetry. There,
the prime physical consequence of the non-trivial topology is the presence of
quantized end charges.",1810.12877v1
2021-01-10,Enhancement of spin-orbit coupling in Dirac semimetal Cd$_{3}$As$_{2}$ films by Sb-doping,"We present a study on magnetotransport in films of the topological Dirac
semimetal Cd$_{3}$As$_{2}$ doped with Sb grown by molecular beam epitaxy. In
our weak antilocalization analysis, we find a significant enhancement of the
spin-orbit scattering rate, indicating that Sb doping leads to a strong
increase of the pristine band-inversion energy. We discuss possible origins of
this large enhancement by comparing Sb-doped Cd$_{3}$As$_{2}$ with other
compound semiconductors. Sb-doped Cd$_{3}$As$_{2}$ will be a suitable system
for further investigations and functionalization of topological Dirac
semimetals.",2101.03560v1
2021-03-04,Observation of an Unusual Colossal Anisotropic Magnetoresistance Effect in an Antiferromagnetic Semiconductor,"Searching for novel antiferromagnetic materials with large magnetotransport
response is highly demanded for constructing future spintronic devices with
high stability, fast switching speed, and high density. Here we report a
colossal anisotropic magnetoresistance effect in an antiferromagnetic binary
compound with layered structure rare-earth dichalcogenide EuTe2. The AMR
reaches 40000%, which is 4 orders of magnitude larger than that in conventional
antiferromagnetic alloys. Combined magnetization, resistivity, and theoretical
analysis reveal that the colossal AMR effect is attributed to a novel mechanism
of vector-field tunable band structure, rather than the conventional spin-orbit
coupling mechanism. Moreover, it is revealed that the strong hybridization
between orbitals of Eu-layer with localized spin and Te-layer with itinerant
carriers is extremely important for the large AMR effect. Our results suggest a
new direction towards exploring AFM materials with prominent magnetotransport
properties, which creates an unprecedented opportunity for AFM spintronics
applications.",2103.02818v1
2022-03-09,First-principles study of the electronic and optical properties of Ho$_{\rm W}$ impurities in tungsten disulfide,"The electronic and optical properties of single-layer (SL) tungsten disulfide
(WS$_2$) in the presence of substitutional Holmium impurities (Ho$_{\rm W}$)
are studied. Although Ho is much larger than W, density functional theory (DFT)
including spin-orbit coupling is used to show that Ho:SL WS$_2$ is stable. The
magnetic moment of the Ho impurity is found to be 4.75$\mu_B$ using
spin-dependent DFT. The optical selection rules identified in the optical
spectrum match exactly the optical selection rules derived by means of group
theory. The presence of neutral Ho$_W$ impurities gives rise to localized
impurity states (LIS) with f-orbital character in the band structure. Using the
Kubo-Greenwood formula and Kohn-Sham orbitals we obtain atom-like sharp
transitions in the in-plane and out-of-plane components of the susceptibility
tensor, Im$\chi_{\parallel}$ and Im$\chi_{\perp}$. The optical resonances are
in good agreement with experimental data.",2203.04730v1
2022-05-18,Dielectric constant of gray Tin: A first-principles study,"$\alpha$-Sn (gray tin) is a group-IV, zero-gap semiconductor with potential
use in infrared detectors, necessitating a clear understanding of its
dielectric properties. We report the first-principles calculations of the band
structure and dielectric function of $\alpha$-Sn using density functional
theory, emphasizing the effects of strain, spin-orbit interaction, and
pseudo-potentials on the electronic and optical properties of $\alpha$-Sn in
the infrared region (photon energy $<$ 1eV). In $\alpha$-Sn, spin-orbit
coupling greatly influences the electronic band structure that leads to unusual
optical behavior. We explain an apparently anomalous absorption at $\sim$ 0.41
eV caused by interbank transitions within the valence band. Infrared
spectroscopic ellipsometry on several $\alpha$-Sn films grown by molecular beam
epitaxy validate our band-structure calculations. Our computational methods and
results are discussed in detail.",2205.08686v3
2022-06-14,Two bands Ising superconductivity from Coulomb interactions in monolayer NbSe$_2$,"The nature of superconductivity in monolayer transition metal dichalcogenides
is still an object of debate. It has already been argued that repulsive Coulomb
interactions, combined with the disjoint Fermi surfaces around the $K$, $K'$
valleys and at the $\Gamma$ point, can lead to superconducting instabilities in
monolayer NbSe$_2$. Here, we demonstrate the two bands nature of
superconductivity in NbSe$_2$. It arises from the competition of repulsive long
range intravalley and short range intervalley interactions together with Ising
spin-orbit coupling. The two distinct superconducting gaps, one for each
spin-orbit split band, consist of a mixture of s-wave and f-wave components.
Their different amplitudes are due to different normal densities of states of
the two bands at the Fermi level. Using a microscopic multiband BCS approach,
we derive and self-consistently solve the gap equation, demonstrating the
stability of nontrivial solutions in a realistic parameter range. We find a
universal behavior of the temperature dependence of the gaps and of the
critical in-plane field which is consistent with various sets of existing
experimental data.",2206.06645v1
2022-09-23,Charging/discharging mechanism in Mg3Bi2 anode for Mg-ion batteries; The role of the spin-orbit coupling,"Using density functional calculations, we examine insertion/extraction of Mg
ions in Mg3Bi2, an interesting Mg-ion battery anode. We found that a (1 1 0)
facet is the most stable termination. Vacating a Mg2+ ion from the octahedral
site is more favourable for both surface and bulk regions of the material.
However, the diffusion barriers among the tetrahedral sites are around 3 times
smaller than those among octahedral sites. Consequently, during the
magnesiation/demagnesiation process, Mg ions first vacate the octahedral sites
and then diffuse through the tetrahedral sites. The spin-orbit interaction
lowers Mg's vacancy formation energy but has a minor effect on diffusion
barriers.",2209.11513v1
2022-10-11,"Effects of charge doping on Mott insulator with strong spin-orbit coupling, Ba$_2$NaOsO$_6$","The effects of doping on the electronic evolution of the Mott insulating
state have been extensively studied in efforts to understand mechanisms of
emergent quantum phases of materials. The study of these effects becomes ever
more intriguing in the presence of entanglement between spin and orbital
degrees of freedom. Here, we present a comprehensive investigation of charge
doping in the double perovskite Ba$_2$NaOsO$_6$, a a complex Mott insulator
where such entanglement plays an important role. We establish that the
insulating magnetic ground state evolves from canted antiferromagnet (cAF)to
N\'eel order for dopant levels exceeding ~ 10 %. Furthermore, we determine that
a broken local point symmetry (BLPS) phase, precursor to the magnetically
ordered state, occupies an extended portion of the (H-T) phase diagram with
increased doping. This finding reveals that the breaking of the local cubic
symmetry is driven by a multipolar order, most-likely of the
antiferro-quadrupolar type.",2210.05077v2
2023-02-28,$\mathbb{Z}_2$ Non-Hermitian skin effect in equilibrium heavy-fermions,"We demonstrate that a correlated equilibrium $f$-electron system with
time-reversal symmetry can exhibit a $\mathbb{Z}_2$ non-Hermitian skin effect
of quasi-particles. In particular, we analyze a two-dimensional periodic
Anderson model with spin-orbit coupling by combining the dynamical mean-field
theory (DMFT) and the numerical renormalization group. We prove the existence
of the $\mathbb{Z}_2$ skin effect by explicitly calculating the topological
invariant and show that spin-orbit interaction is essential to this effect. Our
DMFT analysis demonstrates that the $\mathbb{Z}_2$ skin effect of
quasi-particles is reflected on the pseudo-spectrum. Furthermore, we analyze
temperature effects on this skin effect using the generalized Brillouin zone
technique, which clarifies that the skin modes are strongly localized above the
Kondo temperature.",2302.14366v3
2023-03-28,Synchronization of spin-driven limit cycle oscillators optically levitated in vacuum,"We explore, experimentally and theoretically, the emergence of coherent
coupled oscillations and synchronization between a pair of non-Hermitian,
stochastic, opto-mechanical oscillators, levitated in vacuum. Each oscillator
consists of a polystyrene microsphere trapped in a circularly polarized,
counter-propagating Gaussian laser beam. Non-conservative, azimuthal forces,
deriving from inhomogeneous optical spin, push the micro-particles out of
thermodynamic equilibrium. For modest optical powers each particle shows a
tendency towards orbital circulation. Initially, their stochastic motion is
weakly correlated. As the power is increased, the tendency towards orbital
circulation strengthens and the motion of the particles becomes highly
correlated. Eventually, centripetal forces overcome optical gradient forces and
the oscillators undergo a collective Hopf bifurcation. For laser powers
exceeding this threshold, a pair of limit cycles appear, which synchronize due
to weak optical and hydrodynamic interactions. In principle, arrays of such
Non-Hermitian elements can be arranged, paving the way for opto-mechanical
topological materials or, possibly, classical time crystals. In addition, the
preparation of synchronized states in levitated optomechanics could lead to new
and robust sensors or alternative routes to the entanglement of macroscopic
objects.",2303.15753v1
2023-07-11,Optical Memory for Arbitrary Perfect Poincaré States in an Atomic Ensemble,"Inherent spin angular momentum (SAM) and orbital angular momentum (OAM) which
manifest as polarization and spatial degrees of freedom (DOF) of photons, hold
a promise of large capability for applications in classical and quantum
information processing. To enable these photonic spin and orbital dynamic
properties strongly coupled with each other, Poincar\'{e} states have been
proposed and offer advantages in data multiplexing, information encryption,
precision metrology, and quantum memory. However, since the transverse size of
Laguerre Gaussian beams strongly depends on their topological charge numbers
$\left| l \right|$, it is difficult to store asymmetric Poincar\'{e} states due
to the significantly different light-matter interaction for distinct spatial
modes. Here, we experimentally realize the storage of perfect Poincar\'{e}
states with arbitrary OAM quanta using the perfect optical vortex, in which 121
arbitrarily-selected perfect Poincar\'{e} states have been stored with high
fidelity. The reported work has great prospects in optical communication and
quantum networks for dramatically increased encoding flexibility of
information.",2307.05008v1
2023-09-21,A new generation of effective core potentials: selected Lanthanides and heavy elements,"We construct correlation-consistent effective core potentials (ccECPs) for a
selected set of heavy atoms and f-elements that are of significant current
interest in materials and chemical applications, including Y, Zr, Nb, Rh, Ta,
Re, Pt, Gd, and Tb. As customary, ccECPs consist of spin-orbit averaged
relativistic effective potential (AREP) and effective spin-orbit (SO) terms.
For the AREP part, our constructions are carried out within a relativistic
coupled-cluster framework while also taking into objective function
one-particle characteristics for improved convergence in optimizations. The
transferability is adjusted using binding curves of hydride and oxide
molecules. We address the difficulties encountered with f-elements, such as the
presence of large cores and multiple near-degeneracies of excited levels. For
these elements, we construct ccECPs with core-valence partitioning that
includes 4f-subshell in the valence space. The developed ccECPs achieve an
excellent balance between accuracy, size of the valence space, and
transferability and are also suitable to be used in plane wave codes with
reasonable energy cutoffs.",2309.12145v1
2023-10-09,Micromagnetic textures in exchange coupled-ferromagnetic multiferroic films,"The development of new computing technologies has given a new stimulus in the
study of multiferroics. The use of multiferroics allows the realization of
competitive energy efficient scalable logic and storage devices. The low-power
consumption in Magneto Electric-Spin Orbital logics and Magnetic Random Access
Memory components is provided by magnetoelectric switching in multiferroic
based systems using a low-energy electric field. Our work concerns the
modelling of the Magneto Electric-Spin Orbital elements with an emphasis on the
magnetoelectric component and simulation of magnetization reversal processes in
a model system. The use of the proposed approach makes it possible to analyze
the influence of dimensional factors (film thicknesses, transverse dimensions,
sample shape) affecting the magnetic states of multiferroic nanoelements;
taking into interfacial interactions (magnetic anisotropy and interlayer
exchange); energy-efficient external influences that allow switching magnetic
states using magnetic and electric fields.",2310.05438v1
2023-10-26,Large Quantum Anomalous Hall Effect in Spin-Orbit Proximitized Rhombohedral Graphene,"The quantum anomalous Hall effect (QAHE) is a robust topological phenomenon
featuring quantized Hall resistance at zero magnetic field. We report the QAHE
in a rhombohedral pentalayer graphene/monolayer WS2 heterostructure. Distinct
from other experimentally confirmed QAHE systems, this system has neither
magnetic element nor moir\'e superlattice effect. The QAH states emerge at
charge neutrality and feature Chern numbers C = +-5 at temperatures up to about
1.5 K. This large QAHE arises from the synergy of the electron correlation in
intrinsic flat bands of pentalayer graphene, the gate-tuning effect, and the
proximity-induced Ising spin-orbit-coupling. Our experiment demonstrates the
potential of crystalline two-dimensional materials for intertwined electron
correlation and band topology physics, and may enable a route for engineering
chiral Majorana edge states.",2310.17483v2
2024-02-07,A Non-Abelian Gauge Theory for Surface Excitations of $~^3$He-B,"In $~^3$He-B, two atoms pair in an orbital angular momentum $1$ spin triplet
state above the phase transition temperature with $SO(3) \times SO(3)$
symmetry. Below the transition temperature, this symmetry is spontaneously
broken to the diagonal $SO(3)$ due to spin-orbit coupling. Considerations based
on effective potentials and solitons show that $SO(3)$'s gets enhanced to
$SU(3)$'s and the symmetry breaking is that of $G= SU(3) \times SU(3)\times
U(1)$ to $H= SU(3)$. The theory of the resultant Goldtsone modes can be
naturally formulated as a gauge theory of $H$. Its Gauss law is treated here
and shown to lead to surface states in a container with a dynamics governed by
large gauge transformations.
  Observable consequences are pointed. The transference of the analysis to the
chiral model of QCD is pointed out where $SU(3)$ are the left and right chiral
groups, $U(1)$ is the axial $U(1)$ , the surviving symmetry is flavour $SU(3)$
and the Goldstone modes are the pions.",2402.04714v2
2024-03-25,Spin-orbit proximity in MoS$_2$/bilayer graphene heterostructures,"Van der Waals heterostructures provide a versatile platform for tailoring
electronic properties through the integration of two-dimensional materials.
Among these combinations, the interaction between bilayer graphene and
transition metal dichalcogenides (TMDs) stands out due to its potential for
inducing spin-orbit coupling (SOC) in graphene. Future devices concepts require
the understanding the precise nature of SOC in TMD/bilayer graphene
heterostructures and its influence on electronic transport phenomena. Here, we
experimentally confirm the presence of two distinct types of SOC, Ising (1.55
meV) and Rashba (2.5 meV), in bilayer graphene when interfaced with molybdenum
disulphide, recognized as one of the most stable TMDs. Furthermore, we reveal a
non-monotonic trend in conductivity with respect to the electric displacement
field at charge neutrality. This phenomenon is ascribed to the existence of
single-particle gaps induced by the Ising SOC, which can be closed by a
critical displacement field. Remarkably, our findings also unveil sharp peaks
in the magnetoconductivity around the critical displacement field, challenging
existing theoretical models.",2403.17120v1
2018-06-06,Impurity-induced orbital magnetization in a Rashba electron gas,"We investigate the induced orbital magnetization density in a Rashba electron
gas with magnetic impurities. Relying on classical electrodynamics, we obtain
this quantity through the bound currents composed of a paramagnetic and a
diamagnetic-like contribution which emerge from the spin-orbit interaction.
Similar to Friedel charge ripples, the bound currents and the orbital
magnetization density oscillate as function of distance away from the impurity
with characteristic wavelengths defined by the Fermi energy and the strength of
the Rashba spin-orbit interaction. The net induced orbital magnetization was
found to be of the order of magnitude of its spin counterpart. Besides the
exploration of the impact of the electronic filling of the impurity states, we
investigate and analyze the orbital magnetization induced by an equilateral
frustrated trimer in various non-collinear magnetic states. On the one hand, we
confirm that non-vanishing three-spin chiralities generate a finite orbital
magnetization density. On the other hand, higher order contributions lead to
multiple-spin chiralities affecting non-trivially and significantly the overall
magnitude and sign of the orbital magnetization.",1806.02158v1
2021-10-26,Ultrafast signatures of spin and orbital order in antiferromagnetic $α$-Sr$_2$CrO$_4$,"We used femtosecond optical spectroscopy to study ultrafast spin and orbital
ordering dynamics in the antiferromagnetic Mott insulator
$\alpha$-Sr$_2$CrO$_4$. This chromate system possesses multiple spin and
orbital ordered phases, and therefore could enable us to study the unique
interplay between these collective phases through their non-equilibrium
response to photoexcitation. Here, by varying the pump photon energy, we
selectively drove inter-site spin hopping between neighboring Cr $t_{2g}$
orbitals and charge transfer-type transitions between oxygen 2$p$ and Cr
$e_{g}$ orbitals. The resulting transient reflectivity dynamics revealed
temperature-dependent anomalies across the N${\textrm{\'e}}$el temperature for
spin ordering as well as the transition temperatures linked to different types
of orbital order. Our results reveal distinct relaxation timescales for spin
and orbital orders in $\alpha$-Sr$_2$CrO$_4$ and provide experimental evidence
for the phase transition at $T_\textrm{O}$, possibly related to antiferro-type
orbital ordering.",2110.14004v1
2000-11-28,Paramagnetic-diamagnetic interplay in quantum dots for non-zero temperatures,"In the usual Fock-and Darwin-formalism with parabolic potential characterized
by the confining energy $\eps_o := \hbar\omega_o= 3.37$ meV, but including
explicitly also the Zeeman coupling between spin and magnetic field, we study
the combined orbital and spin magnetic properties of quantum dots in a
two-dimensional electron gas with parameters for GaAs, for N =1 and N >> 1
electrons on the dot.
  For N=1 the magnetization M(T,B) consists of a paramagnetic spin contribution
and a diamagnetic orbital contribution, which dominate in a non-trivial way at
low temperature and fields rsp. high temperature and fields.
  For N >> 1, where orbital and spin effects are intrinsically coupled in a
subtle way and cannot be separated, we find in a simplified Hartree
approximation that at N=m^2, i.e. at a half-filled last shell, M(T,B,N) is
parallel (antiparallel) to the magnetic field, if temperatures and fields are
low enough (high enough), whereas for N\ne m^2 the magnetization oscillates
with B and N as a T-dependent periodic function of the variable
x:=\sqrt{N}eB/(2m^*c\omega_o), with T-independent period \Delta x =1 (where m^*
:= 0.067 m_o is the small effective mass of GaAs, while m_o is the electron
mass). Correspondingly, by an adiabatic demagnetization process, which should
only be fast enough with respect to the slow transient time of the magnetic
properties of the dot, the temperature of the dot diminishes rsp. increases
with decreasing magnetic field, and in some cases we obtain quite pronounced
effects.",0011465v3
2019-07-26,Magnetoelectric control of topological phases in graphene,"Topological antiferromagnetic (AFM) spintronics is an emerging field of
research, which involves the topological electronic states coupled to the AFM
order parameter known as the N$\acute{\rm e}$el vector. The control of these
states is envisioned through manipulation of the N$\acute{\rm e}$el vector by
spin-orbit torques driven by electric currents. Here we propose a different
approach favorable for low-power AFM spintronics, where the control of the
topological states in a two-dimensional material, such as graphene, is
performed via the proximity effect by the voltage induced switching of the
N$\acute{\rm e}$el vector in an adjacent magnetoelectric AFM insulator, such as
chromia. Mediated by the symmetry protected boundary magnetization and the
induced Rashba-type spin-orbit coupling at the interface between graphene and
chromia, the emergent topological phases in graphene can be controlled by the
N$\acute{\rm e}$el vector. Using density functional theory and tight-binding
Hamiltonian approaches, we model a graphene/Cr2O3 (0001) interface and
demonstrate non-trivial band gap openings in the graphene Dirac bands
asymmetric between the K and K' valleys. This gives rise to an unconventional
quantum anomalous Hall effect (QAHE) with a quantized value of $2e^2/h$ and an
additional step-like feature at a value close to $e^2/2h$, and the emergence of
the spin-polarized valley Hall effect (VHE). Furthermore, depending on the
N$\acute{\rm e}$el vector orientation, we predict the appearance and
transformation of different topological phases in graphene across the
$180^{\circ}$ AFM domain wall, involving the QAHE, the valley-polarized QAHE
and the quantum VHE (QVHE), and the emergence of the chiral edge state along
the domain wall. These topological properties are controlled by voltage through
magnetoelectric switching of the AFM insulator with no need for spin-orbit
torques.",1907.11689v1
2019-03-05,Observation of Chiral Surface Excitons in a Topological Insulator Bi$_2$Se$_3$,"The protected electron states at the boundaries or on the surfaces of
topological insulators (TIs) have been the subject of intense theoretical and
experimental investigations. Such states are enforced by very strong spin-orbit
interaction in solids composed of heavy elements. Here, we study the composite
particles -- chiral excitons -- formed by the Coulomb attraction between
electrons and holes residing on the surface of an archetypical
three-dimensional topological insulator (TI), Bi$_2$Se$_3$. Photoluminescence
(PL) emission arising due to recombination of excitons in conventional
semiconductors is usually unpolarized because of scattering by phonons and
other degrees of freedom during exciton thermalization. On the contrary, we
observe almost perfectly polarization-preserving PL emission from chiral
excitons. We demonstrate that the chiral excitons can be optically oriented
with circularly polarized light in a broad range of excitation energies, even
when the latter deviate from the (apparent) optical band gap by hundreds of
meVs, and that the orientation remains preserved even at room temperature.
Based on the dependences of the PL spectra on the energy and polarization of
incident photons, we propose that chiral excitons are made from massive holes
and massless (Dirac) electrons, both with chiral spin textures enforced by
strong spin-orbit coupling. A theoretical model based on such proposal
describes quantitatively the experimental observations. The optical orientation
of composite particles, the chiral excitons, emerges as a general result of
strong spin-orbit coupling in a 2D electron system. Our findings can
potentially expand applications of TIs in photonics and optoelectronics.",1903.01999v1
2001-01-06,A Realistic Description of Nucleon-Nucleon and Hyperon-Nucleon Interactions in the SU_6 Quark Model,"We upgrade a SU_6 quark-model description for the nucleon-nucleon and
hyperon-nucleon interactions by improving the effective meson-exchange
potentials acting between quarks. For the scalar- and vector-meson exchanges,
the momentum-dependent higher-order term is incorporated to reduce the
attractive effect of the central interaction at higher energies. The
single-particle potentials of the nucleon and Lambda, predicted by the G-matrix
calculation, now have proper repulsive behavior in the momentum region q_1=5 -
20 fm^-1. A moderate contribution of the spin-orbit interaction from the
scalar-meson exchange is also included. As to the vector mesons, a dominant
contribution is the quadratic spin-orbit force generated from the rho-meson
exchange. The nucleon-nucleon phase shifts at the non-relativistic energies up
to T_lab=350 MeV are greatly improved especially for the 3E states. The
low-energy observables of the nucleon-nucleon and the hyperon-nucleon
interactions are also reexamined. The isospin symmetry breaking and the Coulomb
effect are properly incorporated in the particle basis. The essential feature
of the Lambda N - Sigma N coupling is qualitatively similar to that obtained
from the previous models. The nuclear saturation properties and the
single-particle potentials of the nucleon, Lambda and Sigma are reexamined
through the G-matrix calculation. The single-particle potential of the Sigma
hyperon is weakly repulsive in symmetric nuclear matter. The single-particle
spin-orbit strength for the Lambda particle is very small, in comparison with
that of the nucleons, due to the strong antisymmetric spin-orbit force
generated from the Fermi-Breit interaction.",0101014v1
2019-02-07,All-electron fully relativistic Kohn-Sham theory for solids based on the Dirac-Coulomb Hamiltonian and Gaussian-type functions,"We present the first full-potential method that solves the fully relativistic
4-component Dirac-Kohn-Sham equation for materials in the solid state within
the framework of atom-centered Gaussian-type orbitals (GTOs). Our GTO-based
method treats one-, two-, and three-dimensional periodic systems on an equal
footing, and allows for a seamless transition to the methodology commonly used
in studies of molecules with heavy elements. The scalar relativistic effects
and spin-orbit interaction are handled variationally. The full description of
the electron-nuclear potential in the core region of heavy nuclei is
straightforward due to the local nature of the GTOs and does not pose any
computational difficulties. We show how the time-reversal symmetry and a
quaternion algebra-based formalism can be exploited to significantly reduce the
increased methodological complexity and computational cost associated with
multiple wave-function components coupled by the spin-orbit interaction. We
provide a description of how to employ the matrix form of the multipole
expansion and an iterative renormalization procedure to evaluate the
conditionally convergent lattice sums arising for periodic systems. We
investigate the problem of inverse variational collapse that arises if the
Dirac operator containing a repulsive periodic potential is expressed in a
basis containing diffuse functions, and suggest a possible solution. We
demonstrate the validity of the method on silver halide crystals with large
relativistic effects, and two-dimensional honeycomb structures (silicene and
germanene) exhibiting the spin-orbit-driven quantum spin Hall effect. Our
results are well-converged with respect to the basis limit using standard bases
developed for molecular calculations, and indicate that the rule of removing
basis functions with small exponents should not be applied when transferring
the molecular basis to solids.",1902.02828v2
2018-10-03,"Landau quantization of nearly degenerate bands, and full symmetry classification of avoided Landau-level crossings","Semiclassical quantization rules compactly describe the energy dispersion of
Landau levels, and are predictive of quantum oscillations in transport and
thermodynamic quantities. Such rules -- as formulated by Onsager, Lifshitz and
Roth -- apply when the spin-orbit interaction dominates over the Zeeman
interaction (or vice versa), but does not generally apply when the two
interactions are comparable in strength. In this work, we present a generalized
quantization rule which treats the spin-orbit and Zeeman interactions on equal
footing, and therefore has wider applicability to spin-orbit-coupled materials
lacking a spatial inversion center, or having magnetic order. More generally,
our rule describes the Landau quantization of any number of nearly degenerate
energy bands -- in any symmetry class. The resultant Landau-level spectrum is
generically non-equidistant but may contain spin (or pseudospin) degeneracies.
To tune to such degeneracies in the absence of crystalline point-group
symmetries, three real parameters are needed. We have exhaustively identified
all symmetry classes of cyclotron orbits for which this number is reduced from
three, thus establishing symmetry-enforced 'non-crossing rules' for Landau
levels. In particular, only one parameter is needed in the presence of spatial
rotation or inversion; this single parameter may be the magnitude or
orientation of the field. Signatures of single-parameter tunability include (i)
a smooth crossover between period-doubled and -undoubled quantum oscillations
in the low-temperature Shubnikov-de Haas effect, as well as (ii) 'magic-angle'
magnetoresistance oscillations. We demonstrate the utility of our quantization
rule, as well as the tunability of Landau-level degeneracies, for the
Rashba-Dresselhaus two-dimensional electron gas -- subject to an arbitrarily
oriented magnetic field.",1810.01908v2
2021-11-08,Theoretical study of the crystal and electronic properties of $α$-RuI$_3$,"The material $\alpha$-RuCl$_3$, with a two-dimensional Ru-honeycomb
sublattice, has attracted considerable attention because it may be a
realization of the Kitaev quantum spin liquid (QSL). Recently, a new honeycomb
material, $\alpha$-RuI$_3$, was prepared under moderate high-pressure and it is
stable under ambient conditions. However, different from $\alpha$-RuCl$_3$,
$\alpha$-RuI$_3$ was reported to be a paramagnetic metal without long-range
magnetic order down to $0.35$ K. Here, the structural and electronic properties
of the quasi-two-dimensional $\alpha$-RuI$_3$ are theoretically studied. First,
based on first-principles density functional theory (DFT) calculations, the ABC
stacking honeycomb-layer $R\overline{3}$ (No. 148) structure is found to be the
most likely stacking order for $\alpha$-RuI$_3$ along the $c$-axis.
Furthermore, both $R\overline{3}$ and $P\overline{3}1c$ are dynamically stable
because no imaginary frequency modes were obtained in the phononic dispersion
spectrum. Moreover, the different physical behavior of $\alpha$-RuI$_3$
compared to $\alpha$-RuCl$_3$ can be understood naturally. The strong
hybridization between Ru $4d$ and I $5p$ orbitals decreases the effective
atomic Hubbard repulsion $U$, leading the electrons of RuI$_3$ to be less
localized than in RuCl$_3$. As a consequence, the effective repulsion $U$ is
reduced from Cl to I, leading to the metallic nature of $\alpha$-RuI$_3$. Based
on the DFT+$U$ ($U_{\rm eff} = 2$ eV), plus spin-orbital coupling (SOC), we
obtained a spin-orbit Mott insulating behavior for $\alpha$-RuCl$_3$ and, by
the same procedure, a metallic behavior for $\alpha$-RuI$_3$, in good agreement
with experimental results. Furthermore, when introducing a large (unrealistic)
$U_{\rm eff} = 6$ eV, the spin-orbit Mott gap opens in $\alpha$-RuI$_3$ as
well, supporting the physical picture we are proposing.",2111.04560v2
2022-02-25,Local multiplet formation around a single vacancy in graphene: an effective Anderson model analysis based on the block-Lanczos DMRG method,"To better understand the electronic structure of a single vacancy in
graphene, we study the ground state property of an effective Anderson model,
consisting of three dangling $sp^2$ orbitals of the surrounding carbon atoms
around the vacancy and the $\pi$ orbitals of carbon atoms that form the
honeycomb lattice with a single vacancy. Employing the block-Lanczos
density-matrix renormalization group method, we show that there are two phases
in the relevant parameter space, i.e., a nonmagnetic phase in the weak coupling
region and a free magnetic moment phase in the realistic parameter region. The
systematic analysis finds that, in the free magnetic moment phase, local
multiplets of the doubly degenerate irreducible representation of the
$\mathcal{C}_3$ point group with spin 1 become dominant in the ground state,
and approximately half of this local spin 1 is screened by electrons in the
surrounding $\pi$ orbitals, indicating the emergence of the residual spin-1/2
free magnetic moment. Furthermore, we find that the emergence of the free
magnetic moment is robust against carrier doping, which is in sharp contrast to
the case of graphene with an adatom, thus explaining the qualitative difference
observed experimentally in these two classes of systems. We also find the
enhancement of the spin correlation function between $\pi$ electrons around the
vacancy and those in the conduction band away from the vacancy in the undoped
case, as compared to that in the doped case, while the spin correlation
function between the $\sigma$ electrons in the $sp^2$ dangling orbitals around
the vacancy and the $\pi$ electrons in the conduction band remains large in
both undoped and doped cases. Our calculations thus support qualitatively the
previous experiment that suggests the emergence of free magnetic moment with
two distinct origins.",2202.12638v1
2023-08-16,Biaxial strain modulated electronic structures of layered two-dimensional MoSiGeN4 Rashba systems,"The two-dimensional (2D) MA2Z4 family has received extensive attention in
manipulating its electronic structure and achieving intriguing physical
properties. However, engineering the electronic properties remains a challenge.
Herein, based on first-principles calculations, we systematically investigate
the effect of biaxial strains on the electronic structures of 2D Rashba
MoSiGeN4 (MSGN), and further explore how the interlayer interactions affect the
Rashba spin splitting in such strained layered MSGNs. After applying biaxial
strains, the band gap decreases monotonically with increasing tensile strains
but increases when the compressive strains are applied. An
indirect-direct-indirect band gap transition is induced by applying a moderate
compressive strain (< 5%) in the MSGNs. Due to the symmetry breaking and
moderate spin-orbit coupling (SOC), the monolayer MSGN possess an isolated
Rashba spin splitting (R) near the Fermi level, which could be effectively
regulated to the Lifshitz transition (L) by biaxial strain. For instance, a
L-R-L transformation of Fermi surface is presented in monolayer and a more
complex and changeable L-R-L-R evolution is observed in bilayer and trilayer
MSGNs as the biaxial strain vary from -8% to 12%, which actually depend on the
appearance, variation, and vanish of the Mexican hat band in the absence of SOC
under different strains. The contribution of Mo-dz2 orbital hybridized with
N-pz orbital in the highest valence band plays a dominant role on the band
evolution under biaxial strains, where the R-L evolution corresponds to the
decreased Mo-dz2 orbital contribution. Our study highlights the biaxial strain
controllable Rashba spin splitting, in particular the introduction and even the
evolution of Lifshitz transition near Fermi surface, which makes the strained
MSGNs as promising candidates for future applications in spintronic devices.",2308.08211v1